Patent Publication Number: US-2015059910-A1

Title: Plasma cvd apparatus, method for forming film and dlc-coated pipe

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a plasma CVD apparatus, a method for forming a film and a DLC-coated pipe. 
     2. Description of a Related Art 
     There will be explained a method for coating a Diamond Like Carbon (DLC) film on an outer peripheral surface of an insulating pipe by a conventional plasma CVD apparatus. 
     An insulating pipe is introduced into a vacuum vessel, an electrode is inserted into the hollow part of the pipe, the vacuum vessel is put into a reduced pressure state, a hydrocarbon gas is supplied to the outer peripheral surface of the pipe by introduction of the hydrocarbon gas into the vacuum vessel, plasma is generated at the outer peripheral surface of the pipe by application of a voltage to the electrode, and thus a DLC film is coated on the outer peripheral surface of the pipe (for example, see Patent Literature 1). 
     In the plasma CVD apparatus, a thin film is formed on the pipe in the vacuum vessel, and thus, when a large pipe is selected, it is necessary to make the vacuum vessel large in accordance with the pipe. For example, when a thin film is to be formed on the inner surface of such a large pipe as transporting fuel gas (for example, methane hydrate), a very large vacuum vessel is required to thereby raise the manufacturing cost of the apparatus. Furthermore, when the work of forming a thin film on the inner surface of the pipe is carried out in a factory, it is necessary to transport the large pipe to the factory and, after forming a film on the inner surface of the pipe, to transport the pipe to a place where the pipe is to be installed. Therefore, the transportation cost is high.
     [Patent Literature 1]: Japanese Patent Laid-Open No. 2012-211349   

     SUMMARY OF THE INVENTION 
     An aspect of the present invention is to provide a plasma CVD apparatus or a method for forming a film, capable of forming a thin film on the inner surface of a pipe, even without a vacuum vessel. 
     Furthermore, an aspect of the present invention is to provide a DLC-coated pipe in which a DLC film is formed on the inner surface of a pipe. 
     Hereinafter, various embodiments of the present invention will be explained. 
     [1] A plasma CVD apparatus, comprising: 
     a first sealing member sealing an end of a pipe; 
     a second sealing member sealing the other end of the pipe; 
     a gas introduction mechanism that is connected to the first sealing member and that introduces a raw material gas into the pipe; 
     an exhausting mechanism that is connected to the second sealing member and that vacuum-exhausts the inside of the pipe; 
     an electrode disposed in the pipe; and 
     a high-frequency power source electrically connected to the electrode or the pipe. 
     [2] The plasma CVD apparatus according to the above [1], wherein an earth is electrically connected to the pipe or the electrode. 
     [3] The plasma CVD apparatus according to the above [1] or [2], wherein the high-frequency power source has a frequency of 10 kHz to 1 MHz. 
     [4] The plasma CVD apparatus according to the above [1] or [2], wherein the high-frequency power source has a frequency of 50 kHz to 500 kHz. 
     [5] A plasma CVD apparatus, comprising: 
     a first sealing member sealing an end of a pipe; 
     a second sealing member sealing the other end of the pipe; 
     a gas introduction mechanism that is connected to the first sealing member and that introduces a raw material gas into the pipe; 
     an exhausting mechanism that is connected to the second sealing member and that vacuum-exhausts the inside of the pipe; 
     an electrode disposed in the pipe; 
     a first high-frequency power source that is electrically connected to the pipe and that has a frequency of 10 kHz to 1 MHz (preferably 50 kHz to 500 kHz); 
     a second high-frequency power source that is electrically connected to the pipe and that has a frequency of 2 MHz to 100 MHz; and 
     an earth electrically connected to the electrode. 
     [6] A plasma CVD apparatus, comprising: 
     a first sealing member sealing an end of a pipe; 
     a second sealing member sealing the other end of the pipe; 
     a gas introduction mechanism that is connected to the first sealing member and that introduces a raw material gas into the pipe; 
     an exhausting mechanism that is connected to the second sealing member and that vacuum-exhausts the inside of the pipe; 
     an electrode disposed in the pipe; 
     a first high-frequency power source that is electrically connected to the electrode and that has a frequency of 10 kHz to 1 MHz (preferably 50 kHz to 500 kHz); 
     a second high-frequency power source that is electrically connected to the electrode and that has a frequency of 2 MHz to 100 MHz; and 
     an earth electrically connected to the pipe. 
