JP3970169B2 - DLC film coated plastic container manufacturing method - Google Patents

Description

【００７２】
（実施例１）
図１に示す高周波を外部電極に印加する高周波プラズマＣＶＤ法でＤＬＣ膜を成膜する。原料ガスとして高純度アセチレンを用いる。チャンバーとプラスチック容器の残存空気ガスを排気してプラスチック容器内の真空圧力を０．０５Ｔｏｒｒ（６.６５Ｐａ）まで減圧した後、排気を継続しながら原料供給バルブ２１を開いてプラスチック容器７内へ原料ガスを導入する。原料ガス流量は５０ｓｃｃｍと一定とした。このとき、マスフローコントローラー２３の背圧と配管２２に滞留する原料ガス量に応じて決定される初期原料ガス流入量によって、プラスチック容器の内圧が一時的に設定成膜圧力０.１０Ｔｏｒｒ（１３.３Ｐａ）よりも高くなり、最高０.４Ｔｏｒｒ（５３.２Ｐａ）程度まで上昇する。このときのプラスチック容器の容器内圧プロファイルを図３に示した。図３のプロファイルは前述した第１の実施形態の成膜方法に対応するものである。そして、図３の▲１▼に対応するタイミング、すなわち第１層成膜工程における第１のタイミングで高周波電力（１３．５６ＭＨｚ）を５００Ｗ供給し、プラズマＣＶＤにより第１層の成膜を行った。圧力の変化に応じて第１層は傾斜組成の膜が形成される。第１層の成膜時間は０.３秒程度であり、設定成膜厚力０．１０Ｔｏｒｒ（１３.３Ｐａ）到達後、そのまま第２層の成膜を行った。第２層の成膜時間は２.０秒程度とした。以上の成膜条件を表２に示した。第１層の厚みは４ｎｍ、第２層の厚みは２０ｎｍであり、これも合わせて表２に整理した。なお、第２層の成膜速度は凡そ１０ｎｍ/秒であり、以下に示す実施例及び比較例では第２層の成膜時間を代えることで第２層の厚みを制御した。
【００７３】
【表２】

【００７４】
（実施例２）
原料ガス流量を５０ｓｃｃｍの一定から１００ｓｃｃｍの一定に変更した以外は実施例１と同様に成膜を行ない、これを実施例２とした。容器内圧プロファイルは図４に示すものである。成膜条件と膜厚を表２に整理した。
【００７５】
（実施例３）
高周波の印加のタイミングを図３の▲２▼とした以外は実施例１と同様に成膜を行ない、これを実施例３とした。前述の第１の実施形態の第１層成膜工程の第２のタイミングに相当する。成膜条件と膜厚を表２に整理した。
【００７６】
（実施例４）
第２層成膜工程における高周波印加時間を実施例３（約１.３秒）よりも長くした（約２.０秒）以外は実施例３と同様に成膜を行ない、これを実施例４とした。成膜条件と膜厚を表２に整理した。
【００７７】
（実施例５）
配管２２の内部空間の体積を大きくして原料ガスの滞留体積を大きくした以外は実施例３と同様に成膜を行ない、これを実施例５とした。容器内圧プロファイルは図５に示す通りとなる。成膜条件と膜厚を表２に整理した。なお、配管２２の内部空間の体積を大きくする代わりにマスフローコントローラーの背圧を高くすることでも同様の容器内圧プロファイルを得ることができる。
【００７８】
（実施例６）
高周波の印加のタイミングを図３の▲３▼とした以外は実施例１と同様に成膜を行ない、これを実施例６とした。前述の第１の実施形態の第１層成膜工程の第２のタイミングに相当する。成膜条件と膜厚を表２に整理した。
【００７９】
（実施例７）
図１に示す高周波を外部電極に印加する高周波プラズマＣＶＤ法でＤＬＣ膜を成膜する。原料ガスとして高純度アセチレンを用いる。チャンバーとプラスチック容器の残存空気ガスを排気してプラスチック容器内の真空圧力を０．０５Ｔｏｒｒ（６.６５Ｐａ）まで減圧した後、排気を継続しながら原料供給バルブ２１を開いてプラスチック容器７内へ原料ガスを導入する。原料ガス流量は１００ｓｃｃｍとした。このときプラスチック容器の内圧が一時的に設定成膜圧力０.１０Ｔｏｒｒ（１３.３Ｐａ）よりも高くなり、最高０.５Ｔｏｒｒ（６６.５Ｐａ）程度まで上昇する。このとき容器内部は原料ガスで充分置換される。その後原料ガス流量を５０ｓｃｃｍに設定することで、容器の内圧を設定成膜圧力０．１０Ｔｏｒｒ（１３.３Ｐａ）にする。このときのプラスチック容器の容器内圧プロファイルを図６に示した。図６のプロファイルは前述した第２の実施形態の成膜方法に対応するものである。そして、図６の▲３▼に対応するタイミングで高周波電力（１３．５６ＭＨｚ）を５００Ｗ供給し、プラズマＣＶＤにより第１層の成膜を行った。圧力の変化に応じて第１層は傾斜組成の膜が形成される。第１層の成膜時間は０.３秒程度であり、設定成膜厚力到達後、そのまま第２層の成膜を行った。第２層の成膜時間は３.８秒程度とした。以上の成膜条件を表２に示した。第１層の厚みは３ｎｍ、第２層の厚みは３８ｎｍであり、これも合わせて表２に整理した。
【００８０】
（実施例８）
実施例７における原料ガス流量１００ｓｃｃｍを２００ｓｃｃｍとしたこと以外は実施例７と同様に成膜を行ない、これを実施例８とした。すなわち、容器内圧を設定成膜圧力にする際の原料ガス流量５０ｓｃｃｍは実施例７と同じである。また実施例８の容器内圧プロファイルは図７に示した。図７のプロファイルは前述した第２の実施形態の成膜方法に対応するものである。そして、図７の▲３▼に対応するタイミングで高周波電力（１３．５６ＭＨｚ）を供給する。
【００８１】
（実施例９）
図１に示す高周波を外部電極に印加する高周波プラズマＣＶＤ法でＤＬＣ膜を成膜する。原料ガスとして高純度アセチレンを用いる。チャンバーとプラスチック容器の残存空気ガスを排気してプラスチック容器内の真空圧力を０．０５Ｔｏｒｒ（６.６５Ｐａ）まで減圧した後、排気を継続しながら原料供給バルブ２１を開いてプラスチック容器７内へ原料ガスを導入する。原料ガス流量は５０ｓｃｃｍとした。このとき、マスフローコントローラー２３の背圧と配管２２に滞留する原料ガス量に応じて決定される初期原料ガス流入量によって、プラスチック容器の内圧が一時的に設定成膜圧力０.１０Ｔｏｒｒ（１３.３Ｐａ）よりも高くなり、最高０.４Ｔｏｒｒ（５３.２Ｐａ）程度まで上昇する。そして排気の継続により設定成膜圧力とする。この段階でプラスチック容器内はほぼ完全に原料ガスで置換される。その後原料ガスを７５ｓｃｃｍに増やして一時的に設定成膜圧力よりも内圧を高くし、最高０.４Ｔｏｒｒ（５３.２Ｐａ）程度まで上昇させる。このときのプラスチック容器の容器内圧プロファイルを図８に示した。図８のプロファイルは前述した第３の実施形態の成膜方法に対応するものである。そして、図８の▲５▼に対応するタイミングで高周波電力（１３．５６ＭＨｚ）を５００Ｗ供給し、プラズマＣＶＤにより第１層の成膜を行った。圧力の変化に応じて第１層は傾斜組成の膜が形成される。第１層の成膜時間は０.３秒程度であり、設定成膜厚力０．１０Ｔｏｒｒ（１３.３Ｐａ）到達後、そのまま第２層の成膜を行った。第２層の成膜時間は１.３秒程度とした。以上の成膜条件を表２に示した。第１層の厚みは２ｎｍ、第２層の厚みは１３ｎｍであり、これも合わせて表２に整理した。
【００８２】
（比較例１）
実施例１において高周波の印加タイミングを図３の０に対応するタイミングとした以外は実施例１と同様とし、これを比較例１とした。成膜条件、膜厚を表２に同様に示した。
【００８３】
（比較例２）
実施例１において高周波の印加タイミングを図３の▲４▼に対応するタイミングとした以外は実施例１と同様とし、これを比較例２とした。成膜条件、膜厚を表２に同様に示した。
【００８４】
（比較例３）
実施例８において高周波の印加タイミングを図７の▲２▼に対応するタイミングとした以外は実施例８と同様とし、これを比較例３とした。成膜条件、膜厚を表２に同様に示した。
【００８５】
実施例１〜９及び比較例１〜３について、水素含量の測定を行った。ＰＥＴボトル内面にSi基板を貼り付け、同一条件同一方法によりＤＬＣ膜をSi基板に200ｎｍ成膜した。RBS法（ラザフォード後方散乱分析法）-HFS法（水素前方散乱法）によるＤＬＣ膜の水素組成調査を行った。測定装置は、日新ハイボルテージ（株）製の後方散乱測定装置AN-2500を使用した。結果を表３に示した。
【００８６】
実施例１〜９及び比較例１〜３について、ホット充填を考慮して、ＤＬＣ膜を成膜後ホット充填時の容器の収縮を再現する加熱処理を行った。各実施例、各比較例のＤＬＣ膜コーティングプラスチック容器を９０℃熱水下で１０分間静置させ、さらに水で急冷し、乾燥後２５℃の空気雰囲気下におく。加熱処理前後の酸素透過度、加熱処理後の付着強度を測定した。
【００８７】
酸素透過度は、MOCON社製Oxtran2/20で測定した。23℃で外側湿度RH60％、内側湿度RH90％で行った。酸素透過度を表３に示した。
【００８８】
加熱処理後の付着強度は、前記条件１による碁盤目テープ法、前記条件２による加重式引掻き法で測定した。碁盤目テープ法は切り傷によって１００分割し、テープにより剥れなかった個数の割合として評価した。結果を表３に示した。
【００８９】
ホット充填向け容器として、加熱処理後においても充分な密着強度を有し且つガスバリア性容器として十分なバリア性を有する場合を総合評価○とし、密着強度、ガスバリア性のいずれか若しくは両方が不充分である場合には総合評価×として表３に示した。
【００９０】
【表３】

【００９１】
実施例１〜９では、ＤＬＣ膜を水素原子含有率の異なる第１層と第２層とで構成したので加熱条件下にさらされた後でも密着性に優れ且つ第２層を主体とした容器のガスバリア性の確保ができていた。また、第１層を第２層につながるように傾斜組成としたので、応力集中等によるマイクロクラックの発生は生じなかった。
【００９２】
それに対して比較例１では設定到達圧力に達した後直ぐに原料供給と放電を開始することから第１層の品質が容器ごとに不安定であった。比較例２では水素原子低含有組成のＤＬＣ膜のみの単一組成構造としたため硬質膜となり、加熱によるプラスチックの収縮条件下で充分な密着性を確保できなかった。比較例３では容器の内圧が０.８Ｔｏｒｒ（１０６Ｐａ）と高いために内部電極の管内で放電が生じてしまい、容器内部でのプラズマが不安定で強度も弱く、膜厚が薄くなり酸素バリア性が充分でなかった。
【００９３】
【発明の効果】
容器内表面に形成するＤＬＣ膜を水素原子高含有組成の第１層とその上に形成した第１層よりも相対的に水素原子低含有組成で少なくとも１３ｎｍ以上の膜厚の第２層とから構成し、且つ第１層を第２層に対して傾斜組成とすることで、ホット充填を含むあらゆる充填方法に対応する容器が得られることを見出したことに伴い、本発明によりこの容器を複雑な装置を用いずに簡単な原料ガス制御により製造する方法を提供することができた。すなわち本発明にかかる製造方法により、第１層はプラスチック素材との密着性が高く、またプラスチックの収縮に追随し得る機能を有し且つ第２層は比較的硬質でガスバリア性の機能を有するものである。さらに第１層を第２層に対して容易に傾斜組成とすることができるので、第１層と第２層との境界における応力集中、マイクロクラックを防止することができる。
【００９４】
特に本発明によれば、ブロー成形機などのプラスチック容器製造ライン等の他装置と同オーダーの量産速度（数百本/分程度）を低コストで信頼性高く実現することができる。
【００９５】
また本発明は、容器の最適容器内圧プロファイルをいくつか提案するものであり、第１層の傾斜組成も複数形態提供することが可能であり、用途に応じて適宜選択することができる。いずれの製造方法も圧力制御に複雑な装置機構は必要とせず、排気量の制御も不要である。
【００９６】
本発明において例えば第１の実施形態のように「ガス置換」と「傾斜膜成膜」の両方を同時に行なう場合には、ガス置換にかかる時間に傾斜膜の成膜も並行して行ない、時間短縮することができる。このガス置換は流量調節器と原料供給バルブの配置関係と動作の工夫により、たとえば１秒以下のきわめて短時間に行なうことができる。
【００９７】
さらに本発明において例えば第２、第３の実施形態のように「ガス置換」と「傾斜膜成膜」の両方を分けてガス置換を完全に行なう場合には、ＤＬＣ膜内に不純物の混入が少なく、再現性に優れるＤＬＣ膜コーティングプラスチック容器を製造することが可能である。
【図面の簡単な説明】
【図１】高周波プラズマＣＶＤ法によるＤＬＣ膜コーティングプラスチック容器の製造装置の概略図を示すものである。
【図２】本発明の実施例で使用するボトル形状の概略図であり、（ａ）は耐熱丸型、（ｂ）は耐熱角型を示す。
【図３】第１の実施形態に対応する容器の容器内圧プロファイルの一形態を示す図である。
【図４】図３と比較して原料ガス流量を多くしたときの容器の容器内圧プロファイルの一形態を示す図である。
【図５】図３と比較して供給開始初期の原料ガス流入量を多くしたときの容器の容器内圧プロファイルの一形態を示す図である。
【図６】第２の実施形態に対応する容器の容器内圧プロファイルの一形態を示す図である。
【図７】図６と比較して原料ガス流量を多くしたときの容器の容器内圧プロファイルの一形態を示す図である。
【図８】第３の実施形態に対応する容器の容器内圧プロファイルの一形態を示す図である。
【符号の説明】
１００,高周波プラズマＣＶＤ成膜装置
１,下部外部電極
２,上部外部電極
３,外部電極
４,絶縁部材
５,蓋部
６,チャンバー
７,ＰＥＴボトル
８,Ｏリング
９,内部電極
９a,ガス吹きだし口
１０,マッチングユニット
１１,高周波電源
１３,真空計
１４,真空バルブ
１６,真空ポンプ
１７,ダクト排気
１２,１５,２０,２２,２４,配管
２１,原料供給バルブ
２３,マスフローコントローラー
２５,原料ガス発生源
２６,原料ガス供給手段[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gas barrier plastic container for filling beverages represented by carbonated beverages, carbonated beverages containing fruit juice, fermented carbonated beverages such as beer and sparkling liquor, fruit juice beverages, and the like, and a method for producing the same. In particular, the gas barrier property is realized by a DLC (diamond-like carbon) film coated on the inner surface of a plastic container.
[0002]
[Prior art]
