JP4400774B2 - Solution film forming method, polarizing plate protective film, optical functional film, and polarizing plate - Google Patents

Description

【００５０】
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。
【００５１】
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。分散溶剤は任意であるが、ポリマー溶液溶剤と近い組成であることが好ましい。
【００５２】
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。
【００５３】
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。
【００５４】
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０．００２〜２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。
【００５５】
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ー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。
【００５６】
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−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。
【００５７】
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１〜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。
【００５８】
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０．００１〜２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。
【００５９】
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ラすることができる。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。
【００６０】
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、ピローラ環、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。
【００６１】
レターデーション上昇剤の分子量は、３００乃至８００であることが好ましい。レターデーション上昇剤の沸点は、２６０℃以上であることが好ましい。沸点は、市販の測定装置（例えば、ＴＧ／ＤＴＡ１００、セイコー電子工業（株）製）を用いて測定できる。
【００６２】
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質量割合で１０〜１０００ｐｐｍが好ましく、５０〜５００ｐｐｍが更に好ましい。
【００６３】
さらに、本発明におけるドープに、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。
【００６４】
本発明に用いるドープを調製する際に、容器内に窒素ガスなどの不活性ガスを充満させてもよい。セルローストリアセテート溶液の製膜直前の粘度は、製膜の際、流延可能な範囲であればよく、通常１０ｐｓ・ｓ〜２０００ｐｓ・ｓの範囲に調製されることが好ましく、特に３０ｐｓ・ｓ〜４００ｐｓ・ｓが好ましい。
【００６５】
本発明に用いるドープの調製は、冷却溶解法、もしくは高温溶解法に従い実施される。冷却溶解法について、以下に説明する。まず室温近辺の温度（−１０〜４０℃）で有機溶剤中にセルロースアセテートを撹拌しながら徐々に添加される。複数の溶剤を用いる場合は、その添加順は特に限定されない。例えば、主溶剤中にセルロースアセテートを添加した後に、他の溶剤（例えばアルコールなどのゲル化溶剤など）を添加してもよいし、逆にゲル化溶剤を予めセルロースアセテートに湿らせた後の主溶剤を加えてもよく、不均一溶解の防止に有効である。セルロースアセテートの量は、この混合物中に１０〜４０質量％含まれるように調整することが好ましい。セルロースアセテートの量は、１０〜３０質量％であることがさらに好ましい。さらに、混合物中には後述する任意の添加剤を添加しておいてもよい。
【００６６】
次に、混合物は−１００〜−１０℃（好ましくは−８０〜−１０℃、さらに好ましくは−５０〜−２０℃、最も好ましくは−５０〜−３０℃）に冷却される。冷却は、例えば、ドライアイス・メタノール浴（−７５℃）や冷却したジエチレングリコール溶液（−３０〜−２０℃）中で実施できる。このように冷却すると、セルロースアセテートと有機溶剤の混合物は固化する。冷却速度は、特に限定されないがバッチ式での冷却の場合は、冷却に伴いセルロースアセテート溶液の粘度が上がり、冷却効率が劣るために所定の冷却温度に達するために効率よい溶解釜とすることが必要である。
【００６７】
また、本発明のドープは膨潤させたあと、所定の冷却温度にした冷却装置を短時間移送することで達成できる。冷却速度は、速いほど好ましいが、１００００℃／秒が理論的な上限であり、１０００℃／秒が技術的な上限であり、そして１００℃／秒が実用的な上限である。なお、冷却速度は、冷却を開始する時の温度と最終的な冷却温度との差を、冷却を開始してから最終的な冷却温度に達するまでの時間で割った値である。さらに、これを０〜２００℃（好ましくは０〜１５０℃、さらに好ましくは０〜１２０℃、最も好ましくは０〜５０℃）に加温すると、有機溶剤中にセルロースアセテートが流動する溶液となる。昇温は、室温中に放置するだけでもよし、温浴中で加温してもよい。この時、圧力を０．３〜３０ＭＰａになることが挙げられるが、特に問題ない。その場合は、極力短時間で実施することが好ましく、０．５〜６０分以内が好ましく、特に０．５〜２分の短時間の加熱が推奨される。
【００６８】
なお、溶解が不充分である場合は冷却、加温の操作を繰り返してもよい。溶解が充分であるかどうかは、目視により溶液の外観を観察するだけで判断することができる。冷却溶解方法においては、冷却時の結露による水分混入を避けるため、密閉容器を用いることが望ましい。また、冷却加温操作において、冷却時に加圧し、加温時に減圧すると溶解時間を短縮することができる。加圧および減圧を実施するためには、耐圧性容器を用いることが望ましい。
【００６９】
高温溶解法によるセルロースアセテート溶液の調整方法について、以下に説明する。まず室温近辺の温度（−１０〜４０℃）で有機溶剤中にセルロースアセテートを撹拌しながら徐々に添加される。複数の溶剤を用いる場合は、その添加順は特に限定されない。例えば、主溶剤中にセルロースアセテートを添加した後に、他の溶剤（例えばアルコールなどのゲル化溶剤など）を添加してもよいし、逆にゲル化溶剤を予めセルロースアセテートに湿らせた後の主溶剤を加えてもよく、不均一溶解の防止に有効である。本発明のセルロースアセテート溶液は、各種溶剤を含有する混合有機溶剤中にセルロースアセテートを添加し予め膨潤させることが好ましい。その場合、−１０〜４０℃でいずれかの溶剤中に、セルロースアセテートを撹拌しながら徐々に添加してもよいし、場合により特定の溶剤で予め膨潤させその後に他の併用溶剤を加えて混合し均一の膨潤液としてもよく、更には２種以上の溶剤で膨潤させしかる後に残りの溶剤を加えても良い。
【００７０】
本発明において酢酸メチルと炭素数４〜１２のケトン溶剤の混合溶剤系の高圧高温での溶解法によるセルロースアセテートの溶解濃度は３０質量％以下が好ましく、フィルム製膜時の乾燥効率の点から、なるべく高濃度であることが好ましい。セルロースアセテートの量は、最終的なドープとして１０〜３０質量％含まれるように調製するが、本発明の有機溶剤組成では、高濃度のセルローストリアセテート溶液を調製することが好ましいが、その範囲内で任意の濃度に仕込めばよい。あまり高濃度になり過ぎると溶液の粘度が大きすぎて、製膜しにくくなる場合もあるので、好ましいセルロースアセテート溶液の濃度は、１５質量％〜３０質量％の範囲である。さらに１７質量％〜２５質量％の範囲が好ましい。
【００７１】
次に有機溶剤混合液は、０．２ＭＰａ〜３０ＭＰａの加圧下で７０〜２４０℃に加熱される（好ましくは８０〜２２０℃、更に好ましく１００〜２００℃、最も好ましくは１００〜１９０℃）。加熱は、例えば高圧蒸気でもよく電気熱源でもよい。高圧のためには耐圧容器あるいは耐圧ラインを必要とするが、鉄やステンレス製あるいは他の金属耐圧容器やラインのいずれでもよく、特に限定されない。次にこれらの加熱溶液はそのままでは塗布できないため、使用された溶剤の最も低い沸点以下に冷却する必要がある。その場合、−１０〜５０℃に冷却して常圧に戻すことが一般的である。冷却はセルロースアセテート溶液が内蔵されている高圧高温容器やラインを、室温に放置するだけでもよく、更に好ましくは冷却水などの冷媒を用いて該装置を冷却してもよい。なお、溶解を早めるために加熱と冷却の操作を繰り返してもよい。溶解が十分であるかどうかは、目視により溶液の概観を観察するだけで判断することができる。高圧高温溶解方法においては、溶剤の蒸発を避けるために密閉容器を用いる。また、膨潤工程おいて、加圧や減圧にしたりすることで更に溶解時間を短縮することが出来る。加圧及び減圧を実施するためには、耐圧性容器あるいはラインが必須である。
【００７２】
本発明の溶液製膜方法で製造されるフィルムは、偏光板保護膜、光学機能性膜（光学補償シート、反射防止膜、防眩膜等）、等に利用することができる。偏光板保護膜、光学機能性膜等は液晶表示装置に利用されており、この液晶表示装置は、液晶セル、偏光板および光学補償シート（位相差板）からなる。透過型液晶表示装置では、二枚の偏光板を液晶セルの両側に取り付け、一枚または二枚の光学補償シートを液晶セルと偏光板との間に配置する。反射型液晶表示装置では、反射板、液晶セル、一枚の光学補償シート、そして一枚の偏光板の順に配置する。
【００７３】
液晶セルは、棒状液晶性分子、それを封入するための二枚の基盤および棒状液晶性部分子に電圧を加えるための電極層からなる。液晶セルは、棒状液晶性分子の配向状態の違いで、透過型については、ＴＮ（Ｔｗｉｓｔｅｄ Ｎｅｍａｔｉｃ）、ＩＰＳ（Ｉｎ−Ｐｌａｎｅ Ｓｗｉｔｃｈｉｎｇ）、ＦＬＣ（Ｆｅｒｒｏｅｌｅｃｔｒｉｃ Ｌｉｑｕｉｄ Ｃｒｙｓｔａｌ）、ＯＣＢ（Ｏｐｔｉｃａｌｌｙ Ｃｏｍｐｅｎｓａｔｏｒｙ Ｂｅｎｄ）、ＳＴＮ（Ｓｕｐｐｅｒ Ｔｗｉｓｔｅｄ Ｎｅｍａｔｉｃ）、ＶＡ（Ｖｅｒｔｉｃａｌｌｙ Ａｌｉｇｎｅｄ）、反射型については、ＨＡＮ（Ｈｙｂｒｉｄ Ａｌｉｇｎｅｄ Ｎｅｍａｔｉｃ）のような様々な表示モードが提案されている。
【００７４】
偏光板は、一般に、偏光膜と透明の偏光板保護膜とからなっており、この偏光膜は、一般に、ポリビニルアルコールにヨウ素または二色性染料の水溶液を含浸させ、さらにこのフィルムを一軸延伸することにより得られる。この偏光膜の両側に二枚の透明の偏光板保護膜を貼りつけた構成を有する。光学補償シートは、画像着色を解消したり、視野角を拡大するために、様々な液晶表示装置で用いられている。光学補償シートとしては、延伸複屈折フィルムが従来から使用されていた。
