TW202132433A - Method for producing optical polyvinyl alcohol film - Google Patents

Method for producing optical polyvinyl alcohol film Download PDF

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TW202132433A
TW202132433A TW109143579A TW109143579A TW202132433A TW 202132433 A TW202132433 A TW 202132433A TW 109143579 A TW109143579 A TW 109143579A TW 109143579 A TW109143579 A TW 109143579A TW 202132433 A TW202132433 A TW 202132433A
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film
drying
drying drum
pva
drum
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TW109143579A
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Chinese (zh)
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川嶋宏希
梅本涼平
高藤勝啟
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日商可樂麗股份有限公司
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
    • B29D11/00—Producing optical elements, e.g. lenses or prisms
    • B29D11/0074—Production of other optical elements not provided for in B29D11/00009- B29D11/0073
    • B29D11/00788—Producing optical films
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C41/00—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor
    • B29C41/24—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor for making articles of indefinite length
    • B29C41/26—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor for making articles of indefinite length by depositing flowable material on a rotating drum
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C41/00—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor
    • B29C41/34—Component parts, details or accessories; Auxiliary operations
    • B29C41/46—Heating or cooling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
    • B29D7/00—Producing flat articles, e.g. films or sheets
    • B29D7/01—Films or sheets
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2029/00—Use of polyvinylalcohols, polyvinylethers, polyvinylaldehydes, polyvinylketones or polyvinylketals or derivatives thereof as moulding material
    • B29K2029/04—PVOH, i.e. polyvinyl alcohol

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Health & Medical Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Ophthalmology & Optometry (AREA)
  • Polarising Elements (AREA)
  • Moulding By Coating Moulds (AREA)
  • Manufacture Of Macromolecular Shaped Articles (AREA)

Abstract

An optical polyvinyl alcohol film manufacturing method characterized in that: a film manufacturing apparatus provided with a plurality of dryer rolls having parallel rotation axes is used, a film-forming stock solution containing polyvinyl alcohol is discharged in the form of a film onto a first dryer roll positioned at the most upstream side of the film manufacturing apparatus and dried, and the film thus obtained is further dried on second and subsequent dryer rolls that are on the downstream side of the first dryer roll; at least one of the second and subsequent dryer rolls is a non-uniform diameter dryer roll; and in at least a portion of areas of the non-uniform diameter dryer roll corresponding to sections of the film in contact with the roll that are 50 mm to 250 mm from both ends of the film toward the center in the width direction, the outer diameter of the non-uniform diameter dryer roll is 1.0 mm to 3.0 mm larger than the outer diameter at the center in the width direction. This method makes it possible to smoothly and continuously manufacture a wide optical polyvinyl alcohol film.

Description

光學用聚乙烯醇薄膜之製造方法Manufacturing method of polyvinyl alcohol film for optics

本發明係關於一種光學用聚乙烯醇薄膜(以下有時將「聚乙烯醇」簡稱為「PVA」)之製造方法。更詳細而言係關於一種寬度廣之光學用聚乙烯醇薄膜的製造方法。The present invention relates to a method for manufacturing a polyvinyl alcohol film for optics (hereinafter, "polyvinyl alcohol" is sometimes abbreviated as "PVA"). More specifically, it relates to a method for manufacturing a wide-width polyvinyl alcohol film for optics.

具有光的穿透及遮蔽功能的偏光板，係與具有光的開關功能的液晶同為液晶顯示器(LCD)的基本構成要素。此LCD的應用領域，亦從開發初期的計算機及手錶等小型機器，於近年擴大為筆記型電腦、文字處理器、液晶投影機、車用導航系統、液晶電視、個人電話及可用於室內外的測量儀器等廣大範圍。伴隨此種LCD應用領域的擴大，而要求一種偏光性能高而在先前產品之上，且因顏色顯示品位提升而色相優良的中性灰色偏光板。The polarizing plate with the function of light penetration and shielding is the basic component of the liquid crystal display (LCD) as well as the liquid crystal with the light switch function. The application field of this LCD has also expanded from small devices such as computers and watches in the early stages of development to notebook computers, word processors, LCD projectors, car navigation systems, LCD TVs, personal phones, and indoor and outdoor use. A wide range of measuring instruments, etc. With the expansion of the application field of such LCDs, a neutral gray polarizer with high polarization performance and superior to previous products, and with an improved color display quality and excellent hue, is required.

偏光板一般係藉由對PVA薄膜進行單軸延伸並染色、或進行染色並單軸延伸後，以硼化合物進行固定處理(視情況可同時進行染色、延伸及固定處理中2種以上之操作)而得到偏光薄膜，在該偏光薄膜上貼合三乙酸纖維素(TAC)薄膜或乙酸・丁酸纖維素(CAB)薄膜等保護膜而構成。The polarizing plate is generally uniaxially stretched and dyed by the PVA film, or dyed and uniaxially stretched, and then fixed with a boron compound (or more than two operations of dyeing, stretching and fixing can be performed at the same time as the case may be) A polarizing film is obtained, and a protective film such as a cellulose triacetate (TAC) film or a cellulose acetate butyrate (CAB) film is laminated on the polarizing film to form a structure.

再者，以提供一種可製造中央部與端部之間穿透率不均少之偏光薄膜的PVA薄膜為目的，迄今主要是從偏光薄膜之製造原料亦即PVA或PVA薄膜之結構、及偏光薄膜之製造條件等觀點進行檢討。例如，專利文獻1中記載一種使用中央部之外徑比兩端部之外徑還大特定量之乾燥滾筒作為乾燥滾筒的方法。依照該文獻記載之方法，寬方向之兩端部側於水中往長方向進行的伸長量會比中央部的該伸長量還多特定量，可平順而連續地製造先前所沒有的PVA薄膜，若使用該PVA，則可容易地製造中央部與端部之間穿透率不均少的偏光薄膜。 [先前技術文獻] [專利文獻]Furthermore, the aim is to provide a PVA film that can produce a polarizing film with less uneven transmittance between the center and the end. Up to now, it is mainly from the structure of the PVA or PVA film, which is the raw material for the production of the polarizing film, and the polarizing film. Review the film manufacturing conditions and other viewpoints. For example, Patent Document 1 describes a method of using a drying drum whose central part has an outer diameter larger than the outer diameter of both ends by a certain amount as the drying drum. According to the method described in this document, the length of both ends of the width direction in the water in the longitudinal direction will be a certain amount greater than the length of the central part, and the PVA film that has not been previously can be produced smoothly and continuously. By using this PVA, it is possible to easily manufacture a polarizing film with less uneven transmittance between the center part and the end part. [Prior Technical Literature] [Patent Literature]

[專利文獻1]國際公開第2013/146146號[Patent Document 1] International Publication No. 2013/146146

[發明欲解決之課題][The problem to be solved by the invention]

近年來，伴隨LCD之大型化，而寬度更大的偏光薄膜的需求提高，所以要求偏光薄膜原料的PVA薄膜進一步的大寬度化。In recent years, with the increase in the size of LCDs, the demand for polarizing films with larger widths has increased. Therefore, PVA films, which are raw materials for polarizing films, have been required to further increase in width.

因此，本發明之目的為提供一種能製造寬度大之光學用PVA薄膜的製造方法。 [用以解決課題之手段]Therefore, the object of the present invention is to provide a method for manufacturing a PVA film for optics with a large width. [Means to solve the problem]

為達成上述目的，本發明人等重覆專心檢討的結果，發現：使用具備旋轉軸互相平行之複數個乾燥滾筒的製膜裝置，將包含PVA之製膜原液以膜狀吐出至位於該製膜裝置之最上游側的第1乾燥滾筒上並乾燥，將所得到之薄膜在接續於該第1乾燥滾筒之下游側的第2乾燥滾筒後之乾燥滾筒上進一步乾燥，而製造PVA薄膜時，若使用從接觸乾燥滾筒之PVA薄膜的兩端部算起，距寬方向中央部側50mm以上250mm以下之位置的至少一部分之外徑，比寬方向中央部之外徑還大1.0mm～3.0mm的乾燥滾筒，來作為第2乾燥滾筒後之乾燥滾筒，則乾燥滾筒與PVA薄膜之密著面積會減低，可更平順而連續地製造寬度比先前還大的PVA薄膜，基於此等知識，進一步重覆檢討，於是完成本發明。In order to achieve the above object, the inventors of the present invention have repeatedly and intensively reviewed the results and found that a film forming apparatus equipped with a plurality of drying drums whose rotating shafts are parallel to each other is used to spit out the film forming stock solution containing PVA in the form of a film. The device is dried on the first drying drum on the most upstream side of the device, and the resulting film is further dried on the drying drum after the second drying drum on the downstream side of the first drying drum, and when the PVA film is manufactured, if Use the outer diameter of at least part of the position 50mm to 250mm from the center of the width direction from the ends of the PVA film contacting the drying drum, which is 1.0mm～3.0mm larger than the outer diameter of the center of the width direction. The drying drum is used as the drying drum after the second drying drum, and the adhesion area between the drying drum and the PVA film will be reduced, and the PVA film with a larger width than before can be manufactured more smoothly and continuously. Based on this knowledge, it is further important After review, the present invention was completed.

