JP2004099754A - Optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film excellent in optical isotropy, not liable to deform in a high temperature environment, favorably good in surface smoothness and water vapor barrier property, extremely low in dimension variation after high temperature heating, and suitable for display use. <P>SOLUTION: This optical film is, for example, a polycarbonate film containing 30-80 mol% fluorene skeleton as a copolymerization component, and contains 0.001-0.3 wt% solvent in the film. <P>COPYRIGHT: (C)2004,JPO

Description

【００１３】
［上記式（１）において、Ｒ_１〜Ｒ_８はそれぞれ独立に水素原子、ハロゲン原子ならびに炭素数１〜１０の飽和および／又は不飽和の炭化水素基から選ばれる少なくとも一種の基である。］
で表される繰り返し単位と、下記式（２）
【００１４】
【化５】

【００１５】
［上記式（２）において、Ｒ_９〜Ｒ_１６はそれぞれ独立に水素原子、ハロゲン原子ならびに炭素数１〜１０の飽和及び／又は不飽和炭化水素基から選ばれる少なくとも一種の基であり、Ｘは下記式群
【００１６】
【化６】

【００１７】
（ここで、Ｙ中のＲ_１７〜Ｒ_１９、Ｒ_２１及びＲ_２２はそれぞれ独立に水素原子、ハロゲン原子及び炭素数１〜２２の炭化水素基からなる群から選ばれる少なくとも１種の基であり、Ｒ_２０及びＲ_２３はそれぞれ独立に炭素数１〜２０の炭化水素基であり、Ａｒ_１〜Ａｒ_３はそれぞれ独立に炭素数６〜１０のアリール基である。）］
で示される繰り返し単位とからなるポリカーボネートを主成分として形成された高分子フィルム（Ｓ）であって、上記式（１）で表される繰り返し単位は全体の３０〜８０モル％であり、かつ該高分子フィルムには０．００１〜０．３重量％の溶媒が含まれる光学用フィルム。
２．　（ｉ）１８０℃２時間加熱後の熱収縮率が０．０５％より小さく、（ｉｉ）全光線透過率が８５％以上であり、かつ（ｉｉｉ）三次元屈折率が下記式（Ａ）及び（Ｂ）を同時に満足する上記の光学用フィルム。
【００１８】
Ｒ（５５０）≦５（ｎｍ）　　　　　　　　　　　　　　　（Ａ）
Ｋ＝［（ｎ_ｘ＋ｎ_ｙ）／２−ｎ_ｚ］×ｄ≦１００（ｎｍ）　　（Ｂ）
（上記式（Ａ）において、Ｒ（５５０）は波長５５０ｎｍの光に対する高分子フィルム（Ｓ）の面内位相差であり、上記式（Ｂ）において、ｎ_ｘ、ｎ_ｙ、ｎ_ｚは高分子フィルム（Ｓ）の厚み方向をｚ軸としたｘ軸、ｙ軸、ｚ軸方向の波長５５０ｎｍの光に対する三次元屈折率であり、ｄは高分子フィルム（Ｓ）の厚さである。）
３．　動的粘弾性測定において損失弾性率がピークを示すときの温度が１９０℃以上であり、この温度から１０℃低い温度における貯蔵弾性率が１．５ＧＰａ以上であり、かつ３０℃における貯蔵弾性率が２．５ＧＰａ以上である上記に記載の光学用フィルム。
４．　高分子フィルム（Ｓ）の少なくとも片面の表面平滑性がＳＲａで３ｎｍ以下である上記に記載の光学用フィルム。
５．　さらに、Ｓｉ、Ａｌ、Ｔｉ、ＭｇおよびＺｒから選ばれた少なくとも１種の金属あるいは２種以上の金属混合物の酸化物、フッ化物、窒化物あるいは酸窒化物の無機材料からなるガスバリア層（Ｂ）を有する上記に記載の光学用フィルム。
６．　さらに、架橋構造を有する少なくとも一層のコーティング層（Ｃ）を有する上記に記載の光学用フィルム。
７．　さらに、少なくとも一層の透明導電層（Ｅ）を有する上記に記載の光学用フィルム。
８．　上記１〜７のいずれかに記載の光学用フィルムの、液晶素子、有機ＥＬ素子、電気泳動素子、フィールドエミッション素子またはプラズマ素子用の基板としての利用。
【００１９】
【発明の実施の形態】
本発明の光学用フィルムの高分子フィルム（Ｓ）は、下記式（１）で表される繰り返し単位と、下記式（２）で表される繰り返し単位とからなるポリカーボネートを主成分とするものであって、溶液流延法により形成したものである。
【００２０】
【化７】

【００２１】
上記式（１）において、Ｒ_１〜Ｒ_８はそれぞれ独立に、水素原子、臭素、フッ素、ヨウ素等のハロゲン原子、メチル基、エチル基、イソプロピル基等のアルキル基、フェニル基等の炭素数１〜１０の飽和および／又は不飽和の炭化水素基が挙げられる。
【００２２】
ここで、Ｒ_２及びＲ_３は水素原子及び／または炭素数１〜３のアルキル基であり、Ｒ_５及びＲ_８は水素原子及び／または炭素数１〜３のアルキル基であるものが成形性、重合性等に優れ好適である。具体的な例としては、フルオレン−９，９−ジ（４−フェノール）、フルオレン−９，９−ジ（３−メチル−４−フェノール）が挙げられる。
【００２３】
下記式（２）
【００２４】
【化８】

【００２５】
で表される繰り返し単位において、Ｒ_９〜Ｒ_１６はそれぞれ独立に水素原子、ハロゲン原子および炭素数１〜１０の飽和及び／又は不飽和炭化水素基から選ばれる少なくとも一種の基であり、Ｘは下記式群
【００２６】
【化９】

