JP2004083657A - Cellulose acylate film and polarizing plate using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prepare a cellulose acylate film which has excellent optical properties, no foreign matter, no stain, an excellent haze value and sufficient tear strength, and to provide a polarizing plate having excellent degree of polarization and durability. <P>SOLUTION: In the cellulose acylate film produced by a solution casting film-forming method, the cellulose acylate film is obtained by casting a cellulose acylate dope composition comprising a polymerizable monomer and/or a functional group-containing polymerizable monomer and a photopolymerization initiator and photopolymerizing the monomer during or after drying and has ≥10 μm and <30 μm thickness. The polarizing plate is obtained by using the cellulose acylate film. <P>COPYRIGHT: (C)2004,JPO

Description

【００３８】
【化２】

【００３９】
【化３】

【００４０】
【化４】

【００４１】
【化５】

【００４２】
【化６】

【００４３】
【化７】

【００４４】
＜光ラジカル重合開始剤＞
本発明に有用な光重合開始剤としては、エチレン性不飽和モノマーがウェブ中で光重合し得る開始剤であれば制限なく使用できるが、これらの光重合開始剤は公知のものを使用し得る。また光増感剤も使用出来る。具体的には、ベンゾインメチルエーテル、ベンゾイン−ｎ−プロピルエーテル、ベンゾイン−ｎ−ブチルエーテル、ベンゾインシリルエーテル、メチルベンゾインホルメート、ベンジル、ベンゾフェノン、ヒドロキシベンゾフェノン、ｐ−メチルベンゾフェノン、α−ヒドロキシイソブチルフェノン、ｐ−イソプロピル−α−ヒドロキシイソブチルフェノン、アセトフェノン、ミヒラーズケトン、α，α′−ジクロロ−４−フェノキシアセトフェノン、１−ヒドロキシ−１−シクロヘキシルアセトフェノン、２，２−ジメトキシ−２−フェニルアセトフェノン、ジアセチル、エオシン、チオニン、２−メチル−１−〔４−（メチルチオ）フェニル〕−２−モルホリノプロペン、ジクロロチオキサントン、ジイソプロピルチオキサントン、フェニルジスルフィド−２−ニトロソフルオレン、ブチロイン、アニソインエチルエーテル、ジ−ｔ−ブチルパーオキシド、ベンゾイルチアゾリルスルフィド、α−アミロキシムエステル、アゾビスイソブチロニトリル、テトラメチルチウラムジスルフィド等を挙げることができる。本発明において、セルロースアシレートドープ組成物中にエチレン性不飽和モノマーと共に光重合開始剤を混合する場合、セルロースアシレートに対してエチレン性不飽和モノマーを５〜３０質量％、また光重合開始剤をエチレン性不飽和モノマーに対して１〜３０質量％程度加えるのがよい。本発明においては、光重合性のエチレン性不飽和モノマーをセルロースアシレートドープ組成物流延後、有機溶媒を多く含むウェブにおいても、またかなり乾燥が進んでいてもウェブ内で光重合を起こさせることができるが、金属支持体上で、紫外線を照射して重合させるのが好ましい。
【００４５】
本発明のエチレン性不飽和モノマーと光重合開始剤を含有するセルロースアシレートドープ組成物に二つのエチレン性不飽和基を有する架橋性モノマーを含有させることにより、光重合後、しなやかさと強靱性を兼ね備えたセルロースアシレートフィルムを得ることが出来る。この二つのエチレン性不飽和基を有する架橋性モノマーとしては、ポリエステルジ（メタ）アクリレート、ポリウレタンジ（メタ）アクリレート等を挙げることができる。市販品として、東亜合成社製のウレタンアクリレート（商品名、Ｍ−１３１０）があり、好ましく用いることができる。
【００４６】
これらのポリエステルまたはポリウレタンのジ（メタ）アクリレートは、数平均分子量として、６，０００〜１００，０００、好ましくは１，０００〜８０，０００のものである。
【００４７】
（３員又は４員環状エーテル類）
本発明のセルロースアシレート上に塗布される重合性モノマー又は重合性化合物の別の一例は３員又は４員環の環状エーテル基を有する化合物である。ここで、３員環の環状エーテル基を有する化合物としてはエポキシ基を有する化合物が挙げられ、又、４員環の環状エーテル基を有する化合物としては、オキセタニル基を有する化合物が挙げられる。前記の環状エーテル基を有する化合物としては、エポキシ基を有する化合物、特に脂環式エポキシ基を有する化合物が反応性が高い点で好ましい。
以下の説明において、３員又は４員環の環状エーテル基を有する化合物の説明において、エポキシ基を有する化合物を例に挙げて説明するが、本発明はオキセタニル基を有する化合物にも容易に拡張できるものである。
これらのエポキシ基を有する化合物もウェブ内で光重合させることができ、でき上がったフィルムに可塑性を付与することができる。エポキシ基を有する化合物としては、通常接着剤等に使用し得るものを使用することができる。本発明に有用なエポキシ基を有する化合物を例示すると、芳香族エポキシ化合物（多価フェノールのポリグリシジルエーテル）としては、水素添加ビスフェノールＡまたはビスフェノールＡとエピクロルヒドリンとの反応物のグリシジルエーテル、エポキシノボラック樹脂（例えば、クレゾールノボラックポリグリシジルエーテル、フェノールノボラックポリグリシジルエーテル）、レゾールエポキシ樹脂、レゾルシノールジグリシジルエーテル等が挙げられ、又、脂肪族エポキシ樹脂としては、脂肪族多価アルコールまたはそのアルキレンオキサイド付加物のポリグリシジルエーテル、脂肪族長鎖多塩基酸のポリグリシジルエステル、グリシジルアクリレートやグリシジルメタクリレートのホモポリマー、コポリマーなどがあり、その代表例としては、エチレングリコールジグリシジルエーテル、プロピレングリコールジグリシジルエーテル、ジエチレングリコールジグリシジルエーテル、ジプロピレングリコールジグリシジルエーテル、トリプロピレングリコールグリシジルエーテル、１，４−ブタンジオールジグリシジルエーテル、１，６−ヘキサンジオールジグリシジルエーテル、ノナプロピレングリコールジグリシジルエーテル、ネオペンチルグリコールジグリシジルエーテル、グリセリントリグリシジルエーテル、ジグリセロールトリグリシジルエーテル、ジグリセロールテトラグリシジルエーテル、トリメチロールプロパントリグリシジルエーテル、ペンタエリスリトールトリグリシジルエーテル、ペンタエリスリトールテトラグリシジルエーテル、ソルビトールのポリグリシジルエーテル、脂環式エポキシ化合物、例えば、３，４−エポキシシクロヘキシルメチル−３′，４′−エポキシシクロヘキサンカルボキシレート、２−（３，４−エポキシシクロヘキシル−５，５−スピロ−３′，４′−エポキシ）シクロヘキサン−メタ−ジオキサン、ビス（３，４−エポキシシクロヘキシルメチル）アジペート、ビニルシクロヘキセンジオキサイド、ビス（３，４−エポキシ−６−メチルシクロヘキシルメチル）アジペート、３，４−エポキシ−６−メチルシクロヘキシル−３′，４′−エポキシ−６−メチルシクロヘキサンカルボキシレート、メチレンビス（３，４−エポキシシクロヘキサン）ジシクロペンタジエンジエポキサイド、エチレングリコールのジ（３，４−エポキシシクロヘキシルメチル）エーテル、エチレンビス（３，４−エポキシシクロヘキサンカルボキシレート）、ジシクロペンタジエンジエポキサイド、トリス（２−ヒドロキシエチル）イソシアヌレートのジグリシジルエーテル、トリス（２−ヒドロキシエチル）イソシアヌレートのトリグリシジルエーテル、ポリグリシジルアクリレート、ポリグリシジルメタクリレート、グリシジルアクリレートまたはグリシジルメタクリレートと他のモノマーとの共重合物、ポリ−２−グリシジルオキシエチルアクリレート、ポリ−２−グリシジルオキシエチルメタクリレート、２−グリシジルオキシエチルアクリレート、２−グリシジルオキシエチルアクリレートまたは２−グリシジルオキシエチルメタクリレートと他のモノマーとの共重合物、ビス−２，２−ヒドロキシシクロヘキシルプロパンジグリシジルエーテル等を挙げることができ、２種以上組み合わせて使用することができる。本発明においては、上記の例示化合物に限定されず、これらから類推される化合物も含むものである。
【００４８】
また、本発明において、エポキシ基を分子内に２つ以上有する化合物以外に、モノエポキサイドも所望の性能に応じて配合して使用することができる。
【００４９】
本発明における紫外線重合性のエポキシ基を有する化合物は、ラジカル重合反応によるのではなく、カチオン重合反応により重合物、架橋構造物または網目構造物を形成する。ラジカル重合と異なり反応系中の酸素に影響を受けないため誘導期間がなく重合を速く行うことができる。
【００５０】
以下に本発明において使用できるエポキシ基を有する化合物又はオキセタニル基を有する化合物の代表例を例示するが、これらに限定されるものではない。
【００５１】
【化８】

【００５２】
【化９】

【００５３】
＜光カチオン重合開始剤＞
本発明に有用なエポキシ基を有する化合物は、紫外線照射によりカチオン重合を開始する物質を生成する化合物が触媒になってカチオン重合反応が進行する。紫外線照射によりカチオン重合を開始するものとしてはルイス酸を放出するオニウム塩の複塩の一群が特に好ましい。
【００５４】
かかる代表的なものは下記一般式（Ｉ）で表される化合物である。
一般式（Ｉ）
〔（Ｒ^１）_ａ（Ｒ^２）_ｂ（Ｒ^３）_ｃ（Ｒ^４）_ｄＺ〕^＋ｗ〔ＭｅＸｖ＋ｗ〕^−ｗ
ここで、式中、カチオンはオニウムであり、ＺはＳ、Ｓｅ、Ｔｅ、Ｐ、Ａｓ、Ｓｂ、Ｂｉ、Ｏ、ハロゲン（例えばＩ、Ｂｒ、Ｃｌ）、またはＮ＝Ｎ（ジアゾ）であり、Ｒ^１ _ａ、Ｒ^２ _ｂ、Ｒ^３ _ｃ、Ｒ^４ _ｄは同一であっても異なっていてもよい有機の基である。ａ、ｂ、ｃ、ｄはそれぞれ０〜３の整数であって、ａ＋ｂ＋ｃ＋ｄはＺの価数に等しい。Ｍｅはハロゲン化物錯体の中心原子である金属または半金属（ｍｅｔａｌｌｏｉｄ）であり、Ｂ、Ｐ、Ａｓ、Ｓｂ、Ｆｅ、Ｓｎ、Ｂｉ、Ａｌ、Ｃａ、Ｉｎ、Ｔｉ、Ｚｎ、Ｓｃ、Ｖ、Ｃｒ、Ｍｎ、Ｃｏ等である。Ｘはハロゲンであり、ｗはハロゲン化錯体イオンの正味の電荷であり、ｖはハロゲン化錯体イオン中のハロゲン原子の数である。
【００５５】
上記一般式（Ｉ）の陰イオン〔ＭｅＸｖ＋ｗ〕^−ｗの具体例としては、テトラフルオロボレート（ＢＦ_４ ⁻）、ヘキサフルオロホスフェート（ＰＦ_６ ⁻）、ヘキサフルオロアンチモネート（ＳｂＦ_６ ⁻）、ヘキサフルオロアルセネート（ＡｓＦ_６ ⁻）、ヘキサクロロアンチモネート（ＳｂＣｌ_６ ⁻）等を挙げることができる。
【００５６】
更に一般式ＭＸｎ（ＯＨ）−の陰イオンも用いることができる。また、その他の陰イオンとしては過塩素酸イオン（ＣｌＯ_４ ⁻）、トリフルオロメタンスルホン酸イオン（ＣＦ_３ＳＯ_３ ⁻）、トルエンスルホン酸イオン、ナフタレンスルホン酸イオン、トリニトロベンゼンカルボン酸陰イオン等を挙げることができる。
【００５７】
このようなオニウム塩の中でも特に芳香族オニウム塩をカチオン重合開始剤として使用するのが、特に有効であり、中でも特開昭５０−１５１９９６号、同５０−１５８６８０号公報等に記載の芳香族ハロニウム塩、特開昭５０−１５１９９７号、同５２−３０８９９号、同５９−５５４２０号、同５５−１２５１０５号公報等に記載のＶＩＡ族芳香族オニウム塩、特開昭５６−８４２８号、同５６−１４９４０２号、同５７−１９２４２９号公報等に記載のオキソスルホキソニウム塩、特公昭４９−１７０４０号公報等に記載の芳香族ジアゾニウム塩、米国特許第４，１３９，６５５号明細書等に記載のチオピリリウム塩等が好ましい。また、アルミニウム錯体や光分解性ケイ素化合物系重合開始剤等を挙げることが出来る。上記カチオン重合開始剤と、前記ベンゾフェノン及びその誘導体、前記ベンゾイン及びその誘導体、前記チオキサントン及びその誘導体等の光増感剤を併用することができる。この増感剤は近紫外線領域から可視光線領域に吸収極大のあるものが好ましい。
以下に、芳香族オニウム塩のカチオン重合開始剤を例示する。
【化１０】

