JP2004226734A - Supporting film for polarizing film and polarizing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a supporting film for a polarizing film which does not decrease the contrast in a liquid crystal display part by specifying the amount of variation of the amplitude of the transmittance measured by a spectrophotometer in the wavelength region from 400 nm to 700 nm, and to provide a polarizing plate using the supporting film. <P>SOLUTION: The supporting film for a polarizing film shows ≤7% variation ΔT of the amplitude of the transmittance for light expressed by ΔT=(Tmax-Tmin)/Tmin×100, wherein Tmax and Tmin are the maximum transmittance (%) and the minimum transmittance (%) in the wavelength region from 400 nm to 700 nm, respectively. The supporting film for a polarizing film has a layered structure of A/B consisting of: a low refractive index layer A having ≤0.15 μm thickness and 1.42 to 1.53 refractive index; and a high refractive index layer B having ≥20 μm thickness and 1.53 to 1.8 refractive index, or a layered structure of A/B/A. The polarizing plate uses the above supporting film. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００２０】
また、Ｒｔは、粗さ曲線の測定長さ内における最大の山と最深の谷の距離を表す。Ｒａが１８ｎｍを越えると表面が荒れ気味となり、光の散乱が大きくなり、また、Ｒｔが１００ｎｍ未満であると空気の抜け具合が低下する傾向となり、滑りが悪くなる傾向にあり、現実的に製膜が難しいため好ましくない。
【００２１】
Ｒａ，Ｒｔを上記した値に制御する方法は特に限定されないが、例えば、前述した粒子の粒径とＡ層の厚みを適宜選択することで達成することができる。
【００２２】
また、基層部であるＢ層にポリエステルフィルムなどの表面が結晶配向した材料を用いた場合は、各種塗料、接着剤、インキなどの接着性に乏しいため、Ａ層としてポリエステル、アクリル、ポリウレタン、アクリルグラフトポリエステルなどの各種樹脂をプライマー層として設ける方法により、易接着性を達成する。例えば、ポリエステル樹脂としては、酸成分としてテレフタル酸、イソフタル酸、セバシン酸、トリメリット酸、ピロメリット酸、５−（２，５−ジオソテトラヒドロフルフリル）−３−メチル−３−シクロヘキセン−１，２ジカルボン酸、グリコール成分としては、エチレングリコール、ジメチレングリコール、ジエチルグリコール、１，４−ブタジオール、ネオペンチルグリコール、から選ばれた共重合体などである。また、これを水系樹脂とした塗液として用いる場合、水溶性化を容易にし、ポリエステル樹脂の接着性を向上させるためにカルボン酸塩基やスルホン酸塩基を含む化合物を共重合することが好ましい。アクリル樹脂としては、メチルメタクリレート、エチルアクリレート、ｎ−ブチルアクリレート、２−ヒドロキシエチルアクリレート、アクリルアミド、ｎ−メチロ−ルアクリルアミド、グリシジルメタクリレート、アクリル酸から選ばれた共重合体などである。また、水系樹脂とした塗液として用いる場合、親水性基を有するモノマ（アクリル酸、メタクリル酸、アクリルアミド、ビニルスルホン酸及びその塩など）との共重合や反応性乳化剤や界面活性剤を用いた乳化重合、懸濁重合、ソープフリー重合などの方法によって作製されたアクリル樹脂が用いられることが好ましい。また、塗布性を向上させるために架橋剤などが含有されていても良い。架橋剤は、架橋反応を起こす化合物であれば特に限定されないが、メチロール化あるいはアルキロール化した尿素系、メラミン系、アクリルアミド系、ポリアミド系化合物、エポキシ化合物、イソシアネート化合物、オキサゾリカップリング剤などがある。
【００２３】
Ａ層の厚みは、支持体フィルムの表裏面で引き起こす光干渉現象を抑制する観点から０．５μｍ以上０．１５μｍ以下であることが好ましい。より好ましくは、０．８μｍ以上０．１２μｍ以下である。また、Ｂ層の厚みは、偏光膜用支持体フィルムとして腰の強さを付与する観点から２０μｍ以上が好ましい。より好ましくは、５０μｍ以上２００μｍ未満である。
【００２４】
本発明の偏光膜用支持体フィルムに用いられるＢ層として好適であるポリエステルフィルムの製造方法は特に限定されないが、腰の強さを引き出す点で延伸による配向結晶化を付与する製造方法が好ましい。例えば、上記溶融ポリマーを押出機に供給して、Ｔ型口金等を用いてシート状に溶融押出し、その後、キャスティングドラム上で冷却固化して未延伸フィルムとし、この未延伸フィルムを樹脂組成物のガラス転移点（Ｔｇ）以上の温度で延伸する方法などで得ることができる。この際の延伸の方法は、公知の如く長手方向に延伸した後に幅方向に延伸する方法、幅方向に延伸した後に長手方向に延伸する方法で行えばよく、長手方向の延伸、幅方向の延伸を複数回組み合わせて行なってもよい。本発明によれば、延伸温度及び延伸倍率はいくらであっても良いが、通常のポリエステルフィルムの場合、延伸温度は８０℃以上１３０℃以下であり、延伸倍率は２倍以上５倍以下が好ましい。次いで、この延伸されたフィルムを熱処理する。この熱処理は、延伸温度より高く、融点より低い温度で行うのが一般的である。通常のポリエステルの場合、１３０℃ないし２３０℃の範囲で行うのが好ましい。この際、フィルムの熱寸法安定性を付与するために弛緩熱処理を施すことも好ましい。
【００２５】
本発明の偏光膜用支持体フィルムのＢ層の主配向軸と偏光膜の偏光方向が、０°±１０°、もしくは９０°±１０°の関係に保たれていることが好ましい。主配向軸とは、面内で分子が最も分極している方位のことであり、屈折率楕円体においては最も屈折率が高い方位のことである。この方位が、偏光膜の偏光方向と一致もしくは、９０°の±１０°の誤差範囲の関係に保たれるように設置することによって、複屈折による光干渉現象を抑制し、液晶表示部のコントラストの低下を防ぐ効果がある。複屈折とは、ニ軸配向ポリエステルフィルムなどのフィルム長手方向と幅方向で屈折率が異なる異方性物質（複屈折体）に光が入射すると、光は２方向に分かれて進み、物が二重に見える現象のことをいう。
【００２６】
本発明の偏光膜用支持体フィルムは、物質自体の複屈折現象を抑える観点からレターデーション（Ｒｅ）が ０ｎｍ以上４００ｎｍ以下または１０００ｎｍ以上２００００ｎｍ以下であることが好ましい。
Ｒｅ＝Δｎ・ｄ （２）
ただし、式（２）で、Δｎは、波長λ＝５９０ｎｍにおけるフィルム面内方向の複屈折であり、ｄはフィルムの厚み（ｎｍ）である。
【００２７】
レターデーションが４００ｎｍ以下であると、複屈折による光の干渉現象を抑えるため好ましい。より好ましくは、１００ｎｍ以下である。
【００２８】
また、フィルムの光学的異方性を測定する装置としては、他にマイクロ波分子配向計が挙げられる。この場合、測定値であるＭＯＲ（Ｍａｘｉｍｕｍ Ｏｒｉｅｎｔｅｄ Ｒａｔｉｏ）値が１．０以上１．２以下であることが好ましい。ＭＯＲ値とは、マイクロ波透過型分子配向計で測定された透過マイクロ波強度の最大値と最小値の比（最大値／最小値）である。このような値にフィルムの面内方向の位相差を設定するフィルム製造方法としては、未延伸もしくは、等方的な二軸配向フィルムによって達成される。先に述べたレターデーションが４００ｎｍ以下に相反して、１０００ｎｍ以上の値を取ることも偏光膜用支持体フィルムとして好ましい。低レターデーションほど複屈折による光干渉抑制効果はないが、逆にレターデーションを大きくすることによっても光干渉を抑制する観点から、より好ましくは１３００ｎｍ以上である。ＭＯＲ値では、１．４以上が好ましい。レターデーションは、フィルムの厚みに比例するために余り厚すぎても実用上の薄膜化の利点から離れてしまうため、上限は２００００ｎｍ以下であることが好ましい。ＭＯＲ値では、７以下が好ましい。
【００２９】
また、光学部材として必要不可欠である透明性の観点から偏光膜支持体フィルムの全光線透過率が８８％以上、かつヘイズが２％以下であることが好ましい。
