201235194 六、發明說明： 【發明所屬之技術領域】 本發明係關於光學膜 製造的光學膜、把此光學 、及具備此偏光板之液晶 【先前技術】 從前，液晶顯示裝置 腦之液晶顯示器之用途上 液晶顯示裝置的大型化， 顯示器之利用，或者使用 共場所的廣告用顯示器之 液晶顯示裝置，具備 片等挾入玻璃板的構成之 式被配置於液晶胞的兩側 光子（亦稱爲偏光膜、偏 方式被配置於偏光子的兩 保護膜，使用例如三乙酸 構成的光學膜。 作爲光學膜之製造方 性樹脂的熔融物由流延模 熔融物外接於冷卻輥之外 挾壓或延伸等使成爲膜之 於專利文獻1，揭示 之製造方法，藉由此製造方法所 膜作爲透明保護膜使用的偏光板 顯示裝置。 (LCD )，在液晶電視或個人電 需求正在擴大。近年來，伴隨著 作爲設置在街頭或者店面的大型 被稱爲數位看板的顯示機器之公 利用等，用途也更爲多樣化。 把透明電極、液晶層、彩色濾光 液晶胞，及以挾住此液晶胞的方 的兩枚偏光板。偏光板，具備偏 光薄膜），與以挾住此偏光子的 側的2枚透明保護膜。作爲透明 纖維素等之纖維素酯樹脂之膜所 法，把包含纖維素酯樹脂等熱塑 具壓出爲膜狀，使被壓出的膜狀 周面冷卻固化，因應必要而進行 熔融流延製膜法係屬已知。 著在以冷卻輥冷卻被熔融押出的 -5- 201235194 樹脂時，於冷卻輥的寬幅方向上設置加熱器，在寬幅方向 之各區域進行溫度調整，使膜溫度在寬幅方向上保持均勻 同時進行冷卻的技術。於專利文獻2記載藉由使從模具吐 出爲薄片狀而到接觸於冷卻輥爲止之熔融樹脂以可在熔融 樹脂的流動方向及寬幅方向上改變輸出的加熱器來進行加 熱，使熔融樹脂的流動方向及寬幅方向的溫度分布抑制在 1 0 °c以內之技術。 [先前技術文獻] [專利文獻] [專利文獻1]日本專利特開2004-2099 1 2號公報（段 落 0008 ) [專利文獻2 ]日本專利特開2 0 0 9 - 7 8 3 5 9號公報（段 落 0008 ， 0010) 【發明內容】 於這樣的熔融流延製膜法，即使想要使流延模之唇緣 間隔（狹縫間隙）於流延模的寬幅方向的各部份調整爲相 同而壓出厚度在寬幅方向爲均勻的膜狀熔融物，厚度也無 法齊一，膜狀熔融物在寬幅方向上會產生厚度相對大的部 分與厚度相對小的部分。 此外，於熔融流延製膜法，爲了除去膜表面以數個 mm間距產生的條紋狀的缺陷而提高膜的平面性，會使由 流延模壓出的膜狀熔融物以主輥與觸碰輥挾壓，於該挾壓 -6- 201235194 時以對膜狀熔融物作用以均勻的壓力的方式，在以主輥與 觸碰輥挾壓的挾壓區域，會使膜狀熔融物的厚度在寬幅方 向中央部爲最大，在寬幅方向兩端部爲最小。 接著，於任一情形，膜狀熔融物在寬幅方向上有厚度 相對大的部分與相對小的部分的話，會產生所製造的光學 膜的延遲不均變大的問題。 於前述專利文獻1、2所揭示之任一技術，也無法對 應於膜狀熔融物在寬幅方向上有厚度相對大的部分與相對 小的部分的話，會產生所製造的光學膜的延遲不均變大的 問題。 本發明的目的在於抑制光學膜的延遲不均，從而對於 液晶顯示裝置的大型化有貢獻。 本發明之一局面，係具有使包含熱塑性樹脂的熔融物 由流延模壓出爲膜狀的壓出步驟，及冷卻被壓出的膜狀熔 融物的冷卻步驟之光學膜之製造方法，其特徵爲：壓出步 驟與冷卻步驟之間，設有加熱被壓出的膜狀熔融物的加熱 步驟，在此加熱步驟，根據膜狀熔融物的寬幅方向的厚度 分布，僅加熱厚度相對小的部分，或者厚度相對較小的部 分比相對大的部分以更高的溫度加熱及/或以更長時間進 行加熱。 本發明之另一局面，係藉由前述製造方法所製造的光 學膜。 本發明之另一局面，係具備偏光子、及以挾著前述偏 光子的方式被配置於偏光子的兩側的2枚透明保護膜之偏 201235194 光板，其特徵爲：前述2枚透明保護膜之中的至少一方， 係前述之光學膜。 本發明之又一局面，係具備液晶胞、以挾住前述液晶 胞的方式被配置於液晶胞的兩側的2枚偏光板之液晶顯示 裝置，其特徵爲：前述2枚偏光板之中至少一方，係前述 偏光板。 本發明之前述以及其他之目的、特徵及優點，應可藉 由以下之詳細記載以及附圖而清楚說明。 【實施方式】 以下，說明本發明之實施型態，但本發明並不以這些 實施型態爲限。 本案發明人，發現如果由流延模壓出的膜狀熔融物的 寬幅方向上有厚度不同的部分的話，最終會遭遇所得到的 膜的延遲變大之不良情形，反覆進行其原因之究明與不良 問題的解決的結果，著眼於因爲厚度的不同導致膜狀熔融 物在冷卻速度進而溫度履歷上有所差異，只要以縮小其差 異的方式加熱膜狀熔融物的話，延遲不均即被抑制，從而 完成了本發明。 <光學膜之製造裝置> 圖1係顯示相關於本實施型態之光學膜的製造裝置1 的方塊構成圖。此光學膜之製造裝置1，藉由熔融流延製 膜法，製造例如包含纖維素酯樹脂等熱塑性樹脂的光學膜 201235194 。所謂熔融流延製膜法’係把包含熱塑性樹脂的膜材料之 混合物加熱熔融至具有流動性的溫度，使該熔融物流延爲 膜狀進行冷卻固化藉以得到光學膜的方法。 圖1所示的光學膜之製造裝置10，具備：壓出機n 、流延模12、主輥1 3、觸碰輥14、冷卻輥1 5、16、剝離 輥17'搬送輥18、延伸裝置19以及捲取裝置20。圖中 ’符號31爲由流延模1 2壓出的膜狀熔融物，符號41是 以剝離輥1 7剝離的冷卻固化後的膜（樹脂膜），符號51 是供加熱膜狀熔融物3 1的加熱裝置，符號7 1，是供檢測 以剝離輥1 7剝離的冷卻固化後的膜4 1的寬幅方向的厚度 進而寬幅方向的厚度分布之用的檢測裝置。 又，搬送輥18設有複數個，藉由使越下游側的搬送 速度（旋轉速度）越大，可以在搬送膜41的同時在MD (機器方向；Machine Direction)方向（搬送方向）上進 行延伸。此外，延伸裝置1 9，例如使用抓握拉幅機（g r i p 161^61")或栓式拉幅機等，搬送膜41的同時在丁0(橫方向 ;Transverse Direction)方向（寬幅方向）上進行延伸。 於本實施型態在混合包含例如纖維素酯樹脂等之熱塑 性樹脂的膜材料後，使用壓出機Η使該混合物之熔融物 由流延模1 2成膜狀地壓出，使被壓出的膜狀熔融物3 1以 主輥13與觸碰輥14挾壓。其後，使膜狀熔融物31依序 外接於2根冷卻輥1 5、1 6之周面冷卻固化，藉由剝離輥 17進行剝離。使被剝離的膜41藉由搬送輥18及延伸裝 置19進行搬送同時延伸之後，藉由捲取裝置20捲取爲卷 -9 - 201235194 狀。 使用於本實施型態之熱塑性樹脂，只要可以藉由熔融 流延製膜法來製膜即可，沒有特別限制。例如可以舉出纖 維素酯樹脂、丙烯酸樹脂、聚碳酸酯樹脂、含有脂環構造 的高分子、聚乙烯醇、聚醯胺樹脂、聚醯亞胺樹脂等。其 中，由光彈性係數小，製造具有高的透明度之光學膜等因 素來看，以纖維素酯樹脂、丙烯酸樹脂、含有脂環構造的 高分子爲較佳。在本實施型態，這些熱塑性樹脂可以單獨 使用或組合兩種以上使用。藉由使用2種以上的熱塑性樹 脂，可以製造具有因應於用途所期待的物理特性之光學膜 。特別是包含纖維素酯樹脂與丙烯酸樹脂的場合，可製造 低吸濕性、透明度高、耐氣候性高、改善了脆性的光學膜 <光學膜之製造方法> 以下舉出作爲熱塑性樹脂使用纖維素酯樹脂的場合爲 例’說明相關於本實施型態的光學膜之製造方法。相關於 本實施型態之光學膜之製造方法，在進行膜材料之混合後 ’作爲主要，包含壓出步驟、加熱步驟、冷卻步驟（包含 挾壓步驟）、剝離步驟、延伸步驟、捲取步驟等。此外， 進而具備檢測步驟、調整步驟、決定步驟等。又，在本實 施型態，於冷卻步驟中進行挾壓步驟。除了最後說明本發 曰月的特徵部分之加熱步驟等以外，以下依序說明各步驟。 -10- 201235194 [膜材料的混合] 首先’使用混合機等進行膜材料的混合。混合機，可 以使用V型混合機、圓錐槳葉型混合機、水平圓筒型混 合機等，一般的混合機。 於本實施型態’混合膜材料後，使用壓出機1 1將該 混合物直接熔融而製膜亦可’亦可先將膜材料錠化之後， 再將該錠以壓出機Π熔融而製膜。此外，在膜材料包含 融點不同的複數材料的場合，可以在僅有融點低的材料熔 融的溫度暫時製作米花糖狀的半熔融物，將半熔融物投入 壓出機11而製膜。膜材料包含容易熱分解的材料的場合 ’依減少熔融次數的目的，以不製做錠而直接製膜的方法 ’或是如前所述製作米花糖狀的半熔融物再進行製膜的方 法爲佳。又，針對膜材料稍後詳述。 [壓出步驟] 壓出步驟，是使用壓出機11，使包含熱塑性樹脂的 熔融物由流延模1 2膜狀地壓出的步驟。 使用的壓出機Π，可以使用市售而可購得的種種壓 出機，其中以熔融混練壓出機爲佳。可以使用單軸壓出機 ，亦可使用2軸壓出機。 於壓出機11內之膜材料的熔融溫度，隨著膜材料的 黏度或吐出量、製造的膜的厚度等因素而使得較佳的條件 有所不同，但是一般而言，對於膜的玻璃轉移溫度Tg而 言，以τ?以上、Tg+100°C以下爲較佳。壓出時的熔融黏 -11 - 201235194 度，爲10〜100,000泊（poise)，較佳者爲100〜 泊（poise)。此外，在壓出機11內的膜材料的滯留 短越好，例如以在5分鐘以內爲佳。此外，壓出榜 內部，以藉由以氮氣或者氬氣等惰性氣體來置換， 行減壓，降低氧氣的濃度爲較佳。 由壓出機1 1吐出的熔融物被供給至流延模1 2 延模12被壓出爲膜狀。圖2係由流延模12壓出的 融物31之寬幅方向的剖面圖。又，於圖2，爲了 熔融物31在寬幅方向的厚度分布更容易理解而在 予以誇張的圖示。冷卻固化後（剝離後）的膜41 伸的話，膜41的厚度分布會改變。特別是，使膜< 於TD方向的話，膜41在寬幅方向的厚度分布會 因此，在本實施型態，如圖1所示，將檢測裝置 於搬送輥18及延伸裝置19之上游。又，在圖1， 裝置71配置於剝離輥1 7與搬送輥1 8之間，但是 述更進一步理解的，只要是在根據主輥13開始冷 位置，亦即只要是冷卻步驟開始後的位置，更佳者 在根據延伸裝置1 9的在TD方向的延伸開始之前 即可，可以因應於不同狀況而配置在任一位置。 製造的光學膜，藉由伴隨著冷卻固化的收縮， 比膜狀熔融物31更薄。但是，厚度的收縮率於膜 方向上幾乎爲均勻，所以冷卻固化之前後的厚度分 幾乎相似的狀態在改變。亦即，以檢測裝置7 1檢 冷卻固化後的膜41的寬幅方向的厚度分布，可以 10,000 時間越 ί 11的 或者進 ，由流 膜狀熔 使膜狀 圖示上 進行延 u延伸 改變。 '1配置 將檢測 如由後 卻後的 爲進而 的位置 使厚度 的寬幅 布是以 測的， 作爲膜 -12- 201235194 狀熔融物31的寬幅方向的厚度分布來使用。 如圖2所示，膜狀熔融物3 1，在後頭的挾壓 由主輥1 3與觸碰輥1 4挾壓，有作爲光學膜使用的 域32，以及在挾壓區域32的寬幅方向的兩端部， 況不同而藉由主輥13與觸碰輥14挾壓或者不被挾 之後被切斷而不作爲光學膜使用的端部區域3 3、 部區域33、34之最大厚度可能會達到挾壓區域32 厚度的1 .2倍〜5倍。因此，在之後的挾壓步驟， 區域3 2被挾壓，端部區域3 3、3 4以不被挾壓爲佳 區域33、34，通常在由膜狀熔融物31的寬幅方向 部起算於內側存在著約l〇mm〜200mm的寬幅。 在本實施型態，膜狀熔融物3 1，於挾壓區域 在寬幅方向中央部厚度（D1)成爲最大，寬幅方 部厚度（D2、D3 )成爲最小的方式，由流延模12 藉此，挾壓時之觸碰輥14的撓曲的影響被抵消， 句的壓力挾壓膜狀熔融物31的挾壓區域32。結果 學膜的表面除去以數個mm的間距產生的條紋狀的 可以提高光學膜的平面性。 '又，由可以確實得到挾壓效果的觀點來看，例 挾壓區域32的寬幅爲1 500mm的場合，（D1-D2) D1-D3)以1.5；czm〜4.5ym爲佳，挾壓區域32的 3000mm 的場合，（D1-D2)或者（D1-D3)以 3//r 从m爲佳◊此外，挾壓區域32之最大厚度（Dl) I： /zm 〜120/zm 爲佳，以 20/zm 〜100/zm 更佳。 步驟藉 挾壓區 因應情 壓，在 3 4。端 的最大 僅挾壓 。端部 的兩緣 32，以 向兩端 壓出。 可以均 ，於光 缺陷而 如，在 或者（ 寬幅爲 1〜9 { 15 -13- 201235194 由流延模12壓出的膜狀熔融物3i的寬幅方向的厚度 分布’依存於流延模1 2的唇緣間隔（狹縫間隙）。亦即 ’使流延模1 2的唇緣間隔在流延模1 2的寬幅方向之各部 分分別地進行調整，可以得到例如具有圖2所示那樣的寬 幅方向的厚度分布之膜狀熔融物31。 圖3係供說明唇緣間隔的調整機構之用的流延模i 2 的重要部位擴大剖面圖。唇緣間隔的調整機構，係預先調 整由流延模12壓出的膜狀熔融物31之寬幅方向的厚度分 布。 形成流延模12的狹縫（吐出口）122之一對唇緣之 中，一方爲剛性很小容易變形的可撓唇緣1 23，另一方爲 剛性大難變形的固定唇緣124。模本體121上有多數加熱 螺栓（僅圖示1個）125在流延模12的寬幅方向上以特 定的間距（亦可爲一定的間距）排列著。各加熱螺栓1 2 5 ，貫通具備埋入電熱器127與冷卻媒體通路（省略圖示） 之區塊1 26。加熱螺栓1 25的頭部被固定於模本體1 2 1， 加熱螺栓125的先端抵接於可撓唇緣123。藉由控制埋入 電熱器127的電流量或冷卻媒體的流量，改變區塊126的 溫度進而改變加熱螺栓125的長度，使可撓唇緣123位移 ，可以調整唇緣間隔。 加熱螺栓125，只要以可對膜狀熔融物31賦予如圖2 所示的寬幅方向的厚度分布之間距來排列即可，例如只要 在20mm〜200mm程度的範圍內選擇間距即可。此外，唇 緣間隔，通常爲500//m〜1500//m程度的範圍，以700 -14- 201235194 em〜1200;/ m程度的範圍爲較佳。 此外，也可以替代加熱螺栓125，而採用藉由手動鎖 緊螺栓而使可撓唇緣123位移以調整唇緣間隔的調整機構 〇 無論採用哪種機構，以此唇緣間隔之調整機構預先調 整的膜狀溶融物之寬幅方向的厚度分布，可以由流延模 12壓出的膜狀熔融物31的寬幅方向的厚度分布來使用。 在此壓出步驟，0.8〜3m寬幅的膜狀熔融物31由流 延模12壓出。如圖2所示，膜狀熔融物31具有挾壓區域 32與端部區域33、34的場合，作爲光學膜使用的挾壓區 域32的寬幅爲0.8〜3m之膜狀熔融物31由流延模12被 壓出。藉此，而製造可以對應於液晶顯示裝置的大型化要 求的尺寸之光學膜。 [挾壓步驟/冷卻步驟] 挾壓步驟，係以除去樹脂膜4 1甚而光學膜的表面所 產生的條紋狀的缺陷提高膜的平面性等爲目的，使被壓出 的膜狀熔融物31以主輥13與觸碰輥14進行挾壓的步驟 。在本實施型態，如前所述，有如圖2所示之挾壓膜狀熔 融物31的挾壓區域32與端部區域33' 34的場合，但更 佳者爲僅挾壓作爲光學膜使用的挾壓區域32。接著，此 挾壓步驟，如前所述，在冷卻步驟中進行。 主輥13，也被稱爲鑄造輥，由流延模12壓出的膜狀 熔融物31以密接於周面的方式使其外接而支撐，係在該 -15- 201235194 狀態下與觸碰輥14之間挾壓膜狀熔融物31之用的輥。 主輥1 3，只要是一般用於根據熔融流延製膜法之膜 製造所使用者即可，沒有特別限制，可以選擇適宜者使用 。通常，爲高剛性的金屬製造之輥，具有冷卻支撐於周面 的膜狀熔融物31的機能。亦即，膜狀熔融物31外接於主 輥1 3的時間點爲冷卻步驟之開始時間點。因此，根據主 輥1 3開始冷卻，是冷卻步驟的開始，根據主輥1 3開始冷 卻的膜狀熔融物31是冷卻固化後的膜41。 爲了均勻而且效率佳地冷卻膜狀熔融物31，於主輥 13的內部，以設有水或者油等冷卻媒體的流道爲佳。作 爲主輥13的周面的材質，可以使用碳鋼、不鏽鋼、鋁、 鈦等。此外，提高主輥13的周面的硬度，或者爲了改良 與樹脂之剝離性，而以施加硬鉻電鍍、或鍍鎳、鍍非晶質 鉻、或者陶瓷熔射等表面處理爲較佳。 觸碰輥1 4也沒有特別限制，可以適當選擇碳鋼、不 鏽鋼、鋁、鈦等金屬製之輥，或者周面以橡膠或樹脂等覆 蓋之輥等習知之輥。 主輥1 3或觸碰輥1 4的周面越平滑，所得到的樹脂膜 41的表面就可以越平滑，所以越佳。輥13、14的表面粗 糙度，以最大高度Ry(JIS B0601: 1994)爲以 下爲較佳，〇.〇5 /Z m以下爲更佳。 由對於膜狀熔融物31施加的壓力可以儘量均勻化的 觀點來看，觸碰輥14，以具有外筒與內筒的雙重筒構造 的彈性觸碰輥爲較佳。此外，爲了謀求外筒的周面溫度的 -16- 201235194 均勻化，在外筒與內筒之間，以設有水或者油等冷卻媒體 的流道爲佳。 外筒的材質以平滑、具有適度彈性、具耐久性者爲佳 。可以使用碳鋼、不鏽鋼、鈦、以電鑄法製造之鎳等。此 外，提高周面的硬度，或者爲了改良與樹脂之剝離性，而 以施加硬鉻電鍍、或鍍鎳、鍍非晶質鉻、或者陶瓷熔射等 表面處理爲較佳。 內筒，以碳鋼、不鏽鋼、鋁、鈦等輕量且具有剛性的 金屬製品爲佳。藉由使內筒具有剛性，可以製觸碰輥14 的旋轉變形。藉由使內筒的厚度爲外筒的2〜1 0倍，可得 充分的剛性。內筒，亦可進而以矽橡膠或氟橡膠等樹脂製 彈性材料來覆蓋。 觸碰輥14的周面溫度，以比製造的光學膜的玻璃移 轉溫度（Tg )更低爲佳。比Tg更高的話，樹脂與觸碰輥 1 4之剝離性有降低的傾向。但是，觸碰輥1 4的周面溫度 太低的話，膜狀熔融物31的揮發成分可能會在觸碰輥14 的周面析出，所以例如以l〇°C〜（Tg-l〇°C )程度的範圍 爲佳。 在本實施型態，挾壓步驟之後，使膜狀熔融物3 1依 序外接於2根冷卻輥1 5、1 6之周面冷卻固化’得到樹脂 膜41。在本實施型態，冷卻輥具有兩根，但不以此爲限 〇 冷卻輥15、1 6，與主輥1 3同樣，是高剛性的金屬製 輥，爲了使外接於周面的挾壓後的膜狀熔融物31均勻而 -17- 201235194 且效率佳地冷卻，於冷卻輥1 5、1 6的內部，以設有水或 油等冷卻媒體的流道爲較佳。冷卻輥1 5、1 6的直徑，只 要是冷卻固化使外接於周面的膜狀熔融物31之用的具有 充分大的容量之大小即可，例如大致由1 〇〇mm至1 m程度 。作爲冷卻輥15、16的周面的材質，可以使用碳鋼、不 鏽鋼、鋁、鈦等。此外，提高冷卻輥1 5、16的周面的硬 度，或者爲了改良與樹脂之剝離性，而以施加硬鉻電鍍、 或鍍鎳、鍍非晶質鉻、或者陶瓷熔射等表面處理爲較佳。 [剝離步驟] 以冷卻輥1 5、1 6的周面冷卻固化而得到的樹脂膜4 1 ，藉由對冷卻輥16以特定的壓力抵接之剝離輥17由冷卻 輥1 6的周面被剝離之後，往下游側給送。 [延伸步驟] 被剝離的樹脂膜41，藉由搬送輥18及延伸裝置19 搬送，同時被延伸於MD方向（搬送方向）及/或TD方 向（寬幅方向）。藉此，製造具有因應於用途所期待的延 遲特性之光學膜。 [捲取步驟] 經過延伸步驟的樹脂膜4 1，最終藉由捲取裝置20捲 取爲卷狀。藉此，結束光學膜的製造。又，在本實施型態 ，圖2所示的膜狀熔融物31之中切斷不要的端部區域33 -18- 201235194 、3 4之切斷步驟例如被設於延伸步驟與捲取步驟之間。 [加熱步驟] 加熱步驟，如圖1所示，是在壓出步驟與冷卻步驟之 間，亦即，由流延模1 2被壓出的膜狀熔融物3 1外接於主 '輥1 3之前，以配置於膜狀熔融物3 1通過的路徑周圍的空 間之加熱裝置51加熱膜狀熔融物31的步驟。接著，在此 加熱步驟，根據膜狀熔融物31的寬幅方向的厚度分布， 僅加熱厚度相對較小的部分，或者使厚度相對較小的部分 比起厚度相對較大的部分以較高的溫度加熱（換句話說， 厚度越小的部分以越高的溫度加熱，厚度越大的部分以越 低的溫度加熱），或者是厚度相對較小的部分以比厚度相 對較大的部分更長的時間進行加熱（換句話說，厚度越小 的部分以越長的時間進行加熱，厚度越大的部分以越短的 時間進行加熱）’或者是厚度相對較小的部分以比厚度相 對較大的部分高的溫度且更長的時間進行加熱（換句話說 ’厚度越小的部分以越高的溫度加熱越長的時間，厚度越 大的部分以越低的溫度加熱越短的時間）。 更具體地說，在本實施型態，作爲基本動作，係於圖 2所示的膜狀熔融物3]之中作爲光學膜使用的挾壓區域 3 2 ’僅加熱厚度相對較小的寬幅方向的端部，或者是寬幅 方向的端部以比厚度相對較大的寬幅方向的中央部以較高 的溫度加熱（換句話說，越朝向寬幅方向的端部以越高的 溫度加熱，越朝向寬幅方向的中央部以越低的溫度加熱） -19- 201235194 ，或者是寬幅方向的端部以比寬幅方向的中央部以更長的 時間進行加熱（換句話說，越朝向寬幅方向的端部以越長 的時間進行加熱，越朝向寬幅方向的中央部以越短的時間 進行加熱），或者是寬幅方向的端部以比寬幅方向的中央 部以更高的溫度且加熱更長的時間（換句話說，越朝向寬 幅方向的端部以越高的溫度加熱越長的時間，越朝向寬幅 方向的中央部以越低的溫度加熱越短的時間）。因此，如 圖2所示，分別可以控制溫度、控制時間的加熱裝置5 i 於膜狀熔融物31的寬幅方向上被排列配置複數個。這些 加熱裝置51·.· 51，加熱膜狀熔融物31之中的挾壓區域32 。原本，就不排除溢出挾壓區域32，連端部區域33、34 之一部分也一倂加熱，或者是端部區域33、34的全部也 被加熱，亦即跨全寬幅加熱膜狀熔融物3 1。 在本實施型態，如前所述，以檢測裝置7 1檢測的， 冷卻固化後的膜41的寬幅方向的厚度分布，作爲膜狀熔 融物31的寬幅方向的厚度分布來使用。以此檢測裝置71 檢測膜41的寬幅方向的厚度分布的步驟作爲檢測步驟。 在本實施型態，此檢測步驟在冷卻步驟與捲取步驟之間。 又，檢測裝置7 1最好爲非接觸式的。此外，能夠以 任意間隔，例如以50mm程度的間隔檢測樹脂膜41的厚 度者爲佳。 此外，在本實施型態，如圖3所示，以流延模1 2的 唇緣間隔之調整機構預先調整的膜狀熔融物31之寬幅方 向的厚度分布，可以作爲由流延模12壓出的膜狀熔融物 -20- 201235194 31的寬幅方向的厚度分布來使用。以此唇緣間隔的調整 機構預先調整由流延模12壓出的膜狀熔融物31之寬幅方 向的厚度分布的步驟爲調整步驟。在本實施型態’調整步 驟是在壓出步驟之前。 設有這樣的加熱步驟的理由如下。圖4表示由流延模 12壓出的膜狀熔融物31之伴隨著時間經過之溫度變化。 時刻tl膜狀熔融物31被壓出，時刻t2膜狀熔融物31外 接於主輥13(冷卻步驟的開始）。此間，膜狀熔融物31 藉由放熱而降低溫度。於該場合，膜狀熔融物31之寬幅 方向上有厚度相對大的部分與相對小的部分的話’厚度相 對大的部分如符號（i )所示溫度降低相對較小’而厚度 相對較小的部分如符號（ii )所示溫度降低相對較大。亦 即，以壓出時的溫度（壓出溫度）「T 1」，冷卻步驟開始 時之溫度爲「T2’」或者「T2”」的話，厚度相對小的部分 之冷卻速度「（T1-T2”）/ (t2-tl)」係比厚度相對較大 的部分的冷卻速度「（T1-T2，）/ (t2-tl)」更大。因此 ，膜狀熔融物3 1由流延模1 2壓出後，直到外接於主輥 13爲止之間的溫度履歷（相當於圖4之在縱向溫度軸與 橫向時間軸與通過時刻t2的縱線與顯示溫度降低的軌跡 之曲線（Ο或（Π)所包圍的面積（以下稱爲「履歷面積 」）），在膜狀熔融物31的寬幅方向上爲參差不齊。接 著，此膜狀熔融物31的溫度履歷之寬幅方向上的差異呈 現爲最終所得到的光學膜的延遲不均。又，膜狀熔融物 31，耷外接於主輥13後，熱爲容量大的主輥13所奪使各 -21 - 201235194 部分均勻而且效率佳地被冷卻。圖4中’溫度「Tr」爲主 輥1 3的周面溫度。 此處，在本實施型態，設有供減低膜狀熔融物31的 溫度履歷之寬幅方向上的差異之加熱步驟。爲了減低溫度 履歷的差異，使圖4之厚度相對較大的部分的溫度降低曲 線（i )與厚度相對較小的部分之溫度降低曲線（ii )相互 接近或使其一致，或者是即使不讓溫度降低曲線彼此接近 或者一致，也只要在結果上使厚度相對較大的部分的溫度 降低曲線（i )所得之履歷面積與厚度相對較小的部分的 溫度降低曲線（ii )所得之履歷面積相互接近或者一致即 可。 因此，例如於1例，如圖5所示，僅加熱厚度相對較 小的部分。藉此，厚度相對較小的部分的冷卻速度變小， 厚度相對較小的部分的溫度降低曲線（iii )接近厚度相對 大的部分的溫度降低曲線（i)。又，圖例，是顯示在膜 狀熔融物3 1由流延模1 2壓出之後（時刻11 )，直到被外 接於主輥1 3爲止（時刻12 )之間，連續進行加熱的場合 。但是，並不以此爲限，由中途開始加熱，或者在中途停 止加熱亦可。此外，間歇地進行複數次加熱亦可，總加熱 時間也爲任意的。加熱裝置51的加熱溫度，或冷卻步驟 開始時的溫度T2”爲何亦不需注意。能夠把這些參數進行 各種組合而以種種模式進行加熱。簡言之，只要至少有1 次使厚度相對較小的部分的冷卻速度，比不進行加熱的場 合更小的狀態即可。但是，在任一場合，都要避免厚度相 -22- 201235194 對較小的部分加熱太過，而使厚度相對較小的部分的溫度 履歷，比厚度相對大的部分的溫度履歷反而增大的情形。 當然，厚度相對較小的部分的溫度履歷最好是一致於厚度 相對大的部分的溫度履歷。 例如，圖6是顯示厚度相對小的部分的加熱是由中途 開始進行的場合。圖例，是厚度相對較小的部分的溫度降 低曲線（iv )所得之履歷面積約略一致於厚度相對大的部 分的溫度降低曲線（i )所得之履歷面積。結果，厚度相 對較小的部分的冷卻步驟開始時的溫度T2”變得比厚度相 對大的部分的冷卻步驟開始時的溫度T2’還要高。原本就 沒有使履歷面積彼此一致的必要’即使T2”變得比T2’更 低亦無妨。此外，加熱的開始時刻相對較遲的場合等’加 熱開始後的溫度降低曲線暫時地或者整體地呈現上升傾向 也沒有關係。 以上，是僅加熱厚度相對較小的部分之加熱模式的場 合，但一倂加熱厚度相對較大的部分亦可。於一倂加熱厚 度相對較大的部分之加熱模式的場合’技術思想上’也是 與僅加熱厚度相對較小的部分之加熱模式爲相同。例如’ 於1例，並非使加熱裝置51的加熱溫度均勻化’而是使 厚度相對小的部分以比厚度相對大的部分更高的溫度進行 加熱。藉此，厚度相對小的部分的冷卻速度與厚度相對大 的部分的冷卻速度都一樣與不共同進行加熱的場合變得更 小，但厚度相對小的部分的冷卻速度變得更小’結果厚度 相對小的部分的溫度降低曲線’接近於厚度相對大的部分 -23- 201235194 的溫度降低曲線，溫度履歷變成相互接近或者一致。 此外，於一倂加熱厚度相對較大的部分之加熱模式的 場合，亦可使厚度相對較小的部分比厚度相對大的部分以 更長的時間進行加熱。例如，使加熱裝置5 1的加熱溫度 爲均一，厚度相對小的部分的加熱在時刻11〜時刻t2之 間連續進行，而設置使厚度相對大的部分的加熱在時刻11 〜時刻t2之間暫時停止的期間。藉此也同樣，可以使厚 度相對較小的部分的溫度履歷與厚度相對大的部分的溫度 履歷相互接近或者一致。 進而，於一倂加熱厚度相對較大的部分之加熱模式的 場合，使厚度相對較小的部分比厚度相對大的部分以更高 的溫度加熱較長時間，亦可使厚度相對較小的部分的溫度 履歷與厚度相對大的部分的溫度履歷相互接近或者一致。 在此場合，與使加熱裝置51之加熱溫度爲均一的場合相 比，可以增長暫時停止厚度相對較大的部分的加熱之期間 〇 於厚度相對大的部分一倂進行加熱的加熱模式的場合 ，關於寬幅方向之各部分的加熱，可以在時刻11〜時刻 t2之間連續進行加熱，或者亦可由途中開始加熱或者亦可 途中停止加熱。此外，間歇地進行複數次加熱亦可，總加 熱時間也爲任意的。加熱裝置51的加熱溫度，或冷卻步 驟開始時的溫度T2’，T2”爲何亦不需注意。能夠把這些 參數進行各種組合而以種種模式進行寬幅方向各部分之加 熱。但是’在任一場合，都要避免厚度相對較小的部分加 -24- 201235194 熱太過，而使厚度相對較小的部分的溫度履歷，比厚度相 對大的部分的溫度履歷增大的情形。當然，厚度相對較小 的部分的溫度履歷最好是一致於厚度相對大的部分的溫度 履歷。 於這樣的加熱步驟，把在前述檢測步驟檢測出的厚度 分布作爲膜狀熔融物31的寬幅方向的厚度分布來使用時 ’因爲參照光學膜之製造中所檢測的實際的厚度分布，所 以具有提高了溫度履歷的差異減低的精度之優點。 此外，在前述的調整步驟預先被調整的厚度分布作爲 膜狀熔融物31的寬幅方向的厚度分布來使用時，因具有 不需要在光學膜之製造中檢測厚度分布之優點。 此外，以設有根據膜狀熔融物31的寬幅方向之厚度 分布，對膜狀熔融物31的寬幅方向的各個部分，在冷卻 步驟決定冷卻開始時（時刻t2 )之目標溫度的決定步驟； 在加熱步驟，以使在決定步驟所決定的各個部分之目標溫 度在冷卻步驟於開始冷卻時（時刻t2 )實現的方式加熱膜 狀熔融物31爲佳。亦即，圖4〜圖6之冷卻步驟開始時 的溫度T2’，T2”，例如以使厚度小的部分的溫度履歷與 厚度大的部分的溫度履歷相互接近或者一致時的溫度的方 式，來進行加熱。藉此，藉由於各部分實現冷卻開始時（ 時刻t2 )的目標溫度，使得溫度履歷之差異更進一步減低 ，可以消除溫度履歷的差異。又，決定步驟設於檢測步驟 與加熱步驟之間，或者調整步驟與加熱步驟之間。 又，這樣的目標溫度，例如於膜狀熔融物31的各厚 -25- 201235194 度，因應於其他種種參數，預先實驗性地設 索該値的方式用地圖形式或者表格形式來準 —來可以使決定步驟的作業縮短。準備的資 收容於記憶體等。接著，供實現該目標溫度 置51的加熱溫度，也可以因應於其他種種 驗性地設定，以可以檢索該値的方式用地圖 形式來準備即可。準備的資料，例如可以與 而收容於記憶體等。原本即不以此爲限，可 變，例如爲了防止記憶體容量過大，藉由根 次進行演算，來決定前述目標溫度及前述加 在本實施型態，如前所述，於加熱步驟 融物31，較佳者爲加熱膜狀熔融物31之中! 。挾壓區域32以主輥13與觸碰輥14以均 壓，在挾壓區域32於膜狀熔融物31的寬幅 度大的部分與厚度小的部分，所以此挾壓區 的差異被適切地降低。 在本實施型態，於加熱步驟，以使分別 的加熱裝置51在膜狀熔融物31的寬幅方向 進行加熱爲較佳。這是因爲溫度履歷的差異 成本範圍內確實減低的緣故。此外，可以良 種加熱模式。未滿3個的話，無法充分減 31的溫度履歷之寬幅方向上的差異。14個 本會太高。例如，在圖2所示之例，分別可 控制時間的加熱裝置5 1於膜狀熔融物3 1的 定，以可以檢 備即可。如此 料，例如可以 之用的加熱裝 參數，預先實 形式或者表格 目標溫度連接 以因應狀況而 據種種參數每 熱溫度亦可。 ，加熱膜狀熔 的挾壓區域32 句的壓力被挾 方向上形成厚 域之溫度履歷 可以控制溫度 排列3〜1 3個 可以在實用的 好地對應於種 低膜狀熔融物 以上的話，成 以控制溫度、 寬幅方向上被 -26- 201235194 排列配置7個。複數加熱裝置51的合計寬幅，以成爲膜 狀熔融物31的全寬幅或者挾壓區域32的寬幅的方式，排 列複數之加熱裝置5 1。特別是，在僅加熱厚度小的部分 的加熱模式的場合，圖2所示那種形狀的膜狀熔融物31 時，至少在寬幅方向中央之1個加熱裝置5 1沒有配置的 必要。 在本實施型態，於加熱步驟，以使分別可以控制溫度 的加熱裝置5 1在膜狀熔融物3 1的壓出方向排列1〜5列 進行加熱爲較佳。可以使膜狀熔融物31加熱充分長的時 間，因爲確實減低溫度履歷的差異。此外，可以良好地對 應於種種加熱模式。6列以上的話，成本會太高。例如， 使厚度小的部分比厚度大的部分加熱更長時間的場合，或 厚度小的部分比厚度大的部分以更高的溫度加熱更長時間 的場合特別有效。 在本實施型態，於加熱步驟，以使分別可以控制溫度 的加熱裝置51配置在膜狀熔融物31的單面側或者雙面側 進行加熱爲較佳。可以因應由流延模12壓出的膜狀熔融 物31通過的路徑周圍的空間而將複數之加熱裝置51以各 種各樣的模式進行配置。 在本實施型態，作爲加熱裝置5 1，沒有特別限定， 例如可以適合使用紅外線加熱器、鹵素加熱器、碳加熱器 、陶瓷加熱器、電熱線加熱器等。這是因爲這些加熱器， 使用電力作爲能源，所以不會污染空氣，操作上也比較簡 單所致。此外，不加熱空氣而以熱放射進行加熱，所以可 -27- 201235194 以局部加熱膜狀熔融物31之僅被瞄準的部分。 又，替代把複數之加熱裝置51排列於膜狀熔融物3 1 的寬幅方向，而把可以在各部分進行溫度控制、時間控制 的單一長尺寸加熱裝置以延伸於膜狀熔融物31的寬幅方 向的方式配置亦可。此外，根據加熱裝置51之加熱溫度 的調節，除了加熱裝置51自身的加熱溫度的控制以外， 也可以進行加熱裝置51與膜狀熔融物31之間的距離的調 節。 <膜材料> 在本實施型態，使用於膜材料的熱塑性樹脂，如前所 述沒有特別限制，在此，作爲熱塑性樹脂舉出使用纖維素 酯樹脂的場合爲例進行說明。 相關於本實施型態的光學膜之製造方法所使用的膜材 料，除了纖維素酯樹脂以外，因應必要，還包含安定化劑 、可塑劑、紫外線吸收劑、襯墊劑（潤滑劑）等。這些膜 材料，藉由目的的光學膜所要求的特性而適當選擇。 [纖維素酯樹脂] 作爲在本實施型態使用的纖維素酯樹脂沒.有特別限定 。例如，可以適切地使用醋酸纖維素、丙酸纖維素、丁酸 纖維素、乙酸丙酸纖維素、乙酸丁酸纖維素、醋酸鄰苯二 甲酸纖維素、鄰苯二甲酸纖維素等》 此外，適當選擇纖維素酯樹脂以外的高分子材料或寡 -28- 201235194 聚體而與纖維素酯樹脂混合亦可。這樣的高分子材料或寡 聚體與纖維素酯樹脂之互溶性優異，做成膜時跨所有可見 光區域（400nm〜800nm )可得到高的透過率。作爲這樣 的高分子材料，例如可以適切使用丙烯酸樹脂而得。又， 針對丙烯酸樹脂稍後詳述。 於本實施型態，纖維素酯樹脂，特別是由脆性的改善 或與丙烯酸樹脂之互溶時的透明性的觀點來看，以醯基的 總置換度（T)爲2.0〜3.0，碳數爲3〜7的醯基之置換度 爲1 .2〜3.0爲佳。亦即，本實施型態之纖維素酯樹脂係 藉由碳數3〜7之醯基置換的纖維素酯樹脂，具體而言， 以丙酸基'丁酸基等適於使用，特別以丙酸基最適於使用 〇 纖維素酯樹脂之醯基的總置換度未滿2.0的場合，亦 即，纖維素酯分子之2,3，6位之羥基的殘留度超過1.0的 場合，與丙烯酸樹脂與纖維素酯樹脂互溶性變得不充分， 在作爲偏光板保護膜使用的場合模糊度（haze )會變成問 題。此外，即使醯基的總置換度達到2.0的場合，在碳數 3〜7之醯基的總置換度未滿1.2的場合，到底無法得到充 分的互溶性’或是脆性會變低。具體而言，例如，即使醯 基的總置換度爲2.0以上的場合，只要碳數2之醯基，例 如，乙醯基的置換度很高，即使碳數3〜7的醯基的置換 度低於1 2的場合’也會互溶性降低而模糊度上升。此外 ，即使醯基的總置換度爲2.0以上的場合，只要碳數8以 上之醯基的置換度很高，碳數3〜7的醢基的置換度低於 -29- 201235194 1.2的場合，會有脆性劣化，而無法得到所要的特性。 於本實施型態，纖維素酯系樹脂之醯基的置換度，只 要總置換度（Τ)爲2.0〜3.0，碳數3〜7的醯基之置換度 爲1.2〜3.0的話就沒有問題，但碳數3〜7以外的醯基， 亦即乙醯基或碳數8以上的醯基之置換度之總計爲1.3以 下爲更佳。 此外，纖維素酯系樹脂之醯基的總置換度（Τ )以在 2.5〜3.0的範圍爲更佳。 於本實施型態，前述醯基，可以是脂肪族醯基，也可 以是芳香族醯基。脂肪族醯基的場合，可以是直鏈也可以 是分歧的，進而有置換基亦可。本實施型態之醯基的碳數 ，係包含醯基之置換基者。 纖維素酯樹脂，以芳香族醯基作爲置換基的場合，置 換爲芳香族環的置換基之數目，以0〜5個爲佳。在此場 合，有必要留意包含置換基的碳數爲3〜7之醯基的置換 度成爲1.2〜3.0。例如，苯甲醯基碳數變成7，所以具有 包含碳的置換基的場合，作爲苯甲醯基之碳數爲8以上， 不會包含於碳數3〜7之醯基。 進而，置換爲芳香族環的置換基之數目爲2個以上的 場合，可爲相同亦可爲互異。此外，相互連結，形成縮合 多環換合物（例如萘、節（indeney、節（indan)、菲（ phenanthrene )、喹啉（quinoline )、異嗤啉（ isoquinoline )、苯并 0比喃（chromene )、色院（ chromane)、酞嗪（phthalazine)、吖 D定（acridine)、 -30- 201235194 口引探（indole) 、D引哄琳（indoline)等）亦可。 於如前所述那樣的纖維素酯樹脂，具有具碳數3〜7 的脂肪族醯基之至少1種的構造，是可以作爲使用於本實 施型態的纖維素酯樹脂的構造來使用。 於本實施型態，纖維素酯樹脂的置換度，爲醯基的總 置換度（T)爲2.0〜3.0，碳數3〜7的醯基之置換度爲 1.2 〜3.0。 此外，碳數3〜7的醯基以外，亦即乙醯基與碳數8 以上的醯基的置換度的總合爲1.3以下爲較佳的構造。 於本實施型態，作爲纖維素酯樹脂，由與丙烯酸樹脂 之良好的互溶性的確保以及製造的光學膜之高透明度的確 保的觀點來看，特別以三醋酸纖維素、乙酸丙酸纖維素、 乙酸丁酸纖維素、乙酸苯甲酸纖維素、丙酸纖維素、丁酸 纖維素所選擇之至少一種爲較佳，亦即，把碳數3或4之 醯基座爲置換基爲佳。 其中，特佳之纖維素酯樹脂，爲三乙酸纖維素、乙酸 丙酸纖維素以及丙酸纖維素。 未以醯基置換的部分，通常是存在著羥基。這些可以 用公知的方法合成。 又’乙醯基之置換度或其他醯基的置換度，係藉由依 照A S T Μ _ D 8 1 7 - 9 6標準所規定的方法來求出》 於本實施型態，纖維素酯樹脂之重量平均分子量（ Mw )，特別是由與丙烯酸樹脂之互溶性、脆性改善的觀 點來看，以75,000以上爲佳，75,000〜300,000之範圍爲 -31 - 201235194 更佳，100,000〜240,000進而又更佳，又以 160,000〜 240,000爲特佳。纖維素酯樹脂之重量平均分子量（Mw) 低於75,000的場合，無法得到充分的耐熱性或脆性的改 善效果。在本實施型態可以混合使用2種以上的纖維素酯 樹脂使用。 於相關於本實施型態之光學膜，丙烯酸樹脂與纖維素 酯樹脂，以30 : 70〜95 : 5之質量比，且在互溶狀態下含 有，但較佳者爲50: 50〜95: 5，進而較佳者爲60: 40〜 90 ： 10 〇 丙烯酸樹脂與纖維素酯樹脂的質量比，在丙烯酸樹酯 比95 : 5更多時，無法充分得到纖維素酯樹脂所導致的效 果，同樣地質量比低於30 : 70而丙烯酸樹脂變少時，耐 濕性變得不夠充分。 [安定化劑] 在本實施型態，爲了防止根據氧化或是光或熱之分解 反應等導致膜材料的變質，以含有安定化劑爲較佳。 安定化劑沒有特別限制，例如可以舉出受阻酚防氧化 劑、氧捕捉劑、受阻胺光安定劑、過氧化物分解劑、自由 基捕捉劑、金屬不活化劑、胺類等。 安定化劑，以在熔融熱塑性樹脂前先混合爲佳。混合 ，可以藉由公知的混合機來進行。於纖維素酯樹脂的調製 過程進行混合亦可。藉由使混合在熱塑性樹脂的融點以下 ，安定化劑的融點以上的溫度進行混合，僅熔融安定化劑 -32- 201235194 而使安定化劑吸附於樹脂表面亦可。 [可塑劑] 在本實施型態，由提高光學膜的機械性質、賦予柔軟 性、賦予耐吸水性、減低水分透過率等觀點來看，含有可 塑劑爲較佳。此外，於相同加熱溫度比起纖維素酯樹脂單 獨的場合更可以使熔融黏度降低的觀點來看，也以包含可 塑劑爲佳。 作爲可塑劑，例如適合使用磷酸酯誘導體、羧酸酯誘 導體。此外，可以把油酸丁酯'蓖酸甲乙酯、癸二酸二丁 酯、三醋酯、三羥甲基丙烷三苯甲酸酯、三羥甲基丙烷三 (3,4,5-三甲氧基苯甲酸酯）、烷基鄰苯二甲醯烷基甘醇 酸酯等作爲可塑劑使用。 [紫外線吸收劑] 隨著製造的光學膜的用途不同，爲了防止偏光子或液 晶顯示裝置等之根據紫外線而劣化，以含有紫外線吸收劑 爲較佳。 