Dielectric barrier plasma generating device and plasma discharge starting method

Abstract

A dielectric barrier plasma generating device comprises: a dielectric substrate; a high-voltage-side electrode disposed on a first surface of the dielectric substrate; a low-voltage-side electrode disposed on a second surface of the dielectric substrate; and an electric current introduction portion disposed at one end of the high-voltage-side electrode. A gas flow path for flowing gas from one end to the other end is formed between the dielectric substrate and the low-voltage-side electrode, and a blowing port is formed at the other end of the gas flow path for blowing out the gas flowing through the gas flow path and plasma generated in the gas flow path. The dielectric substrate has a portion whose thickness decreases as it approaches the blowing port.

Description

Technical Field

[0001] The present invention relates to a dielectric barrier plasma generating device and a plasma discharge starting method of the dielectric barrier plasma generating device. Background Art

[0002] Plasma generators are used in the manufacturing processes of plastics, paper, fibers, semiconductors, liquid crystals, thin films, and other materials. For example, by irradiating the surface of an object with plasma, it is possible to perform surface treatments to improve its hydrophilicity, adhesiveness, or printing adhesion, remove / clean organic matter from the surface of the object, or form an oxide film on the surface of the object.

[0003] Figure 18 1 is a perspective view schematically showing a conventional plasma generating device. In Patent Document 1, a plasma generating device 200 is disclosed. Figure 18 As shown, the plasma generating device 200 includes a pair of opposing electrodes 201 and 201 , and the opposing surface 202 of one electrode 201 is inclined in the opposite direction to the opposing surface 202 of the other electrode 201 .

[0004] In the plasma generating apparatus 200, a voltage is applied between the electrodes 201 and 201 while plasma generating gas G is introduced from the upper surface opening, generating multiple streamer discharges S in the opposing region 202. The plasma generating gas G is introduced from the gas inlet hole 223 into the opposing region 202 through the small holes 225 of the injection plate 224. Thereby, the plasma generating gas G is accelerated by the small holes 225 and injected into the opposing region 202 at high speed. This injection generates a turbulent flow of the plasma generating gas G, causing the streamer discharges S to diffuse and disperse within the opposing region 202. The dispersed streamer discharges S then generate a substantially uniform plasma P throughout the opposing region 202. This plasma P is then blown out as a plasma jet from the lower surface opening of the opposing region 202 into the processing space 205 and onto the workpiece H. Patent Document 1 discloses that the above-described structure can generate a uniform plasma.

[0005] Furthermore, the dielectric is held in place by electrodes, and to ensure overall strength, the electrode layer is designed to be relatively thick. This can lead to the dielectric being easily cracked due to the difference in linear expansion coefficients between the dielectric and the electrode metal, thus posing a lifespan issue. Dielectrics are typically made of ceramic, while electrodes are made of metal. Using a thinner dielectric can cause mechanical deformation due to the difference in linear expansion between the metal and ceramic. Consequently, the thinner ceramic can break.

[0006] As a method to compensate for this shortcoming, one approach is to increase the thickness of the ceramic to increase strength. However, as the thickness of the dielectric layer increases, the dielectric loss also increases, which inevitably leads to a problem of sacrificing the efficiency of plasma generation.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 2010-009890 Summary of the Invention

[0010] Problems to be solved by the invention

[0011] In the plasma generating device 200 disclosed in Patent Document 1, turbulent flow is generated to generate plasma P substantially uniformly throughout the entire opposing region 202. However, in this method of generating plasma throughout the entire opposing region 202 using this electrode structure, the plasma ejected from the blowout port cannot be said to be sufficiently uniform. For example, plasma generated at a location far from the blowout port in the opposing region 202 disappears during its journey to the blowout port. Therefore, it cannot be said that plasma is ejected uniformly from the entire blowout port. Furthermore, the lifetime of active species generated by the plasma is relatively short, and plasma generated at a location far from the blowout port in the opposing region 202, i.e., far from the workpiece, disappears during its journey to the blowout port, preventing efficient plasma ejection.

[0012] The present invention has been made in response to the above-mentioned problems and aims to provide a dielectric barrier plasma generator capable of efficiently generating plasma near a blowout port and uniformly ejecting plasma from the entire blowout port. Furthermore, a method for initiating plasma discharge in the dielectric barrier plasma generator is provided.

[0013] Means for solving problems

[0014] The dielectric barrier plasma generating device of the present invention is characterized by comprising:

[0015] dielectric substrate;

[0016] a high-voltage side electrode provided on the first surface side of the dielectric substrate;

[0017] a low-voltage side electrode provided on the second surface side of the dielectric substrate; and

[0018] an electric lead-in portion provided at one end of the high-voltage side electrode;

[0019] A gas flow path for allowing gas to flow from the one end side to the other end side is formed between the dielectric substrate and the low-voltage side electrode.

[0020] A blowing port for blowing out the gas flowing through the gas flow path and the plasma generated in the gas flow path is formed on the other end side of the gas flow path.

[0021] The dielectric substrate has a portion whose thickness decreases as it approaches the blowing outlet.

[0022] According to the dielectric barrier plasma generating device of the present invention, since the thickness of the dielectric substrate decreases as it approaches the outlet, the electrostatic capacitance increases as it approaches the outlet. Furthermore, discharge occurs at a point where the voltage applied to the gas exceeds the dielectric breakdown voltage. Therefore, by setting the dielectric substrate thickness gradient near the outlet to exceed the dielectric breakdown voltage, plasma can be generated near the outlet. As a result, plasma can be uniformly ejected from the entire area of ​​the outlet.

[0023] Furthermore, since the plasma is generated near the blowing port, the plasma generation efficiency is excellent.

[0024] Furthermore, since the dielectric barrier plasma generator of the present invention does not use microwaves, impedance matching and other techniques for microwave transmission are unnecessary. Therefore, the shapes of the dielectric substrate, high-voltage side electrode, and blowout port are not particularly limited. Furthermore, since microwaves are not used, measures to prevent electromagnetic wave leakage are unnecessary.

[0025] Furthermore, microwave-based plasma generates at higher densities near the antinodes of standing waves, where the electric field strength is high. These standing waves are generated not only in the direction of microwave input but also in directions perpendicular to it. Therefore, when viewing the blowout port from the front, areas with higher and lower plasma densities alternate. Consequently, for microwave-based plasma, uniformly ejecting plasma from the entire blowout port is not easy.

[0026] On the other hand, the dielectric barrier plasma generating device of the present invention is a dielectric barrier type, and discharge is generated at a location where the voltage applied to the gas exceeds the insulation breakdown voltage. Therefore, by setting the thickness gradient of the dielectric substrate near the blowing outlet so as to exceed the insulation breakdown voltage, plasma can be uniformly ejected from the entire area of ​​the blowing outlet.

[0027] In the above configuration, it is preferable to include a power supply device having an applied voltage of 3 kV to 20 kV and a frequency of 20 kHz to 150 kHz.

[0028] If such a power supply device is provided, plasma can be appropriately generated using the dielectric barrier method. The upper limit is set at 150 kHz because the frequency takes into account the plasma irradiation length and the frequency detected by the noise terminal voltage according to the EMC standard is 150 kHz or above.

[0029] In the above configuration, the gas flow path may include a portion where a gap between the dielectric substrate and the low-voltage-side electrode narrows as it approaches the air outlet.

[0030] If the gap between the dielectric substrate and the low-voltage-side electrode has a portion that narrows as it approaches the air outlet, the amount of change in electrostatic capacitance can be further increased.

[0031] In the above configuration, a protective layer for preventing a material constituting the low-voltage-side electrode from scattering is provided near the air outlet and on the low-voltage-side electrode.

