JP5559292B2 - 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 is for solving the above-described problems, and an object of the present invention is a plasma generating apparatus in which the volume of a plasma generating region is increased. In addition, it is to provide such an atmospheric pressure plasma generator.

  According to a first aspect of the present invention, there is provided an atmospheric pressure plasma generating apparatus, wherein a casing portion made of an insulator that forms a columnar plasma region having a longitudinal direction and a plasma region enclosed in the casing portion are separated in the longitudinal direction. A pair of electrodes arranged in this manner, a gas introducing portion for introducing a plasma generating gas into the plasma formation region from a direction perpendicular to the longitudinal direction of the plasma formation region, and a plasma connected to the plasma formation region A plasma generator characterized in that it has a discharge part composed of a plurality of holes arranged in the longitudinal direction of the plasma generation region and extending in the direction of the flow of the plasma generation gas. Device.

The present invention is an apparatus that generates plasma linearly and irradiates an object with linear plasma at atmospheric pressure. The holes in the discharge section may be arranged in a single line or multiple lines along the longitudinal direction. Further, the diameter of the hole may be different between the root portion adjacent to the plasma region and the tip. The diameter of the tip may be smaller than the diameter of the root portion. Conversely, the diameter of the tip may be larger than the diameter of the root portion. The diameter of the hole may change in a taper shape or may change in a stepwise manner. When the tip of the hole is used away from the object, no discharge is formed between the object and the object even if the length of the hole of the discharge portion is shortened. In this case, the treatment effect is reduced, but by increasing the gas flow rate, a sufficient treatment effect can be obtained even if the tip of the hole is separated from the object.
The second aspect, in the first aspect, the gas inlet portion, a plasma generation gas to the plasma region, uniformly supplied in the longitudinal direction, lattice-shaped to guide in a direction perpendicular to the longitudinal direction It has a diffusion part which consists of a large number of holes arranged in and a guide part which is a wall surface of the hole . Thereby, plasma generation gas can be supplied uniformly along the longitudinal direction of the plasma-ized region. The guide portion may be formed in a lattice shape or may be constituted by wall surfaces of a large number of holes.
The third invention is characterized in that, in the first or second invention, the length of the hole in the discharge portion is a length at which no discharge is formed on the object irradiated with plasma. Thereby, an object is not damaged. As for the length of the hole, the shortest length is the best among the lengths in which no discharge is formed, considering radical life and death.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the diameter of the tip of the hole of the discharge portion is 0.1 mm or more and 1 mm or less. Thereby, only a radical can be irradiated to a target object among plasma particles. That is, electrons are absorbed by the wall surface of the hole.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the length of the hole of the discharge portion is set to ½ or more of the distance between the pair of electrodes. In this case, it is possible to prevent discharge from occurring on the object.
According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the hole of the discharge portion includes an inclined portion that is inclined with respect to a vertical direction of the longitudinal direction. In this case, electrons can be efficiently absorbed by the wall surface of the inclined portion of the hole, and the target can be irradiated with higher-purity radicals. Further, it is possible to prevent the object from being irradiated with ultraviolet rays, vacuum ultraviolet rays, visible light, and the like. Further, since the ultraviolet light emitted in the plasma region is blocked by the wall surface of the inclined portion, it is possible to prevent the object from being irradiated with the ultraviolet light from the tip of the hole. Thereby, the damage which a target object receives from the light emitted from plasma-ized area | regions, such as an ultraviolet-ray, can be prevented.
A seventh invention is characterized in that, in any one of the first to sixth inventions, the pair of electrodes are arranged at a distance of 1 cm or more and 50 cm or less.
An eighth invention is characterized in that in any one of the first to seventh inventions, at least one of the pair of electrodes is provided with irregularities on a surface facing the other.
According to a ninth invention, in any one of the first to seventh inventions, 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 ≦ 200. And 3 ≦ σ ≦ 25. In this range, plasma can be generated effectively. More desirably, 2 ≦ Lσ ≦ 100 and 3 ≦ σ ≦ 25.
The tenth invention is characterized in that the cross section perpendicular to the gas flow in the hole of the discharge portion is a circle, an ellipse, or a rectangle or slit having a long side in a direction perpendicular to the arrangement direction.

