JP4382784B2 - Diamond-like carbon film deposition equipment - Google Patents

Description

  The present invention relates to a film forming apparatus for forming a diamond-like carbon film (DLC film) on the inner surface of a bottle-shaped plastic container used as a beverage bottle or a food / pharmaceutical container.

  Plastic containers such as plastic bottles are easy to permeate low-molecular gases such as oxygen and carbon dioxide, so the oxidative degradation of fruit juices and vegetable juices in the containers proceeds in a short period of time. Escapes and feels out of place. In particular, beer has a rapid progress of oxidative deterioration and turns black in about one week, so that it has not been possible to use plastic containers such as plastic bottles that are lightweight, inexpensive, and recyclable. In addition, there is a risk that environmental hormone substances harmful to the human body will dissolve in the contents of the plastic container.

  In view of such circumstances, attempts have been made to form a DLC film excellent in gas barrier properties and the like on the inner surface of a plastic container.

The DLC film is an amorphous carbon mainly composed of SP ³ bonds between carbons, and is a hard carbon film having high hardness, excellent insulation, high refractive index, and very smooth morphology. It has been confirmed that the beer experimentally filled in the plastic bottle formed in has a shelf life comparable to canned beer.

FIG. 2 is a conventional example of a film forming apparatus for forming a DLC film on the inner surface of a bottle-shaped plastic container used as a beverage bottle, and a bottle-shaped plastic container 31 accommodated in an external electrode 30 serving as a vacuum chamber. A tubular internal electrode 33 is inserted into the container 31 from the mouth 32 of the gas, and aliphatic hydrocarbons, aromatic hydrocarbons, oxygen-containing hydrocarbons are fed from a source gas supply pipe 34 connected to the tubular internal electrode 33. A raw material gas composed of a carbon-based gas such as nitrogen-containing hydrocarbons is introduced, and a high frequency of 50 to 1000 W is output between the external electrode 30 and the internal electrode 33 connected to the high frequency power source 36 via the matching unit 35. To generate plasma, electrons are accumulated on the inner surface of the insulated external electrode 30 and the external electrode 30 is self-biased to a negative potential and stored on the external electrode 30 side. An electric potential effect of about 500 to 1000 V is generated by electrons, and at this time, a source gas serving as a carbon source is present in the plasma, so that a positively ionized carbon source is positioned along the inner surface of the external electrode 30. It collides with the inner surface of the plastic container 31 at an accelerated speed, and adjacent carbons are bonded together to form a dense DLC film (see Patent Documents 1 and 2).
JP-A-8-53116 JP-A-8-53117

  2 does not collide with the inner surface of the container 31 unless the distance between the outer electrode 30 and the inner electrode 33 is kept substantially uniform within a range of 10 to 50 mm at any position of the bottle-shaped plastic container 31. As shown in the figure, the internal shape of the external electrode 30 is the same as that of the bottle-shaped plastic container 31 accommodated therein. It is formed in a shape that is substantially similar and forms a space that is slightly larger than the container 31, and the external shape of the internal electrode 33 that is inserted into the plastic container 31 is substantially similar to the plastic container 31 and The container 31 is formed into a shape that can be inserted into the inside thereof from the mouth 32.

  Further, if air is present in the external electrode 30 when the plasma is generated, the air may be heated to a high temperature and the bottle-shaped plastic container 31 may be thermally deformed. The air inside the exhaust pipe 37 is exhausted by a vacuum pump.

  However, since the shape and size of the bottle-shaped plastic container 31 varies depending on the type, the conventional shape of the internal shape of the external electrode 30 and the external shape of the internal electrode 33 is similar to that of the bottle-shaped plastic container 31. For example, the shape and size of the external electrode 30 and the internal electrode 33 must be changed according to the type of the container 31, and there is a problem that the molding cost of the electrodes 30 and 33 increases.

