Dielectric barrier discharge plasma generator

Abstract

To provide a dielectric barrier discharge type plasma generator with which it is possible to effectively spray plasma evenly from all regions of a discharge port.SOLUTION: A dielectric barrier discharge type plasma generator comprises: a dielectric substrate that exhibits a planar shape extending in a first direction; a first electrode which is placed contacting a face of the dielectric substrate; a second electrode which is placed, being separated from the dielectric substrate, on the side opposite the side where the first electrode is placed, regarding a second direction which is orthogonal to the first direction; a gas passage formed by a clearance between the dielectric substrate and the second electrode, in which a gas flows in a third direction that is orthogonal to the first and second directions; and a discharge port which is provided at an edge of the gas passage and extends in the first direction. One of the dielectric substrate and the second electrode is placed so as to sandwich the other of the dielectric substrate and the second electrode in the second direction via the clearance.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a dielectric barrier discharge plasma generator. [Background technology]

[0002] Plasma generators are used in manufacturing processes for plastics, paper, fibers, semiconductors, liquid crystals, films, etc. For example, by irradiating a workpiece with plasma from a plasma generator, surface treatments can be performed to improve the hydrophilicity, adhesiveness, or print adhesion of the surface of the workpiece, to remove and clean organic matter present on the surface of the workpiece, or to form an oxide film on the surface of the workpiece.

[0003] Fig. 16 is a cross-sectional view schematically showing a conventional plasma generator. Patent Document 1 discloses a plasma generator 200 including a pair of opposing electrodes (201, 201) in which the opposing surfaces (202, 202) of the electrodes are inclined so that the distance between them becomes narrower as they approach a workpiece 240, as shown in Fig. 16. In other words, the pair of opposing surfaces (202, 202) are arranged so that the distance between them becomes narrower as they approach a bottom opening 226.

[0004] The plasma generator 200 generates a large number of streamer discharges Sd in a region (discharge region 207) sandwiched between a pair of opposing surfaces (202, 202) by applying a voltage between a pair of electrodes (201, 201) while introducing a plasma source gas Gc from an upper surface opening 223. The plasma source gas Gc is introduced into the discharge region 207 from the upper surface opening 223 through an orifice 225 of an injection plate 224. Therefore, the plasma source gas Gc is accelerated by the orifice 225 and injected into the discharge region 207 at high speed. This injection generates a turbulent flow of the plasma source gas Gc, and the streamer discharge Sd is dispersed within the discharge region 207.

[0005] Thereafter, the dispersed streamer discharge Sd generates plasma Pc almost uniformly throughout the entire discharge region 207. The generated plasma Pc is ejected as a plasma jet into the processing space 205 through the lower opening 226 of the discharge region 207 and is sprayed onto the workpiece 240. Patent Document 1 describes that by employing the above configuration, uniform plasma can be generated.

[0006] The upper surfaces and opposing surfaces (202, 202) of the electrodes (201, 201) are covered with a dielectric 203. The thickness of the coating of the dielectric 203 is uniform over the entire surface, and is, for example, 0.5 mm to 5 mm.

[0007] As another method, a device is known that generates plasma by inputting microwaves between a microstrip line and a ground conductor (see Patent Document 2). In this device, impedance matching is performed by adjusting the thickness by providing a gradient to the dielectric layer. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-009890 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-282784 Summary of the Invention [Problem to be solved by the invention]

[0009] The plasma generation device 200 disclosed in Patent Document 1 aims to generate plasma Pc almost uniformly throughout the entire discharge region 207 by generating turbulence. However, for example, plasma Pc generated in a position far from the bottom opening 226 within the discharge region 207 disappears as it moves toward the bottom opening 226. For this reason, when the electrodes (201, 201) are arranged as shown in FIG. 16, the plasma Pc blown out from the bottom opening 226 is not uniformly irradiated from the entire area of ​​the bottom opening 226. This causes unevenness in the degree of treatment on the surface of the workpiece 240.

[0010] The plasma generator disclosed in Patent Document 2 is a technology that uses microwaves. Microwave-generated plasma is generated at high density at the antinodes of standing waves where the electric field strength is strong. Standing waves are generated not only in the microwave input direction but also in a direction perpendicular to the input direction. Therefore, when viewing the nozzle from the front, areas of high and low plasma density are generated alternately. Therefore, with microwave-generated plasma, it is not easy to spray plasma uniformly from the entire area of ​​the nozzle.

[0011] Furthermore, the device itself cannot be made long in the first place due to the generation of standing waves, so even if it is intended to be used for the surface treatment of a workpiece, the treatment capacity is extremely low, making it practically difficult to apply.

[0012] In view of the above problems, an object of the present invention is to provide a dielectric barrier discharge plasma generator that can efficiently spray plasma uniformly from the entire area of ​​the outlet. [Means for solving the problem]

[0013] The dielectric barrier discharge plasma generator of the present invention comprises: a plate-shaped dielectric substrate extending in a first direction; a first electrode disposed in contact with a surface of the dielectric substrate; a second electrode disposed extending in the first direction, in a state spaced apart from the dielectric substrate on a side opposite to a side on which the first electrode is disposed, in a second direction perpendicular to the first direction; a gas flow path formed by a gap between the dielectric substrate and the second electrode, through which gas flows in a third direction perpendicular to the first direction and the second direction; an air outlet provided at one end of the gas flow path in the third direction and extending in the first direction, When viewed in the first direction, at least one of the dielectric substrate, the first electrode, and the second electrode has an inclined surface in a region between a predetermined position and the air outlet in the third direction, One of the dielectric substrate and the second electrode is arranged to sandwich the other of the dielectric substrate and the second electrode in the second direction via the gap.

[0014] According to the above configuration, gas flows in a third direction toward the outlet through a gas flow path formed by a gap provided between the dielectric substrate and the second electrode in the second direction. Because both the dielectric substrate and the second electrode extend in the first direction, this gap, i.e., the gas flow path, also extends in the first direction. Therefore, gas moves in a third direction toward the outlet through the gas flow path extending in the first direction, and a slit-shaped gas is discharged from the outlet.

[0015] The gas flow path is formed by a gap sandwiched between the dielectric substrate and the second electrode. When viewed in the first direction, at least one of the dielectric substrate, the first electrode, and the second electrode has an inclined surface in a region between a predetermined location and the outlet in the third direction. As a result, when a voltage is applied between the first electrode and the second electrode, the electric field in the gap, i.e., in the gas flow path, changes monotonically with increasing distance from the outlet. This configuration can be achieved, for example, by varying the thickness of the dielectric substrate, the thickness of the first electrode, or the thickness of the second electrode with increasing distance from the outlet in the third direction. As a typical example, by narrowing the flow path width (length in the second direction) of the gas flow path with increasing distance from the outlet in the third direction, the electric field applied to the gas flowing through the gas flow path is increased with increasing distance from the outlet.

[0016] According to the above configuration, an extremely strong electric field is formed near the outlet, and plasma is generated intensively in this region. As a result, the plasma-containing gas can be discharged from the entire area of ​​the outlet in the first direction. Therefore, the plasma-containing gas can be efficiently sprayed from the outlet onto the workpiece, and the workpiece can be efficiently treated.

[0017] In order to discharge the plasma-containing gas from the outlet, it is necessary to generate an extremely strong electric field, particularly near the outlet. Therefore, the flow path width (length in the second direction) of the gas flow path must be designed to be narrow. Therefore, the plasma-containing gas blown out from the outlet extending in the first direction has an extremely thin sheet shape.

[0018] When such a sheet-shaped plasma-containing gas is sprayed onto a workpiece to perform surface treatment, the surface area of ​​the workpiece treated per unit time is limited. However, as described above, it is not possible to increase the width of the gas flow path to improve treatment efficiency, because this would reduce the plasma generation efficiency or even prevent plasma from being generated at all.

[0019] One possible method for increasing the area of ​​the workpiece that can be treated per unit time is to arrange multiple dielectric barrier discharge plasma generators in the second direction. However, in this case, the distance between the air outlets of adjacent dielectric barrier discharge plasma generators increases, resulting in a difference in the degree of treatment of the workpiece between the area facing the air outlets and the area sandwiched between the air outlets. Furthermore, outside air is more likely to flow into the area sandwiched between the air outlets. For these reasons, a certain amount of treatment time is required to achieve the desired degree of surface treatment of the workpiece.

