JP2004331888A - Composition for orientation film, method for producing orientation film and optical element produced by using the film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composition for an orientation film giving a highly solvent-resistant orientation film resisting the dissolution with a solvent present in a liquid crystal composition for forming a liquid crystal layer in the production of an optical element by forming a liquid crystal layer on an orientation film and provide a durable optical element produced by using the composition for orientation film. <P>SOLUTION: The composition for an orientation film is used in the production of an optical element composed of a substrate, an orientation film and an optical function layer composed of a liquid crystal compound. The composition for an orientation film at least contains (A) a polymer, (B) a monomer or an oligomer having ethylenically unsaturated bond and (C) a non-aqueous solvent in an amount of ≥70 mass% and ≤100 mass%. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００２４】
（式中、Ｒ^１ は、水素原子、ハロゲン原子又は炭素原子が１〜６のアルキル基であり、Ｒ^２ は、脂肪族環基、方向族環基又は複素環基である。）
で表される繰り返し単位を含むポリマー、あるいは、次の一般式（２）
【００２５】
【化５】

【００２６】
（式中、Ｒ^３ は、脂肪族環基、方向族環基又は複素環基である。）
で表される繰り返し単位を含むポリマー、あるいは、次の化学式
【００２７】
【化６】

【００２８】
に示される基の少なくとも１種を構成単位として有するポリカーボネート、ポリエステル、またはポリウレタンが挙げられる。
【００２９】
一般式（１）で表される繰り返し単位を含むポリマーの中で、Ｒ^２ が芳香族基であるポリマーは芳香族基を側鎖として有するビニルモノマーの重合により合成することができる。芳香族基を側鎖として有するビニルモノマーのホモポリマーでも、芳香族基を側鎖として有するビニルモノマーと他のモノマーとのコポリマーでもよい。
【００３０】
芳香族基を側鎖として有するビニルモノマーとしては、スチレン類、ビニルナフタレン類、ビニルアントラセン類、ビニルピレン類、ビニルビフェニル類、ビニルカルバゾール類、ビニルピリジン類、ビニルイミダゾール類、ビニルインドール類、ビニルインドリン類、ビニルイソインドール類、ビニルベンゾイミダゾール類、ビニルピリミジン類等が挙げられ、これらのモノマーの芳香族基は置換基を有していてもよい。置換基の例には、アルキル基（例、メチル、エチル、ｔ−ブチル）、置換アルキル基（例、クロロメチル、ヒドロキシメチル、塩化トリメチルアンモニオ）、アルコキシ基（例、メトキシ、エトキシ）、ハロゲン原子（Ｆ、Ｃｌ、Ｂｒ）、カルボキシル基、アシル基（例、ホルミル）、アミノ基、スルホ基、アリール基（例、フェニル）、アリールオキシ基（例、フェノキシ）及びオキソが含まれる。
【００３１】
本発明の配向膜用組成物に含まれる前記ポリマーはエチレン性不飽和結合を有していてもよい。ポリマーがエチレン性不飽和結合を有していることにより、配向膜の耐溶剤性がさらに向上する利点がある。
【００３２】
エチレン性不飽和結合を有するモノマーあるいはオリゴマー
本発明の配向膜用組成物のＢ成分としてのモノマーあるいはオリゴマーは、分子中にエチレン性不飽和結合を複数有するモノマーあるいはオリゴマーであることが望ましい。
【００３３】
ポリマーに対しエチレン性不飽和結合を有するモノマーあるいはオリゴマーの１種または２種以上を添加して配向膜用組成物とすることにより、該配向膜用組成物を用いて形成された配向膜は、ポリマーに不足している性質、即ち、支持体又は光学機能層に対して密着性を高める性質、耐熱・耐溶剤性向上を必要な分だけ付与することができる。
【００３４】
エチレン性不飽和結合を有するモノマーあるいはオリゴマーは、非水系溶剤に可溶であればよく、分子中のエチレン性不飽和結合の数が、１個でも複数でもかまわない。
【００３５】
エチレン性不飽和結合を有するモノマーあるいはオリゴマーとしては、ポリエチレングリコールモノ（メタ）アクリレート、ポリプロピレングリコールモノ（メタ）アクリレート、フェノキシエチル（メタ）アクリレート、等の単官能のアクリレートやメタアクリレート；ポリエチレングリコールジ（メタ）アクリレート、トリメチロールエタントリ（メタ）アクリレート、ネオペンチルグリコールジ（メタ）アクリレート、ペンタエリスリトールトリ（メタ）アクリレート、ペンタエリスリトールテトラ（メタ）アクリレート、ジペンタエリスリトールヘキサ（メタ）アクリレート、ヘキサンジオール（メタ）アクリレート、トリメチロールプロパントリ（アクリロイルオキシプロピル）エーテル、トリ（アクリロイロキシエチル）イソシアヌレート、グリセリンやトリメチロールエタン等の多官能アルコールにエチレンオキサイドやプロピレンオキサイドを付加させた後（メタ）アクリレート化したもの、ウレタンアクリレート類、ポリエステルアクリレート類、エポキシ樹脂と（メタ）アクリル酸の反応生成物であるエポキシアクリレート類等の多官能のアクリレートやメタアクリレートを挙げることが出来る。
【００３６】
エチレン性不飽和結合が分子内に複数あるモノマーあるいはオリゴマーは配向膜の紫外線照射または電子線照射による硬化過程において十分に架橋し、網目状のマトリックスを形成するために耐熱性および耐溶剤性が向上するので有利である。
【００３７】
光学機能層を形成する材料が、重合性液晶化合物であるエチレン性不飽和結合含有液晶化合物の場合、配向膜中のエチレン性不飽和結合を有するモノマー、オリゴマー、あるいは配向膜が硬化の過程で形成される架橋したポリマーは、配向膜と光学機能層との界面において親和性を上げ、両塗膜の密着性を高める。
【００３８】
溶剤
本発明の配向膜用組成物に含まれる非水系溶剤とは水及び／又は低級アルコール（即ち、メタノールあるいはエタノール）以外の溶剤をいい、ケトン（例、メチルエチルケトン、メチルイソブチルケトン、シクロヘキサノン）、炭化水素（例、ベンゼン、ヘキサン、エーテル（例、テトラヒドロフラン、１，２−ジメトキシエタン）、アルキルハライド（例、クロロホルム、ジクロロメタン）、エステル（例、酢酸メチル、酢酸ブチル、プロピレングリコールモノメチルエーテルアセテート）、アミド（例、Ｎ、Ｎ−ジメチルホルムアミド）、スルホキシド（例、ジメチルスルホキシド）、アルコール（例、イソプロピルアルコール）等が挙げられる。本発明に用いる溶剤は非水系溶剤を７０質量％以上１００質量％以内を含む溶剤であり、本発明に用いる溶剤は非水系溶剤に加えて、水及び／又は低級アルコールを３０質量％未満含んでいてもよい。
【００３９】
光重合開始剤
本発明の配向膜は紫外線照射又は電子線照射により硬化させるものである。電子線照射による硬化では特に光重合開始剤は必要ではないが、紫外線照射による硬化を行う場合には光重合開始剤を配向膜用組成物に含む方が、低照射量で硬化反応が進行するために好ましい。
【００４０】
本発明の配向膜用組成物に含まれる光重合開始剤としては、ベンジル（ビベンゾイルとも言う）、ベンゾインイソブチルエーテル、ベンゾインイソプロピルエーテル、ベンゾフェノン、ベンゾイル安息香酸、ベンゾイル安息香酸メチル、４−ベンゾイルー４’−メチルジフェニルサルファイド、ベンジルメチルケタール、ジメチルアミノメチルベンゾエート、２−ｎ−ブトキシエチル−４−ジメチルアミノベンゾエート、ｐ−ジメチルアミノ安息香酸イソアミル、３、３’−ジメチル−４−メトキシベンゾフェノン、メチロベンゾイルフォーメート、２−メチル−１−（４−（メチルチオ）フェニル）−２−モルフォリノプロパン−１−オン、２−ベンジル−２−ジメチルアミノ−１−（４−モルフォリノフェニル）−ブタン−１−オン、１−（４−ドデシルフェニル）−２ヒドロキシ−２−メチルプロパン−１−オン、１−ヒドロキシシクロヘキシルフェニルケトン、２−ヒドロキシ−２−メチル−１フェニルプロパン−１−オン、１−（４−イソプロピルフェニル）−２−ヒドロキシ−２−メチルプロパン−１−オン、２−クロロチオキサントン、２，４−ジエチルチオキサントン、２，４−ジイソプロピルチオキサントン、２，４−ジメチルチオキサントン、イソプロピルチオキサントン、１−クロロ−４−プロポキシチオキサントン等を挙げることができる。なお、光重合開始剤の他に増感剤を、本発明の目的が損なわれない範囲で添加することもできる。
【００４１】
このような光重合開始剤の添加量としては、配向膜用組成物の全固形分に対して一般的には０〜２０質量％、好ましくは０．１〜１０質量％、より好ましくは、０．５〜５質量％の範囲である。
【００４２】
配向膜の製造
本発明における配向膜の製造には、（１）請求項１乃至７の何れか１項に記載の配向膜用組成物を支持体上に塗布、乾燥する工程、（２）得られた塗布膜に紫外線または電子線を照射して硬化させる工程、（３）前記工程（１）の後、又は前記工程（２）の後にラビングを行う工程、が必須である。
【００４３】
ラビングを行う工程を前記工程（１）の後に行うか、前記工程（２）の後に行うのが好ましいかは、配向膜用組成物のポリマー種、エチレン性不飽和結合を有するモノマーあるいはオリゴマーの種類、及びその量により異なる。
【００４４】
エチレン性不飽和結合を有するモノマーあるいはオリゴマーが液状で、添加量が多く、配向膜用組成物を支持体上に塗布、乾燥して得られた塗布膜の表面にタックがある場合は、前記工程（２）の硬化の後にラビングを行うことが好ましい。エチレン性不飽和結合を有するモノマーあるいはオリゴマーの添加量が少ない場合や、エチレン性不飽和結合を有するモノマーあるいはオリゴマーが固体である場合には、ラビングは前記工程（１）の後、前記工程（２）の後のどちらに行ってもよい。
【００４５】
配向膜用塗布液の塗布方法としては、ワイヤーバーコーティング法、押し出しコーティング法、ダイレクトグラビアコーティング法、リバースグラビアコーティング法、スピンコート法、ロールコート法、ディップコート法、カーテンコート法、エクストルージョンコート法、バーコート法およびＥ型塗布法等を挙げることができる。
【００４６】
形成された配向膜の膜厚は、０．１μｍ〜１０μｍの範囲にあることが好ましい。配向膜用組成物を塗布した後、溶剤を乾燥して除去する方法としては、例えば、減圧乾燥もしくは加熱乾燥、さらにはこれらの乾燥を組み合わせる方法等により行う。
【００４７】
液晶性化合物からなる光学機能層から構成される光学素子を作製する場合に使用する配向膜には、光学機能層を形成する際の溶剤に対する耐性が要求されるが、本発明の配向膜は紫外線または電子線の照射により硬化されたものであるので、耐溶剤性が向上する。
【００４８】
支持体
支持体の種類は、目的とする光学素子（支持体、配向膜および光学機能層の積層体）の用途に応じて決定するが、透明ポリマーフィルム、透明ガラス基板等が用いられる。光学素子を、位相差板、偏光素子、ノッチフィルター等の光学補償シートとして用いる場合、支持体としては透明ポリマーフイルムが通常用いられる。透明ポリマーフイルムは、光学的異方性が小さいことが好ましい。透明であるとは、光透過率が８０％以上であることを意味する。
【００４９】
透明ポリマーフィルムの例としては、セルロース系ポリマー、商品名アートン（ＪＳＲ（株）製）および商品名ゼオネックス（日本ゼオン（株）製）などのノルボルネン系ポリマー、商品名ゼオノア（日本ゼオン（株）製）等のシクロオレフィン系ポリマーおよびポリメチルメタクリレートなどが挙げられる。セルロース系ポリマーとしては、セルロースエステルが好ましく、セルロースの低級脂肪酸エステルがさらに好ましい。低級脂肪酸とは、炭素原子数が６以下の脂肪酸を意味する。炭素原子数は、２（セルロースアセテート）、３（セルロースプロピオネート）または４（セルロースブチレート）であることが好ましい。セルロースエステルとしてはセルロースアセテートが好ましく、その例としては、ジアセチルセルロースおよびトリアセチルセルロースなどが挙げられる。セルロースアセテートプロピオネートやセルロースアセテートブチレートのような混合脂肪酸エステルを用いても良い。
【００５０】
目的とする光学素子に光学的等方性が要求される場合は、支持体としては一般にガラスまたはセルロースエステルが用いられる。光学的異方性が要求される場合は、一般に合成ポリマー（例、ポリカーボネート、ポリスルホン、ポリエーテルスルホン、ポリアクリレート、ポリメタクリレート、ノルボルネン樹脂）が用いられる。合成ポリマーフイルムを延伸することによって、光学的異方性を得ることができる。
【００５１】
支持体をセルロースエステルまたは合成ポリマーのフイルムとする場合には、ソルベントキャスト法により形成することが好ましい。位相差板の支持体の厚さは、２０μｍ乃至５００μｍであることが好ましく、５０μｍ乃至２００μｍであることがさらに好ましい。位相差板の支持体とその上に設けられる層（配向膜、光学機能層）との密着性を改善するため、透明支持体に表面処理（例、グロー放電処理、コロナ放電処理、紫外線（ＵＶ）処理、火炎処理）を実施してもよく、プライマー層（接着剤層）、保護層を形成してもよい。
【００５２】
光学機能層
本発明の光学素子は、支持体上に配向膜、さらにその上に光学機能層が形成された構造を有している。光学機能層としては、ネマチック規則性又はスメクチック規則性又はコレステリック規則性を有する液晶であれば特に限定されるものではなく、ポリマー液晶および重合性液晶化合物のどちらでもよい。重合性液晶化合物としては、分子の両末端に重合性官能基があることが耐熱性のよい光学素子を得る上で好ましい。光学機能層は二層以上積層されていてもよい。本発明の配向膜はディスコチック液晶を配向させることもできる。
【００５３】
光学機能層を形成するには、重合性液晶モノマーを用いてもよく、あるいは、重合性液晶オリゴマーや重合性液晶ポリマー等を用いることも可能である。このような重合性液晶オリゴマーや重合性液晶ポリマーとしては、従来提案されているＵＶ硬化型液晶や高分子液晶を適宜選択して用いることが可能である。
【００５４】
光学機能層は、高分子液晶の場合、高分子液晶及び他の化合物を溶剤に溶解した溶液を配向膜上に塗布し、乾燥し、次いで液晶相形成温度まで加熱し、その後配向状態を維持して冷却することにより得られる。
【００５５】
このような高分子液晶の一例としては、例えば下記の一般式（３）で表される繰返し単位を有するポリマーを挙げることができる。
【００５６】
【化７】