  Further, when the bottle-shaped plastic container 31 has a body shape that has a significantly larger inner diameter of the body portion 38 than the inner diameter of the mouth 32, the internal electrode 33 inserted from the mouth 32 has a similar shape to the container 31. It cannot be molded. In other words, since the internal electrode that is similar to the thick bottle-shaped plastic container cannot be inserted from the mouth of the container, the internal electrode that is inserted into the thick bottle-shaped plastic container is connected to the external electrode. Therefore, it is inevitably required to have a non-similar shape that cannot maintain a uniform interval therebetween, and thus it becomes difficult to form an entirely uniform DLC film on the inner surface of the plastic container.

  2 uses a ceramic insulating material 39 to electrically insulate the external electrode 30 and the internal electrode 33 from each other, but the insulating material 39 is exposed in the external electrode 30. If so, impurities may increase due to the vacuum deposition effect that occurs when plasma is generated, which may lead to a decrease in the quality of the DLC film.

  The DLC coating for forming a DLC film on the inner surface of the bottle-shaped plastic container 31 is a high-speed coating with a required time of several seconds to several tens of seconds. Therefore, a vacuum pump in which the air in the external electrode 30 is connected to the exhaust pipe 37 is used. Although high-speed exhaust is required, the high-speed exhaust causes a turbulent flow at a location where the exhaust pipe 37 in the external electrode 30 is connected or in the vicinity of the mouth 32 of the plastic container 31, so Since the local plasma discharge is deteriorated, there is a problem that the coating effect is not good.

  In order to increase the production efficiency of the DLC film, a bottle-shaped plastic housed inside the external electrode by a plurality of ring magnets arranged at regular intervals along the length direction of the external electrode. An invention has been proposed in which a magnetic field is generated in the vicinity of the inner surface of a container to increase the generation rate of the DLC film formed on the inner surface of the container (see Patent Document 3).

In addition, one of the inventors of the present application has a problem in the quality of the DLC film formed by the film forming apparatus of FIG. 2, and a good quality DLC is formed on the inner surface of the bottle-shaped plastic where the inner diameter is not uniform (tapered portion). Since the film could not be formed and the DLC film in that part was easily peeled off from the inner surface of the container or caused microcracks, the gas barrier property might be impaired, so the quality of the DLC film was improved. Therefore, an invention is proposed in which a good quality DLC film is formed on the entire inner surface of a bottle-shaped plastic container by providing a ring-shaped magnet around the outer electrode and forming a magnetic field in a direction matching the central axis of the outer electrode. (See Patent Document 4).
JP-A-11-256331 JP 2000-185997 A

  However, the invention described in Patent Document 3 enables high-speed coating of the DLC film, and the invention described in Patent Document 4 improves the quality of the DLC film. 2, as in the film forming apparatus of FIG. 2, the internal shape of the external electrode and the external shape of the internal electrode are formed into a shape substantially similar to the shape of the bottle-shaped plastic container. By uniforming the distance between the external electrode and the internal electrode, a uniform DLC film is formed on the inner surface of the container. Therefore, depending on the type of container, the shape and size of the external electrode and the internal electrode can be changed. The problem of increasing the molding cost of the electrode had to be changed.

  The present invention provides a uniform overall inner surface of the container without forming the internal shape of the external electrode and the external shape of the internal electrode similar to those of a bottle-shaped plastic container and keeping the distance between the electrodes uniform. Make it possible to form a DLC film, and when exhausting the air inside the external electrode at a high speed, the high-speed exhaustion will not cause a turbulent flow near the mouth of the bottle-shaped plastic container, thereby impairing the coating effect. Is a technical issue.

  In order to solve the above-described problems, the present invention inserts an internal electrode into a container from the mouth of a bottle-shaped plastic container accommodated in the external electrode serving as a vacuum chamber and introduces a source gas into the container. In the film forming apparatus for forming a diamond-like carbon film on the inner surface of the bottle-shaped plastic container by applying a high frequency between the electrode and the internal electrode to generate plasma, the internal shape of the external electrode is the bottle Magnetic field applying means for applying a magnetic field substantially parallel to the axial direction of the bottle-shaped plastic container formed into a shape that can accommodate the shape-shaped plastic container from the bottom side of the container and accommodated inside the external electrode, Apply a magnetic field intensively to the reduced diameter part of the plastic container or apply a stronger magnetic field to the reduced diameter part than other parts. An exhaust flow relaxation vacuum chamber that is communicated with the inside of the external electrode through a plurality of through holes is interposed between the external electrode and an exhaust pipe that exhausts air inside the external electrode. It is characterized by that.

