JP2023008509A - Dielectric barrier discharge electrode and dielectric barrier discharge device - Google Patents

Abstract

To provide a dielectric barrier discharge electrode which materializes driving at low voltage and furthermore enables improvement of durability or reliability thereof.SOLUTION: A dielectric barrier discharge electrode 2 of an embodiment, comprises : a dielectric substance 4 having a first surface 4a; a first electrode 5 provided in such a way as to be exposed onto the first surface 4a of the dielectric substance 4; and a second electrode 6 arranged in such a way as to be opposite to the first electrode 5 via the dielectric substance 4. The dielectric substance 4 comprises: a first dielectric layer 8 arranged in such a way as to construct at least a part of the first surface 4a; and a second dielectric layer 9 which is laminated with the first dielectric layer 8 and is made of a material different from that of the first dielectric layer 8. The dielectric substance layer 8 includes an inorganic dielectric material, and the second dielectric layer 9 includes a dielectric material in which at least one of insulation breakdown voltage and a dielectric constant is larger than that of the inorganic dielectric material.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD Embodiments of the present invention relate to dielectric barrier discharge electrodes and dielectric barrier discharge devices.

As a method for generating stable plasma under atmospheric pressure, a dielectric barrier discharge (DBD) system is used. A discharge device to which the DBD method is applied (hereinafter also referred to as a DBD device) includes a DBD electrode having a pair of electrodes (a discharge electrode and a counter electrode) and a dielectric interposed therebetween. A discharge is generated by applying a high voltage from an AC discharge power supply.

When a voltage is applied between a pair of electrodes, a minute discharge (streamer discharge) is generated at one edge of the discharge electrodes. Dielectrics act like capacitors, so once charge builds up on the surface of the dielectric, the discharge stops at one location and discharges are created elsewhere. Since the discharge at one point ends immediately (several ns to several tens of ns), it does not shift to an arc discharge with a high current density (so-called thermal plasma). By repeating this at high speed, a uniform and stable discharge can be generated over a wide area. By reversing the polarity of the applied voltage before the charge is accumulated on the entire surface of the dielectric, the plasma can be maintained continuously. Plasma generated by dielectric barrier discharge is a collection of many minute discharges (streamer discharges), and the current density of each minute discharge is small. For this reason, only the electron temperature is high (several eV to several tens of eV), and the ion temperature and gas particles are classified as low-temperature plasmas that have the same energy as room temperature (~0.1 eV). It is only as high as the degree.

In conventional DBD electrodes, the thickness of the dielectric is often on the millimeter scale, and the voltage applied between a pair of electrodes is usually 5 kV or more, and has a configuration driven at a high voltage. Therefore, in order to take measures against high voltages such as insulation and noise, the discharge part housing the DBD electrode and the power source for discharge become large and expensive, so low voltage driving of the DBD is desired. Therefore, in order to generate a high electric field, it has been proposed to use a substance with a high dielectric constant (ferroelectric) as the dielectric or to reduce the thickness of the dielectric to a microscale.

For example, by using a flexible dielectric composed of a ferroelectric resin film (relative permittivity 3 to 110), it is driven at a low voltage of 0.2 to 2 kV as a sine wave voltage applied between electrodes. A DBD has been proposed to It has also been proposed to use thin film glass, which is thin, smooth, non-conductive and flexible, as the dielectric. Since thin-film glass requires a dielectric thickness that is sufficient to withstand dielectric breakdown when an electric discharge occurs, using a glass with a thickness of about 4 μm to 500 μm makes it possible to drive at a voltage of the 1 kV class. .

