Dielectric barrier discharge type plasma generating device

Abstract

Provided is a dielectric barrier discharge type plasma generating device capable of efficiently ejecting plasma uniformly from the entire area of a blowout port. The dielectric barrier discharge type plasma generating device includes: a dielectric substrate in the shape of a plate extending in a first direction, having a first surface and a second surface on the side opposite the first surface in a second direction orthogonal to the first direction; a first electrode disposed on the first surface side of the dielectric substrate; a second electrode disposed at a position away from the second surface of the dielectric substrate in the second direction; a gas flow path formed by a gap between the dielectric substrate and the second electrode, through which a gas flows in a third direction orthogonal to the first and second directions; and a blowout port provided at one end, i.e., a first end, of the gas flow path in the third direction and extending in the first direction.

Description

Technical Field

[0001] This invention relates to a dielectric barrier discharge plasma generator. Background Technology

[0002] Plasma generators are used in manufacturing processes of plastics, paper, fibers, semiconductors, liquid crystals, or thin films. For example, by irradiating the workpiece with plasma from a plasma generator, surface treatments are performed to improve the hydrophilicity, adhesion, or printability of the workpiece's surface; organic matter present on the workpiece's surface is removed and cleaned; or an oxide film is formed on the workpiece's surface.

[0003] Figure 18 This is a schematic cross-sectional view of a conventional plasma generator. As shown in Patent Document 1... Figure 18 As shown, a plasma generating apparatus 200 is disclosed, comprising a pair of opposing electrodes (201, 202), with the opposing surfaces (202, 202) of each electrode tilted in opposite directions. That is, the arrangement is such that the spacing between the pair of opposing surfaces (202, 202) narrows as it approaches the lower surface opening 226.

[0004] The plasma generator 200 generates multiple streamer discharges Sd in the region (discharge region 207) sandwiched by a pair of opposing surfaces (202, 202) by introducing plasma source gas Gc through the upper surface opening 223 and applying a voltage between a pair of electrodes (201, 201). The plasma source gas Gc is introduced into the discharge region 207 through the throttling orifice 225 of the jet plate 224 from the upper surface opening 223. Therefore, the plasma source gas Gc is accelerated by the throttling orifice 225 and ejected at high speed into the discharge region 207. This ejection creates turbulence in the plasma source gas Gc, and the streamer discharges Sd are dispersed within the discharge region 207.

[0005] Then, plasma Pc is generated substantially uniformly throughout the discharge region 207 by dispersed streamer discharge Sd. The generated plasma Pc is ejected into the processing space 205 in the form of a plasma jet through the lower surface opening 226 of the discharge region 207, and blown onto the object to be processed 240. Patent Document 1 describes that by adopting the above structure, uniform plasma can be generated.

[0006] The upper surface and the opposite surface (202, 202) of the electrodes (201, 201) are covered by dielectric 203. The thickness of the dielectric film 203 is generally constant, for example, 0.5 mm to 5 mm.

[0007] Alternatively, as another method, there is a known device for generating plasma by inputting microwaves between a microstrip line and a ground conductor (see Patent Document 2). According to this device, impedance matching is achieved by adjusting the thickness of the dielectric layer by tilting it.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 2010-009890

[0011] Patent Document 2: Japanese Patent Application Publication No. 2008-282784 Summary of the Invention

[0012] The problem that the invention aims to solve

[0013] The plasma generating apparatus 200 disclosed in Patent Document 1 aims to generate plasma Pc substantially uniformly throughout the discharge region 207 by generating turbulence. However, for example, plasma Pc generated in the discharge region 207 at positions far from the lower surface opening 226 disappears while moving towards the lower surface opening 226. Therefore, in order to achieve this, the plasma Pc generated at a position far from the lower surface opening 226 disappears. Figure 18 With the electrodes (201, 201) configured as shown, it cannot be said that the plasma Pc blown out from the lower surface opening 226 is uniformly irradiated across the entire area of ​​the lower surface opening 226. This results in uneven treatment of the surface of the workpiece 240.

[0014] The plasma generating device disclosed in Patent Document 2 utilizes microwave technology.

[0015] Microwave-generated plasma is produced at high density at the antinodes of standing waves with strong electric fields. Standing waves are generated not only in the direction of microwave input but also in directions orthogonal to the input direction. Therefore, when observing the nozzle from the front, regions with high and low plasma density alternate. Consequently, it is not easy to uniformly eject plasma from the entire nozzle area using microwave-generated plasma.

[0016] Moreover, from the perspective of generating standing waves, it is impossible to make the device itself longer.

[0017] Therefore, even for applications intended for surface treatment of the object being treated, the processing capacity is extremely low, making it practically difficult to apply.

[0018] In view of the above-mentioned problems, the present invention aims to provide a dielectric barrier discharge plasma generator capable of efficiently and uniformly ejecting plasma from the entire area of ​​the blow-out port.

[0019] Technical solutions for solving the problem

[0020] The dielectric barrier discharge plasma generator of the present invention comprises:

[0021] A dielectric substrate, having a plate shape extending in a first direction, has a first surface and a second surface located on the opposite side of the first surface in a second direction orthogonal to the first direction;

[0022] The first electrode is disposed on the first surface side of the dielectric substrate;

[0023] The second electrode is disposed at a position that separates from the second surface of the dielectric substrate in the second direction;

[0024] A gas flow path is formed by the gap between the dielectric substrate and the second electrode, allowing gas to flow upwards in a third direction orthogonal to the first and second directions; and

[0025] The outlet is located at one end of the gas flow path in the third direction, i.e., the first end, and extends in the first direction. The dielectric barrier discharge plasma generator also exhibits the following features.

[0026] The first surface of the dielectric substrate is a flat surface parallel to the third direction, at least from the end opposite the blow-out port (i.e., the second end) to the first reference portion in the third direction. The second surface of the dielectric substrate is also a flat surface parallel to the third direction, at least from the second end to the second reference portion in the third direction.

[0027] The main surface, i.e. the third surface, of the second electrode, which is opposite to the second surface of the dielectric substrate across the gas flow path, is a flat surface parallel to the third direction, at least between the second end and the third reference portion in the third direction.

[0028] At least one of the following surfaces—the first surface in a first specific region from the first reference point to the first end, the second surface in a second specific region from the second reference point to the first end, and the third surface in a third specific region from the third reference point to the first end—is an inclined surface relative to the third direction.

[0029] The first electrode is disposed at least between the first reference portion and the first end.

[0030] When viewed along the first direction, the angle α formed by the first face in the first specific region and the third direction, the angle β formed by the second face in the second specific region and the third direction, and the angle γ formed by the third face in the third specific region and the third direction satisfy both of the following equations (1) and (2).

[0031] [Formula 1]

[0032] sinα+(ε r -1), sinβ-ε, sinγ<0 (1)

[0033] A α sinα+d1(0)>Aβsinβ>Aγsinγ-d2(0) (2)

[0034] Wherein, ε in equation (1) r It is the relative permittivity of the dielectric substrate.

[0035] In addition, in equation (2), A α A β and A γ The lengths of the first specific region, the second specific region, and the third specific region in the third direction are respectively corresponding to the lengths of the first specific region, the second specific region, and the third specific region. d1(0) is the thickness of the dielectric substrate in the second direction at the reference position of the first reference position and the second reference position on the side of the third direction near the second end. d2(0) is the height of the gas flow path in the second direction at the reference position of the second reference position and the third reference position on the side of the third direction near the second end.

