JP2005023217A - Polybenzazole film and method for forming the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prepare a polybenzazole film having an excellent mechanical strength, good in balance of mechanical physical properties in longitudinal and transverse directions and further having resistance to interlayer separation, being applied to a wide range of fields. <P>SOLUTION: The polybenzazole film is obtained by film formation using a polybenzazole polymer solution having optical isotropy, wherein the following formulae (1)-(6) are satisfied: (1) a tensile modulus in the longitudinal and transverse directions is ≥5.0 GPa; (2) tensile strength in the longitudinal and transverse directions is ≥100 MPa; (3) elongation at break in the longitudinal and transverse directions is ≥10%; (4) (the transverse tensile modulus)/(the longitudinal tensile modulus) is ≥0.85 and ≤1.20; (5) (the transverse tensile strength)/(the longitudinal tensile strength) is ≥0.85 and ≤1.20; and (6) (the transverse elongation at break)/(the longitudinal elongation at break) is ≥0.85 and ≤1.20. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００１４】
ここで、Ａｒ_１，Ａｒ_２，Ａｒ_３は、芳香族単位を示し、各種脂肪族基、芳香族基、ハロゲン基、水酸基、ニトロ基、シアノ基、トリフルオロメチル基等の置換基を有していても良い。これら芳香族単位は、ベンゼン環などの単環系単位、ナフタレン、アントラセン、ピレンなどの縮合環系単位、それらの芳香族単位が２個以上任意の結合を介してつながった多環系芳香族単位でも良い。また、芳香族単位におけるＮおよびＸの位置はベンザゾール環を形成できる配置であれば特に限定されるものではない。さらに、これらは炭化水素系芳香族単位だけでなく、芳香環内にＮ，Ｏ，Ｓ等を含んだヘテロ環系芳香族単位でも良い。ＸはＯ，Ｓ，ＮＨを示す。
上記Ａｒ_１は、下記一般式で表されるものが好ましい。
【００１５】
【化２】

【００１６】
ここで、Ｙ_１、Ｙ_２はＣＨまたはＮを示し、Ｚは直接結合、−Ｏ−，−Ｓ−，−ＳＯ_２−，−Ｃ（ＣＨ_３）_２−，−Ｃ（ＣＦ_３）_２−，−ＣＯ−を示す。
Ａｒ_２は、下記一般式で表されるものが好ましい。
【００１７】
【化３】

【００１８】
ここで、Ｗは−Ｏ−，−Ｓ−，−ＳＯ_２−，−Ｃ（ＣＨ_３）_２−，−Ｃ（ＣＨ_３）_２−，−ＣＯ−を示す。
Ａｒ_３は、下記一般式で表されるものが好ましい。
【００１９】
【化４】

【００２０】
これらポリベンザゾール系ポリマーは、上述の繰り返し単位を有するホモポリマーであっても良いが、上記構造単位を組み合わせたランダム、交互あるいはブロック共重合体であっても良く、例えば米国特許第４７０３１０３号、米国特許第４５３３６９２号、米国特許第４５３３７２４号、米国特許第４５３３６９３号、米国特許第４５３９５６７号、米国特許第４５７８４３２号等に記載されたものなども例示される。
【００２１】
これらポリベンザゾール系構成単位の具体例としては、下記構造式で表すものを例示することができる。
【００２２】
【化５】

【００２３】
【化６】

【００２４】
【化７】

【００２５】
【化８】

【００２６】
【化９】

【００２７】
【化１０】

【００２８】
【化１１】

【００２９】
さらに、これらポリベンザゾール系構成単位だけでなく、他のポリマー構成単位とのランダム、交互あるいはブロック共重合体であっても良い。この時、他のポリマー構成単位としては耐熱性に優れた芳香族系ポリマー構成単位から選ばれることが好ましい。具体的には、ポリイミド系構成単位、ポリアミド系構成単位、ポリアミドイミド系構成単位、ポリオキシジアゾール系構成単位、ポリアゾメチン系構成単位、ポリベンザゾールイミド系構成単位、ポリエーテルケトン系構成単位、ポリエーテルスルホン系構成単位などを挙げることができる。
【００３０】
ポリイミド系構成単位の例としては、下記一般式で表されるものが挙げられる。
【００３１】
【化１２】

【００３２】
ここで、Ａｒ_４は４価の芳香族単位で表されるが、下記構造で表されるものが好ましい。
【００３３】
【化１３】

【００３４】
また、Ａｒ_５は二価の芳香族単位であり、下記構造で表されるものが好ましい。ここで示される芳香環上には、メチル基、メトキシ基、ハロゲン基、トリフルオロメチル基、水酸基、ニトロ基、シアノ基等の各種置換基が存在していても良い。
【００３５】
【化１４】

【００３６】
これらポリイミド系構成単位の具体例としては、下記構造式で表すものを例示することができる。
【００３７】
【化１５】

【００３８】
【化１６】

【００３９】
ポリアミド系構成単位の例としては、下記構造式で表されるのもが挙げられる。
【００４０】
【化１７】

【００４１】
ここで、Ａｒ_６，Ａｒ_７，Ａｒ_８はそれぞれ独立に下記構造から選ばれるものが好ましい。ここで示される芳香環上には、メチル基、メトキシ基、ハロゲン基、トリフルオロメチル基、水酸基、ニトロ基、シアノ基等の各種置換基が存在していても良い。
【００４２】
【化１８】

【００４３】
これらポリアミド系構成単位の具体例としては、下記構造式で表すものを例示することができる。
【００４４】
【化１９】

【００４５】
ポリアミドイミド系構成単位の例としては、下記構造で表されるものが挙げられる。
【００４６】
【化２０】

【００４７】
ここで、Ａｒ_９は上記Ａｒ_５の具体例として示される構造から選ばれるものが好ましい。
【００４８】
これらポリアミドイミド構成単位の具体例としては、下記構造式で表すものを例示することができる。
【００４９】
【化２１】

【００５０】
ポリオキシジアゾール系構成単位の例としては、下記構造式で表されるものが挙げられる。
【００５１】
【化２２】

【００５２】
ここで、Ａｒ_１０は上記Ａｒ_５の具体例として示される構造から選ばれるものが好ましい。
【００５３】
これらポリオキシジアゾール系構成単位の具体例としては、下記構造式で表すものを例示することができる。
【００５４】
【化２３】

【００５５】
ポリアゾメチン系構成単位の例としては、下記構造で表されるものが挙げられる。
【００５６】
【化２４】

【００５７】
ここで、Ａｒ_１１，Ａｒ_１２は、上記Ａｒ_６の具体例として示される構造から選ばれるものが好ましい。
【００５８】
これらポリアゾメチン系構成単位の具体例としては、下記構造式で表すものを例示することができる。
【００５９】
【化２５】

【００６０】
ポリベンザゾールイミド系構成単位の例としては、下記構造式で表されるものが挙げられる。
【００６１】
【化２６】

【００６２】
ここで、Ａｒ_１３、Ａｒ_１４は上記Ａｒ_４の具体例として示される構造から選ばれるものが好ましい。
【００６３】
これらポリベンザゾールイミド系構成単位の具体例としては、下記構造式で表すものを例示することができる。
【００６４】
【化２７】

