JPH10195665A - Electric discharge plasma treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface treating method of a base material using uniform electric discharge plasma generated under a near atmospheric pressure regardless of a kind of an atmospheric gas. SOLUTION: The uniform electrostatic discharge plasma is obtained to be used for the treatment of the base material by generating electric discharge of 0.2-300mA/cm<2> discharge current density between a pair of electrodes 81 and 82 opposed to each other under the near atmospheric pressure, installing a solid dielectric 85 at this time at least on one of a pair of the electrodes and impressing pulse like voltage between the electrodes so that glow discharge is made dominant in the optional atmospheric gas under the near atmospheric pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating a substrate by discharge plasma under a pressure close to atmospheric pressure.

[0002]

2. Description of the Related Art Conventionally, a method of modifying a surface using plasma generated by glow discharge under low pressure conditions has been put to practical use.

[0003] However, processing under low pressure conditions requires a vacuum vessel and a vacuum apparatus, and it is necessary to break and evacuate the vacuum vessel every time the processing is performed in a batch. Is disadvantageous and is applied only to expensive processed articles such as electronic components.

[0004] In view of the above, there has been proposed a method of generating discharge plasma under a pressure near the atmospheric pressure. For example, Japanese Patent Publication No. 2-48626 discloses a method of performing treatment using plasma generated in a mixed atmosphere of helium and ketone near atmospheric pressure, and an atmosphere near atmospheric pressure composed of argon and helium and / or acetone. A method of performing processing using the plasma generated below is disclosed in Japanese Patent Application Laid-Open No. 4-74525.

[0005]

However, in each of the above-mentioned proposed methods, the processing is performed in an atmosphere containing a specific gas such as helium or ketones such as acetone. There is a problem of being limited.

Helium is expensive and therefore disadvantageous for industrial use. When a gas containing an organic compound such as a ketone is contained, the organic compound itself often reacts with the object to be treated. There is also a problem that desired surface modification cannot be performed.

The present invention has been made in view of such circumstances, and a method capable of generating a uniform discharge plasma under a pressure close to the atmospheric pressure regardless of the type of an atmospheric gas, and a method using the method. It is intended to provide a surface treatment method using generated plasma.

[0008]

According to the discharge plasma treatment method of the present invention, a voltage is applied between a pair of electrodes facing each other in a gas atmosphere, and the surface of the substrate is treated by discharge plasma generated in the gas. The method is characterized in that the pressure of the atmosphere gas is near the atmospheric pressure and the discharge current density between the electrodes is 0.2 to 300 mA / cm ² .

Here, in the discharge plasma processing method of the present invention, it is preferable to apply a pulse-like voltage between the pair of electrodes because the degree of freedom of the atmospheric gas to be used can be increased.

The pulse electric field created between the pair of electrodes by the application of the pulse-like voltage has a rise time and a fall time both in the range of 40 ns to 100 μs, and the intensity of the pulse electric field, that is, It is preferable that the maximum electric field strength of the pulse electric field be in the range of 1 to 100 kV / cm.

In the present invention, it is particularly preferable that the frequency of the pulse electric field is 1 kHz to 100 kHz, and the time for forming one pulse electric field is 1 μs to 1000 μs.

In the discharge plasma processing method of the present invention,
The pressure near the atmospheric pressure refers to a pressure of 100 to 800 Torr, and particularly preferably a pressure range of 700 to 780 Torr that facilitates pressure adjustment and facilitates device configuration.

The term “discharge current density between electrodes” in the present invention refers to a value obtained by dividing a value of a current flowing between electrodes by discharge by an area in a direction orthogonal to a direction of current flow in a discharge space. When a flat type is used, it corresponds to a value obtained by dividing the above current value by its facing area.
When a pulsed electric field is formed between the electrodes, a pulsed current flows. In this case, the maximum value of the pulse current, that is, a value obtained by dividing the peak-to-peak value by the above-mentioned area.

In the surface treatment method of the present invention, a solid dielectric is provided on at least one of the opposite surfaces of the pair of electrodes, and the solid dielectric provided on the opposite surface of the one electrode and the other electrode are connected to each other. It is preferable that the substrate is disposed between the solid dielectrics disposed on the opposing surfaces of the pair of electrodes, or between the solid dielectrics, to perform the treatment.

In the discharge plasma processing method of the present invention, the atmosphere gas used can be argon and / or nitrogen. According to the present inventors' research, the glow discharge under a pressure close to the atmospheric pressure, as shown below, shows that the discharge current density reflects the plasma density and is a value that affects the surface treatment effect. As a result of locating, under pressure near atmospheric pressure,
The discharge current density between the electrodes is 0.2 to 300 mA /
In the range of cm ² , uniform discharge plasma can be generated and a good surface treatment result can be obtained.

