Method and apparatus for droplet deposition

Abstract

There is provided a method of depositing droplets of a fluid onto a medium with a droplet deposition head, the method comprising, for an actuation cycle, the steps of: receiving input data; designating, based on the input data, all fluid chambers (12) within the array (10) of fluid chambers as launch chambers or non-launch chambers so as to create a plurality of rows of one or more consecutive launch chambers separated by a plurality of rows of one or more consecutive non-launch chambers; and actuating the walls (14) of said chambers such that, for each non-emission chamber, if the non-emission chamber is adjacent to a row of emission chambers, one wall is actuated in a first direction while the other wall remains in a neutral position, and if the non-emission chamber is a single non-emission chamber between rows of emission chambers, two walls are simultaneously actuated in the first direction while the other wall remains in a neutral position while the other wall remains in a neutral position. And if the non-launch chamber is not adjacent to the row of launch chambers, the two walls remain in a neutral position, or are simultaneously actuated in a first direction, or are simultaneously actuated in a second direction; and for each firing chamber, continuously actuates each of the first wall and the second wall in a first direction. Other methods, droplet deposition heads, droplet deposition apparatuses, and computer programs are also provided.

Description

Field of the Invention

[0001] The present invention relates to a method of depositing droplets of a fluid onto a medium using a droplet deposition head, such as a print head; and a droplet deposition head and a droplet deposition device comprising such a droplet deposition head, which are configured to perform such a method. Background of the Invention

[0002] Droplet deposition heads are now widely used, both in more traditional applications such as inkjet printing, and in material deposition applications such as 3D printing and other rapid prototyping technologies, as well as printing raised patterns on surfaces, such as Braille or decorative raised patterns. In such material deposition applications, it may be necessary to deposit relatively large amounts of fluid on a medium using a droplet deposition head. In some cases, the fluid may have new chemistry to adhere to the new medium and increase the functionality of the deposited material.

[0003] Recently, inkjet print heads have been developed that are able to deposit inks and varnishes directly onto tiles with high reliability and throughput. This allows the patterns on the tiles to be customized to the customer’s exact specifications, while also reducing the need to stock a full range of tile varieties.

[0004] In other applications, the droplet deposition heads may be used to form elements such as color filters in LCD or OLED displays as used in the manufacture of flat-panel televisions.

[0005] It will therefore be appreciated that droplet deposition heads continue to evolve and specialize in order to accommodate new and / or increasingly challenging deposition applications. Nevertheless, despite the many advances that have been made in the field of droplet deposition heads, there is still room for improvement in the field of droplet deposition heads.

[0006] As background for this work, Figure 1 1 shows a mechanism by which droplets of fluid can be ejected from an array of fluid chambers. This shows an array 10' of fluid chambers 12 forming part of a droplet deposition head, and a simplified representation of the same array is shown below. One side of the chamber is bounded by a substrate 15. Adjacent fluid chambers 12 are separated by an actuatable side wall 14 formed of a piezoelectric material such as lead zirconate titanate (also known as PZT). The interior of the chamber 12 on each side of each piezoelectric wall 14 is coated with a metal layer that acts as an electrode for applying a potential difference across the corresponding wall. That is, in this earlier example, within a given chamber 12, the metal electrode layer extends from the inner wall on one side of the chamber to the inner wall on the other side of the chamber. However, this is by no means the only electrode configuration that can be used. For example, each electrode extending from the inner wall on one side of the chamber to the inner wall on the other side of the chamber can be cut along the center of the fluid chamber (e.g., by a laser), effectively dividing the electrode into two independently addressable electrodes (such as Figure 2 as shown).

[0007] If the same potential is applied to the electrodes on either side of a given wall, so that there is no potential difference across the wall, the wall remains stationary. On the other hand, if different potentials are applied to the electrodes on either side of a given wall, the wall moves by virtue of the inverse piezoelectric effect, which converts a potential difference into movement. The wall that moves may be referred to as an "active" wall, while the wall that remains stationary may be referred to as a "non-active" wall.

[0008] Figure 1 A simplified representation of an array of chambers is shown, in which two chambers experience a decrease in their volume due to the inward movement of their walls. As a result, the pressure in these two chambers increases (indicated by "+"), while the pressure in the adjacent chamber decreases (indicated by "-"). If the potential difference applied to the walls is high enough (e.g., to overcome surface tension effects and losses caused by the device), droplets of fluid are forced out of the chamber at the increased pressure ("+") through the nozzle 16. Such chambers are referred to herein as "firing" chambers because they eject ("fire") droplets of fluid. Figure 1 Also shown are two chambers (to the far right of the figure) that do not experience a volume change because their walls remain stationary. These chambers are referred to as "non-firing" chambers because they do not eject droplets of fluid. It should be noted that chambers denoted by "-" can be firing chambers (because they are also capable of firing later in the same actuation cycle) or non-firing chambers (if, in the same actuation cycle, their walls do not move in a manner that causes ejection). However, for simplicity, throughout this specification, firing chambers will be denoted by "+" or "-", while non-firing chambers will be blank because the associated pressure increase / decrease is not sufficient to cause ejection.

[0009] The chambers 12 are formed as channels closed on one side by a cover member 17 contacting an actuable wall; for each chamber, a nozzle 16 for fluid ejection is disposed in the cover member 17. The cover member 17 may include a metal or ceramic cover plate that provides structural support, and a relatively thin overlying nozzle plate in which the nozzles are formed. Alternatively, a relatively thin nozzle plate may be used alone as the cover member.

[0010] exist Figure 1 In the example (and indeed throughout this disclosure), each actuatable piezoelectric wall 14 may include a plurality of piezoelectric elements 14 disposed in an array direction ( Figure 1 from left to right) and the direction of passage extension (entering Figure 1The upper and lower halves of the piezoelectric wall can be polarized in opposite directions perpendicular to the channel extension and the array direction, so that when a potential difference is applied to the wall perpendicular to the array direction, the two halves deflect to bend toward one of the fluid chambers; the shape adopted by the deflected wall is similar to a V-shape, so this can be referred to as actuation in a "V-mode". Alternatively, each of the actuatable piezoelectric walls can be polarized in a uniform manner in a single direction (i.e., not as an upper half and a lower half polarized in opposite directions), so that when a potential difference is applied to the wall, the wall deflects under actuation in a "shear mode". Other methods of providing electrodes and polarizing walls have also been proposed, which provide the ability to deflect the wall in a bending-like motion.

[0011] Particularly relevant background is provided in WO 2010 / 055345 A1 which discloses a method for depositing droplets onto a substrate (so-called "print mode 1"), the method employing a device such as an inkjet printhead having: an array of channels acting as fluid chambers, the array being separated by interspersed walls, each channel being in communication with an orifice or nozzle for releasing a droplet of a fluid (such as ink) contained within the channel. Each of the walls separates two adjacent channels and is actuatable such that in response to a first potential difference the wall will deform to reduce the volume of one channel and increase the volume of the other channel, and in response to a second potential difference the wall will deform to produce an opposite effect on the volume of an adjacent channel. The method comprises the steps of receiving input data, such as an array of image data pixels; designating all channels within the array as either emitting channels or non-emitting channels based on the input data so as to produce a plurality of groups of one or more consecutive emitting channels separated by a plurality of groups of one or more consecutive non-emitting channels; actuating walls of certain channels so that for each non-emitting chamber the walls move in the same manner or they remain stationary, and for each emitting chamber the walls move in opposite directions (see Figure 3 ), or one wall is stationary while the other moves (cf. Figure 4 ). These actuations cause each of the emission channels to release at least one fluid droplet, the resulting droplets forming points arranged on a straight line on the substrate, for example to form a representation of a line of image data pixels. These points are separated on the line by gaps corresponding to non-emitting channels.

[0012] Figure 2A droplet deposition head is shown, which includes an array 10 of fluid chambers 12 separated by partitions 14 formed of a piezoelectric material (e.g. PZT), each fluid chamber 12 is connected to a hole (nozzle) 16 for releasing a droplet of fluid, each of the walls 14 separates two adjacent fluid chambers 12, and each fluid chamber 12 is defined by a first wall in a first direction relative to the fluid chamber and a second wall in a second direction relative to the fluid chamber, the second direction being opposite to the first direction.

[0013] In this example, one side of each wall 14 (the right side in the example shown) has a "common" electrode 19 (to which a common potential is applied), and the other side of each wall 14 (the left side as shown) has an "active" electrode 18. The electrodes are connected to a drive circuit (not shown). Wall motion is induced by applying a drive potential to the "active" electrode 18 by means of a drive waveform comprising a sequence of drive pulses. If the drive potential is greater or less than the common potential, the wall moves towards the electrode with the highest potential.

[0014] Figure 3 Shown in greater detail is how the walls move in Print Mode 1. In this figure and throughout this disclosure, the underlining of the fluid chambers indicates that they are designated (based on input data) as firing chambers in a given cycle, a "-" in a chamber indicates that the chamber is experiencing a decrease in pressure (due to an increase in the volume of the chamber as a result of actuating one or both of the chamber's walls), and a "+" in a chamber indicates that the chamber is experiencing an increase in pressure (due to a decrease in the volume of the chamber as a result of actuating one or both of the chamber's walls).

[0015] exist Figure 3 In print mode 1 shown, the walls of the firing chamber move in opposite ways, meaning that the volume of the chamber alternately increases and decreases to cause ejection, while the walls of the non-firing chamber move in the same way, meaning that there is no change in volume / pressure inside the chamber and therefore no fluid ejection.

[0016] At this point, it should be noted that in order for the walls of the droplet deposition head to move in a bidirectional manner in Print Mode 1, the common potential applied to the "common" electrode is between the highest drive potential and the lowest drive potential. Due to the electrode configuration of this droplet deposition head and the application of a common potential to one of the electrodes on each wall, at least the walls of the non-firing chambers located between firing chambers in different rows will always move in the same manner.

[0017] In other words, if the drive potential applied to the "active" electrode is greater than the common potential, the wall moves toward the "active" electrode, but if the drive potential applied to the "active" electrode is less than the common potential, the wall moves toward the "common" electrode. If the drive potential applied to the "active" electrode is substantially equal to the common potential applied to the "common" electrode, the wall remains stationary (i.e., remains in its neutral, unactuated, stationary position).

[0018] In print mode 1, the movement of the walls of the non-firing chamber prevents the stagnation of fluid, which would otherwise cause the chamber's nozzle to clog over time. However, moving the walls of the non-firing chamber is energetically inefficient and may introduce undesirable levels of heat into the droplet deposition head. In addition, it is difficult to eject a single droplet, i.e., 1 dpd (dpd = drops per dot), because there is not enough energy in the movement of the walls to eject such a droplet.

[0019] It would therefore be desirable to overcome the above limitations of Print Mode 1 and implement a more energy-efficient printing method that is also capable of ejecting a single droplet when required.

[0020] Further relevant background art is provided in WO 2010 / 055344 A1, WO 2017 / 118843 A1 and WO 2018 / 224821 A9. SUMMARY OF THE INVENTION

[0021] Aspects of the invention are set out in the accompanying independent claims, while specific embodiments of the invention are set out in the accompanying dependent claims.

