Electrohydrodynamic printing head with ink pinning

Abstract

The invention relates to an electro-hydraulic power printhead comprising a nozzle carrier (6) on which a plurality of nozzles (4) are arranged. A plurality of jetting electrodes (38) are associated with the nozzles (4). The printhead further comprises at least one multi-layer structure (109) having a bottom layer (110), a top layer (112) and at least one intermediate layer (114) between the bottom layer (110) and the top layer (112). The intermediate layer (114) forms walls (116) extending between the bottom layer (110) and the top layer (112), said walls being arranged in a honeycomb pattern. A plurality of cavities (118) are located in the intermediate layer (114). It is made of a polymeric material and can have a considerable thickness.

Description

Technical Field

[0001] This invention relates to an electro-hydraulic power printhead and its manufacturing method. Background Technology

[0002] WO 2016 / 169956 describes an electro-hydraulic printhead having a nozzle carrier with multiple nozzles. It is designed to eject ink along the jetting direction. Summary of the Invention

[0003] The problem to be solved by this invention is to provide a specific type of printhead and a method for manufacturing it.

[0004] This problem is solved by the printhead of the present invention.

[0005] Therefore, a printhead may include at least the following components:

[0006] - Nozzle carrier: This is a substrate on which the nozzle is arranged.

[0007] - Multiple nozzles arranged on the carrier. The nozzles form the position for ink ejection.

[0008] - Multiple nozzle-associated ejection electrodes are located on the front side of the nozzle: the ejection electrodes are used, for example, to eject ink individually from the associated nozzle.

[0009] The printhead includes at least one multi-layer structure having a bottom layer, a top layer, and at least one intermediate layer located between the bottom layer and the top layer. The intermediate layer forms a wall extending between the bottom layer and the top layer. Multiple cavities are located in the intermediate layer between the bottom layer and the top layer.

[0010] The wall can form at least a portion of the wall of a cavity.

[0011] Advantageously, at least a portion of the cavity, particularly most of the cavity, is a closed cavity, i.e., it is closed on all sides, particularly by the walls and by the bottom and top layers. This aspect of the invention is based on the understanding that such cavities have applications beyond being pipes. In particular, they can be used to reduce mechanical stress and / or generate electric fields.

[0012] In one embodiment, the walls form a honeycomb structure, or hexagonal pattern, between the bottom and top layers. Such a structure has been found to reduce mechanical stress.

[0013] In an important aspect of the invention, at least some cavities are arranged between different electrodes of the printhead or between the electrodes of the printhead and the ink holder. In this case, "different electrodes" are advantageously electrodes that can carry different voltages during the operation of the printhead. This design improves the printhead's ability to withstand the effects of electric fields.

[0014] Advantageously, the different electrodes are separated from the cavity or cavities by one or more solid dielectric layers. These layers help prevent electrical breakdown between the electrodes.

[0015] Electrodes can be mounted on the bottom and / or top layers of a multi-layer structure, specifically one electrode mounted on the bottom layer and another electrode mounted on the top layer.

[0016] Advantageously, the electrodes are embedded in the bottom layer and / or the top layer, wherein the bottom layer and / or the top layer form a dielectric solid layer covering the electrodes from the bottom side and the top side.

[0017] The printhead may also include a guard electrode positioned horizontally behind the jet electrodes. In this case, "horizontally behind the jet electrodes" means that the guard electrode is closer to the nozzle carrier than the jet electrodes. Such guard electrodes can be used to reduce the electric field strength behind them, for example, to reduce the field at structures that hold (pin) the ink.

[0018] In this case, at a given nozzle, at least some of the cavities can be arranged between the protective electrode and the jet electrode, thereby reducing the risk of electrical breakdown between the jet electrode and the protective electrode.

[0019] The printhead may also include at least one shielding electrode arranged horizontally in front of the jet electrode. In this case, "horizontally in front of the jet electrode" means that the jet electrode is closer to the nozzle carrier than the shielding electrode. This shielding electrode can be used to control the field between the printhead and the target.

[0020] In this case, at a given nozzle, at least some cavities can be arranged between the jet electrode and the shielding electrode, thereby reducing the risk of electrical breakdown between the jet electrode and the shielding electrode.

[0021] As previously described, the printhead has a nozzle carrier on which nozzles are mounted. In one embodiment, the nozzle carrier may include the multi-layer structure (or, if multiple such multi-layer structures exist, include at least one of them).

[0022] In a favorable design, the nozzle carrier includes at least the following components:

[0023] - Front layer: The nozzle is installed on the front side of the front layer.

[0024] - The backing layer located on the back of the front layer.

[0025] Electrical vias connected to the jet electrodes can extend through the front and back layers. They supply voltage to the jet electrodes.

[0026] In addition, ink supply pipes are (at least) arranged in the front layer.

[0027] In this configuration, the front layer may include an intermediate layer (or at least one of several such multilayer structures if there are several). This allows for the formation of thick ink channels without generating excessive mechanical strain in the printhead.

[0028] The printhead may include a support structure that supports the jetting electrodes on a nozzle carrier, wherein the support structure includes a plurality of support elements arranged between the nozzles. In this case, the support structure advantageously includes at least an intermediate layer of a multi-layer structure (or at least one of such multi-layer structures if multiple such multi-layer structures exist).

[0029] In this configuration, the printhead may further include multiple ink retainers arranged between the nozzle and the support elements. The ink retainers prevent ink from reaching and wetting the support elements. Along the jetting direction, the front surface of the ink retainer is positioned horizontally behind the nozzle tip (i.e., closer to the nozzle carrier), meaning the ink retainer is positioned rearward relative to the protrusion along the jetting direction.

[0030] The method for manufacturing a printhead advantageously includes at least the following steps:

[0031] - Apply a material layer to the underlying layer: this material layer will later form at least a portion of the intermediate layer. The material may, for example, be a fully permanent photoresist such as SU8.

[0032] -Removing part of the material layer: This will keep the wall in place and create a cavity.

[0033] - Apply a top layer on top of the material layer. Attached Figure Description

[0034] The invention will be better understood when taken in conjunction with the following detailed description, and other objects besides those described above will become apparent. This description is taken with reference to the accompanying drawings, in which:

[0035] Figure 1 A partial cross-sectional view of the print head and target is shown.

[0036] Figure 2 This is a vertical sectional view of the first embodiment of the nozzle.

[0037] Figure 3 It is along Figure 2 A horizontal sectional view of line AA.

[0038] Figure 4 It is along Figure 2 The horizontal section view of the BB line.

[0039] Figure 5 It is along Figure 2 A horizontal section view of the CC line.

[0040] Figure 6 It shows that, in addition to Figure 5 In addition to the cross-shaped design, there are some alternative nozzle tip designs.

[0041] Figure 7 It is along Figure 2 A horizontal sectional view of the DD line.

[0042] Figure 8 It is along Figure 2 A horizontal section view of the EE line.

[0043] Figure 9 This is a vertical sectional view of the second embodiment of the nozzle.

[0044] Figure 10 It is along Figure 9 A horizontal sectional view of line AA.

[0045] Figure 11 This is a vertical sectional view of the third embodiment of the nozzle.

[0046] Figure 12 This is a vertical sectional view of the fourth embodiment of the nozzle, which basically corresponds to the first embodiment, but illustrates the design of the nozzle support.

[0047] Figure 13 It is along Figure 12 A horizontal sectional view of line AA.

[0048] Figure 14 It is along Figure 12 The horizontal section view of the BB line.

