JPH08217897A - Plasma surface treatment method and plastic surface treatment apparatus - Google Patents

Abstract

(57) [Abstract] [Purpose] By bringing discharge plasma into contact with the surface of a substrate in a gas atmosphere,
(EN) Provided are a plasma surface treatment method and a plastic surface treatment apparatus capable of easily performing partial surface treatment of a substrate. A process formed by opposed upper and lower electrodes 2 and 3 arranged in a substantially horizontal direction, and solid dielectric walls 4a and 4b vertically provided around the upper and lower electrodes 2 and 3. The base material 6 is arranged in the space 11 so as to be substantially horizontal with respect to the upper and lower electrodes 2 and 3, and a mixed gas of an inert gas and a processing gas is introduced into the processing space 11 so as to be near atmospheric pressure. The surface of the base material 6 is treated by applying a voltage to the electrodes to generate discharge plasma under the pressure of 1, and bringing the discharge plasma into contact with the surface of the base material 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma surface treatment method and a plastic surface treatment apparatus.

[0002]

2. Description of the Related Art As a dry process for surface treatment of a solid surface, a surface treatment method using glow discharge plasma at a low pressure of about 0.01 to 10 Torr is widely known and widely applied industrially. If the pressure is higher than this, the discharge will be localized and will shift to arc discharge, making it difficult to apply to plastic substrates with poor heat resistance.
It is performed under the above low pressure. To obtain the above low pressure,
The container requires an expensive vacuum chamber, and further an evacuation device needs to be installed. Further, in order to process a large area substrate because it is processed in a vacuum, a large vacuum container must be used and a vacuum exhaust device with a large output is required. As a result, the equipment becomes extremely expensive. Further, when the surface treatment of a plastic substrate having a high water absorption rate is performed, it takes a long time to evacuate, which causes a problem that the cost of the treated product increases.

In order to overcome such problems, there has been proposed a surface treatment method using glow discharge plasma at atmospheric pressure capable of lowering the cost of equipment and facilities and treating a large area substrate. Japanese Patent Publication No. 2-48626 discloses a method of forming a film by using a thin wire type electrode. In this method, a mixture of an inert gas mainly containing He and a fluorine-containing gas or a monomer gas is supplied to a plasma region near the substrate from a porous tube having a plurality of openings.

In the case where only a part of the substrate is partially surface-treated by such a conventional technique, a method of masking the untreated part by a known method and removing the masking after the treatment is generally used. Since it is adopted, there is a disadvantage that an extra step is required for masking.

In Japanese Unexamined Patent Publication No. 6-108257, an electrode is a metal cylinder having a tip portion at the end of a blowout port, a gas is blown from the blowout port to apply a voltage, and discharge plasma is generated under atmospheric pressure. Disclosed is a plasma reactor. However, in this device, only the base material portion that comes into contact with the discharge plasma is surface-treated, and therefore, when processing a region of several cm ² or more, it is necessary to increase the number of devices or scan the devices. There was a drawback that the mechanism became complicated.

[0006]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned drawbacks, and its purpose is to achieve
It is an object of the present invention to provide a plasma surface treatment method and a plastic surface treatment apparatus capable of performing partial surface treatment of a base material by a simple process under a pressure near atmospheric pressure by bringing the surface of the base material into contact with discharge plasma. .

[0007]

According to a first aspect of the plasma surface treatment method of the present invention, opposing metal electrodes are disposed in a substantially horizontal direction, and a solid dielectric is disposed in a direction substantially perpendicular to the metal electrodes. A base material is placed in a processing space surrounded by walls so as to be substantially horizontal with respect to the metal electrode, and a mixed gas of an inert gas and a processing gas is introduced into the processing space, so that the pressure is maintained near the atmospheric pressure. Voltage is applied to the electrodes to generate discharge plasma,
By bringing the discharge plasma into contact with the surface of the substrate,
It is characterized in that the substrate surface is treated.

The plasma surface treatment is to form a functional group layer on the surface or to form a radical layer by discharge plasma to impart hydrophilicity or water repellency to form a surface whose surface energy is controlled. The surface treatment modifies the wettability and adhesiveness of the substrate, and further forms a film having a function excellent in electrical characteristics and optical characteristics on the surface.

The base material is not particularly limited, and plastic films, sheets, molded bodies and the like can be used. Examples of plastics include polyesters such as polyethylene terephthalate and polyethylene naphthalate; polyolefins such as polyethylene and polypropylene, polystyrene, polyamide, polyvinyl chloride, polycarbonate, polyacrylonitrile, and the like. When a plastic film is used as the base material, either a stretched product or an unstretched product can be used.

