KR20230133851A - Electrohydrodynamic print head with ink retention - Google Patents

Abstract

The electrohydrodynamic print head includes a nozzle carrier (6) with a plurality of nozzles (4) arranged thereon. A plurality of discharge electrodes 38 are associated with the nozzle 4. The print head further 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). . The middle layer(s) 114 form a wall 116 extending between the bottom layer 110 and the top layer 112 arranged in a honeycomb pattern. A plurality of cavities 118 are located in the middle layer 114. The middle layer consists of a polymer material and can have a significant thickness.

Description

Electrohydrodynamic print head with ink retention

The present invention relates to an electrohydraulic printing head and a method of manufacturing the same.

WO 2016/169956 describes an electrohydrodynamic print head having a nozzle carrier with a plurality of nozzles. It is designed to eject ink along the ejection direction.

The problem that the present invention seeks to solve is to provide a specific print head of this type and a method of manufacturing the same.

This problem is solved by the print head of claim 1.

Accordingly, the print head may include at least the following elements:

- Nozzle carrier: This nozzle carrier is the substrate on which the nozzle is placed.

- A plurality of nozzles arranged on a carrier. The nozzle forms a location where ink is ejected.

- a plurality of discharge electrodes associated with the nozzle and located on the front side of the nozzle: the discharge electrodes are used, for example, to individually discharge ink from their associated nozzles.

The print head further includes at least one multilayer structure having a bottom layer, a top layer, and at least one intermediate layer between the bottom layer and the top layer. The middle layer(s) form a wall extending between the bottom layer and the top layer. A plurality of cavities are located in the intermediate layer between the bottom layer and the top layer.

The wall may form at least part of a cavity wall.

Advantageously, at least part of the cavity, especially most of the cavity, is a closed cavity, i.e. closed on all sides, in particular by the walls and by the bottom layer and the top layer. This aspect of the invention is based on the understanding that such cavities have applications other than ducts. In particular, cavities can be used to reduce mechanical stresses and/or shape electric fields.

In one embodiment, the wall forms a honeycomb structure, i.e., a hexagonal pattern, between the bottom layer and the top layer. This structure was found to reduce mechanical stress.

In an important aspect of the invention, at least some of the cavities are arranged between different electrodes of the print head or between the electrodes and the ink retainer of the print head. In this context, “different electrodes” are advantageously electrodes capable of delivering different voltages during operation of the print head. This design improves the print head's ability to better withstand the effects of electric fields.

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.

The electrodes may be mounted on the bottom layer and/or the top layer of the multi-layer structure, in particular one electrode is mounted on the bottom layer and the other electrode is mounted on the top layer.

Advantageously, the electrode is embedded in the bottom layer and/or the top layer, the bottom layer and/or the top layer forming a solid dielectric layer covering the electrode from the bottom side and the top side.

The print head may further include a protective electrode arranged at a level behind the discharge electrode. In this context, “at the level behind the discharge electrode” indicates that the protective electrode is closer to the nozzle carrier than the discharge electrode. This protective electrode can be used to reduce the intensity of the electric field behind it, for example to reduce the electric field in a structure that holds (fixes) ink.

In this case, in a given nozzle, at least a portion of the cavity is arranged between the protective electrode and the discharge electrode, thereby reducing the risk of electrical failure between the discharge electrode and the protective electrode.

The print head may further include at least one shielding electrode arranged at a front level of the discharge electrode. In this context, “at the front level of the discharge electrode” indicates that the discharge electrode is closer to the nozzle carrier than the shielding electrode. These shield electrode(s) can be used to control the electric field between the print head and target.

In this case, in a given nozzle, at least a portion of the cavity is arranged between the discharge electrode and the shielding electrode, thereby reducing the risk of electrical failure between the discharge electrode and the shielding electrode.

As mentioned, the print head has a nozzle carrier on which the nozzles are mounted. In one embodiment, the nozzle carrier may include the multi-layer structure (or at least one of the multi-layer structures, if there are multiple such structures).

In an advantageous design, the nozzle carrier includes at least the following parts:

- Front layer: The nozzle is mounted on the front side of the front layer.

- The rear floor located on the rear side of the front floor.

Electrical vias connected to the discharge electrode may extend through the front and back layers. Electrical vias supply voltage to the discharge electrode.

Additionally, an ink supply duct is arranged in (at least) the front layer.

In this case, the front layer may include an intermediate layer (or, if there are several such multi-layer structures, at least one of them). This allows the formation of thick ink ducts without causing excessive mechanical strain on the print head.

The print head may include a support structure supporting the discharge electrode on the nozzle carrier, and the support structure includes a plurality of support elements arranged between the nozzles. In this case, the support structure advantageously comprises at least an intermediate layer of a multilayer structure (or, if there are several such multilayer structures, at least one of them).

In this case, the print head may further include a plurality of ink retainers arranged between the nozzle and the support element. The ink retainer prevents ink from reaching and wetting the support element. Along the discharge direction, the front surface of the ink retainer is located at a level behind the front end of the nozzle (i.e., closer to the nozzle carrier), i.e., along the discharge direction, the ink retainer is set back with respect to the protrusion.

The method of manufacturing a print head advantageously includes at least the following steps:

- Applying a layer of material on said bottom layer: this layer of material will later form at least part of the middle layer. The material may be a permanent photoresist, for example SU8.

- Removing part of the material layer: this leaves the wall in place and forms a cavity.

- Applying the top layer over the material layer.

The invention will be better understood and its objectives other than those set forth above will become apparent upon consideration of the following detailed description. This description refers to the accompanying drawings, in which:
1 shows a partial cross-sectional view of the print head and target;
2 is a vertical cross-sectional view through a first embodiment of the nozzle;
Figure 3 is a horizontal cross-sectional view along line AA in Figure 2;
Figure 4 is a horizontal cross-sectional view along line BB in Figure 2;
Figure 5 is a horizontal cross-sectional view along line CC in Figure 2;
Figure 6 shows several alternative nozzle tip designs in addition to the cross design of Figure 5;
Figure 7 is a horizontal cross-sectional view along line DD in Figure 2;
Figure 8 is a horizontal cross-sectional view along line EE in Figure 2;
9 is a vertical cross-sectional view through a second embodiment of the nozzle;
Figure 10 is a horizontal cross-sectional view along line AA in Figure 9;
11 is a vertical cross-sectional view through a third embodiment of the nozzle;
Figure 12 is a vertical cross-section through a fourth embodiment of the nozzle, corresponding basically to the first embodiment but illustrating the design of the nozzle support;
Figure 13 is a horizontal cross-sectional view along line AA in Figure 12;
Figure 14 is a horizontal cross-sectional view along line BB in Figure 12;
Figure 15 is a horizontal cross-sectional view along line CC in Figure 12;
Figure 16 is a horizontal cross-sectional view along line DD in Figure 12;
17 is a vertical cross-sectional view illustrating two possible via designs for wiring electrodes;
18 illustrates a multi-layer honeycomb structure;
Figure 19 shows the design of the walls of the middle floor,
Figure 20 shows a vertical cross-section of an electrode along with an example of a dielectric layer surrounding the electrode;
Figure 21 is a vertical cross-sectional view of the embodiment without ink retainer.
NOTE: Although the discharge direction (X) in Figure 1 points downward and the target is positioned below the print head, the discharge direction ( It is rotated 180° with respect to all other drawings showing parallel cross sections. The orientation of these drawings is rather based on how manufacturing proceeds, i.e., the lower layers are manufactured before the top layers.

