KR101751611B1

KR101751611B1 - Plasma generating device and method for controlling the device

Info

Publication number: KR101751611B1
Application number: KR1020150157212A
Authority: KR
Inventors: 정규선; 심연근; 김상유
Original assignee: 한양대학교 산학협력단
Priority date: 2015-11-10
Filing date: 2015-11-10
Publication date: 2017-06-28
Also published as: KR20170055044A

Abstract

A plasma generation control method is disclosed. A plasma generation control method includes: applying a voltage to a plasma generation film on which electrodes are formed on both surfaces of an insulation film; Measuring a Vpp value of a voltage applied to the electrode; Comparing the reference Vpp value with the measured Vpp value; And blocking the voltage application if the measured Vpp value falls within a predetermined percentage range of the reference Vpp value.

Description

TECHNICAL FIELD [0001] The present invention relates to a plasma generating apparatus and a plasma generating method.

The present invention relates to a plasma generating apparatus and a plasma generating control method, and more particularly, to a plasma generating apparatus and a plasma generating control method for generating plasma for medical use on atmospheric pressure.

Plasma has been widely used for the surface treatment of semiconductors, display devices, and various parts, and has expanded its applicability to become a fusion technology field used in biotechnology research, medical care, air cleaning, and incinerator. Particularly, the field of medicine is expanding such as tooth whitening, cancer cell death, blood coagulation speed promotion, skin whitening, wound healing, etc. In the case of a laser which has been used mainly in the past, an image due to heat damage and a wide There is a fundamental disadvantage in that it is impossible to uniformly treat the area. However, in the case of plasma, there is no heat damage, and according to the plasma generating apparatus, it is possible to uniformly and efficiently treat a large area of treatment area.

Oxygen radicals such as ultraviolet rays (UV) and ozone generated in the plasma, nitrogen oxides such as nitrogen monoxide, currents and charge carriers are caused to increase in cell immunity, sterilization, cancer cell necrosis and blood circulation .

To date, various fundamental problems have been found in various plasma generating devices developed for medical use for the above-mentioned effects.

First, a direct method of generating plasma by using the human body as a ground electrode (Floating electrode dielectric barrier discharge) has advantages of rapid charge and current for a short period of time, which is relatively low It has been reported that the rate of cell mutation is ten times higher than that of a plasma generating apparatus such as a jet applying an indirect type dielectric barrier discharge principle for generating charged particles.

In addition, if the thickness of the dielectric is large, a high voltage is required to generate the plasma. Such a high voltage causes a cost increase due to the insulation problem of the cable and the system, and causes safety problems in practical medical applications. The high density plasmas generated by the high voltage can be expected to have a rapid effect in the treatment of human body, but the damage of the DNA of the surrounding normal cells can easily occur, resulting in necrosis of unnecessary normal cells and mutations of normal cells .

The plasma generator of the surface dielectric barrier discharge type is a plasma generating device which does not transport the charged particles and the current which cause high mutual change to the human body, and has a wavelength of 320 to 400 nm, a UVB of 280 to 320 wavelength, , Nitrogen oxides, and the like, and it is advantageous in that a large area can be uniformly processed according to the sizes of the designed electrodes and dielectrics. In the plasma generator of the surface dielectric barrier discharge type, when a dielectric is used as a thin polymer containing carbon, it has an advantage that a flexible plasma generator can be produced. The carbon contained in the polymer produces carbon dioxide in the plasma. It is known that carbon dioxide has the effect of skin whitening through promotion of blood circulation and blood circulation and reduction of melanocytes in the skin. However, not all polymers are suitable as dielectric materials for flexible plasma generators. This is because fluorine (F) and chlorine (Cl) contained fluorine (F) and chlorine (Cl), which contain fluorine (PTFE) and polyvinyl chloride (PVC) , Polymers such as Teflon and polyvinyl chloride are not suitable as the dielectric of the plasma generator of the surface dielectric barrier type.

In the case of a plasma generating apparatus having a thin dielectric layer and a large area for large-area processing, the capacitance of the plasma apparatus is increased. Therefore, the frequency of the AC voltage must be varied flexibly according to the area of the designed electrode lower than 20 kHz. Should be changed.

