JP4120380B2 - Method for producing transparent film - Google Patents

Description

【化４】

以下、本発明について詳細に説明する。
【００１１】
上記の構成成分（Ｉ）と構成成分（ＩＩ）からなるマレイミド・オレフィン共重合体は、例えば、マレイミド類とオレフィン類とのラジカル共重合反応により得ることができる。構成成分（Ｉ）を与える化合物としては、マレイミド、Ｎ−メチルマレイミド、Ｎ−エチルマレイミド、Ｎ−ｎ−プロピルマレイミド、Ｎ−ｉ−プロピルマレイミド、Ｎ−ｎ−ブチルマレイミド、Ｎ−ｉ−ブチルマレイミド、Ｎ−ｓ−ブチルマレイミド、Ｎ−ｔ−ブチルマレイミド、Ｎ−ｎ−ペンチルマレイミド、Ｎ−ｎ−ヘキシルマレイミド、Ｎ−シクロプロピルマレイミド、Ｎ−シクロブチルマレイミド、Ｎ−シクロヘキシルマレイミド等のマレイミド類が例示され、耐熱性、機械特性および透明性の点から特にＮ−メチルマレイミドが好ましい。また、これらの化合物は１種または２種以上組み合わせて用いることができる。
【００１２】
構成成分（ＩＩ）を与える化合物としては、イソブテン、２−メチル−１−ブテン、２−メチル−１−ペンテン、２−メチル−１−ヘキセン等のオレフィン類が例示でき、このうち耐熱性、機械特性および透明性の点から特にイソブテンが好ましい。また、これらの化合物は１種または２種以上組み合わせて用いることができる。
【００１３】
構成成分（Ｉ）の含有量は、共重合体全体の４０〜６０モル％であり、耐熱性および機械特性の点から４５〜５５モル％が好ましい。構成成分（Ｉ）が６０モル％を越える場合には得られるフィルムは脆くなり、４０モル％未満の場合では得られるフィルムの耐熱性が低下するため好ましくない。
【００１４】
また、構成成分（Ｉ）と構成成分（ＩＩ）からなるマレイミド・オレフィン共重合体は、必要ならば、本発明の目的を損なわない範囲で他のモノマー成分を含有していても良い。他のモノマー成分としては、スチレン、α−メチルスチレン等のスチレン誘導体、メタクリル酸メチル、メタクリル酸エチル等のメタクリル酸エステル類、アクリル酸メチル、アクリル酸エチル等のアクリル酸エステル類、酢酸ビニル、安息香酸ビニル等のビニルエステル類、メチルビニルエーテル、エチルビニルエーテル、プロピオビニルエーテル、ブチルビニルエーテル等のビニルエーテル類、無水マレイン酸、およびアクリロニトリルより選ばれる１種類以上の化合物が挙げられ、その含有率としては５モル％以下であることが好ましい。
【００１５】
これらモノマーの重合は公知の重合方法、例えば、塊状重合法、溶液重合法、懸濁重合法、沈殿重合法および乳化重合法のいずれもが採用可能である。得られるフィルムの透明性、色調の点から特に沈殿重合法が好ましい。
【００１６】
重合開始剤としては、ベンゾイルパーオキサイド、ラウリルパーオキサイド、オクタノイルパーオキサイド、アセチルパーオキサイド、ジ−ｔ−ブチルパーオキサイド、ｔ−ブチルクミルパーオキサイド、ジクミルパーオキサイド、ｔ−ブチルパーオキシアセテート、ｔ−ブチルパーオキシベンゾエート等の有機過酸化物、または、２，２’−アゾビス（２，４−ジメチルバレロニトリル）、２，２’−アゾビス（２−ブチロニトリル）、２，２’−アゾビスイソブチロニトリル、ジメチル−２，２’−アゾビスイソブチレート、１，１’−アゾビス（シクロヘキサン−１−カルボニトリル）等のアゾ系開始剤が挙げられる。
【００１７】
溶液重合法あるいは沈殿重合法において使用可能な溶媒としては、ベンゼン、トルエン、キシレンなどの芳香族溶媒、メタノール、エタノール、プロパノール、ブタノールなどのアルコール系溶媒、シクロヘキサン、ジオキサン、テトラヒドロフラン、アセトン、メチルエチルケトン、ジメチルホルムアミド、酢酸イソプロピル、芳香族系溶媒とアルコール系溶媒の混合溶媒などが挙げられる。
【００１８】
重合温度は、開始剤の分解温度に応じて適宜設定することができるが、一般的には４０〜１５０℃の範囲で行うことが好ましい。
【００１９】
上述のマレイミド・オレフィン共重合体は、無水マレイン酸とオレフィン類との共重合により得られる樹脂をアンモニア、アルキルアミンを用いて、後イミド化することによっても得ることができる。
【００２０】
このような後イミド化反応は、例えば、無水マレイン酸・オレフィン共重合体をメタノール、エタノール、プロパノールなどのアルコール系溶媒、ベンゼン、トルエンなどの芳香族系溶媒、酢酸エチル、酢酸イソプロピルなどのエステル系溶媒、芳香族系溶媒とアルコール系溶媒の混合溶媒などに溶解あるいは分散させ、アルキルアミンと５０〜２５０℃の温度で反応させることによりアミド化反応およびイミド化反応を連続的に行う方法、あるいはアルキルアミンと反応させてアミド体を得た後、そのアミド体を用いてイミド化反応を行う方法により製造することができる。
【００２１】
ここで、生成する共重合体の数平均分子量（Ｍｎ）は、ゲル・パーミエーション・クロマトグラフィー（ＧＰＣ）により求めることができる。マレイミド・オレフィン共重合体の分子量は１×１０³以上５×１０⁶以下、特に機械特性と製膜性のバランスの点から１×１０⁴以上５×１０⁵以下のものが好ましい。分子量が５×１０⁶を越える場合には、得られるフィルムの表面性が悪くなるとともに、延伸によりフィルムが破断し易くなる。また１×１０³未満の場合には、得られるフィルムの機械強度が乏しくなる。