  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 plasma generating gas is supplied from the gas introduction part in a direction perpendicular to the longitudinal direction of the plasma generation region, and is discharged from a large number of holes of the discharge part. Thereby, radicals with a uniform density along the longitudinal direction are irradiated linearly from the tip of the hole to the object. 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. When the length of the hole in the discharge portion is equal to or greater than ½ of the distance between the pair of electrodes, a discharge may occur to the object irradiated with plasma. Is prevented. The length of the hole is most preferably 1/2 of the distance between the pair of electrodes. If the length is longer than this, the distance from the plasma-ized region until the radical reaches the target becomes longer, and the radical is deadly activated, which is not desirable. It has been found that when the distance between the electrodes is 40 mm, the length of this hole is optimal when it is 20 mm. 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. Further, the range in which plasma can be generated more effectively and effectively is 2 ≦ Lσ ≦ 100 and 3 ≦ σ ≦ 25.

  The casing needs to use a material that is highly resistant to plasma generated therein, and ceramics such as sintered boron nitride (PBN) is preferable. As the electrode material, stainless steel, molybdenum, tantalum, nickel, copper, tungsten, platinum, 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. In addition, the present invention does not generate plasma by high frequency, and the power source connected to the electrode is any direct current, alternating current, pulse, etc., and the frequency is not limited.

  Moreover, although the distance in the case of injecting plasma gas to the target object from the exit of many holes which a discharge part has is related also with the flow velocity of gas, 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. In addition, assuming that the outlets of the plurality of holes are arranged in a straight line, it is possible to irradiate the plasma only on necessary portions by appropriately setting the diameter and length of the holes. 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 very small. Therefore, it is possible to provide a plurality of discharge holes for blowing out the plasma so that the plasma can be irradiated at high density only on the portion where the anisotropic conductive film (ACF) is applied on the substrate. Even in a narrow space where the attaching device is vacant, the present cleaning device can be effectively attached. Moreover, you may make it the hole of a discharge part incline in the arbitrary directions of 360 degree | times centering on the line orthogonal to the longitudinal direction of a plasma-ized area | region. If it does in this way, the blowing direction of plasma can be changed.
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. The diameter of the tip of the hole of the discharge part is preferably 0.1 mm or more and 1 mm or less. The smaller the diameter of this hole, the higher the gas flow rate, and the higher the probability that the object can be irradiated without extinguishing radicals, which is desirable. In this case, radicals can be emitted well. By setting the length of the hole of the discharge portion to ½ or more of the distance between the pair of electrodes, discharge to the object can be effectively prevented.

  FIG. 1 is a cross-sectional view showing a configuration of a plasma generator 100 according to a specific embodiment of the present invention. FIG. 2 is a cross-sectional view (partial view) perpendicular to the longitudinal direction of the plasma region P of the plasma generator 100 of FIG.

The plasma generator 100 of FIG. 1 has a housing 10 made of a sintered body made of alumina (Al ₂ O ₃ ) as a raw material. Inside the housing 10, a plasma-ized region P that extends linearly in the longitudinal direction (hereinafter, this direction is referred to as the x-axis direction) is provided. The housing 10 has a gas introduction part 12 including a hole 15 having a diameter of 8 mm, two holes 13 having a diameter of 5 mm, a diffusion plate 14 in which the hole 13 is formed, and a guide part 16. The hole 13 may have a rectangular shape or a slit shape having long sides in the x-axis direction. The gas is introduced from the hole 15, divided into two in the x-axis direction by the diffusion plate 14, and guided from the hole 13 toward the plasma region P region. The guide portion 16 has a diameter 1... For flowing gas in a direction perpendicular to the x-axis direction (hereinafter, the direction in which the gas flows in this direction is referred to as the y-axis direction) uniformly in the x-axis direction of the plasmified region P. It has a number of holes of 5mm. The guide portion 16 is a wall surface of a large number of holes arranged in a lattice pattern, and the diffusion portion 18 is configured by the large number of holes and the wall surface. A discharge unit 20 including a first discharge unit 21 and a second discharge unit 22 is formed on the downstream side of the plasmification region P. The first discharge portion 21 has a large number of holes 23 having an axial direction in the y-axis direction and disposed in the x-axis direction. In addition, the second discharge portion 22 has a large number of holes 24 having an axial direction in the y-axis direction arranged along the x-axis direction. The diameters of the holes 23 and 24 are 0.5 mm, the length of the hole 23 is 4 mm, and the length of the hole 24 is 16 mm. The distance between the holes 23 and 24 in the x-axis direction is 2.5 mm, and 16 holes are provided.

