TWI763824B - Optical film, polarizing plate, and image display device - Google Patents

Abstract

The present invention provides an optical film with high adhesion between a base film and a surface treatment layer. The optical film of the present invention includes a base film as a stretched film containing an acrylic resin, and a surface treatment layer formed on one side of the base film, and the base film in the optical film is subjected to a tensile force of 98 mN/min on one side. The maximum elongation up to the softening point was 0.40% or more in the TMA measurement in which the temperature was increased from 24°C to 150°C at 5°C/min under tensile load.

Description

Optical film, polarizing plate, and image display device

The present invention relates to an optical film, a polarizing plate, and an image display device.

In recent years, an optical film in which a functional layer (surface treatment layer) such as a hard coat layer, an antiglare layer, and an antireflection layer is formed on one side of a base film containing an acrylic resin is known (Patent Document 1). The surface treatment layer can be formed by coating the resin composition on one side of the base film and drying or hardening. Such an optical film can be used, for example, as a protective film of a polarizing element, or a front panel of an image display device. Prior Art Document Patent Document Patent Document 1: Japanese Patent Laid-Open No. 2016-218478

THE PROBLEM TO BE SOLVED BY THE INVENTION However, in the above-mentioned conventional optical film, in the step of drying the resin composition, there is a case where the base film is wrinkled due to thermal shrinkage, resulting in poor appearance. When the resin composition is dried at a low temperature in order to prevent the abnormality due to thermal shrinkage as described above, there is a problem that the adhesiveness between the base film and the surface treatment layer becomes insufficient. The present invention has been accomplished in order to solve the above-mentioned problems, and its main object is to provide an optical film having high adhesion between a base film and a surface treatment layer, a polarizing plate including such an optical film, and a polarizing plate including such an optical film. the image display device. [Technical Means for Solving the Problems] The optical film system of the present invention includes a base film as a stretched film containing an acrylic resin and an optical film as a surface treatment layer formed on one side of the base film, the base film in the optical film The maximum elongation to the softening point is 0.40% in the TMA (thermomechanical analysis, thermomechanical analysis) measurement of the material film while applying a tensile load of 98 mN/min at 5°C/min from 24°C to 150°C above. In one embodiment, the said base film contains the said acrylic resin and the core-shell type particle|grains which were dispersed in the said acrylic resin. In one Embodiment, the said base film contains 5 weight part - 50 weight part of said core-shell type particle|grains with respect to 100 weight part of said acrylic resins. In one embodiment, the acrylic resin is selected from the group consisting of a glutarimide unit, a lactone ring unit, a maleic anhydride unit, a maleimide unit and a glutaric anhydride unit. at least one of them. In one embodiment, the surface treatment layer is a cured layer of the resin composition coated on the base film. In one embodiment, the surface treatment layer is at least one selected from the group consisting of a hard coat layer, an anti-glare layer, and an anti-reflection layer. According to another aspect of the present invention, a polarizing plate is provided. The polarizing plate includes a polarizing element and a protective layer disposed on one side of the polarizing element, and the protective layer is the optical film. According to another aspect of the present invention, an image display device is provided. This image display device includes the above-described polarizing plate. [Effect of the Invention] According to the present invention, by using the above-mentioned base film having a maximum elongation of 0.40% or more, it is possible to provide an optical film having high adhesion between the base film and the surface treatment layer, and a polarized light having such an optical film. A plate, and an image display device provided with such a polarizing plate.

於通式(1)中，R¹ 及R² 分別獨立地表示氫原子或碳數1～8之烷基，R³ 表示氫原子、碳數1～18之烷基、碳數3～12之環烷基、或碳數6～10之芳基。於通式(1)中，較佳為R¹ 及R² 分別獨立為氫原子或甲基，且R³ 為氫原子、甲基、丁基或環己基。更佳為R¹ 為甲基，R² 為氫原子，且R³ 為甲基。 上述(甲基)丙烯酸烷基酯代表性而言，以下述通式(2)表示： [化2]

