JP4341163B2 - Polarizing plate protective film, polarizing plate using the same, manufacturing method, and liquid crystal display device - Google Patents

Description

【００６０】
式中、Ｒ₁、Ｒ₂、Ｒ₃、Ｒ₄及びＲ₅は同一でも異なってもよく、水素原子、ハロゲン原子、ニトロ基、ヒドロキシル基、アルキル基、アルケニル基、アリール基、アルコキシ基、アシルオキシ基、アリールオキシ基、アルキルチオ基、アリールチオ基、モノ若しくはジアルキルアミノ基、アシルアミノ基または５〜６員の複素環基を表し、Ｒ₄とＲ₅は閉環して５〜６員の炭素環を形成してもよい。
【００６１】
また、上記記載のこれらの基は、任意の置換基を有していて良い。
以下に一般式〔１〕で示される紫外線吸収剤の具体例を挙げるが、これらに限定されない。
【００６２】
ＵＶ−１：２−（２′−ヒドロキシ−５′−メチルフェニル）ベンゾトリアゾール
ＵＶ−２：２−（２′−ヒドロキシ−３′，５′−ジ−ｔｅｒｔ−ブチルフェニル）ベンゾトリアゾール
ＵＶ−３：２−（２′−ヒドロキシ−３′−ｔｅｒｔ−ブチル−５′−メチルフェニル）ベンゾトリアゾール
ＵＶ−４：２−（２′−ヒドロキシ−３′，５′−ジ−ｔｅｒｔ−ブチルフェニル）−５−クロロベンゾトリアゾール
ＵＶ−５：２−（２′−ヒドロキシ−３′−（３″，４″，５″，６″−テトラヒドロフタルイミドメチル）−５′−メチルフェニル）ベンゾトリアゾール
ＵＶ−６：２，２−メチレンビス（４−（１，１，３，３−テトラメチルブチル）−６−（２Ｈ−ベンゾトリアゾール−２−イル）フェノール）
ＵＶ−７：２−（２′−ヒドロキシ−３′−ｔｅｒｔ−ブチル−５′−メチルフェニル）−５−クロロベンゾトリアゾール
ＵＶ−８：２−（２Ｈ−ベンゾトリアゾール−２−イル）−６−（直鎖及び側鎖ドデシル）−４−メチルフェノール（ＴＩＮＵＶＩＮ １７１、Ｃｉｂａ製）
ＵＶ−９：オクチル−３−〔３−ｔｅｒｔ−ブチル−４−ヒドロキシ−５−（クロロ−２Ｈ−ベンゾトリアゾール−２−イル）フェニル〕プロピオネートと２−エチルヘキシル−３−〔３−ｔｅｒｔ−ブチル−４−ヒドロキシ−５−（５−クロロ−２Ｈ−ベンゾトリアゾール−２−イル）フェニル〕プロピオネートの混合物（ＴＩＮＵＶＩＮ １０９、Ｃｉｂａ製）
また本発明において、ベンゾフェノン系紫外線吸収剤としては下記一般式〔２〕で表される化合物が好ましく用いられる。
【００６３】
【化２】

【００６４】
式中、Ｙは水素原子、ハロゲン原子またはアルキル基、アルケニル基、アルコキシ基、及びフェニル基を表し、これらのアルキル基、アルケニル基及びフェニル基は置換基を有していてもよい。Ａは水素原子、アルキル基、アルケニル基、フェニル基、シクロアルキル基、アルキルカルボニル基、アルキルスルホニル基又は−ＣＯ（ＮＨ）_n-1−Ｄ基を表し、Ｄはアルキル基、アルケニル基又は置換基を有していてもよいフェニル基を表す。ｍ及びｎは１または２を表す。
【００６５】
上記において、アルキル基としては、例えば、炭素数２４までの直鎖または分岐の脂肪族基を表し、アルコキシ基としては例えば、炭素数１８までのアルコキシ基で、アルケニル基としては例えば、炭素数１６までのアルケニル基で例えばアリル基、２−ブテニル基などを表す。又、アルキル基、アルケニル基、フェニル基へ置換してもよい置換基としてはハロゲン原子、例えば、塩素原子、臭素原子、フッ素原子など、ヒドロキシル基、フェニル基、（このフェニル基にはアルキル基又はハロゲン原子などを置換していてもよい）などが挙げられる。
【００６６】
以下に一般式〔２〕で表されるベンゾフェノン系化合物の具体例を示すが、これらに限定されない。
【００６７】
ＵＶ−１０：２，４−ジヒドロキシベンゾフェノン
ＵＶ−１１：２，２′−ジヒドロキシ−４−メトキシベンゾフェノン
ＵＶ−１２：２−ヒドロキシ−４−メトキシ−５−スルホベンゾフェノン
ＵＶ−１３：ビス（２−メトキシ−４−ヒドロキシ−５−ベンゾイルフェニルメタン）
市販されているものとしては、ＴＩＮＵＶＩＮ Ｐ、ＴＩＮＵＶＩＮ ３２４、ＴＩＮＵＶＩＮ ３２０、ＴＩＮＵＶＩＮ ３２６、ＴＩＮＵＶＩＮ ３２７、ＴＩＮＵＶＩＮ ３２８、ＴＩＮＵＶＩＮ ３２９、ＴＩＮＵＶＩＮ ７７０、ＴＩＮＵＶＩＮ ７８０、ＴＩＮＵＶＩＮ １４４、ＴＩＮＵＶＩＮ １２０、ＵＶＩＴＥＸ ＯＢ（日本チバガイギー（株）製）等から適宜選択して使用することもできる。
【００６８】
本発明で好ましく用いられる上記記載の紫外線吸収剤は、透明性が高く、偏光板や液晶素子の劣化を防ぐ効果に優れたベンゾトリアゾール系紫外線吸収剤やベンゾフェノン系紫外線吸収剤が好ましく、不要な着色がより少ないベンゾトリアゾール系紫外線吸収剤が特に好ましく用いられる。
【００６９】
本発明に用いるポリエステルの合成方法は、特に限定があるわけではなく、前述したように従来公知のポリエステルの製造方法に従って製造できる。例えば、ジカルボン酸成分をジオール成分と直接エステル化反応させる直接エステル化法、初めにジカルボン酸成分としてジアルキルエステルを用いて、これとジオール成分とでエステル交換反応させ、これを減圧下で加熱して余剰のジオール成分を除去することにより重合させるエステル交換法を用いることができる。この際、必要に応じてエステル交換触媒或いは重合反応触媒を用い、或いは耐熱安定剤を添加することができる。この際、共重合成分である金属スルホネート基を有する芳香族ジカルボン酸類やポリエチレングリコールをエステル交換反応後に添加し、重縮合を行うことが好ましい。また、合成時の各過程で着色防止剤、酸化防止剤、結晶核剤、すべり剤、安定剤、ブロッキング防止剤、紫外線吸収剤、粘度調節剤、消泡剤、透明化剤、帯電防止剤、ｐＨ調整剤、染料、顔料等を添加させてもよい。
【００７０】
次に本発明のポリエステルフィルムの製造方法について説明する。
本発明の実質的に一軸で延伸したポリエステルフィルムとは、二軸延伸製膜において、主にどちらか一方向のみを行うことで得られる。即ち本発明においてポリエステルフィルムは、一方向の延伸倍率が１．００〜２．５倍、それと直交する方向の延伸倍率が２．５〜１０倍に二軸延伸製膜されたポリエステルフィルムであることが好ましく、より好ましくは、縦方向の延伸倍率が１．０〜２．０倍、横方向の延伸倍率が２．５〜７倍に二軸延伸製膜されたポリエステルフィルムであり、さらに好ましくは、縦方向の延伸倍率が１．１〜１．８倍、横方向の延伸倍率が３．０〜６．０倍に二軸延伸製膜されたポリエステルフィルムである。一方向の延伸倍率を大きくすることが好ましく、延伸倍率の比（縦横いずれかの高い方の延伸倍率／縦横いずれかの低い方の延伸倍率）は２以上であることが好ましく、更に４以上であることが好ましく、６以上であることが好ましい。又、未延伸のものに対して延伸後の面積比て４倍以上に延伸されていることが好ましく、更に好ましくは５〜７倍に延伸されていることが好ましい。
【００７１】
上記ポリエステルフィルムを得るには、従来公知の方法で行うことができ、特に限定されないが、以下の様な方法で行うことができる。この場合、縦方向とは、フィルムの製膜方向（長手方向）を、横方向とはフィルムの製膜方向と直角方向のことをいう。
【００７２】
先ず、原料のポリエステルをペレット状に成型し、熱風乾燥又は真空乾燥した後、溶融押出し、Ｔダイよりシート状に押出して、静電印加法等により冷却ドラムに密着させ、冷却固化させ、未延伸シートを得る。次いで、得られた未延伸シートを複数のロール群及び／又は赤外線ヒーター等の加熱装置を介してポリエステルのガラス転移温度（Ｔｇ）からＴｇ＋１００℃の範囲内に加熱し、一段又は多段縦延伸する方法である。
【００７３】
次に、上記のようにして得られた縦方向に延伸されたポリエステルフィルムを、Ｔｇ〜Ｔｍ（融点）−２０℃の温度範囲内で、横延伸し次いで熱固定する。
【００７４】
横延伸する場合、２つ以上に分割された延伸領域で温度差を１〜５０℃の範囲で順次昇温しながら横延伸すると巾方向の物性の分布が低減でき好ましい。さらに横延伸後、フィルムをその最終横延伸温度以下でＴｇ−４０℃以上の範囲に０．０１〜５分間保持すると巾方向の物性の分布がさらに低減でき好ましい。
【００７５】
熱固定は、その最終横延伸温度より高温で、Ｔｍ−２０℃以下の温度範囲内で通常０．５〜３００秒間熱固定する。この際、２つ以上に分割された領域で温度差を１〜１００℃の範囲で順次昇温しながら熱固定することが好ましい。
【００７６】
熱固定されたフィルムは通常Ｔｇ以下まで冷却され、フィルム両端のクリップ把持部分をカットし巻き取られる。この際、最終熱固定温度以下、Ｔｇ以上の温度範囲内で、横方向及び／又は縦方向に０．１〜１０％弛緩処理することが好ましい。また冷却は、最終熱固定温度からＴｇまでを、毎秒１００℃以下の冷却速度で徐冷することが好ましい。冷却、弛緩処理する手段は特に限定はなく、従来公知の手段で行えるが、特に複数の温度領域で順次冷却しながら、これらの処理を行うことが、フィルムの寸法安定性向上の点で好ましい。尚、冷却速度は、最終熱固定温度をＴ１、フィルムが最終熱固定温度からＴｇに達するまでの時間をｔとしたとき、（Ｔ１−Ｔｇ）／ｔで求めた値である。
【００７７】
これら熱固定条件、冷却、弛緩処理条件のより最適な条件は、フィルムを構成するポリエステルにより異なるので、得られた延伸フィルムの物性を測定し、好ましい特性を有するように適宜調整して決定すればよい。
【００７８】
また、上記フィルム製造に際し、延伸の前及び／又は後で帯電防止層、易滑性層、接着層、バリアー層等の機能性層を塗設してもよい。この際、コロナ放電処理、大気圧プラズマ処理、薬液処理等の各種表面処理を必要に応じて施すことができる。
【００７９】
カットされたフィルム両端のクリップ把持部分は、粉砕処理された後、或いは必要に応じて造粒処理や解重合・再重合等の処理を行った後、同じ品種のフィルム用原料として又は異なる品種のフィルム用原料として再利用してもよい。
【００８０】
本発明において、上記のようにして製膜されたポリエステルフィルムの面方向においての屈折率は、横方向の屈折率（ｎ_TD）と縦方向の屈折率（ｎ_MD）との差の絶対値｜ｎ_TD−ｎ_MD｜が０．０５以下であることが好ましく、より好ましくは０．０４以下、さらに好ましくは０．０２５以下である。
【００８１】
本発明のポリエステルフィルムの厚みは３〜１００μｍ、好ましくは５〜６０μｍ、さらに好ましくは膜厚５〜４０μｍ、より好ましくは膜厚１０〜３５μｍである。
【００８２】
本発明の偏光板用保護フィルムの面内方向におけるリターデーションＲ₀（ｎｍ）は小さいほど良く、１０００ｎｍ以下であることが好ましく、８００ｎｍ以下であることがより好ましく、５００ｎｍ以下であることが更に好ましい。本発明のポリエステルフィルムは従来のポリエステルフィルムと比較してＲ₀を低く抑えることができるため好ましい。