亦即，本發明係關於： [1]一種光學用聚乙烯醇薄膜之製造方法，其特徵為使用具備旋轉軸互相平行之複數個乾燥滾筒的製膜裝置，將包含聚乙烯醇之製膜原液以膜狀吐出至位於前述製膜裝置之最上游側的第1乾燥滾筒上並乾燥，將所得到之薄膜在接續於該第1乾燥滾筒之下游側的第2乾燥滾筒後之乾燥滾筒上進一步乾燥，該第2乾燥滾筒後之乾燥滾筒的至少一個為異徑乾燥滾筒，從接觸前述異徑乾燥滾筒之前述薄膜的寬方向兩端部算起，距寬方向中央部側50mm以上250mm以下之位置的至少一部分區域的前述異徑乾燥滾筒之外徑，比寬方向中央部之外徑還大1.0mm～3.0mm； [2]如前述[1]記載之光學用聚乙烯醇薄膜之製造方法，其得到寬度2m以上之聚乙烯醇薄膜； [3]如前述[1]或[2]記載之光學用聚乙烯醇薄膜的製造方法，其中前述外徑大之區域的寬度為10～55mm； [4]如前述[1]至[3]記載之光學用聚乙烯醇薄膜的製造方法，其中前述異徑乾燥滾筒為將氟系樹脂製膠帶貼附於金屬滾筒藉此設置前述外徑較大之區域而成者； [5]如前述[1]至[4]記載之光學用聚乙烯醇薄膜的製造方法，其中前述製膜裝置具備相同寬度之複數個前述異徑乾燥滾筒，越下游側之異徑乾燥滾筒，前述外徑較大之區域的位置越靠近寬方向中央側。 [發明之效果]That is, the present invention relates to: [1] A method for producing a polyvinyl alcohol film for optics, which is characterized by using a film forming device equipped with a plurality of drying drums with rotating shafts parallel to each other, and spit out a film-forming stock solution containing polyvinyl alcohol in a film form to The film device is dried on the first drying drum on the most upstream side, and the obtained film is further dried on the drying drum after the second drying drum on the downstream side of the first drying drum. After the second drying drum At least one of the drying rollers is a different diameter drying roller, and from the widthwise ends of the film contacting the different diameter drying roller, at least a part of the area at a position 50 mm or more and 250 mm or less from the center of the width direction The outer diameter of the drying drum is 1.0mm～3.0mm larger than the outer diameter of the central part in the width direction; [2] The method for producing a polyvinyl alcohol film for optics as described in [1] above, which obtains a polyvinyl alcohol film with a width of 2 m or more; [3] The method for producing a polyvinyl alcohol film for optics as described in [1] or [2], wherein the width of the region with the large outer diameter is 10 to 55 mm; [4] The method for producing a polyvinyl alcohol film for optics as described in [1] to [3], wherein the reducing diameter drying roller is formed by attaching a fluorine-based resin tape to a metal roller to set the outer diameter的区成者； [5] The method for producing a polyvinyl alcohol film for optics as described in [1] to [4], wherein the film forming apparatus is provided with a plurality of the reducing drying drums of the same width, and the reducing drying drums on the downstream side, The position of the region with the larger outer diameter is closer to the center side in the width direction. [Effects of Invention]

若依照本發明，即可提供一種能平順而連續地製造寬度大之光學用PVA薄膜的製造方法。According to the present invention, it is possible to provide a manufacturing method that can smoothly and continuously manufacture a wide-width PVA film for optics.

[用以實施發明的形態][Form to implement the invention]

就形成PVA薄膜之PVA而言，可列舉例如：將乙烯酯聚合所得到之聚乙烯酯皂化而得的PVA(未改質PVA)，使PVA之主鏈與共單體接枝共聚合而得的改質PVA，藉由將乙烯酯與共單體共聚合而得之改質聚乙烯酯皂化所得到的改質PVA，將未改質PVA或改質PVA之羥基之一部分藉由福馬林、丁基醛、苄醛等醛類交聯的所謂聚乙烯醇縮醛樹脂等。在形成PVA薄膜之PVA為改質PVA的情況，PVA中的改質量，以15莫耳%以下為較佳，以5莫耳%以下為更佳。Regarding the PVA forming the PVA film, for example: PVA (unmodified PVA) obtained by saponifying the polyvinyl ester obtained by the polymerization of vinyl ester, and obtained by grafting and copolymerizing the main chain of the PVA with the comonomer The modified PVA is obtained by saponifying the modified polyvinyl ester obtained by copolymerizing vinyl ester and comonomer, and part of the hydroxyl group of the unmodified PVA or the modified PVA is replaced by formalin, So-called polyvinyl acetal resins in which aldehydes such as butyraldehyde and benzaldehyde are cross-linked. When the PVA forming the PVA film is modified PVA, the modified mass in the PVA is preferably 15 mol% or less, and more preferably 5 mol% or less.

就用於PVA之製造的前述乙烯酯而言，可列舉例如：乙酸乙烯酯、甲酸乙烯酯、月桂酸乙烯酯、丙酸乙烯酯、丁酸乙烯酯、三甲基乙酸乙烯酯、新癸酸乙烯酯、硬脂酸乙烯酯、苯甲酸乙烯酯等。此等乙烯酯可單獨或組合使用。此等乙烯酯中，從生產性之觀點而言，以乙酸乙烯酯為較佳。Regarding the aforementioned vinyl esters used in the manufacture of PVA, for example: vinyl acetate, vinyl formate, vinyl laurate, vinyl propionate, vinyl butyrate, trimethyl vinyl acetate, neodecanoic acid Vinyl ester, vinyl stearate, vinyl benzoate, etc. These vinyl esters can be used alone or in combination. Among these vinyl esters, from the viewpoint of productivity, vinyl acetate is preferred.

又，就前述之共單體而言，可列舉例如：乙烯、丙烯、1-丁烯、異丁烯等碳數2～30的烯烴類(α-烯烴等)；丙烯酸或其鹽；丙烯酸甲酯、丙烯酸乙酯、丙烯酸正丙酯、丙烯酸異丙酯、丙烯酸正丁酯、丙烯酸異丁酯、丙烯酸三級丁酯、丙烯酸2-乙基己酯、丙烯酸十二酯、丙烯酸十八酯等丙烯酸酯類(例如，丙烯酸之碳數1～18烷酯等)；甲基丙烯酸或其鹽；甲基丙烯酸甲酯、甲基丙烯酸乙酯、甲基丙烯酸正丙酯、甲基丙烯酸異丙酯、甲基丙烯酸正丁酯、甲基丙烯酸異丁酯、甲基丙烯酸三級丁酯、甲基丙烯酸2-乙基己酯、甲基丙烯酸十二酯、甲基丙烯酸十八酯等之甲基丙烯酸酯類(例如，甲基丙烯酸之碳數1～18烷酯等)；丙烯醯胺、N-甲基丙烯醯胺、N-乙基丙烯醯胺、N,N-二甲基丙烯醯胺、二丙酮丙烯醯胺、丙烯醯胺丙磺酸或其鹽、丙烯醯胺丙基二甲基胺或其鹽、N-羥甲基丙烯醯胺或其衍生物等丙烯醯胺衍生物；甲基丙烯醯胺、N-甲基甲基丙烯醯胺、N-乙基甲基丙烯醯胺、甲基丙烯醯胺丙磺酸或其鹽、甲基丙烯醯胺丙基二甲基胺或其鹽、N-羥甲基甲基丙烯醯胺或其衍生物等甲基丙烯醯胺衍生物；N-乙烯基甲醯胺、N-乙烯基乙醯胺、N-乙烯基吡咯啶酮等N-乙烯基醯胺類；甲基乙烯基醚、乙基乙烯基醚、正丙基乙烯基醚、異丙基乙烯基醚、正丁基乙烯基醚、異丁基乙烯基醚、三級丁基乙烯基醚、十二基乙烯基醚、硬脂基乙烯基醚等乙烯基醚類；丙烯腈、甲基丙烯腈等丙烯腈類；氯乙烯、偏二氯乙烯、氟乙烯、偏二氟乙烯等之鹵乙烯基類；乙酸烯丙酯、氯化烯丙基等烯丙基化合物；馬來酸、衣康酸等不飽和二羧酸、其鹽或其酯等衍生物；乙烯基三甲氧基矽烷等乙烯基矽烷基化合物；乙酸異丙烯酯；不飽和磺酸或其衍生物等。此等中，以α-烯烴為較佳，尤其以乙烯為特佳。In addition, the aforementioned comonomers include, for example, olefins (α-olefins, etc.) having 2 to 30 carbon atoms such as ethylene, propylene, 1-butene, and isobutylene; acrylic acid or its salts; methyl acrylate, Acrylates such as ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tertiary butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, stearyl acrylate, etc. (For example, acrylic acid with 1 to 18 alkyl esters, etc.); methacrylic acid or its salt; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, methyl methacrylate Methacrylates such as n-butyl acrylate, isobutyl methacrylate, tertiary butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, stearyl methacrylate, etc. (For example, methacrylic acid alkyl ester with 1 to 18 carbon atoms, etc.); acrylamide, N-methacrylamide, N-ethacrylamide, N,N-dimethylacrylamide, two Acetone acrylamide, acrylamide propanesulfonic acid or its salt, acrylamide propyl dimethylamine or its salt, N-methylol acrylamide or its derivatives and other acrylamide derivatives; methacrylic acid Amide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamide propanesulfonic acid or its salt, methacrylamide propyldimethylamine or its salt, Methacrylamide derivatives such as N-methylolmethacrylamide or its derivatives; N-vinyl such as N-vinylformamide, N-vinylacetamide, and N-vinylpyrrolidone Amines; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, tertiary butyl ethylene Vinyl ether, dodecyl vinyl ether, stearyl vinyl ether and other vinyl ethers; acrylonitrile, methacrylonitrile and other acrylonitrile; vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, etc. Halovinyl compounds; allyl compounds such as allyl acetate and allyl chloride; unsaturated dicarboxylic acids such as maleic acid and itaconic acid, their salts or their ester derivatives; vinyl trimethoxy Vinyl silyl compounds such as silane; isopropenyl acetate; unsaturated sulfonic acid or its derivatives, etc. Among these, α-olefins are preferred, and ethylene is particularly preferred.

從所得到之偏光薄膜之偏光性能及耐久性等的觀點而言，形成PVA薄膜之PVA的平均聚合度以1000以上為較佳，以1500以上為更佳，以2000以上為進一步更佳。另一方面，從均質之PVA薄膜之製造的容易性、延伸性等觀點而言，該平均聚合度以8000以下為較佳，尤其以6000以下為特佳。其中，本說明書中PVA之「平均聚合度」意指以JIS K6726-1994為基準所測定的平均聚合度，係從將PVA再皂化、精製後，於30℃之水中測定的極限黏度求得。From the viewpoint of the polarization performance and durability of the obtained polarizing film, the average degree of polymerization of the PVA forming the PVA film is preferably 1000 or more, more preferably 1500 or more, and even more preferably 2000 or more. On the other hand, from the viewpoints of the ease of manufacture and extensibility of a homogeneous PVA film, the average degree of polymerization is preferably 8000 or less, and particularly preferably 6000 or less. In this specification, the "average degree of polymerization" of PVA means the average degree of polymerization measured in accordance with JIS K6726-1994, which is obtained from the ultimate viscosity measured in water at 30°C after re-saponification and purification of PVA.

從所得到之偏光薄膜之偏光性能及耐久性等的觀點而言，形成PVA薄膜之PVA的皂化度以95.0莫耳%以上為較佳，以98.0莫耳%以上為更佳，以99.0莫耳%以上為進一步更佳，以99.3莫耳%以上為最佳。其中，本說明書中PVA之「皂化度」意指相對於藉由皂化變換為乙烯醇單元所得到之結構單元(典型而言為乙烯酯單元)與乙烯醇單元的合計莫耳數，該乙烯醇單元之莫耳數所佔的比率(莫耳%)。PVA之皂化度能以JIS K6726-1994之記載為基準而測定。From the viewpoint of the polarization performance and durability of the obtained polarizing film, the degree of saponification of the PVA forming the PVA film is preferably 95.0 mol% or more, more preferably 98.0 mol% or more, and 99.0 mol% % Or more is even more preferable, and 99.3 mol% or more is the most preferable. Here, the "degree of saponification" of PVA in this specification means the total number of moles of structural units (typically vinyl ester units) and vinyl alcohol units obtained by saponification conversion into vinyl alcohol units, the vinyl alcohol The ratio of the number of moles of the unit (mol%). The degree of saponification of PVA can be measured based on the description in JIS K6726-1994.