[0049] Figure 15 It is along Figure 12 A horizontal section view of the CC line.

[0050] Figure 16 It is along Figure 12 A horizontal sectional view of the DD line.

[0051] Figure 17 This is a vertical sectional view illustrating two possible via designs for electrode wiring.

[0052] Figure 18 A multi-layered honeycomb structure is shown.

[0053] Figure 19 The design of the wall of the insertion layer is shown.

[0054] Figure 20 A vertical cross-sectional view of the electrode is shown, illustrating an embodiment with a dielectric layer surrounding the electrode.

[0055] Figure 21This is a vertical cross-sectional view of an embodiment without an ink holder.

[0056] Note: Although Figure 1 In the figure, the jetting direction X points downwards, and when the target is below the printhead, the jetting direction X in all other figures showing a vertical sectional view points upwards. Figure 1 Rotate 180° relative to all other cross-sectional views shown parallel to the jetting direction. The orientation in these figures is based on how the manufacturing process progresses, i.e., the lower layers are manufactured before the top layers. Detailed Implementation

[0057] definition

[0058] "Forward" defines the direction in which the printhead ejects ink. For example, the ejection electrode moves forward from the nozzle.

[0059] "Backward" defines the opposite direction. For example, the nozzle is arranged backward from the injection electrode.

[0060] "In front" and "behind" are understood to indicate a position forward or backward from other objects.

[0061] "Front" and "back" refer to the sides facing forward and backward, respectively.

[0062] The characteristic “at a given nozzle” is advantageously understood to be true for most nozzles, particularly at least 90% of nozzles. For example, if it is said that “at a given nozzle, the protective electrode is arranged between the ejection electrode and the ink holder,” this advantageously means that this is true for most nozzles, particularly for at least 90% of nozzles. For example, there may be some nozzles that do not have an ejection electrode and / or a protective electrode, such as nozzles at the edge of the printhead and / or unused nozzles.

[0063] The printhead's ejection direction X defines the "vertical" upward direction; that is, by definition, the printhead is designed to eject ink upwards. (Of course, in operation, it may be at any angle to the direction of gravity.) Therefore, definitions such as "above" and "below" should be understood in conjunction with the definition of "vertical."

[0064] "Horizontal" refers to any direction that is perpendicular to the vertical direction.

[0065] "Horizontal" refers to objects that are horizontally aligned with other objects.

[0066] Print head

[0067] Figure 1 A schematic cross-sectional view of one embodiment of printhead 1 is shown. It is shown above target 2 and is configured to spray ink onto the target along the jetting direction X.

[0068] The printhead includes multiple nozzles 4 located on the front side of the nozzle carrier 6. The nozzles 4 can be arranged in a one-dimensional or two-dimensional array.

[0069] The printhead has multiple ejection electrodes for ejecting ink from nozzle 4. Figure 1 (Not shown in the image) and optional other electrodes arranged on the support structure 8, the design of which is described in more detail below. Additional electrodes that are in electrical contact with the ink can be provided to set the ink to a defined potential.

[0070] The nozzle carrier 6 includes a front layer 10, wherein the nozzle 4 is mounted to the front side of the front layer 10 and forms a protrusion thereon. It also includes a backing layer 12 located on the back side of the front layer 10.

[0071] The internal structure of the front layer 10 was not in Figure 1 As shown below, it can be, for example, a dielectric, and in particular a polymer.

[0072] The backing layer 12 may be, for example, an insulating semiconductor material, or it may be a dielectric. Advantageously, the backing layer 12 is at least partially made of glass.

[0073] Electrical vias 14 are connected to the jet electrode and extend through the front layer 10 and the backing layer 12 for connecting the jet electrode to the voltage source 17. Advantageously, each nozzle 4 has at least one via 14. Additional vias may be provided to connect other electrodes to the voltage source 17.

[0074] Ink conduits 15 and 16 supply ink to nozzle 4 and (optionally) recirculate ink from nozzle 4 back. They are partially located in the front layer 10 and extend through the peripheral area of ​​the backing layer 12. Their design will be described in more detail below.

[0075] Figure 1 An embodiment of a printhead is shown, which has an ink supply channel 15 and a suction channel 16.

[0076] At least one pump 18 and / or another pressure or vacuum source is provided to supply ink to supply conduit 15, and ink is retrieved from suction conduit 16 if a suction conduit is present.

[0077] Advantageously, the printhead includes a first pressure controller 20 for generating a first defined pressure p1 at the input of the supply line 15, for example in the reservoir 22.

[0078] The ink is supplied to the nozzle 4 through an optional filter 24 and a supply pipe 15.

[0079] If suction pipes 16 are present, they are connected to a suction system, which may include a second pressure controller 26 for generating a second defined pressure p2 at the outlet of the suction pipes 16, for example, in the suction tank 28. The suction system may also include a pump. This may in particular be a pump 18 as described above, in which case pump 18 acts as a circulation pump.

[0080] Suitable pump designs are shown, for example, in US 6631983.

[0081] like Figure 1 As further shown, the printhead may include a circuit carrier 30, such as a PCB, disposed on the back side of the nozzle carrier 6.

[0082] An optional interposer layer 32 can be disposed between the circuit carrier 30 and the nozzle carrier 6 to match the higher density resolution of the vias 14 with the circuit resolution of the circuit carrier 30. Such an interposer layer is used, for example, in flip-chip designs where semiconductor chips are applied to a PCB.

[0083] The circuit carrier 30 carries the control circuit 33, which may, for example, implement at least a portion of the voltage source 17, such as a driver stage of the voltage source that connects the voltage source to the various electrodes of the printhead.

[0084] In the illustrated embodiment, ink conduits 15, 16 extend through the insert layer 32 (if present) and the circuit carrier 30.

[0085] If the vias 14 have a sufficiently large mutual spacing (e.g., greater than 0.4 mm), they can directly interface with the circuit carrier 30 without the insertion layer 32.

[0086] Advantageously, the target 2 is arranged on an accelerating electrode connected to a voltage source 17 to generate an accelerating electric field between the printhead 1 and the target 2.

[0087] Pressure controllers 20 and 26 can be used to maintain pressure, as described in the section on operating the printhead below. Advantageously, they allow for adjustment of the pressure in the supply line 15 and the pressure line 16, respectively.

[0088] Nozzle Design 1

[0089] Figures 2 to 8 A first embodiment of nozzle 4 and surrounding elements is shown. (As described above, with...) Figure 1 on the contrary, Figure 2 The jet direction X points upwards.

[0090] from Figure 2As can be seen, nozzle 4 forms a protrusion on the front side 36 of nozzle carrier 6, for example, on the front side of its front layer 10. It is located at the outlet channel 5, through which ink can be sprayed toward target 2.

[0091] Figure 2 Various electrodes that may be associated with nozzle 4 are also shown.

[0092] The injection electrode 38 is located on the front side of the nozzle 4. Figure 2 and Figure 7 In this embodiment, it is annular with a central opening 39 for ink to pass through. It is connected to one of the through-holes 14, which extends through the support structure 8 and the nozzle carrier 6.

[0093] Figure 3 and Figure 4 Two possible implementations of the via 14 are shown. On the right, under reference numeral 14, a hollow embodiment is shown, wherein the via is formed as a metallic coating 14a within a dielectric tube 14b, which extends along the jetting direction and surrounds a central conduit 14c, which can also serve as a ventilation conduit for supplying gas to / from the area between the printhead and the target. This type of structure can be formed, for example, by:

[0094] a) Forming tube 14b together with the honeycomb structure described below, and

[0095] b) For example, a metal coating 14a is formed inside the tube 14b by sputtering.