[0020] In contrast, according to the above configuration, one of the dielectric substrate and the second electrode is arranged to sandwich the other of the dielectric substrate and the second electrode via a gap in the second direction. As a result, gas flow paths formed by the gaps are formed at multiple positions spaced apart in the second direction. In other words, in this device, even though it is a single device, gas flows through the multiple gas flow paths toward the outlet, and plasma-containing gas is discharged from the outlet through the multiple gas flow paths. Furthermore, the spacing between these gas flow paths is extremely narrow compared to when multiple devices are simply arranged side by side.

[0021] When a plasma-containing gas is sprayed onto the workpiece for surface treatment, the workpiece is positioned very close to the outlet. Therefore, the plasma-containing gas sprayed from the multiple gas flow paths is sprayed onto the surface of the workpiece, and an airflow is also generated in the space between the two gas flow paths due to the difference in flow speeds sprayed from the two gas flow paths and the airflow reflected by the surface of the workpiece. As described above, the distance between adjacent gas flow paths in the second direction is significantly narrower than the distance between adjacent outlets when multiple devices are arranged side by side in the second direction. As a result, the plasma-containing gas also flows into the space between the adjacent gas flow paths, and as a result, the plasma-containing gas can be sprayed over a width wider than the width of the outlet. This increases the surface treatment speed of the workpiece compared to conventional methods.

[0022] Furthermore, the above-mentioned device does not use microwaves because it generates plasma using dielectric barrier discharge. Therefore, there is no need for impedance matching for microwave transmission, and there are no particular restrictions on the shapes of the dielectric substrate, electrodes, or air outlet. In addition, because the above-mentioned device does not use microwaves, there is no need to take measures against electromagnetic wave leakage.

[0023] A blowout port may be provided for each gas flow path, or a common blowout port may be provided that is connected to all the gas flow paths. In the former case, the plasma-containing gas that has flowed through each gas flow path is blown out from each blowout port. In the latter case, the end of each gas flow path in the third direction is located a very small distance back in the third direction from the blowout port, and the gas that has flowed through each gas flow path is blown out from the common blowout port. The very small distance here is, for example, a distance of about 0.5 to 2 times the thickness of the dielectric substrate.

[0024] the gas flow path is formed at two locations spaced apart in the second direction, The blowout ports may be arranged corresponding to the respective gas flow paths.

[0025] The gas flow passages may be formed at two locations spaced apart in the second direction and connected to each other at an end on the outlet side.

[0026] The dielectric substrate may be made primarily of aluminum oxide (Al2O3) or aluminum nitride (AlN), where "main material" refers to a component that accounts for 80% or more of the constituent materials when analyzed.

[0027] Aluminum oxide and aluminum nitride have a relatively low relative dielectric constant and relatively high physical strength and hardness, so by using aluminum oxide or aluminum nitride as the main material of the dielectric substrate, it is possible to increase the amount of plasma generated per unit power and reduce the risk of damage even when the dielectric substrate is made thinner.

[0028] Among these, aluminum nitride has good thermal conductivity and can efficiently dissipate heat from the dielectric substrate. This makes it possible to suppress the temperature rise of the electrode to which high voltage is applied (high-voltage electrode) out of the first and second electrodes, thereby reducing the stress at the interface between the aluminum nitride and the high-voltage electrode due to thermal expansion. As a result, the life of the dielectric barrier discharge plasma generator is extended.

[0029] the dielectric substrate has a slit-shaped hole formed to extend parallel to a main surface, the first electrode has a plate shape and is embedded in the hole to be in contact with the dielectric substrate; The second electrodes may be arranged to sandwich the dielectric substrate from both sides in the first direction at a distance from each other.

[0030] In this case, preferably, the first electrode is a high-voltage electrode and the second electrode is a low-voltage electrode, and with this configuration, the electrode located outside the device becomes the low-voltage electrode, which contributes to the safety of the worker.

[0031] The dielectric barrier discharge plasma generator further comprises: a gas buffer substrate abutting the pair of second electrodes at their peripheral edges from outside; a gas delivery device that introduces the gas into a gap between the gas buffer substrate and the second electrode; The second electrode may be provided with contact holes penetrating the second electrode in the second direction at a plurality of different locations in the first direction.

[0032] According to the above configuration, the gas introduced from the gas delivery device is stored in the gap between the gas buffer substrate and the second electrode, and then flows into the gas flow path through the plurality of communication holes, which allows the gas that has flowed into the gas flow path to be uniformly discharged from the outlet without disrupting the flow.

[0033] In particular, by providing the communication holes at a plurality of positions in the first direction, gas is introduced into the gas flow path from a plurality of different positions in the first direction, which makes it easier to make the gas flowing through the gas flow path a laminar flow.

[0034] The pair of dielectric substrates are spaced apart in the second direction, a pair of the first electrodes are disposed on outer surfaces of the pair of the dielectric substrates, respectively; The second electrode may be disposed at a position spaced apart in the second direction from the inner surfaces of the pair of dielectric substrates.

[0035] In this case, the first electrode may be a foil-like metal. Although the metal material is not limited, a highly conductive material is preferable, and typical examples thereof include one or more materials belonging to the group consisting of copper, silver, aluminum, and gold, or compounds of these materials.

[0036] The first electrode may be a sintered body containing a metal, which can be formed by printing a metal paste, eliminating the need to use an adhesive when forming the first electrode on the dielectric substrate.

[0037] The first electrode may be formed by plating, vapor deposition, sputtering, or thermal spraying. In this case, there is no need to use an adhesive when forming the first electrode on the dielectric substrate.

[0038] An end of the first electrode on the air outlet side is preferably disposed at a position set back from the air outlet in the third direction.

[0039] If the first electrode were to extend to the position of the outlet in the third direction, a direct discharge would occur between the first electrode and the second electrode without passing through the dielectric substrate. Such a discharge would damage the first electrode, the dielectric substrate, or the second electrode, and materials constituting these components would be mixed into the plasma-containing gas as impurities.

[0040] From the viewpoint of discharge efficiency, it is advantageous to arrange the first electrode so that the end of the first electrode coincides with the end of the outlet in the third direction. However, in such an arrangement, there is a risk of creeping discharge occurring on the dielectric substrate due to the above-mentioned circumstances. Once this creeping discharge occurs, direct discharge becomes dominant rather than dielectric barrier discharge, causing an excessive discharge current to flow, which may damage the electrode and ultimately the power supply device.

[0041] In contrast, by adopting the above-described configuration, direct discharge between the first electrode and the second electrode is suppressed, thereby suppressing damage to the electrodes and the dielectric substrate and preventing impurities from being mixed into the plasma gas.

[0042] The dielectric barrier discharge plasma generator may include a power supply connected to the first electrode, and the power supply is preferably configured to be capable of supplying a voltage signal having a voltage of 3 kV to 20 kV and a frequency of 20 kHz to 150 kHz to the first electrode.

[0043] The power supply device described above allows for suitable plasma generation using the dielectric barrier discharge method. The upper limit of 150 kHz was set in consideration of the plasma irradiation length, and also because the frequency detected in the noise terminal voltage under EMC standards is higher than 150 kHz.

[0044] A light-shielding member may be provided on the outer side of the air outlet in the third direction. By providing the light-shielding member at the air outlet, it is possible to prevent light generated by discharge from being irradiated onto the object to be treated.

[0045] The dielectric barrier discharge plasma generator may further include a starting aid arranged on the surface of the dielectric substrate facing the gas flow path. The starting aid is preferably arranged very close to the outlet. However, if the starting aid is arranged so that its position is aligned with the outlet when viewed in the first direction, some of the plasma-containing gas from the outlet may collide with the starting aid, causing the starting aid to be worn or removed. On the other hand, if the starting aid is too far from the outlet in the third direction, it will not function as a starting aid at all. From this perspective, the starting aid is preferably arranged close to the outlet and slightly set back from the outlet in the third direction. This setback distance is preferably less than 10 mm.

[0046] Although a dielectric barrier discharge requires high power at startup (when discharge begins), once discharge occurs, the discharge can be maintained even if the input power is reduced. For this reason, a high power is preferably input at startup. However, this method requires a large power supply device that can handle high power and a trigger electrode placed near the discharge space, which may increase the size of the entire device.