[0036] According to the dielectric barrier discharge plasma generator constructed as described above, since the shapes of the dielectric substrate and electrodes are set to satisfy equations (1) and (2) above, the electric field strength increases as the gas flows in the third direction within the gas flow path and approaches the outlet. Therefore, an extremely high-intensity electric field is formed at a location very close to the outlet, and plasma is generated concentratedly in this region. As a result, it is possible to efficiently blow plasma-containing gas onto the workpiece from the outlet, thereby enabling efficient processing of the workpiece.

[0037] Furthermore, the details of the reason why the electric field strength in the gas flow path increases as it approaches the outlet by satisfying equations (1) and (2) above will be described later in the "Specific Implementation" section.

[0038] The main material of the dielectric substrate can be aluminum oxide (Al2O3) or aluminum nitride (AlN).

[0039] Here, "main material" refers to the component that accounts for more than 80% when the composition of the constituent materials is analyzed.

[0040] Alumina and aluminum nitride have relatively low relative permittivity and relatively high physical strength and hardness. Therefore, by making alumina or aluminum nitride the main material of the dielectric substrate, it is possible to generate more plasma per unit power, and the possibility of breakage can be reduced even if the dielectric substrate is made thinner.

[0041] Aluminum nitride has excellent thermal conductivity, enabling efficient heat dissipation from the dielectric substrate. This suppresses temperature rise on the side of the first and second electrodes where a high voltage is applied (the high-voltage side electrode), thus reducing interfacial stress between the aluminum nitride and the high-voltage side electrode caused by thermal expansion. As a result, a longer lifespan is achieved for the dielectric barrier discharge plasma generator.

[0042] The first electrode may also be a foil-shaped metal. The metal material is not limited, but a material with high conductivity is preferred. Typical examples include one or more materials belonging to the group consisting of copper, silver, aluminum, and gold, or compounds of said materials.

[0043] The first electrode can also be a sintered body containing metal. Since a sintered body containing metal can be formed by printing metal paste, an adhesive is not required when forming the first electrode on the dielectric substrate.

[0044] The first electrode can also be formed by plating, evaporation, sputtering, or spraying. Similarly, in this configuration, no adhesive is required when forming the first electrode on the dielectric substrate.

[0045] Alternatively, the dielectric substrate may have the following shape: the thickness in the second direction is constant regardless of the position in the third direction, or the thickness in the second direction gradually increases from the first reference portion toward the first end.

[0046] Alternatively, the first electrode can be a high-voltage side electrode, and the second electrode can be a low-voltage side electrode.

[0047] In this case, the dielectric barrier discharge plasma generator may also include a power supply device connected to the first electrode. Preferably, the power supply device is capable of supplying a voltage signal of 3kV to 20kV and a frequency of 20kHz to 150kHz to the first electrode.

[0048] If a power supply device as described above is provided, plasma can be appropriately generated using dielectric barrier discharge. The reason for setting the upper limit to 150kHz is that its wavelength takes into account the plasma irradiation length, and also, the frequency detected by the noise terminal voltage under EMC standards is a frequency higher than 150kHz.

[0049] Alternatively, the dielectric barrier discharge plasma generator may also include:

[0050] The gas buffer substrate abuts against the second electrode at its peripheral portion from the side opposite to the dielectric substrate.

[0051] A gas delivery device introduces gas into the gap between the gas buffer substrate and the second electrode; and

[0052] A connecting hole, located at multiple different points in the first direction, penetrates the second electrode in the second direction.

[0053] According to the above structure, 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 multiple connecting holes. This allows the gas flowing into the gas flow path to flow out uniformly from the outlet without disrupting its flow.

[0054] In particular, by providing connecting holes at multiple locations in the first direction, gas is introduced into the gas flow path from multiple different positions in the first direction. This facilitates laminarization of the gas flowing in the gas flow path.

[0055] Alternatively, the connecting hole may be located on the second end side of the first electrode in the third direction.

[0056] Alternatively, the first electrode may be positioned at a location that is moved back from the first end to the second end in the third direction by a distance less than d1(0).

[0057] Near the blow-out port, it is possible for a discharge to occur directly between the first and second electrodes without passing through the dielectric substrate. When such a discharge occurs, it can sometimes damage the first electrode, the second electrode, or the dielectric substrate. In this case, their constituent materials may be mixed into the plasma as impurities and adhere to the surface of the object being treated.

[0058] From the perspective of discharge efficiency, it is more advantageous, in the third direction, to align the end of the first electrode with the foremost point (first end) of the blow-out port. However, in this configuration, due to the aforementioned factors, surface discharge may occur on the dielectric substrate. Once this surface discharge occurs, direct discharge, rather than dielectric barrier discharge, becomes dominant, resulting in excessive discharge current flowing through the electrode, which in turn leads to electrode damage and consequently, damage to the power supply device.

[0059] In contrast, by adopting the structure described above, direct discharge between the first electrode and the second electrode is suppressed, thereby suppressing damage to the electrodes and dielectric substrate and preventing impurities from being mixed into the plasma gas.

[0060] The dielectric barrier discharge plasma generator may also include a start-up auxiliary member disposed on the second surface of the second specific region. This start-up auxiliary member is preferably disposed immediately next to the outlet, i.e., near the first end. However, if the position of the start-up auxiliary member coincides with the position of the outlet when viewed along the first direction, a portion of the plasma gas from both the start-up auxiliary member and the outlet will collide with the start-up auxiliary member, potentially causing it to be worn away or removed. On the other hand, if the start-up auxiliary member is excessively separated from the outlet in the third direction, it cannot function as a start-up aid at all. From this viewpoint, the start-up auxiliary member is preferably disposed near the outlet and slightly recessed towards the second end in the third direction. This recessed distance is preferably less than 10 mm, more preferably less than 10 mm minus the thickness of the dielectric substrate at the first end (equivalent to the following description). Figure 8 The distance obtained by the distance d1a within the range (i.e., 10-d1a).

[0061] Dielectric barrier discharge requires high power at startup (the beginning of the discharge), but once a discharge occurs, it can be maintained even with reduced input power. Therefore, it is preferable to apply high power at startup. However, this method requires a large power supply unit to match the high power and trigger electrodes positioned near the discharge space, potentially increasing the overall size of the device.

[0062] At the start of plasma discharge, initial electrons are required at the plasma generation site. Therefore, if the start-up auxiliary components are configured as described above, initial electrons are supplied to the gas flow path near the blow-out port during the initial start-up phase. This eliminates the need for large power supply units and trigger electrodes, enabling the provision of a small and inexpensive plasma generator.

[0063] Invention Effects

[0064] The dielectric barrier discharge plasma generator according to the present invention can efficiently and uniformly eject plasma from the entire area of ​​the blow-out port. Attached Figure Description

[0065] Figure 1 This is a perspective view schematically illustrating the structure of one embodiment of the dielectric barrier discharge plasma generator of the present invention.

[0066] Figure 2 It is Figure 1 The above-mentioned plasma generator is shown as a schematic cross-sectional view cut along line II-II.

[0067] Figure 3 It is Figure 1 The above-mentioned plasma generator is shown as a schematic cross-sectional view cut along line III-III.

[0068] Figure 4 This is a schematic top view of the second electrode 20 as observed from the +Z side.

[0069] Figure 5A From Figure 2 A cross-sectional magnified view of the dielectric substrate 30 was extracted.

[0070] Figure 5B It is an imitation Figure 5A The figure shows a cross-sectional view of another structural example of the dielectric substrate 30.

[0071] Figure 6A From Figure 2 A cross-sectional magnified view of the second electrode 20 was extracted.

