An array electrohydrodynamic nozzle based on independent heating regulation of each nozzle

Abstract

The present invention belongs to the field of inkjet printing devices, and particularly relates to an arrayed electrohydrodynamic inkjet printhead based on independent heating regulation of each nozzle, comprising: a nozzle plate, a plurality of protruding nozzles arranged on the nozzle plate, a plurality of heating electrodes corresponding to the plurality of protruding nozzles one by one, a power supply circuit for independently supplying power to each heating electrode, and an ink cartridge communicated with the plurality of protruding nozzles; each heating electrode is used for independently heating the corresponding protruding nozzle; the voltage applied to the solution in the ink cartridge satisfies: when the heating electrode is not working, the ink in the ink cartridge will not be ejected due to the electric field force between the ink cartridge and the printing substrate; and when the power supply circuit independently supplies power to each heating electrode, different supply voltages generate unequal resistive heat, so that the temperatures of the solutions in the protruding nozzles corresponding to the heating electrodes are unequal, so as to have different ejection states. The present invention can avoid the problem that faults are likely to occur when the existing independent controllable ejection of the printhead is carried out by regulating the electric field.

Description

Technical Field

[0001] The present invention belongs to the field of inkjet printing devices, and more specifically, relates to an arrayed electrohydrodynamic inkjet printhead based on independent heating adjustment of each nozzle. Background Art

[0002] As an additive manufacturing direct writing technology, inkjet printing has the advantages of no need for a mask, flexible production, high material utilization rate, etc., and has good application prospects in the fields of printed display, printed circuit, printed solar cell, etc.

[0003] Currently, inkjet printing mainly uses piezoelectric and thermal bubble technologies. By deforming a piezoelectric sheet or heating to generate bubbles, the ink is extruded from the printhead to form ink droplets. These two inkjet printing technologies have the disadvantages of being sensitive to ink viscosity and the minimum ink droplet size being larger than the nozzle diameter, which limits the viscosity of the ink available for printing. At the same time, the printing resolution is limited by the nozzle diameter and is difficult to further improve, unable to meet the printing requirements of more materials and higher resolutions. The electrohydrodynamic inkjet printing technology uses the electric field force as the main driving force, greatly enhancing the driving ability of the ink and being able to print high-viscosity ink. At the same time, since the jetting occurs locally at the meniscus, the generated ink droplet size can be much smaller than the nozzle diameter, thus significantly improving the printing resolution. The electrohydrodynamic inkjet printing technology overcomes the two major disadvantages of traditional inkjet printing technologies and has broad application prospects.

[0004] The electrohydrodynamic inkjet printhead is the key to realizing electrohydrodynamic inkjet printing. Currently, the independent controllable jetting of electrohydrodynamic inkjet printheads is achieved by regulating the electric field, but there are problems such as unequal nozzle opening voltages and electric field crosstalk in electric field regulation. In addition, electric field regulation is mainly achieved by relying on an external electrode ring, and during printing, the jet is prone to deflecting onto the electrode ring, causing the printhead to malfunction. For example, Chinese Patent Application CN201410289239.5 proposed a method for realizing independent controllable printing of a printhead. However, due to the extraction electrode being provided below the printhead, not only is the manufacturing and assembly difficult, but also the ink is prone to deflecting and accumulating on the extraction electrode, causing damage to the printhead. Chinese Patent Application CN201510299992.7 proposed a microelectrospray chip device, but it cannot achieve independent control of the jetting state of each nozzle hole. Summary of the Invention

[0005] Aiming at the defects and improvement requirements of the prior art, the present invention provides an arrayed electrohydrodynamic inkjet printhead based on independent heating adjustment of each nozzle, aiming to solve the problem that it is easy to malfunction when realizing independent controllable jetting of an electrohydrodynamic inkjet printhead by regulating the electric field.

