JP3979031B2 - Silicon oxide coating - Google Patents

Description

が知られているにすぎない。
このことから、本発明のケイ素酸化物被膜ではシロキサン結合の他にＳｉ＝Ｏ結合が存在しており、これが波数１２１５乃至１２５０ｃｍ^−１に赤外吸収ピークを示す理由であると信じられる。
また、ケイ素酸化物被膜にＳｉ＝Ｏ結合が生じる理由としては、ケイ素酸化物被膜の生成過程において、下記反応式

に示すとおり、シラノール基の生成とその脱水とが行われるためと思われる。
【００１６】
本発明のケイ素酸化物被膜は、表面粗さ（ＪｌＳ Ｂ０６０１）において２５ｎｍ未満の十点平均粗さ（Ｒｚ）及び１０ｎｍ未満の中心線平均粗さ（Ｒａ）を有することも、ガス遮断性の点で重要である。
ケイ素酸化物被膜の厚みは非常に薄いものであるので、その表面粗さはガス遮断性に関して重大な影響を与える。即ち、この表面粗さがある基準よりも大きくなると粗さの谷の部分を通してのガス透過の影響が大きくなり、結果としてケイ素酸化物被膜全体としてのガス遮断性が低下するのである。
本発明者らの研究によると、表面粗さは、その定義によって粗さの値自体かなり相違するが、十点平均粗さ（Ｒｚ）が２５ｎｍ未満であり、中心線平均粗さ（Ｒａ）が１０ｎｍ未満であれば、表面粗さによるガス透過の影響を回避できる。
【００１７】
即ち、十点平均粗さ（Ｒｚ）が２５ｎｍ以上であり、中心線平均粗さ（Ｒａ）が１０ｎｍ以上である場合（後述する比較例３参照）には、粗さによるガス遮断性低下が認められるのに対して、表面粗さを本発明で規定した範囲に維持することにより、優れたガス遮断性を維持することができる（上述する実施例３参照）。
【００１８】
本発明のケイ素酸化物被膜は、前述した微細構造をとることに関連して、Ｘ線光電子分光分析で測定したケイ素１原子当たりの酸素の原子数が１．５乃至２．０、特に１．６乃至１．８の範囲にあることが好ましい。
添付図面の図４は、本発明のケイ素酸化物被膜を設けたＰＥＴボトルについてＸ線光電子分光分析のチャートを示しており、横軸はエッチング時間（表面からの厚みに対応）、縦軸は原子濃度を示している。
なお、ケイ素酸化物被膜の厚さ方向の組成は、最外表面やプラスチック基体との界面近傍と、厚さ方向の内部とでは異なるのが通例であるが、本発明のケイ素酸化物被膜では上記組成比のものが層としてある厚みで存在すればよいものである。
【００１９】
本発明のケイ素酸化物被膜では、下記式（１）
Ｒｉ＝Ａ_１／Ａ_２ × １００ ‥（１）
式中、Ａ_１は赤外線吸収スペクトルにおいて波数１２１５乃至１２５０ｃｍ^−１の範囲の吸光度の面積を示し、
Ａ_２は上記赤外線吸収スペクトルにおいて波数９８５乃至１２５０ｃｍ^−１の範囲の吸光度の面積を示す、
で定義される吸光度比（Ｒｉ）が１％以上であることが好ましい。
【００２０】
上記吸光度比（Ｒｉ）の求め方を示す図５において、波数１２１５ｃｍ^−１と波数１２５０ｃｍ^−１とを結ぶ線を引き、この直線と波数１２１５から１２５０ｃｍ^−１の赤外線吸収スペクトルで囲まれる面積を測定し、これをＡ_１ とする。次に、波数９８５ｃｍ^−１と波数１２５０ｃｍ^−１とを結ぶ線を引き、この直線と波数９８５から１２５０ｃｍ^−１の赤外線吸収スペクトルで囲まれる面積を測定し、これをＡ_１ とする。
【００２１】
［ケイ素酸化物被膜形成方法及び装置］
本発明においては、ケイ素化合物、酸素及びキャリアーガスを含む雰囲気中で、プラスチツク基体の表面に、プラズマ化学蒸着法によりケイ素酸化物被膜を形成させる。
このケイ素酸化物被膜の形成に用いる装置は、処理すべき基体を含むプラズマ処理室と、プラズマ処理室を減圧状態に保持するための排気系と、プラズマ処理室内に処理用ガスを導入するための処理用ガス導入系と、プラズマ処理室内にプラズマを発生させるための電磁波導入系とを含んでなる。
【００２２】
本発明に用いるマイクロ波プラズマ処理装置の一例の概略配置を示す図６において、全体として１で示すプラズマ処理室には、この処理室１を減圧に保持するための真空ポンプ２が排気管３を介して接続され、またマイクロ波発振器４が導波管５を介して接続される。
この具体例において、導波管５には、処理室からのマイクロ波反射量を最少に調節するための三本チューナー６が設けられており、またプラズマ処理室１には、該処理室の負荷を調節するためのショートプランジャー７も設けられている。
【００２３】
プラズマ処理室１の配置の一例を示す図７において、この具体例ではボトル８のプラズマ処理を行うものであり、ボトル８は倒立状態でプラズマ処理室内に保持されている。ボトル８の内部には処理用ガスの導入パイプ９が挿入されており、この導入パイプ９の先端に金属製のアンテナ１０が上方に延びるように設けられている。
【００２４】
プラズマ処理に際しては、先ず処理すべきボトル８をボトルホルダー（図示せず）に取り付け、ボトル８とボトルホルダーとを気密状態に維持し、真空ポンプ２を駆動して、ボトル８の内部を真空状態に維持する。この際、ボトル８の外圧による変形を防止するために、ボトル外部のプラズマ処理室１をも減圧状態にすることも可能である。
【００２５】
真空ポンプ２により達成されるボトル８内の減圧の程度は、処理用ガスが導入され且つマイクロ波が導入されてグロー放電が発生するような減圧の程度が高いものである。一方、プラズマ処理室１内の減圧の程度は、マイクロ波が導入されてもグロー放電が発生しないような減圧の程度である。
【００２６】
この減圧状態に達した後、処理ガス導入パイプ９によりボトル８内に処理用ガスを導入し、導波管５を通してプラズマ処理室１内にマイクロ波を導入する。この際、金属製のアンテナ１０からの電子放出により、著しく短時間の内に安定にグロー放電によるプラズマが発生するという利点が達成される。
このプラズマ中での電子温度は数万Ｋであり、ガス粒子の温度は数１００Ｋであるのに比して、約２桁ほど低く、熱的に非平衡の状態であり、低温のプラスチック基体に対しても有効にプラズマ処理による被膜形成を行うことができる。
【００２７】
所定のプラズマ処理を行った後、処理用ガスの導入及びマイクロ波の導入を停止すると共に、排気管３を通して空気を徐々に導入して、容器の内外を常圧に復帰させ、プラズマ処理により被膜形成されたボトルをプラズマ処理室外に取り出す。
【００２８】
［処理すべきプラスチック基材］
本発明において、処理すべきプラスチック基材としては、種々のプラスチックを挙げることができる。
