JP2005008803A - Cellulose ester film, method for producing cellulose ester film, optical compensation sheet, polarization plate, retardation plate, electronic paper and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cellulose ester film having high retardation value, a method for producing the cellulose ester film, an optical compensation sheet, a polarization plate, a retardation plate, an electronic paper and a display device. <P>SOLUTION: The cellulose ester film has a substituent A and a substituent B on the molecular side chain. One of the bond polarization anisotropy is ≥50×10<SP>-24</SP>cm<SP>3</SP>when the polarizability values of the substituents parallel to the chemical bond chain are taken as α1a and α1b, the polarizability values perpendicular to the chemical bond chains in the chemical bonds A and B are taken as α2a and α2b, and the polarizability perpendicular to the aromatic carbon ring or the aromatic heterocyclic ring is taken as α3a when the chemical bond A has an aromatic carbon ring or an aromatic heterocyclic ring. The other bond polarization anisotropy value is <50×10<SP>-24</SP>cm<SP>3</SP>. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００４５】
式中、［ｄｉａｇ（α_ｍ）_ｘｙｚ］は、構成官能基の結合分極率テンソルの対角行列で、φとτは、各々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。
【００４６】
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。
【００４７】
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。
【００４８】
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。
【００４９】
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。
【００５０】
得られた結果を下記に示す。
【００５１】
【表１】

【００５２】
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。
【００５３】
表１から、フェニル基などの芳香族環の存在により、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分極率異方性に注目し、その値を大きくするような分子設計を行う観点からは、芳香族環を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、芳香族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｜が４×１０^−２４ｃｍ^３以上であることが好ましく、更に好ましくは、結合分極率異方性、α_ｙｙとα_ｚｚとの差の絶対値｜α_ｙｙ−α_ｚｚ｜が６×１０^−２４ｃｍ^３以上である。
【００５４】
《結合分極率異方性を示す化学結合を含む置換基》
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。
【００５５】
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。
【００５６】
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（例えば、フッ素原子、塩素原子、臭素原子、ヨウ素原子等）、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。
【００５７】
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、カルボニルイミノ基（−Ｃ（＝Ｏ）−ＮＨ−）等を有する置換基が好ましい。
【００５８】
（置換基Ａ、置換基Ｂとして用いられる基）
置換基Ａの結合分極率異方性としては、５０×１０^−２５ｃｍ^３以上３００×１０^−２５ｃｍ^３以下のものが好ましく、そのような結合分極率異方性を置換基Ａに付与する具体例としては、アルキル基（特に炭素数が１８等のような長鎖のアルキル基が好ましい）、アリール基（フェニル基、ナフチル基等）、芳香族環を含むアシル基（例えば、ベンゾイル基、トルオイル基、サリチロイル基、シンナモイル基、ナフトイル基、フタロイル基等）等が挙げられる。
【００５９】
上記アルキル基、アリール基は未置換でも置換基を有していてもよいが、前記置換基としては、ハロゲン原子、硫黄原子またはそれらを有する基を使用してもよいが、特に好ましく用いられるのは、未置換のアリール基である。
【００６０】
また、置換基Ｂの結合分極率異方性としては、３×１０^−２５ｃｍ^３以上５０×１０^−２５ｃｍ^３未満のものが好ましく、これらを満たす置換基Ｂの具体例としては、アシルオキシ基（例えば、アセチルオキシ基、プロピオニルオキシ基、ブチリルオキシ基、バレリルオキシ基、パルミトイルオキシ基、ステアロイルオキシ基、オレオイルオキシ基、ノルボルニルカルボニルオキシ基等）が挙げられる。また、置換基Ｂが上記の結合分極率異方性を示すには、芳香族環は含まないことが好ましい。
【００６１】
置換基Ａは分極率異方性が５０×１０^−２５ｃｍ^３と高いために、これをセルロースエステル分子側鎖に修飾した場合、セルロース主鎖の分極率異方性（およそ３０〜４０×１０^−２５ｃｍ^３と考えられる）よりも高くなり、負の１軸性を示す効果が期待できる。一方、置換基Ｂでは分極率異方性を５０×１０^−２５ｃｍ^３未満とするため、セルロース主鎖の分極率異方性より小さくなり、正の１軸性を示す効果が期待できる。両者の効果を有効に利用することにより、より優れた光学フィルムが得られる。
【００６２】
《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、フィルムの製造時（特に製膜時）に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。
【００６３】
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族環を前記置換基が有することである。
【００６４】
《芳香族環》
本発明に係る芳香族環としては、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。
【００６５】
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。
【００６６】
【化１】

【００６７】
《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。
【００６８】
ここで、置換度が１００％とはセルロース（グルコース基本単位当たり３個の水酸基（ヒドロキシル基）をもつ多価アルコール）の、グルコース基本単位当たりの３個の水素原子が置換基（例えば、アシル基等）により置換されている場合を示す。
【００６９】
また、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。
【００７０】
《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族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。
【００７１】
《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。
【００７２】
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。
【００７３】
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。
【００７４】
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。
【００７５】
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。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。
【００７６】
（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幅方向にクリップでウェブの幅両端をクリップやピン等で幅保持し、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。
【００７７】
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ＭＤ方向（Ｍａｃｈｉｎｅ Ｄｉｒｅｃｔｉｏｎ方向、搬送方向ともいう）または、ＴＤ方向（Ｔｒａｎｓｖｅｒｓｅ Ｄｉｒｅｃｉｔｏｎ方向、巾方向、幅手方向ともいう）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倍〜１．５倍である。更に、最終的に流延の幅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。
【００７８】
《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。
【００７９】
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。
【００８０】
（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、非塩素系溶媒等がある。
【００８１】
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。
【００８２】
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。
【００８３】
《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。
【００８４】
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。
【００８５】
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。
【００８６】
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。
【００８７】
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。
【００８８】
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。
【００８９】
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。
【００９０】
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。
【００９１】
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。
【００９２】
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。
【００９３】
【数３】

【００９４】
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。
【００９５】
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。
【００９６】
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。
【００９７】
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。
【００９８】
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。
【００９９】
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^−１〜１８５０ｃｍ^−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。
【０１００】
《ピークの決め方》
ピークの決め方について述べる。
【０１０１】
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。
【０１０２】
《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。
【０１０３】
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。
【０１０４】
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。
【０１０５】
《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。
【０１０６】
（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。
【０１０７】
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。
【０１０８】
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。
【０１０９】
（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。
【０１１０】
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。
【０１１１】
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、特開２００２−３１７１５号公報に開示の高分子紫外線吸収剤も好ましく用いられる。
【０１１２】
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。
【０１１３】
【化２】

【０１１４】
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。
【０１１５】
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。
【０１１６】
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。
【０１１７】
【化３】

