JP3569145B2 - Method for producing retardation film - Google Patents

Description

【００１９】
２．金型出口における樹脂組成物の温度が、可塑剤の（沸点＋２０℃）以下の温度であること。
【００２３】
本発明において、「フィルム」とは、厚みによって規定される厳密な意味でのフィルムを指すのではなく、厚みによって呼び分けられている薄いフィルム、中位のシート及び肉厚のプレートの総てを含む。
【００２４】
本発明において用いられる熱可塑性樹脂は、延伸して位相差フィルムとして要求される位相差１００〜１０００ｎｍを発現し得る樹脂材料であれば特に限定されるものではないが、例えば、セルロース系樹脂、スチレン系樹脂、塩化ビニル系樹脂、ポリカーボネート系樹脂、アクリロニトリル系樹脂、ポリオレフィン系樹脂、ポリサルホン樹脂、ポリエーテルサルホン系樹脂、ポリアリレート系樹脂、ポリメタクリル酸メチル系樹脂が好ましく、特に、ポリサルホン樹脂は光の波長分散性が液晶に近い特性であり、各波長で異なる楕円偏光を良好に補償できるので液晶表示装置のコントラストがより向上する。
【００２５】
可塑剤としては、使用する熱可塑性樹脂と相溶性の良いものであれば特に限定されるものではないが、例えば、アジピン酸エステル、アゼライン酸エステル、安息香酸エステル、イソ酪酸エステル、チオ酪酸エステル、ブラシル酸エステル、クエン酸エステル、グリコール酸エステル、イタコン酸エステル、オレイン酸エステル、リン酸エステル、ホスフィン酸エステル、フタル酸エステル、フタル酸異性体エステル、テトラヒドロフタル酸エステル、ヘキサヒドロフタル酸エステル、ピロメリット酸エステル、リシノール酸エステル、セバシン酸エステル、コハク酸エステル、スルホンアミドトリアセチレン、トリメリット酸エステル等が挙げられる。ポリサルホン系樹脂に対しては、フタル酸エステル系可塑剤が、透明性に優れ、位相差フィルムの品質安定性の観点から好適に用いられる。
【００２６】
フタル酸エステル系可塑剤としては、特に限定されるものではないが、例えば、フタル酸ジメチル、フタル酸ジエチル、フタル酸ジブチル、フタル酸ジヘプチル、フタル酸エチルヘキシル、フタル酸ジイソノニル、フタル酸ジイソデシル、フタル酸ブチルベンジル等が挙げられる。
【００２７】
可塑剤の熱可塑性樹脂に対する添加量は、熱可塑性樹脂１００重量部に対して０．２〜１０重量部である。
可塑剤の添加量が０．２重量部未満では、該熱可塑性樹脂組成物のＴｇが十分に下がらず、位相差特性自体を低下させるおそれがあり、１０重量部を超えると、フィルムが軟化し、所望の位相差特性が発現し難く、更には、耐熱性も低下するおそれがある。
【００２８】
熱可塑性樹脂に対する可塑剤の添加の時期は、特に限定されるものではないが、例えば、高速ミキサー、リボンブレンダー、タンブラー等の混合機を用いて押出成形機への投入前に行われてもよいが、図１及び図２に例示されているように、先に溶融押出機へ熱可塑性樹脂を投入し、加熱混練されてバレル内を移送されてくる途中から、プランジャーポンプ等の注入装置を用いて可塑剤を圧入し、バレル内で捏和混合してもよい。
【００２９】
上記熱可塑性樹脂と可塑剤が溶融押出機の別の投入口からフィードされる場合の可塑剤の添加量は、溶融押出機の別の投入口からフィードされる熱可塑性樹脂１００重量部に対して、同時刻に別の投入口からフィードされる可塑剤の重量部であって、平均的な重量部を表すものとである。
【００３０】
溶融押出機バレル及び付属装置の分割された複数の加熱部分とは、図１に例示されているように、溶融押出機バレル１〜８、ダイヘッド１３、ギヤポンプ部１４、ネック１５、Ｌ型アダプター１６、ダイ入口１７、金型及び図示されてはいないが、その他必要に応じて用いられたスタティックミキサー、スクリーンチェンジャー等に分割された加熱部分を意味し、予め混合された熱可塑性樹脂と可塑剤とからなる熱可塑性樹脂組成物を樹脂供給部より投入した場合には、可塑剤の供給より金型出口までの溶融押出機バレル及び付属装置の分割された複数の加熱部分とは、上記溶融押出機バレル１〜８及びそれ以降に列挙した総ての加熱部分を指し、図１に例示されたバレル７部分にプランジャーポンプ１２を用いて可塑剤を圧入した場合には、バレル７及びそれ以降に列挙した加熱部分を指すものである。
【００３１】
上記加熱部分は、各々、温度制御装置の一部をなす温度検出装置と加熱及び冷却装置が付設され、各加熱部分毎に前記式（１）を満足する温度Ｔ（℃）〔ｓ（分）及びＷ（重量部）は押出量及び配合によって定まる設定値〕に制御されている。
【００３２】
温度検出装置は、特に限定されるものではないが、例えば、サーモカップル、サーミスター等が挙げられ、加熱及び冷却装置としては、例えば、バンドヒーター、アルミ鋳込ヒーター、赤外線ヒーター等の加熱装置、空冷式冷却器、水冷式冷却器等の冷却装置が挙げられ、温度制御装置としては、例えば、積水化学工業社製、商品名「ＳＰＣＣ」等が挙げられる。
【００３３】
上記加熱部分での樹脂温度は、樹脂流路に熱電対等の温度検出装置を挿入して実測した値を用いるのが好ましいが、加熱部分が温度制御され、定常状態になったときの加熱部分の計器指示温度で代用してもよい。
又、上記加熱部分での樹脂通過時間は、平均的な樹脂の通過時間を示すものである。上記樹脂通過時間も、例えば、カラーバッチを用いて加熱部分毎に各々通過時間を実測するのが好ましいが、各加熱部分の流通容積と樹脂の押出量より算出した値が略同じ値となるので、これを用いてもよい。
【００３４】
本発明の位相差フィルムの製造方法においては、上記のように装備された押出成形機が用いられる。
用いられる金型は、特に限定されるものではなく、例えば、Ｔダイであってもよく、サーキュラーダイであってもよいが、次の延伸工程の制御を容易にする観点からＴダイが好適に用いられる。
【００３５】
溶融押出機への熱可塑性樹脂及び可塑剤の投入は、異物の混入を防止する目的で、メッシュやフィルターを介して行ったり、金属性ないしは導電性の夾雑物を電磁石等の磁性吸着装置を用いて行われる。
特に、本発明において、熱可塑性樹脂がペレット状で用いられる場合、該熱可塑性樹脂ペレットに付着して存在する粉粒状の熱可塑性樹脂もしくは夾雑物を除去した後、押出成形機に投入されることが好ましい。このように粉粒状の熱可塑性樹脂もしくは夾雑物が除去されている場合には、必ずしも上記メッシュやフィルターを装着しなくてもよい。
【００３６】
熱可塑性樹脂ペレットに共存し、もしくは付着して存在する粉粒状の熱可塑性樹脂もしくは夾雑物を除去する手段は、特に限定されるものではないが、例えば、熱可塑性樹脂ペレットを水洗、乾燥する方法、篩分けする方法、風を当てて粉粒状の熱可塑性樹脂もしくは夾雑物を飛散させる方法、イオン風等を当てて粉粒体と熱可塑性樹脂ペレットを分離する方法が挙げられる。これらの方法は、単独で用いられてもよいが、２種以上の方法を組み合わせたり、同一方法が２段以上多段に用いられてもよい。これらの粉粒体の除去装置は、押出成形機に対して、インラインであってもよく、オフラインであってもよい。
【００３７】
特に、熱可塑性樹脂ペレットを水洗、乾燥する方法が好ましく、熱可塑性樹脂ペレットに共存もしくは夾雑する粉粒体は静電気によって付着しているため、水洗によって極めて容易に除電して除去できるので高効率化、低コスト化の方法の一つである。
上記水洗、乾燥する方法を用いる場合、洗浄水からの汚染を防止する配慮が必要であり、安全を求めるならば超純水の使用がすすめられる。
使用水量は、熱可塑性樹脂ペレット全体に洗浄水が接触して流れ落ちる程度であってもよく、水洗方法は、特に限定されるものではないが、例えば、熱可塑性樹脂ペレットの流失措置を講じた上で、流水に曝す方法、洗浄水を噴霧ないしは噴射する方法等が挙げられる。
【００３８】
水洗後、乾燥前に、脱水工程が挿入されてもよい。脱水手段は、特に限定されるものではないが、例えば、延伸分離機や揺動篩等の機械力を用いる脱水方法であってもよいが、重力のみの自然脱水工程と次工程の乾燥気流を用いた乾燥工程を組み合わせた脱水乾燥方法であってもよい。
【００３９】
インラインで篩分けする方法を用いる場合、熱可塑性樹脂ペレットを篩円周上を移動させながら振動させることが好ましい。このように篩分けすることによって、熱可塑性樹脂ペレットの取出を容易にすると共に、篩分け効率を向上させることができる。
上記篩の目開きは、熱可塑性樹脂ペレットが粉粒体と共に落下することがないものであれば、特に限定されるものではないが、好ましくは、目詰まりなく、長時間の使用が可能であるために、熱可塑性樹脂ペレットの１／２程度の目開きが好適に用いられる。
【００４０】
金型出口における樹脂組成物の温度は、可塑剤の（沸点＋２０℃）以下の温度、好ましくは可塑剤の（沸点−１００℃）から可塑剤の（沸点＋２０℃）の範囲の温度、より好ましくは可塑剤の（沸点−５０℃）から可塑剤の（沸点＋２０℃）の範囲の温度である。
上記樹脂組成物の温度が可塑剤の（沸点＋２０℃）の温度を超える場合、可塑剤の沸騰によって熱可塑性樹脂フィルムの発泡が多くなり、表面性質を悪化して、得られる位相差フィルムの位相差特性を低下させ、（沸点−１００℃）の温度未満であると、可塑剤の揮発が十分に行われず、厚さの厚い部分と薄い部分との可塑剤濃度差が形成されず、可塑剤濃度の高い厚い部分の延伸度合が可塑剤濃度の低い薄い部分の延伸度合より大きくなることによってΔｎ×ｄで表されるデターデーション値を均一化させるという位相差均一化効果が得られ難くなる。
【００４１】
金型出口より押出されたフィルム状熱可塑性樹脂組成物からの可塑剤の揮発は、押出直後、即ち、熱可塑性樹脂フィルムの冷却工程直前、冷却工程、養生工程（インライン、オフラインを問わない）、延伸予熱工程或いは延伸工程の少なくとも一工程において行われればよい。特に、押出直後が最も揮発が容易であり、位相差均一化効果が最も効果的に行われる点で好適に用いられる。
【００４２】
このようにして成膜された熱可塑性樹脂フィルムを延伸すると、延伸後のレターデーション値は、ほぼ均一となる。延伸方法については特に限定されず、一軸延伸あるいは二軸延伸の何れであってもよく、より具体的には、ロールにより縦一軸延伸、テンターによる横一軸延伸、これらを組み合わせた二軸延伸、複数枚の熱可塑性樹脂フィルムの周縁部を把持し一軸または二軸に延伸する方法等、従来より公知の適宜の延伸方法を挙げることができるが、得られる位相差フィルムを搭載した液晶表示装置の視野角を拡大するという観点からは、縦一軸ゾーン延伸法が好適に用いられる。
【００４３】
上記延伸手段は、好ましくは予熱工程、延伸工程及び冷却工程の３工程からなるものである。各工程における予熱温度、延伸温度及び冷却温度は、各工程ゾーン内での熱可塑性樹脂フィルムの温度を示すものである。
これらの温度は、赤外線放射温度計、接触式フィルム状熱電対等の温度計によって実測される。但し、熱可塑性樹脂フィルムの温度が上記ゾーン内の雰囲気温度と略同一となっていることが確認されている既知ライン速度で操業中である場合は、上記ゾーン内の雰囲気温度の測定によって代用できる。