[0096] An alternative design shown by reference numeral 14' includes a solid metal core 14'a within the dielectric tube 14'. The tube 14'b can again be formed together with the honeycomb structure, as described below, and the metal core 14'a can be formed, for example, by electroplating.

[0097] The alternative via design 14, 14' is also like Figure 17 As shown. The hollow via design 14 is used to connect the shielding electrode 40, while the filled via design 14' is used for the jet electrode 38 (in... Figure 17 (Not visible in the text). Note: In Figure 17 In the diagram, only the metal parts are shown as shaded areas, while other cross-sectional parts are not shown as shaded areas.

[0098] Typically, a single printhead will use only one via design. Figure 3 , 4 The two different types shown in 17 are for illustrative purposes only.

[0099] Go to Figure 2 and Figure 8The shielding electrode 40 can be located in front of the jet electrode 38 and at a certain distance from the jet electrode 38, that is, the jet electrode 38 is closer to the nozzle carrier 6 than the shielding electrode 40. Advantageously, there is a continuous shielding electrode 40 extending in front of the printhead 1, but there can also be several such shielding electrodes.

[0100] If several shielded electrodes are used, they can be applied to different potentials, for example, by applying a voltage gradient through a voltage divider, which, for example, allows the ink to be gradually deflected across the cross-section of the printhead.

[0101] A shielding electrode 40 is provided to control the field between the printhead 1 and the target 2. For each nozzle 4, an opening 41 in the shielding electrode 40 allows ink to pass through.

[0102] like Figure 2 and Figure 5 As shown, the protective electrode 42 can be located behind the injection electrode 38 and at a certain distance from it, but in front of the nozzle carrier 6 and at a certain distance from it. Figure 2 and Figure 5 As shown, it can also be ring-shaped. Alternatively, it can extend above several nozzles.

[0103] The opening 43 in the protective electrode 42 above the nozzle 4 allows ink to pass through.

[0104] The function of the protective electrode 42 is described below.

[0105] The nozzle 4 in this embodiment includes a tip 46, a shaft 48, and bases 50 and 52. The tip 46 is arranged in front of the shaft 48, and the bases 50 and 52 are located in front of the shaft 48. Figure 2 , 3 It is arranged behind the shaft 48.

[0106] The nozzle design shown relies on ink that wets the side surface of the nozzle 4 and does not pass through the central channel of the nozzle 4 (e.g., known from WO 2016 / 169956), but the latter can also be used.

[0107] If nozzle 4 has a central channel, for example, if outlet pipe 60 extends all the way to the tip of the nozzle, nozzle 4 advantageously remains operational, such that ink wets not only the top of the nozzle but also the lateral outer side of the nozzle. By ensuring that ink covers the outside of all nozzles, all nozzles provide the same ink geometry to the jetting electrode, which allows for more uniform ink jetting throughout the printhead.

[0108] To facilitate the efficient flow of ink along the spray direction X of the nozzle 4, the nozzle 4 advantageously has at least one groove extending along the spray direction X on its side surface, i.e., on the surface extending along the spray direction X. The groove extends along at least a portion of the length of the nozzle 4.

[0109] For example, this can be done Figure 5 As can be seen, the tip 46 is shown in a cross shape (with four recesses 46a formed between the arms of the cross shape), and the axial portion 48 forms two grooves 48a.

[0110] Figure 6 An alternative design for the tip 46 is shown:

[0111] (a) The tip 46 has a raised side surface and is, for example, a cylinder without grooves - this is currently the preferred design because it produces a good meniscus for ejecting ink from it;

[0112] (b) The tip 46 forms two transverse grooves 46a;

[0113] (c) An axial channel 46c is formed at the tip.

[0114] The bases 50 and 52 connect the tip 46 and the shaft 48 to the nozzle carrier 6. It also includes conduits for supplying ink to the nozzle. This is... Figure 2 , Figure 3 and Figure 4 The most obvious example is in the middle.

[0115] Specifically, in the illustrated embodiment, the bases 50, 52 include a bottom sublayer 52 and a top sublayer 50. The bottom sublayer 52 has a central opening 54 that communicates with the end of a supply fixing portion 15a, which supplies ink to the nozzle 4. One or more radially transverse outlet channels 56 extend transversely to the jetting direction X from the central opening 54 outwards to a first annular channel 58.

[0116] exist Figure 2 In the diagram, the flow of ink in the pipe is indicated by arrows.

[0117] The top sublayer 50 may also form an axial outlet conduit 60 that extends toward the tip of the nozzle and connects the supply conduit portion 15a to the groove 48a of the shaft portion 48. Figure 5 This guides the ink directly upwards to the tip 46.

[0118] The top sublayer 50 may be surrounded by a second annular conduit 62 aligned with the first annular conduit 58 surrounding the nozzle 4.

[0119] The nozzle 4 is surrounded by an ink holder 66, the purpose of which is to hold the ink laterally. An annular conduit 62 is located radially between the ink holder 66 and the nozzle 4, thereby communicating with the region 64 between the nozzle 4 and the ink holder 66.

[0120] The front surface 68 of the ink holder 66 (i.e., the forward-facing surface closest to the ejection electrode 38) is positioned rearward relative to the front end 70 of the nozzle 4 along the ejection direction X. Therefore, when ink is present in region 64, the surface of the ink forms an upward slope toward the tip of the nozzle 4, as shown by the dashed line, ensuring that the tip is the position where the ink is closest to the ejection electrode 38, thereby forming a defined point for ejecting ink.

[0121] The main function of the ink holder 66 is to pin the ink, that is, to keep the ink away from the vertical part of the support structure 8, that is, to prevent the ink from climbing up and forming a pool that may flood the nozzle.

[0122] This functionality is achieved through a combination of one or more of the following features:

[0123] a) The ink retainer 66 has a hydrophobic and / or oleophobic surface, for example, by means of a hydrophobic and / or oleophobic coating 73, in Figure 2 The surface has thick black lines. For example, the surface may be formed at least partially of hydrophobic and oleophobic Teflon and / or PTFE. Depending on the range of inks used, it may also be purely hydrophobic (e.g., HMDS, i.e., bis(trimethylsilyl)amine) or purely oleophobic (e.g., polymer-based). In particular, the surface of ink 66 is advantageously more hydrophobic and / or oleophobic than the surface of nozzle 4.

[0124] b) The ink retainer 66 forms a protrusion 66a that is far from the nozzle 4 closest to it, which makes it difficult for ink to creep around it. In other words, when viewed from the nozzle, the protrusion extends outward to form an “undercut” 66b.

[0125] c) The ink holder 66 is located in a region of low electric field. Since a strong electric field tends to reduce the surface tension of the ink, this design reduces the risk of ink wetting its pathway around the ink holder. In the illustrated embodiment, a protective electrode 42 associated with the nozzle 4 is arranged between the jet electrode 38 and the ink holder 66. Herein, "between" advantageously means that the protective electrode 42 intersects with and advantageously divides the space between the jet electrode 38 and the ink holder 66.

[0126] It is important to note that the ink retainer 66 is not the only device used to laterally retain ink, i.e., to prevent ink from reaching the nearest support element. Alternatively or in addition, the ink suction channel 16 can be used to remove any ink that may reach the support element. This is described in more detail in the section on operating the printhead.