As the above-mentioned base material, other than plastic,
Building materials such as metal, glass, paper, fibers, cement and the like, non-woven fabrics and the like can be used, and any of these sheet-like materials and molded products can be used, and the surface thereof may be porous. Examples of the metal include alloys such as stainless steel, carbon steel, and super steel; single-component metals such as aluminum, copper, and nickel.

As the mixed gas, a mixture of an inert gas and a processing gas is used. The treatment gas can be easily surface-treated by selecting it according to the purpose of the plasma surface treatment and supplying it into the discharge plasma atmosphere. For example, when fluorine is chemically bonded to the surface of the base material to reduce the surface energy and impart water repellency, a fluorine-containing gas is preferably used. Examples of such a fluorine-containing gas include carbon tetrafluoride (CF ₄ ) and carbon hexafluoride (C ₂ F ₆ ).
And fluorinated hydrocarbon gas such as propylene hexafluoride (C ₃ F ₆ ); halogenated hydrocarbon gas such as 1 chlorinated 3 fluorocarbon gas (CClF ₃ ); fluorine such as sulfur hexafluoride (SF ₆ ). Examples thereof include sulfurized compounds, but from the viewpoint of safety, carbon tetrafluoride, carbon hexafluoride, propylene hexafluoride, and the like, which do not generate harmful gases such as hydrogen fluoride, are preferable.

When the surface energy of the base material is increased to impart hydrophilicity, a hydrocarbon compound is used to form a layer having a functional group such as a carbonyl group, a hydroxyl group and an amino group on the surface. Gas or steam is preferably used. Examples of such a hydrocarbon compound include alkane gases such as methane, ethane, propane, butane, pentane and hexane; ethylene, propylene, butene,
Alkene-based gases such as pentene; Alkadiene-based gases such as pentadiene and butadiene; Alkyne-based gases such as acetylene and methylacetylene; Benzene, toluene,
Aromatic hydrocarbon gases such as xylene, indene, naphthalene, phenanthrene; cycloalkane gases such as cyclopropane and cyclohexane; cycloalkene gases such as cyclopentene and cyclohexene; alcohol gases such as methanol and ethanol; Examples thereof include ketone-based gases such as acetone and methyl ethyl ketone; aldehyde-based gases such as methanal and ethanal, which may be used alone or in combination of two or more. Also, oxygen gas, a mixed gas of oxygen gas and hydrogen gas;
Steam, a mixed gas of nitrogen gas and hydrogen gas; ammonia gas, etc. can also be used.

When a metal oxide thin film having a high electrical, optical, etc. function such as SiO ₂ , TiO ₂ or SnO ₂ is formed on a substrate, metal hydrogen gas, metal halide gas, It can be formed by using a gas or vapor of a metal organic compound such as a metal alcoholate.

Examples of the above-mentioned inert gas include rare gases such as helium, neon, argon and xenon, and nitrogen gas, and these may be used alone or in combination of two or more kinds. Of the above-mentioned inert gases, helium gas has a long metastable life and is therefore preferable for exciting the processing gas. When an inert gas other than helium is used, it is preferable to mix 2% by volume or less of vapor such as acetone and methanol and hydrocarbon gas such as methane and ethane.

The mixing ratio of the processing gas and the inert gas is
Although appropriately determined depending on the type of gas used, the concentration of the processing gas is preferably 10% by volume or less, more preferably 0.1 to 5 because discharge plasma is less likely to be generated even when a high voltage is applied when the concentration of the processing gas increases. It is in the range of volume%.

Under the pressure near the atmospheric pressure of the mixed gas means
It is under a pressure of 100 to 800 Torr, and especially 700 to 780 Tor where the pressure is easy to adjust and the device is simple.
A range of r is preferred.

An example of the plasma surface treatment method of the first invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing an example of a processing apparatus used in the first invention. This processing apparatus comprises a power supply unit 1, an upper electrode 2 and a lower electrode 3, and solid dielectric walls 4a and 4b. The upper electrode 2 and the lower electrode 3 are arranged so as to face each other in a substantially horizontal direction, and the solid dielectric walls 4a and 4b are vertically provided around the periphery between the upper electrode 2 and the lower electrode 3.