[0032] If a protective layer is provided on the low-voltage side electrode near the plasma generation site, that is, near the blowout port, evaporation and diffusion of the material constituting the low-voltage side electrode can be suppressed, thereby preventing contamination of the irradiated object.

[0033] In the above structure, preferably, the dielectric substrate is made of aluminum oxide or aluminum nitride.

[0034] Aluminum oxide and aluminum nitride have low relative dielectric constants and high strength and hardness. Therefore, using aluminum oxide or aluminum nitride to form the dielectric substrate can increase the amount of plasma generated per unit of electrical power. Furthermore, even if the dielectric substrate is made thinner, the risk of damage can be reduced.

[0035] Aluminum nitride has excellent thermal conductivity, efficiently dissipating heat from the dielectric substrate. This reduces the temperature of the high-voltage electrode and reduces stress at the interface between the aluminum nitride and the high-voltage electrode caused by thermal expansion. Consequently, the life of the device can be extended.

[0036] In the above configuration, the high-voltage side electrode may be a foil-shaped metal.

[0037] In the above structure, the high-voltage-side electrode may be a sintered body containing a conductive metal. The sintered body containing the conductive metal may be formed by printing a metal paste. In this structure, when forming the high-voltage-side electrode on the dielectric substrate, an adhesive is not required.

[0038] In the above structure, the high-voltage side electrode may be formed by plating, vapor deposition, sputtering, or thermal spraying. In this structure, when the high-voltage side electrode is formed on the dielectric substrate, it is not necessary to use an adhesive.

[0039] In the above configuration, a startup assisting member may be arranged near the air outlet and on the second surface of the dielectric substrate.

[0040] Dielectric barrier discharges have the following characteristics: A high power level is required to initiate the discharge, but after ignition, the discharge can be sustained even with a lower power level. Therefore, a high power level is typically used for initial ignition. However, such methods require a power supply capable of outputting high power, or require the use of external trigger electrodes, separate from the device and located near the discharge space, potentially increasing the size of the device.

[0041] The initiation of plasma discharge requires the presence of a certain level of initial electrons at the plasma generation site. Therefore, by placing a starting aid component near the blowout port and on the second surface of the dielectric substrate, where the plasma is generated, initial electrons can be supplied to the space near the blowout port and above the dielectric substrate during the initial startup phase. This eliminates the need for a power supply device or starting circuit device with a large power capacity, enabling the provision of a compact and inexpensive plasma generating device.

[0042] In the above configuration, preferably, a gas introduction path for introducing gas into the gas flow path is provided, and the number of the gas introduction paths is two or more.

[0043] If there are two or more gas introduction paths, gas can be introduced into the gas flow path from two or more locations, making it easier to make the gas flow through the gas flow path laminar.

[0044] In the above configuration, a light shielding member may be provided at the air outlet.

[0045] If a light shielding member is provided at the air outlet, it is possible to prevent light generated by discharge from being irradiated onto an irradiation object.

[0046] In the above configuration, a gas buffer substrate having a cavity therein may be stacked on a surface of the low-voltage-side electrode opposite to the dielectric substrate.

[0047] The gas delivered from the gas delivery device remains in the cavities of the gas buffer substrate and then flows into the gas flow path through the multiple gas introduction paths. This allows the gas flowing into the gas flow path to flow out uniformly from the blowout port without disturbing its flow.

[0048] In the above configuration, preferably, a certain gap is provided between the other end of the high-voltage side electrode and the surface where the air outlet is formed.

[0049] Direct discharge between the high-voltage electrode and the low-voltage electrode near the outlet can occur without passing through the dielectric substrate. This discharge can damage the high-voltage electrode, the dielectric substrate, and the low-voltage electrode, and their constituent materials can be introduced into the plasma as impurities.

[0050] From the perspective of discharge efficiency, placing the high-voltage electrode at the very front end of the blower outlet is more advantageous. However, this significantly shortens the distance between the high-voltage and low-voltage electrodes, potentially causing creeping discharge on the dielectric substrate. Once this discharge occurs, it becomes direct discharge, no longer a dielectric barrier discharge. Excessive discharge current can flow, potentially damaging the electrodes and, ultimately, the power supply device.

[0051] Therefore, if a certain gap is provided between the other end of the high-voltage electrode and the surface where the blowout port is formed, direct discharge between the high-voltage electrode and the low-voltage electrode is suppressed, and discharge occurs between the high-voltage electrode and the low-voltage electrode via the dielectric substrate. This can suppress damage to the high-voltage electrode, the dielectric substrate, and the low-voltage electrode. As a result, it is possible to prevent the materials constituting these from being mixed into the plasma as impurities.

[0052] In the above configuration, a portion of the dielectric substrate where the thickness decreases as it approaches the air outlet may be in a stepped shape.

[0053] Ceramics are prone to cracking and have a problem of insufficient mechanical strength. Therefore, if the portion of the dielectric substrate where the thickness decreases as it approaches the blowout port is formed in a stepped shape, strength can be ensured.

[0054] Furthermore, the plasma discharge starting method of the present invention is a plasma discharge starting method for a dielectric barrier plasma generating apparatus, characterized in that:

[0055] The dielectric barrier plasma generating device comprises:

[0056] dielectric substrate;

[0057] a high-voltage side electrode provided on the first surface side of the dielectric substrate;

[0058] a low-voltage side electrode provided on the second surface side of the dielectric substrate; and

[0059] an electric lead-in portion provided at one end of the high-voltage side electrode;

[0060] A gas flow path for allowing gas to flow from the one end side to the other end side is formed between the dielectric substrate and the low-voltage side electrode.

[0061] A blowing port for blowing out the gas flowing through the gas flow path and the plasma generated in the gas flow path is formed on the other end side of the gas flow path.

[0062] The dielectric substrate has a portion whose thickness becomes thinner as it approaches the blowing outlet.

[0063] The plasma discharge initiation method comprises:

[0064] Step A, during startup, introducing one or more startup gases selected from the group consisting of He, Ne, and Ar into the gas flow path to generate plasma; and

[0065] In step B, after step A, a plasma generating gas is introduced into the gas flow path.

[0066] According to the plasma discharge initiation method of the present invention, at startup, one or more starting gases selected from the group consisting of He, Ne, and Ar are introduced into the gas flow path to generate plasma. After startup, a plasma-generating gas is introduced into the gas flow path. As a result, discharge can be initiated even when the plasma-generating gas is a gas that is difficult to generate plasma discharge.

[0067] Effects of the Invention

[0068] According to the present invention, a dielectric barrier plasma generator capable of efficiently and uniformly ejecting plasma from the entire region of a blowout port can be provided. Furthermore, a plasma discharge initiation method for the dielectric barrier plasma generator can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 It is a perspective view schematically showing the dielectric barrier plasma generation apparatus according to the first embodiment.

[0070] Figure 2 yes Figure 1 AA cross-sectional view of the dielectric barrier plasma generating device shown.

[0071] Figure 3 yes Figure 1 A cross-sectional view of the dielectric barrier plasma generating device is shown, taken perpendicularly to AA.

[0072] Figure 4 yes Figure 1 A top view of a low-voltage side electrode of a dielectric barrier plasma generating device is shown.

[0073] Figure 5 It is a plan view showing a state in which polypropylene (PP) films as irradiated objects are arranged on a table at predetermined intervals.

[0074] Figure 6 It is a line graph showing the measurement results of the water contact angle.

[0075] Figure 7 This is a partial cross-sectional view for explaining Modification 1 of the dielectric barrier plasma generation apparatus of the first embodiment.

[0076] Figure 8 This is a partial cross-sectional view for explaining a second modification of the dielectric barrier plasma generation apparatus according to the first embodiment.