[0047] At the start of plasma discharge, initial electrons must be present at the location where plasma is generated. Therefore, by arranging the starting aid as in the above configuration, initial electrons are supplied to the gas flow path near the nozzle at the beginning of startup. This eliminates the need for a large power supply or trigger electrode, making it possible to provide a small, inexpensive plasma generator. [Effects of the Invention]

[0048] According to the dielectric barrier discharge plasma generator of the present invention, it is possible to efficiently spray plasma uniformly from the entire area of ​​the nozzle. [Brief explanation of the drawings]

[0049] [Figure 1] 1 is a perspective view schematically showing the configuration of a first embodiment of a dielectric barrier discharge plasma generator. FIG. [Figure 2] 2 is a schematic cross-sectional view of the plasma generating device shown in FIG. 1 taken along line II-II. [Figure 3] FIG. 2 is a schematic cross-sectional view of the plasma generating device shown in FIG. 1 taken along line III-III. [Figure 4] FIG. 3 is a schematic cross-sectional view showing only the dielectric substrate extracted from FIG. 2. [Figure 5] FIG. 3 is a schematic cross-sectional view showing only the first electrode extracted from FIG. 2. [Figure 6] 10 is a schematic plan view of the second electrode facing the −Z side surface of the dielectric substrate in the Z direction, as viewed from the +Z side. FIG. [Figure 7] 3 is a cross-sectional view showing the first electrode, the second electrode, and the dielectric substrate extracted from FIG. 2, with the vicinity of the first end being displayed on an enlarged scale. [Figure 8] FIG. 8 is a partially enlarged view of FIG. [Figure 9A] FIG. 1 is a partially enlarged cross-sectional view schematically showing a modified example of the first embodiment of the dielectric barrier discharge plasma generator. [Figure 9B] FIG. 1 is a partially enlarged cross-sectional view schematically showing a modified example of the first embodiment of the dielectric barrier discharge plasma generator. [Figure 9C] FIG. 1 is a partially enlarged cross-sectional view schematically showing a modified example of the first embodiment of the dielectric barrier discharge plasma generator. [Figure 9D] FIG. 1 is a partially enlarged cross-sectional view schematically showing a modified example of the first embodiment of the dielectric barrier discharge plasma generator. [Figure 9E] FIG. 1 is a partially enlarged cross-sectional view schematically showing a modified example of the first embodiment of the dielectric barrier discharge plasma generator. [Figure 9F] FIG. 1 is a partially enlarged cross-sectional view schematically showing a modified example of the first embodiment of the dielectric barrier discharge plasma generator. [Figure 9G] FIG. 1 is a partially enlarged cross-sectional view schematically showing a modified example of the first embodiment of the dielectric barrier discharge plasma generator. [Figure 9H]FIG. 1 is a partially enlarged cross-sectional view schematically showing a modified example of the first embodiment of the dielectric barrier discharge plasma generator. [Figure 9I] FIG. 1 is a partially enlarged cross-sectional view schematically showing a modified example of the first embodiment of the dielectric barrier discharge plasma generator. [Figure 9J] FIG. 1 is a partially enlarged cross-sectional view schematically showing a modified example of the first embodiment of the dielectric barrier discharge plasma generator. [Figure 9K] FIG. 1 is a partially enlarged cross-sectional view schematically showing a modified example of the first embodiment of the dielectric barrier discharge plasma generator. [Figure 10] FIG. 10 is a perspective view schematically showing the configuration of a second embodiment of a dielectric barrier discharge plasma generator. [Figure 11] 11 is a schematic cross-sectional view of the plasma generating device shown in FIG. 10 taken along line XI-XI. [Figure 12] 11 is a schematic cross-sectional view of the plasma generating device shown in FIG. 10 taken along line XII-XII. [Figure 13] 12 is a cross-sectional view showing the first electrode, the second electrode, and the dielectric substrate extracted from FIG. 11 and showing an enlarged view of the vicinity of the first end. [Figure 14] FIG. 14 is a partially enlarged view of FIG. [Figure 15A] FIG. 10 is a partially enlarged cross-sectional view schematically showing a modified example of the second embodiment of the dielectric barrier discharge plasma generator. [Figure 15B] FIG. 10 is a partially enlarged cross-sectional view schematically showing a modified example of the second embodiment of the dielectric barrier discharge plasma generator. [Figure 15C] FIG. 10 is a partially enlarged cross-sectional view schematically showing a modified example of the second embodiment of the dielectric barrier discharge plasma generator. [Figure 15D] FIG. 10 is a partially enlarged cross-sectional view schematically showing a modified example of the second embodiment of the dielectric barrier discharge plasma generator. [Figure 15E] FIG. 10 is a partially enlarged cross-sectional view schematically showing a modified example of the second embodiment of the dielectric barrier discharge plasma generator. [Figure 15F]FIG. 10 is a partially enlarged cross-sectional view schematically showing a modified example of the second embodiment of the dielectric barrier discharge plasma generator. [Figure 15G] FIG. 10 is a partially enlarged cross-sectional view schematically showing a modified example of the second embodiment of the dielectric barrier discharge plasma generator. [Figure 15H] FIG. 10 is a partially enlarged cross-sectional view schematically showing a modified example of the second embodiment of the dielectric barrier discharge plasma generator. [Figure 16] FIG. 1 is a cross-sectional view schematically showing a conventional dielectric barrier discharge plasma generator. DETAILED DESCRIPTION OF THE INVENTION

[0050] An embodiment of a dielectric barrier discharge plasma generator according to the present invention will be described with reference to the drawings as appropriate. Note that the drawings are schematic illustrations, and the dimensional ratios in the drawings do not necessarily match the actual dimensional ratios. Furthermore, the dimensional ratios may not match between drawings.

[0051] [First embodiment] A first embodiment of a dielectric barrier discharge plasma generator will be described with reference to the drawings. Fig. 1 is a perspective view schematically showing a dielectric barrier discharge plasma generator 1 (hereinafter abbreviated as "plasma generator 1") of this embodiment. Fig. 2 is a schematic cross-sectional view of the plasma generator 1 in Fig. 1 taken along line II-II. Fig. 3 is a schematic cross-sectional view of the plasma generator 1 in Fig. 1 taken along line III-III. For convenience of explanation, Fig. 2 also shows a gas delivery device 61, which is omitted from Fig. 1.

[0052] The plasma generator 1 includes a first electrode 10 (see FIG. 2), a second electrode 20, and a dielectric substrate 30. The plasma generator 1 shown in FIGS. 1 to 3 further includes a gas buffer substrate 40, but it is optional whether the plasma generator 1 includes the gas buffer substrate 40 or not.

[0053] The plasma generator 1 is a device that generates a gas containing plasma (hereinafter referred to as "plasma gas G1") therein. The plasma generator 1 has an outlet 5 that blows out the plasma gas G1. As shown in FIG. 1, the outlet 5 extends in the Y direction and has a substantially rectangular shape when viewed in the X direction. The direction perpendicular to the X and Y directions is defined as the Z direction. In the following description, the XYZ coordinate system shown in FIG. 1 will be referred to as appropriate.

[0054] In the following description, when a positive or negative direction is to be distinguished from the positive or negative direction, the direction is described with a positive or negative sign, such as "+X direction" and "-X direction." When a direction is to be described without distinguishing between positive and negative directions, the direction is simply described as "X direction." In other words, in this specification, when simply referring to the "X direction," both the "+X direction" and the "-X direction" are included. The same applies to the Y direction and the Z direction.

[0055] In this specification, the Y direction corresponds to the "first direction", the Z direction corresponds to the "second direction", and the X direction corresponds to the "third direction".

[0056] 1, the plasma generator 1 of this embodiment has two air outlets 5 located close to each other and spaced apart in the Z direction. That is, the plasma gas G1 is blown out from these air outlets 5. Each air outlet 5 is formed in a space between the dielectric substrate 30 and the second electrode 20 in the Z direction.

[0057] (Dielectric substrate 30) 1 to 3, the dielectric substrate 30 is a plate-like member extending in the Y direction. In this embodiment, the first electrode 10 is disposed so that at least a portion of the first electrode 10 is embedded inside the dielectric substrate 30, thereby bringing the dielectric substrate 30 and the first electrode 10 into contact with each other.

[0058] Fig. 4 is a schematic cross-sectional view showing only the dielectric substrate 30 extracted from Fig. 2. Fig. 5 is a schematic cross-sectional view showing only the first electrode 10 extracted from Fig. 2.