A substrate 6 is placed in a substantially horizontal direction in a processing space 11 surrounded by the upper and lower electrodes 2 and 3 and the solid dielectric walls 4a and 4b, and the substrate 6 is subjected to plasma treatment. The shape of the processing space is not particularly limited and may be a rectangular tube shape or a cylindrical shape. The base material 6 is subjected to plasma treatment in a shape and area corresponding to the exposed surfaces of the upper and lower electrodes.

As the electrode arrangement structure, a parallel plate type in which the upper electrode 2 and the lower electrode 3 face each other in the horizontal direction is used in FIG. 1, but other than the parallel plate type, a coaxial cylinder type, a cylinder facing flat plate type, and a sphere facing type. It is possible to use a flat plate type or a hyperboloid facing type that is composed of a plurality of thin wires.

Examples of the material for the upper electrode 2 and the lower electrode 3 include multi-component metals such as stainless steel and brass; pure metals such as copper and aluminum.

The base material 6 is held horizontally at the contact portion between the upper electrode 2 and the lower electrode 3. When a conductive material such as metal or a porous material is used as the base material 6, surface treatment is performed. It is preferable to mount a solid dielectric (not shown) so as to completely cover the surface of the electrode facing the portion to be covered. Examples of the solid dielectric include polytetrafluoroethylene (PTFE) and polyethylene terephthalate (PET).
Such as plastics; glass such as Pyrex glass; S
iO ₂ , Al ₂ O ₃ , TiO _2, etc., or Y ₂ O ₃ and ZrO
Ceramics such as a solid solution of ₂ are listed, and those that do not react with the processing gas are selected.

The distance between the upper electrode 2 and the lower electrode 3 is appropriately determined depending on the thickness of the solid dielectric material, the thickness of the base material 6, the magnitude of the applied voltage, and the like.
A range of less than is preferred. When the distance between the electrodes exceeds 30 mm, the discharge plasma is easily transferred to the arc discharge and the uniformity is deteriorated, which is not preferable.

The power supply unit 1 can apply a voltage having a frequency on the order of kHz. For example, a low frequency of 1 to 30 kHz is preferable for surface treatment of a plastic base material having low heat resistance.

Discharge plasma is generated by applying a voltage to the upper electrode 2 and the lower electrode 3, and the voltage at that time is appropriately determined depending on the electrode shape, the distance between the electrodes, and the like. Is preferably about 0.1 to 40 kV / cm. When the electric field strength is less than 0.1 kV / cm, discharge plasma is difficult to be generated and it takes a long time to process, and when the electric field strength exceeds 40 kV / cm, the behavior of transition to arc discharge is not preferable.

By continuously introducing the mixed gas into the processing space 11, the processing space 11 is replaced with the mixed gas and maintained at a pressure near atmospheric pressure. The flow rate of the mixed gas is adjusted and the mixed gas is directly supplied from the gas introduction pipes 7a and 7b.
Gas may be introduced into the electrode, or a gas introduction tube may be provided in the electrode. In addition, the facing surfaces of the electrode 2 and the lower electrode 3 are shown in FIG.
Alternatively, a mixed gas may be supplied to the processing space 11 through the holes 10 as shown in FIG. Especially, when the processing space 11 is large or has a complicated shape, such a hole 1
By supplying from 0, uniform supply to the processing space 11 becomes possible. Further, the mixed gas may be supplied to the processing space 11 from gas introduction pipes arranged in the solid dielectrics 4a and 4b.

The excessively supplied mixed gas is discharged from the gas discharge holes 8 provided in the solid dielectrics 4a and 4b.
The discharged mixed gas may be detoxified by a detoxifying device or the like and discharged into the atmosphere as necessary, or may be supplied to the processing space and reused. If the solid dielectrics 4a, 4b are porous or have one or more discharge holes, it is not necessary to provide discharge holes, but safety is taken into consideration so that the mixed gas does not diffuse into the air. Then, discharge plasma treatment may be performed in the container, if necessary. When using the solid dielectrics 4a and 4b having such a porous or exhaust hole, it is preferable to slightly pressurize the inside of the processing space so that air is not mixed from the outside.

The above-mentioned base material may be heated or cooled if necessary, but room temperature is sufficient to impart water repellency or hydrophilicity. The thickness of the part of the base material that is subjected to plasma discharge treatment is
Although it is appropriately determined according to the application, it is preferably 0.03 to less than 30 mm in which discharge plasma is easily generated uniformly. The substrate may be subjected to surface cleaning or surface activation treatment by a known treatment method.

