TWI794561B - Polyvinyl alcohol film and method for producing polarizing film using same - Google Patents

Abstract

[式(I)中，R為碳數8～18之烷基，聚氧伸乙基鏈數(n)為2～10]。A kind of PVA film, it contains PVA (A), nonionic surfactant (B) and anionic surfactant (C), it is characterized in that: nonionic surfactant (B) is following formula (I) For the secondary amide type aliphatic alkanolamide shown, the content of the nonionic surfactant (B) is 0.01 to 0.12 parts by mass relative to 100 parts by mass of PVA (A), and the anionic surfactant ( C) Content in a film is 0.01-0.24 mass parts with respect to 100 mass parts of PVA (A). The PVA film of the present invention has less aggregates of active agents, low haze value, good film surface quality, high elongation ratio, and good polarizing performance.

[In the formula (I), R is an alkyl group with 8 to 18 carbon atoms, and the polyoxyethylene chain number (n) is 2 to 10].

Description

Polyvinyl alcohol film and method for producing polarizing film using same

The present invention relates to a polyvinyl alcohol film containing polyvinyl alcohol (A), nonionic surfactant (B) and anionic surfactant (C) and a method for producing a polarizing film using the same.

Polyvinyl alcohol (hereinafter sometimes abbreviated as PVA) films are used in various applications utilizing unique properties regarding transparency, optical properties, mechanical strength, water solubility, and the like. In particular, taking advantage of its excellent optical properties, PVA film is used as a raw material (raw film) for the production of polarizing film of a polarizing plate that constitutes a basic component of a liquid crystal display (LCD), and its use is expanding. Polarizing plates for LCD require high optical performance, and high optical performance is also required for the polarizing film which is the constituent element.

Polarizing plates are generally produced by dyeing and uniaxially stretching the PVA film of the raw material roll, and performing fixation treatment with a boron compound or the like as required to manufacture a polarizing film, and then laminating cellulose triacetate ( TAC) film and other protective films to manufacture. The PVA film of the raw material roll is generally produced by a method of drying the film-forming stock solution containing PVA, such as a casting film-forming method.

Heretofore, there are many known techniques related to PVA film or its manufacturing method. In Patent Document 1, it is described that an aqueous PVA resin solution containing polyoxyethylene laurylamine having a chain number of 2 is prepared as a surfactant, and the aqueous PVA resin solution is brought into contact with a drum-shaped roller for a contact time of 30 to 120 seconds. A film is formed by a casting method, and a PVA film having a water content of 5% by weight or less is obtained by making the evaporation rate of water in the PVA aqueous solution 15 to 30% by weight/min. According to this, it is considered that a PVA film excellent in transportability and free from optical defects can be obtained.

In addition, Patent Document 2 describes a PVA film comprising a PVA resin, sodium lauryl sulfate as a sulfate ester type anionic surfactant (a), and polyvinyl sulfate as an ether type nonionic surfactant (b). Oxyethylene lauryl ether and diethanolamide laurate as the nitrogen-containing nonionic surfactant (c). It is considered that according to this, it has excellent optical properties such as no optical ribs or uneven optical color, and can exert the effect of excellent anti-blocking property.

Furthermore, Patent Document 3 describes a PVA film containing PVA resin, polyoxyethylene lauryl ether as an ether type nonionic surfactant (a), and two kinds of nitrogen-containing nonionic surfactants. (b) polyoxyethylene laurylamine and lauric acid diethanolamide. It is considered that according to this, it has excellent optical properties without optical ribs, etc., and can exert the effect of excellent anti-blocking property. [Prior Art Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 2011-245872 [Patent Document 2] Japanese Patent Laid-Open No. 2005-206809 [Patent Document 3] Japanese Patent Laid-Open No. 2005-206810

[Problem to be solved by the invention]

However, in the PVA films obtained in Patent Documents 1 to 3, active agent aggregates are formed, and Haze (haze) deteriorates, and improvement is required. Also, when tertiary amide type lauric acid diethanolamide is used as a nonionic surfactant as in Patent Documents 2 and 3, it is necessary to greatly increase the blending amount due to its low hydrolysis resistance (heat resistance) , there is room for improvement from an economic point of view. Furthermore, if a large amount of tertiary amide type nonionic surfactant is blended, its decomposed products tend to stay and pollution in the membrane forming step tends to occur, and there is room for improvement from the viewpoint of productivity.