【００７５】
延伸複屈折フィルムからなる光学補償シートに代えて、透明支持体上に液晶性分子（特にディスコティック液晶性分子）から形成された光学異方性層を有する光学補償シートを使用することが提案されている。光学異方性層は、液晶性分子を配向させ、その配向状態固定化することにより形成する。一般に、重合性基を有する液晶性分子を用いて、重合反応によって配向状態を固定化する。液晶性分子は、大きな複屈折を有する。そして、液晶性分子には、多様な配向形態がある。液晶性分子を用いることで、従来の延伸複屈折フィルムでは得ることができない光学的性質を実現することが可能になった。
【００７６】
光学補償シートの光学的性質は、液晶セルの光学的性質、具体的には上記のような表示モードの違いに応じて決定する。液晶性分子、特にディスコティック液晶性分子を用いると液晶セルの様々な表示モードに対応する様々な光学的性質を有する光学補償シートを製造することができる。
【００７７】
ディスコティック液晶性分子を用いた光学補償シートでは、様々な表示モードに対応するものが既に提案されている。例えば、ＴＮモードの液晶セル用光学補償シートは、特開平６−２１４１１６号公報、米国特許５５８３６７９号、同５６４６７０３号、ドイツ特許公報３９１１６２０Ａ１号の各明細書に記載がある。また、ＩＰＳモードまたはＦＬＣモードの液晶セル用光学補償シートは、特開平１０−５４９８２号公報に記載がある。さらに、ＯＣＢモードまたはＨＡＮモードの液晶セル用光学補償シートは、米国特許５８０５２５３号および国際特許出願ＷＯ９６／３７８０４号に記載がある。さらにまた、ＳＴＮモードの液晶セル用光学補償シートは、特開平９ー２６５７２号公報に記載がある。そして、ＶＡモードの液晶セル用光学補償シートは、特許番号第２８６６３７２号公報に記載がある。
【００７８】
液晶性分子を用いた光学補償シートと偏光板とを積層して楕円偏光板とすれば、光学補償シートを、偏光素子の一方の偏光板保護膜として機能させることができる。そのような楕円偏光板は、透明保護膜、偏光膜、透明支持体、そして液晶性分子から形成された光学異方性層の順序の層構成を有する。液晶表示装置は薄型で軽量との特徴があり、構成要素の一つを兼用によって削減すれば、装置をさらに薄く軽量にすることができる。また、液晶表示装置の構成要素を一つ削減すれば、構成要素の貼り付け工程も一つ削減され、装置を製造する際に故障が生じる可能性が低くなる。液晶性分子を用いた光学補償シートの透明支持体と偏光板の一方の保護膜を共通化した一体型楕円偏光板については、特開平７−１９１２１７号、同８−２１９９６号および同８−９４８３８号の各公報に記載がある。
【００７９】
透明支持体上に配向膜及び液晶性分子の配向を固定化した光学異方性層を設けた光学補償シートを製造する場合、透明支持体（通常は、セルロースアセテートフィルム）と配向膜（通常はポリビニルアルコール）との間の密着性が必要になる。通常セルロースアセテートフィルムとポリビニルアルコールは親和性が悪く、剥がれや割れが発生するというの問題があった。その間の密着性を得るためにセルロースアセテートフィルム上にゼラチン下塗り層を設けている。
【００８０】
透明支持体の厚さは、２０乃至５００μｍであることが好ましく、４０乃至２００μｍであることがさらに好ましい。
【００８１】
透明支持体が光学的等方性であることが好ましい場合は、通常のセルロースエステルフィルムを用いることができる。透明支持体に光学的異方性が要求される場合は、レターデーションが高いセルロースエステルフィルムを用いることが好ましい。セルロースエステルフィルムの面内レターデーション（Ｒｅ）は、セルロースエステルフィルムの延伸により調整（高い値と）することができる。セルロースエステルフィルムの厚み方向のレターデーション（Ｒｔｈ）は、（１）レターデーション上昇剤の使用、（２）平均酢化度（アセチル化度）の調整または（３）冷却溶解法によるフィルムの製造により調整（高い値と）することができる。これにより、従来は光学的等方性と考えられていたセルロースエステルフィルムを、光学補償機能を有する光学的異方性透明支持体として使用できるようになった。
【００８２】
光学的異方性支持体の厚み方向のレターデーション値（Ｒｔｈ）は、６０乃至１０００ｎｍであることが好ましい。また、面内のレターデーション値（Ｒｅ）は、−５０乃至５０ｎｍであることが好ましく、−２０乃至２０ｎｍであることが更に好ましい。
【００８３】
厚み方向のレターデーション値は、厚み方向の複屈折率にフィルムの厚みを乗じた値である。面内のレターデーション値は、面内の複屈折率にフィルムの厚みを乗じた値である。具体的な値は、測定光の入射方向をフィルム膜面に対して鉛直方向として、遅相軸を基準とする面内レターデーションの測定結果と、入射方向をフィルム膜面に対する鉛直方向に対して傾斜させた測定結果から外装して求める。測定はエリプソメーター（例えば，Ｍ−１５０：日本分光（株）製）を用い実施できる。測定波長としては、６３２．８ｎｍ（Ｈｅ−Ｎｅレーザー）を採用する。
【００８４】
厚み方向のレターデーション値（Ｒｔｈ）と面内レターデーション値（Ｒｅ）とは、それぞれ下記式（４）および（５）に従って算出する。
式（４） Ｒｔｈ＝｛（ｎｘ＋ｎｙ）／２−ｎｚ｝×ｄ
式（５） Ｒｅ＝（ｎｘ−ｎｙ）×ｄ
【００８５】
式中、ｎｘはフィルム面内のｘ方向の屈折率であり、ｎｙはフィルム平面内のｙ方向の屈折率であり、ｎｚはフィルム面に垂直な方向の屈折率であり、そしてｄはフィルムの厚み（ｎｍ）である。
【００８６】
本発明による溶液製膜方法を実施することができる溶液製膜装置の例を図面を参照して説明する。
【００８７】
図１は溶液製膜方法によるフィルムを製造する装置の概略図である。この図において、１０はドープ調製部、２０はドープを流延支持体に流延する流延部、３０は流延支持体から剥ぎ取ったフィルムをテンター装置で搬送しつつ乾燥させるテンター乾燥部、４０はテンター乾燥部３０で乾燥させたフィルムをさらに乾燥させる乾燥部、５０は完成したフィルムを巻き取る巻取りローラである。
【００８８】
ドープ調製部１０は、セルロースアセテート、溶剤、可塑剤等を撹拌・混合する撹拌タンク１１が設けられ、この撹拌タンク１１には送液ポンプ１２を介してフィルタ１３が連結されている。前記流延部２０は、流延ダイ２１が設けられるとともに、流延支持体としての回転ドラム２２が設けられており、前記フィルタ１３からドープが流延ダイ２１に送られている。また、回転ドラム２２からフィルムを剥ぎ取るための剥ぎ取りローラ２３が設けられるとともに、テンター乾燥部３０へ搬送するための搬送ローラ２４が設けられている。
【００８９】
テンター乾燥部３０は、ピンテンター３１が設けられており、このピンテンター３１がフィルムの両端部を坦持して搬送させつつ、乾燥風により乾燥させるようになっている。乾燥部４０は、搬送ローラ４１が多数設けられ、この搬送ローラ４１で搬送されつつ、乾燥風により乾燥させるようになっている。
【００９０】
前記流延部２０には、凝集装置２５、給気ファン２６、ヒーター２７及びフィルター２８が設けられており、流延部２０の気体から凝集装置２５で溶剤を回収した後、給気ファン２６によりヒーター２７及びフィルター２８を介して再び流延部２０内に循環させている。
【００９１】
前記テンター乾燥部３０にも、流延部２０と同様に、凝集装置３２、給気ファン３３、ヒーター３４及びフィルター３５が設けられており、テンター乾燥部３０の気体から凝集装置３２で溶剤を回収した後、給気ファン３３によりヒーター３４及びフィルター３５を介して再びテンター乾燥部３０内に循環させている。
【００９２】
前記乾燥部４０には、給気ファン４２、ヒーター４３及びフィルター４４が設けられるとともに、給気ファン４２ヘ新鮮風を導入するためのフィルター４５及び給気ファン４２から排出された気体から溶剤を吸着するための吸着回収装置４６が設けられ、給気ファン４２により回収した気体とともに新鮮風をヒーター４３及びフィルター４４を介して乾燥部４０に供給し、また、回収した気体から溶剤を吸着回収装置４６で回収している。
【００９３】
【実施例】
［実施例１］
＜ドープＡ＞
セルローストリアセテート（パルプ原料）………………………１６質量％
（酢化度６０．９％、重合度３０５、６位アセチル置換基比率０．７５、平均粒径１．５ｍｍ）
セルローストリアセテート（パルプ原料）………………………２質量％
（酢化度６１．２％、重合度３２２、６位アセチル置換基比率０．７２、平均粒径１．１ｍｍ）
セルローストリアセテート（リンター原料）……………………２質量％
（酢化度６１．２％、重合度３６２、６位アセチル置換基比率０．７２、平均粒径１．３ｍｍ）
トリフェニルフォスフェート………………………………………２質量％
ビフェニルジフェニルフォスフェート……………………………１質量％
ベンゾトリアゾール系ＵＶ吸収剤……………………………０．２質量％
酸化ケイ素マット剤（１次粒子系２０ｎｍ）………………０．１質量％
塩化メチレン………………………………………………………６７質量％
メタノール……………………………………………………………９質量％
ｎ−ブタノール………………………………………………………１質量％
【００９４】
上記組成のポリマー溶液を公開技術公報２００１−１７４５号に記載されている高温溶解法により溶解、ろ過してドープＡを調製した。
【００９５】
＜ドープＢ＞
ドープＡの組成に、さらに以下の物質を配合し、固形分の濃度を１８．５質量％に希釈したものである。
酸化ケイ素マット剤（１次粒子系２０ｎｍ）………………０．１質量％
剥離促進剤………………………………………………………０．１質量％
（特願昭６３−１２９７４７の具体例６に記載の化合物）
【００９６】
上記組成のポリマー溶液を公開技術公報２００１−１７４５号に記載されている高温溶解法により溶解、ろ過してドープＢを調製した。
【００９７】
＜フィルムの製造＞
流延ダイとしては、マルチマニホールド型のコートハンガー型を用い、流延支持体としては、ハードクロム鍍金を施し、中心性平均粗さを０．０３μになるように鏡面仕上げをした直径２０００ｍｍ、幅２５００ｍｍの回転ドラムを用いた。回転ドラムは、内部に冷媒を通水して表面の平均温度を−５℃に保持し、このときの回転ドラム面上の温度分布は２℃以内であった。
【００９８】
そして、ドープＡが乾燥後厚み７０μｍのコア層を、ドープＢがそれぞれ乾燥後厚み５μｍの両面の外層を構成するように共流延した。
【００９９】
流延ダイから吐出されたドープＡ及びＢは、流延方向に過度に引き伸ばされないようにビードの一時側にバックサクションチャンバーを設置して減圧状態とした。ドラムの回転周速は３０ｍ／分であり、バックサクションチャンバー内部の圧力を周囲の圧力より４００Ｐａ減圧状態とした。バックサクションチャンバーに接続する配管系には長さ１５００ｍｍのサイドブランチを設置してチャンバー内部の圧力変動を抑制した。このときのチャンバー内の圧力変動をデジタル高速フーリエ変換して得られた圧力変動値の特性周波数におけるピーク値は、周波数が１０〜１００Ｈｚの範囲で、いずれも５Ｐａ以下であり、サイドブランチなしの状態でのピーク値の５０％以下であった。
【０１００】
流延されたドープＡ及びＢは、流延直後の１秒間は風速０．５ｍ／ｓ以下で乾燥し、それ以降はドラムの回転方向に対向して風速１５ｍ／ｓで乾燥した。乾燥風の温度は５０℃であった。また乾燥風の溶剤の露点は−３０℃になるようにコンデンサーで溶剤を凝縮回収した。回収溶剤はゼオライトにより脱水して仕込み工程にて再利用した。また循環乾燥風は０．３μｍの捕集効率が９９．９９９％の高性能エアフィルターにより濾過されたのち再利用した。乾燥ゾーン内のガスの清浄度はクラス５以下であり、また、ＦＥＤ−ＳＴＤ−２０９ＥのクラスでＭ３．５以下であった。また、乾燥ゾーン内の酸素濃度は窒素ガスにより５Ｖｏｌ％に保持した。窒素ガスは液体窒素タンクより圧力スイング式窒素分離装置により供給した。