[0077] Figure 9 This is a partial cross-sectional view for explaining a third modification of the dielectric barrier plasma generation apparatus according to the first embodiment.

[0078] Figure 10 This is a partial cross-sectional view for explaining a fourth modification of the dielectric barrier plasma generation apparatus according to the first embodiment.

[0079] Figure 11 It is a cross-sectional view of Modification 5 of the first embodiment.

[0080] Figure 12 It is a cross-sectional view of a dielectric barrier plasma generation apparatus according to a second embodiment.

[0081] Figure 13 It is a cross-sectional view of a dielectric barrier plasma generation apparatus according to a third embodiment.

[0082] Figure 14 It is a perspective view of a dielectric barrier plasma generation apparatus according to a fourth embodiment.

[0083] Figure 15 yes Figure 14 AA cross-sectional view of the dielectric barrier plasma generating device shown.

[0084] Figure 16 It is a cross-sectional view of a dielectric barrier plasma generator according to a fifth embodiment.

[0085] Figure 17 It is a cross-sectional view of a dielectric barrier plasma generator according to a sixth embodiment.

[0086] Figure 18 This is a perspective view schematically showing a conventional dielectric barrier plasma generation device. DETAILED DESCRIPTION

[0087] Hereinafter, a dielectric barrier plasma generation apparatus according to this embodiment will be described with reference to the drawings.

[0088] [First embodiment]

[0089] Figure 1 is a perspective view schematically showing a dielectric barrier plasma generating apparatus according to a first embodiment. Figure 2 yes Figure 1 AA cross-sectional view of the dielectric barrier plasma generating device shown, Figure 3 yes Figure 1 A cross-sectional view of the dielectric barrier plasma generating device shown is taken perpendicularly to AA. Figure 4 yes Figure 1 A top view of a low-voltage side electrode of a dielectric barrier plasma generating device is shown.

[0090] like Figure 1 As shown, a dielectric barrier plasma generation device (hereinafter also referred to as “plasma generation device 10 ”) includes a dielectric substrate 12 , a high-voltage side electrode 14 , a low-voltage side electrode 20 , and a gas buffer substrate 26 .

[0091] The dielectric substrate 12 is flat and has a portion whose thickness decreases as it approaches the outlet 30. Specifically, the dielectric substrate 12 has a flat portion 12a with a constant thickness and an inclined portion 12b that is formed continuously from the flat portion 12a and whose thickness decreases as it approaches the outlet 30. Figure 1 The upper surface in the middle is inclined toward the low-voltage side electrode 20.

[0092] From the perspective of increasing the amount of plasma generated per unit electric power, the dielectric substrate 12 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 limit of the relative dielectric constant of the material is preferably as low as possible, but can be set to 4 or greater, for example.

[0093] The material of dielectric substrate 12 is not particularly limited, but preferably has a dielectric constant as low as possible. Ceramics are particularly preferred from a durability perspective. Examples of such ceramics include aluminum oxide, aluminum nitride, and talc. Aluminum oxide, aluminum nitride, and talc have low relative dielectric constants, high strength, and excellent durability. Therefore, using aluminum oxide, aluminum nitride, or talc to form dielectric substrate 12 can increase the amount of plasma generated per unit of electrical power. Furthermore, even if dielectric substrate 12 is made thinner, the risk of breakage can be reduced.

[0094] Furthermore, dielectric substrate 12 can be made of a material based on the aforementioned dielectric material and containing a substance that assists electron generation. Examples of such substances include silver, platinum, copper, carbon, and transition metal compounds. By applying an electric field to the substance that assists electron generation, initial electrons are generated and released into the discharge space. This advantageously enhances startup performance.

[0095] The content of the substance assisting electron generation is preferably 1% by weight or less relative to the entire dielectric substrate 12 (when the dielectric substrate 12 is assumed to be 100% by weight). If the substance assisting electron generation is present, the content of the substance assisting electron generation is set to 1% by weight or less for the following reason: This material evaporates and scatters during discharge, and these particles are blown away with the plasma, contaminating the irradiated object. Therefore, the content should be minimized.

[0096] In addition, when the substance assisting electron generation is contained, the content is preferably set to 0.05% by weight or more based on experiments.

[0097] The high voltage side electrode 14 is provided on the first surface 13a of the dielectric substrate 12. Figure 2 The left-right direction in FIG. 1 is referred to as the “longitudinal direction”, and the direction perpendicular to the longitudinal direction is referred to as the “width direction”.

[0098] The high-voltage side electrode 14 has a width substantially the same as that of the dielectric substrate 12 and is formed continuously from the middle of the flat portion 12a of the dielectric substrate 12 to the other end (at the Figure 2 The width of the high-voltage-side electrode 14 is not particularly limited. However, since plasma is generated below the high-voltage-side electrode 14, it is preferably as wide as possible from the perspective of ejecting plasma over a wide area from the blowing outlet 30. The width of the high-voltage-side electrode 14 is preferably the same as or greater than the width of the blowing outlet 30.

[0099] In addition, in the plasma generating device 10, since the plasma is generated on the lower side of the inclined portion 12b, it is not necessary to form the high-voltage side electrode 14 on the flat portion 12a. However, it is preferable to form the high-voltage side electrode 14 on the flat portion 12a to a degree suitable for connection to the power supply device 42, etc., as in the present embodiment.

[0100] The other end of the high voltage side electrode 14 (at Figure 2 The right end in the middle does not reach the surface where the blowing outlet 30 is formed. That is, a certain gap 15 is provided between the other end of the high-voltage side electrode 14 and the surface where the blowing outlet 30 is formed.

[0101] Near the blowing port 30, there is a possibility of direct discharge between the high-voltage electrode 14 and the low-voltage electrode 20, without passing through the dielectric substrate 12. Such discharge can damage the high-voltage electrode 14, the dielectric substrate 12, and the low-voltage electrode 20, and the materials constituting these can be mixed into the plasma as impurities.

[0102] From the perspective of discharge efficiency, placing the high-voltage electrode at the very front end of the blower outlet is more advantageous. However, this significantly shortens the distance between the high-voltage and low-voltage electrodes, potentially causing creeping discharge on the dielectric substrate. Once this discharge occurs, it becomes direct discharge, no longer a dielectric barrier discharge. This results in excessive discharge current, potentially damaging the electrode and, ultimately, the power supply device.

[0103] Therefore, the plasma generating device 10 is configured to provide a predetermined gap 15 between the other end of the high-voltage electrode 14 and the surface where the blowout port 30 is formed. This prevents direct discharge between the high-voltage electrode 14 and the low-voltage electrode 20, and instead allows discharge between the high-voltage electrode 14 and the low-voltage electrode 20 via the dielectric substrate 12. This can prevent damage to the high-voltage electrode 14, the dielectric substrate 12, and the low-voltage electrode 20. The gap 15 is preferably within a range of 1 to 5 mm, for example.

[0104] The material of the high-voltage side electrode 14 is not particularly limited, but is preferably a material having high conductivity, and examples thereof include copper, silver, aluminum, and gold compounds.

[0105] The high-voltage side electrode 14 may be a foil-shaped metal. An example of the high-voltage side electrode 14 is a metal foil such as copper foil or aluminum foil with one surface subjected to bonding.

[0106] Alternatively, the high-voltage-side electrode 14 may be a sintered body containing a conductive metal. This sintered body containing a conductive metal may be formed by printing a metal paste on the surface of the dielectric substrate 12. With this configuration, the high-voltage-side electrode 14 does not require an adhesive when formed on the dielectric substrate 12.

