JP4260331B2 - Optical compensation sheet and polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical compensation sheet and a polarizing plate in which the axis of the slow phase of the optical compensation sheet and the transmission axis of the polarizing film are easily arranged to be substantially parallel to each other. SOLUTION: In the optical compensation sheet in a rolled state having a transparent supporting body and an optical anisotropic layer consisting of rod- like liquid crystal molecules, the average direction of the lines formed by projecting the direction of the major axis of the rod-like liquid crystal molecules onto the plane of the transparent supporting body is aligned substantially perpendicular to the longitudinal direction of the optical compensation sheet.

Description

【００１６】
重合性基（Ｑ）は、不飽和重合性基（Ｑ１〜Ｑ７）、エポキシ基（Ｑ８）またはアジリジニル基（Ｑ９）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。
棒状液晶性分子は、短軸方向に対してほぼ対称となる分子構造を有することが好ましい。そのためには、棒状分子構造の両端に重合性基を有することが好ましい。
以下に、棒状液晶性分子の例を示す。
【００１７】
【化２】

【００１８】
【化３】

【００１９】
【化４】

【００２０】
【化５】

【００２１】
【化６】

【００２２】
【化７】

【００２３】
【化８】

【００２４】
【化９】

【００２５】
【化１０】

【００２６】
【化１１】

【００２７】
【化１２】

【００２８】
【化１３】

【００２９】
【化１４】

【００３０】
光学異方性層は、棒状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）を含む液晶組成物（塗布液）を、配向膜の上に塗布することで形成する。
液晶組成物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。
液晶組成物の塗布は、公知の方法（例、ワイヤーバーコーティング法、押し出しコーティング法、ダイレクトグラビアコーティング法、リバースグラビアコーティング法、ダイコーティング法）により実施できる。
【００３１】
棒状液晶性分子の重合反応には、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質量％であることが好ましく、０．５乃至５質量％であることがさらに好ましい。
棒状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。
光学異方性層の厚さは、０．１乃至２０μｍであることが好ましく、０．２乃至１５μｍであることがさらに好ましく、０．３乃至１０μｍであることが最も好ましい。
【００３２】
［透明支持体］
光学補償シートの透明支持体として、ガラス板またはポリマーフイルム、好ましくはポリマーフイルムが用いられる。支持体が透明であるとは、光透過率が８０％以上であることを意味する。
透明支持体として、一般には、光学等方性のポリマーフイルムが用いられている。光学等方性とは、具体的には、面内レターデーション（Ｒｅ）が１０ｎｍ未満であることが好ましく、５ｎｍ未満であることがさらに好ましい。また、光学等方性透明支持体では、厚み方向のレターデーション（Ｒth）も、１０ｎｍ未満であることが好ましく、５ｎｍ未満であることがさらに好ましい。透明支持体の面内レターデーション（Ｒｅ）と厚み方向のレターデーション（Ｒth）は、それぞれ下記式で定義される。
Ｒｅ＝（ｎｘ−ｎｙ）×ｄ
Ｒth＝［｛（ｎｘ＋ｎｙ）／２｝−ｎｚ］×ｄ
式中、ｎｘおよびｎｙは、透明支持体の面内屈折率であり、ｎｚは透明支持体の厚み方向の屈折率であり、そしてｄは透明支持体の厚さである。
【００３３】
液晶表示モードの種類によっては、透明支持体として光学異方性のポリマーフイルムが用いられる場合もある。すなわち、光学異方性層の光学異方性に透明支持体の光学異方性も加えて、液晶セルの光学異方性に対応する（光学的に補償する）場合もある。そのような場合、透明支持体は、光学的一軸性または光学的二軸性を有することが好ましい。光学的一軸性支持体の場合、光学的に正（光軸方向の屈折率が光軸に垂直な方向の屈折率よりも大）であっても負（光軸方向の屈折率が光軸に垂直な方向の屈折率よりも小）であってもよい。光学的二軸性支持体の場合、前記式の屈折率ｎｘ、ｎｙおよびｎｚは、全て異なる値（ｎｘ≠ｎｙ≠ｎｚ）になる。
光学異方性透明支持体の面内レターデーション（Ｒｅ）は、０乃至３００ｎｍであることが好ましく、０乃至２００ｎｍであることがさらに好ましく、０乃至１００ｎｍであることが最も好ましい。光学異方性透明支持体の厚み方向のレターデーション（Ｒth）は、１０乃至１０００ｎｍであることが好ましく、５０乃至４００ｎｍであることがより好ましく、１００乃至３００ｎｍであることがさらに好ましい。
【００３４】
透明支持体を形成する材料は、光学等方性支持体とするか、光学異方性支持体とするかに応じて決定する。光学等方性支持体の場合は、一般にガラスまたはセルロースエステルが用いられる。光学異方性支持体の場合は、一般に合成ポリマー（例、ポリカーボネート、ポリスルホン、ポリエーテルスルホン、ポリアクリレート、ポリメタクリレート、ノルボルネン樹脂）が用いられる。ただし、欧州特許０９１１６５６Ａ２号明細書に記載されている（１）レターデーション上昇剤（複屈折率上昇剤）の使用、（２）セルロースアセテートの酢化度の低下、あるいは（３）冷却溶解法によるフイルムの製造により、光学異方性の（レターデーションが高い）セルロースエステルフイルムを製造することもできる。
ポリマーフイルムからなる透明支持体は、ソルベントキャスト法により形成することが好ましい。
【００３５】
光学異方性透明支持体を得るためには、ポリマーフイルムに延伸処理を実施することが好ましい。
光学的一軸性支持体を製造する場合は、通常の一軸延伸処理または二軸延伸処理を実施すればよい。
光学的二軸性支持体を製造する場合は、アンバランス二軸延伸処理を実施することが好ましい。アンバランス二軸延伸では、ポリマーフイルムをある方向に一定倍率（例えば３乃至１００％、好ましくは５乃至３０％）延伸し、それと垂直な方向にそれ以上の倍率（例えば６乃至２００％、好ましくは１０乃至９０％）延伸する。二方向の延伸処理は、同時に実施してもよい。
延伸方向（アンバランス二軸延伸では延伸倍率の高い方向）と延伸後のフイルムの面内の遅相軸とは、実質的に同じ方向になることが好ましい。延伸方向と遅相軸との角度は、１０゜未満であることが好ましく、５゜未満であることがさらに好ましく、３゜未満であることが最も好ましい。
なお、光学的一軸性または光学的二軸性を有する透明支持体を用いる場合、光学異方性層の棒状液晶性分子の長軸方向を透明支持体面に投影して得られる線の平均方向が、透明支持体の面内の遅相軸と、実質的に平行または直交しているように配置することが好ましい。
【００３６】
透明支持体の厚さは、１０乃至５００μｍであることが好ましく、５０乃至２００μｍであることがさらに好ましい。
透明支持体とその上に設けられる層（密着層、配向膜あるいは光学異方性層）との密着を改善するため、透明支持体に表面処理（例、グロー放電処理、コロナ放電処理、紫外線（ＵＶ）処理、火炎処理）を実施してもよい。
透明支持体に紫外線吸収剤を添加してもよい。
透明支持体の上に、密着層（下塗り層）を設けてもよい。密着層については、特開平７−３３３４３３号公報に記載がある。密着層の厚さは、０．１乃至２μｍであることが好ましく、０．２乃至１μｍであることがさらに好ましい。
【００３７】
［配向膜］
配向膜は、有機化合物（好ましくはポリマー）のラビング処理、無機化合物の斜方蒸着、マイクログルーブを有する層の形成、あるいはラングミュア・ブロジェット法（ＬＢ膜）による有機化合物（例、ω−トリコサン酸、ジオクタデシルメチルアンモニウムクロライド、ステアリル酸メチル）の累積のような手段で、設けることができる。さらに、電場の付与、磁場の付与あるいは光照射により、配向機能が生じる配向膜も知られている。
ポリマーのラビング処理により形成する配向膜または光照射により配向機能が生じる配向膜を用いることが特に好ましい。
ポリマーのラビング処理により形成する配向膜としては、ラビング方向に垂直な方向に棒状液晶性分子の長軸方向を配向させる機能を有する配向膜を用いることが好ましい。そのような機能を有する配向膜を用いると、光学補償シートの長手方向と実質的に平行にラビング処理を実施する（最も実施が容易な方向にラビング処理を実施する）ことで、棒状液晶性分子の長軸方向を透明支持体面に投影して得られる線の平均方向（遅相軸）と光学補償シートの長手方向とを実質的に直交させることができる。上記の機能を有する配向膜については、特開平１１−２１２０９７号公報に記載がある。
ポリマーとしては、ポリイミドが好ましい。ポリイミドは、ジアミンとテトラカルボン酸との縮合反応により得られる。ジアミンとして、４，４−（９−フルオレニリデン）ジアニリンを用いることが特に好ましい。
ラビング処理は、ポリマー層の表面を、紙や布で一定方向に、数回こすることにより実施する。
【００３８】
光照射により配向機能が生じる配向膜は、フォトクロミック化合物または感光性ポリマーを用いて形成する。光としては、直線偏光を照射することが好ましい。光照射により配向機能が生じる配向膜は、光の照射方向または直線偏光の偏光方向によって、棒状液晶性分子の配向方向を制御することができる。光照射により配向機能が生じる配向膜を用いて配向方向を制御することで、棒状液晶性分子の長軸方向を透明支持体面に投影して得られる線の平均方向（遅相軸）と光学補償シートの長手方向とを実質的に直交させることができる。
