JP4067722B2 - Manufacturing method of elliptically polarizing plate - Google Patents

Description

【００４８】
【化２】

【００４９】
【化３】

【００５０】
【化４】

【００５１】
【化５】

【００５２】
【化６】

【００５３】
【化７】

【００５４】
式（Ｉ）において、二価の連結基（Ｌ）は、アルキレン基、アルケニレン基、アリーレン基、−ＣＯ−、−ＮＨ−、−Ｏ−、−Ｓ−およびそれらの組み合わせからなる群より選ばれる二価の連結基であることが好ましい。二価の連結基（Ｌ）は、アルキレン基、アルケニレン基、アリーレン基、−ＣＯ−、−ＮＨ−、−Ｏ−および−Ｓ−からなる群より選ばれる二価の基を少なくとも二つ組み合わせた基であることがさらに好ましい。二価の連結基（Ｌ）は、アルキレン基、アルケニレン基、アリーレン基、−ＣＯ−および−Ｏ−からなる群より選ばれる二価の基を少なくとも二つ組み合わせた基であることが最も好ましい。アルキレン基の炭素原子数は、１乃至１２であることが好ましい。アルケニレン基の炭素原子数は、２乃至１２であることが好ましい。アリーレン基の炭素原子数は、６乃至１０であることが好ましい。アルキレン基、アルケニレン基およびアリーレン基は、置換基（例、アルキル基、ハロゲン原子、シアノ、アルコキシ基、アシルオキシ基）を有していてもよい。
二価の連結基（Ｌ）の例を以下に示す。左側が円盤状コア（Ｄ）に結合し、右側が重合性基（Ｑ）に結合する。ＡＬはアルキレン基またはアルケニレン基を意味し、ＡＲはアリーレン基を意味する。
【００５５】
Ｌ１：−ＡＬ−ＣＯ−Ｏ−ＡＬ−
Ｌ２：−ＡＬ−ＣＯ−Ｏ−ＡＬ−Ｏ−
Ｌ３：−ＡＬ−ＣＯ−Ｏ−ＡＬ−Ｏ−ＡＬ−
Ｌ４：−ＡＬ−ＣＯ−Ｏ−ＡＬ−Ｏ−ＣＯ−
Ｌ５：−ＣＯ−ＡＲ−Ｏ−ＡＬ−
Ｌ６：−ＣＯ−ＡＲ−Ｏ−ＡＬ−Ｏ−
Ｌ７：−ＣＯ−ＡＲ−Ｏ−ＡＬ−Ｏ−ＣＯ−
Ｌ８：−ＣＯ−ＮＨ−ＡＬ−
Ｌ９：−ＮＨ−ＡＬ−Ｏ−
Ｌ10：−ＮＨ−ＡＬ−Ｏ−ＣＯ−
Ｌ11：−Ｏ−ＡＬ−
Ｌ12：−Ｏ−ＡＬ−Ｏ−
【００５６】
Ｌ13：−Ｏ−ＡＬ−Ｏ−ＣＯ−
Ｌ14：−Ｏ−ＡＬ−Ｏ−ＣＯ−ＮＨ−ＡＬ−
Ｌ15：−Ｏ−ＡＬ−Ｓ−ＡＬ−
Ｌ16：−Ｏ−ＣＯ−ＡＬ−ＡＲ−Ｏ−ＡＬ−Ｏ−ＣＯ−
Ｌ17：−Ｏ−ＣＯ−ＡＲ−Ｏ−ＡＬ−ＣＯ−
Ｌ18：−Ｏ−ＣＯ−ＡＲ−Ｏ−ＡＬ−Ｏ−ＣＯ−
Ｌ19：−Ｏ−ＣＯ−ＡＲ−Ｏ−ＡＬ−Ｏ−ＡＬ−Ｏ−ＣＯ−
Ｌ20：−Ｏ−ＣＯ−ＡＲ−Ｏ−ＡＬ−Ｏ−ＡＬ−Ｏ−ＡＬ−Ｏ−ＣＯ−
Ｌ21：−Ｓ−ＡＬ−
Ｌ22：−Ｓ−ＡＬ−Ｏ−
Ｌ23：−Ｓ−ＡＬ−Ｏ−ＣＯ−
Ｌ24：−Ｓ−ＡＬ−Ｓ−ＡＬ−
Ｌ25：−Ｓ−ＡＲ−ＡＬ−
【００５７】
なお、ＳＴＮモードのような棒状液晶性分子がねじれ配向している液晶セルを、光学的に補償するためには、ディスコティック液晶性分子もねじれ配向させることが好ましい。上記ＡＬ（アルキレン基またはアルケニレン基）に、不斉炭素原子を導入すると、ディスコティック液晶性分子を螺旋状にねじれ配向させることができる。また、不斉炭素原子を含む光学活性を示す化合物（カイラル剤）を光学異方性層に添加しても、ディスコティック液晶性分子を螺旋状にねじれ配向させることができる。
【００５８】
式（Ｉ）の重合性基（Ｑ）は、重合反応の種類に応じて決定する。重合性基（Ｑ）の例を以下に示す。
【００５９】
【化８】

【００６０】
重合性基（Ｑ）は、不飽和重合性基（Ｑ１〜Ｑ７）またはエポキシ基（Ｑ８）であることが好ましく、不飽和重合性基であることがさらに好ましく、エチレン性不飽和重合性基（Ｑ１〜Ｑ６）であることが最も好ましい。
式（Ｉ）において、ｎは４乃至１２の整数である。具体的な数字は、ディスコティックコア（Ｄ）の種類に応じて決定される。なお、複数のＬとＱの組み合わせは、異なっていてもよいが、同一であることが好ましい。
【００６１】
二種類以上のディスコティック液晶性分子を併用してもよい。例えば、以上述べたような重合性ディスコティック液晶性分子と非重合性ディスコティック液晶性分子とを併用することができる。
非重合性ディスコティック液晶性分子は、前述した重合性ディスコティック液晶性分子の重合性基（Ｑ）を、水素原子またはアルキル基に変更した化合物であることが好ましい。すなわち、非重合性ディスコティック液晶性分子は、下記式（II）で表わされる化合物であることが好ましい。
（II） Ｄ（−Ｌ−Ｒ）_n
式中、Ｄは円盤状コアであり；Ｌは二価の連結基であり；Ｒは水素原子またはアルキル基であり；そして、ｎは４乃至１２の整数である。
式（II）の円盤状コア（Ｄ）の例は、ＬＱ（またはＱＬ）をＬＲ（またはＲＬ）に変更する以外は、前記の重合性ディスコティック液晶分子の例と同様である。
また、二価の連結基（Ｌ）の例も、前記の重合性ディスコティック液晶分子の例と同様である。
Ｒのアルキル基は、炭素原子数が１乃至４０であることが好ましく、１乃至３０であることがさらに好ましい。環状アルキル基よりも鎖状アルキル基の方が好ましく、分岐を有する鎖状アルキル基よりも直鎖状アルキル基の方が好ましい。Ｒは、水素原子または炭素原子数が１乃至３０の直鎖状アルキル基であることが特に好ましい。
【００６２】
光学異方性層の厚さは、一般には、０．１乃至１０μｍである。厚さは、０．５乃至５μｍであることがさらに好ましく、１乃至５μｍであることが最も好ましい。ただし、液晶セルのモードによっては、高い光学的異方性を得るために、光学異方性層を厚く（５乃至１０μｍ）する場合もある。
光学異方性層内での液晶性分子の配向状態は、前述したように、液晶セルの表示モードの種類に応じて決定される。液晶性分子の配向状態は、具体的には、液晶性分子の種類、配向膜の種類および光学異方性層内の添加剤（例、可塑剤、バインダー、界面活性剤）の使用によって制御される。
【００６３】
［光学異方性層の形成工程］
光学異方性層は、液晶性分子、あるいは下記の重合性開始剤や任意の添加剤（例、可塑剤、モノマー、界面活性剤、セルロースエステル、１，３，５−トリアジン化合物、カイラル剤）を含む塗布液を、配向膜の上に塗布することで形成する。
塗布液の調製に使用する溶媒としては、有機溶媒が好ましく用いられる。有機溶媒の例には、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）、ヘテロ環化合物（例、ピリジン）、炭化水素（例、ベンゼン、ヘキサン）、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）、ケトン（例、アセトン、メチルエチルケトン）、エーテル（例、テトラヒドロフラン、１，２−ジメトキシエタン）が含まれる。アルキルハライドおよびケトンが好ましい。二種類以上の有機溶媒を併用してもよい。
塗布液の塗布は、公知の方法（例、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、ダイコーティング法）により実施できる。
【００６４】
液晶性分子は、実質的に均一に配向していることが好ましく、実質的に均一に配向している状態で固定されていることがさらに好ましく、重合反応により液晶性分子が固定されていることが最も好ましい。重合反応には、熱重合開始剤を用いる熱重合反応と光重合開始剤を用いる光重合反応とが含まれる。光重合反応が好ましい。
光重合開始剤の例には、α−カルボニル化合物（米国特許２３６７６６１号、同２３６７６７０号の各明細書記載）、アシロインエーテル（米国特許２４４８８２８号明細書記載）、α−炭化水素置換芳香族アシロイン化合物（米国特許２７２２５１２号明細書記載）、多核キノン化合物（米国特許３０４６１２７号、同２９５１７５８号の各明細書記載）、トリアリールイミダゾールダイマーとｐ−アミノフェニルケトンとの組み合わせ（米国特許３５４９３６７号明細書記載）、アクリジンおよびフェナジン化合物（特開昭６０−１０５６６７号公報、米国特許４２３９８５０号明細書記載）およびオキサジアゾール化合物（米国特許４２１２９７０号明細書記載）が含まれる。
光重合開始剤の使用量は、塗布液の固形分の０．０１乃至２０重量％であることが好ましく、０．５乃至５重量％であることがさらに好ましい。
ディスコティック液晶性分子の重合のための光照射は、紫外線を用いることが好ましい。
照射エネルギーは、２０ｍＪ／ｃｍ² 乃至５０Ｊ／ｃｍ² であることが好ましく、１００乃至８００ｍＪ／ｃｍ² であることがさらに好ましい。光重合反応を促進するため、加熱条件下で光照射を実施してもよい。
【００６５】
重合反応は、空気中の酸素の光学異方性層内への浸透を抑制した状態で実施する。具体的には、空気中の酸素量を削減するか、空気中と光学異方性層との界面を遮蔽するか、あるいは、酸素捕捉剤を用いて光学異方性層に浸透しようとする酸素を捕捉する。
空気中の酸素量（通常は２０％程度）を削減する場合、密閉容器内で重合反応を実施する必要がある。酸素量は、１３％以下まで削減することが好ましい。空気を不活性な気体（窒素ガス）で置換してもよい。また、気圧を低下させ、酸素の絶対量を削減した状態で、重合反応を実施することもできる。
空気中と光学異方性層との界面は、カバーシートで光学異方性層の表面を覆うことにより遮蔽できる。
酸素捕捉剤を用いる場合は、光学異方性層に化学的および光学的影響を与えない、酸素捕捉剤を選択して用いる必要がある。
空気中の酸素量を削減する方法が好ましく、空気を窒素ガスで置換する方法が最も好ましい。
【００６６】
［ケン化処理処理工程］
透明支持体と光学異方性層との積層体を、アルカリ水溶液に浸漬することによりケン化処理を実施する。
アルカリは、水酸化ナトリウムまたは水酸化カリウムのようなアルカリ金属の水酸化物であることが好ましい。水溶液のｐＨは、１０以上であることが好ましい。アルカリ処理は、アルカリの水溶液に透明支持体の偏光膜側の面を浸漬して実施する。浸漬時間は、２０乃至３００秒であることが好ましい。処理温度は、４０乃至７０℃であることが好ましい。浸漬終了後、積層体を水で洗浄することが好ましい。
【００６７】
［液晶表示装置］
本発明により製造した楕円偏光板は、様々な表示モードの液晶セルに適用できる。前述したように、ＴＮ（Twisted Nematic）、ＩＰＳ（In-Plane Switching）、ＦＬＣ（Ferroelectric Liquid Crystal）、ＯＣＢ（Optically Compensatory Bend）、ＳＴＮ（Supper Twisted Nematic）、ＶＡ（Vertically Aligned）およびＨＡＮ（Hybrid Aligned Nematic）のような様々な表示モードが提案されている。本発明の楕円偏光板は、いずれの表示モードの液晶表示装置においても有効である。
【００６８】
【実施例】
［実施例１］
（透明支持体の作製）
下記の成分をミキシングタンクに投入し、加熱攪拌して、セルロースアセテート溶液を調製した。
【００６９】

【００７０】
別のミキシングタンクに、下記の成分をに投入し、加熱攪拌して、レターデーション上昇剤溶液を調製した。
【００７１】

【００７２】
セルロースアセテート溶液４７４重量部に、レターデーション上昇剤溶液２２重量部を添加し、充分に攪拌して、ドープを調製した。セルロースアセテート１００重量部に対するレターデーション上昇剤の量は３重量部である。
ドープを流延口から０℃に冷却したドラム上に流延した。溶媒含有率７０重量％の場外で剥ぎ取り、フイルムの巾方向の両端をピンテンターで固定し、溶媒含有率が３乃至５重量％の領域で、幅方向（機械方向に垂直な方向）の延伸率が３％となる間隔を保ちつつ乾燥した。その後、熱処理装置のロール間を搬送することにより、さらに乾燥し、ガラス転移温度が１２０゜を越える領域で機械方向の延伸率が実質０％、（剥ぎ取り時に機械方向に４％延伸することを考慮して）巾方向の延伸率と機械方向の延伸率との比が０．７５となるように調整して、厚さ１０７μｍのセルロースアセテートフイルムを作製した。
セルロースアセテートフイルムの弾性率は、機械方向（ＭＤ）で４３０ｋｇ／ｍｍ² 、巾方向（ＴＤ）で３６０ｋｇ／ｍｍ² であり、ＭＤ／ＴＤ比は１．１９であった。作製したフイルムのレターデーションを測定したところ、厚み方向のレターデーション（Ｒth）は８０ｎｍ、面内のレターデーション（Ｒｅ）は１０ｎｍであった。なお、レターデーション上昇剤の析出は、製造直後はもちろん、後述するフイルム製造後の処理においても、全く認められなかった。
【００７３】
（第１下塗り層の形成）
作製したセルロースエステルフイルムを透明支持体として用いた。
透明支持体の上に、下記の組成の塗布液を２８ｍｌ／ｍ² 塗布し、乾燥して第１下塗り層を形成した。
【００７４】