プラスチックとしては、それ自体公知の熱可塑性樹脂、例えば低密度ポリエチレン、高密度ポリエチレン、ポリプロピレン、ポリ１−ブテン、ポリ４−メチル−１−ペンテンあるいはエチレン、ピロピレン、１−ブテン、４−メチル−１−ペンテン等のα−オレフィン同志のランダムあるいはブロック共重合体等のポリオレフィン、エチレン・酢酸ビニル共重合体、エチレン・ビニルアルコール共重合体、エチレン・塩化ビニル共重合体等のエチレン・ビニル化合物共重合体、ポリスチレン、アクリロニトリル・スチレン共重合体、ＡＢＳ、α−メチルスチレン・スチレン共重合体等のスチレン系樹脂、ポリ塩化ビニル、ポリ塩化ビニリデン、塩化ビニル・塩化ビニリデン共重合体、ポリアクリル酸メチル、ポリメタクリル酸メチル等のポリビニル化合物、ナイロン６、ナイロン６−６、ナイロン６−１０、ナイロン１１、ナイロン１２等のポリアミド、ポリエチレンテレフタレート、ポリブチレンテレフタレート、ポリエチレンナフタレート等の熱可塑性ポリエステル、ポリカーボネート、ポリフエニレンオキサイド等あるいはそれらの混合物のいずれかの樹脂であってもよい。
【００２９】
これらの基材は、フィルム乃至シートの形で用いることができるし、またボトル、カップ、チューブ等の容器やその他の成形品の形で本発明のプラズマ処理に付することもできる。
前述した具体例に挙げたボトルとしては、ポリエチレンテレフタレート等のポリエステルから形成された二軸延伸ブロー成形ボトルが挙げられる。
勿論、本発明は上記ポリエステルのカップや二軸延伸フィルムにも同様に適用することができる。
【００３０】
［ケイ素酸化物被膜形成用ガス］
ケイ素酸化物被膜の形成には、四塩化ケイ素、シラン（ＳｉＨ_４ ）、ヘキサメチルジシラン、ビニルトリメチルシラン、メチルシラン、ジメチルシラン、トリメチルシラン、ジエチルシラン、プロピルシラン、フェニルシラン、メチルトリエトキシシラン、ビニルトリエトキシシラン、ビニルトリメトキシシラン、テトラメトキシシラン、テトラエトキシシラン、フェニルトリメトキシシラン、メチルトリメトキシシラン、メチルトリエトキシシラン等の有機シラン化合物、オクタメチルシクロテトラシロキサン、１，１，３，３−テトラメチルジシロキサン、ヘキサメチルジシロキサン等の有機シロキサン化合物等が使用される。また、これらの材料以外にも、アミノシラン、シラザンなども用いられる。これらの原料は単独でも或いは２種以上の組合せでも用いることができる。
酸化性ガスとしては、酸素やＮＯｘが使用され、キャリアーガスとしては、アルゴンやヘリウムなどが使用される。
【００３１】
［処理条件］
本発明において、プラズマ処理の条件は、前述したＩＲ特性吸収を有するケイ素酸化物被膜が形成されるように処理条件の組合せを設定する。
この処理条件としては、製膜時の真空度、原料ガスの供給速度、酸化性ガスの供給速度、マイクロ波出力が挙げられるが、これらの条件は処理すべき容器の大きさや、他の条件によっても相違するので一概に規定することは困難である。
【００３２】
しかしながら、一般的傾向としては、製膜時の真空度が低くなる（圧力が高くなる）と、本発明で規定したＩＲ特性吸収を有するケイ素酸化物被膜が形成されにくくなる。また、ケイ素原料ガスの供給速度が大きくなると、やはり本発明で規定したＩＲ特性吸収を有するケイ素酸化物被膜が形成されにくくなる。更に、酸化性ガスの供給速度が小さくなると、同様に本発明で規定したＩＲ特性吸収を有するケイ素酸化物被膜が形成されにくくなる。
上記傾向を勘案して、本発明で規定したＩＲ特性吸収を有するケイ素酸化物被膜を形成するための条件を実験的に定めることができる。
【００３３】
本発明において、先ずプラズマ処理を行う処理室は、グロー放電が発生する真空度に保持するべきであり、一般的にいって、製膜時の圧力を５〜２００Ｐａ、特に好適には１５〜５０Ｐａの範囲に維持して、マイクロ波放電を行うのが好ましい。
【００３４】
ケイ素原料ガスの導入量は、勿論処理すべき基体の表面積や、原料ガスの種類によっても相違するが、容器１個当たり、ケイ素原料を標準状態で０．５〜５０ｃｃ／ｍｉｎ、特に１〜１０ｃｃ／ｍｉｎ（以下単にｓｃｃｍと記載することがある）の比較的少ない流量で供給するのが望ましい。
【００３５】
酸化性ガスの導入量は、ケイ素原料ガスの組成等によっても相違するが、一般に５〜５００ｓｃｃｍ、特に１０〜３００ｓｃｃｍの比較的多い流量で供給するのが好ましい。
【００３６】
ケイ素原料の供給速度が小さく、製膜時の真空度が高い（圧力が低い）場合には、マイクロ波によるグロー放電が不安定になり、その結果としてケイ素酸化物被膜の形成も不安定になる傾向がある。
これに対して、マイクロ波プラズマ処理に際して、プラズマ処理室内に金属製のアンテナを位置させると、製膜時の真空度が高い（圧力が低い）場合にも、マイクロ波によるグロー放電が安定になり、前述したＩＲ特性吸収を有するケイ素酸化物被膜を安定に形成させることができる。
【００３７】
一般的なグロー放電においては、暗流領域で存在するわずかな気体イオンは、電極電圧の上昇とともに次第に加速されて、中性分子と衝突してこれを電離し、新たに生成した電子は更に他の分子を電離し、陽イオンは陰極面を衝撃して電子放出を起こさせ、この繰り返しがねずみ算的に発展して、拡散再結合によるイオンの消滅と釣り合った定常状態がグロー放電といわれており、マイクロ波プラズマ処理におけるグロー放電発生のメカニズムも、電極電圧印加の代わりにマイクロ波の導入が行われる点を除けば、上記のメカニズムと同様である。
【００３８】
本発明における上記アンテナの設置によるグロー放電の安定化は電子放出によるグロー放電の促進と密接に関係していると思われる。実際に、本発明者らの観察によると、プラズマ処理室に取り付けたアンテナはかなり高温の状態となっており、このことはアンテナから熱電子の放出が生じたり、或いは陽イオンの細線への衝撃により電子の放出が生じていることを示唆している。
【００３９】
更に、ケイ素原料の供給速度を小さくしながら、製膜時の真空度（圧力）をグロー放電の安定化の上で適切な範囲に維持するには、酸化性ガスの供給速度を大きな値に維持することが重要であることも了解されるであろう。
【００４０】
本発明において、製膜時の真空度を高い状態に維持しながら、ケイ素酸化物被膜の形成を行うことにより、形成されるケイ素酸化物被膜の表面粗さを小さな範囲、即ち十点平均粗さ（Ｒｚ）で２５ｎｍ未満、中心線平均粗さ（Ｒａ）で１０ｎｍ未満の範囲に維持することができる。