[0072] Figure 6B It is an imitation Figure 6A A cross-sectional view of another structural example of the second electrode 20 is shown.

[0073] Figure 7 It is an imitation Figure 2 The illustration shows a schematic cross-sectional view of a modified example of a plasma generator.

[0074] Figure 8 This is a schematic diagram used to illustrate the shapes of the first surface 31, the second surface 32, and the third surface 23.

[0075] Figure 9A This is a perspective view schematically showing the structure of the plasma generating device of Comparative Example 1.

[0076] Figure 9B This is a schematic cross-sectional view of the plasma generator shown in Figure 9 after it has been cut along line IXB-IXB.

[0077] Figure 10This is a graph showing the change in hydrophilization efficiency when the plasma generating device 1 of Example 1 is operated continuously.

[0078] Figure 11 It is a top view showing the arrangement of polypropylene (PP) films, which are the objects to be irradiated, on a stage at specified intervals.

[0079] Figure 12 It is a graph showing the measurement results of the water contact angle.

[0080] Figure 13 This is a partially enlarged cross-sectional view schematically illustrating another structure of one embodiment of a dielectric barrier discharge plasma generator.

[0081] Figure 14 This is a partially enlarged cross-sectional view schematically illustrating another structure of one embodiment of a dielectric barrier discharge plasma generator.

[0082] Figure 15 This is a partially enlarged cross-sectional view schematically illustrating another structure of one embodiment of a dielectric barrier discharge plasma generator.

[0083] Figure 16 This is a partially enlarged cross-sectional view schematically illustrating another structure of one embodiment of a dielectric barrier discharge plasma generator.

[0084] Figure 17A This is a partially enlarged cross-sectional view schematically illustrating another structure of one embodiment of a dielectric barrier discharge plasma generator.

[0085] Figure 17B This is a partially enlarged cross-sectional view schematically illustrating another structure of one embodiment of a dielectric barrier discharge plasma generator.

[0086] Figure 17C This is a partially enlarged cross-sectional view schematically illustrating another structure of one embodiment of a dielectric barrier discharge plasma generator.

[0087] Figure 17D This is a partially enlarged cross-sectional view schematically illustrating another structure of one embodiment of a dielectric barrier discharge plasma generator.

[0088] Figure 17E This is a partially enlarged cross-sectional view schematically illustrating another structure of one embodiment of a dielectric barrier discharge plasma generator.

[0089] Figure 17F This is a partially enlarged cross-sectional view schematically illustrating another structure of one embodiment of a dielectric barrier discharge plasma generator.

[0090] Figure 17G This is a partially enlarged cross-sectional view schematically illustrating another structure of one embodiment of a dielectric barrier discharge plasma generator.

[0091] Figure 18 This is a schematic cross-sectional view of an existing dielectric barrier discharge plasma generator. Detailed Implementation

[0092] Embodiments of the dielectric barrier discharge plasma generator according to the present invention will be described with appropriate reference to the accompanying drawings. Please note that the following drawings are schematic and the dimensions shown may not necessarily match the actual dimensions. Furthermore, inconsistencies in dimension ratios may exist between different drawings.

[0093] [structure]

[0094] Figure 1 This is a perspective view schematically illustrating the dielectric barrier discharge plasma generator of this embodiment. The dielectric barrier discharge plasma generator 1 (hereinafter referred to as "plasma generator 1") includes a first electrode 10, a second electrode 20, and a dielectric substrate 30. Furthermore, in Figure 1 The plasma generator 1 shown also includes a gas buffer substrate 40. However, whether or not the plasma generator 1 includes a gas buffer substrate 40 is optional.

[0095] The plasma generator 1 is a device that generates plasma gas G1 internally and has an outlet 5 for blowing out the plasma gas G1. Figure 1 As shown, the blow-out nozzle 5 extends in the Y direction and is approximately rectangular when viewed along the X direction. Furthermore, the direction orthogonal to both the X and Y directions is defined as the Z direction. In the following description, appropriate references will be made to the appended... Figure 1 The XYZ coordinate system.

[0096] Furthermore, in the following explanation, when indicating direction, if a positive or negative orientation is distinguished, it will be written using positive and negative symbols, such as "+X direction" and "-X direction". If a direction is not distinguished by positive or negative, it will simply be written as "X direction". That is, in this specification, the use of "X direction" includes both "+X direction" and "-X direction". The same applies to the Y and Z directions.

[0097] 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".

[0098] Figure 2 It is Figure 1 A schematic cross-sectional view of the plasma generator 1 cut along line II-II. Additionally, Figure 3 It is Figure 1 A schematic cross-sectional view of the plasma generator 1 cut along line III-III.

[0099] (Dielectric substrate 30)

[0100] like Figures 1-3 As shown, the dielectric substrate 30 is a plate-like member extending in the Y direction. The dielectric substrate 30 has a first surface 31 and a second surface 32 (see reference). Figure 2 Additionally, as described later, a first electrode 10 is disposed on the first surface 31 side of the dielectric substrate 30, and a second electrode 20 is disposed separately from the dielectric substrate 30 on the second surface 32 side.

[0101] In addition, Figures 1-2 The example shown employs a configuration where the length (hereinafter referred to as "thickness") of the dielectric substrate 30 in the Z direction thins in the X direction as it approaches the blow-out port 5; however, this configuration is merely an example. A detailed explanation of the thickness of the dielectric substrate 30 will be provided in [reference needed]. Figure 8 To be described later.

[0102] From the viewpoint of generating more plasma per unit of power, the dielectric substrate 30 is preferably made of a material with a low relative permittivity. The relative permittivity of this material is preferably 10 or less. Furthermore, the lower the relative permittivity of the material, the more preferred it is, but typically it can be 4 to 10.

[0103] The material of the dielectric substrate 30 is not particularly limited, but as mentioned above, a material with the lowest possible relative permittivity is preferred. Furthermore, from a durability point of view, ceramic is preferred. Examples of ceramics include alumina, aluminum nitride, and bulk talc. These materials have relatively low relative permittivity and relatively high strength, exhibiting excellent durability. Therefore, if the dielectric substrate 30 is made of alumina, aluminum nitride, or bulk talc, a greater amount of plasma can be generated per unit power. Additionally, due to its excellent durability, the possibility of breakage is low even if the thickness of the dielectric substrate 30 is reduced.

[0104] The dielectric substrate 30 may also be a substrate made of the aforementioned material and containing a substance that assists in electron generation. Examples of such substances include silver, platinum, copper, carbon, or transition metal compounds. Initial electrons are generated by applying an electric field to the substance and released into the discharge space (gas flow path 3 described later). Therefore, by structuring the dielectric substrate 30 as described above, it is advantageous to achieve good start-up performance.

[0105] The content of the aforementioned auxiliary electron-generating substance is preferably 1% by mass or less relative to the entire dielectric substrate 30 (when the dielectric substrate 30 is set to 100% by mass). If the content of this substance is too high, it may evaporate and disperse during discharge, mixing into the plasma gas G1, and potentially being blown onto the workpiece that is irradiated by the plasma gas G1. Furthermore, from the viewpoint of fully expressing the effect of improving start-up performance, the content of the aforementioned substance is experimentally preferably 0.05% by mass or more.

[0106] (First electrode 10)

[0107] like Figure 2 As shown, the first electrode 10 is disposed on the first surface 31 of the dielectric substrate 30.