【００２７】
から選ばれる少なくとも一種の基である。ここで、Ｒ_１７〜Ｒ_１９、Ｒ_２１及びＲ_２２はそれぞれ独立に水素原子、ハロゲン原子及びアルキレン基、アリール基等の炭素数１〜２２の１価の炭化水素基からなる群から選ばれる少なくとも１種であり、Ｒ_２０及びＲ_２３はそれぞれ独立にアルキレン基、フェニレン基等の炭素数１〜２０の２価の炭化水素基であり、Ａｒ_１〜Ａｒ_３はそれぞれ独立にフェニル基等の炭素数６〜１０のアリール基である。
【００２８】
本発明における特に好ましいポリカーボネートとしては、フルオレン−９，９−ジ（３−メチル−４−フェノール）から誘導された上記式（１）で表される繰り返し単位（上記式（１）において、Ｒ_１〜Ｒ_８は水素原子（ただし、Ｒ_２とＲ_３の一方がメチル基であり、Ｒ_５とＲ_８の一方がメチル基）であるものに対応）と、Ｘが２，２−プロピレンであり、かつＲ_９〜Ｒ_１６がすべて水素原子である上記式（２）で表される繰り返し単位とを共重合成分とするポリカーボネートである。ここで、上記式（１）で表される繰り返し単位は、全繰り返し単位の３０〜８０モル％であり、好ましくは３５〜７０モル％であり、さらに好ましくは４０〜６０モル％であるが好ましい。上記式（１）で表される繰り返し単位はが多くなるにつれて耐熱性や弾性率は向上するが、短波長側の光線透過率が低下してくるという問題や耐衝撃性が低下し脆くなる傾向がある。なお、上記のポリカーボネートの分子量としては、数平均分子量で５，０００〜３００，０００が好ましく、１５，０００〜１００，０００がより好ましい。分子量が大きなポリマーほど機械特性ならびに耐熱性が向上する。
【００２９】
本発明の光学用フィルムは溶液流延法によって形成される。溶液流延法は生産性においては溶融押出し法に劣るが、ダイライン、ゲル化物、フィッシュアイ等の欠点が少なく表面平滑性も溶融押出し法に比較し遥かに優れている。また、溶液流延法では溶融押出しでは溶融粘度が高すぎたり着色しやすかったり成形が不可能な高分子量の樹脂でも、用いる溶媒に可溶であれば成形が可能であることから、機械特性ならびに耐熱性に優れたフィルムが得られる。また、溶液流延法では、ダイの特性、キャスティングベルトの状況、乾燥条件およびフィルム張力と搬送条件等を調整することにより、フィルムの三次元屈折率を制御できる。本発明の光学等方性に優れ、加熱後の寸法変化が極めて少ない光学フィルムを得るためには、成形工程内のフィルムが含有する溶媒量と乾燥温度ならびにフィルムに加わる張力の調整が特に重要である。フィルムが含有する溶媒量によりフィルムの見かけ上のＴｇが決まるが、乾燥温度は見かけ上のＴｇ以下に設定することが好ましい。また、フィルムに加わる張力は、例えばロール巻き取り方式により成形を行う場合は、フィルム搬送方向の張力が大きくなる傾向があるが、フィルム搬送方向と垂直方向にも張力を加えることができる装置を用い、両張力に出来るだけ差が生じない条件でかつ張力を出来る限り抑えて成形することも有効である。
【００３０】
溶液流延法では、フィルム中に製膜に使用した溶媒が残存する場合がある（これを残留溶媒ということがある）。残留溶媒はフィルムを可塑化させ、ガラス転移温度の低下および機械特性の低下などをもたらす。このため残留溶媒はできるだけ除去することが好ましく、少なくとも０．００１重量％以上である。また最大でも０．３重量％よりも小さくすることが好ましく、さらに好ましくは０．１重量％以下である。なお、フィルムに可塑化剤または界面活性剤等を添加する場合は、これらの残存量は溶媒残存量に含めない。
【００３１】
ところで残留溶媒量を低減させる方法は、主に加熱処理、真空処理であるが、効果と経済性を考慮した場合にはジクロロメタン等の低沸点溶媒を、溶液流延法の主溶媒にするのが好ましい。なおジクロロメタンに限らず、例えばクロロホルム、１，２−ジクロロエタン、テトラヒドロフラン、１，３−ジオキソラン、１，４−ジオキサン、シクロヘキサノン、クロロベンゼン等の溶媒を単独または混合して用いることも可能である。
【００３２】
上記式（１）で表される繰り返し単位を３０モル％以上にし、上述の溶液流延法にて、残留溶媒量を０．３重量％よりも少なくすることにより、基材となる高分子フィルムの耐熱性が向上し高温環境下においても非常に高度に優れた機械的強度を示す。具体的には、例えば動的粘弾性で表現すると、引張モードの温度分散の測定において、損失弾性率がピークを示すときの温度が１９０℃以上であり、このピーク温度から１０℃低い温度における貯蔵弾性率が１．５ＧＰａ以上であり、かつ３０℃における貯蔵弾性率が２．５ＧＰａ以上となり、各種表示素子を製造する工程の加熱加圧処理においても基板が変形しにくくなる。また、特に高温加熱後の寸法変化が極めて少なく、たとえば１８０℃２時間熱処理した後の寸法変化率が０．０５％以下となり、カラーフィルター等の形成に優位となり表示品位に優れる表示素子が作りやすくなる。また、水蒸気透過度が小さくなり、例えば４０℃１００％ＲＨにおける水蒸気透過係数が４０００ｇ・μｍ／ｍ^２／ｄａｙよりも小さくなるため表示素子の信頼性向上に有効となり。さらには、光学等方性も良好となり、各種液晶に対する耐性も良好となるので、液晶ディスプレイ用途で特に有用である。
【００３３】
ここで、良好な光学等方性とは、下記式（Ａ）及び（Ｂ）
｜Ｒ（５５０）｜≦５（ｎｍ）　　　　　　　　　　　　　　　　（Ａ）
Ｋ＝｜［ｎｚ−（ｎｘ＋ｎｙ）／２］×ｄ｜≦１００（ｎｍ）　　（Ｂ）
を満たすことをいう。上記式（Ａ）において、Ｒ（５５０）は波長５５０ｎｍの光に対する透明高分子基板の面内位相差であり、上記式（Ｂ）において、Ｋは三次元的な光学等方性を表し、ｎｘ、ｎｙ、ｎｚは透明高分子基板の厚み方向をｚ軸としたｘ軸、ｙ軸、ｚ軸方向の波長５５０ｎｍの光に対する三次元屈折率であり、ｄは透明高分子基板の厚さである。
【００３４】
この特性は、特に本発明の光学用フィルムを液晶表示体に用いる場合、液晶表示体の視野角特性や旋光分散を補償する上で非常に有益である。
【００３５】
さらに、上記式（１）で表される繰り返し単位が多くなるにつれて、高分子フィルムの光学等方性が高くなり、３０モル％よりも大きいポリカーボネートを用いた場合、波長４５０ｎｍの光に対する面内位相差Ｒ（４５０）と波長５５０ｎｍの光に対する面内位相差Ｒ（５５０）の夫々の値を小さくすることが可能になり、さらにはＲ（４５０）／Ｒ（５５０）≦１．０６、さらにはＲ（４５０）／Ｒ（５５０）≦１．００となるため、光学等方性に極めて優れるフィルムとなる。
【００３６】
一方で、本発明の光学用フィルムは、下記に示す理由により、位相差フィルムあるいはその原反として用いることができる。位相差フィルムは、三次元屈折率が下記式（Ｃ）、（Ｄ）を同時に満足するものであり、通常は前記の光学等方性に優れるフィルムを延伸することによって得られる。
【００３７】
５ｎｍ＜Ｒ（５５０）≦５００（ｎｍ）　　　　　　　　　（Ｃ）
Ｋ＝［（ｎ_ｘ＋ｎ_ｙ）／２−ｎ_ｚ］×ｄ≦２００（ｎｍ）　　（Ｄ）
上記式（Ｃ）において、Ｒ（５５０）は波長５５０ｎｍの光に対する高分子フィルム（Ｓ）の面内位相差であり、上記式（Ｄ）において、ｎ_ｘ、ｎ_ｙ、ｎ_ｚは高分子フィルム（Ｓ）の厚み方向をｚ軸としたｘ軸、ｙ軸、ｚ軸方向の波長５５０ｎｍの光に対する三次元屈折率であり、ｄは高分子フィルム（Ｓ）の厚さである。延伸は横一軸延伸でも縦一軸延伸、さらには同時二軸延伸でも逐次二軸延伸でもよいが、液晶表示素子の色むらを防ぐためには、同一面内のリターデーション値のバラツキを通常１０ｎｍ以下、好ましくは５ｎｍ以下とするのが良い。このような位相差を有する本発明の光学用フィルムは、加熱処理後の寸法変化が小さいことに加えて、リターデーションの変化も小さいことが特徴である。
【００３８】
また、本発明の光学用フィルムは上記の溶液流延法により形成された、フィルム表面性に優れたものである。溶液流延法によりＳＲａが表面平滑性が良好なフィルムが得られるが、表面平滑性は、ＳＲａで３ｎｍ以下の光学用フィルムが好ましい。
【００３９】
ここで、ＳＲａは三次元中心面平均粗さで、粗さ表面からその中心面上に、面積Ｓｍの部分を抜き取り、その抜き取り部分の中心面に直交する軸をＺ軸で表し、次の式で得られた値をμｍ単位で表す。
【００４０】
【数１】