【００４１】
グロー放電を生じさせる電磁波としては、１３．５６ＭＨｚの高周波や、マイクロ波の内、工業的に使用が許可されている周波数が２．４５ＧＨｚ、５．８ＧＨｚ、２２．１２５ＧＨｚのものを用いることが好ましい。
マイクロ波の出力は、処理すべき基体の表面積や、原料ガスの種類によっても相違するが、一例としてプラスチック容器への表面処理では、容器１個当たり、５０〜６００Ｗ、特に１００〜４００Ｗの電力となるように供給するのが望ましい。
【００４２】
マイクロ波によるグロー放電の誘導期を短縮させるために用いる金属製のアンテナとしては、マイクロ波の波長（λ）の０．０２倍以上の長さを有するもの、最も好適にはλ／４の長さのものが使用される。
アンテナの形状としては、先端部が尖った細線状アンテナ或いは箔状アンテナで長さが前述した範囲にあるものが使用される。そして、前記細線状アンテナの径は一般に先端が２ｍｍ以下のものが適しており、一方、前記箔状アンテナの幅は５乃至１０ｍｍ、厚みは５乃至５００μｍ程度が適している。
この細線は発熱するので、耐熱性に優れたものがよく、例えば白金、ステンレススチール、銅、カーボン、アルミニウム、スチール等の材質で製造されたものが好ましい。
【００４３】
プラズマ処理の時間も、処理すべき基体の表面積、形成させる薄膜の厚さ及び原料ガスの種類等によっても相違し、一概に規定できないが、一例としてプラスチック容器のプラズマ処理について説明すると、容器１個当たり、１秒以上がプラズマ処理の安定性から必要であり、コスト面から短時間化が要求されるが、必要であれば分のオーダーでも良い。
【００４４】
プラズマＣＶＤの場合、蒸着膜の付き回り性は良好であり、全ての表面に蒸着膜を形成させることができる。
一方、処理すべき基体がプラスチック容器のような立体成形品である場合、プラスチック容器内部及び／または外部を処理用ガスを含有する減圧雰囲気に維持し、容器内及び／または容器外でマイクロ波放電を生じさせることにより、容器内面及び／または外面に化学蒸着膜を形成させることができる。
【００４５】
また、図６に示すプラズマ処理法では、プラスチック容器をプラズマ処理室内に保持すると共に、プラスチック容器の外部とプラスチック容器の内部とを気密状態に維持し、プラスチック容器の内部を処理用ガスが導入された状態においてマイクロ波放電が生じる減圧状態に維持し、プラスチック容器の外部を内部に処理用ガスが導入された状態においてマイクロ波放電が生じない減圧状態に維持し、プラズマ処理室のプラスチック容器外部にマイクロ波を導入することにより、プラズマ処理を行うこともできる。
【００４６】
プラスチック容器のような立体成形品では、プラズマ処理室内に前記プラスチック容器の底部に対面するようにマイクロ波の反射板を配置することが、マイクロは放電を安定化させ、処理効率を高めるために好ましい。
【００４７】
本発明のケイ素酸化物被膜において、その厚みは特に制限されないが、ガス遮断性と柔軟性との見地からは、被膜の厚みが２乃至５００ｎｍ、特に５乃至３００ｎｍの範囲にあることが好ましい。
【００４８】
【実施例】
本発明を次の例で説明するが、本発明はいかなる意味においても、次の例に制限されるものではない。
【００４９】
（実施例１）
（マイクロ波プラズマ処理装置）
図６に示した装置を用いた。即ち、周波数が２．４５ＧＨｚで、最大出力が１．５Kwのマイクロ波発振器と、直径３００mm、高さ３００mmの金属製円筒形プラズマ処理室と、処理室を真空にする為の油回転真空式ポンプと、マイクロ波を発振器からプラズマ処理室に導入する矩形導波管とを用いた。プラズマ処理室内は図７に示したボトルホルダー、ガス導入器そしてガス導入器の先端に直径0.5mm長さ30mmの先端が針状に加工された鉄製の線状アンテナそしてボトル内を真空にする為の油回転式真空ポンプを設置した。
ガス導入器は内径4mm、長さ180mm、先端から50mm、100mmの位置の周方向に９０度間隔で、0.9mmの穴を開けたステンレス製管を用いた。
【００５０】
（マイクロ波プラズマ処理方法）
ボトルホルダーに口径２８mm、高さ２２０mmの円筒形ポリエチレンテレフタレート製のボトル（以下PETボトルと記す）を設置し、処理室内のボトル外部の真空度が2Kpaになる様に真空に引き、更にボトル内真空度が2Paになるまで、真空ポンプを作動させた。
真空ポンプを作動させたまま、ヘキサメチルジシロキサン（以下HMDSOと記す）ガスを２sccm、酸素ガスを200sccmそしてアルゴンガスを10sccm導入し、更にバルブ（図示していない）調整により、ボトル内真空度を50Paに調整した。
マイクロ波発振器より0.15Kwの電波を発信させ、ボトル内にプラズマを形成し、12秒間プラズマ処理を行った。
【００５１】
（赤外線吸収スペクトル測定法）
処理したPETボトルの胴部を切り出し、パーキンエルマー社製FT-IR（1600型）の内部多重反射装置（ＡＴＲ）、（プリズムの材質：ゲルマニウム、入射角：４５度）を用い、処理ボトル内面の赤外分光分析を行った。
未処理ボトルを用い、差スペクトル法により得られた赤外吸収スペクトルを図１に示した。図１より、処理ボトル内面にはケイ素酸化物が被覆されている事が明らかである。また波数1215乃至1250cm^−１の吸収ピークの面積（Ａ_１ ）を求め、更に波数980乃至1250cm^−１の吸収ピークの面積（Ａ_２ ）を求め、Ri＝A_１／A_２×100の式からRiを求め、表１に示した。
【００５２】
（膜中の組成分析法）
処理ボトル胴部の内面をPHI社製、Ｘ線光電子分光装置（Scanning ESCA Quantum2000）で、ケイ素と酸素の原子比を求め、表１に示した。
【００５３】
（膜厚測定法）
処理ボトル内面の膜厚を（株）リガク製蛍光Ｘ線分光分析装置（System3080）によりケイ素量を測定し、膜厚に換算し、表１に示した。
【００５４】
（酸素ガス透過量測定法）
処理ボトルと未処理ボトル内を窒素ガスで置換し、シーラント付きアルミ箔積層体でボトルの口部を密封し、30℃80%RHの酸素21％の環境に保存し、経時的にボトル内酸素ガス濃度を測定し、酸素ガス透過量を求め、表１に示した。
【００５５】
（表面粗さ測定法）
処理ボトルの内面をDIGITAL INSTRUMENTS社製の原子間力顕微鏡（タッピングモード）により表面粗さを測定し、表１に示した。
【００５６】
【表１】