於通式(2)中，R⁴ 表示氫原子或甲基，R⁵ 表示氫原子、或者可經取代之碳數1～6之脂肪族或脂環式烴基。作為取代基，例如可列舉鹵素、羥基。作為(甲基)丙烯酸烷基酯之具體例，可列舉：(甲基)丙烯酸甲酯、(甲基)丙烯酸乙酯、(甲基)丙烯酸正丙酯、(甲基)丙烯酸正丁酯、(甲基)丙烯酸第三丁酯、(甲基)丙烯酸正己酯、(甲基)丙烯酸環己酯、(甲基)丙烯酸氯甲酯、(甲基)丙烯酸2-氯乙酯、(甲基)丙烯酸2-羥基乙酯、(甲基)丙烯酸3-羥基丙酯、(甲基)丙烯酸2,3,4,5,6-五羥基己酯及(甲基)丙烯酸2,3,4,5-四羥基戊酯。於通式(2)中，R⁵ 較佳為氫原子或甲基。因此，尤佳之(甲基)丙烯酸烷基酯為丙烯酸甲酯或甲基丙烯酸甲酯。 上述丙烯酸系樹脂可僅含有單一之戊二醯亞胺單元，亦可含有上述通式(1)中之R¹ 、R² 及R³ 不同之複數種戊二醯亞胺單元。 上述丙烯酸系樹脂中之戊二醯亞胺單元之含有比率較佳為2莫耳%～50莫耳%，更佳為2莫耳%～45莫耳%，進而較佳為2莫耳%～40莫耳%，尤佳為2莫耳%～35莫耳%，最佳為3莫耳%～30莫耳%。若含有比率少於2莫耳%，則有不會充分地發揮源自戊二醯亞胺單元而表現之效果(例如，較高之光學特性、較高之機械強度、與偏光元件之優異之接著性、薄型化)之虞。若含有比率超過50莫耳%，則有例如耐熱性、透明性變得不充分之虞。 上述丙烯酸系樹脂可僅含有單一之(甲基)丙烯酸烷基酯單元，亦可含有上述通式(2)中之R⁴ 及R⁵ 不同之複數種(甲基)丙烯酸烷基酯單元。 上述丙烯酸系樹脂中之(甲基)丙烯酸烷基酯單元之含有比率較佳為50莫耳%～98莫耳%，更佳為55莫耳%～98莫耳%，進而較佳為60莫耳%～98莫耳%，尤佳為65莫耳%～98莫耳%，最佳為70莫耳%～97莫耳%。若含有比率少於50莫耳%，則有不會充分地發揮源自(甲基)丙烯酸烷基酯單元而表現之效果(例如，較高之耐熱性、較高之透明性)之虞。若上述含有比率多於98莫耳%，則有樹脂變脆而容易開裂，無法充分地發揮出較高之機械強度，生產性差之虞。 上述丙烯酸系樹脂亦可含有戊二醯亞胺單元及(甲基)丙烯酸烷基酯單元以外之單元。 於一實施形態中，丙烯酸系樹脂可含有未參與下文所述之分子內醯亞胺化反應之不飽和羧酸單元例如0～10重量%。不飽和羧酸單元之含有比率較佳為0～5重量%，更佳為0～1重量%。若含量為此種範圍，則可維持透明性、滯留穩定性及耐濕性。 於一實施形態中，丙烯酸系樹脂可含有上述以外之可進行共聚合之乙烯系單體單元(其他乙烯系單體單元)。作為該其他乙烯系單體，例如可列舉：丙烯腈、甲基丙烯腈、乙基丙烯腈、烯丙基縮水甘油醚、順丁烯二酸酐、伊康酸酐、N-甲基順丁烯二醯亞胺、N-乙基順丁烯二醯亞胺、N-環己基順丁烯二醯亞胺、丙烯酸胺基乙酯、丙烯酸丙基胺基乙酯、甲基丙烯酸二甲胺基乙酯、甲基丙烯酸乙基胺基丙酯、甲基丙烯酸環己基胺基乙酯、N-乙烯基二乙基胺、N-乙醯基乙烯基胺、烯丙基胺、甲基烯丙基胺、N-甲基烯丙基胺、2-異丙烯基㗁唑啉、2-乙烯基㗁唑啉、2-丙烯醯基㗁唑啉、N-苯基順丁烯二醯亞胺、甲基丙烯酸苯基胺基乙酯、苯乙烯、α-甲基苯乙烯、對縮水甘油基苯乙烯、對胺基苯乙烯、2-苯乙烯基㗁唑啉等。該等可單獨使用，亦可併用。較佳為苯乙烯、α-甲基苯乙烯等苯乙烯系單體。其他乙烯系單體單元之含有比率較佳為0～1重量%，更佳為0～0.1重量%。若為此種範圍，則可抑制並非所需之相位差之表現及透明性之降低。 上述丙烯酸系樹脂中之醯亞胺化率較佳為2.5%～20.0%。若醯亞胺化率為此種範圍，則可獲得耐熱性、透明性及成形加工性優異之樹脂，可防止膜成形時之燒焦之產生或機械強度之降低。於上述丙烯酸系樹脂中，醯亞胺化率係以戊二醯亞胺單元與(甲基)丙烯酸烷基酯單元之比表示。該比例如可根據丙烯酸系樹脂之NMR(nuclear magnetic resonance，核磁共振)圖譜、IR(infrared，紅外線)圖譜等而獲得。於本實施形態中，醯亞胺化率可使用¹ HNMR BRUKER AvanceIII(400 MHz)，藉由樹脂之¹ H-NMR測定而求出。更具體而言，將3.5至3.8 ppm附近之源自(甲基)丙烯酸烷基酯之O-CH₃ 質子之波峰面積設為A，將3.0至3.3 ppm附近之源自戊二醯亞胺之N-CH₃ 質子之波峰面積設為B，藉由下式而求出。 醯亞胺化率Im(%)＝{B/(A＋B)}×100 上述丙烯酸系樹脂之酸值較佳為0.10 mmol/g～0.50 mmol/g。若酸值為此種範圍，則可獲得耐熱性、機械物性及成形加工性之平衡性優異之樹脂。若酸值過小，則存在產生因使用用以調整為所需酸值之改性劑引起之成本提高、因改性劑之殘存引起之凝膠狀物之產生等問題之情形。若酸值過大，則有變得容易引起膜成形時(例如，熔融擠出時)之發泡而導致成形品之生產性降低之傾向。關於上述丙烯酸系樹脂，酸值係該丙烯酸系樹脂中之羧酸單元及羧酸酐單元之含量。於本實施形態中，酸值例如可藉由WO2005/054311或日本專利特開2005-23272號公報所記載之滴定法而算出。 上述丙烯酸系樹脂之重量平均分子量較佳為1000～2000000，更佳為5000～1000000，進而較佳為10000～500000，尤佳為50000～500000，最佳為60000～150000。重量平均分子量例如可使用凝膠滲透層析儀(GPC系統，Tosoh製造)，藉由聚苯乙烯換算而求出。再者，可使用四氫呋喃作為溶劑。 上述丙烯酸系樹脂之Tg(玻璃轉移溫度)較佳為110℃以上，更佳為115℃以上，進而較佳為120℃以上，尤佳為125℃以上，最佳為130℃以上。若Tg為110℃以上，則含有由此種樹脂獲得之基材膜之偏光板容易成為耐久性優異者。Tg之上限值較佳為300℃以下，更佳為290℃以下，進而較佳為285℃以下，尤佳為200℃以下，最佳為160℃以下。若Tg為此種範圍，則成形性會優異。 B-2-2.丙烯酸系樹脂之聚合 上述丙烯酸系樹脂例如可藉由以下之方法製造。該方法包括：(I)將與通式(2)所表示之(甲基)丙烯酸烷基酯單元相對應之(甲基)丙烯酸烷基酯單體與不飽和羧酸單體及/或其前驅物單體進行共聚合而獲得共聚物(a)；及(II)利用醯亞胺化劑處理該共聚物(a)，藉此進行該共聚物(a)中之(甲基)丙烯酸烷基酯單體單元與不飽和羧酸單體及/或其前驅物單體單元之分子內醯亞胺化反應，而將通式(1)所表示之戊二醯亞胺單元導入至共聚物中。 作為不飽和羧酸單體，例如可列舉：丙烯酸、甲基丙烯酸、丁烯酸、α-取代丙烯酸、α-取代甲基丙烯酸。作為其前驅物單體，例如可列舉：丙烯醯胺、甲基丙烯醯胺等。該等可單獨使用，亦可併用。較佳之不飽和羧酸單體為丙烯酸或甲基丙烯酸，較佳之前驅物單體為丙烯醯胺。 作為利用醯亞胺化劑對共聚物(a)進行處理之方法，可使用任意合適之方法。作為具體例，可列舉使用擠出機之方法、使用批次式反應槽(壓力容器)之方法。使用擠出機之方法包括使用擠出機將共聚物(a)加熱熔融，並利用醯亞胺化劑對其進行處理。於該情形時，作為擠出機，可使用任意合適之擠出機。作為具體例，可列舉：單軸擠出機、雙軸擠出機、多軸擠出機。使用批次式反應槽(壓力容器)之方法中可使用任意合適之批次式反應槽(壓力容器)。 作為醯亞胺化劑，只要可生成上述通式(1)所表示之戊二醯亞胺單元，則可使用任意合適之化合物。作為醯亞胺化劑之具體例，可列舉：甲胺、乙胺、正丙胺、異丙胺、正丁胺、異丁胺、第三丁胺、正己胺等含有脂肪族烴基之胺；苯胺、苄胺、甲苯胺、三氯苯胺等含有芳香族烴基之胺；環己胺等含有脂環式烴基之胺。進而，例如亦可使用藉由加熱而產生此種胺之脲系化合物。作為脲化合物，例如可列舉：脲、1,3-二甲基脲、1,3-二乙基脲、1,3-二丙基脲。醯亞胺化劑較佳為甲胺、氨、環己胺，更佳為甲胺。 於醯亞胺化中，除了上述醯亞胺化劑以外，亦可視需要添加閉環促進劑。 醯亞胺化中之醯亞胺化劑之使用量相對於共聚物(a)100重量份，較佳為0.5重量份～10重量份，更佳為0.5重量份～6重量份。若醯亞胺化劑之使用量少於0.5重量份，則未達成所需之醯亞胺化率之情形較多。其結果為，存在所獲得之樹脂之耐熱性變得極不充分，而誘發成形後之燒焦等外觀缺陷之情形。若醯亞胺化劑之使用量超過10重量份，則存在樹脂中殘存醯亞胺化劑，而由該醯亞胺化劑誘發成形後之燒焦等外觀缺陷或發泡之情形。 本實施形態之製造方法除了上述醯亞胺化以外視需要亦可包括利用酯化劑所進行之處理。 作為酯化劑，例如可列舉：碳酸二甲酯、2,2-二甲氧基丙烷、二甲基亞碸、原甲酸三乙酯、原乙酸三甲酯、原甲酸三甲酯、碳酸二苯酯、硫酸二甲酯、甲苯磺酸甲酯、三氟甲磺酸甲酯、乙酸甲酯、甲醇、乙醇、異氰酸甲酯、異氰酸對氯苯酯、二甲基碳二醯亞胺、二甲基第三丁基甲矽烷基氯、乙酸異丙烯酯、二甲基脲、氫氧化四甲基銨、二甲基二乙氧基甲矽烷、四正丁氧基甲矽烷、亞磷酸二甲酯(三甲基甲矽烷基)酯、亞磷酸三甲酯、磷酸三甲酯、磷酸三甲苯酯、重氮甲烷、環氧乙烷、環氧丙烷、環氧環己烷、2-乙基己基縮水甘油醚、苯基縮水甘油醚、苄基縮水甘油醚。該等中，就成本及反應性等觀點而言，較佳為碳酸二甲酯。 酯化劑之添加量可以丙烯酸系樹脂之酸值成為所需之值之方式設定。 B-2-3.其他樹脂之併用 於本發明之實施形態中，可將上述丙烯酸系樹脂與其他樹脂併用。即，可將構成丙烯酸系樹脂之單體成分與構成其他樹脂之單體成分進行共聚合，並將該共聚物供於下文B-4項所說明之膜形成；亦可將丙烯酸系樹脂與其他樹脂之摻合物供於膜形成。作為其他樹脂，例如可列舉：苯乙烯系樹脂、聚乙烯、聚丙烯、聚醯胺、聚苯硫醚、聚醚醚酮、聚酯、聚碸、聚苯醚、聚縮醛、聚醯亞胺、聚醚醯亞胺等其他熱塑性樹脂；酚系樹脂、三聚氰胺系樹脂、聚酯系樹脂、聚矽氧系樹脂、環氧系樹脂等熱硬化性樹脂。所併用之樹脂之種類及調配量可視目的及對所獲得之膜所期待之特性等而適當地設定。例如，苯乙烯系樹脂(較佳為丙烯腈-苯乙烯共聚物)可作為相位差控制劑而併用。 於將丙烯酸系樹脂與其他樹脂併用之情形時，丙烯酸系樹脂與其他樹脂之摻合物中之丙烯酸系樹脂之含量較佳為50重量%～100重量%，更佳為60重量%～100重量%，進而較佳為70重量%～100重量%，尤佳為80重量%～100重量%。於含量未達50重量%之情形時，有無法充分地反映出丙烯酸系樹脂本來具有之較高之耐熱性、較高之透明性之虞。 B-3.芯殼型粒子 於上述基材膜中，芯殼型粒子係相對於丙烯酸系樹脂100重量份，而調配較佳為5重量份～50重量份，更佳為5重量份～40重量份。藉此，於在基材膜上形成表面處理層之情形時，可進一步促進形成表面處理層之組合物對基材膜之滲透，可獲得基材膜與表面處理層之密接性較高之光學膜。 芯殼型粒子代表性而言具有包含橡膠狀聚合物之芯、及包含玻璃狀聚合物且被覆該芯之被覆層。芯殼型粒子具有一層以上包含玻璃狀聚合物之層作為最內層或中間層。 構成芯之橡膠狀聚合物之Tg較佳為20℃以下，更佳為-60℃～20℃，進而較佳為-60℃～10℃。若構成芯之橡膠狀聚合物之Tg超過20℃，則有丙烯酸系樹脂之機械強度之提高不充分之虞。構成被覆層之玻璃狀聚合物(硬質聚合物)之Tg較佳為50℃以上，更佳為50℃～140℃，進而較佳為60℃～130℃。若構成被覆層之玻璃狀聚合物之Tg低於50℃，則有丙烯酸系樹脂之耐熱性降低之虞。 芯殼型粒子中之芯之含有比率較佳為30重量%～95重量%，更佳為50重量%～90重量%。芯中之玻璃狀聚合物層之比率相對於芯之總量100重量%，為0～60重量%，較佳為0～45重量%，更佳為10重量%～40重量%。芯殼型粒子中之被覆層之含有比率較佳為5重量%～70重量%，更佳為10重量%～50重量%。 於一實施形態中，分散至丙烯酸系樹脂中之芯殼型粒子可具有扁平形狀。芯殼型粒子可藉由下文B-4項所說明之延伸而扁平化。經扁平化之芯殼型粒子之長度/厚度之比為7.0以下。長度/厚度之比較佳為6.5以下，更佳為6.3以下。另一方面，長度/厚度之比較佳為4.0以上，更佳為4.5以上，進而較佳為5.0以上。於本說明書中，所謂「長度/厚度之比」意指芯殼型粒子之俯視形狀之代表長度與厚度之比。此處，所謂「代表長度」，於俯視形狀為圓形之情形時指直徑，於橢圓形之情形時指長徑，於矩形或多邊形之情形時指對角線之長度。該比例如可按照以下之順序求出。利用穿透式電子顯微鏡(例如，加速電壓80 kV、RuO₄ 染色超薄切片法)對所獲得之膜剖面進行拍攝，自存在於所獲得之照片中之芯殼型粒子中之較長者(獲得接近代表長度之剖面者)中依序選取30個，算出(長度之平均值)/(厚度之平均值)，藉此可獲得該比。 構成芯殼型粒子之芯之橡膠狀聚合物、構成被覆層之玻璃狀聚合物(硬質聚合物)、該等之聚合方法、及其他構成之詳細內容例如記載於日本專利特開2016-33552號公報。該公報之記載係作為參考而引用至本說明書中。 B-4.基材膜之形成 本發明之實施形態之基材膜代表性而言可藉由包括將含有上述丙烯酸系樹脂(於併用其他樹脂之情形時為與該其他樹脂之摻合物)及芯殼型粒子之組合物形成膜之方法而形成。進而，形成基材膜之方法可包括將上述膜加以延伸。 膜形成所使用之芯殼型粒子之平均粒徑較佳為1 nm～500 nm。芯之平均粒徑較佳為50 nm～300 nm，更佳為70 nm～300 nm。 作為形成膜之方法，可採用任意合適之方法。作為具體例，可列舉：流鑄塗敷法(例如，流延法)、擠出成形法、射出成形法、壓縮成形法、轉移成形法、吹塑成形法、粉末成形法、FRP(Fiber Reinforced Plastic，纖維強化塑膠)成形法、壓延成形法、熱壓法。較佳為擠出成形法或流鑄塗敷法。其原因在於：可提高所獲得之膜之平滑性，可獲得良好之光學均一性。尤佳為擠出成形法。其原因在於無需考慮因殘存溶劑引起之問題。其中，使用T模之擠出成形法就膜之生產性及以後之延伸處理之容易性之觀點而言較佳。成形條件可根據所使用之樹脂之組成或種類、對所獲得之膜所期待之特性等而適當設定。 作為延伸方法，可採用任意合適之延伸方法、延伸條件(例如，延伸溫度、延伸倍率、延伸速度、延伸方向)。作為延伸方法之具體例，可列舉自由端延伸、固定端延伸、自由端收縮、固定端收縮。該等可單獨使用，亦可同時使用，亦可依次使用。藉由在合適之延伸條件下對已適當調整芯殼型粒子相對於丙烯酸系樹脂之調配量之膜進行延伸，於在所獲得之基材膜上形成表面處理層之情形時，可進一步促進形成表面處理層之組合物對基材膜之滲透，可獲得基材膜與表面處理層之密接性較高之光學膜。 延伸方向可視目的而採用合適之方向。具體而言，可列舉：長度方向、寬度方向、厚度方向、斜方向。延伸方向可為一方向(單軸延伸)，亦可為兩方向(雙軸延伸)，亦可為三方向以上。於本發明之實施形態中，代表性而言，可採用長度方向之單軸延伸、長度方向及寬度方向之同時雙軸延伸、長度方向及寬度方向之依次雙軸延伸。較佳為雙軸延伸(同時或依次)。其原因在於：容易控制面內相位差，而容易實現光學各向同性。 延伸溫度可根據對基材膜所期待之光學特性、機械特性及厚度、所使用之樹脂之種類、所使用之膜之厚度、延伸方法(單軸延伸或雙軸延伸)、延伸倍率、延伸速度等而變化。具體而言，延伸溫度較佳為Tg～Tg＋50℃，進而較佳為Tg＋15℃～Tg＋50℃，最佳為Tg＋35℃～Tg＋50℃。藉由在此種溫度下進行延伸，可獲得具有合適之特性之基材膜。具體之延伸溫度例如為110℃～200℃，較佳為120℃～190℃，進而較佳為150℃～190℃。若延伸溫度為此種範圍，則藉由適當地調整延伸倍率及延伸速度，於在所獲得之基材膜上形成表面處理層之情形時，可進一步促進形成表面處理層之組合物對基材膜之滲透，可獲得基材膜與表面處理層之密接性較高之光學膜。 又，延伸倍率亦與延伸溫度同樣地可根據光學特性、機械特性及厚度、所使用之樹脂之種類、所使用之膜之厚度、延伸方法(單軸延伸或雙軸延伸)、延伸溫度、延伸速度等而變化。於採用雙軸延伸之情形時，寬度方向(TD)之延伸倍率與長度方向(MD)之延伸倍率之比(TD/MD)較佳為1.0～1.5，更佳為1.0～1.4，進而較佳為1.0～1.3。又，採用雙軸延伸之情形時之面倍率(長度方向之延伸倍率與寬度方向之延伸倍率之積)較佳為2.0～6.0，更佳為3.0～5.5，進而較佳為3.5～5.2。若延伸倍率為此種範圍，則藉由適當調整延伸溫度及延伸速度，於在所獲得之基材膜上形成表面處理層之情形時，可進一步促進形成表面處理層之組合物對基材膜之滲透，可獲得基材膜與表面處理層之密接性較高之光學膜。 又，延伸速度亦與延伸溫度同樣地可根據光學特性、機械特性及厚度、所使用之樹脂之種類、所使用之膜之厚度、延伸方法(單軸延伸或雙軸延伸)、延伸溫度、延伸倍率等而變化。延伸速度較佳為3%/秒～20%/秒，更佳為3%/秒～15%/秒，進而較佳為3%/秒～10%/秒。於採用雙軸延伸之情形時，一方向之延伸速度與另一方向之延伸速度可相同亦可不同。若延伸速度為此種範圍，則藉由適當調整延伸溫度及延伸倍率，於在所獲得之基材膜上形成表面處理層之情形時，可進一步促進形成表面處理層之組合物對基材膜之滲透，可獲得基材膜與表面處理層之密接性較高之光學膜。 以上述方式可形成基材膜。 C.表面處理層 表面處理層係根據對光學膜所要求之功能而形成於基材膜之單側的任意合適之功能層。作為表面處理層之具體例，可列舉硬塗層、防眩層、及抗反射層等。表面處理層之厚度較佳為3 μm～20 μm，更佳為5 μm～15 μm。 表面處理層代表性而言為形成於基材膜上之樹脂組合物之硬化層。形成表面處理層之步驟可包括：於基材膜上塗佈表面處理層形成用之樹脂組合物而形成塗佈層；及將上述塗佈層加以乾燥使之硬化而製成表面處理層。將上述塗佈層加以乾燥使之硬化可包括加熱上述塗佈層。 作為樹脂組合物之塗佈方法，可採用任意合適之方法。