JP2024502652A - Electrohydrodynamic print head with ink pinning - Google Patents

Abstract

The electrohydrodynamic print head comprises a nozzle carrier (6) on which a plurality of nozzles (4) are arranged. A plurality of injection electrodes (38) are associated with nozzles (4). The print head further comprises 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 (114) forms 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 arranged in the middle layer (114). It is a polymeric material and can have a substantial thickness.

Description

TECHNICAL FIELD This invention relates to electrohydrodynamic printheads and methods of manufacturing such electrohydrodynamic printheads.

US Pat. No. 5,001,201 describes an electrohydrodynamic printhead having a nozzle carrier with a plurality of nozzles. The electrohydrodynamic printhead is designed to eject ink along a jetting direction. The nozzle forms a protrusion extending along this jetting direction. The injection electrode is associated with the nozzle and is placed on the target side of the nozzle.

US Patent No. 6,631,983 International Publication No. 2013/000558 International Publication No. 2016/120381 International Publication No. 2016/169956

The problem to be solved by the invention is to provide a particular printhead of this type and a method for its manufacture.

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

Accordingly, the print head may include at least the following elements:
- Nozzle carrier: This is the substrate on which the nozzles are arranged.

- Multiple nozzles arranged on a carrier. The nozzle defines a location from which ink is ejected.

- a plurality of ejection electrodes associated with the nozzle and arranged in front of the nozzle: the ejection electrode is used, for example, to individually eject ink from the nozzle associated with the ejection electrode;

The print head comprises 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 forms a wall extending between the bottom layer and the top layer. A plurality of cavities are arranged in an intermediate layer between the bottom layer and the top layer.

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

Preferably, at least some of the cavities, in particular the majority of the cavities, are closed cavities, ie they are closed on all sides, in particular by walls and by the bottom layer and the top layer. This aspect of the invention is based on the understanding that the cavity has uses other than ducting. In particular, the cavity can be used to reduce mechanical stress and/or to create an electric field.

In one embodiment, the walls form a honeycomb structure, ie, a hexagonal pattern, between the bottom layer and the top layer. The structure has been found to reduce mechanical stress.

In an important aspect of the invention, at least a portion of the cavity is located between different electrodes of the print head or between the electrodes and an ink retaining portion of the print head. In this context, "respectively different electrodes" are preferably electrodes that may be associated with different voltages during operation of the print head. This design improves the printhead's ability to better withstand the effects of electric fields.

Preferably, each different electrode is 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 attached to the bottom layer and/or the top layer of the multilayer structure, in particular some electrodes are attached to the bottom layer and other electrodes to the top layer.

Preferably, the electrodes are embedded in the bottom layer and/or the top layer, the bottom layer and/or the top layer forming a dielectric solid layer covering the electrodes from the bottom side and from the top side.

The print head may further include a guard electrode located at a level behind the ejection electrode. In this context, "at a height behind the ejection electrode" indicates that the guard electrode is closer to the nozzle carrier than the ejection electrode. The guard electrode may be used to reduce the electric field strength behind it, for example in an ink retaining structure.

In this case, in a given nozzle, at least a portion of the cavity may be located between the guard electrode and the injection electrode, thereby reducing the risk of electrical breakdown between the injection electrode and the guard electrode.

The print head may further include at least one shield electrode located at a height in front of the ejection electrode. In this context, "at a height in front of the ejection electrode" indicates that the ejection electrode is closer to the nozzle carrier than the shield electrode. The shield electrode can be used to control the electric field between the print head and the target.

In this case, in a given nozzle, at least a portion of the cavity may be located between the ejection electrode and the shield electrode, thereby reducing the risk of electrical breakdown between the ejection electrode and the shield electrode.

As mentioned, the print head has a nozzle carrier with attached nozzles. In one embodiment, the nozzle carrier may comprise the multilayer structure described above (or at least one of several such multilayer structures, if present).

In a preferred design, the nozzle carrier comprises at least the following parts:
- Front layer: the nozzle is attached to the front side of the front layer.

- Lining layer placed behind the front layer.

Electrical vias connected to the ejection electrodes may extend through the front layer and the backing layer. The electrical via supplies voltage to the ejection electrode.

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

In this case, the front layer may comprise an intermediate layer (or at least one of several such multilayer structures, if present). This allows thick ink ducts to be formed without creating excessive mechanical distortion in the print head.

The print head may include a support structure supporting the firing electrodes on the nozzle carrier, the support structure comprising a plurality of support elements disposed between the nozzles. In this case, the support structure preferably comprises at least an intermediate layer of the multilayer structure (or at least one of several such multilayer structures, if present).

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

The method of manufacturing a printhead preferably includes at least the following steps.
- adding a layer of material on top of said bottom layer: this layer of material will later form at least part of the intermediate layer; The material can be, for example, a permanent photoresist such as SU8.

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

- Adding a top layer above the material layer.

The invention will be more fully understood, and objects other than those set forth above, will become apparent from consideration of the following detailed description of the invention. The description makes reference to the accompanying drawings.

FIG. 1 shows a partial cross-sectional view of the print head and target. FIG. 2 is a vertical section through the first embodiment of the nozzle. FIG. 3 is a horizontal cross-sectional view taken along line AA in FIG. FIG. 4 is a horizontal cross-sectional view taken along line BB in FIG. FIG. 5 is a horizontal cross-sectional view taken along line CC in FIG. FIG. 6 shows several alternative nozzle tip designs in addition to the cross-sectional shape design of FIG. FIG. 7 is a horizontal cross-sectional view taken along line DD in FIG. FIG. 8 is a horizontal cross-sectional view taken along line EE in FIG. FIG. 9 is a vertical cross-sectional view through a second embodiment of the nozzle. FIG. 10 is a horizontal cross-sectional view taken along line AA in FIG. FIG. 11 is a vertical cross-sectional view through a third embodiment of the nozzle. FIG. 12 is a vertical section through a fourth embodiment of the nozzle, essentially corresponding to the first embodiment, but showing the design of the nozzle support. FIG. 13 is a horizontal cross-sectional view taken along line AA in FIG. 12. FIG. 14 is a horizontal cross-sectional view taken along line BB in FIG. 12. FIG. 15 is a horizontal cross-sectional view taken along line CC in FIG. 12. FIG. 16 is a horizontal cross-sectional view taken along line DD in FIG. 12. FIG. 17 is a vertical cross-section showing two possible via designs for electrode wiring. Figure 18 shows a multilayer honeycomb structure. FIG. 19 shows the design of the walls of the intermediate layer. FIG. 20 shows a vertical cross-sectional view of an electrode with an embodiment of a dielectric layer surrounding the electrode. FIG. 21 is a vertical cross-sectional view of an embodiment without an ink retainer.

Note: The jet direction , FIG. 1 is rotated by 180° with respect to all other figures showing cross-sections parallel to the injection direction. Rather, the orientation in the figures is based on the manufacturing sequence, ie, lower layers are manufactured before upper layers.

Definitions "Forward" defines the direction in which the print head is designed to eject ink. For example, the ejection electrode is in front of the nozzle.

