1332090 ^ 九、發明說明： 【發明所屬之技術領域】 本發明係關於一種醯化纖維素薄膜及其製法，尤其是關 於一種醯化纖維素薄膜及其製法，其係用作爲構成偏光濾 光片（polarizing filter)之偏光膜且其係用於光學補償薄 膜、液晶顯示裝置等。 【先前技術】 醯化纖維素薄膜具有透明性、適當的水蒸氣透氣性和高 機械強度。醯化纖維素薄膜之尺寸穩定性（dimensional resistance)並不會太依賴濕度和溫度。因此，醯化纖維素 薄膜廣泛地用作爲光學材料之基體材料。關於醯化纖維素 薄膜之製法，溶液流延法係將一種製自聚合物和溶劑之摻 雜劑（dope )以流延模頭流延在基材上，且在乾燥步驟中 加以乾燥以形成薄膜。 醯化纖維素薄膜也可用作爲一種構成液晶顯示裝置之偏 光濾光片的保護膜。偏光濾光片通常是由聚乙烯醇所構成 的偏光膜所構成，且醯化纖維素薄膜係黏合到偏光膜之一 或兩表面上。因爲聚乙烯醇是親水性聚合物，聚乙烯醇薄 膜之薄膜表面具有優良的親水性特性。然而，醯化纖維素 薄膜之表面具有疏水性特性。有鑒於此，聚乙烯醇薄膜和 醯化纖維素薄膜之至少一薄膜表面的狀況是加以改質，以 將聚乙烯醇薄膜和醯化纖維素薄膜黏合。 茲就薄膜之表面改質而言，醯化纖維素薄膜之薄膜表面 通常是加以皂化。關於主要的皂化處理，一種方法是將鹼 1332090 性溶液塗佈或噴霧在薄膜表面上，一種方法是將醯化纖維 素薄膜浸漬入鹼性溶液中（參閱日本國專利公開申請案第 200 1 - 3 1 8,22 8 號）。 再者，醯化纖維素通常是從木材紙漿（wood pulp)、棉 籽絨（cotton linter)、或其類似物所製得。在醯化緣維素 之慣用的製法中，將木材紙漿或棉籽絨以醋酸或醋酸酐加 以處理。因此，可獲得醢化度（degree of acylation)爲3 之纖維素三醋酸酯。醋酸酐是用作爲酯化劑，因此硫酸是 用作爲觸媒。殘留之作爲觸媒的硫酸是有效地用於所獲得 纖維素三醋酸酯之皂化和熟成，以控制醯化度。因此，可 獲得標的纖維素醋酸酯。在此情況下，係添加鈣化合物及 其類似物以中和過量之數種酸。 日本國專利公開申請案第2002 - 192,541號教導醯化纖 維素薄膜含有數種化合物以改善塑化性（plastication )及 賦予光學性質。該等化合物不僅在醯化纖維素薄膜，而且 在數種光學用薄膜中經常是需要的，以進一歩提高品質。 然而，在任何一種用以改質醯化纖維素薄膜之表面的皂 化處理之方法中，其在溶液流延步驟後之製造設備是極大 且無法連續式配置。因此，將在溶液流延法所製得之醯化 纖維素薄膜加以捲取，然後設置在皂化之系統中。然後， 將醯化纖維素薄膜退繞，以實施皂化。在此情況下，製造 步驟之數量增加一個而變得較大，其係會妨礙到生產率之 提高及成本之降低。再者，皂化經常會導致薄膜之皺紋和 不均勻性，且薄膜之透明性變得較低。 1332090 上述醯化纖維素之親水性特性是視醯化度（平均値）而 定。當平均醯化度是低時，在相同莫耳數之醯化纖維素中 所含有之羥基的數目變大。有鑒於此，平均醯化度較佳爲 低，以使得親水性特性較高。然而，當平均醯化度是低時 ，水蒸氣透氣性、薄膜之尺寸穩定性、易剝離性及其類似 性質變得較低，且醯化纖維素並不適合於實務應用。 欲能使得薄膜之品質較高所添加之數種化合物顯示與醯 化纖維素及其類似物之相容性不佳。因此，彼等會大量沉 澱在薄膜表面或在薄膜形成步驟中揮發。此外，在薄膜形 成步驟中，某些發射（emission )化合物會黏附到零組件 、構件及其類似物，且黏附、滴落等在薄膜上。因此，所 製得薄膜之品質會變得較低。 【發明內容】 發明摘沭 本發明之目的係提供一種光學用具有優良光學性質之醯 化纖維素薄膜及其製法。 本發明之另一目的係提供一種醯化纖維素薄膜及其製法 ，其係可對親水性材料提供黏合性，且在薄膜形成步驟中 並無皂化步驟。 欲能達到該等目的及其他目的，本發明之一種醯化纖維 素薄膜具有數層包括兩表面層及至少一內層，且在兩表面 層之醯化纖維素的平均醯化度是在範圍爲從0.5至2.8»在 內層之醯化纖維素的平均醯化度是高於兩表面層之醯化纖 維素的平均醯化度。 在本發明之較佳的具體實例中，兩表面層之一層是堆疊 在親水性材料上。 本發明之一種醯化纖維素薄膜具有數層，其中醯化纖維 素的平均醯化度是不同，且數層之表面層是將被堆疊在親 水性材料上。在表面層之醯化纖維素的平均醯化度是在範 圍爲從0.5至2.8，且各層的平均醯化度是藉由混合數種具 有不同的平均醯化度之醯化纖維素來加以調整。 本發明之一種醯化纖維素薄膜具有數層包括至少第一層 和第二層，旦該第一層具有將被堆疊在該親水性材料上之 第一表面，且該第二層將形成於其上之第二表面。第一層 的平均醯化度是在範圍爲從0.5至2.8，且第二層的平均醯 化度是不同於第一層者。 在本發明之醯化纖維素薄膜之製法中，其係製備至少第 一溶液和第二溶液。在第一溶液中，係將具有平均醯化度 是在範圍爲從0.5至2.8之第一材料溶解於溶劑中。在第二 溶液中，係將具有平均醯化度不同於第一材料者之第二材 料溶解於溶劑中。第一和第二材料的平均醯化度是藉由混 合數種具有不同的平均醯化度之醯化纖維素來加以調整。 所製備之第一和第二溶液係加以流延在基材上，以形成具 有數層之醯化纖維素薄膜，其中第二層是形成於第一層上 。第一層是由第一溶液所形成，且將與親水性材料相接觸 ，而第二層是由第二溶液所形成。所形成的醯化纖維素薄 膜是從基材剝離，然後疊合在親水性材料上。 根據本發明，醯化纖維素薄膜係以並無皂化之本發明之 製法所獲得，且醯化纖維素薄膜的平均醯化度是藉由混合 數種具有不同的平均醯化度之醯化纖維素來加以控制。有 鑒於此，醯化纖維素薄膜是具有特優的黏合性和光學性質 。因此，醯化纖維素薄膜是可用於偏光濾光片、光學補償 薄膜、液晶顯示器及其類似物。 本發明之較佳的具體實例 在本發明之具體實例中，因爲乙醯化反應是醯化纖維素 之醋化反應所達成，「乙酿化度（degree of acetylation ) 」是視爲醯化度，且在此具體實例中所使用之醯化纖維素 是纖維素醋酸酯。請注意在本發明中，酯化反應並不受限 於乙醯化反應，且醯化纖維素並不受限於纖維素醋酸酯。 如上所述，纖維素醋酸酯之平均乙醯化度通常是藉由皂 化和熟成（ripening)纖維素三醋酸酯之方法來加以調節， 且此已經習知的方法是應用到本發明。在該方法中，製自 木材紙漿或棉籽絨之纖維素是以醋酸或其酐加工，以獲得 具有乙醯化度爲3之纖維素醋酸酯。醋酸酐具有酯化反應 劑之效果，因此硫酸是用作爲觸媒》在酯化反應後，殘留 的硫酸是加以中和，且熟成是以一種已經習知的特定方法 來達成。因此，可獲得一種醯化度已加以調節之纖維素醋 酸酯。殘留的硫酸之中和是藉由添加鈣化合物所達成，使 得其含量相對於醯化纖維素以重量比率計最多爲60 ppm。 然而，在本發明中，係將數種工業級所製得之具有不同的 乙醯化度之纖維素醋酸酯加以混合。藉此混合比率是適當 地加以設定，使得乙醯化度可視需要而加以調整成範圍爲 -9- 1332090 從Ο.5至2.8之預定値。因此，其變得可比產生多種具有不 同的平均乙醯化度之纖維素醋酸酯更容易且精細地控制平 均乙醯化度。 在此具體實例中，其係將數種具有不同的平均乙醯化度 之纖維素醋酸酯加以混合，然後溶解或分散於溶劑中，以 製備一種具有預定平均乙醯化度之纖維素醋酸酯的溶液或 分散液（以下稱爲「摻雜劑」）》然而，製備方法並不受 限於此。例如，使用數種具有不同的平均乙醯化度之纖維 素醋酸酯，.且所有的平均度是已預知者。然後，將各種纖 維素醋酸酯加以溶解。因此，可獲得一種具有與各種相同 醯化度之溶液或分散液。將數種溶液或分散液加以混合， 以獲得具有預定平均乙醯化度之纖維素醋酸酯摻雜劑。 請注意在此具體實例中，雙折射（birefringence )係可 符合延遲値（retardation value) : 0 ^ Re ^ 5 ' 3 0 ^ Rth ^ 40。然而，延遲値是視醯化纖維素薄膜之用途而 不同，且本發明與延遲値並無依存性。請注意本發明係可 應用到當根據用途而變化之適當的光學性質之情況。 在第1A圖中，本發明之薄膜10是具有多層結構，而先 前技藝之薄膜是具有單層結構。此外，本發明之薄膜的厚 度是並不大於先前技藝者。薄膜10是由溶液流延法所形成 ，且具有第一外層11作爲從流延用基材之剝離層。薄膜 1〇係進一步配置內層12及第二外層13,其係依此順序在 第一外層U上。外層和內層11〜13之主要含量是含有添 加劑之纖維素。關於在本發明之具體實例中之添加劑是塑 1332090 化劑、二氧化矽（si02 )顆粒及其類似物、及酸性化合物 。然而，本發明並不受限於該等。此外，另—層可配置在 介於第一外層11與內層12之間、或介於內層12與第二外 層1 3之間。 第一外層11之纖維素醋酸酯是製自作爲原料之木材紙漿 ，且平均乙醯化度是從1.8至2.8。關於添加劑，係含有二 氧化矽顆粒15及酸性材料。此外，內層12之纖維素醋酸 酯是製自作爲原料之木材紙漿，且平均乙醯化度是從2.2 至2.9。在內層12之添加劑是塑化劑、紫外線吸收劑或其 類似物。第二外層13之纖維素醋酸酯是製自木材紙漿，且 平均乙醯化度爲與第一外層11相同之從1.8至2.2之範圍 。第二外層13之添加劑是二氧化矽顆粒15。此外，薄膜 10之厚度T10是至少10微米且最多3 00微米。 在第1B圖中，薄膜10是積層在親水性材料上，使得第 —外層11可與親水性材料17相接觸。關於親水性材料17 是聚乙烯醇及其類似物。在作爲表面層之外層11、13中， 纖維素醋酸酯之平均乙醯化度是非常低，及遠低於內層12 者。有鑒於此，可在並無皂化下對親水性材料· 1 7提供黏合 性。此外，第二外層1 3係經常與另一親水性材料積層。在 考慮此案例時，介於第一與第二外層11、13之間的乙醯化 度是相同，且第二外層13對親水性材料具有較佳的黏合性 。若其係並不需要將第二外層13上積層在另一親水性材料 上，則可在第二外層上形成其他層。 本來欲能符合預定的透濕氣性和光學性質以使其可用於 1332090 偏光濾光片等，將被用作爲薄膜之醯化纖維素的乙醯化度 較佳爲高。然而，在本發明中，薄膜10具有多層結構，且 將與親水性材料17相接觸之第一外層11是形成如同薄層 ，使其具有低乙醯化度，然而內層12是形成如同厚層，使 其具有慣用的乙醯化度。因此，在本發明所製得之醯化纖 維素薄膜具有與先前技藝者幾乎相同的光學性質，且可進 一步對親水性材料具有適當的黏合性。因此，其係可有效 地減少在作爲表面層之外層11、13的平均乙醯化度，且與 作爲內層之內層12的乙醯化度並無依存性。請注意外層（ 最低層和最上層）的平均乙醯化度是並不需要爲相同。 在作爲表面層之外層11、13的醯化纖維素之乙醯化度較 佳的範圍爲從0.5至2.8,特別是在範圍爲從1.8至2.2。 此外，當乙醯化度是較低時，則雙折射變得較大。有鑒 於此，具有較低的乙醯化度之第一外層11是與慣用的乙醯 化度之內層12組合倂用，使其可獲得具有適當的光學性質 之醯化纖維素薄膜。在此具體實例中，第一和第二外層11 、13具有與比內層12較低的乙醯化度之相同値，且內層 12是藉由第一和第二外層11、13而呈三明治層狀結構。 有鑒於此，薄膜10之兩表面皆具有適當的黏合性，且薄膜 10對親水性材料具有適當的光學性質。 較佳的是第一外層11之厚度T11是在範圍爲從1微米至 1〇微米，內層12之厚度T12是在範圍爲從20微米至1〇〇 微米，且第二外層13之厚度T13是在範圍爲從1微米至 1〇微米。欲能改善對親水性材料例如聚乙烯醇及其類似物 -12- 1332090 秦 之黏合性’第一外層11之厚度Til及第二外層13之厚度 T13可爲小’且並不需要爲相同。請注意在本發明中之各 層的厚度並不受限於上述之範圍。 因爲乙醯化度是在上述之低値，第一外層11和內層12 對水之接觸角較佳的是最多60°。對水之接觸角係表示對 水之親和性，且當接觸角是大於60。時，則對親水性材料 例如聚乙烯醇及其類似物之黏合性並不足夠。接觸角特佳 的範圍爲從20°至57°，且尤其是在範圍爲從20。至50。。 有鑒於此，其較佳爲控制在薄膜表面的醢化度，使得接觸 角可符合上述範圍。當其他醯化纖維素是實施酯化反應時 ，其較佳爲介於接觸角與醯化度之間的關係是預先加以決 定。然後，根據該數據，其較佳爲將在表面層的醯化度加 以控制。 此外，在醯化纖維素薄膜中，當醯化度是較低時，則雙 折射變得較大。有鑒於此，具有較低的乙醯化度之第一外 層11是與慣用的乙醯化度之內層12組合倂用，使其可獲 得具有適當的光學性質之醯化纖維素薄膜。 如上所述，第一外層11是從基材之剝離表面。當剝離後 ，其較佳爲第一外層11含有酸性化合物，其在25 °c之水 溶液中的酸解離常數pKa(= - log Ka)是在範圍爲從2.0 至4.5。其理由是當第一外層11對親水性材料之黏合性加 以改善時，則第一外層11對基材之黏合性變得較大，因此 用於剝離之負荷變得較大。當將上述酸包含於摻雜劑中時 ，第一外層對親水性材料具有足夠的黏合性。因此，本發 1332090 明在此情況下也是有效。 關於在第一外層11所含有之酸性材料，在25 °C之水溶 液中的酸解離常數pKa(= - log Ka)較佳的範圍爲從2.0 至4.5，且特佳爲從2.0至3.0。酸性材料可爲鹽類。酸解 離常數是在範圍爲從2.0至4.5之有效的酸性材料爲例如： 醋酸、乳酸、酒石酸、檸檬酸、檸檬酸酯，由於彼等爲工 業用級。彼等可單獨使用、或以彼等之混合物組合倂用。 在本發明之醢化纖維素薄膜中，其係僅對第一外層11添 加半酯形態之檸檬酸乙酯作爲酸性化合物。添加酸性化合 物是用以改善從基材之易剝離性（peelability)。黏附到基 材之第一外層11的親水性是可獲得改善。此改善可強化薄 膜對基材之黏合性。在此情況下，用於從基材剝離之剝離 力變得較大。然而，當添加酸性材料時，薄膜從基材之剝 離變得穩定。因此，薄膜可持續且穩定地製得。有鑒於此 ，可將上述酸性化合物包含於第一外層11與實施剝離之基 材的接觸表面中，且其並不需要在剝離後該酸性化合物殘 留在接觸表面、或是分散於第一外層11中。然而，其係難 以控制使得酸性化合物僅包含於第一外層11與基材之接觸 表面。因此，在本發明中，彼等係包含於第一外層11中。 在本發明中，如上所述，對親水性材料之黏合性是藉由調 節乙醯化度來加以提高，且從基材之易剝離性是藉由添加 酸性化合物來加以調節。請注意雖然酸性化合物對提高黏 合性並無效果，黏合性是依賴乙醯化度來加以提高。 欲能改善從基材之易剝離性，其他基團可用以取代在醯 -14- 4 41332090 化纖維素中之羥基性基團。然而，從作爲本發明之目的之 對親水性材料的黏合性之觀點來看，其較佳爲羥基性基團 保持於醯化纖維素中。有鑒於此，在本發明中較佳爲添加 酸性材料。然而，當所添加之酸性材料的含量高時，薄膜 容易劣化。在此具體實例中，其較佳爲酸性材料是僅包含 於第一外層，亦即以摻雜劑所流延而形成與基材相接觸之 層。在用以形成第一外層11之摻雜劑中所添加酸性材料之 離子等效量是與鹼離子或鹼土離子者相同。請注意對第一 外層添加酸性材料並不會實質地減少對親水性材料17之黏 合性。 半酯形態之檸檬酸乙酯是一種含有數種類型之檸檬酸之 酯類的檸檬酸酯類的混合物。雖然在數種類型之分子中， 以乙氧基對羥基之取代度是不同。平均乙醯化比率是加以 測定作爲全部檸檬酸乙酯之平均乙醯化比率。請注意當以 乙氧基取代所有的羥基時，該平均乙醯化比率爲100%。 在半酯形態之檸檬酸乙酯中，平均乙醯化比率爲5 0 %。 此外，在本發明中，僅醯化纖維素薄膜之多層結構的內 層可含有發射化合物。「發射化合物」是一種並不會停留 在一層，但是會從一層傳送至另一層、或至外面之化合物 ，且通常具有低分子量，例如從固態或液態變成氣態之昇 華性化合物或揮發性化合物。在此具體實例中，作爲發射 化合物之塑化劑是僅添加到作爲內層之內層1 2，而非作爲 表面層之外層11、13。因此，在薄膜製造步驟中，塑化劑 分散於薄膜表面上之速率減少，以降低發射且防止污染製 1332090 程。 此外，二氧化矽顆粒及其類似物通常係添加以改善薄膜 之潤滑性質。在本發明中，顆粒1 5是並不添加到內層1 2 中，但是僅添加到作爲表面層之外層11、1 3。當此等顆粒 之含量太大時，薄膜之光透射比（optical transmittance ) 變得極低。因此，其較佳爲顆粒之含量是儘可能愈小愈佳 。在本發明中，薄膜10具有多層結構，其係與先前技藝僅 具有單層結構之薄膜者不同。有鑒於此，其係具有一長處 是所添加顆粒之分佈可加以控制。因此，當顆粒之總含量 變得較少時，先前技藝之潤滑性質可維持在本發明中，可 防止薄膜之透射比減少，且製造成本變得較低。請注意用 以提供潤滑性質所添加之顆粒是二氧化矽（Si02 )。然而 ，本發明並不受限於此。 在第2圖中，流延模頭21是多重歧管（multi-manifold )型，使其可同時形成如第1圖所例示之三層。在第1圖 .中之外層1 1〜1 3是分別從摻雜劑22 ~ 24所形成，且此等 是藉由用於流延模頭21之摻雜劑供應裝置（圖中未展示） 所供應。在流延模頭21之後表面分別形成用於摻雜劑22 ~ 24之摻雜劑供應開口 26 ~ 28。三種類型之各摻雜劑22〜 24是暫時保持在配置於槽孔30 ~ 32上之袋狀凹槽（ pocket) 33 ~ 35中，且從流延模頭21之模頭唇37流延在 作爲基材之帶38上。在接近模頭唇37之槽孔30〜32匯 合，且三種摻雜劑同時流延以形成多層結構。此流延方法 —般是稱爲「共流延法」。此外，該基材並不受限於帶38 1332090 λ ，也可爲轉筒。 此外，在薄膜製造步驟中，施加到摻雜劑22 ~ 24之擠 壓壓力是各自獨立地加以控制。因此，各層之厚度是選擇 性地加以調整。欲能控制各層之厚度，一種方法是適當地 決定在作爲三種摻雜劑之通道的槽孔之匯合部的槽孔寬度 ，及一種方法是調整施加到摻雜劑之擠壓壓力。 請注意流延模頭21之摻雜劑供應開口 26〜28之位置、 槽孔30〜32之構成、袋式凹槽33〜35之構成、及接近唇 部27之槽孔的匯合部之結構是並不受限於上述具體實例， 但是可爲用於共流延之泛用多重歧管型之流延模頭。當流 延模頭可同時形成N層（N是至少爲2之自然數）時，摻 雜劑之槽孔（或通道）的數目是N，且其基本結構是與如 上所述者相同。 在第3圖中，流延模頭41是一種具有單槽孔之進料套管 (feed block)型。在第2圖中之多重歧管型流延模頭，流 延模頭41可形成由如第1圖所示之三層11〜13所構成的 具有多層結構之薄膜10»流延模頭41之後表面是配置一 具有供應開口 42a〜42c之進料套管42。用以形成外層1 1 〜13之摻雜劑22〜24(參閱第2圖）是分別經由在進料套 管42之供應開口 42a ~ 42c所供應。在進料套管型42中， 從延伸自供應開口 42a〜42c之各槽孔是匯合，使得三種摻 雜劑22〜24在一通道中流動以具有三層結構。然後在流 延模頭41中所供應之摻雜劑22〜24通過單槽孔43，且從 唇44同時流延在作爲基材之轉筒45上。此外，基材並不 1332090 受限於轉筒45，但是也可爲帶38(參閱第2圖）^ 此外，在本發明中，摻雜劑可使用共流延法，以如第2 圖所示之多重歧管型及如第3圖所示之進料套管型的組合 進行流延。而且在此案例中，基材可爲如第2圖所示之帶 38、或如第3圖所示之轉筒45。 在本發明中，摻雜劑可並不使用共流延法，但是使用依 序流延法來進行流延。當N層是使用依序流延法所形成時 ，摻雜劑可以符合2 ^ NC ^ N之條件的流延數NC ( NC是設定爲至少2之自然數）加以流延在基材上。當NC < N時，其係需要在摻雜劑流延步驟中實施至少一次的共 流延。在依序流延法中，較佳的基材是帶。. 關於用於摻雜劑22〜24之溶劑是：有機鹵化物（二氯 甲烷 '二氯亞甲基及其類似物及非氯化化合物，例如 醇類（甲醇、乙醇、正丁醇及其類似物），數種具有酯形 態之化合物（醋酸甲酯 '醋酸乙酯及其類似物）等。有鑒 於此，本發明係顧慮到環境因素所達成。 在第4圖中，本發明之—種醯化纖維素薄膜50具有如第 1圖所示之多層結構，而先前技藝之薄膜具有單層結構^ 薄膜50之層數爲5。薄膜5〇具有第一外層51作爲從基材 之剝離層，且係進一步配置第一至第三內層52〜54，及第 二外層55，其係以此順序重疊在第—外層5丨上。此外， 薄膜50是積層在親水性材料57上。再者，介於層51 ~ 55 之間也可形成其他層。在此具體實例中，此等層51〜55 之主要原料是木材紙漿和棉籽絨之一種。其係注意到在本 -18 - 1332090 發明中，數層之至少一層可製自一種由木材紙漿和棉籽絨 所製得之材料的混合物。薄膜50之厚度T50是在範圍爲從 10微米至300微米。 第一外層51之纖維素醋酸酯的原料是棉籽絨，且平均乙 醯化度是在範圍爲從1.8至2·2。關於添加劑，二氧化矽顆 粒56及酸性材料是包含於第一外層51中。此外，在第一 內層52及第三內層54中，纖維素醋酸酯的原料是木材紙 黎’且平均乙醯化度是在範圍爲從2.2至2.9»在第二內層 53中，纖維素醋酸酯的原料是木材紙漿，且平均乙醯化度 是在範圍爲從1.8至2.2。第一至第三內層52〜54之添加 劑是塑化劑、紫外線吸收劑及其類似物。此外，第二外層 55的原料是木材紙漿，且平均乙醯化度是在範圍爲從1.8 至2.2。請注意薄膜50之厚度T50是在範圍爲從10微米至 3 00微米。 作爲表面層之外層51、55的纖維素醋酸酯之乙醯化度是 極低，且比內層52〜54者甚低。有鑒於此，可在並無皂 化下賦予薄膜50具有對親水性材料例如聚乙烯醇及其類似 物之黏合性。第二外層55通常是積層在另一親水性材料上 。若考慮此情況下，乙醯化度是與介於第一與第二外層51 ' 55之間者相同，使得第二外層55可對親水性材料具有 較佳的黏合性。