例如可列舉：棒式塗佈法、輥式塗佈法、凹版塗佈法、桿式塗佈法、孔縫式塗佈法、淋幕式塗佈法、噴注式塗佈法、缺角輪塗佈法。就使塗佈變得容易之觀點而言，樹脂組合物較佳為含有稀釋用之溶劑。 塗佈層之加熱溫度可設定為對應於樹脂組合物之組成的任意合適之溫度，較佳為設定為基材膜所含之丙烯酸系樹脂之玻璃轉移溫度以下。若於基材膜所含之丙烯酸系樹脂之玻璃轉移溫度以下之溫度下進行加熱，則可獲得抑制了因加熱引起之變形的光學膜。塗佈層之加熱溫度例如為50℃～140℃，較佳為60℃～100℃。藉由在此種加熱溫度下進行加熱，可獲得基材膜與表面處理層之密接性優異之光學膜。 C-1.硬塗層 硬塗層係對基材膜之表面賦予耐擦傷性及耐化學品性等之層。硬塗層於鉛筆硬度試驗中具有較佳為H以上、更佳為3H以上之硬度。鉛筆硬度試驗可依照JIS K 5400而測定。硬塗層形成用之樹脂組合物例如可含有能夠藉由熱、光(紫外線等)或電子束等而硬化之硬化性化合物。硬塗層及硬塗層形成用之樹脂組合物之詳細內容例如記載於日本專利特開2014-240955號公報。該公報之全部記載係作為參考而引用至本說明書中。 C-2.防眩層 防眩層係用以藉由使光散射並反射而防止外界光之映入之層。防眩層形成用之樹脂組合物例如可含有能夠藉由熱、光(紫外線等)或電子束等而硬化之硬化性化合物。防眩層代表性而言於表面具有微細凹凸形狀。作為形成此種微細凹凸形狀之方法，例如可列舉使上述硬化性化合物含有微粒子之方法。防眩層及防眩層形成用之樹脂組合物之詳細內容例如記載於日本專利特開2017-32711號公報。該公報之全部記載係作為參考而引用至本說明書中。 C-3.抗反射層 抗反射層係用以防止外界光之反射之層。抗反射層形成用之樹脂組合物例如可含有能夠藉由熱、光(紫外線等)或電子束等而硬化之硬化性化合物。抗反射層可為僅由1層構成之單層，亦可為包含2層以上之複數層。抗反射層及抗反射層形成用之樹脂組合物之詳細內容例如記載於日本專利特開2012-155050號公報。該公報之全部記載係作為參考而引用至本說明書中。 D.偏光板 上述A至C項所記載之光學膜可應用於偏光板。因此，本發明亦包含使用此種光學膜之偏光板。代表性而言，偏光板具有偏光元件、及配置於偏光元件之單側之本發明之光學膜。對於光學膜，可將其基材膜側與偏光元件加以貼合，而作為偏光元件之保護層發揮功能。 作為偏光元件，可採用任意合適之偏光元件。例如，形成偏光元件之樹脂膜可為單層之樹脂膜，亦可為兩層以上之積層體。 作為包含單層樹脂膜之偏光元件之具體例，可列舉：對聚乙烯醇(PVA)系膜、部分縮甲醛化PVA系膜、乙烯-乙酸乙烯酯共聚物系部分皂化膜等親水性高分子膜實施利用碘或二色性染料等二色性物質之染色處理及延伸處理而成者；PVA之脫水處理物或聚氯乙烯之脫氯化氫處理物等多烯系配向膜等。就光學特性優異之方面而言，較佳為使用以碘將PVA系膜染色並單軸延伸而獲得之偏光元件。 上述利用碘之染色例如係藉由將PVA系膜浸漬於碘水溶液中而進行。上述單軸延伸之延伸倍率較佳為3～7倍。延伸可於染色處理後進行，亦可一邊染色一邊進行。又，亦可於延伸後進行染色。視需要對PVA系膜實施膨潤處理、交聯處理、洗淨處理、乾燥處理等。例如，藉由在染色前將PVA系膜浸漬於水中進行水洗，不僅可洗淨PVA系膜表面之污垢或抗黏連劑，而且可使PVA系膜膨潤而防止染色不均等。 作為使用積層體而獲得之偏光元件之具體例，可列舉使用樹脂基材與積層於該樹脂基材之PVA系樹脂層(PVA系樹脂膜)之積層體、或樹脂基材與塗佈形成於該樹脂基材之PVA系樹脂層之積層體而獲得之偏光元件。使用樹脂基材與塗佈形成於該樹脂基材之PVA系樹脂層之積層體而獲得之偏光元件例如可藉由以下方法製作：將PVA系樹脂溶液塗佈於樹脂基材，加以乾燥而於樹脂基材上形成PVA系樹脂層，從而獲得樹脂基材與PVA系樹脂層之積層體；將該積層體進行延伸及染色而將PVA系樹脂層製成偏光元件。於本實施形態中，延伸代表性而言包括將積層體浸漬於硼酸水溶液中進行延伸。進而，延伸可視需要進而包括於硼酸水溶液中之延伸前將積層體於高溫(例如，95℃以上)下進行空中延伸。所獲得之樹脂基材/偏光元件之積層體可直接使用(即，可將樹脂基材設為偏光元件之保護層)，亦可將樹脂基材從樹脂基材/偏光元件之積層體剝離，於該剝離面積層符合目的之任意合適之保護層而使用。此種偏光元件之製造方法之詳細內容例如記載於日本專利特開2012-73580號公報。該公報之全部記載係作為參考而引用至本說明書中。 偏光元件之厚度例如為1 μm～80 μm。於一實施形態中，偏光元件之厚度較佳為1 μm～20 μm，進而較佳為3 μm～15 μm。 E.圖像顯示裝置 上述D項所記載之偏光板可應用於圖像顯示裝置。因此，本發明亦包含使用此種偏光板之圖像顯示裝置。作為圖像顯示裝置之代表例，可列舉：液晶顯示裝置、有機電致發光(EL)顯示裝置。圖像顯示裝置係採用業界所周知之構成，因此省略詳細之說明。 實施例 以下，藉由實施例對本發明進行具體說明，但本發明並不限定於該等實施例。各特性之測定方法如以下所述。再者，只要無特別明確記載，則實施例中之「份」及「%」為重量基準。 (1)基材膜之最大伸長率(TMA測定) 將基材膜裁斷為寬4 mm×長20 mm之尺寸，製成初始長度為20 mm之測定樣品。再者，準備以基材膜之長邊方向成為長度方向之方式進行裁斷而獲得之測定樣品A、及以與基材膜之長邊方向正交之方向成為長度方向之方式進行裁斷而獲得之測定樣品B。 對於測定樣品A及測定樣品B，分別使用熱機械分析裝置(Hitachi High-Tech Science公司製造，型號「TMA7100」)，將測定樣品安裝於測定治具，一邊沿測定樣品之長度方向施加98 mN/min之拉伸荷重，一邊以5℃/min從24℃升溫至150℃，測定此時之至軟化點為止之最大伸長率。 再者，最大伸長率係使用以下之式算出。 最大伸長率(%)＝(最大伸長時之樣品長度－初期樣品長度)/初期樣品長度×100 測定樣品A之最大伸長率與基材膜之長邊方向之最大伸長率相對應，測定樣品B之最大伸長率與基材膜之短邊方向(與長邊方向正交之方向)之最大伸長率相對應。 (2)密接性評價 依照JIS K-5400之柵格剝離試驗(柵格數：100個)對表面處理層對基材膜之密接性進行評價，藉由以下之指標加以判定。 〇：柵格剝離數為0個 ×：柵格剝離數為1個以上 ＜製造例1＞ 準備以下之組合物A～C作為表面處理層形成用之樹脂組合物。 (1)組合物A 將4-HBA(4-hydroxybutyl acrylate，丙烯酸4-羥基丁酯)(大阪有機化學工業股份有限公司製造)16重量份、NK低聚UA-53H-80BK(新中村化學工業股份有限公司製造)32重量份、Viscoat #300(大阪有機化學工業股份有限公司製造)48重量份、A-GLY-9E(新中村化學工業股份有限公司製造)4重量份、及IRGACURE 907(BASF製造)2.4重量份加以混合，分別藉由MIBK(methyl isobutyl ketone，甲基異丁基酮)：PGM(Propylene glycol monomethylether，丙二醇單甲醚)＝50：50之溶劑以固形物成分濃度成為42.0%之方式進行稀釋而獲得之UV硬化性樹脂。 (2)組合物B 將Viscoat #300(大阪有機化學工業股份有限公司製造)100重量份、及IRGACURE 907(BASF製造)2.4重量份加以混合，藉由MIBK：PGM＝50：50之溶劑以固形物成分濃度成為42.0%之方式進行稀釋而獲得之UV硬化性樹脂。 (3)組合物C 將4-HBA(大阪有機化學工業股份有限公司製造)20重量份、NK低聚UA-53H-80BK(新中村化學工業股份有限公司製造)40重量份、Viscoat #300(大阪有機化學工業股份有限公司製造)60重量份、IRGACURE 907(BASF製造)5重量份、及Techpolymer SSX-103DXE(積水化成品工業股份有限公司製造)0.5重量份加以混合，分別藉由甲苯：MEK(methyl ethyl ketone，甲基乙基酮)＝70：30之溶劑以固形物成分濃度成為40.0%之方式進行稀釋而獲得之UV硬化性樹脂。 ＜實施例1＞ 1.基材膜之製作 利用單甲基胺將MS樹脂(MS-200；甲基丙烯酸甲酯/苯乙烯(莫耳比)＝80/20之共聚物，新日鐵化學股份有限公司製造)進行醯亞胺化(醯亞胺化率：5%)。所獲得之醯亞胺化MS樹脂具有通式(1)所表示之戊二醯亞胺單元(R¹ 及R³ 為甲基，R² 為氫原子)、通式(2)所表示之(甲基)丙烯酸酯單元(R⁴ 及R⁵ 為甲基)、及苯乙烯單元。再者，上述醯亞胺化係使用口徑15 mm之嚙合型同方向旋轉式雙軸擠出機。將擠出機之各調溫區之設定溫度設為230℃，將螺桿轉速設為150 rpm，以2.0 kg/hr供給MS樹脂，單甲基胺之供給量係相對於MS樹脂100重量份而設為2重量份。從料斗投入MS樹脂，藉由捏合段使樹脂熔融及充滿後，從噴嘴注入單甲基胺。於反應區之末端裝入密封圈使樹脂充滿。將排氣口之壓力減壓為-0.08 MPa而將反應後之副產物及過量之甲基胺去除揮發物。以線料形式從設置於擠出機出口之模具排出之樹脂於水槽中冷卻後，藉由造粒機進行顆粒化。所獲得之醯亞胺化MS樹脂之醯亞胺化率為5.0%，酸值為0.5 mmol/g。 將上述所獲得之醯亞胺化MS樹脂100重量份與芯殼型粒子10重量份投入至單軸擠出機中進行熔融混合，通過T模而進行膜形成，藉此獲得擠出膜。將所獲得之擠出膜於延伸溫度160℃下沿長度方向及寬度方向分別同時雙軸延伸為2倍。延伸速度於長度方向及寬度方向均為10%/秒。 由此製作基材膜A。所獲得之基材膜A之厚度為30 μm。測定基材膜A之長邊方向之最大伸長率及短邊方向之最大伸長率。將結果示於表1。 2.光學膜之製作 以硬化後之厚度成為6 μm之方式於上述基材膜A之單側塗佈組合物A而形成塗佈層。繼而，將上述塗佈層於70℃下加以乾燥，並且進行UV硬化，藉此獲得於基材膜A之單側形成有硬塗層之光學膜1。將上述光學膜1供於密接性評價。將結果示於表1。 ＜實施例2＞ 於上述基材膜A之單側塗佈組合物B並加以乾燥使之硬化，藉此形成硬塗層，除此以外，以與實施例1同樣之方式獲得於基材膜A之單側形成有硬塗層之光學膜2。將上述光學膜2供於密接性評價。將結果示於表1。 ＜實施例3＞ 於上述基材膜A之單側塗佈組合物C並加以硬化，藉此形成防眩層，除此以外，以與實施例1同樣之方式獲得於基材膜A之單側形成有防眩層之光學膜3。將上述光學膜3供於密接性評價。將結果示於表1。 ＜實施例4＞ 1.基材膜之製作 將芯殼型粒子之調配量設為15重量份，並且將擠出膜之延伸溫度設為152℃，除此以外，以與實施例1同樣之方式製作基材膜B。測定基材膜B之長邊方向之最大伸長率及短邊方向之最大伸長率。將結果示於表1。 2.光學膜之製作 除了使用上述基材膜B以外，以與實施例1同樣之方式獲得於基材膜B之單側形成有硬塗層之光學膜4。將上述光學膜4供於密接性評價。將結果示於表1。 ＜實施例5＞ 1.基材膜之製作 將上述所獲得之醯亞胺化MS樹脂100重量份與芯殼型粒子10重量份投入至單軸擠出機中進行熔融混合，通過T模而進行膜形成，藉此獲得擠出膜。將所獲得之擠出膜於延伸溫度160℃下沿長度方向及寬度方向分別同時雙軸延伸為2倍。延伸速度於長度方向及寬度方向均為10%/秒。 由此製作基材膜C。所獲得之基材膜C之厚度為40 μm。測定基材膜C之長邊方向之最大伸長率及短邊方向之最大伸長率。將結果示於表1。 2.光學膜之製作 除了使用上述基材膜C以外，以與實施例1同樣之方式獲得於基材膜C之單側形成有硬塗層之光學膜5。將上述光學膜5供於密接性評價。將結果示於表1。 ＜實施例6＞ 1.基材膜之製作 將上述所獲得之醯亞胺化MS樹脂100重量份與芯殼型粒子10重量份投入至單軸擠出機中進行熔融混合，通過T模而進行膜形成，藉此獲得擠出膜。將所獲得之擠出膜於延伸溫度160℃下沿長度方向及寬度方向分別同時雙軸延伸為2倍。延伸速度於長度方向及寬度方向均為10%/秒。 由此製作基材膜D。所獲得之基材膜D之厚度為35 μm。測定基材膜D之長邊方向之最大伸長率及短邊方向之最大伸長率。將結果示於表1。 2.光學膜之製作 除了使用上述基材膜D以外，以與實施例1同樣之方式獲得於基材膜D之單側形成有硬塗層之光學膜6。將上述光學膜6供於密接性評價。將結果示於表1。 ＜實施例7＞ 1.基材膜之製作 除了將擠出膜之延伸溫度設為150℃以外，以與實施例1同樣之方式製作基材膜E。測定基材膜E之長邊方向之最大伸長率及短邊方向之最大伸長率。將結果示於表1。 2.光學膜之製作 除了使用上述基材膜E以外，以與實施例1同樣之方式獲得於基材膜E之單側形成有硬塗層之光學膜7。將上述光學膜7供於密接性評價。將結果示於表1。 ＜實施例8＞ 1.基材膜之製作 將芯殼型粒子之調配量設為23重量份，並且將擠出膜之延伸溫度設為152℃，除此以外，以與實施例1同樣之方式製作基材膜F。測定基材膜F之長邊方向之最大伸長率及短邊方向之最大伸長率。將結果示於表1。 2.光學膜之製作 除了使用上述基材膜F以外，以與實施例1同樣之方式獲得於基材膜F之單側形成有硬塗層之光學膜8。將上述光學膜8供於密接性評價。將結果示於表1。 ＜實施例9＞ 1.基材膜之製作 除了不調配芯殼型粒子以外，以與實施例1同樣之方式製作基材膜G。測定基材膜G之長邊方向之最大伸長率及短邊方向之最大伸長率。將結果示於表1。 2.光學膜之製作 除了使用上述基材膜G以外，以與實施例1同樣之方式獲得於基材膜G之單側形成有硬塗層之光學膜9。將上述光學膜9供於密接性評價。將結果示於表1。 ＜實施例10＞ 1.基材膜之製作 除了將擠出膜之延伸溫度設為140℃以外，以與實施例1同樣之方式製作基材膜H。測定基材膜H之長邊方向之最大伸長率及短邊方向之最大伸長率。將結果示於表1。 2.光學膜之製作 除了使用上述基材膜H以外，以與實施例1同樣之方式獲得於基材膜H之單側形成有硬塗層之光學膜10。將上述光學膜10供於密接性評價。將結果示於表1。 ＜實施例11＞ 1.基材膜之製作 將芯殼型粒子之調配量設為23重量份，並且將擠出膜之延伸溫度設為137℃，除此以外，以與實施例1同樣之方式製作基材膜I。測定基材膜I之長邊方向之最大伸長率及短邊方向之最大伸長率。將結果示於表1。 2.光學膜之製作 除了使用上述基材膜I以外，以與實施例1同樣之方式獲得於基材膜I之單側形成有硬塗層之光學膜11。將上述光學膜11供於密接性評價。將結果示於表1。 ＜實施例12＞ 1.基材膜之製作 不調配芯殼型粒子，並且將擠出膜之延伸溫度設為155℃，除此以外，以與實施例1同樣之方式製作基材膜J。測定基材膜J之長邊方向之最大伸長率及短邊方向之最大伸長率。將結果示於表1。 2.光學膜之製作 除了使用上述基材膜J以外，以與實施例1同樣之方式獲得於基材膜J之單側形成有硬塗層之光學膜12。將上述光學膜12供於密接性評價。將結果示於表1。 ＜實施例13＞ 1.基材膜之製作 將芯殼型粒子之調配量設為5重量份，並且將擠出膜之延伸溫度設為140℃，除此以外，以與實施例1同樣之方式製作基材膜K。測定基材膜K之長邊方向之最大伸長率及短邊方向之最大伸長率。將結果示於表1。 2.光學膜之製作 除了使用上述基材膜K以外，以與實施例1同樣之方式獲得於基材膜K之單側形成有硬塗層之光學膜13。將上述光學膜13供於密接性評價。將結果示於表1。 ＜實施例14＞ 1.基材膜之製作 不調配芯殼型粒子，並且將擠出膜之延伸溫度設為150℃，除此以外，以與實施例1同樣之方式製作基材膜L。測定基材膜L之長邊方向之最大伸長率及短邊方向之最大伸長率。將結果示於表1。 2.光學膜之製作 除了使用上述基材膜L以外，以與實施例1同樣之方式獲得於基材膜L之單側形成有硬塗層之光學膜14。將上述光學膜14供於密接性評價。將結果示於表1。 ＜比較例1＞ 1.基材膜之製作 將芯殼型粒子之調配量設為3重量份，並且將擠出膜之延伸溫度設為140℃，除此以外，以與實施例1同樣之方式製作基材膜M。測定基材膜M之長邊方向之最大伸長率及短邊方向之最大伸長率。將結果示於表1。 2.光學膜之製作 除了使用上述基材膜M以外，以與實施例1同樣之方式獲得於基材膜M之單側形成有硬塗層之光學膜15。將上述光學膜15供於密接性評價。將結果示於表1。 ＜比較例2＞ 1.基材膜之製作 不調配芯殼型粒子，並且將擠出膜之延伸溫度設為140℃，除此以外，以與實施例1同樣之方式製作基材膜N。測定基材膜N之長邊方向之最大伸長率及短邊方向之最大伸長率。將結果示於表1。 2.光學膜之製作 除了使用上述基材膜N以外，以與實施例1同樣之方式獲得於基材膜N之單側形成有硬塗層之光學膜16。將上述光學膜16供於密接性評價。將結果示於表1。 ＜比較例3＞ 於上述基材膜N之單側塗佈組合物B並加以乾燥使之硬化，藉此形成硬塗層，除此以外，以與比較例2同樣之方式獲得於基材膜N之單側形成有硬塗層之光學膜17。將上述光學膜17供於密接性評價。將結果示於表1。 ＜比較例4＞ 於上述基材膜N之單側塗佈組合物C並加以乾燥使之硬化，藉此形成防眩層，除此以外，以與比較例2同樣之方式獲得於基材膜N之單側形成有防眩層之光學膜18。將上述光學膜18供於密接性評價。將結果示於表1。 ＜比較例5＞ 1.基材膜之製作 不調配芯殼型粒子，並且將擠出膜之延伸溫度設為130℃，除此以外，以與實施例1同樣之方式製作基材膜O。測定基材膜O之長邊方向之最大伸長率及短邊方向之最大伸長率。將結果示於表1。 2.光學膜之製作 除了使用上述基材膜O以外，以與實施例1同樣之方式獲得於基材膜O之單側形成有硬塗層之光學膜19。將上述光學膜19供於密接性評價。將結果示於表1。 [表1]

