JP2004177642A - Phase difference film and its manufacturing method, optical compensating film, polarizing plate, and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phase difference film which has a superior field angle characteristic and a small breakage frequency in tenter drawing and its manufacturing method, an optical compensating film, a polarizing plate, and a liquid crystal display device. <P>SOLUTION: The phase difference film is made of at least two kinds of cellulose ester which are selected from cellulose ester of 2.50 to 2.90 in substitution degree of an an acyl group and have a ≥0.02 in difference in substitution degree of the acyl group; and nx>ny>nz and relations shown by expressions (1) and (2) are satisfied. Here, the expression (1) is 2.5<R<SB>t</SB>/T<SB>0</SB>≤20 and the expression (2) is 20 nm≤R<SB>0</SB>≤70 nm, where R<SB>0</SB>=(nx-ny)×d and R<SB>t</SB>=ä(nx+ny)/2-nz}×d. In the expressions, nx is a refractive index in an in-film-surface phase delaying axis direction, ny a refractive index in an in-film-surface phase leading axis direction, nz a refractive index in a film thickness direction, and (d) the thickness (nm) of the film. <P>COPYRIGHT: (C)2004,JPO

Description

【０１８８】
（セルロースエステルフィルムの作製）
上記のように調製したドープをダイからステンレスベルト（流延用支持体ともいう）上にドープ温度３０℃で流延し、ウェブを形成した。ステンレスベルトの裏面から２５℃の温度の温水を接触させて温度制御されたステンレスベルト上でウェブを１分間乾燥した後、更にステンレスベルトの裏面に、１５℃の冷水を接触させて１５秒間保持した後、ウェブをステンレスベルトから剥離した。剥離時のウェブ中の残留溶媒量は１００質量％であった。
【０１８９】
次いでテンターを用いて剥離したウェブの両端をクリップで掴み、クリップ間隔を巾方向に変化させることで、表１に記載の延伸倍率までフィルムを延伸した。その際のフィルム温度は１４０℃になるように調整した。その後、乾燥過程で張力カット装置を導入した部分を通過させることで、巻き取り張力を１００Ｎ／ｍとなるように調整した。このようにして膜厚６０μｍのセルロースエステルフィルム１−１〜１−７を、各々得た。
【０１９０】
作製したセルロースエステルフィルム１−１〜１−７は、各々コア径２００ｍｍのガラス繊維強化樹脂製のコアに巾１ｍ、長さ１０００ｍのフィルムロール状にテーパーテンション法で巻き取った。この際、フィルム端部に温度２５０℃のエンボスリングを押し当て、フィルムの両端部に幅１５ｍｍで高さ１０μｍのエンボス加工を施して、フィルム同士の密着を防止した。
【０１９１】
《セルロースエステルフィルムの光学特性評価》
得られたセルロースエステルフィルム１−１〜１−７の各々について、フィルム面内方向のリターデーション値（Ｒ_０（ｎｍ））、厚み方向のリターデーション値（Ｒ_ｔ（ｎｍ）、Ｒ_ｔ／Ｒ_０）測定を自動複屈折計ＫＯＢＲＡ−２１ＡＤＨ（王子計測機器社製）を用いて、２３℃、５５％ＲＨの環境下で、波長が５９０ｎｍにおける屈折率ｎｘ、ｎｙ、ｎｚを求め、下記式に従って、Ｒ_０およびＲ_ｔを算出した。なお、屈折率ｎｘ、ｎｙ、ｎｚを求める際に用いる平均屈折率の値は、あらかじめアッベの屈折計を用いて測定した。
【０１９２】
Ｒ_０＝（ｎｘ−ｎｙ）×ｄ
Ｒ_ｔ＝（（ｎｘ＋ｎｙ）／２−ｎｚ）×ｄ
ここで、ｎｘはフィルムの面内における遅相軸方向の屈折率、ｎｙはフィルム面内における進相軸方向の屈折率、ｎｚはフィルムの厚み方向の屈折率、ｄはフィルムの厚み（ｎｍ）をそれぞれ表す。
【０１９３】
但し、Ｒ_０、Ｒ_ｔの測定に当たり、幅手５点について各々、測定を実施し、それらのばらつきを評価した。５点の内訳は、フィルムの幅手中央部（Ｃ）、中央から左右それぞれ２００ｍｍのところ（Ｌ１、Ｒ１）、および中央から左右４００ｍｍのところ（Ｌ２、Ｒ２）の５点である。
【０１９４】
得られた結果を表２に示す。
【０１９５】
【表１】

【０１９６】
【表２】

【０１９７】
表１、表２のセルロースエステルフィルム１−１〜１−５から、異なる置換度または異なる置換基を有する２種類のセルロースエステルの混合比を変化させることにより、セルロースエステルフィルムの光学特性（Ｒ_０、Ｒ_ｔ、Ｒ_ｔ／Ｒ_０比）を前記式（１）、（２）の範囲に入るように調整でき、且つ、光学特性のばらつきを小さくできることがわかった。
【０１９８】
実施例２
《セルロースエステルフィルム２−１〜２−６の作製》
下記のようにドープを調製し、そのドープを用いてセルロースエステルフィルムを作製した。
【０１９９】
（ドープの調製）
表３に記載のセルロースエステルＡと酢酸メチルおよびアセトンを所定量混合し、それを二重構造の密閉容器に入れ、ゆっくり撹拌しながら外側のジャケットに冷媒を導入した。これにより内側容器内の混合物を−７０℃まで冷却した。混合物が均一に冷却されるまで３０分冷却した。密閉容器の外側のジャケット内の冷媒を排出し、代わりに温水をジャケットに導入する。続いて内容物を撹拌し、４０分かけて１００℃まで上げた。容器内は２．５気圧となった。撹拌しながら５０℃まで温度を下げ常圧に戻し、一晩そのまま放置しドープ１を得た。その後溶液を安積濾紙社製の安積濾紙Ｎｏ．２４４を使用して濾過し、調製した。
【０２００】
一方、表３のセルロースエステルＢと酢酸エチルおよびアセトンを所定量混合し、同様の方法によりドープ２を調製した。
【０２０１】
（ドープ１の組成）
セルロースエステルＡ ２０質量部
トリフェニルフォスフェート ２質量部
エチルフタリルエチルグリコレート ２質量部
チヌビン１０９（チバスペシャリティーケミカルズ社製） ３質量部
酢酸メチル １８４質量部
エタノール １６質量部
（ドープ２の組成）
セルロースエステルＢ ８０質量部
トリフェニルフォスフェート １質量部
エチルフタリルエチルグリコレート ２質量部
酢酸メチル １８４質量部
エタノール １６質量部
上記レタデーション上昇剤 ５質量部
（セルロースエステルフィルムの作製）
表３に記載のセルロースエステルフィルム２−１、２−３、２−５については、セルロースエステルＡを溶解したドープ１とセルロースエステルＢを溶解したドープ２をインラインミキサーにより流延直前に混合することにより調製し、流延製膜した。
【０２０２】
また、表３に記載のセルロースエステルフィルム２−２、２−４、２−６については、ドープ１を流延したあと、そのドープフィルム上に、各々、２秒後、１０秒後、３０秒後にドープ２を流延する、いわゆる共流延法を用いて流延製膜を行った。
【０２０３】
上記の流延製膜においては、流延直前のドープ温度を３０℃とし、流延してウェブを形成後、ステンレスベルトの裏面から２５℃の温度の温水を接触させて温度制御されたステンレスベルト上でウェブを１分間乾燥した後、更に、ステンレスベルトの裏面に、１５℃の冷水を接触させて１５秒間保持した後、ステンレスベルトからウェブを剥離した。剥離時のウェブ中の残留溶媒量は１００質量％であった。
【０２０４】
次いでテンターを用いて剥離したウェブの両端をクリップで掴み、クリップ間隔を巾方向に変化させることで、表３に記載の延伸倍率までフィルムを延伸した。その際のフィルム温度（延伸温度ともいう）は表３に記載の温度とし、延伸部の入り口におけるフィルム中の残留溶媒量変更は、剥離からの搬送速度とパス長変更により行った。更にローラ搬送しながら乾燥させ、膜厚８０μｍのセルロースエステルフィルム２−１〜２−６を各々得た。
【０２０５】
得られたセルロースエステルフィルム２−１〜２−６の各々については、実施例１に記載と同様に光学特性評価を行った。得られた結果を、表４に示す。
【０２０６】
レタデーションのばらつきの表示等は表２に準じた。
【０２０７】
【表３】

【０２０８】
【表４】

【０２０９】
表３、表４のセルロースエステルフィルム２−１〜２−６から、各々、セルロースエステルの混合比をＡ：Ｂ＝２０：８０にした時に、延伸温度、残留溶媒量、延伸倍率などの製膜条件の変化により、得られるセルロースエステルフィルムの光学特性（Ｒ_０、Ｒ_ｔ、Ｒ_ｔ／Ｒ_０）を前記式（１）、（２）の範囲に入るように調整するための知見を得ることが出来た。
【０２１０】
また、セルロースエステルフィルム２−６の作製から、アセチル置換度、プロピオニル置換度が共に異なるセルロースエステルを用いた場合に得られるセルロースエステルフィルムの光学特性（Ｒ_０、Ｒ_ｔ、Ｒ_ｔ／Ｒ_０比）を前記式（１）、（２）の範囲に入るように調整するための知見を得ることが出来た。
【０２１１】
実施例３
《光学補償フィルムの作製》
実施例１で作製したセルロースエステルフィルム１−１〜１−７を用い、以下のようにして光学補償フィルムを作製した。
【０２１２】
（液晶配向層の作製）
上記セルロースエステルフィルムを支持体とし、直鎖アルキル変性ポリビニルアルコール（ＭＰ２０３；クラレ社製）の水：メタノール＝６０：４０（質量比）の１質量％溶液を作製し、乾燥膜厚が０．２μｍとなるように押し出しコーティング機で塗布した。これらを８０℃温風にて乾燥させた後、ラビング処理を行い、配向層を形成した。
【０２１３】
（光学補償フィルム３−１〜３−７の作製）
上記で作製した液晶配向層上に、下記に示す組成の塗布溶液をワイヤバー＃５を用いて塗設した。さらにこれを５５℃の無風状態で３０秒乾燥、次いで７５度、３０秒熱処理を行い、９８ｋＰａで６０秒間窒素パージした後、酸素濃度０．１％条件下で４５０ｍＪ／ｃｍ^２の紫外線により硬化させた膜を作製した。こうして１層の光学異方層を有する光学補償フィルム３−１〜３−７を、各々得た。
【０２１４】

【０２１５】
【化２】

【０２１６】
【化３】

【０２１７】
【化４】

【０２１８】
上記で作製した光学補償フィルム３−１〜３−７を以下のように評価した。
《光学補償フィルムの寸法安定性評価》
２３±３℃、５５±３％ＲＨの常温常湿雰囲気下における光学補償フィルムの寸法をそれぞれＬｍｄ（ｎｍ セルロースエステルの流延方向）、Ｌｔｄ（ｎｍセルロースエステルの幅方向）とし、８０±３℃、９０±３％ＲＨの高温高湿雰囲気下で２４時間処理後、該常温常湿雰囲気に戻した時のセルロースエステルの流延方向の寸法をＨｍｄ（ｎｍ）、幅方向の寸法をＨｔｄ（ｎｍ）とし、下記式に示す伸縮率ＳｍｄおよびＳｔｄについて評価した。
【０２１９】
Ｓｍｄ（％）＝｛（Ｈｍｄ−Ｌｍｄ）／Ｌｍｄ｝×１００
Ｓｔｄ（％）＝｛（Ｈｔｄ−Ｌｔｄ）／Ｌｔｄ｝×１００
得られた結果を表５に示す。
【０２２０】
【表５】

【０２２１】
表５から、本発明外の比較例に比べて、本発明内の光学補償フィルムは高湿条件下での寸法変化が小さいことが明らかである。
【０２２２】
実施例４
《偏光板４−１〜４−７の作製》
厚さ１２０μｍのポリビニルアルコールフィルムを沃素１質量部、ホウ酸４質量部を含む水溶液１００質量部に浸漬し、５０℃で４倍に延伸して偏光子を作製した。この偏光子の一方の面には、６０℃で２モル／Ｌの水酸化ナトリウム水溶液中に２分間浸漬し水洗した後１００℃で１０分間乾燥した８０μｍの偏光板保護フィルム（コニカタックＫＣ８ＵＸ（コニカ社製））を、完全鹸化型ポリビニルアルコール５％水溶液の粘着剤を用いて貼り合わせ、もう一方の面には実施例３で作製した光学補償フィルム３−１〜３−７を同様の処理を行って貼合した。この場合、光学補償フィルムの光学異方層を有する側が偏光子側になるようにし、アクリル系接着剤を用いて偏光子の透過軸が光学補償フィルムの支持体（セルロースエステルフィルム）の最大屈折率を与える方向と一致するようにして貼合し、偏光板４−１〜４−７を各々得た。
【０２２３】
（偏光板のカール性評価）
作製した偏光板のセルロースエステルフィルム作製時における流延幅手ほぼ中央部から、流延方向３００ｍｍ、幅方向２００ｍｍのサイズで切り出したものを使用し、２３±３℃、８０±３％ＲＨの環境で平らな台上に静置し、偏光板の四隅の浮き上がり高さを複数回（４回〜５回）測定し、平均値を算出して得られた結果を表６に示した。
【０２２４】
【表６】