【０１１８】
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。
【０１１９】
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。
【０１２０】
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。
【０１２１】
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。
【０１２２】
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。
【０１２３】
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。
【０１２４】
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。
【０１２５】
（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。
【０１２６】
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。
【０１２７】
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。
【０１２８】
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。
【０１２９】
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。
【０１３０】
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。
【０１３１】
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。
【０１３２】
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。
【０１３３】
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等に好ましい。
【０１３４】
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。
【０１３５】
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。
【０１３６】
《偏光板、位相差板》
本発明の偏光板について説明する。
【０１３７】
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。
【０１３８】
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。
【０１３９】
《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。
【０１４０】
《表示装置》
本発明の表示装置について説明する。
【０１４１】
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。
【０１４２】
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。
【０１４３】
【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。
【０１４４】
実施例１
《セルロースエステルフィルム１の作製》：本発明
下記のようにして調製したドープＡを用いて、市販の流延製膜法によりセルロースエステルフィルム１を作製した。
【０１４５】
（ドープＡの調製）
ドープＡとして、セルロース分子のグルコース単位当たり３つの水酸基の水素原子に対する、ナフチルカルボニル基の置換度２．０（％表記では、２．０／３．０×１００＝６６．７％）、プロピオニル基の置換度０．６５（％表記では、２１．７％）であり、数平均分子量１５００００のセルロースアセテートナフタレートプロピオネート１００質量部、トリフェニルフォスフェイト８質量部、エチルフタリルエチルグリコレート２質量部、２−（２′−ヒドロキシ−３，５′−ジ−ｔ−ブチルフェニル）−５−クロロベンゾトリアゾール２質量部、２−ヒドロキシ−４−ベンジロキシベンゾフェノン２質量部、塩化メチレン３００質量部、エタノール２６質量部を加圧密閉容器に投入し、８０℃に加温して容器内圧力を２気圧とし、撹拌しながらセルロースアセテートナフタレートプロピオネートを完全に溶解させドープを得た。溶液を安積濾紙（株）製の安積濾紙Ｎｏ．２４４を使用して濾過した後、ドープを３５℃まで下げて一晩静置して、ドープ中の脱泡を行った。
【０１４６】
（製膜工程）
上記のドープＡを市販の流延製膜装置の共流延ダイからステンレスベルト上に流延し１層構成のドープ膜とした。ステンレスベルトの裏面から温水を接触させて３５℃に温度制御されたステンレスベルト上で１分間乾燥した後、更にステンレスベルトの裏面に、１５℃の冷水を接触させて１０秒間保持した後、ステンレスベルトから生乾きのフィルムを剥離した。尚、ステンレスベルトの表面からは６０℃の温風を搬送方向と平行に流した。また、剥離時のフィルム中の残留溶媒量は１００質量％であった。
【０１４７】
次いで剥離したフィルムを、ロールに巻き回しながら搬送するとともに６０℃で乾燥し、テンター直前でのフィルム中の残留溶媒量を３０質量％とした。次いでテンタークリップで両端を把持させながら１００℃で横方向（巾方向）に１．５倍延伸した。次いで巾を保持したまま１２０℃で１０分間搬送しながら乾燥させた。この時フィルム巾が３％収縮するようにテンタークリップ巾を調節した。
【０１４８】
更に、ロール搬送させながら１１０℃で２０分間乾燥し、両表面層５μｍ、コア層６０μｍ、トータル膜厚７０μｍのセルロースエステルフィルム１（位相差フィルム）を得た。最終的なフィルムの残留溶媒量は０．２質量％であった。
【０１４９】
《セルロースエステルフィルム２の作製》：本発明
上記のセルロースエステルフィルム１の作製において、ドープＡの代わりに下記のようにして調製したドープＡ１を用い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。尚、最終的なフィルム残留溶媒量は０．２質量％であった。
【０１５０】
（ドープＡ１の調製）
セルロースエステルフィルム１のドープＡの調製において、ナフチルカルボニル基の置換度２．０、プロピオニル基の置換度０．６５、数平均分子量１５００００のセルロースアセテートナフタレートプロピオネート１００質量部の代わりに、フルオレニルカルボニル基の置換度２．０、プロピオニル基の置換度０．６５、数平均分子量１５００００のセルロースアセテートフルオレネートプロピオネート１００質量部に変更した以外は同様にしてドープＡ１を調製した。
【０１５１】
《リターデーション特性（Ｒ_０、Ｒ_ｔ）評価》
得られたセルロースエステルフィルム１、２と従来公知のセルロースエステルフィルムである、市販のトリアセチルセルロースフィルム（ＴＡＣフィルムともいう）、セルロースアセテートプロピオネートフィルム（ＣＡＰフィルムともいう）とを比較として用い、面内方向のリターデーション特性値（面内リターデーションＲ_０）、フィルムの厚み方向のリターデーション特性値（厚み方向のリターデーションＲ_ｔ）を各々評価した。
【０１５２】
ここで、リターデーション測定は、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）、厚み方向のリターデーション値（Ｒ_ｔ）を各々測定した。
【０１５３】
各セルロースエステルフィルムと置換基の結合分極率異方性とリターデーション特性の関係を下記に示す。
【０１５４】

