Coaxial metal electrode plasma discharge device

Abstract

The present invention provides a coaxial metal electrode plasma discharge device, which includes a positive electrode and a negative electrode coaxially arranged in a reaction chamber. The plasma generation region is located between the positive electrode and the negative electrode. This coaxial double-electrode structure can obtain a truly co-flow plasma under a low-pressure vacuum state. A plurality of through holes are formed on the surface of the positive electrode. Most of the electrons and ions of the co-flow plasma are confined to oscillate back and forth between the electrodes, and more active groups such as metastable atoms, excited molecules, and free radicals gather outside the positive electrode through the through holes and contact and react with the material. The present invention is designed according to the principle of co-flow plasma discharge. Since there is no shielding and blind area during the reaction, and the discharge is stable with good uniformity, it is sensitive to the surface temperature of the material. In particular, it has great advantages in the cleaning, activation, polymerization, etc. of polymer material sheets and films, and has broad industrial application prospects.

Description

Technical Field

[0001] The present invention relates to a plasma discharge device, in particular to a coaxial metal electrode plasma discharge device. Background Art

[0002] Low-temperature plasma, also known as non-equilibrium plasma, is a physical state different from solids, liquids, and gases. This aggregated state is composed of atoms, molecules, excited atoms and molecules, ions, electrons, photons, and free radical groups. During the plasma discharge process, although the electron temperature is very high, the temperature of heavy particles (such as ions, atoms, etc.) is very low, and the whole system presents a low-temperature state. This characteristic enables low-temperature plasma to exhibit high activity in chemical reactions and will not cause great damage to the material body. Therefore, it is widely used in many material processing fields such as surface cleaning, activation, deposition, and polymerization.

[0003] Compared with traditional chemical reaction methods, the low-temperature plasma generated by a plasma discharge device not only has a richer variety of active particles and stronger activity, but also is more likely to react with the surface of the contacted material and various gases. As a gas discharge method, the low-pressure vacuum plasma discharge technology has an equipment principle of maintaining a certain vacuum degree in a vacuum reaction chamber and applying a high-frequency voltage to the electrodes to excite gas ionization and generate glow plasma. This technology has high flexibility and can meet the requirements of various material surface treatments by adopting different discharge structures, introducing diverse process gases, and adjusting parameters such as power, time, and air pressure. However, there are still several problems that are difficult to solve in the prior art. For example, most traditional low-pressure vacuum plasma discharge devices use flat electrodes, and the anode plate and the cathode plate are placed vertically or horizontally. When processing large-area sheet materials or thin film materials, due to electrode shielding, the plasma discharge is uneven, which in turn affects the surface treatment effect of the material. The prior art also uses multiple columnar electrodes for material processing and controls the electrode temperature through water cooling, but a relatively high gas temperature will still be generated between the two electrodes, which will have an adverse impact on temperature-sensitive materials, especially polymer sheets and thin films, and it is impossible to achieve ideal cleaning, activation, and polymerization effects. At the same time, there is also a risk of plasma metal sputtering. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a coaxial metal electrode plasma discharge device, including a box body, and a reaction inner cavity is arranged inside the box body;

[0005] A gas input component for introducing process gas into the reaction inner cavity;

[0006] A plasma generation component for providing excitation energy to the reaction inner cavity to ionize the process gas to generate plasma;

[0007] A vacuum generating assembly for providing and maintaining a vacuum reaction environment in a reaction chamber;

[0008] And at least one set of electrode feeding assemblies disposed in the reaction chamber for connecting the reaction chamber and the plasma generating assembly. Each set of electrode feeding assemblies consists of a columnar cathode and an anode coaxially sleeved outside the cathode to generate plasma between the cathode and the anode, and a plurality of through holes are arranged along the circumference of the anode.

[0009] Further, the through holes are obtained by punching holes in the side wall of a metal pipe fitting.

[0010] Further, the anode is prepared by welding a metal screen.

[0011] Further, the inner diameter of the cathode is 12 - 24 mm, and the wall thickness is 4 - 7 mm; the inner diameter of the anode is 18 - 56 mm, and the wall thickness is 4 - 6 mm; the size difference between the inner diameter of the anode and the outer diameter of the cathode is 5 - 30 mm.