【００４４】
予熱工程は、延伸工程への円滑な温度移行によって急激な熱可塑性樹脂フィルムの熱膨張を抑制するために設けられている。
熱可塑性樹脂フィルムは、厚さムラが存するものであり、厚さムラによって熱可塑性樹脂フィルムに温度ムラが生じるものである。この場合、工程間での温度変化が急であると、温度差と熱膨張差による延伸ムラが生じてしまい、得られる位相差フィルムの位相差ムラを大きなものとしてしまうおそれがある。
そのために予熱温度は、好ましくは（延伸温度−１００℃）から（延伸温度−１０℃）の範囲の温度、より好ましくは（延伸温度−６０℃）から（延伸温度−１５℃）の範囲の温度である。
【００４５】
延伸工程のみで熱可塑性樹脂フィルムの延伸が行われるためには、予熱温度と延伸温度には上記のように一定の温度差が存在することが求められる。
この温度差によって上記両ゾーンにおける加熱された熱可塑性樹脂フィルムに強度差が生じ、予熱工程ゾーンで熱可塑性樹脂フィルムが延伸されないようになされている。
上記熱可塑性樹脂フィルムの強度差は、略１００ＭＰａ以上である。
【００４６】
上記延伸温度は、好ましくは熱可塑性樹脂の｛ガラス転移温度（Ｔｇ）＋１０℃｝から（Ｔｇ＋３５℃）の範囲の温度、より好ましくは（Ｔｇ＋１４℃）から（Ｔｇ＋２５℃）の範囲の温度である。
延伸温度が（Ｔｇ＋１０℃）未満であると、熱可塑性樹脂フィルムが十分な柔軟性を有さないため、延伸時に破断することがあり、延伸温度が（Ｔｇ＋３５℃）を超えると、変形に伴う延伸応力の増加が小さくなり、一旦伸ばされ始めた部分だけが優先的に延伸され、延伸ムラが生じ易くなり、いずれも所望の位相差が発現し難くなる。
【００４７】
冷却工程は、延伸された熱可塑性樹脂フィルムの冷却固化と、急激な熱収縮を抑制するために設けられている。即ち、加熱において延伸工程の前に予熱工程ゾーンを設けると同様に、延伸処理の完了前に冷却工程ゾーンを設けるものであって、この目的から、冷却温度の上限は、好ましくは（延伸温度−１０℃）、より好ましくは（Ｔｇ−１０℃）であり、急激な熱収縮を抑制するためには、下限は、好ましくは（Ｔｇ−９０℃）である。
【００４８】
本発明の位相差フィルムの製造方法は、叙上のように、熱可塑性樹脂組成物中の可塑剤量毎に定まる前記式（１）の温度関数によって、溶融押出機内で、可塑剤の分解を実質的になくすることができる溶融押出の制御システムの実施が可能となるものであるので、溶融押出時に可塑剤の分解等による揮発性成分の発生を実質的に抑制し得るものとなり、溶融押出されたフィルム状熱可塑性樹脂組成物表面に発泡跡やその他ダイラインやギヤマーク等の痕跡を残し、表面状態を悪化させることがなく、液晶表示装置用等の光学機器用途には不適当なフィルムしか製造し得ないとされていた溶融押出法によって、生産性高く、レターデーション値が均一な位相差フィルムを製造し得るものである。
【００５２】
【発明の実施の形態】
以下、本発明の実施例を説明する。
図１は、本発明の位相差フィルムの製造方法に用いられる溶融押出機の一例の要部を示す説明図であり、図面右方の樹脂供給口１１から供給された熱可塑性樹脂ペレットは、バレル１〜６部分において加熱混練され、バレル７部分に到って、プランジャーポンプ１２によって可塑剤が圧入され、バレル７〜８において溶融状態にある熱可塑性樹脂と混合され、図面左端のアダプター１６を経て金型に圧送される。
【００５３】
バレル１〜８、ダイヘッド１３、ギヤポンプ１４、ネック１５、Ｌ型アダプター１６、ダイ入口１７及び金型２と溶融押出機１及び金型２を１４区画し、各々の名称を付した部分は、独立した加熱部分であり、各々、温度制御装置の一部をなす温度検出装置、加熱及び冷却装置が付設され、各加熱部分毎に前記式（１）を満足する温度Ｔ（℃）〔ｓ（分）及びＷ（重量部）は押出量及び配合比によって定まる設定値〕に制御されている。
【００５４】
図２は、本発明の位相差フィルムの製造方法に用いられる溶融押出機の他の例の要部を示す説明図であり、図面下方の溶融押出機１０の樹脂供給口１１０から供給された熱可塑性樹脂ペレットは、加熱部分毎の区画の記載を省略しているが、バレル１〜５部分において加熱混練され、図面上方の押出機１のバレル５部分に異物除去用のスクリーンを介して溶融熱可塑性樹脂を圧入される。これ以降の工程は、図１のバレル５部分以降の工程と同様である。
【００５５】
図３は、本発明の位相差フィルムの製造方法に用いられる溶融押出機の他の例の要部を示す説明図であり、溶融押出機（加熱区分バレル１〜１０）の右上方に熱可塑性樹脂ペレット洗浄装置が付設され、該洗浄装置で水洗浄された熱可塑性樹脂ペレットは、脱水、乾燥され、供給口１１から、溶融押出機のバレル１に供給される。以降の工程は、図１のバレル１部分以降の工程と同様である。
尚、供給口５０より供給された熱可塑性樹脂ペレットの除粉は、水洗シャワー５１、５１、・・・を多数列に設けた除粉ゾーン５２、粉切りゾーン５３、水切りゾーン５４、排水ゾーン５５を備えた水洗装置５と脱水ゾーン６１と排水ゾーン６２、その他を備えた脱水装置６とからなる除粉装置を用いて実施例１で用いたポリサルホン樹脂ペレットに付着する同樹脂粉及び夾雑する異物を水洗、篩分けして除去した。
【００５６】
図４は、図１の左端のアダプター以降のＴダイ溶融押出機の要部を示す説明図であり、金型出口２１から押出された熱可塑性樹脂フィルムは、含有する可塑剤を揮発させながら冷却ロール３１〜３３で冷却固定され、ピンチロール３４を経て次工程へ移送される。
図５は、延伸手段であり、図４の右端のピンチロール４１が左端に描かれており、熱可塑性樹脂フィルムの製造装置と延伸手段４が接続されることを示している。
延伸手段は、予熱ゾーン４２、延伸ゾーン４３及び冷却ゾーン４４に区画され、連通孔４５、４７を除いて断熱壁４６、４８で遮蔽された３ゾーンからなり、予熱工程、延伸工程及び冷却工程の３工程が設けられている。
熱可塑性樹脂フィルムは、予熱ゾーンにおいて可及的緩やかな温度勾配で昇温されるように（延伸温度−１００℃）〜（延伸温度−１０℃）の温度範囲に予熱される。予熱熱源は、熱風であり、熱可塑性樹脂フィルムの全幅にわたって複数本のノズル４９、４９、・・・から、熱可塑性樹脂フィルム面に直角に吹き付けられる。
【００５７】
次いで、延伸ゾーンにおいて（Ｔｇ＋１０℃）〜（Ｔｇ＋３５℃）の温度範囲の延伸温度に加熱され、延伸される。加熱熱源は、熱風であり、前記同様に複数本のノズル４９、４９、・・・から、熱可塑性樹脂フィルム面に直角に吹き付けられる。
又、熱可塑性樹脂フィルムの延伸は、左右端の二対のピンチロール４１及び４１１の速度比を設けることによって行われる。
【００５８】
延伸された熱可塑性樹脂フィルムは、冷却ゾーンにおいて（Ｔｇ−９０℃）〜（Ｔｇ−１０℃）の温度範囲に徐冷される。冷媒は、加熱空気であり、前記同様に複数本のノズル４９、４９、・・・から、熱可塑性樹脂フィルム面に直角に吹き付けられる。
【００５９】
（実施例１）
ポリサルホン樹脂（帝人アモコエンジニアリングプラスチック社製、商品名「Ｐ−３５００」、ペレット形状）を、カワタ社製、除湿乾燥機を用いて１４０℃で４時間乾燥し、重量式フィーダー（ＫＵＭＡエンジ社製）を用いて二軸同方向押出機（日本製鋼所社製、商品名「ＴＥＸ４４」、Ｌ／Ｄ＝３５、バレル加熱部分１〜８）に供給し、加熱捏和して溶融し、バレル７部分に開口するプランジャーポンプ（日本精密社製、商品名「ＮＰ−ＦＸ−２０」）を用いてフタル酸ジエチル（大八化学工業社製、沸点２９６℃）を圧入して両者を均一に混合熱可塑化した。ポリサルホン樹脂とフタル酸ジエチルの配合比は、１００重量部：５重量部とした。
押出機と金型との接続に際して、押出機のバレル８とＬ型アダプターとの間に、ダイヘッド及びネックを介してギヤポンプ（ノルマグ社製、１０．３ｃｃ／ｒｅｖ）を吐出量安定のためにを設けた。
又、上記加熱部分の通過時間（ｓ分）及び温度（Ｔ℃）は各々表１に記載した通りである。
【００６０】
金型はＥＤＩ社製、コートハンガータイプ（面長５００ｍｍ）を用い、表１に記載する金型出口樹脂温２８５℃、押出量６ｋｇ／時で、厚さ７０μｍのポリサルホン樹脂未延伸原反を作製した。
尚、冷却ロールは、いずれも径３００ｍｍφの金属ロールであり、第１ロールの表面温度は１５０℃、第２ロールの表面温度は１１０℃、第３ロールの表面温度は９０℃に各々温度制御された。
【００６１】
金型出口から押出されるフィルム状ポリサルホン樹脂組成物及び冷却ロール表面を移送されるポリサルホン樹脂フィルムの表面状態を目視にて観察し、表面が平滑で、発泡等による凹凸等の表面欠陥が見当たらないものであったので、○（良好）と評価し、表１に記載した。尚、表面欠陥が１点でもあるものは×（不良）と評価することにしている。
【００６２】
（実施例２）
実施例１の押出機に替えて、単軸押出機（ＧＭエンジニアリング社製、商品名「ＧＭ５０−２８」、Ｌ／Ｄ＝３５、バレル１〜８）を用いたこと以外、実施例１と同様にしてポリサルホン樹脂未延伸原反を作製した。
金型出口から押出されるフィルム状ポリサルホン樹脂組成物及び冷却ロール表面を移送されるポリサルホン樹脂フィルムの表面状態は、実施例１と同様にして評価し、○であった。
【００６３】
（実施例３）
実施例１の可塑剤の添加量を、３重量部に変更し、バレル７以降の加熱部分の温度を表１に示すように変更したこと以外、実施例１と同様にしてポリサルホン樹脂未延伸原反を作製した。
金型出口から押出されるフィルム状ポリサルホン樹脂組成物及び冷却ロール表面を移送されるポリサルホン樹脂フィルムの表面状態は、実施例１と同様にして評価し、○であった。
【００６４】
（比較例１）
加熱部分の温度を表１に示すように変更したこと以外、実施例１と同様にしてポリサルホン樹脂未延伸原反を作製した。尚、上記加熱部分の温度は、前記式（１）を満足するものではない。
金型出口から押出されるフィルム状ポリサルホン樹脂組成物及び冷却ロール表面を移送されるポリサルホン樹脂フィルムの表面状態は、実施例１と同様にして評価し、×であった。
【００６５】
（比較例２）
加熱部分の温度を表１に示すように変更したこと以外、実施例２と同様にしてポリサルホン樹脂未延伸原反を作製した。尚、上記加熱部分の温度は、前記式（１）を満足するものではない。
金型出口から押出されるフィルム状ポリサルホン樹脂組成物及び冷却ロール表面を移送されるポリサルホン樹脂フィルムの表面状態は、実施例１と同様にして評価し、×であった。
【００６６】
（比較例３）
ネック部の容積を増加させて、表１に示すように通過時間（ｓ）を変更したこと以外、実施例１と同様にしてポリサルホン樹脂未延伸原反を作製した。尚、上記加熱部分の温度は、前記式（１）を満足するものではない。
金型出口から押出されるフィルム状ポリサルホン樹脂組成物及び冷却ロール表面を移送されるポリサルホン樹脂フィルムの表面状態は、実施例１と同様にして評価し、×であった。
【００６７】
【表１】