【００７５】
（第２下塗り層の形成）
第１下塗り層の上に、下記の組成の塗布液を７ｍｌ／ｍ² 塗布し、乾燥して第２下塗り層を形成した。
【００７６】

【００７７】
【化９】

【００７８】
（バック層の形成）
透明支持体の反対側の面に、下記の組成の塗布液を２５ｍｌ／ｍ² 塗布し、乾燥してバック層を形成した。
【００７９】

【００８０】
（配向膜の形成）
第２下塗り層の上に、長鎖アルキル変性ポリビニルアルコール（ＭＰ−２０３、クラレ（株）製）の水溶液を塗布し、６０℃の温風で９０秒間乾燥した後、ラビング処理を行い配向膜を形成した。
【００８１】
（光学異方性層の形成）
下記のディスコティック液晶性化合物（１）１．８ｇ、エチレンオキサイド変性トリメチロールプロパントリアクリレート（Ｖ＃３６０、大阪有機化学（株）製）０．２ｇ、セルロースアセテートブチレート（ＣＡＢ５３１−１．０、イーストマンケミカル社製）０．０４ｇ、光重合開始剤（イルガキュア９０７、日本チバガイギー（株）製）０．０６ｇおよび増感剤（カヤキュアーＤＥＴＸ、日本化薬（株）製）０．０２ｇを、メチルエチルケトン８．４３ｇに溶解して塗布液を調製した。塗布液を＃３のワイヤーバーで配向膜の上に塗布した。これを金属枠に貼り付けた状態で、１３０℃の恒温槽中で２分間加熱し、ディスコティック液晶性化合物を配向させた。
透明支持体と光学異方性層との積層体を密閉容器内に入れ、酸素濃度が９％以下になるまで空気を窒素ガスに置換した。１３０℃の温度で、１２０Ｗ／ｃｍの高圧水銀灯を用いて１分間紫外線を照射し、ディスコティック液晶性化合物のビニル基を重合させ、配向状態を固定した。その後、室温まで放冷した。
【００８２】
【化１０】

【００８３】
光学異方性層の厚さは、１．５μｍであった。光学異方性層と透明支持体との積層体のレターデーションを、配向膜のラビング方向に沿って測定したところ、光学軸の平均傾斜角は１５゜、厚み方向のレターデーション（Ｒth）は１３８ｎｍ、面内レターデーション（Ｒｅ）は２３ｎｍであった。
【００８４】
（アルカリ処理）
透明支持体と光学異方性層との積層体を、５５℃の１．５Ｎ水酸化ナトリウム水溶液に２分間浸漬してアルカリ処理した。流水で洗浄した後、乾燥した。
アルカリ処理後の面内レターデーション（Ｒｅ）を測定したところ、２２ｎｍ（処理前−１ｎｍ）であった。ディスコティック液晶性分子の溶出量を調べたところ、溶出した液晶性分子は全体の０重量％であった。また、溶出したレターデーション上昇剤は全体の０．２６重量％であった。
【００８５】
（透明保護膜の作製）
レターデーション上昇剤を添加しなかった以外は、透明支持体の作製と同様にして、セルロースアセテートフイルム（透明保護膜）を作製した。
透明保護膜も、透明支持体と光学異方性層との積層体と同様にアルカリ処理を実施した。
【００８６】
（楕円偏光板の作製）
延伸したポリビニルアルコールフイルムにヨウ素を吸着させて、偏光膜を作製した。偏光膜の片側に、ポリビニルアルコール系接着剤を用いて、光学異方性層と透明支持体との積層体を、光学異方性層が外側となるように貼り付けた。反対側には、ポリビニルアルコール系接着剤を用いて、透明保護膜を貼り付けた。偏光膜の透過軸と、光学異方性層と透明支持体の積層体の遅相軸とは、平行になるように配置した。このようにして、楕円偏光板を作製した。
【００８７】
（液晶表示装置の作製）
ＩＴＯ透明電極が設けられたガラス基板の上に、ポリイミド配向膜を設け、ラビング処理を行った。５μｍのスペーサーを介して、二枚の基板を配向膜が向かい合うように重ねた。配向膜のラビング方向が直交するように、基板の向きを調節した。基板の間隙に、棒状液晶性分子（ＺＬ４７９２、メルク社製）を注入し、液晶層を形成した。液晶性分子のΔｎは０．０９６９であった。
以上のように作製したＴＮ液晶セルの両側に、楕円偏光板を、光学異方性層が基板と対面するように貼り付けて液晶表示装置を作製した。光学異方性層と透明支持体の積層体の遅相軸と、液晶セルのラビング方向は、直交するように配置した。
液晶表示装置の液晶セルに、電圧を印加し、白表示２Ｖ、黒表示５Ｖにおける白表示と黒表示との透過率の比をコントラスト比として、上下左右でコントラスト比が１０、かつ階調反転のない領域を視野角として測定した。その結果、上下の視野角は７０゜、左右の視野角は１２６゜であった。また、正面コントラストは、１２２であった。
【００８８】
［比較例１］
（光学異方性層の形成）
ディスコティック液晶性化合物の重合反応（紫外線照射）を空気中で実施した以外は、実施例１と同様に光学異方性層を形成した。
光学異方性層の厚さは、１．０μｍであった。光学異方性層と透明支持体との積層体のレターデーションを、配向膜のラビング方向に沿って測定したところ、光学軸の平均傾斜角は１５゜、厚み方向のレターデーション（Ｒth）は１３８ｎｍ、面内レターデーション（Ｒｅ）は２３ｎｍであった。
【００８９】
（アルカリ処理）
透明支持体と光学異方性層との積層体を、５５℃の１．５Ｎ水酸化ナトリウム水溶液に２分間浸漬してアルカリ処理した。流水で洗浄した後、乾燥した。
アルカリ処理後の面内レターデーション（Ｒｅ）を測定したところ、２０ｎｍ（処理前−３ｎｍ）であった。ディスコティック液晶性分子の溶出量を調べたところ、溶出した液晶性分子は全体の０．０３３重量％であった。また、溶出したレターデーション上昇剤は全体の０．６８重量％であった。
【００９０】
［実施例２］
（配向膜の形成）
下記の変性ポリイミド（１）をメタノールとアセトンとの混合溶媒（容量比＝５０／５０）に溶解して、５重量％溶液を調製した。この溶液をバーコーターを用いて、実施例１で作製した透明支持体の上に１μｍの厚さに塗布した。塗布層を、６０℃の温風で２分間乾燥し、その表面をラビング処理して、配向膜を形成した。
【００９１】
【化１１】

【００９２】
（光学異方性層の形成）
配向膜の上に、以下の組成の塗布液をエクストルージョン法により塗布した。
【００９３】

【００９４】
【化１２】

【００９５】
【化１３】

【００９６】
塗布層を１３０℃で２分間加熱して、ディスコティック液晶性化合物を垂直に配向させた。
透明支持体と光学異方性層との積層体を密閉容器内に入れ、酸素濃度が９％以下になるまで空気を窒素ガスに置換した。１３０℃の温度で、４秒間紫外線を照射し、ディスコティック液晶性化合物を重合させ、垂直配向状態を固定した。このようにして、ディスコティック液晶性化合物が垂直かつねじれて配向している光学異方性層を形成した。
光学異方性層と透明支持体との積層体のレターデーションを測定したところ、面内レターデーション（Ｒｅ）は４４０ｎｍであった。
【００９７】
（アルカリ処理）
透明支持体と光学異方性層との積層体を、５５℃の１．５Ｎ水酸化ナトリウム水溶液に２分間浸漬してアルカリ処理した。流水で洗浄した後、乾燥した。
アルカリ処理後の面内レターデーション（Ｒｅ）を測定したところ、４３９ｎｍ（処理前−１ｎｍ）であった。ディスコティック液晶性分子の溶出量を調べたところ、溶出した液晶性分子は全体の０重量％であった。また、溶出したレターデーション上昇剤は全体の０．２６重量％であった。
【００９８】
（楕円偏光板の作製）
延伸したポリビニルアルコールフイルムにヨウ素を吸着させて、偏光膜を作製した。偏光膜の片側に、ポリビニルアルコール系接着剤を用いて、光学異方性層と透明支持体との積層体を、光学異方性層が外側となるように貼り付けた。反対側には、ポリビニルアルコール系接着剤を用いて、実施例１で作製した透明保護膜を貼り付けた。このようにして、楕円偏光板を作製した。
【００９９】
（液晶表示装置の作製）
作製した楕円偏光板を用いて、ＳＴＮ型液晶表示装置を作成した。液晶セルと光学異方性層とが接する面で、液晶セルの棒状液晶性分子の配向方向と光学異方性層のディスコティック液晶性分子の配向方向とを一致させた。出射側偏光板の吸収軸と液晶セルの出射側の棒状液晶性分子の配向方向との角度は、４５゜に調節した。入射側偏光板の吸収軸と出射側偏光板の吸収軸とは直交するように配置した。
【０１００】
得られたＳＴＮ型液晶表示装置に電圧を印加したところ、ノーマリーブラックモードになった。視覚特性を測定したところ、コントラスト比が５以上の角度範囲が左右で１２０゜以上、上下で１５０゜以上得られた。
【０１０１】
［比較例２］
（光学異方性層の形成）
ディスコティック液晶性化合物の重合反応（紫外線照射）を空気中で実施した以外は、実施例２と同様に光学異方性層を形成した。
光学異方性層と透明支持体との積層体のレターデーションを測定したところ、面内レターデーション（Ｒｅ）は４４０ｎｍであった。
【０１０２】
（アルカリ処理）
透明支持体と光学異方性層との積層体を、５５℃の１．５Ｎ水酸化ナトリウム水溶液に２分間浸漬してアルカリ処理した。流水で洗浄した後、乾燥した。
アルカリ処理後の面内レターデーション（Ｒｅ）を測定したところ、４３６ｎｍ（処理前−４ｎｍ）であった。ディスコティック液晶性分子の溶出量を調べたところ、溶出した液晶性分子は全体の０．０３５重量％であった。また、溶出したレターデーション上昇剤は全体の０．７０重量％であった。
【０１０３】
［実施例３］
（透明支持体の作製）
レターデーション上昇剤の添加量を、透明支持体の１８重量％となるように変更した以外は、実施例１と同様にして厚さ１００μｍのトリアセチルセルロースフイルムを作製した。トリアセチルセルロースフイルムを延伸倍率３％で一軸延伸して、透明支持体を作製した。
波長５４６ｎｍで測定した透明支持体の面内レターデーション（Ｒｅ）は３０ｎｍ、そして、Ｒthレターデーション値は２８０ｎｍであった。
【０１０４】
（配向膜の形成）
透明支持体の上に実施例１と同様に、第１下塗り層、第２下塗り層およびバック層を形成した。
第２下塗り層の上に、下記の組成の塗布液を＃１６のワイヤーバーコーターで２８ｍｌ／ｍ² 塗布した。６０℃の温風で６０秒、さらに９０℃の温風で１５０秒乾燥した。
次に、透明支持体の遅相軸（波長６３２．８ｎｍで測定）と４５゜の方向に、形成した膜にラビング処理を実施した。
【０１０５】

【０１０６】
【化１４】

【０１０７】
（光学異方性層の形成）
配向膜上に、実施例１で用いたディスコティック液晶性化合物（１）４１．０１ｇ、エチレンオキサイド変成トリメチロールプロパントリアクリレート（Ｖ＃３６０、大阪有機化学（株）製）４．０６ｇ、セルロースアセテートブチレート（ＣＡＢ５５１−０．２、イーストマンケミカル社製）０．９０ｇ、セルロースアセテートブチレート（ＣＡＢ５３１−１、イーストマンケミカル社製）０．２３ｇ、光重合開始剤（イルガキュアー９０７、チバガイギー社製）１．３５ｇ、増感剤（カヤキュアーＤＥＴＸ、日本化薬（株）製）０．４５ｇを、１０２ｇのメチルエチルケトンに溶解した塗布液を、＃３のワイヤーバーで塗布した。これを金属の枠に貼り付けて、１３０℃の恒温槽中で２分間加熱し、ディスコティック液晶性化合物を配向させた。
透明支持体と光学異方性層との積層体を密閉容器内に入れ、酸素濃度が９％以下になるまで空気を窒素ガスに置換した。次に、１３０℃で１２０Ｗ／ｃｍ高圧水銀灯を用いて、１分間ＵＶ照射しディスコティック液晶性化合物を重合させた。その後、室温まで放冷した。このようにして、光学異方性層を形成した。
波長５４６ｎｍで測定した光学異方性層の面内レターデーション（Ｒｅ）は３８ｎｍであった。また、ディスコティック液晶性化合物の円盤面と透明支持体面との間の角度（傾斜角）は平均で４０゜であった。
【０１０８】
（アルカリ処理）
透明支持体と光学異方性層との積層体を、５５℃の１．５Ｎ水酸化ナトリウム水溶液に２分間浸漬してアルカリ処理した。流水で洗浄した後、乾燥した。
アルカリ処理後の面内レターデーション（Ｒｅ）を測定したところ、３７ｎｍ（処理前−１ｎｍ）であった。ディスコティック液晶性分子の溶出量を調べたところ、溶出した液晶性分子は全体の０重量％であった。また、溶出したレターデーション上昇剤は全体の０．２６重量％であった。
【０１０９】
（楕円偏光板の作製）
光学異方性層およびの積層体の透明支持体面に、偏光膜を粘着剤を介して貼り合わて、楕円偏光板を作製した。偏光膜の透過軸は、透明支持体の遅相軸と直交させた。
【０１１０】
（ベンド配向液晶セルの作製）
ＩＴＯ電極付きのガラス基板に、ポリイミド膜を配向膜として設け、配向膜にラビング処理を行った。得られた二枚のガラス基板をラビング方向が平行となる配置で向かい合わせ、セルギャップを６μｍに設定した。セルギャップにΔｎが０．１３９６の液晶性化合物（ＺＬＩ１１３２、メルク社製）を注入し、ベンド配向液晶セルを作製した。
ベンド配向液晶セルに、５５Ｈｚ矩形波で、５または５．５Ｖの電圧を印加し、４３６ｎｍ、５４６ｎｍおよび６１１．５ｎｍの波長でＲｅレターデーション値を測定した。
【０１１１】
（液晶表示装置の作製）
作製したベンド配向セルを挟むように、作製した楕円偏光板を二枚貼り付けた。楕円偏光板の光学異方性層がセル基板に対面し、液晶セルのラビング方向とそれに対面する光学異方性層のラビング方向とが反平行となるように配置した。
【０１１２】
［比較例３］
（光学異方性層の形成）
ディスコティック液晶性化合物の重合反応（紫外線照射）を空気中で実施した以外は、実施例３と同様に光学異方性層を形成した。
光学異方性層と透明支持体との積層体のレターデーションを測定したところ、面内レターデーション（Ｒｅ）は３８ｎｍであった。
【０１１３】
（アルカリ処理）
透明支持体と光学異方性層との積層体を、５５℃の１．５Ｎ水酸化ナトリウム水溶液に２分間浸漬してアルカリ処理した。流水で洗浄した後、乾燥した。
アルカリ処理後の面内レターデーション（Ｒｅ）を測定したところ、３５ｎｍ（処理前−３ｎｍ）であった。ディスコティック液晶性分子の溶出量を調べたところ、溶出した液晶性分子は全体の０．０３３重量％であった。また、溶出したレターデーション上昇剤は全体の０．６８重量％であった。
【０１１４】
［実施例４］
（配向膜の形成）
実施例１で作製した透明支持体の第２下塗り層の上に、実施例３で用いた変性ポリビニルアルコールを０．５μｍの厚さに塗布、乾燥して、配向膜を形成した。
【０１１５】
（光学異方性層の形成）
配向膜の上に、以下の組成の塗布液を＃４のバーコーターを用いて塗布した。
【０１１６】

