JP7224036B2 - Electrodes for plasma generation - Google Patents

Description

TECHNICAL FIELD The present invention relates to a plasma generation electrode used for sterilization of objects to be processed.

Conventionally, a plasma electrode is known in which a first electrode and a second electrode are provided on both sides of a dielectric and a high-frequency voltage is applied between the electrodes to generate plasma. Plasma is generated by discharging along the body surface to the electrode on the opposite side.
The following patent documents disclose such plasma generation electrodes.
In Patent Document 1, a common electrode (common circuit portion) and comb-like electrodes (branch circuit portion) branched from the common circuit portion are formed on a dielectric (insulating substrate). It is described that a high frequency voltage is applied between the substrates to cause creeping discharge, thereby generating plasma along the substrate from the first electrode.
Here, creeping discharge means that a discharge path is formed along the surface of the insulator (dielectric) when an insulator (dielectric) exists between the discharge gaps in the gas.

JP 2013-258137 A

However, the plasma generation electrode described in Patent Document 1 is likely to cause dielectric breakdown when a high-frequency voltage is applied to both surfaces of the dielectric.
That is, in the common circuit portion where the comb teeth of the first electrode are bundled, the current is larger than in the comb teeth, and the amount of discharge from the common circuit portion is large, and there is a high possibility that the insulation of the dielectric will be destroyed.
The present invention prevents plasma generation in a common circuit portion where a high current flows in a plasma electrode, and generates plasma only in a comb-teeth-shaped branch circuit portion where a uniform current flows, thereby uniformizing plasma generation, An object of the present invention is to provide an electrode that prevents dielectric breakdown from occurring in a dielectric and improves tracking resistance.

In the present invention, in order to prevent discharge from the common circuit portion and to generate plasma only in the comb tooth-shaped branch circuit portion, the configuration avoids forming the second electrode under the common circuit portion. bottom.
That is, the plasma generating electrode of the present invention is an electrode for generating plasma,
A substrate having insulating properties, a first electrode provided on one surface of the substrate, and a second electrode provided on the other surface of the substrate so as to face the first electrode,
the first electrode has a common circuit and a branch circuit vertically depending from the common circuit;
The second electrode has an upper end that is solidly formed from a position that is moved in the direction of the branch circuit from a position facing the lower end of the common circuit of the first electrode,
In the longitudinal sectional view (BB sectional view), a displacement distance D is formed between the lower end 12c of the common circuit of the first electrode and the upper end 13b of the second electrode,
A through hole is formed between the branch circuits in the first electrode so as to penetrate the front and back of the substrate.

When the solid second electrode is formed directly under the first electrode, the plasma discharge tends to occur preferentially in the portion where the current of the first electrode is large (common circuit portion), and the thin comb-like portion of the circuit tends to occur. Plasma discharge was difficult to occur in the branch circuit portion.
In the plasma generation electrode of the present invention, since the second electrode is not formed directly under the common circuit portion through which a high current flows, the plasma generation in the common circuit portion is suppressed, and the comb tooth-like branches through which a uniform current flows are formed. Plasma generation was made uniform by generating plasma only in the circuit portion.
With such a structure, dielectric breakdown can be prevented from occurring in the dielectric, and tracking resistance can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic which shows the structure of the electrode for plasma generation which concerns on embodiment of this invention, (a) is a top view, (b) is AA sectional drawing of (a), (c) is BB sectional drawing of (a). (Longitudinal sectional view). (a) shows CC sectional view of FIG. 1 and is a vertical cross-sectional shape of the branch circuit of a 1st electrode, (b) is a partially enlarged view of (a). (a) is a schematic plan view showing a state in which a through hole 15 is formed in an electrode, and (b) is a DD cross-sectional view shown in (a). FIG. 4 is an explanatory diagram showing a state in which the plasma generation electrode according to the embodiment is connected to a power supply unit and used;