【００６８】
（実施例４）
実施例１の可塑剤の添加量を、３重量部に変更し、バレル７以降の加熱部分の温度を表２に示すように設定したこと以外、実施例１と同様にしてポリサルホン樹脂未延伸原反をロール状に巻重して作製した。
得られたポリサルホン樹脂未延伸原反のＴｇ、平均厚さ及び厚さのバラツキ（％）は表２に示す通りであった。
【００６９】
次いで、ポリサルホン樹脂未延伸原反を図３に示される予熱ゾーン（長さ２ｍ）、延伸ゾーン（長さ２ｍ）及び冷却ゾーン（長さ１ｍ）の３ゾーンを備えた延伸装置を用いて、表３に示す予熱温度、延伸温度及び冷却温度、ライン速度１ｍ／分及び延伸倍率で縦一軸延伸し、位相差フィルムを作製した。
得られた位相差フィルム性能を評価するため、以下に示す方法で、平均位相差、位相差のバラツキの測定及びこれらのデータに基づく良否の判定を行った。
【００７０】
（試料及び評価）
得られた延伸フィルムの中央部から幅２００ｍｍ×長さ５００ｍｍの位相差フィルム試料を切り出した。得られた位相差フィルム試料の５９０ｎｍにおけるレターデーション値を、幅方向に５ｍｍ間隔、長さ方向に５０ｍｍ間隔で測定し（測定器：大塚電子社製、商品名「ＲＥＳＴ−２０００」、バレイ値測定）、全測定値の平均値及びバラツキの最大値を算出し、バラツキの最大値が５ｎｍ以内のものに○（良好）、５ｎｍを超すものに×（不良）の判定を行った。評価結果は表３に示した。
【００７１】
（実施例５）
加熱部分の温度を表２に示すように設定したこと以外、実施例１と同様にしてポリサルホン樹脂未延伸原反を作製し、表３に示す予熱温度、延伸温度及び冷却温度で実施例４と同様に位相差フィルムを作製した。位相差フィルムの評価は、実施例４と同様に実施され、評価結果は表３に示した。
【００７２】
（比較例４〜６）
実施例４のポリサルホン樹脂未延伸原反を用いて、表３に示す予熱温度、延伸温度及び冷却温度で実施例４と同様に位相差フィルムを作製し、同様に評価を実施した。評価結果は表３に示した。
【００７３】
【表２】

