JP2014032897A - Microwave discharge device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microwave discharge device capable of controlling the bulk and shape of atmospheric pressure plasma.SOLUTION: The microwave discharge device includes: a dielectric substrate 2; a microstrip line 6 formed on one surface 4 of the dielectric substrate 2; and a conductor 10 formed on the other surface 8 of the dielectric substrate 2. At the end of the microstrip line 6, a stable discharge electrode 28 that generates atmospheric pressure plasma between the conductor 10 and the same using the microwave, and at a point between the stable discharge electrode 28 and the conductor 10, an ignition electrode 30 is disposed.

Description

  The present invention relates to a microwave discharge device that generates atmospheric pressure plasma.

  Patent Document 1 describes a microwave discharge device that propagates microwaves between a microstrip line and a ground electrode, and generates atmospheric pressure plasma between a terminal portion of the microstrip line and the ground electrode. ing.

  In the microwave discharge device, an electrode portion is formed at the end portion of the microstrip line, and ignition by spontaneous discharge and stable sustained discharge after the ignition are performed in a discharge space between the electrode portion and the ground electrode. .

JP 2006-107829 A

  As described above, a conventional microwave discharge device has a structure that performs spontaneous discharge and stable sustained discharge in a discharge space between a single electrode portion and a ground electrode. This discharge space is required to be a gap between adjacent conductors in order to perform ignition by spontaneous discharge with low power.

  Therefore, in the conventional microwave discharge device, when trying to suppress the power for ignition, the design freedom of the discharge space becomes very low, that is, the atmospheric pressure plasma generated in the discharge space after ignition. There is a problem that the volume and the degree of freedom of the shape are very low.

  The present invention has been invented in view of the above-described problems, and can suppress power for ignition and can obtain the volume and shape of atmospheric pressure plasma generated after ignition with a high degree of freedom. It is an object to propose a microwave discharge device.

  In order to solve the above-described problems, the microwave discharge device of the present invention has the following configuration.

  That is, the microwave discharge device of the present invention includes a dielectric substrate, a microstrip line formed on one surface side of the dielectric substrate, and a conductor formed on the other surface side of the dielectric substrate, A stable discharge electrode that generates atmospheric pressure plasma with the conductor by microwaves is provided at the end of the microstrip line, and an ignition electrode is disposed at a position sandwiched between the stable discharge electrode and the conductor. Features.

  It is preferable that the ignition electrode has a sharp tip shape toward the conductor.

  It is also preferable that the microstrip line is branched, the stable discharge electrode is provided at the end of one of the branched lines, and the ignition electrode is provided at the end of the other line.

  At this time, before the ignition of the microstrip line, the line from the branch point to the ignition electrode and the line before the branch point are in impedance-matched state, and The line from the branch point to the stable discharge electrode and the line before the branch point are in a state where impedance matching has been lost, and after ignition, the line from the branch point to the ignition electrode And the line before the branch point is in an impedance-matched state, and the line from the branch point to the stable discharge electrode and the line before the branch point are impedance matched. It is preferable to provide such a state.

  It is also preferable to dispose a protective film for protecting the ignition electrode from the atmospheric pressure plasma between the stable discharge electrode and the ignition electrode.

  It is also preferable that the ignition electrode is integrally extended from the end portion of the microstrip line.

  The present invention has an effect that electric power for ignition can be suppressed and the volume and shape of atmospheric pressure plasma generated after ignition can be obtained with a high degree of freedom.

It is a front view of the microwave discharge device of a 1st embodiment of the present invention. It is a top view of a microwave discharge device same as the above. It is the sectional view on the AA line of FIG. It is a perspective view which shows the modification of the electrode for ignition. It is a perspective view which shows the other modification of the electrode for ignition. It is a perspective view which shows the other modification of the electrode for ignition. It is a perspective view which shows the principal part of the microwave discharge device of 2nd Embodiment of this invention. It is a perspective view which shows the principal part of the microwave discharge device of 3rd Embodiment of this invention.

  The present invention will be described based on embodiments shown in the accompanying drawings.

