JPH06108257A - Atmospheric pressure blow-off plasma reaction device - Google Patents

Abstract

PURPOSE:To realize plasma reaction with high efficiency by a simple structure by blowing-off a mixed gas of a rare gas or the like and a reaction gas from a blow-off port of an electrode metallic tube, impressing voltage and generating discharge plasma under atmospheric pressure. CONSTITUTION:A metallic tube 1 in which a projecting end part is provided on the end 3 of a blow-off port 2 is used as an electrode. A rare gas, an inert gas and/or air or a mixed gas 5 of the same and a reaction gas is blown-off from the blow-off port 2, and voltage is impressed to generate discharge plasma 6 under atmospheric pressure. The substrate 7 to be treated or a tubular body is arranged against the blow-off port 2. The electrode metallic tube is constituted of a cylindrical body, square tube body or planar tube body. In this way, stable plasma reaction can be realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an atmospheric pressure blowing type plasma reactor. For more details,
The present invention relates to an atmospheric pressure blowing type plasma reactor capable of treating various substances or materials by gas blowing under atmospheric pressure in any of a gas phase, a solid phase or a liquid phase, or causing reactions such as synthesis and decomposition. It is about.

[0002]

2. Description of the Related Art Conventionally, film attachment to an insulator such as plastic, glass, ceramics, etc., or hydrophilic
Surface treatment such as hydrophobic treatment has been performed by chemical treatment or low-pressure plasma treatment. However, in the surface treatment by the conventional method, generally, dangerous chemicals have been used, and there is a drawback that the treatment is very troublesome. Further, although the low-pressure plasma treatment has an advantage of realizing a good surface treatment, it usually has a problem that it must be performed under a low pressure of several Torr or less. This is because as the pressure is increased, the discharge begins to concentrate at about 100 Torr and shifts to sparks or arc discharge in the vicinity of atmospheric pressure, making it impossible to uniformly process the object to be processed. Therefore, the low-pressure plasma processing requires a vacuum exhaust system, which causes a large-scale apparatus and has a drawback of high cost.

Further, in the conventional low-pressure plasma treatment, it has been quite difficult to perform sufficient discharge treatment with high efficiency. On the other hand, the inventors of the present invention have used an inert gas mainly composed of He as a diluent gas to greatly dilute the reactive gas and maintain a total pressure in the vicinity of atmospheric pressure to generate a glow discharge. I have already proposed a method. In this method, since a stable glow discharge can be generated under atmospheric pressure, the vacuum exhaust system can be omitted,
This makes it possible to significantly reduce the cost of the processing device.

However, in the atmospheric pressure glow plasma reactor already proposed by the present inventors, since a needle electrode, a flat plate electrode covered with an insulator, or a curved electrode is used in combination, a reactive gas is used. Also, the rare gas must be introduced into the reaction zone from a supply section located at a position different from these electrodes, leaving room for improvement in terms of simplification of the apparatus and ease of control. Further, there is a problem that the size and shape of the portion to be treated are restricted, and surface treatment of an article or the like at an arbitrary position is not always easy.

Further, as an application of a plasma reactor to a gas phase reaction, an ozonizer and a plasma treatment device of waste gas are known, but in the case of these conventional devices, energy efficiency is high in comparison with the size of the device. There was a problem such as bad. The present invention has been made in view of the above circumstances, eliminates the drawbacks of the conventional method, achieves stable utilization of highly efficient discharge, and realizes a large amount of discharge treatment with a simple device. It is an object of the present invention to provide a new plasma reactor that can be used and a reaction method using the same.

[0006]

In order to solve the above-mentioned problems, the present invention uses a metal cylinder having a tip portion at the end of a blowout port as an electrode, and the metal pipe from the blowout port of this electrode metal line. A rare gas, an inert gas, and / or air, or a mixed gas of these and a reactive gas is blown to apply a voltage to generate discharge plasma under atmospheric pressure. A plasma reactor is provided.