【００５８】
本発明において、セルロースアシレートドープ中にエポキシ基を有する化合物と共に光重合開始剤及び／または光増感剤を混合する場合、セルロースアシレートに対してエポキシ基を有する化合物が５〜３０質量％、また光重合開始剤がエポキシ基を有する化合物に対して１〜３０質量％、好ましくは１〜１０質量％である。
【００５９】
本発明に有用なエポキシ基と紫外線吸収剤を有する化合物を光重合開始剤と混合してドープとしてもよいし、エポキシ基を有する化合物と共に混合してドープとしてもよい。
【００６０】
本発明に有用なエポキシ基と紫外線吸収性基を有する化合物の紫外線吸収性基としては、ベンゾトリアゾール基、サリチル酸エステル基、ベンゾフェノン基、オキシベンゾフェノン基、シアノアクリレート基等を挙げることができ、本発明においては何れも好ましく用いることができる。特に光反応性が少なく、且つ殆ど着色のないベンゾトリアゾール基が好ましい。
【００６１】
本発明に係るエポキシ基と紫外線吸収性基を有する化合物を含有するセルロースアシレートドープを溶液流延製膜過程において製膜し、紫外線照射したウェブからは、紫外線吸収剤が析出あるいは揮発することがないため生産性よく、品質に優れた液晶画像表示装置用の偏光板用保護フィルムを得ることができる。また、このエポキシ基と紫外線吸収性基を有する化合物のポリマーが前記の如くセルロースアシレートに対して耐水性を合わせ持つことがより好ましく、ポリマーのＴｇを５０℃以下とすることが好ましい。
【００６２】
本発明における光重合したポリマーを構成する紫外線吸収性基を有する化合物単位の割合は、ポリマーのセルロースアシレートとの相溶性、セルロースアシレートフィルムの機械的性質または物理的性質が同等またはそれ以上の性質、あるいは十分な紫外線吸収性能を有するのであれば、如何なるものであってもよい（１〜１００質量％の範囲でよい）。
【００６３】
本発明において、セルロースアシレートドープ中にエポキシ基を有する化合物と共に光重合開始剤（場合によっては光増感剤も）を混合するが、セルロースアシレートに対してエポキシ基を有する化合物が５〜３０質量％、また光重合開始剤がエポキシ基を有する化合物に対して１〜３０質量％、好ましくは１〜１０質量％である。
【００６４】
本発明において積層するセルロースアシレート層形成用ドープに、エチレン性不飽和化合物、光ラジカル重合開始剤、エポキシ基を有する化合物及び光カチオン重合開始剤を添加することもできる。
【００６５】
本発明の塗布で使用する溶媒としては、モノマーと相溶性があれば良く、ここまで説明してきた溶液流延製膜に用いられるものと同じ溶媒をもちいることが好ましい。
【００６６】
本発明の塗布液に使用されるその他の添加剤としては、セルロースアシレート塗布液に溶解・分散するものであれば良く、紫外線吸収能、帯電防止能、劣化防止能、剥離促進能、レターデーション調整能や可塑性、滑り性などを発現するものを添加することができる。微粒子のマット剤と酸化防止剤を具体的に示すが、これらに限定されるものではない。
【００６７】
＜マット剤等＞
本発明のセルロースアシレート塗布液に、微粒子のマット剤を含有させることが好ましく、製膜した後の偏光板用保護フィルムとしてのセルロースアシレートフィルムに、微粒子のマット剤が存在することによって、適度の滑りと耐擦り傷が付与させる。微粒子のマット剤はセルロースアシレート塗布液中に混合・分散して用いる。微粒子のマット剤としては、例えば二酸化ケイ素、二酸化チタン、酸化アルミニウム、酸化ジルコニウム、炭酸カルシウム、カオリン、タルク、焼成ケイ酸カルシウム、水和ケイ酸カルシウム、ケイ酸アルミニウム、ケイ酸マグネシウム、リン酸カルシウム等の無機微粒子や架橋高分子微粒子を含有させることが好ましい。中でも二酸化ケイ素がフィルムのヘイズを小さく出来るので好ましい。微粒子の２次粒子の平均粒径は０．０１〜１．０μｍの範囲で、その含有量はセルロースアシレートに対して０．００５〜０．３質量％が好ましい。二酸化ケイ素のような微粒子には有機物、特にメチル基を有する化合物により表面処理されている場合が多いが、このようなものはフィルムのヘイズを低下出来るため本発明においては好ましい。表面処理で好ましい有機物としては、ハロシラン類、アルコキシシラン類（特にメトキシシラン）、シラザン、シロキサンなどがあげられる。微粒子の平均粒径が大きい方がマット効果は大きく、反対に平均粒径の小さい方は透明性に優れるため、好ましい微粒子の一次粒子の平均粒径は５〜５０ｎｍで、より好ましくは７〜１４ｎｍである。これらの微粒子はセルロースアシレートフィルム中では、通常、凝集体として存在しセルロースアシレートフィルム表面に０．０１〜１．０μｍの凹凸を生成させることが好ましい。二酸化ケイ素の微粒子としてはアエロジル（株）製のＡＥＲＯＳＩＬ　　２００、２００Ｖ、３００、Ｒ９７２、Ｒ９７２Ｖ、Ｒ９７４、Ｒ２０２、Ｒ８１２，ＯＸ５０、ＴＴ６００等を挙げることが出来、好ましくはＡＥＲＯＳＩＬ　　Ｒ９７２、Ｒ９７２Ｖ、Ｒ９７４、Ｒ２０２、Ｒ８１２である。これらのマット剤は２種以上併用してもよい。２種以上併用する場合、任意の割合で混合して使用することが出来る。この場合、平均粒径や材質の異なるマット剤、例えばＡＥＲＯＳＩＬ２００ＶとＲ９７２Ｖを質量比で０．１：９９．９〜９９．９〜０．１の範囲で使用出来る。
【００６８】
更に、本発明のセルロースアシレート塗布液中には、酸化防止剤を含有させることが好ましく、酸化防止剤としては、ヒンダードフェノール系の化合物が好ましく用いられ、２，６−ジ−ｔ−ブチル−ｐ−クレゾール、ペンタエリスリチル−テトラキス〔３−（３，５−ジ−ｔ−ブチル−４−ヒドロキシフェニル）プロピオネート〕、トリエチレングリコール−ビス〔３−（３−ｔ−ブチル−５−メチル−４−ヒドロキシフェニル）プロピオネート〕、１，６−ヘキサンジオール−ビス〔３−（３，５−ジ−ｔ−ブチル−４−ヒドロキシフェニル）プロピオネート〕、２，４−ビス−（ｎ−オクチルチオ）−６−（４−ヒドロキシ−３，５−ジ−ｔ−ブチルアニリノ）−１，３，５−トリアジン、２，２−チオ−ジエチレンビス〔３−（３，５−ジ−ｔ−ブチル−４−ヒドロキシフェニル）プロピオネート〕、オクタデシル−３−（３，５−ジ−ｔ−ブチル−４−ヒドロキシフェニル）プロピオネート、１，３，５−トリメチル−２，４，６−トリス（３，５−ジ−ｔ−ブチル−４−ヒドロキシベンジル）ベンゼン、トリス−（３，５−ジ−ｔ−ブチル−４−ヒドロキシベンジル）−イソシアヌレイト等を挙げることが出来る。特に２，６−ジ−ｔ−ブチル−ｐ−クレゾール、ペンタエリスリチル−テトラキス〔３−（３，５−ジ−ｔ−ブチル−４−ヒドロキシフェニル）プロピオネート〕、トリエチレングリコール−ビス〔３−（３−ｔ−ブチル−５−メチル−４−ヒドロキシフェニル）プロピオネート〕が好ましい。また例えば、Ｎ，Ｎ′−ビス〔３−（３，５−ジ−ｔ−ブチル−４−ヒドロキシフェニル）プロピオニル〕ヒドラジン等のヒドラジン系の金属不活性剤やトリス（２，４−ジ−ｔ−ブチルフェニル）フォスファイト等のリン系加工安定剤を併用してもよい。これらの化合物の添加量は、セルロースアシレートに対して質量割合で１ｐｐｍ〜１．０％が好ましく、１０〜１０００ｐｐｍが更に好ましい。
【００６９】
＜ＵＶ照射＞
本発明において、塗布されたモノマー重合性化合物を重合させるための紫外線照射について説明する。
本発明に係るエチレン性不飽和モノマーまたは３員又は４員環状エーテル類化合物を光重合させる紫外線照射源は低圧水銀ランプ、中圧水銀ランプ、高圧水銀ランプ、超高圧水銀ランプ、キセノンランプ、カーボンアーク、メタルハライドランプ、太陽光線等を挙げることができる。紫外線を照射による光重合は、空気または不活性気体中で行うことができるが、エチレン性不飽和モノマーを使用する場合には、空気中でもよいが、重合の誘導期を短くするためにできるだけ酸素濃度が少ない気体が好ましい。照射する紫外線の照射強度は１〜１０００ｍＷ／ｃｍ^２程度が良く、照射量は１００〜２００００ｍＪ／ｃｍ^２程度が好ましい。
紫外線照射はエチレン性不飽和モノマー及び／又は３員若しくは４員環状エーテル類化合物を含有するセルロースアシレート塗布液を塗布、乾燥した後、行うことが好ましい。
【００７０】
（セルロースアシレート積層フィルムの表面処理）
本発明においては、表面処理を行うことによって、セルロースアシレート積層フィルムと各機能層（例えば、剥離層、下塗層およびバック層）との接着の向上を達成することができる。例えばグロー放電処理、紫外線照射処理、コロナ処理、火炎処理、酸またはアルカリ処理を用いることができる。ここでいうグロー放電処理とは、１０−３〜２０Ｔｏｒｒの低圧ガス下でおこる低温プラズマでもよく、更にまた大気圧下でのプラズマ処理も好ましい。プラズマ励起性気体とは上記のような条件においてプラズマ励起される気体をいい、アルゴン、ヘリウム、ネオン、クリプトン、キセノン、窒素、二酸化炭素、テトラフルオロメタンの様なフロン類及びそれらの混合物などがあげられる。これらについては、詳細が発明協会公開技報（公技番号　２００１−１７４５、２００１年３月１５日発行、発明協会）にて３０頁〜３２頁に詳細に記載されている。なお、近年注目されている大気圧でのプラズマ処理は、例えば１０〜１０００Ｋｅｖ下で２０〜５００Ｋｇｙの照射エネルギーが用いられ、より好ましくは３０〜５００Ｋｅｖ下で２０〜３００Ｋｇｙの照射エネルギーが用いられる。これらの中でも特に好ましくは、アルカリ鹸化処理でありセルロースアシレートフィルムの表面処理としては極めて有効である。
【００７１】
アルカリ鹸化処理は、鹸化液を塗布することで行うことも好ましい。塗布方法としては、ディップコーティング法、カーテンコーティング法、エクストルージョンコーティング法、バーコーティング法およびＥ型塗布法を挙げることができる。アルカリ鹸化処理塗布液の溶媒は、鹸化液の透明支持体に対して塗布するために濡れ性が良く、また鹸化液溶媒によって透明支持体表面に凹凸を形成させずに、面状を良好なまま保つ溶媒を選択することが好ましい。具体的には、アルコール系溶媒が好ましく、イソプロピルアルコールが特に好ましい。また、界面活性剤の水溶液を溶媒として使用することもできる。アルカリ鹸化塗布液のアルカリは、上記溶媒に溶解するアルカリが好ましく、ＫＯＨ、ＮａＯＨがさらに好ましい。鹸化塗布液のｐＨは１０以上が好ましく、１２以上がさらに好ましい。アルカリ鹸化時の反応条件は、室温で１秒以上５分以下が好ましく、２秒以上１分以下がさらに好ましく、３秒以上３０秒以下が特に好ましい。アルカリ鹸化反応後、鹸化液塗布面を水洗あるいは酸で洗浄したあと水洗することが好ましい。また、塗布式鹸化処理と後述の配向膜解塗設を、連続して行うことができ、工程数を減少できる。更に、本発明で得られるセルロースアシレートフィルムは、アルカリ処理を浸漬法で実施してもよい。すなわち、アルカリ処理浴、水洗浴、酸処理浴更に水洗浴、場合によりリンス浴などを連続的あるいは間歇的に配置して、表面処理を実施できる。この場合各溶液は、塗布方式で使用される対応する溶液と内容としては、同一の組成である。
【００７２】
（セルロースアシレート積層フィルムの用途）
本発明で作製されたセルロースアシレート積層フィルムの用途についてまず簡単に述べる。本発明の光学フィルムは特に偏光板保護フィルム用として有用である。偏光板保護フィルムとして用いる場合、偏光板の作製方法は特に限定されず、一般的な方法で作製することができる。得られたセルロースアシレートフィルムをアルカリ処理し、ポリビニルアルコールフィルムを沃素溶液中に浸漬延伸して作製した偏光子の両面に完全ケン化ポリビニルアルコール水溶液を用いて貼り合わせる方法がある。アルカリ処理の代わりに特開平６−９４９１５号、特開平６−１１８２３２号に記載されているような易接着加工を施してもよい。保護フィルム処理面と偏光子を貼り合わせるのに使用される接着剤としては、例えば、ポリビニルアルコール、ポリビニルブチラール等のポリビニルアルコール系接着剤や、ブチルアクリレート等のビニル系ラテックス等が挙げられる。偏光板は偏光子及びその両面を保護する保護フィルムで構成されており、更に該偏光板の一方の面にプロテクトフィルムを、反対面にセパレートフィルムを貼合して構成される。プロテクトフィルム及びセパレートフィルムは偏光板出荷時、製品検査時等において偏光板を保護する目的で用いられる。この場合、プロテクトフィルムは、偏光板の表面を保護する目的で貼合され、偏光板を液晶板へ貼合する面の反対面側に用いられる。又、セパレートフィルムは液晶板へ貼合する接着層をカバーする目的で用いられ、偏光板を液晶板へ貼合する面側に用いられる。液晶表示装置には通常２枚の偏光板の間に液晶を含む基板が配置されているが、本発明の光学フィルムを適用した偏光板保護フィルムはどの部位に配置しても優れた表示性が得られる。特に液晶表示装置の表示側最表面の偏光板保護フィルムには透明ハードコート層、防眩層、反射防止層等が設けられるため、該偏光板保護フィルムをこの部分に用いることが特に好ましい。
【００７３】
本発明のセルロースアシレート積層フィルム（本発明において単に「セルロースアシレートフィルム」ともいう。）は、様々な用途で用いることができ、液晶表示装置の光学補償シートとして用いると特に効果がある。本発明のセルロースアシレートフィルムは、様々な表示モードの液晶セルに用いることができる。ＴＮ（Ｔｗｉｓｔｅｄ　Ｎｅｍａｔｉｃ）、ＩＰＳ（Ｉｎ−Ｐｌａｎｅ　Ｓｗｉｔｃｈｉｎｇ）、ＦＬＣ（Ｆｅｒｒｏｅｌｅｃｔｒｉｃ　Ｌｉｑｕｉｄ　Ｃｒｙｓｔａｌ）、ＡＦＬＣ（Ａｎｔｉ−ｆｅｒｒｏｅｌｅｃｔｒｉｃ　Ｌｉｑｕｉｄ　Ｃｒｙｓｔａｌ）、ＯＣＢ（Ｏｐｔｉｃａｌｌｙ　Ｃｏｍｐｅｎｓａｔｏｒｙ　Ｂｅｎｄ）、ＳＴＮ（Ｓｕｐｐｅｒ　Ｔｗｉｓｔｅｄ　Ｎｅｍａｔｉｃ）、ＶＡ（Ｖｅｒｔｉｃａｌｌｙ　Ａｌｉｇｎｅｄ）およびＨＡＮ（Ｈｙｂｒｉｄ　Ａｌｉｇｎｅｄ　Ｎｅｍａｔｉｃ）のような様々な表示モードが提案されている。また、上記表示モードを配向分割した表示モードも提案されている。セルロースアシレートフィルムは、いずれの表示モードの液晶表示装置においても有効である。また、透過型、反射型、半透過型のいずれの液晶表示装置においても有効である。本発明のセルロースアシレートフィルムを、ＴＮモードの液晶セルを有するＴＮ型液晶表示装置の光学補償シートの支持体として用いてもよい。本発明のセルロースアシレートフィルムを、ＳＴＮモードの液晶セルを有するＳＴＮ型液晶表示装置の光学補償シートの支持体として用いてもよい。一般的にＳＴＮ型液晶表示装置では、液晶セル中の棒状液晶性分子が９０〜３６０度の範囲にねじられており、棒状液晶性分子の屈折率異方性（△ｎ）とセルギャップ（ｄ）との積（△ｎｄ）が３００〜１５００ｎｍの範囲にある。ＳＴＮ型液晶表示装置に用いる光学補償シートについては、特開２０００−１０５３１６号公報に記載がある。本発明のセルロースアシレートフィルムは、ＶＡモードの液晶セルを有するＶＡ型液晶表示装置の光学補償シートの支持体として特に有利に用いられる。本発明のセルロースアシレートフィルムは、ＯＣＢモードの液晶セルを有するＯＣＢ型液晶表示装置あるいはＨＡＮモードの液晶セルを有するＨＡＮ型液晶表示装置の光学補償シートの支持体としても有利に用いられる。
【００７４】
＜光学補償シート＞
本発明のセルロースアシレートフィルムは、ＴＮ型、ＳＴＮ型、ＨＡＮ型、ＧＨ（Ｇｕｅｓｔ−Ｈｏｓｔ）型の反射型液晶表示装置の光学補償シートとしても有利に用いられる。これらの表示モードは古くから良く知られている。ＴＮ型反射型液晶表示装置については、特開平１０−１２３４７８号、ＷＯ９８４８３２０号、特許第３０２２４７７号の各公報に記載がある。反射型液晶表示装置に用いる光学補償シートについては、ＷＯ００−６５３８４号に記載がある。本発明のセルロースアシレートフィルムは、ＡＳＭ（Ａｘｉａｌｌｙ　Ｓｙｍｍｅｔｒｉｃ　Ａｌｉｇｎｅｄ　Ｍｉｃｒｏｃｅｌｌ　）モードの液晶セルを有するＡＳＭ型液晶表示装置の光学補償シートの支持体としても有利に用いられる。ＡＳＭモードの液晶セルは、セルの厚さが位置調整可能な樹脂スペーサーにより維持されているとの特徴がある。その他の性質は、ＴＮモードの液晶セルと同様である。ＡＳＭモードの液晶セルとＡＳＭ型液晶表示装置については、クメ（Ｋｕｍｅ）他の論文（Ｋｕｍｅ　ｅｔ　ａｌ．，　ＳＩＤ　９８　Ｄｉｇｅｓｔ　１０８９　（１９９８））に記載がある。以上述べてきたこれらの詳細なセルロースアシレートフィルムの用途は発明協会公開技報（公技番号　２００１−１７４５、２００１年３月１５日発行、発明協会）にて４５頁〜５９頁に詳細に記載されている。
【００７５】
【実施例】
実施例１
（セルローストリアセテート溶液の調製：Ｄ−１）
攪拌羽根を有するステンレス製溶解タンクに、下記の溶媒混合溶液によく攪拌しつつ、セルローストリアセテート粉体（平均サイズ２ｍｍ）を徐々に添加してドープを調製した。添加後、室温（２５℃）にて１時間、３５℃にて２時間放置しセルローストリアセテートを膨潤させた。なお、溶媒である酢酸メチルとメチルエチルケトン、メタノール、エタノール、ｎ−ブタノールは、すべてその含水率が０．２質量％以下のものを利用した。
【００７６】
実施例１のドープの調製に用いた各成分の成分比を下記に示す。
セルローストリアセテート　　　　　　　　　　　　　　　１８質量部
（置換度２．８３、６位のアシル化の置換度０．９３、
２，３位のアシル化の置換度１．９０、粘度平均重
合度３２０、含水率０．４質量％、メチレンクロラ
イド溶液中６質量％の粘度３０５ｍＰａ・ｓ）
酢酸メチル　　　　　　　　　　　　　　　　　　　　　　５５質量部
メチルエチルケトン　　　　　　　　　　　　　　　　　　１０質量部
メタノール　　　　　　　　　　　　　　　　　　　　　　　５質量部
エタノール　　　　　　　　　　　　　　　　　　　　　　　５質量部
ｎ−ブタノール　　　　　　　　　　　　　　　　　　　　　５質量部
可塑剤Ａ（ジベンタエリスリトールヘキサアセテート）　　　１質量部
可塑剤Ｂ（トリフェニルフォスフェート）　　　　　　　　　１質量部
微粒子（シリカ（粒径２０ｎｍ））　　　　　　　　　　０．１質量部
酢酸ビニル　　　　　　　　　　　　　　　　　　　　０．７２質量部
オクタデシルメタクリレート　　　　　　　　　　　　０．２７質量部
モノマー（ＵＶＭ−１）　　　　　　　　　　　　　　０．２７質量部
光重合開始剤（１−ヒドロキシシクロヘキシルフェニルケトン）０．１５質量部
【００７７】
つぎに、このドープは弱い超音波照射することで泡抜きを実施した。脱泡したドープは１．５ＭＰａに加圧した状態で、最初公称孔径５μｍの焼結金属フィルターを通過させ、ついで同じく２．５μｍの焼結金属フィルターを通過させた。それぞれ１次圧、１．５、１．２であり、２次圧はそれぞれ１．０、０．８ＭＰａであった。濾過後のドープの温度は３５℃に調整してステンレス製のストックタンク内に貯蔵した。ストックタンクは中心軸にアンカー翼を有して周速０．３ｍ／ｓｅｃで常時攪拌された。
【００７８】
（フィルム製膜）
上記の溶解法で得られたドープを５０℃にし、流延ギーサーを通して表面温度２０℃とした鏡面ステンレス支持体上に、流延して製膜した。バンド上に流延されたドープは、最初に平行流の乾燥風を送り乾燥した。乾燥する際の乾燥風からのドープへの総括伝熱係数は２４ｋｃａｌ／ｍ^２・ｈｒ・℃であった。乾燥風の温度はバンド上部で１４０℃、下部で１００℃とした。
流延後５秒間は遮風装置により乾燥風が直接ドープに当たらないようにし、その後、２ｋｗ高圧水銀灯を用いて、ドープ表面の全光照射量が　３５０ｍｊ／ｃｍ^２となる条件で光照射した。しかる後に、多数のロールを有する乾燥ゾーンを搬送することで厚さ２５μｍのセルロースアセテートフィルムを作製した。
【００７９】
比較例１
実施例１のセルローストリアセテート溶液の調製における組成分において、光重合開始剤（１−ヒドロキシシクロヘキシルフェニルケトン）、酢酸ビニル、オクタデシルメタクリレート及びモノマー（ＵＶＭ−１）を除いた他は、実施例の組成分と全く同様のものを用いて、実施例１と同様に操作して、乾燥後の膜厚２５μｍのセルロースアセテートフィルムを作製した。
【００８０】
（偏光子の作製）
ＰＶＡフィルムをヨウ素２．０ｇ／Ｌ、ヨウ化カリウム４．０ｇ／Ｌの水溶液に２５℃にて２４０秒浸漬し、さらにホウ酸１０ｇ／Ｌの水溶液に２５℃にて６０秒浸漬後、テンター延伸機に導入し、５．３倍に延伸し、以降幅を一定に保ち、収縮させながら８０℃雰囲気で乾燥させた後テンターから離脱して巻き取った。延伸開始前のＰＶＡフィルムの含水率は３１％で、乾燥後の含水率は１．５％であった。
左右のテンタークリップの搬送速度差は、０．０５％未満であった。テンター出口におけるシワ、フィルム変形は観察されなかった。
得られた偏光子の５５０ｎｍにおける透過率４３．７％、偏光度９９．９７％であった。
【００８１】
（偏光板の作製）
上記の各製膜したセルローストリアセテートフィルムを５５℃の１．５ＮＮａＯＨ水溶液に１分間浸漬して両面を鹸化した後、希硫酸および水で十分洗浄し、乾燥後それぞれのセルローストリアセテート側にポリビニルアルコール系粘着剤を約３０μｍの厚みに塗布し、上記偏光子の両側に貼り合わせ、さらに８０℃で乾燥して偏光板を作製した。
【００８２】
（結果）
上記の得られたセルローストリアセテートフィルム及び偏光板の性能の結果を表１に記載した。
【表１】