Justice

“Forwardly” defines the direction in which the print head is designed to eject ink. For example, the discharge electrode is ahead of the nozzle.

“Rearwards” defines the opposite direction. For example, the nozzle is arranged backward from the discharge electrode.

“From the front” and “from the back” are understood to specify the position of a level in front or behind another.

“Front” and “Back” are anterior and posterior.

A characteristic “at a given nozzle” is advantageously understood as a characteristic that is true for most nozzles, in particular for at least 90% of nozzles. For example, if we say “in a given nozzle, a protective electrode is arranged between the discharge electrode and the ink retainer”, this advantageously means that this is true for most nozzles, especially for at least 90% of the nozzles. For example, there may be some nozzles that do not have discharge electrodes and/or protective electrodes, such as nozzles at the edge of the print head and/or unused nozzles.

The discharge direction (X) of the print head defines a “vertical” upward direction, i.e. the print head is, by definition, designed to discharge ink upward. (Of course, in operation, it may be at any angle with respect to the direction of gravity.) Accordingly, definitions such as "above" and "below" should be understood with reference to this definition of "vertical."

“Horizontal” is any direction perpendicular to the vertical direction.

“Laterally” means horizontal to another.

print head

Figure 1 shows a schematic cross-sectional view of an embodiment of a print head 1. The print head is shown above the target 2 and is structured to eject ink along the ejection direction (X) onto the target.

The print head includes a plurality of nozzles (4) located on the front side of the nozzle carrier (6). Nozzles 4 may be arranged in a one-dimensional or two-dimensional array.

The print head has a plurality of discharge electrodes (not shown in Figure 1) for ejecting ink from the nozzles 4 and optional additional electrodes arranged on the support structure 8, the design of which is described in more detail below. do. Additional electrodes are provided in electrical contact with the ink to set the ink to a defined potential.

The nozzle carrier 6 includes a front layer 10, and the nozzle 4 is mounted on the front side of the front layer 10 and forms a protrusion thereon. The nozzle carrier also includes a back layer 12 located on the back side of the front layer 10.

The internal structure of the front layer 10 is not shown in Figure 1 and will be described in more detail below. The internal structure can be, for example, dielectric, especially polymer.

The back layer 12 may be an insulating semiconductor material, for example, or may be a dielectric. Advantageously, the back layer 12 is at least partially glass.

Electrical vias 14 connect to the discharge electrode and extend through the front layer 10 and back layer 12 to connect the discharge electrode to the voltage source 17. Advantageously, there is at least one via 14 for each nozzle 4 . Additional vias may be provided to connect other electrodes to the voltage source 17.

Ink ducts 15 and 16 supply ink to the nozzle 4 and (optionally) recycle ink back from the nozzle 4. The ink duct is located partially in the front layer 10 and extends through the peripheral area of the back layer 12. The design is described in more detail below.

Figure 1 shows an embodiment of a print head with a suction duct 16 as well as a supply duct 15 for ink.

At least one pump 18 and/or other pressure or vacuum source is provided to supply ink to the supply duct 15 and, if there is a suction duct, to withdraw ink from the suction duct 16.

Advantageously, the print head comprises a first pressure control 20 for generating a first defined pressure p1 at the inlet of the supply duct 15 , for example in the reservoir tank 22 .

Ink is supplied to the nozzle 4 through an optional filter 24 and supply duct 15.

If there is a suction duct 16, the suction can include a second pressure control 26 for generating a second set pressure p2 at the outlet of the suction duct 16, for example in the suction tank 28. connected to the system. The suction system may also include a pump. This may in particular be a pump 18 as described above, in which case the pump 18 acts as a circulation pump.

A suitable pump design is shown, for example, in US 6631983.

As further shown in Figure 1, the print head may include a circuit carrier 30, such as a PCB, arranged on the rear side of the nozzle carrier 6.

An optional interposer layer 32 may be provided between the circuit carrier 30 and the nozzle carrier 6 to match the circuit resolution of the circuit carrier 30 to the finer resolution of the vias 14. These interposer layers are used, for example, in flip chip design where the semiconductor chip is applied to a PCB.

The circuit carrier 30 supports a control circuit 33 which can implement at least a part of the voltage source 17, for example a driver stage of the voltage source connecting the voltage source to the various electrodes of the print head.

In the depicted embodiment, ink ducts 15, 16 extend through circuit carrier 30 as well as interposer layer 32 (if present).

If the vias 14 have a sufficiently large mutual spacing (eg, greater than 0.4 mm), the vias can interface directly with the circuit carrier 30 without the interposer layer 32.

Advantageously, the target 2 is arranged on an accelerating electrode connected to a voltage source 17 to create an accelerating electric field between the print head 1 and the target 2 .

Pressure controls 20, 26 may be used to maintain pressure as described in the Print Head Operation section below. Advantageously, the pressure control makes it possible to adjust the pressure in the supply duct 15 as well as the pressure duct 16 individually.

Nozzle Design 1

2 to 8 show a first embodiment of the nozzle 4 and surrounding elements. (As mentioned above, unlike FIG. 1, the discharge direction (X) in FIG. 2 points upward.)

As can be seen from Figure 2, the nozzle 4 forms a protrusion on the front side 36 of the nozzle carrier 6, for example on the front side of the front layer 10. The nozzle is located in the outlet passage 5 through which ink can be ejected toward the target 2.

Figure 2 also shows various electrodes that may be associated with the nozzle 4.

The discharge electrode 38 is located on the front side of the nozzle 4. 2 and 7, the discharge electrode is annular with a central opening 39 for passage of ink. The discharge electrode is connected to one of the vias 14 extending through the support structure 8 and the nozzle carrier 6.

3 and 4 show two possible implementations of via 14. On the right, with reference numeral 14, a hollow embodiment is shown, wherein the via extends along the discharge direction and is formed as a metal coating 14a in a dielectric tube 14b surrounding a central duct 14c, Can also be used as a ventilation duct to supply gas to/from the area between the print head and target. This type of structure, for example

a) forming a tube 14b with a honeycomb structure as described below,

b) may be formed by forming a metal coating 14a within the tube 14b, for example by sputtering.