By introducing a mixed gas into the processing space 11 through the holes 10 of the upper electrode 2 and the lower electrode 3 and applying a predetermined voltage to both electrodes to generate discharge plasma, the gas is brought into contact with the substrate 6. The surface of the base material is treated with discharge plasma.

The time required for the discharge plasma treatment is appropriately determined depending on the magnitude of the applied voltage, the base material, the mixed gas composition, and the like. For example, when the plastic surface is subjected to water repellent treatment using fluorocarbon gas, In the range of the applied voltage, the water-repellent performance can be imparted in about 5 seconds, and even if the treatment is performed for a longer time, the effect is not significantly improved, and the treatment for a short time is sufficient.

Next, the plastic surface treating apparatus of the second invention will be described. A plastic surface treatment apparatus according to a second aspect of the present invention is a treatment space formed by opposed upper and lower electrodes arranged in a substantially horizontal direction, and a solid dielectric wall vertically provided around the upper and lower electrodes. A gas introduction pipe for introducing a mixed gas of an inert gas and a treatment gas into the treatment space, and a gas discharge pipe for exhausting the treatment space,
And a power supply for applying a voltage between the metal electrodes.

The processing apparatus of the second invention will be described with reference to the schematic diagram shown in FIG. This processing apparatus includes a power supply unit 1, an upper electrode 2, a lower electrode 3, and a solid dielectric wall 4.
It is composed of a and 4b. The upper electrode 2 and the lower electrode 3 are arranged so as to face each other in a substantially horizontal direction, and the processing space is formed by the upper electrode 2 and the lower electrode 3 and the solid dielectric walls 4a and 4b that are vertically provided around the both electrodes. 11 is formed.

The materials used for the upper electrode 2 and the lower electrode 3 of the second invention are the same as those used in the first invention. Further, as the solid dielectric used in the second invention, the same material as that used in the first invention is used.

Mixed gas introduction pipes 7a and 7b are connected to the upper electrode 2 and the lower electrode 3, respectively, and the mixed gas is supplied to the processing space 11 through the holes 10 provided on the facing surfaces of both electrodes. . Further, a power supply unit 1 for applying a voltage is connected to the upper electrode 2.

An electrode fixture 5 is connected to the upper electrode 2 and the lower electrode 3 via an insulator 9 for opening and closing the device in the vertical direction, and the device is opened by operating the electrode fixture 5. By inserting and closing the base material 6 between the solid dielectric walls 4a and 4b, the base material 6 can be sandwiched between the contact portions of the solid dielectric walls 4a and 4b. By adopting such a structure and performing the partial treatment continuously while moving the base material, it becomes possible to perform treatment on a large base material with a relatively small device.

Further, the solid dielectric walls 4a and 4b are
A discharge pipe 8 for discharging excess mixed gas is connected.

Using this apparatus, in the same manner as in the first aspect of the invention, while supplying the mixed gas from the holes 10 of the upper electrode 2 and the lower electrode 3 to the processing space 11, a predetermined voltage is applied to both electrodes. By applying a discharge plasma to generate a discharge plasma and bringing it into contact with the surface of the base material 6 and performing discharge plasma treatment, for example,
Water repellency and hydrophilicity can be imparted to the substrate.

[0037]

EXAMPLES Examples will be shown below, but the present invention is not limited thereto. (Examples 1 and 2) In the cylindrical device shown in FIG.
Two stainless steel (SUS304) discs with a diameter of 120 mm with holes of 1 mm provided at intervals of 1 cm are arranged so as to face each other to form an upper electrode 2 and a lower electrode 3, and an inner diameter of 90 m
m, a cylinder made of polyethylene terephthalate having an outer diameter of 110 mm as the solid dielectric walls 4a and 4b, and a polycarbonate plate of 150 □ × 3 mm thickness as a base material 6 between the upper and lower solid dielectric walls (“Lexan” manufactured by Asahi Glass Co., Ltd., Static contact angle 67
Degree) was pinched. Then, the mixed gas having the composition shown in Table 1 is continuously supplied to the processing space 11 to bring the mixed gas to atmospheric pressure,
The discharge plasma treatment was performed at the predetermined applied voltage and the treatment time shown in (3) to apply water repellent treatment to both surfaces of the base material 6.