[0059] As shown in FIG. 4, the dielectric substrate 30 has a hole 38 extending in the X direction. This hole 38 is formed to extend in the Y direction. That is, the dielectric substrate 30 has a slit-shaped hole 38. A first electrode 10, which is schematically shown in FIG. 5, is embedded in this slit-shaped hole 38. In the example of FIG. 2, the first electrode 10 is shown to be completely housed in the hole 38, but a portion of the first electrode 10 may protrude from the hole 38 in the −X direction. However, as will be described later, in this embodiment, the first electrode 10 constitutes a high-voltage side electrode. Therefore, from a safety standpoint, it is preferable that the −X side end (end face) of the first electrode 10 be located closer to the +X side than the −X side end (end face) of the dielectric substrate 30.

[0060] In the example shown in Figures 2 and 4, a structure is adopted in which the length in the Z direction of the dielectric substrate 30 (hereinafter referred to as "thickness") becomes thinner as it approaches the air outlet 5 in the X direction, but this structure is merely one example.

[0061] From the viewpoint of increasing the amount of plasma generated per unit power, the dielectric substrate 30 is preferably made of a material with a low relative dielectric constant. The relative dielectric constant of the material is preferably 10 or less. The lower the relative dielectric constant of the material, the more preferable it is, and typically it can be 4 to 10.

[0062] The material of the dielectric substrate 30 is not particularly limited, but as mentioned above, it is preferable that the material be a material with as low a relative dielectric constant as possible. Furthermore, from the viewpoint of durability, the material is preferably ceramic. Examples of ceramics include aluminum oxide, aluminum nitride, and steatite. These materials have a relatively low relative dielectric constant, relatively high strength, and excellent durability. Therefore, if the dielectric substrate 30 is made of aluminum oxide, aluminum nitride, or steatite, the amount of plasma generated per unit power can be increased. Furthermore, because of their excellent durability, there is little risk of breakage even if the thickness of the dielectric substrate 30 is made thin.

[0063] In order to realize the plasma generator 1 having the shape shown in FIG. 2, for example, a method can be adopted in which a rectangular plate-shaped dielectric substrate 30 is cut to form a slit-shaped hole 38, and then the first electrode 10 is fitted into the hole 38 with a conductive adhesive paste applied thereto, and the two are tightly fixed together.

[0064] The dielectric substrate 30 may be made of the above-mentioned material as a base material and contain a substance that assists electron generation. Examples of the substance that assists electron generation include silver, platinum, copper, carbon, and transition metal compounds. Primary electrons are generated by applying an electric field to the substance that assists electron generation and are released into the discharge space (gas flow path 3, described below). Therefore, by configuring the dielectric substrate 30 as described above, starting performance can be advantageously improved.

[0065] The content of the substance that assists electron generation is preferably 1 part by mass or less relative to the entire dielectric substrate 30 (when the dielectric substrate 30 is 100 parts by mass). If the content of this substance is too high, there is a concern that the substance will evaporate and scatter during discharge, become mixed into the plasma gas G1, and be sprayed onto the workpiece to be irradiated with the plasma gas G1. From the viewpoint of fully demonstrating the effect of improving startability, it has been experimentally determined that the content of the substance is preferably 0.05 parts by mass or more.

[0066] (first electrode 10) As described above with reference to Fig. 2, in the plasma generator 1 of this embodiment, at least a portion of the first electrode 10 is embedded in close contact with the dielectric substrate 30. That is, the first electrode 10 is disposed in contact with the surface of the dielectric substrate 30. Note that Fig. 2 shows an example in which the entire first electrode 10 is embedded in the dielectric substrate 30.

[0067] In the plasma generator 1, a voltage is applied between the first electrode 10 and the second electrode 20 (described later) via the dielectric substrate 30 and the gas flow path 3, thereby converting the gas flowing through the gas flow path 3 into plasma and generating the plasma gas G1. Therefore, one of the first electrode 10 and the second electrode 20 serves as the high-voltage electrode, and the other serves as the low-voltage electrode. In the following embodiment, the first electrode 10 is described as the high-voltage electrode and the second electrode 20 as the low-voltage electrode, but these may be reversed. However, in the plasma generator 1 of this embodiment, from the viewpoint of safety, it is preferable that the second electrode 20, which is exposed to the outside and therefore located near the operator, serves as the low-voltage electrode, and the first electrode 10, which is buried inside, serves as the high-voltage electrode.

[0068] 1 and 3, in this embodiment, the length of the first electrode 10 in the Y direction (hereinafter referred to as "width") does not exactly match the width of the dielectric substrate 30, but is approximately the same length. From the viewpoint of ejecting the plasma gas G1 from the outlet 5 over a wide area (a long area in the Y direction), it is preferable to form the first electrode 10 as wide as possible. However, the present invention is not limited to the width of the first electrode 10.

[0069] In this embodiment, the first electrode 10 is slightly set back on the -X side relative to the air outlet 5 in the X direction (see FIG. 2). Referring to FIG. 2, the +X side end 10a of the first electrode 10 is slightly set back on the -X side from the end on the air outlet 5 side (+X side) of the plasma generator 1. For convenience, the end on the air outlet 5 side (+X side) of the plasma generator 1 may be referred to as the "first end 71," and the end on the opposite side from the air outlet 5 (-X side) may be referred to as the "second end 72."

[0070] Near the air outlet 5, there is a risk of a direct discharge occurring between the first electrode 10 and the second electrode 20 without passing through the dielectric substrate 30. If such a discharge occurs, the electrodes (10, 20) or the dielectric substrate 30 may be damaged, and the constituent materials thereof may be mixed into the plasma gas G1 as impurities.

[0071] From the viewpoint of discharge efficiency, it is preferable to bring the +X side end 10a of the first electrode 10 as close as possible to the air outlet 5, i.e., to approximately coincide with the first end 71. However, adopting such a configuration increases the risk of creeping discharge occurring between the first electrode 10 and the second electrode 20, and direct discharge becomes dominant rather than dielectric barrier discharge. Therefore, as described above, a configuration is adopted in which the +X side end 10a of the first electrode 10 is slightly set back from the first end 71 toward the −X side (toward the second end 72). This setback distance, i.e., the distance between the +X side end 10a of the first electrode 10 and the first end 71, is typically 1 mm to 5 mm.

[0072] The material of the first electrode 10 is not particularly limited, but is preferably one with high conductivity, and typical examples include one or more materials belonging to the group consisting of copper, silver, aluminum, and gold, or compounds of these materials.

[0073] The first electrode 10 and the dielectric substrate 30 are preferably in close contact with each other, with no air gap present at their interface. This is because an air gap can cause discharge within the gap, potentially resulting in degradation of the first electrode 10 due to the radicals generated. For this reason, the first electrode 10 and the dielectric substrate 30 are preferably in close contact with each other with a separation distance of the order of μm. To enhance the adhesion between the two, the surface of the dielectric substrate 30 may be roughened to form minute irregularities for the purpose of achieving an anchoring effect. In particular, since the dielectric substrate 30 is cut when forming the hole 38, minute irregularities are likely to form on the inner surface of the hole 38. Therefore, by subsequently fitting the first electrode 10 into the hole 38, the adhesion between the first electrode 10 and the dielectric substrate 30 is enhanced.

[0074] Typically, the thickness (length in the Z direction) of the first electrode 10 is thinner than the thickness of the dielectric substrate 30. In particular, by using the first electrode 10 as the electrode on the high voltage side, even if the material of the first electrode 10 expands due to the application of a high voltage, the influence of the expansion on the dielectric substrate 30 is minor because the thickness of the first electrode 10 is thin.

[0075] When the first electrode 10 is the high-voltage electrode, a portion of the first electrode 10 is connected to the power supply device 63. The method for connecting the power supply device 63 and the first electrode 10 is not particularly limited as long as the method is electrically connected and can withstand the applied voltage. For example, connection by soldering or connection using various connectors (e.g., coaxial connectors, etc.) can be used. Note that, since the plasma generator 1 of this embodiment does not use microwaves to generate plasma, it is not necessary to use a coaxial connector or coaxial cable with a predetermined characteristic impedance.

[0076] The voltage and frequency applied to the first electrode 10 from the power supply device 63 may be within a range that allows for the generation of a dielectric barrier discharge in the plasma generator 1. Typically, the applied voltage is 3 kV to 20 kV, and preferably 3 kV to 10 kV. The frequency of the voltage signal is typically 20 kHz to 1000 kHz, and more preferably 50 kHz to 150 kHz. The reason why the upper limit is preferably 150 kHz is that the plasma irradiation length is taken into consideration when determining the wavelength, and also because the frequency detected in the noise terminal voltage in the EMC standard is higher than 150 kHz.

