JP3716262B2 - Plasma processing apparatus and method for producing carbon coating-formed plastic container - Google Patents

Description

  The present invention relates to a plasma processing apparatus for forming a carbon coating on the inner surface of a plastic container and a method for manufacturing a carbon coating-formed plastic container by a process using plasma.

  In recent years, reduction and recycling of beverage containers have been promoted against the background of reducing environmental burden. Currently, light-weight beverage containers put into practical use are mainly plastic bottles (PET: polyethylene terephthalate), steel cans, aluminum cans, and paper packs. Occupies the largest share.

Each of these containers has the characteristics shown in Table 1. However, in light of the social demand for reducing environmental impact, plastic containers, such as plastic bottles, will be increasingly needed as lightweight returnable beverage containers. It seems that it will be said.

  Of the various beverage containers, beer containers are still predominantly heavy glass bottles. The reason is that glass is an inexpensive material that does not transmit carbon dioxide (carbon dioxide) and oxygen and can prevent deterioration of the beer itself. When carbon dioxide gas escapes from beer, it becomes so-called beer, and there is a problem that when beer comes into contact with oxygen, it is oxidized and the taste drops, so the beer container does not allow carbon dioxide / oxygen to permeate. The only container that can replace the glass bottle is a metal can. However, there is also a characteristic of each container as shown in Table 1 above. If a plastic bottle can be used as a beer container, the social contribution of environmental burden reduction is great. Since it is easy to carry, it is expected that consumers will have more opportunities to drink beer and consume more.

  On the other hand, carbon membranes have attracted attention as carbon dioxide / oxygen gas barrier materials for about 10 years, and the development of beverage containers combining PET bottles and carbon membranes has begun about 5 years ago. In these, a PET film is coated with a carbon film by a CVD method using high-frequency plasma or microwave plasma.

  However, in addition to the purpose of gas barrier, many examples of coating a carbon film on a substrate have been known. For example, for the purpose of improving chemical resistance and strength, a diamond / diamond-like structure is used by using plasma on the inner surface of a container. A method for forming a carbon film (Japanese Patent Laid-Open No. 2-70059), a vacuum material in which the surface of a substrate is coated with a diamond / diamond-like carbon film by ion beam deposition, plasma CVD, or the like (Japanese Patent Laid-Open No. 2-138469) Publication), a method of forming a diamond-like carbon film on a plastic substrate used for optical articles, etc. via a polyimide intermediate layer (Japanese Patent Laid-Open No. 4-304373), containing nitrogen on the surface of plastic articles such as mechanical parts Plastic article having a diamond-like carbon film (Japanese Patent Laid-Open No. 3-130363), A curved plate (Japanese Patent Laid-Open No. 1-100277) in which a uniform hard carbonaceous film is formed by plasma using an electrode having the shape described above, and a plastic blood collection tube (Japanese Patent Laid-Open No. No. 165772) and the like.

As described above, containers coated with a carbon film are known per se, but there are few known technologies and methods for coating carbon films for beverage containers such as PET bottles. It is. The reason is considered as follows.
(1) Beverage containers are usually composed of a three-dimensional curved surface, and it is difficult to uniformly coat this surface.
(2) Since the PET (PET) material absorbs carbon dioxide gas and transmits oxygen gas, the coating needs to be on the inner surface of the bottle. Since the bottle mouth opening diameter is narrower than the inner diameter of the body, it is difficult to coat.
(3) When this coating process is added to or interrupts the existing container manufacturing process, it is necessary to fully consider initial investment, remodeling costs, equipment installation area, equipment installation, operational costs, etc.
(4) Therefore, an idea is necessary that the throughput (processing speed) of the container manufacturing is reduced by adding a new process, and the cost is not increased.

  Up to this point, PET bottles have been mainly described as representative examples of containers. However, since the object to be coated is not limited to this as long as it is used as a container for beverages, hereinafter, plastic is the generic term for beverage containers to be coated. It is described as a container.

  A conventional method proposed as a carbon film coating method for plastic containers will be described below. For example, regarding a method using high-frequency plasma, a basic coating method is disclosed in Japanese Patent Application Laid-Open No. 8-53116 and Japanese Patent No. 2788412 (Japanese Patent Application Laid-Open No. 8-53117). Coating method (Japanese Patent Laid-Open No. 9-272567), a method corresponding to a specially shaped container (Japanese Patent Laid-Open No. 10-226848), and a method of simultaneously coating a plurality of containers as a mass production technique (Japanese Patent Laid-Open No. 10-258825). Issue gazette). References include “K. Takemoto, et al, Proceedings of ADC / FCT '99, p285” and “E. Shimamura et al, 10th years IAPRI World Conference 1997, p251”.

  Among these, the operation will be described with reference to FIG. 11 mainly based on the description of Japanese Patent No. 2788412 (Japanese Patent Laid-Open No. 8-53116). FIG. 11 is a cross-sectional view of a carbon film coating apparatus for a plastic container using high-frequency plasma CVD described in this publication.

  In FIG. 11, a plastic container 101 is installed in an external electrode 103 having an inner shape substantially along the outer shape of the bottle. The base part preferably has an inner shape along the screw shape for the bottle cap. The external electrode 103 also serves as a vacuum boundary. An internal electrode 102 is inserted into the bottle. The internal electrode 102 has a hollow structure, and a plurality of holes are formed on the surface thereof, so that the gas supplied from the CVD medium gas supply port 105 can be supplied into the plastic container 101. The external electrode 103 is installed in the gas exhaust port 106 through a Teflon 104 that is an electrical insulator. Further, the external electrode 103 has an RF input terminal 107, from which high-frequency power for plasma generation is applied. The RF input terminal 107 is electrically insulated from the Teflon 104 and the gas exhaust port 106.

A method for coating a carbon film on a bottle using the apparatus having such a configuration will be described. First, the gas in the external electrode 103 is exhausted from the gas exhaust port 106. At this time, the gas in the space inside and outside the plastic container 101 is exhausted. After reaching the specified degree of vacuum (representative value: 10 ⁻² to 10 ⁻⁵ Torr), medium gas (representative examples: aliphatic hydrocarbons such as benzene, toluene, xylene, cyclohexane, etc.) from the gas supply port 105 through the internal electrode 102, Aromatic hydrocarbons, hydrocarbons, nitrogen-containing hydrocarbons) are supplied (representative values: 10 to 50 ml / min). The pressure in the plastic container (representative value: 2 × 10 ⁻¹ to 1 × 10 ⁻² Torr) is set according to the balance between the gas supply amount and the exhaust amount. Thereafter, high frequency power (representative value: 50 to 1000 W) is applied to the external electrode 103 from the high frequency power source 1 through the matching unit 2 to the RF input terminal 107.

  Thereby, plasma is generated between the external electrode 103 and the internal electrode 102. At this time, since the plastic container 101 is fitted in the external electrode 103 with almost no gap, plasma is generated in the plastic container 101. By this plasma, the medium gas is dissociated or further ionized to generate a film-forming species that forms a carbon film, and this film-forming species is deposited on the inner surface of the plastic container 101 to form a carbon film. When the film is formed to a predetermined thickness, the application of the high-frequency power is stopped, the supply of the medium gas is stopped, the residual gas is exhausted, nitrogen, a rare gas, air, or the like is supplied into the external electrode 103, and the atmosphere is filled with atmospheric pressure Return to. Then, the plastic container 101 is removed from the external electrode 103. By this method, a carbon film thickness of 300 mm is coated in 2 to 3 seconds.

  The method using microwave plasma is described in WO 99/49991 and “ASIA Pacific Food Industry, Aug. 1999, p68”. Here, the operation will be described with reference to FIG. 12 based on W0 99/49991. FIG. 12 is a cross-sectional view of a carbon film coating apparatus for a plastic container 101 using microwave plasma CVD described in this publication.

  In FIG. 12, a three-stub tuner 212 and a microwave oscillator 224 are connected to a microwave cavity resonator 201 via a waveguide 208. A plunger 210 is connected to the opposite side via a waveguide 208. A dielectric tube 203 is concentrically installed in the cavity resonator 201, which also serves as a vacuum boundary. An opening for inserting a plastic container is provided in the upper part of the cavity resonator 201, and a gas exhaust port 225 is provided in the lower part. The plastic container 101 is inserted into the dielectric tube 203 from above so as to hang from the end plate 204 of the cavity resonator 201. The end plate 204 is connected to the gas supply port 207 and the dielectric tube 203 to form a part of the vacuum boundary, and contacts to the cavity resonator 201 to form a part of the cavity resonator 201. Is attached.