【００７４】
【表３】

【００７５】
（実施例６）
〔ポリサルホン樹脂の除粉−１〕
ダルトン社製、振動篩（商品名「４０３」）を用いて実施例１で用いたポリサルホン樹脂ペレットに付着する同樹脂粉及び夾雑する異物を篩分けして除去した後、実施例１で用いたコートハンガータイプＴダイを備えた押出機にチャージし、実施例１と同様に可塑剤フタル酸ジエチルを混練してポリサルホン樹脂未延伸原反を作製し、実施例１と同様にして位相差フィルムを作製した。
尚、押出機のポリサルホン樹脂ペレットチャージ部（スクリュー駆動装置側バレル末端部及び周辺空隙部）に、太陽東洋酸素社製、小型窒素ガス発生装置（商品名「Ｐ３．０」）を用いて、ガス圧４ｋｇ／ｃｍ^２ 、流量２リットル／分の窒素ガスを送風し、同部に存する空気をパージしてポリサルホン樹脂未延伸原反を作製した。
【００７６】
（実施例７）
〔ポリサルホン樹脂の除粉−２〕
図５に示す水洗シャワーを多数列に設けた除粉ゾーン、粉切りゾーン、水切りゾーン、排水ゾーンを備えた水洗装置と脱水ゾーンと排水ゾーンを備えた脱水装置とからなる除粉装置を用いて実施例１で用いたポリサルホン樹脂ペレットに付着する同樹脂粉及び夾雑する異物を水洗、篩分けして除去した後、実施例１で用いたコートハンガータイプＴダイを備えた押出機にチャージし、実施例１と同様に可塑剤フタル酸ジエチルを混練してポリサルホン樹脂未延伸原反を作製し、実施例１と同様にして位相差フィルムを作製した。
尚、押出機のポリサルホン樹脂ペレットチャージ部の窒素ガスパージも実施例６と同様に実施した。
【００７７】
（比較例７）
ポリサルホン樹脂の除粉を行わなかったこと以外、実施例６と同様にポリサルホン樹脂未延伸原反を作製し、実施例１と同様にして位相差フィルムを作製した。
【００７８】
実施例６、７及び比較例７の厚さ７０μｍ、幅５００ｍｍのポリサルホン樹脂未延伸原反の連続する５時間製造分について、５００ｍｍ×２ｍのサンプル３点をランダムサンプリング法にてサンプリングし、サンプルを顕微鏡観察し、５０μｍφ以上の異物の混入個数を計数した。計数結果は表４に示す。
【００７９】
【表４】

【００８０】
【発明の効果】
本発明の位相差フィルムの製造方法は、叙上のように構成されているので、熱可塑性樹脂組成物中の可塑剤量毎に定まる前記式（１）の温度関数によって、溶融押出機内で、可塑剤の分解を実質的になくすることができる溶融押出の制御システムの実施が可能となり、液晶表示装置用等の光学機器用途には不適当なフィルムしか製造し得ないとされていた溶融押出法によって、生産性高く、レターデーション値が均一な位相差フィルムを製造し得るものである。
【００８１】
又、金型出口における可塑化熱可塑性樹脂組成物温度を、該熱可塑性樹脂組成物中の可塑剤の（沸点−１００℃）から可塑剤の（沸点＋２０℃）の範囲にあるように溶融押出法により成膜した後、予熱温度が（延伸温度−１００℃）〜（延伸温度−１０℃）、延伸温度が熱可塑性樹脂の（Ｔｇ＋１０℃）〜（Ｔｇ＋３５℃）、冷却温度が熱可塑性樹脂の（Ｔｇ−９０℃）〜（Ｔｇ−１０℃）の３工程からなる延伸手段にて延伸するものであるので、延伸原反厚さムラで生じる温度差による延伸ムラや急激なフィルムの膨張と収縮を抑制し、これらの外乱を排除して延伸でき、延伸ムラのない、皺のないレターデーション値が均一な位相差フィルムを製造し得るものである。
【００８２】
熱可塑性樹脂ペレットに付着する粉粒体を除粉し、これに夾雑する外部混入異物を除去し、低減し得るものであり、特に、水洗手段によれば、熱可塑性樹脂ペレットに付着する粉粒体も水流により確実に除去されると共に、熱可塑性樹脂ペレット及びこれに付着する粉粒体の静電気をも中和除去し得るものであるので、更に洗浄の効果を高からしめるものであるので、位相差フィルムの品質の向上と共に、製品の歩留りを向上させるものである。
【００８３】
又、熱可塑性樹脂がポリサルホン系樹脂であり、可塑剤がフタル酸エステルである樹脂組成物が使用されるものである場合には、得られる位相差フィルムの光の波長分散性が液晶表示装置に用いられる液晶に近い特性を有するものであって、各波長で異なる楕円偏光を良好に補償することができ、液晶表示装置のコントラストがより向上する。
【図面の簡単な説明】
【図１】本発明の位相差フィルムの製造方法に用いられる溶融押出機の一例の要部を示す説明図である。
【図２】本発明の位相差フィルムの製造方法に用いられる溶融押出機の他の例の要部を示す説明図である。
【図３】本発明の位相差フィルムの製造方法に用いられる溶融押出機の要部を示す説明図であり、押出機の右上方に熱可塑性樹脂ペレット洗浄装置が付設されている。
【図４】図１の左端のアダプター以降のＴダイ溶融押出機の要部を示す説明図である。
【図５】図４の右端のピンチロールに連なる延伸手段の要部を示す説明図である。
【符合の説明】
１、１０：溶融押出機
１１、１１０、５０：樹脂供給口
１２：プランジャーポンプ
１３：ダイヘッド
１４：ギヤポンプ
１５：ネック
１６、１６０：アダプター
１７：ダイ入口
２：金型
２１：金型出口
３１、３２、３３：冷却ロール
３４、４１、４１１：ピンチロール
４：延伸手段
４２：予熱ゾーン
４３：延伸ゾーン
４４：冷却ゾーン
４５、４７：連通孔
４６、４８：断熱壁
４９：熱風ノズル
５：洗浄装置
５１：水洗シャワー
５２：除粉ゾーン
５３：粉切りゾーン
５４：水切りゾーン
５５、６２：排水ゾーン
６：脱水装置
６１：脱水ゾーン[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a retardation film formed using a thermoplastic resin film, and more particularly, to a method for manufacturing a retardation film suitable for compensating for a retardation in a liquid crystal display device.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, TN (twisted nematic) liquid crystal display devices, STN (super twisted nematic) liquid crystal display devices, and the like have been widely used in various OA devices and display devices.
[0003]
The liquid crystal display device has a fatal problem that a display image is colored blue or yellow due to a phase difference generated by the liquid crystal, and it is difficult to perform perfect black and white display.
Therefore, it has been attempted to attach a retardation film made of a thermoplastic resin film to the surface of the liquid crystal display cell, and to compensate for the retardation generated in the liquid crystal by using the birefringence of the stretched thermoplastic resin film. ing.
[0004]
As a retardation film formed by stretching the above-described thermoplastic resin film, those made of various materials have been conventionally proposed. For example, those using a cellulose-based resin (JP-A-63-167363), those using a vinyl chloride-based resin (JP-B-45-34477, JP-A-56-125702), polycarbonate-based resins (JP-B-41-12190, JP-A-56-130703), acrylonitrile-based resin (JP-A-56-130702), and styrene-based resin ( JP-A-56-125703), and those using olefin-based resins (JP-A-60-24502).
Conventionally, a retardation film has been formed by uniaxially stretching the above-described thermoplastic resin film. In this case, as a stretching method, a method of stretching uniaxially in a longitudinal direction (JP-A-2-191904), a method of stretching uniaxially in a horizontal direction (JP-A-2-42406), and the like are known.
[0005]
The retardation compensation performance of the retardation film is represented by a so-called retardation value. The retardation value is represented by Δn × d, where Δn is the anisotropy (that is, birefringence) of the refractive index of the resin film, and d is the thickness of the resin film.
[0006]
On the other hand, in a liquid crystal display device, it is strongly required that color unevenness and contrast unevenness hardly occur over the entire display portion. In order to provide a liquid crystal display device capable of performing such uniform display, it is required that the retardation film has a uniform retardation value over the entire surface.
[0007]
Therefore, as a method of manufacturing a retardation film having a uniform retardation value, a method of stretching a film formed by a casting method has been proposed (Japanese Patent Application Laid-Open No. 8-122526).
However, in the casting film forming method, a thermoplastic resin is dissolved in an organic solvent and cast, and the film is formed by volatilizing the organic solvent in the formed coating film. In addition, the production process is complicated and diversified, and safety and hygiene issues are added. Therefore, it is difficult to say that the production method is highly productive.
[0008]
In view of the facts described above, the present inventors have conventionally found that a film having a large phase difference unevenness due to a thickness unevenness or a die line or a gear mark generated at the time of molding makes the film unsuitable for use in an optical device such as a liquid crystal display device. There has been proposed a method capable of producing a retardation film having a high productivity and a uniform retardation value by a melt extrusion method which has been considered to be capable of producing only a retardation film (JP-A-9-155951).
[0009]
In a method for producing a retardation film by a melt extrusion method, a slight amount of a plasticizer is blended with a thermoplastic resin in order to make the retardation value uniform.
The thermoplastic resin composition containing a small amount of these plasticizers is heated and kneaded in an extruder, transferred to a mold in a sufficiently plasticized state, shaped into a film, and extruded. However, since the film-like thermoplastic resin composition extruded from the mold outlet is fixed by cooling while volatilizing the contained plasticizer, the film thickness varies depending on the thickness of the obtained thermoplastic resin film. The thick part has a high plasticizer concentration, and the thin part has a low plasticizer concentration.
[0010]
The difference in plasticizer concentration caused by the variation in the thickness of the film is caused by the fact that the rate of volatilization of the plasticizer from the surface of the thermoplastic resin film extruded from the mold outlet is constant at the mold outlet. Conceivable.
Therefore, the difference in the refractive index of the thick portion of the film becomes small, and the difference of the refractive index of the thin portion becomes large, and the retardation value represented by Δn × d is in-plane regardless of the variation in the film thickness. Can be made uniform.
By the way, the difference in the refractive index of the thermoplastic resin film is smaller as the plasticizer concentration is higher, and becomes larger as the plasticizer concentration is lower.This is due to the plasticizing effect of the plasticizer. This is because the higher the molecular weight, the weaker the molecular orientation of the thermoplastic resin, and the stronger the molecular orientation as the plasticizer concentration decreases.
[0011]
However, in order to uniformly thermoplasticize a high-molecular-weight thermoplastic resin and a resin composition containing a low-molecular-weight plasticizer whose molecular weight is significantly different from that of the thermoplastic resin, to obtain a thermoplastic resin film as homogeneous as possible, An appropriate means for kneading the thermoplastic resin and the plasticizer without causing decomposition and non-uniform gelation while transporting the same in an extruder usually used for extrusion molding of a thermoplastic resin film is required.
[0012]
For example, when the thermoplastic resin is a polysulfone-based resin and the plasticizer is a phthalate-based plasticizer, while the molding temperature of the polysulfone-based resin is 300 to 350 ° C., the boiling point of the added diethyl phthalate is Is 295 ° C., the boiling point of dimethyl phthalate is 282 ° C., and the decomposition of these phthalic diesters starts around 250 ° C.
[0013]
As described above, when the thermoplastic resin composition containing the plasticizer is heated under a high pressure to a temperature equal to or higher than the boiling point of the plasticizer, a part of the plasticizer is decomposed, and the generated low molecular weight component is vaporized. Further, the extruded thermoplastic resin film deteriorates surface properties due to foaming or the like, and increases the variation in retardation value of the retardation film.
[0014]
[Problems to be solved by the invention]
The present inventors, for a method of suppressing foaming during extrusion molding of a thermoplastic resin composition in which a small amount of a plasticizer is compounded, extruding temperature, the relationship between the extrusion temperature, time and the amount of decomposition of the plasticizer has been earnestly studied, In the plasticizing process of the thermoplastic resin composition, there is a critical amount in the amount of decomposition of the plasticizer, for each extrusion molding temperature, a linear relationship between the addition amount of the plasticizer and the residence time in the extruder cylinder. Thus, the present inventors invented an extrusion molding control system capable of substantially eliminating the amount of decomposition of a plasticizer during extrusion molding, and completed the present invention.
[0015]
The present invention has been made in view of the above facts, and has as its object to improve the appearance performance by an extrusion control system capable of substantially eliminating the amount of decomposition of a plasticizer during extrusion. It is an object of the present invention to provide a method for manufacturing a retardation film capable of producing a high-quality retardation film with high productivity without deteriorating or reducing the retardation characteristics itself.
[0016]
[Means for Solving the Problems]
Departure The method for producing a bright retardation film is as follows. A resin composition containing 100 parts by weight of a thermoplastic resin and 0.2 to 10 parts by weight of a plasticizer is formed by a melt extrusion method under the following conditions, and then stretched. It is characterized by doing.
[0017]
1. The temperature of the resin composition passing through each of the plurality of divided heating portions of the melt extruder barrel and the accessory from the supply of the plasticizer to the mold outlet is T _n (° C.), the time to pass through each of the divided heated portions of the barrel, s _n (Minutes), when the number of parts by weight of the plasticizer in the resin composition is W, these T _n , S _n And W have the following relationship.
[0018]
Embedded image

