JP4196440B2 - Fracture strain enhanced gas barrier film and method for producing the same - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、基材フィルム上にガラス薄膜が蒸着形成されてなるガスバリアフィルムとその製造方法に関し、詳しくは、基材フィルムの破壊ひずみがガラス薄膜のそれよりも大きい構成のガスバリアフィルムに関する。
ガスバリアフィルムが使用される業界によっては、ガラス薄膜や基材の厚さの範囲には制約があるが、本発明では、特に厚さによる適用制限は受けない。
【０００２】
【従来の技術】
近年、ガラス薄膜材料は、産業の至るところで広く使われている。特に食品の包装材料などに用いられるガスバリアフィルムは、基材となるプラスチックフィルムにガラス薄膜をコーティングすることにより、ガスバリア機能を備えた機能性フィルムであり、これらは既に我々の身近に多く存在する。
【０００３】
通常、ガスバリアフィルムは、蒸着やＣＶＤ，スパッタリングなどの各種成膜技術により、基材フィルム上にガスバリア性機能を有した薄膜を形成することにより製造される。
【０００４】
しかしながら、この様なガスバリアフィルムは、薄膜にクラックなどの破壊が生じると、そのガスバリア性が低下または消滅してしまう。また、この様なガスバリアフィルムはそのフレキシブル性も必要なので、基材材料は膜厚数〜数百mmのプラスチックフィルムを用いている。
このように、ガスバリアフィルムは薄くて柔らかいので、製造工程中や製品として市場に出た後も、薄膜が破壊してしまうことがしばしば問題となっている。
【０００５】
【発明が解決しようとする課題】
本発明は、上記の事情に鑑みてなされたものであり、その目的とするところは、ガスバリアフィルムの製造工程中や製品として市場に出た後に、ガラス薄膜に破壊が生じることを防止することで、生産性や品質の信頼性の向上したガスバリアフィルムを提供することである。
これにより、製造する際のコストダウンや、出荷後のガスバリア性の維持、例えば、食品などの賞味期限の大幅な延長などが期待できることになる。
【０００６】
【課題を解決するための手段】
上記目的を実現するために、本発明が提供する手段は、ガスバリアフィルムのガラス薄膜に圧縮残留ひずみを与えることにより、その破壊ひずみを大きくするものである。
【０００７】
請求項１の破壊ひずみ強化ガスバリアフィルムの製造方法は、基材フィルム上にガラス薄膜が蒸着形成されてなるガスバリアフィルムの製造にあたり、基材フィルムとして１２μｍのＰＥＴフィルムを用い、ガラス薄膜として１００ｎｍのＳｉＯＸ薄膜を用い、ガラス薄膜の形成過程での蒸着速度を、３〜１０Å／ｓｅｃの低速な範囲とすることにより、ガラス薄膜に０．４〜０．６％の圧縮残留ひずみ（応力にして２８０〜４３０ＭＰａ）を与え、薄膜の破壊ひずみをその圧縮残留ひずみ分だけ大きくすることを特徴とする。
【０００８】
請求項２の破壊ひずみ強化ガスバリアフィルムの製造方法は、基材フィルム上にガラス薄膜が蒸着形成されてなるガスバリアフィルムの製造にあたり、基材フィルムとして１２μｍのＰＥＴフィルムを用い、ガラス薄膜として１００ｎｍのＳｉＯＸ薄膜を用い、前記フィルムの温度を、ガラス転移点を越えない範囲である約７０〜８０℃の高温にして、ガラス薄膜を蒸着形成し、成膜後の基材フィルムの熱収縮量を大きくするにより、ガラス薄膜に０．１％の圧縮残留ひずみを与え、薄膜の破壊ひずみをその圧縮残留ひずみ分だけ大きくすることを特徴とする。
【００１０】
請求項３の破壊ひずみ強化ガスバリアフィルムは、上記請求項１または２に記載の方法により製造されることを特徴とする。
【００１１】
請求項４の破壊ひずみ強化ガスバリアフィルムは、基材フィルムとして、その破壊ひずみがガラス薄膜の破壊ひずみより大きいものを使用することを特徴とする。
【００１２】
薄膜が破壊する現象について説明する。
薄膜／基材フィルムからなる一般的な２層構造の機能性フィルムで、基材フィルムの破壊ひずみが薄膜のそれよりも大きい場合に、薄膜／基材系を１方向に引っ張ったときに薄膜に生じるクラックについて述べる。
【００１３】
薄膜の引っ張り臨界ひずみ（以後、破壊ひずみと呼ぶ）までは、薄膜・基材フィルム共に同じように伸びるが、ひずみが薄膜の臨海値に達すると、薄膜のみに引っ張り方向に垂直なクラックが生じる。
【００１４】
さらに引っ張り続けると、薄膜・基材間の付着が残っていれば、界面でのずり応力を通して薄膜は引っ張られ、さらなるクラックが薄膜にほぼ等間隔に生じる。結果として、薄膜には無数の引っ張り方向に垂直なクラックが生じることになる。（図１参照）
【００１５】
次に、ガラス薄膜／基材フィルムからなるガスバリアフィルムの場合について述べる。一般的に、ガラス薄膜の破壊ひずみの方が基材フィルムのそれよりも小さいので、上述のように、ガスバリアフィルムを１方向に、ガラス薄膜の破壊ひずみ以上に引っ張った場合、ガラス薄膜のみに、引っ張り方向に垂直な無数のクラックが生じる（図２参照）。これにより、ガスバリアフィルムのガスバリア性はガラス薄膜にクラックが生じる前と比較して、大幅に低下する。
【００１６】
ガラス薄膜に残留ひずみが存在する場合について述べる。
ガラス薄膜の残留ひずみは２種類存在する。一つは引っ張り残留ひずみ、そしてもう一つは圧縮残留ひずみである。前者は、薄膜の成長過程や後処理の際に、薄膜が収縮しようとして、基材はそれを妨げる方向に薄膜を引っ張る状態にある場合の残留ひずみであり、後者は、逆に薄膜が伸びようとして、基材はそれを押し縮めようとする状態にある場合の残留ひずみである。