The device of the present invention can use a metal cylinder having a tip portion of various shapes as an electrode, and the metal cylinder has a cylindrical shape, a rectangular cylinder shape, or a flat plate cylinder shape. It may have various shapes such as a single cylinder or multiple cylinders. The tip may also be formed by a notched inclined surface at the edge, or the peripheral edge may be formed by a tooth-shaped body or a needle-shaped body, or by disposing a plurality of loop-shaped wires. You may.

The plasma reaction can be applied in various ways, and a thin film is formed on the surface of the substrate facing the outlet.
The apparatus of the present invention can be applied to an appropriate object such as surface modification processing, gas compound synthesis, gas decomposition and the like. This device realizes highly efficient plasma reaction at extremely low cost. Therefore, for example, there is no need for an expensive device such as a long cylinder in a conventional ozonizer, which keeps the gap 1 mm uniform. It is advantageously applied to various synthetic and decomposition reactions.

To further explain with reference to the drawings, as shown in FIG. 1, for example, a metal tube (1) is used as an electrode for glow discharge, and an edge of an outlet (2) of the metal tube (1) is used. Form an inclined surface with (3) cut out,
It can be a tip. For atmospheric pressure blow type glow plasma discharge, for example, a voltage is applied to the electrode of the metal tube (1) by a power source (4), and a gas (5) is applied to the conduit of the metal tube (1). Is introduced and blown out from the outlet (2). At the same time as this blowout, a jet-like atmospheric pressure glow plasma (6) is generated outside the conduit.

The surface of the substrate to be treated (7) is treated by this atmospheric pressure glow plasma (6), and film formation or surface modification is performed. Of course, the metal tube (1) may be carbon if it is conductive,
Although the type is not particularly limited, heat resistant materials such as stainless steel, tungsten, molybdenum, etc. are preferable,
When cooling the outside of the pipe with a water cooling jacket or the like, a copper pipe or the like can also be used. The inner diameter and the outer diameter are not limited, and a large-diameter metal tube having an inner diameter of more than 10 cm or a thin tube having a diameter of 0.1 mm or less may be used.

The distance (l) between the metal tube (1) as the electrode and the substrate (7) can be set appropriately depending on the kind of gas, its blowing speed, the state of glow plasma, etc., and is, for example, about 0.1 mm. To 100 mm or more. Further, in order to prevent the external creeping discharge of the metal tube (1), its peripheral surface may be covered with an insulator (8) as shown in FIG.

The power source (4) connected to such a metal tube (1) is also not particularly limited, and can have a low frequency of several KHz to a high frequency of several tens KHz or 13.56 MHz. It should be noted that the discharge is generated in the stray capacitance corresponding to the ground electrode, that is, between the counter electrode and the high voltage electrode. In order to prevent the generation of arc, it is also effective to put the substrate (7) on a dielectric. It is also possible to prevent generation of an arc by adding a capacitor having a small capacity in series between the high voltage electrode and the power supply.

The gas (5) introduced into the metal tube (1)
When a reactive gas is used as, an inorganic compound such as oxygen or ammonia, a fluorinated ethylene-based hydrocarbon such as C ₂ F ₄ or C ₃ F ₆ , a fluorinated paraffin-based hydrocarbon such as CF ₄ or C ₂ F ₆ , Or any organic compound such as a chain hydrocarbon having a side chain containing a fluorine atom, or a hydrocarbon having or not having a functional group such as a fluorinated aromatic hydrocarbon, and further NO _x , SO _x, etc. Waste gas contained therein can be used. Such a reactive gas is diluted with a rare gas such as He or Ar, an inert gas such as N ₂ or air to prepare a mixed gas. In each case, the reactive gas is preferably overdiluted and the total pressure of gas (5) is around 1 atmosphere. From the viewpoint of plasma stabilization, it is also advantageous to mix hydrocarbon compounds such as ketones, methane, and ethane. In this case, the mixing ratio should be on the order of ppm to several percent. Glow plasma is stably generated and can be effectively used as another kind of discharge depending on the selection of conditions. Of course, when the base body (7) is used, it can be made into various shapes such as rubber, plastic, glass, ceramics, etc., and various shapes such as bulk, plate, fibrous, and powder. , Film, etc. It is not necessary to use such a substrate (7) for waste gas treatment or gas phase synthesis.