  A method for coating a carbon film on a bottle using the apparatus having such a configuration will be described. An end plate 204 from which the plastic container 101 is suspended is installed in the cavity resonator 201. The atmosphere is exhausted from the gas exhaust port, and then a medium gas necessary for coating is supplied from the gas supply port 207. The space in the dielectric tube 203 is maintained at a predetermined gas pressure (representative value: 30 Torr) by balancing the gas supply amount and the gas exhaust amount. Thereafter, a microwave is output from the microwave oscillator 224. The three-stub tuner 212 matches the input / reflection of the microwave power, and the plunger 210 forms a predetermined electric field strength distribution in the cavity resonator 201. By adjusting the insertion depth of the plunger 210 so that the electric field strength is strongest on the central axis of the cavity resonator, plasma is generated in the plastic container 101, the medium gas is dissociated, and a film-forming species is generated. This deposits on the inner surface of the plastic container 101 and is coated with a carbon film. When the film is formed to a predetermined thickness, the application of microwave power is stopped, the supply of the medium gas is stopped, the residual gas is exhausted, nitrogen, a rare gas, air, or the like is supplied into the dielectric tube 203, Return to atmospheric pressure. Then, the plastic container 101 is removed from the cavity resonator 201.

The coating method using the high frequency plasma as described above has the following problems.
(1) Uniform coating is difficult unless the inner shape of the external electrode conforms to the outer shape of the plastic container.
(2) Uniform coating is difficult if the internal electrodes are not compliant to some extent within the plastic container. However, since the diameter of the internal electrode is limited by the diameter of the bottle cap, it is difficult to deal with bottles of various shapes. Therefore, inner and outer electrodes corresponding to various bottle shapes and bottle surface patterns are required.
(3) Although the medium gas is supplied from the internal electrode, plasma is also generated around it, so that the gas supply hole may be coated and the hole may be blocked over time.

(4) Since a high-frequency voltage is applied to the external electrode that also serves as a vacuum boundary, measures against electrical insulation are required.
(5) Since vacuum conditions are required for plasma generation, bottle evacuation and gas filling processes are required for each coating operation, and the throughput of the entire plastic container manufacturing process is reduced.
(6) Since the electron density of plasma generated at a general frequency of 13.56 MHz for generating high-frequency plasma is relatively low, the number of dissociating medium gases is reduced, so the coating speed is slow, and the production required for high-quality coating is required. There are problems such as the fact that the number density of film types is reduced and high quality coating is not easy.
In addition, when microwave plasma is used, there are the following problems.

(7) A microwave oscillator, a waveguide, a cavity resonator, a matching unit, and a plunger are required for each plastic container, and the device configuration becomes large, so a relatively wide installation space is required.
(8) Adjustment of the microwave electric field intensity distribution in the cavity resonator needs to be performed for each resonator every time the coating conditions (plastic container shape, gas conditions, etc.) change, which is troublesome in operation.
(9) Since the plasma electron density of the microwave plasma is relatively higher than that of the high-frequency plasma, the number of dissociating medium gases is increased, which is advantageous for high-speed coating. However, since the electron temperature is several times higher, the molecular structure of the medium gas is decomposed more than necessary, and the number density of film forming species required for film formation is reduced.

  In view of the state of the prior art, the present invention is a plastic container using microwave plasma that can simplify the apparatus, simplify the operation method, shorten the working time, and form a more uniform carbon film. An object of the present invention is to provide a plasma processing apparatus for forming a carbon film on the inner surface of the plastic container and a method for producing a plastic container having a carbon film formed on the inner surface.

The present invention includes the following configurations (1) to (5) as means for solving the above problems.
(1) The first electrode is inserted into the plastic container, the second electrode is disposed so as to surround the outer periphery of the plastic container, and high-frequency power is applied to the first electrode so that the interior of the plastic container is Generating a discharge plasma and applying a bias power to the second electrode simultaneously with or during the generation of the discharge plasma to form a thin film having gas barrier properties on the inner surface of the plastic container. A method for producing a carbon film-forming plastic container.

(2) A rod-shaped electrode having an outer diameter smaller than the inner diameter of the plastic container to which the carbon coating is to be applied, and being inserted into the plastic container over substantially the entire length of the plastic container; A cylindrical electrode having an inner diameter larger than the outer diameter and disposed so as to surround the outer periphery of the plastic container, a vacuum container for housing the cylindrical electrode, and a gas supply means for supplying a medium gas into the vacuum container A gas exhaust means for exhausting the inside of the vacuum vessel, a high-frequency power source connected to the rod-shaped electrode via a matching device, and applying high-frequency power to the rod-shaped electrode, and a bias matching device for the cylindrical electrode And a bias power source for applying a bias to the cylindrical electrode, and forming a carbon film on the inner surface of the plastic container. Zuma processing apparatus.

(3) The plasma processing apparatus according to (2), wherein the bias power source is a DC power source or an AC power source, or a power source combining a DC power source and an AC power source.

(4) (a) placing a plastic container on which a carbon coating is to be deposited in a cylindrical electrode having an inner diameter larger than the outer diameter of the plastic container; and (b) placing the plastic container inside the plastic container. Inserting a rod-shaped electrode over substantially the entire length of the plastic container; (c) storing the cylindrical electrode in a vacuum container having a gas supply means and a gas exhaust means; and (d) inserting the rod-shaped electrode into the rod-shaped electrode. A high frequency power source is connected via a matching unit, a bias power source is connected to the cylindrical electrode via a bias matching unit, the inside of the vacuum vessel is exhausted and a medium gas is supplied to the inside of the vacuum vessel. The gas pressure is set to a predetermined value, a bias voltage is applied from the bias power source to the cylindrical electrode via the bias matching device, and the rod-shaped power is supplied from the high-frequency power source via the matching device. Applying high-frequency power to the electrode to generate plasma around the rod-like electrode, and dissociating the medium gas by the plasma to deposit the film-forming species generated on the inner surface of the plastic container. A method for producing a carbon container having a carbon coating as a feature.

(5) The method for producing a carbon coating-formed plastic container according to (4), wherein the bias power source is one of a DC power source and an AC power source, or a power source combining a DC power source and an AC power source. .

  Here, high frequency (VHF) means high frequency in a frequency band from several tens of MHz to several hundreds of MHz.

The present invention has the following effects and has great practical value.
(1) In an aspect in which the electrodes on the inner side, the outer side, or both of the plastic container for forming the carbon coating are not required, there are effects of simplifying the apparatus and simplifying the operation method.
(2) In an embodiment that does not require an evacuation device, there are effects such as simplification of the device, simplification of the operation method, and reduction of working time.
(3) In any embodiment, a uniform carbon film can be formed.

  Hereinafter, various preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the following example, a case where a carbon film is formed on a plastic bottle, which is a typical example of a plastic container, will be described as an example.

(First embodiment)
FIG. 1 is a schematic cross-sectional explanatory view showing a plasma processing apparatus according to a first embodiment of the present invention. The apparatus shown in FIG. 1 has a cylindrical electrode 6 having an inner diameter larger than the outer diameter of a plastic bottle 5 which is a plastic container for forming a carbon coating, and a size capable of installing the plastic bottle 5 inside thereof. A cylindrical electrode provided with a rod-shaped electrode 3 having a size that can be inserted over almost the entire length of the PET bottle 5 in the inside thereof, a gas supply means (not shown), and a gas exhaust means (not shown) A vacuum vessel (not shown) for housing 6, a matching unit 2 and a high-frequency power source 1 connected to the rod-shaped electrode 3 and the cylindrical electrode 6 so that the rod-shaped electrode 3 is on the high-voltage side and the cylindrical electrode 6 is on the ground side. It has.

  The shape of the vacuum vessel is arbitrary. A vacuum container may be configured for each individual plastic container, or a plurality of plastic containers may be included. Further, the cylindrical electrode 6 can be used as a vacuum boundary as it is.

  The diameter of the rod-shaped electrode 3 is set to be equal to or smaller than the diameter of the bottle cap, and the length is set to a length that can be inserted over almost the entire length of the PET bottle 5 in the longitudinal direction. As a guide for the length, the ratio of the PET bottle 5 to the total length is set to about {1-D / (2L)}. Here, D represents the inner diameter of the plastic bottle, L represents the total length of the plastic bottle, and L> (D / 2).

  The rod-shaped electrode 3 is made of a metal material having heat resistance such as tungsten or stainless steel. In the following embodiments, preferred materials for the electrodes are the same.