In addition, the above-described plasma generating apparatus has a feature that plasma generation density is very high right next to the electrode on the dielectric surface, wherein the high reactive plasma causes corrosion of a polymer dielectric composed of carbon, There is a problem that the life of the device is deteriorated and contaminants of the particles constituted of the dielectric substance and the electrode constituting material may flow into the treatment surface in the event of dielectric breakdown.

The location of the dielectric breakdown and the life of the device are determined depending on the shape of the electrode. This is due to the high plasma density caused by the high electric field determined by the spatial gradient of the voltage. Therefore, Is very important.

When the applied power is increased to increase the plasma density for a high treatment effect, a high-temperature heat is generated in the plasma generator of the surface dielectric barrier method. This heat accelerates the generation of nitrogen monoxide necessary for cell immune increase and the like, It is very important to regulate the temperature of the plasma generating apparatus so as to accelerate the chemical action of the dielectric and the dielectric strength, and to have the advantages and disadvantages that cause the lifetime of the apparatus to be lowered.

Further, when the conductive layer such as copper is adhered to the dielectric body through the adhesive layer made of the adhesive, there is a risk that the conductive layer detaches from the dielectric due to a decrease in the chemical performance of the adhesive when the temperature of the plasma generating device is increased. In contrast, in the prior art in which a conductive layer is formed only by sputtering, atomic layer deposition, or ion plating on a dielectric, the height of the conductive layer (several tens of nm) is much smaller than the diameter of the filament in the generated plasma (several tens of μm) In this case, the physicochemical etching of the conductive layer and the dielectric is very accelerated by the filament, and the disadvantage is that it generates a large number of particles.

The present invention provides a plasma generator capable of preventing the occurrence of a medical accident due to the generation of plasma contaminants in a human body treatment process using plasma generation.

In addition, the present invention provides a method of forming the electrode distance and shape for uniform plasma generation, a method of forming the height of the conductive layer at the height level of the plasma, and a method of generating the low density radical by the plasma generated at a low voltage .

In addition, the present invention provides a method of increasing nitrogen monoxide production and carbon dioxide generation using a carbon-containing polymer as a dielectric.

Further, the present invention provides a method for controlling the rate of occurrence of nitrogen monoxide, ozone, and carbon dioxide by controlling the temperature of the plasma generator.

According to another aspect of the present invention, there is provided a plasma generation control method comprising: applying a voltage to a plasma generation film having electrodes formed on both surfaces of an insulation film; Measuring a Vpp value of a voltage applied to the electrode; Comparing the reference Vpp value with the measured Vpp value; And blocking the voltage application if the measured Vpp value falls within a predetermined percentage range of the reference Vpp value.

The reference Vpp value is an average value of Vpp measured at the electrode for a reference time from the start of the voltage application to the electrode, And comparing the measured Vpp value with the measured Vpp value may be performed in units of the reference time.

In addition, the step of interrupting the voltage application may interrupt the voltage application when the measured Vpp value corresponds to 99.5% to 97% of the reference Vpp value.

A plasma generator according to the present invention includes a power source; A plasma generating film on which a grounded electrode is formed on one surface of the insulating film and an electrode connected to the power source is formed on the other surface; A Vpp measurement sensor for measuring a Vpp value of a voltage applied to the electrode; And a controller for comparing the reference Vpp value with the measured Vpp value, and turning off the power when the measured Vpp value falls within a predetermined percentage range of the reference Vpp value.

The reference Vpp value is an average value of Vpp measured at the electrode for a reference time from the start of the voltage application to the electrode, The controller may compare the reference Vpp value with the measured Vpp value in units of the reference time.

Also, the controller may turn off the power when the measured Vpp value corresponds to 99.5% to 97% of the reference Vpp value.

In addition, the thickness of the insulating film is several tens of micrometers, the thickness of the electrodes is several to several tens of micrometers, and the plasma generating film may be flexible.

Another example of monitoring is to monitor the sound waves generated in the plasma. Similar to the previous Vpp monitoring, the variation of the impedance due to the dielectric etching by the plasma affects the frequency and magnitude of the sound waves generated by the plasma, so that the insulation breakdown phenomenon in the plasma generator can be predicted by monitoring the sound waves .

The electrode may be provided in a pattern of a predetermined shape, and the electrode pattern may be provided in a smooth curve in a region where the direction is switched.