"Back" defines the opposite direction. For example, the nozzle is placed behind the injection electrode.

"Ahead" and "behind" are understood to refer to a position at an elevation in front of or behind something else.

"Front" and "rear" refer to the front side and the rear side.

The characteristic "at a given nozzle" is preferably understood as a characteristic that applies for the majority, in particular for at least 90% of the nozzles. For example, when we say "for a given nozzle, the guard electrode is located between the ejection electrode and the ink retainer", this preferably means for the majority of nozzles, especially for at least 90% of the nozzles. means that it applies. For example, it may be some nozzles that do not have firing and/or guard electrodes, such as nozzles at the edge of the print head and/or unused nozzles.

The jetting direction X of the print head defines a "vertical" upward direction, ie, the print head is, by definition, designed to jet ink upward. (Of course, in operation it may be less than any angle relative to the direction of gravity.) Thus, definitions such as "above" and "below" are understood with reference to this definition of "perpendicular". Should.

"Horizontal" is any direction perpendicular to the vertical direction.

"Horizontal" indicates something that is horizontal from something else.

Printhead FIG. 1 shows a schematic cross-sectional view of an embodiment of a printhead 1. FIG. It is depicted above the target 2, and it is configured to jet ink onto the target along the jetting direction X.

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

The print head has a plurality of ejection electrodes (not shown in FIG. 1) for ejecting ink from the nozzles 4 and an optional further electrode arranged on the support structure 8, the design of which It is described in more detail below. Further electrodes may be provided in electrical contact with the ink for setting the ink to a defined electrical potential.

The nozzle carrier 6 comprises a front layer 10, on which the nozzles 4 are attached on the front side and form projections thereon. It also comprises a backing layer 12 located on the rear side of the front layer 10.

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

Backing layer 12 may be, for example, an insulating semiconductor material, or it may be dielectric. Preferably, backing layer 12 is at least partially glass.

Electrical vias 14 are connected to the ejection electrode and extend through the front layer 10 and the backing layer 12 to connect the ejection electrode to the voltage supply 17. Preferably, there is at least one via 14 in each nozzle 4. Further vias may be provided to connect other electrodes to the voltage supply 17.

Ink ducts 15, 16 supply ink to the nozzles 4 and (optionally) return ink from the nozzles 4 for reuse. They are partially arranged in the front layer 10 and they extend through the peripheral area of the backing layer 12. Their design is described in more detail below.

FIG. 1 shows an embodiment of a print head with a supply duct 15 and a suction duct 16 for ink.

In order to supply ink to the supply duct 15, at least one pump 18 and/or another pressure or vacuum source is provided for withdrawing ink from the suction duct 16, if a suction duct is present.

Preferably, the print head comprises a first pressure control 20 which generates a first defined pressure p1 at the input of the supply duct 15, for example at the reservoir tank 22.

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

If a suction duct 16 is present, the suction duct 16 is connected to a suction system which may comprise a second pressure control 26 that generates a second defined pressure p2 at the outlet of the suction duct 16, for example a 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 the pump 18 functions as a circulation pump.

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

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

An optional intervening layer 32 may be provided between the circuit carrier 30 and the nozzle carrier 6 to match the finer resolution of the vias 14 to the resolution of the circuitry of the circuit carrier 30. Such intervening layers are used, for example, in flip-chip designs where a semiconductor chip is added to a PCB.

The circuit carrier 30 supports a control circuit 33 which may, for example, implement at least a part of the voltage supply 17, for example a driver stage of the voltage supply, and which may supply a voltage source to each electrode of the print head. are connected.

In the illustrated embodiment, the ink ducts 15, 16 extend through the intervening layer 32 (if present) and the circuit carrier 30.

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

Preferably, the target 2 is arranged on an accelerating electrode connected to a voltage supply 17 to generate 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 below in the section entitled Printhead Operation. Preferably, they are capable of regulating the pressure in the supply duct 15 and the pressure duct 16 separately.

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

As can be seen in FIG. 2, the nozzle 4 forms a projection on the front side 36 of the nozzle carrier 6, for example on the front side of the front layer 10 thereof. It is arranged in the outlet passage 5 through which ink can be jetted towards the target 2.

FIG. 2 also shows various electrodes that can be associated with the nozzle 4.

The injection electrode 38 is arranged on the front side of the nozzle 4. In the embodiment of FIGS. 2 and 7 it is annular with a central opening 39 for the passage of ink. It 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, under the reference numeral 14, a hollow implementation is shown, where vias are formed as metal coatings 14a in a dielectric tube 14b extending along the injection direction and surrounding a central duct 14c. , the central duct 14c may also be used as a ventilation duct to supply gas to/from the area between the print head and the target. This type of structure is e.g.
It may be formed by: a) forming the tube 14b with a honeycomb structure as described below; and b) forming a metal coating 14a within the tube 14b, for example by sputtering.

An alternative design, shown under reference numeral 14', comprises a solid metal core 14'a within a dielectric tube 14'b. Again, tube 14'b may be formed with a honeycomb structure as described below, and metal core 14'a may be formed, for example, by electroplating.

An alternative via design 14, 14' is also shown in FIG. A hollow via design 14 is depicted for connecting the shield electrode 40, while a filled via design 14' is depicted for the ejection electrode 38 (not visible in FIG. 17). Note: Only the metal parts are shown as hatched areas in FIG. 17, while other cross-sectional parts are not hatched.

Typically, a single printhead will only use one design of vias, and two different types are shown in FIGS. 3, 4, and 17 for illustrative purposes only.

With reference to FIGS. 2 and 8, the shielding electrode 40 may be placed farther in front of the ejection electrode 38, ie, the ejection electrode 38 is closer to the nozzle carrier 6 than the shielding electrode 40. Preferably there is one continuous shielding electrode 40 extending in front of the print head 1, but there may also be several such shielding electrodes.

If several shielding electrodes are used, they are applied to different potentials, e.g. by applying a voltage gradient, e.g. by a voltage divider that makes it possible to gradually deflect the ink in the cross-section of the print head. obtain.

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

As shown in FIGS. 2 and 5, the guard electrode 42 may be placed spaced apart behind the injection electrode 38, but may be spaced away in front of the nozzle carrier 6. Again, it may be annular as shown in FIGS. 2 and 5. Alternatively, it may also extend over several nozzles.

An opening 43 in the guard electrode 42 above the nozzle 4 allows ink to pass through.

The function of guard electrode 42 will be described below.

The nozzle 4 of this embodiment includes a tip portion 46, a shaft portion 48, and base portions 50, 52. The tip portion 46 is disposed in front of the shaft portion 48, and the base portions 50, 52 ( 2, 3) is located behind the shaft portion 48.

The illustrated nozzle design relies on the ink wetting the lateral surfaces of the nozzle 4 (as known, for example, from US Pat. , the latter may be used as well.

If the nozzle 4 has a central flow path, for example if the outlet duct 60 extends all the way to the tip of the nozzle, the nozzle 4 is preferably still such that the ink not only wets the top of the nozzle but also the outside next to it. be operated on. By ensuring that the ink covers the outside of all nozzles, all nozzles present the same ink contour to the ejection electrodes, which allows for more uniform ink jetting across the printhead.