The operation method in the case of manufacturing a carbon film forming plastic container using the apparatus of FIG. 1 is as follows.
After the apparatus is configured as shown in FIG. 1, the inside of the vacuum vessel is evacuated and a medium gas is supplied. The gas supply amount and the gas exhaust amount are balanced and set to a predetermined gas pressure. High frequency power is applied to the rod-shaped electrode 3 from the high frequency power source 1 through the matching unit 2. Thereby, plasma 4 is generated around the rod-shaped electrode 3. The medium gas is dissociated by the plasma 4, and the produced film forming species is deposited on the inner surface of the bottle, thereby forming a coating film. After the predetermined film thickness is formed, the application of the high frequency power is stopped, the supply of the medium gas is stopped, the residual gas is exhausted, nitrogen, a rare gas, air, or the like is supplied, and the space is returned to atmospheric pressure. After that, the bottle is replaced and the next bottle coating operation is started.

  The discharge method in the present embodiment is a capacitive coupling type in which a plastic plastic bottle 5 as a dielectric is sandwiched between the rod-like electrode 3 and the cylindrical electrode 6.

  The frequency of the high frequency is 1 to several tens of MHz, and those of 13.56 MHz, 27.12 MHz and 40.68 MHz which are typically recognized as industrial applications can be applied, but are not limited thereto. For example, a frequency band (several tens to several hundreds of MHz) called high frequency or VHF is also effective under appropriate conditions. Further, the application of high frequency power may be continuous or intermittent (pulsed).

  The medium gas is basically hydrocarbon, for example, alkanes such as methane, ethane, propane, butane, pentane and hexane; alkenes such as ethylene, propylene, butene, pentene and butadiene; alkynes such as acetylene; benzene and toluene Aromatic hydrocarbons such as xylene, indene, naphthalene and phenanthrene; cycloparaffins such as cyclopropane and cyclohexane; cycloolefins such as cyclopentene and cyclohexene; oxygen-containing hydrocarbons such as methyl alcohol and ethyl alcohol; methylamine Nitrogen-containing hydrocarbons such as ethylamine and aniline can be used, and other carbon monoxide and carbon dioxide can also be used. In addition, the medium gas which can be used is the same also in the following embodiment.

  The gas pressure during the plasma treatment is set to about 0.1333 to 133.3 Pa. This embodiment exhibits its effect by operating at a relatively low gas pressure. What is required for film formation is not the plasma itself but the film forming species constituting the film. Although the film-forming species is generated in the vicinity of the plasma, the particles are immediately diffused into the bottle by reaching a low pressure, and quickly reach the inner surface of the bottle. Therefore, as seen in the conventional example, an electrode is formed along the bottle shape and plasma is generated near the inner surface of the bottle. Since the direction of movement changes frequently and it becomes difficult to reach the inner surface of the bottle, it is not necessary to make the film-forming species generation position close to the inner surface of the bottle and make it equidistant). Uniform and homogeneous coating along the curved surface in the bottle is possible by generating plasma.

  This embodiment differs from the conventional example shown in FIG. 11 in that the electrode to which voltage is applied is inside the bottle, the electrode shape to be installed outside the bottle is cylindrical, and strictly conforms to the outer shape of the bottle. This is because there is no gas supply port for each bottle.

  In the embodiment of FIG. 1, the electrode on the high-pressure side is installed inside the bottle, and the operation is performed by lowering the gas pressure, so that the shape of the external electrode can be made uniform on the curved surface inside the bottle without matching the shape of the bottle. A uniform carbon film can be formed.

  When VHF is used for plasma generation, the electron density of the VHF plasma is higher than the density of the high frequency plasma of 13 MHz to 40 MHz, so that the coating speed can be further increased by using the VHF plasma.

  In addition, since the generation of VHF plasma is easy even at a gas pressure relatively higher than that of a high frequency plasma of 13 MHz to 40 MHz, by using VHF plasma, the number density of the above-mentioned film forming species can be increased, and the coating speed can be increased. It can be further increased.

(Second Embodiment)
FIG. 2 is a schematic sectional explanatory view showing a plasma processing apparatus according to a second embodiment of the present invention. The apparatus shown in FIG. 2 includes an internal coiled electrode 7 having a size that can be inserted into a plastic bottle 5 that is a plastic container for forming a carbon coating over almost the entire length in the longitudinal direction of the plastic bottle 5, and gas supply means (FIG. A vacuum vessel (not shown) for storing the PET bottle 5 provided with a gas exhaust means (not shown), a matching unit (not shown) connected to the internal coiled electrode 7 and a high frequency power source (Not shown).

  The shape of the vacuum vessel is arbitrary. A vacuum container may be configured for each individual plastic container, or a plurality of plastic containers may be included.

  The coil diameter of the internal coil electrode 7 should be equal to or smaller than the bottle cap diameter, and the coil thickness and the coil pitch may be set arbitrarily. The length of the PET bottle 5 is such that it can be inserted over almost the entire length in the longitudinal direction. The standard of the length and material of the internal coil electrode 7 are the same as those in the apparatus shown in FIG. The coil may be formed in a tube shape, and a coil cooling refrigerant, such as water, may flow inside the tube. Further, in order to prevent electrical breakdown between the coil pitches or between the coil and other parts, an insulating dielectric may be wound around or covered with the coil surface.

The operation method in the case of manufacturing a carbon film forming plastic container using the apparatus of FIG. 2 is as follows.
An internal coiled electrode 7 having a length extending substantially over the entire length of the bottle is inserted into the PET bottle 5. Next, the PET bottle 5 is placed in a vacuum vessel provided with a gas supply means and a gas exhaust means, and a matching unit and a high frequency power source are connected to the internal coil electrode 7. After configuring the apparatus in this way, the inside of the vacuum vessel is evacuated and a medium gas is supplied. The gas supply amount and the gas exhaust amount are balanced and set to a predetermined gas pressure.

  High frequency power is applied to the internal coil electrode 7 from a high frequency power source through a matching unit. Thereby, plasma 4 is generated around the inner coiled electrode 7. The medium gas is dissociated by the plasma 4, and the produced film forming species is deposited on the inner surface of the bottle, thereby forming a coating film. After the predetermined film thickness is formed, the application of the high frequency power is stopped, the supply of the medium gas is stopped, the residual gas is exhausted, nitrogen, a rare gas, air, or the like is supplied, and the space is returned to atmospheric pressure. After that, the bottle is replaced and the next bottle coating operation is started.

  The discharge method of this embodiment is an inductive coupling method using coiled electrodes. Further, the type of medium gas and the frequency of the high frequency are as described in the embodiment of FIG.

  The gas pressure during the plasma treatment is set to about 0.1333 to 133.3 Pa. This embodiment is the same as the embodiment of FIG. 1 in that the effect is exhibited by operating the gas pressure at a relatively low pressure.

  This embodiment is different from the conventional example shown in FIG. 11 in that an electrode for applying a voltage is provided only inside the bottle, a gas supply port is not provided for each bottle, and the like.

  In this embodiment, by installing a coiled electrode inside the bottle and operating at a low gas pressure, an external electrode is formed along the bottle shape as seen in the conventional example, and plasma is generated near the inner surface of the bottle. Even if it is not generated, it is possible to form a uniform and homogeneous carbon film on the inner surface by generating plasma on the central axis of the bottle.

  Since this embodiment does not require an external electrode, it is characterized in that the apparatus is simplified compared to the apparatus of FIG. 1 as well as the conventional example.

  The effect when using VHF plasma is the same as that of the apparatus of FIG.

(Third embodiment)
FIG. 3 is a schematic cross-sectional explanatory view showing a plasma processing apparatus according to the third embodiment of the present invention. The apparatus shown in FIG. 3 has an external coil electrode 8 that is substantially similar to the outer shape of a plastic bottle 5 that is a plastic container for forming a carbon film, and has a size that allows the PET bottle 5 to be installed inside the external container. A medium gas supply port 30 that opens to a position corresponding to a cap portion of the PET bottle 5 when the PET bottle 5 is installed therein and supplies a medium gas into each PET bottle 5 individually, and each medium attached to the vacuum container A vacuum vessel (not shown) for housing an external coiled electrode 8 provided with a gas supply means (not shown) for supplying gas to the gas supply port 30 and a gas exhaust means (not shown), and an external coiled electrode 8 and a matching device (not shown) and a high-frequency power source (not shown).

  The shape of the vacuum vessel is arbitrary. A vacuum container may be configured for each individual plastic container, or a plurality of plastic containers may be included.

  The coil diameter of the external coil electrode 8 is substantially along the outer diameter of the bottle, but in order to prevent damage to the bottle, the coil is wound so as not to contact the bottle. The cause of the bottle damage is that electrical breakdown may occur between the electrode and the bottle due to the voltage applied to the coiled electrode. Other coil properties are the same as those of the apparatus shown in FIG.

