Atmospheric pressure plasma electrode, surface treatment apparatus, and surface treatment method for filaments

Abstract

The present invention provides an atmospheric pressure plasma electrode and surface treatment apparatus for performing atmospheric pressure plasma treatment on filaments without damaging them. [Solution] An atmospheric pressure plasma electrode for modifying the surface of a filament, comprising two or more drive electrodes and two or more ground electrodes, wherein the drive electrodes and ground electrodes are arranged alternately next to each other with a dielectric material in between, forming an annular structure with open ends, the space inside the annular structure is a plasma processing space through which the filament passes, and the portion of either one or both of the adjacent drive electrodes and ground electrodes facing the plasma processing space is covered with the dielectric material.

Description

Technical Field

[0001] The present invention relates to an atmospheric pressure plasma electrode used for surface treatment of a yarn body, a surface treatment apparatus provided with the atmospheric pressure plasma electrode, and a method for surface treatment of a yarn body.

Background Art

[0002] Yarn bodies are widely used as materials for various products. Examples include fabrics such as woven and knitted fabrics, fishing nets, mesh fabrics, ropes, hollow fiber filters, and the like. For the purpose of imparting special functions to these products, various surface treatments may be performed. Methods such as performing surface treatment on the processed product and methods of processing the yarn body subjected to surface treatment to produce a product are used, and are appropriately selected according to the functions and purposes required for the product. Among them, the method of using a yarn body subjected to surface treatment is preferably used in applications where it is required that each yarn body is subjected to surface treatment, and various treatment methods have been proposed conventionally.

[0003] Patent Document 1 discloses a technique for performing surface treatment by ejecting plasma from a torch-shaped plasma generation source and directly exposing a yarn body being conveyed to the plasma flame.

[0004] Patent Document 2 discloses a technique for treating the surface of a yarn body by generating plasma between the electrodes of a parallel plate type plasma electrode and passing the yarn body therethrough.

[0005] Patent Document 3 discloses a technique for performing surface treatment of an object to be treated by providing a rod-shaped counter electrode near the center of a cylindrical electrode and generating plasma inside the cylinder.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

[0007] However, in the surface treatment method described in Patent Document 1, the filament is directly exposed to a high-density plasma, which can expose the filament to thermal or electrical damage, potentially destroying it if it is made of a delicate material.

[0008] Furthermore, in the surface treatment method described in Patent Document 2, plasma is generated between the two electrodes, so the portion of the filament facing the electrode plate in the circumferential direction is strongly treated, while the portion 90 degrees out of phase from there (the portion not facing the electrode plate) tends to be treated less strongly, which can result in uneven treatment in the circumferential direction of the filament. Moreover, because the structure involves the filament existing between electrode plates to which a high voltage is applied, the filament is transported in a strong electric field, penetrating the electric field lines between the electrode plates, which can cause electrical damage, and in the worst case, the filament may break due to discharge.

[0009] Furthermore, in the surface treatment method described in Patent Document 3, plasma is generated by an electric field between a cylindrical electrode and a rod-shaped electrode, and the substrate between the electrodes is treated. Therefore, similar to Patent Document 2, there is a concern that the object being treated may suffer electrical damage.

[0010] This invention has been made in view of the above-mentioned problems, and provides an atmospheric pressure plasma electrode that can perform surface treatment while suppressing damage to filaments and can be applied to delicate filaments, a surface treatment apparatus equipped with the atmospheric pressure plasma electrode, and a surface treatment method. [Means for solving the problem]

[0011] [1] The present invention, which solves the above problems, is an atmospheric pressure plasma electrode for modifying the surface of a filament, With two or more drive electrodes and two or more ground electrodes, the drive electrodes and ground electrodes are arranged alternately next to each other with a dielectric in between, forming an annular structure with open ends. The space inside the above-mentioned annular structure is a plasma processing space through which the filamentous material passes. Either one or both of the adjacent drive electrode and ground electrode are covered with the dielectric material in the portion facing the plasma processing space.