ここで、上記の結合分極率異方性の数値は下記に示す、セルロースエステルフィルム試料の置換基の分極率異方性データを用いて求めた。
【０１５５】
以下、各試料のリターデーション特性を示す。
試料 Ｒ_０（ｎｍ） Ｒ_ｔ（ｎｍ）
１ ３５ １８５
２ ６０ ２００
ＴＡＣ １．２ ５７
ＣＡＰ ４７ １０９
１：セルロースエステルフィルム１
２：セルロースエステルフィルム２
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エステルフィルム、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）、厚み方向のリターデーション（Ｒ_ｔ）が共に増大し、光学的異方性が向上していることが判る。
【０１５６】
【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、セルロースエステルフィルムの製造方法、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]
BACKGROUND OF THE INVENTION
The present invention relates to a cellulose ester film, a method for producing a cellulose ester film, an optical compensation sheet, a polarizing plate, a retardation plate, electronic paper, and a display device.
[0002]
[Prior art]
Conventionally, a cellulose acetate film has been frequently used as a derivatized cellulose film. Cellulose acetate film is used for various photographic materials and optical materials because of its toughness and flame retardancy. The cellulose acetate film is also used as a support for typical photographic light-sensitive materials. Cellulose acetate films are also used in liquid crystal display devices.
[0003]
Conventionally known cellulose acetate films are characterized by high optical isotropy (low retardation value) compared to other polymer films, and therefore liquid crystals that require optical isotropy. In general, a cellulose acetate film is used for a protective film or a color filter of a display device, for example, a polarizing element.
[0004]
However, an optical compensation sheet (retardation film) which is an element of another liquid crystal display device, on the contrary, requires a high retardation value, but a conventionally known cellulose acetate film cannot sufficiently compensate. Furthermore, it is possible to increase the retardation value by performing a stretching treatment or the like even with a conventionally known cellulose acetate film, but since the amount of change due to stretching is very small, it is necessary to stretch fairly strongly. There is a problem that transparency, which is a characteristic of a cellulose support, is easily impaired, such as white turbidity when strengthened.
[0005]
For this purpose, synthetic polymer films having high retardation values such as polycarbonate films and polysulfone films have been used for such purposes, but separately from the optical compensation sheet made of the polymer film, on the transparent support. An optical compensation sheet provided with an optically anisotropic layer containing a discotic liquid crystal has also been proposed (see, for example, Patent Documents 1, 2, 3, and 4).
[0006]
The above 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 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, the structure is complicated, and the production process is The number of man-hours increases, and there is a problem that it tends to be expensive.
[0008]
Therefore, in this industry, development of a derivatized cellulose sheet (also referred to as a cellulose ester film) having a high retardation value has been desired for use as an optical compensation sheet.
[0009]
[Patent Document 1]
JP-A-3-9325
[0010]
[Patent Document 2]
Japanese Patent Laid-Open No. 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, a method for producing a cellulose ester film, an optical compensation sheet, a polarizing plate, a retardation plate, 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 configurations 1 to 13.
[0015]
1. A cellulose ester comprising a cellulose ester having at least one substituent A having a chemical bond A exhibiting bond polarizability anisotropy and at least one substituent B having a chemical bond B exhibiting bond polarizability anisotropy In film
The polarizabilities in the directions parallel to the chemical bond chains of the chemical bonds A and B are respectively α1a and α1b, the polarizabilities in the orthogonal directions of the chemical bond chains of the chemical bonds A and B are α2a and α2b, and the chemical bonds When A has an aromatic ring, when the polarizability in the direction perpendicular to the aromatic ring is α3a, the bond polarizability anisotropy represented by | α1a-α2a | or | α3a-α2a | × 10^-25cm³And the combined polarizability anisotropy represented by | α1b−α2b | is 50 × 10^-25cm³The cellulose ester film characterized by being less than.
[0016]
2. 2. The cellulose according to 1 above, wherein the substituent A or B has an oxycarbonyl group (—O—C (═O) —) or a carbonylimino (—C (═O) —NH—) group. Ester film.
[0017]
3. 3. The cellulose ester film as described in 1 or 2 above, wherein the substituent A has an aromatic ring.
[0018]
4). A carbonyl group that is a constituent atom group of the oxycarbonyl group or carbonylimino group of the substituent A is made to coincide with the x-axis of the three-dimensional coordinate on a three-dimensional coordinate (x-axis, y-axis, z-axis); The bonds between the atoms constituting the aromatic ring of A are arranged on the xy plane composed of the x axis and the y axis, respectively, and the z axis is perpendicular to the bond axis between the atoms. When the theoretical bond polarizability tensor of the partial structure is represented by the general formula (1), | α_yy-Α_xx| A or | α_yy-Α_zzAt least one of the bond polarizability anisotropy represented by | a is 50 × 10^-25cm³300 × 10−²⁵cm³The carbonyl group which is a constituent atom group of the oxycarbonyl group or carbonylimino group of the substituent B is matched with the x axis of the three-dimensional coordinate on the three-dimensional coordinate (x axis, y axis, z axis), The bonds between the atoms constituting the substituent B are arranged on the xy plane composed of the x axis and the y axis, respectively, and the z axis is perpendicular to the bond axis between the atoms. If the theoretical bond polarizability tensor of the partial structure is represented by the general formula (1), | α_yy-Α_xx| B or | α_yy-Α_zzAt least one of the bond polarizability anisotropies represented by | b is 50 × 10 −²⁵cm³Less than 3 × 10^-25cm³The cellulose ester film according to any one of 2 or 3 above, which is as described above.
[0019]
5. Any one of said 1-4 characterized by the substitution degree to the whole cellulose-ester molecule | numerator of each of the substituent A or the substituent B which shows the said bond polarizability anisotropy being 10%-90%. The cellulose ester film described in 1.
[0020]
6). Any one of said 1-4 whose substitution degree to the whole cellulose-ester molecule | numerator of each of the substituent A or the substituent B which shows the said bond polarizability anisotropy is 25%-85%. The cellulose ester film described in 1.
[0021]
7). In manufacturing the cellulose ester film of any one of said 1-6, it has the process of extending | stretching in the width direction of a film by the draw ratio of 2.0 times or less, The manufacturing method of the cellulose ester film characterized by the above-mentioned. .
[0022]
8). In manufacturing the cellulose ester film of any one of said 1-6, it has the process of extending | stretching in the width direction of a film by the draw ratio of 1.5 times or less, The manufacturing method of the cellulose ester film characterized by the above-mentioned. .
[0023]
9. It has the cellulose-ester film of any one of said 1-6, The optical compensation sheet | seat characterized by the above-mentioned.
[0024]
10. A polarizing plate comprising the cellulose ester film described in any one of 1 to 6 or the optical compensation sheet described in 9 above.
[0025]
11. A retardation plate using the cellulose ester film according to any one of 1 to 6 above.
[0026]
12 Electronic paper using the cellulose ester film described in any one of 1 to 6 above.
[0027]
13. The cellulose ester film according to any one of 1 to 6, the optical compensation sheet according to 9, the polarizing plate according to 10, and the retardation plate according to 11 described above. A display device characterized by using one.
[0028]
Hereinafter, the present invention will be described in detail.
As a result of various studies on the above-mentioned problems, the present inventors have found that substituents A and B containing chemical bonds A and B exhibiting specific bond polarizability anisotropy are respectively present on the molecular side as described in claim 1. It has been found that a cellulose ester film having a high retardation value can be obtained by including a cellulose ester having a chain, and further using the cellulose ester film, an optical compensation sheet having a high optical compensation capability, a polarizing plate, a retardation, and the like. It has been found that boards, electronic paper, display devices, and the like can be provided.
[0029]
《Coupled polarizability anisotropy》
Along with the bond polarizability anisotropy according to the present invention, the optical anisotropy of the cellulose ester, particularly the relationship between the retardation characteristics and the bond polarizability anisotropy will be described.
[0030]
Here, the bond polarizability anisotropy according to the present invention means that the polarizability in the direction parallel to the chemical bond chain of the chemical bond is α1, the polarizability of the chemical bond in the orthogonal direction of the chemical bond chain is α2, When the chemical bond has an aromatic ring (aromatic carbocycle, aromatic heterocycle), when the polarizability in the direction perpendicular to the aromatic carbocycle or the aromatic heterocycle is α3, | α1-α2 |, | Α3-α2 |, etc., and may be expressed by the absolute value of the difference in the bond polarizability, or the bond polarizability anisotropy on the three-dimensional coordinates (x axis, y axis, z axis). The carbonyl group, which is a constituent atom group of an oxycarbonyl group or a carbonylimino group, is made to coincide with the x-axis of the three-dimensional coordinate, and the bonds between the molecules constituting the aromatic ring are represented by the x-axis and y-axis, respectively. One that is placed on the xy plane and that is perpendicular to the bond axis between the molecules To place a z-axis represents a theoretical binding polarizability tensor of the partial structure the general formula (1), is sometimes used as an absolute value binding polarizability anisotropy of the difference of the components constituting the tensor.
[0031]
In the present invention, among the tensors, as described in claim 4, the absolute value of the bond polarizability anisotropy | α_yy-Α_xx|, | Α_yy-Α_zzA cellulose ester film having a substituent in the molecular side chain that shows a value in a specific numerical range for each of | is particularly preferably used.
[0032]
(Retardation value (R₀, R_t)): Optical anisotropy
Bond polarizability anisotropy of substituents on molecular side chains of cellulose ester and optical anisotropy exhibited by the cellulose ester, particularly in-plane retardation value (R₀), Retardation value in the thickness direction (R_tThere is a relationship as shown below.
[0033]
In-plane retardation value (R₀) Is usually represented by the following general formulas (2) and (3).
[0034]
General formula (2)
R₀= (Nx-ny) * d
The retardation in the thickness direction is represented by the following general formula (3).
[0035]
General formula (3)
R_t= ((Nx-ny) / 2-nz) * d
Here, 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 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.
[0036]
(Relationship between birefringence, orientation coefficient and bond polarizability)
Here, when the influence of crystallization can be ignored, the relational expression represented by the following general formula (4) is established.
[0037]
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 = Δ₀There is a relationship of × P. Where Δ₀Is the intrinsic birefringence inherent in the molecule, and P is the orientation coefficient of the molecule. Intrinsic birefringence refers to birefringence that develops when the material is given complete uniaxiality.
[0038]
Furthermore, Okamura et al., Introduction to Polymer Chemistry, 2nd edition, Kagaku Dojin, E. F. Gurne, J .; Appl. Phys. 25, 1232 (1954), etc.₀Is known to satisfy the relational expression represented by the following general formula (5).
[0039]
General formula (5)
Δ₀= (2π / 9) × ((n²+2)²/ N) × (ρN_A/ M) × Δα
Δα is the bond polarizability anisotropy in the molecular structural unit (monomer unit in the case of a polymer), and is defined by the difference in polarizability between the longitudinal direction of the molecule and the direction orthogonal thereto. Intrinsic birefringence Δ₀A large molecular bond, that is, a molecule having a large polarizability anisotropy Δα is strongly oriented in a certain direction (with a large orientation coefficient P), thereby exhibiting a large retardation. In addition, as is apparent from the above formula, birefringence and polarizability anisotropy can be predicted when a polymer molecule is considered in units of single molecules constituting the polymer molecule.
[0040]
On the other hand, the types of molecular polarization include electronic polarization, atomic polarization, dipole polarization, and interface polarization. However, in the visible light region, the wavelength is very short, and it is known that electronic polarization is mainly dominant. It has been. In short, the electronic polarization is caused by the bias of the electron distribution. For example, in an aromatic ring having a flat π electron cloud, the change in polarizability can be said to be large.
[0041]
In the present invention, in order to define the bond polarizability anisotropy of the substituent to be modified on the side chain of the cellulose ester molecule, the actual degree of bond due to the presence of an aromatic ring (aromatic carbocycle, aromatic heterocycle, etc.) It is necessary to grasp whether the polarizability anisotropy occurs, but calculating the bond polarizability anisotropy of the compound unit to be modified to the side chain from the above formula measures the intrinsic birefringence of the modifying compound. It is difficult and very difficult.
[0042]
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 representative method, E.I. Erman, D.M. C. Marvin, P.M. A. Irvine, P.M. J. et al. Calculations were made using the method described in Flory, Macromolecules, 15, 664 (1982).
[0043]
The actual procedure is to determine the molecular shape by conformation analysis, and the anisotropic tensor of each constituent atomic group can be obtained using the following general formula (6).
[0044]
[Expression 2]

