JP4051874B2 - Protective film for polarizing plate and method for producing the same - Google Patents

Description

【００５３】
本発明において、セルロースエステルフィルム中に酸化防止化合物を含有することができる。酸化防止化合物として特に制限はないが、ヒンダードアミン系化合物が好ましく用いられる。ヒンダードアミン系化合物を用いることで光に対する安定性向上、偏光板用保護フィルムの耐久性を向上させることができる。
【００５４】
該ヒンダードアミン系化合物は、セルロースエステルとの相溶性の観点でヒンダードアミン構造単位あたりの分子量が５００よりも小さいものが好ましく用いられる。
【００５５】
上記ヒンダードアミン系化合物の使用量は、セルロースエステルフィルムに対して０．０１〜１０質量％であることが好ましく、特に０．１〜５質量％であることが好ましい。
【００５６】
以下にヒンダードアミン系化合物の具体例を記載するが、これに限定されるものではない。
【００５７】
【化４】

【００５８】
【化５】

【００５９】
本発明のセルロースエステルフィルムは、高い寸法安定性、良好な紫外線吸収性能から液晶表示部材に用いられるのが好ましい。液晶表示部材とは液晶表示装置に使用される部材のことで、例えば偏光板、偏光板用保護フィルム、位相差板、反射板、視野角向上フィルム、防眩フィルム、無反射フィルム、帯電防止フィルムなどが挙げられる。上記の中でも寸法安定性に対して厳しい要求のある偏光板、偏光板用保護フィルムにおいて本発明のセルロースエステルフィルムを好ましく用いることができる。
【００６０】
偏光板は一般的な方法で作製することができる。例えば、本発明のセルロースエステルフィルムをアルカリ鹸化処理し、沃素溶液中に浸漬延伸して作製した偏光膜の両面に、完全鹸化型ポリビニルアルコール水溶液を用いて貼り合わせる方法がある。アルカリ鹸化処理とは、このときの水系接着剤の濡れ性を良くし、接着性を向上させるために、セルロースエステルフィルムを高温の強アルカリ溶液に浸ける処理のことを言う。
【００６１】
アルカリ鹸化処理の代わりに特開平６−９４９１５号、特開平６−１１８２３２号に記載されているような接着性を高める方法を使用しても良い。
【００６２】
本発明に用いられる偏光板の主たる構成要素である偏光膜とは、一定方向の偏波面の光だけを通す素子であり、現在知られている代表的な偏光膜はポリビニルアルコール系偏光膜で、これはポリビニル系偏光フィルムに沃素を染色させたものと二色性染料を染色させたものがある。これらはポリビニルアルコール水溶液を製膜し、これを一軸延伸させて染色するか、染色した後一軸延伸してから、好ましくは硼素化合物で耐久性処理を行ったものが用いられる。該偏光膜の面上に本発明の偏光板用保護フィルムである透明なフィルムが貼り合わされて偏光板を形成する。
【００６３】
特に、最近のノートパソコンなどの偏光板用保護フィルムとしては従来よりも薄膜化したセルロースエステルフィルムが要望される。薄膜化を行っても紫外線に対する保護を十分に行うためには従来よりも紫外線吸収化合物の単位質量あたりの使用量を多くする必要がある。そのため、上記のようなアルカリ鹸化処理時においては紫外線吸収化合物が増量され、かつ、薄膜化された従来の偏光板用保護フィルムは、紫外線吸収化合物の溶出、析出が起こりやすくなる。
【００６４】
しかしながら、本発明に係る紫外線吸収化合物を用いることで、アルカリ鹸化処理時の紫外線吸収化合物の溶出が極めて少なく、生産工程上のメリットが極めて高いことが明らかとなり、また本発明に係る紫外線吸収化合物を含有するセルロースエステルフィルムは薄膜化、十分な紫外線吸収性を示すことが分かった。
【００６５】
本発明に係るセルロースエステルフィルムの製造方法について説明する。
【００６６】
本発明に係るセルロースエステルフィルムの製造は、本発明に係る紫外線吸収化合物をセルロースエステルを溶剤に溶解させたドープ液に直接添加してもよいが、セルロースエステルを溶剤に溶解させたドープ液と、本発明の紫外線吸収化合物と少量のセルロースエステルとを溶解させた溶液とがインラインで添加、混合、撹拌され、ついで混合液が塗布、製膜されることが好ましい。
【００６７】
前記セルロースエステルを溶剤に溶解させたドープ液とは、セルロースエステルが溶剤（溶媒）に溶解している状態であり、前記ドープ液には可塑剤などの添加剤を加えても良く、もちろん、必要に応じてその他の添加剤を加えることもできる。ドープ液中のセルロースエステルの濃度としては、１０〜３０質量％が好ましく、更に好ましくは１８〜２０質量％である。
【００６８】
前記溶媒は、単独でも併用でも良いが、良溶媒と貧溶媒を混合して用いることが生産性効率の点で好ましく、更に好ましくは良溶媒と貧溶媒の混合比率が良溶媒が７０〜９５質量％であり、貧溶媒が３０〜５質量％である。
【００６９】
上記、良溶媒、貧溶媒とは、使用するセルロースエステルを単独で溶解するものを良溶媒、単独で膨潤するか又は溶解しないものを貧溶媒と定義している。そのため、セルロースエステルの結合酢酸量によっては、良溶媒、貧溶媒が変わり、例えばアセトンを溶媒として用いる場合にはセルロースエステルの結合酢酸量５５％では良溶媒になり、結合酢酸量６０％では貧溶媒となってしまう。
【００７０】
上記良溶媒としては、メチレンクロライド等の有機ハロゲン化物やジオキソラン類が挙げられる。
【００７１】
また、貧溶媒としては、例えばメタノール、エタノール、ｎ−ブタノール、シクロヘキサンなどが好ましく用いられる。
【００７２】
上記記載のドープ液を調製するときのセルロースエステルの溶解方法としては、一般的な方法を用いることができるが、好ましい方法としては、セルロースエステルを貧溶媒と混合し、湿潤あるいは膨潤させ、更に良溶媒と混合する方法が好ましく用いられる。このとき、加圧下で、溶媒の常圧での沸点以上でかつ溶媒が沸騰しない範囲の温度で加熱し、撹拌しながら溶解する方法が、ゲルやママコと呼ばれる塊状未溶解物の発生を防止するため、より好ましい。
【００７３】
前記セルロースエステルを溶剤に溶解させたドープ液と、本発明の紫外線吸収化合物とを少量のセルロースエステルとを溶解させた溶液をインライン添加、混合を行うためには、例えば、スタチックミキサー（東レエンジニアリング製）、ＳＷＪ（東レ静止型管内混合器 Ｈｉ−Ｍｉｘｅｒ）等のインラインミキサーなどが好ましく用いられる。インラインミキサーを用いる場合は、高圧下で濃縮溶解することが好ましく、加圧容器の種類は特に問うところではなく、所定の圧力に耐えることができ、加圧下で加熱、撹拌ができればよい。加圧容器はその他圧力計、温度計などの計器類を適宜配設する。
【００７４】
加圧は窒素ガスなどの不活性気体を圧入する方法や、加熱による溶媒の蒸気圧の上昇によって行っても良い。加熱は外部から行うことが好ましく、例えばジャケットタイプのものは温度コントロールが容易で好ましい。
【００７５】
溶媒を添加しての加熱温度は、使用溶媒の沸点以上で、且つ該溶媒が沸騰しない範囲の温度が好ましく、例えば６０℃以上、７０〜１１０℃の範囲に設定するのが好適である。又、圧力は設定温度で、溶媒が沸騰しないように調整される。
【００７６】
溶解後は冷却しながら容器から取り出すか、又は容器からポンプなどで抜き出して熱交換機などで冷却し、これを製膜に共することが好ましい。このときの冷却温度は常温まで冷却しても良いが、沸点より５〜１０℃低い温度まで冷却し、その温度のままキャスティングを行う方がドープ液の粘度を低減できるためより好ましい。
【００７７】
前記セルロースエステル溶剤を溶解させたドープ液と、紫外線吸収化合物と少量のセルロースエステルが溶解している溶液がインラインで添加、混合され、ついで支持体上に流延（キャスト工程）し、加熱して溶媒の一部を除去（支持体上の乾燥工程）した後、支持体から剥離し、剥離したフィルムを乾燥（フィルム乾燥工程）し、セルロースエステルフィルムが得られる。
【００７８】
キャスト工程における支持体は、ベルト状、もしくはドラム状のステンレス鏡面仕上げした支持体が好ましく用いられる。キャスト工程の支持体の温度は一般的な温度範囲０℃〜溶媒の沸点未満の温度で流延することができ、０〜３０℃の支持体上に流延するほうがドープ液をゲル化させ、剥離限界時間を上げられるため好ましく、５〜１５℃の支持体上に流延することが更に好ましい。ここで、剥離限界時間とは、透明で平面製の良好なフィルムを連続的に得られる流延速度の限界において、流延されたドープ液が支持体上にある時間を言う。剥離限界時間は短い方が生産性に優れ好ましい。
【００７９】
また、剥離する際の支持体の温度は１０〜４０℃、更には１５〜３０℃にすることでフィルムと支持体の密着力を低減でき好ましい。
【００８０】
製造時のセルロースエステルフィルムが良好な平面性を示すためには、支持体から剥離する際の残留溶媒量は、１０〜８０％が好ましく、更には２０〜４０％または６０〜８０％であり、特に好ましくは２０〜３０％である。
【００８１】
上記残留溶媒量は下記式で定義できる。
【００８２】
残留溶媒量（％）＝（（加熱処理前質量−加熱処理後質量）／加熱処理後質量）×１００
尚、残留溶媒量を測定する際の加熱処理とは、フィルムを１１５℃で１時間の加熱処理を行うことを表す。
【００８３】
支持体とフィルムを剥離する際の剥離張力は、通常１９６〜２４５Ｎｅｗｔｏｎ／ｍで剥離が行われるが、セルロースエステル単位質量当たりの紫外線吸収化合物の含有量が多く、且つ従来よりも薄膜化される場合は剥離の際にしわが入りやすいため、剥離できる最低張力〜１６７Ｎｅｗｔｏｎ／ｍで剥離することが好ましく、更に好ましくは剥離できる最低張力〜１３７Ｎｅｗｔｏｎ／ｍで剥離することである。
【００８４】
また、セルロースエステルフィルムの乾燥工程においては、支持体より剥離したフィルムを更に乾燥し、残留溶媒量を３質量％以下にすることが好ましく、更に好ましくは０．５質量％以下である。
【００８５】
上記残留溶媒量のほかに以下に示す方法によって溶媒の種類別に残留溶媒量を測定することができる。
【００８６】
フィルム面積として４６．３ｃｍ²を切り出し、これを５ｍｍ程度に細かく刻み専用バイアル瓶に収納し、セプタムとアルミキャップで密閉した後、ヒューレット・パッカード社製ヘッドスペースサンプラーＨＰ７６９４型にセットする。ヘッドスペースサンプラーと接続したガスクロマトグラフィー（ＧＣ）は検出器として水素炎イオン化検出器（ＦＩＤ）を装着したヒューレット・パッカード社製５９７１型を使用する。測定条件は以下の通りである。
【００８７】
ヘッドスペースサンプラー加熱条件：１２０℃、２０分
ＧＣ導入温度１５０℃
カラム：Ｊ＆Ｗ社製 ＤＢ−６２４
昇温：４５℃、３分保持→１００℃（８℃／分）
上記の測定条件を用いてガスクロマトグラムを得る。測定対象溶媒の各々ブタノールにて希釈された一定量をバイアル瓶に収納した後、上記と同様に測定して得られたクロマトグラムのピーク面積を用いて作製した検量線を使用してフィルム中の残留溶媒量を得る。
【００８８】
フィルム乾燥工程では、一般にロール懸垂方式か、ピンまたはクリップによるテンター方式でフィルムを搬送しながら乾燥する方式を採用することが多いが、液晶表示部材用としては、ピンまたはクリップによるテンター方式で幅を保持しながら乾燥させることが、寸法安定性を向上させるために好ましい。特に、支持体より剥離した直後の残留溶媒量の多いところで幅保持を行うことが寸法安定性向上効果をより発揮し、また漏光率を良くできるために特に好ましい。
【００８９】
フィルムを乾燥させる手段には特に制限はなく、一般的に熱風、赤外線、加熱ロール、マイクロ波などで行うことができる。簡便さの点で熱風で行うことが好ましい。乾燥温度は４０〜１５０℃の範囲で３〜５段階の温度に分けて、徐々に高くしていくことが好ましく、８０〜１４０℃の範囲で行うことが寸法安定性を良くするために、より好ましい。
【００９０】
セルロースエステルフィルムの膜厚は、通常５〜５００μｍのものが用いられるが偏光板用保護フィルムとしての強度、偏光板の寸法安定性や湿熱下における保存性の観点で２０〜１２０μｍであるものが好ましく用いられる。
【００９１】
本発明のセルロースエステルフィルムには、可塑剤を含有することが好ましい。用いることのできる可塑剤としては特に限定はないが、リン酸エステル系ではトリフェニルホスフェート、トリクレジルホスフェート、クレジルジフェニルホスフェート、オクチルジフェニルホスフェート、ジフェニルビフェニルホスフェート、トリオクチルホスフェート、トリブチルホスフェート等、フタル酸エステル系ではジエチルフタレート、ジメトキシエチルフタレート、ジメチルフタレート、ジオクチルフタレート、ジブチルフタレート、ジ−２−エチルヘキシルフタレート等、グリコール酸エステル系では、トリアセチン、トリブチリン、ブチルフタリルブチルグリコレート、エチルフタリルエチルグリコレート、メチルフタリルエチルグリコレート等を単独あるいは併用してして用いることができる。
【００９２】
リン酸エステル系の可塑剤の使用比率は、セルロースエステルフィルムの加水分解を引き起こしにくく、耐久性に優れるため、全可塑剤量の５０質量％以下が好ましく、３０質量％以下が更に好ましく、特にはリン酸エステル系可塑剤を用いずフタル酸エステル系やグリコール酸エステル系の可塑剤のみを使用することが好ましい。
【００９３】
上記可塑剤の使用量は、フィルムの性能、加工性等の点でセルロースエステルに対して１〜１５質量％が好ましく、寸法安定性の点で液晶表示部材用としては１〜１０質量％であることが更に好ましく、特に好ましくは３〜７質量％である。
【００９４】
本発明のセルロースエステルフィルムには、必要に応じてマット剤を加えても良く、例えば酸化ケイ素等の微粒子を加えることができる。該微粒子は、有機物によって表面処理されていることがフィルムのヘイズを低下できるため好ましい。
【００９５】
表面処理に用いられる有機物としてはハロシラン類、アルコキシシラン類、シラザン、シロキサン等が挙げられる。前記微粒子は、マット効果、フィルムの透明性などの点から一次粒子の平均粒径が５〜５０ｎｍが好ましく、更には７〜１４ｎｍであることが好ましい。
【００９６】
次いで請求項１０〜２５の発明について詳細に説明する。偏光板用保護フィルム等の光学フィルムに一般的に用いられる、例えばセルロースエステルフィルムの異物故障には、通常の異物故障と押され故障の２種類がある。通常の異物故障と言われるものは、ベース表面にゴミなどが付着して発生するもので、故障部分を拡大して見ると核となる異物が発見される。押され故障とは、ベース表面が微小に凹んでいる故障で、通常の異物故障と異なり、故障部分を拡大して見ても核となる異物がないことが特徴である。通常の異物故障の原因は、製膜工程中のゴミがベース表面に付着して起こるものと推定されるが、押され故障の原因は搬送ロール上に強く付着している異物がフィルム表面を押すことによって変形が発生するものと推定している。
【００９７】
セルロースエステルフィルムは、ベルトまたはドラム支持体上にドープを流延し、剥離可能になるまで乾燥させ、支持体から剥離し、ロールで搬送しながらさらに乾燥させ、端部を１回あるいは２回スリットし、所望の幅になるように調整しながら作製するのが普通である。
【００９８】
通常の異物故障を詳しく解析したところ、中央部よりも両端部に多く発生し、スリット後に多く発生することがわかった。これらの解析結果から、通常の異物故障はスリット時に発生するフィルムの切り粉が主な原因と推定される。
【００９９】
押され故障は幅方向の分布はなく、剥離直後から発生していることがわかった。支持体から剥離した直後のフィルムは残留溶剤量が多く、やわらかいため、搬送するロールに汚れがあると押され故障が発生するのではないかと推定される。
【０１００】
我々は鋭意検討の結果、セルロースエステルフィルムに含有されている紫外線吸収剤が異物故障、面品質に多大な影響を与えていることを見いだした。すなわち、このロールを汚す物質の一つが紫外線吸収剤であることを見いだした。従来技術として、例えば、特開平６−１３０２２６号、同７−１１０５６号等には、ベンゾトリアゾール系の紫外線吸収剤を用いる事が提案されている。又、前記発明においても前述の様な紫外線吸収化合物を用いることを提案している。しかしながら異物故障という観点で検討した結果では、これら紫外線吸収剤の中でもロールを汚すものと、汚さないものがあることがわかり、また、使用する紫外線吸収剤の組み合わせによって、スリット時の切り粉を減らせることもわかった。
【０１０１】
セルロースエステルフィルムの様な光学フィルムに用いられる理想的な紫外線吸収剤は３８０ｎｍ未満の紫外線をすべて吸収し、３８０ｎｍ以上の可視光の吸収がないものであるが、これは現実的には困難なので、実質的には液晶の劣化防止の点より波長３７０ｎｍ以下の紫外線の吸収能に優れ、かつ良好な液晶表示性の点から波長４００ｎｍ以上の可視光の吸収が可及的に少ないものを使用することができる。実際的には、３８０ｎｍにおける透過率が８％以下である光学フィルムを用いる事が良好な液晶表示性の点から必要である。
【０１０２】
一般に用いられる紫外線吸収剤としては、例えばオキシベンゾフェノン系化合物、ベンゾトリアゾール系化合物、サリチル酸エステル系化合物、ベンゾフェノン系化合物、シアノアクリレート系化合物、ニッケル錯塩系化合物などが挙げられる。
【０１０３】
本発明の１つの態様では、上記の紫外線吸収剤において、分配係数が９．２以上の紫外線吸収剤を含有していることが好ましく、１０．０以上がさらに好ましく、１０．１以上がさらに好ましく、１０．３以上が最も好ましい。分配係数が大きい程ロール汚れが発生しにくく、異物や押され故障が減少するため好ましい。
【０１０４】
分配係数が大きいほど、ロール汚れが発生しにくく、異物や押され故障が減少する理由は完全に明らかではないが、分配係数が大きくなることにより、結晶化しにくくなる効果が効いていると考えられる。このために硬い異物にならず、上記故障が減少することが考えられる。
【０１０５】
分配係数とは以下の式で定義できるオクタノールと水の分配率を表す。
【０１０６】
ｌｏｇＰｏ／ｗ Ｐｏ／ｗ＝Ｓｏ／Ｓｗ
Ｓｏ：２５℃でｎ−オクタノール中での該有機化合物の溶解度
Ｓｗ：２５℃で純水中での該有機化合物の溶解度
これらはこの通りにｎ−オクタノールと水を用いて測定することも出来るが、本発明においては、これら分配係数は、ＨＰＬＣによる計算法を用いた。これは高速クロマトグラフィーを用いる方法であり、ＯＥＣＤガイドライン１１７分配係数（ｎ−オクタノール／水）高速クロマトグラフィー法（１９８９年３月３０日採択）に記載されているもので、ＨＰＬＣの測定条件を以下に示す。
【０１０７】
装置：ＬＣモジュール（ウォーターズ社製）
カラム：イナートシルＯＤＳ−２ ２５０ｍｍ×４．６ｍｍ（ＧＬサイエンス社製）
温度：４０℃
溶離液：メタノール：１％リン酸水溶液＝９０：１０
流量：１．０ｍｌ／ｍｉｎ
検出波長：２１０ｎｍ
注入サンプル：約５０ｐｐｍのメタノール溶液
又、光学フィルムは３８０ｎｍにおける透過率が８％以下であることが好ましく、５％以下がさらに好ましい。３８０ｎｍにおける透過率の低い光学フィルムが偏光板を作製したときの耐光性に優れるため好ましい。
【０１０８】
上記、紫外線吸収剤は樹脂フィルムに対し質量で０．５％以上含有されていることが好ましい。これ以下では、紫外線吸収効果が小さく、余りに多すぎるとブリーディングを起こし、又、フィルム強度も損なうので、総量で１０％以下が好ましい。
【０１０９】
これらの紫外線吸収剤のうち、本発明に用いられる好ましい紫外線吸収剤は、以下に示す一般式１で表されるものである。
【０１１０】
【化６】

