JP3701022B2 - Manufacturing method of birefringent optical film, film obtained by the manufacturing method, elliptically polarizing plate using the same, and liquid crystal display device using them - Google Patents

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上記（１）中、Ｘは、置換基を表し、ｑは、その置換数を表す。Ｘは、例えば、ハロゲン原子、低級アルキル基、ハロゲン化アルキル基、低級アルコキシ基、または、ハロゲン化アルコキシ基であり、複数の場合、それぞれ同一であるかまたは異なる。
【００３８】
前記ハロゲン原子としては、例えば、フッ素原子、臭素原子、塩素原子およびヨウ素原子があげられる。これらの中でも、フッ素原子が好ましい。前記低級アルキル基としては、例えば、Ｃ_1-6の直鎖または分岐鎖を有する低級アルキル基が好ましく、Ｃ_1-4の直鎖または分岐鎖のアルキル基がより好ましい。これらの中でも、メチル基、エチル基、プロピル基、イソプロピル基、ブチル基、イソブチル基、sec-ブチル基、および、tert-ブチル基が、さらにより好ましく、特に好ましくは、メチル基およびエチル基である。前記ハロゲン化アルキル基としては、例えば、トリフルオロメチル基等の前記低級アルキル基のハロゲン化物があげられる。前記低級アルコキシ基としては、例えば、Ｃ_1-6の直鎖または分岐鎖のアルコキシ基が好ましく、Ｃ_1-4の直鎖または分岐鎖のアルコキシ基がより好ましい。これらの中でも、メトキシ基、エトキシ基、プロポキシ基、イソプロポキシ基、ブトキシ基、イソブトキシ基、sec-ブトキシ基、および、tert-ブトキシ基が、さらにより好ましく、特に好ましくは、メトキシ基およびエトキシ基である。前記ハロゲン化アルコキシ基としては、例えば、トリフルオロメトキシ基等の前記低級アルコキシ基のハロゲン化物があげられる。
【００３９】
上記（１）中、前記ｑは、０から４までの整数である。そのなかでも、ｑ＝０であり、かつ、ベンゼン環の両端に結合したカルボニル基とエーテル酸素とが互いにパラ位に存在することが好ましい。
【００４０】
また、上記（１）中、Ｒ¹は、下記式（２）で表される基であり、ｍは、０または１の整数である。
【００４１】
【化２】

上記（２）中、Ｘ’は、置換基を表し、ｑ’は、その置換数を表す。Ｘ’は、例えば、前記Ｘがとりうる前記範囲のものであり、複数の場合、それぞれ同一であるかまたは異なる。ｑ’は、０から４までの整数であり、ｑ’＝０であるのが好ましい。また、ｐは、０または１の整数である。
【００４２】
また、上記（２）中、Ｒ²は、２価の芳香族基を表す。この２価の芳香族基としては、例えば、ｏ−、ｍ−もしくはｐ−フェニレン、または、ナフタレン、ビフェニル、アントラセン、ｏ−、ｍ−もしくはｐ−テルフェニル、フェナントレン、ジベンゾフラン、ビフェニルエーテル、もしくは、ビフェニルスルホンから誘導される２価の基等があげられる。これらの２価の芳香族基において、芳香族に直接結合する水素が、ハロゲン原子、低級アルキル基または低級アルコキシ基で置換されてもよい。これらの中でも、前記Ｒ²としては、下記式（３）〜（９）からなる群から選択される芳香族基が好ましい。
【００４３】
【化３】

【００４４】
上記（１）中、前記Ｒ¹としては、好ましくは、下記式（１０）で表される基である。下記式（１０）中、Ｒ²およびｐは上記（２）と同義である。
【００４５】
【化４】

【００４６】
さらに、上記（１）中、ｎは、重合度を表す。ｎの値は、具体的には、例えば、２〜５０００であって、好ましくは、５〜５００である。また、その重合は、同一の繰り返し単位からなるものであってもよく、異なる繰り返し単位からなるものであってもよい。後者の場合には、その重合は、ブロック重合であってもよく、ランダム重合であってもよい。
【００４７】
さらに、上記（１）で示されるポリアリールエーテルケトンの末端は、ｐ−テトラフルオロベンゾイレン基側がフッ素であり、オキシアルキレン基側が水素原子であることが好ましい。すなわち、上記（１）で表されるポリアリールエーテルケトンは、好ましくは、下記一般式（１１）で表される重合体である。なお、ｎは、上記（１）と同様の重合度を表す。
【００４８】
【化５】

【００４９】
本発明の製造方法で用いるポリアリールエーテルケトンの具体例としては、下記式（１２）〜（１５）で表されるものがあげられる。なお、ｎは、上記（１）と同様の重合度を表す。
【００５０】
【化６】

【化７】

【化８】

【化９】

【００５１】
本発明の製造方法に用いられるポリアミドまたはポリエステルとしては、例えば、特表平１０−５０８０４８号公報に記載されるポリアミドまたはポリエステルがあげられ、それらの繰り返し単位は、下記一般式（１６）で表すことができる。
【００５２】
【化１０】

上記（１６）中、Ｙは、ＯまたはＮＨであり、Ｅは、例えば、共有結合、Ｃ₂アルキレン基、ハロゲン化Ｃ₂アルキレン基、ＣＨ₂基、Ｃ(ＣＸ₃)₂基（ここで、Ｘは、ハロゲンまたは水素である。）、ＣＯ基、Ｏ原子、Ｓ原子、ＳＯ₂基、Ｓｉ(Ｒ)₂基（ここで、Ｒは、Ｃ_1-3アルキル基およびＣ_1-3ハロゲン化アルキル基からなる群から選択される少なくとも一種類である。）、および、Ｎ(Ｒ)基（ここで、Ｒは、前記定義のものである。）からなる群から選ばれる。さらに、前記Ｅは、カルボニル官能基またはＹ基に対してメタ位またはパラ位にある。
【００５３】
また、上記（１６）中、ＡおよびＢは、置換基であり、ｔおよびｚは、それぞれの置換数を表す。また、ｐは、０から３までの整数であり、ｑは、１から３までの整数であり、ｒは、０から３までの整数である。
【００５４】
さらに、上記（１６）中、前記Ａは、例えば、水素、ハロゲン、Ｃ_1-3アルキル基、Ｃ_1-3ハロゲン化アルキル基、ＯＲ（ここで、Ｒは、前記定義のものである。）で表されるアルコキシ基、アリール基、ハロゲン化等による置換アリール基、Ｃ_1-9アルコキシカルボニル基、Ｃ_1-9アルキルカルボニルオキシ基、Ｃ_1-12アリールオキシカルボニル基、Ｃ_1-12アリールカルボニルオキシ基およびその置換誘導体、Ｃ_1-12アリールカルバモイル基、ならびに、Ｃ_1-12アリールカルボニルアミノ基およびその置換誘導体からなる群から選択され、複数の場合、それぞれ同一であるかまたは異なる。前記Ｂは、例えば、ハロゲン、Ｃ_1-3アルキル基、Ｃ_1-3ハロゲン化アルキル基、フェニル基および置換フェニル基からなる群から選択され、複数の場合、それぞれ同一であるかまたは異なる。前記置換フェニル基のフェニル環上の置換基としては、例えば、ハロゲン、Ｃ_1-3アルキル基、Ｃ_1-3ハロゲン化アルキル基およびこれらの組み合わせがあげられる。前記ｔは、０から４までの整数であり、前記ｚは、０から３までの整数である。
【００５５】
さらに、上記（１６）で表されるポリアミドまたはポリエステルの繰り返し単位の中でも、下記一般式（１７）で表されるものが好ましい。
【００５６】
【化１１】

上記（１７）中、Ａ、ＢおよびＹは、上記（１６）で定義したものであり、ｖは、０から３、好ましくは、０から２までの整数である。ｘおよびｙは、それぞれ０または１であるが、共に０であることはない。
【００５７】
これらのポリアミドまたはポリエステルの分子量は、特に限定されないが、重量平均分子量（Ｍｗ）として、２０，０００〜５００，０００の範囲が好ましく、より好ましくは、５０，０００〜２００，０００の範囲である。重量平均分子量が、これらの範囲内であれば、十分な強度が得られ、光学フィルム化した場合に、伸縮、歪み等で、クラックが生じにくく、また、ポリアミドまたはポリエステルがゲル化することなく、溶剤に対する良好な溶解性が得られる。
【００５８】
本発明の製造方法で用いるポリイミドとしては、例えば、特表２０００−５１１２９６号公報に記載されたポリイミドがあげられ、９，９-ビス(アミノアリール)フルオレンと芳香族テトラカルボン酸二無水物との縮合重合生成物を含む下記一般式（１８）に対応する繰り返し単位を１つ以上含むポリマーを任意に使用できる。
【００５９】
【化１２】

上記（１８)中、Ｒ³〜Ｒ⁶は、水素、ハロゲン、フェニル基、１〜４個のハロゲン原子またはＣ_1-10のアルキル基で置換されたフェニル基、およびＣ_1-10のアルキル基からなる群からそれぞれ独立に選択される少なくとも一種類の置換基である。好ましくは、Ｒ³〜Ｒ⁶は、ハロゲン、フェニル基、１〜４個のハロゲン原子またはＣ_1-10のアルキル基で置換されたフェニル基、および、Ｃ_1-10のアルキル基からなる群からそれぞれ独立に選択される少なくとも一種類の置換基である。
【００６０】
また、上記（１８)中、Ｄは、例えば、Ｃ_6-20の４価芳香族基である。好ましくは、Ｄは、ピロメリット基、多環式芳香族基、多環式芳香族基の誘導体、または、下記一般式（１９）で表される基である。
【００６１】
【化１３】

上記（１９）中、Ｊは、例えば、共有結合、Ｃ(Ｒ⁷)₂基、ＣＯ基、Ｏ原子、Ｓ原子、ＳＯ₂基、Ｓｉ(Ｃ₂Ｈ₅)₂基、または、ＮＲ⁸基であって、複数の場合、それぞれ同一であるかまたは異なる。ｗは、１から１０までの整数を表し、Ｒ⁷は、それぞれ独立に、水素またはＣ（Ｒ⁹）₃である。Ｒ⁸は、水素、炭素原子数１〜約２０のアルキル基、またはＣ_6-20のアリール基であり、複数の場合、それぞれ同一であるかまたは異なる。Ｒ⁹は、それぞれ独立に、水素、フッ素、または塩素である。
【００６２】
前記多環式芳香族基としては、例えば、ナフタレン、フルオレン、ベンゾフルオレンまたはアントラセンから誘導される４価の基があげられる。また、前記多環式芳香族基の置換誘導体としては、例えば、Ｃ_1-10のアルキル基およびそのフッ素化誘導体、ならびにＦやＣｌ等のハロゲンからなる群から選択される少なくとも一つで置換される前記多環式芳香族基があげられる。
【００６３】
さらに、その他にも、例えば、特表平８−５１１８１２号公報に記載されたポリイミドがあげられる。具体的には、繰り返し単位が一般式（２０）または（２１）で示されるホモポリマー、および繰り返し単位が一般式（２２）で示されるポリイミドがあげられる。なお、式（２２）は式（２０）の好ましい形態である。
【００６４】
【化１４】

【化１５】

【化１６】

【００６５】
上記（２０）〜（２２）中、ＧおよびＦは、例えば、共有結合、ＣＨ₂基、Ｃ(ＣＨ₃)₂基、Ｃ(ＣＦ₃)₂基、Ｃ(ＣＸ₃)₂基（ここで、Ｘは、ハロゲンである。）、ＣＯ基、Ｏ原子、Ｓ原子、ＳＯ₂基、Ｓｉ(ＣＨ₂ＣＨ₃)₂基、および、Ｎ(ＣＨ₃)基からなる群から、それぞれ独立して選択される基を表す。
【００６６】
上記（２０）および（２２）中、Ｌは、置換基であり、ｄおよびｅは、その置換数を表す。Ｌは、例えば、ハロゲン、Ｃ_1-3アルキル基、Ｃ_1-3ハロゲン化アルキル基、フェニル基、または、置換フェニル基であり、複数の場合、それぞれ同一であるかまたは異なる。前記置換フェニル基としては、例えば、ハロゲン、Ｃ_1-3アルキル基、Ｃ_1-3ハロゲン化アルキル基からなる群から選択される少なくとも一種類の置換基を有する置換フェニル基があげられる。また、前記ハロゲンとしては、例えば、フッ素、塩素、臭素またはヨウ素があげられる。ｄは、０から２までの整数であり、ｅは、０から３までの整数である。
【００６７】
上記（２０）〜（２２）中、Ｑは、置換基であり、ｆは、その置換数を表す。Ｑは、例えば、水素、ハロゲン、アルキル基、置換アルキル基、ニトロ基、シアノ基、チオアルキル基、アルコキシ基、アリール基、置換アリール基、アルキルエステル基、および置換アルキルエステル基からなる群から選択される原子または基であって、複数の場合、それぞれ同一であるかまたは異なる。前記ハロゲンとしては、例えば、フッ素、塩素、臭素およびヨウ素があげられる。前記置換アルキル基としては、例えば、ハロゲン化アルキル基があげられる。また前記置換アリール基としては、例えば、ハロゲン化アリール基があげられる。ｆは、０から４までの整数であり、ｇおよびｈは、それぞれ０から３および１から３までの整数である。また、ｇおよびｈは、１より大きいことが好ましい。
【００６８】
上記（２１）中、Ｒ¹⁰およびＲ¹¹は、水素、ハロゲン、フェニル基、置換フェニル基、アルキル基、および置換アルキル基からなる群から、それぞれ独立に、選択される基である。その中でも、Ｒ¹⁰およびＲ¹¹は、それぞれ独立に、ハロゲン化アルキル基であることが好ましい。
【００６９】
上記（２２）中、Ｍ¹およびＭ²は、同一であるかまたは異なり、例えば、ハロゲン、Ｃ_1-3アルキル基、Ｃ_1-3ハロゲン化アルキル基、フェニル基、または、置換フェニル基である。前記ハロゲンとしては、例えば、フッ素、塩素、臭素およびヨウ素があげられる。また、前記置換フェニル基のとしては、例えば、ハロゲン、Ｃ_1-3アルキル基、Ｃ_1-3ハロゲン化アルキル基からなる群から選択される少なくとも一種類の置換基を有する置換フェニル基があげられる。
【００７０】
このようなポリイミドの具体例としては、下記式（２３）で表されるものがあげられる。
【００７１】
【化１７】