  The diameter of the medium gas supply port 30 is set so that conductance is deteriorated when the gas supplied into the bottle is exhausted through the gap between the medium gas supply port 30 and the bottle cap (outflow of gas discharged from the bottle interior). Make it slightly smaller than the diameter of the bottle cap so that the resistance increases.

The operation method in the case of manufacturing a carbon film forming plastic container using the apparatus of FIG. 3 is as follows.
A coiled electrode is wound around the entire length of a plastic bottle 5 which is a plastic container for forming a carbon coating, so that the PET bottle 5 is installed in an external coiled electrode 8 having a shape substantially similar to its outer shape. The electrode 8 is housed in a vacuum vessel (not shown) having a gas supply means (not shown) and a gas exhaust means (not shown), and a matching device (not shown) A high frequency power supply (not shown) is connected.

  After the apparatus is configured in this manner, the inside of the vacuum container is evacuated, the medium gas is supplied to the inside of the PET bottle 5 from the medium gas supply port 30 that opens to the cap portion of the PET bottle 5, and the medium gas supply port 30 and the bottle are supplied. A predetermined gas pressure is set so that the gas pressure inside the PET bottle 5 becomes higher than the outside by exhausting from the gap between the caps (exhaust in the direction of the medium gas exhaust direction 32 in the figure).

  High frequency power is applied to the external coil electrode 8 from a high frequency power source through a matching unit. As a result, plasma 4 is generated inside the plastic bottle 5. The medium gas is dissociated by the plasma 4, and the produced film forming species is deposited on the inner surface of the bottle, thereby forming a coating film. After the predetermined film thickness is formed, the application of the high frequency power is stopped, the supply of the medium gas is stopped, the residual gas is exhausted, nitrogen, a rare gas, air, or the like is supplied, and the space is returned to atmospheric pressure. After that, the bottle is replaced and the next bottle coating operation is started.

  The discharge method in this embodiment is an inductive coupling method using a coiled electrode. Further, the type of medium gas and the frequency of the high frequency are as described in the embodiment of FIG.

  The gas pressure during the plasma treatment is set to about 0.1333 to 133.3 Pa on the outside of the bottle, and is slightly higher on the inside of the bottle. This embodiment is the same as the embodiment of FIG. 1 in that the effect is exhibited by operating at a relatively low gas pressure.

  This embodiment is different from the conventional example shown in FIG. 11 in that an electrode for applying a voltage is provided only on the outside of the bottle, and there is no electrode inside the bottle.

  In this embodiment, the gas pressure inside the bottle is set higher than the outside. Then, a plasma 4 is generated inside the bottle by applying a high-frequency voltage to the external coiled electrode 8 which is substantially similar to the outer shape of the bottle installed outside the bottle and whose coil diameter is close to the outer diameter of the bottle. This method is based on changing the ease of discharge by applying a gas pressure difference inside and outside the bottle. This is based on a principle called Paschen's law (see, for example, “Hayashi, Plasma Engineering, Asakura Shoten”). According to this, the discharge start voltage in a certain gas has a minimum value with respect to the product of the gas pressure and the electric field application distance.

  In this embodiment, the gas pressure inside the bottle is set higher than the outside, and the discharge start voltage becomes lower than the gas pressure inside, in other words, by making the condition close to the above-mentioned minimum value. Furthermore, by making the discharge start voltage higher with respect to the outer gas pressure, in other words, by making the condition away from the above-mentioned minimum value, even if the electrode is installed only outside the bottle, Plasma can be generated inside, and a uniform and homogeneous carbon coating can be formed on the inner surface of the bottle.

  According to the present embodiment, since the internal electrode is not necessary, the apparatus is simplified as compared with the apparatus of FIG. 1 as well as the conventional example. The effect when using VHF plasma is the same as that of the apparatus of FIG.

Next, the results of forming a carbon film on a PET sheet under conditions simulating this embodiment will be described. Differences and additional points of this embodiment from the embodiment of FIG. 3 are the following (1) to (3).
(1) A cylindrical PET sheet was used instead of the PET bottle 5.
(2) As a vacuum boundary, a glass tube was provided between the cylindrical PET sheet and the external coil electrode 8.
(3) The high frequency power source 1 was connected to one end of the coiled electrode 8 via the matching unit 2, and the other end was electrically grounded.

The apparatus conditions are as follows.
Glass tube: Inner diameter 50mm
Coiled electrode: 1/4 inch diameter copper tube, 10 turns
PET sheet: height 200mm, thickness 0.5mm
The coating conditions are as follows.
Medium gas: C ₂ H ₂ medium
Gas pressure: 13.3Pa
Medium gas flow rate: 20 sccm
High frequency frequency: 13.56 MHz
High frequency power: 50W
When coating was performed under the above conditions, the following results were obtained.
Coating speed: 12.3 nm / second
Carbon film quality: DLC
FIG. 14 is a characteristic diagram showing the results of examining the thin film formed by the method of the present embodiment by the Raman spectroscopic analysis with the Raman shift (cm ⁻¹ ) on the horizontal axis and the relative intensity on the vertical axis. is there. A characteristic line A in the figure shows a Raman spectrum (baseline unremoved) as an index for film quality evaluation. As is clear from the figure, it was found that a typical Raman spectrum of DLC having a peak in the vicinity of 1500 cm ⁻¹ and a shoulder on the short wave number side appears.

  According to the embodiment, it was confirmed that a DLC thin film can be coated on PET at a high speed of 10 nm / second or more. In addition, the apparatus conditions and coating conditions in a present Example are not limited only to the above.

(Fourth embodiment)
FIG. 4 is a schematic cross-sectional explanatory view showing a plasma processing apparatus according to the fourth embodiment of the present invention. 4 is provided with a dielectric filling portion 9 filled with a dielectric between the external coil electrode 8 and the PET bottle 5 in addition to the configuration of FIG. The coil diameter of the external coil electrode 8 is substantially along the outer diameter of the bottle, but in order to prevent damage to the dielectric provided therebetween, the coil is wound so as not to contact the dielectric. Other configurations are the same as those of the apparatus of FIG. The dielectric filling portion 9 fills the periphery of the PET bottle 5 with a dielectric having a dielectric constant similar to that of the material of the PET bottle 5 and fills the irregularities on the outer surface of the PET bottle 5. The presence of irregularities on the outer surface causes the thickness of the PET bottle 5 to be different, and makes the dielectric conditions non-uniform when viewed from the outer coiled electrode 8 in the thickness direction. Accordingly, the load condition for plasma generation becomes non-uniform and uniform coating becomes difficult, so that a more uniform carbon film can be formed by suppressing the influence of unevenness by filling the dielectric.

  The relative dielectric constant of the dielectric material to be filled is preferably approximated to the relative dielectric constant of the plastic container forming the carbon film. In the case of a plastic bottle, it is about 3 to 3.3. In addition, since the uneven portion is filled with a dielectric, a gas phase or a liquid phase is desirable. However, a solid phase dielectric having an inner shape along the outer shape of the PET bottle 5 (for example, a plastic having the same quality as a plastic container forming a carbon film) is sufficiently effective. Such a kind of dielectric is, for example, a general resin which is a material of a plastic container. As a method of forming the dielectric filling portion, a mold made of a dielectric material having a shape corresponding to the shape of the bottle is made, and the bottle is attached to the die. For example, a method of filling a gap between the bottle and a dielectric is suitable. The outer shape of the dielectric filling portion 9 shown in FIG. 4 is similar to that of the plastic bottle 5, but is not limited thereto. Furthermore, the dielectric filling portion 9 may be combined.

  You may change the dielectric constant of the dielectric material filled according to the axial direction of the PET bottle 5. FIG. For example, in order to make the load conditions viewed from the external coil electrode 8 seem to be the same in the axial direction, a method of changing the dielectric constant corresponding to the diameters of the different PET bottles 5 in the upper half and the lower half can be considered.

  The operation method in the case of manufacturing a carbon film-forming plastic container using the apparatus of FIG. 4 is the same as that of the apparatus of FIG. 3 except that a dielectric filling portion 9 filled with a dielectric is provided around the PET bottle 5. is there. The dielectric filling portion 9 may be formed by, for example, a method in which the PET bottle 5 is placed in a container having the shape of the dielectric filling portion 9 and a liquid phase dielectric is filled between the container and the PET bottle 5. . Thereafter, the external coil electrode 8 is attached to the outside of the dielectric filling portion 9, and the medium gas supply port 30 is attached to the base portion of the PET bottle 5.