[0077] (Second electrode 20, gas flow path 3) The second electrode 20 has a plate shape extending in the Y direction. More specifically, as shown in Figures 2 and 3, the second electrode 20 is arranged to sandwich the dielectric substrate 30 at a distance from both the +Z side and the -Z side. In other words, the second electrode 20 is arranged at a distance from the dielectric substrate 30 on the opposite side to the side on which the first electrode 10 is arranged in the Z direction.

[0078] When the second electrode 20 is used as the low-voltage electrode, it may be connected to the ground potential directly or via a resistor, or may be connected to the low-voltage output of the power supply device 63 .

[0079] 2 and 3, a recess 27 is formed in a part of the surface of the second electrode 20 facing the dielectric substrate 30. The recess 27 is formed to extend in the Y direction.

[0080] 6 is a schematic plan view of the second electrode 20 facing the -Z side surface of the dielectric substrate 30 in the Z direction, as viewed from the +Z side. Note that the second electrode 20 facing the +Z side surface of the dielectric substrate 30 in the Z direction may have substantially the same shape when viewed from the -Z side. For simplicity of explanation, only the second electrode 20 located on the -Z side of the dielectric substrate 30 will be described below, and a description of the second electrode 20 located on the +Z side will be omitted.

[0081] 2, 3, and 6, it can be seen that the second electrode 20 has a higher height at the outer edge 26 on the +Y side, the −Y side, and the −X side, and that the aforementioned recesses 27 are formed inside the outer edge 26. As shown in FIG. 2, the outer edge 26 of the second electrode 20 abuts against the surface of the dielectric substrate 30. That is, when the outer edge 26 of the second electrode 20 abuts against the dielectric substrate 30, the recesses 27 formed on the Z side of the second electrode 20 form a gap. More specifically, for the second electrode 20 located on the −Z side of the dielectric substrate 30, the recesses 27 formed on the +Z side of the second electrode 20 form a gap, and for the second electrode 20 located on the +Z side of the dielectric substrate 30, the recesses 27 formed on the −Z side of the second electrode 20 form a gap. The gaps formed by these recesses 27 constitute the “gas flow path 3.”

[0082] In the example shown in FIG. 6, communication holes 53 are formed at a plurality of positions spaced apart in the Y direction on the bottom surface of the recess 27. There is no particular limitation on the number of communication holes 53, but it is preferable that there be two or more communication holes 53, as in this embodiment. The communication holes 53 are provided to guide the gas G0 (see FIG. 2) from the gas delivery device 61 to the gas flow path 3, as will be described later. By providing a plurality of communication holes 53 at different positions in the Y direction, the gas flow in the gas flow path 3 can be made more easily laminar. Furthermore, from the viewpoint of distributing the gas over a wide range in the Y direction at the time of introduction into the gas flow path 3, it is preferable that the communication holes 53 are formed over a wide range in the Y direction.

[0083] 6 shows an example in which a plurality of independent communication holes 53 are formed, but a single communication hole 53 that is elongated in the Y direction, for example, in the shape of a rectangular cylinder, may be formed. However, "single" here means a single hole for each recess 27. More specifically, this means that a single communication hole 53 may be formed in the recess 27 of the second electrode 20 located on the -Z side of the dielectric substrate 30, and another single communication hole 53 may be formed in the recess 27 of the second electrode 20 located on the +Z side of the dielectric substrate 30.

[0084] (Gas buffer substrate 40) 1 to 3, the plasma generator 1 includes a gas buffer substrate 40 that is in contact with the second electrode 20 from the side opposite to the dielectric substrate 30, i.e., from the outside in the ±Z directions. In this embodiment, the gas buffer substrate 40 is in contact with the second electrode 20 at its peripheral edge. Therefore, a gap 51 is formed between the second electrode 20 and the gas buffer substrate 40 inside the peripheral edge.

[0085] A gas delivery device 61 (see FIG. 2) is connected to the gap 51. The gas G0 delivered from the gas delivery device 61 is buffered in the gap 51 and then guided to the gas flow path 3 through the communication hole 53. Although FIG. 2 shows a case where a plurality of gas delivery devices 61 are provided, the gas G0 may be delivered from a common gas delivery device 61 to each of the gaps 51.

[0086] In the plasma generator 1 of this embodiment, the gas buffer substrate 40 is made of a conductive material such as a metal.

[0087] (Air outlet 5) The plasma generator 1 is provided with an outlet 5 at the end of the gas flow path 3 on the +X side, i.e., the first end 71. This outlet 5 blows plasma generated during gas flow along the +X direction within the gas flow path 3 to the outside together with the gas flow (plasma gas G1). In the plasma generator 1, as an example, the widths (lengths in the Y direction) of the gas flow path 3 and the outlet 5 are uniform regardless of the X coordinate. This allows the flow of the gas G0 that has flowed into the gas flow path 3 to be prevented from being disturbed, and the plasma gas G1 can be sprayed uniformly from the outlet 5.

[0088] However, the present invention is not limited to this example, and the width of the outlet 5 may be adjusted as necessary. For example, the intensity of the plasma gas G1 can be increased by narrowing the width of the outlet 5 compared to the width of the -X side (second end 72 side) of the gas flow path 3. Conversely, by widening the width of the outlet 5 compared to the width of the -X side (second end 72 side) of the gas flow path 3, the injection width of the plasma gas G1 can be increased, and the range over which the plasma gas G1 can be sprayed at the same time relative to the workpiece can be expanded.

[0089] The gas delivered from the gas delivery device 61 at the start of the plasma generation device 1 may be one or more selected from the group consisting of He, Ne, and Ar. The gas to be delivered after plasma generation may be one or more gases capable of generating desired activated species, specifically one or more selected from the group consisting of hydrogen, oxygen, water, nitrogen, etc.

[0090] In this embodiment, it is preferable that the gas flow through the gas flow passage 3 is a laminar flow. If the gas flow is a laminar flow, the plasma can be ejected more uniformly. Here, the Reynolds number is a parameter that distinguishes between a laminar flow and a turbulent flow. The Reynolds number Re is the density of the fluid ρ (kg / m 3 ), the flow velocity is U (m / s), the characteristic length is L (m), and the viscosity coefficient of the fluid is μ (Pa s), Re=ρ·U·L / μ It is a dimensionless quantity expressed as

[0091] The Reynolds number that marks the boundary between laminar flow and turbulent flow is called the critical Reynolds number, and its value is said to be between 2,000 and 4,000.

[0092] The size of the plasma generator 1 is not particularly limited. As an example, the external dimensions are 750 mm in width (length in the Y direction), 40 mm in length (length in the X direction), and 20 mm in thickness (length in the Z direction, at the thickest point). The outer dimensions of the dielectric substrate 30 are a width of 750 mm, a length of 40 mm, and a thickness at the first end 71 of 0.1 mm. The outer dimensions of the first electrode 10 are a width of 690 mm and a length of 20 mm. The second electrode 20 has outer dimensions of 750 mm in width and 20 mm in length. The thickness of the first end 71 of the second electrode 20 is 0.1 mm on both the +Z side and the −Z side. The outer dimensions of the gas flow passage 3 are a width of 700 mm and a length of 35 mm on both the +Z side and the −Z side. The dimensions of the air outlets 5 on the +Z and -Z sides are an opening width of 700 mm and an opening height of 0.2 mm. The air outlets 5 on the +Z side and the air outlets 5 on the -Z side are spaced apart by an amount equivalent to the thickness of the first end 71 of the dielectric substrate 30.

[0093] FIG. 7 is a cross-sectional view showing only the first electrode 10, the second electrode 20, and the dielectric substrate 30 extracted from the plasma generator 1 shown in FIG. 2, with the vicinity of the first end 71 being enlarged.

[0094] In the plasma generator 1 of this embodiment, a portion of the surface of the dielectric substrate 30 forms the inner surface of the gas flow path 3, and the surface that forms the inner surface of the gas flow path 3 includes a flat surface 31 that is approximately parallel to the XY plane at a position away from the first end 71 in the -X direction, and an inclined surface 32 that is located on the +X side (first end 71 side) of this flat surface 31.

[0095] The first electrode 10 embedded in the dielectric substrate 30 has a flat surface 11 that is approximately parallel to the XY plane at a position away from the first end 71 in the -X direction, and an inclined surface 12 that is located on the +X side (first end 71 side) of the flat surface 11.

[0096] A portion of the surface of the second electrode 20, which is arranged outside (on the ±Z side) of the dielectric substrate 30, forms the inner surface of the gas flow path 3, and the surface that forms the inner surface of the gas flow path 3 has a flat surface 21 that is approximately parallel to the XY plane at a position away from the first end 71 in the -X direction, and an inclined surface 22 that is located on the +X side (first end 71 side) of this flat surface 21.