Beverage containers differ greatly in their filling and sterilization methods depending on the type of beverage. For example, carbonated beverages are filled at a low temperature so as not to allow carbon dioxide to escape, and sterilization for each container is not performed. Fruit drinks, tea, coffee, soup and the like are hot filled, that is, filled at 85 to 90 ° C. Of these, tea, coffee and soup are often sold at a temperature of about 60 ° C.
[0003]
It is well known that plastic containers, particularly PET (polyethylene terephthalate resin) bottles, have been put into practical use as beverage containers for soft drinks, carbonated drinks, carbonated drinks with fruit juice, high fruit juice drinks, tea, coffee, etc. The contents are filled by any one of the filling methods.
[0004]
By the way, PET bottles cannot be said to have sufficient oxygen gas barrier properties for all beverages due to the ease of oxidation of the contents. Therefore, a plasma CVD (Chemical Vapor Deposition) method is used to coat the inner surface of a plastic container with a DLC film to provide gas barrier properties, particularly as a carbonated beverage or high fruit juice beverage container, and to prevent sorption of aroma components. And a DLC film-coated plastic container are disclosed (see, for example, Patent Documents 1 and 2).
[0005]
[Patent Document 1]
JP-A-8-53117
[Patent Document 2]
JP-A-8-53116
[0006]
[Problems to be solved by the invention]
By the way, in hot filling, if the plastic container is a PET bottle, the contents are filled at a temperature higher than the glass transition point of the resin. PET bottles are molded by blow molding, but slightly shrink when exposed to a temperature higher than the glass transition point (63-78 ° C.) of PET.
[0007]
In the DLC film-coated plastic containers disclosed in Patent Documents 1 and 2, the DLC film and the plastic have different elastic coefficients and thermal expansion coefficients, and shrinkage that occurs in a PET bottle above the glass transition point does not occur in the DLC film.
[0008]
When the present inventors examined filling into a container, among the above filling methods, a hot filling case in which expansion / contraction followability of a DLC film is particularly required for a plastic container (the plastic shrinks due to heating). Regarding the filling method), it was found that microcracks occur in the DLC film.
[0009]
Therefore, as a result of earnestly examining whether the DLC film can be given a gas barrier property without causing micro cracks in the DLC film even if any filling method including the above case is performed, the present inventors have determined that the DLC film is made of hydrogen. The first layer is composed of a first layer having a high atomic content composition and a second layer having a low hydrogen atom content and a thickness of at least 13 nm or more than the first layer formed on the first layer. The boundary between the first layer and the second layer is provided by providing a function capable of following the shrinkage of the gas, providing the second layer with a gas barrier function, and further setting the first layer to a gradient composition with respect to the second layer. It has been found that a DLC film-coated plastic container that prevents stress concentration and microcracks in the above becomes a plastic container that can handle any of the above-described filling methods, particularly hot filling. That is, in this container, the first layer having a high hydrogen atom composition has high adhesion to the plastic material, is relatively flexible and follows the shrinkage of the plastic, and has a relatively low hydrogen atom content composition than the first layer. The second layer having a thickness of at least 13 nm is relatively hard and exhibits a gas barrier property if it has a thickness of 13 nm or more. If the first layer has a gradient composition with respect to the second layer, microcracks will not occur.
[0010]
On the other hand, in order to make this technology practical to meet market needs, the mass production speed (several hundreds / minute) of the same order as other equipment such as plastic container production lines such as blow molding machines is low cost. It must be realized with high reliability. For this purpose, it is necessary to keep the total process time of one piece within several seconds, and the film formation time of the first layer needs to be as short as possible, about 1 second to several seconds or less.
[0011]
Accordingly, an object of the present invention is to provide a method for producing a plastic container coated with the above-described DLC film having a two-layer structure, which can be used for hot filling, in a simple manner and in as short a time as possible. That is, the hydrogen atom content in the film can be controlled by the actual film forming pressure level. If the film forming pressure is high, the DLC film has a high hydrogen atom content. If the film forming pressure is low, the DLC film has a low hydrogen atom content. It becomes a composition. In addition, when starting to supply the source gas into the plastic container under the set ultimate pressure, the initial source gas flow rate is intentionally increased in order to promote gas replacement for improving the film quality of the barrier film. By supplying the initial gas, the internal pressure of the container is increased, and a container internal pressure profile is generated in which the pressure is reduced again to the set film formation pressure by the balance between the exhaust gas and the supply amount of the raw material gas. Utilizing these, when the film formation pressure is high, the first layer is formed, and when the set film formation pressure is reached, the second layer is continuously formed, so that a DLC film-coated plastic container having a two-layer structure can be easily formed. It aims at providing the method of manufacturing to. That is, by performing both “gas replacement” and “gradient film formation” at the same time, the film formation of the gradient film can be performed in parallel with the time required for gas replacement, thereby shortening the time. This gas replacement can be performed in a very short time of, for example, 1 second or less by means of the arrangement relationship and operation of the flow rate regulator and the raw material supply valve. At this time, since there is a timing when the internal pressure is rising, a timing when the internal pressure is the highest, or a timing when the internal pressure is reduced again in the internal pressure profile of the container, a DLC film-coated plastic container having a two-layer structure using these three timings. It is an object of the present invention to provide a method for easily and cost-effectively manufacturing a material.