【００６５】
ポリエーテルケトン系構成単位、ポリエーテルスルホン系構成単位は、一般に芳香族ユニットをエーテル結合とともにケトン結合やスルホン結合で連結した構造を有するものであり、下記構造式から選択される構造成分を含む。
【００６６】
【化２８】

【００６７】
ここで、Ａｒ_１５〜Ａｒ_２３はそれぞれ独立に下記構造で表されるものが好ましい。ここで示される芳香環上には、メチル基、メトキシ基、ハロゲン基、トリフルオロメチル基、水酸基、ニトロ基、シアノ基等の各種置換基が存在していても良い。
【００６８】
【化２９】

【００６９】
これらポリエーテルケトン系構成単位の具体例としては、下記構造式で表すものを例示することができる。
【００７０】
【化３０】

【００７１】
これらポリベンザゾール系ポリマー構成単位と共に共重合できる芳香族ポリマー構成単位は、厳密にポリマー鎖内の繰り返し単位を指しているのではなく、ポリマー主鎖中にポリベンザゾール系構成単位と共に存在できる構成単位を示しているものである。これら共重合できる芳香族ポリマー構成単位は一種だけでなく二種以上を組み合わせて共重合することもできる。このような共重合体を合成するには、ポリベンザゾール系ポリマー構成単位からなるユニット末端にアミノ基、カルボキシル基、水酸基、ハロゲン基等を導入して、これらの芳香族系ポリマーの合成における反応成分として重合しても良いし、これらの芳香族系ポリマー構成単位を含むユニット末端にカルボキシル基を導入してポリベンザゾール系ポリマーの合成における反応成分として重合しても良い。
【００７２】
本発明においては上記したポリベンザゾール系ポリマーが８０重量％以上を含有することが好ましく、２０重量％未満は他のポリマー、例えば芳香族ポリイミド等を含有してもよい。より機械的特性に優れるポリベンザゾール系フィルムを得る為には、ポリベンザゾール系ポリマーの含量は９０重量％以上が望ましい。
【００７３】
本発明においては、請求項２に記載のごとく、前記したポリベンザゾール系ポリマーがポリパラフェニレンビスベンゾオキサゾールであることが好ましい実施態様である。該ポリマーにすることで優れた耐熱性と機械的物性が得られる。
【００７４】
本発明のポリベンザゾール系フィルムは、（１）〜（６）式を満たすことを特徴とするポリベンザゾール系フィルムである。
（１）長手方向および幅方向の引張弾性率≧５．０ＧＰａ、
（２）長手方向および幅方向の引張強度≧１００ＭＰａ、
（３）長手方向および幅方向の破断伸度≧１０％、
（４）０．８５≦（幅方向の引張弾性率）／（長手方向の引張弾性率）≦１．２０、
（５）０．８５≦（幅方向の引張強度）／（長手方向の引張強度）≦１．２０、
（６）０．８５≦（幅方向の破断伸度）／（長手方向の破断伸度）≦１．２０。
【００７５】
引張弾性率が５．０ＧＰａ未満であると後加工時や使用される際の巻き取り時の高張力や張力でフィルム変形が生じ好ましくなく、さらに製膜時の薄膜化が困難となる。本発明のポリオベンザゾール系フィルムの引張弾性率はより好ましくは６．０ＧＰａ以上である。さらに、引張強度が１００ＭＰａ未満の場合は高張力化で後加工した場合、フィルムの破断の原因となり好ましくない。また、破断伸度は１０％以上が好ましい。伸度がこれ未満である場合、加工時のハンドリングが困難になるのみならず、使用時にフィルムが脆くなり好ましくない。
【００７６】
また、本発明のポリベンザゾール系フィルムは長手方向の引張弾性率、破断強度および破断伸度と幅方向の引張弾性率、破断強度および破断伸度との関係が下記（４）〜（６）式を同時に満足する必要がある。上記の（４）〜（６）式を同時に満足することにより、フイルムの長手方向と幅方向の機械的物性値のバランスが取れるので、特定方向に裂け易いという従来公知の製造法で得られるフィルムの持っていた欠点を改善でき、各種用途に好適に展開することができる。
【００７７】
本発明においては、前記した特性を発現するには請求項３に記載のごとく、光学的に等方性のポリベンザゾール系ポリマー溶液を用いて製膜する必要がある。該方法により製膜することにより、光学的異方性のポリベンザゾール系ポリマー溶液を用いて製膜した場合に発生する流動方向にポリマー分子鎖が配向し、この分子鎖の配向により発現されるフィルムのフィルムの長手方向と幅方向との機械的物性バランスが崩れるという従来公知技術の欠点が改善される。
【００７８】
また、従来公知の光学的に異方性を示す液晶状態の溶液より製膜することにより得たフィルムはポリマー鎖が面配向しやすく得られるフィルムは厚み方向に層間剥離しやすくなるという欠点を有するが、前記した本発明の方法により得たフィルムは本欠点についても改善される。
【００７９】
ポリベンザゾール系溶液が光学的に等方性であるかどうかの確認は、該溶液をスライドガラス上に薄く延ばしカバーガラスで挟んだプレパラートを偏光顕微鏡により直交ニコル下での観察することにより行う。すなち、光学的に異方性を示す液晶状態であれば、サンプルステージを回転させると液晶構造に由来するドメイン構造が観察され明視野となるが、光学的に等方性な溶液であればサンプルステージを回転させても暗視野のままであり、両者違いを区別することができる。
【００８０】
本発明においては、ポリベンザゾール系フィルムは前記した光学的に等方性を示す溶液から薄膜状に成形し、次いで凝固、洗浄および乾燥等の工程により製膜される。薄膜状に成形する工程おいては、Ｔダイ方式やサーキュラーダイ方式等公知の方法により成形することができるが、押出し時のフィルム長手方向の分子配向を軽減し長手方向と幅方向の機械的物性のバランスをとる上で本発明では以下の方法がより好ましい。
【００８１】
すなわち、少なくとも二枚の支持体の間に挟んだ光学的に等方性を示すポリベンザゾール系溶液を対向ロール、圧延装置あるいはプレス装置等を介して支持体／ポリベンザゾール系溶液／支持体のサンドイッチ状の複合積層体に形成する。
得られたサンドイッチ状の複合積層体は凝固浴に導かれ、凝固浴中で支持体を剥離、凝固させることを特徴とするものである。対向ロール、圧延装置およびプレス装置等の構成および配置はさまざまな組合わせをとることができる。望ましくは、少なくとも二枚の支持体の間に挟んだ光学的に等方性を示すポリベンザゾール系溶液を、少なくとも一対の対向ロールにはさみ、向かい合ったロールを反対方向に回転させ、支持体／ポリベンザゾール系溶液／支持体のサンドイッチ状の複合積層体を形成する方式である。得られた支持体／ポリベンザゾール系溶液／支持体のサンドイッチ状の複合積層体は、ガイドロール等を経て凝固浴に導かれ、凝固浴中で支持体を剥離することにより、該ポリベンザゾール系溶液は凝固される。上記支持体としてはＰＥＴフィルムに代表されるポリエステル系フィルムやポリプロピレン（ＰＰともいう）フィルムなどのポリオレフィン系フィルム等のプラスチックフィルムを用いることが出来る。さらに支持体として透湿性を有する多孔質フィルムや布帛、不織布をそのまま、あるいは上記プラスチックフィルム支持体と併用してもよい。プラスチックフィルムを支持体とした場合は支持体剥離後の凝固時間が、多孔質フィルムを単独で支持体とした場合では上記サンドイッチ状の複合積層体を凝固浴に浸漬後支持体剥離までの時間および支持体剥離後の凝固浴浸漬時間が得られる凝固湿潤フィルムの膜構造および物性に影響し重要である。
【００８２】
本発明においては、前記した光学的に等方性の溶液を得るためには、請求項５に記載のごとく、ポリベンザゾール系ポリマーの濃度を５重量％以下にするのが好ましい。より好ましくは３重量％以下である。一方、０．３重量％以下の濃度では、ポリマー溶液の粘度が小さくなり、適用できる製膜方法が限られるほか、得られるポリベンザゾール系フィルムの引張り弾性率や破断強度及び破断伸度等の機械的物性が小さくなるため好ましくない。経済的にも不利になる。０．５重量％以上がより好ましい。溶液濃度が５重量％を超えると溶液の光学的な異方性が発現し易くなり、かつ溶液粘度が増大し成形性が困難となる。
【００８３】
ポリベンザゾール系ポリマー溶液の濃度を上記で示したような範囲に調整するには次に示すような方法をとる事ができる。すなわち、重合されたポリベンザゾール系ポリマー溶液から一旦ポリマー固体を分離し、再度溶媒を加えて溶解することで濃度調整を行なう方法。さらには、ポリ燐酸中で縮合重合されたままのポリマー溶液からポリマー固体を分離することなく、そのポリマー溶液に溶媒を加えて希釈し、濃度調整を行なう方法。さらにはポリマーの重合組成を調整することで上記濃度範囲のポリマー溶液を直接得る方法などである。
【００８４】