  According to the present invention, since the internal shape of the external electrode is formed into a shape that can accommodate the bottle-shaped plastic container from the bottom side of the container, the bottle shape that accommodates the internal shape of the external electrode therein as in the prior art. The molding cost of the external electrode can be greatly reduced as compared with the case of molding in a shape similar to a plastic container. In addition, when the internal shape of the external electrode is formed so that the bottle-shaped plastic container can be accommodated from the bottom side of the container, the reduced-diameter portion of the bottle-shaped plastic container accommodated inside the external electrode The magnetic field substantially parallel to the axial direction of the bottle-shaped plastic container is concentratedly applied to the reduced-diameter portion, or farther from the inner surface of the external electrode than the other portion. When strongly applied, a DLC film having a thickness comparable to other portions is formed, and a uniform DLC film is formed on the entire inner surface of the container. Further, when the air inside the external electrode is exhausted from the exhaust pipe at a high speed, turbulent flow is generated in the exhaust flow reducing chamber interposed between the exhaust pipe and the external electrode, and the turbulence in the external electrode is generated. By suppressing the generation of the flow, the local plasma discharge in the external electrode becomes good, and the coating effect of the DLC film is improved.

Hereinafter, the discretionary embodiment of the present invention will be specifically described with reference to the drawings.
FIG. 1 is a cross-sectional view showing an example of a film forming apparatus according to the present invention.

  In the film forming apparatus of FIG. 1, the external electrode 1 serving as a vacuum chamber is formed of a cylindrical chamber having a constant inner diameter capable of accommodating the bottle-shaped plastic container 2 from the bottom side, and is accommodated inside the external electrode 1. The internal electrode 4 inserted into the inside of the container 2 from the mouth 3 of the bottle-shaped plastic container 2 is formed of a cylindrical tube having a constant outer diameter. The external electrode 1 and the internal electrode 4 are made of ceramics or the like. The insulating material 5 is electrically insulated and connected to the matching unit 6 and the high frequency power source 7.

  A positioning jig 8 that fits the bottom of a bottle-shaped plastic container 2 accommodated in the external electrode 1 and holds the container 2 at a fixed position where the internal electrode 4 can be inserted is detachable. Is provided.

  The positioning jig 8 is formed in a shape and size that can be inserted into the inside of the opening portion 9 of the external electrode 1 from a difficult vacuum deposition material such as stainless steel. In addition, although illustration is abbreviate | omitted, the jig | tool 8 prepares two or more what was shape | molded in the shape which fits each bottom part according to the bottom part shape of various bottle-shaped plastic containers 2 from which an external shape differs, and these are bottle-shaped. By exchanging depending on the type of the plastic container 2, any bottle-shaped plastic container 2 is held at the center position of the external electrode 1 into which the internal electrode 4 can be inserted from its mouth 3.

  The opening 9 of the external electrode 1 through which the bottle-shaped plastic container 2 is taken in and out from the bottom side of the container is closed with an insulating material 5 that can be moved forward and backward with respect to the opening 9. The surface exposed in the external electrode 1 is covered with a difficult vacuum deposition material 10 such as a stainless steel plate.

  Further, an exhaust flow communicated with the inside of the external electrode 1 through a plurality of through holes 12 formed in the insulating material 5 between the external electrode 1 and an exhaust pipe 11 for exhausting air inside the external electrode 1 with a vacuum pump. A relaxation vacuum chamber 13 is interposed. The chamber 13 is provided integrally with the insulating material 5, and a tubular internal electrode 4 is attached so as to pass through the center of the chamber 13 and the insulating material 5.