  1 to 3 show a microwave discharge device according to a first embodiment of the present invention. 1 is a front view of the microwave discharge device of the present embodiment, FIG. 2 is a plan view, and FIG. 3 is a cross-sectional view taken along line AA of FIG.

  In the microwave discharge device of the present embodiment, a microstrip line 6 made of a conductor is formed on one surface 4 of a dielectric substrate 2 having a rectangular shape in plan view. A conductor 10 that forms a pair with the microstrip line 6 is formed on the other surface 8 facing away from the one surface 4 of the dielectric substrate 2. The microstrip line 6 has a start end connected to the microwave input terminal 12, extends straight from the start end, and branches bifurcated from a branch point P in the middle thereof. One of the second lines after the branch point P of the microstrip line 6 is a stable discharge line 14 and the other is an ignition line 16. The branched lines 14 and 16 extend in a straight line so as to be parallel to each other until reaching the edge 18 of the one surface 4 of the dielectric substrate 2.

  The conductor 10 is formed wide so as to cover the entire other surface 8 of the dielectric substrate 2. The conductor 10 is normally set to the ground potential, and will be referred to as a “ground electrode 10” below.

  The edge 18 of the dielectric substrate 2 includes an end surface 20 formed by cutting the dielectric substrate 2 in the thickness direction, a first tapered surface 22 formed at the end of the one surface 4, and the other surface 8. And a second taper surface 24 formed at an end of the first taper. The first and second tapered surfaces 22 and 24 are inclined so that the distance from each other approaches the end surface 20. For this reason, the end edge portion 18 of the dielectric substrate 2 becomes smaller in thickness as it approaches the end surface 20.

  The stable discharge line 14 of the microstrip line 6 extends in a straight line on the one surface 4 of the dielectric substrate 2 until reaching the boundary line 26 between the first tapered surface 22 and the end surface 20. A terminal portion located on the boundary line 26 of the line 14 becomes a stable discharge electrode 28.

  The ignition line 16 of the microstrip line 6 passes through the first tapered surface 22 on the one surface 4 side of the dielectric substrate 2, extends beyond the boundary line 26 to the end surface 20. The terminal portion located on the end face 20 of the line 16 becomes the ignition electrode 30.

  The ground electrode 10 is formed so as to cover the entire other surface 8 of the dielectric substrate 2 up to the boundary line 32 between the second tapered surface 24 and the end surface 20. The edge portion located on the boundary line 32 of the ground electrode 10 becomes the counter electrode 34.

  In the microwave discharge device of the present embodiment described above, the stable discharge electrode 28 and the counter electrode 34 face each other through the end face 20 at the edge 18 of the dielectric substrate 2, and the space between the electrodes 28, 34. Becomes the discharge space. The ignition electrode 30, which is an electrode different from the stable discharge electrode 28, is disposed at a location sandwiched between the stable discharge electrode 28 and the counter electrode 34.

  More specifically, the ignition electrode 30 which is the terminal portion of the branched line 16 of the microstrip line 6 is formed in an L shape on the end face 20 of the dielectric substrate 2 (see FIG. 1). The tip of the ignition electrode 30 is inserted into the discharge space between the stable discharge electrode 28 and the counter electrode 34 from the side. The distance between the ignition electrode 30 and the counter electrode 34 is set sufficiently smaller than the distance between the stable discharge electrode 28 and the counter electrode 34, and the ignition electrode 30 is sufficiently narrower than the stable discharge electrode 28. Is formed.

  As a result, the ignition electrode 30 has a structure in which molecules and electrons are excited with the adjacent counter electrode 34 to be in a plasma state, and ignition by spontaneous discharge is likely to occur. On the other hand, the stable discharge electrode 28 has a structure in which atmospheric pressure plasma is easily generated stably in a wide discharge space between the counter electrode 34 after ignition by spontaneous discharge.

  Here, the circuit impedance of the entire line as viewed from the input end is such that when microwaves are supplied to the input terminal 12, power flows into the ignition electrode 30 before ignition due to spontaneous discharge, and after ignition to the stable discharge electrode 28. When plasma is induced, the electric power is set to flow into the stable discharge electrode 28 side. The impedance is set before and after plasma generation as follows.