表１記載の評価項目の評価方法は、以下の通りにして行った。
１）ヘイズ
セルローストリアセテートフィルムのヘイズは、日本電色工業（株）製、１００１ＤＰ型を用いて、９０℃／８０％の高温高湿下で５００時間保管しその前後で調べた。
Ａ：初期の値
Ｂ：経時後の値　を示す。
２）引き裂き強度
セルローストリアセテートフィルムの引き裂き強度は、東洋精機製作所製軽過重引き裂き強度試験器を用い、ＩＳＯ６３８３／２−１９８３に従って引き裂きに要する過重を評価した。９０℃／８０％の高温高湿下で５００時間保管しその前後で調べた。試料サイズは５０ｍｍ×６４ｍｍ、２５℃６０％ＲＨで２時間調湿した後に実施した。
Ａ：初期の値
Ｂ：経時後の値　を示す。
３）異物・汚れ
セルローストリアセテートフィルムから全幅で長手方向に１ｍの長さに切り出し、この試料にシャーカステン上で光を透過させながらルーペで異物・汚れの有無及び大きさを観察し、下記グレードで評価した。
Ａ：５０μｍ以上の大きさの異物、汚れはなく、５０μｍ未満のものが、０〜１０個観察された
Ｂ：５０μｍ以上の大きさの異物、汚れはなく、５０μｍ未満のものが１１〜３０個観察された
Ｃ：５０μｍ以上の大きさの異物、汚れが１〜１０個観察され、５０μｍ以下のものが３１〜５０個観察された
Ｄ：５０μｍ以上の大きさの異物、汚れが１１〜３０個観察され、５０μｍ以下のものが５１〜９９個観察された
Ｅ：５０μｍ以上の大きさの異物、汚れが３１個以上観察され、５０μｍ以下のものが、１００個以上観察された
４）偏光度
偏光板の偏光度は、分光光度計により可視領域における並行透過率Ｙｐ、直行透過率Ｙｃを求め、次式に基づき偏光度Ｐを決定した。
Ｐ＝（（Ｙｐ−Ｙｃ）／（Ｙｐ＋Ｙｃ））^１／２
５）耐久性
偏光板から１５０ｍｍ×１５０ｍｍの大きさの試料を２枚切り出し、５０℃／８０％ＲＨの条件下に１００時間保管し、クロスニコルにより偏光板の縁に発生する白抜けの面積を全体の面積に対する面積比として観察して、下記のグレードで評価した。
◎：白抜け部分が全くなかった
○：白抜けが全体の面積に対して２％未満
○△：白抜けが全体の面積に対して２％以上５％未満
△：白抜け部分が全体の面積に対して５％以上１０％未満
×：白抜け部分が全体の面積に対して１０％以上
【００８３】
表１の結果から、本発明のセルローストリアセテートフィルムは、異物や汚れが見られずヘイズ値も良好であった。又、フィルムの引き裂き強度も低下することなく充分であった。比較例１のセルローストリアセテートフィルムは、クラック発生のためにヘイズが高く、又高温高湿経時で引き裂き強度が著しく低下した。又、膜厚が３０μｍ以上、特に３５〜８５μｍである以外は実施例１のセルローストリアセテートフィルムと全く同様に作製した試料は、ヘイズなどの光学特性において劣っていた。
本発明の偏光板は、偏光度・耐久性ともに良好であった。一方、比較例１の偏光板は、実用に供し得ないレベルの不良なものであった。
以上のように、本発明のセルローストリアセテートフィルム及びそれを用いた偏光板は、優れた性能を示した。
【００８４】
実施例２〜８
実施例１における、セルローストリアセテート溶液（Ｄ−１）において、光重合開始剤（１−ヒドロキシシクロヘキシルフェニルケトン）、酢酸ビニル、オクタデシルメタクリレート及びＵＶモノマー（ＵＶＭ−１）の代わりに下記表２記載の各化合物及び所定量を用いた他は、実施例１と同様にして、乾燥後の膜厚２５μｍの各セルローストリアセテートフィルムを作製した。次に、実施例１と同様にして各フィルムを用いて各偏光板を作製した。
【表２】

得られた実施例２〜８の各セルローストリアセテートフィルム及び各偏光板を、実施例１と同様にして性能評価を行った。各実施例のものは、実施例１と同等以上の性能を示し、良好であった。
以下に、重合性モノマーを例示する。
【化１１】