[0012]
Furthermore, the object of the present invention is to supply a source gas by a gas system arranged in the order of at least a source gas generation source, a gas flow rate control means, and a source supply valve that enables supply on / off, and at the time of starting the supply of the source gas By controlling the amount of increase in the internal pressure of the plastic container that is raised along with the supply of the initial gas by at least one of the amount of source gas remaining between the gas flow rate control means and the source supply valve or the back pressure of the gas flow rate control means, An object of the present invention is to provide a method for manufacturing a DLC film-coated plastic container that optimizes the internal pressure profile of the container and contains less impurities.
[0013]
Further, the object of the present invention is to sufficiently perform the source gas replacement, and after the source replacement, the source gas to be supplied is initially supplied in a large amount and then the amount of the source gas supplied is reduced so as to reduce the supply amount. By realizing the profile, the container internal pressure profile is optimized, and there is provided a method for manufacturing a DLC film-coated plastic container having almost no impurities and excellent reproducibility.
[0014]
As the plasma energy source, a high frequency output or a microwave output can be mentioned, but the object of the present invention is to select a high frequency as the plasma energy and generate a self-bias voltage on the wall surface of the container, thereby producing a dense DLC having a gas barrier property. The object is to form a film.
[0015]
The function of the gas barrier property is to secure a gas barrier property of approximately 5 times or more compared with an uncoated container.
[0016]
[Means for Solving the Problems]
Means for solving the above problems are as follows. That is, in the method for manufacturing a DLC film-coated plastic container according to the present invention, a vacuum exhaust process for exhausting the inside of the plastic container to a set pressure, and a raw material gas containing a carbon source gas inside the plastic container while continuing the exhaust. A constant flow rate supply is started by the gas flow rate control means, and the internal pressure of the plastic container is raised to a set film formation pressure or more and further reduced to the set film formation pressure with continued evacuation. A first layer film forming step of supplying energy to make the source gas inside the plastic container into plasma and forming a DLC film having a high hydrogen atom content and a gradient composition on the inner surface of the plastic container as a first layer; Low content of hydrogen atoms on the first layer while maintaining the set film formation pressure while the source gas is in a plasma state The second layer forming step of forming a DLC film having a constant composition as the second layer, characterized by having a city.
[0017]
In the method for manufacturing a DLC film-coated plastic container according to the present invention, in the first layer film forming step, plasma generating energy having a constant output is supplied while the internal pressure of the plastic container is increased to a set film forming pressure or higher. It is preferable to start the raw material gas into plasma.
[0018]
In the DLC film-coated plastic container manufacturing method according to the present invention, in the first layer film forming step, the internal pressure of the plastic container is increased to a set film forming pressure or more, and the set film forming pressure is further increased as evacuation continues. It is preferable that the plasma generation of the raw material gas is started by supplying plasma generating energy with a constant output when the internal pressure becomes almost the maximum during the pressure reduction again.
[0019]
In the method for manufacturing a DLC film-coated plastic container according to the present invention, in the first layer film forming step, plasma having a constant output is obtained while the internal pressure of the plastic container is reduced again to the set film forming pressure as evacuation continues. It is preferable to start generating the raw material gas into plasma by supplying energy for generation.
[0020]
Furthermore, in the method for producing a DLC film-coated plastic container according to the present invention, the supply of the raw material gas to the inside of the plastic container is performed by controlling the flow rate of the raw material gas generated from the raw material gas generation source by a gas flow rate control means, Further, the amount of the raw material gas that is retained between the raw material supply valve from the gas flow control means is determined by performing a gas system that enables the raw material gas flow controlled by the gas flow control means to be turned on and off by the raw material supply valve. It is preferable to control the amount of increase in the internal pressure of the plastic container that is increased with the start of the supply of the source gas by adjusting the amount of the source gas inflow at the beginning of the supply by at least one of the back pressures of the gas flow rate control means. .
[0021]
Here, in the method for manufacturing a DLC film-coated plastic container according to the present invention, it is preferable that the increase amount of the internal pressure of the plastic container is controlled by the increase amount due to the start of supply of the raw material gas, and the adjustment of the exhaust amount is not used. .
[0022]
A method for producing a DLC film-coated plastic container according to the present invention includes a vacuum evacuation process for evacuating a plastic container to a set pressure, and a raw material gas containing a carbon source gas at a predetermined flow rate while continuing the evacuation. To increase the internal pressure of the plastic container to a set film formation pressure or higher, and to replace the gas inside the plastic container with a gas, a gas flow rate smaller than the gas flow rate of the raw material gas in the gas replacement process Then, while the pressure is reduced again to the set film formation pressure as the evacuation is continued, the plasma generation of the source gas inside the plastic container is performed by supplying plasma generating energy with a constant output, and the inner surface of the plastic container A first layer forming step of forming a DLC film having a high hydrogen atom content and a gradient composition as a first layer; A second layer film forming step of forming a DLC film having a low hydrogen atom content and a constant composition as the second layer on the first layer while maintaining the set film forming pressure in a state where the raw material gas is turned into plasma. , And.
[0023]
The method for manufacturing a DLC film-coated plastic container according to the present invention includes a vacuum evacuation process for exhausting the inside of the plastic container to a set pressure, and a raw material gas containing a carbon source gas inside the plastic container is constant at a set film forming pressure. A gas replacement step of stabilizing the flow rate of the plastic container to replace the inside of the plastic container with the source gas, and setting the gas flow rate to be larger than the gas flow rate of the source gas in the gas replacement step The internal pressure of the gas is increased from the set film formation pressure, and after a predetermined time has elapsed, the gas flow rate of the source gas in the gas replacement step is set again to stop the internal pressure increase, and the pressure is further reduced to the set film formation pressure, and When the internal pressure rise stops, plasma generating energy with a constant output is supplied to the inside of the plastic container. A first layer film forming step of forming the DLC film having a high hydrogen atom content and a gradient composition as the first layer by converting the source gas into plasma, and the set film formation pressure in a state where the source gas is converted into plasma. And a second layer film forming step of forming a DLC film having a low hydrogen atom content and a constant composition on the first layer as the second layer while holding.
[0024]
Furthermore, in the method for manufacturing a DLC film-coated plastic container according to the present invention, an internal electrode is inserted into the plastic container from a mouth portion, an external electrode is disposed outside the plastic container, and then high frequency power is applied to the external electrode. It is preferable to supply the raw material gas into plasma.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, although an embodiment and an example are given and the present invention is explained in detail, the present invention is limited to these descriptions and is not interpreted.
[0026]
In describing a method for producing a DLC film-coated plastic container according to the present invention, an embodiment of a production apparatus capable of using this production method will be described first. Since the manufacturing method of the present invention uses a plasma CVD method in which the raw material gas is turned into plasma, high frequency or microwave can be used as the energy source.
[0027]
One form of the apparatus by high frequency plasma CVD method is shown in FIG. 1, and it demonstrates based on it. The high-frequency plasma CVD film forming apparatus 100 includes an external electrode 3, an internal electrode 9, a raw material gas supply unit 26, a matching unit 10, and a high-frequency power source 11.
[0028]
The external electrode 3 constitutes a chamber 6 together with the conductive lid 5 and the insulating member 4. An insulating member 4 is disposed under the lid 5, and an external electrode 3 is disposed under the insulating member 4. The external electrode 3 includes an upper external electrode 2 and a lower external electrode 1, and is configured such that the upper portion of the lower external electrode 1 is detachably attached to the lower portion of the upper external electrode 2 via an O-ring 8. The external electrode 3 is insulated from the lid 5 by an insulating member 4.
[0029]
Although the CVD film forming apparatus 100 is described as a film forming apparatus for one plastic container, the chamber 6 and the internal electrode 9 are arranged in parallel also when a DLC film is simultaneously formed on the inner surfaces of a plurality of plastic containers. It can be applied.
[0030]
In this embodiment, the external electrode 3 is divided into the lower external electrode 1 and the upper external electrode 2. However, in order to make the DLC film thickness uniform, the external electrode is, for example, the bottom electrode, The electrode is divided into three or more, such as a partial electrode and a shoulder electrode, and each electrode is electrically insulated with a fluororesin sheet or a polyimide film, for example, while securing a sealing property with an O-ring interposed therebetween. Also good.
[0031]
A space is formed inside the external electrode 3, and this space is for accommodating a plastic container to be coated, for example, a PET bottle 7 made of polyethylene terephthalate resin. The space in the external electrode 3 is formed to be slightly larger than the outer shape of the PET bottle 7 accommodated therein. The insulating member 4 and the lid 5 are provided with an opening that leads to a space in the external electrode. Further, a space is provided inside the lid portion 5, and this space is connected to the space in the external electrode 3 through the opening. The space in the external electrode 3 is sealed from the outside by an O-ring 8 disposed between the upper external electrode 2 and the lower external electrode 1.
[0032]
The impedance matching unit (matching unit) 10 is connected to the lower external electrode 1. Furthermore, the matching unit 10 is connected to a high frequency power source (RF power source) 11 via a coaxial cable.
[0033]
The high frequency power source generates a high frequency that is energy for converting the raw material gas into plasma in a plastic container. The frequency of the high-frequency power source is 100 kHz to 1000 MHz, and for example, an industrial frequency of 13.56 MHz is used.
