WO2018185837A1

WO2018185837A1 - Plasma-generating device

Info

Publication number: WO2018185837A1
Application number: PCT/JP2017/014092
Authority: WO
Inventors: 神藤　高広
Original assignee: 株式会社Ｆｕｊｉ
Priority date: 2017-04-04
Filing date: 2017-04-04
Publication date: 2018-10-11
Also published as: JPWO2018185837A1; CN110506453A; JP6811844B2; CN110506453B

Abstract

This plasma-generating device generates plasma by discharge between the edges of a pair of electrodes positioned in such a manner that the side surfaces thereof face one another. The edge surfaces of the pair of electrodes that discharge electricity are cut out in such a manner so as to face one another.

Description

Plasma generator

The present invention relates to a plasma generator that generates plasma by discharge between the ends of a pair of electrodes disposed with their side surfaces facing each other.

In the plasma generator, as described in the following patent document, a processing gas is supplied to a reaction chamber, and power is supplied to a plurality of electrodes arranged in the reaction chamber. Thereby, discharge occurs in the reaction chamber, and the processing gas is turned into plasma.

JP 2005-129493 A

In the plasma generator, plasma is generated by discharge between the electrodes. For this reason, it is an object to provide a plasma generator that can stably discharge between electrodes.

In order to solve the above-described problem, the present specification provides a plasma generator that generates plasma by discharge between the ends of a pair of electrodes disposed in a state in which the side surfaces face each other. Disclosed is a plasma generator in which end surfaces on the discharge side of the pair of electrodes are cut away so as to face each other.

According to the present disclosure, since discharge occurs between the end faces of the pair of electrodes facing each other, stable discharge can be achieved.

It is a perspective view which shows an atmospheric pressure plasma generator. It is an exploded view which shows an atmospheric pressure plasma generator. It is sectional drawing which shows an atmospheric pressure plasma generator. It is a perspective view which shows an internal block. It is the front view which shows an internal block, a top view, and a side view. It is a perspective view which shows a holding member. It is a front view, a top view, a bottom view, and a side view showing a holding member. It is a top view which shows an internal block. It is an exploded view which shows the conventional atmospheric pressure plasma generator. It is a top view which shows the internal block of the conventional atmospheric pressure plasma generator. It is sectional drawing which shows the atmospheric pressure plasma generator of a modification.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as modes for carrying out the present invention.

(A) Configuration of Atmospheric Pressure Plasma Generator FIG. 1 to FIG. 3 show an atmospheric pressure plasma generator 10 according to an embodiment of the present invention. The atmospheric pressure plasma generator 10 is an apparatus for generating plasma under atmospheric pressure. The atmospheric pressure plasma generator 10 includes an inner block 12, a lower block 14, an irradiation nozzle 18, a holding member 20, a pair of

electrodes

24 and 26, a connecting member 28, and an upper block 30. . 1 is a perspective view of the atmospheric pressure plasma generator 10, FIG. 2 is an exploded perspective view of the atmospheric pressure plasma generator 10 excluding the upper block 30, and FIG. 3 is an atmospheric pressure plasma generator. 10 is a cross-sectional view of FIG.

The inner block 12 is formed of ceramic, and as shown in FIGS. 4 and 5, is constituted by a generally rectangular parallelepiped body portion 32 and a flange portion 34 formed at the upper edge of the body portion 32. . 4 is a perspective view of the internal block 12, and FIG. 5 is a front view of the internal block 12A, a top view of the internal block 12B, and a side view of the internal block 12C.