[0045]
In the formula, [diag (α_m)_xyz] Is a diagonal matrix of the bond polarizability tensor of the constituent functional group, and φ and τ are the azimuth and polar angle with respect to the coordinate axis of the bond functional group, respectively. Δα for each functional group_xyzIs added to obtain the bond polarizability of the whole molecule. The bond polarizability data of the bond functional group is C = O. Pietrala, H .; R. Schubach, M.M. Dettenmeier, B.M. Heise, Prog. Colloid & Ploym. Sci. 71, 125, (1985), C—O, C—H bonds are described in K.A. G. Denbig, Trans Faraday Soc. , 36, 936 (1940).
[0046]
Hereinafter, as a simulation using the above method, the bond polarizability anisotropy of molecules such as DMC (dimethyl carbonate), MPC (methylphenyl carbonate), and DPC (diphenyl carbonate), and acetyloxy groups ( -O-C (= O) -CH₃), A benzoyloxy group (—O—C (═O) —C) on the side chain of the glucose molecule₆H₅) Was substituted, and the bond polarizability anisotropy of each molecular side chain was calculated.
[0047]
For example, in calculating the bond polarizability anisotropy of chemical bonds of molecules constituting dimethyl carbonate or the like, the bond polarizability anisotropy also changes depending on how the coordinate axis of the compound is taken. Therefore, with reference to the carbonyl group (C═O), the direction of the carbonyl group (C═O) is made to coincide with the x-axis and the coordinate axis is determined as shown in FIG. It represented with the said General formula (1). Further, when the methyl group portion is replaced with a phenyl group in the coordinate system as it is, as shown in FIG. 2, phenyl carbonate is obtained.
[0048]
In the present invention, as described above, α_yyAnd α_xxAbsolute value of difference from_yy-Α_xx｜ and α_yyAnd α_zzAbsolute value of difference from_yy-Α_zzIt is found that a cellulose ester film having a high retardation value can be obtained by adjusting the numerical value of the bond polarizability anisotropy value to a specific value or more, and the cellulose ester film of the present invention is It has been found that it is preferably used for optical compensation sheets, polarizing plates, retardation plates, electronic paper, and the like.
[0049]
Further, in the same manner, an acetyloxy group (CH₃In the case of having —C (═O) —O—), the case of having a benzoyloxy group in the side chain of the glucose molecule, and the bond polarizability anisotropy of the diphenyl carbonate molecule were calculated.
[0050]
The results obtained are shown below.
[0051]
[Table 1]

[0052]
However, in Table 1, Δα₀(× 10^-24)_yy-Α_xx|, Δα_T(× 10^-24)_yy-Α_zzRepresents |.
[0053]
From Table 1, it can be seen that the polarizability anisotropy increases by an order of magnitude due to the presence of an aromatic ring such as a phenyl group. From such a result, paying attention to polarizability anisotropy as a substituent for modifying the side chain, and from the viewpoint of molecular design to increase the value, including one or more aromatic rings, and tertiary On the original coordinates (x, y, z), among the partial structures showing the bond polarizability anisotropy of the substituent, the carbonyl group (C═O group) which is a polar group portion is made to coincide with the x-axis, The bonds between the molecules constituting the aromatic ring are arranged on the xy plane constituted by the x-axis and the y-axis, respectively, and the z-axis is arranged in a direction perpendicular to the bond axis between the molecules. The bond polarizability anisotropy of the substituent in the theoretical bond polarizability tensor represented by the general formula (1), that is, α_yyAnd α_xxAbsolute value of difference from_yy-Α_xx| Is 4 × 10^-24cm³Or more, more preferably, the bond polarizability anisotropy, α_yyAnd α_zzAbsolute value of difference from_yy-Α_zz| Is 6 × 10^-24cm³That's it.
[0054]
<< Substituents containing chemical bonds exhibiting bond polarizability anisotropy >>
The substituent containing a chemical bond exhibiting bond polarizability anisotropy will be described.
[0055]
The chemical bond (including molecular species) exhibiting the bond polarizability anisotropy according to the present invention is described in the quarterly review of chemical reviews and the 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., molecular species include benzene ring, toluene, p-toluene Etc., the polarizability in the direction parallel to the chemical bond chain of the chemical bond is α1, the polarizability of the chemical bond in the orthogonal direction is α2, and the chemical bond is an aromatic carbocycle or aromatic heterocycle Data having α3 as a polarizability in a direction perpendicular to the aromatic carbocyclic ring or the aromatic heterocyclic ring is cited.
[0056]
As a substituent containing a chemical bond (including molecular species) exhibiting the above bond polarizability anisotropy, a polar group is preferable. As the polar group, a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, Iodine atom, etc.), hydroxyl group, amino group, nitro group, carboxyl group, formyl group, alkoxyl group, nitrile group, ester group (-COOR, where R represents an alkyl group or aryl group), oxycarbonyl group And a substituent having (—O—C (═O) —), a substituent having a carbonylimino (—C (═O) —NH—) group, and the like.
[0057]
Among them, an ester group, a substituent having an oxycarbonyl group (—O—C (═O) —), a substituent having a carbonylimino group (—C (═O) —NH—) and the like are preferable.
[0058]
(Groups used as Substituent A and Substituent B)
The bond polarizability anisotropy of the substituent A is 50 × 10^-25cm³300 × 10 or more^-25cm³The following are preferable, and specific examples of imparting such bond polarizability anisotropy to the substituent A include an alkyl group (especially a long-chain alkyl group having 18 carbon atoms, etc.), an aryl group (Phenyl group, naphthyl group, etc.), acyl groups containing aromatic rings (for example, benzoyl group, toluoyl group, salicyloyl group, cinnamoyl group, naphthoyl group, phthaloyl group, etc.).
[0059]
The alkyl group and aryl group may be unsubstituted or may have a substituent. As the substituent, a halogen atom, a sulfur atom or a group having them may be used, but is particularly preferably used. Is an unsubstituted aryl group.
[0060]
The bond polarizability anisotropy of the substituent B is 3 × 10^-25cm³50 × 10 or more^-25cm³Preferred examples of the substituent B satisfying these are acyloxy groups (for example, acetyloxy group, propionyloxy group, butyryloxy group, valeryloxy group, palmitoyloxy group, stearoyloxy group, oleoyloxy group, Norbornylcarbonyloxy group, etc.). Further, in order for the substituent B to exhibit the above bond polarizability anisotropy, it is preferable not to include an aromatic ring.
[0061]
Substituent A has a polarizability anisotropy of 50 × 10^-25cm³Therefore, when this is modified to the side chain of the cellulose ester molecule, the polarizability anisotropy of the cellulose main chain (approximately 30 to 40 × 10^-25cm³It can be expected to have a negative uniaxial effect. On the other hand, in the substituent B, the polarizability anisotropy is 50 × 10 5.^-25cm³Therefore, the polarizability anisotropy of the cellulose main chain is smaller than that, and a positive uniaxial effect can be expected. By effectively utilizing both effects, a more excellent optical film can be obtained.
[0062]
<Effect of polar group>
In the present invention, the reason why the above polar group is preferable is that when a cellulose acetate, cellulose propionate or the like is stretched at a low magnification during film production (particularly during film formation), as described later, Although it becomes clear that the polar group part preferentially changes the orientation, the mechanism by which only the COO group is oriented is unknown, but the present inventors presume that hydrogen bonds are probably involved. Yes.
[0063]
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 is selected. It is preferable to arrange in the side chain of the ester molecule, and more preferably, the substituent has an aromatic ring having a large bond polarizability anisotropy.
[0064]
《Aromatic ring》
Examples of the aromatic ring according to the present invention include aromatic carbocyclic groups (for example, benzene ring, naphthalene ring, etc.) and aromatic heterocyclic groups (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.
[0065]
Hereinafter, although the specific example of the substituent containing the chemical bond which shows bond polarizability anisotropy based on this invention is shown, this invention is not limited to these.
[0066]
[Chemical 1]