【００５７】
（式中、Ｒ^１１は、水素原子又はメチル基を、Ｘ^１ は−ＣＯＯ−基又は−ＯＣＯ−基を、ａは１〜６の正の整数を、ｂ及びｃはそれぞれ独立に１又は２（ただし、ｂ＋ｃ≦３を満足する。）を示す。）
【００５８】
重合性液晶化合物の場合には重合性液晶化合物及び他の化合物（更に、例えば重合性モノマー、光重合開始剤）を溶剤に溶解した溶液を配向膜上に塗布し、乾燥し、次いで液晶相形成温度まで加熱したのちＵＶ照射、または電子線照射により重合させ、さらに冷却することにより光学機能層を得る。
【００５９】
このような重合性液晶化合物の一例としては、例えば下記の一般式（４）及び一般式（５）で表わされる化合物（化合物（Ｉ）という）や下記に示す化合物を挙げることができる。化合物（Ｉ）としては、一般式（４）及び一般式（５）に包含される化合物の２種を混合して使用することも可能である。
【００６０】
【化８】

【００６１】
【化９】

【００６２】
【化１０】

【００６３】
一般式（４）、一般式（５）において、Ｒ^１２、Ｒ^１３、Ｒ^１４及びＲ^１５はそれぞれ水素又はメチル基を示すが、液晶相を示す湿度範囲の広さからＲ^１２、Ｒ^１３、Ｒ^１４及びＲ^１５は共に水素であることが好ましい。Ｘ^２ 及びＸ^３ は水素、塩素、臭素、ヨウ素、炭素数１〜４のアルキル基、メトキシ基、シアノ基、ニトロ基のいずれであっても差し支えない。また、化合物（Ｉ）の分子鎖両端の（メタ）アクリロイルオキシ基と、芳香環とのスペーサーであるアルキレン基の鎖長を示すｄ、ｅ、ｆ及びｇは、それぞれ個別に２〜１２の範囲で任意の整数を取り得るが、４〜１０の範囲であることが好ましい。
【００６４】
本発明においては、また、ネマチック液晶にカイラル剤を加えた、コレステリック規則性を有するカイラルネマチック液晶を、好適に使用することができる。カイラル剤としては、光学活性な部位を有する低分子化合物であり、分子量１５００以下の化合物を意味する。カイラル剤は主として化合物（Ｉ）が発現する正の一軸ネマチック規則性に螺旋ピッチを誘起させる目的で用いられる。この目的が達成される限り、化合物（Ｉ）や上記の化合物と、溶液状態あるいは溶融状態において相溶し、上記ネマチック規則性をとりうる重合性液晶化合物の液晶性を損なうことなく、これに所望の螺旋ピッチを誘起できるものであれば、下記に示すカイラル剤としての低分子化合物の種類は特に限定されないが、分子の両末端に重合性官能基があることが耐熱性のよい光学素子を得る上で好ましい。液晶に螺旋ピッチを誘起させるために使用するカイラル剤は、少なくとも分子中に何らかのキラリティーを有していることが必須である。従って、本発明で使用可能なカイラル剤としては、例えば１つあるいは２つ以上の不斉炭素を有する化合物、キラルなアミン、キラルなスルフォキシド等のようにヘテロ原子上に不斉点がある化合物、あるいはクムレン、ビナフトール等の軸不斉を持つ化合物が例示できる。さらに具体的には、市販のカイラルネマチック液晶、例えばＭｅｒｃｋ社製Ｓ−８１１（商品名）等が挙げられる。
【００６５】
しかし、選択したカイラル剤の性質によっては、化合物（Ｉ）が形成するネマチック規則性の破壊、配向性の低下、あるいは該化合物が非合重合性の場合には、液晶組成物の硬化性の低下、硬化フィルムの信頼性の低下を招く恐れがある。さらに、光学活性な部位を有するカイラル剤の多量使用は、組成物のコストアップを招く。従って、短ピッチのコレステリック規則性を有する円偏光制御光学素子を製造する場合には、液晶組成物に含有させる光学活性な部位を有するカイラル剤には、螺旋ピッチを誘発する効果の大きなカイラル剤を選択することが好ましく、具体的には一般式（６）、（７）または（８）で表されるような分子内に軸不斉を有する低分子化合物（ＩＩ）の使用が好ましい。
【００６６】
【化１１】