紫外線吸收劑沒有特別限制，例如，可以舉出氧基二 苯酮 （oxybenzophenone) 系化合物、苯并三挫 ( Benzotriazole)系化合物、水楊酸酯系化合物、苯甲酮系 化合物、氰基丙嫌酸酯（cyanoacrylate)系化合物、鎳錯 鹽系化合物、等。 -33- 201235194 [襯墊劑] 對於光學膜，爲了提高滑動性、搬送性或捲取性而添 加襯墊劑亦可。作爲襯墊劑，例如可以舉出二氧化矽、二 氧化鈦、氧化鋁、氧化锆、碳酸鈣、高嶺土、滑石、燒結 矽酸鈣、水合矽酸鈣、矽酸鋁、矽酸美、磷酸鈣等無機微 粒子或架橋高分子微粒子。 這些之中，以二氧化矽可以降低膜的霧度所以較佳。 作爲二氧化矽微粒子，可以舉出日本氣膠（股）製造之氣 膠(AEROSIL ) 200、200V、3 00、R972、R972V、R974 、R202、R812、0X50、TT600等。此外，亦可倂用這些 微粒子2種以上。 微粒子的平均粒徑越大滑動性效果越大，相反地平均 粒徑越小透明性越佳。通常，微粒子的平均粒徑以0.005 〜之範圍爲較佳。微粒子凝集而形成二次粒子亦 可。微粒子的含量以對纖維素酯樹脂1〇〇質量份含有 0.005〜0.3質量份較佳。 (丙烯酸樹脂） 於本實施型態使用的丙烯酸樹脂，也含有甲基丙烯酸 樹脂。作爲樹脂沒有特別限制，以由甲基丙烯酸甲酯單位 50〜99質量百分比，及可以與其共聚合之其他單量體1〜 50質量百分比所構成者爲佳。 作爲可共聚合的其他單量體，可以舉出烷基的碳數爲 2〜18之甲基丙烯酸烷基酯、烷基的碳數爲1〜18之丙烯 -34- 201235194 酸烷基酯、丙烯酸、甲基丙烯酸等之α,θ-不飽和酸、馬 來酸（順丁烯二酸）、富馬酸（反丁烯二酸）、亞甲基丁 二酸等含有不飽和基的二價羧酸、苯乙烯、甲基苯乙 烯等芳香族乙烯基化合物、丙烯腈、甲基丙烯腈等之α， 召-不飽和腈、無水馬來酸、馬來醯亞胺、Ν-置換馬來醯 亞胺、戊二酸無水物等，這些可以單獨使用或者倂用2種 以上的單量體。 這些之中，由確保共聚合體的良好的耐熱分解性或流 動性的觀點來看，以丙烯酸甲酯、丙烯酸乙酯、丙烯酸正 丙酯、丙烯酸正丁酯、丙烯酸仲丁酯、丙烯酸2-乙基己 酯等爲佳，又以丙烯酸甲酯或丙烯酸正丁酯爲特佳。 於本實施型態，使用於光學膜的丙烯酸樹脂，特別是 由改善作爲液晶偏光板保護膜之脆性與改善與纖維素酯樹 脂互溶時之透明性的觀點來看，重量平均分子量（Mw ) 爲8 0,000以上。丙烯酸樹脂的重量平均分子量（Mw)未 滿8 0,000的話，無法得到充分的脆性改善，與丙烯酸樹 脂之互溶性會劣化。丙烯酸樹脂的重量平均分子量（Mw )以 80,000〜1,000,000的範圍內爲較佳，100, 〇〇〇〜 600,000的範圍內爲特佳，1 50,000〜400,000的範圍內爲 最佳。丙烯酸樹脂的重量平均分子量（Mw )的上限値沒 有特別限定，由製造上的觀點來看，以1，〇〇〇,〇〇〇以下爲 較佳。 於本實施型態，丙烯酸樹脂的重量平均分子量’可以 藉由凝膠浸透色層分析法來測定。測定條件例如下述。 -35- 201235194 溶媒：二氯甲烷 管柱：Shodex K806、K8 05、K8 03 G (由昭和電工( 股）製造，連接3根而使用） 管柱溫度：25°C 試樣濃度：0.1質量百分比 檢測器：RI Model 504 (GL Science 公司製造） 泵：L6 000 (日立製作所（股）製造） 流量：l.Oml/min 校正曲線：根據標準聚苯乙烯STK standard聚苯乙 烯（東洋曹達Tosoh (股）製造）Mw=2,80 0,000〜500爲 止之1 3個樣本之校正曲線。1 3個樣本大致爲等間隔較佳 〇 於本實施型態，作爲丙烯酸樹脂之製造方法，沒有特 別限制，可以使用懸濁聚合、乳化聚合、塊狀聚合、或者 溶液聚合等公知的方法之任一種。此處，作爲聚合開始劑 ，可以使用通常的過氧化物系以及偶氮系者，此外氧化還 原系亦可。針對聚合溫度，在懸濁或者乳化聚合在3 0〜 100 °C下實施，塊狀或溶液聚合爲8Ό〜160 °C下實施。爲 了控制所得到的共聚合物之還原黏度，可以把烷基硫醇等 作爲連鎖移動劑使用而實施聚合。 於本實施型態，作爲丙烯酸樹脂，可以使用市售品。 例如，可以舉出DELPET60N、80N (旭化成 Chemicals ( 股）製造）、Dianol (音譯 BR52、BR80、BR83、BR85、 BR88 (三菱Rayon (股）製造）、KT75 (電氣化學工業 •36- 201235194 (股）製造）等。丙烯酸樹脂也可以倂用2種以上。 <光學膜> 藉由相關於本實施型態之製造方法製造的光學膜，被 抑制延遲不均，可良好地對應於光學膜的大型化要求。 <偏光板> 把相關於本實施型態的光學膜使用作爲偏光板用保護 膜的場合’偏光板能夠以一般的方法來製作。在相關於本 實施型態的光學膜的背面側設黏接層，於碘溶液中浸漬延 伸而製作的偏光子之至少一方的面上，進行貼合爲佳。 於另一方之面使用相關於本實施型態的光學膜亦可， 使用其他偏光板用保護膜亦可。例如，可以使用市售的纖 維素酯膜（例如 KONICA MINOLTATAC KC8UX、KC4UX 、KC5UX、KC8UY、KC4UY、KC12UR ' KC8UCR-3、 KC8UCR-4、KC8UCR-5 > KC8UE、KC4UE、KC4FR-3、 KC4FR-4 ' KC4HR-1、KC 8 U Y - H A、K C 8 U X - R Η A、以上爲 KONICA MINOLTA OPTO (股）製造）等適於使用。 所謂偏光板的主要構成要素之偏光子，係使一定方向 的偏波面之光通過的元件，係在已知的代表性之偏光膜， 爲聚乙烯醇系偏光膜，有在聚乙烯醇系膜染色以碘者以及 染色以二色性染料者。 偏光子係把聚乙烯醇水溶液進行製膜，將此一軸延伸 進行染色，或是染色之後進行一軸延伸之後，較佳者爲使 -37- 201235194 用以硼化合物進行耐久性處理者。 作爲使用於前述黏接層的黏著劑，於黏接層的 部分使用在25°C之貯藏彈性率在1.0xl04Pa〜1.( 之範圍的黏著劑爲佳，塗布黏著劑，貼合之後藉由 學反應形成高分子量體或者架橋構造的硬化型黏著 使用。 作爲具體例，例如可以舉出胺甲酸乙酯系黏著 氧系黏著劑、水性高分子-異氰酸酯系黏著劑、熱 丙烯酸黏著劑等硬化型黏著劑、濕氣硬化型胺甲酸 著劑、聚醚甲基乙酸酯型、酯系甲基乙酸酯型、氧 醚甲基乙酸酯等厭氣性黏著劑、氰基丙烯酸酯系之 接劑、丙烯酸酯與過氧化物系之2液型瞬間黏著劑 作爲前述黏著劑亦可使用1液型，亦可使用在 混合2液以上的形式。 此外，前述黏著劑亦可爲把有機溶媒作爲媒體 系，亦可爲以水爲主成分的媒體之乳液型、膠體分 、水溶液型等水系亦可，無溶媒型亦可。前述黏著 濃度，只要隨著黏著後的膜厚、塗布方法、塗布條 適當決定即可，通常爲0.1〜50質量百分比。 相關於本實施型態的偏光板，具備偏光子、及 於前述偏光子的表面上之透明保護膜，前述透明保 係藉由相關於本實施型態之製造方法所製造之光學 述的偏光子，是使入射光改變爲偏光而射出的光學 作爲前述偏光板，最好是例如把聚乙烯醇系膜 至少一 )x109Pa 種種化 劑適於 劑、環 硬化型 乙酯黏 化型聚 瞬間黏 等。 使用前 之溶媒 散液型 劑液的 件等而 被配置 護膜， 膜。前 元件。 浸漬於 -38- 201235194 碘溶液中進行延伸而製作的偏光子之至少一方之面上，使 用完全鹼化型聚乙烯醇水溶液，貼合前述光學膜者。此外 ，前述偏光子之另一方表面，亦可使層積前述光學膜，亦 可使層積其他的偏光板用透明保護膜。作爲此其他之偏光 板用透明保護膜，例如作爲市售的纖維素酯，最好是使用 KC8UX2M 、 KC4UX 、 KC5UX 、 KC4UY 、 KC8UY 、 KC12UR、KC8UY-HA、K C 8 U X-RH A (以上爲 Konica Minolta Opto (股）製造）等。或者是使用纖維素酯膜以 外之環狀烯烴樹脂、丙烯酸樹脂、聚酯、聚碳酸酯等樹脂 膜亦可。在此場合，因爲矽化適性低，所以最好是透過適 當的黏接層黏接加工於偏光板。 前述偏光板，如前所述，作爲層積於偏光子之至少一 方的表面側之保護膜’使用前述光學膜。此時，前述光學 膜作爲相位差膜發揮功能的場合，光學膜的遲相軸以實質 上平行或者直交於偏光子的吸收軸的方式被配置爲佳。 此外，作爲前述偏光子的具體例，例如可以舉出聚乙 烯醇系偏光膜。聚乙烯醇系偏光膜，有在聚乙烯醇系膜使 染上碘者與使染上二色性染料者。作爲前述聚乙烯醇系膜 ，較佳爲使用以乙烯變性的變性聚乙烯醇系膜。 前述偏光子’例如可如下述般進行而獲得。首先，使 用水溶液進行製膜。把所得到的聚乙烯醇系膜在單軸延伸 後進行染色，或者在染色之後進行單軸延伸。接著，較佳 者爲以硼化合物施以耐久性處理。 前述偏光子的膜厚，以5〜4〇//m爲佳，又以5〜30 -39- 201235194 更佳’尤以5〜20/zm最佳。 於該偏光子的表面上，張貼纖維素酯系樹脂膜的場合 ，最好是藉由完全鹼化聚乙烯醇等爲主成分的水系黏接劑 來貼合。此外，纖維素酯系樹脂膜以外的樹脂膜的場合， 蓐好是透過適當的黏接層黏接加工於偏光板。 如前所述的偏光板，藉由使用項關於本實施型態的光 學膜作爲透明保護膜，此光學膜因變形充分被抑制，例如 在適用於液晶顯示裝置時，可實現對比的提高等液晶顯示 裝置的高畫質化。此外，作爲偏光板的透明保護膜而適用 的光學膜，因濕度變化導致的尺寸變化也被抑制，所以例 如適用於液晶顯示裝置時，也可以抑制所謂的角隅不均的 產生。 如此，相關於本實施型態之偏光板，係具備偏光子、 及以挾著前述偏光子的方式被配置於偏光子的兩側的2枚 透明保護膜之偏光板，係前述2枚透明保護膜之中的至少 一方，以相關於本實施型態的製造方法所製造的光學膜。 此偏光板使透明保護膜之延遲不均被抑制，可良好地對應 於偏光板的大型化要求。 <液晶顯示裝置> 藉由把相關於本實施型態的光學膜作爲液晶偏光板用 保護膜進行了貼合的偏光板組入液晶顯示裝置’而可以製 作種種視覺確認性優異的液晶顯示裝置’特別是適合用於 大型的液晶顯示裝置或數位告示板等屋外用途之液晶顯示 -40- 201235194 裝置。相關於本實施型態的偏光板，中介著前 貼合於液晶胞。 相關於本實施型態的偏光板可以適切地用 透過型、半透過型LCD或TN型、STN型 HAN 型、VA 型（PVA 型、MVA 型）、IPS FFS方式）等各種驅動方式之LCD。特別是畫 以上，特別是30吋〜54吋之大畫面的顯示裝 邊部不會有泛白等，其效果可以維持長時間。 此外，顏色不均，閃爍或者波紋不均等情 著即使長時間鑑賞也不會使眼睛疲勞的效果。 相關於本實施型態的液晶顯示裝置，具備 以夾住前述易經胞的方式配置的2枚偏光板； 光板之中至少一方，爲前述偏光板。又，液晶 對電極間塡充液晶物質者，藉由對此電極施加 液晶的配向狀態，使透過光量被抑制。這樣的 置，藉由使用相關於本實施型態的偏光板，作 的透明保護膜，使用變形充分被抑制的光學膜 對比等被提高之高畫質的液晶顯示裝置。此外 ，使用具備濕度變化導致的尺寸變化也被抑制 爲透明保護膜，所以也可以抑制所謂的角隅不 如此，相關於本實施型態之液晶顯示裝置 晶胞、以挾住前述液晶胞的方式被配置於液晶 2枚偏光板之液晶顯示裝置，其特徵爲：前述 之中至少一方，係前述偏光板。此液晶顯示裝 述黏接層等 於反射型、 、OCB 型 ' 型（也包含 面在3 0吋 置，畫面周 形很少，有 液晶胞、及 前述2枚偏 胞，係於一 電壓，改變 液晶顯不裝 爲偏光板用 ，所以成爲 ，於偏光板 的光學膜作 均的產生。 ，係具備液 胞的兩側的 2枚偏光板 置，使偏光 -41 - 201235194 板之透明保護膜之延遲不均被抑制，可良好地對應於液晶 顯示裝置的大型化要求。 又，在以上的實施型態，於熔融流延製膜法，目的在 於挾壓時對膜狀熔融物31作用以均勻的壓力，如圖2所 示，刻意舉出在膜狀熔融物31的寬幅方向上形成厚度大 的部分與厚度小的部分的場合爲例來進行說明，但並不以 此爲限，例如，即使要壓出厚度在寬幅方向上爲均勻的膜 狀熔融物31也不會違反本發明之意旨，於膜狀熔融物31 的寬幅方向上產生厚度大的部分與厚度小的部分的場合也 可以良好地適用本發明。 本實施型態之技術特徵整理如下。 相關於本實施型態之光學膜之製造方法，係具有使包 含熱塑性樹脂的熔融物由流延模壓出爲膜狀的壓出步驟， 及冷卻被壓出的膜狀熔融物的冷卻步驟之光學膜之製造方 法，其特徵爲：壓出步驟與冷卻步驟之間，設有加熱被壓 出的膜狀熔融物的加熱步驟，在此加熱步驟，根據膜狀熔 融物的寬幅方向的厚度分布，僅加熱厚度相對小的部分， 或者厚度相對較小的部分比相對大的部分以更高的溫度加 熱及/或以更長時間進行加熱。 根據此光學膜之製造方法，使由流延模壓出的膜狀熔 融物，在冷卻步驟開始冷卻之前，根據膜狀熔融物的寬幅 方向的厚度分布，僅加熱厚度相對小的部分，或者，厚度 相對較小的部分比厚度相對大的部分以更高的溫度加熱， 或者，厚度相對較小的部分比厚度相對大的部分以更長時 -42- 201235194 間進行加熱，或者，厚度相對較小的部分比厚度相對大的 部分以更高的溫度加熱更長時間，所以製造的光學膜之延 遲不均被抑制了。 其理由大致考察如下。亦即，由流延模押出的膜狀熔 融物，直到外接於冷卻輥或主輥（供挾壓之輥）的周面爲 止的其間藉由放熱而降低溫度，外接於冷卻輥或主輥後， 熱爲熱容量大的這些輥所奪走而各部分均勻地而且效率佳 地被冷卻（冷卻步驟的開始）。於該場合，膜狀熔融物 31之寬幅方向上有厚度相對大的部分與相對小的部分的 話，厚度相對大的部分直到外接於輥爲止的期間之溫度降 低相對較小，而厚度相對較小的部分直到外接於輥爲止的 期間之溫度降低相對較大，所以膜狀熔融物由流延模被壓 出後，直到外接於輥爲止的期間的溫度履歷（在甚麼樣的 溫度下暴露多長的時間）在膜狀熔融物的寬幅方向上會產 生不均。接著，此膜狀熔融物的溫度履歷的差異應該會呈 現爲光學膜的延遲不均。亦即，據推測藉由使由流延模壓 出的膜狀熔融物，在冷卻步驟開始之前，根據膜狀熔融物 的寬幅方向的厚度分布，僅加熱厚度相對小的部分（根據 放熱導致溫度降低相對較大的部分），或者，厚度相對較 小的部分比厚度相對大的部分（根據放熱導致溫度降低相 對較小的部分）以更高的溫度加熱，或者，厚度相對較小 的部分比厚度相對大的部分以更長時間進行加熱，或者， 厚度相對較小的部分比厚度相對大的部分以更高的溫度加 熱更長時間，減低膜狀熔融物的溫度履歷在寬幅方向上的 -43- 201235194 差異，因此光學膜之延遲不均被抑制了。 於前述製造方法，在冷卻步驟設有檢測冷卻後的膜的 寬幅方向的厚度分布的檢測步驟，在加熱步驟，把在此檢 測步驟檢測出的厚度分布作爲膜狀熔融物的寬幅方向的厚 度分布來使用爲較佳。參照光學膜製造中所檢測的實際厚 度分布，所以提高溫度履歷的差異減低的精度。 於前述製造方法，其中設有預先調整由流延模壓出的 膜狀熔融物的寬幅方向的厚度分布之調整步驟，在加熱步 驟，把在此調整步驟調整後厚度分布作爲膜狀熔融物的寬 幅方向的厚度分布來使用爲佳。在光學膜製造中可以不檢 測厚度分布。 於前述製造方法，以設有根據膜狀熔融物的寬幅方向 之厚度分布，對膜狀熔融物的寬幅方向的各個部分，在冷 卻步驟決定冷卻開始時之目標溫度的決定步驟；在加熱步 驟’以使在決定步驟所決定的各個部分之目標溫度在冷卻 步驟於開始冷卻時實現的方式加熱膜狀熔融物爲佳。藉由 於各部分實現冷卻開始時的目標溫度，使得溫度履歷之差 異更進一步減低，可以消除溫度履歷的差異。 於前述製造方法，設有把膜狀熔融物以輥挾壓的挾壓 步驟’在加熱步驟，加熱以此挾壓步驟挾壓的挾壓區域爲 佳。於挾壓區域，膜狀熔融物在寬幅方向上有厚度相對大 的部分與相對小的部分的話，溫度履歷的差異被適切地減 低。 於前述製造方法，在加熱步驟，以使分別可以控制溫 • 44 - 201235194 度的加熱裝置在膜狀熔融物的寬幅方向排列3〜1 3個進行 加熱爲較佳。溫度履歷的差異在實用的成本範圍內確實減 低的緣故。此外，可以良好地對應於種種加熱模式。 於前述製造方法，在加熱步驟，以使分別可以控制溫 度的加熱裝置在膜狀熔融物的壓出方向排列1〜5列進行 加熱爲較佳。可以使膜狀熔融物加熱充分長的時間，確實 減低溫度履歷的差異。此外，可以良好地對應於種種加熱 模式》 於前述製造方法，在加熱步驟，以使分別可以控制溫 度的加熱裝置配置在膜狀熔融物的單面側或者雙面側進行 加熱爲較佳。可以因應由流延模壓出的膜狀熔融物通過的 路徑周圍的空間而將複數之加熱裝置以各種各樣的模式進 行配置。 於前述製造方法，加熱裝置以紅外線加熱器、鹵素燈 加熱器、碳加熱器、陶瓷加熱器及電熱線加熱器之中的至 少一種爲較佳。這些加熱器，使用電力作爲能源，所以不 會污染空氣’操作上也比較簡單所致。此外，不加熱空氣 而以熱放射進行加熱，可以局部加熱膜狀熔融物之僅被瞄 準的部分。 於前述製造方法，在壓出步驟，壓出0.8〜3m寬幅的 膜狀熔融物爲較佳。製造可以對應於液晶顯示裝置的大型 化要求的尺寸之光學膜。 於前述製造方法，在壓出步驟，壓出含2種以上熱塑 性樹脂的熔融物爲較佳。製造具有因應於用途所期待的物 -45- 201235194 理特性之光學膜》 於前述製造方法，2種以上熱塑性樹脂之中最少一種 爲纖維素酯樹脂爲佳。可製造具有高透明度的光學膜。特 別是包含纖維素酯樹脂與丙烯酸樹脂的場合，可製造低吸 濕性、透明度高、耐氣候性高、改善了脆性的光學膜。 於前述製造方法，設有在冷卻步驟延伸冷卻後的膜的 延伸步驟爲佳。可製造具有因應於用途所期待的延遲特性 之光學膜。 相關於本實施型態之光學膜，是特徵爲藉由相關於本 實施型態之光學膜的製造方法所製造的光學膜。此光學膜 ，延遲不均被抑制，可良好地對應於光學膜的大型化要求 p 相關於本實施型態的偏光板，係具備偏光子、及以挾 著前述偏光子的方式被配置於偏光子的兩側的2枚透明保 護膜之偏光板，其特徵爲：前述2枚透明保護膜之中的至 少一方，係相關於本實施型態之光學膜。此偏光板使透明 保護膜之延遲不均被抑制，可良好地對應於偏光板的大型 化要求。 相關於本實施型態之液晶顯示裝置，係具備液晶胞、 以挾住前述液晶胞的方式被配置於液晶胞的兩側的2枚偏 光板之液晶顯示裝置，其特徵爲：前述2枚偏光板之中至 少一方，係相關於本實施型態之偏光板。此液晶顯示裝置 ，使偏光板之透明保護膜之延遲不均被抑制，可良好地對 應於液晶顯示裝置的大型化要求。 • 46 - 201235194 根據本實施型態，可以抑制光學膜的延遲不均，所以 對於液晶顯示裝置的大型化有貢獻，有幫助擴大液晶顯示 裝置的用途之效果。 [實施例] 以下，通過實施例進而詳細說明本發明，但本發明並 不以此實施例作出限定的解釋。 [光學膜之製造] 使用圖1所示的光學膜之製造裝置10，將纖維素酯 樹脂包含爲熱塑性樹脂，如圖2所示製造具有挾壓區域 3 2與端部區域3 3、3 4的形狀的光學膜。但是.，·端部區域 33、34，最終由光學膜切除》 首先，把下列之膜材料以V型混合機混合30分鐘後 ，使用（股）池貝製造的2軸壓出機「PCM30」螺桿直徑 :3 0mm )以22 0°C使其熔融，製作出長4mm直徑3mm的 圓筒形的錠。 (膜材料） 乙酸丙酸纖維素（纖維素酯樹脂）（乙醯基之置換度 :1.95、丙酸基之置換度：0.7、算術平均分子量：75,000 、溫度140°C下乾燥5小時，玻璃移轉溫度Tg : 174°C ) 1〇〇質量份 三經甲基丙院三苯甲酸醋（trimethylolpropane -47- 201235194 tribenzoate)(可塑劑）10質量份 IRGANOX (登錄商標）1010 (受阻酣氧化防止劑、 安定化劑）（千葉 Special Chemicals公司製造）1質量 份 其次，對安裝了流延模12的壓出機11 (塑膠工學硏 究所製造之單軸壓出機「GT-50」）供給製做的錠，同時 由設在壓出機1 1的中間部的漏斗開口部添加下列添加劑 ，得到膜材料之混合物的熔融物。接著使所得到的熔融物 由流延模12壓出爲膜狀。 (添加劑） 二氧化矽之微粒子（襯墊劑）（日本氣膠公司製造） 0.05質量份 TINUVIN (登錄商標）3 60 (紫外線吸收劑）（千葉 Special Chemicals 公司製造）0.5質量份 流延模1 2，使用具有如圖3所示的根據加熱螺栓1 2 5 調整純緣間隔的機構者。觸碰輥14，使用具有外筒與內 筒的雙重筒構造之彈性觸碰輥。加熱裝置51使用紅外線 加熱器。來自由流延模12的膜狀熔融物31的壓出溫度（ 圖4〜圖6之溫度「T1」）爲240C。由流延模12的狹縫 (吐出口 122)至主輥13的周面之膜狀熔融物31的外接 位置爲止的距離，亦即膜狀熔融物31的長度爲2 0 0mm。 捲取裝置20的膜捲取速度爲5 m/分鐘。加熱步驟之膜狀 熔融物31的加熱及挾壓步驟之膜狀熔融物31的挾壓，僅 -48 - 201235194 在挾壓區域32進行。光學膜的端部區域 [光學膜之評估] (延遲不均/數値） 測定所製造的光學膜的延遲（面內延 延遲（R〇 )，是以膜的遲相軸方向的折| 軸方向的折射率爲Ny，膜的厚度爲d時 Nx-Ny) xd」來定義。面內延遲的測定， 機器（股）製造之「Kobra-WX150Kj來 長：590nm)。測定’是由光學膜之挾壓 方向中央部起直到挾壓區域32的寬幅方 間在寬幅方向上以5 0mm的間隔進行測定 定的面內延遲的平均値，此外求出標準差 準差/平均値）χ100」之數値（％)，以 指標。此數値越小代表光學膜的延遲不均 示於表1〜表3。 (延遲不均/目視觀察） 所製造的光學膜在正交尼科爾稜鏡下 列基準來評估。結果顯示於表1〜表3。 A :光沒有透過’全體爲均勻的暗視· B :部分看到很少的明暗 C :整體看到很少的明暗 D ’·看到部分的明暗 33、34被切斷。 遲：Ro)。面內 ί率爲N X，進相 ，以式「R 〇 =( 是使用王子計測 進行的（測定波 區域3 2的寬幅 向兩端部爲止之 。接著，求出測 ，算出式「（標 此數値爲延遲的 被抑制。結果顯 目視觀察，以下 -49- 201235194 E :看到全體的明暗 於各表，第1部分〜第5部分，是將膜狀熔融物31 的挾壓區域32在寬幅方向上5等分之各部分。接著，於 圖2，從一方端部（例如由左側的端部）訂爲第1部分、 第2部分...。 紅外線加熱器5 1，對應於各部分，配置於膜狀熔融 物3 1的單面側》紅外線加熱器51與膜狀熔融物3 I的距 離完全相同。紅外線加熱器5 1，於膜狀熔融物3 1的寬幅 方向上相互無間隙地排列配置5個。接著，使該5個之列 於膜狀熔融物31之壓出方向（亦即上下方向）上相互無 間隙地排列2列。在該場合，使膜狀熔融物3 1，由流延 模1 2壓出之後，直到外接於主輥1 3爲止，由中途開始加 熱，以可以加熱至外接於主輥13爲止的方式，把一群紅 外線加熱器5 1 ... 5 1全體於上下方向接近於主輥1 3而配置 〇 在此實施例進行的加熱步驟之加熱模式顯示於圖7。 在此實施例，厚度小的部分與厚度大的部分一倂加熱（亦 即把第1部分〜第5部分全部加熱），在該場合，是使厚 度小的部分（例如第1部分）比厚度大的部分（例如第3 部分）以更高的溫度進行加熱的模式。於圖7,時刻t3是 加熱開始時刻，溫度降低曲線（v )爲厚度大的部分（例 如第3部分）的溫度降低曲線，溫度降低曲線（vi )爲厚 度小的部分（例如第1部分）的溫度降低曲線。 於各表，主輥外接時（圖7之時刻t2)的膜狀熔融物 -50- 201235194 31的目標溫度，於圖7之加熱模式，是於各膜狀熔融物 31的厚度（第1部分〜第5部份等各部分），以使厚度 小的部分（例如第1部分）的溫度履歷相互接近厚度大的 部分（例如第3部分）的溫度履歷的方式，預先實驗性設 定的溫度（冷卻步驟開始時的溫度）。 於各表，供實現目標溫度之加熱器的加熱溫度，係以 使實現前述第1部分〜第5部分各部分的目標溫度的方式 預先實驗性設定的溫度。 於各表，實際進行的加熱器的加熱溫度，係於前述第 1部分〜第5部分各部分實際進行的溫度。 於各表，主輥外接時（圖7之時刻t2)的膜狀熔融物 3 1的實測溫度，是使用非接觸式溫度測定裝置測定的溫 度（冷卻步驟開始時之溫度）。測定，是由挾壓區域3 2 的寬幅方向中央部起直到挾壓區域32的寬幅方向兩端部 爲止之間在寬幅方向上以5 0mm的間隔進行測定。接著， 求出測定的溫度之各部分內的平均値。 表1所示的試驗1〜3，是以流延模1 2的唇緣間隔之 調整機構預先調整的膜狀熔融物31之寬幅方向的厚度分 布，作爲由流延模12壓出的膜狀熔融物31的寬幅方向的 厚度分布來使用的場合。加熱，是在把膜狀熔融物31的 端部區域33、34分別除去100mm的挾壓區域32 (寬幅 8 00mm)的範圍內進行的。試驗1，是以實現在決定步驟 所決定的各部分的目標溫度的方式不加熱膜狀熔融物3 1 的場合（以供實現第3部分的目標溫度之加熱器的加熱溫 -51 - 201235194 度均勻地加熱所有部分的場合），試驗2是以實現在決定 步驟所決定的各部分的目標溫度的方式加熱膜狀熔融物 31的場合，試驗3是不進行加熱步驟的場合。 表2所示之試驗4〜6，是把以檢測裝置7 1所檢測出 的，樹脂膜41的寬幅方向之厚度分布，作爲由流延模12 壓出的膜狀熔融物31的寬幅方向的厚度分布來使用的場 合。加熱，是在把膜狀熔融物31的端部區域33、34分別 除去10 0mm的挾壓區域32 (寬幅80 0mm)的範圍內進行 的。試驗4，是以實現在決定步驟所決定的各部分的目標 溫度的方式不加熱膜狀熔融物31的場合（以供實現第3 部分的目標溫度之加熱器的加熱溫度均勻地加熱所有部分 的場合），試驗5是以實現在決定步驟所決定的各部分的 目標溫度的方式加熱膜狀熔融物31的場合，試驗6是不 進行加熱步驟的場合。 表3所示之試驗7〜9，是把以檢測裝置7 1所檢測出 的，樹脂膜41的寬幅方向之厚度分布，作爲由流延模12 壓出的膜狀熔融物31的寬幅方向的厚度分布來使用的場 合。加熱，是在把膜狀熔融物3 1的端部區域3 3、3 4分別 除去100mm的挾壓區域32 (寬幅l5〇Omm)的範圍內進 行的。試驗7，是以實現在決定步驟所決定的各部分的目 標溫度的方式不加熱膜狀熔融物31的場合（以供實現第 3部分的目標溫度之加熱器的加熱溫度均勻地加熱所有部 分的場合），試驗8是以實現在決定步驟所決定的各部分 的目標溫度的方式加熱膜狀熔融物31的場合，試驗9是 -52- 201235194 不進行加熱步驟的場合。 -53- 201235194 表1 試驗No· 1 2 3 挾壓區域之寬幅（mm) 800 膜狀熔融物之 寬幅方向的厚度方向 (//m) 〈流延模的唇緣間隔〉 第1部分 105 第2部分 110 第3部分 115 第4部分 110 第5部分 105 主輥外接時之 膜狀熔融物的 目標溫度(。〇 第1部分 215 第2部分 210 第3部分 205 第4部分 210 第5部分 215 爲實現目標溫 度之加熱器的 加熱溫度（°c) 第1部分 230 第2部分 220 第3部分 210 第4部分 220 第5部分 230 實際進行的加 熱器的加熱溫度(°c) 第1部分 210 230 Ait m 加熱 第2部分 220 第3部分 210 第4部分 220 第5部分 230 主輥外接時之 膜狀熔融物之 實測溫度(0C) 第1部分 193 214 165 第2部分 199 209 176 第3部分 205 205 188 第4部分 201 208 178 第5部分 195 213 168 延遲之評價 數値⑻ 58 15 89 目視觀察 D A E 本發明之範圍 〇 -54- 201235194 表2 試驗No. 4 5 6 挾壓區域之寬(mm) 800 臟熔融物之 寬幅方向的厚度方向 (Aim) 〈檢測裝置檢測値〉 第1部分 103 106 104 第2部分 108 111 109 第3部分 113 116 114 第4部分 108 111 109 第5部分 103 106 104 主輥外接時之 膜狀熔融物的 目標溫度(。C) 第1部分 217 214 216 第2部分 212 209 211 第3部分 207 204 206 第4部分 212 209 211 第5部分 217 214 216 爲實現目標溫 度之加熱器的 加熱溫度（0C) 第1部分 232 229 231 第2部分 222 219 221 第3部分 212 209 211 第4部分 222 219 221 第5部分 232 229 231 實際進行的加 熱器的加熱溫度(°c) 第1部分 210 229 Μ A 第2部分 219 第3部分 209 第4部分 219 第5部分 229 主輥外接時之 膜狀熔融物之 實測溫度(0c) 第1部分 196 213 165 第2部分 201 208 177 第3部分 207 204 187 第4部分 200 208 173 第5部分 194 213 164 延遲之評價 數値(%) 51 7 75 目視觀察 D A E 本發明之範圍 〇 -55- 201235194 表3 試驗No. 7 8 9 挾壓區域之寬（mm) 1500 臟熔融物之 寬幅方向的厚度方向 (#m) 〈檢測裝置檢測値〉 第1部分 98 101 99 第2部分 103 106 104 第3部分 108 111 109 第4部分 103 106 104 第5部分 98 101 99 主輥外接時之 膜狀熔融物的 目標溫度(°C) 第1部分 216 213 215 第2部分 211 208 210 第3部分 206 203 205 第4部分 211 208 210 第5部分 216 213 215 爲實現目標溫 度之加熱器的 加熱溫度（°C) 第1部分 231 228 230 第2部分 221 218 220 第鄕分 211 208 210 第4部分 221 218 220 第5部分 231 228 230 實際進行的加 熱器的加熱溫度(°c) 第1部分 211 228 m 加熱 第2部分 218 第3部分 208 第4部分 218 第5部分 228 主輥外接時之 膜狀熔融物之 實測溫度(°c) 第1部分 194 212 161 第2部分 201 207 173 第3部分 206 203 186 第4部分 200 207 175 第5部分 194 212 164 延遲之評價 數値W 63 12 92 目視觀察 D A E 本發明之範圍 〇 -56- 201235194 [結果考察] 由表1〜表3可知，以實現各個部分的冷卻步驟開始 時之目標溫度的方式，使厚度小的部分以比厚度大的部分 更高的溫度加熱膜狀熔融物31的試驗2、5、8，於各部 分實現了冷卻步驟開始時的目標溫度，所製造的光學膜的 延遲不均被良好地抑制了。相對於此，以厚度大的部分（ 第3部分）用的溫度均勻地加熱所有部分的試驗1、4、7 以及不加熱膜狀熔融物31的試驗3、6、9，在冷卻步驟 開始時之實測溫度是厚度越小的部分變得越低，所製造的 光學膜的延遲不均變大，膜沒有實用性》 此外，由表1〜表2可知，作爲膜狀熔融物31的寬 幅方向的厚度分布，在調整步驟使用預先被調整的値之試 驗2，以及使用在檢測步驟檢測出的値之試驗5，延遲不 均都是良好的結果。 此外，由表2〜表3可知，使膜狀熔融物3 1的寬幅 由800mm改變爲150 0mm的場合，不加熱膜狀熔融物31 的試驗6、9之延遲變大，但在厚度小的部分以比大的部 分更高的溫度加熱膜狀熔融物31的試驗5、8，即使膜狀 熔融物3 1的寬幅變寬，延遲也是良好的評估結果。 此申請案係以2 0 1 0年1 1月2日申請之日本專利申請 案特願201 0-24 60 85爲基礎，其內容包含於本申請案。 爲了表現本發明’於前述參照圖面同時透過實施型態 適切且充分地說明了本發明，但熟悉該項技藝者當然可以 容易改變及/或改良前述實施型態。亦即，熟悉該向技藝 -57- 201235194 者實施的變更型態或改良型態’只要不脫離申請專利範圍 所記載的請求項的權利範圍的程度，該變更型態或該改良 型態應被解釋爲包括在該請求項的權利範圍。 [產業上利用可能性] 本發明於光學膜之製造方法、光學膜'偏光板及液晶 顯示裝置之技術領域，具有廣泛的產業上可利用性。 【圖式簡單說明】 圖1係顯示相關於本發明的實施型態之光學膜的製造 裝置的方塊構成圖。 圖2係由圖1之光學膜的製造裝置的流延模壓出的膜 狀熔融物的寬幅方向的剖面圖。 圖3係圖1之光學膜的製造裝置的流延模之重要部位 擴大剖面圖。 圖4係由流延模壓出的膜狀熔融物之溫度時間變化圖 〇 圖5係供說明相關於本發明的實施型態的加熱步驟之 —態樣之類似於圖4之圖。 圖6係供說明相關於本發明的實施型態的加熱步驟之 其他態樣之類似於圖4之圖。 圖7係供說明相關於本發明的實施例的加熱步驟之一 態樣之類似於圖4之圖。 -58- 201235194 【主要元件符號說明】 10 :製造裝置 1 1 :壓出機 1 2 :流延模 13 :主輥 1 4 :觸碰輥 1 5、1 6 :冷卻輥 1 7 :剝離輥 1 8 :搬送輥 1 9 :延伸裝置 20 :捲取裝置 3 1 :膜狀熔融物 4 1 :冷卻固化後的膜（樹脂膜） 5 1 :加熱裝置 7 1 :檢測裝置 -59-201235194 6. The invention relates to an optical film for manufacturing an optical film, a liquid for manufacturing the same, and a liquid crystal having the same. The liquid crystal display device is enlarged in size, used for display, or a liquid crystal display device using a display for advertising in a common place, and has a configuration in which a glass plate or the like is placed on both sides of the liquid crystal cell (also referred to as polarized light). The film and the offset method are disposed on the two protective films of the polarizer, and an optical film made of, for example, triacetic acid is used. The melt of the square resin as the optical film is rolled or extended by the casting die melt outside the cooling roll. The polarizing plate display device used as a transparent protective film by the film of this manufacturing method by the manufacturing method disclosed in Patent Document 1, etc. (LCD), the demand for liquid crystal television or personal electric power is expanding. The accompanying work is the public use of a large display device called a digital signage installed on the street or in the storefront. The use is also more diversified. The transparent electrode, the liquid crystal layer, the color filter liquid crystal cell, and the two polarizing plates for holding the liquid crystal cell. The polarizing plate is provided with a polarizing film), and the polarizing film is clamped. 