【０１０１】
回転ドラムから剥ぎ取った時のフィルムの残留溶剤量は２３０質量％であり、フィルムの温度は−６℃であった。流延から剥ぎ取りまでの間における平均乾燥速度は７４４質量％／分であった。また、剥ぎ取り時点でのドープのゲル化温度は約１０℃であった。ドラムからの剥離は安定してできた。
【０１０２】
剥ぎ取ったフィルムは冷媒を通水して表面温度がー５℃に調節されたパスローラによりピンテンターに搬送し、ピンテンターで両端部（厚さ７０μｍ）を坦持した状態で、テンションを付与しつつ乾燥、搬送を行った。剥ぎ取り後のパスローラは３本使用し、いずれもフィルムの反支持体側にラップするように配置した。また、これらのパスローラはドラム回転速度に対して０．５〜１５％までのドロー比を設定でき、それぞれドラムに対して１％、２％、４％のドロー比で運転した。また、ラップ角度は５度以下となるように配置した。剥ぎ取りよりピンテンターの噛み込み部までの距離は１．２ｍであった。
【０１０３】
ピンタンターでフィルムを坦持した際、ピンテンターの温度は２５℃であり、担持されるフィルムの温度は５℃であり、フィルム中の残留溶剤の大部分は塩化メチレンであった。乾燥ゾーン内のガスの飽和温度は−１５℃、酸素濃度は６％であった。蒸発した溶剤は流延部と同様に凝縮回収され、乾燥ゾーン内は窒素ガスによりイナート化されている。また乾燥風の循環経路には、０．３μｍの捕集率が９９．９９９％のエアフィルターを設置し、乾燥ゾーンの気体の清浄度をクラス５以下であり、また、ＦＥＤ−ＳＴＤ−２０９ＥのクラスでＭ３．５以下であった。
【０１０４】
乾燥風の温度は１２０℃であり、このときのフィルムの幅方向の温度分布は５℃以下であり、乾燥の平均風速は５ｍ／ｓ、伝熱係数の平均値は２５ｋｃａｌ／ｍ^２・Ｈr・℃であり、フィルムの幅方向分布はいずれも５％以内であった。また乾燥ゾーン中におけるピンテンター担持部分は遮風装置により乾燥熱風が直接当らないようにした。ピンテンター搬送中のフィルムは、フィルムの平面性を維持するために幅方向の張力を９８Ｎ／ｍ（１０ｋｇ／ｍ）に保持しながら乾燥させた。
【０１０５】
また、ピンテンターは、フィルムが脱離した後、新たにフィルムを担持するまでの間、−５℃の冷却風により総括伝熱係数１５０ｋｃａｌ／ｍ²・Ｈｒ・℃で冷却した。冷却装置により冷却する部分の長さは全体の５０％とした。
【０１０６】
ピンテンターにより担持され乾燥される時間は１０分であり、その間に蒸発した溶剤量は、剥ぎ取りより巻取りまでの間で蒸発した溶剤のトータル量の９７％であった。蒸発した溶剤をコンデンサーによる凝縮回収し、この回収溶剤を蒸留により脱水し含水率０．４％とした後、再度ドープの調製工程の原材料として利用した。
【０１０７】
ピンテンターで乾燥したフィルムは、さらにローラーで搬送しつつ乾燥させる乾燥工程において１４５℃の乾燥風により１５分間乾燥した後、湿度、温度を調整して巻取り時の残留溶剤量０．５５質量％、水分量０．８質量％、温度３５℃で巻き取った。乾燥ゾーンにおける搬送テンションは６５〜１５０Ｎ／ｍであり、フィルムの帯電量の絶対値は３ｋＶ以下に保持した。また、乾燥ゾーン内の溶剤ガス濃度は溶媒の爆発下限界の２０％以下であり、溶剤以外の高沸点成分の露点は８０℃以上であった。また、乾燥風は０．３μｍの捕集効率９９．９７％のエアフィルターを通過させて供給し、その清浄度はＩＳＯクラス５以下であり、また、ＦＥＤ−ＳＴＤ−２０９ＥのクラスでＭ３．５以下であった。
【０１０８】
以上のような方法で製造されたフィルムは、流延ダイから剥ぎ取った後の乾燥工程において、シワや寄りなどの問題もなく、安定して搬送することができた。また、巻き取ったフィルムの平面性及び透明度も良好であり、１０μｍ以上の異物は１ｃｍ²当たり０個であった。
【０１０９】
［比較例１］
回転ドラム上での流延、乾燥条件のうち、コア層の乾燥後厚みを３５μｍ、両外層の乾燥後厚みをそれぞれ２．５μｍとして、乾燥風の平均風速を２５ｍ／分、温度を６０℃にした以外は、実施例１と同様な条件により流延、乾燥した。
【０１１０】
このときの流延から剥ぎ取りまでの平均乾燥速度は１０５０質量％／分に達したが、流延面状に乾燥風による風ムラが発生して平面性が著しく損なわれた。
【０１１１】
［比較例２］
回転ドラム上での流延、乾燥条件のうち、乾燥風中の溶剤の露点を−７℃、平均風速を２．５ｍ／分、温度を２０℃にした以外は、実施例１と同様な条件により流延、乾燥した。
【０１１２】
このときの剥ぎ取り時の残留溶剤量は３１０質量％となり、流延から剥ぎ取りまでの平均乾燥速度は２２０質量％／分であったが、流延速度３０ｍ／分では安定に剥ぎ取ることができなかった。この平均乾燥速度で安定に剥ぎ取るためには、結果的に１０ｍ／分まで流延速度を低下させる必要あり、著しく生産性が低下した。
【０１１３】
［実施例２］
＜ドープＣ＞
セルローストリアセテート（パルプ原料）……………………２０質量％
（酢化度６０．９％、重合度３０５、６位アセチル置換基比率０．８５、平均粒径１．５ｍｍ）
トリフェニルフォスフェート………………………………………２質量％
ビフェニルジフェニルフォスフェート……………………………１質量％
ベンゾトリアゾール系ＵＶ吸収剤……………………………０．２質量％
塩化メチレン………………………………………………………６１質量％
メタノール…………………………………………………………１６質量％
【０１１４】
上記組成のポリマー溶液を公開技術公報２００１−１７４５号に記載されている高温溶解法により溶解、ろ過してドープＣを調製した。
【０１１５】
＜ドープＤ＞
ドープＣの組成に、さらに以下の物質を配合し、固形分の濃度を１８．５質量％に希釈したものである。
酸化ケイ素マット剤（１次粒子系２０ｎｍ）……………………０．１質量％
剥離促進剤……………………………………………………………０．１質量％
（特願昭６３ー１２９７４７の具体例６に記載の化合物）
【０１１６】
上記組成のポリマー溶液を公開技術公報２００１−１７４５号に記載されている高温溶解法により溶解、ろ過してドープＢを調製した。
【０１１７】
＜フィルムの製造＞
フォードブロックを装備したコートハンガー型ダイを用い、ドープＣが乾燥後厚み」７０μｍのコア層を、ドープＤがそれぞれ乾燥後厚み５μｍの両面の外層を構成するように共流延した。その他の流延及び乾燥条件は実施例１と同様である。
【０１１８】
剥ぎ取り時の残留溶剤量は２４５質量％であり、フィルムの温度は−５℃であった。流延から剥ぎ取りまでの平均乾燥速度は６５７質量％／分であった。また、剥ぎ取り時点でのドープのゲル化温度は１５℃であった。
【０１１９】
以上のような方法で製造されたフィルムは、流延ダイから剥ぎ取った後の乾燥工程において、シワや寄りなどの問題もなく、安定して搬送することができた。また、巻き取ったフィルムの平面性及び透明度も良好であり、１０μｍ以上の異物は１ｃｍ²当たり０個であった。
【０１２０】
［比較例３］
回転ドラム上での流延、乾燥条件のうち乾燥風温度を１００℃にした以外は、実施例２と同様の条件で流延、乾燥した。このときの流延から剥ぎ取りまでの平均乾燥速度は１１５０質量％／分に達したが、流延ドープ表面での発泡が生じて、安定に剥ぎ取ることができなかった。
【０１２１】
［比較例４］
剥離後の搬送ローラの表面温度を１４．５℃にした以外は、実施例２と同様の条件で流延した。流延支持体から剥ぎ取ったフィルムは、搬送ローラに接着して搬送ができなかった。
【０１２２】
［偏光板の作製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実施例１および２で製膜されたセルローストリアセテートフィルムを貼合し作製した。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。いずれの実施例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。
【０１２３】
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ーＹｃ）／（ＹＰ＋Ｙｃ））
【０１２４】
［実施例３］
＜光学機能性膜の作製＞
実施例１で作製したトリアセチルセルロースフィルム［厚さ：１００μｍ、｛（ｎＸ＋ｎｙ）／２−ｎｚ｝×ｄ＝７０ｎｍ）］の一方の側にゼラチン層（層厚：０．１μｍ）を塗設した。次に、塗設したゼラチン層の上に長鎖アルキル変性ポバール（ＭＰ−２０３、クラレ（株）製）の塗布液を塗布し、１１０℃の温風３０秒間乾燥させたのち、ラビング処理を行って配向膜を形成した。この配向膜上に、ディスコティック液晶（前記化合物例：特開平８−４３６２５に記載の化合物ＴＥ−８（ｍ＝４）が２０質量％、そして光重合開始剤（イルガキュア９０７、日本チバガイギー（株）製）が０．１質量％となるように、メチルエチルケトン中に溶かした塗布液をスライドコーターにより、塗布速度２０ｍ／分、塗布量１２ｃｃ／ｍ^２で塗布して、層厚２．４μｍのディスコティック液晶層を形成した。この配向膜及び液晶層が形成されたフィルムを、１５０℃に設定された恒温槽に５分間入れてディスコティック液晶を配向させ、熟成させた後に、引き続き１５０℃の条件下で水銀灯（４００ワット）を２分間照射し、室温まで放冷することにより、光学補償シートを得た。
【０１２５】
このようにして得られた光学補償シートを、図２に示すようなＴＮ型液晶セルに装着したところコントラストを低下させることなく、視野角の改善効果が得られた。図２において、ＴＮＣはＴＮ型液晶セル、ＲＦ１及びＲＦ２は光学補償シート、Ａ及びＢは偏光板であり、ＰＡ及びＰＢは偏光軸、Ｌ０は自然光、Ｌ１及びＬ５は直線偏光、Ｌ３、Ｌ４は楕円偏光である。
【０１２６】
【発明の効果】
本発明は、流延支持体から品質を損なうことなく迅速に剥ぎ取ることができるので、透明度が高く、光学的にも等方的で、機械的強度、寸度安定性及び耐久性に優れたフィルムを、安定的かつ高速に製造することができる。
【図面の簡単な説明】
【図１】 本発明による溶液製膜方法を実施する溶液製膜装置の概略図である。
【図２】 本発明による溶液製膜方法で製造したフィルムを用いる液晶表示装置の分解斜視図である。
【符号の説明】
１０…ドープ調製部
２０…流延部
２１…流延ダイ
２２…回転ドラム（流延支持体）
３０…テンター乾燥部
３１…ピンテンター
４０…乾燥部
５０…巻取りロール
ＴＮＣ…ＴＮ型液晶セル
Ａ、Ｂ…偏光板
ＰＡ、ＰＢ…偏光軸
Ｌ０…自然光
Ｌ１、Ｌ５…直線偏光
Ｌ３、Ｌ４…楕円偏光
ＬＣ…ＴＮ型液晶セルに十分に電圧を印加した時の液晶分子の配列状態
ＲＦ１、ＲＦ２…光学補償シート
ＢＬ…バックライト[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a solution casting method for producing a cellulose triacetate film and the like, and a polarizing plate protective film, an optical functional film and a polarizing plate using the film produced by this solution casting method.
