JP2004137358A - Cellulose ester film, optical compensation sheet, polarizing plate, optical retardation plate, electronic paper and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cellulose ester film, an optical compensation sheet, a polarizing plate, an optical retardation plate, an electronic paper and a display device, each having a high retardation value. <P>SOLUTION: The cellulose ester film has at least one substituent group containing a chemical bond exhibiting bond polarization anisotropy. <P>COPYRIGHT: (C)2004,JPO

Description

【００４７】
式中、［ｄｉａｇ（ａ_ｍ）_ｘｙｚ］は、構成官能基ｍの結合分極率テンソルの対角行列で、φとτはそれぞれ結合官能基の座標軸に対する方位角と極角である。各々の構成官能基ごとのΔα_ｘｙｚを加算することにより分子全体の結合分極率が得られる。結合官能基の結合分極率データは、Ｃ＝Ｏ、フェニル基では、Ｍ．Ｐｉｅｔｒａｌｌａ，Ｈ．Ｒ．Ｓｃｈｕｂａｃｈ，Ｍ．Ｄｅｔｔｅｎｍａｉｅｒ，Ｂ．Ｈｅｉｓｅ，Ｐｒｏｇ．Ｃｏｌｌｏｉｄ＆Ｐｌｏｙｍ．Ｓｃｉ．７１，１２５，（１９８５）に記載のデータ、Ｃ−Ｏ、Ｃ−Ｈ結合は、Ｋ．Ｇ．Ｄｅｎｂｉｇｈ，Ｔｒａｎｓ　Ｆａｒａｄａｙ　Ｓｏｃ．，３６，９３６（１９４０）に記載のデータを用いた。
【００４８】
以下、上記の方法を用い、シミュレーションとして、ＤＭＣ（ジメチルカーボネート）、ＭＰＣ（メチルフェニルカーボネート）、ＤＰＣ（ジフェニルカーボネート）等の分子の結合分極率異方性、グルコース分子の側鎖にアセチルオキシ基（−Ｏ−Ｃ（＝Ｏ）−ＣＨ_３）を置換させたもの、グルコース分子の側鎖にベンゾイルオキシ基（−Ｏ−Ｃ（＝Ｏ）−Ｃ_６Ｈ_５）を置換させたもの等の各々の分子側鎖の結合分極率異方性を各々計算した。
【００４９】
例えば、ジメチルカーボネート等を構成する分子の化学結合の結合分極率異方性の計算に当たっては、化合物の座標軸の取り方によっても結合分極率異方性が変化する。そこで、カルボニル基（Ｃ＝Ｏ）を基準として、前記カルボニル基（Ｃ＝Ｏ）の方向をｘ軸に一致させて座標軸を図１のように定め、このときに得られる理論結合分極率テンソルを前記一般式（１）で表した。また、メチル基部分をそのままの座標系でフェニル基に置き換えると図２に示すように、フェニルカーボネートとなる。
【００５０】
本発明においては、上記のように、α_ｙｙとα_ｘｘとの差の絶対値｜α_ｙｙ−α_ｘｘ｜、およびα_ｙｙとα_ｚｚとの差の絶対値｜α_ｙｙ−α_ｚｚ｜に注目し、その結合分極率異方性値の数値を特定の数値以上に調整することにより、リターデーション値の高いセルロースエステルフィルムを得ることを見いだし、且つ、本発明のセルロースエステルフィルムは、光学補償シート、偏光板、位相差板、電子ペーパ等に好ましく用いられることがわかった。
【００５１】
さらに同様な方法で、グルコース分子の側鎖にアセチルオキシ基（ＣＨ_３−Ｃ（＝Ｏ）−Ｏ−）を有する場合、グルコース分子の側鎖にベンゾイルオキシ基を有する場合、及び、ディフェニルカーボネート分子の結合分極率異方性を計算した。
【００５２】
得られた結果を下記に示す。
【００５３】
【表１】

【００５４】
但し、表１において、Δα_０（×１０^−２４）は、｜α_ｙｙ−α_ｘｘ｜、Δα_Ｔ（×１０^−２４）は、｜α_ｙｙ−α_ｚｚ｜を表す。
【００５５】
表１から、フェニル基などの芳香環の存在により、一桁近く分極率異方性が大きくなることが分かる。このような結果から、側鎖を修飾する置換基としては、芳香環を１つ以上含み、且つ、三次元座標（ｘ，ｙ，ｚ）上において、前記置換基の結合分極率異方性を示す部分構造のうち、極性基部分であるカルボニル基（Ｃ＝Ｏ基）をｘ軸に一致させ、更に、芳香環を構成する各々の分子同士の結合を、各々ｘ軸、ｙ軸で構成されるｘｙ平面上に配置し、該分子同士の結合軸に対して垂直な方向にｚ軸を配置し、前記置換基の、前記一般式（１）で表される理論結合分極率テンソルにおける、結合分極率異方性、すなわちα_ｙｙとα_ｘｘとの差の絶対値｜α_ｙｙ−α_ｘｘ｜または結合分極率異方性、α_ｙｙとα_ｚｚとの差の絶対値｜α_ｙｙ−α_ｚｚ｜で表される結合分極率異方性の少なくとも一つが、３×１０^−２４ｃｍ^３以上であることが好ましい。
【００５６】
《結合分極率異方性を示す化学結合を含む置換基》
本発明に係る、結合分極率異方性を示す化学結合を含む置換基について説明する。
【００５７】
本発明に係る結合分極率異方性を示す化学結合（分子種も含む）としては、季刊化学総説、透明ポリマーの屈折率制御（日本化学会編、Ｎｏ．３９，１９９８）に記載があるが、具体的には、Ｃ＝Ｃ（芳香性）、Ｃ＝Ｃ（脂肪性）、Ｃ＝Ｏ、Ｃ−Ｏ、Ｃ−Ｎ等のデータ、分子種としては、ベンゼン環、トルエン、ｐ−トルエン等について、化学結合の化学結合鎖に平行な方向の分極率をα１、前記化学結合の化学結合鎖の直交方向の分極率をα２、更に、化学結合が、芳香族炭素環または芳香族複素環を有する時には、前記芳香族炭素環または前記芳香族複素環に垂直な方向の分極率をα３のデータが挙げられている。
【００５８】
本発明においては、｜α１−α２｜または｜α３−α２｜で表される結合分極率異方性の少なくとも一つが１７×１０^−２４ｃｍ^３以上であるものが好ましい。
【００５９】
上記の結合分極率異方性を示す化学結合（分子種も含む）を含む置換基としては、極性基が好ましく、前記極性基としては、ハロゲン原子（フッ素原子、塩素原子、臭素原子、ヨウ素原子）、ヒドロキシル基、アミノ基、ニトロ基、カルボキシル基、ホルミル基、アルコキシル基、ニトリル基、エステル基（−ＣＯＯＲ、ここで、Ｒはアルキル基、アリール基を表す）、オキシカルボニル基（−Ｏ−Ｃ（＝Ｏ）−）を有する置換基、カルボニルイミノ（−Ｃ（＝Ｏ）−ＮＨ−）基を有する置換基等が挙げられる。
【００６０】
中でもエステル基、オキシカルボニル基（−Ｏ−Ｃ（＝Ｏ）−）を有する置換基、カルボニルイミノ（−Ｃ（＝Ｏ）−ＮＨ−）基を有する置換基が好ましく、特に好ましくは、上記置換基が芳香環を有する場合である。
【００６１】
《極性基の効果》
本発明において、上記の極性基が好ましい理由としては、セルロースアセテート、セルロースプロピオネート等を低倍率で延伸した場合、後述するようにＣＯＯ基のような極性基部分が優先的に配向変化を起こすことが明らかになるが、ＣＯＯ基のみが配向する機構は不明ではあるが、おそらく水素結合が関与しているのではと本発明者等は推定している。
【００６２】
以上から、セルロールエステル分子を効率よく配向させるには、オキシカルボニル基（−Ｏ−Ｃ（＝Ｏ）−）やカルボニルイミノ（−Ｃ（＝Ｏ）−ＮＨ−）基を含む置換基をセルローエステル分子の側鎖に配置することが好ましく、更に好ましくは、結合分極率異方性の大きい芳香環を前記置換基が有することである。
【００６３】
《芳香環》
本発明に係る芳香環としては、芳香族炭素環基（例えば、ベンゼン環、ナフタレン環等）や芳香族複素環基（例えば、フラン環、ピロール環、ピラゾール環、イミダゾール環、オキサゾール環、チアゾール環、１，２，３−オキサジアゾール環、１，２，３−トリアゾール環、１，２，４−トリアゾール環、１，３，４−チアジアゾール環、ピリジン環、ピリダジン環、ピリミジン環、ピラジン環、ｓ−トリアジン環、ベンゾフラン環、インドール環、ベンゾチオフェン環、ベンズイミダゾール環、ベンゾチアゾール環、プリン環、キノリン環及びイソキノリン環等）等が挙げられる。これらは、更に置換基を有していてもよい。
【００６４】
以下、本発明に係る、結合分極率異方性を示す化学結合を含む置換基の具体例を示すが本発明はこれらに限定されない。
【００６５】
【化１】