根據表1可知，使用長邊方向之最大伸長率及短邊方向之最大伸長率中至少一者為0.40%以上之基材膜的實施例1～14之光學膜中表面處理層對基材膜之密接性較高。 [產業上之可利用性] 本發明之光學膜可適宜地用作偏光元件之保護層。具有本發明之光學膜作為保護層之偏光板可適宜地用於圖像顯示裝置。如上所述之圖像顯示裝置可用於：攜帶型資訊終端(PDA，portable information terminal)、智慧型手機、行動電話、時鐘、數位相機、攜帶型遊戲機等攜帶型機器；電腦顯示器、筆記型電腦、影印機等OA機器；攝錄影機、電視、微波爐等家庭用電氣設備；後部監視器、汽車導航系統用監視器、汽車音響等車載用機器；數位標牌、商業店鋪用資訊用顯示器等展示機器；監視用監視器等警備機器；護理用監視器、醫療用監視器等護理、醫療機器等各種用途。Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments. A. Overall Configuration of Optical Film FIG. 1 is a schematic cross-sectional view of an optical film according to an embodiment of the present invention. The optical film 100 includes a base film 10 and a surface treatment layer 20 formed on one side of the base film 10 . The base film 10 is a stretched film containing an acrylic resin. The substrate film 10 has a maximum elongation of 0.40% or more to the softening point in TMA measurement in which the temperature is increased from 24°C to 150°C at 5°C/min while applying a tensile load of 98 mN/min in a specific direction. The maximum elongation of the base film can be cut to a size suitable for TMA measurement as needed, and measured using a thermomechanical analyzer. When the base film is elongated or rectangular, the specific direction is typically at least any one of the long-side direction and the short-side direction (direction orthogonal to the long-side direction) of the base film. When the base film is square, the above-mentioned specific direction is typically a direction along at least any side of the base film. In one embodiment, the base film 10 contains an acrylic resin and core-shell particles dispersed in the acrylic resin. In this case, the base film 10 preferably contains 5 parts by weight to 50 parts by weight of the core-shell type particles with respect to 100 parts by weight of the acrylic resin. The acrylic resin preferably has at least one selected from the group consisting of a glutarimide unit, a lactone ring unit, a maleic anhydride unit, a maleimide unit, and a glutaric anhydride unit. The surface treatment layer 20 is typically a hardened layer of the resin composition coated on the base film 10 . The surface treatment layer 20 is preferably at least one selected from the group consisting of a hard coat layer, an anti-glare layer and an anti-reflection layer. By the above-mentioned optical film, the penetration of the composition for forming the surface treatment layer 20 into the base film 10 can be promoted. As a result, the adhesion between the base film 10 and the surface treatment layer 20 can be improved by the anchor effect. Especially in the case where the surface treatment layer 20 is formed by coating the resin composition on the base film 10 and drying and curing the resin composition, even in the case of drying the above-mentioned resin composition at a low temperature, Sufficient adhesion between the base film 10 and the surface treatment layer 20 can be achieved. Therefore, it is possible to suppress the occurrence of wrinkles in the base film due to the heat at the time of drying the resin composition. B. Base film B-1. Characteristics of base film The base film is a stretched film containing an acrylic resin as described above. In the TMA measurement in which the temperature was raised from 24°C to 150°C, the maximum elongation up to the softening point was 0.40% or more. The above-mentioned maximum elongation is preferably 0.50% or more, more preferably 0.60% or more. On the other hand, the upper limit of the above-mentioned maximum elongation is preferably 2.0%. If the above-mentioned maximum elongation is too high, when the optical film is bonded to the polarizer and used as a protective layer of the polarizer, the polarizer may be cracked due to the difference in shrinkage ratio with the polarizer. In one embodiment, the base film contains an acrylic resin and core-shell particles dispersed in the acrylic resin. The thickness of the base film is preferably 5 μm to 150 μm, more preferably 10 μm to 100 μm. The base film preferably has substantially optical isotropy. In this specification, "substantially optically isotropic" means that the in-plane retardation Re(550) is 0 nm to 10 nm and the thickness direction retardation Rth(550) is -10 nm to +10 nm. The in-plane retardation Re(550) is more preferably 0 nm to 5 nm, more preferably 0 nm to 3 nm, and particularly preferably 0 nm to 2 nm. The retardation Rth(550) in the thickness direction is more preferably -5 nm to +5 nm, further preferably -3 nm to +3 nm, particularly preferably -2 nm to +2 nm. If the Re(550) and Rth(550) of the base film are in such ranges, adverse effects on display characteristics can be prevented when the optical film is applied to an image display device. In addition, Re(550) is the in-plane retardation of a film measured by the light of wavelength 550nm at 23 degreeC. Re(550) can be obtained by the formula: Re(550)=(nx−ny)×d. Rth(550) is the retardation in the thickness direction of the film measured at 23°C with light with a wavelength of 550 nm. Rth(550) can be obtained by the formula: Rth(550)=(nx−nz)×d. Here, the refractive index in the direction in which the refractive index in the nx system becomes the largest (that is, the direction of the slow axis), and the refractive index in the direction of the ny system in the direction orthogonal to the slow axis (that is, the direction of the advance axis), nz is the refractive index in the thickness direction, and d is the thickness (nm) of the film. When the thickness of the base film is 30 μm, the higher the light transmittance at 380 nm, the better. Specifically, the light transmittance is preferably 85% or more, more preferably 88% or more, and still more preferably 90% or more. If the light transmittance is in this range, the required transparency can be ensured. The light transmittance can be measured, for example, by a method according to ASTM-D-1003. The lower the haze of the base film, the better. Specifically, the haze is preferably 5% or less, more preferably 3% or less, still more preferably 1.5% or less, and still more preferably 1% or less. When the haze is 5% or less, a favorable transparency can be imparted to the film. Furthermore, even when the optical film is used as a protective layer of a polarizing plate on the viewing side of an image display device, the display content can be viewed favorably. When the thickness of the base film is 30 μm, YI (Yellowness Index, yellowness index) is preferably 1.27 or less, more preferably 1.25 or less, still more preferably 1.23 or less, particularly preferably 1.20 or less. When YI exceeds 1.3, optical transparency may become insufficient. In addition, YI can be based on, for example, the tristimulus values (X, Y, Z) of the color obtained by measurement using a high-speed integrating sphere spectroscopic transmittance measuring machine (trade name DOT-3C: manufactured by Murakami Color Technology Laboratory), It is calculated|required by the following formula. YI=[(1.28X－1.06Z)/Y]×100 When the thickness of the base film is 30 μm, the b value (according to the scale of the hue of the Hunter color system) is preferably less than 1.5, more Preferably it is 1.0 or less. In the case where the b value is 1.5 or more, an undesired color tone may occur. In addition, the b value can be measured, for example, by cutting a sample of the base film into a 3 cm square, measuring the hue using a high-speed integrating sphere type spectral transmittance measuring machine (trade name DOT-3C: manufactured by Murakami Color Technology Laboratory), and measuring the color according to the Chinese The characteristic color system is obtained by evaluating the hue. The moisture permeability of the base film is preferably 300 g/m ² · 24 hr or less, more preferably 250 g/m ² · 24 hr or less, more preferably 200 g/m ² · 24 hr or less, particularly preferably 150 g/m ² · 24 hr or less, preferably 100 g/m ² · 24 hr or less. When the moisture permeability of the base film is in such a range, when used as a protective layer of a polarizing element, a polarizing plate excellent in durability and moisture resistance can be obtained. The tensile strength of the base film is preferably 10 MPa or more and less than 100 MPa, more preferably 30 MPa or more and less than 100 MPa. In the case where it is less than 10 MPa, there is a case where sufficient mechanical strength cannot be exhibited. If it exceeds 100 MPa, the workability may become insufficient. The tensile strength can be measured, for example, in accordance with ASTM-D-882-61T. The tensile elongation of the base film is preferably 1.0% or more, more preferably 3.0% or more, and still more preferably 5.0% or more. The upper limit of the tensile elongation is, for example, 100%. When the tensile elongation rate is less than 1%, the toughness may become insufficient. The tensile elongation can be measured, for example, in accordance with ASTM-D-882-61T. The tensile modulus of elasticity of the base film is preferably 0.5 GPa or more, more preferably 1 GPa or more, and still more preferably 2 GPa or more. The upper limit of the tensile elastic modulus is, for example, 20 GPa. When the tensile modulus of elasticity is less than 0.5 GPa, there are cases where sufficient mechanical strength cannot be exhibited. The tensile modulus of elasticity can be measured, for example, in accordance with ASTM-D-882-61T. The base film may contain any suitable additives depending on the purpose. Specific examples of additives include: ultraviolet absorbers; antioxidants such as hindered phenols, phosphorus, and sulfur; stabilizers such as light-resistant stabilizers, weather-resistant stabilizers, and thermal stabilizers; reinforcing materials such as glass fibers and carbon fibers; Near-infrared absorbers; flame retardants such as tris(dibromopropyl) phosphate, triallyl phosphate, antimony oxide; antistatic agents such as anionic, cationic, and nonionic surfactants; inorganic pigments, organic Colorants such as pigments and dyes; organic fillers or inorganic fillers; resin modifiers; organic fillers or inorganic fillers; plasticizers; lubricants, etc. The additive may be added during the polymerization of the acrylic resin, or may be added during the film formation. The kind, quantity, combination, addition amount, etc. of the additives can be appropriately set depending on the purpose. B-2. Acrylic resin B-2-1. Configuration of acrylic resin As the acrylic resin, any appropriate acrylic resin can be used. The acrylic resin typically contains an alkyl (meth)acrylate as a main component as a monomer unit. In this specification, "(meth)acrylic acid" means acrylic acid and/or methacrylic acid. As the alkyl (meth)acrylate constituting the main skeleton of the acrylic resin, a linear or branched alkyl group having 1 to 18 carbon atoms can be exemplified. These can be used alone or in combination. Furthermore, any appropriate comonomer may be introduced into the acrylic resin by copolymerization. The kind, amount, copolymerization ratio, and the like of such copolymerized monomers can be appropriately set depending on the purpose. The constituent components (monomer units) of the main skeleton of the acrylic resin will be described below with reference to the general formula (2). The acrylic resin preferably has at least one selected from the group consisting of a glutarimide unit, a lactone ring unit, a maleic anhydride unit, a maleimide unit, and a glutaric anhydride unit. The acrylic resin which has a lactone ring unit is described in Unexamined-Japanese-Patent No. 2008-181078, for example, and the description of this gazette is incorporated in this specification as a reference. The glutarimide unit is preferably represented by the following general formula (1): [Chemical 1]