【０１１７】
塗布層を１３０℃で１分間加熱した。
透明支持体と光学異方性層との積層体を密閉容器内に入れ、酸素濃度が９％以下になるまで空気を窒素ガスに置換した。次に、５００ｍＪ／ｃｍ² の紫外線を照射し、ディスコティック液晶性化合物を重合させ、その配向状態を固定した。このようにして光学異方性層を形成した。
光学異方性層の面内レターデーション（Ｒｅ）は１０ｎｍであった。
【０１１８】
（アルカリ処理）
透明支持体と光学異方性層との積層体を、５５℃の１．５Ｎ水酸化ナトリウム水溶液に２分間浸漬してアルカリ処理した。流水で洗浄した後、乾燥した。
アルカリ処理後の面内レターデーション（Ｒｅ）を測定したところ、９ｎｍ（処理前−１ｎｍ）であった。ディスコティック液晶性分子の溶出量を調べたところ、溶出した液晶性分子は全体の０重量％であった。また、溶出したレターデーション上昇剤は全体の０．２６重量％であった。
【０１１９】
（楕円偏光板の作製）
光学異方性層およびの積層体の透明支持体面に、偏光膜を粘着剤を介して貼り合わて、楕円偏光板を作製した。
【０１２０】
（液晶表示装置の作製）
垂直配向型の液晶セルを使用した液晶モニター（ＶＬ−１５２０Ｔ、富士通（株）製）の裏側と表側の偏光板を剥がし、代わりに作製した楕円偏光板を表側に、市販の偏光板（ＨＬＣ２−５６１８ＨＣＳ、（株）サンリッツ製）を裏側に貼り付けて、液晶表示装置を作製した。
【０１２１】
［比較例４］
（光学異方性層の形成）
ディスコティック液晶性化合物の重合反応（紫外線照射）を空気中で実施した以外は、実施例４と同様に光学異方性層を形成した。
光学異方性層と透明支持体との積層体のレターデーションを測定したところ、面内レターデーション（Ｒｅ）は１０ｎｍであった。
【０１２２】
（アルカリ処理）
透明支持体と光学異方性層との積層体を、５５℃の１．５Ｎ水酸化ナトリウム水溶液に２分間浸漬してアルカリ処理した。流水で洗浄した後、乾燥した。
アルカリ処理後の面内レターデーション（Ｒｅ）を測定したところ、７ｎｍ（処理前−３ｎｍ）であった。ディスコティック液晶性分子の溶出量を調べたところ、溶出した液晶性分子は全体の０．０３３重量％であった。また、溶出したレターデーション上昇剤は全体の０．６５重量％であった。
【０１２３】
［実施例５］
（配向膜の形成）
実施例１で作製した透明支持体の第２下塗り層の上に、実施例１で用いた変性ポリビニルアルコールを０．５μｍの厚さに塗布、乾燥して、配向膜を形成した。配向膜の表面をラビング処理した。
【０１２４】
（光学異方性層の形成）
実施例１で用いたディスコティック液晶性化合物（１）１．８ｇ、エチレンオキサイド変性トリメチロールプロパントリアクリレート（Ｖ＃３６０、大阪有機化学（株）製）０．２ｇ、セルロースアセテートブチレート（ＣＡＢ５５１−０．２、イーストマンケミカル社製）０．０４ｇ、セルロースアセテートブチレート（ＣＡＢ５３１−１．０、イーストマンケミカル社製）０．０１ｇ、光重合開始剤（イルガキュア９０７、日本チバガイギー（株）製）０．０６ｇおよび増感剤（カヤキュアーＤＥＴＸ、日本化薬（株）製）０．０２ｇを、メチルエチルケトン３．３ｇに溶解して塗布液を調製した。塗布液を＃１０のワイヤーバーで配向膜の上に塗布した。これを、１４０℃の恒温槽中で３分間加熱し、ディスコティック液晶性化合物を配向させた。
透明支持体と光学異方性層との積層体を密閉容器内に入れ、酸素濃度が９％以下になるまで空気を窒素ガスに置換した。１４０℃の温度で、１２０Ｗ／ｃｍの高圧水銀灯を用いて１分間紫外線を照射し、ディスコティック液晶性化合物のビニル基を重合させ、配向状態を固定した。その後、室温まで放冷した。
光学異方性層と透明支持体との積層体のレターデーションを測定したところ、面内レターデーション（Ｒｅ）が１６５ｎｍであった。
【０１２５】
（アルカリ処理）
透明支持体と光学異方性層との積層体を、５５℃の１．５Ｎ水酸化ナトリウム水溶液に２分間浸漬してアルカリ処理した。流水で洗浄した後、乾燥した。
アルカリ処理後の面内レターデーション（Ｒｅ）を測定したところ、９ｎｍ（処理前−１ｎｍ）であった。ディスコティック液晶性分子の溶出量を調べたところ、溶出した液晶性分子は全体の０重量％であった。また、溶出したレターデーション上昇剤は全体の０．２６重量％であった。
【０１２６】
（楕円偏光板の作製）
光学異方性層およびの積層体の透明支持体面に、偏光膜を粘着剤を介して貼り合わて、楕円偏光板を作製した。
【０１２７】
（液晶表示装置の作製）
ＩＴＯ透明電極が設けられたガラス基板の上に、ポリイミド配向膜を設け、ラビング処理を行った。ＩＴＯ透明電極が設けられたガラス基板をもう一枚用意し、ＳｉＯ蒸着膜を設けた。二枚のガラス基板を向き合わせ、セルギャップを４μｍに設定した。セルギャップに、棒状液晶性分子（ＺＬＩ１１３２、メルク社製）を注入し、液晶層を形成した。液晶性分子のΔｎは０．１３９６であった。
以上のように作製したＨＡＮ型液晶セルの一方の側に、楕円偏光板を一枚、液晶セルのラビング方向と光学異方性層のラビング方向とは反平行となるように配置した。また、偏光膜の透過軸と液晶セルのラビング方向とは、４５゜の角度となるように配置した。楕円偏光板とは反対側の面に、鏡を反射板として設けた。
作製した反射型液晶表示装置の表示面の法線方向から２０度傾けた方向に光源を置き、光を照射した。液晶セルには、５５Ｈｚの矩形波で電圧を印加した。白表示２Ｖ、黒表示５Ｖのノーマリーホワイトモードとして、上下左右でコントラスト比が１０の領域を視野角として測定した。その結果、上方向の視野角は４９゜、下方向の視野角ＫＨ亜６０゜、そして左右の視野角は１０５゜であった。
【０１２８】
［比較例５］
（光学異方性層の形成）
ディスコティック液晶性化合物の重合反応（紫外線照射）を空気中で実施した以外は、実施例４と同様に光学異方性層を形成した。
光学異方性層と透明支持体との積層体のレターデーションを測定したところ、面内レターデーション（Ｒｅ）は１６５ｎｍであった。
【０１２９】
（アルカリ処理）
透明支持体と光学異方性層との積層体を、５５℃の１．５Ｎ水酸化ナトリウム水溶液に２分間浸漬してアルカリ処理した。流水で洗浄した後、乾燥した。
アルカリ処理後の面内レターデーション（Ｒｅ）を測定したところ、７ｎｍ（処理前−３ｎｍ）であった。ディスコティック液晶性分子の溶出量を調べたところ、溶出した液晶性分子は全体の０．０３３重量％であった。また、溶出したレターデーション上昇剤は全体の０．６８重量％であった。
【図面の簡単な説明】
【図１】楕円偏光板の基本的な構成を示す模式図である。
【図２】楕円偏光板の製造における光学異方性層の形成工程を示す断面模式図である。
【図３】楕円偏光板の製造におけるケン化処理工程を示す断面模式図である。
【図４】透過型液晶表示装置の基本的な構成を示す模式図である。
【図５】反射型液晶表示装置の基本的な構成を示す模式図である。
【符号の説明】
Light 光
Ｎ₂ 窒素ガス
ＮａＯＨ 水酸化ナトリウム水溶液
ＢＬ バックライト
ＲＰ 反射板
０ 配向膜
１、１ａ、１ｂ、１ｃ 透明保護膜
２、２ａ、２ｂ 偏光膜
３、３ａ、３ｂ 透明支持体
３１ 透明支持体のケン化処理面
４、４ａ、４ｂ 光学異方性層
４１ 光学異方性層のケン化処理面
５ａ 液晶セルの下基板
５ｂ 液晶セルの上基板
６ 棒状液晶性分子からなる液晶層[0001]
[Industrial application fields]
The present invention relates to an elliptically polarizing plate in which an optically anisotropic layer formed of a transparent protective film, a polarizing film, a transparent support and liquid crystalline molecules is laminated in this order, and a method for producing the same.
[0002]
[Prior art]
The liquid crystal display device includes a liquid crystal cell, a polarizing element, and an optical compensation sheet (retardation plate). In a transmissive liquid crystal display device, two polarizing elements are attached to both sides of a liquid crystal cell, and one or two optical compensation sheets are disposed between the liquid crystal cell and the polarizing element. In a reflective liquid crystal display device, a reflector, a liquid crystal cell, a single optical compensation sheet, and a single polarizing element are arranged in this order.
The liquid crystal cell is composed of a rod-like liquid crystal molecule, two substrates for enclosing it, and an electrode layer for applying a voltage to the rod-like liquid crystal molecule. The liquid crystal cell is different in the alignment state of rod-like liquid crystal molecules. As for the transmissive type, TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), OCB (Optically Compensatory Bend), STN (STN) Various display modes such as HAN (Hybrid Aligned Nematic) have been proposed for Supper Twisted Nematic (VA), VA (Vertically Aligned), and reflection type.
A polarizing element generally has a configuration in which two transparent protective films are attached to both sides of a polarizing film.
[0003]
Optical compensation sheets are used in various liquid crystal display devices in order to eliminate image coloring and expand the viewing angle. As an optical compensation sheet, a stretched birefringent film has been conventionally used.
It has been proposed to use an optical compensation sheet having an optically anisotropic layer formed from a liquid crystalline molecule (particularly a discotic liquid crystalline molecule) on a transparent support, instead of an optical compensation sheet comprising a stretched birefringent film. ing. The optically anisotropic layer is formed by aligning liquid crystal molecules and fixing the alignment state. In general, the alignment state is fixed by a polymerization reaction using liquid crystalline molecules having a polymerizable group. Liquid crystalline molecules have a large birefringence. The liquid crystal molecules have various alignment forms. By using liquid crystalline molecules, it has become possible to realize optical properties that cannot be obtained with conventional stretched birefringent films.
[0004]
The optical properties of the optical compensation sheet are determined according to the optical properties of the liquid crystal cell, specifically, the display mode differences as described above. When liquid crystal molecules, particularly discotic liquid crystal molecules are used, optical compensation sheets having various optical properties corresponding to various display modes of the liquid crystal cell can be produced.
Optical compensation sheets using discotic liquid crystalline molecules have already been proposed for various display modes. For example, an optical compensation sheet for a TN mode liquid crystal cell is described in each specification of JP-A-6-214116, US Pat. Nos. 5,583,679, 5,646,703, and German Patent 3,911,620A1. Further, an optical compensation sheet for liquid crystal cells in IPS mode or FLC mode is described in JP-A-10-54982. Furthermore, OCB mode or HAN mode liquid crystal cell optical compensation sheets are described in US Pat. No. 5,805,253 and International Patent Application WO 96/37804. Furthermore, an optical compensation sheet for an STN mode liquid crystal cell is described in JP-A-9-26572. A VA mode liquid crystal cell optical compensation sheet is described in Japanese Patent No. 2866372.
[0005]
By laminating an optical compensation sheet using liquid crystalline molecules and a polarizing element to form an elliptically polarizing plate, the transparent support of the optical compensation sheet can function as one transparent protective film of the polarizing element. Such an elliptically polarizing plate has a layer structure in the order of a transparent protective film, a polarizing film, a transparent support, and an optically anisotropic layer formed from liquid crystalline molecules. The liquid crystal display device is characterized by being thin and light, and if one of the constituent elements is reduced by combining it, the device can be made thinner and lighter. Further, if one component of the liquid crystal display device is reduced, one step of bonding the components is also reduced, and the possibility that a failure will occur when the device is manufactured is reduced. Regarding an integrated elliptical polarizing plate in which a transparent support of an optical compensation sheet using liquid crystalline molecules and one protective film of a polarizing element are shared, JP-A-7-191217, 8-21996 and 8-94838 are disclosed. There are descriptions in each publication.
[0006]
[Problems to be solved by the invention]
When producing an integrated elliptical polarizing plate comprising a transparent protective film, a polarizing film, a transparent support and an optically anisotropic layer, a polarizing film (usually polyvinyl alcohol film) and a transparent support (usually cellulose ester film) Affinity with is a problem. There is no suitable adhesive that can strongly bond both polyvinyl alcohol film and cellulose ester film. For this reason, even if the polarizing film and the transparent support are bonded using an adhesive, both are easily peeled off.
The invention described in JP-A-8-94838 solves the problem of affinity between the polarizing film and the transparent support by subjecting the transparent support to a saponification treatment (usually an alkali treatment). When the transparent support is saponified, the ester bond of the cellulose ester on the surface portion is partially hydrolyzed to return to the hydroxyl group originally possessed by the cellulose. Cellulose and polyvinyl alcohol are both polymers having a hydroxyl group and have high affinity. Therefore, the saponified transparent support and the polarizing film can be easily bonded.
[0007]
BookThe purpose of the invention is toMake the saponification treatment work only on the cellulose ester on the surface of the transparent support on the polarizing film sideThat is.
  Another object of the present invention is to provide a method for producing an integrated elliptical polarizing plate in which the alkaline aqueous solution used for the saponification treatment does not change color after the treatment.
[0008]
[Means for Solving the Problems]
  The object of the present invention is the following (1) to(4)This was achieved by the manufacturing method of the elliptically polarizing plate.
  (1) On a transparent support comprising a cellulose ester film,By aligning the polymerizable liquid crystalline molecules and polymerizing the polymerizable liquid crystalline molecules in a state where contact between oxygen in the air and the optically anisotropic layer is suppressedA step of providing an optically anisotropic layer, a step of alkali treatment by immersing a transparent support provided with an optically anisotropic layer in an aqueous alkali solution having a pH of 10 or higher at 40 to 70 ° C. for 20 to 300 seconds, and optical A method for producing an elliptically polarizing plate comprising a step of laminating a transparent support, a transparent protective film and a polarizing film provided with an anisotropic layer in the order of the transparent protective film, the polarizing film, the transparent support and the optically anisotropic layer.
[0009]
  (2) The production method according to (1), wherein the cellulose ester film includes a retardation increasing agent having a molecular structure that has at least two aromatic rings and does not sterically hinder the conformation of the two aromatic rings.
  (3)On a transparent support made of cellulose ester film,Align the polymerizable liquid crystalline molecules, andReduce the amount of oxygen to 13% or lessAn optically anisotropic layer is provided by polymerization.The step of performing an alkali treatment by immersing the transparent support provided with the optically anisotropic layer in an aqueous alkali solution having a pH of 10 or more at 40 to 70 ° C. for 20 to 300 seconds, and the optically anisotropic layer was provided. An elliptically polarizing plate comprising a step of laminating a transparent support, a transparent protective film and a polarizing film in the order of the transparent protective film, the polarizing film, the transparent support and the optically anisotropic layerManufacturing method.
  (4)Cellulose ester film contains a retardation increasing agent having a molecular structure that has at least two aromatic rings and does not sterically hinder the conformation of the two aromatic ringsThe manufacturing method as described in (3).
[0010]
【The invention's effect】
As a result of the study by the present inventors, the amount of liquid crystal molecules eluted in an alkaline aqueous solution is suppressed to less than 0.03% by weight in the saponification treatment (preferably, the amount of dissolution of the retardation increasing agent is further 0.35 wt. By suppressing to less than%, the optical function variation in the manufacturing process was substantially prevented.
The elution of liquid crystalline molecules and retardation increasing agents can be prevented by various means. However, the simplest means is to completely fix the liquid crystalline molecules by polymerization. A method for polymerizing liquid crystal molecules has already been proposed, but in the conventional method, the polymerization reaction is incomplete, and some molecules are contained in the optically anisotropic layer without being polymerized. Unpolymerized liquid crystalline molecules were easily eluted in an alkaline aqueous solution, causing the optical function to fluctuate.
As a result of further research by the present inventor, it has been found that the polymerization reaction of liquid crystalline molecules is inhibited by the influence of oxygen in the air (oxygen has a polymerization inhibiting action). The present inventor completely immobilizes the liquid crystalline molecules by polymerization by carrying out the polymerization reaction of the polymerizable liquid crystalline molecules in a state in which the penetration of oxygen in the air into the optically anisotropic layer is suppressed. Succeeded.
For the above reasons, according to the present invention, it is possible to manufacture an integrated elliptical polarizing plate with little variation in optical properties for each product.
When the liquid crystalline molecules are completely fixed by polymerization, the retardation increasing agent can be prevented from being eluted through the optically anisotropic layer. Although it is impossible to prevent the retardation increasing agent from eluting from the surface of the transparent support, it is possible to suppress the dissolution amount of the retardation increasing agent to about half.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic diagram showing a basic configuration of an elliptically polarizing plate.
The elliptically polarizing plate shown in FIG. 1 is an optically anisotropic film formed from a transparent protective film (1), a polarizing film (2), a transparent support (3) made of cellulose ester film, an alignment film (0) and liquid crystalline molecules. The layer (4) has a layer structure in which the layers are laminated in this order.
The elliptically polarizing plate shown in FIG. 1 includes a step of providing an optically anisotropic layer (4) on a transparent support (3) having an alignment film (0), an optically anisotropic layer (4), an alignment film (0), and A step of saponifying (alkaline treatment) the laminate of the transparent support (3), the transparent protective film (1), the polarizing film (2), the transparent support (3), the alignment film (3) and the optically different film It manufactures by the process laminated | stacked on the order of an anisotropic layer (4).
In the saponification treatment, the surface (31) on the polarizing film side of the transparent support (3) and the surface (41) of the optically anisotropic layer (4) are in contact with the aqueous alkali solution. On the saponification surface (31) of the transparent support (3), the ester bond of the cellulose ester is partially hydrolyzed, and the affinity with the polarizing film (2) is improved. On the other hand, on the saponification surface (41) of the optically anisotropic layer (4), as described above, there arises a problem that the liquid crystalline molecules are eluted into the alkaline aqueous solution.
[0012]
FIG. 2 is a schematic cross-sectional view showing a process for forming an optically anisotropic layer in the production of an elliptically polarizing plate.
In the production of the elliptically polarizing plate, polymerizable liquid crystalline molecules are applied on the alignment film (0) on the transparent support (3), and the liquid crystalline molecules are aligned and polymerized to form an optically anisotropic layer (4 ) Is preferably formed. More preferably, the polymerization reaction of the liquid crystalline molecules is carried out in a state in which the penetration of oxygen in the air into the optically anisotropic layer is suppressed. In the process shown in FIG. 2, the internal air is purged with nitrogen gas (N₂The photopolymerization reaction by light (Light) is carried out in the sealed container replaced with).
[0013]
FIG. 3 is a schematic cross-sectional view showing a saponification process in the production of an elliptically polarizing plate.
In the process shown in FIG. 3, the transparent substrate (3), the alignment film (0), and the optically anisotropic layer (4) are immersed in an aqueous sodium hydroxide solution (NaOH) for treatment. is doing. In the saponification treatment, the surface (31) on the polarizing film side of the transparent support (3) and the surface (41) of the optically anisotropic layer (4) are in contact with the aqueous sodium hydroxide solution.