[0019]
2. The temperature of the resin composition at the exit of the mold is equal to or lower than the (boiling point + 20 ° C.) of the plasticizer.
[0023]
In the present invention, the term “film” does not refer to a film in a strict sense defined by a thickness, but refers to all of a thin film, a medium sheet, and a thick plate that are identified by a thickness. Including.
[0024]
The thermoplastic resin used in the present invention is not particularly limited as long as it is a resin material that can be stretched and exhibit a retardation of 100 to 1000 nm required as a retardation film, and examples thereof include a cellulose resin and styrene. Resins, vinyl chloride resins, polycarbonate resins, acrylonitrile resins, polyolefin resins, polysulfone resins, polyethersulfone resins, polyarylate resins, polymethyl methacrylate resins are preferred. Is a characteristic close to that of liquid crystal, and the elliptically polarized light different at each wavelength can be favorably compensated, so that the contrast of the liquid crystal display device is further improved.
[0025]
The plasticizer is not particularly limited as long as it has good compatibility with the thermoplastic resin to be used.For example, adipic acid ester, azelaic acid ester, benzoic acid ester, isobutyric acid ester, thiobutyric acid ester, Brassyl ester, citrate ester, glycolate ester, itaconic ester, oleate ester, phosphate ester, phosphinate ester, phthalate ester, phthalate isomer ester, tetrahydrophthalate ester, hexahydrophthalate ester, pyro Examples include melitic acid ester, ricinoleic acid ester, sebacic acid ester, succinic acid ester, sulfonamidotriacetylene, trimellitic acid ester and the like. For polysulfone resins, phthalate plasticizers are preferably used from the viewpoint of excellent transparency and quality stability of the retardation film.
[0026]
Examples of the phthalate-based plasticizer include, but are not particularly limited to, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate, ethylhexyl phthalate, diisononyl phthalate, diisodecyl phthalate, and phthalic acid. Butylbenzyl and the like.
[0027]
The amount of the plasticizer added to the thermoplastic resin is 0.2 to 10 parts by weight based on 100 parts by weight of the thermoplastic resin.
If the amount of the plasticizer is less than 0.2 parts by weight, the Tg of the thermoplastic resin composition may not be sufficiently reduced, and the retardation characteristics itself may be reduced. If the amount exceeds 10 parts by weight, the film may be softened. However, the desired retardation characteristics are hardly developed, and the heat resistance may be reduced.
[0028]
The timing of the addition of the plasticizer to the thermoplastic resin is not particularly limited, for example, high-speed mixer, ribbon blender, may be performed before the introduction to the extruder using a mixer such as a tumbler. However, as illustrated in FIG. 1 and FIG. 2, a thermoplastic resin is first charged into a melt extruder, and an injection device such as a plunger pump is used while heating and kneading and being transferred through a barrel. A plasticizer may be press-fitted and kneaded and mixed in a barrel.
[0029]
When the thermoplastic resin and the plasticizer are fed from another inlet of the melt extruder, the added amount of the plasticizer is based on 100 parts by weight of the thermoplastic resin fed from another inlet of the melt extruder. , Is the weight part of the plasticizer fed from another inlet at the same time, and represents the average weight part.
[0030]
As shown in FIG. 1, the melt extruder barrel and the plurality of divided heating parts of the auxiliary equipment include the melt extruder barrels 1 to 8, the die head 13, the gear pump unit 14, the neck 15, the L-shaped adapter 16 and the like. , Die entrance 17, a mold and a heating portion divided into a static mixer, a screen changer, etc., which are not shown, but are used as necessary, and a thermoplastic resin and a plasticizer which are mixed in advance. When the thermoplastic resin composition consisting of the resin extruder is supplied from the resin supply unit, the melt extruder barrel from the supply of the plasticizer to the mold outlet and the plurality of divided heating parts of the attached device are the same as the melt extruder When the plasticizer is press-fitted into the barrel 7 illustrated in FIG. It is intended to refer to heating portion exemplified barrel 7 and later.
[0031]
Each of the heating portions is provided with a temperature detection device and a heating and cooling device which form part of a temperature control device, and a temperature T (° C.) [s (minute) satisfying the above-described expression (1) for each heating portion. And W (parts by weight) are controlled at a set value determined by the extrusion amount and the blending.
[0032]
The temperature detection device is not particularly limited, for example, a thermocouple, a thermistor, etc., as the heating and cooling device, for example, a heating device such as a band heater, an aluminum casting heater, an infrared heater, Examples of the cooling device include an air-cooled cooler and a water-cooled cooler. Examples of the temperature control device include “SPCC” manufactured by Sekisui Chemical Co., Ltd.
[0033]
It is preferable to use a value measured by inserting a temperature detecting device such as a thermocouple into the resin flow path for the resin temperature in the heating section, but the temperature of the heating section is controlled when the heating section is in a steady state. The temperature indicated by the instrument may be substituted.
The resin passage time in the above-mentioned heated portion indicates an average resin passage time. The resin passing time is also preferably measured, for example, for each heated portion using a color batch, but the value calculated from the flow volume of each heated portion and the resin extrusion amount is substantially the same value. , May be used.
[0034]
In the method for producing a retardation film of the present invention, an extruder equipped as described above is used.
The mold used is not particularly limited, and may be, for example, a T-die or a circular die, but the T-die is preferably used from the viewpoint of facilitating control of the next stretching step. Used.
[0035]
The injection of the thermoplastic resin and the plasticizer into the melt extruder is performed through a mesh or a filter for the purpose of preventing foreign matter from being mixed, or a metallic or conductive impurity is removed using a magnetic adsorption device such as an electromagnet. Done.
In particular, in the present invention, when the thermoplastic resin is used in the form of pellets, after removing the granular thermoplastic resin or foreign substances adhered to the thermoplastic resin pellets, the thermoplastic resin is charged into an extruder. Is preferred. When the powdery or granular thermoplastic resin or contaminants are thus removed, it is not always necessary to attach the mesh or the filter.
[0036]
Means for removing the particulate thermoplastic resin or impurities present coexisting with or attached to the thermoplastic resin pellets are not particularly limited, for example, a method of washing and drying the thermoplastic resin pellets with water. Sieving method, a method of applying a wind to scatter the granular thermoplastic resin or foreign matter, and a method of applying an ionic wind or the like to separate the granular material and the thermoplastic resin pellet. These methods may be used alone, but two or more methods may be combined, or the same method may be used in two or more stages. These powder and granular material removing devices may be either in-line or off-line to the extruder.
[0037]
In particular, a method of washing and drying the thermoplastic resin pellets with water is preferable. Since the powdery particles coexisting with or contaminating the thermoplastic resin pellets are attached by static electricity, they can be removed and removed very easily by washing with water, thereby increasing the efficiency. This is one of the methods for cost reduction.
When using the above-mentioned washing and drying methods, care must be taken to prevent contamination from the washing water, and use of ultrapure water is recommended if safety is required.
The amount of water used may be such that the washing water comes into contact with the entire thermoplastic resin pellets and flows down.The washing method is not particularly limited, but, for example, after taking measures to remove the thermoplastic resin pellets. Then, a method of exposing to running water, a method of spraying or spraying cleaning water, and the like can be mentioned.
[0038]
After washing with water and before drying, a dehydration step may be inserted. Dehydration means is not particularly limited, for example, may be a dehydration method using a mechanical force such as a stretch separator or a rocking sieve, the natural air dehydration step of gravity only and the dry air flow of the next step A dehydration drying method combining the drying steps used may be used.
[0039]
When using the in-line sieving method, it is preferable to vibrate the thermoplastic resin pellet while moving it on the circumference of the sieve. By sieving in this manner, the removal of the thermoplastic resin pellets can be facilitated, and the sieving efficiency can be improved.
The mesh size of the sieve is not particularly limited as long as the thermoplastic resin pellets do not fall together with the granules, but are preferably not clogged, and can be used for a long time. For this reason, a mesh of about 1/2 of the thermoplastic resin pellet is preferably used.
[0040]
The temperature of the resin composition at the exit of the mold is not higher than (boiling point + 20 ° C.) of the plasticizer, preferably in the range of (boiling point −20 ° C.) of the plasticizer to (boiling point + 20 ° C.) of the plasticizer, more preferably. Is the temperature in the range from the plasticizer (boiling point −50 ° C.) to the plasticizer (boiling point + 20 ° C.).
If the temperature of the resin composition exceeds the temperature of the plasticizer (boiling point + 20 ° C.), the boiling of the plasticizer increases the foaming of the thermoplastic resin film, deteriorating the surface properties and reducing the order of the obtained retardation film. If the phase difference characteristic is lowered and the temperature is lower than (boiling point −100 ° C.), volatilization of the plasticizer is not sufficiently performed, and a difference in plasticizer concentration between a thick portion and a thin portion is not formed. When the stretching degree of the thick portion having a high concentration is larger than the stretching degree of the thin portion having a low plasticizer concentration, it is difficult to obtain a phase difference uniforming effect of making the retardation value represented by Δnxd uniform.
[0041]
The volatilization of the plasticizer from the film-like thermoplastic resin composition extruded from the mold outlet is performed immediately after the extrusion, that is, immediately before the cooling step of the thermoplastic resin film, the cooling step, the curing step (inline or offline), It may be performed in at least one of the stretching preheating step and the stretching step. In particular, it is preferably used because it is most easily volatilized immediately after extrusion and the phase difference uniforming effect is most effectively performed.
[0042]
When the thermoplastic resin film thus formed is stretched, the retardation value after stretching becomes almost uniform. The stretching method is not particularly limited, and may be any of uniaxial stretching and biaxial stretching. More specifically, longitudinal uniaxial stretching by a roll, horizontal uniaxial stretching by a tenter, biaxial stretching by combining these, and A conventionally known suitable stretching method, such as a method of gripping the peripheral portion of a sheet of thermoplastic resin film and stretching the film uniaxially or biaxially, may be mentioned, but the view of the liquid crystal display device equipped with the obtained retardation film can be mentioned. From the viewpoint of enlarging the corner, the longitudinal uniaxial zone stretching method is suitably used.
[0043]
The stretching means preferably comprises three steps of a preheating step, a stretching step and a cooling step. The preheating temperature, the stretching temperature, and the cooling temperature in each process indicate the temperature of the thermoplastic resin film in each process zone.
These temperatures are measured by a thermometer such as an infrared radiation thermometer or a contact type film thermocouple. However, when operating at a known line speed at which the temperature of the thermoplastic resin film has been confirmed to be substantially the same as the ambient temperature in the zone, measurement of the ambient temperature in the zone can be substituted. .
[0044]
The preheating step is provided to suppress a rapid thermal expansion of the thermoplastic resin film due to a smooth temperature transition to the stretching step.