【００３０】
全光線透過率８８％以上、かつヘイズが２％以下であるフィルムの光学特性は、主にフィルム自体の樹脂特性に依存するが、易滑剤としての粒子の選択及び透明低屈折率層のコーティングなどの表面改質を行うことによって適宜達成される。熱によるフィルムのそりなどによる液晶表示部の熱寸法安定性が必要な観点から、１気圧、１５０℃の熱処理条件で１０分間曝されたときの偏光膜支持体用フィルムの熱処理前後のフィルム長手方向及び幅方向の熱収縮率が、ともに３％以下であることが好ましい。
【００３１】
また、本発明のフィルムのＢ層の主原料としては樹脂が使用される。ここで用いられる樹脂は、従来の液晶表示部を構成する透明部材であるＩＴＯを蒸着したガラス板、偏光子を両側からサンドしたセルロース系フィルムに代替されるものであるため、透明性、低複屈折、寸法安定性は当然ながら、さらに薄型を可能とするための特性である機械的強度（腰の強さ）が求められる。透明性、低複屈折を満たす材料としては、ポリメタクリル酸メチル、トリアセテート、ポリ−４−メチルペンテン、ポリスチレン、ポリカーボーネートが挙げられる。特に吸湿膨張係数、熱膨張係数、経時収縮などの寸法安定性と薄型化を可能とする腰の強さの点でポリカーボネートが好ましく用いられる。ここでいうポリカーボネートとは、炭酸エステルを構造単位に持つもので、その中でビスフェノールＡからなる芳香族ポリカーボネートを意味する。
【００３２】
一方、薄型化を最優先としたときは、その腰の強さの点で最も優れる樹脂として、ポリエステルが好ましい。ここでいうポリエステルとは、芳香族ジカルボン酸または脂肪族ジカルボン酸とジオールを主たる構成成分とする単量体の重合により得られるポリエステルである。ここで、主たるとは、５０モル％以上であることを言う。
【００３３】
このような芳香族ジカルボン酸としては、例えば、テレフタル酸、イソフタル酸、フタル酸、１，４−ナフタレンジカルボン酸、１，５−ナフタレンジカルボン酸、２，６−ナフタレンジカルボン酸、４，４′−ジフェニルジカルボン酸、４，４′−ジフェニルエーテルジカルボン酸、４，４′−ジフェニルスルホンジカルボン酸等を挙げることができる。また、脂肪族ジカルボン酸としては、例えば、アジピン酸、スベリン酸、セバシン酸、ドデカンジオン酸等を挙げることができる。中でも好ましくはテレフタル酸とイソフタル酸を挙げることができる。これらの酸成分は１種のみ用いてもよく、２種以上併用してもよく、さらには、ヒドロキシ安息香酸等のオキシ酸等を一部共重合してもよい。
【００３４】
また、ジオール成分としては、例えば、エチレングリコール、１，２−プロパンジオール、１，３−プロパンジオール、ネオペンチルグリコール、１，３−ブタンジオール、１，４−ブタンジオール、１，５−ペンタンジオール、１，６−ヘキサンジオール、１，２−シクロヘキサンジメタノール、１，３−シクロヘキサンジメタノール、１，４−シクロヘキサンジメタノール、ジエチレングリコール、トリエチレングリコール、ポリアルキレングリコール、２，２−ビス（４−ヒドロキシエトキシフェニル）プロパン等を挙げることができる。中でもエチレングリコールが好ましく用いられる。これらのジオール成分は１種のみ用いてもよく、２種以上併用してもよい。
【００３５】
本発明において、ポリエステルとして、好ましくは、ポリエチレンテレフタレート、エチレンテレフタレートとエチレンイソフタレートとの共重合体、ポリエチレン−２，６−ナフタレート及びその共重合体、ポリブチレンテレフタレート及びその共重合体、ポリブチレンナフタレート及びその共重合体、さらにはポリヘキサメチレンテレフタレート及びその共重合体、ポリヘキサメチレンナフタレート及びその共重合体等を挙げることができ、特にポリエチレンテレフタレートが好ましい。これらのポリエステルは単独ポリマとして使用しても良いし、本発明効果を損なわない範囲で、共重合やブレンド体で使用しても良い。
【００３６】
本発明のフィルムの基材層であるＢ層の主原料として使用する樹脂の製造方法は、特に限定されない。例えば、本発明で好ましく使用されるポリエステルは、次に掲げる方法で製造することができる。例えば、酸成分をジオール成分と直接エステル化反応させた後、この反応の生成物を減圧下で加熱して余剰のジオール成分を除去しつつ重縮合させることによって製造する方法や、酸成分としてジアルキルエステルを用い、これとジオール成分とでエステル交換反応させた後、上記と同様に重縮合させることによって製造する方法等がある。この際、必要に応じて、反応触媒として従来公知のアルカリ金属、アルカリ土類金属、マンガン、コバルト、亜鉛、アンチモン、ゲルマニウム、チタン化合物等を用いることもできる。
【００３７】
本発明におけるポリエステルには、必要に応じてさらに難燃剤、熱安定剤、酸化防止剤、紫外線吸収剤、帯電防止剤、顔料、脂肪酸エステル、ワックス等の有機滑剤あるいはシロキサン等の消泡剤等を配合することができる。滑材としては、有機、無機滑材を用いることができる。その形状としては、凝集粒子、真球状粒子、数珠状粒子、コンペイト状粒子、鱗片状粒子などの形状粒子を使うことができる。また、その材質としては、例えば、無機系としては、酸化珪素、炭酸カルシウム、酸化チタン、アルミナ、ジルコニア、珪酸アルミニウム、マイカ、クレー、タルク、酸化マグネシウム等を、有機系としては、ポリイミド系樹脂、オレフィンあるいは変性オレフィン系樹脂、架橋ないし無架橋ポリスチレン系樹脂、架橋ないし無架橋アクリル樹脂、フッ素系樹脂、シリコン系樹脂等の樹脂、また有機滑材としてステアリン酸アミド、オレイン酸アミド、フマール酸アミドなどの各種アミド化合物を挙げることができる。
このようにして得られた本発明のフィルムは、偏光膜用支持体フィルムとして用いられる。
【００３８】
本発明において、フィルムの特性は以下の方法で測定した。
（１）４００〜７００ｎｍにおける分光光度計による測定：
フィルム幅方向の中央部から、長手４．０×幅３．５ｃｍの寸法に切り出したものをサンプルとし、日立製作所（株）製の分光光度計Ｕ−３４１０を用いて波長４００〜７００ｎｍの光線透過率を分解能２ｎｍ以下、走査速度１２０ｎｍ／ｍｉｎ、ゲイン３、ｒｅｓｐｏｎｓ Ｍｅｄｉｕｍの条件で測定した。また、透過率の変化量は、下記式（１）から求めた。
ΔＴ＝（Ｔｍａｘ−Ｔｍｉｎ）／Ｔｍｉｎ×１００ ・・・（１）
（但し、式（１）で、ΔＴは透過率の振幅の変化量（％）、Ｔｍａｘは最大透過率（％）、Ｔｍｉｎは最小透過率（％）である。）
（２）レターデーション測定：
フィルムのレターデーションは、自動複屈折計（新王子製紙（株）製ＫＯＢＲＡ−２１ＡＤＨ）を用いて、フィルム幅方向の中央部から切り出したサンプル（長手方向４．０ｃｍ×幅方向３．５ｃｍ）について測定した。
【００３９】
（３） ＭＯＲ値：
フィルム幅方向の中央部分を１０×１０ｃｍの寸法で切り出したものを測定サンプルとし、マイクロ波分子配向計を用いてＭＯＲ値を測定した。マイクロ波分子配向計としては、ＫＳシステムズ（株）製（現 王子計測機器（株））の分子配向計ＭＯＡ−２００１（周波数４ＧＨｚ）を用いた。
（３）可視光における光線透過率及びヘイズ
フィルム幅方向の中央部から、長手４．０×幅３．５ｃｍの寸法に切り出したものをサンプルとし、光線透過率及びヘイズは、ヘイズメータ（スガ試験機製ＨＧＭ−２ＤＰ（Ｃ光用））を用いて測定した。
（４）表面粗さ
フィルム幅方向の中央部から、長手４．０×幅３．５ｃｍの寸法に切り出したものをサンプルとし、表面粗さ（中心線平均粗さＲａ及び最大粗さＲｔ）は、小坂研究所製の３次元粗さ計ＳＥ−３ＡＫを用いて測定した。測定は、カットオフ値０．０８、測定長２ｍｍ、送りピッチ５μ、測定本数１０の条件で行った。
（５）熱収縮率：
フィルム幅中央部から１×１０ｃｍのサンプルを切り出し、ギアオーブン（ＴＡＢＡＩ社製ＧＨＰＳ−２２２）で１５０℃で１０分間の条件で熱処理した。その前後におけるフィルム長手方向（ＭＤ：Ｍａｃｈｉｎｅ Ｄｉｒｅｃｔｉｏｎ）と幅方向（ＴＤ：Ｔｒａｎｓｖｅｒｓｅ Ｄｉｒｅｃｔｉｏｎ）の長さをそれぞれ万能投影機（７７−７ニコン社製Ｅ０４）で正確に測長することにより、熱収縮率を求めた。
【００４０】
【実施例】
以下、実施例により本発明をさらに詳細に説明するが、本発明はこれに限定されるものではない。
［実施例１］
２軸混練機を用いて、外部添加剤として平均粒径１．１μｍの炭酸カルシウムを１重量％含有させたポリエチレンテレフタレートのペレットをマスターペレット１とした。 次に、粒子添加を行わなかったポリエチレンテレフタレートのペレットをマスターペレット２とした。
【００４１】
上記ペレット１の粒子濃度が０．０３重量％となるように、粒子添加をおこなっていないポリエチレンテレフタレートのペレットを用いて希釈した後、１８０℃で３時間乾燥し、ベント式二軸混練押出機１に供給し、２８０℃で溶融した。このポリマーを、基層部であるＢ層となるようにフィッシュテール型の口金よりシート状にして押出した後、静電印加キャスト法を用意して２５℃のキャスティングドラムに巻き付けて冷却固化し、未延伸フィルムを作った。その後、９５℃に加熱したロールとラジエーションヒーターによってフィルムを加熱して、延伸することにより長手方向に３．３倍延伸し、続いてテンターにて幅方向に９５℃で３．５倍延伸し、さらに該テンターの後続する熱処理ゾーン２３０℃で熱処理を施すことにより厚み３０μｍのＢ層である屈折率１．６６〜１．６７のポリエステルフィルムを得た。その後、該フィルムの両面に固形濃度０．１重量％である水溶性のポリビニルアルコール液を積層膜成形塗液によるＡ層として塗布し、１５０℃１０分間の乾燥後、屈折率１．４９のポリビニルアルコールを成分とするＡ層の厚み１００ｎｍのＡ／Ｂ／Ａ３層構造である偏光膜用支持体フィルムを得た。この評価結果は、表１に示した通りであり、得られたフィルムに透明電極、さらに偏光特性を持ち合せて実装した液晶パネルは、コントラスト良好であり、視認性の良好なものであった。