【００１７】
これらの残留ひずみは、フィルムがカールする現象として見ることが出来、（図３参照）残留ひずみはフィルムのカールが急なほど（カールの曲率半径が小さいほど）大きい。
【００１８】
ガラス薄膜に圧縮残留ひずみを与える成膜方法について述べる。
通常、ガラス薄膜／基材からなるガスバリアフィルムは、蒸着やＣＶＤ、スパッタリングなどの成膜方法により製造されるが、本発明において成膜方法の制限はない。また、成膜機も巻き取り式とバッチ式があるが、成膜機による制限はない。
【００１９】
薄膜の残留ひずみの原因は主に３つ考えられる。１つ目は成膜中の基材フィルムのテンション、２つ目は成膜中の基材の温度、そして３つ目は成膜スピードである。
【００２０】
成膜中の基材フィルムのテンションは、成膜中に、基材フィルムの降伏点以内で、意図的に基材フィルムをひずませることにより、薄膜に上記した圧縮残留ひずみが付与されることになる。
【００２１】
成膜中の基材の温度により、ガラス薄膜に圧縮残留ひずみを与える方法について述べる。
バリアフィルムにおいて、一般に、基材にはＰＥＴやＰＥなどのプラスチックフィルムが用いられる。これらのプラスチックフィルムと薄膜とは熱膨張係数が違うので、成膜中の温度と成膜後の温度が違うと、成膜後の薄膜には残留ひずみが存在する。特に、成膜後の温度と成膜中の温度差が大きいほど、この残留ひずみも大きい。つまり、成膜中の基材フィルムの温度を大きくすることにより、成膜後の薄膜にはより大きな圧縮残留ひずみが残る。（図４参照）
【００２２】
成膜速度により、ガラス薄膜に圧縮残留ひずみを与える方法について述べる。バリアフィルムにおいて、一般に、バリア性機能を有する薄膜は、ＳｉＯ2 やＭｇＯなどのセラミックスであり、これらは全て真空成膜により成膜されるが、成膜中の真空チャンバー内には、少なからず残留ガスが存在する。
【００２３】
蒸着により真空中に飛び出した薄膜材料となる蒸着粒子は、基材に衝突して成膜される。このとき、チャンバー内の残留ガスを取り込みながら成膜するので、蒸着スピードが遅い方がより多くの残留ガスを取り込むことになる。
【００２４】
残留ガスを取り込んだ薄膜は、そのことにより薄膜が膨張するために、薄膜には圧縮残留ひずみが発現する。つまり、蒸着スピードが遅い方がより多くの残留ガスを取り込み、より大きな圧縮残留ひずみを生み出す。（図５，６参照）
【００２５】
上記のようにして成膜した薄膜／基材からなるガスバリアフィルムは、薄膜に圧縮残留ひずみが存在する。
【００２６】
そして圧縮残留ひずみが存在するフィルムを１方向に引っ張った場合、薄膜は既に縮められているため、薄膜の破壊ひずみに達するまでに、より大きな量のひずみになるまで引っ張らなければならない。従って、見かけの破壊ひずみは圧縮残留応力がない場合よりも増加する。そして、この見かけの破壊ひずみは圧縮の残留応力が大きいほど大きい。
これにより、薄膜／基材からなるガスバリアフィルムは、薄膜に圧縮残留ひずみを与えることにより、破壊ひずみ強化ガスバリアフィルムとなる。
【００２７】
【発明の実施の形態】
以下、本発明に係る圧縮残留ひずみによる破壊ひずみ強化ガスバリアフィルムとその製造方法の実施例を、図面に基づいてさらに詳細に説明する。
【００２８】
＜実施例１＞
１．試料作製
試料として、蒸着速度を３〜１５０Å／ｓｅｃの範囲で変化させて成膜したガスバリアフィルムについて、その残留応力と破壊ひずみの関係を調べた。基材フィルムに厚さ１２μｍのＰＥＴフィルムを用い、その片面に約１００ｎｍ（１０００Å）のＳｉＯＸ薄膜を、バッチ式電子ビーム蒸着装置により成膜した。（試料：図７参照、装置：図１２参照）
【００２９】
蒸着中の真空度は２×10-3 Ｐａ、膜厚は水晶振動子式膜厚モニターによりモニタリングしながら成膜する。
本文中で、ＳｉＯX 薄膜と呼ぶものは、Ｘ線電子分光測定によるＸの値はほぼ２に等しいので、ＳｉＯ2 と同じものと考えられる。
【００３０】
ＰＥＴフィルムの応力−ひずみ曲線を図８に示す。
図８から分かるとおり、ＰＥＴの降伏点は約２％、その時の応力は75ＭＰａである。つまり、成膜中の基材フィルムに加えるテンションは、ＰＥＴが降伏しない範囲（ひずみ２％で以下、応力で75ＭＰａ以下）にとどめる必要がある。
【００３１】
２．残留ひずみ測定
作製した全ての試料は、ＳｉＯX 薄膜中に圧縮残留ひずみが存在し、カールを生じた。（図５参照）
各試料について試料の一部を、２mm×10mmの短冊状に切り出し、カールの曲率半径を測定した。（図９参照）
ＳｉＯX 層のヤング率と試料の反り（カール）から、ＳｉＯX 層の残留ひずみを下記の式により推定した。
【００３２】
【数１】
ただし、上記の式は、異なる弾性を持つ２層材料の曲げ変形を記述する式を元に、
Ｅf ｄ<<Ｅs ｂ
を仮定して求めた。
【００３４】
計算により得られた残留ひずみの結果を図６に示す。このグラフからわかるように、ＳｉＯX 薄膜に存在する残留ひずみは、蒸着スピードが遅いほど大きい。
【００３５】
蒸着速度を３〜10Å／sec の低速な範囲で成膜することにより、ガラス薄膜に0.4 〜0.6 ％の圧縮残留ひずみを生じさせることができた。
【００３６】
３．破壊ひずみ測定
各蒸着スピードで成膜した試料について、試料の一部を、幅方向に１cm×巻き取り方向に10cmの短冊状に切り出し、光学顕微鏡の下での引張り試験を行い、ＶＴＲに記録した薄膜破壊像からクラック数を計測する。概略図を図10に示す。