【０２２５】
表６から、本発明外の比較例に比べて本発明の偏光板は、表裏面のセルロースエステルフィルムの厚みが異なるにもかかわらず、カール特性が良好な偏光板が作製できることがわかる。
【０２２６】
実施例５
《液晶表示装置の作製及び評価》
ＮＥＣ社製１５インチディスプレイＭｕｌｔｉ Ｓｙｎｃ ＬＣＤ１５２５Ｊのあらかじめ貼合されていた光学補償フィルムおよび一対の偏光板を剥がしたものを使用し、その代わりに実施例４の偏光板を実施例１で作製したセルロースエステルフィルムが液晶セル側となるように粘着剤で貼り合わせた。一対の偏光板の透過軸は直交するようにした。
【０２２７】
こうして得られた本発明の光学補償フィルムを貼合した液晶パネル（５−１〜５−７）を、ＥＬＤＩＭ社製ＥＺ−ｃｏｎｔｒａｓｔにより視野角を測定した。視野角は、液晶パネルの白表示と黒表示時のコントラスト比が１０以上を示すパネル面に対する法線方向からの傾き角の範囲であらわし、各光学補償フィルムについて得られた視野角の値とした。
【０２２８】
得られた結果を表７に示す。
【０２２９】
【表７】

【０２３０】
表７から、本発明外の比較例に比べて、本発明の液晶表示装置は、優れた視野角拡大機能を示していることが明らかである。
【０２３１】
実施例６
《セルロースエステルフィルムの作製》
以下に示すようにして、ドープ調製し、次いで、セルロースエステルフィルムを作製した。
【０２３２】
（ドープの調製）
表８または９に記載のロット番号（Ａ〜Ｅ、Ｆ〜Ｊ）を有するセルロースエステルと、下記の材料を所定量混合し、その混合物を密閉容器に入れ、混合物をゆっくり撹拌しながら徐々に昇温し、６０分かけて４５℃まで上げ溶解した。容器内を１．２気圧に調整した。このドープを安積濾紙社製の安積濾紙Ｎｏ．２４４を使用して濾過した後、一晩そのまま放置しドープを得た。
【０２３３】
（ドープ液の組成）
セルロースエステル（表８、９に記載） １００質量部
エチルフタリルエチルグリコレート ４質量部
チヌビン１０９（チバスペシャリティーケミカルズ社製） ３質量部
メチレンクロライド ４５５質量部
エタノール ３６質量部
前記レタデーション上昇剤 ７質量部
（セルロースエステルフィルム６−１〜６−５、７−１〜７−５の作製）
上記作製したドープをダイからステンレスベルト上にドープ温度３０℃で流延し、ウェブ形成した。ステンレスベルトの裏面から２５℃の温度の温水を接触させて温度制御されたステンレスベルト上でウェブを１分間乾燥した後、更にステンレスベルトの裏面に、１５℃の冷水を接触させて１５秒間保持した後、ステンレスベルトからウェブを剥離した。剥離時のウェブ中の残留溶媒量は１００質量％であった。
【０２３４】
但し、インライン添加を行ったセルロースエステルフィルム６−４、６−５、７−４、７−５については、実施例２に記載のセルロースエステルフィルム２−１、２−３、２−５の作製と同様にしてインライン添加を行った。
【０２３５】
次いでテンターを用いて剥離したフィルムの両端をクリップで掴み、クリップ間隔を巾方向に変化させることで、延伸倍率１．１５倍にフィルムを延伸した。その際のフィルム温度は１４０℃あるいは１６０℃とした。その後乾燥過程で張力カット装置を導入した部分を通過させ、巻き取り張力を１００Ｎ／ｍとなるように調整した。このようにして膜厚４０μｍのセルロースエステルフィルム６−１〜６−５、７−１〜７−５を各々得た。得られたセルロースエステルフィルムの光学特性は実施例１に記載と同様に評価した。
【０２３６】
得られた結果を表８、表９に示す。
【０２３７】
【表８】

【０２３８】
【表９】

【０２３９】
表８、表９から、下記のようにインラインブレンドによるＲ_ｔ／Ｒ_０の調整についての知見を得た。
【０２４０】
《インラインブレンドによるＲ_ｔ／Ｒ_０の調整について》
表８のセルロースエステルフィルム６−１〜６−３の各々のＲ_ｔ／Ｒ_０値、表９のセルロースエステルフィルム７−１〜７−３の各々のＲ_ｔ／Ｒ_０値から判るように、流延製膜後、延伸して得られたセルロースエステルフィルムのＲ_ｔ／Ｒ_０値は、作製時に使用したセルロースエステルのロットによって、同じ置換度の材料を用いても得られるセルロースエステルフィルムの光学特性が必ずしも同一にならず、少しずつではあるが変動することが判る。
【０２４１】
このようなロット変動による、Ｒ_ｔ／Ｒ_０値の調整に対応する為には、表８の６−４、６−５に示すように２種類のセルロースエステルＢとＤ、ＣとＥをインラインブレンドすることにより、Ｒ_ｔ／Ｒ_０を調整することができる。
【０２４２】
同様に、表９のセルロースエステルフィルム７−４、７−５に示すように２種類のセルロースエステルＧとＩ、ＨとＪをインラインブレンドすることにより、セルロースエステルフィルム７−１のＲ_ｔ／Ｒ_０（１．８）になるように調整することが出来た。
【０２４３】
以上から、本発明では、置換度の異なるセルロースエステルドープをインラインで混合することで、Ｒ_ｔ／Ｒ_０の値の変動を最小限になるように制御し、ばらつきを防止することが出来た。
【０２４４】
実施例７
実施例１の１−１、１−２、１−３、１−６、１−７で使用したドープを用いて、テンターの延伸温度を１６０℃、延伸倍率を１．５倍とし、膜厚を４０μｍになるようにした以外は実施例１と同様にして、それぞれ８−１、８−２、８−３、８−６、８−７のセルロースエステルフィルムを作製した。得られたフィルムの光学特性を表１０に示した。レタデーションのばらつきの表示等は表２に準じた。
【０２４５】
【表１０】