[0097] In this way, at least one surface of the dielectric substrate 30, the first electrode 10, and the second electrode 20 has an inclined surface at a position close to the first end 71 in the X direction, i.e., at a position close to the outlet 5, so that as the gas flows through the gas flow path 3 and approaches the outlet 5, the electric field strength applied to the gas is increased and the gas is turned into plasma near the outlet 5 (plasma gas G1).

[0098] Fig. 8 is a partially enlarged view of Fig. 7. For convenience of explanation, Fig. 8 also shows the workpiece W onto which the plasma gas G1 is sprayed. In the example of Fig. 8, the plasma gas G1 is sprayed onto the workpiece W while the workpiece W moves in the Z direction.

[0099] According to the plasma generator 1 of this embodiment, gas flow paths 3 are formed at multiple locations spaced apart in the Z direction. Then, gas flowing through these gas flow paths 3 in the +X direction is converted into plasma near the first end 71, and is then sprayed from the outlet 5 onto the workpiece W as plasma gas G1.

[0100] In this embodiment, the distance in the Z direction between the gas flow paths 3 at a position close to the first end 71 in the X direction depends on the thickness (length in the Z direction) of the dielectric substrate 30 at a position close to the first end 71 in the X direction, i.e., the thickness of the end 39 of the dielectric substrate 30. In order to convert the flowing gas into plasma, a high electric field must be applied to the gas, and from this perspective, there is an upper limit to the thickness of the dielectric substrate 30. In the above-mentioned numerical example, the thickness of the end 39 of the dielectric substrate 30 was 0.1 mm, but the upper limit of the thickness of the end 39 is 1.0 mm. The lower limit of the thickness of the end 39 depends on the processing accuracy, but in reality it is 0.01 mm.

[0101] That is, according to the plasma generator 1 of this embodiment, the plasma gas G1 is sprayed onto the workpiece W from multiple positions (multiple outlets 5) spaced apart by a distance of less than 1.0 mm in the Z direction. The plasma gas G1 is usually sprayed onto the workpiece W for the purpose of surface treatment. For this purpose, the workpiece W is positioned as close to the outlets 5 as possible. In practice, the distance between the workpiece W and the outlets 5 (distance d0 in FIG. 8 ) is 1.0 mm to 5.0 mm. Therefore, when the plasma gas G1 is sprayed from the multiple outlets 5 arranged very close to each other in the Z direction, turbulence occurs when the plasma gas G1 collides with the surface of the workpiece W, and a flow of the plasma gas G1 is generated between the two due to a slight difference in the flow velocity of each plasma gas G1. As a result, a gas space PA filled with the plasma gas G1 is formed in an area wider than the opening width of each outlet 5. This improves the surface treatment capability of the workpiece W.

[0102] 2, when a gas delivery device 61 is provided for each gas flow path 3, it is preferable to control the flow rate and flow velocity of the gas delivered from each gas delivery device 61 so as to slightly differ from each other. When the gas delivery device 61 is shared by a plurality of gas flow paths 3, it is preferable to design the gas flow paths 3 so that the flow velocities of the gases flowing through them are different from each other, for example by slightly differing the flow path widths of the gas flow paths 3.

[0103] In the plasma generator 1 of this embodiment, at least one surface of the dielectric substrate 30, the first electrode 10, and the second electrode 20 is an inclined surface as described above. The electric field strength in each of the gas flow paths 3 spaced apart in the Z direction depends on the angle of the inclined surface, etc. During manufacturing processes such as cutting, it is difficult to achieve a shape that is completely symmetrical with respect to the Z direction from the perspective of processing accuracy. In other words, when the plasma generator 1 shown in FIG. 2 is manufactured, it is expected that the gas flow paths 3 spaced apart in the Z direction will differ from one another in terms of their flow path widths, inclinations, and the shapes of slight irregularities formed on the inner surfaces of the gas flow paths 3 during cutting. As a result, even if the gas delivery device 61 is shared by each gas flow path 3, the flow velocities of the gases flowing through each gas flow path 3 are likely to differ slightly from one another.

[0104] (Variation) The configuration of the plasma generator 1 described above is merely an example, and various variations can be adopted for the plasma generator 1 of this embodiment. The structure of each variation will be described below with reference to Figures 9A to 9J, which are shown following Figure 7.

[0105] <1> In the configuration shown in Fig. 7, the first electrode 10 has a shape in which the thickness (length in the Z direction) decreases as it progresses in the +X direction. In contrast, as shown in Fig. 9A, the first electrode 10 may have a shape in which the thickness is uniform regardless of the position on the X coordinate. In other words, the first electrode 10 may have a flat surface 11 even in a position close to the first end 71.

[0106] <2> In the configuration shown in Fig. 7, the dielectric substrate 30 has a shape in which the thickness (length in the Z direction) decreases as it progresses in the +X direction. In contrast, as shown in Fig. 9B, the dielectric substrate 30 may have a shape in which the thickness is uniform regardless of the position on the X coordinate. In other words, the dielectric substrate 30 may have a flat surface 31 even in a position close to the first end 71.

[0107] <3> In the configuration shown in FIG. 7 , the second electrode 20 has the inclined surface 22 so that the thickness (length in the Z direction) increases with increasing distance in the +X direction. In other words, the second electrode 20 has a shape such that the thickness is greatest at the position closest to the first end 71 in the X direction. In contrast, as shown in FIG. 9C , the inclination of the inclined surface 22 of the second electrode 20 may be set so that the thickness decreases slightly at the position closest to the first end 71 in the X direction. More specifically, in a region 81 shown in FIG. 9C , the second electrode 20 is inclined so as to move away from the dielectric substrate 30 in the Z direction.

[0108] <4> In the configuration shown in FIG. 7, the first electrode 10 had a shape in which the thickness (length in the Z direction) decreased as the electrode progressed in the +X direction. Furthermore, in the configuration shown in FIG. 9A, the first electrode 10 had a uniform thickness regardless of the position on the X coordinate. In contrast, as shown in FIG. 9D, the first electrode 10 may have a shape in which the thickness increases as the electrode progresses in the +X direction. That is, the first electrode 10 may have an inclined surface 12 near the first end 71 that approaches the second electrode 20 in the Z direction.

[0109] <5> In the configuration shown in Fig. 7, the +X side end of the first electrode 10 is covered by the dielectric substrate 30. In contrast to this, as shown in Fig. 9E, the +X side end of the first electrode 10 may be covered by an insulating member 82 made of a material different from that of the dielectric substrate 30. By covering the +X side end of the first electrode 10 with the insulating member 82, it is possible to suppress the occurrence of unnecessary discharges such as corona discharges, similar to the case where the end is covered with the dielectric substrate 30. Examples of materials for the insulating member 82 include glass, a sintered body containing glass, and resin materials such as silicone or epoxy.

[0110] 7, the +X side end of the first electrode 10 is covered by the dielectric substrate 30. In contrast, as shown in FIGS. 9F to 9G, the +X side end of the first electrode 10 is not covered by the dielectric substrate 30, but the +X side end of the dielectric substrate 30 at a position outside the first electrode 10 in the Z direction may be made to protrude further toward the +X side than the +X side end of the first electrode 10.

[0111] In this case, the +X side end of first electrode 10 may be located on the −X side of first end 71 as shown in Fig. 9F, or may be located on the +X side of first end 71 as shown in Fig. 9G. Furthermore, although not shown in the figure, the +X side end of first electrode 10 may be located at the same X coordinate as first end 71.

[0112] As shown in FIGS. 9F to 9G, even if the end of the first electrode 10 on the +X side is not covered with the dielectric substrate 30, the surrounding dielectric substrate 30 protrudes to the +X side, thereby ensuring an electrical distance between the first electrode 10 and the second electrode 20 and suppressing direct discharge.

[0113] <7> As shown in Fig. 9H, a protective film 85 may be formed on the surface of the second electrode 20 near the air outlet 5. This protective film 85 is provided for the purpose of preventing the material constituting the second electrode 20 from scattering. In the example of Fig. 9H, the second electrode 20 has an inclined surface 22, and the protective film 85 is formed on this inclined surface 22. The protective film 85 may be made of, for example, aluminum oxide, aluminum nitride, or steatite, and is preferably made of the same material as the dielectric substrate 30.