[0012] The atmospheric pressure plasma electrode of the present invention is preferably in any of the following embodiments [2] to [5]. [2] The atmospheric pressure plasma electrode of [1], comprising an air supply mechanism for introducing gas into the plasma processing space from one opening of the annular structure. [3] The atmospheric pressure plasma electrode of [1], comprising an exhaust mechanism for discharging the gas from the plasma processing space through one opening of the annular structure. [4] The atmospheric pressure plasma electrode of [1], comprising an air supply mechanism for introducing gas into the plasma processing space from one opening of the annular structure and an exhaust mechanism for discharging the gas from the plasma processing space from the other opening. [5] An atmospheric pressure plasma electrode according to any of the above [1] to [4], wherein, in adjacent driving electrodes and ground electrodes, the shortest distance along the surface of the dielectric from the portion of the driving electrode not facing the plasma processing space to the portion of the ground electrode not facing the plasma processing space is 8 mm or more.

[0013] [6] The present invention, which achieves the above objectives, is a surface treatment apparatus for modifying the surface of a filament, One or more atmospheric pressure plasma electrodes from any of the above [1] to [5] are arranged such that there is a path line for a filament running inside the annular structure, A thread passing through the plasma treatment space described above is subjected to atmospheric pressure plasma treatment.

[0014] [7] The surface treatment apparatus described in [6] above comprises a pair of guide rolls, The path line of the yarn body is defined such that the traveling yarn body reciprocates once or more between the pair of guide rolls. For each of the two or more path lines between the pair of guide rolls, it is preferable that the one or more atmospheric pressure plasma treatment electrodes are arranged side by side along the path line so that the path line is inside the annular structure.

[0015] [8] The present invention for achieving the above object is a surface treatment method for modifying the surface of a yarn body, using the atmospheric pressure plasma electrode according to any one of the above [1] to [5], passing the yarn body through the plasma treatment space to perform plasma treatment on the surface of the yarn body.

[0016] [9] The present invention for achieving the above object is a surface treatment method for modifying the surface of a yarn body, Two or more drive electrodes and two or more ground electrodes are alternately arranged adjacent to each other in a ring shape to form a plasma treatment space surrounded by the drive electrodes and the ground electrodes and having both ends communicating to the outside. Applying a voltage to generate an electric field between the adjacent drive electrode and the ground electrode to generate plasma in the plasma treatment space. Passing the yarn body through the center of the plasma treatment space to perform plasma treatment on the surface of the yarn body.

[0017] In the present invention, the "portion facing the plasma treatment space" of the drive electrode and the ground electrode refers to the portion actually facing the plasma treatment space or the portion that would face the plasma treatment space if the dielectric were removed.

[0018] In the present invention, the "center of the plasma treatment space" refers to the geometric center in the plane orthogonal to the yarn conveyance direction of the plasma treatment space.

[0019] In the present invention, the "shortest distance between the two electrodes along the surface of the dielectric" refers to the length that becomes the shortest when the distance between the two electrodes is measured along the surface of the dielectric as shown in FIG. 4.

Effect of the Invention

[0020] According to the present invention, an atmospheric pressure plasma electrode capable of performing necessary surface treatment without damaging the filament body, a surface treatment apparatus provided with the atmospheric pressure plasma electrode, and a surface treatment method are provided.

Brief Description of the Drawings

[0021] [Figure 1] FIG. 1 is a schematic cross-sectional view showing the configuration of the atmospheric pressure plasma electrode of the present invention. [Figure 2] FIG. 2 is a view taken along the line A-A of FIG. 1. [Figure 3] FIG. 3 is a schematic view of a surface treatment apparatus using the atmospheric pressure plasma electrode of the present invention. [Figure 4] FIG. 4 is a diagram for explaining "the shortest distance between both electrodes along the surface of the dielectric". [Figure 5] FIG. 5 is a schematic view of a surface treatment apparatus in which a plurality of atmospheric pressure plasma electrodes of the present invention are arranged in a spiral shape on the pass line of a filament body configured between guide rolls. [Figure 6] FIG. 6 is a schematic view of the corona treatment electrode used in Comparative Example 1.