Then, as a result of diligent research by the inventors of the present invention, it was found that the secondary amide type nonionic surfactant is superior in heat resistance compared to the tertiary amide type nonionic surfactant. That is, from the viewpoint of economy and productivity during PVA film production, it is preferable to use a secondary amide type nonionic surfactant. However, the inventors of the present case have confirmed that when the secondary amide type nonionic surfactant is used alone, in the obtained PVA film, the number of active agent aggregates is large, the haze value is high, and optical defects will occur. Thereby, the purpose of the present invention is to provide a kind of PVA film and the manufacture method of the polarizing film using it, and this PVA film system is active even when using the secondary amide type nonionic surfactant of high heat resistance. The number of agent aggregates is small, the haze value is low, the optical defect is small, the elongation ratio is high, and the polarizing performance when processed into a polarizing film is also good. [Means to solve the problem]

The above-mentioned problems can be solved by providing a polyvinyl alcohol film, which is a polyvinyl alcohol film containing polyvinyl alcohol (A), a nonionic surfactant (B) and an anionic surfactant (C), wherein, The nonionic surfactant (B) is a secondary amide type aliphatic alkanolamide shown in the following formula (I), Content of nonionic surfactant (B) is 0.01-0.12 mass parts with respect to 100 mass parts of polyvinyl alcohol (A), The content of the anionic surfactant (C) is 0.01 to 0.24 parts by mass relative to 100 parts by mass of polyvinyl alcohol (A);

[式(I)中，R為碳數8～18之烷基，聚氧伸乙基鏈數(n)為2～10]。

[In the formula (I), R is an alkyl group with 8 to 18 carbon atoms, and the polyoxyethylene chain number (n) is 2 to 10].

At this time, it is preferable that the total content (B+C) of the nonionic surfactant (B) and the anionic surfactant (C) is 0.05 to 0.24 parts by mass with respect to 100 parts by mass of polyvinyl alcohol (A).

Moreover, it is preferable that the content mass ratio (B:C) of a nonionic surfactant (B) and anionic surfactant (C) is 20:80-80:20.

Preferably, the film width is 1.5 m or more. It is also preferable that the length of the film is 3000 m or more. It is also preferable that the thickness of the film is 10-70 μm.

The above-mentioned problems can also be solved by providing a method of manufacturing a polarizing film, which includes the step of dyeing the above-mentioned polyvinyl alcohol film and the step of extending it.

The above-mentioned problems can also be solved by providing a production method of a polyvinyl alcohol film containing polyvinyl alcohol (A), nonionic surfactant (B) and anionic surfactant (C) , where, with: A step of preparing a film-forming stock solution by mixing polyvinyl alcohol (A), a nonionic surfactant (B) and an anionic surfactant (C), and a step of using the film-forming stock solution to form a film, Wherein, the nonionic surfactant (B) is a secondary amide type aliphatic alkanolamide shown in the following formula (I), The blending amount of the nonionic surfactant (B) in the aforementioned film-forming stock solution is 0.01 to 0.12 parts by mass relative to 100 parts by mass of polyvinyl alcohol (A), The blending amount of the anionic surfactant (C) in the film-forming stock solution is 0.01-0.24 parts by mass relative to 100 parts by mass of polyvinyl alcohol (A);

[式(I)中，R為碳數8～18之烷基，聚氧伸乙基鏈數(n)為2～10]。 [發明之效果]

[In the formula (I), R is an alkyl group with 8 to 18 carbon atoms, and the polyoxyethylene chain number (n) is 2 to 10]. [Effect of Invention]

The PVA film of the present invention has few active agent aggregates, low haze value, few optical defects, and high elongation ratio. Therefore, by using this PVA film as a raw material roll, a polarizing film with good optical performance can be obtained. Furthermore, since the nonionic surfactant (B) is a secondary amide type having high heat resistance, it is excellent in economy and productivity at the time of PVA film production.

The PVA film of the present invention contains polyvinyl alcohol (A) (hereinafter sometimes abbreviated as PVA (A)), the nonionic surfactant (B) represented by the following formula (I) and the anionic surfactant ( C).

[式(I)中，R為碳數8～18之烷基，聚氧伸乙基鏈數(n)為2～10]。

[In the formula (I), R is an alkyl group with 8 to 18 carbon atoms, and the polyoxyethylene chain number (n) is 2 to 10].