【００６６】
《セルロースエステル分子側鎖の置換度》
本発明のセルロースエステルフィルムの作製に用いられる、セルロースエステル分子の側鎖に結合分極率異方性を示す化学結合を含む置換基を配置する場合、置換基効果として十分なリターデーション値向上効果を奏し、且つ、フィルムの白濁、透明度の低下などを防止する観点から、本発明のセルロースエステル分子全体への置換度は、１０％〜９０％の範囲が好ましく、更に好ましくは、２５％〜８５％である。
【００６７】
ここで、上記の置換度は、当該業者公知の方法（例えば、酢酸セルロースなどでは、酢化度、アセチル価、酢酸価）や反応した水酸基のモル％等で表す。
【００６８】
《セルロースフィルムの延伸処理》
上記の表１のように、セルロースエステル分子の側鎖に高い分極率異方性を有する芳香環や高い分極率異方性を示す化学結合である、オキシカルボニル基（−Ｏ−Ｃ（＝Ｏ）−）またはカルボニルイミノ（−Ｃ（＝Ｏ）−ＮＨ−）基を有する置換基を持たせることにより、高い固有複屈折を示し、前記のリターデション値の高い（光学異方性が大きいともいう）セルロースエステルフィルムが得られるが、更に、光学異方性の大きい、即ち、リターデーション値を高め、十分な光学補償機能を示すセルロースエステルフィルムや光学補償シートを得るためには、後述する延伸処理をセルロースエステルフィルムの製造時（製膜時ともいう）に行うことが好ましい。
【００６９】
《溶液流延製膜》
本発明のセルロースエステルフィルムの製造方法としては、セルロースエステルを溶媒に溶解し、調製したドープ液を支持体上に流延、製膜し、得られたフィルムを支持体から剥ぎ取り、その後、張力をかけて乾燥ゾーン中を搬送させながら乾燥する、溶液流延製膜法が好ましい。
【００７０】
溶液流延製膜法と、無限に移送する無端の金属ベルト（例えばステンレスベルト）あるいは回転する金属ドラム（例えば鋳鉄で表面をクロムメッキしたドラム）等の流延用金属支持体（以降、単に金属支持体ともいう）上に、加圧ダイからドープ（セルロースエステル溶液のこと）を流延（キャスティング）し、該支持体上のウェブ（ドープ膜）を該支持体から剥離し、乾燥させて製造するものである。
【００７１】
本発明においては、流延後６０秒以内に剥離し、張力を掛けながら乾燥させて得られたフィルムはその上に形成した金属酸化物層にクラックが入りにくく、特に好ましい。
【００７２】
流延用金属支持体から剥離する際の剥離張力は３００Ｎ／ｍ以下であることが好ましく、搬送張力は３００Ｎ／ｍ以下であることが好ましく、更に好ましくは２５０Ｎ／ｍ以下であることが好ましく、更に好ましくは１００Ｎ／ｍ〜２００Ｎ／ｍである。
【００７３】
本発明における乾燥工程では、金属支持体から剥離した後、テンターによって幅手方向または長手方向に張力を付与しながら乾燥させることが本発明の方法で形成した金属酸化物層を有する光学フィルムの耐久性が優れ好ましい。幅手方向または長手方向に張力を付与するとは、一方向だけではなく、幅手方向及び長手方向に張力を付与する２軸延伸方式も好ましく用いられる。
【００７４】
あるいはウェブの乾燥過程で１０質量％以上の高い残留溶媒量のときと１０質量％未満の低い残留溶媒量のときにそれぞれ１回以上延伸する方法も好ましい。２回の延伸によって、乾燥時に生じた歪が緩和されるように調整されることが好ましい。
【００７５】
（テンターを用いる延伸処理）
上記のウェブの乾燥工程においては、ウェブを延伸する方法は特に限定しないが、例えば、複数のロールに周速差をつけ、その間でロール周速差を利用して縦方向に延伸する方法や、特開昭６２−４６６２５号公報に示されているような乾燥全工程あるいは一部の工程を巾方向にクリップでウェブの巾両端をクリップやピン等で巾保持し、延伸処理を行いながら、且つ、乾燥をも行う方法（テンター方式）が好ましい。
【００７６】
テンター方式を用いて延伸処理を行う場合、延伸処理後のセルロースエステルフィルムの、白濁による透明度の低下を防止し、硬く脆くなるなど物性変動を効果的に抑制する観点から、テンターを用いてのセルロースエステルフィルムの延伸倍率は、２．０倍以下であることが好ましく、更に好ましくは、１．５倍以下であり、特に好ましくは、１．０１〜１．５倍である。更に、最終的に流延の巾手方向の屈折率が面内で最大となるように延伸することが好ましい。また、延伸の際の残留溶媒量は３質量％〜３０質量％であることが好ましい。残留溶媒量やドープ調製に用いる溶媒については後述する。
【００７７】
《ウェブの残留溶媒量の測定》
本発明において、ウェブの残留溶媒量は下記式で定義される。
【００７８】
残留溶媒量（％）＝〔（ウェブの加熱処理前質量−ウェブの加熱処理後質量）／（ウェブの加熱処理後質量）〕×１００
尚、残留溶媒量を測定する際の、加熱処理は、１１０℃、３時間の加熱処理を行った。
【００７９】
（ドープ液調製用の溶媒）
ドープ液調製に用いられる溶媒としては、塩素系溶媒、非塩素系溶媒がある。
【００８０】
塩素系溶媒としては、アリルクロリド、２−エチルヘキシルクロリド、塩化アミル、塩化イソプロピル、塩化エチル、塩化ブチル、塩化ヘキシル、塩化メチル、塩化メチレン（メチレンクロライド）、ｏ−クロロトルエン、ｐ−クロロトルエン、クロロベンゼン、クロロホルム、四塩化炭素、１，１−ジクロロエタン、１．２−ジクロロエタン、１，１−ジクロロエチレン、１，２−ジクロロエチレン、１，１，１，２−テトラクロロエタン、１，１，２，２−テトラクロロエタン、テトラクロロエチレン、テトラメチレンクロロブロミド、１，１，１−トリクロロエタン、１，１，２−トリクロロエタン、トリクロロエチレン等が挙げられる。
【００８１】
非塩素系溶媒としては、炭素原子数が２〜１２のエーテル（例えば、ジイソプロピルエーテル、ジメトキシメタン、ジメトキシエタン、１，４−ジオキサン、１，３−ジオキソラン、テトラヒドロフラン、アニソールおよびフェネトール等）、炭素原子数が３〜１２のケトン（例えば、アセトン、メチルエチルケトン、ジエチルケトン、ジイソブチルケトン、シクロペンタノン、シクロヘキサノンおよびメチルシクロヘキサノン等）、炭素原子数が２〜１２のエステル（例えば、メチルホルメート、エチルホルメート、プロピルホルメート、ペンチルホルメート、メチルアセテート、エチルアセテートおよびペンチルアセテート等）が挙げられる。また、二種類以上の官能基を有する有機溶媒として、２−エトキシエチルアセテート、２−メトキシエタノールおよび２−ブトキシエタノール等を用いてもよい。
【００８２】
《延伸処理とセルロースエステルフィルムの配向性挙動》
上記の延伸倍率を付与する延伸処理が本発明のセルロースエステルフィルムの配向性に与える効果を偏光ＡＴＲ−ＦＴＩＲ法（偏向ＡＴＲ法ともいう）により検討した。
【００８３】
例えば、セルロースエステルシート（例えば、ＴＡＣ（トリアセチルセルロース）シート、ＣＡＰ（セルロースアセテートプロピオネート）シート等）をごくわずかに延伸させた（延伸率≦２００％、延伸倍率が２．０倍以下）場合、このような低倍率延伸では、面内ではセルロース骨格（主鎖）の配向変化はほとんどなく、主に側鎖のアセチル基部分のみが配向変化を起こすこと、そして更に、ＭＤ（ｍａｃｈｉｎｅ　ｄｉｒｅｃｔｉｏｎ）方向に延伸した場合に、側鎖の配向はこれとは直交する方向に配向する傾向があることが分かった。
【００８４】
低倍率延伸（微小延伸ともいう）においては、このように側鎖のＣＯＯ基のみが主として配向するメカニズムは不明であるが、ＣＯＯ基と近傍の置換基とで形成される水素結合との関連があると予想される。
【００８５】
したがって、セルロースエステルを用いて、リターデション値の高いセルロースエステルフィルムを製造する際の延伸条件を設定するにおいては、延伸倍率が２．０倍以下では、主鎖である、セルロースエステル分子骨格の面内における配向変化がほとんど認められないので、セルロースエステル分子の主鎖に帰属され、１１２５ｃｍ^−１〜１１４５ｃｍ^−１付近に極大吸収を有するエーテル結合の吸収における面内の赤外２色比ｆ_ｘｙが、−０．０５を超え０．１未満になるように調整することが好ましく、更に好ましくは、−０．０２５を超え０．０５未満の範囲に調整することである。
【００８６】
ここで、赤外２色比ｆ_ｘｙは、後述するが、面内方向の配向係数を表す。
《配向係数》
本発明に係る配向係数の理論的な考察について述べる。
【００８７】
赤外分光法を利用した配向性評価方法は、長手方向（ｘ）、幅方向（ｙ）、および厚み（ｚ）方向の空間的な吸収係数の比率ｋ_ｘ／ｋ_ｙ、ｋ_ｘ／ｋ_ｚ、およびｋ_ｙ／ｋ_ｚを求めることである。このためにはｘ、ｙ、ｚ軸方向に沿って偏光された光を用いて赤外吸収を測定し、各成分の吸収比率を計算する必要がある。
【００８８】
赤外吸収の測定においては、ｘ、ｙ、ｚ軸方向に独立に偏光させた光で測定することが最も理想的であるが、実際には特に厚み方向ｚ軸の測定が最も難しい。
【００８９】
偏光ＡＴＲ法では、ｘ方向、ｙ方向、ｘｚ（ｘ軸とｚ軸成分の両方の吸収成分を含む）方向、およびｙｚ（ｙ軸とｚ軸成分の両方の吸収成分を含む）方向に４つの吸収スペクトルを測定し、この測定データからｘ、ｙ、ｚ方向の吸収係数を計算する手順をとる。
【００９０】
図３に、偏光ＡＴＲ法による測定における４つの基本的な光学配置を示す。試料平面の一方をｘ、他方をｙ、厚みをｚ、例えば２軸延伸フィルムではｍａｃｈｉｎｅ方向（ＭＤ方向：ｍａｃｈｉｎｅ　ｄｉｒｅｃｔｉｏｎ方向）をｘ、これと垂直な方向（ＴＤ方向：ｔｒａｎｓｖｅｒｓｅ　ｄｉｒｅｃｔｉｏｎ方向）をｙとし、入射する光と反射する光で構成される入射面に対して、垂直な偏光（ｓ−偏光；ＴＥ：ｔｒａｎｓｖｅｒｓｅ　ｅｌｅｃｔｒｉｃ）および水平な偏光（ＴＭ：ｔｒａｎｓｖｅｒｓｅ　ｍａｇｎｅｔｉｃ）をワイヤーグリッド偏光子を用いて入射する。このときｘ軸をＴＥ偏光の方向に合わせておく（ＴＥｘ、ＴＭｘ）。次に試料を９０°回転させ、すなわちｘ軸方向とｙ軸方向を入れ替えて、同様に測定する（ＴＥｙ、ＴＭｙ）。ここで得られた４つの吸収スペクトルをそれぞれＡ_ＴＥｘ、Ａ_ＴＭｘ、Ａ_ＴＥｙ、Ａ_ＴＭｙとすると、下記一般式（７）で表される関係を満たす。
【００９１】
一般式（７）
Ａ_ＴＥｘ＝αｋ_ｘ
Ａ_ＴＭｘ＝βｋ_ｙ−γｋ_ｚ
Ａ_ＴＥｙ＝αｋ_ｙ
Ａ_ＴＭｙ＝βｋ_ｘ−γｋ_ｚ
上記一般式（７）で表される関係式が得られる。ここでα、β、γは、入射角と試料の屈折率に依存する定数であり、入射角が４５度の場合は、Ｐ．Ａ．Ｆｌｏｕｍｏｙ，ａｎｄ　Ｗ．Ｊ．Ｓｃｈａｆｆｅｒｓ，Ｓｐｅｃｔｒｏｃｈｉｍｉｃａ　Ａｃｔａ，２２，５（１９６６）、Ｋ．Ｐａｌｍ，Ｖｉｂ．Ｓｐｅｃｔｒｏｓｃ．，６，１８５，（１９９４）を参照して、下記一般式（８）により求められる。
【００９２】
【数３】

【００９３】
ここで、ｐ＝（試料の屈折率）^２／（プリズムの屈折率）^２である。
上記より、試料の前記空間的の吸収係数、ｋ_ｘ、ｋ_ｙ、ｋ_ｚが下記一般式（９）のように計算できる。
【００９４】
一般式（９）
ｋ_ｘ＝Ａ_ＴＥｘ／α
ｋ_ｙ＝Ａ_ＴＥｙ／α
ｋ_ｚ＝（（Ａ_ＴＭｘ−βｋ_ｙ）／γ＋（Ａ_ＴＭｙ−βｋ_ｘ）／γ）／２
以上より、赤外２色比は、下記一般式（１０）で表される。
【００９５】
一般式（１０）
Ｄ_ｘｙ＝ｋ_ｘ／ｋ_ｙ
Ｄ_ｘｚ＝ｋ_ｘ／ｋ_ｚ
式中、Ｄ_ｘｙ、Ｄ_ｘｚは、全く空間的に等方性の無配向試料では、いずれも１．００の値をとる。配向性が強くなるにつれて、この数値は増大する。別な評価式として、より定量的な評価が可能なものとして、Ｐ．Ａ．Ｆｌｏｕｍｏｙ，ａｎｄＷ．Ｊ．Ｓｃｈａｆｆｅｒｓ，Ｓｐｅｃｔｒｏｃｈｉｍｉｃａ　Ａｃｔａ，２２，５（１９６６）に開示されている、１軸配向係数（ｆ_ｘｙ、ｆ_ｘｚ）があり、下記一般式（１１）で表される。
【００９６】
一般式（１１）
ｆ_ｘｙ＝（（Ｄ_ｘｙ−１）／（Ｄ_ｘｙ＋２））×（（Ｄ_０＋２）／（Ｄ_０−１））
ｆ_ｘｚ＝（（Ｄ_ｘｚ−１）／（Ｄ_ｘｚ＋２））×（（Ｄ_０＋２）／（Ｄ_０−１））
式中、ｆ_ｘｙは、面内方向の配向係数を、また、ｆ_ｘｚは、膜厚方向の配向係数をしめす。ここで、Ｄ_０＝ｃｏｔ^２（δ）であり、δは分子振動により形成される遷移モーメントベクトルと、分子軸との成す角度である。これを厳密に計算するには分子振動のモーメントの方向を調べる必要があるが、通常は分子軸に平行な振動モードと垂直なモードを選び、これをそれぞれ０°、９０°として計算すれば十分配向性に関する情報が得られる。この配向係数は理論上、無配向の場合は０、観測方向に完全に配向している場合には１．０、逆に観測方向と直交している場合は−０．５となる。
【００９７】
本発明のセルロースエステルフィルムでは、セルロースエステル分子骨格部のＯ−Ｃ−Ｃ伸縮振動（１０３５ｃｍ^−１±１０ｃｍ^−１の最大ピーク値）を分子軸に平行な振動モード（δ＝０度）とし、側鎖のエステル基（Ｃ＝Ｏ、ＣＨ_３、Ｃ−Ｃ−Ｏ、それぞれ１７１３ｃｍ^−１±１０ｃｍ^−１、１３６７ｃｍ^−１±１０ｃｍ^−１、１２１４ｃｍ^−１±１０ｃｍ^−１）を分子軸に垂直な方向の振動モード（δ＝９０度）として計算した。実際の分子モデル（文献）でも上記官能基は、ほぼ上述のような関係にあった。
【００９８】
ベースラインは、Ｃ−Ｃ−Ｏについては１５１０ｃｍ^−１〜１５３０ｃｍ^−１間の最小値と９３０ｃｍ^−１〜１０００ｃｍ^−１間の最小値を結んだ直線とし、Ｃ＝Ｏについては、１８００ｃｍ^−１〜１８５０ｍ^−１間の最小値と１５１０ｃｍ^−１〜１５３０ｃｍ^−１間の最小値を結んだ直線とした。
【００９９】
《ピークの決め方》
ピークの決め方について述べる。
【０１００】
赤外２色比の測定には、減衰全反射赤外分光法（ＡＴＲ−ＩＲ法）を用いて測定できる。計算方法は、Ｊ．Ｐ．Ｈｏｂｂｓ，Ｃ．Ｓ．Ｐ．Ｓｕｎｇ（Ｊ．Ｐ．Ｈｏｂｂｓ，Ｃ．Ｓ．Ｐ．Ｓｕｎｇ，Ｋ．Ｋｒｉｓｈａｎ，ａｎｄ，Ｓ．Ｈｉｌｌ，Ｍａｃｒｏｍｏｌｅｃｕｌｅｓ，１６，１９３（１９８３））を参照して行った。
【０１０１】
《赤外２色比の求め方》
赤外２色比の求め方は、セルロースエステル分子における、Ｃ−Ｏ対照伸縮振動に由来するピーク（１１５０ｃｍ^−１〜１０２５ｃｍ^−１の間に現れる最も強いピーク）の強度を測定する。ピーク強度は、そのピークトップの波数（ｘｃｍ^−１とする）と、ｘｃｍ^−１〜ｘ＋５０ｃｍ^−１のなかの最も吸光度の小さな点とｘｃｍ^−１〜ｘ−５０ｃｍ^−１の中の最も吸光度の小さい点を結び、これをベースラインとし、そこからのピーク強度を測定し求める。まず、長手方向に平行に光を入射し、入射面に偏光が垂直な時の吸光度（Ａ_ＴＥｘ）および入射面に偏光面が平行な時の吸光度（Ａ_ＴＭｘ）を求め、次に幅方向に平行に入射して同様にＡ_ＴＥｙとＡ_ＴＭｙを測定し、前記一般式（１１）により、赤外２色比ｆ_ｘｙ、ｆ_ｘｚ（ｆ_ｘｙは、面内の配向係数、ｆ_ｘｚは、膜厚方向の配向係数である。）を計算することができる。
【０１０２】
具体的には、次の偏光ＡＴＲ法の測定条件で測定する。
測定装置：Ｍａｇｎａ　８６０（ニコレ社製）
単反射ＡＴＲ装置：ＨＡＲＲＩＣＫ　ＳＥＡＧＵＬ
プリズム：ゲルマニウム
プリズムと試料間の圧力：トルクドライバーで８０ｃＮ・ｍ
測定サンプル面積：１ｃｍ^２
入射角　　：４５°
反射回数　：１回
分解能　　：４ｃｍ^−１
データ補間：０．５ｃｍ^−１
試料の屈折率は、例えば、ＣＡＰ（セルロースアセテートプロピオネート）では１．４７７、ＴＡＣ（トリアセチルセルロース）では１．４８２として計算した。またプリズム（ゲルマニウム）は４．００とした。サンプル表面に入射する光と反射する光で構成される入射面に対して、垂直な偏光および水平な偏光をワイヤーグリッド偏光子を用いて入射し、ＦＴＩＲ−ＡＴＲスペクトルを測定した。上記測定をＭＤ方向をｘ軸、垂直方向（幅方向ＴＤ）をｙ軸、厚み方向をｚ軸に設定して測定した。
【０１０３】
なお、この方法で配向係数を求める場合は、試料面と測定用プリズム面とがほぼ完全に密着していることが重要である。このためここで用いるＡＴＲ装置は高い密着圧力に耐えうる市販の、または改良された高耐圧ＡＴＲ装置の使用が望ましい。
【０１０４】
《添加剤》
本発明のセルロースエステルフィルムの保存性、寸度安定性、耐候性等を向上させる目的で、他に所望により可塑剤、紫外線吸収剤、可塑剤、滑り剤及びマット剤等を含有させてもよい。
【０１０５】
（可塑剤）
可塑剤としては例えば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、トリナフチルホスフェート、トリキシリルオスフェート、トリスオルト−ビフェニルホスフェート等のリン酸エステル系の可塑剤、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のフタル酸エステル系の可塑剤、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、ブチルフタリルブチルグリコレート等のグリコール酸エステル系の可塑剤などが挙げられる。中でも、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は、セルロースエステルの加水分解を引き起こし難いことから好ましい。又、凝固点が２０℃以下の可塑剤が含まれることが好ましい。このような可塑剤としては、例えばトリクレジルホスフェート、クレジル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、エチルフタリルエチルグリコレートなどが挙げられる。
【０１０６】
又、特に可塑剤の中でも不揮発性を有するものが好ましく使用される。不揮発性可塑剤とは、２００℃における蒸気圧が１０ｍｍＨｇ以下の化合物であり、極めて低い蒸気圧を有し、かつ低い揮発度を有する性質のものである。好ましくは５ｍｍＨｇ以下、更に好ましくは１ｍｍＨｇ以下である。具体的には特表平６−５０１０４０号に記載されている不揮発性燐酸エステルが挙げられ、例えばアリーレンビス（ジアリールホスフェート）エステルが好ましい。
【０１０７】
本発明に用いられる可塑剤の含有量は寸法安定性の観点から、セルロースエステルフィルム全体の質量に対して、０．１質量％〜３０質量％が好ましく、特に好ましくは、０．５質量％〜１５質量％の範囲である。
【０１０８】
（紫外線吸収剤）
本発明のセルロースエステルフィルムには、必要に応じて紫外線吸収剤を添加することもできる。
【０１０９】
紫外線吸収剤としては、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観点から、波長４００ｎｍ以上の可視光の吸収が少ないものが好ましく用いられる。
【０１１０】
本発明に用いられる紫外線吸収剤の具体例としては、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、トリアジン系化合物、ベンゾエート系化合物などが挙げられる。又、特開平６−１４８４３０号記載の高分子紫外線吸収剤、特願２０００−２１４１３４号の高分子紫外線吸収剤も好ましく用いられる。
【０１１１】
ベンゾトリアゾール系紫外線吸収剤としては下記一般式〔Ａ〕で示される化合物が好ましく用いられる。
【０１１２】
【化２】