【０２４６】
８−１、８−２、８−３は、レタデーションのばらつきが小さく良好な光学特性を有していた。８−６、８−７は、レタデーションのばらつきが大きく、位相差フィルムとしては不十分な品質であった。また、８−１、８−２、８−３の製膜中は、テンターでの破断の発生はなかったが、８−６、８−７の製膜中は、テンターでの破断が度々発生し生産性に劣るものであった。
【０２４７】
【発明の効果】
本発明により、特定の面内レタデーション及び厚み方向レタデーションと面内レタデーションの比を有し、かつ製品幅全幅に亘ってそのレタデーションのばらつきが小さく、視野角特性にも優れ、更にテンター延伸時の破断頻度の少ない位相差フィルムとその製造方法、光学補償フィルム、偏光板及び液晶表示装置を提供することが出来る。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a retardation film and a method for producing the same, an optical compensation film, a polarizing plate, and a liquid crystal display.
[0002]
[Prior art]
Liquid crystal display devices are characterized by the fact that they can be made smaller in depth and save space as compared with CRTs, and they consume less power, and are widely used for monitors and the like. However, there is a problem that the liquid crystal display device has a difficulty in increasing its size and has a narrow viewing angle, and there is a demand for technical improvement so that a wide viewing angle can be obtained on a large screen.
[0003]
In order to increase the viewing angle, a method of arranging a retardation film between a polarizing plate and a liquid crystal cell is known. Conventionally, a retardation film typically has a large in-plane retardation of 100 to 200 nm, such as a λλ plate. However, in a display device having a large screen size, it has been known that the use of a retardation film having a smaller in-plane retardation and a larger retardation in the thickness direction than before is effective for expanding the viewing angle.
[0004]
JP-A-2002-139621 proposes an optical compensation sheet comprising a stretched cellulose acetate film having an in-plane retardation of 20 to 70 nm, a retardation in the thickness direction of 70 to 400 nm, and a film thickness of 10 to 70 μm, which contains a retardation increasing agent. ing.
[0005]
Specifically, a solution-cast cellulose acetate film having an acetylation degree of 60.7% or 60.9% is laterally stretched in a state where the solvent remains in the film, so that the in-plane retardation is 20 to 50 nm and the thickness is 20 to 50 nm. It is described that by using a stretched cellulose acetate film having a directional retardation of 90 to 135 nm and a film thickness of 38.5 to 52.0 μm as an optical compensation sheet, the viewing angle of a VA mode, OCB mode and TN mode liquid crystal display device can be expanded. ing. However, when the stretched cellulose acetate film used for the optical compensatory sheet is actually manufactured with a product width of 1 m or more, the retardation in the width direction is large, and the only part that can be actually used is the central part of the product. Was inferior. Further, when the tenter is stretched in a transverse direction, stress is concentrated on the gripping portions at both ends of the film, and there is an inherent danger of breaking. In particular, when the film thickness is reduced, the influence becomes remarkable, and there is a problem that the frequency of breakage increases and the productivity decreases.
[0006]
[Patent Document 1]
JP-A-2002-139621
[0007]
[Patent Document 2]
JP 2001-253971 A (described later)
[0008]
[Problems to be solved by the invention]
As a result of examining the above-mentioned problems, it was found that when the in-plane retardation was adjusted to be relatively small, the variation in the retardation was greatly changed due to a slight change in the stretching conditions. In particular, it was found that when a retardation increasing agent was added, the change was significantly amplified.
[0009]
As a method of reducing the variation of the retardation of the retardation film having the characteristic that the in-plane retardation is relatively small and the thickness direction retardation is large as described above, for example, there is a method described in JP-A-11-183724. . This is a method of sequentially or simultaneously biaxially stretching a polymer resin film in a state of containing a solvent, specifically, using polycarbonate to adjust the temperature and the magnification to a specified range, and then vertically or horizontally or horizontally and vertically. It is biaxially stretched sequentially. However, even in this method, the actual product width satisfying the retardation quality is at most 83% of the entire width.
[0010]
Thus, it has been difficult to make the retardation uniform over the entire large-sized product.
[0011]
Also, in order to prevent breakage in tenter stretching, a method of reducing stretching stress by stretching in a state in which a solvent is contained in the film can be considered, but in this method, the film near the grip portion is also softened. In some cases, the number of breaks increased. As a countermeasure against this, Japanese Patent Application Laid-Open No. 2002-127245 proposes a method in which the content of volatile components in the film at the grip portion is made smaller than the content of volatile components in the film at the central portion to make it less likely to break. Again, there was a problem with its productivity.
[0012]
An object of the present invention is to have a specific in-plane retardation and a ratio of thickness-direction retardation to in-plane retardation, and have a small variation in retardation over the entire width of the product, excellent viewing angle characteristics, and further excellent tenter stretching. It is an object of the present invention to provide a retardation film having a low breaking frequency, a manufacturing method thereof, an optical compensation film, a polarizing plate, and a liquid crystal display device.
[0013]
[Means for Solving the Problems]
The inventor of the present invention has made intensive studies on the above problems, and as a result, by mixing cellulose esters having different degrees of acyl group substitution, adjustment of the in-plane retardation and the retardation in the thickness direction of the film is facilitated, and over the entire product width. As a result, it has been found that these variations in retardation can be remarkably reduced, and furthermore, it is difficult to cause breakage in tenter transverse stretching. Also, by mixing cellulose esters having different types of substituents of the acyl group, similarly, adjustment of the in-plane retardation and the retardation in the thickness direction of the film become easy, and the variation of these retardations is remarkable over the entire product width. The present invention has been found to be able to reduce the number and to reduce the possibility of breakage in the transverse stretching of the tenter, thereby leading to the present invention.
[0014]
JP-A-2001-253971 discloses a vinegar mixture of a cellulose acetate having a maximum acetylation degree and a cellulose acetate having a minimum acetylation degree comprising a mixture of two or more cellulose acetates having different acetylation degrees. A cellulose acetate film having a difference in the degree of conversion of 2.0 to 6.0% is disclosed. Specifically, by mixing two kinds of cellulose acetates having different degrees of acetylation within a certain range, a λ / 4 plate or a λ / 2 plate which can easily adjust the wavelength dispersion characteristics in a wide wavelength region is achieved. I have. However, with respect to the retardation characteristics as in the present invention, it is not suggested that the retardation can be easily adjusted and the variation of the retardation can be reduced over the entire width of the product.
[0015]
That is, the object of the present invention is achieved by adopting any of the following configurations.
[1] nx> ny comprising at least two kinds of cellulose esters having a degree of acyl group substitution selected from cellulose esters having a degree of substitution of 2.50 to 2.90 and having a degree of substitution of acyl groups of 0.02 or more. > Nz and satisfying the following formulas (1) and (2).
[0016]
Formula (1) 2.5 <R _t / R ₀ ≦ 20
Formula (2): 20 nm ≦ R ₀ ≦ 70 nm
Where R ₀ = (Nx-ny) × d
R _t = {(Nx + ny) / 2-nz} × d
(Where nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, nz is the refractive index in the film thickness direction, and d is the film thickness (nm). .)
[2] Cellulose acetate having a degree of acetyl substitution of 2.50 to 2.90 and cellulose acetate propionate satisfying the following formulas (3) and (4), where A is the degree of acetyl substitution and B is the degree of propionyl substitution The retardation film according to [1], comprising:
[0017]
Formula (3) 2.50 ≦ (A + B) ≦ 2.90
Formula (4) 1.40 ≦ A ≦ 2.30
[3] It is produced by mixing cellulose ester A having a degree of acyl group substitution of 2.70 to 2.90 and cellulose ester B having a degree of acyl group substitution of 2.50 to less than 2.70. [1] The retardation film according to [1].
[0018]
[4] The retardation film according to any one of [1] to [3], wherein the content of cellulose acetate propionate in the entire cellulose ester is at least 60% by mass.
[0019]
[5] It is characterized by containing two or more kinds of cellulose acetate propionates having different degrees of substitution, and having an average degree of substitution satisfying the above formulas (3) and (4) [1] to [4]. The retardation film according to any one of the above.
[0020]
[6] The retardation film according to any one of [1] to [5], wherein the retardation film contains an aromatic compound having at least two aromatic rings in an amount of 0.01 to 20% by mass relative to the polymer. Retardation film.
[0021]
[7] The retardation film according to any one of [1] to [5], wherein the retardation film contains an aromatic compound having at least one 1,3,5-triazine ring.
[0022]
[8] In producing the retardation film according to any one of [1] to [7], a resin solution containing a solvent is cast on a support to form a web, and a web is formed. The web is peeled off from the support and dried to reduce the residual solvent amount in the web to less than 100% by mass, and then stretched while maintaining the temperature of the web in a range of 110 to 160 ° C. A method for producing a retardation film.
[0023]
[9] Two or more types of solutions having different substituents or containing cellulose esters having different degrees of substitution are mixed by an inline mixer immediately before casting to prepare a cellulose ester dope, and a casting film forming method is used. The method for producing a retardation film according to [8], which comprises forming a film.
[0024]
[10] The method according to [8], wherein two or more types of solutions having different degrees of substitution or containing cellulose esters having different substituents are simultaneously or sequentially cast on a support to form a film. A method for producing the retardation film according to the above.
[0025]
[11] The retardation film according to any one of [1] to [7], and an optical difference in which the orientation of a liquid crystal compound is fixed on the retardation film directly or via another layer. An optical compensation film, which is provided with an isotropic layer.
[0026]
[12] A polarizing plate comprising the optical compensation film according to [11].
[0027]
[13] A liquid crystal display device comprising the polarizing plate according to [12]. As the arrangement form of the optical compensation film of the present invention, if it is between the glass substrate or the plastic substrate of the driving liquid crystal cell and the polarizer, it can be arranged and used in various forms in a TN type TFT liquid crystal device. .
[0028]
The optical anisotropic body of the present invention is disposed between each polarizer on both sides of the liquid crystal panel and the glass substrate or the plastic substrate of the cell, and is provided on either the incident light side or the outgoing light side in the case of a transmission type panel. Can also be arranged. Alternatively, one or two or more optical compensation films may be similarly arranged on one surface.
[0029]
Further, the method of arranging the optical compensation film for more effectively expressing the object of the present invention is to dispose the optical compensation film in the direction in which the cellulose ester film surface of the optical compensation film is in contact with the surface closest to the driving liquid crystal cell, and The direction in which the maximum refractive index direction of the cellulose ester film of the compensation film is substantially perpendicular to the in-plane maximum refractive index direction of the optically anisotropic layer is preferable. Substantially orthogonal means that the angle between each of the reference directions is in the range of 80 to 100 °, preferably 87 to 93 °, more preferably 89 to 91 °, but essentially 90 °. Preferably, there is.
[0030]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
[0031]
(Cellulose ester film used in the present invention)
As the optical properties of the cellulose ester film of the present invention, the retardation value (R ₀ ) Needs to be 20 to 70 nm.
[0032]
In the present invention, the retardation value (R _t ) And R ₀ Ratio (R _t / R ₀ ) Needs to be in the range of 2.5 to 20, and when the condition of nx>ny> nz is satisfied at the same time, the cellulose ester film of the present invention having excellent optical properties is obtained, The viewing angle expansion effect of the liquid crystal panel having the optical compensation film using the same is exhibited.
[0033]
Also, this R _t / R ₀ The values may vary between lots even when cellulose esters having the same degree of substitution are used. In order to avoid the problem, the retardation value immediately after film formation is measured and R _t / R ₀ If the value deviates from the target set value, a dope in which a cellulose ester having a different degree of substitution is dissolved is mixed by an in-line addition method or the like, and can be adjusted so as to have optimal optical characteristics. In addition, a high-quality cellulose ester film can be produced.
[0034]
The method for producing the cellulose ester film of the present invention will be described later in detail, but a preferable production method from the viewpoint of productivity is to prepare a cellulose ester solution (dope) on a support (for example, a belt or a drum is used). In this mode, a web is formed by casting, a web is formed, and the web is peeled from a support (belt or drum) in a state where the solvent remains, and then stretched while drying to obtain a cellulose ester film.
[0035]
nx is the refractive index in the x direction which is the maximum refractive index direction in the plane of the cellulose ester film, and ny is the refractive index in the y direction which is a direction perpendicular to the x direction in the plane. nz represents the refractive index in the thickness direction, and d represents the thickness (nm) of the film.
[0036]
For the measurement of the entire refractive index of the cellulose ester film, an ordinary refractometer can be used. After measuring the entire refractive index, a three-dimensional refractive index measurement is performed using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments) at 23 ° C. and 55% RH at a wavelength of 590 nm. , Nx, ny, nz, and the thickness of the film is measured to determine the retardation R ₀ , R _t Ask for.
[0037]
The optically biaxial cellulose ester according to the present invention can be usually obtained by applying tension in a certain direction in the process of producing the cellulose ester by casting. For example, it is particularly effective to perform an operation such as stretching under the condition that a residual solvent is present after casting the cellulose ester film. When the film is stretched substantially in the width direction as in the present invention, a distribution may occur in the refractive index at the width. This may be particularly observed when the tenter method is used.However, when the film is stretched in the width direction, a contraction force is generated at the center of the film, and the edge is fixed. It is thought to be called. In the present invention, by mixing and using a plurality of cellulose esters, the desired R _t / R ₀ At the same time, the above-described bowing phenomenon can be suppressed.
[0038]
The cellulose ester used in the cellulose ester film of the present invention is obtained by using cellulose derived from cotton linter, wood pulp, kenaf, etc., and reacting them with acetic anhydride, propionic anhydride, or butyric anhydride by a conventional method. A cellulose having a degree of substitution of a hydroxyl group of cellulose with an acyl group (also referred to as a total degree of substitution) of 2.50 to 2.90 is used. Examples of the substituent of the acyl group include an acetyl group, a propionyl group, a butyryl group, and the like. It is preferably used. In the present invention, it is preferable to use a mixture of two or more types of cellulose esters contained in these ranges in order to achieve the object of the present invention.
[0039]
In order to obtain the cellulose ester film having the optical characteristics described in the formulas (1) and (2) according to claim 1, as one method, the degree of acyl group substitution is 2.50 to 2. And a mixture of two or more cellulose esters having a difference in the degree of substitution of the acyl group of at least 0.02. At this time, it is preferable to mix a cellulose ester having an acyl group substitution degree in the range of 2.50 to less than 2.70 and a cellulose ester in the range of 2.70 to 2.90.
[0040]
The total substitution degree of the cellulose ester having an acyl group substitution degree of 2.50 to 2.90 and an acetyl group and a propionyl group is 2.50 to 2.90, and the acetyl substitution degree is 1.40 to 2.90. It is preferred to mix cellulose esters containing cellulose acetate propionate in the range of 2.30.
[0041]
The addition ratio is preferably such that the cellulose ester having the lower total substitution degree is in the range of 5% by mass to 95% by mass, and from the viewpoint of the film strength and the mixing property of the dope at the time of in-line addition, is preferably 50% by mass or more and 100% by mass. It is more preferably less than 70% by mass and less than 100% by mass.
[0042]
When cellulose acetate propionate is contained, the content of cellulose acetate propionate is preferably from 60 to 100% by mass, and more preferably from 80 to 100% by mass for obtaining more desired optical characteristics.
[0043]
Here, the total degree of substitution (also referred to as the degree of substitution of an acyl group) of the cellulose ester according to the present invention will be described.
[0044]
The method for measuring the degree of substitution of the acyl group of the cellulose ester according to the present invention can be carried out according to ASTM D-817-96. The molecular weight of these cellulose esters is preferably in the range of 50,000 to 300,000 as the number average molecular weight, because the mechanical strength when formed into a film is strong. Further, 70,000 to 200,000 is preferable. Usually, the cellulose ester becomes a flake after the water washing treatment after the reaction or the like, and is used in the shape. However, the particle size hastens the solubility by setting the particle size in the range of 0.05 to 2.0 mm. This is preferable. In addition, when the particle size is small, the handling property in production deteriorates, and a granulation step may be performed for the purpose.
[0045]
(Production method of cellulose ester film)
The method for producing the cellulose ester film of the present invention will be described.
[0046]
As a method for producing a cellulose ester film, a dope solution is cast on a support, a film is formed, the obtained film is peeled off from the support, and then dried while being transported through a drying zone under tension. A solution casting film forming method is preferred. More preferably, two or more solutions each containing a cellulose ester having a different substituent or a different degree of substitution are mixed with an in-line mixer immediately before casting, to prepare a cellulose ester dope, and by a casting film forming method. It is preferable to form a film. Here, "before casting" means that the time from preparation of the dope solution to application is within one hour, but preferably within 30 minutes.
[0047]
The solution casting method will be described below.
(1) Dissolution step: This is a step of dissolving the flakes in an organic solvent mainly containing a good solvent for cellulose ester flakes in a dissolving vessel with stirring to form a cellulose ester solution (dope). The dissolution is carried out at normal pressure, at a temperature below the boiling point of the main solvent, at a pressure at or above the boiling point of the main solvent, M. G. FIG. Makromol. chem. 143, p. 105 (1971), and a cooling dissolution method of dissolving at a low temperature as described in JP-A-9-95544 and JP-A-9-95557, a method of high-pressure dissolution, and the like. There is a dissolution method. After dissolution, the dope is filtered with a filter medium, defoamed, and sent to the next step by a pump.
[0048]
(2) Casting step: The dope is fed to a pressurizing die through a pressurized metering gear pump and, at a casting position, an endless metal belt or a casting support for a rotating metal drum (hereinafter simply referred to as a casting support). This is a step of casting a dope from a pressure die onto a support. The surface of the casting support is a mirror surface. Other casting methods include a doctor blade method in which the thickness of the cast dope film is adjusted with a blade, and a method using a reverse roll coater in which the film is adjusted with a counter-rotating roll. A pressure die that can be formed and is easy to make the film thickness uniform is preferable. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used. In order to increase the film forming speed, two or more pressure dies may be provided on the casting support, and the doping amount may be divided to form an overlying layer.
[0049]
(3) Solvent evaporation step: a step of evaporating the solvent by heating the web (the web is referred to as a dope film after casting the dope on the casting support) on the casting support. . In order to evaporate the solvent, there are a method of blowing air from the web side and / or a method of transferring heat with liquid from the back surface of the support, a method of transferring heat from the front and back by radiant heat, and the like. Drying efficiency is good and preferable. A method of combining them is also preferable.
[0050]
(4) Peeling step: This is a step of peeling the web, on which the solvent has evaporated on the support, at the peeling position. The peeled web is sent to the next step. If the residual solvent amount (the following formula) of the web at the time of peeling is too large, it is difficult to peel the web, or conversely, if the web is sufficiently dried on the support and then peeled, a part of the web is peeled in the middle.
[0051]
As a method of increasing the film forming speed (the film forming speed can be increased because the film is peeled off while the amount of the residual solvent is as large as possible), there is a gel casting method (gel casting) that can peel even if the amount of the residual solvent is large. The film formation speed can be increased because the film is separated as much as possible.) Examples of the method include a method in which a poor solvent for the cellulose ester is added to the dope, gelling is performed after casting the dope, and a method in which the temperature of the support is lowered to gelate. There is also a method of adding a metal salt to the dope. By gelling on the support to strengthen the film, peeling can be accelerated and the film forming speed can be increased. If the residual solvent amount is greater at the time of peeling, if the web is too soft, the flatness at the time of peeling will be impaired, or the shear and vertical stripes due to the peel tension are likely to occur, and the amount of the residual solvent peeling will be reduced in consideration of economic speed and quality. I can decide.
[0052]
(5) Drying step: a step of drying the web using a drying device that alternately transports the web through rolls arranged in a staggered manner and / or a tenter device that transports the web by clipping both ends of the web with clips. In general, hot air is blown to both sides of the web as a drying means, but there is also a method of heating by applying a microwave instead of the wind. Too fast drying tends to impair the flatness of the finished film. Drying at a high temperature is preferably performed when the residual solvent is about 8% by mass or less. In general, the drying temperature is usually 40 to 250C, preferably 70 to 180C. The drying temperature, the amount of drying air, and the drying time vary depending on the solvent used, and the drying conditions may be appropriately selected according to the type and combination of the solvents used.
[0053]
In the drying step after peeling off from the surface of the casting support, the web tends to shrink in the width direction due to evaporation of the solvent. The quicker it dries at higher temperatures, the greater the shrinkage. Drying while suppressing this shrinkage as much as possible is preferable for improving the flatness of the resulting film. From this viewpoint, for example, a method of drying all the steps or a part of the steps as described in Japanese Patent Application Laid-Open No. Sho 62-46625 while holding both ends of the width of the web with clips in the width direction (tenter method) Is preferred.
[0054]
(6) Winding step: This is a step of winding the web as a film after the residual solvent amount becomes 2% or less by mass. By setting the amount of the residual solvent to 0.4% or less, a film having good dimensional stability can be obtained. As the winding method, a generally used method may be used, and there are a constant torque method, a constant tension method, a taper tension method, a program tension control method with constant internal stress, and the like.
[0055]
To adjust the thickness of the cellulose ester film, the dope concentration, the amount of liquid supplied by the pump, the slit gap of the die cap, the extrusion pressure of the die, and the speed of the casting support are controlled so that the desired thickness is obtained. Is good. Further, as means for making the film thickness uniform, it is preferable that the programmed feedback information is fed back to each of the above-mentioned devices using a film thickness detecting means for adjustment.
[0056]
In the process from immediately after casting through the solution casting film forming method to drying, the atmosphere in the drying apparatus may be air, or may be performed in an inert gas atmosphere such as nitrogen gas or carbon dioxide gas. . However, it is a matter of course that the danger of explosion must always be considered, for example, by setting the concentration of the evaporated solvent in the dry atmosphere outside the explosion limit.
[0057]
In the present invention, when the amount of the residual solvent in the film at the time of stretching is too small, stretching may not be performed, and there is a possibility that the film may be broken.On the contrary, if the amount is too large, a very large stretching ratio is required to obtain a desired retardation. , Special equipment may be required. Therefore, the amount of the residual solvent in the present invention is preferably less than 90% by mass.
[0058]
The cellulose ester produced by the solution casting film forming method according to the present invention is preferably stretched by heating. However, if the temperature of the web is too high, the plasticizer volatilizes, so the range of room temperature (15 ° C) to 160 ° C or less is preferable. In the present invention, it is more preferable that the film is stretched at a temperature of 110 to 160 ° C. because the optical characteristic distribution of the film width can be made uniform.
[0059]
Here, the amount of the residual solvent is determined by the following equation.
Residual solvent amount (% by mass) = {(M−N) / N} × 100
Here, M is the mass of the web at an arbitrary point, and N is the mass of M when dried at 110 ° C. for 3 hours.
[0060]