A pair of cylindrical

concave portions

36 and 38 are formed on the upper surface of the flange portion 34 of the inner block 12. Further, a pair of

cylindrical recesses

36 and 38 are connected, and a connection recess 40 is formed from the bottom surface of the pair of

cylindrical recesses

36 and 38 toward the inside of the main body 32. Since the width of the connecting recess 40 is smaller than the diameter of the

cylindrical recesses

36, 38, the bottom surfaces of the

cylindrical recesses

36, 38 are generally

U-shaped step surfaces

46, 48. Moreover, the connection recessed part 40 is made into the stepped shape where a width | variety becomes narrow toward the bottom face, and the six 1st flow paths 50 are formed in the bottom face of the connection recessed part 40 so that it may extend in an up-down direction. . The six first flow paths 50 are open on the lower surface of the internal block 12. In the present specification, the width direction of the component means a short direction when the component is generally rectangular, that is, a direction orthogonal to the longitudinal direction. Moreover, a longitudinal direction is described as a length direction.

As shown in FIG. 2, the lower block 14 has a generally rectangular parallelepiped shape and is formed of ceramic. On the upper surface of the lower block 14, a storage portion 60 for storing the internal block 12 is formed. The storage unit 60 is a bottomed hole that opens to the upper surface of the lower block 14, and, as shown in FIG. 3, includes a first storage unit 62 positioned on the bottom surface side and a second storage unit 64 positioned on the opening side. It is configured.

The depth dimension of the first storage part 62 is substantially the same as the height dimension of the main body part 32 of the inner block 12, and the width dimension and the length dimension of the first storage part 62 are the same as those of the main body part 32 of the inner block 12. Slightly longer than the width and length dimensions. The depth dimension of the second storage part 64 is longer than the height dimension of the flange part 34 of the internal block 12, and the width dimension and length dimension of the second storage part 64 are the width of the flange part 34 of the internal block 12. Slightly longer than dimension and length. For this reason, the internal block 12 is inserted from the opening of the storage portion 60, the main body portion 32 of the internal block 12 is stored in the first storage portion 62, and the flange portion 34 of the internal block 12 is stored in the second storage portion 64. The Since the depth dimension of the second storage portion 64 is longer than the height dimension of the flange portion 34, the top surface of the flange portion 34, that is, the top surface of the internal block 12 is the top surface of the lower block 14 inside the storage portion 60. Located below. That is, the entire inner block 12 enters in a state where it is buried inside the storage portion 60 of the lower block 14.

In addition, six second flow paths 66 are formed on the bottom surface of the storage unit 60, that is, the bottom surface of the first storage unit 62 so as to extend in the vertical direction. The lower block 14 has an opening on the lower surface. Then, by storing the internal block 12 in the storage unit 60, the second flow path 66 and the first flow path 50 of the internal block 12 communicate with each other.

The irradiation nozzle 18 is fixed to the lower surface of the lower block 14. Six third flow paths 70 are formed in the irradiation nozzle 18 so as to extend in the vertical direction, and the six third flow paths 70 are opened on the upper surface and the lower surface of the irradiation nozzle 18. Each third flow path 70 communicates with each second flow path 66 of the internal block 12.

The holding member 20 is formed of ceramic, and includes a pair of

holders

72 and 74 and a connecting portion 76 as shown in FIGS. The pair of

holders

72 and 74 are spaced apart with their side surfaces facing each other, and are connected by a connecting portion 76. Each of the pair of

holders

72 and 74 includes a main body portion 78 and a protruding portion 80. The main body 78 has a generally cylindrical shape with a bottom. Further, the protruding portion 80 has a short cylindrical shape with a smaller diameter than the main body portion 78 and slightly protrudes downward from the bottom surface of the main body portion 78. The upper end of the projecting portion 80 is open to the bottom surface of the main body portion 78.

The outer diameter of the main body portion 78 is substantially the same as the width dimension of the flange portion 34 of the inner block 12, and the outer diameter of the protruding portion 80 is slightly smaller than the inner diameter of the

cylindrical recesses

36 and 38 of the inner block 12. The dimensions are small. In addition, the shaft centers of the protrusions 80 of the pair of

holders

72 and 74 are shifted from each other in a direction approaching the shaft center of the main body 78, and the distance between the pair of protrusions 80 is that of the inner block 12. The distance between the pair of

cylindrical recesses

36 and 38 is the same.