【００８５】
実施例９
（セルローストリアセテート溶液の調製）
実施例１におけるセルローストリアセテート溶液の組成物の代わりに、下記内容の組成物を用いた他は、実施例１と同様にしてセルローストリアセテート溶液を得た。
セルローストリアセテート　　　　　　　　　　　　　　　２０質量部
（置換度２．８２、６位アセチル基の置換度０．９３、
粘度平均重合度３２０、含水率０．２質量％）
ジクロロメタン　　　　　　　　　　　　　　　　　　　　６２質量部
アセトン　　　　　　　　　　　　　　　　　　　　　　　　５質量部
メタノール　　　　　　　　　　　　　　　　　　　　　　　６質量部
ブタノール　　　　　　　　　　　　　　　　　　　　　　　５質量部
可塑剤Ｃ（ジトリメチロールプロパンテトラアセテート）　　１質量部
可塑剤Ｄ（ビフェニルヂフェニルフォスフェート）　　　０．２質量部
シリカ微粒子（粒径２０ｎｍ）　　　　　　　　　　　　０．１質量部
酢酸ビニル　　　　　　　　　　　　　　　　　　　　　０．８質量部
モノマー（ＵＶＭ−１５）　　　　　　　　　　　　　０．４８質量部
モノマー（ＡＳＭ−１３）　　　　　　　　　　　　　０．３２質量部
光重合開始剤（２，２−ジエトキシフェニルアセトフェノン）０．１７質量部
次に、上述したセルローストリアセテート溶液をスクリュー押し出し機で送液して、−７０℃で１０分間となるように冷却部分を通過させた。冷却は冷凍機で冷却した−８０℃の冷媒（３Ｍ社製、『フロリナート』）を用いて実施した。そして、冷却により得られた溶液は、静止型混合器を設置した熱交換器により１２０℃まで温度を上昇させ、３分間保持した後冷却し５０℃としてステンレス製の容器に移送し、５０℃で２時間攪拌し脱泡を行った。この後、絶対濾過精度０．０１ｍｍの濾紙（東洋濾紙（株）製、『＃６３』）で濾過し、さらに、絶対濾過精度０．００２５ｍｍの濾紙（ボール社製、『ＦＨ０２５』）にて濾過し、セルローストリアセテートドープ溶液を調製した。
（フィルム製膜）
実施例１と同様にして、膜厚２２μｍのセルローストリアセテートフィルムを作製した。
（偏光板の作製）
上記のフィルムを用いて、実施例１と同様にして、偏光板を作製した。
得られたセルロースアセテートフィルム及び偏光板の性能を実施例１と同様にして評価した結果、実施例１と同等の良好なものであった。
【００８６】
【発明の効果】
本発明によれば、フィルム膜厚が薄く、光学特性に優れ、異物や汚れが見られず、ヘイズ値が良好で、かつ引き裂き強度の十分なセルロースアシレートフィルムを得ることができる。また、本発明のセルロースアシレートフィルムを用いることで、偏光度や耐久性に優れた偏光板を得ることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cellulose acylate film particularly suitable for optical applications and a polarizing plate using the same.
[0002]
[Prior art]
In recent years, the demand for thin transparent plastic films has increased as protective films for polarizing plates, optical compensation films such as retardation plates, plastic substrates, photographic supports, moving cells and optical filters, and optical materials such as OHP films. doing. In particular, liquid crystal displays have recently improved in quality, such as TN, STN, and TFT, and are lightweight and have excellent portability, so personal computers, word processors, portable terminals, TVs, and digital still cameras and movie cameras In this liquid crystal display, a polarizing plate is essential for image display. Along with the improvement in the quality of liquid crystal displays, an improvement in the quality of the polarizing plate is required, and at the same time, a transparent plastic film that is a protective film for the polarizing plate is also required to have a higher quality.
[0003]
For optical films such as protective films for polarizing plates, high transparency, low optical anisotropy, flatness, easy surface treatment, high durability (dimensional stability, moisture and heat resistance, Water resistance), no foreign matter in the film and on the film surface, no scratches on the surface or difficult to stick (scratch resistance), moderate film rigidity (handleability), moderate water permeability, etc. It is necessary to have characteristics.
[0004]
Examples of plastic films having these characteristics include films made of cellulose acylate, norbornene resin, acrylic resin, polyarylate resin, polycarbonate resin, etc., but cellulose acylate is mainly used from the viewpoint of productivity and material price. Has been. In particular, a film of cellulose triacetate is particularly advantageously used for optical applications because it has extremely high transparency, low optical anisotropy, and low retardation.
[0005]
As a method for forming these plastic films, various film forming techniques such as a solution film forming method, a melt film forming method and a rolling method can be used, but in order to obtain good flatness and low optical anisotropy. For this, the solution casting method is particularly suitable. The solution casting method involves dissolving raw material flakes in a solvent and adding various additives such as a plasticizer, an ultraviolet absorber, a deterioration preventing agent, a slipping agent and a peeling accelerator as necessary (“ The dope is called “dope”) on a support composed of a horizontal endless metal belt or a rotating drum by a dope supply means (referred to as “die”) and then dried to some extent on the support. Then, the film to which rigidity has been imparted is peeled off from the support, and then the solvent is removed by passing through the drying section by various conveying means.
[0006]
However, in cellulose acylate, additives such as added plasticizers, UV absorbers, deterioration inhibitors, slipping agents, peeling accelerators, etc., precipitate during the manufacturing process and become defective, and are exposed to high temperatures and high humidity. In some cases, this causes a failure such as precipitation and a decrease in transmittance. Furthermore, in order to eliminate the above-mentioned condensation that causes defects, it is necessary to stop the film production line and clean it over time, which not only reduces productivity, but also dirt attached to the film, etc. All of these factors have increased costs, such as inspections to check for defects, removal of defective parts, and a decrease in yield due to removal of defective parts. Therefore, as a countermeasure against this failure, in JP-A-2002-20410, a polymerizable monomer having an effect as an additive is added to a cellulose acylate dope, polymerized by light irradiation after casting the solution, A method for preventing crying is disclosed.
[0007]
However, in the method described in the publication, the peelability of the dope film from the metal support is poor, the trouble that the film is cut at the time of web handling occurs, and the optical characteristics such as transmittance are bad. Moreover, it became clear that there was a fault that flatness was bad compared with the conventional cellulose acylate film, and haze was also high.
[0008]
[Problems to be solved by the invention]
The problem to be solved by the present invention is to provide a cellulose acylate film having excellent optical properties, no foreign matter and dirt, a good haze value, and sufficient tear strength. Moreover, it is providing the polarizing plate excellent in the polarization degree and durability.
[0009]
[Means for Solving the Problems]
The problems of the present invention have been solved by the methods described in the following (1) to (3).
(1) In a cellulose acylate film produced by a solution casting film-forming method, a cellulose acylate dope composition containing a polymerizable monomer and / or a polymerizable monomer having a functional group and a photopolymerization initiator is cast. And a cellulose acylate film having a thickness of 10 μm or more and less than 30 μm obtained by photopolymerizing the monomer during or after drying.
(2) The cellulose acylate film as described in (1), which contains fine particles.
(3) A polarizing plate using the cellulose acylate film described in (1) or (2).
[0010]
DETAILED DESCRIPTION OF THE INVENTION
(Cellulose acylate)
First, the cellulose acylate used in the solution casting film formation of the present invention will be described in detail. The cellulose acylate of the present invention is not particularly limited as long as the effects of the present invention are exhibited. In the present invention, two or more different cellulose acylates may be mixed and used. However, among them, preferable cellulose acylates include the following materials. That is, the cellulose acylate satisfies all of the following formulas (I) to (III) with respect to the degree of substitution of cellulose with a hydroxyl group.
(I) 2.6 ≦ SA + SB ≦ 3.0
(II) 2.0 ≦ SA ≦ 3.0
(III) 0 ≦ SB ≦ 0.8
In the formula, SA and SB represent a substituent of an acyl group substituted with a hydroxyl group of cellulose, SA is a substitution degree of an acetyl group, and SB is a substitution degree of an acyl group having 3 to 22 carbon atoms.
[0011]
Glucose units having β-1,4 bonds constituting cellulose have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer obtained by esterifying some or all of these hydroxyl groups with acyl groups. The degree of acyl substitution means the proportion of cellulose esterified at each of the 2-position, 3-position and 6-position (100% esterification has a degree of substitution of 1). In the present invention, the total sum of the substitution degree of the hydroxyl group SA and SB is more preferably 2.7 to 2.96, and particularly preferably 2.80 to 2.95. The degree of substitution of SB is preferably 0 to 0.8, particularly preferably 0 to 0.6. Further, 28% or more of SB is a substituent at the 6-position hydroxyl group, more preferably 30% or more is a substituent at the 6-position hydroxyl group, more preferably 31%, particularly preferably 32% or more is the 6-position hydroxyl group. It is a substituent of a hydroxyl group. Furthermore, the cellulose acylate film in which the sum of the substitution degrees of SA and SB at the 6-position of cellulose acylate is 0.8 or more, more preferably 0.85, and particularly preferably 0.90 can be mentioned. it can. These cellulose acylate films can produce a solution having a preferable solubility, and in particular, a non-chlorine organic solvent can produce a good solution.
[0012]
The acyl group (SB) having 3 to 22 carbon atoms of the cellulose acylate used in the present invention may be an aliphatic group or an aryl group, and is not particularly limited. These are, for example, cellulose alkylcarbonyl esters, alkenylcarbonyl esters, aromatic carbonyl esters, aromatic alkylcarbonyl esters, and the like, each of which may further have a substituted group. These preferred SBs include propionyl, butanoyl, keptanoyl, hexanoyl, octanoyl, decanoyl, dodecanoyl, tridecanoyl, tetradecanoyl, hexadecanoyl, octadecanoyl, iso-butanoyl, t-butanoyl, cyclohexanecarbonyl, oleoyl, benzoyl , Naphthylcarbonyl, cinnamoyl group and the like. Among these, preferred SB is propionyl, butanoyl, dodecanoyl, octadecanoyl, t-butanoyl, oleoyl, benzoyl, naphthylcarbonyl, cinnamoyl and the like.
[0013]
The basic principle of the cellulose acylate synthesis method is described in Mita et al., Wood Chemistry pages 180-190 (Kyoritsu Shuppan, 1968). A typical synthesis method is a liquid phase acetylation method using a carboxylic acid anhydride-acetic acid-sulfuric acid catalyst. Specifically, cellulose raw materials such as cotton linter and wood pulp are pretreated with an appropriate amount of acetic acid, and then put into a pre-cooled carboxylic acid mixture to be esterified to complete cellulose acylate (2nd, 3rd and 6th). The total degree of acyl substitution at the position is approximately 3.00). The carboxylated mixed solution generally contains acetic acid as a solvent, carboxylic anhydride as an esterifying agent, and sulfuric acid as a catalyst. The carboxylic anhydride is usually used in a stoichiometric excess over the sum of the cellulose that reacts with it and the water present in the system. In order to hydrolyze excess carboxylic anhydride remaining in the system after completion of the acylation reaction and to partially neutralize the esterification catalyst, neutralizing agents (for example, calcium, magnesium, iron, An aqueous solution of aluminum or zinc carbonate, acetate or oxide) is added. Next, the obtained complete cellulose acylate is saponified and aged by maintaining it at 50 to 90 ° C. in the presence of a small amount of an acetylation reaction catalyst (generally, remaining sulfuric acid) to obtain the desired degree of acyl substitution and polymerization. The cellulose acylate having a degree is changed. When the desired cellulose acylate is obtained, the catalyst remaining in the system is completely neutralized with a neutralizing agent as described above, or in water or dilute sulfuric acid without neutralization. The cellulose acylate solution is added (or water or dilute sulfuric acid is added into the cellulose acylate solution) to separate the cellulose acylate, and the cellulose acylate is obtained by washing and stabilizing treatment.
[0014]
The cellulose acylate film of the present invention is preferably composed of a cellulose acylate in which the polymer component constituting the film substantially has the above definition. “Substantially” means 55% by mass or more of the total polymer component, preferably 70% by mass or more, and more preferably 80% by mass or more. Cellulose acylate particles are preferably used as a raw material for film production. 90% by mass or more of the particles to be used preferably have a particle diameter of 0.1 to 5 mm. Moreover, it is preferable that 50 mass% or more of the particle | grains to be used have a particle diameter of 0.2-4 mm. The cellulose acylate particles preferably have a flat or spherical shape as much as possible.
[0015]
The degree of polymerization of the cellulose acylate preferably used in the present invention is a viscosity average degree of polymerization of 200 to 700, preferably 230 to 550, more preferably 230 to 350, and particularly preferably a viscosity average degree of polymerization of 240 to 320. The average degree of polymerization can be measured by Uda et al.'S intrinsic viscosity method (Kazuo Uda, Hideo Saito, Journal of Textile Society, Vol. 18, No. 1, pages 105-120, 1962). Further details are described in JP-A-9-95538.
[0016]
When the low molecular component is removed, the average molecular weight (average polymerization degree) is increased, but the viscosity is lower than that of ordinary cellulose acylate, which is useful. Cellulose acylate having a small amount of low molecular components can be obtained by removing low molecular components from cellulose acylate synthesized by a usual method. The removal of the low molecular component can be carried out by washing the cellulose acylate with an appropriate organic solvent. In addition, when manufacturing a cellulose acylate with few low molecular components, it is preferable to adjust the sulfuric acid catalyst amount in an acetylation reaction to 0.5-25 mass parts with respect to 100 weight of celluloses. When the amount of the sulfuric acid catalyst is within the above range, cellulose acylate that is preferable in terms of molecular weight distribution (uniform molecular weight distribution) can be synthesized. When the cellulose acylate of the present invention is used during film production, its water content is preferably 2% by mass or less, more preferably 1% by mass or less, and particularly preferably 0.7% by mass or less. It is a cellulose acylate having a water content. In general, cellulose acylate contains water and is known to be 2.5 to 5% by mass. In order to obtain the moisture content of the cellulose acylate in the present invention, it is necessary to dry, and the method is not particularly limited as long as the desired moisture content can be achieved.
These cellulose acylates of the present invention are described in detail on pages 7 to 12 of the raw material cotton and the synthesis method in the Technical Report of the Japan Society of Invention (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society of Invention). It is described in.
[0017]
(Cellulose acylate solution)
In the cellulose acylate solution of the present invention, various additives (for example, plasticizers, ultraviolet inhibitors, deterioration inhibitors, optical anisotropy control agents, fine particles, release agents, infrared rays) according to the use in each preparation step. Absorbents, etc.) can be added and they can be solid or oily. That is, the melting point and boiling point are not particularly limited. For example, mixing of ultraviolet absorbing materials at 20 ° C. or lower and 20 ° C. or higher, and similarly mixing of a plasticizer is described in, for example, Japanese Patent Application Laid-Open No. 2001-151901. Furthermore, infrared absorbing dyes are described, for example, in JP-A No. 2001-194522. Moreover, the addition time may be added at any time in the dope preparation step, but may be added by adding an additive to the final preparation step of the dope preparation step. Furthermore, the amount of each material added is not particularly limited as long as the function is manifested. Furthermore, for these details, materials described in detail on pages 16 to 22 in the Japan Institute of Invention Disclosure Technical Bulletin (Public Technical Number 2001-1745, published on March 15, 2001, Japan Institute of Invention) are preferably used.
[0018]
Next, the organic solvent that dissolves the cellulose acylate of the present invention will be described.
As the solvent to be used, a lower aliphatic hydrocarbon chloride or a lower aliphatic alcohol is generally used. Examples of lower aliphatic hydrocarbon chlorides include methylene chloride. Examples of lower aliphatic alcohols include methanol, ethanol, n-propyl alcohol, isopropyl alcohol and n-butanol. Examples of other solvents include acetone substantially free of halogenated hydrocarbons, ketones having 4 to 12 carbon atoms (for example, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone, and methylcyclohexanone), carbon atoms 3-12 esters (such as ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, pentyl acetate and 2-ethoxy-ethyl acetate), alcohols having 1 to 6 carbon atoms (for example, Methanol, ethanol, propanol, isopropanol, 1-butanol, t-butanol, 2-methyl-2-butanol, 2-methoxyethanol, 2-butoxyethanol and the like, ethers having 3 to 12 carbon atoms (for example, diisopropyl ether, dimethoate) Cymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole, phenetole, etc.) and cyclic hydrocarbons having 5 to 8 carbon atoms (for example, cyclopentane, cyclohexane, cycloheptane, cyclooctane, etc.) ). In the present invention, it is preferable to use a solvent selected from methylene chloride, acetone, methyl acetate and dioxolane or a mixture thereof as the main solvent among the above solvents.
[0019]
As the solvent, it is preferable from the viewpoint of solubility of cellulose acylate that methyl acetate is used as a main solvent and a mixed solvent to which ketones and alcohols are further added is used as a dope preparation solvent. In this case, it is preferable to use 20 to 90% by mass of methyl acetate, 5 to 60% by mass of ketones, and 5 to 30% by mass of alcohols.
Examples of non-halogen organic solvent systems that do not contain a halogenated hydrocarbon such as methylene chloride include, for example, paragraph numbers 0021 to 0025 of JP-A No. 2002-146043 and paragraph numbers of JP-A No. 2002-146045. Examples of the solvent system described in 0016 to 0021 are listed.
[0020]
The cellulose acylate of the present invention is preferably a solution in which 10 to 30% by mass is dissolved in an organic solvent, more preferably 13 to 27% by mass, and particularly 15 to 25% by mass. A cellulose acylate solution is preferred. The method for carrying out the cellulose acylate at these concentrations may be carried out so as to obtain a predetermined concentration at the stage of dissolution, or it is prepared as a low-concentration solution (for example, 9 to 14% by mass) and then concentrated as described later. You may adjust to a predetermined high concentration solution by a process. In addition, a cellulose acylate solution having a high concentration may be added to the cellulose acylate solution at a predetermined low concentration by adding various additives, and the cellulose acylate solution concentration of the present invention may be obtained by any method. There is no particular problem if it is implemented.
[0021]