【００７２】
またさらに、本発明の製造方法で用いるポリイミドとしては、例えば、前記骨格以外の酸二無水物やジアミンを適宜共重合させたコポリマーがあげられる。
【００７３】
前記酸二無水物としては、例えば、芳香族テトラカルボン酸二無水物があげられる。この芳香族テトラカルボン酸二無水物の例として、ピロメリト酸二無水物、ベンゾフェノンテトラカルボン酸二無水物、ナフタレンテトラカルボン酸無水物、複素環式芳香族テトラカルボン酸二無水物、２，２−置換ビフェニルテトラカルボン酸二無水物等があげられる。
【００７４】
前記ピロメリト酸二無水物の例として、ピロメリト酸二無水物、３，６−ジフェニルピロメリト酸二無水物、３，６−ビス（トリフルオロメチル）ピロメリト酸二無水物、３，６−ジブロモピロメリト酸無水物、３，６−ジクロロピロメリト酸二無水物等があげられる。前記ベンゾフェノンテトラカルボン酸二無水物の例として、３，３′，４，４′−ベンゾフェノンテトラカルボン酸二無水物、２，３，３′，４′−ベンゾフェノンテトラカルボン酸二無水物、２，２′，３，３′−ベンゾフェノンテトラカルボン酸二無水物等があげられる。前記ナフタレンテトラカルボン酸無水物の例として、２，３，６，７−ナフタレン−テトラカルボン酸二無水物、１，２，５，６−ナフタレン−テトラカルボン酸二無水物、２，６−ジクロロ−ナフタレン−１，４，５，８−テトラカルボン酸二無水物等があげられる。前記複素環式芳香族テトラカルボン酸二無水物の例として、チオフェン−２，３，４，５−テトラカルボン酸二無水物、ピラジン−２，３，５，６−テトラカルボン酸二無水物、ピリジン−２，３，５，６−テトラカルボン酸二無水物等があげられる。前記２，２−置換ビフェニルテトラカルボン酸二無水物の例として、２，２′−ジブロモ−４，４′，５，５′−ビフェニルテトラカルボン酸二無水物、２，２′−ジクロロ−４，４′−５，５′−ビフェニルテトラカルボン酸二無水物、２，２−ビス（トリフルオロメチル）−４，４′−５，５′−ビフェニルテトラカルボン酸二無水物等があげられる。
【００７５】
また、前記芳香族テトラカルボン酸二無水物のその他の例として、３，３′４，４′−ビフェニルカルボン酸二無水物、ビス（２，３−ジカルボキシフェニル）メタン二無水物、ビス（２，５，６−トリフルオロ−３，４−ジカルボキシフェニル）メタン二無水物、２，２−ビス（３，４−ジカルボキシフェニル）−１，１，１，３，３，３−ヘキサフルオロプロパン二無水物、４,４'-ビス(3,4-ジカルボキシフェニル)-2,2-ジフェニルプロパン二無水物、ビス（３，４−ジカルボキシフェニル）エーテル二無水物（４，４′−オキシジフタル酸無水物）、ビス（３，４−ジカルボキシフェニル）スルホン酸二無水物（３，３′，４，４′−ジフェニルスルホンテトラカルボン酸無水物）、４，４′−〔４，４′−イソプロピリデン−ジ（ｐ−フェニレンオキシ）〕ビス（フタル酸無水物）、Ｎ，Ｎ−（３，４−ジカルボキシフェニル）−Ｎ−メチルアミン二無水物、ビス（３，４−ジカルボキシフェニル）ジエチルシラン二無水物等があげられる。
【００７６】
前記の中でも、芳香族テトラカルボン酸二無水物として、２，２′−置換ビフェニルテトラカルボン酸二無水物が好ましく、より好ましくは、２，２′−ビス（トリハロメチル）−４，４′，５，５′−ビフェニルテトラカルボン酸二無水物であり、さらにより好ましくは、２，２−ビス（トリフルオロメチル）−４，４′−５，５′−ビフェニルテトラカルボン酸二無水物である。
【００７７】
前記ジアミンとしては、芳香族ジアミンがあげられる。この芳香族ジアミンの例としては、ベンゼンジアミン、ジアミノベンゾフェノン、ナフタレンジアミン、複素環式芳香族ジアミン、およびその他の芳香族ジアミンがあげられる。
【００７８】
前記ベンゼンジアミンの例としては、ｏ−、ｍ−およびｐ−フェニレンジアミン、２，４−ジアミノトルエン、１，４−ジアミノ−２−メトキシベンゼン、１，４−ジアミノ−２−フェニルベンゼンおよび１，３−ジアミノ−４−クロロベンゼンのようなベンゼンジアミンから成る群から選択されるジアミン等があげられる。前記ジアミノベンゾフェノンの例としては、２，２′−ジアミノベンゾフェノン、および３，３′−ジアミノベンゾフェノン等があげられる。前記ナフタレンジアミンの例としては、１，８−ジアミノナフタレン、および１，５−ジアミノナフタレン等があげられる。前記複素環式芳香族ジアミンの例としては、２，６−ジアミノピリジン、２，４−ジアミノピリジン、および２，４−ジアミノ−Ｓ−トリアジン等があげられる。
【００７９】
また、前記芳香族ジアミンのその他の例としては、４，４′−ジアミノビフェニル、４，４−ジアミノジフェニルメタン、２，２−ビス（４−アミノフェニル）プロパン、４，４−（９−フルオレニリデン)-ジアニリン、２，２'−ビス(トリフルオロメチル)−４，４'−ジアミノビフェニル、３，３'−ジクロロ−４，４'−ジアミノフェニルメタン、２，２'−ジクロロ−４，４'−ジアミノビフェニル、２，２'，５，５'−テトラクロロベンジジン、２，２−ビス（４−アミノフェノキシフェニル)プロパン、２，２−ビス（４−アミノフェニル）−１，１，１，３，３，３−ヘキサフルオロプロパン、４，４′−ジアミノジフェニルエーテル、３，４′−ジアミノジフェニルエーテル、１，３−ビス（３−アミノフェノキシ）ベンゼン、１，３−ビス（４−アミノフェノキシ）ベンゼン、１，４−ビス（４−アミノフェノキシ）ベンゼン、４，４′−ビス（４−アミノフェノキシ）ビフェニル、４，４′−ビス（３−アミノフェノキシ）ビフェニル、２，２−ビス（４−〔４−アミノフェノキシ〕フェニル）プロパン、２，２−ビス〔４−（４−アミノフェノキシ）フェニル〕−１，１，１，３，３，３−ヘキサフルオロプロパン、４，４′−ジアミノジフェニルチオエーテル、４，４′−ジアミノジフェニルスルホン等があげられる。
【００８０】
これらのポリイミドの分子量としては、特に限定されないが、重量平均分子量として、例えば、１，０００〜１，０００，０００の範囲が好ましく、より好ましくは、２，０００〜５００，０００の範囲である。
【００８１】
本発明の製造方法に用いられる成膜材料溶液中の成膜材料としては、前記のポリアリールエーテルケトン、ポリアミド、ポリエステル、ポリイミド等を単独で用いても良いし、例えばポリアリールエーテルケトンとポリアミドの混合物のように異なる官能基を持つ２種以上の混合物として使用してもよい。
【００８２】
また、前記成膜材料に、配向性が著しく低下しない範囲で、構造の異なる他の樹脂を配合してもよい。その際使用される他の樹脂としては、例えば、汎用樹脂、エンジニアリングプラスチック、熱可塑性樹脂、熱硬化性樹脂等があげられる。前記汎用樹脂の例としては、ポリエチレン（ＰＥ）、ポリプロピレン（ＰＰ）、ポリスチレン（ＰＳ）、ポリメチルメタクリレート（ＰＭＭＡ）、ＡＢＳ樹脂、およびＡＳ樹脂等があげられる。前記エンジニアリングプラスチックの例としては、ポリアセテート（ＰＯＭ）、ポリカーボネート（ＰＣ）、ポリアミド（ＰＡ：ナイロン）、ポリエチレンテレフタレート（ＰＥＴ）、およびポリブチレンテレフタレート（ＰＢＴ）等があげられる。前記熱可塑性樹脂の例としては、ポリフェニレンスルフィド（ＰＰＳ）、ポリエーテルスルホン（ＰＥＳ）、ポリケトン（ＰＫ）、ポリイミド（ＰＩ）、ポリシクロヘキサンジメタノールテレフタレート（ＰＣＴ）、ポリアリレート（ＰＡＲ）、および液晶ポリマー（ＬＣＰ）等があげられる。前記熱硬化性樹脂の例としては、エポキシ樹脂、フェノールノボラック樹脂等があげられる。
【００８３】
また、前記他の樹脂等を、前記成膜材料に配合する場合、前記他の樹脂の配合量は、配向性が著しく低下しない範囲であれば特に制限されないが、通常、成膜材料溶液中の成膜材料に対して、０〜５０質量％であり、好ましくは、０〜３０質量％である。
【００８４】
本発明の製造方法に用いられる成膜材料溶液の溶媒としては、前記成膜材料等を溶解できるものであれば特に制限はなく、前記成膜材料の種類に応じて適宜選択できる。その溶媒としては、例えば、クロロホルム、ジクロロメタン、四塩化炭素、ジクロロエタン、テトラクロロエタン、トリクロロエチレン、テトラクロロエチレン、クロロベンゼン、オルソジクロロベンゼン等のハロゲン化炭化水素類；フェノール、バラクロロフェノール等のフェノール類；ベンゼン、トルエン、キシレン、メトキシベンゼン、１，２−ジメトキシベンゼン等の芳香族炭化水素類；アセトン、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、シクロペンタノン、２−ピロリドン、Ｎ−メチル−２−ピロリドン等のケトン系溶媒；酢酸エチル、酢酸ブチル等のエステル系溶媒；t−ブチルアルコール、グリセリン、エチレングリコール、トリエチレングリコール、エチレングリコールモノメチルエーテル、ジエチレングリコールジメチルエーテル、プロピレングリコール、ジプロピレングリコール、２−メチル−２，４−ペンタンジオールのようなアルコール系溶媒；ジメチルホルムアミド、ジメチルアセトアミドのようなアミド系溶媒；アセトニトリル、ブチロニトリルのようなニトリル系溶媒；ジエチルエーテル、ジブチルエーテル、テトラヒドロフランのようなエーテル系溶媒；あるいは二硫化炭素、エチルセルソルブ、ブチルセルソルブ等があげられる。これらの溶媒は、単独あるいは混合して使用できる。
【００８５】
また、さらに、前記成膜材料溶液中には、安定剤、可塑剤、金属類等を含む、種々の従来公知である添加剤を、必要に応じて配合できる。
【００８６】
前記成膜材料溶液を塗工する延伸可能な基材の材料としては、特に制限されないが、本発明の複屈折性光学フィルムを、前記塗工基材との一体品として使用する場合は、光学的に透明なものが好ましい。前記基材の材用としては、例えば、トリアセチルセルロース等のアセテート系樹脂、ポリエステル系樹脂、ポリエーテルスルホン系樹脂、ポリスルホン系樹脂、ポリカーボネート系樹脂、ポリアミド系樹脂、ポリイミド系樹脂、ポリオレフィン系樹脂、アクリル系樹脂、ポリノルボルネン系樹脂、セルロース系樹脂、ポリアリレート系樹脂、ポリスチレン系樹脂、ポリビニルアルコール系樹脂、ポリ塩化ビニル系樹脂、ポリ塩化ビニリデン系樹脂、ポリアクリル系樹脂、側鎖に置換イミド基または非置換イミド基を有する熱可塑性樹脂と側鎖に置換フェニル基または非置換フェニル基とニトリル基を有する熱可塑性樹脂との混合物、液晶ポリマー系等があげられる。
【００８７】
前記基材の厚みは、使用目的等に応じて適宜決定できるが、強度や薄層化等の点より、５〜５００μｍの範囲であるのが好ましく、より好ましくは１０〜２００μｍ、さらに好ましくは１５〜１５０μｍの範囲である。
【００８８】
本発明は、さらに、本発明の複屈折性光学フィルムと偏光子とを含む積層体である楕円偏光板を提供する。
【００８９】
本発明の楕円偏光板を作製する方法としては、例えば、▲１▼基材上の本発明の複屈折性光学フィルムを、接着剤または粘着剤を介して、偏光子または偏光板に転写して積層する方法、▲２▼基材上に形成した本発明の複屈折性光学フィルムを積層体として用い、接着剤または粘着剤を介して、偏光板に積層する方法、▲３▼基材との積層体である本発明の複屈折性光学フィルムを保護層として利用し、接着剤または粘着剤を介して、さらに偏光子を積層する方法、▲４▼偏光子を基材として用い、直接前記偏光子上に本発明の複屈折性光学フィルムを形成する方法等があげられる。
【００９０】
前記接着剤または粘着剤としては、特に限定はなく、例えば、アクリル系、シリコーン系、ポリエステル系、ポリウレタン系、ポリエーテル系、ゴム系等の透明な感圧接着剤等、適宜な接着剤または粘着剤を用いることができる。中でも、光学フィルム等の光学特性の変化を防止する点より、硬化や乾燥の際に高温のプロセスを要しないもの、長時間の硬化処理や乾燥時間を要しないものが好ましい。また、液晶表示装置等に用いる場合、加熱・加湿による発泡現象や剥がれ現象の防止、液晶セルの反り防止、高品質で耐久性に優れる形成性等の点より、吸湿率が低く、耐熱性に優れる接着剤または粘着剤であることが好ましい。
【００９１】
前記偏光板としては、特に限定されないが、その基本的な構成は、二色性物質を含有するポリビニルアルコール系偏光フィルム等からなる偏光子の片側または両側に、適宜の接着層、例えばビニルアルコール系ポリマー等からなる接着剤層を介して、保護層となる透明保護フィルムを積層したものからなる。
【００９２】
前記偏光子としては、自然光を入射させると直線偏光を透過するものであれば、特に限定されない。前記偏光子の材料としては、例えば、ポリビニルアルコールや部分ホルマール化ポリビニルアルコール等のビニルアルコール系ポリマーのフィルムがあげられる。このフィルムに、ヨウ素や二色性染料等よりなる二色性物質による染色処理、延伸処理、架橋処理等の処理をすることで、前記偏光子を得ることができる。また、材料としてポリビニルアルコールの脱水処理物やポリ塩化ビニルの脱塩酸処理物等のポリエン配向フィルム等を用いた偏光子でもよい。これらの中でも、ヨウ素または二色性染料を吸着配向させたポリビニルアルコール系フィルムの偏光子が好ましく、さらに光透過率や偏光度に優れるものがより好ましい。偏光子の厚みは、１〜８０μｍが一般的であるが、これに限定されない。
【００９３】
前記透明保護フィルムの材料としては、特に限定されないが、透明性や機械的強度、熱安定性や水分遮蔽性等に優れるポリマーのフィルム等が好ましい。そのポリマーの例としては、アセテート樹脂、ポリエステル樹脂、ポリエーテルスルホン樹脂、ポリカーボネート樹脂、ポリアミド樹脂、ポリイミド樹脂、ポリノルボルネン樹脂、ポリオレフィン樹脂、アクリル樹脂、側鎖に置換イミド基または非置換イミド基を有する熱可塑性樹脂と側鎖に置換フェニル基または非置換フェニル基とニトリル基を有する熱可塑性樹脂との混合物等があげられる。前記アセテート樹脂の具体例としては、トリアセチルセルロースがあげられ、前記熱可塑性樹脂の混合物の具体例としては、特開２００１−３４３５２９号公報（ＷＯ０１／３７００７）に記載のイソブテンとＮ−メチルマレイミドとからなる交互共重合体とアクリロニトリル・スチレン共重合体とを含有する樹脂組成物があげられる。偏光特性や耐久性等の点より、表面をアルカリ等でケン化処理したトリアセチルセルロースフィルムが好ましい。前記透明保護フィルムの厚みとしては、任意であるが、通常、偏光板の薄型化等の点より、５００μｍ以下が好ましく、より好ましくは、５〜３００μｍ、さらにより好ましくは、５〜１５０μｍである。なお、前記偏光子の両側に前記透明保護フィルムを設ける場合、その表裏で異なるポリマー等からなる透明保護フィルムであってもよい。
【００９４】