In the general formula (1), R ¹ and R ² each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and R ³ represents a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, and an alkyl group having 3 to 12 carbon atoms. A cycloalkyl group or an aryl group having 6 to 10 carbon atoms. In the general formula (1), it is preferable that R ¹ and R ² are each independently a hydrogen atom or a methyl group, and R ³ is a hydrogen atom, a methyl group, a butyl group or a cyclohexyl group. More preferably, R ¹ is a methyl group, R ² is a hydrogen atom, and R ³ is a methyl group. The above-mentioned alkyl (meth)acrylate is typically represented by the following general formula (2):

In the general formula (2), R ⁴ represents a hydrogen atom or a methyl group, and R ⁵ represents a hydrogen atom, or a substituted aliphatic or alicyclic hydrocarbon group having 1 to 6 carbon atoms. As a substituent, halogen and a hydroxyl group are mentioned, for example. Specific examples of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, 3-butyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, chloromethyl (meth)acrylate, 2-chloroethyl (meth)acrylate, (meth)acrylate ) 2-hydroxyethyl acrylate, 3-hydroxypropyl (meth)acrylate, 2,3,4,5,6-pentahydroxyhexyl (meth)acrylate and 2,3,4 (meth)acrylate, 5-tetrahydroxypentyl ester. In the general formula (2), R ⁵ is preferably a hydrogen atom or a methyl group. Therefore, a particularly preferred alkyl (meth)acrylate is methyl acrylate or methyl methacrylate. The above-mentioned acrylic resin may contain only a single glutarimide unit, or may contain a plurality of glutarimide units in which R ¹ , R ² and R ³ in the general formula (1) are different. The content ratio of the glutarimide unit in the above-mentioned acrylic resin is preferably 2 mol % to 50 mol %, more preferably 2 mol % to 45 mol %, and more preferably 2 mol % to 2 mol %. 40 mol %, preferably 2 mol % to 35 mol %, and most preferably 3 mol % to 30 mol %. If the content ratio is less than 2 mol%, the effects derived from the glutarimide unit (for example, higher optical properties, higher mechanical strength, and excellent polarizing elements may not be fully exhibited) Adhesion and thinning). If the content ratio exceeds 50 mol %, for example, heat resistance and transparency may become insufficient. The above-mentioned acrylic resin may contain only a single (meth)acrylic acid alkyl ester unit, or may contain plural (meth)acrylic acid alkyl ester units in which R ⁴ and R ⁵ in the general formula (2) are different. The content ratio of the alkyl (meth)acrylate unit in the above-mentioned acrylic resin is preferably 50 mol % to 98 mol %, more preferably 55 mol % to 98 mol %, and more preferably 60 mol % Ear% to 98 mol%, preferably 65 mol% to 98 mol%, and most preferably 70 mol% to 97 mol%. If the content ratio is less than 50 mol %, there is a possibility that the effects (for example, higher heat resistance and higher transparency) derived from the alkyl (meth)acrylate unit may not be sufficiently exhibited. If the above-mentioned content ratio exceeds 98 mol %, the resin becomes brittle and easily cracks, and high mechanical strength cannot be sufficiently exhibited, resulting in poor productivity. The said acrylic resin may contain the unit other than a glutarimide unit and an alkyl (meth)acrylate unit. In one embodiment, the acrylic resin may contain, for example, 0 to 10% by weight of unsaturated carboxylic acid units that do not participate in the intramolecular imidization reaction described below. The content ratio of the unsaturated carboxylic acid unit is preferably 0 to 5% by weight, more preferably 0 to 1% by weight. When the content is within such a range, transparency, retention stability, and moisture resistance can be maintained. In one embodiment, the acrylic resin may contain a copolymerizable vinyl monomer unit (other vinyl monomer unit) other than the above. Examples of the other vinyl monomers include acrylonitrile, methacrylonitrile, ethacrylonitrile, allyl glycidyl ether, maleic anhydride, itaconic anhydride, and N-methylmaleic acid. Imide, N-ethylmaleimide, N-cyclohexylmaleimide, aminoethyl acrylate, propylaminoethyl acrylate, dimethylaminoethyl methacrylate Esters, ethylaminopropyl methacrylate, cyclohexylaminoethyl methacrylate, N-vinyldiethylamine, N-acetylvinylamine, allylamine, methallyl Amine, N-Methallylamine, 2-Isopropenyloxazoline, 2-Vinyloxazoline, 2-Propenyloxazoline, N-Phenylmaleimide, Methyl Phenylaminoethyl acrylate, styrene, α-methylstyrene, p-glycidyl styrene, p-aminostyrene, 2-styryl oxazoline, etc. These may be used alone or in combination. Preferred are styrene-based monomers such as styrene and α-methylstyrene. The content ratio of other vinyl monomer units is preferably 0 to 1% by weight, more preferably 0 to 0.1% by weight. If it is such a range, the expression of an undesired phase difference and the fall of transparency can be suppressed. The imidization rate in the above-mentioned acrylic resin is preferably 2.5% to 20.0%. When the imidization ratio is in this range, a resin excellent in heat resistance, transparency, and moldability can be obtained, and the occurrence of scorch and reduction in mechanical strength during film forming can be prevented. In the said acrylic resin, the imidization rate is represented by the ratio of a glutarimide unit and an alkyl (meth)acrylate unit. The ratio can be obtained from, for example, an NMR (nuclear magnetic resonance, nuclear magnetic resonance) spectrum, an IR (infrared, infrared) spectrum of the acrylic resin, and the like. In the present embodiment, the imidization rate can be determined by ¹ H-NMR measurement of resin using ¹ HNMR BRUKER AvanceIII (400 MHz). More specifically, let the peak area of the O-CH ₃ proton derived from alkyl (meth)acrylate in the vicinity of 3.5 to 3.8 ppm be A, and let the peak area of glutarimide derived in the vicinity of 3.0 to 3.3 ppm be A. The peak area of the N-CH ₃ proton is set as B, and is obtained by the following formula. Imidization rate Im(%)={B/(A+B)}×100 The acid value of the above-mentioned acrylic resin is preferably 0.10 mmol/g to 0.50 mmol/g. When the acid value is in such a range, a resin excellent in the balance of heat resistance, mechanical properties, and moldability can be obtained. If the acid value is too small, problems such as increase in cost due to use of a modifier for adjusting to a desired acid value, generation of gel-like substances due to residual modifier, and the like may occur. When the acid value is too large, foaming at the time of film formation (for example, at the time of melt extrusion) tends to easily occur, and the productivity of the formed product tends to decrease. Regarding the above-mentioned acrylic resin, the acid value is the content of the carboxylic acid unit and the carboxylic acid anhydride unit in the acrylic resin. In the present embodiment, the acid value can be calculated by, for example, the titration method described in WO2005/054311 or Japanese Patent Laid-Open No. 2005-23272. The weight average molecular weight of the acrylic resin is preferably 1,000-2,000,000, more preferably 5,000-1,000,000, further preferably 10,000-500,000, particularly preferably 50,000-500,000, and most preferably 60,000-150,000. The weight average molecular weight can be determined in terms of polystyrene using, for example, a gel permeation chromatography (GPC system, manufactured by Tosoh). Furthermore, tetrahydrofuran can be used as a solvent. The Tg (glass transition temperature) of the acrylic resin is preferably 110°C or higher, more preferably 115°C or higher, further preferably 120°C or higher, particularly preferably 125°C or higher, and most preferably 130°C or higher. When Tg is 110 degreeC or more, the polarizing plate containing the base material film obtained from such a resin tends to be excellent in durability. The upper limit of Tg is preferably 300°C or lower, more preferably 290°C or lower, further preferably 285°C or lower, particularly preferably 200°C or lower, and most preferably 160°C or lower. If Tg is in such a range, the formability will be excellent. B-2-2. Polymerization of Acrylic Resin The above acrylic resin can be produced, for example, by the following method. The method comprises: (1) combining the (meth)acrylic acid alkyl ester monomer corresponding to the (meth)acrylic acid alkyl ester unit represented by the general formula (2) with the unsaturated carboxylic acid monomer and/or its The precursor monomer is copolymerized to obtain the copolymer (a); and (II) the copolymer (a) is treated with an imidizing agent, whereby the alkyl (meth)acrylate in the copolymer (a) is carried out Intramolecular imidization reaction between the base ester monomer unit and the unsaturated carboxylic acid monomer and/or its precursor monomer unit, and the glutarimide unit represented by the general formula (1) is introduced into the copolymer middle. Examples of the unsaturated carboxylic acid monomers include acrylic acid, methacrylic acid, crotonic acid, α-substituted acrylic acid, and α-substituted methacrylic acid. Examples of the precursor monomers thereof include acrylamide, methacrylamide, and the like. These may be used alone or in combination. The preferred unsaturated carboxylic acid monomer is acrylic acid or methacrylic acid, and the preferred precursor monomer is acrylamide. As a method of treating the copolymer (a) with an imidizing agent, any appropriate method can be used. As a specific example, the method of using an extruder, and the method of using a batch-type reaction tank (pressure vessel) are mentioned. The method of using an extruder includes heating and melting the copolymer (a) using the extruder, and treating it with an imidizing agent. In this case, as the extruder, any appropriate extruder can be used. Specific examples include a uniaxial extruder, a biaxial extruder, and a multiaxial extruder. Any suitable batch-type reaction tank (pressure vessel) can be used in the method using the batch-type reaction tank (pressure vessel). As the imidizing agent, any appropriate compound can be used as long as the glutarimide unit represented by the above-mentioned general formula (1) can be generated. Specific examples of the imidizing agent include amines containing aliphatic hydrocarbon groups such as methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, tert-butylamine, and n-hexylamine; aniline, Amines containing aromatic hydrocarbon groups such as benzylamine, toluidine, trichloroaniline; amines containing alicyclic hydrocarbon groups such as cyclohexylamine. Furthermore, for example, a urea-based compound which generates such an amine by heating can also be used. As a urea compound, urea, 1, 3- dimethyl urea, 1, 3- diethyl urea, and 1, 3- dipropyl urea are mentioned, for example. The imidizing agent is preferably methylamine, ammonia, and cyclohexylamine, more preferably methylamine. In the imidization, in addition to the imidization agent described above, a ring-closure accelerator may also be added as required. The usage-amount of the imidizing agent in the imidization is preferably 0.5 to 10 parts by weight, more preferably 0.5 to 6 parts by weight relative to 100 parts by weight of the copolymer (a). If the usage-amount of the imidization agent is less than 0.5 parts by weight, there are many cases where the desired imidization rate is not achieved. As a result, the heat resistance of the obtained resin becomes extremely insufficient, and appearance defects such as burnt after molding may be induced. If the amount of the imidizing agent used exceeds 10 parts by weight, the imidizing agent may remain in the resin, and the imidizing agent may induce appearance defects such as burnt after molding or foaming. In addition to the above-mentioned imidization, the production method of the present embodiment may include, if necessary, a treatment with an esterification agent. Examples of the esterification agent include dimethyl carbonate, 2,2-dimethoxypropane, dimethyl sulfoxide, triethyl orthoformate, trimethyl orthoacetate, trimethyl orthoformate, dicarbonate Phenyl ester, dimethyl sulfate, methyl tosylate, methyl triflate, methyl acetate, methanol, ethanol, methyl isocyanate, p-chlorophenyl isocyanate, dimethylcarbodiamide Imine, dimethyl tert-butyl silyl chloride, isopropenyl acetate, dimethyl urea, tetramethyl ammonium hydroxide, dimethyl diethoxy silane, tetra-n-butoxy silane, phosphorous acid Dimethyl (trimethylsilyl) ester, trimethyl phosphite, trimethyl phosphate, tricresyl phosphate, diazomethane, ethylene oxide, propylene oxide, cyclohexane oxide, 2- Ethylhexyl glycidyl ether, phenyl glycidyl ether, benzyl glycidyl ether. Among these, from the viewpoints of cost, reactivity, etc., dimethyl carbonate is preferred. The addition amount of the esterification agent can be set so that the acid value of an acrylic resin may become a desired value. B-2-3. Combination of other resins In the embodiment of the present invention, the above-mentioned acrylic resin and other resins may be used in combination. That is, the monomer components constituting the acrylic resin and the monomer components constituting other resins may be copolymerized, and the copolymer may be used for the film formation described in the following item B-4; the acrylic resin may also be mixed with other resins. A blend of resins is used for film formation. Examples of other resins include styrene-based resins, polyethylene, polypropylene, polyamide, polyphenylene sulfide, polyether ether ketone, polyester, polysiloxane, polyphenylene ether, polyacetal, and polyamide Other thermoplastic resins such as amine and polyetherimide; thermosetting resins such as phenolic resins, melamine-based resins, polyester-based resins, polysiloxane-based resins, and epoxy-based resins. The type and compounding amount of the resin to be used in combination are appropriately set depending on the purpose, the properties expected for the film to be obtained, and the like. For example, a styrene-based resin (preferably an acrylonitrile-styrene copolymer) can be used in combination as a retardation control agent. When the acrylic resin is used together with other resins, the content of the acrylic resin in the blend of the acrylic resin and other resins is preferably 50% by weight to 100% by weight, more preferably 60% by weight to 100% by weight %, more preferably 70% by weight to 100% by weight, particularly preferably 80% by weight to 100% by weight. When the content is less than 50% by weight, the high heat resistance and high transparency inherent in the acrylic resin may not be sufficiently reflected. B-3. Core-Shell Particles In the above-mentioned base film, the core-shell particles are preferably 5 to 50 parts by weight, more preferably 5 to 40 parts by weight relative to 100 parts by weight of the acrylic resin. parts by weight. In this way, when the surface treatment layer is formed on the base film, the penetration of the composition for forming the surface treatment layer into the base film can be further promoted, and an optical fiber with high adhesion between the base film and the surface treatment layer can be obtained. membrane. The core-shell type particle typically has a core containing a rubbery polymer, and a coating layer containing a glassy polymer and covering the core. The core-shell type particle has one or more layers containing a glassy polymer as the innermost layer or the middle layer. The Tg of the rubber-like polymer constituting the core is preferably 20°C or lower, more preferably -60°C to 20°C, and still more preferably -60°C to 10°C. If the Tg of the rubbery polymer constituting the core exceeds 20° C., there is a possibility that the improvement of the mechanical strength of the acrylic resin will be insufficient. The Tg of the glassy polymer (hard polymer) constituting the coating layer is preferably 50°C or higher, more preferably 50°C to 140°C, and still more preferably 60°C to 130°C. When Tg of the glassy polymer which comprises a coating layer is lower than 50 degreeC, there exists a possibility that the heat resistance of an acrylic resin may fall. The content ratio of the core in the core-shell type particle is preferably 30 to 95% by weight, more preferably 50 to 90% by weight. The ratio of the glassy polymer layer in the core is 0 to 60 wt %, preferably 0 to 45 wt %, and more preferably 10 to 40 wt % with respect to 100 wt % of the total core. The content ratio of the coating layer in the core-shell type particle is preferably 5 to 70% by weight, more preferably 10 to 50% by weight. In one embodiment, the core-shell particles dispersed in the acrylic resin may have a flat shape. Core-shell particles can be flattened by stretching as described in item B-4 below. The length/thickness ratio of the flattened core-shell particles is 7.0 or less. The length/thickness ratio is preferably 6.5 or less, more preferably 6.3 or less. On the other hand, the ratio of length/thickness is preferably 4.0 or more, more preferably 4.5 or more, and still more preferably 5.0 or more. In this specification, "length/thickness ratio" means the ratio of the representative length and thickness of the top view shape of a core-shell particle. Here, the so-called "representative length" refers to the diameter in the case of a circular shape in plan view, the long diameter in the case of an ellipse, and the length of the diagonal in the case of a rectangle or a polygon. This ratio can be calculated|required by the following procedure, for example. The film section obtained is photographed using a transmission electron microscope (eg, accelerating voltage 