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

Alternative via designs 14, 14' are also shown in Figure 17. A hollow via design 14 is shown for connecting the shield electrode 40, while a filled via design 14' is shown for the discharge electrode 38 (not visible in FIG. 17). Note: In Figure 17, only the metal parts are shown as hatched areas and other cross-sectional parts are not hatched.

Typically, a single print head uses only one design of vias, and the two different types in Figures 3, 4 and 17 are shown for illustrative purposes only.

2 and 8, the shielding electrode 40 may be positioned on the front side of the discharge electrode 38 and at a distance from the discharge electrode, that is, the discharge electrode 38 is positioned at a higher angle than the shielding electrode 40. Closer to the nozzle carrier (6). Advantageously, there is one continuous shielding electrode 40 extending over the front surface of the print head 1, although there may be several such shielding electrodes.

If multiple shielding electrodes are used, the shielding electrodes can be applied at different potentials by applying a voltage gradient, for example by a voltage divider, which can gradually deflect the ink across the cross-section of the print head, for example. there is.

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

2 and 5, the protective electrode 42 may be positioned behind and at a distance from the discharge electrode 38 but in front of the nozzle carrier 6 and at a distance from the nozzle carrier. It can be. As shown in Figures 2 and 5, the protective electrode may again be annular. Alternatively, the protective electrode may also extend across multiple nozzles.

The opening 43 of the protective electrode 42 above the nozzle 4 allows the passage of ink.

The function of the protective electrode 42 is explained below.

The nozzle 4 of this embodiment includes a tip section 46, a shaft section 48, and a base section 50, 52, where the tip section 46 is arranged in front of the shaft section 48 and the base section ( 50, 52) (FIGS. 2 and 3) are arranged behind the shaft section 48.

The nozzle design shown relies on ink wetting the lateral surface of the nozzle 4 and not passing through the central channel of the nozzle 4 (e.g. known from WO 2016/169956), but the central channel could also be used. .

If the nozzle 4 has a central channel, for example if the outlet duct 60 extends to the tip of the nozzle, the nozzle 4 will still operate advantageously so that the ink wets not only the top of the nozzle but also the lateral outer sides. Let’s do it. By ensuring ink covers the exterior of all nozzles, all nozzles provide the same ink geometry to the discharge electrodes, achieving more uniform ink discharge across the entire print head.

In order to facilitate a good ink flow along the nozzle 4 in the discharge direction It has at least one groove extending along the discharge direction (X). These groove(s) extend along at least part of the length of the nozzle 4.

The grooves can be identified, for example, in Figure 5, where the tip section 46 is shown to be cross-shaped (with four recesses 46a formed between the cross-shaped arms) and the shaft section 48. forms two grooves 48a.

Figure 6 shows an alternative design of the tip section 46:

(a) is a tip section 46 with a convex lateral surface, for example a cylinder without grooves - this is the currently preferred design as it creates a good meniscus through which the ink can be ejected;

(b) is the tip section 46 forming two lateral grooves 46a;

(c) is the tip section forming the axial tube 46c.

Base sections 50, 52 connect tip section 46 and shaft section 48 to nozzle carrier 6. The base section also includes duct(s) for supplying ink to the nozzles. The base section is best identified in Figures 2, 3 and 4.

In particular, in the depicted embodiment, base sections 50, 52 include a bottom sub-layer 52 and a top sub-layer 50. The bottom sublayer 52 has a central opening 54 that communicates with the end of the supply duct section 15a which supplies ink to the nozzle 4. One or more radially transverse outlet ducts 56 extend transversely to the discharge direction X from the central opening 54 outward to the first annular duct 58 .

In Figure 2, the flow of ink in the duct is indicated by arrows.

The top sublayer 50 also forms an axial outlet duct 60 that extends towards the tip of the nozzle and connects the supply duct section 15a to the groove 48a (Figure 5) of the shaft section 48, thereby The ink can be guided directly upward towards section 46.

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

The nozzle 4 is surrounded by an ink retainer 66 whose purpose is to retain the ink laterally. The annular duct 62 is located between the ink retainer 66 and the nozzle 4 in the radial direction, thereby communicating with the area 64 between the nozzle 4 and the ink retainer 66.

The front surface 68 of the ink retainer 66 (i.e., the front facing surface closest to the discharge electrode 38) is set back with respect to the front end 70 of the nozzle 4 along the discharge direction X. Accordingly, when there is ink in the area 64, the surface of the ink forms an upward slope toward the tip of the nozzle 4, as shown by the dashed-dotted line, such that the tip causes the ink to be closest to the discharge electrode 38. By ensuring a close location, a designated point for discharging ink is formed.

The main function of the ink retainer 66 is to hold the ink, i.e. to keep the ink away from the vertical part of the support structure 8, i.e. to form a pool through which the ink can rise and submerge the nozzle. is to prevent it.

This functionality is implemented by a combination of one or more of the following features:

a) The ink retainer 66 is provided with a hydrophobic and/or oleophobic surface, for example by means of a hydrophobic and/or oleophobic coating 73 , shown in thick black lines in FIG. 2 . For example, the surface may be formed at least in part from Teflon and/or PTFE, which are hydrophobic and oleophobic. Depending on the range of inks used, they may be only hydrophobic (eg HMDS, ie bis(trimethylsilyl)amine) or only oleophobic (eg polymer based). In particular, the surface of the ink retainer 66 is advantageously more hydrophobic and/or oleophobic than the surface of the nozzle 4.

b) The ink retainer 66 forms a ledge 66a facing away from the nozzle 4 closest to the ink retainer, which makes it difficult for ink to crawl around it. In other words, when viewed from the nozzle, the ledge extends outward, forming an “undercut” 66b.

c) The ink retainer 66 is located in an area of low electric field. Because strong electric fields tend to reduce the surface tension of ink, this design reduces the risk of ink soaking the entire ink retainer. In the illustrated embodiment, the protective electrode 42 associated with the nozzle 4 is arranged between the discharge electrode 38 and the ink retainer 66. In this context, “between” advantageously means that the protective electrode 42 intersects the spatial volume between the discharge electrode 38 and the ink retainer 66, advantageously dividing it in two.

It should be noted that the ink retainer 66 is not the only means for retaining the ink laterally, i.e. preventing it from reaching the nearest support element. Alternatively or additionally, the ink intake duct 16 may be used to remove any ink that may reach the support element. More details on this are described in the Printhead Operation section.