2 transparent protective films on the side. As a film of a cellulose ester resin such as a transparent cellulose, a thermoplastic tool such as a cellulose ester resin is extruded into a film shape, and the film-form peripheral surface to be pressed is cooled and solidified, and melt-casting is performed as necessary. The film forming method is known. When cooling the melted -5 - 201235194 resin by a cooling roll, a heater is placed in the width direction of the cooling roll, and the temperature is adjusted in various areas in the wide direction to keep the film temperature uniform in the wide direction. The technology of cooling at the same time. In the patent document 2, the molten resin which is discharged from the mold into a sheet shape and which is in contact with the cooling roll is heated by a heater which can change the output in the flow direction and the wide direction of the molten resin to melt the resin. The technique of suppressing the temperature distribution in the flow direction and the wide direction within 10 ° C. [Prior Art Document] [Patent Document 1] Japanese Patent Laid-Open Publication No. 2004-2099 No. 1 (paragraph 0008) [Patent Document 2] Japanese Patent Laid-Open No. 2000-78 (Paragraph 0008, 0010) SUMMARY OF THE INVENTION In such a melt casting film forming method, even if it is desired to adjust the lip gap (slit gap) of the casting die in each portion of the width direction of the casting die to Similarly, the film-like melt having a uniform thickness in the width direction is extruded, and the thickness is not uniform. The film-like melt produces a portion having a relatively large thickness and a relatively small thickness in the width direction. Further, in the melt casting film forming method, in order to remove the stripe-like defects generated by the film surface at a pitch of several mm, the flatness of the film is improved, and the film-like melt extruded by the casting die is caused by the main roll and the touch. The roll is pressed, and the thickness of the film-like melt is caused by the action of the film-like melt at a uniform pressure in the rolling region where the main roll and the touch roll are pressed at the pressure of -6-201235194. It is the largest at the center in the width direction and the smallest at both ends in the width direction. Then, in any case, when the film-like melt has a portion having a relatively large thickness and a relatively small portion in the width direction, there is a problem that the retardation unevenness of the produced optical film becomes large. In any of the techniques disclosed in Patent Documents 1 and 2, there is no possibility that the film-like melt has a relatively large thickness portion and a relatively small portion in the wide direction, and the retardation of the produced optical film may not occur. The problem of getting bigger. An object of the present invention is to suppress unevenness in retardation of an optical film and contribute to an increase in size of a liquid crystal display device. In one aspect of the invention, there is provided an extrusion step of casting a melt containing a thermoplastic resin into a film shape by casting, and a method for producing an optical film for cooling a film-like melt which is extruded, and characterized in that Between the pressing step and the cooling step, there is provided a heating step of heating the film-like melt extruded, wherein the heating step is based on the thickness distribution of the film-like melt in the width direction, and only the heating thickness is relatively small. The portion, or the portion having a relatively small thickness, is heated at a higher temperature than the relatively large portion and/or heated for a longer period of time. Another aspect of the present invention is an optical film produced by the aforementioned production method. Another aspect of the present invention provides a polarizing plate and a polarizing plate of two transparent protective films disposed on both sides of the polarizer so as to sandwich the polarizers, and the two transparent protective films are provided. At least one of them is the optical film described above. According to still another aspect of the invention, there is provided a liquid crystal display device comprising two liquid crystal cells and two polarizing plates disposed on both sides of a liquid crystal cell so as to sandwich the liquid crystal cell, wherein at least two of the two polarizing plates are included One side is the aforementioned polarizing plate. The foregoing and other objects, features and advantages of the present invention will be apparent from [Embodiment] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments. The inventors of the present invention have found that if the film-like melt extruded by the casting die has a portion having a different thickness in the width direction, the resulting film will eventually suffer from a problem that the retardation of the obtained film becomes large, and the cause of the film is repeatedly corrected. As a result of the problem of the problem, the film-like melt differs in the cooling rate and the temperature history due to the difference in thickness. If the film-like melt is heated to reduce the difference, the delay unevenness is suppressed. The present invention has thus been completed. <Manufacturing Apparatus of Optical Film> Fig. 1 is a block diagram showing a manufacturing apparatus 1 relating to the optical film of the present embodiment. In the optical film manufacturing apparatus 1, an optical film 201235194 containing a thermoplastic resin such as a cellulose ester resin is produced by a melt casting film forming method. The melt casting film forming method is a method in which a mixture of film materials containing a thermoplastic resin is heated and melted to a temperature having fluidity, and the molten stream is stretched into a film form to be cooled and solidified to obtain an optical film. The optical film manufacturing apparatus 10 shown in Fig. 1 includes an extruder n, a casting die 12, a main roll 13, a touch roll 14, a cooling roll 15, and a peeling roll 17' conveying roller 18, and an extension. Device 19 and take-up device 20. In the figure, reference numeral 31 denotes a film-like melt extruded from a casting die 12, reference numeral 41 denotes a film which is cooled and solidified by a peeling roll 17 (resin film), and reference numeral 51 denotes a film-like melt 3 for heating. In the heating device of 1, reference numeral 71 is a detecting device for detecting the thickness in the width direction of the film 41 which is cooled and solidified by the peeling roller 17 and the thickness distribution in the width direction. In addition, a plurality of the transport rollers 18 are provided, and the transport speed (rotation speed) on the downstream side can be increased, and the film 41 can be extended in the MD (machine direction) direction (transport direction). . Further, the extension device 19, for example, uses a grip tenter (grip 161^61") or a pin tenter, and conveys the film 41 in the direction of the transverse direction (wide direction). Extend on. In the present embodiment, after a film material containing a thermoplastic resin such as a cellulose ester resin is mixed, the melt of the mixture is extruded in a film form by a casting die 12 using an extruder, so that it is pressed out. The film-like melt 31 is pressed by the main roll 13 and the touch roll 14. Thereafter, the film-like melt 31 is sequentially externally attached to the circumferential surfaces of the two cooling rolls 15 and 16 to be cooled and solidified, and peeled off by the peeling roll 17. The peeled film 41 is conveyed while being conveyed by the conveyance roller 18 and the stretching device 19, and then wound up by the winding device 20 into a roll -9 - 201235194 shape. The thermoplastic resin to be used in the present embodiment is not particularly limited as long as it can be formed by a melt casting film forming method. For example, a cellulose ester resin, an acrylic resin, a polycarbonate resin, a polymer containing an alicyclic structure, a polyvinyl alcohol, a polyamide resin, or a polyimide resin may be mentioned. Among them, a cellulose ester resin, an acrylic resin, and a polymer having an alicyclic structure are preferable because the photoelastic coefficient is small and an optical film having high transparency is produced. In the present embodiment, these thermoplastic resins may be used singly or in combination of two or more. By using two or more kinds of thermoplastic resins, an optical film having physical properties expected in accordance with the use can be produced. In particular, when a cellulose ester resin and an acrylic resin are contained, an optical film having low hygroscopicity, high transparency, high weather resistance, and improved brittleness can be produced. <Production Method of Optical Film> Hereinafter, a method of producing an optical film according to the present embodiment will be described as an example in which a cellulose ester resin is used as a thermoplastic resin. In the method for producing an optical film according to the present embodiment, after the mixing of the film material, the main step includes a pressing step, a heating step, a cooling step (including a rolling step), a peeling step, an extending step, and a winding step. Wait. Further, it further includes a detection step, an adjustment step, a determination step, and the like. Further, in the present embodiment, the rolling step is carried out in the cooling step. Except for the final description of the heating step of the characteristic portion of the present month, the steps are described in order below. -10- 201235194 [Mixing of membrane material] First, the membrane material is mixed using a mixer or the like. As the mixer, a general mixer can be used, such as a V-type mixer, a conical blade type mixer, a horizontal cylinder type mixer, or the like. In the present embodiment, after the 'mixed film material, the mixture is directly melted by using the extruder 1 1 to form a film, or the film material may be ingot first, and then the ingot is melted by the extruder. membrane. Further, when the film material contains a plurality of materials having different melting points, it is possible to temporarily prepare a popcorn-like semi-melt at a temperature at which only a material having a low melting point is melted, and to introduce the semi-melt into the extruder 11 to form a film. When the film material contains a material which is easily thermally decomposed, 'the method of directly forming a film without making an ingot for the purpose of reducing the number of times of melting, or the method of preparing a half-melt of a popcorn sugar as described above and then forming a film It is better. Also, the film material will be described in detail later. [Extrusion Step] The extrusion step is a step of pressing the melt containing the thermoplastic resin from the casting die 12 in a film form using the extruder 11. As the extruder to be used, various commercially available extruders can be used, and a melt-kneading extruder is preferred. A single-axis extruder can be used, or a 2-axis extruder can be used. The melting temperature of the film material in the extruder 11 varies depending on factors such as the viscosity or discharge amount of the film material, the thickness of the film to be produced, and the like, but in general, the glass transfer to the film The temperature Tg is preferably τ? or more and Tg+100 °C or less. The melt viscosity at the time of extrusion -11 - 201235194 degrees, is 10 to 100,000 poise, preferably 100 to poise. Further, the retention of the film material in the extruder 11 is preferably as short as possible, for example, within 5 minutes. Further, it is preferable to reduce the concentration of oxygen by replacing it with an inert gas such as nitrogen or argon. The melt discharged from the extruder 11 is supplied to the casting die 1 2 The die 12 is extruded into a film shape. Fig. 2 is a cross-sectional view in the width direction of the melt 31 extruded from the casting die 12. Further, in Fig. 2, an exaggerated illustration is made for the thickness distribution of the melt 31 in the wide direction to be more easily understood. The thickness distribution of the film 41 changes when the film 41 is cooled and solidified (after peeling). In particular, make the film < In the TD direction, the thickness distribution of the film 41 in the width direction is such that, in the present embodiment, as shown in Fig. 1, the detecting device is placed upstream of the conveying roller 18 and the extending device 19. Further, in Fig. 1, the device 71 is disposed between the peeling roller 17 and the conveying roller 18, but it is further understood that the position is as long as the cooling step is started, that is, as long as the cooling step is started. Preferably, the extension may be performed before the start of the extension of the extension device 19 in the TD direction, and may be disposed at any position depending on the situation. The produced optical film is thinner than the film-like melt 31 by shrinkage accompanying cooling solidification. However, the shrinkage ratio of the thickness is almost uniform in the film direction, so the state in which the thickness is almost similar after the cooling and solidification is changed. That is, the thickness distribution in the width direction of the film 41 after cooling and solidification by the detecting means 7 1 can be extended by the film-like pattern by the film-like melting for more than 10,000 times. The '1 configuration will detect the position as the subsequent position, and the thickness of the film is measured as the thickness distribution of the film -12-201235194-like melt 31 in the width direction. As shown in Fig. 2, the rolling of the film-like melt 31 is suppressed by the main roll 13 and the touch roll 14, the field 32 used as an optical film, and the width of the rolling area 32. The end portions of the direction are different, and the maximum thickness of the end portion 3 3 and the portion regions 33 and 34 which are cut off by the main roller 13 and the touch roller 14 after being pressed or not used as an optical film It may reach 1.2 times to 5 times the thickness of the rolling area 32. Therefore, in the subsequent rolling step, the region 3 2 is pressed, and the end regions 3 3, 34 are preferably not pressed, preferably in the wide direction direction of the film-like melt 31. There is a width of about l〇mm~200mm on the inner side. In the present embodiment, the film-like melt 31 has a maximum thickness (D1) in the center portion in the wide direction in the rolling region, and the thickness (D2, D3) in the width portion is minimized, and the casting die 12 is formed. Thereby, the influence of the deflection of the touch roller 14 at the time of rolling is canceled, and the pressure of the sentence presses the rolling region 32 of the film-like melt 31. As a result, the surface of the film was removed by stripe which was produced at a pitch of several mm to improve the planarity of the optical film. 'Furthermore, from the viewpoint that the rolling effect can be surely obtained, in the case where the width of the rolling region 32 is 1,500 mm, (D1-D2) D1-D3) is preferably 1.5; czm to 4.5 ym, which is pressed. In the case of 3000 mm of the region 32, (D1-D2) or (D1-D3) is preferably 3//r from m. Further, the maximum thickness (Dl) of the rolling region 32 is preferably: /zm to 120/zm. More preferably 20/zm to 100/zm. Steps to borrow the pressure zone in response to the pressure, at 3 4 . The maximum of the end is only the pressure. The two edges 32 of the ends are pressed out to the ends. For example, in the case of a light defect, the thickness distribution in the width direction of the film-like melt 3i which is extruded by the casting die 12 in the width of 1 to 9 {15 -13-201235194 depends on the casting die. The lip gap (slit gap) of 12, that is, 'the lip spacing of the casting die 12 is adjusted separately in each part of the width direction of the casting die 12, for example, having the shape of FIG. Fig. 3 is an enlarged cross-sectional view showing an important portion of the casting die i 2 for explaining the adjustment mechanism of the lip interval. The thickness distribution in the width direction of the film-like melt 31 extruded by the casting die 12 is adjusted in advance. One of the slits (discharge ports) 122 forming the casting die 12 is one of the lips, and the rigidity is small. The deformed flexible lip 133, and the other side is a rigid lip that is hard to deform. The mold body 121 has a plurality of heating bolts (only one shown) 125 in the width direction of the casting die 12 to be specific. The spacing (also a certain spacing) is arranged. Each heating bolt 1 2 5 , the penetration The heater 127 and the block 1 26 of the cooling medium passage (not shown) are embedded. The head of the heating bolt 145 is fixed to the die body 1 2 1, and the tip end of the heating bolt 125 abuts against the flexible lip 123. By controlling the amount of current buried in the electric heater 127 or the flow rate of the cooling medium, changing the temperature of the block 126 and changing the length of the heating bolt 125, the flexible lip 123 is displaced, and the lip spacing can be adjusted. The film-like melt 31 may be arranged with a distance between the thickness distributions in the width direction as shown in FIG. 2. For example, the pitch may be selected within a range of about 20 mm to 200 mm. The range of about 500//m to 1500//m is preferably in the range of 700 -14 - 201235194 em~1200; / m. In addition, instead of the heating bolt 125, the bolt can be manually locked. The adjustment mechanism for displacing the flexible lip 123 to adjust the lip spacing can be cast by the thickness distribution of the film-like melt pre-adjusted by the