Embodiments for Carrying Out the Invention

[0022] Hereinafter, examples of embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing the configuration of the atmospheric pressure plasma electrode of the present invention. Two drive electrodes 1 and two ground electrodes 2 are alternately adjacent to each other through a dielectric 3 and arranged side by side to form an annular structure 8 with both ends open. The two drive electrodes 1 and the two ground electrodes 2 are each connected to a high-frequency power source 5, and further, the two ground electrodes 2 are grounded. The space inside the annular structure 8 is a plasma treatment space 4. The drive electrode 1 and the ground electrode 2 are each held in a state of being electrically insulated from each other by a plate support 6, and this extends in the depth direction of the paper surface.

[0023] When the required voltage is applied between the drive electrode 1 and the ground electrode 2 using the high-frequency power supply 5, the gas in the plasma processing space 4 is ionized and discharge begins. At this time, the dielectric 3 covering the portion of the ground electrode 2 facing the plasma processing space 4 blocks the current, preventing a transition to an arc discharge accompanied by a momentary large current. Instead, a non-equilibrium atmospheric pressure plasma is generated in the plasma generation region 7, mainly at the four corners of the plasma processing space 4.

[0024] In Figure 1, a plate-shaped dielectric 3 is sandwiched between the driving electrode 1 and the ground electrode 2. However, the dielectric 3 may also be placed on the portion of the driving electrode 1 facing the plasma processing space 4, and that portion may be covered with the dielectric 3. Alternatively, the portion of the ground electrode 2 facing the plasma processing space 4 may not be covered with the dielectric 3, while the portion of the driving electrode 1 facing the plasma processing space 4 may be covered with the dielectric 3. Alternatively, the entire surface of the driving electrode 1 or the ground electrode 2, or the entire surfaces of both the driving electrode 1 and the ground electrode 2, may be covered with the dielectric 3. In any of these configurations, the same effect as the configuration in Figure 1 can be obtained.

[0025] Here, "required voltage" refers to the voltage at which the gas between electrodes breaks down and glow discharge begins in a typical parallel-plate dielectric barrier electrode, and its magnitude increases as the distance between electrodes increases. In the atmospheric pressure plasma electrode of the present invention, the driving electrode 1 and the ground electrode 2 are placed adjacent to each other with a dielectric 3 in between, so the distance between electrodes can be minimized to the thickness of the dielectric 3, and discharge can be performed at a lower voltage while utilizing the surface discharge phenomenon.

[0026] In the plasma processing space 4, the electric field generated by the high-frequency power supply 5 converges between the drive electrode 1 and the ground electrode 2, being strongest at the four corners where the distance between the electrodes is small, and gradually weakening as you move away from the corners. Furthermore, the electric field strength is zero between the drive electrodes 1 and between the ground electrodes 2, as they are at the same potential. Due to this spatial electric field strength distribution, the vicinity of the plasma generation region 7 becomes a region with a strong electric field that is necessary and sufficient for plasma generation, and the electric field strength is almost zero near the central axis of the plasma processing space 4, theoretically creating a region through which no electric field lines pass. By performing atmospheric pressure plasma processing while passing a thread through the center of the plasma processing space 4 configured in this way, plasma processing can be performed without causing electrical damage to the thread being processed. Note that the same effect can be obtained by using two or more pairs of drive electrodes 1 and ground electrodes 2, arranged alternately.

[0027] The drive electrode 1 and the ground electrode 2 can be made of metal materials as appropriate. From the viewpoint of electrical conductivity and thermal conductivity, aluminum, copper, and their alloys are preferably used, and from the viewpoint of durability such as corrosion resistance, stainless steel or various metal materials with a plated coating can also be used.