また、前記透明保護フィルムは、例えば、色付きがないことが好ましい。具体的には、前記透明保護フィルムの厚み方向の位相差値Ｒｔｈが、−９０ｎｍ〜＋７５ｎｍであることが好ましい。この範囲のＲｔｈを有する透明保護フィルムであれば、この透明保護フィルムに起因する偏光板の光学的な着色をほぼ解消できる。前記Ｒｔｈは、−８０ｎｍ〜＋６０ｎｍの範囲がより好ましく、さらにより好ましくは、−７０ｎｍ〜＋４５ｎｍの範囲である。
【００９５】
前記透明保護フィルムは、本発明の目的を損なわない限り、さらに、ハードコート処理、反射防止処理、スティッキングの防止処理、拡散処理、アンチグレア処理等が施されたものでもよい。
【００９６】
前記ハードコート処理は、偏光板表面の傷付き防止等を目的とし、例えば、前記透明保護フィルムの表面に、硬化型樹脂から構成される硬度や滑り性に優れた硬化被膜を形成する処理である。前記硬化型樹脂としては、例えば、シリコーン系、ウレタン系、アクリル系、エポキシ系等の紫外線硬化型樹脂が使用でき、前記処理は、従来公知の方法によって行うことができる。前記反射防止処理は、偏光板表面での外光の反射防止を目的とし、従来公知の反射防止フィルム等の形成により達成できる。
【００９７】
前記スティッキング防止処理は、隣接層との密着防止を目的とし、前記拡散処理は、偏光板透過光を拡散して視角を拡大して視角補償すること等を目的とし、前記アンチグレア処理は、偏光板の表面で外光が反射して偏光板透過光の視認を阻害することの防止等を目的とする。これらの処理は、例えば、前記透明保護フィルムの表面に微細凹凸構造を形成することにより行うことができる。このような凹凸構造の形成方法としては、例えば、サンドブラスト方式やエンボス加工方式等による粗面化方式、透明微粒子を前記透明保護フィルムの材料に配合する方式等があげられる。
【００９８】
前記透明微粒子としては、例えば、シリカ、アルミナ、チタニア、ジルコニア、酸化カルシウム、酸化錫、酸化インジウム、酸化カドミウム、酸化アンチモン等の導電性または非導電性の無機系微粒子があげられる。この他にも、前記透明微粒子としては、例えば、ポリメタクリレートやポリウレタン等の架橋または未架橋のポリマー粒状物等からなる有機系微粒子等もあげれれる。前記透明微粒子の平均粒径は、例えば、０．１〜２０μｍの範囲であり、好ましくは、０．５〜１５μｍ、より好ましくは、０．５〜１０μｍの範囲である。また、前記透明微粒子の使用量は、特に制限されないが、通常、前記透明保護フィルムの材料１００重量部あたり２〜７０重量部の範囲が好ましく、より好ましくは、５〜５０重量部である。
【００９９】
前記透明微粒子が配合されたアンチグレアを目的とする層は、例えば、前述のように前記透明保護フィルムそのものを使用することもでき、また、前記保護層の表面に塗工層等として形成されてもよい。さらに、このアンチグレアを目的とする層は、拡散層を兼ねるものであってもよい。同様に、前記反射防止、スティッキング防止、拡散等を目的とする層は、それらの層を設けたシート等から構成される光学層として、前記透明保護フィルムとは別層のものとして設けることもできる。
【０１００】
前記偏光子と保護層である前記透明保護フィルムとの接着処理は、特に限定されず、例えば、アクリル系ポリマーやビニルアルコール系ポリマーからなる接着剤を使用して行うことができる。湿度や熱の影響で剥がれにくく、光透過率や偏光度に優れる偏光板とすることができる等の点から、さらに、ホウ酸、ホウ砂、グルタルアルデヒド、メラミン、シュウ酸等のビニルアルコール系ポリマーの水溶性架橋剤等を含む接着剤等が好ましい。これらの接着剤の層は、例えば、水溶液を塗工し、乾燥させる等して形成できる。前記水溶液の調製に際しては、必要に応じて、他の添加剤や、酸等の触媒も配合できる。これらの中でも、前記接着剤としては、ＰＶＡフィルムとの接着性に優れる点から、ポリビニルアルコールからなる接着剤が好ましい。
【０１０１】
また、本発明の複屈折性光学フィルムおよび楕円偏光板は、例えば、各種位相差板、拡散制御フィルム、輝度向上フィルム等と組合せて用いることもできる。前記位相差板としては、ポリマーを一軸延伸または二軸延伸したもの、Ｚ軸配向処理したもの、液晶性高分子を塗布したもの等があげられる。前記拡散制御フィルムとしては、例えば、視野角を制御するための拡散、散乱、屈折を利用したフィルムや、解像度に関わるギラツキや散乱光等を制御するための拡散、散乱、屈折を利用したフィルム等を用いることができる。輝度向上フィルムとしては、例えば、コレステリック液晶の選択反射とλ／４板とを用いた輝度向上フィルムや、偏光方向による異方性散乱を利用した散乱フィルム等を用いることができる。また、ワイヤーグリッド型偏光子と組合せて用いてもよい。
【０１０２】
本発明の光学フィルムや楕円偏光板は、例えば、各種液晶表示装置の形成等に用いることが好ましい。その適用に際しては、必要に応じて、前記接着剤または粘着剤を介して、偏光板、反射板、半透過反射板、輝度向上フィルム等の他の光学層を積層できる。前記光学層は、一層でもよいし、二層以上を積層してもよい。
【０１０３】
前記反射板を、例えば、本発明の楕円偏光板にさらに積層すれば、反射型偏光板を形成できる。この反射型偏光板は、通常、液晶セルの裏側に配置され、視認側（表示側）からの入射光を反射させて表示するタイプの液晶表示装置（反射型液晶表示装置）等の形成に使用される。このような液晶表示装置では、例えば、バックライト等の光源の内蔵を省略できることから、液晶表示装置の薄型化を図り易い等の利点を有する。
【０１０４】
前記反射型偏光板は、例えば、前記楕円偏光板の片面に、金属等からなる反射板を配置する方式等、従来公知の方法により形成できる。具体例には、例えば、前記透明保護フィルムの片面（露出面）に、必要に応じマット処理を行い、その表面に、アルミニウム等の反射性金属からなる箔や蒸着膜を反射板として形成する方法等があげられる。
【０１０５】
また、前記反射型偏光板の他の例として、前述のようにして表面を微細凹凸構造とした前記透明保護フィルムの上に、その微細凹凸構造を反映させた前記反射板を形成したもの等もあげられる。表面微細凹凸構造の反射板は、入射光を乱反射により拡散させ、指向性やギラギラした見栄えを防止し、明暗のムラを抑制しうる利点を有する。
【０１０６】
前記反射板の形成方法としては、例えば、真空蒸着方式、イオンプレーティング方式もしくはスパッタリング方式等の蒸着方式またはメッキ方式等の従来公知の手段で、金属を前記透明保護フィルムの表面に直接形成させる方法等があげられる。
【０１０７】
また、前記反射型偏光板は、前述のように前記反射板を前記楕円偏光板の保護層に直接形成する方式に代えて、前記保護層に使用される透明保護フィルムのような適当なフィルムに反射板を設けた反射シート等を使用して形成してもよい。前記反射型偏光板の反射板は、通常、金属から構成されるため、酸化による反射率の低下防止、ひいては初期反射率の長期持続等の点から、その使用形態は、前記反射板の反射面が前記保護層や楕円偏光板等で被覆された状態であることが好ましい。
【０１０８】
一方、半透過型偏光板とは、前記反射型偏光板において、反射型の反射板を、半透過型の反射板としたものであり、反射板で光を反射しかつ透過するハーフミラー等があげられる。
【０１０９】
前記半透過型偏光板は、通常、液晶セルの裏側に設けられ、液晶表示装置等を比較的明るい雰囲気で使用する場合には、視認側（表示側）からの入射光を反射させて画像を表示する。また、比較的暗い雰囲気においては、前記半透過型偏光板のバックサイドに内蔵されているバックライト等の内蔵光源を使用して画像を表示する。すなわち、前記半透過型偏光板は、明るい雰囲気下では、バックライト等の光源使用のエネルギーを節約でき、比較的暗い雰囲気下においても内蔵光源を用いて使用できるタイプの液晶表示装置等の形成に有用である。
【０１１０】
さらに、前記輝度向上フィルムとしては、例えば、誘電体の多層薄膜や屈折率異方性が相違する薄膜フィルムの多層積層体のような、所定偏光軸の直線偏光を透過して他の光は反射する特性を示すもの等が使用でき、例えば、３Ｍ社製商品名「Ｄ−ＢＥＦ」等があげられる。また、コレステリック液晶層、特にコレステリック液晶ポリマーの配向フィルム、その配向液晶層をフィルム基材上に支持したもののように、左回りまたは右回りのいずれか一方の円偏光を反射して他の光は透過する特性を示すものであってもよく、例えば、日東電工社製商品名「ＰＣＦ３５０」、Ｍｅｒｃｋ社製商品名「Ｔｒａｎｓｍａｘ」等が使用できる。
【０１１１】
前述のように、２層以上積層した光学部材は、液晶表示装置等の製造過程で順次別個に積層する方式によっても形成できるが、予め積層して前記光学部材としたものは、品質の安定性や組立作業性等に優れ、液晶表示装置等の製造効率を向上させることができる利点がある。なお、積層には、例えば、前述のような接着剤または粘着剤等を使用でき、微粒子を含有することにより光拡散性を示す接着剤または粘着剤等も使用できる。なお、前記接着剤または粘着剤等の層は、必要に応じて必要な面に適宜設ければよい。
【０１１２】
本発明の複屈折性光学フィルムや楕円偏光板等に設けた前記接着剤または粘着剤等の層が表面に露出する場合には、前記接着剤または粘着剤等の層を実用に供するまでの間、汚染防止等を目的として、セパレータにより仮着カバーすることが好ましい。前記セパレータは、前記保護層の透明保護フィルム等のような薄葉体に対して、必要に応じて、シリコーン系、長鎖アルキル系、フッ素系、硫化モリブデン等の剥離剤の層を一層以上含む剥離コート等により形成できる。
【０１１３】
なお、前記光学部材等に使用する前記複屈折性光学フィルム、前記偏光子、前記透明保護フィルム、前記接着剤または粘着剤等の各層は、例えば、サリチル酸エステル系化合物、ベンゾフェノン系化合物、ベンゾトリアゾール系化合物、シアノアクリレート系化合物、ニッケル錯塩系化合物等の紫外線吸収剤で処理すること等により紫外線吸収能を付与してもよい。
【０１１４】
本発明の複屈折性光学フィルムおよび楕円偏光板は、液晶表示装置等の各種装置の形成等に適用することが好ましく、例えば、前記のさまざまな偏光板等を液晶セルの片側または両側に配置した、反射型、半透過型、あるいは透過・反射両用型等の液晶表示装置に適用できる。
【０１１５】
また、前記液晶セルの両側に前記偏光板、光学部材等を設ける場合、それらは同じものであってもよいし、異なるものであってもよい。さらに、液晶表示装置の形成に際しては、例えば、プリズムアレイシートやレンズアレイシート、光拡散板やバックライト等の適宜な部品を適宜な位置に１層又は２層以上配置できる。
【０１１６】
このように本発明は、本発明の複屈折性光学フィルムまたは楕円偏光板を少なくとも１つ含む液晶表示装置を提供する。前記液晶表示装置における液晶セルの種類は、特に制限されず、例えば、薄膜トランジスタ型に代表されるアクティブマトリクス駆動型、ツイストネマチック型やスーパーツイストネマチック型に代表される単純マトリクス駆動型を適宜使用できる。
【０１１７】
なお、本発明の光学フィルムは、ＶＡ（Vertical Alighned）セルの光学補償に非常に優れているので、ＶＡモードの液晶表示装置用の視角補償フィルムとして、非常に有用である。
【０１１８】
また、本発明の複屈折性光学フィルムおよび楕円偏光板は、有機ＥＬディスプレイ、ＰＤＰ、ＦＥＤ等の自発光型表示装置にも、液晶表示装置と同様にして用いることができる。自発光型フラットディスプレイに設ける場合は、本発明の複屈折性光学フィルムのΔｎｄをλ／４にすることで、円偏光を得ることができ、反射防止フィルターとして利用できる。
【０１１９】
【実施例】
以下、実施例及び比較例を用いて本発明をさらに具体的に説明するが、本発明は以下の実施例に限定されるものではない。
【０１２０】
（実施例１）
２，２'−ビス（３，４−ジカルボキシフェニル）ヘキサフルオロプロパン二無水物（６ＦＤＡ）および２，２'−ビス（トリフルオロメチル）−４，４'−ジアミノビフェニル（ＰＦＭＢまたはＴＦＭＢ）から合成された重量平均分子量Ｍｗ＝１００,０００のポリイミドを、シクロヘキサノン溶媒に溶解し、１５質量％のポリイミド溶液を調製した。この溶液を、厚み８０μｍのトリアセチルセルロース（ＴＡＣ）フィルム上に塗布し、その後すぐに（約３０秒後に）１６０℃で乾燥処理しながら、前記ＴＡＣフィルムを自由端縦一軸延伸によって４％延伸し、延伸されたＴＡＣフィルム上に複屈折性光学フィルムを得た。前記延伸時のフィルム状塗膜のポリイミド濃度は、約７５質量％であった。得られたフィルムの特性は、ｄ＝６μｍ、Δｎｄ＝６０ｎｍ、Ｒｔｈ＝２５０ｎｍであり、その光学異方性は、ｎｘ＞ｎｙ＞ｎｚであった。また、得られた複屈折性光学フィルムの複屈折率（Δｎ＝ｎｘ−ｎｚ）は、０．０４２であった。
【０１２１】
（実施例２）
実施例１と同様のポリイミド溶液を、実施例１と同様のＴＡＣフィルム上に塗布し、その後すぐに（約３０秒後に）１６０℃で乾燥処理しながら、前記ＴＡＣフィルムを固定端横一軸延伸によって１０％延伸し、延伸されたＴＡＣフィルム上に複屈折性光学フィルムを得た。前記延伸時のフィルム状塗膜のポリイミド濃度は、約７０質量％であった。得られたフィルムの特性は、ｄ＝６μｍ、Δｎｄ＝７０ｎｍ、Ｒｔｈ＝２７０ｎｍであり、その光学異方性は、ｎｘ＞ｎｙ＞ｎｚであった。また、得られた複屈折性光学フィルムの複屈折率（Δｎ＝ｎｘ−ｎｚ）は、０．０４５であった。
【０１２２】
（比較例１）
ポリノルボルネン系フィルム（ＪＳＲ製、商品名ＡＲＴＯＮフィルム）を１７５℃で自由端縦一軸延伸によって１０％延伸し、複屈折性光学フィルムを得た。そのフィルムの特性は、ｄ＝９５μｍ、Δｎｄ＝８０ｎｍ、Ｒｔｈ＝８０ｎｍであり、その光学異方性は、ｎｘ＞ｎｙ＝ｎｚであった。また、得られた複屈折性光学フィルムの複屈折率（Δｎ＝ｎｘ−ｎｚ）は、０．０００８４であった。
【０１２３】
（比較例２）
比較例１と同様のフィルムを、１７５℃で固定端横一軸延伸によって１０％延伸し、複屈折性光学フィルムを得た。そのフィルムの特性は、ｄ＝８０μｍ、Δｎｄ＝５０ｎｍ、Ｒｔｈ＝１１５ｎｍであり、その光学異方性は、ｎｘ＞ｎｙ＞ｎｚであった。また、得られた複屈折性光学フィルムの複屈折率（Δｎ＝ｎｘ−ｎｚ）は、０．００１４であった。
【０１２４】
（比較例３）
実施例１同様の溶液を、実施例１と同様のＴＡＣフィルム上に塗布し、その後１００℃で乾燥処理し、前記ＴＡＣフィルム上に形成された複屈折性光学フィルムを得た。このフィルムの特性は、ｄ＝５μｍ、Δｎｄ＝０．７ｍ、Ｒｔｈ＝１８０ｎｍであり、その光学異方性は、ｎｘ≒ｎｙ＞ｎｚであった。また、得られた複屈折性光学フィルムの複屈折率（Δｎ＝ｎｘ−ｎｚ）は、０．０３６であった。
【０１２５】
（位相差測定）
実施例１および２、比較例１から３で得られた複屈折性光学フィルムの、Δｎｄ＝（ｎｘ−ｎｙ）ｄ、Ｒｔｈ＝（ｎｘ−ｎｚ）ｄ、および、配向軸精度（光軸分布）を、王子計測機器製商品名ＫＯＢＲＡ２１ＡＤＨを用いて測定した。その結果を表１にまとめて示す。なお、測定波長は５９０ｎｍである。
【０１２６】