乙醯化度是根據另一親水性材料的種類來 決定。請注意第一外層（如第4圖所示之最低層）51及第 二外層（如第4圖所示之最上層）55的平均乙醯化度並不 需要爲相同。 1332090 再者，當乙醯化度是較低時，則光學異方向性（optical anisotropy)變得較大。有鑒於此，具有較低的醯化度之層 是與具有較高的醯化度之層組合倂用，使其可獲得具有預 定雙折射之醯化纖維素薄膜。例如，在第一和第二外層51 、55及第二內層53的平均醯化度是高於第一和第三內層 52、54者。因此，在本發明中，具有較高的平均醯化度之 層是與具有較低者組合倂用，使其所製得薄膜之光學性質 獲得改善。此外，具有較高的平均醯化度之層是與具有較 低者呈夾層結構，使得薄膜50之兩表面對親水性材料具有 適當的黏合性，且亩更進一步地改善所製得薄膜之光學性 質。 請注意光學性質是與對於液晶顯示裝置等是重要的視野 角性質及平均雙折射相關。 此外，當第一外層51是由製自棉籽絨之纖維素醋酸酯所 形成時，從基材之易剝離性及光學性質可獲得改善》介於 製自棉籽絨之醯化纖維素與製自木材紙漿者之間的光學性 質是具有差異。因此，其係視目的而有效地選擇纖維素醋 酸酯之類型。尤其是製自棉籽絨之纖維素醋酸酯是比製自 木材紙漿者具有極其特優的從基材之剝離性質。因此，第 一外層51可使用低剝離力加以剝離。關於酸性化合物，係 添加半酯形態之檸檬酸乙酯與乙醇以使得易剝離性更爲穩 定。在本具體實例中’二氧化矽顆粒56是添加到作爲表面 層之外層51、55’使得薄膜50具有潤滑性質。有鑒於此 ’其係並不需要將顆粒56添加到作爲內層之內層52〜54 -20- 1332090 其較佳爲至少一層是僅由棉籽絨所製得，或其主要的原 料是棉籽絨。因爲製自棉籽絨之物質是昂貴的，其較佳爲 以製自木材紙漿之物質來形成其他層。有鑒於此，在多層 結構中，用以形成從基材之剝離表面的表面層是由棉籽絨 所形成，且至少另一層是由木材紙漿所形成。 請注意各外層及內層51〜55的原料不僅可爲棉籽絨和 木材紙漿之一種，但是也可爲混合物。其係藉由適當地混 合兩種纖維素醋酸酯以有效地形成層，且考慮到微細控制 薄膜之性質和特性，例如光學性質和從基材之易剝離性、 及數造成本。例如，當可獲得從基材之預定的易剝離性時 ，則構成剝離表面之層可爲由兩種纖維素醋酸酯之混合物 所形成。視薄膜製造的速率、及在從基材所剝離薄膜中之 溶劑的含量而定，藉此可決定兩種醯化纖維素之混合比率 。此外，欲能微細控制薄膜之性質，其係有效地配置至少 一層或較佳爲數層，其中係混合數種原料。 在此具體實例中，塑化劑是添加到作爲內層之內層52〜 54，且並不是添加到作爲表面層之外層51、55。因此，發 射是降低且可防止製程之污染。請注意當層數爲至少4時 ’其中並未添加發射化合物例如塑化劑之層是並不受限於 僅在表面層，且發射化合物不可添加到至少表面層。 在上述具體實例中，其較佳爲作爲表面層之外層51、55 是薄。並未含有塑化劑之層的大厚度會降低薄膜之例如張 力強度和彎曲強度的機械強度。否則，當具有極低的乙醯 1332090 化度之纖維素醋酸酯層是厚時，薄膜是具有大吸濕性和吸 水性。在後者案例中，薄膜之情況會喪失穩定性，其通常 會導致例如捲曲等之變形。表面層之厚度是在範圍爲從1 微米至50微米，且較佳的範圍爲從1微米至10微米》 在第5圖中，一種流延模頭61是用以形成具有如第4圖 所示之五層結構的纖維素醋酸酯薄膜50。流延模頭61具 有單槽孔65且爲進料套管型，使其可同時形成五層。兩組 進料套管62、63是堆叠在流延模頭61之後表面，且具有 摻雜劑供應開口 62a、62b、63a ~ 63c。用以形成外層和內 層51〜55 (參閱第4圖）之摻雜劑（並未展示）是分別經 由供應開口 62a、62b ' 63a〜63c所供應。在進料套管63 中，延伸自供應開口 63a〜63c之槽孔匯合成單槽孔；且在 進料套管62中，單槽孔與延伸自供應開口 62a ' 62b之槽 孔匯合。因此，在槽孔65中，五種摻雜劑形成五層結構， 且從唇部66流延在作爲基材之轉筒上。此外，基材並不受 限於轉筒67，而可爲帶38(參閱第2圖）。 本發明之醯化纖維素特佳爲纖維素醋酸酯，但是可爲數 種醯化纖維素。此外，在本發明中可使用單一或彼等之混 合物。聚合物並不受限於醯化纖維素。本發明可應用到若 在聚合物中，作爲酶基對羥基之取代度的醯化度可加以控 制之案例，及尤其是若聚合物並無光學異方向性且可用於 溶液流延法者。 本發明尤其是可有效地用以形成不僅具有如第1和4圖 所例示之最多5層，而且也可形成最多20層之薄膜。薄膜 1332090 較佳爲具有3至15層，且特佳爲具有3至10層。本發明 可適當地應用於當具有此等多層結構之醯化纖維素是具有 厚度爲10微米至3 00微米時。然而，各層之厚度分佈並不 受限。當薄膜具有至少三層結構時，薄膜對於介於前表面 與後表面之間的多層結構之中心可爲不對稱性》 此外，與在先前技藝中之單層結構者不同，在本發明之 醯化纖維素薄膜是具有多層結構，且多層結構之全部各層 可爲非由醯化纖維素所形成者。某些層之其他材料是選擇 使其可避免損害到光學用醯化纖維素薄膜的性質。此外， 當醯化纖維素薄膜及其他薄膜是加以堆疊以形成堆疊薄膜 片時，醯化纖維素薄膜可形成堆叠薄膜片之表面或內薄膜 。當醯化纖維素薄膜是配置於堆疊薄膜片之內部時，在醯 化纖維素薄膜之兩側上的其他薄膜可具有單層或多層結構 ，其對內醯化纖維素薄膜可爲對稱性或不對稱性。 此外，當用於層之摻雜劑的溶劑之種類或組成物、或添 加劑之種類或數量具有差異時，或不論是否添加添加劑， 則鄰近層可爲由具有相同的乙醯化度之醯化纖維素所形成 。在此案例中，此等鄰近層是視爲兩種不同層。 當所獲得醯化纖維素薄膜是積層在親水性材料或其他材 料上時，積層是以習知的方法所製成。例如，一種方法是 將薄膜與親水性材料以壓製積層或壓製封合；一種方法是 以黏合劑黏合；或一種方法是其中醯化纖維素溶液是直接 施用到作爲應用基材之親水性材料上。在本發明中，在應 用時是形成數層，以使得醯化纖維素薄膜構成在應用基材 -23 - 上，然而在先前技藝中，僅形成單層，以使得醯化纖維素 薄膜構成在應用基材上。在此案例中，如上所述，已習知 的多重歧管型之流延模頭、進料套管型、或其他數種類型 可用於流延。此外，在以黏合劑黏合時，例如有一案例是 聚乙烯醇（PVA )薄膜是用作爲一種偏光濾光片用之偏光 膜，且黏合劑將被施用到通常爲親水性材料之偏光膜上。 在此案例中，當其係使用本發明之薄膜時，薄膜對黏合劑 之黏合性可獲得改善。當其係設計成使用PVA薄膜作爲偏 光膜時，則PVA溶液是用作爲黏合劑。有鑒於此，本發明 之親水性材料是並不受限於薄膜、薄片、板等，且可含有 黏合劑。 此外，在本發明中，在溶液流延法所製得之薄膜是用作 爲偏光濾光片、光學補償薄膜、及液晶顯示裝置之元件。 此外，薄膜是用作爲感光性材料。欲能獲得偏光濾光片， 在上述具體實例之溶液流延法所製得之纖維素醋酸酯薄膜 10、40、50是作爲保護膜黏合到一種由聚乙烯醇系（PVA )薄膜所形成之偏光膜的兩表面。偏光膜是藉由將聚乙烯 醇系薄膜加以染色所獲得。染色法通常爲氣相或液相吸附 法，且兩種方法皆可使用。在本發明中，薄膜是以液相吸 附法加以染色。1332090 ^ IX. Description of the Invention: [Technical Field] The present invention relates to a deuterated cellulose film and a process for the preparation thereof, and more particularly to a deuterated cellulose film and a process for the same, which are used as a polarizing filter A polarizing film of a polarizing filter and used for an optical compensation film, a liquid crystal display device, or the like. [Prior Art] The deuterated cellulose film has transparency, appropriate water vapor permeability, and high mechanical strength. The dimensional resistance of the deuterated cellulose film does not depend too much on humidity and temperature. Therefore, deuterated cellulose films are widely used as a matrix material for optical materials. Regarding the preparation method of the deuterated cellulose film, the solution casting method casts a dope prepared from a polymer and a solvent on a substrate by a casting die, and dries in a drying step to form a film. film. The deuterated cellulose film can also be used as a protective film for a polarizing filter constituting a liquid crystal display device. The polarizing filter is usually composed of a polarizing film composed of polyvinyl alcohol, and the deuterated cellulose film is bonded to one or both surfaces of the polarizing film. Since polyvinyl alcohol is a hydrophilic polymer, the surface of the film of the polyvinyl alcohol film has excellent hydrophilic properties. However, the surface of the deuterated cellulose film has hydrophobic properties. In view of this, the condition of at least one of the surface of the film of the polyvinyl alcohol film and the bismuth cellulose film is modified to bond the polyvinyl alcohol film and the bismuth cellulose film. In terms of surface modification of the film, the surface of the film of the deuterated cellulose film is usually saponified. Regarding the main saponification treatment, one method is to apply or spray a base 1332090 solution on the surface of the film, and one method is to impregnate the bismuth cellulose film into an alkaline solution (refer to Japanese Patent Application Laid-Open No. 2001- 3 1 8, 22 8). Further, deuterated cellulose is usually produced from wood pulp, cotton linter, or the like. In the conventional method of deuterated fossil, wood pulp or cottonseed is treated with acetic acid or acetic anhydride. Therefore, cellulose triacetate having a degree of acylation of 3 can be obtained. Acetic anhydride is used as an esterifying agent, so sulfuric acid is used as a catalyst. The residual sulfuric acid as a catalyst is effectively used for the saponification and ripening of the obtained cellulose triacetate to control the degree of deuteration. Therefore, the target cellulose acetate can be obtained. In this case, a calcium compound and its analog are added to neutralize an excess of several acids. Japanese Patent Laid-Open Publication No. 2002-192,541 teaches that a cellulose film contains several compounds to improve plastication and impart optical properties. These compounds are often required not only in deuterated cellulose films, but also in several optical films to further improve quality. However, in any of the methods for saponifying the surface of the modified cellulose film, the manufacturing equipment after the solution casting step is extremely large and cannot be continuously disposed. Therefore, the cellulose film obtained by the solution casting method is taken up and then placed in a saponification system. Then, the deuterated cellulose film is unwound to carry out saponification. In this case, the number of manufacturing steps is increased by one and becomes larger, which hinders productivity improvement and cost reduction. Further, saponification often causes wrinkles and unevenness of the film, and the transparency of the film becomes lower. 1332090 The hydrophilic character of the above deuterated cellulose is determined by the degree of visual enthalpy (average enthalpy). When the average degree of deuteration is low, the number of hydroxyl groups contained in the same molar number of deuterated cellulose becomes large. In view of this, the average degree of deuteration is preferably low so that the hydrophilic property is high. However, when the average degree of deuteration is low, water vapor permeability, dimensional stability of the film, easy peelability, and the like become lower, and deuterated cellulose is not suitable for practical use. Several compounds added to make the film of higher quality show poor compatibility with deuterated cellulose and the like. Therefore, they will precipitate a large amount on the surface of the film or volatilize in the film forming step. Further, in the film forming step, some of the emission compound adheres to the components, members, and the like, and adheres, drops, and the like on the film. Therefore, the quality of the resulting film becomes lower. Disclosure of the Invention An object of the present invention is to provide a fluorinated cellulose film having excellent optical properties for optical use and a process for producing the same. Another object of the present invention is to provide a bismuth cellulose film which is capable of providing adhesion to a hydrophilic material and which has no saponification step in the film forming step, and a process for producing the same. To achieve these and other objects, a deuterated cellulose film of the present invention has several layers including two surface layers and at least one inner layer, and the average degree of deuteration of the deuterated cellulose in the two surface layers is in the range The average degree of deuteration of the deuterated cellulose from 0.5 to 2.8» in the inner layer is higher than the average degree of deuteration of the deuterated cellulose in the two surface layers. In a preferred embodiment of the invention, one of the two surface layers is stacked on a hydrophilic material. A deuterated cellulose film of the present invention has several layers in which the average degree of deuteration of the deuterated cellulose is different, and the surface layers of the plurality of layers are