[0012] Further, mounting plates are provided on both sides of the reaction chamber of the box body. The two ends of the anode are connected to the inner side of the mounting plate, and the two ends of the cathode extend out of the box body.

[0013] Further, the gas input assembly includes a gas source, and the gas source is connected to the reaction chamber through an intake pipeline; a flow meter for monitoring the gas flow and a solenoid valve for controlling the on / off of the intake pipeline are connected to the intake pipeline. The flow meter and the solenoid valve are electrically connected to a control center to control the input of process gas according to the instructions of the control center.

[0014] Further, the plasma generating assembly includes a matcher connected to the side of the box body. The matcher is connected to a plasma generator through a signal line. The pulse frequency of the plasma generator is 25 - 100 kHz, and the industrial frequency bands are 2 MHz, 15.56 MHz, 27.12 MHz, 40.68 MHz, and 60 MHz.

[0015] Further, the vacuum generating assembly includes a vacuum pump disposed outside the box body, and the vacuum pump is connected to the reaction chamber through a vacuum pipeline. A vacuum gauge for monitoring and feedbacking the vacuum degree is installed on the side wall of the box body to monitor and feedback the vacuum degree in the reaction chamber in real time.

[0016] Further, a temperature control assembly is also provided. The temperature control assembly includes a temperature control source disposed outside the box body. A liquid medium is loaded in the temperature control source, and the temperature control source transmits the liquid medium to each cathode through a circulation pipeline.

[0017] Further, conduits for connecting the circulation pipeline are provided at both ends of the cathode.

[0018] The present invention provides a coaxial metal electrode plasma discharge device, which includes a box body, a gas input component, a vacuum generation component, a plasma generation component, and a positive electrode and a negative electrode coaxially arranged in a reaction cavity. The area between the positive electrode and the negative electrode is the plasma generation region. This coaxial double-electrode structure can obtain a true co-current plasma under a low-pressure vacuum state. A plurality of through holes are formed on the surface of the positive electrode. Most of the electrons and ions of the co-current plasma are confined to oscillate back and forth between the electrodes, and part of the photons are radiated out. More active groups such as metastable atoms, excited molecules, and free radicals gather outside the positive electrode through the through holes and contact and react with the material, which belongs to non-destructive plasma chemical treatment.

[0019] The present invention is designed according to the principle of co-current plasma discharge. Since there is no shielding and blind area during the reaction, and the discharge is stable and has good uniformity, it is sensitive to the surface temperature of the material. Especially for the cleaning, activation, polymerization, etc. of polymer material sheets and films, it has great advantages and broad industrial application prospects. Description of the Drawings

[0020] Figure 1 is a schematic structural diagram of the coaxial metal electrode plasma discharge device;

[0021] Figure 2 is a schematic diagram of the position of the electrode feeding component in the box body;

[0022] Figure 3 is a schematic diagram of the connection between the electrode feeding component and the mounting plate;

[0023] Figure 4 is a schematic structural diagram of the electrode feeding component;

[0024] Figure 5 is the position of each particle in the electrode feeding component;

[0025] Figure 6 is a schematic diagram of the water contact angle test comparison of a sample material;

[0026] Figure 7 is a schematic diagram of the water contact angle test comparison of another position of the sample material.

[0027] Reference numerals: box body 1, reaction inner cavity 11, door panel 12, observation window 13, mounting plate 14, fastening sleeve 15, lining 16;

[0028] gas input component 2, gas source 21, intake pipeline 22, solenoid valve 23, flowmeter 24;

[0029] vacuum generation component 3, vacuum pump 31, vacuum pipeline 32, vacuum gauge 33;

[0030] Plasma generation component 4, plasma generator 41, matcher 42, signal line 43;

[0031] Electrode feeding component 5, cathode 51, anode 52, through hole 53;

[0032] Temperature control component 6, temperature control source 61, circulation pipeline 62, conduit 63;

[0033] Positive ions a, electrons b, photons c, excited atoms d, excited molecules e, free radicals f. Specific implementation mode

[0034] As Figure 1 shown, the coaxial metal electrode plasma discharge device includes a box body 1. Inside the box body 1, there is a reaction cavity 11 for providing plasma treatment. A gas input component 2, a vacuum generation component 3, and a plasma generation component 4 are connected to the side of the box body 1. The gas input component 2 is used to introduce process gas into the reaction cavity 11; the plasma generation component 4 provides excitation energy to the reaction cavity 11 to ionize the process gas to generate plasma; the vacuum generation component 3 provides and maintains a vacuum reaction environment for the reaction cavity 11.