フォトクロミック化合物は、光の作用で化学構造に変化が生じ、それにより光に対する挙動（例えば色調）も変化する化合物である。一般に、それらの変化は可逆的である。
液晶セルについて従来提案されたフォトクロミック化合物には、アゾベンゼン化合物（K. Ichimura et al., Langmuir, vol. 4, page 1214 (1988)；K. Aoki et al., Langmuir, vol. 8, page 1007 (1992)；Y. Suzuki et al., Langmuir, vol. 8, page 2601 (1992)；K. Ichimura et al., Appl. Phys. Lett., vol. 63, No. 4, page 449 (1993)；N. Ishizuki, Langmuir, vol. 9, page 3298 (1993) ；N. Ishizuki, Langmuir, vol. 9, page 857 (1993)）、ヒドラゾノ−β−ケトエステル化合物（S. Yamamura et al., Liquid Crystals, vol. 13, No. 2, page 189 (1993)）、スチルベン化合物（市村國宏他、高分子論文集、第４７巻、１０号、７７１頁(1990)）およびスピロピラン化合物（K. Ichimura et al., Chemistry Letters, page 1063 (1992) ；K. Ichimura et al., Thin Solid Films, vol. 235, page 101 (1993) ）が含まれる。
【００３９】
Ｃ＝Ｃ、Ｃ＝ＮまたはＮ＝Ｎからなる二重結合構造を含むフォトクロミック化合物が、特に好ましい。二重結合構造を有するフォトクロミック化合物は、下記（１）および（２）の必須要素と、下記（３）〜（５）の任意要素からなる。
（１）Ｃ＝Ｃ、Ｃ＝ＮまたはＮ＝Ｎからなる二重結合構造
（２）上記（１）の結合の両側に（直結しなくてもよく）存在する環状構造
（３）任意の（１）と（２）との間の連結基
（４）任意の（１）の炭素原子の置換基
（５）任意の（２）の環状構造の置換基
上記（１）の二重結合構造は、シス型よりもトランス型が好ましい。二重結合構造は、分子内に二つ以上存在していてもよい。複数の二重結合構造は、共役の関係にあることが好ましい。
上記（２）の環状構造の例には、ベンゼン環、ナフタレン環および含窒素複素環（例、ピリジニウム環、ベンゾピリジニウム環）が含まれる。含窒素複素環の場合、環を構成する（窒素原子ではなく）炭素原子が（１）の二重結合構造の炭素原子または窒素原子と結合することが好ましい。ベンゼン環が特に好ましい。
【００４０】
上記（３）の連結基の例には、−ＮＨ−および−ＣＯ−が含まれる。ただし、（３）の連結基がなく、（１）と（２）とが直結していることが好ましい。
上記（４）の置換基の例には、アリール基（例、フェニル）およびシアノが含まれる。ただし、（４）の置換基がなく、二重結合構造に含まれる炭素原子が、（２）との結合以外は無置換（−ＣＨ＝ＣＨ−または−ＣＨ＝Ｎ−）であることが好ましい。
上記（５）の置換基の例には、アルコキシ基（例、メトキシ、ヘキシルオキシ）、シアノ、アルキル基（例、ブチル、ヘキシル）およびアルキルアミノ基（例、ジメチルアミノ）を挙げることができる。（２）の環状構造がベンゼン環の場合、パラ位に置換基が結合することが好ましい。なお、後述するように、フォトクロミック化合物をポリマーに化学的結合させて使用する場合は、ポリマーに化学的結合させるための官能基を、（５）の置換基としてフォトクロミック化合物に導入する。
【００４１】
配向膜の形成において、フォトクロミック化合物は、何らかの手段を用いて支持体表面に対して固定して使用する必要がある。フォトクロミック化合物の固定手段としては、（ａ）ポリマーとフォトクロミック化合物の混合物塗布による固定、（ｂ）フォトクロミック化合物のポリマーへの化学的結合、（ｃ）フォトクロミック化合物の支持体表面への吸着および（ｄ）フォトクロミック化合物の支持体表面への化学的結合がある。
液晶セルでは、（ｃ）または（ｄ）の手段を用いて、液晶セルの基板である石英ガラス表面に、フォトクロミック化合物を吸着または結合させる手段が普通に用いられていた。しかし、光学補償シートでは、液晶表示装置の軽量化のため、ガラス板よりもプラスチックフイルムを支持体として用いることが好ましい。そのため、光学補償シートでは、（ａ）または（ｂ）の手段を用いることが好ましい。フォトクロミック化合物を安定に固定するため、（ｂ）の手段を用いることが特に好ましい。
【００４２】
（ａ）または（ｂ）の手段に使用するポリマーは、親水性ポリマー（例、ゼラチン、ポリビニルアルコール）であることが好ましい。ポリビニルアルコールが特に好ましく用いられる。
（ｂ）の手段における、フォトクロミック化合物とポリマーとの反応は、ポリマーの種類（特に官能基の種類）に応じて決定する。ポリビニルアルコールのような水酸基を有するポリマーの場合は、酸ハライドと水酸基との反応を利用して、フォトクロミック化合物をポリマーと結合させることができる。具体的には、ハロゲン化アシル基（−ＣＯＸ、Ｘはハロゲン）を、フォトクロミック化合物に置換基として導入し、ハロゲン化アシル基とポリマーの水酸基との反応（Ｐｈ−ＣＯＸ＋ＨＯ−Ｐｌ→Ｐｈ−ＣＯ−Ｏ−Ｐｌ＋ＨＸ、Ｐｈはフォトクロミック化合物、Ｐｌはポリマーの主鎖）により化学的に結合させる。
【００４３】
感光性ポリマーは、光異性化ポリマー、光二量化ポリマーおよび光分解ポリマーに分類できる。光異性化ポリマーとしては、上記のようにフォトクロミック化合物を結合させたポリマーが代表的（実質的には同義）である。光二量化ポリマーの例には、ポリビニルシンナメートが含まれる。光分解ポリマーの例には、ポリイミドが含まれる。光分解型ポリイミドについては、特開平５−３４６９９号、同６−２８９３９９号、同８−１２２７９２号の各公報および第２２回液晶討論会講演予稿集、１６７２頁Ａ１７(1996)に記載がある。
フォトクロミック化合物または感光性ポリマーを含む膜は、適当な溶媒を用いた溶液または分散液の塗布により、透明支持体上に形成することができる。なお、配向膜の構成成分は、液晶としての性質を示さないことが好ましい。
以上のようにフォトクロミック化合物または感光性ポリマーを含む膜を形成してから、光照射により膜に配向機能を付与する。照射する光は、直線偏光であることが特に好ましい。露光量は、１００乃至６０００ｍＪ／ｃｍ² であることが好ましく、３００乃至５０００ｍＪ／ｃｍ² であることがさらに好ましい。短時間で膜に配向機能を付与するためには、加熱しながら光を照射することが好ましい。加熱温度は、４０乃至２５０℃であることが好ましい。
【００４４】
配向膜の厚さは、０．０１乃至５μｍであることが好ましく、０．０５乃至１μｍであることがさらに好ましい。
なお、配向膜を用いて、光学異方性層の棒状液晶性分子を配向させてから、光学異方性層を透明支持体上に転写してもよい。配向状態で固定された棒状液晶性分子は、配向膜がなくても配向状態を維持することができる。
【００４５】
［偏光膜］
偏光膜には、ヨウ素系偏光膜、二色性染料を用いる染料系偏光膜やポリエン系偏光膜がある。ヨウ素系偏光膜および染料系偏光膜は、一般にポリビニルアルコール系フイルムを用いて製造する。偏光膜の透過軸は、フイルムの延伸方向に垂直な方向に相当する。
偏光膜の透過軸は、棒状液晶性分子の長軸方向を透明支持体面に投影して得られる線の平均方向（遅相軸）と、実質的に平行になるように配置する。
【００４６】
［透明保護膜］
透明保護膜としては、透明なポリマーフイルムが用いられる。保護膜が透明であるとは、光透過率が８０％以上であることを意味する。
透明保護膜としては、一般にセルロースエステルフイルム、好ましくはトリアセチルセルロースフイルムが用いられる。セルロースエステルフイルムは、ソルベントキャスト法により形成することが好ましい。
透明保護膜の厚さは、２０乃至５００μｍであることが好ましく、５０乃至２００μｍであることがさらに好ましい。
【００４７】
［液晶表示装置］
本発明は、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、液晶性分子を用いた光学補償シートは、ＴＮ（Twisted Nematic）、ＩＰＳ（In-Plane Switching）、ＦＬＣ（Ferroelectric Liquid Crystal）、ＯＣＢ（Optically Compensatory Bend）、ＳＴＮ（Supper Twisted Nematic）、ＶＡ（Vertically Aligned）、ＥＣＢ（Electrically Controlled Birefringence ）およびＨＡＮ（Hybrid Aligned Nematic）モードの液晶セルに対応するものが既に提案されている。
本発明の光学補償シートおよび偏光板は、光学補償シートの遅相軸と偏光膜の透過軸とを実質的に平行になるように配置することが好ましい液晶表示装置、例えば、ＴＮモードやＶＡモードの液晶表示装置に用いることが好ましい。本発明は、ＶＡモードの液晶表示装置において、特に効果がある。
ＶＡモードの液晶セルには、（１）棒状液晶性分子を電圧無印加時に実質的に垂直に配向させ、電圧印加時に実質的に水平に配向させる狭義のＶＡモードの液晶セル（特開平２−１７６６２５号公報記載）に加えて、（２）視野角拡大のため、ＶＡモードをマルチドメイン化した（ＭＶＡモードの）液晶セル（ＳＩＤ９７、Digest of tech. Papers（予稿集）２８（１９９７）８４５記載）、（３）棒状液晶性分子を電圧無印加時に実質的に垂直配向させ、電圧印加時にねじれマルチドメイン配向させるモード（ｎ−ＡＳＭモード）の液晶セル（日本液晶討論会の予稿集５８〜５９（１９９８）記載）および（４）ＳＵＲＶＡＩＶＡＬモードの液晶セル（ＬＣＤインターナショナル９８で発表）が含まれる。
【００４８】
【実施例】
［実施例１］
（透明支持体の作製）
セルローストリアセテートに下記の複屈折率上昇剤を３．５質量％添加し、厚さ１００μｍのロール状セルローストリアセテートフイルムを作製した。得られたセルローストリアセテートフイルムを、透明支持体として用いた。
【００４９】
【化１５】