  A through-hole 14 is formed in the center of the insulating material 5 so as to pass through the internal electrode 4 in a non-contact manner. A through-hole for fixing the internal electrode 4 in an airtight manner in the center of the exhaust flow reducing vacuum chamber 13. 15 is provided. In addition, a raw material gas composed of a mixed gas of carbon-based gas and hydrogen gas is introduced into the plastic container 2 through the tube of the internal electrode 4 at the end of the internal electrode 4 protruding from the through hole 15 of the chamber 13. A source gas supply pipe 16 is connected.

  The internal electrode 4, the exhaust flow relaxation vacuum chamber 13, and the insulating material 5 are integrally moved forward and backward with respect to the opening 9 of the external electrode 1 by a double-acting cylinder or the like.

  Further, the film forming apparatus shown in FIG. 1 includes magnetic field applying means 17 that applies a magnetic field M substantially parallel to the axial direction of the bottle-shaped plastic container 2 housed inside the external electrode 1. The magnetic field applying means 17 is composed of an annular permanent magnet or a direct current coil disposed so as to surround the outer periphery of the external electrode 1, and is cylindrical when applying a high frequency between the external electrode 1 and the internal electrode 4. A magnetic field M is intensively applied to the reduced diameter portion 18 of the bottle-shaped plastic container 2 which is relatively far from the inner surface of the external electrode 1 formed of a chamber, or a strong magnetic field is applied to the reduced diameter portion 18. However, the magnetic field is weakly applied to the other portions.

  The above is the configuration of the film forming apparatus shown in FIG. First, when the bottle-shaped plastic container 2 is accommodated inside the external electrode 1, the internal electrode 4, the insulating material 5, and the exhaust flow relaxation vacuum chamber 13 having an integrated structure are retracted upward as viewed in FIG. The opening 9 of the electrode 1 is opened, and a positioning jig 8 is loaded in advance into the external electrode 1 from the opening 9.

  In this state, when the bottle-shaped plastic container 2 is inserted into the external electrode 1 from the bottom side, the bottom of the container 2 is fitted into the positioning jig 8, and the container 2 is connected to the inside from the mouth 3. It is automatically held at the center position in the external electrode 1 where the electrode 4 can be inserted.

  When the bottle-shaped plastic container 2 is accommodated in the external electrode 1 in this way, the internal electrode 4, the insulating material 5, and the exhaust flow relaxation vacuum chamber 13, which have been retracted upward, are advanced downward, and FIG. As shown, the internal electrode 4 is inserted into the inside of the bottle-shaped plastic container 2 through the mouth 3, and at the same time, the insulating material 5 is pressed around the opening 9 of the external electrode 1 to close the opening 9 with the insulating material 5. At the same time, the inside of the external electrode 1 is brought into an airtight state by the insulating material and the exhaust flow relaxation vacuum chamber 13.

  Next, the air inside the external electrode 1 is exhausted from the exhaust pipe 11 connected to the vacuum pump through the exhaust flow relaxation vacuum chamber 13 at a high speed, and the bottle-shaped plastic container 2 is passed from the source gas supply pipe 16 through the tubular internal electrode 4. The source gas is supplied into

  Then, a high frequency is applied between the external electrode 1 and the internal electrode 4 by the high frequency power source 7, and the magnetic field M is parallel to the axial direction of the bottle-shaped plastic container 2 accommodated inside the external electrode 1 by the magnetic field applying means 17. Apply.

  As a result, plasma is generated between the external electrode 1 and the internal electrode 4, the inner surface of the external electrode 1 is self-biased to a negative potential, and is ionized positively in the raw material gas introduced into the bottle-shaped plastic container 2. The carbon source collides with the inner surface of the container 2, and a DLC film is formed on the inner surface.

  At this time, the magnetic field M is applied to the reduced diameter portion 18 of the bottle-shaped plastic container 2 to increase the energy of ions directed toward the inner surface of the reduced diameter portion 18, thereby being relatively far from the inner surface of the external electrode 1. A uniform DLC film comparable to other portions can be formed on the reduced diameter portion 18 at a distance, so that the internal shape of the external electrode and the external shape of the internal electrode can be changed to a bottle-shaped plastic as in the conventional example of FIG. There is no need to mold the container into a similar shape.