[0127] The protective electrode 42 is connected to the voltage source 17, for example, through a via 14' or 14, and during operation, the potential of the protective electrode 42 can be set closer to the potential of the ink holder 66 (i.e., the ink) than the (maximum) potential of the jet electrode. Specifically, the voltage source 17 can be adapted to maintain the protective electrode 42 at the same potential as the ink holder 66. This allows the electric field at the ink holder 66 to be kept very low.

[0128] like Figure 2 As shown, the protective electrode 42 is advantageously positioned at the same "height" (in the vertical direction defined by the jetting direction X) as the tip 70 of the nozzle 4, for example, within 25% accuracy of the vertical distance d between the jetting electrode 38 and the tip 70 of the nozzle 4. This provides good shielding against ink below the tip of the nozzle 4 while still strongly exposing the tip to the field of the jetting electrode 38.

[0129] like Figure 2 As shown, an air-filled cavity 71 is formed in the gap between the protective electrode 42 and the ink holder 66 to prevent ink from reaching the protective electrode 42.

[0130] To retain the ink laterally within region 64, an ink retainer 66 is advantageously positioned on and protrudes from the front side 36 of the nozzle carrier 6. Figure 2-4 In one embodiment, it includes a first ring 72 mounted on the front surface 36 of the nozzle carrier 6 and a second ring 74 mounted on the front side of the first ring 72. The second ring 74 forms the aforementioned protrusion 66a.

[0131] Ink suction

[0132] As mentioned above, in Figure 1 and Figure 2 In one embodiment, a suction conduit 16 is provided to recover ink from the nozzle 4. This allows for the maintenance of a flow of fresh ink at a given nozzle.

[0133] In this configuration, at a given nozzle, the nearest ink holder 66 advantageously surrounds not only the nozzle 4 and the end 15a of the supply conduit, but also the end 16a of the suction conduit 16. Therefore, both conduits can be used to control the flow of ink to and from the nozzle.

[0134] Adjust the pressure at the supply pipe 15 and the suction pipe 16 to hold the ink in region 64 in a certain position, for example, as... Figure 2 As shown, it lies between the upper horizontal plane 64a and the lower horizontal plane 64b. Advantageously, as described in more detail in the "Operating the Printhead" section below, the ink is maintained at the lower level 64b.

[0135] To provide good lateral confinement of the ink, each nozzle 4 is advantageously surrounded by the opening of one or more suction channels. For example, this could be a single annular opening (e.g., by...). Figure 2 (Formed by an annular opening 62), or possibly a series of annular suction openings. This opening or these openings are arranged between the nozzle and the adjacent support element 78.

[0136] Support structure

[0137] As described above, a support structure 8 is provided for connecting the electrodes 38, 40, 42 to the nozzle carrier 6. It is disposed on the front side 36 of the nozzle carrier 6.

[0138] The support structure 8 includes multiple support elements 76, 78 arranged between the nozzles 4.

[0139] The ink retainer 66 is advantageously designed to prevent ink from reaching these support elements 76, 78 and to prevent ink from wetting them, thereby reducing the tendency of ink to immerse the nozzle.

[0140] The support structure 8 advantageously includes at least one electrode carrier layer. Figure 2 In one embodiment, there are three such layers 80, 82, and 84. Each such electrode carrier layer includes at least one electrode 38, 40, or 42 and may extend parallel to the top surface 36.

[0141] Typically, electrodes 38, 40, and 42 are embedded within their electrode carrier layers 80, 82, and 84, and are covered on their front and back sides by at least one dielectric sublayer 80a, 80b, 82a, 82b, or 84a, 84b.

[0142] At least a portion of the support element is formed by vertical walls 76 that form a honeycomb structure, see Figure 3 Each of these honeycomb structures is part of a multilayer structure used in various parts of the printhead, and will be described in more detail below.

[0143] In addition to or alternatively to the walls 76 forming the honeycomb structure, in the illustrated embodiment, the support element includes a vertical wall 78 surrounding the outlet channel 5 of each nozzle 4. The wall 78 can be, for example, a cylindrical wall, but it can also be, for example, a polygonal wall. It is advantageously centered on the nozzle 4.

[0144] In another embodiment, wall 78 can be omitted, and the wall surrounding outlet channel 5 can be formed by a honeycomb structure wall 76. In this case, the honeycomb structure needs to be aligned with the nozzle.

[0145] In yet another embodiment, several nozzles may be surrounded by a single wall 78.

[0146] In the embodiment shown here, support elements 76 and / or 78 are disposed between each of the electrode carrier layers 80, 82, 84 and between the last electrode carrier layer 80a and the nozzle carrier 6. However, they may also be provided only between subsets of these structures.

[0147] from Figure 2 As can be clearly seen, there is a first recess between the nozzle 4 and its ink holder 66, which is formed by annular first and second annular channels 58, 62. It provides a volume to accommodate at least a portion of the ink pool 64. Along the jetting direction X, the bottom of the first recess 58, 62 is located behind the front surface 68 of the ink holder 66 (i.e., closer to the nozzle carrier 6 than the front surface 68).

[0148] In the illustrated embodiment, the second recess 86 is located between the ink holder 66 and the nearest support element 78. It provides space for the protrusion 66a and / or makes it more difficult for ink to reach the support element 78. Along the jetting direction X, the bottom of the recess 86 is located rearward relative to the front surface 68 of the ink holder 66 (i.e., closer to the nozzle carrier 6 than the front surface 68).

[0149] Nozzle Design 2

[0150] Figure 9 and Figure 10 A second embodiment of the nozzle design is shown. Its main difference from the first embodiment is that it has only one ink supply conduit 15 (its end 15a is as shown in the diagram). Figure 10 (as shown), but there is no suction pipe for the nozzle.

[0151] Furthermore, there is no recess between the nozzle 4 and the ink holder 66. In addition, the ink holder 66 is arranged laterally on the nozzle 4, and its front surface 68 is spaced apart from the tip (point) 70 of the nozzle 4.

[0152] In other words, its front surface 68 is positioned rearward relative to the front end 70 of the nozzle 4 to form an upward slope of ink in region 64 and reduce the risk of immersion in the nozzle.

[0153] Advantageously, the ink retainer 66 is mounted "low" on the nozzle 4 to minimize the possibility of nozzle immersion. In particular, the front surface 68 of the ink retainer 66 is closer to the front dimension 36 of the nozzle carrier 6 than the front end 70 of the nozzle 4.

[0154] As can be seen, in this embodiment, the ink holder 66 is formed by a sublayer 52 of the base of the nozzle 4.

[0155] Nozzle Design 3

[0156] Figure 11A third embodiment of the nozzle design is shown. Its main difference from the second embodiment is that it lacks a protective electrode. To maintain a low electric field at the location of the ink holder 66, the ink holder 66 is located further back.

[0157] In particular, such as Figure 11 As shown, the distance d' between the front surface 68 of the ink holder 66 and the front end 70 of the nozzle 4 along the spraying direction X is relatively large.

[0158] Quantitatively, if d represents the distance along the injection direction X between the injection electrode 38 and the front end 70 of the nozzle 4, then the following condition is advantageously maintained:

[0159] d'>k·d

[0160] Where k is at least 0.5, and in particular at least 1.0.

[0161] Ink Holder-Free Nozzle Design

[0162] In the embodiments shown so far, the nozzle 4 is surrounded by an ink retainer 66 that protrudes upward from the top surface 36 of the nozzle carrier 6. However, this ink retainer can be omitted by using ink suction. This is as follows Figure 21 As shown, Figure 21 It shows a basic similarity to Figure 2 The embodiments in the text correspond to embodiments without ink retainers. Therefore, forming Figure 2 In the embodiments, the base layers 50 and 52 can be omitted.

