JP2004109381A - Optical film, optical compensator comprising the film, and liquid crystal display device incorporating the compensator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film which is easily synthesized, which does not need a complicated operation of inert gas substitution in bridging and which is formed of a bridging layer of discotic liquid crystal compound. <P>SOLUTION: The optical film is composed of the discotic liquid crystal compound having an oxetanyl group, and an orientation state that the compound forms in a liquid crystal state is bridged/fixed by light and/or heat. <P>COPYRIGHT: (C)2004,JPO

Description

【００１５】
オキセタニル基を利用した液晶も知られているが、いずれもオキセタニル基の開環重合で得られるポリエーテルを主鎖骨格にするものであり、前述のメソゲンとしてベンゼン環２個あるいは３個を−ＣＯ−Ｏ−や−Ｏ−で結合した基を側鎖として組み込み液晶性を発現させる側鎖型液晶性高分子である（元井正敏、高分子加工、４４（１）、１２（１９９５）、　遠藤竜太、元井正敏　他、Ｐｏｌｙｍｅｒ　Ｐｒｅｐｒｉｎｔｓ、　Ｊａｐａｎ、　４８（２）、　２７２（１９９９）等）。
しかしながらディスコティック液晶性化合物にオキセタニル基を導入した例は知られていない。
【００１６】
ディスコティック液晶性化合物に結合させるオキセタニル基を有する化合物の合成法としては、通常の有機化学で用いられる方法を適用することができ、特に限定されるものではない。例えば、まずオキセタニル基部分と必要に応じて液晶化学の分野で一般に用いられているスペーサ部分とをＷｉｌｌｉａｍｓｏｎのエーテル合成などの方法や、ＤＣＣ（ジシクロヘキシルカルボジイミド）などの縮合剤を用いるエステル合成法等で合成することができる。さらに、液晶性を制御する目的でアルコール、フェノール、カルボン酸などの各種化合物を次々に反応させることもあり、適宜保護基の活用を考慮してもよい。合成されたオキセタニル基を有する化合物は、再結晶、カラムクロマトグラフィーなどの方法で精製してもよい。特に結晶性がある程度高いものについては、再結晶は有効な手段であり、常温で再結晶が不可能な化合物についても、−２０℃などの低温に冷却することで再結晶が可能になることもある。このようにして得られたオキセタニル基を有する化合物は、主に^１Ｈ−ＮＭＲ（核磁気共鳴法）などの分析手段により、同定が可能である。
【００１７】
前記のスペーサ部分は、単結合または炭素数が１から８の直鎖状炭化水素基である。なお、目的とする化合物が液晶性を持つなら、スペーサ部分は存在せずに、剛直な構造を持つ部分とカチオン重合性基部分が直接結合（単結合）していてもよい。一般に、スペーサ部分が短すぎると液晶性が発現する温度領域が狭くなる恐れがあり、またスペーサ部分が長すぎても、重合・架橋後のフィルムの耐熱性が悪化する恐れがあるため、スペーサ部分の炭素数は２から６であることが好ましい。
【００１８】
かくして得られるオキセタニル基を有する化合物は、前記のディスコティック液晶性化合物と反応させることにより本発明のオキセタニル基を結合したディスコティック液晶性化合物を得ることができる。反応は両者の有する官能基の性質とオキセタニル基の反応性を考慮して、通常の有機化学で使用される反応から適宜な条件を選べばよい。なお、オキセタニル基を有する化合物としてオキセタン骨格の合成で得られる化合物を上記のような反応を行わずに直接ディスコティック液晶性化合物と反応させてもよく、また得られたオキセタニル基を結合したディスコティック液晶性化合物は前述のように再結晶、カラムクロマトグラフィーなどの方法で精製してもよい。
【００１９】
こうして得られたオキセタニル基を有するディスコティック液晶性化合物および／または該ディスコティック液晶性化合物を含有するディスコティック液晶性組成物を用い、当該液晶性化合物および／または液晶性組成物が液晶状態で形成した配向状態を光および／または熱により架橋固定化することにより、本発明の光学フィルムが製造される。
当該液晶性組成物としては、当該ディスコティック液晶性化合物と混和し、かつその配向を阻害せず、また本発明の目的を損なわない範囲において種々の化合物を適宜配合することができる。当該液晶性組成物中のディスコティック液晶性化合物の割合は、少なくとも３０質量％以上であることが好ましく、５０質量％以上であることが望ましい。ディスコティック液晶性化合物の含有量が３０質量％未満では組成物中に占めるディスコティック液晶性化合物の濃度が低くなり、ディスコティック液晶相の発現が困難になる恐れがある。
【００２０】
ディスコティック液晶性組成物に含有できる化合物としては、例えば、少なくとも１個のカチオン重合性基を有する化合物（ただし、本発明のディスコティック液晶性化合物を除く。）、フィルム形成能を有する各種高分子、ネマチック液晶性、コレステリック液晶性またはディスコティック液晶性を示す各種の低分子液晶性化合物あるいは高分子液晶性化合物などが挙げられる。また、本発明のディスコティック液晶性化合物および／またはディスコティック液晶性組成物にコレステリック液晶性を発現させる目的で、液晶性の有無を問わず各種の光学活性化合物を配合することもできる。これらの中でもカチオン重合性官能基が結合した化合物は、本発明のディスコティック液晶性化合物またはディスコティック液晶性組成物を架橋させる際に、ディスコティック液晶性化合物またはディスコティック液晶性組成物を構成するオキセタニル基と共架橋できるため好ましい。また、架橋後の液晶フィルムの熱安定性を損なわない範囲で、非架橋性の低分子化合物や各種高分子材料を組成物として含ませることも可能である。
【００２１】
本発明のディスコティック液晶性化合物またはディスコティック液晶性組成物は、光カチオン発生剤および／または熱カチオン発生剤（以下、両者を合わせてカチオン発生剤ということがある。）を含有することが望ましい。
本発明に使用できるカチオン発生剤について説明する。
本発明のディスコティック液晶性化合物またはディスコティック液晶性組成物は、オキセタニル基を結合したディスコティック液晶性化合物からなるため、その架橋（重合）にはカチオン発生剤の添加が好ましい。これらのカチオン発生剤は、光および／または熱などの外部刺激でカチオンを発生しうる化合物が望ましく、例えばトリクロロメチル基やキノンジアジド基を有する化合物、有機スルフォニウム塩系、ヨードニウム塩系、フォスフォニウム塩等が挙げられる。必要によっては各種の増感剤を併用してもよい。
【００２２】
光カチオン発生剤とは、適当な波長の光を照射することによりカチオンを発生できる化合物を意味し、有機スルフォニウム塩系、ヨードニウム塩系、フォスフォニウム塩系などを例示することが出来る。これら化合物の対イオンとしては、アンチモネート、フォスフェート、ボレートなどが好ましく用いられる。具体的な化合物としては、Ａｒ_３Ｓ^＋ＳｂＦ_６ ⁻、Ａｒ_３Ｐ^＋ＢＦ_４ ⁻、Ａｒ_２Ｉ^＋ＰＦ_６ ⁻（ただし、Ａｒはフェニル基または置換フェニル基を示す。）などが挙げられる。また、スルホン酸エステル類、トリアジン類、ジアゾメタン類、β−ケトスルホン、イミノスルホナート、ベンゾインスルホナートなども用いることができる。
【００２３】
熱カチオン発生剤とは、適当な温度に加熱されることによりカチオンを発生できる化合物であり、例えば、ベンジルスルホニウム塩類、ベンジルアンモニウム塩類、ベンジルピリジニウム塩類、ベンジルホスホニウム塩類、ヒドラジニウム塩類、カルボン酸エステル類、スルホン酸エステル類、アミンイミド類、五塩化アンチモン−塩化アセチル錯体、ジアリールヨードニウム塩−ジベンジルオキシ銅、ハロゲン化ホウ素−三級アミン付加物、などを挙げることができる。
【００２４】
また、ルイス酸などのカチオンを発生する化合物を予め添加したディスコティック液晶性化合物またはディスコティック液晶性組成物を調製し、液晶配向形成後、あるいは液晶配向形成と同時にオキセタニル基を重合させる方法を採ることも出来るが、液晶配向工程と重合工程を分離できた方が、十分な液晶配向と架橋度（重合度）とを両立できることが多く、実際には以下に示すように熱あるいは光などにより顕在化するカチオン発生剤を用いることがより好ましい。
【００２５】
熱カチオン発生剤を用いる場合には、熱カチオン発生剤の活性化温度（通常用いられる指標としては、５０％解離温度）よりも低い温度でディスコティック液晶性化合物またはディスコティック液晶性組成物の配向のための熱処理を行い、ついで本工程において活性化温度以上に加熱することにより、用いた熱カチオン発生剤を解離させ、発生したカチオンによりオキセタニル基を反応させることが出来る。この方法のメリットとしては、熱処理設備のみにより液晶配向と重合反応を行うことが出来る点が挙げられる。しかしながら、化合物の種類や液晶性組成物の組成比等によっては、熱（温度の違い）のみにより配向と重合の工程を分離しているため、配向時に若干重合反応が進行してしまったり、あるいは重合工程においても十分反応が進行しない場合が考えられる。したがって熱カチオン発生剤を利用する場合には、当該工程の反応制御を厳密に行う必要がある。
【００２６】
光カチオン発生剤を用いた場合、液晶配向のための熱処理を暗条件（光カチオン発生剤が解離しない程度の光遮断条件）で行えば、ディスコティック液晶性化合物またはディスコティック液晶性組成物は配向段階で重合や分解をすることなく、十分な流動性をもって配向することが出来る。この後、適当な波長光を発する光源からの光を照射することによりカチオンを発生させ、ディスコティック液晶性化合物またはディスコティック液晶性組成物を重合させればよい。
【００２７】
これらのカチオン発生剤のディスコティック液晶性化合物またはディスコティック液晶性組成物中への添加量は、用いるディスコティック液晶性化合物またはディスコティック液晶性組成物の構造や、オキセタニル基当量、液晶の配向条件などにより異なるため一概には言えないが、ディスコティック液晶性化合物に対して、通常１００質量ｐｐｍ〜２０質量％、好ましくは１０００質量ｐｐｍ〜１０質量％、より好ましくは０．２質量％〜７質量％、最も好ましくは０．５質量％〜５質量％の範囲である。１００質量ｐｐｍよりも少ない場合には、発生するカチオンの量が十分でなく重合が進行しないおそれがあり、また２０質量％よりも多い場合には、ディスコティック液晶性化合物またはディスコティック液晶性組成物の液晶性が低下して液晶の配向が不完全になったり、得られるフィルム中に残存するカチオン発生剤の分解残存物等が多くなり耐光性などが悪化するおそれがあるため、どちらの場合も好ましくない。
【００２８】
前記のカチオン発生剤の中では、光でカチオンを発生しうる光カチオン発生剤は、前記のディスコティック液晶性化合物またはディスコティック液晶性組成物が液晶相を発現する任意の温度でカチオンを発生させて重合を行うことができるため、特に好ましい。
【００２９】
次に、本発明のディスコティック液晶性化合物またはディスコティック液晶性組成物を用いた光学フィルムの製造方法について説明する。光学フィルム製造の方法としてはこれらに限定されるものではないが、下記の方法に示される各工程を踏むことが望ましい。
【００３０】
本発明のディスコティック液晶性化合物またはディスコティック液晶性組成物を配向させ、配向構造を架橋固定化した層（以下、液晶フィルムということがある）からなる光学フィルムは、配向基板上に形成されたままの形態（配向基板／（配向膜）／液晶フィルム）、配向基板とは異なる透明基板フィルム等に液晶フィルムを転写した形態（透明基板フィルム／液晶フィルム）、または液晶フィルムに自己支持性がある場合には液晶フィルム単層形態（液晶フィルム）のいずれの形態であってもよい。
【００３１】
本発明に用いることのできる配向基板としては、例えば、ポリイミド、ポリアミド、ポリアミドイミド、ポリフェニレンスルフィド、ポリフェニレンオキシド、ポリエーテルケトン、ポリエーテルエーテルケトン、ポリエーテルスルフォン、ポリスルフォン、ポリエチレンテレフタレート、ポリエチレンナフタレート、ポリアリレート、トリアセチルセルロース、エポキシ樹脂、フェノール樹脂等のフィルムおよびこれらフィルムの一軸延伸フィルム等が例示できる。