【００８３】
また、本発明の偏光板用保護フィルムはフィルム面内の屈折率が最大となる方向とフィルムの幅手方向（フィルムの長尺方向）とのなす角度が０°±１５°もしくは９０°±１５°であることが好ましく、更に０°±１０°もしくは９０°±１０°であることが好ましく、より好ましくは０°±５°もしくは９０°±５°であることであり、０°±２°もしくは９０°±２°であることが更に好ましい。
【００８４】
本発明のポリエステルフィルムは、上記ポリエステルフィルムからなる単独（単層）のフィルムでもよいが、本発明の効果を阻害しない範囲で、上記ポリエステルからなる層を少なくとも１層含む、複数の樹脂層からなる多層フィルムとしてもよい。上記ポリエステル層をＡ、その他の樹脂層をＢ及びＣとすると、例えばＡ／Ｂ、Ａ／Ｂ／Ａ、Ｂ／Ａ／Ｂ、Ｂ／Ａ／Ｃのように構成できる。もちろん４層以上の構成にすることもできる。この様に多層構成にすることで、例えば、強度や水バリアー性の高いフィルムをコア層や外層に積層することにより、複数の機能を同時に付与することができる。
【００８５】
上記樹脂層としては、前述のポリエステルなどが好ましく用いられる。
また、滑り性を付与するためマット剤等の微粒子を添加する場合は、最外層のみに添加すれば効果が得られるので、透明性等を劣化させずに機能付与することが可能となる。
【００８６】
添加できる微粒子としては特に限定はされないが、無機化合物の微粒子または有機化合物の微粒子が挙げられる。
【００８７】
無機化合物としては、珪素を含む化合物、二酸化珪素、酸化アルミニウム、酸化ジルコニウム、炭酸カルシウム、タルク、クレイ、焼成カオリン、焼成ケイ酸カルシウム、水和ケイ酸カルシウム、ケイ酸アルミニウム、ケイ酸マグネシウム及びリン酸カルシウム等が好ましく、更に好ましくは、ケイ素を含む無機化合物や酸化ジルコニウムであるが、二酸化珪素が特に好ましく用いられる。
【００８８】
二酸化珪素の微粒子としては、例えば、アエロジルＲ９７２、Ｒ９７２Ｖ、Ｒ９７４、Ｒ８１２、２００、２００Ｖ、３００、Ｒ２０２、ＯＸ５０、ＴＴ６００（以上日本アエロジル（株）製）等の市販品が使用できる。
【００８９】
酸化ジルコニウムの微粒子としては、例えば、アエロジルＲ９７６及びＲ８１１（以上日本アエロジル（株）製）等の市販品が使用できる。
【００９０】
有機化合物としては、例えば、シリコーン樹脂、弗素樹脂及びアクリル樹脂等のポリマーが好ましく、中でも、シリコーン樹脂が好ましく用いられる。
【００９１】
上記記載のシリコーン樹脂の中でも、特に三次元の網状構造を有するものが好ましく、例えば、トスパール１０３、同１０５、同１０８、同１２０、同１４５、同３１２０及び同２４０（以上東芝シリコーン（株）製）等の商品名を有する市販品が使用できる。
【００９２】
本発明に係る微粒子の１次平均粒子径としては、ヘイズを低く抑えるという観点から、２０ｎｍ以下が好ましく、更に好ましくは、５〜１６ｎｍであり、特に好ましくは、５〜１２ｎｍである。
【００９３】
多層フィルムを製造する方法としては、共押し出しによる方法、エクストルージョンラミネートによる方法、ドライラミネーションによる方法などを好ましく用いることができる。
【００９４】
本発明において、光学フィルムの表面が導電性を有することが好ましく、表面比抵抗（２３℃、２５％ＲＨ）が１×１０¹²Ω／□以下であることが好ましい。より好ましくは、１×１０¹¹Ω／□以下、さらに好ましくは１×１０¹⁰Ω／□以下である。
【００９５】
本発明においては吸湿性物質又は導電性物質を含有させることにより光学フィルムに導電性を付与することができる。これら導電性を付与させる物質としては、例えば、界面活性剤、導電性ポリマー、無機金属酸化物を挙げることができる。
【００９６】
用いることができる界面活性剤としては、アニオン性、カチオン性、両性及びノニオン性のいずれでもよい。アニオン性界面活性剤としては、例えば、アルキルカルボン酸塩、アルキルスルフォン酸塩、アルキルベンゼンスルフォン酸塩、アルキルナフタレンスルフォン酸塩、アルキル硫酸エステル類、アルキルリン酸エステル類、Ｎ−アシル−Ｎ−アルキルタウリン酸、スルホコハク酸エステル類、スルホアルキルポリオキシエチレンアルキルフェニルエーテル類、ポリオキシエチレンアルキルリン酸エステル類等の様なカルボキシ基、スルホ基、ホスホ基、硫酸エステル基、燐酸エステル基等の酸性基を含むものが好ましい。
【００９７】
カチオン性界面活性剤としては、例えば、アルキルアミン塩類、脂肪族或いは芳香族第４級アンモニウム塩類、ピリジニウム、イミダゾリウム等の複素環第４アンモニウム塩類、及び脂肪族又は複素環を含むホスホニウム又はスルホニウム塩類等が好ましい。
【００９８】
両性界面活性剤としては、例えば、アミノ酸類、アミノアルキルスルホン酸類、アミノアルキル硫酸又は燐酸エステル類、アルキルベタイン類、アミンオキシド類等が好ましい。
【００９９】
ノニオン性界面活性剤としては、例えば、サポニン（ステロイド系）、アルキレンオキサイド誘導体（例えば、ポリエチレングリコール、ポリエチレングリコール／ポリプロピレングリコール縮合物、ポリエチレングリコールアルキルエーテル類又はポリエチレングリコールアルキルアリールエーテル類、ポリエチレングリコールエステル類、ポリエチレングリコールソルビタンエステル類、ポリアルキレングリコールアルキルアミン又はアミド類、シリコーンのポリエチレンオキサイド付加物類）、グリシドール誘導体（例えば、アルケニルコハク酸ポリセリド、アルキルフェノールポリグリセリド）、多価アルコール脂肪酸エステル類等のアルキルエステル類等が好ましい。
【０１００】
導電性ポリマーは、特に限定されず、アニオン性、カチオン性、両性及びノニオン性のいずれでもよいが、その中でも好ましいのは、アニオン性、カチオン性である。より好ましいのは、アニオン性では、スルホン酸系、カルボン酸系、カチオン性では、３級アミン系、４級アンモニウム系のポリマー又はラテックスである。
【０１０１】
これらの導電性ポリマーは、例えば、特公昭５２−２５２５１号、特開昭５１−２９９２３号、特公昭６０−４８０２４号記載のアニオン性ポリマー又はラテックス、特公昭５７−１８１７６号、同５７−５６０５９号、同５８−５６８５６号、米国特許４，１１８，２３１号等に記載のカチオン性ポリマー又はラテックスを挙げることができる。
【０１０２】
例えば、特願２０００−８００４３号記載のプラズマ処理で帯電防止層あるいは導電層を設けることもできる。
【０１０３】
本発明の光学フィルムは、偏光子の少なくとも１面に張り合わせることで偏光板を構成する。偏光子の他の面は、公知の偏光板保護フィルムを張り合わせてもよいし、本発明の光学フィルムを張り合わせてもよい。本発明の光学フィルムを偏光板保護フィルムとして用いると、従来のポリエステルフィルムでは巻き癖が取れず、偏光板とした後もカールが残ってしまったり、強い巻き癖に起因して接着部が剥離しやすいといった問題があったが、本発明の光学フィルムは巻き癖が容易に解消するため、特に偏光板保護フィルムに適している。特に偏光子と貼合する前あるいは後に水あるいは水溶液に浸すあるいは蒸気をあてる等によって容易に巻き癖を解消することができ、平面性に優れた偏光板を提供することができる。又、従来のポリエステルと比較して本発明の光学フィルムは吸湿膨張係数がトリアセチルセルロースに近いため、偏光子の一方にトリアセチルセルロース等のセルロースエステル系偏光板保護フィルム、もう一方に本発明の光学フィルムを用いたハイブリット偏光板であっても、吸湿等によって液晶表示装置に張り付けた偏光板が剥離したり皺が発生しにくく、優れている。
【０１０４】
本発明の光学フィルムと偏光子を貼り合わせるのに使用される接着剤としては、十分な接着性を持ち、透明で、偏光機能を阻害しないものが好ましく用いられ、例えば、ポリエステル系接着剤、ポリアクリル系接着剤、エポキシ系接着剤、シアノアクリレート系接着剤、ポリウレタン系接着剤、ポリビニルアルコール、ポリビニルブチラール等のポリビニルアルコール系接着剤などが挙げられる。
【０１０５】
接着性向上のため、コロナ放電処理、グロー放電処理、紫外線処理、火炎処理、大気圧ガス中放電プラズマ処理、薬液処理などの各種表面処理を必要に応じて施すことができる。さらに接着性向上の為、下引層を塗設してもよい。下引層としては偏光子との接着性に優れる親水性コロイド層が特に好ましい。
【０１０６】
例えば、偏光板保護フィルムとして偏光子との接着性を向上させるために特願２０００−９７０６１号の方法等でプラズマ処理を行うことによって、ポリビニルアルコール系接着剤等を用いた場合の接着性をさらに向上させることができる。本発明の光学フィルムには必要に応じて、クリアハードコート層、防眩層、反射防止層、帯電防止層、導電層、光拡散層、易接着層、防汚層を単独であるいは適宜組み合わせて設けることができる。
【０１０７】
【実施例】
以下、実施例により本発明をさらに具体的に説明するが、本発明の実施態様はこれらに限定されるものではない。
【０１０８】
〔ポリエステルの合成〕
（ポリエステルＡ）
テレフタル酸ジメチル１００質量部、エチレングリコール６４質量部に酢酸カルシウム水和物０．１質量部を添加し、常法によりエステル交換反応を行なった。得られた生成物に５−ナトリウムスルホジ（β−ヒドロキシエチル）イソフタル酸のエチレングリコール溶液（濃度３５質量％）３９質量部（７モル％／全ジカルボン酸成分）、ポリエチレングリコール（数平均分子量３０００）５．８質量部（５質量％／生成したポリエステル）、三酸化アンチモン０．０５質量部、リン酸トリメチルエステル０．１３質量部を添加した。次いで徐々に昇温、減圧にし、２８０℃、４０Ｐａで重合を行ない、ポリエステルＡを得た。以下に示す方法に従って固有粘度を求めた。その結果、固有粘度は０．５０であった。
【０１０９】
固有粘度についてはウベローデ型粘度計を用いて以下の手順で算出した。質量比が約５５：４５（流下時間４２．０±０．１秒に調整）であるフェノールと１，１，２，２−テトラクロロエタンとの混合溶媒を用い、サンプルを溶かして濃度０．２，０．６，１．０（ｇ／ｄｌ）の溶液（温度２０℃）を調製した。ウベローデ型粘度計によって、それぞれの濃度（Ｃ）における比粘度（η_sp）を求め、式［η_sp／Ｃ］を濃度零に補外（Ｃ→０）し固有粘度［η］を求めた。固有粘度［η］の単位はｄｌ／ｇである。
【０１１０】
（ポリエステルＢ）
添加量を５−ナトリウムスルホジ（β−ヒドロキシエチル）イソフタル酸のエチレングリコール溶液（濃度３５質量％）２２質量部（４モル％／全ジカルボン酸成分）、ポリエチレングリコール（数平均分子量３０００）１２．２質量部（１０．５質量％／生成したポリエステル）に変更した以外は上記と同様にして、ポリエステルＢを得た。前期同様に測定した固有粘度は０．５５であった。
【０１１１】