In the PVA film of the present invention, it is important to use the nonionic surfactant (B) and the anionic surfactant (C) represented by the above formula (I) in combination with a predetermined content of PVA (A). The inventors of the present case have confirmed that when the nonionic surfactant (B) represented by the above formula (I) is used alone for PVA (A), the number of active agent aggregates is large, the haze value is high, and optical defect. In addition, the inventors of the present invention have confirmed that when the anionic surfactant (C) is used alone for PVA (A), the ability to lower the surface tension is not sufficient, the step passability is deteriorated, and optical defects are generated in the PVA film.

In the present invention, the active agent aggregate can be obtained by using the nonionic surfactant (B) and the anionic surfactant (C) represented by the above formula (I) with a predetermined content of PVA (A) PVA film with few number, low haze value, few optical defects, high elongation ratio, and good polarizing performance when processed into polarizing film. In addition, since the nonionic surfactant (B) is a secondary amide type having high heat resistance, it is excellent in economy and productivity at the time of PVA film production.

The nonionic surfactant (B) used in the present invention is a secondary amide type aliphatic alkanolamide represented by the above formula (I). As a result of studies by the inventors of the present invention, it has been found that the secondary amide type aliphatic alkanolamide system is excellent in heat resistance. Therefore, by using the secondary amide-type aliphatic alkanolamide as the nonionic surfactant (B), it is possible to continuously produce PVA with a small number of active agent aggregates, a low haze value, and a high film surface quality. film. Based on this point of view, the advantage of using the secondary amide-type aliphatic alkanolamide represented by the above formula (I) as the nonionic surfactant (B) is extremely remarkable.

[PVA(A)] As PVA (A), those produced by saponifying vinyl ester-based polymers obtained by polymerizing vinyl esters can be used. Vinyl esters include, for example, vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl laurate, vinyl stearate, vinyl benzoate, and trimethylvinyl acetate. , vinyl neodecanoate, etc. These may be used alone or in combination of two or more, but the former is preferred. Vinyl acetate is preferred as the vinyl ester from the viewpoints of availability, cost, productivity of PVA(A), and the like.

Other monomers that can be copolymerized with vinyl esters include, for example, ethylene; olefins with 3 to 30 carbon atoms such as propylene, 1-butene, and isobutylene; acrylic acid or its salts; methyl acrylate, ethyl acrylate, Acrylates such as n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tertiary butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, octadecyl acrylate; methacrylic acid or its salts; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tertiary butyl methacrylate Esters, 2-ethylhexyl methacrylate, lauryl methacrylate, stearyl methacrylate and other methacrylates; acrylamide, N-methacrylamide, N-ethylacrylamide , N,N-dimethylacrylamide, diacetoneacrylamide, acrylamidopropanesulfonic acid or its salt, acrylamidopropyldimethylamine or its salt, N-methylolacrylamide or Acrylamide derivatives such as its derivatives; methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamide propanesulfonic acid or its salt, methyl Acrylamidopropyldimethylamine or its salt, N-methylolmethacrylamide or its derivatives and other methacrylamide derivatives; N-vinylformamide, N-vinylacetylamide Amines, N-vinyl amides such as N-vinylpyrrolidone; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, Isobutyl vinyl ether, tertiary butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether and other vinyl ethers; vinyl cyanide such as acrylonitrile and methacrylonitrile; vinyl chloride, partial Vinyl halides such as vinyl dichloride, vinyl fluoride, and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; maleic acid or its salt, ester, or anhydride; itaconic acid or its salt, ester or acid anhydride; vinyl silicon-based compounds such as vinyl trimethoxysilane; isopropenyl acetate, etc. These other monomers may be used individually by 1 type, and may use 2 or more types together. Among them, ethylene and an olefin having 3 to 30 carbon atoms are preferred as other monomers, and ethylene is more preferred.

The proportion of structural units derived from the above other monomers in the aforementioned vinyl ester polymer is not particularly limited, but based on the number of moles of the total structural units constituting the vinyl ester polymer, it is 15 mol% or less. Preferably, it is more preferably below 5 mol%.