In order to promote the desired flow of ink along the nozzle 4 in the jetting direction and at least one groove extending therethrough. This groove extends along at least part of the length of the nozzle 4.

This can be seen, for example, in Figure 5, where the tip section 46 is shown in cross-section (with four recesses 46a formed between the arms of the cross) and the shaft section 48 has two grooves 48a. is forming.

FIG. 6 shows an alternative design for the tip portion 46.
(a) is a tip portion 46 having convex lateral surfaces and being, for example, a cylinder without grooves - this is the currently preferred design because it is This is to create a desirable meniscus for the ink.
(b) is a tip portion 46 in which two lateral grooves 46a are formed,
(c) shows the tip portion forming an axial tube 46c.

Base portions 50 , 52 connect tip portion 46 and shaft portion 48 to nozzle carrier 6 . It also includes ducts that supply ink to the nozzles. This is best seen in FIGS. 2, 3, and 4.

In particular, in the illustrated embodiment, the base portions 50, 52 include a bottom sub-layer 52 and a top sub-layer 50. The bottom sub-layer 52 has a central opening 54 leading to the end of the supply duct portion 15a that supplies ink to the nozzle 4. One or more radially transverse outlet ducts 56 extend outwardly from the central opening 54 transversely to the injection direction X toward a first annular duct 58 .

In FIG. 2, the flow of ink within the duct is depicted by arrows.

The upper sub-layer 50 may also form an axial outlet duct 60 extending towards the tip of the nozzle and connecting the feed duct portion 15a to the groove 48a of the shaft portion 48 (see FIG. 5), thereby guiding the ink directly upwards towards the tip portion 46.

The upper sub-layer 50 may be surrounded by a second annular duct 62 aligned with the first annular duct 58 surrounding the nozzle 4 .

The nozzle 4 is surrounded by an ink holding part 66, the purpose of which is to hold the ink laterally. The annular duct 62 is arranged radially between the ink retainer 66 and the nozzle 4 and thereby communicates with the region 64 between the nozzle 4 and the ink retainer 66 .

The front surface 68 of the ink holding portion 66 (that is, the front facing surface closest to the ejection electrode 38) is set rearward along the ejection direction X with respect to the front end 70 of the nozzle 4. Therefore, when ink is present in the region 64, the plane of the ink forms an upward slope toward the tip of the nozzle 4, as shown by the dash-dotted line, and the tip is at the position where the ink is closest to the ejection electrode 38. This ensures that there is a defined point from which the ink is delivered.

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

This functionality is implemented by a combination of one or more of the following features.
a) The ink holding portion 66 is provided with a hydrophobic and/or oleophobic surface, for example by a hydrophobic and/or oleophobic coating 73, as shown by the thick black line in FIG. For example, the surface may be formed, at least in part, of Teflon and/or PTFE, which are hydrophobic and oleophobic. Depending on the range of inks used, the surface may also be exclusively hydrophobic (e.g. HMDS, i.e. bis(trimethylsilyl)amine) or exclusively oleophobic (e.g. polymer-based). . In particular, the surface of the ink 66 holding portion is preferably more hydrophobic and/or oleophobic than the surface of the nozzle 4.

b) The ink retainer 66 forms a ledge portion 66a pointing away from the nozzle 4 closest to it, making it difficult for the ink to travel around it. In other words, when viewed from the nozzle, the ledge extends outwardly to form an "undercut" 66b.

c) The ink holding portion 66 is arranged in a region where the electric field is low. Since strong electric fields tend to reduce the surface tension of the ink, this design reduces the risk of wetting the area around the ink retainer with ink. In the illustrated embodiment, the guard electrode 42 associated with the nozzle 4 is arranged between the ejection electrode 38 and the ink holding portion 66. In this context, "between" preferably means that the guard electrode 42 crosses, preferably bisects, the volume of the space between the ejection electrode 38 and the ink retainer 66.

It should be noted that the ink retainer 66 is not the only means of laterally retaining ink, ie preventing ink from reaching the nearest support element. Alternatively, or in addition, the ink suction duct 16 may be used to remove any ink that may reach the support element. This is described in more detail in the section entitled Printhead Operation.

The guard electrode 42 is connected to the voltage supply 17 by, for example, a via 14' or 14, which during operation is closer to the potential of the ink retainer 66 (i.e. of the ink) than the (maximum) potential of the ejection electrode. can be set to a potential. In particular, voltage supply 17 may be configured to maintain guard electrode 42 at the same potential as ink retainer 66 . Thereby, the electric field in the ink holding section 66 can be maintained very low.

As shown in FIG. 2, the guard electrode 42 is preferably at the same "height" (the vertical direction is defined by the injection direction X) as the forward end 70 of the nozzle 4, e.g. 70 within an accuracy of 25% of the vertical distance d. This provides the desired shielding of the ink below the tip of the nozzle 4 while still significantly exposing the tip to the field of the ejection electrode 38.

As can be seen in FIG. 2, there is an air-filled cavity 71 forming a gap between the guard electrode 42 and the ink retainer 66, which prevents ink from reaching the guard electrode 42.

In order to retain the ink laterally within the region 64, the ink retainer 66 is preferably located on the front side 36 of the nozzle carrier 6 and projects therefrom. In the embodiment of FIGS. 2-4, it includes a first ring 72 attached to the front face 36 of the nozzle carrier 6 and a second ring 74 attached to the front side of the first ring 72. Be prepared. The second ring 74 forms the ledge portion 66a mentioned above.

Ink Suction As mentioned above, in the embodiment of FIGS. 1 and 2, a suction duct 16 is provided for collecting ink from the nozzle 4. This allows a fresh flow of ink to be maintained at a given nozzle.

In that case, for a given nozzle, the nearest ink retaining portion 66 preferably surrounds not only the nozzle 4 and the end portion 15a of the supply duct, but also the end of the end portion 16a of the suction duct 16. Thus, two ducts may be used to control the flow of ink towards and back from the nozzle.

The pressure in the supply duct 15 and suction duct 16 is adjusted to maintain the ink within the region 64 somewhere between the upper height 64a and the lower height 64b as shown in FIG. 2, for example. be done. Preferably, the ink is maintained at a lower level 64b, as described in more detail in the "Printhead Operation" section below.

Due to the desired lateral confinement of the ink, each nozzle 4 is preferably surrounded by one or more suction duct openings or openings. This may be, for example, a single annular opening (such as formed by annular opening 62 in FIG. 2), or it may be an annular series of suction openings. This 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 respective different electrodes 38 , 40 , 42 to the nozzle carrier 6 . It is arranged on the front side 36 of the nozzle carrier 6.

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

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

The support structure 8 preferably comprises at least one electrode carrier layer. In the embodiment of FIG. 2, there are three such layers 80, 82, 84. Each of the electrode carrier layers 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 within their electrode carrier layers 80, 82, 84, with at least one dielectric sublayer 80a, 80b, or 82a, 82b, or 84a on their front and rear sides. , 84b.