Also, the bottom surface of each main body 78 of the pair of

holders

72 and 74 is a step surface, and is constituted by a first bottom surface 82 and a second bottom surface 84. The second bottom surface 84 projects downward from the first bottom surface 82. The second bottom surface 84 is formed so as to expand in a generally fan shape in a direction away from the side surface 86 and the side surface 88 opposite to each other of the protrusions 80 of the pair of

holders

72 and 74. That is, the first bottom surface 82 is formed on the side surface 86 side of the protruding portion 80, and the second bottom surface 84 is formed on the side surface 88 side of the protruding portion 80. The second bottom surface 84 projects downward from the first bottom surface 82, but is located above the lower end of the projecting portion 80.

Further, the connecting portion 76 connects the pair of

holders

72 and 74 on the side surfaces of the pair of

holders

72 and 74 facing each other. The width dimension of the connecting portion 76 is substantially the same as the outer diameter of the main body portion 78 of the

holders

72 and 74, and the outer wall surface of the connecting portion 76 and the outer peripheral surface of the main body portion 78 are smoothly continuous. The outer diameter of the main body 78 of the

holders

72 and 74 is substantially the same as the width of the flange portion 34 of the inner block 12 as described above. Further, the length dimension of the connecting portion 76 is designed so that the length dimension of the holding member 20 matches the length dimension of the flange portion 34 of the internal block 12. Thereby, the width dimension and the length dimension of the holding member 20 are substantially the same as the width dimension and the length dimension of the flange portion 34 of the internal block 12.

The bottom surface 90 of the connecting portion 76 is flush with the first bottom surface 82 of the main body portion 78 of the

holders

72 and 74, and the bottom surface 90 of the connecting portion 76 and the first bottom surface 82 of the main body portion 78 are smooth and flat. It is considered as a surface. The connecting portion 76 is formed with a through hole 96 extending in the vertical direction between the pair of

holders

72 and 74. The through hole 96 opens at the upper surface of the connecting portion 76 at the upper end and at the lower end. An opening is formed on the lower surface of the connecting portion 76.

The holding member 20 having such a structure is combined with the internal block 12 as shown in FIG. Specifically, the protrusions 80 of the pair of

holders

72 and 74 of the holding member 20 are inserted into the pair of

cylindrical recesses

36 and 38 of the inner block 12. Thereby, the lower end of the protrusion 80 faces the step surfaces 46 and 48 of the

cylindrical recesses

36 and 38. However, the depth dimension of the

cylindrical recesses

36 and 38 is larger than the protrusion amount of the protrusion 80 from the second bottom surface 84. For this reason, the 2nd bottom face 84 of the holding member 20 contacts the upper surface of the internal block 12, and the lower end of the protrusion part 80 and the level | step difference surfaces 46 and 48 of the cylindrical recessed

parts

36 and 38 oppose in a state with clearance. . As described above, the holding member 20 is combined with the inner block 12, so that the connecting recess 40 of the inner block 12 is closed by the holding member 20, and the reaction chamber 100 is partitioned by the connecting recess 40 and the holding member 20. .

Further, as described above, the width dimension and the length dimension of the holding member 20 are substantially the same as the width dimension and the length dimension of the flange portion 34 of the internal block 12. For this reason, the lower end portion of the holding member 20 combined with the inner block 12 is housed in the second housing portion 64 of the lower block 14 together with the flange portion 34 of the inner block 12.

Each of the pair of

electrodes

24 and 26 has a generally cylindrical shape, and the outer diameter of the

electrodes

24 and 26 is smaller than the inner diameter of the

holders

72 and 74 of the holding member 20. The

electrodes

24 and 26 are held by the socket 102 in a posture extending vertically in the

holders

72 and 74. The lower end portions of the

electrodes

24 and 26 protrude from the lower end portion of the holder 72, that is, the lower end of the protruding portion 80, and are inserted into the reaction chamber 100.