[0163] In this embodiment, the ink is held around the nozzle 4 by being drawn into the end 16a of the ink suction conduit 16 surrounding the nozzle.

[0164] In one embodiment, a single annular (or, for example, hexagonal or other closed-loop) end 16a of the suction conduit 16 may be arranged around the nozzle 4.

[0165] In another embodiment, a plurality of individual ends 16a may be provided, which are closely spaced and arranged around the nozzle 4, for example, along a ring or another closed ring.

[0166] In this embodiment, the protective electrode 42 may still be useful because it reduces the tendency for ink to spread along the surface 36 of the nozzle carrier 6.

[0167] In the illustrated embodiment, the outlet conduit 60 extends all the way to the top 70 of the nozzle. Therefore, ink flows axially through the nozzle. Advantageously, the pressure in the outlet conduit 60 is selected such that the ink overflows the nozzle and flows downwards along its transverse sidewalls. From there, it reaches the end 16a of the suction conduit 16 and is carried away. This provides continuous ink exchange within the nozzle.

[0168] In another embodiment, the ink can be applied along the outer surface of the nozzle, for example... Figure 2-5 In the embodiment shown, the ink is guided upward in the groove, and the ink can be drawn away from the end 16a, for example, through an axial opening in the nozzle.

[0169] However, alternatively, this part can also be designed in conjunction with, for example, a simple ink holder 66 (as shown in dashed lines) surrounding the end 16a of the suction pipe 16.

[0170] Nozzle carrier

[0171] Figure 12-16 Possible designs for nozzle carrier 6 are shown. It should be noted that, compared to... Figure 12 compared to, Figure 13-15 The scale has been reduced to show how adjacent nozzles are interconnected via supply and suction lines. Figure 16 The scale is reduced even further, showing the entire cross-section of the printhead at the level of backing layer 12.

[0172] These figures show Figure 2 The nozzle, but similar nozzle carriers can be used for different nozzle designs, such as Figure 9 and Figure 11 The design.

[0173] As described above, the nozzle carrier 6 includes a front layer 10 and a backing layer 12 located behind the front layer 10, wherein the nozzle 4 is mounted to its front side 36. The front layer 10 and the backing layer 12 can also be a multi-layer structure.

[0174] They will be described in more detail below.

[0175] The front layer 10 consists of several sublayers 10a-10d and forms at least a portion of conduits 15, 16 for supplying ink to the nozzle and, where applicable, for supplying ink from the nozzle.

[0176] exist Figure 12 In one embodiment, the front layer 10 includes sublayers 10a, 10b, 10c, and 10d for forming pipes in a front-to-back order.

[0177] Sublayer 10a forms front surface 10a and includes openings 15a, 16a for supply conduit and (if necessary) suction conduit, respectively.

[0178] Sublayer 10b forms (if necessary) the horizontal portion 16b of the suction pipe and the vertical portion 15b of the supply pipe.

[0179] like Figure 13As shown, the horizontal portion 16b of the suction conduit interconnects all or at least a plurality of nozzles 4. Furthermore, between the conduits, the sublayer 10b includes vertical walls 90 forming a honeycomb pattern similar to that in the support structure 8. The honeycomb patterned areas can be separated from the conduits 16b and / or 15b by vertical partition walls 92.

[0180] Figure 13 The vias 14, 14' extending along the injection direction X through the entire front layer 10 are also shown.

[0181] The vertical portion 15b of the supply pipe connects to the vertical portion 15c of the supply pipe in sublayer 10c, see... Figure 14 .

[0182] like Figure 15 As shown, sublayer 10d forms the horizontal portion 15d of the supply pipe, interconnecting adjacent nozzles.

[0183] Similarly, sublayer 10d may include vertical walls 94 forming a honeycomb pattern similar to that in support structure 8. The honeycomb patterned area may be separated from conduit 10d by vertical partition walls 96.

[0184] Figure 15 The vias 14, 14' extending along the injection direction X through the entire front layer 10 are also shown.

[0185] Figure 16 The possible arrangement of the electrical vias 14 (and 14'), supply conduit 15, and suction conduit 16 at the level of the backing layer 12 is shown. Since the horizontal distribution of the ink conduits 14, 16 is achieved in the front layer 10 above the backing layer 12, ink can be supplied through one or more potentially large ink conduits arranged outside the bulges 96 of the regular array of electrical vias 14. This simplifies the design of the backing layer 12, as no ink conduits extend through the bulges 96 within the backing layer 12.

[0186] Instead of using a honeycomb structure in sublayers 10b and / or 10d, a solid layer such as glass can be used.

[0187] Honeycomb multi-layer structure

[0188] As described above, the printhead shown here advantageously utilizes one or more honeycomb multilayer structures. One such multilayer structure 109 is as follows: Figure 18 , 19 As shown. It has a bottom layer 110, a top layer 112, and at least one intermediate layer 114 located between the bottom layer 110 and the top layer 112. The intermediate layer 114 forms walls 116 extending between the bottom layer 110 and the top layer 112. These walls form at least a portion of the walls of a plurality of cavities 118 in the intermediate layer 114 between the bottom layer 110 and the top layer 112.

[0189] Wall 114 forms a honeycomb pattern in an advantageous manner.

[0190] It has been found that such a structure can reduce mechanical stress, especially if the bottom or top layer 110, 112 is made of a different material than the intermediate layer 114 and / or if it is close to or adjacent to another layer made of a different material than the intermediate layer 114.

[0191] An example of this honeycomb multilayer structure from the above examples is as follows:

[0192] -exist Figure 2 , Figure 11 , Figure 12 In the middle: the front layer 10 or sub-layer 10a is the "bottom layer" 110, the layer 80 of the supporting structure 8 is the "top layer" 112, and the wall 76 between them forms the "intermediate layer" 114.

[0193] -exist Figure 2 , Figure 11 , Figure 12 In the middle: layer 80 of the supporting structure is the "bottom layer" 110, layer 82 of the supporting structure 8 is the "top layer" 112, and the wall 76 between them forms the "intermediate layer" 114.

[0194] -exist Figure 2 , Figure 11 , Figure 12 In the middle: layer 82 of the supporting structure is the "bottom layer" 110, layer 84 of the supporting structure 8 is the "top layer" 102, and the wall 76 between them forms the "intermediate layer" 114.

[0195] -exist Figure 12 , 13 In the middle: sublayer 10c is the "bottom layer" 110, sublayer 10a is the "top layer" 112, and the wall 90 of sublayer 10b between them forms the "intermediate layer" 114.

[0196] -exist Figure 12 , 15 In the middle: the backing layer 12 is the "bottom layer" 110, the sub-layer 10c is the "top layer" 112, and the wall 94 of the sub-layer 10d between them forms the "intermediate layer" 114.

[0197] In the first three examples, the support structure 8 includes at least a multi-layered intermediate layer 114.

[0198] In the last two examples, the nozzle carrier 6 includes at least a multi-layered intermediate layer 114.

[0199] If the thickness t of the intermediate layer 114 (see...) Figure 18 When the thickness t is relatively large, the stress reduction achieved by the multilayer structure is particularly significant. Advantageously, the thickness t is greater than 1 μm, especially greater than 10 μm.