<Overview of Plasma Generation Electrode 10>
FIG. 1 shows a plasma generation electrode according to an embodiment of the present invention.
As shown in FIG. 1, the plasma generation electrode 10 of the embodiment is an electrode for generating plasma.
A first electrode 12 is formed on one surface (front surface) of an insulating substrate 11, and a second electrode 13 is provided on the other surface (back surface) of the substrate 11 so as to face the first electrode. ing.
The first electrode has a common circuit 12a and three branch circuits 12b vertically branched from the common circuit 12a.
The second electrode 13 has an upper end 13b formed in a solid (flat) shape from a position shifted from the lower end 12c of the common circuit 12a of the first electrode 12 toward the branch circuit 12b.
As a result, as shown in the BB cross-sectional view (longitudinal cross-sectional view) of FIG. It is
Here, the lower end 12c of the common circuit 12a of the first electrode 12 means the end of the common circuit 12a formed on the substrate 11 in the width direction (the right direction in FIG. 1(a)). The upper end 13b of the electrode 13 refers to the end of the second electrode 13 formed on the back surface of the substrate 11 in the direction of the second electrode connection terminal 13a (leftward in FIG. 1A).

<Substrate>
In the plasma generation electrode 10 of the embodiment, an insulator such as a dielectric is used as the substrate 11 on which the first electrode 12 and the second electrode 13 are formed on the front and back sides.
As the insulator, ceramics (including glass), paper, fiber cloth, resin, and mixtures (mixtures) of these materials are preferably used.
Examples of resins include resin films such as PET, PEN, polyester, nylon, Teflon (registered trademark), polyethylene, and polystyrene.
As a mixture, a glass epoxy substrate, a paper phenol substrate, a paper epoxy substrate, a glass composite substrate, a glass polyimide substrate, and the like are also used.
Among them, the glass epoxy substrate is widely used as a substrate, which is made of a material in which an epoxy resin is impregnated into a glass woven cloth made of glass fibers.
The thickness of the substrate is not specified, but since the thickness affects the insulation properties, it must be thick enough to withstand dielectric breakdown during plasma generation, and is appropriately determined depending on the application.
When glass epoxy resin is selected, a thickness of 0.2 mm or more is suitable.
For example, if a voltage of 2 kv or more is applied, dielectric breakdown is likely to occur if the thickness is 0.2 mm or less.
Among them, the one having a thickness of 0.4 mm can be applied to various uses and can be preferably used.
Also, the size and shape of the substrate 11 are not specified, but various sizes from a postage stamp size to 10 cm square can be mentioned, and can be appropriately determined depending on the application.

<Shape of first electrode>
The first electrode 12 formed on one surface (front surface) of the substrate 11 has a common circuit 12a and a comb-like branch circuit 12b vertically extending from the common circuit 12a.
The common circuit 12a has a first electrode connection terminal 12d for connection with an external power supply.
Although the shape of such a comb-teeth branch circuit 12b is not particularly defined, for example, the following may be mentioned.
The gap between the branch circuits 12b is preferably 2 to 10 mm or more.
If this gap is narrow, discharge is likely to occur between the branch circuits 12b.
The width of the branch circuit 12b is preferably 1 mm or more, usually 1 mm to 5 mm.
If this width is narrow, the amount of current cannot be secured, making it difficult to generate uniform plasma.
The length of the branch circuit 12b (leg length) is preferably 5 mm or more, usually 5 mm to 50 mm.
If this length is short, the efficiency of plasma generation will be poor.
The height h (thickness) of the branch circuit 12b is preferably 10 to 50 μm, preferably 15 to 30 μm.
If this thickness is too small, the amount of current cannot be ensured, and the efficiency of plasma generation deteriorates.
The higher the height h of the branch circuit 12b, the longer the life of the electrode, which is preferable.
Although the number of branch circuits 12b is not particularly specified, it is usually preferable to set the number to 2 to 20 in relation to the external power supply device.
The cross section of the branch circuit 12b in the width direction preferably has a trapezoidal shape such that the dimension on the outer surface side<the dimension on the substrate contact side. This is because the branch circuit 12b can be stably formed.
(See Figure 2)

<Shape of second electrode>
A second electrode 13 is formed on the other surface (rear surface) of the substrate 11 so as to face the first electrode 12 .
The shape of the second electrode 13 is not comb-shaped like the first electrode 12, but is solid (flat), and has a second electrode connection terminal 13a to be connected to an external power supply device. .