Although the method of stretching the web is not particularly limited, for example, a method in which a plurality of rolls are provided with a difference in peripheral speed, and a method of stretching in the longitudinal direction using the difference in roll peripheral speed therebetween, or both ends of the web are fixed with clips or pins Then, a method of extending the space between the clips and pins in the horizontal direction and stretching in the horizontal direction, that is, a so-called tenter method can be used. In the present invention, it is convenient and preferable to use a tenter method to stretch the cast so that the refractive index in the width direction of the cast finally becomes the maximum in the plane.
[0061]
The stretching ratio in the width direction is not limited in order to achieve the object of the present invention, but it is preferably from 1.05 to 2.0 times, and more preferably from 1.1 to 2.0, to exert the effect of the invention. 1.5 times.
[0062]
The film obtained as described above preferably has a residual solvent content of 2% by mass or less, more preferably 0.4% by mass or less in the final finished film, in order to obtain a film having good dimensional stability.
[0063]
In the stretched film, stress may remain inside and the dimensional change may occur in a high-humidity atmosphere. If this is directly adhered to a polarizing plate or the like, peeling over time becomes a problem. In the present invention, in order to prevent this peeling, it is useful to subject the cellulose ester film to some treatment in advance.
[0064]
As one method, there is a method of storing the rolled film which has been dried after being formed and wound up in a high-humidity state, a method of re-winding the film in another high-humidity state, and a method of combining them. In this case, since the optical characteristics immediately after the production are changed due to the shrinkage of the film, it is necessary to optimize the winding tension and the environmental temperature. The take-up tension is not particularly limited as long as the flatness of the taken-up film is maintained, but if it is too strong, the film stretches in the transport direction, while if it is too weak, a winding deviation occurs. Therefore, 30 to 200 N / m is preferable. The temperature is preferably equal to or lower than the glass transition temperature of the film. However, in order to alleviate the internal stress of the film, the higher the temperature, the shorter the processing time. From such a point, it is preferable that the temperature is in the range of 25 to 100 ° C.
[0065]
As another method, a similar effect can be obtained by providing a difference in peripheral speed between the front and rear rolls and providing a zone in which the roll span between the rolls is wider than usual in the drying zone in the film production process.
[0066]
Examples of the solvent for dissolving the cellulose ester to form a dope include methylene chloride, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolan, cyclohexanone, 2,2,2-trifluoroethanol, Examples thereof include 2,2,3,3-hexafluoro-1-propanol and 1,3-difluoro-2-propanol.
[0067]
Particularly, methylene chloride, methyl acetate, ethyl acetate, acetone and the like are preferably used. In particular, it is preferable that methyl acetate be contained in 50% or more of the total organic solvent.
[0068]
The cellulose ester dope used in the present invention preferably contains 1 to 30% by mass of an alcohol having 1 to 4 carbon atoms in addition to the above organic solvent. As a result, after casting the dope on the casting support, the solvent starts to evaporate, and when the proportion of alcohol increases, the web (dope film) gels, making the web strong and peeling off the casting support. And the effect of accelerating the dissolution of the cellulose ester in the organic solvent can be obtained. Examples of the alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol and tert-butanol. Of these, ethanol is preferred because it has good stability of the dope, a relatively low boiling point, good drying properties, and no toxicity.
[0069]
Usually, the solid content concentration of the dope is preferably 10 to 40% by mass, and the dope viscosity is preferably adjusted to the range of 10 to 50 Pa · sec from the viewpoint of obtaining good flatness of the film.
[0070]
As a mixing method for mixing two or more types of cellulose esters, two or more types of cellulose esters are introduced into the same container, and mixed and dissolved to prepare a dope. In addition, each cellulose ester can be dissolved in advance and mixed and cast in a pipe just before casting. In the present invention, in producing the optical compensation film, the optical characteristics can be controlled according to the characteristics of the optically anisotropic layer provided on the cellulose ester film, and the fluctuation of the optical characteristics caused by the material and the manufacturing conditions is adjusted. Therefore, it is preferable to mix them in a pipe. In that case, a conventional method such as an in-line mixer can be used. According to this method, when a change in the optical characteristics of the film caused by a difference in the production lot of the material is detected during the production, the optical characteristics of the obtained film are controlled by adjusting the mixing ratio of the cellulose ester. be able to. More preferably, the optical characteristics are measured continuously or intermittently in the film forming process, and the mixing ratio is changed and adjusted by feedback control.
[0071]
In the dope, a plasticizer, a matting agent, an ultraviolet absorption inhibitor, an antioxidant, a dye, and the like may be added.
[0072]
Since the cellulose ester having an acetyl group and a propionyl substituent used in the present invention itself exhibits an effect as a plasticizer, sufficient film properties can be obtained without adding a plasticizer or with a small addition amount. However, a plasticizer may be added for other purposes. For example, for the purpose of improving the moisture resistance of the film, alkylphthalylalkyl glycolates, phosphate esters, carboxylate esters, and the like can be mentioned.
[0073]
Examples of the alkylphthalylalkyl glycolates include, for example, methylphthalylmethyl glycolate, ethylphthalylethyl glycolate, propylphthalylpropyl glycolate, butylphthalylbutyl glycolate, octylphthalyloctyl glycolate, and methylphthalyl Ethyl glycolate, ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl phthalyl ethyl glycolate, propyl phthalyl butyl Glycolate, butylphthalylpropyl glycolate, methylphthalyloctyl glycolate, ethylphthalyloctyl glycolate, octylphthalylmethyl glycolate, octylphthalate Ethyl glycolate, and the like.
[0074]
Examples of the phosphate esters include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, phenyl diphenyl phosphate, octyl diphenyl phosphate, trioctyl phosphate, tributyl phosphate, and the like.
[0075]
Examples of the carboxylate include phthalates, citrates, and the like,
Examples of the phthalates include, for example, dimethyl phthalate, diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, and the like.
Examples of the citrates include acetyltriethyl citrate, acetyltriethyl citrate, and acetyltributyl citrate.
[0076]
In addition, butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, triacetin and the like are preferably used alone or in combination. Moreover, you may use a plasticizer in combination of 2 or more types as needed.
[0077]
The amount of the plasticizer used for this purpose is preferably from 1 to 30% by mass, particularly preferably from 4 to 18%, based on the cellulose ester.
[0078]
[Retardation increasing agent]
The retardation film of the present invention preferably contains a retardation increasing agent for adjusting retardation.
[0079]
The retardation increasing agent is preferably used in an amount of 0.01 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, and more preferably 0.1 to 10 parts by mass, based on 100 parts by mass of cellulose acetate. It is more preferably used in the range of 2 to 5 parts by mass, and most preferably used in the range of 0.5 to 2 parts by mass. Two or more retardation increasing agents may be used in combination. It is preferable that the retardation increasing agent has a maximum absorption in a wavelength region of 250 to 400 nm. It is preferable that the retardation increasing agent has substantially no absorption in the visible region.
[0080]
As the retardation increasing agent, it is preferable to use a compound having at least two 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). Aromatic heterocycles are generally unsaturated heterocycles. The aromatic hetero ring is preferably a 5-, 6-, or 7-membered ring, more preferably a 5- 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 the aromatic hetero ring include a furan ring, a thiophene ring, a pyrrole ring, an oxazole ring, an isoxazole ring, a thiazole ring, an isothiazole ring, an imidazole ring, a pyrazole ring, a furazane ring, a triazole ring, a pyran ring, and a pyridine ring. , Pyridazine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring. As the aromatic ring, a benzene ring, a furan ring, a thiophene ring, a pyrrole ring, an oxazole ring, a thiazole ring, an imidazole ring, a triazole ring, a pyridine ring, a pyrimidine ring, a pyrazine ring and a 1,3,5-triazine ring are preferable.
[0081]
The number of aromatic rings contained in the retardation increasing agent is preferably 2 to 20, more preferably 2 to 12, further preferably 2 to 8, and most preferably 2 to 6. preferable. The bonding relationship between two aromatic rings can be classified into (a) a case where a condensed ring is formed, (b) a case where they are directly connected by a single bond, and (c) a case where they are bonded via a linking group. , A spiro bond cannot be formed). The connection relationship may be any of (a) to (c).
[0082]
Examples of the condensed ring of (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, phenoxatiin ring, phenoxazine ring and thiant It includes emissions ring. A naphthalene ring, an azulene ring, an indole ring, a benzoxazole ring, a benzothiazole ring, a benzimidazole ring, a benzotriazole ring and a quinoline ring are preferred.
[0083]
The single bond in (b) is preferably a bond between carbon atoms of two aromatic rings. Two aromatic rings may be linked by two or more single bonds to form an aliphatic ring or a non-aromatic heterocyclic ring between the two aromatic rings.
[0084]
The linking group (c) is also preferably bonded to carbon atoms of two aromatic rings. The linking group is preferably an alkylene group, alkenylene group, alkynylene group, -CO-, -O-, -NH-, -S-, or a combination thereof. Examples of the linking group consisting of a combination are shown below. Note that the left and right relationships in the following examples of the linking group may be reversed.
[0085]
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-
The aromatic ring and the linking group may have a substituent. Examples of the substituent include a halogen atom (F, Cl, Br, I), hydroxyl, carboxyl, cyano, amino, nitro, sulfo, carbamoyl, sulfamoyl, ureido, alkyl, alkenyl, alkynyl, and aliphatic acyl. , Aliphatic acyloxy group, alkoxy group, alkoxycarbonyl group, alkoxycarbonylamino group, alkylthio group, alkylsulfonyl group, aliphatic amide group, aliphatic sulfonamide group, aliphatic substituted amino group, aliphatic substituted carbamoyl group, aliphatic It includes substituted sulfamoyl groups, aliphatic substituted ureido groups and non-aromatic heterocyclic groups.
[0086]
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 the alkenyl group 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 the alkynyl group include ethynyl, 1-butynyl and 1-hexynyl.
[0087]
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 alkoxy group preferably has 1 to 8 carbon atoms. The alkoxy group may further have a substituent (eg, an 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 alkoxycarbonylamino group preferably has 2 to 10 carbon atoms. Examples of the alkoxycarbonylamino group include methoxycarbonylamino and ethoxycarbonylamino.
[0088]
These compounds may be added together with the polymer or the solvent when preparing the solution, or may be added during or after the solution is prepared.
[0089]
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 sulfonamide group include methanesulfonamide, butanesulfonamide and n-octanesulfonamide. The aliphatic substituted amino group preferably has 1 to 10 carbon atoms. 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 aliphatic substituted ureido group preferably has 2 to 10 carbon atoms. Examples of the aliphatic substituted ureido group include methyl ureide. Examples of the non-aromatic heterocyclic group include piperidino and morpholino. The molecular weight of the retardation increasing agent is preferably from 300 to 800.
[0090]
[Other additives and auxiliary layer]
These compounds may be added together with the cellulose ester and the solvent when preparing the cellulose ester solution, or may be added during or after the solution is prepared.
[0091]
If the films are not slippery, the films may block each other, resulting in poor handling. In this case, the film according to the present invention may contain fine particles as described below.
[0092]
Fine particles of inorganic compounds include compounds containing silicon, silicon dioxide, aluminum oxide, titanium oxide, zirconium oxide, calcium carbonate, tin oxide, zinc oxide, barium sulfate, calcium sulfate, talc, clay, calcined kaolin, calcined calcium silicate Hydrated calcium silicate, aluminum silicate, magnesium silicate, calcium phosphate, and the like are preferable, and more preferably, an inorganic compound containing silicon or zirconium oxide is used. Silicon dioxide can reduce the turbidity of the cellulose ester laminated film. Is particularly preferably used.
[0093]
As organic fine particles, polymethacrylate methyl acrylate resin powder, acrylic styrene resin powder, polymethyl methacrylate resin powder, silicon resin powder, polystyrene resin powder, polycarbonate resin powder, benzoguanamine resin powder, melamine resin powder And polyolefin-based resin powder, polyester-based resin powder, polyamide-based resin powder, polyimide-based resin powder, and polyfluoroethylene-based resin powder, but are not particularly limited thereto.
[0094]
Fine particles such as silicon dioxide are preferably surface-treated with an organic substance because the haze of the film can be reduced. Preferred organic materials for the surface treatment include halosilanes, alkoxysilanes, silazanes, siloxanes, and the like. The larger the average diameter of the fine particles, the greater the matting effect, and the smaller the average diameter, the better the transparency. Therefore, the average diameter of the primary particles of the fine particles is preferably 5 to 50 nm, more preferably 7 to 20 nm. These fine particles are usually present in the film as agglomerates, and it is preferable to form irregularities of 0.01 to 1.0 μm on the film surface. Examples of the fine particles of silicon dioxide include AEROSIL 200, 200V, 300, R972, R972V, R974, R202, R812, OX50, and TT600 manufactured by Aerosil, and preferably AEROSIL 200V, R972V, R974, R202, R812, and the like. Is raised.
[0095]
The primary average particle diameter of these fine particles was measured using a transmission electron microscope (magnification: 500,000 to 2,000,000 times), the particles were observed, and 100 particles were observed. Let be the particle size.
[0096]
The content of the matting agent used for this purpose is preferably 0.005 to 0.3% by mass relative to the cellulose ester.
[0097]
If it is necessary to make the surface of the cellulose ester film on which the optically anisotropic layer is provided as smooth as possible, without intentionally adding fine particles to the film, a coating layer containing fine particles on the surface opposite to the optically anisotropic layer side By providing a back coat layer or the like, the slipperiness can be improved.
[0098]
In the cellulose ester film and the optical compensation film of the present invention, the dynamic friction coefficient between the front and back surfaces of a long film (support) wound on a roll is more preferably 1.0 or less, more preferably, 0.4 or less. Therefore, by adding fine particles to the long film (support), the dynamic friction coefficient between the front and back surfaces of the film can be made 0.4 or less. For this reason, the support may have a laminated structure having fine particles in at least one surface layer. Although the haze may be increased by the addition of fine particles, the support used in the present invention preferably has a haze of 1% or less, more preferably 0.5% or less, and particularly preferably 0.1% or less. The following is preferred.
[0099]
For example, by providing a layer containing fine particles on at least one surface of the support, two or more alignment layers and a polymerizable liquid crystal compound layer are provided on the support of the long roll film, and a desired alignment is provided. The optical compensatory sheet having the above can be provided.
[0100]
That is, by applying a coating composition containing fine particles on one surface of the support to form a back coat layer, the coefficient of friction can be reduced. Preferably, the back coat layer is applied before the polymerizable liquid crystal layer is provided.
[0101]
The back coat layer can be obtained by applying a coating solution in which fine particles are mixed and dispersed in a resin on one surface of the support.
[0102]
Examples of the fine particles contained in the back coat layer include fine particles of an inorganic compound and fine particles of an organic compound.
[0103]
The apparent specific gravity of the fine particles is preferably 70 g / l or more, more preferably 90 to 200 g / l, and particularly preferably 100 to 200 g / l. The higher the apparent specific gravity, the higher the concentration of the dispersion can be made.
[0104]
Silicon dioxide fine particles having an average primary particle diameter of 20 nm or less and an apparent specific gravity of 70 g / liter or more, for example, are obtained by burning a mixture of vaporized silicon tetrachloride and hydrogen at 1000 to 1200 ° C. in air. For example, they are commercially available under the trade names of Aerosil 200V and Aerosil R972V (all manufactured by Nippon Aerosil Co., Ltd.), and these can be used.
[0105]
As a dispersion method, the concentration of fine particles when fine particles such as silicon dioxide are mixed with a solvent or the like is preferably 5 to 30% by mass, more preferably 10 to 25% by mass, and most preferably 15 to 20% by mass. . The higher the dispersion concentration, the lower the liquid turbidity with respect to the amount added, which is preferable because haze and aggregates are improved.
[0106]
As the solvent to be used, lower alcohols preferably include methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol and the like. The solvent other than the lower alcohol is not particularly limited, but it is preferable to use a solvent used when forming a cellulose ester film.
[0107]
The amount of the fine particles to be added to the binder of the back coat layer is preferably 0.01 to 0.3 parts by mass, more preferably 0.05 to 0.2 parts by mass, and more preferably 0.08 to 0.3 parts by mass with respect to 100 parts by mass of the resin. 0.12 parts by weight is most preferred. The larger the added amount, the better the dynamic friction coefficient, and the smaller the added amount, the lower the haze and the smaller the agglomerates.
[0108]
As the disperser, an ordinary disperser can be used, and examples thereof include the media disperser and the medialess disperser described in the section of dispersion of silicon dioxide fine particles in cellulose ester. For dispersing silicon dioxide fine particles, a medialess disperser is preferred because it has a low haze. Specifically, the dispersing machine used for dispersing and adding the fine particles to the support described above can be used.
[0109]
Although the back coat layer also has an anti-blocking effect, it is desired that the back coat layer has an effect of preventing curling, particularly when an alignment film and a polymerizable liquid crystal layer are provided only on one surface of the support.
[0110]
The cellulose ester film of the present invention may have additives distributed in the thickness direction of the film depending on the purpose. In this case, co-casting can be used as a manufacturing method for providing a distribution.
[0111]
Co-casting is a simultaneous multilayer casting method in which two or more layers are merged in a die having two or more slits to form two or more layers, a sequential multilayer casting method in which two or more layers are formed through different dies, Any of the multilayer casting methods combining the simultaneous multilayer casting and the sequential multilayer casting may be used.
[0112]
By changing the amount of each additive in each dope, the distribution of the amount of the additive in the film thickness direction can be provided. The additive herein refers to the above-mentioned plasticizer, matting agent, ultraviolet absorber, antioxidant, dye and the like.
[0113]
In the case where the amount of the plasticizer has a distribution, it is preferable to increase the amount of the internal plasticizer, because it is possible to secure more excellent moisture permeability of the film and to suppress the scattering to the process. When the amount of the plasticizer at the center in the thickness direction is 100% by mass, the vicinity of the front and back surfaces of the film is preferably less than 100% by mass, more preferably 80 to 99% by mass. Here, the vicinity of the front and back surfaces means a region from the front surface to a depth of 5 μm.
[0114]
The same applies to the case of an ultraviolet absorber, and it is preferable to increase the amount of addition inside to suppress process contamination. When the amount of the ultraviolet absorber in the center in the thickness direction is 100% by mass, the vicinity of the front and back surfaces of the film is preferably less than 100% by mass, more preferably from 80% by mass to 99% by mass.
[0115]
While the matting agent is mainly effective in improving the handleability of the film and stabilizing the quality of the rolled film, the matting agent itself flows out due to a saponifying agent or the like at the time of laminating the polarizing plate, and the flatness associated therewith is deteriorated. It can be the cause. In addition, when the film thickness is reduced by stretching or the like, the matting agent is more likely to come out to the surface, which may adversely affect subsequent processes such as application and bonding. From such a viewpoint, in the present invention, it is preferable that the layer containing the matting agent is contained only on one of the surfaces. In particular, the effect is more exerted when the surface is opposite to the surface to be bonded to the polarizing plate or opposite to the surface on which the coating layer is formed. Further, since the matting agent is generally opaque spherical particles, there is a problem that the haze value becomes high when the matting agent is contained in a large amount in the whole film. However, it is effective that the haze value can be suppressed to a low level by including it on only one surface by this method.
[0116]
The cellulose ester film of the present invention can provide a long roll in which both ends are embossed. As a result, it is possible to remarkably reduce unevenness caused when an alignment film is provided on a long film wound into a roll or when a polymerizable liquid crystal compound is further applied.
[0117]
The width of the embossing is preferably 5 to 40 mm, more preferably 7 to 15 mm. It is preferable that embossing is applied to a portion of 0 to 50 mm from the end of the film, and the form of embossing is not limited, but the number of embossing to be processed in one place may be one or two or more. I don't care. It is particularly preferred that both ends are formed.
[0118]
The height of the embossing is preferably 2 to 80 μm, more preferably 5 to 50 μm, and particularly preferably 7 to 25 μm. If the embossing is too high, the end of the film is distorted, such as turbulence or swelling at the end of the roll. On the other hand, if it is too low, the effect of suppressing the disorder of the alignment becomes poor. It is preferable to adjust the height in the range of 1 to 25% of the thickness of the resin film.
[0119]
It is preferable that the ratio of the area of the portion observed as the projection of each embossed portion to the entire embossed portion is about 15 to 50%, and when the projection included in each of these portions is discontinuous, Number is 1cm ² The number is preferably about 10 to 30 pieces.
[0120]
The embossing can be usually performed by pressing an embossed ring with a stamp on the film on a back roll of metal, rubber, or the like. Although processing can be performed at room temperature, it is preferable to process at Tg + 20 ° C. or higher and melting point (Tm) + 30 ° C. or lower.
[0121]
The application of the anti-curl function is specifically performed by applying a composition containing a solvent that dissolves or swells the resin film substrate used as the support. As the solvent to be used, in addition to a solvent to be dissolved or a mixture of solvents to be swollen, a solvent that may not be further dissolved may be contained, and a composition and a coating amount in which these are mixed at an appropriate ratio depending on the curl degree of the resin film and the type of the resin. This is performed using
[0122]
When it is desired to increase the curl toward the back coat layer side, it is effective to increase the mixing ratio of the solvent for dissolving or swelling the solvent composition to be used, and to decrease the ratio of the solvent that does not dissolve. The mixing ratio is preferably (solvent to be dissolved or swellable) :( solvent not to be dissolved) = 10: 0 to 1: 9. Examples of the solvent contained in such a mixed composition that dissolves or swells the resin film substrate include, for example, benzene, toluene, xylene, dioxane, acetone, methyl ethyl ketone, N, N-dimethylformamide, methyl acetate, ethyl acetate, Examples include trichloroethylene, methylene chloride, ethylene chloride, tetrachloroethane, trichloroethane, chloroform, N-methylpyrrolidone, and 1,3-dimethyl-2-imidazolidinone. Examples of the solvent that does not dissolve include methanol, ethanol, n-propyl alcohol, i-propyl alcohol, and n-butanol, but the solvent is not particularly limited thereto.
[0123]
It is preferable to apply these coating compositions to the surface of the resin film using a gravure coater, dip coater, wire bar coater, reverse coater, extrusion coater, or the like, with a wet film thickness of 1 to 100 μm, and particularly preferably 5 to 30 μm. .
[0124]
Examples of the resin used for the back coat layer include a vinyl chloride / vinyl acetate copolymer, a vinyl chloride resin, a vinyl acetate resin, a copolymer of vinyl acetate and vinyl alcohol, and a partially hydrolyzed vinyl chloride / vinyl acetate copolymer. Vinyl, vinyl chloride / vinylidene chloride copolymer, vinyl chloride / acrylonitrile copolymer, ethylene / vinyl alcohol copolymer, chlorinated polyvinyl chloride, ethylene / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, etc. Copolymer or copolymer, nitrocellulose, cellulose acetate propionate, diacetylcellulose, triacetylcellulose, cellulose acetate resin such as cellulose acetate phthalate, cellulose acetate butyrate resin, maleic acid and / or acrylic acid Coalescing, Acrylate copolymer, acrylonitrile / styrene copolymer, chlorinated polyethylene, acrylonitrile / chlorinated polyethylene / styrene copolymer, methyl methacrylate / butadiene / styrene copolymer, acrylic resin, polyvinyl acetal resin, polyvinyl butyral resin, Rubber resins such as polyester polyurethane resin, polyether polyurethane resin, polycarbonate polyurethane resin, polyester resin, polyether resin, polyamide resin, amino resin, styrene / butadiene resin, butadiene / acrylonitrile resin, silicone resin, fluorine resin, poly Examples include, but are not limited to, methyl methacrylate, a copolymer of polymethyl methacrylate and polymethyl acrylate, and the like. Particularly preferred are cellulose resin layers such as diacetyl cellulose and cellulose acetate propionate.
[0125]
The back coat layer is desirably applied before applying an optically functional layer (alignment layer, polymerizable liquid crystal layer, etc.) on the opposite side of the resin film substrate. It can be applied later.