【００３２】
これらフィルムは製造方法によっては改めて配向能を発現させるための処理を行わなくとも本発明のディスコティック液晶性化合物またはディスコティック液晶性組成物に対して十分な配向能を示すものもあるが、配向能が不十分、または配向能を示さない等の場合には、必要によりこれらのフィルムを適度な加熱下に延伸する、フィルム面をレーヨン布等で一方向に擦るいわゆるラビング処理を行う、フィルム上にポリイミド、ポリビニルアルコール、シランカップリング剤等の公知の配向剤からなる配向膜を設けてラビング処理を行う、酸化珪素等の斜方蒸着処理、あるいはこれらを適宜組み合わせるなどして配向能を発現させたフィルムを用いても良い。また表面に規則的な多数の微細溝を設けたアルミニウム、鉄、銅などの金属板や各種ガラス板等も配向基板として使用することができる。
【００３３】
配向基板として光学的に等方でない、あるいは得られる光学フィルムが最終的に目的とする使用波長領域において不透明な配向基板を使用した場合は、配向基板上で形成された形態から光学的に等方なフィルムや最終的に使用される波長領域において透明な基板上に転写した形態も使用しうる。該転写方法としては、例えば特開平４−５７０１７号公報や特開平５−３３３３１３号公報に記載されているように液晶フィルム層を粘・接着剤を介して、配向基板とは異なる他の透明な基板を積層した後に、必要により粘・接着剤に硬化処理を施し、該積層体から配向基板を剥離することで液晶フィルムのみを転写する方法等を挙げることができる。
【００３４】
前記透明な基板としては、例えばフジタック（富士写真フィルム（株）製品）、コニカタック（コニカ（株）製品）などのトリアセチルセルロースフィルム、ＴＰＸフィルム（三井化学（株）製品）、アートンフィルム（ＪＳＲ（株）製品）、ゼオネックスフィルム（日本ゼオン（株）製品）、アクリプレンフィルム（三菱レーヨン（株）製品）等が挙げられ、また必要によっては透明な基板として偏光板を使用することもできる。これら基板は接着性や耐候性の向上のために、鹸化処理やコロナ放電処理等の各種表面処理を施したものであってもよい。さらに、石英板やガラス板を使用することもある。なお、前記の偏光板は保護層の有無を問わず使用することができる。
【００３５】
転写に使用される粘・接着剤は光学グレードのものであれば特に制限はなく、例えば、アクリル系、エポキシ樹脂系、エチレン−酢酸ビニル共重合体系、ゴム系、ウレタン系およびこれらの混合物系や、熱硬化型および／または光硬化型、電子線硬化型等の各種反応性のものを挙げることができる。
【００３６】
前記反応性のものの反応（硬化）条件は、粘・接着剤を構成する成分、粘度や反応温度等の条件により変化するため、それぞれに適した条件を選択して行えばよい。例えば、光硬化型の場合は後述の光カチオン発生剤の場合と同様な光源を使用し同様な照射量でよく、電子線硬化型の場合の加速電圧は、通常２５ｋＶ〜２００ｋＶ、好ましくは５０ｋＶ〜１００ｋＶである。
【００３７】
本発明のディスコティック液晶性化合物またはディスコティック液晶性組成物から形成される光学フィルムは、ディスコティック液晶性化合物またはディスコティック液晶性組成物を溶融状態で配向基板上に塗布する方法や、ディスコティック液晶性化合物またはディスコティック液晶性組成物の溶液を配向基板上に塗布する方法等により製造することができる。すなわち、配向基板上に塗布された塗膜は乾燥、熱処理（液晶の配向）および光照射および／または加熱処理（重合）を経て光学フィルムが製造される。
【００３８】
前記溶液の調製に用いる溶媒に関しては、本発明のディスコティック液晶性化合物またはディスコティック液晶性組成物や該液晶性組成物を構成する成分等を溶解でき、適当な条件で留去できる溶媒であれば特に制限は無く、一般的にアセトン、メチルエチルケトン、イソホロンなどのケトン類、ブトキシエチルアルコール、ヘキシルオキシエチルアルコール、メトキシ−２−プロパノールなどのエーテルアルコール類、エチレングリコールジメチルエーテル、ジエチレングリコールジメチルエーテルなどのグリコールエーテル類、酢酸エチル、酢酸メトキシプロピル、乳酸エチルなどのエステル系、フェノール、クロロフェノールなどのフェノール類、Ｎ、Ｎ−ジメチルホルムアミド、Ｎ、Ｎ−ジメチルアセトアミド、Ｎ−メチルピロリドンなどのアミド系、クロロホルム、テトラクロロエタン、ジクロロベンゼンなどのハロゲン化炭化水素系などやこれらの混合系が好ましく用いられる。また、配向基板上に均一な塗膜を形成するために、界面活性剤、消泡剤、レベリング剤等を溶液に添加しても良い。さらに、着色を目的として液晶性の発現を妨げない範囲内で二色性染料や通常の染料や顔料等を添加することもできる。
【００３９】
塗布方法については、塗膜の均一性が確保される方法であれば、特に限定されることはなく公知の方法を採用することができる。例えば、ロールコート法、ダイコート法、ディップコート法、カーテンコート法、スピンコート法などを挙げることができる。塗布の後に、ヒーターや温風吹きつけなどの方法による溶媒除去（乾燥）工程を入れても良い。
【００４０】
続いて、必要なら熱処理などにより液晶配向を形成し、光照射および／または加熱処理で重合（架橋）を行う。この加熱処理では、使用したディスコティック液晶性化合物またはディスコティック液晶性組成物の液晶相発現温度範囲に加熱することにより、該液晶性組成物が本来有する自己配向能により液晶を配向させる。熱処理の条件としては、用いるディスコティック液晶性化合物またはディスコティック液晶性組成物の液晶相挙動温度（転移温度）により最適条件や限界値が異なるため一概には言えないが、通常１０〜２００℃、好ましくは２０〜１５０℃の範囲である。あまり低温では、液晶の配向が十分に進行しないおそれがあり、また高温では、オキセタニル基や基板に悪影響を与えるおそれがある。また、熱処理時間については、通常３秒〜３０分、好ましくは１０秒〜１０分の範囲である。３秒よりも短い熱処理時間では、液晶の配向が十分に完成しないおそれがあり、また３０分を超える熱処理時間では、生産性が極端に悪くなるため、どちらの場合も好ましくない。該液晶性組成物が熱処理などにより液晶の配向が完成したのち、そのままの状態で配向基板上の液晶性組成物を重合反応により硬化させる。本発明における重合（架橋）工程とは、完成した液晶配向を重合（架橋）反応により液晶配向状態を固定化することであり、より強固な膜とすることを目的としている。
【００４１】
光カチオン発生剤を用いた場合、カチオンを発生させるためには、適当な波長の光を発する光源からの光を照射すればよい。光照射の方法としては、用いる光カチオン発生剤の種類や量により照射波長、照射強度、照射時間等の最適値が異なるが、光カチオン発生剤の吸収波長領域付近にスペクトルを有するようなメタルハライドランプ、高圧水銀灯、低圧水銀灯、キセノンランプ、アークランプ、レーザー、シンクロトロン光源などの光源からの光を照射し、光カチオン発生剤を解裂させる。光照射量としては、積算照射量として通常１〜２０００ｍＪ／ｃｍ^２、好ましくは１０〜１０００ｍＪ／ｃｍ^２の範囲である。ただし、光カチオン発生剤の吸収領域と光源のスペクトルが著しく異なる場合や、あるいはディスコティック液晶性化合物またはディスコティック液晶性組成物自身に光源波長の吸収能がある場合などにはこの限りではない。これらの場合には、適当な光増感剤や、あるいは吸収波長の異なる２種以上の光カチオン発生剤を混合して用いるなどの方法を採ることも出来る。
【００４２】
光照射の時の温度は、前述の液晶を配向させる時の加熱温度範囲、すなわち通常１０〜２００℃、好ましくは２０〜１５０℃の範囲で行えば十分である。また、本発明に用いられるディスコティック液晶性化合物またはディスコティック液晶性組成物は、カチオン重合性であるため、ラジカル重合と異なり空気中の酸素による重合阻害が起きないので不活性ガス雰囲気下で重合を行う必要もない
【００４３】
以上のような工程により製造した液晶フィルムは、十分強固な膜になっている。具体的には、重合反応によりディスコティック液晶が３次元的に結合され、重合前に比べて耐熱性（液晶配向保持の上限温度）が向上するのみでなく、耐スクラッチ性、耐摩耗性、耐クラック性などの機械的強度に関しても大幅に向上する。本発明は、液晶配向という緻密な配向制御と、熱的・機械的強度の向上という相反する目的を同時に達成できる方法を提供する意味で工業的な意義が大きい。
【００４４】
なお、本発明のディスコティック液晶性化合物またはディスコティック液晶性化合物からなるディスコティック液晶性組成物は、必要に応じて配合する化合物を適宜選定することにより、その配向構造を制御することができ、ネマチック配向、ねじれネマチック配向、コレステリック配向、ネマチックハイブリッド配向等を固定化した光学フィルムを製造することが可能であり、その配向構造によって種々の用途がある。
【００４５】
これらの光学フィルムのなかで、例えばネマチック配向、ねじれネマチック配向を固定化した光学フィルムは位相差フィルムとして機能し、ＳＴＮ、ＴＮ、ＯＣＢ、ＨＡＮ、ＶＡ、ＭＶＡ、ＩＰＳ等の透過型、反射型または半透過型液晶表示素子の光学補償素子として使用できる。コレステリック配向を固定化した光学フィルムは、輝度向上用の偏光反射フィルム、反射型のカラーフィルター、選択反射能に基因する視角による反射光の色変化を生かした各種の装飾フィルムなどに利用できる。またネマチックハイブリッド配向を固定化したフィルムは、正面から見たときのリターデーションを利用して、位相差フィルムや波長板として利用でき、またリターデーション値の向き（フィルムの傾き）による非対称性を生かしてＴＮ型液晶表示素子の光学補償素子（視野角改善フィルム）などに利用できる。また、１／４波長板機能を有する光学フィルムは、偏光板と組み合わせ、反射型の液晶表示素子やＥＬ表示素子の反射防止フィルターとして用いることができる。
【００４６】
【実施例】
以下に実施例を挙げ本発明を具体的に説明するが、本発明はこれらに制限されるものではない。
なお実施例で用いた各分析法は以下の通りである。
（１）化学構造決定
４００ＭＨｚの^１Ｈ−ＮＭＲ（日本電子社製ＪＮＭ−ＧＸ４００）で測定した。
（２）光学顕微鏡観察
オリンパス光学社製の偏光顕微鏡ＢＸ−５０を用いて、オルソスコープ観察およびコノスコープ観察を行った。また、液晶相の同定はメトラーホットステージ（ＦＰ−８０）上で加熱しながらテクスチャー観察することにより行った。
（３）偏光解析
（株）溝尻光学工業所製エリプソメーターＤＶＡ−３６ＶＷＬＤを用いて行った。リターデーションの値は５５０ｎｍの波長におけるものを採用した。
（４）膜厚測定
（株）小坂研究所製高精度薄膜段差測定器ＥＴ−１０を主に用いた。また、干渉波測定（日本分光社製　　紫外・可視・近赤外分光光度計Ｖ−５７０）と屈折率のデータから膜厚を求める方法も併用した。
【００４７】
［合成例１］
２，３，７，８，１２，１３−ヘキサヒドロキシトルクセンの合成
攪拌機、還流冷却器を付けた５Ｌ三ツ口フラスコに、３−（３，４−ジメトキシフェニル）プロピオン酸３００ｇおよびポリリン酸１５００ｇを入れ、窒素雰囲気下、６５℃で３０分反応させた。反応後冷却してから脱イオン水２０００ｍＬを徐々に添加した。室温で２時間攪拌後、５Ｌ分液ロートにフラスコ内容物を移し、クロロホルム６００ｍＬで抽出を６回行った。クロロホルム抽出液を炭酸水素ナトリウム飽和水溶液で洗浄し、無水硫酸マグネシウムで乾燥後濾過した。濾液をロータリーエバポレーターで濃縮し、５，６−ジメトキシインダノン−１を１７０ｇ得た。得られた５，６−ジメトキシインダノン−１を１７０ｇおよびポリリン酸エチル８５０ｇを攪拌機、還流冷却器を付けた３Ｌ三ツ口フラスコに入れ、窒素雰囲気下で攪拌しながら１４０℃に加熱し２時間反応後、フラスコを氷冷しながらエタノール　１Ｌを徐々に添加した。室温で１時間攪拌後、沈殿物を吸引濾過で回収した。この回収物をアセトンで洗浄した後、５０℃の真空乾燥器で一夜乾燥し、２，３，７，８，１２，１３−ヘキサメトキシトルクセンの粗結晶１４０ｇを得た。得られた粗結晶をジメチルホルムアミド溶媒から回収率９９％で再結晶した。
【００４８】
トルエン４００ｍＬの入った攪拌機、還流冷却器付き１Ｌ三ツ口フラスコに得られた２，３，７，８，１２，１３−ヘキサメトキシトルクセン４０．０ｇを加えて懸濁させ、攪拌下、氷冷しながら三臭化ホウ素１８７ｇを逐次添加した。ついでフラスコを６０℃から徐々に１２０℃まで昇温し、昇温後同温度で３時間反応させた。途中生成する臭化水素等はアルカリ水溶液を入れたトラップに吸収させた。
【００４９】
反応終了後、フラスコを室温まで冷却し、メタノール２００ｍＬを徐々に加えた。この際多量に発生する臭化水素、臭化メチル、メチルボレート等は−７８℃に冷却したトラップ、アルカリトラップ等で回収処理した。ついでアセトニトリルで洗浄してから高減圧下、６０℃にて揮発分を除去し、２，３，７，８，１２，１３−ヘキサヒドロキシトルクセン（下記式）の結晶２５．３ｇを得た。
【００５０】
【化２】