At least part of the support element is formed by vertical walls 76 forming a honeycomb structure, see FIG. Each of the honeycomb structures is part of a multilayer structure used in different parts of the print head and described in more detail below.

In addition to or as an alternative to the walls 76 forming a honeycomb structure, in the illustrated embodiment the support element comprises a vertical wall 78 surrounding the outlet passage 5 of each nozzle 4 . Wall 78 may be, for example, a cylindrical wall, but it may also be, for example, polygonal. Preferably it is centered on the nozzle 4.

In another embodiment, the wall 78 can also be omitted and the peripheral wall of the outlet passage 5 can be formed by a honeycomb-structured wall 76. In this case, it is necessary to align the honeycomb structure with the nozzle.

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

In the embodiment shown here, support elements 76 and/or 78 are provided between each of the electrode carrier layers 80, 82, 84 and between the rearmost electrode carrier layer 80a and the nozzle carrier 6. . However, they can also be provided only between a subset of these structures.

As best seen in FIG. 2, there is a first recess located between the nozzle 4 and its ink retaining portion 66, which is formed by an annular first and second annular duct 58, 62. has been done. It provides a volume for receiving at least a portion of the ink pool 64. Along the jetting direction X, the bottoms of the first recesses 58, 62 are rearward with respect to the front surface 68 of the ink retainer 66 (ie closer to the nozzle carrier 6 than to the front surface 68).

In the illustrated embodiment, there is a second recess 86 located between the ink retainer 66 and the nearest support element 78 . It provides space for the ledge portion 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 rearward with respect to the front surface 68 of the ink retainer 66 (ie, closer to the nozzle carrier 6 than the front surface 68 is).

Nozzle design 2
9 and 10 show a second embodiment of the nozzle design. It differs from the first one mainly in that there is only an ink supply duct 15 (the end part 15a of which is shown in Figure 10) relative to the nozzle, but no suction duct.

Further, there is no recess between the nozzle 4 and the ink holding portion 66. Rather, the ink retainer 66 is disposed laterally over the nozzle 4 and its front surface 68 is spaced from the forward end (tip) 70 of the nozzle 4 .

In other words, its front face 68 is set rearwardly with respect to the front end 70 of the nozzle 4 in order to form an upward slope for the ink within the region 64 and reduce the risk of sinking the nozzle. .

Preferably, the ink retainer 66 is mounted "low" onto the nozzle 4 to reduce the possibility of sinking the nozzle. In particular, the front surface 68 of the ink retainer 66 is closer to the front end 70 of the nozzle 4 than the front size 36 of the nozzle carrier 6 .

As can be seen, in this embodiment, the ink holding portion 66 is formed by the sub-layer 52 of the base portion of the nozzle 4.

Nozzle design 3
FIG. 11 shows a third embodiment of the nozzle design. It differs from the second one primarily in that it does not have a guard electrode. In order to maintain a low electric field at the position of the ink retainer 66, the ink retainer 66 is disposed far to the rear.

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

Quantitatively, if d denotes the distance along the injection direction X between the injection electrode 38 and the front end 70 of the nozzle 4, preferably the following conditions are maintained:
d'>k・d
k is at least 0.5, especially at least 1.0.

Nozzle Design Without Ink Retainer In the embodiments illustrated so far, the nozzle 4 was surrounded by an ink retainer 66 projecting upwardly from the top surface 36 of the nozzle carrier 6 . However, by using the ink suction section, the ink holding section can be omitted. This is illustrated in Figure 21, which shows an embodiment essentially corresponding to that of Figure 2 but without the ink retainer. Accordingly, the layers that formed the base portions 50, 52 of the embodiment of FIG. 2 may be omitted.

In this embodiment, ink is retained around the nozzle 4 by suction into the end portion 16a of the ink suction duct 16 surrounding the nozzle.

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

In another embodiment, a plurality of individual end portions 16a may be provided surrounding the nozzle 4 with close spacing, for example arranged along a circle or another closed loop.

In this embodiment, the guard 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 illustrated embodiment, the outlet duct 60 extends all the way to the top 70 of the nozzle. Ink thus flows axially through the nozzle. Preferably, the pressure in the outlet duct 60 is selected such that the ink overflows the nozzle and flows down along its lateral sidewalls. From there, the ink reaches the end portion 16a of the suction duct 16 and is removed. This provides continuous ink exchange within the nozzle.

In another embodiment, the ink may be guided up along the outer surface of the nozzle in, for example, grooves as shown in the embodiments of FIGS. Suction can be drawn from the end portion 16a through the opening.

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

Nozzle Carrier Figures 12 to 16 show possible nozzle carrier 6 designs. 13-15 are on a reduced scale compared to FIG. 12 to show how adjacent nozzles can be interconnected by supply and suction ducts, and FIG. Note that it is shown on a much more reduced scale, showing the entire cross-section of the printhead at a height of .

Although these figures show the nozzle of FIG. 2, similar nozzle carriers may be used with various nozzle designs, such as the designs of FIGS. 9 and 11.

As mentioned above, the nozzle carrier 6 comprises a front layer 10, on the front side 36 of which the nozzles 4 are attached, and furthermore the backing layer 12 is arranged on the rear side of the front layer 10. Front layer 10 and backing layer 12 may then be of multilayer construction.

They are described in more detail below.

The front layer 10 is composed of several sub-layers 10a to 10d and forms at least part of the ducts 15, 16 that supply ink to and, if applicable, from the nozzles. There is.

In the embodiment of FIG. 12, the front layer 10 comprises, in order from front to rear, duct-forming sub-layers 10a, 10b, 10c and 10d.

The sub-layer 10a forms a front surface 10a and is provided with openings 15a, 16a for supply and (if required) suction ducts, respectively.

The sub-layer 10b forms (if required) a horizontal part 16b of the suction duct and a vertical part 15b of the supply duct.

As best seen in FIG. 13, the horizontal portion 16b of the suction duct interconnects all or at least several nozzles 4. In addition, between the ducts the sublayer 10b comprises vertical walls 90 forming a honeycomb pattern similar to that of the support structure 8. The area of the honeycomb pattern may be separated from the duct 16b and/or 15b by a vertical separating wall 92.

FIG. 13 also shows vias 14, 14' extending along the jet direction X through all of the front layer 10.

The vertical portion 15b of the supply duct is connected to the vertical portion 15c of the supply duct in the sub-layer 10c, see FIG.

As shown in FIG. 15, sublayer 10d forms a horizontal portion 15d of the supply duct interconnected with adjacent nozzles.

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

FIG. 15 also shows vias 14, 14' extending along the jet direction X through all of the front layer 10.

FIG. 16 shows a possible arrangement for the electrical vias 14 (and 14') at the level of the backing layer 12, the supply ducts 15 and the suction ducts 16. The horizontal distribution of ink ducts 14 , 16 is implemented in the front layer 10 above the backing layer 12 , so that one or several of them are placed outside the convex hull 96 of the regular array of electrical vias 14 . , in some cases it is possible to supply the ink through a large ink duct, which simplifies the design of the backing layer 12, i.e. the ink duct is routed through the backing layer 12 within the convex hull 96. It is designed to not stretch.

