Plasma processing apparatus and plasma processing method

Abstract

To provide a plasma treatment device capable of continuously and efficiently treating gas with plasma and excellent in handleability and workability at the time of production.SOLUTION: A plurality of flat electrode layers 5 each having a dielectric layer 2 on one surface side and a support layer 3 made of a dielectric on the other surface side are laminated with a space layer 7 in between. The plasma processing apparatus includes a plasma generating part 10 having a structure laminated in parallel, a power source part for applying a volts alternating current between a plurality of electrodes 5, and a gas flowing part capable of flowing a gas to a space layer 7. The electrode layer 5 has a plurality of through-holes 6 penetrating in the thickness direction, the outer edge part of the electrode layer 5 and the through-holes 6 are sealed with an insulating member 1, and the gas passing through the space layer 7 is plasma-treated by the plasma generated in the plasma generating part 10. The plasma processing method uses the plasma processing apparatus.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a plasma processing apparatus and a plasma processing method, and more particularly to a plasma processing apparatus and a method capable of continuously plasma processing gases. [Background technology]

[0002] In recent years, a method called Dielectric Barrier Discharge (DBD) has been developed in plasma processing technology, making it possible to generate low-temperature plasma at atmospheric pressure. As a result, the application fields of plasma processing have expanded, and it is being used in a variety of applications. The purposes of plasma processing include sterilization, deodorization, surface modification, and decomposition of chemical substances.

[0003] Various plasma processing apparatuses have been developed to perform continuous plasma processing while flowing air. For example, Patent Document 1 discloses a plasma generating apparatus in which two or more plasma generating units are stacked, each of which has a flat first electrode and a flat second electrode facing each other across a gap. Patent Document 2 also discloses an air purifier that includes a plasma generator having a structure in which electrode members, at least a portion of which is covered with a dielectric, are arranged in the thickness direction and generate plasma in the gap between adjacent electrode members, a power source that applies voltage, and a blower that blows air through the gap and releases the generated ozone along with the air. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-190472 [Patent Document 2] Japanese Patent Application Publication No. 2018-130208 Summary of the Invention [Problem to be solved by the invention]

[0005] Both the plasma generator described in Patent Document 1 and the air purifier described in Patent Document 2 generate plasma in a slit-shaped space sandwiched between multiple metal layers and dielectric layers, and plasma treat the air flowing through the space. However, both devices have a structure in which multiple metal layers, dielectric layers, and gap spaces are stacked, and during manufacturing, the process of stacking each thin layer in order must be repeated many times, resulting in poor handling and workability during manufacturing.

[0006] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a plasma processing apparatus that can continuously and efficiently process gases with plasma and that is easy to handle and operate during manufacturing. [Means for solving the problem]

[0007] Manufacturing a plasma generating unit for a plasma processing apparatus requires carefully stacking relatively thin materials, such as electrode layers and dielectric layers, with uniform thicknesses. The inventors discovered that by configuring the plasma generating unit with a support layer, it becomes easier to sequentially stack the electrode layers, dielectric layers, and other layers on top of the support layer, thereby resolving the above-mentioned problems encountered during the manufacture of a plasma processing apparatus. Furthermore, the inventors discovered that forming multiple through-holes penetrating the electrode layer in the thickness direction facilitates plasma generation in the spatial layer, enabling efficient plasma processing of gases. It is believed that this is because the through-holes formed in the electrode layer have sharp edges at their ends, which facilitate plasma generation. Here, the through-holes penetrate the stacked electrode layers in the thickness direction, but do not penetrate the dielectric layer or the support layer. The present invention has been completed through the above-mentioned investigations, and has the following features.