[0022] According to a first aspect of the present invention, there is provided a method for depositing droplets of a fluid onto a medium using a droplet deposition head, the droplet deposition head comprising: An array of fluid chambers separated by walls formed of a piezoelectric material, each fluid chamber being in communication with a hole for releasing a droplet of a fluid, each of the walls separating two adjacent fluid chambers, and each fluid chamber being defined by a first wall in a first direction relative to the fluid chamber and a second wall in a second direction relative to the fluid chamber, the second direction being opposite to the first direction; wherein each of the walls has a first electrode on a first side of the wall and a second electrode on a second side of the wall, wherein the second electrode of each of the walls is connected to a common potential, and wherein the first electrode of each of the walls is selectively set to one of: (a) a drive potential different from the common potential and (b) a common potential; wherein each of the walls is actuatable such that in response to application of a drive potential to the corresponding first electrode, the corresponding wall will move from a neutral position to a deformed position in a first direction, and in response to application of a common potential to the corresponding first electrode, the corresponding wall will return to or remain in the neutral position; For the actuation cycle, the method comprises the following steps: Receive input data; designating all fluid chambers within the array as firing chambers or non-firing chambers based on the input data to produce a plurality of rows of one or more consecutive firing chambers separated by a plurality of rows of one or more consecutive non-firing chambers; and A common potential is applied to the second electrode, and based on the input data, a drive potential or a common potential is selectively applied to the first electrode to actuate the wall of the chamber such that: For each non-emitting chamber, If a non-firing chamber is adjacent to a row of firing chambers, one wall is actuated in a first direction while the other wall is held in a neutral position, if the non-firing chamber is a single non-firing chamber between multiple rows of firing chambers, actuating both walls simultaneously in a first direction, and If the non-firing chamber is not adjacent to a row of firing chambers, the two walls remain in a neutral position and are either simultaneously actuated in a first direction or simultaneously actuated in a second direction; and For each firing chamber, continuously actuating each of the first wall and the second wall in a first direction; The actuation during the actuation cycle causes each of the firing chambers in a row of one or more consecutive firing chambers to release at least one droplet, the resulting droplets forming a body of fluid disposed in a line on the media, the body of fluid being separated in the line by a respective gap for each of the plurality of rows of non-firing chambers, the size of each such gap corresponding substantially in size to the respective row of non-firing chambers.

[0023] With the walls of the firing chamber moving in the same direction but at different times during the actuation cycle, this provides a more energy efficient way of printing than Print Mode 1 described above which is also capable of ejecting individual drops when required.

[0024] According to a second aspect of the present invention, there is provided a method for depositing droplets of a fluid onto a medium using a droplet deposition head, the droplet deposition head comprising: an array of fluid chambers separated by walls formed of a piezoelectric material, each fluid chamber being in communication with an orifice for releasing a droplet of a fluid, each of the walls separating two adjacent fluid chambers, and each fluid chamber being defined by a first wall in a first direction relative to the fluid chamber and a second wall in a second direction relative to the fluid chamber, the second direction being opposite to the first direction; wherein each of the walls has a first electrode on a first side of the wall and a second electrode on a second side of the wall, wherein the second electrode of each of the walls is connected to a common potential, and wherein the first electrode of each of the walls is selectively set to one of: (a) a drive potential different from the common potential and (b) a common potential; wherein each of the walls is actuatable such that in response to application of a drive potential to the corresponding first electrode, the corresponding wall will move from a neutral position to a deformed position in a first direction, and in response to application of a common potential to the corresponding first electrode, the corresponding wall will return to or remain in the neutral position; For the actuation cycle, the method comprises the following steps: Receive input data; designating all fluid chambers within the array as firing chambers or non-firing chambers based on the input data to produce a plurality of rows of one or more consecutive firing chambers separated by a plurality of rows of one or more consecutive non-firing chambers; and A common potential is applied to the second electrode, and based on the input data, a drive potential or a common potential is selectively applied to the first electrode to actuate the wall of the chamber such that: For at least the first firing chamber, The first wall of the first firing chamber is repeatedly actuated in a first direction and then returned to a neutral position while the second wall of the first firing chamber is maintained in the neutral position; and At a point in the actuation cycle when the first firing chamber is about to eject a drop of fluid in the first firing chamber, substantially simultaneously with the first wall of the first firing chamber returning to the neutral position, selectively actuating the second wall of the first firing chamber in a first direction so that the first firing chamber ejects a drop of fluid in the first firing chamber, and then the second wall of the first firing chamber returns to the neutral position; The actuation during the actuation cycle causes each of the firing chambers in a row of one or more consecutive firing chambers to release at least one droplet, the resulting droplets forming a body of fluid disposed in a line on the media, the body of fluid being separated in the line by a respective gap for each of the plurality of rows of non-firing chambers, the size of each such gap corresponding substantially in size to the respective row of non-firing chambers.

[0025] According to a third aspect of the present invention, there is provided a method for depositing droplets of a fluid onto a medium using a droplet deposition head, the droplet deposition head comprising: an array of fluid chambers separated by walls formed of a piezoelectric material, each fluid chamber being in communication with an orifice for releasing a droplet of a fluid, each of the walls separating two adjacent fluid chambers, and each fluid chamber being defined by a first wall in a first direction relative to the fluid chamber and a second wall in a second direction relative to the fluid chamber, the second direction being opposite to the first direction; wherein each of the walls has a first electrode on a first side of the wall and a second electrode on a second side of the wall, wherein the second electrode of each of the walls is connected to a common potential, and wherein the first electrode of each of the walls is selectively set to one of: (a) a first drive potential, (b) a second drive potential, and (c) a common potential, the common potential being between the first drive potential and the second drive potential; wherein each of the walls is actuatable such that in response to application of a first drive potential to the respective first electrode, the respective wall will move from a neutral position to a deformed position in a first direction, in response to application of a second drive potential to the respective first electrode, the respective wall will move from the neutral position to the deformed position in a second direction, and in response to application of a common potential to the respective first electrode, the respective wall will return to or remain in the neutral position; For the actuation cycle, the method comprises the following steps: Receive input data; designating all fluid chambers within the array as firing chambers or non-firing chambers based on the input data to produce a plurality of rows of one or more consecutive firing chambers separated by a plurality of rows of one or more consecutive non-firing chambers; and applying a common potential to the second electrode, and selectively applying the first drive potential, the second drive potential, or the common potential to the first electrode based on the input data to actuate the wall of the chamber such that: For at least the first firing chamber, repeatedly actuating the first wall of the first firing chamber in a first direction and then in a second direction while the second wall of the first firing chamber is maintained primarily in a neutral position; and selectively actuating the second wall of the first firing chamber in the first direction substantially simultaneously with actuating the first wall of the firing chamber in the second direction at a time during the actuation cycle when the first firing chamber is to eject a drop of the fluid in the first firing chamber, thereby causing the first firing chamber to eject a drop of the fluid in the first firing chamber, and then returning the second wall of the first firing chamber to a neutral position; Optionally wherein the second wall of the first firing chamber is actuated in the second direction simultaneously with actuating the first wall of the first firing chamber in the first direction immediately before the moment in the actuation cycle when the first firing chamber is to eject a droplet of fluid in the first firing chamber; The actuation during the actuation cycle causes each of the firing chambers in a row of one or more consecutive firing chambers to release at least one droplet, the resulting droplets forming a body of fluid disposed in a line on the media, the body of fluid being separated in the line by a respective gap for each of the plurality of rows of non-firing chambers, the size of each such gap corresponding substantially in size to the respective row of non-firing chambers.

[0026] With regard to the second and third aspects of the invention, preferably the repeated actuation occurs substantially at the resonant frequency of the firing chamber, or substantially at a harmonic or sub-harmonic of the resonant frequency of the firing chamber.

[0027] Advantageously therefore, the printing modes of the second and third aspects of the invention enable actuation of the droplet deposition head at a high frequency whilst also achieving a reduction in the number of unintended droplets and the amount of ink seeping from the fluid chamber during use which would otherwise result in the generation and ejection of unintended large droplets.

[0028] There is also provided a droplet deposition head, a droplet deposition apparatus and a computer program for performing the methods of the first, second and third aspects of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows an array of fluid chambers forming part of a droplet deposition head, in which some of the walls of the chambers have been actuated, and below this a simplified representation of the same array with the same actuated walls; Figure 2 showing an end view of an array of fluid chambers showing a common electrode connected to a common potential and active electrodes; Figure 3 It is a simplified representation of the so-called "Print Mode 1"; Figure 4 It is another simplified representation of printing mode 1; Figure 5 is a simplified representation of a so-called "print mode 2" of an array of fluid chambers and the corresponding steps of ejecting droplets; Figure 6 A first and second mirror-image array of fluid chambers are shown, each array being configured to achieve Figure 5 Print mode 2; Figure 7is another representation of print mode 2 and the corresponding steps of ejecting droplets; Figure 8 Shows the use of Figure 7 a pattern of pixels to be printed in a printing mode; Fig. 9 shows an array of fluid chambers in which certain chamber walls are repeatedly actuated according to a first "harmonic" actuation mode; Fig.10 Shows Fig. 9 an array of fluid chambers wherein additional walls are selectively actuated to cause ejection of droplets; Fig.11 shows an array of fluid chambers in which certain chamber walls are repeatedly actuated according to a second "harmonic" actuation pattern, and other walls are selectively actuated to cause ejection of droplets; Fig.12 The printing of multiple consecutive lines (in this case, four consecutive lines) using a bank of multiple consecutive firing chambers is shown; Fig.13 Shows the use of Fig.12 a pattern of pixels to be printed in a printing mode; Fig.14 Shows Fig.11 A variation of the printing mode in which some of the selectively actuated walls are driven by a so-called "priming pulse" immediately before the droplet ejection moment; Fig.15 Shows the use of Fig.14 a pattern of pixels to be printed in a printing mode; Fig.16 An example of a drive waveform including a starting pulse immediately preceding an ejection pulse is shown; Fig.17 Shows Fig.11 Another variation of the printing mode in which some of the selectively actuated walls are driven by a so-called "cancelation pulse" before the droplet ejection moment; Fig.18 Shows the use of Fig.17 a pattern of pixels to be printed in a printing mode; and Fig.19 An example of a drive waveform including an erase pulse preceding an ejection pulse is shown.

[0030] In the drawings, like elements are indicated by like reference numerals throughout. Detailed Description of the Preferred Embodiments

[0031] The embodiments represent the best way known to the applicant to put the invention into practice. However, they are not the only way to achieve this goal.

[0032] This embodiment relates to what is referred to herein as "Print Mode 2".

[0033] Overview of droplet deposition heads and droplet deposition devices Again specific reference Figure 2 The droplet deposition head used in the printing mode 2 includes an array 10 of fluid chambers 12 separated by partitions 14 formed of piezoelectric material, each fluid chamber 12 is connected to a hole 16 for releasing a droplet of fluid, and each of the walls 14 separates two adjacent fluid chambers 12. Each fluid chamber 12 is defined by a first wall in a first direction relative to the fluid chamber 12 and a second wall in a second direction relative to the fluid chamber 12, the second direction being opposite to the first direction. Figure 2 In the embodiment shown, the first direction is to the left and the second direction is to the right, but this is not necessarily the case. It should also be noted that the array 10 of fluid chambers 12 may not be the total number of fluid chambers present in the droplet deposition head; additional arrays of fluid chambers may also be present (e.g., Figure 6 ), which may optionally be separated or terminated by one or more non-emitting chambers.