【００２２】
本発明で使用されるアクリロニトリル・スチレン共重合体のアクリロニトリル含量は、組成全体の２１〜４５重量％が好ましい。この範囲を外れるとマレイミド・オレフィン共重合体とアクリロニトリル・スチレン共重合体の相溶性が低下するため、得られるフィルムは不透明になり、また耐熱性も低下するため好ましくない。
【００２３】
本発明で使用されるマレイミド・オレフィン共重合体とアクリロニトリル・スチレン共重合体の割合は、１：９９〜９９：１（重量％）、加工性、耐熱性、光学特性のバランスの点から１０：９０〜９０：１０（重量％）、特に５０：５０〜９０：１０（重量％）が好ましい。マレイミド・オレフィン共重合体が１重量％未満の場合には、フィルムの耐熱性が乏しくなるとともに、フィルムの光学特性、特に複屈折が応力に対して変化し易くなるため好ましくない。また、マレイミド・オレフィン共重合体が９９重量％を越える場合には、フィルムの機械強度が乏しくなるため好ましくない。
【００２４】
本発明における透明性フィルムには、発明の主旨を越えない範囲で、その他ポリマー、界面活性剤、高分子電解質、導電性錯体、無機フィラー、顔料、染料、熱安定剤、紫外線吸収剤、帯電防止剤、アンチブロッキング剤、滑剤、可塑剤等が加えられていても良い。
【００２５】
本発明は、ａ）マレイミド・オレフィン共重合体１〜９９重量％およびｂ）アクリロニトリル単位を２１〜４５重量％含むアクリロニトリル・スチレン共重合体９９〜１重量％よりなる樹脂組成物１０〜４０重量％、および溶媒９０〜６０重量％からなる溶液を支持基板上に流延し、溶媒を含む流延フィルムから溶媒を蒸発させることを特徴とする透明性フィルムの製造方法であって、上記溶媒が塩化メチレンを９９〜８５重量％含有し、且つ炭素数１〜６の直鎖状または分岐状の脂肪族アルコールを１〜１５重量％含有するものであることを特徴とする透明性フィルムの製造方法に関するものである。
【００２６】
塩化メチレンは、本発明におけるマレイミド・オレフィン共重合体とアクリロニトリル・スチレン共重合体よりなる樹脂組成物の良溶媒ではあるが、塩化メチレンのみを溶媒として用い、高粘度溶液（ドープ）を作製した場合、時間の経過とともにドープの粘度が上昇し、最終的にゼリー状の固化に至る。ドープの粘度は所望するフィルムの厚み、溶媒の乾燥時間等を考慮して調整されるため、ドープの粘度が安定しない場合、ドープ作製後の時間経過に伴い、フィルムの厚みが変化する等の問題が発生する。また、ドープの一部あるいは全体がゼリー状に固化した場合、フィルムの表面平滑性が悪化するばかりか、成膜自体ができなくなる場合もある。
【００２７】
本発明者らは、ドープの安定性を向上させるために、溶媒として、塩化メチレンを９９〜８５重量％含有し、且つ炭素数１〜６の直鎖状または分岐状の脂肪族アルコールを１〜１５重量％含有する混合溶媒を用いることにより、上記問題を解決するに至った。
【００２８】
本発明に用いられるアルコールとしては、炭素数１〜６の直鎖状、あるいは分岐した脂肪族アルコールが好ましく、特に好ましくは炭素数１〜４の直鎖状、あるいは分岐した脂肪族アルコール、具体的にはメタノール、エタノール、イソプロパノール、ターシャリーブタノールなどが挙げられる。炭素数６を超える高級アルコールは、高沸点であるためフィルム製膜後も残留しやすくなるので好ましくない。また、これらアルコールは単独で加えても良いし、２種類以上組み合わせても問題ない。
【００２９】
本発明における溶媒中のアルコール含有量は１〜１５重量％、より好ましくは２〜１０重量％、特に好ましくは４〜１０重量％である。含有量が１５重量％を超える場合、マレイミド・オレフィン共重合体とアクリロニトリル・スチレン共重合体よりなる樹脂組成物の溶媒への溶解性が低下するため、ドープが濁るなどの問題があり、１重量％に満たない場合は、ドープの安定性向上効果が乏しくなる。一方、溶媒中の塩化メチレン含有量は９９〜８５重量％であり、７０重量％に満たない場合は、マレイミド・オレフィン共重合体とアクリロニトリル・スチレン共重合体よりなる樹脂組成物の溶媒への溶解性が低下するため好ましくない。
【００３０】
また、本発明に用いられる溶媒は、溶液流延法により製膜したフイルムの表面性向上、溶媒の蒸発速度やドープの粘度調節などを目的に、樹脂組成物の溶媒への溶解性やドープの安定性を犠牲にしない範囲で、塩化メチレンおよびアルコール以外の溶媒を含有させることができる。塩化メチレンおよびアルコール以外の溶媒として、例えばクロロホルム、１，２−ジクロロエタン、１，１，２−トリクロロエタン、クロロベンゼン、ジクロロベンゼンなどのハロゲン系溶媒、１，３−ジオキソラン、１，４−ジオキサン、テトラヒドロフラン等の環状エーテル系溶媒、シクロヘキサノン、メチルエチルケトン、アセトン等のケトン系溶媒、酢酸イソプロピル、酢酸エチル等のエステル系溶媒、ベンゼン、トルエン、キシレン等の芳香族系溶媒、ｎ−ヘキサン、ｎ−ヘプタン、ｎ−ブタン等の脂肪族系溶媒、Ｎ−メチルピロリドン、ジメチルホルムアミドなどが挙げられる。
【００３１】