本發明之光學用PVA薄膜的製造方法，係使用具備旋轉軸互相平行之複數個乾燥滾筒(從最上游側向下游側，依序稱為第1乾燥滾筒、第2乾燥滾筒…)的製膜裝置，將包含PVA之製膜原液以膜狀吐出至位於前述製膜裝置之最上游側的第1乾燥滾筒上並乾燥，將所得到之薄膜在接續於該第1乾燥滾筒之下游側的第2乾燥滾筒後之乾燥滾筒上進一步乾燥，前述第2乾燥滾筒後之乾燥滾筒的至少一個為異徑乾燥滾筒，從接觸前述異徑乾燥滾筒之前述薄膜的寬方向之兩端部算起，距寬方向中央部側50mm以上250mm以下之位置的至少一部分區域的前述異徑乾燥滾筒之外徑，比寬方向中央部之外徑還大1.0mm～3.0mm。若依照本發明之製造方法，則可平順而連續地製造光學用PVA薄膜。The manufacturing method of the optical PVA film of the present invention uses a plurality of drying drums (from the most upstream side to the downstream side, called the first drying drum, the second drying drum...) with rotating shafts parallel to each other. The device discharges the film-forming stock solution containing PVA in a film form onto the first drying drum located on the most upstream side of the above-mentioned film-making device and is dried. 2 Dry further on the drying drum after the drying drum, and at least one of the drying drums after the second drying drum is a reducing drying drum. The outer diameter of the reducing-diameter drying drum in at least a part of the area at a position 50 mm or more and 250 mm or less at the center in the width direction is 1.0 mm to 3.0 mm larger than the outer diameter of the center in the width direction. According to the manufacturing method of the present invention, the optical PVA film can be manufactured smoothly and continuously.

本發明之製造方法中，使用具備旋轉軸互相平行之複數個乾燥滾筒的製膜裝置，將包含PVA之製膜原液以膜狀吐出至位於該製膜裝置之最上游側的第1乾燥滾筒上並乾燥，將所得到之薄膜在接續於該第1乾燥滾筒之下游側的第2乾燥滾筒後之乾燥滾筒上進一步乾燥，藉此製備PVA薄膜。In the manufacturing method of the present invention, a film forming apparatus equipped with a plurality of drying drums whose rotating shafts are parallel to each other is used, and the film forming stock solution containing PVA is discharged in a film form onto the first drying drum located on the most upstream side of the film forming apparatus It is dried, and the obtained film is further dried on a drying drum following the second drying drum on the downstream side of the first drying drum, thereby preparing a PVA film.

在該製膜裝置中，乾燥滾筒之數目(包含第1乾燥滾筒(鑄造滾筒)的乾燥滾筒之支數)以9～30支為較佳，以12～26支為更佳。再者，本發明中所謂乾燥滾筒，意指將接觸之薄膜加熱的滾筒，與無加熱功能之引導滾筒或捲取薄膜用之捲取滾筒有所區別。In this film forming apparatus, the number of drying drums (including the number of drying drums of the first drying drum (casting drum)) is preferably 9-30, and more preferably 12-26. Furthermore, the so-called drying roller in the present invention means a roller that heats the film in contact with it, which is different from a guide roller without heating function or a take-up roller used to take up a film.

前述乾燥滾筒，例如，以由鎳、鉻、銅、鐵、不鏽鋼等金屬形成為較佳，尤其以乾燥滾筒之表面，由難以腐蝕，且具有鏡面光澤的金屬材料形成為更佳。又，為了提高乾燥滾筒之耐久性，亦可使用藉由電鍍，組合鎳層、鉻層、鎳/鉻合金層等單層或2層以上而成的乾燥滾筒。The aforementioned drying drum, for example, is preferably formed of metals such as nickel, chromium, copper, iron, stainless steel, etc. It is particularly preferable that the surface of the drying drum is formed of a metal material that is difficult to corrode and has a mirror-like luster. In addition, in order to improve the durability of the drying drum, a drying drum formed by combining a single layer or two or more layers such as a nickel layer, a chromium layer, and a nickel/chromium alloy layer by electroplating can also be used.

關於在從第1乾燥滾筒至最後乾燥滾筒之過程中將薄膜乾燥時的加熱方向，無特別限制，基於能將薄膜更均勻地乾燥，較佳為於薄膜之任何部分中，接觸第1乾燥滾筒之膜面(以下有時稱為「第1乾燥滾筒接觸面」)與不接觸第1乾燥滾筒之膜面(以下有時稱為「第1乾燥滾筒非接觸面」)呈交互對向地於第1乾燥滾筒至最後乾燥滾筒為止的各乾燥滾筒上進行乾燥。Regarding the heating direction when drying the film in the process from the first drying drum to the final drying drum, there is no particular limitation. Since the film can be dried more uniformly, it is preferable to contact the first drying drum in any part of the film. The film surface (hereinafter sometimes referred to as the "first drying drum contact surface") and the film surface that does not touch the first drying drum (hereinafter sometimes referred to as the "first drying drum non-contact surface") are alternately opposed to each other. Drying is performed on each drying drum from the first drying drum to the last drying drum.

當將包含PVA的製膜原液以膜狀吐出至製膜裝置之第1乾燥滾筒(鑄造滾筒)上時，例如，只要使用T型狹縫模頭、料斗板(hopper plate)、I-模頭、唇狀塗布模頭等已知之膜狀吐出裝置(膜狀流延裝置)，將包含PVA之製膜原液以膜狀吐出(流延)至第1乾燥滾筒上即可。When the film-forming stock solution containing PVA is discharged in a film form onto the first drying drum (casting drum) of the film-forming device, for example, only a T-slit die, a hopper plate, and an I-die can be used. , Lip-shaped coating die and other known film-shaped discharge device (film-shaped casting device), it is sufficient to discharge (cast) the film-forming stock solution containing PVA onto the first drying drum in a film shape.

藉由將PVA與液態媒體混合作成溶液，或將包含液態媒體等之PVA膠粒熔融而形成熔融液等，可調製包含PVA薄膜之製膜原液。就此時所用的液態媒體而言，可列舉例如：水、二甲基亞碸、二甲基甲醯胺、二甲基乙醯胺、N-甲基吡咯啶酮、伸乙基二胺、二伸乙基三胺等，此等液態媒體，可以一種單獨使用，或將2種以上併用。此等中，以使用水、二甲基亞碸、或兩者之混合物為較佳，以使用水為更佳。By mixing PVA and a liquid medium to form a solution, or melting PVA colloidal particles containing a liquid medium and the like to form a molten liquid, etc., a film-forming stock solution containing a PVA film can be prepared. Regarding the liquid medium used at this time, for example, water, dimethyl sulfide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylenediamine, two Ethylene triamine, etc., these liquid media can be used alone or in combination of two or more. Among these, it is preferable to use water, dimethyl sulfoxide, or a mixture of the two, and it is more preferable to use water.

從促進PVA對液態媒體之溶解或熔融、提高PVA薄膜製造時之製程通過性、提高所得到之PVA薄膜之延伸性等的觀點而言，在製膜原液中以添加塑化劑為較佳。就塑化劑而言，以使用多元醇為較佳，可列舉例如：乙二醇、甘油、二甘油、丙二醇、二乙二醇、三乙二醇、四乙二醇、三羥甲基丙烷等，此等塑化劑能以1種單獨使用，或將2種以上併用。此等中，從提高延伸性之效果優良的觀點而言，以甘油、二甘油及乙二醇中之1種或2種以上為較佳。From the viewpoints of promoting the dissolution or melting of PVA in the liquid medium, improving the process passability during PVA film manufacturing, and improving the extensibility of the obtained PVA film, it is better to add a plasticizer to the film forming stock solution. As for the plasticizer, it is preferable to use polyhydric alcohols, such as ethylene glycol, glycerin, diglycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane Etc., these plasticizers can be used alone or in combination of two or more. Among these, one or more of glycerin, diglycerin, and ethylene glycol are preferably used from the viewpoint of excellent effect of improving extensibility.

塑化劑之添加量，相對於100質量份之PVA，以0～30質量份為較佳，以3～25質量份為更佳，以5～20質量份為特佳。藉由塑化劑之添加量，相對於100質量份之PVA，為30質量份以下，所得到之PVA薄膜不會變得過於柔軟，能抑制操作性降低。The addition amount of the plasticizer is preferably 0-30 parts by mass relative to 100 parts by mass of PVA, more preferably 3-25 parts by mass, and particularly preferably 5-20 parts by mass. When the added amount of the plasticizer is 30 parts by mass or less with respect to 100 parts by mass of PVA, the resulting PVA film does not become too soft, and the decrease in handleability can be suppressed.

從提高製造PVA薄膜時對乾燥滾筒之剝離性、及所得到之PVA薄膜之操作性等觀點而言，以在製膜原液中添加界面活性劑為較佳。就界面活性劑之種類而言，無特別限定，而以使用陰離子性界面活性劑或非離子性界面活性劑為較佳。From the viewpoints of improving the releasability of the drying drum during the production of the PVA film, and the handling properties of the obtained PVA film, it is preferable to add a surfactant to the film-forming stock solution. The type of surfactant is not particularly limited, but it is preferable to use an anionic surfactant or a nonionic surfactant.

就陰離子性界面活性劑而言，較適合為例如：月桂酸鉀等羧酸型、硫酸辛酯等硫酸酯型、十二基苯磺酸鹽等磺酸型等陰離子性界面活性劑。As for anionic surfactants, anionic surfactants such as carboxylic acid types such as potassium laurate, sulfate ester types such as octyl sulfate, and sulfonic acid types such as dodecylbenzenesulfonate are more suitable.