<Positional relationship between the first electrode and the second electrode>
As for the positional relationship between the first electrode 12 and the second electrode 13, the second electrode 13 is formed so as to cover the branch circuit 12b of the first electrode 12, as shown in the plan view of FIG. 1(a).
That is, the width Y of the second electrode 13 is made larger than the width X of the first electrode 12 .
However, as shown in (a) AA sectional view (longitudinal sectional view) and (b) BB sectional view (longitudinal sectional view) of FIG. 12c and the upper end 13b of the second electrode 13a are provided so that a displacement distance D is formed.
The second electrode 13 is formed so that the upper end 13b of the first electrode 12 extends solidly from a position facing the lower end 12c of the common circuit 12a toward the branch circuit 12b.
The second electrode 13 is provided so as to form a shift distance D from a portion of the first electrode 12 facing the common circuit 12a toward the branch circuit 12b.
That is, the second electrode 13 is not provided on the rear surface side of the first electrode 12 facing the common circuit 12a, and discharge from the common circuit 12a during plasma generation is prevented as much as possible, resulting in a comb-shaped branch circuit. Plasma generation by discharge between the portion 12b and the solid second electrode 13 is promoted.
As a result, the generation of plasma in the common circuit 12a portion of the first electrode 12 can be suppressed, the oxidation of the electrode of the common circuit 12a can be suppressed, and the life of the plasma electrode can be extended as a whole.
Here, the amount of the deviation distance D is more than 0 and 5 mm or less, preferably 2 to 3 mm, considering the balance between plasma generation and electrode life.
If the deviation distance D is set to 0 mm or less (there is an overlapping portion in plan view), plasma is preferentially generated in the common circuit 12a.
For this reason, a large current flows through the common circuit 12a, and the copper foil of the common circuit 12a is oxidized and deteriorated by continuous use for a long period of time, leading to a shortened life of the electrodes.
On the other hand, if the deviation distance D exceeds 5 mm, the length of the branch circuit 12b is shortened and the plasma generation area is reduced, which is not preferable.
In this way, by setting the shift distance D for the formation of the second electrode 13 on the back surface facing the common circuit 12a, it is possible to improve the life of the electrodes as a whole.

<Material>
Materials for the first electrode and the second electrode are not particularly limited, and any material having a predetermined conductivity can be used.
Examples include copper, aluminum, carbon, silver, iron, tungsten, molybdenum, manganese, titanium, chromium, zirconium, nickel, gold, silver, platinum, palladium, or alloys thereof. Conductive polymers, carbon nanotubes, and the like can also be used depending on the application. Furthermore, transparent electrodes such as ITO and IZO can also be applied.
The surface of the electrode is preferably flash-plated with gold or the like.
As a result, it is possible to prevent oxidation deterioration of the electrodes during plasma generation.

<Formation of Front Protective Layer and Back Protective Layer>
The first electrode and the second electrode are desirably covered with a front protective layer and a back protective layer, respectively, made of a dielectric.
Examples of the dielectric include inorganic materials such as ceramics and glass.
Ceramics include silica, alumina, zirconia, magnesia, silicon oxide, mullite, spinel, cordierite, aluminum nitride, silicon nitride, titanium-barium oxide, barium-titanium-zinc oxide.
The surface protective layer and the back protective layer can be provided by coating the substrate on which the second electrode and the first electrode are formed by making a paste of these dielectric powders. Electrodes can be protected.
In addition, since the plasma generation electrode of the present embodiment applies a high voltage to the electrode as described later, not only the above inorganic materials but also epoxy, acrylic, polyamine, acrylic silicon, urethane, and Teflon (registered trademark) can be used. Organic materials such as lacquer clear can also be applied as the surface protective layer and the back protective layer if a film thickness of 10 μm or more can be obtained.
As described above, by protecting the first electrode and the second electrode, it is possible to generate plasma even in a humid atmosphere, and it is possible to obtain an electrode for plasma generation with excellent moisture resistance and weather resistance. .
From the viewpoint of plasma generation, the front protective layer and back protective layer preferably have a thickness of about 5 to 100 μm.
Although it is possible to make the thickness larger than that, it is not preferable because the applied voltage may be increased and tracking may easily occur.
In addition to the protective layer, the first electrode and the second electrode may be flash-plated with a precious metal such as gold to prevent deterioration of the electrodes due to oxidation during discharge.