adjustment mechanism of the lip interval regardless of the mechanism used. Mold 12 extruded film The thickness distribution of the melt 31 in the width direction is used. In this extrusion step, the film-like melt 31 having a width of 0.8 to 3 m is extruded by the casting die 12. As shown in Fig. 2, the film-like melt 31 has In the case of the rolling region 32 and the end regions 33 and 34, the film-like melt 31 having a width of 0.8 to 3 m which is a rolling region 32 used as an optical film is extruded by the casting die 12. An optical film of a size required for the enlargement of the liquid crystal display device. [Twisting step/cooling step] The rolling step is performed by removing the resin film 41 and even the stripe-like defects generated on the surface of the optical film to improve the film. For the purpose of planarity or the like, the film-like melt 31 to be pressed is subjected to a step of rolling the main roll 13 and the touch roll 14. In the present embodiment, as described above, there is a case where the rolled region 32 and the end portion 33' 34 of the film-like melt 31 are rolled as shown in Fig. 2, but more preferably, only the rolling is used as the optical film. The rolling area 32 used. Next, this rolling step, as previously described, is carried out in the cooling step. The main roll 13 is also referred to as a casting roll, and the film-like melt 31 extruded by the casting die 12 is externally supported and supported in close contact with the circumferential surface, and is in the state of the -15-201235194 and the touch roll. A roller for pressing the film-like melt 31 between 14. The main roller 13 is not particularly limited as long as it is generally used for film production by a melt casting film forming method, and may be selected as appropriate. Generally, a roll made of a highly rigid metal has a function of cooling the film-like melt 31 supported on the peripheral surface. That is, the time point at which the film-like melt 31 is externally connected to the main roll 13 is the start time point of the cooling step. Therefore, the start of cooling by the main roll 13 is the start of the cooling step, and the film-like melt 31 which is cooled by the main roll 13 is the film 41 which is cooled and solidified. In order to uniformly and efficiently cool the film-like melt 31, a flow path in which a cooling medium such as water or oil is provided inside the main roll 13 is preferable. As the material of the circumferential surface of the main roll 13, carbon steel, stainless steel, aluminum, titanium, or the like can be used. Further, it is preferable to increase the hardness of the peripheral surface of the main roll 13, or to improve the peeling property with the resin, and to apply surface treatment such as hard chrome plating, nickel plating, amorphous chromium plating, or ceramic spraying. The touch roller 14 is not particularly limited, and a roller made of a metal such as carbon steel, stainless steel, aluminum or titanium, or a roller having a circumferential surface covered with a rubber or a resin may be appropriately selected. The smoother the circumferential surface of the main roller 13 or the touch roller 14, the smoother the surface of the obtained resin film 41, and therefore the better. The surface roughness of the rolls 13, 14 is preferably at a maximum height Ry (JIS B0601: 1994), and more preferably 〇.5 / Z m or less. From the viewpoint that the pressure applied to the film-like melt 31 can be made as uniform as possible, the touch roller 14 is preferably an elastic touch roller having a double cylinder structure of an outer cylinder and an inner cylinder. Further, in order to homogenize the -16 - 201235194 of the circumferential temperature of the outer cylinder, it is preferable to provide a flow path of a cooling medium such as water or oil between the outer cylinder and the inner cylinder. The material of the outer cylinder is preferably smooth, moderately elastic, and durable. Carbon steel, stainless steel, titanium, nickel produced by electroforming, or the like can be used. Further, it is preferable to increase the hardness of the peripheral surface or to improve the peeling property with the resin by surface treatment such as hard chrome plating, nickel plating, amorphous chromium plating, or ceramic spraying. The inner cylinder is preferably a lightweight and rigid metal product such as carbon steel, stainless steel, aluminum or titanium. By making the inner cylinder rigid, the rotational deformation of the touch roller 14 can be made. By making the thickness of the inner cylinder 2 to 10 times the outer cylinder, sufficient rigidity can be obtained. The inner cylinder may be further covered with an elastic material such as silicone rubber or fluororubber. The peripheral surface temperature of the touch roller 14 is preferably lower than the glass transition temperature (Tg) of the manufactured optical film. When it is higher than Tg, the peeling property of the resin and the touch roll 14 tends to be lowered. However, if the temperature of the peripheral surface of the touch roll 14 is too low, the volatile component of the film-like melt 31 may be deposited on the circumferential surface of the touch roll 14, so that, for example, l〇°C~(Tg-l〇°C) The extent of the degree is good. In the present embodiment, after the rolling step, the film-like melt 3 1 is externally circumsed to the circumferential surfaces of the two cooling rolls 15 and 16 to be cooled and solidified to obtain the resin film 41. In the present embodiment, the cooling rolls have two, but not limited thereto, the cooling rolls 15, 16 are the same as the main rolls 13 and are high-rigidity metal rolls, in order to externally press the peripheral surface. The film-like melt 31 is uniform and is efficiently cooled from -17 to 201235194. It is preferable to provide a flow path for cooling medium such as water or oil inside the cooling rolls 15 and 16. The diameter of the cooling rolls 15 and 16 may be such a size as to have a sufficiently large capacity for cooling and solidifying the film-like melt 31 circumscribing the peripheral surface, for example, approximately 1 〇〇 mm to 1 m. As the material of the circumferential surface of the cooling rolls 15 and 16, carbon steel, stainless steel, aluminum, titanium or the like can be used. Further, the hardness of the circumferential surface of the cooling rolls 15 and 16 is increased, or in order to improve the peeling property with the resin, surface treatment such as hard chrome plating, nickel plating, amorphous chromium plating, or ceramic spraying is used. good. [Peeling Step] The resin film 4 1 obtained by cooling and solidifying the circumferential surfaces of the cooling rolls 15 and 16 is separated from the circumferential surface of the cooling roll 16 by the peeling roll 17 which abuts the cooling roll 16 at a specific pressure. After peeling, feed to the downstream side. [Extension Step] The peeled resin film 41 is conveyed by the conveyance roller 18 and the stretching device 19 while being extended in the MD direction (transport direction) and/or the TD direction (wide direction). Thereby, an optical film having a delay characteristic expected in accordance with the use is produced. [Winding step] The resin film 41 which has passed through the stretching step is finally taken up in a roll shape by the winding device 20. Thereby, the manufacture of an optical film is completed. Further, in the present embodiment, the cutting step of the unnecessary end regions 33 -18 to 201235194 and 34 in the film-like melt 31 shown in Fig. 2 is set, for example, in the stretching step and the winding step. between. [Heating Step] The heating step, as shown in Fig. 1, is between the pressing step and the cooling step, that is, the film-like melt 31 extruded from the casting die 12 is externally attached to the main 'roll 1 3 Previously, the step of heating the film-like melt 31 by the heating device 51 disposed in the space around the path through which the film-like melt 31 passes. Then, in this heating step, depending on the thickness distribution in the width direction of the film-like melt 31, only a portion having a relatively small thickness is heated, or a portion having a relatively small thickness is higher than a portion having a relatively large thickness. Temperature heating (in other words, the portion where the thickness is smaller is heated at a higher temperature, the portion having a larger thickness is heated at a lower temperature), or the portion having a relatively small thickness is longer than a portion having a relatively large thickness. The time is heated (in other words, the portion having a smaller thickness is heated for a longer period of time, and the portion having a larger thickness is heated in a shorter time)" or a portion having a relatively small thickness is relatively larger than the thickness. The portion is heated at a high temperature for a longer period of time (in other words, the portion where the thickness is smaller is heated at a higher temperature for a longer period of time, and the portion having a larger thickness is heated at a lower temperature for a shorter period of time). More specifically, in the present embodiment, as a basic operation, the rolling region 3 2 ' used as an optical film among the film-like melts 3 shown in Fig. 2 only heats a relatively small thickness. The end portion of the direction, or the end portion in the wide direction direction, is heated at a higher temperature than the central portion of the width direction which is relatively larger in thickness (in other words, the higher the temperature toward the end portion in the wide direction direction) Heating, the temperature toward the center of the wide direction is heated at a lower temperature) -19- 201235194, or the end portion in the wide direction is heated for a longer period of time than the central portion in the wide direction (in other words, The end portion in the width direction is heated for a longer period of time, and the heating is performed toward the center portion in the width direction in a shorter period of time, or the end portion in the width direction is in the center portion in the width direction. Higher temperature and heating for a longer period of time (in other words, the longer the temperature is heated toward the end in the wide direction, the longer the temperature is toward the center of the wide direction, the lower the temperature is, the shorter the heating is. time). Therefore, as shown in Fig. 2, a plurality of heating devices 5i capable of controlling the temperature and the control time are arranged in a plurality in the width direction of the film-like melt 31. These heating devices 51·.·51 heat the rolling region 32 among the film-like melts 31. Originally, the overflow rolling zone 32 is not excluded, and a portion of the end regions 33, 34 are also heated, or all of the end regions 33, 34 are also heated, i.e., the film melt is heated across the full width. 3 1. In the present embodiment, as described above, the thickness distribution in the width direction of the film 41 after cooling and solidification detected by the detecting device 7 1 is used as the thickness distribution in the width direction of the film-like melt 31. The step of detecting the thickness distribution of the film 41 in the width direction by the detecting means 71 is taken as a detecting step. In this embodiment, the detecting step is between the cooling step and the winding step. Further, the detecting device 7 1 is preferably non-contact type. Further, it is preferable that the thickness of the resin film 41 can be detected at an arbitrary interval, for example, at intervals of about 50 mm. Further, in the present embodiment, as shown in FIG. 3, the thickness distribution in the width direction of the film-like melt 31 adjusted in advance by the adjustment mechanism of the lip interval of the casting die 12 can be used as the casting die 12 by the casting die 12. The film thickness of the extruded film-like melt-20-201235194 31 is used in the width direction. The step of adjusting the thickness distribution in the width direction of the film-like melt 31 extruded from the casting die 12 by the adjustment mechanism of the lip interval is an adjustment step. In the present embodiment, the adjustment step is before the extrusion step. The reason for providing such a heating step is as follows. Fig. 4 shows the temperature change accompanying the passage of time of the film-like melt 31 extruded from the casting die 12. At time t1, the film-like melt 31 is extruded, and at time t2, the film-like melt 31 is externally attached to the main roll 13 (start of the cooling step). At this time, the film-like melt 31 lowers the temperature by exothermic heat. In this case, when the film-like melt 31 has a relatively large thickness portion and a relatively small portion in the width direction, the portion having a relatively large thickness has a relatively small temperature decrease as indicated by the symbol (i) and the thickness is relatively small. The temperature of the portion shown by the symbol (ii) is relatively large. In other words, when the temperature at the time of extrusion (extrusion temperature) "T 1" and the temperature at the start of the cooling step is "T2" or "T2", the cooling rate of the portion having a relatively small thickness "(T1-T2) ") / (t2-tl)" is larger than the cooling rate "(T1-T2,) / (t2-tl)" in a portion having a relatively large thickness. Therefore, the temperature history of the film-like melt 31 after being extruded by the casting die 12 is externally connected to the main roller 13 (corresponding to the longitudinal temperature axis and the lateral time axis of FIG. 4 and the longitudinal direction through the time t2) The curve of the line and the trajectory showing the decrease in temperature (the area surrounded by Ο or (Π) (hereinafter referred to as "history area") is jagged in the width direction of the film-like melt 31. Then, the film The difference in the width direction of the temperature history of the molten material 31 is the unevenness of the delay of the finally obtained optical film. Further, the film-like melt 31, after being externally attached to the main roll 13, is a main roll having a large capacity. Each of the 21 - 201235194 parts is uniformly and efficiently cooled. In Fig. 4, 'temperature Tr' is the circumferential temperature of the main roll 13 . Here, in this embodiment, a film for reducing the film is provided. The heating step of the difference in the width direction of the temperature history of the molten material 31. In order to reduce the difference in the temperature history, the temperature decrease curve (i) of the portion having a relatively large thickness in Fig. 4 and the portion having a relatively small thickness are The temperature reduction curve (ii) is close to each other or one Or, even if the temperature reduction curves are not close to or coincide with each other, as long as the temperature reduction curve (i) of the portion having a relatively large thickness is obtained as a result, the temperature reduction curve of the portion having a relatively small history and a relatively small thickness ( Ii) The obtained history areas may be close to or coincide with each other. Therefore, for example, in one example, as shown in Fig. 5, only a portion having a relatively small thickness is heated. Thereby, the cooling rate of the portion having a relatively small thickness becomes small. The temperature decrease curve (iii) of the portion having a relatively small thickness is close to the temperature decrease curve (i) of the portion having a relatively large thickness. Further, the legend is shown after the film-like melt 31 is pressed out by the casting die 12 ( At time 11), heating is continued until it is externally connected to the main roller 13 (time 12). However, the heating is not started in the middle, or the heating may be stopped in the middle. The heating may be performed plural times intermittently, and the total heating time is also arbitrary. The heating temperature of the heating device 51 or the temperature T2 at the start of the cooling step is not required to be noted. These parameters are combined in various modes and heated in various modes. In short, it is sufficient that the cooling rate of the portion having a relatively small thickness is smaller than the case where heating is not performed at least once. However, in any case It is necessary to avoid the thickness phase-22-201235194 heating too small part, and the temperature history of