ポリマー溶液の濃度調整に用いるのに好ましい溶媒としては、メタンスルホン酸、ジメチル硫酸、ポリ燐酸、硫酸、トリフルオロ酢酸などがあげられ、あるいはこれらの溶媒を組み合わせた混合溶媒を用いることもできる。中でも特にメタンスルホン酸、ポリリン酸が好ましい。
【００８５】
本発明のポリベンザゾール系フィルムを得る為に用いられる、前記ポリベンザゾール系ポリマー溶液中のポリマーの重合度は極限粘度で表される。この極限粘度は１５ｄｌ／ｇ以上３５ｄｌ／ｇ以下が好ましく、２０ｄｌ／ｇ以上３０ｄｌ／ｇ以下であることがより好ましい。この範囲未満では、得られるポリベンザゾール系フィルムの力学物性が低下し、またこの範囲を越えると、溶液の粘度が高く加工困難となる。
【００８６】
上記の凝固液としては前記した溶液を形成する溶媒と相溶し、かつポリマーの貧溶媒であるものであれば限定されず任意であるが、例えば、水、金属塩水溶液、多価アルコール、非プロトン性極性溶媒、プロトン性極性溶媒等が挙げられる。
【００８７】
本発明おける凝固条件は均質な、優れた機械的強度、平滑性および耐層間剥離性を兼ね備えたポリベンザゾール系フィルムを得るために特に重要である。具体的には、凝固液温度を高くし、凝固液濃度を高くすることが重要であり、これによりボイド（微細な気泡）構造の少ない均質な、優れた耐熱性、機械的強度、および耐層間剥離性を兼ね備えたポリベンザゾール系フィルム得られる。しかしながら、凝固液温度および凝固液濃度を高くしすぎると、凝固性が低下しハンドリング性が低下するのみならず所望の物性が得られない。凝固液の温度は１０℃以上７０℃以下が好ましい。さらに好ましくは２０℃以上６０℃以下である。
【００８８】
凝固液として金属塩水溶液を用いる場合、水に対する飽和溶解度の半分の濃度から飽和溶解度の濃度の金属塩水溶液を用いることが好ましい。特にボイド（微細な気泡）構造の少なく均一で優れた耐熱性、機械的強度、および耐層間剥離性を兼ね備えたポリベンザゾール系フィルムを得るためには、凝固液として金属塩水溶液を用いることが好適である。金属塩の種類は多数挙げられるが、リチウム、ナトリウム、マグネシウム、カルシウム、アルミニウム、バリウム、ストロンチウム、ガリウム、インジウム、クロム、鉄、コバルト、ニッケル、マンガン等水和数の多い金属種がより好ましい。
【００８９】
多価アルコールとしてはエチレングリコール、ジエチレングリコール、トリエチレングリコール、テトラエチレングリコール、ポリエチレングリコール、グリセリン等が挙げられる。多価アルコール／水は重量比で１０／９０から１００／０の割合でもちいるのが好ましい。さらに好ましくは３０／７０から８０／２０である。
【００９０】
非プロトン性極性溶媒としては、Ｎ−メチルピロリドン、γ−ブチロラクトン、ジメチルホルムアミド、ジメチルアセトアミド、ジメチルスルホキシド等が挙げられる。非プロトン性極性溶媒／水は重量比で１０／９０から１００／０の割合でもちいるのが好ましい。さらに好ましくは３０／７０から８０／２０である。さらには、ポリベンザゾール系ポリマー溶液を支持体に塗布し、空気中、水蒸気中および制御された雰囲気下暴露により凝固させてもよい。これらは凝固プロセスの一例であり、他の条件によっても凝固させることができる。
【００９１】
凝固されたフィルムはポリマー溶液の溶媒である酸等を含むため、酸の洗浄、除去をおこなう必要がある。洗浄液は通常、水が用いられるが、必要に応じて温水で行ったり、アルカリ水溶液で中和洗浄した後、水等で洗浄してもよい。洗浄は、例えば洗浄液中でフィルムを走行させたり、洗浄液を噴霧する等の方法がある。
【００９２】
本発明における乾燥工程とは、緊張下、定張下フィルムの収縮を制限して行うことが望ましい。自由収縮で乾燥させた場合には、部分収縮がおこるため厚み斑となったり、さらにはフィルムの平面性が損なわれる場合がある。収縮を制限しつつ乾燥するには、例えばテンター乾燥機や金属枠に挟んでの乾燥などをおこなうことができる。乾燥に懸かる他の条件は特に制限されるものではなく、空気、窒素などの加熱気体や常温気体を用いた乾燥方法や、ヒーターや赤外線ランプを用いた乾燥方法等が挙げられる。
【００９３】
フィルム状に成形する工程、凝固工程、洗浄工程および乾燥工程等は連続的に行ってもよく、また、バッチ式で行ってもよい。さらに各工程の間に、その他の特別な工程を加えてもよい。
【００９４】
本発明で用いられるポリベンザゾール系フィルムは、磁気記録層や金属蒸着層などとの接着力を上げるために、アンカー剤を塗布したり、ケミカルエッチング処理、コロナ処理、プラズマ処理などを行ってもよい。
【００９５】
本発明のフィルムには公知の添加剤、たとえば、紫外線吸収剤、熱安定剤、延伸助剤、滑剤などが添加されていてもよい。
【００９６】
【実施例】
以下、本発明の内容および効果を実施例によって説明するが、本発明は、その要旨を逸脱しない限り以下の実施例に限定されるものではない。なお、以下の実施例における物性の評価方法は以下の通りである。
【００９７】
１．極限粘度
メタンスルホン酸を溶媒として、０．５ｇ／ｌの濃度に調整したポリマー溶液の粘度をオストワルド粘度計を用いて３０℃恒温槽中で測定し、算出した。
【００９８】
２．ポリマー溶液の光学的等方性評価
溶液をスライドガラス上にのせカバーガラスで挟み薄く伸ばしたものを、偏光顕微鏡を用いた直交ニコル下の観察することによりおこなった。サンプルステージを回転させても暗視野であり、ドメイン構造が観察されない場合を、光学的に等方性な溶液であると判断した。
【００９９】
３．引張弾性率、引張強度及び破断伸度
乾燥後のフィルムを長手方向（ＭＤ方向）および幅方向（ＴＤ方向）にそれぞれ長さ１００ｍｍ、幅１０ｍｍの短冊状に切り出して試験片とし、引張試験機（島津製作所製オートグラフ（Ｒ） 機種名ＡＧ−５０００Ａ）を用い、引張速度５０ｍｍ／分、チャック間距離４０ｍｍで測定し、引張弾性率、引張強度及び破断伸度を求めた。
【０１００】
４．層間剥離試験
乾燥後のフィルムを長手方向（ＭＤ方向）および幅方向（ＴＤ方向）にそれぞれ長さ２０ｍｍ、幅１０ｍｍの短冊状に切り出して試験片とし、フィルムの表裏面に、粘着テープ（ニチバン製 セロテープ（Ｒ） ＣＴ４０５）の接着面を張り合わせた。５）の接着面を張り合わせた。引張試験機（島津製作所製オートグラフ（Ｒ） 機種名ＡＧ−５０００Ａ）を用い、引張速度５０ｍｍ／分、チャック間距離４０ｍｍで、テープをはがし、両方の粘着テープの粘着面に破壊したフィルムが移行する層間剥離現象の有無を調べた。詳細図を図１に示す。
【０１０１】
（実施例１）
ポリ燐酸中で重合することにより得た極限粘度ＩＶ＝２５ｄＬ／ｇのポリパラフェニレンシスベンゾビスオキサゾールポリマー（ＰＢＯともいう）を１４重量％含んだポリマー溶液にメタンスルホン酸を加えて希釈し、ＰＢＯ濃度１．０重量％の製膜用ポリマー溶液を調製した。この製膜用ポリマー溶液は光学的に等方性を示した。さらにこの溶液を５０℃に加熱し公称目開き２０μｍフィルターを通してから、図２に示すように配置した２枚のＰＥＴフィルム支持体（１８８μｍの二軸延伸フィルム）に挟んで５０℃に加熱した１対の対向ロール上に供給した。対向ロールは周速０．３ｍ／分で回転させ、支持体／ＰＢＯ溶液／支持体のサンドイッチ状の複合積層体を形成した。対向ロールのギャップは乾燥ＰＢＯ膜の厚みが５μｍ程度になるようシックネスゲージを用いて調整した。このようにして得られる複合積層体は連続的に凝固浴中に導かれ、凝固浴中で支持体を連続剥離し凝固させた。この際、凝固液は５０℃の４．５ｍｏｌ／ｌ塩化マグネシウム水溶液とした。また、支持体を剥離させてからの凝固浴中でのＰＢＯフィルムの滞留時間（凝固時間）は約２分とした。凝固したＰＢＯフィルムは０．３１ｍ／分の速さで巻き上げた。さたに凝固させたフィルムを十分に水洗した後にテンターで両端を把持しつつ１５０℃で３０秒間熱固定して厚み５．５μｍのポリベンザゾールフィルムを得た。
【０１０２】
（実施例２）
凝固液として２５℃に保った水を用いる以外は、実施例１と同じ方法で厚み５．０μｍのＰＢＯフィルムを得た。
【０１０３】
（比較例１）
実施例１の方法において、メタンスルホン酸による希釈度を変更しＰＢＯポリマー濃度を８．０重量％の製膜用ポリマー溶液を得た。得られた製膜用ポリマー溶液は光学的に異方性を有していた。該製膜用ポリマー溶液を用い、Ｔダイよりの押し出し温度を８０℃に変更する以外は、実施例１と同様にして厚み６．０μｍのポリベンザゾールフィルムを得た。
【０１０４】
実施例１、２および比較例１で得られたＰＢＯフィルムの測定結果を表１に示した。
【０１０５】
【表１】