[0028] It is preferable to offset the driving electrode 1 and the ground electrode 2 so that their ends in the depth direction of the paper are not in the same location. This is because the edges of the plate experience electric field concentration, and if the edges are aligned in the same location, it is likely to become a starting point for abnormal discharge.

[0029] The plate thickness of the drive electrode 1 and the ground electrode 2 is a parameter that determines the volume of the plasma processing space 4. A thinner plate allows for an expansion of the plasma generation region 7 within the plasma processing space 4, thus contributing to improved processing efficiency. On the other hand, a thinner plate thickness increases handling risks, such as contact with the walls during the transport of the filament, and also restricts the amount of gas that can circulate inside the plasma processing space 4. Therefore, a plate thickness of 1 mm to 5 mm is preferable.

[0030] When discharging at high power for an extended period, the drive electrode 1 and ground electrode 2 may become hot due to the heat of the plasma. Therefore, various cooling structures may be provided to maintain the temperatures of the drive electrode 1 and ground electrode 2 below a certain level.

[0031] The dielectric 3 can be made of various dielectric materials such as ceramics, glass, or resin. The thickness of the dielectric 3 must be set to a thickness that has sufficient insulating strength to withstand the applied voltage, but if it is too thick, the voltage required for discharge will increase, so it should be selected appropriately based on the balance between the dielectric strength and the voltage during discharge. The thickness of the dielectric 3 is preferably 0.05 mm to 1.5 mm.

[0032] The high-frequency power supply 5 is a discharge power supply for generating atmospheric pressure plasma. A power supply capable of oscillating various voltage waveforms such as sine waves, square waves, and pulse waves at high frequencies of 1 kHz or higher is preferably used. In Figure 1, the grounding electrode 2 is connected to earth, but if a power supply capable of so-called floating output, where the drive circuit is disconnected from earth, is used, it is not always necessary to connect the grounding electrode 2 to earth.

[0033] Various insulating materials can be used for the electrode plate support 6. The electrode plate support 6 has the function of supporting the drive electrode 1 and the ground electrode 2, and insulation between the two electrodes is ensured by manufacturing it from an insulating material. Alternatively, the electrode plate support 6 can be manufactured from a conductive material and then structurally configured to ensure electrical insulation from the drive electrode 1 and the ground electrode 2. Due to manufacturing precision issues, tiny gaps may occur between the drive electrode 1, the ground electrode 2, and the dielectric 3, and abnormal discharge may occur within these tiny gaps. Also, abnormal surface discharge may travel along the surface of the dielectric 3 and penetrate between the dielectric 3 and the electrode plate support 6. In this case, to avoid electrical conductivity between the drive electrode 1 and the ground electrode 2 due to a decrease in the insulating performance of the dielectric 3 surface or between the drive electrode 1 and the ground electrode 2, it is preferable to use a material with high arc resistance.

[0034] Figure 2 is a view taken along arrow AA in Figure 1. Both ends of the annular structure 8 are openings 9. The openings 9 are the entrances and exits to the plasma processing space 4 in Figure 1. The filament is introduced through one opening 9, subjected to plasma processing inside the plasma processing space 4, and then transported to be discharged through the other opening 9.

[0035] In Figure 2, the driving electrode 1 is longer than the ground electrode 2, but the ground electrode 2 can also be made longer. As mentioned above, it is preferable to avoid arranging both electrodes with equal lengths and their ends aligned.

[0036] The length of the dielectric 3 is preferably equal to or greater than the length of the longer of the driving electrode 1 or the ground electrode 2. If it is shorter, the two exposed electrodes will be in close proximity to each other, which can become the starting point for abnormal discharge. Even if the dielectric is covered to such an extent that the two exposed electrodes are not in close proximity to each other, if the applied voltage is too high, an abnormal surface discharge phenomenon may occur in which current flows along the surface of the dielectric like an arc discharge. The likelihood of this phenomenon occurring changes depending on various parameters such as the dielectric constant of the dielectric 3, the magnitude of the applied voltage, and the humidity of the surrounding atmosphere, but according to the inventors' knowledge, it is preferable to set the shortest distance L between the two electrodes along the surface of the dielectric 3, as illustrated in Figure 4, to 8 mm or more. By setting the length of the dielectric 3 so that the shortest distance L is 8 mm or more, it becomes easier to suppress the occurrence of the surface discharge phenomenon.