[0108] The plasma generating device 1 generates plasma gas G1 by applying a voltage between the first electrode 10 and the second electrode 20 (described later) via the dielectric substrate 30 and the gas flow path 3, thereby plasmaifying the gas flowing within the gas flow path 3. Therefore, either the first electrode 10 or the second electrode 20 is a high-voltage side electrode, and the other is a low-voltage side electrode. In the following embodiment, the case where the first electrode 10 is a high-voltage side electrode and the second electrode 20 is a low-voltage side electrode will be described, but the reverse is also possible.

[0109] like Figure 1 and Figure 3 As shown, in this embodiment, the length (hereinafter referred to as "width") of the first electrode 10 in the Y direction is approximately equal to the width of the dielectric substrate 30. The plasma generating device 1 generates plasma on the -Z side of the region where the first electrode 10 is provided. Therefore, considering the viewpoint of ejecting plasma gas G1 from the blow-out port 5 in a wide area (a longer area in the Y direction), it is preferable to form the first electrode 10 as wide as possible. However, the present invention does not limit the width of the first electrode 10.

[0110] In this embodiment, the first electrode 10 is slightly recessed in the X direction from the outlet 5 towards the -X side. That is, referring to... Figure 2 The end 10a of the first electrode 10 on the +X side is slightly recessed from the end on the outlet 5 side (+X side) of the plasma generator 1 toward the -X side. In addition, for convenience, the end on the outlet 5 side (+X side) of the plasma generator 1 is sometimes referred to as the "first end 71", and the end on the side opposite to the outlet 5 (-X side) is referred to as the "second end 72".

[0111] Near the blow-out port 5, it is possible to discharge directly between the first electrode 10 and the second electrode 20 without passing through the dielectric substrate 30. When such a discharge occurs, it will damage the electrodes (10, 20) or the dielectric substrate 30, and their constituent materials will be mixed into the plasma gas G1 as impurities.

[0112] From the viewpoint of discharge efficiency, it is preferable to make the +X side end 10a of the first electrode 10 as close as possible to the blow-out port 5, that is, to be approximately aligned with the first end 71. However, when such a structure is adopted, the risk of surface discharge between the first electrode 10 and the second electrode 20 increases, resulting in direct discharge becoming dominant instead of dielectric barrier discharge. Therefore, as described above, a structure is adopted in which the +X side end 10a of the first electrode 10 is slightly recessed from the first end 71 toward the -X side (second end 72 side). This recessed distance, that is, 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.

[0113] The material of the first electrode 10 is not particularly limited, but a material with high conductivity is preferred. Typical examples include one or more materials belonging to the group consisting of copper, silver, aluminum, and gold, or compounds of the aforementioned materials. Alternatively, the first electrode 10 can be a foil-shaped metal. For example, copper foil, aluminum foil, or other metal foils with one side bonded together can be used.

[0114] The first electrode 10 can also be a sintered body containing a conductive metal. This sintered body containing metal can be formed by printing metal paste onto the first surface 31 of the dielectric substrate 30, thus eliminating the need for adhesives during manufacturing. Furthermore, from the viewpoint of not using adhesives, the first electrode 10 can also be formed by plating, vapor deposition, sputtering, or spraying.

[0115] The first electrode 10 is in close contact with the dielectric substrate 30 (first surface 31), preferably without an air layer at their interface. This is because if an air layer exists, a discharge will occur within that space, and the first electrode 10 may degrade due to the generated free radicals. For this reason, the first electrode 10 and the dielectric substrate 30 are preferably in close contact within a separation distance on the order of μm. (Refer to...) Figure 16 As will be described later, from the viewpoint of improving the adhesion between the two, the surface of the first surface 31 of the dielectric substrate 30 can be roughened to form tiny bumps and depressions with the anchoring effect as the goal.

[0116] Typically, the length (hereinafter referred to as "thickness") of the first electrode 10 in the Z direction 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 with the application of a high voltage, the effect of the expansion is slight for the dielectric substrate 30 due to the thin thickness of the first electrode 10.

[0117] When the first electrode 10 is a high-voltage side electrode, a portion of the first electrode 10 is connected to the power supply device 63. The connection method between the power supply device 63 and the first electrode 10 is not particularly limited as long as it is an electrical connection capable of withstanding the applied voltage. Examples include connections using solder or connections using various connectors (e.g., coaxial connectors). Furthermore, in the plasma generating apparatus 1 of this embodiment, since microwaves are not used when generating plasma, it is not necessary to use a coaxial connector or coaxial cable with a specified characteristic impedance.

[0118] The voltage and frequency applied from the power supply device 63 to the first electrode 10 can be within a range sufficient to generate dielectric barrier discharge in the plasma generator 1. Typically, the applied voltage is 3kV to 20kV, preferably 3kV to 10kV. Furthermore, the frequency of the voltage signal is typically 20kHz to 1000kHz, more preferably 50kHz to 150kHz. The upper limit is preferably 150kHz because its wavelength takes into account the plasma irradiation length, and also because the frequency detected by the noise terminal voltage under EMC standards is higher than 150kHz.

[0119] (Second electrode 20)

[0120] The second electrode 20 is in the shape of a plate extending in the Y direction and is disposed at a position away from the second surface 32 of the dielectric substrate 30 in the Z direction. When the second electrode 20 is used as an electrode on the low-voltage side, it can be connected directly or via a resistor to the ground potential, or it can be connected to the output on the low-voltage side of the power supply device 63.

[0121] like Figure 2 and Figure 3 As shown, a recess 27 is formed in a portion of the surface on the +Z side of the second electrode 20. This recess 27 extends in the Y direction.

[0122] Figure 4 This is a schematic top view of the second electrode 20 as observed from the +Z side. According to... Figures 2-4 It can be seen that the second electrode 20 has a higher height at its outer edge 26 on the +Y, -Y, and -X sides, and the aforementioned recess 27 is formed on the inner side of the outer edge 26. For example... Figures 2-3As shown, the outer edge 26 of the second electrode 20 abuts against the second surface 32 of the dielectric substrate 30. That is, when the outer edge 26 of the second electrode 20 abuts against the dielectric substrate 30, the recess 27 formed on the +Z side of the second electrode 20 forms a gap. This gap forms a "gas flow path 3".

[0123] exist Figure 4 In the example shown, multiple connecting holes 53 are formed at various locations separated in the Y direction on the bottom surface of the recess 27. The number of connecting holes 53 is not particularly limited, but it is preferable to have two or more, as in this embodiment. The connecting holes 53 are provided for introducing gas G0 from the gas delivery device 61 into the gas flow path 3, as described later. By providing multiple connecting holes 53 at different locations in the Y direction, it is easier to make the gas flow within the gas flow path 3 laminar. Furthermore, from the viewpoint that the gas should spread over a large area in the Y direction at the time of introduction into the gas flow path 3, it is preferable to form connecting holes 53 over a large area in the Y direction.

[0124] In addition, Figure 4 The example shown is an example of multiple independent connecting holes 53, but a single connecting hole 53 that is longer in the Y direction, such as a rectangular cylindrical shape, can also be formed.

[0125] (Gas buffer substrate 40)

[0126] like Figures 1-3 As shown, the plasma generating apparatus 1 includes a gas buffer substrate 40 that abuts against the second electrode 20 from the side opposite to the dielectric substrate 30, i.e., from the -Z side. In this embodiment, the gas buffer substrate 40 abuts against the second electrode 20 at its peripheral portion. Therefore, a gap 51 is formed between the second electrode 20 and the gas buffer substrate 40 on the inner side of this peripheral portion.