The degree of polymerization of PVA (A) is not necessarily limited, but since the film strength tends to decrease as the degree of polymerization decreases, it is preferably 200 or more, more preferably 300 or more, further preferably 400 or more, especially preferably more than 500. Also, if the polymerization is too high, the viscosity of the aqueous solution of PVA (A) or molten PVA (A) will become high, and it will tend to be difficult to form a film. Therefore, it is preferably 10,000 or less, and more preferably 9,000 or less. More preferably, it is 8,000 or less, and most preferably, it is 7,000 or less. The degree of polymerization of PVA (A) referred to here refers to the average degree of polymerization measured according to the records of JIS K6726-1994, which is the limit measured in water at 30°C after resaponification and purification of PVA (A). Viscosity [η] (unit: deciliter/g) was obtained by the following formula. Degree of polymerization = ([η]×10 ⁴ /8.29) ^(1/0.62)

The degree of saponification of PVA (A) is not particularly limited, and for example, PVA (A) of 60 mol% or more can be used. However, from the viewpoint of using it as a raw material roll film for the production of optical films such as polarizing films, the amount of PVA (A) The degree of saponification is preferably above 95 mole %, more preferably above 98 mole %, and even more preferably above 99 mole %. The degree of saponification of PVA (A) referred to here refers to the structural units (typically vinyl ester monomer units) and vinyl alcohol units that can be converted into vinyl alcohol units by saponification in PVA (A). The total number of moles, the proportion of the moles of vinyl alcohol units (mole %). The degree of saponification of PVA (A) can be measured according to the description of JISK6726-1994.

For PVA (A), one type of PVA may be used alone, or two or more types of PVA different in degree of polymerization, degree of saponification, degree of modification, etc. may be used in combination. However, if the PVA film contains the following PVA, the secondary processability of the PVA film will deteriorate due to the crosslinking reaction between PVA molecules: PVA with acidic functional groups such as carboxyl and sulfonic acid groups; PVA with acid anhydride groups PVA; PVA with basic functional groups such as amine groups; PVA with functional groups that promote cross-linking reactions such as these neutralizers. Therefore, when excellent secondary processability is required, such as the raw material roll film for optical film manufacturing, PVA with acidic functional groups, PVA with acid anhydride groups, and PVA with basic functional groups in PVA (A) The content of PVA and these neutralized substances is preferably 0.1% by mass or less, and it is more preferable not to contain any of them.

The content of PVA (A) in the PVA film is preferably at least 50% by mass, more preferably at least 70% by mass, and still more preferably at least 85% by mass.

[Nonionic Surfactant (B)] In the present invention, it is important that the nonionic surfactant (B) is a secondary amide type aliphatic alkanolamide represented by the following formula (I).

[式(I)中，R為碳數8～18之烷基，聚氧伸乙基鏈數(n)為2～10]。

[In the formula (I), R is an alkyl group with 8 to 18 carbon atoms, and the polyoxyethylene chain number (n) is 2 to 10].

In the above formula (I), R is an alkyl group having 8 to 18 carbon atoms. The aforementioned alkyl group may be straight or branched, but is preferably straight. When the carbon number (alkyl chain length) of R is less than 8, a large number of optical defects will be generated in the PVA film. The carbon number (alkyl chain length) of R is preferably 9 or more, more preferably 10 or more. On the other hand, when the number of carbon atoms (alkyl chain length) of R exceeds 18, the so-called problem of increasing the number of active agent aggregates in the PVA film and increasing the haze value occurs. The carbon number (alkyl chain length) of R is preferably 15 or less, more preferably 13 or less.

In the above formula (I), the polyoxyethylene chain number (n) is 2-10. By setting the number of polyoxyethylene chains (n) within this range, the formation of active agent aggregates in the PVA film can be suppressed when used together with the anionic surfactant (C) described later. When the number of polyoxyethylene chains (n) is less than 2, the so-called problem that the number of active agent aggregates in the PVA film increases and the haze value increases occurs. The polyoxyethylene chain number (n) is preferably 4 or more. On the other hand, when the number of polyoxyethylene chains (n) exceeds 10, a large number of optical defects will be generated in the PVA film. The polyoxyethylene chain number (n) is preferably 8 or less.

Content of the nonionic surfactant (B) represented by said formula (I) is 0.01-0.12 mass parts with respect to 100 mass parts of PVA (A). When the content of the nonionic surfactant (B) is less than 0.01 parts by mass, the ability to lower the surface tension is not sufficient, the step passability is deteriorated, and a large number of optical defects are generated in the PVA film. The content of the nonionic surfactant (B) is preferably 0.02 parts by mass or more. On the other hand, when the content of the nonionic surfactant (B) exceeds 0.12 parts by mass, the number of active agent aggregates in the PVA film increases and the haze value increases. The content of the nonionic surfactant (B) is preferably at most 0.1 parts by mass, more preferably at most 0.08 parts by mass, and even more preferably at most 0.06 parts by mass. The nonionic surfactant (B) used in the present invention may be used alone or in combination of two or more.