to be stacked on the hydrophilic material. The average degree of deuteration of the deuterated cellulose in the surface layer is in the range of from 0.5 to 2.8, and the average degree of deuteration of each layer is adjusted by mixing several deuterated celluloses having different average degrees of deuteration. A deuterated cellulose film of the present invention has a plurality of layers including at least a first layer and a second layer, wherein the first layer has a first surface to be stacked on the hydrophilic material, and the second layer is formed on The second surface thereon. The average degree of deuteration of the first layer is in the range of from 0.5 to 2.8, and the average degree of deuteration of the second layer is different from that of the first layer. In the process for producing a deuterated cellulose film of the present invention, at least a first solution and a second solution are prepared. In the first solution, the first material having an average degree of deuteration is dissolved in a solvent in a range of from 0.5 to 2.8. In the second solution, a second material having an average degree of deuteration different from that of the first material is dissolved in a solvent. The average degree of deuteration of the first and second materials is adjusted by mixing several deuterated celluloses having different degrees of deuteration. The prepared first and second solutions are cast on a substrate to form a film of deuterated cellulose having a plurality of layers, wherein the second layer is formed on the first layer. The first layer is formed from the first solution and will be in contact with the hydrophilic material, while the second layer is formed from the second solution. The formed deuterated cellulose film is peeled off from the substrate and then laminated on the hydrophilic material. According to the present invention, the deuterated cellulose film is obtained by the process of the present invention which is not saponified, and the average degree of deuteration of the deuterated cellulose film is obtained by mixing several deuterated fibers having different average degrees of deuteration. It has always been controlled. In view of this, the deuterated cellulose film has excellent adhesion and optical properties. Therefore, the deuterated cellulose film can be used for a polarizing filter, an optical compensation film, a liquid crystal display, and the like. A preferred embodiment of the present invention is a specific example of the present invention, since the acetylation reaction is achieved by the acetification reaction of deuterated cellulose, and the "degree of acetylation" is regarded as the degree of deuteration. And the deuterated cellulose used in this specific example is cellulose acetate. Note that in the present invention, the esterification reaction is not limited to the acetylation reaction, and the cellulose deuterated is not limited to cellulose acetate. As described above, the average degree of acetylation of cellulose acetate is usually adjusted by saponifying and ripening cellulose triacetate, and the conventional method is applied to the present invention. In this method, cellulose made from wood pulp or cotton linter is processed with acetic acid or its anhydride to obtain cellulose acetate having a degree of acetylation of 3. The acetic anhydride has the effect of an esterification reactant, so sulfuric acid is used as a catalyst. After the esterification reaction, the residual sulfuric acid is neutralized, and the ripening is achieved by a specific method which has been conventionally known. Thus, a cellulose acetate having a reduced degree of oximation can be obtained. The residual sulfuric acid neutralization is achieved by adding a calcium compound so as to be at most 60 ppm by weight relative to the deuterated cellulose. However, in the present invention, cellulose acetates having different degrees of acetylation prepared by several industrial grades are mixed. Thereby, the mixing ratio is appropriately set so that the degree of acetylation can be adjusted to a predetermined range of -9 - 1332090 from Ο.5 to 2.8 as needed. Therefore, it becomes easier and finer to control the average degree of acetylation than the production of a plurality of cellulose acetates having different average degrees of acetylation. In this specific example, a plurality of cellulose acetates having different average degrees of acetylation are mixed and then dissolved or dispersed in a solvent to prepare a cellulose acetate having a predetermined average degree of acetylation. Solution or dispersion (hereinafter referred to as "dopant") However, the preparation method is not limited thereto. For example, several cellulose acetates having different average degrees of acetylation are used, and all averages are foreseen. Then, various cellulose acetates were dissolved. Therefore, a solution or dispersion having the same degree of deuteration as various kinds can be obtained. Several solutions or dispersions are mixed to obtain a cellulose acetate dopant having a predetermined average degree of acetylation. Note that in this specific example, the birefringence can be in accordance with the retardation value: 0 ^ Re ^ 5 ' 3 0 ^ Rth ^ 40. However, the delayed enthalpy differs depending on the use of the fluorene cellulose film, and the present invention has no dependence on delayed enthalpy. It is to be noted that the present invention can be applied to the case where appropriate optical properties vary depending on the use. In Fig. 1A, the film 10 of the present invention has a multilayer structure, and the film of the prior art has a single layer structure. Moreover, the thickness of the film of the present invention is not greater than that of the prior art. The film 10 is formed by a solution casting method and has a first outer layer 11 as a release layer from a substrate for casting. The film 1 is further provided with an inner layer 12 and a second outer layer 13 which are in this order on the first outer layer U. The main content of the outer layer and the inner layers 11 to 13 is cellulose containing an additive. The additives in the specific examples of the present invention are a plastic 1332090 agent, cerium oxide (si02) particles and the like, and an acidic compound. However, the invention is not limited to these. Further, the additional layer may be disposed between the first outer layer 11 and the inner layer 12 or between the inner layer 12 and the second outer layer 13. The cellulose acetate of the first outer layer 11 is made from wood pulp as a raw material, and the average degree of acetylation is from 1.8 to 2.8. The additive contains cerium oxide particles 15 and an acidic material. Further, the cellulose acetate of the inner layer 12 is made from wood pulp as a raw material, and the average degree of acetylation is from 2.2 to 2.9. The additive in the inner layer 12 is a plasticizer, an ultraviolet absorber or the like. The cellulose acetate of the second outer layer 13 is made from wood pulp, and the average degree of acetylation is from 1.8 to 2.2 which is the same as that of the first outer layer 11. The additive of the second outer layer 13 is cerium oxide particles 15. Further, the thickness T10 of the film 10 is at least 10 μm and at most 300 μm. In Fig. 1B, the film 10 is laminated on a hydrophilic material such that the first outer layer 11 can be in contact with the hydrophilic material 17. The hydrophilic material 17 is polyvinyl alcohol and the like. In the outer layers 11, 13 as the surface layer, the average degree of acetylation of the cellulose acetate is very low, and is much lower than that of the inner layer 12. In view of this, the hydrophilic material can be provided with adhesion without saponification. Further, the second outer layer 13 is often laminated with another hydrophilic material. In considering this case, the degree of acetylation between the first and second outer layers 11, 13 is the same, and the second outer layer 13 has a better adhesion to the hydrophilic material. If it is not necessary to laminate the second outer layer 13 on another hydrophilic material, other layers may be formed on the second outer layer. Originally, it is intended to be compatible with a predetermined moisture permeability and optical properties so that it can be used for a 1332090 polarizing filter or the like, and the degree of acetylation of the cellulose to be used as a film is preferably high. However, in the present invention, the film 10 has a multilayer structure, and the first outer layer 11 which is in contact with the hydrophilic material 17 is formed like a thin layer to have a low degree of acetylation, whereas the inner layer 12 is formed like a thick layer. The layer is made to have a conventional degree of acetylation. Therefore, the cellulose-fibrin film produced by the present invention has almost the same optical properties as those of the prior art, and can further have an appropriate adhesiveness to the hydrophilic material. Therefore, it is possible to effectively reduce the average degree of acetylation of the layers 11 and 13 as the surface layer, and is not dependent on