     (7) A plasma CVD apparatus, comprising: 
     a first sealing member sealing an end of a pipe; 
     a second sealing member sealing the other end of the pipe; 
     a gas introduction mechanism that is connected to the first sealing member and that introduces a raw material gas into the pipe; 
     an exhausting mechanism that is connected to the second sealing member and that vacuum-exhausts the inside of the pipe; 
     an electrode disposed in the pipe; 
     a first high-frequency power source that is electrically connected to the pipe and that has a frequency of 10 kHz to 1 MHz (preferably 50 kHz to 500 kHz); and 
     a second high-frequency power source that is electrically connected to the electrode and that has a frequency of 2 MHz to 100 MHz. 
     [8] A plasma CVD apparatus, comprising: 
     a first sealing member sealing an end of a pipe; 
     a second sealing member sealing the other end of the pipe; 
     a gas introduction mechanism that is connected to the first sealing member and that introduces a raw material gas into the pipe; 
     an exhausting mechanism that is connected to the second sealing member and that vacuum-exhausts the inside of the pipe; 
     an electrode disposed in the pipe; 
     a first high-frequency power source that is electrically connected to the electrode and that has a frequency of 10 kHz to 1 MHz (preferably 50 kHz to 500 kHz); and 
     a second high-frequency power source that is electrically connected to the pipe and that has a frequency of 2 MHz to 100 MHz. 
     [9] The plasma CVD apparatus according to any one of the above [1] to [8], wherein each of the first sealing member and the second sealing member has a vacuum sealing member to be contacted with an end part of the pipe. 
     [10] The plasma CVD apparatus according to the above [9], wherein each of the first sealing member and the second sealing member has an insulating member disposed in contact with the vacuum sealing member. 
     [11] The plasma CVD apparatus according to any one of the above [1] to [10], including a plurality of earth plates disposed in a vicinity of at least one of the first sealing member and the second sealing member and inside the pipe. 
     [12] The plasma CVD apparatus according to the above [11], wherein mutual distance between the plurality of earth plates is preferably 5 mm or less. 
     [13] The plasma CVD apparatus according to the above [11], wherein mutual distance between the plurality of earth plates is preferably 3 mm or less. 
     [14] The plasma CVD apparatus according to any one of the above [1] to [13], wherein the exhausting mechanism has a gas-gathering member gathering gas inside the pipe. 
     [15] A method for forming a film, comprising the steps of: 
     sealing both ends of a pipe; 
     introducing a raw material gas into the pipe; and 
     forming a film on an inner surface of the pipe by a plasma CVD method by supplying a high-frequency output to the inside of the pipe. 
     [16] The method for forming a film according to the above [15], wherein the high-frequency output has a frequency of 10 kHz to 1 MHz (preferably 50 kHz to 500 kHz). 
     [17] The method for forming a film according to the above [15], wherein both a high-frequency output having a frequency of 2 MHz to 100 MHz and a high-frequency output having a frequency of 10 kHz to 1 MHz (preferably 50 kHz to 500 kHz) are supplied to the inside of the pipe. 
     [18] A DLC-coated pipe, including: 
     a pipe; and 
     a DLC film formed on the inner surface of the pipe. 
     [19] The DLC-coated pipe according to the above [18], wherein the pipe is a metallic pipe, or a ceramics pipe, or a resin pipe. 
     According to an aspect of the present invention, there can be provided a plasma CVD apparatus or a method for forming a film, capable of forming a thin film on the inner surface of a pipe even without a vacuum vessel. 
     Furthermore, according to an aspect of the present invention, there can be provided a DLC-coated pipe with a DLC film formed on the inner surface of the pipe. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view showing schematically the plasma CVD apparatus according to an aspect of the present invention. 
         FIG. 2  is a cross-sectional view showing schematically a modification 1 of the plasma CVD apparatus shown in  FIG. 1 . 
         FIG. 3  is a cross-sectional view showing schematically a modification 2 of the plasma CVD apparatus shown in  FIG. 1 . 
         FIG. 4  is a cross-sectional view showing schematically the plasma CVD apparatus according to an aspect of the present invention. 
         FIG. 5  is a cross-sectional view showing schematically a modification 1 of the plasma CVD apparatus shown in  FIG. 4 . 
         FIG. 6  is a cross-sectional view showing schematically a modification 2 of the plasma CVD apparatus shown in  FIG. 4 . 