In general, the electron density in plasma, that is, the plasma density, is measured by a probe method or an electromagnetic wave method. However, at pressures near atmospheric pressure, the discharge between the electrodes is inherently susceptible to arc discharge. Therefore, the probe method in which the probe is inserted into the plasma causes an arc current to flow through the probe, resulting in accurate measurement. Can not. In addition, the electromagnetic wave method based on emission spectroscopy, laser absorption analysis, or the like is difficult to analyze because the information obtained varies depending on the gas type.

In a glow discharge at a pressure close to the atmospheric pressure, the gas molecule density is larger than that in a low gas pressure discharge, so that the lifetime from ionization to recombination is short, and the mean free path of electrons is short. Therefore, there is a feature that the glow discharge space is limited to the space between the electrodes. Therefore, electrons in the plasma are directly converted into a current value through the electrode, and the electron density (plasma density) is considered to be a value reflecting the discharge current density. This can be rephrased that the electrode functions as a kind of probe.

FIG. 1 shows a discharge plasma generator used by the present inventors and a measurement circuit diagram used for measuring a discharge voltage and a discharge current thereof. In this discharge plasma generator, a pulse power source 3 is provided between a pair of parallel plate-type electrodes 1 and 2.
By applying a pulse-like voltage in the order of kV from above, a pulsed electric field is formed between the electrodes 1 and 2, and the solid dielectric 4 is placed on the surface facing the one electrode 2.
Then, a resistor 5 is connected in series between one electrode 2 and the ground potential, and both ends of the resistor 5 are connected to an oscilloscope 7 via a BNC terminal 6 to measure a voltage value at both ends of the resistor 5. The resistance value of the resistor 5 was used to convert to a discharge current. In addition, the discharge voltage was attenuated to 1/1000 by the high voltage probe 8 with the potential of the electrode 1, and then the BNC was applied.
The measurement was performed by measuring the potential difference from the ground potential using the terminals 9 to the oscilloscope 7.

In this measurement circuit, the discharge current caused by the pulsed electric field repeats energization / interruption at high speed.
The oscilloscope 7 used for the measurement was a high-frequency oscilloscope capable of measuring on the order of nanoseconds corresponding to the rising speed of the pulse, specifically, an oscilloscope DS-9122 manufactured by Iwasaki Communication Co., Ltd. The high voltage probe 8 used for attenuating the discharge voltage is a high voltage probe SK manufactured by Iwasaki Tsushin Co., Ltd.
-301 HV. The measurement result is illustrated in FIG. FIG.
, Waveform 1 is a discharge voltage, and waveform 2 is a waveform representing a discharge current. The discharge current density due to the formation of the pulse electric field is a value obtained by dividing the peak-to-peak current conversion value of the waveform 2 by the area of the electrode facing surface.

In the present invention, the discharge current density between the electrodes under a pressure close to the atmospheric pressure is compared regardless of the type of the atmospheric gas, and therefore, the degree of freedom in selecting the atmospheric gas to be used is increased. 0.2 to 3 described above
As a method of realizing the range of 00 mA / cm ² , a method of applying a pulsed voltage between a pair of electrodes can be exemplified.

That is, it is known that in plasma generation by glow discharge used for surface treatment or the like, the higher the density of electrons existing in the space, the more efficiently the gas is decomposed and the higher the treatment effect. Further, gas discharge under a high gas pressure is effective to obtain a high electron density by decomposing a large amount of gas by discharge. However, it is known that under a pressure close to the atmospheric pressure, a glow discharge state is not stably maintained in a gas other than a specific gas such as helium, ketone, etc., and an instantaneous transition to arc discharge occurs.

Therefore, in the present invention, when an atmosphere gas other than such a specific gas, that is, an atmosphere gas which does not contain a component having a long time from the glow discharge state to the arc discharge state, is used, the ambient gas near the atmospheric pressure is used. In order to make the glow discharge dominant in the above-mentioned gas atmosphere under pressure, a pulsed voltage is applied between the electrodes to form a pulsed electric field therebetween. Due to the formation of such a pulsed electric field, the discharge between the electrodes stops before the transition from the glow discharge to the arc discharge, and if such a pulsed electric field is formed between the electrodes periodically, it is microscopically pulse-like. Glow discharge is repeatedly generated, and as a result, the glow discharge state is continued.

As described above, under an atmosphere near the atmospheric pressure and in an atmosphere having no long-time component such as helium or ketone from the glow discharge state to the arc discharge state, pulsing between the electrodes is performed. A stable discharge plasma can be generated for the first time by forming a generated electric field and setting the discharge current density to 0.2 to 300 mA / cm ² .

By satisfying such conditions, according to the discharge plasma processing method of the present invention, it is possible to generate discharge plasma in air. In addition to the known plasma treatment under low pressure conditions, it is essential to perform the treatment in a closed container shielded from the outside air, even in the plasma treatment under a pressure close to the atmospheric pressure with a specific gas contained. However, by using the discharge plasma treatment method of the present invention, treatment in an open system becomes possible.

Further, according to the method of forming a pulsed electric field, a high-density plasma state can be generated, so that high-speed continuous processing can be achieved, which has a great advantage in application to various industrial processes.