<Embodiment 2>
The plasma generation electrode of the second embodiment is different in that the substrate 11 has a through hole 15, but other parts are the same as those of the first embodiment.
That is, in the plasma generation electrode 10 of Embodiment 2, the through hole 15 is formed between the branch circuits 12b in the first electrode 12 so as to penetrate the front and back of the substrate 11. Characterized by
Thereby, plasma is generated around the through hole 15, and the plasma generation area can be increased.
That is, the object to be processed can be activated by passing the plasmatized gas through the through holes 15 of the substrate and blowing gas such as air toward the object to be processed.
For example, the object to be processed can be activated by irradiating the object to be processed with the plasma gas that has passed through the through holes 15 of the electrode.
Examples of the object to be treated include fins of an air conditioner.

The through holes 15 may be arranged on the base of the substrate 11 (the area where the branch electrodes 12b are not formed) between the branch electrodes 12b as shown in FIG. , may be formed on the branch electrode 12b.
It is appropriately determined according to the specifications of the object to be processed.
Although the size of the through hole 15 is not particularly specified, a diameter of 1 to 5 mm is preferable from the viewpoint of gas permeability.

<Power supply unit for plasma generation>
The plasma generating electrode 10 of the present invention is used by being connected to a power supply unit as shown in FIG.
The voltage applied to the plasma generation electrode 10 is preferably in the range of about 200 V to 2.0 kV in order to ensure the insulating properties of the substrate 11 .
If the applied voltage is less than 200 V, it may be difficult to generate plasma on the electrode surface.

<Method for producing first electrode and second electrode>
Next, a method for manufacturing the plasma electrode of the embodiment will be described.
<Etching method>
Various methods can be used to form the first electrode and the second electrode on the substrate. can be formed.

<Coating (printing) method>
A circuit can also be formed by applying (printing) a paste onto a substrate.
As the coating method in this case, any coating method such as screen printing, calendar roll printing, dip method, vapor deposition, and physical vapor deposition method can be used.
When electrodes are formed by a coating method, powders of the various metals or alloys described above are mixed with an organic binder and a solvent (terpineol, etc.) to prepare a conductive paste, which is then coated on a substrate. dry.