【００６７】
【化１２】

【００６８】
【化１３】

【００６９】
カイラル剤（ＩＩ）を表す一般式（６）、（７）又は、（８）において、Ｒ^１６は水索又はメチル基を示す。Ｙは上記に示す式（ｉ）〜（ｘｘｉｖ）の任意の一つであるが、なかでも、式（ｉ）、（ｉｉ）、（ｉｉｉ）、（ｖ）及び（ｖｉｉ）の何れか一つであることが好ましい。また、アルキレン基の鎖長を示すｈ及びｊは、それぞれ個別に２〜１２の範囲で任意の整数をとり得るが、４〜１０の範囲であることが好ましく、６〜１０の範囲であることがさらに好ましい。ｈ又はｊの値が０又は１である一般式（６）又は（７）で表される化合物は、安定性に欠け、加水分解を受けやすく、結晶性も高い。一方、ｈ又はｊの値が１３以上である化合物は融点（Ｔｍ）が低い。これらの化合物は液晶性を示す化合物（Ｉ）との相溶性が低下し、濃度によっては相分離等が起こるおそれがある。
【００７０】
本発明における重合性液晶化合物に配合されるカイラル剤の量は、螺旋ピッチ誘起能力や最終的に得られる光学素子のコレステリック性を考慮して最適値が決められる。具体的には、用いる重合性液晶化合物により大きく異なるものではあるが、重合性液晶化合物の合計量１００質量部当り、０．０１から６０質量部、最も好ましくは１〜２０質量部の範囲で選ばれる。この配合量が上記範囲を超える場合は、分子の配向が阻害され、活性放射線によって硬化させる際に悪影響を及ぼす危惧がある。少ない場合は、充分なコレステリック性を付与できない場合がある。
【００７１】
本発明において、このようなカイラル剤としては、特に重合性を有することが必須ではない。しかしながら、得られる光学機能層の熱安定性等を考慮すると、上述した重合性液晶化合物と重合し、コレステリック規則性を固定化することが可能な重合性のカイラル剤を用いることが好ましい。特に、分子の両末端に重合性官能基があることが、耐熱性のよい光学素子を得る上で好ましい。
【００７２】
重合性液晶化合物に添加される光重合開始剤としては、ベンジル、ベンゾインイソブチルエーテル、ベンゾインイソプロピルエーテル、ベンゾフェノン、ベンゾイル安息香酸、ベンゾイル安息香酸メチル、４−ベンゾイルー４’−メチルジフェニルサルファイド、ベンジルメチルケタール、ジメチルアミノメチルベンゾエート、２−ｎ−ブトキシエチル−４−ジメチルアミノベンゾエート、ｐ−ジメチルアミノ安息香酸イソアミル、３、３’−ジメチル−４−メトキシベンゾフェノン、メチロベンゾイルフォーメート、２−メチル−１−（４−（メチルチオ）フェニル）−２−モルフォリノプロパン−１−オン、２−ベンジル−２−ジメチルアミノ−１−（４−モルフォリノフェニル）−ブタン−１−オン、１−（４−ドデシルフェニル）−２ヒドロキシ−２−メチルプロパン−１−オン、１−ヒドロキシシクロヘキシルフェニルケトン、２−ヒドロキシ−２−メチル−１フェニルプロパン−１−オン、１−（４−イソプロピルフェニル）−２−ヒドロキシ−２−メチルプロパン−１−オン、２−クロロチオキサントン、２，４−ジエチルチオキサントン、２，４−ジイソプロピルチオキサントン、２，４−ジメチルチオキサントン、イソプロピルチオキサントン、１−クロロ−４−プロポキシチオキサントン等を挙げることができる。なお、光重合開始剤の他に増感剤を、本発明の目的が損なわれない範囲で添加することもできる。
【００７３】
このような光重合開始剤の添加量としては、一般的には０．０１〜２０質量％、好ましくは０．１〜１０質量％、より好ましくは、０．５〜５質量％の範囲で重合性液晶化合物に添加することができる。
【００７４】
光学機能層を形成するためのコーティング液には、上記液晶性化合物、カイラル剤、光重合開始剤以外に、界面活性剤、重合性モノマー（例えば、ビニル基、ビニルオキシ基、アクリロイル基及びメタクリロイル基を有する化合物）、及びポリマーを液晶性化合物の配向を阻害しない限り添加してもよい。これらの界面活性剤、重合性モノマー及びポリマーを選択することにより表面側（空気側）の液晶の傾斜角を調整することができる。
【００７５】
また、光学機能層を形成するためのコーティング液に用いられる溶剤としては、上記液晶性化合物、カイラル剤が溶解し、かつ配向性を有する基材上の配向性を阻害しなければ特に限定されるものではない。具体的にはケトン（例、メチルエチルケトン、メチルイソブチルケトン、シクロヘキサノン）、炭化水素（例、ベンゼン、ヘキサン）、エーテル（例、テトラヒドロフラン、１，２−ジメトキシエタン）、アルキルハライド（例、クロロホルム、ジクロロメタン）、エステル（例、酢酸メチル、酢酸ブチル、プロピレングリコールモノメチルエーテルアセテート）、アミド（例、Ｎ，Ｎ−ジメチルホルムアミド）、スルホキシド（例、ジメチルスルホキシド）等が挙げられる。
【００７６】
光学素子
図１に本発明の光学素子の一般的な層構成を示す。図１において１は支持体、２は支持体１上に形成された配向膜、３は配向膜２上に形成された液晶性化合物からなる光学機能層である。このような積層構造の光学素子には、位相差板、偏光素子が挙げられる。
【００７７】
光学素子の製造
本発明の光学素子の製造方法は、次のようにして行うことができる。前記配向膜の製造方法により得られた支持体上に形成された配向膜上に、液晶性ポリマー及び他の化合物を溶剤に溶解した溶液を塗布し、乾燥し、次いで液晶相形成温度まで加熱し、その後配向状態を維持して冷却することにより光学機能層を形成し、光学素子を得る。あるいは、重合性液晶化合物及び他の化合物（さらに、例えば、重合性モノマー、光重合開始剤）を溶剤に溶解した溶液を上記配向膜に塗布し、乾燥し、次いで液晶相形成温度まで加熱した後、ＵＶ照射、または電子線照射により重合させ、さらに冷却することにより光学機能層を形成し、光学素子を得る。
【００７８】
本発明の光学素子は、光学機能層が一層であっても、二層以上から形成されていてもよい。本発明の光学素子を位相差板として使用した場合、位相差板と偏光板を貼り合わせる工程がある。支持体、配向膜、及び液晶性化合物からなる光学機能層からなる光学素子をそのまま位相差板として偏光板に貼り合わせてもよいし、転写により液晶性化合物からなる光学機能層を偏光板に貼り合わせてもよい。
【００７９】
【実施例】
［実施例１］
（配向膜の形成）
ポリ（ビスフェノールＡカーボネート）（Ａｌｄｒｉｃｈ社製）８質量部、ペンタエリスリトールトリアクリレート２質量部、光重合開始剤イルガキュア９０７（商品名、チバスペシャリティーケミカルズ製）０．３質量部をトルエン／シクロヘキサノン混合溶剤（容量比１／２）４０重量部に溶解した。得られた溶液をワイヤーバーコーターを用いてガラス支持体上に塗布した。塗布層を加熱乾燥後、高圧水銀灯を用いて５００ｍＪ／ｃｍ^２ の紫外線を照射して塗膜を硬化させた。その塗膜の表面をラビング処理して、配向膜を作製した。
【００８０】
（ネマチック液晶層の形成）
次の化学式（６）
【００８１】
【化１４】