【００４２】
［実施例２］
実施例１と同様に平均粒径１．１μｍの炭酸カルシウムの粒子濃度が０．０３重量％であるポリエチレンテレフタレートを溶融して口金から押出し、２５℃のキャスティングドラムで冷却固化した後、８６℃に加熱したロールとラジエーションヒーターによってフィルムを加熱して、延伸することにより長手方向に３．３倍延伸した。該一軸延伸フィルムに空気中でコロナ放電処理を施した。Ａ層として次の組成の塗液Ａ、塗液Ｂ、粒子Ｃを固形分量比で、液Ａ／液Ｂ／粒子Ｃ＝１００／２５／３で混合したものを積層膜成形塗液として、該一軸延伸フィルムのコロナ放電面に塗布した。
［積層膜形成塗液］
液Ａ：下記の共重合組成からなるアクリル樹脂（ガラス転移温度：４２℃、屈折率１．５２）を粒子状に水に分散させた水系分散液。
・共重合成分
メチルメタクリレート ６３重量％
メチルアクリレート ３５重量％
アクリル酸 １重量％
Ｎ−メチロ−ルアクリルアミド １重量％
液Ｂ：メラミン系架橋剤として、メチロール基型メラミン架橋剤（三和ケミカル（株）製“ニカラック”ＭＷ１２ＬＦ）を水に溶解した水系塗液。
粒子Ｃ：粒径８０ｎｍのコロイダルシリカ粒子の水分散体。
【００４３】
続いてテンターにて幅方向に１００℃で３．７倍延伸し、さらに該テンターの後続する熱処理ゾーン２３０℃で熱処理し、幅方向に５％の弛緩処理を施すことにより厚み５０μｍのＡ／Ｂ２層構造である偏光膜用支持体フィルムを得た。Ｂ層の屈折率は、１．６４〜１．６６のポリエステルフィルムであった。積層膜成形塗液によるＡ層の厚みは１００ｎｍであった。この評価結果は、表１に示した通りであり、得られたフィルムに透明電極、さらに偏光特性を持ち合せて実装した液晶パネルは、コントラスト良好であり、視認性の良好なものであった。
【００４４】
［実施例３］
Ｂ層の厚みを７５μｍにする以外、実施例２と同様にしてＡ／Ｂ２層構造である偏光膜用支持体フィルムを得た。この評価結果は、表１に示した通りであり、得られたフィルムに透明電極、さらに偏光特性を持ち合せて実装した液晶パネルは、コントラスト良好であり、視認性の良好なものであった。
【００４５】
［実施例４］
屈折率１．５８、厚み５０μｍ、レターデーション３０ｎｍのポリカーボネートフィルムに実施例２で用いた積層塗膜液を塗布し、１５０℃１０分の乾燥後Ａ／Ｂ２層構造である偏光膜用支持体フィルムを得た。積層塗膜液により得られたＡ層の厚みは、１００ｎｍであった。この評価結果は、表１に示した通りであり、得られたフィルムに透明電極、さらに偏光特性を持ち合せて実装した液晶パネルは、コントラスト良好であり、視認性の良好なものであった。
【００４６】
［実施例５］
実施例１と同様に平均粒径１．１μｍの炭酸カルシウムの粒子濃度が０．０３重量％であるポリエチレンテレフタレートを溶融して口金から押出し、２５℃のキャスティングドラムで冷却固化した後、８６℃に加熱したロールとラジエーションヒーターによってフィルムを加熱して、延伸することにより長手方向に２．８倍延伸した。該一軸延伸フィルムに空気中でコロナ放電処理を施した。Ａ層として実施例２で用いた積層膜成形塗液と同様にして、該一軸延伸フィルムのコロナ放電面に塗布した。続いてテンターにて幅方向に１１０℃で３．７倍延伸し、さらに該テンターの後続する熱処理ゾーン２３０℃で熱処理を施すことにより厚み３８μｍのＡ／Ｂ２層構造である偏光膜用支持体フィルムを得た。Ｂ層の屈折率は、１．６３〜１．６７のポリエステルフィルムであった。積層膜成形塗液によるＡ層の厚みは１００ｎｍであった。この評価結果は、表１に示した通りであり、得られたフィルムに透明電極、さらに偏光特性を持ち合せて実装した液晶パネルは、コントラスト良好であり、視認性の良好なものであった。
【００４７】
［比較例１］
実施例１において、積層膜成形塗液によるＡ層としてポリビニルアルコールを塗布しなかった厚み３０μｍのポリエステルフィルムを単膜構造である偏光膜用支持体フィルムとした。この評価結果は、表１に示した通りであり、得られたフィルムに透明電極、さらに偏光特性を持ち合せて実装した液晶パネルは、コントラスト、視認性の良好なものではなかった。
【００４８】
［比較例２］
実施例１と同様に、平均粒径１．１μｍの炭酸カルシウムを１重量％含有させたポリエチレンテレフタレートのマスターペレット１と粒子添加を行わなかったポリエチレンテレフタレートのマスターペレット２を用意した。
【００４９】
上記ペレット１の粒子濃度が０．０３重量％となるように、粒子添加をおこなっていないポリエチレンテレフタレートのペレットを用いて希釈した後、１８０℃で３時間乾燥し、ベント式二軸混練押出機１に供給し、２８０℃で溶融した（ポリマＡ層）。さらに、もう一台の押出機２を用意し、粒子を添加をおこなっていないポリエチレンテレフタレートのペレットを１８０℃で３時間乾燥し、押出機に供給して２８０℃で溶融した（ポリマＢ層）。この二つのポリマを、それぞれ高精度濾過した後、矩形積層部を備えた２層合流ブロックにて、基層部にポリマＢ層を、片面積層部にポリマＡ層がくるように積層し、フィッシュテール型の口金よりシート状にして押出した後、静電印加キャスト法を用意して２５℃のキャスティングドラムに巻き付けて冷却固化し、未延伸フィルムを作った。
【００５０】
この未延伸フィルムを長手方向に、８５．５℃で３．３倍に延伸し、次いで幅方向に１１０の温度で３．７倍に延伸した後に２２０℃の熱処理温度で熱固定し、幅方向に４％の弛緩処理を施して、厚さ１８μｍのＡ／Ｂ２層構造である偏光膜用支持体フィルムを得た。Ａ／Ｂ２層構造の屈折率は、１．６４〜１．６６のポリエステルフィルムであった。Ａ層の積層厚みは、２μｍであった。この評価結果は、表１に示した通りであり、得られたフィルムに透明電極、さらに偏光特性を持ち合せて実装した液晶パネルは、コントラスト、視認性の良好なものではなかった。
【００５１】
［比較例３］
積層膜成形塗液によるＡ層の厚みを５００ｎｍにする以外は、実施例２と同様の製造方法で厚み２５μｍのＡ／Ｂ２層構造である偏光膜用支持体フィルムを得た。この評価結果は、表１に示した通りであり、得られたフィルムに透明電極、さらに偏光特性を持ち合せて実装した液晶パネルは、コントラスト、視認性の良好なものではなかった。
【００５２】
［比較例４］
５ｍｏｌ重量％のイソフタルスルホン酸ナトリウム塩の共重合ポリエチレンテレフタレートのペレットをマスターペレット３とした。粒子添加を行わなかったポリエチレンテレフタレートのペレットをマスターペレット２を用意した。
【００５３】
上記ペレット３を１８０℃で３時間乾燥し、ベント式二軸混練押出機１に供給し、２８０℃で溶融した（ポリマＡ層）。さらに、もう一台の押出機２を用意し、マスターペレット２を１８０℃で３時間乾燥し、押出機に供給して２８０℃で溶融した（ポリマＢ層）。この二つのポリマを、それぞれ高精度濾過した後、矩形積層部を備えた２層複合ブロックにて、基層部にポリマＢ層を、両面積層部にポリマＡ層がくるように積層し、フィッシュテール型の口金よりシート状にして押出した後、静電印加キャスト法を用意して２５℃のキャスティングドラムに巻き付けて冷却固化し、未延伸フィルムを作った。
【００５４】
この未延伸フィルムを長手方向に、８５．５℃で３．３倍に延伸し、次いで幅方向に１００の温度で３．７倍に延伸した後に２２０℃の熱処理温度で熱固定し、幅方向に４％の弛緩処理を施して、厚さ２８μｍのＡ／Ｂ／Ａ３層構造である偏光膜用支持体フィルムを得た。Ａ層単膜時の屈折率は、１．５７であり、Ｂ層の屈折率は、１．６４〜１．６６のポリエステルフィルムであった。Ａ層の積層厚みは、２μｍであった。この評価結果は、表１に示した通りであり、得られたフィルムに透明電極、さらに偏光特性を持ち合せて実装した液晶パネルは、コントラスト、視認性の良好なものではなかった。
【００５５】
【表１】

【００５６】
【発明の効果】
本発明は、波長４００〜７００ｎｍの範囲における分光光度計の透過率の振幅の変化量が７％以下であるので、液晶表示部のコントラストを低下させることのない偏光膜用支持体フィルムを提供することができる。また、本発明は、厚みが０．１５μｍ以下、屈折率が１．４２〜１．５３である低屈折率層Ａ層）と厚みが２０μｍ以上、屈折率１．５３〜１．８である高屈折率層Ｂ層で構成されたＡ／Ｂ積層構造またはＡ／Ｂ／Ａ積層構造を有することにより、液晶表示部のコントラストを低下させることのない偏光膜用支持体フィルムを提供することができる。
【図面の簡単な説明】
【図１】偏光板の構造を示す概略図である。
【図２】図１とは異なる偏光板の構造を示す概略図である。
【図３】分光測定における透明フィルムの光干渉現象を示す透過率の波長分散結果である。
【符号の説明】
１：偏光フィルム
２：表面保護フィルム
３：粘着剤層
４：離型フィルム
５：支持体フィルム