【０１１１】
式中、Ｒ₁、Ｒ₂、Ｒ₃、Ｒ₄、Ｒ₅は一価の有機基であり、Ｒ₁、Ｒ₂、Ｒ₃、Ｒ₄、Ｒ₅はそれぞれ同じでも異なっていてもよい。但し、Ｒ₁、Ｒ₂、Ｒ₃の少なくとも１つは総炭素数１０〜２０の無置換の分岐または直鎖のアルキル基である。
【０１１２】
ここで、一価の有機基としては、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、モノ又はジアルキルアミノ基、アシルアミノ基又は５〜６員の複素環基等を表す。
【０１１３】
Ｒ₁、Ｒ₂、Ｒ₃の少なくとも１つは総炭素数１０〜２０の無置換の分岐または直鎖のアルキル基であるが、更に好ましいのは総炭素数１１〜１８であり、最も好ましいのは総炭素数１２〜１５である。この範囲にあるとき、分配係数が上記の好ましい範囲となり、ロール汚れが減少すると同時に樹脂との相溶性にも優れる。総炭素数の多い方がロール汚れが減少する点で優れ、総炭素数の少ない方が樹脂との相溶性に優れる。余り炭素数が多くなると樹脂との相溶性が損なわれる。これらの紫外線吸収剤の具体的な化合物例を以下にあげるが、これらに限定されるものではない。
【０１１４】
【化７】

【０１１５】
又、好ましい紫外線吸収剤は、以下の一般式２で表される。
【０１１６】
【化８】

【０１１７】
式中、Ｒ₁、Ｒ₂、Ｒ₄、Ｒ₅は一価の有機基であり、一般式１におけるＲ₁〜Ｒ₅と同じものを表す。又、Ｒ₆は分岐のアルキル基である。
【０１１８】
分岐のアルキル基としてはイソプロピル基、イソブチル基等の炭素数３〜２０迄の分岐のアルキル基であり、好ましくは炭素数３〜１８、更に好ましくは３〜１５である。
【０１１９】
これらの具体例としては、以下の化合物が挙げられるが、これらに限定されない。
【０１２０】
【化９】

【０１２１】
本発明においては又、紫外線吸収剤を０．１ｇ／リットルの濃度で溶媒に希釈し、１ｃｍ角のセルで溶媒をブランクとして、Ｓｐｅｃｔｒｏｐｈｏｔｏｍｅｔｅｒ Ｕ−３２００（日立製作所製）で分光吸収スペクトルを測定したときの透過率５０％における波長Ｔ₁（以下Ｔ₁と省略）が、３９２〜４２０ｎｍの範囲にある紫外線吸収剤と３６０〜３９０ｎｍの範囲にある紫外線吸収剤の両方を含有している場合、加工性が良化して、両端部付近の異物が少なく、好ましいことがわかった。Ｔ₁は３９６〜４１０ｎｍの範囲にある紫外線吸収剤と３７０〜３９０ｎｍの範囲にある紫外線吸収剤を組み合わせる場合がさらに好ましい。Ｔ₁が３９２〜４２０ｎｍの範囲にある紫外線吸収剤と３６０〜３９０ｎｍの範囲にある紫外線吸収剤の比率は２０：８０〜８０：２０が好ましく、３０：７０〜７０：３０がさらに好ましい。本発明の測定において、溶媒は塩化メチレン：エタノール＝９２：８（質量で）の混合溶媒を用いた。
【０１２２】
Ｔ₁が長波側、３９０〜４１０ｎｍの範囲にある紫外線吸収剤はフィルムに添加したときの紫外線吸収能が高い反面余り多く添加するとフィルムの黄色の着色の原因となる。従って、これらの欠点を補うため、Ｔ₁が長波側の３９０〜４１０ｎｍの範囲にある紫外線吸収剤を、この様な着色のないＴ₁が短波側の３６０〜３８７ｎｍの範囲にある紫外線吸収剤と併用することにより紫外線吸収効果が大きく、かつ着色の少ない紫外線吸収剤を含有する光学フィルムを得ることが出来る。又、紫外線吸収剤を２種以上含有することにより融点低下を生ぜしめる事から、ロール上へ付着しにくく、異物故障や押され故障の生じにくい紫外線吸収剤混合物が得られるという２重の効果がある。
【０１２３】
これらの紫外線吸収剤の例としては、例えば以下の様な化合物が挙げられる。
【０１２４】
【化１０】