又，就非離子性界面活性劑而言，較適合為例如：聚氧伸乙基油基醚等烷基醚型；聚氧伸乙基辛基苯基醚等烷基苯基醚型；聚氧伸乙基月桂酸酯等烷酯型；聚氧伸乙基月桂基胺基醚等烷基胺型；聚氧伸乙基月桂酸醯胺等烷基醯胺型；聚氧伸乙基聚氧伸丙基醚等聚丙二醇醚型；月桂酸二乙醇醯胺、油酸二乙醇醯胺等烷醇醯胺型；聚氧伸烷基烯丙基苯基醚等烯丙基苯基醚型等非離子性界面活性劑。此等界面活性劑能以1種單獨使用，或將2種以上併用。In addition, the nonionic surfactants are preferably, for example, alkyl ether types such as polyoxyethylene oleyl ether; alkyl phenyl ether types such as polyoxyethylene octyl phenyl ether; and polyoxyethylene octyl phenyl ether. Alkyl ester type such as oxyethylene laurate; Alkylamine type such as polyoxyethylene lauryl amino ether; Alkyl amine type such as polyoxyethylene laurate; Polyoxyethylene poly Polypropylene glycol ether type such as oxypropylene ether; Alkanol amide type such as diethanolamide laurate and diethanolamide oleate; Allyl phenyl ether type such as polyoxypropylene allyl phenyl ether Other nonionic surfactants. These surfactants can be used singly or in combination of two or more.

界面活性劑之添加量，相對於100質量份之PVA，以0.01～1質量份為較佳，以0.02～0.5質量份為更佳，以0.05～0.3質量份為特佳。藉由界面活性劑之添加量，相對於100質量份之PVA，為0.01質量份以上，變得容易呈現製膜性、剝離性等之提高效果。另一方面，在超過1質量份的情況，一則界面活性劑溶出至薄膜表面，成為阻塞(blocking)之原因，再則操作性變得容易降低。The addition amount of the surfactant is preferably 0.01 to 1 part by mass relative to 100 parts by mass of PVA, more preferably 0.02 to 0.5 part by mass, and particularly preferably 0.05 to 0.3 part by mass. When the addition amount of the surfactant is 0.01 parts by mass or more with respect to 100 parts by mass of PVA, it becomes easy to exhibit the effect of improving film-forming properties, releasability, and the like. On the other hand, when it exceeds 1 part by mass, a surfactant eluted to the surface of the film to cause blocking, and furthermore, the operability tends to be lowered.

製膜原液除上述之成分以外，亦可包含各種添加劑，例如：安定化劑(抗氧化劑、紫外線吸收劑、熱安定劑等)、相溶化劑、阻塞防止劑、難燃劑、抗靜電劑、滑劑、分散劑、流動化劑、抗菌劑等。此等添加劑能以1種單獨使用，或將2種以上併用。In addition to the above-mentioned ingredients, the film-forming stock solution can also contain various additives, such as stabilizers (antioxidants, ultraviolet absorbers, heat stabilizers, etc.), compatibility agents, blocking inhibitors, flame retardants, antistatic agents, Slip agent, dispersant, fluidizer, antibacterial agent, etc. These additives can be used alone or in combination of two or more.

使用於PVA薄膜之製造的製膜原液之揮發分率，以50～90質量%為較佳，以55～80質量%為更佳，以60～75質量%為進一步更佳，以65～70質量%為特佳。在製膜原液之揮發分率小於50質量%的情況，製膜原液之黏度變得過高，過濾或脫泡變得困難，或製膜本身變得困難。另一方面，在製膜原液之揮發分率超過90質量%的情況，黏度變得過低，PVA薄膜之厚度均勻性有損傷。其中，本發明中所謂「製膜原液之揮發分率」意指藉由下述之式(I)所求得的揮發分率。 製膜原液之揮發分率(質量%)={(Wa-Wb)/Wa}×100(I) (其中，Wa表示製膜原液之質量(g)，Wb表示將Wa(g)之製膜原液於105℃之電熱乾燥機中乾燥16小時後的質量(g))The volatile content of the film-forming stock solution used in the manufacture of PVA film is preferably 50-90% by mass, more preferably 55-80% by mass, more preferably 60-75% by mass, and 65-70 The quality% is particularly good. When the volatile fraction of the film-forming stock solution is less than 50% by mass, the viscosity of the film-forming stock solution becomes too high, filtration or defoaming becomes difficult, or the film forming itself becomes difficult. On the other hand, when the volatile content of the film-forming stock solution exceeds 90% by mass, the viscosity becomes too low, and the thickness uniformity of the PVA film is impaired. Here, in the present invention, the "volatile fraction of the film-forming stock solution" means the volatile fraction obtained by the following formula (I). The volatile fraction of the film-making stock solution (mass%)={(Wa-Wb)/Wa}×100(I) (Wa represents the mass (g) of the film-forming stock solution, and Wb represents the mass (g) after drying the film-forming stock solution of Wa(g) in an electric dryer at 105°C for 16 hours)

藉由第1乾燥滾筒進行乾燥時，從均勻乾燥性、乾燥速度等觀點而言，第1乾燥滾筒之滾筒表面溫度以80～120℃為較佳，以85～105℃為更佳。When drying by the first drying drum, the drum surface temperature of the first drying drum is preferably 80 to 120°C, and more preferably 85 to 105°C from the viewpoint of uniform dryness, drying speed, and the like.

以膜狀吐出的製膜原液於第1乾燥滾筒上進行之乾燥，藉由僅由第1乾燥滾筒予以加熱而進行即可，然而從乾燥均勻性、乾燥速度等觀點而言，較佳為於以第1乾燥滾筒加熱的同時吹送熱風至第1乾燥滾筒非接觸面，藉以從薄膜之兩面供熱而進行乾燥。The drying of the film-forming stock solution discharged in the form of a film on the first drying drum can be carried out by heating only the first drying drum, but from the viewpoints of drying uniformity, drying speed, etc., it is preferably While heating by the first drying drum, hot air is blown to the non-contact surface of the first drying drum, so that heat is supplied from both sides of the film for drying.

當對第1乾燥滾筒上的薄膜的第1乾燥滾筒非接觸面吹送熱風時，對第1乾燥滾筒非接觸面之全區域以吹送風速1～10m/秒之熱風為較佳，以吹送風速2～8m/秒之熱風為更佳，以吹送風速3～8m/秒之熱風為進一步更佳。若對第1乾燥滾筒非接觸面吹送的熱風之風速過小，則於第1乾燥滾筒上乾燥時會產生水蒸氣等的結露，其水滴恐怕會滴入薄膜，使最終得到之PVA薄膜產生缺陷。另一方面，若對第1乾燥滾筒非接觸面吹送的熱風之風速過大，則最終得到之PVA薄膜容易產生厚度不均，有伴隨其而產生染色不均等麻煩。When blowing hot air to the non-contact surface of the first drying drum of the film on the first drying drum, it is better to blow the hot air at a speed of 1-10m/sec to the entire area of the non-contact surface of the first drying drum, and the blowing speed is 2 The hot air of ~8m/sec is more preferable, and the hot air of blowing wind speed of 3-8m/sec is even more preferable. If the wind speed of the hot air blown to the non-contact surface of the first drying drum is too low, condensation such as water vapor may occur during drying on the first drying drum, and the water droplets may drip into the film, causing defects in the final PVA film. On the other hand, if the wind speed of the hot air blown to the non-contact surface of the first drying drum is too high, the finally obtained PVA film is likely to have uneven thickness, which may cause troubles such as uneven dyeing.

從乾燥效率、乾燥之均勻性等觀點而言，對薄膜之第1乾燥滾筒非接觸面吹送的熱風之溫度以50～150℃為較佳，以70～120℃為更佳，以80～95℃為進一步更佳。若對薄膜之第1乾燥滾筒非接觸面吹送的熱風之溫度過低，則恐怕有水蒸氣等之結露產生，該水滴落入薄膜中，使最終得到之PVA薄膜產生缺陷。另一方面，若該溫度太過高，恐怕會沿著熱風之風向產生乾燥不均，而使最終所得到之PVA薄膜產生厚度不均。From the viewpoints of drying efficiency and drying uniformity, the temperature of the hot air blowing to the non-contact surface of the first drying drum of the film is preferably 50-150°C, more preferably 70-120°C, and 80-95 °C is further preferable. If the temperature of the hot air blown to the non-contact surface of the first drying drum of the film is too low, there may be condensation of water vapor, etc., and the water droplets fall into the film, causing defects in the finally obtained PVA film. On the other hand, if the temperature is too high, uneven drying may occur along the wind direction of the hot air, and the resulting PVA film may have uneven thickness.

又，對薄膜之第1乾燥滾筒非接觸面吹送的熱風之露點溫度以5～20℃為較佳，以10～15℃為更佳，以11～13℃為進一步更佳。若對薄膜之第1乾燥滾筒非接觸面吹送的熱風之露點溫度過低，則乾燥效率、均勻乾燥性等容易降低，另一方面，若露點溫度過高，變得容易產生發泡。In addition, the dew point temperature of the hot air blown to the non-contact surface of the first drying drum of the film is preferably 5-20°C, more preferably 10-15°C, and still more preferably 11-13°C. If the dew point temperature of the hot air blown to the non-contact surface of the first drying drum of the film is too low, drying efficiency, uniform dryness, etc. are likely to decrease. On the other hand, if the dew point temperature is too high, foaming is likely to occur.

用於對薄膜之第1乾燥滾筒非接觸面吹送熱風的方式無特別限制，可採取將風速均勻且溫度均勻之熱風，對薄膜之第1乾燥滾筒非接觸面，較佳為對其整體均勻地吹送的方式之任一種，其中以採用噴嘴方式、整流板方式或彼等之組合等為較佳。對薄膜之第1乾燥滾筒非接觸面的熱風之吹送方向，可為與第1乾燥滾筒非接觸面相對之方向，亦可為約略沿著薄膜之第1乾燥滾筒非接觸面的圓周形狀之方向(約略沿著第1乾燥滾筒之滾筒表面之圓周的方向)或其以外之方向。The method of blowing hot air to the non-contact surface of the first drying drum of the film is not particularly limited. Hot air with a uniform wind speed and uniform temperature can be used. The non-contact surface of the first drying drum of the film is preferably uniform throughout Any of the blowing methods, among them, a nozzle method, a rectifying plate method, or a combination of them is preferable. The blowing direction of the hot air to the non-contact surface of the first drying drum of the film may be the direction opposite to the non-contact surface of the first drying drum, or may be approximately along the circumferential shape of the non-contact surface of the first drying drum of the film (Approximately along the circumference of the drum surface of the first drying drum) or other directions.

又，於第1乾燥滾筒上之薄膜乾燥時，以藉由乾燥將薄膜產生的揮發分及吹送後之熱風進行排氣為較佳。排氣之方法無特別限制，然而以採用對薄膜之第1乾燥滾筒非接觸面吹送之熱風不產生風速不均及溫度不均的排氣方法為較佳。In addition, when the film on the first drying drum is dried, it is preferable to exhaust the volatile matter generated from the film and the blown hot air by drying. The method of exhausting is not particularly limited. However, it is preferable to use a method of exhausting hot air that is blown to the non-contact surface of the first drying drum of the film without causing uneven wind speed and temperature unevenness.