【００３７】
各実験条件は以下の通りである。
視野：縦63mm×横82mm（ＣＲＴモニター１画面）
試験時の試料形状：約47mm（長さ) ×10mm（幅）の短冊型
引張り速度：4.9 mm/sec
【００３８】
結果を図11に示す。横軸にＳｉＯX 薄膜に存在する圧縮残留ひずみ、縦軸にＳｉＯX 薄膜の破壊ひずみを示す。ただし、破壊ひずみとは、試料を１方向に引っ張ったとき、ＳｉＯX 薄膜に１本目のクラックが発生した時点のひずみの値である。
【００３９】
このグラフから分かるように、ＳｉＯX 薄膜に存在する圧縮残留ひずみが大きいほど、ＳｉＯX 薄膜の破壊ひずみも大きい。また、ほぼ圧縮残留ひずみの増加分だけ破壊ひずみも直線的に増加していることが分かる。（図11参照）
【００４０】
これらの結果から、蒸着スピードを３〜10Å／sec の低速な範囲で成膜することにより、ガラス薄膜に0.4 〜0.6 ％の圧縮残留ひずみを生じさせ、おおよそその圧縮残留ひずみ分だけ破壊ひずみを大きくすることができた。（図６，11参照)
【００４１】
＜実施例２＞
１．試料作製
次に、成膜中の基材の温度を50〜80℃の範囲で変化させて蒸着を行ったバリアフィルムにおいて、残留ひずみと破壊ひずみの関係を調べた。
【００４２】
基材は、一般にはんだごてなどに用いられる抵抗加熱式ヒーターによりにより加熱する。また、蒸着中の基材の温度は、放射温度計により常に測定し続ける。
【００４３】
ちなみに、本実施例で用いたＰＥＴフィルム（２軸延伸）のガラス転移点は約80℃であるので、それ以下の温度で蒸着する必要がある。
【００４４】
本実施例においても、基材フィルムに厚さ１２μｍのＰＥＴフィルムを用い、その片面に約１００ｎｍ（１０００Å）のＳｉＯＸ薄膜をバッチ式電子ビーム蒸着装置により成膜した。場着スピードは全て約４Å／ｓｅｃ、蒸着中の真空度は２×１０−３Ｐａで成膜し、膜厚は水晶振動子式膜厚モニターによりモニタリングした。
【００４５】
２．残留ひずみ測定
作製した全ての試料は、ＳｉＯX 薄膜中に圧縮残留ひずみが存在し、カールを生じた。上記実施例１と同様の方法で、カールの曲率半径から残留ひずみ測定を行った。基材の温度と残留ひずみの結果を図13に示す。
【００４６】
図13からわかるように、蒸着蒸着中の温度が高いほどＳｉＯX 薄膜に存在する残留ひずみは大きい。これはＳｉＯX とＰＥＴの熱膨張係数の違いによるものである。一般に、ＰＥＴの熱膨張係数はＳｉＯ2 のそれよりも大きいので、蒸着後にＰＥＴの温度が室温まで下がると、ＳｉＯ2 よりも大きな量だけ縮もうとするため、ＳｉＯX 薄膜に圧縮残留ひずみが生じる。この圧縮残留ひずみは、蒸着中の基材の温度が大きいほど、大きい。
【００４７】
しかしながら、実際にフィルムのカールとして現れる薄膜の圧縮残留ひずみには、蒸着中の基材にかかるテンションによるものや、蒸着スピードや真空度によって生じる薄膜固有のひずみなど、その他の要因も含まれていおり、本実施例の基材ＰＥＴとＳｉＯ2 の熱膨張係数の違いによる薄膜の圧縮残留ひずみは、薄膜に生じる圧縮残留ひずみ全体の一部であり、支配的なものではない。このことは図13のグラフにおいて各測定点を直線近似した場合、蒸着後の温度が室温と同じ25℃の位置では、約0.59％の圧縮残留ひずみが存在することからも分かる。
【００４８】
３．破壊ひずみ測定
結果を図17に示す。横軸にＳｉＯX 薄膜に存在する圧縮残留ひずみ、縦軸にＳｉＯX 薄膜の破壊ひずみを示す。このグラフから分かるように、ＳｉＯX 薄膜に存在する圧縮残留ひずみが大きいほど、ＳｉＯX 薄膜の破壊ひずみも大きい。また、ほぼ圧縮残留ひずみの増加分だけ破壊ひずみも直線的に増加していることが分かる。（図17参照）このことはは実施例１で示した通りである。
【００４９】
これらの結果から、蒸着後の室温を25℃とした場合、蒸着中の基材ＰＥＴの温度を70〜80℃の高温で成膜することにより、ガラス薄膜に約0.1 ％の圧縮残留ひずみを生じさせ、そしてその圧縮残留ひずみ分だけ破壊ひずみを大きくすることができた。（図13，17参照）
【００５０】
＜実施例３＞
１．酸素透過度測定
蒸着速度 90 Å／sec で成膜した試料についてのみ、酸素透過度測定装置（ＭＯＣＯＮ社製）を改造した、引っ張り酸素透過度測定装置により引っ張り酸素透過度を測定した。装置の写真及び概略図を図14に示す。この試料のカールから測定した圧縮残留ひずみは0.15％である。
【００５１】
引っ張り率とクラック密度の結果を図15に、引っ張り率と酸素透過度の結果を図16に示す。図15からこの試料の破壊ひずみは約1.07％であることが分かる。２つのグラフの比較からわかるように、クラックの発生により酸素透過度が劣化していることは明らかである。
【００５２】
【発明の効果】
以上説明したように、本発明により、薄膜の圧縮残留応力を増加させることが出来、破壊ひずみが増加させた破壊ひずみ強化ガスバリアフィルムを作製することが可能である。
これにより、例えばガスバリアフィルムなどの機能性フィルムの製造する際の生産性が増加し、製造コストの大幅な低下が期待できる。また、ガスバリアフィルムは主に食品の包装材料などに使用されるので、賞味期限（品質保証期間）の大幅な延長も期待できる。
【００５３】
【図面の簡単な説明】
【図１】薄膜／基材からなる機能性フィルム（破壊ひずみは、基材＞薄膜）を一方向に引っ張った際、薄膜に生じるクラックを示す説明図。
【図２】ガラス薄膜／基材からなるガスバリアフィルム（破壊ひずみは、基材＞ガラス薄膜）を一方向に引っ張った際、薄膜に生じるクラックを示す写真。