[0037] Preferably, the gas inside the plasma processing space 4 is replaced by an air supply mechanism or exhaust mechanism (not shown) provided at one of the openings 9. By removing the gas that has finished reacting from inside the plasma processing space 4 and introducing new undecomposed gas to ionize it, the inside of the plasma processing space 4 can be kept in an active state. When new gas is introduced from the air supply mechanism, the gas that has finished reacting is pushed out from the opening 9 on the side where the air supply mechanism is not provided. Alternatively, when the gas that has finished reacting is sucked out from the exhaust mechanism, undecomposed air is sucked in from the opening 9 on the side where the exhaust mechanism is not provided. This replaces the gas inside the plasma processing space 4. More preferably, by providing an air supply mechanism at one opening 9 and an exhaust mechanism at the other opening 9, the gas inside the plasma processing space 4 can be actively replaced by introducing undecomposed gas from the air supply mechanism while exhausting the reacted gas from the exhaust mechanism.

[0038] The gas introduced from the air supply mechanism is generally the atmosphere. Depending on the purpose of the treatment, various gases can be selected, such as active gases like oxygen and hydrogen, inert gases like nitrogen and argon, and reactive gases mainly composed of compounds such as nitrogen oxides. When using a gas other than the atmosphere, it is preferable to control the gas concentration inside the plasma treatment space 4 by appropriately adjusting the supply and exhaust balance, including the amount of gas introduced from the air supply mechanism and the amount of gas discharged from the exhaust mechanism, and the amount of gas leaking to the outside from the openings 9 on both sides.

[0039] Figure 3 is a schematic diagram of a surface treatment apparatus using an atmospheric pressure plasma electrode according to the present invention. A filament 33 is supplied from a filament supply mechanism 31, plasma-treated while passing through the annular structure 8 that constitutes the atmospheric pressure plasma electrode 35, and guided by a guide 34 to be collected by a filament recovery mechanism 32.

[0040] The yarn supply mechanism 31 can be any mechanism that feeds out yarn for atmospheric pressure plasma treatment with the atmospheric pressure plasma electrode 35. It may be an unwinding mechanism that feeds out yarn from a bobbin on which it is wound, a spinning mechanism that melts raw materials and spins them or spins them from raw cotton, or a processing mechanism that applies some kind of processing to the yarn, such as coating, washing, or crimping.

[0041] The filament recovery mechanism 32 can be any mechanism that recovers the filament that has been treated with atmospheric pressure plasma by the atmospheric pressure plasma electrode 35. It may be a winding mechanism that takes in and winds up the filament, or it may be a processing mechanism that applies some kind of processing to the filament, such as coating, washing, or crimping.

[0042] The guide 34 guides the filament 33 to the atmospheric pressure plasma electrode 35. The guide 34 can be a rod-shaped or ring-shaped structure that guides the direction of travel of the filament along its guide surface, or a cylindrical surface that rotatably holds the filament and guides it while it rotates. However, it is preferable to use a guide 34 with a structure that prevents friction between the guide surface of the guide 34 and the surface of the filament 33.

[0043] Although only one atmospheric pressure plasma electrode 35 is shown in Figure 3, a structure in which multiple atmospheric pressure plasma electrodes 35 are provided between two guides 34 and the filament 33 is transported by passing through them sequentially is also possible. In that case, the processing strength can be improved compared to when processing with a single atmospheric pressure plasma electrode, and the transport speed of the filament 33 can also be improved by the amount by which the processing strength can be increased.