[0002]
[Prior art]
In general, some films of cellulose acetate, polycarbonate, cellophane, etc. are produced by a solution casting method. This solution casting method involves casting a dope, which is a polymer solution, from a casting die onto a belt-type or drum-type casting support, drying it to some extent on the casting support, solidifying it, and then peeling it off. The peeled film is dried while being conveyed by a tenter device or the like, and further dried while being conveyed by a roller (Japanese Patent Laid-Open Nos. 62-46625, 62-46626, etc.).
[0003]
In order to improve productivity in such a solution casting method, it is necessary to quickly strip off the dope cast on the casting support. Therefore, various techniques that can be quickly removed have been proposed. For example, sequential layer casting method (Japanese Patent Laid-Open Nos. 52-50078, 53-134869, 61-104413, etc.), gelling prescription dope, cooling drum casting method (Japanese Patent Publication No. 5-17844) Japanese Laid-Open Patent Publication No. 62-64514), a method of casting a dope of a gelling formulation on a surface in contact with a casting support by co-casting (Japanese Patent Laid-Open No. 61-94724), and the like have been proposed. .
[0004]
[Problems to be solved by the invention]
By the way, in any of the conventional methods described above, the film needs to have sufficient self-supporting property when being peeled off from the casting support. Therefore, a particularly high drying rate is required between the casting and the peeling point. In addition, it is desirable to dry after peeling with a non-contact type transport method such as a tenter, but depending on the drying conditions, the film may foam or the physical properties of the film, for example, mechanical strength, transparency, It was found that retardation, flatness, etc. were impaired.
[0005]
The present invention solves the above problems and provides a solution casting method capable of stably producing a high-quality film with high productivity by drying according to a certain range of drying patterns. With the goal.
[0006]
[Means for Solving the Problems]
The present inventor has intensively studied to achieve the above object, and adjusts the drying performed from casting the dope onto the casting support until the dope is slightly solidified from the casting support. It can be quickly peeled off from the casting support and has good quality, i.e. high transparency, optically isotropic, excellent mechanical strength, dimensional stability and durability. It was found that a film can be obtained. Specifically, the present invention has been completed by finding a suitable drying rate in a range limited in distance and time from casting to stripping.
[0007]
The invention according to claim 1 is a method in which a dope is cast from a casting die onto a casting support, the cast dope is dried to some extent to form a film, and the film is peeled off from the casting support. Further, the film is produced by drying, wherein the mass fraction of the solid content in the dope is 17% by mass or more and 30% by mass or less, and the average drying rate from dope casting to stripping is 300% by mass. % / Min and below 1000% by mass / min In addition, the drying air in the casting support is used by passing it through an air filter having an absolute pore diameter of 0.5 μm or less at least once. It is configured as a feature.
[0008]
In the invention according to claim 2, the dope is cast from the casting die onto the casting support, the cast dope is dried to some extent to form a film, and the film is peeled off from the casting support. A method for producing a film by further drying, wherein a mass fraction of solid content in the dope is 17% by mass or more and 30% by mass or less, and an average drying speed in a range within 15 m from a casting point of the dope, Over 300% by mass / min and below 1000% by mass / min In addition, the drying air in the casting support is used by passing it through an air filter having an absolute pore diameter of 0.5 μm or less at least once. It is configured as a feature.
[0009]
The invention according to claim 3 is a method in which a dope is cast from a casting die onto a casting support, the cast dope is dried to some extent to form a film, and the film is peeled off from the casting support. A method for producing a film by further drying, wherein the mass fraction of the solid content in the dope is 17% by mass or more and 30% by mass or less, and the average drying is performed for 3 seconds after casting to 20 seconds after casting. The speed is over 300% by mass / min and below 1000% by mass / min. In addition, the drying air in the casting support is used by passing it through an air filter having an absolute pore diameter of 0.5 μm or less at least once. It is configured as a feature.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, a dope having a specific composition is premised, that is, the mass fraction of solids in the dope is 17% by mass or more and 30% by mass or less, preferably 20% by mass or more and 28% by mass or less. Preferably they are 22 mass% or more and 25 mass% or less. Here, solid content includes additives such as plasticizers in addition to polymers such as cellulose acylate.
[0011]
If the mass fraction of the solid content is less than 17% by mass, the drying load of the solvent increases and the productivity decreases, which is not preferable. On the other hand, if it exceeds 30% by mass, the viscosity of the dope is remarkably increased, and casting and liquid feeding become difficult.
[0012]
In the invention according to claim 1, the average drying speed from casting of the dope to peeling is more than 300% by mass and not more than 1000% by mass / min, preferably more than 400% by mass / min. And 900 mass% / min or less, more preferably more than 500 mass% / min and 800 mass% / min or less.
[0013]
When the average drying rate is 300% by mass / min or less, the film cannot be peeled off at high speed, resulting in poor productivity. When the average drying rate exceeds 1000% by mass / min, Wind unevenness occurs, and the flatness of the film deteriorates.
[0014]
The average drying speed is a value obtained by dividing the amount of change in the solvent content of the casting dope by the time.
[0015]
To adjust the average drying speed, the temperature of the drying air, the air volume, the concentration of the solvent gas, the surface temperature of the casting support, the temperature of the casting dope, the wet thickness of the casting dope, the solvent of the casting dope It can be performed by appropriately adjusting the composition and the like.
[0016]
In the invention according to claim 2, the average drying speed in the range within 15 m from the casting point of the dope is more than 300 mass% / min and not more than 1000 mass% / min, preferably more than 400 mass% / min. And 900 mass% / min or less, more preferably more than 500 mass% / min and 800 mass% / min or less. The reason why the upper limit and the lower limit of the average drying speed are specified is the same as that of the above-described first aspect. In addition, the average drying speed is not particularly limited at locations exceeding 15 m from the casting point, but it is preferably performed in the same range.
[0017]
In the invention according to claim 3, the average drying speed during 3 seconds after casting to 20 seconds after casting is more than 300 mass% / min and not more than 1000 mass% / min, preferably 400 mass% / min. More than 900% by weight / minute, more preferably more than 500% by weight / minute and not more than 800% by weight / minute. The reason for defining the upper limit and the lower limit of the average drying rate is the same as in the case of claim 1 described above. In addition, the average drying speed is not particularly limited in the range exceeding 20 seconds after casting.
[0018]
The casting support is preferably cooled to promote solidification of the dope. Specifically, the surface temperature of the casting support is preferably 10 ° C. or less, more preferably 8 ° C. or less. Preferably, it is most preferable to make it 5 degrees C or less. The means for cooling the casting support is not particularly limited, and various conventionally used means can be used.
[0019]
Moreover, it is preferable that the temperature difference between two arbitrary points of the part by which the dope of a casting support body is cast is 5 degrees C or less, and it is more preferable that it is 3 degrees C or less. When the temperature difference exceeds 5 ° C., drying is not uniform, and peelability may be deteriorated.
[0020]
Furthermore, by setting the surface temperature of the casting support to 10 ° C. or less and the temperature difference between the two points to 5 ° C. or less, the stripping speed can be increased, and the drying can be made uniform. Since a uniform film can be obtained, it is extremely preferable.
[0021]
Further, the oxygen concentration of the drying wind for drying the dope cast on the casting support is preferably 10 vol% or less, more preferably 5 vol% or less, and the dew point of the solvent contained in the drying wind Is preferably 5 ° C. or more lower than the surface temperature of the casting support, more preferably 10 ° C. or more. By adopting such a configuration, ignition and explosion can be prevented even when a flammable solvent is used. Further, by reducing the dew point, it is possible to prevent condensation on the casting support and the casting bead.
[0022]
The cleanliness (ISO-14644, Part1) of the gas in the drying zone where the casting support is installed is preferably ISO class 7 or less, more preferably ISO class 6 or less, and ISO class 5 or less. Most preferred. By adopting such a configuration, it is possible to suppress the occurrence of defects in quality due to foreign matter adhesion to the casting support or the casting dope surface. Further, the cleanliness of the gas in the drying zone of the casting part is preferably higher than M5.5 in the class of FED-STD-209E. In some cases, defects in quality may occur due to foreign matter adhering to the casting dope surface. Such cleanliness is the same in the drying zone following the casting support.
[0023]
The drying air in the casting support is preferably used by passing it through an air filter having an absolute pore diameter of 0.5 μm or less at least once. By passing the air filter, the above-mentioned cleanliness can be easily ensured. it can.
[0024]
The dope cast from the casting die to the casting support is dried on the casting support to be in a solid state that is dry to dryness. Then, the film solidified to some extent is sent to a drying section including a tenter device and dried.