  Therefore, as shown in FIG. 1, the internal shape of the external electrode 1 is formed into a cylindrical shape capable of accommodating the bottle-shaped plastic container 2 from the bottom side and accommodating other types of bottle-shaped plastic containers having different external shapes. The molding cost of the external electrode 1 can be significantly reduced compared to the conventional case. Also, the external shape of the internal electrode 4 can be formed into a simple tubular shape, and the forming cost can be reduced.

  Further, the positioning jig 8 to be inserted into the external electrode 1 is formed of a hardly vacuum deposition material, and the insulating material 5 is also covered with the hardly vacuum deposition material 10 on the surface exposed in the external electrode 1. There is no risk of generating impurities that impair the quality of the DLC film during plasma generation.

  Further, since the exhaust flow relaxation vacuum chamber 13 is interposed between the external electrode 1 and the exhaust pipe 11 for exhausting the air in the interior at high speed, the external electrode 1 and the vicinity of the mouth 3 of the bottle-shaped plastic container 2 are disposed. This eliminates the possibility of creating turbulence that adversely affects plasma discharge and high-speed coating.

In addition, a DLC film formed using a mixed gas of carbon-based gas and hydrogen gas has an excellent gas barrier property compared to a film formed using only a carbon-based gas. For example, carbon-based gas CH ₄ and hydrogen A PET bottle in which a DLC film is formed using a source gas having a gas H ₂ mixing ratio of 1: 1 has an oxygen permeability of about 1/15. Further, when CH ₄ : H ₂ = 3: 1, the oxygen permeability is about 1/12, and when CH ₄ : H ₂ = 1: 3, it is about 1/8, and the diamond is formed only with a carbon-based gas. It has better gas barrier properties than the like carbon film.

Note that as the ratio of hydrogen gas becomes smaller than CH ₄ : H ₂ = 3: 1, the gas barrier property is rapidly lowered, and there is no significant difference from a DLC film made of only carbon-based gas. Further, as the ratio of hydrogen gas becomes larger than CH ₄ : H ₂ = 1: 3, it tends to become difficult to form a film, and at 1: 6, film formation becomes impossible. Therefore, the mixing ratio of the carbon-based gas and the hydrogen gas is preferably selected within the range of 3: 1 to 1: 3.

  The present invention contributes to improving the productivity of DLC films and reducing processing costs.

The figure which shows an example of the film forming apparatus which concerns on this invention A diagram showing a conventional film forming apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 External electrode 2 Bottle-shaped plastic container 3 Port of bottle-shaped plastic container 4 Internal electrode 5 Insulation material 11 Exhaust pipe 12 Through-hole 13 Exhaust flow relaxation vacuum chamber 17 Magnetic field applying means M Magnetic field 18 Reduced diameter portion of bottle-shaped plastic container

Claims (1)

An internal electrode is inserted into the container from the opening of a bottle-shaped plastic container housed inside the external electrode serving as a vacuum chamber, and a raw material gas is introduced, and a high frequency is applied between the external electrode and the internal electrode. In the film forming apparatus for forming a diamond-like carbon film on the inner surface of the bottle-shaped plastic container by generating plasma, the inner shape of the external electrode can accommodate the bottle-shaped plastic container from the bottom side of the container. Magnetic field applying means for applying a magnetic field substantially in parallel with the axial direction of the bottle-shaped plastic container that is molded into a shape and accommodated inside the external electrode is concentrated on the reduced diameter portion of the bottle-shaped plastic container. It is configured to apply a magnetic field, or to apply a stronger magnetic field to the reduced diameter portion than the other portions, and Between the exhaust pipe for exhausting the air inside, film forming apparatus, wherein the internal exhaust stream relaxation vacuum chamber to be passed, with the said external electrodes are disposed through the plurality of through holes.

Images