[0006] To achieve the above object, according to one aspect of the present invention, an arrayed electrohydrodynamic inkjet printhead based on independent heating and adjustment of each nozzle is provided, including: a nozzle plate, a plurality of protruding nozzles arrayed on the nozzle plate, a plurality of heating electrodes corresponding to the plurality of protruding nozzles one by one, a power supply circuit for independently supplying power to each heating electrode, and an ink cartridge communicating with the plurality of protruding nozzles;

[0007] Each heating electrode is used to independently heat the corresponding protruding nozzle; the voltage applied to the solution in the ink cartridge satisfies: when the heating electrode is not working, the ink in the ink cartridge will not be ejected due to the electric field force between the ink cartridge and the printing substrate; and when the power supply circuit independently supplies power to each heating electrode, different supply voltages generate unequal resistive heats, so that the temperatures of the solutions in the protruding nozzles corresponding to the heating electrodes are unequal, so as to have different ejection states.

[0008] The beneficial effects of the present invention are as follows: The present invention abandons the existing mechanism of controlling electrohydrodynamic injection through an electrode ring, newly introduces heating electrodes, and adjusts the temperature of each nozzle hole separately to control parameters such as the surface tension, viscosity, and contact angle of the end solution. When the solution temperature rises, its surface tension and viscosity decrease, and the ejection resistance decreases; when the resistance is less than the electric field force, the solution will change from non-ejection to ejection. The voltage applied to the solution in the ink cartridge satisfies: when the heating electrode is not working, the ink in the ink cartridge will not be ejected due to the electric field force between the ink cartridge and the printing substrate; when the power supply circuit independently supplies power to each heating electrode, different supply voltages generate unequal resistive heats, so that the temperatures of the solutions in each nozzle are unequal, and thus the surface tension, viscosity, and contact angle are unequal, so as to have different ejection states, thereby realizing independent control of the nozzle holes, and being able to avoid the problems that are prone to occur when the existing electrohydrodynamic inkjet printhead realizes independently controllable injection by regulating the electric field.

[0009] Further, the material of the heating electrode is iron-nickel alloy, nickel-chromium alloy, hafnium diboride, polysilicon or tantalum aluminum (oxygen, nitrogen).

[0010] The further beneficial effects of the present invention are as follows: Materials such as iron-nickel alloy, nickel-chromium alloy, hafnium diboride, polysilicon or tantalum aluminum (oxygen, nitrogen) have the characteristics of rapid temperature rise and can meet the rapid response requirements of the nozzles.

[0011] Further, the maximum operating voltage of the heating electrode does not exceed 100V, and the maximum operating temperature does not exceed 200°C.

[0012] The further beneficial effects of the present invention are as follows: The maximum operating voltage of the heating electrode 3 does not exceed 100V, and the maximum operating temperature does not exceed 200°C, which can avoid premature aging of the printhead caused by high temperature.

[0013] Further, the heating electrode is a closed or open-loop electrode that surrounds the outer periphery of the protruding nozzle; or the heating electrode is a thin film attached to the inner wall of the protruding nozzle or the inner wall of the nozzle cavity above it.

[0014] According to application requirements, the resistance value of the heating electrode is adjusted by changing the resistance material and the resistance geometric dimensions.

[0015] Further, there are multiple power supply circuits, which correspond to the heating electrodes one by one. The power supply circuits are separated from each other. Each power supply circuit has a pin at its distal end, and is connected to an external circuit through the pin and a switch to independently control the operation of the heating electrode.

[0016] Further, an insulating layer is also provided on the heating electrode and the power supply circuit.

[0017] A further beneficial effect of the present invention is that the insulating layer covers the heating electrode and the power supply circuit to isolate the external solution and prevent conduction between the heating electrodes and between the power supply circuits. The material used for the insulating layer has good insulation and heat resistance.

[0018] Further, the outer surface of the insulating layer is designed as a micro-ripple structure.

[0019] A further beneficial effect of the present invention is that the outer surface of the insulating layer can be designed as a micro-ripple structure to increase the contact area with air and improve the heat dissipation effect.

[0020] The present invention also provides a printing system that employs an arrayed electrohydrodynamic inkjet head based on independent heating regulation of each nozzle as described above.