[0126]
An orientation layer can be provided on the cellulose ester film of the present invention by rubbing treatment or the like directly or via another layer.
[0127]
The rubbed alignment layer according to the present invention is disposed on a cellulose ester film, and is used for aligning and fixing the optically anisotropic layer applied thereon.
[0128]
Here, the material constituting the alignment layer will be described. Specific examples include the following resins, but are not limited thereto. For example, polyimide, polyamide imide, polyamide, polyether imide, polyether ether ketone, polyether ketone, polyketone sulfide, polyether sulfone, polysulfone, polyphenylene sulfide, polyphenylene oxide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyacetal , Polycarbonate, polyarylate, acrylic resin, polyvinyl alcohol, polypropylene, cellulose ester, epoxy resin, phenol resin and the like.
[0129]
For example, the alignment layer can be obtained by applying the above-mentioned alignment layer on the cellulose ester film of the present invention, drying the layer, and then performing a rubbing treatment.
[0130]
A polyimide film (preferably polyimide containing a fluorine atom) which is widely used as an alignment layer for aligning a liquid crystal compound is also preferable as the alignment film. This is obtained by applying a polyamic acid (for example, LQ / LX series manufactured by Hitachi Chemical Co., Ltd., SE series manufactured by Nissan Chemical Co., Ltd.), heat-treating, and then rubbing.
[0131]
For the rubbing treatment, a treatment method widely used as a liquid crystal alignment treatment step of an LCD can be used. That is, a method of rubbing the surface of the alignment film in a certain direction using paper, gauze, felt, rubber, nylon, polyester fiber, or the like can be used to obtain the alignment. In general, the rubbing is performed by using a cloth in which fibers having a uniform length and thickness are planted on average.
[0132]
(Optical anisotropic layer)
The optical anisotropic layer according to the present invention will be described.
[0133]
The optically anisotropic layer according to the present invention is provided on the alignment layer, and is formed by fixing the liquid crystal compound in an aligned state.
[0134]
The thickness of the optically anisotropic layer depends on the birefringence of the liquid crystal compound constituting the layer and the orientation of the liquid crystal compound, but the thickness is 0.2 to 5 μm, preferably 0.4 to 3 μm. It is. If the thickness of the optically anisotropic layer is thinner than this, it becomes difficult to obtain the desired optical anisotropy. On the other hand, if the optically anisotropic layer is thicker than the above-described range, the optical anisotropy is more than necessary and the viewing angle is changed. In many cases, the characteristics tend to deteriorate, and another problem is that the optical compensation film tends to curl.
[0135]
At least one optically anisotropic layer according to the present invention can be provided on a cellulose ester film support. Optical compensation films can also be provided to provide appropriate compensation for various liquid crystal display modes.
[0136]
Since the cellulose ester film of the present invention has special optical characteristics, a liquid crystal layer coated on the support can be used to produce a liquid crystal panel having sufficient viewing angle characteristics by using only one layer. As a result, The advantages in cost reduction and productivity are extremely large.
[0137]
Further, the optical compensation film of the present invention is arranged so as to sandwich the driving liquid crystal cell, and at least one film can be arranged on one or both surfaces of a pair of polarizers.
[0138]
Further, the optically anisotropic layer may be coated on the cellulose ester film of the present invention directly or via an alignment layer, may be provided with an adhesive layer, and may be provided on the polarizing plate protective film by the optical as described above. One coated with an anisotropic layer may be bonded to the cellulose ester film of the present invention.
[0139]
When the liquid crystal display device is a twisted nematic (TN) liquid crystal display device in particular, the liquid crystal display device is bonded to the surface closest to the TN type liquid crystal cell in a direction in which the surface of the cellulose ester film support of the optical compensation film comes into contact with the liquid crystal display device. The effect of the present invention is that the direction of the maximum refractive index in the plane of the cellulose ester film support of the compensation film is substantially perpendicular to the orientation direction of the nematic liquid crystal on the surface adjacent to the optical compensation film. Can be expressed. The term “substantially orthogonal” refers to 90 ° ± 5 °, preferably 90 ° ± 1 °.
[0140]
In the optically anisotropic layer according to the present invention, the average tilt angle of the aligned and fixed liquid crystal is preferably oblique when observed from the cross-sectional direction of the optically anisotropic layer, and the tilt angle is May be constant in the thickness direction, or the orientation angle may change in the thickness direction. The average tilt angle varies depending on the design of the display in order to compensate for the viewing angle of the display. However, it is preferable that the average tilt angle is 15 to 50 °, particularly when the display device is applied to a TN liquid crystal display device. The tilt angle of the liquid crystalline compound constituting the optically anisotropic layer more preferably changes in the thickness direction, and it is more effective in the present invention that the tilt angle changes by increasing or decreasing from the alignment film side. It is a target.
[0141]
In the present invention, the direction in which the direction of the maximum refractive index of the optically anisotropic layer is projected on the surface of the cellulose ester film support is preferably substantially equal to the ny direction of the cellulose ester film support. Here, “substantially equal to the ny direction” means that the angle between the axes in these two directions is within ± 2 °.
[0142]
The liquid crystalline compound according to the present invention will be described.
The liquid crystal compound as used herein is used for the purpose of fixing in an oriented state to form an optically anisotropic layer.
[0143]
The liquid crystal compound according to the present invention is not particularly limited as long as the liquid crystal compound can be oriented, and optical anisotropy is imparted by the orientation without light scattering in a visible light region.
[0144]
When the liquid crystal compound according to the present invention is a polymer liquid crystal, for example, Japanese Patent Nos. 2592694, 2687035, 2711585, and 2660601, JP-A-10-186356, and JP-A-10-206637. Compounds described in JP-A-10-333134 can be used, and those having optically positive birefringence are particularly preferable.
[0145]
As the liquid crystal compound other than the polymer liquid crystal, the liquid crystal compound according to the present invention generally includes a rod-shaped liquid crystal compound, preferably a liquid crystal compound having an optically positive birefringence, more preferably an unsaturated compound. Positive birefringent liquid crystalline compounds having an ethylenic group are preferred from the viewpoint of fixing the alignment, and examples thereof include, but are not particularly limited to, compounds having structures described in JP-A-9-281480 and JP-A-9-281481. .
[0146]
The structure of the liquid crystal compound according to the present invention is not particularly limited, but the orientation of the liquid crystal compound is fixed by a treatment using a chemical reaction or a temperature difference in a state where the liquid crystal molecules are oriented to express optical anisotropy. It is required to use it in the state where it was done.
[0147]
It is preferable that an alignment layer as described above is provided on a transparent resin substrate, and a liquid crystal compound is applied thereon to perform alignment processing. The alignment treatment of the liquid crystal compound is preferably performed at a temperature higher than the liquid crystal transition temperature, and is preferably performed at a temperature lower than the temperature at which the transparent resin substrate is not deteriorated. When the liquid crystalline compound according to the present invention is a polymer liquid crystal, it is preferable to perform a temperature treatment at a temperature equal to or higher than the glass transition temperature of the polymer liquid crystal in order to align the polymer liquid crystal.
[0148]
Further, a solution containing a liquid crystal compound and an organic solvent is prepared, and the solution is applied and dried to produce an optically anisotropic layer. It is also possible to perform an orientation treatment.
[0149]
When the liquid crystal compound according to the present invention is a liquid crystal polymer, examples of the compound structure include a main chain type liquid crystal polymer such as polyester, polyimide, polyamide, polyester, polycarbonate, and polyesterimide. Further, a side-chain type liquid crystalline polymer such as polyacrylate, polymethacrylate, polysiloxane, or polymalonate may be used.
[0150]
When a solution containing a liquid crystal compound is applied, the solvent is dried and removed after the application, so that a liquid crystal layer having a uniform film thickness can be obtained. The liquid crystal layer can fix the orientation of the liquid crystal by the action of heat or light energy or a chemical reaction using a combination of heat and light energy. In particular, a monomeric liquid crystal compound that is not a high-molecular liquid crystal compound generally has a low viscosity, and the orientation of the liquid crystal is liable to change due to heat externally. It can be fixed by performing a curing reaction by a radical reaction or the like.
[0151]
In the present invention, when the orientation of the liquid crystal compound is fixed, when an ethylenically unsaturated group is used as the polymerizable group, the use of a photopolymerization initiator increases the activity of the reaction, thereby increasing the curing time during production. Can be shortened. As an active ray for generating radicals for photopolymerization, an electron beam, an ultraviolet ray, a visible light ray, and an infrared ray (a heat ray) can be used as needed, but an ultraviolet ray is generally preferred.
[0152]
On the other hand, radical polymerization initiators for the polymerization reaction of ethylenically unsaturated groups include, for example, azobis compounds, peroxides, hydroperoxides, redox catalysts, such as potassium persulfate, ammonium persulfate, tert-butyl peroctoate, benzoyl Peroxide, isopropyl percarbonate, 2,4-dichlorobenzoyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, dicumyl peroxide, azobisisobutyronitrile, 2,2′-azobis (2-amidinopropane) Examples thereof include hydrochloride or benzophenones, acetophenones, benzoins, thioxanthones, and the like. Details of these are described in "Ultraviolet Curing System" General Technology Center, pp. 63-147, 1989. For polymerization of a compound having an epoxy group, allyldiazonium salt (hexafluorophosphate, tetrafluoroborate), diallyliodonium salt, group VIa allylonium salt (PF) may be used as a UV-activated cationic catalyst. ₆ , AsF ₆ , SbF ₆ Allylsulfonium salts having an anion such as
[0153]
When a curing reaction is performed by using a radical reaction, irradiation with the above-mentioned actinic ray under an atmosphere of an inert gas such as nitrogen or argon in order to avoid a delay of a polymerization reaction due to the presence of oxygen in the air requires a reaction time. This is preferable in that it can be cured with a reduced amount of light and a small amount of light.
[0154]
On the other hand, when the liquid crystal compound is a polymer liquid crystal, it is not necessary to fix the alignment of the liquid crystal by performing a curing reaction by the above chemical reaction. This is because when the polymer liquid crystalline compound exhibits a liquid crystal transition temperature in a temperature range where the cellulose ester film does not deteriorate due to heat, the polymer liquid crystal is applied on the alignment film, and then placed within the liquid crystal transition temperature range. After the alignment, the liquid crystal is cooled to a temperature lower than the glass transition temperature to maintain the alignment of the liquid crystal.
[0155]
When the glass transition temperature of the polymer liquid crystal is higher than the heat resistance temperature of the cellulose ester film, the alignment film is provided on another heat-resistant support, and the polymer liquid crystal is applied. It can be oriented by heating to a temperature higher than the transition temperature. This is allowed to cool to room temperature to fix the orientation of the polymer liquid crystal, and then transferred to the support of the present invention using an adhesive to form an optically anisotropic layer.
[0156]
The elution block layer used in the present invention will be described.
It is preferable to provide an elution block layer in order to improve the adhesion between the cellulose ester film support of the invention and the alignment layer and prevent the alignment from being hindered.
[0157]
The elution block layer is an optical layer in which the alignment layer or the liquid crystal compound is present from the cellulose ester film support due to the presence of the organic solvent when the alignment layer or the liquid crystal compound is coated as an organic solvent solution. This means that elution of any of the compounds constituting the cellulose ester film support into the anisotropic layer is suppressed. When an alignment layer or a liquid crystal compound layer is provided as a thin film, it is a preferable method to prepare and apply an organic solvent solution of these compounds. However, in particular, resins such as cellulose ester films often contain a plasticizer and other additives, and the dissolution thereof may hinder the alignment of the liquid crystal.
[0158]
For this reason, by providing a resin that is insoluble or hardly soluble in the above-mentioned organic solvent as an undercoat of the alignment layer, it is possible to suppress interlayer diffusion and interlayer mixing during coating. As the solute block layer, a water-soluble polymer or an active ray-curable resin is preferably used.
[0159]
Providing the cellulose ester film support of the present invention with an elution block layer containing a water-soluble polymer, for example, an organic acid group-containing polymer, is preferred from the viewpoint of improving the adhesiveness between the cellulose ester film support and the alignment layer. The benefits are large and effective.
[0160]
Examples of the organic acid group-containing polymer include a structure having an organic acid group in a polymer side chain, but are not particularly limited. Examples of the organic acid group include a -COOH group. Examples of such a compound are not particularly limited, and examples thereof include a structure represented by General Formula [1] or General Formula [2] described in JP-A-7-333436. The hydrogen of the —COOH group may be replaced by ammonia or an alkali metal cation (sodium cation, lithium cation). Examples of the monomer unit constituting the polymer having an organic acid group include acrylic acid, methacrylic acid, itaconic acid, maleic acid, and fumaric acid. Further, after increasing the molecular weight of maleic anhydride as a copolymerized monomer, the acid anhydride ring may be opened to obtain an organic acid group.
[0161]
Further, as a form of the elution block layer according to the present invention, there is an active ray-curable resin layer. Particularly, an ultraviolet curable resin is preferably used.
[0162]
Actinic radiation-curable resins are those having two or more polymerizable groups such as a polymerizable vinyl group, an allyl group, an acryloyl group, a methacryloyl group, an isopropenyl group, and an epoxy group. Those which form a network structure are preferred. Among these active groups, an acryloyl group, a methacryloyl group or an epoxy group is preferable from the viewpoint of polymerization rate and reactivity, and a polyfunctional monomer or oligomer is preferable. For example, UV-curable acrylurethane-based resins, polyester acrylate-based resins, epoxy acrylate-based resins, and polyol acrylate-based resins are preferably used.
[0163]
Examples of the ultraviolet curing resin include, for example, an ultraviolet curing acrylic urethane resin, an ultraviolet curing polyester acrylate resin, an ultraviolet curing epoxy acrylate resin, an ultraviolet curing polyol acrylate resin, and an ultraviolet curing epoxy resin. Can be done.
[0164]
UV-curable acrylic urethane-based resins are generally obtained by reacting a polyester polyol with an isocyanate monomer or a prepolymer, and further adding 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate (hereinafter acrylate includes methacrylate). These compounds can be easily obtained by reacting an acrylate monomer having a hydroxyl group such as 2-hydroxypropyl acrylate (for example, JP-A-59-151110).
[0165]
The UV-curable polyester acrylate resin can be easily obtained by generally reacting a polyester polyol with 2-hydroxyethyl acrylate or 2-hydroxy acrylate monomer (for example, JP-A-59-151112).
[0166]
Specific examples of the UV-curable epoxy acrylate resin include epoxy acrylate as an oligomer, a reactive diluent and a photoreaction initiator added thereto, and reacted (for example, Japanese Patent Application Laid-Open No. No. 105738). As the photoreaction initiator, one or more of a benzoin derivative, an oxime ketone derivative, a benzophenone derivative, a thioxanthone derivative and the like can be selected and used.
[0167]
Specific examples of the ultraviolet-curable polyol acrylate resin include trimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, and alkyl-modified dipentaerythritol pentaacrylate. And the like. These resins are usually used together with a known photosensitizer. Further, the above-mentioned photoreaction initiator can also be used as a photosensitizer. Specific examples include acetophenone, benzophenone, hydroxybenzophenone, Michler's ketone, α-amyloxime ester, thioxanthone, and the like, and derivatives thereof. When an epoxy acrylate-based photoreactive agent is used, a sensitizer such as n-butylamine, triethylamine, tri-n-butylphosphine and the like can be used. The photoreaction initiator or photosensitizer contained in the ultraviolet-curable resin composition excluding the solvent component that evaporates after coating and drying is particularly preferably 0.5 to 5% by mass of the composition.
[0168]
Known methods such as a gravure coater, a spinner coater, a wire bar coater, a roll coater, a reverse coater, an extrusion coater, and an air doctor coater can be used as a method for applying the ultraviolet curable resin composition coating liquid. The thickness of the actinic radiation-curable resin layer after curing is suitably from 0.05 to 30 μm, and preferably from 0.1 to 15 μm. If the dry film thickness is too small, the elution blockability decreases, and if the dry film thickness is too large, the film is apt to curl and handling becomes difficult.
[0169]
The coating solvent for the elution block layer will be described. It is an object of the present invention to select a solvent that hardly dissolves or an insoluble solvent as a coating solvent for the elution block layer, rather than an organic solvent that dissolves the resin or plasticizer constituting the cellulose ester film support. Preferred for
[0170]
As a solvent for coating the elution block layer according to the present invention, water, alcohols, ketones, esters, glycol ethers, and other solvents can be mixed and used. Examples of alcohols include methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, n-butanol, 2-butanol, tert-butanol, pentanol, 2-methyl-2-butanol, cyclohexanol and the like, and ketones Examples include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, and esters include methyl formate, ethyl formate, methyl acetate, ethyl acetate, isopropyl acetate, amyl acetate, ethyl lactate, and methyl lactate. And glycol ethers (C1 to C4) such as methyl cellosolve, ethyl cellosolve, propylene glycol monomethyl ether (PGME), propylene glycol monoethyl ether, propylene glycol Mono-n-propyl ether, propylene glycol monoisopropyl ether, propylene glycol monobutyl ether, or propylene glycol mono (C1-C4) alkyl ether esters, such as propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, and other solvents Examples include methylene chloride and N-methylpyrrolidone. It is not particularly limited to these.
[0171]
The higher the molecular weight of the resin in the elution block layer, the more preferable it is from the viewpoint of difficulty in diffusing into the alignment layer and the liquid crystal layer, and the number average molecular weight is preferably 800,000 or more.
[0172]
This elution block layer serves to prevent the dissolution of additives such as a plasticizer and an ultraviolet absorber from the cellulose ester film support, and also improves the adhesion between the support and the optically anisotropic layer or the alignment layer. It is also required to have a function of preventing peeling. For this purpose, it is effective to perform a plasma treatment on the cellulose ester film support. Performing the plasma treatment while transporting the cellulose ester film enables continuous treatment, and in particular, performing the treatment under a reactive gas atmosphere at atmospheric pressure without applying a vacuum does not affect the film surface. The above is preferable because the necessary reaction can be performed.
[0173]
The reactive gas is not particularly limited, but includes a rare gas, nitrogen, oxygen, hydrogen, carbon monoxide, carbon dioxide, nitrogen monoxide, nitrogen dioxide, hydrogen peroxide, ozone, and the like. In the present invention, the plasma processing is to use a plasma discharge, and to generate a plasma state by the discharge. Preferably, this is done by applying a voltage to at least two opposing electrodes.
[0174]
In the present invention, the processing system is a processing space in which plasma discharge is performed in the presence of the reactive gas, and specifically, a processing chamber which is separated by providing a partition with walls or the like. In the case of vacuum plasma discharge treatment performed at a pressure of 0.007 to 27 hPa close to vacuum in the processing chamber, it is necessary to adjust the introduction of the reactive gas. In order to increase the processing speed, it is necessary to increase the voltage applied to the electrode. However, if the electric field intensity is too high, the object to be processed may be damaged.
[0175]
Further, as another embodiment, in the case of atmospheric pressure plasma processing in which the pressure in the processing chamber is set at or near atmospheric pressure, an inert gas other than the reactive gas is introduced as a gas to be introduced into the processing chamber. Is preferable for generating a stable discharge. Atmospheric pressure or near atmospheric pressure means a pressure of 133 to 1064 hPa, preferably in the range of 931 to 1037 hPa.
[0176]
An inert gas is a gas that does not cause a reaction by plasma discharge, and includes an argon gas, a helium gas, a xenon gas, and a krypton gas. Among them, preferred gas is argon gas or helium gas. It is preferable that the inert gas introduced into the processing chamber during the atmospheric pressure plasma processing be adjusted to 90% or more from the viewpoint of stably generating discharge. When the applied voltage is high, the processing speed can be increased. However, care must be taken because if the electric field intensity is too high, the object to be processed will be damaged.
[0177]
However, even in the above-mentioned atmospheric pressure plasma processing, when generating plasma with a pulsed electric field, an inert gas is not necessarily required, and the concentration of a reactive gas in the processing system can be increased, Production efficiency can be increased.
[0178]
The polarizing plate of the present invention and the liquid crystal display device of the present invention using the polarizing plate will be described.
As the polarizer used for the polarizing plate of the present invention, a conventionally known polarizer can be used. For example, a film made of a hydrophilic polymer such as polyvinyl alcohol and stretched by treating with a dichroic dye such as iodine, or a film obtained by treating and orienting a plastic film such as vinyl chloride is used. The polarizer thus obtained is laminated with a cellulose ester film.
[0179]
Then, the polarizing plate is configured as a laminate of the optical compensation film of the present invention on at least one side of the polarizer, and in the case of only one side, the cellulose ester film support of the present invention in which the other surface is not coated with a liquid crystal layer or Other transparent supports or TAC (triacetate) films may be used.
[0180]
The polarizing plate thus obtained may be provided on one side of the liquid crystal cell or on both sides thereof. When provided on one side, the optical compensation film of the present invention can be attached to the polarizer closer to the liquid crystal cell to obtain the liquid crystal display device of the present invention.
[0181]
When the optical compensation film of the present invention is installed in a liquid crystal display device, an upper polarizer and a lower polarizer arranged above and below a pair of substrates located on both sides of a driving liquid crystal cell are usually configured. At least one optical compensation film of the present invention is provided between the substrate and one of the upper and lower polarizers, or between the substrate and the upper and lower polarizers. In order to effectively exhibit the object of the present invention, one optical compensation film of the present invention is provided between the polarizer on the observer side and the substrate on the drive cell side in the case of a display device. preferable.
[0182]
When the liquid crystal display device is a twisted nematic type (TN type) liquid crystal display device in particular, the optical compensation film is bonded to the substrate closest to the TN type liquid crystal cell in the direction in which the cellulose ester film support surface of the optical compensation film comes into contact. The effect of the present invention is that the maximum refractive index direction in the surface of the cellulose ester film support of the optical compensation film is bonded in a direction substantially orthogonal to the alignment direction of the nematic liquid crystal of the substrate closest to the liquid crystal cell. Can be expressed. The term “substantially orthogonal” refers to 90 ° ± 5 °, preferably 90 °.
[0183]
【Example】
Hereinafter, the present invention will be described with reference to examples. However, embodiments of the present invention are not limited thereto.
[0184]
Example 1
<< Preparation of cellulose ester films 1-1 to 1-7 >>
A dope was prepared as described below, and a cellulose ester film was prepared using the dope.
[0185]
(Preparation of dope)
Predetermined amounts of the following materials were mixed with the cellulose esters A and B having the substituents and the degree of substitution described in Table 1, and the mixture was placed in a closed container. The solution was heated to 45 ° C. and dissolved. The pressure in the vessel was adjusted to 1.2 atm. Azumi filter paper No. No. manufactured by Azumi Filter Paper Co., Ltd. After filtration using 244, the mixture was allowed to stand overnight to obtain a dope.
[0186]
100 parts by mass of cellulose ester A A and B in total
Cellulose ester B
Triphenyl phosphate 3 parts by mass
Methylphthalylethyl glycolate 4 parts by mass
Tinuvin 109 (manufactured by Ciba Specialty Chemicals) 3 parts by mass
455 parts by mass of methylene chloride
Ethanol 36 parts by mass
5 parts by mass of the following retardation enhancer
[0187]
Embedded image