[0107] The high-voltage side electrode 14 can be formed by plating, vapor deposition, sputtering, or thermal spraying. In the case of this structure, when the high-voltage side electrode is formed on the dielectric substrate, it is not necessary to use an adhesive.

[0108] The high-voltage side electrode 14 and the dielectric substrate 12 are preferably in close contact with each other, with no air layer at the interface. If there is an air layer, discharge will occur inside the space, and the generated radicals may cause electrode deterioration.

[0109] Therefore, the high-voltage side electrode 14 and the dielectric substrate 12 are preferably formed so as to be in close contact with each other at a micrometer level at the connection interface.

[0110] Furthermore, the high-voltage-side electrode 14 is extremely thin compared to the dielectric substrate 12. Since the high-voltage-side electrode 14 is thin, even if metal expansion occurs, the thin metal absorbs the expansion, and the dielectric substrate 12 is minimally affected by the expansion coefficient.

[0111] Furthermore, while conventional methods require a thicker dielectric substrate 12 to prevent ceramic damage, this embodiment utilizes a thinner dielectric substrate, which reduces dielectric loss within the dielectric layer, improves the efficiency of energy introduction into the gas, and enables efficient plasma generation. Overall, this allows for a highly efficient device to be provided using a relatively small amount of material, which is beneficial in terms of resources and the environment.

[0112] The high-voltage side electrode 14 is connected to the power supply device 42 at one end. In the first embodiment, the one end of the high-voltage side electrode 14 is an electrical lead-in portion 34 for connection to the power supply device 42. There is no particular limitation on the method for connecting the power supply device 42 and the high-voltage side electrode 14 at the electrical lead-in portion 34, as long as it is a method for electrically connecting and being able to withstand the application of voltage. For example, there can be cited connection using solder and connection using various connectors (for example, coaxial connectors, etc.). However, in this embodiment, since microwaves are not used, there is no need to use a coaxial connector or coaxial cable having a specified characteristic impedance.

[0113] The applied voltage and frequency supplied by the power supply 42 can be within any range sufficient to induce dielectric barrier discharge in the plasma generating device 10. Specifically, the applied voltage supplied by the power supply 42 is preferably within the range of 3 kV to 20 kV, and more preferably 10 kV or less. Furthermore, the frequency of the applied voltage supplied by the power supply 42 is preferably within the range of 20 kHz to 1000 kHz, and more preferably 100 kHz to 150 kHz. The upper limit is preferably 150 kHz because the wavelength takes into account the plasma irradiation length, and the frequency detected by the noise terminal voltage in accordance with EMC standards is 150 kHz or higher.

[0114] The low voltage side electrode 20 is in the form of a plate and is provided on the second surface 13b (at Figure 2 The middle is the lower side).

[0115] The low-voltage-side electrode 20 may be connected to the ground potential (earth potential) directly or via a resistor. Alternatively, it may be connected to the low-voltage-side output of the power supply device 42 .

[0116] like Figure 2 As shown, on the surface of the low voltage side electrode 20 on the dielectric substrate 12 side, from the length direction ( Figure 2 in the left and right directions) (at one end side Figure 2 The left end side) to the other end side (in Figure 2 A groove portion 22 is formed on the right end side. Specifically, Figure 4 As shown, the groove portion 22 is formed by forming the portion other than the outer peripheral portions 23 a on both sides in the width direction of the low-voltage side electrode 20 and the outer peripheral portion 23 b on one end side.

[0117] The dielectric substrate 12 and the low-voltage-side electrode 20 are stacked so that their outer peripheries 23a and 23b are in contact. A space is formed between the portion where the groove 22 is formed, that is, between the groove 22 and the second surface 13b of the dielectric substrate 12. This space forms a gas flow path 25 for allowing gas to flow from one end to the other.

[0118] like Figure 4 As shown, a gas introduction path 24 composed of a plurality of through holes is provided at equal intervals along the width direction on one end side of the groove portion 22. The number of gas introduction paths 24 is not particularly limited, but preferably, there are two or more gas introduction paths 24 as in the present embodiment. If there are two or more gas introduction paths 24, gas can be introduced into the gas flow path 25 from two or more locations, thereby making it easier to achieve laminar flow of the gas flow path 25. It is preferable to provide a plurality of gas introduction paths 24 along the width direction so that gas can be introduced into the gas flow path 25 over a wider range at the time of introduction.

[0119] Alternatively, the gas introduction path 24 may be a single hole that is widened in the width direction.

[0120] like Figure 2 、 Figure 3 As shown, a gas buffer substrate 26 having a cavity 27 therein is stacked on the lower side of the low-voltage side electrode 20 (the surface opposite to the dielectric substrate 12 ).

[0121] The gas delivery device 40 is connected to the cavity 27 of the gas buffer substrate 26 (see Figure 2 When the gas is delivered from the gas delivery device 40 , the gas remains in the cavity 27 and then flows into the gas flow path 25 through the plurality of gas introduction paths 24 .

[0122] At the other end of the gas flow path 25, a blowout port 30 is formed for blowing out the gas flowing through the gas flow path 25 and the plasma generated therein. In the first embodiment, the width of the groove 22 (gas flow path 25) is uniform from one end to the other, and the width of the blowout port 30 is the same as the width of the groove 22 (gas flow path 25). This allows the gas flowing into the gas flow path 25 to flow out uniformly from the blowout port 30 without disrupting its flow. This has been confirmed by the inventors through simulations.

[0123] However, the present invention is not limited to this example; the width of the outlet 30 can be adjusted as needed. For example, if the width of the outlet 30 is narrower than the width of the other end of the gas flow path 25, plasma can be ejected at a high pressure. By narrowing the width of the outlet 30 to match the discharge area, high-density and uniform plasma can be generated. Furthermore, if the width of the outlet 30 is wider than the width of the other end of the gas flow path 25, plasma with a wider jet width can be ejected.

[0124] As the gas supplied to the gas flow path 25 (gas delivered from the gas delivery device 40), as the startup gas at the time of startup, one or more selected from the group consisting of He, Ne, and Ar can be cited. In addition, as the plasma generating gas after the plasma is generated, a gas capable of generating desired active species can be cited, specifically one or more selected from the group consisting of hydrogen, oxygen, water, nitrogen, etc.

[0125] In this embodiment, it is preferable that the gas flow through the gas flow path 25 is a laminar flow. If the gas flow is a laminar flow, plasma can be ejected more uniformly.

[0126] Here, the Reynolds number is a parameter that distinguishes laminar flow from turbulent flow.

[0127] Let the density of the fluid be ρ(kg / m 3 ), let the flow velocity be U (m / s), the characteristic length be L (m), the viscosity coefficient of the liquid be μ (Pa·s), and the Reynolds number Re be a dimensionless quantity expressed by the following formula.

[0128] Re=ρ·U·L / μ

[0129] The Reynolds number that serves as the dividing line between laminar flow and turbulent flow is called the limiting Reynolds number, and its value is generally considered to be 2000 to 4000.

[0130] In the plasma generating device used in the following embodiment 1, if the flow rate is: 0.005m 3 / sec(300L / min), short side: 0.5mm, long side: 700mm, then U = 14.3(m / s), L = 9.99×10 -4 (m), the fluid is set to dry air under standard atmospheric pressure, if ρ = 1.205 (kg / m 3 ), μ=1.822×10 -5 (Pa·s), the Reynolds number is about 945, which is a value below the limit Reynolds number and can be determined to be laminar flow.

