JP4947532B2

JP4947532B2 - Method for producing retardation film

Info

Publication number: JP4947532B2
Application number: JP2001271879A
Authority: JP
Inventors: 丈也酒井; 正雄植月; 喜弘川月
Original assignee: Hayashi Telempu Corp
Current assignee: Hayashi Telempu Corp
Priority date: 2001-09-07
Filing date: 2001-09-07
Publication date: 2012-06-06
Anticipated expiration: 2021-09-07
Also published as: JP2003075640A

Description

【０００１】
【発明の属する技術分野】
本発明は、液晶表示装置の視野角拡大に用いられるような位相差フィルムの製造方法に関する。
【０００２】
【従来の技術】
位相差フィルムは、互いに垂直な主軸方向に振動する直線偏光成分を透過させ、この二成分間に必要な位相差を与える複屈折を有するフィルムである。このような位相差フィルムでは、特定の光学特性を付与することにより光学補償フィルムとして液晶表示装置の視野角拡大に役立つ。
このような位相差フィルムを製造する従来技術が幾つか報告されている。
例えば、特許登録２６４００８３号には、ラビング配向膜、ＳｉＯ斜方蒸着配向膜上に３つの主屈折率ｎｘ、ｎｙ、ｎｚがｎｘ＝ｎｙ＞ｎｚであるディスコティック液晶を傾斜配列させた位相フィルムが記載されている。
また、特開平１０−３３２９３３号では、３つの主屈折率がｎｘ＞ｎｙ＝ｎｚである屈折率楕円体を有する液晶性高分子をラビング配向膜、ＳｉＯ斜方蒸着配向膜上に傾斜配列させたフィルムと負の屈折率楕円体の層とによって構成される位相差フィルムが記載されている。
更に、特開２０００−１２１８３１号では、無機化合物である五酸化タンタルを斜方蒸着した３つの主屈折率がｎｘ＞ｎｙ＞ｎｚである２軸性の屈折率楕円体を傾斜配列させた位相差フィルムが記載されている。
しかしながら、上記のような配向膜を用いる方法では、配向膜の配向処理、液晶材料の配向など工程が煩雑になるなどの問題があり、無機化合物を斜方蒸着する方法では、長尺状シート上に連続して蒸着膜を形成するには、装置が大掛かりになる、工程が煩雑になるなどの問題がある。
【０００３】
光照射により位相差を発現させる方法として、特開平７−１３８３０８号にポリビニルシンナメートなどの感光性重合体に直線偏光性の光を照射する方法が記載されており、また、本発明者も特開平１０−２７８１２３号公報では感光性を有する側鎖型液晶性高分子への直線偏光性の紫外線照射により、光軸の傾いた位相差フィルムを製造する方法を提案したが、これら直線偏光性の光を照射する方法では３つの主屈折率がｎｘ＞ｎｙ＝ｎｚである屈折率楕円体を傾斜配向させた位相差フィルムを製造することができる。
しかしながら、該位相差フィルムを液晶表示装置において視野角拡大の目的に位相差フィルムを用いる場合、十分な効果が得られない場合があり、十分な視野角拡大効果を得るには複屈折性もしくは３つの主屈折率ｎｘ、ｎｙ、ｎｚとＸ軸の傾きを制御することが望ましい。
【０００４】
【課題を解決するための手段】
本発明では、図１に示すように正の屈折率楕円体構造を含有する感光性の重合体ないしは該重合体と低分子化合物の混合体からなるフィルム１１に非偏光性の光またはＰ成分（Ｌｐ）とＳ成分（Ｌｓ）からなる完全偏光成分と非偏光成分が混在する光（Ｌ）を照射する操作により、複屈折性もしくはフィルム中の屈折率楕円体の３つの主屈折率ｎｘ（１ａ）、ｎｙ（１ｂ）、ｎｚ（１ｃ）とｎｘ軸のフィルム面法線方向に対する傾きを制御した位相差フィルムを提供できる。ここで、複屈折性を制御するとは、ベンド配向または傾斜配向した屈折率楕円体ないしはこれらと傾斜していない一軸性の屈折率楕円体とを組み合わせた場合と同等の複屈折性を発現させることをいう。
【０００５】
【発明の実施の形態】
以下に、本発明の詳細を説明する。
本発明の位相差フィルムの製造には、本発明者が、特開平１１−１８９６６５号特許公報、特願２０００−４００３５６号で記載したような、光の照射と加熱冷却により複屈折を生じる材料を用いることができる。
これらの材料は、液晶性高分子のメソゲン成分として多用されているビフェニル、ターフェニル、フェニルベンゾエート、アゾベンゼンなどの置換基と、シンナモイル基、カルコン基、シンナミリデン基、β−（２−フリル）アクリロイル基（または、それらの誘導体）などの感光性基を結合した構造を含む側鎖を有し、炭化水素、アクリレート、メタクリレート、マレイミド、Ｎ−フェニルマレイミド、シロキサンなどの構造を主鎖に有する高分子が挙げられる。該重合体は同一の繰り返し単位からなる単一重合体または構造の異なる側鎖を有する単位の共重合体でもよく、あるいは感光性基を含まない側鎖を有する単位を共重合させることも可能である。また、低分子化合物を混合する場合、該低分子化合物はメソゲン成分として多用されているビフェニル、ターフェニル、フェニルベンゾエート、アゾベンゼンなどの置換基を有する結晶性または、液晶性を有する化合物が挙げられる。混合する低分子化合物は、単一の化合物のみとは限らず複数種の化合物を混合することも可能である。更には、液晶性を損なわない程度に配向性を向上させるための配向助剤や耐熱性を向上させるための架橋剤を添加することや、液晶性を損なうことなく液晶性を示さない単量体を感光性の重合体に共重合してもかまわない。但し、感光性の重合体と低分子化合物は、上記に限定されるものではない。
これらの感光性の重合体は、特開平７−１３８３０８号にポリビニルシンナメートなどの感光性重合体に直線偏光性の光を照射し光反応のみで複屈折を発現させるのとは異なり、光反応後、加熱冷却による配向を伴い光の照射エネルギ量が少なくて済み、複屈折を発現の原理は全く異なるものである。また、光照射により位相差を発現させる提案はこれまで幾つかあるものの、光照射により複屈折性ないしは屈折率楕円体の３つの主屈折率を制御するとうい観点から、本発明の照射光の偏光度によりこれらを達成した事例は全く無く、またこのような位相差フィルムが液晶表示装置の視野角拡大に有効であることをはじめて確認した。
【０００６】