80 kV, RuO4 _- stained ultrathin sectioning), from the longer of the core-shell particles present in the obtained photograph (obtained 30 are selected in sequence from the cross-sections that are close to the representative length, and (average value of length)/(average value of thickness) are calculated, thereby obtaining the ratio. Details of the rubber-like polymer constituting the core of the core-shell particle, the glass-like polymer (hard polymer) constituting the coating layer, the polymerization method of these, and other structures are described in, for example, Japanese Patent Laid-Open No. 2016-33552 Gazette. The description of this gazette is incorporated in this specification as a reference. B-4. Formation of base film The base film according to the embodiment of the present invention can be represented by including the above-mentioned acrylic resin (in the case of using other resin in combination, it is a blend with the other resin) And the composition of the core-shell particle is formed by the method of forming a film. Further, the method of forming the substrate film may include extending the above-described film. The average particle diameter of the core-shell particles used for film formation is preferably 1 nm to 500 nm. The average particle size of the core is preferably 50 nm to 300 nm, more preferably 70 nm to 300 nm. As a method of forming the film, any appropriate method can be adopted. Specific examples include casting coating method (eg, casting method), extrusion molding method, injection molding method, compression molding method, transfer molding method, blow molding method, powder molding method, FRP (Fiber Reinforced) Plastic, fiber reinforced plastic) forming method, calendering method, hot pressing method. The extrusion molding method or the casting coating method is preferable. The reason is that the smoothness of the obtained film can be improved, and good optical uniformity can be obtained. Particularly preferred is the extrusion molding method. The reason for this is that there is no need to consider the problem caused by the residual solvent. Among them, the extrusion molding method using a T-die is preferable from the viewpoint of the productivity of the film and the ease of the subsequent stretching process. The molding conditions can be appropriately set according to the composition and type of the resin to be used, the desired properties of the film to be obtained, and the like. As the stretching method, any suitable stretching method and stretching conditions (eg, stretching temperature, stretching ratio, stretching speed, stretching direction) can be adopted. Specific examples of the stretching method include free-end stretching, fixed-end stretching, free-end shrinking, and fixed-end shrinking. These may be used individually, may be used simultaneously, or may be used sequentially. When the surface treatment layer is formed on the obtained base film, the formation of the film can be further accelerated by extending the film in which the compounding amount of the core-shell particles to the acrylic resin has been appropriately adjusted under suitable extending conditions. The permeation of the composition of the surface treatment layer to the base film can obtain an optical film with high adhesion between the base film and the surface treatment layer. The extending direction may be an appropriate direction depending on the purpose. Specifically, a longitudinal direction, a width direction, a thickness direction, and an oblique direction are mentioned. The extension direction may be one direction (uniaxial extension), two directions (biaxial extension), or three or more directions. In the embodiment of the present invention, typically, uniaxial stretching in the longitudinal direction, simultaneous biaxial stretching in the longitudinal and width directions, and sequential biaxial stretching in the longitudinal and width directions can be employed. Biaxial extension (simultaneous or sequential) is preferred. The reason for this is that it is easy to control the in-plane retardation and to realize optical isotropy. The stretching temperature can be determined according to the expected optical properties, mechanical properties and thickness of the base film, the type of resin used, the thickness of the film used, the stretching method (uniaxial stretching or biaxial stretching), the stretching ratio, and the stretching speed. etc. to change. Specifically, the stretching temperature is preferably Tg to Tg+50°C, more preferably Tg+15°C to Tg+50°C, and most preferably Tg+35°C to Tg+50°C. By extending at such a temperature, a base film having suitable properties can be obtained. The specific stretching temperature is, for example, 110°C to 200°C, preferably 120°C to 190°C, and more preferably 150°C to 190°C. If the stretching temperature is in this range, by appropriately adjusting the stretching ratio and the stretching speed, when the surface treatment layer is formed on the obtained base film, the composition for forming the surface treatment layer can be further accelerated to the base material. Through the penetration of the film, an optical film with high adhesion between the base film and the surface treatment layer can be obtained. In addition, the stretching ratio, like the stretching temperature, can vary depending on the optical properties, mechanical properties and thickness, the type of resin used, the thickness of the film used, the stretching method (uniaxial stretching or biaxial stretching), the stretching temperature, the stretching speed, etc. In the case of biaxial stretching, the ratio (TD/MD) of the stretching ratio in the width direction (TD) to the stretching ratio in the longitudinal direction (MD) is preferably 1.0-1.5, more preferably 1.0-1.4, and more preferably is 1.0 to 1.3. In addition, the area magnification (the product of the stretching magnification in the longitudinal direction and the stretching magnification in the width direction) in the case of biaxial stretching is preferably 2.0 to 6.0, more preferably 3.0 to 5.5, and still more preferably 3.5 to 5.2. If the stretching ratio is in this range, by appropriately adjusting the stretching temperature and the stretching speed, when the surface treatment layer is formed on the obtained base film, the composition for forming the surface treatment layer can be further promoted to the base film. Through the penetration, an optical film with high adhesion between the base film and the surface treatment layer can be obtained. In addition, the stretching speed, like the stretching temperature, may vary depending on the optical properties, mechanical properties and thickness, the type of resin used, the thickness of the film used, the stretching method (uniaxial stretching or biaxial stretching), the stretching temperature, the stretching magnification, etc. The extension speed is preferably 3%/sec to 20%/sec, more preferably 3%/sec to 15%/sec, and still more preferably 3%/sec to 10%/sec. In the case of biaxial extension, the extension speed in one direction and the extension speed in the other direction may be the same or different. If the stretching speed is in this range, by appropriately adjusting the stretching temperature and the stretching ratio, when the surface treatment layer is formed on the obtained base film, the composition for forming the surface treatment layer can be further accelerated to the base film. Through the penetration, an optical film with high adhesion between the base film and the surface treatment layer can be obtained. The base film can be formed in the above-described manner. C. Surface Treatment Layer The surface treatment layer is any suitable functional layer formed on one side of the base film according to the function required for the optical film. As a specific example of a surface treatment layer, a hard-coat layer, an anti-glare layer, an antireflection layer, etc. are mentioned. The thickness of the surface treatment layer is preferably 3 μm to 20 μm, more preferably 5 μm to 15 μm. The surface treatment layer is typically a hardened layer of the resin composition formed on the base film. The step of forming the surface treatment layer may include: coating the resin composition for forming the surface treatment layer on the base film to form a coating layer; and drying and curing the coating layer to form the surface treatment layer. Drying and hardening the coating layer may include heating the coating layer. As a coating method of the resin composition, any appropriate method can be adopted. For example, bar coating method, roll coating method, gravure coating method, bar coating method, slot coating method, curtain coating method, spray coating method, corner coating method Wheel coating method. From the viewpoint of facilitating coating, the resin composition preferably contains a solvent for dilution. The heating temperature of the coating layer can be set to any appropriate temperature corresponding to the composition of the resin composition, and it is preferably set to be equal to or lower than the glass transition temperature of the acrylic resin contained in the base film. When heating is performed at a temperature lower than or equal to the glass transition temperature of the acrylic resin contained in the base film, an optical film in which deformation due to heating is suppressed can be obtained. The heating temperature of the coating layer is, for example, 50°C to 140°C, preferably 60°C to 100°C. By heating at such a heating temperature, the optical film excellent in the adhesiveness of a base film and a surface treatment layer can be obtained. C-1. Hard coat layer The hard coat layer is a layer that imparts scratch resistance and chemical resistance to the surface of the base film. The hard coat layer has a hardness of preferably H or more, more preferably 3H or more in a pencil hardness test. The pencil hardness test can be measured according to JIS K 5400. The resin composition for forming a hard coat layer may contain, for example, a curable compound that can be cured by heat, light (ultraviolet rays, etc.), electron beams, or the like. Details of the hard coat layer and the resin composition for forming the hard coat layer are described in, for example, Japanese Patent Laid-Open No. 2014-240955. The entire description of this gazette is incorporated herein by reference. C-2. Anti-glare layer The anti-glare layer is a layer for preventing reflection of external light by scattering and reflecting light. The resin composition for antiglare layer formation can contain, for example, a curable compound that can be cured by heat, light (ultraviolet rays, etc.), electron beams, or the like. The anti-glare layer typically has a fine concavo-convex shape on the surface. As a method of forming such a fine concavo-convex shape, for example, a method of containing fine particles in the above-mentioned curable compound can be mentioned. Details of the anti-glare layer and the resin composition for forming the anti-glare layer are described in, for example, Japanese Patent Laid-Open No. 2017-32711. The entire description of this gazette is incorporated herein by reference. C-3. Anti-reflection layer The anti-reflection layer is a layer used to prevent the reflection of external light. The resin composition for antireflection layer formation may contain, for example, a curable compound that can be cured by heat, light (ultraviolet rays, etc.), electron beams, or the like. The antireflection layer may be a single layer composed of only one layer, or may be a plurality of layers including two or more layers. Details of the antireflection layer and the resin composition for forming the antireflection layer are described in, for example, Japanese Patent Laid-Open No. 2012-155050. The entire description of this gazette is incorporated herein by reference. D. Polarizing Plate The optical films described in the above items A to C can be applied to polarizing plates. Therefore, the present invention also includes a polarizing plate using such an optical film. Typically, the polarizing plate has a polarizing element and the optical film of the present invention arranged on one side of the polarizing element. The optical film can function as a protective layer of the polarizing element by bonding the base film side with the polarizing element. As the polarizing element, any suitable polarizing element can be used. For example, the resin film forming the polarizing element may be a single-layer resin film, or may be a laminate of two or more layers. Specific examples of polarizers including a single-layer resin film include hydrophilic polymers such as polyvinyl alcohol (PVA)-based films, partially formalized PVA-based films, and ethylene-vinyl acetate copolymer-based partially saponified films. The film is obtained by dyeing and stretching treatment with dichroic substances such as iodine or dichroic dyes; polyene-based alignment films such as dehydration products of PVA or dehydrochlorination products of polyvinyl chloride, etc. In terms of excellent optical properties, it is preferable to use a polarizing element obtained by uniaxially extending a PVA-based film by dyeing with iodine. The above-mentioned dyeing with iodine is performed, for example, by immersing the PVA-based film in an aqueous iodine solution. The stretching ratio of the above-mentioned uniaxial stretching is preferably 3 to 7 times. The stretching may be carried out after the dyeing treatment, or may be carried out while dyeing. Moreover, you may dye it after extending|stretching. The PVA-based film is subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment, and the like as necessary. For example, by immersing the PVA film in water and washing it before dyeing, not only the dirt and anti-blocking agent on the surface of the PVA film can be removed, but also the PVA film can be swelled to prevent uneven dyeing. Specific examples of the polarizing element obtained by using the laminate include a laminate using a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a resin substrate and coating formed on A polarizing element obtained by a laminate of PVA-based resin layers of the resin substrate. A polarizing element obtained by using a laminate of a resin substrate and coating a PVA-based resin layer formed on the resin substrate can be produced, for example, by the following method: apply a PVA-based resin solution to a resin substrate, dry it, and A PVA-based resin layer is formed on the resin substrate to obtain a laminate of the resin substrate and the PVA-based resin layer; the laminate is stretched and dyed to form the PVA-based resin layer into a polarizer. In the present embodiment, the stretching typically involves immersing the layered body in a boric acid aqueous solution for stretching. Further, the stretching may further include performing in-air stretching of the laminate at a high temperature (eg, 95° C. or higher) before stretching in a boric acid aqueous solution, if necessary. The obtained laminate of resin substrate/polarizer can be used as it is (that is, the resin substrate can be used as a protective layer of the polarizer), or the resin substrate can be peeled off from the laminate of resin substrate/polarizer, Any suitable protective layer suitable for the purpose of the peeling area layer is used. The details of the manufacturing method of such a polarizing element are described in, for example, Japanese Patent Laid-Open No. 2012-73580. The entire description of this gazette is incorporated herein by reference. The thickness of the polarizing element is, for example, 1 μm to 80 μm. In one embodiment, the thickness of the polarizing element is preferably 1 μm to 20 μm, and more preferably 3 μm to 15 μm. E. Image Display Device The polarizing plate described in the above item D can be applied to an image display device. Therefore, the present invention also includes an image display device using such a polarizing plate. Typical examples of the image display device include a liquid crystal display device and an organic electroluminescence (EL) display device. The image display device adopts a well-known structure in the industry, so detailed description is omitted. EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. The measurement method of each characteristic is as follows. In addition, unless otherwise specified, "parts" and "%" in the examples are based on weight. (1) Maximum elongation of base film (TMA measurement) The base film was cut to a size of 4 mm in width x 20 mm in length to prepare a measurement sample with an initial length of 20 mm. Furthermore, the measurement sample A obtained by cutting so that the longitudinal direction of the base film becomes the longitudinal direction, and the measurement sample A obtained by cutting so that the direction orthogonal to the longitudinal direction of the base film becomes the longitudinal direction are prepared. Measure sample B. For measurement sample A and measurement sample B, a thermomechanical analyzer (manufactured by Hitachi High-Tech Science, model "TMA7100") was used, respectively, and the measurement sample was mounted on a measurement jig, while applying 98 mN/ The tensile load for min was heated from 24°C to 150°C at 5°C/min, and the maximum elongation at this time until the softening point was measured. In addition, the maximum elongation was calculated using the following formula. Maximum elongation (%) = (sample length at maximum elongation - initial sample length)/initial sample length × 100 The maximum elongation of the measured sample A corresponds to the maximum elongation of the