【０１２５】
又、光学フィルム中にこの様な紫外線吸収剤の組み合わせを適用する、好ましい方法としては、紫外線吸収剤が、前記一般式１で示される化合物において、Ｒ₄、Ｒ₅の少なくとも１つの置換基がハロゲン原子である紫外線吸収剤と、Ｒ₄、Ｒ₅の置換基のいずれもがハロゲン原子でない紫外線吸収剤を光学フィルム中に含有させ、これらの比を２０：８０〜８０：２０にすることが好ましく、３０：７０〜７０：３０がさらに好ましい。ハロゲン原子を含む紫外線吸収剤の比率の多い方が紫外線吸収性能に優れ、ハロゲン原子を含まない紫外線吸収剤の比率が多い方が黄色みが少なく好ましい。
【０１２６】
又、本発明のもう一つの態様においては、３種類以上の紫外線吸収剤を含有していることが好ましく、４種類以上の紫外線吸収剤を含有していることがさらに好ましい。多くの紫外線吸収剤を組み合わせることで、紫外線吸収剤３８０ｎｍ未満の紫外線をすべて吸収し、３８０ｎｍ以上の可視光の吸収がないという理想的な分光吸収スペクトルにより近づけることができるため好ましい。
【０１２７】
又、融点降下による溶解性の向上や析出の防止によると思われるが、異物故障、押され故障の低減を果たすことができ好ましい。
【０１２８】
好ましい紫外線吸収剤の組み合わせは、一般式１および２の中から選ばれるのが更に好ましく、又、上記のうち、ハロゲン原子を有する紫外線吸収剤およびハロゲン原子を有しない紫外線吸収剤と組み合わせる場合に、ハロゲン原子を有する紫外線吸収剤を複数、又、ハロゲン原子を有しない紫外線吸収剤を複数使用することは、ハロゲン原子を有する紫外線吸収能の高い紫外線吸収剤と、ハロゲン原子を含まない紫外線吸収剤とを併用するメリットに加え、３種以上の紫外線吸収剤を含有させるという上記のメリット両方をもたらすことができ好ましい。
【０１２９】
これらの紫外線吸収剤の使用量は化合物の種類、使用条件などにより一様ではないが、通常はセルロースエステルのような光学フィルム１ｍ²当り、０．２ｇ〜１０．０ｇが好ましく、０．５ｇ〜５．０ｇがさらに好ましく、０．８ｇ〜２．０ｇが特に好ましい。
【０１３０】
樹脂に対する比率で表すと、質量で０．５％以上、１０％以下、更に好ましくは０．８％以上５％以下、特に好ましくは、０．８％以上２．０％以下である。
【０１３１】
本発明の樹脂フィルムとしてはセルロースエステルフィルムが好ましいが、セルロースエステルフィルムの膜厚が薄すぎると、偏光板の保護フィルムとしての強度が不足し、偏光板の寸法安定性や湿熱での保存安定性が悪化する。膜厚が厚いと偏光板が厚くなり、液晶ディスプレイの薄膜化が困難になる。
【０１３２】
これらの紫外線吸収剤の添加方法としては、直接添加してもよいが、前述のように、生産性の優れるインライン添加が好ましい。インライン添加は、予め有機溶剤（例えばメタノール、メチレンクロライドなど）に溶解したものに、少量のトリアセチルセルロースを添加、溶解した後、インラインのミキサーでドープ組成中に添加するのがよい。好ましいトリアセチルセルロースの量は、溶剤１００質量部に対して１〜１０質量部で、より好ましくは、３〜５質量部である。トリアセチルセルロースを添加すると、紫外線吸収剤含有液の粘度が高くなり、インラインで多く添加することが容易になる。
【０１３３】
請求項８〜２３の光学フィルムが用いられる偏光膜、偏光板については請求項１〜７の発明について述べたものと同様であり、既に記載した。又、請求項８〜２３の光学フィルムとしても、透明性に優れる点、又屈折率の異方性の小さな膜を容易に作製できるためセルロースエステルフィルムが好ましく、該セルロースエステルフィルムについては、好ましいセルロースエステル、ドープ液をエンドレスの支持体（ベルト状もしくはドラム状のステンレスを鏡面仕上げした支持体）上にキャスティング（流延）することで製造するセルロースエステルの製造方法、支持体からの剥離の条件、剥離時の残留溶剤、乾燥条件等、好ましい製造条件は請求項１〜７の発明について述べた通りである。
【０１３４】
本発明においても前述の可塑剤を含有することにより、寸法安定性、耐水性に優れたフィルムが得られるため特に好ましい。
【０１３５】
特にこれらの可塑剤のうちでも、融点２０℃以下の可塑剤が含有されていることが好ましい。光学フィルムに含まれる全可塑剤の内、１０質量％以上が２０℃以下の可塑剤であることが好ましく、２０質量％以上がさらに好ましい。分配係数９．２以上の紫外線吸収剤と２０℃以下の可塑剤を組み合わせて使うと、ロール汚れがさらに良化するため好ましい。融点２０℃以下の可塑剤比率の多い方がロール汚れが良化するため好ましい。
【０１３６】
請求項８〜２３に係わる発明においては前述の（９．２以上の分配係数を有する）紫外線吸収剤とこれらの可塑剤のうち融点２０℃以下の可塑剤を併用することが加工性に優れ、前記異物故障や面品質の上で好ましい。融点２０℃以下の可塑剤としては、融点が２０℃以下であれば特に限定されず、前記可塑剤の中から選ぶことができる。例えば、トリクレジルホスフェート、クレジルジフェニルホスフェート、トリブチルホスフェート、ジエチルフタレート、ジメチルフタレート、ジオクチルフタレート、ジブチルフタレート、ジ−２−エチルヘキシルフタレート、トリアセチン、エチルフタリルエチルグリコレート等をあげることができる。これらの可塑剤を単独あるいは併用するのも好ましい。
【０１３７】
本発明中の融点とは、共立出版株式会社出版の化学大辞典に記載されている真の融点を融点としている。
【０１３８】
これらの可塑剤の使用量は、フィルム性能、加工性等の点で、セルロースエステルに対して１〜１５質量％が好ましい。液晶表示部材用としては、寸法安定性の観点から５〜１５質量％が更に好ましく、特に好ましくは、７〜１２質量％である。
【０１３９】
またセルロースエステルに対して融点が２０℃以下の可塑剤の含有量は１質量％〜１０質量％が好ましく、更に好ましくは、３質量％〜７質量％である。
【０１４０】
加工性とはベースフィルムや液晶表示部材をスリット加工や打ち抜き加工する際の加工のしやすさのことで、加工性が悪いと切断面がノコギリ状になり切り屑が発生し、製品に付着して異物故障となるため好ましくない。
【０１４１】
請求項８〜２３に係わる発明に用いられる光学フィルムには、他に必要ならマット剤として微粒子を加えてもよい。前記のマット剤について更に詳細に述べると、無機化合物の例として、二酸化珪素、二酸化チタン、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、焼成珪酸カルシウム、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を挙げることができる。微粒子はケイ素を含むものが濁度が低くなる点で好ましく、特に二酸化珪素が好ましい。二酸化珪素の微粒子は、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）の商品名で市販されており、使用することができる。酸化ジルコニウムの微粒子は、例えば、アエロジルＲ９７６及びＲ８１１（以上日本アエロジル（株）製）の商品名で市販されており、使用することができる。
【０１４２】
ポリマーの例として、シリコーン樹脂、弗素樹脂及びアクリル樹脂を挙げることができる。シリコーン樹脂が好ましく、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）の商品名で市販されており、使用することができる。
【０１４３】
これらの中でアエロジル２００Ｖ、アエロジルＲ９７２Ｖが光学フィルムの濁度を低く保ちながら、摩擦係数をさげる効果が大きいため特に好ましい。
【０１４４】
本発明の光学フィルム（セルロースエステルフィルムが好ましい）は、高い寸法安定性、良好な紫外線カット性能から液晶表示用部材に用いられるのが好ましい。液晶表示用部材とは液晶表示装置に使用される部材のことで、例えば、偏光板、偏光板用保護フィルム、位相差板、反射板、視野角向上フィルム、防眩フィルム、無反射フィルム、帯電防止フィルム等があげられる。上記記載の中でも、寸法安定性に対しても厳しい要求のある偏光板、偏光板用保護フィルムにおいて、本発明のセルロースエステルフィルムは更に好ましく用いられる。
【０１４５】
【実施例】
以下に実施例を用いて本発明の態様を具体的に説明するが、本発明はこれらに限定されるものではない。
【０１４６】
実施例１
試料１
トリアセチルセルロース １００質量部
エチルフタリルエチルグリコレート ５質量部
メチレンクロライド ４７５質量部
エタノール ５０質量部
以上を密閉容器に投入し、加熱、撹拌しながら完全に溶解し、濾過してドープ液を調製した。これとは別に
紫外線吸収化合物 Ｌ−２ １０質量部
トリアセチルセルロース ４質量部
メチレンクロライド １００質量部
以上を密閉容器に投入し、加熱、撹拌しながら完全に溶解し、濾過し、紫外線吸収化合物含有溶液を調製した。
【０１４７】
上記のドープ液１００質量部に対して紫外線吸収化合物含有溶液４質量部の割合で加えてインラインミキサーで十分に混合した。次いで、ベルト流延装置を用い、ドープ液と紫外線吸収化合物含有溶液を温度３３℃、１５００ｍｍ幅でステンレスバンド支持体上に均一に流延した。ステンレスバンド支持体上で流延したトリアセチルセルロースフィルム中の残留溶媒量が２５％になるまで溶媒を蒸発させた後、剥離張力１２７Ｎｅｗｔｏｎ／ｍでステンレスバンド支持体上から剥離した。剥離したセルローストリアセテート１３００ｍｍにスリットし、その後乾燥ゾーンを多数のロールで搬送させながら乾燥を終了させ、１１００ｍｍ幅にスリットして膜厚４０μｍのトリアセチルセルロースフィルムの試料１を得た。
【０１４８】
試料２〜１１
試料１の紫外線吸収化合物の種類と添加量を表１に記載のように変えた以外は同様にして試料２〜１１を作製した。
【０１４９】
試料１２〜１４
試料１の紫外線吸収化合物の種類と添加量を表１に記載のように変え、試料１２の膜厚を８０μｍにした以外は同様にして試料１２〜１４を得た。尚、試料１２は単位面積当たりの紫外線吸収化合物量が試料１と同じになるように調製した。
【０１５０】
アルカリ鹸化処理
鹸化工程：２ｍｏｌ／ｌ−ＮａＯＨ ６０℃ ９０秒
水洗工程：水 ３０℃ ４５秒
中和工程：１０質量％ＨＣｌ ３０℃ ４５秒
水洗工程：水 ３０℃ ４５秒
上記の条件でトリアセチルセルロースフィルムを鹸化→水洗→中和→水洗の順に行い、次いで８０℃で乾燥を行った。
【０１５１】
（紫外線吸収化合物の溶出）
前記アルカリ鹸化処理条件において、アルカリ鹸化液３リットルに対して３５ｍ２のトリアセチルセルロースフィルム試料１〜１４を処理したときのアルカリ鹸化液をそれぞれ採取し目視評価した。
【０１５２】
◎ 液中に紫外線吸収化合物が浮遊しているのが分からない
○ 液中に紫外線吸収化合物が浮遊しているのがかすかに分かる
× 液中に紫外線吸収化合物が浮遊しているのが容易に分かる
×× 液中に紫外線吸収化合物が大量に浮遊している
（色相変化）
試料１〜１４について８０℃、ＲＨ９０％の雰囲気下で１０００時間の耐久性試験を行い、耐久性試験前後での色相の変化をＪＩＳ Ｚ ８７２０に規定する標準光の下で、ＪＩＳ Ｚ ８７２９の方法に従って１０度視野ＸＹＺ系における三刺激値から求められるａ値、ｂ値の変化量をそれぞれ測定した。
【０１５３】
○ ａ値変化量０．１未満、ｂ値変化量０．３未満
× ａ値変化量０．１以上、ｂ値変化量０．３以上
偏光板の作製
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、ホウ酸４質量部を含む水溶液１００質量部に浸漬し、５０℃で４倍に延伸して偏光膜を作製した。この偏光膜の両面にアルカリ鹸化処理を行ったトリアセチルセルロースフィルム試料１〜１４を完全鹸化型ポリビニルアルコール５％水溶液を粘着剤として各々貼り合わせて偏光板を作製した。
【０１５４】
（偏光度変化）
上記のようにして作製した偏光板についてまず平行透過率と直行透過率を測定し、下記式に従って偏光度を算出したその後、各偏光板をキセノンロングライフウェザーメーターで照度７万ルクス、６０℃で５００時間放置（強制劣化）後、再度平行透過率と直行透過率を測定し測定し、下記式に従って偏光度を算出した。
【０１５５】
偏光度Ｐ＝（（Ｈ₀−Ｈ₉₀）／（Ｈ₀＋Ｈ₉₀））^1/2×１００
偏光度変化量＝Ｐ₀−Ｐ₅₀₀
Ｈ₀：平行透過率
Ｈ₉₀：直行透過率
Ｐ₀：強制劣化前の偏光度
Ｐ₅₀₀：強制劣化５００時間後の偏光度
◎ 偏光度変化量１％未満
○ 偏光度変化量１〜２％未満
△ 偏光度変化量２〜５％未満
× 偏光度変化量５％以上
【０１５６】
【表１】

【０１５７】
※１ ＤＨＢＰ：イーストマンケミカル社製 ２，４−ジヒドロキシベンゾフェノン
【０１５８】
【化１１】

【０１５９】
【表２】

【０１６０】
以上のように、本発明の紫外線吸収化合物を用いることでアルカリ鹸化中での紫外線吸収化合物の溶出が抑制され、また、セルロースエステルフィルムの色相変化が低減できかつ偏光度の変化の小さいセルロースエステルフィルムを提供することができた。
【０１６１】
実施例２
〈試料２０１〜２１３〉
（酸化珪素分散液）
アエロジル２００Ｖ（日本アエロジル（株）製）
（一次粒子の平均径１２ｎｍ、見掛け比重１００ｇ／リットル）１０質量部
エタノール ９０質量部
以上をディゾルバーで３０分間撹拌混合した後、マントンゴーリンで分散を行った。分散後の液濁度は９３ｐｐｍであった。
（添加液Ａの作製）
紫外線吸収剤（例示化合物８） １０質量部
リンター綿から合成されたトリアセチルセルロース ４質量部
メチレンクロライド １００質量部
以上を密閉容器に投入し、加熱し、撹拌しながら、完全に溶解し、濾過した。
【０１６２】
これに酸化珪素分散液１０質量部を撹拌しながら加えて、さらに３０分間撹拌した後、濾過し、添加液Ａを調製した。
（ドープ液Ａの調製）
リンター綿から合成されたトリアセチルセルロース ８５質量部
木材パルプから合成されたトリアセチルセルロース １５質量部
エチルフタリルエチルグリコレート ２質量部
トリフェニルホスフェート ８．５質量部
メチレンクロライド ４７５質量部
エタノール ５０質量部
以上を密閉容器に投入し、加熱し、撹拌しながら、完全に溶解し、濾過し、ドープ液を調製した。
【０１６３】
ドープ液１００質量部に対して添加液を表１に示す質量部を加えて、インラインミキサー（東レ静止型管内混合機 Ｈｉ−Ｍｉｘｅｒ、ＳＷＪ）で十分混合し、濾過した。次いで、ベルト流延装置を用い、温度３３℃、１５００ｍｍ幅でステンレスバンド支持体に均一に流延した。ステンレスバンド支持体で、残留溶媒量が２５％になるまで溶媒を蒸発させ、剥離張力１２７Ｎｅｗｔｏｎ／ｍでステンレスバンド支持体上から剥離した。剥離したセルローストリアセテートフィルムを１３００ｍｍ幅にスリットし、その後、乾燥ゾーンを多数のロールで搬送させながら乾燥を終了させ、１１００ｍｍ幅にスリットし、セルローストリアセテートフィルム試料２０１を得た。このときのセルローストリアセテートフィルムの膜厚は４０μｍであった。
【０１６４】
試料２０１の添加液Ａにかえて、表３に示すように下記の添加液と添加量及びドープ液もかえた以外は同様にして試料２０２〜２１３を作製した。
（添加液Ｂ） 添加液Ａの紫外線吸収剤例示化合物８の１０質量部を紫外線吸収剤例示化合物４の１０質量部にかえた以外は同様にして添加液Ｂを作製した。
（添加液Ｃ） 添加液Ａの紫外線吸収剤例示化合物８の１０質量部を紫外線吸収剤例示化合物７の１０質量部にかえた以外は同様にして添加液Ｃを作製した。
（添加液Ｄ） 添加液Ａの紫外線吸収剤例示化合物８の１０質量部を紫外線吸収剤例示化合物９の３質量部及び紫外線吸収剤例示化合物３の９質量部にかえた以外は同様にして添加液Ｄを作製した。
（添加液Ｅ） 添加液Ａの紫外線吸収剤例示化合物８の１０質量部を紫外線吸収剤例示化合物９の１０質量部及び紫外線吸収剤例示化合物７の５質量部と紫外線吸収剤例示化合物５の５質量部にかえた以外は同様にして添加液Ｅを作製した。
（添加液Ｆ） 添加液Ａの紫外線吸収剤例示化合物８の１０質量部を紫外線吸収剤例示化合物９の１．５質量部と紫外線吸収剤例示化合物４の８．５質量部にかえた以外は同様にして添加液Ｆを作製した。
（添加液Ｇ） 添加液Ａの紫外線吸収剤例示化合物８の１０質量部を紫外線吸収剤例示化合物９の１０質量部にかえた以外は同様にして添加液Ｇを作製した。
（添加液Ｈ） 添加液Ａの紫外線吸収剤例示化合物８の１０質量部を紫外線吸収剤例示化合物１０の１０質量部にかえた以外は同様にして添加液Ｈを作製した。
（ドープ液Ｂの作製）
リンター綿から合成されたトリアセチルセルロース ８５質量部
木材パルプから合成されたトリアセチルセルロース １５質量部
トリフェニルホスフェート １１．５質量部
メチレンクロライド ４７５質量部
エタノール ５０質量部
以上を密閉容器に投入し、加熱し、撹拌しながら、完全に溶解し、濾過し、ドープ液を調製した。
【０１６５】
上記で得られた試料２０１〜２１３について、各々、評価した。測定および評価法については実施例４のあとに纏めて示した。
【０１６６】
【表３】