【００５０】
（配向膜の形成）
下記のポリイミドのＮ−メチルピロリドン／ブチルセロソルブ溶液を、＃５のバーコーターを用いて、ロール状透明支持体を搬送しながらその上に連続的に塗布した。１４０℃で３分間加熱して、厚さ０．５μｍの配向膜を形成した。
【００５１】
【化１６】

【００５２】
配向膜を設けたロール状透明支持体を搬送しながら、長手方向（搬送方向）に連続的にラビング処理を実施した。
【００５３】
（光学補償シートの作製）
棒状液晶性分子（Ｎ２６）１００質量部、光重合開始剤（イルガキュア９０７、日本チバガイギー（株）製）１質量部、光重合増感剤（カヤキュアーＤＥＴＸ、日本化薬（株）製）０．３質量部を、メチレンクロライド９００質量部に溶解して塗布液を調製した。塗布液を、配向膜の上に、＃２のバーコーターを用いて連続的に塗布した。塗布層を１１０℃で２分間加熱し、５００ｍＪ／ｃｍ² の紫外線を照射して、棒状液晶性分子を重合させ、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、光学補償シートを作製した。棒状液晶性分子は、長軸方向が光学補償シートの長手方向と直交するように配向していた。
波長５５０ｎｍにおける光学補償シート全体の面内レターデーション（Ｒｅ）および厚み方向のレターデーション（Ｒth）を、エリプソメーター（Ｍ−１５０、日本分光（株）製）で測定した。結果は、第１表に示す。
【００５４】
（偏光板の作製）
厚さ８０μｍのロール状ポリビニルアルコールフイルムをヨウ素水溶液中で連続して５倍に延伸し、乾燥して偏光膜を得た。偏光膜の一方の面に、ケン化処理したロール状セルローストリアセテートフイルム（フジタックＴＤ８０ＵＦ、富士写真フイルム（株）製）を、他方の面にケン化処理したロール状光学補償シートの透明支持体を、連続して貼り合わせ、偏光板を作製した。光学補償シートの遅相軸（棒状液晶性分子の長軸方向）と偏光膜の透過軸とは平行であった。
【００５５】
（液晶表示装置の作製）
市販のＭＶＡ液晶表示装置（ＶＬ−１５３０Ｓ、富士通（株）製）から、観察者側およびバックライト側の偏光板と光学補償シートとを削除し、代わりに作製した偏光板を二枚貼り付けた。
作製したＭＶＡ液晶表示装置について、視野角を視野角測定装置（ＥＺContrast１６０Ｄ、ＥＬＤＩＭ社製）で測定した。その結果、偏光膜の透過軸方向の視野角および透過軸方向から４５゜の方向の視野角は、いずれも８０゜を越える値であった。
【００５６】
［実施例２］
（透明支持体の作製）
セルローストリアセテートに実施例１で用いた複屈折率上昇剤を７．８質量％添加し、厚さ１００μｍのロール状セルローストリアセテートフイルムを作製した。得られたセルローストリアセテートフイルムを、透明支持体として用いた。
【００５７】
（配向膜の形成）
実施例１で用いたポリイミドのＮ−メチルピロリドン／ブチルセロソルブ溶液を、＃５のバーコーターを用いて、ロール状透明支持体を搬送しながらその上に連続的に塗布した。１４０℃で３分間加熱して、厚さ０．５μｍの配向膜を形成した。
配向膜を設けたロール状透明支持体を搬送しながら、長手方向（搬送方向）に連続的にラビング処理を実施した。
【００５８】
（光学補償シートの作製）
実施例１で用いた塗布液を、配向膜の上に、＃３のバーコーターを用いて連続的に塗布した。塗布層を１１０℃で２分間加熱し、５００ｍＪ／ｃｍ² の紫外線を照射して、棒状液晶性分子を重合させ、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、光学補償シートを作製した。棒状液晶性分子は、長軸方向が光学補償シートの長手方向と直交するように配向していた。
波長５５０ｎｍにおける光学補償シート全体の面内レターデーション（Ｒｅ）および厚み方向のレターデーション（Ｒth）を、エリプソメーター（Ｍ−１５０、日本分光（株）製）で測定した。結果は、第１表に示す。
【００５９】
（偏光板の作製）
厚さ８０μｍのロール状ポリビニルアルコールフイルムをヨウ素水溶液中で連続して５倍に延伸し、乾燥して偏光膜を得た。偏光膜の一方の面に、ケン化処理したロール状セルローストリアセテートフイルム（フジタックＴＤ８０ＵＦ、富士写真フイルム（株）製）を、他方の面にケン化処理したロール状光学補償シートの透明支持体を、連続して貼り合わせ、偏光板を作製した。光学補償シートの遅相軸（棒状液晶性分子の長軸方向）と偏光膜の透過軸とは平行であった。
【００６０】
（液晶表示装置の作製）
市販のＭＶＡ液晶表示装置（ＶＬ−１５３０Ｓ、富士通（株）製）から、観察者側およびバックライト側の偏光板と光学補償シートとを削除し、観察者側に作製した偏光板を一枚貼り付けた。バックライト側には、市販の偏光板（ＨＬＣ２−５６１８ＨＣＳ、（株）サンリッツ製）を一枚貼り付けた。
作製したＭＶＡ液晶表示装置について、視野角を視野角測定装置（ＥＺContrast１６０Ｄ、ＥＬＤＩＭ社製）で測定した。その結果、偏光膜の透過軸方向の視野角および透過軸方向から４５゜の方向の視野角は、いずれも８０゜を越える値であった。
【００６１】
［実施例３］
（透明支持体の作製）
セルローストリアセテートに実施例１で用いた複屈折率上昇剤を７．８質量％添加し、厚さ１００μｍのロール状セルローストリアセテートフイルムを作製した。得られたセルローストリアセテートフイルムを、透明支持体として用いた。
【００６２】
（配向膜の形成）
実施例１で用いたポリイミドのＮ−メチルピロリドン／ブチルセロソルブ溶液を、＃５のバーコーターを用いて、ロール状透明支持体を搬送しながらその上に連続的に塗布した。１４０℃で３分間加熱して、厚さ０．５μｍの配向膜を形成した。
配向膜を設けたロール状透明支持体を搬送しながら、長手方向（搬送方向）に連続的にラビング処理を実施した。
【００６３】
（光学補償シートの作製）
実施例１で用いた塗布液を、配向膜の上に、＃８のバーコーターを用いて連続的に塗布した。塗布層を１１０℃で２分間加熱し、５００ｍＪ／ｃｍ² の紫外線を照射して、棒状液晶性分子を重合させ、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、光学補償シートを作製した。棒状液晶性分子は、長軸方向が光学補償シートの長手方向と直交するように配向していた。
波長５５０ｎｍにおける光学補償シート全体の面内レターデーション（Ｒｅ）および厚み方向のレターデーション（Ｒth）を、エリプソメーター（Ｍ−１５０、日本分光（株）製）で測定した。結果は、第１表に示す。
【００６４】
（偏光板の作製）
厚さ８０μｍのロール状ポリビニルアルコールフイルムをヨウ素水溶液中で連続して５倍に延伸し、乾燥して偏光膜を得た。偏光膜の一方の面に、ケン化処理したロール状セルローストリアセテートフイルム（フジタックＴＤ８０ＵＦ、富士写真フイルム（株）製）を、他方の面にケン化処理したロール状光学補償シートの光学異方性層を、連続して貼り合わせ、偏光板を作製した。光学補償シートの遅相軸（棒状液晶性分子の長軸方向）と偏光膜の透過軸とは平行であった。
【００６５】
（液晶表示装置の作製）
市販のＭＶＡ液晶表示装置（ＶＬ−１５３０Ｓ、富士通（株）製）から、観察者側およびバックライト側の偏光板と光学補償シートとを削除し、観察者側に作製した偏光板を一枚貼り付けた。バックライト側には、市販の偏光板（ＨＬＣ２−５６１８ＨＣＳ、（株）サンリッツ製）を一枚貼り付けた。
作製したＭＶＡ液晶表示装置について、視野角を視野角測定装置（ＥＺContrast１６０Ｄ、ＥＬＤＩＭ社製）で測定した。その結果、偏光膜の透過軸方向の視野角および透過軸方向から４５゜の方向の視野角は、いずれも８０゜を越える値であった。
【００６６】
［実施例４］
（偏光板の作製）
厚さ８０μｍのロール状ポリビニルアルコールフイルムをヨウ素水溶液中で連続して５倍に延伸し、乾燥して偏光膜を得た。偏光膜の一方の面に、ケン化処理したロール状セルローストリアセテートフイルム（フジタックＴＤ８０ＵＦ、富士写真フイルム（株）製）を、他方の面に実施例１で作製したロール状光学補償シートをケン化処理したシートの光学異方性層を、連続して貼り合わせ、偏光板を作製した。光学補償シートの遅相軸（棒状液晶性分子の長軸方向）と偏光膜の透過軸とは平行であった。
【００６７】
（液晶表示装置の作製）
市販のＭＶＡ液晶表示装置（ＶＬ−１５３０Ｓ、富士通（株）製）から、観察者側およびバックライト側の偏光板と光学補償シートとを削除し、代わりに作製した偏光板を二枚貼り付けた。
作製したＭＶＡ液晶表示装置について、視野角を視野角測定装置（ＥＺContrast１６０Ｄ、ＥＬＤＩＭ社製）で測定した。その結果、偏光膜の透過軸方向の視野角は、いずれも８０゜を越える値であった。また、透過軸方向から４５゜の方向の視野角は、６７゜であった。
【００６８】
［実施例５］
（透明支持体の作製）
セルローストリアセテートに実施例１で用いた複屈折率上昇剤を３．５質量％添加し、厚さ１００μｍのロール状セルローストリアセテートフイルムを作製した。得られたセルローストリアセテートフイルムを、透明支持体として用いた。
【００６９】
（配向膜の形成）
ポリビニルシンナメートのメチレンクロライド／クロロベンゼン溶液を、＃５のバーコーターを用いて、ロール状透明支持体を搬送しながらその上に連続的に塗布した。１４０℃で３分間加熱して、厚さ０．５μｍの配向膜を形成した。
配向膜を設けたロール状透明支持体を搬送しながら、長手方向（搬送方向）に直線偏光を平行照射した。
【００７０】
（光学補償シートの作製）
実施例１で用いた塗布液を、配向膜の上に、＃２のバーコーターを用いて連続的に塗布した。塗布層を１１０℃で２分間加熱し、５００ｍＪ／ｃｍ² の紫外線を照射して、棒状液晶性分子を重合させ、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、光学補償シートを作製した。棒状液晶性分子は、長軸方向が光学補償シートの長手方向と直交するように配向していた。
波長５５０ｎｍにおける光学補償シート全体の面内レターデーション（Ｒｅ）および厚み方向のレターデーション（Ｒth）を、エリプソメーター（Ｍ−１５０、日本分光（株）製）で測定した。結果は、第１表に示す。
【００７１】
（偏光板の作製）
厚さ８０μｍのロール状ポリビニルアルコールフイルムをヨウ素水溶液中で連続して５倍に延伸し、乾燥して偏光膜を得た。偏光膜の一方の面に、ケン化処理したロール状セルローストリアセテートフイルム（フジタックＴＤ８０ＵＦ、富士写真フイルム（株）製）を、他方の面にケン化処理したロール状光学補償シートの透明支持体を、連続して貼り合わせ、偏光板を作製した。光学補償シートの遅相軸（棒状液晶性分子の長軸方向）と偏光膜の透過軸とは平行であった。
【００７２】
（液晶表示装置の作製）
市販のＭＶＡ液晶表示装置（ＶＬ−１５３０Ｓ、富士通（株）製）から、観察者側およびバックライト側の偏光板と光学補償シートとを削除し、代わりに作製した偏光板を二枚貼り付けた。
作製したＭＶＡ液晶表示装置について、視野角を視野角測定装置（ＥＺContrast１６０Ｄ、ＥＬＤＩＭ社製）で測定した。その結果、偏光膜の透過軸方向の視野角および透過軸方向から４５゜の方向の視野角は、いずれも８０゜を越える値であった。
【００７３】
［実施例６］
（透明支持体の作製）
セルローストリアセテートに実施例１で用いた複屈折率上昇剤を３．５質量％添加し、厚さ１００μｍのロール状セルローストリアセテートフイルムを作製した。得られたセルローストリアセテートフイルムを、透明支持体として用いた。
【００７４】
（配向膜の形成）
実施例１で用いたポリイミドのＮ−メチルピロリドン／ブチルセロソルブ溶液を、＃５のバーコーターを用いて、ロール状透明支持体を搬送しながらその上に連続的に塗布した。１４０℃で３分間加熱して、厚さ０．５μｍの配向膜を形成した。
配向膜を設けたロール状透明支持体を搬送しながら、幅方向（搬送方向に垂直な方向）に直線偏光を平行照射した。
【００７５】
（光学補償シートの作製）
実施例１で用いた塗布液を、配向膜の上に、＃２のバーコーターを用いて連続的に塗布した。塗布層を１１０℃で２分間加熱し、５００ｍＪ／ｃｍ² の紫外線を照射して、棒状液晶性分子を重合させ、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、光学補償シートを作製した。棒状液晶性分子は、長軸方向が光学補償シートの長手方向と直交するように配向していた。
波長５５０ｎｍにおける光学補償シート全体の面内レターデーション（Ｒｅ）および厚み方向のレターデーション（Ｒth）を、エリプソメーター（Ｍ−１５０、日本分光（株）製）で測定した。結果は、第１表に示す。
【００７６】
（偏光板の作製）
厚さ８０μｍのロール状ポリビニルアルコールフイルムをヨウ素水溶液中で連続して５倍に延伸し、乾燥して偏光膜を得た。偏光膜の一方の面に、ケン化処理したロール状セルローストリアセテートフイルム（フジタックＴＤ８０ＵＦ、富士写真フイルム（株）製）を、他方の面にケン化処理したロール状光学補償シートの透明支持体を、連続して貼り合わせ、偏光板を作製した。光学補償シートの遅相軸（棒状液晶性分子の長軸方向）と偏光膜の透過軸とは平行であった。
【００７７】
（液晶表示装置の作製）
市販のＭＶＡ液晶表示装置（ＶＬ−１５３０Ｓ、富士通（株）製）から、観察者側およびバックライト側の偏光板と光学補償シートとを削除し、代わりに作製した偏光板を二枚貼り付けた。
作製したＭＶＡ液晶表示装置について、視野角を視野角測定装置（ＥＺContrast１６０Ｄ、ＥＬＤＩＭ社製）で測定した。その結果、偏光膜の透過軸方向の視野角および透過軸方向から４５゜の方向の視野角は、いずれも８０゜を越える値であった。
【００７８】
【表１】

