KR100817038B1 - Methods and apparatus for treating the surface of materials by atmospheric pressure plasma - Google Patents

Abstract

The present invention relates to an atmospheric pressure plasma generating apparatus for surface treatment of materials and a surface treatment method using the same. The present invention relates to a high treatment effect and improved applicability to various to-be-processed objects and materials, and to enable economical device implementation and operation. Therefore, it is possible to apply to a wider area.

In the present invention, by injecting a low-cost gas such as air, nitrogen, oxygen into the plasma generating region through a gas injection port of the plasma generator, plasma is generated by applying a voltage between a pin or cylindrical power electrode and a cylindrical ground electrode. The generated plasma is sprayed to the outside of the plasma generating apparatus through the plasma transfer passage and the spray nozzle, and the surface of the metal or the non-metallic workpiece is treated by the injected plasma to improve the surface properties.

Description

Atmospheric pressure plasma generator for surface treatment of materials and surface treatment method using the same {METHODS AND APPARATUS FOR TREATING THE SURFACE OF MATERIALS BY ATMOSPHERIC PRESSURE PLASMA}

1 is a diagram schematically illustrating an atmospheric pressure plasma generating apparatus without an injection nozzle.

2 is a view schematically showing an atmospheric pressure plasma generating apparatus having an injection nozzle.

FIG. 3 is a schematic view of an atmospheric pressure plasma generator connected in parallel for processing area expansion.

<Description of reference numerals for main parts of the drawings>

10: atmospheric pressure plasma generator

14: Insulator 16: Grounding electrode

18: power electrode 20: gas inlet

22: Plasma feed passage 24: Injection nozzle

26: plasma 28: plasma power supply

30: To-be-processed object

The present invention relates to an atmospheric pressure plasma generating apparatus for surface treatment of materials and a surface treatment method using the same. The present invention relates to a high treatment effect and improved applicability to various to-be-processed objects and materials, and to enable economical device implementation and operation. Therefore, it is possible to apply to a wider area.

In general, the surface treatment technology of a material using plasma refers to a technology of generating plasma under atmospheric pressure or vacuum, and modifying, cleaning, etching, and depositing a surface of an object by using the generated plasma. In particular, the surface treatment technology using plasma can replace the conventional wet treatment process as an environmentally friendly surface treatment technique of a dry treatment method. In addition, unlike the wet treatment method, it is possible to obtain desired characteristics by changing only the epidermal layer that needs to be modified without changing the inherent bulk characteristics of the workpiece.

However, the surface treatment technology using a vacuum plasma requires a large and expensive vacuum equipment, is limited in the size of the object to be processed and has a disadvantage in that it is difficult to in-line because of a batch type process. Atmospheric plasma technology is being researched as a new surface treatment technology that can be in-line, simplifies equipment, and can reduce operating costs.

Conventional surface treatment techniques using atmospheric plasma include dielectric barrier discharge, corona discharge, atmospheric glow discharge, and the like.

Dielectric barrier discharge is widely used in the field of papermaking, printing, packaging, etc. by installing a dielectric barrier on one side or both sides of two paired electrodes to prevent arc generation and generate plasma in a relatively large area. Corona discharge uses at least one of the two electrodes in the form of needles, wires, or pins to take advantage of the electric field concentration effect, and to suppress arcing using a high voltage power source having a large internal resistance and to generate a low current plasma. It is used. Dielectric barrier discharges and corona discharges have the advantage of being able to operate inexpensively using air as the discharge gas.However, due to the low plasma density, the treatment effect is inferior. There are disadvantages in that it is unsuitable for a three-dimensional workpiece that is not in the form of a film. In addition, spots are formed during treatment in the metallic workpiece, which makes it impossible to uniformly treat and damages the workpiece.

K. Kogoma et al suggest that 1) helium is used as the discharge gas, 2) there is a dielectric barrier on at least one of the two electrodes, and 3) stable glow plasma is generated under atmospheric pressure when using high frequency power supplies (J. Phys. D. 21 (1988). R. F. Hicks et al. Describe an injection-type atmospheric plasma generator that can be applied to a three-dimensional object by improving the method of K. Kogoma (Appl. Phys. Lett. 76 (2000)). However, since this method requires a high frequency power source and uses expensive helium gas for plasma generation, there is a disadvantage in that the price and operating cost of the device are increased, which makes it difficult to be applied to a wide range of industrial fields.