The protective electrode 42 is connected to the voltage source 17, for example by a via 14' or 14, and during operation the potential of the ink retainer 66 (i.e. of the ink) is lower than the (maximum) potential of the discharge electrode. It can be set to a potential that is closer to the potential. In particular, the voltage source 17 may be configured to maintain the protective electrode 42 at the same potential as the ink retainer 66. This keeps the electric field in the ink retainer 66 very low.

As shown in Figure 2, the protective electrode 42 is advantageously at the same “height” (having a vertical direction defined by the discharge direction X) as the front end 70 of the nozzle 4, e.g. For example, it is arranged within 25% accuracy of the vertical distance d between the discharge electrode 38 and the front end 70 of the nozzle 4. This provides excellent shielding of the ink under the tip of the nozzle 4 while still exposing the tip strongly to the electric field of the discharge electrode 38.

As can be seen in Figure 2, there is an air-filled cavity 71 that forms a gap between the protective electrode 42 and the ink retainer 66, preventing ink from reaching the protective electrode 42.

In order to retain the ink laterally in the area 64 , an ink retainer 66 is advantageously arranged on the front side 36 of the nozzle carrier 6 and protrudes therefrom. 2-4, the ink retainer includes a first ring 72 mounted on the front surface 36 of the nozzle carrier 6 and a second ring mounted on the front side of the first ring 72. 74). The second ring 74 forms the ledge 66a described above.

ink suction

As mentioned above, in the embodiment of Figures 1 and 2, a suction duct 16 is provided to recover ink from the nozzle 4. This allows maintaining a fresh ink flow in a given nozzle.

In this case, in a given nozzle, the nearest ink retainer 66 advantageously surrounds the nozzle 4 and the end section 15a of the supply duct as well as the end of the end section 16a of the suction duct 16. Therefore, the flow of ink toward and back from the nozzle can be controlled using two ducts.

The pressure in the supply duct 15 and suction duct 16 is such that the ink is kept somewhere, for example in the area 64 between the upper level 64a and the lower level 64b as shown in FIG. It is regulated. Advantageously, and as explained in more detail in the “Print Head Operation” section below, the ink is maintained at the lower level 64b.

For good lateral confinement of the ink, each nozzle 4 is advantageously surrounded by an opening or openings of one or more suction ducts. This may be, for example, a single annular opening (such as that formed by annular opening 62 in Figure 2), or it may be a series of annular suction openings. This opening or these openings are arranged between the nozzle and the support element 78 next to it.

support structure

As mentioned, a support structure 8 is provided for connecting the various electrodes 38, 40, 42 to the nozzle carrier 6. The support structure is arranged on the front side 36 of the nozzle carrier 6.

The support structure 8 includes a plurality of support elements 76, 78 arranged between the nozzles 4.

The ink retainer 66 is advantageously designed to prevent ink from reaching and wetting these support elements 76, 78, thereby reducing the tendency of ink to flood the nozzles.

The support structure 8 advantageously comprises at least one electrode carrier layer. In the embodiment of Figure 2, there are three such layers 80, 82, 84. Each such electrode carrier layer may include at least one electrode (38, 40, 42) and extend parallel to the top surface (36).

Typically, the electrodes 38, 40, 42 are embedded in their electrode carrier layers 80, 82, 84 and connected on their front sides and by at least one dielectric sublayer 80a, 80b or 82a, 82b or 84a, 84b. The rear side is covered.

At least a portion of the support elements are formed by vertical walls 76, forming a honeycomb structure (see Figure 3). Each such honeycomb structure is part of a multi-layer structure used in various parts of the print head and is described in more detail below.

Additionally or alternatively to the wall 76 forming the honeycomb structure, the support element comprises, in the embodiment shown, a vertical wall 78 surrounding the outlet passage 5 of each nozzle 4 . Wall 78 may be, for example, a cylindrical wall, but may also be, for example, polygonal. The wall is advantageously centered on the nozzle (4).

In another embodiment, the wall 78 may also be omitted and the wall around the outlet passage 5 may be formed by a honeycomb structured wall 76. In this case, the honeycomb structure must be aligned with the nozzle.

In another embodiment, multiple nozzles may be surrounded by a single wall 78.

In the embodiment shown herein, the support elements 76 and/or 78 are between each electrode carrier layer 80, 82, 84 as well as between the rearmost electrode carrier layer 80a and the nozzle carrier 6. provided. However, support elements may be provided only between a subset of these structures.

As can best be seen from Figure 2, there is a first recess located between the nozzle 4 and its ink retainer 66, which is formed by the first and second annular ducts 58, 62. . The first recess provides a volume to receive at least a portion of the ink pool 64. Along the discharge direction close).

In the depicted embodiment, there is a second recess 86 located between the ink retainer 66 and the nearest support element 78. The second recess provides space for the ledge 66a and/or makes it more difficult for ink to reach the support element 78. Along the discharge direction

Nozzle Design 2

9 and 10 show a second embodiment of the nozzle design. This mainly differs from the first embodiment in that there is only an ink supply duct 15 (the end section 15a of which is shown in Figure 10) and no suction duct for the nozzles.

Additionally, there is no recess between the nozzle 4 and the ink retainer 66. Rather, the ink retainer 66 is arranged laterally on the nozzle 4, with its front surface 68 at a distance from the front end (tip) 70 of the nozzle 4.

In other words, its front surface 68 is set back with respect to the front end 70 of the nozzle 4 to create an upward slope for the ink in area 64 and reduce the risk of locking the nozzle.

Advantageously, the ink retainer 66 is mounted “low” to the nozzle 4, making it less likely that the nozzle will become locked. In particular, the front surface 68 of the ink retainer 66 is closer to the front side 36 of the nozzle carrier 6 than the front end 70 of the nozzle 4.

As can be seen, in this embodiment, the ink retainer 66 is formed by the lower layer 52 of the base section of the nozzle 4.

Nozzle Design 3

Figure 11 shows a third embodiment of the nozzle design. This mainly differs from the second embodiment in that there is no protective electrode. To keep the electric field low at the location of the ink retainer 66, the ink retainer 66 is located further back.

In particular, as shown in FIG. 11, along the ejection direction X, the distance d' between the front surface 68 of the ink retainer 66 and the front end 70 of the nozzle 4 is large.

Quantitatively, if d represents the distance between the discharge electrode 38 and the front end 70 of the nozzle 4, along the discharge direction X, the following condition advantageously holds:

d' > k·d

Here, k is at least 0.5, especially at least 1.0.

Nozzle design without ink retainer

In the embodiment shown so far, the nozzle 4 is surrounded by an ink retainer 66 projecting upwardly from the top surface 36 of the nozzle carrier 6. However, if ink suction is used, this ink retainer can be omitted. This is illustrated in Figure 21 which shows an embodiment essentially corresponding to the nozzle of Figure 2 but without the ink retainer. Accordingly, the layers forming the base sections 50, 52 of the embodiment of Figure 2 may be omitted.