[0025]
It is preferable to start drying the film peeled off from the casting support while applying tension by a tenter within a predetermined range. That is, it is preferable to start drying of the film peeled off from the casting support while applying tension with a tenter within 0.1 to 10 seconds after peeling, and the film peeled off from the casting support. It is preferable to start drying while applying tension with a tenter within a transport range of 0.1 to 10 m from the point of peeling from the casting support. By setting it as such a structure, the flatness inhibition by the drying shrinkage | contraction of a film can be prevented. In addition, it is possible to prevent the occurrence of film defects caused by bringing a high residual solvent amount film into direct contact with a high-temperature transport roller.
[0026]
The film peeled off from the casting support is transported to the tenter by the peeling roller and the transport roller. At this time, after being peeled off from the casting support, the film is transported by the cooling roller until it is carried by the tenter and cooled. The surface temperature of the roller is preferably 1 to 20 ° C. lower than the gelation temperature of the dope. By setting it as such a structure, generation | occurrence | production of the defect of the film which arises by making a high residual solvent amount film contact a high temperature conveyance roller directly can be prevented.
[0027]
In the solution casting method according to the present invention, a single layer liquid may be cast on a smooth band or a drum as a casting support, and a plurality of dopes of two or more layers are sequentially cast or co-cast. You may cast by. When casting a plurality of dopes, a film may be produced while casting and laminating the dopes from a plurality of casting openings provided at intervals in the traveling direction of the support. -158414, JP-A-1-122419, JP-A-11-198285, and the like can be applied. Further, the dope may be cast from two casting ports or formed into a film. For example, JP-B-60-27562, JP-A-61-94724, JP-A-61-947245, JP-A-sho No. 61-104813, JP-A 61-158413, JP-A 6-134933. Alternatively, a cellulose acylate film casting method described in JP-A No. 56-162617 may be used in which a high-viscosity dope is wrapped with a low-viscosity dope and the high- and low-viscosity dopes are simultaneously extruded.
[0028]
Alternatively, using two casting ports, the film cast on the support is peeled off by the first casting port, and the second casting is performed on the side that is in contact with the support surface to produce a film. For example, it is a method described in Japanese Patent Publication No. 44-20235.
[0029]
The dope to be cast may be the same solution or a different solution, and is not particularly limited. In order to give a function to a plurality of cellulose acylate layers, a dope corresponding to the function may be extruded from each casting port. Further, the dope of the present invention may be cast simultaneously with other functional layers (for example, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, a UV absorbing layer, a polarizing layer).
[0030]
In a single-layer solution, it is necessary to extrude a high-concentration and high-viscosity dope in order to obtain the required film thickness. In this case, the dope stability is poor, and solids are generated, causing a failure. In many cases, the flatness is poor. As a solution to this, by casting a plurality of dopes from the casting port, it is possible to simultaneously extrude a high-viscosity solution onto the support, improving the flatness and producing an excellent planar film. However, by using a thick dope, a reduction in drying load can be achieved and the production speed of the film can be increased.
[0031]
As the dope, a solution of cellulose acylate, polycarbonate, aramid polymer, norbornene polymer or the like can be used. As the cellulose acylate, it is preferable to use a lower fatty acid ester of cellulose. Lower fatty acid means a fatty acid having 6 or less carbon atoms. The number of carbon atoms is preferably 2 (cellulose acetate), 3 (cellulose propionate) or 4 (cellulose butyrate). Cellulose acetate is particularly preferred. Mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate may be used.
[0032]
The average acetylation degree (acetylation degree) of cellulose acetate is preferably 55.0% or more and less than 62.5%. From the viewpoint of the physical properties of the film, the average degree of acetylation is more preferably 58.0% or more and less than 62.5%. However, when cellulose acetate having an average degree of acetylation of 55.0% or more and less than 58.0% (preferably 57.0% or more and less than 58.0%) is used, a film having a high retardation in the thickness direction is produced. be able to.
[0033]
When a cellulose acylate solution is used as the dope, it contains at least 10% cellulose acylate, and the substitution ratio A of the 6-position acylate group and the substitution ratio B of the remaining acylate group are represented by the formulas (1) and ( A cellulose acylate satisfying the relationship 2) is preferable. In (1), A ≧ 0.8 is more desirable.
A ≧ 0.75 ……………………………… (1)
2.5 ≦ A + B ≦ 3.0 ……………… (2)
[0034]
Organic solvents used for dope include hydrocarbons (eg benzene, toluene, cyclopentane, cyclohexane, cycloheptane, cyclooctane), halogenated hydrocarbons (eg methylene chloride, chlorobenzene), alcohols (eg methanol, ethanol, Diethylene glycol, n-propyl alcohol, isopropyl alcohol, n-butanol, propanol, iso-propanol, 1-butanol, t-butanol, 2-methyl-2-butanol, 2-methoxyethanol, 2-butoxyethanol), ketone (eg, acetone) , Methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone, methylcyclohexanone), ester (eg, methyl acetate, ethyl acetate, propyl acetate, ethyl formate, propyl formate, Pentyl, butyl acetate, pentyl acetate and 2-ethoxy-ethyl acetate) and ethers (eg, tetrahydrofuran, methyl cellosolve, diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, anisole, phenetole), etc. Can be given.
[0035]
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.
[0036]
The dope used in the solution casting method of the present invention has various additives (for example, plasticizer, ultraviolet absorber, deterioration inhibitor, fine particle powder, mold release agent, optical property adjustment) in each preparation step depending on the application. Agents, fluorosurfactants). 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.
[0037]
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. Is 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.
[0038]
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.
[0039]
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.
[0040]
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.
[0041]
In addition, in the present invention, as a plasticizer for reducing the optical anisotropy, (di) pentaerythritol esters described in JP-A No. 11-124445, glycerola esters described in JP-A No. 11-246704, Diglycerola esters described in 2000-63560, citrate esters described in JP-A No. 11-92574, substituted phenyl phosphate esters described in JP-A No. 11-90946, and the like are preferably used.
[0042]
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-crawlerbenzotriazole, 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 -Crawler benzotriazole, 2 (2'-hydroxy-5'-tert-octylphenyl) benzotriazole and the like can be mentioned. 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-crawler benzotriazole, 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-crawlerbenzotriazole is particularly preferred.
[0043]
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.
[0044]
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.
[0045]
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.
[0046]
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 a UV absorber 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.
[0047]
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).
[0048]
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).
[0049]
[Chemical 1]

[0050]
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.
[0051]
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. Although a dispersion solvent is arbitrary, it is preferable that it is a composition close | similar to a polymer solution solvent.
[0052]
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.
[0053]
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.
[0054]
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. The amount of the release agent added is preferably 0.002 to 2% 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 sufficiently exerted, and if the addition amount exceeds 2% by mass, precipitation or insoluble matter may occur.
[0055]
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.
[0056]
Examples of the anionic surfactant include carboxylate, sulfate, sulfonate, and phosphate ester salt. Representative examples include fatty acid salt, alkylbenzene sulfonate, alkyl naphthalene sulfonate, alkyl sulfonate, α-olefin sulfonate, dialkylsulfosuccinate, α-sulfonated fatty acid salt, N-methyl-N oleyl taurine, petroleum sulfonate, alkyl sulfate, sulfated oil, polyoxyethylene alkyl ether sulfate, Polyoxyethylene alkyl phenyl ether sulfate, polyoxyethylene styrenated phenyl ether sulfate, alkyl phosphate, polyoxyethylene alkyl ether phosphate, naphthalene sulfonate formaldehyde condensate and the like.
[0057]
Examples of cationic surfactants include amine salts, quaternary ammonium salts, pyridinium salts, etc., and 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.
[0058]
By adding the fluorosurfactant, an antistatic effect can be exhibited. 0.001-2 mass% is preferable with respect to a cellulose acylate, and, as for the addition amount of a fluorine-type surfactant, 0.01-0.5 mass% is more preferable. 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.
[0059]
In the present invention, a retardation increasing agent (optical property adjusting agent) can be added. By adding a retardation increasing agent, the optical anisotropy can be controlled. 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.
[0060]
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.
[0061]
The molecular weight of the retardation increasing agent is preferably 300 to 800. The boiling point of the retardation increasing agent is preferably 260 ° C. or higher. The boiling point can be measured using a commercially available measuring device (for example, TG / DTA100, manufactured by Seiko Electronics Industry Co., Ltd.).
[0062]
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 added amount of the colorant is preferably 10 to 1000 ppm, more preferably 50 to 500 ppm in terms of mass ratio with respect to cellulose acylate.
[0063]
Furthermore, a heat stabilizer such as a salt of an alkaline earth metal such as lucium or magnesium, an antistatic agent, a flame retardant, a lubricant, an oil agent, or the like can be appropriately added to the dope in the present invention as necessary.
[0064]
When preparing the dope used in the present invention, the container may be filled with an inert gas such as nitrogen gas. The viscosity of the cellulose triacetate solution immediately before film formation may be within a range that allows casting, and is usually adjusted to a range of 10 ps · s to 2000 ps · s, particularly 30 ps · s to 400 ps. -S is preferable.
[0065]
The dope used in the present invention is prepared according to a cooling dissolution method or a high temperature dissolution method. The cooling dissolution method will be described below. First, cellulose acetate is gradually added to an organic solvent with stirring at a temperature around room temperature (-10 to 40 ° C.). When using a plurality of solvents, the order of addition is not particularly limited. For example, after adding cellulose acetate to the main solvent, another solvent (for example, a gelling solvent such as alcohol) may be added, or conversely, the main solvent after the gelling solvent is previously wetted with cellulose acetate. A solvent may be added, which is effective for preventing non-uniform dissolution. The amount of cellulose acetate is preferably adjusted so as to be contained in the mixture in an amount of 10 to 40% by mass. The amount of cellulose acetate is more preferably 10 to 30% by mass. Furthermore, you may add the arbitrary additive mentioned later in a mixture.
[0066]
The mixture is then cooled to -100 to -10 ° C (preferably -80 to -10 ° C, more preferably -50 to -20 ° C, most preferably -50 to -30 ° C). The cooling can be performed, for example, in a dry ice / methanol bath (−75 ° C.) or a cooled diethylene glycol solution (−30 to −20 ° C.). When cooled in this way, the mixture of cellulose acetate and organic solvent solidifies. Although the cooling rate is not particularly limited, in the case of batch-type cooling, the viscosity of the cellulose acetate solution increases with cooling, and the cooling efficiency is inferior. is necessary.
[0067]
In addition, the dope of the present invention can be achieved by swelling and then transferring the cooling device at a predetermined cooling temperature for a short time. The faster the cooling rate, the better. However, 10,000 ° C./second is the theoretical upper limit, 1000 ° C./second is the technical upper limit, and 100 ° C./second is the practical upper limit. The cooling rate is a value obtained by dividing the difference between the temperature at the start of cooling and the final cooling temperature by the time from the start of cooling to the final cooling temperature. Furthermore, when this is heated to 0 to 200 ° C. (preferably 0 to 150 ° C., more preferably 0 to 120 ° C., most preferably 0 to 50 ° C.), a solution in which cellulose acetate flows in an organic solvent is obtained. The temperature can be raised by simply leaving it at room temperature or in a warm bath. At this time, the pressure may be 0.3 to 30 MPa, but there is no particular problem. In that case, it is preferable to carry out in as short a time as possible, preferably within 0.5 to 60 minutes, and in particular, heating in a short time of 0.5 to 2 minutes is recommended.