【００５７】
（比較例１）
実施例１に記載の処理装置を用い、処理条件においてHMDSO導入量を10sccmとした以外は実施例１記載の処理条件でPETボトルをプラズマ処理し、赤外線吸収スペクトル、酸素ガス透過量を測定し、図２、表２にその結果を示した。
【００５８】
【表２】
波数1215乃至1250cm^−１の吸収ピークの有無 無い
未処理PETボトルの酸素ガス透過量（cc/m^２/day/atm） 5.2
処理PETボトルの酸素ガス透過量（cc/m^２/day/atm） 5.3
【００５９】
（実施例２）
実施例１に記載の処理装置を用い、処理条件において酸素導入量を100sccm、150sccmとした以外は実施例１記載の処理条件でPETボトルをプラズマ処理し、赤外線吸収スペクトル、酸素ガス透過量を測定し、図８、表３にその結果を示した。
【００６０】
【表３】

【００６１】
（比較例２）
実施例１に記載の処理装置を用い、処理条件において酸素導入量を20sccm、50sccmとした以外は実施例１記載の処理条件でPETボトルをプラズマ処理し、赤外線吸収スペクトル、酸素ガス透過量を測定し、図９、表４にその結果を示した。
【００６２】
【表４】

【００６３】
（実施例３）
SMC社製の焼結金属（公称濾過精度：120μｍ）から作成したガス導入器を用いる以外は実施例１記載のマイクロ波プラズマ処理装置を用い、酸素ガス導入量を50sccm、マイクロ波出力を0.3Kwとした以外は実施例１記載の処理条件でPETボトルをプラズマ処理し、赤外線吸収スペクトル、膜中の組成分析、膜厚、酸素ガス透過量、表面粗さ測定し、図１０、表５にその結果を示した。
【００６４】
【表５】

【００６５】
（実施例４）
実施例１に記載の処理装置を用い、処理条件において処理時間を２，５，10そして20秒に設定した以外は実施例１記載の処理条件でPETボトルをプラズマ処理し、赤外線吸収スペクトル、膜厚、酸素ガス透過量を測定し、図１１、表６にその結果を示した。
【００６６】
【表６】

【００６７】
（実施例５）
実施例３に記載の処理装置を用い、処理条件において製膜真空度を20、30、40Paに設定した以外は実施例３記載の処理条件でPETボトルをプラズマ処理し、赤外線吸収スペクトル、表面粗さ、酸素ガス透過量を測定し、図１２、表７にその結果を示した。
【００６８】
【表７】

【００６９】
（比較例３）
実施例３に記載の処理装置を用い、処理条件において製膜真空度を70、110、150Paに設定した以外は実施例３記載の処理条件でPETボトルをプラズマ処理し、赤外線吸収スペクトル、表面粗さ、酸素ガス透過量を測定し、図１３、表８にその結果を示した。
【００７０】
【表８】

【００７１】
【発明の効果】
本発明によれば、プラスチック基材の表面に形成されたケイ素酸化物被膜において、ケイ素酸化物被膜が赤外線吸収スペクトルにおいて波数１２１５乃至１２５０ｃｍ^−１に吸収ピークを有し且つ前記被膜が表面粗さ（ＪｌＳ Ｂ０６０１）において２５ｎｍ未満の十点平均粗さ（Ｒｚ）及び１０ｎｍ未満の中心線平均粗さ（Ｒａ）を有するようにしたことにより、ガス遮断性（ガスバリアー性）に特に優れており、従来のものに比して小さい膜厚で優れたガス遮断性を達成できると共に、形成される被膜が柔軟性及び可撓性に優れており、生産性にも優れているという利点が達成される。
【図面の簡単な説明】
【図１】実施例１のケイ素酸化物被膜の赤外線吸収スペクトルである。
【図２】比較例１のケイ素酸化物被膜の赤外線吸収スペクトルである。
【図３】公知のＰＶＤ法によるケイ素酸化物被膜の赤外線吸収スペクトルである。
【図４】本発明のケイ素酸化物被膜を設けたＰＥＴボトルのＸ線光電子分光分析のチャートである。
【図５】吸光度比（Ｒｉ）の求め方を示す説明図である。
【図６】本発明に用いるマイクロ波プラズマ処理装置の一例の概略配置図である。
【図７】プラズマ処理室の配置の一例を示す断面図である。
【図８】実施例２のケイ素酸化物被膜の赤外線吸収スペクトルである。
【図９】比較例２のケイ素酸化物被膜の赤外線吸収スペクトルである。
【図１０】実施例３のケイ素酸化物被膜の赤外線吸収スペクトルである。
【図１１】実施例４のケイ素酸化物被膜の赤外線吸収スペクトルである。
【図１２】実施例５のケイ素酸化物被膜の赤外線吸収スペクトルである。
【図１３】比較例３のケイ素酸化物被膜の赤外線吸収スペクトルである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a silicon oxide film and a packaging material including the same, and more particularly to a silicon oxide film that is excellent in gas barrier properties and useful as a packaging material.
[0002]
[Prior art]
Conventionally, metal cans, glass bottles, various plastic containers, and the like have been used as packaging containers, but plastic containers have the advantage of being lightweight and having some excellent impact resistance. Deterioration of contents and flavor reduction due to oxygen passing through the walls are problematic.
[0003]
In particular, oxygen permeation through the container wall is zero in metal cans and glass bottles, and only oxygen remaining in the container is a problem. In the case of plastic containers, oxygen permeation through the container wall can be ignored. This is a problem in terms of storability of contents.
[0004]
In order to prevent this, a plastic container has a multi-layered container wall, and an oxygen-permeable resin such as an ethylene-vinyl alcohol copolymer is used as at least one layer.
[0005]
However, multi-layer plastic containers require techniques such as co-extrusion and co-injection of multiple resins, requiring more troublesome molding operations and lower productivity than single-layer resin containers. is doing.
[0006]
It is already known to improve gas barrier properties by forming a vapor deposition film on a single layer plastic material, and a silicon oxide film (SiOx) or a hard carbon film (DLC) can be formed already. Are known.
Japanese Utility Model Laid-Open Nos. 49-50563 and 49-58171 describe a silicon oxide film in which a plastic film is coated by physical vapor deposition (PVD).
Japanese Unexamined Patent Publication No. 5-345383 discloses a silicon oxide film formed by chemical vapor deposition (CVD).
[0007]
Japanese Patent No. 2526766, which is filed by the present applicant, describes a plastic material and at least a silicon, carbon, and oxygen composition provided on the plastic material in which silicon is 15% or more, carbon is 20% or more, and the remainder is oxygen-containing heavy. A gas barrier laminated plastic material comprising a first layer formed by coalescence and a second layer of silicon oxide provided on the first layer is described.
[0008]
[Problems to be solved by the invention]
However, the conventional silicon oxide film has to have a considerably large film thickness necessary for providing gas barrier properties, which is disadvantageous in that the formed coating is subjected to flexibility and flexibility. There is a disadvantage of being inferior.
In particular, the silicon oxide film formed by physical vapor deposition (PVD) is inferior in oxygen gas barrier property compared to the same film thickness, and is quite thick to achieve the same level of gas barrier property. Has the disadvantage of having to form.
[0009]
Therefore, the object of the present invention is particularly excellent in gas barrier properties (gas barrier properties), and can achieve excellent gas barrier properties with a smaller film thickness than conventional ones, and the formed film is flexible. In addition, the present invention provides a silicon oxide film that is excellent in flexibility and productivity.
[0010]
[Means for Solving the Problems]
According to the present invention, in the silicon oxide film formed on the surface of the plastic substrate, the silicon oxide film has a wave number of 1215 to 1250 cm in the infrared absorption spectrum. ^-1 Silicon oxide, characterized in that the film has an absorption peak and has a 10-point average roughness (Rz) of less than 25 nm and a centerline average roughness (Ra) of less than 10 nm in surface roughness (JlS B0601). A physical coating is provided.
In the silicon oxide film of the present invention, the number of oxygen atoms per silicon atom measured by X-ray photoelectron spectroscopy is preferably in the range of 1.5 to 2.0, and the following formula (1)
Ri = A ₁ / A ₂ × 100 (1)
Where A ₁ Is a wave number of 1215 to 1250 cm in the infrared absorption spectrum ^-1 Indicates the area of absorbance in the range of
A ₂ Is a wave number of 985 to 1250 cm in the infrared absorption spectrum. ^-1 Indicates the area of absorbance in the range of
It is preferable that the absorbance ratio defined by is 1% or more.
The silicon oxide film of the present invention is not necessarily limited to this, but can be formed by microwave plasma chemical vapor deposition (MPCVD).
[0011]
DETAILED DESCRIPTION OF THE INVENTION
[Action]
The present invention relates to a silicon oxide film formed on the surface of a plastic substrate,
This silicon oxide film has a wave number of 1215 to 1250 cm in the infrared absorption spectrum. ^-1 The characteristic is that it exhibits an absorption peak, which can remarkably improve the gas barrier property of the silicon oxide film.
[0012]
The infrared absorption spectrum of the silicon oxide film can be obtained as a difference spectrum between the infrared absorption spectrum of the plastic substrate provided with the silicon oxide film and the infrared absorption spectrum of the untreated plastic substrate.
FIG. 1 of the accompanying drawings is an infrared absorption spectrum of the silicon oxide film (see Example 1 described later in detail) obtained in this manner.
From FIG. 1, the silicon oxide film according to the present invention has a wave number of 1215 to 1250 cm. ^-1 It can be seen that a clear infrared absorption peak is exhibited.
[0013]
A silicon oxide film showing an infrared absorption peak in the above region shows a significantly improved gas barrier property.
See the examples below. According to Example 1, the untreated polyethylene terephthalate (PET) bottle has an oxygen transmission rate of 5.3 cc / m. ² / day / atm, the oxygen permeation rate of the PET bottle provided with the silicon oxide film is 0.5 cc / m. ² It is / day / atm, and the oxygen transmission rate is suppressed to 1/10.
On the other hand, as shown in the infrared absorption spectrum of FIG. 2, the oxygen permeation amount of the PET bottle (Comparative Example 1) provided with the silicon oxide film not showing the infrared absorption peak in the above region is 5.3 cc / m. ² / day / atm and gas barrier performance has hardly been improved.
From the above fact, the improvement of the gas barrier property in the silicon oxide film of the present invention is the wave number 1215 to 1250 cm. ^-1 It is clear that it originates from a chemical structure that appears as a clear infrared absorption peak.
[0014]
In the present invention, wave numbers from 1215 to 1250 cm ^-1 The silicon oxide film exhibiting an infrared absorption peak in FIG. 3 is a novel film that is not observed in conventional silicon oxide films.
FIG. 3 is an infrared absorption spectrum of a commercially available silicon oxide film prepared by the PVD method.
According to these infrared absorption spectra, wave number 1000 to 1100 cm based on SiO ^-1 Absorption peak, but wave number 1215 to 1250 cm ^-1 It is clear that the infrared absorption peak of is substantially not recognized.
[0015]
Wave number 1215 to 1250cm ^-1 Silicon compounds having an infrared absorption peak are not well known, and a slight amount of lithium metasilicate, that is,