However, from the viewpoint of practical use, when the surface of a ferroelectric resin film with a high relative dielectric constant is exposed to an electric discharge, it is decomposed by reactive species (radicals) generated by the electric discharge, and the surface becomes dug. There is a problem that the resin film is thinned, the insulation resistance performance of the dielectric itself is lowered, and the durability as a DBD electrode is lowered. In addition, when a single thin film glass or the like is used as a dielectric to reduce the thickness in order to reduce the voltage, defects may occur due to discharge exposure, vibration, collision of flying objects, etc. on the dielectric surface. There is a problem that the insulation resistance performance of the dielectric itself tends to deteriorate due to such defects as defects, and the reliability of the DBD electrode tends to decrease.

Japanese Patent No. 6488088 JP 2018-181452 A

The problem to be solved by the present invention is to provide a dielectric barrier discharge electrode and a dielectric barrier discharge device that can be driven at a low voltage and have improved durability and reliability. .

A dielectric barrier discharge electrode of an embodiment comprises a dielectric having a first surface, a first electrode provided so as to be exposed on the first surface of the dielectric, and the first electrode through the dielectric. a second electrode arranged to face an electrode, the dielectric comprising: a first dielectric layer arranged to form at least a portion of the first surface; and the first dielectric a second dielectric layer laminated on a surface opposite to the surface constituting the first surface of the layer and made of a material different from that of the first dielectric layer, wherein the first dielectric layer is an inorganic dielectric and the second dielectric layer includes a dielectric material having at least one of a dielectric breakdown voltage and a dielectric constant higher than that of the inorganic dielectric material.

1 is a cross-sectional view showing a dielectric barrier discharge device of a first embodiment; FIG. FIG. 2 is a cross-sectional view showing a first modification of the dielectric barrier discharge device shown in FIG. 1; 5 is a graph showing the relationship between discharge energy accumulated over time and the amount of burrowing of typical materials used for the dielectric in the embodiment. FIG. 3 is a cross-sectional view showing a second modification of the dielectric barrier discharge device shown in FIG. 1; FIG. 5 is a cross-sectional view showing a dielectric barrier discharge device of a second embodiment; FIG. 6 is a cross-sectional view showing a first modification of the dielectric barrier discharge device shown in FIG. 5;

A dielectric barrier discharge electrode and a dielectric barrier discharge device according to embodiments will be described below with reference to the drawings. In addition, in each embodiment, the same code|symbol may be attached|subjected to the substantially same component part, and the description may be partially abbreviate|omitted. The drawings are schematic, and the relationship between the thickness of each part and the planar dimension, the ratio of the thickness of each part, etc. may differ from the actual one.

(First embodiment)
FIG. 1 is a sectional view showing a dielectric barrier discharge electrode (DBD electrode) and a dielectric barrier discharge device (DBD device) using the dielectric barrier discharge electrode (DBD electrode) of the first embodiment. A DBD device 1 shown in FIG. 1 comprises a DBD electrode 2 and a power source 3 for applying a voltage thereto. The DBD electrode 2 includes a plate-shaped dielectric 4 , a first electrode 5 and a second electrode 6 . A power source 3 is electrically connected to the first electrode 5 and the second electrode 6 . The power supply 3 may be electrically connected to the first electrode 5 and the second electrode 6 may be grounded (0 V), as shown in FIG. By applying a voltage from the power supply 3 to the first electrode 5 and the second electrode 6, a discharge is generated and plasma P is generated.

In the DBD electrode 2, the first electrode 5 is provided so as to be exposed on the first surface 4a of the dielectric 4, that is, so as to be exposed to the gas on the first surface 4a. It has a shape such as The second electrode 6 is arranged to face the first electrode 5 with the dielectric 4 interposed therebetween. The first electrode 5 and the second electrode 6 are insulated by the dielectric 4 . The second electrode 6 may be covered with a base material 7 made of an insulating material such as a resin material or an electrode installation base so that the surface opposite to the surface in contact with the dielectric 4 is not exposed to the gas. . The first electrode 5 exposed on the first surface 4a of the dielectric 4 functions as a discharge electrode, and the second electrode 6 arranged to face the first electrode 5 with the dielectric 4 therebetween It functions as an electrode.