【００４１】
（ただし、Ｌｘ×Ｌｙ＝Ｓｍ）
本発明における高分子フィルム（Ｓ）の厚さは、各種ディスプレイに加工された時の表示品位と、基板を成形する工程での取り扱いやすさと、ディスプレイ組立て工程での取り扱いやすさ、さらには溶液流延製膜時の製膜効率の観点から、２０〜５００μｍ、好ましくは５０〜４００μｍ、さらには好ましくは７０〜２００μｍである。また、かかる高分子フィルム（Ｓ）を用いた本発明の光学用フィルムに透明導電層からなる電極を設けて液晶ディスプレイ用電極として使用する場合、液晶セルのギャップ斑が表示品位を劣化させるため、かかるポリカーボネートフィルムの厚み斑を±５％以下にすることが好ましく、さらには±２％以下にするのが好ましい。
【００４２】
本発明の光学用フィルムは、前記高分子フィルムの少なくもと一方の面上に、好ましくは前述のＳＲａが１ｎｍよりも小さい面上に、無機薄膜から実質的になるガスバリア層を形成することができる。
【００４３】
ガスバリア層の例としては、Ｓｉ、Ａｌ、Ｔｉ、ＭｇおよびＺｒ等から選ばれた少なくとも１種の金属あるいは２種以上の金属混合物の酸化物、フッ化物、窒化物あるいは酸窒化物の無機材料が挙げられる。なかでも、Ｓｉの酸化物、窒化物、酸窒化物を主成分とする無機材料が透明性、ガスバリア性、表面平滑性、前述の高分子フィルムとの密着性に優れ好ましい。特に珪素と酸素が主成分である酸化珪素が好ましい。または珪素と酸素が主成分であり、少なくともフッ素、マグネシウムを含有し、かつ珪素とフッ素が化学結合している薄膜が、ガスバリア性、透明性、表面平滑性、膜応力が少ないという点で好ましい。ここで、珪素原子に対する酸素原子の割合は１．５以上２未満が好ましい。この割合により薄膜の透明性とガスバリア性が二律背反性の関係で変化し、１．５未満ではディスプレイ用途で要求される透明性が得られないことがある。さらに、フッ素原子は珪素ならびにマグネシウムと化学結合しており、フッ素原子と珪素原子の結合（Ａ）とフッ素原子とマグネシウムの結合（Ｂ）の割合が（Ａ）＞（Ｂ）であることが好ましく、かつガスバリア層中に含まれるマグネシウムの比率は、共存する珪素に対し元素比で２．５〜２０ａｔｏｍ％の範囲が好ましい。このような割合にすることで、良好なガスバリア性、透明性は勿論のこと、特に膜応力を小さくできると推定され、したがって、ガスバリア層の膜厚を厚くしても光学用フィルムの変形が少なくできる。ガスバリア膜中に存在するフッ素元素の化学結合状態は、例えばＸ線光電子分光法により分析、決定される。Ｘ線光電子分光法において、Ｘ線源にＡｌのＫα線を用い、中性炭素Ｃ１ｓの２８４．６ｅＶで横軸を補正した際、フッ素の化学結合状態は、６８７ｅＶ近傍に観測されるフッ素と珪素の結合に由来するＦ１ｓピーク（Ａ）とこれより約１．５ｅＶ低結合エネルギー側に観測されるフッ素とマグネシウムの結合に由来するＦ１ｓピーク（Ｂ）の存在ならびに、これらの強度比により決定される。
【００４４】
ガスバリア層（Ｂ）の作成方法としては、例えばスパッタ法、真空蒸着法、イオンプレーティング法、プラズマＣＶＤ法等の気相中より材料を堆積させて膜形成する気相堆積法が挙げられる。これらのガスバリア層は単独あるいは二種類以上組み合わせて用いることができる。ガスバリア層の膜厚は、１ｎｍ〜１μｍの範囲が好ましく、さらに好ましくは２ｎｍ〜２００ｎｍの範囲が好ましい。ガスバリア層の厚みが１ｎｍ未満では均一に膜を形成することは困難であり、膜が形成されない部分が発生するため気体透過度が大きくなる。一方、１μｍよりも厚くなると透明性を欠くだけでなく、光学用フィルムを屈曲させた際に、ガスバリア層にクラックが発生して気体透過度が上昇する。
【００４５】
本発明によれば、特に、前述の高分子フィルムのＳＲａが１ｎｍ以下の面側に、前述の珪素の酸化物、窒化物あるいは酸窒化物を主成分とするガスバリア層（Ｂ）を形成すると、下記式（Ｉ）及び（ＩＩ）式を満足する高温さらには高湿環境下においても優れたガスバリア性を有する光学用フィルムが得られる。
【００４６】
Ｐ_１＜１×１０^７ｅｘｐ（−５０００／Ｔ）［ｃｃ／ｍ^２／２４ｈｒ／ａｔｍ　（Ｉ）
Ｐ_２＜５×１０^１１ｅｘｐ（−８０００／Ｔ）［ｇ／ｍ^２／２４ｈｒ］　　　　　（ＩＩ）
上記式（Ｉ）、（ＩＩ）において、Ｐ_１は該基板の相対湿度０％における酸素透過度、Ｐ_２は相対湿度１００％における水蒸気透過度であり、Ｔは酸素透過度ならびに水蒸気透過度の測定温度を絶対温度（Ｋ）で表したものである。
【００４７】
なお、ガスバリア層の表面平坦性をさらに向上させることを目的に高分子フィルム（Ｂ）とガスバリア層（Ｓ）の間に、平坦性に優れるアンダーコート層を形成してもよい。また、本発明の光学用フィルムには、必要に応じて、該フィルムの少なくとも片面に、例えば、ガスバリア層（Ｂ）の面側に直接または中間層を介して、あるいはガスバリア層（Ｂ）の形成させていない側の高分子フィルム面上に、直接または中間層を介して架橋構造を有する有機及び／又は無機化合物からなるコーティング層を形成することができる。
【００４８】
ここでアンダーコート層ならびに架橋構造を有するコーティング層としては、ポリシロキサン系樹脂の架橋構造体、アクリル系樹脂の架橋構造体、エポキシ系樹脂の架橋構造体等を公知の塗工法および硬化法を用いることにより形成できる。ここで架橋性を有するコーティング層はパネル組立て時の溶剤や化学薬品に対する耐久性を付与するために使用する（耐薬品層ということがある）。ガスバリア層および耐薬品層を相互に積層させる場合には、各層間の接着性を向上させる目的で適宜プライマー層を設ける事ができる。プライマー層としてはシランカップリング剤等を含むシリコン系材料、アクリル系材料、アクリル−ウレタン系材料あるいはアルコキシチタン等を含む材料を用いることができる。耐薬品層の膜厚は、概して０．０１〜２０μｍの範囲から適宜選択することができる。また、本発明の光学用フィルムを液晶表示素子あるいは有機ＥＬ表示素子に用いる場合は、高分子フィルムの液晶層あるいはＥＬ層側に積層する耐薬品層の表面は、前述の高分子フィルムの表面平滑性と同等なＳＲａが得られるようにコーティング液の調整および塗工方法の条件を選択することが好ましい。
【００４９】
本発明の光学用フィルムは、その用途に応じて透明導電層を形成し、例えば電極とすることができる。透明導電層としては、公知の金属膜、金属酸化物膜等が適用できるが、中でも、透明性、導電性、機械的特性の点から、金属酸化物膜が好ましい。例えば、不純物としてスズ、テルル、カドミウム、モリブテン、タングステン、フッ素、亜鉛、ゲルマニウム等を添加した酸化インジウム、酸化カドミウム及び酸化スズ、不純物としてアルミニウムを添加した酸化亜鉛、酸化チタン等の金属酸化物膜が挙げられる。なかでも、インジウム酸化物を主成分とし、酸化錫及び酸化亜鉛からなる群から選ばれた１種以上の酸化物を含むことを特徴とし、酸化錫が２〜２０重量％及び／または酸化亜鉛が２〜２０重量％含有する透明導電層が透明性、導電性が優れており好ましく用いられる。また、本発明のフィルムを有機ＥＬに用いる場合、透明導電層の仕事関数を制御して発光効率を向上させる目的で、インジウム酸化物を主成分とし、酸化錫及び酸化亜鉛からなる群から選ばれた１種以上の酸化物を含む膜に、さらに錫、亜鉛以外の元素を添加してもよい。
【００５０】
透明導電層を形成する方法は、主にスパッタリング法が使用され、直流マグネトロンスパッタリング法、高周波マグネトロンスパッタリング法、イオンビームスパッタリング法などが適用できる。透明導電層の膜厚は、十分な導電性を得るために、１０〜１０００ｎｍであることが好ましい。本発明のディスプレイ用透明高分子フィルムは、可視光領域に対する全光線透過率が８０％以上であることが好ましく、さらには８５％以上が好ましい。８０％未満では、視認性の低下を招く等の問題が生じることがある。
【００５１】
【発明の効果】
本発明によれば、フルオレン骨格を有するポリカーボネートフィルムを用いることにより、３次元屈折率が小さく光学等方性が良好であり、また耐熱性に優れ、高温加熱後の寸法変化が極めて少なく、更には表面平滑性に極めて優れた透明高分子基板として有用な光学用フィルムが得られる。特に、具体的には動的粘弾性測定において損失弾性率がピークを示すときの温度が１９０℃以上であり、この温度から１０℃低い温度における貯蔵弾性率が１．５ＧＰａ以上であり、かつ３０℃における貯蔵弾性率が２．５ＧＰａ以上である優れた効果を有する。
【００５２】
本発明の光学用フィルムは、その少なくとも一方の面上に金属酸化物を主成分とする薄膜層を積層することにより高温高湿環境下においても極めて優れたガスバリア性を付与することができ、ヒートシールコネクターや異方導電性フィルム等の導電粒子を含む接続材料を用いてプリント配線板を接続した場合に優れた信頼性が得られるディスプレイ用に好適な光学用フィルムを提供することができる。
【００５３】
かかる光学用フィルムは、例えば液晶表示素子、光導電性感光体、面発光体、無機ならびに有機ＥＬ素子、電気泳動、フィールドエミッション素子、プラズマ素子、面発熱体などの透明基板として利用した際に高温高湿下に長時間放置しても信頼性に優れたフラットパネルディスプレイあるいは電子ペーパーを与えるガスバリア性透明フィルムとして特に有用である。
【００５４】
【実施例】
以下、実施例を挙げ、本発明をさらに具体的に説明するが、本発明は、かかる実施例に限定されるものではない。なお、実施例中、部および％は、特に断らない限り重量基準である。また、実施例中における各種の測定は、下記のとおり行った。
（１）全光線透過率
日本電色工業社製ＣＯＨ−３００Ａを用いて測定した。
（２）動的粘弾性
レオメトリックス社製ＲＳＡ―ＩＩを用いて、引張モードにて２５℃〜２８０℃の温度範囲で、昇温速度３℃／分、周波数１Ｈｚにて測定した。
（３）水蒸気透過度
ＭＯＣＯＮ社製、パーマトランＷ１Ａを用いて、４０℃１００％ＲＨにおける水蒸気透過度を測定した。
（４）リターデーション値、三次元屈折率
高分子フィルム（Ｓ）の複屈折△ｎと膜厚ｄの積である位相差および三次元屈折率の値は、分光エリプソメ−ターである日本分光（株）製の商品名「Ｍ１５０」により測定した。リターデーション値は入射光線とフィルム表面が直交する状態で測定した。また、三次元屈折率は波長５５０ｎｍの入射光線とフィルム表面の角度を変えることにより、各角度での位相差値を測定し、公知の屈折率楕円体の式でカーブフィッティングすることにより三次元屈折率であるｎｘ、ｎｙ、ｎｚを求めた。
（５）寸法変化率
幅１０ｍｍ、長さ１００ｍｍのサイズの高分子フィルム（Ｓ）を、夫々フィルムの流れ方向（ＭＤ）と幅方向（ＴＤ）に沿って切り出し、電子マイクロメーターで長さを精密に測定した後、１８０℃２時間で加熱処理し、２５℃５０％ＲＨの環境下で１時間以上放置した後の長さを精密に測定し、加熱前後の長さの差を加熱前の長さで割った値を％で算出した。
（６）フィルム膜厚
アンリツ社製の電子マイクロで測定した。
（７）表面平滑性の評価
表面平滑性は、小坂研究所社製の増幅支持装置ＳＥ３ＣＫ、解析装置ＳＰＡ−１１（株）用いて測定し、カットオフ０．０８ｍｍ、走査ピッチ２μｍ、記録ピッチ２ｍｍ、測定長１ｍｍ、走査本数８０本の条件で測定しＳＲａを算出した。ここで、ＳＲａは三次元中心面平均粗さで、粗さ表面からその中心面上に、面積Ｓｍの部分を抜き取り、その抜き取り部分の中心面に直交する軸をＺ軸で表し、次の式で得られた値をμｍ単位で表す。
【００５５】
【数２】