[0188]
(Preparation of cellulose ester film)
The dope prepared as described above was cast from a die onto a stainless steel belt (also referred to as a casting support) at a dope temperature of 30 ° C. to form a web. After the web was dried for 1 minute on a stainless steel belt whose temperature was controlled by contacting warm water at a temperature of 25 ° C. from the back surface of the stainless steel belt, cold water of 15 ° C. was further contacted with the back surface of the stainless steel belt and held for 15 seconds. Thereafter, the web was peeled from the stainless steel belt. The residual solvent amount in the web at the time of peeling was 100% by mass.
[0189]
Next, both ends of the peeled web were gripped with clips using a tenter, and the film was stretched to a stretching ratio shown in Table 1 by changing the clip interval in the width direction. At that time, the film temperature was adjusted to 140 ° C. Thereafter, in the drying process, the winding tension was adjusted to 100 N / m by passing through the portion where the tension cutting device was introduced. In this way, cellulose ester films 1-1 to 1-7 each having a thickness of 60 μm were obtained.
[0190]
Each of the produced cellulose ester films 1-1 to 1-7 was wound around a glass fiber reinforced resin core having a core diameter of 200 mm into a film roll having a width of 1 m and a length of 1000 m by a taper tension method. At this time, an emboss ring at a temperature of 250 ° C. was pressed against the end of the film, and embossing was performed on both ends of the film to a width of 15 mm and a height of 10 μm to prevent adhesion between the films.
[0191]
<< Evaluation of optical properties of cellulose ester film >>
For each of the obtained cellulose ester films 1-1 to 1-7, a retardation value (R ₀ (Nm)), the retardation value in the thickness direction (R _t (Nm), R _t / R ₀ The measurement was performed using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments) under the environment of 23 ° C. and 55% RH to determine the refractive indices nx, ny, and nz at a wavelength of 590 nm. R ₀ And R _t Was calculated. The values of the average refractive index used for obtaining the refractive indexes nx, ny, and nz were measured in advance using an Abbe refractometer.
[0192]
R ₀ = (Nx-ny) × d
R _t = ((Nx + ny) / 2-nz) × d
Here, nx is the refractive index in the slow axis direction in the plane of the film, ny is the refractive index in the fast axis direction in the plane of the film, nz is the refractive index in the thickness direction of the film, and d is the thickness (nm) of the film. Respectively.
[0193]
Where R ₀ , R _t In the measurement, the measurement was carried out for each of the five widths, and their variation was evaluated. The five points are the center of the width (C) of the film, 200 mm left and right from the center (L1, R1), and 400 mm left and right from the center (L2, R2).
[0194]
Table 2 shows the obtained results.
[0195]
[Table 1]