[0131] When a voltage is applied to the high-voltage side electrode 14 from the current introduction portion 34, a discharge occurs within the gas flow path 25 at a location where the voltage applied to the gas exceeds the dielectric breakdown voltage. Specifically, in the plasma generating device 10, the thickness of the dielectric substrate 12 decreases as it approaches the blowout port 30, so the electrostatic capacitance increases as it approaches the blowout port 30. Therefore, by setting the thickness gradient of the dielectric substrate 12 and applying a voltage near the blowout port 30 so as to exceed the dielectric breakdown voltage, plasma can be generated over a wide area along the width of the blowout port 30. This plasma is then blown out of the blowout port 30 as the gas flows. With the above structure, the plasma generating device 10 can uniformly eject plasma from the entire area of ​​the blowout port 30. Furthermore, since the plasma is generated near the blowout port 30, the plasma generation efficiency is excellent.

[0132] In the plasma generating device 10, a groove 22 is formed in the low-voltage-side electrode 20. The portion enclosed by the groove 22 and the second surface 13b of the dielectric substrate 12 serves as the gas flow path 25. The dielectric substrate 12 itself has no grooves or holes and is flat. Generally speaking, processing the low-voltage-side electrode 20 (forming the groove 22 in the first embodiment) made of metal is easier than processing dielectric substrates made of ceramic or the like. Therefore, the plasma generating device 10 can be easily manufactured.

[0133] Furthermore, in the plasma generating device 10 , the dielectric substrate 12 is flat, and thus can be made thin. Consequently, the amount of plasma generated per unit electric power can be increased, and plasma can be generated efficiently.

[0134] In the first embodiment, the width of the groove 22 (gas flow path 25) is uniform from one end to the other, but the present invention is not limited to this example. The width of the groove (gas flow path) may be non-uniform from one end to the other. For example, the width of the groove (gas flow path) may narrow as it moves from one end to the other. Alternatively, the width of the groove (gas flow path) may widen as it moves from one end to the other.

[0135] In the first embodiment, a gas introduction path 24 is provided in the groove portion 22 of the low-voltage-side electrode 20, and gas is introduced into the gas flow path 25 from the bottom side of the low-voltage-side electrode 20. However, in the present invention, the location of the gas introduction path is not limited to this example. In the present invention, the gas introduction path can be provided at a location that allows gas to flow from the outside into one end of the gas flow path. For example, it can be provided on the side surface of one end of the low-voltage-side electrode 20.

[0136] The size of the plasma generating device 10 is not particularly limited, but can be as follows as an example.

[0137] Dimensions: Width 750mm, Length 40mm, Thickness (thickest part) 20mm

[0138] The outer dimensions of the dielectric substrate 12 are: width 750 mm, length of the flat portion 12a 20 mm, thickness of the flat portion 12a 4 mm, length of the inclined portion 12b 20 mm, thickness of the inclined portion 12b just above the blowout port 30 0.1 mm

[0139] The outer dimensions of the low-voltage side electrode 20 are: width 750 mm, length 20 mm, thickness 0.1 mm. The approximate dimensions of the gas flow path 25 are: width 700 mm, length 35 mm, thickness 1.5 mm.

[0140] Dimensions of the blowout port 30: opening width 700 mm, opening height 0.2 mm

[0141] A plasma generating device having the aforementioned dimensions, using alumina as the material for the dielectric substrate 12, a conductive material primarily composed of copper as the material for the high-voltage-side electrode 14, and copper as the material for the low-voltage-side electrode 20 (hereinafter also referred to as the "plasma generating device of Example 1") was generated by applying voltage and flowing gas under the following conditions.

[0142] Applied voltage: 7.6kVpp, frequency 38kHz

[0143] Gas type: Nitrogen

[0144] Gas flow rate: 300L / min

[0145] [Confirmation of uniform plasma spray]

[0146] Figure 5 It is a plan view showing a state in which polypropylene (PP) films as irradiated objects are arranged on a table at predetermined intervals.

[0147] like Figure 5As shown, polypropylene (PP) films were placed on a table at a predetermined distance as the irradiated object, and plasma was applied from above using the plasma generator of Example 1. The PP films were fixed on a uniaxial table at a distance of 2 mm from the blower nozzle (irradiation distance), and the blower nozzle was reciprocated at a speed of 100 mm / second to irradiate the plasma. The water contact angle of each PP film surface was measured after two irradiations (after two reciprocating movements), ten irradiations (after ten reciprocating movements), and 200 irradiations (after 200 reciprocating movements).

[0148] The water contact angle was measured under the following conditions.

[0149] Contact angle meter: DMs-401 (Kyoho Interface Science)

[0150] Liquid volume: 2μL

[0151] Approximation is performed by ellipse fitting.

[0152] Figure 6 It is a line graph showing the measurement results of water contact angle. Figure 6 It was found that the water contact angle was within ±10% of the average value in the width direction under any irradiation condition.

[0153] In addition, Figure 6 The 10mm, 30mm, and 50mm parts of the film were also equipped with polypropylene (PP) films, and the same test was carried out. Figure 6 Within ±10% of the mean shown.

[0154] From the above results, it can be seen that plasma is uniformly ejected from the entire region of the blowing outlet.

[0155] The plasma generation device 10 according to the first embodiment has been described above.

[0156] [Modification]

[0157] Figures 7 to 11 This is a partial cross-sectional view illustrating a modified example of the dielectric barrier plasma generator of the first embodiment. The structure of the unillustrated portions is identical to that of the plasma generator 10 of the first embodiment. The following description focuses on differences from the aforementioned plasma generator 10, while descriptions of identical aspects are omitted or simplified. Components identical to those of the plasma generator 10 are denoted by the same reference numerals.

[0158] exist Figure 7 Modification 1 shown, Figure 8In the variant example 2 shown, a protrusion (protrusion 92 in variant example 1 and protrusion 94 in variant example 2) is provided on the dielectric substrate 12 between the high-voltage side electrode 14 and the blow-out port 30, and the dielectric substrate has a protrusion portion that separates the high-voltage side electrode 14 from the low-voltage side electrode 20.

[0159] Specifically, in Modification 1, protrusion 92 is provided at the end of dielectric substrate 12 (directly above blowout port 30). In Modification 2, protrusion 94 is provided so as to contact the end of the high-voltage-side electrode 14 closest to blowout port 30. Alternatively, protrusion 94 may be provided at the same time as protrusion 92.

[0160] The materials for protrusions 92 and 94 include the materials exemplified as the materials for dielectric substrate 12. The materials for protrusions 92 and 94 may be the same as or different from the materials for dielectric substrate 12. Protrusions 92 and 94 may be integrally formed with dielectric substrate 12 or attached to dielectric substrate 12 as separate components.

[0161] Modifications 1 and 2 reduce the distance between the high-voltage and low-voltage electrodes while maintaining a sufficient creepage distance. In Modifications 1 and 2, ensuring both the creepage distance and the spatial distance between the high-voltage and low-voltage electrodes further suppresses unnecessary discharges such as short circuits and creepage discharges between the two electrodes.

[0162] exist Figure 9 In the third modified example shown, the dielectric substrate 12 is provided with projections and depressions 96 in the region from the end of the high-voltage-side electrode 14 closest to the air outlet 30 to directly above the air outlet 30, thereby ensuring a sufficient creeping distance. The projections and depressions 96 increase the creeping distance and the resistance value, thereby reducing the risk of creeping discharge.

[0163] exist Figure 10 In the fourth modification shown, a tapered portion 98 is provided in the groove 22 of the low-voltage electrode 20 so that the opening height increases as it approaches the blowout port 30. This ensures a distance between the high-voltage electrode 14 and the low-voltage electrode 20 on the creepage side.