（ポリエステルＣ）
テレフタル酸ジメチル１００質量部、エチレングリコール６５質量部、ジエチレングリコール２質量部にエステル交換触媒として酢酸マグネシウム水和物０．０５質量部を添加し、常法に従ってエステル交換反応を行った。得られた生成物に、三酸化アンチモン０．０５質量部、リン酸トリメチルエステル０．０３質量部を添加した。次いで、徐々に昇温、減圧にし、２８０℃、８０Ｐａで重合を行い、固有粘度０．６５のポリエステルＣを得た。
【０１１２】
〔光学フィルムの作製〕
（光学フィルム１）
ポリエステルＢのペレットを１５０℃で８時間真空乾燥した後、押出機を用いて２８５℃で溶融押出し、３０℃の冷却ドラム上に静電印加しながら密着させ、冷却固化させ未延伸シートを得た。この未延伸シートをロール式縦延伸機を用いて、８５℃で縦方向に１．２倍延伸した。表裏面の温度差は５℃以内であった。
【０１１３】
得られた一軸延伸フィルムをテンター式横延伸機を用いて、９５℃で横方向に４．５倍延伸した。次いで、７０℃で２秒間熱処理し、さらに第一熱固定ゾーン１５０℃で１０秒間熱固定し、第二熱固定ゾーン１８０℃で１５秒間熱固定して、次いで１６０℃で横（幅手）方向に５％弛緩処理し巻き取り、横方向の長さ１５００ｍｍ、厚さ３５μｍのポリエステルフィルム（光学フィルム１）を作製した。
【０１１４】
（光学フィルム２）
ポリエステルＡのペレットを１５０℃で８時間真空乾燥した後、押出機を用いて２８５℃で溶融押出し、３０℃の冷却ドラム上に静電印加しながら密着させ、冷却固化させ未延伸シートを得た。この未延伸シートをロール式縦延伸機を用いて、９０℃で縦方向に４．０倍延伸した。表裏面の温度差は５℃以内であった。
【０１１５】
得られた一軸延伸フィルムをテンター式横延伸機を用いて、１００℃で横方向に１．２倍延伸した。次いで、７０℃で２秒間熱処理し、さらに第一熱固定ゾーン１５０℃で１０秒間熱固定し、第二熱固定ゾーン１８０℃で１５秒間熱固定して、次いで１６０℃で横（幅手）方向に２％弛緩処理し巻き取り、横方向の長さ１５００ｍｍ、厚さ３５μｍのポリエステルフィルム（光学フィルム２）を作製した。
【０１１６】
（光学フィルム３）
ポリエステルＡとポリエステルＣのペレットを質量比で３：７になるようにタンブラー型混合機で混合し、１５０℃で８時間真空乾燥した。また、ポリエステルＢのペレットも１５０℃で８時間真空乾燥した。ポリエステルＡとポリエステルＣの混合物及びポリエステルＢを２台の押出機を用いて２８５℃で溶融押出し、マルチマニホールドダイを用いてシート状に押し出し、３０℃の冷却ドラム上に静電印加しながら密着させ、冷却固化させ未延伸シートを得た。この時各層の厚みの比は１：１となるようにした。この未延伸シートをロール式縦延伸機を用いて、９５℃で縦方向に１．０５倍延伸した。表裏面の温度差は５℃以内であった。
【０１１７】
得られた一軸延伸フィルムをテンター式横延伸機を用いて、１０５℃で横方向に４．０倍延伸した。次いで、７０℃で２秒間熱処理し、さらに第一熱固定ゾーン１５０℃で１０秒間熱固定し、第二熱固定ゾーン１８０℃で１５秒間熱固定して、次いで１６０℃で横（幅手）方向に５％弛緩処理し巻き取り、横方向の長さ１５００ｍｍ、厚さ３０μｍのポリエステルフィルム（光学フィルム３）を作製した。
【０１１８】
（光学フィルム４）
ポリエステルＣのペレットを１５０℃で８時間真空乾燥し、押出機を用いて２９０℃で溶融押出し、３０℃の冷却ドラム上に静電印加しながら密着させ、冷却固化させ未延伸シートを得た。この未延伸シートをロール式縦延伸機を用いて、９５℃で縦方向に１．２倍延伸した。表裏面の温度差は５℃以内であった。
【０１１９】
得られた一軸延伸フィルムをテンター式横延伸機を用いて、１０５℃で横方向に４．５倍延伸した。次いで、７０℃で２秒間熱処理し、さらに第一熱固定ゾーン１５０℃で１０秒間熱固定し、第二熱固定ゾーン１８０℃で１５秒間熱固定して、次いで１６０℃で横（幅手）方向に５％弛緩処理し巻き取り、横方向の長さ１５００ｍｍ、厚さ３０μｍのポリエステルフィルム（光学フィルム４）を作製した。
【０１２０】
（光学フィルム５）
酢化度６１．０％のセルローストリアセテート１００質量部とトリフェニルフォスフェート１５質量部を塩化メチレン４５０質量部とメタノール５０質量部の混合溶媒に溶解し、３５℃のステンレスベルト上に流延し、剥離可能となったところでステンレスベルトから剥がし、ロール搬送装置を用いて搬送しながら、徐々に温度を上げ、最終的に１２０℃で乾燥し、３８μｍのセルローストリアセテートフィルム（光学フィルム５）を作製した。
【０１２１】
以上のようにして得られた光学フィルム１〜５について下記の方法で含水率、寸法安定性、透湿性、カール値を評価した。結果を表１に示した。
【０１２２】
〈平衡含水率〉
フィルムサンプルを２３℃、相対湿度２０％に調湿された部屋に４時間以上放置した後、２３℃の蒸留水に２４時間浸漬させ、しかる後、表面の水分をふき取り、サンプルを微量水分計（例えば三菱化学（株）製、ＣＡ−２０型）を用いて温度１５０℃で水分を乾燥・気化させた後カールフィッシャー法により定量した。
【０１２３】
〈寸法安定性〉
フィルムを８０℃、９０％ＲＨで１０００時間処理した前後の、フィルムの面内の屈折率が最大の方向について、寸法変化率を求め評価した。収縮方向をマイナス、伸び方向を＋とした。
【０１２４】
〈透湿性〉
ＪＩＳ Ｚ０２０８により求めた。
【０１２５】
〈カール値〉
１５０ｍｍ×３０ｍｍに断裁した試料を、内径２５ｍｍ高さ３０ｍｍの円筒内に丸めて収納し、この状態で２３℃、５５％ＲＨ環境下で１０００時間放置して巻き癖を付けた。それぞれの試料を５０℃の温水に２分間浸漬した後、乾燥させた。該試料を長手方向５０ｍｍ、幅手方向２ｍｍに切断し、その試料小片を２３±２℃、５５％ＲＨ下で２４時間調湿し、曲率スケールを用いて、該試料と合致するカーブを有する曲率半径（１／ｍ）を確認し、その曲率半径を該試料のカール値とした。
【０１２６】
○ ： ほとんど巻き癖が残っていない。 カール値 １０未満
△ ： やや巻き癖が認められる。 カール値 １０〜２５未満
× ： 強い巻き癖が認められる。 カール値 ２５以上
〈リターデーション及び配向角の測定〉
自動複屈折率計ＫＯＢＲＡ−２１ＡＤＨ（王子計測機器（株）製）を用いて、２３℃、５５％ＲＨの環境下で、５９０ｎｍの波長において、３次元屈折率測定を行い、屈折率Ｎｘ、Ｎｙ、Ｎｚを求めた。下記一般式（１）に従って、面内リターデーションＲ₀を算出した。又、フィルム面内の屈折率が最大となる方向とフィルムの幅手方向とのなす角度θ（配向角）を求めた。
【０１２７】
Ｒ₀＝（Ｎｘ−Ｎｙ）×ｄ
式中、Ｎｘはフィルム面内の屈折率が最大となる方向の屈折率、ＮｙはＮｘに対し直角な方向のフィルム面内の屈折率である。ｄはフィルムの膜厚（ｎｍ）をそれぞれ表す。又、Ｎｘとフィルムの幅手方向とのなす角度をθ（°）とした。
【０１２８】
【表１】

【０１２９】
〔偏光子の作製〕
厚さ１２０μｍのポリビニルアルコールフィルムを沃素１質量部、沃化カリウム２質量部、ホウ酸４質量部を含む水溶液に浸漬し５０℃で４倍に延伸し偏光子を作製した。
【０１３０】
〔偏光板の作製〕
（偏光板１）
光学フィルム１の１方の表面に、春日電機（株）製コロナ放電処理装置（ＨＦＳ−２０２）を用いて、１２Ｗ・ｍｉｎ／ｍ²の条件で易接着処理を施した。
【０１３１】
前記で作製した偏光子の両面に、完全鹸化型ポリビニルアルコール５％水溶液を接着剤として、前記光学フィルム１の易接着処理を施した面側が偏光子側となるようにして貼合し、偏光板を作製した。この時、光学フィルムのフィルム面内での屈折率の最大方向が偏光子の偏光軸に平行になるように張り合わせた。
【０１３２】
（偏光板２〜４）
偏光板１と同様にして、光学フィルム１に代え、それぞれ２，３，４を用いて偏光板２〜４を作製した。なお、偏光板３の作製に際しては、光学フィルム３のポリエステルＢ層が偏光子側になる様に貼合した。
【０１３３】
（偏光板５）
光学フィルム５を４０℃の２．５ｍｏｌ／Ｌの水酸化ナトリウム水溶液中に６０秒間浸せきした後、水洗乾燥した。得られた鹸化処理済み光学フィルム５と前記で作製した偏光子の両面に完全鹸化型ポリビニルアルコール５％水溶液を接着剤として貼合し、偏光板５を作製した。この時、光学フィルムのフィルム面内での屈折率の最大方向が偏光子の偏光軸に平行になるように張り合わせた。
【０１３４】
以上のように作製した偏光板１〜５について、以下の方法で評価を行った。その結果を表２に示した。
【０１３５】
〈偏光度の高温高湿下での変化〉
偏光板サンプルを、８０℃、９０％ＲＨ１０００時間処理した後、波長５５０ｎｍで、１組の偏光板の偏光軸を平行にした場合の透過率（Ｈ₀）と、直交させた場合での透過率（Ｈ₉₀）をそれぞれ測定し、下記式で偏光度を求めた。なお、処理前の偏光板サンプルでの偏光度も同様に求めた。
【０１３６】
偏光度（％）＝｛（Ｈ₀−Ｈ₉₀）／（Ｈ₀＋Ｈ₉₀）｝^1/2×１００
〈乾燥性〉
偏光子と保護フィルムを貼合したときの接着剤が乾くまでに要した時間により下記の基準でランク付けした。
【０１３７】
○ ： ５分以内
△ ： １０分以内
× ： １０分を超えた場合
〈接着性〉
偏光板サンプルを、８０℃、９０％ＲＨで１０００時間処理した後の偏光子と保護フィルムとの張り合わせ状態を観察し下記の基準でランク付けした。
【０１３８】
○ ： 剥離なし
△ ： 僅かに剥離認められるが実用上問題ないレベル
× ： 剥離発生
〈加工性〉
偏光板サンプルを、２３℃、５５±５％ＲＨで２４時間放置した後、カッターで切断し端部を観察した。
【０１３９】
○ ： 切断した端部にバリの発生が認められず、容易に切断できた
△ ： 切断した端部に僅かにバリの発生が認められた
× ： 切断した端部にバリが発生し、切断しにくかった
【０１４０】
【表２】

【０１４１】
本発明の光学フィルムを用いた偏光板は優れた特性を有することがわかる。
【０１４２】
【発明の効果】
液晶ディスプレイ等の各種表示装置、特に偏光板保護フィルム等の光学フィルムとして優れた特性を有するポリエステル樹脂フィルムが得られた。[0001]
BACKGROUND OF THE INVENTION
The optical film of this invention is related with the optical film used for various display apparatuses, such as a liquid crystal display and an organic electroluminescent display, Specifically, It is related with the polyester resin film used as optical films, such as a polarizing plate protective film.