In the optically anisotropic layer formed by completely polymerizing liquid crystalline molecules as in the treatment step shown in FIG. 2, the liquid crystalline molecules may be eluted from the surface (41) of the optically anisotropic layer (4). Can be prevented. In addition, in the optically anisotropic layer formed by completely polymerizing liquid crystalline molecules, the retardation increasing agent contained in the transparent support (3) forms the alignment film (0) and the optically anisotropic layer (4). It is also possible to prevent elution by passing through. Accordingly, the saponification treatment functions only for the cellulose ester on the surface (31) on the polarizing film side of the transparent support (3).
[0014]
FIG. 4 is a schematic diagram showing a basic configuration of a transmissive liquid crystal display device.
The transmissive liquid crystal display device shown in FIG. 4A has a transparent protective film (1a), a polarizing film (2a), a transparent support (3a), an optically anisotropic layer (in order from the backlight (BL) side). 4a), lower substrate (5a) of the liquid crystal cell, liquid crystal layer (6) composed of rod-like liquid crystalline molecules, upper substrate (5b) of the liquid crystal cell, optically anisotropic layer (4b), transparent support (3b), polarized light It consists of a film (2b) and a transparent protective film (1b). The transparent protective film (1a) to the optically anisotropic layer (4a) and the optically anisotropic layer (4b) to the transparent protective film (1b) constitute two elliptical polarizing plates.
The transmissive liquid crystal display device shown in FIG. 4B has a transparent protective film (1a), a polarizing film (2a), a transparent support (3a), an optically anisotropic layer (in order) from the backlight (BL) side. 4a), lower substrate (5a) of liquid crystal cell, liquid crystal layer (6) made of rod-like liquid crystalline molecules, upper substrate (5b) of liquid crystal cell, transparent protective film (1b), polarizing film (2b), and transparent protective film (1c). The transparent protective film (1a) to the optically anisotropic layer (4a) constitute an elliptically polarizing plate.
The transmissive liquid crystal display device shown in FIG. 4C has a transparent protective film (1a), a polarizing film (2a), a transparent protective film (1b), and a lower substrate of the liquid crystal cell (in order from the backlight (BL) side). 5a), liquid crystal layer (6) composed of rod-like liquid crystalline molecules, upper substrate (5b) of liquid crystal cell, optical anisotropic layer (4b), transparent support (3b), polarizing film (2b), and transparent protective film (1c). The optically anisotropic layer (4b) to the transparent protective film (1c) constitute an elliptically polarizing plate.
[0015]
FIG. 5 is a schematic diagram showing a basic configuration of a reflective liquid crystal display device.
The reflective liquid crystal display device shown in FIG. 5 includes, in order from the reflective plate (RP) side, a lower substrate (5a) of a liquid crystal cell, a liquid crystal layer (6) made of rod-like liquid crystalline molecules, an upper substrate (5b) of a liquid crystal cell, It consists of an optically anisotropic layer (4b), a transparent support (3b), a polarizing film (2b), and a transparent protective film (1b). The optically anisotropic layer (4b) to the transparent protective film (1b) constitute an elliptically polarizing plate.
[0016]
[Transparent protective film]
As the transparent protective film, an optically isotropic polymer film is used. That the protective film is transparent means that the light transmittance is 80% or more. Specifically, the optical isotropy means that in-plane retardation (Re) is preferably 10 nm or less, and more preferably 5 nm or less. The thickness direction retardation (Rth) is preferably 40 nm or less, and more preferably 20 nm or less. The definition of the in-plane retardation (Re) and the retardation in the thickness direction (Rth) will be described later for the transparent support.
As the transparent protective film, generally a cellulose ester film, preferably a triacetyl cellulose film is used. The cellulose ester film is preferably formed by a solvent cast method.
The thickness of the transparent protective film is preferably 20 to 500 μm, and more preferably 50 to 200 μm.
[0017]
[Polarizing film]
Examples of the polarizing film include an iodine polarizing film, a dye polarizing film using a dichroic dye, and a polyene polarizing film. The iodine polarizing film and the dye polarizing film are generally manufactured using a polyvinyl alcohol film. The polarization axis of the polarizing film corresponds to a direction perpendicular to the film stretching direction.
[0018]
[Transparent support]
In the present invention, a cellulose ester film is used as a transparent support.
The thickness of the transparent support is preferably 20 to 500 μm, and more preferably 50 to 200 μm.
When it is preferable that the transparent support is optically isotropic, a normal cellulose ester film can be used in the same manner as the transparent protective film.
When the transparent support is required to have optical anisotropy, a cellulose ester film having a high retardation is produced and used.
[0019]
The in-plane retardation (Re) of the cellulose ester film can be increased by stretching the cellulose ester film. The thickness direction retardation (Rth) of the cellulose ester film can be determined by (1) using a retardation increasing agent, (2) adjusting the average degree of acetylation (degree of acetylation), or (3) producing the film by a cooling dissolution method. It can be set to the high value mentioned above. Therefore, a cellulose ester film which has been conventionally considered to be optically isotropic can be used as an optically anisotropic film having an optical compensation function.
The retardation value (Rth) and the in-plane retardation value (Re) in the thickness direction are calculated according to the following formulas (1) and (2), respectively.
Formula (1)
Retardation value in thickness direction (Rth) = {(nx + ny) / 2−nz} × d formula (2)
In-plane retardation value (Re) = (nx−ny) × d
Where nx is the refractive index in the x direction in the film plane, ny is the refractive index in the y direction in the film plane, nz is the refractive index in the direction perpendicular to the film plane, and d is the film refractive index. Thickness (nm).
[0020]
When an optically anisotropic transparent support is used, the retardation value in the thickness direction at a wavelength of 550 nm (Rth⁵⁵⁰ ) Is preferably 70 to 400 nm, more preferably 100 to 400 nm, still more preferably 150 to 400 nm, still more preferably 200 to 400 nm, and more preferably 200 to 300 nm. Most preferred.
The birefringence {(nx + ny) / 2−nz} in the thickness direction is 7 × 10.^-FourTo 4 × 10^-3Is preferably 1 × 10^-3To 4 × 10^-3More preferably, 1.5 × 10^-3To 4 × 10^-3More preferably, 2 × 10^-3To 4 × 10^-3It is further preferable that 2 × 10^-3To 3 × 10^-3Most preferably, 2 × 10^-3To 2.5 × 10^-3It is particularly preferred that
[0021]
Hereinafter, a method for producing a cellulose ester film having a high retardation will be described.
As the cellulose ester, it is preferable to use a lower fatty acid ester of cellulose. 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). Cellulose acetate is particularly preferred. Mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate may be used.
The average acetylation degree (acetylation degree) of cellulose acetate is preferably 55.0% or more and less than 62.5%. From the viewpoint of the physical properties of the film, the average acetylation degree is more preferably 58.0% or more and less than 62.5%. However, when cellulose acetate having an average degree of acetylation of 55.0% or more and less than 58.0% (preferably 57.0% or more and less than 58.0%) is used, a film having a high retardation in the thickness direction is produced. be able to.
[0022]
The retardation in the thickness direction can be increased by using a retardation increasing agent. As the retardation increasing agent, a compound having at least two aromatic rings and a molecular structure that does not sterically hinder the conformation of the two aromatic rings can be used. The retardation increasing agent is preferably used in the range of 0.3 to 20 parts by weight with respect to 100 parts by weight of the cellulose ester.
A compound having at least two aromatic rings has a π-bonding plane of 7 or more carbon atoms. If the conformation of the two aromatic rings is not sterically hindered, the two aromatic rings form the same plane. According to the study of the present inventor, in order to increase the retardation of the cellulose ester film, it is important to form the same plane by a plurality of aromatic rings.
In the present specification, the “aromatic ring” includes an aromatic hetero ring in addition to an aromatic hydrocarbon ring. The aromatic hydrocarbon ring is particularly preferably a 6-membered ring (that is, a benzene ring).
[0023]
The aromatic heterocycle is generally an unsaturated heterocycle. The aromatic heterocycle is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring. Aromatic heterocycles generally have the most double bonds. As the hetero atom, a nitrogen atom, an oxygen atom and a sulfur atom are preferable, and a nitrogen atom is particularly preferable. Examples of aromatic heterocycles include furan ring, thiophene ring, pyrrole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, pyrazole ring, furazane ring, triazole ring, pyran ring, pyridine ring , Pyridazine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring.
As the aromatic ring, benzene ring, furan ring, thiophene ring, pyrrole ring, oxazole ring, thiazole ring, imidazole ring, triazole ring, pyridine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring are preferable.
[0024]
The number of aromatic rings contained in the retardation increasing agent is preferably 2 to 20, more preferably 2 to 12, still more preferably 2 to 8, and most preferably 2 to 6. preferable. In the case of having three or more aromatic rings, the conformation of at least two aromatic rings should not be sterically hindered.
The bonding relationship between two aromatic rings can be classified into (a) when a condensed ring is formed, (b) when directly linked by a single bond, and (c) when linked via a linking group (for aromatic rings). , Spiro bonds cannot be formed). From the viewpoint of the retardation increasing function, any of (a) to (c) may be used. However, in the case of (b) or (c), it is necessary not to sterically hinder the conformation of the two aromatic rings.
[0025]
Examples of the condensed ring (a condensed ring of two or more aromatic rings) include an indene ring, a naphthalene ring, an azulene ring, a fluorene ring, a phenanthrene ring, an anthracene ring, an acenaphthylene ring, a biphenylene ring, a naphthacene ring, Pyrene ring, indole ring, isoindole ring, benzofuran ring, benzothiophene ring, indolizine ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring, purine ring, indazole ring, chromene ring, quinoline ring, isoquinoline Ring, quinolidine ring, quinazoline ring, cinnoline ring, quinoxaline ring, phthalazine ring, pteridine ring, carbazole ring, acridine ring, phenanthridine ring, xanthene ring, phenazine ring, phenothiazine ring, phenoxathiin ring, phenoxazine ring and thiant It includes emissions ring. Naphthalene ring, azulene ring, indole ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring and quinoline ring are preferred.
The single bond (b) is preferably a bond between carbon atoms of two aromatic rings. Two aromatic rings may be bonded with two or more single bonds to form an aliphatic ring or a non-aromatic heterocyclic ring between the two aromatic rings.
[0026]
The linking group in (c) is also preferably bonded to carbon atoms of two aromatic rings. The linking group is preferably an alkylene group, an alkenylene group, an alkynylene group, —CO—, —O—, —NH—, —S—, or a combination thereof. Examples of linking groups composed of combinations are shown below. In addition, the relationship between the left and right in the following examples of linking groups may be reversed.
c1: -CO-O-
c2: —CO—NH—
c3: -alkylene-O-
c4: —NH—CO—NH—
c5: —NH—CO—O—
c6: —O—CO—O—
c7: -O-alkylene-O-
c8: -CO-alkenylene-
c9: -CO-alkenylene-NH-
c10: -CO-alkenylene-O-
c11: -alkylene-CO-O-alkylene-O-CO-alkylene-
c12: -O-alkylene-CO-O-alkylene-O-CO-alkylene-O-
c13: -O-CO-alkylene-CO-O-
c14: -NH-CO-alkenylene-
c15: -O-CO-alkenylene-
[0027]
The aromatic ring and the linking group may have a substituent. However, the substituent is required not to sterically hinder the conformation of the two aromatic rings. In steric hindrance, the type and position of substituents are problematic. As the type of the substituent, a sterically bulky substituent (for example, a tertiary alkyl group) tends to cause steric hindrance. As the position of the substituent, steric hindrance is likely to occur when a position adjacent to the bond of the aromatic ring (ortho position in the case of a benzene ring) is substituted.
Examples of the substituent include halogen atom (F, Cl, Br, I), hydroxyl, carboxyl, cyano, amino, nitro, sulfo, carbamoyl, sulfamoyl, ureido, alkyl group, alkenyl group, alkynyl group, aliphatic acyl group , Aliphatic acyloxy group, alkoxy group, alkoxycarbonyl group, alkoxycarbonylamino group, alkylthio group, alkylsulfonyl group, aliphatic amide group, aliphatic sulfonamido group, aliphatic substituted amino group, aliphatic substituted carbamoyl group, aliphatic Substituted sulfamoyl groups, aliphatic substituted ureido groups and non-aromatic heterocyclic groups are included.
[0028]
The alkyl group preferably has 1 to 8 carbon atoms. A chain alkyl group is preferable to a cyclic alkyl group, and a linear alkyl group is particularly preferable. The alkyl group may further have a substituent (eg, hydroxy, carboxy, alkoxy group, alkyl-substituted amino group). Examples of alkyl groups (including substituted alkyl groups) include methyl, ethyl, n-butyl, n-hexyl, 2-hydroxyethyl, 4-carboxybutyl, 2-methoxyethyl and 2-diethylaminoethyl.
The alkenyl group preferably has 2 to 8 carbon atoms. A chain alkenyl group is preferable to a cyclic alkenyl group, and a linear alkenyl group is particularly preferable. The alkenyl group may further have a substituent. Examples of alkenyl groups include vinyl, allyl and 1-hexenyl.
The alkynyl group preferably has 2 to 8 carbon atoms. A chain alkynyl group is preferable to a cyclic alkynyl group, and a linear alkynyl group is particularly preferable. The alkynyl group may further have a substituent. Examples of alkynyl groups include ethynyl, 1-butynyl and 1-hexynyl.
[0029]
The aliphatic acyl group preferably has 1 to 10 carbon atoms. Examples of the aliphatic acyl group include acetyl, propanoyl and butanoyl.
The aliphatic acyloxy group preferably has 1 to 10 carbon atoms. Examples of the aliphatic acyloxy group include acetoxy.
The number of carbon atoms of the alkoxy group is preferably 1 to 8. The alkoxy group may further have a substituent (eg, alkoxy group). Examples of alkoxy groups (including substituted alkoxy groups) include methoxy, ethoxy, butoxy and methoxyethoxy.
The alkoxycarbonyl group preferably has 2 to 10 carbon atoms. Examples of the alkoxycarbonyl group include methoxycarbonyl and ethoxycarbonyl.
The number of carbon atoms of the alkoxycarbonylamino group is preferably 2 to 10. Examples of the alkoxycarbonylamino group include methoxycarbonylamino and ethoxycarbonylamino.
[0030]
The alkylthio group preferably has 1 to 12 carbon atoms. Examples of the alkylthio group include methylthio, ethylthio and octylthio.
The alkylsulfonyl group preferably has 1 to 8 carbon atoms. Examples of the alkylsulfonyl group include methanesulfonyl and ethanesulfonyl.
The aliphatic amide group preferably has 1 to 10 carbon atoms. Examples of the aliphatic amide group include acetamide.
The aliphatic sulfonamide group preferably has 1 to 8 carbon atoms. Examples of the aliphatic sulfonamido group include methanesulfonamido, butanesulfonamido and n-octanesulfonamido.
The number of carbon atoms of the aliphatic substituted amino group is preferably 1 to 10. Examples of the aliphatic substituted amino group include dimethylamino, diethylamino and 2-carboxyethylamino.
The aliphatic substituted carbamoyl group preferably has 2 to 10 carbon atoms. Examples of the aliphatic substituted carbamoyl group include methylcarbamoyl and diethylcarbamoyl.
The aliphatic substituted sulfamoyl group preferably has 1 to 8 carbon atoms. Examples of the aliphatic substituted sulfamoyl group include methylsulfamoyl and diethylsulfamoyl.
The number of carbon atoms in the aliphatic substituted ureido group is preferably 2 to 10. Examples of the aliphatic substituted ureido group include methylureido.
Examples of non-aromatic heterocyclic groups include piperidino and morpholino.
The molecular weight of the retardation increasing agent is preferably 300 to 800. The boiling point of the retardation increasing agent is preferably 260 ° C. or higher.
[0031]
It is preferable to produce a cellulose ester film by a solvent cast method. In the solvent cast method, a film is produced using a solution (dope) in which cellulose ester is dissolved in an organic solvent.