[0164] exist Figure 11 In the fifth modification shown, an insulating film 99 is formed on the end of the high-voltage-side electrode 14 on the air outlet 30 side, covering the high-voltage-side electrode 14. Covering the end of the high-voltage-side electrode 14 with the insulating film 99 can suppress the occurrence of unnecessary discharges such as corona discharge. Examples of the insulating film 99 include glass, a sintered body containing glass, silicon, and resin materials such as epoxy resin.

[0165] In Modifications 1 to 5, a constant creeping distance and / or spatial distance can be maintained between the high-voltage-side electrode 14 and the low-voltage-side electrode 20. This prevents the materials that make up these electrodes from entering the plasma as impurities. Furthermore, this prevents electrode wear and damage to the power supply unit, contributing to a longer device lifespan.

[0166] By taking these measures to ensure the creeping distance, the end portion of the high-voltage side electrode 14 on the side closer to the blowing outlet 30 can be arranged closer to the blowing outlet 30 , and plasma can be generated efficiently.

[0167] From the perspective of electrical energy, it is preferable to keep the distance between the high-voltage electrode and the low-voltage electrode short during discharge. Specifically, it is advantageous to extend the high-voltage electrode to the very front end of the blowout port. However, this arrangement significantly shortens the distance between the high-voltage and low-voltage electrodes, potentially causing creeping discharge on the dielectric substrate.

[0168] Therefore, it is preferable to arrange the high-voltage side electrode at a position away from right above the blowing outlet to such an extent that creeping discharge does not occur, thereby ensuring an appropriate creeping distance.

[0169] As mentioned above, in order to make the distance between the high-voltage side electrode and the low-voltage side electrode closer, it is ideal to configure the high-voltage side electrode closer to the front end of the blower outlet. Therefore, a strategy is needed to reduce the distance between the high-voltage side electrode and the low-voltage side electrode while ensuring the surface distance.

[0170] Therefore, as in Modification 1 and Modification 2, the following method can be used: a protrusion is provided on the dielectric substrate between the high-voltage side electrode and the blowing outlet, and the dielectric substrate is provided with a protrusion that isolates the high-voltage side electrode from the low-voltage side electrode.

[0171] As a strategy for ensuring the creeping distance, as in Modification 3, there is a method of providing a structure in which the creeping distance is ensured by providing unevenness on the dielectric substrate in the section from the high-voltage side electrode to the front end of the blowing outlet.

[0172] Moreover, as a strategy for ensuring the creeping distance, as in variant example 4, the following method can be listed: the structure of the blowing outlet is enlarged by cutting the end of the low-voltage side electrode near the blowing outlet to ensure the creeping distance between the high-voltage side electrode and the low-voltage side electrode.

[0173] Furthermore, as in Modification 5, there is also a method of adopting a structure in which the occurrence of direct discharge on the creeping surface is forcibly prevented by covering the end portion of the high-voltage-side electrode on the blowing outlet side with an insulator.

[0174] By adopting these measures to ensure the creeping distance, the end portion of the high-voltage side electrode on the side closer to the blowing outlet can be arranged closer to the blowing outlet, thereby enabling efficient plasma generation.

[0175] By ensuring the creeping distance and spatial distance between the high-voltage side electrode and the low-voltage side electrode in this manner, it is possible to suppress unnecessary discharges such as short circuits between the two electrodes and the occurrence of creeping discharge.

[0176] [Second embodiment]

[0177] The following describes a plasma generation device 50 according to a second embodiment. The plasma generation device 50 of the second embodiment differs from the plasma generation device 10 in the dielectric substrate, high-voltage electrode, and low-voltage electrode shapes; otherwise, the device is identical. Therefore, the following description will focus primarily on the differences, while the description of the identical aspects will be omitted or simplified. Components identical to those of the plasma generation device 10 according to the first embodiment are denoted by the same reference numerals.

[0178] Figure 12 FIG is a cross-sectional view of a dielectric barrier plasma generating device according to a second embodiment. Figure 12 As shown, the plasma generation device 50 includes a dielectric substrate 52 , a high-voltage-side electrode 54 , and a low-voltage-side electrode 56 .

[0179] Like dielectric substrate 12, dielectric substrate 52 includes a flat portion 52a having a constant thickness and an inclined portion 52b formed continuously from flat portion 52a and having a thickness that decreases as it approaches air outlet 30. However, in dielectric substrate 52, compared to dielectric substrate 12, flat portion 52a is shorter than flat portion 12a, and inclined portion 52b is more gently inclined than inclined portion 12b.

[0180] The high-voltage-side electrode 54 has substantially the same width as the dielectric substrate 52 and is provided on the inclined portion 52b of the dielectric substrate 52. In the second embodiment, the high-voltage-side electrode 54 is not provided on the flat portion 52a.

[0181] As in the first embodiment, the other end of the high voltage side electrode 54 (at Figure 12 The right end in the middle does not reach the surface where the blowout port 30 is formed. That is, a certain gap 55 is provided between the other end of the high-voltage side electrode 54 and the surface where the blowout port 30 is formed.

[0182] The low voltage side electrode 56 is plate-shaped and is provided on the second surface 53b (at Figure 12 The middle is the lower side).

[0183] The low-voltage-side electrode 56 is formed with a groove portion 22 similar to the low-voltage-side electrode 20 of the first embodiment. The groove portion 22 is formed with an inclined portion 56b whose thickness increases as it approaches the outlet 30. Thus, the gas flow path 25 is provided with a portion 58 in which the gap between the dielectric substrate 52 and the low-voltage-side electrode 56 narrows as it approaches the outlet 30.

[0184] In the second embodiment, since the gap between the dielectric substrate 52 and the low-voltage-side electrode 56 is narrowed toward the air outlet 30 , the amount of change in electrostatic capacitance can be further increased.

[0185] Furthermore, by having a portion where the gap between the high-voltage and low-voltage electrodes narrows as they approach the outlet 30, the probability of discharge initiation can be increased. Since the discharge initiation voltage is proportional to the product of pressure and distance, discharge initially begins near the front end, where the distance between the high-voltage and low-voltage electrodes is relatively close, and then spreads to the rear portion, where the dielectric layer is thicker. By having a portion where the gap between the dielectric substrate 52 and the low-voltage electrode 56 narrows as they approach the outlet 30, the plasma generating device can be reliably started and discharge can be stably performed.

[0186] In addition, by setting a portion where the high-voltage side electrode and the low-voltage side electrode are closer throughout the length direction of the blowing outlet, even with a plasma discharge of lower electric power, plasma can be uniformly generated near the front end of the blowing outlet, enabling uniform treatment.

[0187] As a result, the electric power input to the plasma generating device can be adjusted, and the application range of plasma processing can be expanded.

[0188] The plasma generation device 50 according to the second embodiment has been described above.

[0189] [Third embodiment]

[0190] The following describes a plasma generation device 60 according to a third embodiment. The plasma generation device 60 of the third embodiment differs from the plasma generation device 50 in that it includes a protective layer near the blowout port and on the low-voltage-side electrode; otherwise, the device is identical to the plasma generation device 50. Therefore, the following description will focus primarily on the differences, while the description of the identical aspects will be omitted or simplified. Components identical to those of the plasma generation device 50 of the second embodiment are denoted by the same reference numerals.

[0191] Figure 13 FIG is a cross-sectional view schematically showing a dielectric barrier plasma generating apparatus according to a third embodiment. Figure 13As shown, the plasma generation device 60 includes a dielectric substrate 52 , a high-voltage-side electrode 54 , and a low-voltage-side electrode 56 .

[0192] A protective layer 64 is formed near the air outlet 30 and on the low-voltage-side electrode 56 to prevent the material constituting the low-voltage-side electrode 56 from scattering. In this embodiment, the protective layer 64 is formed to cover at least the inclined portion 56b. The protective layer 64 is preferably a dielectric. The material of the protective layer 64 is preferably the same as that of the dielectric substrate 52. Specific examples of the material of the protective layer 64 include aluminum oxide, aluminum nitride, and talc.