【００５６】
（ただし、Ｌｘ×Ｌｙ＝Ｓｍ）
（８）ＡＣＦ接続試験：日立化成（株）社製のＡＣＦを用いて、本発明の光学用フィルムとプリント配線板を、１５０℃、３０ｋｇ／ｃｍ^２で接続し、初期接続信頼性を調べた。さらに、熱衝撃試験を−２０℃から６０℃まで５００回繰り返し、接続不良となるかを調べた。
【００５７】
なお、後掲の化合物名は以下の略号を用いた。
ＢｉｓＡ：２，２−ビス（４−ヒドロキシフェニル）プロパン
ＢＣＦ：９，９−ビス（４−ヒドロキシ−３−メチルフェニル）フルオレン
ＩＰ：３，３，５−トリメチル−１，１−ジ（４−フェノール）シクロヘキシリデン
ＩＴＯ：インジウム−スズ酸化物
ＥＣＨＥＴＭＯＳ：２−（３，４−エポキシシクロヘキシル）エチルトリメトキシシラン
ＡＰＴＭＯＳ：３−アミノプロピルトリメトキシシラン
ＥＶＯＨ：エチレンビニルアルコール共重合体（クラレ製「エバール」）
ＤＣＰＡ：ジメチロールトリシクロデカンジアクリレート（共栄社化学社製「ライトアクリレートＤＣＰ−Ａ」）
ＵＡ：ウレタンアクリレート（新中村化学製「ＮＫオリゴＵ−１５ＨＡ」）
【００５８】
［実施例１］
ビスフェノール成分がＢｉｓＡ／ＢＣＦ＝７０／３０からなる平均分子量３７，０００の共重合ポリカーボネート樹脂をメチレンクロライドに２０重量％になるように溶解した。そしてこの溶液をダイコーティング法により厚さ１７５μｍのポリエステルフィルム上に流延した。次いで、乾燥炉で残留溶媒濃度が１３重量％になるまで乾燥し、ポリエステルフィルムから剥離した。そして、得られたポリカーボネートフィルムを温度１８０℃の乾燥炉で縦横の張力にできるだけ差が生じないように、かつフィルムを保持しうる最小限の張力でバランスさせながら、該フィルム中の残留溶媒濃度が０．１重量％になるまで乾燥させた厚さ１００μｍのフィルムを得た。
【００５９】
こうして得られたフィルムの特性を表１に示す。ディスプレイ用基材フィルムとして有用であることがわかった。
【００６０】
［実施例２］
ＢｉｓＡ／ＢＣＦ＝５０／５０（モル比）のポリカーボネート共重合体からなる厚み１２０μｍの透明フィルムを用いて残留溶媒量を０．０８ｗｔ％になるまで乾燥した以外は、実施例１と同様にしてフィルムを得た。得られたフィルムの評価結果は表１に示すように良好であった。
【００６１】
［実施例３］
ＢｉｓＡ／ＢＣＦ＝３３／６７（モル比）のポリカーボネート共重合体からなる厚み１４０μｍの透明高分子フィルム（Ｓ）を用いる以外は、実施例１と同様にして透明なフィルムを得た。得られたフィルムの評価結果は表１に示すように良好であった。
【００６２】
［実施例４］
実施例３で得られたポリカーボネートフィルムの片面上に、ポリシロキサン系樹脂層を与えるコーティング組成物をコーティングし、１３０℃３分熱処理を行い、厚みが０．０５μｍのポリシロキサン系樹脂層を形成した。なお、ポリシロキサン系樹脂を与えるコーティング組成物は、水７２０重量部、２−プロパノール１０８０重量部の混合溶媒に、酢酸８８重量部を加えた後、ＥＣＨＥＴＭＯＳ６４０重量部とＡＰＴＭＯＳ１５４重量部を順次加えて３時間攪拌して得た。次いで、ポリシロキサン樹脂層上に、スパッタリング法により、厚さ３５０オングストロームのＳｉＯ_２膜からなるガスバリア層を積層した。
【００６３】
さらに、ガスバリア性を有する耐薬品層を形成するコーティング組成物を以下のように調整した。
【００６４】
ＥＶＯＨ１００部を、水７２０部、ｎ−プロパノール１０８０部の混合溶媒に加熱溶解させ、均一溶液を得た。この溶液にレベリング剤（東レダウコーニング社製「ＳＨ３０ＰＡ」）を０．１部、酢酸３９部加えた後、ＥＣＨＥＴＭＯＳ２１１部を加え１０分間撹拌した。更にこの溶液にＡＰＴＭＯＳ７７部を加えて３時間撹拌しコーティング組成物を得た。このコーティング組成物を、ポリカーボネートフィルムの、ポリシロキサン系樹脂層とＳｉＯ_２からなるガスバリア層が積層されたフィルムの両面上にコーティングし、１３０℃３分熱処理を行い、厚みが２μｍの耐薬品層を形成した。
【００６５】
ついで、該フィルムのガスバリア層（ＳｉＯ_２）が積層された面と反対側の面に、ＩＴＯをスパッタリング法により、厚さ１２０ｎｍで形成することによりフィルムを得た。得られたフィルムの評価結果は表１に示すように良好であった。
【００６６】
［実施例５］
ＩＴＯの直下に、以下のような方法にて厚み４μｍで耐薬品層を形成した以外は、実施例４と同様にしてディスプレイ用透明フィルムを得た。
【００６７】
ＤＣＰＡを２０重量部、ＵＡを１０重量部、１−メトキシ−２−プロパノールを３０重量部、開始剤として１−ヒドロキシシクロヘキシルフェニルケトンを２重量部を混合しコーティング組成物を得た。この組成物をコーティングし、６０℃１分間加熱した後、高圧水銀灯を用い積算光量７００ｍＪ／ｍ^２で光硬化を行い耐薬品層として硬化樹脂層を形成した。
【００６８】
得られたフィルムの評価結果は表１に示すように良好であった。
【００６９】
【表１】

※　損失弾性率がピークを示すときの温度から１０℃低い温度における値。
※※　３０℃における値
【００７０】
［実施例６］
実施例３に記載の透明フィルムの片面に実施例４と同様な条件で、スパッタリング法により、厚さ５００オングストロームのＳｉＯ_２膜からなるガスバリア層を積層し、さらに該ガスバリア層上に、実施例４と同様な条件でＩＴＯをスパッタリング法により、厚さ１２０ｎｍで形成することによりフィルムを得た。得られたフィルムの評価結果は表２に示すように良好であった。
【００７１】
［実施例７］
実施例２に記載の透明フィルムの両面に実施例４と同様な条件で、スパッタリング法により、厚さ５００オングストロームのＳｉＯ_２膜からなるガスバリア層を積層し、さらに該ガスバリア層の一方の面上に、実施例４と同様な条件でＩＴＯをスパッタリング法により、厚さ１２０ｎｍで形成することによりフィルムを得た。得られたフィルムの評価結果は表２に示すように良好であった。
【００７２】
［実施例８］
ＩＴＯを形成する前に実施例４と同様な条件で、スパッタリング法により厚さ５００オングストロームのＳｉＯ_２膜からなるガスバリア層を積層した以外は、実施例４と同様にフィルムを得た。得られたフィルムの評価結果は表２に示すように良好であった。
【００７３】
【表２】

【００７４】
［比較例１］
常法によりＢｉｓＡのみからなるポリカーボネートを製造し、これを乾燥炉の温度を１４５℃にした以外は、実施例１と同様にしてフィルムを作成した。
【００７５】
得られたフィルムの評価結果は表３に示すように、透明性は良好であるが、耐熱性、光学等方性に劣り、水蒸気透過係数も大きく、なによりも加熱後の寸法変化が大きい結果となった。
【００７６】
［比較例２］
ＢｉｓＡ／ＩＰ＝４０／６０からなるポリカーボネート共重合体を用いる以外は、実施例１と同様にしてフィルムを得た。
【００７７】
得られたフィルムの評価結果は表３に示すように、耐熱性や透明性は良好であるが、光学等方性に劣り、水蒸気透過係数も大きく、加熱後の寸法変化が大きい結果となった。
【００７８】
［比較例３］
比較例１と同様のＢｉｓＡのみからなるポリカーボネートを用いる以外は、実施例７と同様にしてフィルムを得た。得られた透明導電性基板の評価結果は表３に示すように透明性は良好であったが、透明電極にクラックが入りＡＣＦ接続信頼性が初期から不良であった。
【００７９】
［比較例４］
残留溶媒量が０．５ｗｔ％になるまで乾燥した以外は実施例２と同様にして透明フィルムを得た。得られたフィルムは加熱後の寸法変化が０．１％と大きい結果となった。
【００８０】
［比較例５］
実施例２と同じポリカーボネートを用い溶融押し出し成型法にて厚さ１００μｍのフィルムを得た。得られたフィルムは着色が激しく光学用には不向きであった。
【００８１】
【表３】