[0034] Each of the walls 14 has a first ("active") electrode 18 on a first side of the wall and a second ("common") electrode 19 on a second side of the wall, which is connected to a drive circuit (not shown). In the embodiment shown, the first side is in a first direction relative to the wall, and the second side is in a second direction relative to the wall, but this is not necessarily the case, and in alternative embodiments the first and second electrodes may be reversed.

[0035] The second electrode 19 of each wall is connected to a common potential (which may be ground potential, 0V, or another value, such as a positive potential greater than ground potential). The first electrode 18 of each wall is selectively set to one of the following by a drive waveform: (a) a drive potential different from the common potential and (b) a common potential. In the illustrated embodiment, the drive potential (e.g., +V) is higher than the common potential (e.g., 0V). However, as described above, in alternative embodiments, the drive potential may be less than the common potential.

[0036] In the illustrated embodiment, all second electrodes 19 are simultaneously and constantly controlled to the same common potential to simplify the drive circuit and control electronics. However, in alternative embodiments, all second electrodes 19 need not be controlled to the same common potential; instead, different groups of one or more second electrodes 19 may be controlled to different common potentials. Thus, the common potential does not have to be the same for each wall 14. Furthermore, different groups of one or more second electrodes 19 may receive a common potential at different times, rather than simultaneously and constantly receiving a common potential.

[0037] Each of the walls 14 is actuatable such that in response to application of a drive potential to the corresponding first electrode 18, the corresponding wall will move from a neutral position to a deformed position in a first direction, and in response to application of a common potential to the corresponding first electrode 18, the corresponding wall will return to or remain in the neutral position; In other words, by applying a drive potential signal to the first electrode 18 and a common potential signal to the second electrode 19, a potential difference is applied across the corresponding wall 14, which potential difference is the difference between the drive potential signal and the common potential signal. This potential difference causes deformation (actuation) of the wall. If the wall does not deform, there must be no potential difference across the wall; this is achieved by applying the same signal (i.e., the common potential signal) to both the first electrode and the second electrode.

[0038] Such as Figure 2 The device depicted is often referred to as a "side-shooter" due to the placement of the nozzles generally to the sides of the fluid chamber; the nozzles are typically located equidistant from each end. In this configuration, the ends of the channels are typically left open to allow all channels to communicate with one or more common fluid manifolds. This further allows flow to be established along the length of the channel during use of the device in order to prevent fluid stagnation and sweep debris within the fluid away from the nozzles. It is generally found to be advantageous to have this flow along the length of the channel greater than the maximum flow through the nozzle due to fluid release. In other words, when the device is operated at maximum jetting frequency, the average fluid flow through each nozzle is less than the flow along each channel. Preferably, the flow is at least three times, or more preferably five times, the maximum flow through the nozzle due to fluid release.

[0039] In order to provide maximum density of deposited droplets, preferably each channel or chamber within the array is filled with an ejection fluid, such as ink, during use and is provided with an orifice or nozzle for ejecting the fluid.

[0040] Print Mode 2 To address the temperature increases and high power consumption experienced with Print Mode 1, the present Print Mode 2 was introduced whereby the walls of the firing chamber generally move in the same direction (in the same manner) but at different times within a single actuation cycle.

[0041] As described in more detail below, Figure 5 Provided Figure 2 This is a first example of a device undergoing a series of actuations according to Print Mode 2 and helps to illustrate the general principles of this mode. The naming and direction conventions used above are maintained (ie, references to a first direction and a second direction).

[0042] At different times within a single cycle, chambers 1-5 experience an increase in pressure (as indicated by a "+") due to the inward movement of one of their walls, resulting in a decrease in the volume of those chambers. It can also be seen in the figure that this inward movement causes a decrease in pressure in the adjacent chambers (as indicated by a "-"), because the wall movement acts to increase the volume of those adjacent chambers. In the simplified representation used herein, the walls are represented by V-shapes ("<" or ">") or vertical lines: the direction of deflection of the wall is represented by the direction in which the V-shape points, while the undeformed wall is represented by a vertical line.

[0043] In more detail, Figure 5 An actuator is schematically shown comprising an array of seven fluid chambers separated by actuatable walls, the array being configured as Figure 2 A row of firing chambers 1 to 5 (indicated by underlining) is separated by non-firing chambers 0 and 6.

[0044] Thus, in this example, all fluid chambers within the array of fluid chambers are designated as either firing chambers (1 to 5) or non-firing chambers (0 and 6). As is characteristic of a shared-wall device, each fluid chamber shares its walls with an adjacent chamber. This means that in a row of firing chambers, not all fluid chambers fire at exactly the same time.

[0045] In previous applications (e.g., WO 2010 / 055345 A1), it has been described that (substantially) half of the firing chambers fire in the first half of the cycle, while (substantially) the other half of the firing chambers fire in the second half of the cycle. However, the ejection of droplets from all firing chambers (first half cycle and second half cycle) occurs substantially simultaneously, forming a single droplet line in the deposition medium separated by gaps corresponding to non-firing chambers.

[0046] In contrast, in the present printing mode 2, the printing process is performed in at least two stages (e.g., Figure 5 Phases 2.1 and 2.2, or Figure 7 All wall movements responsible for ejecting droplets are provided in stages 2.1, 2.2 and 2.3). The ejection of droplets in these stages occurs within a single cycle.

[0047] In the print mode 2 shown, each of the walls 14 is actuatable such that in response to application of a drive potential to the corresponding first electrode 18, the corresponding wall will move from its neutral (resting) position to its deformed (actuated) position in a first direction, and in response to application of a common potential to the corresponding first electrode 18, the corresponding wall will return to or remain in the neutral position.

[0048] For a given (single) actuation cycle, the present actuation method comprises the following steps: Receive input data; designating all fluid chambers 12 within array 10 as firing chambers or non-firing chambers based on the input data to produce multiple rows of one or more consecutive firing chambers separated by multiple rows of one or more consecutive non-firing chambers; and A common potential is applied to the second electrode 19 , and based on the input data, a drive potential or a common potential is selectively applied to the first electrode 18 to actuate the wall 14 of the chamber 12 .

[0049] More specifically, for each non-emitting chamber, If a non-firing chamber is adjacent to a row of firing chambers, one wall is actuated in a first direction while the other wall remains in a neutral position (i.e., stationary), If the non-firing chamber is a single non-firing chamber between multiple rows of firing chambers, actuating both walls simultaneously in a first direction (so as not to change the volume of the chamber), and If the non-firing chamber is not adjacent to a row of firing chambers, the two walls remain in a neutral position or are actuated simultaneously in a first direction (or alternatively, can be actuated simultaneously in a second direction if the chamber is configured for actuation in a second direction).

[0050] At the same time, for each firing chamber, Each of the first wall and the second wall are actuated sequentially in the first direction (but not necessarily one in front of the other).

[0051] Actuation during an actuation cycle causes each firing chamber in a row of one or more consecutive firing chambers to release at least one droplet, the resulting droplets forming a body of fluid disposed on a line on the media separated by a respective gap for each of the plurality of rows of non-firing chambers, the size of each such gap corresponding substantially in size to the respective row of non-firing chambers.

[0052] Figure 5 Example exist Figure 5 In the specific example of FIG. 1 , the actuation of the wall 14 is performed in the following steps: Step 1: Start an actuation cycle and designate all fluid chambers as either firing chambers (1 to 5) or non-firing chambers (0 and 6) For simplicity, at the beginning of the actuation cycle, all of the walls 14 within the array of fluid chambers 10 are in their neutral position (i.e., at rest) by applying a common potential to the first electrode 18 and the second electrode 19. In this way, the volume of each fluid chamber 12 is initially constant. However, this may not always be the case.

[0053] Based on the input data, all fluid chambers 12 within array 10 are designated as either firing chambers or non-firing chambers for an actuation cycle to produce rows of one or more consecutive firing chambers separated by rows of one or more consecutive non-firing chambers.

[0054] Step 2.1 and Step 2.2: Actuating the wall to eject one or more droplets For each fluid chamber that is designated as a non-emitting chamber: If a non-firing chamber is adjacent to a row of firing chambers, one wall is actuated in a first direction while the other wall remains in a neutral position, i.e., stationary (e.g., Figure 5 (Incidentally, the movement of a single wall does generate a pressure wave, but it is not sufficient by itself to cause an ejection.)

[0055] If the non-firing chamber is a single non-firing chamber between multiple rows of firing chambers, both walls are actuated simultaneously in a first direction so as not to change the volume of the chamber (e.g., Figure 7 The fluid chamber 2 is shown in FIG.

[0056] If the non-firing chamber is not adjacent to a row of firing chambers, the two walls remain in a neutral position or are actuated simultaneously in a first direction (or alternatively, can be actuated simultaneously in a second direction if the chamber is configured for actuation in a second direction).

[0057] At the same time, for each firing chamber, each of the first wall 18 and the second wall 19 are actuated sequentially in the first direction (but, as discussed in more detail below, not necessarily one before the other). Figure 5 As shown, due to the common wall architecture, the wall can be actuated in two stages as shown below:

[0058] In the first stage (2.1): Simultaneously actuating walls W1, W3, and W5 in a first direction increases the volume of firing chambers 1, 3, and 5 and draws fluid (e.g., ink) into firing chambers 1, 3, and 5 (the so-called "draw" step of the first phase); Walls W2, W4, and W6 remain in their neutral positions (i.e., stationary); After a short time between 2.1 and 2.2, walls W1, W3 and W5 are released and return to the neutral position, reducing the volume of chambers 1, 3 and 5 and increasing the pressure inside the chambers (the so-called "release" step of the first stage); and In the second stage (2.2): Actuating walls W2, W4 and 6 simultaneously in the same first direction reduces the volume of firing chambers 1, 3 and 5, reinforcing the actuation and forming droplets for ejection at the nozzles (the so-called "reinforcement" step of the first stage), and simultaneously increases the volume of firing chambers 2 and 4 and draws fluid (e.g., ink) into firing chambers 2 and 4 (the "drawing" step of the second stage); Walls W1 , W3 and W5 remain in their neutral position (ie, stationary).

[0059] Step 3: End the actuation cycle After a short time, walls W2, W4 and W6 are released and return to their neutral position, reducing the volume of firing chambers 2 and 4, increasing the pressure inside the firing chambers (the "release" step of the second stage) and forming droplets for spraying at the corresponding nozzles.

[0060] Droplets are ejected by the nozzles corresponding to the firing chambers because each firing chamber receives energy from its two walls during the two phases 2.1 and 2.2 of the cycle, unlike the non-firing chambers 6 which do not receive energy from the walls 7 during the first phase and therefore do not fire.

[0061] That is, in phase 2.2, droplets are ejected from chambers 1, 3, and 5 due to the actuation of walls W2, W4, and W6 in the first direction reducing the volume of chambers 1, 3, and 5 and forcing the droplets to be expelled. This is after the following operations: in phase 2.1, walls W1, W3, and W5 were actuated in the first direction to increase the volume of chambers 1, 3, and 5 and draw in fluid. Therefore, for these chambers 1, 3, and 5, each of the first and second walls has been actuated non-simultaneously (the first wall before the second wall). Therefore, each of chambers 1, 3, and 5 receives energy from both of its walls during the cycle.