【００８２】
で表される重合性液晶性化合物１０質量部をメチルイソブチルケトン４０質量部に溶解し、さらに光重合開始剤イルガキュア９０７（商品名、チバスペシャリティ−ケミカルズ製）０．５質量部を添加し、光学的異方性層形成用塗布液を得た。この塗布液を前記工程で作製した配向膜上にワイヤーバーコーターにて塗工し、乾燥後、８５℃で１分間加熱し、その温度で高圧水銀灯を用いて５０ｍＪ／ｃｍ^２ の紫外線を照射することにより配向状態を固定化した。
【００８３】
ＫＯＢＲＡ（商品名、王子計測器（株）製）により測定したところ、ネマチック液晶分子のダイレクタはラビング方向と同じ方向であり、波長５５０ｎｍにおける厚み方向のリタデーションは６５ｎｍであった。
【００８４】
［実施例２］
（配向膜の形成）
前記実施例１のポリ（ビスフェノールＡカーボネート）を次の化学式
【００８５】
【化１５】

【００８６】
で表されるポリカーボネートに変更する以外は、前記実施例１と同様にして配向膜を形成した。
【００８７】
（ネマチック液晶層の形成）
前記実施例１の配向膜を本実施例２の前記工程で得られた配向膜に変更する以外は前記実施例１と同様にしてネマチック液晶層を形成し、測定を行った。ネマチック液晶分子のダイレクタはラビング方向に対し直交方向であり、波長５５０ｎｍにおける厚み方向のリタデーションは７０ｎｍであった。
【００８８】
［実施例３］
（配向膜の形成）
前記実施例１のポリ（ビスフェノールＡカーボネート）をポリビニルカルバゾール（Ｍｗ．２００００）に変更する以外は、前記実施例１と同様にして配向膜を形成した。
【００８９】
（ネマチック液晶層の形成）
前記実施例１の配向膜を本実施例３の前記工程で得られた配向膜に変更する以外は前記実施例１と同様にしてネマチック液晶層を形成し、測定を行った。ネマチック液晶分子のダイレクタはラビング方向に対し直交方向であり、波長５５０ｎｍにおける厚み方向のリタデーションは７０ｎｍであった。
【００９０】
［実施例４］
（配向膜の形成）
前記実施例１のポリ（ビスフェノールＡカーボネート）を次の化学式
【００９１】
【化１６】

【００９２】
で表されるポリビニルカルバゾールに変更する以外は、前記実施例１と同様にして配向層を形成した。
【００９３】
（ネマチック液晶層の形成）
前記実施例１の配向膜を本実施例４の前記工程で得られた配向膜に変更する以外は前記実施例１と同様にしてネマチック液晶層を形成し、測定を行った。ネマチック液晶分子のダイレクタはラビング方向に対し直交方向であり、波長５５０ｎｍにおける厚み方向のリタデーションは７５ｎｍであった。
【００９４】
［比較例１］
（配向膜の形成）
ポリ（ビスフェノールＡカーボネート）（Ａｌｄｒｉｃｈ社製）をトルエン／シクロヘキサン混合溶剤（容量比１／２）に溶解して４質量％溶液を調製した。この溶液を、ワイヤーバーコーターを用いてガラス支持体上に塗布した。塗布層を８０℃で５分間加熱乾燥し、０．８μｍの塗膜を得た。その塗膜の表面をラビング処理して、配向膜を作製した。
【００９５】
（ネマチック液晶層の形成）
前記実施例１の配向膜を比較列１の前記工程で得られた配向膜に変更する以外は前記実施例１と同様にしてネマチック液晶層を形成した。しかしながら、ポリマーが液晶層作製用溶剤に溶解するため、液晶層の配向性は悪く、白濁していた。
【００９６】
［比較例２］
（配向膜の形成）
ポリビニルカルバゾールをトルエンに溶解して４質量％溶液を調製した。この溶液を、ワイヤーバーコーターを用いてガラス支持体上に塗布した。塗布層を１００℃で５分間加熱乾燥し、０．８μｍの塗膜を得た。その塗膜の表面をラビング処理して、配向膜を作製した。
【００９７】
（ネマチック液晶層の形成）
前記実施例１の配向膜を比較列２の前記工程で得られた配向膜に変更する以外は前記実施例１と同様にしてネマチック液晶層を形成し、測定を行った。しかしながら、ポリマーが液晶層作製用溶剤に溶解するため、液晶層の配向性は悪く、白濁していた。
【００９８】
【発明の効果】
本発明の配向膜は、配向膜上に液晶層を形成する光学素子の作製において、液晶層の形成に用いる液晶組成物中に含まれる溶剤に溶解されることがない耐溶剤性の配向膜とすることができる。
【００９９】
本発明の配向膜用組成物を用いて成膜した配向膜は、配向膜と光学機能層、配向膜と基材の密着性を高め、耐湿耐熱性等に優れた耐久性のあるものとなる。
【図面の簡単な説明】
【図１】本発明の光学素子の層構成を示す図である。
１ 支持体
２ 配向膜
３ 光学機能層[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides an alignment film, which has a property of aligning liquid crystal molecules in a direction different from the rubbing direction, and an optical element using the alignment film, specifically, a retardation film and a polarizing film. And optical elements such as color filters for displays.
[0002]
[Prior art]
[0003]
[Patent Document 1]
JP 2002-533742 A
[Patent Document 2]
JP-A-5-215921
[Patent Document 3]
JP-A-9-152509
[Patent Document 4]
Japanese Patent Publication No. 7-92568
[Patent Document 5]
Japanese Patent No. 3102973
[Patent Document 6]
JP-A-2002-62427
[Patent Document 7]
JP-A-2002-98836
[0004]
In addition to display media utilizing reversible motion of liquid crystal molecules such as TN type and STN type display elements, liquid crystals also have orientation and anisotropy of physical properties such as refractive index, dielectric constant and magnetic susceptibility. Various applications such as a phase difference plate, a deflecting plate, an optical deflecting prism, various optical filters, and the like are being studied.
[0005]
In recent years, liquid crystal compounds having various structures have been developed. Liquid crystal compounds include liquid crystalline polymers and polymerizable liquid crystals. Since liquid crystal polymers require long-term aging at high temperatures to align, their productivity is extremely low, and they are not suitable for mass production. is increasing. For example, Patent Document 1 discloses a polymerizable liquid crystal compound for producing an optical element.
[0006]
As an optical element using a liquid crystal compound, Patent Document 2 discloses a retardation plate comprising a support and a liquid crystal layer of a polymerizable rod-shaped compound having a liquid crystallinity and a positive birefringence. Document 3 discloses a retardation plate comprising a support, an alignment film, and a liquid crystal layer of a discotic liquid crystal compound.
[0007]
Polyvinyl alcohol having a function of aligning liquid crystal in the same direction as the rubbing direction is mainly used for an alignment film in an optical element such as a retardation plate. However, recently, it is required that the optical axis of the phase difference plate be at an angle different from the absorption direction of the polarizing plate with respect to the flow direction of the film, for example, 90 degrees, and the rubbing direction and the liquid crystal alignment direction are different. An alignment film is required.
[0008]
As an example of a polymer compound for a liquid crystal display device that orients liquid crystal molecules in a direction perpendicular to a rubbing direction, a polymer having a ring structure in a side chain is exemplified. Specifically, Patent Document 4 discloses that, in the side chain, a cyclopentane ring, a cyclohexane ring, a benzene ring, a naphthalene ring, a furan ring, an oxolane ring, a dioxolane ring, a thiophene ring, a pyrrole ring, a pyran ring, an oxane ring, and a dioxane ring , A pyridine ring, a piperidine ring, a pyrimidine ring, a pyrazine ring and the like, and more typical examples include polystyrene, polyphenylacetylene, polyvinylpyridine, polyvinylpyrimidine and derivatives thereof. Patent Document 5 discloses polyvinyl carbazole. Since these polymers have high solubility in general organic solvents, they are often not suitable as an alignment film of a retardation film in which a liquid crystal solution is coated on an alignment film and dried to form a liquid crystal layer.
[0009]
A copolymer having a repeating unit in which a cyclic structure (aliphatic ring, aromatic ring, or heterocycle) is directly connected to a vinyl group, a copolymer having a repeating unit composed of vinyl alcohol (Patent Document 6), or a cyclic structure (aliphatic) in a vinyl group An alignment film using a copolymer having a repeating unit in which a ring, an aromatic ring, or a heterocyclic ring) is directly connected and a repeating unit having a carboxylic acid (Patent Document 7) has been proposed. The repeating unit composed of vinyl alcohol of Patent Document 6 and the repeating unit having a carboxylic acid of Patent Document 7 have a role of preventing the alignment film from being dissolved in a solvent for forming a liquid crystal layer, It is necessary to increase the content of the repeating unit composed of vinyl alcohol and the repeating unit having a carboxylic acid. Therefore, the content of the repeating unit in which a cyclic structure (aliphatic ring, aromatic ring, or heterocyclic ring) is directly connected to a vinyl group effective for orienting the liquid crystal in a direction different from the rubbing direction is reduced. The orientation of the molecules is not sufficient.
[0010]
Among the conventional alignment film materials described above, polyvinyl alcohol, a copolymer having a repeating unit having a cyclic structure directly connected to a vinyl group and a repeating unit composed of vinyl alcohol, or a repeating unit having a cyclic structure directly connected to a vinyl group and A copolymer having a repeating unit having a carboxylic acid is a polymer that dissolves in an aqueous solvent and has high hygroscopicity. Therefore, an optical element using the polymer as an alignment film may be wrinkled by storage at high humidity and high temperature. Such a problem is likely to occur. In addition, since an aqueous solvent is used as a solvent for the composition for an alignment film, there is a drawback that the drying property is poor as compared with a general organic solvent and that the drying conditions must be strict.
[0011]
[Problems to be solved by the invention]
An object of the present invention is to provide a composition for an alignment film that can easily align a liquid crystal compound with an alignment regulating force of the alignment film by subjecting the surface of the alignment film to a rubbing treatment, and to provide an optical element having good durability. And more preferably, in the production of an optical element for forming a liquid crystal layer on an alignment film, a highly solvent-resistant alignment film that is not dissolved in a solvent contained in a liquid crystal composition used for forming the liquid crystal layer. And a durable optical element using the composition for an alignment film.