The width of the electrode pattern may be 0.2 to 2 mm.

In addition, the distance between the electrode patterns of the electrode may be larger than twice the electric field area generated in the electrode pattern.

Also, the concentration of carbon dioxide produced in the plasma generating film may be greater than the concentration of carbon dioxide in the atmosphere.

Further, the dielectric of the plasma generating film is characterized in that it does not contain fluorine and chlorine, and is a polymer that necessarily contains carbon and at least two or more elements of hydrogen-oxygen-nitrogen constitute a chemical bond with carbon.

According to the present invention, by monitoring the Vpp value of the voltage applied to the electrode, the generation time of the insulation breakdown between the insulation film and the electrode is predicted, and the generation of the insulation breakdown is prevented by the power off so as to prevent the contaminants from entering the inside and the outside of the human body .

Further, according to the present invention, since plasma is uniformly generated and dielectric breakdown is prevented, the life of the plasma apparatus can be increased.

Further, according to the present invention, the use of a nitrogen-containing polymer can increase the incidence of nitrogen oxides and generate carbon dioxide, which can provide a high therapeutic effect on human skin.

1 is a view showing a plasma generator according to an embodiment of the present invention.
2 is a view showing one surface of a plasma generating film according to an embodiment of the present invention.
3 is a photograph showing a plasma generating film according to another embodiment of the present invention.
Fig. 4 is an SEM photograph showing a state in which dielectric breakdown occurs on the surface of the insulating film and the electrode.
5 is a flowchart showing a plasma generation control method according to an embodiment of the present invention.
FIG. 6 is a graph illustrating changes in the Vpp value according to an exemplary embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the technical spirit of the present invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments disclosed herein are provided so that the disclosure can be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

In this specification, when an element is referred to as being on another element, it may be directly formed on another element, or a third element may be interposed therebetween. Further, in the drawings, the thicknesses of the films and regions are exaggerated for an effective explanation of the technical content.

Also, while the terms first, second, third, etc. in the various embodiments of the present disclosure are used to describe various components, these components should not be limited by these terms. These terms have only been used to distinguish one component from another. Thus, what is referred to as a first component in any one embodiment may be referred to as a second component in another embodiment. Each embodiment described and exemplified herein also includes its complementary embodiment. Also, in this specification, 'and / or' are used to include at least one of the front and rear components.

The singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. It is also to be understood that the terms such as " comprises "or" having "are intended to specify the presence of stated features, integers, Should not be understood to exclude the presence or addition of one or more other elements, elements, or combinations thereof. Also, in this specification, the term "connection " is used to include both indirectly connecting and directly connecting a plurality of components.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

1 is a view showing a plasma generator according to an embodiment of the present invention.

Referring to Figure 1, the plasma generator 100 generates a plasma at atmospheric pressure. The generated plasma can be used for medical purposes. Plasma can be used to treat skin such as skin and bacteria, remove bacteria and bacteria in organs such as stomach, esophagus, mouth, and large intestine, and promote skin regeneration.

The plasma generating apparatus 100 includes a plasma generating film 110, a power source 120, a transformer 130, a Vpp measuring sensor 140, and a controller 150.

The plasma generating film 110 generates a plasma. The plasma generating film 110 is provided in a structure in which electrodes 112 and 113 are formed on both sides of the insulating film 111, and generates a plasma. The insulating film 111 has a thickness of several tens of micrometers (um). According to the embodiment, the insulating film 111 may have a thickness of 12 to 38 mu m. The insulating film 111 is provided as a polymer-based film. The insulating film 111 may be made of a material such as polyimide (PI), polyethylene terephthalate (PET), polyethersulfone, polycarbonate, or the like. According to the embodiment, the insulating film 111 is made of polyimide material. The polyimide has a higher adhesive force and a higher glass transition temperature than other polymer materials and is most suitable as a dielectric of the plasma generating film 110. [ In addition, since polyimide does not contain a halogen element, it is most suitable for medical use because no harmful substances are generated.