The thermoplastic resin film has uneven thickness, and the uneven thickness causes uneven temperature in the thermoplastic resin film. In this case, if the temperature change between the steps is abrupt, stretching unevenness occurs due to the temperature difference and the thermal expansion difference, and the phase difference unevenness of the obtained retardation film may be increased.
For this purpose, the preheating temperature is preferably a temperature in the range of (stretching temperature -100 ° C) to (stretching temperature -10 ° C), more preferably a temperature in the range of (stretching temperature -60 ° C) to (stretching temperature -15 ° C). It is.
[0045]
In order for the thermoplastic resin film to be stretched only in the stretching step, it is required that the preheating temperature and the stretching temperature have a certain temperature difference as described above.
The difference in temperature causes a difference in strength between the heated thermoplastic resin films in the two zones, so that the thermoplastic resin film is not stretched in the preheating step zone.
The difference in strength between the thermoplastic resin films is about 100 MPa or more.
[0046]
The stretching temperature is preferably in the range of {glass transition temperature (Tg) + 10 ° C.} to (Tg + 35 ° C.) of the thermoplastic resin, and more preferably in the range of (Tg + 14 ° C.) to (Tg + 25 ° C.).
If the stretching temperature is lower than (Tg + 10 ° C.), the thermoplastic resin film does not have sufficient flexibility, and may be broken at the time of stretching. If the stretching temperature exceeds (Tg + 35 ° C.), the stretching accompanying the deformation may occur. The increase in stress is reduced, and only the portion that has once started to be stretched is preferentially stretched, and stretching unevenness is likely to occur.
[0047]
The cooling step is provided in order to cool and solidify the stretched thermoplastic resin film and to suppress rapid thermal contraction. That is, similarly to providing a preheating step zone before the stretching step in heating, a cooling step zone is provided before the completion of the stretching treatment, and for this purpose, the upper limit of the cooling temperature is: Preferably (Stretching temperature -10 ° C), more preferably (Tg-10 ° C), and the lower limit is preferably (Tg-90 ° C) in order to suppress rapid thermal contraction.
[0048]
Departure As described above, the method for producing a bright retardation film substantially decomposes a plasticizer in a melt extruder according to the temperature function of the above-mentioned formula (1) determined for each amount of the plasticizer in the thermoplastic resin composition. Since it is possible to implement a control system of melt extrusion that can be eliminated, it is possible to substantially suppress generation of volatile components due to decomposition of a plasticizer at the time of melt extrusion. It leaves foam marks and other marks such as die lines and gear marks on the surface of the film-like thermoplastic resin composition, and does not deteriorate the surface condition, and manufactures only films that are unsuitable for optical equipment such as liquid crystal display devices. It is possible to produce a retardation film having a high productivity and a uniform retardation value by a melt extrusion method which has been considered unobtainable.
[0052]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, examples of the present invention will be described.
FIG. 1 is an explanatory view showing a main part of an example of a melt extruder used in the method for producing a retardation film of the present invention. A thermoplastic resin pellet supplied from a resin supply port 11 on the right side of the drawing is a barrel. Heating and kneading are performed in portions 1 to 6 and a plasticizer is pressed into the barrel 7 by a plunger pump 12 and mixed with a thermoplastic resin in a molten state in barrels 7 to 8. After that, it is pumped to the mold.
[0053]
The barrel 1 to 8, the die head 13, the gear pump 14, the neck 15, the L-shaped adapter 16, the die inlet 17 and the mold 2, the melt extruder 1 and the mold 2 are divided into 14 sections. Each of the heating portions is provided with a temperature detection device and a heating and cooling device which are part of a temperature control device, and a temperature T (° C.) [s (min. ) And W (parts by weight) are controlled to a set value determined by the extrusion amount and the compounding ratio.
[0054]
FIG. 2 is an explanatory diagram showing a main part of another example of the melt extruder used in the method for producing a retardation film of the present invention, in which heat supplied from a resin supply port 110 of the melt extruder 10 below the drawing. Although the plastic resin pellets are not shown in the section for each heating portion, they are heated and kneaded in the barrels 1 to 5 and melted through a screen for removing foreign matter in the barrel 5 of the extruder 1 above the drawing. A plastic resin is press-fitted. Subsequent steps are the same as the steps after the barrel 5 in FIG.
[0055]
FIG. 3 is an explanatory view showing a main part of another example of the melt extruder used in the method for producing a retardation film of the present invention. The melt extruder (heating section barrels 1 to 10) has a thermoplastic resin at the upper right. A resin pellet washing device is provided, and the thermoplastic resin pellets washed with water by the washing device are dehydrated, dried, and supplied from a supply port 11 to a barrel 1 of a melt extruder. Subsequent steps are the same as the steps after barrel 1 in FIG.
In addition, powder removal of the thermoplastic resin pellets supplied from the supply port 50 includes a powder removal zone 52, a powder removal zone 53, a water removal zone 54, and a drainage zone 55 in which a large number of washing showers 51, 51,. Resin powder attached to the polysulfone resin pellets used in Example 1 and a contaminant foreign material using a powder removing device including a water washing device 5 provided with a dewatering zone 61, a drainage zone 62, and a dewatering device 6 provided with others. Was washed with water and sieved to remove.
[0056]
FIG. 4 is an explanatory view showing a main part of the T-die melt extruder after the adapter at the left end of FIG. 1. The thermoplastic resin film extruded from the mold outlet 21 is cooled while volatilizing the contained plasticizer. It is cooled and fixed by the rolls 31 to 33, and is transferred to the next process via the pinch roll 34.
FIG. 5 shows the stretching means, in which the pinch roll 41 on the right end in FIG. 4 is drawn on the left end, and shows that the apparatus for manufacturing a thermoplastic resin film and the stretching means 4 are connected.
The stretching means is divided into a preheating zone 42, a stretching zone 43, and a cooling zone 44, and includes three zones shielded by heat insulating walls 46, 48 except for the communication holes 45, 47, and includes a preheating step, a stretching step, and a cooling step. Three steps are provided.
The thermoplastic resin film is preheated in a temperature range of (stretching temperature -100 ° C) to (stretching temperature -10 ° C) so as to be heated at a temperature gradient as gentle as possible in the preheating zone. The preheating heat source is hot air, and is blown at right angles to the surface of the thermoplastic resin film from a plurality of nozzles 49, 49,... Over the entire width of the thermoplastic resin film.
[0057]
Next, in the stretching zone, the film is heated to a stretching temperature in a temperature range of (Tg + 10 ° C.) to (Tg + 35 ° C.) and stretched. The heating heat source is hot air, and is blown from the plurality of nozzles 49, 49,.
The stretching of the thermoplastic resin film is performed by providing a speed ratio between two pairs of pinch rolls 41 and 411 at the left and right ends.
[0058]
The stretched thermoplastic resin film is gradually cooled in a cooling zone to a temperature range of (Tg-90 ° C) to (Tg-10 ° C). The refrigerant is heated air, and is blown at right angles to the surface of the thermoplastic resin film from the plurality of nozzles 49, 49,.
[0059]
(Example 1)
Polysulfone resin (manufactured by Teijin Amoko Engineering Plastics Co., Ltd., trade name "P-3500", pellet shape) is dried at 140 ° C. for 4 hours using a dehumidifying drier manufactured by Kawata Co., Ltd. And supplied to a twin-screw co-extruder (trade name "TEX44", L / D = 35, barrel heating parts 1 to 8 by Nippon Steel Works), melted by heating and kneading, and barrel 7 parts Using a plunger pump (trade name "NP-FX-20", manufactured by Nippon Seimitsu Co., Ltd.), diethyl phthalate (manufactured by Daihachi Chemical Industry Co., Ltd., boiling point: 296 ° C.) is press-fitted to uniformly mix the two. Plasticized. The mixing ratio of the polysulfone resin and diethyl phthalate was 100 parts by weight: 5 parts by weight.
When connecting the extruder and the mold, a gear pump (10.3 cc / rev, manufactured by Normag) is connected between the barrel 8 of the extruder and the L-shaped adapter via a die head and a neck to stabilize the discharge amount. Provided.
Further, the passing time (s minute) and the temperature (T ° C.) of the heating portion are as shown in Table 1.
[0060]
Using a coat hanger type (surface length 500 mm) manufactured by EDI Co., Ltd., an unstretched polysulfone resin sheet having a thickness of 70 μm was produced at a mold outlet resin temperature of 285 ° C. and an extrusion rate of 6 kg / hour described in Table 1. did.
Each of the cooling rolls is a metal roll having a diameter of 300 mmφ. The surface temperature of the first roll is 150 ° C, the surface temperature of the second roll is 110 ° C, and the surface temperature of the third roll is 90 ° C. Was.
[0061]
The surface condition of the film-like polysulfone resin composition extruded from the mold outlet and the surface of the polysulfone resin film transferred on the cooling roll surface are visually observed, and the surface is smooth and no surface defects such as unevenness due to foaming or the like are found. ○ (good) and described in Table 1. In addition, those having one surface defect are evaluated as x (defective).
[0062]
(Example 2)
Same as Example 1 except that a single-screw extruder (trade name “GM50-28”, manufactured by GM Engineering, L / D = 35, barrels 1 to 8) was used instead of the extruder of Example 1. Thus, an unstretched raw polysulfone resin was prepared.
The surface condition of the film-like polysulfone resin composition extruded from the mold outlet and the surface of the polysulfone resin film transferred on the surface of the cooling roll were evaluated in the same manner as in Example 1, and were evaluated as ○.
[0063]
(Example 3)
Except that the amount of the plasticizer added in Example 1 was changed to 3 parts by weight and the temperature of the heated portion after the barrel 7 was changed as shown in Table 1, the unstretched polysulfone resin was produced in the same manner as in Example 1. Made anti.
The surface condition of the film-like polysulfone resin composition extruded from the mold outlet and the surface of the polysulfone resin film transferred on the surface of the cooling roll were evaluated in the same manner as in Example 1, and were evaluated as ○.
[0064]
(Comparative Example 1)
An unstretched polysulfone resin sheet was produced in the same manner as in Example 1, except that the temperature of the heated portion was changed as shown in Table 1. In addition, the temperature of the above-mentioned heating part does not satisfy the above-mentioned expression (1).
The surface condition of the film-like polysulfone resin composition extruded from the mold outlet and the surface of the polysulfone resin film transferred on the cooling roll surface were evaluated in the same manner as in Example 1, and were evaluated as x.
[0065]
(Comparative Example 2)
An unstretched raw polysulfone resin was prepared in the same manner as in Example 2, except that the temperature of the heated portion was changed as shown in Table 1. In addition, the temperature of the above-mentioned heating part does not satisfy the above-mentioned expression (1).
The surface condition of the film-like polysulfone resin composition extruded from the mold outlet and the surface of the polysulfone resin film transferred on the cooling roll surface were evaluated in the same manner as in Example 1, and were evaluated as x.
[0066]
(Comparative Example 3)
An unstretched polysulfone resin fabric was produced in the same manner as in Example 1, except that the passage time (s) was changed as shown in Table 1 by increasing the volume of the neck portion. In addition, the temperature of the above-mentioned heating part does not satisfy the above-mentioned expression (1).
The surface condition of the film-like polysulfone resin composition extruded from the mold outlet and the surface of the polysulfone resin film transferred on the cooling roll surface were evaluated in the same manner as in Example 1, and were evaluated as x.
[0067]
[Table 1]