Is only known.
Therefore, in the silicon oxide film of the present invention, there are Si═O bonds in addition to siloxane bonds, and these are wave numbers 1215 to 1250 cm. ^-1 It is believed that this is the reason for showing an infrared absorption peak.
In addition, the reason why Si═O bond is generated in the silicon oxide film is as follows.

This is probably because silanol groups are generated and dehydrated.
[0016]
The silicon oxide film of the present invention has a 10-point average roughness (Rz) of less than 25 nm and a centerline average roughness (Ra) of less than 10 nm in surface roughness (JlS B0601). Is important.
Since the thickness of the silicon oxide coating is very thin, its surface roughness has a significant effect on gas barrier properties. That is, when the surface roughness is larger than a certain standard, the influence of gas permeation through the roughness valley portion is increased, and as a result, the gas barrier property of the entire silicon oxide film is lowered.
According to the study by the present inventors, the surface roughness is considerably different depending on the definition, but the ten-point average roughness (Rz) is less than 25 nm, and the centerline average roughness (Ra) is If it is less than 10 nm, the influence of gas permeation due to surface roughness can be avoided.
[0017]
That is, when the ten-point average roughness (Rz) is 25 nm or more and the center line average roughness (Ra) is 10 nm or more (see Comparative Example 3 described later), a gas barrier property deterioration due to the roughness is recognized. On the other hand, excellent gas barrier properties can be maintained by maintaining the surface roughness within the range defined in the present invention (see Example 3 described above).
[0018]
The silicon oxide film of the present invention has an oxygen atom number of 1.5 to 2.0, particularly 1. in relation to the fine structure described above, as measured by X-ray photoelectron spectroscopy. It is preferably in the range of 6 to 1.8.
FIG. 4 of the accompanying drawings shows a chart of X-ray photoelectron spectroscopic analysis of the PET bottle provided with the silicon oxide film of the present invention. The horizontal axis represents etching time (corresponding to the thickness from the surface), and the vertical axis represents atoms. The concentration is shown.
The composition in the thickness direction of the silicon oxide film is usually different between the outermost surface and the vicinity of the interface with the plastic substrate, and the inside in the thickness direction. It is sufficient that the composition ratio is present as a layer with a certain thickness.
[0019]
In the silicon oxide film of the present invention, the following formula (1)
Ri = A ₁ / A ₂ × 100 (1)
Where A ₁ Is a wave number of 1215 to 1250 cm in the infrared absorption spectrum ^-1 Indicates the area of absorbance in the range of
A ₂ Is a wave number of 985 to 1250 cm in the infrared absorption spectrum. ^-1 Indicates the area of absorbance in the range of
The absorbance ratio (Ri) defined by is preferably 1% or more.
[0020]
In FIG. 5 showing how to determine the absorbance ratio (Ri), the wave number is 1215 cm. ^-1 And wave number 1250cm ^-1 And draw a line connecting the straight line and the wave number 1215 to 1250 cm ^-1 Measure the area surrounded by the infrared absorption spectrum of ₁ And Next, wave number 985cm ^-1 And wave number 1250cm ^-1 And draw a line connecting the straight line and wave number 985 to 1250cm ^-1 Measure the area surrounded by the infrared absorption spectrum of ₁ And
[0021]
[Method and apparatus for forming silicon oxide film]
In the present invention, a silicon oxide film is formed on the surface of a plastic substrate by a plasma chemical vapor deposition method in an atmosphere containing a silicon compound, oxygen, and a carrier gas.
The apparatus used for forming the silicon oxide film includes a plasma processing chamber containing a substrate to be processed, an exhaust system for maintaining the plasma processing chamber in a reduced pressure state, and a gas for introducing a processing gas into the plasma processing chamber. A processing gas introduction system and an electromagnetic wave introduction system for generating plasma in the plasma processing chamber are included.
[0022]
In FIG. 6 which shows a schematic arrangement of an example of a microwave plasma processing apparatus used in the present invention, a vacuum pump 2 for holding the processing chamber 1 under reduced pressure is connected to an exhaust pipe 3 in a plasma processing chamber indicated by 1 as a whole. And the microwave oscillator 4 is connected via a waveguide 5.
In this specific example, the waveguide 5 is provided with a three-tuner 6 for adjusting the amount of microwave reflection from the processing chamber to a minimum, and the plasma processing chamber 1 has a load on the processing chamber. A short plunger 7 is also provided for adjusting the angle.
[0023]
In FIG. 7 showing an example of the arrangement of the plasma processing chamber 1, in this specific example, the plasma processing of the bottle 8 is performed, and the bottle 8 is held in an inverted state in the plasma processing chamber. A processing gas introduction pipe 9 is inserted inside the bottle 8, and a metal antenna 10 is provided at the tip of the introduction pipe 9 so as to extend upward.
[0024]
In plasma processing, the bottle 8 to be processed is first attached to a bottle holder (not shown), the bottle 8 and the bottle holder are maintained in an airtight state, the vacuum pump 2 is driven, and the inside of the bottle 8 is evacuated. To maintain. At this time, in order to prevent deformation of the bottle 8 due to the external pressure, the plasma processing chamber 1 outside the bottle can also be in a reduced pressure state.
[0025]
The degree of depressurization in the bottle 8 achieved by the vacuum pump 2 is such that the depressurization is such that glow gas is generated when the processing gas is introduced and the microwave is introduced. On the other hand, the degree of decompression in the plasma processing chamber 1 is such that no glow discharge occurs even when microwaves are introduced.
[0026]
After reaching the reduced pressure state, a processing gas is introduced into the bottle 8 through the processing gas introduction pipe 9, and a microwave is introduced into the plasma processing chamber 1 through the waveguide 5. At this time, the advantage that the plasma due to the glow discharge is stably generated within a very short time due to the emission of electrons from the metal antenna 10 is achieved.
The electron temperature in this plasma is tens of thousands of K, and the temperature of gas particles is about two orders of magnitude lower than that of several hundred K. In contrast, it is possible to effectively form a film by plasma treatment.
[0027]
After performing the predetermined plasma treatment, the introduction of the processing gas and the introduction of the microwave are stopped, and air is gradually introduced through the exhaust pipe 3 to return the inside and outside of the container to normal pressure, and the coating is performed by the plasma treatment. The formed bottle is taken out of the plasma processing chamber.