the degree of acetylation of the inner layer 12 as the inner layer. Please note that the average degree of acetylation of the outer layer (lowest and uppermost layers) does not need to be the same. The degree of acetylation of the deuterated cellulose as the outer layer 11, 13 of the surface layer is preferably in the range of from 0.5 to 2.8, particularly in the range of from 1.8 to 2.2. Further, when the degree of acetylation is low, the birefringence becomes larger. In view of this, the first outer layer 11 having a lower degree of acetylation is used in combination with the conventional inner layer 12 of the degree of acetylation to obtain a fluorinated cellulose film having appropriate optical properties. In this embodiment, the first and second outer layers 11, 13 have the same degree of oxime that is lower than the inner layer 12, and the inner layer 12 is formed by the first and second outer layers 11, 13. Sandwich layered structure. In view of this, both surfaces of the film 10 have appropriate adhesion, and the film 10 has suitable optical properties for the hydrophilic material. Preferably, the thickness T11 of the first outer layer 11 is in the range of from 1 micrometer to 1 micrometer, the thickness T12 of the inner layer 12 is in the range of from 20 micrometers to 1 micrometer, and the thickness T13 of the second outer layer 13 It is in the range of from 1 micron to 1 micron. It is desired to improve the adhesion to the hydrophilic material such as polyvinyl alcohol and the like -12-1332090. The thickness Til of the first outer layer 11 and the thickness T13 of the second outer layer 13 may be small' and need not be the same. Note that the thickness of each layer in the present invention is not limited to the above range. Since the degree of acetylation is lower than the above, the contact angle of the first outer layer 11 and the inner layer 12 with respect to water is preferably at most 60°. The contact angle to water indicates affinity for water, and when the contact angle is greater than 60. In this case, the adhesion to hydrophilic materials such as polyvinyl alcohol and the like is not sufficient. The contact angle is particularly preferably in the range of from 20 to 57, and especially in the range of from 20. To 50. . In view of this, it is preferable to control the degree of deuteration on the surface of the film so that the contact angle can satisfy the above range. When other deuterated cellulose is subjected to an esterification reaction, it is preferred that the relationship between the contact angle and the degree of deuteration is determined in advance. Then, based on the data, it is preferred to control the degree of deuteration in the surface layer. Further, in the deuterated cellulose film, when the degree of deuteration is low, the birefringence becomes large. In view of this, the first outer layer 11 having a lower degree of acetylation is used in combination with the conventional inner layer 12 of the degree of acetylation to obtain a fluorinated cellulose film having appropriate optical properties. As described above, the first outer layer 11 is a peeling surface from the substrate. When peeled off, it is preferred that the first outer layer 11 contains an acidic compound whose acid dissociation constant pKa (= - log Ka) in an aqueous solution at 25 ° C is in the range of from 2.0 to 4.5. The reason for this is that when the adhesion of the first outer layer 11 to the hydrophilic material is improved, the adhesion of the first outer layer 11 to the substrate becomes large, so that the load for peeling becomes large. When the above acid is contained in the dopant, the first outer layer has sufficient adhesion to the hydrophilic material. Therefore, this is also valid in this case 1332090. With respect to the acidic material contained in the first outer layer 11, the acid dissociation constant pKa (= - log Ka) in an aqueous solution at 25 ° C preferably ranges from 2.0 to 4.5, and particularly preferably from 2.0 to 3.0. The acidic material can be a salt. Acidic dissociation constants which are effective in the range of from 2.0 to 4.5 are, for example, acetic acid, lactic acid, tartaric acid, citric acid, citric acid esters, since they are industrial grades. They may be used alone or in combination with a mixture of them. In the deuterated cellulose film of the present invention, only the citrate ethyl ester having a half ester form is added to the first outer layer 11 as an acidic compound. The addition of an acidic compound is used to improve the peelability from the substrate. The hydrophilicity of the first outer layer 11 adhered to the substrate is improved. This improvement enhances the adhesion of the film to the substrate. In this case, the peeling force for peeling from the substrate becomes large. However, when an acidic material is added, the peeling of the film from the substrate becomes stable. Therefore, the film can be produced stably and stably. In view of the above, the acidic compound may be included in the contact surface of the first outer layer 11 and the substrate to be peeled off, and it is not required that the acidic compound remains on the contact surface or is dispersed in the first outer layer 11 after peeling. in. However, it is difficult to control so that the acidic compound is contained only on the contact surface of the first outer layer 11 with the substrate. Therefore, in the present invention, they are included in the first outer layer 11. In the present invention, as described above, the adhesion to the hydrophilic material is improved by adjusting the degree of acetylation, and the easy peelability from the substrate is adjusted by adding an acidic compound. Please note that although acidic compounds have no effect on improving adhesion, adhesion is dependent on the degree of acetylation. In order to improve the easy peelability from the substrate, other groups may be used to replace the hydroxyl group in the cellulose of 醯-14-4 41332090. However, from the viewpoint of the adhesion to the hydrophilic material as the object of the present invention, it is preferred that the hydroxyl group be retained in the deuterated cellulose. In view of this, it is preferred to add an acidic material in the present invention. However, when the content of the added acidic material is high, the film is easily deteriorated. In this embodiment, it is preferred that the acidic material be included only in the first outer layer, i.e., cast with a dopant to form a layer in contact with the substrate. The ionic equivalent amount of the acidic material added to the dopant used to form the first outer layer 11 is the same as that of the alkali ion or alkaline earth ion. Please note that the addition of an acidic material to the first outer layer does not substantially reduce the adhesion to the hydrophilic material 17. The half ester form of citrate is a mixture of citrate esters containing esters of several types of citric acid. Although in several types of molecules, the degree of substitution of ethoxy groups with hydroxyl groups is different. The average acetylation ratio was determined as the average acetylation ratio of all ethyl citrate. Note that when all of the hydroxyl groups are replaced by an ethoxy group, the average acetylation ratio is 100%. In the half ester form of citric acid ethyl ester, the average acetylation ratio was 50%. Further, in the present invention, only the inner layer of the multilayer structure of the deuterated cellulose film may contain an emissive compound. An "emissive compound" is a compound which does not stay in one layer but which is transferred from one layer to another, or to the outside, and usually has a low molecular weight, such as a sublimating compound or a volatile compound which changes from a solid or a liquid state to a gaseous state. In this specific example, the plasticizer as the emissive compound is added only to the inner layer 12 as the inner layer, not to the outer layers 11, 13 as the surface layer. Therefore, in the film manufacturing step, the rate at which the plasticizer is dispersed on the surface of the film is reduced to reduce the emission and prevent contamination. Further, cerium oxide particles and the like are usually added to improve the lubricating properties of the film. In the present invention, the particles 15 are not added to the inner layer 12, but are added only to the outer layers 11, 13 as the surface layer. When the content of such particles is too large, the optical transmittance of the film becomes extremely low. Therefore, it is preferred that the content of the particles be as small as possible as possible. In the present invention, the film 10 has a multilayer structure which is different from those of the prior art which has only a single layer structure. In view of this, it has a advantage that the distribution of the added particles can be controlled. Therefore, when the total content of the particles becomes less, the lubricating properties of the prior art can be maintained in the present invention, the transmittance of the film can be prevented from being reduced, and the manufacturing cost becomes lower. Note that