The present invention has been proposed in view of the above problems, and an object of the present invention is to show a high treatment effect under atmospheric pressure without the need for vacuum equipment, and at the same time suitable for the surface treatment of materials having various shapes and materials, and To provide a way.

It is a further object of the present invention to provide an apparatus and method for surface treatment of materials using simple yet inexpensive power supplies and reactive gases.

Atmospheric pressure plasma generating apparatus for achieving the above object is injecting a low-cost gas such as air, nitrogen, oxygen, etc. through the gas injection port and 100KHz or less between the pin or cylindrical power electrode and the cylindrical ground electrode More preferably, after generating a plasma by the discharge between the two electrodes by applying a high voltage of a commercial frequency, it is characterized in that the generated plasma is sprayed to the outside through the plasma transfer passage by the flow of the injected gas. Since there is no insulator in the discharge region between the power electrode and the ground electrode, a high current plasma is generated, and the density of active species in the plasma is also increased, thereby improving the treatment characteristics by the plasma.

In this case, the plasma generated between the two electrodes has a narrow conductive channel at a high temperature in the discharge region, and spots are formed on the electrodes to erode the electrodes by local heating as well as nonuniformity of the plasma. Therefore, it is necessary to remove and alleviate this phenomenon. For stability of the plasma, there is a method of forming turbulence on the gas flow or increasing diffusion of the plasma. Concentration of locally generated charges can be mitigated by turbulence or diffusion to form stable plasma in a wider area. This turbulence or diffusion can be achieved by increasing the flow rate U of the injected gas or by reducing the size L of the discharge region. Depending on the type of gas and the shape of the discharge region, there may be differences, but the rough plasma stable conditions

U / L ≥ 10 ³ [s ^-1 ]

It may be described as. In FIG. 1, the size L of the discharge region can be considered as the shortest distance between the power electrode 18 and the ground electrode 16. From this, when the power electrode and the ground electrode are cylindrical and have a diameter of about several mm, the required flow rate is more than several tens of liters per liter (liter per minute). In addition to the flow rate or the size of the discharge region, the direction in which the gas inlet is directed away from the central axis may be improved by allowing the gas flow to form a vortex in the plasma generation region.

It is preferable that the power electrode and the ground electrode are kept coaxial with the insulator and are positioned coaxially. The proper distance between the two electrodes is appropriate depending on the power supply voltage and gas flow rate, but several mm to several tens of mm is appropriate. The shorter the distance, the smaller the amount of power that can be put in, and the longer the distance, the higher the voltage required and the more difficult plasma is generated. The power electrode and the ground electrode may have a structure capable of adjusting an interval in the axial direction for controlling plasma characteristics. Insulators can be made of materials that are highly resistant to heat in case of thermal damage. The power electrode and the ground electrode may use copper and its alloys, aluminum and its alloys, stainless steel and the like, but may also use tungsten, molybdenum, zirconium, tantalum, or the like or alloys or compounds thereof resistant to erosion.

Plasma transport passage cools the relatively high temperature plasma generated between the two electrodes and delivers the object to the workpiece at a high flow rate, and separates the workpiece from the power electrode to form spots on the workpiece. Serves to prevent this from happening. The plasma transfer passage may be configured separately using an insulator, but may be used by extending the ground electrode. The diameter of the plasma transport passage is suitable for several mm and the length of several to several tens of millimeters. If the length of the plasma transport passage is too short, the ejected plasma temperature is relatively high and there is a possibility that spots may occur in the case of a metal workpiece, and if it is too long, the plasma treatment effect may be reduced.

When the diameter of the plasma transfer passage is small and the treatment area is insufficient, or when a plasma form other than a cylindrical shape is required, the injection nozzle unit may be processed at the end of the transfer passage or a separate injection nozzle may be mounted. From this, in addition to the narrow cylindrical plasma, various types of plasma spraying such as-ruler and + ruler are possible.

The gas inlet is located at the insulator or the ground electrode and can be used at one or more places. The direction of the gas inlet may be arranged in a vertical direction or at an angle in the axial direction. The radial direction may be configured to face the central axis, but may also be configured to deviate from the central axis for vortex formation as described above.