[0127] A gas delivery device 61 is connected to the aforementioned gap 51 (see reference). Figure 2 If processing gas G0 is delivered from the gas delivery device 61, it is buffered in the gap 51 and then introduced into the gas flow path 3 through the connecting hole 53.

[0128] (Blowout 5)

[0129] The plasma generator 1 has an outlet 5 at the +X side end, i.e., the first end 71, of the gas flow path 3. This outlet 5 ejects the plasma generated during the flow of gas along the +X direction within the gas flow path 3, along with the gas flow (plasma gas G1), outwards. For example, the width (length in the Y direction) of the gas flow path 3 and the outlet 5 of the plasma generator 1 is uniform regardless of the X coordinate. Therefore, the flow of the processing gas G0 into the gas flow path 3 is not turbulent, and the plasma gas G1 can be uniformly ejected from the outlet 5. It should be noted that this has also been confirmed through simulations conducted by the inventors of this invention.

[0130] However, the present invention is not limited to this example, and the width of the blow-out port 5 can be adjusted as needed. For example, by making the width of the blow-out port 5 narrower than the width of the -X side (second end 72 side) of the gas flow path 3, the intensity of the plasma gas G1 is increased. Conversely, by making the width of the blow-out port 5 wider than the width of the -X side (second end 72 side) of the gas flow path 3, the spray width of the plasma gas G1 is widened, thereby expanding the range of simultaneous spraying of the processed material.

[0131] The gas supplied from the gas delivery device 61, used as the gas for starting the plasma generator 1, can be one or more selected from the group consisting of He, Ne, and Ar. Furthermore, the gas after plasma generation can be a gas capable of generating the desired active species; specifically, one or more selected from the group consisting of hydrogen, oxygen, water, nitrogen, etc.

[0132] In this embodiment, the gas flow in the gas flow path 3 is preferably laminar. If the gas flow is laminar, the plasma can be ejected more uniformly. Here, the Reynolds number is used as a parameter to distinguish between laminar and turbulent flow.

[0133] Let the density of the fluid be ρ (kg / m³). 3 Let the flow velocity be U (m / s), the characteristic length be L (m), the fluid viscosity be μ (Pa·s), and the Reynolds number Re be given by:

[0134] Re = ρ·U·L / μ,

[0135] It represents a dimensionless quantity.

[0136] The Reynolds number that marks the boundary between laminar and turbulent flow is called the limiting Reynolds number, and its value ranges from 2000 to 4000.

[0137] In the plasma generating apparatus 1 used in Embodiment 1 described later, the flow rate of the processing gas G0 is set to 0.005 m³ / s. 3When the gas flow path 3 has a height (short side) in the Z direction of 300 L / min and a width (long side) in the Y direction of 700 mm, U = 14.3 (m / s) and L = 9.99 × 10⁻⁶ m / s. -4 (m), if the fluid is set as dry air at standard atmospheric pressure, ρ = 1.205 (kg / m³). 3 μ = 1.822 × 10 -5 If (Pa·s), then the Reynolds number is around 945, which is below the threshold Reynolds number, indicating laminar flow.

[0138] [Correlation between the shape of dielectric substrate 30 and second electrode 20]

[0139] Next, the shapes of the dielectric substrate 30 and the second electrode 20 will be described.

[0140] Figure 5A From Figure 2 The accompanying drawings show only an enlarged view of the dielectric substrate 30. For ease of explanation, the illustrations may be exaggerated, especially in the following drawings.

[0141] As described above, the dielectric substrate 30 has a first surface 31 on the +Z side and a second surface 32 on the -Z side. Figure 5A In the example shown, the region of the first surface 31 from the second end 72 to a designated location (referred to as the "first reference location 81") in the X direction is a flat surface parallel to the X direction, while the region from the first reference location 81 to the first end 71 (referred to as the "first specific region 91") is a surface inclined relative to the X direction. In contrast, Figure 5A The second surface 32 of the dielectric substrate 30 shown is a flat surface that is parallel to the X direction and is independent of the position of the X coordinate.

[0142] However, in this embodiment, it is not excluded that the second surface 32 of the dielectric substrate 30 may have an inclined surface. For example, in Figure 5B In the example shown, the region of the second surface 32 of the dielectric substrate 30 from the second end 72 to a predetermined portion (referred to as the "second reference portion 82") in the X direction is a flat surface parallel to the X direction, while the region from the second reference portion 82 to the first end 71 (referred to as the "second specific region 92") is a surface inclined relative to the X direction. Furthermore, Figure 5B The first surface 31 of the dielectric substrate 30 shown is... Figure 5A Similarly, the region from the second end 72 to the first reference portion 81 is a flat surface parallel to the X direction, and the region from the first reference portion 81 to the first end 71 (first specific region 91) is a surface inclined relative to the X direction.

[0143] That is, in the plasma generating apparatus 1 of this embodiment, the region of the first surface 31 of the dielectric substrate 30 relative to the second end 72 of the first reference portion 81 is a flat surface parallel to the X direction.

[0144] On the other hand, the region (first specific region 91) on the first surface 31 of the dielectric substrate 30 that is closer to the first end 71 than the first reference portion 81 is an inclined surface relative to the X direction. However, if the electric field strength is increased toward the first end 71, the first specific region 91 can also be a flat surface parallel to the X direction.

[0145] Similarly, in the plasma generating apparatus 1 of this embodiment, the region of the second surface 32 of the dielectric substrate 30 that is closer to the second end 72 than the second reference portion 82 which serves as a reference is a flat surface parallel to the X direction. On the other hand, the region (second specific region 92) that is closer to the first end 71 than the second reference portion 82 is a flat surface parallel to the X direction, or a surface that is inclined relative to the X direction.

[0146] Figure 6A From Figure 2 The accompanying drawings show only an enlarged view of the second electrode 20. As described above, the second electrode 20 has a surface that forms the bottom surface of the recess 27. Hereinafter, for ease of explanation, this surface will be referred to as "third surface 23".

[0147] exist Figure 6A In the example shown, the third surface 23 is a flat surface parallel to the X direction, independent of its position on the X coordinate. However, in this embodiment, it is not excluded that the third surface 23 may be a surface inclined relative to the X direction (an inclined surface). For example, in Figure 6B In the example shown, the region of the third surface 23 from the second end 72 to the designated location (referred to as the "third reference location 83") in the X direction is a flat surface parallel to the X direction, and the region from the third reference location 83 to the first end 71 (referred to as the "third specific region 93") is a surface inclined relative to the X direction.

[0148] That is, in the plasma generating apparatus 1 of this embodiment, the region of the third surface 23 that is closer to the second end 72 than the third reference portion 83 which serves as a reference is a flat surface parallel to the X direction. On the other hand, the region (third specific region 93) that is closer to the first end 71 than the third reference portion 83 is a flat surface parallel to the X direction, or a surface that is inclined relative to the X direction.

[0149] Furthermore, the inclination of the first surface 31, the second surface 32, and the third surface 23 is set such that, near the outlet 5, the electric field strength increases as the gas flows towards the +X side within the gas flow path 3. This relationship will be discussed in reference to... Figure 8 To be described later.

[0150] However, the first electrode 10 may also be disposed only near the first end 71 in the X direction (see reference). Figure 7 By applying a high voltage at a location near the blow-out port 5, a high electric field is applied to the gas flowing through the gas flow path 3 at that location, causing it to plasmaize.

[0151] Figure 8 This is a schematic diagram used to illustrate the shapes of the first surface 31, the second surface 32, and the third surface 23. In addition, for ease of understanding, some of the structures are exaggerated.