[0002]
[Prior art]
With the remarkable development of the information industry, display devices are being used in various places. In particular, the development of liquid crystal display devices has been remarkable and has come to be installed in various devices. On the other hand, there is an increasing demand for reduction in size and weight, and there is an increasing demand for thinning the polarizing plate and other members. The polarizing plate is usually made by sandwiching a polarizer with two polarizing plate protective films, and a cellulose ester film such as triacetyl cellulose is preferably used as the polarizing plate protective film.
[0003]
However, if the triacetyl cellulose film (TAC film), which is a protective film, is thinned in order to make the polarizing plate thin, there is a problem that the moisture permeability deteriorates or the dimensional stability is lowered, especially in a thin film of less than 40 μm. Since significant physical property deterioration occurred, it was difficult to impart sufficient durability to the polarizing plate.
[0004]
On the other hand, it is known that polyester can be used as a polarizing plate protective film. For example, it is known to use polyethylene terephthalate film, but polyethylene terephthalate film has low moisture permeability and is superior in dimensional stability compared to TAC film. In addition to being inferior, there was a problem that the drying property of the adhesive was extremely bad at the time of bonding with the polarizer.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to obtain a thinned optical film having a polyester resin layer used for various display devices such as a liquid crystal display, specifically, a polarizing plate protective film for a liquid crystal display.
[0006]
[Means for Solving the Problems]
  The above object of the present invention is achieved by the following configurations.
  (1) A polarizing plate protective film that is directly attached to at least one surface of a polarizer, and is made of a polyester resin film produced by a reaction of at least an aromatic dicarboxylic acid and a glycol, and having an equilibrium water content of 1 to 5%. Has a group selected from sulfonic acid or a salt thereof.
  (2) The polarizing plate protective film as described in (1) above, wherein the content of sulfur element in the polyester resin is 0.15 to 2% by mass.
  (3) 1-10 mol% of the polyester resin is 1-10 mol% with respect to the total aromatic dicarboxylic acid, 1-10 mol% with respect to the aromatic dicarboxylic acid having a group selected from sulfonic acids and salts thereof, or with respect to the total aromatic dicarboxylic acid The polarizing plate protective film according to (1) or (2), which is produced using a glycol having a group selected from sulfonic acid and a salt thereof.
  (4) The above-mentioned (3), wherein the polyester resin is produced using an aromatic dicarboxylic acid having a group selected from 1 to 10 mol% of a sulfonic acid and a salt thereof based on the total aromatic dicarboxylic acid. The polarizing plate protective film of description.
  (5) In any one of the above (2) to (4), the polyester resin is produced using 0.1 to 10% by mass of polyalkylene glycol with respect to the total amount of polyester of the reaction product. The polarizing plate protective film of description.
  (6) The polarizing plate protective film according to any one of (1) to (5), wherein the main component of the polyester resin is polyethylene terephthalate.
  (7) Any one of (1) to (6) above, wherein the film thickness is 5 to 40 μm, the equilibrium moisture content is 1 to 5%, and the dimensional stability is within ± 0.05%. Polarizing plate protective film.
  (8) It is a long film continuously formed by melt extrusion, and the angle θ formed between the direction in which the in-plane refractive index is the largest and the width direction of the long film is 0 ± 15 ° or 90 The polarizing plate protective film as described in (7) above, which is either ± 15 °.
  (9) It is a manufacturing method of the polarizing plate protective film as described in said (7) or (8), Comprising: The film which has a polyester resin layer which has group chosen from a sulfonic acid or its salt is 1.0- A method for producing a polarizing plate protective film, wherein the film is stretched 2.5 times and 2.5 to 10 times in a direction perpendicular thereto.
  (10) A polarizing plate using the polarizing plate protective film according to (7) or (8).
  (11) A liquid crystal display device using the polarizing plate according to (10) or the polarizing plate protective film according to any one of (1) to (8).
  In addition, the following 1-13 is a structure used as a reference.
[0007]
1. An optical film comprising a polyester resin layer produced by a reaction of at least an aromatic dicarboxylic acid and a glycol and having an equilibrium water content of 1 to 5%.
[0008]
2. 2. The optical film as described in 1 above, wherein the polyester resin has a group selected from sulfonic acid or a salt thereof.
[0009]
3. 3. The optical film as described in 2 above, wherein the sulfur content of the polyester resin is 0.15 to 2% by mass.
[0010]
4). The polyester resin is produced using an aromatic dicarboxylic acid or glycol having a group selected from 1 to 10 mol% of a sulfonic acid and a salt thereof based on the total aromatic dicarboxylic acid, 1, 2 or 3. The optical film as described in 3.
[0011]
5). 5. The optical film as described in 4 above, wherein the polyester resin is produced using an aromatic dicarboxylic acid having a group selected from 1 to 10 mol% of a sulfonic acid and a salt thereof based on the total aromatic dicarboxylic acid. .
[0012]
6). 6. The optical film as described in any one of 3 to 5 above, wherein the polyester resin is produced using 0.1 to 10% by mass of polyalkylene glycol with respect to the total amount of polyester of the reaction product.
[0013]
7. 7. The optical film as described in any one of 1 to 6 above, wherein the main component of the polyester resin is polyethylene terephthalate.
[0014]
A polarizing plate protective film comprising the optical film according to any one of 8.1 to 7.
[0015]
9. A polarizing plate protective film having a thickness of 5 to 40 μm, an equilibrium moisture content of 1 to 5%, and dimensional stability within ± 0.05%.
[0016]
10. It is a long film continuously formed by melt extrusion, and the angle θ between the direction in which the refractive index in the film surface is the largest and the width direction of the long film is 0 ± 15 ° or 90 ± 15 ° 10. The polarizing plate protective film as described in 8 or 9 above.
[0017]
11. A polarizing plate characterized by stretching a film having a polyester resin layer having a group selected from sulfonic acid or a salt thereof by 1.0 to 2.5 times in one direction and 2.5 to 10 times in a direction orthogonal thereto A method for producing a protective film.
[0018]
12 11. A polarizing plate comprising the polarizing plate protective film according to the above 8, 9 or 10.
[0019]
13. 13. A liquid crystal display device using the polarizing plate according to 12 or the optical film according to any one of 1 to 7.
[0020]
Details of the present invention will be described below.
In order to solve the above-mentioned problems found in conventional polyester films when used as a polarizing plate protective film, as a result of intensive studies, the present inventors have obtained a polyester having an equilibrium water content of 1 to 5%. It has been found that the above problem can be solved by using an optical film having a resin layer.
[0021]
In the present invention, the polyester resin layer having an equilibrium water content of 1 to 5% may form a polyester film alone, or may be laminated with a polyester resin layer having an equilibrium water content of less than 1%, or other materials. The resin used for the support is not particularly limited.
[0022]
Here, the equilibrium water content is a percentage of the amount of water contained in the sample in an equilibrium state with respect to the sample mass. Specifically, the polyester film (or the polyester resin layer film peeled off from the base when it is laminated on another film) is conditioned at 23 ° C. and a relative humidity of 20%. For 4 hours or more, and then immersed in distilled water at 23 ° C. for 24 hours. After that, the sample was subjected to moisture at a temperature of 150 ° C. using a trace moisture meter (for example, CA-20 type, manufactured by Mitsubishi Chemical Corporation). Is dried and vaporized and then quantified by the Karl Fischer method.
[0023]
Polyester is a direct esterification method in which an aromatic dicarboxylic acid component is directly esterified with a glycol component. First, a dialkyl ester is used as an aromatic dicarboxylic acid component, and this is subjected to an ester exchange reaction with the glycol component. It can be produced using a transesterification method in which polymerization is carried out by removing the excess glycol component by heating under reduced pressure. At this time, it is produced using a transesterification catalyst or a polymerization reaction catalyst, if necessary, or using a heat-resistant stabilizer.
[0024]
In the present invention, even when a dialkyl ester of a dicarboxylic acid is first used or when an esterification method in which a dicarboxylic acid component and a glycol component are once esterified is used, the raw material and its copolymer component are referred to. , Aromatic dicarboxylic acid, glycol equivalent amount.
[0025]
In the above process, for example, a copolymer component such as an aromatic dicarboxylic acid or a polyalkylene glycol having a group selected from a sulfonic acid and a salt thereof is added after the transesterification reaction, and polycondensation is performed, thereby these copolymer components. A polyester resin containing is obtained.