Examples of the material of the electrode used in the discharge plasma generation method of the present invention include simple metals such as copper and aluminum, alloys such as stainless steel and brass, and intermetallic compounds.

Further, in order to avoid the occurrence of arc discharge due to electric field concentration, it is preferable that the electrode has a structure in which the distance between the electrodes is substantially constant. Examples thereof include an opposed flat plate type, a spherical opposed flat plate type, a hyperboloid opposed flat plate type, and a coaxial cylindrical type structure.

In the present invention, it is preferable to provide a solid dielectric on one or both of the opposing surfaces of the electrodes, and if there is a part where the electrodes directly oppose each other without being covered by the fixed dielectric, the solid dielectric may be used. Since an arc discharge is likely to occur, the solid dielectric must be in close contact with the electrode on which the solid dielectric is provided, and completely cover the opposing surface of the contacting electrode.

The solid dielectric may be in the form of a sheet or a film, but preferably has a thickness of about 0.5 to 5 mm. If the thickness is too large, a high voltage is required to generate discharge plasma, If it is too thin, dielectric breakdown occurs when voltage is applied, and arc discharge occurs.

Examples of the material of the solid dielectric include plastics such as polytetrafluoroethylene and polyethylene terephthalate, glass, metal oxides such as silicon dioxide, aluminum oxide, zirconium dioxide and titanium dioxide, and double oxides such as barium titanate. Is mentioned.

However, the solid dielectric has a relative dielectric constant of 2
It is preferable that the above conditions are satisfied (in a 25 ° C. environment, the same applies hereinafter). Examples of such a dielectric include polytetrafluoroethylene, glass, and a metal oxide film.
Further, in order to stably generate discharge plasma having a discharge current density of 0.2 to 300 mA, a relative dielectric constant of 10
It is advantageous to use the above fixed dielectric. The upper limit of the relative permittivity is not particularly limited, but is 1 in actual materials.
About 8,500 are known. Dielectric constant of 10
The above-mentioned solid dielectric comprises a metal oxide film mixed with 5 to 50% by weight of titanium oxide and 50 to 95% by weight of aluminum oxide, or a metal oxide film containing zirconium oxide. Is 10 to 10
It is preferable to use one having a thickness of 00 μm.

The distance between the pair of electrodes in the present invention is determined in consideration of the thickness of the solid dielectric, the magnitude of the applied voltage, the purpose of using plasma, and the like, and is preferably 1 to 50 mm. If it is less than 1 mm, it is insufficient to provide a space for disposing the base material when plasma generated during the process is used for surface treatment or the like, and if it exceeds 50 mm, it becomes difficult to generate uniform discharge plasma. .

In the present invention, when a pulse voltage is applied between the electrodes, the pulse waveform is not particularly limited, but may be an impulse type as shown in FIGS. ) And a modulation type as illustrated in (D) can be used. This figure 3
Has been described as an example in which the applied voltage is a repetition of positive and negative, but a pulse voltage of only positive or negative polarity, that is, a so-called single-wave pulse voltage may be applied.

In the present invention, the pulse voltage applied between the electrodes is such that the shorter the rise time and the fall time of the pulse, the more efficiently the gas is ionized during the generation of plasma.

In particular, the rise and fall times of the pulse voltage applied between the electrodes, in other words, the rise and fall times of the pulse electric field formed between the electrodes are preferably 40 ns to 100 μs. . If it is less than 40 ns, it is not practical. If it exceeds 100 μs, the discharge state easily shifts to arc discharge and becomes unstable.

It should be noted that the rise time mentioned herein refers to the time during which the direction of the voltage change is continuously positive, and the fall time refers to the time during which the direction of the voltage change is continuously negative. I do.

The pulse electric field formed between the electrodes may have its pulse waveform, rise and fall times, and frequency appropriately modulated, and such modulation is effective in performing high-speed continuous surface treatment. is there. The pulse electric field having a higher frequency and a shorter pulse width is more suitable for high-speed continuous surface treatment.

In the present invention, the frequency of the pulse electric field formed between the electrodes is preferably in the range of 1 kHz to 100 kHz. When the frequency is less than 1 kHz, when the discharge plasma is used for, for example, surface treatment, the processing takes too much time. When the frequency exceeds 100 kHz, an arc discharge is easily generated.

The formation time of one pulse electric field is 1
It is preferably from μs to 1000 μs, more preferably from 3 μs to 200 μs. If it is less than 1 μs, the discharge becomes unstable, and if it exceeds 1000 μs, it becomes easy to shift to arc discharge. Here, the formation time of one pulse electric field means ON / OFF as illustrated in FIG.
Are repeated in a pulse electric field, the duration of one pulse waveform, in other words, the pulse duty time.

Further, in the present invention, the intensity of the pulse electric field is appropriately selected depending on the purpose of use of the discharge plasma and the like, but is preferably 1 to 100 kV / cm. 1
If it is less than kV / cm, the time required for surface treatment is long, and if it is more than 100 kV, an arc discharge occurs, which is not preferable.