[0008] (1) A plasma processing apparatus having a plasma generation unit having a structure in which multiple flat electrode layers, each having a dielectric layer on one side and a support layer made of a dielectric on the other side, are stacked in parallel with a space layer sandwiched between them, a power supply unit that applies an AC voltage between the multiple electrode layers, and a gas flow unit that can flow gas through the space layer, wherein the electrode layers have multiple through holes that penetrate in the thickness direction, and the outer edge of the electrode layers and the through holes are sealed with an insulating member, and the plasma processing apparatus is characterized in that the gas passing through the space layer is plasma-processed by plasma generated in the plasma generation unit. (2) The plasma processing apparatus according to (1), wherein the plurality of electrode layers are stacked with the surface side of the dielectric layer and the surface side of the support layer alternately alternating. (3) The total perimeter of the plurality of through holes on the plane of the electrode layer is equal to or less than 1 cm of the area occupied by the electrode layer without the through holes. 2 The plasma processing apparatus according to (1) or (2), characterized in that the thickness is 0.5 cm or more. (4) A plasma processing apparatus as described in (1) or (2), characterized in that the total area occupied by the multiple through holes on the plane of the electrode layer is 20% or more of the area occupied by the electrode layer without the through holes. (5) A plasma processing apparatus according to (1) or (2), characterized in that not only the gas passing through the spatial layer but also the gas passing through the outer space is plasma-processed by flowing gas into the space outside the laminated structure. (6) The plasma processing apparatus according to (1) or (2), wherein the plasma generating section has a flat or curved surface. (7) The plasma processing apparatus according to (1) or (2), wherein the gas contains carbon dioxide, and the carbon dioxide is subjected to plasma processing to generate carbon monoxide. (8) A plasma processing method, characterized in that a gas passing through the spatial layer is plasma-processed using the plasma processing apparatus according to (1) or (2). (9) The plasma processing method according to (8) above, wherein the gas contains carbon dioxide, and the carbon dioxide is subjected to plasma processing to generate carbon monoxide. [Effects of the Invention]

[0009] The plasma processing apparatus of the present invention is capable of continuously and efficiently processing gases with plasma, and is excellent in handleability and workability during manufacturing. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic perspective view of a plasma generating unit of a plasma processing apparatus according to the present embodiment, which has a structure in which two electrode layers are stacked in parallel with a space layer sandwiched between them. [Figure 2] FIG. 2 is a schematic cross-sectional view of the plasma generating unit of FIG. 1 taken along the line AA. [Figure 3] FIG. 3 is a schematic cross-sectional view of the plasma generating unit of FIG. 1 taken along the line BB. [Figure 4] 4A and 4B are schematic plan views showing through holes in the electrode layer of the plasma processing apparatus of this embodiment. Fig. 4A shows a pattern in which many oblong shapes, each longer in the gas flow direction than in the direction perpendicular to the gas flow direction, are arranged in parallel. Fig. 4B shows a pattern in which many circles are arranged in a regular pattern vertically and horizontally. Fig. 4C shows a pattern in which many rectangles, each shorter in the gas flow direction than in the direction perpendicular to the gas flow direction, are arranged in parallel. Fig. 4D shows a pattern in which many squares are arranged in a regular pattern vertically and horizontally. [Figure 5] 5A and 5B are schematic cross-sectional views of modified examples of the plasma generating unit of the plasma processing apparatus of this embodiment. Fig. 5A shows a plasma generating unit having a structure in which three electrode layers are stacked in parallel with a space layer between them. Fig. 5B shows a plasma generating unit having a structure in which four electrode layers are stacked in parallel with a space layer between them. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail, but the embodiments of the present invention are not limited to the specific embodiments described below. The embodiments can be applied in appropriate combinations. Furthermore, terms indicating directions such as "up and down" and "left and right" in the description are used for convenience of explanation and do not limit the directions of the present invention.

[0012] The plasma generation unit of the plasma processing apparatus of this embodiment has a structure in which multiple flat electrode layers, each having a dielectric layer on one side and a dielectric support layer on the other side, are stacked in parallel with a space layer sandwiched between them. The plasma processing apparatus of this embodiment also has a power supply unit that applies an AC voltage between the multiple electrode layers to generate plasma in the space layer. The plasma processing apparatus of this embodiment also has a gas flow unit that can flow a gas through the space layer to process the gas with plasma.

[0013] Dielectric barrier discharge can be classified into a single-barrier discharge type in which a dielectric layer is provided on only one of the electrodes, and a double-barrier discharge type in which a dielectric layer is provided on both of the electrodes. The plasma processing apparatus of this embodiment is a plasma processing apparatus using the double-barrier discharge type. That is, the plasma processing apparatus of this embodiment has a structure in which a dielectric layer or a support layer made of a dielectric is provided on one side of each of a plurality of electrode layers, on the side facing a space layer present between the pair of electrode layers. The plasma processing apparatus of this embodiment then generates plasma in the space layer sandwiched between the two dielectric layers.

[0014] The plasma processing apparatus of this embodiment has a dielectric layer between each of the electrode layers, which prevents localized concentration of plasma between the electrode layers and allows for uniform plasma generation in the space between the electrode layers. This also reduces the risk of localized temperature increases in the space between the electrode layers, allowing for stable generation of low-temperature plasma.

[0015] Furthermore, when electrons, ions, radicals, etc. in the plasma present in the space between the electrode layers collide with neutral particles, the neutral particles are excited. The excited neutral particles may then emit light when returning to their ground state. As a result, purple visible light or ultraviolet light may be observed from the plasma processing apparatus of this embodiment.