In this embodiment, ink is retained around the nozzle 4 by being sucked into the end section(s) 16a of the ink intake duct 16 surrounding the nozzle.

In one embodiment, a single annular (or for example hexagonal or otherwise closed loop) end section 16a of the suction duct 16 may be arranged around the nozzle 4 .

In other embodiments, a plurality of individual end sections 16a may be provided, closely spaced and surrounding the nozzle 4, for example arranged along a circle or other closed loop.

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

In the depicted embodiment, outlet duct 60 extends to the top 70 of the nozzle. Therefore, ink flows axially through the nozzle. Advantageously, the pressure in the outlet duct 60 is selected such that the ink overflows the nozzle and flows down along its lateral sidewall. From there, it reaches the end section(s) 16a of the suction duct 16 and is sucked in. This provides continuous ink exchange in the nozzles.

In another embodiment, the ink may be guided up along the outer surface of the nozzle in the groove, for example as shown in the embodiment of Figures 2-5, with the ink flowing through the axial opening of the nozzle, for example. It can be sucked from the end section 16a through.

However, optionally, the design of this section could also be combined with, for example, a simple ink retainer 66 (as shown in dashed lines) surrounding the end section(s) 16a of the suction duct 16.

nozzle carrier

12 to 16 show possible designs of the nozzle carrier 6. 13 to 15 are to scale compared to FIG. 12 to illustrate how neighboring nozzles may be interconnected by supply and suction ducts, and FIG. 16 shows a view of the print head at the level of the back layer 12. It should be noted that it is drawn to a much larger scale illustrating the entire cross-section.

Although these drawings show the nozzle of Figure 2, similar nozzle carriers may be used in different nozzle designs, such as the designs of Figures 9 and 11.

As described above, the nozzle carrier 6 is connected to the front layer 10, on which the nozzle 4 is mounted on its front side 36, as well as the back layer 12 located on the rear side of the front layer 10. ) includes. The front layer 10 as well as the back layer 12 may in turn have a multi-layer structure.

These are explained in more detail below.

The front layer 10 is comprised of several sublayers 10a-10d and forms at least part of the ducts 15, 16 for supplying ink to and, if applicable, from the nozzles.

In the embodiment of Figure 12, the front layer 10 includes sublayers 10a, 10b, 10c, 10d in front-to-back order to form ducts.

The lower layer 10a forms the front surface 10a and includes openings 15a, 16a for the supply duct and (if necessary) the suction duct respectively.

The lower layer 10b forms a vertical section 15b of the supply duct as well as (if necessary) a horizontal section 16b of the suction duct.

As best seen in Figure 13, the horizontal section 16b of the suction duct interconnects all or at least a plurality of nozzles 4. Additionally, between the ducts, the lower layer 10b includes vertical walls 90 forming a honeycomb pattern similar to that of the support structure 8. The region of the honeycomb pattern may be separated from the ducts 16b and/or 15b by a vertical separation wall 92.

Figure 13 also shows vias 14, 14' extending along the discharge direction (X) throughout the front layer 10.

The vertical section 15b of the supply duct is connected to the vertical section 15c of the supply duct of the lower layer 10c (see Figure 14).

As shown in Figure 15, the lower layer 10d forms a horizontal section 15d of the supply duct, interconnecting neighboring nozzles.

Again, lower layer 10d may include vertical walls 94 forming a honeycomb pattern similar to that of support structure 8. The area of the honeycomb pattern may be separated from the duct 10d by a vertical separation wall 96.

Figure 15 also shows vias 14, 14' extending along the discharge direction (X) throughout the front layer 10.

Figure 16 shows a possible arrangement of electrical vias 14 (and 14'), supply duct 15 and suction duct 16 at the level of back layer 12. Since the horizontal distribution of ink ducts 14, 16 is implemented in the front layer 10 over the back layer 12, the ink is arranged outside the convex shell 96 of a regular array of electrical vias 14. Alternatively, it could be supplied through several potentially large ink ducts, which simplifies the design of the back layer 12, i.e. no ink ducts extend through the back layer 12 within the convex shell 96.

Instead of using a honeycomb structure for the lower layers 10b and/or 10d, a solid layer, for example made of glass, may be used.

Honeycomb multi-layer structure

Following from the above, the print head shown here advantageously uses one or more honeycomb multilayer structures. One such multilayer structure 109 is illustrated in FIGS. 18 and 19. The multilayer structure has a bottom layer 110, a top layer 112, and at least one intermediate layer 114 between the bottom layer 110 and the top layer 102. The middle layer 114 forms a wall 116 extending between the bottom layer 110 and the top layer 112. These walls form at least part of the walls of a plurality of cavities 118 in the intermediate layer 114 between the bottom layer 110 and the top layer 112.

Wall 114 advantageously forms a honeycomb pattern.

This structure is particularly useful when the bottom layer 110 or top layer 112 is made of a different material than the middle layer 114 and/or is located close to or adjacent to another layer made of a different material than the middle layer 114. It has been found to reduce mechanical stress.

Examples of such honeycomb multilayer structures in the example above are as follows:

2, 11, 12: the front layer 10 or lower layer 10a is the “bottom layer” 110, the layer 80 of the support structure 8 is the “top layer” 112, , the wall 76 between them forms an “intermediate layer” 114.

- in FIGS. 2, 11, 12: the layer 80 of the support structure is the “bottom layer” 110, the layer 82 of the support structure 8 is the “top layer” 112, and between them The walls 76 form the “middle layer” 114.

- in FIGS. 2, 11, 12: the layer 82 of the support structure is the “bottom layer” 110, the layer 84 of the support structure 8 is the “top layer” 102, and between them The walls 76 form the “middle layer” 114.

12, 13: the lower layer 10c is the “bottom layer” 110, the lower layer 10a is the “top layer” 112, and the wall 90 of the lower layer 10b between them is “ forming an “intermediate layer” (114).

12, 15: the back layer 12 is the “bottom layer” 110, the lower layer 10c is the “top layer” 112, and the wall 94 of the lower layer 10d between them is Forms the “middle layer” (114).

In the first three examples, the support structure 8 includes at least an intermediate layer 114 of a multilayer structure.

In the last two examples, the nozzle carrier 6 includes at least an intermediate layer 114 of multilayer structure.

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

Advantageously, the intermediate layer 114 is formed from a polymer layer, for example a SU-8 layer after structuring. These types of layers are easy to manufacture and structure (see manufacturing information below) and, when used in multilayer structures as shown, reduce stresses compared to solid layers of these materials.

Therefore, advantageously, the print head comprises at least one layer of a material different from the intermediate layer, in particular a semiconductor or glass layer.