【０１６７】
実施例３
〈試料２１４〜２１７〉
試料２０１の添加液Ａにかえて、表４に記載されたように、以下の添加液と添加量を、及びドープ液も表４の様にかえた以外は同様にして試料２１４〜２１７を作製した。
（添加液Ｉ） 添加液Ａの紫外線吸収剤例示化合物８の１０質量部を紫外線吸収剤例示化合物４の５質量部と紫外線吸収剤例示化合物７の７質量部にかえた以外は同様にして添加液Ｉを作製した。
（添加液Ｊ） 添加液Ａの紫外線吸収剤例示化合物８の１０質量部を紫外線吸収剤例示化合物９の５質量部と紫外線吸収剤例示化合物１０の５質量部にかえた以外は同様にして添加液Ｊを作製した。
【０１６８】
上記で得られた試料２１４〜２１７について、各々、評価した。結果を表４に示す。測定および評価法については以下に纏めて示した。
【０１６９】
【表４】

【０１７０】
実施例４
（添加液Ｋの作製）
紫外線吸収剤（例示化合物１） ５質量部
紫外線吸収剤（例示化合物５） ５質量部
リンター綿から合成された酢化度６１．０％のトリアセチルセルロース
４質量部
メチレンクロライド １００質量部
以上を密閉容器に投入し、加熱し、撹拌しながら、完全に溶解し、濾過した。これに実施例２の酸化珪素分散液１０重量部を撹拌しながら加えて、さらに３０分間撹拌した後、濾過し、添加液Ｋを調製した。
実施例２のドープ液１００質量部に対して添加液を表５に示す重量部を加えて、インラインミキサー（東レ静止型管内混合機 Ｈｉ−Ｍｉｘｅｒ、ＳＷＪ）で十分混合し、濾過した。次いで、ベルト流延装置を用い、温度３３℃、１５００ｍｍ幅でステンレスバンド支持体に均一に流延した。ステンレスバンド支持体で、残留溶媒量が２５％になるまで溶媒を蒸発させ、剥離張力１２７Ｎｅｗｔｏｎ（１３ｋｇｆ）／ｍでステンレスバンド支持体上から剥離した。剥離したセルローストリアセテートフィルムを１３００ｍｍ幅にスリットし、その後テンターで幅方向に１．０５倍延伸し、その後、乾燥ゾーンを多数のロールで搬送させながら乾燥を終了させ、１１００ｍｍ幅にスリットし、セルローストリアセテートフィルム試料３０１を得た。このときのセルローストリアセテートフィルムの膜厚は４０μｍであった。
【０１７１】
試料３０１の添加液Ｋにかえて、表５に示すように下記の添加液と添加量をかえた以外は同様にして試料３０１〜３０８を作製した。
【０１７２】
（添加液Ｌ） 添加液Ｋの紫外線吸収剤例示化合物を紫外線吸収剤例示化合物１の１０質量部にかえた以外は同様にして添加液Ｌを作製した。
【０１７３】
（添加液Ｍ） 添加液Ｋの紫外線吸収剤例示化合物を紫外線吸収剤例示化合物１の５質量部と紫外線吸収剤例示化合物２の５質量部にかえた以外は同様にして添加液Ｍを作製した。
【０１７４】
（添加液Ｎ） 添加液Ｋの紫外線吸収剤例示化合物を紫外線吸収剤例示化合物２の５質量部と紫外線吸収剤例示化合物３の５質量部にかえた以外は同様にして添加液Ｎを作製した。
【０１７５】
（添加液Ｏ） 添加液Ｋの紫外線吸収剤例示化合物を紫外線吸収剤例示化合物２の１０質量部にかえた以外は同様にして添加液Ｏを作製した。
【０１７６】
（添加液Ｐ） 添加液Ｋの紫外線吸収剤例示化合物を紫外線吸収剤例示化合物５の１０質量部にかえた以外は同様にして添加液Ｐを作製した。
【０１７７】
（添加液Ｑ） 添加液Ｋの紫外線吸収剤例示化合物を紫外線吸収剤例示化合物１の５質量部と紫外線吸収剤例示化合物６の５質量部にかえた以外は同様にして添加液Ｑを作製した。
【０１７８】
（添加液Ｒ） 添加液Ｋの紫外線吸収剤例示化合物を紫外線吸収剤例示化合物９の１０質量部にかえた以外は同様にして添加液Ｒを作製した。
【０１７９】
上記で得られた試料３０１〜３０８について、各々評価した。結果を表５に示す。
【０１８０】
【表５】

【０１８１】
《測定方法》
（分配係数）
分配率とはオクタノールと水の分配率を表し以下の式で定義できる。
【０１８２】
ｌｏｇＰｏ／ｗ Ｐｏ／ｗ＝Ｓｏ／Ｓｗ
Ｓｏ：２５℃でｎ−オクタノール中での該有機化合物の溶解度
Ｓｗ：２５℃で純水中での該有機化合物の溶解度
これらの分配率を測定する方法として、本発明においてはＨＰＬＣによる計算法を用いた。この方法はＯＥＣＤガイドライン１１７分配係数（ｎ−オクタノール／水）高速クロマトグラフィー法（１９８９年３月３０日採択）に記載されている。ＨＰＬＣの測定条件を以下に示す。
【０１８３】
装置：ＬＣモジュール（ウォーターズ社製）
カラム：イナートシルＯＤＳ−２ ２５０ｍｍ×４．６ｍｍ（ＧＬサイエンス社製）
温度：４０℃
溶離液：メタノール：１％リン酸水＝９０：１０
流量：１．０ｍｌ／ｍｉｎ
検出波長：２１０ｎｍ
注入サンプル：約５０ｐｐｍのメタノール溶液
（ロール汚れ）
１００００ｍのセルロースエステルフィルムを作製した後、ステンレスバンド支持体から剥離したフィルムが接する一本目のロールの汚れ具合を目視で観察し、以下のランクに分けて評価した。
【０１８４】
Ａ…ロールが汚れているのが全くわからない
Ｂ…ロールが部分的に汚れているのがかすかにわかる
Ｃ…ロールが全面的に汚れているのがかすかにわかる
Ｄ…ロールが全面的に汚れているのがはっきりわかる
Ａ〜Ｃは生産が続けられるレベル。Ｄは生産を中断してロールを清掃するレベル。
（押され故障）
１００００ｍセルロースエステルフィルムを作製した所で、フィルムをサンプリングし、得られたフィルム１ｍ²上に存在する３０μｍ以上の押され故障の数を数えて求めた。
（異物故障）
セルロースエステルフィルムをサンプリングし、得られたフィルムの両端部３０ｃｍ幅、長さ１ｍ上に存在する３０μｍ以上の異物の数を数えて求めた。
（３８０ｎｍ透過率）
Ｓｐｅｃｔｒｏｐｈｏｔｏｍｅｔｅｒ Ｕ−３２００（日立製作所製）を用い、フィルムの分光吸収スペクトルを測定し、３８０ｎｍにおける透過率を求めた。
【０１８５】
Ａ 透過率８％未満
Ｂ 透過率８％以上２５％未満
Ｃ 透過率２５％以上
（加工性）
２０ｃｍ×２０ｃｍの大きさに裁断したセルロースエステルフィルム試料を、１０等分に折り畳んで２０ｃｍ×２．０ｃｍにし、押し切り式のペーパーカッターＤＮ−３（コクヨ株式会社製）で１０ｃｍ×２．０ｃｍに切断し、その断面を評価し、下記のレベルに分けた。△以上であれば、実用上使用できるレベルである。
【０１８６】
◎：切断面が透明で、指で触ってもざらつき感がない
○：切断面は透明だが、指で触るとややざらつき感がある
△：切断面が白く不透明で、指で触るとざらついている
×：切断面が白い粉を吹いたようになり、指で触るとひどくざらついている。（耐光性）
作製した偏光板について先ず平行透過率と直行透過率を測定し、下記処方にしたがって偏光度を算出した。その後各々の偏光板をサンシャインウェザーメーター２００時間、ＵＶカットフィルター無しでの条件で強制劣化後、再度平行透過率と直行透過率を測定し、下記式に従って偏光度を算出した。偏光度変化量を下記式により求めた。
【０１８７】
偏光度Ｐ＝（（Ｈ₀−Ｈ₉₀）／（Ｈ₀＋Ｈ₉₀））^1/2×１００
偏光度変化量＝Ｐ₀−Ｐ₅₀₀
Ｈ₀ ：平行透過率
Ｈ₉₀ ：直行透過率
Ｐ₀ ：強制劣化前の偏光度
Ｐ₅₀₀：強制劣化５００時間後の偏光度
◎：偏光度変化率１０％未満
○：偏光度変化率１０％以上２５％未満
△：偏光度変化率２５％以上４０％未満
×：偏光度変化率４０％以上。
（ブリードアウト）
８０℃、９０％ＲＨの高温高湿雰囲気下に１０００時間放置後、フィルムの表面を観察することによりブリードアウトの有無を評価した。
【０１８８】
◎：フィルム表面にブリードアウトが全くない
○：フィルム表面に部分的なブリードアウトがかすかにわかる
△：フィルム表面に全面的なブリードアウトがかすかにわかる
×：フィルム表面に全面的なブリードアウトがハッキリわかる。
（ＹＩ）
Ｓｐｅｃｔｒｏｐｈｏｔｏｍｅｔｅｒ Ｕ−３２００（日立製作所製）を用い、ＪＩＳ Ｋ７１０３に定められるフィルムのＹＩ（Ｙｅｌｌｏｗｎｅｓｓ Ｉｎｄｅｘ：黄色みの指数）を下記式により求める。
【０１８９】
ＹＩ＝１００（１．２８Ｘ−１．０６Ｚ）／Ｙ
ここで、Ｘ、Ｙ、ＺはＪＩＳ Ｚ８７０１に定められた光源色の三刺激値。
（漏光率Ｐ） 自動複屈折率計ＫＯＢＲＡ−２１ＡＤＨ（王子計測機器（株）製）を用いて試料を２３℃、５５％ＲＨの環境下で、５９０ｎｍの波長に於いて３次元屈折率測定を行い、遅相軸角θ及び屈折率Ｎｘ、Ｎｙ、Ｎｚを求める。下記式（１）に従って面内方向のレターデーション値Ｒ₀を算出し、式（２）に従ってＰを算出し、以下のランクに分けて評価した。
【０１９０】
○・・・０．００００５未満
△・・・０．００００５以上 ０．０００１未満
×・・・０．０００１以上
式（１） Ｒ₀値＝（Ｎｘ−Ｎｙ）×ｄ
式中、Ｎｘはフィルム面内の遅相軸方向の屈折率、Ｎｙはフィルム面内の進相軸方向の屈折率、Ｎｚはフィルムの厚み方向の屈折率、ｄはフィルムの厚み（ｎｍ）をそれぞれ表す。
【０１９１】
式（２） Ｐ＝ｓｉｎ²（２πθ／１８０）・ｓｉｎ²（πＲ₀／λ）
λはＲ₀及びθ（°）を求めるための三次元屈折率測定の際の光の波長５９０ｎｍである。また、πは円周率である。
【０１９２】
【発明の効果】
液晶表示装置、有機ＥＬディスプレイ、プラズマディスプレイ等の各種表示装置に偏光板用保護フィルム、位相差フィルム、視野角拡大フィルム、反射防止フィルム等として用いられる黄色みや異物故障の少ない高品質の光学フィルムが得られる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cellulose ester film, and more specifically, for a polarizing plate provided with ultraviolet (UV) absorption capability for the durability of the cellulose ester film itself used for a polarizing plate of a liquid crystal display device and protection of a liquid crystal substance. The present invention relates to a protective film. The present invention also relates to an optical film used for optical applications and a method for producing the same, and particularly used for a protective film for a polarizing plate, a retardation film, a viewing angle widening film and a plasma display used for a liquid crystal display device and the like. The present invention relates to an optical film that can be used for various functional films such as an antireflection film and various functional films used in organic EL displays and the like, and a method for producing the same.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, cellulose ester films have been widely used in optical applications such as protective films for polarizing plates because they can easily produce films with excellent transparency and small refractive index anisotropy.
[0003]
Particularly in recent years, the development of thinner and lighter cellulose ester films has been progressed with the spread of notebook computers and the like. Along with this, there is an increasing demand for thinner protective films for polarizing plates for liquid crystals.
[0004]
In general, a triacetyl cellulose film is widely used as a protective film for a polarizing plate. However, the triacetyl cellulose film has a drawback inherent to the film that yellows when exposed to ultraviolet light for a long time. For this reason, hitherto, the bad influence by ultraviolet rays has been prevented by the method of mixing an ultraviolet-absorbing compound in a triacetyl cellulose film previously. Moreover, the triacetylcellulose film used for the protective film for polarizing plates uses an ultraviolet absorbing compound for the purpose of protecting the polarizer and the liquid crystal from ultraviolet rays.
[0005]
As described above, as the protective film for polarizing plates has been made thinner, the triacetyl cellulose film has also been made thinner. However, our research has shown that various problems occur if the triacetyl cellulose film is simply made thinner. Became clear.
[0006]
That is, if the triacetyl cellulose film is simply thinned, the ultraviolet rays cannot be sufficiently cut, and it is necessary to increase the amount of the ultraviolet absorbing compound by the amount of the thinned film.
[0007]
However, it has been found that simply increasing the amount of the ultraviolet absorbing compound causes a new problem that the ultraviolet absorbing compound is eluted during the alkali saponification treatment for improving the adhesiveness and the productivity is greatly reduced.
[0008]
As described above, a cellulose ester film is generally widely used as a protective film for polarizing plates. However, with the increase in definition, there is a strict requirement for surface quality and failure of foreign substances in the cellulose ester film. Yes.
[0009]
Regarding improvement of foreign matter failure, means for improving foreign matter by a process is proposed in Japanese Patent Laid-Open Nos. 4-85011, 5-185443, and 8-25459. However, these methods are insufficient as the level of foreign object failure.
[0010]
In addition, some of the recent high-definition liquid crystal systems and viewing angle expansion systems appear slightly yellow, and the cellulose ester film is also slightly yellow. Therefore, when a liquid crystal panel is produced by combining these, the liquid crystal panel looks slightly yellow. There was a problem that. The ultraviolet absorber greatly affects the yellowness of the cellulose ester film. Regarding ultraviolet absorbers, ultraviolet absorbers having different structures have been proposed in JP-A-6-130226 and JP-A-7-11056. However, even in these proposals, yellowness is not considered so much and is insufficient. In addition, foreign matter failure and surface quality were not considered at all.
[0011]
[Problems to be solved by the invention]
An object of the present invention is to provide a cellulose ester film having excellent ultraviolet absorbing ability and having a saponification treatment with little elution of an ultraviolet absorbing compound, and a method for producing the same. And it is providing the optical film with little yellowishness, and its manufacturing method.
[0012]
[Means for Solving the Problems]
The above object of the present invention is achieved by the following means.