<Target of plasma treatment>
The object to be treated (target) for plasma treatment using the plasma generating electrode of the present invention is not particularly limited as long as it can be plasma treated, and examples thereof include the following.
(i) Treatment process Surface modification of the object to be treated (hydrophilic treatment: Hydrophilic treatment of the surface of the object to be treated before applying adhesive or paint to the object to improve wettability, adhesion of coloring agent or paint sterilization or sterilization treatment, organic matter removal/organic matter decomposition treatment, gas modification treatment, purification treatment of harmful gas components, and the like.
(ii) Items to be processed Resin products (polyethylene, polypropylene, polystyrene, polyimide, tetrafluoroethylene, etc.), ceramics, metals, glass, semiconductor wafers, liquid crystal glass substrates, etc. Medical instruments and medical materials (blister packs, sheets for blister packs , syringes, gaskets for syringes, rubber stoppers for vials, injection needles, gauze, non-woven fabric, etc.),
Food packaging sheets, air conditioner filters, etc.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<Example 1>
EXAMPLE 1 A plasma generation electrode according to Example 1 of the present invention will be described with reference to FIG.
(a) is a plan view of the plasma generating electrode, (b) is a cross-sectional view along AA in FIG. 1, and (c) is a cross-sectional view along BB in FIG.
In the plasma generating electrode 10 of Example 1, the substrate 11 is made of rectangular glass epoxy resin with a thickness of 0.5 mm.
A copper foil having a thickness of 0.2 mm was used for forming the first electrode and the second electrode.
On the surface of the substrate 11, three comb-teeth branch circuits 12b of the first electrode 12 were formed by an etching method.
Further, a solid second electrode 13 was formed on the back surface of the substrate 11 .
Furthermore, the entire front and back surfaces of the substrate were covered with a protective layer 14 of glass (see FIG. 2).
In addition, the second electrode 13 is not formed in a portion of the first electrode 12 facing the common circuit 12a in plan view.
A shift distance D (+0.5 mm, + is indicated when there is a gap in a plan view) is provided in the extension direction of the comb teeth (the tip direction of the comb teeth).
Other specifications of the plasma generation electrode of Example 1 are as follows.
(in the direction shown in Figure 1)
Board size: 14mm long x 25mm wide
Branch circuit leg length: 15mm
Branch circuit width: 1.25 mm
Spacing between branch circuits: 2mm
Width X of the first electrode: 8 mm
Width Y of second electrode: 12 mm
As an evaluation method of the plasma generation electrode, the time until the copper foil formed as the branch circuit of the first electrode 12 was oxidized and plasma generation became difficult was measured.
The plasma generating electrode of Example 1 could be used for 18 months or more as a result of continuous 24-hour operation.

<Example 2>
An electrode was formed in the same manner as in Example 1, except that the displacement distance D was +2 mm.
The plasma generating electrode of Example 2 could be used for 18 months or more as a result of continuous 24-hour operation.

<Example 3>
An electrode was formed in the same manner as in Example 1, except that the displacement distance D was +5 mm.
The plasma generating electrode of Example 3 could be used for 18 months or more as a result of continuous 24-hour operation.

<Comparative Example 1>
An electrode was formed in the same manner as in Example 1, except that the displacement distance D was set to 0 mm.
The plasma generating electrode of Comparative Example 1 could be used for 6 months as a result of continuous 24-hour operation.

<Comparative Example 2>
An electrode was formed in the same manner as in Example 1, except that the displacement distance D was -5 mm (when the upper end 13b of the second electrode overlaps the common circuit 12a by 5 mm in plan view).
The plasma generating electrode of Comparative Example 2 could be used for 3 months as a result of continuous 24-hour operation.

The plasma-generating electrode of the present invention can be used for activation treatment of resin products such as polyethylene, polypropylene, polystyrene, polyimide, tetrafluoroethylene, ceramics, metals, glass, semiconductor wafers, liquid crystal glass substrates, etc., medical instruments and medical materials, etc. It can be used for sterilization, packaging sheets for foodstuffs, sterilization of air conditioner filters, and the like.

10 plasma generation electrode 11 substrate 12 first electrode 12a common circuit 12b branch circuit 12c lower end 12d of common circuit first electrode connection terminal 13 second electrode 13a second electrode connection terminal 13b second electrode upper end 14 protective layer 15 through hole D deviation distance

Claims (1)

An electrode for generating a plasma,
a substrate having insulating properties;
a first electrode provided on one surface of the substrate;
a second electrode provided on the other surface of the substrate so as to face the first electrode;
The first electrode is
having a common circuit and branch circuits depending vertically from the common circuit;
The upper end of the second electrode is
The first electrode is solidly formed from a position moved toward the branch circuit direction from a position facing the lower end of the common circuit,
In longitudinal section,
A shift distance D is formed between the lower end of the common circuit of the first electrode and the upper end of the second electrode,
In the first electrode, between the branch circuits,
A plasma generating electrode , wherein a through hole is formed so as to penetrate the front and back of the substrate .

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