Next, in this invention, it is preferable that the aggregate molecular weight of the cellulose acylate of the diluted solution which made the cellulose acylate solution 0.1-5 mass% with the organic solvent of the same composition is 10,000-15 million. More preferably, the associated molecular weight is 1 million to 10 million. This associated molecular weight can be determined by a static light scattering method. It is preferable to melt | dissolve so that the inertial square radius calculated | required simultaneously in that case may be 40-200 nm. A more preferable inertial square radius is 70 to 200 nm. Furthermore, the second virial coefficient is −2 × 10.^-4~ 4x10^-4The second virial coefficient is preferably −2 × 10.^-4~ 2x10^-4It is.
Here, the definition of the associated molecular weight, the inertial square radius and the second virial coefficient in the present invention will be described. These were measured using the static light scattering method according to the following method. Although the measurement was performed in a dilute region for the convenience of the apparatus, these measured values reflect the behavior of the dope in the high concentration region of the present invention. First, cellulose acylate was dissolved in a solvent used for the dope to prepare 0.1 mass%, 0.2 mass%, 0.3 mass%, and 0.4 mass% solutions. In order to prevent moisture absorption, the cellulose acylate was dried at 120 ° C. for 2 hours and measured at 25 ° C. and 10% RH. The dissolution method was carried out according to the method employed at the time of dope dissolution (room temperature dissolution method, cooling dissolution method, high temperature dissolution method). Subsequently, these solutions and the solvent were filtered through a 0.2 μm Teflon (registered trademark) filter. The filtered solution was measured for static light scattering at intervals of 10 degrees from 30 degrees to 140 degrees at 25 ° C. using a light scattering measuring device (DLS-700 manufactured by Otsuka Electronics Co., Ltd.). The obtained data was analyzed by the BERRY plot method. In addition, the refractive index required for this analysis uses the value of the solvent calculated | required with the Abbe refractive system, and the refractive index concentration gradient (dn / dc) uses the differential refractometer (Otsuka Electronics Co., Ltd. product DRM-1021). The measurement was performed using the solvent and the solution used for the light scattering measurement.
[0022]
Next, regarding the preparation of the cellulose acylate solution (dope) of the present invention, the dissolution method is not particularly limited, and may be a room temperature dissolution method, a cooling dissolution method or a high temperature dissolution method, or a combination thereof. . Regarding these, for example, JP-A-5-163301, JP-A-61-106628, JP-A-58-127737, JP-A-9-95544, JP-A-10-95854, JP-A-10-45950, JP-A-2000-53784, Kaihei 11-322946, JP-A-11-322947, JP-A-2-276830, JP-A-2000-273239, JP-A-11-71463, JP-A-04-259511, JP-A-2000-273184, JP-A-11-323017, JP-A-11-323017 11-302388 describes a method for preparing a cellulose acylate solution. The above-described method for dissolving cellulose acylate in an organic solvent is applicable to the present invention as long as it is within the scope of the present invention. Details of these are described in detail on pages 22 to 25 of the non-chlorine-based solvent system in the Japan Society for Invention and Innovation Technical Report (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society for Invention). Be implemented in a way that Furthermore, the cellulose acylate dope solution of the present invention is usually subjected to solution concentration and filtration. Similarly, the dope solution of the invention is published in the technical report of the Invention Association (public technical number 2001-1745, published on March 15, 2001, Invention Association). It is described in detail on the page. In addition, when it melt | dissolves at high temperature, it is the case where it is more than the boiling point of the organic solvent to be used, and in that case, it uses in a pressurized state.
[0023]
The cellulose acylate solution of the present invention preferably has a viscosity and dynamic storage modulus within the range. 1 mL of the sample solution was measured on a rheometer (CLS 500) using a Steel Cone having a diameter of 4 cm / 2 ° (both manufactured by TA Instruments). Measurement conditions were measured using Oscillation Step / Temperature Ramp with the range of 40 ° C to -10 ° C varied at 2 ° C / min, and static non-Newtonian viscosity at 40 ° C n * (Pa · sec) and storage at -5 ° C The elastic modulus G ′ (Pa) was determined. The measurement was started after the sample solution was kept warm at the measurement start temperature until the liquid temperature became constant. In the present invention, the viscosity at 40 ° C. is 1 to 300 Pa · sec, and the dynamic storage elastic modulus at −5 ° C. is 10,000 to 1,000,000 Pa. More preferably, the viscosity at 40 ° C. is 1 to 200 Pa · sec, and the dynamic storage elastic modulus at −5 ° C. is 30,000 to 500,000 Pa, and particularly preferably, the viscosity at 40 ° C. is 10 to 10 150 Pa · sec and dynamic storage elastic modulus at −5 ° C. is 50,000 to 500,000 Pa.
[0024]
(Casting of cellulose acylate solution)
Next, a method for producing a film using the cellulose acylate solution of the present invention will be described. For the method and equipment for producing the cellulose acylate film of the present invention, a solution casting film forming method and a solution casting film forming apparatus conventionally used for producing a cellulose triacetate film are used. The dope (cellulose acylate solution) prepared from the dissolving machine (kettle) is temporarily stored in a storage kettle, and the foam contained in the dope is defoamed for final preparation. The dope is sent from the dope discharge port to the pressure die through a pressure metering gear pump capable of delivering a constant amount of liquid with high accuracy, for example, by the number of rotations, and the dope is run endlessly from the die (slit) of the pressure die. The dry-dried dope film (also referred to as web) is peeled off from the metal support at a peeling point that is uniformly cast on the metal support and substantially rounds the metal support. Both ends of the obtained web are sandwiched between clips, transported by a tenter while keeping the width, dried, then transported by a roll group of a drying device, dried, and wound up to a predetermined length by a winder. The combination of the tenter and the roll group dryer varies depending on the purpose. In the solution casting film forming method used for silver halide photographic light-sensitive materials and functional protective films for electronic displays, in addition to the solution casting film forming apparatus, an undercoat layer, an antistatic layer, an antihalation layer, a protective layer, etc. In many cases, a coating device is added to the surface processing of the film. Each of these manufacturing processes is described in detail on pages 25 to 30 in the Invention Association's Public Technical Report (Public Technical Number 2001-1745, Issued March 15, 2001, Invention Association). (Including rolling), metal support, drying, peeling, stretching and the like.
[0025]
Here, although the space temperature of a casting part is not specifically limited in this invention, It is preferable that it is -50-50 degreeC. Furthermore, it is preferable that it is -30-40 degreeC, and it is especially preferable that it is -20-30 degreeC. In particular, the cellulose acylate solution cast at a low space temperature can be cooled on the support instantly to increase the gel strength, thereby holding the film containing the organic solvent. Thereby, without evaporating the organic solvent from the cellulose acylate, it can be peeled off from the support in a short time, and high-speed casting can be achieved. The means for cooling the space may be normal air, nitrogen, argon, helium or the like, and is not particularly limited. The humidity in that case is preferably 0 to 70% RH, and more preferably 0 to 50% RH. Moreover, in this invention, the temperature of the support body of the casting part which casts a cellulose acylate solution is -50-130 degreeC, Preferably it is -30-25 degreeC, Furthermore, it is -20-15 degreeC. In order to keep the casting part at the temperature of the present invention, it may be achieved by introducing a cooled gas into the casting part, or a cooling device may be arranged in the casting part to cool the space. At this time, it is important to take care not to attach water, and it can be carried out by a method such as using dry gas.
[0026]
In the present invention, as the cellulose acylate solution, one or a plurality of solutions can be used, and it is preferable to adopt one or more of the following configurations particularly for the contents and casting of each solution. That is, (1) The cellulose acylate solution is a cellulose acylate solution containing 0.1 to 20% by mass of at least one liquid or solid plasticizer with respect to the cellulose acylate at 25 ° C. ( 2) A cellulose acylate solution containing 0.001 to 5% by mass of at least one liquid or solid UV absorber with respect to cellulose acylate, and (3) an average particle size of at least one solid. A cellulose acylate solution containing 0.001 to 5% by mass of a fine particle powder having a particle size of 5 to 3000 nm based on cellulose acylate, and (4) cellulose acylate containing at least one fluorine-based surfactant. A cellulose acylate solution containing 0.001 to 2% by mass based on (5) at least one type A cellulose acylate solution containing 0.0001 to 2% by mass of a release agent with respect to cellulose acylate; (6) 0.0001 to 2% by mass of at least one kind of deterioration inhibitor with respect to cellulose acylate. (7) at least one optical anisotropy control agent is contained in an amount of 0.1 to 15% by mass with respect to the cellulose acylate, and (8) at least one kind. A cellulose acylate solution containing 0.1 to 5% by mass of the infrared absorbing agent for cellulose acylate. Moreover, the cellulose acylate film produced from said cellulose acylate solution said to be preferable has preferable characteristics.
[0027]
In the casting step, one type of cellulose acylate solution may be cast as a single layer, or two or more types of cellulose acylate solutions may be cast simultaneously and / or sequentially. In the case of having a casting process consisting of two or more layers, the composition of the chlorine-based solvent in each layer is either the same or different in each of the produced cellulose acylate solution and cellulose acylate film, and each layer The additive is one kind or a mixture of two or more kinds, the addition position of the additive to each layer is either the same layer or a different layer, The concentration in the solution is either the same or different in each layer, the aggregate molecular weight of each layer is either the same or a different aggregate molecular weight, Either the temperature is the same or a different temperature, the coating amount of each layer is the same or different, and the viscosity of each layer is the same Either one of the different viscosities, the film thickness after drying of each layer is the same or different, and the material present in each layer is the same or distribution or different or A cellulose acylate that is characterized by the distribution, the physical properties of each layer being the same or different, and the physical properties of each layer being either uniform or different. A rate solution and a cellulose acylate film produced from the solution are also preferred. Here, the physical properties include physical properties described in detail on pages 6 to 7 of the Japan Society of Invention and Innovation Technical Report (Public Technical Number 2001-1745, issued on March 15, 2001, Japan Society of Inventions). For example, haze, transmittance, spectral characteristics, retardation Re, Rth, molecular orientation axis, axial misalignment, tear strength, folding strength, tensile strength, roll-in / out Rt difference, creaking, dynamic friction, alkaline hydrolysis, curl value, water content Rate, residual solvent amount, heat shrinkage rate, high humidity dimensional evaluation, moisture permeability, base flatness, dimensional stability, heat shrinkage starting temperature, elastic modulus, and measurement of bright spot foreign matter, etc. Impedance and surface shape used for evaluation are also included. In addition, the Yellow Index, Transparency, Thermophysical Properties (Tg) of Cellulose Acylate described in detail on page 11 in the Japan Society for Invention and Innovation Technical Report (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society for Invention) , Heat of crystallization) and the like.
[0028]
Although the dry thickness of the cellulose acylate film of the present invention is required to be less than 30 μm, a thickness of 10 μm or more and less than 30 μm is preferable, and a thickness of 15 μm or more to less than 30 μm is particularly preferable. The film thickness of the produced film can be measured by a conventionally known measuring method using a micrometer or the like. In the present invention, the thickness of the film after standing for 24 hours in an environment of a temperature of 25 ° C. and 65% RH was measured. The dry thickness of the cellulose acylate film can be adjusted by the cellulose acylate solid content concentration contained in the dope and the casting thickness of the dope.
[0029]
(Polymerizable monomer)
The polymerizable monomer or polymerizable compound coated on the cellulose acylate film of the present invention may be any one that dissolves and disperses in the cellulose acylate coating solution, and is capable of absorbing ultraviolet light, preventing antistatic properties, preventing deterioration, and promoting peeling. It is more preferably a polyfunctional monomer having a functional group that exhibits performance, retardation adjusting ability, plasticity, slipperiness, and the like.
As the polymerizable monomer, an ethylenically unsaturated monomer and / or a compound having a 3-membered or 4-membered cyclic ether group can be used. As the polymerizable monomer having a functional group, an ethylenically unsaturated monomer having a functional group and / or a compound having a 3-membered or 4-membered cyclic ether group having a functional group can be used. Here, examples of the compound having a 3-membered cyclic ether group include compounds having an epoxy group, and examples of the compound having a 4-membered cyclic ether group include compounds having an oxetanyl group.
[0030]
<Ethylenically unsaturated monomer>
Specifically, ethylenically unsaturated monomers and / or ethylenically unsaturated monomers having a functional group are preferable examples. For example, vinyl acetates such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, and valeric acid Vinyl, vinyl pivalate, vinyl caproate, vinyl enanthate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl sorbate, vinyl benzoate Acrylic acid esters or methacrylic acid esters (hereinafter, acrylic acid esters or methacrylic acid esters may be abbreviated as (meth) acrylic acid esters). Acrylate, Eth Acrylate, n-butyl (meth) acrylate, heptyl (meth) acrylate, 2-methylbutyl (meth) acrylate, 3-methylbutyl (meth) acrylate, hexyl (meth) acrylate, 3-methoxypropyl (meth) acrylate, 2-methoxy Ethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 2-ethylbutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 3-ethoxypropyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl ( (Meth) acrylate, isononyl (meth) acrylate, isomyristyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, ε-caprolactone (me T) acrylate, benzyl (meth) acrylate, phenethyl (meth) acrylate, 4-cyanobutyl (meth) acrylate, 2-cyanoethyl (meth) acrylate, etc., as vinyl ethers, methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, 2 -Ethylhexyl vinyl ether, hexyl vinyl ether, etc. As styrenes, styrene, 4-[(2-butoxyethoxy) methyl] styrene, 4-butoxymethoxystyrene, 4-butylstyrene, 4-decylstyrene, 4- (2-ethoxymethyl) ) Styrene, 4- (1-ethylhexyloxymethyl) styrene, 4-hydroxymethylstyrene, 4-hexylstyrene, 4-nonylstyrene, 4-octyloxymethylstyrene 2-octyl styrene, 4-octyl styrene, 4-propoxymethyl styrene, maleic acids such as dimethylmaleic acid, diethylmaleic acid, dipropylmaleic acid, dibutylmaleic acid, dicyclohexylmaleic acid, di-2-ethylhexylmaleic acid, di Nonylmaleic acid, dibenzylmaleic acid and the like can be mentioned, but are not limited thereto.
More preferable ethylenically unsaturated monomers include vinyl esters, acrylates and methacrylates.
[0031]
The ethylenically unsaturated monomer having a functional group useful in the present invention is preferably one having an ultraviolet absorbing group or an antistatic group in the side chain of the polymer. As the ethylenic group of the ethylenically unsaturated monomer having a functional group, a vinyl group, an acryloyl group or a methacryloyl group is preferably used.
[0032]
Examples of the ultraviolet absorbing group of the ethylenically unsaturated monomer having an ultraviolet absorbing group useful in the present invention include a benzotriazole group, a salicylic acid ester group, a benzophenone group, an oxybenzophenone group, and a cyanoacrylate group. Any of them can be preferably used in the invention. In particular, a monomer having a benzotriazole group with little photoreactivity and almost no coloring is preferred.
[0033]
In the present invention, a commercially available ethylenically unsaturated monomer having an ultraviolet absorbing group may be used, or may be obtained by synthesis. As a commercially available product, for example, 1-hydroxy-2- (2-benzotriazole) -4- (2-methacryloyloxyethyl) benzene is commercially available as a reactive ultraviolet absorber RUVA-93 manufactured by Otsuka Chemical Co., Ltd. Yes. Similarly, 1-hydroxy-2- (2-benzotriazole) -4- (2-acryloyloxyethyl) benzene can be preferably used in the present invention. In addition, an ethylenically unsaturated monomer having an ultraviolet absorbing group described in JP-A-2002-20410 may be used.
[0034]
Examples of the antistatic group of the ethylenically unsaturated monomer having an antistatic group useful in the present invention include a quaternary ammonium group, a sulfonate group, and a polyethylene oxide group. A quaternary ammonium group is preferable from the viewpoint of performance.
[0035]
The copolymerization ratio of the ethylenically unsaturated monomer having an antistatic group to the polymer obtained by photopolymerization in the present invention is 40 mass from the viewpoint of water absorption, durability, plasticity, necessary antistatic properties, etc. of the cellulose acylate film. % Or less, preferably 5 to 30% by mass.
[0036]
Although the typical example of the ethylenically unsaturated monomer which has a functional group which can be used in this invention is illustrated below, it is not limited to these. The UVM series shows examples of monomers having ultraviolet absorbing residues, and the ASM series shows examples of monomers having antistatic residues.
[0037]
[Chemical 1]