[0012]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention has focused on enhancing the hydrophobicity of the alignment film. That is, the composition for an alignment film of the present invention is a composition for an alignment film used for manufacturing an optical element composed of a support, an alignment film, and an optical functional layer composed of a liquid crystal compound. The composition for a film is characterized by containing at least A) a polymer, B) a monomer or oligomer having an ethylenically unsaturated bond, and C) a solvent containing 70% by mass or more and 100% by mass or less of a non-aqueous solvent.
[0013]
In the present invention, the “non-aqueous solvent” refers to a solvent other than water and / or a lower alcohol. Here, the lower alcohol refers to methanol or ethanol. The solvent of the present invention may contain less than 30% by mass of water and / or a lower alcohol in addition to the non-aqueous solvent.
[0014]
The alignment film formed using the composition for an alignment film of the present invention has high durability such as high heat resistance and moisture resistance, which enhances the adhesion between the alignment film and the optical functional layer, the alignment film and the substrate. . Conventionally, crosslinked polyvinyl alcohol and modified polyvinyl alcohol have been improved in moisture resistance and adhesion between the alignment film and the optical functional layer by crosslinking treatment and modification treatment. Moisture resistance was not sufficient due to use. The composition for an alignment film of the present invention can solve these problems.
[0015]
That is, when the alignment film is formed by using the polymer as the component A, generally a polymer soluble in a non-aqueous solvent alone as an alignment film component, when forming an optical functional layer on the obtained alignment film, The non-aqueous solvent contained in the liquid crystal compound solution dissolves the alignment film, making it difficult to form an optical functional layer on the alignment film. On the other hand, in the present invention, since a monomer or oligomer having an ethylenically unsaturated bond is contained in the composition for an alignment film as a B component, such a composition for an alignment film is coated on a support, After drying, it becomes possible to cure by irradiating ultraviolet rays or electron beams, and the cured alignment film is resistant to non-aqueous solvents, has excellent adhesion to a support, and is composed of a liquid crystalline compound. It becomes an moisture- and heat-resistant alignment film having excellent adhesion to the optical functional layer.
[0016]
Further, the composition for an alignment film of the present invention, even if the polymer is soluble in a non-aqueous solvent, by adding a monomer or oligomer having an ethylenically unsaturated bond to the polymer, the alignment of the present invention. Since the alignment film of the present invention formed using the film composition is not dissolved in the solvent of the optical functional layer formed on the alignment film, it has not been conventionally used as the alignment film composition. There is an advantage that a polymer soluble in a non-aqueous solvent can be selected widely.
[0017]
The method for producing an alignment film according to the present invention comprises: (1) a step of coating and drying the composition for an alignment film according to any one of claims 1 to 7 on a support; and (2) a coating film obtained. Irradiating the substrate with ultraviolet rays or an electron beam, and (3) performing rubbing after the step (1) or after the step (2).
[0018]
The method for producing an alignment film of the present invention is characterized by irradiating an ultraviolet ray or an electron beam to a coating film to which the composition for an alignment film has been applied, and curing the coating film. Even when an optical functional layer made of a liquid crystal compound is formed, there is no possibility that the alignment film is affected by a non-aqueous solvent contained in a solution of the liquid crystal compound. Further, in the method for producing an alignment film of the present invention, since the coating film is irradiated with an ultraviolet ray or an electron beam, the reaction is faster and the productivity is higher as compared with thermosetting. In addition, the method for producing an alignment film of the present invention is characterized in that the alignment film is cured by irradiation with ultraviolet rays or electron beams before the application of the liquid crystal compound for forming the optical functional layer. , The alignment film is not deteriorated by the heat treatment for alignment of the liquid crystal having a high alignment temperature when the optical function layer is formed.
[0019]
The optical element of the present invention is an optical element in which a support, an alignment film, and an optical functional layer composed of a liquid crystalline compound are laminated in this order, wherein the alignment film has the composition for an alignment film described above. It is characterized by being manufactured using a product. Since the optical element of the present invention is manufactured using the composition for an alignment film described above, both the alignment film and the optical functional layer in the optical element of the present invention using the composition for an alignment film are non-functional. Since a compound soluble in an aqueous organic solvent is a main component, the adhesion between the alignment film and the optical functional layer is good, and the adhesion to the support is also good.
[0020]
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Composition for alignment film
The composition for an alignment film of the present invention essentially contains the components A) to C). The alignment film of the present invention formed using the alignment film composition is either an alignment film that aligns liquid crystals in the same direction as the rubbing direction or an alignment film that aligns liquid crystals in a direction different from the rubbing direction. Is also good. The angle between the direction of the line obtained by projecting the director of the liquid crystal molecules on the alignment film surface with respect to the rubbing direction is determined by the type of the polymer of the alignment film composition, the type of the monomer or oligomer having an ethylenically unsaturated bond, It differs depending on factors such as the mixing ratio of the polymer and the monomer or oligomer having an ethylenically unsaturated bond, rubbing conditions, etc., but mainly depends on the type of polymer. In the case of curing by irradiation with ultraviolet rays, it is preferable that a photopolymerization initiator is contained as the component D) in addition to the components A) to C). By including the photopolymerization initiator, the coating film can be cured with a small irradiation amount.
[0021]
polymer
Examples of the polymer that can obtain an alignment film in which the direction of a line obtained by projecting the liquid crystal molecule onto the alignment film surface of the director with respect to the rubbing direction are substantially the same are polybisphenol A carbonate, polymethyl methacrylate, and alkyl (meth) acrylate. / (Meth) acrylic acid-based copolymer, alkyl (meth) acrylate / hydroxyalkyl (meth) acrylate-based copolymer, polyarylate, vinyl acetate / vinylinyl alcohol-based copolymer, vinyl acetate / vinyl chloride copolymer , Hydroxypropylcellulose, ethylene / vinyl acetate copolymer, polybenzyl (meth) acrylate, polyvinyl chloride and the like.
[0022]
As a polymer that can obtain an alignment film in which the direction of a line obtained by projecting a director of liquid crystal molecules on the alignment film surface with respect to the rubbing direction is obtained, the following general formula (1)
[0023]
Embedded image