図２に基づいて、感光性の重合体と低分子化合物の混合体を塗布（スピンコートないしキャスト）し製膜されたフィルムについて説明する。図２は、製膜後の膜（フィルム）を模式的に表したものである。
膜（２２）は、製膜時には等方性であり、感光性の重合体の側鎖部および低分子化合物は特定方向を向いていない。すなわち、膜（２２）中で、長楕円で示される感光基を有する側鎖（２ａ、２ｂ）および円柱で示される低分子化合物（２ｃ）は無秩序に存在（共存）している。
この膜にＰ成分（Ｌｐ）とＳ成分（Ｌｓ）からなる完全偏光成分と非偏光成分が混在する紫外線疑似平行光束（Ｌ）を照射すると、照射紫外線の進行方向と垂直方向に向いた側鎖（２ａ）は、平行方向を向いた側鎖（２ｂ）より感光しやすいため、選択的に反応が進む。これは、ベンゼン環などを含有する感光性部分の共役系が側鎖の長軸方向に延びているためであり、このような側鎖を光のような放射場に置いたとき、光の電界振動方向が側鎖の長軸方向と一致する場合に相互作用が極大となり、光の進行方向と側鎖の長軸方向が一致した場合には相互作用が極小となることによる。
このことから、完全偏光成分と非偏光成分が混在する紫外線の照射により、特定方向の光反応を進めた膜とすることができる。この光反応を進めるには、感光性基の部分が反応し得る波長の光の照射を要する。この波長は、感光性基の種類によっても異なるが、一般に２００-５００ｎｍであり、中でも２５０-４００ｎｍの有効性が高い場合が多い。
【０００７】
図３は、図２の膜にＰ成分とＳ成分からなる完全偏光成分と非偏光成分が混在する光紫外線を照射した後の配向が促進された膜（３３）の模式図を示す。
図３に示すように、膜（３３）中の光反応をしなかった側鎖（３ｂ）または低分子化合物（３ｃ）は、完全偏光成分と非偏光成分が混在する紫外線の照射後の分子運動により、特定方向の光反応が進んだ膜中に発現した異方性の影響を受け配向する（側鎖（３ａ）は完全偏光成分と非偏光成分が混在する光の照射により感光し反応した側鎖、側鎖（３ｂ）は照射紫外線の進行方向と平行方向を向いたため反応しなかった側鎖をそれぞれ表している。）。その結果、膜全体において複屈折が誘起され、その複屈折性もしくは膜の３つの主屈折率ｎｘ、ｎｙ、ｎｚの比とｎｘ軸のフィルム面法線方向に対する傾きは、完全偏光成分と非偏光成分が混在する光のＰ成分とＳ成分の比とその照射する角度および感光性の材料の特性によって制御できる。
更には、後述の実施例のような感光性材料に非偏光性の光または完全偏光成分と非偏光成分が混在する光を照射することにより、ベンド配向または傾斜配向した屈折率楕円体ないしはこれらと傾斜していない一軸性の屈折率楕円体とを組み合わせた場合と同等の複屈折性を発現させ得ることもできる。
【０００８】
非偏光性の光または完全偏光成分と非偏光成分が混在する紫外線の照射後の分子運動による配向は、膜を加熱すると促進される。
膜の加熱温度は、光反応した部分の軟化点より低く、光反応しなかった側鎖と低分子の軟化点より高いことが望ましい。また、膜の配向を促進するには加熱下（室温からＴｉ＋５℃まで）で完全偏光成分と非偏光成分が混在する紫外線を照射することも有効である。ここで、Ｔｉは液晶相から等方相へ変化するときの相転移温度を指す。好ましくはＴｉ前後で完全偏光成分と非偏光成分が混在する紫外線を照射することが有効である。このように完全偏光成分と非偏光成分が混在する紫外線を照射したのち加熱、または加熱下で完全偏光成分と非偏光成分が混在する紫外線を照射したフィルムを該高分子の軟化点以下まで冷却すると分子が凍結され、本発明の位相差フィルムが得られる。
【０００９】
本発明において感光性の重合体に混合する低分子化合物が低分子化合物同士、もしくは該重合体に対して熱または光反応性を有している場合には、配向が強固に固定されるため耐熱性の向上が期待される。このような場合、再配向時の分子運動を妨げないよう、露光量を抑えるか反応性を調整するなどして、光反応点の密度を制御する必要がある。低分子化合物は、適量ならば曇り度を抑制する効果がある反面、過剰に添加すると曇り度の増加、配向性の低下を引き起こす。このような観点から、感光性の重合体または低分子化合物の種類にもよるが、低分子化合物を０．１ｗｔ％〜８０ｗｔ％添加しても位相差フィルムは製造可能であるが、好ましくは５ｗｔ％〜５０ｗｔ％であることが望ましい。ここで、感光性の重合体と低分子化合物の相溶性が十分でない場合には、製膜時ないしは露光後の基板の加熱によって相分離や可視光の散乱を誘起しうる大きさの結晶を生成し曇り度の増加の原因となる。
【００１０】
膜厚を厚くしより大きな位相差のフィルムを得る手法として、膜を積層する方法が挙げられる。この場合には、先に製膜して完全偏光成分と非偏光成分が混在する紫外線を照射した膜上に材料溶液を塗布し積層する工程で、この先に形成された膜の破壊を防ぐために、溶解性を下げた溶媒に重合体および低分子化合物を溶解し用いることが有効である。また、感光性化合物の膜に表裏面から完全偏光成分と非偏光成分が混在する紫外線を照射すると、複屈折がより効率よく発現するようになる。感光性の化合物は支持体上に塗布するなどして製膜され、完全偏光成分と非偏光成分が混在する紫外線の照射は化合物に直接または支持体を介してもよい。支持体を介する場合には、支持体は感光性の化合物の反応しうる波長の光の透過性を有している限りどのような材料でも良いが、光透過率が高い程、照射量が少なくて済み、製造工程上有利となる。また、剥離性の支持体上で感光性の化合物を製膜し、剥離後、膜の表裏面より完全偏光成分と非偏光成分が混在する紫外線を照射することもできる。
【００１１】
図４には、本発明の位相差フィルムの製造方法（装置）を、例を挙げて示す。
電源（４２）によって励起された紫外線ランプ（４１）で発生した非偏光性の紫外線（４６）を、所望の偏光度が得られる偏光子を介して支持体（４５）上に塗布（コート）された感光性の重合体と低分子化合物の混合体の膜（４４）に照射する。実施例１から１０は、本発明の製造法により複屈折性またはフィルム中の３つの主屈折率ｎｘ、ｎｙ、ｎｚとｎｘ軸のフィルム面法線方向に対する傾きを制御した位相差フィルムを作製した各実施例である。
（実施例１）
３．７５重量％のポリ（４−メタクリロイルオキシヘキシルオキシ−４’−シンナモイルオキシエチルオキシビフェニル）および１．２５重量％の４，４’−ビス（イソブチルオキシヘキシルオキシ）ビフェニルをジクロロエタンに溶解し、ガラス基板上に約１．５μｍの厚さで塗布した。該基板を水平面に対して４５度傾くように配置し、偏光度：Ｐ−Ｓ／Ｐ＋Ｓ（ＰとＳは、それぞれＰ成分とＳ成分の透過光強度であり、完全偏光成分の強度はＰ−Ｓで示され、Ｐ＋Ｓは完全偏光成分と非偏光成分を合わせた全透過光強度である。）が１５．６（％）である、紫外線を、水平面に対し垂直方向から室温で基板の裏表両面からそれぞれ５００ｍＪ／ｃｍ²ずつ照射し後、１００℃まで加熱し室温まで冷却した。続いて、未反応の感光性基の反応を促進し配向を強固にするために非偏光性の紫外線を１Ｊ／ｃｍ²照射した。