FIG. 5 is a block diagram showing an example of the configuration of a power supply circuit for forming a pulse electric field satisfying the above conditions, and FIG. 6 is an equivalent circuit diagram showing the principle of the operation. Indicated by In FIG. 6, SW1 to SW4 are semiconductor elements that function as switches in the switching inverter circuit shown in FIG.
By using a semiconductor device having a turn-on time and a turn-off time of not more than 00 ns, an electric field strength of 1 to 1
The formation of a high-voltage and high-speed pulsed electric field of 00 kV / cm and pulse rise and fall times of both 40 ns to 100 μs can be realized.

Next, the principle of operation will be briefly described with reference to FIG. + E is a positive DC voltage supply unit, and -E is a negative DC voltage supply unit. SW1 to SW4 are switching elements made of the high-speed semiconductor elements described above. D
Reference numerals _{1 to 4} denote diodes, and I _{1 to} I ₄ indicate the directions in which electric charges move.

First, when SW1 is turned on, the electric charge becomes I ₁
Then, one side (positive load) of a pair of electrodes placed at both ends of the discharge space is charged. Next, S
By turning off W1 and then turning on SW2 instantaneously, the charge charged to the positive load becomes SW2 and D
4 through movement in the direction of I _3.

Next, after SW2 is turned off, SW3
The When ON instantaneously charge to charge the electrodes of the other side moves in the direction of I ₂ (negative loading). Furthermore, SW3
The after to OFF, by turning ON the SW4 instantaneously, the electric charge charged in the negative polarity load is moved in the direction of I ₄ through SW4 and D2.

By repeating the above operation, an output pulse having the waveform shown in FIG. 7 can be obtained. [Table 1]
The operation table is shown in FIG. The numerical values shown in Table 1 correspond to the numerical values given to the waveforms in FIG.

[0046]

[Table 1]

The advantage of the above circuit is that even if the load impedance is high, the charged electric charge is transferred to SW
2 and D4 or SW4 and D2 can be reliably discharged, and high-speed charging can be performed using SW1 and SW3, which are high-speed turn-on switching elements. 4, it is possible to apply a pulse-like voltage having an extremely short rise time and fall time to a load, that is, between a pair of electrodes.

The pulse electric field used in the discharge plasma generating method of the present invention does not prevent superposition of a DC electric field. The discharge plasma treatment method of the present invention utilizes a plasma generated between a pair of electrodes by the above-described method of generating a discharge plasma specific to the present invention, and is used between a pair of electrodes or a counter electrode of one electrode. When a solid dielectric is placed on the surface, it must be treated between the solid dielectric and the other electrode, or between the solid dielectrics when the solid dielectric is placed on the opposite surface of both electrodes. The base material is placed, and surface treatment is performed by discharge plasma.

The material of the substrate subjected to the surface treatment using the discharge plasma treatment method of the present invention may be polyethylene,
Examples thereof include plastics such as polypropylene, polystyrene, polycarbonate, polyethylene terephthalate, polytetrafluoroethylene, and acrylic resin, glass, ceramic, and metal. As the shape of the substrate, plate-like,
Film-like and sheet-like materials are exemplified, but not particularly limited thereto. According to the discharge plasma treatment method of the present invention, it is possible to easily cope with the treatment of substrates having various shapes. .

In the discharge plasma processing of the present invention, any processing can be performed by selecting a gas (hereinafter referred to as a processing gas) existing in the discharge plasma generation space. By using a fluorine-containing compound gas as the processing gas, it is possible to form a fluorine-containing group on the surface of the base material, lower the surface energy, and form a water-repellent surface.

Examples of the fluorine-containing compound gas include carbon tetrafluoride (CF ₄ ), carbon hexafluoride (C ₂ F ₆ ), propylene hexafluoride (CF ₃ CFCF ₂ ), and cyclobutane octafluoride (C ₄ F ₈ ) Fluorine-carbon compounds such as monochloride
Halogen, such as fluorocarbon (CClF ₃₎ - carbon compound,
6 fluoride such as sulfur hexafluoride (SF ₆₎ - sulfur compounds and the like. From the viewpoint of safety, it is preferable to use carbon tetrafluoride, carbon hexafluoride, propylene hexafluoride, and cyclobutane 8-fluoride which do not generate hydrogen fluoride which is a harmful gas.

Also, the following oxygen element-containing compounds, nitrogen element-containing compounds and sulfur element-containing compounds are used as the processing gas to contain oxygen gas, a combination of oxygen gas and hydrogen gas, ozone, water vapor, and oxygen element. A hydrophilic functional group such as a carbonyl group, a hydroxyl group, or an amino group is formed on the surface of the base material by using an organic compound gas, thereby increasing the surface energy and forming a hydrophilic surface.