Instead of using a honeycomb structure in the sub-layers 10b and/or 10d, for example a solid layer of glass can be used.

Honeycomb Multilayer Structure As noted above and below, the printheads shown herein preferably employ one or more honeycomb multilayer structures. One such multilayer structure 109 is shown in FIGS. 18 and 19. It 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. Intermediate layer 114 forms a wall 116 extending between bottom layer 110 and 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.

Walls 114 preferably form a honeycomb pattern.

Particularly if the bottom layer 110 or the top layer 112 is a different material than the middle layer 114 and/or if it is placed near or adjacent to another layer that is a different material than the middle layer 114. , the structure has been found to reduce mechanical stress.

An example of the honeycomb multilayer structure in the above example is as follows.
- In FIGS. 2, 11, 12: the front layer 10 or sublayer 10a is the "bottom layer" 110, the layer 80 of the support structure 8 is the "top layer" 112, and the wall 76 between them is It forms an "intermediate layer" 114.

- In Figures 2, 11 and 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 the wall 76 between them is the "middle layer" 110; 114.

- In Figures 2, 11 and 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 the wall 76 between them is the "middle layer" 110; 114.

- In FIGS. 12, 13: the sublayer 10c is the "bottom layer" 110, the sublayer 10a is the "top layer" 112, and the wall 90 of the sublayer 10b between them forms the "middle layer" 114. is forming.

- In FIGS. 12, 15: the backing layer 12 is the "bottom layer" 110, the sublayer 10c is the "top layer" 112, and the walls 94 of the sublayer 10d between them are the "middle layer" 114; is forming.

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

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

The stress reduction achieved by the multilayer structure is particularly evident when the thickness t (see FIG. 18) of the intermediate layer 114 is relatively large. Preferably, the thickness t is greater than 1 μm, in particular greater than 10 μm.

Preferably, the intermediate layer 114 is a polymer layer formed, for example, from a SU-8 layer after structuring. This type of layer can be easily manufactured and structured (see manufacturing information below) and reduces stress compared to solid layers of the material when used in multilayer structures such as the one shown. .

Preferably, therefore, the print head comprises at least one layer of a different material than the intermediate layer, in particular a layer of semiconductor or glass.

Cavity 118 is preferably a closed cavity, ie, cavity 118 does not form part of ink duct portion 15b or 16d of FIGS. 15 and 13, and cavity 118 does not communicate with the surrounding atmosphere. not present.

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

Preferably, the wall 116 has a thickness m that is less than 25% of the minimum diameter M of the cavity (see FIG. 19). This leads to a low content of solid material in the intermediate layer, further reducing mechanical stresses. In this context, thickness m is the extent of wall 116 perpendicular to the plane of wall 116. The cavity diameter M is the extent of the cavity 118 in a direction parallel to the bottom and top layers 110, 114.

For optimal strain relief, the minimum diameter M of the cavity 118 is preferably greater than the thickness t of the intermediate layer 114, ie, M>t. The smaller the cavity extending through the intermediate layer 114, the higher the mechanical stress will be generated in the intermediate layer.

Wall 116 preferably extends perpendicular 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 the walls by anisotropic material removal techniques, in particular by photolithography of light-active polymers.

Note that the top and bottom layers of the multilayer structure are parallel to each other.

The closed cavity 118 is not in communication with the ink duct, ie, the closed cavity 118 is not used to guide ink through the print head. If the print head has ventilation ducts, the closed cavity 118 does not even communicate with these ventilation ducts.

Closed cavity 118 may be filled with air. Alternatively, closed cavity 118 may be evacuated. Alternatively, closed cavity 118 may be filled with a gas such as nitrogen. Preferably, the closed cavity 118 may be filled with a gas having a high breakdown voltage, such as SF ₆ or C ₄ F ₈ . Gases may be introduced by performing the respective manufacturing steps (see below) in a workspace with the desired gas composition.

Electrode Design The print head is designed to withstand the high electric fields encountered during operation with minimal structural damage.

To this end, electrodes 38, 40, 42 are arranged between solid dielectric layers 80a, 80b, 82a, 82b, 84a, 84b that bound the cavity. In the illustrated embodiment, the cavity is formed, for example, by a cavity 71 , 71 ′, 71 ″ below the electrode carrier layer 80 , 82 , 84 and/or by a cavity 118 formed by the wall 116 . There is.

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

At least part of the cavity may be an open cavity, in particular a cavity that opens adjacent to the outlet passage 5 of the nozzle 4, such as the cavities 71, 71', 71'' of the embodiments described above.

In such designs, the solid dielectric layer around the electrode can typically withstand higher fields than the gas in the cavity and also has a higher dielectric constant ε, thus preventing total breakdown. At the same time, since there are no fixed molecular or atomic structures within the cavity, the cavity is less susceptible to permanent damage caused by large electric fields. The present design thus improves the printhead's ability to withstand the effects of the electrode's electric field even during long-term operation.

As can be seen in the embodiment illustrated here, there is a solid support structure, such as walls 76 and 78, extending vertically between adjacent electrode carrier layers 80, 82, 84. However, preferably there is no such solid support structure extending directly between adjacent 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. This condition should be met if some, or especially all, of the adjacent electrodes of the print head are, in operation, at substantially different potentials, in particular by at least 100 V of voltage.

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

In yet another embodiment, the strength of the electric field may be reduced by designing the electrical track to be very narrow at locations where no cavities are provided between the electrodes. In that case, the tracks are preferably no more than half the width of the wall structures 76, 78. For example, if the wall structure has a height of 5 μm, the tracks should be no more than 2.5 μm wide.

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

Preferably, at least one of the dielectric layers protecting the electrodes has a high dielectric constant ε. Therefore, the field is weakened therein and the main voltage drop shifts to the lower dielectric constant layer, especially the cavity. This makes it possible to protect the structure even more fully from electrical breakdown.

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

Preferably, several dielectric layers are provided between the cavity 120 and the electrode 122, as shown in FIG. (Cavity 120 in FIG. 20 represents, for example, cavity 118 or 71, 71', 71'' in the example above, and electrode 122 represents one of the electrodes 38, 40, 42 in the example above, in particular the injection Represents electrode 38.

In the illustrated embodiment, the electrode 122 is surrounded by a first dielectric layer 124a, 124b, which in turn is surrounded by a second dielectric layer 126. There is.

The first dielectric layer 124a, 124b is preferably a polymer layer, for example composed of patterned SU-8 (see fabrication process below). The polymer layer has a low dielectric constant, for example between 2.5 and 3.0. It corresponds, for example, to the sublayers 80a, 80b, 82a, 82b, 84a, 84b of the electrode carrier layers 80, 82, 84 described above and is manufactured, at least in part, using lamination techniques (see below). obtain.

The second dielectric layer 126 is an inorganic layer that has a higher electrical breakdown threshold than the first dielectric layers 124a, 124b. It preferably has a dielectric constant higher, in particular twice, than the first dielectric layer 124a, 124b. It can be, for example, Si ₃ N ₄ or Al ₂ O ₃ for the reasons mentioned above. It has the highest breakdown resistance of all components between two electrodes and usually prevents electrical breakdown.