【図３】残留ひずみ（引っ張り，圧縮）によるフィルムのカールを示す説明図。
【図４】成膜中の基材の温度に依存する残留ひずみによるフィルムのカールを示す説明図。
【図５】成膜速度に依存する残留ひずみによるフィルムのカールを示す写真と説明図。
【図６】成膜速度と圧縮残留ひずみとの関係を示すグラフ。
【図７】本発明の実施例でのガスバリアフィルムの構成を示す説明図。
【図８】ＰＥＴフィルム（単体）の応力とひずみとの関係を示すグラフ。
【図９】ガスバリアフィルムのカールの曲率半径を測定する状態を示す説明図。
【図１０】実験試料（ガスバリアフィルム）を解析する状態を示す説明図。
【図１１】実験結果（ＳｉＯX 薄膜の圧縮残留ひずみと破壊ひずみとの関係）を示すグラフ。
【図１２】本発明の実施例でのガスバリアフィルムの製造装置を示す説明図。
【図１３】成膜中の基材の温度と圧縮残留ひずみとの関係を示すグラフ。
【図１４】ガスバリアフィルムの酸素透過度を測定する装置を示す説明図。
【図１５】測定結果（引っ張り率とクラック密度との関係）を示すグラフ。
【図１６】測定結果（引っ張り率と酸素透過度との関係）を示すグラフ。
【図１７】ＳｉＯX 薄膜の圧縮残留ひずみと破壊ひずみとの関係を示すグラフ。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gas barrier film in which a glass thin film is formed by vapor deposition on a base film and a method for producing the same, and more particularly to a gas barrier film having a structure in which the fracture strain of the base film is larger than that of the glass thin film.
Depending on the industry in which the gas barrier film is used, the range of the thickness of the glass thin film or the substrate is limited, but in the present invention, there is no particular limitation on the application due to the thickness.
[0002]
[Prior art]
In recent years, glass thin film materials have been widely used throughout the industry. In particular, gas barrier films used for food packaging materials and the like are functional films having a gas barrier function by coating a glass thin film on a plastic film serving as a base material.
[0003]
Usually, a gas barrier film is manufactured by forming a thin film having a gas barrier function on a base film by various film forming techniques such as vapor deposition, CVD, and sputtering.
[0004]
However, when such a gas barrier film is broken such as a crack in the thin film, the gas barrier property is reduced or eliminated. In addition, since such a gas barrier film needs to be flexible, a plastic film having a film thickness of several to several hundred mm is used as the base material.
As described above, since the gas barrier film is thin and soft, it is often a problem that the thin film is broken during the manufacturing process or after being put on the market as a product.
[0005]
[Problems to be solved by the invention]
This invention is made | formed in view of said situation, The place made into the objective is to prevent that a glass thin film breaks during the manufacturing process of a gas barrier film, or after being marketed as a product. It is to provide a gas barrier film with improved productivity and quality reliability.
