JP4285721B2 - Solution casting method - Google Patents

Description

【００３８】
劣化防止剤の添加量は、０．００１〜５％が好ましく、０．０１〜１％がより好ましい。添加量が０．００１％未満であると添加効果が少なく、添加量が５％を超えると、原料コストが上昇して不利である。
【００３９】
前記微粒子粉体としては、シリカ、カオリン、タルク、ケイソウ土、石英、炭酸カルシウム、硫酸バリウム、酸化チタン、アルミナなどを目的に応じ、任意に用いることができる。これら微粒子粉体はポリマー溶液に添加する前に、高速ミキサー、ボールミル、アトライター、超音波分散機等、任意の手段でバインダー溶液中に分散を行うことが好ましい。バインダーとしてはセルロースアシレートが好ましい。紫外線吸収剤等、他の添加物と共に分散を行うことも好ましい。分散溶媒は任意であるが、ポリマー溶液溶媒と近い組成であることが好ましい。
【００４０】
微粒子粉体の数平均粒径は０．０１〜１００μｍが好ましく、０．１〜１０μｍが特に好ましい。上記の分散液はセルロースアシレート溶解工程に同時に添加しても良いし、任意の工程でポリマー溶液に添加できるが、紫外線吸収剤同様スタティックミキサ等を用い、流延直前に添加する形態が好ましい。
【００４１】
微粒子粉体の含有量は、セルロースアシレートに対して０．００１〜５質量％であることが好ましく、０．０１〜１質量％であることがより好ましい。添加量が０．００１質量％未満では添加効果を十分に発揮することができず、添加量が５質量％を超えると、外観面状が悪くなる場合がある。
【００４２】
前記離型剤としては、界面活性剤が有効であり、リン酸系、スルフォン酸系、カルボン酸系、ノニオン系、カチオン系など特に限定されない。これらは、例えば特開昭６１−２４３８３７号などに記載されている。離型剤の添加量は、セルロースアシレートに対して０．００１〜２質量％が好ましく、０．０１〜１質量％がより好ましい。添加量が０．００１質量％未満であれば添加効果を十分に発揮することができず、添加量が２質量％を超えると、析出したり、不溶解物を生じたりすることがある。
【００４３】
ノニオン系界面活性剤としては、ポリオキシエチレン、ポリオキシプロピレン、ポリオキシブチレン、ポリグリシジルやソルビタンをノニオン性親水性基とする界面活性剤であり、具体的には、ポリオキシエチレンアルキルエーテル、ポリオキシエチレンアルキルフェニールエーテル、ポリオキシエチレン−ポリオキシプロピレングリコール、多価アルコール脂肪酸部分エステル、ポリオキシエチレン多価アルコール脂肪酸部分エステル、ポリオキシエチレン脂肪酸エステル、ポリグリセリン脂肪酸エステル、脂肪酸ジエタノールアミド、トリエタノールアミン脂肪酸部分エステルを挙げることができる。
【００４４】
アニオン系界面活性剤としてはカルボン酸塩、硫酸塩、スルフォン酸塩、リン酸エステル塩であり、代表的なものとしては脂肪酸塩、アルキルベンゼンスルフォン酸塩、アルキルナフタレンスルフォン酸塩、アルキルスルフォン酸塩、α−オレフィンスルフォン酸塩、ジアルキルスルフォコハク酸塩、α−スルフォン化脂肪酸塩、Ｎ−メチルーＮオレイルタウリン、石油スルフォン酸塩、アルキル硫酸塩、硫酸化油脂、ポリオキシエチレンアルキルエーテル硫酸塩、ポリオキシエチレンアルキルフェニールエーテル硫酸塩、ポリオキシエチレンスチレン化フェニールエーテル硫酸塩、アルキルリン酸塩、ポリオキシエチレンアルキルエーテルリン酸塩、ナフタレンスルフォン酸塩ホルムアルデヒド縮合物などである。
【００４５】
カチオン系界面活性剤としてはアミン塩、４級アンモニウム塩、ピリジュム塩などを挙げることができ、第一〜第３脂肪アミン塩、第４級アンモニウム塩（テトラアルキルアンモニウム塩、トリアルキルベンジルアンモニウム塩、アルキルピリジウム塩、アルキルイミダゾリウム塩など）を挙げることが出来る。両性系界面活性剤としてはカルボキシベタイン、スルフォベタインなどであり、Ｎ−トリアルキル−Ｎ−カルボキシメチルアンモニウムベタイン、Ｎ−トリアルキル−Ｎ−スルフォアルキレンアンモニウムベタインなどである。
【００４６】
前記フッ素系界面活性剤を添加することにより、帯電防止効果を発揮することができる。フッ素系界面活性剤の添加量は、セルロースアシレートに対して０．００２〜２質量％が好ましく、０．０１〜０．５質量％がより好ましい。添加量が０．００２質量％未満であれば添加効果を十分に発揮することができず、添加量が２質量％を超えると、析出したり、不溶解物を生じたりすることがある。
【００４７】
本発明においては、レターデーション上昇剤（光学特性調整剤）を添加することができる。レターデーション上昇剤を添加することにより、光学異方性をコントロールすることができる。レターデーション上昇剤は、セルロースアシレートフイルムのレターデーションを調整するため、少なくとも二つの芳香族環を有する芳香族化合物を使用することが好ましい。芳香族化合物は、セルロースアシレート１００質量部に対して、０．０１〜２０質量部の範囲で使用する。芳香族化合物は、セルロースアセレート１００質量部に対して、０．０５〜１５質量部の範囲で使用することが好ましく、０．１〜１０質量部の範囲で使用することがさらに好ましい。二種類以上の芳香族化合物を併用してもよい。芳香族化合物の芳香族環には、芳香族炭化水素環に加えて、芳香族性ヘテロ環を含む。
【００４８】
芳香族炭化水素環は、６員環（すなわち、ベンゼン環）であることが特に好ましい。芳香族性ヘテロ環は一般に、不飽和ヘテロ環である。芳香族性ヘテロ環は、５員環、６員環または７員環であることが好ましく、５員環または６員環であることがさらに好ましい。芳香族性ヘテロ環は一般に、最多の二重結合を有する。ヘテロ原子としては、窒素原子、酸素原子および硫黄原子が好ましく、窒素原子が特に好ましい。芳香族性ヘテロ環の例には、フラン環、チオフェン環、ピロール環、オキサゾール環、イソオキサゾール環、チアゾール環、イソチアゾール環、イミダゾール環、ピラゾール環、フラザン環、トリアゾール環、ピラン環、ピリジン環、ピリダジン環、ピリミジン環、ピラジン環および１，３，５−トリアジン環が含まれる。
【００４９】
本発明においては、着色剤を添加することができる。着色剤を添加することにより、感光材料支持体等に用いる場合、ライトパイピングを防止することができる。着色剤の添加量は、セルロースアシレートに対する重量割合で１０〜１０００ｐｐｍが好ましく、５０〜５００ｐｐｍが更に好ましい。
【００５０】
また、本発明におけるポリマー溶液には、ルシウム、マグネシウムなどのアルカリ土類金属の塩などの熱安定剤、帯電防止剤、難燃剤、滑剤、油剤などを、必要に応じて適宜添加することができる。
【００５１】
本発明の溶液製膜方法により製造されるフィルムの光学特性について記す。まず、フィルムの面内のレターデーション（Ｒｅ）について記すと、その測定法はエリプソメーター（偏光解析計ＡＥＰ−１００：島津製作所（株）製）を用いて、波長６３２．８ｎｍにおける面内の縦横の屈折率差にフィルム膜厚さを乗じたものであり、下記の式で求められる。
Ｒｅ＝（ｎｘ−ｎｙ）×ｄ
ｎｘ：横方向の屈折率
ｎｙ：縦方向の屈折率
【００５２】
レターデーション（Ｒｅ）は、小さいほど面内方向の光学異方性がないことを示し、０〜３００ｎｍの範囲で用途に応じて用いられる。又、フィルムの厚さ方向のレターデーション（Ｒｔｈ）も重要であり、波長６３２．８ｎｍにおける厚さ方向の複屈折にフィルム膜厚さを乗じたものであり、下記の式で求められる。Ｒｔｈ＝｛（ｎｘ＋ｎｙ）／２−ｎｚ｝×ｄ
ｎｘ：横方向の屈折率
ｎｙ：縦方向の屈折率
ｎｚ：厚さ方向の屈折率
【００５３】
厚さ方向の屈折率が小さいほど、厚さ方向の光学異方性がないことを示すが、その使用用途によって好ましい範囲は定まる。一般には、本発明により製造されたセルロースアシレートフィルムのＲｔｈは１００μｍ当たり、０ｎｍ〜６００ｎｍであり、さらには０ｎｍ〜４００ｎｍで用いられる。
【００５４】
本発明の溶液製膜方法で製造されるフィルムは、例えば、偏光板保護膜、光学補償シート、ＡＲ、ＬＲ、ＡＧ膜用支持体フィルム等の光学用途フィルム、写真感光材料用支持体フィルムとしても利用することができる。
【００５５】
本発明の溶液製膜方法で製造されるフィルムを光学補償シートに利用する場合、フイルムそのものを光学補償シートとして用いることができる。なお、フイルムそのものを光学補償シートとして用いる場合は、偏光板の透過軸と、光学補償シートの遅相軸とを実質的に平行または垂直になるように配置することが好ましい。このような偏光板と光学補償シートとの配置については、特開平１０−４８４２０号公報に記載がある。液晶表示装置は、二枚の電極基板の間に液晶を担持してなる液晶セル、その両側に配置された二枚の偏光板、および該液晶セルと該偏光板との間に少なくとも一枚の光学補償シートを配置した構成を有している。
【００５６】
液晶セルの液晶層は、通常は、二枚の基板の間にスペーサーを挟み込んで形成した空間に液晶を封入して形成する。透明電極層は、導電性物質を含む透明な膜として基板上に形成する。液晶セルには、さらにガスバリアー層、ハードコート層あるいは（透明電極層の接着に用いる）アンダーコート層（下塗り層）を設けてもよい。これらの層は、通常、基板上に設けられる。液晶セルの基板は、一般に５０μｍ〜２ｍｍの厚さを有する。
【００５７】
光学補償シートは複屈折性を有し、液晶表示装置の表示画面の着色を取り除いたり、視野角特性を改善したりする目的で用いられる。本発明によるセルロースアシレートフィルムそのものを、光学補償シートとして用いることができる。さらに反射防止層、防眩性層、λ／４層や２軸延伸セルロースアシレートフィルムとして機能を付与してもよい。また、液晶表示装置の視野角を改良するため、本技術のセルロースアシレートフィルムと、それとは（正／負の関係が）逆の複屈折を示すフィルムを重ねて光学補償シートとして用いてもよい。
【００５８】