[0026]
Therefore, the polyester resin that forms the polyester resin layer having an equilibrium water content of 1 to 5% used in the present invention is specifically a polyester resin obtained by the reaction of at least an aromatic dicarboxylic acid and a glycol, A polyester resin having a group selected from sulfonic acid or a salt thereof in the resin structure is preferable.
[0027]
These sulfonic acid groups are prepared by mixing a predetermined amount of an aromatic dicarboxylic acid or glycol having a group selected from sulfonic acid and salts thereof as a copolymer component of a dicarboxylic acid such as terephthalic acid or a glycol such as ethylene glycol. By doing so, it can be introduced into the polyester resin.
[0028]
The sulfur element content contained in the polyester resin thus obtained is preferably 0.15 to 2% by mass.
[0029]
When the content of these sulfur elements exceeds 2%, the content of sulfonic acid groups may be too high and the mechanical strength may be inferior. When the content is less than 0.15%, the number of sulfonic acid groups is sufficient. It does not exist in proportion and does not give the effect of the present invention.
[0030]
The elemental sulfur in the polyester resin is not necessarily all derived from a group selected from a sulfonic acid group or a salt thereof, but 50% or more, preferably 80% or more is a sulfonic acid contained in the polyester as a sulfonic acid or a salt thereof. It is preferably derived from a group.
[0031]
Although the determination method of the elemental sulfur in the polyester resin is not particularly limited, it can be determined, for example, by ICP-AES (inductively coupled plasma emission spectroscopy). Specifically, sodium carbonate was added to the sample, water was added to the decomposition product obtained by heating and melting at 1000 ° C. to obtain an aqueous solution, and this was used with SPS-4000 manufactured by Seiko Electronics Industry Co., Ltd. It can be obtained by ICP-AES analysis.
[0032]
Therefore, the polyester resin containing a sulfonic acid group is, therefore, at least 1 to 10 mol% of a sulfonic acid and a salt thereof with respect to a wholly aromatic dicarboxylic acid used when produced by a reaction of an aromatic dicarboxylic acid and a glycol. It can be obtained by using an aromatic dicarboxylic acid or glycol having a group selected from In addition, in order to introduce sulfonic acid into polyester, it is possible to produce an aromatic dicarboxylic acid having a group selected from sulfonic acid and a salt thereof using 1 to 10 mol% with respect to the total aromatic dicarboxylic acid. It is more preferable from the viewpoint of ease of use.
[0033]
Moreover, it is preferable that the polyester resin used for this invention is manufactured using 0.1-10 mass% copolymerization component with respect to the whole quantity of the produced | generated polyester further.
[0034]
By these components, the characteristics as a polarizing plate protective film such as adhesiveness with a polarizer and drying property of an adhesive at the time of bonding when a polyester resin is used for a polarizing plate protective film or the like are greatly improved.
[0035]
In the polyester resin used in the present invention, the main component of the polyester is preferably polyethylene terephthalate obtained using terephthalic acid and ethylene glycol.
[0036]
In the present invention, as will be described later, a film obtained by substantially uniaxially stretching a melt-cast film is particularly preferably used. The film thus obtained has an appropriate moisture permeability even if it has a film thickness of 5 to 40 μm in particular, so that it has excellent drying properties of the adhesive during the production of the polarizing plate and also has good adhesion to the polarizer. there were. Moreover, even if the film of this invention was 5-40 micrometers in film thickness, a wrinkle did not enter easily at the time of polarizing plate manufacture, and the bonding with a polarizer was easy.
[0037]
The polarizing plate using the polarizing plate protective film of the present invention has a remarkably little decrease in the degree of polarization under high-temperature and high-humidity conditions even when a polarizing plate protective film having a film thickness of 5 to 40 μm is used. It was confirmed to be excellent.
[0038]
Examples of the aromatic dicarboxylic acid used in the production of the polyester used in the present invention include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, and the like, and these lower alkyl esters (anhydrides, lower alkyl esters). Etc.) can be used. Examples of the glycol include ethylene glycol, propylene glycol, butanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, diethylene glycol, and p-xylylene glycol. Of these, polyethylene terephthalate obtained by the reaction of terephthalic acid and ethylene glycol is preferred as the main component.
[0039]
The main component being polyethylene terephthalate means that it contains 80% by mass or more of a polyethylene terephthalate copolymer or a copolymer having 80% by mol or more of repeating units of polyethylene terephthalate.
[0040]
Examples of the aromatic dicarboxylic acid having a group selected from sulfonic acid and a salt thereof used for incorporating a sulfonic acid group in the polyester used in the present invention include 5-sodium sulfoisophthalic acid and 2-sodium sulfoisophthalic acid. 4-sodium sulfoisophthalic acid, 4-sodium sulfo-2,6-naphthalenedicarboxylic acid or an ester-forming derivative thereof, and a compound obtained by replacing these sodium with other metals (for example, potassium, lithium, etc.) are used.
[0041]
In addition, a glycol having a group selected from a sulfonic acid and a salt thereof may be used. However, a preferable compound for containing a sulfonic acid group in the polyester is preferably the sulfonic acid group or a salt thereof. An aromatic dicarboxylic acid having
[0042]
If the aromatic dicarboxylic acid component having these sulfonic acid groups or salts thereof exceeds 10 mol% of the total aromatic dicarboxylic acid used during production, the stretchability may be inferior or the mechanical strength may be inferior. Moreover, if it is less than 1 mol%, sufficient drying property may not be obtained.
[0043]
Furthermore, the polyester used in the present invention preferably contains polyalkylene glycol as a copolymerization component. As described above, the polyester contains 0.1 to 10 polyalkylene glycol with respect to the total amount of polyester of the reaction product. It is preferable to manufacture by mass%. More preferably, it is 0.2-8 mass%. If the polyalkylene glycol is less than 0.1% by mass, sufficient drying properties may not be obtained. If the polyalkylene glycol exceeds 10% by mass, the Young's modulus may be lowered and the mechanical strength may be inferior.
[0044]
As the polyalkylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like are used. Among them, polyethylene glycol is preferable, and the molecular weight (number average molecular weight) is not particularly limited, but is preferably 300 to 20000, more preferably. 600-10000, especially 1000-5000 are preferably used. These molecular weights can be measured by using GPC.
[0045]
In the polyester used for the optical film of the present invention, other components may be copolymerized or other polymers may be blended as long as the effects of the present invention are not impaired.
[0046]
Other aromatic dicarboxylic acids other than the above or derivatives thereof include aromatic dicarboxylic acids such as 2,7-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenyletherdicarboxylic acid and lower alkyl esters thereof (anhydrous And derivatives capable of forming an ester such as a lower alkyl ester). In addition, during production, alicyclic dicarboxylic acids such as cyclopropanedicarboxylic acid, cyclobutanedicarboxylic acid and hexahydroterephthalic acid and derivatives thereof (anhydrides, derivatives capable of forming esters such as lower alkyl esters), adipic acid, succinic acid, Aliphatic dicarboxylic acids such as oxalic acid, azelaic acid, sebacic acid and dimer acid and derivatives thereof (an ester-forming derivative such as anhydride and lower alkyl ester) are used in an amount of 10 mol% or less of the total dicarboxylic acid. Also good.
[0047]
As glycols that can be used in the present invention, in addition to ethylene glycol and the aforementioned glycols, trimethylene glycol, triethylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, bisphenol A, p, p'-dihydroxyphenyl Examples include sulfone, 1,4-bis (β-hydroxyethoxyphenyl) propane, polyalkylene (eg, ethylene, propylene) glycol, p-phenylenebis (dimethylolcyclohexane), and the like. You may use it in the quantity of 10 mol% or less.
[0048]
The polyester used in the present invention may be one having a terminal hydroxyl group and / or carboxyl group blocked with a monofunctional compound such as benzoic acid, benzoylbenzoic acid, benzyloxybenzoic acid, methoxypolyalkylene glycol, Alternatively, it may be modified so that a substantially linear copolymer can be obtained with a very small amount of a trifunctional or tetrafunctional ester-forming compound such as glycerin or pentaerythritol.
[0049]
Moreover, the polyester used for this invention can be copolymerized with the compound which has a bisphenol type compound, a naphthalene ring, or a cyclohexane ring for the purpose of improving the heat resistance of a film.
[0050]
The intrinsic viscosity (Intrinsic Viscosity) of the polyester used in the present invention is preferably in the range of 0.35 to 0.65. Below this range, the brittleness of the resulting film may be insufficient, and when this range is exceeded, the melt viscosity may be too great during melt extrusion, and planarity may deteriorate.
[0051]
The intrinsic viscosity was calculated using an Ubbelohde viscometer. A mixed solvent of phenol and 1,1,2,2-tetrachloroethane having a mass ratio of about 55:45 (adjusted to a flow time of 42.0 ± 0.1 seconds) was used, and the sample was dissolved in this to obtain a concentration of 0. A solution of 2.0.6, 1.0 (g / dl) (temperature 20 ° C.) is prepared. The specific viscosity (η at each concentration (C) was measured by an Ubbelohde viscometer._sp) And the formula [η_sp/ C] was extrapolated to zero concentration (C → 0), and the intrinsic viscosity [η] was determined. The unit of intrinsic viscosity [η] is dl / g.
[0052]
The polyester used in the present invention preferably has a glass transition temperature (Tg) of 55 ° C. or higher, more preferably 60 ° C. or higher. If it is less than 55 degreeC, the dimensional stability of the obtained film under high temperature and high humidity may be inferior. Tg is obtained as an average value of the temperature at which the baseline measured by the differential scanning calorimeter starts to deviate and the temperature at which the baseline returns to the baseline.
[0053]
The polyester used in the present invention may contain an antioxidant. The effect is particularly remarkable when the polyester contains a compound having a polyoxyalkylene group. There are no particular restrictions on the type of antioxidant to be added, and various types of antioxidants can be used. Examples thereof include antioxidants such as hindered phenol compounds, phosphite compounds, and thioether compounds. be able to. Among these, an antioxidant of a hindered phenol compound is preferable in terms of transparency. Content of antioxidant is 0.01-2 mass% normally with respect to polyester, Preferably it is 0.1-0.5 mass%.
[0054]
The polyester film of the present invention can be provided with easy slipperiness if necessary. The slipperiness imparting means is not particularly limited, but the external particle addition method for adding inert inorganic particles to the polyester, the internal particle precipitation method for precipitating the catalyst to be added at the time of polyester synthesis, or a surfactant, etc. A method of applying to the surface is common.
[0055]
An ultraviolet absorber may be added to the polyester film of the present invention as necessary.
[0056]
As the ultraviolet absorber, those excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less and having a small absorption of visible light having a wavelength of 400 nm or more are preferably used from the viewpoint of good liquid crystal display properties.
[0057]
Specific examples of the ultraviolet absorber used in the present invention include, for example, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex salts compounds, triazine compounds, benzoate compounds. Compound etc. are mentioned. Further, a polymeric ultraviolet absorber described in JP-A-6-148430 and a polymeric ultraviolet absorber described in Japanese Patent Application No. 2000-214134 are also preferably used.
[0058]
As the benzotriazole ultraviolet absorber, a compound represented by the following general formula [1] is preferably used.