Also, the lower ends of the

electrodes

24 and 26 inserted into the reaction chamber 100 are formed in a wedge shape in which the end faces face each other. Specifically, the lower end portions of the pair of

electrodes

24 and 26 are notched downward from the side surface 106 of the pair of

electrodes

24 and 26 facing each other toward the side surface 108 opposite to the side surface 106. That is, the lower end surfaces 110 of the pair of

electrodes

24 and 26 are cut out so as to face each other. In other words, the angle formed between the side surface 106 and the lower end surface 110 is an obtuse angle, and the angle formed between the side surface 108 and the lower end surface 110 is an acute angle. In other words, the lower end surfaces 110 of the

electrodes

24 and 26 are tapered surfaces that incline downward from the side surface 106 toward the side surface 108.

Further, the connecting member 28 has a plate shape, and the connecting member 28 is formed with an insertion hole 120 extending in the vertical direction. The insertion hole 120 opens to the upper surface of the connecting member 28 at the upper end, and opens to the lower surface of the connecting member 28 at the lower end. The inner dimension of the insertion hole 120 is slightly larger than the dimension of the holding member 20 in the width direction and the length direction. The connecting member 28 is fixed to the upper surface of the lower block 14 with the holding member 20 inserted through the insertion hole 120. The upper surface of the connecting member 28 and the upper surface of the connecting portion 76 of the holding member 20 are substantially the same height, and the upper end portions of the

holders

72 and 74 of the holding member 20, that is, the main body portion 78 is connected to the connecting member 28. It extends upward from the upper surface of.

Further, the upper block 30 has a generally rectangular parallelepiped shape, and a pair of recesses 126 opening on the lower surface of the upper block 30 is formed. The inner dimension of the recess 126 is slightly larger than the outer dimension of the main body 78 of the

holders

72 and 74. And the lower surface of the upper block 30 is being fixed to the upper surface of the connection member 28 in the state in which the main-body part 78 of the

holders

72 and 74 was inserted in the recessed part 126. FIG. In addition, the depth dimension of the recessed part 126 is larger than the extension amount from the upper surface of the connection member 28 of the main-body part 78. FIG. For this reason, there is a clearance between the bottom surface of the recess 126 and the main body portion 78. An annular elastic body 128 is inserted into the clearance in a compressed state. Thereby, the holding member 20 is urged downward by the elastic force of the elastic body 128, and the inner block 12 and the holding member 20 are in close contact with each other inside the storage portion 60 of the lower block 14.

In the upper block 30, a pair of first communication passages 130 communicating with the pair of recesses 126 are formed. The first communication path 130 is connected to a supply device (not shown) that supplies a processing gas composed only of an inert gas such as nitrogen. Furthermore, a second communication path 132 that communicates with the through hole 96 of the holding member 20 is also formed in the upper block 30. The second communication path 132 is connected to a supply device (not shown) that supplies a processing gas in which an active gas such as oxygen in the air and an inert gas such as nitrogen are mixed at an arbitrary ratio.

(B) Generation of Plasma by Atmospheric Pressure Plasma Generator In the atmospheric pressure plasma generator 10, the processing gas is converted into plasma inside the reaction chamber 100 by the above-described configuration, and plasma is generated from the third flow path 70 of the irradiation nozzle 18. Is irradiated. Hereinafter, generation of plasma by the atmospheric pressure plasma generator 10 will be described in detail.