[0062] On the other hand, with regard to the ejection of droplets from chambers 2 and 4, this occurs in phase 3 due to the movement of walls W2, W4 and W6 back to the neutral position, reducing the volume of chambers 2 and 4 to their original volumes, and due to the earlier movement of walls W3 and W5 in phase 2.1 of the cycle. Therefore, for these chambers 2 and 4, each of the first and second walls has been actuated non-simultaneously (the second wall before the first wall). Therefore, each of chambers 2 and 4 receives energy from its two walls during the cycle. In addition, the initial draw pulse of walls W3 and W5 (in step 2.1) can be regarded as a pre-push pulse for the ejection of chambers 2 and 4, to introduce energy into the chamber in question so that when the other wall returns to the neutral position, it will be able to carry out the desired ejection.

[0063] Chamber 1, chamber 3 and chamber 5 represent a first group of firing chambers, wherein all firing chambers in the first group are actuated simultaneously to eject droplets. Similarly, chambers 2 and chamber 4 represent a second group of firing chambers, wherein all firing chambers in the second group are actuated simultaneously to eject droplets. The second group of firing chambers is actuated to eject droplets after the first group, wherein both the first group and the second group are actuated within a single actuation cycle. Thus, within an actuation cycle, the firing chambers within each group are actuated simultaneously to eject droplets, wherein each group itself is actuated continuously. However, droplets from subsequent groups land on the medium substantially simultaneously with the first group.

[0064] Therefore, in conclusion, about Figure 5 For the first firing chamber (e.g., chamber 1), the actuation method comprises in the actuation cycle: actuating a first wall (wall W1) of a first firing chamber (chamber 1) in a first direction while a second wall (wall W2) of the first firing chamber is maintained in a neutral position, thereby increasing the volume of the first firing chamber and causing it to draw a certain amount of fluid, and then returning the first wall (wall W1) of the first firing chamber to the neutral position; and then Actuating the second wall (wall W2) of the first firing chamber (chamber 1) in a first direction while the first wall (wall W1) of the first firing chamber (chamber 1) is maintained in a neutral position, thereby reducing the volume of the first firing chamber and causing the first firing chamber to eject droplets of the fluid in the first firing chamber, and then returning the second wall (wall W2) of the first firing chamber to the neutral position.

[0065] like Figure 5 As shown, the second firing chamber (chamber 2) can be adjacent to the first firing chamber (chamber 1), the second firing chamber being in a second direction relative to the first firing chamber, such that the second wall (wall W2) of the first firing chamber is the first wall of the second firing chamber. During the actuation cycle, the actuation of the second wall (wall W2) of the first firing chamber in the first direction is performed while the second wall (wall W3) of the second firing chamber is maintained in a neutral position, thereby increasing the volume of the second firing chamber and causing the second firing chamber to draw in a certain amount of fluid simultaneously with ejection of droplets from the first firing chamber.

[0066] As described above, the return of the second wall (wall W2) of the first firing chamber to the neutral position during the actuation cycle causes a drop of fluid to be ejected from the second firing chamber due to the energy already present in the second firing chamber (due to the second wall (wall W3) of the second firing chamber having moved earlier in the actuation cycle).

[0067] However, if desired, the method may also include the following additional steps in the actuation cycle: actuating the second wall (wall W3) of the second firing chamber in the first direction while the first wall (wall W2) of the second firing chamber is maintained in a neutral position, thereby reducing the volume of the second firing chamber so that the second firing chamber ejects a droplet of the fluid in the second firing chamber, and then returning the second wall (wall W3) of the second firing chamber to the neutral position. In addition, the potential difference applied to the second wall in the additional step may be varied to "fine tune" the characteristics (such as volume and / or velocity) of the ejected droplets released by the second firing chamber.

[0068] As mentioned above, Figure 5 The array of fluid chambers shown need not be the entire total number of fluid chambers present in the droplet deposition head. Figure 6 As shown, there may also be additional arrays of fluid chambers, with the first array comprising fluid chambers 0 through 6, and the second array comprising fluid chambers 7 through 13. Chambers 1 through 5 form a first row of firing chambers, and chambers 8 through 12 form a second row of firing chambers. As shown, the firing chambers of the first and second arrays of fluid chambers may be separated by one or more non-firing chambers (in the example shown, chambers 6 and 7) to advantageously isolate actuation of the first array from actuation of the second array.

[0069] As shown, in order to operate the first array and the second array in a balanced manner, the second array of fluid chambers (chambers 7 to 13) can be arranged to be substantially a mirror image of the first array of fluid chambers (chambers 1 to 12). In addition, as also shown, the movement of the walls of the second array of fluid chambers can substantially mirror the movement of the walls of the first array of fluid chambers to again operate the first array and the second array in a balanced manner, wherein any vibration in one array substantially cancels out the corresponding vibration in the other array, achieving more accurate printing.

[0070] from Figure 6 It can be understood from the example that the two walls of each firing chamber in the first row of firing chambers (chambers 1 to 5) move continuously in the first direction, and the two walls of each firing chamber in the second row of firing chambers (chambers 8 to 12) move continuously in the second direction. The movement of the walls of the firing chambers in the second row of firing chambers (chambers 8 to 12) reflects the movement of the walls of the firing chambers in the first row of firing chambers (chambers 1 to 5), and in this example, the two rows of firing chambers are separated by a row of non-firing chambers including two fluid chambers (chambers 6 and chamber 7).

[0071] However, it should be noted that not all of these features are required. For example, the first row of firing chambers and the second row of firing chambers may be separated by any number of non-firing chambers, and the movement of the walls of the firing chambers in the second row of firing chambers need not mirror the movement of the walls of the firing chambers in the first row of firing chambers. The actuation cycle may begin with the first wall of each of the first and second rows of firing chambers, or with the second wall of each of the first and second rows of firing chambers, or any combination thereof. (In other words, in the second row of firing chambers, walls W8, W10, and W12 (but not walls W9, W11, and W13) may be actuated in the first phase.)

[0072] Figure 7 Example Figure 7 Provided Figure 2 A second example of a device undergoing a series of actuations according to printing mode 2. Figure 8 A pattern of pixels to be printed is shown. This example will focus specifically on the highlighted row of pixels, where the first, third, and fifth pixels are white pixels, and the second and fourth pixels are black pixels. This means that, to print this particular row, fluid chamber 0, fluid chamber 2, and fluid chamber 4 are designated as non-emitting chambers, and fluid chamber 1 and fluid chamber 3 are designated as emitting chambers.

[0073] As described above, the wall of each non-emitting chamber is actuated so that: If a non-firing chamber is adjacent to a row of firing chambers, one wall is actuated in a first direction while the other wall remains in a neutral position, i.e., stationary (e.g., Figure 7 The fluid chamber 0 and the fluid chamber 6 are shown in FIG.

[0074] If the non-firing chamber is a single non-firing chamber between multiple rows of firing chambers, both walls are actuated simultaneously in a first direction so as not to change the volume of the non-firing chamber (e.g., Figure 7 The fluid chamber 2 is shown in FIG.

[0075] If the non-firing chamber is not adjacent to a row of firing chambers, the two walls remain in a neutral position or are actuated simultaneously in a first direction (or alternatively, can be actuated simultaneously in a second direction if the chamber is configured for actuation in a second direction).

[0076] At the same time, for each firing chamber, each of the first wall and the second wall is actuated sequentially in the first direction (but not necessarily one before the other). Figure 7 As shown, the wall can be actuated as follows:

[0077] In the first stage (2.1): Actuating wall W1 in a first direction increases the volume of firing chamber 1 and draws fluid (e.g., ink) into firing chamber 1 (the first stage of the “drawing” step); Walls W2, W3, and W4 remain in their neutral positions (i.e., stationary); After a short time between 2.1 and 2.2, wall W1 is released and returns to the neutral position, reducing the volume of chamber 1 and increasing the pressure inside chamber 1 (the "release" step of the first stage); In the second stage (2.2): Actuating wall W2 and wall W3 simultaneously in the same first direction reduces the volume of firing chamber 1, enhances actuation and forms a droplet for ejection at the nozzle (the "enhancement" step of the first stage), while maintaining the volume of non-firing chamber 2 constant by moving both wall W2 and wall W3 in the first direction, and simultaneously increases the volume of firing chamber 3 and draws fluid (e.g., ink) into firing chamber 3 (the "drawing" step of the second stage); Wall W1 and wall W4 remain in their neutral position (i.e., stationary); After a short time between 2.2 and 2.3, walls W2 and W3 are released and return to the neutral position, keeping the volume of non-firing chamber 2 constant, and reducing the volume of firing chamber 3 and increasing the pressure inside firing chamber 3 (the "release" step of the second stage); and In the third stage (2.3): actuating the wall W4 in the same first direction, reducing the volume of the firing chamber 3, enhancing the actuation and forming the droplets for ejection at the nozzle (the "enhancement" step of the second phase), and After a short time, wall W3 is released and returns to its neutral position.

[0078] More generally, about Figure 7 The actuation method enables a first row of firing chambers (chamber 1; the first row may include one or more chambers) and a second row of firing chambers (chamber 3; the second row may also include one or more chambers) to be separated by a single non-firing chamber (chamber 2), the non-firing chamber being in a second direction relative to the first row of firing chambers (chamber 1), and the second row of firing chambers (chamber 3) being in a second direction relative to the non-firing chambers (chamber 2), so that, In the first row of firing chambers, the second wall (wall W2) of the first firing chamber (chamber 1) adjacent to the non-firing chamber (chamber 2) is the first wall of the non-firing chamber (chamber 2), and In the second row of firing chambers, the first wall (wall W3) of the second firing chamber (chamber 3) adjacent to the non-firing chamber (chamber 2) is the second wall of the non-firing chamber (chamber 2).

[0079] The method comprises, during an actuation cycle: actuating a first wall (wall W1) of a first firing chamber (chamber 1) in a first direction while a second wall (wall W2) of the first firing chamber is maintained in a neutral position, and then returning the first wall (wall W1) of the first firing chamber to the neutral position; and then Actuating the second wall (wall W2) of the first firing chamber (chamber 1) and the first wall (wall W3) of the second firing chamber (chamber 3) simultaneously in a first direction, thereby maintaining a constant volume of the non-firing chamber (chamber 2), while maintaining the second wall (wall W4) of the second firing chamber (chamber 3) in a neutral position, thereby causing the first firing chamber (chamber 1) to eject droplets of the fluid in the first firing chamber, and then returning the second wall (wall W2) of the first firing chamber (chamber 1) and the first wall (wall W3) of the second firing chamber (chamber 3) to a neutral position; and then Actuating the second wall (wall W4) of the second firing chamber (chamber 3) in a first direction while the first wall (wall W3) of the second firing chamber (chamber 3) is maintained in a neutral position, so that the second firing chamber (chamber 3) ejects droplets of the fluid in the second firing chamber, and then returning the second wall (wall W4) of the second firing chamber (chamber 3) to the neutral position.

[0080] Harmonic Actuation Mode It is observed that at higher printing frequencies, Print Mode 1 and Print Mode 2 are most stable at a subharmonic of the acoustic resonance frequency (or within a small band around this subharmonic). In conventional multi-cycle printing modes, a "cancellation pulse" is used to effectively cancel the pressure wave left in the channel after actuation and essentially restore the pressure in the channel to its initial state before actuation. Single-cycle firing schemes generally do not allow for (effective) cancellation pulses. However, in the "harmonic actuation mode" to be described now, the inventors have discovered that intentionally actuating at or near the fundamental acoustic resonance frequency (also referred to herein as the "harmonic frequency") or its subharmonics (i.e., 1 / N of the acoustic resonance frequency, where N is an integer) can turn this into an advantage.