[0068]
If the dissolution is insufficient, the cooling and heating operations may be repeated. Whether or not the dissolution is sufficient can be determined by merely observing the appearance of the solution with the naked eye. In the cooling and melting method, it is desirable to use a sealed container in order to avoid moisture mixing due to condensation during cooling. In the cooling and heating operation, when the pressure is applied during cooling and the pressure is reduced during heating, the dissolution time can be shortened. In order to perform pressurization and decompression, it is desirable to use a pressure-resistant container.
[0069]
A method for adjusting the cellulose acetate solution by the high temperature dissolution method will be described below. First, cellulose acetate is gradually added to an organic solvent with stirring at a temperature around room temperature (-10 to 40 ° C.). When using a plurality of solvents, the order of addition is not particularly limited. For example, after adding cellulose acetate to the main solvent, another solvent (for example, a gelling solvent such as alcohol) may be added, or conversely, the main solvent after the gelling solvent is previously wetted with cellulose acetate. A solvent may be added, which is effective for preventing non-uniform dissolution. The cellulose acetate solution of the present invention is preferably swollen in advance by adding cellulose acetate into a mixed organic solvent containing various solvents. In that case, cellulose acetate may be gradually added to any solvent at −10 to 40 ° C. with stirring, or in some cases, it may be pre-swelled with a specific solvent and then mixed with another combined solvent. A uniform swelling liquid may be used, and the remaining solvent may be added after swelling with two or more solvents.
[0070]
In the present invention, the dissolution concentration of cellulose acetate by a high-pressure high-temperature dissolution method of a mixed solvent system of methyl acetate and a ketone solvent having 4 to 12 carbon atoms is preferably 30% by mass or less, from the viewpoint of drying efficiency during film formation, It is preferable that the concentration be as high as possible. The amount of cellulose acetate is adjusted so as to be included as 10 to 30% by mass as the final dope. In the organic solvent composition of the present invention, it is preferable to prepare a high concentration cellulose triacetate solution. What is necessary is just to prepare in arbitrary density | concentrations. If the concentration is too high, the viscosity of the solution is too high and film formation may be difficult. Therefore, the preferable concentration of the cellulose acetate solution is in the range of 15% by mass to 30% by mass. Furthermore, the range of 17 mass%-25 mass% is preferable.
[0071]
Next, the organic solvent mixed solution is heated to 70 to 240 ° C. under a pressure of 0.2 MPa to 30 MPa (preferably 80 to 220 ° C., more preferably 100 to 200 ° C., most preferably 100 to 190 ° C.). The heating may be, for example, high-pressure steam or an electric heat source. A pressure vessel or a pressure line is required for high pressure, but any of iron, stainless steel, or other metal pressure vessel or line may be used, and is not particularly limited. Next, since these heated solutions cannot be applied as they are, it is necessary to cool them below the lowest boiling point of the solvent used. In that case, it is common to cool to -10-50 degreeC and to return to a normal pressure. For cooling, the high-pressure and high-temperature vessel or line containing the cellulose acetate solution may be left at room temperature, and more preferably, the apparatus may be cooled using a coolant such as cooling water. Note that heating and cooling operations may be repeated in order to accelerate dissolution. Whether or not the dissolution is sufficient can be determined by merely observing the appearance of the solution visually. In the high-pressure and high-temperature dissolution method, a sealed container is used to avoid evaporation of the solvent. In addition, the dissolution time can be further shortened by increasing the pressure or reducing the pressure in the swelling step. In order to perform pressurization and decompression, a pressure-resistant container or line is essential.
[0072]
The film produced by the solution casting method of the present invention can be used for a polarizing plate protective film, an optical functional film (optical compensation sheet, antireflection film, antiglare film, etc.) and the like. A polarizing plate protective film, an optical functional film, and the like are used in a liquid crystal display device, and the liquid crystal display device includes a liquid crystal cell, a polarizing plate, and an optical compensation sheet (retardation plate). In a transmissive liquid crystal display device, two polarizing plates are attached to both sides of a liquid crystal cell, and one or two optical compensation sheets are disposed between the liquid crystal cell and the polarizing plate. In a reflective liquid crystal display device, a reflector, a liquid crystal cell, one optical compensation sheet, and one polarizing plate are arranged in this order.
[0073]
The liquid crystal cell is composed of a rod-like liquid crystal molecule, two substrates for enclosing it, and an electrode layer for applying a voltage to the rod-like liquid crystal part molecule. The liquid crystal cell is different in the alignment state of rod-like liquid crystal molecules. As for the transmissive type, TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), OCB (Optically Compensatory N) (OCB). Various display modes such as Super Twisted Nematic (VA), Vertically Aligned (VA), and reflection type, such as HAN (Hybrid Aligned Nematic), have been proposed.
[0074]
A polarizing plate generally comprises a polarizing film and a transparent polarizing plate protective film. This polarizing film generally impregnates polyvinyl alcohol with an aqueous solution of iodine or a dichroic dye, and further uniaxially stretches the film. Can be obtained. It has a configuration in which two transparent polarizing plate protective films are attached to both sides of this polarizing film. Optical compensation sheets are used in various liquid crystal display devices in order to eliminate image coloring and expand the viewing angle. As an optical compensation sheet, a stretched birefringent film has been conventionally used.
[0075]
It has been proposed to use an optical compensation sheet having an optically anisotropic layer formed of liquid crystalline molecules (particularly discotic liquid crystalline molecules) on a transparent support, instead of an optical compensation sheet made of a stretched birefringent film. ing. The optically anisotropic layer is formed by aligning liquid crystalline molecules and fixing the alignment state. In general, the alignment state is fixed by a polymerization reaction using liquid crystalline molecules having a polymerizable group. Liquid crystalline molecules have a large birefringence. The liquid crystal molecules have various alignment forms. By using liquid crystalline molecules, it has become possible to realize optical properties that cannot be obtained with conventional stretched birefringent films.
[0076]
The optical properties of the optical compensation sheet are determined according to the optical properties of the liquid crystal cell, specifically, the display mode differences as described above. When liquid crystalline molecules, particularly discotic liquid crystalline molecules are used, optical compensation sheets having various optical properties corresponding to various display modes of the liquid crystal cell can be produced.
[0077]
Optical compensation sheets using discotic liquid crystalline molecules have already been proposed for various display modes. For example, an optical compensation sheet for a TN mode liquid crystal cell is described in each specification of JP-A-6-214116, US Pat. Nos. 5,583,679, 5,646,703, and German Patent 3,911,620A1. Further, an optical compensation sheet for liquid crystal cells in IPS mode or FLC mode is described in JP-A-10-54982. Further, optical compensation sheets for OCB mode or HAN mode liquid crystal cells are described in US Pat. No. 5,805,253 and International Patent Application WO 96/37804. Furthermore, an optical compensation sheet for an STN mode liquid crystal cell is described in JP-A-9-26572. A VA mode liquid crystal cell optical compensation sheet is described in Japanese Patent No. 2866372.
[0078]
If an optical compensation sheet using liquid crystal molecules and a polarizing plate are laminated to form an elliptical polarizing plate, the optical compensation sheet can function as one polarizing plate protective film of the polarizing element. Such an elliptically polarizing plate has a layer structure in the order of a transparent protective film, a polarizing film, a transparent support, and an optically anisotropic layer formed from liquid crystalline molecules. The liquid crystal display device is characterized by being thin and light, and if one of the constituent elements is reduced by combining it, the device can be made thinner and lighter. Further, if one component of the liquid crystal display device is reduced, one step of attaching the component is also reduced, and the possibility that a failure will occur when the device is manufactured is reduced. Regarding an integrated elliptical polarizing plate in which a transparent support of an optical compensation sheet using liquid crystalline molecules and one protective film of a polarizing plate are made common, JP-A Nos. 7-191217, 8-21996 and 8-94838 are disclosed. There are descriptions in each publication.
[0079]
When producing an optical compensatory sheet provided with an optically anisotropic layer in which the orientation film and the orientation of liquid crystalline molecules are fixed on a transparent support, a transparent support (usually a cellulose acetate film) and an orientation film (usually (Polyvinyl alcohol). Usually, the cellulose acetate film and polyvinyl alcohol have poor affinity and have a problem of peeling or cracking. In order to obtain adhesion between them, a gelatin subbing layer is provided on the cellulose acetate film.
[0080]
The thickness of the transparent support is preferably 20 to 500 μm, and more preferably 40 to 200 μm.
[0081]
When it is preferable that the transparent support is optically isotropic, an ordinary cellulose ester film can be used. When optical anisotropy is required for the transparent support, it is preferable to use a cellulose ester film having a high retardation. The in-plane retardation (Re) of the cellulose ester film can be adjusted (high value) by stretching the cellulose ester film. The thickness direction retardation (Rth) of the cellulose ester film can be determined by (1) using a retardation increasing agent, (2) adjusting the average degree of acetylation (degree of acetylation), or (3) producing the film by a cooling dissolution method. Can be adjusted (with higher values). As a result, it has become possible to use a cellulose ester film, which has conventionally been considered optically isotropic, as an optically anisotropic transparent support having an optical compensation function.
[0082]
The retardation value (Rth) in the thickness direction of the optically anisotropic support is preferably 60 to 1000 nm. The in-plane retardation value (Re) is preferably -50 to 50 nm, and more preferably -20 to 20 nm.
[0083]
The retardation value in the thickness direction is a value obtained by multiplying the birefringence index in the thickness direction by the thickness of the film. The in-plane retardation value is a value obtained by multiplying the in-plane birefringence by the film thickness. The specific values are the measurement results of the in-plane retardation with respect to the slow axis as the incident direction of the measuring light perpendicular to the film film surface, and the incident direction relative to the vertical direction relative to the film film surface. Obtained from the tilted measurement results. The measurement can be performed using an ellipsometer (for example, M-150: manufactured by JASCO Corporation). As a measurement wavelength, 632.8 nm (He—Ne laser) is adopted.
[0084]
The retardation value (Rth) in the thickness direction and the in-plane retardation value (Re) are calculated according to the following formulas (4) and (5), respectively.
Formula (4) Rth = {(nx + ny) / 2−nz} × d
Expression (5) Re = (nx−ny) × d
[0085]
Where nx is the refractive index in the x direction in the film plane, ny is the refractive index in the y direction in the film plane, nz is the refractive index in the direction perpendicular to the film plane, and d is the film refractive index. Thickness (nm).
[0086]
An example of a solution casting apparatus capable of performing the solution casting method according to the present invention will be described with reference to the drawings.