【０１１３】
式中、Ｒ_１、Ｒ_２、Ｒ_３、Ｒ_４及びＲ_５は同一でも異なってもよく、水素原子、ハロゲン原子、ニトロ基、ヒドロキシル基、アルキル基、アルケニル基、アリール基、アルコキシ基、アシルオキシ基、アリールオキシ基、アルキルチオ基、アリールチオ基、モノ若しくはジアルキルアミノ基、アシルアミノ基または５〜６員の複素環基を表し、Ｒ_４とＲ_５は閉環して５〜６員の炭素環を形成してもよい。
【０１１４】
また、上記記載のこれらの基は、任意の置換基を有していて良い。
以下に一般式〔Ａ〕で示される紫外線吸収剤の具体例を挙げるが、これらに限定されない。
【０１１５】
ＵＶ−１：２−（２′−ヒドロキシ−５′−メチルフェニル）ベンゾトリアゾール
ＵＶ−２：２−（２′−ヒドロキシ−３′，５′−ジ−ｔｅｒｔ−ブチルフェニル）ベンゾトリアゾール
ＵＶ−３：２−（２′−ヒドロキシ−３′−ｔｅｒｔ−ブチル−５′−メチルフェニル）ベンゾトリアゾール
ＵＶ−４：２−（２′−ヒドロキシ−３′，５′−ジ−ｔｅｒｔ−ブチルフェニル）−５−クロロベンゾトリアゾール
ＵＶ−５：２−（２′−ヒドロキシ−３′−（３″，４″，５″，６″−テトラヒドロフタルイミドメチル）−５′−メチルフェニル）ベンゾトリアゾール
ＵＶ−６：２，２−メチレンビス（４−（１，１，３，３−テトラメチルブチル）−６−（２Ｈ−ベンゾトリアゾール−２−イル）フェノール）
ＵＶ−７：２−（２′−ヒドロキシ−３′−ｔｅｒｔ−ブチル−５′−メチルフェニル）−５−クロロベンゾトリアゾール
ＵＶ−８：２−（２Ｈ−ベンゾトリアゾール−２−イル）−６−（直鎖及び側鎖ドデシル）−４−メチルフェノール（ＴＩＮＵＶＩＮ　１７１、Ｃｉｂａ製）
ＵＶ−９：オクチル−３−〔３−ｔｅｒｔ−ブチル−４−ヒドロキシ−５−（クロロ−２Ｈ−ベンゾトリアゾール−２−イル）フェニル〕プロピオネートと２−エチルヘキシル−３−〔３−ｔｅｒｔ−ブチル−４−ヒドロキシ−５−（５−クロロ−２Ｈ−ベンゾトリアゾール−２−イル）フェニル〕プロピオネートの混合物（ＴＩＮＵＶＩＮ　１０９、Ｃｉｂａ製）
また本発明において、ベンゾフェノン系紫外線吸収剤としては下記一般式〔Ｂ〕で表される化合物が好ましく用いられる。
【０１１６】
【化３】