the part with relatively small thickness is increased compared with the temperature history of the part with relatively large thickness. Of course, the thickness is relatively The temperature history of the smaller portion is preferably the same as the temperature history of the portion having a relatively large thickness. For example, Fig. 6 shows a case where the heating of the portion having a relatively small thickness is started from the middle. The legend is a relatively small thickness. The history area obtained by the partial temperature decrease curve (iv) is approximately the same as the history area obtained by the temperature decrease curve (i) of the portion having a relatively large thickness. As a result, the temperature T2" at the start of the cooling step of the portion having a relatively small thickness becomes higher than the temperature T2' at the start of the cooling step of the portion having a relatively large thickness. There is no need to make the history areas coincide with each other even if T2" becomes lower than T2'. Further, when the start timing of heating is relatively late, etc., the temperature decrease curve after the start of heating has a tendency to rise temporarily or collectively. The above is a case where only the heating mode of the portion having a relatively small thickness is heated, but a portion having a relatively large heating thickness may be used. In the case of a heating mode in which a portion having a relatively large thickness is heated, the technical idea is also the same as the heating mode in which only a portion having a relatively small thickness is heated. For example, in one case, the heating temperature of the heating device 51 is not made uniform, but the portion having a relatively small thickness is heated at a temperature higher than a portion having a relatively large thickness. Thereby, the cooling rate of the portion having a relatively small thickness is the same as the cooling rate of the portion having a relatively large thickness, and the case where the heating is not performed together is smaller, but the cooling rate of the portion having a relatively small thickness becomes smaller. The temperature drop curve of the relatively small portion is close to the temperature decrease curve of the relatively large thickness portion -23-201235194, and the temperature history becomes close to or coincident with each other. Further, in the case of heating a portion in which a relatively thick portion is heated, a portion having a relatively small thickness can be heated for a longer period of time than a portion having a relatively large thickness. For example, the heating temperature of the heating device 51 is uniform, and the heating of the portion having a relatively small thickness is continuously performed from the time 11 to the time t2, and the heating of the portion having the relatively large thickness is temporarily set between the time 11 and the time t2. The period of the stop. Also in this manner, the temperature history of the portion having a relatively small thickness and the temperature history of the portion having a relatively large thickness can be made close to or coincide with each other. Further, in the case of heating a portion of a portion having a relatively large thickness, a portion having a relatively small thickness is heated at a higher temperature for a longer period of time than a portion having a relatively large thickness, and a portion having a relatively small thickness can be made. The temperature history and the temperature history of the portion having a relatively large thickness are close to or coincide with each other. In this case, as compared with the case where the heating temperature of the heating device 51 is uniform, it is possible to increase the period in which the heating of the portion having a relatively large thickness is temporarily stopped, and the heating mode in which the portion having a relatively large thickness is heated. Regarding the heating of each portion in the wide direction, heating may be continuously performed from time 11 to time t2, or heating may be started from the middle or heating may be stopped in the middle. Further, the heating may be performed plural times intermittently, and the total heating time is also arbitrary. There is no need to pay attention to the heating temperature of the heating device 51 or the temperature T2', T2" at the start of the cooling step. These parameters can be combined in various ways to heat the various portions in the wide direction in various modes. It is necessary to avoid the case where the relatively small thickness is added to -24-201235194, and the temperature history of the portion having a relatively small thickness is increased as compared with the temperature history of the portion having a relatively large thickness. Of course, the thickness is relatively high. The temperature history of the small portion is preferably the same as the temperature history of the portion having a relatively large thickness. In such a heating step, the thickness distribution detected in the above-described detecting step is defined as the thickness distribution in the width direction of the film-like melt 31. In the case of use, the actual thickness distribution detected in the production of the reference optical film has an advantage of improving the accuracy of the difference in the temperature history. Further, the thickness distribution adjusted in advance in the above-described adjustment step is used as the film-like melt. When the thickness distribution of the width direction of 31 is used, it is not necessary to detect the thickness in the manufacture of the optical film. In addition, the thickness of the film-like melt 31 in the width direction is set, and the target temperature in the width direction of the film-like melt 31 is determined at the start of cooling (time t2) in the cooling step. Determining step; in the heating step, it is preferable to heat the film-like melt 31 in such a manner that the target temperature of each portion determined in the determining step is achieved at the start of cooling (time t2). That is, FIG. 4 The temperature T2', T2" at the start of the cooling step of FIG. 6 is heated, for example, such that the temperature history of the portion having a small thickness and the temperature history of the portion having a large thickness approach or match each other. Thereby, the difference in temperature history can be further reduced by the target temperature at the start of cooling (time t2) in each part, and the difference in temperature history can be eliminated. Further, the determining step is provided between the detecting step and the heating step, or between the adjusting step and the heating step. Further, such a target temperature, for example, each thickness of the film-like melt 31 is -25 to 35,315,194 degrees, and depending on various other parameters, the method of preliminarily setting the cockroach in advance may be in the form of a map or a table. Shorten the work of the decision step. The prepared funds are stored in memory and the like. Next, the heating temperature for realizing the target temperature setting 51 may be set in accordance with other kinds of types, and may be prepared in a map form so that the cockroach can be retrieved. The prepared materials can be stored in a memory or the like, for example. The original is not limited to this, and is variable. For example, in order to prevent the memory capacity from being excessively large, the target temperature is determined by the root calculation and the foregoing addition is applied to the present embodiment. 31, preferably heated in the film-like melt 31! The rolling region 32 is uniformly pressed by the main roller 13 and the touch roller 14, and is in a portion where the width of the film-like melt 31 is large and a portion having a small thickness in the rolling region 32, so the difference in the rolling region is appropriately adapted. reduce. In the present embodiment, it is preferable to heat the respective heating means 51 in the wide direction of the film-like melt 31 in the heating step. This is because the difference in temperature history is indeed reduced within the cost range. In addition, a heating mode can be improved. If there are less than three, the difference in the width direction of the temperature history of 31 cannot be sufficiently reduced. 14 clubs are too high. For example, in the example shown in Fig. 2, the heating means 5 1 of the time can be controlled in the film-like melt 31 to be ready for inspection. In this case, for example, the heating parameters that can be used, the pre-real form or the table target temperature connection can be used depending on the conditions and the various parameters per thermal temperature. In the case where the temperature of the squeezing zone of the film is heated, the pressure of the sentence is 32, and the temperature history of the thick region is controlled by the enthalpy. The temperature can be controlled by 3 to 1 3, which can be used in a practically good manner in response to a low-melting melt. Seven are arranged in -26-201235194 in order to control temperature and width. The total width of the plurality of heating devices 51 is such that a plurality of heating devices 51 are arranged so as to have a full width of the film-like melt 31 or a wide width of the pressing region 32. In particular, when only the heating mode of the portion having a small thickness is heated, in the case of the film-like melt 31 having the shape shown in Fig. 2, at least one heating device 51 in the center in the width direction is not required. In the present embodiment, in the heating step, it is preferable to heat the heating means 5 1 which can control the temperature in the direction in which the film-like melts 3 1 are extruded in the order of 1 to 5 rows. The film-like melt 31 can be heated for a sufficiently long period of time because the difference in temperature history is surely reduced. In addition, various heating modes can be well matched. If you have more than 6 columns, the cost will be too high. For example, it is particularly effective when the portion having a small thickness is heated for a longer period of time than the portion having a larger thickness, or the portion having a smaller thickness is heated at a higher temperature for a longer period of time than a portion having a larger thickness. In the present embodiment, in the heating step, it is preferable to arrange the heating means 51, which can control the temperature, on one side or both sides of the film-like melt 31. The plurality of heating devices 51 can be arranged in various modes in accordance with the space around the path through which the film-like melt 31 extruded by the casting die 12 passes. In the present embodiment, the heating device 5 1 is not particularly limited, and for example, an infrared heater, a halogen heater, a carbon heater, a ceramic heater, a hot wire heater or the like can be suitably used. This is because these heaters use electricity as an energy source, so they do not pollute the air and are relatively simple to operate. Further, since the air is heated by heat radiation without heating the air, the only portion to be targeted of the film-like melt 31 can be locally heated by -27-201235194. Further, instead of arranging the plurality of heating devices 51 in the wide direction of the film-like melt 3 1 , a single long-sized heating device capable of temperature control and time control in each portion is extended to extend the width of the film-like melt 31 . The configuration of the width direction is also possible. Further, in accordance with the adjustment of the heating temperature of the heating device 51, in addition to the control of the heating temperature of the heating device 51 itself, the adjustment of the distance between the heating device 51 and the film-like melt 31 can be performed. <Film material> In the present embodiment, the thermoplastic resin used for the film material is not particularly limited as described above. Here, a case where a cellulose ester resin is used as the thermoplastic resin will be described as an example. The film material used in the method for producing an optical film according to the present embodiment contains, in addition to the cellulose ester resin, a stabilizer, a plasticizer, an ultraviolet absorber, a spacer (lubricant), and the like. These film materials are appropriately selected by the characteristics required for the intended optical film. [Cellulose Ester Resin] The cellulose ester resin used in the present embodiment is not particularly limited. For example, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate, cellulose phthalate, etc. can be suitably used. A polymer material other than the cellulose ester resin or an oligomer of -28-201235194 may be appropriately selected and mixed with the cellulose ester resin. Such a polymer material or oligomer is excellent in mutual solubility with a cellulose ester resin, and a high transmittance can be obtained across all visible light regions (400 nm to 800 nm) when a film is formed. As such a polymer material, for example, an acrylic resin can be used as appropriate. Also, the acrylic resin will be described in detail later. In the present embodiment, the cellulose ester resin, in particular, from the viewpoint of improvement in brittleness or transparency in mutual solubility with an acrylic resin, the total degree of substitution (T) of the thiol group is 2.0 to 3.0, and the carbon number is The substitution degree of the thiol group of 3 to 7 is preferably 1.2 to 3.0. That is, the cellulose ester resin of the present embodiment is a cellulose ester resin substituted with a mercapto group having 3 to 7 carbon atoms, and specifically, a propionic acid group 'butyric acid group or the like is suitable for use, particularly C. The acid group is most suitable when the total degree of substitution of the fluorenyl group of the phthalocyanate resin is less than 2.0, that is, when the residual degree of the hydroxyl group at the 2, 3, and 6 positions of the cellulose ester molecule exceeds 1.0, and the acrylic resin The miscibility with the cellulose ester resin is insufficient, and the haze is a problem when used as a polarizing plate protective film. Further, even when the total degree of substitution of the fluorenyl group reaches 2.0, when the total degree of substitution of the fluorenyl group having 3 to 7 carbon atoms is less than 1.2, sufficient mutual solubility cannot be obtained or the brittleness is lowered. Specifically, for example, even when the total degree of substitution of the fluorenyl group is 2.0 or more, the degree of substitution of the fluorenyl group having a carbon number of 2, for example, the thiol group having a carbon number of 3 to 7 is high. In the case of less than 12, the mutual solubility is lowered and the ambiguity is increased. Further, when the total degree of substitution of the fluorenyl group is 2.0 or more, the degree of substitution of the fluorenyl group having a carbon number of 8 or more is high, and the degree of substitution of the fluorenyl group having 3 to 7 carbon atoms is lower than -29 to 201235194 1.2. There is a deterioration in brittleness, and the desired characteristics cannot be obtained. In the present embodiment, the degree of substitution of the thiol group of the cellulose ester-based resin is not problematic as long as the total degree of substitution (Τ) is 2.0 to 3.0, and the degree of substitution of the fluorenyl group having 3 to 7 carbon atoms is 1.2 to 3.0. However, the total of the substitution ratio of the fluorenyl group other than the carbon number of 3 to 7 or the fluorenyl group having 8 or more carbon atoms is preferably 1.3 or less. Further, the total degree of substitution (?) of the thiol group of the cellulose ester-based resin is more preferably in the range of 2.5 to 3.0. In the present embodiment, the sulfhydryl group may be an aliphatic fluorenyl group or an aromatic fluorenyl group. In the case of an aliphatic sulfhydryl group, it may be a straight chain or a divergent one, and further a substituent may be used. The carbon number of the fluorenyl group of this embodiment is a substituent group containing a fluorenyl group. In the case of a cellulose ester resin, when the aromatic fluorenyl group is used as a substituent, the number of substituents substituted with an aromatic ring is preferably 0 to 5. In this case, it is necessary to pay attention to the degree of substitution of the fluorenyl group having a