【０１２７】
【発明の効果】
以上説明したとおり、本発明は、延伸可能な基材上に成膜材料溶液を塗工し、前記溶液を乾燥させながら延伸を行うことにより、光学的な異方性を付与する工程を含む複屈折性光学フィルムの製造方法であるから、本発明によれば、少ない工程で、容易に、ｎｘ＞ｎｙ＞ｎｚという光学特性を有し、液晶セルの光学補償に好適な複屈折性光学フィルム、それを用いた楕円偏光板およびそれらを用いた液晶表示装置を得ることができる。
【図面の簡単な説明】
【図１】本発明の複屈折性光学フィルムの軸方向を示す図である。
【図２】本発明の複屈折性光学フィルムの製造方法の一例を示す概略図である。
【図３】本発明の複屈折性光学フィルムの製造方法の一例を示す概略図である。
【符号の説明】
１：光学フィルム
２、３：ニップロール
４：ポリマー基材
５：塗布用ダイ
６：フィルム状塗膜
７：加熱装置
８：光学フィルム
９：ポリマー基材
１０：塗布用ダイ
１１：フィルム状塗膜
１２：加熱装置
１３：光学フィルム
１４：予熱ゾーン
１５：加熱延伸ゾーン
１６：緩和ゾーン
１７：冷却ゾーン[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a production method of a birefringent optical film that can be used for optical compensation of a liquid crystal cell, a film obtained by the production method, an elliptically polarizing plate using the same, and a liquid crystal display device using them.
[0002]
[Prior art]
Conventionally, biaxial retardation plates for optical compensation of various liquid crystal display devices have been produced by a polymer film stretching technique. Examples of the stretching method include an inter-roll tensile stretching method, an inter-roll compression stretching method, a tenter transverse uniaxial stretching method, and the like (for example, see Patent Document 1). In addition, a retardation plate can be obtained by biaxial stretching under conditions that have anisotropy in relation to film strength (see, for example, Patent Document 2). In addition to this, there is also a method of producing a birefringent film having negative uniaxiality by forming a soluble polyimide into a film, which is different from the stretching technique (see, for example, Patent Document 3). By using these stretching techniques and the like, a retardation film having optical characteristics of nx ≧ ny> nz is produced, and this is used as a viewing angle compensation film for a liquid crystal cell disposed between a driving cell and a polarizer. An angular liquid crystal display device can be obtained.
[0003]
For example, in a multi-domain aligned vertical alignment (VA) mode liquid crystal cell, a biaxial birefringent film is used as a birefringence compensation film for a liquid crystal display device in order to obtain a wide viewing angle. This biaxial birefringent film can be obtained, for example, by stretching a polymer film. In this case, as the stretching method, a fixed end uniaxial stretching method in which the longitudinal direction of the film is fixed and stretched in the width direction, such as stretching in two directions in the plane (x, y direction) or transverse stretching by a tenter, Conventionally used. Also, a biaxial birefringent film including a step of placing a film forming material solution on a substrate and drying to obtain an optically negative uniaxial film, and a step of stretching the solution to form a biaxial film Is also known (see, for example, Patent Document 4).
[0004]
In a biaxial refractive film, the three-dimensional refractive index can be controlled. The three-dimensional refractive index is a main refractive index nx, ny in the plane (nx is defined as a slow axis) and a refractive index nz in the thickness direction. In particular, the in-plane retardation value Δnd. [Δnd = (nx−ny) d; d is film thickness] and thickness direction retardation value Rth [Rth = (nx−nz) d] can be controlled. Control of Δnd and Rth by biaxial stretching can be performed by, for example, stretching temperature and stretching ratios in the x and y directions. That is, Δnd can be controlled by the ratio of the stretch ratio in the x direction and the y direction, and Rth can be controlled by the stretch ratio in the x direction and the y direction. In the biaxial birefringent film, the formation of Rth is important, and in particular, the role of compensating the birefringence of the VA mode liquid crystal greatly depends on Rth. That is, in order to positively express Rth, the stretching amount in the x direction and the y direction is actively increased, so that the stretching ratio is generally increased. Therefore, in the current biaxial stretching technique, there is a problem that the accuracy of Δnd and Rth and the accuracy of the optical axis due to the bowing phenomenon are likely to decrease as the stretching ratio increases.
[0005]
[Patent Document 1]
JP-A-3-33719
[Patent Document 2]
Japanese Patent Laid-Open No. 3-24502
[Patent Document 3]
Japanese National Patent Publication No. 8-511812
[Patent Document 4]
JP 2000-190385 A
[0006]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described conventional problems, and is suitable for optical compensation of a liquid crystal cell with improved in-plane retardation value Δnd, thickness direction retardation value Rth, and optical axis accuracy. It aims at providing the manufacturing method of a refractive optical film, the optical film obtained by the said manufacturing method, the elliptically polarizing plate using the same, and the liquid crystal display device which has arrange | positioned them.
[0007]
[Means for Solving the Problems]
  In order to achieve the above object, the method for producing a birefringent optical film of the present invention comprises forming a film-like coating film by coating a film forming material solution, and evaporating and removing the solvent in the coating film. When forming, it includes a step of imparting optical anisotropy to the film by stretching the film-like coating film.The birefringent optics in which stretching of the film-like coating film is performed by coating the film-forming material solution on a stretchable substrate to form a film-like coating film and stretching the substrate. It is a manufacturing method of a film.
[0008]
The inventors of the present invention have made extensive studies on optical film manufacturing technology. As a result, the film forming material solution is applied to form a film-like coating film, and the stretching is performed while the solution is dried, for example, the thickness direction retardation value Rth is controlled by the application amount of the solution, The inventors have found that the in-plane retardation value Δnd can be controlled by the stretching amount of the stretching, and have reached the present invention. According to the present invention, it is possible to easily obtain a birefringent optical film having optical characteristics of nx> ny> nz and suitable for optical compensation of a liquid crystal cell in one step, regardless of the stretching direction. it can.
[0009]
For example, when a polymer having a very high glass transition temperature (Tg) such as polyimide is used, it is necessary that the solvent remains in the coating film when the orientation is oriented. That is, for example, as described in JP-A-2000-190385 and JP-A-2001-318227, paragraph 0025, in the method of stretching after the coating film is dried, the stretching orientation such as polyimide is particularly good. In the case of a high material, that is, a material whose (nx−ny) becomes large by stretching, it is difficult to control Δnd and its orientation axis. This is because, for example, the in-plane retardation value Δnd necessary for optical compensation of a VA mode liquid crystal display device may be about 100 nm or less, and can be obtained with a very low draw ratio. However, according to the method of the present invention in which the stretching orientation is performed while the solution is dried, since the solvent acts as a plasticizer, the stretching orientation of the film forming material is relaxed, and stretching can be performed at a certain stretching ratio. The orientation axis can be controlled.
[0010]
Here, in the present invention, nx, ny and nz are the refractive indexes in the three directions of the x-direction, y-direction and z-direction of the birefringent optical film 1 of the present invention, respectively, as shown in FIG. The x direction and the y direction are directions orthogonal to each other, and the z direction is the thickness direction. The x direction is the direction (the direction of the slow axis) showing the maximum refractive index in the film plane. Δnd and Rth are
Δnd = (nx−ny) d
Rth = (nx−nz) d
D represents the thickness of the film.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Next, the production method of the birefringent optical film of the present invention, the optical film obtained by the production method, the elliptically polarizing plate using the same, and the liquid crystal display device using them will be described in more detail.
[0012]
  The stretching in the present invention is performed by, for example, coating the film forming material solution on a stretchable substrate to form a film-like coating film, and stretching the substrate.Is done.In the step of stretching as described above, the drying temperature is preferably not less than the glass transition temperature of the stretchable substrate and not more than the melting point, depending on the type of the substrate, the type of solvent, the stretch ratio, etc. Can be selected as appropriate. If the drying temperature is equal to or higher than the glass transition temperature, it is preferable because generation of grace or the like on the substrate can be suppressed. Specifically, the temperature is usually preferably 40 ° C. or higher and 250 ° C. or lower, more preferably 80 ° C. or higher and 220 ° C. or lower, and even more preferably 100 ° C. or higher and 200 ° C. or lower.
[0013]
The density | concentration of the film-forming material solution used for the said coating can be suitably determined according to the molecular weight etc. of material, for example. For example, the concentration is preferably in the range of 0.5 to 60% by mass, more preferably 1 to 55% by mass, and still more preferably 2 to 50% by mass. When the concentration is 0.5% by mass or more, for example, a film having a sufficiently uniform film thickness distribution is obtained without being affected by a sudden volume change due to drying. Further, when the concentration is 60% by mass or less, for example, a film having sufficient strength and uniformity can be obtained without being affected by the molecular weight of the material. That is, even when the molecular weight of the film forming material is relatively increased and the viscosity of the film forming material solution is increased, the film thickness distribution of the coated film is sufficiently uniform.
[0014]
The stretching operation is preferably performed at a time when the ratio of the film forming material in the film-like coating film is, for example, in the range of 20 to 99.5% by mass, more preferably 30 to 99% by mass, Even more preferably, the time is 40 to 98.5% by mass. If the ratio of the film forming material is 20% by mass or more, the effect of stretching is sufficient, and the film is preferable because it can easily take a structure of nx> ny> nz. Further, if the ratio of the film forming material is 99.5% by mass or less, the amount of the solvent that acts as a plasticizer is sufficient, and the formed film can easily take a structure of nx> ny> nz, This is preferred because uneven stretching is less likely to occur.
[0015]
Although it does not restrict | limit especially as a draw ratio of the said film-form coating film, For example, 1.01-4 times are preferable, More preferably, it is 1.015-3 times, More preferably, it is 1.02- 2 times. If the draw ratio is 1.01 times or more, a sufficient drawing effect can be obtained, and thus the formed film is preferable because it can easily take a structure of nx> ny> nz. Moreover, if the said draw ratio is 4 or less, since a uniform film without a stretching nonuniformity can be maintained, it is preferable. Further, as a stretching method, for example, when performing stretching between rolls (stretching in the longitudinal direction) or the like, the film forming material is oriented by, for example, the shrinkage force of the base material in the width direction even when the stretching ratio is kept at 1. Thus, a film having a structure of nx> ny> nz can be obtained.
[0016]
In the production method of the present invention, the stretchable substrate is preferably a strip-shaped polymer film substrate, and the polymer film substrate is continuously supplied, that is, a continuous production method. In this case, the film-like coating film can be stretched by applying the film-forming material solution on the polymer film substrate to form a film-like coating film and stretching the polymer film substrate. .
[0017]
Although the extending | stretching direction of the said strip | belt-shaped polymer film base material is not specifically limited, For example, the longitudinal direction of the said polymer film base material, the width direction of the said polymer film base material, or the said both directions are mention | raise | lifted.
[0018]
The stretching (longitudinal stretching) operation in the longitudinal direction is not particularly limited, and a conventionally known method can be applied. For example, free end longitudinal stretching that does not hold the width direction end of the polymer film substrate, or the polymer The fixed end longitudinal stretching or the like that holds the width direction of the film substrate is preferable.
[0019]
In the free end longitudinal stretching, if a minimum necessary tension is applied to the transport of the polymer film substrate, molecular orientation in the plane is caused by contraction in the width direction of the polymer film substrate, and the in-plane retardation value is obtained. Δnd may be expressed, which is preferable. Even if the stretching amount is small, molecular orientation in the plane is easily promoted by necking in the width direction of the polymer film substrate, and λ / 2 plates and λ / 4 plates can be easily obtained.
[0020]
The fixed-end longitudinal stretching is preferable in the case where, for example, the molecular orientation in the plane is more easily controlled and a small Δnd is obtained because stretching is performed in the longitudinal direction while controlling necking.
[0021]
In FIG. 2, an example of the manufacturing method of this invention in case a extending | stretching direction is a longitudinal direction is shown. A film-forming material solution is applied from a coating die 5 onto a polymer film substrate 4 to which a minimum necessary tension is applied between the two nip rolls 2 and 3 in the direction of the arrow. 6 is formed. By heating in the oven 7 at the glass transition temperature or higher and the melting point or lower of the polymer film substrate, drying and stretching in the longitudinal direction can be performed, and the birefringent optical film 8 of the present invention can be obtained. Further, in the oven 7, in addition to the zone for heating and drying, for example, there may be a zone for preheating and a zone for cooling. The temperature of the zone to which the preheating is applied may be equal to or higher than the glass transition temperature as long as it is equal to or lower than the melting point of the polymer film substrate. Moreover, it is preferable that the said zone to cool is below a glass transition temperature.
[0022]
Further, the stretching (lateral stretching) operation in the width direction is not particularly limited. For example, the stretching may include a fixed-end lateral stretching for fixing the longitudinal direction of the polymer film substrate and a step of further relaxing (shrinking). A method or the like is preferable. As the relaxation (shrinkage) method, for example, a method of relaxing in the width direction after transverse stretching, a method of stretching in the width direction while relaxing in the longitudinal direction (lateral stretching longitudinal shrinkage), and the like are preferable.
[0023]
The fixed end transverse stretching is preferable when a smaller Δnd is obtained. Further, after the fixed-end transverse stretching, if an operation of relaxing (shrinking) in a direction opposite to the stretching direction is performed, Δnd, Rth and alignment axis accuracy can be further improved.
[0024]
The transverse stretching longitudinal shrinkage is preferable when obtaining a larger Δnd. In order to obtain a large Δnd by the transverse stretching at the fixed end, it is necessary to increase the stretching amount, and the orientation axis tends to shift due to the bowing phenomenon. However, the transverse stretching and longitudinal shrinkage does not have such an effect, and high alignment axis accuracy can be obtained. Therefore, Δnd larger than Δnd obtained by the fixed end transverse stretching can be easily obtained.
[0025]
Furthermore, as another example of the advantage of performing stretching in the width direction (lateral stretching), an arrangement in which the direction of the maximum refractive index in the birefringent optical film surface of the present invention is orthogonal to the absorption axis of the polarizing plate. In the case of obtaining an elliptically polarizing plate having, the birefringent optical film of the present invention and the polarizing plate or polarizing element can be easily bonded in a roll state, and therefore, it is industrially preferable.
[0026]
FIG. 3 shows an example of the production method of the present invention when the stretching direction is the width direction. On the polymer film substrate 9 conveyed in the direction of the arrow, a film forming material solution is applied from a coating die 10 to form a film-like coating film 11. In the oven 12, the film is stretched in the width direction while being heated and dried at a glass transition temperature or higher and a melting point or lower of the polymer film substrate to obtain the birefringent optical film 13 of the present invention. In addition, in the oven 12, in addition to the zone 15 that stretches above the glass transition temperature and below the melting point of the polymer film substrate, for example, the zone 14 that further preheats, relaxes (shrinks) in the direction opposite to the stretching direction. Zone 16 to be cooled, zone 17 to be cooled, and the like. The temperature 14 of the zone to which the preheating is applied and the temperature of the zone 16 to be relaxed (shrinked) may be equal to or higher than the glass transition temperature of the polymer film substrate as long as it is equal to or lower than the melting point of the polymer film substrate. . Moreover, it is preferable that the said zone 17 to cool is below the glass transition temperature of the said polymer film base material.
[0027]
In the production method of the present invention, a method for coating a film forming material solution on a stretchable substrate to form a film-like coating film is not particularly limited, and a conventionally known method can be applied. Specific examples include a spin coating method, a roll coating method, a flow coating method, a printing method, a dip coating method, a casting film forming method, a bar coating method, and a gravure printing method.
[0028]
The present invention also provides a birefringent optical film thus obtained. The birefringent optical film of the present invention may be used in a form peeled from the stretchable base material. When the optically transparent film is used as the base material, the base material is used. And may be used in the form of a laminate.
[0029]
The birefringent optical film of the present invention preferably has optical characteristics that satisfy all of the following conditions (i) to (iii).
nx> ny> nz (i)
0.005 ≦ (nx−nz) ≦ 0.3 (ii)
10 nm ≦ (nx−ny) d ≦ 600 nm (iii)
[0030]
If the birefringent optical film of the present invention satisfies the above (i) and (iii), the birefringence of the VA mode and OCB mode liquid crystal cells is preferably compensated, and the field of view is effective. In the above (iii), the in-plane retardation value (Δnd = (nx−ny) d) is preferably in the range of 10 nm ≦ Δnd ≦ 500 nm, and more preferably in the range of 20 nm ≦ Δnd ≦ 300 nm. is there.
[0031]
If the refractive index (nx-nz) in the thickness direction of the birefringent optical film of the present invention is 0.005 or more as shown in (ii) above, sufficient Rth is obtained without increasing the thickness. be able to. Moreover, if the refractive index (nx-nz) of the said thickness direction is 0.3 or less, phase difference control of the birefringent optical film of this invention will become easy. The range of refractive index (nx-nz) in the thickness direction is preferably 0.007 ≦ (nx−nz) ≦ 0.2, more preferably 0.01 ≦ (nx−nz) ≦ 0. A range of 15.
[0032]
In the birefringent optical film of the present invention, the projection direction distribution of the film optical axis onto the film plane is preferably within ± 3 °. Since the birefringent optical film produced by the production method of the present invention has good stretch orientation, the distribution of the optical axis is projected on the film plane even though the draw ratio is not large. Except for the coating end of the solution, it can usually be within ± 3 °. The optical axis distribution (alignment axis accuracy) is more preferably within a range of ± 2.5 °, and still more preferably within a range of ± 2 °.
[0033]
As the stretching operation in the production method of the present invention, when the longitudinal stretching is performed, the optical axis distribution can be made within ± 2.5 ° by setting conditions such as stretching temperature. In addition, when the transverse stretching is performed, as described above, a method of relaxing in the width direction after transverse stretching at the fixed end, a method of stretching in the width direction while relaxing in the longitudinal direction (lateral stretching longitudinal shrinkage), or the like is used. Thus, similarly, the optical axis distribution can be within ± 2.5 °.
[0034]
When optical compensation of a VA mode liquid crystal cell is performed, the in-plane retardation value Δnd is preferably a small value of 100 nm or less, and therefore, if the optical axis distribution is ± 2.5 °, the birefringence characteristics of the present invention. In a liquid crystal display device using an optical film, good display characteristics can be obtained.
[0035]
The film forming material in the film forming material solution used in the production method of the present invention preferably contains at least one polymer selected from the group consisting of polyamide, polyimide, polyester, polyetherketone, polyamideimide and polyesterimide. .
[0036]
Examples of the polyether ketone used in the production method of the present invention include, for example, polyaryl ether ketones described in JP-A No. 2001-49110 and represented by the following general formula (1).
[0037]
[Chemical 1]