The cavity 118 is advantageously a closed cavity, i.e. neither forms part of the ink duct section 15b or 16d in FIGS. 15 and 13 nor is it in communication with the surrounding atmosphere.

If the walls 116 form a regular, repeating pattern, homogeneity may be improved and stresses may be further reduced.

Advantageously, the wall 116 has a thickness (m) less than 25% of the minimum diameter (M) of the cavity (see Figure 19). This lowers the solid material content of the intermediate layer, thereby further reducing mechanical stress. In this context, the thickness m is the extension of the wall 116 perpendicular to the surface. The diameter of the cavity (M) is the extension of the cavity (118) in a direction parallel to the bottom and top layers (110, 114).

For best strain relief, the minimum diameter M of the cavity 118 is advantageously larger than the thickness t of the intermediate layer 114, i.e. M > t. Smaller cavities extending through the middle layer 114 will create higher mechanical stresses in the middle layer.

Wall 116 extends advantageously orthogonally to bottom layer 110 and top layer 112 . This not only improves the mechanical stability against forces acting perpendicular to the layer, but also makes it possible to form walls by anisotropic material removal techniques, especially by photolithography of photoactive polymers.

It should be noted that the top and bottom layers of the multi-layer structure are parallel to each other.

The closed cavity 118 does not communicate with an ink duct, ie, no ink duct is used to guide ink through the print head. If the print head has ventilation ducts, the closed cavity 118 also does not communicate with these ventilation ducts.

The closed cavity 118 can be filled with air. Alternatively, the closed cavity can be vacuumed. Alternatively, it can be filled with a gas such as nitrogen. Advantageously, the closed cavity can be filled with a gas with a high breakdown voltage, such as SF ₆ or C ₄ F ₈ . Gases can be introduced by performing each manufacturing step (see below) in a workspace with the desired gas composition.

Electrode design

Print heads are designed to withstand the high electrical fields encountered during operation with minimal structural damage.

For this purpose, electrodes 38, 40, 42 are arranged between the solid dielectric layers 80a, 80b, 82a, 82b, 84a, 84b facing the cavity. In the illustrated embodiment, these cavities are, for example, cavities 118 formed by walls 116 and/or by cavities 71, 71', 71" below electrode carrier layers 80, 82, 84. ) is formed by.

At least a portion of the cavity may be a closed cavity (i.e., surrounded on all sides by walls, such as cavity 118).

At least part of the cavity may be an open cavity, especially a cavity adjacent to and in communication with the outlet passage 5 of the nozzle 4, such as the cavities 71, 71', 71" in the above embodiment.

In this design, the solid dielectric layer around the electrode can typically withstand higher electric fields than the gas in the cavity and also has a higher relative permittivity (ε), thus preventing total failure. At the same time, since there are no fixed molecular or atomic structures within the cavity, the cavity is not vulnerable to permanent damage caused by large electric fields. Therefore, this design improves the print head's ability to withstand the effects of the electrode's electric field even during long-term operation.

As can be seen in the embodiment shown here, there is a solid support structure extending vertically between neighboring electrode carrier layers 80, 82, 84, for example walls 76 and 78. However, it is advantageous that there is no such solid support structure extending directly between neighboring electrodes. In other words, any straight line extending between two adjacent electrodes extends through at least one of the cavities 71, 71', 71" or 118. In operation, they are operated at substantially different potentials, especially by a voltage of at least 100 V. This condition must be fulfilled for some or especially all neighboring electrodes of the print head when carrying different potentials.

This condition can be met by not arranging the solid support structure to extend vertically between the electrodes and/or by locally removing a section of the support structure, for example at the location of the contact lead 38b in Figure 7.

In another embodiment, the electric field strength can be reduced by designing the electrical tracks to be very narrow in locations where no cavities are provided between the electrodes. In this case, the track advantageously has a width of less than half the height of the wall structures 76, 78. For example, if the height of the wall structure is 5 μm, the track width should not be wider than 2.5 μm.

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

Advantageously, at least one of the dielectric layers protecting the electrode has a high relative dielectric constant (ε). Therefore, the electric field inside it is weak, and the mains voltage drop is transferred to the low-permittivity layers, especially the cavity. This provides better protection of the structure from electrical failure.

In this context, the high relative dielectric constant (ε) is advantageously at least 5. Suitable materials are, for example, Si ₃ N ₄ (relative dielectric constant (ε) of 9.5 to 10.5) or Al ₂ O ₃ (relative dielectric constant (ε) of 9.3 to 11.5).

Advantageously, several dielectric layers are provided between cavity 120 and electrode 122, as shown in Figure 20. (For example, cavity 120 and electrode 122 in FIG. 20, which represent cavity 118 or 71, 71', 71" in the example above, are one of the electrodes 38, 40, 42 in the example above, In particular, it represents the discharge electrode 38.)

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

The first dielectric layer 124a, 124b is advantageously a polymer layer composed, for example, of patterned SU-8 (see manufacturing process below). These polymer layers have a low relative dielectric constant, for example between 2.5 and 3.0. This corresponds, for example, to the sublayers 80a, 80b, 82a, 82b, 84a, 84b of the electrode carrier layers 80, 82, 84 described above and can be manufactured at least in part using a lamination technique (see below) ).

The second dielectric layer 126 is an inorganic layer with a higher electrical breakdown threshold than the first dielectric layers 124a and 124b. Advantageously, it has a relative dielectric constant that is in particular two times higher than that of the first dielectric layers 124a, 124b. For example, for the reasons described above, it may be made of Si ₃ N ₄ or Al ₂ O ₃ . The second dielectric layer has the highest breakdown resistance of all components between the two electrodes and typically prevents electrical failure.

Placing the first dielectric layers 124a, 124b between the electrodes 122 and the second dielectric layer 126 means, for example, that the peak electric field intensity at the edge of the electrodes 122 is within the first dielectric layer, and thus the second dielectric layer. The dielectric layer 126 has the advantage of increasing its ability to prevent failure.

Accordingly, in an advantageous embodiment, at least part of the cavity 120 is arranged between different electrodes of the print head or between the electrodes of the print head and the ink retainer 66 of the print head.

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

In particular, it is advantageous for one or more of the solid dielectric layers 124a, 124b, 126 to include polymer layers 124a, 124 and/or inorganic layers 126. Advantageously, the polymer layers 124a, 124 are arranged between the electrode 122 and the inorganic layer 126.

print head operation

During operation, i.e. during printing, ink is supplied to the print head through the supply duct 15. This ink is confined to the area 64 between the nozzle 4 and the ink retainer 66.