carbon number of 3 to 7 including a substituent group of 1.2 to 3.0. For example, when the number of carbon atoms of the benzamidine group is changed to 7, the carbon number of the benzamidine group is 8 or more and is not contained in the fluorenyl group having 3 to 7 carbon atoms. Further, when the number of substitution groups substituted with an aromatic ring is two or more, they may be the same or different. In addition, they are linked to each other to form a condensed polycyclic compound (for example, naphthalene, indeney, indan, phenanthrene, quinoline, isoquinoline, chromene chromene ), chromane, phthalazine, acridine, -30- 201235194 indole, indoline, etc. The cellulose ester resin having at least one structure having an aliphatic fluorenyl group having 3 to 7 carbon atoms can be used as a structure of the cellulose ester resin used in the present embodiment. The degree of substitution of the cellulose ester resin is such that the total degree of substitution (T) of the fluorenyl group is from 2.0 to 3.0, and the degree of substitution of the fluorenyl group having a carbon number of from 3 to 7 is from 1.2 to 3.0. That is, the total of the substitution ratio of the thiol group to the fluorenyl group having 8 or more carbon atoms is preferably 1.3 or less. In the present embodiment, the cellulose ester resin is excellent in mutual solubility with the acrylic resin. The assurance of ensuring the high transparency of the manufactured optical film, especially At least one selected from the group consisting of cellulose triacetate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate benzoate, cellulose propionate, and cellulose butyrate is preferred, that is, carbon number 3 or 4 The ruthenium base is preferably a substituent group. Among them, a particularly preferred cellulose ester resin is cellulose triacetate, cellulose acetate propionate, and cellulose propionate. A portion which is not substituted with a thiol group usually has a hydroxyl group. These can be synthesized by a known method. Further, the degree of substitution of the ethyl acetate group or the degree of substitution of other sulfhydryl groups is determined by the method specified in the AST Μ _ D 8 1 7 - 9 6 standard. The type, the weight average molecular weight (Mw) of the cellulose ester resin, particularly from the viewpoint of improvement in compatibility with the acrylic resin and brittleness, preferably 75,000 or more, and 75,000 to 300,000 is -31 - 201235194. Further, 100,000 to 240,000 and more preferably 160,000 to 240,000. When the weight average molecular weight (Mw) of the cellulose ester resin is less than 75,000, sufficient heat resistance or brittleness improvement effect cannot be obtained. In the present embodiment, two or more kinds of cellulose ester resins may be used in combination. In the optical film according to the present embodiment, the acrylic resin and the cellulose ester resin have a mass ratio of 30:70 to 95:5, and It is contained in a mutually soluble state, but preferably 50:50 to 95:5, and more preferably 60:40 to 90: 10 by mass ratio of the acrylic resin to the cellulose ester resin, in the acrylic resin ratio 95: When the amount is more than 5, the effect by the cellulose ester resin cannot be sufficiently obtained. Similarly, when the mass ratio is less than 30:70 and the amount of the acrylic resin is small, the moisture resistance is insufficient. [Stabilizing agent] In the present embodiment, in order to prevent deterioration of the film material due to oxidation or decomposition reaction of light or heat, it is preferred to contain a stabilizer. The stabilizer is not particularly limited, and examples thereof include a hindered phenol antioxidant, an oxygen scavenger, a hindered amine light stabilizer, a peroxide decomposer, a radical scavenger, a metal activator, and an amine. The stabilizer is preferably mixed prior to melting the thermoplastic resin. Mixing can be carried out by a known mixer. It is also possible to mix in the preparation process of the cellulose ester resin. By mixing at a temperature equal to or higher than the melting point of the thermoplastic resin and above the melting point of the stabilizer, only the stabilizerization agent -32 to 201235194 may be melted, and the stabilizer may be adsorbed on the surface of the resin. [Plasticizer] In the present embodiment, it is preferred to contain a plasticizer from the viewpoint of improving the mechanical properties of the optical film, imparting flexibility, imparting water absorption resistance, and reducing water permeability. Further, it is preferable to include a plasticizer from the viewpoint that the same heating temperature is more likely to lower the melt viscosity than when the cellulose ester resin is used alone. As the plasticizer, for example, a phosphate ester inducer or a carboxylate inducer is suitably used. In addition, butyl oleate, methyl ethyl citrate, dibutyl sebacate, triacetate, trimethylolpropane tribenzoate, trimethylolpropane tris (3, 4, 5-) Trimethoxy benzoate), alkylphthalic acid alkyl glycolate or the like is used as a plasticizer. [Ultraviolet absorber] It is preferable to contain an ultraviolet absorber in order to prevent deterioration of a polarizer or a liquid crystal display device or the like depending on the use of the optical film to be produced. The ultraviolet absorber is not particularly limited, and examples thereof include an oxybenzophenone-based compound, a Benzotriazole-based compound, a salicylate-based compound, a benzophenone-based compound, and a cyanopropylamide. A cyanoacrylate compound, a nickel salt fault compound, or the like. -33- 201235194 [Cushion agent] For the optical film, a spacer may be added to improve the slidability, transportability, or take-up property. Examples of the spacer agent include inorganic oxides such as ceria, titania, alumina, zirconia, calcium carbonate, kaolin, talc, sintered calcium citrate, calcium citrate hydrate, aluminum citrate, citrate, and calcium phosphate. Microparticles or bridging polymer microparticles. Among these, it is preferable to use cerium oxide to lower the haze of the film. Examples of the cerium oxide microparticles include AEROSIL 200, 200V, 300, R972, R972V, R974, R202, R812, 0X50, TT600, and the like which are manufactured by Japan Aerogel Co., Ltd. Further, two or more kinds of these fine particles may be used. The larger the average particle diameter of the microparticles, the larger the slidability effect, and conversely, the smaller the average particle diameter, the better the transparency. Usually, the average particle diameter of the fine particles is preferably in the range of 0.005 〜. It is also possible to form a secondary particle by aggregating the fine particles. The content of the fine particles is preferably 0.005 to 0.3 parts by mass per 1 part by mass of the cellulose ester resin. (Acrylic resin) The acrylic resin used in the present embodiment also contains a methacrylic resin. The resin is not particularly limited, and it is preferably composed of 50 to 99% by mass of the methyl methacrylate unit and 1 to 50% by mass of the other monomer which can be copolymerized therewith. Examples of the other monomer to be copolymerizable include an alkyl methacrylate having an alkyl group having 2 to 18 carbon atoms, and an propylene-34-201235194 acid alkyl ester having an alkyl group having 1 to 18 carbon atoms. Acrylic acid, methacrylic acid, etc., α, θ-unsaturated acid, maleic acid (maleic acid), fumaric acid (fumaric acid), methylene succinic acid, etc. An aromatic vinyl compound such as carboxylic acid, styrene or methyl styrene, α such as acrylonitrile or methacrylonitrile, s-unsaturated nitrile, anhydrous maleic acid, maleic imine, and hydrazine-substituted horse These may be used alone or in combination of two or more kinds of singly. Among these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, sec-butyl acrylate, 2-ethyl acrylate are used from the viewpoint of ensuring good thermal decomposition resistance or fluidity of the copolymer. Preferably, hexyl hexyl ester or the like is particularly preferred as methyl acrylate or n-butyl acrylate. In the present embodiment, the acrylic resin used in the optical film, in particular, from the viewpoint of improving the brittleness of the protective film of the liquid crystal polarizing plate and improving the transparency when it is miscible with the cellulose ester resin, the weight average molecular weight (Mw) is More than 80,000. When the weight average molecular weight (Mw) of the acrylic resin is less than 80,000, sufficient brittleness cannot be obtained, and the mutual solubility with the acrylic resin is deteriorated. The weight average molecular weight (Mw) of the acrylic resin is preferably in the range of 80,000 to 1,000,000, particularly preferably in the range of 100, 〇〇〇 to 600,000, and most preferably in the range of 1 50,000 to 400,000. The upper limit of the weight average molecular weight (Mw) of the acrylic resin is not particularly limited, and from the viewpoint of production, it is preferably 1 or less. In the present embodiment, the weight average molecular weight ' of the acrylic resin' can be determined by gel permeation chromatography. The measurement conditions are as follows, for example. -35- 201235194 Solvent: dichloromethane column: Shodex K806, K8 05, K8 03 G (manufactured by Showa Denko (share), used for connection of 3) Column temperature: 25 °C Sample concentration: 0.1 mass% Detector: RI Model 504 (manufactured by GL Science) Pump: L6 000 (manufactured by Hitachi, Ltd.) Flow: l.Oml/min Calibration curve: according to standard polystyrene STK standard polystyrene (Toyo Soda Tosoh) ) A calibration curve of 13 samples up to Mw = 2, 80 0,000 to 500. The sample of the acrylic resin is not particularly limited, and a known method such as suspension polymerization, emulsion polymerization, bulk polymerization, or solution polymerization can be used. One. Here, as the polymerization initiator, a usual peroxide system or an azo group can be used, and an oxidation reduction system can also be used. For the polymerization temperature, the suspension or emulsion polymerization is carried out at 30 to 100 ° C, and the bulk or solution polymerization is carried out at 8 to 160 ° C. In order to control the reduction viscosity of the obtained copolymer, an alkylthiol or the like can be used as a chain shifting agent to carry out polymerization. In the present embodiment, a commercially available product can be used as the acrylic resin. For example, DELPET60N, 80N (made by Asahi Kasei Chemicals), Dianol (transliteration BR52, BR80, BR83, BR85, BR88 (Mitsubishi Rayon), KT75 (Electrical Chemical Industry • 36-201235194 (share)) Manufacturing), etc. Two or more types of acrylic resin may be used. <Optical film> The optical film produced by the production method according to the present embodiment is suppressed in retardation unevenness, and can satisfactorily correspond to an increase in size of the optical film. <Polarizing Plate> When the optical film according to the present embodiment is used as a protective film for a polarizing plate, the polarizing plate can be produced by a general method. It is preferable to provide an adhesive layer on the back side of the optical film according to the present embodiment, and to bond the surface of at least one of the polarizers prepared by immersing the iodine solution. The optical film according to this embodiment may be used on the other side, and a protective film for other polarizing plates may be used. For example, a commercially available cellulose ester film (for example, KONICA MINOLTATAC KC8UX, KC4UX, KC5UX, KC8UY, KC4UY, KC12UR 'KC8UCR-3, KC8UCR-4, KC8UCR-5 > KC8UE, KC4UE, KC4FR-3, KC4FR- can be used. 4 ' KC4HR-1, KC 8 UY - HA, KC 8 UX - R Η A, the above is manufactured by KONICA MINOLTA OPTO (share)), etc. are suitable for use. The polarizer of the main component of the polarizing plate is a member that passes light of a polarized surface in a certain direction, and is a known polarizing film, and is a polyvinyl alcohol-based polarizing film, and is a polyvinyl alcohol-based film. Those who dyed with iodine and those who dyed with dichroic dyes. The polarizer is formed by forming a film of a polyvinyl alcohol aqueous solution, stretching the one axis for dyeing, or performing one-axis stretching after dyeing, and preferably using -37-201235194 for durability treatment with a boron compound. As the adhesive used for the above-mentioned adhesive layer, it is preferable to use an adhesive at a temperature of 25 ° C at a portion of the adhesive layer of 1.0 x 10 Pa to 1. (the adhesive is preferably applied, and the adhesive is applied, after bonding) The reaction is carried out to form a high-molecular weight or a hardening type of a bridging structure. Specific examples thereof include a hardening type such as an urethane-based adhesive oxygen-based adhesive, an aqueous polymer-isocyanate-based adhesive, and a thermal acrylic adhesive. An anaerobic adhesive such as an adhesive, a moisture-curing urethane extract, a polyether methyl acetate type, an ester type methyl acetate type, an oxygen ether methyl acetate, or a cyanoacrylate type As the adhesive, a two-liquid type instantaneous adhesive of a conjugate, an acrylate, and a peroxide may be used in the form of one liquid, or may be used in a form in which two or more liquids are mixed. Further, the above-mentioned adhesive may be an organic solvent. The media system may be an aqueous solution such as an emulsion type, a gel fraction or an aqueous solution type which is mainly composed of water, and may be a solvent-free type. The adhesion concentration may be as long as the film thickness after adhesion, the coating method, and the coating method. Coating The strip may be appropriately determined, and is usually 0.1 to 50% by mass. The polarizing plate according to the embodiment has a polarizer and a transparent protective film on the surface of the polarizer, and the transparent protection is related to the present invention. The optically-oriented polarizer produced by the manufacturing method of the embodiment is an optical lens that changes the incident light into polarized light and is used as the polarizing plate. Preferably, for example, at least one of the polyvinyl alcohol-based films is used as a seeding agent. Agent, ring-hardened ethyl ester, sticky type, instant adhesion, etc. A film or a film is placed in the form of a solvent-dispersed liquid before use. Front component. The surface of at least one of the polarizers prepared by stretching in the iodine solution is immersed in a surface of the above-mentioned optical film using a fully alkalized polyvinyl alcohol aqueous solution. Further, the other surface of the polarizer may be formed by laminating the optical film, or may be laminated with another transparent protective film for a polarizing plate. As the other transparent protective film for a polarizing plate, for example, as a commercially available cellulose ester, it is preferable to use KC8UX2M, KC4UX, KC5UX, KC4UY, KC8UY, KC12UR, KC8UY-HA, KC 8 U X-RH A (above Konica Minolta Opto (manufacturing) and so on. Alternatively, a resin film such as a cyclic olefin resin, an acrylic resin, a polyester or a polycarbonate other than the cellulose ester film may be used. In this case, since the enthalpy is low in suitability, it is preferable to bond it to the polarizing plate through a suitable adhesive layer. As described above, the polarizing plate is used as the protective film ‘ laminated on the surface side of at least one of the polarizers. In this case, when the optical film functions as a retardation film, the slow axis of the optical film is preferably arranged so as to be substantially parallel or orthogonal to the absorption axis of the polarizer. Further, as a specific example of the above-mentioned polarizer, for example, a polyvinyl alcohol-based polarizing film is exemplified. The polyvinyl alcohol-based polarizing film may be one in which iodine is dyed on a polyvinyl alcohol-based film and dyed with a dichroic dye. As the polyvinyl alcohol-based film, a denatured polyvinyl alcohol-based film denatured with ethylene is preferably used. The aforementioned polarizer ' can be obtained, for example, as follows. First, an aqueous solution is used for film formation. The obtained polyvinyl alcohol-based film is dyed after being uniaxially stretched, or uniaxially stretched after dyeing. Next, it is preferred to apply a durability treatment to the boron compound. The film thickness of the aforementioned polarizer is preferably 5 to 4 Å/m, and more