The plasmified region P had a rectangular shape with a short side of 2 mm and a long side of 5 mm perpendicular to the x-axis direction, a long side as the y-axis direction, and a length in the x-axis direction of 4 cm. The electrodes 2a and 2b have the shape shown in FIG. As shown in FIG. 3, the electrodes 2 a and 2 b are uneven surfaces having a large number of recesses (hollows) H having a depth of about 0.5 mm. As a power source, a commercial AC power source of 60 Hz and 100 V is used. The voltage applied to the electrodes 2a and 2b was raised to about 9 kV from the commercial power supply voltage, and the feeding current between the electrodes 2a and 2b was 20 mA. When argon was introduced from the gas introduction part 12 in the x-axis direction, the formation of plasma was confirmed even when the electrodes 2a and 2b were separated by 4 cm.
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 4 cm, the cross section of the plasma region P was square, and the length of one side 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.

Next, using this apparatus, the surface of the glass substrate of the liquid crystal display was subjected to a hydrophilic treatment with plasma of argon gas. The contact angle before the treatment was 50 degrees, but the contact angle after the treatment was 7 degrees. In FIG. 1, in the case of the apparatus in which the second discharge part 22 was not provided, discharge was observed between the glass substrate and the tip of the hole 23. However, according to the apparatus of this example of FIG. 1, such discharge was not seen. From this, in this apparatus, plasma processing can be performed without damaging an object. Further, in FIG. 1, with respect to the apparatus in which the second discharge part 22 is not provided and the apparatus in FIG. 1 in which the second discharge part 22 is provided, oxygen is supplied as a plasma generating gas together with argon gas, and from the tip of the hole The oxygen radical concentration at a position of 5 mm was measured. The mixing ratio of oxygen was changed in the range of 0% to 4%, and in each case, the oxygen radical density was measured using vacuum ultraviolet absorption spectroscopy. Even if the second discharge unit 22 is provided, the oxygen radical density can be 3 × 10 ¹⁴ / cm ^{3 to} 7 × 10 ¹⁴ / cm ³ , and in an apparatus without the second discharge unit 22, 3 × 10 ¹⁴ / was ^{cm 3 ~2.4 × 10 15 / cm} 3. Even if the second discharge portion 22 is provided, the effect of the hydrophilic treatment is not particularly deteriorated. Further, the electron density in the plasma region P was 2 × 10 ¹⁶ / cm ³ when the mixing ratio of oxygen was 3% and the gas flow rate was 3 L / min.

  Next, the apparatus of this embodiment will be described with reference to FIG. In the present embodiment, the second discharge portion 22 of the first embodiment is configured by an inclined discharge portion 27 having a hole 26 inclined with respect to the y-axis direction and a straight discharge portion 25 along the y-axis direction. Other configurations are the same as those of the first embodiment. The inclined discharge part 22 was inclined 10 degrees with respect to the y-axis. The inclination range is preferably in the range of 3 degrees to 30 degrees. The range of 5 to 20 degrees is more desirable. In short, it is preferable that the opening of the hole 23 cannot be seen from the opening of the hole 24 and is not on one axis. The length of the projection onto the y-axis is 12 mm, and the length of the straight discharge portion 25 is 4 mm. With such a configuration, in the discharge unit 20, electrons can be reliably absorbed by the wall surface of the hole, and only radicals can be emitted from the tip of the hole 24. In the apparatus of Example 2, the contact angle after performing plasma treatment and hydrophilic treatment was 9.5 degrees, which was slightly larger than that of the apparatus of Example 1, but the discharge of the object was We were able to reliably prevent it. Further, by providing the inclined discharge portion 27, it becomes impossible to see the plasma region P from the opening of the hole 24. For this reason, the ultraviolet light emitted in the plasma region P is blocked by the wall surface of the hole 26, and the ultraviolet light is no longer irradiated to the object. As a result, the object was prevented from being damaged by ultraviolet rays.