[0013]
1. A cellulose ester film comprising an ultraviolet absorbing compound having a melting point of 20 ° C or lower.
[0014]
2. A cellulose ester film comprising an ultraviolet absorbing compound having an ester group in a molecule.
[0015]
3. A cellulose ester film comprising an ultraviolet absorbing compound having a melting point of 20 ° C or lower and an ultraviolet absorbing compound having a melting point higher than 20 ° C.
[0016]
4). 4. The cellulose ester film as described in any one of 1 to 3 above, which contains an antioxidant compound.
[0017]
5. 5. The cellulose ester film as described in 4 above, wherein the antioxidant compound is a hindered amine compound.
[0018]
6). 6. The cellulose ester film as described in any one of 1 to 5 above, wherein the cellulose ester is a lower fatty acid ester.
[0019]
7. The cellulose ester film according to any one of 1 to 6 above, wherein the cellulose ester film is a protective film for a polarizing plate.
[0020]
8. An optical film comprising an ultraviolet absorber having a distribution coefficient of 8.9.2 or more.
[0021]
9. The optical film as described in 8 above, wherein the transmittance at 380 nm is 8% or less.
[0022]
10. 10. The optical film as described in 8 or 9 above, wherein the ultraviolet absorber is contained in an amount of 0.5% or more based on the resin constituting the film.
[0023]
11. 11. The optical film as described in any one of 8 to 10 above, which contains a plasticizer having a melting point of 20 ° C. or lower.
[0024]
12 A film thickness is 20-50 micrometers, The optical film of any one of said 8-11 characterized by the above-mentioned.
[0025]
13. An optical film comprising an ultraviolet absorber represented by the general formula 1.
[0026]
14 An optical film comprising an ultraviolet absorber represented by the general formula 2.
[0027]
15. The wavelength at which the transmittance is 50% when a spectral absorption spectrum is measured by comparing a sample of only a solvent in a 1 cm square cell with a concentration of 0.1 g / liter in a 1 cm square cell is in the range of 392 to 420 nm. An optical film comprising an ultraviolet absorber having a certain spectral absorption spectrum and an ultraviolet absorber having a spectral absorption spectrum having a wavelength in the range of 360 to 390 nm.
[0028]
16. In the general formula 1 (compound represented by), R_Four, R_FiveAn ultraviolet absorber in which at least one of the substituents is a halogen atom, and R_Four, R_FiveIn which any of the substituents is a halogen atom and the ratio of the ultraviolet absorber having the halogen atom to the ultraviolet absorber having no halogen atom is in the range of 20:80 to 80:20. An optical film characterized by the above.
[0029]
17. An optical film comprising three or more kinds of ultraviolet absorbers.
[0030]
18. The optical film as described in any one of 8 to 16 above, which contains three or more kinds of ultraviolet absorbers.
[0031]
19. The optical film of 8 to 18 is obtained by mixing and stirring an ultraviolet absorbent solution containing a resin and a dope solution in which the resin is dissolved in-line, casting on a belt or drum support, and forming a film. A method for producing an optical film.
[0032]
20. 20. An optical film produced using the production method as described in 19 above.
[0033]
21. 21. The optical film as described in any one of 8 to 18 and 20, which is a cellulose ester film.
[0034]
22. 20. The method for producing an optical film as described in 19 above, wherein the optical film is a cellulose ester film.
[0035]
23. 22. The optical film as described in 21 above, wherein the cellulose ester is a lower fatty acid ester of cellulose.
[0036]
This will be described in detail below.
[0037]
The cellulose ester film according to claims 1 to 9 of the present invention will be described.
[0038]
As the cellulose ester used in the first to ninth aspects of the present invention, the cellulose ester is preferably a lower fatty acid ester.
[0039]
The lower fatty acid in the lower fatty acid ester of cellulose ester means a fatty acid having 6 or less carbon atoms. For example, cellulose acetate, cellulose propionate, cellulose butyrate and the like can be mentioned as preferred examples of the cellulose lower fatty acid ester.
[0040]
In addition to the above, mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate described in JP-A Nos. 10-45804, 8-231761, U.S. Pat. No. 2,319,052 are used. be able to. The total acyl group substitution degree of the mixed fatty acid ester used is preferably 2.3 to 3.0, and particularly preferably 2.0 or less. The total acyl substitution degree is more preferably 2.5 to 2.8.
[0041]
Among the above description, the cellulose lower fatty acid ester particularly preferably used is cellulose acetate.
[0042]
Further, from the viewpoint of the strength of the film, cellulose triacetate having a polymerization degree of 250 to 400 and a bound acetic acid amount of 54 to 62.5% is preferably used, and a bound acetic acid amount of 58 to 62.5% is more preferable. In particular, it is preferably 58 to 59%. As the cellulose ester, either a cellulose ester synthesized from cotton linter or a cellulose ester synthesized from wood pulp can be used alone or as a mixture thereof. In the production of cellulose ester film, mixing a large amount of cellulose ester synthesized from cotton linter from the viewpoint of releasability from the support when cast on a belt or drum to improve productivity This is preferable. When cellulose esters synthesized from wood pulp are mixed and used, the ratio of cellulose esters synthesized from cotton linters is preferably 40% by mass or more, and more preferably 60% by mass or more. Most preferably, the cellulose ester synthesized from cotton linter is used alone.
[0043]
Next, an ultraviolet absorbing compound (hereinafter sometimes referred to as an ultraviolet absorber) contained in the cellulose ester film of the invention represented by claims 1 to 9 will be described.
[0044]
In the present invention, an ultraviolet absorbing compound having a melting point of 20 ° C. or lower can be used.
[0045]
In the present invention, an ultraviolet absorbing compound having an ester group in the molecule can be used.
[0046]
In the present invention, by using an ultraviolet absorbing compound having a melting point of 20 ° C. or less or a compound having an ester group in the molecule, elution of the ultraviolet absorbing compound from the cellulose ester film in the alkali saponification step can be suppressed.
[0047]
In the present invention, the ultraviolet absorbing compound having a melting point of 20 ° C. or lower can be used in combination with an ultraviolet absorbing compound having a melting point higher than 20 ° C. Similarly, an ultraviolet absorbing compound having an ester group in the molecule and an ultraviolet absorbing compound having no ester group in the molecule may be used in combination.
[0048]
The ultraviolet absorbing compound used in the present invention may have a melting point of 20 ° C. or lower. Specific examples include benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, and cyanoacrylate compounds. Of these compounds, the compounds are particularly preferred. Furthermore, the ultraviolet absorbing compound of the present invention preferably has an alkyl chain, alkenyl chain, alkylene chain or alkylene oxide chain having 8 or more carbon atoms from the viewpoint of compatibility with the cellulose ester. Further, the ultraviolet absorbing compound of the present invention preferably has a molecular weight of 3000 or less, particularly preferably 2000 or less.
[0049]
Further, as the ultraviolet absorbing compound that can be used in combination with the ultraviolet absorbing compound of the present invention, commonly used ultraviolet absorbing compounds can be used. Specifically, for example, oxybenzophenone compounds, benzotriazole compounds, Examples include salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, and nickel complex compounds. Of these, benzotriazole compounds are preferred.
[0050]
The usage-amount of the ultraviolet absorption compound of this invention is 0.01-10 mass% with respect to a cellulose-ester film, Preferably it is 0.1-5 mass%. The amount of the ultraviolet absorbing compound that can be used in combination with the ultraviolet absorbing compound of the present invention is preferably 0.05 to 10 times, more preferably 0.1 to 5 times that of the ultraviolet absorbing compound of the present invention. .
[0051]
Specific examples of the ultraviolet absorbing compound used in the present invention are shown below, but the present invention is not limited thereto.
[0052]
[Chemical Formula 3]