         FIG. 7A  is a photograph obtained by photographing the inner surface of a pipe before forming a DLC film, and  FIG. 7B  is a photograph obtained by photographing the inner surface of the pipe after forming a DLC film on the inner surface of the pipe. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be explained in detail using the drawings. However, a person skilled in the art would easily understand that the present invention is not limited to the explanation below, but that modes and details thereof can be changed in various ways without departing from the purport and the scope of the present invention. Accordingly, the present invention should not be construed as being limited to the description of the present embodiments shown below. 
     First Embodiment 
     &lt;Plasma CVD Apparatus&gt; 
       FIG. 1  is a cross-sectional view showing schematically the plasma CVD apparatus according to an aspect of the present invention. 
     The plasma CVD apparatus is an apparatus forming a thin film (for example a DLC film) on the inner surface of a pipe  11 . The pipe  11  is, for example, a metallic pipe, a ceramics pipe, or a resin pipe. 
     The plasma CVD apparatus has a first sealing member sealing an end of the pipe  11 , and a second sealing member sealing the other end of the pipe  11 . The first sealing member has a first cover member  12   a , an insulating member  13   a  is disposed on a surface of the first cover member  12   a , and a first vacuum sealing member  31   a  is disposed in contact with a surface of the insulating member  13   a . The second sealing member has a second cover member  12   b , an insulating member  13   b  is disposed on a surface of the second cover member  12   b , and a second vacuum sealing member  31   b  is disposed on a surface of the insulating member  13   b.    
     The first cover member  12   a  covers an end of the pipe  11 , and the second cover member  12   b  covers the other end of the pipe  11 . The first vacuum sealing member  31   a  makes contact with the end part of the pipe  11  when an end of the pipe  11  is sealed with the first sealing member, and maintains the airtightness between the pipe  11  and the first cover member  12   a . The insulating member  13   a  insulates reliably the first cover member  12   a  from the pipe  11 . The second vacuum sealing member  31   b  makes contact with the end part of the pipe  11  when an end of the pipe  11  is sealed with the second sealing member, and maintains the airtightness between the pipe  11  and the second cover member  12   b . The insulating member  13   b  insulates reliably the second cover member  12   b  from the pipe  11 . Each of the first and second vacuum sealing members  31   a ,  31   b  is a plate formed of, for example, an elastic material (for example rubber). Even when the plate becomes thinner, the insulating members  13   a  and  13   b  can insulate reliably each of the first and second cover members  12   a  and  12   b  from the pipe  11 , to thereby be able to suppress the generation of abnormal discharge. 
     A gas introduction mechanism introducing a raw material gas into the pipe  11  is connected to the first sealing member. The gas introduction mechanism has a nozzle  15 , a vacuum valve  16 , a mass flow controller  17  and a raw material gas generation source  18 . 
     The nozzle  15  passes through the first cover member  12   a , the insulating member  13   a  and the first vacuum sealing member  31   a , and airtightness is maintained between each of the first cover member  12   a , insulating member  13   a  and first vacuum sealing member  31   a , and the nozzle  15 . 
     It is configured such that the tip of the nozzle  15  is positioned inside the pipe  11 , and that the base end of the nozzle  15  is positioned outside the pipe  11 . The base end of the nozzle  15  is connected to one end side of the mass flow controller  17  via the vacuum valve  16 , and the other end side of the mass flow controller  17  is connected to the raw material gas generation source  18  via a vacuum valve or the like, not shown. The raw material gas generation source  18  generates different kinds of raw material gases depending on a thin film to be formed on the inner surface of the pipe  11 , and when a DLC film is to be formed, a gas containing, for example, carbon and hydrogen may be used. Furthermore, a plurality of holes (not shown) for blowing off the raw material gas is provided on the tip side of the nozzle  15  lying inside the pipe  11 . 
     To the second sealing member, an exhausting mechanism (not shown) vacuum-exhausting the inside of the pipe  11  is connected. The exhausting mechanism has a through-hole (not shown) passing through the second cover member  12   b , the insulating member  13   b  and the second vacuum sealing member  31   b , and the through-hole is connected to a vacuum pump (PUMP). Thus, the gas inside the pipe  11  is exhausted by the vacuum pump (PUMP) through an exhaust channel  19  and a vacuum valve  33  to the outside of the pipe. 
     The nozzle  15  functions also as an electrode, and is electrically connected to the earth. Further, each of the first cover member  12   a  and the second cover member  12   b  is electrically connected to the earth. 