このようにして得られた基板の屈折率楕円体は、３つの主屈折率の比がｎｘ＝１．６、ｎｙ＝１．５、ｎｚ＝１．５であり、ｎｘ軸が基板面法線方向に対し０〜９０°、ベンド配向した屈折率楕円体と３つの主屈折率の比がｎｘ＝１．６、ｎｙ＝１．５、ｎｚ＝１．５であり、ｎｘ軸が基板面法線方向に対し０°である一軸配向したフィルムを組み合わせたものと同等であった。
【００１２】
（実施例２）
３．７５重量％のポリ（４−メタクリロイルオキシヘキシルオキシ−４’−シンナモイルオキシエチルオキシビフェニル）および１．２５重量％の４，４’−ビス（イソブチリルオキシヘキシルオキシ）ビフェニルをジクロロエタンに溶解し、ガラス基板上に約１．５μｍの厚さで塗布した。該基板を水平面に対して４５度傾くように配置し、偏光度が−１５．６（％）である、紫外線を、水平面に対し垂直方向から室温で基板の裏表両面からそれぞれ５００ｍＪ／ｃｍ²ずつ照射し後、１００℃まで加熱し室温まで冷却した。続いて、未反応の感光性基の反応を促進し配向を強固にするために非偏光性の紫外線を１Ｊ／ｃｍ²照射した。このようにして得られた基板の屈折率楕円体は、３つの主屈折率の比がｎｘ＝１．５５、ｎｙ＝１．６、ｎｚ＝１．５であり、ｎｘ軸が基板面法線方向に対し４５°傾いているものであった。
【００１３】
（実施例３）
３．７５重量％のポリ（４−メタクリロイルオキシヘキシルオキシ−４’−シンナモイルオキシエチルオキシビフェニル）および１．２５重量％の４，４’−ビス（イソブチリルオキシヘキシルオキシ）ビフェニルをジクロロエタンに溶解し、ガラス基板上に約１．５μｍの厚さで塗布した。該基板を水平面に対して４５度傾くように配置し、偏光度：Ｐ−Ｓ／Ｐ＋Ｓ（ＰとＳは、それぞれＰ成分とＳ成分の透過光強度であり、完全偏光成分の強度はＰ−Ｓで示され、Ｐ＋Ｓは完全偏光成分と非偏光成分を合わせた全透過光強度である。）が７．９（％）である、紫外線を、水平面に対し垂直方向から室温で基板の裏表両面からそれぞれ５００ｍＪ／ｃｍ²ずつ照射し後、１００℃まで加熱し室温まで冷却した。続いて、未反応の感光性基の反応を促進し配向を強固にするために非偏光性の紫外線を１Ｊ／ｃｍ²照射した。
このようにして得られた基板の屈折率楕円体は、３つの主屈折率の比がｎｘ＝１．６５、ｎｙ＝１．５１、ｎｚ＝１．５であり、ｎｘ軸が基板面法線方向に対し１０〜４０°ベンド配向した屈折率楕円の場合と同等であった。。
【００１４】
（実施例４）
３．７５重量％のポリ（４−メタクリロイルオキシヘキシルオキシ−４’−シンナモイルオキシエチルオキシビフェニル）および１．２５重量％の４，４’−ビス（イソブチリルオキシヘキシルオキシ）ビフェニルをジクロロエタンに溶解し、ガラス基板上に約１．５μｍの厚さで塗布した。該基板を水平面に対して４５度傾くように配置し、偏光度が−７．９（％）である、紫外線を、水平面に対し垂直方向から室温で基板の裏表両面からそれぞれ５００ｍＪ／ｃｍ²ずつ照射し後、１００℃まで加熱し室温まで冷却した。続いて、未反応の感光性基の反応を促進し配向を強固にするために非偏光性の紫外線を１Ｊ／ｃｍ²照射した。
このようにして得られた基板の屈折率楕円体は、３つの主屈折率の比がｎｘ＝１．６、ｎｙ＝１．５４、ｎｚ＝１．５であり、ｎｘ軸が基板面法線方向に対し２５°傾いているものであった。
【００１５】
（実施例５）
３．７５重量％のポリ（４−メタクリロイルオキシヘキシルオキシ−４’−シンナモイルオキシエチルオキシビフェニル）および１．２５重量％の４，４’−ビス（イソブチリルオキシヘキシルオキシ）ビフェニルをジクロロエタンに溶解し、ガラス基板上に約１．５μｍの厚さで塗布した。該基板を水平面に対して４５度傾くように配置し、非偏光性の紫外線〔偏光度＝０（％）〕を、水平面に対し垂直方向から室温で基板の裏表両面からそれぞれ５００ｍＪ／ｃｍ²ずつ照射し後、１００℃まで加熱し室温まで冷却した。続いて、未反応の感光性基の反応を促進し配向を強固にするために非偏光性の紫外線を１Ｊ／ｃｍ²照射した。
このようにして得られた基板の屈折率楕円体は、３つの主屈折率の比がｎｘ＝１．６、ｎｙ＝１．５３、ｎｚ＝１．５であり、ｎｘ軸が基板面法線方向に対し３２°傾いているものであった。
【００１６】
（実施例６）
３．７５重量％のポリ（４−メタクリロイルオキシヘキシルオキシ−４’−シンナモイルオキシエチルオキシビフェニル）および１．２５重量％の４−ペンチル−４’−シアノビフェニルをジクロロエタンに溶解し、ガラス基板上に約１．５μｍの厚さで塗布した。該基板を水平面に対して４５度傾くように配置し、偏光度：Ｐ−Ｓ／Ｐ＋Ｓ（ＰとＳは、それぞれＰ成分とＳ成分の透過光強度であり、完全偏光成分の強度はＰ−Ｓで示され、Ｐ＋Ｓは完全偏光成分と非偏光成分を合わせた全透過光強度である。）が１５．６（％）である、紫外線を、水平面に対し垂直方向から室温で基板の裏表両面からそれぞれ５００ｍＪ／ｃｍ²ずつ照射し後、１００℃まで加熱し室温まで冷却した。続いて、未反応の感光性基の反応を促進し配向を強固にするために非偏光性の紫外線を１Ｊ／ｃｍ²照射した。このようにして得られた基板の複屈折性は、３つの主屈折率の比がｎｘ＝１．６、ｎｙ＝１．５、ｎｚ＝１．５であり、ｎｘ軸が基板面法線方向に対し５０〜９０°ベンド配向した屈折率楕円と３つの主屈折率の比がｎｘ＝１．６、ｎｙ＝１．５、ｎｚ＝１．５であり、ｎｘ軸が基板面法線方向に対し０°である一軸配向したフィルムを組み合わせたものと同等であった。
【００１７】
（実施例７）
３．７５重量％のポリ（４−メタクリロイルオキシヘキシルオキシ−４’−シンナモイルオキシエチルオキシビフェニル）および１．２５重量％の４−ペンチル−４’−シアノビフェニルをジクロロエタンに溶解し、ガラス基板上に約１．５μｍの厚さで塗布した。該基板を水平面に対して４５度傾くように配置し、偏光度が−１５．６（％）である、紫外線を、水平面に対し垂直方向から室温で基板の裏表両面からそれぞれ５００ｍＪ／ｃｍ²ずつ照射し後、１００℃まで加熱し室温まで冷却した。続いて、未反応の感光性基の反応を促進し配向を強固にするために非偏光性の紫外線を１Ｊ／ｃｍ²照射した。