[0016] Fig. 1 is a schematic perspective view of a plasma generating unit 10 of a plasma processing apparatus according to this embodiment. Fig. 2 is a schematic cross-sectional view of the plasma generating unit taken along line AA in Fig. 1. Fig. 3 is a schematic cross-sectional view of the plasma generating unit taken along line BB in Fig. 1. Fig. 2 is a cross section taken along line AA of the plasma generating part in Fig. 1, and is a schematic cross section of a portion where a through-hole 6, which will be described later, exists in the electrode layer 5. On the other hand, Fig. 3 is a cross section taken along line BB of the plasma generating part in Fig. 1, and is a schematic cross section of a portion where a through-hole 6, which will be described later, does not exist in the electrode layer 5.

[0017] The space layer 5 is a slit-like space that communicates from the gas inlet of the plasma generation unit 10 to the gas outlet. In FIG. 1, as indicated by the arrows, the gas inlet is at the back of the page in the upper right corner and the gas outlet is at the front of the page in the lower left corner. Plasma can be generated in the space layer 7 by applying an AC voltage between the two electrode layers 5 located above and below. By flowing gas into the space layer 7 from one inlet of the space layer 7, the gas is plasma-treated in the space layer 7 and is discharged from the other outlet of the space layer 7.

[0018] 1 to 3, spacers 4 are provided on both sides of the gas flow path in the space layer 7. That is, the space layer 7 has a cross-sectional shape that is partitioned from above and below by the dielectric layer 2 or the support layer 3, and from left and right by the spacers 4. The spacers 4 play a role in maintaining the shape of the space layer 7 so that the space layer 7 can be maintained at a predetermined height. The height of the space layer 7 can be adjusted by changing the height of the spacer 4. The height of the space layer 7 is not particularly limited, but from the viewpoint of increasing the efficiency of the plasma treatment, it is preferably 0.5 to 20 mm, and more preferably 1 to 10 mm.

[0019] 1 to 3, the electrode layer 5 must have its outer edge (the peripheral edge surface of the electrode layer 5) sealed with an insulating member 1. That is, the insulating member 1 serves to insulate the electrode layer 5, which is exposed to high temperatures and active substances when an AC voltage is applied, from the outside world and to protect it from deterioration. The insulating member 1 also prevents short circuits from occurring between the electrode layers 5 to which an AC voltage is applied via the peripheral edge surfaces or surfaces of components.

[0020] Fig. 2 discloses a plurality of through holes 6 that penetrate the electrode layer 5 in the thickness direction. In Fig. 1, the electrode layer 5 present inside and the shapes of the through holes 6 formed in the electrode layer 5 are indicated by dotted lines. Fig. 1 discloses a pattern of through holes 6 formed in the electrode layer 5 in which four oblong through holes, each with a length in the gas flow direction greater than the length in the direction perpendicular to the gas flow direction, are arranged in parallel.

[0021] 2, the through-holes 6 penetrate the electrode layer 5 in the thickness direction, but do not penetrate the dielectric layer 2 or the support layer 3. The gas to be plasma processed flows through a space layer 7 sandwiched between two opposing dielectric layers 2 that do not have through-holes 6 and are smooth.

[0022] The present inventors fabricated a prototype plasma generation unit 10 having a plurality of through-holes 6 penetrating the electrode layer 5 in the thickness direction as shown in Fig. 1, and measured its performance, and found that the provision of the through-holes 6 makes it easier for plasma to be generated in the space layer 7, enabling efficient plasma treatment of gas. It is presumed that when the through-holes 6 are formed in the electrode layer 5, an acute-angled edge portion exists near the cross-section portion 8 of the electrode layer 5 within the through-holes 6, making it easier for plasma to be generated in the space layer 7.

[0023] However, when a plurality of through holes 6 are formed in the electrode layer 5, if there are cavities (spaces) at the locations where the through holes 6 are formed, discharges are likely to occur between the electrode layers 5 through the cavities (spaces), which may reduce the durability of the plasma generating unit 10. Therefore, similar to the case of the outer edge of the electrode layer 5 described above, after the through holes 6 are formed, it is necessary to seal the through holes 6 with the insulating member 1.

[0024] Furthermore, a phenomenon may occur in which a part of the plasma generated near the cross section 8 of the electrode layer 5 in the through hole 6 leaks beyond the dielectric layer 2 or the support layer 3 to the outside thereof. As a result, a part of the plasma generated in the plasma generating unit 10 spreads to the space above and below the plasma generating unit 10, and the gas present in the space outside the plasma generating unit 10 can be plasma treated. Therefore, if a gas flow section is used that is configured to allow gas to flow not only through the spatial layer 7 but also in the space outside the dielectric layer 2 or the support layer 3, it becomes possible to plasma treat not only the gas passing through the spatial layer 7 but also the gas passing through the outer space (not shown).