【０１０６】
【発明の効果】
本発明により得られるポリベンザゾール系フィルムは、優れた機械的強度とフィルム長手方向と幅方向との機械的物性バランスが良くさらに、耐層間剥離性を兼ね備えたポリベンザゾールフィルムであり、広範囲の分野において使用することができる。また、本発明の製造法により前記した特性のフイルムが経済的に製造することができる。
【図面の簡単な説明】
【図１】フィルムの層間剥離試験の模式図
【図２】本発明のポリベンザゾール系フィルム製造法の模式図
【符号の説明】
１：溶液供給配管
２：溶液
３：支持体１
４：支持体２
５：支持体１送り出しロール
６：支持体２送り出しロール
７：対向ロール
８：支持体／溶液／支持体複合積層体
９：ポリベンザゾール系湿潤フィルム
１０：ポリベンザゾール系湿潤フィルム巻き上げロール
１１：支持体２巻き上げロール
１２：支持体１巻き上げロール
１３：凝固浴[0001]
BACKGROUND OF THE INVENTION
The present invention relates to providing a polybenzazole film excellent in mechanical properties and a balance between mechanical properties in the longitudinal direction and the width direction and free from delamination and a method for producing the same.
[0002]
[Prior art]
In order to obtain a rigid polymer film such as polybenzazole, the melting point is very high and the decomposition temperature is very close to the melting point, so-called melt film forming technique cannot be used. Therefore, in order to obtain a film from these rigid polymers, a solution casting technique is generally used.
[0003]
On the other hand, a high-concentration solution of a rigid polymer tends to form a liquid crystal phase having optical anisotropy. Such a rigid polymer solution has a problem that, since the molecular chains are easily oriented in the flow direction, it takes time until the molecular chains change to a random direction once the molecular chains are arranged. Therefore, a so-called casting method as described in US Pat. No. 4,487,735 is known as a method for processing into a film. In this film forming method, the polymer solution is extruded, and the difference in mechanical properties between the stretched direction and the perpendicular direction is large, and this is to be improved. However, Robert R. As described in Chapter 3 of "Application of High Temperature Polymers" CRC Press 1997, edited by Luise, the molecules are arranged in the discharge direction and the drawdown direction. was there. Therefore, in US Pat. No. 2,898,924, a technique for producing a thin film by biaxial stretching by a blow molding method, and in US Pat. No. 4,939,235, anisotropy of mechanical properties is achieved by orienting in the different directions on the front and back of the film. Attempts have been made to improve.
[0004]
However, when these rigid polymers are biaxially stretched or oriented in different directions on the front and back sides of the film as described above, the molecular chain tends to cause so-called in-plane orientation, and therefore delamination or brittleness occurs in the thickness direction of the film. There is a problem that destruction easily occurs.
[0005]
Each of the above methods focuses on the characteristic that the shear viscosity during processing is relatively low in a high concentration region where the solution of the rigid polymer exhibits optical anisotropy, ie, liquid crystallinity. When a film is formed with a solution exhibiting anisotropy, the mechanical properties of the film in the longitudinal direction (MD, film flow direction, machine direction) and the width direction (TD, direction perpendicular to MD, transverse direction) are balanced. Further, there is a problem of delamination in the film thickness direction already described. Japanese Patent Laid-Open No. 9-118758 discloses a method for solving the problem relating to the balance of mechanical properties, in which the process up to die extrusion is carried out in an optically anisotropic phase, and after die extrusion, the optically isotropic phase is changed by a composition change or temperature change A film-forming method for phase transition to is disclosed. Further, JP-A-2000-273214 discloses a method equivalent to the method disclosed in JP-A-9-118758, that is, a polybenzazole solution having optical anisotropy is cast on a support, and then optical In particular, a polybenzazole-based film having a high elastic modulus and an appropriate elongation obtained by changing the state to an isotropic state is disclosed.
[0006]
However, in any of the above methods, the film formed from the liquid crystalline anisotropic solution is likely to be uneven due to alignment spots derived from the polydomain structure of the liquid crystal phase, and delaminated in the film thickness direction. The problem is not solved. Furthermore, it cannot be said that the balance between mechanical properties in the longitudinal direction and the width direction has been sufficiently solved.
[0007]
In order to eliminate such drawbacks, it is necessary to process from a low-concentration solution, and a method of forming a low-concentration solution by spin coating has been attempted. For example, L.M. A. Cintavey et al., Journal of Applied Polymer Science, Vol. 76, pp 1448-1456 (2000), a polybenzazole thin film is formed on a silicon wafer by using a 0.5% polyparaphenylenebenzobisthiazole methanesulfonic acid solution, and its optical characteristics are described. However, in such a system, it is difficult to obtain a large amount of film at a time, which is not preferable from an industrial viewpoint.
[0008]
Polybenzazole has excellent heat resistance, high strength, high elastic modulus and low dielectric constant, so it can be used for magnetic tapes, flexible printed circuit board (FPC) base films, electrical insulation materials, speaker vibration plates, voice coil materials, etc. Applications are expected, and there is a strong demand for solutions to the problems described above.
[0009]
[Patent Document 1]
U.S. Pat. No. 4,487,735
[Patent Document 2]
U.S. Pat. No. 2,898,924
[Patent Document 3]
U.S. Pat. No. 4,939,235
[Patent Document 3]
JP-A-9-118758
[Patent Document 3]
Japanese Unexamined Patent Publication No. 2000-273214
[0010]
[Problems to be solved by the invention]
The present invention solves such problems, and provides a polybenzazole-based film having excellent mechanical properties and a balance between mechanical properties in the longitudinal direction and the width direction and having no delamination, and a method for producing the same. .
[0011]
[Means for Solving the Problems]
The polybenzazole film of the present invention is a polybenzazole film characterized by satisfying the formulas (1) to (6).
(1) Tensile elastic modulus in the longitudinal direction and the width direction ≧ 5.0 GPa,
(2) Tensile strength in the longitudinal direction and the width direction ≧ 100 MPa,
(3) Elongation at break in the longitudinal and width directions ≧ 10%,
(4) 0.85 ≦ (tensile modulus in the width direction) / (tensile modulus in the longitudinal direction) ≦ 1.20,
(5) 0.85 ≦ (tensile strength in the width direction) / (tensile strength in the longitudinal direction) ≦ 1.20,
(6) 0.85 ≦ (breaking elongation in the width direction) / (breaking elongation in the longitudinal direction) ≦ 1.20.
The method for producing a polybenzazole-based film of the present invention is characterized by being formed using an optically isotropic polybenzazole-based polymer solution.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The polybenzazole-based polymer in the present invention refers to a polymer having a structure containing an oxazo ring, a thiazole ring, and an imidazole ring in the polymer chain, and includes a repeating unit represented by the following general formula in the polymer chain.
[0013]
[Chemical 1]