【００５１】
（合成例２）
２，３，６，７，１０，１１−ヘキサヒドロキシトリフェニレンの合成
氷冷した２Ｌの三ツ口フラスコに、硫酸第二鉄６水塩４６０ｇおよびイオン交換水２００ｍＬを入れ、溶解後、１，２−ジメトキシベンゼン５９．０ｇを添加した。その後、水冷下で濃硫酸９００ｍＬを徐々に添加した。２４時間後、氷水１０Ｌ中に徐々に注ぎ、５時間後、反応混合物を濾過し、２，３，６，７，１０，１１−ヘキサメトキシトリフェニレンの粗結晶５０．１ｇを得た。
トルエン９００ｍＬの入った攪拌機、還流冷却器付き３Ｌ三ツ口フラスコに得られた２，３，６，７，１０，１１−ヘキサメトキシトリフェニレンの粗結晶５０．１ｇを加えて懸濁させ、攪拌下、氷冷しながら三臭化ホウ素３００ｇを徐々に添加した。次いでフラスコを６０℃から徐々に１２０℃まで昇温し、昇温後同温度で３時間反応させた。途中生成する臭化水素等はアルカリ水溶液を入れたトラップに吸収させた。
反応終了後、フラスコを室温まで冷却し、メタノール２００ｍＬを徐々に加えた。この際多量に発生する臭化水素、臭化メチル、メチルボレート等は−７８℃に冷却したトラップ、アルカリトラップ等で回収処理した。次いで高減圧下、６０℃にて揮発分を除去し、アセトニトリルとジクロロメタンの混合溶媒で洗浄し、２、３、６、７、１０、１１−ヘキサヒドロキシトリフェニレン（下記式）の結晶３０．１ｇを得た。
【００５２】
【化３】

【００５３】
（合成例３）
４−［７−（３−エチル−３−オキセタニル）−１，６−ジオキサヘプチル］安息香酸の合成
２Ｌの三ツ口フラスコに、東亜合成（株）製ＯＸＴ−１０１（３−ヒドロキシメチル−３−エチルオキセタン）４６．３ｇ、１，４−ジブロモブタン２５０．３ｇおよびヘキサン３７５ｍＬを仕込み、２ｇのテトラ−ｎ−ブチルアンモニウムブロミドを含む５００ｍＬの３３％水酸化ナトリウム水溶液を加えて、５時間攪拌した。その後さらに８０℃で１時間還流させた後、５００ｍＬの脱イオン水を加え、分液し、水層から１６０ｍＬのヘキサンで３回抽出した。有機層と抽出層を合わせて、硫酸マグネシウムで乾燥した後、溶剤を減圧で留去した。得られた透明な液体をさらに減圧蒸留して、１０９℃／４ｍｍＨｇ（５３２Ｐａ）の留分として、３−［（４−ブロモブトキシ）メチル］−３−エチルオキセタン　４４．５ｇを得た。なお、得られた化合物の構造は、^１Ｈ−ＮＭＲで確認した。
１Ｌの三ツ口フラスコに、３−［（４−ブロモブトキシ）メチル］−３−エチルオキセタン　４０ｇ、ｐ−ヒドロキシ安息香酸エチル　２６．７ｇ、炭酸カリウム２４．１ｇを入れ、２５０ｍＬのジメチルホルムアミドを加えて溶液とし、溶液が濁ったまま８０℃に加熱して４時間攪拌し、溶媒を減圧で、その後真空（８０℃）で留去する。得られた黄色オイル状物に水酸化ナトリウム１０ｇを７５ｍＬの脱イオン水と７５ｍＬのメタノールに溶かした溶液を加え、２時間半加熱還流する。１規定塩酸をｐＨが３程度になるまで加えて析出した白色沈殿を濾過、真空乾燥して、４−［７−（３−エチル−３−オキセタニル）−１，６−ジオキサヘプチル］安息香酸４４．１ｇを得た。
【００５４】
（合成例４）
４−（６−アクリロイルオキシヘキシルオキシ）安息香酸クロリドの合成
１Ｌの三ツ口フラスコに、ｐ−ヒドロキシ安息香酸エチル６６ｇ、６−ブロモヘキサノール１０８ｇ、炭酸カリウム８２ｇおよびＮ，Ｎージメチルホルムアミド４００ｍＬを入れ、１２０℃で５時間攪拌した。攪拌後冷却してから反応混合物を水１Ｌに注ぎ、１Ｌの酢酸エチルで抽出し、水２００ｍＬで２回洗浄した。無水硫酸マグネシウムで乾燥した後濾過を行った。溶媒を減圧濃縮後、メタノール３００ｍＬに溶解し、水酸化カリウム３４ｇのメタノール溶液８０ｍＬを徐々に滴下し２時間加熱還流した。冷却後生じた結晶を濾別し、結晶を水１Ｌに溶解した。濃塩酸７０ｍＬを加え、析出した結晶を減圧濾過し、脱イオン水で洗浄した。この結晶を乾燥し、４−（６−ヒドロキシヘキシルオキシ）安息香酸９５．３ｇを得た。攪拌機、還流冷却管付き３００ｍＬ三ツ口フラスコに、得られた４−（６−ヒドロキシヘキシルオキシ）安息香酸２３．８ｇおよびジオキサン１００ｍＬ、Ｎ、Ｎ−ジメチルアニリン１４．５ｇを入れた後、５０℃に昇温し、攪拌しながらアクリル酸クロリド１０．９ｇとジオキサン５０ｍＬの溶液を３０分かけて逐次添加した。添加後、さらに５０℃で２時間加熱攪拌を行ったのち、反応液を脱イオン水１Ｌに注ぎ、結晶を析出させた。この析出物を濾過した後、ヘキサン２００ｍＬで洗浄、乾燥し、４−（６−アクリロイルオキシヘキシルオキシ）安息香酸２５．０ｇを得た。
５００ｍｌ三ツ口フラスコに上記で得た４−（６−アクリロイルオキシヘキシルオキシ）安息香酸２５．０ｇと塩化チオニル５０ｍｌを入れ、２時間加熱還流した。反応終了後、過剰の塩化チオニルをアルカリトラップを付して減圧下留去し、ヘキサン２００ｍｌで洗浄、乾燥後、４−（６−アクリロイルヘキシルオキシ）安息香酸クロリド２５．３ｇを得た。この酸クロリドは熱的に不安定なため精製が難しいので未精製のまま使用した。
【００５５】
（合成例５）
オキセタニル基を結合したディスコティック液晶性トルクセン誘導体の合成
撹拌機、冷却管付き１Ｌ三つ口フラスコに、合成例１で得た２，３，７，８，１２，１３−ヘキサヒドロキシトルクセン１７．３ｇ、４−ノニルオキシ安息香酸（試薬）２６．１ｇ、合成例３で得た４−［７−（３−エチル−３−オキセタニル）−１，６−ジオキサヘプチル］安息香酸３６．５ｇおよびステアリン酸（試薬）５．６ｇ、４−ジメチルアミノピリジン５．８ｇおよびジクロロメタン４００ｍＬを入れ、ジシクロヘキシルカルボジイミド５１．３ｇをジクロロメタン２００ｍＬに溶解した溶液を室温下に徐々に加えた後、１昼夜攪拌反応を行った。
生成した固体を濾別し、濾液を１規定塩酸５００ｍＬ、飽和炭酸水素ナトリウム水溶液５００ｍＬおよび飽和塩化ナトリウム水溶液５００ｍＬで洗浄後、無水硫酸マグネシウムで乾燥し、溶媒を留去しオキセタニル基を結合した液晶性トルクセン誘導体（下記式）６５．０ｇを得た。得られたトルクセン誘導体の^１Ｈ−ＮＭＲ分析から仕込み通りの組成を有することが確認された。このトルクセン誘導体は、６０℃以上の温度でネマチック・ディスコティック（ＮＤ）相を示し、ＮＤ相は少なくとも１５０℃までは存在していたが、それ以上の温度ではトルクセン誘導体の変質が起きたようで、等方相転移温度は確認できなかった。
【００５６】
【化４】