[0025] A large number of through holes 6 and a large area of ​​the through holes 6 increase the amount of cross-sectional area 8 of the electrode layer 5 inside the through holes 6, which increases the amount of plasma generated, and is therefore preferable. Furthermore, although the shape and pattern of the through holes 6 are not particularly limited, it is preferable that the through holes 6 are formed uniformly in the same pattern over the entire surface of the electrode layer 5, since this prevents localization of the amount of plasma generated and makes it uniform across the entire electrode layer 5.

[0026] 4 is a schematic plan view showing a through hole 6 formed in the electrode layer 5 of the plasma processing apparatus 10. Several representative examples are shown for the planar shape of the through hole 6. The planar shape of the through hole 6 indicates the shape of a region formed in the electrode layer 5 and sealed with an insulating member.

[0027] Figure 4(a) shows a pattern in which many oblong shapes, each longer in the direction of gas flow than in the direction perpendicular to the gas flow, are arranged in parallel. Figure 4(b) shows a pattern in which many circles are arranged in a regular pattern both vertically and horizontally. Figure 4(c) shows a pattern in which many rectangles, each shorter in the direction of gas flow than in the direction perpendicular to the gas flow, are arranged in parallel. Figure 4(d) shows a pattern in which many squares are arranged in a regular pattern both vertically and horizontally.

[0028] A large number of through holes 6 and a large area of ​​the through holes 6 are preferable because the length of the cross-sectional portion 8 of the electrode layer 5 inside the through holes 6 increases, thereby increasing the amount of plasma generated. Therefore, various types of plasma generating units 10 with different numbers and shapes of through holes 6 were fabricated and the relationship with the plasma processing performance was evaluated. As a result, the total (average) perimeter of the through holes 6 per unit area on the plane of the electrode layer 5 was measured, and it was found that the area occupied by the electrode layer 5 without the through holes 6 was 1 cm 2 It has been found that the total perimeter of each through hole is preferably 0.5 cm or more, more preferably 1 cm or more, even more preferably 2 cm or more, and most preferably 3 cm or more.

[0029] Furthermore, it was found that the total area (average value) occupied by the through holes 6 on the plane of the electrode layer 5 is preferably 20% or more of the area occupied by the electrode layer 5 in a state where the through holes 6 are not present. The total area occupied by the through holes 6 is more preferably 30% or more, and even more preferably 40% or more.

[0030] There are no particular restrictions on the number and planar shape of the through holes 6. The number and shape can be appropriately selected depending on the purpose of the plasma treatment, the effect of the plasma treatment, etc. Furthermore, the planar shape patterns of the through holes 6 between the electrode layers 5 in the plasma generating unit 10 can be the same or different.

[0031] In the present embodiment, flat electrode layers 5 each having a dielectric layer 2 on one side and a dielectric support layer 3 on the other side are stacked in parallel with a space layer 7 sandwiched therebetween. However, if necessary, a structure in which multiple electrode layers 5 are stacked can be used. There is no limit to the number of electrode layers 5 that can be stacked. Therefore, if it is desired to increase the cross-sectional area of ​​the space layer 7 and thereby increase the plasma processing amount per unit time, the number of stacked electrode layers 5 can be increased.

[0032] The plasma generating unit 10 shown in Figures 1 to 3 has a structure in which two electrode layers 5 are stacked. The electrode layers 5 are stacked with the dielectric layer 2 sides of the electrode layers 5 facing each other with a space layer 7 sandwiched between them. Figure 5 is a schematic cross-sectional view of a modified example of the plasma generating unit of the plasma processing apparatus of this embodiment. Figure 5(a) shows a plasma generating unit having a structure in which three electrode layers 5 are stacked in parallel with a space layer sandwiched between them. Figure 5(b) shows a plasma generating unit 10 having a structure in which four electrode layers are stacked in parallel with a space layer 7 sandwiched between them.