[0114] The method for forming the protective film 85 on the surface of the second electrode 20 is not particularly limited, but from the viewpoint of ease of the method, a suitable method is to apply the material constituting the protective film 85 by thermal spraying onto the surface of the second electrode 20. The thickness of the protective film 85 can be set as appropriate as long as it has the function of suppressing scattering of the material of the second electrode 20, and is, for example, 10 μm to 100 μm.

[0115] <8> As shown in FIG. 9I, a starting aid member 86 may be formed on the surface of the dielectric substrate 30 near the outlet 5. Examples of materials for the starting aid member 86 include carbon and transition metal compounds. Examples of materials for the starting aid member 86 include substances with a higher dielectric constant than the dielectric substrate 30. In this case, due to dielectric loss, the constituent material of the starting aid member 86 is heated and primary electrons are supplied into the gas flow path 3. Carbon is particularly preferable as the material for the starting aid member 86. Because carbon has high thermal stability, the starting aid member 86 is less likely to evaporate even when the temperature rises, thereby improving the reliability of the plasma generation device 1.

[0116] The starting aid member 86 may be made of a material with a low work function so that the electron emission effect can be achieved with a lower applied voltage.

[0117] 9I, the plasma generator 1 is provided with a starting aid 86 near the outlet 5, which allows primary electrons to be supplied into the gas flow path 3, improving starting performance. This eliminates the need for a microwave oscillator or starter circuit device with a large power supply capacity, allowing the plasma generator 1 to be manufactured compactly and inexpensively.

[0118] <9> As shown in Fig. 9J, the plasma generator 1 may be provided with a light-shielding member 87 at a position adjacent to the outlet 5 on the +X side. The light-shielding member 87 has a pipe 88 therein through which gas can flow, and this pipe 88 is connected to the gas flow path 3. In the example shown in Fig. 9J, the pipe 88 changes the blowing direction of the plasma gas G1 to the -Z direction. This configuration prevents light originating from the discharge in the gas flow path 3 from being irradiated onto the workpiece.

[0119] 9K, the +X side end of the dielectric substrate 30 may be set back a small distance toward the -X side from the first end 71. In this case, the plasma gas G1 flowing through the gas flow path 3 on the +Z side and the plasma gas G1 flowing through the gas flow path 3 on the -Z side are blown out from a common blow-out port 5.

[0120] <11> The above-described modifications can be combined as appropriate.

[0121] [Second embodiment] A second embodiment of a dielectric barrier discharge plasma generator will be described with reference to the drawings. In the following, elements common to the first embodiment will be assigned the same reference numerals, and descriptions thereof will be appropriately simplified or omitted.

[0122] Fig. 10 is a perspective view schematically showing the plasma generator 1 of this embodiment. Fig. 11 is a schematic cross-sectional view of the plasma generator 1 in Fig. 10 taken along line XI-XI. Fig. 12 is a schematic cross-sectional view of the plasma generator 1 in Fig. 10 taken along line XII-XII. Figs. 10 to 12 are illustrated following Figs. 1 to 3, respectively.

[0123] The plasma generator 1 of this embodiment includes a housing 45 arranged to sandwich the second electrode 20 in the Y direction. The material of this housing 45 is arbitrary, and it may be made of a conductive material such as metal, or may be made of an insulating material such as ceramic or resin.

[0124] (Dielectric substrate 30) 10 to 12, the dielectric substrate 30 is a plate-like member extending in the Y direction. However, in the case of the plasma generator 1 of this embodiment, unlike the first embodiment, the pair of dielectric substrates 30 are arranged spaced apart in the Z direction as shown in FIG.

[0125] The dielectric substrate 30 can be made of the same material as in the first embodiment.

[0126] (first electrode 10) 11, in the plasma generator 1 of this embodiment, a pair of first electrodes 10 are arranged spaced apart in the Z direction. More specifically, each first electrode 10 is arranged on the outer surface of the dielectric substrate 30, i.e., on a surface that does not form the inner surface of the gas flow path 3. The material of the first electrode 10 is the same as in the first embodiment.

[0127] In the present embodiment, the first electrode 10 is formed on the outer surface of the dielectric substrate 30, and therefore a metal foil can be used. Examples include metal foils such as copper foil and aluminum foil with adhesive processing on one side.

[0128] As another example, the first electrode 10 may be a sintered body containing a conductive metal. The sintered body containing a metal can be formed by printing a metal paste on the surface of the dielectric substrate 30, so there is no need to use an adhesive during production. In addition, from the viewpoint of not using an adhesive, the first electrode 10 can also be formed by plating, vapor deposition, sputtering, or thermal spraying.

[0129] In this embodiment, as in the first embodiment, the first electrode 10 and the dielectric substrate 30 are in close contact with each other as much as possible, and it is preferable that there is no air layer at the interface between them.

[0130] (Second electrode 20, gas flow path 3) The second electrode 20 has a plate shape extending in the Y direction. As shown in Fig. 11 and Fig. 12, in the plasma generator 1 of this embodiment, the second electrode 20 is arranged so as to be sandwiched between a pair of dielectric substrates 30 arranged at a distance in the Z direction. That is, in this embodiment as well, the second electrode 20 is arranged at a distance from the dielectric substrate 30 on the opposite side to the side on which the first electrode 10 is arranged in the Z direction.

[0131] 12, the second electrode 20 is in contact with the dielectric substrate 30 at both ends in the Y direction. The second electrode 20 has a recess 27 in the center in the Y direction. That is, when the end of the second electrode 20 abuts against the dielectric substrate 30, the recess 27 formed in the second electrode 20 forms a gap, similar to the plasma generator 1 of the first embodiment. The gap formed by this recess 27 constitutes the "gas flow path 3."

[0132] (Gas buffer substrate 40) The plasma generator 1 of this embodiment includes a gas buffer substrate 40 that is in contact with the dielectric substrate 30 at a position on the −X side of the second electrode 20. The gas buffer substrate 40 includes a gap 51, and the gas G0 from the gas delivery device 61 is introduced into the gap 51.

[0133] The gas buffer substrate 40 has communication holes 53 at multiple different positions in the Y direction. When the gas G0 is delivered from the gas delivery device 61, it is buffered in the gap 51 and then guided to the gas flow path 3 through the communication holes 53. However, the communication hole 53 may be a single hole extending in the Y direction.

[0134] (Air outlet 5) The plasma generator 1 includes an outlet 5 at the end of the gas flow path 3 on the +X side, i.e., at the first end 71. In this embodiment, too, plasma generated while the gas flows in the +X direction within the gas flow path 3 is blown outward from the outlet 5 together with the gas flow (plasma gas G1).

[0135] FIG. 13 is a cross-sectional view showing only the first electrode 10, the second electrode 20, and the dielectric substrate 30 extracted from the plasma generator 1 shown in FIG. 11, with the vicinity of the first end 71 enlarged.

[0136] In the plasma generator 1 of this embodiment, the dielectric substrate 30 has a flat surface 31 that forms the inner surface of the gas flow path 3. The dielectric substrate 30 also has, at a position opposite to the flat surface 31, i.e., at a position outside the gas flow path 3, a flat surface 33 and an inclined surface 34 located on the +X side (first end 71 side) of the flat surface 33.

[0137] The first electrode 10 is disposed at least on the upper surface of the inclined surface 34. In the example of FIG.

[0138] The second electrode 20 has both a +Z side surface and a -Z side surface that form the inner surface of the gas flow path 3, and each has a flat surface 21 and an inclined surface 22 that is located on the +X side (first end 71 side) of the flat surface 21.

[0139] In this way, at least one of the surfaces of the dielectric substrate 30, the first electrode 10, and the second electrode 20 has an inclined surface at a position close to the first end 71 in the X direction, i.e., at a position close to the outlet 5. As the gas flows through the gas flow path 3 and approaches the outlet 5, the electric field strength applied to the gas is increased, and the gas is turned into plasma in the vicinity of the outlet 5.

[0140] Fig. 14 is a partially enlarged view of Fig. 13. For convenience of explanation, Fig. 14 also shows the workpiece W onto which the plasma gas G1 is sprayed, as in Fig. 8. The workpiece W is sprayed with the plasma gas G1 while moving in the Z direction.

[0141] In the plasma generator 1 of this embodiment, similarly to the first embodiment, gas flow paths 3 are formed at multiple locations spaced apart in the Z direction. Then, gas flowing through these gas flow paths 3 in the +X direction is converted into plasma near the first end 71, and is then sprayed from the outlet 5 onto the workpiece W as plasma gas G1.