【００５７】
（合成例６）
オキセタニル基を結合したディスコティック液晶性トリフェニレン誘導体の合成
撹拌機、冷却管付き１Ｌ三ツ口フラスコに、合成例２で得た２，３，６，７，１０，１１−ヘキサヒドロキシトリフェニレン１０．０ｇ、４−［７−（３−エチル−３−オキセタニル）−１，６−ジオキサヘプチル］安息香酸５７．１ｇおよび４−ジメチルアミノピリジン４．５ｇおよびジクロロメタン３００ｍＬを入れ、ジシクロヘキシルカルボジイミド４０．１ｇをジクロロメタン２５０ｍＬに溶解した溶液を室温下に徐々に加えた後、１昼夜攪拌反応を行った。
生成した固体を濾別し、濾液を１規定塩酸２５０ｍＬ、飽和炭酸水素ナトリウム水溶液２５０ｍＬおよび飽和塩化ナトリウム水溶液２５０ｍＬで洗浄後、無水硫酸マグネシウムで乾燥し、溶媒を留去しオキセタニル基を結合した液晶性トリフェニレン誘導体（下記式）４７．５ｇを得た。生成物の^１Ｈ−ＮＭＲ分析からトリフェニレンに結合していた水酸基に基づく水素が消失し、代わりに同数のオキセタニル基が結合していることがわかった。
【００５８】
【化５】

【００５９】
（合成例７）
アクリロイル基を結合したディスコティック液晶性トリフェニレン誘導体の合成
合成例６と同様の三ツ口フラスコに、２，３，７，８，１０，１１−ヘキサヒドロキシトリフェニレン１０．０ｇ、トリエチルアミン１９．７ｇおよび１、２−ジメトキシエタン４００ｍＬを入れ、合成例４で得た４−（６−アクリロイルヘキシルオキシ）安息香酸クロリド５７．５ｇを１，２−ジメトキシエタン２００ｍＬに溶解した溶液を５０℃で徐々に添加し、同温度で３時間攪拌した。冷却後、メチルエチルケトン５００ｍＬと飽和炭酸水素ナトリウム水溶液２００ｍＬを加え、分液し、有機層を無水硫酸マグネシウムで乾燥し、溶媒を留去してアクリロイル基を結合した液晶性トリフェニレン誘導（下記式）体４５．１ｇを得た。
【００６０】
【化６】

【００６１】
［実施例１］
紫外線照射までの工程はすべて銀塩写真用赤色光下で行った。
合成例５で得たオキセタニル基を結合した液晶性トルクセン誘導体２．５ｇを２５ｍｌの１，１，２，２−テトラクロロエタンに溶かし、トリアリルスルフォニウムヘキサフルオロアンチモネート５０％プロピレンカーボネート溶液（アルドリッチ社製、試薬）０．２ｇを加えた後、孔径０．４５μｍのポリテトラフロオロエチレン製フィルターで不溶分を濾過して液晶性組成物溶液を調製した。
この溶液を、表面をレーヨン布によりラビング処理した厚み５０μｍのポリエチレンナフタレートフィルム（ＰＥＮ）上にスピンコート法を用いて塗布し、６０℃のホットプレート上で乾燥させた。得られたＰＥＮフィルム上の液晶性組成物層を１００℃に加熱しながら、空気雰囲気下、高圧水銀ランプにより積算照射量４５０ｍＪ／ｃｍ^２の紫外線光を照射した後、冷却して硬化した液晶性組成物層（液晶フィルム）を得た。
【００６２】
基板として用いたＰＥＮフィルムは大きな複屈折を持ち光学用フィルムとして好ましくないため、得られた液晶フィルムを紫外線硬化型接着剤ＵＶ−３４００（東亜合成（株）製）を介して、トリアセチルセルロース（ＴＡＣ）フィルムに転写し光学フィルムａを得た。すなわち、ＰＥＮフィルム上の重合させた液晶性組成物層の上に、ＵＶ−３４００を５μｍ厚となるように塗布し、ＴＡＣフィルムでラミネートして、ＴＡＣフィルム側から４００ｍＪ／ｃｍ^２の紫外線を照射して接着剤を硬化させた後、ＰＥＮフィルムを剥離し本発明の光学フィルムａを得た。
【００６３】
得られた光学フィルムａを偏光顕微鏡下で観察すると、ディスクリネーションなどがないモノドメインの均一なネマチック液晶配向が観察され、正面から見たとき一軸性のネマチック配向と同様なリターデーション（６０ｎｍ）を有していたが、ラビング方向に沿って斜めから観察したとき、見かけのリターデーションは傾ける方向により異なる値を示し、液晶性組成物層が厚み方向で配向の傾きを変えたハイブリッド配向していることがわかった。さらに光学フィルムａの液晶性組成物層部分のみをかきとり、ＤＳＣを用いてガラス転移点（Ｔｇ）を測定したところ、Ｔｇは１０５℃であった。また光学フィルムａの液晶性組成物層表面の鉛筆硬度はＨ程度であり、充分に強固な膜が得られた。
光学フィルムａを２枚用い、ＴＦＴ電極を有する９０度ねじれの液晶セル（ＴＮ型液晶セル）に対し、図１のような配置で補償を行った。その結果、光学フィルムａが無い場合に比べ、著しく視野角の広い表示が得られることが分かった。
【００６４】
［実施例２］
実施例１のトルクセン誘導体に代えて合成例６で得たオキセタニル基を結合した液晶性トリフェニレン誘導体を用いた以外は実施例１と同様に行い光学フィルムｂを得た。
得られた光学フィルムｂを偏光顕微鏡下で観察すると、ディスクリネーションなどがないモノドメインの均一なネマチック液晶配向が観察され、そのリターデーションは１０３ｎｍであった。さらに光学フィルムｂの液晶性組成物層部分のみをかきとり、ＤＳＣを用いてガラス転移点（Ｔｇ）を測定したところ、Ｔｇは１１０℃であった。また光学フィルムｂの液晶性組成物層表面の鉛筆硬度はＨ程度であり、充分に強固な膜が得られた。
【００６５】
［比較例１］
合成例７で得たアクリロイル基を結合した液晶性トリフェニレン誘導体を１０質量％のメチルエチルケトン溶液とし、該溶液に、光重合開始剤としてトリフェニレン誘導体に対して２質量％となるようにミヒラーケトン＋ベンゾフェノン（１：１質量比）を加えた。その溶液を用いる以外は実施例１と同様に行い、光学フィルムｃを得た。
得られた光学フィルムｃを偏光顕微鏡下で観察すると、ディスクリネーションなどがないモノドメインの均一なネマチック液晶配向が観察され、そのリターデーションは１１０ｎｍであった。さらに光学フィルムｃの液晶性組成物層部分のみをかきとり、ＤＳＣを用いてガラス転移点（Ｔｇ）を測定したところ、Ｔｇは７５℃であった。また光学フィルムｃの液晶性組成物層表面の鉛筆硬度はＢ〜２Ｂ程度であった。
【００６６】
［実施例３］
実施例１、２および比較例１で得た光学フィルムａ〜ｃを１０ｃｍ×１０ｃｍの大きさに切り出し、洗浄したガラス板にＴＡＣフィルム面がガラス板側となるように粘着剤で貼合し、８０℃の高温槽内に１週間放置した後、変化の度合を見たところ、光学フィルムａおよびｂは何の変化も見られなかったが、光学フィルムｃは表面は悪化していた。
このことから光学フィルムｃは、空気中での架橋のため、酸素阻害を受けて架橋が十分に進行せず、それがＤＳＣによる低Ｔｇおよび本試験による耐熱性の低下結果として現れたと考えられる。
【図面の簡単な説明】
【図１】実施例１で用いた液晶表示装置の模式図である。
【符号の説明】
１　：上側偏光板
２　：光学フィルムａ
３　：粘着剤を有するトリアセチルセルロースフィルム
４　：ＴＮ型液晶セル
５　：下側偏光板
６、１０：偏光板の透過軸
７　：ポリエチレンナフタレートフィルムのラビング方向に対応する方向
８、９：電極基板のラビング方向[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical film made of a discotic liquid crystalline compound having a specific polymerizable functional group, and a liquid crystal display device having the optical film.
[0002]
[Prior art]
Research and development for applying liquid crystal compounds to optical materials are being actively conducted, and many of them have already been put to practical use. When a liquid crystal compound is used as an optical material, it is essential that the alignment structure of the liquid crystal fixed after alignment be maintained under actual use conditions. As a method for maintaining the alignment structure of the liquid crystal, a method using a polymerizable liquid crystal compound, a method using a polymer liquid crystal substance, and a method using a polymer liquid crystal substance having a polymerizable reactive group have been proposed.
[0003]
As a method of using a polymerizable liquid crystal compound, Japanese Patent Application Laid-Open No. 11-13019 or Japanese Patent Application Laid-Open No. 11-513360 describes a mesogen in which two or three benzene rings are bonded by an ester group. I have. When these low-molecular liquid crystal compounds are used as a material for an optical film, a method in which the low-molecular liquid crystal compound is heated and melted and applied on a substrate film in a liquid crystal state can be considered, but this method requires the optical film. It is difficult to achieve film uniformity and film thickness accuracy. In addition, when the solution is applied on a film substrate, the solution viscosity is low, and the application itself is often difficult. Therefore, according to the above publication, when a self-standing optical film is produced, a liquid crystal material is filled in a glass cell, and the glass substrate is cured by irradiating ultraviolet rays under heating, and then the glass substrate is removed and the self-standing optical film is removed. Although a method of forming an optical film has been proposed, it is more complicated than a method of applying the film on a film substrate.
[0004]
JP-A-7-306317, JP-A-7-325221, JP-A-8-27284, and JP-A-9-104656 disclose using a discotic liquid crystal compound which is a polymerizable liquid crystal compound different from the above. Although gazettes and the like are known, most of the polymerizable groups described in these gazettes are (meth) acryloyl groups, and so-called oxygen inhibition occurs during polymerization / crosslinking. And the production of the compensation film is complicated. A vinyloxy group or an oxiranyl (epoxy) group is also exemplified as a polymerizable group other than the (meth) acryloyl group. However, the vinyloxy group is easily removed even by a weak acid, and the epoxy group is also highly reactive. Finally, a difficult method of introducing the group using a peracid is employed.
[0005]
As a method using a high-molecular liquid crystal substance, a liquid crystalline polyester excellent in alignment holding ability has been proposed as disclosed in JP-A-11-158258. However, with the spread of mobile devices, there is a demand for optical films made of these liquid crystalline polyesters to have an alignment holding ability in a more severe use environment and a better mechanical strength.
[0006]
On the other hand, as a method of using a polymer liquid crystal substance having a polymerizable reactive group, a method of introducing a polymerizable reactive group into a polymer main chain and a method of using a polymerizable reactive group in a side chain are disclosed in JP-A-9-3454. Methods for introducing a monomer unit having the following have been proposed, but in any of these methods, the liquid crystallinity is reduced, and thus there is a limit to the introduction of a large amount of polymerizable reactive groups until the mechanical strength is sufficiently increased. There is a need for other approaches.
[0007]
[Problems to be solved by the invention]
The present invention does not require a complicated process such as an inert gas atmosphere at the time of crosslinking such as a (meth) acryloyl group, and does not include a functional group such as an epoxy group, which is difficult to synthesize. It is an object of the present invention to provide a highly polymerizable discotic liquid crystalline compound, and to provide an optical film having excellent alignment holding ability and mechanical strength after liquid crystal alignment is fixed.
[0008]
[Means for Solving the Problems]
The present inventors have studied a polymerizable discotic liquid crystal compound that is easy to synthesize and has good liquid crystal alignment properties.As a result, the polymerizable discotic compound obtained by selecting an oxetanyl group as a polymerizable reactive group is obtained. A new optical film having excellent liquid crystal alignment, liquid crystal alignment, polymerization (crosslinking), and film formation after liquid crystal alignment is obtained. It was developed.
[0009]
That is, the first aspect of the present invention relates to an optical film comprising a discotic liquid crystalline compound having an oxetanyl group, wherein the alignment state formed in a liquid crystal state of the compound is cross-linked and fixed by light and / or heat.
A second aspect of the present invention relates to the optical film described above, wherein the discotic liquid crystalline compound has a hybrid orientation.
A third aspect of the present invention relates to an optical compensator having at least one optical film described above.
Furthermore, a fourth aspect of the present invention relates to a liquid crystal display device comprising at least one optical compensation element described above.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
The optical film of the present invention is composed of a discotic liquid crystalline compound having an oxetanyl group, and can be obtained by crosslinking and fixing an alignment state formed by the compound in a liquid crystal state by light and / or heat.
[0011]
The discotic liquid crystal compound having an oxetanyl group used in the present invention generally has a discotic liquid crystal compound (mesogen) serving as a mother nucleus at the center of a molecule, and is opposite to a binding site with the discotic liquid crystal compound. A linear alkyl group, an alkoxy group, and one to three benzene rings each having an oxetanyl group bonded thereto through a single bond, an ester bonding group (—CO—O—), an ether bonding group (—O—), or the like. It has a structure in which a bonded group or the like is radially substituted as a side chain. Examples of the discotic liquid crystal compound (mesogen) serving as a mother nucleus include 2,3,7,8,12,13-hexahydroxyturqucene, 2,3,6,7,10,11-hexahydroxytriphenylene, , 3,7,8,12,13-Hexahydroxy-5,10,15-trioxatorxene, hexahydroxybenzene, leucoquinizarin, 1,2,3,5,6,7-hexahydroxy-anthracene-9,10 -Dione, 1,3,5-trihydroxybenzene and acetylated products thereof can be used. Of these, 2,3,7,8,12,13-hexahydroxyturqucene, 3,6,7,10,11-hexahydroxytriphenylene and their reactive derivatives are preferred.
[0012]
For these compounds, C.I. {Destrade, Mol. {Cryst. {Liq. {Cryst. ,71, {111 (1981); {Kohne, Angew. {Chem. ,96, 70 (1984), J. Mol. M. {Lehn, J .; {Chem. Soc, Chem. {Commun. , {1794 (1085), J.A. {Zhang, J .; S. {Moore, J .; {Am. {Chem. {Soc. ,116, {2655 (1994)} and Shunsuke Takenaka, "Chemistry of Liquid Crystals", Chemical Review, 22, 60 (1994). For discotic liquid crystals, C.I. According to Destrade et al., Depending on the orientational order of the molecule, an ND phase (discotic nematic @ phase), a Dho phase (hexagonal @ ordered @ collumnar @ phase), a Dhd phase (hexagonal * ordered @ bordered * cordnard @ nard @ phase), a coronal * ordered * border * corundar @ nard @ phase. (C. Destrade et al. Mol. Cryst. Liq. Cryst. 106, 121 (1984)).
[0013]
In the present invention, the orientational order of these molecules is not particularly limited, but from the viewpoint of easiness of orientation, a material having at least an ND 配 向 phase having the lowest orientational order is preferable, and only the ND phase is the only liquid crystal phase. It has as.
The oxetanyl group used in the synthesis of the discotic liquid crystal compound of the present invention has various side reactions such as elimination and ring opening compared with other cationically polymerizable groups such as a vinyloxy group and an epoxy group. The synthesis reaction becomes easier.
[0014]
The following is particularly preferred as the structure of the oxetanyl group.
Embedded image