As the oxygen-containing compound, oxygen,
Contains oxygen elements such as ozone, water, carbon monoxide, carbon dioxide, nitric oxide, nitrogen dioxide, alcohols such as methanol and ethanol, ketones such as acetone and methyl ethyl ketone, and aldehydes such as methanal and ethanal. Organic compounds and the like can be mentioned.

These may be used alone or in combination of two or more. Further, a mixed gas of the above oxygen element-containing compound and a hydrocarbon compound gas such as methane and ethane may be used.

By adding a fluorine element-containing compound to the oxygen element-containing compound at 50% by volume or less,
Hydrophilization is promoted. As this fluorine-containing compound, those equivalent to the above-mentioned fluorine-containing compounds can be used.

Examples of the nitrogen-containing compound include nitrogen gas and ammonia. The nitrogen-containing compound and hydrogen may be used as a mixture. Further, examples of the sulfur-containing compound include sulfur dioxide and sulfur trioxide.

Further, sulfuric acid may be used after being vaporized, and these may be used alone or as a mixture of two or more. Furthermore, by performing the treatment in an atmosphere of a monomer having a hydrophilic group and a polymerizable unsaturated bond in the molecule, a hydrophilic polymer film can be deposited on the substrate surface. Examples of the hydrophilic group used herein include a hydroxyl group, a sulfonic acid group, a sulfonic acid group, a primary or secondary or tertiary amino group, an amide group, a quaternary ammonium base, a carboxylic acid group, and a carboxylic acid group. Can be mentioned.

Even when a monomer having a polyethylene glycol chain is used, a hydrophilic polymer film can be similarly deposited. Examples of the monomer include acrylic acid, methacrylic acid, acrylamide, methacrylamide, N, N-dimethylacrylamide, sodium acrylate, sodium methacrylate, potassium acrylate, potassium methacrylate, sodium styrenesulfonate, allyl alcohol, allylamine, and polyethylene. Glycol dimethacrylate, polyethylene glycol diacrylate and the like. These monomers are used alone or as a mixture.

Since the above hydrophilic monomer is generally a solid, it is used by dissolving it in a solvent and evaporating it by a means such as reduced pressure. The solvent used here is methanol,
Examples thereof include organic solvents such as ethanol and acetone, water, and mixtures thereof.

Further, metals such as Si, Ti, Sn, etc.
Using a processing gas such as a hydrogen compound, a metal-halogen compound, or a metal alcoholate, SiO ₂ , TiO ₂ , SnO
It is also possible to form a metal oxide thin film such as _{2 on the} surface of the base material and give the surface an electrical and optical function.

Here, from the viewpoint of economy and safety,
It is preferable to perform the treatment in an atmosphere gas in which the various treatment gases described above are diluted with an inert gas. Examples of the inert gas include rare gases such as helium, neon, argon, and xenon, and nitrogen gas. These may be used alone or in combination of two or more.

Conventionally, treatment has been carried out in the presence of helium at a pressure close to the atmospheric pressure. However, according to the method of the present invention, stable treatment in argon or nitrogen gas, which is less expensive than helium, is performed. Since these treatments can be performed, the use of these has a great industrial advantage.

Here, it is preferable that the processing gas is uniformly supplied to the plasma generation space. When processing in a mixed gas of a processing gas and an inert gas, the inert gas is generally lighter than the processing gas. In particular, when processing a substrate having a large area, care must be taken because the atmosphere gas tends to be in a non-uniform mixed state. In order to make the mixed state of the atmosphere gas composed of the processing gas and the inert gas uniform, for example, the upper electrode of the pair of electrodes has a porous structure, and a gas introduction pipe is connected to the upper electrode. Then, the processing gas is supplied, and the processing gas is guided to the plasma generation space from above the base material placed between the electrodes through a number of holes of the upper electrode. On the other hand, the inert gas is guided from the surroundings to the plasma generation space using another introduction pipe and a discharge port.
Such measures can be taken. In addition, as long as the gas can be supplied uniformly, the present invention is not limited to such a measure, and a means such as stirring or blowing the gas at a high speed may be employed.

In the apparatus to which the discharge plasma generation method and the surface treatment method of the present invention are applied, the pair of electrodes is usually housed in a container, and the container is filled with an atmospheric gas. As the material of the resin, resin, glass and the like can be preferably used, but it is not particularly limited. Metals such as stainless steel and aluminum can also be used as long as they have a structure insulated from the electrodes.

In the surface treatment method using the discharge plasma of the present invention, the substrate to be treated may be heated or cooled, but the treatment can be performed sufficiently even at room temperature. When the surface treatment method of the present invention is applied to the surface treatment of a low melting point material such as a polymer material, the value of the discharge current density depends on the thickness of the solid dielectric, the dielectric constant of the solid dielectric, and the electrode. It is determined by various conditions such as the electric field strength formed between the electrodes, the distance between the electrodes, and the purpose of the treatment, but is preferably 1 to 200 mA / cm ² . If the discharge current density is less than 1 mA / cm ² , the discharge tends to be unstable, or uniform glow discharge is unlikely to occur, and a sufficient treatment effect cannot be obtained. Discharge current density is 2
If it exceeds 00 mA / cm ² , the substrate to be treated may be thermally deteriorated by being exposed to high-density plasma. Therefore, when processing at a discharge current density exceeding 200 mA / cm ² , a short-time processing of 5 seconds or less may be performed,
Preferably, the substrate is cooled.