[0035] As Figure 2 and Figure 4 shown, the box body 1 is generally in the shape of a box with a hollow interior. The reaction cavity 11 is provided with multiple electrode feeding components 5 composed of a cathode 51 and an anode 52. The electrode feeding component 5 is used to connect the plasma generation component 4 and the reaction cavity 11. Both the cathode 51 and the anode 52 are tubular electrodes. Axial sides of the cathode 51 penetrate through both sides of the reaction cavity 11 and are electrically connected to the high-voltage electrode. The anode 52 is sleeved outside the cathode 51 and is grounded. The anode 52 and the cathode 51 are coaxially arranged. The process gas between the anode 52 and the cathode 51 will be ionized to generate plasma under vacuum conditions.

[0036] A plurality of through holes 53 are arranged on the circumference of the anode 52. The anode 52 with the through holes 53 can be obtained by punching holes in the side wall of the metal tube, or by welding a metal material with a mesh structure into a tubular structure. The through holes 53 can be circular, square, polygonal or other special-shaped shapes. The aperture of each through hole 53 is preferably 3 - 10 mm. Combined with Figure 5The working principle of the present invention is as follows: the gas molecules and atoms between the anode electrode 52 and the cathode electrode 51 are excited to the energy level due to the energy obtained. Due to the electric field formed by the electrode feed assembly 5, most of the electrons b and positive ions a generated by the gas ionization are confined in the gap between the anode electrode 52 and the cathode electrode 51 to oscillate back and forth, while the excited atoms d, excited molecules e, free radicals f and other active groups and a small amount of free electrons b will be collected from the through hole 53 to the outside of the anode electrode 52. The excited atoms d and excited molecules e will also radiate part of the photons c of a specific wavelength and color to the outside of the anode electrode 52 when they transition to the ground state. The part of the active groups has certain energy and chemical characteristics with the photons c, and can interact with the atoms or molecules on the surface of the material, implementing a non-destructive plasma chemical treatment process for the material body. The through holes 53 are evenly arranged along the length direction and circumference of the anode electrode 52 to ensure that the active groups outside the anode electrode 52 can be evenly distributed as much as possible.

[0037] The electrode feed components 5 of this embodiment are arranged in two rows along the upper and lower sides of the box body 1. The material is placed on the surface of the anode electrode 52 according to the processing position of the material, and the surface of the electrode feed component 5 is the processing area. For example, if both sides of the material need to be processed, the material can be placed between two rows of electrode feed components 5. Since the anode electrode 52 is a columnar structure, it has only a very small contact area with the surface of the material. There is almost no shielding and blind area when the active ions react with the surface of the material, and the surface of the material can fully react. The electrode feed components 5 of each row are arranged in multiple columns side by side to fully support the material and maintain the uniformity of the reaction of the material everywhere.

[0038] The radius and length of each group of positive electrodes 52 and negative electrodes 51 do not need to be set to be exactly the same, and can be set according to the specific requirements of the product shape and the shape of the reaction cavity 11. For example, each electrode feed assembly 5 is subjected to a diameter reduction treatment for special materials. In this embodiment, the inner diameter of the negative electrode 51 is 12-24 mm, and the wall thickness is 4-7 mm; the inner diameter of the positive electrode 52 is 18-56 mm, and the wall thickness is 4-6 mm; the size difference between the inner diameter of the positive electrode 52 and the outer diameter of the negative electrode 51 is preferably 5-30 mm, and under the above conditions, a better plasma dispersion effect is achieved.