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical film, more specifically, using a specific polycarbonate film, a liquid crystal display element, a photoconductive photoreceptor, a surface light emitter, an inorganic and organic EL element, electrophoresis, a field emission element, a plasma element, The present invention relates to an optical film suitably used for a flat panel display such as a surface heating element.
[0002]
[Prior art]
In recent years, in the field of flat panel displays such as liquid crystal display devices, organic EL display devices, and electrophoretic display devices, a plastic film made of a transparent polymer has been replaced with a conventional glass substrate due to demands for improved breakage resistance, weight reduction, and thickness reduction. The study to replace it has been continued.
[0003]
When a plastic film is used for a liquid crystal display device, the conventional plastic film has optical anisotropy due to distortion during molding, easily transmits gas and water vapor, and is used in a panel manufacturing process. Because of insufficient resistance to various chemicals and lack of heat resistance and mechanical strength required for firing the alignment film and sealant and connecting the drive circuit, heat-resistant plastic molded products with excellent optical isotropy As a base material, a laminate of a gas barrier layer, a chemical resistant layer, and a transparent conductive layer is used. Furthermore, in recent years, the display is becoming finer and more multicolored, and in the process of alignment films, circuit connection materials, color filters, etc., a base material that is not easily deformed in a high-temperature environment and has little dimensional change after high-temperature heating is required. Have been.
[0004]
Further, a plastic film for an organic EL display element requires extremely excellent smoothness on the surface on which an EL layer is formed and excellent gas barrier properties. In particular, a water vapor barrier property is higher than that of a liquid crystal display element. Excellent performance is required for the difference. In addition, resistance to various chemicals used in a panel manufacturing process, heat resistance required in a process of connecting a cathode partition wall and a seal, and connecting a driving circuit are required.
[0005]
On the other hand, Patent Document 1 discloses a transparent conductive film for a display in which an indium oxide film is laminated on a polyether sulfone film having a small birefringence, but the film has excellent heat resistance, The heat shrinkage is large, the dimensional change due to water absorption is remarkable, and since the film is produced by heat-melt extrusion molding, there are many defects such as die lines, gels, and fish eyes on the film surface, and the film has excellent display quality. Is difficult to achieve.
[0006]
Patent Document 2 discloses that a display substrate is made of a polycarbonate or polyester carbonate made of 1,1-bis (4-hydroxyphenyl) -alkylcycloalkane having a retardation adjusted in a range of 10 to 2000 nm and a substituted product thereof. Although it is described, the film is more excellent in heat resistance than general polycarbonate, but it cannot be said that the amount of dimensional change after deformation or high-temperature heating in a high-temperature environment is sufficient, and because it has poor water vapor barrier properties. It is difficult to obtain a display having excellent display quality using the film.
[0007]
[Patent Document 1]
JP-A-59-158015 (page 3)
[0008]
[Patent Document 2]
JP-A-7-246661 (page 1)
[0009]
[Problems to be solved by the invention]
The present invention has been made in view of such a situation, and has excellent optical isotropy, does not easily deform even in a high-temperature environment, preferably has good surface smoothness and water vapor barrier properties, and has extremely small dimensional change after high-temperature heating. It is an object to provide an optical film suitable for a small number of display applications.
[0010]
[Means for Solving the Problems]
The present inventors have conducted intensive studies on polymer materials for displays such as liquid crystals in order to solve the above problems, and as a result, formed a polymer material having a specific molecular structure into a film by a highly accurate solution casting film forming technique, By strictly controlling the amount of the solvent in the film, an optical film having excellent heat resistance, optical isotropy, and dimensional stability, particularly having a very small dimensional change after high-temperature heating, and having good surface smoothness is obtained. And completed the present invention. Furthermore, they have found that, when an inorganic thin film layer mainly composed of a metal oxide or the like is laminated on at least one surface of this film, the film has extremely excellent gas barrier properties even under a high temperature and high humidity environment.
[0011]
That is, the present invention is as follows.
1. According to the solution casting method, the following formula (1)
[0012]
Embedded image

[0013]
[In the above formula (1), R ₁ ~ R ₈ Is each independently at least one group selected from a hydrogen atom, a halogen atom and a saturated and / or unsaturated hydrocarbon group having 1 to 10 carbon atoms. ]
And a repeating unit represented by the following formula (2)
[0014]
Embedded image

[0015]
[In the above formula (2), R ₉ ~ R ₁₆ Is independently at least one group selected from a hydrogen atom, a halogen atom and a saturated and / or unsaturated hydrocarbon group having 1 to 10 carbon atoms, and X is a group represented by the following formula:
[0016]
Embedded image

[0017]
(Where R in Y ₁₇ ~ R ₁₉ , R ₂₁ And R ₂₂ Is independently at least one group selected from the group consisting of a hydrogen atom, a halogen atom and a hydrocarbon group having 1 to 22 carbon atoms; ₂₀ And R ₂₃ Are each independently a hydrocarbon group having 1 to 20 carbon atoms, and Ar is ₁ ~ Ar ₃ Is each independently an aryl group having 6 to 10 carbon atoms. )]
Wherein the repeating unit represented by the above formula (1) accounts for 30 to 80 mol% of the entire polymer film (S). An optical film in which the polymer film contains 0.001 to 0.3% by weight of a solvent.
2. (I) the heat shrinkage after heating at 180 ° C. for 2 hours is less than 0.05%, (ii) the total light transmittance is 85% or more, and (iii) the three-dimensional refractive index has the following formula (A) and The above optical film that simultaneously satisfies (B).
[0018]
R (550) ≦ 5 (nm) (A)
K = [(n _x + N _y ) / 2-n _z ] × d ≦ 100 (nm) (B)
(In the above formula (A), R (550) is the in-plane retardation of the polymer film (S) with respect to light having a wavelength of 550 nm, and in the above formula (B), n _x , N _y , N _z Is the three-dimensional refractive index for light having a wavelength of 550 nm in the x-axis, y-axis, and z-axis directions with the thickness direction of the polymer film (S) as the z-axis, and d is the thickness of the polymer film (S). . )
3. In the dynamic viscoelasticity measurement, the temperature at which the loss modulus shows a peak is 190 ° C. or more, the storage modulus at a temperature 10 ° C. lower than this temperature is 1.5 GPa or more, and the storage modulus at 30 ° C. The optical film as described above, which has a strength of 2.5 GPa or more.
4. The optical film as described above, wherein at least one surface of the polymer film (S) has a surface smoothness of 3 nm or less in SRa.
5. Further, a gas barrier layer (B) made of an oxide, fluoride, nitride or oxynitride inorganic material of at least one metal selected from Si, Al, Ti, Mg and Zr or a mixture of two or more metals. The optical film according to the above, having:
6. The optical film described above, further comprising at least one coating layer (C) having a crosslinked structure.
7. The optical film as described above, further comprising at least one transparent conductive layer (E).
8. Use of the optical film according to any one of 1 to 7 above as a substrate for a liquid crystal element, an organic EL element, an electrophoretic element, a field emission element, or a plasma element.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
The polymer film (S) of the optical film of the present invention is mainly composed of a polycarbonate comprising a repeating unit represented by the following formula (1) and a repeating unit represented by the following formula (2). It was formed by a solution casting method.
[0020]
Embedded image

[0021]
In the above formula (1), R ₁ ~ R ₈ Each independently represents a hydrogen atom, a halogen atom such as bromine, fluorine or iodine, an alkyl group such as a methyl group, an ethyl group or an isopropyl group, or a saturated and / or unsaturated hydrocarbon having 1 to 10 carbon atoms such as a phenyl group. Groups.
[0022]
Where R ₂ And R ₃ Is a hydrogen atom and / or an alkyl group having 1 to 3 carbon atoms; ₅ And R ₈ Is preferably a hydrogen atom and / or an alkyl group having 1 to 3 carbon atoms, which is excellent in moldability, polymerizability and the like. Specific examples include fluorene-9,9-di (4-phenol) and fluorene-9,9-di (3-methyl-4-phenol).
[0023]
The following equation (2)
[0024]
Embedded image

[0025]
In the repeating unit represented by ₉ ~ R ₁₆ Is independently at least one group selected from a hydrogen atom, a halogen atom and a saturated and / or unsaturated hydrocarbon group having 1 to 10 carbon atoms, and X is a group represented by the following formula:
[0026]
Embedded image