[0021] Generally speaking, through the above technical solutions conceived by the present invention, the following beneficial effects can be achieved:

[0022] The present invention abandons the existing mechanism of controlling electrohydrodynamic jetting through an electrode ring, and newly introduces a heating electrode to separately adjust the temperature of each nozzle hole, so as to regulate parameters such as the surface tension, viscosity, and contact angle of the end solution, thereby achieving independent control of the nozzle holes. It can avoid the problems that are prone to occur when the existing electrohydrodynamic inkjet head is independently controllably jetted by regulating the electric field. Among them, the role of the heating electrode is to heat the nozzle end to adjust the surface tension of the Taylor cone liquid surface, control the jetting of the liquid surface, and thus achieve independently controllable printing of each nozzle, with the advantages of low crosstalk, high resolution, and low cost. Description of the Drawings

[0023] Figure 1 is a three-dimensional view of an arrayed electrohydrodynamic inkjet head that achieves independent controllability based on independent heating regulation of each nozzle provided by an embodiment of the present invention;

[0024] Figure 2 Cross-sectional view of an arrayed electrohydrodynamic inkjet printhead with independent controllability achieved by independent heating and adjustment of each nozzle provided by an embodiment of the present invention;

[0025] Figure 3 Another layout diagram of the heating electrodes of an arrayed electrohydrodynamic inkjet printhead with independent controllability achieved by independent heating and adjustment of each nozzle provided by an embodiment of the present invention;

[0026] Figure 4 Schematic diagram of independent controllability of an arrayed electrohydrodynamic inkjet printhead with independent controllability achieved by independent heating and adjustment of each nozzle provided by an embodiment of the present invention.

[0027] In all the drawings, the same reference numerals are used to represent the same elements or structures, where:

[0028] 1 is the nozzle plate, 2 is the protruding nozzle, 3 is the heating electrode, 4 is the power supply circuit, 5 is the insulating layer, 6 is the ink cartridge, and 7 is the substrate. Detailed implementation manners

[0029] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0030] Embodiment 1

[0031] An arrayed electrohydrodynamic inkjet printhead with independent heating and adjustment of each nozzle, as shown in Figure 1 and Figure 2 , includes: a nozzle plate 1, a plurality of protruding nozzles 2 arrayed on the nozzle plate, a plurality of heating electrodes 3, a power supply circuit 4 for independently supplying power to each heating electrode, and an ink cartridge 6 communicating with the plurality of protruding nozzles; the plurality of protruding nozzles correspond to the plurality of heating electrodes one by one, and the position of the heating electrode is at the end where the nozzle contacts the nozzle hole (actually, it can also be above or on the side of the nozzle); the voltage applied to the solution in the ink cartridge satisfies: when the heating electrode is not working, the ink in the ink cartridge will not be ejected due to the electric field force between the ink cartridge and the printing substrate; when the power supply circuit independently supplies power to each heating electrode, different voltages generate unequal resistive heat, so that the temperatures of the solutions in each nozzle are unequal, and thus the surface tension, viscosity, and contact angle are unequal, and thus have different ejection states.

[0032] It should be noted that a hole for adding solution is opened at the upper part of the ink cartridge 6, and a groove communicating with the through holes on the nozzle plate 1 is opened at the bottom of the ink cartridge 6 for supplying the solution. There are a plurality of through holes on the nozzle plate 1 and they are connected to the holes of the protruding nozzle 2 to form a solution channel. The heating electrode 3 surrounds the protruding nozzle 2 and is directly connected to the power supply circuit 4. The heating electrode 3 corresponds to the protruding nozzle 2 one by one. Since the solution resistance changes with temperature, different supply voltages correspond to different temperature rises of the protruding nozzle. Different temperature rises result in different ejection states of the electrofluid. By heating the nozzle end, independent control of the ejection state of each nozzle is achieved. The voltage of each heating electrode can be independently adjusted. The heating electrode is made of electrothermal material, and unequal resistive heat is generated by changing the voltage applied to the heating electrode.

[0033] For further explanation, the voltage applied to the heating electrode changes with different working solutions. Different solutions have different specific heat capacities, and the energies required to raise the same temperature are not equal; at the same time, the surface tension coefficients and viscosities of different solutions change differently with temperature. By heating the local solution at the protruding nozzle 2, its ejection resistance is reduced. When the ejection resistance is less than the electric field force between the ink cartridge and the printing substrate, the solution ejects and the nozzle opens.