[0152] Here, the side of the first surface 31 that is +X closer to the first reference portion 81 (the side of the first end 71) is defined as an inclined surface, and the inclination angle is defined as α. Furthermore, in this specification, the term "inclination angle" is defined as the angle relative to a line parallel to the X direction when viewing the object surface along the Y direction, and counterclockwise is defined as a positive angle. The inclination angle is also synonymous with the angle of the object surface relative to the XY plane. The same applies to the second surface 32 and the third surface 23 described below.

[0153] exist Figure 8 In the middle, the X coordinate of the first reference part 81 is set as x α Alternatively, α = 0°. In this case, the first surface 31 is a flat surface, independent of the X-coordinate.

[0154] Let the second surface 32 be an inclined surface located on the +X side (the side of the first end 71) relative to the second reference portion 82, and let the inclination angle be β. Figure 8 In the middle, the X coordinate of the second reference part 82 is set as x. β Alternatively, β = 0°. In this case, the second surface 32 is a flat surface, independent of the X-coordinate.

[0155] Let the third surface 23 be an inclined surface located on the +X side (the side of the first end 71) relative to the third reference part 83, and let the inclination angle be γ. Figure 8 In the middle, the X coordinate of the third reference part 83 is set as x. γ Alternatively, γ = 0°. In this case, the third surface 23 is a flat surface independent of the X-coordinate.

[0156] Let the electric field at a certain X-coordinate value x be E(x), the thickness of the dielectric substrate 30 be d1(x), and the height of the gas flow path 3 be d2(x). Let the relative permittivity of the dielectric substrate 30 be ε. r When the relative permittivity of the gas flowing in the gas flow path 3 is set to ε0, the electric field E(x) is defined by the following equation (3).

[0157] [Formula 2]

[0158]

[0159] Here, the portion where the thickness of the dielectric substrate 30 begins to change as it advances in the +X direction is the -X side (the side closer to the second end 72) of the first reference portion 81 and the second reference portion 82. Figure 8 In the example, it corresponds to the first reference portion 81. The thickness of the dielectric substrate 30 at the portion where the thickness of the dielectric substrate 30 begins to change is defined as d1(0).

[0160] Similarly, the part where the height of the gas flow path 3 begins to change as it moves in the +X direction is the -X side (the side closer to the second end 72) of the second reference part 82 and the third reference part 83. Figure 8 In the example, it corresponds to the third reference part 83. The height of the gas flow path 3 at the part where the height of the gas flow path 3 begins to change is defined as d2(0).

[0161] According to the above regulations and Figure 8 According to plane geometry, the thickness d1(x) of the dielectric substrate 30 and the height d2(x) of the gas flow path 3 at the position with X coordinate x are represented by the following equations (4) and (5), respectively.

[0162] [Formula 3]

[0163] d1(x)=(xx α sinα-(xx) β sinβ+d1(0) (4)

[0164] d2(x)=(xx β sinβ-(xx) γ sinγ+d2(0) (5)

[0165] When equations (4) and (5) are substituted into equation (3) above, equation (6) is obtained.

[0166] [Formula 4]

[0167]

[0168] Here, the numerator in equation (6) is a constant. Therefore, in equation (6), in order for the electric field E(x) at the position with X coordinate x to increase monotonically, it is only necessary for the denominator of the above equation to decrease monotonically; in other words, it is only necessary for [the differential value of the denominator] < 0 to hold. Thus, the above equation (1) is derived. Hereinafter, equation (1) is expressed again.

[0169] [Formula 5]

[0170] sinα+(ε r -1)sinβ-εr sinγ<0 (1)

[0171] However, the thickness d1(x) of the dielectric substrate 30 and the height d2(x) of the gas flow path 3 at the position of X coordinate x also need to be positive at the position of the first end 71. Therefore, when the length of the region (first specific region 91) from the first reference portion 81 to the first end 71 in the X direction is set to A α Let A be the length of the region (second specific region 92) from the second reference part 82 to the first end 71 in the X direction. β Let A be the length of the region (third specific region 93) from the third reference part 83 to the first end 71 in the X direction. γ In order to make the thickness d1(x) of the dielectric substrate 30 at the position of the first end 71 and the height d2(x) of the gas flow path 3 positive, the above equation (2) is derived based on the relationship of plane geometry. Hereinafter, equation (2) is expressed again.

[0172] [Formula 6]

[0173] A α sinα+d1(0)>A β sinβ>A γ sinγ-d2(0) (2)

[0174] That is, by shaping the surfaces (first surface 31, second surface 32) of the dielectric substrate 30 and the surface (third surface 23) of the second electrode 20 to satisfy equations (1) and (2) above, the electric field strength of the gas flowing toward the outlet 5 in the gas flow path 3 increases monotonically. As a result, an extremely high electric field strength is achieved near the outlet 5, thus enabling efficient plasma generation.

[0175] There is no particular limitation on the size of the plasma generating device 1. In addition, the dielectric substrate 30 and the second electrode 20 are configured to satisfy the above equations (1) and (2).

[0176] As an example, the dimensions of the exterior are: width (length in the Y direction) 750mm, length (length in the X direction) 40mm, and thickness (length in the Z direction, the thickest part) 20mm.

[0177] The dielectric substrate 30 has the following dimensions: a width of 750 mm, a length of 40 mm, and a thickness (d1a) of 0.1 mm at the first end 71.

[0178] The second electrode 20 has the following dimensions: a width of 750 mm, a length of 20 mm, and a thickness of 0.1 mm at the first end 71.

[0179] The external dimensions of the gas flow path 3 are 700 mm in width and 35 mm in length.

[0180] The dimensions of the blow-out nozzle 5 are: opening width of 700mm and opening height of 0.2mm.

[0181] [Example]

[0182] Will have Figures 1-3 The structure shown, in which the surfaces of the dielectric substrate 30 (first surface 31, second surface 32) and the surface of the second electrode 20 (third surface 23) present shapes that satisfy equations (1) and (2), and a plasma generating device 1 with the above-mentioned dimensions is used as Embodiment 1. In addition, the dielectric substrate 30 is made of aluminum oxide, and both the first electrode 10 and the second electrode 20 are made of copper as the main material.

[0183] Will have Figures 9A-9B The plasma generator 100, schematically illustrated, serves as Comparative Example 1. Furthermore, Figures 9A-9B The illustration of the gas buffer substrate has been omitted. Figure 9B yes Figure 9A Sectional view along line IXB-IXB.

[0184] That is, the plasma generating device 100 of Comparative Example 1 includes a first electrode 110, a second electrode 120 and a dielectric substrate 130, but both main surfaces of the dielectric substrate 130 and the dielectric substrate 130 side surface of the second electrode 120 are all flat surfaces. Therefore, although it satisfies the above equation (2), it does not satisfy equation (1).

[0185] In the plasma generating apparatus 100 of Comparative Example 1, the gas flowing in the gas flow path 103 formed between the second electrode 120 and the dielectric substrate 130 is plasmaified when it passes through the high electric field region 108 and is ejected from the blow-out port 105 in the form of plasma gas G1.

[0186] Both the plasma generator 1 of Example 1 and the plasma generator 100 of Comparative Example 1 were operated under the following conditions, and a polypropylene substrate, which was to be processed, was passed at a speed of 10 mm / s from a position 2 mm away from the blow-out port (5, 105). The water contact angle of the substrate surface was measured using a contact angle meter (DMs-401 manufactured by Kyowa Interface Chemical Co., Ltd.).