【０１１７】
式中、Ｙは水素原子、ハロゲン原子またはアルキル基、アルケニル基、アルコキシ基、及びフェニル基を表し、これらのアルキル基、アルケニル基及びフェニル基は置換基を有していてもよい。Ａは水素原子、アルキル基、アルケニル基、フェニル基、シクロアルキル基、アルキルカルボニル基、アルキルスルホニル基又は−ＣＯ（ＮＨ）_ｎ−１−Ｄ基を表し、Ｄはアルキル基、アルケニル基又は置換基を有していてもよいフェニル基を表す。ｍ及びｎは１または２を表す。
【０１１８】
上記において、アルキル基としては、例えば、炭素数２４までの直鎖または分岐の脂肪族基を表し、アルコキシ基としては例えば、炭素数１８までのアルコキシ基で、アルケニル基としては例えば、炭素数１６までのアルケニル基で例えばアリル基、２−ブテニル基などを表す。又、アルキル基、アルケニル基、フェニル基へ置換してもよい置換基としてはハロゲン原子、例えば、塩素原子、臭素原子、フッ素原子など、ヒドロキシル基、フェニル基、（このフェニル基にはアルキル基又はハロゲン原子などを置換していてもよい）などが挙げられる。
【０１１９】
以下に一般式〔Ｂ〕で表されるベンゾフェノン系化合物の具体例を示すが、これらに限定されない。
【０１２０】
ＵＶ−１０：２，４−ジヒドロキシベンゾフェノン
ＵＶ−１１：２，２′−ジヒドロキシ−４−メトキシベンゾフェノン
ＵＶ−１２：２−ヒドロキシ−４−メトキシ−５−スルホベンゾフェノン
ＵＶ−１３：ビス（２−メトキシ−４−ヒドロキシ−５−ベンゾイルフェニルメタン）
市販されているものとしては、ＴＩＮＵＶＩＮ　Ｐ、ＴＩＮＵＶＩＮ　３２４、ＴＩＮＵＶＩＮ　３２０、ＴＩＮＵＶＩＮ　３２６、ＴＩＮＵＶＩＮ　３２７、ＴＩＮＵＶＩＮ　３２８、ＴＩＮＵＶＩＮ　３２９、ＴＩＮＵＶＩＮ　７７０、ＴＩＮＵＶＩＮ　７８０、ＴＩＮＵＶＩＮ　１４４、ＴＩＮＵＶＩＮ　１２０、ＵＶＩＴＥＸ　ＯＢ（日本チバガイギー（株）製）等から適宜選択して使用することもできる。
【０１２１】
本発明で好ましく用いられる上記記載の紫外線吸収剤は、透明性が高く、偏光板や液晶素子の劣化を防ぐ効果に優れたベンゾトリアゾール系紫外線吸収剤やベンゾフェノン系紫外線吸収剤が好ましく、不要な着色がより少ないベンゾトリアゾール系紫外線吸収剤が特に好ましく用いられる。
【０１２２】
本発明においては、紫外線吸収剤は、セルロースエステルフィルム全体に対して、０．１質量％〜２０質量％添加することが好ましく、更に０．５質量％〜１０質量％添加することが好ましく、更に１質量％〜５質量％添加することが好ましい。
【０１２３】
これらは２種以上を併用したほうが好ましい効果があることが多いので、製造条件、使用条件等により適宜最適な組み合わせを探索するのが好ましい。
【０１２４】
（マット剤）
本発明のセルロースエステルフィルムには、滑り性を付与するためにマット剤等の微粒子を添加することができる。微粒子としては、無機化合物の微粒子又は有機化合物の微粒子が挙げられる。
【０１２５】
無機化合物としては、珪素を含む化合物、二酸化珪素、酸化アルミニウム、酸化ジルコニウム、炭酸カルシウム、タルク、クレイ、焼成カオリン、焼成ケイ酸カルシウム、水和ケイ酸カルシウム、ケイ酸アルミニウム、ケイ酸マグネシウム及びリン酸カルシウム等が好ましく、更に好ましくは、ケイ素を含む無機化合物や酸化ジルコニウムであり、二酸化珪素が特に好ましく用いられる。
【０１２６】
二酸化珪素の微粒子としては、例えば、アエロジルＲ９７２、Ｒ９７２Ｖ、Ｒ９７４、Ｒ８１２、２００、２００Ｖ、３００、Ｒ２０２、ＯＸ５０、ＴＴ６００（以上日本アエロジル（株）製）等の市販品が使用できる。
【０１２７】
酸化ジルコニウムの微粒子としては、例えば、アエロジルＲ９７６及びＲ８１１（以上日本アエロジル（株）製）等の市販品が使用できる。
【０１２８】
有機化合物としては、例えばシリコーン樹脂、弗素樹脂及びアクリル樹脂等のポリマーが好ましく、中でもシリコーン樹脂が好ましく用いられる。
【０１２９】
上記のシリコーン樹脂の中でも、特に三次元の網状構造を有するものが好ましく、例えばトスパール１０３、同１０５、同１０８、同１２０、同１４５、同３１２０及び同２４０（以上、東芝シリコーン（株）製）等の商品名を有する市販品が使用できる。
【０１３０】
本発明に係る微粒子の１次平均粒子径としては、ヘイズを低く抑えるという観点から２０ｎｍ以下が好ましく、更に好ましくは１６ｎｍ〜５ｎｍであり、特に好ましくは１２ｎｍ〜５ｎｍである。
【０１３１】
本発明に係る微粒子の１次平均粒子径の測定は、透過型電子顕微鏡（倍率５０万〜２００万倍）で粒子の観察を行い、粒子１００個を観察し、その平均値をもって１次平均粒子径とした。
【０１３２】
これら微粒子の添加方法は常法によって混練するなどにより行うことができるが、特に好ましくは予め溶媒に分散した微粒子とセルロースエステル及び／又は可塑剤及び／又は紫外線吸収剤を混合分散させた後、溶媒を揮発させた固形物とし、これをセルロースエステル溶融物の製造過程で用いることが均一な溶融物が得られる点で特に好ましい。
【０１３３】
上記のセルロースエステルフィルム、光学補償シート等は、例えば米国特許第２，４９２，９７８号明細書、同第２，７３９，０７０号明細書、同第２，７３９，０６９号明細書、同第２，４９２，９７７号明細書、同第２，３３６，３１０号明細書、同第２，３６７，６０３号明細書、同第２，６０７，７０４号明細書、英国特許第６４，０７１号明細書、同第７３５，８９２号明細書、特公昭４５−９０７４号公報、同４９−４５５４号公報、同４９−５６１４号公報、同６０−２７５６２号公報、同６１−３９８９０号公報、同６２−４２０８号公報に記載の方法を参照して製膜できる。
【０１３４】
また、着色防止剤、酸化防止剤、結晶核剤、すべり剤、安定剤、ブロッキング防止剤、紫外線吸収剤、粘度調節剤、消泡剤、透明化剤、帯電防止剤、ｐＨ調整剤、染料、顔料等を添加させてもよい。
【０１３５】
《偏光板、位相差板》
本発明の偏光板について説明する。
【０１３６】
本発明のセルロースエステルフィルムや本発明の光学補償シートは特に偏光板保護フィルムとして有用であり、これらを用いて公知の方法で偏光板を作製することができる。
【０１３７】
本発明の光学フィルムまたは光学補償シートを有する偏光板や表示装置はきわめて視認性に優れており、過酷な環境下であっても優れた視認性を提供することができたのである。
【０１３８】
《表示素子、電子ペーパ》
本発明のセルロースエステルフィルム、それを用いる光学補償シート等の用途としては特に限定されないが、バックライトを有する液晶表示素子、液晶表示装置等に好ましく適用でき、また、タッチパネル、フレキシブルに屈曲する表示素子である電子ペーパ等にも適用可能である。
【０１３９】
《表示装置》
本発明の表示装置について説明する。
【０１４０】
また、本発明の光学フィルムは反射型、透過型、半透過型液晶表示装置あるいはＴＮ型、ＳＴＮ型、ＯＣＢ型、ＨＡＮ型、ＶＡ型、ＩＰＳ型等の各種駆動方式の液晶表示装置で好ましく用いられ、プラズマディスプレイ、有機ＥＬディスプレイ、無機ＥＬディスプレイ等の各種表示装置にも好ましく用いられる。
【０１４１】
また、本発明の光学フィルムは反射防止フィルム、帯電防止フィルム、位相差フィルム、導電性フィルム、電磁波遮蔽フィルム、偏光板等の保護フィルム、光学補償フィルム、視野角拡大フィルム、輝度向上フィルム、偏光板、プラズマディスプレイ前面フィルター等に好ましく用いられる。特に複数の金属酸化物層を形成する反射防止フィルムに有用である。
【０１４２】
【実施例】
以下、実施例により本発明を説明するが、本発明はこれらに限定されない。
【０１４３】
実施例１
《セルロースエステルの合成》
以下に本発明のセルロースエステルフィルム（誘導体化セルロースともいう）の合成例の一例を示す。尚、本発明のセルロースエステルの合成方法は、下記の合成例に限定されない。
【０１４４】
（セルロースエステル１の合成）：フタル酸エステル化物
セルロース原料であるサルファイト法溶解パルプ（αセルロース含量９５％）をフラッフ状に解砕後、このフラッフ状パルプ（水分含量５．５％）１００部に対し３４部の酢酸を噴霧添加し、２０℃で１８分間前処理活性化した。
【０１４５】
次に、前処理活性化したパルプを撹拌しているエステル化反応機に仕込み、エステル化剤であるフタル酸無水物２４３部、反応溶媒である酢酸３３６部、触媒である硫酸２部を同時に仕込んだ。その後、２０℃から３０分かけて６２℃に昇温し、さらに５０℃で２５分保持してエステル化処理した。ついで、反応系に中和剤である２４％酢酸マグネシウム水溶液１４．０部を３分かけて添加して中和処理した。添加開始から５分後の反応系中の水濃度は１．０％であり、反応系温度は５０℃〜６０℃であった。
【０１４６】
次に、中和処理後の反応混合物に６０℃の７５％酢酸水溶液１２５部を加え、撹拌混合した。この混合物をオートクレーブに移し、１９１℃（１．１８ＭＰａ）の水蒸気をジャケット加熱法で６０分かけて１５０℃にした。その後、１５０℃で３０分保持する高温熟成法で鹸化・熟成を行い、セルロースエステル誘導体を含む反応混合物を得た。この反応混合物を激しく撹拌しながら希酢酸水溶液を加え、フレーク状セルロースエステル誘導体を分離した後、十分に水洗して取り出し、乾燥して、セルロースエステル１を得た。
【０１４７】
（セルロースエステル２の合成）：テレフタル酸エステル化物
セルロースエステル１の合成において、フタル酸無水物の代わりに、無水テレフタル酸を用いた以外は全く同様にして、セルロースエステル２を合成した。
【０１４８】
《セルロースエステルフィルム１の作製》
上記合成例に記載のセルロースエステル１を１７質量部、塩化メチレン／メタノール混合溶媒（混合比＝８０／１５質量％）８０．２８質量部およびトリフェニルホスフェート（可塑剤）２．７２質量部を混合した。室温では、セルロースエステル１は溶解せずに混合溶媒中で膨潤した。得られた膨潤混合物は、溶解せずにスラリーを形成していた。次に、膨潤混合物を二重構造の容器に入れ、混合物をゆっくり撹拌しながら外側のジャケットに冷媒として水／エチレングリコール混合物を流し込んだ。これにより内側容器内の混合物の温度を−３０℃まで冷却し（冷却速度：８℃／分）、混合物が均一に冷却されて固化するまで（３０分間）、冷媒による冷却を継続した。
【０１４９】
容器の外側のジャケット内の冷媒を除去し、代わりに温水をジャケットに流し込んだ。内容物のゾル化がある程度進んだ段階で、内容物の撹拌を開始した。このようにして、室温まで加温した（加温速度：８℃／分）。さらに、以上の冷却および加温の操作を、もう一回繰り返した。冷却溶解法により得られた溶液（ドープ）を、有効長６ｍのバンド流延機（流延製膜機ともいう）に流延した。
【０１５０】
６０℃の乾燥風で乾燥し、流延６０秒後に、０℃に冷却されたバンド（ステンレス支持体）からフィルムを剥離した。剥離したフィルムはテンターで横方向（ＴＤ）及び縦方向（ＭＤ）に各々１．２倍及び１．０５倍に延伸し、１００℃、３分、１３０℃で５分、そして、１６０℃で５分乾燥させた後、フィルムを固定せず、自由に収縮させて段階的に乾燥して、残りの溶剤を蒸発させた。
【０１５１】
得られたフィルム（揮発分：１０質量％）を、さらに１５０℃で１時間熱処理し、最終的に乾燥膜厚が１００μｍのセルロースエステルフィルム１を得た。また、フィルム幅は１３３０ｍｍ、巻き取り長は３０００ｍとした。
【０１５２】
（セルロースエステルフィルム２の作製）
上記のセルロースエステルフィルム１の作製において、セルロースエステル１（フタル酸エステル化物）の代わりにセルロースエステル２（テレフタル酸エステル化物）に変更した以外は同様にして、セルロースエステルフィルム２を作製した。
【０１５３】
（比較用のセルロースエステルフィルムの調製）
比較用のセルロースエステルフィルムとして、市販のトリアセチルセルロース（ＴＡＣともいう）フィルム、セルロースアセテートプロピオネートフィルムを各々入手した。
【０１５４】
得られたセルロースエステルフィルム１（フタル酸エステル化物）、セルロースエステルフィルム２（テレフタル酸エステル化物）と、従来公知のセルロースエステルフィルムとして、市販のトリアセチルセルロース（ＴＡＣともいう）フィルム、セルロースアセテートプロピオネートフィルムを比較として用い、下記の評価を行った。
【０１５５】
《面内リターデーション値（Ｒ_０（５５０））の測定》
本発明のセルロースエステルフィルム１、２及び、比較のトリアセチルセルロースフィルム、セルロースアセテートプロピオネートフィルムの各々について、エリプソメーター（Ｍ−１５０、日本分光（株）製）を用いて波長５５０ｎｍにおける面内リターデーション値（Ｒ_０（５５０））をそれぞれ測定した。
【０１５６】
ここで、面内リターデーション値（Ｒ_０（５５０））とは、下記式（ａ）により定義される面内リターデーション特性である。
【０１５７】
（ａ）Ｒ_０（５５０）＝（ｎｘ−ｎｙ）×ｄ
式中、ｎｘはセルロースエステルフィルムの面内での最大屈折率方向であるｘ方向、ｎｙはｘ方向に垂直な前記セルロースエステルフィルム面内の方向であるｙ方向の屈折率である。ｄは該セルロースエステルフィルムの厚み（ｎｍ）である。
【０１５８】
《赤外２色比の測定》
赤外２色比測定は、前記赤外２色比の求め方に記載の方法、及び測定装置を用いて、セルロースエステル分子を構成する主鎖に帰属され、１１２５ｃｍ^−１〜１１５０ｃｍ^−１の間に極大吸収を有するエーテル結合の吸収における面内の赤外２色比ｆ_ｘｙ（面内の配向係数を表す）を求めた。
【０１５９】
得られた結果を下記に示す。