[0033] In the plasma generating unit 10 of this embodiment, when a flat electrode layer 5 having a dielectric layer 2 on one side and a dielectric support layer 3 on the other side is laminated, it is possible to freely select whether the electrode layer 5 is laminated on the side of the dielectric layer 2 or the side of the support layer 3 relative to the spacer 7. Both the dielectric layer 2 and the support layer 3 are made of a dielectric, so either side does not pose any significant problems. The electrode layers 5 may be laminated so that the dielectric layer 2 sides of the electrode layers 5 face each other with the spacer 7 sandwiched therebetween, or so that the support layer 3 sides of the electrode layers 5 face each other with the spacer 7 sandwiched therebetween. Therefore, the electrode layers 5 may be laminated so that the dielectric layer 2 sides of the electrode layers 5 face each other with the spacer 7 sandwiched therebetween. However, from the perspective of uniformity of plasma generation, it is preferable to laminate the electrode layers 5 so that the dielectric layer 2 sides of the electrode layers 5 face each other with the spacer 7 sandwiched therebetween, or so that the support layer 3 sides of the electrode layers 5 face each other. That is, when stacking multiple electrode layers 5, it is preferable to stack them while alternately switching between the surface side of the dielectric layer 2 and the surface side of the support layer 3 (the front and back sides of the electrode layer 5) (see Figures 1 to 3).

[0034] In this embodiment, the purpose of plasma treatment is various, such as sterilization, deodorization, surface modification, decomposition of chemical substances, etc., and there are no particular limitations on the gas to be treated. Furthermore, the treatment time and strength of the gas flow can be adjusted appropriately by changing the flow rate and the strength and frequency of the applied AC voltage depending on the purpose and application.

[0035] The electrode layer 5 is made of a conductive material, and may be a metal plate (including metal foil), conductive paint, conductive polymer, conductive film, etc., but is preferably a metal plate. Preferred metal materials include copper, aluminum, stainless steel, and iron, which have excellent conductivity. Of these, copper is more preferred from the standpoints of conductivity and cost.

[0036] The surface of the electrode layer 5 is preferably smooth. If the surface of the electrode layer 5 is smooth, it will be a so-called solid flat plate, and the plasma generated when an AC voltage is applied between the two electrode layers 5 will be less likely to be localized in some places, allowing for uniform plasma to be generated in the space layer 7. If the surface of the electrode layer 5 is uneven, localized discharge will be more likely to occur from the convex parts, raising the concern that plasma generation will be localized.

[0037] Furthermore, if the surface of the electrode layer 5 is smooth, it becomes possible to repeatedly reflect the visible light and ultraviolet light generated in the space layer 7 between the two electrode layers 5, thereby further enhancing the treatment effect of irradiating the gas to be treated with visible light and ultraviolet light. In order to improve the smoothness of the surface of the electrode layer 5, it is preferable that a metal layer is formed on the surface by plating or vapor deposition. The type of metal is gold, silver, aluminum, or the like. The thickness of the electrode layer 11 is not particularly limited, but in order to obtain a lightweight and compact processing device, it is preferably 10 μm to 1 mm, more preferably 10 μm to 0.2 mm, and even more preferably 10 μm to 0.1 mm.

[0038] The material constituting the dielectric layer 2 must be an insulating material so as to prevent easy discharge between the pair of electrode layers 5. Furthermore, since the material constituting the dielectric layer 2 will be exposed to the plasma generated in the space layer 7, it is preferable that the material be durable against the active substances generated in the plasma. Specific examples of materials constituting the dielectric layer 2 include glass, ceramics, and synthetic resins. Examples of glass include soda-lime glass (soda glass), borosilicate glass, quartz glass, lead glass, and oxide glass. Examples of ceramics include alumina, silica, titanium oxide, and zinc oxide. Examples of synthetic resins include thermoplastic resins and thermosetting resins. Thermoplastic resins include general-purpose resins such as polyolefin, polystyrene, polyvinyl acetate, polyurethane, polylactic acid, ABS resin, AS resin, acrylic resin, polyvinyl chloride, and polyvinylidene chloride; engineering plastics such as polyamide, polyacetal, polycarbonate, modified polyphenylene ether, polyester, and cyclic polyolefin; and super-engineering plastics such as polyphenylene sulfide, polysulfone, polyethersulfone, polyarylate, liquid crystal polymer, polyetheretherketone, polyimide, polyamideimide, polyetherimide, fluorine-based resin, and silicone-based resin. Thermosetting resins include phenolic resin, melamine resin, urea resin, alkyd resin, epoxy resin, unsaturated polyester resin, and polyurethane resin. Among these, it is preferable that the material is mainly composed of glass or silicone resin, where "mainly" means that the component composition is 50% by mass or more (the same applies hereinafter). The thickness of the dielectric layer 2 is not particularly limited, but is preferably 0.1 to 5 mm, more preferably 0.1 to 1 mm, in order to obtain a lightweight and compact processing device.