The power for plasma generation may be used by using a high voltage AC power supply of 100KHz or less, or more preferably, boosting up to 1kV to 100kV using a transformer using a commercially available frequency of 100 to 240V.

As the injection gas, air, nitrogen, oxygen, or a mixture thereof may be used, thereby enabling inexpensive operation. When active species other than nitrogen or oxygen are required for effective plasma treatment, a mixture of additional gases or liquids may be injected in addition to the air, nitrogen, and oxygen. Separate gases or liquids are well-known fluorine or chlorine-containing gases such as helium, argon and CF4, SF6, NF3, CCl4, hydrogen, ammonia and the like, liquid organics, monomers, oligomers, polymers, etc. It may include.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 illustrates the inside of an atmospheric pressure plasma generating apparatus without an injection nozzle according to an exemplary embodiment of the present invention.

As shown in FIG. 1, the atmospheric pressure plasma generating apparatus 10 for surface treatment of a material according to an exemplary embodiment of the present invention may include a pin type power electrode 18, a cylindrical ground electrode 16, and an insulator ( 14), a gas injection port 20, a plasma transfer passage 22, and a commercial frequency high voltage AC power supply 28.

As shown in FIG. 1, the atmospheric pressure plasma generator 10 has a high flow rate (several lpm) of air, nitrogen, oxygen, etc. injected into the plasma generator through the gas inlet 20 and the power electrode 18. And plasma are generated by the discharge between the ground electrode 16 and the ground electrode 16. The generated plasma is injected at high speed to the outside of the generator through the plasma transfer passage 22. Surface treatment of the object 30 is performed by using the plasma 26 injected at a high speed to the outside.

The power electrode 18 is separated from and fixed to the ground electrode 16 by the insulator 14 and is made of tungsten which is resistant to heat and corrosion.

The gas injection holes 20 are arranged at regular intervals on the side surfaces of the ground electrode 16, and the generated plasma is injected to the outside through the plasma transfer passage 22. The plasma transfer passage 22 has a structure having a smaller diameter than the plasma generation unit for high-speed injection of plasma generated inside the generator.

The injection length by visual confirmation of the plasma 26 injected through the plasma transfer passage 22 has a value of 10 to 50 mm depending on the gas used, the flow rate, and the applied voltage. It can be applied to the workpiece 30 of the shape.

The plasma 26 sprayed to the outside is maintained at a temperature of less than 60 degrees so that the surface treatment can be performed without thermal damage even when the object is a polymer.

Arc and spots do not occur on the surface of the object to be processed even if the object 30 is a non-metal as well as a metal, and uniform processing is possible.

The power supply 28 for plasma generation boosts a commercially available frequency of 60 Hz and 220 V with a transformer to generate a high voltage of several kV and is applied between the two electrodes. The use of such an AC power supply makes it possible to manufacture a power supply device at a lower cost than a plasma generator using a high frequency power supply device.

Figure 2 shows the inside of the atmospheric pressure plasma generating apparatus having an injection nozzle according to a second embodiment of the present invention.

As shown in FIG. 2, an injection nozzle 24 is mounted at the outlet of the plasma transfer passage 22 to expand the processing width of the injected plasma 26.

The spray nozzle 24 is in the form of a hollow hemisphere and has a -shaped slit to form a fan-shaped plasma in a wide area.

3 is a configuration diagram of an atmospheric pressure plasma generator connected in parallel to expand a treatment area according to a third exemplary embodiment of the present invention.

As illustrated in FIG. 3, three atmospheric pressure plasma generating apparatuses 10 may be connected in parallel to expand a treatment area.

(Example)

It was applied to surface modification of polypropylene using the plasma generator of FIG. 2. As the discharge gas, 40lpm of nitrogen and 20lpm of air were used, respectively. The degree of adhesion improvement of polypropylene after atmospheric plasma treatment was measured by the change in shear strength according to ASTM D3163-96, and was bonded using 3M polyurethane adhesive (DP605-NS) after plasma treatment. In order to test the adhesion, polypropylene having a thickness of 5 mm was cut into a width of 25 mm and a length of 110 mm to prepare a specimen for plasma surface treatment. The shear strength of the polypropylene adhesive surface before treatment was significantly increased from 0.182 MPa to 10.5 MPa after 8 seconds of nitrogen plasma treatment.