the particles added to provide lubricity are cerium oxide (SiO 2 ). However, the invention is not limited thereto. In Fig. 2, the casting die 21 is of a multi-manifold type so that it can simultaneously form three layers as illustrated in Fig. 1. In Fig. 1, the outer layers 1 1 to 1 3 are formed from the dopants 22 to 24, respectively, and these are supplied by a dopant supply device (not shown) for casting the die 21. Supplyed. The dopant supply openings 26 to 28 for the dopants 22 to 24 are formed on the surface after the casting die 21, respectively. Each of the three types of dopants 22 to 24 is temporarily held in pockets 33 to 35 disposed in the slots 30 to 32, and is cast from the die lip 37 of the casting die 21. On the belt 38 as a substrate. The slots 30 to 32 close to the die lip 37 merge and the three dopants are simultaneously cast to form a multilayer structure. This casting method is generally called "co-casting method". Further, the substrate is not limited to the belt 13 1332090 λ, and may be a drum. Further, in the film manufacturing step, the pressing pressures applied to the dopants 22 to 24 are independently controlled. Therefore, the thickness of each layer is selectively adjusted. In order to control the thickness of each layer, one method is to appropriately determine the slot width of the junction of the slots as the passage of the three dopants, and one method is to adjust the pressing pressure applied to the dopant. Note that the positions of the dopant supply openings 26 to 28 of the casting die 21, the configuration of the slots 30 to 32, the configuration of the pocket grooves 33 to 35, and the structure of the confluence portion of the slot close to the lip portion 27 are noted. It is not limited to the above specific examples, but may be a casting die of a multi-manifold type for co-casting. When the casting die can simultaneously form the N layer (N is a natural number of at least 2), the number of slots (or channels) of the dopant is N, and the basic structure is the same as described above. In Fig. 3, the casting die 41 is of a feed block type having a single slit. In the multi-manifold type casting die in Fig. 2, the casting die 41 can form a film 10»casting die 41 having a multilayer structure composed of three layers 11 to 13 as shown in Fig. 1. The surface is then configured with a feed sleeve 42 having supply openings 42a-42c. The dopants 22 to 24 (see Fig. 2) for forming the outer layers 1 1 to 13 are supplied via the supply openings 42a to 42c of the feed sleeve 42, respectively. In the feed sleeve type 42, the slots extending from the supply openings 42a to 42c are merged so that the three dopants 22 to 24 flow in one channel to have a three-layer structure. Then, the dopants 22 to 24 supplied in the casting die 41 pass through the single slits 43 and are simultaneously cast from the lip 44 on the drum 45 as a substrate. Further, the substrate is not limited to the reel 45, but may be the belt 38 (see Fig. 2). Further, in the present invention, the dopant may be co-cast, as shown in Fig. 2. The combination of the multi-manifold type shown and the feed sleeve type as shown in Fig. 3 is cast. Also in this case, the substrate may be a belt 38 as shown in Fig. 2 or a drum 45 as shown in Fig. 3. In the present invention, the dopant may be cast without using a co-casting method, but using a sequential casting method. When the N layer is formed by the sequential casting method, the dopant can be cast on the substrate by a number of castings NC (NC is set to a natural number of at least 2) in accordance with the condition of 2 ^ NC ^ N . When NC < N, it is necessary to carry out at least one co-casting in the dopant casting step. In the sequential casting method, the preferred substrate is a tape. The solvents used for the dopants 22 to 24 are: organic halides (dichloromethane dichloromethylene and its analogs and non-chlorinated compounds such as alcohols (methanol, ethanol, n-butanol and their Analogs), several compounds having an ester form (methyl acetate 'ethyl acetate and the like), etc. In view of the above, the present invention is achieved in consideration of environmental factors. In Figure 4, the present invention - The deuterated cellulose film 50 has a multilayer structure as shown in Fig. 1, whereas the prior art film has a single layer structure. The film 50 has a layer number of 5. The film 5 has a first outer layer 51 as a peeling from the substrate. The layers are further provided with first to third inner layers 52 to 54 and a second outer layer 55 which are superposed on the first outer layer 5 in this order. Further, the film 50 is laminated on the hydrophilic material 57. Furthermore, other layers may be formed between the layers 51 to 55. In this specific example, the main raw materials of the layers 51 to 55 are one of wood pulp and cotton linters. 1332090 Inventive, at least one of several layers can be made from a wood pulp and a mixture of materials prepared from cotton linters. The thickness T50 of the film 50 is in the range of from 10 micrometers to 300 micrometers. The raw material of the cellulose acetate of the first outer layer 51 is cotton linter, and the average degree of acetylation is in the range. It is from 1.8 to 2.2. Regarding the additive, the cerium oxide particles 56 and the acidic material are contained in the first outer layer 51. Further, in the first inner layer 52 and the third inner layer 54, the cellulose acetate raw material is used. It is wood paper and the average degree of acetylation is in the range from 2.2 to 2.9» In the second inner layer 53, the raw material of cellulose acetate is wood pulp, and the average degree of acetylation is in the range of 1.8. To 2.2. The additives of the first to third inner layers 52 to 54 are a plasticizer, an ultraviolet absorber, and the like. Further, the raw material of the second outer layer 55 is wood pulp, and the average degree of acetylation is in the range of From 1.8 to 2.2. Please note that the thickness T50 of the film 50 is in the range of from 10 μm to 300 μm. The cellulose acetate as the outer layer 51, 55 of the surface layer has an extremely low degree of acetylation and is lower than the inner layer. 52 to 54 are very low. In view of this, the film 5 can be imparted without saponification. 0 has adhesion to a hydrophilic material such as polyvinyl alcohol and the like. The second outer layer 55 is usually laminated on another hydrophilic material. If this case is considered, the degree of acetylation is between The second outer layer 51' 55 is the same, so that the second outer layer 55 can have better adhesion to the hydrophilic material. The degree of acetylation is determined according to the kind of another hydrophilic material. Please pay attention to the first outer layer ( The average degree of acetylation of the lowest layer 51 and the second outer layer (as shown in Fig. 4) 55 as shown in Fig. 4 do not need to be the same. 1332090 Furthermore, when the degree of acetylation is higher When it is low, the optical anisotropy becomes larger. In view of this, a layer having a lower degree of deuteration is used in combination with a layer having a higher degree of deuteration, so that a deuterated cellulose film having a predetermined birefringence can be obtained. For example, the average degree of deuteration of the first and second outer layers 51, 55 and the second inner layer 53 is higher than that of the first and third inner layers 52, 54. Therefore, in the present invention, a layer having a higher average degree of deuteration is used in combination with the lower one, so that the optical properties of the film produced are improved. In addition, the layer having a higher average degree of deuteration is in a sandwich structure with the lower one, so that the two surfaces of the film 50 have an appropriate adhesiveness to the hydrophilic material, and the optical of the obtained film is further improved. nature. Note that the optical properties are related to the viewing angle properties and average birefringence which are important for liquid crystal display devices and the like. In addition, when the first outer layer 51 is formed of cellulose acetate made from cotton linter, the easy peelability and optical properties can be improved from the substrate. The optical properties between wood pulpers are different. Therefore, it is effective to select the type of cellulose acetate for the purpose. In particular, cellulose acetate made from cotton linter is an extremely superior peeling property from the substrate than those made from wood pulp. Therefore, the first outer layer 51 can be peeled off using a low peeling force. Regarding the acidic compound, ethyl citrate and ethanol in a half ester form are added to make the peeling property more stable. In the present embodiment, the cerium oxide particles 56 are added to the outer layers 51, 55' as the surface layer so that the film 50 has lubricating properties. In view of the above, it is not necessary to add the particles 56 to the inner layer 52 to 54-20-1332090 as the inner layer. It is preferred that at least one layer is made only from cotton linters, or