ＴＡＣ：トリアセチルセルロースフィルム
ＣＡＰ：セルロースアセテートプロピオネートフィルム
上記から、本発明のセルロースエステルフィルム１、２は、比較のフィルム（トリアセチルセルロースフィルム、セルロースアセテートプロピオネートフィルム）と比べて、面内方向のリターデーション（Ｒ_０）が極めて大きく、光学的異方性が向上していることが判る。
【０１６０】
また、赤外２色比ｆ_ｘｙデータから、本発明のセルロースエステルフィルム１、２は、セルロース部分の主鎖の配向係数はＴＡＣ，ＣＡＰと大きな相違はないが、分極率異方性の高い官能基の存在により、少ない延伸率で一層高いリターデーションを示すフィルムが効率よく得られていることが分かる。
【０１６１】
【発明の効果】
本発明により、リターデーション値の高いセルロースエステルフィルム、光学補償シート、偏光板、位相差板、電子ペーパ及び表示装置を提供することが出来た。
【図面の簡単な説明】
【図１】結合分極率異方性算定時の座標軸設定を示す模式図である。
【図２】結合分極率異方性算定時の座標軸設定を示す模式図である。
【図３】偏光ＡＴＲ測定時の光学配置の一例を示す模式図である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a cellulose ester film, an optical compensation sheet, a polarizing plate, a retardation plate, electronic paper, and a display device.
[0002]
[Prior art]
Conventionally, cellulose acetate films have been frequently used as derivatized cellulose films. Cellulose acetate films are used for various photographic materials and optical materials because of their toughness and flame retardancy. Cellulose acetate films are also widely used as supports for typical photographic light-sensitive materials. Cellulose acetate films are also used in liquid crystal display devices.
[0003]
Conventionally known cellulose acetate films have a feature that they have higher optical isotropy (lower retardation value) than other polymer films, and therefore, liquid crystals that require optical isotropy are required. In general, a cellulose acetate film is used for a device of a display device, for example, a protective film or a color filter of a polarizing element.
[0004]
However, an optical compensatory sheet (retardation film), which is an element of another liquid crystal display device, requires a high retardation value, but a conventionally known cellulose acetate film cannot sufficiently compensate for the retardation value. Further, it is possible to increase the retardation value by performing a stretching treatment or the like in a conventionally known cellulose acetate film, but the amount of change due to stretching is very small, so it is necessary to stretch considerably strongly. There is a problem that the transparency, which is a feature of the cellulose support, is liable to be impaired, for example, when the strength is increased, the film becomes cloudy.
[0005]
Therefore, for such purposes, a synthetic polymer film having a high retardation value such as a polycarbonate film or a polysulfone film has been used, but separately from the optical compensation sheet made of the polymer film, on a transparent support. An optical compensation sheet provided with an optically anisotropic layer containing a discotic liquid crystal has also been proposed (for example, see Patent Documents 1, 2, 3, and 4).
[0006]
The above-described optical compensation sheet provided with an optically anisotropic layer containing a polycarbonate film, a polysulfone film, or a discotic liquid crystal achieves a high retardation value required for the optical compensation sheet.
[0007]
However, in each of these methods, it is necessary to separately provide two or more layers having a high retardation value on a transparent support having a low retardation value. However, there is a problem in that the number of steps increases, and the cost tends to be high.
[0008]
Therefore, there is a need in the art for the development of a derivatized cellulose sheet (also referred to as a cellulose ester film) having a high retardation value for an optical compensation sheet.
[0009]
[Patent Document 1]
JP-A-3-9325
[0010]
[Patent Document 2]
JP-A-6-148429
[0011]
[Patent Document 3]
JP-A-8-50206
[0012]
[Patent Document 4]
JP-A-9-26572
[0013]
[Problems to be solved by the invention]
An object of the present invention is to provide a cellulose ester film having a high retardation value, an optical compensation sheet, a polarizing plate, a retardation plate, an electronic paper, and a display device.
[0014]
[Means for Solving the Problems]
The above object of the present invention has been achieved by the following constitutions 1 to 16.
[0015]
1. A cellulose ester film having at least one substituent containing a chemical bond exhibiting bond polarizability anisotropy.
[0016]
2. 2. The cellulose ester film as described in 1 above, wherein the substituent has an oxycarbonyl group (—O—C (＝ O) —) or a carbonylimino (—C (＝ O) —NH—) group.
[0017]
3. 3. The cellulose ester film according to the above 1 or 2, wherein the substituent has an aromatic ring.
[0018]
4. The polarizability of the chemical bond in the direction parallel to the chemical bond chain is α1, the polarizability of the chemical bond in the direction perpendicular to the chemical bond chain is α2, and the chemical bond has an aromatic carbocyclic ring or an aromatic heterocyclic ring. Sometimes, when the polarizability in a direction perpendicular to the aromatic carbon ring or the aromatic heterocyclic ring is α3, at least one of the bond polarizability anisotropy represented by | α1−α2 | or | α3−α2 | One is 17 × 10⁻²⁴cm³The cellulose ester film according to any one of the above items 1 to 3, wherein:
[0019]
5. On three-dimensional coordinates (x-axis, y-axis, z-axis), a carbonyl group, which is a group of constituent atoms of an oxycarbonyl group or a carbonylimino group, is made to match the x-axis of the three-dimensional coordinates, and each of the aromatic rings A bond between molecules is arranged on an xy plane composed of an x-axis and a y-axis, respectively, and the z-axis is arranged in a direction perpendicular to the bond axis between the molecules. When the rate tensor is represented by the general formula (1), | α_yy−α_xx| Or | α_yy−α_zzAt least one of the bond polarizability anisotropy represented by |⁻²⁴cm³The cellulose ester film according to any one of the above items 2 to 4, wherein
[0020]
6. At the time of infrared spectroscopic absorption measurement, it was assigned to the main chain constituting the cellulose ester molecule, and^-1~ 1150cm^-1In-plane infrared dichroic ratio f in the absorption of an ether bond having a maximum absorption between_xyIs in the range of -0.05 to 0.1, wherein the cellulose ester film according to any one of 1 to 5 above.
[0021]
7. At the time of infrared spectroscopic absorption measurement, it was attributed to the main chain constituting the cellulose ester molecule and was 1125 cm^-1~ 1150cm^-1In-plane infrared dichroic ratio f in the absorption of an ether bond having a maximum absorption between_xyIs in the range of -0.025 to 0.05. The cellulose ester film according to any one of the above 1 to 5, wherein
[0022]
8. 8. The cellulose ester film according to any one of the above items 1 to 7, wherein the stretching ratio is 2.0 times or less.
[0023]
9. The stretch ratio is 1.5 times or less, The cellulose ester film as described in any one of 1 to 7 above, wherein
[0024]
10. 10. The cellulose ester film according to any one of 1 to 9, wherein the degree of substitution of the substituent exhibiting the bond polarizability anisotropy to the whole molecule is 10% to 90%.
[0025]
11. 10. The cellulose ester film according to any one of 1 to 9, wherein a degree of substitution of the substituent exhibiting the bond polarizability anisotropy to the whole molecule is 25% to 85%.
[0026]
12. An optical compensation sheet using the cellulose ester film according to any one of the above items 1 to 11.
[0027]
13. 13. A polarizing plate, wherein the cellulose ester film according to any one of 1 to 11 or the optical compensation sheet according to 12 is used.
[0028]
14． A retardation plate using the cellulose ester film according to any one of the above items 1 to 11.
[0029]
15. An electronic paper using the cellulose ester film according to any one of the above items 1 to 11.
[0030]
16. 13. A cellulose ester film according to any one of the above items 1 to 11, at least one selected from the group consisting of an optical compensation sheet according to the above item 12 and a polarizing plate according to the above item 13. Display device.
[0031]
Hereinafter, the present invention will be described in detail.
The present inventors have conducted various studies on the above problems, and as a result, by providing a substituent containing a chemical bond exhibiting bond polarizability anisotropy in the molecular side chain, a cellulose ester film having a high retardation value and It has been found that by using such an optical compensation sheet, an optical compensation sheet, a polarizing plate, a retardation plate, an electronic paper, and a display device having high optical compensation ability can be provided.
[0032]
《Coupling polarizability anisotropy》
The optical anisotropy of the cellulose ester, in particular, the relationship between the retardation characteristics and the bond polarizability anisotropy will be described together with the bond polarizability anisotropy according to the present invention.
[0033]
Here, the bond polarizability anisotropy according to the present invention means, as described in claim 4, a polarizability in a direction parallel to a chemical bond chain of a chemical bond as α1, and a perpendicularity of the chemical bond chain of the chemical bond. When the polarizability in the direction is α2, and when the chemical bond has an aromatic carbocycle or an aromatic heterocycle, the polarizability in the direction perpendicular to the aromatic carbocycle or the aromatic heterocycle is α3, In some cases, | α1−α2 |, | α3−α2 |, etc., may be represented by the absolute value of the difference between the binding polarizabilities, or on three-dimensional coordinates (x-axis, y-axis, z-axis). Anisotropically, the carbonyl group, which is a group of constituent atoms of the oxycarbonyl group or carbonylimino group, is made to coincide with the x-axis of the three-dimensional coordinates, and the bond between the molecules constituting the aromatic ring is represented by the x-axis, placed on the xy plane composed of the y-axis, and And the z-axis is arranged in the vertical direction, the theoretical coupling polarizability tensor of the partial structure is represented by the general formula (1), and the absolute value of the difference between the components constituting the tensor is defined as the coupling polarizability anisotropy. Sometimes used. In the present invention, among the tensors, the absolute value of the anisotropy | α_yy−α_xx|, | Α_yy−α_zzParticularly preferred is a cellulose ester film having a substituent having a specific value or more for each of | on the molecular side chain.
[0034]
(Retardation value (R₀, R_t)): Optical anisotropy
Bond polarizability anisotropy of the substituent on the molecular side chain of the cellulose ester and the optical anisotropy exhibited by the cellulose ester, particularly the in-plane retardation value (R₀), The retardation value in the thickness direction (R_tHas the following relationship.
[0035]
In-plane retardation value (R₀) Is generally represented by the following general formulas (2) and (3).
[0036]
General formula (2)
R₀= (Nx-ny) × d
The retardation in the thickness direction is represented by the following general formula (3).
[0037]
General formula (3)
R_t= ((Nx−ny) / 2−nz) × d
Here, nx is the refractive index in the x direction which is the maximum refractive index direction in the plane of the cellulose ester film, and ny is the refractive index in the y direction which is the direction in the plane of the cellulose ester film perpendicular to the x direction. d is the thickness (nm) of the cellulose ester film.
[0038]
(Relationship between birefringence, orientation coefficient and coupling polarizability)
Here, when the influence of crystallization can be neglected, a relational expression represented by the following general formula (4) holds.
[0039]
General formula (4)
R₀= Δ × d
Here, Δ is birefringence (also referred to as orientation birefringence), and d is as defined above (film thickness). Δ = Δ₀× P. Where Δ₀Is the intrinsic birefringence inherent in the molecule, and P is the orientation coefficient of the molecule. The intrinsic birefringence indicates the birefringence that occurs when the material is given complete uniaxiality.
[0040]
Further, Okamura et al., Introduction to Polymer Chemistry, 2nd ed. F. Gurne, J .; Appl. Phys. 25, 1232 (1954), Δ₀Is known to satisfy the relational expression represented by the following general formula (5).
[0041]
General formula (5)
Δ₀= (2π / 9) × ((n²+2)²/ N) × (ρN_A/ M) × Δα
Δα is the anisotropy of the bond polarizability in the structural unit of the molecule (in the case of a polymer, the monomer unit), and is defined by the difference between the polarizability in the longitudinal direction of the molecule and the direction perpendicular thereto. Intrinsic birefringence Δ₀When a molecular bond having a large polarizability, that is, a molecule having a large polarizability anisotropy Δα is strongly oriented in a certain direction (the orientation coefficient P is large), a large retardation is exhibited. Further, as is apparent from the above equation, birefringence and polarizability anisotropy can be predicted by considering a polymer molecule in terms of a single molecule constituting the same.
[0042]
On the other hand, the types of molecular polarization include electronic polarization, atomic polarization, dipole polarization, and interfacial polarization. However, since the wavelength is very short in the visible light region, it is known that electronic polarization is mainly dominant. Have been. Simply stated, the electron polarization is caused by the bias of the electron distribution. For example, it can be said that the polarizability change is large in an aromatic ring having a π electron cloud having a flat distribution.
[0043]
In the present invention, in order to define the bond polarizability anisotropy of the substituent modifying the side chain of the cellulose ester molecule, it is necessary to understand how much the bond polarizability anisotropy actually occurs due to the presence of the aromatic ring. However, it is very difficult to calculate the intrinsic birefringence of the compound to be modified itself from the above formula to calculate the bond polarizability anisotropy of the compound to be modified into the side chain.
[0044]
As another known method, the bond polarizability of each chemical bond unit of the compound to be modified is calculated, and the polarizability anisotropy is theoretically calculated by adding the polarizabilities of the bond units. It has been known. Here, a typical method is E.I. Erman, D .; C. Marvin, P .; A. Irvine, P .; J. Calculated using the method described in Flory, Macromolecules, 15, 664 (1982).
[0045]
In the actual procedure, the molecular shape is determined by conformation analysis, and the anisotropy tensor of each constituent atomic group can be obtained using the following general formula (6).
[0046]
(Equation 2)

[0047]
Where [diag (a_m)_xyz] Is the diagonal matrix of the bond polarizability tensor of the constituent functional group m, and φ and τ are the azimuth and polar angle of the bond functional group with respect to the coordinate axis, respectively. Δα for each constituent functional group_xyzIs added to obtain the bond polarizability of the whole molecule. The binding polarizability data of the binding functional group is as follows: C = O; Pietrala, H .; R. Schubach, M .; Dettenmaier, B .; Heise, Prog. Colloid & Ploym. Sci. 71, 125, (1985), C—O and C—H bonds are described in K.K. G. FIG. Denbig, Trans @ Faraday @ Soc. , 36, 936 (1940).
[0048]
Hereinafter, using the above-described method, as a simulation, the bond polarizability anisotropy of molecules such as DMC (dimethyl carbonate), MPC (methylphenyl carbonate), and DPC (diphenyl carbonate), and an acetyloxy group ( -OC (= O) -CH₃), A benzoyloxy group (-OC (= O) -C₆H₅) Were calculated for the bond polarizability anisotropy of each molecular side chain, such as those obtained by substituting).
[0049]
For example, in calculating the bond polarizability anisotropy of a chemical bond of a molecule constituting dimethyl carbonate or the like, the bond polarizability anisotropy changes depending on how to set a coordinate axis of the compound. Therefore, based on the carbonyl group (C = O), the coordinate axis is determined as shown in FIG. 1 with the direction of the carbonyl group (C = O) coincident with the x-axis. It was represented by the general formula (1). When the methyl group is replaced with a phenyl group in the coordinate system as it is, phenyl carbonate is obtained as shown in FIG.
[0050]
In the present invention, as described above, α_yyAnd α_xxThe absolute value of the difference | α_yy−α_xx| And α_yyAnd α_zzThe absolute value of the difference | α_yy−α_zzAnd found that a cellulose ester film having a high retardation value was obtained by adjusting the value of the bond polarizability anisotropy value to a specific value or more, and the cellulose ester film of the present invention It was found that it was preferably used for an optical compensation sheet, a polarizing plate, a retardation plate, electronic paper, and the like.
[0051]
In a similar manner, an acetyloxy group (CH₃The bond polarizability anisotropy was calculated for the case of having -C (= O) -O-), the case of having a benzoyloxy group in the side chain of the glucose molecule, and the case of diphenyl carbonate molecule.
[0052]
The results obtained are shown below.
[0053]
[Table 1]