本発明における溶液は、マレイミド・オレフィン共重合体とアクリロニトリル・スチレン共重合体よりなる樹脂組成物１０〜４０重量％、および溶媒９０〜６０重量％からなる溶液であり、より好ましくは、マレイミド・オレフィン共重合体とアクリロニトリル・スチレン共重合体よりなる樹脂組成物１５重量％〜３０重量％、溶媒８５〜７０重量％である。樹脂組成物の溶液中含有量が４０重量％を超えると溶媒への溶解性が低下するとともに、ドープの安定性が乏しくなる問題がある。一方、樹脂組成物の溶液中含有量が１０重量％に満たない場合、ドープの安定性は問題ないが、溶液流延法により成膜した場合、フィルムの表面平滑性が不十分となることや、厚み精度が得られないなどの問題がある。
【００３２】
本発明における溶液の作製法としては、特に限定されるものではなく、例えば、塩化メチレンに溶解させた樹脂組成物溶液に、アルコール等の溶媒を所定量添加する方法、あるいは塩化メチレン、アルコール等を含有する混合溶媒に樹脂組成物を添加し、溶液を作製する方法などが挙げられる。
【００３３】
本発明においては、ドープを支持基板上に流延した後、加熱することにより溶媒を蒸発させてフイルムを得る。一般に流延する方法として、Ｔダイ法、ドクターブレード法、バーコーター法、ロールコータ法、リップコーター法等が用いられる。工業的には、ダイからドープをベルト状もしくはドラム状の支持基板に連続的に押し出す方法が最も一般的である。用いられる支持基板としてはガラス基板、ステンレスやフェロタイプ等の金属基板、ポリエチレンテレフタレート等のプラスチック基板などがある。高度に表面性、光学均質性の優れたフィルムを工業的に連続製膜するには、表面を鏡面仕上げした金属基板が最も一般的に用いられる。
【００３４】
溶液流延法において、高い透明性を有し、且つ厚み精度、表面平滑性に優れたフイルムを製膜する目的において、溶液粘度は極めて重要な因子である。溶液粘度はポリマーの濃度、分子量および溶媒の種類に依存するが、本発明の溶液の粘度は、好ましくは７００〜３００００ｃｐｓ、より好ましくは１０００〜１００００ｃｐｓである。溶液粘度が７００〜３００００ｃｐｓの範囲を外れる場合、フィルムの表面平滑性、厚み精度が得られ難くなるため、好ましくない。
【００３５】
本発明のフィルムの厚みは、１０〜５００μｍであり、より好ましくは２０〜２００μｍの範囲である。フィルム厚みが１０μｍ未満の場合は、機械特性が低下し、５００μｍを超える場合には、溶媒の除去に長時間を要し、生産性が低下するため、好ましくない。
【００３６】
【実施例】
以下、本発明を実施例により説明するが、本発明は実施例に限定されるものではない。
【００３７】
実施例に示す諸物性は、以下の方法により測定した。
【００３８】
分子量：ゲル・パーミエーション・クロマトグラフィー（ＧＰＣ、東ソー株式会社製 ＨＬＣ−８０２Ａ）を用い、ポリスチレン換算により求めた。
【００３９】
組成比：主として元素分析、¹Ｈ−ＮＭＲ測定により決定した。
【００４０】
全光線透過率：日本分光（株）製 紫外可視分光器（Ｖ５３０）を用い、フィルム中心部の全光線透過率を測定した。
【００４１】
表面平滑性：（株）キーエンス製 レーザー顕微鏡（ＶＫ−８５５０）を用い、中心線平均粗さ（Ｒａ）を求め、この値により表面平滑性を評価した。
【００４２】
合成例 マレイミド・オレフィン共重合体の合成
攪拌機、窒素導入管、温度計および脱気管の付いた３０Ｌオートクレーブに、Ｎ−メチルマレイミド １．２ｋｇ、ｔ−ブチルパーオキシネオデカノエート ８ｇおよびトルエンとメタノールの混合溶媒（１：１重量比）１５Ｌを仕込み、窒素で数回パージした後、イソブテン８．５Ｌを仕込み、６０℃で６時間反応を行った。得られた粒子を遠心分離後乾燥した。収量は１．７ｋｇであった。
【００４３】
得られたポリマーの元素分析結果（Ｃ；６４．７重量％、Ｈ；７．８重量％、Ｎ；８．４重量％）より、生成ポリマー中のマレイミド単位およびイソブテン単位は、それぞれ５０モル％であった。得られたポリマーは、数平均分子量（Ｍｎ）９５０００であった。
【００４４】
実施例１〜２、比較例１〜２
合成例で合成したＮ−メチルマレイミド・イソブテン共重合体、およびアクリロニトリル含量３０重量％のアクリロニトリル・スチレン共重合体を８０：２０の重量比にてドライブレンドした後、３０ｍｍφ２軸押出機（（株）日本製鋼所製）に供して溶融混練を行い、ペレット化した。そして、表１に示す塩化メチレンとアルコールの混合溶媒に、上述のペレットを溶液中の含有量が２０重量％となるように溶解し、ドープを得た。アルコールを１〜１５重量％の範囲内で含有する溶媒を用いた場合のドープは、均一透明であった。また、得られたドープを静置し、４日間観察したが、ドープに変化は認められなかった。一方、アルコールを添加しない場合、ドープ作製直後は均一透明であったが、静置後、４日間経過した時点にてゼリー状固化物が発生した。また、アルコールを１〜１５重量％の範囲を超えて添加した場合、ドープ作製直後において濁りが認められた。ドープ作製直後および４日間静置後のドープの状態について表１に示す。次いで、４日間静置後のドープを用い、Ｔダイ法により溶液流延装置の支持体に流延し、乾燥後、幅３００ｍｍのフィルムを得た。そして、成膜したフィルムを一片２００ｍｍの正方形に裁断し、全光線透過率、Ｒａを測定した。その結果を表１に示す。
【００４５】
【表１】