[0039] like Figure 3As shown, the box body 1 is made of metal materials such as aluminum alloy and stainless steel. One side of the box body 1 is open, and a door panel 12 is hinged to the open end face. Materials can be loaded into the reaction inner cavity 11 at this open end face. An observation window 13 is provided on the door panel 12, which can observe the processing state of the materials during the reaction process. On both sides of the reaction inner cavity 11 of the box body 1, mounting plates 14 are provided respectively. Mounting perforations are provided at both ends of each group of electrode feeding assemblies 5 corresponding to the mounting plates 14. The two ends of the positive electrode 52 can be abutted or clamped against the inner side of the mounting plate 14, and then the negative electrode 51 is loaded into the mounting perforation from the outside of the box body 1 to quickly locate the installation position of the negative electrode 51, which is convenient for installation and realizes the coaxial fixation of the positive electrode 52 and the negative electrode 51 at the same time. A fastening assembly is provided at the position of the box body 1 corresponding to the mounting perforation for fixing the two ends of the negative electrode 51. The fastening assembly can adopt common threads or other common fastening methods. In this embodiment, a lining 16 is installed in the installation through hole 53. One end of the lining 16 extends out of the installation through hole 53 and is fixedly connected to the outside of the box body 1, which can prevent the negative electrode 51 from being worn due to direct contact with the pipe wall of the mounting perforation; a fastening sleeve 15 is sleeved outside the negative electrode 51, and the fastening sleeve 15 is radially clamped between the negative electrode 51 and the lining 16. When loading the negative electrode 51 into the installation through hole 53, the fastening sleeve 15 can be sleeved on one side of the negative electrode 51 first. After the negative electrode 51 is in place, the fastening sleeve 15 is clamped in the lining 16; then the lining 16 and the fastening sleeve 15 are installed on the other side of the negative electrode 51 to complete the fixation of the negative electrode 51.

[0040] The gas input assembly 2 includes a gas source 21, and the gas source 21 is connected to the reaction inner cavity 11 through an air inlet pipeline 22. A flowmeter 24 for monitoring the gas flow and an electromagnetic valve 23 for controlling the on-off of the air inlet pipeline 22 are connected to the air inlet pipeline 22. The flowmeter 24 and the electromagnetic valve 23 are electrically connected to the control center to control the input of process gas according to the instructions of the control center.

[0041] The plasma generation assembly 4 includes a matcher 42 connected to the side of the box body 1. The matcher 42 is connected to a plasma generator 41 through a signal line 43. The signal released by the plasma generator 41 drives the high-frequency boost module through the matcher 42, and then high-voltage electric energy is generated. The matcher 42 adjusts the impedance of the matching network to make the output impedance of the high-frequency generator match the load impedance. This high voltage is applied to the electrode feeding assembly 5. When the preset critical value is reached, it will cause the surrounding process gas to be ionized and trigger a discharge phenomenon, and finally generate low-temperature plasma.

[0042] In this embodiment, the plasma generator 41 adopts a sine wave or pulse wave power supply, and the pulse frequency is between 25 - 100 kHz. High-frequency scenarios such as 2 MHz, 15.56 MHz, 27.12 MHz, 40.68 MHz, and 60 MHz are selected in the industrial frequency band.

[0043] The vacuum generating assembly 3 includes a vacuum pump 31 disposed outside the box body 1. The vacuum pump 31 is connected to the reaction inner cavity 11 through a vacuum pipeline 32 to maintain a vacuum environment in the reaction inner cavity 11. A vacuum gauge 33 is installed on the side wall of the box body 1 for real-time monitoring and feedback of the vacuum degree in the reaction inner cavity 11.

[0044] Each part of the electrode feeding assembly 5 provided by the present invention has uniform reactions on the surface of the material, and the temperature difference caused by local reaction differences is small. Therefore, the material can be processed at a relatively appropriate temperature. On this basis, a temperature control assembly 6 is further provided in this embodiment. The temperature control assembly 6 includes a temperature control source 61 disposed outside the box body 1. A liquid medium is loaded in the temperature control source 61, and the liquid medium is transmitted to each negative electrode 51 through a circulation pipeline 62. In this embodiment, cooling water is used as the liquid medium, and heating kerosene or the like can be used when the temperature needs to be increased. Specifically, conduits 63 for connecting the circulation pipeline 62 are provided at both ends of the negative electrode 51. The circulating water enters or exits the negative electrode 51 through the openings of the conduits 63, and heat exchange of the reaction area is achieved through the circulating water, so as to perform plasma treatment in a low-temperature environment.