[0187] (Operating conditions)

[0188] Applied voltage: 7.6kVpp, frequency: 38kHz

[0189] Gas type: Nitrogen,

[0190] Gas flow rate: 300L / min.

[0191] The results are shown in Table 1.

[0192] [Table 1]

[0193] Example 1 60±2 Comparative Example 1 70±3

[0194] As shown in Table 1, Example 1 exhibits a smaller water contact angle compared to Comparative Example 1, enabling further hydrophilization. Furthermore, Example 1 shows that, compared to Comparative Example 1, deviations in the water contact angle are suppressed, allowing for more uniform treatment of the substrate.

[0195] Next, the change in hydrophilization efficiency during continuous operation of the plasma generator 1 of Example 1 will be shown. Figure 10 Hydrophilization efficiency is an indicator representing the proportion of the change in the difference (Δθ(t)) between the water contact angle before and after treatment over time. More specifically, it is an indicator expressed as the ratio of the difference (Δθ(t)) over the operating time t, based on the difference (Δθ(0)) immediately after the start of operation (set as t=0 for convenience). That is, a ratio close to 100% indicates that the same treatment capacity as at the start of operation can be achieved.

[0196] according to Figure 10 It is known that, in the case of plasma generator 1 of Example 1, even after continuous operation for more than 6,000 hours, no damage to the dielectric substrate 30 and the electrodes (10, 20) was found, and the initial performance was maintained.

[0197] In contrast, when the plasma generator 100 of Comparative Example 1 was operated continuously, damage began to occur after more than 1 hour. Therefore, the plasma generator 100 of Comparative Example 1 is not suitable for continuous operation for more than 1 hour.

[0198] Figure 11 This is a top view showing polypropylene (PP) films, which are the materials to be processed, arranged at specified intervals on a stage. For example... Figure 11 As shown, polypropylene (PP) films, serving as the irradiated objects, are arranged at predetermined intervals on a stage, and plasma gas G1 is irradiated from above using the plasma generating apparatus 1 described in Example 1. More specifically, the PP films are fixed on a uniaxial stage at a position 2 mm (irradiation distance) from the blow-out port 5, and the blow-out port 5 is reciprocated at 100 mm / s to irradiate with plasma gas G1. The water contact angle of each PP film surface is measured at timed intervals of 2 times (after 2 reciprocations), 10 times (after 10 reciprocations), and 200 times (after 200 reciprocations).

[0199] The water contact angle was measured under the following conditions.

[0200] Contact angle meter: DMs-401 (manufactured by Kyowa Interface Science Co., Ltd.)

[0201] Liquid volume: 2μL,

[0202] An approximation using an ellipse is used.

[0203] Figure 12 This is a graph representing the measurement results of the water contact angle. (From...) Figure 12 It can be seen that the water contact angle, under any irradiation conditions, deviates from the average value by less than ±10% in the width direction (Y direction). Furthermore, when polypropylene (PP) films are also placed at Y-coordinates of 10mm, 30mm, and 50mm and the same test is conducted, the results show... Figure 12 The values ​​shown are within ±10% of the average values. From the above results, it can be seen that the plasma generator 1 according to Embodiment 1 can uniformly eject plasma gas G1 from the entire area in the Y direction of the outlet 5.

[0204] In the plasma generating device 1, the orientation of the tilt of the surfaces (first surface 31, second surface 32) of the dielectric substrate 30 and the surface (third surface 23) of the second electrode 20 is not limited as long as they have shapes that satisfy equations (1) and (2). For example, as Figure 13 As shown, it can also be a structure in which the first surface 31 is inclined towards the -Z side relative to the X direction, the second surface 32 is inclined towards the +Z side relative to the X direction, and the third surface 23 is inclined towards the -Z side relative to the X direction. In this case, the height d2(x) of the gas flow path 3 increases as it approaches the first end 71 (blowing outlet 5).

[0205] In addition, such as Figure 14 As shown, it can also be a structure in which the first surface 31 is inclined towards the +Z side relative to the X direction, the second surface 32 is inclined towards the -Z side relative to the X direction, and the third surface 23 is inclined towards the +Z side relative to the X direction. In this case, the height d2(x) of the gas flow path 3 decreases as it approaches the first end 71 (blowing outlet 5).

[0206] like Figure 15 As shown, the first surface 31 can also be a curved surface. In this case, since it can be considered a plane in a small region, it is sufficient to use a plane 31a that approximates the first surface 31 to satisfy equations (1) and (2). The same applies to the second surface 32 and the third surface 23.

[0207] like Figure 16As shown, a portion of the first surface 31 may also have irregularities. As described above, from the viewpoint of improving the contact with the first electrode 10, it is possible to use a method of providing irregularities on the first surface 31. In this case, it is sufficient to use a plane 31a that connects the ends (10a, 10b) of the first electrode 10 in the X direction to the contact portion of the dielectric substrate 30 to satisfy equations (1) and (2).

[0208] [Variation Example]

[0209] In the plasma generator 1, as long as the surfaces of the dielectric substrate 30 (first surface 31, second surface 32) and the surface of the second electrode 20 (third surface 23) have shapes that satisfy equations (1) and (2), it is possible to use the following... Figures 17A to 17G The various deformations shown. Figures 17A to 17G This is a modified example of the plasma generator 1, and is a schematic cross-sectional view showing only a portion of its elements. Furthermore, in the following... Figures 17A to 17G In order to facilitate explanation, some parts are sometimes exaggerated and illustrated.

[0210] Furthermore, in the following description of variations, only the parts that differ from the above-described embodiments will be described.

[0211] <1> Figure 17A The plasma generator 1 of the modified example shown has a protrusion 43 on the first surface 31 of the dielectric substrate 30, in the X direction, between the first electrode 10 and the first end 71, that is, between the first electrode 10 and the blow-out port 5. The protrusion 43 can be made of materials exemplified as the material of the dielectric substrate 30. The protrusion 43 can be integrally formed with the dielectric substrate 30, or it can be mounted as a separate component.

[0212] By providing a protrusion 43 in the X direction between the first electrode 10 and the outlet 5, the surface distance between the first electrode 10 and the second electrode 20 on the outlet 5 side is ensured. This suppresses unwanted discharges such as short circuits and surface discharges between the first electrode 10 and the second electrode 20.

[0213] Starting from the same point of view, such as Figure 17B As shown, the protrusion 43 can also be formed to abut against the +X side end 10a of the first electrode 10.

[0214] <2> Figure 17C The plasma generator 1 of the modified example shown has a protrusion 31 on the first surface 31 of the dielectric substrate 30, in the X direction, between the first electrode 10 and the first end 71, that is, between the first electrode 10 and the blow-out port 5. With this structure, the surface distance between the first electrode 10 and the second electrode 20 on the blow-out port 5 side is also ensured.

[0215] <3> Figure 17D The plasma generating apparatus 1 of the modified example shown has an insulating film 45 covering the first electrode 10 at the +X side end 10a. This structure can suppress unwanted discharges such as corona discharge. Examples of insulating films 45 include glass, sintered bodies containing glass, or resin materials such as silicone or epoxy resin.

[0216] <4> Figure 17E The plasma generator 1 of the modified example shown has a protective layer 46 disposed on the third surface 23 of the second electrode 20 near the first end 71, that is, near the blow-out port 5.

[0217] The protective layer 46 is preferably a dielectric material, and more preferably a material that is the same as the dielectric substrate 30. Specific examples of the material of the protective layer 46 include alumina, aluminum nitride, and bulk talc.