In the atmospheric pressure plasma generation apparatus 10, a processing gas composed only of an inert gas is supplied from the first communication path 130 to the reaction chamber 100 through the insides of the

holders

72 and 74 of the holding member 20. Further, a processing gas composed of an inert gas and an active gas is supplied from the second communication path 132 to the reaction chamber 100 through the through hole 96 of the holding member 20. At that time, in the reaction chamber 100, a voltage is applied to the pair of

electrodes

24 and 26, and a current flows between the pair of

electrodes

24 and 26. Thereby, a discharge is generated between the pair of

electrodes

24 and 26, and the processing gas is turned into plasma by the discharge. Further, in the reaction chamber 100, since the

electrodes

24 and 26 are disposed at positions close to the wall surface of the connection recess 40 of the internal block 12, current is applied along the wall surface of the connection recess 40 by application to the

electrodes

24 and 26. Flowing. As a result, discharge occurs not only between the pair of

electrodes

24 and 26 but also along the wall surface of the connecting recess 40, and the process gas is turned into plasma by the discharge. The plasma generated in the reaction chamber 100 flows into the second flow channel 66 of the lower block 14 via the first flow channel 50 of the internal block 12. Further, the plasma flows into the third flow path 70 of the irradiation nozzle 18, and the object to be processed is irradiated from the lower end of the third flow path 70.

(C) Durability Improvement of Atmospheric Pressure Plasma Generator In this way, in the atmospheric pressure plasma generator 10, the process gas is turned into plasma by the discharge occurring inside the reaction chamber 100, and the third of the irradiation nozzle 18. Plasma is irradiated from the channel 70. Note that plasma is a state in which molecules constituting a gas are ionized and separated into cations and electrons, and corresponds to an ionized gas. Such plasma is generated in the reaction chamber 100 and is ejected from the reaction chamber 100 to the first flow path 50.

However, the gas ionized inside the reaction chamber 100 is sequentially ejected from the reaction chamber 100 to the first flow path 50. However, when entering the very narrow region, the ionized gas stays in the narrow region. There is. For example, it is considered that there is no gap between the contact surfaces of the members that define the reaction chamber 100 because the surfaces contact each other. However, when the size of the molecules constituting the gas is considered as a reference, the ionized gas enters the contact surface between the members even at the contact surface. When the ionized gas enters the contact surface in such a very narrow region, the ionized gas stays inside the contact surface, and the discharge concentrates on the ionized gas, thereby causing the contact surface to burn. There is a fear. In particular, in the reaction chamber 100, a discharge is generated between the pair of

electrodes

24 and 26. Therefore, if a contact surface exists between the pair of

electrodes

24 and 26, the contact surface is likely to be burned, and the reaction occurs. The members that define the chamber 100, that is, the internal block 12, the holding member 20, and the like are easily deteriorated. Further, the discharge may not be stable due to the concentration of the discharge on the contact surface.

In view of the above, the atmospheric pressure plasma generator 10 is configured such that the contact surface exists only on the opposite side of the reaction chamber 100 from between the pair of

electrodes

24 and 26. Specifically, as described above, the reaction chamber 100 is defined by the holding member 20 and the internal block 12, and the protrusions 80 of the pair of

holders

72 and 74 of the holding member 20 are paired with the pair of internal blocks 12. The cylindrical recesses 36 and 38 are inserted. Thereby, the lower end of the protrusion 80 faces the step surfaces 46 and 48 of the

cylindrical recesses

36 and 38. However, the depth dimension of the

cylindrical recesses

parts

36 and 38 oppose in a state with clearance. . That is, only the second bottom surface 84 of the holding member 20 is in contact with the internal block 12. In other words, as shown in FIG. 8, on the upper surface of the flange portion 34 of the inner block 12, only a portion (shaded line in the drawing) corresponding to the shape of the second bottom surface 84 of the holding member 20 is attached to the holding member 20. It becomes the contact surface 140.

The contact surface 140 is located on the opposite side between the pair of

electrodes

24 and 26 inserted into the connecting recess 40 of the inner block 12. That is, in the atmospheric pressure plasma generator 10, in the reaction chamber 100, the contact surface between the inner block 12 and the holding member 20, that is, the second bottom surface 84 and the contact only on the opposite side of the pair of

electrodes

24 and 26. The surface 140 is configured to exist.