また、支持体の上に液晶性化合物（特にディスコティック液晶性分子）を含む光学的異方性層を設けた光学補償シートも提案されている（特開平３−９３２５号、同６−１４８４２９号、同８−５０２０６号、同９−２６５７２号の各公報記載）。本発明の溶液製膜方法で製造されるフィルムそのような光学補償シートの支持体としても用いることができる。
【００５９】
前記偏光板の偏光素子には、ヨウ素系偏光膜、二色性染料を用いる染料系偏光膜やポリエン系偏光膜がある。いずれの偏光素子も、一般にポリビニルアルコール系フィルムを用いて製造する。偏光板の保護膜は、２５〜３５０μｍの厚さを有することが好ましく、４０〜２００μｍの厚さを有することがさらに好ましい。液晶表示装置には、表面処理膜を設けてもよい。表面処理膜の機能には、ハードコート、防曇処理、防眩処理および反射防止処理が含まれる。
【００６０】
前記光学的異方性層は、負の一軸性を有し傾斜配向したディスコティック液晶性分子を含む層であることが好ましい。ディスコティック液晶性分子を含む層が、円盤面と支持体面とのなす角が光学的異方性層の深さ方向において変化したハイブリッド配向していても構わないし、円盤面が支持体面と平行なホメオトロピック配向、円盤面が支持体面と垂直なホモジニアス配向、または、円盤面が光学的異方性層の深さ方向でねじれているツイスト配向を取っていても構わない。また、これらの配向が混在した配向（例えば、ハイブリッド配向＋ツイスト配向）していても構わない。そのなかでもハイブリッド配向していることが好ましい。ディスコティック液晶性分子ひとつひとつの光軸は、円盤面の法線方向に存在する。しかし、ディスコティック液晶性分子がハイブリッド配向している層全体としては、光軸は存在しない。
【００６１】
本発明の溶液製膜方法により製造されるフィルムは、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。
【００６２】
本発明の溶液製膜方法で製造されるフィルムを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。ＴＮモードの液晶セルとＴＮ型液晶表示装置については、古くから良く知られている。ＴＮ型液晶表示装置に用いる光学補償シートについては、特開平３−９３２５号、同６−１４８４２９号、同８−５０２０６号、同９−２６５７２号の各公報に記載がある。また、モリ（Ｍｏｒｉ）他の論文（Ｊｐｎ．Ｊ．Ａｐｐｌ．Ｐｈｙｓ．Ｖｏｌ．３６（１９９７）ｐ．１４３や、Ｊｐｎ．Ｊ．Ａｐｐｌ．Ｐｈｙｓ．Ｖｏｌ．３６（１９９７）ｐ．１０６８）に記載がある。ＴＮ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。
【００６３】
本発明の溶液製膜方法で製造されるフィルムを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（Δｎ）とセルギャップ（ｄ）との積（Δｎｄ）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。
【００６４】
本発明の溶液製膜方法で製造されるフィルムを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用いてもよい。ＶＡ型液晶表示装置に用いる光学補償シートには、レターデーションの絶対値が最小となる方向が光学補償シートの面内にも法線方向にも存在しないことが好ましい。ＶＡ型液晶表示装置に用いる光学補償シートの光学的性質は、光学的異方性層の光学的性質、支持体の光学的性質および光学的異方性層と支持体との配置により決定される。ＶＡ型液晶表示装置に光学補償シートを二枚使用する場合は、光学補償シートの面内レターデーションを、−５ｎｍ〜５ｎｍの範囲内にすることが好ましい。従って、二枚の光学補償シートのそれぞれの面内レターデーションの絶対値は、０〜５とすることが好ましい。ＶＡ型液晶表示装置に光学補償シートを一枚使用する場合は、光学補償シートの面内レターデーションを、−１０ｎｍ〜１０ｎｍの範囲内にすることが好ましい。
【００６５】
本発明の溶液製膜方法で製造されるフィルムを、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用いてもよい。ＯＣＢ型液晶表示装置あるいはＨＡＮ型液晶表示装置に用いる光学補償シートには、レターデーションの絶対値が最小となる方向が光学補償シートの面内にも法線方向にも存在しないことが好ましい。ＯＣＢ型液晶表示装置あるいはＨＡＮ型液晶表示装置に用いる光学補償シートの光学的性質も、光学的異方性層の光学的性質、支持体の光学的性質および光学的異方性層と支持体との配置により決定される。ＯＣＢ型液晶表示装置あるいはＨＡＮ型液晶表示装置に用いる光学補償シートについては、特開平９−１９７３９７号公報に記載がある。また、モリ（Ｍｏｒｉ）他の論文（Ｊｐｎ．Ｊ．Ａｐｐｌ．Ｐｈｙｓ．Ｖｏｌ．３８（１９９９）ｐ．２８３７）に記載がある。
【００６６】
本発明の溶液製膜方法で製造されるフィルムを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用いてもよい。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）外の論文（Ｋｕｍｅ ｅｔ ａｌ．，ＳＩＤ ９８ Ｄｉｇｅｓｔ １０８９（１９９８））に記載がある。
【００６７】
【実施例】
［実施例１］
溶剤含有量２０重量％のセルロースアセテートを塩化メチレン、メタノール９２：８の混合溶液とし支持体バンド上に流延し、熱風により乾燥し剥離した。剥離したフィルムの残留溶剤量が乾量基準で４０重量％になるまでの乾燥排気ガスを−５℃で凝縮回収した。それ以降の乾燥ゾーンで発生した乾燥排気を活性炭吸着層によって回収し、回収した溶剤を蒸留により脱水分離し塩化メチレン、メタノール９２：８の混合溶液を得た。
【００６８】
［実施例２］
溶剤含有量２０重量％のセルロースアセテートを塩化メチレン、メタノール９２：８の混合溶液とし支持体バンド上に流延し、熱風により乾燥し剥離した。剥離したフィルムの残留溶剤量が乾量基準で１０重量％になるまでの乾燥排気ガスを−５℃で凝縮回収した。それ以降の乾燥ゾーンで発生した乾燥排気を活性炭吸着層によって回収し、回収した溶剤を蒸留により脱水分離し塩化メチレン、メタノール９２：８の混合溶液を得た。
【００６９】
［実施例３］
酢酸メチル８０、エタノール１５、ブタノール５の混合溶剤に酢化度５９．２％のセルロースアセテート１７、トリフェニルフォスフェート３を分散したのち、−７０℃に冷却し、しかるのちに１２０℃まで加熱して得た固形分濃度２０重量％のポリマー溶液を支持体上に流延した。フィルム残留溶剤の量が８０重量％になるまで乾燥した乾燥排気を０℃で凝縮回収し、フィルム残留溶剤の量が５％になるまでの乾燥排気を活性炭で吸着回収し、蒸留により分離精製した。また残りの乾燥ゾーンにおける乾燥排気を蒸熱方式の燃焼装置で燃焼処理した。
【００７０】
分離精製した溶剤は協和化学工業社製「ＤＨＴ−４Ａ」を充填したカラムにて処理した。
【００７１】
［比較例１］
溶剤含有量２０重量％のセルロースアセテートを塩化メチレン、メタノール８５：１５の混合溶液とし支持体バンド上に流延し、熱風により乾燥し剥離した剥離したフィルムの残留溶剤量が乾量基準で１００重量％になるまでの乾燥排気ガスを−５℃で凝縮回収した。それ以降の乾燥ゾーンで発生した乾燥排気を活性炭吸着層によって回収し、回収した溶剤を蒸留により脱水分離し塩化メチレン、メタノール９２：８の混合溶液を得た。
【００７２】
［比較例２］
酢酸メチル８０、エタノール１５、ブタノール５の混合溶剤に酢化度５９．２％のセルロースアセテート１７、トリフェニルフォスフェート３を分散したのち、−７０℃に冷却し、しかるのちに１２０℃まで加熱して得た固形分濃度２０重量％のポリマー溶液を支持体上に流延した。フィルム残留溶剤の量が１２０重量％になるまで乾燥した乾燥排気を０℃で凝縮回収し、残りのフィルム残留溶剤を乾燥した乾燥排気を活性炭で吸着回収し、蒸留により分離精製した。
【００７３】
なお、実施例１〜３においては、凝縮回収する乾燥ゾーンの雰囲気の酸素濃度を５ｖｏｌ％にするために窒素ガスを注入した。比較例１、２においては、凝集回収する乾燥ゾーンの雰囲気は、通常の大気組成とした。
【００７４】
その結果、実施例１〜３においては酸素濃度は５ｖｏｌ％に保たれ、安定に操業することができた。これに対し、比較例１〜２においては、乾燥ゾーン内の雰囲気が爆発下限界濃度と上限界濃度の間を通過することがあった。
【００７５】
実施例１〜３の方法で製膜したフィルムを偏光板保護膜とする偏光板を作製し、耐久性を評価した。
【００７６】
［偏光板の作成方法および評価方法］
偏光板サンプルはポリビニルアルコールを延伸してヨウ素を吸着させた偏光素子の両面にポリビニルアルコール系接着剤により貼合し作製した。この偏光板サンプルを６０℃，９０％ＲＨの雰囲気下で５００時間暴露した。いずれにおいても偏光度は９９．６％以上であり、十分な耐久性が認められた。
【００７７】
なお、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）、直交透過率（Ｙｃ）を求め次式に基づいて偏光度Ｐを決定した。
【００７８】
【数１】

【００７９】
【表１】

【００８０】
また、前記偏光板１組をＴＦＴ（薄膜トランジスター）方式の液晶表示装置に実装した結果、良好なコントラストを得ることができた。
【００８１】
［実施例４］
＜セルローストリアセテート溶液の作製＞
攪拌羽根を有するステンレス性溶解タンクに、下記の溶剤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）を徐々に添加して仕込んだ。添加後、室温（２５℃）にて３時間，２５℃にて放置し、セルローストリアセテートを膨潤させた。なお、溶剤である酢酸メチルとシクロペンタノン、アセトン、メタノール及びエタノールは、すべてその含水率が０．２質量％以下のものを利用した。
【００８２】
セルローストリアセテート １６質量部
（置換度２．８３、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 ５３質量部