[0034]
The internal electrode 9 is disposed in the external electrode 3 and is disposed in the PET bottle 7. That is, the internal electrode 9 is inserted into the space in the external electrode 3 from the upper part of the cover part 5 through the space in the cover part 5 and the opening part of the cover part 5 and the insulating member 4. On the other hand, the tip 9 a of the internal electrode 9 is a space in the external electrode 3 and is disposed inside the PET bottle 7 accommodated in the external electrode 3. The internal electrode 9 has a tube shape whose inside is hollow. A gas outlet 9 a is provided at the tip of the internal electrode 9. The internal electrode 9 is grounded through the lid 5 to the ground.
[0035]
The raw material gas supply means 26 introduces the raw material gas supplied from the raw material gas generation source 25 into the PET bottle 7. That is, one side of the pipe 20 is connected to the base end of the internal electrode 9, the other side of the pipe 20 is connected to the raw material supply valve 21, and one side of the pipe 22 is connected to the other side of the raw material supply valve 21. One side of the mass flow controller 23 is connected to the other side of the pipe 22. The other side of the mass flow controller 23 is connected to a source gas generation source 25 through a pipe 24. The source gas generation source 25 generates source gas.
[0036]
As the carbon source gas constituting the source gas, aliphatic hydrocarbons, aromatic hydrocarbons, oxygen-containing hydrocarbons, nitrogen-containing hydrocarbons, etc. that are gaseous or liquid at normal temperature are used. For example, (1) methane CH₄, Ethane C₂H₆Propane C_ThreeH₆, Butane C_FourH_Ten(2) Ethylene C as ethylene₂H_Four, Propylene C_ThreeH₆, Butylene C_FourH₈(3 isomers), (3) acetylene C as acetylene series₂H₂, Methylacetylene C_ThreeH_Four, Ethylacetylene (C_FourH₆), (4) Other normal hexane C₆H₁₄, Cyclohexane C₆H₁₂(5) Benzene C as aromatic₆H₆, Toluene C₆H_FiveCH_Three, Xylene C₆H_Four(CH_Three)₂Can be illustrated. In particular, benzene, toluene, o-xylene, m-xylene, p-xylene, cyclohexane, etc. having 6 or more carbon atoms are desirable. However, when used for containers such as foods, aliphatic hydrocarbons, particularly methane hydrocarbons, ethylene hydrocarbons, and acetylene hydrocarbons are preferred from the viewpoint of hygiene. These carbon source gases may be used alone as a raw material gas, but may be used as a mixed gas of two or more kinds. Further, these gases may be diluted with a rare gas such as argon or helium. In addition, when a silicon-containing DLC film is formed, a Si-containing hydrocarbon gas is used.
[0037]
The DLC film referred to in the present invention is a film called i-carbon film or hydrogenated amorphous carbon film (aC: H), and the hydrogen content including hard carbon film and polymer-like carbon is 0 to 67%. The carbon film. The DLC film is an amorphous carbon film, and SP³It also has a bond. A hydrocarbon gas such as acetylene gas is used as a source gas for forming the DLC film, and a Si-containing hydrocarbon gas is used as a source gas for forming the Si-containing DLC film. By forming such a DLC film on the inner surface of a plastic container, a container that can be used one-way or returnably as a container for carbonated beverages, sparkling beverages, and the like is obtained.
[0038]
The space in the lid 5 is connected to one side of the pipe 12 where the vacuum gauge 13 is installed, the other side of the pipe 12 is connected to one side of the vacuum valve 14, and the other side of the vacuum valve 14 is connected to the pipe 15. The other side of the pipe 15 is connected to the vacuum pump 16. The vacuum pump 16 is connected to a duct exhaust 17.
[0039]
Resin used when molding the plastic container of the present invention is polyethylene terephthalate resin (PET), polyethylene terephthalate-based copolyester resin (copolymer using cyclohexane dimethanol instead of ethylene glycol as the alcohol component of polyester) Eastman), polybutylene terephthalate resin, polyethylene naphthalate resin, polyethylene resin, polypropylene resin (PP), cycloolefin copolymer resin (COC, cyclic olefin copolymer), ionomer resin, poly-4-methylpentene -1 resin, polymethyl methacrylate resin, polystyrene resin, ethylene-vinyl alcohol copolymer resin, acrylonitrile resin, polyvinyl chloride resin, polyvinylidene chloride resin, Polyamide resin, polyamideimide resin, polyacetal resin, polycarbonate resin, polysulfone resin, or ethylene tetrafluoride resin, acrylonitrile - styrene resins, acrylonitrile - butadiene - styrene resin, can be exemplified. Among these, PET is particularly preferable.
[0040]
Next, a method of forming a DLC film inside the container using the high-frequency plasma CVD film forming apparatus 100 shown in FIG. 1 will be described.
[0041]
(First embodiment)
(Installation of PET bottles)
First, a vacuum valve (not shown) is opened to open the chamber 6 to the atmosphere. Thereby, air enters the space in the lid 5 and the space in the external electrode 3, and the inside of the chamber 6 is brought to atmospheric pressure. Next, the lower external electrode 1 of the external electrode 3 is removed from the upper external electrode 2, and the PET bottle 7 is inserted into the space in the upper external electrode 2 from below the upper external electrode 2 and installed. At this time, the internal electrode 9 is inserted into the PET bottle 7. Next, the lower external electrode 1 is attached to the lower part of the upper external electrode 2, and the external electrode 3 is sealed with an O-ring 8.
[0042]
(Evacuation process)
Then, after closing a vacuum valve (not shown), the vacuum valve 14 is opened and the vacuum pump 16 is operated. Thereby, the inside of the chamber 6 including the inside of the PET bottle 7 is exhausted through the pipe 12, and the inside of the chamber 6 is evacuated. The vacuum pressure in the chamber 6 at this time is 10^{- 2}-10^{- 1}It is Torr (1.33 to 13.3 Pa), and this vacuum pressure is set as a set ultimate pressure. Until this stage, the raw material supply valve 21 is closed.
[0043]
(First layer deposition process)
Next, the raw material supply valve 21 is opened while continuing the exhaust to generate a raw material gas, for example, acetylene, in the raw material gas generation source 25, and this raw material gas is introduced into the pipe 20. The raw material gas whose flow rate is controlled by the mass flow controller 23 is blown out from the gas outlet 9a through the pipe 20 and the internal electrode 9 at the ground potential. The source gas supply amount is set to 50 sccm, for example. As a result, the source gas is introduced into the PET bottle 7. At this time, with the start of the supply of the raw material gas, the internal pressure of the PET bottle 7 is increased to a set film formation pressure, for example, 0.05 to 0.5 Torr (6.65 to 66.5 Pa) or more, and further set as the evacuation continues. The pressure is reduced again to the film forming pressure. This increase in pressure is caused by the flow of the raw material gas retained between the gas control means 23 and the raw material supply valve 13 at the beginning of the gas supply. This is about 0.1 to 0.3 seconds. Then, when the pressure is increased to a value equal to or higher than the set film forming pressure and further reduced to the set film forming pressure again, the RF output (for example, 13. 56 MHz). The high-frequency supply power is set to a constant output of 300 to 500 W, for example. Thereby, plasma is ignited between the external electrode 3 and the internal electrode 9. At this time, the matching unit 10 matches the discharge impedance between the external electrode and the internal electrode so that the reflected power is minimized when the second layer is formed by the inductance L and the capacitance C. As a result, a source gas plasma is generated in the PET bottle 7, but the initial discharge impedance differs greatly from that at the time of the second layer film formation. Input power is reduced. Thereafter, since the impedance approaches when the second layer is formed, the reflected power decreases, and the effective input power gradually approaches the output value. Due to the effect of increasing the pressure and reducing the pressure, and the effect of increasing the effective input power from a small power, the DLC film as the first layer having a high hydrogen atom content and a gradient composition on the inner surface of the PET bottle 7 plastic container. Is deposited. The film formation time at this time is as short as about 0.1 to 1 second and at most about several seconds. The film thickness of the first layer is 2 to 6 nm, for example. This first layer has a high hydrogen atom content composition in order to make the DLC film followable to shrinkage of the container during hot filling and to improve adhesion. This utilizes the fact that the pressure is high and the energy of ions incident on the film is low because the power is small.
[0044]
In the first layer deposition step, the start timing of the high-frequency output is roughly classified into three types. First, as a first timing, high-frequency output is started while the internal pressure of the PET bottle 7 is increased to a set film formation pressure or higher. While the internal pressure rises and then returns to the set film formation pressure again, the hydrogen atom content of the first layer changes as follows. That is, the composition changes from a plastic surface as a starting point toward the thickness direction of the film, such as a low hydrogen atom content composition, a high hydrogen atom content composition, and a low hydrogen atom content composition. The first layer contains a low hydrogen atom content composition, but has a relatively high hydrogen atom content composition compared to the second layer, and the first layer is a flexible film and has a gradient composition. Excellent adhesion to the container. In addition to the fact that the low hydrogen atom content composition portion of the second layer exhibits gas barrier properties, the low hydrogen atom content composition portion of the first layer also exhibits gas barrier properties, so the first of the three timings. The method of forming the layer for the longest time and increasing the film thickness has the highest gas barrier property.
[0045]
As a second timing, when the internal pressure of the PET bottle 7 is increased to a value equal to or higher than the set film formation pressure and further reduced to the set film formation pressure again as evacuation continues, the high frequency output is started when the internal pressure becomes almost the maximum. How to do it. In this method, the hydrogen atom content of the first layer changes as follows. That is, the composition changes to a high hydrogen atom content composition and a low hydrogen atom content composition as it goes from the plastic surface to the film thickness direction. Even when the composition of the second layer is taken into consideration, the entire DLC film smoothly changes from a plastic surface as a starting point toward the film thickness direction to a high hydrogen atom content composition and a low hydrogen atom content composition. For this reason, since the first layer does not have a low hydrogen atom content composition immediately above the substrate as compared with the case of the first timing, the first layer has a more flexible film and a gradient composition. Among them, it has the best adhesion to plastic containers.