[0027]
At least one group selected from Where R ₁₇ ~ R ₁₉ , R ₂₁ And R ₂₂ Is independently at least one selected from the group consisting of a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having 1 to 22 carbon atoms such as an alkylene group and an aryl group; ₂₀ And R ₂₃ Are each independently a divalent hydrocarbon group having 1 to 20 carbon atoms such as an alkylene group and a phenylene group; ₁ ~ Ar ₃ Is each independently an aryl group having 6 to 10 carbon atoms such as a phenyl group.
[0028]
Particularly preferred polycarbonates in the present invention include a repeating unit represented by the above formula (1) derived from fluorene-9,9-di (3-methyl-4-phenol) (in the above formula (1), R ₁ ~ R ₈ Is a hydrogen atom (however, R ₂ And R ₃ Is a methyl group, and R ₅ And R ₈ One of which is a methyl group), X is 2,2-propylene, and R ₉ ~ R ₁₆ Is a polycarbonate having a repeating unit represented by the above formula (2) wherein all are hydrogen atoms. Here, the repeating unit represented by the above formula (1) is 30 to 80 mol% of all the repeating units, preferably 35 to 70 mol%, and more preferably 40 to 60 mol%. . As the number of repeating units represented by the above formula (1) increases, the heat resistance and the elastic modulus increase, but the light transmittance on the short wavelength side decreases, and the impact resistance decreases and the material tends to become brittle. There is. The molecular weight of the above polycarbonate is preferably 5,000 to 300,000, more preferably 15,000 to 100,000, in number average molecular weight. The higher the molecular weight of the polymer, the better the mechanical properties and heat resistance.
[0029]
The optical film of the present invention is formed by a solution casting method. The solution casting method is inferior to the melt extrusion method in terms of productivity, but has few defects such as die lines, gels, fish eyes and the like, and has much better surface smoothness than the melt extrusion method. Also, in the solution casting method, even in the case of a high molecular weight resin that is too high in melt viscosity or easily colored or cannot be molded by melt extrusion, molding is possible if it is soluble in the solvent used, so that the mechanical properties and A film with excellent heat resistance can be obtained. In the solution casting method, the three-dimensional refractive index of the film can be controlled by adjusting the characteristics of the die, the state of the casting belt, the drying conditions, the film tension and the transport conditions. In order to obtain an optical film having excellent optical isotropy of the present invention and an extremely small dimensional change after heating, it is particularly important to adjust the amount of the solvent contained in the film in the forming step, the drying temperature and the tension applied to the film. is there. Although the apparent Tg of the film is determined by the amount of the solvent contained in the film, the drying temperature is preferably set to be equal to or lower than the apparent Tg. Also, the tension applied to the film, for example, when forming by a roll winding method, the tension in the film transport direction tends to increase, but using a device that can also apply tension in the direction perpendicular to the film transport direction It is also effective to mold under the condition that the difference between both tensions is as small as possible and the tension is suppressed as much as possible.
[0030]
In the solution casting method, the solvent used for film formation may remain in the film (this may be referred to as a residual solvent). Residual solvents plasticize the film, leading to lower glass transition temperatures and lower mechanical properties. Therefore, it is preferable to remove the residual solvent as much as possible, and it is at least 0.001% by weight or more. Further, it is preferably smaller than 0.3% by weight at the maximum, more preferably 0.1% by weight or less. When a plasticizer or a surfactant is added to the film, the remaining amount thereof is not included in the remaining amount of the solvent.
[0031]
By the way, the method of reducing the residual solvent amount is mainly a heat treatment and a vacuum treatment, but in consideration of the effect and economy, a low boiling solvent such as dichloromethane is used as a main solvent in the solution casting method. preferable. In addition, not only dichloromethane but also solvents such as chloroform, 1,2-dichloroethane, tetrahydrofuran, 1,3-dioxolan, 1,4-dioxane, cyclohexanone, and chlorobenzene can be used alone or as a mixture.
[0032]
By setting the repeating unit represented by the above formula (1) to 30 mol% or more and reducing the residual solvent amount to less than 0.3 wt% by the above-mentioned solution casting method, a polymer film as a base material Has improved heat resistance and exhibits very high mechanical strength even in a high temperature environment. Specifically, for example, when expressed in terms of dynamic viscoelasticity, the temperature at which the loss elastic modulus shows a peak in the measurement of the temperature dispersion in the tensile mode is 190 ° C. or more, and the storage at a temperature 10 ° C. lower than this peak temperature is performed. The elastic modulus is 1.5 GPa or more, and the storage elastic modulus at 30 ° C. becomes 2.5 GPa or more, so that the substrate is hardly deformed even in the heating and pressurizing treatment in the process of manufacturing various display elements. In addition, the dimensional change particularly after high-temperature heating is extremely small. For example, the dimensional change after heat treatment at 180 ° C. for 2 hours becomes 0.05% or less, which makes it easy to produce a display element which is superior in forming color filters and the like and has excellent display quality. Become. In addition, the water vapor permeability is reduced, for example, the water vapor transmission coefficient at 40 ° C. and 100% RH is 4000 g · μm / m ² / Day is effective for improving the reliability of the display element. Further, the optical isotropy is improved, and the resistance to various liquid crystals is also improved, which is particularly useful for liquid crystal display applications.
[0033]
Here, good optical isotropy is defined by the following formulas (A) and (B).
| R (550) | ≦ 5 (nm) (A)
K = | [nz− (nx + ny) / 2] × d | ≦ 100 (nm) (B)
Means to satisfy In the above formula (A), R (550) is an in-plane retardation of the transparent polymer substrate with respect to light having a wavelength of 550 nm, and in the above formula (B), K represents three-dimensional optical isotropy, and nx , Ny, and nz are three-dimensional refractive indices for light having a wavelength of 550 nm in the x-axis, y-axis, and z-axis directions with the thickness direction of the transparent polymer substrate being the z-axis, and d is the thickness of the transparent polymer substrate. .
[0034]
This characteristic is very useful in compensating for viewing angle characteristics and optical rotation dispersion of the liquid crystal display particularly when the optical film of the present invention is used for a liquid crystal display.
[0035]
Further, as the number of repeating units represented by the above formula (1) increases, the optical isotropy of the polymer film increases, and when a polycarbonate having a molecular weight of more than 30 mol% is used, the in-plane position with respect to light having a wavelength of 450 nm is used. Each value of the phase difference R (450) and the in-plane phase difference R (550) for light having a wavelength of 550 nm can be reduced, and furthermore, R (450) / R (550) ≦ 1.06, and Since R (450) / R (550) ≦ 1.00, a film having extremely excellent optical isotropy is obtained.
[0036]
On the other hand, the optical film of the present invention can be used as a retardation film or its raw material for the following reasons. The retardation film has a three-dimensional refractive index satisfying the following formulas (C) and (D) at the same time, and is usually obtained by stretching a film having excellent optical isotropy.
[0037]
5 nm <R (550) ≦ 500 (nm) (C)
K = [(n _x + N _y ) / 2-n _z ] × d ≦ 200 (nm) (D)
In the above formula (C), R (550) is the in-plane retardation of the polymer film (S) with respect to light having a wavelength of 550 nm, and in the above formula (D), n _x , N _y , N _z Is the three-dimensional refractive index for light having a wavelength of 550 nm in the x-axis, y-axis, and z-axis directions with the thickness direction of the polymer film (S) as the z-axis, and d is the thickness of the polymer film (S). . Stretching may be horizontal uniaxial stretching or longitudinal uniaxial stretching, or may be simultaneous biaxial stretching or sequential biaxial stretching. Preferably, the thickness is 5 nm or less. The optical film of the present invention having such a phase difference is characterized by a small change in retardation in addition to a small dimensional change after heat treatment.
[0038]
The optical film of the present invention is formed by the solution casting method and has excellent film surface properties. Although a film having SRa with good surface smoothness can be obtained by the solution casting method, an optical film having a surface smoothness of 3 nm or less with SRa is preferable.
[0039]
Here, SRa is a three-dimensional center plane average roughness, a portion having an area Sm is extracted from the roughness surface on the center plane, and an axis orthogonal to the center plane of the extracted part is represented by the Z axis. Is expressed in μm unit.
[0040]
(Equation 1)