[0039] The material constituting the spacer 4 also needs to be an insulating material so as to prevent easy discharge between the pair of electrode layers 5. Furthermore, since the material constituting the spacer 4 will be exposed to the plasma generated in the space layer 7, it is preferable that the material be durable against the active substances generated in the plasma. Specific examples of the material constituting the spacer 4 include glass, ceramics, and synthetic resins. Specific examples of glass, ceramics, and synthetic resins are the same as those of the material constituting the dielectric layer 2. Specific examples of the material constituting the insulating member 1 include the synthetic resins described as the material constituting the dielectric layer 2, and an adhesive that bonds the electrode layer 5 (described below) and the dielectric layer 2. Specific examples of the synthetic resins are the same as those of the synthetic resins constituting the dielectric layer 2.

[0040] The support layer 3 is a layer that supports the structure of the plasma generating part 10, and is a layer that maintains the shape of the plasma generating part 10 and stabilizes the shape. The support layer 3 is made of a dielectric material, similar to the dielectric layer 2. The material constituting the support layer 3 must be an insulating material so as to prevent easy discharge between the pair of electrode layers 5. Specific examples of insulating materials include glass, ceramics, and synthetic resins. Specific examples of glass, ceramics, and synthetic resins are the same as those of the material constituting the dielectric layer 2. As a result, the support layer 3 has the same function as the dielectric layer 2 with respect to the electrode layer 5.

[0041] The insulating material constituting the support layer 3 is not particularly limited, but it is preferable to use a synthetic resin to improve handling and provide appropriate flexibility. Similar to the synthetic resins constituting the dielectric layer 2, examples of the synthetic resin include thermoplastic resins such as general-purpose resins, engineering plastics, and super engineering plastics, and thermosetting resins. Among these, preferred are thermosetting resins such as silicone resins, phenolic resins, melamine resins, urea resins, alkyd resins, epoxy resins, unsaturated polyester resins, and polyurethane resins. Of the thermosetting resins, preferred is epoxy resin, which is easy to handle and inexpensive. In order to reinforce the synthetic resin, it is preferable to add a filler to the synthetic resin, such as glass fiber, carbon fiber, aramid fiber, whisker, or cellulose fiber, or inorganic particles such as calcium carbonate, silica, talc, mica, clay, alumina, or kaolin.

[0042] Among these, composites using epoxy resin, phenolic resin, or polyimide resin as the synthetic resin and glass fiber or cellulose fiber (paper) as the filler are preferred. Furthermore, composites mainly made of glass fiber and epoxy resin are even more preferred. Specific examples include so-called printed wiring boards, such as glass-epoxy substrates made of glass fiber and thermosetting epoxy resin, paper-phenolic substrates made of paper and phenolic resin, polyimide resin substrates, and liquid crystal polymer substrates. Copper-clad laminates, in which these substrates are bonded with copper foil, are particularly preferred because the copper foil can be used as is as the electrode layer 5 of this embodiment.

[0043] The electrode layer 5 and the dielectric layer 2 that constitute the plasma generating unit 10 are both thin layers, making them difficult to handle and work with. For example, when laminating the electrode layer 5 and the dielectric layer 2, both layers are thin and weak, and are prone to wrinkling, air bubbles, and cracking due to deflection under their own weight when laminating and crimping, or when applying adhesive. On the other hand, the support layer 3 of this embodiment is flexible enough to bend to a certain extent, absorbing the distortion of each layer and allowing the support layer 3 to bend while laminating the electrode layer 5 and the dielectric layer 2. As a result, wrinkling, air bubbles, and cracking can be reduced when laminating and crimping, or when applying adhesive.

[0044] In this way, in this embodiment, by providing the support layer 3, the handling and workability of the electrode layer 5 and the dielectric layer 2 that constitute the plasma generation section 10 are improved, making it possible to manufacture the plasma processing apparatus efficiently and with a high yield.

[0045] The plasma generating unit 10 of this embodiment may be flat or curved. By appropriately selecting the type and thickness of materials constituting the plasma generating unit 10, such as the support layer 3, electrode layer 5, and dielectric layer 2, the multilayer structure can be bent. The dimensions and shape of the plasma generating unit 10 must be adapted to various requirements, depending on the purpose and application of the plasma processing, the type of gas, and the like. This embodiment offers a high degree of freedom in the selection of the constituent materials and excellent handling and workability during manufacturing, making it possible to form various shapes according to desired needs. Curved shapes can also be cylindrical, conical, spiral, U-shaped, W-shaped, and other shapes.