     To the pipe  11 , a high-frequency power source  14   a  is electrically connected, and the high-frequency power source  14   a  is electrically connected to the earth. The frequency of the high-frequency power source may exceed 1 MHz, but preferably is 10 kHz to 1 MHz, more preferably 50 kHz to 500 kHz. 
     &lt;Method for Forming a Film&gt; 
     A method for forming a thin film on the inner surface of the pipe  11  using the plasma CVD apparatus shown in  FIG. 1  will be explained. 
     First, both ends of the pipe  11  are sealed by pushing the first vacuum sealing member  31   a  against an end of the pipe  11  to cover the end of the pipe  11  with the first cover member  12   a  and pushing the second vacuum sealing member  31   b  against the other end of the pipe  11  to cover the other end of the pipe  11  with the second cover member  12   b . Further, to the pipe  11 , the high-frequency power source  14   a  is electrically connected. Thus, the plasma CVD apparatus shown in  FIG. 1  is installed on the pipe  11 . 
     Next, a raw material gas (for example toluene (C 7 H 8 )) is generated in the raw material gas generation source  18 , the raw material gas is controlled to a prescribed flow rate by the mass flow controller  17 , and the raw material gas is blown off from the plurality of holes of the nozzle  15  into the pipe  11 . Then the inside of the pipe  11  is kept at a pressure suitable for forming a film by a CVD method, by the balance between the flow rate of the raw material gas thus controlled and the exhaust capacity of the exhausting mechanism. 
     Next, a high-frequency output of 10 kHz to 1 MHz (preferably 50 kHz to 500 kHz) is supplied from the high-frequency power source  14   a  to the pipe  11 . At this time, the nozzle  15  is connected to the earth. Consequently, plasma is ignited between the pipe  11  and the nozzle  15 , and plasma is generated inside the pipe  11  to form a thin film (for example, a DLC film) on the inner surface of the pipe  11 . 
     According to the first embodiment, a thin film can be formed on the inner surface of the pipe  11 , even without a vacuum vessel used in conventional technology. Therefore, even when the pipe  11  is large, a large vacuum vessel in accordance with the pipe is unnecessary, and the manufacturing cost of a plasma CVD apparatus can be suppressed to be low. Further, since a work for forming a thin film on the inner surface of the pipe  11  can be carried out in a site where the pipe is to be installed, the cost can be reduced as compared with the case where the film forming operation is carried out in a factory. 
     Further, in the embodiment, since an RF plasma having a frequency of 10 kHz to 1 MHz is used, induction heating is hardly generated in the pipe  11 , and since a sufficient V DC  is supplied to the inner surface of the pipe  11  in the film forming, a thin film with high hardness can be formed. 
     Meanwhile, in the embodiment, the high-frequency power source  14   a  having a single frequency is electrically connected to the pipe  11  to thereby supply a high-frequency power of a single frequency to the pipe  11 . However, the embodiment is not limited to the case, and both a first high-frequency power source having a frequency of 10 kHz to 1 MHz (preferably 50 kHz to 500 kHz) and a second high-frequency power source having a frequency of 2 MHz to 100 MHz may be electrically connected to the pipe  11  to thereby supply simultaneously a high-frequency power having a frequency of 10 kHz to 1 MHz (preferably 50 kHz to 500 kHz) and a high-frequency power having a frequency of 2 MHz to 100 MHz to the pipe  11 . 
     Modification 1 
       FIG. 2  is a cross-sectional view showing schematically a modification 1 of the plasma CVD apparatus shown in  FIG. 1 , in which the same sign is attached to the same part as in  FIG. 1  and only different parts will be explained. 
     The earth is electrically connected to the pipe  11 , and the high-frequency power source  14   a  is electrically connected to the nozzle  15 . The nozzle  15  and the first con member  12   a  are insulated from each other by the insulating member  35 . 
     Also in the modification, the same effect as that in the first embodiment can be obtained. 
     Meanwhile, in the modification, the high-frequency power source  14   a  having a single frequency is electrically connected to the nozzle  15  to thereby supply a high-frequency power of a single frequency to the nozzle  15 . However, the modification is not limited to the case, and both the first high-frequency power source having a frequency of 10 kHz to 1 MHz (preferably 50 kHz to 500 kHz) and the second high-frequency power source having a frequency of 2 MHz to 100 MHz may be electrically connected to the nozzle  15  to thereby supply simultaneously a high-frequency power having a frequency of 10 kHz to 1 MHz (preferably 50 kHz to 500 kHz) and a high-frequency power having a frequency of 2 MHz to 100 MHz to the nozzle  15 . 