Content of anionic surfactant (C) is 0.01-0.24 mass parts with respect to 100 mass parts of PVA (A). When the content of the anionic surfactant (C) is less than 0.01 parts by mass, the number of active agent aggregates increases and the haze value increases. Also, the limit elongation ratio will decrease. The content of the anionic surfactant (C) is preferably at least 0.02 parts by mass, more preferably at least 0.03 parts by mass. On the other hand, if the content of the anionic surfactant (C) exceeds 0.24 parts by mass, not only the number of active agent aggregates will increase, but also a problem of so-called air bubbles being mixed into the PVA film may occur. The content of the anionic surfactant (C) is preferably not more than 0.18 parts by mass, more preferably not more than 0.16 parts by mass, more preferably not more than 0.14 parts by mass, and most preferably not more than 0.12 parts by mass.

The anionic surfactant (C) is not particularly limited, but at least one selected from the group consisting of sulfate ester type and sulfonate type is preferred.

Examples of the aforementioned sulfate ester salt type include alkyl sodium sulfate, alkyl potassium sulfate, alkyl ammonium sulfate, alkyl triethanolamine sulfate, polyoxyethylene alkyl ether sodium sulfate, and polyoxypropylene alkyl ether sodium sulfate. , Sodium polyoxyethylene alkylphenyl ether sulfate, etc. As for the aforementioned alkyl group, an alkyl group having 8 to 20 carbon atoms is preferred, and an alkyl group having 10 to 16 carbon atoms is more preferred.

As for the aforementioned sulfonate type, sodium alkylsulfonate, potassium alkylsulfonate, ammonium alkylsulfonate, triethanolamine alkylsulfonate, sodium alkylbenzenesulfonate, dodecyldiphenyl Disodium ether disulfonate, sodium alkylnaphthalene sulfonate, disodium alkyl sulfosuccinate, disodium polyoxyethylene alkyl sulfosuccinate, etc. As for the aforementioned alkyl group, an alkyl group having 8 to 20 carbon atoms is preferred, and an alkyl group having 10 to 16 carbon atoms is more preferred.

The said surfactant may be used individually by 1 type, and may use 2 or more types together. Among them, it is preferable that the anionic surfactant (C) is a sulfate ester salt type from the viewpoint of the ability to lower the surface tension and the step-passability.

In the present invention, it is preferred that the total content (B+C) of the nonionic surfactant (B) and anionic surfactant (C) represented by the above formula (I) is relative to 100 mass of PVA (A) The part is 0.05 to 0.24 parts by mass. When the total content (B+C) is less than 0.05 parts by mass, the ability to reduce the surface tension is not sufficient to deteriorate the step passability, and a large number of optical defects may be generated in the PVA film. The total content (B+C) is more preferably 0.06 parts by mass or more. On the other hand, if the total content (B+C) exceeds 0.24 parts by mass, the number of active agent aggregates in the so-called PVA film may increase and the haze value may increase. The total content (B+C) is more preferably at most 0.22 parts by mass, still more preferably at most 0.2 parts by mass, and most preferably at most 0.15 parts by mass.

In the present invention, it is preferable that the content mass ratio (B:C) of the nonionic surfactant (B) represented by the above formula (I) and the anionic surfactant (C) is 20:80 to 80: 20. When the content mass ratio (B:C) is less than 20:80, there is a possibility that a large amount of optical defects may be generated in the PVA film. The content mass ratio (B:C) is more preferably at least 25:75, and more preferably at least 30:70. On the other hand, when the mass ratio (B:C) exceeds 80:20, there is a possibility that the number of active agent aggregates in the so-called PVA film increases and the haze value increases. In addition, there is a possibility that the limit elongation ratio may be lowered. The content mass ratio (B:C) is more preferably 75:25 or less, further preferably 70:30 or less.

[PVA film] From the viewpoint of imparting flexibility to the PVA film, the PVA film of the present invention preferably contains a plasticizer. Preferable plasticizers include polyhydric alcohols, specifically ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, etc. . These may use only 1 type of plasticizers, and may use 2 or more types of plasticizers together. Among these, ethylene glycol or glycerin is preferred from the viewpoint of compatibility with PVA (A), availability, and the like.

It is preferable that content of a plasticizer exists in the range of 1-30 mass parts with respect to 100 mass parts of PVA (A). When the content of the plasticizer is 1 part by mass or more, it is difficult for problems to occur in mechanical properties such as impact strength or in step passability during secondary processing. On the other hand, when the content of the plasticizer is 30 parts by mass or less, the film becomes moderately soft and handleability improves.