[0046] The electrode layer 5 and the dielectric layer 2 may be laminated without using an adhesive, or may be bonded with an adhesive. Because the adhesive is in close proximity to the plasma generated in the spatial layer 7, a material that is durable against the active substances generated in the plasma is preferred. Adhesives include epoxy-based, acrylic-based, urethane-based, phenol-based, urea-based, melamine-based, silicone-based, cyanoacrylate-based, rubber-based, and vinyl acetate-based adhesives. Among these, silicone-based adhesives and UV-curable epoxy-based adhesives are preferred from the standpoint of durability, with silicone-based adhesives being more preferred. The thickness of the adhesive layer is preferably 0.01 to 0.2 mm, more preferably 0.01 to 0.1 mm.

[0047] Since plasma processing equipment is subject to temperature changes during use, if there is a large difference in the thermal expansion coefficient between the materials constituting the multilayer structure, there is a concern that problems such as peeling may occur over time. Therefore, it is preferable that the materials and adhesives constituting the dielectric layer 2 and support layer 3 laminated with the electrode layer 5 are highly flexible materials that can follow dimensional changes in the electrode layer 5. Synthetic resin-based materials are preferred as such materials, and it is preferable to select and use an appropriate material from among synthetic resin-based materials.

[0048] To manufacture the plasma generation unit 10 of the plasma processing apparatus of this embodiment, it is necessary to carefully stack materials such as the support layer 3, electrode layer 5, dielectric layer 2, spacer 4, and insulating member 1 in order.

[0049] The power supply unit (not shown) of this embodiment applies an AC voltage between the multiple electrode layers to generate plasma in the space layer 7. In this embodiment, the plasma generation unit 10 preferably has multiple electrode layers 5 stacked while alternately switching between the surface side of the dielectric layer 2 and the surface side of the support layer 3. Therefore, as shown in Figures 3, 5(a), and 5(b), adjacent pairs of electrode layers 5 are stacked so as to be line-symmetrical with each other across the space layer 7. Therefore, it is preferable to alternately change the polarity of the AC voltage applied to the electrode layers 5 in order from the end. As a result, AC voltages of different polarities are applied to a pair of electrode layers 5 facing each other across the space layer 7.

[0050] As for the specific contents of the power supply unit, there are no particular restrictions as long as it can apply an AC voltage of a predetermined voltage at a predetermined frequency to the pair of electrode layers 5 of the plasma generating unit 10, and any known power supply device can be used. The frequency of the AC voltage is preferably 50 Hz to 30 MHz, more preferably 50 Hz to 100 kHz, and the AC voltage is preferably 1 to 50 kV, more preferably 2 to 10 kV.

[0051] The gas flow unit (not shown) of this embodiment is not particularly limited as long as it is a device that can cause a gas to flow through the spatial layer 7 in order to treat the gas with plasma. As shown in Fig. 1, a gas is supplied to the spatial layer 7 from one side of the plasma generation unit 10, and the gas is discharged from the spatial layer 7 on the other side of the plasma generation unit 10. It is preferable that the gas discharged from the spatial layer 7 can be discharged to the outside. As a driving device for moving the gas, a known device such as a centrifugal blower (such as a sirocco fan, a radial fan, or a turbo fan), an axial flow blower (such as a propeller fan), a mixed flow blower (such as a line fan), a cross flow blower, or a blower can be appropriately used.

[0052] Functions exhibited by performing plasma treatment using the plasma treatment apparatus of this embodiment include sterilization, virus inactivation, deodorization, surface modification, decomposition of chemical substances, and decomposition of carbon dioxide. The mechanism by which these functions are exhibited is thought to be that plasma treatment generates reactive oxygen species (Reactive Oxygen Species) such as singlet oxygen, hydrogen peroxide, OH radicals, superoxide, peroxy radicals, and ozone in the gas, which then kill or inactivate target microorganisms or decompose or modify chemical substances through oxidation reactions or the like. Examples of microorganisms include various bacteria, viruses, and mold.

[0053] In the plasma processing apparatus of this embodiment, the gas that has passed through the space layer 7 and been plasma-processed is subjected to sterilization, deodorization, etc. by killing or inactivating microorganisms present in the gas and decomposing chemical substances due to active species generated by the plasma while passing through the space layer 7. Furthermore, in the plasma processing apparatus of this embodiment, some active species do not disappear but remain (remain) in the gas that has been plasma-processed after passing through the space layer 7. Therefore, by spraying the gas that has been plasma-processed after passing through the plasma processing apparatus of this embodiment onto an object, microorganisms present in the object can be killed or inactivated, and chemical substances can be decomposed, thereby sterilizing, inactivating, deodorizing, etc. the object. Furthermore, the gas that has been plasma-treated using the plasma processing apparatus of this embodiment and that contains some active species can be mixed with a liquid such as water to produce a liquid containing plasma-activated species, which can be used for sterilizing, inactivating, deodorizing, etc., objects.