[0044] Figure 5 is a schematic diagram of a surface treatment apparatus in which multiple atmospheric pressure plasma electrodes of the present invention are arranged on a pass line of a spirally arranged filament between guide rollers. As shown in Figure 5, a technique is generally known in which a guide roller having a length in the direction of the cylindrical axis is used as a guide 34, and a filament 33 is wound spirally between two guide rollers to improve the frictional force between the guide roller surface and the filament. The configuration in which the pass line of the filament 33 is configured to reciprocate between the guide rollers, and one or more atmospheric pressure plasma electrodes 35 are provided on each of the multiple pass lines of the filament 33 reciprocating between the guide rollers, is preferable because it can improve the treatment strength without increasing the size of the apparatus. [Examples]

[0045] The surface treatment apparatus of the present invention will be described in the following examples, but the present invention is not limited to these examples.

[0046] [Example 1] An atmospheric pressure plasma electrode, as shown in Figure 1, was fabricated, and a polyolefin monofilament in motion was surface-treated. Experiments were then conducted to evaluate the pure water contact angle by arranging the treated filaments in a planar configuration, thereby verifying the effect of the surface treatment on the filament.

[0047] Aluminum alloy was used for the drive electrode and ground electrode, a 0.3 mm thick laminated mica sheet formed from flake-shaped mica with silicone resin as a binder was used as the dielectric, and PTFE was used for the electrode holder. The plasma processing space was designed to be 3 mm long x 3 mm wide x 90 mm long.

[0048] Polyolefin monofilaments with a wire diameter of 0.3 mm to 0.4 mm were used, transported at a conveying speed of 2.0 m / min, passing through the center of the plasma-treated space cross-section, and wound with a winding tension of 7 g ± 2 g.

[0049] The atmospheric pressure plasma electrode was driven with a 30 kHz alternating pulse voltage, and the pulse width was adjusted so that the load-side peak voltage was ±3.5 kV and the peak current was ±0.8 A. The load-side effective power at this time was 667 W.

[0050] In Example 1, no air supply or exhaust mechanism was provided, and gas replacement within the plasma processing space was left to chance.

[0051] The fibers treated with atmospheric pressure plasma were cut to a length of approximately 5 cm and arranged in one direction to form a 5 cm x 1 cm sheet. When 2 μL of pure water was dropped onto this sheet and the contact angle was measured, the pure water contact angle was approximately 90°. Furthermore, no fiber breakage occurred during the experiment. The pure water contact angle of the sample that had not been treated with atmospheric pressure plasma was 110°.

[0052] [Example 2] The experiment was conducted under the same conditions as in Example 1, except that a supply mechanism and an exhaust mechanism were provided to replace the gas in the plasma processing space, and nitrogen gas was introduced at a rate of 15 L / min through the supply mechanism and exhausted at a rate of 10 L / min through the exhaust mechanism. As a result, the pure water contact angle was approximately 80°, and no thread breakage occurred during the experiment.

[0053] [Comparative Example 1] In the experimental setup of Example 1, the atmospheric pressure plasma electrode was replaced with the corona-treated electrode shown in Figure 6. The corona-treated electrode used a driving electrode consisting of a ceramic pipe 61 with an outer diameter of approximately 20 mm and a thickness of approximately 2 mm, with a metal block 62 measuring 10 mm wide and 100 mm long inserted inside. A metal plate 63 was used as the counter electrode.

[0054] The discharge area was approximately 10 mm x 100 mm, and the setup was designed to transport the filament in the 100 mm length direction. The electrode gap was set to approximately 1 mm, and the filament was transported to the center of the electrode gap. The corona electrode was driven with a sinusoidal voltage of approximately 37 kHz, and a peak voltage of ±5 kV was applied to the load side. The effective power on the load side at this time was 201 W.

[0055] In the same manner as in Example 1, a surface treatment was performed on a polyolefin monofilament, and the treatment effect was evaluated. The pure water contact angle was approximately 50°, which was a higher treatment effect than in Example 1. However, a problem of thread breakage occurred frequently immediately after the start of discharge. Through holes were observed in the monofilament at and near the broken parts. After comprehensively considering the shape of the holes and the insulating strength of the material, it was concluded that the current passed through the monofilament during the discharge, and the resulting Joule heating caused it to burn out.