Water droplets of 2 mm were dropped at 1 cm intervals on the surface of the water-repellent treated substrate 6, and static contact was made on both sides of the substrate using a contact angle measuring device "trade name CA-X150" manufactured by Kyowa Interface Science Co., Ltd. When the angle was measured, it was found that only the circular region with a diameter of 90 mm in contact with the discharge plasma showed a larger contact angle than the base material before the treatment and was made water repellent. Table 1
Shows the maximum and minimum static contact angles.

(Embodiment 3) In the cylindrical apparatus shown in FIG. 2, 500 μm thick Y is formed on the surface of the upper electrode 2 made of stainless steel (SUS304) in which 1 mm holes are provided at 1 cm intervals.
_{A 2} O ₃ stabilized ZrO ₂ sprayed film is formed, polyethylene terephthalate is used as the upper solid dielectric wall 4a without using the lower solid dielectric wall 4b, and the base material 6 is
A 0 □ × 2 mm thick surface-polished stainless steel (SUS304) plate was placed in contact with the lower electrode 3. Then, after introducing the mixed gas shown in Table 1 into the processing space to bring it to atmospheric pressure,
The discharge plasma treatment was performed at the predetermined applied voltage and treatment time shown in Table 1, and only the upper side of the substrate 6 was subjected to the water repellent treatment. The static contact angle of the water-repellent treated surface of the substrate was measured in the same manner as in Example 1, and the results are shown in Table 1.

(Examples 4 and 5) Both sides of the polycarbonate plate substrate were processed in the same manner as in Example 1 except that discharge plasma treatment was carried out with the mixed gas having the composition shown in Table 1, the applied voltage and the treatment time. Hydrophilized. The static contact angle was measured on both surfaces of the hydrophilically treated substrate in the same manner as in Example 1, and the results are shown in Table 1.

(Embodiment 6) In the cylindrical apparatus shown in FIG. 2, mixed gases having different compositions shown in Table 1 were respectively introduced from the mixed gas introduction pipes 7a and 7b, and the applied voltage shown in Table 1 and Both sides of the polycarbonate plate substrate were treated in the same manner as in Example 1 except that the discharge plasma treatment was performed for the treatment time. The static contact angle was measured on both sides of the water-repellent treated substrate in the same manner as in Example 1, and the results are shown in Table 1. From the static contact angle measurement results, on the upper surface of the base material, only the circular area with a diameter of 90 mm in contact with the discharge plasma was subjected to water repellent treatment, and on the lower surface of the base material, only the circular area with a diameter of 90 mm in contact with the discharge plasma was performed. Was found to have been hydrophilized.

[0042]

[Table 1]

[0043]

The plasma surface treatment method of the first invention has the above-mentioned constitution, and the base material surface is brought into contact with the discharge plasma in a gas atmosphere, so that the base material can be easily treated under a pressure near atmospheric pressure. Partial surface treatment can be performed. The plastic surface treatment apparatus of the second invention is configured as described above, and can simultaneously perform surface treatment on both sides of the base material in an atmosphere near atmospheric pressure, so that the surface treatment process is simplified and the surface treatment is facilitated. The process can be inlined.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a surface treatment apparatus used in the first invention.

FIG. 2 is a schematic view showing an example of a surface treatment apparatus of the second invention.

[Explanation of symbols]

 1 Power Supply 2 Upper Electrode 3 Lower Electrode 4a, 4b Solid Dielectric Wall 5 Electrode Fixing Jig 6 Base Material 7a, 7b Mixed Gas Introducing Pipe 8 Gas Discharging Pipe 9 Insulator 10 Hole 11 Processing Space

Claims (2)

[Claims] 1. A substrate is placed in a processing space formed by opposed upper and lower electrodes arranged in a substantially horizontal direction, and a solid dielectric wall vertically provided around the upper and lower electrodes. And the lower electrode so as to be substantially horizontal, a mixed gas of an inert gas and a processing gas is introduced into the processing space, and a voltage is applied to the electrode under a pressure near atmospheric pressure to generate discharge plasma. A plasma surface treatment method, wherein the surface of the substrate is treated by generating and contacting the discharge plasma with the surface of the substrate. 2. A processing space formed by opposed upper and lower electrodes arranged in a substantially horizontal direction and solid dielectric walls vertically provided around the upper and lower electrodes, and a processing space formed in the processing space. A gas introducing pipe for introducing a mixed gas of an active gas and a processing gas; a gas discharging pipe for exhausting the processing space; and a power source for applying a voltage between the metal electrodes. Characteristic plastic surface treatment equipment.