Electrodes 112 and 113 are formed on both sides of the insulating film 111, respectively. The electrodes 112 and 113 are made of a conductive material. According to the embodiment, the electrodes 112 and 113 may be provided with copper. The electrodes 112 and 113 may be formed by sequentially performing a sputtering, a plating process, and an etching process. Electroless plating or electroless plating may be used for the plating process, and a dry or wet etching process may be used for the etching process. The manufacturing process of the electrodes 112 and 113 minimizes the variation of the capacitance of the plasma generating device by forming the very tight roughness between the insulating film 111 and the electrodes 112 and 113, The reliability of the device control technology can be provided.

Any one of the electrodes 112 and 113 may be provided in a pattern of various shapes. In addition, the interval between the patterns of the electrodes 112 can be variously adjusted.

2 is a view showing one surface of a plasma generating film according to an embodiment of the present invention.

Referring to Figure 2, the electrode 112 has a pattern comprised of a combination of generally straight lines and smooth curves. According to the embodiment, the electrode 112 pattern is provided in C shape. Alternatively, the electrode pattern may be provided in S or O shape. When the providing direction of the electrode 112 pattern is suddenly changed, for example, when there is a corner portion bent at a right angle, electric field formation is concentrated at the corner portion, and a relatively high density plasma is formed. The dielectric 111 and the electrode 112 can be etched by the high density plasma. Due to such a problem, the electrode 112 pattern of the present invention has a smooth curve in the region where the direction is switched.

In addition, the end portions 112c and 112d of the electrode 112 pattern are provided as curved surfaces. According to the embodiment, the end portions 112c and 112d of the electrode 112 pattern may be provided in a semicircle. When the end portions 112c and 112d of the electrode 112 pattern are provided in an angular shape, for example, a rectangular shape, electric field formation is concentrated in the corner portion, and a relatively high density plasma is formed. The dielectric 111 and the electrode 112 can be etched by the plasma of high density. Due to this problem, the end portions 112c and 112d of the electrode 112 pattern of the present invention are provided with curved surfaces.

In addition, the electrode 112 may have a width (w) of 0.2 to 2.0 mm. When the width w of the electrode 112 is 0.2 mm or less, the electrode 112 can be easily detached due to etching occurring at the boundary between the dielectric 111 and the electrode 112 during plasma generation.

The distance d between the pattern 112a and the pattern 112b of the electrode 112 is determined according to the type and thickness of the dielectric 111 and the magnitude of the applied voltage. According to the embodiment, the distance d between the pattern 112a and the pattern 112b of the electrode 112 is required to be at least twice as large as the electric field generated in the pattern 112a and 112b. The electric field region generated in the patterns 112a, 112b can be obtained through plasma generation experiments. When the distance between the patterns 112a and 112b is narrower than that, the electric field generated in one pattern 112a overlaps with the electric field generated in the other pattern 112b, and the electric field can be canceled. This results in a low density plasma due to the low Townsend coefficient due to the low electric field. Therefore, the distance between the patterns 112a and 112b should be at least twice as large as the electric field generated in the patterns 112a and 112b, and the plasma may be generated with a uniform intensity.

In addition, the electrodes 112 and 113 may have a thickness of several to several tens of micrometers. The electrodes 112 and 113 may have a thickness smaller than that of the insulating film 111. According to the embodiment, the electrodes 112 and 113 may have a thickness of 2 to 10 mu m. The plasma generating film 110 is provided in a flexible manner by the material and thickness of the insulating film 111 and the electrodes 112 and 113 described above.

3 is a photograph showing a plasma generating film according to another embodiment of the present invention. As shown in Fig. 3, the electrode pattern formed on the plasma generating film can be variously changed.

Referring again to FIG. 1, the electrode 112 formed on one side of the insulating film 111 is grounded, and the electrode 113 formed on the other side is connected to the power source 120. When the plasma generating apparatus 100 is used in the inside or outside of the human body, the ground electrode 112 secures stability from electrical shock caused by a contact accident. The plasma generating film 110 is characterized in that the charged particles and the current do not touch the surface of the object to be treated with the insulating film 111 interposed between the electrodes 112 and 113 and the low density radicals , The incidence of DNA mutations may be relatively low.

The power source 120 applies a voltage to the electrodes 112 and 113. The voltage is 220V and can have a frequency of 1 to 300kHz.

A transformer 130 may be provided between the power source 120 and the electrode 113. The transformer 130 can boost the voltage to a high voltage and convert the frequency to several tens to several tens of kHz. According to the embodiment, the transformer 130 can convert a voltage from 0 to 15 KV and a frequency from several hundred Hz to several tens of kHz.