[0046]
As a third timing, a high-frequency output is started while the internal pressure of the PET bottle 7 is reduced again to the set film-forming pressure as evacuation continues. In this method, the hydrogen atom content of the first layer changes as follows. That is, the composition changes to a high hydrogen atom content composition and a low hydrogen atom content composition as it goes from the plastic surface to the film thickness direction. Although the state of the composition change is similar to the case of the second timing, the hydrogen atom content just above the inner surface of the plastic container is slightly lower than that of the second timing. Adhesion is good next to the second timing. The discharge time can be shortened.
[0047]
The supply of the raw material gas to the inside of the PET bottle 7 is performed by controlling the flow rate of the raw material gas generated from the raw material gas generation source 25 by the mass flow controller 23 (gas flow rate control means) and further controlling the flow rate by the mass flow controller 23. Is performed by a gas system that enables supply on and off with the raw material supply valve 21, and the supply is initially started by at least one of the amount of raw material gas accumulated between the mass flow controller 23 and the raw material supply valve 21 and the back pressure of the mass flow controller 23. It is preferable to control the amount of the raw material gas inflow, that is, the amount of increase in the internal pressure of the PET bottle 7 that is increased as the supply starts. For example, by increasing the length of the pipe between the mass flow controller 23 and the raw material supply valve 21 or providing a storage space for the raw material gas of, for example, 0.5 to 200 cc capacity between them, the internal pressure of the PET bottle 7 is increased. The amount can be increased. When the amount of increase in the internal pressure of the PET bottle 7 is increased, the hydrogen atom content becomes higher, and the first layer having a more flexible but less gas barrier function can be formed. On the other hand, if the length of the pipe between the mass flow controller 23 and the raw material supply valve 21 is shortened and no storage space for the raw material gas is provided, the amount of increase in the internal pressure of the PET bottle 7 can be reduced. If the amount of increase in the internal pressure of the PET bottle 7 is reduced, the hydrogen atom content will be lowered (but higher than the hydrogen atom content of the second layer), and the first layer will be somewhat less flexible with some gas barrier function. Can be formed. Further, when the back pressure of the mass flow controller 23 is set high, the amount of increase can be increased, and when it is set low, the amount of increase can be controlled small. The initial inflow gas is controlled as follows, for example. The pipe 22 between the mass flow controller 23 and the raw material supply valve 21 is set in advance to supply a certain amount of raw material gas through the mass flow controller 23 during the idling time before film formation, so that the pressure in the pipe 22 is controlled. The gas is allowed to stay so as to be the same pressure as the back pressure. When the same pressure is reached, the mass flow controller 23 cannot flow any more gas regardless of the supply amount, and the inside of the pipe 22 is kept stable. In this state, a forced valve closing signal is once sent to the mass flow controller 23, and a variable flow valve (not shown) in the mass flow controller 23 is fully closed. Next, the raw material supply valve 21 is opened while continuing the evacuation, and at the same time, the signal for closing the forced flow valve of the mass flow controller 23 is canceled, and the control for setting the flow rate to the film formation set flow rate is started. If it does in this way, the gas which stayed in the piping 22 will blow out from the gas blowing outlet 9a through the piping 20 first. This is the gas that flows into the PET bottle 7 in the initial stage. Then, the flow rate of the mass flow controller 23 gradually increases, and if the mass flow controller responds quickly, the set film formation flow rate is controlled within 1 second, for example, about 0.2 seconds.
[0048]
In addition, since it is preferable to promote gas replacement necessary for improving the film quality of the second-layer barrier film at the initial stage of the supply of the source gas, the amount of the source gas inflow at the beginning of the supply is intentionally increased. preferable. Incidentally, the gas that needs to be replaced is air (oxygen and nitrogen) and moisture adsorbed on the inner surface of the PET bottle 7.
[0049]
In this embodiment, the vacuum pump 16 is operated at a constant pumping speed, and the opening degree of the vacuum valve 14 is not changed while the raw material gas is supplied, so that the pumping speed is constant. On the other hand, the internal pressure of the PET bottle 7 is set to a set film formation pressure, for example, 0.05 to 0 by setting the raw material gas inflow amount at the beginning of supply for promoting gas replacement to be larger than the set film formation flow rate of the second layer. .5 Torr (6.65 to 66.5 Pa) or higher, for example, about 0.2 to 1.0 Torr (26.6 to 133 Pa), and after the replacement is completed, the continuation of exhaust and the setting controlled by the mass flow controller 23 When the film formation flow rate, for example, 50 sccm is balanced, the pressure can be reduced again to the set film formation pressure of the second layer and stabilized. This operation is a simple configuration using the mass flow controller 23 and the source gas supply valve 21, and can be performed in a very short time by controlling the arrangement and operating conditions, for example, about 0.1 to 0.5 seconds. It is. That is, it is preferable that the increase amount of the internal pressure of the plastic container is controlled by the increase amount due to the start of the supply of the raw material gas, and the adjustment of the exhaust amount is not used. If the same pressure increase operation is performed by changing the pumping speed of the vacuum pump 16 or adjusting the opening of the vacuum valve 14, both of them are expensive devices that require difficult high-speed control and are very suitable for application to mass production equipment. It becomes inconvenient. By simultaneously forming the first layer for improving adhesion at the time of supplying the raw material gas for the gas replacement, it is possible to reduce an extra time required for forming the first layer. Of course, if a larger pressure or longer time than the change in gas pressure necessary for gas replacement is required for film formation of the first layer, an initial gas supply amount corresponding to that pressure may be flowed. It is not necessary to be bound by the conditions.
[0050]
(Second layer deposition process)
A DLC film having a low hydrogen atom content and a constant composition is formed as the second layer on the first layer while maintaining the set film forming pressure in a state where the source gas is turned into plasma. The first layer has a gradient composition according to the change in the film formation pressure, and the film formation pressure at the end of the first layer film formation process and the film formation pressure at the start of the second layer film formation process are the same. Therefore, there is no difference in composition and film stress at the boundary between the first layer and the second layer. The thickness of the second layer can be set to 13 to 200 nm in consideration of stress, but it is particularly preferable to set the thickness to 13 to 38 nm in consideration of gas barrier properties and adhesion. When the thickness is less than 13 nm, the gas barrier property is not sufficiently improved, and when the thickness exceeds 38 nm, microcracks may be generated due to the internal stress of the film.
[0051]
The DLC film may be formed to have a film thickness of, for example, 0.003 to 0.2 μm, but is preferably 15 to 40 nm from the viewpoint of gas barrier properties, productivity, residual stress in the film, and adhesion. .
[0052]
(Finished film)
Next, the RF output from the high frequency power supply 11 is stopped, the raw material supply valve 21 is closed, and the supply of the raw material gas is stopped. Thereafter, the source gas in the PET bottle 7 is exhausted by the vacuum pump 16. Thereafter, the vacuum valve 14 is closed and the vacuum pump 16 is stopped. The pressure in the chamber 6 at this time is 10^{- 2}-10^{- 1}Torr (1.33 to 13.3 Pa). Thereafter, the vacuum valve (not shown) is opened to open the chamber 6 to the atmosphere, and the above-described film forming method is repeated to form a DLC film composed of the first layer and the second layer in the next PET bottle. Is done.
[0053]
(Second Embodiment)
The installation of the PET bottle, the evacuation process, and the second layer film forming process are the same as those in the first embodiment.
[0054]
(Gas replacement process)
Next, the raw material supply valve 21 is opened while continuing the exhaust to generate a raw material gas, for example, acetylene, in the raw material gas generation source 25, and this raw material gas is introduced into the pipe 20. The raw material gas whose flow rate is controlled by the mass flow controller 23 is blown out from the gas outlet 9a through the pipe 20 and the internal electrode 9 at the ground potential. The source gas supply amount is set to 100 sccm, for example. As a result, the source gas is introduced into the PET bottle 7. The inside of the PET bottle 7 is supplied so that the supply of the source gas and the exhaust of the residual gas are simultaneously performed for a predetermined time, for example, 0.1 to 1 second, and the inside of the PET bottle 7 is replaced with the source gas. Gas replacement is performed to remove impurities in the film. By supplying the raw material gas, the internal pressure of the PET bottle 7 is increased to a set film forming pressure, for example, 0.05 to 0.5 Torr (6.65 to 66.5 Pa) or more.
[0055]
(First layer deposition process)
After performing the gas replacement, in order to return to the set film formation pressure at an early stage, after setting the gas flow rate to be smaller than the gas flow rate of the source gas in the gas replacement process, for example, 50 sccm, the gas is again returned to the set film formation pressure as the exhaust is continued. During decompression, an RF output (for example, 13.56 MHz) is supplied from a high frequency power source (RF power source) 11 to the external electrode 3 via the matching unit 10. The high-frequency supply power is set to a constant output of 300 to 500 W, for example. Thereby, plasma is ignited between the external electrode 3 and the internal electrode 9. At this time, the matching unit 10 matches the discharge impedance between the external electrode and the internal electrode so that the reflected power is minimized when the second layer is formed by the inductance L and the capacitance C. As a result, source gas plasma is generated in the PET bottle 7, and a DLC film having a high hydrogen atom content and a gradient composition is formed as a first layer on the inner surface of the PET bottle 7 plastic container. The film formation time at this time is as short as about 0.1 to 1 second and at most about several seconds. The film thickness of the first layer is 2 to 6 nm, for example. This first layer has a high hydrogen atom content composition in order to make the DLC film followable to shrinkage of the container during hot filling and to improve adhesion. In the second embodiment, by controlling the gas flow rate of the source gas, it is possible to reduce the impurities in the film by intentionally setting the pressure higher than the set film formation pressure and sufficiently replacing the gas. .
[0056]
(Third embodiment)
The installation of the PET bottle, the evacuation process, and the second layer film forming process are the same as those in the first embodiment.