To further exemplify the metal cylinder as the electrode, in the device of the present invention, as shown in FIG. 3, even if the inner periphery of the end edge (3) of the metal tube (1) has an inclined surface. Alternatively, as illustrated in FIGS. 4 and 5, the tooth-like body (9) or the needle-like body (10) may be arranged at the peripheral edge.
In any case, the electric field is made to concentrate on these tips, that is, the portions having a small radius of curvature. A suitable range of the radius of curvature is determined depending on the type of gas.

As shown in FIG. 6 (a), a plurality of loop-shaped wires (11) may be arranged on the edge (3). In this case, the suitable thickness is determined by the gas used. Therefore, the discharge can be controlled by the thickness of the wire (11). For example, argon (A
In case of r), about 0.3 mm, N ₂ , and in case of air, about 0.02
About 5mm is considered. Further, as shown in FIG. 6B, a wire having the same thickness can be filled in the pipe leading to the outlet with a constant bulk density. Furthermore, a dielectric solid cylinder such as glass may be filled with a metal wire coated with an insulator. These coated wires will form the tip of the present invention.

At this time, in order to supply energy from the high voltage power source, as shown in FIG.
0), the metal tube (111) is coated with an insulator such as glass (112)
It may be arranged in the cylinder. The thickness of the coating wire (110) is the same as described above. Since this coating wire (110) is coated, even if it comes into contact with the metal tube (111), its entire length effectively works as an electrode.

Such various types of tips can be adopted in either a single metal cylinder or in a multiple structure as illustrated in FIG. By using multiple structure,
For example, a gas (A) that is hard to discharge is blown into the center,
By blowing out the gas (B) that is more likely to be discharged to the outside, it is possible to further improve the discharge efficiency even for a gas that is difficult to be discharged.

An apparatus as shown in FIG. 8 may be used for fine processing such as surface etching of the substrate (7). Further, in the waste gas treatment or the gas phase synthesis, as illustrated in FIG. 9, the electrode metal cylinder (14) is opposed to the lower cylinder (13) covered or not covered with the dielectric (12). You may do it.

[0019]

EXAMPLES Examples will be shown below to describe the apparatus of the present invention in more detail. Example 1 Surface treatment of polymer film Figure 3 shows the tip of a stainless steel cylinder with an outer diameter of 3 mm and an inner diameter of 2 mm.
A discharge tube is sharply polished as in. A stainless steel plate having a thickness of 5 mm was used as the lower electrode, and a soft polyethylene film having a thickness of 40 μm was attached as a sample on the stainless steel plate. The gap between the tip of the discharge tube and the lower electrode was 20 mm. The circumference of the discharge tube is open to the atmosphere.

Argon from the upper end into the discharge tube at 1000 cm ^-1 mi
When a high-frequency high voltage with a frequency of 3 kHz is applied at a flow rate of n ^−1, a sharp flame-like plasma jet is blown out from the nozzle at the tip. This is because discharge breakdown occurs first at the tip with an extremely small radius of curvature, and the generated Ar ions and excited Ar
This is because the atoms become seeds and the atmospheric pressure glow discharge occurs along the Ar flow.

The surface of the sample polyethylene placed at the tip of the jet stream is exposed to a stream of excited argon atoms generated in the plasma, causing a chemical change. However, since the gas temperature in the jet stream remains low, even soft polyethylene having a low melting point does not melt. Table 1 shows contact angles of water droplets on the surface of polyethylene treated by the above method.