The Vpp measurement sensor 140 measures the Vpp value of the voltage applied to the electrode 113. [ The Vpp value is the peak-to-peak voltage, which is the maximum difference of the voltage amplitude. The Vpp measurement sensor 140 is directly connected to the electrodes 112 and 113 to measure the Vpp value.

The controller 150 compares the measured Vpp value measured by the Vpp measurement sensor 140 with the reference Vpp value and turns off the power supply 120 when the measured Vpp value falls within a predetermined percentage range of the reference Vpp value .

Here, the reference Vpp value is an average value of the Vpp values measured at the electrode 113 for the reference time from the start of the voltage application from the power source 120. [ The measured Vpp value is an average value of the Vpp values measured at the electrode 113 in units of the reference time after the voltage application exceeds the reference time.

According to the embodiment, the controller 150 sets the reference time to 5 seconds, obtains the Vpp average value measured for the first 5 seconds as the reference Vpp value, and measures the Vpp average value measured in 5 seconds after 5 seconds as the measured Vpp value .

The controller 150 cuts off the power supply 120 when the measured Vpp value falls within a predetermined percentage range of the reference Vpp value. The predetermined percentage range is a critical range of the Vpp value at which generation of strong dielectric breakdown in the insulating film 111 and the electrodes 112 and 113 starts in the process of plasma generation. When the plasma is generated beyond this range, dielectric breakdown occurs in the insulating film 111 and the electrodes 112 and 113 as shown in FIG. 4, and contaminants generated from the dielectric breakdown are introduced into the inside and outside of the human body, .

According to an embodiment, the predetermined percentage range may be from 99.5% to 97%. The controller 150 may cut off the power supply 120 when the measured Vpp value corresponds to 99.5% to 97% of the reference Vpp value.

The interruption of the power source 120 interrupts the plasma generation and prevents the occurrence of dielectric breakdown. This can prevent the occurrence of medical accidents due to the generation of pollutants.

5 is a flowchart showing a plasma generation control method according to an embodiment of the present invention.

Referring to FIG. 5, the plasma generation control method includes the steps of applying a voltage to the plasma generating film 110 (S10), measuring a Vpp value of a voltage applied to the electrode 112 (S20) (Step S30) comparing the measured Vpp values, and interrupting the voltage application when the measured Vpp value falls within a predetermined percentage range of the reference Vpp value (steps S40 and S50).

The step of cutting off the voltage application (S50) is performed when the measured Vpp value falls within a predetermined percentage range of the reference Vpp value. According to the embodiment, step S50 of interrupting the voltage application cuts off the voltage application when the measured Vpp value corresponds to 99.5% to 97% of the reference Vpp value.

FIG. 6 is a graph illustrating changes in the Vpp value according to an exemplary embodiment of the present invention.

Referring to FIG. 6, the reference time is set to 30 seconds, and the average Vpp value is calculated in units of 30 seconds and displayed on the graph. The Vpp value displayed in the first 30 seconds was set as the reference Vpp value, and in the experiment, it was 3.40 kV. When the percentage range was set to 97%, the power supply was cut off at 6 minutes in which 3.30 kV corresponding to 97% of the reference Vpp value appeared as the Vpp value.

Table 1 below shows the characteristics of the plasma generating film and the plasma generating process according to an embodiment of the present invention.

Insulation film thickness 25.4 ~ 50 um Relative dielectric constant of insulating film 2.2 to 3.2 Electrode thickness 2 to 12 μm Operating frequency 1 to 10 kHz Electrode-applied voltage 0.6 to 2.5 kV Vpp band 1.2 to 5.0 kVpp Plasma temperature Plasma generator: 20-100 ° C
Surface temperature: 20 ~ 45 ℃ Film manufacturing method After the plasma treatment of the surface of the insulating film, the adhesive layer and the conductive layer were deposited by sputtering, and then the thickness of the conductive layer was increased by electrolytic plating Electrode gap shape and electrode design method - The distance between the electrodes is at least twice the range of plasma generation
- Semicircle of edge of electrode.
- The shape of the electrode should be C, S, O type.
- The electrode width is 0.2 to 2.0 mm

The characteristics of Table 1 have the following advantages.