[0066]

EXAMPLES Examples in which a discharge plasma is actually generated by applying the method of the present invention or surface treatment is performed using the discharge plasma will be described together with comparative examples.

<Embodiment 1> The apparatus used in Embodiment 1 is schematically shown in FIG. In this device, glass capacity 8
An upper electrode 81 and a lower electrode 82 are arranged in a liter chamber 80 so as to face each other.
A pulse voltage was applied from a pulse power supply 83 between the two. The lower electrode 82 is in a so-called electrically floating state by being supported on the chamber 80 via an insulator 84. Further, a fixed dielectric 85 was placed in close contact with the upper surface of the lower electrode 82, that is, the surface facing the upper electrode 81. Further, an oil rotary pump (not shown) was connected to the container 80, and the inside thereof was evacuated.

The upper electrode 81 has a porous structure, and is configured such that an atmosphere gas can be introduced into the chamber from a large number of holes of the upper electrode 81 by connecting a gas introduction pipe 86.

The upper electrode 81 is made of stainless steel and has a size and a shape of a disk having a diameter of 80 mm. A large number of holes having a diameter of 1 mm for discharging an atmospheric gas are provided at intervals of 5 mm.

The lower electrode 82 was made of stainless steel and had a disk shape with a diameter of 80 mm, and the distance between the lower electrode 82 and the upper electrode 81 was 4 mm. The material of the solid dielectric 85 covering the upper surface of the lower electrode 82 is glass, the size and shape are 140 mm square and 2 mm thick.
And the relative dielectric constant is 5.

With the above configuration, the facing area of the electrodes is 50
cm ² , and the thickness of the discharge space was 2 mm. Although not shown in FIG. 8, the discharge voltage and the discharge current were measured by the circuit shown in FIG.

In the above-described apparatus, the inside of the container 80 is evacuated to 0.1 Torr or less by the oil rotary pump, and then the gas is introduced into the container 80 through the gas introduction pipe 86 at a flow rate of 1000 s.
Ar gas of ccm was introduced, and the pressure in the container 80 was increased to 760.
Torr. A frequency of 4 kHz between the electrodes 81 and 82,
When an impulse voltage of 5 μs in both rise and fall times and a peak-to-peak voltage of 5 kV was applied, uniform light emission appeared between the electrodes 81 and 82. This light emission was observed to have a main bright line at a wavelength of 763 nm.

In the above discharge, the voltage between the electrodes is 5 k
V, and thus the electric field strength is 25 kV / cm, at which time a current of 400 mA flows between the electrodes and 8 mA / cm ²
Was obtained.

<Embodiment 2> The solid dielectric 85 of the apparatus shown in FIG.
A 50 mm square polyethylene terephthalate film (Lumirror T150, manufactured by Toray Industries, contact angle: 60 °), and a CF having a flow rate of 20 sccm through a gas introduction pipe 86.
A mixed gas of _four gases and an Ar gas having a flow rate of 980 sccm was introduced into the container 80. Further, the pulse voltage applied between the electrodes 81 and 82 was set to 10 kV in peak-peak value, and the above-mentioned polyethylene terephthalate film (hereinafter referred to as PET film) was subjected to a discharge plasma treatment for 15 seconds. I assumed the same.

<Embodiment 3> An embodiment 2 was adopted except that the solid dielectric 85 in the apparatus of FIG. 8 was made of polytetrafluoroethylene (size and shape: 140 mm square, 2 mm thick, relative dielectric constant 2.5). And the same.

<Embodiment 4> 13% by weight of titanium oxide and 87% by weight of aluminum oxide were applied to one side of 140 × 140 mm × 10 mm thick carbon steel (SS41) as a solid dielectric 85 in the apparatus of FIG. % (Having a relative dielectric constant of 14) with a thickness of 500 μm, and using the lower electrode 82 such that the coating surface faces the upper electrode 81.
Placed above. Also, the pulse voltage applied between the electrodes is
The peak-to-peak value was 5 kV. The other conditions were the same as in Example 2.

In the fourth embodiment, the distance between the electrodes was set to 12 mm so that the thickness of the discharge space became 2 mm. <Embodiment 5> As the solid dielectric material 85 in the apparatus of FIG. 8, a ZrO ₂ coating containing 8% by weight of Y ₂ O ₃ (relative dielectric constant: 16) was formed at a thickness of 500 μm on one surface of the same carbon steel as above. The same as Example 4 except that was used.