[0014]
Where Ar ₁ , Ar ₂ , Ar ₃ Represents an aromatic unit and may have various aliphatic groups, aromatic groups, halogen groups, hydroxyl groups, nitro groups, cyano groups, trifluoromethyl groups and other substituents. These aromatic units are monocyclic units such as benzene rings, condensed ring units such as naphthalene, anthracene, and pyrene, and polycyclic aromatic units in which two or more of these aromatic units are connected via an arbitrary bond. But it ’s okay. Moreover, the position of N and X in an aromatic unit will not be specifically limited if it is the arrangement | positioning which can form a benzazole ring. Furthermore, these may be not only hydrocarbon aromatic units but also heterocyclic aromatic units containing N, O, S, etc. in the aromatic ring. X represents O, S, NH.
Ar ₁ Are preferably those represented by the following general formula.
[0015]
[Chemical 2]

[0016]
Where Y ₁ , Y ₂ Represents CH or N, Z represents a direct bond, —O—, —S—, —SO. ₂ -, -C (CH ₃ ) ₂ -, -C (CF ₃ ) ₂ -, -CO-.
Ar ₂ Are preferably those represented by the following general formula.
[0017]
[Chemical 3]

[0018]
Here, W is -O-, -S-, -SO. ₂ -, -C (CH ₃ ) ₂ -, -C (CH ₃ ) ₂ -, -CO-.
Ar ₃ Are preferably those represented by the following general formula.
[0019]
[Formula 4]

[0020]
These polybenzazole-based polymers may be homopolymers having the above-mentioned repeating units, but may be random, alternating or block copolymers in which the above structural units are combined. For example, US Pat. No. 4,703,103, Examples thereof include those described in US Pat. No. 4,533,692, US Pat. No. 4,533,724, US Pat. No. 4,533,693, US Pat. No. 4,359,567, US Pat. No. 4,578,432, and the like.
[0021]
Specific examples of these polybenzazole-based structural units include those represented by the following structural formulas.
[0022]
[Chemical formula 5]

[0023]
[Chemical 6]

[0024]
[Chemical 7]

[0025]
[Chemical 8]

[0026]
[Chemical 9]

[0027]
Embedded image

[0028]
Embedded image

[0029]
Furthermore, not only these polybenzazole-based structural units, but also random, alternating or block copolymers with other polymer structural units may be used. At this time, the other polymer constituent unit is preferably selected from aromatic polymer constituent units having excellent heat resistance. Specifically, polyimide structural unit, polyamide structural unit, polyamideimide structural unit, polyoxydiazole structural unit, polyazomethine structural unit, polybenzazoleimide structural unit, polyether ketone structural unit, Examples thereof include polyethersulfone structural units.
[0030]
As an example of a polyimide-type structural unit, what is represented by the following general formula is mentioned.
[0031]
Embedded image