  In all the embodiments described above, a large number of these plasma generators may be provided in the axial direction or in parallel with the axis so as to enable large area processing. When n pieces are provided in the axial direction, the object can be processed with a width of 4 ncm in the above example. At this time, an object can be processed in a larger area by being conveyed in a direction perpendicular to the axis (in a direction perpendicular to the x-axis and the y-axis). In addition, when a large number are provided parallel to the axis and the object is conveyed in a direction perpendicular to the x-axis and the y-axis, the plasma irradiation process can be reliably performed. In addition, the cross-sectional shape perpendicular to the gas flow in the holes 23, 24, and 26 may be a circle, an ellipse, a rectangle having a longitudinal direction in the direction perpendicular to the x-axis and the y-axis in FIGS. It may be.

  The present invention can be used in an apparatus for performing surface treatment by irradiating a target object with plasma in a straight line.

Sectional drawing which shows the structure of the plasma generator which concerns on one specific Example of this invention. Sectional drawing of the principal part of the Example apparatus. Sectional drawing which showed the structure of the electrode of the Example apparatus. Sectional drawing which showed the structure of the plasma generator which concerns on the concrete other Example of this invention.

DESCRIPTION OF SYMBOLS 100: Plasma generator 10: Housing | casing 12: Gas introduction part P: Plasmaization area | region 16: Guide part 18: Diffusion part 23,25,26: Hole 20: Discharge part 21: 1st discharge part 22: 2nd discharge part 27: Inclined discharge part
25 : Straight discharge section

Claims (10)

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 gas introduction part for introducing a plasma generating gas into the plasma region from a direction perpendicular to the longitudinal direction of the plasma region;
Connected to the plasmalized region, discharges the plasma generated in the plasmatized region, and is arranged along the longitudinal direction of the plasmatized region, and from a plurality of holes extending long in the direction in which the plasma generating gas flows And a discharge unit comprising: a plasma generating device. The gas introduction unit supplies the plasma generating gas uniformly to the plasma region in the longitudinal direction, and a plurality of holes arranged in a lattice shape to guide the plasma generating gas in a direction perpendicular to the longitudinal direction ; The plasma generating apparatus according to claim 1, further comprising a diffusion portion including a guide portion that is a wall surface of the hole .   3. The plasma generating apparatus according to claim 1, wherein a length of the hole in the discharge unit is a length at which no discharge is formed with respect to an object to be irradiated with the plasma.   4. The plasma generating apparatus according to claim 1, wherein a diameter of a tip portion of the hole of the discharge portion is 0.1 mm or more and 1 mm or less.   5. The plasma generation apparatus according to claim 1, wherein a length of the hole of the discharge unit is equal to or more than ½ of a distance between the pair of electrodes.   The plasma generating apparatus according to any one of claims 1 to 5, wherein the hole of the discharge portion includes an inclined portion that is inclined with respect to a direction perpendicular to the longitudinal direction.   The plasma generating apparatus according to any one of claims 1 to 6, wherein the pair of electrodes are spaced apart by a distance of 1 cm or more and 50 cm or less. The plasma generating apparatus according to any one of claims 1 to 7, wherein at least one of the pair of electrodes is provided with unevenness on a surface facing the other. 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 ≦ 200 and 3 ≦ σ ≦ 25. The plasma generator of any one of Claims 8.   10. The cross section perpendicular to the gas flow in the hole of the discharge part is a circle, an ellipse, a rectangle having a long side in a direction perpendicular to the arrangement direction, or a slit shape. 2. The plasma generator according to item 1.

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