JP5126983B2 - Plasma generator - Google Patents

Description

  The present invention relates to a plasma generator. In particular, it relates to a so-called atmospheric pressure plasma generator.

  The inventors have applied for an atmospheric pressure plasma generator described in Patent Documents 1 and 2. By applying micro-sized uneven shapes to the opposing electrode surfaces, a hollow cathode discharge is generated to generate plasma. If the plasma generation gas is introduced so as to pass through the plasma generation region (plasmaization region), at least a part of the gas can be ejected. Thereby, a high frequency of about several kV can be generated from a single-phase commercial 100V power source with a booster, and high-density atmospheric pressure plasma can be easily generated.

JP 2006-196210 A JP 2006-272039 A

  In the techniques of Patent Documents 1 and 2, when the electrode interval is widened, the discharge becomes unstable. Conversely, when the interval is set to 1 cm or more, the discharge cannot be maintained. Therefore, in Patent Documents 1 and 2, for example, when a region having a longitudinal direction is a plasma region, an electrode having a length in the longitudinal direction is used. However, when such long electrodes face each other, there is a problem in uniformizing the plasma. For this reason, it cannot be effectively used for plasma processing to a relatively wide region such as a part of the surface of a liquid crystal panel or the like. Alternatively, it is difficult to increase the volume of the plasma generation region itself. For this reason, although the high-density atmospheric pressure plasma can be generated, its effective use range is limited.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide an atmospheric pressure plasma generator in which the volume of the plasma generation region is increased.

The invention according to claim 1 is the atmospheric pressure plasma generator, wherein the casing portion made of an insulator that forms a columnar plasma formation region having a longitudinal direction, and the plasma formation region contained in the casing portion in the longitudinal direction A pair of electrodes disposed apart from each other, a plasma generating gas inlet for introducing the plasma generating gas into the plasma generating region along the longitudinal direction of the plasma generating region, and the longitudinal direction of the plasma generating region And a jet port disposed along the longitudinal direction of the plasma formation region, and the plasma conversion region has a length in the longitudinal direction of 1 cm or more. The atmospheric pressure plasma generator is characterized by having a cross-sectional area of 50 mm or less and perpendicular to the longitudinal direction of 3 mm ² or more and 25 mm ² or less.

  The invention according to claim 2 is characterized in that a width perpendicular to the longitudinal direction of the plasma region and the gas flow direction is 2 mm or more and 5 mm or less.

The invention according to claim 3 is characterized in that the inside of the housing is an atmospheric pressure plasma generation source that is neither pressurized nor depressurized. In the present invention, atmospheric pressure plasma means under a pressure in the range of 0.5 to 2 atmospheres.
The invention according to claim 4 is characterized in that the pair of electrodes are spaced apart by a distance of 1 cm to 50 cm.
The invention according to claim 5 is characterized in that at least one of the pair of electrodes is provided with irregularities on the surface facing the other electrode.
In the invention according to claim 6, the relationship between the longitudinal length Lcm of the columnar plasma region and the cross-sectional area σmm ² perpendicular to the longitudinal direction is 2 ≦ Lσ ≦ 200 and 3 ≦ σ ≦ 25. Features.

  Atmospheric pressure plasma is formed in a space surrounded or sandwiched by a casing made of an insulator. The length of the plasma is increased in a columnar space surrounded or sandwiched between the insulators. Here, it is considered that the role of the insulator is to stabilize the plasma formation of the entire plasma formation region having a large volume in the longitudinal direction by charging the inner surface thereof.