[0200] Advantageously, the intermediate layer 114 is a polymer layer, for example formed from a structured SU-8 layer. This type of layer can be easily manufactured and structured (see manufacturing information below), and if used in a multilayer structure as shown, it reduces stress compared to solid layers of this material.

[0201] Therefore, advantageously, the printhead includes at least one layer of material different from the insertion layer, particularly a semiconductor or glass layer.

[0202] Cavities 118 are advantageously closed cavities, i.e., they do not constitute... Figure 15 and Figure 13 Part of the ink pipe section 15b or 16d is also not connected to the surrounding atmosphere.

[0203] If the wall 116 forms a regular, repeating pattern, the uniformity is improved and the stress can be further reduced.

[0204] Advantageously, the thickness m of wall 116 is less than 25% of the minimum diameter m of the cavity (see...). Figure 19 This results in a low content of solid material in the insert layer, thereby further reducing mechanical stress. In this case, the thickness m is the extension of wall 116 perpendicular to its surface. The diameter M of the cavity is the extension of cavity 118 in a direction parallel to the bottom layer 110 and the top layer 114.

[0205] To best remove strain, the minimum diameter M of cavity 118 is advantageously larger than the thickness t of intermediate layer 114, i.e., M > t. A smaller cavity extending through intermediate layer 114 would generate higher mechanical stress in the insert layer.

[0206] Wall 116 extends advantageously perpendicular to the bottom layer 110 and the top layer 112. This not only improves mechanical stability against forces perpendicular to the layers, but also allows for the formation of the wall using isotropic material removal techniques, particularly photolithography of photoactive polymers.

[0207] It is important to note that the top and bottom layers of a multi-layered structure are parallel to each other.

[0208] The enclosed cavities 118 are not connected to ink ducts, meaning they are not used to guide ink through the printhead. If the printhead has ventilation ducts, the enclosed cavities 118 are also not connected to these ventilation ducts.

[0209] The enclosed cavities 118 may be filled with air. Alternatively, they may be evacuated. Or they may be filled with a gas such as nitrogen. Advantageously, they may be filled with a gas with a high breakdown voltage, such as SF6 or C4F8. The gas may be introduced by performing appropriate manufacturing steps (see below) in a workspace with the desired gas composition.

[0210] Electrode design

[0211] The printhead is designed to withstand the high electric fields that occur during operation and to minimize structural damage.

[0212] For this purpose, electrodes 38, 40, and 42 are arranged between solid dielectric layers 80a, 80b, 82a, 82b, 84a, and 84b that define cavities. In the illustrated embodiment, such cavities are formed, for example, by cavities 71, 71', and 71" beneath the electrode carrier layers 80, 82, and 84 and / or by cavity 118 formed by wall 116.

[0213] At least some of the cavities may be closed cavities (i.e., closed by walls on all sides, such as cavity 118).

[0214] At least some cavities may be open cavities, especially those that communicate with and are adjacent to the outlet channel 5 of the nozzle 4, such as cavities 71, 71', and 71" in the above embodiment.

[0215] In this design, the solid dielectric layer surrounding the electrodes can typically withstand higher electric fields than the gas in the cavity and also has a higher relative permittivity ε, thus preventing complete breakdown. Simultaneously, since there is no fixed molecular or atomic structure within the cavity, it is less susceptible to permanent damage from large electric fields. Therefore, this design improves the printhead's ability to withstand the effects of electrode electric fields even during prolonged operation.

[0216] As can be seen from the embodiments shown here, there are vertically extending solid support structures between adjacent electrode carrier layers 80, 82, 84, for example, between walls 76 and 78. However, advantageously, there is no such solid support structure extending directly between adjacent electrodes. In other words, any straight extension between two adjacent electrodes passes through at least one of cavities 71, 71', 71" or 118. This condition should be satisfied if some, or particularly all, of the adjacent electrodes of the printhead have substantially different potentials during operation, particularly voltages differing by at least 100V.

[0217] This condition can be achieved by not placing a vertically extending solid support structure between the electrodes and / or by partially removing portions of the support structure, for example in Figure 7 The position of contact lead 38b in the middle.

[0218] In yet another embodiment, the electric field strength can be reduced by designing the traces to be very narrow where no cavity is provided between the electrodes. In this case, the width of the traces advantageously does not exceed half the height of the wall structures 76, 78. For example, if the height of the wall structure is 5 μm, the width of the traces should not exceed 2.5 μm.

[0219] Advantageously, for at least one of two adjacent electrodes, the lateral offset between the electrode and the next (i.e., the nearest) support structure should be at least 25% of the vertical distance between the two adjacent electrodes.

[0220] Advantageously, at least one of the dielectric layers of the protective electrode has a high relative permittivity ε. Therefore, the electric field therein is weak, and the main voltage drop is transferred to the layers with lower permittivity, particularly the cavity. This allows for better protection of the structure from electrical breakdown.

[0221] In this case, a high relative permittivity ε is advantageously at least 5. Suitable materials are, for example, Si3N4 (with a relative permittivity ε between 9.5 and 10.5) or Al2O3 (with ε between 9.3 and 11.5).

[0222] Advantages, such as Figure 20 As shown, several dielectric layers are provided between the cavity 120 and the electrode 122. For example, Figure 20 Cavity 120 in the above example represents cavity 118 or 71, 71', 71" in the above example. Electrode 122 represents one of electrodes 38, 40, 42 in the above example, especially jet electrode 38.

[0223] In the illustrated embodiment, electrode 122 is surrounded by first dielectric layers 124a and 124b, which in turn are surrounded by a second dielectric layer 126.

[0224] The first dielectric layers 124a, 124b are advantageously polymer layers, for example, composed of patterned SU-8 (see manufacturing process below). Such polymer layers have a low relative permittivity, for example, between 2.5 and 3.0. They correspond to, for example, the sublayers 80a, 80b, 82a, 82b, 84a, 84b of the electrode carrier layers 80, 82, 84 described above, and can be manufactured at least partially using lamination techniques (see below).

[0225] The second dielectric layer 126 is an inorganic layer having a higher electrical breakdown threshold than the first dielectric layers 124a and 124b. It advantageously has a higher relative permittivity than the first dielectric layers 124a and 124b, particularly a factor of 2. For the reasons described above, it can be, for example, Si3N4 or Al2O3. It has the highest breakdown resistance of all components between the two electrodes, and generally prevents electrical breakdown.

[0226] The advantage of placing the first dielectric layers 124a and 124b between the electrode 122 and the second dielectric layer 126 is that, for example, the peak field intensity at the edge of the electrode 122 is within the first dielectric layer, thereby increasing the ability of the second dielectric layer 126 to prevent breakdown.

[0227] Therefore, in an advantageous embodiment, at least some of the cavities 120 are arranged between different electrodes of the printhead or between the electrodes of the printhead and the ink holder 66 of the printhead.

[0228] Advantageously, the different electrodes 38, 40, 42, 122 are separated from the cavity 120 by one or more solid dielectric layers 124a, 124b, 126.

[0229] Specifically, one or more solid dielectric layers 124a, 124b, 126 advantageously comprise polymer layers 124a, 124 and / or inorganic layer 126. Advantageously, polymer layers 124a, 124 are disposed between electrode 122 and inorganic layer 126.

[0230] Operating the print head

[0231] During operation, i.e. during printing, ink is supplied to the print head through the supply pipe 15. The ink is confined within the region 64 between the nozzle 4 and the ink holder 66.