[0015]
Liquid crystals using oxetanyl groups are also known, but all use a polyether obtained by ring-opening polymerization of the oxetanyl group as the main chain skeleton, and use two or three benzene rings as the mesogen as described above. It is a side-chain type liquid crystalline polymer that incorporates a group linked by -O- or -O- as a side chain to exhibit liquid crystallinity (Masatoshi Motoi, Polymer Processing, 44 (1), 12 (1995), Endo Corporation) Ryuta, Motoi Masatoshi, et al., Polymer Preprints, Japan, 48 (2), 272 (1999), etc.).
However, there is no known example of introducing an oxetanyl group into a discotic liquid crystal compound.
[0016]
As a method for synthesizing a compound having an oxetanyl group to be bonded to a discotic liquid crystalline compound, a method used in ordinary organic chemistry can be applied, and is not particularly limited. For example, first, an oxetanyl group portion and, if necessary, a spacer portion generally used in the field of liquid crystal chemistry are combined by a method such as Williamson's ether synthesis or an ester synthesis method using a condensing agent such as DCC (dicyclohexylcarbodiimide). Can be synthesized. Further, various compounds such as alcohol, phenol, and carboxylic acid may be successively reacted for the purpose of controlling liquid crystallinity, and the use of protecting groups may be appropriately considered. The synthesized compound having an oxetanyl group may be purified by a method such as recrystallization or column chromatography. In particular, recrystallization is an effective means for those having a high degree of crystallinity, and even for compounds that cannot be recrystallized at room temperature, recrystallization can be performed by cooling to a low temperature such as -20 ° C. is there. The compound having an oxetanyl group thus obtained is mainly¹Identification is possible by analytical means such as H-NMR (nuclear magnetic resonance method).
[0017]
The spacer portion is a single bond or a linear hydrocarbon group having 1 to 8 carbon atoms. If the target compound has liquid crystallinity, a portion having a rigid structure and a cation polymerizable group portion may be directly bonded (single bond) without a spacer portion. In general, if the spacer portion is too short, the temperature region where liquid crystallinity is exhibited may be narrow, and if the spacer portion is too long, the heat resistance of the film after polymerization / crosslinking may be deteriorated. Preferably has 2 to 6 carbon atoms.
[0018]
The thus obtained compound having an oxetanyl group can be reacted with the above-mentioned discotic liquid crystal compound to obtain the discotic liquid crystal compound having an oxetanyl group of the present invention. In the reaction, appropriate conditions may be selected from reactions used in ordinary organic chemistry, taking into account the properties of the functional groups possessed by both and the reactivity of the oxetanyl group. In addition, the compound obtained by the synthesis of the oxetane skeleton as the compound having an oxetanyl group may be directly reacted with the discotic liquid crystal compound without performing the above-described reaction, and the discotic compound obtained by bonding the obtained oxetanyl group may be used. The liquid crystal compound may be purified by a method such as recrystallization or column chromatography as described above.
[0019]
Using the thus obtained discotic liquid crystal compound having an oxetanyl group and / or the discotic liquid crystal composition containing the discotic liquid crystal compound, the liquid crystal compound and / or the liquid crystal composition is formed in a liquid crystal state. The optical film of the present invention is manufactured by cross-linking and fixing the aligned state by light and / or heat.
As the liquid crystal composition, various compounds can be appropriately compounded as long as they are miscible with the discotic liquid crystal compound, do not inhibit the alignment thereof, and do not impair the object of the present invention. The proportion of the discotic liquid crystalline compound in the liquid crystalline composition is preferably at least 30% by mass or more, and more preferably 50% by mass or more. If the content of the discotic liquid crystal compound is less than 30% by mass, the concentration of the discotic liquid crystal compound in the composition becomes low, which may make it difficult to develop a discotic liquid crystal phase.
[0020]
Examples of the compound that can be contained in the discotic liquid crystalline composition include a compound having at least one cationically polymerizable group (however, excluding the discotic liquid crystalline compound of the present invention), and various polymers having film-forming ability. And various low molecular weight liquid crystal compounds or polymer liquid crystal compounds exhibiting nematic liquid crystallinity, cholesteric liquid crystallinity or discotic liquid crystallinity. In addition, various optically active compounds can be blended with or without the liquid crystal property for the purpose of exhibiting cholesteric liquid crystal property in the discotic liquid crystal compound and / or discotic liquid crystal composition of the present invention. Among these, the compound having a cationically polymerizable functional group bonded thereto constitutes the discotic liquid crystal compound or the discotic liquid crystal composition when the discotic liquid crystal compound or the discotic liquid crystal composition of the present invention is crosslinked. This is preferable because it can be co-crosslinked with an oxetanyl group. Further, as long as the thermal stability of the liquid crystal film after cross-linking is not impaired, a non-cross-linkable low molecular compound or various polymer materials can be included as a composition.
[0021]
It is desirable that the discotic liquid crystal compound or the discotic liquid crystal composition of the present invention contains a photocation generator and / or a thermal cation generator (hereinafter, both may be referred to as a cation generator). .
The cation generator that can be used in the present invention will be described.
Since the discotic liquid crystal compound or the discotic liquid crystal composition of the present invention is composed of a discotic liquid crystal compound having an oxetanyl group bonded thereto, it is preferable to add a cation generator for crosslinking (polymerization). These cation generators are preferably compounds capable of generating cations by external stimuli such as light and / or heat, such as compounds having a trichloromethyl group or a quinonediazide group, organic sulfonium salts, iodonium salts, and phosphonium salts. And the like. If necessary, various sensitizers may be used in combination.
[0022]
The photocation generator refers to a compound capable of generating a cation upon irradiation with light having an appropriate wavelength, and examples thereof include organic sulfonium salts, iodonium salts, and phosphonium salts. As a counter ion of these compounds, antimonate, phosphate, borate and the like are preferably used. Specific compounds include Ar₃S⁺SbF₆ ⁻, Ar₃P⁺BF₄ ⁻, Ar₂I⁺PF₆ ⁻(However, Ar represents a phenyl group or a substituted phenyl group.). Further, sulfonic acid esters, triazines, diazomethanes, β-ketosulfone, iminosulfonate, benzoin sulfonate and the like can also be used.
[0023]
A thermal cation generator is a compound capable of generating a cation when heated to an appropriate temperature, for example, benzylsulfonium salts, benzylammonium salts, benzylpyridinium salts, benzylphosphonium salts, hydrazinium salts, carboxylic acid esters, Examples include sulfonic acid esters, amine imides, antimony pentachloride-acetyl chloride complex, diaryliodonium salt-dibenzyloxy copper, and boron halide-tertiary amine adducts.
[0024]
Further, a method of preparing a discotic liquid crystal compound or a discotic liquid crystal composition to which a compound generating a cation such as a Lewis acid is added in advance, and polymerizing an oxetanyl group after forming the liquid crystal alignment or simultaneously with forming the liquid crystal alignment is adopted. However, it is often the case that separating the liquid crystal alignment step and the polymerization step can achieve both a sufficient liquid crystal alignment and a degree of cross-linking (degree of polymerization). It is more preferable to use a cation generator which is converted into a cation generator.
[0025]
When a thermal cation generator is used, the orientation of the discotic liquid crystalline compound or the discotic liquid crystalline composition at a temperature lower than the activation temperature of the thermal cation generator (a commonly used index is 50% dissociation temperature). Is performed, and then heated to an activation temperature or higher in this step, so that the used thermal cation generator is dissociated, and the oxetanyl group can be reacted with the generated cation. An advantage of this method is that the liquid crystal alignment and the polymerization reaction can be performed only by the heat treatment equipment. However, depending on the type of compound, the composition ratio of the liquid crystal composition, and the like, since the alignment and polymerization steps are separated only by heat (difference in temperature), the polymerization reaction slightly proceeds during alignment, or In some cases, the reaction does not proceed sufficiently in the polymerization step. Therefore, when a thermal cation generator is used, it is necessary to strictly control the reaction in this step.
[0026]
When a photocation generator is used, if the heat treatment for liquid crystal alignment is performed under dark conditions (light blocking conditions that do not dissociate the photocation generator), the discotic liquid crystal compound or the discotic liquid crystal composition will be aligned. The alignment can be performed with sufficient fluidity without polymerizing or decomposing in a step. Thereafter, light is emitted from a light source that emits light having an appropriate wavelength to generate cations and polymerize the discotic liquid crystal compound or the discotic liquid crystal composition.
[0027]
The amount of these cation generators added to the discotic liquid crystal compound or discotic liquid crystal composition depends on the structure of the discotic liquid crystal compound or discotic liquid crystal composition to be used, the oxetanyl group equivalent, and the liquid crystal alignment conditions. Although it cannot be said unconditionally because it differs depending on the like, it is usually 100% by mass to 20% by mass, preferably 1000% by mass to 10% by mass, more preferably 0.2% by mass to 7% by mass based on the discotic liquid crystal compound. %, Most preferably in the range 0.5% to 5% by weight. When the amount is less than 100 mass ppm, the amount of generated cations may not be sufficient and polymerization may not proceed. When the amount is more than 20 mass%, a discotic liquid crystalline compound or a discotic liquid crystalline composition may be used. The liquid crystallinity of the liquid crystal is reduced and the orientation of the liquid crystal becomes incomplete, or the decomposition residue and the like of the cation generator remaining in the obtained film may be increased and the light resistance may be deteriorated. Not preferred.
[0028]
Among the cation generators, a photo cation generator capable of generating a cation by light generates cations at any temperature at which the discotic liquid crystal compound or the discotic liquid crystal composition exhibits a liquid crystal phase. It is particularly preferable because the polymerization can be carried out.
[0029]
Next, a method for producing an optical film using the discotic liquid crystalline compound or the discotic liquid crystalline composition of the present invention will be described. The method for producing an optical film is not limited to these, but it is desirable to take the steps shown in the following method.
[0030]
An optical film comprising a layer in which the discotic liquid crystal compound or the discotic liquid crystal composition of the present invention is oriented and the orientation structure is cross-linked and fixed (hereinafter, sometimes referred to as a liquid crystal film) is formed on an orientation substrate. As-is (alignment substrate / (alignment film) / liquid crystal film), transfer of liquid crystal film to transparent substrate film different from alignment substrate (transparent substrate film / liquid crystal film), or self-supporting liquid crystal film In this case, the liquid crystal film may be in any form of a single layer (liquid crystal film).
[0031]
Examples of the alignment substrate that can be used in the present invention include, for example, polyimide, polyamide, polyamideimide, polyphenylene sulfide, polyphenylene oxide, polyether ketone, polyether ether ketone, polyether sulfone, polysulfone, polyethylene terephthalate, polyethylene naphthalate, Examples thereof include films of polyarylate, triacetyl cellulose, epoxy resin, phenolic resin and the like, and uniaxially stretched films of these films.
[0032]
Depending on the production method, these films may exhibit sufficient alignment ability with respect to the discotic liquid crystal compound or the discotic liquid crystal composition of the present invention without performing a treatment for expressing the alignment ability again. If the performance is insufficient, or does not show alignment ability, etc., if necessary, these films are stretched under appropriate heating, so-called rubbing treatment in which the film surface is rubbed in one direction with a rayon cloth or the like, on the film Polyimide, polyvinyl alcohol, rubbing treatment is performed by providing an orientation film made of a known orientation agent such as a silane coupling agent, oblique deposition treatment of silicon oxide or the like, or by appropriately combining these, to express the orientation ability. May be used. In addition, a metal plate such as aluminum, iron, or copper having various regular fine grooves formed on the surface, various glass plates, or the like can be used as the alignment substrate.
[0033]
When the alignment film is not optically isotropic, or when the obtained optical film finally uses an opaque alignment substrate in the intended wavelength region to be used, it is optically isotropic from the form formed on the alignment substrate. It is also possible to use a film transferred onto a transparent substrate in a wavelength region to be finally used. As the transfer method, for example, as described in JP-A-4-57017 and JP-A-5-333313, another transparent material different from the alignment substrate is applied to the liquid crystal film layer via a tacky / adhesive. After laminating the substrates, a method may be used in which, if necessary, a curing treatment is applied to the viscous / adhesive agent, and the alignment substrate is peeled off from the laminate to transfer only the liquid crystal film.
[0034]
Examples of the transparent substrate include triacetyl cellulose films such as Fujitac (product of Fuji Photo Film Co., Ltd.) and Konikatak (product of Konica Corporation), TPX film (product of Mitsui Chemicals, Inc.), Arton Film (JSR) Products), ZEONEX film (Nippon Zeon Co., Ltd. product), acrylene film (Mitsubishi Rayon Co., Ltd. product) and the like. If necessary, a polarizing plate can be used as a transparent substrate. . These substrates may be subjected to various surface treatments such as a saponification treatment or a corona discharge treatment in order to improve adhesion and weather resistance. Further, a quartz plate or a glass plate may be used. The above-mentioned polarizing plate can be used with or without a protective layer.
[0035]
The adhesive or adhesive used for the transfer is not particularly limited as long as it is of an optical grade.Examples include acrylic, epoxy resin, ethylene-vinyl acetate copolymer, rubber, urethane and mixtures thereof. , A thermosetting type and / or a photocuring type, and an electron beam curing type.
[0036]
Since the reaction (curing) conditions of the above-mentioned reactive substances vary depending on the components constituting the viscous / adhesive agent, the viscosity, the reaction temperature, and the like, conditions suitable for each may be selected. For example, in the case of the photo-curing type, the same irradiation amount may be used using the same light source as in the case of the photo-cation generator described later, and the acceleration voltage in the case of the electron beam-curing type is usually 25 kV to 200 kV, preferably 50 kV to 100 kV.
[0037]
The optical film formed from the discotic liquid crystal compound or the discotic liquid crystal composition of the present invention includes a method of applying the discotic liquid crystal compound or the discotic liquid crystal composition in a molten state on an alignment substrate, It can be produced by a method of applying a solution of a liquid crystal compound or a discotic liquid crystal composition on an alignment substrate. That is, the coating film applied on the alignment substrate is dried, heat-treated (alignment of liquid crystal), irradiated with light and / or heat-treated (polymerized) to produce an optical film.
[0038]
With respect to the solvent used for preparing the solution, any solvent that can dissolve the discotic liquid crystal compound or the discotic liquid crystal composition of the present invention, components constituting the liquid crystal composition, and the like and can be distilled off under appropriate conditions. There is no particular limitation, and generally ketones such as acetone, methyl ethyl ketone and isophorone, ether alcohols such as butoxyethyl alcohol, hexyloxyethyl alcohol and methoxy-2-propanol, glycol ethers such as ethylene glycol dimethyl ether and diethylene glycol dimethyl ether , Ethyl acetate, methoxypropyl acetate, ethyl lactate and other ester compounds, phenols such as phenol, chlorophenol, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolide Amide such as chloroform, tetrachloroethane, halogenated hydrocarbon such or a mixture of these systems, such as dichlorobenzene are preferably used. Further, in order to form a uniform coating film on the alignment substrate, a surfactant, an antifoaming agent, a leveling agent, and the like may be added to the solution. Further, a dichroic dye, a normal dye, a pigment, or the like may be added for the purpose of coloring within a range that does not hinder the development of liquid crystallinity.
[0039]
The application method is not particularly limited as long as uniformity of the coating film is ensured, and a known method can be employed. For example, a roll coating method, a die coating method, a dip coating method, a curtain coating method, a spin coating method, and the like can be used. After the application, a solvent removing (drying) step by a method such as a heater or hot air blowing may be included.
[0040]
Subsequently, if necessary, a liquid crystal alignment is formed by heat treatment or the like, and polymerization (crosslinking) is performed by light irradiation and / or heat treatment. In this heat treatment, the liquid crystal is oriented by the self-orienting ability inherent in the liquid crystal composition by heating the discotic liquid crystal compound or the discotic liquid crystal composition used to a temperature range in which a liquid crystal phase is exhibited. The conditions of the heat treatment cannot be unequivocally determined because optimum conditions and limit values differ depending on the liquid crystal phase behavior temperature (transition temperature) of the discotic liquid crystal compound or the discotic liquid crystal composition to be used. Preferably it is in the range of 20 to 150 ° C. If the temperature is too low, the alignment of the liquid crystal may not proceed sufficiently, and if the temperature is high, the oxetanyl group and the substrate may be adversely affected. The heat treatment time is usually in the range of 3 seconds to 30 minutes, preferably 10 seconds to 10 minutes. If the heat treatment time is shorter than 3 seconds, the orientation of the liquid crystal may not be sufficiently completed, and if the heat treatment time exceeds 30 minutes, the productivity is extremely deteriorated. After the liquid crystal composition completes the alignment of the liquid crystal by heat treatment or the like, the liquid crystal composition on the alignment substrate is cured by a polymerization reaction as it is. The polymerization (crosslinking) step in the present invention is to fix the completed liquid crystal alignment to a liquid crystal alignment state by a polymerization (crosslinking) reaction, and has an object of forming a stronger film.
[0041]
When a photocation generator is used, cations may be generated by irradiating light from a light source that emits light of an appropriate wavelength. As for the method of light irradiation, the optimum values of irradiation wavelength, irradiation intensity, irradiation time, etc. differ depending on the type and amount of the photocation generator used, but a metal halide lamp having a spectrum near the absorption wavelength region of the photocation generator. Irradiate light from a light source such as a high-pressure mercury lamp, a low-pressure mercury lamp, a xenon lamp, an arc lamp, a laser, or a synchrotron light source to cleave the photocation generator. The light irradiation amount is usually 1 to 2000 mJ / cm as an integrated irradiation amount.², Preferably 10 to 1000 mJ / cm²Range. However, this is not the case when the absorption region of the photocation generator and the spectrum of the light source are significantly different, or when the discotic liquid crystal compound or the discotic liquid crystal composition itself has an absorption capacity at the light source wavelength. In these cases, an appropriate photosensitizer or a method of mixing and using two or more kinds of photocation generators having different absorption wavelengths can be employed.
[0042]
The temperature at the time of light irradiation is sufficient if the temperature is in the heating temperature range for aligning the liquid crystal described above, that is, usually in the range of 10 to 200 ° C, preferably 20 to 150 ° C. In addition, the discotic liquid crystal compound or the discotic liquid crystal composition used in the present invention is cationically polymerizable, and unlike radical polymerization, does not inhibit polymerization by oxygen in the air. No need to do
[0043]
The liquid crystal film manufactured by the above steps is a sufficiently strong film. Specifically, the discotic liquid crystal is three-dimensionally bonded by the polymerization reaction, and not only the heat resistance (upper limit temperature for maintaining the liquid crystal alignment) is improved, but also the scratch resistance, the abrasion resistance, The mechanical strength such as cracking property is also greatly improved. The present invention has great industrial significance in that it provides a method capable of simultaneously achieving the contradictory objectives of precise alignment control of liquid crystal alignment and improvement of thermal and mechanical strength.
[0044]
The discotic liquid crystal composition of the present invention or the discotic liquid crystal composition composed of the discotic liquid crystal compound can control its alignment structure by appropriately selecting a compound to be added as necessary. It is possible to manufacture an optical film in which a nematic orientation, a twisted nematic orientation, a cholesteric orientation, a nematic hybrid orientation or the like is fixed, and there are various uses depending on the orientation structure.
[0045]
Among these optical films, for example, an optical film in which a nematic orientation, a twisted nematic orientation is fixed functions as a retardation film, and is a transmission type such as STN, TN, OCB, HAN, VA, MVA, IPS, or a reflection type or a reflection type. It can be used as an optical compensation element of a transflective liquid crystal display element. The optical film in which the cholesteric orientation is fixed can be used for a polarizing reflection film for improving brightness, a reflection type color filter, various decorative films utilizing color change of reflected light depending on a viewing angle due to selective reflection ability, and the like. In addition, a film in which the nematic hybrid orientation is fixed can be used as a retardation film or a wave plate using retardation when viewed from the front, and also makes use of the asymmetry due to the direction of the retardation value (film tilt). Thus, it can be used as an optical compensation element (viewing angle improving film) of a TN type liquid crystal display element. An optical film having a quarter-wave plate function can be used in combination with a polarizing plate as an anti-reflection filter of a reflective liquid crystal display device or an EL display device.
[0046]
【Example】
Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto.
In addition, each analysis method used in the Example is as follows.
(1) Determination of chemical structure
400MHz¹It was measured by H-NMR (JNM-GX400 manufactured by JEOL Ltd.).
(2) Optical microscope observation
Orthoscope observation and conoscopic observation were performed using a polarizing microscope BX-50 manufactured by Olympus Optical Co., Ltd. The liquid crystal phase was identified by observing the texture while heating on a Mettler hot stage (FP-80).
(3) Polarization analysis
The measurement was performed using an ellipsometer DVA-36VWLD manufactured by Mizojiri Optical Industrial Co., Ltd. The retardation value at a wavelength of 550 nm was employed.
(4) Film thickness measurement
A high-precision thin film step measuring device ET-10 manufactured by Kosaka Laboratory Co., Ltd. was mainly used. In addition, a method of obtaining a film thickness from data of refractive index and interference wave measurement (Ultraviolet / Visible / Near-infrared spectrophotometer V-570 manufactured by JASCO Corporation) was also used.
[0047]
[Synthesis Example 1]
Synthesis of 2,3,7,8,12,13-hexahydroxytorxcene
A 5-L three-necked flask equipped with a stirrer and a reflux condenser was charged with 300 g of 3- (3,4-dimethoxyphenyl) propionic acid and 1500 g of polyphosphoric acid, and reacted at 65 ° C. for 30 minutes under a nitrogen atmosphere. After the reaction was cooled, 2000 mL of deionized water was gradually added. After stirring at room temperature for 2 hours, the contents of the flask were transferred to a 5 L separating funnel, and extracted with 600 mL of chloroform six times. The chloroform extract was washed with a saturated aqueous solution of sodium hydrogen carbonate, dried over anhydrous magnesium sulfate, and filtered. The filtrate was concentrated using a rotary evaporator to obtain 170 g of 5,6-dimethoxyindanone-1. 170 g of the obtained 5,6-dimethoxyindanone-1 and 850 g of ethyl polyphosphate are put into a 3 L three-necked flask equipped with a stirrer and a reflux condenser, heated to 140 ° C. while stirring under a nitrogen atmosphere, and reacted for 2 hours. Then, ethanol (1 L) was gradually added while cooling the flask with ice. After stirring at room temperature for 1 hour, the precipitate was collected by suction filtration. The collected product was washed with acetone, and dried overnight in a vacuum dryer at 50 ° C. to obtain 140 g of crude crystals of 2,3,7,8,12,13-hexamethoxytorxene. The obtained crude crystals were recrystallized from a dimethylformamide solvent at a recovery of 99%.
[0048]
40.0 g of the obtained 2,3,7,8,12,13-hexamethoxytorxene was added and suspended in a 1 L three-necked flask equipped with a stirrer and a reflux condenser containing 400 mL of toluene, and the suspension was cooled with ice under stirring. While adding 187 g of boron tribromide sequentially. Then, the temperature of the flask was gradually raised from 60 ° C. to 120 ° C., and after the temperature was raised, the reaction was carried out at the same temperature for 3 hours. Hydrogen bromide and the like generated on the way were absorbed in a trap containing an aqueous alkali solution.
[0049]
After completion of the reaction, the flask was cooled to room temperature, and 200 mL of methanol was gradually added. At this time, a large amount of hydrogen bromide, methyl bromide, methyl borate and the like generated were recovered by a trap cooled to -78 ° C, an alkali trap and the like. Then, after washing with acetonitrile, volatile components were removed at 60 ° C. under a high vacuum to obtain 25.3 g of 2,3,7,8,12,13-hexahydroxyturqusene (the following formula) crystals.
[0050]
Embedded image