[0053]
In the present invention, an antioxidant compound can be contained in the cellulose ester film. The antioxidant compound is not particularly limited, but a hindered amine compound is preferably used. By using a hindered amine compound, the stability to light can be improved and the durability of the protective film for polarizing plate can be improved.
[0054]
As the hindered amine compound, those having a molecular weight per hindered amine structural unit smaller than 500 are preferably used from the viewpoint of compatibility with the cellulose ester.
[0055]
It is preferable that the usage-amount of the said hindered amine type compound is 0.01-10 mass% with respect to a cellulose-ester film, and it is especially preferable that it is 0.1-5 mass%.
[0056]
Although the specific example of a hindered amine type compound is described below, it is not limited to this.
[0057]
[Formula 4]

[0058]
[Chemical formula 5]

[0059]
The cellulose ester film of the present invention is preferably used for a liquid crystal display member because of high dimensional stability and good ultraviolet absorption performance. A liquid crystal display member is a member used for a liquid crystal display device. For example, a polarizing plate, a protective film for a polarizing plate, a retardation plate, a reflector, a viewing angle improving film, an antiglare film, an antireflective film, and an antistatic film. Etc. Among them, the cellulose ester film of the present invention can be preferably used in polarizing plates and polarizing plate protective films that have strict requirements on dimensional stability.
[0060]
The polarizing plate can be produced by a general method. For example, there is a method in which the cellulose ester film of the present invention is subjected to alkali saponification treatment and bonded to both surfaces of a polarizing film prepared by immersing and stretching in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. The alkali saponification treatment is a treatment in which the cellulose ester film is immersed in a high-temperature strong alkaline solution in order to improve the wettability of the aqueous adhesive and improve the adhesion.
[0061]
Instead of the alkali saponification treatment, a method for enhancing adhesiveness as described in JP-A-6-94915 and JP-A-6-118232 may be used.
[0062]
The polarizing film that is the main component of the polarizing plate used in the present invention is an element that allows only light in the plane of polarization in a certain direction to pass through. A typical polarizing film currently known is a polyvinyl alcohol polarizing film, There are one in which a polyvinyl polarizing film is dyed with iodine and one in which a dichroic dye is dyed. These are formed by forming a polyvinyl alcohol aqueous solution into a film and dyeing the film by uniaxial stretching or dyeing and then uniaxially stretching, and then performing a durability treatment with a boron compound. A transparent film, which is a protective film for a polarizing plate of the present invention, is bonded onto the surface of the polarizing film to form a polarizing plate.
[0063]
In particular, as a protective film for a polarizing plate of a recent notebook personal computer or the like, a cellulose ester film having a thinner film than before is desired. In order to sufficiently protect the ultraviolet rays even if the film thickness is reduced, it is necessary to increase the amount of the ultraviolet absorbing compound used per unit mass than before. Therefore, during the alkali saponification treatment as described above, the amount of the ultraviolet absorbing compound is increased, and the conventional protective film for polarizing plate having a reduced thickness tends to cause elution and precipitation of the ultraviolet absorbing compound.
[0064]
However, it is clear that by using the ultraviolet absorbing compound according to the present invention, elution of the ultraviolet absorbing compound during the alkali saponification treatment is extremely small and the merit in the production process is extremely high. It turned out that the cellulose-ester film to contain shows thin film formation and sufficient ultraviolet absorptivity.
[0065]
The manufacturing method of the cellulose-ester film which concerns on this invention is demonstrated.
[0066]
The production of the cellulose ester film according to the present invention may be directly added to the dope solution obtained by dissolving the cellulose ester in the solvent, the dope solution obtained by dissolving the cellulose ester in the solvent, It is preferred that the ultraviolet absorbing compound of the present invention and a solution in which a small amount of cellulose ester is dissolved are added, mixed and stirred in-line, and then the mixed solution is applied and formed into a film.
[0067]
The dope solution in which the cellulose ester is dissolved in a solvent is a state in which the cellulose ester is dissolved in a solvent (solvent), and an additive such as a plasticizer may be added to the dope solution. Depending on the case, other additives can be added. As a density | concentration of the cellulose ester in dope liquid, 10-30 mass% is preferable, More preferably, it is 18-20 mass%.
[0068]
The solvent may be used alone or in combination, but it is preferable to use a mixture of a good solvent and a poor solvent in terms of productivity efficiency, and more preferably, the mixing ratio of the good solvent and the poor solvent is 70 to 95 mass. %, And the poor solvent is 30 to 5% by mass.
[0069]
The above-mentioned good solvent and poor solvent are defined as a good solvent if it dissolves the cellulose ester used alone, and a poor solvent if it swells or does not dissolve alone. Therefore, depending on the amount of acetic acid bonded to the cellulose ester, the good solvent and the poor solvent change. For example, when acetone is used as the solvent, the amount of acetic acid bonded to the cellulose ester is 55%, and the amount of acetic acid is 60%. End up.
[0070]
Examples of the good solvent include organic halides such as methylene chloride and dioxolanes.
[0071]
Moreover, as a poor solvent, methanol, ethanol, n-butanol, cyclohexane etc. are used preferably, for example.
[0072]
As a method for dissolving the cellulose ester when preparing the dope described above, a general method can be used. However, as a preferable method, the cellulose ester is mixed with a poor solvent and wetted or swollen. A method of mixing with a solvent is preferably used. At this time, the method of heating under stirring at a temperature not lower than the boiling point of the solvent at normal pressure and in a range where the solvent does not boil and dissolving while stirring prevents the generation of massive undissolved material called gel or mamako. Therefore, it is more preferable.
[0073]
In order to perform in-line addition and mixing of a solution obtained by dissolving the cellulose ester in a solvent and a small amount of the cellulose ester in the ultraviolet absorbing compound of the present invention, for example, a static mixer (Toray Engineering) is used. In-line mixers such as SWJ (Toray Static In-Pipe Mixer Hi-Mixer) are preferably used. When using an in-line mixer, it is preferable to concentrate and dissolve under high pressure, and the type of the pressurized container is not particularly limited, as long as it can withstand a predetermined pressure and can be heated and stirred under pressure. The pressure vessel is appropriately provided with other instruments such as a pressure gauge and a thermometer.
[0074]
The pressurization may be performed by a method of injecting an inert gas such as nitrogen gas or by increasing the vapor pressure of the solvent by heating. Heating is preferably performed from the outside. For example, a jacket type is preferable because temperature control is easy.
[0075]
The heating temperature with the addition of the solvent is preferably a temperature that is not lower than the boiling point of the solvent used and does not boil, and is preferably set in the range of 60 ° C. or higher and 70 to 110 ° C., for example. The pressure is adjusted at a set temperature so that the solvent does not boil.
[0076]
After dissolution, it is preferably taken out of the container while cooling, or extracted from the container with a pump or the like and cooled with a heat exchanger or the like, and this is preferably used for film formation. Although the cooling temperature at this time may be cooled to room temperature, it is more preferable to cool to a temperature 5 to 10 ° C. lower than the boiling point and perform casting at that temperature because the viscosity of the dope solution can be reduced.
[0077]
The dope solution in which the cellulose ester solvent is dissolved and the solution in which the ultraviolet absorbing compound and a small amount of the cellulose ester are dissolved are added and mixed in-line, and then cast on a support (casting process) and heated. After removing a part of the solvent (drying process on the support), the film is peeled off from the support, and the peeled film is dried (film drying process) to obtain a cellulose ester film.
[0078]
As the support in the casting step, a belt-shaped or drum-shaped stainless steel mirror-finished support is preferably used. The temperature of the support in the casting process can be cast at a general temperature range of 0 ° C. to a temperature lower than the boiling point of the solvent, and casting on a support at 0 to 30 ° C. causes the dope solution to gel. It is preferable because the peeling limit time can be increased, and it is more preferable to cast it on a support at 5 to 15 ° C. Here, the peeling limit time means the time during which the cast dope solution is on the support at the limit of the casting speed at which a transparent and flat film can be continuously obtained. A shorter peeling limit time is preferable because of excellent productivity.
[0079]
Moreover, the temperature of the support at the time of peeling is preferably 10 to 40 ° C., and more preferably 15 to 30 ° C., so that the adhesion between the film and the support can be reduced.
[0080]
In order for the cellulose ester film during production to exhibit good flatness, the residual solvent amount when peeling from the support is preferably 10 to 80%, more preferably 20 to 40% or 60 to 80%, Most preferably, it is 20 to 30%.
[0081]
The residual solvent amount can be defined by the following formula.
[0082]
Residual solvent amount (%) = ((mass before heat treatment−mass after heat treatment) / mass after heat treatment) × 100
The heat treatment for measuring the residual solvent amount means that the film is heat treated at 115 ° C. for 1 hour.
[0083]
Peeling tension when peeling the support and film is usually 196 to 245 Newton / m, but the content of UV-absorbing compound per unit mass of cellulose ester is large and the film is made thinner than before Since wrinkles tend to occur at the time of peeling, peeling is preferably performed with a minimum tension at which peeling is possible to 167 Newton / m, and more preferably peeling with a minimum tension at which peeling is possible to 137 Newton / m.
[0084]
Moreover, in the drying process of the cellulose ester film, the film peeled off from the support is further dried, and the residual solvent amount is preferably 3% by mass or less, more preferably 0.5% by mass or less.
[0085]
In addition to the residual solvent amount, the residual solvent amount can be measured for each type of solvent by the following method.
[0086]
46.3cm as film area²Is cut into 5 mm pieces, stored in a dedicated vial, sealed with a septum and an aluminum cap, and then set on a head space sampler HP7694 manufactured by Hewlett-Packard. Gas chromatography (GC) connected to a headspace sampler uses a 5971 model manufactured by Hewlett-Packard Co. equipped with a flame ionization detector (FID) as a detector. The measurement conditions are as follows.
[0087]
Headspace sampler heating conditions: 120 ° C, 20 minutes
GC introduction temperature 150 ° C
Column: DB-624 manufactured by J & W
Temperature rise: 45 ° C, hold for 3 minutes → 100 ° C (8 ° C / min)
A gas chromatogram is obtained using the above measurement conditions. After storing a certain amount of each solvent to be measured diluted with butanol in a vial, using a calibration curve prepared using the peak area of the chromatogram obtained by measuring in the same manner as described above, Obtain the amount of residual solvent.
[0088]
In the film drying process, in general, a roll hanging method or a tenter method using a pin or clip is used to dry the film while it is transported, but for liquid crystal display members, the width is increased using a pin or clip tenter method. Drying while holding is preferable in order to improve dimensional stability. In particular, it is particularly preferable to maintain the width where the amount of residual solvent is large immediately after peeling from the support because the effect of improving the dimensional stability can be further exhibited and the light leakage rate can be improved.
[0089]
There is no restriction | limiting in particular in the means to dry a film, Generally it can carry out with a hot air, infrared rays, a heating roll, a microwave. It is preferable to carry out with hot air in terms of simplicity. The drying temperature is preferably divided into 3 to 5 stages in the range of 40 to 150 ° C. and gradually increased, and the temperature in the range of 80 to 140 ° C. is more suitable for improving dimensional stability. preferable.
[0090]
The film thickness of the cellulose ester film is usually 5 to 500 μm, but is preferably 20 to 120 μm from the viewpoint of the strength as a protective film for a polarizing plate, the dimensional stability of the polarizing plate and the storage stability under wet heat. Used.
[0091]
The cellulose ester film of the present invention preferably contains a plasticizer. The plasticizer that can be used is not particularly limited. However, in the case of phosphate ester, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, etc. Diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, etc. for acid ester systems, triacetin, tributyrin, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycol for glycolic acid ester systems A rate, methylphthalyl ethyl glycolate, etc. can be used alone or in combination.
[0092]
The use ratio of the phosphate ester plasticizer is less likely to cause hydrolysis of the cellulose ester film and is excellent in durability, so that it is preferably 50% by mass or less, more preferably 30% by mass or less, particularly preferably 30% by mass or less. It is preferable to use only a phthalate ester or glycolate ester plasticizer without using a phosphate ester plasticizer.
[0093]
The amount of the plasticizer used is preferably 1 to 15% by mass relative to the cellulose ester in terms of film performance, processability, etc., and 1 to 10% by mass for liquid crystal display members in terms of dimensional stability. More preferably, it is 3-7 mass% especially preferably.
[0094]
If necessary, a matting agent may be added to the cellulose ester film of the present invention. For example, fine particles such as silicon oxide can be added. The fine particles are preferably surface-treated with an organic substance because the haze of the film can be reduced.
[0095]
Examples of the organic substance used for the surface treatment include halosilanes, alkoxysilanes, silazane, and siloxane. The fine particles preferably have an average primary particle size of 5 to 50 nm, more preferably 7 to 14 nm, from the viewpoint of mat effect and film transparency.
[0096]
Next, the invention of claims 10 to 25 will be described in detail. There are two types of foreign matter failure of, for example, a cellulose ester film that are generally used for optical films such as a protective film for a polarizing plate: normal foreign matter failure and pressed failure. What is said to be a normal foreign matter failure occurs when dust or the like adheres to the surface of the base, and a foreign matter that becomes a nucleus is found when the failed portion is enlarged. The pressed failure is a failure in which the base surface is slightly dented, and is characterized in that there is no core foreign matter even when the failure portion is enlarged unlike a normal foreign matter failure. The cause of normal foreign matter failure is presumed to be caused by dust adhering to the base surface during the film forming process, but the cause of the failure caused by pressing is that the foreign matter strongly adhering to the transport roll presses the film surface. It is estimated that deformation will occur.
[0097]
The cellulose ester film is cast on a belt or drum support, dried until it becomes peelable, peeled off from the support, further dried while being transported by a roll, and the edge is slit once or twice. However, it is usual to produce the film while adjusting it to a desired width.
[0098]
A detailed analysis of normal foreign matter failures revealed that they occurred more frequently at both ends than at the center, and more often after the slit. From these analysis results, it is presumed that the normal foreign matter failure is mainly caused by film chips generated at the time of slitting.
[0099]
It was found that the pressed failure had no distribution in the width direction and occurred immediately after peeling. Since the film immediately after peeling from the support has a large amount of residual solvent and is soft, it is presumed that if the transporting roll is contaminated, it will be pushed and cause a failure.
[0100]
As a result of intensive studies, we have found that the ultraviolet absorber contained in the cellulose ester film has a great influence on foreign matter failure and surface quality. That is, it was found that one of the substances that contaminate this roll is an ultraviolet absorber. As conventional techniques, for example, JP-A-6-130226 and JP-A-7-11056 propose use of a benzotriazole-based ultraviolet absorber. In the invention, it is proposed to use the ultraviolet absorbing compound as described above. However, as a result of examination from the viewpoint of foreign matter failure, it can be seen that some of these UV absorbers soil the roll and some do not stain, and the combination of UV absorbers used reduces the amount of chips when slitting. I also understood that.
[0101]
Ideal UV absorbers used in optical films such as cellulose ester films absorb all UV light below 380 nm and do not absorb visible light above 380 nm, but this is practically difficult, Use a substance that is substantially superior in absorbing ultraviolet light with a wavelength of 370 nm or less from the viewpoint of preventing deterioration of the liquid crystal and that absorbs as little visible light as possible with a wavelength of 400 nm or more from the viewpoint of good liquid crystal display properties. Can do. In practice, it is necessary to use an optical film having a transmittance at 380 nm of 8% or less from the viewpoint of good liquid crystal display properties.
[0102]
Examples of commonly used ultraviolet absorbers include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like.
[0103]
In one aspect of the present invention, the above ultraviolet absorber preferably contains an ultraviolet absorber having a distribution coefficient of 9.2 or more, more preferably 10.0 or more, and even more preferably 10.1 or more. 10.3 or more is most preferable. A larger distribution coefficient is more preferable because roll contamination is less likely to occur and foreign matter or pressing failure is reduced.
[0104]
The larger the distribution coefficient, the less likely it is to cause roll contamination, and the reason why foreign matter and pressing and failures are reduced is not completely clear, but it is thought that the effect of making it difficult to crystallize is effective by increasing the distribution coefficient. . For this reason, it is conceivable that the failure is not reduced and the failure is reduced.
[0105]
The partition coefficient represents the partition ratio of octanol and water that can be defined by the following formula.
[0106]
logPo / w Po / w = So / Sw
So: Solubility of the organic compound in n-octanol at 25 ° C
Sw: Solubility of the organic compound in pure water at 25 ° C
These can also be measured using n-octanol and water in this way, but in the present invention, these partition coefficients were calculated by HPLC. This is a method using high-speed chromatography, which is described in the OECD guideline 117 partition coefficient (n-octanol / water) high-speed chromatography method (adopted on March 30, 1989). Shown in
[0107]
Apparatus: LC module (manufactured by Waters)
Column: Inertsil ODS-2 250 mm x 4.6 mm (manufactured by GL Sciences)
Temperature: 40 ° C
Eluent: Methanol: 1% phosphoric acid aqueous solution = 90: 10
Flow rate: 1.0 ml / min
Detection wavelength: 210 nm
Injection sample: about 50ppm methanol solution
The optical film preferably has a transmittance at 380 nm of 8% or less, more preferably 5% or less. An optical film having a low transmittance at 380 nm is preferable because of excellent light resistance when a polarizing plate is produced.
[0108]
The ultraviolet absorber is preferably contained in an amount of 0.5% or more with respect to the resin film. Below this, the ultraviolet ray absorbing effect is small, and if it is too much, bleeding occurs and the film strength is also impaired, so the total amount is preferably 10% or less.
[0109]
Among these ultraviolet absorbers, preferred ultraviolet absorbers used in the present invention are those represented by the following general formula 1.
[0110]
[Chemical 6]

[0111]
Where R₁, R₂, R_Three, R_Four, R_FiveIs a monovalent organic group, R₁, R₂, R_Three, R_Four, R_FiveMay be the same or different. However, R₁, R₂, R_ThreeAt least one of them is an unsubstituted branched or linear alkyl group having 10 to 20 carbon atoms in total.
[0112]
Here, as the monovalent organic group, a hydrogen atom, halogen atom, nitro group, hydroxyl group, alkyl group, alkenyl group, aryl group, alkoxy group, acyloxy group, aryloxy group, alkylthio group, arylthio group, mono or A dialkylamino group, an acylamino group, or a 5- to 6-membered heterocyclic group is represented.
[0113]
R₁, R₂, R_ThreeAt least one is an unsubstituted branched or straight chain alkyl group having 10 to 20 carbon atoms, more preferably 11 to 18 carbon atoms, and most preferably 12 to 15 carbon atoms. is there. When it is in this range, the distribution coefficient is in the above-mentioned preferable range, and roll contamination is reduced, and at the same time, compatibility with the resin is excellent. A higher total carbon number is superior in reducing roll stains, and a lower total carbon number is excellent in compatibility with the resin. If the number of carbon atoms is excessive, compatibility with the resin is impaired. Specific examples of these ultraviolet absorbers are listed below, but are not limited thereto.
[0114]
[Chemical 7]

[0115]
A preferable ultraviolet absorber is represented by the following general formula 2.
[0116]
[Chemical 8]

[0117]
Where R₁, R₂, R_Four, R_FiveIs a monovalent organic group, R in general formula 1₁~ R_FiveRepresents the same thing. R₆Is a branched alkyl group.
[0118]
The branched alkyl group is a branched alkyl group having 3 to 20 carbon atoms such as isopropyl group and isobutyl group, preferably 3 to 18 carbon atoms, more preferably 3 to 15 carbon atoms.
[0119]
Specific examples of these include, but are not limited to, the following compounds.
[0120]
[Chemical 9]

[0121]
In the present invention, when the ultraviolet absorber is diluted in a solvent at a concentration of 0.1 g / liter, the spectral absorption spectrum is measured with a Spectrophotometer U-3200 (manufactured by Hitachi, Ltd.) using a 1 cm square cell with the solvent as a blank. Wavelength T at 50% transmittance₁(T₁Is omitted), when both the ultraviolet absorber in the range of 392 to 420 nm and the ultraviolet absorber in the range of 360 to 390 nm are contained, the workability is improved, and there are few foreign substances near both ends. It turned out to be preferable. T₁Is more preferably a combination of an ultraviolet absorber in the range of 396 to 410 nm and an ultraviolet absorber in the range of 370 to 390 nm. T₁Is preferably 20: 80-80: 20, more preferably 30: 70-70: 30. The ratio of the ultraviolet absorber in the range of 392 to 420 nm and the ultraviolet absorber in the range of 360 to 390 nm is preferably 20:80 to 80:20. In the measurement of the present invention, a mixed solvent of methylene chloride: ethanol = 92: 8 (by mass) was used as the solvent.
[0122]
T₁The ultraviolet absorber having a wavelength of 390 to 410 nm on the long wave side has a high ultraviolet absorbing ability when added to the film, but if added too much, it causes yellowing of the film. Therefore, to compensate for these drawbacks, T₁A UV absorber having a wavelength of 390 to 410 nm on the long wave side,₁Is used in combination with an ultraviolet absorber having a wavelength of 360 to 387 nm on the short wave side, an optical film containing an ultraviolet absorber having a large ultraviolet absorption effect and little coloration can be obtained. In addition, since the melting point is lowered by containing two or more kinds of ultraviolet absorbers, there is a double effect that an ultraviolet absorber mixture is obtained which is difficult to adhere on the roll and is less likely to cause foreign matter failure or pressing failure. is there.
[0123]
Examples of these ultraviolet absorbers include the following compounds.
[0124]
Embedded image