[0067]
《Substitution degree of cellulose ester molecule side chain》
When placing a substituent containing a chemical bond exhibiting bond polarizability anisotropy on the side chain of the cellulose ester molecule used for the production of the cellulose ester film of the present invention, a sufficient retardation value improving effect as a substituent effect The degree of substitution with the whole cellulose ester molecule of the present invention is preferably in the range of 10% to 90%, more preferably in the range of 25% to 85%. It is.
[0068]
Here, the substitution degree of 100% means that three hydrogen atoms per glucose basic unit of cellulose (polyhydric alcohol having three hydroxyl groups (hydroxyl groups) per glucose basic unit) are substituents (for example, acyl groups). Etc.) is shown.
[0069]
The degree of substitution is expressed by a method known to those skilled in the art (for example, in the case of cellulose acetate or the like, the degree of acetylation, the acetyl value or the acetic acid value) or the mol% of the hydroxyl group reacted.
[0070]
<Stretching process of cellulose film>
As shown in Table 1, an aromatic ring having high polarizability anisotropy in the side chain of the cellulose ester molecule or an oxycarbonyl group (—O—C (= O)-) or a substituent having a carbonylimino (—C (═O) —NH—) group gives a high intrinsic birefringence and a high retardation value (high optical anisotropy) In order to obtain a cellulose ester film or an optical compensation sheet having a large optical anisotropy, that is, a retardation value and exhibiting a sufficient optical compensation function, it will be described later. The stretching treatment is preferably performed during the production of the cellulose ester film (also referred to as film formation).
[0071]
《Solution casting film formation》
As a method for producing a cellulose ester film of the present invention, cellulose ester is dissolved in a solvent, the prepared dope solution is cast on a support, a film is formed, the resulting film is peeled off from the support, and then tension is applied. A solution casting film forming method is preferable in which the film is dried while being conveyed in the drying zone.
[0072]
Solution casting film forming method and endless metal belt (for example, stainless steel belt) for infinite transfer or metal support for casting such as a rotating metal drum (for example, a drum whose surface is chrome-plated with cast iron) The dope (cellulose ester solution) is cast (casting) from a pressure die onto the support), and the web (dope film) on the support is peeled off from the support and dried. To do.
[0073]
In the present invention, a film obtained by peeling off within 60 seconds after casting and drying while applying tension is particularly preferred because the metal oxide layer formed thereon is difficult to crack.
[0074]
The peel tension at the time of peeling from the casting metal support is preferably 300 N / m or less, the transport tension is preferably 300 N / m or less, more preferably 250 N / m or less, More preferably, it is 100 N / m-200 N / m.
[0075]
In the drying process, after peeling from the metal support, the optical film having the metal oxide layer formed by the method of the present invention can be dried while applying tension in the width direction or the longitudinal direction with a tenter, and the durability of the optical film is excellent. preferable. The application of tension in the width direction or the longitudinal direction is preferably a biaxial stretching method in which tension is applied not only in one direction but also in the width direction and the longitudinal direction. Alternatively, it is also preferable to stretch the film once or more when it has a high residual solvent amount of 10% by mass or more and a low residual solvent amount of less than 10% by mass. It is preferable to adjust so as to relieve the strain generated during drying by stretching twice.
[0076]
(Stretching process using a tenter)
In the web drying step, the method of stretching the web is not particularly limited, for example, a method of stretching the circumferential speed difference between a plurality of rolls, using the circumferential speed difference between the rolls in the longitudinal direction, The entire drying process or a part of the process as shown in Japanese Patent Application Laid-Open No. 62-46625 is held in a width direction with clips in the width direction, and the width ends of the web are held with clips and pins, etc. A method (tenter method) in which drying is also performed is preferable.
[0077]
When performing a stretching process using a tenter method, cellulose using a tenter is used from the viewpoint of effectively suppressing changes in physical properties such as hardening and becoming hard and brittle, and preventing a decrease in transparency due to cloudiness of the cellulose ester film after the stretching process. The stretching ratio of the ester film in the MD direction (also referred to as Machine Direction direction or conveyance direction) or TD direction (also referred to as Transverse Directon direction, width direction or width direction) is preferably 2.0 times or less, and more preferably. Is 1.5 times or less, and preferably 1.01 times 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 maximum in the plane. Moreover, it is preferable that the amount of residual solvent in the case of extending | stretching is 3 mass%-30 mass%. The amount of residual solvent and the solvent used for dope preparation will be described later.
[0078]
<Measurement of amount of residual solvent in web>
In the present invention, the residual solvent amount of the web is defined by the following formula.
[0079]
Residual solvent amount (%) = [(mass before heat treatment of web−mass after heat treatment of web) / (mass after heat treatment of web)] × 100
The heat treatment for measuring the residual solvent amount was performed at 110 ° C. for 3 hours.
[0080]
(Solvent for dope solution preparation)
Examples of the solvent used for preparing the dope solution include chlorinated solvents and non-chlorinated solvents.
[0081]
Chlorinated solvents 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, 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, tetramethylene chlorobromide, 1,1,1-trichloroethane, 1,1,2-trichloroethane, and trichloroethylene.
[0082]
Examples of non-chlorine solvents include ethers having 2 to 12 carbon atoms (for example, diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, 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), esters having 2 to 12 carbon atoms (for example, methyl formate, ethyl formate) Propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate). Moreover, 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.
[0083]
《Stretching treatment and orientation behavior of cellulose ester film》
The effect of the stretching treatment giving 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 deflection ATR method).
[0084]
For example, a cellulose ester sheet (for example, a TAC (triacetyl cellulose) sheet, a CAP (cellulose acetate propionate) sheet, etc.) was slightly stretched (stretch ratio ≦ 200%, stretch ratio is 2.0 times or less). In such a case, in such a low magnification stretching, there is almost no change in the orientation of the cellulose skeleton (main chain) in the plane, and only the acetyl group portion of the side chain causes an orientation change, and further MD (machine direction). When stretched in the direction, it was found that the orientation of the side chain tends to be oriented in a direction perpendicular thereto.
[0085]
In low-strength stretching (also called microstretching), the mechanism by which only the COO groups in the side chain are mainly oriented in this way is unknown, but there is a relationship between hydrogen bonds formed by COO groups and nearby substituents. Expected to be.
[0086]
Therefore, in setting the stretching conditions for producing a cellulose ester film having a high retardation value using cellulose ester, the surface of the cellulose ester molecular skeleton, which is the main chain, at a stretching ratio of 2.0 times or less Since the orientation change in the inside is hardly recognized, it is assigned to the main chain of the cellulose ester molecule and is 1125 cm.^-1~ 1145cm^-1In-plane infrared dichroic ratio f in the absorption of an ether bond having a maximum absorption in the vicinity_xyHowever, it is preferable to adjust so that it may exceed -0.05 and may be less than 0.1, More preferably, it may adjust in the range exceeding -0.025 and less than 0.05.
[0087]
Here, infrared two-color ratio f_xyRepresents an orientation coefficient in the 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.
[0088]
The orientation evaluation method using infrared spectroscopy is 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.
[0089]
In the measurement of infrared absorption, it is most ideal to measure with light polarized independently in the x, y, and z axis directions, but in practice, measurement in the thickness direction z axis is particularly difficult.
[0090]
In the polarization ATR method, there are four directions in the x direction, the y direction, the xz direction (including both x-axis and z-axis component absorption components), and the yz direction (including both the y-axis and z-axis component absorption components). A procedure for measuring an absorption spectrum and calculating absorption coefficients in the x, y, and z directions from the measurement data is taken.
[0091]
FIG. 3 shows four basic optical arrangements in the 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 this (TD direction: transverse direction direction) is y. , Perpendicularly polarized light (s-polarized light; TE: transversal magnetic) and TM (transverse magnetic) are incident on a plane composed of incident light and reflected light using a wire grid polarizer. To do. At this time, the x-axis is aligned with the direction of TE polarization (TEx, TMx). Next, the sample is rotated by 90 °, that is, the x-axis direction and the y-axis direction are switched, and the measurement is similarly performed (TEy, TMy). The four absorption spectra obtained here are respectively A_TEx, A_TMx, A_TEy, A_TMyThen, the relationship represented by the following general formula (7) is satisfied.
[0092]
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 that depend on the incident angle and the refractive index of the sample. A. Flumoy, and W.C. J. et al. Schaffers, Spectrochimica Acta, 22, 5 (1966), K.A. Palm, Vib. Spectrosc. , 6, 185, (1994), the following general formula (8) is obtained.
[0093]
[Equation 3]