  That is, before the discharge, the impedance of the line before the branch point P of the microstrip line 6 is equal to the impedance of the ignition line 16 after the branch point P (that is, between the ignition line 16 and the line 16). Impedance matching state) and larger or smaller than the impedance of the stable discharge line 14 after the branch point P (that is, the impedance matching has been lost with the stable discharge line 14). The impedance of each line is set so that

  After the discharge, the impedance of the line before the branch point P of the microstrip line 6 is larger or smaller than the impedance of the ignition line 16 after the branch point P (that is, the ignition line). 16 and the impedance of the stable discharge line 14 after the branch point P (that is, the impedance between the stable discharge line 14 and the stable discharge line 14). The impedance of each line is set so as to make a transition to a matching state.

  Specifically, for example, before discharge, the impedance of the line before the branch point P of the microstrip line 6 is 50 [Ω], and the impedance of the ignition line 16 after the branch point P is 50 [Ω]. The impedance of the stable discharge line 14 after the branch point P is set to 1 [kΩ]. After the discharge, the impedance of the line before the branch point P of the microstrip line 6 becomes 50 [Ω], and the impedance of the ignition line 16 after the branch point P decreases according to (10 + jβ) [Ω]. The impedance of the stable discharge line 14 after the branch point P may be set to 50 [Ω]. Each impedance of the microstrip line 6 before and after the discharge can be designed based on high-frequency circuit simulation or plasma measurement.

  According to the microwave discharge device of the present embodiment, the stable discharge electrode 28 and the ignition electrode 30 are separately provided. First, the ignition electrode 30 close to the counter electrode 34 causes ignition by spontaneous discharge with low power, Since the role of the electrode is shared so that the stable discharge electrode 28 can stably generate the atmospheric pressure plasma after ignition, the discharge space for generating the atmospheric pressure plasma is widely provided while suppressing the power required for ignition. Therefore, a plasma having a larger volume can be obtained.

  The ignition electrode 30 may have a structure that is not branched from the microstrip line 6. That is, the ignition electrode 30 is formed on the dielectric substrate 2 as a line independent of the stable discharge line 14, and high voltage power from a DC power source is applied to the start end of the ignition electrode 30, or Ignition may be generated by applying a microwave from a wave power source. When applying high-voltage DC power, an ignition device that instantaneously applies high-voltage power by means such as storing energy in a capacitor can be used. In any case, the distance between the ignition electrode 30 and the counter electrode 34 can be set small, and the power required for ignition can be suppressed.

  In this embodiment, the ignition electrode 30 extends to the end surface 20 through the one surface 4 of the dielectric substrate 2, but it may extend to the end surface 20 through the side surface of the dielectric substrate 2.

  Moreover, the shape of the electrode 30 for ignition is not limited to what is shown in FIG. 1, For example, a shape as shown in FIGS. 4-6 may be sufficient.

  In the example of FIG. 4, when the ground electrode 10 is positioned below and the microstrip line 6 is positioned above, the tip of the ignition electrode 30 is positioned directly below the side end of the stable discharge electrode 28. The ignition electrode 30 is formed. Even in this example, ignition is reliably performed with low power by the ignition electrode 30 located between the stable discharge electrode 28 and the counter electrode 34.

  In the example of FIG. 5, the tip of the ignition electrode 30 is provided in a sharp shape with a sharp angle. In the case of this example, the electric lines of force are more likely to be concentrated at the tip of the ignition electrode 30, that is, the ignition between the ignition electrode 30 and the counter electrode 34 is reliably performed with lower power. Become.

  In the example of FIG. 6, the tip of the ignition electrode 30 in the example of FIG. 5 is further inclined toward the counter electrode 34 side. That is, the ignition electrode 30 of this example has a tip shape that is pointed toward the counter electrode 34 side. Therefore, the lines of electric force are more likely to be concentrated at the tip of the ignition electrode 30, that is, the ignition between the ignition electrode 30 and the counter electrode 34 is reliably performed at a further lower voltage. .