The flow path of the plasma generating gas may be a flow path along the longitudinal direction of the plasma generation region, or may be one that crosses vertically. When the flow path of the plasma generating gas is a flow path along the longitudinal direction of the plasma generation region, for example, when the processing target is a gas, the processing target gas and the plasma generating gas are mixed to introduce the inlet Can be introduced into the plasma region.
When hollow cathode discharge using an electrode having an uneven surface described in Patent Documents 1 and 2 is used, atmospheric pressure plasma can be easily generated.
The length L (cm) in the longitudinal direction of the columnar plasma region of the present invention is 1 or more and 50 or less, and the cross-sectional area σ (mm ² ) perpendicular to the longitudinal direction is 3 or more and 25 or less. In the columnar plasma region, the length L can be increased as the cross-sectional area σ is smaller. Further, the length L can be increased when the casing is substantially cylindrical. It has been experimentally confirmed that plasma can be stably generated if the relationship between L and σ is 2 ≦ Lσ ≦ 200.

1. 1A is a cross-sectional view showing a configuration of a plasma generating apparatus 100 according to a specific embodiment of the present invention, FIG. B is a figure which shows the detail of the shape of electrodes 2a and 2b. 2. 1A is a cross-sectional view showing a configuration of a plasma generator 110 according to another specific embodiment of the present invention, FIG. B is a cross-sectional view (partial view) perpendicular to the longitudinal direction of the plasma region P. FIG.

  For the casing, it is necessary to use a material that is highly resistant to plasma generated therein, and ceramics such as sintered boron nitride (PBN) is preferable.

  As the material of the electrode, stainless steel, molybdenum, tantalum, nickel, copper, tungsten, or an alloy thereof can be used. The surface on which the concave portion that causes hollow cathode discharge is formed preferably has a thickness of about 1 to 30 mm. By increasing the thickness, the recesses can be formed in multiple stages, the gas flow rate can be improved, and the plasma generation density can be improved. For example, the depth of the recess that causes the hollow cathode discharge may be about 0.5 mm. The concave portions may be formed discontinuously in a dot shape or may be formed continuously in a groove shape, but it is desirable that the concave portions be continuous. The shape of the concave portion can be arbitrarily formed as a cylindrical surface, a hemispherical surface, a prismatic surface, a pyramid, or the like.

  As a gas for generating plasma, air, oxygen, for example, He, Ne, Ar or other rare gas, nitrogen, hydrogen, or the like can be used at atmospheric pressure. By using air or oxygen, active oxygen radicals can be obtained, and organic contaminants can be effectively removed. Moreover, it is economical if air is used. For example, when Ar, which is a rare gas, is used, when Ar plasma is irradiated to the processing target, surrounding oxygen molecules become oxygen radicals by Ar plasma. With this oxygen radical, organic contaminants on the surface of the object to be treated can be effectively removed. Moreover, since it is not used as gas other than Ar gas, it is also economical. For the above reasons, a mixed gas of air and Ar may be used. The gas flow rate, supply amount, or degree of vacuum can be set arbitrarily. Further, the present invention does not generate plasma by high frequency, and the power source connected to the electrode is direct current, alternating current, or any other, and the frequency is not limited.

  Moreover, although the distance in the case of injecting plasma gas to a process target from a jet nozzle is also related with the gas flow velocity, the range of 2 mm-20 mm is desirable, for example. More desirably, it is 3 mm to 12 mm, and most desirably 4 mm to 8 mm. When generating oxygen radicals, it is preferable to set the distance so that the density of oxygen radicals is highest and the electron density is lowest on the surface to be treated. Thereby, the charge-up damage of the processing object can be prevented, and the most efficient cleaning is possible. Further, plasma may be irradiated to the processing target from an oblique direction. By irradiating the plasma from an oblique direction, for example, the polarizing film or the liquid crystal sealant is irradiated with the plasma, and adverse effects on the product can be prevented. Further, a gas such as air that does not contain plasma can be sprayed on a portion where plasma is not desired to prevent the plasma from diffusing.