The PVA film of the present invention may further contain other components other than PVA, a surfactant, and a plasticizer as required. Such other components include, for example, moisture, antioxidants, ultraviolet absorbers, slip agents, colorants, fillers (inorganic particles, starch, etc.), preservatives, antifungal agents, and other polymers other than the above-mentioned components. compounds etc. The content of other components in the PVA film is preferably 10% by mass or less.

The width of the PVA film of the present invention is not particularly limited. In recent years, a wide-width polarizing film has been sought, and the width is preferably 1.5 m or more. Also, if the width of the PVA film is too wide, the manufacturing cost of the film-forming device used to manufacture the PVA film will increase; Situation, therefore, the width of the PVA film is usually 7.5m or less.

The shape of the PVA film of the present invention is not particularly limited, but a long film is preferable because it can continuously and smoothly produce a more uniform PVA film, or it can be used continuously in the production of optical films. The length (length in the flow direction) of the elongated film is not particularly limited and can be appropriately set. The length of the film is preferably 3000m or more. On the other hand, the length of the film is preferably 30,000 m or less. It is preferable to make a long film into a film roll by winding it on a core or the like.

The thickness of the PVA film of the present invention is not particularly limited and can be set appropriately. The thickness of the film is preferably 10 to 70 μm from the viewpoint of use as a raw film for producing optical films such as polarizing films. In addition, the thickness of the PVA film can be calculated|required as the average value of the value measured at arbitrary 10 places.

The haze and the number of active agent aggregates of the PVA film of the present invention can be measured by the methods described in the following examples. The haze value is preferably below 0.5, more preferably below 0.4. In addition, the number of active agent aggregates is preferably less than 550, more preferably less than 420, and still more preferably less than 300.

The production method of the PVA film of the present invention is not particularly limited, but a preferred production method is the production of a polyvinyl alcohol film containing polyvinyl alcohol (A), nonionic surfactant (B) and anionic surfactant (C). A production method comprising the steps of mixing polyvinyl alcohol (A), nonionic surfactant (B) and anionic surfactant (C) to prepare a film-forming stock solution, and using the film-forming stock solution to form a film The step; Wherein, the nonionic surfactant (B) is the secondary amide type aliphatic alkanolamide shown in the above formula (I), the nonionic surfactant (B) in the aforementioned film-making stock solution The blending amount of the polyvinyl alcohol (A) is 0.01 to 0.12 parts by mass relative to 100 parts by mass of polyvinyl alcohol (A). ) is 0.01 to 0.24 parts by mass for 100 parts by mass.

In the step of preparing the membrane-forming stock solution, a liquid medium can also be further mixed. As the liquid medium at this time, for example, water, dimethyloxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, dimethicone, etc. Ethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, ethylenediamine, diethylenetriamine, and the like can be used alone or in combination of two or more. Among them, water is preferable because of its small burden on the environment and its recyclability.

In the manufacture method of the PVA film of the present invention, for example can use the nonionic surfactant (B) that contains PVA (A), above-mentioned formula (I), anionic surfactant (C), liquid medium and A film-forming stock solution further containing the above-mentioned plasticizer or other components as required is prepared by known methods such as casting film-forming method or melt-extrusion film-forming method. In addition, the film-forming stock solution may be obtained by dissolving PVA(A) in a liquid medium, or may be obtained by melting PVA(A).

The volatile content of the film-forming stock solution (the proportion of volatile components in the film-forming stock solution that are removed by volatilization or evaporation during film-forming) also varies depending on the film-forming method and film-forming conditions, but The range of 50-90 mass % is preferable, and the range of 55-80 mass % is more preferable. Since the volatile content of the film-forming stock solution is 50% by mass or more, the viscosity of the film-forming stock solution does not become too high and it is easy to form a film. On the other hand, since the volatile content of the film-forming stock solution is below 90% by mass, the viscosity of the film-forming stock solution will not become too low, and the thickness uniformity of the obtained PVA film is improved.