  The discharge method of this embodiment is an inductive coupling method using coiled electrodes. The medium gas and the high frequency are as described in the embodiment of FIG.

  The gas pressure during the plasma treatment is set to about 0.1333 to 133.3 Pa on the outside of the bottle as in the case of the apparatus of FIG. 3, and is slightly higher on the inside of the bottle. The present embodiment is the same as the embodiment of FIG. 1 in that the effect is exhibited by operating at a relatively low gas pressure.

  The present embodiment is different from the conventional example shown in FIG. 11 in that an electrode for applying a voltage is provided only outside the bottle, there is no electrode inside the bottle, and an external coil electrode 8 outside the PET bottle 5. In addition to this, a dielectric filling portion 9 is provided.

  In the embodiment of FIG. 4, in addition to the effects of the embodiment of FIG. 3, the thickness of the dielectric viewed from the external coil electrode 8 can be made apparently uniform. Even in some cases, the plasma load conditions can be made uniform, and there is an effect that a uniform and homogeneous carbon coating can be formed on the inner surface of the bottle.

(Fifth embodiment)
5 and 6 are schematic cross-sectional explanatory views showing a plasma processing apparatus according to the fifth embodiment of the present invention. The apparatus of this embodiment has a shape that can be inserted into the inside of a plastic bottle 5 that is a plastic container for forming a carbon film, from the base of the plastic bottle 5 to the vicinity of the center of the bottom, substantially along the inner wall surface of the bottle, A bent bar electrode 29 having a size, a gas replacement container (not shown) for storing the PET bottle 5 having a gas supply means (not shown) and a gas exhaust means (not shown), and a bent bar shape A bending bar electrode 29, a matching unit (not shown) connected to the gas replacement container, and a high-frequency power source (not shown) so that the electrode 29 is on the high pressure side and the gas replacement container is on the ground side, and The bendable rod-shaped electrode 29 and the PET bottle 5 are configured to be relatively rotatable with the central axis of the PET bottle 5 as a rotation axis. Here, the ground side wiring is connected to the gas replacement container, but the present invention is not limited to this, and may be an arbitrary grounded portion of the plasma processing apparatus, for example, a framework (frame) of the apparatus. .

  The shape of the gas replacement container is arbitrary. A gas replacement container may be formed for each individual plastic container, or a plurality of plastic containers may be included.

  The bending-type rod-shaped electrode 29 has one or more bent portions 10 and can be bent to a shape close to the inner shape of the PET bottle 5 when inserted into the PET bottle 5, and the tip portion is the bottom of the bottle. It is installed so as to reach the vicinity of the central portion along. In the apparatus shown in FIG. 5, the number of the bent portions 10 is three. However, the present invention is not limited to this, and the bent rod-shaped electrode 29 has a shape that follows the inner surface of the PET bottle 5 as much as possible. Therefore, it is preferable to provide four or more bent portions 10 corresponding to the inner shape of the PET bottle 5. The diameter of the bent rod-shaped electrode (high-pressure side) 29 is set to be equal to or smaller than the diameter of the bottle cap. For example, it is considered effective to make the plasma generation easier by reducing the diameter to, for example, about 1 mm so that the electric field is easily concentrated there. .

  5 and 6 has a mechanism in which the bent rod-shaped electrode 29 rotates in the axial center direction as indicated by an arrow 11 in the figure, and a mechanism in which the PET bottle 5 rotates in the axial center direction as indicated by an arrow 12 in the figure. Or both of these mechanisms (the electrode and the bottle rotate as indicated by arrows 13 and 12 in the figure), respectively, and the bent rod-shaped electrode 29 and the plastic bottle 5 are the center of the plastic bottle 5. The shaft is configured to be relatively rotatable about a rotation shaft.

  As a trigger for plasma ignition, a pin-shaped ground electrode (not shown) is placed in the vicinity of the bent rod-shaped electrode (high voltage side) 29 with the PET bottle 5 interposed therebetween, and discharge can be started between them. The Tesla coil is installed in the vicinity of the bending rod electrode 29 (high-pressure side) 29 with the PET bottle 5 interposed therebetween, and the electric field generated in the vicinity of the bending rod electrode 29 and the magnetic field generated in the vicinity of the Tesla coil are It is also effective to make plasma ignition easier.

The operation method in the case of manufacturing a carbon film formation plastic container using the apparatus of FIG.5 and FIG.6 is as follows.
A bendable rod-shaped electrode 29 is inserted into a plastic bottle 5 which is a plastic container for forming a carbon coating from the base portion of the plastic container to the vicinity of the center of the bottom surface so as to be substantially along the inner wall surface of the bottle. Is housed in a gas replacement container (not shown) having a gas supply means (not shown) and a gas exhaust means (not shown), and the bent bar electrode 29 and the bent bar electrode are placed in the gas replacement container. A matching unit (not shown) and a high-frequency power source (not shown) are connected so that is the high-pressure side and the gas replacement container is the ground side.

  After such a configuration, the atmosphere in the gas replacement container is purged. In this method, the atmosphere may be exhausted with a vacuum device, or a large amount of nitrogen gas or the like may be blown to extrude the atmosphere. Thereafter, a medium gas is supplied and maintained at atmospheric pressure. Then, high-frequency power is applied from the high-frequency power source to the bending-type rod-shaped electrode (high-voltage side) 29 through the matching unit while relatively rotating the bending-shaped rod-shaped electrode (high-voltage side) 29 and the PET bottle 5, Plasma 4 is generated. The medium gas is dissociated by the plasma 4, and the produced film forming species is deposited on the inner surface of the bottle, thereby forming a coating film. After the predetermined film thickness is formed, stop the application of high-frequency power, stop the supply of medium gas, purge the residual gas, supply nitrogen, noble gas, air, etc., then open the container and replace the bottle. Move on to coating work.

(Fifth embodiment: application example 1)
FIG. 7 is a schematic sectional explanatory view showing a plasma processing apparatus according to a fifth embodiment of the present invention. The apparatus of the present embodiment corresponds to a first application example of the apparatus of the fifth embodiment (FIG. 5), and is a mode in which a plurality of bending rod electrodes (high voltage side) 29 are provided in the embodiment of FIG. Here, an open / close bar electrode 15 having three bent bar electrodes combined into one is used. The open / close bar electrode 15 is used as a shape close to the inner shape of the PET bottle 5 by extending the bent portion 10 in a straight line when inserted into the PET bottle 5 and then expanding after the insertion. Also in this case, the PET bottle 5 and the open / close bar electrode 15 are rotated and used. However, when the number of the bent bar electrodes is large, the PET bottle 5 and the open / close bar electrode 15 may not be rotated.

(Fifth embodiment: application example 2)
FIG. 8 is a schematic cross-sectional explanatory view showing a plasma processing apparatus according to the fifth embodiment of the present invention. The apparatus of the present embodiment corresponds to the second application example of the fifth embodiment (FIG. 5), and is a mode in which the one-turn electrode 16 is provided instead of the bent rod-shaped electrode (high voltage side) 29 in the embodiment of FIG. It is. Here, a one-turn electrode 16 having a diameter as shown in the figure equal to or smaller than the diameter of the cap of the PET bottle 5 is inserted, and plasma 4 is generated in the vicinity thereof. At this time, in order to coat the entire inner surface of the PET bottle 5, the one-turn electrode 16 and / or the PET bottle 5 are moved in the direction of movement 17 or 18, that is, are relatively moved in the central axis direction (vertical direction). .

  In the application examples 1 and 2 (FIGS. 7 and 8), the operation method for the other portions is as described in the fifth embodiment (FIG. 5).

  The discharge method in the fifth embodiment (FIGS. 5, 7, and 8) is corona discharge by a rod-shaped electrode. At this time, the ground electrode for the bent rod-shaped electrode (high-voltage side) 29 or the one-turn electrode 16 serves as a container for replacing the gas atmosphere installed outside the PET bottle 5. The medium gas and the high frequency are as described in the embodiment of FIG.

(Fifth Embodiment: Application Example 3)
FIG. 9 is a schematic cross-sectional explanatory view showing a plasma processing apparatus according to the fifth embodiment of the present invention. The apparatus of the present embodiment corresponds to the third application example of the fifth embodiment (FIG. 5), and an external electrode having a shape substantially similar to the outer shape of the plastic bottle is installed outside the plastic bottle. A dielectric filling portion for filling the dielectric with the electrode was formed. In this case, the external electrode becomes the ground side electrode.