To eject an ink drop, the voltage of the desired ejection electrode(s) is temporarily increased (relative to the ink voltage). For example, a voltage pulse of 400 V can be generated. While not printing, the voltage of the discharge electrode is maintained at a level where ink is not discharged. However, advantageously it is not zero, for example at 200 V.

As mentioned above, the electric field in the ink retainer 66 is advantageously kept low, for example less than 50%, especially less than 10%, of the electric field strength at the front end 70 of the nozzle. Because high electric field strengths reduce the surface tension of the ink, this procedure reduces the tendency of the ink to wet and cross the ink retainer.

Suction duct 16, if present, is used to withdraw ink from the nozzle. Advantageously, the printing method comprises the following steps:

- individually supplying ink to the nozzles using the supply duct (15) of the nozzle carrier (6), and

- Separately suctioning ink from the nozzles using the suction duct (16) of the nozzle carrier (6).

This maintains a reservoir of fresh ink in the nozzle.

In operation, the pressure px at the end of the suction duct 16 at a given nozzle is advantageously maintained to keep ink away from the ink retainer 66, such as at level 64b in FIG. 2. Advantageously, px should not be too low to prevent air from being drawn into the intake duct 16. The appropriate pressure can be calculated from the radial width w of the annular duct 62. For an ink with w = 5 μm and the surface tension of water, the Young Laplace equation yields a differential pressure (dp) of 144 mbar. For a liquid with the surface tension of an alkane, the differential pressure (dp) is 40 mbar. Therefore, by keeping the pressure px less than dp the ambient pressure, the surface 64b can be maintained and no air will be drawn in.

If instead of the annular duct 62 several circular openings with a diameter, for example 5 μm, are used, dp will be doubled.

If the difference between ambient pressure and px is less than dp, the liquid level will rise, for example to line 64a in Figure 2. There, the curvature is much lower than line 64b. In a simplified example, assuming the curvature is 10 times lower, the corresponding differential pressure is 14 mbar (for water). Accordingly, ink can be prevented from reaching levels as high as line 64a, for example by keeping the pressure px below atmospheric pressure 50 mbar.

On the other hand, the pressure py at the end of the supply duct 15 at a given nozzle can be adjusted to maintain the desired ink flow through the nozzle. Additionally, as previously discussed, ink flow through outlet ducts 56 and 60 can be controlled by selecting appropriate diameters in these ducts.

In another embodiment, the differential pressure (less than ambient pressure) at the end section 16a of the suction duct 16 may be selected to be greater than dp at the lower level 64b. Accordingly, air will be drawn into the intake duct 16.

In this case, if the ink returning through the suction duct 16 is to be recycled, a separation device can be used to separate the ink and air before the ink is supplied to the recirculation pump 18.

manufacturing

The print head can be manufactured using techniques known, for example, from semiconductor manufacturing and packaging, as described for example in WO 2013/000558, WO 2016/120381, and WO 2016/169956.

Advantageously, at least some of the layers of the print head are polymer layers, especially the intermediate layer 114 of a multilayer structure of the type of Figures 18 and 19 used in the print head.

Manufacturing such multilayer structures advantageously includes the following steps:

1. Providing a bottom layer (110). This may be, for example, a top layer formed by a previous manufacturing step.

2. Applying a layer of material on top of the bottom layer (110). This layer of material will form middle layer 114.

3. Applying the top layer 112 over the material layer.

The material layers deposited in Steps 2 and 3 can be applied using a variety of techniques such as lamination, spin coating, sputtering, or vapor deposition.

Lamination is particularly advantageous for applying the top layer 112. In lamination, layers are applied as sheet materials and connected to a substructure using, for example, heat and pressure. This makes it possible to easily span the cavity and/or create a protruding structure.

The material layer of stage 2 is advantageously a photoresist such as SU-8, which allows for easy structuring. In this case, step 2 includes at least the following substeps:

2a: Illuminating the material layer with light collimated through a mask to define illuminated and unilluminated areas in the material layer.

2b: Selectively removing illuminated or unilluminated areas from the material layer depending on whether positive or negative photoresist is used.

Alternatively, top layer 112 may also be formed from a solid material, such as a glass wafer, that is bonded to middle layer 114 by, for example, adhesive bonding, fusion bonding, eutectic bonding, etc.

Inorganic dielectric layer 126 (FIG. 20) may be fabricated, for example, by depositing on polymer dielectric layers 124a and 124b via an atomic layer deposition process.

note

In most of the embodiments shown so far, each nozzle is surrounded by an ink retainer that defines a limited area through which ink can flow from the nozzle.

In one example, each nozzle is surrounded by its own ink retainer. Alternatively, several nozzles may be surrounded by a common ink retainer, ie one ink retainer may surround several nozzles.

Alternatively or additionally, each support element of the support structure 8 may be surrounded by an ink retainer defining 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 individual, isolated pillars.

As can be seen in the embodiment shown above, the protective electrode 42 is advantageously close to the axis of the nozzle. This is illustrated, for example, in Figure 12.

Here, the central axis 100 of the nozzle 4 when extending along the discharge direction (X) is shown as a dotted line. x1 is the distance between the protective electrode 42 and the nozzle axis 100. x2 is the distance between the ink retainer 66 and the nozzle axis 100. x3 is the distance between the nearest support element 78 and the nozzle axis 2, with the support element 78 adjacent to the nozzle carrier 6.

The following relationships are advantageous:

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

x1 < x3, especially x1 < 0.8·x3, especially x1 < 0.5·x3: Again, by placing the nearest support element 78 farther from the axis 100 than the protective electrode 42, the support element is also shielded.

Additionally or alternatively, the difference x2-x1 is advantageously at least 50% of the vertical distance d' between the protective electrode 42 and the ink retainer 66.

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

Accordingly, the following relationships are advantageous alone or in combination:

- The distance (x1) between the protective electrode 42 and the nozzle axis 100 is smaller than the distance (x2) between the ink retainer 66 and the nozzle axis 100.

- the distance between the protective electrode 42 and the nozzle axis 100 (x1) is the distance between the axis 100 and the support element 78 adjacent to the nozzle carrier 6 closest to the nozzle axis 100 (x3) smaller than

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

- the distance x3 (between the axis 100 and the support element 78 adjacent to the nozzle carrier 6) is at least 1 μm, in particular at least As large as 5 μm.

- The difference (x2-x1) (between the distance (x1) between the protective electrode 42 and the nozzle axis 100 and the distance (x2) between the ink retainer 66 and the nozzle axis 100) advantageously provides protection. It is at least 50% of the vertical distance between the electrodes 42 and the ink retainer 66.

As mentioned, the print head may also include gas ducts for supplying gas to and/or recovering gas from the area between the print head and the target. These gas duct supplies also, similarly to the ink ducts shown in FIGS. 13 and 15 , have interconnection sections, for example in the front layer 10 and/or back layer 12 and/or interposer layer 32. May contain the same horizontal sections.