[0041]
(However, Lx × Ly = Sm)
The thickness of the polymer film (S) in the present invention depends on the display quality when processed into various displays, the ease of handling in the process of forming the substrate, the ease of handling in the display assembling process, and the solution flow. From the viewpoint of film forming efficiency at the time of film forming, the thickness is 20 to 500 μm, preferably 50 to 400 μm, and more preferably 70 to 200 μm. Further, when an electrode made of a transparent conductive layer is provided on the optical film of the present invention using such a polymer film (S) and used as an electrode for a liquid crystal display, unevenness in the gap of a liquid crystal cell deteriorates display quality. The thickness unevenness of such a polycarbonate film is preferably set to ± 5% or less, more preferably ± 2% or less.
[0042]
In the optical film of the present invention, a gas barrier layer substantially consisting of an inorganic thin film may be formed on at least one surface of the polymer film, preferably on a surface where SRa is smaller than 1 nm. it can.
[0043]
Examples of the gas barrier layer include an inorganic material such as an oxide, a fluoride, a nitride, or an oxynitride of at least one metal selected from Si, Al, Ti, Mg, and Zr or a mixture of two or more metals. No. Among them, inorganic materials mainly composed of oxides, nitrides, and oxynitrides of Si are preferable because they are excellent in transparency, gas barrier properties, surface smoothness, and adhesion to the above-mentioned polymer film. Particularly, silicon oxide containing silicon and oxygen as main components is preferable. Alternatively, a thin film containing silicon and oxygen as main components, containing at least fluorine and magnesium, and chemically bonding silicon and fluorine is preferable in terms of gas barrier properties, transparency, surface smoothness, and low film stress. Here, the ratio of oxygen atoms to silicon atoms is preferably 1.5 or more and less than 2. Depending on this ratio, the transparency of the thin film and the gas barrier property change in a trade-off relationship, and if it is less than 1.5, the transparency required for display applications may not be obtained. Further, the fluorine atom is chemically bonded to silicon and magnesium, and the ratio of the bond (A) between the fluorine atom and the silicon atom and the bond (B) between the fluorine atom and the magnesium is preferably (A)> (B). The ratio of magnesium contained in the gas barrier layer is preferably in the range of 2.5 to 20 atom% in terms of elemental ratio with respect to coexisting silicon. By adopting such a ratio, it is presumed that not only good gas barrier properties and transparency, but also particularly the film stress can be reduced. Therefore, even if the thickness of the gas barrier layer is increased, the deformation of the optical film is reduced. it can. The chemical bonding state of the elemental fluorine present in the gas barrier film is analyzed and determined by, for example, X-ray photoelectron spectroscopy. In X-ray photoelectron spectroscopy, when the horizontal axis is corrected to 284.6 eV of neutral carbon C1s using Al Kα ray as the X-ray source, the chemical bond state of fluorine is fluorine and silicon observed near 687 eV. Is determined by the existence of the F1s peak (A) derived from the bond of (A) and the F1s peak (B) derived from the bond of fluorine and magnesium observed on the lower binding energy side of about 1.5 eV lower than this, and their intensity ratio. .
[0044]
Examples of a method for forming the gas barrier layer (B) include a vapor deposition method in which a material is deposited from a gas phase to form a film, such as a sputtering method, a vacuum deposition method, an ion plating method, and a plasma CVD method. These gas barrier layers can be used alone or in combination of two or more. The thickness of the gas barrier layer is preferably in the range of 1 nm to 1 μm, more preferably in the range of 2 nm to 200 nm. If the thickness of the gas barrier layer is less than 1 nm, it is difficult to form a film uniformly, and a portion where the film is not formed occurs, so that the gas permeability increases. On the other hand, when the thickness is more than 1 μm, not only does the film lack transparency, but when the optical film is bent, cracks occur in the gas barrier layer to increase the gas permeability.
[0045]
According to the present invention, in particular, when the gas barrier layer (B) containing silicon oxide, nitride or oxynitride as a main component is formed on the surface of the polymer film having an SRa of 1 nm or less, An optical film having excellent gas barrier properties even under a high temperature and high humidity environment satisfying the following formulas (I) and (II) is obtained.
[0046]
P ₁ <1 × 10 ⁷ exp (-5000 / T) [cc / m ² / 24hr / atm (I)
P ₂ <5 × 10 ¹¹ exp (-8000 / T) [g / m ² / 24hr] (II)
In the above formulas (I) and (II), P ₁ Is the oxygen permeability of the substrate at 0% relative humidity, P ₂ Is the water vapor transmission rate at a relative humidity of 100%, and T is the measurement temperature of the oxygen transmission rate and the water vapor transmission rate expressed in absolute temperature (K).
[0047]
Note that an undercoat layer having excellent flatness may be formed between the polymer film (B) and the gas barrier layer (S) for the purpose of further improving the surface flatness of the gas barrier layer. In the optical film of the present invention, if necessary, at least one surface of the film, for example, directly or through an intermediate layer on the surface side of the gas barrier layer (B), or formation of the gas barrier layer (B) A coating layer made of an organic and / or inorganic compound having a crosslinked structure can be formed directly or via an intermediate layer on the polymer film surface on the side where the coating is not performed.
[0048]
As the undercoat layer and the coating layer having a crosslinked structure, a known coating method and a curing method of a crosslinked structure of a polysiloxane resin, a crosslinked structure of an acrylic resin, a crosslinked structure of an epoxy resin, or the like are used. Can be formed. Here, the coating layer having a cross-linking property is used for imparting durability to a solvent or a chemical at the time of assembling the panel (sometimes referred to as a chemical resistant layer). When the gas barrier layer and the chemical resistant layer are laminated on each other, a primer layer can be appropriately provided for the purpose of improving the adhesion between the respective layers. As the primer layer, a silicon-based material containing a silane coupling agent or the like, an acrylic-based material, an acryl-urethane-based material, or a material containing an alkoxytitanium or the like can be used. The thickness of the chemical resistant layer can be appropriately selected generally from a range of 0.01 to 20 μm. When the optical film of the present invention is used for a liquid crystal display device or an organic EL display device, the surface of the chemical resistant layer laminated on the liquid crystal layer or the EL layer side of the polymer film has a smooth surface. It is preferable to adjust the coating liquid and select the conditions of the coating method so as to obtain SRa equivalent to the property.
[0049]
The optical film of the present invention can be formed into a transparent conductive layer depending on the application, and can be used as, for example, an electrode. As the transparent conductive layer, a known metal film, metal oxide film, or the like can be used. Among them, a metal oxide film is preferable from the viewpoint of transparency, conductivity, and mechanical properties. For example, metal oxide films such as indium oxide, cadmium oxide, and tin oxide to which tin, tellurium, cadmium, molybdenum, tungsten, fluorine, zinc, and germanium are added as impurities, zinc oxide and titanium oxide to which aluminum is added as impurities are used. No. Above all, indium oxide is a main component, and at least one oxide selected from the group consisting of tin oxide and zinc oxide is included, wherein tin oxide is 2 to 20% by weight and / or zinc oxide is A transparent conductive layer containing 2 to 20% by weight has excellent transparency and conductivity and is preferably used. Further, when the film of the present invention is used for an organic EL, the film is selected from the group consisting of tin oxide and zinc oxide containing indium oxide as a main component for the purpose of controlling the work function of the transparent conductive layer to improve luminous efficiency. Elements other than tin and zinc may be further added to the film containing one or more oxides.
[0050]
As a method for forming the transparent conductive layer, a sputtering method is mainly used, and a DC magnetron sputtering method, a high-frequency magnetron sputtering method, an ion beam sputtering method, or the like can be applied. The thickness of the transparent conductive layer is preferably 10 to 1000 nm in order to obtain sufficient conductivity. The transparent polymer film for a display of the present invention preferably has a total light transmittance of 80% or more in the visible light region, and more preferably 85% or more. If it is less than 80%, problems such as a decrease in visibility may occur.
[0051]
【The invention's effect】
According to the present invention, by using a polycarbonate film having a fluorene skeleton, the three-dimensional refractive index is small, the optical isotropy is good, and the heat resistance is excellent, and the dimensional change after high-temperature heating is extremely small. An optical film useful as a transparent polymer substrate having extremely excellent surface smoothness can be obtained. In particular, specifically, the temperature at which the loss modulus shows a peak in the dynamic viscoelasticity measurement is 190 ° C. or more, the storage modulus at a temperature 10 ° C. lower than this temperature is 1.5 GPa or more, and 30 It has an excellent effect that the storage elastic modulus at ℃ is 2.5 GPa or more.
[0052]
The optical film of the present invention can provide extremely excellent gas barrier properties even in a high-temperature and high-humidity environment by laminating a thin film layer containing a metal oxide as a main component on at least one surface thereof, It is possible to provide an optical film suitable for a display which can obtain excellent reliability when a printed wiring board is connected using a connection material containing conductive particles such as a seal connector or an anisotropic conductive film.
[0053]
Such an optical film has a high temperature when used as a transparent substrate such as a liquid crystal display element, a photoconductive photoreceptor, a surface light emitter, an inorganic or organic EL element, electrophoresis, a field emission element, a plasma element, and a surface heating element. It is particularly useful as a gas barrier transparent film that gives a flat panel display or electronic paper with excellent reliability even when left for a long time under high humidity.
[0054]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In the examples, parts and% are by weight unless otherwise specified. Various measurements in the examples were performed as described below.
(1) Total light transmittance
It measured using Nippon Denshoku Industries COH-300A.
(2) Dynamic viscoelasticity
The measurement was performed using RSA-II manufactured by Rheometrics Co., Ltd. in a tensile mode in a temperature range of 25 ° C. to 280 ° C. at a rate of temperature increase of 3 ° C./min and a frequency of 1 Hz.
(3) Water vapor permeability
The water vapor transmission rate at 40 ° C. and 100% RH was measured using Percontran W1A manufactured by MOCON.
(4) Retardation value, three-dimensional refractive index
The value of the phase difference and the three-dimensional refractive index, which are the product of the birefringence Δn and the film thickness d, of the polymer film (S) are measured by a spectroscopic ellipsometer, trade name “M150” manufactured by JASCO Corporation. did. The retardation value was measured with the incident light and the film surface orthogonal to each other. The three-dimensional refractive index is measured by changing the angle between the incident light having a wavelength of 550 nm and the film surface, measuring the phase difference value at each angle, and performing curve fitting using a known refractive index ellipsoidal equation. The ratios nx, ny and nz were determined.
(5) Dimensional change rate
A polymer film (S) having a width of 10 mm and a length of 100 mm is cut out along the film flow direction (MD) and the width direction (TD), and the length is precisely measured with an electronic micrometer. Heat treatment at 2 ° C. for 2 hours, accurately measure the length after leaving for 1 hour or more in an environment of 25 ° C. and 50% RH, and divide the difference in length before and after heating by the length before heating. It was calculated in%.
(6) Film thickness
The measurement was performed with an electronic microscope manufactured by Anritsu Corporation.
(7) Evaluation of surface smoothness
The surface smoothness was measured using an amplification support device SE3CK and an analyzer SPA-11 (manufactured by Kosaka Laboratory Co., Ltd.). The cutoff was 0.08 mm, the scanning pitch was 2 μm, the recording pitch was 2 mm, the measurement length was 1 mm, and the number of scans was 80. SRa was calculated by measuring under these conditions. Here, SRa is a three-dimensional center plane average roughness, a portion having an area Sm is extracted from the roughness surface on the center plane, and an axis orthogonal to the center plane of the extracted part is represented by the Z axis. Is expressed in μm unit.
[0055]
(Equation 2)