The organic solvent is a solvent selected from ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, esters having 3 to 12 carbon atoms, and halogenated hydrocarbons having 1 to 6 carbon atoms. It is preferable to contain.
The ether, ketone and ester may have a cyclic structure. A compound having two or more functional groups of ether, ketone and ester (that is, —O—, —CO— and —COO—) can also be used as the organic solvent. The organic solvent may have another functional group such as an alcoholic hydroxyl group. In the case of an organic solvent having two or more types of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group.
[0032]
Examples of the ether having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole.
Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone and methylcyclohexanone.
Examples of the esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate.
Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.
The number of carbon atoms of the halogenated hydrocarbon is preferably 1 or 2, and most preferably 1. The halogen of the halogenated hydrocarbon is preferably chlorine. The proportion of halogenated hydrocarbon hydrogen atoms substituted with halogen is preferably 25 to 75 mol%, more preferably 30 to 70 mol%, and more preferably 35 to 65 mol%. More preferably, it is 40 to 60 mol%, and most preferably. Methylene chloride is a representative halogenated hydrocarbon.
Two or more organic solvents may be mixed and used.
[0033]
The solution may be prepared by a general method without adopting the cooling dissolution method. The general method means that the treatment is performed at a temperature of 0 ° C. or higher (room temperature or high temperature). The solution can be prepared using a dope preparation method and apparatus in a normal solvent cast method. In the case of a general method, it is preferable to use a halogenated hydrocarbon (particularly methylene chloride) as the organic solvent.
The amount of the cellulose ester is adjusted so as to be contained in the obtained solution by 10 to 40% by weight. The amount of cellulose ester is more preferably 10 to 30% by weight. Arbitrary additives described later may be added to the organic solvent (main solvent).
The solution can be prepared by stirring the cellulose ester and the organic solvent at room temperature (0 to 40 ° C.). High concentration solutions may be stirred under pressure and heating conditions. Specifically, the cellulose ester and the organic solvent are placed in a pressure vessel and sealed, and stirred while heating to a temperature not lower than the boiling point of the solvent at normal temperature and in a range where the solvent does not boil. The heating temperature is usually 40 ° C. or higher, preferably 60 to 200 ° C., more preferably 80 to 110 ° C.
[0034]
Each component may be coarsely mixed in advance and then placed in a container. Moreover, you may put into a container sequentially. The container needs to be configured so that it can be stirred. The container can be pressurized by injecting an inert gas such as nitrogen gas. Moreover, you may utilize the raise of the vapor pressure of the solvent by heating. Or after sealing a container, you may add each component under pressure.
When heating, it is preferable to heat from the outside of the container. For example, a jacket type heating device can be used. The entire container can also be heated by providing a plate heater outside the container and piping to circulate the liquid.
It is preferable to provide a stirring blade inside the container and stir using this. The stirring blade preferably has a length that reaches the vicinity of the wall of the container. A scraping blade is preferably provided at the end of the stirring blade in order to renew the liquid film on the vessel wall.
Instruments such as a pressure gauge and a thermometer may be installed in the container. Each component is dissolved in a solvent in the container. The prepared dope is taken out of the container after cooling, or taken out and then cooled using a heat exchanger or the like.
[0035]
A solution can also be prepared by a cooling dissolution method. In the cooling dissolution method, the cellulose ester can be dissolved in an organic solvent (an organic solvent other than the halogenated hydrocarbon) that is difficult to dissolve by a normal dissolution method. In addition, even if it is a solvent (for example, halogenated hydrocarbon) which can melt | dissolve a cellulose ester with a normal melt | dissolution method, there exists an effect that a uniform solution can be obtained rapidly according to a cooling melt | dissolution method. Further, when the cooling dissolution method is used, the retardation of the cellulose ester film to be produced becomes high.
In the cooling dissolution method, first, a cellulose ester is gradually added to an organic solvent with stirring at room temperature.
The amount of the cellulose ester is preferably adjusted so as to be contained in the mixture by 10 to 40% by weight. The amount of cellulose ester is more preferably 10 to 30% by weight. Furthermore, you may add the arbitrary additive mentioned later in a mixture.
[0036]
The mixture is then cooled to -100 to -10 ° C (preferably -80 to -10 ° C, more preferably -50 to -20 ° C, most preferably -50 to -30 ° C). The cooling can be performed, for example, in a dry ice / methanol bath (−75 ° C.) or a cooled diethylene glycol solution (−30 to −20 ° C.). When cooled in this manner, the mixture of cellulose ester and organic solvent solidifies.
The cooling rate is preferably 4 ° C./min or more, more preferably 8 ° C./min or more, and most preferably 12 ° C./min or more. The faster the cooling rate, the better. However, 10,000 ° C./second is the theoretical upper limit, 1000 ° C./second is the technical upper limit, and 100 ° C./second is the practical upper limit. The cooling rate is a value obtained by dividing the difference between the temperature at the start of cooling and the final cooling temperature by the time from the start of cooling until the final cooling temperature is reached.
[0037]
Further, when this is heated to 0 to 200 ° C. (preferably 0 to 150 ° C., more preferably 0 to 120 ° C., most preferably 0 to 50 ° C.), the cellulose ester is dissolved in the organic solvent. The temperature can be raised by simply leaving it at room temperature or in a warm bath.
The heating rate is preferably 4 ° C./min or more, more preferably 8 ° C./min or more, and most preferably 12 ° C./min or more. The higher the heating rate, the better. However, 10,000 ° C./second is the theoretical upper limit, 1000 ° C./second is the technical upper limit, and 100 ° C./second is the practical upper limit. The heating rate is a value obtained by dividing the difference between the temperature at the start of heating and the final heating temperature by the time from the start of heating until the final heating temperature is reached. .
A uniform solution is obtained as described above. If the dissolution is insufficient, the cooling and heating operations may be repeated. Whether or not the dissolution is sufficient can be determined by merely observing the appearance of the solution with the naked eye.
[0038]
In the cooling dissolution method, it is desirable to use a sealed container in order to avoid moisture mixing due to condensation during cooling. In the cooling and heating operation, when the pressure is applied during cooling and the pressure is reduced during heating, the dissolution time can be shortened. In order to perform pressurization and decompression, it is desirable to use a pressure-resistant container.
In addition, according to differential scanning calorimetry (DSC), a 20 wt% solution obtained by dissolving cellulose acetate (acetylation degree: 60.9%, viscosity average polymerization degree: 299) in methyl acetate by the cooling dissolution method was 33. There exists a quasi-phase transition point between a sol state and a gel state in the vicinity of ° C., and a uniform gel state is obtained below this temperature. Therefore, this solution needs to be stored at a temperature equal to or higher than the pseudo phase transition temperature, preferably about the gel phase transition temperature plus about 10 ° C. However, this pseudo phase transition temperature varies depending on the average degree of acetylation, the degree of viscosity average polymerization, the concentration of the solution, and the organic solvent used.
[0039]
From the prepared cellulose ester solution (dope), a cellulose ester film is produced by a solvent cast method.
The dope is cast on a drum or band, and the solvent is evaporated to form a film. It is preferable to adjust the concentration of the dope before casting so that the solid content is 18 to 35%. The surface of the drum or band is preferably finished in a mirror state. The casting and drying methods in the solvent casting method are described in U.S. Pat. Nos. 2,336,310, 2,367,603, 2,429,078, 2,429,297, 2,429,978, 2,607,704, 2,739,69, British Patent 6,407,331, No. 736892, JP-B Nos. 45-4554, 49-5614, JP-A-60-176834, No. 60-203430, and No. 62-1115035.
The dope is preferably cast on a drum or band having a surface temperature of 10 ° C. or less. It is preferable that the cast is dried for 2 seconds or longer after being cast. The obtained film can be peeled off from the drum or band, and further dried by high-temperature air whose temperature is successively changed from 100 to 160 ° C. to evaporate the residual solvent. The above method is described in Japanese Patent Publication No. 5-17844. According to this method, it is possible to shorten the time from casting to stripping. In order to carry out this method, it is necessary for the dope to gel at the surface temperature of the drum or band during casting. The solution (dope) prepared according to the present invention satisfies this condition.
The thickness of the film to be produced is preferably 40 to 120 μm, more preferably 70 to 110 μm.
[0040]
A plasticizer can be added to the cellulose ester film in order to improve mechanical properties or increase the drying rate. As the plasticizer, phosphoric acid ester or carboxylic acid ester is used. Examples of phosphate esters include triphenyl phosphate (TPP) and tricresyl phosphate (TCP). Representative examples of the carboxylic acid ester include phthalic acid esters and citric acid esters. Examples of phthalic acid esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethylhexyl phthalate (DEHP). Examples of citrate esters include triethyl O-acetylcitrate (OACTE) and tributyl O-acetylcitrate (OACTB). Examples of other carboxylic acid esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic acid esters. Phthalate plasticizers (DMP, DEP, DBP, DOP, DPP, DEHP) are preferably used. DEP and DPP are particularly preferred.
The addition amount of the plasticizer is preferably 0.1 to 25% by weight, more preferably 1 to 20% by weight, and most preferably 3 to 15% by weight of the amount of the cellulose ester.
[0041]
Degradation inhibitors (eg, antioxidants, peroxide decomposers, radical inhibitors, metal deactivators, acid scavengers, amines) and UV inhibitors may be added to the cellulose ester film. The deterioration preventing agents are described in JP-A-3-199201, JP-A-51907073, JP-A-5-194789, JP-A-5-271471, and JP-A-6-107854. The addition amount of the deterioration preventing agent is preferably 0.01 to 1% by weight of the solution (dope) to be prepared, and more preferably 0.01 to 0.2% by weight. When the addition amount is less than 0.01% by weight, the effect of the deterioration preventing agent is hardly recognized. When the added amount exceeds 1% by weight, bleed-out (bleeding out) of the deterioration preventing agent to the film surface may be observed. As a particularly preferred example of the deterioration preventing agent, butylated hydroxytoluene (BHT) can be mentioned. The ultraviolet ray preventing agent is described in JP-A-7-11056.
In order to improve the adhesion between the transparent support and the alignment film or the optically anisotropic layer, it is preferable to provide a gelatin undercoat layer. The thickness of the gelatin undercoat layer is preferably 0.01 to 1 μm, more preferably 0.02 to 0.5 μm, and most preferably 0.05 to 0.2 μm.
[0042]
[Alignment film]
The alignment film is an organic compound (eg, ω-tricosanoic acid) formed by rubbing treatment of an organic compound (preferably polymer), oblique deposition of an inorganic compound, formation of a layer having a microgroove, or Langmuir-Blodgett method (LB film). , Dioctadecylmethylammonium chloride, methyl stearylate). Furthermore, an alignment film in which an alignment function is generated by application of an electric field, application of a magnetic field, or light irradiation is also known. An alignment film formed by a polymer rubbing treatment is particularly preferable. The rubbing treatment is carried out by rubbing the surface of the polymer layer several times in a certain direction with paper or cloth.
The type of polymer used for the alignment film is determined according to the type of display mode of the liquid crystal cell. In a display mode (eg, VA, OCB, HAN) in which many rod-like liquid crystal molecules in the liquid crystal cell are aligned substantially vertically, the liquid crystal molecules in the optically anisotropic layer are aligned substantially horizontally. An alignment film having a function is used. In a display mode in which many rod-like liquid crystal molecules in the liquid crystal cell are aligned substantially horizontally (eg, STN), the alignment has a function of aligning the liquid crystal molecules of the optically anisotropic layer substantially vertically. Use a membrane. In a display mode (eg, TN) in which many rod-like liquid crystalline molecules in the liquid crystal cell are substantially obliquely aligned, the alignment has a function of substantially obliquely aligning the liquid crystalline molecules of the optically anisotropic layer. Use a membrane.
[0043]
Specific polymer types are described in the literature on optical compensation sheets using discotic liquid crystalline molecules corresponding to the various display modes described above.
The polymer used for the alignment film may be cross-linked to enhance the strength of the alignment film. By introducing a crosslinkable group into the polymer used for the alignment film and reacting the crosslinkable group, the polymer can be crosslinked. In addition, about bridge | crosslinking of the polymer used for an alignment film, Unexamined-Japanese-Patent No. 8-338913 has description.
The thickness of the alignment film is preferably 0.01 to 5 μm, and more preferably 0.05 to 1 μm.
In addition, after aligning the liquid crystalline molecules using the alignment film, the liquid crystalline molecules are fixed in the aligned state to form an optically anisotropic layer, and only the optically anisotropic layer is transferred onto the support. May be. The liquid crystalline molecules fixed in the alignment state can maintain the alignment state even without the alignment film.
[0044]
[Optically anisotropic layer]
The optically anisotropic layer is formed from liquid crystal molecules.
As the liquid crystal molecule, a rod-like liquid crystal molecule or a discotic liquid crystal molecule is preferable, and a discotic liquid crystal molecule is particularly preferable.
Examples of rod-like liquid crystalline molecules include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines. , Phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used. In addition to the above low-molecular liquid crystalline molecules, high-molecular liquid crystalline molecules can also be used. The high-molecular liquid crystalline molecule is a polymer having a side chain corresponding to the above low-molecular liquid crystalline molecule. An optical compensation sheet using polymer liquid crystalline molecules is described in JP-A-5-53016.
[0045]
Discotic liquid crystalline molecules are described in various literature (C. Destrade et al., Mol. Crysr. Liq. Cryst., Vol. 71, page 111 (1981); edited by the Chemical Society of Japan, Quarterly Review, No. 22, Liquid Crystal Chemistry, Chapter 5, Chapter 10 Section 2 (1994); B. Kohne et al., Angew. Chem. Soc. Chem. Comm., Page 1794 (1985); J. Zhang et al., J Am. Chem. Soc., Vol. 116, page 2655 (1994)). The polymerization of discotic liquid crystalline molecules is described in JP-A-8-27284.
In order to fix the discotic liquid crystalline molecules by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystalline molecules. However, when the polymerizable group is directly connected to the disc-shaped core, it becomes difficult to maintain the orientation state in the polymerization reaction. Therefore, a linking group is introduced between the discotic core and the polymerizable group. Accordingly, the discotic liquid crystalline molecule is preferably a compound represented by the following formula (I).
[0046]
(I) D (-LQ)_n
Where D is a discotic core; L is a divalent linking group; Q is a polymerizable group; and n is an integer from 4 to 12.
Examples of the disk-shaped core (D) of the formula (I) are shown below. In each of the following examples, LQ (or QL) means a combination of a divalent linking group (L) and a polymerizable group (Q).
[0047]
[Chemical 1]