  In this embodiment, an external electrode (bottle-like electrode 20) and a dielectric filling portion 9 are added to the apparatus of FIG. That is, the PET bottle 5 is installed in the bottle-like electrode (ground side) 20 and the gap is filled with a dielectric having a dielectric constant equivalent to the material of the PET bottle 5. Then, an atmospheric pressure capacitively coupled plasma (plasma 4 in the figure) is generated between the open / close bar electrode 15 and the bottle-like electrode (ground side) 20. The aim of filling the dielectric is the same as in the case of the fourth embodiment, and the unevenness of the outer surface of the PET bottle 5 is filled to make the thickness of the dielectric as seen from the openable bar electrode 15 apparently uniform. It is intended.

  Also in the third application example, the operation method for the parts other than the connection method of the high frequency power supply is the same as the first application example.

  The fifth embodiment (FIGS. 5, 7, 8, and 9) differs from the conventional example of FIG. 11 in that it can be operated under atmospheric pressure conditions and does not require an evacuation device. Except for the case of 9, the external electrode is unnecessary.

  In the fifth embodiment, the plasma generating electrode is installed near the inner surface of the bottle, and the bottle and the electrode are moved relative to each other to enable uniform film formation under atmospheric pressure conditions. There are advantages that the cost for installation and operation can be reduced, and that the time required for evacuation is not required, so that the throughput of bottle production is improved.

(Sixth embodiment)
FIG. 6 is a schematic cross-sectional explanatory view showing a sixth embodiment of the plasma processing apparatus according to the present invention. The apparatus of FIG. 6 has a shape and size that can be inserted into the inside of a plastic bottle 5 that is a plastic container for forming a carbon coating from the base of the plastic bottle 5 to the vicinity of the center of the bottom surface, almost along the inner wall surface of the bottle. And a pair of bent rod-like electrodes in which the high-voltage-side bent rod-like electrode 29 and the ground-side bent rod-like electrode 14 are combined, a gas supply means (not shown), and a gas exhaust means (not shown). A gas replacement container (not shown) for storing the PET bottle 5, a matching unit 2 connected to the bending rod electrode so that one of the pair of bending rod electrodes is on the high voltage side and the other is on the ground side, and a high frequency The power supply 1 is provided, and the pair of bent rod-shaped electrodes and the plastic bottle 5 are configured to be relatively rotatable with the central axis of the plastic bottle 5 as a rotation axis.

  In this apparatus, a bent rod-shaped electrode (high-pressure side) 29 having a bent portion 10 and a similar bent rod-shaped electrode (grounded side) 14 are inserted in combination in a PET bottle 5 and the gas pressure is set to atmospheric pressure. In this method, the plasma 4 is generated and the inner surface of the bottle is coated. However, in principle, the distance between the two electrodes is kept uniform over the length direction. The shape of the gas replacement container is arbitrary. A gas replacement container may be formed for each individual plastic container, or a plurality of plastic containers may be included. In FIG. 6, the number of the bent portions 10 is three at each bent rod electrode. However, the number of the bent portions 10 is not limited to this, and the bent rod electrodes 29 and 14 are set to be as close to the inner surface of the PET bottle 5 as possible. Since it is more preferable, four or more bent portions 10 may be provided corresponding to the inner shape of the PET bottle 5. The interval between the combined bent-type rod-shaped electrodes is equal to or less than the diameter of the bottle cap, and the diameter of each electrode is reduced to about 1 mm, for example, as shown in the fifth embodiment. It is effective to make it easier.

  The operation method in the case of manufacturing a carbon film forming plastic container using the apparatus of FIG. 6 is as follows. Inside a plastic bottle 5 which is a plastic container for forming a carbon coating, a bent bar electrode (high-pressure side) 29 and a bent type are formed substantially along the inner wall surface of the bottle from the base of the plastic container to the vicinity of the center of the bottom surface. A gas replacement container in which a pair or a plurality of bent rod-shaped electrodes combined with a rod-shaped electrode (ground side) 14 is inserted, and the PET bottle 5 is provided with a gas supply means (not shown) and a gas exhaust means (not shown). The matching unit 2 and the high-frequency power source 1 are connected to a bent bar electrode (high voltage side) 29 and a bent bar electrode (ground side) 14. After configuring in this way, the same operation as in the fifth embodiment is performed. In the case of the present embodiment, when high frequency power is applied from the high frequency power source 1 to the bent bar electrode (high voltage side) 29 via the matching unit 2, between this electrode and the bent bar electrode (ground side) 14. Plasma 4 is generated. The subsequent operation method is the same as that of the fifth embodiment.

  The discharge method in the present embodiment is corona discharge using a rod-shaped electrode. The medium gas and the high frequency are as described in the embodiment of FIG.

  This embodiment (FIG. 6) differs from the conventional example shown in FIG. 11 in that it can be operated under atmospheric pressure conditions, no evacuation device is required, and no external electrode is required.

  In this embodiment, there is an advantage that the cost for installing and operating the vacuum exhaust equipment can be reduced, and the time required for the vacuum exhaust is unnecessary, so that the throughput of the bottle manufacturing is improved.

(Seventh embodiment)
FIG. 10 is a schematic sectional view showing a plasma processing apparatus according to the seventh embodiment of the present invention. This embodiment is a method using helicon wave plasma. This plasma generation method was first shown by RW Boswell (Phys. Lett. Vol. 33A, No. 7 (1970) 457) and is known as a plasma generation method.

  The apparatus in FIG. 10 is a cylindrical vacuum container having an inner diameter larger than the outer diameter of a plastic bottle 5 which is a plastic container for forming a carbon coating, and having a size capable of accommodating the plastic bottle 5 inside thereof. A medium gas inlet 34 serving as a supply unit and a vacuum exhaust port 35 serving as a gas exhaust unit are provided. One end is closed on one side surface (the dilution gas introduction port 33 is provided), and the other end is disposed in the vacuum container. A non-magnetic cylindrical vacuum vessel 26 provided with a glass tube 23, which is a dielectric tube having a communicating space, so that the central axis of the glass tube 23 coincides with the central axis of the vacuum vessel, and a dielectric tube An antenna 22 wound around the cylindrical vacuum vessel 26, magnetic field coils 24 and 25 installed around the cylindrical vacuum vessel 26 so as to be movable in the central axis direction of the vacuum vessel 26, a matching unit 2 and a high-frequency power source 1 connected to the antenna 22. With That.

  The vacuum vessel 26 is required to be made of a nonmagnetic material such as stainless steel, and the dielectric tube is made of a dielectric material such as quartz glass. Magnetic field coils 24 and 25 are arranged around the vacuum vessel 26. Usually, the conductors forming the magnetic field coils 24 and 25 are formed in a copper tube shape, and a coolant, for example, cooling water is flowed therein to prevent heating of the coils. Each of the magnetic field coils 24 and 25 is connected to a direct current power source (not shown), and supplies power to the magnetic field coils.

  The positions of the gas introduction ports 33 and 34 and the vacuum exhaust port 35 are not limited to the positions shown in FIG. The number of gas inlets is not limited to two. The position of the dilution gas introduction port 33 is also arbitrary, and it may be installed in the vacuum vessel 26 or may be introduced by mixing with a medium gas. The diameter of the glass tube 23 and the diameter of the antenna 22 associated therewith are also arbitrary. The number of antenna turns is not limited to two turns. The antenna 22 may be formed in a tube shape, and cooling water may flow through it to prevent antenna overheating. The magnetic field coils 24 and 25 are provided with a mechanism that moves in the axial direction (directions 27 and 28 in the figure). Accordingly, the positions of the magnetic field coils 24 and 25 can be arbitrarily set in the axial direction. A permanent magnet may be arranged in place of the magnetic field coils 24 and 25.

  The operation method in the case of manufacturing a carbon film forming plastic container using the apparatus of FIG. 10 is as follows. A plastic bottle 5 which is a plastic container for forming a carbon coating is a cylindrical vacuum container having an inner diameter larger than the outer diameter of the PET bottle 5 and having a size capable of accommodating the PET bottle 5 inside thereof. A medium gas inlet 34 as a means and a vacuum outlet 35 as a gas exhaust means, one end is closed on one side and a dilution gas inlet 33 is provided, and the other end communicates with the inside of the vacuum vessel. The glass tube 23, which is a dielectric tube having a space, is placed in a non-magnetic cylindrical vacuum vessel 26 provided so that the central axis of the glass tube 23 coincides with the central axis of the vacuum vessel 5. The open end of the bottle is positioned on the glass tube 23 side, and the central axis of the plastic bottle 5 is stored so as to coincide with the central axes of the glass tube 23 and the vacuum vessel 26.