[0032]
Where Ar ₄ Is represented by a tetravalent aromatic unit, but is preferably represented by the following structure.
[0033]
Embedded image

[0034]
Ar ₅ Is a divalent aromatic unit, preferably represented by the following structure. Various substituents such as a methyl group, a methoxy group, a halogen group, a trifluoromethyl group, a hydroxyl group, a nitro group, and a cyano group may be present on the aromatic ring shown here.
[0035]
Embedded image

[0036]
Specific examples of these polyimide-based structural units include those represented by the following structural formulas.
[0037]
Embedded image

[0038]
Embedded image

[0039]
Examples of the polyamide-based structural unit include those represented by the following structural formula.
[0040]
Embedded image

[0041]
Where Ar ₆ , Ar ₇ , Ar ₈ Are preferably independently selected from the following structures. Various substituents such as a methyl group, a methoxy group, a halogen group, a trifluoromethyl group, a hydroxyl group, a nitro group, and a cyano group may be present on the aromatic ring shown here.
[0042]
Embedded image

[0043]
Specific examples of these polyamide-based structural units include those represented by the following structural formulas.
[0044]
Embedded image

[0045]
Examples of the polyamideimide-based structural unit include those represented by the following structure.
[0046]
Embedded image

[0047]
Where Ar ₉ Is the above Ar ₅ Those selected from the structures shown as specific examples are preferred.
[0048]
Specific examples of these polyamideimide structural units include those represented by the following structural formulas.
[0049]
Embedded image

[0050]
Examples of the polyoxydiazole-based structural unit include those represented by the following structural formula.
[0051]
Embedded image

[0052]
Where Ar ₁₀ Is the above Ar ₅ Those selected from the structures shown as specific examples are preferred.
[0053]
Specific examples of these polyoxydiazole structural units include those represented by the following structural formulas.
[0054]
Embedded image