[0218] There are no particular limitations on the method for forming the protective layer 46 on the third surface 23 of the second electrode 20. As an example, a coating method can be used by spraying the constituent material of the protective layer 46. The thickness of the protective layer 46 can be appropriately set from the viewpoint of preventing contamination, for example, to 100 μm or less.

[0219] according to Figure 17E The plasma generator 1 shown in the modified example has a protective layer 46 near the outlet 5, or in other words, near the plasma generation site, which suppresses the evaporation and diffusion of the constituent material of the second electrode 20. This prevents contamination of the processed material by the sprayed plasma gas G1.

[0220] <5> Figure 17F The plasma generator 1 of the modified example shown has an activation auxiliary member 47 disposed on the second surface 32 of the dielectric substrate 30 near the first end 71, that is, near the blow-out port 5.

[0221] Examples of materials that can be used for the start-up auxiliary member 47 include carbon or transition metal compounds. Alternatively, materials with a higher dielectric constant than the dielectric substrate 30 can be used as materials for the start-up auxiliary member 47. In this case, due to dielectric loss, the constituent material of the start-up auxiliary member 47 is heated, and initial electrons are supplied into the gas flow path 3. Carbon is particularly preferred as the material for the start-up auxiliary member 47. Because carbon has high thermal stability, the start-up auxiliary member 47 is less prone to evaporation even with temperature increases, thus improving the reliability of the plasma generator 1.

[0222] In addition, the material used for the starting auxiliary component 47 can also be a material with a low work function, so that the electron emission effect can be confirmed with less applied voltage.

[0223] according to Figure 17F The plasma generator 1 shown in the modified example has an activation aid 47 near the blow-out port 5, which enables the initial electrons to be supplied into the gas flow path 3, thus improving the start-up capability.

[0224] Therefore, without the need for microwave oscillation devices and start-up circuits with large power capacity, plasma generators can be manufactured in a small and inexpensive manner.

[0225] <6> Figure 17G The plasma generator 1 in the modified example shown has a light-shielding member 48 adjacent to the outlet 5 on the +X side. The light-shielding member 48 has an internal tube 49 for gas flow, which communicates with the gas flow path 3. Figure 17G In the example shown, the blowing direction of plasma gas G1 is changed to the -Z direction by tube 49. This structure prevents light from the discharge within the gas flow path 3 from irradiating the workpiece.

[0226] <7> Furthermore, the aforementioned variations can be appropriately combined.

[0227] [Action Method]

[0228] When activating the plasma generating device 1 described above, firstly, during startup, one or more start-up gases selected from the group consisting of He, Ne, and Ar are introduced into the gas flow path 3 to generate plasma within the gas flow path 3. Then, a processing gas G0 is introduced into the gas flow path 3. The processing gas G0 is appropriately selected depending on the processing of the object being processed; for example, gases capable of generating the desired active species, such as hydrogen, oxygen, water, and nitrogen, are used. According to this method, even if the processing gas G0 is a gas that is relatively difficult to discharge plasma, a plasma gas G1 containing the processing gas G0 can be sprayed onto the object being processed.

[0229] Label Explanation

[0230] 1: Dielectric barrier discharge plasma generator

[0231] 3: Gas flow path

[0232] 5: Blowout

[0233] 10: First electrode

[0234] 10a, 10b: Ends of the first electrode

[0235] 20: Second electrode

[0236] 23: The surface of the second electrode (the third surface)

[0237] 26: Outer edge

[0238] 27: concave part

[0239] 30: Dielectric substrate

[0240] 31: Surface of the dielectric substrate (first surface)

[0241] 32: Surface of the dielectric substrate (second surface)

[0242] 40: Gas buffer substrate

[0243] 51: Gap

[0244] 53: Connecting hole

[0245] 61: Gas delivery device

[0246] 63: Power supply device

[0247] 71: First End

[0248] 72: Second end

[0249] 81: First reference part

[0250] 82: Second reference location

[0251] 83: Third reference part

[0252] 91: First Specific Region

[0253] 92: Second Specific Region

[0254] 93: Third Specific Area

Claims

1. A dielectric barrier discharge plasma generator, characterized in that, have: A dielectric substrate, having a plate shape extending in a first direction, has a first surface and a second surface located on the opposite side of the first surface in a second direction orthogonal to the first direction; The first electrode is disposed on the first surface side of the dielectric substrate; The second electrode is disposed at a position that separates from the second surface of the dielectric substrate in the second direction; A gas flow path is formed by the gap between the dielectric substrate and the second electrode, allowing gas to flow upward in a third direction orthogonal to the first and second directions; The outlet is located at one end of the gas flow path in the third direction, i.e., the first end, and extends in the first direction; and A power supply device, connected to the first electrode, is used to apply voltage and generate a dielectric barrier discharge between the first electrode and the second electrode via the dielectric substrate and the gas flow path. The first surface of the dielectric substrate is a flat surface parallel to the third direction, at least from the end opposite the blow-out port (i.e., the second end) to the first reference portion in the third direction. The second surface of the dielectric substrate is also a flat surface parallel to the third direction, at least from the second end to the second reference portion in the third direction. The main surface (i.e., the third surface) of the second electrode, which is opposite to the second surface of the dielectric substrate across the gas flow path, is a flat surface parallel to the third direction, at least from the second end to the third reference portion. At least one of the following surfaces—the first surface in a first specific region from the first reference point to the first end, the second surface in a second specific region from the second reference point to the first end, and the third surface in a third specific region from the third reference point to the first end—is an inclined surface relative to the third direction. The first electrode is disposed at least between the first reference portion and the first end. When viewed along the first direction, the angle α formed by the first surface in the first specific region and the third direction, the angle β formed by the second surface in the second specific region and the third direction, and the angle γ formed by the third surface in the third specific region and the third direction satisfy both of the following equations (1) and (2). Wherein, ε in equation (1) r A is the relative permittivity of the dielectric substrate, in equation (2), where A α A β and A γ The lengths of the first specific region, the second specific region, and the third specific region in the third direction are respectively corresponding to the lengths of the first specific region, the second specific region, and the third specific region. d1(0) is the thickness of the dielectric substrate in the second direction at the reference position of the first reference position and the second reference position on the side of the third direction near the second end. d2(0) is the height of the gas flow path in the second direction at the reference position of the second reference position and the third reference position on the side of the third direction near the second end.

2. The dielectric barrier discharge plasma generator according to claim 1, characterized in that, The dielectric substrate has the following shape: the thickness in the second direction is constant regardless of the position in the third direction, or the thickness in the second direction gradually increases from the first reference portion toward the first end.

3. The dielectric barrier discharge plasma generator according to claim 1 or 2, characterized in that, The first electrode is a high-voltage side electrode, and the second electrode is a low-voltage side electrode.

4. The dielectric barrier discharge plasma generator according to claim 1 or 2, characterized in that, have: The gas buffer substrate abuts against the second electrode at its peripheral portion from the side opposite to the dielectric substrate. A gas delivery device introduces gas into the gap between the gas buffer substrate and the second electrode; and A connecting hole, located at multiple different points in the first direction, penetrates the second electrode in the second direction.

5. The dielectric barrier discharge plasma generator according to claim 4, characterized in that, The connecting hole is located on the third-party side, closer to the second end than the first electrode.

6. The dielectric barrier discharge plasma generator according to claim 1 or 2, characterized in that, The main material of the dielectric substrate is aluminum oxide or aluminum nitride.

7. The dielectric barrier discharge plasma generator according to claim 1 or 2, characterized in that, The first electrode is positioned at a location that is recessed less than 10 mm from the first end toward the second end in the third direction.

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