６：透明導電層
７：偏光膜
８：粘着剤層
９：離型フィルム[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a polarizing plate, and more specifically, to a support film on which a polarizing film for exhibiting polarization characteristics is laminated.
[0002]
[Prior art]
2. Description of the Related Art In recent years, with the development of IT industrial equipment, an STN (Super Twisted Nematic) type or a TFT (Thin Film Transistor) type liquid crystal display LCD, which has advantages of thin and light weight, low power consumption, and high image quality as compared with a CRT (Cathode Ray Tube). (Liquid Crystal Display) continues to grow rapidly. In particular, there is a strong demand for a thin and lightweight display unit, and research and development have been promoted. However, since the configuration of the optical member of the conventional display unit is extremely complicated and requires many steps, it has almost reached the limit. However, recently, with the introduction of a new polarizing plate different from the polarizing plate of the conventional optical member, the number of steps in the related art can be greatly simplified, and the possibility of reducing the thickness and weight is further expanding (for example, Non-Patent Document 1). , 2).
[0003]
Here, the polarizing plate is an indispensable optical member having a function of giving light and dark to transmitted light of the LCD and changing a hue.
[0004]
A conventional polarizing plate usually includes a polarizing film 1, a surface protection film 2, an adhesive layer 3, and a release film 4, as shown in FIG. The polarizing film 1 is made of a polarizer having a polarizing axis and a polarizing axis in which a polarizing element such as iodine or a dichroic dye is adsorbed and oriented on a hydrophilic film such as a polyvinyl alcohol film, and is coated with a cellulose film from above and below. It has a structure in which the upper and lower surfaces are coated with an acrylic resin. Due to the laminated structure of the amorphous polymer, the thickness of the polarizing film 1 needs to be several hundreds μ or more.
[0005]
The surface protective film 2 is made of a transparent plastic film having a low moisture permeability and a small deformation such as elongation like a polyester film. The surface protective film 2 and the polarizing film 1 are adhered by an adhesive (not shown), and the surface protective film 2 is firmly adhered to the adhesive, but easily peels off from the polarizing film 1 even with time. What you get is used. The pressure-sensitive adhesive layer 3 is provided for adhering the polarizing film 1 to a liquid crystal cell (not shown) and is made of a pressure-sensitive pressure-sensitive adhesive or the like. However, in the state of the polarizing plate shown in FIG. The mold film is adhered. As the release film 4, a biaxially oriented polyester film (hereinafter, also simply referred to as "polyester film") is used because it is excellent in transparency, strength, heat resistance, flatness, and the like.
[0006]
On the other hand, since the polarization characteristic is developed by the self-alignment of the molecular chains in the applied liquid crystal paint, two usage methods have been developed at present (for example, see Non-Patent Document 3). First, it is directly applied to a liquid crystal cell to serve as a polarizing plate, and second, it is applied to a plastic film on which a transparent conductive material is laminated to form a polarizing plate. As shown in FIG. 2, the latter polarizing plate includes a support film 5, a transparent conductive layer 6, a polarizing film 7, an adhesive layer 8, and a release film 9. As the support film 5, a polyester film excellent in transparency, heat resistance, strength, and the like is mainly used. As the transparent conductive layer 6, ITO (Indum-Tin-Oxide) having excellent transparency and conductivity is used. Since the polarizing film 7 is obtained by applying a water-soluble liquid crystal paint and drying it, it is possible to reduce the thickness to a submicron level.