このようにして得られた基板の屈折率楕円体は、３つの主屈折率の比がｎｘ＝１．６、ｎｙ＝１．５９、ｎｚ＝１．５であり、ｎｘ軸が基板面法線方向に対し３７°傾いているものであった。
【００１８】
（実施例８）
３．７５重量％のポリ（４−メタクリロイルオキシヘキシルオキシ−４’−シンナモイルオキシエチルオキシビフェニル）および１．２５重量％の４−ペンチル−４’−シアノビフェニルをジクロロエタンに溶解し、ガラス基板上に約１．５μｍの厚さで塗布した。該基板を水平面に対して４５度傾くように配置し、偏光度：Ｐ−Ｓ／Ｐ＋Ｓ（ＰとＳは、それぞれＰ成分とＳ成分の透過光強度であり、完全偏光成分の強度はＰ−Ｓで示され、Ｐ＋Ｓは完全偏光成分と非偏光成分を合わせた全透過光強度である。）が７．９（％）である、紫外線を、水平面に対し垂直方向から室温で基板の裏表両面からそれぞれ５００ｍＪ／ｃｍ²ずつ照射し後、１００℃まで加熱し室温まで冷却した。続いて、未反応の感光性基の反応を促進し配向を強固にするために非偏光性の紫外線を１Ｊ／ｃｍ²照射した。
このようにして得られた基板の複屈折性は、３つの主屈折率の比がｎｘ＝１．５８、ｎｙ＝１．５、ｎｚ＝１．５であり、ｎｘ軸が基板面法線方向に対し０〜３０°ベンド配向した屈折率楕円の場合と同等であった。
【００１９】
（実施例９）
３．７５重量％のポリ（４−メタクリロイルオキシヘキシルオキシ−４’−シンナモイルオキシエチルオキシビフェニル）および１．２５重量％の４−ペンチル−４’−シアノビフェニルをジクロロエタンに溶解し、ガラス基板上に約１．５μｍの厚さで塗布した。該基板を水平面に対して４５度傾くように配置し、偏光度：Ｐ−Ｓ／Ｐ＋Ｓ（ＰとＳは、それぞれＰ成分とＳ成分の透過光強度であり、完全偏光成分の強度はＰ−Ｓで示され、Ｐ＋Ｓは完全偏光成分と非偏光成分を合わせた全透過光強度である。）が−７．９（％）である、紫外線を、水平面に対し垂直方向から室温で基板の裏表両面からそれぞれ５００ｍＪ／ｃｍ²ずつ照射し後、１００℃まで加熱し室温まで冷却した。続いて、未反応の感光性基の反応を促進し配向を強固にするために非偏光性の紫外線を１Ｊ／ｃｍ²照射した。このようにして得られた基板の複屈折性は、３つの主屈折率の比がｎｘ＝１．５８、ｎｙ＝１．５６、ｎｚ＝１．５であり、ｎｘ軸が基板面法線方向に対し０〜９０°ベンド配向した屈折率楕円と３つの主屈折率の比がｎｘ＝１．５５、ｎｙ＝１．５、ｎｚ＝１．５であり、ｎｘ軸が基板面法線方向に対し０°である一軸配向したフィルムを組み合わせたものと同等であった。
【００２０】
（実施例１０）
３．７５重量％のポリ（４−メタクリロイルオキシヘキシルオキシ−４’−シンナモイルオキシエチルオキシビフェニル）および１．２５重量％の４−ペンチル−４’−シアノビフェニルをジクロロエタンに溶解し、ガラス基板上に約１．５μｍの厚さで塗布した。該基板を水平面に対して４５度傾くように配置し、非偏光性の紫外線〔偏光度＝０（％）〕を、水平面に対し垂直方向から室温で基板の裏表両面からそれぞれ５００ｍＪ／ｃｍ²ずつ照射し後、１００℃まで加熱し室温まで冷却した。続いて、未反応の感光性基の反応を促進し配向を強固にするために非偏光性の紫外線を１Ｊ／ｃｍ²照射した。
このようにして得られた基板の複屈折性は、３つの主屈折率の比がｎｘ＝１．６、ｎｙ＝１．５３、ｎｚ＝１．５であり、ｎｘ軸が基板面法線方向に対し３０°傾斜した屈折率楕円と３つの主屈折率の比がｎｘ＝１．６、ｎｙ＝１．５、ｎｚ＝１．５であり、ｎｘ軸が基板面法線方向に対し０°である一軸配向したフィルムを組み合わせたものと同等であった。
【００２１】
（評価方法）
実施例５と同様の塗布膜を、フィルム面法線方向に対し４０°傾いた方向おける位相差が４０ｎｍであるＴＡＣフィルム上に約１．５μｍの厚さで形成し、該ＴＡＣフィルムと２軸性の屈折率楕円体が傾斜した層を積層した位相差フィルムを、カシオ製液晶カラーテレビＥＶ−５１０の偏光シートを剥がし、液晶セルの上面もしくは下面に１枚貼り合わせ、次いで、偏光シート（日東電工製ＨＥＧ１４２５ＤＵ）を上下１枚ずつ貼り合わせた。各光学素子の軸配置は、図５のようにした。
図５において、６１は本発明の位相差フィルムであり、ａはフィルム中の屈折率楕円体のｎｘ軸の傾斜方向を示し、５２は液晶セルであり、ｂ、ｂ’がプレチルト方向を示し、５３、５３’は偏光シートであり、ｃ、ｃ’がそれぞれの光吸収軸方向を示している。
このような構成で液晶カラーテレビを駆動し、白表示および黒表示した場合のコントラスト比が５になるところを視野角と定義し、上下左右方向の視野角を測定した。コントラスト比の測定には、トプコン製ＢＭ−５Ａを用いた。
表１のとおり、本発明の実施例で作製した位相差フィルムを液晶表示装置に装着した場合、一枚で視野角が拡大されることも確認された。
【００２２】
【表１】

【００２３】
【発明の効果】
正の屈折率楕円体構造を含有する感光性の重合体ないしは該重合体と低分子化合物の混合体からなるフィルムに非偏光性の光または完全偏光成分と非偏光成分が混在する光を照射する操作により、フィルム中の屈折率楕円体の３つの主屈折率ｎｘ、ｎｙ、ｎｚとｎｘ軸のフィルム面法線方向に対する傾きを制御した位相差フィルムの製造が実現できた。このような位相差フィルムは、旋光モード、複屈折モードを利用したねじれネマチック液晶を使った液晶表示装置において視野角拡大用の光学補償フィルムとして活用できる。従来このような、大面積の位相差フィルムを低コストで作製できなかったが、本発明によって、非偏光性の光または完全偏光成分と非偏光成分が混在する光を照射するという簡便な操作で大面積化が可能となった。
【００２４】
【図面の簡単な説明】
【図１】本発明の位相差フィルムの製造方法を示す概念図
【図２】完全偏光成分と非偏光成分が混在する紫外線の照射により感光した側鎖を示す模式図
【図３】完全偏光成分と非偏光成分が混在する紫外線を照射した後の分子運動により配向したフィルムを示す模式図
【図４】実施例の位相差フィルムの製造方法を示す概念図
【図５】視野角特性評価時の光学系
【符号の説明】
１１・・膜（位相差フィルム）
１２・・・屈折率楕円体
ｎｘ(1a)、ｎｙ(1b)、ｎｚ(1c)・・・主屈折率（方向軸）
Ｌ・・・完全偏光成分と非偏光成分が混在する光
Ｌｐ・・・Ｐ成分
Ｌｓ・・・Ｓ成分[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a retardation film as used for expanding a viewing angle of a liquid crystal display device.