[0045] The material to be processed by the plasma discharge device is an FEP sheet. Figure 6 and Figure 7 They are respectively schematic diagrams of the water contact angle tests at two positions of the material. Among them, Figure a represents the water contact angle test diagrams before treatment at the two positions, both of which are 106°; Figure b shows the water contact angles obtained by testing at the same positions after treatment with the discharge device provided in this embodiment, which are 41.5° and 40.5° respectively; Figure c shows the water contact angles of 62° and 50.5° obtained by using a conventional square plate type discharge device and performing corresponding tests. It can be seen that the discharge device provided by the present invention can better perform plasma reaction with the material, and the uniformity of each part of the material has been significantly improved.

[0046] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A coaxial metal electrode plasma discharge device, characterized in that: It comprises a box body (1), wherein a reaction cavity (11) is provided inside the box body (1); A gas input component (2) for introducing process gas into the reaction chamber (11); A plasma generating component (4) is used to provide excitation energy to the reaction cavity (11) to ionize the process gas to generate plasma; A vacuum generating assembly (3) for providing and maintaining a vacuum reaction environment for the reaction chamber (11); and a plurality of electrode feed assemblies (5) disposed in the reaction cavity (11) and used to connect the reaction cavity (11) and the plasma generating assembly (4), wherein each electrode feed assemblies (5) is composed of a columnar cathode electrode (51) and an anode electrode (52) coaxially sleeved on the outside of the cathode electrode (51) so as to generate plasma between the cathode electrode (51) and the anode electrode (52), and a plurality of through holes (53) are evenly arranged along the circumference of the anode electrode (52); A temperature control component (6) is also provided, the temperature control component (6) comprising a temperature control source (61) provided outside the box (1), the temperature control source (61) being loaded with a liquid medium, the temperature control source (61) transmitting the liquid medium to each cathode electrode (51) via a circulation pipeline (62).

2. The coaxial metal electrode plasma discharge device according to claim 1, characterized in that: The through hole (53) is obtained by punching a hole in the side wall of the metal pipe.

3. The coaxial metal electrode plasma discharge device according to claim 1, characterized in that: The positive electrode (52) is prepared by welding a metal mesh.

4. The coaxial metal electrode plasma discharge device according to claim 1, characterized in that: The inner diameter of the cathode electrode (51) is 12-24 mm, and the wall thickness is 4-7 mm; the inner diameter of the anode electrode (52) is 18-56 mm, and the wall thickness is 4-6 mm; the size difference between the inner diameter of the anode electrode (52) and the outer diameter of the cathode electrode (51) is 5-30 mm.

5. The coaxial metal electrode plasma discharge device according to claim 1, characterized in that: The box body (1) is provided with mounting plates (14) on both sides of the reaction cavity (11); two ends of the anode electrode (52) are connected to the inner side of the mounting plates (14); and two ends of the cathode electrode (51) extend out of the outer side of the box body (1).

6. The coaxial metal electrode plasma discharge device according to claim 1, characterized in that: The gas input assembly (2) comprises a gas source (21), the gas source (21) being connected to the reaction chamber (11) via an air intake pipeline (22); a flow meter (24) for monitoring the gas flow rate and a solenoid valve (23) for controlling the on-off of the air intake pipeline (22) are connected to the air intake pipeline (22); the flow meter (24) and the solenoid valve (23) are electrically connected to a control center, and the input of the process gas is controlled according to instructions from the control center.

7. The coaxial metal electrode plasma discharge device according to claim 1, characterized in that: The plasma generating assembly (4) comprises a matching device (42) connected to the side of the housing (1); the matching device (42) is connected to the plasma generator (41) via a signal line (43); the pulse frequency of the plasma generator (41) is 25-100 kHz, and the industrial frequency range is 2 MHz, 15.56 MHz, 27.12 MHz, 40.68 MHz, and 60 MHz.

8. The coaxial metal electrode plasma discharge device according to claim 1, characterized in that: The vacuum generating assembly (3) comprises a vacuum pump (31) arranged outside the box (1), and the vacuum pump (31) is connected to the reaction chamber (11) via a vacuum pipeline (32); a vacuum gauge (33) for monitoring and providing feedback of the vacuum degree is installed on the side wall of the box (1), and is used for real-time monitoring and providing feedback of the vacuum degree in the reaction chamber (11).

9. The coaxial metal electrode plasma discharge device according to claim 1, characterized in that: Both end portions of the cathode electrode (51) are provided with conduits (63) for connecting to a circulation pipeline (62).

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