【図面の簡単な説明】
【図１】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２】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。
【図３】ロール状偏光素子とロール状光学補償シートとの貼り合わせ工程を示す模式図である。
【符号の説明】
ＢＬ バックライト
ＬＤ 長手方向
ＲＰ 反射板
ＳＡ 光学異方性層の遅相軸
ＴＡ 偏光膜の透過軸
１、１ａ、１ｂ、１ｃ 透明保護膜
２、２ａ、２ｂ 偏光膜
３、３ａ、３ｂ 透明支持体
４、４ａ、４ｂ 光学異方性層
５ａ 液晶セルの下基板
５ｂ 液晶セルの上基板
６ 棒状液晶性分子層[0001]
[Industrial application fields]
The present invention relates to an optical compensation sheet having an optically anisotropic layer formed from liquid crystalline molecules, and a polarizing plate using 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 crystalline molecular layer, two substrates for enclosing it, an electrode layer for applying a voltage to the rod-like liquid crystalline molecules, and an alignment film layer for controlling the orientation of the rod-like liquid crystalline molecules. 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 TN, HAN (Hybrid Aligned Nematic), and GH (Guest-Host) have been proposed for Supper Twisted Nematic (VA), VA (Vertically Aligned), ECB (Electrically Controlled Birefringence), and reflective type. .
[0003]
Optical compensation sheets are used in various liquid crystal display devices in order to eliminate image coloring and expand the viewing angle. As the optical compensation sheet, a stretched birefringent polymer film has been conventionally used.
It has been proposed to use an optical compensation sheet having an optically anisotropic layer formed of liquid crystalline molecules on a transparent support, instead of the optical compensation sheet made of a stretched birefringent film. Since liquid crystal molecules have various alignment forms, the use of liquid crystal molecules makes it possible to realize optical properties that cannot be obtained with conventional stretched birefringent polymer 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 crystalline molecules are used, optical compensation sheets having various optical properties corresponding to various display modes of the liquid crystal cell can be produced. In general, rod-like liquid crystal molecules or discotic liquid crystal molecules are used as the liquid crystal molecules.
Optical compensation sheets using liquid crystal 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]
[Problems to be solved by the invention]
In an optical compensation sheet having an optically anisotropic layer formed from rod-like liquid crystalline molecules, the average direction of the lines obtained by projecting the major axis direction of the rod-like liquid crystalline molecules onto the transparent support surface is the slow phase of the optical compensation sheet. Corresponds to the axis. The average direction of the lines obtained by projecting the major axis direction of the rod-like liquid crystalline molecules on the transparent support surface generally corresponds to the rubbing direction of the alignment film. The optical compensation sheet is roll-shaped in actual production, and the rubbing process is most easily performed in the longitudinal direction of the roll-shaped optical compensation sheet. Therefore, in an optical compensation sheet having an optically anisotropic layer formed from rod-like liquid crystalline molecules, an embodiment having a slow axis in the longitudinal direction can be most easily produced.
The transmission axis of the polarizing film corresponds to a direction perpendicular to the stretching direction of the polymer film constituting the polarizing film. The polarizing element is also roll-shaped in actual production, and the stretching process is most easily performed in the longitudinal direction of the roll-shaped polarizing film. Therefore, a polarizing element having a transmission axis in a direction perpendicular to the longitudinal direction (width direction) can be most easily produced.
[0006]
From the above relationship, when laminating a roll-shaped optical compensation sheet and a roll-shaped polarizing element, it is most produced to arrange the slow axis of the optical compensation sheet and the transmission axis of the polarizing film to be substantially perpendicular to each other. Is easy. However, depending on the display mode of the liquid crystal cell, it may be preferable to arrange the slow axis of the optical compensation sheet and the transmission axis of the polarizing film so as to be substantially parallel.
An object of the present invention is to provide an optical compensation sheet that can be easily arranged so that the slow axis of the optical compensation sheet and the transmission axis of the polarizing film are substantially parallel to each other.
[0007]
[Means for Solving the Problems]
The object of the present invention was achieved by the following optical compensation sheets (1) to (7) and the following polarizing plates (8) to (9).
(1) A roll-shaped optical compensation sheet having an optically anisotropic layer formed from a transparent support and rod-like liquid crystalline molecules, obtained by projecting the major axis direction of the rod-like liquid crystalline molecules onto the transparent support surface. An optical compensation sheet, wherein the average direction of the lines and the longitudinal direction of the optical compensation sheet are substantially perpendicular to each other.
(2) The optical compensation sheet according to (1), wherein the rod-like liquid crystalline molecules are oriented with an average inclination angle between the major axis direction of the rod-like liquid crystalline molecules and the transparent support surface being less than 5 °.
(3) The optical film according to (1), wherein an alignment film is provided between the transparent support and the optically anisotropic layer, and the rubbing direction of the alignment film is substantially parallel to the longitudinal direction of the optical compensation sheet. Compensation sheet.
(4) The optical compensation sheet according to (1), wherein an alignment film is provided between the transparent support and the optically anisotropic layer, and the alignment function of the alignment film is generated by light irradiation.
(5) The optical compensation sheet according to (4), wherein the irradiated light is linearly polarized light.
(6) The optical compensation sheet according to (5), wherein the average direction of the lines obtained by projecting the major axis direction of the rod-like liquid crystalline molecules onto the transparent support surface is perpendicular to the polarization direction of the irradiated linearly polarized light.
(7) The optical compensation sheet according to (5), wherein the average direction of the lines obtained by projecting the major axis direction of the rod-like liquid crystalline molecules on the transparent support surface is parallel to the polarization direction of the linearly polarized light irradiated.
[0008]
(8) A roll-shaped polarizing plate having an optically anisotropic layer, a transparent support, a polarizing film and a transparent protective film formed from rod-like liquid crystalline molecules in this order, and the major axis direction of the rod-like liquid crystalline molecules The average direction of the line obtained by projecting the major axis direction of the rod-like liquid crystalline molecules on the transparent support surface is that the rod-like liquid crystalline molecules are oriented with the average inclination angle between the surface and the transparent support surface being less than 5 ° And the longitudinal direction of the polarizing plate are substantially perpendicular to each other, and the transmission axis of the polarizing film and the average direction of the lines obtained by projecting the major axis direction of the rod-like liquid crystalline molecules onto the transparent support surface are substantially A polarizing plate characterized by being parallel.
(9) A roll-shaped polarizing plate having a transparent support, an optically anisotropic layer formed from rod-like liquid crystalline molecules, a polarizing film and a transparent protective film in this order, and the major axis direction of the rod-like liquid crystalline molecules The average direction of the line obtained by projecting the major axis direction of the rod-like liquid crystalline molecules on the transparent support surface is that the rod-like liquid crystalline molecules are oriented with the average inclination angle between the surface and the transparent support surface being less than 5 ° And the longitudinal direction of the polarizing plate are substantially perpendicular to each other, and the transmission axis of the polarizing film and the average direction of the lines obtained by projecting the major axis direction of the rod-like liquid crystalline molecules onto the transparent support surface are substantially A polarizing plate characterized by being parallel.
In this specification, “substantially parallel” or “substantially orthogonal” means that the difference in angle from strict parallel or strict orthogonal is less than 5 °. The difference in angle is preferably less than 4 °, more preferably less than 3 °, even more preferably less than 2 °, and most preferably less than 1 °.
[0009]
【The invention's effect】
As a result of the inventor's research, the average direction of the lines obtained by projecting the major axis direction of the rod-like liquid crystalline molecules onto the transparent support surface and the longitudinal direction of the roll-shaped optical compensation sheet are substantially orthogonal to each other. It has been found that an arrangement state in which the slow axis of the compensation sheet and the transmission axis of the polarizing film are substantially parallel can be easily realized.
The average direction of the lines obtained by projecting the long axis direction of the rod-like liquid crystalline molecules on the transparent support surface and the longitudinal direction of the roll-shaped optical compensation sheet can be substantially orthogonal by improving the alignment film. . This makes it possible to easily produce a roll-shaped optical compensation sheet having a slow axis in a direction (width direction) perpendicular to the longitudinal direction.
On the other hand, as described above, a roll-shaped polarizing element having a transmission axis in a direction (width direction) perpendicular to the longitudinal direction can be most easily produced. Therefore, the polarizing plate in which the slow axis of the optical compensation sheet and the transmission axis of the polarizing film are substantially parallel by bonding the roll-shaped optical compensation sheet and the roll-shaped polarizing element according to the present invention in a roll state. Can be produced.
As described above, by using the optical compensation sheet of the present invention, the slow axis of the optical compensation sheet and the transmission axis of the polarizing film can be easily arranged so as to be substantially parallel.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic diagram showing a basic configuration of a transmissive liquid crystal display device.
The transmissive liquid crystal display device shown in FIG. 1A includes, in order from the backlight (BL) side, a transparent protective film (1a), a polarizing film (2a), a transparent support (3a), an optically anisotropic layer ( 4a), lower substrate (5a) of liquid crystal cell, rod-like liquid crystalline molecular layer (6), upper substrate (5b) of liquid crystal cell, optical anisotropic layer (4b), transparent support (3b), polarizing film (2b) ) And a transparent protective film (1b).
The transparent support and the optically anisotropic layer (3a to 4a and 4b to 3b) constitute an optical compensation sheet. And a transparent protective film, a polarizing film, a transparent support body, and an optically anisotropic layer (1a-4a and 4b-1b) comprise a polarizing plate.
The transmissive liquid crystal display device shown in FIG. 1B has, in order from the backlight (BL) side, a transparent protective film (1a), a polarizing film (2a), a transparent support (3a), an optically anisotropic layer ( 4a), lower substrate (5a) of liquid crystal cell, rod-like liquid crystalline molecular layer (6), upper substrate (5b) of liquid crystal cell, transparent protective film (1b), polarizing film (2b), and transparent protective film (1c) Consists of.
The transparent support and the optically anisotropic layer (3a to 4a) constitute an optical compensation sheet. And a transparent protective film, a polarizing film, a transparent support body, and an optically anisotropic layer (1a-4a) comprise a polarizing plate.
[0011]
The transmissive liquid crystal display device shown in FIG. 1C has a transparent protective film (1a), a polarizing film (2a), a transparent protective film (1b), and a lower substrate ( 5a), rod-like liquid crystalline molecular layer (6), upper substrate (5b) of liquid crystal cell, optically anisotropic layer (4b), transparent support (3b), polarizing film (2b), and transparent protective film (1c) Consists of.
The transparent support and the optically anisotropic layer (4b to 3b) constitute an optical compensation sheet. And a transparent protective film, a polarizing film, a transparent support body, and an optically anisotropic layer (4b-1c) comprise a polarizing plate.
FIG. 2 is a schematic diagram showing a basic configuration of a reflective liquid crystal display device.
The reflective liquid crystal display device shown in FIG. 2 includes a lower substrate (5a), a reflector (RP), a rod-like liquid crystalline molecular layer (6), an upper substrate (5b) of the liquid crystal cell, It consists of an anisotropic layer (4), a transparent support (3), a polarizing film (2), and a transparent protective film (1).
The transparent support and the optically anisotropic layer (4-3) constitute an optical compensation sheet. And a transparent protective film, a polarizing film, a transparent support body, and an optically anisotropic layer (4-1) comprise a polarizing plate.
[0012]
FIG. 3 is a schematic diagram showing a bonding process between a roll-shaped polarizing element and a roll-shaped optical compensation sheet.
As shown in FIG. 3, the roll-shaped polarizing element comprises a transparent protective film (1) and a polarizing film (2). The roll-shaped optical compensation sheet comprises a transparent support (3) and an optically anisotropic layer (4).
The transmission axis (TA) of the polarizing film (2) is substantially orthogonal to the longitudinal direction (LD) of the roll-shaped polarizing element. The average direction of the lines obtained by projecting the major axis direction of the rod-like liquid crystalline molecules of the optically anisotropic layer (4) onto the transparent support surface, that is, the slow axis (SA) is the longitudinal direction of the roll-shaped optical compensation sheet ( LD). Therefore, as shown in FIG. 3, simply by laminating the roll-shaped polarizing element and the roll-shaped optical compensation sheet as they are, the transmission axis (TA) of the polarizing film (2) and the slow phase of the optically anisotropic layer (4). It can arrange | position so that an axis | shaft (SA) may become substantially parallel.
1 to 3, the order of the transparent support (3) and the optically anisotropic layer (4) may be reversed.
[0013]
[Optically anisotropic layer]
The optically anisotropic layer is formed from rod-like liquid crystalline molecules. The rod-like liquid crystalline molecules are preferably aligned in a state where the average inclination angle between the major axis direction of the rod-like liquid crystalline molecules and the transparent support surface is less than 5 °.
It is preferable to adjust the retardation of the entire optical compensation sheet by providing an optically anisotropic layer. The in-plane retardation (Re) of the entire optical compensation sheet is preferably 20 to 200 nm, more preferably 20 to 100 nm, and most preferably 20 to 70 nm. The retardation (Rth) in the thickness direction of the entire optical compensation sheet is preferably 70 to 500 nm, more preferably 70 to 400 m, and still more preferably 70 to 300 nm. In-plane retardation (Re) and thickness direction retardation (Rth) of the optical compensation sheet are defined by the following equations, respectively.
Re = (nx−ny) × d
Rth = [{(nx + ny) / 2} -nz] × d
In the formula, nx and ny are the in-plane refractive indexes of the optical compensation sheet, nz is the refractive index in the thickness direction of the optical compensation sheet, and d is the thickness of the optical compensation sheet.
The retardation of the entire optical compensation sheet can be adjusted by combining the optically anisotropic layer and a transparent support having optical uniaxiality or optical biaxiality. The transparent support having optical uniaxiality or optical biaxiality will be described later.
[0014]
The rod-like liquid crystal molecules used for the optically anisotropic layer are preferably fixed in an aligned state. The alignment state can be fixed using a polymer binder, but is preferably fixed by a polymerization reaction.
Depending on the display mode of the liquid crystal cell, the rod-like liquid crystalline molecules may be cholesterically aligned. When the rod-like liquid crystalline molecules are cholesterically oriented, the selective reflection region is preferably outside the visible region.
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. The rod-like liquid crystalline molecule includes a metal complex. In addition, a liquid crystal polymer containing a rod-like liquid crystalline molecule in a repeating unit can also be used as the rod-like liquid crystalline molecule. In other words, the rod-like liquid crystal molecule may be bonded to a (liquid crystal) polymer.
For rod-like liquid crystalline molecules, quarterly review of chemical review, Vol. 22, Chemistry of Liquid Crystals (1994), Chapter 4, Chapter 7 and Chapter 11 of the Chemical Society of Japan, and Liquid Crystal Device Handbook, 142th Committee of the Japan Society for the Promotion of Science Is described in Chapter 3.
The birefringence of the rod-like liquid crystal molecule is preferably 0.001 to 0.7.
The rod-like liquid crystal molecule preferably has a polymerizable group. Examples of the polymerizable group (Q) are shown below.
[0015]
[Chemical 1]