シクロペンタン １０質量部
アセトン ５質量部
メタノール ５質量部
エタノール ５質量部
可塑剤Ａ（ジペンタエリスリトールヘキサアセテート） ３質量部
可塑剤Ｂ（トリフェニルフォスフェート） ３質量部
微粒子粉体（シリカ（粒径２０ｎｍ）） ０．１質量部
紫外線吸収剤ａ ０．１質量部
（２，４−ビス−（ｎ−オクチルチオ）−６−（４−ヒドロキシ−３，５−ジ−ｔｅｒｔ−ブチルアニリノ）−１，３，５−トリアジン）
紫外線吸収剤ｂ ０．１質量部
（２（２’−ヒドロキシ−３’，５’−ジ−ｔｅｒｔ−ブチルフェニル）−５−クロルベンゾトリアゾール）
紫外線吸収剤ｃ ０．１質量部
（２（２’−ヒドロキシ−３’，５’−ジ−ｔｅｒｔ−アミルフェニル）−５−クロルベンゾトリアゾール
Ｃ₁₂Ｈ₂₅ＯＣＨ₂ＣＨ₂Ｏ−Ｐ(＝Ｏ)−(ＯＫ)₂ ０．０５質量部
【００８３】
なお、後述する冷却溶解法で得られたこの溶液の粘度は１６０Ｐａ・Ｓ（４５℃）であった。
【００８４】
＜セルローストリアセテート溶液の冷却溶解＞
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３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時間撹拌し脱泡を行った。このように調製したセルローストリアセテート溶液を、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（ポール社製，『ＦＨ ０２５』）にて濾過した。
【００８５】
＜セルローストリアセテートフィルムの作製＞
上述した溶解法で得られたセルローストリアセテート溶液を５０℃にし、流延ギーザ−を通して鏡面ステンレスの流延支持体上に流延した。流延支持体温度は１０℃であり、流延スピードは４０ｍ／分で、その塗布幅は１００ｃｍとした。乾燥は１２０℃の乾燥風を送風した。２分後に鏡面ステンレスの流延支持体から剥ぎ取り、その後、１１０℃、１０分、さらに１５０℃で３０分乾燥して、セルローストリアセテートフィルム（膜厚４０μｍ）を得た。
【００８６】
この時、フィルム残留溶剤の量が３０重量％になるまで乾燥した乾燥排気を−５℃で凝縮回収し、フィルム残留溶剤の量が０．２％になるまでの乾燥排気を活性炭で吸着回収し、蒸留により分離精製した。また残りの乾燥ゾーンにおける乾燥排気を蒸熱方式の燃焼装置で燃焼処理した。この溶剤の回収率は、９９．５％であった。
【００８７】
＜偏光板ａの作製＞
延伸したポリビニルアルコールフィルムにヨウ素を吸着させて偏光素子を作製し、ポリビニルアルコール系接着剤を用いて、上記セルローストリアセテートフィルムを、その遅相軸が偏光素子の透過軸と平行になるように両側に貼り付けた。
【００８８】
＜偏光性の評価＞
偏光板ａを８０℃、９０ＲＨの雰囲気下で５００時間暴露し、上述した方法で偏光度を測定した。偏光度は９９．６％以上であり、十分な耐久性が認められた。
【００８９】
＜偏光板ｂの作製＞
延伸したポリビニルアルコールフィルムにヨウ素を吸着させて偏光素子を作製し、ポリビニルアルコール系接着剤を用いて、上記セルローストリアセテートフィルムを、その遅相軸が偏光膜の透過軸と平行になるように片側に貼り付けるとともに、上記セルローストリアセテートフィルムにケン化処理を行い、ポリビニルアルコール系接着剤を用いて、偏光膜の反対側に貼り付けた。さらに、光学補償シート（富士写真フイルム（株）製，『ＷＶフィルム』）をセルローストリアセテートフィルム側に、その遅相軸が互いに平行になるように粘着剤を用いて貼り付け、光学補償シートを貼合した偏光板を作製した。
【００９０】
＜液晶表示装置での評価＞
上記偏光板ａ及び偏光板ｂをＴＦＴ（薄膜トランジスター）方式の液晶表示装置に実装した。その結果、良好な視野角およびコントラストを得ることができた。
【００９１】
［実施例５］
＜内層用セルローストリアセテート溶液の作製＞
攪拌羽根を有するステンレス性溶解タンクに、下記の溶剤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）を徐々に添加して仕込んだ。添加後、室温（２５℃）にて３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、溶剤である酢酸メチルとシクロペンタノン、アセトン、メタノール及びエタノールは、すべてその含水率が０．２質量％以下のものを利用した。
【００９２】
セルローストリアセテート １６質量部
（置換度２．８３、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 ５３質量部
シクロペンタン １０質量部
アセトン ５質量部
メタノール ５質量部
エタノール ５質量部
可塑剤Ａ（ジペンタエリスリトールヘキサアセテート） ３質量部
可塑剤Ｂ（トリフェニルフォスフェート） ３質量部
微粒子粉体（シリカ（粒径２０ｎｍ）） ０．１質量部
紫外線吸収剤ａ ０．１質量部
（２，４−ビス−（ｎ−オクチルチオ）−６−（４−ヒドロキシ−３，５−ジ−ｔｅｒｔ−ブチルアニリノ）−１，３，５−トリアジン）
紫外線吸収剤ｂ ０．１質量部
（２（２’−ヒドロキシ−３’，５’−ジ−ｔｅｒｔ−ブチルフェニル）−５−クロルベンゾトリアゾール）
紫外線吸収剤ｃ ０．１質量部
（２（２’−ヒドロキシ−３’，５’−ジ−ｔｅｒｔ−アミルフェニル）−５−クロルベンゾトリアゾール
Ｃ₁₂Ｈ₂₅ＯＣＨ₂ＣＨ₂Ｏ−Ｐ(＝Ｏ)−(ＯＫ)₂ ０．０５質量部
【００９３】
なお、冷却溶解法で得られたこの溶液の粘度は６０Ｐａ・Ｓ（４５℃）であった。
【００９４】
＜内層用セルローストリアセテート溶液の冷却溶解＞
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３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時間撹拌し脱泡を行った。このセルローストリアセテート溶液を絶対濾過精度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（ポール社製，『ＦＨ ０２５』）で濾過した。
【００９５】
＜外層用セルローストリアセテート溶液の調整＞
上述した内層用セルローストリアセテート溶液において、セルローストリアセテートを１９質量部、酢酸メチルを４４質量部に変更した他は、同様に仕込んだ。なお、冷却溶解法で得られたこの溶液の粘度は２５Ｐａ・Ｓ（４５℃）であった。
【００９６】
＜外層用セルローストリアセテート溶液の冷却溶解＞
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３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時間撹拌し脱泡を行った。このセルローストリアセテート溶液を絶対濾過精度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（ポール社製，『ＦＨ ０２５』）で濾過した。
【００９７】
＜セルローストリアセテートフィルムの作製＞
上述したセルローストリアセテート溶液を三層共流延ダイを用い、内層用セルローストリアセテート溶液が内側に、外層用セルローストリアセテート溶液が両外側になるように配置して、金属ならなる流延支持体上に同時に吐出させて重層流延した後、流延膜を流延支持体から剥ぎ取り、乾燥して三層構造のセルローストリアセテートフィルム積層体（内層の厚さ：８０μｍ、各表面層の厚さ：２μｍ）を作製した。
【００９８】
この時、フィルム残留溶剤の量が４５重量％になるまで乾燥した乾燥排気を５℃で凝縮回収し、フィルム残留溶剤の量が０．５％になるまでの乾燥排気を活性炭で吸着回収し、蒸留により分離精製した。また残りの乾燥ゾーンにおける乾燥排気を蒸熱方式の燃焼装置で燃焼処理した。この溶剤の回収率は、９９％であった。
【００９９】
流延支持体から剥ぎ取ったフィルムは、テンターにより搬送しつつ乾燥させ、１００℃で３分、１３０℃で５分乾燥させた後、１５０℃で１０分で段階的に乾燥させて溶剤を蒸発させてセルローストリアセテートフィルムを得た。
【０１００】
＜偏光板ｃの作製＞
延伸したポリビニルアルコールフィルムにヨウ素を吸着させて偏光素子を作製し、ポリビニルアルコール系接着剤を用いて、上記セルローストリアセテートフィルムを、その遅相軸が偏光素子の透過軸と平行になるように両側に貼り付けた。
【０１０１】
＜偏光性の評価＞
偏光板ｃを８０℃、９０ＲＨの雰囲気下で５００時間暴露し、上述した方法で偏光度を測定した。偏光度は９９．６％以上であり、十分な耐久性が認められた。
【０１０２】
＜偏光板ｄの作製＞
延伸したポリビニルアルコールフィルムにヨウ素を吸着させて偏光素子を作製し、ポリビニルアルコール系接着剤を用いて、上記セルローストリアセテートフィルムを、その遅相軸が偏光素子の透過軸と平行になるように片側に貼り付けるとともに、上記セルローストリアセテートフィルムにケン化処理を行い、ポリビニルアルコール系接着剤を用いて、偏光素子の反対側に貼り付けた。さらに、光学補償シート（富士写真フイルム（株）製，『ＷＶフィルム』）をセルローストリアセテートフィルム側に、その遅相軸が互いに平行になるように粘着剤を用いて貼り付け、光学補償シートを貼合した偏光板を作製した。
【０１０３】
＜液晶表示装置での評価＞
上記偏光板ｃ及び偏光板ｄをＴＦＴ（薄膜トランジスター）方式の液晶表示装置に実装した。その結果、良好な視野角およびコントラストを得ることができた。
【０１０４】
【発明の効果】
本発明により、溶液製膜方法において、流延されたフィルムから発生する溶剤を効率よく回収して再利用することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a polymer film used for a support of a photographic light-sensitive material or a polarizing plate protective film by a solution casting method.