[0038]
[Chemical 2]

[0039]
[Chemical 3]

[0040]
[Formula 4]

[0041]
[Chemical formula 5]

[0042]
[Chemical 6]

[0043]
[Chemical 7]

[0044]
<Radical radical polymerization initiator>
The photopolymerization initiator useful in the present invention can be used without limitation as long as the ethylenically unsaturated monomer is an initiator that can be photopolymerized in the web, but known photopolymerization initiators can be used. . Photosensitizers can also be used. Specifically, benzoin methyl ether, benzoin-n-propyl ether, benzoin-n-butyl ether, benzoin silyl ether, methyl benzoin formate, benzyl, benzophenone, hydroxybenzophenone, p-methylbenzophenone, α-hydroxyisobutylphenone, p -Isopropyl-α-hydroxyisobutylphenone, acetophenone, Michler's ketone, α, α'-dichloro-4-phenoxyacetophenone, 1-hydroxy-1-cyclohexylacetophenone, 2,2-dimethoxy-2-phenylacetophenone, diacetyl, eosin, thionine 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropene, dichlorothioxanthone, diisopropylthioxanthone, pheny Disulfide-2-nitrosofluorene, butyroin, anisoin ethyl ether, di-t-butyl peroxide, benzoylthiazolyl sulfide, α-amyloxime ester, azobisisobutyronitrile, tetramethylthiuram disulfide, etc. it can. In this invention, when mixing a photoinitiator with an ethylenically unsaturated monomer in a cellulose acylate dope composition, 5-30 mass% of ethylenically unsaturated monomers with respect to a cellulose acylate, and a photoinitiator It is good to add about 1-30 mass% with respect to an ethylenically unsaturated monomer. In the present invention, after the photopolymerizable ethylenically unsaturated monomer is distributed in the cellulose acylate dope composition, the photopolymerization is caused in the web containing a lot of organic solvent or in the web even if the drying is considerably advanced. However, it is preferable to polymerize by irradiating with ultraviolet rays on a metal support.
[0045]
By incorporating a crosslinkable monomer having two ethylenically unsaturated groups into the cellulose acylate dope composition containing the ethylenically unsaturated monomer and the photopolymerization initiator of the present invention, the flexibility and toughness can be obtained after photopolymerization. A combined cellulose acylate film can be obtained. Examples of the crosslinkable monomer having two ethylenically unsaturated groups include polyester di (meth) acrylate and polyurethane di (meth) acrylate. A commercially available product is urethane acrylate (trade name, M-1310) manufactured by Toa Gosei Co., Ltd., which can be preferably used.
[0046]
These di (meth) acrylates of polyester or polyurethane have a number average molecular weight of 6,000 to 100,000, preferably 1,000 to 80,000.
[0047]
(3- or 4-membered cyclic ethers)
Another example of the polymerizable monomer or polymerizable compound applied on the cellulose acylate of the present invention is a compound having a 3-membered or 4-membered cyclic ether group. Here, examples of the compound having a 3-membered cyclic ether group include compounds having an epoxy group, and examples of the compound having a 4-membered cyclic ether group include compounds having an oxetanyl group. As the compound having a cyclic ether group, a compound having an epoxy group, particularly a compound having an alicyclic epoxy group is preferable from the viewpoint of high reactivity.
In the following description, in the description of the compound having a 3-membered or 4-membered cyclic ether group, a compound having an epoxy group will be described as an example. However, the present invention can be easily extended to a compound having an oxetanyl group. Is.
These compounds having an epoxy group can also be photopolymerized in the web, and plasticity can be imparted to the finished film. As a compound which has an epoxy group, what can be normally used for an adhesive agent etc. can be used. Examples of compounds having an epoxy group useful in the present invention include aromatic epoxy compounds (polyglycidyl ethers of polyhydric phenols), hydrogenated bisphenol A or glycidyl ethers of bisphenol A and epichlorohydrin, and epoxy novolac resins. (For example, cresol novolac polyglycidyl ether, phenol novolac polyglycidyl ether), resole epoxy resin, resorcinol diglycidyl ether and the like, and as the aliphatic epoxy resin, an aliphatic polyhydric alcohol or an alkylene oxide adduct thereof is used. Typical examples include polyglycidyl ethers, polyglycidyl esters of aliphatic long-chain polybasic acids, and homopolymers and copolymers of glycidyl acrylate and glycidyl methacrylate. As ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether, tripropylene glycol glycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol di Glycidyl ether, nonapropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, glycerin triglycidyl ether, diglycerol triglycidyl ether, diglycerol tetraglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol triglycidyl ether, pentaerythritol tetra Of glycidyl ether and sorbitol Liglycidyl ether, cycloaliphatic epoxy compounds such as 3,4-epoxycyclohexylmethyl-3 ', 4'-epoxycyclohexanecarboxylate, 2- (3,4-epoxycyclohexyl-5,5-spiro-3', 4'-epoxy) cyclohexane-meta-dioxane, bis (3,4-epoxycyclohexylmethyl) adipate, vinylcyclohexenedioxide, bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate, 3,4-epoxy- 6-methylcyclohexyl-3 ', 4'-epoxy-6-methylcyclohexanecarboxylate, methylenebis (3,4-epoxycyclohexane) dicyclopentadiene diepoxide, ethylene glycol di (3,4-epoxycyclohexylmethyl) Tellurium, ethylenebis (3,4-epoxycyclohexanecarboxylate), dicyclopentadiene diepoxide, diglycidyl ether of tris (2-hydroxyethyl) isocyanurate, triglycidyl ether of tris (2-hydroxyethyl) isocyanurate, poly Glycidyl acrylate, polyglycidyl methacrylate, glycidyl acrylate or copolymer of glycidyl methacrylate and other monomers, poly-2-glycidyloxyethyl acrylate, poly-2-glycidyloxyethyl methacrylate, 2-glycidyloxyethyl acrylate, 2-glycidyl Copolymers of oxyethyl acrylate or 2-glycidyloxyethyl methacrylate and other monomers, bis-2,2-hydroxycyclohexane Can be exemplified Le propane diglycidyl ether, it may be used in combination of two or more. In this invention, it is not limited to said exemplary compound, The compound analogized from these is also included.
[0048]
In the present invention, in addition to a compound having two or more epoxy groups in the molecule, monoepoxide can also be used depending on the desired performance.
[0049]
The compound having an ultraviolet polymerizable epoxy group in the present invention forms a polymer, a crosslinked structure or a network structure not by radical polymerization but by cationic polymerization. Unlike radical polymerization, it is not affected by oxygen in the reaction system, so there is no induction period and the polymerization can be performed quickly.
[0050]
Although the representative example of the compound which has the epoxy group which can be used in this invention below, or the compound which has oxetanyl group is illustrated, it is not limited to these.
[0051]
[Chemical 8]

[0052]
[Chemical 9]