As a result, it is possible to expect cost reduction during production, maintenance of gas barrier properties after shipment, for example, significant extension of the expiration date of food and the like.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the means provided by the present invention increases the fracture strain by applying compressive residual strain to the glass thin film of the gas barrier film.
[0007]
The method for producing a fracture strain strengthened gas barrier film according to
[0008]
The method for producing a fracture strain strengthened gas barrier film according to
[0010]
A fracture strain enhanced gas barrier film according to a third aspect is manufactured by the method according to the first or second aspect.
[0011]
The fracture strain-enhanced gas barrier film according to
[0012]
The phenomenon that the thin film breaks will be described.
A functional film with a general two-layer structure consisting of a thin film / base film. When the fracture strain of the base film is larger than that of the thin film, the thin film / base system is turned into a thin film when pulled in one direction. The cracks that occur are described.
[0013]
Up to the critical tensile strain of the thin film (hereinafter referred to as the fracture strain), both the thin film and the base film grow in the same way.
[0014]
If the film is further pulled, if the adhesion between the thin film and the substrate remains, the thin film is pulled through the shear stress at the interface, and further cracks are generated in the thin film at almost equal intervals. As a result, innumerable cracks perpendicular to the pulling direction are generated in the thin film. (See Figure 1)
[0015]
Next, the case of a gas barrier film comprising a glass thin film / base film will be described. Generally, since the fracture strain of the glass thin film is smaller than that of the base film, as described above, when the gas barrier film is pulled in one direction, more than the fracture strain of the glass thin film, only the glass thin film, Innumerable cracks perpendicular to the pulling direction are generated (see FIG. 2). Thereby, the gas barrier property of a gas barrier film falls significantly compared with before the crack arises in a glass thin film.