[0016]
The polymerizable group (Q) is preferably an unsaturated polymerizable group (Q1 to Q7), an epoxy group (Q8) or an aziridinyl group (Q9), more preferably an unsaturated polymerizable group, and an ethylenic group. Most preferably, it is an unsaturated polymerizable group (Q1 to Q6).
The rod-like liquid crystal molecules preferably have a molecular structure that is substantially symmetric with respect to the minor axis direction. For that purpose, it is preferable to have a polymerizable group at both ends of the rod-like molecular structure.
Examples of rod-like liquid crystalline molecules are shown below.
[0017]
[Chemical formula 2]

[0018]
[Chemical 3]

[0019]
[Formula 4]

[0020]
[Chemical formula 5]

[0021]
[Chemical 6]

[0022]
[Chemical 7]

[0023]
[Chemical 8]

[0024]
[Chemical 9]

[0025]
[Chemical Formula 10]

[0026]
Embedded image

[0027]
Embedded image

[0028]
Embedded image

[0029]
Embedded image

[0030]
The optically anisotropic layer is a rod-like liquid crystalline molecule or the following polymerizable initiator or any additive (eg, plasticizer, monomer, surfactant, cellulose ester, 1,3,5-triazine compound, chiral agent). A liquid crystal composition (coating liquid) containing is applied on the alignment film.
As the solvent used for preparing the liquid crystal composition, 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 liquid crystal composition can be applied by a known method (eg, wire bar coating method, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method).
[0031]
The polymerization reaction of rod-like liquid crystalline molecules 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 mass, more preferably 0.5 to 5% by mass, based on the solid content of the coating solution.
The light irradiation for polymerizing the rod-like liquid crystalline molecules preferably uses ultraviolet rays.
Irradiation energy is 20mJ / cm ² ~ 50J / cm ² Preferably, 100 to 800 mJ / cm ² More preferably. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions.
The thickness of the optically anisotropic layer is preferably 0.1 to 20 μm, more preferably 0.2 to 15 μm, and most preferably 0.3 to 10 μm.
[0032]
[Transparent support]
As the transparent support of the optical compensation sheet, a glass plate or a polymer film, preferably a polymer film is used. That the support is transparent means that the light transmittance is 80% or more.
In general, an optically isotropic polymer film is used as the transparent support. Specifically, the optical isotropy preferably has an in-plane retardation (Re) of less than 10 nm, more preferably less than 5 nm. In the optically isotropic transparent support, the thickness direction retardation (Rth) is preferably less than 10 nm, more preferably less than 5 nm. The in-plane retardation (Re) and the thickness direction retardation (Rth) of the transparent support are respectively defined by the following formulas.
Re = (nx−ny) × d
Rth = [{(nx + ny) / 2} -nz] × d
In the formula, nx and ny are in-plane refractive indexes of the transparent support, nz is the refractive index in the thickness direction of the transparent support, and d is the thickness of the transparent support.
[0033]
Depending on the type of liquid crystal display mode, an optically anisotropic polymer film may be used as the transparent support. In other words, in addition to the optical anisotropy of the optically anisotropic layer, the optical anisotropy of the transparent support may be added to correspond to (optically compensate for) the optical anisotropy of the liquid crystal cell. In such a case, the transparent support preferably has optical uniaxiality or optical biaxiality. In the case of an optically uniaxial support, even if it is optically positive (the refractive index in the optical axis direction is larger than the refractive index in the direction perpendicular to the optical axis), it is negative (the refractive index in the optical axis direction is It may be smaller than the refractive index in the vertical direction. In the case of an optical biaxial support, the refractive indices nx, ny and nz in the above formula are all different values (nx ≠ ny ≠ nz).
The in-plane retardation (Re) of the optically anisotropic transparent support is preferably 0 to 300 nm, more preferably 0 to 200 nm, and most preferably 0 to 100 nm. The thickness direction retardation (Rth) of the optically anisotropic transparent support is preferably 10 to 1000 nm, more preferably 50 to 400 nm, and even more preferably 100 to 300 nm.
[0034]
The material for forming the transparent support is determined depending on whether it is an optically isotropic support or an optically anisotropic support. In the case of an optically isotropic support, glass or cellulose ester is generally used. In the case of an optically anisotropic support, a synthetic polymer (eg, polycarbonate, polysulfone, polyethersulfone, polyacrylate, polymethacrylate, norbornene resin) is generally used. However, (1) Use of a retardation increasing agent (birefringence increasing agent) described in the specification of European Patent 0911656A2, (2) Decreasing degree of acetylation of cellulose acetate, or (3) by cooling dissolution method By producing the film, a cellulose ester film having optical anisotropy (high retardation) can also be produced.
The transparent support made of a polymer film is preferably formed by a solvent cast method.
[0035]
In order to obtain an optically anisotropic transparent support, the polymer film is preferably subjected to a stretching treatment.
When an optical uniaxial support is produced, a normal uniaxial stretching process or biaxial stretching process may be performed.
When producing an optical biaxial support, it is preferable to perform an unbalanced biaxial stretching process. In unbalanced biaxial stretching, the polymer film is stretched in a certain direction (for example, 3 to 100%, preferably 5 to 30%) in a certain direction, and further in the direction perpendicular thereto (for example, 6 to 200%, preferably 10 to 90%). The bi-directional stretching process may be performed simultaneously.
The stretching direction (the direction in which the stretching ratio is high in unbalanced biaxial stretching) and the in-plane slow axis of the film after stretching are preferably substantially the same direction. The angle between the stretching direction and the slow axis is preferably less than 10 °, more preferably less than 5 °, and most preferably less than 3 °.
When a transparent support having optical uniaxiality or optical biaxiality is used, the average direction of lines obtained by projecting the major axis direction of rod-like liquid crystalline molecules of the optically anisotropic layer onto the transparent support surface is It is preferable that the transparent support is disposed so as to be substantially parallel or orthogonal to the slow axis in the plane of the transparent support.
[0036]
The thickness of the transparent support is preferably 10 to 500 μm, and more preferably 50 to 200 μm.
In order to improve the adhesion between the transparent support and the layer (adhesion layer, alignment film or optically anisotropic layer) provided thereon, surface treatment (eg, glow discharge treatment, corona discharge treatment, ultraviolet ray ( UV) treatment, flame treatment).
An ultraviolet absorber may be added to the transparent support.
An adhesion layer (undercoat layer) may be provided on the transparent support. The adhesive layer is described in JP-A-7-333433. The thickness of the adhesion layer is preferably 0.1 to 2 μm, and more preferably 0.2 to 1 μm.
[0037]
[Alignment film]
The alignment film is an organic compound (eg, ω-tricosanoic acid) formed by rubbing treatment of an organic compound (preferably a 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.
It is particularly preferable to use an alignment film formed by a rubbing treatment of a polymer or an alignment film that generates an alignment function by light irradiation.
As the alignment film formed by the rubbing treatment of the polymer, an alignment film having a function of aligning the major axis direction of the rod-like liquid crystalline molecules in a direction perpendicular to the rubbing direction is preferably used. When an alignment film having such a function is used, a rubbing treatment is performed substantially in parallel with the longitudinal direction of the optical compensation sheet (the rubbing treatment is performed in the direction in which it can be most easily carried out), whereby rod-like liquid crystalline molecules The average direction (slow axis) of the lines obtained by projecting the major axis direction of the optical compensation sheet onto the transparent support surface and the longitudinal direction of the optical compensation sheet can be substantially perpendicular to each other. The alignment film having the above function is described in JP-A-11-212097.
As the polymer, polyimide is preferable. A polyimide is obtained by the condensation reaction of diamine and tetracarboxylic acid. As the diamine, it is particularly preferable to use 4,4- (9-fluorenylidene) dianiline.
The rubbing treatment is carried out by rubbing the surface of the polymer layer several times in a certain direction with paper or cloth.
[0038]
An alignment film that generates an alignment function by light irradiation is formed using a photochromic compound or a photosensitive polymer. The light is preferably irradiated with linearly polarized light. In the alignment film in which the alignment function is generated by light irradiation, the alignment direction of the rod-like liquid crystalline molecules can be controlled by the light irradiation direction or the polarization direction of linearly polarized light. By controlling the alignment direction using an alignment film that generates alignment functions by light irradiation, the average direction (slow axis) of the line obtained by projecting the long axis direction of rod-like liquid crystalline molecules onto the transparent support surface and optical compensation The longitudinal direction of the sheet can be made substantially orthogonal.