在第1乾燥滾筒上以膜狀吐出之製膜原液係在第1乾燥滾筒上乾燥，所得到之薄膜係從第1乾燥滾筒剝離。若從第1乾燥滾筒剝離時之薄膜的揮發分率太過低，則PVA薄膜之生產性有變得容易降低的傾向。另一方面，若從第1乾燥滾筒剝離時之薄膜的揮發分率太過高，則容易變得難以從第1乾燥滾筒剝離，視情況有時造成斷裂，或變得容易產生不均。The film-forming stock solution discharged in the form of a film on the first drying drum is dried on the first drying drum, and the obtained film is peeled from the first drying drum. If the volatile fraction of the film at the time of peeling from the first drying drum is too low, the productivity of the PVA film tends to be easily reduced. On the other hand, if the volatile fraction of the film at the time of peeling from the first drying drum is too high, it is likely to become difficult to peel from the first drying drum, breakage may be caused in some cases, or unevenness may be easily generated.

從如上述之觀點而言，從第1乾燥滾筒剝離時之薄膜的揮發分率，以10質量%以上為較佳，以15質量%以上為更佳，以18質量%以上為進一步更佳，又，以30質量%以下為較佳，以29質量%以下為更佳，以28質量%以下為進一步更佳，以27質量%以下為特佳。其中，本說明書中「薄膜之揮發分率」意指藉由下述之式(II)所求得的揮發分率。 M(質量%)={(Wc-Wd)/Wc}×100  (II) (其中，M表示薄膜之揮發分率(質量%)，Wc表示取自薄膜的樣本之質量(g)，Wd表示將前述樣本Wc(g)放入溫度50℃，壓力0.1kPa以下之真空乾燥機中，經4小時乾燥後的質量(g))From the above-mentioned point of view, the volatile content of the film when peeled from the first drying drum is preferably 10% by mass or more, more preferably 15% by mass or more, and still more preferably 18% by mass or more. Moreover, 30 mass% or less is preferable, 29 mass% or less is more preferable, 28 mass% or less is still more preferable, and 27 mass% or less is particularly preferable. Here, in this specification, "the volatile fraction of the film" means the volatile fraction obtained by the following formula (II). M(mass%)={(Wc-Wd)/Wc}×100 (II) (Among them, M represents the volatile fraction of the film (mass%), Wc represents the mass (g) of the sample taken from the film, and Wd represents the vacuum drying of the aforementioned sample Wc(g) at a temperature of 50°C and a pressure below 0.1kPa In the machine, the mass after 4 hours of drying (g))

再者，由使用PVA、甘油等多元醇(塑化劑)、界面活性劑及水調製而成之製膜原液所形成的薄膜，於前述「溫度50℃，壓力0.1kPa以下，4小時」之條件下乾燥時，主要只有水揮發，水以外之其他成分幾乎不揮發而殘留於薄膜中，故薄膜之揮發分率可藉由測定薄膜中所含的水分量(水分率)而求得。In addition, the film formed by the film-forming stock solution prepared by using polyols (plasticizers) such as PVA and glycerin, surfactants, and water, at the aforementioned "temperature of 50°C, pressure of 0.1kPa or less, 4 hours" When drying under the conditions, only water volatilizes, and other components other than water hardly volatilize and remain in the film. Therefore, the volatile fraction of the film can be obtained by measuring the moisture content (moisture content) contained in the film.

將在第1乾燥滾筒上乾燥之薄膜從第1乾燥滾筒剝離，然後使薄膜之第1乾燥滾筒非接觸面與第2乾燥滾筒對向，於第2乾燥滾筒上將薄膜乾燥。再者，視需要可在第3乾燥滾筒以下之乾燥滾筒上將薄膜乾燥。此時，以使當前之乾燥滾筒中之薄膜的非接觸面與繼而接觸之乾燥滾筒成為對向下，乾燥薄膜為較佳。The film dried on the first drying drum is peeled off from the first drying drum, and then the non-contact surface of the first drying drum of the film is opposed to the second drying drum, and the film is dried on the second drying drum. Furthermore, if necessary, the film can be dried on the drying drum below the third drying drum. At this time, it is better to dry the film so that the non-contact surface of the film in the current drying drum and the subsequent drying drum are facing downward.

在本發明之製造方法中，第2乾燥滾筒後之乾燥滾筒中的至少一個乾燥滾筒為異徑乾燥滾筒1。圖1為異徑乾燥滾筒1與其所接觸之薄膜2之一例的示意圖。如圖1所示，就異徑乾燥滾筒1而言，使用從前述異徑乾燥滾筒1所接觸之薄膜2之兩端部算起，距寬方向中央部側50mm以上250mm以下之位置3(圖1之斜線部分)之至少一部區域4中，前述異徑乾燥滾筒1之外徑t1 比前述寬方向中央部之外徑t2 大1.0mm～3.0mm的乾燥滾筒。就乾燥滾筒而言，一般使用中央部之外徑與兩端部之外徑相同的圓筒形狀之乾燥滾筒(平滾筒(flat roller))。在本發明之製造方法中，藉由使用如上述之異徑乾燥滾筒1，可平順地製造本發明之PVA薄膜。雖並不構成對本發明之任何限定，然而就其理由而言，在從異徑乾燥滾筒1所接觸的薄膜2之兩端部約略靠近寬方向中央部側之前述異徑乾燥滾筒1之外徑t1 變大的情況，薄膜2之兩端抬起。結果，前述異徑乾燥滾筒1與薄膜2之密著面積減低，伴隨密著而產生的薄膜2之缺陷可受到抑制，作為製品使用之PVA薄膜的寬度(製品有效寬度)被認為可以增加。In the manufacturing method of the present invention, at least one of the drying drums after the second drying drum is a different-diameter drying drum 1. Fig. 1 is a schematic diagram of an example of a reducing-diameter drying drum 1 and a film 2 in contact with it. As shown in Figure 1, for the different diameter drying drum 1, a position 3 (Figures In at least a part of the area 4 of 1), the outer diameter t 1 of the reducing drying drum 1 is 1.0 mm to 3.0 mm larger than the outer diameter t 2 of the central part in the width direction. As for the drying roller, a cylindrical drying roller (flat roller) with the same outer diameter at the center part and the outer diameter at both ends is generally used. In the manufacturing method of the present invention, the PVA film of the present invention can be smoothly manufactured by using the different-diameter drying roller 1 as described above. Although it does not constitute any limitation to the present invention, for the reason, the outer diameter of the aforementioned reducing dryer drum 1 that is slightly close to the widthwise center side from the opposite ends of the film 2 contacted by the reducing dryer drum 1 When t 1 becomes larger, both ends of the film 2 are lifted. As a result, the adhesion area between the aforementioned different diameter drying drum 1 and the film 2 is reduced, the defects of the film 2 caused by the adhesion can be suppressed, and the width of the PVA film used as a product (product effective width) is considered to be increased.

在上述異徑乾燥滾筒1中，外徑t1 較大之區域4的寬度t3 ，以10～55mm為較佳。若在此範圍內，則本發明之效果特高。前述外徑t1 較大之區域4的較佳寬度t3 為10～40mm。In the above-mentioned different-diameter drying drum 1, the width t 3 of the region 4 with the larger outer diameter t 1 is preferably 10 to 55 mm. If it is within this range, the effect of the present invention is extremely high. The preferred width t 3 of the region 4 with the larger outer diameter t 1 is 10-40 mm.

又，異徑乾燥滾筒1，以藉由在外徑均勻之金屬滾筒上，從前述金屬滾筒接觸之PVA薄膜的兩端部算起，在距寬方向中央部50mm以上250mm以下之位置的至少一部分區域貼合氟系樹脂製膠帶，設置前述外徑較大之區域者為較佳。如此，藉由在前述金屬滾筒之設定位置貼合氟系樹脂製膠帶，設置外徑t1 較大之區域4為較佳。若依照此種方法，則外徑t1 較大之區域4的位置、寬度、及外徑t1 可容易地調整。In addition, the different diameter drying roller 1 is used on a metal roller with a uniform outer diameter, from the two ends of the PVA film contacted by the metal roller, in at least a part of the area 50 mm to 250 mm from the center in the width direction For laminating fluorine-based resin tape, it is preferable to provide the aforementioned area with a larger outer diameter. Thus, by setting the position of the metal cylinder made of a fluororesin laminated tape, provided the larger outer diameter region 4 t 1 is preferred. If in accordance with this method, the outer diameter of the large area position t 1 to 4, the width t 1 and the outer diameter can be easily adjusted.

如上述之本發明之製造方法，係在第2乾燥滾筒後之乾燥滾筒中的至少1個中，使用本發明之異徑乾燥滾筒。其中，從第2乾燥滾筒至最後乾燥滾筒中可只有1個為本發明之異徑乾燥滾筒，亦可有2個以上為本發明之異徑乾燥滾筒。以第2乾燥滾筒為本發明之異徑乾燥滾筒為較佳，以從第2乾燥滾筒及第3乾燥滾筒至最後乾燥滾筒之乾燥滾筒的1個以上，合計2個以上為本發明之異徑乾燥滾筒為更佳。以從第2乾燥滾筒至最後乾燥滾筒之全部乾燥滾筒均為本發明之異徑乾燥滾筒亦為更佳。再者，第1乾燥滾筒之形狀，以通常之圓筒形狀，亦即中央部之外徑與兩端部之外徑相同的形狀為較佳。In the manufacturing method of the present invention as described above, the reducing drying drum of the present invention is used in at least one of the drying drums after the second drying drum. Among them, from the second drying drum to the last drying drum, there may be only one of the reducing drying drums of the present invention, or two or more of the reducing drying drums of the present invention. The second drying drum is preferably the reducing drying drum of the present invention, and one or more drying drums from the second drying drum and the third drying drum to the last drying drum, and a total of 2 or more are the reducing drying drums of the present invention Dry drum is better. It is also preferable that all the drying drums from the second drying drum to the last drying drum are the reducing drying drums of the present invention. Furthermore, the shape of the first drying drum is preferably a normal cylindrical shape, that is, a shape in which the outer diameter of the center part and the outer diameter of both ends are the same.