[0007]
[Non-Patent Document 1] Bobrov, C .; Cobb, P .; Lazarev, P .; Bos, D.A. Bryand, H .; Wonderly, "Lyotropic Thin Film Polarizers", Int. Symp. Digest of Technical Papers, Long Beach, California USA, Society for Information Display, May 16-18 2000, Vol. XXXX, 1102-1107.
[0008]
[Non-Patent Document 2] L. Ignatov, P .; Lazarev, N.W. Ovchinnikova, "Thin Film Polarizers: Optical and Color Chronicstics. Thermostability", Int. Symp. Digest of Technical Papers, Long Beach, California USA, SID, May 16-18 2000, Vol. XXXI, 834-838.
[0009]
[Non-Patent Document 3] Bobrov, P .; Lazarev, D.M. McMirtry and S.M. Remizov, "Incorporation of Optiva Polarizer In LCD Production Line", Int. Symp. Seminar & Exhibition, San Jose, California, USA, SID June 5-8 2001.
[0010]
[Problems to be solved by the invention]
However, although the above-mentioned polarizing plate can be made as thin as 100 μm or less, when it is used as a polarizing plate of a liquid crystal display section, there is a problem that the contrast is lowered. In view of such circumstances, an object of the present invention is to provide a support film for a polarizing film and a polarizing plate that do not reduce the contrast of a display portion.
[0011]
[Means for Solving the Problems]
The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, have found that the main cause of lowering the contrast of the liquid crystal display portion is an optical interference phenomenon that occurs on the front and back surfaces of a transparent film support. By suppressing the amount of change in transmittance in the visible light region due to this phenomenon, more specifically, by suppressing the oscillation curve of transmittance with respect to wavelength, a polarizing film support film that does not easily lower the contrast of the liquid crystal display unit has been completed. Was.
[0012]
That is, the present invention provides a support film for a polarizing film, wherein the variation ΔT of the amplitude of light transmittance represented by the formula (1) is 7% or less.
ΔT = (Tmax−Tmin) / Tmin × 100 (1)
Here, Tmax and Tmin are the maximum transmittance (%) and the minimum transmittance (%) in the wavelength range of 400 to 700 nm, respectively.
[0013]
Further, a low refractive index layer A layer having a thickness of 0.15 μm or less and a refractive index in a range of 1.42 to 1.53 and a high refractive index having a thickness of 20 μm or more and a refractive index in a range of 1.53 to 1.8. It is a support film for a polarizing film having an A / B laminated structure or an A / B / A laminated structure composed of a rate layer B layer.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in more detail.
[0015]
In the support film for a polarizing film according to the first invention of the present invention, the change in the amplitude of the transmittance of the spectrophotometer in the wavelength range of 400 to 700 nm defined by the formula (1) is preferably 7% or less. is necessary.
ΔT = (Tmax−Tmin) / Tmin × 100 (1)
However, in the equation (1), ΔT is a change amount (%) of the amplitude of the transmittance, Tmax is a maximum transmittance (%), and Tmin is a minimum transmittance (%).
[0016]
Here, the spectrophotometer is a device capable of measuring the light transmittance of each wavelength of 1 nm from infrared to ultraviolet regions by passing light through a band-pass filter. For example, when a transparent film is measured using this apparatus, a wavelength dispersion result of the transmittance as shown in FIG. 3 is usually obtained due to a light interference phenomenon. If the variation of the transmittance defined by the expression (1) at the wavelength of 400 to 700 nm of the transmittance oscillation curve is larger than 7%, the contrast of the liquid crystal display unit is reduced. More preferably, it is 0% or more and 3% or less.
[0017]
That is, the support film for a polarizing film according to the second invention of the present invention suppresses light interference phenomenon and light reflection on the film surface, and has a low refractive index layer (hereinafter sometimes referred to as an A layer) from the viewpoint of thinning. It is necessary to have an A / B two-layer structure or an A / B / A three-layer structure composed of a high refractive index layer (hereinafter, may be referred to as a B layer). Here, it is preferable that the layer A has a thickness of 0.15 μm or less and a refractive index of 1.42 to 1.53, and the layer B has a thickness of 20 μm or more and a refractive index of 1.53 to 1.8. Is preferred. The A / B two-layer and A / B / A three-layer structures may be formed, for example, by co-extrusion of different polymers by a two-layer merging block each having a rectangular laminated portion using a T base or the like, or a B layer as a base layer portion. It is produced by laminating an A layer as a coating layer on one side or both sides.
[0018]
The substance used as the layer A may exhibit transparency when used at a thickness of 0.15 μm or less, and may have a refractive index of 1.42 to 1.53. However, a support film generally used as an optical member varies depending on various uses. When a surface modification is required, the layer A may correspond thereto. For example, in order to raise the transparency as an optical member to an extreme level, the haze due to light scattering is reduced by making the layer B substantially particle-free and by adding particles only to the layer A so that lubricity can be imparted. Suppress, achieve transparency and lubricity. From this viewpoint, Ra and Rt on the surface of the layer A are preferably 10 nm or more and 18 nm or less, respectively, and 100 nm or more and less than 600 nm. More preferably, Ra and Rt are respectively 11 nm or more and 16 nm or less, and 120 nm or more and less than 400 nm. Here, Ra and Rt mean the center line average roughness and the maximum roughness, respectively. Ra is the measured length L portion taken from the roughness curve in the direction of its center, the center line of this extraction is taken as the X axis, the vertical axis is taken as Y, and the roughness curve is expressed as Y = f (x), It is given by the following equation.
[0019]
(Equation 1)

[0020]
Rt represents the distance between the largest peak and the deepest valley within the measured length of the roughness curve. When Ra exceeds 18 nm, the surface becomes rough and light scattering increases. When Rt is less than 100 nm, the degree of escape of air tends to decrease, and slip tends to deteriorate. It is not preferable because the film is difficult.
[0021]
The method of controlling Ra and Rt to the above-mentioned values is not particularly limited, but can be achieved, for example, by appropriately selecting the particle diameter of the above-described particles and the thickness of the A layer.
[0022]
When a material such as a polyester film having a crystallographic surface is used for the layer B as the base layer, the adhesiveness of various paints, adhesives, inks, etc. is poor, so that the layer A is made of polyester, acrylic, polyurethane, acrylic or the like. Easy adhesion is achieved by a method in which various resins such as graft polyester are provided as a primer layer. For example, as the polyester resin, terephthalic acid, isophthalic acid, sebacic acid, trimellitic acid, pyromellitic acid, 5- (2,5-disotetrahydrofurfuryl) -3-methyl-3-cyclohexene-1 as an acid component , 2 dicarboxylic acid and a glycol component include a copolymer selected from ethylene glycol, dimethylene glycol, diethyl glycol, 1,4-butadiol, and neopentyl glycol. When this is used as a coating liquid in the form of an aqueous resin, it is preferable to copolymerize a compound containing a carboxylate group or a sulfonic acid group in order to facilitate water solubility and improve the adhesiveness of the polyester resin. Examples of the acrylic resin include a copolymer selected from methyl methacrylate, ethyl acrylate, n-butyl acrylate, 2-hydroxyethyl acrylate, acrylamide, n-methylol acrylamide, glycidyl methacrylate, and acrylic acid. In addition, when used as a coating liquid in the form of an aqueous resin, a copolymer with a monomer having a hydrophilic group (such as acrylic acid, methacrylic acid, acrylamide, vinyl sulfonic acid and a salt thereof) or a reactive emulsifier or a surfactant is used. It is preferable to use an acrylic resin produced by a method such as emulsion polymerization, suspension polymerization, or soap-free polymerization. Further, a cross-linking agent or the like may be contained in order to improve applicability. The cross-linking agent is not particularly limited as long as it is a compound that causes a cross-linking reaction.Examples include methylolated or alkylolated urea-based, melamine-based, acrylamide-based, polyamide-based compounds, epoxy compounds, isocyanate compounds, oxazoly coupling agents, and the like. is there.