A photochromic compound is a compound in which a chemical structure is changed by the action of light, and thereby behavior (for example, color tone) with respect to light is also changed. In general, these changes are reversible.
Photochromic compounds previously proposed for liquid crystal cells include azobenzene compounds (K. Ichimura et al., Langmuir, vol. 4, page 1214 (1988); K. Aoki et al., Langmuir, vol. 8, page 1007 ( 1992); Y. Suzuki et al., Langmuir, vol. 8, page 2601 (1992); K. Ichimura et al., Appl. Phys. Lett., Vol. 63, No. 4, page 449 (1993); N. Ishizuki, Langmuir, vol. 9, page 3298 (1993); N. Ishizuki, Langmuir, vol. 9, page 857 (1993)), hydrazono-β-ketoester compounds (S. Yamamura et al., Liquid Crystals, vol. 13, No. 2, page 189 (1993)), stilbene compounds (Kunihiro Ichimura et al., Polymers, Vol. 47, No. 10, p. 771 (1990)) and spiropyran compounds (K. Ichimura et al Chemistry Letters, page 1063 (1992); K. Ichimura et al., Thin Solid Films, vol. 235, page 101 (1993)).
[0039]
A photochromic compound containing a double bond structure consisting of C = C, C = N or N = N is particularly preferred. The photochromic compound having a double bond structure comprises the following essential elements (1) and (2) and optional elements (3) to (5) below.
(1) Double bond structure consisting of C = C, C = N or N = N
(2) An annular structure existing on both sides of the bond of (1) (not necessarily directly connected)
(3) Any linking group between (1) and (2)
(4) any carbon atom substituent of (1)
(5) Any substituent of the cyclic structure of (2)
The double bond structure (1) is preferably a trans type rather than a cis type. Two or more double bond structures may exist in the molecule. The plurality of double bond structures are preferably conjugated.
Examples of the cyclic structure (2) include a benzene ring, a naphthalene ring, and a nitrogen-containing heterocyclic ring (eg, pyridinium ring, benzopyridinium ring). In the case of a nitrogen-containing heterocyclic ring, it is preferable that a carbon atom (not a nitrogen atom) constituting the ring is bonded to a carbon atom or a nitrogen atom of the double bond structure of (1). A benzene ring is particularly preferred.
[0040]
Examples of the linking group (3) include —NH— and —CO—. However, it is preferable that there is no linking group (3) and (1) and (2) are directly connected.
Examples of the substituent of the above (4) include an aryl group (eg, phenyl) and cyano. However, it is preferable that the carbon atom contained in the double bond structure without the substituent (4) is unsubstituted (—CH═CH— or —CH═N—) except for the bond with (2). .
Examples of the substituent of the above (5) include an alkoxy group (eg, methoxy, hexyloxy), cyano, an alkyl group (eg, butyl, hexyl) and an alkylamino group (eg, dimethylamino). When the cyclic structure (2) is a benzene ring, a substituent is preferably bonded to the para position. As will be described later, when the photochromic compound is used by being chemically bonded to the polymer, a functional group for chemically bonding to the polymer is introduced into the photochromic compound as a substituent in (5).
[0041]
In the formation of the alignment film, the photochromic compound needs to be used fixed to the support surface by some means. The fixing means of the photochromic compound includes (a) fixing by application of a mixture of polymer and photochromic compound, (b) chemical bonding of the photochromic compound to the polymer, (c) adsorption of the photochromic compound to the support surface, and (d) There is a chemical bond of the photochromic compound to the support surface.
In the liquid crystal cell, a means for adsorbing or bonding a photochromic compound to the surface of quartz glass that is a substrate of the liquid crystal cell using the means (c) or (d) has been generally used. However, in the optical compensation sheet, it is preferable to use a plastic film as a support rather than a glass plate in order to reduce the weight of the liquid crystal display device. Therefore, it is preferable to use the means (a) or (b) in the optical compensation sheet. In order to stably fix the photochromic compound, it is particularly preferable to use the means (b).
[0042]
The polymer used for the means (a) or (b) is preferably a hydrophilic polymer (eg, gelatin, polyvinyl alcohol). Polyvinyl alcohol is particularly preferably used.
The reaction between the photochromic compound and the polymer in the means (b) is determined according to the type of polymer (particularly the type of functional group). In the case of a polymer having a hydroxyl group such as polyvinyl alcohol, a photochromic compound can be bonded to the polymer by utilizing a reaction between an acid halide and a hydroxyl group. Specifically, an acyl halide group (—COX, X is halogen) is introduced as a substituent into the photochromic compound, and a reaction between the acyl halide group and the hydroxyl group of the polymer (Ph—COX + HO—Pl → Ph—CO—). O-Pl + HX, Ph is a photochromic compound, and Pl is a polymer main chain).
[0043]
Photosensitive polymers can be classified into photoisomerized polymers, photodimerized polymers and photodegradable polymers. As the photoisomerization polymer, a polymer in which a photochromic compound is bonded as described above is representative (substantially synonymous). Examples of photodimerized polymers include polyvinyl cinnamate. Examples of photodegradable polymers include polyimide. The photodegradable polyimide is described in JP-A-5-34699, JP-A-6-289399, JP-A-8-122792, and the 22nd Liquid Crystal Symposium Proceedings Collection, page 1672, A17 (1996).
A film containing a photochromic compound or a photosensitive polymer can be formed on a transparent support by coating a solution or dispersion using an appropriate solvent. Note that the constituent components of the alignment film preferably do not exhibit properties as liquid crystals.
After forming a film containing a photochromic compound or a photosensitive polymer as described above, an alignment function is imparted to the film by light irradiation. The irradiation light is particularly preferably linearly polarized light. Exposure amount is 100 to 6000 mJ / cm ² Preferably, it is 300 to 5000 mJ / cm ² More preferably. In order to impart an alignment function to the film in a short time, it is preferable to irradiate light while heating. The heating temperature is preferably 40 to 250 ° C.
[0044]
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 rod-like liquid crystalline molecules of the optically anisotropic layer using the alignment film, the optically anisotropic layer may be transferred onto the transparent support. The rod-like liquid crystalline molecules fixed in the alignment state can maintain the alignment state even without the alignment film.
[0045]
[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 transmission axis of the polarizing film corresponds to a direction perpendicular to the stretching direction of the film.
The transmission axis of the polarizing film is arranged so as to be substantially parallel to the average direction (slow axis) of the lines obtained by projecting the long axis direction of the rod-like liquid crystalline molecules onto the transparent support surface.
[0046]
[Transparent protective film]
A transparent polymer film is used as the transparent protective film. That the protective film is transparent means that the light transmittance is 80% or more.
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.
[0047]
[Liquid Crystal Display]
The present invention can be applied to liquid crystal cells in various display modes. As described above, optical compensation sheets using liquid crystalline molecules are TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), OCB (Optically Compensatory Bend), STN (Supper Twisted Nematic). A liquid crystal cell corresponding to a liquid crystal cell of VA (Vertically Aligned), ECB (Electrically Controlled Birefringence) and HAN (Hybrid Aligned Nematic) modes has already been proposed.
The optical compensation sheet and polarizing plate of the present invention are preferably arranged such that the slow axis of the optical compensation sheet and the transmission axis of the polarizing film are substantially parallel, such as a TN mode or a VA mode. The liquid crystal display device is preferably used. The present invention is particularly effective in a VA mode liquid crystal display device.
The VA mode liquid crystal cell includes (1) a narrowly defined VA mode liquid crystal cell in which rod-like liquid crystalline molecules are aligned substantially vertically when no voltage is applied, and substantially horizontally when a voltage is applied (Japanese Patent Laid-Open No. Hei 2-). 176625) (2) Liquid crystal cell (SID97, Digest of tech. Papers (Preliminary Proceed) 28 (1997) 845 in which the VA mode is converted into a multi-domain (MVA mode) for widening the viewing angle ), (3) A liquid crystal cell in a mode (n-ASM mode) in which rod-like liquid crystalline molecules are substantially vertically aligned when no voltage is applied and twisted multi-domain alignment is applied when a voltage is applied (Preliminary collections 58-59 of the Japan Liquid Crystal Society) (1998)) and (4) SURVAVAL mode liquid crystal cells (announced at LCD International 98).
[0048]
【Example】
[Example 1]
(Preparation of transparent support)
To the cellulose triacetate, 3.5% by mass of the following birefringence increasing agent was added to prepare a roll cellulose triacetate film having a thickness of 100 μm. The obtained cellulose triacetate film was used as a transparent support.
[0049]
Embedded image