[0232] To eject ink droplets, the voltage at the desired ejection electrode (relative to the ink voltage) is temporarily increased. For example, a voltage pulse of 400V can be generated. When not printing, the voltage at the ejection electrode remains at the level when no ink is ejected. However, advantageously, it is non-zero, for example, at 200V.

[0233] As described above, the electric field at ink holder 66 is advantageously kept at a low level, for example less than 50% of the field strength at nozzle tip 70, and particularly less than 10%. Since the high electric field strength reduces the surface tension of the ink, the process reduces the tendency of the ink to wet the ink holder and pass through it.

[0234] A suction pipe 16 (if present) is used to retrieve ink from the nozzle. Advantageously, the method for printing includes the following steps:

[0235] - Ink is supplied individually to the nozzle using the supply pipe 15 in the nozzle carrier 6, and

[0236] - Use the suction pipe 16 in the nozzle carrier 6 to draw ink separately from the nozzle.

[0237] This allows for a reservoir that retains fresh ink at the nozzle.

[0238] During operation, the pressure px at the end of the suction conduit 16 at a given nozzle is advantageously maintained to keep the ink away from the ink holder 66, for example in Figure 2At level 64b. Advantageously, px should not be too low to pre-expel air drawn into the suction pipe 16. The appropriate pressure can be calculated based on the radial width w of the annular pipe 62. For ink with w = 5 μm and the surface tension of water, the Young Laplace equation yields a pressure differential dp of 144 mbar. For liquids with the surface tension of alkane, the pressure differential dp will be 40 mbar. Therefore, by maintaining the pressure px at no greater than or below the normal pressure dp, surface 64b can be maintained and air cannot be drawn in.

[0239] If several circular openings with a diameter of, for example, 5 μm are used instead of the annular pipe 62, then dp will be twice as large.

[0240] If the difference between the ambient pressure and px is less than dp, the liquid level will rise, for example, rise to... Figure 2 Line 64a. There, the curvature is much lower than that at line 64b. If we assume, in a simplified example, that the curvature is ten times lower, the corresponding pressure difference is 14 millibars (for water). Therefore, by keeping the pressure px, for example, 50 millibars below atmospheric pressure, it is possible to prevent the ink from reaching the same level as at line 64a.

[0241] On the other hand, the pressure py at the end of the supply pipe 15 at a given nozzle can be adjusted to maintain the desired ink flow through the nozzle. Furthermore, as described above, the ink flow rate through the outlet pipes 56 and 60 can be adjusted by selecting appropriate diameters in these pipes.

[0242] In yet another embodiment, the pressure difference (below ambient pressure) in the end 16a of the suction conduit 16 can be selected to be greater than dp at the lower level 64b. Therefore, air will be drawn into the suction conduit 16.

[0243] In this case, if the ink returned through the suction pipe 16 is to be recovered, a separation device can be used to separate the ink and air before the ink is supplied to the recirculation pump 18.

[0244] manufacture

[0245] This printhead can be manufactured using techniques known from semiconductor manufacturing and packaging, such as those described in WO2013 / 000558, WO 2016 / 120381 and WO 2016 / 169956.

[0246] Advantageously, at least some layers of the printhead are polymer layers, particularly those used in the printhead. Figure 18 , 19 The intermediate layer 114 of the multi-layer structure of the type.

[0247] Advantageously, manufacturing such a multi-layered structure includes the following steps:

[0248] 1. Provide the bottom layer 110. This can be, for example, the top layer formed through previous manufacturing steps.

[0249] 2. Apply a material layer on top of the bottom layer 110. This material layer will form the intermediate layer 114.

[0250] 3. Apply top layer 112 on top of the material layer.

[0251] The material layers deposited in steps 2 and 3 can be applied using various techniques, such as lamination, spin coating, sputtering, or vapor deposition.

[0252] Lamination is particularly advantageous, especially for applying the top layer 112. In lamination, the layer is applied as a sheet and attached to the underlying structure, for example, using heat and pressure. This allows for easy crossing of cavities and / or the creation of overhanging structures.

[0253] The material layer in step 2 is advantageously a photoresist, such as SU-8, which allows for easy structuring. In this case, step 2 includes at least the following sub-steps:

[0254] 2a: Illuminated and unilluminated areas are defined in the material layer by illuminating the material layer with collimated light through a mask.

[0255] 2b: Depending on whether positive or negative photoresist is used, selectively remove the illuminated or non-illuminated areas from the material layer.

[0256] Alternatively, the top layer 112 may also be formed of a solid material, such as a glass wafer, which is bonded to the intermediate layer 114, for example, by adhesive bonding, fusion bonding, eutectic bonding, etc.

[0257] Inorganic dielectric layer 126 ( Figure 20 It can be manufactured, for example, by depositing it on polymer dielectric layers 124a and 124b using an atomic layer deposition process.

[0258] Notice

[0259] In most of the embodiments described so far, each nozzle is surrounded by an ink retainer that defines a restricted area from which ink can flow out of the nozzle.

[0260] In these examples, each nozzle is surrounded by its own ink holder. Alternatively, multiple nozzles can be surrounded by a shared ink holder, meaning one ink holder can surround multiple nozzles.

[0261] Alternatively or otherwise, each support element of support structure 8 may be surrounded by an ink retainer that defines an ink-free area around the support element, preventing ink from reaching the support element. This may be particularly advantageous if the support elements form separate, isolated pillars.

[0262] As can be seen from the above embodiments, the protective electrode 42 is advantageously located close to the axis of the nozzle. Figure 12 The example illustrates this point.

[0263] Here, the central axis 100 of the nozzle 4 is shown as a dashed line as it extends along the jetting direction X. x1 is the distance between the protective electrode 42 and the nozzle axis 100. x2 is the distance between the ink holder 66 and the nozzle axis 100. x3 is the distance between the nearest support element 78 and the nozzle axis 2, wherein the support element 78 is the support element adjacent to the nozzle carrier 6.

[0264] The following relationships are favorable:

[0265] x1 < x2, especially x1 < 0.8·x2: By placing the protective electrode 42 closer to the nozzle axis 100 than the ink holder 66, better shielding of the ink holder 66 is achieved.

[0266] x1 < x3, especially x1 < 0.8·x3, especially x1 < 0.5·x3: Similarly, the support element is also shielded by placing the nearest support element 78 further away from the axis 100 than the protection electrode 42.

[0267] Alternatively, the difference x2–x1 is advantageously at least 50% of the vertical distance d' between the protective electrode 42 and the ink holder 66.

[0268] In particular, x3 should be at least 1 μm larger than x2, and especially at least 5 μm.

[0269] Therefore, the following relationships are advantageous, whether individually or in any combination:

[0270] - The distance x1 between the protective electrode 42 and the nozzle axis 100 is less than the distance x2 between the ink holder 66 and the nozzle axis 100.

[0271] - The distance x1 between the protective electrode 42 and the nozzle axis 100 is less than the distance x3 between the axis 100 and the support element 78 adjacent to the nozzle carrier 6, which is closest to the nozzle axis 100.

[0272] The difference between -x2 and x1 (the distance x1 between the protective electrode 42 and the nozzle axis 100 and the distance x2 between the ink holder 66 and the nozzle axis 100) is at least 50% of the vertical distance between the protective electrode 42 and the ink holder 66.

[0273] - The distance x3 (between axis 100 and support element 78 adjacent to nozzle carrier 6) is at least 1 μm larger than the distance x2 between ink holder 66 and nozzle axis 100, and in particular at least 5 μm larger.