In the above (1), X represents a substituent, and q represents the number of substitutions. X is, for example, a halogen atom, a lower alkyl group, a halogenated alkyl group, a lower alkoxy group, or a halogenated alkoxy group, and in a plurality of cases, they are the same or different.
[0038]
Examples of the halogen atom include a fluorine atom, a bromine atom, a chlorine atom, and an iodine atom. Among these, a fluorine atom is preferable. Examples of the lower alkyl group include C_1-6And a lower alkyl group having a straight chain or branched chain is preferably C_1-4The linear or branched alkyl group is more preferable. Among these, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group are even more preferable, and a methyl group and an ethyl group are particularly preferable. . Examples of the halogenated alkyl group include halides of the lower alkyl group such as a trifluoromethyl group. Examples of the lower alkoxy group include C_1-6And a linear or branched alkoxy group of_1-4The linear or branched alkoxy group is more preferable. Among these, a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, an isobutoxy group, a sec-butoxy group, and a tert-butoxy group are even more preferable, and a methoxy group and an ethoxy group are particularly preferable. is there. Examples of the halogenated alkoxy group include halides of the lower alkoxy group such as a trifluoromethoxy group.
[0039]
In the above (1), q is an integer from 0 to 4. Among these, it is preferable that q = 0 and that the carbonyl group and ether oxygen bonded to both ends of the benzene ring are present in the para position.
[0040]
In the above (1), R¹Is a group represented by the following formula (2), and m is an integer of 0 or 1.
[0041]
[Chemical 2]