[0056] [Comparative Example 2] The experiment was conducted under the same conditions as in Comparative Example 1, except that the monofilament transport speed was set to 25 m / min. As a result, the pure water contact angle was approximately 90°, and thread breakage occurred, albeit infrequently. In addition, cases of through-holes occurring without thread breakage were also observed. [Industrial applicability]

[0057] The atmospheric pressure plasma electrode of the present invention can be suitably used for surface treatment of filaments for the purpose of surface modification of delicate materials, but its scope of application is not limited to these applications. [Explanation of Symbols]

[0058] 1. Driving electrode 2 Ground electrode 3 Dielectrics 4 Plasma processing space 5 High frequency power supply 6 Plate support 7 Plasma generation region 8. Ring-shaped structures 9 aperture 31 Thread supply mechanism 32. Fibre retrieval mechanism 33 filaments 34 Guide 35 Atmospheric pressure plasma electrode 61 Ceramic Pipe 62 Metal block (drive electrode) 63. Metal plate (counter electrode) L is the shortest distance between the two electrodes along the surface of the dielectric.

Claims

1. An atmospheric pressure plasma electrode for modifying the surface of a filamentous body, With two or more drive electrodes and two or more ground electrodes, the drive electrodes and ground electrodes are arranged alternately next to each other with a dielectric in between, forming an annular structure with open ends. The space inside the aforementioned annular structure is a plasma processing space through which the filament passes. An atmospheric pressure plasma electrode in which either or both of the adjacent drive electrode and ground electrode are covered with the dielectric material in the portion facing the plasma processing space.

2. The atmospheric pressure plasma electrode according to claim 1, further comprising an air supply mechanism for introducing gas into the plasma processing space from one opening of the annular structure.

3. The atmospheric pressure plasma electrode according to claim 1, further comprising an exhaust mechanism for discharging gas from the plasma processing space through one opening of the annular structure.

4. The atmospheric pressure plasma electrode according to claim 1, comprising an air supply mechanism for introducing gas into the plasma processing space from one opening of the annular structure, and an exhaust mechanism for discharging the gas from the plasma processing space from the other opening.

5. The atmospheric pressure plasma electrode according to claim 1, wherein, between adjacent drive electrodes and ground electrodes, the shortest distance along the surface of the dielectric from the portion of the drive electrode not facing the plasma processing space to the portion of the ground electrode not facing the plasma processing space is 8 mm or more.

6. A surface treatment apparatus for modifying the surface of a filamentous body, One or more atmospheric pressure plasma electrodes according to claims 1 to 5 are arranged such that there is a path line for a filament running inside the annular structure, A surface treatment apparatus for applying atmospheric pressure plasma treatment to a filament that passes through the aforementioned plasma treatment space.

7. Equipped with a pair of guide rolls, The path line of the yarn is defined such that the yarn traveling between the pair of guide rolls makes one or more round trips. The surface treatment apparatus according to claim 6, wherein, for each of the two or more pass lines between the pair of guide rolls, one or more atmospheric pressure plasma treatment electrodes are arranged in a line along the pass line such that the pass line is inside the annular structure.

8. A surface treatment method for modifying the surface of a filament, Using an atmospheric pressure plasma electrode according to any of claims 1 to 5, A method for surface treatment of a filament, comprising passing the filament through the plasma treatment space to perform plasma treatment on the surface of the filament.

9. A surface treatment method for modifying the surface of a filament, Two or more drive electrodes and two or more ground electrodes are arranged alternately next to each other in a ring shape to form a plasma processing space surrounded by the drive electrodes and the ground electrodes, with both ends open to the outside. A voltage is applied to generate an electric field between adjacent drive electrodes and ground electrodes, thereby generating plasma in the plasma processing space. A method for surface treatment of a filament, comprising passing the filament through the center of the plasma treatment space and applying plasma treatment to the surface of the filament.

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