substrate film in the longitudinal direction, and the measured sample B The maximum elongation ratio corresponds to the maximum elongation ratio in the short-side direction (direction orthogonal to the long-side direction) of the base film. (2) Adhesion evaluation The adhesion of the surface treatment layer to the base film was evaluated according to the grid peeling test of JIS K-5400 (number of grids: 100), and was determined by the following indexes. ○: The number of grid peelings is 0 ×: The number of grid peelings is 1 or more <Production Example 1> The following compositions A to C were prepared as resin compositions for surface treatment layer formation. (1) Composition A 16 parts by weight of 4-HBA (4-hydroxybutyl acrylate, 4-hydroxybutyl acrylate) (manufactured by Osaka Organic Chemical Industry Co., Ltd.), NK oligo UA-53H-80BK (Shin Nakamura Chemical Industry Co., Ltd.) Co., Ltd.) 32 parts by weight, Viscoat #300 (manufactured by Osaka Organic Chemical Industry Co., Ltd.) 48 parts by weight, A-GLY-9E (manufactured by Shin-Nakamura Chemical Co., Ltd.) 4 parts by weight, and IRGACURE 907 (BASF Production) 2.4 parts by weight were mixed, and the solid content concentration was 42.0% by a solvent of MIBK (methyl isobutyl ketone, methyl isobutyl ketone): PGM (Propylene glycol monomethyl ether, propylene glycol monomethyl ether) = 50:50. The UV curable resin obtained by diluting in this way. (2) Composition B 100 parts by weight of Viscoat #300 (manufactured by Osaka Organic Chemical Industry Co., Ltd.) and 2.4 parts by weight of IRGACURE 907 (manufactured by BASF) were mixed, and the mixture was solidified with a solvent of MIBK:PGM=50:50. UV curable resin obtained by diluting so that the concentration of the chemical components becomes 42.0%. (3) Composition C 20 parts by weight of 4-HBA (manufactured by Osaka Organic Chemical Industry Co., Ltd.), 40 parts by weight of NK oligomer UA-53H-80BK (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.), Viscoat #300 ( 60 parts by weight of Osaka Organic Chemical Industry Co., Ltd., 5 parts by weight of IRGACURE 907 (manufactured by BASF), and 0.5 parts by weight of Techpolymer SSX-103DXE (manufactured by Sekisui Chemical Industry Co., Ltd.) were mixed with toluene: MEK (methyl ethyl ketone, methyl ethyl ketone) = 70:30 of the UV curable resin obtained by diluting the solvent so that the solid content concentration may be 40.0%. <Example 1> 1. Preparation of base film MS resin (MS-200; copolymer of methyl methacrylate/styrene (mol ratio) = 80/20, Nippon Steel Chemicals) was prepared using monomethylamine. Co., Ltd. product) imidization was performed (imidation rate: 5%). The obtained imidized MS resin has glutarimide units represented by the general formula (1) (R ¹ and R ³ are methyl groups, R ² is a hydrogen atom), and ( Meth)acrylate units (R ⁴ and R ⁵ are methyl groups), and styrene units. In addition, the above-mentioned imidization was carried out using a meshing type co-rotating twin-screw extruder with a diameter of 15 mm. The set temperature of each tempering zone of the extruder was set to 230° C., the screw speed was set to 150 rpm, and the MS resin was supplied at 2.0 kg/hr. The supply amount of monomethylamine was based on 100 parts by weight of the MS resin. 2 parts by weight. The MS resin was injected from the hopper, and after the resin was melted and filled by the kneading stage, monomethylamine was injected from the nozzle. A sealing ring was installed at the end of the reaction zone to fill the resin. The pressure of the exhaust port was reduced to -0.08 MPa to remove the by-products and excess methylamine after the reaction to remove volatiles. The resin discharged from the die set at the outlet of the extruder in the form of strands is cooled in a water tank, and then pelletized by a pelletizer. The imidization rate of the obtained imidized MS resin was 5.0%, and the acid value was 0.5 mmol/g. 100 parts by weight of the imidized MS resin obtained above and 10 parts by weight of the core-shell particles were put into a uniaxial extruder, melt-mixed, and passed through a T-die to form a film to obtain an extruded film. The obtained extruded film was simultaneously biaxially stretched by 2 times in the longitudinal direction and the width direction at a stretching temperature of 160°C. The extension speed was 10%/sec in both the longitudinal direction and the width direction. Thereby, the base film A was produced. The thickness of the obtained base film A was 30 μm. The maximum elongation in the long-side direction and the maximum elongation in the short-side direction of the base film A were measured. The results are shown in Table 1. 2. Production of optical film The composition A was applied to one side of the above-mentioned base film A so that the thickness after curing was 6 μm to form a coating layer. Then, the said coating layer was dried at 70 degreeC, and UV hardening was performed, and the optical film 1 in which the hard-coat layer was formed in the one side of the base film A was obtained. The said optical film 1 was used for adhesiveness evaluation. The results are shown in Table 1. <Example 2> It was obtained in the same manner as in Example 1, except that the composition B was coated on one side of the above-mentioned base film A, and dried and hardened to form a hard coat layer. The optical film 2 having a hard coat layer is formed on one side of A. The said optical film 2 was used for adhesiveness evaluation. The results are shown in Table 1. <Example 3> A single side of the base film A was obtained in the same manner as in Example 1, except that the composition C was applied to one side of the base film A and cured to form an anti-glare layer. An optical film 3 with an anti-glare layer is formed on the side. The said optical film 3 was used for adhesiveness evaluation. The results are shown in Table 1. <Example 4> 1. Preparation of base film The same procedure as in Example 1 was carried out, except that the blending amount of the core-shell particles was 15 parts by weight, and the stretching temperature of the extruded film was 152° C. The base film B was produced in the same manner. The maximum elongation in the long-side direction and the maximum elongation in the short-side direction of the base film B were measured. The results are shown in Table 1. 2. Preparation of optical film Except having used the said base film B, it carried out similarly to Example 1, and obtained the optical film 4 which formed the hard-coat layer on one side of the base film B. The said optical film 4 was used for adhesiveness evaluation. The results are shown in Table 1. <Example 5> 1. Preparation of base film 100 parts by weight of the imidized MS resin obtained above and 10 parts by weight of core-shell type particles were put into a uniaxial extruder, melt-mixed, and passed through a T-die. Film formation was performed, whereby an extruded film was obtained. The obtained extruded film was simultaneously biaxially stretched by 2 times in the longitudinal direction and the width direction at a stretching temperature of 160°C. The extension speed was 10%/sec in both the longitudinal direction and the width direction. Thereby, the base film C was produced. The thickness of the obtained base film C was 40 μm. The maximum elongation in the long-side direction and the maximum elongation in the short-side direction of the base film C were measured. The results are shown in Table 1. 2. Preparation of optical film Except having used the said base film C, it carried out similarly to Example 1, and obtained the optical film 5 which formed the hard-coat layer on one side of the base film C. The said optical film 5 was used for adhesiveness evaluation. The results are shown in Table 1. <Example 6> 1. Preparation of base film 100 parts by weight of the imidized MS resin obtained above and 10 parts by weight of core-shell particles were put into a uniaxial extruder, melt-mixed, and passed through a T-die. Film formation was performed, whereby an extruded film was obtained. The obtained extruded film was simultaneously biaxially stretched by 2 times in the longitudinal direction and the width direction at a stretching temperature of 160°C. The extension speed was 10%/sec in both the longitudinal direction and the width direction. Thereby, the base film D was produced. The thickness of the obtained base film D was 35 μm. The maximum elongation in the long-side direction and the maximum elongation in the short-side direction of the base film D were measured. The results are shown in Table 1. 2. Production of Optical Film The optical film 6 in which the hard coat layer was formed on one side of the base film D was obtained in the same manner as in Example 1, except that the above-mentioned base film D was used. The said optical film 6 was used for adhesiveness evaluation. The results are shown in Table 1. <Example 7> 1. Production of base film A base film E was produced in the same manner as in Example 1, except that the stretching temperature of the extrusion film was set to 150°C. The maximum elongation in the long-side direction and the maximum elongation in the short-side direction of the base film E were measured. The results are shown in Table 1. 2. Preparation of optical film Except having used the said base film E, it carried out similarly to Example 1, and obtained the optical film 7 which formed the hard-coat layer on one side of the base film E. The said optical film 7 was used for adhesiveness evaluation. The results are shown in Table 1. <Example 8> 1. Preparation of base film The same procedure as in Example 1 was carried out, except that the blending amount of the core-shell particles was 23 parts by weight, and the stretching temperature of the extruded film was 152° C. The base film F was produced by the method. The maximum elongation in the long-side direction and the maximum elongation in the short-side direction of the base film F were measured. The results are shown in Table 1. 2. Preparation of optical film Except having used the said base film F, it carried out similarly to Example 1, and obtained the optical film 8 which formed the hard-coat layer on one side of the base film F. The said optical film 8 was used for adhesiveness evaluation. The results are shown in Table 1. <Example 9> 1. Production of base film A base film G was produced in the same manner as in Example 1, except that the core-shell particles were not prepared. The maximum elongation in the long-side direction and the maximum elongation in the short-side direction of the base film G were measured. The results are shown in Table 1. 2. Preparation of optical film Except having used the said base film G, it carried out similarly to Example 1, and obtained the optical film 9 which formed the hard-coat layer on one side of the base film G. The said optical film 9 was used for adhesiveness evaluation. The results are shown in Table 1. <Example 10> 1. Production of base film A base film H was produced in the same manner as in Example 1, except that the stretching temperature of the extrusion film was set to 140°C. The maximum elongation in the long-side direction and the maximum elongation in the short-side direction of the base film H were measured. The results are shown in Table 1. 2. Production of Optical Film The optical film 10 in which the hard coat layer was formed on one side of the base film H was obtained in the same manner as in Example 1, except that the above-mentioned base film H was used. The said optical film 10 was used for adhesiveness evaluation. The results are shown in Table 1. <Example 11> 1. Preparation of base film The same procedure as in Example 1 was carried out, except that the blending amount of the core-shell particles was 23 parts by weight and the stretching temperature of the extruded film was 137° C. The base film I was produced in the same manner. The maximum elongation in the long-side direction and the maximum elongation in the short-side direction of the base film I were measured. The results are shown in Table 1. 2. Production of Optical Film The optical film 11 in which the hard coat layer was formed on one side of the base film 1 was obtained in the same manner as in Example 1, except that the above-mentioned base film I was used. The said optical film 11 was used for adhesiveness evaluation. The results are shown in Table 1. <Example 12> 1. Preparation of base film A base film J was produced in the same manner as in Example 1, except that the core-shell particles were not prepared and the stretching temperature of the extrusion film was set to 155°C. The maximum elongation in the long-side direction and the maximum elongation in the short-side direction of the base film J were measured. The results are shown in Table 1. 2. Production of Optical Film The optical film 12 in which the hard coat layer was formed on one side of the base film J was obtained in the same manner as in Example 1, except that the above-mentioned base film J was used. The said optical film 12 was used for adhesiveness evaluation. The results are shown in Table 1. <Example 13> 1. Production of base film The same procedure as in Example 1 was carried out, except that the blending amount of the core-shell particles was set to 5 parts by weight, and the stretching temperature of the extruded film was set to 140° C. The base film K is produced by the method. The maximum elongation in the long-side direction and the maximum elongation in the short-side direction of the base film K were measured. The results are shown in Table 1. 2. Production of Optical Film The optical film 13 in which the hard coat layer was formed on one side of the base film K was obtained in the same manner as in Example 1, except that the above-mentioned base film K was used. The said optical film 13 was used for adhesiveness evaluation. The results are shown in Table 1. <Example 14> 1. Preparation of base film A base film L was produced in the same manner as in Example 1, except that the core-shell particles were not prepared and the stretching temperature of the extruded film was set to 150°C. The maximum elongation in the long-side direction and the maximum elongation in the short-side direction of the base film L were measured. The results are shown in Table 1. 2. Production of Optical Film The optical film 14 in which the hard coat layer was formed on one side of the base film L was obtained in the same manner as in Example 1 except that the above-mentioned base film L was used. The said optical film 14 was used for adhesiveness evaluation. The results are shown in Table 1. <Comparative Example 1> 1. Preparation of base film The same procedure as in Example 1 was carried out, except that the blending amount of the core-shell particles was set to 3 parts by weight, and the stretching temperature of the extruded film was set to 140° C. The base film M was produced by the method. The maximum elongation in the long-side direction and the maximum elongation in the short-side direction of the base film M were measured. The results are shown in Table 1. 2. Production of Optical Film The optical film 15 in which the hard coat layer was formed on one side of the base film M was obtained in the same manner as in Example 1, except that the above-mentioned base film M was used. The said optical film 15 was used for adhesiveness evaluation. The results are shown in Table 1. <Comparative example 2> 1. Preparation of base film A base film N was produced in the same manner as in Example 1, except that the core-shell particles were not prepared and the stretching temperature of the extrusion film was set to 140°C. The maximum elongation in the long-side direction and the maximum elongation in the short-side direction of the base film N were measured. The results are shown in Table 1. 2. Production of Optical Film The optical film 16 in which the hard coat layer was formed on one side of the base film N was obtained in the same manner as in Example 1, except that the above-mentioned base film N was used. The said optical film 16 was used for adhesiveness evaluation. The results are shown in Table 1. <Comparative example 3> It was obtained in the same manner as in Comparative Example 2, except that the composition B was coated on one side of the above-mentioned base film N, and dried and hardened to form a hard coat layer. The optical film 17 of the hard coat layer is formed on one side of N. The said optical film 17 was used for adhesiveness evaluation. The results are shown in Table 1. <Comparative Example 4> It was obtained in the same manner as in Comparative Example 2, except that the composition C was applied to one side of the above-mentioned base film N, and dried and cured to form an anti-glare layer. The optical film 18 of the anti-glare layer is formed on one side of N. The said optical film 18 was used for adhesiveness evaluation. The results are shown in Table 1. <Comparative example 5> 1. Preparation of base film A base film O was produced in the same manner as in Example 1, except that the core-shell particles were not prepared and the stretching temperature of the extruded film was set to 130°C. The maximum elongation in the long-side direction and the maximum elongation in the short-side direction of the base film O were measured. The results are shown in Table 1. 2. Preparation of Optical Film The optical film 19 in which the hard coat layer was formed on one side of the base film O was obtained in the same manner as in Example 1, except that the above-mentioned base film O was used. The said optical film 19 was used for adhesiveness evaluation. The results are shown in Table 1. [Table 1]