  Next, after evacuating the inside of the vacuum vessel 26, a dilution gas and a medium gas are supplied to balance the gas exhaust amount, and the inside of the vacuum vessel 26 is set to a predetermined gas pressure. Next, after a predetermined magnetic field configuration is set by passing current through magnetic field coils 24 and 25 installed around the vacuum vessel 26, the high frequency power is supplied from the high frequency power source 1 to the antenna 22 wound around the glass tube 23 via the matching unit 2. Is applied to generate a plasma 4 inside the PET bottle 5, and a film forming species generated by dissociating a medium gas by the plasma 4 is deposited on the inner surface of the PET bottle 5 to form a carbon coating. Subsequent operations are the same as those in the first embodiment.

  The setting of the magnetic field configuration is controlled by the way in which the current flows to the magnetic field coil. As the method, the current flows in the magnetic field coils 24 and 25 in the same direction, and the generated magnetic field lines are parallel to the central axis of the vacuum vessel 26. In order to achieve (homogeneous magnetic field), a current is supplied only to the magnetic field coil 24 so that the magnetic lines of force spread from the central axis of the vacuum vessel 26 in a trumpet shape (diffuse magnetic field). There is a method in which a current flows in the opposite direction so that the magnetic field lines extending in a trumpet shape from each magnetic field coil are in a shape facing each other between two magnetic field coils (cusp magnetic field). What is necessary is just to use properly by conditions, such as making it respond | correspond to a shape. Moreover, the shape of the magnetic field lines of each magnetic field configuration can also be adjusted by increasing or decreasing the value of the current flowing through each magnetic field coil.

  The discharge method in this embodiment uses a wave excitation method. Further, the type of medium gas and the frequency of the high frequency are as described in the embodiment of FIG. The gas pressure during the plasma treatment is about 0.1333 to 13.33 Pa.

  This embodiment (FIG. 10) is different from the conventional example shown in FIG. 11 in that no electrode is required inside or outside the PET bottle 5.

  In the present embodiment, the plasma 4 can be generated inside the bottle without forming an electrode inside or outside the PET bottle 5, and a carbon film can be formed on the inner surface of the bottle. Further, since the helicon wave plasma has a higher electron density than the above-described capacitively coupled plasma and inductively coupled plasma, the amount of dissociating the medium gas can be increased. Therefore, the coating speed can be improved. Further, since the helicon wave plasma has a high electron density even at a gas pressure lower than that of the above-described capacitively coupled plasma or inductively coupled plasma, the helicon wave plasma has an effect similar to that of the first embodiment (FIG. 1), and is close to the container. High-speed coating is possible without installing an electrode on the substrate.

(Eighth embodiment)
FIG. 13 is a schematic cross-sectional explanatory view showing a plasma processing apparatus according to an eighth embodiment of the present invention. The present embodiment is a method developed from the first embodiment (FIG. 1). The difference from the first embodiment is that the high-frequency power source 51 is connected to the rod-shaped electrode 3 via the matching unit 52. The cylindrical electrode 6 is not grounded, but is connected to the bias power source 53 via the bias matching unit 54 as a cylindrical electrode (for bias application) 55. However, a combination of the high-frequency power source 1 and the matching unit 2 may be connected to the rod-shaped electrode 3. Further, the bias power source 53 may be a DC power source, an AC power source, or a combination thereof.

  The operation method in the case of manufacturing a carbon film-formed plastic container using the apparatus of FIG. 13 is different from the embodiment of FIG. 1 in that the high-frequency power is supplied from the high-frequency power source and the bias power is supplied from the bias power source to each electrode. It is only to apply simultaneously. Other operation methods are the same as those in FIG. In this embodiment, plasma generated by applying high-frequency power to the rod-shaped electrode 3 is drawn into a plastic bottle by a bias voltage applied to the cylindrical electrode (for bias application) 55, and thereby the following three actions are performed. Give birth.

  First, when high-frequency power is used, a high electron density is obtained compared to high-frequency power, particularly under low gas pressure conditions, so that the frequency of collision with the medium gas increases and the film-forming seed density can be increased.

  Secondly, by adjusting the bias potential, the potential difference from the plasma potential can be made variable, so that the ion energy incident on the substrate (pet bottle) can be adjusted.

  Third, since the ion density is proportional to the electron density, the ion flux incident on the substrate can be controlled by using it together with the adjustment of the potential difference.

The effects are the following three.
(1) Improvement of coating speed
(2) Control of carbon film quality
(3) Control of coating speed Next, the results of forming a carbon film on a PET sheet using an apparatus simulating this embodiment will be described in the following order.
(Condition 1)
Compared with and without bias applied to confirm the effect of bias. (Results of coating on flat PET sheet)
As a device used for the experiment, FIG. 16 shows a case where no bias is applied, and FIG. 17 shows a case where a bias is not applied. These are circular parallel plate type electrode structures, which are generally referred to as capacitively coupled plasma generation methods. In FIG. 16, a high-frequency power source 51 is connected to a parallel plate electrode (high voltage side) 60 via a matching unit 52, and the other parallel plate electrode (ground side) 61 is grounded. The PET sheet 59 was installed on the parallel plate electrode (high voltage side) 60. These electrodes were installed in a vacuum vessel equipped with a gas supply / exhaust device (not shown). The operation method is as follows. After setting the inside of the vacuum vessel under predetermined gas conditions, high-frequency power was applied to the parallel plate electrodes (high voltage side) 60 to generate plasma between the electrodes, and coating the PET sheet 59 was attempted.

The apparatus conditions are as follows.
Parallel plate electrode size: φ100mm
Spacing between parallel plate electrodes: 25 mm
PET sheet: Coating thickness 0.5mm
The coating conditions are as follows.
Medium gas: C ₂ H ₂
Medium gas pressure: 13.3 Pa
Medium gas flow rate: 20 sccm
High frequency frequency: 100 MHz
High and high frequency power: 65W
Coating was carried out under the above conditions, and the following results were obtained.
Coating speed: 2.8 nm / sec Carbon film quality: Polymer (Hydrogen content is very high)
Next, when a bias is applied, the difference from FIG. 16 is that one electrode is a parallel plate electrode (bias application side) 62 and the high frequency power source 1 is connected via the matching unit 2 and PET is connected to this electrode. That is, the seat 59 is installed. The difference in operation method is that bias power and high-frequency power are applied simultaneously.

The apparatus conditions are as follows.
Parallel plate electrode size: φ100mm
Spacing between parallel plate electrodes: 25 mm
PET sheet: 0.5mm coating thickness
The coating conditions are as follows.
Medium gas: C ₂ H ₂
Medium gas pressure: 13.3 Pa
Medium gas flow rate: 20 sccm
High frequency frequency: 100 MHz
High and high frequency power: 55W
Power supply frequency for bias: 13 MHz
Power supply for bias: 70W
Coating was carried out under the above conditions, and the following results were obtained.
Coating speed: 1.9 nm / sec Carbon film quality: DLC
FIG. 18 is a characteristic diagram showing the results of examining the thin film formed by the method of this embodiment by Raman spectroscopy with the horizontal axis representing the Raman shift (cm ⁻¹ ) and the vertical axis representing the relative intensity. is there. The characteristic line C in the figure shows a Raman spectrum (baseline unremoved) as an index for film quality evaluation with bias applied, and the characteristic line D shows a Raman spectrum (baseline unremoved) as an index for film quality evaluation without bias applied. Is shown. As is apparent from the figure, when no bias is applied, a pattern is shown in which the intensity increases to the right on the long wave number side, indicating that the carbon is a polymer-like carbon with a high hydrogen content. When a bias is applied, a pattern having a peak in the vicinity of 1500 cm ⁻¹ and a shoulder on the short wave number side is found to be a typical DLC.

(Condition 2)
Results of Coating on Cylindrical PET Sheet Simulating Bottle Shape Difference from FIG. 13 is that a cylindrical PET sheet was used instead of PET bottle 5.

The apparatus conditions are as follows.
Rod electrode: φ15mm x Length 200mm
Cylindrical electrode (for bias application): φ68mm a little x height 200mm
PET sheet: height 200mm x thickness 0.5mm
The coating conditions are as follows.
Medium gas: C ₂ H ₂
Medium gas pressure: 13.3 Pa
Medium gas flow rate: 20 sccm
High frequency frequency: 100 MHz
High and high frequency power: 50W
Bias power supply frequency: 13.56 MHz
Power supply for bias: 20W
Cylindrical electrode bias voltage: -50V
Coating was carried out under the above conditions, and the following results were obtained.
Coating speed: 5.8 nm / sec Carbon film quality: DLC
FIG. 15 is a characteristic diagram showing the results of examining the thin film formed by the method of this embodiment by Raman spectroscopy with the horizontal axis representing the Raman shift (cm ⁻¹ ) and the vertical axis representing the relative intensity. is there. A characteristic line B in the figure shows a Raman spectrum (baseline unremoved) as an index for film quality evaluation. As is clear from the figure, it was found that a typical Raman spectrum of DLC having a peak in the vicinity of 1500 cm ⁻¹ and a shoulder on the short wave number side appears.