[0056]
(However, Lx × Ly = Sm)
(8) ACF connection test: Using an ACF manufactured by Hitachi Chemical Co., Ltd., the optical film of the present invention and the printed wiring board were placed at 150 ° C. and 30 kg / cm. ² And the initial connection reliability was examined. Further, the thermal shock test was repeated 500 times from −20 ° C. to 60 ° C., and it was examined whether or not a connection failure occurred.
[0057]
In addition, the following abbreviations were used for the compound names described later.
BisA: 2,2-bis (4-hydroxyphenyl) propane
BCF: 9,9-bis (4-hydroxy-3-methylphenyl) fluorene
IP: 3,3,5-trimethyl-1,1-di (4-phenol) cyclohexylidene
ITO: Indium-tin oxide
ECHEMOS: 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane
APTMOS: 3-aminopropyltrimethoxysilane
EVOH: Ethylene vinyl alcohol copolymer (Kuraray “EVAL”)
DCPA: dimethylol tricyclodecane diacrylate (“Light acrylate DCP-A” manufactured by Kyoeisha Chemical Co., Ltd.)
UA: urethane acrylate (“NK Oligo U-15HA” manufactured by Shin-Nakamura Chemical)
[0058]
[Example 1]
A copolycarbonate resin having a bisphenol component of BisA / BCF = 70/30 and an average molecular weight of 37,000 was dissolved in methylene chloride so as to be 20% by weight. Then, this solution was cast on a polyester film having a thickness of 175 μm by a die coating method. Next, it was dried in a drying oven until the residual solvent concentration became 13% by weight, and was peeled off from the polyester film. Then, while keeping the obtained polycarbonate film in a drying oven at a temperature of 180 ° C. so as to minimize the difference in vertical and horizontal tension, and while balancing the film with the minimum tension capable of holding the film, the residual solvent concentration in the film is reduced. A 100 μm thick film dried to 0.1% by weight was obtained.
[0059]
Table 1 shows the properties of the film thus obtained. It was found to be useful as a display base film.
[0060]
[Example 2]
A film was produced in the same manner as in Example 1 except that a 120 μm-thick transparent film made of a polycarbonate copolymer of BisA / BCF = 50/50 (molar ratio) was used to dry the residual solvent amount to 0.08 wt%. Got. The evaluation results of the obtained film were good as shown in Table 1.
[0061]
[Example 3]
A transparent film was obtained in the same manner as in Example 1, except that a 140 μm-thick transparent polymer film (S) made of a polycarbonate copolymer of BisA / BCF = 33/67 (molar ratio) was used. The evaluation results of the obtained film were good as shown in Table 1.
[0062]
[Example 4]
One surface of the polycarbonate film obtained in Example 3 was coated with a coating composition for providing a polysiloxane-based resin layer, and heat-treated at 130 ° C. for 3 minutes to form a polysiloxane-based resin layer having a thickness of 0.05 μm. . The coating composition for providing the polysiloxane-based resin was prepared by adding 88 parts by weight of acetic acid to a mixed solvent of 720 parts by weight of water and 1080 parts by weight of 2-propanol, and then adding 640 parts by weight of ECHETMOS and 154 parts by weight of APTMOS in order. Stirred for hours. Next, a 350 angstrom thick SiO.sub.2 is formed on the polysiloxane resin layer by a sputtering method. ₂ A gas barrier layer composed of a film was laminated.
[0063]
Further, a coating composition for forming a chemical resistant layer having gas barrier properties was prepared as follows.
[0064]
100 parts of EVOH was heated and dissolved in a mixed solvent of 720 parts of water and 1080 parts of n-propanol to obtain a homogeneous solution. 0.1 parts of a leveling agent (“SH30PA” manufactured by Dow Corning Toray Co., Ltd.) and 39 parts of acetic acid were added to this solution, and 211 parts of ECHEMOS were added, followed by stirring for 10 minutes. Further, 77 parts of APTMOS was added to this solution and stirred for 3 hours to obtain a coating composition. This coating composition is coated with a polysiloxane resin layer of a polycarbonate film and SiO ₂ Was coated on both sides of a film on which a gas barrier layer composed of was laminated, and heat-treated at 130 ° C. for 3 minutes to form a chemical resistant layer having a thickness of 2 μm.
[0065]
Then, the gas barrier layer (SiO ₂ A film was obtained by forming ITO to a thickness of 120 nm on the surface opposite to the surface on which) was laminated by a sputtering method. The evaluation results of the obtained film were good as shown in Table 1.
[0066]
[Example 5]
A transparent film for a display was obtained in the same manner as in Example 4, except that a chemical-resistant layer having a thickness of 4 μm was formed directly below ITO by the following method.
[0067]
20 parts by weight of DCPA, 10 parts by weight of UA, 30 parts by weight of 1-methoxy-2-propanol, and 2 parts by weight of 1-hydroxycyclohexylphenyl ketone as an initiator were mixed to obtain a coating composition. After coating this composition and heating at 60 ° C. for 1 minute, the integrated light amount was 700 mJ / m using a high-pressure mercury lamp. ² To form a cured resin layer as a chemical resistant layer.
[0068]
The evaluation results of the obtained film were good as shown in Table 1.
[0069]
[Table 1]

* Value at a temperature 10 ° C lower than the temperature at which the loss modulus shows a peak.
** Value at 30 ℃
[0070]
[Example 6]
On one side of the transparent film described in Example 3, under the same conditions as in Example 4, a 500 angstrom thick SiO ₂ A film was obtained by laminating a gas barrier layer composed of a film, and further forming ITO on the gas barrier layer by sputtering under the same conditions as in Example 4 to a thickness of 120 nm. The evaluation results of the obtained film were good as shown in Table 2.
[0071]
[Example 7]
On both sides of the transparent film described in Example 2, under the same conditions as in Example 4, a 500 angstrom thick SiO film was formed by sputtering. ₂ A film was obtained by laminating a gas barrier layer made of a film, and further forming ITO on one surface of the gas barrier layer by sputtering under the same conditions as in Example 4 to a thickness of 120 nm. The evaluation results of the obtained film were good as shown in Table 2.
[0072]
Example 8
Prior to the formation of the ITO, a 500 angstrom thick SiO 2 was formed by sputtering under the same conditions as in Example 4. ₂ A film was obtained in the same manner as in Example 4, except that a gas barrier layer composed of a film was laminated. The evaluation results of the obtained film were good as shown in Table 2.
[0073]
[Table 2]

[0074]
[Comparative Example 1]
A film was prepared in the same manner as in Example 1 except that a polycarbonate consisting of BisA alone was produced by a conventional method, and the temperature of the drying furnace was set to 145 ° C.
[0075]
As shown in Table 3, the evaluation results of the obtained film showed that the transparency was good, but the heat resistance and optical isotropy were poor, the water vapor transmission coefficient was large, and above all, the dimensional change after heating was large. It became.
[0076]
[Comparative Example 2]
A film was obtained in the same manner as in Example 1, except that a polycarbonate copolymer composed of BisA / IP = 40/60 was used.
[0077]
As shown in Table 3, the evaluation results of the obtained film showed that the heat resistance and the transparency were good, but the optical isotropy was poor, the water vapor transmission coefficient was large, and the dimensional change after heating was large. .
[0078]
[Comparative Example 3]
A film was obtained in the same manner as in Example 7, except that the same polycarbonate made of BisA as in Comparative Example 1 was used. The evaluation results of the obtained transparent conductive substrate showed that the transparency was good as shown in Table 3, but the transparent electrode was cracked and the ACF connection reliability was poor from the beginning.
[0079]
[Comparative Example 4]
A transparent film was obtained in the same manner as in Example 2, except that drying was performed until the amount of the residual solvent became 0.5 wt%. The resulting film showed a large dimensional change of 0.1% after heating.
[0080]
[Comparative Example 5]
Using the same polycarbonate as in Example 2, a film having a thickness of 100 μm was obtained by a melt extrusion molding method. The resulting film was strongly colored and was not suitable for optical use.
[0081]
[Table 3]

Claims (8)

According to the solution casting method, the following formula (1)

[In the above formula (1), R _{1 to} R ₈ are each independently at least one group selected from a hydrogen atom, a halogen atom, and a saturated and / or unsaturated hydrocarbon group having 1 to 10 carbon atoms. ]
And a repeating unit represented by the following formula (2)

[In the above formula (2), R _{9 to} R ₁₆ are each independently at least one group selected from a hydrogen atom, a halogen atom and a saturated and / or unsaturated hydrocarbon group having 1 to 10 carbon atoms, and X is The following formula group

(Here, R _{17 to} R ₁₉ , R ₂₁ and R ₂₂ in Y are each independently at least one group selected from the group consisting of a hydrogen atom, a halogen atom and a hydrocarbon group having 1 to 22 carbon atoms. , R ₂₀ and R ₂₃ are each independently a hydrocarbon group having 1 to 20 carbon atoms, and Ar _{1 to} Ar ₃ are each independently an aryl group having 6 to 10 carbon atoms.)
Wherein the repeating unit represented by the above formula (1) accounts for 30 to 80 mol% of the entire polymer film (S). An optical film in which the polymer film contains 0.001 to 0.3% by weight of a solvent. (I) the heat shrinkage after heating at 180 ° C. for 2 hours is less than 0.05%, (ii) the total light transmittance is 85% or more, and (iii) the three-dimensional refractive index has the following formula (A) and The optical film according to claim 1, which satisfies (B) simultaneously.
R (550) ≦ 5 (nm) (A)
K = [( _nx + _ny ) / 2- _nz ] × d ≦ 100 (nm) (B)
(In the above formula (A), R (550) is a plane retardation of the polymer film (S) with respect to light having a wavelength of 550 nm, in the formula _{(B), n x, n} y, n z is a polymer (The three-dimensional refractive index for light having a wavelength of 550 nm in the x-axis, y-axis, and z-axis directions where the thickness direction of the film (S) is the z-axis, and d is the thickness of the polymer film (S).) In the dynamic viscoelasticity measurement, the temperature at which the loss modulus shows a peak is 190 ° C. or more, the storage modulus at a temperature 10 ° C. lower than this temperature is 1.5 GPa or more, and the storage modulus at 30 ° C. The optical film according to claim 1, wherein the optical film has a strength of 2.5 GPa or more. The optical film according to any one of claims 1 to 3, wherein the surface smoothness of at least one surface of the polymer film (S) is 3 nm or less in SRa. Further, a gas barrier layer (B) made of an oxide, fluoride, nitride or oxynitride inorganic material of at least one metal selected from Si, Al, Ti, Mg and Zr or a mixture of two or more metals. The optical film according to claim 1, comprising: The optical film according to any one of claims 1 to 5, further comprising at least one coating layer (C) having a crosslinked structure. The optical film according to any one of claims 1 to 6, further comprising at least one transparent conductive layer (E). Use of the optical film according to any one of claims 1 to 7 as a substrate for a liquid crystal element, an organic EL element, an electrophoresis element, a field emission element, or a plasma element.