[0057]
(Gas replacement process)
While continuing the exhaust, the material supply valve 21 is opened, a material gas, for example, acetylene is generated in the material gas generation source 25, and this material gas is introduced into the pipe 20. The raw material gas whose flow rate is controlled by the mass flow controller 23 is blown out from the gas outlet 9a through the pipe 20 and the internal electrode 9 at the ground potential. The source gas supply amount is set to 50 sccm, for example. As a result, the source gas is introduced into the PET bottle 7. The inside of the PET bottle 7 is supplied so that the supply of the source gas and the exhaust of the residual gas are simultaneously performed for a predetermined time, for example, 0.1 to 1 second, and the inside of the PET bottle 7 is replaced with the source gas. Simultaneously with the replacement, the inside of the container is adjusted to a set film forming pressure of the DLC film, for example, about 0.05 to 0.5 Torr (6.65 to 66.5 Pa). That is, a gas replacement step of stabilizing the inside of the plastic container with the source gas by stabilizing the source gas containing the carbon source gas inside the plastic container at a constant flow rate, for example, 50 sccm, under the set film forming pressure. Is done. Here, the gas replacement is performed to remove impurities in the film.
[0058]
(First layer deposition process)
In order to forcibly increase the internal pressure of the container, a gas flow rate larger than the gas flow rate of the source gas in the gas replacement step, for example, 100 sccm is set, and the internal pressure of the PET bottle 7 is increased above the set film formation pressure. Further, after a lapse of a predetermined time, for example, 0.1 to 1 second, the gas flow rate of the source gas in the gas replacement process is set again to return to the set film formation pressure. As a result, the increase in the internal pressure of the plastic container stops and the pressure is reduced again to the set film formation pressure. When the internal pressure of the plastic container stops increasing and reaches the maximum internal pressure, an RF output (for example, 13.56 MHz) is supplied from the high frequency power source (RF power source) 11 to the external electrode 3 via the matching unit 10. The high-frequency supply power is set to a constant output of 300 to 500 W, for example. Thereby, plasma is ignited between the external electrode 3 and the internal electrode 9. At this time, the matching unit 10 matches the discharge impedance between the external electrode and the internal electrode so that the reflected power is minimized when the second layer is formed by the inductance L and the capacitance C. As a result, a source gas plasma is generated in the PET bottle 7, and a DLC film having a high hydrogen atom content and a gradient composition is formed as the first layer on the inner surface of the PET bottle 7 plastic container. The film formation time at this time is as short as about 0.1 to 1 second and at most about several seconds. The film thickness of the first layer is 2 to 6 nm, for example. This first layer has a high hydrogen atom content composition in order to make the DLC film followable to shrinkage of the container during hot filling and to improve adhesion. In the third embodiment, after the gas replacement step, the reproducibility is extremely high by controlling the gas flow rate of the source gas, and the impurities in the film can be almost eliminated by sufficiently performing the gas replacement.
[0059]
In the present invention, the pressure during plasma discharge is preferably 0.05 to 0.50 Torr (6.65 to 66.5 Pa). If it is less than 0.05 Torr, it is difficult to discharge, and if it exceeds 0.60 Torr, discharge occurs in the tube of the internal electrode and the plasma discharge becomes unstable. It is preferable that the maximum pressure in the first layer film forming step (top pressure for pressure increase) is not less than the set film forming pressure and not more than 1.0 Torr (133 Pa). The reason why the pressure is 1.0 Torr or less is that it takes longer than necessary to return to the set film-forming pressure. The pressure during the first layer deposition is preferably higher than the second layer deposition pressure and not more than 0.5 Torr (66.5 Pa). When the internal pressure is increased above the set film formation pressure after opening the valve in the first layer film formation process, the discharge impedance is matched to the discharge impedance during the second layer film formation (impedance matching is matched to the discharge impedance during the second layer film formation). Therefore, the reflected power is increased, and thus the power that is effectively incident on the plasma is reduced. For this reason, the ion energy incident on the film is lowered, the hydrogen content is high, the adhesion is high, and a flexible film is formed. The switch-on pressure during plasma ignition is preferably 0.2 to 0.5 Torr (26.6 to 66.5 Pa). Similarly, the hydrogen atom content of the first layer is increased within the stable discharge region pressure to provide a flexible film quality. The pressure during the second layer deposition (set deposition pressure) is preferably 0.05 to 0.2 Torr (6.65 to 26.6 Pa). This is because the content of hydrogen atoms is less than that of the first layer and a hard film is formed to provide gas barrier properties. The present invention has found an optimum container internal pressure profile and its pressure range in order to form a DLC film having followability and gas barrier properties that can withstand bottle shrinkage during hot filling. Therefore, in order to obtain the DLC film bottle shrinkage followability and gas barrier property required by the present invention, the control of providing a pressure difference between the internal pressures in which the film is formed at a high internal pressure at the beginning of film formation and then formed at a low internal pressure. Insufficient.
[0060]
In the first, second, and third embodiments, the displacement is constant and the internal pressure of the container is determined by the back pressure of the mass flow controller or the volume of the pipe 22 between the mass flow controller and the raw material supply valve or the supplied raw material gas flow rate. A desired container internal pressure profile is obtained. Therefore, since the displacement is not controlled, the apparatus is simple and the internal pressure response is good.
[0061]
In the first, second, and third embodiments, in the present invention, not only a high-frequency power source but also a microwave power source may be used as means for converting the source gas into plasma. For example, 2.45 GHz is supplied as the microwave. Since microwaves are used as a plasma energy supply source, there are differences in the devices used, such as supplying microwaves inside the container and eliminating the need for internal electrodes, but the manufacturing method is the same as when using a high-frequency power supply. is there.
[0062]
Further, a DLC film may be formed by a magnetic field type plasma CVD method by installing a magnet near the outer wall of the container.
[0063]
In the embodiment, a PET bottle for beverage is used as a container for forming a thin film inside, but a container used for other purposes can also be used.
[0064]
In the present invention, the number of component parts such as the number of film forming chambers and the number of high-frequency power sources may be appropriately changed according to the required capability of the apparatus.
[0065]
Next, a DLC film-coated plastic container composed of a first layer and a second layer will be described. The DLC film-coated plastic container according to the present invention is obtained by coating the inner surface of a plastic container with a DLC film. Here, the DLC film is composed of a first layer having a high hydrogen atom content composition formed on the inner surface and a second layer having a lower hydrogen atom content composition than the first layer formed on the first layer. . The second layer is preferably at least 13 nm thick. The hydrogen atom content of DLC can theoretically be 0 to 67 atom%. When it is 67 atomic%, it is close to ethylene polymer.
[0066]
According to the experience of the present inventors, a DLC film having a small hydrogen atom content is hard, has a large internal stress, and has a high gas barrier property. On the other hand, when the hydrogen atom content is large, the DLC film becomes relatively flexible, the internal stress is small, and the gas barrier property is low. In the present invention, the reason why the first layer has a composition containing a high amount of hydrogen atoms is to increase the adhesion of the film by being flexible and capable of following the shrinkage of the plastic by reducing the internal stress in the film. Here, the high hydrogen atom content does not mean that it is close to 67 hydrogen atom%, but means that it is relatively high in comparison with the hydrogen atom content of the second layer. On the other hand, the meaning of the low hydrogen atom content composition of the second layer also means that it is relatively low in comparison with the hydrogen atom content of the first layer. This is to ensure gas barrier properties, and the hydrogen atom content of the second layer is preferably set to 42 atom% or more and 48 atom% or less. Therefore, as described above, the thickness of the second layer is particularly preferably 13 to 38 nm from the viewpoint of ensuring gas barrier properties. The thickness of the first layer is preferably 2 to 6 nm from the viewpoint of adhesion and shortening the film formation time. The adhesion here refers to the adhesion of the DLC film against the shrinkage of the plastic by heating after filling.
[0067]
The reason why the portion of the first layer in contact with the second layer has a gradient composition is to alleviate the difference in characteristics between the first layer and the second layer. In the present invention, the gradient composition can be easily obtained by controlling the film forming pressure.
[0068]
From the viewpoint of manufacturing a container that can be used regardless of the filling method of the contents, a DLC film having different properties depending on the relationship between the first layer and the second layer is considered as follows, and a composition for forming this DLC film is formed. The membrane pressure condition is adjusted as appropriate. That is, the DLC film-coated plastic container is allowed to stand for 10 minutes under hot water at 90 ° C., further quenched with water, and after drying, placed in an air atmosphere at 25 ° C. At this time, since the plastic is heated beyond the glass transition point, shrinkage of 1 to 2% occurs. Thus, the relationship between the first layer and the second layer is determined so that the DLC film placed under the shrinkage condition of the plastic by heating is not peeled off by the cross tape method of JISK5400 in Condition 1. At this time, it is particularly preferable as a container for hot filling. As condition 1, the gap between the cuts is 1 mm, and the number of squares is 100.
[0069]
Further, the DLC film may be taken as follows. That is, the relationship between the first layer and the second layer is such that the DLC film placed under the same heat-shrinking condition of the plastic has an adhesion strength of 1.8 mN or more in the vertical load in the weighted scratching method of Condition 2. Is to decide. This is also preferable as a container for hot filling. As condition 2, the tester is Shimadzu scanning type scratch tester SST-101 manufactured by Shimadzu Corporation, the scratching needle is diamond, the radius of curvature is 15 μm, the load speed is 1 μm / s, the amplitude is 10 μm, the feed rate is 2 μm / s, and the vertical load is The weight applied to the scratching needle when the film begins to peel. The DLC film formed on the inner body of the container is measured.
[0070]
When the DLC film-coated plastic container according to the present invention is a container for hot filling, the hydrogen atom content of the first layer is 50 atomic% or more and 60 hydrogen atom% or less, and the hydrogen atom content of the second layer is 42. It is preferable to set the atomic percentage to 48 atomic% or less, preferably 42 atomic% to 46 atomic% or less. The reason why the hydrogen atom content of the first layer is 50 atomic% or more and 60 hydrogen atom% or less is that internal stress is applied to the film due to the shrinkage of the plastic, so that internal stress does not remain in the film as much as possible when the first layer is formed. This is because better and better flexibility of the film can follow the shrinkage of the plastic.