[0024]
(Where R¹Is a hydrogen atom, a halogen atom or an alkyl group having 1 to 6 carbon atoms;²Is an aliphatic ring group, a directional group ring or a heterocyclic group. )
Or a polymer containing a repeating unit represented by the following general formula (2)
[0025]
Embedded image

[0026]
(Where R³Is an aliphatic ring group, a directional group ring or a heterocyclic group. )
Or a polymer containing a repeating unit represented by the following formula:
[0027]
Embedded image

[0028]
Polycarbonate, polyester, or polyurethane having at least one of the groups shown in (1) as a constituent unit.
[0029]
In the polymer containing the repeating unit represented by the general formula (1), R²Can be synthesized by polymerization of a vinyl monomer having an aromatic group as a side chain. A homopolymer of a vinyl monomer having an aromatic group as a side chain or a copolymer of a vinyl monomer having an aromatic group as a side chain with another monomer may be used.
[0030]
Vinyl monomers having an aromatic group as a side chain include styrenes, vinylnaphthalenes, vinylanthracenes, vinylpyrenes, vinylbiphenyls, vinylcarbazoles, vinylpyridines, vinylimidazoles, vinylindoles, and vinylindolines , Vinylisoindoles, vinylbenzimidazoles, vinylpyrimidines and the like, and the aromatic group of these monomers may have a substituent. Examples of the substituent include an alkyl group (eg, methyl, ethyl, t-butyl), a substituted alkyl group (eg, chloromethyl, hydroxymethyl, trimethylammonio chloride), an alkoxy group (eg, methoxy, ethoxy), halogen It includes atoms (F, Cl, Br), carboxyl groups, acyl groups (eg, formyl), amino groups, sulfo groups, aryl groups (eg, phenyl), aryloxy groups (eg, phenoxy), and oxo.
[0031]
The polymer contained in the composition for an alignment film of the present invention may have an ethylenically unsaturated bond. When the polymer has an ethylenically unsaturated bond, there is an advantage that the solvent resistance of the alignment film is further improved.
[0032]
Monomer or oligomer having ethylenically unsaturated bond
The monomer or oligomer as the component B of the composition for an alignment film of the present invention is preferably a monomer or oligomer having a plurality of ethylenically unsaturated bonds in the molecule.
[0033]
By adding one or two or more monomers or oligomers having an ethylenically unsaturated bond to the polymer to form an alignment film composition, an alignment film formed using the alignment film composition is: The required properties of the polymer, that is, the property of improving the adhesion to the support or the optical functional layer, and the improvement of heat resistance and solvent resistance can be imparted as required.
[0034]
The monomer or oligomer having an ethylenically unsaturated bond may be soluble in a non-aqueous solvent, and the number of ethylenically unsaturated bonds in the molecule may be one or more.
[0035]
Monomers or oligomers having an ethylenically unsaturated bond include monofunctional acrylates and methacrylates such as polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, and phenoxyethyl (meth) acrylate; (Meth) acrylate, trimethylolethane tri (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, hexanediol ( (Meth) acrylate, trimethylolpropane tri (acryloyloxypropyl) ether, tri (acryloyloxyethyl) isocyanate (Meth) acrylates after addition of ethylene oxide or propylene oxide to polyfunctional alcohols such as nurate, glycerin, and trimethylolethane, and reaction products of urethane acrylates, polyester acrylates, and epoxy resins with (meth) acrylic acid Polyacrylates such as epoxy acrylates and methacrylates.
[0036]
Monomers or oligomers with multiple ethylenically unsaturated bonds in the molecule are sufficiently cross-linked during the curing process of the alignment film by ultraviolet irradiation or electron beam irradiation, and form a network-like matrix to improve heat resistance and solvent resistance. This is advantageous.
[0037]
When the material forming the optical functional layer is a liquid crystal compound containing an ethylenically unsaturated bond, which is a polymerizable liquid crystal compound, a monomer, oligomer, or alignment film having an ethylenically unsaturated bond in the alignment film is formed during the curing process. The crosslinked polymer increases affinity at the interface between the alignment film and the optical function layer, and enhances the adhesion between the two coating films.
[0038]
solvent
The non-aqueous solvent contained in the composition for an alignment film of the present invention refers to a solvent other than water and / or a lower alcohol (ie, methanol or ethanol), and includes ketones (eg, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone), hydrocarbons (Eg, benzene, hexane, ether (eg, tetrahydrofuran, 1,2-dimethoxyethane), alkyl halide (eg, chloroform, dichloromethane), ester (eg, methyl acetate, butyl acetate, propylene glycol monomethyl ether acetate), amide ( Examples include N, N-dimethylformamide), sulfoxide (eg, dimethylsulfoxide), alcohol (eg, isopropyl alcohol), etc. The solvent used in the present invention contains a nonaqueous solvent in an amount of 70% by mass or more and 100% by mass or less. Solvent Solvent used in the invention in addition to the non-aqueous solvent, water and / or a lower alcohol may contain less than 30 wt%.
[0039]
Photopolymerization initiator
The alignment film of the present invention is cured by ultraviolet irradiation or electron beam irradiation. In the case of curing by electron beam irradiation, a photopolymerization initiator is not particularly necessary, but when curing by ultraviolet irradiation is carried out, the curing reaction proceeds at a lower irradiation amount when the photopolymerization initiator is included in the composition for an alignment film. Preferred for.
[0040]
Examples of the photopolymerization initiator contained in the composition for an alignment film of the present invention include benzyl (also referred to as bibenzoyl), benzoin isobutyl ether, benzoin isopropyl ether, benzophenone, benzoyl benzoic acid, methyl benzoyl benzoate, and 4-benzoyl-4′-. Methyl diphenyl sulfide, benzyl methyl ketal, dimethylaminomethyl benzoate, 2-n-butoxyethyl-4-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, 3,3'-dimethyl-4-methoxybenzophenone, methylobenzoyl phophorate Mate, 2-methyl-1- (4- (methylthio) phenyl) -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butane-1- ON, 1 (4-dodecylphenyl) -2-hydroxy-2-methylpropan-1-one, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1phenylpropan-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 2-chlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 1-chloro-4-propoxy Thioxanthone and the like can be mentioned. In addition, a sensitizer may be added in addition to the photopolymerization initiator, as long as the object of the present invention is not impaired.
[0041]
The amount of the photopolymerization initiator to be added is generally 0 to 20% by mass, preferably 0.1 to 10% by mass, more preferably 0 to 10% by mass based on the total solid content of the composition for an alignment film. It is in the range of 0.5 to 5% by mass.
[0042]
Manufacture of alignment film
The method for producing an alignment film according to the present invention comprises: (1) a step of applying and drying the composition for an alignment film according to any one of claims 1 to 7 on a support; and (2) a coating film obtained. (3) rubbing after the step (1) or after the step (2) is essential.
[0043]
Whether the rubbing step is performed after the step (1) or preferably after the step (2) depends on the type of the polymer for the alignment film composition, the type of the monomer or the oligomer having an ethylenically unsaturated bond. , And its amount.
[0044]
When the monomer or oligomer having an ethylenically unsaturated bond is in a liquid state, the amount of addition is large, and the composition for an alignment film is coated on a support and dried, and the surface of the coating film obtained is tacky, It is preferable to perform rubbing after the curing of (2). When the amount of the monomer or oligomer having an ethylenically unsaturated bond added is small or when the monomer or oligomer having an ethylenically unsaturated bond is solid, rubbing is performed after the step (1) and the step (2). ) May be performed after either.
[0045]
The coating method of the coating solution for the alignment film includes a wire bar coating method, an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, a spin coating method, a roll coating method, a dip coating method, a curtain coating method, and an extrusion coating method. , Bar coating method and E-type coating method.
[0046]
The thickness of the formed alignment film is preferably in the range of 0.1 μm to 10 μm. As a method of drying and removing the solvent after applying the composition for an alignment film, for example, drying under reduced pressure or drying by heating, or a method of combining these dryings is performed.
[0047]
The alignment film used when producing an optical element composed of an optical functional layer made of a liquid crystal compound is required to have resistance to a solvent when forming the optical functional layer. Alternatively, since it is cured by irradiation with an electron beam, solvent resistance is improved.
[0048]
Support
The type of the support is determined according to the intended use of the optical element (the laminate of the support, the alignment film and the optical functional layer), and a transparent polymer film, a transparent glass substrate, or the like is used. When the optical element is used as an optical compensation sheet for a retardation plate, a polarizing element, a notch filter, or the like, a transparent polymer film is usually used as a support. The transparent polymer film preferably has a small optical anisotropy. Being transparent means that the light transmittance is 80% or more.
[0049]
Examples of the transparent polymer film include cellulosic polymers, norbornene-based polymers such as Arton (trade name, manufactured by JSR Corporation) and Zeonex (trade name, manufactured by Zeon Corporation), and Zeonoa (trade name, manufactured by Zeon Corporation) ) And polymethyl methacrylate. As the cellulosic polymer, a cellulose ester is preferable, and a lower fatty acid ester of cellulose is more preferable. A lower fatty acid means a fatty acid having 6 or less carbon atoms. The number of carbon atoms is preferably 2 (cellulose acetate), 3 (cellulose propionate) or 4 (cellulose butyrate). As the cellulose ester, cellulose acetate is preferable, and examples thereof include diacetyl cellulose and triacetyl cellulose. Mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate may be used.
[0050]
When the desired optical element requires optical isotropy, glass or cellulose ester is generally used as the support. When optical anisotropy is required, a synthetic polymer (eg, polycarbonate, polysulfone, polyethersulfone, polyacrylate, polymethacrylate, norbornene resin) is generally used. By stretching the synthetic polymer film, optical anisotropy can be obtained.
[0051]
When the support is a cellulose ester or synthetic polymer film, it is preferably formed by a solvent casting method. The thickness of the support of the retardation plate is preferably from 20 μm to 500 μm, and more preferably from 50 μm to 200 μm. In order to improve the adhesion between the support of the retardation plate and the layers (alignment film, optical functional layer) provided thereon, the transparent support is subjected to surface treatment (eg, glow discharge treatment, corona discharge treatment, ultraviolet (UV) ) Treatment and flame treatment), and a primer layer (adhesive layer) and a protective layer may be formed.
[0052]
Optical function layer
The optical element of the present invention has a structure in which an alignment film is formed on a support, and an optical functional layer is further formed thereon. The optical functional layer is not particularly limited as long as the liquid crystal has nematic regularity, smectic regularity, or cholesteric regularity, and may be either a polymer liquid crystal or a polymerizable liquid crystal compound. The polymerizable liquid crystal compound preferably has polymerizable functional groups at both ends of the molecule in order to obtain an optical element having good heat resistance. Two or more optical functional layers may be laminated. The alignment film of the present invention can also align a discotic liquid crystal.
[0053]
To form the optical function layer, a polymerizable liquid crystal monomer may be used, or a polymerizable liquid crystal oligomer, a polymerizable liquid crystal polymer, or the like may be used. As such a polymerizable liquid crystal oligomer or polymerizable liquid crystal polymer, a conventionally proposed UV curable liquid crystal or polymer liquid crystal can be appropriately selected and used.
[0054]
In the case of a high-molecular liquid crystal, the optical functional layer is formed by applying a solution of the high-molecular liquid crystal and other compounds in a solvent onto the alignment film, drying, and then heating to a liquid crystal phase formation temperature, and then maintaining the alignment state. And cooled.
[0055]
An example of such a polymer liquid crystal is a polymer having a repeating unit represented by the following general formula (3).
[0056]
Embedded image