[0016]
The case where residual strain exists in the glass thin film will be described.
There are two types of residual strain in glass thin films. One is the tensile residual strain and the other is the compressive residual strain. The former is the residual strain when the thin film tends to shrink during the thin film growth process or after-treatment, and the base material is in a state of pulling the thin film in the direction that prevents it, and the latter is conversely the thin film will stretch. As a residual strain when the substrate is in a state of being compressed.
[0017]
These residual strains can be seen as a phenomenon that the film curls (see FIG. 3), and the residual strain increases as the curl of the film becomes sharper (the curl radius of curvature decreases).
[0018]
A film forming method for applying compressive residual strain to a glass thin film will be described.
Usually, a gas barrier film composed of a glass thin film / base material is produced by a film formation method such as vapor deposition, CVD, or sputtering, but there is no limitation on the film formation method in the present invention. In addition, the film forming machine includes a winding type and a batch type, but there is no limitation by the film forming machine.
[0019]
There are mainly three causes of the residual strain of the thin film. The first is the tension of the substrate film during film formation, the second is the temperature of the substrate during film formation, and the third is the film formation speed.
[0020]
The tension of the base film during film formation is such that the compressive residual strain described above is imparted to the thin film by intentionally distorting the base film within the yield point of the base film during film formation. Become.
[0021]
A method of applying compressive residual strain to the glass thin film depending on the temperature of the substrate during film formation will be described.
In the barrier film, a plastic film such as PET or PE is generally used as the base material. Since these plastic films and thin films have different thermal expansion coefficients, if the temperature during film formation is different from the temperature after film formation, there is residual strain in the thin film after film formation. In particular, the larger the difference between the temperature after film formation and the temperature during film formation, the greater this residual strain. That is, by increasing the temperature of the base film during film formation, a larger compressive residual strain remains in the thin film after film formation. (See Figure 4)
[0022]
A method for applying compressive residual strain to a glass thin film according to the film formation rate will be described. In a barrier film, generally, a thin film having a barrier function is a ceramic such as SiO 2 or MgO, and these are all formed by vacuum film formation, but not a little remains in the vacuum chamber during film formation. Gas is present.
[0023]
Vapor-deposited particles that become a thin film material that jumps out into the vacuum by vapor deposition collide with the substrate to form a film. At this time, since the film is formed while taking in the residual gas in the chamber, more residual gas is taken in when the deposition speed is slower.
[0024]
Since the thin film that has taken in the residual gas expands due to this, compressive residual strain appears in the thin film. That is, the slower the deposition speed, the more residual gas is taken in and a larger compressive residual strain is produced. (See Figs. 5 and 6)
[0025]
The thin film / substrate gas barrier film formed as described above has compressive residual strain in the thin film.
[0026]
And when a film with compressive residual strain is pulled in one direction, the thin film has already been shrunk and must be pulled until a larger amount of strain is reached before reaching the fracture strain of the thin film. Therefore, the apparent fracture strain is increased as compared with the case where there is no compressive residual stress. The apparent fracture strain increases as the compressive residual stress increases.
Thereby, the gas barrier film which consists of a thin film / base material turns into a fracture-strain-enhanced gas barrier film by giving a compressive residual strain to a thin film.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Examples of the fracture strain-enhanced gas barrier film due to compressive residual strain and the manufacturing method thereof according to the present invention will be described below in more detail with reference to the drawings.
[0028]
<Example 1>
1. Sample preparation As a sample, the relationship between the residual stress and the fracture strain of a gas barrier film formed by changing the deposition rate in a range of 3 to 150 liters / sec was examined. A PET film having a thickness of 12 μm was used as the base film, and a SiO X thin film having a thickness of about 100 nm (1000 mm) was formed on one surface thereof by a batch type electron beam evaporation apparatus. (Sample: see FIG. 7; apparatus: see FIG. 12)
[0029]
The degree of vacuum during vapor deposition is 2 × 10 −3 Pa, and the film thickness is monitored while being monitored by a crystal oscillator type film thickness monitor.
In the text, what is called a SiO x thin film is considered to be the same as SiO 2 because the value of X by X-ray electron spectroscopy is almost equal to 2 .
[0030]
FIG. 8 shows a stress-strain curve of the PET film.
As can be seen from FIG. 8, the yield point of PET is about 2%, and the stress at that time is 75 MPa. That is, it is necessary to keep the tension applied to the base film during film formation within a range where PET does not yield (strain 2% or less, stress 75 MPa or less).