preferably 5 to 30 -39 to 201235194, especially 5 to 20/zm. When the cellulose ester-based resin film is applied to the surface of the polarizer, it is preferable to bond it by a water-based adhesive which is a basic alkali metal hydroxide or the like as a main component. Further, in the case of a resin film other than the cellulose ester resin film, it is preferably processed by a suitable adhesive layer on the polarizing plate. In the polarizing plate as described above, the optical film of the present embodiment is used as a transparent protective film, and the optical film is sufficiently suppressed by deformation. For example, when applied to a liquid crystal display device, liquid crystals such as contrast can be improved. The display device is highly imaged. Further, the optical film which is used as the transparent protective film of the polarizing plate is also suppressed in dimensional change due to humidity change. Therefore, when applied to a liquid crystal display device, for example, the occurrence of so-called corner unevenness can be suppressed. In this way, the polarizing plate according to the present embodiment is provided with a polarizing plate and a polarizing plate which is disposed on both sides of the polarizer so as to sandwich the polarizers, and the two transparent protective members are provided. At least one of the films is an optical film produced in accordance with the production method of the present embodiment. This polarizing plate suppresses the unevenness of the retardation of the transparent protective film, and satisfies the requirements for the enlargement of the polarizing plate. <Liquid Crystal Display Device> By incorporating a polarizing plate that is bonded to the optical film of the present embodiment as a protective film for a liquid crystal polarizing plate into a liquid crystal display device, it is possible to produce various liquid crystal displays having excellent visibility. The device is particularly suitable for liquid crystal display-40-201235194 devices for outdoor applications such as large-scale liquid crystal display devices or digital signage boards. The polarizing plate according to this embodiment is bonded to the liquid crystal cell before being interposed. The polarizing plate according to this embodiment can be suitably used in various driving methods such as a transmissive type, a transflective LCD or a TN type, an STN type HAN type, a VA type (PVA type, MVA type), or an IPS FFS type. In particular, the above, in particular, the display side of the large screen of 30 吋 to 54 不会 does not have whitening, etc., and the effect can be maintained for a long time. In addition, uneven color, flicker or uneven ripples will not cause eye fatigue even if it is appreciated for a long time. In the liquid crystal display device of the present embodiment, two polarizing plates are disposed so as to sandwich the easy-to-use cells, and at least one of the light plates is the polarizing plate. Further, when the liquid crystal is intercalated between the liquid crystal counter electrodes, the amount of transmitted light is suppressed by applying an alignment state of the liquid crystal to the electrodes. In such a manner, by using a polarizing plate according to the present embodiment, a transparent protective film is used, and a high-definition liquid crystal display device in which an optical film having a sufficiently suppressed deformation is improved is used. Further, since the dimensional change caused by the change in humidity is also suppressed as a transparent protective film, it is possible to suppress the so-called corner defects, and the liquid crystal display device unit cell of the present embodiment can be used to hold the liquid crystal cell. In a liquid crystal display device which is disposed on two liquid crystal polarizing plates, at least one of the above is a polarizing plate. The liquid crystal display shows that the adhesive layer is equal to the reflective type, OCB type ' (including the surface at 30 ,, the pattern is small, there are liquid crystal cells, and the above two partial cells are tied to a voltage, change Since the liquid crystal display is not used as a polarizing plate, it is produced in the optical film of the polarizing plate. It is provided with two polarizing plates on both sides of the liquid cell, and the transparent protective film of the polarizing-41 - 201235194 plate is used. The unevenness of the retardation is suppressed, and it can satisfactorily correspond to the increase in size of the liquid crystal display device. Further, in the above embodiment, in the melt casting film forming method, the film-like melt 31 is uniformly applied during the rolling. As shown in FIG. 2, the pressure is described as an example in which a portion having a large thickness and a portion having a small thickness are formed in the width direction of the film-like melt 31, but it is not limited thereto. Even if the film-like melt 31 having a uniform thickness in the wide direction is to be extruded, it does not violate the intention of the present invention, and a portion having a large thickness and a portion having a small thickness are formed in the width direction of the film-like melt 31. The occasion can also be well adapted According to the present invention, the technical method of the present embodiment is as follows. The method for producing an optical film according to the present embodiment has an extrusion step of casting a melt containing a thermoplastic resin into a film shape by casting molding, and A method for producing an optical film for cooling a film-like melt to be extruded, characterized in that a heating step of heating the film-like melt to be extruded is provided between the pressing step and the cooling step, and heating is performed there a step of heating only a portion having a relatively small thickness according to a thickness distribution in a wide direction of the film-like melt, or heating a portion having a relatively small thickness at a higher temperature than a relatively large portion and/or heating for a longer period of time According to the method for producing an optical film, the film-like melt extruded by the casting die is heated only in a portion having a relatively small thickness depending on the thickness distribution of the film-like melt in the width direction before the cooling step starts to be cooled, or a portion having a relatively small thickness is heated at a higher temperature than a portion having a relatively large thickness, or a portion having a relatively small thickness is longer than a portion having a relatively large thickness The heating is carried out between -42 and 201235194, or the portion having a relatively small thickness is heated at a higher temperature for a longer period than the portion having a relatively large thickness, so that the retardation of the manufactured optical film is suppressed. That is, the film-like melt extruded by the casting die is lowered by the heat release until it is circumscribed to the circumferential surface of the cooling roll or the main roll (roller for pressing), and is externally connected to the cooling roll or the main roll. Thereafter, the heat is taken away by the rolls having a large heat capacity and the portions are uniformly and efficiently cooled (the start of the cooling step). In this case, the film-like melt 31 has a relatively large thickness portion in the width direction. In the case of a relatively small portion, the temperature of the portion having a relatively large thickness until the temperature is circumscribing the roller is relatively small, and the portion having a relatively small thickness is relatively large until the temperature is circumscribing the roller, so that the film is in a film shape. The temperature history of the melted material after being extruded by the casting die until it is externally attached to the roller (how long temperature is exposed) the width of the film-like melt Direction will produce unevenness. Next, the difference in temperature history of the film-like melt should appear as a delay unevenness of the optical film. That is, it is presumed that only the portion having a relatively small thickness (temperature according to the heat generation) is heated according to the thickness distribution of the film-like melt in the width direction by the film-like melt extruded by the casting mold before the start of the cooling step. Lowering a relatively large portion), or a portion having a relatively small thickness is heated at a higher temperature than a portion having a relatively large thickness (a portion having a relatively small temperature decrease depending on an exotherm), or a portion having a relatively small thickness The portion having a relatively large thickness is heated for a longer period of time, or the portion having a relatively small thickness is heated at a higher temperature for a portion having a relatively larger thickness for a longer period of time, and the temperature history of the film-like melt is reduced in a wide direction. -43- 201235194 Difference, so the retardation of the optical film is suppressed. In the above manufacturing method, a step of detecting a thickness distribution in the width direction of the film after cooling is provided in the cooling step, and in the heating step, the thickness distribution detected in the detecting step is taken as the width direction of the film-like melt. The thickness distribution is preferably used. Since the actual thickness distribution detected in the production of the optical film is referred to, the accuracy of the difference in the temperature history is improved. In the above manufacturing method, there is provided an adjustment step of adjusting the thickness distribution in the width direction of the film-like melt extruded by the casting mold in advance, and in the heating step, the thickness distribution after the adjustment step is adjusted as the film-like melt The thickness distribution in the wide direction is preferably used. The thickness distribution may not be detected in the manufacture of optical films. In the above-described manufacturing method, a step of determining the target temperature at the start of cooling in the cooling step for each portion in the wide direction of the film-like melt according to the thickness distribution in the width direction of the film-like melt is provided; The step 'heats the film-like melt in such a manner that the target temperature of each portion determined in the determining step is achieved in the cooling step at the start of cooling. By achieving the target temperature at the start of cooling in each part, the difference in temperature history is further reduced, and the difference in temperature history can be eliminated. In the above production method, a rolling step of rolling the film-like melt by a roll is provided. In the heating step, it is preferable to heat the rolling region which is pressed by the rolling step. In the rolling region, when the film-like melt has a relatively large portion and a relatively small portion in the width direction, the difference in temperature history is appropriately reduced. In the above-described production method, in the heating step, it is preferable to heat the heating means capable of controlling the temperature of 44 - 201235194 degrees in the width direction of the film-like melt by 3 to 13 pieces. The difference in temperature history is indeed reduced within the practical cost range. In addition, it can correspond well to various heating modes. In the above production method, in the heating step, it is preferred to heat the heating means which can control the temperature in the direction in which the film-like melt is extruded in the order of 1 to 5 rows. The film-like melt can be heated for a sufficiently long period of time, and the difference in temperature history is surely reduced. Further, it is preferable to cope with various heating modes in the above-described manufacturing method. In the heating step, it is preferable to arrange the heating means which can control the temperature, respectively, on one side or both sides of the film-like melt. A plurality of heating means can be arranged in various modes in accordance with the space around the path through which the film-like melt extruded by the casting is passed. In the above manufacturing method, the heating means is preferably at least one of an infrared heater, a halogen lamp heater, a carbon heater, a ceramic heater, and a heater. These heaters use electricity as an energy source, so they do not pollute the air. Further, by heating without heating the air, it is possible to locally heat only the portion to be targeted of the film-like melt. In the above production method, it is preferred to press a film-like melt having a width of 0.8 to 3 m in the extrusion step. An optical film of a size that can correspond to the size of the liquid crystal display device is manufactured. In the above production method, it is preferred to extrude a melt containing two or more kinds of thermoplastic resins in the extrusion step. In the above production method, at least one of two or more types of thermoplastic resins is preferably a cellulose ester resin, in order to produce an optical film having a property which is expected to be used in accordance with the application. An optical film having high transparency can be manufactured. In particular, when a cellulose ester resin and an acrylic resin are contained, an optical film having low moisture absorption, high transparency, high weather resistance, and improved brittleness can be produced. In the above manufacturing method, it is preferable to provide an extending step of the film which is extended and cooled in the cooling step. An optical film having a delay characteristic expected in accordance with the use can be produced. The optical film according to the present embodiment is an optical film which is characterized by being manufactured by the method for producing an optical film according to the present embodiment. In the optical film, the unevenness of the retardation is suppressed, and the polarizing plate according to the present embodiment is required to be excellent in response to the increase in the size of the optical film. The polarizing plate is provided with a polarizer and is disposed in the polarized light so as to be adjacent to the polarizer. A polarizing plate of two transparent protective films on both sides of the sub-segment is characterized in that at least one of the two transparent protective films is an optical film according to the present embodiment. This polarizing plate suppresses the unevenness of the retardation of the transparent protective film, and satisfies the requirements for the enlargement of the polarizing plate. A liquid crystal display device according to the present embodiment is a liquid crystal display device including two liquid crystal cells and two polarizing plates disposed on both sides of the liquid crystal cell so as to sandwich the liquid crystal cell, and is characterized in that the two polarized lights are provided. At least one of the plates is a polarizing plate according to the present embodiment. In the liquid crystal display device, the unevenness of the retardation of the transparent protective film of the polarizing plate is suppressed, and the size of the liquid crystal display device can be satisfactorily increased. • 46 - 201235194 According to this embodiment, it is possible to suppress the unevenness of the retardation of the optical film. Therefore, it contributes to an increase in the size of the liquid crystal display device, and it is advantageous in expanding the use of the liquid crystal display device. [Examples] Hereinafter, the present invention will be described in detail by way of examples, but the invention should not be construed as limited. [Production of Optical Film] Using the optical film manufacturing apparatus 10 shown in Fig. 1, the cellulose ester resin is contained as a thermoplastic resin, and as shown in Fig. 2, a rolled region 3 2 and end regions 3 3, 3 4 are produced. The shape of the optical film. However, the end regions 33 and 34 are finally cut by the optical film. First, the following film materials are mixed in a V-type mixer for 30 minutes, and then a 2-axis extruder "PCM30" screw manufactured by using a cell is used. Diameter: 30 mm) was melted at 22 ° C to prepare a cylindrical ingot having a length of 4 mm and a diameter of 3 mm. (Film material) Cellulose acetate propionate (cellulose ester resin) (degree