実施例３〜４、比較例３
実施例１〜２、比較例１〜２の方法と同様にしてペレット化した樹脂組成物を得た。そして、表２に示す塩化メチレンとアルコールの混合溶媒に、上述のペレットを溶液中の含有量が２０重量％となるように溶解し、ドープを得た。ドープ作製直後および４日間静置後のドープの状態について表２に示す。次いで、４日間静置後のドープを用い、実施例１〜２、比較例１〜２の方法と同様にして成膜、裁断を行い、一片２００ｍｍの正方形フィルム試験片を得た。フィルムの全光線透過率、Ｒａを測定した結果について表２に示す。
【００４６】
【表２】

比較例４〜５
実施例１〜２、比較例１〜２の方法と同様にしてペレット化した樹脂組成物を得た。そして、表３に示す塩化メチレンとアルコールの混合溶媒に、上述のペレットを表３に示す溶液中の含有量となるように溶解し、ドープを得た。ドープ作製直後および４日間静置後のドープの状態について表３に示す。次いで、４日間静置後のドープを用い、実施例１〜２、比較例１〜２の方法と同様にして成膜、裁断を行い、一片２００ｍｍの正方形フィルム試験片を得た。フィルムの全光線透過率、Ｒａを測定した結果について表３に示す。
【００４７】
【表３】

実施例５〜６
実施例１〜２、比較例１〜２の方法と同様にしてペレット化した樹脂組成物を得た。そして、表４に示す混合溶媒に、上述のペレットを溶液中の含有量が２０重量％となるように溶解し、ドープを得た。ドープ作製直後および４日間静置後のドープの状態について表４に示す。次いで、４日間静置後のドープを用い、実施例１〜２、比較例１〜２の方法と同様にして成膜、裁断を行い、一片２００ｍｍの正方形フィルム試験片を得た。フィルムの全光線透過率、Ｒａを測定した結果について表４に示す。
【００４８】
【表４】