在本發明PVA薄膜之製造中，前述薄膜隨著乾燥進展，向寬方向中央側收縮。另一方面，在本發明中，異徑乾燥滾筒之外徑較大之區域的位置，係以距薄膜之端部的距離來定義。因此，使用複數個本發明之異徑乾燥滾筒，在所有異徑乾燥滾筒之寬度皆相同的情況，前述外徑較大之區域的位置，以異徑乾燥滾筒之端部為基準，以越是薄膜進行方向下游側之乾燥滾筒越向寬方向中央側靠近為較佳。In the production of the PVA film of the present invention, the aforementioned film shrinks toward the center side in the width direction as the drying progresses. On the other hand, in the present invention, the position of the area where the outer diameter of the reducing dryer drum is larger is defined by the distance from the end of the film. Therefore, using a plurality of different diameter drying drums of the present invention, when the width of all the different diameter drying drums is the same, the position of the area with the larger outer diameter mentioned above is based on the end of the different diameter drying drum. The drying drum on the downstream side in the film advancing direction is preferably closer to the center in the width direction.

從本發明之PVA薄膜生產時的搬送性、及擔保作為製品時之剛性的觀點而言，第2乾燥滾筒後之乾燥滾筒的表面溫度以50～100℃為較佳，以60～95℃為更佳。From the viewpoint of transportability during production of the PVA film of the present invention and guarantee of rigidity as a product, the surface temperature of the drying drum after the second drying drum is preferably 50-100°C, and 60-95°C Better.

亦可只使用第2乾燥滾筒後之乾燥滾筒中最後乾燥滾筒，或者比第1乾燥滾筒靠近最後乾燥滾筒之1個或2個以上的乾燥滾筒及最後乾燥滾筒，使其表面溫度比其他乾燥滾筒高，作為熱處理滾筒。亦即，上述之製膜裝置中的乾燥滾筒，在使用熱處理滾筒之情況，亦包含該熱處理滾筒。在使用乾燥滾筒作為熱處理滾筒之情況，該乾燥滾筒之表面溫度以90～120℃為較佳，以100～110℃為更佳。藉由於此種溫度進行熱處理，則PVA之結晶化適度地進行，耐熱水性提高。It is also possible to use only the last drying drum of the drying drum after the second drying drum, or one or more drying drums and the last drying drum that are closer to the last drying drum than the first drying drum, so that the surface temperature of the drying drum is higher than that of other drying drums. High, as a heat treatment roller. That is, the drying drum in the above-mentioned film forming apparatus includes the heat treatment drum when the heat treatment drum is used. In the case of using a drying drum as the heat treatment drum, the surface temperature of the drying drum is preferably 90-120°C, more preferably 100-110°C. By performing the heat treatment at such a temperature, the crystallization of PVA proceeds moderately, and the hot water resistance is improved.

從均勻乾燥性、乾燥速度及PVA薄膜之生產性等的觀點而言，第1乾燥滾筒之周速(S1)以5～30m/分為較佳，以7～25m/分為更佳。若第1乾燥滾筒之周速(S1)小於5m/分，則生產性降低，同時所得到之PVA薄膜的延伸性有降低之傾向。另一方面，若第1乾燥滾筒之周速(S1)超過30m/分，則從第1乾燥滾筒之剝離變得不均勻，有容易產生缺點的傾向。From the viewpoints of uniform drying properties, drying speed, and PVA film productivity, the peripheral speed (S1) of the first drying drum is preferably 5-30 m/min, and more preferably 7-25 m/min. If the peripheral speed (S1) of the first drying drum is less than 5 m/min, productivity will decrease, and the extensibility of the obtained PVA film will tend to decrease. On the other hand, if the peripheral speed (S1) of the first drying drum exceeds 30 m/min, the peeling from the first drying drum becomes uneven, which tends to cause defects.

為能更平順地製造本發明之PVA薄膜，最後乾燥滾筒之周速(ST)對第1乾燥滾筒之周速(S1)的比(ST/S1)，以0.960～1.100為較佳。若此比(ST/S1)太過低，則於乾燥滾筒間薄膜變得容易下垂，又若太過高，則遲滯變大，寬方向之相位差不均容易變大。另一方面，此比(ST/S1)以1.050以下為更佳，以1.030以下為進一步更佳。In order to make the PVA film of the present invention more smoothly, the ratio (ST/S1) of the peripheral speed (ST) of the final drying drum to the peripheral speed (S1) of the first drying drum is preferably 0.960-1.100. If the ratio (ST/S1) is too low, the film tends to sag between the drying drums, and if it is too high, the hysteresis becomes larger, and the retardation unevenness in the width direction tends to become larger. On the other hand, the ratio (ST/S1) is more preferably 1.050 or less, and even more preferably 1.030 or less.

上述之製膜裝置，可視需要具有熱風爐式之熱風乾燥裝置、熱處理裝置、調濕裝置等，例如，可在藉由上述乾燥滾筒之乾燥(包含藉由熱處理滾筒之熱處理)後，使用此等裝置施行調濕處理。又，視需要可將薄膜兩端部(耳部)切除。The above-mentioned film forming device may optionally have a hot-air oven type hot-air drying device, a heat treatment device, a humidity control device, etc., for example, can be used after drying by the above-mentioned drying drum (including heat treatment by the heat treatment drum) The device is subject to humidity control treatment. Furthermore, if necessary, both ends (ears) of the film can be cut off.

藉由上述一連串之處理，最後，所得到之PVA薄膜的揮發分率(典型而言為水分率)，通常於1～5質量%之範圍。若該揮發分率過高，則水中尺寸變化量容易變高。所得到之PVA薄膜，以依照設定長度，成滾筒狀地捲取為較佳。Through the above series of treatments, finally, the volatile content (typically moisture content) of the obtained PVA film is usually in the range of 1 to 5 mass%. If the volatile fraction is too high, the dimensional change in water is likely to increase. The obtained PVA film is preferably wound in a roll shape according to the set length.

PVA薄膜，除包含上述之PVA外，可進一步以例如上述之量包含本發明之製造方法中所使用者，如上述之塑化劑、界面活性劑、彼等以外的各種添加劑等。In addition to the above-mentioned PVA, the PVA film may further include the aforementioned plasticizers, surfactants, and various additives other than those used in the manufacturing method of the present invention, for example, in the above-mentioned amounts.

依照本發明之製造方法所得到的PVA薄膜，可適合於光學用，尤其偏光薄膜製造用之捲材。PVA薄膜之厚度無特別限定，以5～80μm為較佳。為此種厚度之PVA薄膜，可適合使用作為偏光薄膜製造用之捲材等。更佳之厚度為20～80μm。藉由PVA薄膜之厚度成為上述上限以下，則製造偏光薄膜時的乾燥變得容易快速地進行，另一方面，藉由PVA薄膜之厚度成為上述下限以上，則用於製造偏光薄膜之單軸延伸時，可更有效地抑制薄膜之破斷的發生。The PVA film obtained according to the manufacturing method of the present invention can be suitable for optical applications, especially rolls for polarizing film manufacturing. The thickness of the PVA film is not particularly limited, but is preferably 5 to 80 μm. The PVA film of this kind of thickness can be suitably used as a roll material for the manufacture of polarizing film, etc. More preferably, the thickness is 20 to 80 μm. When the thickness of the PVA film is less than the above upper limit, drying during the production of the polarizing film becomes easy and rapid. On the other hand, when the thickness of the PVA film is more than the above lower limit, it is used for uniaxial stretching of the polarizing film. At this time, the breakage of the film can be suppressed more effectively.

PVA薄膜之寬度無特別限制，然而近年來由於液晶電視或監視器大畫面化，為了能有效地使用於彼等之用途，以寬度為2m以上為較佳，以3m以上為更佳，以4m以上為進一步更佳。PVA薄膜之寬度越廣，本發明之效果變得更顯著，可得到大面積之偏光薄膜為較佳。另一方面，在以現實之生產機器製造偏光板的情況，由於若薄膜之寬度過廣，均勻之單軸延伸變得困難，PVA薄膜之寬度以7.5m以下為較佳，以7m以下為更佳。PVA薄膜之長度無特別限制，例如可為50～30000m。The width of the PVA film is not particularly limited. However, in recent years, due to the large screen of LCD TVs or monitors, in order to be effectively used for their purposes, the width is preferably 2m or more, more preferably 3m or more, and 4m The above is further and better. The wider the width of the PVA film, the more significant the effect of the present invention becomes, and it is better to obtain a large-area polarizing film. On the other hand, in the case of manufacturing polarizing plates with actual production machines, since the width of the film is too wide, uniform uniaxial stretching becomes difficult. The width of the PVA film is preferably 7.5m or less, and more preferably 7m or less. good. The length of the PVA film is not particularly limited, and it can be 50 to 30000 m, for example.

PVA薄膜之遲滯值無特別限定，然而從遲滯值越小則所得到之偏光薄膜寬方向的相位差不均有越得到改善之傾向的觀點而言，以40nm以下為較佳。The retardation value of the PVA film is not particularly limited, but from the viewpoint that the smaller the retardation value, the more the retardation in the width direction of the obtained polarizing film tends to be improved, preferably 40 nm or less.

從本發明之PVA薄膜製造偏光薄膜時，例如，只要將PVA薄膜進行染色、單軸延伸、固定處理、乾燥處理、進一步視需要進行熱處理即可。染色及單軸延伸之順序無特別限定，可在單軸延伸處理之前進行染色處理，或在單軸延伸處理同時進行染色處理，或在單軸延伸處理之後進行染色處理。又，單軸延伸、染色等步驟可重覆複數次。尤其若將單軸延伸分為2段以上，由於變得容易進行均勻的延伸，為較佳。When manufacturing a polarizing film from the PVA film of the present invention, for example, the PVA film may be dyed, uniaxially stretched, fixed, dried, and further heat-treated as necessary. The order of dyeing and uniaxial stretching is not particularly limited, and the dyeing treatment may be performed before the uniaxial stretching treatment, or the dyeing treatment may be performed simultaneously with the uniaxial stretching treatment, or the dyeing treatment may be performed after the uniaxial stretching treatment. In addition, the steps of uniaxial stretching and dyeing can be repeated multiple times. In particular, if the uniaxial stretching is divided into two or more stages, since it becomes easy to perform uniform stretching, it is preferable.