[0002]
[Prior art]
In the solution casting method, not only the polymer as the main raw material but also the recycling and recycling of the solvent are important in terms of production cost and environment. Condensation recovery and adsorption recovery are often used for solvent gas recovery and recycling. For example, JP-A-9-38451 discloses a method for adsorbing and recovering a solvent from at least three types of solvent-containing exhaust gases having different solvent concentrations.
[0003]
[Problems to be solved by the invention]
However, the adsorption recovery has an advantage that a dilute gas can be recovered, but has a disadvantage that a large amount of energy is consumed. This is because a large amount of steam or high-temperature nitrogen must be used for desorption of the solvent from the adsorbent such as activated carbon, and water and components must be separated by distillation or the like. Further, in the adsorption recovery method, there is a risk that exhaust gas containing an organic solvent is released to the atmosphere depending on conditions.
[0004]
An object of the present invention is to provide a solution casting method using an organic solvent, in which the solvent can be recycled and reused, which is advantageous in terms of energy and can be efficiently recovered.
[0005]
The present invention has been made to solve the above-mentioned problems, and a polymer solution in which a polymer is dissolved in a solvent is cast on a support from a casting die, and the cast film is peeled off from the support. In a solution casting process in which drying is performed in at least two or more drying zones, 80 to 98% of the solvent released from the cast film until it is dried is condensed and recovered in the first drying zone. This object is achieved by a solution casting method characterized in that the residue is adsorbed and collected by an adsorbent in the second and subsequent drying zones .
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Cellulose acylate is used as the material polymer of the polymer solution used in the solution casting method of the present invention. Details of the cellulose acylate are described below. Preferred cellulose acylates are those in which the substitution degree of the hydroxyl group of cellulose satisfies all of the following formulas (1) to (4).
(1) 2.6 ≦ A + B ≦ 3.0
(2) 2.0 ≦ A ≦ 3.0
(3) 0 ≦ B ≦ 0.8
(4) 1.9 <AB
[0007]
Here, A and B represent the substituent of the acyl group substituted by the hydroxyl group of cellulose, A is the substitution degree of an acetyl group, and B is the substitution degree of a C3-C5 acyl group. . Cellulose has three hydroxyl groups in one glucose unit, and the above number represents the degree of substitution with respect to the hydroxyl group 3.0, and the maximum degree of substitution is 3.0. Cellulose triacetate generally has a substitution degree of A of 2.6 or more and 3.0 or less (in this case, there is a maximum of 0.4 hydroxyl groups not substituted), and B = 0 is cellulose triacetate. The cellulose acylate used in the polymer solution of the solution film-forming method of the present invention is cellulose triacetate whose acyl groups are all acetyl groups, and an acetyl group of 2.0 or more and an acyl group of 3 to 5 carbon atoms is 0.00. It is preferably 8 or less and an unsubstituted hydroxyl group of 0.4 or less, particularly preferably cellulose triacetate having a substitution degree of 2.6 to 3.0. The degree of substitution can be obtained by calculation by measuring the degree of binding of acetic acid substituted with a hydroxyl group of cellulose and a fatty acid having 3 to 5 carbon atoms. As a measuring method, it can carry out according to ASTM D-817-91.
[0008]
Other acyl groups having 3 to 5 carbon atoms such as acetyl group are propionyl group (C ₂ H ₅ CO—), butyryl group (C ₃ H ₇ CO—) (n-, iso-), valeryl group (C ₄ H ₉ CO-) (n-, iso-, sec-, tert-), among which n-substituted ones are preferred from the viewpoint of mechanical strength when formed into a film, ease of dissolution, etc., and in particular, n-propionyl Groups are preferred. Moreover, when the substitution degree of an acetyl group is low, mechanical strength and heat-and-moisture resistance deteriorate. When the degree of substitution of the acyl group having 3 to 5 carbon atoms is high, the solubility in an organic solvent is improved. However, if the degree of substitution is within the above range, good physical properties are exhibited.
[0009]
The degree of polymerization (average viscosity) of cellulose acylate is preferably from 200 to 700, particularly preferably from 250 to 550. The viscosity average degree of polymerization (DP) can be determined with an Ostwald viscometer, and is determined from the measured intrinsic viscosity [η] of cellulose acylate according to the following formula.
DP = [η] / Km (where Km is a constant 6 × 10 ⁻⁴ )
[0010]
Examples of cellulose as a cellulose acylate raw material include cotton linter and wood pulp. Any cellulose acylate obtained from any raw material cellulose may be used, or these may be used in combination.
[0011]
Examples of organic solvents that dissolve cellulose acylate include hydrocarbons (eg benzene, toluene), halogenated hydrocarbons (eg methylene chloride, chlorobenzene), alcohols (eg methanol, ethanol, diethylene glycol), ketones (eg : Acetone), esters (eg, methyl acetate, ethyl acetate, propyl acetate) and ethers (eg, tetrahydrofuran, methyl cellosolve) and the like.
[0012]
A halogenated hydrocarbon having 1 to 7 carbon atoms is preferably used, and methylene chloride is most preferably used. From the viewpoint of physical properties such as solubility of cellulose acylate, peelability from the support, mechanical strength of the film, optical properties, etc., in addition to methylene chloride, one or several alcohols having 1 to 5 carbon atoms are mixed. It is preferable. 2-25 mass% is preferable with respect to the whole solvent, and, as for content of alcohol, 5-20 mass% is more preferable. Specific examples of the alcohol include methanol, ethanol, n-propanol, isopropanol, n-butanol, etc., but methanol, ethanol, n-butanol, or a mixture thereof is preferably used.
[0013]
Moreover, it is preferable to use the solvent which consists of methyl acetate, ketones, and alcohol and whose solvent ratio is 20-90 mass% of methyl acetate, 5-60 mass% of ketones, and 5-30 mass% of alcohol.
[0014]
Recently, a solvent composition not using methylene chloride has been proposed in order to minimize the influence on the environment. For this purpose, ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, and esters having 3 to 12 carbon atoms are preferable, and these are used by appropriately mixing them. These ethers, ketones and esters may have a cyclic structure. A compound having two or more functional groups of ether, ketone and ester (that is, —O—, —CO— and —COO—) can also be used as the organic solvent. The organic solvent may have another functional group such as an alcoholic hydroxyl group. In the case of an organic solvent having two or more types of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group.
[0015]
Examples of ethers having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole. Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone and methylcyclohexanone. Examples of the esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate. Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.
[0016]
In a system that cannot be easily dissolved at room temperature and a system that contains a large amount of insoluble matter, a good polymer solution can be prepared by using cooling or heating at the time of dissolution or a combination of both. In the cooling dissolution method, dissolution is accelerated by allowing a solvent to rapidly and effectively penetrate into the polymer. The effective temperature condition is −100 to −10 ° C., and a polymer solution with better solubility can be obtained by heating to room temperature to 200 ° C. after cooling.
[0017]
The polymer solution as described above is cast from a casting die onto a band or drum support, and when the cast film is peeled off from the support and dried, a gas containing a solvent (generally Air or nitrogen). In the present invention, the solvent is recovered by condensing the first part of the solvent-containing gas having a high solvent concentration, and the latter part is adsorbed by the adsorbent and recovered.
[0018]
The amount of solvent recovered by this condensation is 80% or more of the total amount of solvent removed by drying, preferably 90% or more, more preferably 95% or more, and the amount of solvent recovered by adsorption is preferably 2% or more, preferably Is 4%. In order to condense and recover more than 98% of the solvent, it is necessary to set the condensation temperature very low, which is inefficient.
[0019]
Recovery by condensation may be performed using an ordinary condenser, and the temperature depends on the type of solvent, but when methylene chloride is used as the main solvent, it is about -40 to + 10 ° C, preferably about -30 to 0 ° C. When methyl acetate is used as the main solvent, about −30 to + 20 ° C., preferably about −20 to + 10 ° C. is appropriate.
[0020]
A circulation system is generally used in which the exhaust gas after condensation is heated again as dry air and supplied to the drying zone.
[0021]
For recovery by adsorption, activated carbon, zeolite, or the like may be used as the adsorbent, and steam, high-temperature nitrogen gas, or the like can be used for desorption of the solvent from the adsorbent.
[0022]
Further, when a flammable solvent such as methyl acetate or acetone is used as the main solvent, it may be advantageous in terms of energy consumption to burn a certain amount of the diluted gas. However, since the combustion treatment is disadvantageous in terms of solvent recovery and reuse, it is necessary to determine the treatment amount in consideration of the solvent recovery rate. The amount of the solvent to be combusted is less than 5% of the whole, and about 0.5 to 2% is appropriate.