[0081] For this purpose, we will now refer to Figures 9 to 19 A variation of the above-described printing mode 2 is described in which certain walls (typically but not necessarily every other wall) within a row of one or more firing chambers are moved in an oscillating manner between a neutral position and a first direction (e.g. Fig. 9 and Fig.10 ) or between the first direction and the second direction (such as Fig.11) are repeatedly and simultaneously actuated. At a particular moment in the actuation cycle when the firing chamber is to eject a droplet, another wall of the firing chamber is selectively actuated in an inward direction within the firing chamber substantially simultaneously with the instance of the opposite inward movement of the repeatedly actuated wall. The phrase "substantially simultaneously" should be understood to mean "at the same moment, or slightly earlier, or slightly later" than the instance of the opposite inward movement of the repeatedly actuated wall, in any case, such as to place the fluid within the chamber below an increased pressure sufficient to cause droplet ejection. For example, substantially at the moment when another wall of the chamber is selectively actuated from its neutral position in a first direction, the repeatedly actuated wall may move inward from the first direction to the neutral direction (e.g., Fig.10 ), or moving inward from a first direction to a second direction (e.g. Fig.11 ). In order to optimize the efficiency of the actuation process, the repeatedly actuated wall is preferably actuated substantially at the fundamental resonant frequency (also referred to herein as the "harmonic frequency") of the emission chamber or substantially at a harmonic or subharmonic of the resonant frequency of the emission chamber.

[0082] Fig. 9 and Fig.10 Example (first example of harmonic actuation mode) Fig. 9 and Fig.10 A first example of a harmonic actuation mode is shown. Fig.10 Essentially Fig. 9 The continuation of Fig. 9 It is shown that a repeated actuation of certain walls (walls W1, W3 and W5) is established between a first direction and a neutral position, preferably at a harmonic frequency of the chamber. Then, Fig.10 One approach is shown in which certain fluid chambers (Chambers 1 to 5), designated as firing chambers, are able to draw in liquid and then eject droplets of the fluid when opposing walls are actuated at specific times in a first direction (inward direction) (simultaneously with opposing inward motion of the repetitively actuated walls).

[0083] Therefore, in Fig. 9 In step 0, staggered walls W1, W3 and W5 are actuated in a first direction at (or substantially at) a harmonic frequency of the chamber and returned to a neutral position. This movement is repeated in an oscillating manner and provides energy to the system without ejecting droplets because the energy imparted to the meniscus of the fluid in the adjacent chamber of the wall is insufficient to overcome the surface tension effects and losses caused by the nozzle. Walls W2, W4 and W6 remain in a neutral position (i.e., stationary). Following the naming and directional conventions used above, the repeatedly actuated walls W1, W3 and W5 can be considered to be the first walls in a first direction relative to chambers 1, 3 and 5, while walls W2, W4 and W6 can be considered to be the second walls in a second direction relative to chambers 1, 3 and 5.

[0084] like Fig. 9 The underscore in Fig.10 As indicated by the above (maintained in the middle), in step 1 of the actuation method, all fluid chambers are designated as firing chambers (chambers 1 to 5) or non-firing chambers (chambers 0 and 6) based on the input data. The above-mentioned repeated actuation of the first wall can be performed before the chambers are designated, but in any case continues after the chambers are designated.

[0085] Then, refer to Fig.10 , the wall of each non-emitting chamber (chamber 0 and chamber 6) is actuated so that: If the non-firing chamber is a single non-firing chamber between multiple rows of firing chambers, actuating both walls simultaneously in a first direction so as not to change the volume of the non-firing chamber; otherwise One wall is actuated in a first direction while the other wall is maintained in a neutral position, or both walls are maintained in a neutral position.

[0086] The walls of each firing chamber (Chamber 1 to Chamber 5) are actuated so that: In the first stage (2.1): Walls W1, W3 and W5 keep moving in a first direction (substantially) at the harmonic frequency of the chamber; while Walls W2, W4, and W6 remain in a neutral position (i.e., stationary); After a short time between stages 2.1 and 2.2, walls W1, W3 and W5 are released and return to a neutral position (substantially) at the harmonic frequency of the chamber, reducing the volume of chambers 1, 3 and 5 and increasing the pressure within chambers 1, 3 and 5; In the second stage (2.2): As a result of the ejection pulse in the drive waveform, walls W2, W4 and W6 are actuated in the same first direction substantially simultaneously with the return of walls W1, W3 and W5 to the neutral position, so that the energy required to eject all droplets from all firing chambers is added to the actuation cycle, reducing the volume of firing chambers 1, 3 and 5 and forming droplets for ejection at each corresponding nozzle; and Increase the volume of firing chamber 2 and firing chamber 4 and draw ink into firing chamber 2 and firing chamber 4; Walls W1, W3, and W5 remain in neutral position (i.e., stationary); After a short time between 2.2 and 2.3, walls W2, W4 and W6 are released and return to the neutral position; In the third stage (2.3): Walls W1, W3 and W5 are kept moving in a first direction (substantially) at the harmonic frequency of the chamber, reducing the volume of firing chambers 2 and 4 and forming droplets for ejection at each respective nozzle; Walls W2, W4, and W6 remain in a neutral position (i.e., stationary); After a short time between 2.3 and 3, walls W1, W3 and W5 are released and return to a neutral position (essentially) at the harmonic frequency of the chamber; After firing, walls W1 , W3 and W5 are actuated again in the first direction and then return to a neutral position (substantially) at the harmonic frequency of the chamber, as shown in step 0 .

[0087] More generally, about Fig. 9 and Fig.10 For a given (single) actuation cycle, the method comprises the following steps: Receive input data; designating all fluid chambers within the array as firing chambers or non-firing chambers based on the input data to produce a plurality of rows of one or more consecutive firing chambers separated by a plurality of rows of one or more consecutive non-firing chambers; and A common potential is applied to the second electrode, and based on the input data, a drive potential or a common potential is selectively applied to the first electrode to actuate the wall of the chamber such that: For at least the first emission chamber (e.g., chamber 1, chamber 3, and chamber 5), The first wall (walls W1, W3 and W5) of the or each first firing chamber is repeatedly actuated in a first direction and then returned to a neutral position while the second wall (walls W2, W4 and W6) of the or each first firing chamber is maintained in the neutral position; and At a time in the actuation cycle when one or more first firing chambers are to eject droplets of the fluid in the one or more first firing chambers, substantially simultaneously with the return of the first wall of the first firing chamber to the neutral position (i.e., before the first wall of the corresponding first firing chamber is actuated again in the first direction), the second wall (walls W2, W4, and W6) of the corresponding first firing chamber is selectively actuated in the first direction, so that the corresponding first firing chamber ejects droplets of the fluid in the corresponding first firing chamber, and then the second wall (walls W2, W4, and W6) of the corresponding first firing chamber returns to the neutral position. The aforementioned “time in the actuation cycle” at which the selective actuation of the second wall occurs may be immediately after the designated firing chamber and before the first repeated actuation of the first wall is completed, although preferably the first wall is repeatedly actuated at least once before the selective actuation of the second wall occurs.

[0088] Actuation during an actuation cycle causes each of a row of one or more consecutive firing chambers to release at least one droplet, the resulting droplets forming a body of fluid disposed on a line on the media separated by a respective gap for each of the plurality of rows of non-firing chambers, the size of each such gap corresponding substantially in size to a respective row of non-firing chambers.

[0089] like Fig.10 As shown, the or each first firing chamber may be a member of a first group of one or more firing chambers (chamber 1, chamber 3, and chamber 5) that are interleaved with corresponding firing chambers in a second group of one or more firing chambers (chamber 2 chamber 4), wherein the first wall (walls W1, W3, and W5) of each member of the first group of firing chambers is simultaneously and repeatedly actuated in a first direction and then returned to a neutral position.

[0090] Thus, a second firing chamber (e.g., chamber 2) that is a member of a second group of firing chambers can be adjacent to a corresponding first firing chamber (e.g., chamber 1), the second firing chamber being in a second direction relative to the first firing chamber such that a second wall of the first firing chamber (e.g., wall W2) is a first wall of the second firing chamber.

[0091] The method may further comprise, during the actuation cycle: maintaining the second wall (wall W3) of the second firing chamber (chamber 2) in a neutral position while the second wall (wall W2) of the first firing chamber (chamber 1) is actuated to eject droplets of the fluid in the first firing chamber; and then Substantially simultaneously with the first wall (wall W2) of the second firing chamber (chamber 2) being in the neutral position, the second wall (wall W3) of the second firing chamber (chamber 2) is actuated in the first direction, thereby causing the second firing chamber (chamber 2) to eject droplets of the fluid in the second firing chamber, and then the second wall (wall W3) of the second firing chamber (chamber 2) is returned to the neutral position.

[0092] It should be understood that the second wall (wall W3) of the second firing chamber (chamber 2) itself is repeatedly actuated in the first direction and returned to the neutral position in synchronization with the repeated actuation of the first wall (wall W1) of the first firing chamber (chamber 1), not only because the second wall (wall W3) of the second firing chamber can be the first wall of the subsequent firing chamber in the first group (e.g., chamber 3 as shown), and all the first walls of the firing chambers in the first group are repeatedly actuated in synchronization with each other.

[0093] Chamber 1, chamber 3, and chamber 5 represent a first group of firing chambers, wherein all firing chambers in the first group are actuated simultaneously to eject droplets. Similarly, chambers 2 and chamber 4 represent a second group of firing chambers, wherein all firing chambers in the second group are actuated simultaneously to eject droplets. The second group of firing chambers is actuated to eject droplets after the first group, wherein both the first group and the second group are actuated within a single actuation cycle. Thus, within an actuation cycle, the firing chambers within each group are actuated simultaneously to eject droplets, wherein each group itself is actuated continuously.

[0094] Fig.11 Example (Second example of harmonic actuation mode) Fig.11 Shows something like Fig.10 The second example of a harmonic actuation mode. However, in Fig.10 In the embodiment, the wall is actuatable between a neutral position and a first direction, and in the embodiment Fig.11 In the case of a first wall, the wall is actuatable between a first direction and a second direction. This is achieved by the following operation: the second electrode of each wall is connected to a common potential (e.g., +V), and the first electrode of each wall is selectively set to one of the following: (a) a first drive potential (e.g., 0V), (b) a second drive potential (e.g., ++V), and (c) a common potential (e.g., +V), the common potential being between the first drive potential and the second drive potential. Each of the walls is actuatable so that in response to applying the first drive potential to the corresponding first electrode, the corresponding wall will move from a neutral position to a deformed position in the first direction, in response to applying the second drive potential to the corresponding first electrode, the corresponding wall will move from a neutral position to a deformed position in the second direction, and in response to applying the common potential to the corresponding first electrode, the corresponding wall will return to or remain in the neutral position.