[0071]
【Example】
The plastic container was a PET bottle. The height of the PET bottle is 207 mm, the wall thickness is 0.3 mm, the container capacity is 500 ml, and the inner surface area is 400 cm.²It was. The bottle shape (heat resistant round shape) shown in FIG. 2A was used for the bottle shape when the heat treatment was performed. In addition, when performing heat processing, the PET bottle of the container (heat-resistant square shape) of FIG.2 (b) can also be used. The PET bottle of the container (heat-resistant round shape) in FIG. 2 (a) and the container (heat-resistant square shape) in FIG. 2 (b) has a reduced pressure absorption surface or panel. Since the carbonic acid container has an internal pressure of carbon dioxide gas, it has a cylindrical conical shape. However, the heat-resistant container has a concavo-convex part in its body part. When the contents processed at a temperature of about 80 to 95 ° C. are filled and sealed in a container while keeping the temperature, and shipped as a product, the container is depressurized when the contents are cooled to room temperature. A change in the shape of the container itself is inevitable. A wall surface such as a body portion having the uneven portion is referred to as a reduced pressure absorption surface or a panel. Table 1 shows the characteristics of each container shown in FIGS.
[Table 1]

[0072]
Example 1
A DLC film is formed by a high frequency plasma CVD method in which a high frequency shown in FIG. 1 is applied to the external electrode. High purity acetylene is used as a source gas. Residual air gas in the chamber and the plastic container is exhausted and the vacuum pressure in the plastic container is reduced to 0.05 Torr (6.65 Pa), and then the raw material supply valve 21 is opened while continuing the exhaustion to supply the raw material into the plastic container 7. Introduce gas. The raw material gas flow rate was fixed at 50 sccm. At this time, the internal pressure of the plastic container is temporarily set to a film formation pressure of 0.10 Torr (13.3 Pa) according to the back pressure of the mass flow controller 23 and the initial raw material gas inflow amount determined according to the amount of raw material gas remaining in the pipe 22. ) And rises up to about 0.4 Torr (53.2 Pa). The internal pressure profile of the plastic container at this time is shown in FIG. The profile in FIG. 3 corresponds to the film forming method of the first embodiment described above. Then, 500 W of high frequency power (13.56 MHz) was supplied at the timing corresponding to (1) in FIG. 3, that is, the first timing in the first layer deposition step, and the first layer was deposited by plasma CVD. . A film having a gradient composition is formed in the first layer in accordance with the change in pressure. The film formation time of the first layer was about 0.3 seconds. After reaching the set film thickness of 0.10 Torr (13.3 Pa), the second layer was formed as it was. The film formation time for the second layer was about 2.0 seconds. The above film forming conditions are shown in Table 2. The thickness of the first layer was 4 nm, and the thickness of the second layer was 20 nm. The film formation rate of the second layer was about 10 nm / second. In the following examples and comparative examples, the thickness of the second layer was controlled by changing the film formation time of the second layer.
[0073]
[Table 2]

[0074]
(Example 2)
Film formation was performed in the same manner as in Example 1 except that the raw material gas flow rate was changed from a constant value of 50 sccm to a constant value of 100 sccm. The container internal pressure profile is shown in FIG. The film formation conditions and the film thickness are shown in Table 2.
[0075]
(Example 3)
A film was formed in the same manner as in Example 1 except that the high-frequency application timing was changed to (2) in FIG. This corresponds to the second timing of the first layer deposition step of the first embodiment described above. The film formation conditions and the film thickness are shown in Table 2.
[0076]
Example 4
Film formation was performed in the same manner as in Example 3 except that the high-frequency application time in the second layer film forming step was longer (about 2.0 seconds) than in Example 3 (about 1.3 seconds). It was. The film formation conditions and the film thickness are shown in Table 2.
[0077]
(Example 5)
A film was formed in the same manner as in Example 3 except that the volume of the internal space of the pipe 22 was increased to increase the retention volume of the raw material gas. The container internal pressure profile is as shown in FIG. The film formation conditions and the film thickness are shown in Table 2. Note that a similar container internal pressure profile can be obtained by increasing the back pressure of the mass flow controller instead of increasing the volume of the internal space of the pipe 22.
[0078]
(Example 6)
A film was formed in the same manner as in Example 1 except that the high-frequency application timing was changed to (3) in FIG. This corresponds to the second timing of the first layer deposition step of the first embodiment described above. The film formation conditions and the film thickness are shown in Table 2.
[0079]
(Example 7)
A DLC film is formed by a high frequency plasma CVD method in which a high frequency shown in FIG. 1 is applied to the external electrode. High purity acetylene is used as a source gas. Residual air gas in the chamber and the plastic container is exhausted and the vacuum pressure in the plastic container is reduced to 0.05 Torr (6.65 Pa). Introduce gas. The raw material gas flow rate was 100 sccm. At this time, the internal pressure of the plastic container temporarily becomes higher than the set film forming pressure of 0.10 Torr (13.3 Pa) and rises to a maximum of about 0.5 Torr (66.5 Pa). At this time, the inside of the container is sufficiently replaced with the raw material gas. Thereafter, the internal gas pressure is set to 0.10 Torr (13.3 Pa) by setting the raw material gas flow rate to 50 sccm. The internal pressure profile of the plastic container at this time is shown in FIG. The profile in FIG. 6 corresponds to the film forming method of the second embodiment described above. Then, 500 W of high-frequency power (13.56 MHz) was supplied at a timing corresponding to (3) in FIG. 6, and the first layer was formed by plasma CVD. A film having a gradient composition is formed in the first layer in accordance with the change in pressure. The film formation time for the first layer was about 0.3 seconds, and after reaching the set film thickness, the second layer was formed as it was. The film formation time for the second layer was about 3.8 seconds. The above film forming conditions are shown in Table 2. The thickness of the first layer was 3 nm, and the thickness of the second layer was 38 nm.
[0080]
(Example 8)
A film was formed in the same manner as in Example 7 except that the raw material gas flow rate of 100 sccm in Example 7 was changed to 200 sccm. That is, the raw material gas flow rate of 50 sccm when the container internal pressure is set to the set film-forming pressure is the same as that of the seventh embodiment. The container internal pressure profile of Example 8 is shown in FIG. The profile in FIG. 7 corresponds to the film forming method of the second embodiment described above. Then, high-frequency power (13.56 MHz) is supplied at a timing corresponding to (3) in FIG.
[0081]
Example 9
A DLC film is formed by a high frequency plasma CVD method in which a high frequency shown in FIG. 1 is applied to the external electrode. High purity acetylene is used as a source gas. Residual air gas in the chamber and the plastic container is exhausted and the vacuum pressure in the plastic container is reduced to 0.05 Torr (6.65 Pa). Introduce gas. The raw material gas flow rate was 50 sccm. At this time, the internal pressure of the plastic container is temporarily set to a film formation pressure of 0.10 Torr (13.3 Pa) according to the back pressure of the mass flow controller 23 and the initial raw material gas inflow amount determined according to the amount of raw material gas remaining in the pipe 22. ) And rises up to about 0.4 Torr (53.2 Pa). The set film-forming pressure is set by continuing the exhaust. At this stage, the inside of the plastic container is almost completely replaced with the raw material gas. Thereafter, the source gas is increased to 75 sccm, and the internal pressure is temporarily made higher than the set film formation pressure, and the pressure is raised to a maximum of about 0.4 Torr (53.2 Pa). The internal pressure profile of the plastic container at this time is shown in FIG. The profile in FIG. 8 corresponds to the film forming method of the third embodiment described above. Then, 500 W of high frequency power (13.56 MHz) was supplied at a timing corresponding to (5) in FIG. 8, and the first layer was formed by plasma CVD. A film having a gradient composition is formed in the first layer in accordance with the change in pressure. The film formation time of the first layer was about 0.3 seconds. After reaching the set film thickness of 0.10 Torr (13.3 Pa), the second layer was formed as it was. The film formation time for the second layer was about 1.3 seconds. The above film forming conditions are shown in Table 2. The thickness of the first layer was 2 nm, and the thickness of the second layer was 13 nm.
[0082]
(Comparative Example 1)
A high frequency application timing in Example 1 was the same as Example 1 except that the timing corresponding to 0 in FIG. The film forming conditions and film thickness are shown in Table 2 in the same manner.
[0083]
(Comparative Example 2)
A high frequency application timing in Example 1 was the same as that in Example 1 except that the timing corresponding to (4) in FIG. The film forming conditions and film thickness are shown in Table 2 in the same manner.
[0084]
(Comparative Example 3)
In Example 8, the application timing of the high frequency was the same as that of Example 8 except that the timing corresponding to (2) in FIG. The film forming conditions and film thickness are shown in Table 2 in the same manner.
[0085]
About Examples 1-9 and Comparative Examples 1-3, the hydrogen content was measured. A Si substrate was attached to the inner surface of the PET bottle, and a DLC film was formed to 200 nm on the Si substrate by the same method under the same conditions. The hydrogen composition of the DLC film was investigated by the RBS method (Rutherford backscattering analysis method) -HFS method (hydrogen forward scattering method). As a measuring device, a back scattering measuring device AN-2500 manufactured by Nissin High Voltage Co., Ltd. was used. The results are shown in Table 3.
[0086]
In Examples 1 to 9 and Comparative Examples 1 to 3, in consideration of hot filling, heat treatment was performed to reproduce the shrinkage of the container during hot filling after the DLC film was formed. The DLC film-coated plastic containers of each Example and each Comparative Example are allowed to stand for 10 minutes under hot water at 90 ° C., further quenched with water, dried, and then placed in an air atmosphere at 25 ° C. The oxygen permeability before and after the heat treatment and the adhesion strength after the heat treatment were measured.