[0054]
However, in Table 1, Δα₀(× 10⁻²⁴) Is | α_yy−α_xx|, Δα_T(× 10⁻²⁴) Is | α_yy−α_zz|.
[0055]
Table 1 shows that the presence of an aromatic ring such as a phenyl group increases polarizability anisotropy by almost one digit. From these results, the substituent that modifies the side chain contains one or more aromatic rings, and has a bond polarizability anisotropy of the substituent on three-dimensional coordinates (x, y, z). In the partial structure shown, the carbonyl group (C = O group) which is a polar group part is made to coincide with the x-axis, and further, the bonds between the molecules constituting the aromatic ring are constituted by the x-axis and the y-axis, respectively. The z-axis in a direction perpendicular to the bond axis of the molecules, the bond of the substituent in the theoretical bond polarizability tensor represented by the general formula (1) Polarizability anisotropy, ie α_yyAnd α_xxThe absolute value of the difference | α_yy−α_xx| Or bond polarizability anisotropy, α_yyAnd α_zzThe absolute value of the difference | α_yy−α_zzAt least one of the bond polarizability anisotropy represented by |⁻²⁴cm³It is preferable that it is above.
[0056]
<< Substituents containing a chemical bond exhibiting bond polarizability anisotropy >>
The substituent according to the present invention and containing a chemical bond exhibiting bond polarizability anisotropy will be described.
[0057]
Chemical bonds (including molecular species) exhibiting bond polarizability anisotropy according to the present invention are described in Quarterly Review of Chemistry, Refractive index control of transparent polymers (edited by The Chemical Society of Japan, No. 39, 1998). Specifically, data such as C ＝ C (aromatic), C ＝ C (fatty), C ＝ O, C—O, C—N, etc., and the molecular species include a benzene ring, toluene, p-toluene For example, the polarizability of the chemical bond in the direction parallel to the chemical bond chain is α1, the polarizability of the chemical bond in the direction orthogonal to the chemical bond chain is α2, and the chemical bond is an aromatic carbon ring or an aromatic heterocyclic ring. , The data of the polarizability in the direction perpendicular to the aromatic carbocyclic ring or the aromatic heterocyclic ring is α3.
[0058]
In the present invention, at least one of the bond polarizability anisotropy represented by | α1-α2 | or | α3-α2 |⁻²⁴cm³Those described above are preferred.
[0059]
As the substituent containing a chemical bond (including a molecular species) exhibiting the above-described bond polarizability anisotropy, a polar group is preferable. As the polar group, a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, an iodine atom) ), A hydroxyl group, an amino group, a nitro group, a carboxyl group, a formyl group, an alkoxyl group, a nitrile group, an ester group (—COOR, where R represents an alkyl group or an aryl group), an oxycarbonyl group (—O— And a substituent having a carbonylimino (-C (= O) -NH-) group.
[0060]
Above all, an ester group, a substituent having an oxycarbonyl group (—O—C (＝ O) —), and a substituent having a carbonylimino (—C (＝ O) —NH—) group are preferable, and particularly preferable is the above-mentioned substitution. This is the case when the group has an aromatic ring.
[0061]
《Effect of polar group》
In the present invention, the reason why the above-mentioned polar group is preferable is that when cellulose acetate, cellulose propionate or the like is stretched at a low magnification, a polar group portion such as a COO group preferentially causes an orientation change as described later. Although it is clear that the mechanism by which only the COO group is oriented is unknown, the present inventors presume that hydrogen bonds are probably involved.
[0062]
From the above, in order to orient the cellulose ester molecules efficiently, a substituent containing an oxycarbonyl group (—O—C (＝ O) —) or a carbonylimino (—C (＝ O) —NH—) group must be substituted with cellulose. It is preferable that the substituent is arranged on the side chain of the ester molecule, and more preferably that the substituent has an aromatic ring having a large bond polarizability anisotropy.
[0063]
《Aromatic ring》
As the aromatic ring according to the present invention, an aromatic carbocyclic group (for example, benzene ring, naphthalene ring, etc.) or an aromatic heterocyclic group (for example, furan ring, pyrrole ring, pyrazole ring, imidazole ring, oxazole ring, thiazole ring) , 1,2,3-oxadiazole ring, 1,2,3-triazole ring, 1,2,4-triazole ring, 1,3,4-thiadiazole ring, pyridine ring, pyridazine ring, pyrimidine ring, pyrazine ring , S-triazine ring, benzofuran ring, indole ring, benzothiophene ring, benzimidazole ring, benzothiazole ring, purine ring, quinoline ring and isoquinoline ring). These may further have a substituent.
[0064]
Hereinafter, specific examples of the substituent containing a chemical bond exhibiting bond polarizability anisotropy according to the present invention will be shown, but the present invention is not limited thereto.
[0065]
Embedded image

[0066]
<< Degree of substitution of side chain of cellulose ester molecule >>
When a substituent containing a chemical bond exhibiting bond polarizability anisotropy is arranged on a side chain of a cellulose ester molecule used for producing the cellulose ester film of the present invention, a sufficient retardation value improving effect as a substituent effect is obtained. From the viewpoint of playing and preventing the film from becoming cloudy and lowering the transparency, the degree of substitution of the cellulose ester molecules of the present invention with the entire cellulose ester molecule is preferably in the range of 10% to 90%, more preferably 25% to 85%. It is.
[0067]
Here, the above-mentioned degree of substitution is represented by a method known to those skilled in the art (for example, in cellulose acetate or the like, the degree of acetylation, acetyl value, or acetic acid value) or the mol% of the reacted hydroxyl group.
[0068]
<< Stretching of cellulose film >>
As shown in Table 1 above, an oxycarbonyl group (-OC (= O), which is an aromatic ring having high polarizability anisotropy or a chemical bond having high polarizability anisotropy in the side chain of the cellulose ester molecule. )-) Or a substituent having a carbonylimino (-C (= O) -NH-) group, thereby exhibiting a high intrinsic birefringence and having a high retardation value (even if the optical anisotropy is large). A cellulose ester film is obtained, but in order to obtain a cellulose ester film or an optical compensatory sheet having a large optical anisotropy, that is, a retardation value and exhibiting a sufficient optical compensation function, a stretching method described later is used. The treatment is preferably performed at the time of producing the cellulose ester film (also referred to as film forming).
[0069]
《Solution casting film》
As a method for producing a cellulose ester film of the present invention, a cellulose ester is dissolved in a solvent, the prepared dope solution is cast on a support, a film is formed, the obtained film is peeled off from the support, and then tension is applied. And drying while transporting in a drying zone is preferred.
[0070]
A solution casting film forming method and a casting metal support such as an endless metal belt (for example, a stainless steel belt) or a rotating metal drum (for example, a drum whose surface is chrome-plated with cast iron) (hereinafter simply referred to as metal) A dope (cellulose ester solution) is cast from a pressure die on a support, and the web (dope film) on the support is peeled off from the support and dried to produce a dope. Is what you do.
[0071]
In the present invention, a film obtained by peeling within 60 seconds after casting and drying while applying tension is particularly preferred because a metal oxide layer formed thereon is less likely to crack.
[0072]
The peeling tension at the time of peeling from the casting metal support is preferably 300 N / m or less, the transporting tension is preferably 300 N / m or less, more preferably 250 N / m or less, More preferably, it is 100 N / m to 200 N / m.
[0073]
In the drying step of the present invention, after peeling from the metal support, drying is performed while applying tension in the width direction or the longitudinal direction by a tenter. Excellent in properties and preferred. To apply the tension in the width direction or the longitudinal direction, not only one direction but also a biaxial stretching method in which the tension is applied in the width direction and the longitudinal direction is preferably used.
[0074]
Alternatively, a method in which the web is stretched one or more times at a high residual solvent amount of 10% by mass or more and a low residual solvent amount of less than 10% by mass, respectively, in the process of drying the web is also preferable. It is preferable that the stretching performed twice is adjusted so that the strain generated during drying is reduced.
[0075]
(Stretching using a tenter)
In the web drying step, the method of stretching the web is not particularly limited, for example, a method in which a plurality of rolls are provided with a peripheral speed difference, and a method in which the web is stretched in the longitudinal direction using a roll peripheral speed difference therebetween, The entire drying process or a part of the process as disclosed in Japanese Patent Application Laid-Open No. Sho 62-46625 is held in the width direction by clips in the width direction and both ends of the web are held in width by clips or pins. A method of performing drying (tenter method) is also preferable.
[0076]
When performing a stretching treatment using a tenter method, from the viewpoint of preventing a decrease in transparency due to cloudiness of the cellulose ester film after the stretching treatment and effectively suppressing a change in physical properties such as becoming hard and brittle, cellulose using a tenter is used. The stretch ratio of the ester film is preferably 2.0 times or less, more preferably 1.5 times or less, and particularly preferably 1.01 to 1.5 times. Further, it is preferable that the film is finally stretched so that the refractive index in the width direction of the casting becomes the maximum in the plane. Further, the amount of the residual solvent at the time of stretching is preferably 3% by mass to 30% by mass. The amount of the residual solvent and the solvent used for preparing the dope will be described later.
[0077]
<< Measurement of residual solvent content of web >>
In the present invention, the residual solvent amount of the web is defined by the following equation.
[0078]
Residual solvent amount (%) = [(weight before heat treatment of web−weight after heat treatment of web) / (weight after heat treatment of web)] × 100
In addition, when measuring the residual solvent amount, the heat treatment was performed at 110 ° C. for 3 hours.
[0079]
(Solvent for dope solution preparation)
Examples of the solvent used for preparing the dope solution include a chlorine-based solvent and a non-chlorine-based solvent.
[0080]
Examples of the chlorinated solvent include allyl chloride, 2-ethylhexyl chloride, amyl chloride, isopropyl chloride, ethyl chloride, butyl chloride, hexyl chloride, methyl chloride, methylene chloride (methylene chloride), o-chlorotoluene, p-chlorotoluene, and chlorobenzene. , Chloroform, carbon tetrachloride, 1,1-dichloroethane, 1.2-dichloroethane, 1,1-dichloroethylene, 1,2-dichloroethylene, 1,1,1,2-tetrachloroethane, 1,1,2,2- Examples include tetrachloroethane, tetrachloroethylene, tetramethylenechlorobromide, 1,1,1-trichloroethane, 1,1,2-trichloroethane, trichloroethylene and the like.
[0081]
Examples of the non-chlorinated solvent include ethers having 2 to 12 carbon atoms (for example, diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolan, tetrahydrofuran, anisole and phenetole), carbon atoms Ketones having 3 to 12 carbon atoms (for example, acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, and methylcyclohexanone), and esters having 2 to 12 carbon atoms (for example, methyl formate, ethyl formate) Propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate, etc.). Further, as an organic solvent having two or more kinds of functional groups, 2-ethoxyethyl acetate, 2-methoxyethanol, 2-butoxyethanol, or the like may be used.
[0082]
<< Stretching and orientation behavior of cellulose ester film >>
The effect of the stretching treatment for imparting the above stretching ratio on the orientation of the cellulose ester film of the present invention was examined by a polarized ATR-FTIR method (also referred to as a polarized ATR method).
[0083]
For example, a cellulose ester sheet (for example, a TAC (triacetylcellulose) sheet, a CAP (cellulose acetate propionate) sheet, or the like) was slightly stretched (stretch rate ≦ 200%, stretch ratio 2.0 times or less). In such a case, in such low-magnification stretching, the orientation of the cellulose skeleton (main chain) hardly changes in the plane, and only the acetyl group portion of the side chain mainly changes the orientation. Further, MD (machineＭＤdirection) It was found that when stretched in the direction, the orientation of the side chains tends to be oriented in a direction orthogonal to this.
[0084]
In low-magnification stretching (also referred to as micro-stretching), the mechanism in which only the COO group in the side chain is mainly oriented is unknown, but the relationship between the COO group and a hydrogen bond formed by a nearby substituent is unclear. Expected to be.
[0085]
Therefore, in setting the stretching conditions when producing a cellulose ester film having a high retardation value using a cellulose ester, when the stretching ratio is 2.0 times or less, the surface of the cellulose ester molecular skeleton which is the main chain. Since almost no change in orientation was observed in the inside, it was assigned to the main chain of the cellulose ester molecule, and it was 1125 cm.^-1~ 1145cm^-1In-plane infrared dichroic ratio f at the absorption of an ether bond having a local maximum absorption near_xyIs preferably adjusted to be more than -0.05 and less than 0.1, and more preferably adjusted to be more than -0.025 and less than 0.05.
[0086]
Here, the infrared two-color ratio f_xyRepresents an orientation coefficient in an in-plane direction, which will be described later.
《Orientation coefficient》
The theoretical consideration of the orientation coefficient according to the present invention will be described.
[0087]
The orientation evaluation method using infrared spectroscopy is based on a ratio k of spatial absorption coefficients in the longitudinal direction (x), the width direction (y), and the thickness (z) direction._x/ K_y, K_x/ K_z, And k_y/ K_zIs to seek. For this purpose, it is necessary to measure infrared absorption using light polarized along the x, y, and z-axis directions and calculate the absorption ratio of each component.
[0088]
In the measurement of infrared absorption, it is most ideal to perform measurement with light that is independently polarized in the x, y, and z-axis directions, but actually, it is particularly difficult to measure the z-axis in the thickness direction.
[0089]
In the polarization ATR method, four directions are defined in an x direction, a y direction, an xz (including both x-axis and z-axis components), and a yz (including both y-axis and z-axis components) directions. The procedure of measuring the absorption spectrum and calculating the absorption coefficients in the x, y, and z directions from the measured data is taken.
[0090]
FIG. 3 shows four basic optical configurations in measurement by the polarization ATR method. One of the sample planes is x, the other is y, and the thickness is z. For example, in a biaxially stretched film, the machine direction (MD direction: machine direction direction) is x, and the direction perpendicular to the machine direction (TD direction: transverse direction direction) is y. A perpendicularly polarized light (s-polarized light; TE: transversal electric) and a horizontally polarized light (TM: transverse magnetic) are incident on an incident surface composed of incident light and reflected light using a wire grid polarizer. I do. At this time, the x-axis is aligned with the direction of the TE polarized light (TEx, TMx). Next, the sample is rotated by 90 °, that is, the x-axis direction and the y-axis direction are interchanged, and the measurement is performed similarly (TEy, TMy). The four absorption spectra obtained here are represented by A_TEx, A_TMx, A_TEy, A_TMyThen, the relationship represented by the following general formula (7) is satisfied.
[0091]
General formula (7)
A_TEx= Αk_x
A_TMx= Βk_y-Γk_z
A_TEy= Αk_y
A_TMy= Βk_x-Γk_z
The relational expression represented by the general formula (7) is obtained. Here, α, β, and γ are constants depending on the incident angle and the refractive index of the sample. A. Flooomoy, and @W. J. Schaffers, Spectrochimica @ Acta, 22, 5 (1966); Palm, Vib. Spectrosc. , 6,185, (1994), it is obtained by the following general formula (8).
[0092]
(Equation 3)