In the above (2), X ′ represents a substituent, and q ′ represents the number of substitutions. X ′ is, for example, in the above-mentioned range that X can take, and in the case of a plurality, X ′ is the same or different. q 'is an integer from 0 to 4 and preferably q' = 0. P is an integer of 0 or 1.
[0042]
In the above (2), R²Represents a divalent aromatic group. Examples of the divalent aromatic group include o-, m- or p-phenylene, naphthalene, biphenyl, anthracene, o-, m- or p-terphenyl, phenanthrene, dibenzofuran, biphenyl ether, or And divalent groups derived from biphenyl sulfone. In these divalent aromatic groups, hydrogen directly bonded to the aromatic group may be substituted with a halogen atom, a lower alkyl group or a lower alkoxy group. Among these, R²Is preferably an aromatic group selected from the group consisting of the following formulas (3) to (9).
[0043]
[Chemical 3]

[0044]
In the above (1), the R¹Is preferably a group represented by the following formula (10). In the following formula (10), R²And p are as defined in (2) above.
[0045]
[Formula 4]

[0046]
Furthermore, in said (1), n represents a polymerization degree. Specifically, the value of n is, for example, 2 to 5000, and preferably 5 to 500. Moreover, the polymerization may consist of the same repeating unit or may consist of different repeating units. In the latter case, the polymerization may be block polymerization or random polymerization.
[0047]
Furthermore, it is preferable that the terminal of the polyaryl ether ketone represented by the above (1) is fluorine on the p-tetrafluorobenzoylene group side and a hydrogen atom on the oxyalkylene group side. That is, the polyaryl ether ketone represented by the above (1) is preferably a polymer represented by the following general formula (11). In addition, n represents the polymerization degree similar to said (1).
[0048]
[Chemical formula 5]

[0049]
Specific examples of the polyaryl ether ketone used in the production method of the present invention include those represented by the following formulas (12) to (15). In addition, n represents the polymerization degree similar to said (1).
[0050]
[6]

[7]

[8]

[Chemical formula 9]

[0051]
Examples of the polyamide or polyester used in the production method of the present invention include polyamides and polyesters described in JP-T-10-508048, and their repeating units are represented by the following general formula (16). Can do.
[0052]
[Chemical Formula 10]

In the above (16), Y is O or NH, and E is, for example, a covalent bond, C₂Alkylene group, halogenated C₂Alkylene group, CH₂Group, C (CX_Three)₂Group (where X is halogen or hydrogen), CO group, O atom, S atom, SO₂Group, Si (R)₂A group (where R is C_1-3Alkyl groups and C_1-3At least one selected from the group consisting of halogenated alkyl groups. ) And an N (R) group (where R is as defined above). Furthermore, E is in the meta or para position relative to the carbonyl functional group or Y group.
[0053]
Moreover, in said (16), A and B are substituents, and t and z represent the number of each substitution. P is an integer from 0 to 3, q is an integer from 1 to 3, and r is an integer from 0 to 3.
[0054]
Further, in the above (16), A is, for example, hydrogen, halogen, C_1-3Alkyl group, C_1-3A halogenated alkyl group, an alkoxy group represented by OR (where R is as defined above), an aryl group, a substituted aryl group by halogenation, etc., C_1-9Alkoxycarbonyl group, C_1-9Alkylcarbonyloxy group, C_1-12Aryloxycarbonyl group, C_1-12Arylcarbonyloxy group and substituted derivatives thereof, C_1-12Arylcarbamoyl group and C_1-12It is selected from the group consisting of an arylcarbonylamino group and substituted derivatives thereof, and in the plurality of cases, they are the same or different. B is, for example, halogen, C_1-3Alkyl group, C_1-3It is selected from the group consisting of a halogenated alkyl group, a phenyl group, and a substituted phenyl group. Examples of the substituent on the phenyl ring of the substituted phenyl group include halogen, C_1-3Alkyl group, C_1-3And halogenated alkyl groups and combinations thereof. The t is an integer from 0 to 4, and the z is an integer from 0 to 3.
[0055]
Furthermore, among the repeating units of polyamide or polyester represented by (16), those represented by the following general formula (17) are preferred.
[0056]
Embedded image

In the above (17), A, B and Y are as defined in the above (16), and v is an integer from 0 to 3, preferably from 0 to 2. x and y are each 0 or 1, but are not 0 at the same time.
[0057]
The molecular weight of these polyamides or polyesters is not particularly limited, but the weight average molecular weight (Mw) is preferably in the range of 20,000 to 500,000, more preferably in the range of 50,000 to 200,000. If the weight average molecular weight is within these ranges, sufficient strength can be obtained, and when an optical film is formed, it is difficult to cause cracks due to expansion and contraction, distortion, etc., and the polyamide or polyester does not gel. Good solubility in solvents is obtained.
[0058]
As the polyimide used in the production method of the present invention, for example, the polyimide described in JP-T-2000-511296 is exemplified, and 9,9-bis (aminoaryl) fluorene and aromatic tetracarboxylic dianhydride are used. A polymer containing one or more repeating units corresponding to the following general formula (18) containing a condensation polymerization product can be arbitrarily used.
[0059]
Embedded image

In (18) above, R^Three~ R⁶Is hydrogen, halogen, phenyl group, 1 to 4 halogen atoms or C_1-10A phenyl group substituted with an alkyl group of_1-10These are at least one kind of substituent each independently selected from the group consisting of alkyl groups. Preferably R^Three~ R⁶Is a halogen, a phenyl group, 1 to 4 halogen atoms or C_1-10A phenyl group substituted with an alkyl group of_1-10These are at least one kind of substituent each independently selected from the group consisting of alkyl groups.
[0060]
In the above (18), D is, for example, C_6-20These are tetravalent aromatic groups. Preferably, D is a pyromellitic group, a polycyclic aromatic group, a derivative of a polycyclic aromatic group, or a group represented by the following general formula (19).
[0061]
Embedded image

In the above (19), J is, for example, a covalent bond, C (R⁷)₂Group, CO group, O atom, S atom, SO₂Group, Si (C₂H_Five)₂Group or NR⁸A plurality of groups, each being the same or different. w represents an integer from 1 to 10, and R⁷Each independently represents hydrogen or C (R⁹)_ThreeIt is. R⁸Is hydrogen, an alkyl group having 1 to about 20 carbon atoms, or C_6-20In the case of plural, they are the same or different. R⁹Are each independently hydrogen, fluorine or chlorine.
[0062]
Examples of the polycyclic aromatic group include a tetravalent group derived from naphthalene, fluorene, benzofluorene or anthracene. Examples of the substituted derivative of the polycyclic aromatic group include C_1-10And the above polycyclic aromatic group substituted with at least one selected from the group consisting of halogens such as F and Cl.
[0063]
In addition, for example, the polyimide described in JP-A-8-511812 is exemplified. Specific examples include a homopolymer having a repeating unit represented by the general formula (20) or (21) and a polyimide having a repeating unit represented by the general formula (22). In addition, Formula (22) is a preferable form of Formula (20).
[0064]
Embedded image

Embedded image

Embedded image

[0065]
In the above (20) to (22), G and F are, for example, a covalent bond, CH₂Group, C (CH_Three)₂Group, C (CF_Three)₂Group, C (CX_Three)₂Group (where X is halogen), CO group, O atom, S atom, SO₂Group, Si (CH₂CH_Three)₂Group and N (CH_Three) Represents a group independently selected from the group consisting of groups.
[0066]
In the above (20) and (22), L is a substituent, and d and e represent the number of substitutions. L is, for example, halogen, C_1-3Alkyl group, C_1-3A halogenated alkyl group, a phenyl group, or a substituted phenyl group, and in the case of plural, they are the same or different. Examples of the substituted phenyl group include halogen and C_1-3Alkyl group, C_1-3Examples thereof include a substituted phenyl group having at least one type of substituent selected from the group consisting of halogenated alkyl groups. Examples of the halogen include fluorine, chlorine, bromine and iodine. d is an integer from 0 to 2, and e is an integer from 0 to 3.
[0067]
In the above (20) to (22), Q is a substituent, and f represents the number of substitutions. Q is selected from the group consisting of, for example, hydrogen, halogen, alkyl group, substituted alkyl group, nitro group, cyano group, thioalkyl group, alkoxy group, aryl group, substituted aryl group, alkyl ester group, and substituted alkyl ester group. A plurality of atoms or groups that are the same or different from each other. Examples of the halogen include fluorine, chlorine, bromine and iodine. Examples of the substituted alkyl group include a halogenated alkyl group. Examples of the substituted aryl group include a halogenated aryl group. f is an integer from 0 to 4, and g and h are integers from 0 to 3 and 1 to 3, respectively. Further, g and h are preferably larger than 1.
[0068]
In (21) above, R^TenAnd R¹¹Are groups independently selected from the group consisting of hydrogen, halogen, phenyl group, substituted phenyl group, alkyl group, and substituted alkyl group. Among them, R^TenAnd R¹¹Are preferably each independently a halogenated alkyl group.
[0069]
In (22) above, M¹And M²Are the same or different, eg halogen, C_1-3Alkyl group, C_1-3A halogenated alkyl group, a phenyl group, or a substituted phenyl group. Examples of the halogen include fluorine, chlorine, bromine and iodine. Examples of the substituted phenyl group include halogen, C_1-3Alkyl group, C_1-3Examples thereof include a substituted phenyl group having at least one type of substituent selected from the group consisting of halogenated alkyl groups.
[0070]
Specific examples of such polyimide include those represented by the following formula (23).
[0071]
Embedded image