[0051]
(Synthesis example 2)
Synthesis of 2,3,6,7,10,11-hexahydroxytriphenylene
460 g of ferric sulfate hexahydrate and 200 mL of ion-exchanged water were placed in an ice-cooled 2 L three-necked flask, and after dissolution, 59.0 g of 1,2-dimethoxybenzene was added. Thereafter, 900 mL of concentrated sulfuric acid was gradually added under water cooling. After 24 hours, the mixture was gradually poured into 10 L of ice water, and after 5 hours, the reaction mixture was filtered to obtain 50.1 g of crude crystals of 2,3,6,7,10,11-hexamethoxytriphenylene.
In a 3 L three-necked flask equipped with a stirrer and a reflux condenser containing 900 mL of toluene, 50.1 g of the obtained crude 2,3,6,7,10,11-hexamethoxytriphenylene crystal was added and suspended. While cooling, 300 g of boron tribromide was gradually added. Next, the temperature of the flask was gradually raised from 60 ° C. to 120 ° C., and after the temperature was raised, a reaction was performed at the same temperature for 3 hours. Hydrogen bromide and the like generated on the way were absorbed in a trap containing an aqueous alkali solution.
After completion of the reaction, the flask was cooled to room temperature, and 200 mL of methanol was gradually added. At this time, a large amount of hydrogen bromide, methyl bromide, methyl borate and the like generated were recovered by a trap cooled to -78 ° C, an alkali trap and the like. Then, volatiles were removed at 60 ° C. under a high vacuum, washed with a mixed solvent of acetonitrile and dichloromethane, and 30.1 g of 2,3,6,7,10,11-hexahydroxytriphenylene (the following formula) crystals were obtained. Obtained.
[0052]
Embedded image