[0093]
Here, p = (refractive index of sample)²/ (Refractive index of prism)²It is.
From the above, the spatial absorption coefficient of the sample, k_x, K_y, K_zCan be calculated as in the following general formula (9).
[0094]
General formula (9)
k_x= A_TEx/ Α
k_y= A_TEy/ Α
k_z= ((A_TMx-Βk_y) / Γ + (A_TMy-Βk_x) / Γ) / 2
As described above, the infrared two-color ratio is represented by the following general formula (10).
[0095]
General formula (10)
D_xy= K_x/ K_y
D_xz= K_x/ K_z
Where D_xy, D_xzTakes a value of 1.00 for all spatially isotropic non-oriented samples. This value increases as the orientation increases. As another evaluation formula, one that can be evaluated more quantitatively is described in P.S. A. Flooomoy, andW. J. Schaffers, Spectrochimica @ Acta, 22, 5 (1966)._xy, F_xz) And is represented by the following general formula (11).
[0096]
General formula (11)
f_xy= ((D_xy-1) / (D_xy+2)) × ((D₀+2) / (D₀-1))
f_xz= ((D_xz-1) / (D_xz+2)) × ((D₀+2) / (D₀-1))
Where f_xyIs the in-plane orientation coefficient, and f_xzIndicates the orientation coefficient in the film thickness direction. Where D₀= Cot²(Δ), where δ is the angle between the transition moment vector formed by molecular vibration and the molecular axis. To calculate this precisely, it is necessary to examine the direction of the moment of molecular vibration. Usually, however, it is sufficient to select the vibration mode parallel to the molecular axis and the mode perpendicular to the molecular axis and calculate them as 0 ° and 90 °, respectively. Information on orientation is obtained. The orientation coefficient is theoretically 0 for no orientation, 1.0 for complete orientation in the observation direction, and -0.5 for perpendicular to the observation direction.
[0097]
In the cellulose ester film of the present invention, the OCC stretching vibration (1035 cm^-1± 10cm^-1Is the vibration mode (δ = 0 degrees) parallel to the molecular axis, and the ester group (C = O, CH₃, C—C—O, 1713 cm each^-1± 10cm^-1, 1367cm^-1± 10cm^-1, 1214cm^-1± 10cm^-1) Was calculated as the vibration mode in the direction perpendicular to the molecular axis (δ = 90 degrees). Even in an actual molecular model (literature), the above functional groups had almost the above-described relationship.
[0098]
Baseline is 1510 cm for CCO^-1~ 1530cm^-1Minimum between 930cm^-1~ 1000cm^-1A straight line connecting the minimum values between C = O and 1800 cm^-1~ 1850m^-1Minimum between 1510cm^-1~ 1530cm^-1A straight line connecting the minimum values between them was used.
[0099]
《How to determine the peak》
How to determine the peak will be described.
[0100]
The infrared two-color ratio can be measured using attenuated total reflection infrared spectroscopy (ATR-IR method). The calculation method is described in J. P. Hobbs, C.I. S. P. Sung (JP Hobbs, CSP Sung, K. Krishan, and, S. Hill, Macromolecules, 16, 193 (1983)).
[0101]
<< How to determine the infrared two-color ratio >>
The method for determining the infrared two-color ratio is based on the peak (1150 cm) derived from the CO contrast stretching vibration in the cellulose ester molecule.^-1-1025cm^-1The intensity of the strongest peak that appears between the two) is measured. The peak intensity is determined by the wave number (xcm^-1Xcm)^-1~ X + 50cm^-1The point with the smallest absorbance and xcm^-1~ X-50cm^-1The point having the smallest absorbance is connected to each other, and this is set as a base line, and the peak intensity from this is measured and obtained. First, light is incident parallel to the longitudinal direction, and the absorbance (A) when polarized light is perpendicular to the incident surface._TEx) And the absorbance when the plane of polarization is parallel to the plane of incidence (A_TMx), And then incident parallel to the width direction,_TEyAnd A_TMyIs measured, and the infrared two-color ratio f is calculated by the general formula (11)._xy, F_xz(F_xyIs the in-plane orientation coefficient, f_xzIs the orientation coefficient in the film thickness direction. ) Can be calculated.
[0102]
Specifically, the measurement is performed under the following measurement conditions of the polarization ATR method.
Measuring device: Magna # 860 (manufactured by Nicole)
Single reflection ATR device: HARRICK @ SEAGUL
Prism: Germanium
Pressure between prism and sample: 80 cN · m with torque driver
Measurement sample area: 1cm²
Incident angle: 45 °
Number of reflections: 1
Resolution: 4cm^-1
Data interpolation: 0.5cm^-1
The refractive index of the sample was calculated as, for example, 1.477 for CAP (cellulose acetate propionate) and 1.482 for TAC (triacetyl cellulose). The prism (germanium) was 4.00. Using a wire grid polarizer, vertically polarized light and horizontally polarized light were incident on an incident surface composed of light incident on the sample surface and reflected light, and an FTIR-ATR spectrum was measured. The measurement was performed with the MD direction set to the x axis, the vertical direction (width direction TD) set to the y axis, and the thickness direction set to the z axis.
[0103]
When the orientation coefficient is determined by this method, it is important that the sample surface and the measurement prism surface are almost completely adhered. For this reason, it is desirable to use a commercially available or improved high-withstand-voltage ATR device that can withstand high contact pressure as the ATR device used here.
[0104]
"Additive"
For the purpose of improving the storage stability, dimensional stability, weather resistance, and the like of the cellulose ester film of the present invention, a plasticizer, an ultraviolet absorber, a plasticizer, a slipping agent, a matting agent, and the like may be additionally contained as desired. .
[0105]
(Plasticizer)
Examples of the plasticizer include phosphorus such as triphenyl phosphate, tricresyl phosphate, cresyl phenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, trinaphthyl phosphate, trixylyl phosphate, and tris-ortho-biphenyl phosphate. Acid ester plasticizer, phthalate plasticizer such as diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, triacetin, tributyrin, butyl phthalyl butyl glycolate, Ethylphthalylethyl glycolate, methylphthalylethyl glycolate, butylphthalylbutylglycol Glycolic acid ester based plasticizers such as over bets, and the like. Among them, phthalic acid ester type and glycolic acid ester type plasticizers are preferable because they hardly cause hydrolysis of cellulose ester. Further, it is preferable that a plasticizer having a freezing point of 20 ° C. or less is contained. Examples of such a plasticizer include tricresyl phosphate, cresyl phenyl phosphate, tributyl phosphate, diethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, and ethyl phthalyl ethyl glycolate. Can be
[0106]
Further, among the plasticizers, those having non-volatility are preferably used. The non-volatile plasticizer is a compound having a vapor pressure at 200 ° C. of 10 mmHg or less, having a very low vapor pressure and a low volatility. Preferably it is 5 mmHg or less, more preferably 1 mmHg or less. Specific examples include non-volatile phosphate esters described in JP-A-6-501040, and for example, arylene bis (diaryl phosphate) esters are preferable.
[0107]
The content of the plasticizer used in the present invention is preferably from 0.1% by mass to 30% by mass, particularly preferably from 0.5% by mass, from the viewpoint of dimensional stability, based on the total mass of the cellulose ester film. The range is 15% by mass.
[0108]
(UV absorber)
An ultraviolet absorber may be added to the cellulose ester film of the present invention as needed.
[0109]
As the ultraviolet absorber, those having excellent absorption of ultraviolet light having a wavelength of 370 nm or less and little absorption of visible light having a wavelength of 400 nm or more are preferably used from the viewpoint of good liquid crystal display properties.
[0110]
Specific examples of the ultraviolet absorber used in the present invention include, for example, oxybenzophenone-based compounds, benzotriazole-based compounds, salicylate-based compounds, benzophenone-based compounds, cyanoacrylate-based compounds, nickel complex salt-based compounds, triazine-based compounds, and benzoate-based compounds And the like. Also, a polymer ultraviolet absorber described in JP-A-6-148430 and a polymer ultraviolet absorber described in Japanese Patent Application No. 2000-214134 are preferably used.
[0111]
As the benzotriazole-based ultraviolet absorber, a compound represented by the following general formula [A] is preferably used.
[0112]
Embedded image

[0113]
Where R₁, R₂, R₃, R₄And R₅May be the same or different; a hydrogen atom, a halogen atom, a nitro group, a hydroxyl group, an alkyl group, an alkenyl group, an aryl group, an alkoxy group, an acyloxy group, an aryloxy group, an alkylthio group, an arylthio group, a mono- or dialkylamino group Represents an acylamino group or a 5- to 6-membered heterocyclic group,₄And R₅May be closed to form a 5- to 6-membered carbon ring.
[0114]
Further, these groups described above may have an arbitrary substituent.
Specific examples of the ultraviolet absorbent represented by the general formula [A] are shown below, but are not limited thereto.
[0115]
UV-1: 2- (2'-hydroxy-5'-methylphenyl) benzotriazole
UV-2: 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) benzotriazole
UV-3: 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) benzotriazole
UV-4: 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5-chlorobenzotriazole
UV-5: 2- (2'-hydroxy-3 '-(3 ", 4", 5 ", 6" -tetrahydrophthalimidomethyl) -5'-methylphenyl) benzotriazole
UV-6: 2,2-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol)
UV-7: 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole
UV-8: 2- (2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol (TINUVIN # 171, manufactured by Ciba)
UV-9: octyl-3- [3-tert-butyl-4-hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl- Mixture of 4-hydroxy-5- (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate (TINUVIN # 109, manufactured by Ciba)
Further, in the present invention, a compound represented by the following general formula [B] is preferably used as the benzophenone-based ultraviolet absorber.
[0116]
Embedded image