[0094]
Where p = (refractive index of the 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).
[0095]
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
From the above, the infrared two-color ratio is represented by the following general formula (10).
[0096]
General formula (10)
D_xy= K_x/ K_y
D_xz= K_x/ K_z
Where D_xy, D_xzAre all spatially isotropic non-oriented samples and all take a value of 1.00. This number increases as the orientation becomes stronger. As another evaluation formula, P.P. A. From Floymoy, and W. J. et al. The uniaxial orientation factor (f) disclosed in Schaffers, Spectrochimica Acta, 22, 5 (1966)._xy, F_xz) And is represented by the following general formula (11).
[0097]
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 orientation coefficient in the in-plane direction, and f_xzIndicates the orientation coefficient in the film thickness direction. Where D₀= Cot²(Δ), where δ is the angle formed by the transition moment vector formed by molecular vibration and the molecular axis. In order to calculate this precisely, it is necessary to examine the direction of the moment of molecular vibration, but it is usually sufficient to select a vibration mode parallel to the molecular axis and a mode perpendicular to the molecular axis, and calculate these as 0 ° and 90 °, respectively. Information about orientation can be obtained. Theoretically, the orientation coefficient is 0 in the case of non-orientation, 1.0 in the case of being completely oriented in the observation direction, and -0.5 in the case of being orthogonal to the observation direction.
[0098]
In the cellulose ester film of the present invention, the O—C—C stretching vibration (1035 cm) of the cellulose ester molecular skeleton is obtained.^-1± 10cm^-1Is the vibration mode (δ = 0 degree) parallel to the molecular axis, and the side chain ester group (C═O, CH₃, C-C-O, each 1713 cm^-1± 10cm^-1, 1367cm^-1± 10cm^-1, 1214cm^-1± 10cm^-1) As a vibration mode (δ = 90 degrees) in a direction perpendicular to the molecular axis. Even in an actual molecular model (document), the above functional groups were in the relationship as described above.
[0099]
Baseline is 1510 cm for C-C-O^-1~ 1530cm^-1Minimum value between and 930cm^-1~ 1000cm^-1A straight line connecting the minimum values between them, and for C = O, 1800 cm^-1~ 1850cm^-1Minimum value between and 1510cm^-1~ 1530cm^-1A straight line connecting the minimum values between them was used.
[0100]
<How to determine the peak>
Describe how to determine the peak.
[0101]
The measurement of the infrared dichroic ratio can be performed by using attenuated total reflection infrared spectroscopy (ATR-IR method). The calculation method is described in J. K. P. Hobbs, C.I. S. P. Sung (JP P. Hobbs, C. S. P. Sung, K. Krishan, and, S. Hill, Macromolecules, 16, 193 (1983)).
[0102]
<< How to find the infrared dichroic ratio >>
The method for obtaining the infrared dichroic ratio is a peak derived from the CO control stretching vibration (1150 cm) in the cellulose ester molecule.^-1-1025cm^-1Measure the intensity of the strongest peak that appears between. The peak intensity is the wave number of the peak top (xcm^-1And xcm^-1~ X + 50cm^-1Xcm^-1~ X-50cm^-1The point with the lowest absorbance is connected, and this is used as the baseline, and the peak intensity is measured and determined. First, light is incident parallel to the longitudinal direction, and the absorbance when the polarized light is perpendicular to the incident surface (A_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 and A_TEyAnd A_TMyAnd the infrared two-color ratio f according to 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.
[0103]
Specifically, the measurement is performed under the measurement conditions of the following polarization ATR method.
Measuring apparatus: Magna 860 (manufactured by Nicole)
Single reflection ATR equipment: 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 1.477 for CAP (cellulose acetate propionate) and 1.482 for TAC (triacetyl cellulose), for example. The prism (germanium) was 4.00. Vertically polarized light and horizontally polarized light were incident on an incident surface composed of light incident on the sample surface and reflected light using a wire grid polarizer, and an FTIR-ATR spectrum was measured. The above measurement was performed by setting the MD direction as the x axis, the vertical direction (width direction TD) as the y axis, and the thickness direction as the z axis.
[0104]
When obtaining the orientation coefficient by this method, it is important that the sample surface and the measuring prism surface are in close contact with each other. For this reason, it is desirable that the ATR device used here is a commercially available or improved high voltage ATR device that can withstand high contact pressure.
[0105]
"Additive"
For the purpose of improving the storage stability, dimensional stability, weather resistance, etc. 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 added as desired. .
[0106]
(Plasticizer)
Examples of the plasticizer include phosphorous such as triphenyl phosphate, tricresyl phosphate, cresyl phenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, trinaphthyl phosphate, trixylyl phosphate, tris ortho-biphenyl phosphate, etc. Acid ester plasticizers, diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, and other phthalate ester plasticizers, triacetin, tributyrin, butyl phthalyl butyl glycolate, Ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate, butyl phthalyl butyl glycol Glycolic acid ester based plasticizers such as over bets, and the like. Of these, phthalate ester and glycolate ester plasticizers are preferred because they hardly cause hydrolysis of cellulose esters. Further, it is preferable that a plasticizer having a freezing point of 20 ° C. or lower is included. Examples of such plasticizers 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. It is done.
[0107]
In particular, 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, it is 1 mmHg or less. Specific examples include non-volatile phosphate esters described in JP-A-6-501040. For example, arylene bis (diaryl phosphate) esters are preferred.
[0108]
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 to the mass of the whole cellulose ester film, from the viewpoint of dimensional stability. It is in the range of 15% by mass.
[0109]
(UV absorber)
An ultraviolet absorber can be added to the cellulose ester film of the present invention as necessary.
[0110]
As the ultraviolet absorber, those excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less and having 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.
[0111]
Specific examples of the ultraviolet absorber used in the present invention include, for example, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex salts compounds, triazine compounds, benzoate compounds. Compound etc. are mentioned. Further, a polymeric ultraviolet absorber described in JP-A-6-148430 and a polymeric ultraviolet absorber disclosed in JP-A-2002-31715 are preferably used.
[0112]
As the benzotriazole ultraviolet absorber, a compound represented by the following general formula [A] is preferably used.
[0113]
[Chemical formula 2]