The blending amount of the nonionic surfactant (B) in the film-forming stock solution is preferably 0.01 to 0.12 parts by mass relative to 100 parts by mass of polyvinyl alcohol (A). When the blending amount of the nonionic surfactant (B) is less than 0.01 parts by mass, the ability to lower the surface tension is not sufficient and the step passability is deteriorated, and a large number of optical defects are generated in the obtained PVA film. The blending amount of the nonionic surfactant (B) is preferably 0.02 parts by mass or more. On the other hand, when the blending amount of the nonionic surfactant (B) exceeds 0.12 parts by mass, the so-called problem that the number of active agent aggregates in the resulting PVA film increases and the haze value increases . The blending amount of the nonionic surfactant (B) is more preferably at most 0.1 parts by mass, more preferably at most 0.08 parts by mass, and most preferably at most 0.06 parts by mass. The nonionic surfactant (B) used in the present invention may be used alone or in combination of two or more.

The blending amount of the anionic surfactant (C) in the film-forming stock solution is preferably 0.01 to 0.24 parts by mass relative to 100 parts by mass of polyvinyl alcohol (A). When the blending amount of the anionic surfactant (C) is less than 0.01 parts by mass, the number of active agent aggregates in the obtained PVA film increases and the haze value increases. In addition, the ultimate elongation ratio of the obtained PVA film decreases. The blending amount of the anionic surfactant (C) is more preferably at least 0.02 parts by mass, and more preferably at least 0.03 parts by mass. On the other hand, when the blending amount of the anionic surfactant (C) exceeds 0.24 parts by mass, not only the number of active agent aggregates in the obtained PVA film will increase, but also the so-called air bubbles will be mixed into the PVA film. the risk of problems. The blending amount of the anionic surfactant (C) is more preferably not more than 0.18 parts by mass, more preferably not more than 0.16 parts by mass, particularly preferably not more than 0.14 parts by mass, most preferably not more than 0.12 parts by mass.

Next, the steps for film formation will be described. The PVA film of the present invention can be conveniently produced by casting film-forming method or melt-extruding film-forming method using the above-mentioned film-forming stock solution. The specific production method at this time is not particularly limited, for example, it can be obtained by casting or discharging the film-forming stock solution on a support such as a drum or a conveyor belt to form a film, and drying it on the support. The obtained film may be further dried with a drying roll or a hot air drying device, heat-treated with a heat treatment device, or conditioned with a humidity control device as required. The produced PVA film is preferably wound on a core or the like to make a film roll. In addition, both ends in the width direction of the produced PVA film may be cut off.

The PVA film of the present invention can be suitably used as a raw material roll film for manufacturing polarizing films, retardation films, special light-concentrating films, and the like. By means of the present invention, a PVA film with high light transmittance and high quality can be obtained. Therefore, the PVA film for optics is a preferable embodiment of the present invention.

A method for manufacturing a polarizing film having the steps of dyeing and stretching the aforementioned PVA film is a preferred embodiment of the present invention. This manufacturing method may further have a fixing treatment step, a drying treatment step, a heat treatment step, and the like. The sequence of dyeing and stretching is not particularly limited, and the dyeing treatment can be performed before the stretching treatment, the dyeing treatment can be performed simultaneously with the stretching treatment, or the dyeing treatment can be performed after the stretching treatment. In addition, steps such as extension and staining can be repeated multiple times. In particular, dividing the stretching into two or more stages is preferable because uniform stretching is easy.

As far as the dyes used for the dyeing of PVA films are concerned, iodine or dichroic organic dyes (such as DirectBlack 17, 19, 154; DirectBrown 44, 106, 195, 210, 223; DirectRed 2, 23, 28, 31, 37, 39, 79, 81, 240, 242, 247; DirectBlue 1, 15, 22, 78, 90, 98, 151, 168, 202, 236, 249, 270; DirectViolet 9, 12, 51, 98; DirectGreen 1 , 85; DirectYellow 8, 12, 44, 86, 87; DirectOrange 26, 39, 106, 107 and other dichroic dyes) etc. 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 dyes, but the treatment conditions or treatment methods are not particularly limited.

Examples of methods for stretching the PVA film include a uniaxial stretching method and a biaxial stretching method, with the former being preferred. The uniaxial stretching of the PVA film in the flow direction (MD), etc. can be carried out by any of the wet stretching method or the dry heat stretching method, but based on the stability of the performance and quality of the obtained polarizing film, wet stretching The extension method is preferred. The wet stretching method includes a method of stretching a PVA film in pure water, an aqueous solution containing various components such as additives or water-soluble organic solvents, or an aqueous dispersion in which various components are dispersed. Specific examples of the uniaxial stretching method by the wet stretching method include a method of uniaxial stretching in warm water containing boric acid, and a method of uniaxial stretching in a solution containing the aforementioned dye or in a fixing treatment bath described later. Axis extension methods, etc. Moreover, it is also possible to perform uniaxial stretching in air using a PVA film after water absorption, or to perform uniaxial stretching by other methods.