[0072]
Furthermore, examples of the polyimide used in the production method of the present invention include a copolymer obtained by appropriately copolymerizing an acid dianhydride other than the skeleton and a diamine.
[0073]
Examples of the acid dianhydride include aromatic tetracarboxylic dianhydrides. Examples of this aromatic tetracarboxylic dianhydride include pyromellitic dianhydride, benzophenone tetracarboxylic dianhydride, naphthalene tetracarboxylic anhydride, heterocyclic aromatic tetracarboxylic dianhydride, 2,2- Examples thereof include substituted biphenyltetracarboxylic dianhydrides.
[0074]
Examples of the pyromellitic dianhydride include pyromellitic dianhydride, 3,6-diphenylpyromellitic dianhydride, 3,6-bis (trifluoromethyl) pyromellitic dianhydride, 3,6-dibromopyro Examples include mellitic anhydride, 3,6-dichloropyromellitic dianhydride, and the like. Examples of the benzophenone tetracarboxylic dianhydride include 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 2,3,3 ′, 4′-benzophenone tetracarboxylic dianhydride, 2, 2 ', 3,3'-benzophenone tetracarboxylic dianhydride and the like. Examples of the naphthalene tetracarboxylic anhydride include 2,3,6,7-naphthalene-tetracarboxylic dianhydride, 1,2,5,6-naphthalene-tetracarboxylic dianhydride, 2,6-dichloro. -Naphthalene-1,4,5,8-tetracarboxylic dianhydride and the like. Examples of the heterocyclic aromatic tetracarboxylic dianhydride include thiophene-2,3,4,5-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, Examples thereof include pyridine-2,3,5,6-tetracarboxylic dianhydride. Examples of the 2,2-substituted biphenyltetracarboxylic dianhydride include 2,2'-dibromo-4,4 ', 5,5'-biphenyltetracarboxylic dianhydride, 2,2'-dichloro-4 , 4'-5,5'-biphenyltetracarboxylic dianhydride, 2,2-bis (trifluoromethyl) -4,4'-5,5'-biphenyltetracarboxylic dianhydride, and the like.
[0075]
Other examples of the aromatic tetracarboxylic dianhydride include 3,3′4,4′-biphenylcarboxylic dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis ( 2,5,6-trifluoro-3,4-dicarboxyphenyl) methane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexa Fluoropropane dianhydride, 4,4′-bis (3,4-dicarboxyphenyl) -2,2-diphenylpropane dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride (4,4 '-Oxydiphthalic anhydride), bis (3,4-dicarboxyphenyl) sulfonic dianhydride (3,3', 4,4'-diphenylsulfonetetracarboxylic anhydride), 4,4 '-[4 , 4'-isopropylidene-di (p-ph Nyleneoxy)] bis (phthalic anhydride), N, N- (3,4-dicarboxyphenyl) -N-methylamine dianhydride, bis (3,4-dicarboxyphenyl) diethylsilane dianhydride, etc. can give.
[0076]
Among these, 2,2′-substituted biphenyltetracarboxylic dianhydride is preferable as the aromatic tetracarboxylic dianhydride, and more preferably 2,2′-bis (trihalomethyl) -4,4 ′, 5,5'-biphenyltetracarboxylic dianhydride, and more preferably 2,2-bis (trifluoromethyl) -4,4'-5,5'-biphenyltetracarboxylic dianhydride .
[0077]
Examples of the diamine include aromatic diamines. Examples of this aromatic diamine include benzene diamine, diaminobenzophenone, naphthalene diamine, heterocyclic aromatic diamine, and other aromatic diamines.
[0078]
Examples of the benzenediamine include o-, m- and p-phenylenediamine, 2,4-diaminotoluene, 1,4-diamino-2-methoxybenzene, 1,4-diamino-2-phenylbenzene and 1, Examples include diamines selected from the group consisting of benzenediamines such as 3-diamino-4-chlorobenzene. Examples of the diaminobenzophenone include 2,2′-diaminobenzophenone and 3,3′-diaminobenzophenone. Examples of the naphthalene diamine include 1,8-diaminonaphthalene and 1,5-diaminonaphthalene. Examples of the heterocyclic aromatic diamine include 2,6-diaminopyridine, 2,4-diaminopyridine, and 2,4-diamino-S-triazine.
[0079]
Other examples of the aromatic diamine include 4,4'-diaminobiphenyl, 4,4-diaminodiphenylmethane, 2,2-bis (4-aminophenyl) propane, and 4,4- (9-fluorenylidene). -Dianiline, 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl, 3,3'-dichloro-4,4'-diaminophenylmethane, 2,2'-dichloro-4,4 ' -Diaminobiphenyl, 2,2 ', 5,5'-tetrachlorobenzidine, 2,2-bis (4-aminophenoxyphenyl) propane, 2,2-bis (4-aminophenyl) -1,1,1, 3,3,3-hexafluoropropane, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 1,3-bis (3-aminophenoxy) benzene, 1,3- Bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4′-bis (4-aminophenoxy) biphenyl, 4,4′-bis (3-aminophenoxy) biphenyl, 2,2-bis (4- [4-aminophenoxy] phenyl) propane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane 4,4'-diaminodiphenyl thioether, 4,4'-diaminodiphenyl sulfone and the like.
[0080]
Although it does not specifically limit as molecular weight of these polyimides, As a weight average molecular weight, the range of 1,000-1,000,000 is preferable, for example, More preferably, it is the range of 2,000-500,000.
[0081]
As the film forming material in the film forming material solution used in the production method of the present invention, the above-mentioned polyaryl ether ketone, polyamide, polyester, polyimide, etc. may be used alone, for example, polyaryl ether ketone and polyamide. You may use as a 2 or more types of mixture which has a different functional group like a mixture.
[0082]
Moreover, you may mix | blend other resin with a different structure in the said film-forming material in the range which orientation does not fall remarkably. Examples of other resins used at this time include general-purpose resins, engineering plastics, thermoplastic resins, and thermosetting resins. Examples of the general-purpose resin include polyethylene (PE), polypropylene (PP), polystyrene (PS), polymethyl methacrylate (PMMA), ABS resin, and AS resin. Examples of the engineering plastic include polyacetate (POM), polycarbonate (PC), polyamide (PA: nylon), polyethylene terephthalate (PET), and polybutylene terephthalate (PBT). Examples of the thermoplastic resin include polyphenylene sulfide (PPS), polyethersulfone (PES), polyketone (PK), polyimide (PI), polycyclohexanedimethanol terephthalate (PCT), polyarylate (PAR), and liquid crystal polymer. (LCP) and the like. Examples of the thermosetting resin include epoxy resins and phenol novolac resins.
[0083]
In addition, when the other resin or the like is blended into the film forming material, the blending amount of the other resin is not particularly limited as long as the orientation is not significantly reduced. It is 0-50 mass% with respect to film-forming material, Preferably, it is 0-30 mass%.
[0084]
The solvent for the film forming material solution used in the production method of the present invention is not particularly limited as long as it can dissolve the film forming material and the like, and can be appropriately selected according to the type of the film forming material. Examples of the solvent include halogenated hydrocarbons such as chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, and orthodichlorobenzene; phenols such as phenol and parachlorophenol; benzene, toluene, Aromatic hydrocarbons such as xylene, methoxybenzene, 1,2-dimethoxybenzene; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, 2-pyrrolidone, N-methyl-2-pyrrolidone; Ester solvents such as ethyl acetate and butyl acetate; t-butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, die Alcohol solvents such as tylene glycol dimethyl ether, propylene glycol, dipropylene glycol, 2-methyl-2,4-pentanediol; amide solvents such as dimethylformamide and dimethylacetamide; nitrile solvents such as acetonitrile and butyronitrile; Examples include ether solvents such as diethyl ether, dibutyl ether and tetrahydrofuran; carbon disulfide, ethyl cellosolve, butyl cellosolve and the like. These solvents can be used alone or in combination.
[0085]
Furthermore, various conventionally known additives including stabilizers, plasticizers, metals and the like can be blended in the film forming material solution as necessary.
[0086]
The stretchable base material for coating the film forming material solution is not particularly limited, but when the birefringent optical film of the present invention is used as an integral part of the coated base material, it is optical. Transparent is preferable. Examples of the base material include acetate resin such as triacetyl cellulose, polyester resin, polyethersulfone resin, polysulfone resin, polycarbonate resin, polyamide resin, polyimide resin, polyolefin resin, Acrylic resin, polynorbornene resin, cellulose resin, polyarylate resin, polystyrene resin, polyvinyl alcohol resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyacrylic resin, substituted imide group in side chain Alternatively, a thermoplastic resin having an unsubstituted imide group and a mixture of a substituted phenyl group or a thermoplastic resin having a substituted phenyl group and a nitrile group in the side chain, a liquid crystal polymer system, and the like can be given.
[0087]
The thickness of the substrate can be appropriately determined according to the purpose of use and the like, but is preferably in the range of 5 to 500 μm, more preferably 10 to 200 μm, and still more preferably 15 from the viewpoint of strength and thinning. It is in the range of ˜150 μm.
[0088]
The present invention further provides an elliptically polarizing plate which is a laminate including the birefringent optical film of the present invention and a polarizer.
[0089]
As a method for producing the elliptically polarizing plate of the present invention, for example, (1) the birefringent optical film of the present invention on a substrate is transferred to a polarizer or a polarizing plate via an adhesive or an adhesive. A method of laminating, (2) a method of laminating the birefringent optical film of the present invention formed on a substrate as a laminate, and laminating on a polarizing plate via an adhesive or an adhesive, and (3) A method of further laminating a polarizer through an adhesive or a pressure-sensitive adhesive using the birefringent optical film of the present invention as a laminate, and (4) directly using the polarizer as a substrate, Examples thereof include a method for forming the birefringent optical film of the present invention on the core.
[0090]
The adhesive or pressure-sensitive adhesive is not particularly limited. For example, a suitable pressure-sensitive adhesive or pressure-sensitive adhesive such as a transparent pressure-sensitive adhesive such as acrylic, silicone, polyester, polyurethane, polyether, or rubber. An agent can be used. Among these, those that do not require a high-temperature process during curing and drying and those that do not require a long curing process or drying time are preferable from the viewpoint of preventing changes in optical properties such as an optical film. Also, when used in liquid crystal display devices, etc., it has a low moisture absorption rate and heat resistance from the viewpoints of prevention of foaming and peeling phenomena due to heating and humidification, prevention of warpage of liquid crystal cells, and high quality and durability. An excellent adhesive or pressure-sensitive adhesive is preferred.
[0091]
Although it does not specifically limit as said polarizing plate, The basic composition is a suitable adhesive layer, for example, vinyl alcohol type | system | group, on the one or both sides of the polarizer which consists of a polyvinyl-alcohol-type polarizing film etc. containing a dichroic substance. It consists of what laminated | stacked the transparent protective film used as a protective layer through the adhesive bond layer which consists of a polymer etc.
[0092]
The polarizer is not particularly limited as long as it transmits linearly polarized light when natural light is incident thereon. Examples of the material for the polarizer include films of vinyl alcohol polymers such as polyvinyl alcohol and partially formalized polyvinyl alcohol. The polarizer can be obtained by subjecting this film to a treatment such as a dyeing treatment with a dichroic substance such as iodine or a dichroic dye, a stretching treatment, and a crosslinking treatment. Moreover, a polarizer using a polyene oriented film such as a dehydrated polyvinyl alcohol product or a dehydrochlorinated polyvinyl chloride product may be used. Among these, a polarizer of a polyvinyl alcohol film in which iodine or a dichroic dye is adsorbed and oriented is preferable, and a polarizer excellent in light transmittance and polarization degree is more preferable. The thickness of the polarizer is generally 1 to 80 μm, but is not limited thereto.
[0093]
The material for the transparent protective film is not particularly limited, but a polymer film that is excellent in transparency, mechanical strength, thermal stability, moisture shielding properties, and the like is preferable. Examples of the polymer include acetate resin, polyester resin, polyethersulfone resin, polycarbonate resin, polyamide resin, polyimide resin, polynorbornene resin, polyolefin resin, acrylic resin, and a substituted or unsubstituted imide group in the side chain. Examples thereof include a mixture of a thermoplastic resin and a thermoplastic resin having a substituted phenyl group or an unsubstituted phenyl group and a nitrile group in the side chain. Specific examples of the acetate resin include triacetyl cellulose, and specific examples of the thermoplastic resin mixture include isobutene and N-methylmaleimide described in JP-A-2001-343529 (WO01 / 37007). And a resin composition containing an alternating copolymer of acrylonitrile / styrene copolymer. A triacetyl cellulose film whose surface is saponified with an alkali or the like is preferable from the viewpoint of polarization characteristics and durability. Although it is arbitrary as thickness of the said transparent protective film, Usually, 500 micrometers or less are preferable from points, such as thickness reduction of a polarizing plate, More preferably, it is 5-300 micrometers, More preferably, it is 5-150 micrometers. In addition, when providing the said transparent protective film on both sides of the said polarizer, the transparent protective film which consists of a polymer etc. which is different in the front and back may be sufficient.
[0094]
Moreover, it is preferable that the said transparent protective film does not have coloring, for example. Specifically, the thickness direction retardation value Rth of the transparent protective film is preferably −90 nm to +75 nm. If it is the transparent protective film which has Rth of this range, the optical coloring of the polarizing plate resulting from this transparent protective film can be almost eliminated. The Rth is more preferably in the range of −80 nm to +60 nm, and still more preferably in the range of −70 nm to +45 nm.
[0095]
The transparent protective film may be further subjected to a hard coat treatment, an antireflection treatment, a sticking prevention treatment, a diffusion treatment, an antiglare treatment or the like as long as the object of the present invention is not impaired.
[0096]
The hard coat treatment is for the purpose of preventing scratches on the surface of the polarizing plate, for example, forming a cured film having excellent hardness and slipperiness composed of a curable resin on the surface of the transparent protective film. . As the curable resin, for example, an ultraviolet curable resin such as silicone, urethane, acrylic, and epoxy can be used, and the treatment can be performed by a conventionally known method. The antireflection treatment is aimed at preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming a conventionally known antireflection film or the like.
[0097]
The anti-sticking treatment is for the purpose of preventing adhesion to an adjacent layer, the diffusion treatment is for the purpose of diffusing the light transmitted through the polarizing plate to enlarge the viewing angle and compensating the viewing angle, and the anti-glare treatment is for polarizing plate It is intended to prevent the outside light from being reflected on the surface of the light and hindering the viewing of the light transmitted through the polarizing plate. These treatments can be performed, for example, by forming a fine uneven structure on the surface of the transparent protective film. Examples of a method for forming such a concavo-convex structure include a roughening method such as a sandblasting method or an embossing method, a method of blending transparent fine particles into the material of the transparent protective film, and the like.
[0098]
Examples of the transparent fine particles include conductive or nonconductive inorganic fine particles such as silica, alumina, titania, zirconia, calcium oxide, tin oxide, indium oxide, cadmium oxide, and antimony oxide. In addition, examples of the transparent fine particles include organic fine particles composed of crosslinked or uncrosslinked polymer granules such as polymethacrylate and polyurethane. The average particle diameter of the transparent fine particles is, for example, in the range of 0.1 to 20 μm, preferably in the range of 0.5 to 15 μm, and more preferably in the range of 0.5 to 10 μm. Moreover, the usage-amount of the said transparent fine particle is although it does not restrict | limit in particular, Usually, the range of 2-70 weight part is preferable with respect to 100 weight part of materials of the said transparent protective film, More preferably, it is 5-50 weight part.
[0099]
The layer intended for anti-glare in which the transparent fine particles are blended may be, for example, the transparent protective film itself as described above, or may be formed as a coating layer on the surface of the protective layer. Good. Further, the layer intended for anti-glare may also serve as a diffusion layer. Similarly, the layer for the purpose of preventing reflection, preventing sticking, diffusing, etc. can be provided as an optical layer composed of a sheet or the like provided with these layers as a layer separate from the transparent protective film. .
[0100]
The adhesion treatment between the polarizer and the transparent protective film as the protective layer is not particularly limited, and can be performed using, for example, an adhesive made of an acrylic polymer or a vinyl alcohol polymer. In addition, vinyl alcohol polymers such as boric acid, borax, glutaraldehyde, melamine, oxalic acid, etc., from the point of being able to be a polarizing plate that is difficult to peel off due to the influence of humidity and heat and can be excellent in light transmittance and degree of polarization. An adhesive containing a water-soluble crosslinking agent is preferable. These adhesive layers can be formed, for example, by applying an aqueous solution and drying. In preparing the aqueous solution, other additives and catalysts such as acids can be blended as necessary. Among these, as the adhesive, an adhesive made of polyvinyl alcohol is preferable from the viewpoint of excellent adhesiveness with the PVA film.
[0101]
In addition, the birefringent optical film and the elliptically polarizing plate of the present invention can be used in combination with, for example, various retardation plates, diffusion control films, brightness enhancement films, and the like. Examples of the retardation plate include a uniaxially or biaxially stretched polymer, a Z-axis aligned treatment, and a liquid crystal polymer coated. Examples of the diffusion control film include a film that uses diffusion, scattering, and refraction for controlling the viewing angle, and a film that uses diffusion, scattering, and refraction for controlling the glare and scattered light related to the resolution. Can be used. As the brightness enhancement film, for example, a brightness enhancement film using selective reflection of cholesteric liquid crystal and a λ / 4 plate, a scattering film using anisotropic scattering by the polarization direction, or the like can be used. Moreover, you may use in combination with a wire grid type polarizer.
[0102]
The optical film and the elliptically polarizing plate of the present invention are preferably used for forming various liquid crystal display devices, for example. In the application, other optical layers such as a polarizing plate, a reflecting plate, a semi-transmissive reflecting plate, and a brightness enhancement film can be laminated as necessary via the adhesive or the pressure-sensitive adhesive. The optical layer may be a single layer or a laminate of two or more layers.
[0103]
A reflective polarizing plate can be formed by further laminating the reflective plate, for example, on the elliptical polarizing plate of the present invention. This reflective polarizing plate is usually placed on the back side of a liquid crystal cell and used to form liquid crystal display devices (reflective liquid crystal display devices) that reflect incident light from the viewing side (display side). Is done. In such a liquid crystal display device, for example, since it is possible to omit the incorporation of a light source such as a backlight, there is an advantage that the liquid crystal display device can be easily thinned.
[0104]
The reflective polarizing plate can be formed by a conventionally known method such as a method of arranging a reflective plate made of metal or the like on one surface of the elliptical polarizing plate. Specific examples include, for example, a method in which a matte treatment is performed on one surface (exposed surface) of the transparent protective film as necessary, and a foil or a vapor deposition film made of a reflective metal such as aluminum is formed on the surface as a reflector. Etc.
[0105]
As another example of the reflective polarizing plate, the reflective plate reflecting the fine concavo-convex structure on the transparent protective film having a fine concavo-convex structure on the surface as described above may be used. can give. The reflector having a fine surface irregular structure has the advantage that it diffuses incident light by irregular reflection, prevents directivity and glaring appearance, and suppresses uneven brightness.
[0106]
As a method for forming the reflector, for example, a method of directly forming a metal on the surface of the transparent protective film by a conventionally known means such as a vacuum deposition method, an ion plating method or a sputtering method, or a plating method. Etc.
[0107]
In addition, the reflective polarizing plate may be an appropriate film such as a transparent protective film used for the protective layer, instead of directly forming the reflective plate on the protective layer of the elliptical polarizing plate as described above. You may form using the reflective sheet etc. which provided the reflecting plate. Since the reflection plate of the reflection type polarizing plate is usually made of metal, its use form is the reflection surface of the reflection plate from the viewpoint of preventing the decrease in the reflectance due to oxidation, and thus the long-term maintenance of the initial reflectance. Is preferably covered with the protective layer or the elliptically polarizing plate.
[0108]
On the other hand, the transflective polarizing plate is a reflective polarizing plate in which the reflective reflective plate is a semi-transmissive reflective plate, such as a half mirror that reflects and transmits light by the reflective plate. can give.
[0109]
The transflective polarizing plate is usually provided on the back side of a liquid crystal cell. When a liquid crystal display device or the like is used in a relatively bright atmosphere, the incident light from the viewing side (display side) is reflected to display an image. indicate. In a relatively dark atmosphere, an image is displayed using a built-in light source such as a backlight built in the back side of the transflective polarizing plate. That is, the transflective polarizing plate can save the energy of using a light source such as a backlight in a bright atmosphere, and can be used to form a liquid crystal display device that can be used with a built-in light source even in a relatively dark atmosphere. Useful.
[0110]
Further, the brightness enhancement film transmits linearly polarized light having a predetermined polarization axis and reflects other light, such as a multilayer thin film of dielectric or a multilayer laminate of thin film having different refractive index anisotropy. The thing which shows the characteristic to do can be used, for example, 3M company brand name "D-BEF" etc. are mention | raise | lifted. In addition, like a cholesteric liquid crystal layer, particularly an oriented film of a cholesteric liquid crystal polymer, and the oriented liquid crystal layer supported on a film substrate, it reflects either left-handed or right-handed circularly polarized light and other light is reflected. For example, a product name “PCF350” manufactured by Nitto Denko Corporation, a product name “Transmax” manufactured by Merck Co., etc. can be used.
[0111]
As described above, an optical member in which two or more layers are laminated can be formed by a method of sequentially laminating separately in the manufacturing process of a liquid crystal display device or the like. In addition, it is excellent in assembly workability and the like, and has an advantage that the manufacturing efficiency of a liquid crystal display device and the like can be improved. For the lamination, for example, the above-mentioned adhesive or pressure-sensitive adhesive can be used, and an adhesive or pressure-sensitive adhesive that exhibits light diffusibility by containing fine particles can also be used. In addition, what is necessary is just to provide the layers, such as the said adhesive agent or an adhesive, suitably in a required surface as needed.
[0112]
When the layer of the adhesive or the pressure-sensitive adhesive provided on the birefringent optical film or the elliptically polarizing plate of the present invention is exposed on the surface, the layer of the adhesive or the pressure-sensitive adhesive is put to practical use. For the purpose of preventing contamination, it is preferable to temporarily cover with a separator. The separator is a release containing at least one layer of a release agent such as silicone, long chain alkyl, fluorine, molybdenum sulfide, etc., as needed, on a thin leaf body such as a transparent protective film of the protective layer. It can be formed by coating or the like.
[0113]
In addition, each layer of the birefringent optical film, the polarizer, the transparent protective film, the adhesive, or the adhesive used for the optical member is, for example, a salicylic acid ester compound, a benzophenone compound, a benzotriazole Ultraviolet absorbing ability may be imparted by treatment with an ultraviolet absorber such as a compound, a cyanoacrylate compound, or a nickel complex salt compound.
[0114]
The birefringent optical film and the elliptically polarizing plate of the present invention are preferably applied to formation of various devices such as a liquid crystal display device. For example, the various polarizing plates described above are arranged on one side or both sides of a liquid crystal cell. The present invention can be applied to a liquid crystal display device such as a reflective type, a transflective type, or a transmissive / reflective type.
[0115]
Moreover, when providing the said polarizing plate, an optical member, etc. in the both sides of the said liquid crystal cell, they may be the same and may differ. Furthermore, when forming the liquid crystal display device, for example, appropriate components such as a prism array sheet, a lens array sheet, a light diffusing plate, and a backlight can be arranged in one or more layers at appropriate positions.
[0116]
Thus, the present invention provides a liquid crystal display device including at least one birefringent optical film or elliptically polarizing plate of the present invention. The type of the liquid crystal cell in the liquid crystal display device is not particularly limited, and for example, an active matrix drive type typified by a thin film transistor type, a simple matrix drive type typified by a twist nematic type and a super twist nematic type can be used as appropriate.
[0117]
The optical film of the present invention is very useful as a viewing angle compensation film for a VA mode liquid crystal display device because it is very excellent in optical compensation of VA (Vertical Alighned) cells.
[0118]
Further, the birefringent optical film and the elliptically polarizing plate of the present invention can be used in self-luminous display devices such as organic EL displays, PDPs, and FEDs in the same manner as liquid crystal display devices. When provided on a self-luminous flat display, circularly polarized light can be obtained by setting Δnd of the birefringent optical film of the present invention to λ / 4, which can be used as an antireflection filter.
[0119]
【Example】
EXAMPLES Hereinafter, although this invention is demonstrated further more concretely using an Example and a comparative example, this invention is not limited to a following example.
[0120]
Example 1
From 2,2′-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) and 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl (PFMB or TFMB) The synthesized polyimide having a weight average molecular weight Mw = 100,000 was dissolved in a cyclohexanone solvent to prepare a 15% by mass polyimide solution. This solution was applied onto an 80 μm thick triacetylcellulose (TAC) film, and immediately thereafter (after about 30 seconds), the TAC film was stretched 4% by free-end longitudinal uniaxial stretching while being dried at 160 ° C. A birefringent optical film was obtained on the stretched TAC film. The polyimide concentration of the film-like coating film at the time of stretching was about 75% by mass. The properties of the obtained film were d = 6 μm, Δnd = 60 nm, Rth = 250 nm, and the optical anisotropy was nx> ny> nz. The birefringence (Δn = nx−nz) of the obtained birefringent optical film was 0.042.
[0121]
(Example 2)
The same polyimide solution as in Example 1 was applied on the same TAC film as in Example 1, and immediately thereafter (after about 30 seconds), the TAC film was subjected to a fixed end lateral uniaxial stretching while being dried at 160 ° C. The film was stretched 10%, and a birefringent optical film was obtained on the stretched TAC film. The polyimide concentration of the film-like coating film at the time of stretching was about 70% by mass. The properties of the obtained film were d = 6 μm, Δnd = 70 nm, Rth = 270 nm, and the optical anisotropy was nx> ny> nz. The birefringence (Δn = nx−nz) of the obtained birefringent optical film was 0.045.
[0122]
(Comparative Example 1)
A polynorbornene-based film (manufactured by JSR, trade name ARTON film) was stretched 10% by free end longitudinal uniaxial stretching at 175 ° C. to obtain a birefringent optical film. The characteristics of the film were d = 95 μm, Δnd = 80 nm, Rth = 80 nm, and the optical anisotropy was nx> ny = nz. Further, the birefringence (Δn = nx−nz) of the obtained birefringent optical film was 0.00084.
[0123]
(Comparative Example 2)
A film similar to Comparative Example 1 was stretched 10% at 175 ° C. by fixed-end lateral uniaxial stretching to obtain a birefringent optical film. The characteristics of the film were d = 80 μm, Δnd = 50 nm, Rth = 115 nm, and the optical anisotropy was nx> ny> nz. Further, the birefringence (Δn = nx−nz) of the obtained birefringent optical film was 0.0014.
[0124]
(Comparative Example 3)
The same solution as in Example 1 was applied on the same TAC film as in Example 1, and then dried at 100 ° C. to obtain a birefringent optical film formed on the TAC film. The characteristics of this film were d = 5 μm, Δnd = 0.7 m, Rth = 180 nm, and the optical anisotropy was nx≈ny> nz. The birefringence (Δn = nx−nz) of the obtained birefringent optical film was 0.036.
[0125]
(Phase difference measurement)
Δnd = (nx−ny) d, Rth = (nx−nz) d, and alignment axis accuracy (optical axis distribution) of the birefringent optical films obtained in Examples 1 and 2 and Comparative Examples 1 to 3 Was measured using the product name KOBRA21ADH manufactured by Oji Scientific Instruments. The results are summarized in Table 1. The measurement wavelength is 590 nm.
[0126]