[0196]
[Table 2]

[0197]
From the cellulose ester films 1-1 to 1-5 in Tables 1 and 2, by changing the mixing ratio of two types of cellulose esters having different degrees of substitution or different substituents, the optical properties (R ₀ , R _t , R _t / R ₀ Ratio) can be adjusted so as to fall within the ranges of the expressions (1) and (2), and the variation in optical characteristics can be reduced.
[0198]
Example 2
<< Preparation of cellulose ester films 2-1 to 2-6 >>
A dope was prepared as described below, and a cellulose ester film was prepared using the dope.
[0199]
(Preparation of dope)
Predetermined amounts of cellulose ester A, methyl acetate and acetone described in Table 3 were mixed, placed in a closed container having a double structure, and a refrigerant was introduced into the outer jacket while stirring slowly. This allowed the mixture in the inner vessel to cool to -70 ° C. The mixture was cooled for 30 minutes until it was cooled uniformly. The refrigerant in the jacket outside the closed container is discharged, and instead, hot water is introduced into the jacket. The contents were subsequently stirred and raised to 100 ° C. over 40 minutes. The inside of the container became 2.5 atm. While stirring, the temperature was lowered to 50 ° C., and the pressure was returned to normal pressure. Thereafter, the solution was subjected to Azumi Filter Paper No. Prepared by filtration using 244.
[0200]
On the other hand, a predetermined amount of the cellulose ester B shown in Table 3, ethyl acetate and acetone were mixed, and a dope 2 was prepared in the same manner.
[0201]
(Composition of dope 1)
20 parts by mass of cellulose ester A
Triphenyl phosphate 2 parts by mass
Ethylphthalylethyl glycolate 2 parts by mass
Tinuvin 109 (manufactured by Ciba Specialty Chemicals) 3 parts by mass
Methyl acetate 184 parts by mass
Ethanol 16 parts by mass
(Composition of Dope 2)
Cellulose ester B 80 parts by mass
Triphenyl phosphate 1 part by mass
Ethylphthalylethyl glycolate 2 parts by mass
Methyl acetate 184 parts by mass
Ethanol 16 parts by mass
5 parts by mass of the above retardation increasing agent
(Preparation of cellulose ester film)
For the cellulose ester films 2-1, 2-3 and 2-5 described in Table 3, dope 1 in which cellulose ester A is dissolved and dope 2 in which cellulose ester B is dissolved are mixed by an in-line mixer immediately before casting. And a cast film was prepared.
[0202]
Further, for the cellulose ester films 2-2, 2-4, and 2-6 described in Table 3, after casting the dope 1, 2 seconds, 10 seconds, and 30 seconds on the dope film, respectively. A casting film was formed using a so-called co-casting method in which the dope 2 was cast later.
[0203]
In the above casting film formation, the dope temperature immediately before casting is set to 30 ° C., and after casting to form a web, a stainless steel belt whose temperature is controlled by contacting hot water at a temperature of 25 ° C. from the back surface of the stainless belt. After the web was dried for 1 minute, cold water at 15 ° C. was brought into contact with the back surface of the stainless steel belt and held for 15 seconds, and then the web was peeled from the stainless steel belt. The residual solvent amount in the web at the time of peeling was 100% by mass.
[0204]
Next, both ends of the peeled web were gripped with clips using a tenter, and the film was stretched to a stretching ratio shown in Table 3 by changing the clip interval in the width direction. At that time, the film temperature (also referred to as a stretching temperature) was set to the temperature shown in Table 3, and the amount of the residual solvent in the film at the entrance of the stretching portion was changed by changing the conveying speed and the path length after peeling. Further, the film was dried while being conveyed with rollers, to obtain cellulose ester films 2-1 to 2-6 having a film thickness of 80 μm.
[0205]
For each of the obtained cellulose ester films 2-1 to 2-6, optical properties were evaluated in the same manner as described in Example 1. Table 4 shows the obtained results.
[0206]
The display of retardation variation and the like are in accordance with Table 2.
[0207]
[Table 3]