[0048]
[Chemical formula 2]

[0049]
[Chemical Formula 3]

[0050]
[Formula 4]

[0051]
[Chemical formula 5]

[0052]
[Chemical 6]

[0053]
[Chemical 7]

[0054]
In the formula (I), the divalent linking group (L) is selected from the group consisting of an alkylene group, an alkenylene group, an arylene group, —CO—, —NH—, —O—, —S—, and combinations thereof. A divalent linking group is preferred. The divalent linking group (L) is a combination of at least two divalent groups selected from the group consisting of an alkylene group, an alkenylene group, an arylene group, —CO—, —NH—, —O—, and —S—. More preferably, it is a group. The divalent linking group (L) is most preferably a group obtained by combining at least two divalent groups selected from the group consisting of an alkylene group, an alkenylene group, an arylene group, -CO- and -O-. The alkylene group preferably has 1 to 12 carbon atoms. The alkenylene group preferably has 2 to 12 carbon atoms. The number of carbon atoms in the arylene group is preferably 6 to 10. The alkylene group, alkenylene group and arylene group may have a substituent (eg, alkyl group, halogen atom, cyano, alkoxy group, acyloxy group).
Examples of the divalent linking group (L) are shown below. The left side is bonded to the discotic core (D), and the right side is bonded to the polymerizable group (Q). AL represents an alkylene group or an alkenylene group, and AR represents an arylene group.
[0055]
L1: -AL-CO-O-AL-
L2: -AL-CO-O-AL-O-
L3: -AL-CO-O-AL-O-AL-
L4: -AL-CO-O-AL-O-CO-
L5: -CO-AR-O-AL-
L6: -CO-AR-O-AL-O-
L7: -CO-AR-O-AL-O-CO-
L8: -CO-NH-AL-
L9: -NH-AL-O-
L10: -NH-AL-O-CO-
L11: -O-AL-
L12: -O-AL-O-
[0056]
L13: -O-AL-O-CO-
L14: -O-AL-O-CO-NH-AL-
L15: -O-AL-S-AL-
L16: -O-CO-AL-AR-O-AL-O-CO-
L17: -O-CO-AR-O-AL-CO-
L18: -O-CO-AR-O-AL-O-CO-
L19: -O-CO-AR-O-AL-O-AL-O-CO-
L20: -O-CO-AR-O-AL-O-AL-O-AL-O-CO-
L21: -S-AL-
L22: -S-AL-O-
L23: -S-AL-O-CO-
L24: -S-AL-S-AL-
L25: -S-AR-AL-
[0057]
In order to optically compensate a liquid crystal cell in which rod-like liquid crystalline molecules such as STN mode are twisted, it is preferable that the discotic liquid crystalline molecules are also twisted. When an asymmetric carbon atom is introduced into the AL (alkylene group or alkenylene group), the discotic liquid crystalline molecules can be twisted and aligned in a spiral shape. Further, even when a compound (chiral agent) having an optical activity containing an asymmetric carbon atom is added to the optically anisotropic layer, the discotic liquid crystalline molecules can be twisted and aligned in a spiral shape.
[0058]
The polymerizable group (Q) of the formula (I) is determined according to the type of polymerization reaction. Examples of the polymerizable group (Q) are shown below.
[0059]
[Chemical 8]

[0060]
The polymerizable group (Q) is preferably an unsaturated polymerizable group (Q1 to Q7) or an epoxy group (Q8), more preferably an unsaturated polymerizable group, and an ethylenically unsaturated polymerizable group ( Most preferably Q1-Q6).
In the formula (I), n is an integer of 4 to 12. A specific number is determined according to the type of discotic core (D). In addition, although the combination of several L and Q may differ, it is preferable that it is the same.
[0061]
Two or more kinds of discotic liquid crystal molecules may be used in combination. For example, a polymerizable discotic liquid crystalline molecule and a non-polymerizable discotic liquid crystalline molecule as described above can be used in combination.
The non-polymerizable discotic liquid crystalline molecule is preferably a compound in which the polymerizable group (Q) of the polymerizable discotic liquid crystalline molecule is changed to a hydrogen atom or an alkyl group. That is, the non-polymerizable discotic liquid crystalline molecule is preferably a compound represented by the following formula (II).
(II) D (-LR)_n
Where D is a discotic core; L is a divalent linking group; R is a hydrogen atom or an alkyl group; and n is an integer from 4 to 12.
The example of the discotic core (D) of the formula (II) is the same as the example of the polymerizable discotic liquid crystal molecule except that LQ (or QL) is changed to LR (or RL).
Examples of the divalent linking group (L) are the same as the examples of the polymerizable discotic liquid crystal molecules.
The alkyl group for R preferably has 1 to 40 carbon atoms, and more preferably 1 to 30 carbon atoms. A chain alkyl group is preferred to a cyclic alkyl group, and a linear alkyl group is preferred to a branched chain alkyl group. R is particularly preferably a hydrogen atom or a linear alkyl group having 1 to 30 carbon atoms.
[0062]
The thickness of the optically anisotropic layer is generally 0.1 to 10 μm. The thickness is more preferably 0.5 to 5 μm, and most preferably 1 to 5 μm. However, depending on the mode of the liquid crystal cell, the optically anisotropic layer may be thickened (5 to 10 μm) in order to obtain high optical anisotropy.
As described above, the alignment state of the liquid crystalline molecules in the optically anisotropic layer is determined according to the type of display mode of the liquid crystal cell. Specifically, the alignment state of liquid crystal molecules is controlled by the type of liquid crystal molecules, the type of alignment film, and the use of additives (eg, plasticizers, binders, surfactants) in the optically anisotropic layer. The
[0063]
[Process for forming optically anisotropic layer]
The optically anisotropic layer is a liquid crystalline molecule, or the following polymerizable initiator or any additive (eg, plasticizer, monomer, surfactant, cellulose ester, 1,3,5-triazine compound, chiral agent). It is formed by applying a coating solution containing, onto the alignment film.
As the solvent used for preparing the coating solution, an organic solvent is preferably used. Examples of organic solvents include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, , Chloroform, dichloromethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination.
The coating liquid can be applied by a known method (eg, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method).
[0064]
The liquid crystalline molecules are preferably substantially uniformly aligned, more preferably fixed in a substantially uniformly aligned state, and the liquid crystalline molecules are fixed by a polymerization reaction. Is most preferred. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator. A photopolymerization reaction is preferred.
Examples of the photopolymerization initiator include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (described in US Pat. No. 2,448,828), α-hydrocarbon substituted aromatic acyloin. Compound (described in US Pat. No. 2,722,512), polynuclear quinone compound (described in US Pat. Nos. 3,046,127 and 2,951,758), a combination of triarylimidazole dimer and p-aminophenyl ketone (US Pat. No. 3,549,367) Acridine and phenazine compounds (JP-A-60-105667, U.S. Pat. No. 4,239,850) and oxadiazole compounds (U.S. Pat. No. 4,212,970).
The amount of the photopolymerization initiator used is preferably 0.01 to 20% by weight, more preferably 0.5 to 5% by weight, based on the solid content of the coating solution.
Light irradiation for polymerization of discotic liquid crystalline molecules is preferably performed using ultraviolet rays.
Irradiation energy is 20mJ / cm² ~ 50J / cm² Preferably, 100 to 800 mJ / cm² More preferably. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions.
[0065]
The polymerization reaction is performed in a state where the penetration of oxygen in the air into the optically anisotropic layer is suppressed. Specifically, the amount of oxygen in the air is reduced, the interface between the air and the optically anisotropic layer is shielded, or oxygen that attempts to penetrate into the optically anisotropic layer using an oxygen scavenger. To capture.
When reducing the amount of oxygen in the air (usually about 20%), it is necessary to carry out the polymerization reaction in a sealed container. The amount of oxygen is preferably reduced to 13% or less. The air may be replaced with an inert gas (nitrogen gas). Further, the polymerization reaction can be carried out in a state where the atmospheric pressure is lowered and the absolute amount of oxygen is reduced.
The interface between the air and the optically anisotropic layer can be shielded by covering the surface of the optically anisotropic layer with a cover sheet.
In the case of using an oxygen scavenger, it is necessary to select and use an oxygen scavenger that does not chemically and optically affect the optically anisotropic layer.
A method of reducing the amount of oxygen in the air is preferable, and a method of replacing air with nitrogen gas is most preferable.
[0066]
[Saponification treatment process]
The saponification treatment is performed by immersing the laminate of the transparent support and the optically anisotropic layer in an alkaline aqueous solution.
The alkali is preferably an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide. The pH of the aqueous solution is preferably 10 or more. The alkali treatment is performed by immersing the surface of the transparent support on the polarizing film side in an aqueous solution of alkali. The immersion time is preferably 20 to 300 seconds. The treatment temperature is preferably 40 to 70 ° C. After completion of the immersion, the laminate is preferably washed with water.
[0067]
[Liquid Crystal Display]
The elliptically polarizing plate manufactured according to the present invention can be applied to liquid crystal cells of various display modes. As described above, TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), OCB (Optically Compensatory Bend), STN (Supper Twisted Nematic), VA (Vertically Aligned), and HAN (Hybrid Aligned) Various display modes such as Nematic) have been proposed. The elliptically polarizing plate of the present invention is effective in any display mode liquid crystal display device.
[0068]
【Example】
[Example 1]
(Preparation of transparent support)
The following components were put into a mixing tank and heated and stirred to prepare a cellulose acetate solution.
[0069]