[0028]
[Plastic base material to be treated]
In the present invention, examples of the plastic substrate to be treated include various plastics.
Examples of the plastic include thermoplastic resins known per se, such as low density polyethylene, high density polyethylene, polypropylene, poly 1-butene, poly 4-methyl-1-pentene, or ethylene, pyropyrene, 1-butene, 4-methyl-1 -Random or block copolymers such as pentene and other random or block copolymers, ethylene / vinyl acetate copolymers, ethylene / vinyl alcohol copolymers, ethylene / vinyl chloride copolymers and other ethylene / vinyl compound copolymers Styrene resin such as polymer, polystyrene, acrylonitrile / styrene copolymer, ABS, α-methylstyrene / styrene copolymer, polyvinyl chloride, polyvinylidene chloride, vinyl chloride / vinylidene chloride copolymer, polymethyl acrylate, Polyvinyl chloride such as polymethyl methacrylate Nyl compounds, polyamides such as nylon 6, nylon 6-6, nylon 6-10, nylon 11 and nylon 12, thermoplastic polyesters such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate, polycarbonate, polyphenylene oxide and the like Any of the resins may be used.
[0029]
These base materials can be used in the form of a film or a sheet, or can be subjected to the plasma treatment of the present invention in the form of a container such as a bottle, a cup or a tube, or other molded products.
Examples of the bottles mentioned in the above-mentioned specific examples include biaxial stretch blow molded bottles formed from polyester such as polyethylene terephthalate.
Of course, the present invention can be applied to the polyester cup and biaxially stretched film as well.
[0030]
[Gas for forming silicon oxide film]
For the formation of the silicon oxide film, silicon tetrachloride, silane (SiH ₄ ), Hexamethyldisilane, vinyltrimethylsilane, methylsilane, dimethylsilane, trimethylsilane, diethylsilane, propylsilane, phenylsilane, methyltriethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, tetramethoxysilane, tetraethoxysilane, Organic silane compounds such as phenyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, etc., organic siloxane compounds such as octamethylcyclotetrasiloxane, 1,1,3,3-tetramethyldisiloxane, hexamethyldisiloxane, etc. used. In addition to these materials, aminosilane, silazane and the like are also used. These raw materials can be used alone or in combination of two or more.
Oxygen or NOx is used as the oxidizing gas, and argon or helium is used as the carrier gas.
[0031]
[Processing conditions]
In the present invention, the plasma treatment conditions are set to a combination of treatment conditions so that the above-described silicon oxide film having IR characteristic absorption is formed.
Examples of the processing conditions include the degree of vacuum at the time of film formation, the supply rate of the source gas, the supply rate of the oxidizing gas, and the microwave output. These conditions depend on the size of the container to be processed and other conditions. It is also difficult to define in general.
[0032]
However, as a general tendency, when the degree of vacuum at the time of film formation becomes low (pressure becomes high), it becomes difficult to form a silicon oxide film having IR characteristic absorption defined in the present invention. Further, when the supply rate of the silicon source gas increases, it becomes difficult to form a silicon oxide film having IR characteristic absorption as defined in the present invention. Further, when the supply rate of the oxidizing gas is reduced, it becomes difficult to form a silicon oxide film having IR characteristic absorption similarly defined in the present invention.
Considering the above tendency, the conditions for forming the silicon oxide film having the IR characteristic absorption defined in the present invention can be experimentally determined.
[0033]
In the present invention, the processing chamber for plasma treatment should be maintained at a vacuum level where glow discharge is generated. Generally speaking, the pressure during film formation is 5 to 200 Pa, particularly preferably 15 to 50 Pa. It is preferable to perform microwave discharge while maintaining the above range.
[0034]
The amount of silicon raw material gas introduced depends of course on the surface area of the substrate to be treated and the type of raw material gas, but the silicon raw material per container is 0.5 to 50 cc / min, particularly 1 to 10 cc in a standard state. It is desirable to supply at a relatively low flow rate of / min (hereinafter sometimes simply referred to as sccm).
[0035]
The amount of the oxidizing gas introduced varies depending on the composition of the silicon source gas, but it is generally preferable to supply it at a relatively high flow rate of 5 to 500 sccm, particularly 10 to 300 sccm.
[0036]
When the supply rate of silicon raw material is low and the degree of vacuum at the time of film formation is high (pressure is low), the glow discharge by microwave becomes unstable, and as a result, the formation of the silicon oxide film becomes unstable. Tend.
On the other hand, if a metal antenna is placed in the plasma processing chamber during microwave plasma processing, the glow discharge caused by microwave becomes stable even when the degree of vacuum during film formation is high (pressure is low). The silicon oxide film having the IR characteristic absorption described above can be stably formed.
[0037]
In a general glow discharge, a few gas ions existing in the dark current region are gradually accelerated as the electrode voltage rises, collide with neutral molecules and ionize them, and newly generated electrons are further absorbed by other electrons. The molecule is ionized, the cation bombards the cathode surface to cause electron emission, and this repetition develops in an arithmetic manner, and the steady state balanced with the disappearance of ions due to diffusion recombination is said to be glow discharge. The mechanism of glow discharge generation in the microwave plasma processing is the same as that described above except that microwaves are introduced instead of application of the electrode voltage.
[0038]
It seems that stabilization of glow discharge by the installation of the antenna in the present invention is closely related to promotion of glow discharge by electron emission. Actually, according to the observations by the present inventors, the antenna attached to the plasma processing chamber is in a very high temperature state, which may cause the emission of thermoelectrons from the antenna or the impact on the cation fine wire. This suggests that electron emission occurs.
[0039]
Furthermore, maintaining the supply rate of oxidizing gas at a large value in order to maintain the vacuum level (pressure) during film formation within an appropriate range in order to stabilize glow discharge while reducing the supply rate of silicon raw material. It will also be appreciated that it is important to do.
[0040]
In the present invention, the surface roughness of the silicon oxide film to be formed is reduced to a small range, that is, the ten-point average roughness by forming the silicon oxide film while maintaining a high degree of vacuum during film formation. (Rz) can be maintained in a range of less than 25 nm, and centerline average roughness (Ra) can be maintained in a range of less than 10 nm.