[0053]
(Synthesis example 3)
Synthesis of 4- [7- (3-ethyl-3-oxetanyl) -1,6-dioxaheptyl] benzoic acid
A 2 L three-necked flask was charged with 46.3 g of OXT-101 (3-hydroxymethyl-3-ethyloxetane), 250.3 g of 1,4-dibromobutane, and 375 mL of hexane, and 2 g of tetra-n. 500 mL of a 33% aqueous sodium hydroxide solution containing -butylammonium bromide was added, and the mixture was stirred for 5 hours. Then, after further refluxing at 80 ° C. for 1 hour, 500 mL of deionized water was added, the layers were separated, and the aqueous layer was extracted three times with 160 mL of hexane. After the organic layer and the extract layer were combined and dried over magnesium sulfate, the solvent was distilled off under reduced pressure. The resulting clear liquid was further distilled under reduced pressure to obtain 4-4.5 g of 3-[(4-bromobutoxy) methyl] -3-ethyloxetane as a fraction at 109 ° C./4 mmHg (532 Pa). The structure of the obtained compound is¹Confirmed by 1 H-NMR.
In a 1 L three-necked flask, 3-[(4-bromobutoxy) methyl] -3-ethyloxetane {40 g, ethyl p-hydroxybenzoate} 26.7 g, and potassium carbonate 24.1 g were added, and 250 mL of dimethylformamide was added. The solution is kept cloudy and heated to 80 ° C. and stirred for 4 hours, the solvent is distilled off under reduced pressure and then under vacuum (80 ° C.). A solution of 10 g of sodium hydroxide dissolved in 75 mL of deionized water and 75 mL of methanol is added to the obtained yellow oil, and the mixture is refluxed for 2 and a half hours. 1N hydrochloric acid was added until the pH became about 3, and the precipitated white precipitate was filtered and dried in vacuo to give 4- [7- (3-ethyl-3-oxetanyl) -1,6-dioxaheptyl] benzoic acid. 44.1 g were obtained.
[0054]
(Synthesis example 4)
Synthesis of 4- (6-acryloyloxyhexyloxy) benzoic acid chloride
In a 1 L three-necked flask, 66 g of ethyl p-hydroxybenzoate, 108 g of 6-bromohexanol, 82 g of potassium carbonate and 400 mL of N, N-dimethylformamide were put, and stirred at 120 ° C. for 5 hours. After stirring and cooling, the reaction mixture was poured into 1 L of water, extracted with 1 L of ethyl acetate, and washed twice with 200 mL of water. After drying over anhydrous magnesium sulfate, filtration was performed. After the solvent was concentrated under reduced pressure, it was dissolved in 300 mL of methanol, and 80 mL of a methanol solution of 34 g of potassium hydroxide was gradually added dropwise, followed by heating under reflux for 2 hours. After cooling, the crystals formed were filtered off and the crystals were dissolved in 1 L of water. 70 mL of concentrated hydrochloric acid was added, and the precipitated crystals were filtered under reduced pressure and washed with deionized water. The crystals were dried to obtain 95.3 g of 4- (6-hydroxyhexyloxy) benzoic acid. In a 300 mL three-necked flask equipped with a stirrer and a reflux condenser, 23.8 g of the obtained 4- (6-hydroxyhexyloxy) benzoic acid, 100 mL of dioxane, and 14.5 g of N, N-dimethylaniline were added, and the temperature was raised to 50 ° C. While warming and stirring, a solution of 10.9 g of acrylic acid chloride and 50 mL of dioxane was successively added over 30 minutes. After the addition, the mixture was further heated and stirred at 50 ° C. for 2 hours, and then the reaction solution was poured into 1 L of deionized water to precipitate crystals. This precipitate was filtered, washed with 200 mL of hexane and dried to obtain 25.0 g of 4- (6-acryloyloxyhexyloxy) benzoic acid.
25.0 g of 4- (6-acryloyloxyhexyloxy) benzoic acid obtained above and 50 ml of thionyl chloride were placed in a 500 ml three-necked flask, and the mixture was refluxed for 2 hours. After completion of the reaction, excess thionyl chloride was distilled off under reduced pressure by attaching an alkali trap, washed with 200 ml of hexane and dried to obtain 25.3 g of 4- (6-acryloylhexyloxy) benzoic acid chloride. Since this acid chloride is thermally unstable and difficult to purify, it was used without purification.
[0055]
(Synthesis example 5)
Synthesis of Discotic Liquid Crystalline Turksene Derivatives Linked with Oxetanyl Groups
In a 1-L three-necked flask equipped with a stirrer and a condenser, 17.3 g of 2,3,7,8,12,13-hexahydroxyturqusene obtained in Synthesis Example 1 and 26.1 g of 4-nonyloxybenzoic acid (reagent) were obtained. 36.5 g of 4- [7- (3-ethyl-3-oxetanyl) -1,6-dioxaheptyl] benzoic acid obtained in Synthesis Example 3 and 5.6 g of stearic acid (reagent), 4-dimethylaminopyridine 5.8 g and 400 mL of dichloromethane were put therein, and a solution of 51.3 g of dicyclohexylcarbodiimide dissolved in 200 mL of dichloromethane was gradually added at room temperature, followed by stirring reaction for 24 hours.
The resulting solid was separated by filtration, and the filtrate was washed with 500 mL of 1 N hydrochloric acid, 500 mL of a saturated aqueous solution of sodium hydrogencarbonate and 500 mL of a saturated aqueous solution of sodium chloride, dried over anhydrous magnesium sulfate, and evaporated to remove the solvent. 65.0 g of a tolcene derivative (following formula) was obtained. Of the obtained torquesen derivative¹H-NMR analysis confirmed that the composition had the composition as charged. This torcene derivative exhibits a nematic and discotic (ND) phase at a temperature of 60 ° C. or higher, and the ND phase was present at least up to 150 ° C., but at a temperature higher than this, the alteration of the torcene derivative seems to have occurred. The isotropic phase transition temperature could not be confirmed.
[0056]
Embedded image