[0070]
The following components were put into another mixing tank, and heated and stirred to prepare a retardation increasing agent solution.
[0071]

[0072]
A dope was prepared by adding 22 parts by weight of the retardation increasing agent solution to 474 parts by weight of the cellulose acetate solution and stirring sufficiently. The amount of the retardation increasing agent with respect to 100 parts by weight of cellulose acetate is 3 parts by weight.
The dope was cast from a casting port onto a drum cooled to 0 ° C. Stripped in the field with a solvent content of 70% by weight, fixed at both ends in the width direction of the film with a pin tenter, and stretched in the width direction (direction perpendicular to the machine direction) in the region where the solvent content was 3 to 5% by weight Was dried while maintaining an interval of 3%. After that, it is further dried by transporting between the rolls of the heat treatment apparatus, and in the region where the glass transition temperature exceeds 120 °, the stretching rate in the machine direction is substantially 0% (4% stretching in the machine direction when stripping. A cellulose acetate film having a thickness of 107 μm was prepared by adjusting the ratio of the stretching ratio in the width direction to the stretching ratio in the machine direction to be 0.75.
The elastic modulus of cellulose acetate film is 430 kg / mm in the machine direction (MD).², 360 kg / mm in the width direction (TD)²The MD / TD ratio was 1.19. When the retardation of the produced film was measured, the retardation (Rth) in the thickness direction was 80 nm, and the in-plane retardation (Re) was 10 nm. In addition, precipitation of the retardation increasing agent was not recognized at all in the processing after film production described later as well as immediately after production.
[0073]
(Formation of first undercoat layer)
The produced cellulose ester film was used as a transparent support.
On a transparent support, a coating solution having the following composition was 28 ml / m.²It was applied and dried to form a first undercoat layer.
[0074]

[0075]
(Formation of second undercoat layer)
On the first undercoat layer, a coating solution having the following composition is 7 ml / m.²It was applied and dried to form a second undercoat layer.
[0076]

[0077]
[Chemical 9]

[0078]
(Formation of back layer)
On the opposite surface of the transparent support, a coating solution having the following composition was applied at 25 ml / m.²It was applied and dried to form a back layer.
[0079]

[0080]
(Formation of alignment film)
On the second undercoat layer, an aqueous solution of long-chain alkyl-modified polyvinyl alcohol (MP-203, manufactured by Kuraray Co., Ltd.) is applied, dried with hot air at 60 ° C. for 90 seconds, and then subjected to rubbing treatment to form an alignment film. Formed.
[0081]
(Formation of optically anisotropic layer)
1.8 g of the following discotic liquid crystalline compound (1), 0.2 g of ethylene oxide-modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.), cellulose acetate butyrate (CAB531-1.0, Eastman Chemical Co., Ltd. (0.04 g), photopolymerization initiator (Irgacure 907, Nippon Ciba Geigy Co., Ltd.) 0.06 g, and sensitizer (Kayacure DETX, Nippon Kayaku Co., Ltd.) 0.02 g, methyl ethyl ketone A coating solution was prepared by dissolving in 8.43 g. The coating solution was applied onto the alignment film with a # 3 wire bar. In a state where this was affixed to a metal frame, it was heated in a thermostatic bath at 130 ° C. for 2 minutes to align the discotic liquid crystalline compound.
The laminate of the transparent support and the optically anisotropic layer was placed in a sealed container, and air was replaced with nitrogen gas until the oxygen concentration was 9% or less. Ultraviolet rays were irradiated for 1 minute at a temperature of 130 ° C. using a 120 W / cm high-pressure mercury lamp to polymerize the vinyl group of the discotic liquid crystalline compound, and the alignment state was fixed. Then, it stood to cool to room temperature.
[0082]
[Chemical Formula 10]

[0083]
The thickness of the optically anisotropic layer was 1.5 μm. When the retardation of the laminate of the optically anisotropic layer and the transparent support was measured along the rubbing direction of the alignment film, the average tilt angle of the optical axis was 15 °, and the retardation (Rth) in the thickness direction was 138 nm. The in-plane retardation (Re) was 23 nm.
[0084]
(Alkali treatment)
The laminated body of the transparent support and the optically anisotropic layer was immersed in a 1.5N sodium hydroxide aqueous solution at 55 ° C. for 2 minutes for alkali treatment. After washing with running water, it was dried.
When the in-plane retardation (Re) after alkali treatment was measured, it was 22 nm (-1 nm before treatment). When the elution amount of the discotic liquid crystalline molecules was examined, the eluted liquid crystalline molecules were 0% by weight of the whole. The eluted retardation increasing agent was 0.26% by weight of the whole.
[0085]
(Preparation of transparent protective film)
A cellulose acetate film (transparent protective film) was produced in the same manner as the production of the transparent support except that the retardation increasing agent was not added.
The transparent protective film was also subjected to alkali treatment in the same manner as the laminate of the transparent support and the optically anisotropic layer.
[0086]
(Production of elliptically polarizing plate)
Iodine was adsorbed on the stretched polyvinyl alcohol film to prepare a polarizing film. A laminated body of the optically anisotropic layer and the transparent support was attached to one side of the polarizing film using a polyvinyl alcohol-based adhesive so that the optically anisotropic layer was on the outside. On the opposite side, a transparent protective film was attached using a polyvinyl alcohol-based adhesive. The transmission axis of the polarizing film and the slow axis of the laminate of the optically anisotropic layer and the transparent support were arranged so as to be parallel. In this manner, an elliptically polarizing plate was produced.
[0087]
(Production of liquid crystal display device)
A polyimide alignment film was provided on a glass substrate on which an ITO transparent electrode was provided, and a rubbing treatment was performed. The two substrates were stacked with a 5 μm spacer so that the alignment films face each other. The orientation of the substrate was adjusted so that the rubbing directions of the alignment film were orthogonal. A rod-like liquid crystal molecule (ZL4792, manufactured by Merck & Co., Inc.) was injected into the gap between the substrates to form a liquid crystal layer. The Δn of the liquid crystal molecule was 0.0969.
An elliptically polarizing plate was attached to both sides of the TN liquid crystal cell produced as described above so that the optically anisotropic layer faced the substrate, thereby producing a liquid crystal display device. The slow axis of the laminate of the optically anisotropic layer and the transparent support and the rubbing direction of the liquid crystal cell were arranged so as to be orthogonal to each other.
A voltage is applied to the liquid crystal cell of the liquid crystal display device, and the contrast ratio is the transmittance ratio between the white display and the black display in the white display 2V and the black display 5V. The area where there was no viewing angle was measured. As a result, the vertical viewing angle was 70 ° and the horizontal viewing angle was 126 °. The front contrast was 122.
[0088]
[Comparative Example 1]
(Formation of optically anisotropic layer)
An optically anisotropic layer was formed in the same manner as in Example 1 except that the polymerization reaction (ultraviolet irradiation) of the discotic liquid crystalline compound was performed in air.
The thickness of the optically anisotropic layer was 1.0 μm. When the retardation of the laminate of the optically anisotropic layer and the transparent support was measured along the rubbing direction of the alignment film, the average tilt angle of the optical axis was 15 °, and the retardation (Rth) in the thickness direction was 138 nm. The in-plane retardation (Re) was 23 nm.
[0089]
(Alkali treatment)
The laminated body of the transparent support and the optically anisotropic layer was immersed in a 1.5N sodium hydroxide aqueous solution at 55 ° C. for 2 minutes for alkali treatment. After washing with running water, it was dried.
When the in-plane retardation (Re) after alkali treatment was measured, it was 20 nm (-3 nm before treatment). When the elution amount of the discotic liquid crystalline molecules was examined, the eluted liquid crystalline molecules were 0.033% by weight of the whole. The eluted retardation increasing agent was 0.68% by weight of the total.
[0090]
[Example 2]
(Formation of alignment film)
The following modified polyimide (1) was dissolved in a mixed solvent of methanol and acetone (volume ratio = 50/50) to prepare a 5 wt% solution. This solution was applied to a thickness of 1 μm on the transparent support prepared in Example 1 using a bar coater. The coating layer was dried with hot air at 60 ° C. for 2 minutes, and the surface was rubbed to form an alignment film.
[0091]
Embedded image

[0092]
(Formation of optically anisotropic layer)
On the alignment film, a coating solution having the following composition was applied by an extrusion method.
[0093]

[0094]
Embedded image

[0095]
Embedded image

[0096]
The coating layer was heated at 130 ° C. for 2 minutes to align the discotic liquid crystalline compound vertically.
The laminate of the transparent support and the optically anisotropic layer was placed in a sealed container, and air was replaced with nitrogen gas until the oxygen concentration was 9% or less. Ultraviolet rays were irradiated for 4 seconds at a temperature of 130 ° C. to polymerize the discotic liquid crystalline compound, and the vertical alignment state was fixed. In this way, an optically anisotropic layer in which the discotic liquid crystalline compound was aligned vertically and twisted was formed.
When the retardation of the laminate of the optically anisotropic layer and the transparent support was measured, the in-plane retardation (Re) was 440 nm.
[0097]
(Alkali treatment)
The laminated body of the transparent support and the optically anisotropic layer was immersed in a 1.5N sodium hydroxide aqueous solution at 55 ° C. for 2 minutes for alkali treatment. After washing with running water, it was dried.
When the in-plane retardation (Re) after alkali treatment was measured, it was 439 nm (-1 nm before treatment). When the elution amount of the discotic liquid crystalline molecules was examined, the eluted liquid crystalline molecules were 0% by weight of the whole. The eluted retardation increasing agent was 0.26% by weight of the whole.
[0098]
(Production of elliptically polarizing plate)
Iodine was adsorbed on the stretched polyvinyl alcohol film to prepare a polarizing film. A laminated body of the optically anisotropic layer and the transparent support was attached to one side of the polarizing film using a polyvinyl alcohol-based adhesive so that the optically anisotropic layer was on the outside. On the opposite side, the transparent protective film produced in Example 1 was attached using a polyvinyl alcohol-based adhesive. In this manner, an elliptically polarizing plate was produced.
[0099]
(Production of liquid crystal display device)
An STN type liquid crystal display device was produced using the produced elliptically polarizing plate. On the surface where the liquid crystal cell and the optically anisotropic layer are in contact, the alignment direction of the rod-like liquid crystalline molecules of the liquid crystal cell and the alignment direction of the discotic liquid crystalline molecules of the optically anisotropic layer were matched. The angle between the absorption axis of the exit side polarizing plate and the orientation direction of the rod-like liquid crystalline molecules on the exit side of the liquid crystal cell was adjusted to 45 °. The absorption axis of the incident side polarizing plate and the absorption axis of the outgoing side polarizing plate were arranged so as to be orthogonal to each other.
[0100]
When a voltage was applied to the obtained STN type liquid crystal display device, a normally black mode was obtained. When visual characteristics were measured, an angle range with a contrast ratio of 5 or more was obtained at 120 ° or more on the left and right, and 150 ° or more on the top and bottom.
[0101]
[Comparative Example 2]
(Formation of optically anisotropic layer)
An optically anisotropic layer was formed in the same manner as in Example 2 except that the polymerization reaction (ultraviolet irradiation) of the discotic liquid crystalline compound was performed in air.
When the retardation of the laminate of the optically anisotropic layer and the transparent support was measured, the in-plane retardation (Re) was 440 nm.
[0102]
(Alkali treatment)
The laminated body of the transparent support and the optically anisotropic layer was immersed in a 1.5N sodium hydroxide aqueous solution at 55 ° C. for 2 minutes for alkali treatment. After washing with running water, it was dried.
When the in-plane retardation (Re) after alkali treatment was measured, it was 436 nm (-4 nm before treatment). When the elution amount of the discotic liquid crystalline molecules was examined, the amount of the eluted liquid crystalline molecules was 0.035% by weight. The eluted retardation increasing agent was 0.70% by weight of the whole.
[0103]
[Example 3]
(Preparation of transparent support)
A triacetylcellulose film having a thickness of 100 μm was prepared in the same manner as in Example 1 except that the amount of the retardation increasing agent was changed to 18% by weight of the transparent support. The triacetylcellulose film was uniaxially stretched at a stretch ratio of 3% to prepare a transparent support.
The in-plane retardation (Re) of the transparent support measured at a wavelength of 546 nm was 30 nm, and the Rth retardation value was 280 nm.
[0104]
(Formation of alignment film)
A first undercoat layer, a second undercoat layer and a back layer were formed on the transparent support in the same manner as in Example 1.
On the second undercoat layer, a coating solution having the following composition was 28 ml / m with a # 16 wire bar coater.² Applied. Drying was performed with warm air of 60 ° C. for 60 seconds, and further with warm air of 90 ° C. for 150 seconds.
Next, the formed film was rubbed in the direction of 45 ° with the slow axis of the transparent support (measured at a wavelength of 632.8 nm).
[0105]