When a voltage is applied between the first electrode 5 and the second electrode 6, the gas on the first surface 4a on the side of the first electrode 5 is ionized to generate barrier discharge. Plasma P is generated from the first electrode 5 along the first surface 4a of the dielectric 4 by such a barrier discharge. As the waveform of the voltage applied to the first electrode 5 and the second electrode 6, an AC waveform or a pulse waveform is used. The AC frequency can range from several Hz to several GHz. The frequency of alternating current is typically several kHz to several MHz, and it is also possible to use microwaves on the order of GHz. In addition, mains power frequency (50 or 60 Hz) can also be used. As the pulse waveform, a waveform having a rise time of several nanoseconds to several hundred microseconds can be used.

The first surface 4a of the dielectric 4 on which the first electrode 5 is arranged is exposed to the barrier discharge and plasma P described above. Therefore, in the DBD electrode 2 of the first embodiment, the dielectric 4 has a first dielectric layer 8 arranged to constitute its first surface 4a, and the first dielectric layer 8 has a first surface 4a. A laminate having at least a second dielectric layer 9 (9A) laminated on the surface opposite to the constituting surface is provided. For the first dielectric layer 8 exposed to the barrier discharge and plasma P, an inorganic dielectric material having excellent discharge resistance is used. Examples of the inorganic dielectric material constituting the first dielectric layer 8 include glass materials such as alkali-free glass and borosilicate glass, which have a low coefficient of thermal expansion and are excellent in heat resistance, chemical resistance, electrical insulation, etc.; Ceramic materials such as alumina ceramics, aluminum nitride ceramics and silicon nitride ceramics are preferred.

Here, when polyimide resin, which is an organic dielectric material widely used in typical barrier discharge electrodes, is used as the dielectric, and when borosilicate glass, which is an inorganic dielectric material, is used as the dielectric, FIG. 3 shows the results of comparative experiments on damage to dielectric surfaces exposed to discharge. FIG. 3 shows an example of the results of a comparative experiment conducted by the inventors on damage due to discharge on a dielectric surface, and shows the relationship between the discharge energy accumulated over time (accumulated discharge energy) and the amount of recess. As shown in FIG. 3, damage to the dielectric surface exposed to the discharge is much less for the inorganic dielectric material, borosilicate glass, than for the organic dielectric material, polyimide resin. Borosilicate glass is less than 1/8000 of the polyimide resin in terms of the dielectric surface recession with respect to the discharge integrated energy of the same discharge exposure, and borosilicate glass is a dielectric with excellent durability against discharge exposure. has been confirmed.

In the case of organic materials such as polyimide resin, highly reactive radicals (oxygen (O) radicals, etc.) generated by discharge break the bonds of C atoms on the surface of the organic material, and the C atoms bond with O radicals, etc. It is conceivable that CO ₂ or CO will be gasified and released from the surface of the organic matter. As a result, the surface of the organic substance in the region exposed to the discharge is dug over time, and the thickness of the dielectric itself is reduced. Ultimately, the dielectric becomes unable to withstand the voltage applied between the electrodes, leading to solid dielectric breakdown of the dielectric. On the other hand, since the surfaces of inorganic materials such as glass materials and ceramic materials described above undergo little deterioration when exposed to O radicals, etc., it is possible to suppress burrowing of the surfaces of the inorganic materials even if they are placed in a region exposed to discharge. can.

In the DBD electrode 2 of the embodiment, the first surface 4a of the dielectric 4 exposed to discharge is composed of the first dielectric layer 8 containing an inorganic dielectric material. As a result, the surface of the dielectric 4 is dented by exposure to electric discharge, the thickness thereof is reduced, the insulation resistance of the dielectric 4 itself is lowered due to the thickness reduction, and the durability of the DBD electrode 2 is improved. Decrease can be suppressed. The thickness of the first dielectric layer 8 may be such that the thickness of the dielectric 4 is in the range of 1 mm or less. When the thickness of the first dielectric layer 8 exceeds 500 μm, the overall thickness of the dielectric 4 becomes too thick, which prevents the DBD electrode 2 from being driven at a low voltage. On the other hand, if the thickness of the first dielectric layer 8 is less than 5 μm, there is a possibility that sufficient discharge resistance and durability cannot be obtained even if an inorganic dielectric material is used.