  Next, a microwave discharge device according to a second embodiment of the present invention will be described with reference to FIG. However, detailed description of the same configuration as that of the microwave discharge device of the first embodiment described above will be omitted, and only the specific configuration of the present embodiment will be described in detail below.

  In the microwave discharge device of the present embodiment, the protective film 40 is formed on the ignition electrode 30 disposed on the end face 20 of the dielectric substrate 2 so as to cover the tip portion of the ignition electrode 30. The protective film 40 suppresses the ignition electrode 30 from being exposed to atmospheric pressure plasma during stable discharge. By the interposition of the protective film 40, deterioration due to discharge of the ignition electrode 30 is suppressed. The protective film 40 is made of a dielectric thin film having plasma resistance, and is formed on the end face 20 using, for example, glass, alumina, sapphire, or the like.

  Next, a microwave discharge device according to a third embodiment of the present invention will be described with reference to FIG. However, detailed description of the same configuration as that of the microwave discharge device of the first embodiment described above will be omitted, and only the specific configuration of the present embodiment will be described in detail below.

  In the microwave discharge device of the present embodiment, the microstrip line 6 is not branched into the Y-shape and the ignition electrode 30 is formed at the terminal portion of one line 16 as in the first embodiment. An ignition electrode 30 is integrally extended from a part of the stable discharge electrode 28, which is a terminal portion of the line 6, toward the counter electrode 34.

  That is, in the present embodiment, the termination portion of the microstrip line 6 is located at a position facing the ground electrode 10 (that is, the counter electrode 34 formed of the end edge of the ground electrode 10) across the end surface 20 of the dielectric substrate 2. The stable discharge electrode 28 is arranged, and a part of the edge of the stable discharge electrode 28 is extended sharply toward the counter electrode 34 side on the end face 20, so that the extended portion is stably discharged. The ignition electrode 30 is different from the electrode 28. The ignition electrode 30 is located in the discharge space between the stable discharge electrode 28 and the counter electrode 34, and the distance between the ignition electrode 30 and the counter electrode 34 is larger than the distance between the stable discharge electrode 28 and the counter electrode 34. Set sufficiently small. The ignition electrode 30 is formed to be sufficiently narrower than the stable discharge electrode 28.

  Therefore, also in this embodiment, the ignition electrode 30 has a structure capable of generating spontaneous discharge with a low voltage between the counter electrode 34. On the other hand, the stable discharge electrode 28 can generate atmospheric pressure plasma in a wide discharge space between the counter electrode 34 after ignition by spontaneous discharge.

  In the microwave discharge device of the present embodiment, when a microwave is supplied to the microstrip line 6, an electric field is first concentrated on the tip of the ignition electrode 30, and ignition is performed with low power. After ignition, atmospheric pressure plasma is stably generated between the stable discharge electrode 28 and the counter electrode 34 due to the impedance change. According to this structure, the microstrip line 6 for supplying the microwave does not have to be branched and formed on the way. Therefore, the whole line is simplified and necessary power is suppressed.

  As described above, the microwave discharge device according to each embodiment of the present invention includes the dielectric substrate 2, the microstrip line 6 formed on the one surface 4 side of the dielectric substrate 2, and the other surface 8 of the dielectric substrate 2. And a conductor (ground electrode) 10 formed on the side. A stable discharge electrode 28 that generates atmospheric pressure plasma with the conductor 10 by microwaves is provided at the end of the microstrip line 6, and an ignition electrode 30 is provided at a location between the stable discharge electrode 28 and the conductor 10. Is arranged.

As described above, the stable discharge electrode 28 and the ignition electrode 30 are separately provided, and the ignition electrode 30 relatively close to the conductor 10 is first ignited, and the stable discharge relatively distant from the conductor 10 by the ignition. By providing the atmospheric pressure plasma stably by the electrode 28,
A discharge space for generating atmospheric pressure plasma can be provided widely while suppressing power for ignition. By generating a large volume of plasma in this discharge space, reaction with the atmosphere is promoted, and a large amount of active ingredients can be obtained.