[0022]

[Table 1]

Example 2 Surface Treatment of Polymer Film The lower electrode in Example 1 was removed, and only the polyethylene film was supported by an insulator support rod and stretched perpendicularly to the blowing electrode. 20 from the sample film surface to the discharge tube tip
A plasma jet was sprayed on the surface at a distance of mm.

Table 2 shows the contact angle of water droplets on the surface of the treated sample.

[0025]

[Table 2]

Several seconds to 10 together with the first and second embodiments
The contact angle of the surface has dropped extremely within a very short time such as seconds. Originally, it has a high water-repellency, so the polyethylene surface lacking the ability to bond with various adhesives
By the above method, the active surface can be easily modified to be hydrophilic, that is, to be adhered. In addition, in Example 2,
Since it is possible to emit a low-temperature plasma jet without a counter electrode, the discharge tube can be moved up and down, left and right, or by using a discharge tube with a different diameter, regardless of the size and shape of the object to be processed or the presence or absence of the lower electrode. It has been shown that surface treatment can be performed with any shape and width, which is an extremely useful method. It goes without saying that the opposite electrode in this case is the earth potential placed at infinity, and is the discharge through the stray capacitance of the discharge tube.

At this time, the surface to be treated discolors whitish for a long time of 20 seconds or more, suggesting a chemical change such as oxidation. Metastable excited atoms, which are high electron energy states of Ar, are generated in the plasma and blown onto the surface, resulting in the breaking of the polymer chains on the surface. It seems that a sexually reactive group has arisen.

Since only the electronic state of the metastable atom is in a highly excited state and the gas temperature is around room temperature, the metastable atom is chemically excited without causing a phenomenon such as melting of the surface to be treated, which is likely to occur in high temperature plasma jet treatment. Only change can be made. Example 3 Thin-Film Forming Method Using the same apparatus as in Example 1, a gas to be polymerized is mixed with a carrier gas such as Ar and blown out, dissociated in a plasma jet of the carrier gas, and the sample substrate placed on the other electrode. It was formed as a polymerized film on top.

As a sample substrate, a mirror-polished silicon wafer having a thickness of 0.5 mm was placed on a stainless electrode and used. C ₂ F ₄ was used as the polymerizable gas, and the experimental conditions were as follows. Ar flow rate: 2000 cm ³ min ^-1 C ₂ F ₄ flow rate: 10 cm ³ min ^-1 Discharge output 10 W, frequency 3000 Hz, distance between electrodes 10 mm Discharge time 10 minutes As a result, the surface area of the sample substrate sprayed with the plasma jet is approximately the diameter. It was covered by a disk-shaped transparent thin film of 7 mm and a thickness of 1 μm. The transmitted infrared spectrum of this powder is shown in FIG.

From FIG. 10, it can be seen that a polymer film similar to polytetrafluoroethylene is clearly formed on the surface of the silicon substrate. Further, since this film was inactive to any solvent, it is considered to be a film having a three-dimensional structure with advanced cross-linking. Example 4 Combustion Waste Gas Decomposition Treatment Model A mixed gas containing NO ₂ and NO of 1000 ppm as waste gas was mixed in N ₂ carrier gas, blown out with N ₂ plasma, decomposed, and then discharged downstream from the plasma. Sampling was performed using a 10 mm glass tube and analyzed by gas chromatography. The experimental conditions are listed below.

N ₂ flow rate: 1000 cm ³ min ^-1 synthetic waste gas flow rate: 50 cm ³ min ^-1 Discharge power up to 50 W, frequency 50 kHz As a result, the correlation between the discharge power and the concentration of each gas shown in FIG. 11 was obtained. . It should be noted that this is a value converted as waste gas excluding the carrier gas.