[0023]
In addition, it is important to remove the trace amount of acid generated in the solvent at the same time as separating water from the recovered solvent in order to maintain the quality of the solvent and suppress corrosion of the equipment. Therefore, it is necessary to treat the recovered solvent with a deoxidizer. As the deoxidizer, hydrotalcite-based compounds can be used. A contact method with an alkaline aqueous solution can also be used.
[0024]
In the polymer solution used in the solution casting method of the present invention, various additives (for example, plasticizers, ultraviolet absorbers, deterioration inhibitors, fine particle powders, mold release agents, optical properties) according to the use in each preparation step. Regulators, fluorosurfactants) can be added. Further, the addition may be performed at any time in the polymer solution preparation step, but may be performed by adding an additive to the final preparation step of the polymer solution preparation step.
[0025]
As the plasticizer, phosphoric acid ester or carboxylic acid ester is used. Examples of phosphate esters include triphenyl phosphate (TPP) and tricresyl phosphate (TCP), cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, etc. Can be given. Representative examples of the carboxylic acid ester include phthalic acid esters and citric acid esters. Examples of phthalic acid esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethyl hexyl phthalate (DEHP). Examples of citrate esters include triethyl O-acetylcitrate (OACTE) and tributyl O-acetylcitrate (OACTB), acetyltriethyl citrate, and acetyltributyl citrate.
[0026]
Examples of other carboxylic acid esters include trimellitic acid esters such as butyl oleate, methyl acetyl ricinoleate, dibutyl sebacate, and trimethyl trimellitate. Examples of glycolic acid esters include triacetin, tributyrin, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate, and butyl phthalyl butyl glycolate.
[0027]
Among the plasticizers exemplified above, triphenyl phosphate, biphenyl diphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, tributyl phosphate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, diethyl hexyl phthalate , Triacetin, ethyl phthalyl ethyl glycolate, trimethyl trimellitate and the like are preferably used. In particular, triphenyl phosphate, biphenyl diphenyl phosphate, diethyl phthalate, ethyl phthalyl ethyl glycolate, and trimethyl trimellitate are preferable.
[0028]
The above plasticizers may be used alone or in combination of two or more. 0.1-20 mass% is preferable with respect to a cellulose acylate, and, as for the addition amount of a plasticizer, 5-15 mass% is more preferable. When the addition amount is less than 0.1% by mass, the effect of addition cannot be sufficiently exhibited, and when the addition amount exceeds 20% by mass, the film surface may bleed out.
[0029]
In addition, in the present invention, (di) pentaerythritol esters described in JP-A No. 11-124445, glycerol esters described in JP-A No. 11-246704, and JP-A No. 2000 are used as plasticizers for reducing the optical anisotropy. Diglycerol esters described in JP-A No.-63560, citric acid esters described in JP-A No. 11-92574, substituted phenyl phosphate esters described in JP-A No. 11-90946 are preferably used.
[0030]
The ultraviolet absorber can be selected from any type according to the purpose, and a salicylic acid ester-based, benzophenone-based, benzotriazole-based, benzoate-based, cyanoacrylate-based, nickel complex-based absorber or the like is used. However, benzophenone series, benzotriazole series, and salicylic acid ester series are preferred. Examples of benzophenone ultraviolet absorbers include 2,4-dihydroxybenzophenone, 2-hydroxy-4-acetoxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2′-di-hydroxy-4-methoxybenzophenone, 2, 2′-di-hydroxy-4,4′-methoxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2-hydroxy-4- (2-hydroxy-3- And methacryloxy) propoxybenzophenone. As a benzotriazole ultraviolet absorber, 2 (2′-hydroxy-3′-tert-butyl-5′-methylphenyl) -5-chlorobenzotriazole, 2 (2′-hydroxy-5′-tert-butylphenyl) ) Benzotriazole, 2 (2′-hydroxy-3 ′, 5′-di-tert-amylphenyl) benzotriazole, 2 (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) -5 And chlorobenzotriazole, 2 (2′-hydroxy-5′-tert-octylphenyl) benzotriazole, and the like. Examples of salicylic acid esters include phenyl salicylate, p-octylphenyl salicylate, and p-tert-butylphenyl salicylate. Among these exemplified ultraviolet absorbers, in particular, 2-hydroxy-4-methoxybenzophenone, 2,2′-di-hydroxy-4,4′-methoxybenzophenone, 2 (2′-hydroxy-3′-tert-butyl- 5'-methylphenyl) -5-chlorobenzotriazole, 2 (2'-hydroxy-5'-tert-butylphenyl) benzotriazole, 2 (2'-hydroxy-3 ', 5'-di-tert-amylphenyl) ) Benzotriazole, 2 (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) -5-chlorobenzotriazole is particularly preferred.
[0031]
As the ultraviolet absorber, it is preferable to use a combination of a plurality of absorbers having different absorption wavelengths because a high blocking effect can be obtained in a wide wavelength range. From the viewpoint of preventing deterioration of the liquid crystal, the ultraviolet absorbent for liquid crystal is preferably excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less, and from the viewpoint of liquid crystal display properties, the absorption of visible light having a wavelength of 400 nm or more is small. Examples include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. Particularly preferred ultraviolet absorbers are benzotriazole compounds and benzophenone compounds. Among these, a benzotriazole-based compound is preferable because unnecessary coloring with respect to the cellulose ester is small.
[0032]
As for the ultraviolet absorber, JP-A-60-235852, JP-A-3-199201, JP-A-51907073, JP-A-5-194789, JP-A-5-271471, JP-A-6-107854, JP-A-6-107854, 118233, 6-148430, 7-11056, 7-11055, 7-11056, 8-29619, 8-239509, and JP-A-2000-204173. There is a description.
[0033]
0.001-5 mass% is preferable with respect to a cellulose acylate, and, as for the addition amount of a ultraviolet absorber, 0.01-1 mass% is more preferable. If the addition amount is less than 0.001% by mass, the effect of addition cannot be sufficiently exhibited. If the addition amount exceeds 5% by mass, the ultraviolet absorber may bleed out to the film surface.
[0034]
Further, the ultraviolet absorber may be added at the same time as dissolving the cellulose acylate, or may be added to the polymer solution after dissolution. In particular, a mode in which an ultraviolet absorbent solution is added to a polymer solution immediately before casting using a static mixer or the like is preferable because spectral absorption characteristics can be easily adjusted.
[0035]
The deterioration inhibitor can prevent cellulose triacetate and the like from deteriorating and decomposing. Examples of the deterioration preventing agent include butylamine, hindered amine compounds (JP-A-8-325537), guanidine compounds (JP-A-5-271471), benzotriazole-based UV absorbers (JP-A-6-235819), and benzophenone-based compounds. There are compounds such as UV absorbers (JP-A-6-118233).
[0036]
Among these, examples of hindered amine compounds include t-butylamine, triphenylamine, and tribenzylamine. Examples of guanidine derivatives include compounds represented by the following formulas (1a) and (1b).
[0037]
[Chemical 1]

[0038]
The addition amount of the deterioration preventing agent is preferably 0.001 to 5%, more preferably 0.01 to 1%. If the addition amount is less than 0.001%, the effect of addition is small, and if the addition amount exceeds 5%, the raw material cost increases, which is disadvantageous.
[0039]
As the fine particle powder, silica, kaolin, talc, diatomaceous earth, quartz, calcium carbonate, barium sulfate, titanium oxide, alumina and the like can be arbitrarily used depending on the purpose. These fine particle powders are preferably dispersed in the binder solution by any means such as a high-speed mixer, a ball mill, an attritor, or an ultrasonic disperser before being added to the polymer solution. As the binder, cellulose acylate is preferable. It is also preferable to carry out dispersion together with other additives such as ultraviolet absorbers. The dispersion solvent is arbitrary, but a composition close to that of the polymer solution solvent is preferable.
[0040]
The number average particle size of the fine particle powder is preferably from 0.01 to 100 μm, particularly preferably from 0.1 to 10 μm. The above dispersion may be added simultaneously to the cellulose acylate dissolving step, or can be added to the polymer solution in any step, but it is preferable to add it just before casting using a static mixer or the like as with the ultraviolet absorber.
[0041]
The content of the fine particle powder is preferably 0.001 to 5% by mass, and more preferably 0.01 to 1% by mass with respect to the cellulose acylate. If the addition amount is less than 0.001% by mass, the effect of addition cannot be exhibited sufficiently, and if the addition amount exceeds 5% by mass, the appearance surface may be deteriorated.
[0042]
As the mold release agent, a surfactant is effective, and is not particularly limited, such as a phosphoric acid type, a sulfonic acid type, a carboxylic acid type, a nonionic type, and a cationic type. These are described in, for example, JP-A-61-243837. 0.001-2 mass% is preferable with respect to a cellulose acylate, and, as for the addition amount of a mold release agent, 0.01-1 mass% is more preferable. If the addition amount is less than 0.001% by mass, the effect of addition cannot be sufficiently exerted, and if the addition amount exceeds 2% by mass, precipitation or insoluble matter may occur.
[0043]
Nonionic surfactants include surfactants having nonionic hydrophilic groups such as polyoxyethylene, polyoxypropylene, polyoxybutylene, polyglycidyl and sorbitan, and specifically include polyoxyethylene alkyl ethers, polyoxyethylene alkyl ethers, and polyoxyethylene alkyl ethers. Oxyethylene alkyl phenyl ether, polyoxyethylene-polyoxypropylene glycol, polyhydric alcohol fatty acid partial ester, polyoxyethylene polyhydric alcohol fatty acid partial ester, polyoxyethylene fatty acid ester, polyglycerin fatty acid ester, fatty acid diethanolamide, triethanolamine Mention may be made of fatty acid partial esters.