In order to prevent oxidation of the electrode, it is preferable to lower the oxygen concentration by using nitrogen, Ar, or a gas containing hydrogen having a reducing action. Further, by generating a plurality of types of plasma, it is possible to remove only organic contaminants and not react with other regions. In addition, it is desirable to suck in the gas after reaction from a portion irradiated with plasma to the processing target. This prevents molecules that have reacted with organic contaminants from adhering to other areas. Furthermore, the plasma temperature and density are measured using absorption spectroscopy analysis of laser light, and the magnitude of the applied voltage and, if a pulse is applied, the duty ratio, the irradiation time, and the gas so that the predetermined temperature and density are obtained. It is desirable to feedback control the flow rate. Thereby, it is possible to realize high-quality cleaning and shortening of the cleaning time. Further, assuming that the jet port is formed in a straight line or a plurality of jet ports arranged in a straight line, the width and length of the jet port can be set appropriately to irradiate the plasma only on necessary portions. It becomes possible. Further, it is desirable to cool the gas and supply it to the apparatus to turn it into plasma. Thereby, it is possible to prevent the temperature of the plasma from rising more than necessary, and for example, it is possible to prevent the influence on the liquid crystal display device, for example, damage to the polarizing film. The present invention can be made very small, and can freely design the gas supply direction, the plasma blowing direction, the shape of the blowing plasma, and the like. Therefore, it is possible to provide a plurality of openings through which these plasmas are blown, and to supply gas from any direction. Therefore, it is possible to irradiate plasma only on the ACF-attached portion of the substrate with high density, and to effectively attach the cleaning device even in a vacant narrow space of the liquid crystal display assembly device. It becomes possible.
In all the above inventions, atmospheric pressure is desirable, but it may be reduced or pressurized, and the atmospheric pressure is about 0.5 to 2 atmospheres.

  FIG. A is a cross-sectional view showing a configuration of a plasma generating apparatus 100 according to a specific embodiment of the present invention. FIG. B is shown in FIG. It is a figure which shows the detail of the shape of the electrodes 2a and 2b of the plasma generator 100 of A. FIG.

FIG. The plasma generating apparatus 100 of A has a cylindrical casing 10 made of a sintered body made of alumina (Al ₂ O ₃ ) as a raw material, and openings at both ends thereof are connected to a gas inlet 10i and a gas outlet 10o. It was. The electrode 2a is disposed in the vicinity of the gas inlet 10i inside the housing 10 and the electrode 2b is disposed in the vicinity of the gas outlet 10o inside the housing 10. The electrodes 2a and 2b are shown in FIG. As shown in B, the surfaces facing each other are uneven surfaces having many recesses (hollows) H having a depth of about 0.5 mm. The casing 10 is a tube having an inner diameter of 2 to 5 mm, a thickness of 0.2 to 0.3 mm, and a length of 25 cm, and the electrodes 2a and 2b have a diameter of about 1 mm. Thus, when the voltage is increased to about 9 kV using commercial AC voltage 60 Hz and 100 V, 20 mA is applied between the electrodes 2a and 2b, and argon is introduced from the gas inlet 10i, the electrodes 2a and 2b are separated to a maximum of 24 cm. Even then, plasma (the hatched area marked P in FIG. 1.A) was generated.
When the length between the electrodes 2a and 2b was 24 cm and the inner diameter of the cylindrical casing 10 was changed, the battery was stably discharged with an inner diameter of 3 mm or less. Further, when the inner diameter of the cylindrical casing 10 was set to 3 mm and the length between the electrodes 2a and 2b was changed, the battery was stably discharged at a distance of 24 cm or less.

FIG. In the plasma generating apparatus 100 of A, for example, soot can be decomposed by introducing oxygen (O ₂ ) into plasma. That is, it can be seen that the plasma generator 100 can be used for purification of diesel exhaust gas. That is, FIG. In the plasma generating apparatus 100 of A, oxygen (O ₂ ) and pre-treatment exhaust gas (S) are introduced from the gas inlet 10i, and an alternating voltage is applied between the electrodes 2a and 2b. A treated exhaust gas (S ′) containing oxygen (O ₂ ), carbon dioxide (CO ₂ ) and water (H ₂ O) is obtained.