the main raw material thereof is cotton linter. . Since the material made from cotton linter is expensive, it is preferred to form other layers from the material made from wood pulp. In view of this, in the multilayer structure, the surface layer for forming the peeling surface from the substrate is formed of cotton linter, and at least the other layer is formed of wood pulp. Note that the raw materials of the outer and inner layers 51 to 55 may be not only one of cotton linter and wood pulp, but may also be a mixture. It is effective to form a layer by appropriately mixing two kinds of cellulose acetate, and takes into consideration the properties and characteristics of the fine control film, such as optical properties and easy peelability from the substrate, and the number. For example, when a predetermined easy peelability from the substrate is obtained, the layer constituting the release surface may be formed of a mixture of two cellulose acetates. The mixing ratio of the two kinds of deuterated cellulose can be determined depending on the rate of film production and the content of the solvent in the film peeled off from the substrate. Further, in order to finely control the properties of the film, it is effective to arrange at least one layer or preferably several layers in which a plurality of raw materials are mixed. In this specific example, the plasticizer is added to the inner layers 52 to 54 as the inner layer and is not added to the outer layers 51, 55 as the surface layers. Therefore, the emission is reduced and the process contamination can be prevented. Note that when the number of layers is at least 4', the layer in which the emissive compound such as the plasticizer is not added is not limited to only the surface layer, and the emissive compound may not be added to at least the surface layer. In the above specific examples, it is preferable that the outer layers 51, 55 are thin as the surface layer. The large thickness of the layer which does not contain the plasticizer lowers the mechanical strength of the film such as tensile strength and bending strength. Otherwise, when the cellulose acetate layer having an extremely low acetylation ratio of 1332090 is thick, the film is highly hygroscopic and water absorbing. In the latter case, the condition of the film loses stability, which usually causes deformation such as curling. The thickness of the surface layer is in the range of from 1 micrometer to 50 micrometers, and preferably ranges from 1 micrometer to 10 micrometers. In FIG. 5, a casting die 61 is formed to have a shape as shown in FIG. A five-layer structure of cellulose acetate film 50 is shown. The casting die 61 has a single slit 65 and is of the feed sleeve type so that it can form five layers at the same time. The two sets of feed sleeves 62, 63 are stacked on the surface behind the casting die 61 and have dopant supply openings 62a, 62b, 63a - 63c. The dopants (not shown) for forming the outer and inner layers 51 to 55 (see Fig. 4) are supplied through the supply openings 62a, 62b' 63a to 63c, respectively. In the feed sleeve 63, the slots extending from the supply openings 63a to 63c merge into a single slot; and in the feed sleeve 62, the single slot merges with the slot extending from the supply opening 62a' 62b. Therefore, in the slot 65, the five kinds of dopants form a five-layer structure, and are cast from the lip portion 66 on the drum as a substrate. Further, the substrate is not limited to the drum 67, but may be a belt 38 (see Fig. 2). The cellulose of the present invention is particularly preferably cellulose acetate, but may be several kinds of cellulose. Furthermore, a single or a mixture of them may be used in the present invention. The polymer is not limited to deuterated cellulose. The present invention can be applied to a case where the degree of deuteration of the substitution degree of the hydroxyl group as an enzyme group can be controlled in a polymer, and especially if the polymer has no optical anisotropy and can be used for a solution casting method. The present invention is particularly effective for forming a film having not only 5 layers as exemplified in Figs. 1 and 4 but also up to 20 layers. The film 1332090 preferably has 3 to 15 layers, and particularly preferably has 3 to 10 layers. The present invention can be suitably applied to when the deuterated cellulose having such a multilayer structure has a thickness of from 10 μm to 300 μm. However, the thickness distribution of each layer is not limited. When the film has at least three layers of structure, the film may be asymmetrical for the center of the multilayer structure between the front surface and the back surface. Further, unlike the single layer structure in the prior art, in the present invention The cellulose film has a multilayer structure, and all of the layers of the multilayer structure may be formed of non-deuterated cellulose. Other materials of certain layers are selected to avoid damage to the properties of the optically modified cellulose film. Further, when the deuterated cellulose film and other films are stacked to form a stacked film sheet, the deuterated cellulose film can form a surface or an inner film of the stacked film sheet. When the deuterated cellulose film is disposed inside the stacked film sheet, the other film on both sides of the deuterated cellulose film may have a single layer or a multilayer structure, which may be symmetrical to the inner deuterated cellulose film or Asymmetry. Further, when there is a difference in the kind or composition of the solvent for the dopant of the layer, or the kind or amount of the additive, or whether or not the additive is added, the adjacent layer may be deuterated by the same degree of acetylation. Formed by cellulose. In this case, these adjacent layers are treated as two different layers. When the obtained deuterated cellulose film is laminated on a hydrophilic material or other materials, the laminate is formed by a known method. For example, one method is to seal the film with a hydrophilic material by compression lamination or pressing; one method is to bond with a binder; or one method is to apply the deuterated cellulose solution directly to a hydrophilic material as a substrate for application. . In the present invention, several layers are formed in application so that the deuterated cellulose film is formed on the application substrate -23 -, however, in the prior art, only a single layer is formed so that the deuterated cellulose film is formed in Applied on the substrate. In this case, as described above, a conventional multi-manifold type casting die, a feed sleeve type, or the like can be used for casting. Further, in the case of bonding with a binder, for example, a polyvinyl alcohol (PVA) film is used as a polarizing film for a polarizing filter, and a binder is applied to a polarizing film which is usually a hydrophilic material. In this case, when the film of the present invention is used, the adhesion of the film to the adhesive can be improved. When the system is designed to use a PVA film as a polarizing film, the PVA solution is used as a binder. In view of this, the hydrophilic material of the present invention is not limited to a film, a sheet, a plate or the like, and may contain a binder. Further, in the present invention, the film obtained by the solution casting method is used as an element of a polarizing filter, an optical compensation film, and a liquid crystal display device. Further, the film is used as a photosensitive material. In order to obtain a polarizing filter, the cellulose acetate film 10, 40, 50 obtained by the solution casting method of the above specific example is bonded as a protective film to a film formed of a polyvinyl alcohol (PVA) film. Both surfaces of the polarizing film. The polarizing film is obtained by dyeing a polyvinyl alcohol film. The dyeing method is usually a gas phase or liquid phase adsorption method, and both methods can be used. In the present invention, the film is dyed by liquid phase adsorption.