[0044]
Examples of the anionic surfactant include carboxylate, sulfate, sulfonate, and phosphate ester salt. Representative examples include fatty acid salt, alkylbenzene sulfonate, alkylnaphthalene sulfonate, alkyl sulfonate, α-olefin sulfonate, dialkylsulfosuccinate, α-sulfonated fatty acid salt, N-methyl-N oleyl taurine, petroleum sulfonate, alkyl sulfate, sulfated fat, polyoxyethylene alkyl ether sulfate, poly Examples thereof include oxyethylene alkyl phenyl ether sulfate, polyoxyethylene styrenated phenyl ether sulfate, alkyl phosphate, polyoxyethylene alkyl ether phosphate, and naphthalene sulfonate formaldehyde condensate.
[0045]
Examples of the cationic surfactant include amine salts, quaternary ammonium salts, pyridinium salts, and the like. Primary to tertiary fatty amine salts, quaternary ammonium salts (tetraalkyl ammonium salts, trialkylbenzyl ammonium salts, Alkyl pyridium salt, alkyl imidazolium salt, etc.). Examples of amphoteric surfactants include carboxybetaine and sulfobetaine, such as N-trialkyl-N-carboxymethylammonium betaine and N-trialkyl-N-sulfoalkyleneammonium betaine.
[0046]
By adding the fluorosurfactant, an antistatic effect can be exhibited. The addition amount of the fluorosurfactant is preferably 0.002 to 2% by mass and more preferably 0.01 to 0.5% by mass with respect to the cellulose acylate. If the addition amount is less than 0.002% by mass, the effect of addition cannot be sufficiently exhibited, and if the addition amount exceeds 2% by mass, precipitation or insoluble matter may occur.
[0047]
In the present invention, a retardation increasing agent (optical property adjusting agent) can be added. The optical anisotropy can be controlled by adding a retardation increasing agent. The retardation increasing agent is preferably an aromatic compound having at least two aromatic rings in order to adjust the retardation of the cellulose acylate film. An aromatic compound is used in 0.01-20 mass parts with respect to 100 mass parts of cellulose acylates. The aromatic compound is preferably used in the range of 0.05 to 15 parts by mass, and more preferably in the range of 0.1 to 10 parts by mass with respect to 100 parts by mass of the cellulose acylate. Two or more aromatic compounds may be used in combination. The aromatic ring of the aromatic compound includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring.
[0048]
The aromatic hydrocarbon ring is particularly preferably a 6-membered ring (that is, a benzene ring). The aromatic heterocycle is generally an unsaturated heterocycle. The aromatic heterocycle is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring. Aromatic heterocycles generally have the most double bonds. As the hetero atom, a nitrogen atom, an oxygen atom and a sulfur atom are preferable, and a nitrogen atom is particularly preferable. Examples of aromatic heterocycles include furan ring, thiophene ring, pyrrole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, pyrazole ring, furazane ring, triazole ring, pyran ring, pyridine ring , Pyridazine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring.
[0049]
In the present invention, a colorant can be added. By adding a colorant, light piping can be prevented when used for a photosensitive material support. The amount of the colorant added is preferably 10 to 1000 ppm, more preferably 50 to 500 ppm, by weight with respect to cellulose acylate.
[0050]
In the polymer solution of the present invention, a heat stabilizer such as a salt of an alkaline earth metal such as lucium and magnesium, an antistatic agent, a flame retardant, a lubricant, an oil agent and the like can be appropriately added as necessary. .
[0051]
It describes about the optical characteristic of the film manufactured by the solution casting method of this invention. First, the in-plane retardation (Re) of the film will be described. The measurement method uses an ellipsometer (Ellipsometer AEP-100: manufactured by Shimadzu Corporation), and the in-plane longitudinal and lateral directions at a wavelength of 632.8 nm. Is obtained by multiplying the difference in refractive index by the film thickness.
Re = (nx−ny) × d
nx: refractive index in the horizontal direction ny: refractive index in the vertical direction
The smaller the retardation (Re) is, the smaller the optical anisotropy in the in-plane direction is, and it is used in the range of 0 to 300 nm depending on the application. In addition, retardation in the thickness direction (Rth) of the film is also important, which is obtained by multiplying birefringence in the thickness direction at a wavelength of 632.8 nm by the film thickness, and is obtained by the following formula. Rth = {(nx + ny) / 2−nz} × d
nx: refractive index in the horizontal direction ny: refractive index in the vertical direction nz: refractive index in the thickness direction
A smaller refractive index in the thickness direction indicates that there is no optical anisotropy in the thickness direction, but a preferable range is determined depending on the intended use. In general, the Rth of the cellulose acylate film produced according to the present invention is 0 nm to 600 nm per 100 μm, and further used at 0 nm to 400 nm.
[0054]
Films produced by the solution casting method of the present invention can be used as optical films such as polarizing plate protective films, optical compensation sheets, AR, LR, AG film support films, and support films for photographic materials. Can be used.
[0055]
When the film produced by the solution casting method of the present invention is used as an optical compensation sheet, the film itself can be used as the optical compensation sheet. When the film itself is used as an optical compensation sheet, it is preferable to arrange the transmission axis of the polarizing plate and the slow axis of the optical compensation sheet so that they are substantially parallel or perpendicular. The arrangement of the polarizing plate and the optical compensation sheet is described in JP-A-10-48420. The liquid crystal display device includes a liquid crystal cell having a liquid crystal supported between two electrode substrates, two polarizing plates disposed on both sides thereof, and at least one sheet between the liquid crystal cell and the polarizing plate. An optical compensation sheet is arranged.
[0056]
The liquid crystal layer of the liquid crystal cell is usually formed by sealing liquid crystal in a space formed by sandwiching a spacer between two substrates. The transparent electrode layer is formed on the substrate as a transparent film containing a conductive substance. The liquid crystal cell may further be provided with a gas barrier layer, a hard coat layer, or an undercoat layer (undercoat layer) (used for adhesion of the transparent electrode layer). These layers are usually provided on the substrate. The substrate of the liquid crystal cell generally has a thickness of 50 μm to 2 mm.
[0057]
The optical compensation sheet has birefringence and is used for the purpose of removing the color of the display screen of the liquid crystal display device or improving the viewing angle characteristics. The cellulose acylate film itself according to the present invention can be used as an optical compensation sheet. Further, the function may be imparted as an antireflection layer, an antiglare layer, a λ / 4 layer or a biaxially stretched cellulose acylate film. In addition, in order to improve the viewing angle of the liquid crystal display device, the cellulose acylate film of the present technology and a film exhibiting a birefringence opposite to that (a positive / negative relationship) may be used as an optical compensation sheet. .
[0058]
In addition, optical compensation sheets in which an optically anisotropic layer containing a liquid crystal compound (particularly a discotic liquid crystal molecule) is provided on a support have been proposed (Japanese Patent Laid-Open Nos. 3-9325 and 6-148429). 8-50206 and 9-26572). The film produced by the solution casting method of the present invention can also be used as a support for such an optical compensation sheet.
[0059]
Examples of the polarizing element of the polarizing plate include an iodine polarizing film, a dye polarizing film using a dichroic dye, and a polyene polarizing film. Any polarizing element is generally manufactured using a polyvinyl alcohol film. The protective film of the polarizing plate preferably has a thickness of 25 to 350 μm, and more preferably 40 to 200 μm. The liquid crystal display device may be provided with a surface treatment film. The functions of the surface treatment film include hard coat, anti-fogging treatment, anti-glare treatment and antireflection treatment.
[0060]
The optically anisotropic layer is preferably a layer containing negatively uniaxially tilted and aligned discotic liquid crystal molecules. The layer containing the discotic liquid crystalline molecules may be hybrid-aligned in which the angle formed by the disk surface and the support surface changes in the depth direction of the optically anisotropic layer, and the disk surface is parallel to the support surface. Homeotropic orientation, homogeneous orientation in which the disc surface is perpendicular to the support surface, or twist orientation in which the disc surface is twisted in the depth direction of the optically anisotropic layer may be adopted. Moreover, the orientation in which these orientations are mixed (for example, hybrid orientation + twist orientation) may be used. Among these, the hybrid orientation is preferable. The optical axis of each discotic liquid crystalline molecule exists in the normal direction of the disk surface. However, the optical axis does not exist in the entire layer in which the discotic liquid crystalline molecules are hybrid-aligned.
[0061]
The film produced by the solution casting method 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 Crystals), AFLC (Anti-Ferroelectric Liquid Crystals), OCB (Optically Charged TNS). 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 type, a reflective type, and a transflective liquid crystal display device.
[0062]
The film produced by the solution casting method 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. TN mode liquid crystal cells and TN type liquid crystal display devices have been well known for a long time. The optical compensation sheet used for the TN liquid crystal display device is described in JP-A-3-9325, JP-A-6-148429, JP-A-8-50206, and JP-A-9-26572. Moreover, it is described in Mori et al. (Jpn. J. Appl. Phys. Vol. 36 (1997) p. 143 and Jpn. J. Appl. Phys. Vol. 36 (1997) p. 1068). is there. The TN liquid crystal display device is described in JP-A-10-123478, WO98848320, and Japanese Patent No. 3022477.
[0063]
You may use the film manufactured by the solution casting method of this invention as a support body of the optical compensation sheet | seat of the STN type liquid crystal display device which has a liquid crystal cell of STN mode. 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) of the rod-like liquid crystalline molecules. Product (Δnd) is 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.