[0114]
Where R₁, R₂, R₃, R₄And R₅May be the same or different, and may be 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 dialkylamino group Represents an acylamino group or a 5- to 6-membered heterocyclic group, R₄And R₅May be closed to form a 5-6 membered carbocyclic ring.
[0115]
Moreover, these groups described above may have an arbitrary substituent.
Although the specific example of the ultraviolet absorber shown by general formula [A] is given to the following, it is not limited to these.
[0116]
UV-1: 2- (2'-hydroxy-5'-methylphenyl) benzotriazole
UV-2: 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) benzotriazole
UV-3: 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) benzotriazole
UV-4: 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5-chlorobenzotriazole
UV-5: 2- (2′-hydroxy-3 ′-(3 ″, 4 ″, 5 ″, 6 ″ -tetrahydrophthalimidomethyl) -5′-methylphenyl) benzotriazole
UV-6: 2,2-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol)
UV-7: 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole
UV-8: 2- (2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol (TINUVIN 171 from Ciba)
UV-9: Octyl-3- [3-tert-butyl-4-hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl- Mixture of 4-hydroxy-5- (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate (TINUVIN 109, manufactured by Ciba)
In the present invention, as the benzophenone ultraviolet absorber, a compound represented by the following general formula [B] is preferably used.
[0117]
[Chemical Formula 3]

[0118]
In the formula, Y represents a hydrogen atom, a halogen atom or an alkyl group, an alkenyl group, an alkoxy group, and a phenyl group, and these alkyl group, alkenyl group, and phenyl group may have a substituent. A is a hydrogen atom, an alkyl group, an alkenyl group, a phenyl group, a cycloalkyl group, an alkylcarbonyl group, an alkylsulfonyl group, or —CO (NH)._n-1-D group is represented, D represents the alkyl group, the alkenyl group, or the phenyl group which may have a substituent. m and n represent 1 or 2.
[0119]
In the above, the alkyl group represents, for example, a linear or branched aliphatic group having up to 24 carbon atoms, the alkoxy group has, for example, an alkoxy group having up to 18 carbon atoms, and the alkenyl group has, for example, 16 carbon atoms. An alkenyl group up to, for example, an allyl group, a 2-butenyl group, or the like. In addition, as a substituent that may be substituted with an alkyl group, an alkenyl group, or a phenyl group, a halogen atom such as a chlorine atom, a bromine atom, or a fluorine atom, a hydroxyl group, a phenyl group, (this phenyl group is an alkyl group or A halogen atom or the like may be substituted).
[0120]
Specific examples of the benzophenone-based compound represented by the general formula [B] are shown below, but are not limited thereto.
[0121]
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, TINUVIN O 120, UVITEX O ) And the like can be used as appropriate.
[0122]
The ultraviolet absorber described above preferably used in the present invention is preferably a benzotriazole-based ultraviolet absorber or a benzophenone-based ultraviolet absorber, which is highly transparent and excellent in the effect of preventing the deterioration of a polarizing plate or a liquid crystal element, and unnecessary coloring. A benzotriazole-based ultraviolet absorber with a lower content is particularly preferably used.
[0123]
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, and more preferably, based on the whole cellulose ester film. It is preferable to add 1% by mass to 5% by mass.
[0124]
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 depending on production conditions, use conditions, and the like.
[0125]
(Matting agent)
Fine particles such as a matting agent can be added to the cellulose ester film of the present invention in order to impart slipperiness. The fine particles include inorganic compound fine particles and organic compound fine particles.
[0126]
Inorganic compounds include silicon-containing compounds, silicon dioxide, aluminum oxide, zirconium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, calcium phosphate, etc. More preferred is an inorganic compound containing silicon or zirconium oxide, and silicon dioxide is particularly preferably used.
[0127]
As the silicon dioxide fine particles, for example, commercially available products such as Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (manufactured by Nippon Aerosil Co., Ltd.) can be used.
[0128]
As the fine particles of zirconium oxide, for example, commercially available products such as Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) can be used.
[0129]
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.
[0130]
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 (above, manufactured by Toshiba Silicones Co., Ltd.) Commercial products having a trade name such as can be used.
[0131]
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 keeping the haze low.
[0132]
The primary average particle diameter of the fine particles according to the present invention is measured by observing particles with a transmission electron microscope (magnification of 500,000 to 2,000,000 times), observing 100 particles, and using the average value, the primary average particle size is measured. The diameter.
[0133]
These fine particles can be added by kneading by a conventional method. Particularly preferably, the fine particles dispersed in a solvent in advance are mixed with a cellulose ester and / or a plasticizer and / or an ultraviolet absorber, and then the solvent is added. It is preferable that the solid is made to be volatilized and used in the process of producing the cellulose ester melt in that a uniform melt is obtained.
[0134]
The above cellulose ester film, optical compensation sheet and the like are, for example, U.S. Pat. Nos. 2,492,978, 2,739,070, 2,739,069, and second. No. 4,492,977, No. 2,336,310, No. 2,367,603, No. 2,607,704, British Patent No. 64,071. No. 735,892, No. 45-9074, No. 49-4554, No. 49-5614, No. 60-27562, No. 61-39890, No. 62-4208. The film can be formed with reference to the method described in the publication.
[0135]
In addition, anti-coloring agents, antioxidants, crystal nucleating agents, slipping agents, stabilizers, anti-blocking agents, UV absorbers, viscosity modifiers, antifoaming agents, clearing agents, antistatic agents, pH adjusting agents, dyes, A pigment or the like may be added.
[0136]
<Polarizing plate, retardation plate>
The polarizing plate of the present invention will be described.
[0137]
The cellulose ester film of the present invention and the optical compensation sheet of the present invention are particularly useful as a polarizing plate protective film, and a polarizing plate can be produced by a known method using these.
[0138]
The polarizing plate and the display device having the optical film or the optical compensation sheet of the present invention are extremely excellent in visibility, and can provide excellent visibility even in a harsh environment.
[0139]
<< Display element, electronic paper >>
Although it does not specifically limit as a cellulose ester film of this invention, an optical compensation sheet using the same, etc., It can apply preferably to the liquid crystal display element which has a backlight, a liquid crystal display device, etc. Moreover, a touch panel, the display element which bends flexibly It can also be applied to electronic paper and the like.
[0140]
<Display device>
The display device of the present invention will be described.
[0141]
Further, the optical film of the present invention is preferably used in a reflection type, a transmission type, a semi-transmission type liquid crystal display device or a liquid crystal display device of various driving systems such as a TN type, STN type, OCB type, HAN type, VA type, IPS type and the like. And is preferably used for various display devices such as a plasma display, an organic EL display, and an inorganic EL display.
[0142]
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. It is preferably used for a plasma display front filter and the like. It is particularly useful for an antireflection film for forming a plurality of metal oxide layers.
[0143]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these.
[0144]
Example 1
<< Preparation of Cellulose Ester Film 1 >>: Present Invention
Cellulose ester film 1 was produced by a commercially available casting film forming method using dope A prepared as described below.
[0145]
(Preparation of dope A)
As the dope A, substitution degree of naphthylcarbonyl group to hydrogen atoms of three hydroxyl groups per glucose unit of cellulose molecule is 2.0 (2.0 / 3.0 × 100 = 66.7% in% notation), propionyl group Of cellulose acetate naphthalate propionate having a number average molecular weight of 150,000, 8 parts by mass of triphenyl phosphate, ethyl phthalyl ethyl glycolate 2 2 parts by mass of 2- (2'-hydroxy-3,5'-di-t-butylphenyl) -5-chlorobenzotriazole, 2 parts by mass of 2-hydroxy-4-benzyloxybenzophenone, 300 parts by mass of methylene chloride And 26 parts by mass of ethanol are put into a pressure sealed container, heated to 80 ° C., and the pressure in the container is set to 2 atm. While to obtain a dope to completely dissolve the cellulose acetate naphthalate propionate. The solution was Azumi Filter Paper No. After filtering using 244, the dope was lowered to 35 ° C. and allowed to stand overnight to degas the dope.
[0146]
(Film forming process)
The above-mentioned dope A was cast on a stainless steel belt from a co-casting die of a commercially available casting film forming apparatus to form a dope film having a single layer structure. After contacting with hot water from the back of the stainless steel belt and drying on a stainless steel belt controlled to 35 ° C. for 1 minute, and then holding the back of the stainless steel belt with 15 ° C. cold water for 10 seconds, The dried film was peeled off. In addition, 60 degreeC warm air was flowed in parallel with the conveyance direction from the surface of the stainless steel belt. Moreover, the amount of residual solvent in the film at the time of peeling was 100 mass%.
[0147]
Next, the peeled film was conveyed while being wound around a roll and dried at 60 ° C., and the amount of residual solvent in the film immediately before the tenter was 30% by mass. Next, the film was stretched 1.5 times in the transverse direction (width direction) at 100 ° C. while holding both ends with a tenter clip. Next, it was dried while being conveyed at 120 ° C. for 10 minutes while maintaining the width. At this time, the tenter clip width was adjusted so that the film width contracted by 3%.
[0148]
Further, the film was dried at 110 ° C. for 20 minutes while being conveyed to obtain a cellulose ester film 1 (retardation film) having a surface layer of 5 μm, a core layer of 60 μm, and a total film thickness of 70 μm. The amount of residual solvent in the final film was 0.2% by mass.
[0149]
<< Production of Cellulose Ester Film 2 >>
Cellulose ester film 2 was prepared in the same manner except that dope A1 prepared as described below was used instead of dope A in the preparation of cellulose ester film 1 described above. The final film residual solvent amount was 0.2% by mass.
[0150]
(Preparation of dope A1)
In the preparation of the dope A of the cellulose ester film 1, instead of 100 parts by mass of cellulose acetate naphthalate propionate having a naphthylcarbonyl group substitution degree of 2.0, a propionyl group substitution degree of 0.65 and a number average molecular weight of 150,000, Dope A1 was prepared in the same manner except that it was changed to 100 parts by mass of cellulose acetate fluorinate propionate having an oleenylcarbonyl group substitution degree of 2.0, a propionyl group substitution degree of 0.65 and a number average molecular weight of 150,000.
[0151]
<< Retardation characteristics (R₀, R_t) Evaluation >>
Using the obtained cellulose ester films 1 and 2 and a conventionally known cellulose ester film, a commercially available triacetyl cellulose film (also referred to as a TAC film), a cellulose acetate propionate film (also referred to as a CAP film) as a comparison, In-plane retardation characteristic value (in-plane retardation R₀), Retardation characteristic value in the thickness direction of the film (retardation R in the thickness direction)_t) Was evaluated.
[0152]
Here, the retardation measurement is performed by using an ellipsometer (M-150, manufactured by JASCO Corporation) and an in-plane retardation value (R) at a wavelength of 550 nm.₀), Retardation value in the thickness direction (R_t) Were measured.
[0153]
The relationship between the bond polarizability anisotropy of each cellulose ester film and the substituent and the retardation property is shown below.
[0154]