[0041]
As the electromagnetic wave that causes the glow discharge, it is preferable to use a high frequency of 13.56 MHz or a microwave that has an industrially permitted frequency of 2.45 GHz, 5.8 GHz, or 22.125 GHz. .
The microwave output varies depending on the surface area of the substrate to be processed and the type of the raw material gas. For example, in the surface treatment of a plastic container, the power of 50 to 600 W, particularly 100 to 400 W, per container. It is desirable to supply as follows.
[0042]
As a metal antenna used for shortening the induction period of glow discharge by microwaves, an antenna having a length of 0.02 times or more of the wavelength (λ) of the microwaves, most preferably a length of λ / 4 Thing is used.
As the shape of the antenna, a thin wire antenna having a sharp tip or a foil antenna having a length in the above-described range is used. The diameter of the thin wire antenna is generally 2 mm or less at the tip. On the other hand, the width of the foil antenna is 5 to 10 mm and the thickness is about 5 to 500 μm.
Since this fine wire generates heat, it should be excellent in heat resistance, and for example, those made of a material such as platinum, stainless steel, copper, carbon, aluminum or steel are preferable.
[0043]
The plasma treatment time also varies depending on the surface area of the substrate to be treated, the thickness of the thin film to be formed, the type of the raw material gas, and the like. One second or more is necessary from the viewpoint of the stability of the plasma processing, and a reduction in the time is required from the viewpoint of cost.
[0044]
In the case of plasma CVD, the deposition property of the deposited film is good, and the deposited film can be formed on all surfaces.
On the other hand, when the substrate to be processed is a three-dimensional molded product such as a plastic container, the inside and / or outside of the plastic container is maintained in a reduced-pressure atmosphere containing a processing gas, and microwave discharge is performed inside and / or outside the container. By generating the chemical vapor deposition film on the inner surface and / or outer surface of the container.
[0045]
In the plasma processing method shown in FIG. 6, the plastic container is held in the plasma processing chamber, the outside of the plastic container and the inside of the plastic container are maintained in an airtight state, and processing gas is introduced into the inside of the plastic container. In a state where the microwave discharge is generated, the pressure is maintained in a reduced pressure state, and the outside of the plastic container is maintained in a reduced pressure state where no microwave discharge is generated in the state where the processing gas is introduced. Plasma treatment can also be performed by introducing a microwave.
[0046]
In a three-dimensional molded product such as a plastic container, it is preferable to arrange a microwave reflector so as to face the bottom of the plastic container in the plasma processing chamber in order to stabilize the discharge and increase the processing efficiency. .
[0047]
The thickness of the silicon oxide film of the present invention is not particularly limited, but from the viewpoint of gas barrier properties and flexibility, the thickness of the film is preferably in the range of 2 to 500 nm, particularly 5 to 300 nm.
[0048]
【Example】
The present invention will be described in the following examples, but the present invention is not limited to the following examples in any way.
[0049]
Example 1
(Microwave plasma processing equipment)
The apparatus shown in FIG. 6 was used. That is, a microwave oscillator with a frequency of 2.45 GHz and a maximum output of 1.5 Kw, a metal cylindrical plasma processing chamber having a diameter of 300 mm and a height of 300 mm, and an oil rotary vacuum pump for evacuating the processing chamber And a rectangular waveguide for introducing microwaves from an oscillator into the plasma processing chamber. In the plasma processing chamber, the bottle holder shown in Fig. 7, the gas inlet, the tip of the gas inlet, an iron wire antenna with a tip of 0.5mm in diameter and 30mm in length, and a vacuum inside the bottle An oil rotary vacuum pump was installed.
The gas introducing device used was a stainless steel tube having an inner diameter of 4 mm, a length of 180 mm, 50 mm from the tip, and a hole of 0.9 mm at intervals of 90 degrees in the circumferential direction.
[0050]
(Microwave plasma processing method)
A bottle made of cylindrical polyethylene terephthalate (hereinafter referred to as PET bottle) with a diameter of 28 mm and a height of 220 mm is installed in the bottle holder, and the vacuum inside the bottle is pulled so that the degree of vacuum outside the bottle becomes 2 Kpa. The vacuum pump was operated until the temperature reached 2 Pa.
With the vacuum pump in operation, 2 sccm of hexamethyldisiloxane (hereinafter referred to as HMDSO) gas, 200 sccm of oxygen gas, and 10 sccm of argon gas were introduced, and the degree of vacuum in the bottle was adjusted by adjusting the valve (not shown). Adjusted to 50 Pa.
A 0.15 Kw radio wave was transmitted from a microwave oscillator, plasma was formed in the bottle, and plasma treatment was performed for 12 seconds.
[0051]
(Infrared absorption spectrum measurement method)
Cut out the body of the treated PET bottle and use the Perkin Elmer FT-IR (1600 type) internal multiple reflector (ATR) (prism material: germanium, incident angle: 45 degrees) Infrared spectroscopic analysis was performed.
An infrared absorption spectrum obtained by a difference spectrum method using an untreated bottle is shown in FIG. FIG. 1 clearly shows that the inner surface of the processing bottle is coated with silicon oxide. Also wave number 1215 ~ 1250cm ^-1 Absorption peak area (A ₁ ), And wave number 980-1250cm ^-1 Absorption peak area (A ₂ ), Ri = A ₁ / A ₂ Ri was determined from the x100 equation and shown in Table 1.
[0052]
(Method for analyzing composition in film)
Table 1 shows the atomic ratio of silicon and oxygen determined on the inner surface of the treatment bottle body using an X-ray photoelectron spectrometer (Scanning ESCA Quantum 2000) manufactured by PHI.
[0053]
(Thickness measurement method)
The amount of silicon on the inner surface of the treatment bottle was measured by a fluorescent X-ray spectroscopic analyzer (System 3080) manufactured by Rigaku Corporation.
[0054]
(Oxygen gas permeation measurement method)
Replace treated bottles and untreated bottles with nitrogen gas, seal the bottle mouth with an aluminum foil laminate with sealant, store in an environment of 30% 80% RH oxygen 21%, and over time oxygen in the bottles The gas concentration was measured and the oxygen gas permeation amount was determined and shown in Table 1.
[0055]
(Surface roughness measurement method)
The inner surface of the treatment bottle was measured for surface roughness with an atomic force microscope (tapping mode) manufactured by DIGITAL INSTRUMENTS, and shown in Table 1.
[0056]
[Table 1]