[0064]
The film produced by the solution casting method of the present invention may be used as a support for an optical compensation sheet of a VA liquid crystal display device having a VA mode liquid crystal cell. In the optical compensation sheet used for the VA liquid crystal display device, it is preferable that the direction in which the absolute value of retardation is minimum does not exist in the plane of the optical compensation sheet or in the normal direction. The optical properties of the optical compensation sheet used in the VA liquid crystal display device are determined by the optical properties of the optically anisotropic layer, the optical properties of the support, and the arrangement of the optically anisotropic layer and the support. . When two optical compensation sheets are used in the VA liquid crystal display device, the in-plane retardation of the optical compensation sheet is preferably in the range of −5 nm to 5 nm. Therefore, the absolute value of the in-plane retardation of each of the two optical compensation sheets is preferably 0 to 5. When one optical compensation sheet is used in the VA liquid crystal display device, it is preferable that the in-plane retardation of the optical compensation sheet be in the range of −10 nm to 10 nm.
[0065]
The film produced by the solution casting method of the present invention may be 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. Good. In the optical compensation sheet used for the OCB type liquid crystal display device or the HAN type liquid crystal display device, it is preferable that the direction in which the absolute value of retardation is minimum does not exist in the plane of the optical compensation sheet or in the normal direction. The optical properties of the optical compensation sheet used in the OCB type liquid crystal display device or the HAN type liquid crystal display device are also the optical properties of the optical anisotropic layer, the optical properties of the support, and the optical anisotropic layer and the support. Is determined by the arrangement of An optical compensation sheet used for an OCB type liquid crystal display device or a HAN type liquid crystal display device is described in JP-A-9-197397. Further, it is described in a paper by Mori et al. (Jpn. J. Appl. Phys. Vol. 38 (1999) p. 2837).
[0066]
The film produced by the solution casting method of the present invention may be used as a support for an optical compensation sheet of an ASM type liquid crystal display device having a liquid crystal cell of ASM (Axial 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 a paper (Kume et al., SID 98 Digest 1089 (1998)) outside Kume.
[0067]
【Example】
[Example 1]
Cellulose acetate having a solvent content of 20% by weight was cast as a mixed solution of methylene chloride and methanol 92: 8 on a support band, dried with hot air and peeled off. Dry exhaust gas was condensed and recovered at -5 ° C. until the residual solvent amount of the peeled film reached 40% by weight on a dry basis. The dried exhaust gas generated in the subsequent drying zone was recovered by the activated carbon adsorption layer, and the recovered solvent was dehydrated and separated by distillation to obtain a mixed solution of methylene chloride and methanol 92: 8.
[0068]
[Example 2]
Cellulose acetate having a solvent content of 20% by weight was cast as a mixed solution of methylene chloride and methanol 92: 8 on a support band, dried with hot air and peeled off. Dry exhaust gas was condensed and recovered at −5 ° C. until the residual solvent amount of the peeled film reached 10% by weight on a dry basis. The dried exhaust gas generated in the subsequent drying zone was recovered by the activated carbon adsorption layer, and the recovered solvent was dehydrated and separated by distillation to obtain a mixed solution of methylene chloride and methanol 92: 8.
[0069]
[Example 3]
Cellulose acetate 17 having an acetylation degree of 59.2% and triphenyl phosphate 3 are dispersed in a mixed solvent of methyl acetate 80, ethanol 15 and butanol 5, and then cooled to -70 ° C and then heated to 120 ° C. The polymer solution having a solid content of 20% by weight obtained above was cast on a support. The dry exhaust dried until the amount of residual solvent in the film reached 80% by weight was condensed and recovered at 0 ° C., and the dry exhaust until the amount of residual solvent in the film reached 5% was adsorbed and recovered with activated carbon and separated and purified by distillation. . Further, the dry exhaust in the remaining drying zone was combusted with a steam-heat combustion system.
[0070]
The separated and purified solvent was treated in a column packed with “DHT-4A” manufactured by Kyowa Chemical Industry Co., Ltd.
[0071]
[Comparative Example 1]
Cellulose acetate with a solvent content of 20% by weight is cast as a mixed solution of methylene chloride and methanol 85:15 on a support band, dried with hot air and peeled off, and the residual solvent amount of the peeled film is 100% by dry weight. % Of the exhaust exhaust gas was condensed and recovered at -5 ° C. The dried exhaust gas generated in the subsequent drying zone was recovered by the activated carbon adsorption layer, and the recovered solvent was dehydrated and separated by distillation to obtain a mixed solution of methylene chloride and methanol 92: 8.
[0072]
[Comparative Example 2]
Cellulose acetate 17 having an acetylation degree of 59.2% and triphenyl phosphate 3 are dispersed in a mixed solvent of methyl acetate 80, ethanol 15 and butanol 5, and then cooled to -70 ° C and then heated to 120 ° C. The polymer solution having a solid content of 20% by weight obtained above was cast on a support. The dry exhaust dried until the amount of residual solvent in the film was 120% by weight was condensed and recovered at 0 ° C., and the dry exhaust after drying the remaining residual solvent was adsorbed and recovered with activated carbon, and separated and purified by distillation.
[0073]
In Examples 1 to 3, nitrogen gas was injected in order to make the oxygen concentration in the atmosphere of the drying zone to be condensed and recovered 5 vol%. In Comparative Examples 1 and 2, the atmosphere in the drying zone for aggregation and recovery was a normal atmospheric composition.
[0074]
As a result, in Examples 1 to 3, the oxygen concentration was maintained at 5 vol%, and the operation was stable. On the other hand, in Comparative Examples 1 and 2, the atmosphere in the drying zone sometimes passed between the lower explosion limit concentration and the upper limit concentration.
[0075]
A polarizing plate was prepared using the film formed by the method of Examples 1 to 3 as a polarizing plate protective film, and the durability was evaluated.
[0076]
[Method for producing and evaluating polarizing plate]
A polarizing plate sample was prepared by pasting polyvinyl alcohol on both surfaces of a polarizing element on which iodine was adsorbed by stretching polyvinyl alcohol. This polarizing plate sample was exposed for 500 hours in an atmosphere of 60 ° C. and 90% RH. In any case, the degree of polarization was 99.6% or more, and sufficient durability was recognized.
[0077]
The degree of polarization was determined by obtaining the parallel transmittance (Yp) and orthogonal transmittance (Yc) in the visible region with a spectrophotometer, and determining the degree of polarization P based on the following equation.
[0078]
[Expression 1]

[0079]
[Table 1]

[0080]
Further, as a result of mounting one set of the polarizing plates on a TFT (Thin Film Transistor) type liquid crystal display device, good contrast could be obtained.
[0081]
[Example 4]
<Preparation of cellulose triacetate solution>
Cellulose triacetate powder (average size 2 mm) was gradually added to a stainless steel dissolution tank having stirring blades while stirring well in the following solvent mixed solution. After the addition, the mixture was allowed to stand at room temperature (25 ° C.) for 3 hours at 25 ° C. to swell the cellulose triacetate. The solvents methyl acetate, cyclopentanone, acetone, methanol, and ethanol were all used with a water content of 0.2% by mass or less.
[0082]
16 parts by weight of cellulose triacetate (degree of substitution 2.83, viscosity average degree of polymerization 320, water content 0.4% by weight, viscosity of 6% by weight in methylene chloride solution 305 mPa · s)
Methyl acetate 53 parts by weight cyclopentane 10 parts by weight acetone 5 parts by weight methanol 5 parts by weight ethanol 5 parts by weight plasticizer A (dipentaerythritol hexaacetate) 3 parts by weight plasticizer B (triphenyl phosphate) 3 parts by weight fine particle powder (Silica (particle size 20 nm)) 0.1 part by mass UV absorber a 0.1 part by mass (2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert- Butylanilino) -1,3,5-triazine)
UV absorber b 0.1 part by mass (2 (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) -5-chlorobenzotriazole)
UV absorber c 0.1 parts by mass (2 (2′-hydroxy-3 ′, 5′-di-tert-amylphenyl) -5-chlorobenzotriazole C ₁₂ H ₂₅ OCH ₂ CH ₂ O—P (═O )-(OK) ₂ 0.05 parts by mass
The viscosity of this solution obtained by the cooling dissolution method described later was 160 Pa · S (45 ° C.).
[0084]
<Cooling dissolution of cellulose triacetate solution>
The cellulose triacetate solution described above was fed by a screw extruder and passed through the cooling part at −70 ° C. for 3 minutes. Cooling was performed using a refrigerant at −80 ° C. (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. The mixture was stirred for 2 hours for defoaming. The cellulose triacetate solution thus prepared was filtered with a filter paper having an absolute filtration accuracy of 0.01 mm (manufactured by Toyo Filter Paper Co., Ltd., “# 63”), and further, a filter paper having an absolute filtration accuracy of 0.0025 mm (manufactured by Pall, (FH 025)).
[0085]
<Production of cellulose triacetate film>
The cellulose triacetate solution obtained by the above-described dissolution method was brought to 50 ° C. and cast on a mirror-surface stainless steel casting support through a casting Gieser. The casting support temperature was 10 ° C., the casting speed was 40 m / min, and the coating width was 100 cm. For drying, 120 ° C. drying air was blown. After 2 minutes, the film was peeled off from the mirror stainless steel casting support, and then dried at 110 ° C. for 10 minutes and further at 150 ° C. for 30 minutes to obtain a cellulose triacetate film (film thickness 40 μm).
[0086]
At this time, the dry exhaust dried until the amount of residual solvent in the film reaches 30% by weight is condensed and recovered at -5 ° C, and the dry exhaust until the amount of residual solvent in the film reaches 0.2% is adsorbed and recovered with activated carbon. The product was separated and purified by distillation. Further, the dry exhaust in the remaining drying zone was combusted with a steam-heat combustion system. The solvent recovery rate was 99.5%.
[0087]
<Preparation of polarizing plate a>
A polarizing element is prepared by adsorbing iodine to a stretched polyvinyl alcohol film, and the cellulose triacetate film is placed on both sides so that its slow axis is parallel to the transmission axis of the polarizing element using a polyvinyl alcohol-based adhesive. Pasted.