of substitution of ethyl ketone group: 1.95, degree of substitution of propionic acid group: 0.7, arithmetic mean molecular weight: 75,000, drying at 140 ° C for 5 hours, glass Transfer temperature Tg : 174 ° C ) 1 part by mass of trimethylolpropane -47 - 201235194 tribenzoate (plasticizer) 10 parts by mass of IRGANOX (registered trademark) 1010 (blocking oxidation prevention 1st part by mass of the agent and the stabilizer (manufactured by Chiba Special Chemicals Co., Ltd.), and the extruder 11 (the GT-50 which is manufactured by the Plastics Engineering Research Institute) is attached to the extruder 11 to which the casting die 12 is attached. The ingot prepared was supplied, and the following additives were added from the opening of the funnel provided in the intermediate portion of the extruder 11 to obtain a melt of a mixture of film materials. Then, the obtained melt is extruded from the casting die 12 into a film shape. (Additive) cerium oxide microparticles (liner) (manufactured by Nippon Gum Co., Ltd.) 0.05 parts by mass of TINUVIN (registered trademark) 3 60 (ultraviolet absorber) (manufactured by Chiba Special Chemicals Co., Ltd.) 0.5 part by mass casting die 1 2 A mechanism having a pure edge spacing adjusted according to the heating bolt 1 2 5 as shown in FIG. 3 is used. The touch roller 14 uses an elastic touch roller having a double cylinder structure of an outer cylinder and an inner cylinder. The heating device 51 uses an infrared heater. The extrusion temperature (temperature "T1" in Fig. 4 to Fig. 6) from the film-like melt 31 of the casting die 12 was 240C. The distance from the slit (discharge port 122) of the casting die 12 to the external position of the film-like melt 31 on the circumferential surface of the main roll 13, that is, the length of the film-like melt 31 is 200 mm. The film take-up speed of the take-up device 20 was 5 m/min. The heating of the film-like melt 31 in the heating step and the rolling of the film-like melt 31 in the rolling step are performed only in the rolling region 32 at -48 - 201235194. End region of optical film [Evaluation of optical film] (delay unevenness/number 値) The retardation of the optical film produced (in-plane retardation (R〇) is the fold of the film in the direction of the slow axis | The refractive index of the direction is Ny, and the thickness of the film is defined as Nx-Ny) xd". In-plane retardation measurement, "Kobra-WX150Kj length: 590 nm" manufactured by the machine (strand). The measurement is from the center of the pressing direction of the optical film until the width of the rolling region 32 is in the width direction. The average 値 of the measured in-plane retardation was measured at intervals of 50 mm, and the standard deviation (average 値) χ 100 之 (%) was obtained as an index. The smaller the number, the uneven retardation of the optical film is shown in Tables 1 to 3. (Delayed unevenness/visual observation) The produced optical film was evaluated on the basis of crossed Nicols. The results are shown in Tables 1 to 3. A: The light does not pass through. The whole is a squint. B: Partially sees a small amount of light and dark C: The whole sees very little light and dark D ’·The part of the light and dark 33, 34 is cut off. Late: Ro). The in-plane ί rate is NX, and the phase is entered by the formula "R 〇 = (It is measured by the prince (measuring the width of the wave region 3 2 to both ends. Then, the calculation is performed, and the calculation formula is obtained. The number 値 is delayed, and the result is visually observed. The following -49-201235194 E: seeing the whole light and dark in the respective tables, the first part to the fifth part are the rolling regions 32 of the film-like melt 31. Each of the portions is divided into five equal parts in the width direction. Next, in Fig. 2, the first end portion and the second portion are defined from one end portion (for example, the end portion on the left side). Infrared heater 5 1, corresponding In each portion, the distance between the infrared heater 51 and the film-like melt 31 is completely the same on the one-side side of the film-like melt 31. The infrared heater 51 is in the width direction of the film-like melt 31. The five are arranged in a row without gaps. Then, the five columns are arranged in two rows without any gaps in the direction in which the film-like melt 31 is extruded (that is, in the vertical direction). In this case, the film is formed. The melt 31 is pressed out by the casting die 12, and then it is circumscribing to the main roller 13 and starts from the middle. The heat is heated so as to be externally connected to the main roller 13, and a plurality of infrared heaters 5 1 ... 5 1 are arranged in the vertical direction close to the main roller 13 to be heated in the heating step performed in this embodiment. The mode is shown in Fig. 7. In this embodiment, the portion having a small thickness is heated with a portion having a large thickness (i.e., all of the first portion to the fifth portion are heated), and in this case, a portion having a small thickness (for example, Part 1) A mode in which a portion having a larger thickness (for example, the third portion) is heated at a higher temperature. In Fig. 7, a time t3 is a heating start time, and a temperature decrease curve (v) is a portion having a large thickness (for example, The temperature reduction curve of the 3 part), the temperature decrease curve (vi) is the temperature decrease curve of the portion having a small thickness (for example, the first portion). In each of the tables, the film-like melt is circumscribed at the main roller (time t2 in Fig. 7). The target temperature of -50-201235194 31 is the thickness of each film-like melt 31 (the first part to the fifth part, etc.) in the heating mode of Fig. 7, so that the thickness is small (for example, the first part) Part of the temperature history is close to each other The temperature history of the large part (for example, the third part), the temperature set in advance (the temperature at the start of the cooling step). In each table, the heating temperature of the heater for achieving the target temperature is achieved. The temperature of the target temperature of each of the first to fifth portions is experimentally set in advance. In each of the tables, the heating temperature of the heater actually performed is actually performed in each of the first to fifth portions. The measured temperature of the film-like melt 31 in the case where the main roll is circumscribed (time t2 in Fig. 7) is the temperature measured by the non-contact temperature measuring device (the temperature at the start of the cooling step). The measurement was carried out at intervals of 50 mm in the width direction from the central portion in the width direction of the rolling region 3 2 to the both end portions in the width direction of the pressing region 32. Next, the average enthalpy in each part of the measured temperature was determined. In Tests 1 to 3 shown in Table 1, the thickness distribution in the width direction of the film-like melt 31 adjusted in advance by the adjustment mechanism of the lip gap of the casting die 12 is used as the film extruded from the casting die 12. The thickness distribution of the molten material 31 in the width direction is used. The heating was carried out in a range in which the end regions 33 and 34 of the film-like melt 31 were removed by a pressing region 32 (width of 800 mm) of 100 mm. Test 1 is a case where the film-like melt 3 1 is not heated in such a manner as to achieve the target temperature of each part determined in the determining step (the heating temperature of the heater for achieving the target temperature of the third part -51 - 201235194 degrees) When all the parts are uniformly heated, the test 2 is to heat the film-like melt 31 so as to achieve the target temperature of each part determined in the determination step, and the test 3 is a case where the heating step is not performed. Tests 4 to 6 shown in Table 2 are thickness distributions in the width direction of the resin film 41 detected by the detecting device 71, and are used as the width of the film-like melt 31 extruded from the casting die 12. The thickness distribution of the direction is used. The heating was carried out in a range in which the end regions 33 and 34 of the film-like melt 31 were removed from the rolling region 32 (width 80 mm) of 100 mm. Test 4 is a case where the film-like melt 31 is not heated in such a manner that the target temperature of each part determined in the determining step is not achieved (the heating temperature of the heater for achieving the target temperature of the third part is uniformly heated for all the parts). In the case where the test 5 is to heat the film-like melt 31 so as to achieve the target temperature of each part determined in the determination step, the test 6 is a case where the heating step is not performed. Tests 7 to 9 shown in Table 3 are thickness distributions of the resin film 41 in the width direction detected by the detecting device 71, and are used as the width of the film-like melt 31 extruded from the casting die 12. The thickness distribution of the direction is used. The heating was carried out in a range in which the end regions 3 3 and 34 of the film-like melt 31 were removed by a pressing region 32 (width l5 〇 Omm) of 100 mm. In the test 7, when the film-like melt 31 is not heated so as to achieve the target temperature of each part determined in the determining step (the heating temperature of the heater for achieving the target temperature of the third part is uniformly heated for all the parts) In the case where the test 8 is to heat the film-like melt 31 so as to achieve the target temperature of each part determined in the determination step, the test 9 is -52-201235194, and the heating step is not performed. -53- 201235194 Table 1 Test No. 1 2 3 Wide width (mm) of the rolling area 800 Thickness direction of the film-like melt in the width direction (//m) <Clip spacing of the casting die> Part 1 105 Part 2 110 Part 3 115 Part 4 110 Part 5 105 Target temperature of film-like melt when the main roll is externally connected (.) Part 1 215 Part 2 210 Part 3 205 Part 4 210 Section 215 Heating temperature (°c) of the heater to achieve the target temperature Part 1 230 Part 2 220 Part 3 210 Part 4 220 Part 5 230 Actual heating temperature of the heater (°c) Section 210 230 Ait m Heating Part 2 220 Part 3 210 Part 4 220 Part 5 230 Measured temperature of film-like melt when external roll is externally connected (0C) Part 1 193 214 165 Part 2 199 209 176 3 Section 205 205 188 Part 4 201 208 178 Part 5 195 213 168 Delayed evaluation number 値 (8) 58 15 89 Visual observation of DAE Range of the invention 〇-54- 201235194 Table 2 Test No. 4 5 6 Rolling area Width (mm) 800 width of dirty melt Thickness direction of direction (Aim) <Detection device detection 第> Part 1 103 106 104 Part 2 108 111 109 Part 3 113 116 114 Part 4 108 111 109 Part 5 103 106 104 Film shape when the main roller is externally connected Target temperature of the melt (.C) Part 1 217 214 216 Part 2 212 209 211 Part 3 207 204 206 Part 4 212 209 211 Part 5 217 214 216 Heating temperature of the heater to achieve the target temperature ( 0C) Part 1 232 229 231 Part 2 222 219 221 Part 3 212 209 211 Part 4 222 219 221 Part 5 232 229 231 Actual heating temperature of the heater (°c) Part 1 210 229 Μ A Part 2 219 Part 3 209 Part 4 219 Part 5 229 Measured temperature of film-like melt when external roll is external (0c) Part 1 196 213 165 Part 2 201 208 177 Part 3 207 204 187 Part 4 200 208 173 Part 5 194 213 164 Delayed evaluation number % (%) 51 7 75 Visual observation of DAE Range of the invention 〇-55- 201235194 Table 3 Test No. 7 8 9 Width of the rolling area (mm ) 1500 dirty melt Thickness direction in the width direction (#m) <Detection device detection 第> Part 1 98 101 99 Part 2 103 106 104 Part 3 108 111 109 Part 4 103 106 104 Part 5 98 101 99 When the main roller is externally connected Target temperature of the film-like melt (°C) Part 1 216 213 215 Part 2 211 208 210 Part 3 206 203 205 Part 4 211 208 210 Part 5 216 213 215 To achieve the target temperature of the heater Heating temperature (°C) Part 1 231 228 230 Part 2 221 218 220 Part 211 208 210 Part 4 221 218 220 Part 5 231 228 230 Actual heating temperature of the heater (°c) 1 Portion 211 228 m Heating Part 2 218 Part 3 208 Part 4 218 Part 5 228 Measured temperature of film-like melt when external roll is externally connected (°c) Part 1 194 212 161 Part 2 201 207 173 3 parts 206 203 186 part 4 200 207 175 part 5 194 212 164 evaluation number of delay 63W 63 12 92 visual observation of DAE range of the invention 〇-56- 201235194 [results of investigation] It is known from Table 1 to Table 3, To achieve each part The second, fifth, and eighth steps of heating the film-like melt 31 at a temperature higher than the thickness portion by the target temperature at the start of the cooling step, and achieving the target at the start of the cooling step in each portion At the temperature, the retardation of the optical film produced was well suppressed. On the other hand, the tests 1, 4, and 7 in which all the portions were heated uniformly at the temperature for the portion having the large thickness (the third portion) and the tests 3, 6, and 9 which did not heat the film-like melt 31 were started at the start of the cooling step. The measured temperature is such that the smaller the thickness is, the lower the unevenness of the optical film to be produced is, and the film is not practical. Further, as shown in Tables 1 to 2, the width of the film-like melt 31 is wide. The thickness distribution in the direction, the test 2 using the previously adjusted enthalpy in the adjustment step, and the test 5 using the enthalpy detected in the detection step, the delay unevenness was a good result. Further, as is clear from Tables 2 to 3, when the width of the film-like melt 31 is changed from 800 mm to 150 mm, the retardation of the tests 6 and 9 for not heating the film-like melt 31 is large, but the thickness is small. In the test 5, 8 in which the film-like melt 31 was heated at a higher temperature than the larger portion, the retardation was a good evaluation result even if the width of the film-like melt 31 was widened. The application is based on Japanese Patent Application No. 201 0-24 60 85 filed on Jan. 2, 2010, the content of which is incorporated herein. The present invention has been described with respect to the above-described embodiments, and the present invention is fully described and described, but those skilled in the art can readily change and/or modify the foregoing embodiments. That is, it is familiar with the modified form or the modified form implemented by the person skilled in the art-57-201235194, as long as the degree of the right of the claim item described in the patent application scope is not deviated, the modified form or the modified form should be Interpreted as included in the scope of the claim. [Industrial Applicability] The present invention has wide industrial applicability in the technical fields of the optical film manufacturing method, the optical film 'polarizing plate, and the liquid crystal display device. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram showing a manufacturing apparatus of an optical film relating to an embodiment of the present invention. Fig. 2 is a cross-sectional view in the width direction of a film-like melt which is cast and molded by the apparatus for producing an optical film of Fig. 1. Fig. 3 is an enlarged cross-sectional view showing an important part of a casting die of the apparatus for manufacturing an optical film of Fig. 1. Fig. 4 is a graph showing the temperature time change of the film-like melt extruded by casting molding. Fig. 5 is a view similar to Fig. 4 for explaining a heating step relating to the embodiment of the present invention. Fig. 6 is a view similar to Fig. 4 for explaining other aspects of the heating step relating to the embodiment of the present invention. Fig. 7 is a view similar to Fig. 4 for explaining one aspect of the heating step relating to the embodiment of the present invention. -58- 201235194 [Explanation of main component symbols] 10 : Manufacturing apparatus 1 1 : Extrusion machine 1 2 : Casting die 13 : Main roller 1 4 : Touch roller 1 5, 1 6 : Cooling roller 1 7 : Stripping roller 1 8 : conveying roller 1 9 : stretching device 20 : winding device 3 1 : film-like melt 4 1 : film after cooling and solidification (resin film) 5 1 : heating device 7 1 : detecting device - 59-