     Modification 2 
       FIG. 3  is a cross-sectional view showing schematically a modification 2 of the plasma CVD apparatus shown in  FIG. 1 , in which the same sign is attached to the same part as in  FIG. 1  and only different parts will be explained. 
     The high-frequency power source  14   a  having a frequency of 10 kHz to 1 MHz (preferably 50 kHz to 500 kHz) is electrically connected to the pipe  11 , and the high-frequency power source  14   b  having a frequency of 2 MHz to 100 MH is electrically connected to the nozzle  15 . The nozzle  15  and the first cover member  12   a  are insulated from each other by the insulating member  35 . 
     Also in the modification, the same effect as that in the first embodiment can be obtained. 
     Meanwhile, in the modification, the high-frequency power source  14   a  is electrically connected to the pipe  11  and the high-frequency power source  14   b  is electrically connected to the nozzle  15 . However, the high-frequency power source  14   a  may be electrically connected to the nozzle and the high-frequency power source  14   b  may be electrically connected to the pipe  11 . 
     Second Embodiment 
     &lt;Plasma CVD Apparatus&gt; 
       FIG. 4  is a cross-sectional view showing schematically the plasma CVD apparatus according to an aspect of the present invention, in which the same sign is attached to the same portion as in  FIG. 1  and only different portions will be explained. 
     The gas introduction mechanism has a nozzle  25 , the vacuum valve  16 , the mass flow controller  17  and the raw material gas generation source  18 . The nozzle  25  has a length extending in the pipe  11  shorter than that of the nozzle  15  in the first embodiment. A plurality of openings (not shown) for blowing off the raw material gas is provided on the tip side of the nozzle  25  positioned inside the pipe  11 . 
     An exhausting mechanism vacuum-exhausting the inside of the pipe  11  is connected to the second sealing member. The exhausting mechanism has an exhaust channel  21 ,  29  passing through the second cover member  12   b , and an end of the exhaust channel  21 ,  29  is connected to a vacuum pump (PUMP). The other end of the exhaust channel  21 ,  29  has a gas-gathering member  21   a  gathering the gas inside the pipe  11 . The gas-gathering member  21   a  has a shape having a concave face that opens from the center of the pipe  11  toward the inside surface side thereof. Hereby, the raw material gas blown off from the tip side of the nozzle  25  is gathered by the gas-gathering member  21   a  and the gathered raw material gas passes through the exhaust channel  21 ,  29  and the vacuum valve  34  to be exhausted to the outside of the pipe  11 . 
     In the vicinity of the nozzle  25 , the first cover member  12   a , the insulating member  23   a  and the first vacuum sealing member  32   a , a plurality of earth plates  27  electrically connected to the earth are disposed. That is, the plurality of earth plates  27  is disposed in the vicinity of the first sealing member and inside the pipe  11 . Hereby, discharge can be carried out between the plurality of earth plates  27  and the inner surface of the pipe  11 . 
     In the vicinity of the gas-gathering member  21   a , the exhaust channel  21 ,  29 , the second cover member  12   b , the insulating member  23   b  and the second vacuum sealing member  32   b , a plurality of earth plates  28  electrically connected to the earth are disposed. That is, the plurality of earth plates  28  is disposed in the vicinity of the second sealing member and inside the pipe  11 . Discharge can be carried out between the plurality of earth plates  28  and the inner surface of the pipe  11 . 
     In the case where the apparatus is operated for a long period of time to thereby form a CVD film of an insulating body on the surface of the nozzle  25 , and as a result, the discharge stops to be generated between the nozzle  25  and the pipe  11 , the plurality of earth plates  27  and  28  work as an opposite electrode in place of the nozzle  25  to make it possible to generate discharge between the plurality of earth plates  27  and  28  and the inner surface of the pipe  11 . Accordingly, the provision of the plurality of earth plates  27  and  28  makes it possible to operate continuously the apparatus for a long period of time. 
     The mutual distance between the plurality of earth plates  27  and  28  is preferably 5 mm or less (more preferably 3 mm or less). Hereby, the formation of the CVD film in the gap between mutual plates in the plurality of earth plates  27  and  28  can be suppressed. As a result, the apparatus can be operated continuously for a longer period of time. 