The term “between the pair of

electrodes

24, 26” means a width corresponding to the diameter of the

electrodes

24, 26, and does not indicate only a region connecting the pair of

electrodes

24, 26, but a pair of

electrodes

24, 26. An area between two straight lines passing through a pair of

electrodes

24 and 26 is shown. Specifically, a region connecting the pair of

electrodes

24 and 26 with a width corresponding to the diameter of the

electrodes

24 and 26 is a region surrounded by a one-dot chain line 146 in FIG. On the other hand, two straight lines passing through the pair of

electrodes

24 and 26 and passing through the pair of

electrodes

24 and 26 are two-dot chain lines 148 in FIG. Therefore, between the pair of

electrodes

24 and 26 means between the two two-dot chain lines 148. That is, in the atmospheric pressure plasma generator 10, the contact surface between the internal block 12 and the holding member 20 exists only on the opposite side of the reaction chamber 100 between the pair of two-dot chain lines 148.

On the other hand, as shown in FIG. 9, the conventional atmospheric pressure plasma generator 150 includes a pair of holders 152, an internal block 154, a connecting member 156, a lower block 158, an irradiation nozzle (not shown), and an upper part. And a block (not shown). Here, in the atmospheric pressure plasma generator 150, the lower surface of the pair of holders 152 is assembled on the upper surface of the internal block 154, so that the inside of the internal block 154 functions as a reaction chamber. For this reason, only the holder 152 and the internal block 154 will be described.

The pair of holders 152 has a cylindrical shape, and its lower end surface is a flat surface. The inner block 154 includes a generally rectangular parallelepiped main body 166 and a flange 168 formed at the upper end of the main body 166. A recess 170 is formed in the internal block 154, and the recess 170 opens to the upper surface of the flange portion 168 and reaches the inside of the main body portion 166. The upper surface of the flange portion 168 is a flat surface except for the concave portion 170, and the width dimension of the flange portion 168 is approximately the same as the diameter of the holder 152. Then, the holder 152 and the internal block 154 are combined so that the lower surface of the holder 152 is in contact with the upper surface of the internal block 154, that is, the upper surface of the flange portion 168. As a result, the recess 170 of the internal block 154 is partitioned as a reaction chamber by the holder 152. Then, a pair of electrodes (see FIG. 10) 176 and 178 are inserted into the pair of holders 152 so that the lower ends of the pair of

electrodes

176 and 178 enter the recess 170.

In the atmospheric pressure plasma generator 150, as described above, the holder 152 and the internal block 154 are combined so that the lower end surface of the flat holder 152 is in contact with the upper end surface of the flat internal block 154. For this reason, on the upper surface of the internal block 154, as shown in FIG. 10, a portion (shaded line in the drawing) corresponding to the shape of the lower end surface of the holder 152 becomes a contact surface 180 to the holder 152. The contact surface 180 extends between the pair of

electrodes

176 and 178. That is, the contact surface 180 extends straight to a straight line connecting the pair of

electrodes

176 and 178 and to a region between the two straight lines 182 passing through the pair of

electrodes

176 and 178.

Thus, when the contact surface between the holder 152 and the internal block 154 that partitions the reaction chamber exists between the pair of

electrodes

176 and 178, the gas ionized by the discharge generated between the

electrodes

176 and 178 is It is easy to enter the contact surface 180. In particular, when discharge occurs along the wall surface that defines the reaction chamber, the ionized gas easily enters the contact surface 180. When the ionized gas enters the contact surface 180 and stays there, discharge concentrates on the contact surface 180. Thereby, the contact surface 180 is burnt and deteriorates. Thus, in the conventional atmospheric pressure plasma generator 150, the holder 152 and the internal block 154 that partition the reaction chamber are easily deteriorated, and the durability is low. In order to increase the durability, it is conceivable to use a material having high heat resistance as the material for the holder 152 and the like, but the cost is increased.