In the DBD electrode 2 of the embodiment, the second dielectric layer 9A, which is not exposed to discharge, is not required to have discharge resistance or the like because the dielectric itself is not damaged by discharge exposure. Therefore, even if the dielectric material is inferior in discharge resistance, etc., it is possible to use a dielectric material that is excellent in insulation resistance. For the second dielectric layer 9A, it is preferable to use a dielectric material that is different from the dielectric material used for the first dielectric layer 8 and has excellent insulation resistance. Thereby, a thinned structure of the dielectric 4 can be realized. The dielectric material used for the second dielectric layer 9A should have at least a dielectric breakdown voltage higher than that of the dielectric material used for the first dielectric layer 8, and preferably has a dielectric breakdown voltage of 100 kV/mm or more. .

Dielectric materials used for the second dielectric layer 9A include, for example, polyimide resin with a dielectric breakdown voltage of 400 kV/mm at a thickness of 12.5 μm and fluorine resin with a dielectric breakdown voltage of 130 kV/mm at a thickness of 100 μm. Preferably, organic dielectric materials are used. The thickness of the second dielectric layer 9A may be such that the thickness of the dielectric 4 is in the range of 1 mm or less. If the thickness of the second dielectric layer 9A exceeds 500 μm, the total thickness of the dielectric 4 becomes too thick, which prevents the DBD electrode 2 from being driven at a low voltage. On the other hand, if the thickness of the second dielectric layer 9A is less than 5 μm, it may not be possible to obtain sufficient insulation resistance.

As described above, the first surface 4a of the dielectric 4 exposed to the discharge is composed of the first dielectric layer 8 containing the inorganic dielectric material, and the portion not exposed to the discharge is composed of the organic dielectric material having excellent insulation resistance. By forming the second dielectric layer 9A including the second dielectric layer 9A, it is possible to suppress the surface erosion of the dielectric 4 due to discharge, the thickness reduction caused by the discharge, and furthermore, the deterioration of the insulation resistance performance and durability of the dielectric 4 itself. Therefore, a thin film structure of the dielectric 4 can be realized, and the DBD electrode 2 can be driven at a low voltage. It is preferable that the driving voltage of the DBD electrode 2 is, for example, 1 kV or less. Therefore, it is possible to provide the DBD electrode 2 and the DBD device 1 which are excellent in durability and reliability and can be driven at a low voltage such as 1 kV or less.

In the DBD electrode 2 shown in FIG. 1, the first dielectric layer 8 is arranged over the entire first surface 4a of the dielectric 4 exposed to discharge. It is not limited. For example, as shown in FIG. 4, the first dielectric layer 8 is the discharge formation region (plasma formation region) on the first surface 4a of the dielectric 4 among the first layers of the dielectric 4 on the first electrode 5 side. It may be arranged only in the area P). In other words, the first dielectric layer 8 may be placed only in those areas that are exposed to the discharge. Thus, the first dielectric layer 8 can be arranged to form at least part of the first surface 4 a of the dielectric 4 .

A third dielectric layer 10 is arranged in a region of the first layer of the dielectric 4 (the region where the first dielectric layer 8 in FIG. 1 is entirely arranged) except for the first dielectric layer 8. can be done. That is, the first layer of dielectric 4 can be composed of a composite material of first dielectric layer 8 and third dielectric layer 10 . At this time, the constituent material of the third dielectric layer 10 is not limited to an inorganic dielectric material, and various dielectric materials can be applied, and the material is not particularly limited. The third dielectric layer 10 may be either an inorganic dielectric material or an organic dielectric material, and the specific material is not particularly limited as long as it functions as a dielectric.