[0142] In this embodiment, the distance in the Z direction between the gas flow paths 3 at a position close to the first end 71 in the X direction depends on the thickness (length in the Z direction) of the second electrode 20 at a position close to the first end 71 in the X direction, i.e., the thickness of the end 29 of the second electrode 20. In order to convert the flowing gas into plasma, a high electric field must be applied to the gas, and from this perspective, there is an upper limit to the thickness of the second electrode 20. The thickness of the end 29 of the second electrode 20 is set to be 1.0 mm to 10.0 mm.

[0143] That is, according to the plasma generator 1 of this embodiment, the plasma gas G1 is sprayed onto the workpiece W from a plurality of positions (a plurality of outlets 5) spaced apart by a distance of less than 10.0 mm in the Z direction. Therefore, for the same reason as in the plasma generator 1 of the first embodiment, a gas space PA filled with the plasma gas G1 is formed in an area wider than the opening width of each outlet 5. This improves the surface treatment capability for the workpiece W.

[0144] (Variation) The configuration of the plasma generator 1 described above with reference to Figures 10 to 14 is merely an example, and various variations can be adopted for the plasma generator 1 of this embodiment. The structure of each variation will be described below with reference to Figures 15A to 15G, which are shown following Figure 13.

[0145] <1> In the configuration shown in Fig. 10, the dielectric substrate 30 had a shape in which the thickness (length in the Z direction) became thinner as it progressed in the +X direction. More specifically, the inclined surface 34 of the dielectric substrate 30 was inclined so as to approach the gas flow path 3 as it progressed in the +X direction. In contrast, as shown in Fig. 15A, the dielectric substrate 30 may have a shape in which the thickness becomes thicker as it progresses in the +X direction. In other words, the inclined surface 34 of the dielectric substrate 30 may be inclined so as to move away from the gas flow path 3 as it progresses in the +X direction.

[0146] <2> In the configuration shown in FIG. 10 , the second electrode 20 has an inclined surface 22 such that the thickness (length in the Z direction) increases with increasing distance in the +X direction. In other words, the second electrode 20 has a shape such that the thickness is greatest at the position closest to the first end 71 in the X direction. In contrast, as in FIG. 9C described above, the inclination of the inclined surface 22 of the second electrode 20 may be set so that the thickness decreases slightly at the position closest to the first end 71 in the X direction (see FIG. 15B ). More specifically, in a region 81 shown in FIG. 15B , the second electrode 20 is inclined in the Z direction so as to move away from the dielectric substrate 30.

[0147] 15C , an insulating member 91 may be formed on the dielectric substrate 30, contacting the end of the first electrode 10 on the +X side. According to this configuration, the insulating member 91 is provided between the first electrode 10 and the air outlet 5 in the X direction, thereby ensuring a creeping distance between the first electrode 10 and the second electrode 20 on the air outlet 5 side. This suppresses unnecessary discharges, such as short circuits and creeping discharges between the first electrode 10 and the second electrode 20.

[0148] Examples of materials for the insulating member 91 include those exemplified as materials for the dielectric substrate 30.

[0149] 15D, the dielectric substrate 30 may be provided with an insulating protrusion 92 at a position spaced from the end of the first electrode 10 on the +X side. In the example shown in Fig. 15D, the protrusion 92 is formed integrally with the dielectric substrate 30, but the protrusion 92 may be formed of a member separate from the dielectric substrate 30.

[0150] <4> As described above with reference to FIG. 9H, in this embodiment, a protective film 85 may be formed on the surface of the second electrode 20 near the air outlet 5 (see FIG. 15E).

[0151] As described above with reference to FIG. 9I, in this embodiment too, a starting aid member 86 may be formed on the surface of the dielectric substrate 30 in the vicinity of the air outlet 5 (see FIG. 15F).

[0152] As described above with reference to FIG. 9J, in this embodiment too, a light blocking member 87 may be provided at a position adjacent to the +X side of the air outlet 5 (see FIG. 15G).

[0153] 15H, the +X side end of second electrode 20 may be set back a small distance toward the −X side from first end 71. In this case, plasma gas G1 flowing through gas flow path 3 on the +Z side and plasma gas G1 flowing through gas flow path 3 on the −Z side are blown out from a common outlet 5.

[0154] <7> Fig. 11 illustrates an example in which a common power supply device 63 is connected to a pair of first electrodes 10. However, an individual power supply device 63 may be connected to each first electrode 10.

[0155] <8> The above-described modifications can be combined as appropriate. [Explanation of symbols]

[0156] 1: Dielectric barrier discharge plasma generator 3: Gas flow path 5:Air outlet 10:First electrode 20:Second electrode 27: Recess 30: Dielectric substrate 40: Gas buffer substrate 45: Housing 51 :Void 53: Connection hole 61: Gas delivery device 63: Power supply 82: Insulating material 85:Protective film 86: Starting aid 87: Light blocking material 88: Body 91: Insulating material 92: Protrusion

Claims

1. A dielectric substrate having a plate shape extending in a first direction; a first electrode disposed in contact with a surface of the dielectric substrate; a second electrode disposed extending in the first direction, at a distance from the dielectric substrate on a side opposite to a side on which the first electrode is disposed, in a second direction perpendicular to the first direction; a gas flow path formed by a gap between the dielectric substrate and the second electrode in the second direction, through which gas flows in a third direction perpendicular to the first direction and the second direction; an air outlet provided at one end of the gas flow path in the third direction and extending in the first direction, When viewed in the first direction, at least one of the dielectric substrate, the first electrode, and the second electrode has an inclined surface in a region between a predetermined position and the air outlet in the third direction, one of the dielectric substrate and the second electrode is disposed to sandwich the other of the dielectric substrate and the second electrode with the gap therebetween in the second direction, the dielectric substrate has a slit-shaped hole formed to extend parallel to a main surface, the first electrode has a plate shape and is embedded in the hole to be in contact with the dielectric substrate; The dielectric barrier discharge plasma generator, characterized in that the second electrodes are arranged to sandwich the dielectric substrate at a distance from both sides in the first direction.

2. the first electrode is a high-voltage electrode, 2. The dielectric barrier discharge plasma generator according to claim 1, wherein the second electrode is an electrode on the low voltage side.

3. a gas buffer substrate abutting the pair of second electrodes at their peripheral edges from outside; a gas delivery device that introduces the gas into a gap between the gas buffer substrate and the second electrode; 2. The dielectric barrier discharge plasma generator according to claim 1, further comprising: communication holes penetrating the second electrode in the second direction at a plurality of different locations in the first direction.

4. 2. The dielectric barrier discharge plasma generator according to claim 1, wherein the dielectric substrate is mainly made of aluminum oxide or aluminum nitride.

5. A dielectric substrate having a plate shape extending in a first direction; a first electrode disposed in contact with a surface of the dielectric substrate; a second electrode disposed extending in the first direction, at a distance from the dielectric substrate on a side opposite to a side on which the first electrode is disposed, in a second direction perpendicular to the first direction; a gas flow path formed by a gap between the dielectric substrate and the second electrode in the second direction, through which gas flows in a third direction perpendicular to the first direction and the second direction; an air outlet provided at one end of the gas flow path in the third direction and extending in the first direction, When viewed in the first direction, at least one of the dielectric substrate, the first electrode, and the second electrode has an inclined surface in a region between a predetermined position and the air outlet in the third direction, one of the dielectric substrate and the second electrode is disposed to sandwich the other of the dielectric substrate and the second electrode with the gap therebetween in the second direction, The pair of dielectric substrates are spaced apart in the second direction, a pair of the first electrodes are disposed on outer surfaces of the pair of the dielectric substrates, respectively; The dielectric barrier discharge plasma generator, characterized in that the second electrode is disposed at a position spaced apart from each inner surface of the pair of dielectric substrates in the second direction.

6. the first electrode is a high-voltage electrode, The dielectric barrier discharge plasma generator according to claim 5, wherein the second electrode is an electrode on the low voltage side.

7. 6. The dielectric barrier discharge plasma generator according to claim 5, further comprising an insulating protrusion arranged on a surface of the dielectric substrate at a position between the first electrode and the outlet in the third direction.

8. 6. The dielectric barrier discharge plasma generator according to claim 5, wherein the dielectric substrate is mainly made of aluminum oxide or aluminum nitride.

9. the gas flow path is formed at two locations spaced apart in the second direction, 9. The dielectric barrier discharge plasma generator according to claim 1, wherein the outlets are arranged corresponding to the respective gas flow paths.

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