[0087]
FIG. 1 is a schematic view of an apparatus for producing a film by a solution casting method. In this figure, 10 is a dope preparation unit, 20 is a casting unit for casting a dope onto a casting support, 30 is a tenter drying unit for drying the film peeled off from the casting support while being transported by a tenter device, Reference numeral 40 denotes a drying unit that further dries the film dried by the tenter drying unit 30, and reference numeral 50 denotes a winding roller that winds the completed film.
[0088]
The dope preparation unit 10 is provided with a stirring tank 11 for stirring and mixing cellulose acetate, a solvent, a plasticizer, and the like, and a filter 13 is connected to the stirring tank 11 via a liquid feed pump 12. The casting part 20 is provided with a casting die 21 and a rotary drum 22 as a casting support, and the dope is sent from the filter 13 to the casting die 21. Further, a peeling roller 23 for peeling the film from the rotating drum 22 is provided, and a conveying roller 24 for conveying the film to the tenter drying unit 30 is provided.
[0089]
The tenter drying unit 30 is provided with a pin tenter 31. The pin tenter 31 supports and conveys both ends of the film, and is dried with a drying air. The drying unit 40 is provided with a large number of conveying rollers 41, and is dried by drying air while being conveyed by the conveying rollers 41.
[0090]
The casting unit 20 is provided with a coagulation device 25, an air supply fan 26, a heater 27, and a filter 28. After the solvent is collected from the gas in the casting unit 20 by the coagulation device 25, the air supply fan 26 It is circulated again in the casting part 20 through the heater 27 and the filter 28.
[0091]
Similarly to the casting unit 20, the tenter drying unit 30 is also provided with a coagulating device 32, an air supply fan 33, a heater 34, and a filter 35. The solvent is recovered from the gas in the tenter drying unit 30 by the coagulating device 32. After that, the air supply fan 33 circulates again in the tenter drying unit 30 through the heater 34 and the filter 35.
[0092]
The drying unit 40 is provided with an air supply fan 42, a heater 43, and a filter 44, and adsorbs a solvent from a gas discharged from the filter 45 and the air supply fan 42 for introducing fresh air to the air supply fan 42. An adsorbing / recovering device 46 is provided to supply fresh air together with the gas recovered by the air supply fan 42 to the drying unit 40 via the heater 43 and the filter 44, and the adsorbing / recovering device 46 removes the solvent from the recovered gas. It collects in.
[0093]
【Example】
[Example 1]
<Dope A>
Cellulose triacetate (pulp raw material): 16% by mass
(Acetylation degree 60.9%, polymerization degree 305, 6-position acetyl substituent ratio 0.75, average particle size 1.5 mm)
Cellulose triacetate (pulp raw material) 2% by mass
(Acetylation degree 61.2%, polymerization degree 322, 6-position acetyl substituent ratio 0.72, average particle diameter 1.1 mm)
Cellulose triacetate (Linter raw material) …………………… 2% by mass
(Acetylation degree 61.2%, polymerization degree 362, 6-position acetyl substituent ratio 0.72, average particle size 1.3 mm)
Triphenyl phosphate ……………………………………… 2% by mass
Biphenyl diphenyl phosphate …………………………… 1% by mass
Benzotriazole-based UV absorber ……………………… 0.2% by mass
Silicon oxide matting agent (primary particle system 20nm) ………… 0.1% by mass
Methylene chloride ………………………………………………… 67% by mass
Methanol ………………………………………………………… 9% by mass
n-Butanol ……………………………………………………… 1% by mass
[0094]
A dope A was prepared by dissolving and filtering the polymer solution having the above composition by a high temperature dissolution method described in Japanese Patent Application Laid-Open No. 2001-1745.
[0095]
<Dope B>
The following substances are further added to the composition of the dope A, and the solid content is diluted to 18.5% by mass.
Silicon oxide matting agent (primary particle system 20nm) ………… 0.1% by mass
Peeling accelerator ... ……………………………………………… 0.1% by mass
(Compound described in specific example 6 of Japanese Patent Application No. 63-129747)
[0096]
A polymer solution having the above composition was dissolved and filtered by a high-temperature dissolution method described in Japanese Unexamined Patent Publication No. 2001-1745 to prepare Dope B.
[0097]
<Manufacture of film>
As a casting die, a multi-manifold type coat hanger type is used, and as a casting support, a hard chrome plating is applied and a mirror finish is applied so that the central average roughness becomes 0.03 μm. A 2500 mm rotating drum was used. In the rotating drum, the refrigerant was passed through to maintain the average surface temperature at −5 ° C., and the temperature distribution on the rotating drum surface at this time was within 2 ° C.
[0098]
Then, the core layer having a thickness of 70 μm after drying was co-cast so that the core layer having a thickness of 70 μm after drying and the outer layers on both sides having a thickness of 5 μm after drying were formed.
[0099]
The back suction chamber was installed on the temporary side of the bead so that the dopes A and B discharged from the casting die were not excessively stretched in the casting direction. The rotational peripheral speed of the drum was 30 m / min, and the pressure inside the back suction chamber was reduced to 400 Pa from the surrounding pressure. A 1500 mm long side branch was installed in the piping system connected to the back suction chamber to suppress pressure fluctuations inside the chamber. The peak value in the characteristic frequency of the pressure fluctuation value obtained by digital fast Fourier transform of the pressure fluctuation in the chamber at this time is in the range of 10 to 100 Hz, and all are 5 Pa or less, and there is no side branch It was 50% or less of the peak value.
[0100]
The cast dopes A and B were dried at a wind speed of 0.5 m / s or less for 1 second immediately after casting, and thereafter dried at a wind speed of 15 m / s facing the drum rotation direction. The temperature of the drying air was 50 ° C. Further, the solvent was condensed and recovered with a condenser so that the dew point of the solvent in the dry air was -30 ° C. The recovered solvent was dehydrated with zeolite and reused in the charging process. The circulating drying air was reused after being filtered through a high-performance air filter with a collection efficiency of 0.3 μm and a 99.999% collection efficiency. The cleanliness of the gas in the drying zone was class 5 or less, and it was M3.5 or less in the class of FED-STD-209E. The oxygen concentration in the drying zone was kept at 5 Vol% with nitrogen gas. Nitrogen gas was supplied from a liquid nitrogen tank by a pressure swing type nitrogen separator.
[0101]
When the film was peeled off from the rotating drum, the residual solvent amount of the film was 230% by mass, and the film temperature was −6 ° C. The average drying speed from casting to stripping was 744% by mass / min. Further, the gelation temperature of the dope at the time of stripping was about 10 ° C. Peeling from the drum was stable.
[0102]
The peeled film is passed through a coolant and transported to a pin tenter by a pass roller whose surface temperature is adjusted to −5 ° C., and dried while applying tension while holding both ends (thickness 70 μm) with the pin tenter. And carried. Three pass rollers after peeling off were used, and all were arranged so as to wrap on the side opposite to the support of the film. Moreover, these pass rollers were able to set a draw ratio of 0.5 to 15% with respect to the drum rotation speed, and were operated at a draw ratio of 1%, 2% and 4% with respect to the drum, respectively. Moreover, it arrange | positioned so that a wrap angle might be 5 degrees or less. The distance from the stripping to the bitten portion of the pin tenter was 1.2 m.
[0103]
When the film was supported by a pin tanter, the temperature of the pin tenter was 25 ° C., the temperature of the supported film was 5 ° C., and most of the residual solvent in the film was methylene chloride. The saturation temperature of the gas in the drying zone was −15 ° C., and the oxygen concentration was 6%. The evaporated solvent is condensed and recovered in the same manner as the casting portion, and the drying zone is inerted with nitrogen gas. In addition, an air filter with a collection rate of 0.3 μm of 99.999% is installed in the circulation path of the drying air, the cleanliness of the gas in the drying zone is class 5 or less, and FED-STD-209E M3.5 or less in class.
[0104]
The temperature of the drying air is 120 ° C., the temperature distribution in the width direction of the film at this time is 5 ° C. or less, the average wind speed of drying is 5 m / s, and the average value of the heat transfer coefficient is 25 kcal / m. ² -It was Hr * degreeC and the width direction distribution of the film was all within 5%. Also, the pin tenter carrying part in the drying zone was prevented from being directly exposed to the dry hot air by a wind shield. The film being conveyed by the pin tenter was dried while maintaining the tension in the width direction at 98 N / m (10 kg / m) in order to maintain the flatness of the film.
[0105]
In addition, the pin tenter has an overall heat transfer coefficient of 150 kcal / m with cooling air of −5 ° C. until the film is newly supported after the film is detached. ² -It cooled at Hr * degreeC. The length of the portion cooled by the cooling device was 50% of the whole.
[0106]
The time to be supported and dried by the pin tenter was 10 minutes, and the amount of solvent evaporated during that time was 97% of the total amount of solvent evaporated between stripping and winding. The evaporated solvent was condensed and recovered by a condenser, and this recovered solvent was dehydrated by distillation to a water content of 0.4%, and then used again as a raw material for the dope preparation process.
[0107]
The film dried with a pin tenter is further dried with a drying air of 145 ° C. for 15 minutes in a drying process in which the film is dried while being conveyed by a roller, and then the humidity and temperature are adjusted to adjust the residual solvent amount at winding to 0.55% by mass, The film was wound up at a moisture content of 0.8 mass% and a temperature of 35 ° C. The conveyance tension in the drying zone was 65 to 150 N / m, and the absolute value of the charge amount of the film was kept at 3 kV or less. Further, the solvent gas concentration in the drying zone was 20% or less of the lower limit of explosion of the solvent, and the dew point of the high boiling point components other than the solvent was 80 ° C. or more. The dry air is supplied through a 0.3 μm air filter with a collection efficiency of 99.97%, and its cleanliness is ISO class 5 or lower, and the FED-STD-209E class is M3.5. It was the following.
[0108]
The film produced by the method as described above could be stably conveyed without problems such as wrinkles and offsets in the drying step after peeling off from the casting die. Moreover, the flatness and transparency of the wound film are good, and a foreign matter of 10 μm or more is 1 cm. ² It was 0 per hit.
[0109]
[Comparative Example 1]
Of the casting and drying conditions on the rotating drum, the thickness after drying of the core layer is 35 μm, the thickness after drying of both outer layers is 2.5 μm, the average wind speed of the drying air is 25 m / min, and the temperature is 60 ° C. Except that, casting and drying were performed under the same conditions as in Example 1.
[0110]
At this time, the average drying speed from casting to stripping reached 1050% by mass / min., But wind unevenness due to the drying wind occurred on the casting surface, and the flatness was remarkably impaired.
[0111]
[Comparative Example 2]
Of the casting and drying conditions on the rotating drum, the same conditions as in Example 1 except that the dew point of the solvent in the drying wind was −7 ° C., the average wind speed was 2.5 m / min, and the temperature was 20 ° C. And then dried.