[0127]
【The invention's effect】
As described above, the present invention includes a step of applying optical anisotropy by applying a film forming material solution onto a stretchable substrate and stretching the solution while drying the solution. Since it is a method for producing a refractive optical film, according to the present invention, a birefringent optical film having optical characteristics of nx> ny> nz and suitable for optical compensation of a liquid crystal cell can be easily obtained with few steps. An elliptically polarizing plate using the same and a liquid crystal display device using them can be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram showing an axial direction of a birefringent optical film of the present invention.
FIG. 2 is a schematic view showing an example of a method for producing a birefringent optical film of the present invention.
FIG. 3 is a schematic view showing an example of a method for producing a birefringent optical film of the present invention.
[Explanation of symbols]
1: Optical film
2, 3: Nip roll
4: Polymer substrate
5: Application die
6: Film-like coating film
7: Heating device
8: Optical film
9: Polymer substrate
10: Die for coating
11: Film-like coating film
12: Heating device
13: Optical film
14: Preheating zone
15: Heat stretching zone
16: Relaxation zone
17: Cooling zone

Claims (10)

A method for producing a birefringent optical film,
When the film-forming material solution is applied to form a film-like coating film, and the solvent in the coating film is removed by evaporation to form a film, the film-like coating film is stretched to increase the optical anisotropy. Including the step of applying to the film,
Stretching of the film-like coating film is carried out by applying the film-forming material solution to a stretchable substrate to form a film-like coating film, and stretching the substrate . Production method. The stretchable substrate is a band-shaped polymer film substrate, and the polymer film substrate is continuously supplied, and the solution is applied onto the polymer film substrate to continuously form a film-like coating film. The method for producing a birefringent optical film according to claim 1, wherein the belt-like polymer film substrate is stretched when formed and the solvent in the film-like coating film is removed by evaporation. The method for producing a birefringent optical film according to claim 2, wherein the stretching direction of the band-shaped polymer film substrate is at least one of a longitudinal direction of the film and a width direction of the film. 4. The compound according to claim 1, wherein the film forming material solution is a solution containing at least one polymer selected from the group consisting of polyamide, polyimide, polyester, polyetherketone, polyamideimide, and polyesterimide. A method for producing a refractive optical film. The method for producing a birefringent optical film according to claim 4, wherein the film forming material solution is a solution containing polyimide. The method for producing a birefringent optical film according to any one of claims 1 to 5, wherein the stretching of the substrate is performed at a temperature not lower than the glass transition temperature and not higher than the melting point of the substrate. It is a manufacturing method of the birefringent optical film in any one of Claim 1 to 6, Comprising: The birefringent optical film manufactured WHEREIN: The main refractive index of two directions in a film plane is nx and ny, thickness direction The manufacturing method of the birefringent optical film which is a birefringent optical film which has the optical characteristics which satisfy | fill all the conditions of following (i) to (iii) when the refractive index of nz is set to nz and the film thickness is set to d.
nx> ny> nz ・ ・ (I)
0.005 ≦ (nx−nz) ≦ 0.3 .. (ii)
10 nm ≦ (nx−ny) d ≦ 600 nm .. (iii) It is a manufacturing method of the birefringent optical film in any one of Claim 1 to 7, Comprising: The projection direction distribution to the film plane of the film optical axis of the manufactured birefringent optical film is less than +/- 3 degrees. A method for producing a birefringent optical film. A method for producing an elliptically polarizing plate, including a birefringent optical film preparation step, a polarizer preparation step, and a lamination step of laminating the birefringent optical film and the polarizer to form a laminate, A method for producing an elliptically polarizing plate, wherein the birefringent optical film preparation step is performed by the method for producing a birefringent optical film according to any one of claims 1 to 8. A method for manufacturing a liquid crystal display device, comprising: an elliptically polarizing plate preparing step, a liquid crystal cell preparing step, and an arrangement step of disposing at least one elliptically polarizing plate on at least one side of the liquid crystal cell, wherein the elliptically polarizing plate preparation The manufacturing method of the liquid crystal display device with which a process is performed with the manufacturing method of the elliptically polarizing plate of Claim 9.

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