就使用於PVA薄膜之染色的染料而言，可使用碘或二色性有機染料(例如，Direct Black 17、19、154；Direct Brown 44、106、195、210、223；Direct Red 2、23、28、31、37、39、79、81、240、242、247；Direct Blue 1、15、22、78、90、98、151、168、202、236、249、270；Direct Violet 9、12、51、98；Direct Green 1、85；Direct Yellow 8、12、44、86、87；Direct Orange 26、39、106、107等之二色性染料)等。此等染料能以1種單獨使用，或將2種以上組合而使用。染色，通常可藉由將PVA薄膜浸漬於含有上述染料之溶液中而進行，然而其處理條件或處理方法無特別限制。As for the dyes used in the dyeing of PVA films, iodine or dichroic organic dyes (for example, Direct Black 17, 19, 154; Direct Brown 44, 106, 195, 210, 223; Direct Red 2, 23, 28, 31, 37, 39, 79, 81, 240, 242, 247; Direct Blue 1, 15, 22, 78, 90, 98, 151, 168, 202, 236, 249, 270; Direct Violet 9, 12, 51, 98; Direct Green 1, 85; Direct Yellow 8, 12, 44, 86, 87; Direct Orange 26, 39, 106, 107 and other dichroic dyes) and so on. These dyes can be used individually by 1 type or in combination of 2 or more types. Dyeing can usually be performed by immersing the PVA film in a solution containing the above-mentioned dye, but the treatment conditions or treatment methods are not particularly limited.

於長度方向(MD)等延伸PVA薄膜的單軸延伸，可藉由濕式延伸法或乾熱延伸法之任一種進行，然而從所得到之偏光薄膜之性能及品質之安定性的觀點而言，以濕式延伸法為較佳。就濕式延伸法而言，可列舉將PVA薄膜在包含純水、添加劑或水性媒體等各種成分的水溶液，或有各種成分分散之水分散液中延伸的方法，就藉由濕式延伸法之單軸延伸方法的具體例而言，可列舉在包含硼酸之溫水中單軸延伸的方法，在含有前述之染料的溶液中或後述固定處理浴中單軸延伸之方法等。又，可使用吸水後之PVA薄膜於空氣中單軸延伸，亦可藉由其他方法單軸延伸。The uniaxial stretching of the PVA film stretched in the longitudinal direction (MD) can be performed by either the wet stretching method or the dry heat stretching method. However, from the viewpoint of the performance and quality stability of the polarizing film obtained , The wet stretching method is preferred. As for the wet stretching method, a method of stretching the PVA film in an aqueous solution containing various components such as pure water, additives, or aqueous media, or an aqueous dispersion in which various components are dispersed, can be cited. Specific examples of the uniaxial stretching method include a method of uniaxial stretching in warm water containing boric acid, a method of uniaxial stretching in a solution containing the aforementioned dye, or in a fixed treatment bath described later. In addition, the PVA film after water absorption can be uniaxially stretched in the air, or it can be uniaxially stretched by other methods.

單軸延伸時之延伸溫度無特別限定，而於濕式延伸之情況，較佳為採用20～90℃，更佳為25～70℃，進一步更佳為30～65℃之範圍內的溫度，於乾熱延伸之情況，較佳為採用50～180℃之範圍內的溫度。The stretching temperature during uniaxial stretching is not particularly limited. In the case of wet stretching, a temperature in the range of 20 to 90°C is preferred, 25 to 70°C is more preferred, and 30 to 65°C is still more preferred. In the case of dry heat extension, it is preferable to use a temperature in the range of 50 to 180°C.

單軸延伸處理之延伸倍率(在以多段進行單軸延伸的情況為合計之延伸倍率)，從偏光性能的觀點而言，以盡可能延伸至薄膜即將切斷前為止為較佳，具體而言，以4倍以上為較佳，以5倍以上為更佳，以5.5倍以上為進一步更佳。延伸倍率之上限，只要薄膜不破斷即可，無特別限制，然而為了進行均勻之延伸，以8.0倍以下為較佳。The stretching magnification of the uniaxial stretching treatment (in the case of multi-stage uniaxial stretching is the total stretching magnification), from the viewpoint of polarization performance, it is better to stretch as far as possible just before the film is cut. Specifically, , Preferably 4 times or more, more preferably 5 times or more, and even more preferably 5.5 times or more. The upper limit of the stretching ratio is not particularly limited as long as the film does not break. However, for uniform stretching, it is preferably 8.0 times or less.

當製造偏光薄膜時，為了使染料對經單軸延伸之薄膜的吸附變得強固，大多會進行固定處理。固定處理一般廣泛地採用將薄膜浸漬於添加硼酸及/或硼化合物之處理浴中的方法。此時，可視需要在處理浴中添加碘化合物。When making polarizing films, in order to make the dye's adsorption to the uniaxially stretched film stronger, most of them are fixed. The fixing treatment generally uses a method of immersing the film in a treatment bath added with boric acid and/or a boron compound. At this time, an iodine compound may be added to the treatment bath as needed.

以將經單軸延伸處理、或單軸延伸處理及固定處理之薄膜繼而進行乾燥處理(熱處理)為較佳。乾燥處理(熱處理)之溫度為30～150℃，尤其以50～140℃為特佳。若乾燥處理(熱處理)之溫度過低，則所得到之偏光薄膜的尺寸安定性變得容易降低，另一方面，若過高，則伴隨染料之分解等的偏光性能之降低變得容易發生。It is preferable to dry the film after uniaxial stretching treatment, or uniaxial stretching treatment and fixation treatment (heat treatment). The temperature of the drying treatment (heat treatment) is 30 to 150°C, especially 50 to 140°C. If the temperature of the drying treatment (heat treatment) is too low, the dimensional stability of the obtained polarizing film will tend to decrease. On the other hand, if it is too high, the degradation of the polarization performance accompanying dye decomposition and the like will easily occur.

在如上述之方式所得到之偏光薄膜的兩面或單面，貼合光學上透明，且具有機械強度之保護膜，可形成偏光板。就此情況之保護膜而言，可使用三乙酸纖維素(TAC)薄膜、乙酸・丁酸纖維素(CAB)薄膜、丙烯酸系薄膜、聚酯系薄膜等。又，就用於貼合保護膜之接著劑而言，一般可使用PVA系接著劑或胺基甲酸酯系接著劑等，其中以使用PVA系接著劑為較佳。On both sides or one side of the polarizing film obtained as described above, a protective film that is optically transparent and has mechanical strength is bonded to form a polarizing plate. For the protective film in this case, cellulose triacetate (TAC) film, cellulose acetate butyrate (CAB) film, acrylic film, polyester film, etc. can be used. Moreover, as for the adhesive used for laminating the protective film, a PVA-based adhesive, a urethane-based adhesive, etc. can generally be used, and among them, it is preferable to use a PVA-based adhesive.

如上述之方式所得到的偏光板，在被覆丙烯酸系等之黏著劑後，貼合於玻璃基板，可使用作為液晶顯示器裝置之零件。將偏光板貼合於玻璃基板時，亦可同時貼合相位差薄膜、視野角度提高薄膜、亮度提高薄膜等。 [實施例]The polarizing plate obtained as described above can be used as a part of a liquid crystal display device after being coated with an acrylic adhesive or the like, and then bonded to a glass substrate. When bonding a polarizing plate to a glass substrate, a retardation film, a viewing angle improvement film, a brightness improvement film, etc. can also be bonded at the same time. [Example]

以下，將本發明藉由實施例，具體地說明，然而本發明不受以下實施例的任何限定。 在以下實施例及比較例中，PVA薄膜之製品有效寬度係依照下列之方法測定或評價。Hereinafter, the present invention will be specifically explained through examples, but the present invention is not limited in any way by the following examples. In the following examples and comparative examples, the effective width of the PVA film product is measured or evaluated according to the following methods.

(1)製品有效寬度 以將存在於PVA薄膜兩端的氟系樹脂製膠帶之痕跡、及密著所伴隨而產生的密著痕跡、偏光不均等缺陷產生之部分排除後之部分的寬度，當作製品有效寬度。製品有效寬度，以相對於PVA系聚合體薄膜之製膜原液澆鑄至乾燥滾筒的寬度而言為80%以上的情況，當作合格。(1) Product effective width The width of the part after excluding the traces of the fluorine-based resin tape existing on both ends of the PVA film, and the parts caused by the adhesion marks and uneven polarization caused by the adhesion, is regarded as the effective width of the product. If the effective width of the product is 80% or more relative to the width of the film-forming dope of the PVA-based polymer film cast to the drying drum, it is regarded as a pass.

實施例1 製作包含100質量份之藉由將聚乙酸乙烯酯皂化所得到的PVA(皂化度99.9莫耳%，平均聚合度2400)、10.5質量份之甘油、0.04質量份之月桂酸二乙醇醯胺且水的揮發分率為67質量%之製膜原液。繼而，從T模頭(鑄造寬度6380mm)，將前述製膜原液以膜狀吐出至具備旋轉軸互相平行，長度相同之複數個乾燥滾筒的製膜裝置之第1乾燥滾筒(表面溫度93℃，周速(S1)14.5m/分)上，於第1乾燥滾筒上，對第1乾燥滾筒非接觸面之全體，以5m/秒之風速吹送90℃之熱風，並乾燥至揮發分率成為18質量%為止，繼而，將所得到之薄膜從第1乾燥滾筒剝離，以薄膜之任何部分的表面及背面與各乾燥滾筒交互接觸之方式，藉由第2乾燥滾筒後之乾燥滾筒進行乾燥。Example 1 The preparation contained 100 parts by mass of PVA obtained by saponifying polyvinyl acetate (degree of saponification: 99.9 mol%, average degree of polymerization: 2400), 10.5 parts by mass of glycerin, 0.04 parts by mass of lauric acid diethanolamide, and water The volatile content of the film is 67% by mass. Then, from the T die head (casting width 6380mm), the aforementioned film-forming stock solution was ejected in a film form to the first drying drum of the film forming apparatus equipped with a plurality of drying drums with parallel rotation shafts and the same length (surface temperature 93°C, On the peripheral speed (S1) 14.5m/min), on the first drying drum, blow hot air at 90℃ at a wind speed of 5m/sec to the entire non-contact surface of the first drying drum, and dry until the volatile content becomes 18 Then, the obtained film is peeled from the first drying drum, and the surface and back of any part of the film are alternately contacted with each drying drum, and the drying drum after the second drying drum is used for drying.