[0054] The plasma processing apparatus of this embodiment can be used to decompose chemical substances by performing plasma processing. In particular, by performing plasma processing on a gas containing carbon dioxide using the plasma processing apparatus of this embodiment, it is possible to decompose the carbon dioxide to generate carbon monoxide and convert it into a gas containing carbon monoxide. This can contribute to reducing carbon dioxide, which is a cause of global warming.

[0055] By utilizing these functions, the plasma processing apparatus of this embodiment can be used for purposes such as deodorization, odor removal, sterilization, disinfection, infection prevention, gas purification, and water purification in many industrial fields such as medicine (fiberscopes, endoscopes, various small cameras, etc.), housing, civil engineering, construction, agriculture, fisheries, livestock farming, food processing, transportation, storage, and retail. [Example]

[0056] An experiment was conducted to plasma treat carbon dioxide using the plasma treatment apparatus of this embodiment. (1) Measuring equipment A plasma processing enclosure having the plasma generating unit shown in Figure 1 inside and a gas inlet and outlet for the spatial layer, a power supply unit (neon transformer, variac), a small high-pressure carbon dioxide cylinder, a carbon dioxide regulator with an integrated low-flow solenoid valve, a portable carbon dioxide concentration meter, and a polyurethane pressure-resistant tube. (2) Processing conditions Carbon dioxide gas (99 vol% or more) was supplied from a high-pressure carbon dioxide cylinder via a carbon dioxide regulator and a pressure-resistant tube to the gas inlet of the plasma processing enclosure (gas flow rate 1 L / min). Plasma processing of carbon dioxide gas was performed at room temperature with a voltage of 6 kV. The carbon monoxide concentration of the gas discharged from the gas outlet was measured using a carbon monoxide concentration meter via a pressure-resistant tube. (3) Processing results At room temperature, the carbon monoxide concentration was recorded as 100 ppm approximately 1 minute after the start of plasma treatment with carbon dioxide gas, and as 870 ppm approximately 3 minutes after the start of plasma treatment.

[0057] As can be seen from the above description, the plasma processing apparatus of this embodiment has the following features. (1) The plasma processing apparatus of the present invention can continuously and efficiently process gases with plasma. (2) The plasma processing apparatus of the present invention can be manufactured with high yield by improving the handling and workability during manufacturing. (3) The plasma processing apparatus of the present invention can reduce the thickness of the dielectric layer, thereby reducing the energy required for plasma processing. (4) The plasma processing apparatus of the present invention can be made smaller in size. [Explanation of symbols]

[0058] 1. Insulating material 2. Dielectric Layer 3 Support layer 4 spacers 5 Electrode layer 6 through holes 7 Spatial layer 10 Plasma generation unit

Claims

1. a plasma generating unit having a structure in which a plurality of flat electrode layers, each having a dielectric layer on one side and a dielectric support layer on the other side, are stacked in parallel with a space layer sandwiched between them; a power supply unit that applies an AC voltage between the plurality of electrode layers; a gas flow unit that can flow a gas through the spatial layer, the electrode layer has a plurality of through holes penetrating in a thickness direction, an outer edge portion of the electrode layer and the through hole are sealed with an insulating member; A plasma processing apparatus, characterized in that a gas passing through the spatial layer is plasma-processed by the plasma generated in the plasma generating unit.

2. 2. The plasma processing apparatus according to claim 1, wherein the plurality of electrode layers are stacked such that the surface side of the dielectric layer and the surface side of the support layer are alternately changed.

3. The total perimeter of the plurality of through holes on the plane of the electrode layer is 1 cm ２ 3. The plasma processing apparatus according to claim 1, wherein the thickness of the surface is 0.5 cm or more.

4. 3. The plasma processing apparatus according to claim 1, wherein the total area of ​​the electrode layer occupied by the plurality of through holes is 20% or more of the area of ​​the electrode layer without the through holes.

5. 3. The plasma processing apparatus according to claim 1, wherein not only the gas passing through the spatial layer but also the gas passing through the outer space is plasma-processed by flowing gas into the outer space of the laminated structure.

6. 3. The plasma processing apparatus according to claim 1, wherein the plasma generating section has a flat surface or a curved surface.

7. 3. The plasma processing apparatus according to claim 1, wherein the gas contains carbon dioxide, and the carbon dioxide is subjected to a plasma processing to generate carbon monoxide.

8. 3. A plasma processing method, comprising: using the plasma processing apparatus according to claim 1 or 2 to plasma-process a gas passing through the spatial layer.

9. 9. The plasma processing method according to claim 8, wherein the gas contains carbon dioxide, and the carbon dioxide is subjected to plasma processing to generate carbon monoxide.

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