當染色是以液相吸附法來實施時，其係使用碘。然而， 本發明是並不受限於此。聚乙烯醇薄膜是在碘/碘化鉀（KI )之水溶液中浸漬爲期30至5,000秒鐘。在水溶液中之碘 的濃度較佳爲0.1至20克/公升，且碘化鉀的濃度爲1至 -24- 1332090 ♦ 100克/公升。此外，當將聚乙烯醇進行浸漬時，水溶液之 溫度是設定在5至50°c。 液相吸附法是並不受限於浸漬法，且可爲習知的方法， 例如一種方法是將碘或其他染色溶液施塗或噴霧在聚乙烯 醇薄膜上。染色是在將聚乙烯醇薄膜進行拉張（tensing) 之後或之前實施。然而，因爲聚乙嫌醇在染色時會適當地 潤脹而使其容易拉張，其較佳爲染色步驟是配置在拉張步 驟之前。 染色較佳爲使用雙色性染料，而非碘系。關於雙色性染 料之染料化合物，例如偶氮染料、二苯乙嫌染料、吡唑酮 染料、三苯基甲烷染料、喹啉染料、噁畊染料、噻啶染料 、蒽醌染料、及其類似物。請注意特佳爲染料化合物是可 溶於水。此外，雙色性染料較佳爲具有親水性基團，例如 硫酸基、胺基、羥基、或其類似基。 用以將聚乙烯醇交聯化的化合物是使用於一種藉由將已 染色之聚乙烯醇系薄膜加以拉張以製造偏光膜的步驟中。 具體言之，聚乙烯醇系薄膜是在拉張步驟之前或期間浸漬 於交聯劑之溶液中，使得在薄膜中含有交聯劑。也可使用 施塗法，而非浸漬法》當聚乙烯醇系薄膜含有交聯劑時， 其係可充分地硬化。結果導致可賦予聚乙烯醇系薄膜適當 的配向（orientation )。請注意特佳的聚乙烯醇之交聯劑 是硼酸類，但是交聯劑之種類並不受限於該等。 用於所獲得之偏光膜和纖維素醋酸酯薄膜的黏合劑是可 使用數種已習知的化合物，使得保護膜可黏合在偏光膜上 -25- 1332090 。特佳爲硼化合物，及具有乙醯乙醯基、磺酸基' 羧基、 氧化烯基、及其類似基之含改質聚乙烯醇的聚乙烯醇系聚 合物。在乾燥後，黏合劑之厚度較佳爲0.01至10微米， 特佳爲0.05至5微米。此外，可將抗反射層、防眩層、潤 滑層 '易黏合層配置在纖維素醋酸酯薄膜之表面，其係附 加作爲對聚乙烯醇薄膜之保護膜。 此外，一種光學補償片是施用在纖維素醋酸酯薄膜上， 使得纖維素醋酸酯薄膜可用作爲所獲得之光學補償薄膜。 當在偏光濾光片上形成抗反射層時，則可獲得抗反射膜且 用作爲保護膜之兩表面之一，使其可使用於透射型、反射 型、或透射反射型，例如扭轉向列型（TN ) '超扭轉向列 型（STN)、垂直分子排列型（VA)、水平電場驅動型（ IPS)、光學補償彎曲元件型（OCB)、及其類似物之液晶 顯示裝置。此外，光學補償薄膜（例如用以使得液晶顯示 裝置之視野角變寬之廣視角薄膜）及雙折射濾光片可與本 發明之薄膜組合倂用。當本發明之薄膜是使用於透射型或 透射反射型之液晶顯示裝置時，其係同時使用市售亮度強 化膜（具有偏光選擇層之偏光分隔膜（polarization splitter film )，例如製自住友· 3M ( Sumitomo-3M )有限公司之 D-BEF)。因此，所製得之液晶顯示裝置具有高視認性。 【實施方式】 本發明之實施例是具體地加以說明。然而，本發明並不 受限於該等。 竇施例 -26- 1332090 在實施例1係製得具有三層結構之纖維素醋酸酯薄膜10 ，且評估對聚乙烯醇之黏合性。薄膜10是以進料套管型之 共流延法所形成，以使其具有：厚度爲18微米之第一外層 11，4微米之內層12，18微米之第二外層13，及40微米 之總厚度T10。關於基材，係使用帶38。外層11、13之纖 維素醋酸酯是製自木材紙漿，且具有平均乙醯化度爲2.8; 而內層.12是製自木材紙漿，且具有平均乙醯化度爲1.8。 外層和內層11 ~ 13是由摻雜劑22〜24所形成。一種用於 摻雜劑22〜24之溶劑混合物是藉由將二氯甲烷、甲醇、 正丁醇以85 : 1 2 : 3之體積比率加以混合所製得。添加到 溶劑混合物之固體材料（含有添加劑）及其含量是如下所 示。請注意塑化劑是一種含有重量比率爲3 : 1之磷酸三苯 酯（TPP )和磷酸聯苯基二苯酯（BDP )的混合物。第一外 層之表面是加以皂化，然後將聚乙烯醇黏合在其表面上。 欲能黏合聚乙烯醇，其係製備且施塗改質聚乙烯醇之水溶 液。 第一外層： 纖維素醋酸酯 1 9重量份 二氧化矽顆粒 0.13重量份 檸檬酸（相對於纖維素醋酸酯） 3 0 0 ppm 丨層： 纖維素醋酸酯 19重量份 塑化劑 1 6重量份 紫外線吸收劑 2重量份 -27- 1332090 第二外層： 纖維素醋酸酯 19重量份 二氧化矽顆粒 0.13重量份 欲能評估纖維素醋酸酯和聚乙烯醇之黏合性，其係將彼 等黏合，然後浸漬入60°C之溫水中爲期10小時。然後， 以人類肉眼觀察纖維素醋酸酯薄膜從聚乙烯醇剝離之狀況 。在評估尺寸穩定性時，係將纖維素醋酸酯薄膜放置在90 °C之大氣下爲期120小時，然後量測纖維素醋酸酯薄膜之 尺寸的變化。從基材之易剝離性是藉由量測剝離力來加以 評估。 關於實施例1之檢視結果，所獲得纖維素醋酸酯之厚度 方向的延遲値Rth爲40奈米，因此作爲光學用是極佳的。 聚合物薄膜和聚乙烯醇之組合是具有特優的黏合性、尺寸 穩定性、及從基材之易剝離性。 實施例2 在實施例2係製得如第4圖所示之具有五層結構的之纖 維素醋酸酯薄膜50，且評估對聚乙烯醇之黏合性。薄膜50 是具有：厚度爲3微米之外層51、55，15微米之第一和第 三內層52、54，及4微米之第二內層53。第一至第三內層 52〜54之纖維素醋酸酯、及第二外層55是製自木材紙漿 ，且僅第一外層51是製自棉籽絨》在外層51、55之乙醯 化度爲1.8,在第一和第三內層52、54爲2.8，且在第二內 層53爲2.75。添加到用於各層之摻雜劑的固體材料和添加 劑之混合比率是如下所示。醯化纖維素薄膜是黏合在聚乙 -28 - 1332090 烯醇上，第一外層51之表面的並無皂化。其他條件，例如 塑化劑和顆粒之種類、評估方法 '及其類似物是與在實施 例1中者相同。 第一外層： 纖維素醋酸酯 1 9重量份 二氧化矽顆粒 〇 · 1 3重量份 檸檬酸（相對於纖維素醋酸酯） 300 ppm 第一內層： 纖維素醋酸酯 19重量份 塑化劑 16重量份 紫外線吸收劑 2重量份 第二內層： 纖維素醋酸酯 1 9重量份 塑化劑 1 6重量份 紫外線吸收劑 2重量份 第三內層： 纖維素醋酸酯 1 9重量份 塑化劑 1 6重量份 紫外線吸收劑 2重量份 第二外層： 纖維素醋酸酯 1 9重量份 二氧化矽顆粒 0.1 3重量份When the dyeing is carried out by a liquid phase adsorption method, it uses iodine. However, the invention is not limited thereto. The polyvinyl alcohol film is immersed in an aqueous solution of iodine/potassium iodide (KI) for a period of 30 to 5,000 seconds. The concentration of iodine in the aqueous solution is preferably from 0.1 to 20 g/liter, and the concentration of potassium iodide is from 1 to -24 to 1332090 ♦ 100 g/liter. Further, when the polyvinyl alcohol is impregnated, the temperature of the aqueous solution is set at 5 to 50 °C. The liquid phase adsorption method is not limited to the dipping method, and may be a conventional method, for example, a method of applying or spraying iodine or other dyeing solution onto a polyvinyl alcohol film. The dyeing is carried out after or before the stretching of the polyvinyl alcohol film. However, since the polyethyl alcohol is properly swelled during dyeing to make it easy to stretch, it is preferred that the dyeing step be disposed before the stretching step. The dyeing is preferably carried out using a dichroic dye instead of an iodine system. a dye compound for a dichroic dye, such as an azo dye, a diphenylethyl dye, a pyrazolone dye, a triphenylmethane dye, a quinoline dye, a bad dye, a thiaridine dye, an anthraquinone dye, and the like . Please note that the dye compound is particularly soluble in water. Further, the dichroic dye preferably has a hydrophilic group such as a sulfate group, an amine group, a hydroxyl group, or the like. The compound for crosslinking the polyvinyl alcohol is used in a step of producing a polarizing film by stretching a dyed polyvinyl alcohol-based film. Specifically, the polyvinyl alcohol-based film is immersed in a solution of a crosslinking agent before or during the stretching step so that a crosslinking agent is contained in the film. It is also possible to use the application method instead of the dipping method. When the polyvinyl alcohol-based film contains a crosslinking agent, it can be sufficiently hardened. As a result, an appropriate orientation to the polyvinyl alcohol-based film can be imparted. Please note that the particularly preferred crosslinking agent for polyvinyl alcohol is boric acid, but the type of crosslinking agent is not limited thereto. As the binder for the obtained polarizing film and cellulose acetate film, several conventional compounds can be used, so that the protective film can be bonded to the polarizing film -25-1332090. Particularly preferred are boron compounds, and polyvinyl alcohol-based polymers containing modified polyvinyl alcohol having an ethyl oxime group, a sulfonic acid group 'carboxy group, an oxyalkylene group, and the like. After drying, the thickness of the binder is preferably from 0.01 to 10 μm, particularly preferably from 0.05 to 5 μm. Further, the antireflection layer, the antiglare layer, and the lubricating layer 'adhesive layer' may be disposed on the surface of the cellulose acetate film, which is added as a protective film for the polyvinyl alcohol film. Further, an optical compensation sheet is applied on a cellulose acetate film so that a cellulose acetate film can be used as the obtained optical compensation film. When an anti-reflection layer is formed on the polarizing filter, an anti-reflection film can be obtained and used as one of the two surfaces of the protective film, so that it can be used for a transmissive type, a reflective type, or a transflective type, for example, a twisted nematic A liquid crystal display device of the type (TN) 'super twisted nematic (STN), vertical molecular alignment type (VA), horizontal electric field driven type (IPS), optically compensated bending element type (OCB), and the like. Further, an optical compensation film (e.g., a wide viewing angle film for widening the viewing angle of the liquid crystal display device) and a birefringent filter can be used in combination with the film of the present invention. When the film of the present invention is used in a transmissive or transflective liquid crystal display device, a commercially available brightness enhancement film (a polarization splitter film having a polarization selective layer, for example, from Sumitomo 3M) is used at the same time. (D-BEF) of Sumitomo-3M). Therefore, the liquid crystal display device produced has high visibility. [Embodiment] An embodiment of the present invention is specifically described. However, the invention is not limited to these. Sinus application -26 - 1332090 A cellulose acetate film 10 having a three-layer structure was obtained in Example 1, and the adhesion to polyvinyl alcohol was evaluated. The film 10 is formed by a co-casting method of a feed sleeve type having a first outer layer 11 having a thickness of 18 μm, an inner layer 12 of 4 μm, a second outer layer 13 of 18 μm, and 40 μm. The total thickness T10. For the substrate, a belt 38 is used. The cellulose acetate of the outer layers 11, 13 was made from wood pulp and had an average degree of acetylation of 2.8; while the inner layer .12 was made from wood pulp and had an average degree of acetylation of 1.8. The outer and inner layers 11 to 13 are formed of dopants 22 to 24. A solvent mixture for the dopants 22 to 24 is obtained by mixing dichloromethane, methanol, and n-butanol in a volume ratio of 85:1 2:3. The solid material (containing the additive) added to the solvent mixture and its content are as follows. Note that the plasticizer is a mixture containing triphenyl phosphate (TPP) and biphenyldiphenyl phosphate (BDP) in a weight ratio of 3:1. The surface of the first outer layer is saponified and then the polyvinyl alcohol is adhered to the surface. To be able to bond polyvinyl alcohol, it is prepared and applied with an aqueous solution of modified polyvinyl alcohol. First outer layer: cellulose acetate 19 parts by weight of cerium oxide particles 0.13 parts by weight of citric acid (relative to cellulose acetate) 3 0 0 ppm 丨 layer: cellulose acetate 19 parts by weight of plasticizer 16 parts by weight Ultraviolet absorber 2 parts by weight -27-1332090 Second outer layer: Cellulose acetate 19 parts by weight of cerium oxide particles 0.13 parts by weight To evaluate the adhesion of cellulose acetate and polyvinyl alcohol, which are bonded to each other, It was then immersed in warm water at 60 ° C for 10 hours. Then, the state in which the cellulose acetate film was peeled off from the polyvinyl alcohol was observed by human eyes. In evaluating the dimensional stability, the cellulose acetate film was placed in an atmosphere at 90 ° C for 120 hours, and then the change in the size of the cellulose acetate film was measured. The easy peelability from the substrate was evaluated by measuring the peel force. As a result of the examination of Example 1, the obtained cellulose acetate had a retardation 値Rth of 40 nm in the thickness direction, and therefore it was excellent for optical use. The combination of the polymer film and polyvinyl alcohol has excellent adhesion, dimensional stability, and easy peelability from the substrate. Example 2 In Example 2, a cellulose acetate film 50 having a five-layer structure as shown in Fig. 4 was obtained, and the adhesion to polyvinyl alcohol was evaluated. The film 50 is a layer having a thickness of 3 μm, layers 51, 55, 15 μm of the first and third inner layers 52, 54, and a 4 μm second inner layer 53. The cellulose acetate of the first to third inner layers 52 to 54 and the second outer layer 55 are made of wood pulp, and only the first outer layer 51 is made of cotton velvet. The degree of acetylation of the outer layers 51, 55 is 1.8 is 2.8 at the first and third inner layers 52, 54 and 2.75 at the second inner layer 53. The mixing ratio of the solid material and the additive added to the dopants for the respective layers is as follows. The deuterated cellulose film is bonded to the polyethyl 28 - 1332090 enol, and the surface of the first outer layer 51 is not saponified. Other conditions, such as the type of plasticizer and granules, the evaluation method 'and the like, are the same as those in Example 1. First outer layer: cellulose acetate 19 parts by weight of cerium oxide particles 1 · 13 parts by weight of citric acid (relative to cellulose acetate) 300 ppm first inner layer: cellulose acetate 19 parts by weight plasticizer 16 2 parts by weight of the ultraviolet absorber 2 parts by weight of the second inner layer: cellulose acetate 19 parts by weight of the plasticizer 1 6 parts by weight of the ultraviolet absorber 2 parts by weight of the third inner layer: cellulose acetate 19 parts by weight of the plasticizer 1 6 parts by weight of the ultraviolet absorber 2 parts by weight of the second outer layer: cellulose acetate, 19 parts by weight of cerium oxide particles 0.1 3 parts by weight