The above Examples 2 to 5 are examples relating to the water repellent treatment of the PET film, and the results of these treatments are summarized in Table 2. FIG. 9 is a graph showing the discharge current density dependence of the processing effect based on [Table 2]. From these results, when any of the dielectrics was used,
It is clear that a water-repellent effect is obtained, and that the magnitude of the discharge current density with respect to the electric field strength between the electrodes can be controlled by the relative dielectric constant of the solid dielectric.

In Table 2 or FIG. 9, the surface F /
C is the ratio of the amount of fluorine and the amount of carbon on the surface of the substrate obtained by X-ray photoelectron spectroscopy, and it is clear that the higher the discharge current density during the treatment, the more the surface is fluorinated. .

[0080]

[Table 2]

<Example 6> Example 6 was the same as Example 2 except that the magnitude of the pulse voltage applied between the electrodes 81 and 82 was 2.2 kV in peak-to-peak value. In this example, when a glass dielectric was used, the discharge was performed at the minimum voltage value at which uniform discharge occurred, and the discharge current density was 1 mA / cm ² . The contact angle of the treated PET film was 100 °, and a water-repellent treatment effect was obtained on the entire surface of the substrate under discharge.

<Embodiment 7> In the apparatus shown in FIG. 8, N ₂ gas at a flow rate of 1000 sccm is introduced into the container 80 through the gas introduction pipe 86, and the pulse voltage applied between the electrodes 81 and 82 is changed to a peak-to-peak value. As 30kV,
It was the same as Example 2 except that the hydrophilic treatment was performed.

<Embodiment 8> In the apparatus of FIG. 8, N ₂ gas at a flow rate of 1000 sccm is introduced into the vessel 80 through the gas introduction pipe 86, and the pulse voltage applied between the electrodes 81 and 82 is changed to a peak-to-peak value. As 30kV,
It was the same as Example 3 except that the hydrophilic treatment was performed.

<Embodiment 9> In the apparatus shown in FIG. 8, N ₂ gas at a flow rate of 1000 sccm is introduced into the container 80 through the gas introduction pipe 86, and the pulse voltage applied between the electrodes 81 and 82 is changed to a peak-to-peak value. As 14 kV,
It was the same as Example 4 except that the hydrophilic treatment was performed.

<Embodiment 10> In the apparatus of FIG. 8, a flow rate of 1000 sccm
While introducing N ₂ gas, a pulse voltage applied between the electrodes 81 and 82 peaks - as 14kV peak value, other than performing the hydrophilic treatment was the same as in Example 5.

The processing results of the seventh to tenth embodiments are summarized in [Table 3]. FIG. 10 is a graph showing the dependence of the hydrophilic treatment effect on the discharge current density based on [Table 3]. From these results, it is clear that a hydrophilic effect was obtained in any of the dielectrics, and the relative dielectric constant of the solid dielectric caused the discharge current density to the electric field strength between the electrodes to be reduced. The ability to control the size was the same as in the case of the water-repellent treatment.

In Table 3 or FIG. 10, the surface N
/ C is the ratio of the amount of nitrogen to the amount of carbon on the surface of the substrate obtained by X-ray photoelectron spectroscopy, and the higher the discharge current density during the treatment, the more nitrogen is present on the surface. It is clear that is more aminated.

[0088]

[Table 3]

<Embodiment 11> The same as Embodiment 10 except that the peak-to-peak value of the applied pulse voltage was set to 30 kV. The discharge current density was 100 mA / cm ² .
The initial contact angle was 21 °, and the surface N / C was 0.5.

<Comparative Example 1> A corona discharge treatment device (manufactured by Kasuga Electric Co., type: HFSS-10)
Using 3), a voltage of 30 kV was applied and corona discharge was performed for 15 seconds to obtain a hydrophilic surface-treated product having an initial contact angle of 35 °.

<Comparative Example 2> In the apparatus of FIG. 8, N ₂ having a flow rate of 10 sccm was introduced into the container 80 through the gas introduction pipe 86.
A mixed gas of a gas and a He gas having a flow rate of 990 sccm is introduced, and the voltage applied between the electrodes 81 and 82 is set to a frequency 1
Example 10 was the same as Example 10 except that the hydrophilic treatment was performed using a sine wave voltage (discharge current density 0.1 ma) having a frequency value of 5 kHz and a peak-to-peak voltage value of 2 kV. The initial contact angle was 30 °, and the surface N / C was 0.1.

The samples subjected to the hydrophilic treatment obtained in Example 11, Comparative Example 1 and Comparative Example 2 were subjected to a hydrophilic durability promotion test in an environment of 60 ° C. (ST-110 manufactured by Tabai Espec Corp.). The contact angle change θ when the initial contact angle of the treated product is represented by θ0, the contact angle after t minutes is represented by θt, and the initial contact angle of the base material is represented by θ に よ り is calculated by the following equation.

[0093]

(Equation 1)

FIG. 11 shows the results of examining the change with time of the hydrophilicity of the above three samples using the above equation. This figure 1
As is clear from FIG. 1, the durability was improved about 10 times in the hydrophilic treatment according to Example 11 of the present invention as compared with the conventional corona discharge treatment and the treatment using the atmospheric pressure plasma using He. .