[0057]
(Synthesis example 6)
Synthesis of discotic liquid crystalline triphenylene derivatives with oxetanyl groups
In a 1 L three-necked flask equipped with a stirrer and a condenser, 10.0 g of 2,3,6,7,10,11-hexahydroxytriphenylene obtained in Synthesis Example 2, 4- [7- (3-ethyl-3-oxetanyl) [-1,6-dioxaheptyl] benzoic acid (57.1 g), 4-dimethylaminopyridine (4.5 g) and dichloromethane (300 mL) were added, and a solution of dicyclohexylcarbodiimide (40.1 g) in dichloromethane (250 mL) was gradually added at room temperature. A stirring reaction was carried out day and night.
The generated solid was separated by filtration, and the filtrate was washed with 1N hydrochloric acid (250 mL), a saturated aqueous solution of sodium hydrogencarbonate (250 mL) and a saturated aqueous solution of sodium chloride (250 mL), dried over anhydrous magnesium sulfate, and the solvent was distilled off to remove the oxetanyl group. 47.5 g of a triphenylene derivative (following formula) was obtained. Product¹From H-NMR analysis, it was found that hydrogen based on the hydroxyl group bonded to triphenylene disappeared, and the same number of oxetanyl groups were bonded instead.
[0058]
Embedded image

[0059]
(Synthesis example 7)
Synthesis of Discotic Liquid Crystalline Triphenylene Derivative with Acryloyl Group
The same three-necked flask as in Synthesis Example 6 was charged with 10.0 g of 2,3,7,8,10,11-hexahydroxytriphenylene, 19.7 g of triethylamine and 400 mL of 1,2-dimethoxyethane, and obtained in Synthesis Example 4. A solution of 57.5 g of 4- (6-acryloylhexyloxy) benzoic acid chloride in 200 mL of 1,2-dimethoxyethane was gradually added at 50 ° C., and the mixture was stirred at the same temperature for 3 hours. After cooling, 500 mL of methyl ethyl ketone and 200 mL of a saturated aqueous solution of sodium hydrogencarbonate were added, the layers were separated, the organic layer was dried over anhydrous magnesium sulfate, the solvent was distilled off, and the liquid crystalline triphenylene derivative (the following formula) body 45 bonded with an acryloyl group was removed. .1 g were obtained.
[0060]
Embedded image

[0061]
[Example 1]
All steps up to ultraviolet irradiation were performed under red light for silver salt photography.
Dissolve 2.5 g of the liquid-crystalline tolcene derivative having an oxetanyl group obtained in Synthesis Example 5 in 25 ml of 1,1,2,2-tetrachloroethane, and use a 50% propylene carbonate solution of triallylsulfonium hexafluoroantimonate (Aldrich). After adding 0.2 g of a reagent (manufactured by the company), insoluble components were filtered through a polytetrafluoroethylene filter having a pore size of 0.45 μm to prepare a liquid crystal composition solution.
This solution was applied on a 50 μm-thick polyethylene naphthalate film (PEN) having a surface rubbed with a rayon cloth by using a spin coating method, and dried on a hot plate at 60 ° C. While heating the obtained liquid crystalline composition layer on the PEN film to 100 ° C., the integrated irradiation amount was 450 mJ / cm by a high-pressure mercury lamp in an air atmosphere.², And then cooled and cured to obtain a liquid crystalline composition layer (liquid crystal film).
[0062]
Since the PEN film used as the substrate has a large birefringence and is not preferable as an optical film, the obtained liquid crystal film is coated with triacetyl cellulose (UVA) by an ultraviolet curable adhesive UV-3400 (manufactured by Toagosei Co., Ltd.). (TAC) film to obtain an optical film a. That is, UV-3400 is applied to a thickness of 5 μm on the polymerized liquid crystalline composition layer on the PEN film, laminated with a TAC film, and 400 mJ / cm from the TAC film side.²After the adhesive was cured by irradiating ultraviolet light, the PEN film was peeled off to obtain an optical film a of the present invention.
[0063]
When the obtained optical film a is observed under a polarizing microscope, a monodomain uniform nematic liquid crystal alignment without disclination or the like is observed. When viewed from the front, the same retardation (60 nm) as uniaxial nematic alignment is observed. However, when observed obliquely along the rubbing direction, the apparent retardation shows different values depending on the tilting direction, and the liquid crystal composition layer has a hybrid orientation in which the orientation inclination is changed in the thickness direction. I knew it was there. Further, only the liquid crystal composition layer portion of the optical film a was scraped off, and the glass transition point (Tg) was measured by using DSC. As a result, Tg was 105 ° C. The pencil hardness of the surface of the liquid crystal composition layer of the optical film a was about H, and a sufficiently strong film was obtained.
Using two optical films a, compensation was performed for a 90-degree twisted liquid crystal cell (TN type liquid crystal cell) having a TFT electrode in the arrangement shown in FIG. As a result, it was found that a display with a remarkably wide viewing angle was obtained as compared with the case where the optical film a was not provided.
[0064]
[Example 2]
An optical film b was obtained in the same manner as in Example 1, except that the liquid crystal triphenylene derivative bonded with an oxetanyl group obtained in Synthesis Example 6 was used instead of the tolcene derivative of Example 1.
When the obtained optical film b was observed under a polarizing microscope, monodomain uniform nematic liquid crystal alignment without disclination and the like was observed, and the retardation was 103 nm. Further, only the liquid crystal composition layer portion of the optical film b was scraped off, and the glass transition point (Tg) was measured by using DSC. As a result, Tg was 110 ° C. The pencil hardness of the liquid crystal composition layer surface of the optical film b was about H, and a sufficiently strong film was obtained.
[0065]
[Comparative Example 1]
The liquid crystalline triphenylene derivative bound to the acryloyl group obtained in Synthesis Example 7 was used as a 10% by mass solution in methyl ethyl ketone, and as a photopolymerization initiator, Michler's ketone + benzophenone (1 : 1 mass ratio). An optical film c was obtained in the same manner as in Example 1 except that the solution was used.
When the obtained optical film c was observed under a polarizing microscope, monodomain uniform nematic liquid crystal alignment without disclination was observed, and its retardation was 110 nm. Further, only the liquid crystal composition layer portion of the optical film c was scraped off, and the glass transition point (Tg) was measured by using DSC. The pencil hardness of the surface of the liquid crystal composition layer of the optical film c was about B to 2B.
[0066]
[Example 3]
The optical films a to c obtained in Examples 1 and 2 and Comparative Example 1 were cut into a size of 10 cm × 10 cm, and bonded to a washed glass plate with an adhesive such that the TAC film surface was on the glass plate side, After standing in a high-temperature bath at 80 ° C. for one week, the degree of change was checked. As a result, no change was observed in the optical films a and b, but the surface of the optical film c was deteriorated.
From this, it is considered that the optical film c was cross-linked in the air and thus did not undergo sufficient crosslinking due to oxygen inhibition, which appeared as a result of a low Tg by DSC and a decrease in heat resistance by this test.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a liquid crystal display device used in Example 1.
[Explanation of symbols]
1: Upper polarizing plate
2: Optical film a
3: Triacetyl cellulose film with adhesive
4: TN type liquid crystal cell
5: Lower polarizing plate
6, 10: transmission axis of polarizing plate
7: Direction corresponding to the rubbing direction of polyethylene naphthalate film
8, 9: rubbing direction of electrode substrate

Claims (4)

An optical film comprising a discotic liquid crystalline compound having an oxetanyl group, wherein an alignment state formed in a liquid crystal state of the compound is cross-linked and fixed by light and / or heat. 2. The optical film according to claim 1, wherein the alignment of the discotic liquid crystalline compound is a hybrid alignment. An optical compensator comprising at least one optical film according to claim 1. A liquid crystal display device comprising at least one optical compensation element according to claim 3 incorporated therein.

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