【発明の効果】
本発明である透明性フィルムの製造方法によれば、フラットパネルディスプレイ用透明性フィルム、例えば、偏光子保護フィルム、位相差フィルム、視野角補償フィルム、透明電極フィルム、光拡散フィルム、光反射フィルム、電磁波遮蔽フィルム、ディスプレイ表面保護フィルムに利用できる透明性フィルムを製造することが可能となる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a transparent film excellent in surface smoothness and thickness accuracy comprising a resin composition comprising a maleimide / olefin copolymer and an acrylonitrile / styrene copolymer.
[0002]
[Prior art]
In recent years, flat panel displays typified by liquid crystal displays, organic ELs, PDPs, etc. have features that are thin and lightweight to meet market needs, and are rapidly spreading or expanding their use range. In these flat panel displays, a number of polymer films are used. For example, a polarizer protective film, a retardation film, a viewing angle compensation film, a transparent electrode film, a light diffusion film, a light reflection film, and an electromagnetic wave shielding film. It is used for display surface protection film. These polymer films generally require very high transparency, excellent surface smoothness and thickness accuracy so as not to deteriorate the visibility of the display. Examples of transparent films used in flat panel displays include polyethylene terephthalate film, polycarbonate film, polyether sulfone film, cyclic polyolefin film, linear polyolefin film, polymethyl methacrylate film, triacetyl cellulose film, and thermosetting. A typical example is a mold resin film.
[0003]
In general, the transparent film is produced by a T-die melt extrusion method or a solution casting method. Since the T-die melt extrusion method is excellent in productivity and relatively inexpensive in production equipment, it is widely used as a method for producing a transparent film. However, in the case of the melt extrusion method, fine streaks, sharkskin-like roughness, die lines, and the like are likely to occur on the film surface due to kneading history, kneading unevenness, discharge unevenness, resin burning, etc. during melt kneading. In addition, after kneading a high-viscosity molten resin in an extruder, it is expanded in the width direction in a T-die and a take-off operation is performed, so it is difficult to obtain a high thickness accuracy. For these reasons, it is actually difficult to achieve very high surface smoothness and thickness accuracy as required for transparent films for flat panel displays by the T-die melt extrusion method.
[0004]
On the other hand, in the solution casting method, a high-viscosity solution (dope) in which a polymer is dissolved in a solvent is cast on a support substrate, and then heated to remove most of the solvent to support it as a self-supporting film. This is a film formation method in which the remaining solvent is removed by peeling from the substrate and further drying by heating. When the solution casting method is compared with the T-die melt extrusion method, there is no occurrence of kneading unevenness due to melt kneading extrusion, discharge unevenness, or resin burning due to thermal deterioration, so that high surface smoothness can be easily obtained, and further, Since the solution viscosity is low, there is an advantage that high thickness accuracy is easily obtained. Therefore, when a particularly high surface smoothness and thickness accuracy are required, such as a transparent film for a flat panel display, a film by a solution casting method is often used.
[0005]
The present inventors previously proposed a transparent film excellent in optical properties, heat resistance, and mechanical properties comprising a resin composition containing a maleimide / olefin copolymer (see, for example, Patent Document 1). Thereafter, the present inventors have studied a method for producing a transparent film comprising a resin composition comprising a maleimide / olefin copolymer and an acrylonitrile / styrene copolymer, and have earnestly studied to obtain excellent surface smoothness and thickness accuracy. As a result of efforts, the present invention has been completed.
[0006]
[Patent Document 1]
JP2000-80240
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide a method for producing a transparent film having excellent surface smoothness and thickness accuracy.
[0008]
[Means for Solving the Problems]
As a result of intensive studies in view of the above problems, the present inventors dissolved a resin composition comprising a maleimide / olefin copolymer and an acrylonitrile / styrene copolymer in a mixed solvent of methylene chloride containing a small amount of a lower aliphatic alcohol. It has been found that a film produced by a solution casting method using a solution satisfies the above object, and has completed the present invention.
[0009]
That is, the present invention comprises: a) the following component (I) is 40 to 60 mol%, the component (II) is 60 to 40 mol%, and the number average molecular weight is 1 × 10 ³ or more and 5 × 10 ⁶ or less. 1 to 99% by weight of a certain maleimide / olefin copolymer and b) a resin composition of 10 to 40% by weight comprising 99 to 1% by weight of an acrylonitrile / styrene copolymer containing 21 to 45% by weight of an acrylonitrile unit, and a solvent 90 to 90% A method for producing a transparent film, comprising casting a solution comprising 60% by weight on a support substrate and evaporating the solvent from a cast film containing the solvent, wherein the solvent contains 99 to 85 methylene chloride. The present invention relates to a method for producing a transparent film characterized by comprising 1 to 15% by weight of a linear or branched aliphatic alcohol having 1% by weight and containing 1 to 6 carbon atoms. It is intended.
[0010]
[Chemical 3]

[Formula 4]