[0034] The protruding nozzle 2 can concentrate the electric field and reduce the starting voltage of ejection. When performing inkjet printing, first apply a voltage to the solution in the ink cartridge to form a Taylor cone at the nozzle tip, and then energize the heating electrode to make the nozzle start to eject. The starting voltage of the inkjet head in this embodiment is lower than that of the existing electrofluid ejection controlled by an electrode ring. The heating electrode 3 serves as an auxiliary energy source during the operation of the inkjet head to control the ejection of the ink liquid, acting as an ink liquid ejection switch, which can reduce the working voltage of the inkjet head by 20% - 30% and reduce the requirement for the high-voltage power supply.

[0035] As a preferred embodiment, the heating electrode 3 and the power supply circuit 4 are processed below the nozzle plate 1. The processing methods used are evaporation or magnetron sputtering. The selected heating electrode material is iron-nickel alloy, and the power supply circuit material is gold.

[0036] The material used for the heating electrode 3 should have the characteristic of rapid temperature rise to meet the fast response requirements of the nozzle. Therefore, materials such as iron-nickel alloy, nickel-chromium alloy, hafnium diboride, polysilicon, tantalum aluminum (oxygen, nitrogen), etc. can be selected.

[0037] As a preferred embodiment, the maximum working voltage of the heating electrode 3 does not exceed 100V, and the maximum working temperature does not exceed 200 °C to avoid premature aging of the inkjet head caused by high temperature.

[0038] As a preferred embodiment, the heating electrode is a closed or open-loop electrode that surrounds the periphery of the protruding nozzle; alternatively, the heating electrode is a thin film attached to the inner wall of the protruding nozzle or the inner wall of the nozzle cavity above it, such as Figure 3 shown, the heating electrode is arranged within the flow channel wall; additionally, according to application requirements, the resistance of the heating electrode is adjusted by changing the resistance material and resistance geometry.

[0039] As a preferred embodiment, there are multiple power supply circuits, which correspond to the heating electrodes one by one. The power supply circuits are separated from each other. Each power supply circuit has a pin at its distal end, and is connected to an external circuit through the pin and a switch to independently control whether the heating electrode operates or not.

[0040] The power supply circuits are separated from each other, enabling independent adjustment of the voltage of each heating electrode. And each power supply branch is independently controlled by a switch to independently control the ejection of the solution in each protruding nozzle.

[0041] As a preferred embodiment, the nozzle further includes an insulating layer provided on the heating electrode and the power supply circuit.

[0042] The insulating layer 5 covers the heating electrode 3 and the power supply circuit 4 to isolate the external solution and prevent conduction between the heating electrodes and between the power supply circuits. The material used for the insulating layer has good insulation and heat resistance.

[0043] It should be noted that the insulating layer 5 covers the heating electrode 3 and the power supply circuit 4 to prevent the overflowing solution from causing conduction between the circuits, but the pins of the power supply circuit 4 need to be left for connection to the external circuit.

[0044] As a preferred embodiment, the outer surface of the insulating layer is designed as a micro-ripple structure to increase the contact area with air and improve the heat dissipation effect.

[0045] To describe this embodiment more clearly, the following example is given:

[0046] The heating electrode surrounds the outside of the protruding nozzle 2. The protruding nozzle 2 is prepared by lithography using SU-8 photoresist. The outer diameter of the nozzle is 50μm, the height is 100μm, the pitch is 300μm, and the number of nozzles is 8. The heating electrode 3 is made of iron-nickel alloy material, and a perforated PI tape is used as a mask and prepared by magnetron sputtering. Its outer diameter is 100μm and the thickness is 200nm. The power supply circuit 4 is also prepared by magnetron sputtering, the material is gold, the width is 40μm, and the thickness is 200nm. The insulating layer 5 uses Teflon material and is prepared by evaporation. The ink cartridge 6 uses acrylic material and is prepared by 3D printing.