[0059]
[Chemical 1]

[0060]
Where R₁, R₂, R_Three, R_FourAnd R_FiveMay be the same or different and are a hydrogen atom, a halogen atom, a nitro group, a hydroxyl group, an alkyl group, an alkenyl group, an aryl group, an alkoxy group, an acyloxy group, an aryloxy group, an alkylthio group, an arylthio group, a mono- or dialkylamino group Represents an acylamino group or a 5- to 6-membered heterocyclic group, R_FourAnd R_FiveMay be closed to form a 5-6 membered carbocyclic ring.
[0061]
Moreover, these groups described above may have an arbitrary substituent.
Although the specific example of the ultraviolet absorber shown by General formula [1] is given to the following, it is not limited to these.
[0062]
UV-1: 2- (2'-hydroxy-5'-methylphenyl) benzotriazole
UV-2: 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) benzotriazole
UV-3: 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) benzotriazole
UV-4: 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5-chlorobenzotriazole
UV-5: 2- (2'-hydroxy-3 '-(3 ", 4", 5 ", 6" -tetrahydrophthalimidomethyl) -5'-methylphenyl) benzotriazole
UV-6: 2,2-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol)
UV-7: 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole
UV-8: 2- (2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol (TINUVIN 171 from Ciba)
UV-9: Octyl-3- [3-tert-butyl-4-hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl- Mixture of 4-hydroxy-5- (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate (TINUVIN 109, manufactured by Ciba)
In the present invention, as the benzophenone ultraviolet absorber, a compound represented by the following general formula [2] is preferably used.
[0063]
[Chemical formula 2]

[0064]
In the formula, Y represents a hydrogen atom, a halogen atom or an alkyl group, an alkenyl group, an alkoxy group, and a phenyl group, and these alkyl group, alkenyl group, and phenyl group may have a substituent. A is a hydrogen atom, an alkyl group, an alkenyl group, a phenyl group, a cycloalkyl group, an alkylcarbonyl group, an alkylsulfonyl group, or —CO (NH)._n-1-D group is represented, D represents the alkyl group, the alkenyl group, or the phenyl group which may have a substituent. m and n represent 1 or 2.
[0065]
In the above, the alkyl group represents, for example, a linear or branched aliphatic group having up to 24 carbon atoms, the alkoxy group has, for example, an alkoxy group having up to 18 carbon atoms, and the alkenyl group has, for example, 16 carbon atoms. An alkenyl group up to, for example, an allyl group, a 2-butenyl group, or the like. In addition, as a substituent that may be substituted into an alkyl group, an alkenyl group, or a phenyl group, a halogen atom, for example, a chlorine atom, a bromine atom, a fluorine atom, a hydroxyl group, a phenyl group, (this phenyl group is an alkyl group or A halogen atom or the like may be substituted).
[0066]
Specific examples of the benzophenone-based compound represented by the general formula [2] are shown below, but are not limited thereto.
[0067]
UV-10: 2,4-dihydroxybenzophenone
UV-11: 2,2'-dihydroxy-4-methoxybenzophenone
UV-12: 2-hydroxy-4-methoxy-5-sulfobenzophenone
UV-13: Bis (2-methoxy-4-hydroxy-5-benzoylphenylmethane)
TINUVIN P, TINUVIN 324, TINUVIN 320, TINUVIN 326, TINUVIN 327, TINUVIN 328, TINUVIN 329, TINUVIN 770, TINUVIN 780, TINUVIN 144, TINUVIN 120, UVITEX O ) And the like can be used as appropriate.
[0068]
The ultraviolet absorber described above preferably used in the present invention is preferably a benzotriazole-based ultraviolet absorber or a benzophenone-based ultraviolet absorber, which has high transparency and is excellent in the effect of preventing the deterioration of the polarizing plate and the liquid crystal element, and unnecessary coloring. A benzotriazole-based ultraviolet absorber with a lower content is particularly preferably used.
[0069]
The method for synthesizing the polyester used in the present invention is not particularly limited, and can be produced according to a conventionally known polyester production method as described above. For example, a direct esterification method in which a dicarboxylic acid component is directly esterified with a diol component. First, a dialkyl ester is used as a dicarboxylic acid component, this is transesterified with the diol component, and this is heated under reduced pressure. A transesterification method of polymerizing by removing excess diol component can be used. At this time, if necessary, a transesterification catalyst or a polymerization reaction catalyst can be used, or a heat-resistant stabilizer can be added. At this time, it is preferable to carry out polycondensation by adding an aromatic dicarboxylic acid having a metal sulfonate group as a copolymerization component or polyethylene glycol after the transesterification reaction. In addition, in each process during synthesis, anti-coloring agent, antioxidant, crystal nucleating agent, slipping agent, stabilizer, anti-blocking agent, ultraviolet absorber, viscosity modifier, antifoaming agent, clearing agent, antistatic agent, You may add a pH adjuster, dye, a pigment, etc.
[0070]
Next, the manufacturing method of the polyester film of this invention is demonstrated.
The substantially uniaxially stretched polyester film of the present invention is obtained by mainly performing only one direction in biaxially stretched film formation. That is, in the present invention, the polyester film is a polyester film formed by biaxial stretching so that the stretching ratio in one direction is 1.00 to 2.5 times, and the stretching ratio in the direction orthogonal thereto is 2.5 to 10 times. More preferably, it is a polyester film biaxially stretched to a stretching ratio of 1.0 to 2.0 times in the longitudinal direction and a stretching ratio of 2.5 to 7 times in the lateral direction, and more preferably The polyester film is biaxially stretched to a stretch ratio of 1.1 to 1.8 times in the longitudinal direction and a stretch ratio of 3.0 to 6.0 times in the transverse direction. It is preferable to increase the stretch ratio in one direction, and the ratio of stretch ratios (higher stretch ratio in either length or width / lower stretch ratio in either length or width) is preferably 2 or more, and more preferably 4 or more. It is preferable that it is 6 or more. Moreover, it is preferable that it is extended | stretched 4 times or more with respect to the area ratio after extending | stretching with respect to an unstretched thing, More preferably, it is extended | stretched 5-7 times.
[0071]
The polyester film can be obtained by a conventionally known method, and is not particularly limited, but can be carried out by the following method. In this case, the longitudinal direction refers to the film forming direction (longitudinal direction) of the film, and the horizontal direction refers to a direction perpendicular to the film forming direction of the film.
[0072]
First, the raw material polyester is molded into pellets, dried with hot air or vacuum, melt-extruded, extruded into a sheet from a T-die, brought into close contact with a cooling drum by an electrostatic application method, etc., cooled and solidified, and unstretched Get a sheet. Next, the obtained unstretched sheet is heated in the range of Tg + 100 ° C. from the glass transition temperature (Tg) of the polyester via a plurality of roll groups and / or heating devices such as an infrared heater, and then stretched in one or more stages. It is.
[0073]
Next, the polyester film stretched in the machine direction obtained as described above is stretched in the transverse direction within a temperature range of Tg to Tm (melting point) −20 ° C. and then heat-set.
[0074]
In the case of transverse stretching, it is preferable to perform transverse stretching while sequentially raising the temperature difference in the range of 1 to 50 ° C. in a stretching region divided into two or more, because the distribution of physical properties in the width direction can be reduced. Further, after the transverse stretching, it is preferable that the film is held in the range of Tg-40 ° C. or higher at a temperature equal to or lower than the final transverse stretching temperature for 0.01 to 5 minutes because the distribution of physical properties in the width direction can be further reduced.
[0075]
In the heat setting, heat setting is usually performed for 0.5 to 300 seconds at a temperature higher than the final transverse stretching temperature and within a temperature range of Tm-20 ° C. or lower. At this time, it is preferable to heat-fix while sequentially raising the temperature difference in the range of 1 to 100 ° C. in the region divided into two or more.
[0076]
The heat-set film is usually cooled to Tg or less, and clip holding portions at both ends of the film are cut and wound. At this time, it is preferable to perform a relaxation treatment of 0.1 to 10% in the horizontal direction and / or the vertical direction within the temperature range of the final heat setting temperature or lower and Tg or higher. In addition, it is preferable that the cooling is gradually performed from the final heat setting temperature to Tg at a cooling rate of 100 ° C. or less per second. The means for cooling and relaxation treatment is not particularly limited and can be performed by a conventionally known means. However, it is preferable to perform these treatments while sequentially cooling in a plurality of temperature ranges, from the viewpoint of improving the dimensional stability of the film. The cooling rate is a value obtained by (T1−Tg) / t, where T1 is the final heat setting temperature and t is the time until the film reaches Tg from the final heat setting temperature.
[0077]
More optimal conditions of these heat setting conditions, cooling, and relaxation treatment conditions vary depending on the polyester constituting the film, so if the physical properties of the obtained stretched film are measured and appropriately adjusted to have favorable characteristics, Good.
[0078]
In the production of the film, functional layers such as an antistatic layer, a slippery layer, an adhesive layer, and a barrier layer may be coated before and / or after stretching. At this time, various surface treatments such as corona discharge treatment, atmospheric pressure plasma treatment, and chemical treatment can be performed as necessary.
[0079]
The clip gripping portions at both ends of the cut film are pulverized, or after granulation, depolymerization / repolymerization, etc., if necessary, as a film raw material of the same variety or of different varieties. You may reuse as a raw material for films.
[0080]
In the present invention, the refractive index in the plane direction of the polyester film formed as described above is the lateral refractive index (n_TD) And the longitudinal refractive index (n_MD) Absolute value of difference from |_TD-N_MD| Is preferably 0.05 or less, more preferably 0.04 or less, and still more preferably 0.025 or less.
[0081]
The thickness of the polyester film of the present invention is 3 to 100 μm, preferably 5 to 60 μm, more preferably 5 to 40 μm, and more preferably 10 to 35 μm.
[0082]
Retardation R in the in-plane direction of the protective film for polarizing plate of the present invention₀(Nm) is preferably as small as possible, preferably 1000 nm or less, more preferably 800 nm or less, and even more preferably 500 nm or less. The polyester film of the present invention is R in comparison with the conventional polyester film.₀Can be kept low, which is preferable.
[0083]
In the protective film for polarizing plate of the present invention, the angle formed by the direction in which the in-plane refractive index is maximum and the width direction of the film (the film length direction) is 0 ° ± 15 ° or 90 ° ± 15. Is preferably 0 ° ± 10 ° or 90 ° ± 10 °, more preferably 0 ° ± 5 ° or 90 ° ± 5 °, and 0 ° ± 2 °. Alternatively, 90 ° ± 2 ° is more preferable.
[0084]
The polyester film of the present invention may be a single (single layer) film composed of the polyester film, but is composed of a plurality of resin layers including at least one layer composed of the polyester as long as the effects of the present invention are not impaired. It is good also as a multilayer film. When the polyester layer is A and the other resin layers are B and C, for example, A / B, A / B / A, B / A / B, and B / A / C can be configured. Of course, it is possible to have a structure of four or more layers. By adopting such a multilayer structure, for example, a plurality of functions can be simultaneously imparted by laminating a film having high strength and water barrier properties on the core layer and the outer layer.
[0085]
As the resin layer, the aforementioned polyester or the like is preferably used.
In addition, when adding fine particles such as a matting agent in order to impart slipperiness, an effect can be obtained if it is added only to the outermost layer, so that a function can be imparted without degrading transparency and the like.