Placing the first dielectric layers 124a, 124b between the electrode 122 and the second dielectric layer 126 means that, for example, the peak electric field strength at the edge of the electrode 122 is within the first dielectric layer; Therefore, it has the advantage of increasing the ability of the second dielectric layer 126 to prevent breakdown.

Accordingly, in a preferred embodiment, at least a portion of the cavity 120 is located between several different electrodes of the printhead, or between an electrode of the printhead and an ink retainer 66 of the printhead.

Preferably, 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, the one or more solid dielectric layers 124a, 124b, 126 preferably comprise a polymeric layer 124a, 124 and/or an inorganic layer 126. Preferably, polymer layers 124a, 124 are disposed between electrode 122 and inorganic layer 126.

Operation of the print head During operation, ie during printing, ink is supplied to the print head by means of the supply duct 15. This ink is confined to a region 64 between the nozzle 4 and the ink holding portion 66.

To eject an ink droplet, the voltage at the desired ejection electrode (relative to the voltage of the ink) is temporarily increased. For example, a voltage pulse of 400V may be generated. While not printing, the voltage at the ejection electrode is maintained at a level at which no ink is being ejected. Preferably it is not zero, but for example 200V.

As mentioned above, the electric field at the ink retainer 66 is preferably maintained low, eg, less than 50%, particularly less than 10%, of the strength of the electric field at the forward end 70 of the nozzle. Since the high field strength reduces the surface tension of the ink, this procedure reduces the tendency of the ink to wet and traverse the ink receptacle.

Suction duct 16, if present, is used to withdraw ink from the nozzle. Preferably, the printing method includes the following steps.
- individually supplying ink to the nozzles using the supply ducts 15 in the nozzle carrier 6; and - individually suctioning ink from the nozzles using the suction ducts 16 in the nozzle carrier 6.

Thereby, fresh ink can be maintained in the nozzle.

In operation, the pressure px at the end of the suction duct 16 at a given nozzle is preferably maintained to keep ink away from the ink retainer 66, such as at height 64b in FIG. Preferably, px should not be too low to prevent air from being drawn into the suction duct 16. A suitable 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 pressure difference dp of 144 mbar (about 14.4 kPa). For a liquid with a surface tension of an alkane, the pressure difference dp is 40 mbar (approximately 4 kPa). Therefore, by keeping the pressure px below the ambient pressure at or below dp, the surface 64b can be maintained and no air is aspirated.

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

If the difference between the ambient pressure and px is less than dp, the liquid height rises, for example to line 64a in FIG. 2. There, the curvature is much lower than line 64b. In a simplified example, assuming a 10 times lower curvature, the corresponding pressure difference (for water) is 14 mbar (approximately 1.4 kPa). Thus, for example, by maintaining the pressure px 50 mbar (approximately 5 kPa) below atmospheric pressure, the ink can be prevented from reaching a height as high as that of line 64a.

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. Also, as mentioned above, ink flow through outlet ducts 56 and 60 can be adjusted by selecting suitable diameters in these ducts.

In yet another embodiment, the pressure difference at the end portion 16a of the suction duct 16 (below the ambient pressure) may be selected to be greater than dp at the lower height 64b. Air is thus drawn into the suction duct 16.

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

Manufacturing The present print head may be manufactured using techniques such as those known from semiconductor manufacturing and packaging, such as those described in US Pat.

Preferably, at least some of the layers of the printhead, in particular the intermediate layer 114 of the multilayer structure used therein of the type of FIGS. 18 and 19, are polymeric layers.

The production of the multilayer structure preferably includes the following steps.
1. providing a bottom layer 110; This can be, for example, an upper layer formed by a previous manufacturing step.

2. adding a layer of material on top of the bottom layer 110; This layer of material forms the intermediate layer 114.

3. Adding a top layer 112 above the material layer.

The material layers deposited in steps 2 and 3 may be applied using various techniques such as lamination, spin coating, sputtering, or evaporation.

In particular, lamination is particularly preferred for adding the top layer 112. In lamination, layers are applied as sheet materials and connected to the underlying structure using, for example, heat and pressure. This allows the cavity to be easily bridged and/or an overhang structure to be created.

The material layer of step 2 is preferably a photoresist, such as SU-8, which allows easy structuring of the material layer. In this case, step 2 includes at least the following substeps.
2a: substep of irradiating the material layer with collimated light through a mask, thereby defining irradiated and non-irradiated areas in the material layer.

2b: Substep of selectively removing irradiated or non-irradiated areas from the material layer, depending on whether a positive or negative photoresist is used.

Alternatively, top layer 112 may also be formed from a solid material, such as a glass wafer, which is bonded to intermediate layer 114 by, for example, adhesive bonding, fusion bonding, eutectic bonding, or the like.

Inorganic dielectric layer 126 (FIG. 20) may be fabricated, for example, by an atomic layer deposition process that deposits it over polymeric dielectric layers 124a, 124b.

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

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

Alternatively, or in addition, each support element of the support structure 8 may be surrounded by an ink retainer that defines an ink-free area around the support element and prevents ink from reaching the support element. prevent. This may be particularly advantageous when the support elements form individual isolated columns.

As can be seen in the embodiments illustrated above, the guard electrode 42 is preferably close to the axis of the nozzle. This is shown by way of example in FIG.

Here, the central axis 100 of the nozzle 4 extending along the injection direction X is shown by a broken line. x1 is the distance between the guard electrode 42 and the nozzle axis 100. x2 is the distance between the ink holding portion 66 and the nozzle axis 100. x3 is the distance between the nearest support element 78 and the nozzle axis 2, the support element 78 being the element adjacent to the nozzle carrier 6.

The following relationships are preferred.
x1<x2, particularly x1<0.8×2: By arranging the guard electrode 42 closer to the nozzle axis 100 than the ink holding portion 66, more sufficient shielding of the ink holding portion 66 is achieved.

x1<x3, in particular x1<0.8.x3, in particular x1<0.5.x3: Again, by arranging the nearest support element 78 further from the axis 100 than the guard electrode 42, the support element also Similarly shielded.

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

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

Therefore, the following relationships are preferred alone or in any combination.
- The distance x1 between the guard electrode 42 and the nozzle axis 100 is smaller than the distance x2 between the ink holding portion 66 and the nozzle axis 100.

- the distance x1 between the guard electrode 42 and the nozzle axis 100 is smaller 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;

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

- the distance x3 (between the axis 100 and the support element 78 adjacent to the nozzle carrier 6) is greater by at least 1 μm, in particular by at least 5 μm, than the distance x2 between the ink retainer 66 and the nozzle axis 100; .

- the difference x2-x1 (between the distance x1 between the guard electrode 42 and the nozzle axis 100 and the distance x2 between the ink retainer 66 and the nozzle axis 100) is preferably the difference between the guard electrode 42 and the ink retainer; portion 66.

As mentioned, the print head may also include a gas duct for supplying gas to and/or withdrawing gas from the region between the print head and the target. The gas duct supply may also comprise horizontal portions, such as interconnect portions, for example in the front layer 10 and/or the backing layer 12 and/or the intervening layer 32, similar to the ink ducts shown in FIGS. 13 and 15. .