On the other hand, in the atmospheric pressure plasma generator 10, as shown in FIG. 8, in the reaction chamber 100, the contact surface 140 between the internal block 12 and the holding member 20 is provided only on the opposite side between the pair of

electrodes

24 and 26. Exists. That is, the contact surface 140 between the inner block 12 and the holding member 20 does not exist between the pair of

electrodes

24 and 26. For this reason, even if a discharge occurs between the pair of

electrodes

24 and 26, the ionized gas does not easily enter the contact surface 140 between the inner block 12 and the holding member 20. Further, even when a discharge is generated from the pair of

electrodes

24 and 26 along the wall surface defining the reaction chamber 100, it is difficult to enter the contact surface 140. As a result, it is possible to prevent deterioration of the contact surface 140 between the internal block 12 and the holding member 20 due to scoring, and the durability of the internal block 12 and the holding member 20 is improved. As described above, in the atmospheric pressure plasma generation apparatus 10, by devising the shape of the internal block 12 or the like without changing the material of the internal block 12 or the like, the high cost due to the material change is prevented, and the internal block 12 or the like is prevented. Durability is improved. Moreover, stable discharge is ensured by suppressing the concentration of discharge on the contact surface.

Further, as shown in FIG. 3, a protruding portion 80 that protrudes downward from the second bottom surface 84 is formed between the second bottom surface 84 of the holding member 20 and the

electrodes

24 and 26, and the internal block 12. Between the contact surface 140 and the

electrodes

24 and 26, step surfaces 46 and 48 that are recessed downward are formed. And the protrusion part 80 and the level | step difference surfaces 46 and 48 have faced in the state with clearance. With such a structure, the contact surface between the inner block 12 and the holding member 20 is positioned above the lower ends of the

electrodes

24 and 26. Further, the projecting portion 80 extends so as to close the contact surface between the inner block 12 and the holding member 20. Thereby, the gas ionized by the discharge at the

electrodes

24 and 26 becomes more difficult to enter the contact surface between the inner block 12 and the holding member 20, and the durability of the inner block 12 and the like is further improved.

The holding member 20 is supported by the upper surface of the internal block 12 only on the second bottom surface 84 of the pair of

holders

72 and 74. That is, the

holders

72 and 74 are supported by the upper surface of the inner block 12 only at one end portion of both ends in the diameter direction of the generally annular bottom surface, and the stability is low. For this reason, the pair of

holders

72 and 74 are connected by the connecting portion 76, and the stability of the holding member 20 is ensured.

(D) Stable Plasma Generation by Electrode Discharge Further, in the atmospheric pressure plasma generator 10, as described above, discharge is generated between the

electrodes

24 and 26, thereby generating plasma. For this reason, in the atmospheric pressure plasma generator 10, the lower ends of the

electrodes

24 and 26 are wedge-shaped in order to stably discharge between the electrodes.

Specifically, in the conventional atmospheric pressure plasma generator, the electrode has a cylindrical shape, and the angle formed between the side surface of the electrode and the lower end surface of the electrode is a right angle. That is, in the lower end portions of the pair of electrodes, the corner portions where the side surface and the lower end surface form 90 degrees face each other, and the lower end surfaces face directly below and do not face each other at all. Then, electric power is supplied to the pair of electrodes, and discharge occurs between the lower ends of the pair of electrodes. At this time, since the lower end surfaces of the pair of electrodes do not face each other at all, it is difficult for discharge to occur between one lower end surface of the pair of electrodes and the other lower end surface. It is thought that discharge occurs between the corner and the other 90-degree corner.

If the discharge concentrates on the corner of the electrode in this way, a slight disturbance may occur in the power supplied to the electrode. Specifically, when a current is stably supplied to the electrode, the current changes periodically. On the other hand, in the conventional atmospheric pressure plasma generator, the amplitude may decrease in several cycles of hundreds to thousands of cycles. In such a case, although it is an instant, there is a possibility that the discharge stops, which is not desirable.