[0002]
[Prior art]
The retardation film is a film having birefringence that transmits linearly polarized components that vibrate in directions of principal axes perpendicular to each other and gives a necessary retardation between the two components. Such a retardation film is useful for expanding the viewing angle of a liquid crystal display device as an optical compensation film by imparting specific optical characteristics.
Several conventional techniques for producing such a retardation film have been reported.
For example, Patent Registration No. 2640083 discloses a phase film in which a discotic liquid crystal having three main refractive indexes nx, ny, and nz of nx = ny> nz is tilted on a rubbing alignment film and a SiO oblique deposition alignment film. Are listed.
In JP-A-10-332933, a liquid crystalline polymer having a refractive index ellipsoid having three main refractive indexes of nx> ny = nz is arranged on a rubbing alignment film and a SiO oblique deposition alignment film. A retardation film composed of a film and a negative refractive index ellipsoid layer is described.
Further, in Japanese Patent Laid-Open No. 2000-121831, a phase difference in which biaxial refractive index ellipsoids having three main refractive indexes nx>ny> nz in which oblique deposition of tantalum pentoxide, which is an inorganic compound, is obliquely arranged are arranged in an inclined manner. A film is described.
However, in the method using the alignment film as described above, there are problems such as the alignment process of the alignment film and the alignment of the liquid crystal material, etc., and the method of obliquely depositing the inorganic compound has a problem on the long sheet. In order to continuously form a deposited film, there are problems such as a large apparatus and complicated processes.
[0003]
JP-A-7-138308 discloses a method of irradiating a photosensitive polymer such as polyvinyl cinnamate with linearly polarized light as a method of developing a phase difference by light irradiation. In Kaihei 10-278123, a method for producing a retardation film with an inclined optical axis by irradiating a linearly polarized UV light to a photosensitive side chain type liquid crystalline polymer was proposed. In the method of irradiating light, it is possible to produce a retardation film in which refractive index ellipsoids having three main refractive indexes nx> ny = nz are inclined and oriented.
However, when the retardation film is used for the purpose of enlarging the viewing angle in a liquid crystal display device, a sufficient effect may not be obtained. To obtain a sufficient viewing angle enlarging effect, birefringence or 3 It is desirable to control the two main refractive indices nx, ny, nz and the inclination of the X axis.
[0004]
[Means for Solving the Problems]
In the present invention, as shown in FIG. 1, a non-polarizing light or P component (a non-polarizing light or P component) is formed on a photosensitive polymer containing a positive refractive index ellipsoid structure or a mixture of the polymer and a low molecular compound. Three main refractive indexes nx (1a) of birefringence or a refractive index ellipsoid in a film by irradiating light (L) in which a completely polarized component and a non-polarized component composed of Lp) and S component (Ls) are mixed. ), Ny (1b), nz (1c) and a retardation film in which the inclination of the nx axis with respect to the normal direction of the film surface can be controlled. Here, controlling birefringence means expressing a birefringence equivalent to that when a bend-orientated refractive index ellipsoid or a non-tilted uniaxial refractive index ellipsoid is combined. Say.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Details of the present invention will be described below.
In the production of the retardation film of the present invention, the inventor uses a material that generates birefringence by light irradiation and heating and cooling as described in Japanese Patent Application Laid-Open No. 11-189665 and Japanese Patent Application No. 2000-400366. Can be used.
These materials include substituents such as biphenyl, terphenyl, phenylbenzoate and azobenzene, which are frequently used as mesogenic components of liquid crystalline polymers, cinnamoyl groups, chalcone groups, cinnamylidene groups, and β- (2-furyl) acryloyl groups. (Or a derivative thereof) having a side chain including a structure to which a photosensitive group is bonded, and a polymer having a structure such as hydrocarbon, acrylate, methacrylate, maleimide, N-phenylmaleimide, and siloxane in the main chain Can be mentioned. The polymer may be a single polymer composed of the same repeating unit or a copolymer of units having side chains with different structures, or a unit having side chains not containing a photosensitive group can be copolymerized. . In the case of mixing a low molecular weight compound, examples of the low molecular weight compound include crystalline or liquid crystalline compounds having substituents such as biphenyl, terphenyl, phenylbenzoate, and azobenzene, which are frequently used as mesogenic components. The low molecular compound to be mixed is not limited to a single compound, and a plurality of types of compounds can be mixed. Furthermore, a monomer which does not exhibit liquid crystallinity without adding an alignment aid for improving alignment to the extent that liquid crystallinity is not impaired or a crosslinking agent for improving heat resistance, or without impairing liquid crystallinity. May be copolymerized with a photosensitive polymer. However, the photosensitive polymer and the low molecular compound are not limited to the above.
These photosensitive polymers are different from photoreactions in that a photopolymer such as polyvinyl cinnamate is irradiated with linearly polarized light to develop birefringence only by photoreaction in JP-A-7-138308. After that, the amount of irradiation energy of light can be reduced with orientation by heating and cooling, and the principle of developing birefringence is completely different. Although there have been several proposals for developing a phase difference by light irradiation, the polarization of the irradiation light of the present invention can be controlled from the viewpoint of controlling the three main refractive indexes of birefringence or refractive index ellipsoid by light irradiation. There were no examples of achieving these depending on the degree, and it was confirmed for the first time that such a retardation film was effective in expanding the viewing angle of a liquid crystal display device.
[0006]
Based on FIG. 2, a film formed by applying (spin coating or casting) a mixture of a photosensitive polymer and a low molecular compound will be described. FIG. 2 schematically shows a film (film) after film formation.
The film (22) is isotropic at the time of film formation, and the side chain portion and the low molecular compound of the photosensitive polymer are not oriented in a specific direction. That is, in the film (22), the side chain (2a, 2b) having a photosensitive group represented by an ellipse and the low molecular compound (2c) represented by a cylinder are present randomly (coexisting).
When this film is irradiated with an ultraviolet quasi-parallel light beam (L) in which a completely polarized component and a non-polarized component composed of P component (Lp) and S component (Ls) are mixed, side chains oriented in a direction perpendicular to the traveling direction of the irradiated ultraviolet rays. Since (2a) is more sensitive than the side chain (2b) oriented in the parallel direction, the reaction proceeds selectively. This is because the conjugated system of the photosensitive portion containing a benzene ring or the like extends in the longitudinal direction of the side chain, and when such a side chain is placed in a radiation field such as light, the electric field of light This is because the interaction becomes maximum when the vibration direction coincides with the long axis direction of the side chain, and when the light traveling direction coincides with the long axis direction of the side chain, the interaction becomes minimum.
From this, it can be set as the film | membrane which advanced the photoreaction of a specific direction by irradiation of the ultraviolet-ray in which a perfect polarization component and a non-polarization component are mixed. In order to advance this photoreaction, it is necessary to irradiate light having a wavelength at which the photosensitive group portion can react. Although this wavelength varies depending on the type of photosensitive group, it is generally 200-500 nm, and in particular, the effectiveness of 250-400 nm is often high.