[0088]
<Evaluation of polarization>
The polarizing plate a was exposed at 80 ° C. and 90 RH for 500 hours, and the degree of polarization was measured by the method described above. The degree of polarization was 99.6% or more, and sufficient durability was recognized.
[0089]
<Preparation of polarizing plate b>
A polarizing element is prepared by adsorbing iodine to a stretched polyvinyl alcohol film, and using the polyvinyl alcohol adhesive, the cellulose triacetate film is placed on one side so that its slow axis is parallel to the transmission axis of the polarizing film. At the same time, the cellulose triacetate film was saponified, and attached to the opposite side of the polarizing film using a polyvinyl alcohol-based adhesive. Furthermore, an optical compensation sheet (manufactured by Fuji Photo Film Co., Ltd., “WV film”) is attached to the cellulose triacetate film side using an adhesive so that the slow axes thereof are parallel to each other, and an optical compensation sheet is attached. A combined polarizing plate was prepared.
[0090]
<Evaluation with liquid crystal display>
The polarizing plate a and the polarizing plate b were mounted on a TFT (Thin Film Transistor) type liquid crystal display device. As a result, a good viewing angle and contrast could be obtained.
[0091]
[Example 5]
<Preparation of cellulose triacetate solution for inner layer>
Cellulose triacetate powder (average size 2 mm) was gradually added to a stainless steel dissolution tank having stirring blades while stirring well in the following solvent mixed solution. After the addition, the mixture was left at room temperature (25 ° C.) for 3 hours to swell the cellulose triacetate. The solvents methyl acetate, cyclopentanone, acetone, methanol, and ethanol were all used with a water content of 0.2% by mass or less.
[0092]
16 parts by weight of cellulose triacetate (degree of substitution 2.83, viscosity average degree of polymerization 320, water content 0.4% by weight, viscosity of 6% by weight in methylene chloride solution 305 mPa · s)
Methyl acetate 53 parts by weight cyclopentane 10 parts by weight acetone 5 parts by weight methanol 5 parts by weight ethanol 5 parts by weight plasticizer A (dipentaerythritol hexaacetate) 3 parts by weight plasticizer B (triphenyl phosphate) 3 parts by weight fine particle powder (Silica (particle size 20 nm)) 0.1 part by mass UV absorber a 0.1 part by mass (2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert- Butylanilino) -1,3,5-triazine)
UV absorber b 0.1 parts by mass (2 (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) -5-chlorobenzotriazole)
UV absorber c 0.1 parts by mass (2 (2′-hydroxy-3 ′, 5′-di-tert-amylphenyl) -5-chlorobenzotriazole C ₁₂ H ₂₅ OCH ₂ CH ₂ O—P (═O )-(OK) ₂ 0.05 parts by mass
The viscosity of this solution obtained by the cooling dissolution method was 60 Pa · S (45 ° C.).
[0094]
<Cooling dissolution of cellulose triacetate solution for inner layer>
The cellulose triacetate solution described above was fed by a screw extruder and passed through the cooling part at −70 ° C. for 3 minutes. Cooling was performed using a refrigerant at −80 ° C. (3M, “Fluorinert”) cooled by a refrigerator. The solution obtained by cooling is heated to 120 ° C. by a heat exchanger equipped with a static mixer, held for 3 minutes, cooled, transferred to a stainless steel container at 50 ° C., and heated at 50 ° C. The mixture was stirred for 2 hours for defoaming. The cellulose triacetate solution is filtered with a filter paper having an absolute filtration accuracy of 0.01 mm (“Toyo Filter Paper Co., Ltd.,“ # 63 ”), and further filtered with an absolute filtration accuracy of 0.0025 mm (“ FH 025 ”, manufactured by Paul). Filtered through.
[0095]
<Preparation of cellulose triacetate solution for outer layer>
The above-described inner layer cellulose triacetate solution was charged in the same manner except that cellulose triacetate was changed to 19 parts by mass and methyl acetate was changed to 44 parts by mass. The viscosity of this solution obtained by the cooling dissolution method was 25 Pa · S (45 ° C.).
[0096]
<Cooling dissolution of cellulose triacetate solution for outer layer>
The cellulose triacetate solution described above was fed by a screw extruder and passed through the cooling part at −70 ° C. for 3 minutes. Cooling was performed using a refrigerant at −80 ° C. (3M, “Fluorinert”) cooled by a refrigerator. The solution obtained by cooling is heated to 120 ° C. by a heat exchanger equipped with a static mixer, held for 3 minutes, cooled, transferred to a stainless steel container at 50 ° C., and heated at 50 ° C. The mixture was stirred for 2 hours for defoaming. The cellulose triacetate solution is filtered with a filter paper having an absolute filtration accuracy of 0.01 mm (“Toyo Filter Paper Co., Ltd.,“ # 63 ”), and further filtered with an absolute filtration accuracy of 0.0025 mm (“ FH 025 ”, manufactured by Paul). Filtered through.
[0097]
<Production of cellulose triacetate film>
Using the three-layer co-casting die, the cellulose triacetate solution described above is placed so that the cellulose triacetate solution for the inner layer is on the inside and the cellulose triacetate solution for the outer layer is on both sides. After discharging and multilayer casting, the casting film is peeled off from the casting support, and dried to form a three-layer cellulose triacetate film laminate (inner layer thickness: 80 μm, each surface layer thickness: 2 μm) Was made.
[0098]
At this time, the dry exhaust dried until the amount of residual solvent in the film reached 45% by weight was condensed and recovered at 5 ° C., and the dry exhaust until the amount of residual solvent in the film reached 0.5% was adsorbed and recovered with activated carbon. It was separated and purified by distillation. Further, the dry exhaust in the remaining drying zone was combusted with a steam-heat combustion system. The solvent recovery rate was 99%.
[0099]
The film peeled off from the casting support is dried while being conveyed by a tenter, dried at 100 ° C. for 3 minutes and 130 ° C. for 5 minutes, and then dried stepwise at 150 ° C. for 10 minutes to evaporate the solvent. To obtain a cellulose triacetate film.
[0100]
<Preparation of polarizing plate c>
A polarizing element is prepared by adsorbing iodine to a stretched polyvinyl alcohol film, and the cellulose triacetate film is placed on both sides so that its slow axis is parallel to the transmission axis of the polarizing element using a polyvinyl alcohol-based adhesive. Pasted.
[0101]
<Evaluation of polarization>
The polarizing plate c was exposed in an atmosphere of 80 ° C. and 90 RH for 500 hours, and the degree of polarization was measured by the method described above. The degree of polarization was 99.6% or more, and sufficient durability was recognized.
[0102]
<Preparation of polarizing plate d>
A polarizing element is prepared by adsorbing iodine to a stretched polyvinyl alcohol film, and using the polyvinyl alcohol adhesive, the cellulose triacetate film is placed on one side so that its slow axis is parallel to the transmission axis of the polarizing element. At the same time, the cellulose triacetate film was subjected to saponification treatment and attached to the opposite side of the polarizing element using a polyvinyl alcohol-based adhesive. Furthermore, an optical compensation sheet (manufactured by Fuji Photo Film Co., Ltd., “WV film”) is attached to the cellulose triacetate film side using an adhesive so that the slow axes thereof are parallel to each other, and an optical compensation sheet is attached. A combined polarizing plate was prepared.
[0103]
<Evaluation with liquid crystal display>
The polarizing plate c and the polarizing plate d were mounted on a TFT (Thin Film Transistor) type liquid crystal display device. As a result, a good viewing angle and contrast could be obtained.
[0104]
【The invention's effect】
According to the present invention, in the solution casting method, the solvent generated from the cast film can be efficiently recovered and reused.

Claims (10)

In a solution casting method, a polymer solution in which a polymer is dissolved in a solvent is cast on a support from a casting die, and the cast film is peeled off from the support and dried in at least two or more drying zones. 80% to 98% of the solvent released from the cast film until it is dried is condensed and recovered in the first drying zone, and the remainder is adsorbed on the adsorbent in the second and subsequent drying zones. Solution casting method characterized by collecting   2. The solution casting method according to claim 1, wherein the recovered solvent is brought into contact with a deoxidizer.   The polymer and the solvent are cooled to −100 to −10 ° C., and both are heated in a mixed state to form a polymer solution. The polymer solution is cast on a support from a casting die, and the cast film is 2. The solution casting method according to claim 1, wherein the solution is peeled off from the support and dried.   The polymer solution is a cellulose acylate solution, and the solvent is composed of methyl acetate, ketones and alcohols, and the solvent ratio is 20 to 90% by mass for methyl acetate, 5 to 60% by mass for ketones, The solution casting method according to claim 1, 2 or 3.   5. The solution casting according to claim 1, wherein the polymer solution is a cellulose acylate solution and contains at least one plasticizer in an amount of 0.1 to 20% by mass with respect to the cellulose acylate. Method.   The said polymer solution is a cellulose acylate solution, and contains 0.001-5 mass% of at least 1 type of ultraviolet absorber with respect to a cellulose acylate, Claim 1, 2, 3, 4 or 5 Solution casting method.   The said polymer solution is a cellulose acylate solution, and contains 0.001-5 mass% of at least 1 type of fine particle powder with respect to a cellulose acylate, 1, 2, 3, 4, 5 or 6 The solution casting method described.   The said polymer solution is a cellulose acylate solution, and contains 0.001-2 mass% of at least 1 type of mold release agent with respect to a cellulose acylate, Claim 1, 2, 3, 4, 5, 6 Or the solution casting method of 7.   The polymer solution is a cellulose acylate solution, and contains at least one fluorine-based surfactant in an amount of 0.002 to 2% by mass with respect to the cellulose acylate. The solution casting method according to 3, 4, 5, 6, 7 or 8.   The solution casting method according to claim 1, 2, 3, 4, 5, 6, 7, 8 or 9, wherein the oxygen concentration in a part or all of the drying zone is 10 vol% or less.