In the embodiments described so far, three electrodes at three different vertical heights are mentioned: a jetting electrode, a guard electrode, and a shielding electrode. However, it should be noted that other electrodes may also be present, such as:
- electrodes can be provided in the nozzle carrier 6, for example in the supply duct 15 and/or in the suction duct 16 and/or in the nozzle and/or ink holding part, in order to determine the potential of the ink; This electrode makes it possible, for example, to maintain the ink at a similar or the same potential as the guard electrode 42. Preferably, the electrode is platinum and/or gold.

- Further electrodes (for example between the firing electrode 38 and the shielding electrode 40 in FIG. 2) may be provided if different sized nozzles are present in the print head. This is particularly useful for nozzles where the distance between the firing electrode and the nozzle is significantly smaller than the distance between the shielding electrode and the firing electrode.

While presently preferred embodiments of the invention have been illustrated and described, the invention is not limited thereto, but may be embodied and carried out in various other ways within the scope of the following claims. should be clearly understood.

The sub-layer 10a forms a front face 36 and is provided with openings 15a, 16a for the supply and (if required) suction ducts, respectively.

Again, the sublayer 10d may comprise vertical walls 94 forming a honeycomb pattern similar to that of the support structure 8. The area of the honeycomb pattern may be separated from the duct 15 by a vertical separation wall 96.

FIG. 16 shows a possible arrangement for the electrical vias 14 (and 14') at the level of the backing layer 12, the supply ducts 15 and the suction ducts 16. A horizontal distribution of ink ducts 15 , 16 is implemented in the front layer 10 above the backing layer 12 so that one or several are placed outside the convex hull 96 of the regular array of electrical vias 14 . , in some cases it is possible to supply the ink through a large ink duct, which simplifies the design of the backing layer 12, i.e. the ink duct is routed through the backing layer 12 within the convex hull 96. It is designed to not stretch.

Here, the central axis 100 of the nozzle 4 extending along the injection direction X is shown by a broken line. x1 is the distance between the guard electrode 42 and the nozzle axis 100. x2 is the distance between the ink holding portion 66 and the nozzle axis 100. x3 is the distance between the nearest support element 78 and the nozzle axis 100 , the support element 78 being the element adjacent to the nozzle carrier 6.

While presently preferred embodiments of the invention have been illustrated and described, the invention is not limited thereto, but may be embodied and carried out in various other ways within the scope of the following claims. should be clearly understood.
In addition, some embodiments of the present invention are shown below.
[Aspect 1]
An electrohydrodynamic print head comprising:
a nozzle carrier (6);
a plurality of nozzles (4) arranged on the nozzle carrier (6);
a plurality of injection electrodes (38) associated with the nozzle (4) and arranged on the front side of the nozzle (4);
Equipped with
The print head comprises 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 (114) forming a wall (116) extending between the bottom layer (110) and the top layer (112);
An electrohydrodynamic printhead, wherein a plurality of cavities (118, 120) are arranged in the intermediate layer (114) between the bottom layer (110) and the top layer (112).
[Aspect 2]
Printhead according to aspect 1, wherein at least some of the cavities (118), in particular the majority of the cavities (118), are closed cavities.
[Aspect 3]
A printhead according to any of the preceding aspects, wherein at least some of the cavities (118) form a repeating regular pattern.
[Aspect 4]
Printhead according to any of the preceding aspects, wherein the wall (116) forms a honeycomb structure between the bottom layer (110) and the top layer (112).
[Aspect 5]
A printhead according to any of the preceding aspects, wherein the wall (116) has a thickness (M) of less than 25% of the minimum diameter (M) of the cavity (118).
[Aspect 6]
Print head according to any of the preceding aspects, wherein the minimum diameter (M) of the cavity (118) is greater than the thickness (t) of the intermediate layer (114).
[Aspect 7]
Printhead according to any of the preceding aspects, wherein the wall (116) extends perpendicularly to the bottom layer (110) and the top layer (112).
[Aspect 8]
Any of aspects 1 to 7, wherein at least a part of the cavity (71, 71', 71'', 120) communicates with and is adjacent to an outlet passageway (5) arranged in the nozzle (4). A print head according to any of the aspects.
[Aspect 9]
at least a portion of the cavity (71) is located between different electrodes (38, 40, 42, 122) of the print head;
In particular, embodiments in which any straight line extending between two adjacent electrodes (38, 40, 42, 122) extends through at least one of said cavities (71, 71', 71''). 9. The print head according to any one of aspects 1 to 8.
[Aspect 10]
An embodiment in which at least a part of the cavity (71', 71'') is arranged between an electrode (38, 42, 122) of the print head and an ink retaining part (66) of the print head. 10. The print head according to any one of aspects 1 to 9.
[Aspect 11]
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); The print head according to any one of aspects 9 and 10.
[Aspect 12]
According to any of aspects 10 or 11, the electrodes (38, 40, 42, 122) are attached to the bottom layer (110) and/or the top layer (112) of the multilayer structure (109). Print head as described.
[Aspect 13]
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 are embedded in the bottom layer (110) and/or the top layer (112) of the multilayer structure (109). 112) Print head according to aspect 12, forming a dielectric solid layer covering the electrodes (38, 40, 42, 122) from the bottom side and from the top side.
[Aspect 14]
The one or more solid dielectric layers (124a, 124b, 126) comprise a polymeric layer (124a, 124b) and/or an inorganic layer (126), in particular the polymeric layer (124a, 124) comprises: The print head according to any one of aspects 11 to 13, wherein the print head is arranged between the electrode (122) and the inorganic layer (126).
[Aspect 15]
It further comprises a guard electrode (42) arranged at a level behind said ejection electrode (38), at least a part of said cavity (71') being connected to at least one of said ejection electrode (38) and said ejection electrode (38). 15. A print head according to any of aspects 10 to 14, wherein the print head is located between at least one of the guard electrodes (42).
[Aspect 16]
It further comprises at least one shielding electrode (40) arranged at a height in front of said ejection electrodes (38), at least a part of said cavity (71'') being connected to at least one of said ejection electrodes (38). 16. A printhead according to any one of aspects 10 to 15, wherein the printhead is arranged between one of the printheads and the shielding electrode (42).
[Aspect 17]
Print head according to any of the preceding aspects, wherein the nozzle carrier (6) comprises at least the intermediate layer (114) of the multilayer structure (109).
[Aspect 18]
The nozzle carrier (6) includes:
- a front layer (10), wherein the nozzle (4) is attached to the front side (36) of the front layer (10);
- a lining layer (12) arranged on the rear side of the front layer (10);
- an electrical via (14) connected to the injection electrode (38) and extending through the front layer (10) and the backing layer (12);
- an ink supply duct (15, 16) arranged in the front layer (10);
Equipped with
The front layer (10) comprises at least the middle layer (114),
Print head according to any of the preceding embodiments, in particular, wherein there is a closed cavity (118) not communicating with the ink duct (15, 16).
[Aspect 19]
It further comprises a support structure (8) supporting the ejection electrode (38) on the nozzle carrier (6), the support structure (8) comprising a plurality of support elements (76) arranged between the nozzles (4). , 78),
Printhead according to any of the preceding aspects, wherein the support structure (8) comprises at least the intermediate layer (114) of the multilayer structure (109).
[Aspect 20]
further comprising a plurality of ink retainers (66) arranged between the nozzle (4) and the support element (76, 78), the ink retainers (66) being arranged between the nozzles (4) and the support elements (76, 78); 20. Printhead according to aspect 19, wherein the front surface (68) of (66) is arranged at a level behind the front end (70) of said nozzle (4).
[Aspect 21]
Printhead according to any of the preceding aspects, wherein the thickness (t) of said intermediate layer (114) is at least 1 μm, in particular at least 10 μm.
[Aspect 22]
22. A print head according to any one of aspects 1 to 21, wherein the intermediate layer (114) is a polymer layer.
[Aspect 23]
Print head according to any of the preceding aspects, comprising at least one material layer of a different material than said intermediate layer (114), in particular a semiconductor or glass layer.
[Aspect 24]
A method of manufacturing a print head according to any one of aspects 1 to 23, comprising:
adding a layer of material on top of the bottom layer (110);
removing a portion of the material layer forming the cavity (118);
adding the top layer (112) above the material layer;
including methods.
[Aspect 25]
The material layer is a photoresist, in particular SU-8, and the method comprises:
irradiating the material layer with collimated light through a mask, the irradiation defining irradiated and non-irradiated areas in the material layer;
selectively removing the irradiated area or the non-irradiated area from the material layer;
25. The method according to aspect 24, comprising:
[Aspect 26]
26. A method according to any of aspects 24 or 25, comprising applying the top layer (112) above the material layer using lamination.