[0086]
The fine particles that can be added are not particularly limited, and examples thereof include inorganic compound fine particles and organic compound fine particles.
[0087]
Inorganic compounds include silicon-containing compounds, silicon dioxide, aluminum oxide, zirconium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, calcium phosphate, etc. More preferred are inorganic compounds containing silicon and zirconium oxide, with silicon dioxide being particularly preferred.
[0088]
As the fine particles of silicon dioxide, for example, commercially available products such as Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above Nippon Aerosil Co., Ltd.) can be used.
[0089]
As the fine particles of zirconium oxide, for example, commercially available products such as Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) can be used.
[0090]
As the organic compound, for example, polymers such as silicone resin, fluorine resin and acrylic resin are preferable, and among them, silicone resin is preferably used.
[0091]
Among the above-described silicone resins, those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, 105, 108, 120, 145, 3120, and 240 (manufactured by Toshiba Silicone Co., Ltd.) ) Etc. can be used.
[0092]
The primary average particle size of the fine particles according to the present invention is preferably 20 nm or less, more preferably 5 to 16 nm, and particularly preferably 5 to 12 nm, from the viewpoint of keeping the haze low.
[0093]
As a method for producing a multilayer film, a method by coextrusion, a method by extrusion lamination, a method by dry lamination, and the like can be preferably used.
[0094]
In the present invention, the surface of the optical film preferably has conductivity, and the surface specific resistance (23 ° C., 25% RH) is 1 × 10.¹²It is preferable that it is below Ω / □. More preferably, 1 × 10¹¹Ω / □ or less, more preferably 1 × 10^TenΩ / □ or less.
[0095]
In this invention, electroconductivity can be provided to an optical film by including a hygroscopic substance or a conductive substance. Examples of the substance that imparts conductivity include a surfactant, a conductive polymer, and an inorganic metal oxide.
[0096]
The surfactant that can be used may be any of anionic, cationic, amphoteric and nonionic. Examples of the anionic surfactant include alkyl carboxylate, alkyl sulfonate, alkyl benzene sulfonate, alkyl naphthalene sulfonate, alkyl sulfate, alkyl phosphate, N-acyl-N-alkyl taurine. Acid groups such as carboxy groups, sulfo groups, phospho groups, sulfate ester groups, phosphate ester groups such as acids, sulfosuccinates, sulfoalkyl polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl phosphate esters, etc. The inclusion is preferred.
[0097]
Examples of the cationic surfactant include alkylamine salts, aliphatic or aromatic quaternary ammonium salts, heterocyclic quaternary ammonium salts such as pyridinium and imidazolium, and phosphonium or sulfonium salts containing aliphatic or heterocyclic rings. Etc. are preferred.
[0098]
As the amphoteric surfactant, for example, amino acids, aminoalkylsulfonic acids, aminoalkylsulfuric acid or phosphate esters, alkylbetaines, amine oxides and the like are preferable.
[0099]
Nonionic surfactants include, for example, saponins (steroidal), alkylene oxide derivatives (for example, polyethylene glycol, polyethylene glycol / polypropylene glycol condensates, polyethylene glycol alkyl ethers or polyethylene glycol alkyl aryl ethers, polyethylene glycol esters). , Polyethylene glycol sorbitan esters, polyalkylene glycol alkylamines or amides, polyethylene oxide adducts of silicone), glycidol derivatives (eg, alkenyl succinic acid polychloride, alkylphenol polyglycerides), alkyl esters such as polyhydric alcohol fatty acid esters Etc. are preferred.
[0100]
The conductive polymer is not particularly limited, and may be any of anionic, cationic, amphoteric and nonionic, but among them, anionic and cationic are preferable. More preferred are sulfonic acid-based, carboxylic acid-based, anionic, and tertiary amine-based, quaternary ammonium-based polymers or latexes for cationic.
[0101]
These conductive polymers are, for example, anionic polymers or latexes described in JP-B-52-25251, JP-A-51-29923, JP-B-60-48024, JP-B-57-18176, and 57-56059. No. 58-56856, U.S. Pat. No. 4,118,231 and the like.
[0102]
For example, an antistatic layer or a conductive layer can be provided by plasma treatment described in Japanese Patent Application No. 2000-80043.
[0103]
The optical film of the present invention constitutes a polarizing plate by being bonded to at least one surface of a polarizer. The other surface of the polarizer may be laminated with a known polarizing plate protective film or the optical film of the present invention. When the optical film of the present invention is used as a polarizing plate protective film, curling wrinkles cannot be removed with a conventional polyester film, curls may remain even after forming a polarizing plate, or the adhesive part peels off due to strong curling wrinkles. However, the optical film of the present invention is particularly suitable for a polarizing plate protective film because the curl easily disappears. In particular, before or after bonding with a polarizer, curling can be easily eliminated by immersing in water or an aqueous solution or applying steam, and a polarizing plate having excellent flatness can be provided. In addition, since the optical film of the present invention has a hygroscopic expansion coefficient close to that of triacetyl cellulose as compared to conventional polyester, one of the polarizers is a cellulose ester-based polarizing plate protective film such as triacetyl cellulose, and the other is of the present invention. Even a hybrid polarizing plate using an optical film is excellent in that a polarizing plate attached to a liquid crystal display device by moisture absorption or the like hardly peels off or wrinkles.
[0104]
As the adhesive used for laminating the optical film of the present invention and the polarizer, those having sufficient adhesiveness, transparent, and not impairing the polarization function are preferably used. Examples thereof include acrylic adhesives, epoxy adhesives, cyanoacrylate adhesives, polyurethane adhesives, polyvinyl alcohol adhesives such as polyvinyl alcohol and polyvinyl butyral.
[0105]
In order to improve adhesion, various surface treatments such as corona discharge treatment, glow discharge treatment, ultraviolet treatment, flame treatment, atmospheric pressure gas discharge plasma treatment, and chemical treatment can be applied as necessary. Further, an undercoat layer may be provided for improving the adhesion. As the undercoat layer, a hydrophilic colloid layer excellent in adhesiveness with a polarizer is particularly preferable.
[0106]
For example, in order to improve adhesiveness with a polarizer as a polarizing plate protective film, plasma treatment is performed by the method of Japanese Patent Application No. 2000-97061, etc., thereby further improving the adhesiveness when using a polyvinyl alcohol-based adhesive or the like. Can be improved. In the optical film of the present invention, a clear hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, a conductive layer, a light diffusion layer, an easy adhesion layer, and an antifouling layer may be used alone or in combination as appropriate. Can be provided.
[0107]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, the embodiment of this invention is not limited to these.
[0108]
[Synthesis of polyester]
(Polyester A)
To 100 parts by mass of dimethyl terephthalate and 64 parts by mass of ethylene glycol, 0.1 part by mass of calcium acetate hydrate was added, and a transesterification reaction was performed by a conventional method. To the obtained product, 39 parts by mass (7 mol% / total dicarboxylic acid component) of ethylene glycol solution (concentration 35% by mass) of 5-sodium sulfodi (β-hydroxyethyl) isophthalic acid, polyethylene glycol (number average molecular weight 3000) 5.8 parts by mass (5% by mass / generated polyester), 0.05 parts by mass of antimony trioxide, and 0.13 parts by mass of trimethyl phosphate. Next, the temperature was gradually raised and the pressure was reduced, and polymerization was carried out at 280 ° C. and 40 Pa to obtain polyester A. The intrinsic viscosity was determined according to the method shown below. As a result, the intrinsic viscosity was 0.50.
[0109]
The intrinsic viscosity was calculated by the following procedure using an Ubbelohde viscometer. Using a mixed solvent of phenol and 1,1,2,2-tetrachloroethane having a mass ratio of about 55:45 (adjusted to a flow time of 42.0 ± 0.1 seconds), the sample was dissolved to a concentration of 0.2 , 0.6, 1.0 (g / dl) solution (temperature 20 ° C.). The specific viscosity (η at each concentration (C) was measured by an Ubbelohde viscometer._sp) And the formula [η_sp/ C] was extrapolated to zero concentration (C → 0), and the intrinsic viscosity [η] was determined. The unit of intrinsic viscosity [η] is dl / g.
[0110]
(Polyester B)
11. Addition amount of 5-sodium sulfodi (β-hydroxyethyl) isophthalic acid in ethylene glycol solution (concentration 35% by mass) 22 parts by mass (4 mol% / total dicarboxylic acid component), polyethylene glycol (number average molecular weight 3000) Polyester B was obtained in the same manner as above except that the amount was changed to 2 parts by mass (10.5% by mass / generated polyester). The intrinsic viscosity measured in the same manner as in the previous period was 0.55.
[0111]
(Polyester C)
To 100 parts by mass of dimethyl terephthalate, 65 parts by mass of ethylene glycol, and 2 parts by mass of diethylene glycol, 0.05 part by mass of magnesium acetate hydrate was added as a transesterification catalyst, and a transesterification reaction was performed according to a conventional method. To the obtained product, 0.05 part by mass of antimony trioxide and 0.03 part by mass of trimethyl phosphate were added. Next, the temperature was gradually raised and the pressure was reduced, and polymerization was carried out at 280 ° C. and 80 Pa to obtain a polyester C having an intrinsic viscosity of 0.65.
[0112]
[Production of optical film]
(Optical film 1)
The polyester B pellets were vacuum-dried at 150 ° C. for 8 hours, melt-extruded at 285 ° C. using an extruder, closely adhered to a 30 ° C. cooling drum while being electrostatically applied, and cooled and solidified to obtain an unstretched sheet. . This unstretched sheet was stretched 1.2 times in the longitudinal direction at 85 ° C. using a roll type longitudinal stretching machine. The temperature difference between the front and back surfaces was within 5 ° C.
[0113]
The obtained uniaxially stretched film was stretched 4.5 times in the transverse direction at 95 ° C. using a tenter-type transverse stretching machine. Next, heat treatment was performed at 70 ° C. for 2 seconds, heat-fixed at 150 ° C. for the first heat setting zone for 10 seconds, heat-fixed for 15 seconds at the second heat setting zone at 180 ° C., and then transverse (width) direction at 160 ° C. The polyester film (optical film 1) having a lateral length of 1500 mm and a thickness of 35 μm was produced.
[0114]
(Optical film 2)
Polyester A pellets were vacuum dried at 150 ° C. for 8 hours, melt-extruded at 285 ° C. using an extruder, closely adhered to a 30 ° C. cooling drum while being electrostatically applied, and cooled and solidified to obtain an unstretched sheet. . This unstretched sheet was stretched 4.0 times in the longitudinal direction at 90 ° C. using a roll type longitudinal stretching machine. The temperature difference between the front and back surfaces was within 5 ° C.
[0115]
The obtained uniaxially stretched film was stretched 1.2 times in the transverse direction at 100 ° C. using a tenter transverse stretching machine. Next, heat treatment was performed at 70 ° C. for 2 seconds, heat-fixed at 150 ° C. for the first heat setting zone for 10 seconds, heat-fixed for 15 seconds at the second heat setting zone at 180 ° C., and then transverse (width) direction at 160 ° C. A polyester film (optical film 2) having a lateral length of 1500 mm and a thickness of 35 μm was produced.