[0125]
Further, as a preferable method for applying such a combination of ultraviolet absorbers in an optical film, the ultraviolet absorber is a compound represented by the above general formula 1, and R_Four, R_FiveAn ultraviolet absorber in which at least one of the substituents is a halogen atom, and R_Four, R_FiveIn the optical film, an ultraviolet absorber in which any of the substituents is not a halogen atom is contained, and the ratio thereof is preferably 20:80 to 80:20, and more preferably 30:70 to 70:30. A larger proportion of the ultraviolet absorber containing a halogen atom is more excellent in ultraviolet absorption performance, and a larger proportion of the ultraviolet absorber containing no halogen atom is preferable because of less yellowing.
[0126]
In another embodiment of the present invention, it is preferable to contain three or more types of ultraviolet absorbers, and it is more preferable to contain four or more types of ultraviolet absorbers. It is preferable to combine many ultraviolet absorbers because the ultraviolet absorber can absorb all ultraviolet rays less than 380 nm and can be brought closer to an ideal spectral absorption spectrum in which there is no visible light absorption of 380 nm or more.
[0127]
Moreover, although it seems that it is based on the improvement of the solubility by melting | fusing point fall and prevention of precipitation, a foreign material failure and a pushing failure can be reduced, and it is preferable.
[0128]
A preferable combination of ultraviolet absorbers is more preferably selected from the general formulas 1 and 2, and among the above, when combined with an ultraviolet absorber having a halogen atom and an ultraviolet absorber not having a halogen atom, The use of a plurality of ultraviolet absorbers having halogen atoms or a plurality of ultraviolet absorbers having no halogen atoms means that an ultraviolet absorber having a halogen atom and a high ultraviolet absorbing ability, and an ultraviolet absorber not containing a halogen atom, In addition to the merit of using the combination, it is preferable that both of the above merit of containing three or more kinds of ultraviolet absorbers can be provided.
[0129]
The amount of these ultraviolet absorbers used is not uniform depending on the type of compound, the conditions of use, etc., but usually an optical film such as cellulose ester 1 m²It is preferably 0.2 g to 10.0 g, more preferably 0.5 g to 5.0 g, and particularly preferably 0.8 g to 2.0 g.
[0130]
When expressed as a ratio to the resin, it is 0.5% to 10% by mass, more preferably 0.8% to 5%, and particularly preferably 0.8% to 2.0%.
[0131]
As the resin film of the present invention, a cellulose ester film is preferable. However, if the film thickness of the cellulose ester film is too thin, the strength as a protective film of the polarizing plate is insufficient, and the dimensional stability of the polarizing plate and the storage stability with wet heat are sufficient. Gets worse. If the film thickness is thick, the polarizing plate becomes thick and it becomes difficult to reduce the thickness of the liquid crystal display.
[0132]
As a method for adding these ultraviolet absorbers, they may be added directly, but as described above, in-line addition with excellent productivity is preferable. In-line addition is preferably carried out by adding a small amount of triacetyl cellulose to a solution previously dissolved in an organic solvent (for example, methanol, methylene chloride, etc.) and then adding it to the dope composition with an in-line mixer. A preferable amount of triacetyl cellulose is 1 to 10 parts by mass, and more preferably 3 to 5 parts by mass with respect to 100 parts by mass of the solvent. When triacetyl cellulose is added, the viscosity of the ultraviolet absorbent-containing liquid increases, and it becomes easy to add more in-line.
[0133]
The polarizing film and polarizing plate in which the optical films of claims 8 to 23 are used are the same as those described in the inventions of claims 1 to 7 and have already been described. In addition, as the optical film of claims 8 to 23, a cellulose ester film is preferable because it is excellent in transparency and a film having a small refractive index anisotropy can be easily produced. The cellulose ester film is preferably a cellulose. A method for producing a cellulose ester produced by casting (casting) an ester or a dope solution on an endless support (a support having a mirror-finished belt-like or drum-like stainless steel), conditions for peeling from the support, Preferred production conditions such as residual solvent at the time of peeling, drying conditions, and the like are as described in the inventions of claims 1 to 7.
[0134]
Also in the present invention, the inclusion of the above-mentioned plasticizer is particularly preferable because a film having excellent dimensional stability and water resistance can be obtained.
[0135]
Among these plasticizers, it is preferable that a plasticizer having a melting point of 20 ° C. or lower is contained. Of all the plasticizers contained in the optical film, 10% by mass or more is preferably a plasticizer having a temperature of 20 ° C. or less, and more preferably 20% by mass or more. It is preferable to use a combination of an ultraviolet absorber having a distribution coefficient of 9.2 or more and a plasticizer having a temperature of 20 ° C. or less because the roll dirt is further improved. A higher plasticizer ratio with a melting point of 20 ° C. or lower is preferable because roll dirt is improved.
[0136]
In the invention according to claims 8 to 23, it is excellent in workability to use the above-mentioned ultraviolet absorber (having a distribution coefficient of 9.2 or more) and a plasticizer having a melting point of 20 ° C. or less among these plasticizers, It is preferable in terms of foreign matter failure and surface quality. The plasticizer having a melting point of 20 ° C. or lower is not particularly limited as long as the melting point is 20 ° C. or lower, and can be selected from the plasticizers. Examples thereof include tricresyl phosphate, cresyl diphenyl phosphate, tributyl phosphate, diethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, triacetin, ethyl phthalyl ethyl glycolate and the like. These plasticizers are also preferably used alone or in combination.
[0137]
The melting point in the present invention is the true melting point described in the chemistry dictionary published by Kyoritsu Publishing Co., Ltd.
[0138]
The amount of these plasticizers used is preferably 1 to 15% by mass with respect to the cellulose ester in terms of film performance and processability. For a liquid crystal display member, 5 to 15% by mass is more preferable from the viewpoint of dimensional stability, and 7 to 12% by mass is particularly preferable.
[0139]
Moreover, 1 mass%-10 mass% are preferable, and, as for content of the plasticizer whose melting | fusing point is 20 degrees C or less with respect to a cellulose ester, More preferably, they are 3 mass%-7 mass%.
[0140]
Processability is the ease of processing when slitting or punching a base film or liquid crystal display member. If the processability is poor, the cut surface will be sawtoothed, generating chips and adhering to the product. This is not preferable because it causes a foreign matter failure.
[0141]
If necessary, fine particles may be added to the optical film used in the inventions according to claims 8 to 23 as a matting agent. The matting agent will be described in more detail. Examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, silica Mention may be made of aluminum oxide, magnesium silicate and calcium phosphate. Fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable. Silicon dioxide fine particles are commercially available, for example, under the trade names Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (manufactured by Nippon Aerosil Co., Ltd.). it can. Zirconium oxide fine particles are commercially available, for example, under the trade names Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) and can be used.
[0142]
Examples of the polymer include silicone resin, fluorine resin, and acrylic resin. Silicone resins are preferable, and 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.) It is marketed by name and can be used.
[0143]
Among these, Aerosil 200V and Aerosil R972V are particularly preferable because they have a great effect of reducing the friction coefficient while keeping the turbidity of the optical film low.
[0144]
The optical film of the present invention (preferably a cellulose ester film) is preferably used for a liquid crystal display member because of high dimensional stability and good ultraviolet cut performance. A liquid crystal display member is a member used in a liquid crystal display device. For example, a polarizing plate, a protective film for a polarizing plate, a retardation plate, a reflective plate, a viewing angle improving film, an antiglare film, an antireflective film, and a charge Prevention films and the like. Among the above descriptions, the cellulose ester film of the present invention is more preferably used in polarizing plates and protective films for polarizing plates that have strict requirements on dimensional stability.
[0145]
【Example】
Examples of the present invention will be specifically described below using examples, but the present invention is not limited to these.
[0146]
Example 1
Sample 1
100 parts by mass of triacetyl cellulose
5 parts by weight of ethyl phthalyl ethyl glycolate
475 parts by mass of methylene chloride
50 parts by mass of ethanol
The above was put into a sealed container, completely dissolved with heating and stirring, and filtered to prepare a dope solution. Aside from this
UV absorbing compound L-2 10 parts by mass
4 parts by mass of triacetyl cellulose
100 parts by mass of methylene chloride
The above was put into an airtight container, completely dissolved with heating and stirring, filtered, and an ultraviolet absorbing compound-containing solution was prepared.
[0147]
It added in the ratio of 4 mass parts of ultraviolet absorption compound containing solutions with respect to 100 mass parts of said dope liquids, and mixed fully with the in-line mixer. Next, using a belt casting apparatus, the dope solution and the ultraviolet absorbing compound-containing solution were uniformly cast on a stainless steel band support at a temperature of 33 ° C. and a width of 1500 mm. After the solvent was evaporated until the residual solvent amount in the triacetylcellulose film cast on the stainless steel band support was 25%, the film was peeled off from the stainless steel band support with a peel tension of 127 Newton / m. After slitting to 1300 mm of peeled cellulose triacetate, drying was completed while transporting the drying zone with a number of rolls, and slitting to a width of 1100 mm, a sample 1 of a triacetyl cellulose film having a thickness of 40 μm was obtained.
[0148]
Samples 2-11
Samples 2 to 11 were prepared in the same manner except that the type and amount of the ultraviolet absorbing compound in Sample 1 were changed as shown in Table 1.
[0149]
Samples 12-14
Samples 12 to 14 were obtained in the same manner except that the type and amount of the ultraviolet absorbing compound in Sample 1 were changed as shown in Table 1 and the film thickness of Sample 12 was changed to 80 μm. Sample 12 was prepared so that the amount of the ultraviolet absorbing compound per unit area was the same as that of Sample 1.
[0150]
Alkali saponification treatment
Saponification step: 2 mol / l-NaOH 60 ° C. 90 seconds
Washing process: Water 30 ° C 45 seconds
Neutralization step: 10% by mass HCl 30 ° C. 45 seconds
Washing process: Water 30 ° C 45 seconds
Under the above conditions, the triacetylcellulose film was saponified, washed with water, neutralized, washed with water, and then dried at 80 ° C.
[0151]
(Elution of UV absorbing compounds)
Under the alkali saponification treatment conditions, alkali saponification solutions obtained by treating 35 m 2 of triacetyl cellulose film samples 1 to 14 with respect to 3 liters of the alkali saponification solution were collected and visually evaluated.
[0152]
◎ I don't know that UV-absorbing compounds are floating in the liquid.
○ It can be seen faintly that UV-absorbing compounds are floating in the liquid.
× Easily understand that UV-absorbing compounds are floating in the liquid
XX A large amount of UV-absorbing compound is suspended in the liquid.
(Hue change)
The samples 1 to 14 were subjected to a durability test for 1000 hours in an atmosphere of 80 ° C. and RH 90%. In accordance with the above, the change amount of the a value and the b value obtained from the tristimulus values in the 10 degree visual field XYZ system was measured.
[0153]
○ a value change less than 0.1, b value change less than 0.3
X a value change amount 0.1 or more, b value change amount 0.3 or more
Production of polarizing plate
A 120 μm thick polyvinyl alcohol film was immersed in 100 parts by mass of an aqueous solution containing 1 part by mass of iodine and 4 parts by mass of boric acid, and stretched 4 times at 50 ° C. to prepare a polarizing film. Tripolar cellulose film samples 1 to 14 that had been subjected to alkali saponification treatment on both surfaces of the polarizing film were bonded to each other using a 5% aqueous solution of completely saponified polyvinyl alcohol as an adhesive to prepare a polarizing plate.
[0154]
(Change in polarization degree)
First, the parallel transmittance and the direct transmittance were measured for the polarizing plate prepared as described above, and the degree of polarization was calculated according to the following formula. After standing for 500 hours (forced deterioration), the parallel transmittance and the direct transmittance were measured and measured again, and the degree of polarization was calculated according to the following formula.
[0155]
Polarization degree P = ((H₀-H₉₀) / (H₀+ H₉₀))^1/2× 100
Polarization degree change = P₀-P₅₀₀
H₀: Parallel transmittance
H₉₀: Direct transmittance
P₀: Degree of polarization before forced deterioration
P₅₀₀: Degree of polarization after 500 hours of forced deterioration
◎ Less than 1% change in polarization degree
○ Polarization degree change less than 1-2%
△ Change of polarization degree is less than 2-5%
× Polarization degree change 5% or more
[0156]
[Table 1]

[0157]
* 1 DHBP: 2,4-dihydroxybenzophenone manufactured by Eastman Chemical Company
[0158]
Embedded image

[0159]
[Table 2]