[0007]
FIG. 3 is a schematic diagram of a film (33) whose orientation is promoted after irradiation with light ultraviolet rays in which a completely polarized component composed of P component and S component and a non-polarized component are mixed.
As shown in FIG. 3, the side chain (3b) or the low molecular compound (3c) that did not undergo photoreaction in the film (33) has a molecular motion after irradiation with ultraviolet rays in which a completely polarized component and a non-polarized component are mixed. Is oriented under the influence of anisotropy expressed in the film in which the photoreaction in a specific direction has progressed (the side chain (3a) is exposed and reacted by irradiation with light in which a completely polarized component and a non-polarized component are mixed) The chain and the side chain (3b) represent side chains that did not react because they were oriented parallel to the traveling direction of the irradiated ultraviolet rays.) As a result, birefringence is induced in the entire film, and the birefringence or the ratio of the three main refractive indices nx, ny, and nz of the film and the inclination of the nx axis with respect to the normal direction of the film surface are completely polarized and non-polarized. It can be controlled by the ratio of the P component and S component of the light in which the components are mixed, the irradiation angle, and the characteristics of the photosensitive material.
Furthermore, the refractive index ellipsoid or the bend-orientated refractive index ellipsoid or these by irradiating the non-polarizing light or the light in which the completely polarized component and the non-polarized component are mixed to the photosensitive material as in Examples described later. Birefringence equivalent to that in the case of combining with a uniaxial refractive index ellipsoid that is not inclined can also be exhibited.
[0008]
Orientation by molecular motion after irradiation with non-polarizing light or ultraviolet light in which a completely polarized component and a non-polarized component are mixed is promoted when the film is heated.
The heating temperature of the film is preferably lower than the softening point of the photoreacted portion and higher than the softening point of the side chain and low molecule that did not photoreact. In order to promote the orientation of the film, it is also effective to irradiate ultraviolet rays in which a completely polarized component and a non-polarized component are mixed under heating (from room temperature to Ti + 5 ° C.). Here, Ti indicates a phase transition temperature when changing from a liquid crystal phase to an isotropic phase. Preferably, it is effective to irradiate ultraviolet rays in which a completely polarized component and a non-polarized component are mixed before and after Ti. In this way, after irradiating ultraviolet rays in which a completely polarized component and a non-polarized component are mixed and then heating or cooling a film irradiated with ultraviolet rays in which a completely polarized component and a non-polarized component are mixed under heating to below the softening point of the polymer The molecules are frozen to obtain the retardation film of the present invention.
[0009]
In the present invention, when the low molecular weight compound mixed in the photosensitive polymer has low molecular weight compounds or heat or photoreactivity with the polymer, the orientation is firmly fixed, so that the heat resistance Improvement in sex is expected. In such a case, it is necessary to control the density of the photoreactive points by suppressing the exposure amount or adjusting the reactivity so as not to hinder the molecular motion during reorientation. The low molecular weight compound has an effect of suppressing the haze when it is an appropriate amount, but when added in excess, it causes an increase in haze and a decrease in orientation. From this point of view, although depending on the type of photosensitive polymer or low molecular weight compound, the retardation film can be produced even when the low molecular weight compound is added at 0.1 wt% to 80 wt%, but preferably 5 wt%. % To 50 wt% is desirable. Here, when the compatibility between the photosensitive polymer and the low molecular weight compound is not sufficient, a crystal having a size capable of inducing phase separation or visible light scattering is generated by heating the substrate during film formation or after exposure. This causes an increase in haze.
[0010]
As a method of increasing the film thickness and obtaining a film having a larger retardation, a method of laminating films can be mentioned. In this case, in order to prevent the destruction of the previously formed film in the step of coating and laminating the material solution on the film irradiated with ultraviolet rays in which the completely polarized component and the non-polarized component are mixed, It is effective to dissolve and use the polymer and the low molecular weight compound in a solvent having reduced solubility. Further, when the film of the photosensitive compound is irradiated with ultraviolet rays in which a completely polarized component and a non-polarized component are mixed from the front and back surfaces, birefringence is more efficiently expressed. The photosensitive compound is formed into a film by, for example, coating on a support, and irradiation with ultraviolet rays in which a completely polarized component and a non-polarized component are mixed may be applied directly to the compound or via the support. When the support is interposed, any material may be used as long as the support has a light transmittance of a wavelength at which the photosensitive compound can react. However, the higher the light transmittance, the smaller the irradiation amount. This is advantageous for the manufacturing process. Alternatively, a photosensitive compound can be formed on a releasable support, and after peeling, the front and back surfaces of the film can be irradiated with ultraviolet rays in which a completely polarized component and a non-polarized component are mixed.
[0011]
In FIG. 4, the manufacturing method (apparatus) of the retardation film of the present invention is shown by way of example.
The non-polarizing ultraviolet ray (46) generated by the ultraviolet lamp (41) excited by the power source (42) is applied (coated) onto the support (45) through a polarizer capable of obtaining a desired degree of polarization. The film (44) of the mixture of the photosensitive polymer and the low molecular compound is irradiated. In Examples 1 to 10, a retardation film in which the birefringence or the inclination of the three main refractive indexes nx, ny, nz, and nx axes in the film with respect to the normal direction of the film surface was controlled by the production method of the present invention was produced. Each example.
Example 1
3.75% by weight of poly (4-methacryloyloxyhexyloxy-4'-cinnamoyloxyethyloxybiphenyl) and 1.25% by weight of 4,4'-bis (isobutyloxyhexyloxy) biphenyl were dissolved in dichloroethane. The film was applied on a glass substrate with a thickness of about 1.5 μm. The substrate is disposed so as to be inclined at 45 degrees with respect to the horizontal plane, and the degree of polarization: PS / P + S (P and S are transmitted light intensities of the P component and S component, respectively, and the intensity of the completely polarized component is P−. S +, and P + S is the total transmitted light intensity of the fully polarized component and the non-polarized component.) Is 15.6 (%). 500mJ / cm each ² After each irradiation, it was heated to 100 ° C. and cooled to room temperature. Subsequently, in order to accelerate the reaction of the unreacted photosensitive group and strengthen the orientation, non-polarizing ultraviolet light is applied at 1 J / cm. ² Irradiated.
In the refractive index ellipsoid of the substrate thus obtained, the ratio of the three main refractive indexes is nx = 1.6, ny = 1.5, nz = 1.5, and the nx axis is the substrate surface normal. The ratio of the refractive ellipsoid bend-aligned to 0 to 90 ° with respect to the direction and the three main refractive indexes is nx = 1.6, ny = 1.5, nz = 1.5, and the nx axis is the substrate surface method. It was equivalent to a combination of uniaxially oriented films that were 0 ° to the linear direction.