[0274] The difference between -x2 and x1 (the distance x1 between the protective electrode 42 and the nozzle axis 100 and the distance x2 between the ink holder 66 and the nozzle axis 100) is advantageously at least 50% of the vertical distance between the protective electrode 42 and the ink holder 66.

[0275] As described above, the printhead may also include gas conduits to supply gas to and / or retrieve gas from the area between the printhead and the target. These gas conduits may also include horizontal portions, such as interconnected portions, for example in the front layer 10 and / or the backing layer 12 and / or the insert layer 32, similar to... Figure 13 and 15 The ink pipe shown.

[0276] In the embodiments described so far, three electrodes of three different vertical and horizontal orientations have been mentioned: a jet electrode, a protective electrode, and a shielding electrode. However, it should be noted that other electrodes may also be present, such as:

[0277] - An electrode may be disposed in the nozzle carrier 6, for example at the supply conduit 15 and / or the suction conduit 16, and / or at the nozzle and / or ink holder, for defining the potential of the ink. Such an electrode allows, for example, the ink to be maintained at a potential similar to or the same as that of the protective electrode 42. Advantageously, such an electrode is made of platinum and / or gold.

[0278] - If different sized nozzles are present on the printhead, additional electrodes can be provided (e.g.) Figure 2 (between the jet electrode 38 and the shield electrode 40). This is particularly useful for nozzles where the distance between the jet electrode and the nozzle is significantly smaller than the distance between the shield electrode and the jet electrode.

[0279] While presently preferred embodiments of the invention have been shown and described, it should be clearly understood that the invention is not limited thereto, but may be implemented and practiced in other ways within the scope of the following claims.

Claims

1. An electro-hydraulic printhead, comprising: Nozzle carrier (6). Multiple nozzles (4) are arranged on the nozzle carrier (6). Multiple injection electrodes (38) are associated with the nozzle (4) and located on the front side of the nozzle (4). The printhead includes at least one multilayer structure (109) having a bottom layer (110), a top layer (112) and at least one intermediate layer (114) between the bottom layer (110) and the top layer (112), wherein the at least one intermediate layer (114) forms a wall (116) extending between the bottom layer and the top layer (112). Multiple cavities (118, 120) are located in the intermediate layer (114) between the bottom layer (110) and the top layer (112), and in, At least a portion of the cavity (118) is a closed cavity.

2. The printhead according to claim 1, wherein, At least a portion of the cavity (118) forms a repeating regular pattern.

3. The printhead according to claim 1 or 2, wherein, The wall (116) forms a honeycomb structure between the bottom layer (110) and the top layer (112).

4. The printhead according to claim 1 or 2, wherein, The thickness (m) of the wall (116) is less than 25% of the minimum diameter (M) of the cavity (118).

5. The printhead according to claim 1 or 2, wherein, The minimum diameter (M) of the cavity (118) is greater than the thickness (t) of the intermediate layer (114).

6. The printhead according to claim 1 or 2, wherein, The wall (116) extends perpendicular to the bottom layer (110) and the top layer (112).

7. The printhead according to claim 1 or 2, wherein, At least some of the cavities (71, 71', 71'', 120) are in communication with and adjacent to the outlet channel (5) located at the nozzle (4).

8. The printhead according to claim 1, wherein, At least some of the cavities (71) are arranged between the different electrodes (38, 40, 42, 122) of the printhead.

9. The printhead according to claim 1, wherein, At least some of the cavities (71', 71'') are disposed between the electrodes (38, 42, 122) of the printhead and the ink holder (66) of the printhead.

10. The printhead according to claim 8, wherein, The different electrodes (38, 40, 42, 122) are separated from the one or more cavities (118, 120) by one or more solid dielectric layers (124a, 124b, 126).

11. The printhead according to claim 9, wherein, The electrodes (38, 40, 42, 122) are mounted to the bottom layer (110) and / or top layer (112) of the multilayer structure (109).

12. The printhead according to claim 11, wherein, The electrodes (38, 40, 42, 122) are embedded in the bottom layer (110) and / or the top layer (112) of the multilayer structure (109), the bottom layer and / or the top layer (112) forming a dielectric solid layer covering the electrodes (38, 40, 42, 122) from the bottom side and the top side.

13. The printhead according to claim 10, wherein, The one or more solid dielectric layers (124a, 124b, 126) include a polymer layer (124a, 124b) and / or an inorganic layer (126).

14. The printhead according to claim 9 further includes a protective electrode (42) disposed horizontally behind the jet electrode (38), wherein at least some cavities in the cavity (71') are disposed between at least one of the jet electrodes (38) and at least one of the protective electrodes (42).

15. The printhead according to claim 9, further comprising at least one shielding electrode (42) disposed horizontally in front of the jetting electrode (38), wherein, At least some of the cavities in the cavity (71' ') are disposed between at least one of the jet electrode (38) and the shielding electrode (42).

16. The printhead according to claim 1 or 2, wherein, The nozzle carrier (6) includes at least the intermediate layer (114) of the multilayer structure (109).

17. The printhead according to claim 1 or 2, wherein, The nozzle carrier (6) includes: - Front layer (10), wherein the nozzle (4) is mounted to the front side (36) of the front layer (10), and - Backing layer (12), the backing layer is located on the back side of the front layer (10), - Electrical via (14), which is connected to the jet electrode (38) and extends through the front layer (10) and the backing layer (12), and -Ink supply pipes (15, 16) arranged in the front layer (10). The front layer (10) includes at least the middle layer (114).

18. The printhead according to claim 1 or 2 further includes a support structure (8) supporting the jet electrode (38) on the nozzle carrier (6), wherein the support structure (8) includes a plurality of support elements (76, 78) arranged between the nozzles (4). And the support structure (8) therein includes at least the middle layer (114) of the multi-layer structure (109).

19. The printhead of claim 18, further comprising a plurality of ink retainers (66) disposed between the nozzle (4) and the support elements (76, 78), wherein, Along the jetting direction (X) of the printhead, the front surface (68) of the ink holder (66) is located horizontally behind the front end (70) of the nozzle (4).

20. The printhead according to claim 1 or 2, wherein, The thickness (t) of the intermediate layer (114) is at least 1 μm.

21. The printhead according to claim 1 or 2, wherein the intermediate layer (114) is a polymer layer.

22. The printhead according to claim 1 or 2, comprising at least one material layer of a different material from the intermediate layer (114).

23. The printhead according to claim 1, wherein, Most of the cavity (118) is a closed cavity.

24. The printhead according to claim 8, wherein, Any straight line extending between two adjacent electrodes (38, 40, 42, 122) extends through at least one of the cavities (71, 71', 71'').

25. The printhead according to claim 13, wherein, The polymer layers (124a, 124b) are disposed between the electrode (122) and the inorganic layer (126).

26. The printhead according to claim 17, wherein, A closed cavity (118) is provided that is not connected to the ink supply pipes (15, 16).

27. A method for manufacturing a printhead according to claim 1 or 2, comprising the following steps: A material layer is applied on the bottom layer (110). Remove a portion of the material layer used to form the cavity (118). The top layer (112) is applied over the material layer.

28. The method according to claim 27, wherein, The material layer is a photoresist, and the method includes the following steps: A material layer is illuminated with collimated light through a mask, thereby defining irradiated and non-irradiated areas within the material layer. The irradiated area or the non-irradiated area is selectively removed from the material layer.

29. The method of claim 27, comprising the step of applying the top layer (112) over the material layer using lamination.

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