Here, the numerical value of the above bond polarizability anisotropy was obtained using the polarizability anisotropy data of the substituent of the cellulose ester film sample shown below.
[0155]
Hereafter, the retardation characteristic of each sample is shown.
Sample R₀(Nm) R_t(Nm)
1 35 185
2 60 200
TAC 1.2 57
CAP 47 109
1: Cellulose ester film 1
2: Cellulose ester film 2
From the above, the cellulose ester films 1 and 2 of the present invention have an in-plane retardation (R) as compared with comparative films (triacetyl cellulose ester film and cellulose acetate propionate film).₀), Retardation in the thickness direction (R_t) Both increase and the optical anisotropy is improved.
[0156]
【The invention's effect】
According to the present invention, a cellulose ester film having a high retardation value, a method for producing a cellulose ester film, an optical compensation sheet, a polarizing plate, a retardation plate, electronic paper, and a display device can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing the setting of coordinate axes when calculating the bond polarizability anisotropy.
FIG. 2 is a schematic diagram showing the setting of coordinate axes when calculating the bond polarizability anisotropy.
FIG. 3 is a schematic diagram showing an example of an optical arrangement at the time of measuring polarized ATR.

Claims (13)

A cellulose ester comprising a cellulose ester having at least one substituent A having a chemical bond A exhibiting bond polarizability anisotropy and at least one substituent B having a chemical bond B exhibiting bond polarizability anisotropy In film
The polarizabilities in the directions parallel to the chemical bond chains of the chemical bonds A and B are respectively α1a and α1b, the polarizabilities in the orthogonal directions of the chemical bond chains of the chemical bonds A and B are α2a and α2b, and the chemical bonds When A has an aromatic ring, when the polarizability in the direction perpendicular to the aromatic ring is α3a, the bond polarizability anisotropy represented by | α1a-α2a | or | α3a-α2a | × is at ¹⁰ -25 cm ³ or more, and, | cellulose ester film bond polarizability anisotropy represented by is equal to or less than ^{50 × 10 -25 cm 3 | α1b} -α2b. The substituent A or B has an oxycarbonyl group (—O—C (═O) —) or a carbonylimino (—C (═O) —NH—) group. Cellulose ester film. The cellulose ester film according to claim 1, wherein the substituent A has an aromatic ring. A carbonyl group that is a constituent atom group of the oxycarbonyl group or carbonylimino group of the substituent A is made to coincide with the x-axis of the three-dimensional coordinate on a three-dimensional coordinate (x-axis, y-axis, z-axis); The bonds between the atoms constituting the aromatic ring of A are arranged on the xy plane composed of the x axis and the y axis, respectively, and the z axis is perpendicular to the bond axis between the atoms. When the theoretical bond polarizability tensor of the partial structure is represented by the following general formula (1), the bond polarizability anisotropy represented by | α _yy −α _xx | a or | α _yy −α _zz | a At least one of the properties is 50 × 10 ⁻²⁵ cm ³ or more and 300 × 10 ⁻²⁵ cm ³ or less, and the carbonyl group that is a constituent atom group of the oxycarbonyl group or the carbonylimino group of the substituent B is represented in three-dimensional coordinates ( x axis, y axis, z axis) The bonds between the atoms constituting the substituent B are arranged on the xy plane composed of the x-axis and the y-axis, respectively, so as to coincide with the x-axis of the three-dimensional coordinates, and the bond axes between the atoms When the z axis is arranged in a direction perpendicular to the structure and the theoretical bond polarizability tensor of the partial structure is represented by the following general formula (1), | α _yy −α _xx | b or | α _yy −α _zz | b ^{4. The method according} to claim 2, wherein at least one of the bond polarizability anisotropy represented by the ^{formula is} less than 50 × 10 ⁻²⁵ cm ³ and 3 × 10 ⁻²⁵ cm ³ or more. The cellulose ester film as described.

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 The coupling polarizability is represented, and α _zx , α _zy , and α _zz represent the coupling polarizabilities of the zx component, the zy component, and the zz component, respectively. ] The degree of substitution of the substituent A or the substituent B exhibiting the bond polarizability anisotropy with respect to the entire cellulose ester molecule is 10% to 90%. The cellulose ester film according to item. The degree of substitution of each of the substituent A or the substituent B exhibiting the bond polarizability anisotropy with respect to the whole cellulose ester molecule is 25% to 85%. The cellulose ester film according to item. When manufacturing the cellulose-ester film of any one of Claims 1-6, it has the process extended | stretched in the width direction of a film by the draw ratio of 2.0 times or less, The manufacture of the cellulose-ester film characterized by the above-mentioned. Method. When manufacturing the cellulose-ester film of any one of Claims 1-6, it has the process of extending | stretching in the width direction of a film by the draw ratio of 1.5 times or less, The manufacture of the cellulose-ester film characterized by the above-mentioned. Method. An optical compensation sheet comprising the cellulose ester film according to claim 1. A polarizing plate comprising the cellulose ester film according to claim 1 or the optical compensation sheet according to claim 9. A phase difference plate using the cellulose ester film according to claim 1. An electronic paper comprising the cellulose ester film according to any one of claims 1 to 6. A cellulose ester film according to any one of claims 1 to 6, an optical compensation sheet according to claim 9, a polarizing plate according to claim 10, and a retardation plate according to claim 11 are selected. A display device using at least one of the above.

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