[0050]
(Formation of alignment film)
The following N-methylpyrrolidone / butyl cellosolve solution of polyimide was continuously coated thereon while conveying the roll-shaped transparent support using a # 5 bar coater. An alignment film having a thickness of 0.5 μm was formed by heating at 140 ° C. for 3 minutes.
[0051]
Embedded image

[0052]
While transporting the roll-shaped transparent support provided with the alignment film, the rubbing treatment was continuously performed in the longitudinal direction (transport direction).
[0053]
(Production of optical compensation sheet)
100 parts by mass of rod-like liquid crystalline molecules (N26), 1 part by mass of a photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy Japan), photopolymerization sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) 0.3 Mass parts were dissolved in 900 parts by mass of methylene chloride to prepare a coating solution. The coating solution was continuously applied onto the alignment film using a # 2 bar coater. The coating layer is heated at 110 ° C. for 2 minutes, 500 mJ / cm ² The rod-like liquid crystalline molecules were polymerized by irradiating the ultraviolet rays, and the alignment state was fixed. Thus, an optically anisotropic layer was formed, and an optical compensation sheet was produced. The rod-like liquid crystalline molecules were aligned so that the major axis direction was orthogonal to the longitudinal direction of the optical compensation sheet.
In-plane retardation (Re) and retardation in the thickness direction (Rth) of the entire optical compensation sheet at a wavelength of 550 nm were measured with an ellipsometer (M-150, manufactured by JASCO Corporation). The results are shown in Table 1.
[0054]
(Preparation of polarizing plate)
A roll-like polyvinyl alcohol film having a thickness of 80 μm was continuously stretched 5 times in an iodine aqueous solution and dried to obtain a polarizing film. A saponified roll-shaped cellulose triacetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) is applied to one surface of the polarizing film, and a transparent support of a roll-shaped optical compensation sheet saponified to the other surface, Bonding was continued to produce a polarizing plate. The slow axis of the optical compensation sheet (long axis direction of the rod-like liquid crystalline molecules) and the transmission axis of the polarizing film were parallel.
[0055]
(Production of liquid crystal display device)
From the commercially available MVA liquid crystal display device (VL-1530S, manufactured by Fujitsu Ltd.), the polarizing plate and the optical compensation sheet on the observer side and the backlight side were deleted, and two produced polarizing plates were pasted instead. .
About the produced MVA liquid crystal display device, the viewing angle was measured with the viewing angle measuring apparatus (EZContrast160D, ELDIM company make). As a result, the viewing angle in the transmission axis direction of the polarizing film and the viewing angle in the direction of 45 ° from the transmission axis direction were values exceeding 80 °.
[0056]
[Example 2]
(Preparation of transparent support)
7.8% by mass of the birefringence increasing agent used in Example 1 was added to cellulose triacetate to prepare a roll cellulose triacetate film having a thickness of 100 μm. The obtained cellulose triacetate film was used as a transparent support.
[0057]
(Formation of alignment film)
The N-methylpyrrolidone / butyl cellosolve solution of polyimide used in Example 1 was continuously applied thereon while conveying the roll-shaped transparent support using a # 5 bar coater. An alignment film having a thickness of 0.5 μm was formed by heating at 140 ° C. for 3 minutes.
While transporting the roll-shaped transparent support provided with the alignment film, the rubbing treatment was continuously performed in the longitudinal direction (transport direction).
[0058]
(Production of optical compensation sheet)
The coating solution used in Example 1 was continuously applied onto the alignment film using a # 3 bar coater. The coating layer is heated at 110 ° C. for 2 minutes, 500 mJ / cm ² The rod-like liquid crystalline molecules were polymerized by irradiating the ultraviolet rays, and the alignment state was fixed. Thus, an optically anisotropic layer was formed, and an optical compensation sheet was produced. The rod-like liquid crystalline molecules were aligned so that the major axis direction was orthogonal to the longitudinal direction of the optical compensation sheet.
In-plane retardation (Re) and retardation in the thickness direction (Rth) of the entire optical compensation sheet at a wavelength of 550 nm were measured with an ellipsometer (M-150, manufactured by JASCO Corporation). The results are shown in Table 1.
[0059]
(Preparation of polarizing plate)
A roll-like polyvinyl alcohol film having a thickness of 80 μm was continuously stretched 5 times in an iodine aqueous solution and dried to obtain a polarizing film. A saponified roll-shaped cellulose triacetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) is applied to one surface of the polarizing film, and a transparent support of a roll-shaped optical compensation sheet saponified to the other surface, Bonding was continued to produce a polarizing plate. The slow axis of the optical compensation sheet (long axis direction of the rod-like liquid crystalline molecules) and the transmission axis of the polarizing film were parallel.
[0060]
(Production of liquid crystal display device)
From the commercially available MVA liquid crystal display device (VL-1530S, manufactured by Fujitsu Limited), the polarizing plate and the optical compensation sheet on the viewer side and the backlight side are deleted, and a single polarizing plate prepared on the viewer side is attached. I attached. A commercially available polarizing plate (HLC2-5618HCS, manufactured by Sanlitz Corporation) was attached to the backlight side.
About the produced MVA liquid crystal display device, the viewing angle was measured with the viewing angle measuring apparatus (EZContrast160D, ELDIM company make). As a result, the viewing angle in the transmission axis direction of the polarizing film and the viewing angle in the direction of 45 ° from the transmission axis direction were values exceeding 80 °.
[0061]
[Example 3]
(Preparation of transparent support)
7.8% by mass of the birefringence increasing agent used in Example 1 was added to cellulose triacetate to prepare a roll cellulose triacetate film having a thickness of 100 μm. The obtained cellulose triacetate film was used as a transparent support.
[0062]
(Formation of alignment film)
The N-methylpyrrolidone / butyl cellosolve solution of polyimide used in Example 1 was continuously applied thereon while conveying the roll-shaped transparent support using a # 5 bar coater. An alignment film having a thickness of 0.5 μm was formed by heating at 140 ° C. for 3 minutes.
While transporting the roll-shaped transparent support provided with the alignment film, the rubbing treatment was continuously performed in the longitudinal direction (transport direction).
[0063]
(Production of optical compensation sheet)
The coating solution used in Example 1 was continuously coated on the alignment film using a # 8 bar coater. The coating layer is heated at 110 ° C. for 2 minutes, 500 mJ / cm ² The rod-like liquid crystalline molecules were polymerized by irradiating the ultraviolet rays, and the alignment state was fixed. Thus, an optically anisotropic layer was formed, and an optical compensation sheet was produced. The rod-like liquid crystalline molecules were aligned so that the major axis direction was orthogonal to the longitudinal direction of the optical compensation sheet.
In-plane retardation (Re) and retardation in the thickness direction (Rth) of the entire optical compensation sheet at a wavelength of 550 nm were measured with an ellipsometer (M-150, manufactured by JASCO Corporation). The results are shown in Table 1.
[0064]
(Preparation of polarizing plate)
A roll-like polyvinyl alcohol film having a thickness of 80 μm was continuously stretched 5 times in an iodine aqueous solution and dried to obtain a polarizing film. An optically anisotropic layer of a roll-shaped optical compensation sheet having a saponified roll-shaped cellulose triacetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) on one surface of the polarizing film and a saponified surface on the other surface Were laminated together to produce a polarizing plate. The slow axis of the optical compensation sheet (long axis direction of the rod-like liquid crystalline molecules) and the transmission axis of the polarizing film were parallel.
[0065]
(Production of liquid crystal display device)
From the commercially available MVA liquid crystal display device (VL-1530S, manufactured by Fujitsu Limited), the polarizing plate and the optical compensation sheet on the viewer side and the backlight side are deleted, and a single polarizing plate prepared on the viewer side is attached. I attached. A commercially available polarizing plate (HLC2-5618HCS, manufactured by Sanlitz Corporation) was attached to the backlight side.
About the produced MVA liquid crystal display device, the viewing angle was measured with the viewing angle measuring apparatus (EZContrast160D, ELDIM company make). As a result, the viewing angle in the transmission axis direction of the polarizing film and the viewing angle in the direction of 45 ° from the transmission axis direction were values exceeding 80 °.
[0066]
[Example 4]
(Preparation of polarizing plate)
A roll-like polyvinyl alcohol film having a thickness of 80 μm was continuously stretched 5 times in an iodine aqueous solution and dried to obtain a polarizing film. Saponified roll-shaped cellulose triacetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) is saponified on one surface of the polarizing film, and the roll-shaped optical compensation sheet prepared in Example 1 is saponified on the other surface. The optically anisotropic layer of the obtained sheet was continuously bonded to produce a polarizing plate. The slow axis of the optical compensation sheet (long axis direction of the rod-like liquid crystalline molecules) and the transmission axis of the polarizing film were parallel.
[0067]
(Production of liquid crystal display device)
From the commercially available MVA liquid crystal display device (VL-1530S, manufactured by Fujitsu Ltd.), the polarizing plate and the optical compensation sheet on the observer side and the backlight side were deleted, and two produced polarizing plates were pasted instead. .
About the produced MVA liquid crystal display device, the viewing angle was measured with the viewing angle measuring apparatus (EZContrast160D, ELDIM company make). As a result, the viewing angle in the transmission axis direction of the polarizing film was a value exceeding 80 °. The viewing angle in the direction of 45 ° from the transmission axis direction was 67 °.
[0068]
[Example 5]
(Preparation of transparent support)
3.5% by mass of the birefringence increasing agent used in Example 1 was added to cellulose triacetate to prepare a roll cellulose triacetate film having a thickness of 100 μm. The obtained cellulose triacetate film was used as a transparent support.
[0069]
(Formation of alignment film)
A methylene chloride / chlorobenzene solution of polyvinyl cinnamate was continuously coated on the roll-shaped transparent support using a # 5 bar coater while being conveyed. An alignment film having a thickness of 0.5 μm was formed by heating at 140 ° C. for 3 minutes.
While transporting the roll-shaped transparent support provided with the alignment film, linearly polarized light was irradiated in parallel in the longitudinal direction (transport direction).
[0070]
(Production of optical compensation sheet)
The coating solution used in Example 1 was continuously coated on the alignment film using a # 2 bar coater. The coating layer is heated at 110 ° C. for 2 minutes, 500 mJ / cm ² The rod-like liquid crystalline molecules were polymerized by irradiating the ultraviolet rays, and the alignment state was fixed. Thus, an optically anisotropic layer was formed, and an optical compensation sheet was produced. The rod-like liquid crystalline molecules were aligned so that the major axis direction was orthogonal to the longitudinal direction of the optical compensation sheet.
In-plane retardation (Re) and retardation in the thickness direction (Rth) of the entire optical compensation sheet at a wavelength of 550 nm were measured with an ellipsometer (M-150, manufactured by JASCO Corporation). The results are shown in Table 1.
[0071]
(Preparation of polarizing plate)
A roll-like polyvinyl alcohol film having a thickness of 80 μm was continuously stretched 5 times in an iodine aqueous solution and dried to obtain a polarizing film. A saponified roll-shaped cellulose triacetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) is applied to one surface of the polarizing film, and a transparent support of a roll-shaped optical compensation sheet saponified to the other surface, Bonding was continued to produce a polarizing plate. The slow axis of the optical compensation sheet (long axis direction of the rod-like liquid crystalline molecules) and the transmission axis of the polarizing film were parallel.
[0072]
(Production of liquid crystal display device)
From the commercially available MVA liquid crystal display device (VL-1530S, manufactured by Fujitsu Ltd.), the polarizing plate and the optical compensation sheet on the observer side and the backlight side were deleted, and two produced polarizing plates were pasted instead. .
About the produced MVA liquid crystal display device, the viewing angle was measured with the viewing angle measuring apparatus (EZContrast160D, ELDIM company make). As a result, the viewing angle in the transmission axis direction of the polarizing film and the viewing angle in the direction of 45 ° from the transmission axis direction were values exceeding 80 °.
[0073]
[Example 6]
(Preparation of transparent support)
3.5% by mass of the birefringence increasing agent used in Example 1 was added to cellulose triacetate to prepare a roll cellulose triacetate film having a thickness of 100 μm. The obtained cellulose triacetate film was used as a transparent support.
[0074]
(Formation of alignment film)
The N-methylpyrrolidone / butyl cellosolve solution of polyimide used in Example 1 was continuously applied thereon while conveying the roll-shaped transparent support using a # 5 bar coater. An alignment film having a thickness of 0.5 μm was formed by heating at 140 ° C. for 3 minutes.
While transporting the roll-shaped transparent support provided with the alignment film, parallel polarized light was irradiated in the width direction (direction perpendicular to the transport direction).
[0075]
(Production of optical compensation sheet)
The coating solution used in Example 1 was continuously coated on the alignment film using a # 2 bar coater. The coating layer is heated at 110 ° C. for 2 minutes, 500 mJ / cm ² The rod-like liquid crystalline molecules were polymerized by irradiating the ultraviolet rays, and the alignment state was fixed. Thus, an optically anisotropic layer was formed, and an optical compensation sheet was produced. The rod-like liquid crystalline molecules were aligned so that the major axis direction was orthogonal to the longitudinal direction of the optical compensation sheet.
In-plane retardation (Re) and retardation in the thickness direction (Rth) of the entire optical compensation sheet at a wavelength of 550 nm were measured with an ellipsometer (M-150, manufactured by JASCO Corporation). The results are shown in Table 1.
[0076]
(Preparation of polarizing plate)
A roll-like polyvinyl alcohol film having a thickness of 80 μm was continuously stretched 5 times in an iodine aqueous solution and dried to obtain a polarizing film. A saponified roll-shaped cellulose triacetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) is applied to one surface of the polarizing film, and a transparent support of a roll-shaped optical compensation sheet saponified to the other surface, Bonding was continued to produce a polarizing plate. The slow axis of the optical compensation sheet (long axis direction of the rod-like liquid crystalline molecules) and the transmission axis of the polarizing film were parallel.
[0077]
(Production of liquid crystal display device)
From the commercially available MVA liquid crystal display device (VL-1530S, manufactured by Fujitsu Ltd.), the polarizing plate and the optical compensation sheet on the observer side and the backlight side were deleted, and two produced polarizing plates were pasted instead. .
About the produced MVA liquid crystal display device, the viewing angle was measured with the viewing angle measuring apparatus (EZContrast160D, ELDIM company make). As a result, the viewing angle in the transmission axis direction of the polarizing film and the viewing angle in the direction of 45 ° from the transmission axis direction were values exceeding 80 °.
[0078]
[Table 1]