[0116]
(Optical film 3)
The pellets of polyester A and polyester C were mixed with a tumbler mixer so that the mass ratio was 3: 7, and vacuum dried at 150 ° C. for 8 hours. Polyester B pellets were also vacuum dried at 150 ° C. for 8 hours. A mixture of polyester A and polyester C and polyester B are melt-extruded at 285 ° C. using two extruders, extruded into a sheet using a multi-manifold die, and brought into close contact with a 30 ° C. cooling drum while electrostatically applied. And solidified by cooling to obtain an unstretched sheet. At this time, the ratio of the thickness of each layer was set to 1: 1. This unstretched sheet was stretched 1.05 times in the longitudinal direction at 95 ° C. using a roll type longitudinal stretching machine. The temperature difference between the front and back surfaces was within 5 ° C.
[0117]
The obtained uniaxially stretched film was stretched 4.0 times in the transverse direction at 105 ° C. using a tenter-type transverse stretching machine. Next, heat treatment was performed at 70 ° C. for 2 seconds, heat-fixed at 150 ° C. for the first heat setting zone for 10 seconds, heat-fixed for 15 seconds at the second heat setting zone at 180 ° C., and then transverse (width) direction at 160 ° C. The polyester film (optical film 3) having a lateral length of 1500 mm and a thickness of 30 μm was produced.
[0118]
(Optical film 4)
Polyester C pellets were vacuum-dried at 150 ° C. for 8 hours, melt-extruded at 290 ° C. using an extruder, brought into close contact with a 30 ° C. cooling drum while being electrostatically applied, and cooled and solidified to obtain an unstretched sheet. This unstretched sheet was stretched 1.2 times in the longitudinal direction at 95 ° C. using a roll type longitudinal stretching machine. The temperature difference between the front and back surfaces was within 5 ° C.
[0119]
The obtained uniaxially stretched film was stretched 4.5 times in the transverse direction at 105 ° C. using a tenter-type transverse stretching machine. Next, heat treatment was performed at 70 ° C. for 2 seconds, heat-fixed at 150 ° C. for the first heat setting zone for 10 seconds, heat-fixed for 15 seconds at the second heat setting zone at 180 ° C., and then transverse (width) direction at 160 ° C. The polyester film (optical film 4) having a lateral length of 1500 mm and a thickness of 30 μm was prepared.
[0120]
(Optical film 5)
100 parts by weight of cellulose triacetate having an acetylation degree of 61.0% and 15 parts by weight of triphenyl phosphate are dissolved in a mixed solvent of 450 parts by weight of methylene chloride and 50 parts by weight of methanol, and cast on a stainless steel belt at 35 ° C. When it became peelable, it was peeled off from the stainless steel belt, gradually raised in temperature while being conveyed using a roll conveying device, and finally dried at 120 ° C. to produce a 38 μm cellulose triacetate film (optical film 5).
[0121]
The optical films 1 to 5 obtained as described above were evaluated for moisture content, dimensional stability, moisture permeability, and curl value by the following methods. The results are shown in Table 1.
[0122]
<Equilibrium moisture content>
The film sample is left in a room conditioned at 23 ° C. and a relative humidity of 20% for 4 hours or more, then immersed in distilled water at 23 ° C. for 24 hours, and then the surface moisture is wiped off. For example, moisture was dried and vaporized at a temperature of 150 ° C. using Mitsubishi Chemical Corporation CA-20, and then quantified by the Karl Fischer method.
[0123]
<Dimensional stability>
The dimensional change rate was determined and evaluated in the direction in which the in-plane refractive index was the maximum before and after the film was treated at 80 ° C. and 90% RH for 1000 hours. The shrinkage direction was negative and the elongation direction was positive.
[0124]
<Moisture permeability>
It calculated | required by JISZ0208.
[0125]
<Curl value>
The sample cut to 150 mm × 30 mm was rolled and stored in a cylinder having an inner diameter of 25 mm and a height of 30 mm, and in this state, the sample was left in a 23 ° C., 55% RH environment for 1000 hours to be curled. Each sample was immersed in warm water at 50 ° C. for 2 minutes and then dried. The sample is cut into a longitudinal direction of 50 mm and a width direction of 2 mm, and the sample piece is conditioned at 23 ± 2 ° C. and 55% RH for 24 hours, and using a curvature scale, the curvature has a curve that matches the sample. The radius (1 / m) was confirmed, and the radius of curvature was taken as the curl value of the sample.
[0126]
○: Almost no curl remains. Curl value less than 10
Δ: Slightly curly wrinkles are observed. Curl value less than 10-25
X: A strong curl is recognized. Curl value 25 or more
<Measurement of retardation and orientation angle>
Using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments), a three-dimensional refractive index measurement is performed at a wavelength of 590 nm under an environment of 23 ° C. and 55% RH, and the refractive indexes Nx and Ny Nz was determined. In-plane retardation R according to the following general formula (1)₀Was calculated. Further, the angle θ (orientation angle) formed by the direction in which the in-plane refractive index is maximum and the width direction of the film was determined.
[0127]
R₀= (Nx−Ny) × d
In the formula, Nx is a refractive index in the direction in which the refractive index in the film plane is maximum, and Ny is a refractive index in the film plane in a direction perpendicular to Nx. d represents the film thickness (nm) of the film. The angle formed by Nx and the width direction of the film was θ (°).
[0128]
[Table 1]

[0129]
(Production of polarizer)
A 120 μm-thick polyvinyl alcohol film was immersed in an aqueous solution containing 1 part by mass of iodine, 2 parts by mass of potassium iodide, and 4 parts by mass of boric acid, and stretched 4 times at 50 ° C. to produce a polarizer.
[0130]
[Preparation of polarizing plate]
(Polarizing plate 1)
Using one surface of the optical film 1 using a corona discharge treatment device (HFS-202) manufactured by Kasuga Electric Co., Ltd., 12 W · min / m²The easy adhesion treatment was performed under the conditions described above.
[0131]
A polarizing plate is bonded to both sides of the polarizer prepared above using a 5% aqueous solution of a fully saponified polyvinyl alcohol as an adhesive so that the surface of the optical film 1 subjected to easy adhesion treatment becomes the polarizer side. Was made. At this time, the optical film was laminated so that the maximum direction of the refractive index in the film plane was parallel to the polarization axis of the polarizer.
[0132]
(Polarizing plates 2 to 4)
In the same manner as the polarizing plate 1, polarizing plates 2 to 4 were prepared using 2, 3, and 4, respectively, instead of the optical film 1. In addition, in producing the polarizing plate 3, the optical film 3 was bonded so that the polyester B layer was on the polarizer side.
[0133]
(Polarizing plate 5)
The optical film 5 was immersed in a 2.5 mol / L sodium hydroxide aqueous solution at 40 ° C. for 60 seconds, and then washed with water and dried. A fully saponified polyvinyl alcohol 5% aqueous solution was bonded as an adhesive to both surfaces of the obtained saponified optical film 5 and the polarizer prepared above to produce a polarizing plate 5. At this time, the optical film was laminated so that the maximum direction of the refractive index in the film plane was parallel to the polarization axis of the polarizer.
[0134]
About the polarizing plates 1-5 produced as mentioned above, the following method evaluated. The results are shown in Table 2.
[0135]
<Change in polarization degree under high temperature and high humidity>
After the polarizing plate sample was treated at 80 ° C. and 90% RH for 1000 hours, the transmittance (H) when the polarizing axis of a pair of polarizing plates was made parallel at a wavelength of 550 nm.₀) And the transmittance (H₉₀) Were measured, and the degree of polarization was determined by the following formula. In addition, the polarization degree in the polarizing plate sample before a process was calculated | required similarly.
[0136]
Degree of polarization (%) = {(H₀-H₉₀) / (H₀+ H₉₀)}^1/2× 100
<Dryness>
Ranking was performed according to the following criteria according to the time required for the adhesive to dry when the polarizer and the protective film were bonded.
[0137]
○: Within 5 minutes
△: Within 10 minutes
×: When more than 10 minutes
<Adhesiveness>
After the polarizing plate samples were treated at 80 ° C. and 90% RH for 1000 hours, the bonded state of the polarizer and the protective film was observed and ranked according to the following criteria.
[0138]
○: No peeling
△: Slight peeling is observed, but there is no practical problem
×: occurrence of peeling
<Processability>
The polarizing plate sample was allowed to stand at 23 ° C. and 55 ± 5% RH for 24 hours, and then cut with a cutter to observe the end.
[0139]
○: Generation of burrs was not observed at the cut end, and cutting was easy.
Δ: Slight burring was observed at the cut edge.
×: Burr was generated at the cut end and was difficult to cut.
[0140]
[Table 2]

[0141]
It turns out that the polarizing plate using the optical film of this invention has the outstanding characteristic.
[0142]
【The invention's effect】
Polyester resin films having excellent characteristics as various display devices such as liquid crystal displays, particularly optical films such as polarizing plate protective films, were obtained.

Claims (11)

It is a polarizing plate protective film that is directly attached to at least one surface of a polarizer, and is made of a polyester resin film that is produced by a reaction of at least an aromatic dicarboxylic acid and a glycol, and has an equilibrium water content of 1 to 5%. Or a polarizing plate protective film having a group selected from salts thereof . A polarizing plate protective film according to claim 1, sulfur element content of the polyester resin is characterized by 0.15 to 2% by mass Rukoto. 1-10 mol% of a polyester resin with respect to the total aromatic dicarboxylic acid, an aromatic dicarboxylic acid having a group selected from sulfonic acids and salts thereof, or a sulfone with 1-10 mol% with respect to the total aromatic dicarboxylic acid The polarizing plate protective film according to claim 1 , wherein the polarizing plate protective film is produced using a glycol having a group selected from an acid and a salt thereof . The polarized light according to claim 3 , wherein the polyester resin is produced using an aromatic dicarboxylic acid having a group selected from 1 to 10 mol% of a sulfonic acid and a salt thereof with respect to the wholly aromatic dicarboxylic acid. Board protection film. Polyester resin, a polarizing plate protective according to any one of claims 2-4, characterized in that the polyalkylene glycol is granulated made using 0.1 to 10 mass% of the polyester the total amount of the reaction product the film. A polarizing plate protective film according to any one of claims 1-5 in which the main component of the polyester resin is characterized in that it is a polyethylene terephthalate. The polarizing plate protective film according to any one of claims 1 to 6, wherein the polarizing plate protective film has a thickness of 5 to 40 µm, an equilibrium moisture content of 1 to 5%, and a dimensional stability of ± 0.05% or less . It is a long film continuously formed by melt extrusion, and an angle θ between the direction in which the refractive index in the film surface is the largest and the width direction of the long film is 0 ± 15 ° or 90 ± 15 ° It is either of these, The polarizing plate protective film of Claim 7 characterized by the above-mentioned . It is a manufacturing method of the polarizing plate protective film of Claim 7 or 8, Comprising: The film which has the polyester resin layer which has group chosen from a sulfonic acid or its salt is 1.0 to 2.5 times in one direction, and method for manufacturing a polarizing plate protective film characterized that you stretched 2.5 to 10 times in a direction perpendicular. A polarizing plate using the polarizing plate protective film according to claim 7 or 8. A liquid crystal display device using the polarizing plate according to claim 10 or the polarizing plate protective film according to any one of claims 1 to 8.