[0095] Therefore, in Fig.11 In step 0, staggered walls W1, W3 and W5 are actuated in a first direction and then in a second direction at (or substantially at) a harmonic frequency of the chamber without stopping at a neutral position. This movement is repeated in an oscillating manner and provides energy to the system without ejecting droplets because the energy imparted to the meniscus of the fluid in the adjacent chamber of the wall is insufficient to overcome the surface tension effects and losses caused by the nozzle. Walls W2, W4 and W6 remain in a neutral position (i.e., stationary). Following the naming and directional conventions used above, the repeatedly actuated walls W1, W3 and W5 can be considered to be the first walls in the first direction relative to chambers 1, 3 and 5, while walls W2, W4 and W6 can be considered to be the second walls in the second direction relative to chambers 1, 3 and 5.

[0096] like Fig.11As indicated by the underline in , the fluid chambers are designated as firing chambers (in this case, chambers 1, 3, and 5) or non-firing chambers (chambers 0, 2, 4, and 6) based on the input data. The above-described repeated actuation of the first wall may be performed before the chambers are designated, but in any case continues after the chambers are designated.

[0097] The walls of each firing chamber (Chamber 1 to Chamber 5) are actuated so that: In the first stage (2.1): actuating walls W1, W3 and W5 in a first direction (substantially) at a harmonic frequency of the chamber; and Walls W2, W4, and W6 remain in a neutral position (i.e., stationary); In the second stage (2.2): actuating walls W1, W3 and W5 in a second direction (substantially) at a harmonic frequency of the chamber; and actuating walls W2, W4 and W6 in a first direction substantially simultaneously with actuating walls W1, W3 and W5 in a second direction due to the firing pulse in the drive waveform so that the energy required to eject all droplets from all firing chambers is added to the actuation cycle, reducing the volume of firing chambers 1, 3 and 5 and forming a droplet for ejection at each respective nozzle; and After firing, walls W1 , W3 and W5 are actuated again in a first direction and then in a second direction (substantially) at a harmonic frequency of the chamber, as indicated in step 0 .

[0098] For each non-firing chamber, if a row of non-firing chambers is not a single non-firing chamber located between multiple rows of firing chambers, the wall is actuated during the actuation cycle such that: actuating one wall only in a first direction (e.g., wall W6) or in both a first direction and a second direction (e.g., wall W1) while the other wall remains in a neutral position (e.g., wall W0 and wall W7); or Both walls are kept in neutral position.

[0099] On the other hand, if a single non-firing chamber is between multiple rows of firing chambers, the wall is actuated during the actuation cycle such that: In a first phase (2.1), one wall (e.g., wall W3) is actuated in a first direction while a second wall (e.g., wall W2) is held in a neutral position; then In the second phase (2.2), one wall (eg, wall W2 and wall W4) is actuated in a first direction, while another wall (eg, wall W3 and wall W5) is actuated in a second direction.

[0100] More generally, about Fig.11 For a given (single) actuation cycle, the method comprises the following steps: Receive input data; designating all fluid chambers within the array as firing chambers or non-firing chambers based on the input data to produce a plurality of rows of one or more consecutive firing chambers separated by a plurality of rows of one or more consecutive non-firing chambers; and applying a common potential to the second electrode, and selectively applying the first drive potential, the second drive potential, or the common potential to the first electrode based on the input data to actuate the wall of the chamber such that: For at least the first emission chamber (e.g., chamber 1, chamber 3, and chamber 5), repeatedly actuating the first wall of the or each first firing chamber (walls W1, W3 and W5) in a first direction and then in a second direction without stopping at a neutral position while the second wall of the or each first firing chamber (walls W2, W4 and W6) remains in the neutral position; and At a point in the actuation cycle when one or more first firing chambers are to eject a drop of the fluid in the one or more first firing chambers, substantially simultaneously with actuating the first wall of the firing chamber in the second direction, the second wall (walls W2, W4, and W6) of the corresponding first firing chamber is selectively actuated in the first direction, so that the corresponding first firing chamber ejects a drop of the fluid in the corresponding first firing chamber, and then the second wall (walls W2, W4, and W6) of the corresponding first firing chamber returns to the neutral position. As described above, the aforementioned "point in the actuation cycle" at which the selective actuation of the second wall occurs may be immediately after the designated firing chamber and before the first repeated actuation of the first wall is completed, although preferably the first wall is repeatedly actuated at least once before the selective actuation of the second wall occurs.

[0101] The or each first firing chamber may be a member of a first group of one or more firing chambers (chamber 1, chamber 3, and chamber 5) that are interleaved with corresponding firing chambers in a second group of one or more firing chambers (chamber 2 and chamber 4), wherein the first wall (walls W1, W3, and W5) of each member of the first group of firing chambers is repeatedly actuated simultaneously in a first direction and then in a second direction.

[0102] Fig.12 Example - Print multiple lines Reference now Fig.12 , where it is desired to print a series of five droplets from chamber 1 to chamber 5, all chambers from chamber 1 to chamber 5 will be designated as firing chambers. However, in practice, the release of walls W2 and W4 and the movement of walls W3 and W5 in the first direction may or may not be sufficient to cause droplets to be ejected from chambers 2 and 4.

[0103] If the drive pulses applied to walls W2 and W4 have a high enough potential difference to overcome the surface tension effects of these walls when released, drops will be ejected from chambers 2 and 4. However, the drops can be expected to have variations in velocity and / or volume resulting in a loss of printing uniformity.

[0104] One way to solve this problem is to print the droplets as multiple continuous lines, e.g. Fig.12 As shown, for example, Fig.13 Thus, the energy of the previous pulse causes all chambers 1 to 5 to overcome the surface tension effect and Fig.12 However, this can result in successive droplets merging in flight, again affecting print uniformity.

[0105] It should be noted that reference Fig.11 and Fig.12 The wall motion described is the same. Droplets may be ejected from every other nozzle, or from every nozzle. This may depend on the number of lines printed. This may result in uneven droplet formation in the printhead. The basic embodiment will now be referred to Figures 14 to 19 The more advanced techniques described are improved.

[0106] Fig.14 A variation of this, using a starting pulse Fig.14 Shows Fig.11 A variation of the harmonic actuation mode of FIG. 4 . In this example, a so-called “fire pulse” is included in the drive waveform to ensure differential droplet ejection.

[0107] and Fig.11 As in the example, Fig.14 In the embodiment, the staggered walls W1, W3 and W5 are actuated in the first and second directions (substantially) at the harmonic frequency of the chamber. This motion is repeated and some energy is provided to the system without ejecting droplets ( Fig.11 and Fig.14 Step 0).

[0108] For firing, all fluid chambers are designated as either firing chambers (1, 2, 3, 4, and 5) or non-firing chambers (0 and 6). Fig.14 The wall is shown to move to eject a single line, resulting in Fig.15 The pattern shown.

[0109] To explain the effect of the priming pulse, note that wall W2 (the second wall of the first firing chamber (chamber 1)) Fig.11 remains in neutral position in phase 2.1, but in Fig.14In stage 2.1 of the variant, substantially simultaneously with actuating the first wall (W1) of the first firing chamber in the first direction, the wall W2 is actuated (by means of a priming pulse) in the second direction. This actuation of the second wall (W2) of the first firing chamber occurs immediately before stage 2.2, in which the first firing chamber ejects a droplet of the fluid in the first firing chamber. In fact, the actuation of the wall W2 in stage 2.1 serves to prime the wall W2 so as to give more energy to the wall W2 when it is actuated to cause droplet ejection in stage 2.2. Therefore, after stage 2.2, the wall W2 still has enough energy to effectively promote successful droplet ejection in stage 2.3.

[0110] More specifically, the walls of each firing chamber (Chamber 1 to Chamber 5) are actuated so that: In the first stage (2.1): actuating walls W1, W3 and W5 in a first direction (substantially) at a harmonic frequency of the chamber, providing some energy to the chamber; The walls W2 and W4 are actuated in a second direction due to the starting pulse, imparting some starting energy to the chamber; In the second stage (2.2): actuating walls W1, W3 and W5 in a second direction (substantially) at a harmonic frequency of the chamber; and Due to the ejection pulse in the drive waveform, walls W2, W4 and W6 are actuated in the first direction substantially simultaneously with the actuation of walls W1, W3 and W5 in the second direction, so that the energy required to eject all droplets from all firing chambers is added to the actuation cycle, reducing the volume of firing chambers 1, 3 and 5 and forming a droplet for ejection at each respective nozzle; In the third stage (2.3): Again actuating walls W1, W3 and W5 in a first direction (substantially) at the harmonic frequency of the chamber, providing some energy to the chamber; Walls W2, W4, and W6 are released, and chambers 2 and 4 eject droplets due to the firing energy previously imparted by the firing pulse; and After firing, walls W1 , W3 and 5W are actuated again in a first direction and then in a second direction (substantially) at a harmonic frequency of the chamber, as shown in step 0 .

[0111] For each non-emitting chamber, the walls are actuated such that: actuating one wall only in a first direction (e.g. wall W6) or in both a first direction and a second direction (e.g. wall W1) while the other wall remains stationary (e.g. walls W0 and W7); or Both walls are kept in neutral position.

[0112] Fig.16It shows that it can be applied to Fig.14 2.1 , causing actuation in the second direction) followed by an ejection pulse (a pulse of the “first drive potential” at a nominal level of 0 V, causing actuation in the first direction in stage 2.2) followed by a return to the common potential (at a nominal level of +V).

[0113] from Fig.16 It can be seen that when the start pulse is delivered, the relative amplitudes of the second drive potential (++V), the first drive potential (0V) and the common potential (+V) can optionally make the difference between the second drive potential (++V) and the common potential (+V) smaller than the difference between the common potential (+V) and the first drive potential (0V).

[0114] Fig.17 A variation of this approach uses pulse elimination Fig.17 Shows Fig.11 A variation of the harmonic actuation mode of FIG. 1. In this example, a so-called “killing pulse” is included in the drive waveform to ensure that only every other nozzle ejects a droplet.

[0115] and Fig.11 and Fig.14 As in the example, Fig.17 In the embodiment of the present invention, the staggered walls W1, W3 and W5 are moved in the first direction and the second direction (substantially) at the harmonic frequency of the chamber. This movement is repeated and some energy is provided to the system without ejecting droplets (step 0).

[0116] For firing, all fluid chambers are designated as either firing chambers (1, 3, and 5) or non-firing chambers (0, 2, 4, and 6).

[0117] To explain the effect of pulse elimination, it should be noted that Fig.17 Phases 2.3 and 2.4 correspond to Fig.11 Phases 2.1 and 2.2. However, Fig.17 Additionally included are stages 2.1 and 2.2 (in stage 2.2, the elimination pulse is delivered) prior to stages 2.3 and 2.4. Referring again to wall W2 (the second wall of the first emission chamber (chamber 1)), in Fig.17 In phase 2.2 of the actuation of the first wall (W1) of the first firing chamber in the second direction, the wall W2 is actuated in the second direction (by means of a removal pulse). This occurs Fig.17Prior to stage 2.4 of , in which the first firing chamber ejects a droplet of the fluid in the first firing chamber. In stage 2.2, the same actuation occurs in walls W3 and W4 of the next firing chamber (chamber 3), which is separated from chamber 1 by a non-firing chamber (chamber 2), and in walls W5 and W6 of another firing chamber (chamber 5), which is separated from chamber 3 by another non-firing chamber (chamber 4). Fig.17 The effect of the elimination pulse in stage 2.2 of is to move both walls of non-firing chamber 2 and non-firing chamber 4 simultaneously (i.e., in stage 2.2) in the same direction (i.e., the second direction). This ensures that during the remainder of the actuation cycle, surface tension effects are not overcome in non-firing chamber 2 and non-firing chamber 4. Therefore, in stage 2.4, when droplets are ejected from each of firing chambers 1, 3, and 5, no droplets are ejected from non-firing chamber 2 and non-firing chamber 4.