[0057]
(Where R¹¹Represents a hydrogen atom or a methyl group, X¹Represents a —COO— group or —OCO— group, a represents a positive integer of 1 to 6, b and c each independently represent 1 or 2 (provided that b + c ≦ 3 is satisfied). )
[0058]
In the case of a polymerizable liquid crystal compound, a solution in which a polymerizable liquid crystal compound and other compounds (for example, a polymerizable monomer and a photopolymerization initiator) are dissolved in a solvent is applied on an alignment film, dried, and then a liquid crystal phase is formed. After heating to a temperature, polymerization is performed by UV irradiation or electron beam irradiation, and further cooling is performed to obtain an optical functional layer.
[0059]
Examples of such a polymerizable liquid crystal compound include, for example, compounds represented by the following general formulas (4) and (5) (referred to as compound (I)) and the following compounds. As the compound (I), it is also possible to use a mixture of two kinds of compounds included in the general formulas (4) and (5).
[0060]
Embedded image

[0061]
Embedded image

[0062]
Embedded image

[0063]
In the general formulas (4) and (5), R¹², R^Thirteen, R¹⁴And R^FifteenRepresents a hydrogen or a methyl group, respectively, and R represents a liquid crystal phase,¹², R^Thirteen, R¹⁴And R^FifteenAre preferably both hydrogen. X²And X³May be hydrogen, chlorine, bromine, iodine, an alkyl group having 1 to 4 carbon atoms, a methoxy group, a cyano group, or a nitro group. Further, d, e, f and g, which indicate the chain length of the (meth) acryloyloxy group at both ends of the molecular chain of the compound (I) and the alkylene group which is a spacer to the aromatic ring, are each independently in the range of 2 to 12. Can take any integer, but preferably ranges from 4 to 10.
[0064]
In the present invention, a chiral nematic liquid crystal having cholesteric regularity obtained by adding a chiral agent to a nematic liquid crystal can be preferably used. The chiral agent is a low-molecular compound having an optically active site and means a compound having a molecular weight of 1500 or less. The chiral agent is used mainly for the purpose of inducing a helical pitch in the positive uniaxial nematic regularity expressed by the compound (I). As long as this object is achieved, it is compatible with the compound (I) or the above-mentioned compound in a solution state or a molten state, and without impairing the liquid crystallinity of the polymerizable liquid crystal compound capable of maintaining the nematic regularity. The type of the low-molecular compound as a chiral agent shown below is not particularly limited as long as it can induce a helical pitch of, but it is possible to obtain an optical element having good heat resistance having a polymerizable functional group at both ends of the molecule. Preferred above. It is essential that the chiral agent used to induce a helical pitch in the liquid crystal has at least some chirality in the molecule. Accordingly, chiral agents usable in the present invention include, for example, compounds having one or more asymmetric carbon atoms, compounds having an asymmetric point on a hetero atom such as chiral amine, chiral sulfoxide and the like, Alternatively, compounds having axial asymmetry such as cumulene and binaphthol can be exemplified. More specifically, a commercially available chiral nematic liquid crystal, for example, S-811 (trade name) manufactured by Merck and the like can be mentioned.
[0065]
However, depending on the properties of the selected chiral agent, the nematic regularity formed by the compound (I) is broken, the alignment is reduced, or when the compound is non-polymerizable, the curability of the liquid crystal composition is reduced. However, there is a possibility that the reliability of the cured film is reduced. Further, the use of a large amount of a chiral agent having an optically active site causes an increase in the cost of the composition. Therefore, when manufacturing a circularly polarized light controlling optical element having a cholesteric regularity of a short pitch, a chiral agent having an optically active site to be contained in the liquid crystal composition is a chiral agent having a large effect of inducing a helical pitch. It is preferably selected, and specifically, use of a low molecular compound (II) having axial asymmetry in a molecule represented by the general formula (6), (7) or (8) is preferable.
[0066]
Embedded image

[0067]
Embedded image

[0068]
Embedded image

[0069]
In the general formula (6), (7) or (8) representing the chiral agent (II), R¹⁶Represents a water cable or a methyl group. Y is any one of the formulas (i) to (xxiv) shown above, and in particular, any one of the formulas (i), (ii), (iii), (v), and (vii) It is preferable that Further, h and j indicating the chain length of the alkylene group can each independently take any integer in the range of 2 to 12, but are preferably in the range of 4 to 10, and preferably in the range of 6 to 10. Is more preferred. The compound represented by the general formula (6) or (7) in which the value of h or j is 0 or 1 lacks stability, easily undergoes hydrolysis, and has high crystallinity. On the other hand, compounds having a value of h or j of 13 or more have a low melting point (Tm). These compounds have reduced compatibility with the compound (I) exhibiting liquid crystallinity, and may cause phase separation or the like depending on the concentration.
[0070]
The optimum amount of the chiral agent to be incorporated in the polymerizable liquid crystal compound in the present invention is determined in consideration of the helical pitch inducing ability and the cholesteric property of the optical element finally obtained. Specifically, although it varies greatly depending on the polymerizable liquid crystal compound used, it is selected in the range of 0.01 to 60 parts by mass, most preferably 1 to 20 parts by mass, per 100 parts by mass of the total amount of the polymerizable liquid crystal compound. It is. If the compounding amount exceeds the above range, the orientation of the molecules is hindered, and there is a concern that the curing may be adversely affected by actinic radiation. If the amount is too small, sufficient cholesteric properties may not be provided.
[0071]
In the present invention, it is not essential that such a chiral agent has polymerizability. However, in consideration of the thermal stability and the like of the obtained optical functional layer, it is preferable to use a polymerizable chiral agent capable of polymerizing with the above-mentioned polymerizable liquid crystal compound and fixing the cholesteric regularity. In particular, it is preferable to have a polymerizable functional group at both ends of the molecule in order to obtain an optical element having good heat resistance.
[0072]
Examples of the photopolymerization initiator to be added to the polymerizable liquid crystal compound include benzyl, benzoin isobutyl ether, benzoin isopropyl ether, benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-benzoyl-4′-methyldiphenyl sulfide, benzyl methyl ketal, Dimethylaminomethylbenzoate, 2-n-butoxyethyl-4-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, 3,3'-dimethyl-4-methoxybenzophenone, methylobenzoylformate, 2-methyl-1- (4- (methylthio) phenyl) -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, 1- (4-dodecyl) Phenyl)- Hydroxy-2-methylpropan-1-one, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1phenylpropan-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2-methyl Examples thereof include propan-1-one, 2-chlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, and 1-chloro-4-propoxythioxanthone. In addition, a sensitizer may be added in addition to the photopolymerization initiator, as long as the object of the present invention is not impaired.
[0073]
The addition amount of such a photopolymerization initiator is generally in the range of 0.01 to 20% by mass, preferably 0.1 to 10% by mass, and more preferably 0.5 to 5% by mass. Can be added to the ionic liquid crystal compound.
[0074]
The coating liquid for forming the optical functional layer includes a surfactant, a polymerizable monomer (for example, a vinyl group, a vinyloxy group, an acryloyl group, and a methacryloyl group) in addition to the liquid crystal compound, the chiral agent, and the photopolymerization initiator. Compounds) and a polymer as long as they do not hinder the alignment of the liquid crystal compound. By selecting these surfactants, polymerizable monomers and polymers, the tilt angle of the liquid crystal on the surface side (air side) can be adjusted.
[0075]
In addition, the solvent used in the coating liquid for forming the optical functional layer is not particularly limited as long as the liquid crystal compound and the chiral agent dissolve therein and do not inhibit the alignment on the substrate having the alignment. Not something. Specifically, ketones (eg, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone), hydrocarbons (eg, benzene, hexane), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane), alkyl halides (eg, chloroform, dichloromethane) , Esters (eg, methyl acetate, butyl acetate, propylene glycol monomethyl ether acetate), amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide) and the like.
[0076]
Optical element
FIG. 1 shows a general layer configuration of the optical element of the present invention. In FIG. 1, reference numeral 1 denotes a support, 2 denotes an alignment film formed on the support 1, and 3 denotes an optical functional layer formed of a liquid crystalline compound formed on the alignment film 2. Examples of the optical element having such a laminated structure include a retardation plate and a polarizing element.
[0077]
Manufacture of optical elements
The method for manufacturing an optical element of the present invention can be performed as follows. A solution obtained by dissolving a liquid crystalline polymer and other compounds in a solvent is applied onto the alignment film formed on the support obtained by the method for producing an alignment film, dried, and then heated to a liquid crystal phase formation temperature. Thereafter, the optical function layer is formed by cooling while maintaining the alignment state, thereby obtaining an optical element. Alternatively, a solution in which a polymerizable liquid crystal compound and another compound (for example, a polymerizable monomer and a photopolymerization initiator) are dissolved in a solvent is applied to the alignment film, dried, and then heated to a liquid crystal phase formation temperature. The polymer is polymerized by UV irradiation or electron beam irradiation, and further cooled to form an optical functional layer, thereby obtaining an optical element.
[0078]
The optical element of the present invention may have one optical functional layer or may be formed of two or more layers. When the optical element of the present invention is used as a retardation plate, there is a step of bonding the retardation plate and the polarizing plate. An optical element composed of a support, an alignment film, and an optical functional layer made of a liquid crystalline compound may be directly attached to a polarizing plate as a retardation plate, or an optical functional layer made of a liquid crystalline compound may be attached to the polarizing plate by transfer. May be combined.
[0079]
【Example】
[Example 1]
(Formation of alignment film)
8 parts by mass of poly (bisphenol A carbonate) (manufactured by Aldrich), 2 parts by mass of pentaerythritol triacrylate, 0.3 part by mass of a photopolymerization initiator Irgacure 907 (trade name, manufactured by Ciba Specialty Chemicals) are mixed solvents of toluene / cyclohexanone. (Volume ratio 1/2) dissolved in 40 parts by weight. The obtained solution was applied on a glass support using a wire bar coater. After heating and drying the coating layer, using a high pressure mercury lamp, 500 mJ / cm²To cure the coating. The surface of the coating film was rubbed to prepare an alignment film.
[0080]
(Formation of nematic liquid crystal layer)
The following chemical formula (6)
[0081]
Embedded image