[0193] The method for forming the protective layer 64 on the low-voltage side electrode 56 is not particularly limited, but a method of applying the material forming the protective layer 64 by spraying can be used. Spraying to form the protective layer 64 is advantageous in terms of ease of manufacture. The thickness of the protective layer 64 can be appropriately set from the perspective of preventing contamination, and can be, for example, 100 μm or less.

[0194] According to the plasma generating device 60 of the third embodiment, since a protective layer 64 is provided on the low-voltage side electrode 56 near the location where plasma is generated, i.e., near the blowing outlet 30, the material constituting the low-voltage side electrode 56 can evaporate and diffuse, thereby preventing the irradiated object from being contaminated.

[0195] The plasma generation device 60 according to the third embodiment has been described above.

[0196] [Fourth embodiment]

[0197] The following describes a plasma generation device 70 according to a fourth embodiment. The plasma generation device 70 of the fourth embodiment differs from the plasma generation device 10 of the first embodiment in that a startup assist component is disposed on the second surface of the dielectric substrate near the blowout port. Other aspects are identical. Therefore, the following description will focus primarily on the differences, while the description of the identical aspects will be omitted or simplified. Components identical to those of the plasma generation device 10 of the first embodiment are denoted by the same reference numerals.

[0198] Figure 14 is a perspective view schematically showing a dielectric barrier plasma generating apparatus according to a fourth embodiment. Figure 15 yes Figure 14 AA cross-sectional view of the dielectric barrier plasma generating device shown in FIG. Figure 15 In the figure, the gas buffer substrate is omitted. Figure 14 、 Figure 15As shown, the plasma generation device 70 includes a dielectric substrate 12 , a high-voltage-side electrode 14 , a low-voltage-side electrode 20 , and a gas buffer substrate 26 .

[0199] A startup assisting member 72 is disposed near the air outlet 30 and on the second surface 13 b of the dielectric substrate 12 .

[0200] Examples of materials for the starting aid component 72 include carbon (C) and transition metal compounds. Furthermore, examples of materials for the starting aid component 72 include materials with a higher relative dielectric constant than the dielectric substrate 12. When using a material with a higher relative dielectric constant than the dielectric substrate 12 as the material for the starting aid component 72, the material is heated due to dielectric loss, thereby supplying initial electrons to the space. Carbon is particularly preferred as the material for the starting aid component 72. Carbon has high thermal stability, preventing the starting aid component 72 from evaporating due to heating after attachment, thereby improving the reliability of the plasma generating device 70.

[0201] Alternatively, the starting auxiliary member 72 may be made of a material having a low work function that exhibits an electron emission effect at a lower applied voltage.

[0202] In the plasma generating device 70, the starting auxiliary component 72 is disposed near the blowing port 30, where plasma is generated, and on the second surface 13b of the dielectric substrate 12. This allows initial electrons to be supplied to the space near the blowing port 30 and on the second surface 13b of the dielectric substrate 12. This eliminates the need for a microwave oscillator or starting circuit device with a large power supply capacity, making it possible to provide a compact and inexpensive plasma generating device.

[0203] In the fourth embodiment, the case where the protective layer 64 is not provided has been described. However, a configuration may be adopted in which the starting assisting member 72 is provided and the protective layer 64 is provided.

[0204] The plasma generation device 70 according to the fourth embodiment has been described above.

[0205] [Fifth embodiment]

[0206] The following describes a plasma generation device 80 according to a fifth embodiment. The plasma generation device 80 of the fifth embodiment differs from the plasma generation device 10 of the first embodiment in that a light shielding member is provided at the blowout port; otherwise, the device is identical to the plasma generation device 10 of the first embodiment. Therefore, the following description will focus primarily on the differences, while the description of the identical aspects will be omitted or simplified. Components identical to those of the plasma generation device 10 of the first embodiment are denoted by the same reference numerals.

[0207] Figure 16FIG is a cross-sectional view schematically showing a dielectric barrier plasma generating apparatus according to a fifth embodiment. Figure 16 As shown, the plasma generation device 80 includes a dielectric substrate 12 , a high-voltage-side electrode 14 , and a low-voltage-side electrode 20 .

[0208] like Figure 16 As shown, a light shielding member 82 is provided at the air outlet 30. The light shielding member 82 has a cavity 83 through which the gas flowing through the gas flow path 25 can flow, and the cavity 83 is connected to the gas flow path 25. Furthermore, the cavity 83 of the light shielding member 82 is arranged at a right angle to the direction of gas flow in the gas flow path 25. This prevents light generated by the discharge in the gas flow path 25 from irradiating the irradiation object.

[0209] The plasma generation device 80 according to the fifth embodiment has been described above.

[0210] In the above-mentioned embodiment, the case where the dielectric substrate has a flat portion has been described. However, in the present invention, the dielectric substrate may not have a flat portion but may have only an inclined portion.

[0211] In the above embodiment, the "portion whose thickness decreases as it approaches the air outlet" in the present invention is described as an inclined portion, that is, as the thickness decreases linearly from the flat portion 12a to the air outlet 30. However, the "portion whose thickness decreases as it approaches the air outlet" in the present invention is not limited to this example and may also be a portion that decreases in thickness according to a polynomial such as a quadratic curve or a cubic curve, or an exponential function. Furthermore, a portion that decreases in thickness discontinuously, such as in a step-like manner, may also be described.

[0212] [Sixth embodiment]

[0213] The following describes a plasma generation device 100 according to a sixth embodiment. The plasma generation device 100 of the sixth embodiment differs from the plasma generation device 10 of the first embodiment in the dielectric substrate, the high-voltage electrode, and the shape of the grooves formed in the low-voltage electrode. All other aspects are identical. Therefore, the following description will focus primarily on the differences, while the description of the identical aspects will be omitted or simplified. Components identical to those of the plasma generation device 10 of the first embodiment are denoted by the same reference numerals.

[0214] Figure 17 FIG. 1 is a cross-sectional view of a dielectric barrier plasma generating device according to a sixth embodiment. Figure 17 As shown, the plasma generation device 100 includes a dielectric substrate 102 , a high-voltage-side electrode 104 , and a low-voltage-side electrode 110 .

[0215] The dielectric substrate 102 includes a flat portion 102 a having a constant thickness and a stepped portion 102 b which is formed in a step-like manner from the flat portion 102 a and becomes thinner in a step-like manner as it approaches the air outlet 30 .

[0216] Ceramics are prone to cracking and have a problem of insufficient mechanical strength. Therefore, by providing multiple steps such as two or three steps, it is possible to ensure strength.

[0217] The low voltage side electrode 110 is plate-shaped and is provided on the second surface 103b of the dielectric substrate 102 (at Figure 17 The middle is the lower side).

[0218] The low-voltage electrode 110 is formed with a groove 22 similar to the low-voltage electrode 20 of the first embodiment. A stepped portion 123 is formed in the groove 22, the thickness of which increases as it approaches the outlet 30. As a result, the gas flow path 25 is provided with a portion 124 in which the gap between the dielectric substrate 102 and the low-voltage electrode 110 narrows as it approaches the outlet 30.

[0219] In the sixth embodiment, since the gap between the dielectric substrate 102 and the low-voltage-side electrode 110 is narrowed toward the air outlet 30 , the amount of change in electrostatic capacitance can be further increased.

[0220] Furthermore, the plasma generation devices 50 , 60 , 70 , 80 , and 100 according to the second to sixth embodiments achieve the same effects as the plasma generation device 10 according to the first embodiment in addition to the effects described above.