[0118] More specifically, the walls of each chamber are actuated such that: In the first stage (2.1): actuating walls W1, W3 and W5 in a first direction (substantially) at a harmonic frequency of the chamber; and Walls W2, W4, and W6 remain stationary; In the second stage (step 2.2): Actuation of walls W1 to W6 in a second direction due to the action of the kill pulse (more specifically, which is applied to walls W2, W4 and W6 to ensure that no droplets are ejected from chambers 2, 4 and 6); In the third stage (2.3): walls W1, W3 and W5 are again actuated in the first direction (substantially) at the harmonic frequency of the chamber; Walls W2, W4, and W6 remain stationary; In the fourth stage (2.4): walls W1, W3 and W5 are again actuated in a second direction (substantially) at the channel harmonic frequency; actuating walls W2, W4 and W6 in a first direction substantially simultaneously with actuating walls W1, W3 and W5 in a second direction due to the firing pulse in the drive waveform so that the energy required to eject all droplets from all firing chambers is added to the actuation cycle, reducing the volume of firing chambers 1, 3 and 5 and forming a droplet for ejection at each respective nozzle; and After firing, walls W1 , W3 and 5W are actuated again in a first direction and then in a second direction (substantially) at a harmonic frequency of the chamber, as shown in step 0 .

[0119] Fig.19 It shows that it can be applied to Fig.172 , the drive waveform comprising an erasure pulse (a pulse of the “second drive potential” at a nominal level ++V, causing actuation in the second direction in phase 2.2), followed by an ejection pulse (a pulse of the “first drive potential” at a nominal level 0V, causing actuation in the first direction in phase 2.4) before returning to a common potential (at a nominal level +V). It can be seen that the drive waveform also returns to a common potential during the brief period between the erasure pulse and the ejection pulse, which brief period corresponds to the duration of phase 2.3, wherein the wall W2 is temporarily in a neutral position.

[0120] from Fig.19 It can also be seen that when the elimination pulse is delivered, the relative amplitudes of the second drive potential (++V), the first drive potential (0V) and the common potential (+V) can optionally be such that the difference between the second drive potential (++V) and the common potential (+V) is less than the difference between the common potential (+V) and the first drive potential (0V).

[0121] General considerations In all of the above printing modes, the droplet deposition device (including one or more droplet deposition heads) may also include a computer in data communication with the droplet deposition head, wherein the computer is programmed to perform specified steps based on input data. The computer may also be programmed to provide instructions to the droplet deposition head so that the droplet deposition head performs an actuation step.

[0122] Alternatively or additionally, the or each droplet deposition head may be provided with an on-board processor programmed to perform said specified steps based on said input data.

[0123] A computer program may be provided comprising instructions for causing a droplet deposition head or a droplet deposition device to perform the printing method in question.

[0124] Further details on how a droplet deposition head can be controlled in response to provided image data and in response to the generation of a drive waveform used to provide a potential signal to actuate the walls of the firing chamber are provided, for example, in WO 2018 / 224821 A9.

[0125] It should be understood that a variety of fluids may be deposited using the methods and droplet deposition heads described herein, depending on the application.

[0126] For example, the droplet deposition head can eject ink droplets that can travel to a piece of paper or card, or to other receiving media such as a tile or a shaped article (e.g., a can, bottle, etc.) to form an image, as is the case in an inkjet printing application (where the droplet deposition head can be an inkjet printhead, or more specifically, a drop-on-demand inkjet printhead).

[0127] Alternatively, droplets of fluid can be used to build structures. For example, an electroactive fluid can be deposited onto a receiving medium such as a circuit board in order to prototype an electrical device.

[0128] In another example, a polymer including a fluid or molten polymer may be deposited in successive layers to produce a prototype model of an object (as in 3D printing).

[0129] In other applications, the droplet deposition head may be adapted to deposit droplets of a solution containing biological or chemical material onto a receiving medium such as a microarray.

[0130] Droplet deposition heads suitable for use with such alternative fluids are generally similar in construction to print heads, with some adjustments made to handle the particular fluid in question.

[0131] The droplet deposition head as described herein may be a drop-on-demand droplet deposition head. In such a head, the pattern of ejected droplets varies according to input data provided to the head.

[0132] With all of the above printing modes, the potential difference applied to the chamber walls can be varied to "fine tune" the properties of the ejected droplets (such as volume and / or velocity). In addition, additional wall motions of varying amplitudes can also or alternatively be used to "fine tune" such properties of the ejected droplets.

[0133] Furthermore, in the example drive waveforms given above, the potential levels applied to the electrodes on the chamber walls are described as being positive potentials (e.g., +V or ++V) or zero / ground potentials. However, if the drive electronics permit, one or more of the drive potential and the common potential may take negative values, provided of course that the relative relationship of the drive potential and the common potential results in the desired actuation behavior of the wall (if two such drive potentials are used to achieve bidirectional actuation of the wall, the common potential is between the first drive potential and the second drive potential).

[0134] Finally, it should be noted that a wide range of examples and variations are contemplated within the scope of the appended claims. Therefore, the foregoing description should be understood as providing numerous non-limiting examples that aid those skilled in the art in understanding the invention and showing how to implement the invention.

Claims

1. A method for depositing droplets of a fluid onto a medium using a droplet deposition head, the droplet deposition head comprising: An array of fluid chambers separated by walls formed of a piezoelectric material, each fluid chamber being in communication with an orifice for releasing a droplet of a fluid, each of the walls separating two adjacent fluid chambers, and each fluid chamber being defined by a first wall in a first direction relative to the fluid chamber and a second wall in a second direction relative to the fluid chamber, the second direction being opposite to the first direction; wherein each of the walls has a first electrode on a first side of the wall and a second electrode on a second side of the wall, wherein the second electrode of each of the walls is connected to a common potential, and wherein the first electrode of each of the walls is selectively settable to one of: (a) a drive potential different from the common potential and (b) the common potential; wherein each of the walls is actuatable such that in response to application of the drive potential to the corresponding first electrode, the corresponding wall will move from a neutral position to a deformed position in the first direction, and in response to application of the common potential to the corresponding first electrode, the corresponding wall will return to or remain in the neutral position; For the actuation cycle, the method comprises the following steps: Receive input data; designating all fluid chambers within the array as firing chambers or non-firing chambers based on the input data to produce a plurality of rows of one or more consecutive firing chambers separated by a plurality of rows of one or more consecutive non-firing chambers; and applying the common potential to the second electrode, and based on the input data, selectively applying the drive potential or the common potential to the first electrode to actuate the wall of the chamber, such that: For each non-emitting chamber, If the non-firing chamber is adjacent to a row of firing chambers, actuating one wall in the first direction while the other wall remains in the neutral position, if the non-firing chamber is a single non-firing chamber between multiple rows of firing chambers, actuating both walls simultaneously in the first direction, and If the non-firing chamber is not adjacent to a row of firing chambers, the two walls remain in the neutral position and are either simultaneously actuated in the first direction or simultaneously actuated in the second direction; and For each firing chamber, continuously actuating each of the first wall and the second wall in the first direction; The actuation during the actuation cycle causes each of the firing chambers in a row of one or more consecutive firing chambers to release at least one droplet, the resulting droplets forming a body of fluid disposed in a line on the medium, the body of fluid being separated in the line by a respective gap for each of the plurality of rows of non-firing chambers, the size of each such gap corresponding substantially in size to a respective row of non-firing chambers.

2. The method according to claim 1, wherein: For a first firing chamber, the method includes, during the actuation cycle: actuating the first wall of the first firing chamber in the first direction while the second wall of the first firing chamber is maintained in the neutral position, thereby increasing the volume of the first firing chamber and causing the first firing chamber to draw a certain amount of fluid, and then returning the first wall of the first firing chamber to the neutral position; and then Actuating the second wall of the first firing chamber in the first direction while the first wall of the first firing chamber is maintained in the neutral position, thereby reducing the volume of the first firing chamber and causing the first firing chamber to eject droplets of the fluid in the first firing chamber, and then returning the second wall of the first firing chamber to the neutral position.

3. The method according to claim 2, wherein: a second firing chamber adjacent to the first firing chamber, the second firing chamber being in the second direction relative to the first firing chamber such that the second wall of the first firing chamber is the first wall of the second firing chamber, Wherein, during the actuation cycle, the actuation of the second wall of the first firing chamber in the first direction is performed while the second wall of the second firing chamber is maintained at the neutral position, thereby increasing the volume of the second firing chamber and causing the second firing chamber to absorb a certain amount of fluid while ejecting droplets from the first firing chamber.

4. The method according to claim 3, wherein: During the actuation cycle, returning the second wall of the first firing chamber to the neutral position causes a drop of fluid to be ejected from within the second firing chamber.

5. The method according to claim 3, further comprising: During the actuation cycle, the second wall of the second firing chamber is actuated in the first direction while the first wall of the second firing chamber is maintained in the neutral position, thereby reducing the volume of the second firing chamber to cause the second firing chamber to eject droplets of the fluid in the second firing chamber, and then returning the second wall of the second firing chamber to the neutral position.

6. The method according to claim 1, wherein: For a first row of firing chambers and a second row of firing chambers separated by a single non-firing chamber, the non-firing chambers are in the second direction relative to the first row of firing chambers, and the second row of firing chambers are in the second direction relative to the non-firing chambers, such that, In the first row of firing chambers, the second wall of a first firing chamber adjacent to the non-firing chamber is the first wall of the non-firing chamber, and In the second row of firing chambers, the first wall of the second firing chamber adjacent to the non-firing chamber is the second wall of the non-firing chamber, The method comprises, during the actuation cycle: actuating the first wall of the first firing chamber in the first direction while the second wall of the first firing chamber is maintained in the neutral position, and then returning the first wall of the first firing chamber to the neutral position; and then actuating the second wall of the first firing chamber and the first wall of the second firing chamber simultaneously in the first direction while the second wall of the second firing chamber is maintained in the neutral position, thereby causing the first firing chamber to eject droplets of the fluid in the first firing chamber, and then returning the second wall of the first firing chamber and the first wall of the second firing chamber to the neutral position; and then Actuating the second wall of the second firing chamber in the first direction while the first wall of the second firing chamber is maintained in the neutral position causes the second firing chamber to eject droplets of fluid in the second firing chamber, and then returning the second wall of the second firing chamber to the neutral position.