[0055]
Examples of polyazomethine structural units include those represented by the following structure.
[0056]
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[0057]
Where Ar ₁₁ , Ar ₁₂ Is the above Ar ₆ Those selected from the structures shown as specific examples are preferred.
[0058]
Specific examples of these polyazomethine structural units include those represented by the following structural formulas.
[0059]
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[0060]
Examples of the polybenzazole imide-based structural unit include those represented by the following structural formula.
[0061]
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[0062]
Where Ar ₁₃ , Ar ₁₄ Is the above Ar ₄ Those selected from the structures shown as specific examples are preferred.
[0063]
Specific examples of these polybenzazole imide-based structural units include those represented by the following structural formulas.
[0064]
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[0065]
The polyether ketone structural unit and the polyether sulfone structural unit generally have a structure in which aromatic units are connected together with an ether bond by a ketone bond or a sulfone bond, and include a structural component selected from the following structural formula.
[0066]
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[0067]
Where Ar ₁₅ ~ Ar ₂₃ Are preferably independently represented by the following structures. Various substituents such as a methyl group, a methoxy group, a halogen group, a trifluoromethyl group, a hydroxyl group, a nitro group, and a cyano group may be present on the aromatic ring shown here.
[0068]
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[0069]
Specific examples of these polyetherketone structural units include those represented by the following structural formula.
[0070]
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[0071]
The aromatic polymer structural unit that can be copolymerized with these polybenzazole-based polymer structural units does not strictly indicate a repeating unit in the polymer chain, but can be present together with the polybenzazole-based structural units in the polymer main chain. Indicates the unit. These copolymerizable aromatic polymer structural units can be copolymerized not only alone but also in combination of two or more. In order to synthesize such a copolymer, an amino group, a carboxyl group, a hydroxyl group, a halogen group, etc. are introduced at the end of a unit consisting of a polybenzazole polymer constituent unit, and the reaction in the synthesis of these aromatic polymers. It may be polymerized as a component, or may be polymerized as a reaction component in the synthesis of a polybenzazole-based polymer by introducing a carboxyl group into the terminal of a unit containing these aromatic polymer constituent units.
[0072]
In the present invention, the polybenzazole-based polymer described above preferably contains 80% by weight or more, and less than 20% by weight may contain other polymers such as aromatic polyimide. In order to obtain a polybenzazole film having more excellent mechanical properties, the content of the polybenzazole polymer is desirably 90% by weight or more.
[0073]
In the present invention, as described in claim 2, it is a preferred embodiment that the polybenzazole-based polymer is polyparaphenylenebisbenzoxazole. By using the polymer, excellent heat resistance and mechanical properties can be obtained.
[0074]
The polybenzazole film of the present invention is a polybenzazole film characterized by satisfying the formulas (1) to (6).
(1) Tensile elastic modulus in the longitudinal direction and the width direction ≧ 5.0 GPa,
(2) Tensile strength in the longitudinal direction and the width direction ≧ 100 MPa,
(3) Elongation at break in the longitudinal and width directions ≧ 10%,
(4) 0.85 ≦ (tensile modulus in the width direction) / (tensile modulus in the longitudinal direction) ≦ 1.20,
(5) 0.85 ≦ (tensile strength in the width direction) / (tensile strength in the longitudinal direction) ≦ 1.20,
(6) 0.85 ≦ (breaking elongation in the width direction) / (breaking elongation in the longitudinal direction) ≦ 1.20.
[0075]
When the tensile elastic modulus is less than 5.0 GPa, film deformation occurs due to high tension or tension at the time of post-processing or winding at the time of use, and it is not preferable to make a thin film at the time of film formation. The tensile modulus of the polyobenzazole film of the present invention is more preferably 6.0 GPa or more. Furthermore, when the tensile strength is less than 100 MPa, when the post-processing is performed with a high tension, the film is not preferable. Further, the breaking elongation is preferably 10% or more. If the elongation is less than this, not only the handling during processing becomes difficult, but also the film becomes brittle during use, which is not preferable.
[0076]
The polybenzazole-based film of the present invention has the following relationships (4) to (6) in relation to the tensile modulus, breaking strength and breaking elongation in the longitudinal direction and the tensile modulus, breaking strength and breaking elongation in the width direction. It is necessary to satisfy the expression at the same time. By satisfying the above expressions (4) to (6) at the same time, the mechanical properties of the film in the longitudinal direction and the width direction can be balanced, so that the film can be obtained by a conventionally known production method that is easy to tear in a specific direction. Can be improved and can be suitably developed for various uses.
[0077]
In the present invention, it is necessary to form a film using an optically isotropic polybenzazole polymer solution as described in claim 3 in order to exhibit the above-described properties. By forming the film by this method, the polymer molecular chain is oriented in the flow direction generated when the film is formed using the optically anisotropic polybenzazole-based polymer solution, and is expressed by the orientation of the molecular chain. The disadvantage of the prior art that the balance of mechanical properties between the longitudinal direction and the width direction of the film is lost is improved.
[0078]
In addition, a film obtained by forming a film from a conventionally known optically anisotropic liquid crystal state solution has a defect that a polymer chain is easily plane-aligned and a film obtained is easily delaminated in the thickness direction. However, the film obtained by the above-described method of the present invention is improved with respect to this defect.
[0079]
Whether or not the polybenzazole-based solution is optically isotropic is confirmed by observing a preparation prepared by thinly extending the solution on a slide glass and sandwiching the solution with a cover glass under a crossed Nicol. In other words, if the liquid crystal state is optically anisotropic, when the sample stage is rotated, a domain structure derived from the liquid crystal structure is observed and a bright field is obtained. For example, even if the sample stage is rotated, the dark field remains, and the difference between the two can be distinguished.
[0080]
In the present invention, the polybenzazole-based film is formed into a thin film from the optically isotropic solution described above, and then formed into a film by processes such as coagulation, washing and drying. In the process of forming into a thin film, it can be formed by a known method such as a T-die method or a circular die method, but it reduces the molecular orientation in the longitudinal direction of the film during extrusion, and mechanical properties in the longitudinal and width directions. In the present invention, the following method is more preferable.
[0081]
That is, an optically isotropic polybenzazole solution sandwiched between at least two supports is supported via a counter roll, a rolling device, a press device, or the like, support / polybenzazole solution / support. To form a sandwich-like composite laminate.
The obtained sandwich composite laminate is guided to a coagulation bath, and the support is peeled off and coagulated in the coagulation bath. The configuration and arrangement of the facing roll, the rolling device, the pressing device, and the like can be variously combined. Desirably, an optically isotropic polybenzazole-based solution sandwiched between at least two supports is sandwiched between at least a pair of opposing rolls, and the opposite rolls are rotated in the opposite direction, whereby the support / This is a method of forming a polybenzazole-based solution / support sandwich composite laminate. The obtained support / polybenzazole-based solution / support sandwich composite laminate was guided to a coagulation bath through a guide roll and the like, and the support was peeled off in the coagulation bath. The system solution is solidified. As the support, a plastic film such as a polyester film typified by a PET film or a polyolefin film such as a polypropylene (also referred to as PP) film can be used. Further, a porous film, fabric or nonwoven fabric having moisture permeability as a support may be used as it is or in combination with the plastic film support. When the plastic film is used as a support, the solidification time after the support is peeled off. When the porous film is used as a support alone, the time until the support is peeled off after the sandwich composite laminate is immersed in the coagulation bath and This is important because it affects the film structure and physical properties of the coagulated wet film that provides the time for immersion in the coagulation bath after peeling off the support.
[0082]
In the present invention, in order to obtain the above-mentioned optically isotropic solution, it is preferable that the concentration of the polybenzazole-based polymer is 5% by weight or less as described in claim 5. More preferably, it is 3% by weight or less. On the other hand, at a concentration of 0.3% by weight or less, the viscosity of the polymer solution becomes small, and the applicable film forming method is limited, and the obtained polybenzazole film has a tensile elastic modulus, a breaking strength, a breaking elongation, and the like. This is not preferable because the mechanical properties are small. It becomes economically disadvantageous. 0.5% by weight or more is more preferable. When the concentration of the solution exceeds 5% by weight, the optical anisotropy of the solution tends to be exhibited, and the viscosity of the solution increases and the moldability becomes difficult.
[0083]
In order to adjust the concentration of the polybenzazole polymer solution to the range shown above, the following method can be used. That is, a method in which a polymer solid is once separated from a polymerized polybenzazole-based polymer solution, and the concentration is adjusted by adding a solvent again and dissolving. Furthermore, a method of adjusting the concentration by adding a solvent to the polymer solution and diluting the polymer solution without separating the polymer solid from the polymer solution that has been subjected to condensation polymerization in polyphosphoric acid. Furthermore, there is a method of directly obtaining a polymer solution in the above concentration range by adjusting the polymerization composition of the polymer.
[0084]
Preferred solvents for use in adjusting the concentration of the polymer solution include methanesulfonic acid, dimethylsulfuric acid, polyphosphoric acid, sulfuric acid, trifluoroacetic acid, and the like, or a mixed solvent combining these solvents can also be used. Of these, methanesulfonic acid and polyphosphoric acid are particularly preferred.
[0085]
The degree of polymerization of the polymer in the polybenzazole-based polymer solution used for obtaining the polybenzazole-based film of the present invention is represented by an intrinsic viscosity. The intrinsic viscosity is preferably 15 dl / g or more and 35 dl / g or less, and more preferably 20 dl / g or more and 30 dl / g or less. If it is less than this range, the mechanical properties of the resulting polybenzazole-based film will decrease, and if it exceeds this range, the viscosity of the solution will be high and processing will be difficult.
[0086]
The coagulating liquid is not limited as long as it is compatible with the solvent forming the above solution and is a poor solvent for the polymer. For example, water, aqueous metal salt solution, polyhydric alcohol, Examples include protic polar solvents and protic polar solvents.
[0087]
The solidification conditions in the present invention are particularly important in order to obtain a polybenzazole-based film that is homogeneous and has excellent mechanical strength, smoothness and delamination resistance. Specifically, it is important to increase the temperature of the coagulation liquid and the concentration of the coagulation liquid, so that it has a uniform, excellent heat resistance, mechanical strength, and interlayer resistance with little void (fine bubble) structure. A polybenzazole film having releasability can be obtained. However, if the coagulation liquid temperature and the coagulation liquid concentration are too high, the coagulation property is lowered and the handling property is lowered, and desired physical properties cannot be obtained. The temperature of the coagulation liquid is preferably 10 ° C. or higher and 70 ° C. or lower. More preferably, it is 20 degreeC or more and 60 degrees C or less.
[0088]
When using a metal salt aqueous solution as the coagulation liquid, it is preferable to use a metal salt aqueous solution having a concentration of half the saturation solubility in water to a saturation solubility. In particular, in order to obtain a polybenzazole-based film having a uniform void structure (fine bubbles) and excellent heat resistance, mechanical strength, and delamination resistance, it is necessary to use an aqueous metal salt solution as a coagulating liquid. Is preferred. Although many types of metal salts are mentioned, metal species with many hydration numbers, such as lithium, sodium, magnesium, calcium, aluminum, barium, strontium, gallium, indium, chromium, iron, cobalt, nickel, manganese, are more preferable.
[0089]
Examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, and glycerin. The polyhydric alcohol / water is preferably used in a weight ratio of 10/90 to 100/0. More preferably, it is 30/70 to 80/20.
[0090]
Examples of the aprotic polar solvent include N-methylpyrrolidone, γ-butyrolactone, dimethylformamide, dimethylacetamide, dimethylsulfoxide and the like. The aprotic polar solvent / water is preferably used in a weight ratio of 10/90 to 100/0. More preferably, it is 30/70 to 80/20. Furthermore, a polybenzazole-based polymer solution may be applied to a support and solidified by exposure in air, water vapor, and a controlled atmosphere. These are examples of the solidification process and can be solidified under other conditions.
[0091]
Since the coagulated film contains an acid that is a solvent of the polymer solution, it is necessary to wash and remove the acid. Water is usually used as the cleaning liquid, but it may be washed with warm water as necessary, or may be washed with water after neutralizing and washing with an aqueous alkali solution. Cleaning includes, for example, a method of running the film in the cleaning liquid or spraying the cleaning liquid.
[0092]
In the present invention, the drying step is desirably performed under tension and by restricting shrinkage of the film under constant tension. When the film is dried by free shrinkage, partial shrinkage occurs, resulting in uneven thickness, and the flatness of the film may be impaired. In order to dry the film while restricting the shrinkage, for example, a tenter dryer or a metal frame can be used for drying. Other conditions related to drying are not particularly limited, and examples include a drying method using a heated gas such as air or nitrogen or a room temperature gas, a drying method using a heater or an infrared lamp, and the like.
[0093]
The film forming step, the coagulation step, the washing step, the drying step, and the like may be performed continuously or in a batch manner. Furthermore, you may add another special process between each process.
[0094]
The polybenzazole-based film used in the present invention may be applied with an anchor agent or subjected to chemical etching treatment, corona treatment, plasma treatment, etc. in order to increase the adhesive strength with a magnetic recording layer or a metal vapor deposition layer. Good.
[0095]
The film of the present invention may contain known additives such as ultraviolet absorbers, heat stabilizers, stretching aids, lubricants and the like.
[0096]
【Example】
Hereinafter, the contents and effects of the present invention will be described by way of examples. However, the present invention is not limited to the following examples without departing from the gist thereof. In addition, the evaluation method of the physical property in the following examples is as follows.
[0097]
1. Intrinsic viscosity
The viscosity of the polymer solution adjusted to a concentration of 0.5 g / l using methanesulfonic acid as a solvent was measured and calculated in an oven at 30 ° C. using an Ostwald viscometer.
[0098]
2. Optical isotropy evaluation of polymer solutions
The solution was placed on a slide glass and sandwiched between cover glasses and stretched thinly, and observation was performed under crossed Nicols using a polarizing microscope. Even when the sample stage was rotated, it was a dark field, and when the domain structure was not observed, it was judged as an optically isotropic solution.
[0099]
3. Tensile modulus, tensile strength and elongation at break
The dried film is cut into strips with a length of 100 mm and a width of 10 mm in the longitudinal direction (MD direction) and the width direction (TD direction), respectively, as test pieces, and a tensile tester (Shimadzu Autograph (R)) Using AG-5000A), the tensile modulus was measured at 50 mm / min and the distance between chucks was 40 mm, and the tensile modulus, tensile strength and elongation at break were determined.
[0100]
4). Delamination test
The dried film was cut into strips having a length of 20 mm and a width of 10 mm in the longitudinal direction (MD direction) and the width direction (TD direction), respectively, and used as test pieces. Adhesive tape (Nichiban cello tape (R ) The bonding surface of CT405) was pasted together. The adhesive surface of 5) was laminated. Using a tensile tester (Autograph (R) model name AG-5000A manufactured by Shimadzu Corporation) at a tensile speed of 50 mm / min and a distance between chucks of 40 mm, the tape is peeled off, and the broken film is transferred to the adhesive surface of both adhesive tapes. The presence or absence of delamination phenomenon was investigated. A detailed view is shown in FIG.
[0101]
(Example 1)
A polymer solution containing 14% by weight of a polyparaphenylenecisbenzobisoxazole polymer (also referred to as PBO) having an intrinsic viscosity of IV = 25 dL / g obtained by polymerization in polyphosphoric acid was diluted by adding methanesulfonic acid, A polymer solution for film formation having a concentration of 1.0% by weight was prepared. This film-forming polymer solution was optically isotropic. Further, the solution was heated to 50 ° C., passed through a filter having a nominal opening of 20 μm, and sandwiched between two PET film supports (188 μm biaxially stretched film) arranged as shown in FIG. On opposite rolls. The opposing roll was rotated at a peripheral speed of 0.3 m / min to form a sandwich / composite laminate of support / PBO solution / support. The gap between the opposing rolls was adjusted using a thickness gauge so that the thickness of the dry PBO film was about 5 μm. The composite laminate thus obtained was continuously introduced into a coagulation bath, and the support was continuously peeled and coagulated in the coagulation bath. At this time, the coagulation liquid was a 4.5 mol / l magnesium chloride aqueous solution at 50 ° C. Moreover, the residence time (coagulation time) of the PBO film in the coagulation bath after the support was peeled was about 2 minutes. The solidified PBO film was wound up at a speed of 0.31 m / min. The coagulated film was sufficiently washed with water, and then heat fixed at 150 ° C. for 30 seconds while holding both ends with a tenter to obtain a polybenzazole film having a thickness of 5.5 μm.
[0102]
(Example 2)
A PBO film having a thickness of 5.0 μm was obtained in the same manner as in Example 1 except that water kept at 25 ° C. was used as the coagulation liquid.
[0103]
(Comparative Example 1)
In the method of Example 1, the dilution with methanesulfonic acid was changed to obtain a polymer solution for film formation having a PBO polymer concentration of 8.0% by weight. The obtained polymer solution for film formation was optically anisotropic. A polybenzazole film having a thickness of 6.0 μm was obtained in the same manner as in Example 1 except that the polymer solution for film formation was used and the extrusion temperature from the T-die was changed to 80 ° C.
[0104]
The measurement results of the PBO films obtained in Examples 1 and 2 and Comparative Example 1 are shown in Table 1.
[0105]
[Table 1]