  FIG. A is a cross-sectional view showing a configuration of a plasma generating apparatus 110 according to another specific embodiment of the present invention. FIG. B is shown in FIG. It is sectional drawing (partial drawing) perpendicular | vertical to the longitudinal direction of the plasma-ized area | region P of the plasma generator 110 of A. FIG.

FIG. A plasma generator 110 of A has a casing 11 made of a sintered body made of alumina (Al ₂ O ₃ ) as a raw material. The housing unit 11 has the structure shown in FIG. A gas inlet 11i and a plurality of cylindrical gas outlets 11o extending in a slit shape in the left-right direction in A are provided. From the gas inlet 11i to just above the plasma region P, the slit width (front / rear direction with respect to FIG. 2.A paper plane, left / right direction in FIG. 2B) is 1 mm, and the gas outlet 11o having an inner diameter of 1 to 2 mm is converted to plasma. It is formed in a straight line along the longitudinal direction of the region P. The plasma region P has a square of 2 to 5 mm on one side of the cross section perpendicular to the longitudinal direction and a length of 4 cm. The electrodes 2a and 2b have the same shape as that used in Example 1. Thus, when the voltage is increased to about 9 kV using commercial AC voltage 60 Hz and 100 V, 20 mA is applied between the electrodes 2a and 2b, and argon is introduced from the gas inlet 11i, the electrodes 2a and 2b are separated by 4 cm. Even so, plasma was confirmed.
The plasma generator 110 can improve the degree of adhesion of the ACF to the substrate by cleaning the portion of the glass substrate of the liquid crystal display where the anisotropic conductive film (ACF) is attached before attaching the ACF. it can.
Further, when the length between the electrodes 2a and 2b was set to 4 cm and the length of one side of the cross section of the plasma region P was changed, the discharge was stably performed at 5 mm or less. Further, when the length of one side of the cross section of the plasmified region P was 5 mm and the length between the electrodes 2a and 2b was changed, the discharge was stably performed at a distance of 4 cm or less.

DESCRIPTION OF SYMBOLS 100,110: Plasma generator 10, 11: Housing | casing part 10i, 11i: Gas inlet 10o, 11o: Gas jet 2a, 2b: A pair of electrode which has a recessed part (hollow) in the surface which faces each other P: Plasma-ized Region H: recesses (hollows) formed on the surfaces of the pair of electrodes 2a and 2b facing each other

Claims (6)

In the atmospheric pressure plasma generator,
A casing made of an insulator that forms a columnar plasma region having a longitudinal direction;
A pair of electrodes disposed in the longitudinal direction in the plasma region included in the housing;
A plasma generating gas inlet for introducing a plasma generating gas into the plasma generating region along the longitudinal direction of the plasma generating region;
Along with the longitudinal direction of the plasmatized region, the at least a part of the gasified gas is ejected, and a jet port disposed along the longitudinal direction of the plasmatized region,
The plasma generation region has a longitudinal length of 1 cm or more and 50 cm or less, and a cross-sectional area perpendicular to the longitudinal direction is 3 mm ² or more and 25 mm ² or less.   2. The atmospheric pressure plasma generator according to claim 1, wherein a width perpendicular to the longitudinal direction and the gas flow direction of the plasma region is 2 mm or more and 5 mm or less. The atmospheric pressure plasma generation apparatus according to claim 1 or 2, wherein the inside of the casing is an atmospheric pressure plasma generation source that is neither pressurized nor depressurized.   The atmospheric pressure plasma generation apparatus according to any one of claims 1 to 3, wherein the pair of electrodes are spaced apart by a distance of 1 cm or more and 50 cm or less.   The atmospheric pressure plasma generator according to any one of claims 1 to 4, wherein at least one of the pair of electrodes is provided with irregularities on a surface facing the other electrode. . The relationship between the length Lcm in the longitudinal direction of the columnar plasma region and the cross-sectional area σmm ² perpendicular to the longitudinal direction is 2 ≦ Lσ ≦ 100 and 3 ≦ σ ≦ 25. The atmospheric pressure plasma generator according to claim 5.

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