  The ignition electrode 30 can have a pointed tip shape toward the conductor 10. This makes it easier for the electric field to concentrate on the tip of the ignition electrode 30 and further suppresses the power required for ignition.

  In the microwave discharge device according to the first and second embodiments, the microstrip line 6 is branched, the stable discharge electrode 28 is provided at the end of one of the branched lines 14, and the end of the other line 16 is ignited. An electrode 30 is provided. As a result, ignition can be performed by the microwaves input to the microstrip line 6, and the structure is simplified because it is not necessary to separately provide an ignition device such as an igniter.

  In addition, before the ignition of the microstrip line 6, the line 16 from the branch point P to the ignition electrode 30 and the line before the branch point P are impedance matched, and The line 14 from the branch point P to the stable discharge electrode 28 and the line before the branch point P are out of impedance matching, and after ignition, from the branch point P to the ignition electrode 30. The line 16 and the line before the branch point P are out of impedance matching, and the line 14 from the branch point P to the stable discharge electrode 28 and the line before the branch point P are The impedance matching is provided. By such impedance setting, generation of power reflection in the microstrip line 6 can be suppressed both before and after ignition.

  In the microwave discharge device of the second embodiment, a protective film 40 that protects the ignition electrode 30 from atmospheric pressure plasma is disposed between the stable discharge electrode 28 and the ignition electrode 30. Thereby, the situation where the ignition electrode 30 is damaged by atmospheric pressure plasma can be suppressed.

  In the microwave discharge device of the third embodiment, the ignition electrode 30 is integrally extended from the end portion of the microstrip line 6. Thereby, it is not necessary to branch the microstrip line 6 in the middle thereof, the entire line is simplified, and necessary power is suppressed.

  As mentioned above, although this invention was demonstrated based on embodiment shown to an accompanying drawing, this invention is not limited to embodiment of each said example. For example, the branching of the microstrip line 6 is not limited to the Y-shaped branching as in the first embodiment, but may be branched into three or more, and the terminal portions of two or more of them may be used as the ignition electrode 30. . In this case, two or more ignition electrodes 30 may be inserted from both sides toward the space between the stable discharge electrode 28 and the counter electrode 34. Of course, other configurations can be appropriately modified in each example, and the configurations of the examples can be applied in appropriate combinations within the range intended by the present invention. .

2 Dielectric substrate 4 One side 6 Microstrip line 8 Other side 10 Conductor 14 Line 16 Line 28 Stable discharge electrode 30 Ignition electrode 40 Protective film

Claims (6)

A dielectric substrate;
A microstrip line formed on one side of the dielectric substrate;
A conductor formed on the other surface side of the dielectric substrate,
Provided at the end of the microstrip line with a stable discharge electrode that generates atmospheric pressure plasma with the conductor by microwaves,
A microwave discharge device characterized in that an ignition electrode is disposed at a location sandwiched between the stable discharge electrode and the conductor. The ignition electrode is
The microwave discharge device according to claim 1, wherein the microwave discharge device has a pointed tip shape toward the conductor. 3. The microstrip line is branched, the stable discharge electrode is provided at a terminal portion of one of the branched lines, and the ignition electrode is provided at a terminal portion of the other line. The microwave discharge device described. The microstrip line,
Before ignition, the line from the branch point to the ignition electrode and the line before the branch point are impedance matched, and the branch point reaches the stable discharge electrode. The line up to and the line before the branch point are in a state out of impedance matching,
After ignition, the line from the branch point to the ignition electrode and the line before the branch point are out of impedance matching, and from the branch point to the stable discharge electrode The microwave discharge device according to claim 3, wherein the line and the line before the branch point are provided in a state in which impedance matching is achieved. The micro of any one of claims 1 to 4, wherein a protective film for protecting the ignition electrode from the atmospheric pressure plasma is disposed between the stable discharge electrode and the ignition electrode. Wave discharge device. The ignition electrode is
The microwave discharge device according to claim 1 or 2, wherein the microwave discharge device is integrally extended from a terminal portion of the microstrip line.

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