[0106]
Embedded image

[0107]
(Formation of optically anisotropic layer)
On the alignment film, 41.01 g of the discotic liquid crystalline compound (1) used in Example 1, 4.06 g of ethylene oxide-modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.), cellulose acetate 0.90 g of butyrate (CAB551-0.2, manufactured by Eastman Chemical), 0.23 g of cellulose acetate butyrate (CAB531-1, manufactured by Eastman Chemical), photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy) ) A coating solution prepared by dissolving 1.35 g and 0.45 g of a sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) in 102 g of methyl ethyl ketone was applied with a # 3 wire bar. This was attached to a metal frame and heated in a thermostatic chamber at 130 ° C. for 2 minutes to align the discotic liquid crystalline compound.
The laminate of the transparent support and the optically anisotropic layer was placed in a sealed container, and air was replaced with nitrogen gas until the oxygen concentration was 9% or less. Next, using a 120 W / cm high pressure mercury lamp at 130 ° C., UV irradiation was performed for 1 minute to polymerize the discotic liquid crystalline compound. Then, it stood to cool to room temperature. In this way, an optically anisotropic layer was formed.
The in-plane retardation (Re) of the optically anisotropic layer measured at a wavelength of 546 nm was 38 nm. The angle (tilt angle) between the disc surface of the discotic liquid crystalline compound and the transparent support surface was 40 ° on average.
[0108]
(Alkali treatment)
The laminated body of the transparent support and the optically anisotropic layer was immersed in a 1.5N sodium hydroxide aqueous solution at 55 ° C. for 2 minutes for alkali treatment. After washing with running water, it was dried.
When in-plane retardation (Re) after alkali treatment was measured, it was 37 nm (-1 nm before treatment). When the elution amount of the discotic liquid crystalline molecules was examined, the eluted liquid crystalline molecules were 0% by weight of the whole. The eluted retardation increasing agent was 0.26% by weight of the whole.
[0109]
(Production of elliptically polarizing plate)
A polarizing film was bonded to the transparent support surface of the laminate of the optically anisotropic layer and the laminated body with an adhesive to produce an elliptically polarizing plate. The transmission axis of the polarizing film was orthogonal to the slow axis of the transparent support.
[0110]
(Preparation of bend alignment liquid crystal cell)
A polyimide film was provided as an alignment film on a glass substrate with an ITO electrode, and the alignment film was rubbed. The obtained two glass substrates were faced to each other so that the rubbing directions were parallel to each other, and the cell gap was set to 6 μm. A bend-aligned liquid crystal cell was prepared by injecting a liquid crystal compound (ZLI1132, manufactured by Merck & Co., Inc.) having a Δn of 0.1396 into the cell gap.
A voltage of 5 or 5.5 V was applied to the bend alignment liquid crystal cell with a 55 Hz rectangular wave, and Re retardation values were measured at wavelengths of 436 nm, 546 nm, and 611.5 nm.
[0111]
(Production of liquid crystal display device)
Two produced elliptical polarizing plates were attached so as to sandwich the produced bend alignment cell. The optically anisotropic layer of the elliptically polarizing plate was arranged so as to face the cell substrate, and the rubbing direction of the liquid crystal cell and the rubbing direction of the optically anisotropic layer facing it were antiparallel.
[0112]
[Comparative Example 3]
(Formation of optically anisotropic layer)
An optically anisotropic layer was formed in the same manner as in Example 3 except that the polymerization reaction (ultraviolet irradiation) of the discotic liquid crystalline compound was performed in air.
When the retardation of the laminate of the optically anisotropic layer and the transparent support was measured, the in-plane retardation (Re) was 38 nm.
[0113]
(Alkali treatment)
The laminated body of the transparent support and the optically anisotropic layer was immersed in a 1.5N sodium hydroxide aqueous solution at 55 ° C. for 2 minutes for alkali treatment. After washing with running water, it was dried.
When the in-plane retardation (Re) after alkali treatment was measured, it was 35 nm (before treatment −3 nm). When the elution amount of the discotic liquid crystal molecules was examined, the eluted liquid crystal molecules were 0.033% by weight of the whole. The eluted retardation increasing agent was 0.68% by weight of the total.
[0114]
[Example 4]
(Formation of alignment film)
On the second undercoat layer of the transparent support produced in Example 1, the modified polyvinyl alcohol used in Example 3 was applied to a thickness of 0.5 μm and dried to form an alignment film.
[0115]
(Formation of optically anisotropic layer)
On the alignment film, a coating solution having the following composition was applied using a # 4 bar coater.
[0116]

[0117]
The coating layer was heated at 130 ° C. for 1 minute.
The laminate of the transparent support and the optically anisotropic layer was placed in a sealed container, and air was replaced with nitrogen gas until the oxygen concentration was 9% or less. Next, 500 mJ / cm²The ultraviolet light was irradiated to polymerize the discotic liquid crystalline compound, and the alignment state was fixed. Thus, an optically anisotropic layer was formed.
The in-plane retardation (Re) of the optically anisotropic layer was 10 nm.
[0118]
(Alkali treatment)
The laminated body of the transparent support and the optically anisotropic layer was immersed in a 1.5N sodium hydroxide aqueous solution at 55 ° C. for 2 minutes for alkali treatment. After washing with running water, it was dried.
When the in-plane retardation (Re) after alkali treatment was measured, it was 9 nm (-1 nm before treatment). When the elution amount of the discotic liquid crystalline molecules was examined, the eluted liquid crystalline molecules were 0% by weight of the whole. The eluted retardation increasing agent was 0.26% by weight of the whole.
[0119]
(Production of elliptically polarizing plate)
A polarizing film was bonded to the transparent support surface of the laminate of the optically anisotropic layer and the laminated body with an adhesive to produce an elliptically polarizing plate.
[0120]
(Production of liquid crystal display device)
The polarizing plate on the back side and the front side of a liquid crystal monitor (VL-1520T, manufactured by Fujitsu Ltd.) using a vertical alignment type liquid crystal cell is peeled off. 5618HCS (manufactured by Sanritz Co., Ltd.) was pasted on the back side to produce a liquid crystal display device.
[0121]
[Comparative Example 4]
(Formation of optically anisotropic layer)
An optically anisotropic layer was formed in the same manner as in Example 4 except that the polymerization reaction (ultraviolet irradiation) of the discotic liquid crystalline compound was performed in air.
When the retardation of the laminate of the optically anisotropic layer and the transparent support was measured, the in-plane retardation (Re) was 10 nm.
[0122]
(Alkali treatment)
The laminated body of the transparent support and the optically anisotropic layer was immersed in a 1.5N sodium hydroxide aqueous solution at 55 ° C. for 2 minutes for alkali treatment. After washing with running water, it was dried.
When the in-plane retardation (Re) after alkali treatment was measured, it was 7 nm (-3 nm before treatment). When the elution amount of the discotic liquid crystal molecules was examined, the eluted liquid crystal molecules were 0.033% by weight of the whole. The eluted retardation increasing agent was 0.65% by weight of the whole.
[0123]
[Example 5]
(Formation of alignment film)
On the second undercoat layer of the transparent support produced in Example 1, the modified polyvinyl alcohol used in Example 1 was applied to a thickness of 0.5 μm and dried to form an alignment film. The surface of the alignment film was rubbed.
[0124]
(Formation of optically anisotropic layer)
1.8 g of the discotic liquid crystalline compound (1) used in Example 1, 0.2 g of ethylene oxide-modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.), cellulose acetate butyrate (CAB551- 0.2, manufactured by Eastman Chemical Co., Ltd.) 0.04 g, cellulose acetate butyrate (CAB531-1.0, manufactured by Eastman Chemical Co., Ltd.) 0.01 g, photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy Japan, Inc.) 0.06 g and 0.02 g of a sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) were dissolved in 3.3 g of methyl ethyl ketone to prepare a coating solution. The coating solution was applied onto the alignment film with a # 10 wire bar. This was heated in a constant temperature bath at 140 ° C. for 3 minutes to align the discotic liquid crystalline compound.
The laminate of the transparent support and the optically anisotropic layer was placed in a sealed container, and air was replaced with nitrogen gas until the oxygen concentration was 9% or less. Ultraviolet rays were irradiated for 1 minute using a 120 W / cm high-pressure mercury lamp at a temperature of 140 ° C. to polymerize the vinyl group of the discotic liquid crystalline compound, and the alignment state was fixed. Then, it stood to cool to room temperature.
When the retardation of the laminate of the optically anisotropic layer and the transparent support was measured, the in-plane retardation (Re) was 165 nm.
[0125]
(Alkali treatment)
The laminated body of the transparent support and the optically anisotropic layer was immersed in a 1.5N sodium hydroxide aqueous solution at 55 ° C. for 2 minutes for alkali treatment. After washing with running water, it was dried.
When the in-plane retardation (Re) after alkali treatment was measured, it was 9 nm (-1 nm before treatment). When the elution amount of the discotic liquid crystalline molecules was examined, the eluted liquid crystalline molecules were 0% by weight of the whole. The eluted retardation increasing agent was 0.26% by weight of the whole.
[0126]
(Production of elliptically polarizing plate)
A polarizing film was bonded to the transparent support surface of the laminate of the optically anisotropic layer and the laminated body with an adhesive to produce an elliptically polarizing plate.
[0127]
(Production of liquid crystal display device)
A polyimide alignment film was provided on a glass substrate on which an ITO transparent electrode was provided, and a rubbing treatment was performed. Another glass substrate provided with an ITO transparent electrode was prepared, and an SiO vapor deposition film was provided. The two glass substrates were faced to each other, and the cell gap was set to 4 μm. A rod-like liquid crystal molecule (ZLI1132, manufactured by Merck & Co., Inc.) was injected into the cell gap to form a liquid crystal layer. The Δn of the liquid crystalline molecule was 0.1396.
On one side of the HAN type liquid crystal cell produced as described above, one elliptically polarizing plate was disposed so that the rubbing direction of the liquid crystal cell and the rubbing direction of the optically anisotropic layer were antiparallel. The transmission axis of the polarizing film and the rubbing direction of the liquid crystal cell were arranged at an angle of 45 °. A mirror was provided as a reflector on the surface opposite to the elliptically polarizing plate.
A light source was placed in a direction inclined 20 degrees from the normal direction of the display surface of the produced reflective liquid crystal display device, and light was irradiated. A voltage was applied to the liquid crystal cell with a rectangular wave of 55 Hz. In a normally white mode with a white display of 2 V and a black display of 5 V, a region having a contrast ratio of 10 in the vertical and horizontal directions was measured as a viewing angle. As a result, the upper viewing angle was 49 °, the lower viewing angle KH was 60 °, and the left and right viewing angles were 105 °.
[0128]
[Comparative Example 5]
(Formation of optically anisotropic layer)
An optically anisotropic layer was formed in the same manner as in Example 4 except that the polymerization reaction (ultraviolet irradiation) of the discotic liquid crystalline compound was performed in air.
When the retardation of the laminate of the optically anisotropic layer and the transparent support was measured, the in-plane retardation (Re) was 165 nm.
[0129]
(Alkali treatment)
The laminated body of the transparent support and the optically anisotropic layer was immersed in a 1.5N sodium hydroxide aqueous solution at 55 ° C. for 2 minutes for alkali treatment. After washing with running water, it was dried.
When the in-plane retardation (Re) after alkali treatment was measured, it was 7 nm (-3 nm before treatment). When the elution amount of the discotic liquid crystal molecules was examined, the eluted liquid crystal molecules were 0.033% by weight of the whole. The eluted retardation increasing agent was 0.68% by weight of the total.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a basic configuration of an elliptically polarizing plate.
FIG. 2 is a schematic cross-sectional view showing a process for forming an optically anisotropic layer in the production of an elliptically polarizing plate.
FIG. 3 is a schematic cross-sectional view showing a saponification process in manufacturing an elliptically polarizing plate.
FIG. 4 is a schematic diagram showing a basic configuration of a transmissive liquid crystal display device.
FIG. 5 is a schematic diagram showing a basic configuration of a reflective liquid crystal display device.
[Explanation of symbols]
Light
N₂  Nitrogen gas
NaOH aqueous solution of sodium hydroxide
BL backlight
RP reflector
0 Alignment film
1, 1a, 1b, 1c Transparent protective film
2, 2a, 2b Polarizing film
3, 3a, 3b transparent support
31 Saponification surface of transparent support
4, 4a, 4b Optically anisotropic layer
41 Saponification surface of optically anisotropic layer
5a Lower substrate of liquid crystal cell
5b Upper substrate of liquid crystal cell
6 Liquid crystal layer consisting of rod-like liquid crystalline molecules

Claims (4)

Opticality is achieved by aligning polymerizable liquid crystalline molecules on a transparent support made of cellulose ester film and polymerizing polymerizable liquid crystalline molecules in a state where contact between oxygen in the air and the optically anisotropic layer is suppressed. A step of providing an anisotropic layer, a step of alkali treatment by immersing a transparent support provided with an optically anisotropic layer in an aqueous alkali solution having a pH of 10 or higher at 40 to 70 ° C. for 20 to 300 seconds; A method for producing an elliptically polarizing plate comprising a step of laminating a transparent support, a transparent protective film and a polarizing film provided with an anisotropic layer in the order of a transparent protective film, a polarizing film, a transparent support and an optically anisotropic layer.   The production method according to claim 1, wherein the cellulose ester film comprises a retardation increasing agent having a molecular structure having at least two aromatic rings and having no steric hindrance to the conformation of the two aromatic rings. A step of providing an optically anisotropic layer by orienting polymerizable liquid crystalline molecules on a transparent support made of cellulose ester film and further reducing the amount of oxygen to 13% or less to polymerize the polymerizable liquid crystalline molecules. A step of alkali treatment by immersing the transparent support provided with the optically anisotropic layer in an aqueous alkali solution having a pH of 10 or more at 40 to 70 ° C. for 20 to 300 seconds, and a transparent provided with the optically anisotropic layer A method for producing an elliptically polarizing plate comprising a step of laminating a support, a transparent protective film and a polarizing film in the order of a transparent protective film, a polarizing film, a transparent support and an optically anisotropic layer . The production method according to claim 3, wherein the cellulose ester film contains a retardation increasing agent having a molecular structure having at least two aromatic rings and having no steric hindrance to the conformation of the two aromatic rings .

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