<Comparative Example 3> In the apparatus of FIG.
Example 3 was the same as Example 3 except that the pulse voltage applied between 1, 82 was 1.5 kV in peak-peak value.

The discharge occurs in about one third of the area of the electrode.
The discharge current density was 0.1 mA / cm ² . The contact angle was 80 ° at the discharge part and 70 ° or less at other places, and a sufficient water-repellent effect could not be obtained.

<Comparative Example 4> In the apparatus of FIG.
Example 10 was the same as Example 10 except that the pulse voltage applied between 1, 82 was set to 50 kV in peak-peak value.

The discharge current density became 250 mA / cm ² , a part of the base material was melted, and the upper electrode 8
Holes corresponding to the inlet gas discharge holes formed in No. 1 were opened.

[0099]

As described above, according to the present invention, a stable and uniform discharge plasma treatment can be performed under a pressure near the atmospheric pressure. In addition, by forming a pulsed electric field between the electrodes, it is possible to generate a stable, uniform, and high-density discharge plasma regardless of the type of atmospheric gas in the discharge space, and in a short time. High-level plasma processing can be performed. This means that high-speed continuous plasma processing can be performed, and particularly when applied to surface treatment of various materials or components in an industrial process, extremely significant results can be obtained.

Further, according to the present invention, the gas atmosphere is not limited, and a stable discharge plasma can be generated in the air depending on the setting conditions such as the rise and fall times of the pulse electric field and the frequency thereof. Because
Open-system processing can be performed, and the applicable field of discharge plasma processing is greatly expanded.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an example of a circuit for measuring a discharge voltage and a discharge current in an apparatus to which the present invention is applied.

FIG. 2 is a discharge voltage (waveform 1) obtained by the apparatus of FIG.
Showing the measurement results of the discharge current and the discharge current (waveform 2)

FIG. 3 is an explanatory diagram of an example of a waveform of a pulse voltage applied between a pair of electrodes in the present invention.

FIG. 4 is an explanatory diagram of a formation time of one pulse electric field according to the present invention.

FIG. 5 is a block diagram showing a configuration example of a power supply circuit suitable for use in an apparatus to which the present invention is applied.

FIG. 6 is an explanatory diagram of the operation principle of the circuit of FIG. 5 shown in an equivalent circuit diagram.

FIG. 7 is an explanatory diagram of a pulse voltage waveform that can be obtained by the operation principle shown in FIG.

FIG. 8 is a schematic diagram showing a configuration of a discharge plasma generator used in each embodiment of the present invention.

FIG. 9 is a graph showing the discharge current density dependence of the water-repellent effect of the PET film during the water-repellent treatment, which was created based on the results of Examples 2 to 5 of the present invention.

FIG. 10 is a graph showing the discharge current density dependence of the hydrophilic effect at the time of hydrophilic treatment of a PET film, which was created based on the results of Examples 7 to 10 of the present invention.

FIG. 11 is a graph showing the time-dependent changes in hydrophilicity of the PET films obtained in Example 11 of the present invention and Comparative Examples 1 and 2 after the hydrophilic treatment.

[Explanation of symbols]

 1, 2 electrode 3 pulse power supply 4 solid dielectric 5 resistance 6, 9 BNC terminal 7 oscilloscope 8 high voltage probe 80 chamber 81 upper electrode 82 lower electrode 83 pulse power supply 85 solid dielectric 86 gas introduction tube

Claims (6)

[Claims] In a method of performing a surface treatment of a substrate by using a discharge plasma generated in a gas by applying a voltage between a pair of electrodes facing each other in a gas atmosphere, the pressure of the atmosphere gas is close to the atmospheric pressure. And a discharge current density between the electrodes is 0.2 to 300 mA / cm ² . 2. The discharge plasma processing method according to claim 1, wherein a pulse-like voltage is applied between said pair of electrodes. 3. The rising and / or falling time of a pulse electric field generated between the electrodes by applying the pulse-like voltage is both in the range of 40 ns to 100 μs, and the intensity of the pulse electric field is 1 to 100 μs. 100kV / c
The discharge plasma processing method according to claim 2, wherein the range is m. 4. The pulse electric field has a frequency of 1 kHz to 1 kHz.
00 kHz, and the time for forming one pulsed electric field is 1 μs to 1000 μs.
The discharge plasma processing method according to claim 2. 5. A solid dielectric is provided on at least one of the opposite surfaces of the pair of electrodes, and between the solid dielectric provided on the opposite surface of the one electrode and the electrode of the other electrode, or between the electrodes of the other electrode. Characterized in that the substrate is disposed between the solid dielectrics disposed on both opposing surfaces of the electrodes and the treatment is performed.
The discharge plasma processing method according to claim 1, 2, 3, or 4. 6. The method according to claim 1, wherein said atmospheric gas is argon and / or nitrogen.
Or the discharge plasma treatment method according to 5.