Claims (26)

An electrohydrodynamic print head comprising:
a nozzle carrier (6);
a plurality of nozzles (4) arranged on the nozzle carrier (6);
a plurality of injection electrodes (38) associated with the nozzle (4) and arranged on the front side of the nozzle (4);
Equipped with
The print head comprises 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 (114) forming a wall (116) extending between the bottom layer (110) and the top layer (112);
An electrohydrodynamic printhead, wherein a plurality of cavities (118, 120) are arranged in the intermediate layer (114) between the bottom layer (110) and the top layer (112). Printhead according to claim 1, wherein at least some of the cavities (118), in particular the majority of the cavities (118), are closed cavities. Printhead according to any preceding claim, wherein at least some of the cavities (118) form a repeating regular pattern. Print head according to any one of the preceding claims, wherein the wall (116) forms a honeycomb structure between the bottom layer (110) and the top layer (112). Printhead according to any one of the preceding claims, wherein the wall (116) has a thickness (M) of less than 25% of the minimum diameter (M) of the cavity (118). Print head according to any of the preceding claims, wherein the minimum diameter (M) of the cavity (118) is greater than the thickness (t) of the intermediate layer (114). Printhead according to any of the preceding claims, wherein the wall (116) extends perpendicularly to the bottom layer (110) and the top layer (112). Among claims 1 to 7, at least a part of the cavity (71, 71', 71'', 120) communicates with and adjoins an outlet passage (5) arranged in the nozzle (4). The print head according to any one of the preceding items. at least a portion of the cavity (71) is located 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 said cavities (71, 71', 71''). The print head according to any one of items 1 to 8. At least a portion of the cavity (71', 71'') is arranged between an electrode (38, 42, 122) of the print head and an ink retainer (66) of the print head. The print head according to any one of items 1 to 9. 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); A print head according to any one of claims 9 or 10. Any one of claims 10 or 11, wherein the electrode (38, 40, 42, 122) is attached to the bottom layer (110) and/or the top layer (112) of the multilayer structure (109). The print head described in . 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 are embedded in the bottom layer (110) and/or the top layer (112) of the multilayer structure (109). 13. Print head according to claim 12, wherein 112) forms a dielectric solid layer covering the electrodes (38, 40, 42, 122) from the bottom and from the top. The one or more solid dielectric layers (124a, 124b, 126) comprise a polymeric layer (124a, 124b) and/or an inorganic layer (126), in particular the polymeric layer (124a, 124) comprises: Print head according to any one of claims 11 to 13, wherein the print head is arranged between the electrode (122) and the inorganic layer (126). It further comprises a guard electrode (42) arranged at a level behind said ejection electrode (38), at least a part of said cavity (71') being connected to at least one of said ejection electrode (38) and said ejection electrode (38). Print head according to any one of claims 10 to 14, wherein the print head is arranged between at least one of the guard electrodes (42). It further comprises at least one shielding electrode (40) arranged at a height in front of said ejection electrodes (38), at least a part of said cavity (71'') being connected to at least one of said ejection electrodes (38). 16. Print head according to any one of claims 10 to 15, wherein the print head is arranged between one and the shielding electrode (42). Print head according to any one of the preceding claims, wherein the nozzle carrier (6) comprises at least the intermediate layer (114) of the multilayer structure (109). The nozzle carrier (6) includes:
- a front layer (10), wherein the nozzle (4) is attached to the front side (36) of the front layer (10);
- a lining layer (12) arranged on the rear side of the front layer (10);
- an electrical via (14) connected to the injection electrode (38) and extending through the front layer (10) and the backing layer (12);
- an ink supply duct (15, 16) arranged in the front layer (10);
Equipped with
The front layer (10) comprises at least the middle layer (114),
Print head according to any one of the preceding claims, in particular, wherein there is a closed cavity (118) that does not open into the ink duct (15, 16). It further comprises a support structure (8) supporting the ejection electrode (38) on the nozzle carrier (6), the support structure (8) comprising a plurality of support elements (76) arranged between the nozzles (4). , 78),
Print head according to any one of the preceding claims, wherein the support structure (8) comprises at least the intermediate layer (114) of the multilayer structure (109). further comprising a plurality of ink retainers (66) arranged between the nozzle (4) and the support element (76, 78), the ink retainers (66) being arranged between the nozzles (4) and the support elements (76, 78); 20. Print head according to claim 19, wherein the front face (68) of (66) is arranged at a level behind the front end (70) of the nozzle (4). Print head according to any of the preceding claims, wherein the thickness (t) of the intermediate layer (114) is at least 1 μm, in particular at least 10 μm. Print head according to any of the preceding claims, wherein the intermediate layer (114) is a polymer layer. Print head according to any of the preceding claims, comprising at least one material layer of a different material than the intermediate layer (114), in particular a semiconductor or glass layer. A method for manufacturing a print head according to any one of claims 1 to 23, comprising:
adding a layer of material on top of the bottom layer (110);
removing a portion of the material layer forming the cavity (118);
adding the top layer (112) above the material layer;
including methods. The material layer is a photoresist, in particular SU-8, and the method comprises:
irradiating the material layer with collimated light through a mask, the irradiation defining irradiated and non-irradiated areas in the material layer;
selectively removing the irradiated area or the non-irradiated area from the material layer;
25. The method of claim 24, comprising: 26. A method according to any one of claims 24 or 25, comprising applying the top layer (112) above the material layer using lamination.

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