As can be seen from this figure, at the output power of 40 W or more, both NO ₂ and NO mixed in advance have decreased to 1/100 of the initial concentration, and they are almost completely decomposed in the plasma to generate N ₂ Has become O ₂ . As can be seen from this, it is an extremely effective method for treating combustion waste gas.

[0033]

As described above in detail, the present invention realizes a highly efficient and stable plasma reaction with a simple structure.

[Brief description of drawings]

[Figure 1]

[Fig. 2]

[Figure 3]

[Figure 4]

[Figure 5]

[Figure 6]

[Figure 7]

[Figure 8]

FIG. 9 is a configuration diagram showing an example of the apparatus of the present invention.

FIG. 10 is a spectrum diagram of wavelength and absorption.

FIG. 11 is a correlation diagram between discharge power and concentration in waste gas.

[Explanation of symbols]

 1 Metal Tube 2 Blowout Port 3 Edge 4 Power 5 Gas 6 Atmospheric Pressure Glow Plasma 7 Base Material 8 Insulator 9 Tooth-like Body 10 Needle-like Body 11 Wire 12 Dielectric 13 Lower Cylinder 14 Electrode Metal Cylinder

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[Procedure amendment]

[Submission date] December 12, 1991

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 11

[Correction method] Change

[Correction content]

FIG. 11

[Procedure amendment]

[Submission date] September 24, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a device of the present invention.

FIG. 2 is a sectional view showing an example of a device of the present invention.

FIG. 3 is a cross-sectional view showing an example of the device of the present invention.

FIG. 4 is a sectional view showing an example of a device of the present invention.

FIG. 5 is a cross-sectional view showing an example of the device of the present invention.

FIG. 6 is a cross-sectional view showing an example of the device of the present invention.

FIG. 7 is a cross-sectional view showing an example of the device of the present invention.

FIG. 8 is a sectional view showing an example of the device of the present invention.

FIG. 9 is a configuration diagram showing an example of a device of the present invention.

FIG. 10 is a spectrum diagram of wavelength and absorption.

FIG. 11 is a correlation diagram between discharge power and concentration in waste gas.

[Explanation of Codes] 1 Metal tube 2 Blowout port 3 Edge 4 Power supply 5 Gas 6 Atmospheric pressure glow plasma 7 Base material 8 Insulator 9 Tooth-like body 10 Needle-like body 11 Wire 12 Dielectric body 13 Lower cylinder 14 Electrode metal cylinder

Claims (9)

[Claims] 1. A metal cylinder having a tip portion at the end of the blowout port is used as an electrode, and a rare gas is discharged from the blowout port of the electrode metal barrel.
An atmospheric pressure blowing type plasma reaction apparatus, characterized in that an inert gas and / or air or a mixed gas of these and a reactive gas is blown to apply a voltage to generate discharge plasma under atmospheric pressure. 2. The atmospheric pressure type plasma reactor according to claim 1, wherein an oxygen-containing compound and other reactive gases are mixed with a rare gas, an inert gas and / or air. 3. The plasma reactor according to claim 1, wherein the substrate to be treated or the cylindrical body is arranged so as to face the outlet. 4. The plasma reactor according to claim 1, 2 or 3, wherein the electrode metal cylinder is formed of a cylindrical body, a rectangular cylinder body, or a flat plate cylinder body. 5. The plasma reactor according to claim 1, 2, 3 or 4, wherein the electrode metal cylinder has a multiple structure. 6. The plasma reactor according to claim 1, wherein the tip portion is formed by a notched inclined surface at the edge. 7. The plasma reactor according to claim 1, wherein the tip portion is formed of a tooth-shaped body or a needle-shaped body of the peripheral edge. 8. The plasma reactor according to claim 1, wherein the tip portion is formed by arranging a plurality of loop wires on the peripheral edge. 9. A plasma reaction method of atmospheric pressure blowing type, characterized in that a plasma reaction is carried out by the apparatus of any one of claims 1, 2, 3, 4, 5, 6, 7 or 8.