[0012]
(Example 2)
3.75 wt% poly (4-methacryloyloxyhexyloxy-4'-cinnamoyloxyethyloxybiphenyl) and 1.25 wt% 4,4'-bis (isobutyryloxyhexyloxy) biphenyl in dichloroethane It melt | dissolved and it apply | coated by the thickness of about 1.5 micrometers on the glass substrate. The substrate is disposed so as to be inclined at 45 degrees with respect to the horizontal plane, and the degree of polarization is -15.6 (%), and ultraviolet rays are respectively applied from the vertical direction to the horizontal plane at room temperature and 500 mJ / cm from the front and back surfaces of the substrate. ² After each irradiation, it was heated to 100 ° C. and cooled to room temperature. Subsequently, in order to accelerate the reaction of the unreacted photosensitive group and strengthen the orientation, non-polarizing ultraviolet light is applied at 1 J / cm. ² Irradiated. The refractive index ellipsoid of the substrate thus obtained has a ratio of three main refractive indexes of nx = 1.55, ny = 1.6, nz = 1.5, and the nx axis is the substrate surface normal. It was inclined 45 ° with respect to the direction.
[0013]
(Example 3)
3.75 wt% poly (4-methacryloyloxyhexyloxy-4'-cinnamoyloxyethyloxybiphenyl) and 1.25 wt% 4,4'-bis (isobutyryloxyhexyloxy) biphenyl in dichloroethane It melt | dissolved and it apply | coated by the thickness of about 1.5 micrometers on the glass substrate. The substrate is disposed so as to be inclined at 45 degrees with respect to the horizontal plane, and the degree of polarization: PS / P + S (P and S are transmitted light intensities of the P component and S component, respectively, and the intensity of the completely polarized component is P−. S, where P + S is the total transmitted light intensity of the fully polarized component and the non-polarized component.) Is 7.9 (%). 500mJ / cm each ² After each irradiation, it was heated to 100 ° C. and cooled to room temperature. Subsequently, in order to accelerate the reaction of the unreacted photosensitive group and strengthen the orientation, non-polarizing ultraviolet light is applied at 1 J / cm. ² Irradiated.
In the refractive index ellipsoid of the substrate thus obtained, the ratio of the three main refractive indexes is nx = 1.65, ny = 1.51, nz = 1.5, and the nx axis is the substrate surface normal. This was equivalent to the case of a refractive index ellipse bend-aligned by 10 to 40 ° with respect to the direction. .
[0014]
Example 4
3.75 wt% poly (4-methacryloyloxyhexyloxy-4'-cinnamoyloxyethyloxybiphenyl) and 1.25 wt% 4,4'-bis (isobutyryloxyhexyloxy) biphenyl in dichloroethane It melt | dissolved and it apply | coated by the thickness of about 1.5 micrometers on the glass substrate. The substrate is disposed so as to be inclined by 45 degrees with respect to the horizontal plane, and the degree of polarization is −7.9 (%), and ultraviolet rays are irradiated at 500 mJ / cm from the front and back surfaces of the substrate at a room temperature from the direction perpendicular to the horizontal plane. ² After each irradiation, it was heated to 100 ° C. and cooled to room temperature. Subsequently, in order to accelerate the reaction of the unreacted photosensitive group and strengthen the orientation, non-polarizing ultraviolet light is applied at 1 J / cm. ² Irradiated.
In the refractive index ellipsoid of the substrate thus obtained, the ratio of the three main refractive indexes is nx = 1.6, ny = 1.54, nz = 1.5, and the nx axis is the substrate surface normal. It was inclined by 25 ° with respect to the direction.
[0015]
(Example 5)
3.75 wt% poly (4-methacryloyloxyhexyloxy-4'-cinnamoyloxyethyloxybiphenyl) and 1.25 wt% 4,4'-bis (isobutyryloxyhexyloxy) biphenyl in dichloroethane It melt | dissolved and it apply | coated by the thickness of about 1.5 micrometers on the glass substrate. The substrate is disposed so as to be inclined at 45 degrees with respect to the horizontal plane, and non-polarizing ultraviolet rays [degree of polarization = 0 (%)] are applied at 500 mJ / cm from the front and back surfaces of the substrate at room temperature from the direction perpendicular to the horizontal plane. ² After each irradiation, it was heated to 100 ° C. and cooled to room temperature. Subsequently, in order to accelerate the reaction of the unreacted photosensitive group and strengthen the orientation, non-polarizing ultraviolet light is applied at 1 J / cm. ² Irradiated.
In the refractive index ellipsoid of the substrate thus obtained, the ratio of the three main refractive indexes is nx = 1.6, ny = 1.53, nz = 1.5, and the nx axis is the substrate surface normal. It was inclined by 32 ° with respect to the direction.
[0016]
(Example 6)
3.75% by weight of poly (4-methacryloyloxyhexyloxy-4′-cinnamoyloxyethyloxybiphenyl) and 1.25% by weight of 4-pentyl-4′-cyanobiphenyl are dissolved in dichloroethane, on a glass substrate. To a thickness of about 1.5 μm. The substrate is disposed so as to be inclined at 45 degrees with respect to the horizontal plane, and the degree of polarization: PS / P + S (P and S are transmitted light intensities of the P component and S component, respectively, and the intensity of the completely polarized component is P−. S +, and P + S is the total transmitted light intensity of the fully polarized component and the non-polarized component.) Is 15.6 (%). 500mJ / cm each ² After each irradiation, it was heated to 100 ° C. and cooled to room temperature. Subsequently, in order to accelerate the reaction of the unreacted photosensitive group and strengthen the orientation, non-polarizing ultraviolet light is applied at 1 J / cm. ² Irradiated. The birefringence of the substrate thus obtained is that the ratio of the three main refractive indexes is nx = 1.6, ny = 1.5, nz = 1.5, and the nx axis is the normal direction of the substrate surface. The ratio of the refractive index ellipse with the bend orientation of 50 to 90 ° to the three main refractive indexes is nx = 1.6, ny = 1.5, nz = 1.5, and the nx axis is in the normal direction of the substrate surface. It was equivalent to the combination of uniaxially oriented films at 0 °.
[0017]
(Example 7)
3.75% by weight of poly (4-methacryloyloxyhexyloxy-4′-cinnamoyloxyethyloxybiphenyl) and 1.25% by weight of 4-pentyl-4′-cyanobiphenyl are dissolved in dichloroethane, on a glass substrate. To a thickness of about 1.5 μm. The substrate is disposed so as to be inclined at 45 degrees with respect to the horizontal plane, and the degree of polarization is -15.6 (%), and ultraviolet rays are respectively applied from the vertical direction to the horizontal plane at room temperature and 500 mJ / cm from the front and back surfaces of the substrate. ² After each irradiation, it was heated to 100 ° C. and cooled to room temperature. Subsequently, in order to accelerate the reaction of the unreacted photosensitive group and strengthen the orientation, non-polarizing ultraviolet light is applied at 1 J / cm. ² Irradiated.
In the refractive index ellipsoid of the substrate thus obtained, the ratio of the three main refractive indexes is nx = 1.6, ny = 1.59, nz = 1.5, and the nx axis is the substrate surface normal. It was inclined by 37 ° with respect to the direction.
[0018]
(Example 8)
3.75% by weight of poly (4-methacryloyloxyhexyloxy-4′-cinnamoyloxyethyloxybiphenyl) and 1.25% by weight of 4-pentyl-4′-cyanobiphenyl are dissolved in dichloroethane, on a glass substrate. To a thickness of about 1.5 μm. The substrate is disposed so as to be inclined at 45 degrees with respect to the horizontal plane, and the degree of polarization: PS / P + S (P and S are transmitted light intensities of the P component and S component, respectively, and the intensity of the completely polarized component is P−. S, where P + S is the total transmitted light intensity of the fully polarized component and the non-polarized component.) Is 7.9 (%). 500mJ / cm each ² After each irradiation, it was heated to 100 ° C. and cooled to room temperature. Subsequently, in order to accelerate the reaction of the unreacted photosensitive group and strengthen the orientation, non-polarizing ultraviolet light is applied at 1 J / cm. ² Irradiated.