[0082]
Is dissolved in 40 parts by mass of methyl isobutyl ketone, and 0.5 part by mass of a photopolymerization initiator Irgacure 907 (trade name, manufactured by Ciba Specialty Chemicals) is added. Thus, a coating liquid for forming an anisotropic layer was obtained. This coating solution is applied on the alignment film prepared in the above step using a wire bar coater, dried, heated at 85 ° C. for 1 minute, and heated at that temperature to 50 mJ / cm using a high-pressure mercury lamp.²The alignment state was fixed by irradiating ultraviolet rays.
[0083]
As measured by KOBRA (trade name, manufactured by Oji Scientific Instruments), the director of the nematic liquid crystal molecules was in the same direction as the rubbing direction, and the retardation in the thickness direction at a wavelength of 550 nm was 65 nm.
[0084]
[Example 2]
(Formation of alignment film)
The poly (bisphenol A carbonate) of Example 1 is represented by the following chemical formula
[0085]
Embedded image

[0086]
An alignment film was formed in the same manner as in Example 1 except that the polycarbonate was changed to
[0087]
(Formation of nematic liquid crystal layer)
A nematic liquid crystal layer was formed and measured in the same manner as in Example 1 except that the alignment film of Example 1 was changed to the alignment film obtained in the process of Example 2. The director of the nematic liquid crystal molecules was perpendicular to the rubbing direction, and the retardation in the thickness direction at a wavelength of 550 nm was 70 nm.
[0088]
[Example 3]
(Formation of alignment film)
An alignment film was formed in the same manner as in Example 1 except that the poly (bisphenol A carbonate) in Example 1 was changed to polyvinyl carbazole (Mw. 20,000).
[0089]
(Formation of nematic liquid crystal layer)
A nematic liquid crystal layer was formed and measured in the same manner as in Example 1 except that the alignment film of Example 1 was changed to the alignment film obtained in the above step of Example 3. The director of the nematic liquid crystal molecules was perpendicular to the rubbing direction, and the retardation in the thickness direction at a wavelength of 550 nm was 70 nm.
[0090]
[Example 4]
(Formation of alignment film)
The poly (bisphenol A carbonate) of Example 1 is represented by the following chemical formula
[0091]
Embedded image

[0092]
An alignment layer was formed in the same manner as in Example 1 except that polyvinyl carbazole represented by the following formula was used.
[0093]
(Formation of nematic liquid crystal layer)
A nematic liquid crystal layer was formed and measured in the same manner as in Example 1 except that the alignment film of Example 1 was changed to the alignment film obtained in the above step of Example 4. The director of the nematic liquid crystal molecules was perpendicular to the rubbing direction, and the retardation in the thickness direction at a wavelength of 550 nm was 75 nm.
[0094]
[Comparative Example 1]
(Formation of alignment film)
Poly (bisphenol A carbonate) (manufactured by Aldrich) was dissolved in a mixed solvent of toluene / cyclohexane (volume ratio: 1/2) to prepare a 4% by mass solution. This solution was applied on a glass support using a wire bar coater. The coating layer was dried by heating at 80 ° C. for 5 minutes to obtain a 0.8 μm coating film. The surface of the coating film was rubbed to prepare an alignment film.
[0095]
(Formation of nematic liquid crystal layer)
A nematic liquid crystal layer was formed in the same manner as in Example 1 except that the alignment film of Example 1 was changed to the alignment film obtained in the above-described step of Comparative Column 1. However, since the polymer was dissolved in the solvent for preparing the liquid crystal layer, the orientation of the liquid crystal layer was poor and the liquid crystal layer was clouded.
[0096]
[Comparative Example 2]
(Formation of alignment film)
Polyvinylcarbazole was dissolved in toluene to prepare a 4% by mass solution. This solution was applied on a glass support using a wire bar coater. The coating layer was dried by heating at 100 ° C. for 5 minutes to obtain a 0.8 μm coating film. The surface of the coating film was rubbed to prepare an alignment film.
[0097]
(Formation of nematic liquid crystal layer)
A nematic liquid crystal layer was formed and measured in the same manner as in Example 1 except that the alignment film of Example 1 was changed to the alignment film obtained in the above-described step of Comparative Column 2. However, since the polymer was dissolved in the solvent for preparing the liquid crystal layer, the orientation of the liquid crystal layer was poor and the liquid crystal layer was clouded.
[0098]
【The invention's effect】
The alignment film of the present invention is a solvent-resistant alignment film that is not dissolved in a solvent contained in a liquid crystal composition used for forming a liquid crystal layer in the production of an optical element that forms a liquid crystal layer on the alignment film. can do.
[0099]
The alignment film formed using the composition for an alignment film of the present invention has high durability such as high heat resistance and moisture resistance, which enhances the adhesion between the alignment film and the optical functional layer, the alignment film and the substrate. .
[Brief description of the drawings]
FIG. 1 is a diagram showing a layer configuration of an optical element of the present invention.
1 Support
2 Alignment film
3 Optical function layer

Claims (10)

A support, an alignment film, and a composition for an alignment film used for manufacturing an optical element including an optical functional layer composed of a liquid crystal compound, wherein the composition for an alignment film includes:
A) polymer,
B) a monomer or oligomer having an ethylenically unsaturated bond, and
C) a solvent containing 70% by mass or more and 100% by mass or less of a non-aqueous solvent;
A composition for an alignment film, comprising at least: The composition for an alignment film according to claim 1, further comprising:
D) A composition for an alignment film, comprising a photopolymerization initiator. The composition for an alignment film according to claim 1, wherein the monomer or oligomer having an ethylenically unsaturated bond has a plurality of ethylenically unsaturated bonds in a molecule. The polymer has the following general formula (1)

(In the formula, R ¹ is a hydrogen atom, a halogen atom, or an alkyl group having 1 to 6 carbon atoms, and R ² is an aliphatic ring group, an aromatic group, or a heterocyclic group.)
The composition for an alignment film according to claim 1, wherein the composition comprises a repeating unit represented by the formula: The polymer has the following general formula (2)

(In the formula, R ³ is an aliphatic ring group, an aromatic group, or a heterocyclic group.)
The composition for an alignment film according to claim 1, wherein the composition comprises a repeating unit represented by the formula: The polymer has the following chemical formula

4. The composition for an alignment film according to claim 1, wherein the composition is a polymer selected from polycarbonate, polyester, and polyurethane containing at least one of the following as a structural unit. 5. The polymer is polybisphenol A carbonate, polymethyl methacrylate, alkyl (meth) acrylate / (meth) acrylic acid-based copolymer, alkyl (meth) acrylate / hydroxyalkyl (meth) acrylate-based copolymer, polyarylate, acetic acid Claims: One or more polymers selected from the group consisting of vinyl / vinyl alcohol copolymers, vinyl acetate / vinyl chloride copolymers, hydroxypropyl cellulose, and ethylene / vinyl acetate copolymers. Item 4. The composition for an alignment film according to Item 1, 2 or 3. (1) a step of applying and drying the composition for an alignment film according to any one of claims 1 to 7 on a support;
(2) a step of irradiating the obtained coating film with ultraviolet rays or electron beams to cure the coating film;
(3) a step of performing rubbing after the step (1) or after the step (2);
A method for producing an alignment film, comprising: An optical element comprising a support, an alignment film, and an optical functional layer made of a liquid crystalline compound, wherein the alignment film is formed using the composition for an alignment film according to any one of claims 1 to 7. An optical element characterized by being manufactured. The optical element according to claim 9, wherein the liquid crystal compound mainly contains a polymerizable nematic liquid crystal or a polymerizable nematic liquid crystal and a polymerizable chiral agent.

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