在本實施例中，於比外徑沿寬方向為固定的乾燥滾筒(金屬滾筒)之兩端更靠近寬方向中央部側之位置(滾筒端部至膠帶端部之距離示於表1)，將氟系樹脂製膠帶(寬度40mm)沿圓周方向捲繞複數次，且以高度成為1.26mm之方式貼附，形成異徑乾燥滾筒。對於各異徑乾燥滾筒，貼附前述膠帶之位置係調整成從薄膜之端部至膠帶之滾筒端部側的距離為85mm。在貼附前述膠帶之位置，與不貼附之位置相比，乾燥滾筒的外徑大2.52mm。又，如表1所示，將從第2乾燥滾筒至第13乾燥滾筒之12個滾筒，作成前述異徑乾燥滾筒。從第14乾燥滾筒至為最後乾燥滾筒之第18乾燥滾筒的5個滾筒，使用不貼附前述膠帶的平(flat)滾筒。第2～13、15、17乾燥滾筒之表面溫度調成75～95℃。將第14乾燥滾筒及第16乾燥滾筒之表面溫度調成105℃，作為熱處理滾筒。又，為最後乾燥滾筒之第18乾燥滾筒(熱處理滾筒，表面溫度105℃)的周速(S18)調成14.1m/分。然後，以滾筒狀捲取，得到PVA薄膜(厚度60μm，寬度6080mm)。由於該PVA薄膜的製品有效寬度為5800mm，為鑄造寬度之91%，判定為合格。In this embodiment, at a position closer to the central side in the width direction than both ends of the drying drum (metal drum) whose outer diameter is fixed in the width direction (the distance from the end of the drum to the end of the tape is shown in Table 1), A fluorine-based resin tape (width 40mm) was wound several times in the circumferential direction and pasted so that the height became 1.26mm to form a different-diameter drying drum. For each different diameter drying drum, the position where the aforementioned tape is attached is adjusted so that the distance from the end of the film to the side of the drum end of the tape is 85mm. In the position where the aforementioned tape is attached, the outer diameter of the drying drum is 2.52mm larger than the position where it is not attached. In addition, as shown in Table 1, twelve rollers from the second drying roller to the thirteenth drying roller were made into the aforementioned different-diameter drying rollers. The five rollers from the 14th drying roller to the 18th drying roller, which is the last drying roller, use flat rollers without the aforementioned tape. The surface temperature of the 2nd-13th, 15th and 17th drying drums is adjusted to 75-95℃. The surface temperature of the 14th drying drum and the 16th drying drum were adjusted to 105°C to serve as heat treatment drums. In addition, the peripheral speed (S18) of the 18th drying drum (heat treatment drum, surface temperature 105°C), which is the final drying drum, was adjusted to 14.1 m/min. Then, it was wound up in a roll shape to obtain a PVA film (thickness 60 μm, width 6080 mm). Since the effective width of the PVA film product is 5800mm, which is 91% of the casting width, it is judged as qualified.

[表1] 乾燥滾筒 編號 膠帶條件 捲取薄膜 寬度 (mm) 高度 (mm) 滾筒端部至 膠帶端部之距離 (mm) 薄膜端部至 膠帶端部之距離 (mm) 製品 有效寬度 (mm) 製品有效寬度對 鑄造寬度之比率 判定 2 40 1.26 213 85 5800 91% 合格 5 40 1.26 248 85 8 40 1.26 253 85 11 40 1.26 263 85 13 38 1.26 270 85 14 - - - - 18(最後) - - - - [Table 1] Drying drum number Tape condition Take-up film Width(mm) Height (mm) Distance from the end of the roller to the end of the tape (mm) Distance from the end of the film to the end of the tape (mm) Product effective width (mm) The ratio of the effective width of the product to the casting width determination 2 40 1.26 213 85 5800 91% qualified 5 40 1.26 248 85 8 40 1.26 253 85 11 40 1.26 263 85 13 38 1.26 270 85 14 - - - - 18 (last) - - - -

實施例2 除在實施例1中，將T模頭之鑄造寬度(4900mm)、乾燥滾筒之支數改為24支，將貼附氟系樹脂製膠帶之乾燥滾筒改為從第2乾燥滾筒至第17乾燥滾筒的16個滾筒，將前述膠帶之寬度及貼附位置如下述之表2所示的方式變更，將第2～19、22～23乾燥滾筒之表面溫度調成75～95℃，將第20乾燥滾筒及第21乾燥滾筒之表面溫度調成105℃，作為熱處理滾筒，將為最後乾燥滾筒之第24乾燥滾筒(熱處理滾筒，表面溫度105℃)的周速(S24)調為15.6m/分以外，以與實施例1同樣之方法，得到PVA薄膜。由於該PVA薄膜之製品有效寬度為4250mm，為鑄造寬度之87%，判定為合格。Example 2 Except in Example 1, the casting width of the T die (4900mm) and the number of drying drums were changed to 24, and the drying drum attached with fluorine-based resin tape was changed from the second drying drum to the 17th drying drum. For the 16 rollers of the roller, the width of the aforementioned tape and the attachment position are changed as shown in Table 2 below, and the surface temperature of the second to 19th and 22nd to 23rd drying rollers is adjusted to 75 to 95°C, and the 20th The surface temperature of the drying drum and the 21st drying drum is adjusted to 105℃. As a heat treatment drum, the peripheral speed (S24) of the 24th drying drum (heat treatment drum, surface temperature 105℃) of the final drying drum is adjusted to 15.6m/min. Otherwise, the same method as in Example 1 was used to obtain a PVA film. Since the effective width of the PVA film product is 4250mm, which is 87% of the casting width, it is judged as qualified.

[表2] 乾燥滾筒 編號 膠帶條件 捲取薄膜 寬度 (mm) 高度 (mm) 滾筒端部至 膠帶端部之距離  (mm) 薄膜端部至 膠帶端部之距離  (mm) 製品 有效寬度 (mm) 製品有效寬度對 鑄造寬度之比率 判定 2 15 1.26 188 73 4250 87% 合格 5 15 1.26 223 73 8 15 1.26 238 73 11 15 1.26 248 73 14 15 1.26 253 73 17 15 1.26 258 73 18 - - - - 20 - - - - 24(最後) - - - - [Table 2] Drying drum number Tape condition Take-up film Width(mm) Height (mm) Distance from the end of the roller to the end of the tape (mm) Distance from the end of the film to the end of the tape (mm) Product effective width (mm) The ratio of the effective width of the product to the casting width determination 2 15 1.26 188 73 4250 87% qualified 5 15 1.26 223 73 8 15 1.26 238 73 11 15 1.26 248 73 14 15 1.26 253 73 17 15 1.26 258 73 18 - - - - 20 - - - - 24 (last) - - - -

比較例1 在實施例1中，除不將氟系樹脂製膠帶貼附於乾燥滾筒以外，以同樣方法，得到PVA薄膜。由於該PVA薄膜之製品有效寬度為4720mm，為鑄造寬度的74%，判定為不合格。Comparative example 1 In Example 1, a PVA film was obtained in the same manner except that the fluorine-based resin tape was not attached to the drying drum. Since the effective width of the PVA film product was 4720mm, which was 74% of the casting width, it was judged as unqualified.

如上述，藉由使用本發明之PVA薄膜製造方法，可製造製品有效寬度大的PVA薄膜。該PVA薄膜在作為特大面積之偏光薄膜製造用的捲材薄膜上有用。As mentioned above, by using the PVA film manufacturing method of the present invention, a PVA film with a large effective product width can be manufactured. The PVA film is useful as a roll film for the production of a polarizing film with a large area.

1:異徑乾燥滾筒 2:薄膜 3:位置 4:區域 t1 ,t2 :外徑 t3 :寬度1: Reducing drying drum 2: Film 3: Position 4: Area t 1 , t 2 : Outer diameter t 3 : Width

圖1為本發明之製造方法中，異徑乾燥滾筒及與其接觸之薄膜之一例的示意圖。Fig. 1 is a schematic diagram of an example of a reducing-diameter drying drum and a film in contact with it in the manufacturing method of the present invention.

1:異徑乾燥滾筒 1: Reducing drying drum

2:薄膜 2: film

3:位置 3: location

4:區域 4: area

t1,t2:外徑 t 1 , t 2 : outer diameter

t3:寬度 t 3 : width

Claims (5)

一種光學用聚乙烯醇薄膜之製造方法，其特徵為使用具備旋轉軸互相平行之複數個乾燥滾筒的製膜裝置，將包含聚乙烯醇之製膜原液以膜狀吐出至位於該製膜裝置之最上游側的第1乾燥滾筒上並乾燥，將所得到之薄膜在接續於該第1乾燥滾筒之下游側的第2乾燥滾筒後之乾燥滾筒上進一步乾燥， 該第2乾燥滾筒後之乾燥滾筒的至少一個為異徑乾燥滾筒， 從該異徑乾燥滾筒所接觸之該薄膜的寬方向兩端部算起，距寬方向中央部側50mm以上250mm以下之位置的至少一部分區域中的該異徑乾燥滾筒之外徑，比寬方向中央部之外徑還大1.0mm～3.0mm。A method for manufacturing a polyvinyl alcohol film for optics, which is characterized by using a film-making device with a plurality of drying rollers whose rotating shafts are parallel to each other, and spit out a film-forming stock solution containing polyvinyl alcohol in a film form to the film-making device. It is dried on the first drying drum on the most upstream side, and the obtained film is further dried on the drying drum after the second drying drum on the downstream side of the first drying drum. At least one of the drying drums after the second drying drum is a reducing drying drum, The outer diameter of the reducing dryer drum in at least a part of the area at a position 50 mm or more and 250 mm or less from the center side of the width direction from the widthwise ends of the film contacted by the reducing dryer drum is greater than the width direction The outer diameter of the central part is also 1.0mm～3.0mm larger. 如請求項1之光學用聚乙烯醇薄膜之製造方法，其得到寬度2m以上之聚乙烯醇薄膜。Such as the manufacturing method of optical polyvinyl alcohol film of claim 1, which obtains a polyvinyl alcohol film with a width of 2 m or more. 如請求項1或2之光學用聚乙烯醇薄膜之製造方法，其中該外徑較大之區域的寬度為10～55mm。According to claim 1 or 2, the method for manufacturing a polyvinyl alcohol film for optics, wherein the width of the area with the larger outer diameter is 10 to 55 mm. 如請求項1或2之光學用聚乙烯醇薄膜之製造方法，其中該異徑乾燥滾筒為藉由將氟系樹脂製膠帶貼附於金屬滾筒而設置該外徑較大之區域者。The method for manufacturing a polyvinyl alcohol film for optics according to claim 1 or 2, wherein the reducing diameter drying roller is one in which the area with the larger outer diameter is provided by attaching a fluorine-based resin tape to a metal roller. 如請求項1或2之光學用聚乙烯醇薄膜之製造方法，其中該製膜裝置具備相同寬度之複數個該異徑乾燥滾筒，越下游側之異徑乾燥滾筒，該外徑較大之區域的位置越靠近寬方向中央側。For example, the manufacturing method of optical polyvinyl alcohol film of claim 1 or 2, wherein the film forming device is provided with a plurality of the reducing drying drums of the same width, and the downstream reducing drying drum is the area with the larger outer diameter The closer to the center in the width direction.
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