Hereinafter, the present invention will be described in detail.
[0011]
The maleimide / olefin copolymer composed of the constituent component (I) and the constituent component (II) can be obtained, for example, by radical copolymerization reaction of maleimides and olefins. Examples of compounds that give component (I) include maleimide, N-methylmaleimide, N-ethylmaleimide, Nn-propylmaleimide, Ni-propylmaleimide, Nn-butylmaleimide, Ni-butylmaleimide , Ns-butylmaleimide, Nt-butylmaleimide, Nn-pentylmaleimide, Nn-hexylmaleimide, N-cyclopropylmaleimide, N-cyclobutylmaleimide, N-cyclohexylmaleimide, and other maleimides N-methylmaleimide is particularly preferable from the viewpoint of heat resistance, mechanical properties and transparency. These compounds can be used alone or in combination of two or more.
[0012]
Examples of the compound giving the constituent component (II) include olefins such as isobutene, 2-methyl-1-butene, 2-methyl-1-pentene, and 2-methyl-1-hexene. Isobutene is particularly preferred from the viewpoint of properties and transparency. These compounds can be used alone or in combination of two or more.
[0013]
The content of component (I) is 40 to 60 mol% of the entire copolymer, and is preferably 45 to 55 mol% from the viewpoint of heat resistance and mechanical properties. When the component (I) exceeds 60 mol%, the resulting film becomes brittle, and when it is less than 40 mol%, the heat resistance of the obtained film decreases, which is not preferable.
[0014]
Further, the maleimide / olefin copolymer comprising the constituent component (I) and the constituent component (II) may contain other monomer components as long as the purpose of the present invention is not impaired. Other monomer components include styrene derivatives such as styrene and α-methylstyrene, methacrylic acid esters such as methyl methacrylate and ethyl methacrylate, acrylic acid esters such as methyl acrylate and ethyl acrylate, vinyl acetate, and benzoic acid. One or more compounds selected from vinyl esters such as vinyl acid, vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, propio vinyl ether, and butyl vinyl ether, maleic anhydride, and acrylonitrile are included. % Or less is preferable.
[0015]
For the polymerization of these monomers, any of known polymerization methods such as bulk polymerization, solution polymerization, suspension polymerization, precipitation polymerization and emulsion polymerization can be employed. The precipitation polymerization method is particularly preferred from the viewpoint of the transparency and color tone of the obtained film.
[0016]
As polymerization initiators, benzoyl peroxide, lauryl peroxide, octanoyl peroxide, acetyl peroxide, di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, t-butyl peroxide acetate, organic peroxides such as t-butylperoxybenzoate, or 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2-butyronitrile), 2,2′-azobis Examples include azo initiators such as isobutyronitrile, dimethyl-2,2′-azobisisobutyrate, 1,1′-azobis (cyclohexane-1-carbonitrile).
[0017]
Solvents that can be used in the solution polymerization method or precipitation polymerization method include aromatic solvents such as benzene, toluene, and xylene, alcohol solvents such as methanol, ethanol, propanol, and butanol, cyclohexane, dioxane, tetrahydrofuran, acetone, methyl ethyl ketone, and dimethyl. Examples include formamide, isopropyl acetate, a mixed solvent of an aromatic solvent and an alcohol solvent.
[0018]
The polymerization temperature can be appropriately set according to the decomposition temperature of the initiator, but generally it is preferably performed in the range of 40 to 150 ° C.
[0019]
The maleimide / olefin copolymer described above can also be obtained by post-imidizing a resin obtained by copolymerization of maleic anhydride and olefins with ammonia or alkylamine.
[0020]
Such post-imidation reaction may be carried out, for example, by using maleic anhydride / olefin copolymer as an alcohol solvent such as methanol, ethanol or propanol, an aromatic solvent such as benzene or toluene, or an ester solvent such as ethyl acetate or isopropyl acetate. A method in which an amidation reaction and an imidation reaction are continuously performed by dissolving or dispersing in a solvent, a mixed solvent of an aromatic solvent and an alcohol solvent, and reacting with an alkylamine at a temperature of 50 to 250 ° C. It can be produced by a method of reacting with an amine to obtain an amide, and then performing an imidization reaction using the amide.
[0021]
Here, the number average molecular weight (Mn) of the copolymer to be produced can be determined by gel permeation chromatography (GPC). The molecular weight of the maleimide / olefin copolymer is preferably 1 × 10 ³ or more and 5 × 10 ⁶ or less, particularly preferably 1 × 10 ⁴ or more and 5 × 10 ⁵ or less from the viewpoint of the balance between mechanical properties and film forming property. When the molecular weight exceeds 5 × 10 ⁶ , the surface property of the obtained film is deteriorated and the film is easily broken by stretching. On the other hand, if it is less than 1 × 10 ³ , the resulting film has poor mechanical strength.
[0022]
The acrylonitrile content of the acrylonitrile / styrene copolymer used in the present invention is preferably 21 to 45% by weight of the total composition. Outside this range, the compatibility of the maleimide / olefin copolymer and the acrylonitrile / styrene copolymer is lowered, so that the resulting film becomes opaque and the heat resistance is also lowered.
[0023]
The ratio of the maleimide / olefin copolymer and the acrylonitrile / styrene copolymer used in the present invention is 10:99 to 99: 1 (% by weight), in terms of the balance of processability, heat resistance, and optical properties. 90 to 90:10 (% by weight), particularly 50:50 to 90:10 (% by weight) is preferable. When the maleimide / olefin copolymer is less than 1% by weight, the heat resistance of the film becomes poor and the optical properties of the film, in particular, the birefringence easily changes with respect to stress, such being undesirable. On the other hand, when the maleimide / olefin copolymer exceeds 99% by weight, the mechanical strength of the film becomes poor, such being undesirable.
[0024]
For the transparent film in the present invention, other polymers, surfactants, polymer electrolytes, conductive complexes, inorganic fillers, pigments, dyes, heat stabilizers, ultraviolet absorbers, antistatic agents are used within the scope of the invention. An agent, an antiblocking agent, a lubricant, a plasticizer, or the like may be added.
[0025]
The present invention relates to a resin composition comprising 10) to 40% by weight of a) 1) to 99% by weight of a maleimide / olefin copolymer and b) 99 to 1% by weight of an acrylonitrile / styrene copolymer containing 21 to 45% by weight of an acrylonitrile unit. And a solution comprising 90 to 60% by weight of a solvent is cast on a support substrate, and the solvent is evaporated from the cast film containing the solvent, wherein the solvent is chlorinated. The present invention relates to a method for producing a transparent film comprising 99 to 85 % by weight of methylene and 1 to 15% by weight of a linear or branched aliphatic alcohol having 1 to 6 carbon atoms. Is.
[0026]
Methylene chloride is a good solvent for the resin composition comprising a maleimide / olefin copolymer and an acrylonitrile / styrene copolymer in the present invention, but when a high viscosity solution (dope) is prepared using only methylene chloride as a solvent. The viscosity of the dope increases with the passage of time, and finally leads to jelly-like solidification. Since the viscosity of the dope is adjusted in consideration of the desired film thickness, solvent drying time, etc., if the dope viscosity is not stable, the film thickness will change over time after the dope is produced. Occurs. Further, when a part or the whole of the dope is solidified in a jelly shape, not only the surface smoothness of the film is deteriorated but also the film formation itself may not be possible.
[0027]
In order to improve the stability of the dope, the present inventors contain 99 to 85 % by weight of methylene chloride as a solvent and 1 to 6 linear or branched aliphatic alcohols having 1 to 6 carbon atoms. By using a mixed solvent containing 15% by weight, the above problems have been solved.
[0028]