[0208]
[Table 4]

[0209]
From the cellulose ester films 2-1 to 2-6 in Tables 3 and 4, when the mixing ratio of the cellulose ester was set to A: B = 20: 80, the film formation such as the stretching temperature, the residual solvent amount, and the stretching ratio was performed. By changing the conditions, the optical properties (R ₀ , R _t , R _t / R ₀ ) Was adjusted to fall within the ranges of the above expressions (1) and (2).
[0210]
Further, from the production of the cellulose ester film 2-6, the optical properties (R) of the cellulose ester film obtained when using cellulose esters having different degrees of acetyl substitution and propionyl substitution are both used. ₀ , R _t , R _t / R ₀ Ratio) was adjusted so as to fall within the range of the above formulas (1) and (2).
[0211]
Example 3
<< Preparation of optical compensation film >>
Using the cellulose ester films 1-1 to 1-7 produced in Example 1, an optical compensation film was produced as follows.
[0212]
(Preparation of liquid crystal alignment layer)
Using the cellulose ester film as a support, a 1% by mass solution of linear alkyl-modified polyvinyl alcohol (MP203; manufactured by Kuraray Co., Ltd.) in water: methanol = 60: 40 (mass ratio) was prepared, and the dry film thickness was 0.2 μm. Was applied by an extrusion coating machine so that After drying with hot air at 80 ° C., a rubbing treatment was performed to form an alignment layer.
[0213]
(Production of Optical Compensation Films 3-1 to 3-7)
On the liquid crystal alignment layer prepared above, a coating solution having the following composition was applied using a wire bar # 5. Further, this was dried in a windless state at 55 ° C. for 30 seconds, then heat-treated at 75 ° C. for 30 seconds, purged with nitrogen at 98 kPa for 60 seconds, and then 450 mJ / cm under an oxygen concentration of 0.1%. ² A film cured by ultraviolet light was produced. Thus, optical compensation films 3-1 to 3-7 each having one optically anisotropic layer were obtained.
[0214]

[0215]
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[0216]
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[0219]
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[0218]
The optical compensation films 3-1 to 3-7 produced above were evaluated as follows.
<< Evaluation of dimensional stability of optical compensation film >>
The dimensions of the optical compensation film in a normal temperature and normal humidity atmosphere of 23 ± 3 ° C. and 55 ± 3% RH are Lmd (nm casting direction of cellulose ester) and Ltd (nm width direction of cellulose ester), respectively, and 80 ± 3 ° C. , 90 ± 3% RH in a high-temperature and high-humidity atmosphere for 24 hours, and when returned to the normal temperature and normal humidity atmosphere, the dimension in the casting direction of the cellulose ester is Hmd (nm), and the dimension in the width direction is Htd (nm). ), And the expansion ratios Smd and Std shown in the following formula were evaluated.
[0219]
Smd (%) = {(Hmd−Lmd) / Lmd} × 100
Std (%) = {(Htd−Ltd) / Ltd} × 100
Table 5 shows the obtained results.
[0220]
[Table 5]

[0221]
From Table 5, it is clear that the dimensional change of the optical compensation film of the present invention under high humidity conditions is smaller than that of the comparative examples other than the present invention.
[0222]
Example 4
<< Preparation of Polarizing Plates 4-1 to 4-7 >>
A polyvinyl alcohol film having a thickness of 120 μm was immersed in 100 parts by mass of an aqueous solution containing 1 part by mass of iodine and 4 parts by mass of boric acid, and stretched 4 times at 50 ° C. to produce a polarizer. On one surface of this polarizer, an 80 μm polarizing plate protective film (Konica Cat KC8UX (Konica) was immersed in a 2 mol / L sodium hydroxide aqueous solution at 60 ° C. for 2 minutes, washed with water, and dried at 100 ° C. for 10 minutes. ) Was bonded using a 5% aqueous solution of completely saponified polyvinyl alcohol with an adhesive, and the other surface was treated in the same manner with the optical compensation films 3-1 to 3-7 prepared in Example 3. I went and glued. In this case, the side having the optically anisotropic layer of the optical compensation film is set to the polarizer side, and the transmission axis of the polarizer is adjusted to the maximum refractive index of the support (cellulose ester film) of the optical compensation film using an acrylic adhesive. The polarizing plates 4-1 to 4-7 were obtained by laminating them in the same direction.
[0223]
(Evaluation of curling property of polarizing plate)
An environment of 23 ± 3 ° C. and 80 ± 3% RH was used, which was cut out at a size of 300 mm in the casting direction and 200 mm in the width direction from almost the center of the casting width at the time of producing the cellulose ester film of the polarizing plate. Table 6 shows the results obtained by measuring the rising height of the four corners of the polarizing plate a plurality of times (four to five times) and calculating the average value.
[0224]
[Table 6]

[0225]
From Table 6, it can be seen that the polarizing plate of the present invention can produce a polarizing plate with good curl characteristics, despite the different thicknesses of the cellulose ester films on the front and back surfaces, as compared to the comparative examples outside the present invention.
[0226]
Example 5
<< Production and evaluation of liquid crystal display device >>
A cellulose ester prepared by peeling off the optical compensation film and a pair of polarizing plates, which were previously bonded, of a 15-inch display Multi Sync LCD 1525J manufactured by NEC, and using the polarizing plate of Example 4 in Example 1 instead. The films were bonded with an adhesive so that the film was on the liquid crystal cell side. The transmission axes of the pair of polarizing plates were orthogonal.
[0227]
The viewing angles of the thus obtained liquid crystal panels (5-1 to 5-7) to which the optical compensation film of the present invention was bonded were measured by EZ-contrast manufactured by ELDIM. The viewing angle is defined as a range of the inclination angle from the normal direction to the panel surface where the contrast ratio between the white display and the black display of the liquid crystal panel is 10 or more, and is a value of the viewing angle obtained for each optical compensation film. .
[0228]
Table 7 shows the obtained results.
[0229]
[Table 7]

[0230]
From Table 7, it is clear that the liquid crystal display device of the present invention has an excellent viewing angle enlarging function as compared with Comparative Examples other than the present invention.
[0231]
Example 6
<< Preparation of cellulose ester film >>
As shown below, a dope was prepared, and then a cellulose ester film was produced.
[0232]
(Preparation of dope)
A predetermined amount of a cellulose ester having a lot number (A to E, F to J) described in Table 8 or 9 and the following materials are mixed, and the mixture is placed in a closed container. Warm up to 45 ° C. over 60 minutes to dissolve. The pressure in the vessel was adjusted to 1.2 atm. Azumi filter paper No. No. manufactured by Azumi Filter Paper Co., Ltd. After filtration using 244, the mixture was allowed to stand overnight to obtain a dope.
[0233]
(Composition of dope solution)
Cellulose ester (described in Tables 8 and 9) 100 parts by mass
Ethylphthalylethyl glycolate 4 parts by mass
Tinuvin 109 (manufactured by Ciba Specialty Chemicals) 3 parts by mass
455 parts by mass of methylene chloride
Ethanol 36 parts by mass
7 parts by mass of the retardation increasing agent
(Production of cellulose ester films 6-1 to 6-5 and 7-1 to 7-5)
The prepared dope was cast from a die onto a stainless steel belt at a dope temperature of 30 ° C. to form a web. After the web was dried for 1 minute on a stainless steel belt whose temperature was controlled by contacting hot water at a temperature of 25 ° C. from the back surface of the stainless steel belt, cold water of 15 ° C. was further contacted with the back surface of the stainless steel belt and held for 15 seconds. Thereafter, the web was peeled from the stainless steel belt. The residual solvent amount in the web at the time of peeling was 100% by mass.
[0234]
However, for the cellulose ester films 6-4, 6-5, 7-4, and 7-5 to which in-line addition was performed, production of the cellulose ester films 2-1, 2-3, and 2-5 described in Example 2 was performed. In-line addition was performed in the same manner as described above.
[0235]
Next, both ends of the peeled film were gripped with clips using a tenter, and the film was stretched to a stretch ratio of 1.15 times by changing the clip interval in the width direction. The film temperature at that time was 140 ° C. or 160 ° C. Thereafter, in the drying process, the sheet was passed through the portion where the tension cutting device was introduced, and the winding tension was adjusted to 100 N / m. Thus, cellulose ester films 6-1 to 6-5 and 7-1 to 7-5 having a thickness of 40 μm were obtained. The optical properties of the obtained cellulose ester film were evaluated in the same manner as described in Example 1.
[0236]
Tables 8 and 9 show the obtained results.
[0237]
[Table 8]

[0238]
[Table 9]

[0239]
From Tables 8 and 9, it was found that R by in-line blending was as follows. _t / R ₀ Gained knowledge about the adjustment of
[0240]
<< R by in-line blending _t / R ₀ About adjustment of
R of each of the cellulose ester films 6-1 to 6-3 in Table 8 _t / R ₀ Value, R of each of the cellulose ester films 7-1 to 7-3 in Table 9 _t / R ₀ As can be seen from the values, the R of the cellulose ester film obtained by stretching after casting film formation was obtained. _t / R ₀ It can be seen that the optical properties of the obtained cellulose ester films are not always the same and vary little by little depending on the lot of the cellulose ester used at the time of production, even when the materials having the same degree of substitution are used.
[0241]
Due to such lot fluctuation, R _t / R ₀ In order to cope with the adjustment of the values, as shown in 6-8 and 6-5 in Table 8, two types of cellulose esters B and D, and C and E were in-line blended to obtain R. _t / R ₀ Can be adjusted.
[0242]
Similarly, as shown in the cellulose ester films 7-4 and 7-5 in Table 9, two types of cellulose esters G and I, and H and J were in-line blended to obtain the R of the cellulose ester film 7-1. _t / R ₀ It could be adjusted to (1.8).
[0243]
As described above, in the present invention, by mixing in-line cellulose ester dopes having different degrees of substitution, R _t / R ₀ Was controlled so as to minimize the fluctuation of the value, thereby preventing the variation.
[0244]
Example 7
Using the dope used in 1-1, 1-2, 1-3, 1-6, and 1-7 of Example 1, the stretching temperature of the tenter was set to 160 ° C., the stretching ratio was set to 1.5 times, and the film thickness was set. Was set to 40 μm, and cellulose ester films 8-1, 8-2, 8-3, 8-6, and 8-7 were produced in the same manner as in Example 1. Table 10 shows the optical characteristics of the obtained film. The display of retardation variation and the like are in accordance with Table 2.
[0245]
[Table 10]

[0246]
8-1, 8-2, and 8-3 had good optical characteristics with little variation in retardation. 8-6 and 8-7 had a large variation in retardation, and had insufficient quality as a retardation film. Also, during the film formation of 8-1, 8-2, and 8-3, no breakage occurred in the tenter, but during the formation of 8-6, 8-7, breakage frequently occurred in the tenter. And the productivity was poor.
[0247]
【The invention's effect】
According to the present invention, it has a specific in-plane retardation and a ratio of thickness direction retardation to in-plane retardation, and has a small variation in retardation over the entire product width, excellent viewing angle characteristics, and furthermore, breakage during tenter stretching. An infrequent retardation film, a method for producing the same, an optical compensation film, a polarizing plate, and a liquid crystal display device can be provided.

Claims (13)

Nx>ny> nz, wherein at least two kinds of cellulose esters having a degree of acyl group substitution of at least 2.50 selected from cellulose esters having a degree of substitution of 2.50 to 2.90. And a retardation film that satisfies the relationship of the following formulas (1) and (2).
Formula (1) 2.5 <R _t / R ₀ ≦ 20
Formula (2): 20 nm ≦ R ₀ ≦ 70 nm
Where R ₀ = (nx−ny) × d
R _t = {(nx + ny) / 2−nz} × d
(Where nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, nz is the refractive index in the film thickness direction, and d is the film thickness (nm). .) Cellulose acetate having a degree of acetyl substitution of 2.50 to 2.90 and cellulose acetate propionate satisfying the following formulas (3) and (4) when the degree of acetyl substitution is A and the degree of propionyl substitution is B: The retardation film according to claim 1, wherein:
Formula (3) 2.50 ≦ (A + B) ≦ 2.90
Formula (4) 1.40 ≦ A ≦ 2.30 The cellulose ester A having a degree of acyl group substitution of 2.70 to 2.90 and a cellulose ester B having a degree of acyl group substitution of 2.50 to less than 2.70 are produced by mixing. Item 7. The retardation film according to Item 1. The retardation film according to any one of claims 1 to 3, wherein the content of cellulose acetate propionate in the entire cellulose ester is 60% or more by mass ratio. The composition according to any one of claims 1 to 4, comprising two or more kinds of cellulose acetate propionates having different degrees of substitution, and having an average degree of substitution satisfying the formulas (3) and (4). 3. The retardation film according to item 1. The retardation film according to any one of claims 1 to 5, wherein the retardation film contains an aromatic compound having at least two aromatic rings in an amount of 0.01 to 20% by mass relative to the polymer. The retardation film according to any one of claims 1 to 5, wherein the retardation film contains an aromatic compound having at least one 1,3,5-triazine ring. In producing the retardation film according to any one of claims 1 to 7, a web is formed by casting a resin solution containing a solvent on a support to form a web, and peeling the web from the support. Drying the web to reduce the amount of residual solvent in the web to less than 100% by mass, and then stretching the web while maintaining the temperature of the web in the range of 110 to 160 ° C. . Immediately before casting, two or more solutions having different substituents or containing cellulose esters having different degrees of substitution are mixed with an in-line mixer to prepare a cellulose ester dope and form a film by a casting film forming method. The method for producing a retardation film according to claim 8, wherein: 9. The method according to claim 8, wherein two or more kinds of solutions having different degrees of substitution or containing cellulose esters having different substituents are simultaneously or sequentially cast on a support to form a film. A method for manufacturing a retardation film. A retardation film according to any one of claims 1 to 7, and an optically anisotropic layer in which the orientation of a liquid crystal compound is fixed directly or via another layer on the retardation film. An optical compensation film, which is provided. A polarizing plate comprising the optical compensation film according to claim 11. A liquid crystal display device comprising the polarizing plate according to claim 12.