[0112]
At this time, the amount of residual solvent at the time of stripping was 310% by mass, and the average drying speed from casting to stripping was 220% by mass / min. However, it can be stripped stably at a casting speed of 30 m / min. could not. In order to peel off stably at this average drying speed, it was necessary to reduce the casting speed to 10 m / min as a result, and the productivity was significantly reduced.
[0113]
[Example 2]
<Dope C>
Cellulose triacetate (pulp raw material): 20% by mass
(Acetylation degree 60.9%, polymerization degree 305, 6-position acetyl substituent ratio 0.85, average particle size 1.5 mm)
Triphenyl phosphate ……………………………………… 2% by mass
Biphenyl diphenyl phosphate …………………………… 1% by mass
Benzotriazole-based UV absorber ……………………… 0.2% by mass
Methylene chloride ……………………………………………………… 61% by mass
Methanol ………………………………………………………… 16% by mass
[0114]
A polymer solution having the above composition was dissolved and filtered by a high-temperature dissolution method described in Japanese Unexamined Patent Publication No. 2001-1745 to prepare Dope C.
[0115]
<Dope D>
The following substances are further added to the composition of the dope C, and the solid content is diluted to 18.5% by mass.
Silicon oxide matting agent (primary particle system 20nm) ……………… 0.1% by mass
Peeling accelerator ... …………………………………………………… 0.1% by mass
(Compound described in Example 6 of Japanese Patent Application No. 63-129747)
[0116]
A polymer solution having the above composition was dissolved and filtered by a high-temperature dissolution method described in Japanese Unexamined Patent Publication No. 2001-1745 to prepare Dope B.
[0117]
<Manufacture of film>
Using a coat hanger type die equipped with a Ford block, the core layer having a thickness of 70 μm after the dope C was dried was co-cast so that the dope D could constitute an outer layer on both sides having a thickness of 5 μm after drying. Other casting and drying conditions are the same as in Example 1.
[0118]
The residual solvent amount at the time of peeling was 245% by mass, and the temperature of the film was −5 ° C. The average drying speed from casting to peeling was 657% by mass / min. The gelation temperature of the dope at the time of peeling was 15 ° C.
[0119]
The film produced by the method as described above could be stably conveyed without problems such as wrinkles and offsets in the drying step after peeling off from the casting die. Moreover, the flatness and transparency of the wound film are good, and a foreign matter of 10 μm or more is 1 cm. ² It was 0 per hit.
[0120]
[Comparative Example 3]
Casting and drying were carried out under the same conditions as in Example 2 except that the drying air temperature was 100 ° C. among casting and drying conditions on a rotating drum. At this time, the average drying speed from casting to stripping reached 1150% by mass / minute, but foaming occurred on the casting dope surface and could not be stripped stably.
[0121]
[Comparative Example 4]
The film was cast under the same conditions as in Example 2 except that the surface temperature of the transport roller after peeling was 14.5 ° C. The film peeled off from the casting support could not be transported by adhering to the transport roller.
[0122]
[Production Method and Evaluation Method of Polarizing Plate]
The polarizing plate sample was prepared by pasting the cellulose triacetate films formed in Examples 1 and 2 with a polyvinyl alcohol-based adhesive on both surfaces of a polarizing element obtained by stretching polyvinyl alcohol and adsorbing iodine. This polarizing plate sample was exposed for 500 hours in an atmosphere of 60 ° C. and 90% RH. In all the examples, the degree of polarization was 99.6% or more, and sufficient durability was recognized.
[0123]
The degree of polarization was determined by calculating the parallel transmittance YP and the direct transmittance Yc in the visible region with a spectrophotometer, and determining the degree of polarization P based on the following equation.
P = √ ((YP−Yc) / (YP + Yc))
[0124]
[Example 3]
<Preparation of optical functional film>
A gelatin layer (layer thickness: 0.1 μm) was applied on one side of the triacetyl cellulose film [thickness: 100 μm, {(nX + ny) / 2−nz} × d = 70 nm)] prepared in Example 1. . Next, a coating solution of long-chain alkyl-modified poval (MP-203, manufactured by Kuraray Co., Ltd.) is applied on the gelatin layer thus coated, dried at 110 ° C. for 30 seconds and then rubbed. Thus, an alignment film was formed. On this alignment film, a discotic liquid crystal (compound example: compound TE-8 (m = 4) described in JP-A-8-43625 is 20% by mass) and a photopolymerization initiator (Irgacure 907, Nippon Ciba Geigy Co., Ltd.) The coating solution dissolved in methyl ethyl ketone was applied with a slide coater such that the coating rate was 20 mass / min and the coating amount was 12 cc / m. ² Was applied to form a discotic liquid crystal layer having a layer thickness of 2.4 μm. The film on which the alignment film and the liquid crystal layer are formed is placed in a thermostatic chamber set at 150 ° C. for 5 minutes to align the discotic liquid crystal and ripen. Was irradiated for 2 minutes and allowed to cool to room temperature to obtain an optical compensation sheet.
[0125]
When the optical compensation sheet thus obtained was mounted on a TN type liquid crystal cell as shown in FIG. 2, the effect of improving the viewing angle was obtained without reducing the contrast. In FIG. 2, TNC is a TN type liquid crystal cell, RF1 and RF2 are optical compensation sheets, A and B are polarizing plates, PA and PB are polarization axes, L0 is natural light, L1 and L5 are linearly polarized light, L3 and L4 are It is elliptically polarized light.
[0126]
【The invention's effect】
Since the present invention can be quickly peeled off from the casting support without losing quality, it is highly transparent, optically isotropic, and excellent in mechanical strength, dimensional stability and durability. The film can be manufactured stably and at high speed.
[Brief description of the drawings]
FIG. 1 is a schematic view of a solution casting apparatus for performing a solution casting method according to the present invention.
FIG. 2 is an exploded perspective view of a liquid crystal display device using a film manufactured by the solution casting method according to the present invention.
[Explanation of symbols]
10 ... Dope preparation section
20 ... Casting part
21 ... Casting die
22 ... Rotating drum (casting support)
30 ... Tenter drying section
31 ... pin tenter
40 ... Drying section
50 ... Winding roll
TNC ... TN type liquid crystal cell
A, B ... Polarizing plate
PA, PB ... Polarization axis
L0 ... Natural light
L1, L5 ... Linearly polarized light
L3, L4 ... elliptically polarized light
LC: Alignment state of liquid crystal molecules when a sufficient voltage is applied to the TN liquid crystal cell
RF1, RF2 ... Optical compensation sheet
BL ... Backlight

Claims (17)

  A dope is cast from a casting die onto a casting support, the cast dope is dried to some extent to form a film, and the film is peeled off from the casting support and further dried to produce a film. In the method, the mass fraction of the solid content in the dope is set to 17% by mass or more and 30% by mass or less, and the average drying rate from casting to stripping of the dope exceeds 300% by mass / min. A solution casting method characterized in that the drying air in the casting support is passed through an air filter having an absolute pore diameter of 0.5 μm or less at least once and is used at a mass% / min or less.   A dope is cast from a casting die onto a casting support, the cast dope is dried to some extent to form a film, and the film is peeled off from the casting support and further dried to produce a film. The mass fraction of the solid content in the dope is 17% by mass or more and 30% by mass or less, and the average drying rate in a range within 15 m from the casting point of the dope exceeds 300% by mass / min. The solution casting method is characterized in that it is used at a rate of 1000 mass% / min or less and the drying air in the casting support is passed through an air filter having an absolute pore diameter of 0.5 μm or less at least once.   A dope is cast from a casting die onto a casting support, the cast dope is dried to some extent to form a film, and the film is peeled off from the casting support and further dried to produce a film. In the method, the mass fraction of solid content in the dope is set to 17% by mass or more and 30% by mass or less, and the average drying rate during 3 seconds after casting to 20 seconds after casting is set to 300% by mass / min. And at least once through an air filter having an absolute pore diameter of 0.5 μm or less, and using the dry air in the casting support at a rate of 1000 mass% / min or less Method.   The surface temperature of the casting support is 10 ° C. or less, and the temperature difference between any two points of the portion of the casting support where the dope is cast is 5 ° C. or less. Item 4. The method for forming a solution film according to Item 1, 2 or 3.   The oxygen concentration of the drying wind for drying the dope cast on the casting support is 10 vol% or less, and the dew point of the solvent contained in the drying wind is 5 ° C. or more lower than the casting support surface temperature. 5. The solution casting method according to claim 1, 2, 3 or 4.   The solution casting method according to 1, 2, 3, 4 or 5, wherein the cleanliness of the gas in the drying zone of the casting part and the subsequent drying zone is ISO class 7 or less.   The cleanliness of the gas in the drying zone of the casting section and the subsequent drying zone is cleanliness cleaner than M5.5 in the class of FED-STD-209E. The solution casting method according to 3, 4, or 5.   The solution dope according to claim 1, 2, 3, 4, 5, 6 or 7, wherein the dope comprises at least two kinds of cellulose acylate solutions, and the plurality of dopes are co-cast. Method.   The said dope consists of at least 2 or more types of cellulose acylate solutions, These several dope is cast | casted sequentially, The 1, 2, 3, 4, 5, 6, 7 or 8 characterized by the above-mentioned. Solution casting method.   The drying of the film peeled off from the casting support is started while applying tension with a tenter within 0.1 to 10 seconds after peeling off. , 6, 7, 8 or 9.   The drying of the film peeled off from the casting support is started while applying tension by a tenter within a transport range of 0.1 to 10 m from the point of peeling from the casting support. The solution casting method according to 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.   The film peeled off from the casting support is transported by a cooling roller until peeled off from the casting support until it is supported by a tenter, and the surface temperature of the cooling roller is 1 to 20 ° C. higher than the gelation temperature of the dope. The solution casting method according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11.   The dope is made of a cellulose acylate solution and contains 0.1 to 20% by mass of at least one plasticizer with respect to the cellulose acylate. The solution casting method according to 6, 7, 8, 9, 10, 11 or 12.   The said dope consists of a cellulose acylate solution, and contains 0.001-5 mass% of at least 1 type of ultraviolet absorber with respect to a cellulose acylate, The 1, 2, 3, 4, 5 characterized by the above-mentioned. , 6, 7, 8, 9, 10, 11, 12 or 13.   The said dope consists of 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, The 1, 2, 3, 4, 5 characterized by the above-mentioned. , 6, 7, 8, 9, 10, 11, 12, 13 or 14.   The said dope consists of a cellulose acylate solution, and contains 0.002-2 mass% of at least 1 type of mold release agents with respect to a cellulose acylate, The 1, 2, 3, 4, 5 characterized by the above-mentioned. , 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15.   The said dope consists of a cellulose acylate solution, and contains 0.001-2 mass% of at least 1 type of fluorosurfactant with respect to a cellulose acylate, The 1, 2, 3, 4 characterized by the above-mentioned. The solution casting method according to 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or 16.

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