(Second embodiment)
FIG. 5 is a sectional view showing a dielectric barrier discharge electrode (DBD electrode) and a dielectric barrier discharge device (DBD device) using the dielectric barrier discharge electrode (DBD electrode) of the second embodiment. Like the DBD device 1 shown in FIG. 1, the DBD device 1 shown in FIG. 5 comprises a DBD electrode 2 and a power source 3 for applying a voltage thereto. The DBD electrode 2 includes a dielectric 4, a first electrode 5, and a second electrode 6. The first electrode 5 is arranged on the first surface 4a of the dielectric 4, similar to the DBD electrode 2 shown in FIG. A second electrode 6 is arranged so as to face the first electrode 5 with the dielectric 4 interposed therebetween. The DBD device 1 of the second embodiment shown in FIG. 5 differs from the DBD device 1 of the first embodiment in the structure of the dielectric 4 . Differences of the DBD device 1 of the second embodiment from the first embodiment will be described in detail below.

The dielectric 4 in the DBD electrode 2 shown in FIG. comprises a laminate comprising at least a second dielectric layer 9 (9B) laminated on the opposite surface. For the first dielectric layer 8 exposed to the barrier discharge and the plasma P, an inorganic dielectric material with excellent discharge resistance is used as in the first embodiment. Examples of the inorganic dielectric material constituting the first dielectric layer 8 include glass materials such as alkali-free glass and borosilicate glass, which have a low coefficient of thermal expansion and are excellent in heat resistance, chemical resistance, electrical insulation, etc.; Ceramic materials such as alumina ceramics, aluminum nitride ceramics and silicon nitride ceramics are preferred.

In the DBD electrode 2 of the second embodiment, the second dielectric layer 9B, which is not exposed to discharge, is not required to have discharge resistance or the like because the dielectric itself is not damaged by discharge exposure. Therefore, the second dielectric layer 9B is made of a dielectric material different from the dielectric material used for the first dielectric layer 8 and having a high dielectric constant. Accordingly, by applying the second dielectric layer 9B having a high dielectric constant, the DBD electrode 2 can be driven at a low voltage. The dielectric material used for the second dielectric layer 9B should have at least a dielectric constant higher than that of the dielectric material used for the first dielectric layer 8, and preferably has a dielectric constant of 3 or more.

Dielectric materials used for the second dielectric layer 9B include, for example, organic dielectric materials such as polyester resin with a relative dielectric constant of 2.8 to 8.1 and polyimide resin with a relative dielectric constant of 3 to 4; It is preferable to use an inorganic dielectric material such as soda-lime glass with a dielectric constant of 6 to 8 and barium titanate with a dielectric constant of 1200. The thickness of the second dielectric layer 9B may be such that the thickness of the dielectric 4 is in the range of 1 mm or less. If the thickness of the second dielectric layer 9B exceeds 500 μm, the overall thickness of the dielectric 4 becomes too thick, which prevents the DBD electrode 2 from being driven at a low voltage. If the thickness of the second dielectric layer 9B is less than 5 μm, sufficient dielectric properties cannot be obtained, and low voltage driving of the DBD electrode 2 may be hindered.

As described above, the first surface 4a of the dielectric 4 exposed to the discharge is composed of the first dielectric layer 8 containing an inorganic dielectric material, and the portion not exposed to the discharge is made of an organic or inorganic dielectric having an excellent relative dielectric constant. By forming the second dielectric layer 9B containing the material, it is possible to suppress the surface erosion of the dielectric 4 due to electric discharge, the thickness reduction caused by the discharge, and the deterioration of the insulation resistance and durability of the dielectric 4 itself. In addition, it is possible to drive the DBD electrode 2 at a low voltage. It is preferable that the driving voltage of the DBD electrode 2 is, for example, 1 kV or less. Therefore, it is possible to provide the DBD electrode 2 and the DBD device 1 which are excellent in durability and reliability and can be driven at a low voltage such as 1 kV or less.