[0057]
(Comparative Example 1)
Using the processing apparatus described in Example 1, the PET bottle was plasma-treated under the processing conditions described in Example 1 except that the HMDSO introduction amount was 10 sccm under the processing conditions, and the infrared absorption spectrum and oxygen gas permeation amount were measured. The results are shown in FIG. 2 and Table 2.
[0058]
[Table 2]
Wave number 1215 to 1250cm ^-1 Absence of absorption peak
Oxygen gas permeation rate of untreated PET bottle (cc / m ² / day / atm) 5.2
Oxygen gas permeation rate of treated PET bottle (cc / m ² / day / atm) 5.3
[0059]
(Example 2)
Using the processing apparatus described in Example 1, plasma treatment was performed on the PET bottle under the processing conditions described in Example 1 except that the oxygen introduction amounts were set to 100 sccm and 150 sccm under the processing conditions, and the infrared absorption spectrum and oxygen gas permeation amount were measured. FIG. 8 and Table 3 show the results.
[0060]
[Table 3]

[0061]
(Comparative Example 2)
Using the processing apparatus described in Example 1, plasma treatment was performed on the PET bottle under the processing conditions described in Example 1 except that the oxygen introduction amount was 20 sccm and 50 sccm under the processing conditions, and the infrared absorption spectrum and oxygen gas permeation amount were measured. The results are shown in FIG. 9 and Table 4.
[0062]
[Table 4]

[0063]
(Example 3)
The microwave plasma treatment apparatus described in Example 1 was used except that a gas introducer made from sintered metal (nominal filtration accuracy: 120 μm) manufactured by SMC was used, the oxygen gas introduction amount was 50 sccm, and the microwave output was 0.3 Kw. The PET bottle was plasma-treated under the processing conditions described in Example 1, except that the infrared absorption spectrum, composition analysis in the film, film thickness, oxygen gas permeation amount, and surface roughness were measured. Results are shown.
[0064]
[Table 5]

[0065]
Example 4
The PET bottle was plasma treated under the processing conditions described in Example 1 except that the processing time described in Example 1 was used and the processing time was set to 2, 5, 10 and 20 seconds under the processing conditions. Thickness and oxygen gas permeation amount were measured, and the results are shown in FIG.
[0066]
[Table 6]

[0067]
(Example 5)
Using the processing apparatus described in Example 3, the PET bottle was plasma-treated under the processing conditions described in Example 3 except that the film forming vacuum was set to 20, 30, and 40 Pa under the processing conditions, and the infrared absorption spectrum, surface roughness The oxygen gas permeation amount was measured, and the results are shown in FIG.
[0068]
[Table 7]

[0069]
(Comparative Example 3)
Using the processing apparatus described in Example 3, the PET bottle was plasma-treated under the processing conditions described in Example 3 except that the film forming vacuum was set to 70, 110, and 150 Pa under the processing conditions. The oxygen gas permeation amount was measured, and the results are shown in FIG.
[0070]
[Table 8]

[0071]
【The invention's effect】
According to the present invention, in the silicon oxide film formed on the surface of the plastic substrate, the silicon oxide film has a wave number of 1215 to 1250 cm in the infrared absorption spectrum. ^-1 In addition, the coating film has a ten-point average roughness (Rz) of less than 25 nm and a center line average roughness (Ra) of less than 10 nm in the surface roughness (JlS B0601). It is particularly excellent in barrier properties (gas barrier properties), can achieve excellent gas barrier properties with a smaller film thickness than conventional ones, and the formed film has excellent flexibility and flexibility, The advantage of excellent productivity is achieved.
[Brief description of the drawings]
1 is an infrared absorption spectrum of the silicon oxide film of Example 1. FIG.
2 is an infrared absorption spectrum of the silicon oxide film of Comparative Example 1. FIG.
FIG. 3 is an infrared absorption spectrum of a silicon oxide film by a known PVD method.
FIG. 4 is a chart of X-ray photoelectron spectroscopy analysis of a PET bottle provided with a silicon oxide film of the present invention.
FIG. 5 is an explanatory diagram showing how to determine the absorbance ratio (Ri).
FIG. 6 is a schematic layout diagram of an example of a microwave plasma processing apparatus used in the present invention.
FIG. 7 is a cross-sectional view showing an example of an arrangement of a plasma processing chamber.
8 is an infrared absorption spectrum of the silicon oxide film of Example 2. FIG.
9 is an infrared absorption spectrum of the silicon oxide film of Comparative Example 2. FIG.
10 is an infrared absorption spectrum of the silicon oxide film of Example 3. FIG.
11 is an infrared absorption spectrum of the silicon oxide film of Example 4. FIG.
12 is an infrared absorption spectrum of the silicon oxide film of Example 5. FIG.
13 is an infrared absorption spectrum of the silicon oxide film of Comparative Example 3. FIG.

Claims (5)

In a silicon oxide film formed on the surface of a plastic substrate, the silicon oxide film has an absorption peak at a wave number of 1215 to 1250 cm ⁻¹ in an infrared absorption spectrum, and the film has a surface roughness (JlS B0601) of less than 25 nm A silicon oxide film having a ten-point average roughness (Rz) and a centerline average roughness (Ra) of less than 10 nm. 2. The silicon oxide film according to claim 1, wherein the number of oxygen atoms per one silicon atom measured by X-ray photoelectron spectroscopy is in the range of 1.5 to 2.0. Following formula (1)
Ri = A ₁ / A ₂ × 100 (1)
In the formula, A ₁ represents an area of absorbance in the range of wave numbers 1215 to 1250 cm ⁻¹ in the infrared absorption spectrum,
A ₂ represents an area of absorbance in the range of wave numbers 985 to 1250 cm ⁻¹ in the infrared absorption spectrum.
The silicon oxide film according to claim 1, wherein the absorbance ratio defined by the above is 1% or more. The silicon oxide film according to any one of claims 1 to 3, wherein the thickness of the film is in the range of 2 to 500 nm. A packaging material comprising the silicon oxide film according to claim 1.

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