[0031]
2. Residual strain measurement All the prepared samples had a compressive residual strain in the SiO x thin film, and curled. (See Figure 5)
A part of each sample was cut into a 2 mm × 10 mm strip, and the radius of curvature of the curl was measured. (See Figure 9)
From the Young's modulus of the SiO x layer and the warp (curl) of the sample, the residual strain of the SiO x layer was estimated by the following equation.
[0032]
[Expression 1]
However, the above equation is based on the equation describing the bending deformation of a two-layer material with different elasticity,
E f d << E s b
Assuming
[0034]
The result of the residual strain obtained by calculation is shown in FIG. As can be seen from this graph, the residual strain existing in the SiO x thin film increases as the deposition speed decreases.
[0035]
By forming the film in a low deposition rate range of 3 to 10 liters / sec, a compressive residual strain of 0.4 to 0.6% could be generated in the glass thin film.
[0036]
3. Breaking strain measurement For each sample deposited at each deposition speed, a part of the sample was cut into a strip of 1 cm in the width direction and 10 cm in the winding direction, subjected to a tensile test under an optical microscope, and recorded in the VTR. The number of cracks is measured from the thin film destruction image. A schematic diagram is shown in FIG.
[0037]
Each experimental condition is as follows.
Field of view: 63 mm long x 82 mm wide (CRT monitor 1 screen)
Sample shape at the time of test: Approx. 47 mm (length) × 10 mm (width) strip-type pulling speed: 4.9 mm / sec
[0038]
The results are shown in FIG. The horizontal axis represents the compressive residual strain existing in the SiO x thin film, and the vertical axis represents the fracture strain of the SiO x thin film. However, the fracture strain is a strain value at the time when the first crack is generated in the SiO x thin film when the sample is pulled in one direction.
[0039]
As it can be seen from this graph, as the compressive residual strain present in the SiO X film is large, greater fracture strain of SiO X film. It can also be seen that the fracture strain increases linearly by the amount of increase in compressive residual strain. (See Fig. 11)
[0040]
From these results, by forming a film at a low deposition rate of 3 to 10 liters / sec, a compressive residual strain of 0.4 to 0.6% is generated in the glass thin film, and the fracture strain is increased by approximately the compressive residual strain. We were able to. (See Figures 6 and 11)
[0041]
<Example 2>
1. Sample Preparation Next, the relationship between residual strain and fracture strain was examined in a barrier film deposited by changing the temperature of the substrate during film formation in the range of 50 to 80 ° C.
[0042]
The substrate is heated by a resistance heating heater generally used for a soldering iron or the like. Moreover, the temperature of the base material during vapor deposition is continuously measured with a radiation thermometer.
[0043]
Incidentally, since the glass transition point of the PET film (biaxial stretching) used in this example is about 80 ° C., it is necessary to deposit at a temperature lower than that.
[0044]
Also in this example, a PET film having a thickness of 12 μm was used as a base film, and a SiO X thin film having a thickness of about 100 nm (1000 mm) was formed on one side thereof by a batch type electron beam evaporation apparatus. All the deposition speeds were about 4 cm / sec, the degree of vacuum during vapor deposition was 2 × 10 −3 Pa, and the film thickness was monitored by a crystal oscillator type film thickness monitor.
[0045]
2. Residual strain measurement All the prepared samples had a compressive residual strain in the SiO x thin film, and curled. Residual strain was measured from the radius of curvature of the curl in the same manner as in Example 1. The results of the substrate temperature and residual strain are shown in FIG.
[0046]
As can be seen from FIG. 13, the higher the temperature during vapor deposition, the greater the residual strain present in the SiO x thin film. This is due to the difference in thermal expansion coefficient between SiO x and PET. In general, since the thermal expansion coefficient of PET is larger than that of SiO 2 , when the temperature of PET decreases to room temperature after vapor deposition, it tends to shrink by a larger amount than SiO 2 , resulting in compressive residual strain in the SiO x thin film. . This compressive residual strain increases as the temperature of the substrate during vapor deposition increases.
[0047]
However, the compressive residual strain of the thin film that actually appears as curl of the film includes other factors such as those due to the tension applied to the substrate during vapor deposition and the inherent strain of the thin film caused by the vapor deposition speed and degree of vacuum. The compressive residual strain of the thin film due to the difference in thermal expansion coefficient between the base material PET and SiO 2 of this example is a part of the entire compressive residual strain generated in the thin film and is not dominant. This can also be seen from the fact that when the measurement points are linearly approximated in the graph of FIG. 13, there is a compressive residual strain of about 0.59% at the position where the temperature after vapor deposition is 25 ° C., which is the same as the room temperature.