The alcohol used in the present invention is preferably a linear or branched aliphatic alcohol having 1 to 6 carbon atoms, particularly preferably a linear or branched aliphatic alcohol having 1 to 4 carbon atoms, specifically Examples include methanol, ethanol, isopropanol, and tertiary butanol. Higher alcohols having more than 6 carbon atoms are not preferred because they have a high boiling point and are likely to remain after film formation. These alcohols may be added alone or in combination of two or more.
[0029]
The alcohol content in the solvent in the present invention is 1 to 15% by weight, more preferably 2 to 10% by weight, and particularly preferably 4 to 10% by weight. If the content exceeds 15% by weight, the solubility of the resin composition comprising a maleimide / olefin copolymer and an acrylonitrile / styrene copolymer in a solvent is lowered, resulting in problems such as clouding of the dope. If it is less than%, the effect of improving the stability of the dope becomes poor. On the other hand, the methylene chloride content in the solvent is 99 to 85% by weight. When the content is less than 70% by weight, the resin composition comprising the maleimide / olefin copolymer and the acrylonitrile / styrene copolymer is dissolved in the solvent. This is not preferable because the properties are lowered.
[0030]
In addition, the solvent used in the present invention is a resin composition having a solubility in a solvent or a dope for the purpose of improving the surface property of a film formed by the solution casting method, adjusting the evaporation rate of the solvent or the viscosity of the dope. Solvents other than methylene chloride and alcohol can be included as long as stability is not sacrificed. Examples of solvents other than methylene chloride and alcohol include halogen solvents such as chloroform, 1,2-dichloroethane, 1,1,2-trichloroethane, chlorobenzene, dichlorobenzene, 1,3-dioxolane, 1,4-dioxane, tetrahydrofuran and the like. Cyclic ether solvents such as cyclohexanone, ketone solvents such as methyl ethyl ketone and acetone, ester solvents such as isopropyl acetate and ethyl acetate, aromatic solvents such as benzene, toluene and xylene, n-hexane, n-heptane, n- Aliphatic solvents such as butane, N-methylpyrrolidone, dimethylformamide and the like can be mentioned.
[0031]
The solution in the present invention is a solution comprising 10 to 40% by weight of a resin composition comprising a maleimide / olefin copolymer and an acrylonitrile / styrene copolymer, and 90 to 60% by weight of a solvent, more preferably maleimide / olefin. The resin composition consisting of a copolymer and an acrylonitrile / styrene copolymer is 15 to 30% by weight, and the solvent is 85 to 70% by weight. When the content of the resin composition in the solution exceeds 40% by weight, there is a problem that the solubility in the solvent is lowered and the stability of the dope becomes poor. On the other hand, when the content of the resin composition in the solution is less than 10% by weight, the dope stability is not a problem, but when the film is formed by the solution casting method, the surface smoothness of the film becomes insufficient. There is a problem that the thickness accuracy cannot be obtained.
[0032]
The method for preparing the solution in the present invention is not particularly limited. For example, a method of adding a predetermined amount of a solvent such as alcohol to a resin composition solution dissolved in methylene chloride, or methylene chloride, alcohol, etc. Examples thereof include a method of preparing a solution by adding a resin composition to a mixed solvent to be contained.
[0033]
In the present invention, after the dope is cast on a support substrate, the solvent is evaporated by heating to obtain a film. In general, a T-die method, a doctor blade method, a bar coater method, a roll coater method, a lip coater method or the like is used as a casting method. Industrially, the most common method is to continuously extrude a dope from a die onto a belt-like or drum-like support substrate. Examples of the support substrate used include a glass substrate, a metal substrate such as stainless steel and ferrotype, and a plastic substrate such as polyethylene terephthalate. In order to industrially continuously form a film having a high surface property and optical homogeneity, a metal substrate having a mirror-finished surface is most commonly used.
[0034]
In the solution casting method, the solution viscosity is an extremely important factor for the purpose of forming a film having high transparency and excellent thickness accuracy and surface smoothness. Although the solution viscosity depends on the polymer concentration, molecular weight and the type of solvent, the viscosity of the solution of the present invention is preferably 700 to 30000 cps, more preferably 1000 to 10000 cps. When the solution viscosity is out of the range of 700 to 30000 cps, it is difficult to obtain the surface smoothness and thickness accuracy of the film.
[0035]
The thickness of the film of this invention is 10-500 micrometers, More preferably, it is the range of 20-200 micrometers. When the film thickness is less than 10 μm, the mechanical properties are deteriorated. When it exceeds 500 μm, it takes a long time to remove the solvent and the productivity is lowered, which is not preferable.
[0036]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to an Example.
[0037]
Various physical properties shown in the examples were measured by the following methods.
[0038]
Molecular weight: It calculated | required by polystyrene conversion using the gel permeation chromatography (GPC, the Tosoh Corporation make HLC-802A).
[0039]
Composition ratio: mainly determined by elemental analysis and ¹ H-NMR measurement.
[0040]
Total light transmittance: The total light transmittance at the center of the film was measured using an ultraviolet-visible spectrometer (V530) manufactured by JASCO Corporation.
[0041]
Surface smoothness: A center line average roughness (Ra) was determined using a laser microscope (VK-8550) manufactured by Keyence Corporation, and the surface smoothness was evaluated based on this value.
[0042]
Synthesis Example Synthesis of Maleimide / Olefin Copolymer In a 30 L autoclave equipped with a stirrer, nitrogen introduction tube, thermometer and deaeration tube, 1.2 kg of N-methylmaleimide, 8 g of t-butylperoxyneodecanoate and toluene and methanol Was added with 15 L of a mixed solvent (1: 1 weight ratio) and purged several times with nitrogen, and then 8.5 L of isobutene was charged and reacted at 60 ° C. for 6 hours. The resulting particles were centrifuged and dried. The yield was 1.7 kg.
[0043]
From the results of elemental analysis of the obtained polymer (C; 64.7% by weight, H; 7.8% by weight, N; 8.4% by weight), the maleimide unit and the isobutene unit in the produced polymer were each 50 mol%. Met. The obtained polymer had a number average molecular weight (Mn) of 95,000.
[0044]
Examples 1-2 and Comparative Examples 1-2
The N-methylmaleimide / isobutene copolymer synthesized in the synthesis example and the acrylonitrile / styrene copolymer having an acrylonitrile content of 30% by weight were dry blended at a weight ratio of 80:20, and then a 30 mmφ twin screw extruder (Corporation) The product was melt kneaded and pelletized. And the above-mentioned pellet was melt | dissolved in the mixed solvent of the methylene chloride and alcohol shown in Table 1 so that content in a solution might be 20 weight%, and dope was obtained. The dope in the case of using a solvent containing alcohol in the range of 1 to 15% by weight was uniformly transparent. The obtained dope was allowed to stand and observed for 4 days, but no change was observed in the dope. On the other hand, when no alcohol was added, it was uniform and transparent immediately after the dope preparation, but a jelly-like solidified product was generated after 4 days from standing. Moreover, when alcohol was added exceeding the range of 1-15 weight%, the turbidity was recognized immediately after dope preparation. Table 1 shows the state of the dope immediately after the dope production and after standing for 4 days. Next, using the dope after standing for 4 days, it was cast on a support of a solution casting apparatus by the T-die method, and after drying, a film having a width of 300 mm was obtained. And the formed film was cut | judged to the square of 200 mm piece, and the total light transmittance and Ra were measured. The results are shown in Table 1.
[0045]
[Table 1]