Figure 1. Variation of shear strength of polypropylene bonding surface with plasma treatment time

According to the atmospheric pressure plasma generating apparatus and the surface treatment method by the atmospheric pressure plasma according to the present invention as described above, it shows a high treatment effect for the workpiece having a variety of shapes and materials of film form, three-dimensional form, metal, non-metal Economical treatment is possible by using electric power and gas such as air, nitrogen and oxygen.

Claims (18)

Atmospheric low temperature plasma generator, A plasma power supply 28 having a frequency of commercial frequency (60 Hz) to 100 kHz or less; A power electrode 18 and a ground electrode 16 to which the plasma power supply 28 is applied; An insulator (14) inserted between the power electrode and the ground electrode for electrical insulation between the power electrode (18) and the ground electrode (16); One or more gas inlets 20 for injecting gas between the power electrode 18 and the ground electrode 16 to generate the plasma; And a plasma transport passage 22 for injecting plasma generated between the power electrode 18 and the ground electrode 16 to the outside of the plasma generator. And a flow rate of the gas injected through the gas inlet is 10 ³ times or more (U / L ≥ 10 ³ [s ⁻¹ ]) of the distance between the power electrode and the ground electrode. The atmospheric pressure low-temperature plasma generating device according to claim 1, wherein the plasma power supply has a frequency of 100 kHz or less. According to claim 1, wherein the plasma power source atmospheric pressure low temperature plasma generator, characterized in that to boost the power using a commercial frequency 100 ~ 240V power supply using a transformer. The atmospheric pressure low-temperature plasma generating device according to claim 1, wherein the voltage of the plasma power supply is 1 kV to 100 kV. The atmospheric pressure low-temperature plasma generator according to claim 1, wherein the power electrode and the ground electrode are each made of one of copper, an alloy of copper, aluminum, an aluminum alloy, and stainless steel. According to claim 1, wherein the power electrode and the ground electrode is tungsten, molybdenum, zirconium, tantalum and tungsten alloy, molybdenum alloy, zirconium alloy, tantalum alloy,  An atmospheric pressure low temperature plasma generator comprising one of a tungsten compound, a molybdenum compound, a zirconium compound, and a tantalum compound. delete The atmospheric pressure low temperature plasma generating apparatus of claim 1, wherein a distance between the power electrode and the ground electrode is adjustable. The atmospheric pressure cold plasma generator of claim 1, wherein a direction toward the end of the gas injection port is configured to deviate from a central axis of the power electrode to form a vortex. The atmospheric pressure cold plasma generating device according to claim 1, wherein an injection nozzle having a shape different from a cross section of the end of the transfer passage for expanding and changing the shape of the plasma is provided at the end of the plasma transfer passage. 11. The atmospheric pressure low temperature plasma generator as claimed in claim 10, wherein the nozzle is a separate spray nozzle which is detachable. As a surface treatment method of a material using atmospheric plasma, Providing a power electrode and a ground electrode connected to the plasma power source, Injecting a high speed gas for stable plasma generation between the power electrode and the ground electrode; Generating a plasma by applying a voltage to the power electrode and the ground electrode; Injecting the generated plasma to the outside through a transfer passage to react the plasma on the surface of the workpiece; Surface treatment method of the material using an atmospheric pressure cold plasma comprising a. The method of claim 12, wherein the gas is injected at a high speed injecting the gas at a high speed of 10 ³ times or more the distance between the power electrode and the ground electrode. The method of claim 12, wherein the gas to be injected is any one of air, nitrogen, oxygen, and mixtures thereof. Helium, argon and CF4, SF6, NF3, CCl4, hydrogen, ammonia and liquid organics, monomers, oligomers, polymers in addition to the gas of claim 14 to increase the treatment effect Method for treating the surface of the material using an atmospheric pressure cold plasma, characterized in that the selected and mixed. 13. The method of claim 12, wherein the workpiece has any shape including a film and a three-dimensional shape and includes both metal and nonmetal. 13. The method of claim 12, further comprising providing various types of spray nozzles at the end of the plasma transfer passage according to the shape and size of the workpiece. 18. The method of any one of claims 12 to 17, further comprising providing a plurality of atmospheric pressure plasma generators in parallel according to the shape and size of the workpiece.

Images