[0023]
The thickness of the layer A is preferably 0.5 μm or more and 0.15 μm or less from the viewpoint of suppressing the light interference phenomenon caused on the front and back surfaces of the support film. More preferably, it is 0.8 μm or more and 0.12 μm or less. Further, the thickness of the layer B is preferably 20 μm or more from the viewpoint of imparting stiffness as a support film for a polarizing film. More preferably, it is 50 μm or more and less than 200 μm.
[0024]
The method for producing a polyester film suitable as the layer B used in the support film for a polarizing film of the present invention is not particularly limited, but a production method in which orientation crystallization is imparted by stretching from the point of extracting stiffness is preferred. For example, the molten polymer is supplied to an extruder, melt-extruded into a sheet using a T-type die or the like, and then cooled and solidified on a casting drum to form an unstretched film. It can be obtained by, for example, a method of stretching at a temperature equal to or higher than the glass transition point (Tg). The stretching method at this time may be a method of stretching in the width direction after stretching in the longitudinal direction as is known, or a method of stretching in the longitudinal direction after stretching in the width direction. Stretching in the longitudinal direction and stretching in the width direction may be performed. May be combined plural times. According to the present invention, the stretching temperature and the stretching ratio may be any, but in the case of a normal polyester film, the stretching temperature is from 80 ° C to 130 ° C, and the stretching ratio is preferably from 2 times to 5 times. . Next, the stretched film is heat-treated. This heat treatment is generally performed at a temperature higher than the stretching temperature and lower than the melting point. In the case of ordinary polyester, it is preferable to carry out at a temperature in the range of 130 ° C to 230 ° C. At this time, it is also preferable to carry out a relaxation heat treatment in order to impart thermal dimensional stability to the film.
[0025]
It is preferable that the relationship between the main orientation axis of the layer B of the support film for a polarizing film of the present invention and the polarizing direction of the polarizing film is 0 ° ± 10 ° or 90 ° ± 10 °. The main orientation axis refers to the direction in which molecules are most polarized in the plane, and the direction having the highest refractive index in a refractive index ellipsoid. By installing this orientation so as to match the polarization direction of the polarizing film or to maintain a relationship of 90 ° ± 10 ° error range, the optical interference phenomenon due to birefringence is suppressed, and the contrast of the liquid crystal display unit is reduced. This has the effect of preventing the decrease. Birefringence means that when light is incident on an anisotropic substance (birefringent body) having a different refractive index in the longitudinal direction and the width direction of a film such as a biaxially oriented polyester film, the light is split into two directions and the object travels in two directions. A phenomenon that looks heavy.
[0026]
The support film for a polarizing film of the present invention preferably has a retardation (Re) of from 0 nm to 400 nm or from 1000 nm to 20,000 nm from the viewpoint of suppressing the birefringence phenomenon of the substance itself.
Re = Δn · d (2)
Here, in the equation (2), Δn is birefringence in the in-plane direction of the film at a wavelength λ = 590 nm, and d is the thickness (nm) of the film.
[0027]
It is preferable that the retardation is 400 nm or less to suppress the light interference phenomenon due to birefringence. More preferably, it is 100 nm or less.
[0028]
In addition, as an apparatus for measuring the optical anisotropy of a film, a microwave molecular orientation meter may be used. In this case, it is preferable that the MOR (Maximum Oriented Ratio) value, which is a measured value, be 1.0 or more and 1.2 or less. The MOR value is a ratio (maximum value / minimum value) of the maximum value and the minimum value of the transmitted microwave intensity measured by the microwave transmission type molecular orientation meter. A film manufacturing method for setting the in-plane retardation of the film to such a value is achieved by an unstretched or isotropic biaxially oriented film. It is also preferable that the retardation described above has a value of 1000 nm or more, as opposed to 400 nm or less, as a support film for a polarizing film. The lower the retardation, the less the effect of suppressing light interference due to birefringence. However, from the viewpoint of suppressing the light interference by increasing the retardation, it is more preferably 1300 nm or more. The MOR value is preferably 1.4 or more. Since the retardation is proportional to the thickness of the film, and if it is too thick, it will depart from the practical advantage of thinning, so the upper limit is preferably 20,000 nm or less. The MOR value is preferably 7 or less.
[0029]
Further, from the viewpoint of transparency, which is indispensable as an optical member, the polarizing film support film preferably has a total light transmittance of 88% or more and a haze of 2% or less.
[0030]
The optical properties of a film having a total light transmittance of 88% or more and a haze of 2% or less mainly depend on the resin properties of the film itself, such as selection of particles as a lubricant and coating of a transparent low refractive index layer. It is appropriately achieved by performing the surface modification. From the viewpoint that the thermal dimensional stability of the liquid crystal display portion due to warpage of the film due to heat is required, the film longitudinal direction before and after the heat treatment of the film for the polarizing film support when subjected to the heat treatment at 1 atm and 150 ° C. for 10 minutes. It is preferable that both the heat shrinkage in the width direction and the heat shrinkage in the width direction are 3% or less.
[0031]
In addition, a resin is used as a main raw material of the layer B of the film of the present invention. The resin used here is replaced with a glass plate on which ITO is deposited, which is a transparent member constituting a conventional liquid crystal display portion, or a cellulose film in which a polarizer is sandwiched from both sides. As a matter of course, refraction and dimensional stability are required to have a mechanical strength (strength of stiffness) which is a characteristic for enabling further thinning. Materials satisfying transparency and low birefringence include polymethyl methacrylate, triacetate, poly-4-methylpentene, polystyrene, and polycarbonate. In particular, polycarbonate is preferably used in terms of dimensional stability such as a coefficient of hygroscopic expansion, a coefficient of thermal expansion, and shrinkage with time, and a stiffness enabling thinning. The polycarbonate herein has a carbonate unit as a structural unit, and means an aromatic polycarbonate made of bisphenol A among them.
[0032]
On the other hand, when priority is given to thinning, polyester is preferable as the resin having the best stiffness. The polyester referred to here is a polyester obtained by polymerization of a monomer having an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid and a diol as main components. Here, “mainly” means that the content is 50 mol% or more.
[0033]
Examples of such aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 4,4′- Examples thereof include diphenyl dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, and 4,4'-diphenyl sulfone dicarboxylic acid. In addition, examples of the aliphatic dicarboxylic acid include adipic acid, suberic acid, sebacic acid, dodecandionic acid, and the like. Among them, terephthalic acid and isophthalic acid are preferred. One of these acid components may be used alone, or two or more thereof may be used in combination. Further, an oxyacid such as hydroxybenzoic acid may be partially copolymerized.
[0034]
Examples of the diol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, and 1,5-pentanediol. , 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2-bis (4- (Hydroxyethoxyphenyl) propane and the like. Among them, ethylene glycol is preferably used. These diol components may be used alone or in combination of two or more.
[0035]
In the present invention, the polyester is preferably polyethylene terephthalate, a copolymer of ethylene terephthalate and ethylene isophthalate, polyethylene-2,6-naphthalate and its copolymer, polybutylene terephthalate and its copolymer, polybutylene naphthalate Phthalate and its copolymer, furthermore, polyhexamethylene terephthalate and its copolymer, polyhexamethylene naphthalate and its copolymer and the like can be mentioned, and polyethylene terephthalate is particularly preferred. These polyesters may be used as a single polymer or may be used in a copolymer or a blend as long as the effects of the present invention are not impaired.
[0036]
The method for producing the resin used as the main raw material of the layer B, which is the substrate layer of the film of the present invention, is not particularly limited. For example, the polyester preferably used in the present invention can be produced by the following method. For example, a method in which an acid component is directly esterified with a diol component, and then the product of this reaction is heated under reduced pressure to remove the excess diol component and polycondensate to produce a dialkyl acid. There is a method of using an ester, performing a transesterification reaction between the ester and a diol component, and then performing polycondensation in the same manner as described above. At this time, if necessary, a conventionally known alkali metal, alkaline earth metal, manganese, cobalt, zinc, antimony, germanium, titanium compound or the like can be used as a reaction catalyst.