As can be seen from Table 1, in the optical films of Examples 1 to 14 in which at least one of the maximum elongation in the long-side direction and the maximum elongation in the short-side direction was used as a substrate film of 0.40% or more, the surface treatment layer to the substrate film The tightness is high. [Industrial Applicability] The optical film of the present invention can be suitably used as a protective layer of a polarizing element. The polarizing plate having the optical film of the present invention as a protective layer can be suitably used for an image display device. The image display device as described above can be used for portable devices such as portable information terminals (PDAs), smart phones, mobile phones, clocks, digital cameras, and portable game consoles; computer monitors, notebook computers, etc. OA equipment such as photocopiers; home electrical equipment such as camcorders, televisions, microwave ovens; rear monitors, monitors for car navigation systems, car audio and other in-vehicle equipment; digital signage, information displays for commercial stores, etc. Equipment; security equipment such as monitoring monitors; nursing care and medical equipment such as nursing care monitors and medical monitors.

10‧‧‧Substrate film20‧‧‧Surface treatment layer100‧‧‧Optical film

FIG. 1 is a schematic cross-sectional view of an optical film according to an embodiment of the present invention.

10‧‧‧Substrate film

20‧‧‧Surface treatment layer

100‧‧‧Optical Film

Claims (8)

An optical film comprising a base film as a stretched film containing an acrylic resin, and a surface treatment layer formed on one side of the base film, and the base film in the above-mentioned optical film is applied with 98 mN/ The maximum elongation up to the softening point is 0.40% or more in the TMA measurement of heating from 24°C to 150°C at 5°C/min under tensile load for min. The optical film according to claim 1, wherein the base film contains the acrylic resin and core-shell particles dispersed in the acrylic resin. The optical film according to claim 2, wherein the base film contains 5 parts by weight to 50 parts by weight of the core-shell particles with respect to 100 parts by weight of the acrylic resin. The optical film according to any one of claims 1 to 3, wherein the above-mentioned acrylic resin has a unit selected from the group consisting of a glutarimide unit, a lactone ring unit, a maleic anhydride unit, a maleimide unit, and At least one of the group consisting of glutaric anhydride units. The optical film according to any one of claims 1 to 3, wherein the surface treatment layer is a hardened layer of the resin composition coated on the base film. The optical film according to any one of claims 1 to 3, wherein the surface treatment layer is at least one selected from the group consisting of a hard coat layer, an antiglare layer, and an antireflection layer. A polarizing plate comprising a polarizing element and a protective layer disposed on one side of the polarizing element, wherein the protective layer is the optical film according to any one of claims 1 to 6. An image display device including the polarizing plate as claimed in claim 7.

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