[0068]
(Example 4)
Except that the amount of the plasticizer added in Example 1 was changed to 3 parts by weight and the temperature of the heated portion after the barrel 7 was set as shown in Table 2, the polysulfone resin unstretched raw material was the same as in Example 1. The counter was wound in a roll shape.
The Tg, average thickness and thickness variation (%) of the obtained unstretched polysulfone resin raw material were as shown in Table 2.
[0069]
Next, the unstretched polysulfone resin sheet was placed in a table using a stretching apparatus having three zones of a preheating zone (length 2 m), a stretching zone (length 2 m) and a cooling zone (length 1 m) shown in FIG. The film was longitudinally and uniaxially stretched at a preheating temperature, a stretching temperature and a cooling temperature, a line speed of 1 m / min, and a stretching ratio shown in 3 to produce a retardation film.
In order to evaluate the obtained retardation film performance, the average retardation and the dispersion of the retardation were measured and the quality was judged based on these data by the following method.
[0070]
(Sample and evaluation)
A phase difference film sample having a width of 200 mm and a length of 500 mm was cut out from the center of the obtained stretched film. The retardation value at 590 nm of the obtained retardation film sample was measured at intervals of 5 mm in the width direction and at intervals of 50 mm in the length direction (Measuring instrument: Otsuka Electronics Co., Ltd., trade name "REST-2000", valley value measurement). ), The average value of all the measured values and the maximum value of the variation were calculated, and those having a maximum value of the variation within 5 nm were evaluated as ○ (good), and those exceeding 5 nm were determined as x (bad). The evaluation results are shown in Table 3.
[0071]
(Example 5)
Addition Except that the temperature of the heat portion was set as shown in Table 2, an unstretched polysulfone resin sheet was prepared in the same manner as in Example 1, and the preheating temperature, the stretching temperature, and the cooling temperature shown in Table 3 were used as in Example 4 Similarly, a retardation film was produced. Evaluation of the retardation film was performed in the same manner as in Example 4, and the evaluation results are shown in Table 3.
[0072]
(Comparative Examples 4 to 6)
Using the unstretched polysulfone resin raw material of Example 4, a retardation film was produced in the same manner as in Example 4 at a preheating temperature, a stretching temperature, and a cooling temperature shown in Table 3, and was similarly evaluated. The evaluation results are shown in Table 3.
[0073]
[Table 2]