[0087]
The oxygen permeability was measured with Oxtran2 / 20 manufactured by MOCON. The test was performed at 23 ° C. with an outside humidity of RH 60% and an inside humidity of RH 90%. The oxygen permeability is shown in Table 3.
[0088]
The adhesion strength after the heat treatment was measured by a grid tape method according to the condition 1 and a weighted scratching method according to the condition 2. The cross-cut tape method was evaluated as a ratio of the number of 100 divided by cuts and not peeled off by the tape. The results are shown in Table 3.
[0089]
As a container for hot filling, a case where it has sufficient adhesion strength even after heat treatment and has sufficient barrier properties as a gas barrier container is evaluated as a comprehensive evaluation, and either or both of adhesion strength and gas barrier property are insufficient. In some cases, the overall evaluation is shown in Table 3.
[0090]
[Table 3]

[0091]
In Examples 1 to 9, since the DLC film was composed of the first layer and the second layer having different hydrogen atom contents, the container having excellent adhesion and being mainly composed of the second layer even after being exposed to heating conditions The gas barrier property of was able to be secured. In addition, since the first layer has a gradient composition so as to be connected to the second layer, generation of microcracks due to stress concentration or the like did not occur.
[0092]
On the other hand, in Comparative Example 1, since the material supply and the discharge were started immediately after reaching the set ultimate pressure, the quality of the first layer was unstable for each container. In Comparative Example 2, since it had a single composition structure with only a DLC film having a low hydrogen atom content, it became a hard film, and sufficient adhesion could not be secured under the shrinkage condition of the plastic by heating. In Comparative Example 3, since the internal pressure of the container is as high as 0.8 Torr (106 Pa), a discharge occurs in the tube of the internal electrode, the plasma inside the container is unstable, the strength is weak, the film thickness is reduced, and the oxygen barrier property Was not enough.
[0093]
【The invention's effect】
A DLC film formed on the inner surface of the container is composed of a first layer having a high hydrogen atom content and a second layer having a low hydrogen atom content and a thickness of at least 13 nm as compared with the first layer formed thereon. Constructing the first layer with a gradient composition with respect to the second layer, the present invention complicates this container by finding that a container compatible with all filling methods including hot filling can be obtained. It was possible to provide a method of manufacturing by simple source gas control without using a simple apparatus. That is, according to the manufacturing method of the present invention, the first layer has high adhesion to the plastic material, has a function capable of following the shrinkage of the plastic, and the second layer is relatively hard and has a gas barrier function. It is. Furthermore, since the first layer can easily have a gradient composition with respect to the second layer, stress concentration and microcracks at the boundary between the first layer and the second layer can be prevented.
[0094]
In particular, according to the present invention, a mass production rate (several hundreds / minute) of the same order as other devices such as a plastic container production line such as a blow molding machine can be realized with low cost and high reliability.
[0095]
In addition, the present invention proposes several optimum container internal pressure profiles for the container, and it is possible to provide a plurality of forms of the gradient composition of the first layer, which can be appropriately selected according to the application. Neither manufacturing method requires a complicated device mechanism for pressure control, and it is not necessary to control the displacement.
[0096]
In the present invention, when both “gas replacement” and “gradient film formation” are performed simultaneously as in the first embodiment, for example, the gradient film is formed in parallel with the time required for gas replacement. It can be shortened. This gas replacement can be performed in a very short time of, for example, 1 second or less by means of the arrangement relationship and operation of the flow rate regulator and the raw material supply valve.
[0097]
Furthermore, in the present invention, for example, in the case of performing gas replacement completely by dividing both “gas replacement” and “gradient film formation” as in the second and third embodiments, impurities are mixed in the DLC film. It is possible to produce a DLC film-coated plastic container that is small and excellent in reproducibility.
[Brief description of the drawings]
FIG. 1 is a schematic view of an apparatus for producing a DLC film-coated plastic container by a high-frequency plasma CVD method.
2A and 2B are schematic views of a bottle shape used in an embodiment of the present invention, in which FIG. 2A shows a heat-resistant round shape and FIG. 2B shows a heat-resistant square shape.
FIG. 3 is a view showing one form of a container internal pressure profile of a container corresponding to the first embodiment.
4 is a view showing one form of a container internal pressure profile of the container when the raw material gas flow rate is increased as compared with FIG. 3. FIG.
FIG. 5 is a view showing one form of a container internal pressure profile of the container when the amount of inflow of raw material gas at the beginning of supply is increased as compared with FIG.
FIG. 6 is a view showing one form of a container internal pressure profile of a container corresponding to the second embodiment.
7 is a view showing one form of a container internal pressure profile of the container when the raw material gas flow rate is increased as compared with FIG. 6. FIG.
FIG. 8 is a view showing one form of a container internal pressure profile of a container corresponding to the third embodiment.
[Explanation of symbols]
100, high-frequency plasma CVD film deposition system
1. Lower external electrode
2, upper external electrode
3. External electrode
4. Insulation material
5, lid
6. Chamber
7, PET bottle
8, O-ring
9. Internal electrode
9a, gas outlet
10. Matching unit
11. High frequency power supply
13. Vacuum gauge
14. Vacuum valve
16, vacuum pump
17. Duct exhaust
12, 15, 20, 22, 24, piping
21, Raw material supply valve
23. Mass flow controller
25. Source gas generation source
26. Raw material gas supply means

Claims (9)

A vacuum evacuation process for evacuating the inside of the plastic container to a set ultimate pressure, while starting evacuation, a raw gas containing carbon source gas is started to be supplied at a constant flow rate by the gas flow control means, While the internal pressure is raised above the set film formation pressure and the pressure is reduced again to the set film formation pressure as the evacuation continues, a constant output of plasma generating energy is supplied to plasma the source gas inside the plastic container. A first layer film forming step of forming a DLC film having a high hydrogen atom content and a gradient composition on the inner surface of the plastic container as the first layer, and the set film formation while the source gas is still in plasma state A second layer forming step of forming a DLC film having a low hydrogen atom content and a constant composition as the second layer on the first layer while maintaining the pressure. Method for manufacturing a DLC film coated plastic container according to claim. In the first layer film forming step, plasma generation of the source gas is started by supplying plasma generating energy with a constant output while raising the internal pressure of the plastic container to a set film forming pressure or higher. The method for producing a DLC film-coated plastic container according to claim 1. In the first layer film forming step, constant when the internal pressure of the plastic container is increased to the set film forming pressure or more and further reduced to the set film forming pressure again as evacuation continues until the internal pressure becomes almost the maximum internal pressure. 2. The method for producing a DLC film-coated plastic container according to claim 1, wherein the plasma generation of the raw material gas is started by supplying output plasma generating energy. In the first layer film forming step, plasma generation of the raw material gas is started by supplying a constant output of plasma generating energy while the internal pressure of the plastic container is reduced again to the set film forming pressure as evacuation continues. The method for producing a DLC film-coated plastic container according to claim 1, wherein: The supply of the raw material gas to the inside of the plastic container is performed by controlling the flow rate of the raw material gas generated from the raw material gas generation source by a gas flow rate control means, and further using the raw material gas whose flow rate is controlled by the gas flow rate control means as a raw material. Supply is performed by a gas system that enables supply on / off with a supply valve, and is supplied by at least one of the amount of raw material gas accumulated between the raw material supply valve and the back pressure of the gas flow control means from the gas flow control means. 5. The DLC film according to claim 1, wherein an amount of increase in the internal pressure of the plastic container, which is increased with the start of supply of the source gas, is controlled by adjusting a source gas inflow amount at an initial stage. Manufacturing method of coated plastic container. The DLC according to claim 1, 2, 3, 4, or 5, wherein the control of the increase amount of the internal pressure of the plastic container is performed by an increase amount by the start of supply of the raw material gas, and adjustment of the exhaust amount is not used. A method of manufacturing a membrane-coated plastic container. A vacuum evacuation process for evacuating the inside of the plastic container to a set ultimate pressure, while supplying the raw material gas containing a carbon source gas at a predetermined flow rate to the inside of the plastic container while evacuating, and setting the internal pressure of the plastic container The gas replacement step of gas replacement inside the plastic container and the gas flow rate smaller than the gas flow rate of the raw material gas in the gas replacement step is set to the set film formation pressure as evacuation continues. While the pressure is reduced again, plasma generating energy having a constant output is supplied to turn the source gas inside the plastic container into plasma, and a DLC film having a high hydrogen atom content and a gradient composition is formed on the inner surface of the plastic container. A first layer forming step for forming a layer, and the set film forming pressure is maintained in a state in which the source gas is plasmatized. The second layer deposition process, the manufacturing method of the DLC film coated plastic container and having a capital of forming a DLC film having a constant composition at a content lower hydrogen atoms in the first layer as the second layer while. An evacuation process for evacuating the interior of the plastic container to a set ultimate pressure, and stabilizing the interior of the plastic container so that a source gas containing a carbon source gas flows at a constant flow rate at a set film forming pressure inside the plastic container. A gas replacement step of replacing the gas with the source gas, a gas flow rate larger than the gas flow rate of the source gas in the gas replacement step, and increasing the internal pressure of the plastic container above the set film formation pressure for a predetermined time After the elapse of time, the gas flow rate of the source gas in the gas replacement step is set again to stop the increase in internal pressure, and the pressure is further reduced to the set film formation pressure. To make the source gas inside the plastic container into plasma, and a DLC film having a high hydrogen atom content and a gradient composition A first layer film forming step for forming a first layer, a DLC film having a low hydrogen atom content and a constant composition on the first layer while maintaining the set film forming pressure in a state where the source gas is turned into plasma. And a second layer film forming step of forming a DLC film-coated plastic container as a second layer. An internal electrode is inserted into the inside of the plastic container and an external electrode is disposed outside the plastic container, and then high frequency power is supplied to the external electrode to convert the source gas into plasma. A method for producing a DLC film-coated plastic container according to claim 1, 2, 3, 4, 5, 6, 7 or 8.

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