(1) Since the insulation film and the electrode thickness are micro-sized and thin, a flexible plasma generating film can be realized.

(2) Since it is possible to reduce the operating frequency flexibly, the electrode impedance can be increased and the electrode design capable of large-area processing is possible.

(3) Since the thickness of the insulating film is very thin, it is possible to generate plasma at a low applied voltage.

(4) Since the thickness of the plasma-generating film is low, the plasma generation density is low, and the radicals generated in the plasma are diffused into the human body by natural diffusion and a temperature reduction effect is caused by the diffusion with molecules in the air during the diffusion process That is, the skin temperature is low. This prevents DNA damage by unnecessarily high density radicals while preventing the skin from burning due to heat generation in the plasma generating film.

(5) According to the film production method described above, since the surface roughness of the insulating film is small and the interface between the insulating film and the conductive layer is uniform, high reliability can be secured in the power cutoff function through the Vpp monitor.

(6) The shape of the above-described electrode pattern generates a uniform plasma density on the surface of the electrode, and a uniform treatment effect on the surface to be treated and an increase in the life of the plasma generating apparatus can be expected.

(7) The concentration of carbon dioxide produced in the above-mentioned plasma generating film is larger than the concentration of carbon dioxide in the atmosphere. The resulting carbon dioxide promotes skin fat breakdown, increased blood circulation, and decreased melanocytes.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the scope of the present invention is not limited to the disclosed exemplary embodiments. It will also be appreciated that many modifications and variations will be apparent to those skilled in the art without departing from the scope of the invention.

100: Plasma generator
110: Plasma generating film
111: insulating film
112, 113: electrode
120: Power supply
130: Trance
140: Vpp measuring sensor
150: controller

Claims

Applying a voltage to a plasma generating film on which electrodes are formed on both sides of an insulating film, respectively;
Measuring a Vpp value of a voltage applied to the electrode;
Comparing the reference Vpp value with the measured Vpp value; And
And blocking the voltage application if the measured Vpp value falls within a predetermined percentage range of the reference Vpp value,
Wherein the reference Vpp value is an average value of Vpp values measured at the electrode for a reference time from the start of applying the voltage to the electrode,
Wherein the measured Vpp value is an average value of Vpp values measured at the electrode in the reference time unit after the elapse of the reference time,
Wherein the step of comparing the reference Vpp value with the measured Vpp value is performed in units of the reference time.

delete

The method according to claim 1,
Wherein the step of interrupting the voltage application cuts off the application of the voltage when the measured Vpp value corresponds to 99.5% to 97% of the reference Vpp value.

power;
A plasma generating film on which a grounded electrode is formed on one surface of the insulating film and an electrode connected to the power source is formed on the other surface;
A Vpp measuring sensor for measuring a Vpp value of a voltage applied to an electrode connected to the power source; And
And a controller for comparing the reference Vpp value with the measured Vpp value and turning off the power supply when the measured Vpp value falls within a predetermined percentage range of the reference Vpp value,
The reference Vpp value is an average value of Vpp measured at an electrode connected to the power source for a reference time from the start of the voltage application to the electrode connected to the power source,
Wherein the measured Vpp value is an average value of Vpp values measured at electrodes connected to the power source in units of the reference time after the elapse of the reference time,
Wherein the controller compares the reference Vpp value with the measured Vpp value in units of the reference time.

delete

5. The method of claim 4,
Wherein the controller turns off the power when the measured Vpp value corresponds to 99.5% to 97% of the reference Vpp value.

The method according to claim 4 or 6,
The thickness of the insulating film is several tens of micrometers,
The thickness of the grounded electrode and the electrode connected to the power source is several to several tens of micrometers,
Wherein the plasma generating film is a flexible plasma generating device.

The method according to claim 4 or 6,
The grounded electrode is provided in a pattern of a predetermined shape,
Wherein the electrode pattern is provided in a smooth curve in a region where the direction is switched.

9. The method of claim 8,
And the width of the pattern of the grounded electrode is 0.2 to 2 mm.

delete

The method according to claim 4 or 6,
Wherein the concentration of carbon dioxide produced in the plasma generating film is greater than the concentration of carbon dioxide in the atmosphere.