In the DBD electrode 2 shown in FIG. 5, the first dielectric layer 8 is arranged over the entire first surface 4a of the dielectric 4 exposed to the discharge. It is not limited. As in the first embodiment, the first dielectric layer 8 may be arranged only in the discharge formation region (plasma formation region P) on the first surface 4a of the dielectric 4, as shown in FIG. good. In other words, the first dielectric layer 8 may be placed only in those areas that are exposed to the discharge. A third dielectric layer 10 can be arranged in a region other than the first dielectric layer 8, as in the first embodiment. The dielectric 4 is composed of a first dielectric layer 8 and a third dielectric layer 10 which are composed of a composite material having excellent resistance to discharge, and a second dielectric layer which is made of an organic or inorganic dielectric material having an excellent relative permittivity. It may be formed by a laminate of the second layer composed of the body layer 9B.

It should be noted that while several embodiments of the invention have been described, these embodiments are provided by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and equivalents thereof.

DESCRIPTION OF SYMBOLS 1... Dielectric barrier discharge apparatus, 2... Dielectric barrier discharge electrode, 3... Power supply, 4... Dielectric, 5... First electrode, 6... Second electrode, 8... First dielectric layer, 9 (9A, 9B) ) . . . second dielectric layer.

Claims (10)

a dielectric having a first surface;
a first electrode exposed on the first surface of the dielectric;
a second electrode arranged to face the first electrode with the dielectric interposed therebetween;
The dielectric is provided on a first dielectric layer arranged to constitute at least part of the first surface and on a surface of the first dielectric layer opposite to the surface constituting the first surface. A second dielectric layer laminated and made of a material different from that of the first dielectric layer,
The induced barrier discharge electrode, wherein the first dielectric layer contains an inorganic dielectric material, and the second dielectric layer contains a dielectric material having at least one of a dielectric breakdown voltage and a dielectric constant higher than that of the inorganic dielectric material. . 2. The inductive barrier discharge electrode according to claim 1, wherein said inorganic dielectric material includes at least one selected from the group consisting of non-alkali glass, borosilicate glass, alumina ceramics, aluminum nitride ceramics, and silicon nitride ceramics. 3. The induced barrier discharge electrode according to claim 1, wherein said second dielectric layer includes an organic dielectric material having a dielectric breakdown voltage higher than that of said inorganic dielectric material. 4. The inductive barrier discharge electrode according to claim 3, wherein said organic dielectric material has a dielectric breakdown voltage of 100 kV/mm or more. 5. The inductive barrier discharge electrode according to claim 3, wherein said organic dielectric material contains at least one selected from the group consisting of polyimide resin and fluororesin. 3. The induced barrier discharge electrode according to claim 1, wherein said second dielectric layer includes an organic or inorganic dielectric material having a dielectric constant greater than that of said inorganic dielectric material. 7. The inductive barrier discharge electrode of claim 6, wherein said organic or inorganic dielectric material has a dielectric constant of 3 or greater. 8. The inductive barrier discharge electrode according to claim 6, wherein said organic or inorganic dielectric material includes at least one selected from the group consisting of polyester resin, polyimide resin, soda lime glass, and barium titanate. . The first dielectric layer is arranged to be exposed to at least a discharge region formed by ionizing gas on the first surface,
9. The inductive barrier discharge electrode of any one of claims 1 to 8, wherein said second dielectric layer is arranged so as not to be exposed to said discharge region. an inductive barrier discharge electrode according to any one of claims 1 to 9;
an AC power source electrically connected to at least the first electrode of the inductive barrier discharge electrodes; and an inductive barrier discharge device comprising:

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