[0221] Next, a method for starting plasma discharge in the dielectric barrier plasma generator of this embodiment will be described.

[0222] The plasma discharge starting method of the dielectric barrier plasma generator of the present embodiment uses the plasma generators 10 , 50 , 60 , 70 , 80 , and 100 .

[0223] The plasma discharge starting method comprises:

[0224] Step A, during startup, introducing one or more startup gases selected from the group consisting of He, Ne, and Ar into the gas flow path to generate plasma; and

[0225] In step B, after step A, a plasma generating gas is introduced into the gas flow path.

[0226] According to the plasma discharge initiation method of the dielectric barrier plasma generating device of this embodiment, at startup, one or more starting gases selected from the group consisting of He, Ne, and Ar are introduced into the gas flow path to generate plasma. After startup, a plasma generating gas (a gas capable of generating desired active species, such as hydrogen, oxygen, water, and nitrogen) is introduced into the gas flow path. Therefore, even if the plasma generating gas is a gas that is difficult to generate plasma discharge, discharge can be initiated.

[0227] As mentioned above, although embodiment of this invention was demonstrated, this invention is not limited to the said example, and design change is not allowed as appropriate within the range which has the structure of this invention.

[0228] Description of Reference Numerals

[0229] 10, 50, 60, 70, 80, 100 Dielectric barrier plasma generating device (plasma generating device)

[0230] 12, 52, 102 dielectric substrate

[0231] 12a, 52a, 102a flat portion

[0232] 12b, 52b inclined portion

[0233] 13a Page 1

[0234] 13b, 53b, 103b, side 2

[0235] 14, 54, 104 high voltage side electrodes

[0236] 15 Gap

[0237] 20, 56, 110 low voltage side electrodes

[0238] 22 groove

[0239] 23a, 23b outer periphery

[0240] 24 Gas inlet line

[0241] 25 Gas flow path

[0242] 26 Gas buffer substrate

[0243] 27 Hollow

[0244] 30 Blowing outlet

[0245] 34 Electric inlet

[0246] 40 Gas delivery device

[0247] 42 Power supply unit

[0248] 56b (low voltage side electrode) inclined portion

[0249] 64 protection layer

[0250] 72 Startup Auxiliary Components

[0251] 82 light shielding parts

[0252] 83 Hollow

[0253] 102b Step-shaped portion

[0254] 123 Step-shaped part

Claims

1. A dielectric barrier plasma generating device, characterized in that: The device comprises: a dielectric substrate; a high-voltage side electrode provided on a first surface side of the dielectric substrate; and a low-voltage side electrode provided on a second surface side of the dielectric substrate. and an electric lead-in portion provided at one end of the high-voltage-side electrode, configured to generate a dielectric barrier discharge between the high-voltage-side electrode and the low-voltage-side electrode via the dielectric substrate by applying a voltage to the high-voltage-side electrode; a gas flow path for allowing gas to flow from one end to the other end formed between the dielectric substrate and the low-voltage-side electrode, a blowing port formed at the other end of the gas flow path for blowing out gas flowing through the gas flow path and plasma generated in the gas flow path; the dielectric substrate having a portion whose thickness decreases as it approaches the blowing port, and a predetermined gap being provided on the first surface of the dielectric substrate between the other end of the high-voltage-side electrode and the surface where the blowing port is formed.

2. The dielectric barrier plasma generating device according to claim 1, wherein: The dielectric barrier plasma generation device includes a power supply device that applies a voltage of 3 kV to 20 kV and a frequency of 20 kHz to 150 kHz to the high-voltage side electrode.

3. The dielectric barrier plasma generating device according to claim 1 or 2, characterized in that: The gas flow path has a portion where a gap between the dielectric substrate and the low-voltage-side electrode narrows as it approaches the blowing outlet.

4. The dielectric barrier plasma generating device according to claim 1 or 2, characterized in that: A protective layer for preventing a material constituting the low-voltage side electrode from scattering is provided near the air outlet and on the low-voltage side electrode.

5. The dielectric barrier plasma generating device according to claim 1 or 2, characterized in that: The dielectric substrate is made of aluminum oxide or aluminum nitride.

6. The dielectric barrier plasma generating device according to claim 1 or 2, characterized in that: The high-voltage side electrode is a foil-shaped metal.

7. The dielectric barrier plasma generating device according to claim 6, wherein: The high-voltage side electrode is a sintered body containing a conductive metal.

8. The dielectric barrier plasma generating device according to claim 6, wherein: The high-voltage side electrode is formed by plating, evaporation, or sputtering.

9. The dielectric barrier plasma generating device according to claim 1 or 2, characterized in that: A startup assisting member is arranged near the air outlet and on the second surface of the dielectric substrate.

10. The dielectric barrier plasma generating device according to claim 1 or 2, characterized in that: The dielectric barrier plasma generating apparatus includes a gas introduction path for introducing gas into the gas flow path, and the number of the gas introduction paths is two or more.

11. The dielectric barrier plasma generating device according to claim 1 or 2, characterized in that: The air outlet is provided with a light shielding member.

12. The dielectric barrier plasma generating device according to claim 1 or 2, characterized in that: A gas buffer substrate having a cavity therein is stacked on a surface of the low-voltage side electrode opposite to the dielectric substrate.

13. The dielectric barrier plasma generating device according to claim 1 or 2, characterized in that: The portion of the dielectric substrate where the thickness becomes thinner as it approaches the blowing outlet is in a step-like shape.

14. A dielectric barrier plasma generating device, characterized in that: The device comprises: a dielectric substrate; a high-voltage side electrode provided on a first surface side of the dielectric substrate; and a low-voltage side electrode provided on a second surface side of the dielectric substrate. and an electric conduction portion provided at one end of the high-voltage-side electrode, configured to generate a dielectric barrier discharge between the high-voltage-side electrode and the low-voltage-side electrode via the dielectric substrate by applying a voltage to the high-voltage-side electrode; a gas flow path for allowing gas to flow from one end to the other end formed between the dielectric substrate and the low-voltage-side electrode, and a blowing port formed at the other end of the gas flow path for blowing out gas flowing through the gas flow path and plasma generated in the gas flow path; the dielectric substrate having a portion whose thickness decreases as it approaches the blowing port; and a power supply device for applying a voltage to the high-voltage-side electrode at a voltage of 3 kV to 20 kV and a frequency of 20 kHz to 150 kHz.

15. A method for starting plasma discharge in a dielectric barrier plasma generating device, characterized in that: The dielectric barrier plasma generating device comprises: a dielectric substrate; a high-voltage-side electrode provided on the first surface side of the dielectric substrate; and a low-voltage-side electrode provided on the second surface side of the dielectric substrate; and an electric introduction portion provided at one end of the high-voltage-side electrode, configured to generate a dielectric barrier discharge between the high-voltage-side electrode and the low-voltage-side electrode via the dielectric substrate by applying a voltage to the high-voltage-side electrode; a gas flow path formed between the dielectric substrate and the low-voltage-side electrode for flowing gas from one end to the other end, and a blowout port formed at the other end of the gas flow path for blowing out gas flowing through the gas flow path and plasma generated in the gas flow path; the dielectric substrate having a portion whose thickness decreases toward the blowout port, and a predetermined gap formed on a first surface of the dielectric substrate between the other end of the high-voltage-side electrode and a surface where the blowout port is formed. The plasma discharge initiation method comprises: a step A of, at startup, introducing one or more startup gases selected from the group consisting of He, Ne, and Ar into the gas flow path to generate plasma; and a step B of, after step A, introducing a plasma-generating gas into the gas flow path.

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