[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a basic configuration of a transmissive liquid crystal display device.
FIG. 2 is a schematic diagram showing a basic configuration of a reflective liquid crystal display device.
FIG. 3 is a schematic diagram illustrating a bonding process between a roll-shaped polarizing element and a roll-shaped optical compensation sheet.
[Explanation of symbols]
BL backlight
LD Longitudinal direction
RP reflector
SA Slow axis of optically anisotropic layer
TA Transmission axis of polarizing film
1, 1a, 1b, 1c Transparent protective film
2, 2a, 2b Polarizing film
3, 3a, 3b transparent support
4, 4a, 4b Optically anisotropic layer
5a Lower substrate of liquid crystal cell
5b Upper substrate of liquid crystal cell
6 Rod-like liquid crystalline molecular layer

Claims (10)

  An optical compensation sheet in the form of a roll having an optically anisotropic layer formed from a transparent support and rod-like liquid crystalline molecules, the average of the lines obtained by projecting the major axis direction of the rod-like liquid crystalline molecules on the transparent support surface An optical compensation sheet, wherein the direction and the longitudinal direction of the optical compensation sheet are substantially orthogonal to each other.   2. The optical compensation sheet according to claim 1, wherein the rod-like liquid crystalline molecules are oriented in a state where the average inclination angle between the major axis direction of the rod-like liquid crystalline molecules and the transparent support surface is less than 5 °.   The optical compensation sheet according to claim 1, wherein an alignment film is provided between the transparent support and the optically anisotropic layer, and the rubbing direction of the alignment film is substantially parallel to the longitudinal direction of the optical compensation sheet.   The optical compensation sheet according to claim 1, wherein an alignment film is provided between the transparent support and the optically anisotropic layer, and an alignment function of the alignment film is generated by light irradiation.   The optical compensation sheet according to claim 4, wherein the irradiated light is linearly polarized light.   6. The optical compensation sheet according to claim 5, wherein the average direction of the lines obtained by projecting the major axis direction of the rod-like liquid crystalline molecules onto the transparent support surface is perpendicular to the polarization direction of the irradiated linearly polarized light.   6. The optical compensation sheet according to claim 5, wherein the average direction of the lines obtained by projecting the major axis direction of the rod-like liquid crystal molecules on the transparent support surface is parallel to the polarization direction of the irradiated linearly polarized light. 7. The polyimide alignment film is applied and formed on a roll-shaped transparent support, and then linearly polarized light is irradiated in parallel in the width direction of the film, and a rod-like liquid crystal layer is applied and formed thereon. Optical compensation sheet . It is a roll-shaped polarizing plate having an optically anisotropic layer, a transparent support, a polarizing film and a transparent protective film formed from rod-like liquid crystalline molecules in this order. The average direction of the line obtained by projecting the major axis direction of the rod-like liquid crystalline molecules on the transparent support surface, with the rod-like liquid crystalline molecules aligned with the average tilt angle with the body surface being less than 5 °, and the polarizing plate Are substantially perpendicular to each other, and the transmission axis of the polarizing film is substantially parallel to the average direction of the lines obtained by projecting the long axis direction of the rod-like liquid crystalline molecules onto the transparent support surface. A polarizing plate characterized by that .   A roll-shaped polarizing plate having a transparent support, an optically anisotropic layer formed from rod-like liquid crystalline molecules, a polarizing film and a transparent protective film in this order, and the major axis direction of the rod-like liquid crystalline molecules and the transparent support The average direction of the line obtained by projecting the major axis direction of the rod-like liquid crystalline molecules on the transparent support surface, with the rod-like liquid crystalline molecules aligned with the average tilt angle with the body surface being less than 5 °, and the polarizing plate Are substantially perpendicular to each other, and the transmission axis of the polarizing film is substantially parallel to the average direction of the lines obtained by projecting the long axis direction of the rod-like liquid crystal molecules onto the transparent support surface. A polarizing plate characterized by that.

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