[0037]
The polyester in the present invention may further contain, if necessary, a flame retardant, a heat stabilizer, an antioxidant, an ultraviolet absorber, an antistatic agent, an organic lubricant such as a pigment, a fatty acid ester, a wax, or an antifoaming agent such as siloxane. Can be blended. As the lubricant, an organic or inorganic lubricant can be used. As the shape, shape particles such as aggregated particles, true spherical particles, beads, composite particles, and scale-like particles can be used. Examples of the material include, for example, inorganic oxides such as silicon oxide, calcium carbonate, titanium oxide, alumina, zirconia, aluminum silicate, mica, clay, talc, and magnesium oxide. Resins such as olefin or modified olefin resin, cross-linked or non-cross-linked polystyrene resin, cross-linked or non-cross-linked acrylic resin, fluorine resin, silicon resin, and organic lubricants such as stearamide, oleic amide, fumaric amide, etc. Of various amide compounds.
The film of the present invention thus obtained is used as a support film for a polarizing film.
[0038]
In the present invention, the properties of the film were measured by the following methods.
(1) Measurement with a spectrophotometer at 400 to 700 nm:
A sample cut out from the center in the width direction of the film to a size of 4.0 × 3.5 cm in length was used as a sample, and light was transmitted at a wavelength of 400 to 700 nm using a spectrophotometer U-3410 manufactured by Hitachi, Ltd. The rate was measured under the conditions of a resolution of 2 nm or less, a scanning speed of 120 nm / min, a gain of 3, and a response medium. Further, the amount of change in the transmittance was obtained from the following equation (1).
ΔT = (Tmax−Tmin) / Tmin × 100 (1)
(However, in equation (1), ΔT is a change amount (%) of the amplitude of the transmittance, Tmax is a maximum transmittance (%), and Tmin is a minimum transmittance (%).)
(2) Retardation measurement:
The retardation of the film was measured using an automatic birefringence meter (KOBRA-21ADH manufactured by Shin-Oji Paper Co., Ltd.) using a sample cut out from the center in the film width direction (longitudinal direction 4.0 cm × width direction 3.5 cm). It was measured.
[0039]
(3) MOR value:
The MOR value was measured using a microwave molecular orientation meter by using a sample cut out of the central portion in the film width direction at a size of 10 × 10 cm as a measurement sample. As a microwave molecular orientation meter, a molecular orientation meter MOA-2001 (frequency 4 GHz) manufactured by KS Systems Co., Ltd. (currently Oji Scientific Instruments) was used.
(3) Light transmittance and haze in visible light
A sample cut out from the center in the film width direction to a length of 4.0 × 3.5 cm in width was used as a sample, and the light transmittance and haze were measured using a haze meter (HGM-2DP manufactured by Suga Test Instruments (for C light)). Measured.
(4) Surface roughness
A sample cut out from the center in the film width direction to a length of 4.0 × 3.5 cm in width was used as a sample, and the surface roughness (center line average roughness Ra and maximum roughness Rt) was manufactured by Kosaka Laboratory. It measured using the three-dimensional roughness meter SE-3AK. The measurement was performed under the conditions of a cut-off value of 0.08, a measurement length of 2 mm, a feed pitch of 5 μ, and 10 measurement lines.
(5) Heat shrinkage:
A sample of 1 × 10 cm was cut out from the center of the film width and heat-treated at 150 ° C. for 10 minutes in a gear oven (GHPS-222 manufactured by TABAI). By accurately measuring the length of the film in the longitudinal direction (MD: Machine Direction) and the length in the width direction (TD: Transverse Direction) before and after the film with a universal projector (E04 manufactured by 77-7 Nikon Corporation), the heat shrinkage rate is improved. I asked.
[0040]
【Example】
Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.
[Example 1]
Using a twin-screw kneader, a pellet of polyethylene terephthalate containing 1% by weight of calcium carbonate having an average particle size of 1.1 μm as an external additive was used as a master pellet 1. Next, a pellet of polyethylene terephthalate to which no particles were added was designated as master pellet 2.
[0041]
The pellets 1 were diluted using pellets of polyethylene terephthalate to which no particles were added so that the particle concentration of the pellets 1 was 0.03% by weight, and then dried at 180 ° C. for 3 hours. And melted at 280 ° C. This polymer was extruded in a sheet form from a fishtail-type die so as to form a layer B as a base layer portion, and was then cast by an electrostatic application casting method, wrapped around a casting drum at 25 ° C, and cooled and solidified. A stretched film was made. Thereafter, the film is heated by a roll heated to 95 ° C. and a radiation heater, and stretched 3.3 times in the longitudinal direction by stretching, and subsequently stretched 3.5 times in the width direction at 95 ° C. by a tenter. Further, the polyester film was subjected to a heat treatment in a heat treatment zone 230 ° C. subsequent to the tenter to obtain a polyester film having a refractive index of 1.66 to 1.67 as a B layer having a thickness of 30 μm. Thereafter, a water-soluble polyvinyl alcohol solution having a solid concentration of 0.1% by weight is applied to both sides of the film as an A layer by a coating liquid for forming a laminated film, and dried at 150 ° C. for 10 minutes. A support film for a polarizing film having an A / B / A three-layer structure having a thickness of 100 nm and an A layer containing an alcohol as a component was obtained. The evaluation results are as shown in Table 1. The liquid crystal panel in which the obtained film was mounted with the transparent electrode and the polarization property was excellent in contrast and visibility.
[0042]
[Example 2]
As in Example 1, polyethylene terephthalate having an average particle diameter of 1.1 μm and calcium carbonate having a particle concentration of 0.03% by weight was melted, extruded from a die, cooled and solidified by a 25 ° C. casting drum, and then heated to 86 ° C. The film was heated by a heated roll and a radiation heater and stretched, whereby the film was stretched 3.3 times in the longitudinal direction. The uniaxially stretched film was subjected to a corona discharge treatment in air. The layer A was prepared by mixing a coating liquid A, a coating liquid B, and particles C having the following compositions at a solid content ratio of liquid A / liquid B / particle C = 100/25/3. It was applied to the corona discharge surface of a uniaxially stretched film.
[Laminated film forming coating liquid]
Liquid A: an aqueous dispersion in which an acrylic resin having the following copolymer composition (glass transition temperature: 42 ° C., refractive index 1.52) is dispersed in water in the form of particles.
・ Copolymer component
63% by weight of methyl methacrylate
35% by weight of methyl acrylate
Acrylic acid 1% by weight
N-methylol acrylamide 1% by weight
Liquid B: a water-based coating liquid obtained by dissolving a methylol-based melamine crosslinking agent (“Nikalac” MW12LF manufactured by Sanwa Chemical Co., Ltd.) in water as a melamine-based crosslinking agent.
Particle C: an aqueous dispersion of colloidal silica particles having a particle size of 80 nm.
[0043]
Subsequently, the film is stretched 3.7 times in the width direction at 100 ° C. with a tenter, and further heat-treated in a heat treatment zone 230 ° C. subsequent to the tenter, and subjected to a 5% relaxation treatment in the width direction to obtain an A / B 2 having a thickness of 50 μm. A support film for a polarizing film having a layer structure was obtained. The refractive index of the B layer was a polyester film of 1.64 to 1.66. The thickness of the layer A by the coating liquid for forming a laminated film was 100 nm. The evaluation results are as shown in Table 1. The liquid crystal panel in which the obtained film was mounted with the transparent electrode and the polarization property was excellent in contrast and visibility.
[0044]
[Example 3]
A support film for a polarizing film having an A / B two-layer structure was obtained in the same manner as in Example 2 except that the thickness of the B layer was changed to 75 μm. The evaluation results are as shown in Table 1. The liquid crystal panel in which the obtained film was mounted with the transparent electrode and the polarization property was excellent in contrast and visibility.
[0045]
[Example 4]
A laminate film solution used in Example 2 was applied to a polycarbonate film having a refractive index of 1.58, a thickness of 50 μm, and a retardation of 30 nm, dried at 150 ° C. for 10 minutes, and then subjected to an A / B two-layer structure. Got. The thickness of the layer A obtained from the laminated coating solution was 100 nm. The evaluation results are as shown in Table 1. The liquid crystal panel in which the obtained film was mounted with the transparent electrode and the polarization property was excellent in contrast and visibility.