關於實施例2之檢視結果，所獲得纖維素醋酸酯之厚度 方向的延遲値Rth爲40奈米，因此作爲光學用是極佳的。 •29- 1332090 聚合物薄膜和聚乙烯醇之組合是具有特優的黏合性、尺寸 穩定性、及從基材之易剝離性。 比較例1 在比較例1中，具有平均醯化度爲2.8之醯化纖維素是 用以形成一種具有單層結構且厚度爲40微米之薄膜。纖維 素醋酸酯的原料是木材紙漿。在摻雜劑中之固體材料的混 合比率如下所示。其他條件，例如溶劑之種類、評估方法 、及其類似物是與在實施例1中者相同。請注意在從基材 剝離之表面上是加以皂化。 · 纖維素醋酸酯 19重量份 二氧化矽顆粒 0.13重量份 塑化劑 1 6重量份 紫外線吸收劑 2重量份 關於比較例1之檢視結果，聚合物薄膜和聚乙烯醇之組 合是具有特優的黏合性、尺寸穩定性、及從基材之易剝離 性。然而，所獲得纖維素醋酸酯之厚度方向的延遲値Rth 爲24奈米，因此其係並不適合作爲光學用β 比較例2 在比較例2中’具有平均醯化度爲2.7之醯化纖維素是 用以形成一種具有單層結構且厚度爲40微米之薄膜。纖維 素醋酸酯的原料是木材紙發。在摻雜劑中之固體材料的混 合比率如下所示。其他條件，例如溶劑之種類、評估方法 '及其類似物是與在實施例i中者相同。請注意在從基材 剝離之表面上是加以皂化。 -30- 1332090 纖維素醋酸酯 二氧化矽顆粒 塑化劑 紫外線吸收劑 1 9重量份 0.1 3重量份 . 16重量份 2重量份 關於比較例2之檢視結果，所獲得纖維素醋酸酯之厚度 方向的延遲値Rth爲39奈米，因此是較佳的。聚合物薄膜 - 和聚乙烯醇之組合是具有特優的黏合性、尺寸穩定性，但 是從基材之易剝離性並不優良。 實施例3 · 在實施例3中，將厚度爲75微米之聚乙烯醇薄膜（製自 可樂麗（Kuraray)有限公司）浸漬於25°C之水溶液中，其 - 中碘之含量爲0.3克/公升.，且碘化鉀之含量爲18.0克/公 升。然後，將薄膜在50°C之水溶液中加以拉張，其中硼酸 之含量爲80克/公升，且碘化鉀之含量爲30克/公升。因 此，薄膜變得五倍大於偏光膜。將在實施例2所獲得纖維 素醋酸酯薄膜以黏合劑黏合在偏光膜上，然後在空氣之溫 度是維持在80°C之恆溫箱中加以乾燥爲期30分鐘。請注 ® 意黏合劑是一種聚乙烯醇（商品名：PVA-11 7H，製自可樂 麗有限公司）之4 %水溶液。 根據所獲得之偏光濾光片，在可見光範圍之平行透射比 Yp和交叉透射比Yc是以分光光度計（spectrophotometer )所獲得，且偏光係數PY是根據下式計算得： PY = { ( Yp - Yc ) / ( Yp + Yc ) }1/2 x 100 ( % ) 關於實施例3之檢視結果，由在實施例2所製得薄膜所 -31 - 1332090 構成的任何一種偏光濾光片之偏光係數PY爲至少99.6 % 。在本發明之溶液流延法所獲得之薄膜是適用於偏光濾光 片。 奮施例4 在實施例3所製得偏光濾光片是用作爲在筆記型個人電 腦所配置之扭轉向列型（ΤΝ )液晶顯示裝置之透射型的螢 幕側中之偏光濾光片。此液晶顯示裝置介於背光與液晶胞 (liquid crystal cell)之間具有偏光分隔膜（商品名：D-BEF，製自住友-3M有限公司）。 關於實施例4之檢視結果，在所獲得之液晶顯示裝置中 ，背景之反射是極其降低，且影像之品質非常高。在本發 明之溶液流延法所獲得之薄膜是適用於液晶顯示裝置。 在本發明中，各種不同的變化和改質是可能的，且應可 了解其係包括在本發明之範圍內。 【圖式簡單說明】 當閱讀如上所述之詳細敘述且與附圖相互對照時，如上 所述本發明之目的及優點對一般熟諳此項技藝者將變得更 容易了解" 第1A圖是本發明之第一具體實例之纖維素醋酸酯薄膜 的剖面示意圖； 第1B圖是用以例示如第1A圖所示之纖維素醋酸酯薄膜 積層在親水性材料上的剖面示意圖： 第2圖是多重歧管型之流延模頭的剖面示意圖； 第3圖是進料套管型之流延模頭的剖面示意圖； -32- 1332090 第4圖是本發明之第二具體實例之纖維素醋酸酯薄膜的 剖面示意圖； 第5圖是一種進料套管型之流延模頭之另一具體實例的 剖面示意圖。 【主要元件符號說明】 10、50 醯化纖維素薄膜 1 1、5 1 第一外層 12 內層 13 ' 5 5 第二外層 15、56 二氧化矽顆粒 17 ' 57 親水性材料 21 、 41 、 61 流延模頭 22 ' 23 ' 24 摻雜劑 26、27、28 ' 42a ' 42b ' 42c 、 62a 、 62b ' 63a 、 63b ' 6 3c 摻雜劑供應開口 30 、 31 、 32 槽孔 33 、 34 、 35 摻雜劑用袋狀凹 37 、 44 、 66 模頭唇部 3 8 帶 42 ' 62 、 63 進料套管 43、65 單槽孔 45、6 7 轉筒 52 第一內層 53 第二內層 54 第三內層As a result of the examination of Example 2, the obtained cellulose acetate had a retardation 値Rth of 40 nm in the thickness direction, and therefore it was excellent for optical use. • 29-1332090 The combination of polymer film and polyvinyl alcohol has excellent adhesion, dimensional stability, and easy peelability from the substrate. Comparative Example 1 In Comparative Example 1, deuterated cellulose having an average degree of deuteration of 2.8 was used to form a film having a single layer structure and having a thickness of 40 μm. The raw material of cellulose acetate is wood pulp. The mixing ratio of the solid materials in the dopant is as follows. Other conditions such as the kind of the solvent, the evaluation method, and the like are the same as those in the embodiment 1. Note that the surface is peeled off from the substrate. Cellulose acetate 19 parts by weight of cerium oxide particles 0.13 parts by weight of plasticizer 16 parts by weight of ultraviolet absorber 2 parts by weight. As a result of the examination of Comparative Example 1, the combination of the polymer film and the polyvinyl alcohol is excellent. Adhesion, dimensional stability, and easy peelability from the substrate. However, the obtained cellulose acetate had a retardation 値Rth of 24 nm in the thickness direction, and thus it was not suitable as the optical β. Comparative Example 2 In Comparative Example 2, 'the cellulose having an average degree of deuteration of 2.7 It is used to form a film having a single layer structure and having a thickness of 40 μm. The raw material of cellulose acetate is wood paper. The mixing ratio of the solid materials in the dopant is as follows. Other conditions such as the kind of the solvent, the evaluation method 'and the like are the same as those in the example i. Note that the surface is peeled off from the substrate. -30- 1332090 Cellulose acetate cerium oxide granule plasticizer UV absorber 1 9 parts by weight 0.1 3 parts by weight. 16 parts by weight 2 parts by weight of the results of the comparison of Comparative Example 2, the thickness direction of the obtained cellulose acetate The delay 値Rth is 39 nm, so it is preferable. The combination of the polymer film - and polyvinyl alcohol has excellent adhesion and dimensional stability, but is not excellent in peelability from the substrate. Example 3 In Example 3, a polyvinyl alcohol film (made from Kuraray Co., Ltd.) having a thickness of 75 μm was immersed in an aqueous solution at 25 ° C, and the content of iodine therein was 0.3 g / Liters., and the content of potassium iodide is 18.0 g / liter. Then, the film was stretched in an aqueous solution at 50 ° C, wherein the content of boric acid was 80 g / liter, and the content of potassium iodide was 30 g / liter. Therefore, the film becomes five times larger than the polarizing film. The cellulose acetate film obtained in Example 2 was adhered to the polarizing film with a binder, and then dried in an oven maintained at 80 ° C for 30 minutes. Please note that the adhesive is a 4% aqueous solution of polyvinyl alcohol (trade name: PVA-11 7H, manufactured by Kelly Co., Ltd.). According to the obtained polarizing filter, the parallel transmittance Yp and the cross transmittance Yc in the visible light range are obtained by a spectrophotometer, and the polarization coefficient PY is calculated according to the following formula: PY = { ( Yp - Yc ) / ( Yp + Yc ) } 1/2 x 100 ( % ) Regarding the inspection result of Example 3, the polarizing coefficient of any one of the polarizing filters composed of the film -31 - 1332090 obtained in Example 2 PY is at least 99.6 %. The film obtained by the solution casting method of the present invention is suitable for use in a polarizing filter. Example 4 The polarizing filter produced in Example 3 was used as a polarizing filter in the transmissive screen side of a twisted nematic (ΤΝ) liquid crystal display device disposed on a notebook personal computer. This liquid crystal display device has a polarizing separation film (trade name: D-BEF, manufactured by Sumitomo-3M Co., Ltd.) between the backlight and the liquid crystal cell. With respect to the inspection results of Example 4, in the obtained liquid crystal display device, the reflection of the background was extremely lowered, and the quality of the image was extremely high. The film obtained by the solution casting method of the present invention is suitable for a liquid crystal display device. In the present invention, various changes and modifications are possible, and it should be understood that they are included in the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS When reading the above detailed description and in conjunction with the drawings, the objects and advantages of the present invention as described above will become more readily apparent to those skilled in the art. A schematic cross-sectional view of a cellulose acetate film according to a first embodiment of the present invention; FIG. 1B is a schematic cross-sectional view showing a cellulose acetate film layer as shown in FIG. 1A on a hydrophilic material: FIG. 2 is a schematic view FIG. 3 is a schematic cross-sectional view of a casting die of a feed sleeve type; -32-1332090 A schematic cross-sectional view of an ester film; Fig. 5 is a schematic cross-sectional view showing another embodiment of a casting die of a feed sleeve type. [Main component symbol description] 10, 50 deuterated cellulose film 1 1 , 5 1 first outer layer 12 inner layer 13 ' 5 5 second outer layer 15, 56 cerium oxide particles 17 ' 57 hydrophilic material 21, 41, 61 Casting die 22 ' 23 ' 24 dopants 26, 27, 28 ' 42a ' 42b ' 42c , 62a , 62b ' 63a , 63b ' 6 3c dopant supply openings 30 , 31 , 32 slots 33 , 34 , 35 dopant pockets 37, 44, 66 die lip 3 8 belt 42 ' 62 , 63 feed sleeve 43, 65 single slot 45 , 6 7 drum 52 first inner layer 53 second inner Layer 54 third inner layer