[0053]
<Photocationic polymerization initiator>
The compound having an epoxy group useful in the present invention undergoes a cationic polymerization reaction using a compound that generates a substance that initiates cationic polymerization upon irradiation with ultraviolet rays as a catalyst. A group of double salts of onium salts that release a Lewis acid is particularly preferred as the one that initiates cationic polymerization upon UV irradiation.
[0054]
A typical example of such a compound is a compound represented by the following general formula (I).
Formula (I)
[(R¹)_a(R²)_b(R³)_c(R⁴)_dZ]^{+ W}[MeXv + w]^-W
Wherein the cation is onium, Z is S, Se, Te, P, As, Sb, Bi, O, halogen (eg, I, Br, Cl), or N = N (diazo), R¹ _a, R² _b, R³ _c, R⁴ _dAre organic groups which may be the same or different. a, b, c, and d are each an integer of 0 to 3, and a + b + c + d is equal to the valence of Z. Me is a metal or metalloid which is a central atom of a halide complex, and B, P, As, Sb, Fe, Sn, Bi, Al, Ca, In, Ti, Zn, Sc, V, Cr, Mn, Co, etc. X is halogen, w is the net charge of the halogenated complex ion, and v is the number of halogen atoms in the halogenated complex ion.
[0055]
Anion of general formula (I) [MeXv + w]^-WSpecific examples of tetrafluoroborate (BF)₄ ⁻), Hexafluorophosphate (PF)₆ ⁻), Hexafluoroantimonate (SbF)₆ ⁻), Hexafluoroarsenate (AsF)₆ ⁻), Hexachloroantimonate (SbCl₆ ⁻And the like.
[0056]
Furthermore, an anion of the general formula MXn (OH)-can also be used. Other anions include perchlorate ion (ClO).₄ ⁻), Trifluoromethanesulfonate ion (CF₃SO₃ ⁻), Toluenesulfonate ion, naphthalenesulfonate ion, trinitrobenzenecarboxylate anion, and the like.
[0057]
Among these onium salts, it is particularly effective to use an aromatic onium salt as a cationic polymerization initiator. Among them, aromatic haloniums described in JP-A-50-151996, JP-A-50-158680 and the like are particularly effective. Salts, group VIA aromatic onium salts described in JP-A-50-151997, 52-30899, 59-55420, 55-125105, etc., JP-A-56-8428, 56- 149402, 57-192429, etc., oxosulfoxonium salts described in JP-B-49-17040, etc., aromatic diazonium salts described in US Pat. No. 4,139,655, etc. A thiopyrylium salt or the like is preferable. Moreover, an aluminum complex, a photodegradable silicon compound type | system | group polymerization initiator, etc. can be mentioned. The cationic polymerization initiator may be used in combination with a photosensitizer such as the benzophenone and derivatives thereof, the benzoin and derivatives thereof, and the thioxanthone and derivatives thereof. The sensitizer preferably has an absorption maximum from the near ultraviolet region to the visible light region.
Below, the cationic polymerization initiator of an aromatic onium salt is illustrated.
Embedded image

[0058]
In the present invention, when a photopolymerization initiator and / or a photosensitizer is mixed with a compound having an epoxy group in a cellulose acylate dope, the compound having an epoxy group with respect to cellulose acylate is 5 to 30% by mass, The photopolymerization initiator is 1 to 30% by mass, preferably 1 to 10% by mass, based on the compound having an epoxy group.
[0059]
A compound having an epoxy group and an ultraviolet absorber useful in the present invention may be mixed with a photopolymerization initiator to form a dope, or may be mixed with a compound having an epoxy group to form a dope.
[0060]
Examples of the ultraviolet absorbing group of the compound having an epoxy group and an ultraviolet absorbing group useful in the present invention include a benzotriazole group, a salicylic acid ester group, a benzophenone group, an oxybenzophenone group, and a cyanoacrylate group. Any of them can be preferably used. In particular, a benzotriazole group having low photoreactivity and almost no coloring is preferred.
[0061]
A cellulose acylate dope containing a compound having an epoxy group and an ultraviolet absorbing group according to the present invention is formed in a solution casting film forming process, and an ultraviolet absorber is precipitated or volatilized from a web irradiated with ultraviolet rays. Therefore, it is possible to obtain a protective film for a polarizing plate for a liquid crystal image display device having good productivity and excellent quality. Further, it is more preferable that the polymer of the compound having an epoxy group and an ultraviolet absorbing group has a water resistance with respect to cellulose acylate as described above, and the Tg of the polymer is preferably 50 ° C. or less.
[0062]
The proportion of the compound unit having an ultraviolet absorbing group constituting the photopolymerized polymer in the present invention is such that the compatibility of the polymer with the cellulose acylate, the mechanical property or the physical property of the cellulose acylate film is equivalent or more. Any material may be used as long as it has properties or sufficient ultraviolet absorption performance (may be in the range of 1 to 100% by mass).
[0063]
In the present invention, a photopolymerization initiator (also a photosensitizer as the case may be) is mixed with a compound having an epoxy group in a cellulose acylate dope. It is 1-30 mass% with respect to the compound whose mass% and a photoinitiator have an epoxy group, Preferably it is 1-10 mass%.
[0064]
In the present invention, an ethylenically unsaturated compound, a photoradical polymerization initiator, a compound having an epoxy group, and a photocationic polymerization initiator can be added to the cellulose acylate layer forming dope to be laminated.
[0065]
The solvent used in the coating of the present invention is only required to be compatible with the monomer, and it is preferable to use the same solvent as that used for the solution casting film formation described so far.
[0066]
Other additives used in the coating solution of the present invention may be those that can be dissolved / dispersed in the cellulose acylate coating solution, such as UV absorbing ability, antistatic ability, deterioration preventing ability, release promoting ability, retardation. What expresses adjustability, plasticity, slipperiness, etc. can be added. Specific examples of the particulate matting agent and the antioxidant are shown below, but the invention is not limited thereto.
[0067]
<Matting agent, etc.>
The cellulose acylate coating liquid of the present invention preferably contains a fine particle matting agent. The presence of the fine particle matting agent in the cellulose acylate film as the protective film for a polarizing plate after film formation is suitable. Sliding and scratch-resistant. The fine particle matting agent is used by mixing and dispersing in a cellulose acylate coating solution. Examples of the fine particle matting agent include inorganic substances such as silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate. It is preferable to contain fine particles and crosslinked polymer fine particles. Of these, silicon dioxide is preferable because it can reduce the haze of the film. The average particle size of the secondary particles of the fine particles is in the range of 0.01 to 1.0 μm, and the content thereof is preferably 0.005 to 0.3% by mass with respect to the cellulose acylate. In many cases, fine particles such as silicon dioxide are surface-treated with an organic substance, particularly a compound having a methyl group, but such a substance is preferable in the present invention because the haze of the film can be reduced. Preferred organic substances for the surface treatment include halosilanes, alkoxysilanes (particularly methoxysilane), silazane, siloxane and the like. The larger the average particle size of the fine particles, the greater the mat effect, and on the contrary, the smaller the average particle size, the better the transparency. Therefore, the average particle size of the preferred primary particles is 5 to 50 nm, more preferably 7 to 14 nm. It is. In the cellulose acylate film, these fine particles are usually present as aggregates, and it is preferable that irregularities of 0.01 to 1.0 μm are generated on the surface of the cellulose acylate film. Examples of the silicon dioxide fine particles include Aerosil 200, 200V, 300, R972, R972V, R974, R202, R812, OX50, TT600, etc. manufactured by Aerosil Co., Ltd., preferably AEROSIL R972, R972V, R974, R202, R812. Two or more of these matting agents may be used in combination. When using 2 or more types together, it can mix and use in arbitrary ratios. In this case, matting agents having different average particle sizes and materials, for example, AEROSIL 200V and R972V can be used in a mass ratio of 0.1: 99.9 to 99.9 to 0.1.
[0068]
Further, the cellulose acylate coating liquid of the present invention preferably contains an antioxidant, and as the antioxidant, a hindered phenol-based compound is preferably used, and 2,6-di-t-butyl is used. -P-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl) -4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine, 2,2-thio-diethylenebis [3- (3 -Di-t-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 1,3,5-trimethyl-2,4,6 -Tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanurate and the like can be mentioned. In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred. Further, for example, hydrazine-based metal deactivators such as N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di-t A phosphorus-based processing stabilizer such as -butylphenyl) phosphite may be used in combination. The amount of these compounds added is preferably 1 ppm to 1.0%, more preferably 10 to 1000 ppm in terms of mass ratio with respect to cellulose acylate.
[0069]
<UV irradiation>
In the present invention, ultraviolet irradiation for polymerizing the applied monomer polymerizable compound will be described.
The ultraviolet irradiation source for photopolymerizing the ethylenically unsaturated monomer or the 3-membered or 4-membered cyclic ether compound according to the present invention is a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a xenon lamp, a carbon arc. , Metal halide lamps, solar rays and the like. Photopolymerization by irradiation with ultraviolet rays can be carried out in air or in an inert gas, but in the case of using an ethylenically unsaturated monomer, it may be in air, but in order to shorten the induction period of polymerization, the oxygen concentration is as much as possible. A gas with less is preferred. Irradiation intensity of ultraviolet rays to be irradiated is 1-1000 mW / cm²The degree is good and the irradiation amount is 100 to 20000 mJ / cm.²The degree is preferred.
The ultraviolet irradiation is preferably performed after applying and drying a cellulose acylate coating solution containing an ethylenically unsaturated monomer and / or a 3-membered or 4-membered cyclic ether compound.
[0070]
(Surface treatment of cellulose acylate laminate film)
In the present invention, an improvement in adhesion between the cellulose acylate laminated film and each functional layer (for example, a release layer, an undercoat layer and a back layer) can be achieved by performing a surface treatment. For example, glow discharge treatment, ultraviolet irradiation treatment, corona treatment, flame treatment, acid or alkali treatment can be used. The glow discharge treatment here may be low-temperature plasma that occurs under a low pressure gas of 10-3 to 20 Torr, and plasma treatment under atmospheric pressure is also preferred. A plasma-excitable gas is a gas that is plasma-excited under the above conditions, and includes chlorofluorocarbons such as argon, helium, neon, krypton, xenon, nitrogen, carbon dioxide, tetrafluoromethane, and mixtures thereof. It is done. Details of these are described in detail on pages 30 to 32 in the Japan Society of Invention Disclosure Technical Bulletin (Public Technical Number 2001-1745, published on March 15, 2001, Invention Association). Note that, in the plasma treatment at atmospheric pressure which has been attracting attention in recent years, for example, irradiation energy of 20 to 500 Kgy is used under 10 to 1000 Kev, and more preferably irradiation energy of 20 to 300 Kgy is used under 30 to 500 Kev. Among these, an alkali saponification treatment is particularly preferable, and it is extremely effective as a surface treatment of a cellulose acylate film.
[0071]
The alkali saponification treatment is also preferably performed by applying a saponification solution. Examples of the coating method include a dip coating method, a curtain coating method, an extrusion coating method, a bar coating method, and an E-type coating method. The solvent of the alkali saponification coating solution has good wettability because it is applied to the transparent support of the saponification solution, and the surface state remains good without forming irregularities on the surface of the transparent support by the saponification solution solvent. It is preferred to select a solvent to keep. Specifically, an alcohol solvent is preferable, and isopropyl alcohol is particularly preferable. An aqueous solution of a surfactant can also be used as a solvent. The alkali of the alkali saponification coating solution is preferably an alkali that dissolves in the above solvent, and more preferably KOH or NaOH. The pH of the saponification coating solution is preferably 10 or more, more preferably 12 or more. The reaction conditions during alkali saponification are preferably 1 second to 5 minutes at room temperature, more preferably 2 seconds to 1 minute, and particularly preferably 3 seconds to 30 seconds. After the alkali saponification reaction, it is preferable to wash the surface on which the saponification solution is applied with water or with an acid and then with water. Further, the coating-type saponification treatment and the alignment film uncoating described later can be performed continuously, and the number of steps can be reduced. Furthermore, the cellulose acylate film obtained in the present invention may be subjected to alkali treatment by a dipping method. That is, the surface treatment can be carried out by continuously or intermittently arranging an alkali treatment bath, a water washing bath, an acid treatment bath, a water washing bath, and optionally a rinse bath. In this case, each solution has the same composition as the corresponding solution used in the coating method.
[0072]
(Use of cellulose acylate laminated film)
The use of the cellulose acylate laminated film produced in the present invention will be briefly described first. The optical film of the present invention is particularly useful for a polarizing plate protective film. When using as a polarizing plate protective film, the manufacturing method of a polarizing plate is not specifically limited, It can manufacture by a general method. There is a method in which the obtained cellulose acylate film is treated with an alkali and bonded to both sides of a polarizer prepared by immersing and stretching a polyvinyl alcohol film in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. Instead of alkali treatment, easy adhesion processing as described in JP-A-6-94915 and JP-A-6-118232 may be performed. Examples of the adhesive used to bond the protective film treated surface and the polarizer include polyvinyl alcohol adhesives such as polyvinyl alcohol and polyvinyl butyral, vinyl latexes such as butyl acrylate, and the like. The polarizing plate is composed of a polarizer and a protective film that protects both surfaces of the polarizer, and further includes a protective film bonded to one surface of the polarizing plate and a separate film bonded to the other surface. The protective film and the separate film are used for the purpose of protecting the polarizing plate at the time of shipping the polarizing plate and at the time of product inspection. In this case, the protect film is bonded for the purpose of protecting the surface of the polarizing plate, and is used on the side opposite to the surface where the polarizing plate is bonded to the liquid crystal plate. Moreover, a separate film is used in order to cover the adhesive layer bonded to a liquid crystal plate, and is used for the surface side which bonds a polarizing plate to a liquid crystal plate. In a liquid crystal display device, a substrate containing liquid crystal is usually disposed between two polarizing plates. However, a polarizing plate protective film to which the optical film of the present invention is applied can provide excellent display properties regardless of the location. . In particular, since the polarizing plate protective film on the outermost surface of the display side of the liquid crystal display device is provided with a transparent hard coat layer, an antiglare layer, an antireflection layer, and the like, the polarizing plate protective film is particularly preferably used in this portion.
[0073]
The cellulose acylate laminate film of the present invention (also simply referred to as “cellulose acylate film” in the present invention) can be used in various applications, and is particularly effective when used as an optical compensation sheet for liquid crystal display devices. The cellulose acylate film of the present invention can be used for liquid crystal cells in various display modes. TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), AFLC (Anti-Ferroelectric Liquid Crystal), OCB (OpticallySyPB). Various display modes such as HAN (Hybrid Aligned Nematic) have been proposed. In addition, a display mode in which the above display mode is oriented and divided has been proposed. The cellulose acylate film is effective in any display mode liquid crystal display device. Further, it is effective in any of a transmissive, reflective, and transflective liquid crystal display device. The cellulose acylate film of the present invention may be used as a support for an optical compensation sheet of a TN type liquid crystal display device having a TN mode liquid crystal cell. The cellulose acylate film of the present invention may be used as a support for an optical compensation sheet of an STN type liquid crystal display device having an STN mode liquid crystal cell. In general, in a STN type liquid crystal display device, rod-like liquid crystalline molecules in a liquid crystal cell are twisted in the range of 90 to 360 degrees, and the refractive index anisotropy (Δn) and cell gap (d ) In the range of 300 to 1500 nm. The optical compensation sheet used in the STN type liquid crystal display device is described in JP-A-2000-105316. The cellulose acylate film of the present invention is particularly advantageously used as a support for an optical compensation sheet of a VA liquid crystal display device having a VA mode liquid crystal cell. The cellulose acylate film of the present invention is also advantageously used as a support for an optical compensation sheet of an OCB type liquid crystal display device having an OCB mode liquid crystal cell or a HAN type liquid crystal display device having a HAN mode liquid crystal cell.
[0074]
<Optical compensation sheet>
The cellulose acylate film of the present invention is also advantageously used as an optical compensation sheet for TN-type, STN-type, HAN-type, and GH (Guest-Host) type reflective liquid crystal display devices. These display modes have been well known since ancient times. The TN type reflection type liquid crystal display device is described in JP-A-10-123478, WO98848320, and Japanese Patent No. 3022477. The optical compensation sheet used for the reflection type liquid crystal display device is described in WO00-65384. The cellulose acylate film of the present invention is also advantageously used as a support for an optical compensation sheet of an ASM type liquid crystal display device having a liquid crystal cell in an ASM (Axially Symmetrical Microcell) mode. The ASM mode liquid crystal cell is characterized in that the thickness of the cell is maintained by a resin spacer whose position can be adjusted. Other properties are the same as those of the TN mode liquid crystal cell. The ASM mode liquid crystal cell and the ASM type liquid crystal display device are described in Kume et al. (Kume et al., SID 98 Digest 1089 (1998)). The detailed uses of the cellulose acylate films described above are described in detail on pages 45 to 59 in the Japan Society for Invention and Innovation Technical Report (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society for Invention). Has been.
[0075]
【Example】
Example 1
(Preparation of cellulose triacetate solution: D-1)
A cellulose triacetate powder (average size 2 mm) was gradually added to a stainless steel dissolution tank having stirring blades while thoroughly stirring the following solvent mixed solution to prepare a dope. After the addition, the mixture was allowed to stand at room temperature (25 ° C.) for 1 hour and at 35 ° C. for 2 hours to swell cellulose triacetate. Note that methyl acetate and methyl ethyl ketone, methanol, ethanol, and n-butanol, which are solvents, all have a water content of 0.2% by mass or less.
[0076]
The component ratio of each component used for the preparation of the dope of Example 1 is shown below.
Cellulose triacetate 18 parts by mass
(Substitution degree 2.83, substitution degree 0.93 of acylation at the 6-position,
Substitution degree of acylation at position 2,3, 1.90, viscosity average weight
Total degree 320, moisture content 0.4% by mass, methylene chlora
(Viscosity of 6% by mass in id solution 305 mPa · s)
Methyl acetate 55 parts by mass
Methyl ethyl ketone 10 parts by mass
Methanol 5 parts by mass
Ethanol 5 parts by mass
n-Butanol 5 parts by mass
Plasticizer A (Diventaerythritol hexaacetate) 1 part by mass
Plasticizer B (Triphenyl phosphate) 1 part by mass
Fine particles (silica (particle diameter 20 nm)) 0.1 parts by mass
Vinyl acetate 0.72 parts by mass of vinyl acetate
Octadecyl methacrylate 0.27 parts by mass
Monomer (UVM-1) 0.27 parts by mass
0.15 parts by mass of photopolymerization initiator (1-hydroxycyclohexyl phenyl ketone)
[0077]
Next, the dope was defoamed by irradiating weak ultrasonic waves. The defoamed dope was first passed through a sintered metal filter having a nominal pore diameter of 5 μm while being pressurized to 1.5 MPa, and then passed through a sintered metal filter of 2.5 μm. The primary pressures were 1.5 and 1.2, respectively, and the secondary pressures were 1.0 and 0.8 MPa, respectively. The temperature of the dope after filtration was adjusted to 35 ° C. and stored in a stainless steel stock tank. The stock tank had an anchor blade on the central axis and was constantly stirred at a peripheral speed of 0.3 m / sec.
[0078]
(Film casting)
The dope obtained by the above-described dissolution method was heated to 50 ° C., and cast onto a mirror surface stainless steel support having a surface temperature of 20 ° C. through a casting Giesser to form a film. The dope cast on the band was first dried by sending parallel-flow drying air. The overall heat transfer coefficient from the drying wind to the dope when drying is 24 kcal / m²· Hr · ° C. The temperature of the drying air was 140 ° C. at the upper part of the band and 100 ° C. at the lower part.
For 5 seconds after casting, dry air is not directly applied to the dope by a wind shield, and then the total light irradiation amount on the dope surface is 350 mj / cm using a 2 kW high pressure mercury lamp.²The light was irradiated under the following conditions. Thereafter, a cellulose acetate film having a thickness of 25 μm was produced by conveying a drying zone having a large number of rolls.
[0079]
Comparative Example 1
In the composition in the preparation of the cellulose triacetate solution of Example 1, except for the photopolymerization initiator (1-hydroxycyclohexyl phenyl ketone), vinyl acetate, octadecyl methacrylate and the monomer (UVM-1), the composition of the example A cellulose acetate film having a film thickness of 25 μm after drying was produced in the same manner as in Example 1 using the same material as in Example 1.
[0080]
(Production of polarizer)
The PVA film was immersed in an aqueous solution of 2.0 g / L of iodine and 4.0 g / L of potassium iodide at 25 ° C. for 240 seconds, and further immersed in an aqueous solution of boric acid 10 g / L at 25 ° C. for 60 seconds, followed by tenter stretching. The film was introduced into a machine, stretched 5.3 times, and thereafter, the width was kept constant and dried in an atmosphere at 80 ° C. while shrinking, and then separated from the tenter and wound up. The moisture content of the PVA film before starting stretching was 31%, and the moisture content after drying was 1.5%.
The difference in transport speed between the left and right tenter clips was less than 0.05%. Wrinkles and film deformation at the tenter exit were not observed.
The transmittance of the obtained polarizer at 550 nm was 43.7%, and the degree of polarization was 99.97%.
[0081]
(Preparation of polarizing plate)
Each cellulose triacetate film formed above is immersed in a 1.5N NaOH aqueous solution at 55 ° C. for 1 minute to saponify both surfaces, washed thoroughly with dilute sulfuric acid and water, dried and then coated with a polyvinyl alcohol-based adhesive on each cellulose triacetate side. The agent was applied to a thickness of about 30 μm, bonded to both sides of the polarizer, and further dried at 80 ° C. to prepare a polarizing plate.
[0082]
(result)
The performance results of the cellulose triacetate film and the polarizing plate obtained above are shown in Table 1.
[Table 1]