The birefringence of the substrate thus obtained is that the ratio of the three main refractive indexes is nx = 1.58, ny = 1.5, nz = 1.5, and the nx axis is the normal direction of the substrate surface. The refractive index ellipse was 0-30 ° bend-oriented.
[0019]
Example 9
3.75% by weight of poly (4-methacryloyloxyhexyloxy-4′-cinnamoyloxyethyloxybiphenyl) and 1.25% by weight of 4-pentyl-4′-cyanobiphenyl are dissolved in dichloroethane, on a glass substrate. To a thickness of about 1.5 μm. The substrate is disposed so as to be inclined at 45 degrees with respect to the horizontal plane, and the degree of polarization: PS / P + S (P and S are transmitted light intensities of the P component and S component, respectively, and the intensity of the completely polarized component is P−. S +, and P + S is the total transmitted light intensity of the total polarization component and the non-polarization component.) Is −7.9 (%). 500 mJ / cm from each side ² After each irradiation, it was heated to 100 ° C. and cooled to room temperature. Subsequently, in order to accelerate the reaction of the unreacted photosensitive group and strengthen the orientation, non-polarizing ultraviolet light is applied at 1 J / cm. ² Irradiated. The birefringence of the substrate thus obtained is that the ratio of the three main refractive indexes is nx = 1.58, ny = 1.56, nz = 1.5, and the nx axis is the normal direction of the substrate surface. The ratio of the refractive index ellipse with 0 to 90 ° bend orientation and the three main refractive indices is nx = 1.55, ny = 1.5, nz = 1.5, and the nx axis is in the normal direction of the substrate surface. It was equivalent to the combination of uniaxially oriented films at 0 °.
[0020]
(Example 10)
3.75% by weight of poly (4-methacryloyloxyhexyloxy-4′-cinnamoyloxyethyloxybiphenyl) and 1.25% by weight of 4-pentyl-4′-cyanobiphenyl are dissolved in dichloroethane, on a glass substrate. To a thickness of about 1.5 μm. The substrate is disposed so as to be inclined at 45 degrees with respect to the horizontal plane, and non-polarizing ultraviolet rays [degree of polarization = 0 (%)] are applied at 500 mJ / cm from the front and back surfaces of the substrate at room temperature from the direction perpendicular to the horizontal plane. ² After each irradiation, it was heated to 100 ° C. and cooled to room temperature. Subsequently, in order to accelerate the reaction of the unreacted photosensitive group and strengthen the orientation, non-polarizing ultraviolet light is applied at 1 J / cm. ² Irradiated.
The birefringence of the substrate thus obtained is that the ratio of the three main refractive indexes is nx = 1.6, ny = 1.53, nz = 1.5, and the nx axis is the normal direction of the substrate surface. The ratio of the refractive index ellipse tilted by 30 ° to the three main refractive indexes is nx = 1.6, ny = 1.5, nz = 1.5, and the nx axis is 0 ° with respect to the normal direction of the substrate surface. It was equivalent to what combined the uniaxially oriented film which is.
[0021]
(Evaluation methods)
A coating film similar to that of Example 5 was formed on a TAC film having a phase difference of 40 nm in a direction inclined by 40 ° with respect to the normal direction of the film surface to a thickness of about 1.5 μm. The polarizing film of the Casio liquid crystal color television EV-510 is peeled off from the phase difference film in which the refractive index ellipsoid is inclined, and one sheet is attached to the upper or lower surface of the liquid crystal cell. Electric engineering HEG1425DU) were bonded one above the other. The axial arrangement of each optical element was as shown in FIG.
In FIG. 5, 61 is the retardation film of the present invention, a is the tilt direction of the nx axis of the refractive index ellipsoid in the film, 52 is the liquid crystal cell, b and b ′ indicate the pretilt direction, Reference numerals 53 and 53 ′ denote polarizing sheets, and c and c ′ indicate the respective light absorption axis directions.
A liquid crystal color television was driven with such a configuration, and the viewing angle was defined as a viewing angle where the contrast ratio was 5 when displaying white and black, and the viewing angles in the vertical and horizontal directions were measured. For the measurement of the contrast ratio, Topcon BM-5A was used.
As shown in Table 1, it was also confirmed that when the retardation film produced in the example of the present invention was mounted on a liquid crystal display device, the viewing angle was enlarged by one sheet.
[0022]
[Table 1]

[0023]
【Effect of the invention】
Irradiate a light-sensitive polymer containing a positive refractive index ellipsoid structure or a film composed of a mixture of the polymer and a low-molecular compound with non-polarizing light or light with a mixture of a completely polarized component and a non-polarized component. By the operation, it was possible to produce a retardation film in which the inclinations of the three principal refractive indexes nx, ny, nz and nx axes of the refractive index ellipsoid in the film with respect to the normal direction of the film surface were controlled. Such a retardation film can be used as an optical compensation film for expanding a viewing angle in a liquid crystal display device using a twisted nematic liquid crystal using an optical rotation mode and a birefringence mode. Conventionally, such a large-area retardation film could not be produced at low cost, but according to the present invention, it is possible to perform simple operation of irradiating non-polarizing light or light in which a completely polarized component and a non-polarized component are mixed. Larger area became possible.
[0024]
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing a method for producing a retardation film of the present invention.
FIG. 2 is a schematic diagram showing a side chain exposed by irradiation with ultraviolet rays in which a completely polarized component and a non-polarized component are mixed.
FIG. 3 is a schematic diagram showing a film oriented by molecular motion after irradiation with ultraviolet light in which a completely polarized component and a non-polarized component are mixed.
FIG. 4 is a conceptual diagram showing a method for producing a retardation film of an example.
FIG. 5: Optical system for viewing angle characteristic evaluation
[Explanation of symbols]
11..Membrane (retardation film)
12 ... Refractive index ellipsoid
nx (1a), ny (1b), nz (1c) ... main refractive index (direction axis)
L: Light with a completely polarized component and a non-polarized component mixed
Lp ... P component
Ls ... S component

Claims

A film having a positive refractive index ellipsoidal structure and having a side chain containing a photoreactive group or a film made of a mixture of the polymer and a low molecular compound has a completely polarized component and a non-polarized component. Perform the operation of irradiating mixed light,
In the film, a side chain of the photosensitive polymer that is perpendicular to the traveling direction of the irradiated light is selectively photoreacted, and the photoreactive side chain is irradiated with the irradiated light. and a side chain that responds to a side chain and S components that reacts to the P component, are reacted respectively in different directions, then promote the orientation of photosensitive groups of the unreacted by heating and cooling the film, P The ratio of the three principal refractive indices nx, ny, nz and the nx axis of the refractive index ellipsoid in this film by controlling the respective ratios of the fully polarized and non-polarized components including the component and the S component. A method for producing a retardation film, wherein an inclination of the film relative to a normal direction of the film surface is controlled.