     &lt;Method for Forming Film&gt; 
     The method for forming a thin film on the inner surface of the pipe  11  using the plasma CVD apparatus shown in  FIG. 4  is the same as that in the first embodiment. 
     Also in the embodiment, the same effect as that in the first embodiment can be obtained. 
     Meanwhile, in the embodiment, the high-frequency power source  14   a  having a single frequency is electrically connected to the pipe  11  to thereby supply a high-frequency power of a single frequency to the pipe  11 . However, the embodiment is not limited to the case, and both the first high-frequency power source having a frequency of 10 kHz to MHz (preferably 50 kHz to 500 kHz) and the second high-frequency power source having a frequency of 2 MHz to 100 MHz may be electrically connected to the pipe  11  to thereby supply simultaneously a high-frequency power having a frequency of 10 kHz to 1 MHz (preferably 50 kHz to 500 kHz) and a high-frequency power having a frequency of 2 MHz to 100 MHz to the pipe  11 . 
     Modification 1 
       FIG. 5  is a cross-sectional view showing schematically a modification 1 of the plasma CVD apparatus shown in  FIG. 4 , in which the same sign is attached to the same part as in  FIG. 4  and only different parts will be explained. 
     The earth is electrically connected to the pipe  11 , and the high-frequency power source  14   a  is electrically connected to the nozzle  25 . The nozzle  25  and the first con member  12   a  are insulated from each other by the insulating member  35 . 
     Also in the modification, the same effect as that in the second embodiment can be obtained. 
     Meanwhile, in the modification, the high-frequency power source  14   a  having a single frequency is electrically connected to the nozzle  25  to thereby supply a high-frequency power of a single frequency to the nozzle  25 . However, the example is not limited to the case, and both the first high-frequency power source having a frequency of 10 kHz to 1 MHz (preferably 50 kHz to 500 kHz) and the second high-frequency power source having a frequency of 2 MHz to 100 MHz may be electrically connected to the nozzle  25  to thereby supply simultaneously a high-frequency power having a frequency of 10 kHz to 1 MHz (preferably 50 kHz to 500 kHz) and a high-frequency power having a frequency of 2 MHz to 100 MHz to the nozzle  25 . 
     Modification 2 
       FIG. 6  is a cross-sectional view showing schematically a modification 2 of the plasma CVD apparatus shown in  FIG. 4 , in which the same sign is attached to the same part as in  FIG. 4  and only different parts will be explained. 
     The high-frequency power source  14   a  having a frequency of 10 kHz to 1 MHz (preferably 50 kHz to 500 kHz) is electrically connected to the pipe  11 , and the high-frequency power source  14   b  having a frequency of 2 MHz to 100 MHz is electrically connected to the nozzle  25 . The nozzle  25  and the first cover member  12   a  are insulated from each other by the insulating member  35 . 
     Also in the modification, the same effect as that in the second embodiment can be obtained. 
     Meanwhile, in the modification, the high-frequency power source  14   a  is electrically connected to the pipe  11  and the high-frequency power source  14   b  is electrically connected to the nozzle  25 . However, the high-frequency power source  14   a  may be electrically connected to the nozzle and the high-frequency power source  14   b  may be electrically connected to the pipe  11 . 
     Example 
       FIG. 7A  is a photograph obtained by photographing the inner surface of a pipe before forming a DLC film.  FIG. 7B  is a photograph obtained by photographing the inner surface of the pipe after forming a DLC film on the inner surface of the pipe. 
     As shown in  FIG. 7B , it was confirmed that a DLC film could be formed on the inner surface of the pipe. 
     DESCRIPTION OF REFERENCE SYMBOLS 
     
         
           1  pipe 
           12   a  first cover member 
           12   b  second cover member 
           13   a  and  13   b  insulating member 
           14   a  and  14   b  high-frequency power source 
           15  nozzle 
           16  vacuum valve 
           17  mass flow controller 
           18  raw material gas generation source 
           19  and  21  exhaust channel 
           21   a  gas-gathering member 
           23   a  and  23   b  insulating member 
           25  nozzle 
           27  and  28  plurality of earth plates 
           29  exhaust channel 
           31   a  first vacuum sealing member 
           31   b  second vacuum sealing member 
           32   a  first vacuum sealing member 
           32   b  second vacuum sealing member 
           33  and  34  vacuum valve 
           35  insulating member