In view of the above, in the atmospheric pressure plasma generator 10, the lower ends of the

electrodes

24 and 26 are wedge-shaped, and the lower end surfaces 110 of the pair of

electrodes

24 and 26 face each other. That is, at the lower end portions of the pair of

electrodes

24 and 26, the corner portions where the side surface 106 and the lower end surface 110 form an obtuse angle face each other, and the lower end surfaces 110 also face each other. Then, electric power is supplied to the pair of

electrodes

24 and 26, thereby generating a discharge between one obtuse corner of the pair of

electrodes

24 and 26 and the other obtuse corner. It is considered that a discharge is also generated between one lower end surface 110 of the pair of

electrodes

24 and 26 and the other lower end surface 110. At this time, electric power is stably supplied to the electrodes as compared with the case where discharge is concentrated between one 90-degree corner of the pair of electrodes and the other 90-degree corner. That is, the amplitude does not decrease even in several cycles of hundreds to thousands of cycles. Thereby, it becomes possible to discharge stably between electrodes, and it becomes possible to ensure the generation of stable plasma.

Incidentally, in the above embodiment, the atmospheric pressure plasma generator 10 is an example of a plasma generator. The

electrodes

24 and 26 are examples of electrodes. The side surface 106 is an example of a first side surface. The side surface 108 is an example of a second side surface. The lower end surface 110 is an example of an end surface.

In addition, this invention is not limited to the said Example, It is possible to implement in the various aspect which gave various change and improvement based on the knowledge of those skilled in the art. Specifically, for example, in the above-described embodiment, as shown in FIG. 3, a protrusion 80 that protrudes downward from the second bottom surface 84 is formed on the bottom surface of the

holders

72 and 74, and on the top surface of the lower block 14, Step surfaces 46 and 48 that are recessed downward from the contact surface 140 are formed. And the 2nd bottom face 84 and the contact surface 140 contact, and the protrusion part 80 and the level | step difference surfaces 46 and 48 are facing in the state with clearance. On the other hand, as shown in FIG. 11, a stepped surface 200 that is recessed above the second bottom surface 84 is formed on the bottom surfaces of the

holders

72 and 74, and a protruding portion 210 that protrudes above the contact surface 140 on the top surface of the lower block 14. May be formed. And the 2nd bottom face 84 and the contact surface 140 may contact, and the level | step difference surface 200 and the protrusion part 210 may oppose in the state with clearance.

Further, in the above embodiment, the present invention is applied to the atmospheric pressure plasma generator 10, but the present invention can be applied to a plasma generator that generates plasma under reduced pressure.

In the above embodiment, the lower end surface 110 of the

electrodes

24 and 26 is a flat surface, but it can be formed in various shapes such as a curved surface and a step surface.

Also, dry air may be used as the processing gas in the above embodiment.

10: Atmospheric pressure plasma generator (plasma generator) 24: Electrode 26: Electrode 106: Side surface (first side surface) 108: Side surface (second side surface) 110: Lower end surface (end surface)

Claims

A plasma generator for generating plasma by discharge between the ends of a pair of electrodes arranged with their side surfaces facing each other,
A plasma generator in which end surfaces on the discharge side of the pair of electrodes are cut away so as to face each other.
A plasma generator for generating plasma by discharge between the ends of a pair of electrodes arranged with their side surfaces facing each other,
The plasma generating apparatus in which the end portions on the discharge side of the pair of electrodes have a wedge shape whose end faces face each other.
A plasma generator for generating plasma by discharge between the ends of a pair of electrodes arranged with their side surfaces facing each other,
The plasma generator according to claim 1, wherein an angle formed between a first side surface of the pair of electrodes facing each other and an end surface of each of the pair of discharge sides continuous from the first side surface is an obtuse angle.
The angle formed by the second side surface opposite to the first side surface with the electrode shaft as the center and the end surfaces of the pair of discharge sides that are continuous from the second side surface are acute angles. Item 4. The plasma generator according to Item 3.
The plasma generator according to any one of claims 1 to 4, wherein each of the pair of electrodes has a cylindrical shape except for an end portion on a discharge side.