(Condition 1) Results of confirming the effect of bias (coating result on flat PET sheet) by comparing with and without applying bias (Condition 2) To cylindrical PET sheet simulating bottle shape Table 2 summarizes the coating results.

  In the absence of bias application, a coating speed higher than that in the case of bias application was obtained, but the film quality is not suitable for reducing gas permeability, and there is no meaning of high-speed coating. However, by applying a bias, the film quality can be improved while maintaining a coating speed of a predetermined level or higher, and the coating speed is also improved in the cylindrical PET sheet substrate simulating the bottle shape. The effectiveness of was confirmed.

  Note that the apparatus conditions and coating conditions in the present embodiment are not limited to the above, and are limited to the above as long as the apparatus and method for applying a bias to the substrate are provided in addition to the plasma generation for generating the film forming species. There are no requirements. The evaluation method of film quality from the viewpoint of Raman spectrum is, for example, “Raman spectrum of diamond-like carbon film”, Masanobu Yoshikawa, NEW DIAMOND, Vol.4, No.2, p16, or “Evaluation of diamond thin film by Raman spectroscopy” ”, Masanobu Yoshikawa, Surface Technology, Vol.42, No.12 (1991) p35.

  As mentioned above, although the case where the plastic container which forms a carbon film is a PET bottle was demonstrated mainly, this invention is polyethylene resin, polypropylene resin, polystyrene resin, cycloolefin copolymer resin, polyethylene terephthalate resin (PET), polyethylene naphthalate resin , Ethylene-vinyl alcohol copolymer resin, poly-4-methylpentene-1 resin, polymethyl methacrylate resin, polyacrylonitrile resin, polyvinyl chloride resin, polyvinylidene chloride resin, acrylonitrile / styrene resin, acrylonitrile / butadiene / styrene resin , Polyamide resin, polyamideimide resin, polyacetal resin, polycarbonate resin, polybutylene terephthalate resin, ionomer resin, polysulfone resin, tetrafluoroethylene resin, etc. Applied to the container is possible.

  ADVANTAGE OF THE INVENTION According to this invention, a carbon coating film can be formed in the inner surface of the plastic container represented by a PET bottle as a lightweight returnable drink container which can respond to the social request of environmental load reduction.

1 is a schematic block cross-sectional view showing a first embodiment of a plasma processing apparatus according to the present invention. FIG. 3 is a schematic block sectional view showing a second embodiment of the plasma processing apparatus according to the present invention. FIG. 5 is a schematic block sectional view showing a third embodiment of the plasma processing apparatus according to the present invention. The schematic block sectional drawing which shows the 4th embodiment of the plasma processing apparatus which concerns on this invention. FIG. 9 is a schematic block sectional view showing a fifth embodiment of the plasma processing apparatus according to the present invention. The schematic block sectional drawing which shows the 6th embodiment of the plasma processing apparatus which concerns on this invention. FIG. 6 is a schematic block sectional view showing a first application example of the apparatus of FIG. 5. FIG. 6 is a schematic block sectional view showing a second application example of the apparatus of FIG. 5. FIG. 6 is a schematic block sectional view showing a third application example of the apparatus of FIG. 5. FIG. 9 is a schematic block sectional view showing a seventh embodiment of the plasma processing apparatus according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view showing an apparatus for coating a carbon film on a plastic container using high-frequency plasma CVD described in JP-A-8-53116, which is an example of the prior art. The schematic sectional drawing which shows the carbon film coating apparatus to the plastic container using microwave plasma CVD of WO99 / 49991 which is an example of a prior art. The schematic block sectional drawing which shows the 8th embodiment of the plasma processing apparatus which concerns on this invention. The Raman spectrum line figure of the carbon film obtained by the coating device which simulated the 3rd embodiment of the plasma treatment equipment concerning the present invention. The Raman spectrum line figure of the carbon film obtained by the coating device which simulated the 8th embodiment of the plasma processing apparatus concerning the present invention. The schematic block sectional drawing which shows the coating apparatus 2 which simulated the 8th embodiment of the plasma processing apparatus which concerns on this invention. The schematic block sectional drawing which shows the coating apparatus 3 which simulated the 8th embodiment of the plasma processing apparatus which concerns on this invention. The Raman spectrum line figure of the carbon film obtained by the coating apparatus 2 and 3 which simulated the 8th embodiment of the plasma processing apparatus which concerns on this invention.

Explanation of symbols

1 ... High frequency power supply,
2 ... Matching device,
3 ... Rod electrode (high voltage side),
4 ... Plasma,
5 ... PET bottles
6 ... Cylindrical electrode (ground side),
7: Internal coiled electrode,
8: External coiled electrode,
9: dielectric filling portion,
10 ... bent portion,
11, 13 ... Direction of rotation of the bending rod electrode,
12 ... PET bottle rotation direction,
14: Bending bar electrode (ground side),
15 ... Open / close bar electrode,
16: One-turn electrode,
17 ... Movement direction of one-turn electrode,
18 ... Direction of movement of the plastic bottle,
20 ... Bottle-like electrode (ground side),
22 ... Antenna,
23 ... Glass tube,
24, 25 ... Magnetic coil,
26 ... Vacuum container,
27, 28 ... direction of movement of the magnetic field coil,
33 ... Dilution gas inlet,
34 ... Medium gas inlet,
35 ... Vacuum exhaust port,
51. High frequency power supply,
52. Matching device,
53 ... Power supply for bias,
54 ... Bias matching unit,
55 ... Cylindrical electrode (for bias application),
59 ... PET sheet,
60 ... Parallel plate electrode (high voltage side),
61 ... Parallel plate electrode (ground side),
62: High-frequency power supply.

Claims (5)

The first electrode is inserted into the plastic container, the second electrode is disposed so as to surround the outer periphery of the plastic container, and high frequency power is applied to the first electrode to discharge plasma into the plastic container. And a thin film having gas barrier properties is formed on the inner surface of the plastic container by applying a bias power to the second electrode simultaneously with or during the generation of the discharge plasma. A method for producing a carbon coating-formed plastic container. A rod-shaped electrode having an outer diameter smaller than the inner diameter of the plastic container to which the carbon coating is to be applied, and being inserted into the plastic container over substantially the entire length of the plastic container;
A cylindrical electrode having an inner diameter larger than the outer diameter of the plastic container and arranged to surround the outer periphery of the plastic container;
A vacuum vessel that houses the cylindrical electrode;
Gas supply means for supplying a medium gas into the vacuum vessel;
Gas exhaust means for exhausting the inside of the vacuum vessel;
A high-frequency power source connected to the rod-shaped electrode via a matching unit and applying high-frequency power to the rod-shaped electrode;
A bias power source connected to the cylindrical electrode via a bias matching unit and applying a bias to the cylindrical electrode;
A plasma processing apparatus for forming a carbon film on the inner surface of a plastic container. 3. The plasma processing apparatus according to claim 2, wherein the bias power source is one of a DC power source and an AC power source, or a power source combining a DC power source and an AC power source. (A) placing a plastic container to be coated with a carbon coating in a cylindrical electrode having an inner diameter larger than the outer diameter of the plastic container;
(B) inserting a rod-shaped electrode into the inside of the plastic container over almost the entire length of the plastic container;
(C) storing the cylindrical electrode in a vacuum vessel provided with a gas supply means and a gas exhaust means;
(D) A high-frequency power source is connected to the rod-like electrode via a matching unit, a bias power source is connected to the cylindrical electrode via a bias matching unit, and the inside of the vacuum vessel is evacuated and a medium gas is supplied. Then, the inside of the vacuum vessel is set to a predetermined gas pressure, a bias voltage is applied from the bias power source to the cylindrical electrode via the bias matching device, and the high-frequency power source passes through the matching device to apply the bias voltage. Applying high-frequency electric power to the rod-shaped electrode to generate plasma around the rod-shaped electrode, and dissociating the medium gas by the plasma to deposit the film-forming species generated on the inner surface of the plastic container. A method for producing a carbon coating-formed plastic container. 5. The method for manufacturing a carbon coating-formed plastic container according to claim 4, wherein the bias power source is one of a DC power source and an AC power source, or a power source combining a DC power source and an AC power source.

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