[0047] When using a nozzle for inkjet printing, first make the solution uniformly reach the tips of each nozzle to wet the nozzles. Then apply a pulsed voltage to the solution, and this voltage is less than the starting voltage of the nozzle. Apply a voltage to the heating electrode and adjust the magnitude of the voltage to find the voltage value at which the nozzle starts to eject. According to the printing requirements, heat the corresponding nozzles and then cooperate with the moving workbench to perform patterned printing.

[0048] When the solution in the nozzle is electrified but the heating electrode is not electrified, the electric field force is less than the ejection resistance, and the liquid surface sags but does not eject; after the heating electrode is also electrified, the temperature of the solution rises, the surface tension coefficient decreases, the ejection resistance decreases, and after the electric field force is greater than the ejection resistance, the liquid surface ejects. As Figure 4 shown, by electrifying the heating electrode of a specific nozzle, the independent controllability of the array nozzle can be achieved. ( Figure 4 In, the heating electrodes of the 2nd, 3rd, 6th, and 7th nozzles from the left are electrified, and the other nozzles are not)

[0049] For ethylene glycol ink, the opening voltage of the nozzle at room temperature of 25 °C is 1200V. When using the nozzle, it is necessary to first pre-print to explore the appropriate voltage value of the heating electrode. Apply a voltage of 1000V to the whole solution, then electrify a specific heating electrode and gradually increase the voltage until the nozzle ejects stably, and record this voltage value. Use this voltage value as the working voltage of the heating electrode to start formal printing. If you want to adjust the size of the jet, you can change the working voltage of the heating electrode.

[0050] Embodiment 2

[0051] A printing system adopts an array electrohydrodynamic nozzle based on independent heating and adjustment of each nozzle as described above.

[0052] The related technical solutions are the same as those in Embodiment 1 and will not be elaborated here.

[0053] Those skilled in the art can easily understand that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. An array electrohydrodynamic nozzle based on independent heating and adjustment of each nozzle, characterized in that, Comprising: A nozzle plate, a plurality of protruding nozzles arrayed on the nozzle plate, a plurality of heating electrodes corresponding to the plurality of protruding nozzles one by one, a power supply circuit for independently supplying power to each heating electrode, and an ink cartridge communicating with the plurality of protruding nozzles; Each heating electrode is used to independently heat the corresponding protruding nozzle; the voltage applied to the solution in the ink cartridge satisfies: when the heating electrode is not working, the ink in the ink cartridge will not be ejected due to the electric field force between the ink cartridge and the printing substrate; and when the power supply circuit independently supplies power to each heating electrode, different supply voltages generate unequal resistive heats, so that the temperatures of the solutions in the protruding nozzles corresponding to the heating electrodes are unequal, so as to have different ejection states; It further includes an insulating layer provided on the heating electrode and the power supply circuit, and the insulating layer adopts a design for enhancing heat dissipation, and the outer surface is designed as a micro-ripple structure.

2. The arrayed electrohydrodynamic nozzle according to claim 1, characterized in that, The material of the heating electrode is iron-nickel alloy, nickel-chromium alloy, hafnium diboride or polysilicon.

3. The arrayed electrohydrodynamic nozzle according to claim 1, characterized in that The maximum operating voltage of the heating electrode does not exceed 100V, and the maximum operating temperature does not exceed 200°C.

4. The arrayed electrohydrodynamic nozzle according to claim 1, wherein The heating electrode is a closed or unclosed annular electrode surrounding the periphery of the protruding nozzle; or the heating electrode is a thin film attached to the inner wall of the protruding nozzle or the inner wall of the nozzle cavity above the inner wall of the protruding nozzle; According to application requirements, the resistance value of the heating electrode is adjusted by changing the resistance material and the resistance geometric size.

5. The arrayed electrohydrodynamic nozzle according to claim 1, wherein There are a plurality of the power supply circuits, corresponding to the heating electrodes one by one, and the power supply circuits are separated from each other. Each power supply circuit is provided with pins at the distal end, and is connected to an external circuit through the pins and a switch to independently control the operation of the heating electrode.

6. A printing system, characterized in that, An arrayed electrohydrodynamic nozzle using the arrayed electrohydrodynamic nozzle for independent heating adjustment of each nozzle according to any one of claims 1 to 5.

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