The evaluation method of the evaluation items described in Table 1 was performed as follows.
1) Haze
The haze of the cellulose triacetate film was measured using a 1001DP type manufactured by Nippon Denshoku Industries Co., Ltd. for 500 hours under a high temperature and high humidity of 90 ° C./80% and examined before and after that.
A: Initial value
B: Shows the value after aging.
2) Tear strength
The tear strength of the cellulose triacetate film was evaluated by using a light heavy tear strength tester manufactured by Toyo Seiki Seisakusho, according to ISO 6383 / 2-1983. The sample was stored for 500 hours at a high temperature and high humidity of 90 ° C./80% and examined before and after. The sample size was 50 mm × 64 mm and the humidity was adjusted at 25 ° C. and 60% RH for 2 hours.
A: Initial value
B: Shows the value after aging.
3) Foreign matter and dirt
The cellulose triacetate film was cut out to a length of 1 m in the longitudinal direction with a full width, and the sample was observed for the presence and size of foreign matter and dirt with a loupe while allowing light to pass through the Schacus Ten, and evaluated according to the following grades.
A: There were no foreign matter and dirt having a size of 50 μm or more, and 0 to 10 pieces of less than 50 μm were observed.
B: No foreign matter or dirt having a size of 50 μm or more was observed, and 11 to 30 particles having a size of less than 50 μm were observed.
C: 1 to 10 foreign matters and dirt having a size of 50 μm or more were observed, and 31 to 50 foreign matters and 50 μm or less were observed.
D: 11 to 30 foreign matters and dirt having a size of 50 μm or more were observed, and 51 to 99 foreign matters having a size of 50 μm or less were observed.
E: 31 or more foreign matters and dirt having a size of 50 μm or more were observed, and 100 or more foreign matters and stains of 50 μm or less were observed.
4) Degree of polarization
For the polarization degree of the polarizing plate, the parallel transmittance Yp and the direct transmittance Yc in the visible region were obtained by a spectrophotometer, and the polarization degree P was determined based on the following equation.
P = ((Yp−Yc) / (Yp + Yc))^1/2
5) Durability
Two samples of 150 mm × 150 mm in size are cut out from the polarizing plate and stored for 100 hours under the condition of 50 ° C./80% RH, and the blank area generated at the edge of the polarizing plate by crossed Nicols is relative to the total area. The area ratio was observed and evaluated according to the following grade.
A: There were no white spots
○: White spots are less than 2% of the entire area
○ △: White spots are 2% or more and less than 5% of the entire area
Δ: White area is 5% or more and less than 10% of the entire area
×: The white portion is 10% or more with respect to the entire area.
[0083]
From the results in Table 1, the cellulose triacetate film of the present invention showed no foreign matter or dirt, and had a good haze value. Further, the tear strength of the film was sufficient without lowering. The cellulose triacetate film of Comparative Example 1 had a high haze due to the occurrence of cracks, and the tear strength was remarkably reduced over time at high temperature and high humidity. Moreover, the sample produced in exactly the same manner as the cellulose triacetate film of Example 1 except that the film thickness was 30 μm or more, particularly 35 to 85 μm, was inferior in optical properties such as haze.
The polarizing plate of the present invention had good polarization degree and durability. On the other hand, the polarizing plate of Comparative Example 1 was poor at a level that could not be put to practical use.
As described above, the cellulose triacetate film of the present invention and the polarizing plate using the same showed excellent performance.
[0084]
Examples 2-8
In the cellulose triacetate solution (D-1) in Example 1, in place of the photopolymerization initiator (1-hydroxycyclohexyl phenyl ketone), vinyl acetate, octadecyl methacrylate and UV monomer (UVM-1), each of the following Table 2 Each cellulose triacetate film having a thickness of 25 μm after drying was prepared in the same manner as in Example 1 except that the compound and a predetermined amount were used. Next, in the same manner as in Example 1, each polarizing plate was produced using each film.
[Table 2]

The obtained cellulose triacetate films and the polarizing plates of Examples 2 to 8 were evaluated in the same manner as in Example 1. Each of the examples showed a performance equal to or better than that of Example 1 and was good.
Below, a polymerizable monomer is illustrated.
Embedded image

[0085]
Example 9
(Preparation of cellulose triacetate solution)
A cellulose triacetate solution was obtained in the same manner as in Example 1 except that the composition having the following contents was used instead of the composition of the cellulose triacetate solution in Example 1.
Cellulose triacetate 20 parts by mass
(Substitution degree 2.82, 6-position acetyl group substitution degree 0.93,
(Viscosity average polymerization degree 320, water content 0.2% by mass)
Dichloromethane 62 parts by mass
Acetone 5 parts by mass
Methanol methanol 6 parts by mass
Butanol 5 parts by mass
Plasticizer C (ditrimethylolpropane tetraacetate) 1 part by mass
Plasticizer D (biphenyldiphenyl phosphate) 0.2 parts by mass
Silica fine particles (particle size 20 nm) 0.1 parts by mass
Vinyl acetate 0.8 parts by mass
Monomer (UVM-15) 0.48 parts by mass
Monomer (ASM-13) 0.32 parts by mass
Photopolymerization initiator (2,2-diethoxyphenylacetophenone) 0.17 parts by mass
Next, the above-mentioned cellulose triacetate solution was fed with a screw extruder, and allowed to pass through the cooling part at −70 ° C. for 10 minutes. Cooling was performed using a refrigerant at −80 ° C. (manufactured by 3M, “Fluorinert”) cooled by a refrigerator. The solution obtained by cooling is heated to 120 ° C. by a heat exchanger provided with a static mixer, held for 3 minutes, cooled, transferred to a stainless steel container at 50 ° C., and heated at 50 ° C. Defoaming was performed by stirring for 2 hours. After that, it is filtered with a filter paper with absolute filtration accuracy of 0.01 mm (“# 63” manufactured by Toyo Filter Paper Co., Ltd.), and further filtered with a filter paper with absolute filtration accuracy of 0.0025 mm (“FH025” manufactured by Ball Corp.). Then, a cellulose triacetate dope solution was prepared.
(Film casting)
In the same manner as in Example 1, a cellulose triacetate film having a thickness of 22 μm was produced.
(Preparation of polarizing plate)
Using the above film, a polarizing plate was produced in the same manner as in Example 1.
As a result of evaluating the performance of the obtained cellulose acetate film and polarizing plate in the same manner as in Example 1, it was as good as that in Example 1.
[0086]
【The invention's effect】
According to the present invention, it is possible to obtain a cellulose acylate film having a thin film thickness, excellent optical characteristics, no foreign matter and dirt, a good haze value, and sufficient tear strength. Moreover, the polarizing plate excellent in the polarization degree and durability can be obtained by using the cellulose acylate film of this invention.

Claims (3)

A cellulose acylate film produced by a solution casting film-forming method, wherein a cellulose acylate dope composition containing a polymerizable monomer and / or a polymerizable monomer having a functional group and a photopolymerization initiator is cast. A cellulose acylate film characterized by being a film having a thickness of 10 μm or more and less than 30 μm obtained by photopolymerizing the monomer during or after drying. The cellulose acylate film according to claim 1, comprising fine particles. A polarizing plate using the cellulose acylate film according to claim 1.