[0074]
[Table 3]

[0075]
(Example 6)
[Powder removal of polysulfone resin-1]
Using the vibration sieve (trade name “403”) manufactured by Dalton Co., Ltd., the resin powder and the contaminant foreign substances adhering to the polysulfone resin pellets used in Example 1 were removed by sieving, and then used in Example 1. An extruder equipped with a coat hanger type T die was charged, and a plasticizer diethyl phthalate was kneaded in the same manner as in Example 1 to prepare an unstretched polysulfone resin, and a retardation film was formed in the same manner as in Example 1. Produced.
In addition, a small nitrogen gas generator (trade name “P3.0”, manufactured by Taiyo Toyo Oxygen Co., Ltd.) was used for charging the polysulfone resin pellet charging section (the end of the barrel on the screw drive side and the peripheral gap) of the extruder. Pressure 4kg / cm ² A nitrogen gas was blown at a flow rate of 2 liters / minute, and the air existing in the same portion was purged to produce an unstretched raw polysulfone resin.
[0076]
(Example 7)
[Powder removal of polysulfone resin-2]
Using a powder removing device including a powder removing zone provided with a plurality of rows of water washing showers shown in FIG. 5, a powder removing zone, a draining zone, a water washing device having a drain zone, and a dehydrating zone and a dehydrating device having a drain zone. After removing the resin powder and contaminating foreign substances adhered to the polysulfone resin pellets used in Example 1 by washing with water and sieving, the extruder equipped with the coat hanger type T die used in Example 1 was charged, In the same manner as in Example 1, a plasticizer diethyl phthalate was kneaded to prepare an unstretched polysulfone resin, and a retardation film was prepared in the same manner as in Example 1.
The nitrogen gas purge of the polysulfone resin pellet charging section of the extruder was performed in the same manner as in Example 6.
[0077]
(Comparative Example 7)
Except that the polysulfone resin was not powdered, an unstretched polysulfone resin sheet was produced in the same manner as in Example 6, and a retardation film was produced in the same manner as in Example 1.
[0078]
For the continuous 5-hour production of the unstretched polysulfone resin having a thickness of 70 μm and a width of 500 mm in Examples 6, 7 and Comparative Example 7, three 500 mm × 2 m samples were sampled by a random sampling method. Microscopic observation was performed, and the number of foreign substances having a diameter of 50 μmφ or more was counted. Table 4 shows the counting results.
[0079]
[Table 4]

[0080]
【The invention's effect】
Since the method for manufacturing a retardation film of the present invention is configured as described above, the temperature function of the above-described formula (1) determined for each amount of the plasticizer in the thermoplastic resin composition allows the following methods to be performed in a melt extruder: It has become possible to implement a melt extrusion control system that can substantially eliminate the decomposition of plasticizers, and it has been said that only an unsuitable film can be manufactured for optical devices such as liquid crystal display devices. By this method, a retardation film having high productivity and a uniform retardation value can be produced.
[0081]
The temperature of the plasticized thermoplastic resin composition at the exit of the mold is set so as to be in the range of (boiling point−100 ° C.) of the plasticizer in the thermoplastic resin composition to (boiling point + 20 ° C.) of the plasticizer. After forming a film by the method, the preheating temperature is (stretching temperature -100 ° C) to (stretching temperature -10 ° C), the stretching temperature is (Tg + 10 ° C) to (Tg + 35 ° C) of the thermoplastic resin, and the cooling temperature is the thermoplastic resin. (Tg-90 ° C.) to (Tg-10 ° C.), which are stretched by stretching means consisting of three steps, so that stretching unevenness due to a temperature difference caused by unevenness in the thickness of the stretched raw material and rapid expansion and contraction of the film. The film can be stretched while suppressing such disturbances, and can produce a retardation film having no stretching unevenness and having a uniform retardation value without wrinkles.
[0082]
It can remove powder particles attached to the thermoplastic resin pellets, and remove and reduce external contaminants contaminating the particles. Particularly, according to the washing means, the powder particles attached to the thermoplastic resin pellets can be removed. Since the body is also reliably removed by the water stream, it is also capable of neutralizing and removing the static electricity of the thermoplastic resin pellets and the powder particles attached thereto, so that the cleaning effect is further enhanced. It is intended to improve the yield of products as well as the quality of the retardation film.
[0083]
Further, when the thermoplastic resin is a polysulfone-based resin and a resin composition in which the plasticizer is a phthalic acid ester is used, the wavelength dispersion of light of the obtained retardation film is reduced to a liquid crystal display device. It has characteristics close to those of the liquid crystal used, and can satisfactorily compensate for different elliptically polarized light at each wavelength, thereby further improving the contrast of the liquid crystal display device.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing a main part of an example of a melt extruder used in a method for producing a retardation film of the present invention.
FIG. 2 is an explanatory view showing a main part of another example of a melt extruder used in the method for producing a retardation film of the present invention.
FIG. 3 is an explanatory view showing a main part of a melt extruder used in the method for producing a retardation film of the present invention, and a thermoplastic resin pellet washing device is provided at the upper right of the extruder.
FIG. 4 is an explanatory view showing a main part of a T-die melt extruder after an adapter at the left end of FIG. 1;
FIG. 5 is an explanatory view showing a main part of a stretching means connected to the pinch roll at the right end in FIG. 4;
[Description of sign]
1, 10: melt extruder
11, 110, 50: resin supply port
12: Plunger pump
13: Die head
14: Gear pump
15: Neck
16, 160: Adapter
17: Die entrance
2: Mold
21: Mold exit
31, 32, 33: cooling roll
34, 41, 411: Pinch roll
4: Stretching means
42: Preheating zone
43: Stretching zone
44: Cooling zone
45, 47: Communication hole
46, 48: thermal insulation wall
49: Hot air nozzle
5: Cleaning device
51: Rinse shower
52: Powder removal zone
53: powder cutting zone
54: Drain zone
55, 62: drainage zone
6: Dehydration device
61: Dehydration zone

Claims (1)

A resin composition containing 100 parts by weight of a thermoplastic resin and 0.2 to 10 parts by weight of a plasticizer, is formed into a film by a melt extrusion method under the following conditions, and then is stretched. Production method.
1. The temperature of the resin composition passing through each of a plurality of divided heating portions of the melt extruder barrel and ancillary equipment from the supply of the plasticizer to the mold outlet is T _n (° C.), and each of the divided heating portions of the barrel is the time to pass through the s _n (min), when the number of parts by weight of a plasticizer in the resin composition was W, these T _n, s _n and W, it is in the following relation.

2. The temperature of the resin composition at the exit of the mold is equal to or lower than the (boiling point + 20 ° C.) of the plasticizer.

Images