[0160]
As described above, by using the ultraviolet absorbing compound of the present invention, elution of the ultraviolet absorbing compound during alkali saponification is suppressed, and the change in hue of the cellulose ester film can be reduced and the change in polarization degree is small. Could be provided.
[0161]
Example 2
<Samples 201 to 213>
(Silicon oxide dispersion)
Aerosil 200V (Nippon Aerosil Co., Ltd.)
(Average primary particle diameter 12 nm, apparent specific gravity 100 g / liter) 10 parts by mass
90 parts by mass of ethanol
The above was stirred and mixed with a dissolver for 30 minutes, and then dispersed with Manton Gorin. The liquid turbidity after dispersion was 93 ppm.
(Preparation of additive liquid A)
UV absorber (Exemplary Compound 8) 10 parts by mass
4 parts by mass of triacetyl cellulose synthesized from linter cotton
100 parts by mass of methylene chloride
The above was put into a sealed container, heated, stirred and completely dissolved and filtered.
[0162]
To this, 10 parts by mass of the silicon oxide dispersion was added with stirring, and the mixture was further stirred for 30 minutes, followed by filtration to prepare additive liquid A.
(Preparation of dope solution A)
85 parts by mass of triacetyl cellulose synthesized from linter cotton
15 parts by mass of triacetyl cellulose synthesized from wood pulp
2 parts by weight of ethyl phthalyl ethyl glycolate
8.5 parts by mass of triphenyl phosphate
475 parts by mass of methylene chloride
50 parts by mass of ethanol
The above was put into an airtight container, heated, stirred and completely dissolved and filtered to prepare a dope solution.
[0163]
To 100 parts by mass of the dope solution, the part of the additive solution shown in Table 1 was added, and the mixture was sufficiently mixed with an in-line mixer (Toray static in-tube mixer Hi-Mixer, SWJ) and filtered. Next, using a belt casting apparatus, the belt was uniformly cast on a stainless steel band support at a temperature of 33 ° C. and a width of 1500 mm. With the stainless steel band support, the solvent was evaporated until the residual solvent amount was 25%, and the film was peeled off from the stainless steel band support with a peeling tension of 127 Newton / m. The peeled cellulose triacetate film was slit to a width of 1300 mm, and then the drying was terminated while the drying zone was conveyed by a number of rolls, and slit to a width of 1100 mm to obtain a cellulose triacetate film sample 201. The film thickness of the cellulose triacetate film at this time was 40 μm.
[0164]
Samples 202 to 213 were prepared in the same manner as shown in Table 3, except that the following additive solution, addition amount, and dope solution were changed instead of the additive solution A of the sample 201.
(Additive Liquid B) An additive liquid B was prepared in the same manner except that 10 parts by mass of the ultraviolet absorbent exemplified compound 8 in the additive liquid A was changed to 10 parts by mass of the ultraviolet absorbent illustrative compound 4.
(Additive liquid C) An additive liquid C was prepared in the same manner except that 10 parts by mass of the ultraviolet absorber exemplified compound 8 of the additive liquid A was changed to 10 parts by mass of the ultraviolet absorber illustrative compound 7.
(Additive liquid D) Added in the same manner except that 10 parts by mass of the UV absorber exemplified compound 8 in the additive liquid A was changed to 3 parts by mass of the UV absorber exemplified compound 9 and 9 parts by mass of the UV absorber exemplified compound 3. Liquid D was prepared.
(Additive liquid E) 10 parts by mass of the ultraviolet absorber exemplary compound 8 of the additive liquid A, 10 parts by mass of the ultraviolet absorber exemplary compound 9, 5 parts by mass of the ultraviolet absorber exemplary compound 7, and 5 of the ultraviolet absorber exemplary compound 5 An additive solution E was prepared in the same manner except that the amount was changed to parts by mass.
(Additive liquid F) Except having replaced 10 mass parts of the ultraviolet absorber illustrative compound 8 of the additive liquid A with 1.5 mass parts of the ultraviolet absorber illustrative compound 9 and 8.5 mass parts of the ultraviolet absorber illustrative compound 4. Similarly, additive liquid F was prepared.
(Additive liquid G) An additive liquid G was prepared in the same manner except that 10 parts by mass of the ultraviolet absorber exemplified compound 8 of the additive liquid A was changed to 10 parts by mass of the ultraviolet absorber illustrative compound 9.
(Additive liquid H) An additive liquid H was prepared in the same manner except that 10 parts by mass of the ultraviolet absorber exemplified compound 8 of the additive liquid A was changed to 10 parts by mass of the ultraviolet absorber illustrative compound 10.
(Preparation of dope solution B)
85 parts by mass of triacetyl cellulose synthesized from linter cotton
15 parts by mass of triacetyl cellulose synthesized from wood pulp
11.5 parts by mass of triphenyl phosphate
475 parts by mass of methylene chloride
50 parts by mass of ethanol
The above was put into an airtight container, heated, stirred and completely dissolved and filtered to prepare a dope solution.
[0165]
Each of the samples 201 to 213 obtained above was evaluated. The measurement and evaluation methods are summarized after Example 4.
[0166]
[Table 3]

[0167]
Example 3
<Samples 214 to 217>
Samples 214 to 217 were prepared in the same manner as described in Table 4 except that the following additive solution and addition amount were changed, and the dope solution was also changed as shown in Table 4, instead of additive solution A of sample 201. did.
(Additive liquid I) Added in the same manner except that 10 parts by mass of the ultraviolet absorber exemplified compound 8 of the additive liquid A was changed to 5 parts by mass of the ultraviolet absorber illustrative compound 4 and 7 parts by mass of the ultraviolet absorber illustrative compound 7. Liquid I was prepared.
(Additive liquid J) Added in the same manner except that 10 parts by mass of the ultraviolet absorber exemplified compound 8 in the additive liquid A was changed to 5 parts by mass of the ultraviolet absorber exemplified compound 9 and 5 parts by mass of the ultraviolet absorber exemplified compound 10. Liquid J was prepared.
[0168]
Each of the samples 214 to 217 obtained above was evaluated. The results are shown in Table 4. The measurement and evaluation methods are summarized below.
[0169]
[Table 4]

[0170]
Example 4
(Preparation of additive liquid K)
Ultraviolet absorber (Exemplary Compound 1) 5 parts by mass
Ultraviolet absorber (Exemplary Compound 5) 5 parts by mass
Triacetyl cellulose synthesized from linter cotton with 61.0% acetylation degree
4 parts by mass
100 parts by mass of methylene chloride
The above was put into a sealed container, heated, stirred and completely dissolved and filtered. To this, 10 parts by weight of the silicon oxide dispersion of Example 2 was added with stirring, and the mixture was further stirred for 30 minutes, followed by filtration to prepare additive liquid K.
The weight part shown in Table 5 was added to 100 parts by mass of the dope liquid of Example 2, and the mixture was sufficiently mixed with an in-line mixer (Toray static type in-pipe mixer Hi-Mixer, SWJ) and filtered. Next, using a belt casting apparatus, the belt was uniformly cast on a stainless steel band support at a temperature of 33 ° C. and a width of 1500 mm. The solvent was evaporated with a stainless steel band support until the residual solvent amount was 25%, and the film was peeled from the stainless steel band support with a peel tension of 127 Newton (13 kgf) / m. The peeled cellulose triacetate film is slit to 1300 mm width, then stretched 1.05 times in the width direction with a tenter, and then dried while being transported by a number of rolls in the drying zone, slit to 1100 mm width, and cellulose triacetate A film sample 301 was obtained. The film thickness of the cellulose triacetate film at this time was 40 μm.
[0171]
Samples 301 to 308 were prepared in the same manner except that the following additive solution and addition amount were changed as shown in Table 5 instead of the additive solution K of sample 301.
[0172]
(Additive Liquid L) An additive liquid L was prepared in the same manner except that the ultraviolet absorbent exemplified compound in the additive liquid K was replaced with 10 parts by mass of the ultraviolet absorbent exemplified compound 1.
[0173]
(Additive liquid M) An additive liquid M was prepared in the same manner except that the ultraviolet absorber exemplified compound of the additive liquid K was changed to 5 parts by mass of the ultraviolet absorber exemplified compound 1 and 5 parts by mass of the ultraviolet absorber exemplified compound 2. .
[0174]
(Additive liquid N) An additive liquid N was prepared in the same manner except that the ultraviolet absorber exemplified compound of the additive liquid K was changed to 5 parts by mass of the ultraviolet absorber exemplified compound 2 and 5 parts by mass of the ultraviolet absorber exemplified compound 3. .
[0175]
(Additive liquid O) An additive liquid O was prepared in the same manner except that the ultraviolet absorber exemplified compound of the additive liquid K was replaced with 10 parts by mass of the ultraviolet absorbent exemplified compound 2.
[0176]
(Additive liquid P) An additive liquid P was prepared in the same manner except that the ultraviolet absorber exemplified compound of the additive liquid K was replaced with 10 parts by mass of the ultraviolet absorber exemplified compound 5.
[0177]
(Additive liquid Q) An additive liquid Q was prepared in the same manner except that the ultraviolet absorber exemplified compound of the additive liquid K was changed to 5 parts by mass of the ultraviolet absorber exemplified compound 1 and 5 parts by mass of the ultraviolet absorber exemplified compound 6. .
[0178]
(Additive liquid R) The additive liquid R was produced in the same manner except that the ultraviolet absorber exemplified compound of the additive liquid K was replaced with 10 parts by mass of the ultraviolet absorber exemplified compound 9.
[0179]
Each of the samples 301 to 308 obtained above was evaluated. The results are shown in Table 5.
[0180]
[Table 5]

[0181]
"Measuring method"
(Distribution coefficient)
The distribution ratio represents the distribution ratio of octanol and water and can be defined by the following formula.
[0182]
logPo / w Po / w = So / Sw
So: Solubility of the organic compound in n-octanol at 25 ° C
Sw: Solubility of the organic compound in pure water at 25 ° C
In the present invention, a calculation method by HPLC was used as a method for measuring these partition rates. This method is described in the OECD guideline 117 partition coefficient (n-octanol / water) high-performance chromatography method (adopted on March 30, 1989). The measurement conditions for HPLC are shown below.
[0183]
Apparatus: LC module (manufactured by Waters)
Column: Inertsil ODS-2 250 mm x 4.6 mm (manufactured by GL Sciences)
Temperature: 40 ° C
Eluent: Methanol: 1% phosphoric acid water = 90: 10
Flow rate: 1.0 ml / min
Detection wavelength: 210 nm
Injection sample: about 50ppm methanol solution
(Roll dirt)
After producing a 10000 m cellulose ester film, the degree of soiling of the first roll contacting the film peeled off from the stainless steel band support was visually observed and evaluated according to the following ranks.
[0184]
A ... I don't know that the roll is dirty
B ... It is faintly understood that the roll is partially dirty.
C ... It is faint to know that the roll is completely dirty
D ... You can clearly see that the roll is completely dirty
A to C are levels where production can continue. D is the level at which production is interrupted and the roll is cleaned.
(Pressed failure)
At the place where the 10000 m cellulose ester film was produced, the film was sampled, and the obtained film 1 m²The number of pressed failures of 30 μm or more existing above was counted and obtained.
(Foreign matter failure)
The cellulose ester film was sampled, and the number of foreign matters having a size of 30 μm or more present on both ends 30 cm width and 1 m length of the obtained film was counted.
(380 nm transmittance)
Using Spectrophotometer U-3200 (manufactured by Hitachi, Ltd.), the spectral absorption spectrum of the film was measured, and the transmittance at 380 nm was determined.
[0185]
A Transmission less than 8%
B Transmittance 8% or more and less than 25%
C Transmittance 25% or more
(Processability)
A cellulose ester film sample cut to a size of 20 cm x 20 cm is folded into 10 equal parts to 20 cm x 2.0 cm, and cut into 10 cm x 2.0 cm with a push-cut paper cutter DN-3 (manufactured by KOKUYO Corporation). The cross section was evaluated and divided into the following levels. If it is more than Δ, it is a practically usable level.
[0186]
A: The cut surface is transparent, and there is no roughness when touched with a finger.
○: The cut surface is transparent, but feels somewhat rough when touched with a finger
Δ: The cut surface is white and opaque, and rough when touched with a finger
X: The cut surface is blown with white powder, and is rough when touched with a finger. (Light resistance)
First, parallel transmittance and direct transmittance were measured for the produced polarizing plate, and the degree of polarization was calculated according to the following prescription. Thereafter, each polarizing plate was forcibly deteriorated under the conditions of a sunshine weather meter for 200 hours without a UV cut filter, and then the parallel transmittance and the direct transmittance were measured again, and the degree of polarization was calculated according to the following formula. The amount of change in polarization degree was determined by the following formula.
[0187]
Polarization degree P = ((H₀-H₉₀) / (H₀+ H₉₀))^1/2× 100
Polarization degree change = P₀-P₅₀₀
H₀  : Parallel transmittance
H₉₀  : Direct transmittance
P₀  : Degree of polarization before forced deterioration
P₅₀₀: Degree of polarization after 500 hours of forced deterioration
A: Polarization degree change rate less than 10%
○: Polarization degree change rate of 10% or more and less than 25%
Δ: Polarization degree change rate 25% or more and less than 40%
X: Polarization degree change rate of 40% or more.
(Bleed out)
After leaving in a high temperature and high humidity atmosphere of 80 ° C. and 90% RH for 1000 hours, the presence or absence of bleed out was evaluated by observing the surface of the film.
[0188]
A: No bleed out on the film surface
○: Partial bleed-out is slightly visible on the film surface
Δ: A slight bleed-out is found on the film surface.
X: A clear bleed-out is clearly seen on the film surface.
(YI)
Using Spectrophotometer U-3200 (manufactured by Hitachi, Ltd.), the YI (Yellowness Index) of the film defined in JIS K7103 is determined by the following formula.
[0189]
YI = 100 (1.28X-1.06Z) / Y
Here, X, Y, and Z are tristimulus values of the light source color defined in JIS Z8701.
(Light Leakage Rate P) Using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments), the sample was measured at a wavelength of 590 nm at a wavelength of 590 nm at 23 ° C. and 55% RH. The slow axis angle θ and the refractive indexes Nx, Ny, and Nz are obtained. In-plane retardation value R according to the following formula (1)₀Was calculated, P was calculated according to the formula (2), and the evaluation was divided into the following ranks.
[0190]
○ ・ ・ ・ less than 0.00005
△ ... 0.00005 or more, less than 0.0001
× ・ ・ ・ 0.0001 or more
Formula (1) R₀Value = (Nx−Ny) × d
In the formula, Nx is the refractive index in the slow axis direction in the film plane, Ny is the refractive index in the fast axis direction in the film plane, Nz is the refractive index in the film thickness direction, and d is the film thickness (nm). Represent each.
[0191]
Formula (2) P = sin²(2πθ / 180) · sin²(ΠR₀/ Λ)
λ is R₀And the wavelength of light at the time of measuring the three-dimensional refractive index for obtaining θ (°) is 590 nm. Further, π is a circumference ratio.
[0192]
【The invention's effect】
High-quality optical films with little yellowing and foreign matter failure used as protective films for polarizing plates, retardation films, viewing angle widening films, antireflection films, etc. in various display devices such as liquid crystal display devices, organic EL displays, and plasma displays can get.

Claims (4)

A protective film for a polarizing plate, comprising at least one selected from the following two UV absorbers.

The protective film for a polarizing plate according to claim 1 is prepared by in-line mixing and stirring an ultraviolet absorbent solution containing a resin and a dope solution in which the resin is dissolved, and casting and forming a film on a belt or drum support. A method for producing a protective film for a polarizing plate, characterized in that it is obtained. The said protective film for polarizing plates is a cellulose-ester film, The protective film for polarizing plates of Claim 1 characterized by the above-mentioned. The method for producing a protective film for a polarizing plate according to claim 2, wherein the protective film for the polarizing plate is a cellulose ester film.