7. A method for depositing droplets of a fluid onto a medium using a droplet deposition head, the droplet deposition head comprising: An array of fluid chambers separated by walls formed of a piezoelectric material, each fluid chamber being in communication with an orifice for releasing a droplet of a fluid, each of the walls separating two adjacent fluid chambers, and each fluid chamber being defined by a first wall in a first direction relative to the fluid chamber and a second wall in a second direction relative to the fluid chamber, the second direction being opposite to the first direction; wherein each of the walls has a first electrode on a first side of the wall and a second electrode on a second side of the wall, wherein the second electrode of each of the walls is connected to a common potential, and wherein the first electrode of each of the walls is selectively settable to one of: (a) a drive potential different from the common potential and (b) the common potential; wherein each of the walls is actuatable such that in response to application of the drive potential to the corresponding first electrode, the corresponding wall will move from a neutral position to a deformed position in the first direction, and in response to application of the common potential to the corresponding first electrode, the corresponding wall will return to or remain in the neutral position; For the actuation cycle, the method comprises the following steps: Receive input data; designating all fluid chambers within the array as firing chambers or non-firing chambers based on the input data to produce a plurality of rows of one or more consecutive firing chambers separated by a plurality of rows of one or more consecutive non-firing chambers; and applying the common potential to the second electrode, and based on the input data, selectively applying the drive potential or the common potential to the first electrode to actuate the wall of the chamber, such that: For at least the first firing chamber, The first wall of the first firing chamber is repeatedly actuated in the first direction and then returns to the neutral position while the second wall of the first firing chamber is maintained in the neutral position; and selectively actuating the second wall of the first firing chamber in the first direction substantially simultaneously with returning the first wall of the first firing chamber to the neutral position at a time in the actuation cycle when the first firing chamber is to eject a drop of the fluid in the first firing chamber, thereby causing the first firing chamber to eject a drop of the fluid in the first firing chamber, and then returning the second wall of the first firing chamber to the neutral position; The actuation during the actuation cycle causes each of the firing chambers in a row of one or more consecutive firing chambers to release at least one droplet, the resulting droplets forming a body of fluid disposed in a line on the medium, the body of fluid being separated in the line by a respective gap for each of the plurality of rows of non-firing chambers, the size of each such gap corresponding substantially in size to a respective row of non-firing chambers.

8. The method according to claim 7, wherein: The first firing chamber is a member of a first group of firing chambers that is interleaved by corresponding firing chambers of a second group of one or more firing chambers, and wherein the first wall of each of the members of the first group of firing chambers is simultaneously and repeatedly actuated in the first direction and then returned to the neutral position.

9. The method according to claim 7 or claim 8, in, a second firing chamber that is a member of the second group of firing chambers is adjacent to the first firing chamber, the second firing chamber being in the second direction relative to the first firing chamber such that the second wall of the first firing chamber is the first wall of the second firing chamber, And wherein the method further comprises, during the actuation cycle: maintaining the second wall of the second firing chamber in the neutral position while the second wall of the first firing chamber is actuated to eject droplets of the fluid in the first firing chamber; and then Substantially simultaneously with the first wall of the second firing chamber being in the neutral position, actuating the second wall of the second firing chamber in the first direction to cause the second firing chamber to eject a droplet of the fluid in the second firing chamber, and then returning the second wall of the second firing chamber to the neutral position.

10. The method according to claim 9, wherein: The second wall of the second firing chamber is repeatedly actuated in the first direction and returns to the neutral position in synchronization with the repeated actuation of the first wall of the first firing chamber.

11. The method according to any one of claims 7 to 10, wherein: During the actuation cycle, for each non-firing chamber, If the non-firing chamber is a single non-firing chamber between multiple rows of firing chambers, both walls are actuated simultaneously in the first direction, otherwise One wall is actuated in the first direction while the other wall is maintained in the neutral position, or both walls are maintained in the neutral position.

12. A method according to any one of the preceding claims, wherein: The common potential is a ground potential or 0V.

13. The method according to any one of claims 1 to 11, wherein: The common potential is a positive potential greater than the ground potential.

14. A method according to any one of the preceding claims, wherein: The driving potential is greater than the common potential.

15. A method for depositing droplets of a fluid onto a medium using a droplet deposition head, the droplet deposition head comprising: An array of fluid chambers separated by walls formed of a piezoelectric material, each fluid chamber being in communication with an orifice for releasing a droplet of a fluid, each of the walls separating two adjacent fluid chambers, and each fluid chamber being defined by a first wall in a first direction relative to the fluid chamber and a second wall in a second direction relative to the fluid chamber, the second direction being opposite to the first direction; wherein each of the walls has a first electrode on a first side of the wall and a second electrode on a second side of the wall, wherein the second electrode of each of the walls is connected to a common potential, and wherein the first electrode of each of the walls is selectively settable to one of: (a) a first drive potential, (b) a second drive potential, and (c) the common potential, the common potential being between the first drive potential and the second drive potential; wherein each of the walls is actuatable such that in response to application of the first drive potential to the corresponding first electrode, the corresponding wall will move from a neutral position to a deformed position in the first direction, in response to application of the second drive potential to the corresponding first electrode, the corresponding wall will move from the neutral position to a deformed position in the second direction, and in response to application of the common potential to the corresponding first electrode, the corresponding wall will return to or remain in the neutral position; For the actuation cycle, the method comprises the following steps: Receive input data; designating all fluid chambers within the array as firing chambers or non-firing chambers based on the input data to produce a plurality of rows of one or more consecutive firing chambers separated by a plurality of rows of one or more consecutive non-firing chambers; and applying the common potential to the second electrode, and selectively applying the first drive potential, the second drive potential, or the common potential to the first electrode based on the input data to actuate a wall of the chamber such that: For at least the first firing chamber, repeatedly actuating a first wall of the first firing chamber in the first direction and then in the second direction while a second wall of the first firing chamber is maintained in the neutral position; and selectively actuating the second wall of the first firing chamber in the first direction substantially simultaneously with actuating the first wall of the firing chamber in the second direction at a time during the actuation cycle when the first firing chamber is to eject a drop of the fluid in the first firing chamber, thereby causing the first firing chamber to eject a drop of the fluid in the first firing chamber, and then returning the second wall of the first firing chamber to the neutral position; Optionally, wherein a second wall of the first firing chamber is actuated in the second direction simultaneously with actuating the first wall of the first firing chamber in the first direction (i.e., due to the waveform providing a firing pulse) immediately before the moment in the actuation cycle when the first firing chamber is to eject a droplet of fluid in the first firing chamber; The actuation during the actuation cycle causes each of the firing chambers in a row of one or more consecutive firing chambers to release at least one droplet, the resulting droplets forming a body of fluid disposed in a line on the medium, the body of fluid being separated in the line by a respective gap for each of the plurality of rows of non-firing chambers, the size of each such gap corresponding substantially in size to a respective row of non-firing chambers.

16. The method according to claim 15, wherein: The first firing chamber is a member of a first group of firing chambers that is interleaved by corresponding firing chambers of a second group of one or more firing chambers, and wherein a first wall of each of the members of the first group of firing chambers is simultaneously and repeatedly actuated in the first direction and then in the second direction.

17. The method according to claim 15 or claim 16, wherein: During the actuation cycle, for each non-firing chamber, the wall is actuated such that: If the row of non-firing chambers is not a single non-firing chamber located between multiple rows of firing chambers, actuating one wall in only the first direction or in both the first direction and the second direction while the other wall remains in the neutral position; or Both walls remain in the neutral position.

18. The method according to claim 15 or claim 16, wherein: During the actuation cycle, for each non-firing chamber, the wall is actuated such that: If a single non-firing chamber is between multiple rows of firing chambers, then: actuating one wall in said first direction while a second wall is maintained in said neutral position; and then One wall is actuated in the first direction while the other wall is actuated in the second direction.

19. The method according to any one of claims 15 to 18, wherein: For a row of multiple consecutive firing chambers, the firing chambers are actuated to deposit droplets as multiple consecutive lines.

20. The method according to claim 15, wherein: A second wall of the first firing chamber is actuated in the second direction simultaneously with actuating the first wall of the first firing chamber in the first direction immediately before the moment in the actuation cycle when the first firing chamber is to eject a drop of fluid in the first firing chamber.

21. The method according to claim 15, wherein: A second wall of the first firing chamber is actuated in the second direction simultaneously with actuating the first wall of the first firing chamber in the second direction before a time in the actuation cycle when the first firing chamber is to eject a drop of fluid in the first firing chamber.

22. The method of claim 20 or claim 21, wherein: The actuation of the second wall of the first firing chamber in the second direction is performed by applying a second drive potential to the first electrode of the second wall of the first firing chamber, the second drive potential being such that a difference between the second drive potential and the common potential is smaller than a difference between the common potential and the first drive potential.

23. The method according to claims 15 to 22, wherein: The common potential is a positive potential greater than the ground potential.

24. The method according to claim 23, wherein: The first driving potential is greater than the common potential, and the second driving potential is less than the common potential.

25. The method according to claim 24, wherein: The second driving potential is a ground potential or 0V.

26. The method according to any one of claims 7 to 25, wherein: Prior to the step of designating all fluid chambers within the array as firing chambers or non-firing chambers based on the input data, the repetitively actuated wall is actuated one or more times.

27. The method according to any one of claims 7 to 26, wherein: The first wall of the or each firing chamber is actuated substantially at a resonant frequency of the firing chamber, or substantially at a harmonic or sub-harmonic of the resonant frequency of the firing chamber.

28. A method according to any one of claims 3 to 6, 9 or 10, wherein: the first firing chamber is a member of a first group of firing chambers and the second firing chamber is a member of a second group of firing chambers, wherein, during an actuation cycle, the firing chambers in the first group are actuated simultaneously to eject droplets, and The firing chambers in the second group are actuated simultaneously to eject droplets after the firing chambers in the first group.

29. A method according to any one of the preceding claims, wherein: The array of fluid chambers is a first array of fluid chambers and the droplet deposition head further comprises a second array of fluid chambers.

30. The method of claim 29, wherein: The firing chambers of the first array of fluid chambers and the second array of fluid chambers are separated by one or more non-firing chambers.

31. The method of claim 29 or claim 30, wherein: The second array of fluid chambers is arranged to be substantially a mirror image of the first array of fluid chambers.

32. The method according to claim 31, wherein: Movement of the walls of the second array of fluid chambers substantially mirrors movement of the walls of the first array of fluid chambers.

33. A method according to any one of the preceding claims, wherein: The walls are each formed of two regions of piezoelectric material of opposite polarity so as to exhibit a V-shaped pattern of deformation in response to application of the drive potential to the corresponding first electrode.

34. The method according to any one of claims 1 to 32, wherein: Each wall is formed of a piezoelectric material that is uniformly polarized in a single direction so as to exhibit shear mode deformation in response to application of the drive potential to the corresponding first electrode.

35. A method according to any one of the preceding claims, wherein: Different walls or different groups of walls can be set to different common potentials.

36. A droplet deposition head configured to perform a method according to any preceding claim.

37. A droplet deposition head according to claim 36, comprising a processor programmed to perform the specified steps based on the input data.

38. A droplet deposition apparatus comprising one or more droplet deposition heads, the droplet deposition apparatus being configured to perform the method according to any one of claims 1 to 35.

39. The droplet deposition apparatus of claim 38, further comprising a computer in data communication with the one or more droplet deposition heads, wherein: The computer is programmed to perform the specified steps based on the input data.

40. A droplet deposition apparatus according to claim 39, wherein: The computer is further programmed to send instructions to the one or more droplet deposition heads to cause the one or more droplet deposition heads to perform the actuating step.

41. A computer program comprising instructions for causing a droplet deposition head according to claim 36 or a droplet deposition apparatus according to any one of claims 37 to 40 to perform a method according to any one of claims 1 to 35.

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