In the embodiments described so far, three electrodes at three different vertical levels have been mentioned: a discharge electrode, a protection electrode and a shielding electrode. However, it should be noted that there may be other electrodes such as:

- Electrodes may be provided on the nozzle carrier 6, for example on the supply duct 15 and/or on the suction duct 16, and/or on the nozzle and/or on the ink retainer for defining the potential of the ink. This electrode maintains the ink at a potential similar or the same as the protective electrode 42, for example. Advantageously, these electrodes are platinum and/or gold.

- If nozzles of different sizes are present in the print head, additional electrodes (eg between discharge electrode 38 and shielding electrode 40 in Figure 2) may be provided. This is particularly useful for nozzles where the distance between the discharge electrode and the nozzle is significantly smaller than the distance between the shielding electrode and the discharge electrode.

Although the presently preferred embodiment of the invention has been shown and described, it should be clearly understood that the invention is not limited thereto and may be embodied and practiced in various other ways within the scope of the following claims.

Claims (26)

It is an electrohydrodynamic print head,
nozzle carrier (6),
A plurality of nozzles (4) arranged on the nozzle carrier (6),
Comprising a plurality of discharge electrodes (38) associated with the nozzle (4) and located on the front side of the nozzle (4),
The print head 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 middle layer(s) 114 form a wall 116 extending between the bottom layer 110 and the top layer 112,
A print head wherein a plurality of cavities (118, 120) are located in an intermediate layer (114) between a bottom layer (110) and a top layer (112). A print head according to claim 1, wherein at least a portion of the cavity (118), particularly a majority of the cavity (118), is a closed cavity. A print head according to claim 1 or 2, wherein at least some of the cavities (118) form a repetitive, regular pattern. A print head according to any one of claims 1 to 3, wherein the wall (116) forms a honeycomb structure between the bottom layer (110) and the top layer (112). A print head according to any one of claims 1 to 4, wherein the wall (116) has a thickness (m) less than 25% of the minimum diameter (M) of the cavity (118). A print head according to any one of claims 1 to 5, wherein the minimum diameter (M) of the cavity (118) is greater than the thickness (t) of the intermediate layer (114). A print head according to any one of claims 1 to 6, wherein the wall (116) extends orthogonally to the bottom layer (110) and the top layer (112). 8. The method according to any one of claims 1 to 7, wherein at least some of the cavities (71, 71', 71", 120) communicate with and are adjacent to an outlet passage (5) located in the nozzle (4). , print head. 9. The method according to any one of claims 1 to 8, wherein at least part of the cavity (71) is arranged between different electrodes (38, 40, 42, 122) of the print head,
In particular, any straight line extending between two adjacent electrodes (38, 40, 42, 122) extends through at least one of the cavities (71, 71', 71"). 10. The method according to any one of claims 1 to 9, wherein at least some of the cavities (71', 71") are arranged between the electrodes (38, 42, 122) of the print head and the ink retainer (66) of the print head. Being a print head. 11. Printing according to claim 9 or 10, wherein the different electrodes (38, 40, 42, 122) are separated from the cavity or cavities (118, 120) by one or more solid dielectric layers (124a, 124b, 126). head. 12. Print head according to claim 10 or 11, wherein the electrodes (38, 40, 42, 122) are mounted on the bottom layer (110) and/or the top layer (112) of the multi-layer structure (109). 13. The method of claim 12, 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), and the bottom layer (110) and/or the top layer (112) forms a solid dielectric layer covering the electrodes (38, 40, 42, 122) from the bottom side and the top side. 14. The method according to any one of claims 11 to 13, wherein the at least one solid dielectric layer (124a, 124b, 126) comprises a polymer layer (124a, 124b) and/or an inorganic layer (126), in particular the polymer layer (124a, 124b, 126). Layers (124a, 124) are arranged between the electrode (122) and the inorganic layer (126). 15. The method according to any one of claims 10 to 14, further comprising a protective electrode (42) arranged at a level behind the discharge electrode (38), wherein at least a portion of the cavity (71') is one of the discharge electrodes (38). A print head, arranged between at least one and at least one of the protective electrodes (42). 16. The method according to any one of claims 10 to 15, further comprising at least one shielding electrode (40) arranged at a front level of the discharge electrode (38), wherein at least some of the cavities (71") are located at the discharge electrode (38). A print head arranged between at least one of (38) and the shielding electrode (42). 17. Print head according to any one of claims 1 to 16, wherein the nozzle carrier (6) comprises at least an intermediate layer (114) of a multilayer structure (109). 18. The method according to any one of claims 1 to 17, wherein the nozzle carrier (6):
- a front layer (10), wherein the nozzles (4) are mounted on the front side (36) of the front layer (10), and
- a rear layer (12) located on the rear side of the front layer (10),
- an electrical via (14) connected to the discharge electrode (38) and extending through the front layer (10) and the back layer (12), and
- Comprising ink supply ducts (15, 16) arranged in the front layer (10),
The front layer 10 includes at least a middle layer 114,
In particular, a print head with a closed cavity (118) not in communication with the ink ducts (15, 16). 19. The method according to any one of claims 1 to 18, further comprising a support structure (8) supporting the discharge electrode (38) on the nozzle carrier (6), wherein the support structure (8) supports the nozzle. (4) comprising a plurality of support elements (76, 78) arranged between,
A print head, wherein the support structure (8) comprises at least an intermediate layer (114) of a multilayer structure (109). 20. The method of claim 19, further comprising a plurality of ink retainers (66) arranged between the nozzle (4) and the support elements (76, 78), comprising: The front surface (68) of the print head (66) is located at a level behind the front end (70) of the nozzle (4). 21. Print head according to any one of claims 1 to 20, wherein the thickness t of the intermediate layer (114) is at least 1 μm, in particular at least 10 μm. 22. A print head according to any one of claims 1 to 21, wherein the intermediate layer (114) is a polymer layer. 23. Print head according to any one of claims 1 to 22, comprising at least one material layer of a different material than the intermediate layer (114), in particular a semiconductor or glass layer. A method of manufacturing the print head of any one of claims 1 to 23,
applying a layer of material on the bottom layer (110);
removing a portion of the layer of material to form the cavity (118);
A method comprising applying a top layer (112) over the layer of material. 25. The method of claim 24, wherein the layer of material is a photoresist, particularly SU-8, and the method comprises:
illuminating the material layer with light collimated through a mask to define illuminated and unilluminated areas in the material layer, and
A method comprising selectively removing illuminated or unilluminated areas from a layer of material. 26. A method according to claims 24 or 25, comprising applying a top layer (112) over the layer of material using lamination.

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