[0048]
3. Fig. 17 shows the fracture strain measurement results. The horizontal axis represents the compressive residual strain existing in the SiO x thin film, and the vertical axis represents the fracture strain of the SiO x thin film. As it can be seen from this graph, as the compressive residual strain present in the SiO X film is large, greater fracture strain of SiO X film. It can also be seen that the fracture strain increases linearly by the amount of increase in compressive residual strain. (See FIG. 17) This is as shown in the first embodiment.
[0049]
From these results, when the room temperature after vapor deposition is set to 25 ° C, the compression residual strain of about 0.1% is generated in the glass thin film by forming the substrate PET during vapor deposition at a high temperature of 70-80 ° C. The fracture strain was increased by the amount of compressive residual strain. (See Figures 13 and 17)
[0050]
<Example 3>
1. Oxygen permeability measurement Tensile oxygen permeability was measured only by using a tensile oxygen permeability measuring device obtained by modifying an oxygen permeability measuring device (manufactured by MOCON) for a sample formed at a deposition rate of 90 Å / sec. A photograph and schematic of the device are shown in FIG. The compression residual strain measured from the curl of this sample is 0.15%.
[0051]
FIG. 15 shows the results of the tensile rate and crack density, and FIG. 16 shows the results of the tensile rate and oxygen permeability. FIG. 15 shows that the fracture strain of this sample is about 1.07%. As can be seen from the comparison of the two graphs, it is clear that the oxygen permeability has deteriorated due to the occurrence of cracks.
[0052]
【The invention's effect】
As described above, according to the present invention, it is possible to increase the compressive residual stress of a thin film and to produce a fracture strain enhanced gas barrier film with an increased fracture strain.
Thereby, productivity at the time of manufacturing a functional film such as a gas barrier film is increased, and a significant reduction in manufacturing cost can be expected. In addition, since the gas barrier film is mainly used for food packaging materials and the like, a significant extension of the shelf life (quality assurance period) can be expected.
[0053]
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing cracks generated in a thin film when a functional film composed of a thin film / base material (breaking strain is base material> thin film) is pulled in one direction.
FIG. 2 is a photograph showing a crack generated in a thin film when a gas barrier film composed of a glass thin film / substrate (fracture strain is substrate> glass thin film) is pulled in one direction.
FIG. 3 is an explanatory diagram showing curling of a film due to residual strain (tensile, compression).
FIG. 4 is an explanatory diagram showing curling of a film due to residual strain depending on the temperature of a base material during film formation.
FIGS. 5A and 5B are a photograph and an explanatory view showing curling of a film due to residual strain depending on a film forming speed. FIGS.
FIG. 6 is a graph showing the relationship between the deposition rate and the compressive residual strain.
FIG. 7 is an explanatory diagram showing a configuration of a gas barrier film in an example of the present invention.
FIG. 8 is a graph showing the relationship between stress and strain of a PET film (single unit).
FIG. 9 is an explanatory view showing a state in which the radius of curvature of the curl of the gas barrier film is measured.
FIG. 10 is an explanatory diagram showing a state in which an experimental sample (gas barrier film) is analyzed.
FIG. 11 is a graph showing experimental results (relationship between compressive residual strain and fracture strain of SiO x thin film).
FIG. 12 is an explanatory view showing a gas barrier film manufacturing apparatus in an example of the present invention.
FIG. 13 is a graph showing the relationship between the temperature of the base material during film formation and the compressive residual strain.
FIG. 14 is an explanatory diagram showing an apparatus for measuring oxygen permeability of a gas barrier film.
FIG. 15 is a graph showing measurement results (relationship between tensile rate and crack density).
FIG. 16 is a graph showing measurement results (relationship between tensile rate and oxygen permeability).
FIG. 17 is a graph showing the relationship between compressive residual strain and fracture strain of a SiO x thin film.
Claims (4)
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| US10159120B2 (en) | 2015-06-12 | 2018-12-18 | Sharp Kabushiki Kaisha | EL display device and method for manufacturing EL display device |
| US10181580B2 (en) | 2014-12-05 | 2019-01-15 | Sharp Kabushiki Kaisha | Organic EL display device |
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| JP4107040B2 (en) * | 2002-10-09 | 2008-06-25 | セイコーエプソン株式会社 | Manufacturing method of substrate on which thin film is formed, manufacturing method of electro-optical device, electro-optical device, and electronic apparatus |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US10181580B2 (en) | 2014-12-05 | 2019-01-15 | Sharp Kabushiki Kaisha | Organic EL display device |
| US10497901B2 (en) | 2014-12-05 | 2019-12-03 | Sharp Kabushiki Kaisha | Display device |
| US10159120B2 (en) | 2015-06-12 | 2018-12-18 | Sharp Kabushiki Kaisha | EL display device and method for manufacturing EL display device |
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