[0046]
[Example 5]
Similarly to Example 1, polyethylene terephthalate having an average particle diameter of 1.1 μm and having a particle concentration of calcium carbonate of 0.03% by weight was melted, extruded from a die, cooled and solidified with a 25 ° C. casting drum, and then heated to 86 ° C. The film was heated by a heated roll and a radiation heater and stretched 2.8 times in the longitudinal direction by stretching. The uniaxially stretched film was subjected to a corona discharge treatment in air. The layer A was applied to the corona discharge surface of the uniaxially stretched film in the same manner as in the laminated film forming coating liquid used in Example 2. Subsequently, the film is stretched 3.7 times in the width direction at 110 ° C. by a tenter, and further subjected to a heat treatment in a heat treatment zone 230 ° C. subsequent to the tenter to form a 38 μm thick support film for a polarizing film having an A / B two-layer structure. Got. The refractive index of the B layer was a polyester film having a refractive index of 1.63 to 1.67. The thickness of the layer A by the coating liquid for forming a laminated film was 100 nm. The evaluation results are as shown in Table 1. The liquid crystal panel in which the obtained film was mounted with the transparent electrode and the polarization property was excellent in contrast and visibility.
[0047]
[Comparative Example 1]
In Example 1, a 30-μm-thick polyester film, to which no polyvinyl alcohol was applied, was used as the polarizing film support film having a single film structure as the A layer formed by the coating liquid for forming a laminated film. The evaluation results are as shown in Table 1. The liquid crystal panel in which the obtained film was mounted with the transparent electrode and the polarization property was not good in contrast and visibility.
[0048]
[Comparative Example 2]
As in Example 1, a master pellet 1 of polyethylene terephthalate containing 1% by weight of calcium carbonate having an average particle diameter of 1.1 μm and a master pellet 2 of polyethylene terephthalate without addition of particles were prepared.
[0049]
The pellets 1 were diluted using pellets of polyethylene terephthalate to which no particles were added so that the particle concentration of the pellets 1 was 0.03% by weight, and then dried at 180 ° C. for 3 hours. And melted at 280 ° C. (polymer A layer). Further, another extruder 2 was prepared, and polyethylene terephthalate pellets to which no particles were added were dried at 180 ° C. for 3 hours, supplied to the extruder and melted at 280 ° C. (polymer B layer). After high-precision filtration of each of the two polymers, a two-layer merging block having a rectangular laminated portion is used to laminate the polymer B layer on the base layer and the polymer A layer on the one-sided layer portion. After extruding into a sheet from a die, an electrostatic application casting method was prepared and wound around a casting drum at 25 ° C. to be cooled and solidified to produce an unstretched film.
[0050]
This unstretched film is stretched 3.3 times at 85.5 ° C. in the longitudinal direction, then 3.7 times at a temperature of 110 in the width direction, and then heat-set at a heat treatment temperature of 220 ° C. Was subjected to a 4% relaxation treatment to obtain a polarizing film support film having an A / B two-layer structure with a thickness of 18 μm. The refractive index of the A / B two-layer structure was a polyester film having a refractive index of 1.64 to 1.66. The layer thickness of the layer A was 2 μm. The evaluation results are as shown in Table 1. The liquid crystal panel in which the obtained film was mounted with the transparent electrode and the polarization property was not good in contrast and visibility.
[0051]
[Comparative Example 3]
A support film for a polarizing film having an A / B two-layer structure with a thickness of 25 μm was obtained by the same manufacturing method as in Example 2 except that the thickness of the A layer by the multilayer film forming coating liquid was changed to 500 nm. The evaluation results are as shown in Table 1. The liquid crystal panel in which the obtained film was mounted with the transparent electrode and the polarization property was not good in contrast and visibility.
[0052]
[Comparative Example 4]
A pellet of 5 mol% by weight of copolymerized polyethylene terephthalate of sodium isophthalsulfonic acid was used as a master pellet 3. A master pellet 2 was prepared from polyethylene terephthalate pellets to which no particles were added.
[0053]
The pellets 3 were dried at 180 ° C. for 3 hours, supplied to the vented twin-screw kneading extruder 1, and melted at 280 ° C. (polymer A layer). Further, another extruder 2 was prepared, and the master pellet 2 was dried at 180 ° C. for 3 hours, supplied to the extruder, and melted at 280 ° C. (polymer B layer). After each of these two polymers is subjected to high-precision filtration, a polymer B layer is laminated on the base layer and a polymer A layer is laminated on the double-sided laminated portion using a two-layer composite block having a rectangular laminated portion. After extruding into a sheet from a die, an electrostatic application casting method was prepared and wound around a casting drum at 25 ° C. to be cooled and solidified to produce an unstretched film.
[0054]
This unstretched film is stretched 3.3 times in the longitudinal direction at 85.5 ° C., then stretched 3.7 times in the width direction at a temperature of 100, and then heat-set at a heat treatment temperature of 220 ° C. Was subjected to a 4% relaxation treatment to obtain a 28 μm-thick A / B / A 3-layered polarizing film support film. The refractive index of the single layer A was 1.57, and the refractive index of the layer B was a polyester film having a refractive index of 1.64 to 1.66. The layer thickness of the layer A was 2 μm. The evaluation results are as shown in Table 1. The liquid crystal panel in which the obtained film was mounted with the transparent electrode and the polarization property was not good in contrast and visibility.
[0055]
[Table 1]

[0056]
【The invention's effect】
The present invention provides a support film for a polarizing film, which does not reduce the contrast of a liquid crystal display section, since the change in the amplitude of the transmittance of the spectrophotometer in the wavelength range of 400 to 700 nm is 7% or less. be able to. In addition, the present invention provides a low refractive index layer A layer having a thickness of 0.15 μm or less and a refractive index of 1.42 to 1.53) and a high refractive index of 1.5 μm to 1.8 μm and a refractive index of 1.53 to 1.8. By having the A / B laminated structure or the A / B / A laminated structure composed of the refractive index layer B layer, it is possible to provide a support film for a polarizing film without lowering the contrast of the liquid crystal display portion. .
[Brief description of the drawings]
FIG. 1 is a schematic view showing the structure of a polarizing plate.
FIG. 2 is a schematic diagram showing a structure of a polarizing plate different from FIG.
FIG. 3 is a wavelength dispersion result of transmittance showing a light interference phenomenon of a transparent film in spectroscopic measurement.
[Explanation of symbols]
1: Polarizing film
2: Surface protection film
3: adhesive layer
4: Release film
5: Support film
6: transparent conductive layer
7: Polarizing film
8: Adhesive layer
9: Release film

Claims (8)

A support film for a polarizing film, wherein a change ΔT in amplitude of light transmittance represented by the formula (1) is 7% or less.
ΔT = (Tmax−Tmin) / Tmin × 100 (1)
(However, Tmax and Tmin are the maximum transmittance (%) and the minimum transmittance (%) in the wavelength range of 400 to 700 nm, respectively) A low refractive index layer A layer having a thickness of 0.15 μm or less and a refractive index in the range of 1.42 to 1.53 and a high refractive index layer having a thickness of 20 μm or more and a refractive index in the range of 1.53 to 1.8. A support film for a polarizing film having an A / B laminated structure or an A / B / A laminated structure composed of a B layer. The support film for a polarizing film according to claim 1, wherein the layer B is a polyester. The support film for a polarizing film according to any one of claims 1 to 3, wherein a main orientation axis of the B layer and a polarization direction of the polarizing film are maintained at 0 ° ± 10 ° or 90 ° ± 10 °. . The support film for a polarizing film according to any one of claims 1 to 3, wherein the retardation (Re) represented by the formula (2) is 400 nm or less or 1000 nm or more.
Re = Δn · d (2)
(However, Δn is the birefringence in the in-plane direction of the film at a wavelength λ = 590 nm, and d is the thickness (nm) of the film.) The support film for a polarizing film according to any one of claims 1 to 5, wherein the total light transmittance is 88% or more and the haze is 2% or less. The support film for a polarizing film according to any one of claims 1 to 6, wherein the heat shrinkage after heat treatment at 150 ° C for 10 minutes is 3% or less. A polarizing plate comprising the support film for a polarizing film according to claim 1.

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