[0117]
In the formula, Y represents a hydrogen atom, a halogen atom or an alkyl group, an alkenyl group, an alkoxy group, and a phenyl group, and these alkyl group, alkenyl group, and phenyl group may have a substituent. A is a hydrogen atom, an alkyl group, an alkenyl group, a phenyl group, a cycloalkyl group, an alkylcarbonyl group, an alkylsulfonyl group, or -CO (NH)_n-1-D represents a group, wherein D represents an alkyl group, an alkenyl group or a phenyl group which may have a substituent. m and n represent 1 or 2.
[0118]
In the above, the alkyl group represents, for example, a linear or branched aliphatic group having up to 24 carbon atoms, the alkoxy group is, for example, an alkoxy group having up to 18 carbon atoms, and the alkenyl group is, for example, 16 carbon atoms. And alkenyl groups up to, for example, allyl group, 2-butenyl group and the like. Examples of the substituent which may be substituted with an alkyl group, an alkenyl group, or a phenyl group include a halogen atom, for example, a hydroxyl group, a phenyl group, a chlorine atom, a bromine atom, and a fluorine atom. Halogen atom or the like may be substituted).
[0119]
Specific examples of the benzophenone-based compound represented by the general formula [B] are shown below, but are not limited thereto.
[0120]
UV-10: 2,4-dihydroxybenzophenone
UV-11: 2,2'-dihydroxy-4-methoxybenzophenone
UV-12: 2-hydroxy-4-methoxy-5-sulfobenzophenone
UV-13: bis (2-methoxy-4-hydroxy-5-benzoylphenylmethane)
Commercially available products include TINUVIN P, TINUVIN 324, TINUVIN 320, TINUVIN 326, TINUVIN 327, TINUVIN 328, TINUVIN 329, TINUVIN 770, TINUVIN 780, TINUVIN 144, TINUGI O (UVITEX) ) Etc. can be used as appropriate.
[0121]
The above-mentioned ultraviolet absorber preferably used in the present invention is preferably a benzotriazole-based ultraviolet absorber or a benzophenone-based ultraviolet absorber which has high transparency and has an excellent effect of preventing deterioration of a polarizing plate or a liquid crystal element, and unnecessary coloring. Particularly preferred is a benzotriazole-based ultraviolet absorber having a smaller content.
[0122]
In the present invention, the ultraviolet absorber is preferably added in an amount of 0.1% by mass to 20% by mass, more preferably 0.5% by mass to 10% by mass, based on the whole cellulose ester film. It is preferable to add 1% by mass to 5% by mass.
[0123]
Since it is often preferable to use two or more of these in combination, it is preferable to search for an optimal combination as appropriate according to manufacturing conditions, use conditions, and the like.
[0124]
(Mat agent)
Fine particles such as a matting agent can be added to the cellulose ester film of the present invention in order to impart lubricity. Examples of the fine particles include fine particles of an inorganic compound and fine particles of an organic compound.
[0125]
As inorganic compounds, compounds containing silicon, silicon dioxide, aluminum oxide, zirconium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, calcium phosphate, etc. And more preferably an inorganic compound containing silicon or zirconium oxide, and silicon dioxide is particularly preferably used.
[0126]
As the fine particles of silicon dioxide, commercially available products such as Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (all manufactured by Nippon Aerosil Co., Ltd.) can be used.
[0127]
As the fine particles of zirconium oxide, commercially available products such as Aerosil R976 and R811 (all manufactured by Nippon Aerosil Co., Ltd.) can be used.
[0128]
As the organic compound, for example, polymers such as silicone resin, fluorine resin and acrylic resin are preferable, and among them, silicone resin is preferably used.
[0129]
Among the above silicone resins, those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, 105, 108, 120, 145, 3120 and 240 (all manufactured by Toshiba Silicone Co., Ltd.) Commercial products having trade names such as
[0130]
The primary average particle diameter of the fine particles according to the present invention is preferably 20 nm or less, more preferably 16 nm to 5 nm, and particularly preferably 12 nm to 5 nm, from the viewpoint of suppressing haze.
[0131]
The primary average particle diameter of the fine particles according to the present invention is measured by observing the particles with a transmission electron microscope (magnification: 500,000 to 2,000,000), observing 100 particles, and determining the average value of the primary average particles. Diameter.
[0132]
The method for adding these fine particles can be carried out by kneading in a conventional manner. Particularly preferably, the fine particles previously dispersed in a solvent are mixed and dispersed with a cellulose ester and / or a plasticizer and / or an ultraviolet absorber, and then the solvent is added. Is preferably used in the production process of the cellulose ester melt in that a uniform melt can be obtained.
[0133]
The above-mentioned cellulose ester films, optical compensation sheets and the like are described, for example, in US Pat. Nos. 2,492,978, 2,739,070, 2,739,069 and 2nd. No. 2,492,977, No. 2,336,310, No. 2,367,603, No. 2,607,704, British Patent No. 64,071. No. 735,892, JP-B-45-9074, JP-A-49-4554, JP-A-49-5614, JP-A-60-27562, JP-A-61-39890, and JP-A-62-4208. The film can be formed with reference to the method described in Japanese Patent Application Laid-Open Publication No. H10-260, 1988.
[0134]
In addition, a coloring inhibitor, an antioxidant, a crystal nucleating agent, a slipping agent, a stabilizer, an antiblocking agent, an ultraviolet absorber, a viscosity regulator, an antifoaming agent, a clarifying agent, an antistatic agent, a pH regulator, a dye, A pigment or the like may be added.
[0135]
《Polarizer, retarder》
The polarizing plate of the present invention will be described.
[0136]
The cellulose ester film of the present invention and the optical compensatory sheet of the present invention are particularly useful as a protective film for a polarizing plate, and a polarizing plate can be prepared by a known method using these films.
[0137]
The polarizing plate and the display device having the optical film or the optical compensatory sheet of the present invention are extremely excellent in visibility, and can provide excellent visibility even in a severe environment.
[0138]
《Display element, electronic paper》
The use of the cellulose ester film of the present invention, such as an optical compensatory sheet using the same, is not particularly limited, but can be preferably applied to a liquid crystal display device having a backlight, a liquid crystal display device, and the like, and also a touch panel, a display device that flexibly bends. It is also applicable to electronic paper and the like.
[0139]
《Display device》
The display device of the present invention will be described.
[0140]
Further, the optical film of the present invention is preferably used in a reflective, transmissive, transflective liquid crystal display device or a liquid crystal display device of various drive systems such as TN type, STN type, OCB type, HAN type, VA type, IPS type. It is also preferably used for various display devices such as a plasma display, an organic EL display, and an inorganic EL display.
[0141]
Further, the optical film of the present invention is an antireflection film, an antistatic film, a retardation film, a conductive film, an electromagnetic wave shielding film, a protective film such as a polarizing plate, an optical compensation film, a viewing angle widening film, a brightness enhancement film, and a polarizing plate. , For plasma display front filters and the like. In particular, it is useful for an antireflection film having a plurality of metal oxide layers.
[0142]
【Example】
Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited thereto.
[0143]
Example 1
《Synthesis of cellulose ester》
Hereinafter, an example of a synthesis example of the cellulose ester film (also referred to as derivatized cellulose) of the present invention will be described. The method for synthesizing the cellulose ester of the present invention is not limited to the following synthesis examples.
[0144]
(Synthesis of cellulose ester 1): phthalic acid ester
After the sulphite-dissolved pulp (α-cellulose content 95%), which is a cellulose raw material, is pulverized in a fluff shape, 34 parts of acetic acid is spray-added to 100 parts of the fluff-like pulp (5.5% water content). Pretreatment activated for 18 minutes at ° C.
[0145]
Next, the pretreated activated pulp is charged into a stirring esterification reactor, and 243 parts of phthalic anhydride as an esterifying agent, 336 parts of acetic acid as a reaction solvent, and 2 parts of sulfuric acid as a catalyst are simultaneously charged. It is. Thereafter, the temperature was raised from 20 ° C. to 62 ° C. over 30 minutes, and further kept at 50 ° C. for 25 minutes to carry out esterification treatment. Then, 14.0 parts of a 24% aqueous solution of magnesium acetate as a neutralizing agent was added to the reaction system over 3 minutes for neutralization. Five minutes after the start of the addition, the water concentration in the reaction system was 1.0%, and the reaction system temperature was 50 ° C to 60 ° C.
[0146]
Next, 125 parts of a 75% acetic acid aqueous solution at 60 ° C. was added to the reaction mixture after the neutralization treatment, followed by stirring and mixing. The mixture was transferred to an autoclave, and steam at 191 ° C (1.18 MPa) was heated to 150 ° C over 60 minutes by a jacket heating method. Thereafter, saponification and aging were performed by a high-temperature aging method that was maintained at 150 ° C. for 30 minutes to obtain a reaction mixture containing a cellulose ester derivative. A dilute acetic acid aqueous solution was added to the reaction mixture with vigorous stirring to separate the flaky cellulose ester derivative, which was then thoroughly washed with water, taken out and dried to obtain cellulose ester 1.
[0147]
(Synthesis of cellulose ester 2): Terephthalic acid ester
In the synthesis of cellulose ester 1, cellulose ester 2 was synthesized in exactly the same manner except that terephthalic anhydride was used instead of phthalic anhydride.
[0148]
<< Preparation of cellulose ester film 1 >>
17 parts by mass of the cellulose ester 1 described in the above Synthesis Example, 80.28 parts by mass of a methylene chloride / methanol mixed solvent (mixing ratio = 80/15% by mass), and 2.72 parts by mass of triphenyl phosphate (plasticizer) are mixed. did. At room temperature, the cellulose ester 1 did not dissolve and swelled in the mixed solvent. The resulting swelling mixture formed a slurry without dissolving. Next, the swollen mixture was placed in a double-layered container, and a water / ethylene glycol mixture was poured as a refrigerant into the outer jacket while slowly stirring the mixture. Thereby, the temperature of the mixture in the inner container was cooled to -30 ° C (cooling rate: 8 ° C / min), and cooling with the refrigerant was continued until the mixture was uniformly cooled and solidified (30 minutes).
[0149]
The refrigerant in the jacket outside the vessel was removed and warm water was instead poured into the jacket. When the sol of the content was advanced to some extent, stirring of the content was started. In this way, the mixture was heated to room temperature (heating rate: 8 ° C./min). Further, the above cooling and heating operations were repeated once. The solution (dope) obtained by the cooling dissolution method was cast on a band casting machine (also called a casting film forming machine) having an effective length of 6 m.
[0150]
The film was dried with a drying air at 60 ° C., and after 60 seconds from the casting, the film was peeled off from the band (stainless steel support) cooled to 0 ° C. The peeled film is stretched in a transverse direction (TD) and a longitudinal direction (MD) in a transverse direction (TD) and a longitudinal direction (MD) 1.2 times and 1.05 times, respectively, at 100 ° C. for 3 minutes, at 130 ° C. for 5 minutes, and at 160 ° C. for 5 minutes. After minute drying, the film was not fixed, but was shrunk freely and dried stepwise to evaporate the remaining solvent.
[0151]
The obtained film (volatile content: 10% by mass) was further heat-treated at 150 ° C. for 1 hour to finally obtain a cellulose ester film 1 having a dry film thickness of 100 μm. The film width was 1330 mm and the winding length was 3000 m.
[0152]
(Preparation of cellulose ester film 2)
A cellulose ester film 2 was produced in the same manner as in the production of the cellulose ester film 1 except that cellulose ester 2 (terephthalate) was used instead of cellulose ester 1 (phthalate).
[0153]
(Preparation of cellulose ester film for comparison)
As comparative cellulose ester films, commercially available triacetyl cellulose (also referred to as TAC) films and cellulose acetate propionate films were obtained.
[0154]
The obtained cellulose ester film 1 (phthalic acid esterified product), cellulose ester film 2 (terephthalic acid esterified product), and conventionally known cellulose ester films, commercially available triacetyl cellulose (also referred to as TAC) film, cellulose acetate propionate The following evaluations were performed using the nate film as a comparison.
[0155]
<< In-plane retardation value (R₀Measurement of (550)) >>
For each of the cellulose ester films 1 and 2 of the present invention, the comparative triacetyl cellulose film, and the cellulose acetate propionate film, the in-plane at a wavelength of 550 nm using an ellipsometer (M-150, manufactured by JASCO Corporation). Retardation value (R₀(550)).
[0156]
Here, the in-plane retardation value (R₀(550)) is an in-plane retardation characteristic defined by the following equation (a).
[0157]
(A) R₀(550) = (nx−ny) × d
In the formula, nx is the x direction which is the maximum refractive index direction in the plane of the cellulose ester film, and ny is the refractive index in the y direction which is a direction in the plane of the cellulose ester film perpendicular to the x direction. d is the thickness (nm) of the cellulose ester film.
[0158]
<< Measurement of infrared two-color ratio >>
The infrared two-color ratio measurement is attributed to the main chain constituting the cellulose ester molecule using the method described in the above-described method for determining the infrared two-color ratio, and a measuring device, and is measured at 1125 cm^-1~ 1150cm^-1In-plane infrared dichroic ratio f in the absorption of an ether bond having a maximum absorption between_xy(Representing the in-plane orientation coefficient) was determined.
[0159]
The results obtained are shown below.

TAC: triacetyl cellulose film
CAP: Cellulose acetate propionate film
As described above, the cellulose ester films 1 and 2 of the present invention have an in-plane retardation (R) which is lower than that of comparative films (triacetyl cellulose film and cellulose acetate propionate film).₀) Is extremely large, indicating that the optical anisotropy is improved.
[0160]
In addition, the infrared two-color ratio f_xyFrom the data, it is found that the cellulose ester films 1 and 2 of the present invention have the same orientation coefficient of the main chain of the cellulose portion as TAC and CAP, but have a small stretching ratio due to the presence of the functional group having high polarizability anisotropy. It can be seen that a film exhibiting even higher retardation was efficiently obtained.
[0161]
【The invention's effect】
According to the present invention, a cellulose ester film, an optical compensation sheet, a polarizing plate, a retardation plate, an electronic paper, and a display device having a high retardation value can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a coordinate axis setting at the time of calculating a bond polarizability anisotropy.
FIG. 2 is a schematic diagram showing a coordinate axis setting at the time of calculating a bond polarizability anisotropy.
FIG. 3 is a schematic diagram showing an example of an optical arrangement at the time of polarization ATR measurement.

Claims (16)

A cellulose ester film having at least one substituent containing a chemical bond exhibiting bond polarizability anisotropy. The cellulose ester film according to claim 1, wherein the substituent has an oxycarbonyl group (-OC (= O)-) or a carbonylimino (-C (= O) -NH-) group. . The cellulose ester film according to claim 1, wherein the substituent has an aromatic ring. The polarizability of the chemical bond in the direction parallel to the chemical bond chain is α1, the polarizability of the chemical bond in the direction perpendicular to the chemical bond chain is α2, and the chemical bond has an aromatic carbocyclic ring or an aromatic heterocyclic ring. Sometimes, when the polarizability in a direction perpendicular to the aromatic carbon ring or the aromatic heterocyclic ring is α3, at least one of the bond polarizability anisotropy represented by | α1−α2 | or | α3−α2 | The cellulose ester film according to any one of claims 1 to 3, wherein one of them is 17 × 10 ⁻²⁴ cm ³ or more. On three-dimensional coordinates (x-axis, y-axis, z-axis), a carbonyl group, which is a group of constituent atoms of an oxycarbonyl group or a carbonylimino group, is made to coincide with the x-axis of the three-dimensional coordinates, and each of the aromatic rings is formed. The bond between molecules is arranged on an xy plane composed of an x-axis and a y-axis, respectively, and the z-axis is arranged in a direction perpendicular to the bond axis between the molecules. When the rate tensor is represented by the following general formula (1), at least one of the bond polarizability anisotropies represented by | α _yy -α _xx | or | α _yy -α _zz | is 3 × 10 ⁻²⁴ cm The cellulose ester film according to any one of claims 2 to 4, wherein the number is ³ or more.

Wherein, alpha _xx, alpha _xy, alpha _xz each xx component, xy components represents a bond polarizability of the xz component, alpha _yx, alpha _yy, alpha _yz, respectively yx component, yy component, the yz components It represents a bond polarizability, alpha _zx, alpha _zy, alpha _zz represent each zx component, zy component, the bond polarizability of the zz component. ] At the time of infrared spectroscopic absorption measurement, the in-plane infrared two-color ratio f _xy in the absorption of an ether bond belonging to the main chain constituting the cellulose ester molecule and having a maximum absorption between 1125 cm ^{−1 and} 1150 cm ⁻¹ is: The cellulose ester film according to any one of claims 1 to 5, wherein the thickness is in the range of -0.05 to 0.1. At the time of infrared spectroscopic absorption measurement, the in-plane infrared two-color ratio f _xy in the absorption of an ether bond belonging to the main chain constituting the cellulose ester molecule and having a maximum absorption between 1125 cm ^{−1 and} 1150 cm ⁻¹ is: The cellulose ester film according to any one of claims 1 to 5, wherein the thickness is in the range of -0.025 to 0.05. The stretch ratio is 2.0 times or less, The cellulose ester film as described in any one of Claims 1-7 characterized by the above-mentioned. The stretch ratio is 1.5 times or less, The cellulose ester film as described in any one of Claims 1-7 characterized by the above-mentioned. The cellulose ester film according to any one of claims 1 to 9, wherein the degree of substitution of the substituent exhibiting the bond polarizability anisotropy to the whole molecule is 10% to 90%. The cellulose ester film according to any one of claims 1 to 9, wherein the substitution degree of the substituent exhibiting the bond polarizability anisotropy to the whole molecule is 25% to 85%. An optical compensation sheet using the cellulose ester film according to claim 1. A polarizing plate comprising the cellulose ester film according to any one of claims 1 to 11 or the optical compensation sheet according to claim 12. A retardation plate comprising the cellulose ester film according to claim 1. An electronic paper using the cellulose ester film according to claim 1. A method using at least one selected from the group consisting of the cellulose ester film according to any one of claims 1 to 11, the optical compensation sheet according to claim 12, and the polarizing plate according to claim 13. Characteristic display device.

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