Examples 3-4, Comparative Example 3
The pelletized resin composition was obtained in the same manner as in Examples 1-2 and Comparative Examples 1-2. And the above-mentioned pellet was melt | dissolved in the mixed solvent of the methylene chloride and alcohol shown in Table 2 so that content in a solution might be 20 weight%, and dope was obtained. Table 2 shows the state of the dope immediately after the dope production and after standing for 4 days. Next, using the dope after standing for 4 days, a film was formed and cut in the same manner as in Examples 1 and 2 and Comparative Examples 1 and 2 to obtain a square film test piece of 200 mm piece. The results of measuring the total light transmittance and Ra of the film are shown in Table 2.
[0046]
[Table 2]

Comparative Examples 4-5
The pelletized resin composition was obtained in the same manner as in Examples 1-2 and Comparative Examples 1-2. And the above-mentioned pellet was melt | dissolved in the mixed solvent of the methylene chloride and alcohol shown in Table 3 so that it might become content in the solution shown in Table 3, and dope was obtained. Table 3 shows the state of the dope immediately after the dope production and after standing for 4 days. Next, using the dope after standing for 4 days, a film was formed and cut in the same manner as in Examples 1 and 2 and Comparative Examples 1 and 2 to obtain a square film test piece of 200 mm piece. The results of measuring the total light transmittance and Ra of the film are shown in Table 3.
[0047]
[Table 3]

Examples 5-6
The pelletized resin composition was obtained in the same manner as in Examples 1-2 and Comparative Examples 1-2. And the above-mentioned pellet was melt | dissolved in the mixed solvent shown in Table 4 so that content in a solution might be 20 weight%, and dope was obtained. Table 4 shows the state of the dope immediately after the dope production and after standing for 4 days. Next, using the dope after standing for 4 days, a film was formed and cut in the same manner as in Examples 1 and 2 and Comparative Examples 1 and 2 to obtain a square film test piece of 200 mm piece. The results of measuring the total light transmittance and Ra of the film are shown in Table 4.
[0048]
[Table 4]

【The invention's effect】
According to the method for producing a transparent film of the present invention, a transparent film for a flat panel display, for example, a polarizer protective film, a retardation film, a viewing angle compensation film, a transparent electrode film, a light diffusion film, a light reflection film, It becomes possible to produce a transparent film that can be used for an electromagnetic wave shielding film and a display surface protective film.

Claims (1)

a) Maleimide / olefin copolymer having 40 to 60 mol% of the following component (I) and 60 to 40 mol% of the component (II) and having a number average molecular weight of 1 × 10 ³ or more and 5 × 10 ⁶ or less A solution comprising 10 to 40% by weight of a resin composition comprising 99 to 1% by weight of an acrylonitrile / styrene copolymer containing 21 to 45% by weight of an acrylonitrile unit and 90 to 60% by weight of a solvent. Is cast on a support substrate, and the solvent is evaporated from the cast film containing the solvent, wherein the solvent contains 99 to 85 % by weight of methylene chloride, and A method for producing a transparent film comprising 1 to 15% by weight of a linear or branched aliphatic alcohol having 1 to 6 carbon atoms.

(R ¹ represents hydrogen or an alkyl group having 1 to 6 carbon atoms)

(R ² and R ³ each represent hydrogen or an alkyl group having 1 to 6 carbon atoms)