[0106]
【The invention's effect】
The polybenzazole-based film obtained by the present invention is a polybenzazole film having excellent mechanical strength and a good mechanical property balance between the film longitudinal direction and the width direction, and also having delamination resistance. Can be used in the field. Further, the film having the above-described characteristics can be economically produced by the production method of the present invention.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a film delamination test.
FIG. 2 is a schematic diagram of the polybenzazole film production method of the present invention.
[Explanation of symbols]
1: Solution supply piping
2: Solution
3: Support 1
4: Support body 2
5: Support 1 feed roll
6: Support 2 feed roll
7: Opposite roll
8: Support / solution / support composite laminate
9: Polybenzazole-based wet film
10: Polybenzazole-based wet film winding roll
11: Support 2 roll-up roll
12: Support 1 roll-up roll
13: Coagulation bath

Claims (4)

A polybenzazole film characterized by satisfying the following formulas (1) to (6).
(1) Tensile elastic modulus in the longitudinal direction and the width direction ≧ 5.0 GPa,
(2) Tensile strength in the longitudinal direction and the width direction ≧ 100 MPa,
(3) Elongation at break in the longitudinal and width directions ≧ 10%,
(4) 0.85 ≦ (tensile modulus in the width direction) / (tensile modulus in the longitudinal direction) ≦ 1.20,
(5) 0.85 ≦ (tensile strength in the width direction) / (tensile strength in the longitudinal direction) ≦ 1.20,
(6) 0.85 ≦ (breaking elongation in the width direction) / (breaking elongation in the longitudinal direction) ≦ 1.20. The polybenzazole-based film according to claim 1, wherein the polybenzazole is polyparaphenylenebisbenzoxazole. 3. The method for producing a polybenzazole film according to claim 1, wherein the film is formed using an optically isotropic polybenzazole polymer solution. The method for producing a polybenzazole-based film according to claim 3, wherein the polymer concentration of the polybenzazole-based polymer solution is 0.5 to 5% by weight.

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