The stretching temperature in uniaxial stretching is not particularly limited, but in wet stretching, it is preferably in the range of 20 to 90°C, more preferably 25 to 70°C, and even more preferably 30 to 65°C. The temperature in the range of 50-180° C. is preferred for dry heat extension.

The elongation ratio of the uniaxial stretching treatment (the total elongation ratio when multi-stage uniaxial stretching is carried out), from the point of view of the polarizing performance, it is better to stretch the film as much as possible before it is about to break, specifically, it is more than 4 times More preferably, it is more than 5 times, and it is still more preferable that it is more than 5.5 times. The upper limit of the stretching ratio is not particularly limited as long as the film is not broken, but it is preferably 8.0 times or less for uniform stretching.

When manufacturing a polarizing film, in order to make the adsorption of the dye to the uniaxially stretched PVA film stronger, it is preferable to perform a fixation treatment. For the fixation treatment, a general method of immersing the PVA film in a treatment bath containing boric acid and/or a boron compound can be used. At this time, an iodine compound may be added to the treatment bath as needed.

Preferably, the PVA film that has been uniaxially stretched, or uniaxially stretched and fixed is then subjected to drying or heat treatment. The temperature of drying treatment or heat treatment is preferably 30-150°C, particularly preferably 50-140°C. If the temperature is too low, the dimensional stability of the obtained polarizing film will easily deteriorate. On the other hand, if the temperature is too high, deterioration of the polarizing performance due to decomposition of the dye or the like is likely to occur.

A protective film that is optically transparent and has mechanical strength can be bonded to both surfaces or one surface of the polarizing film obtained as described above to form a polarizing plate. As the protective film at this time, a cellulose triacetate (TAC) film, a cellulose acetate-butyrate (CAB) film, an acrylic film, a polyester film, or the like is used. In addition, as an adhesive for attaching a protective film, a PVA-based adhesive, a urethane-based adhesive, or the like is generally used, and among them, a PVA-based adhesive is preferably used.

The polarizing plate obtained as described above can be used as a component of a liquid crystal display device after being coated with an adhesive such as an acrylic system, and then bonded to a glass substrate. When bonding the polarizing plate to the glass substrate, a retardation film, a viewing angle improving film, a brightness improving film, etc. can be bonded at the same time. [Example]

The present invention will be specifically described below based on examples and the like, but the present invention is not limited by these examples.

[Heat resistance of nonionic surfactant (B)] A 10-m area was cut out from the surface layer side of the PVA film roll to be measured, and a sample piece of MD 100 mm×TD 100 mm (thickness 60 μm) was taken from an arbitrary position. The collected samples were pretreated under the following conditions.

(preprocessing conditions) 1. Precisely weigh 0.3g of sample in a 50ml sample tube. 2. Add 15ml of HFIP (hexafluoroisopropanol), stir and dissolve at 50°C. 3. Cool to room temperature after dissolving, add dropwise to 60ml of methanol (at room temperature, under stirring) to make reprecipitation. 4. Filter with a cotton plug to remove the precipitate. 5. Concentrate the filtrate with an evaporator (40° C.). 6. After concentration, dilute to 2 ml with methanol to make an analysis sample.

(quantitative determination of nonionic surfactants) Quantify the pretreated sample by HPLC to obtain the retention rate of the nonionic surfactant (B) (the content of the nonionic surfactant in the film/the nonionic interface blended during film manufacture) Active agent blending amount). HPLC was implemented under the following conditions.

(HPLC measurement conditions for nonionic surfactants) ・Apparatus: LC-20A1 (manufactured by Shimadzu Corporation) ・Mobile phase: Mixture of 0.1% formic acid aqueous solution and methanol ・Gradient time and methanol concentration of mobile phase: [Table 1] time (minutes) 0 10 15 16 25 Methanol concentration (%) 50 95 95 50 stop ・Flow rate: 1ml/min ・Column: TSKgel ODS-80Ts (4.6×150mm, 5μm, TOSOH) ・Temperature: 40℃ ・Injection volume: 20μL ・Detector: ELSD (Gain50, Gas40, Neb36℃, D.Tube45℃ )

(HPLC measurement conditions for polyoxyethylene lauryl ether sulfate sodium) ・Apparatus: AQUITY UPLC (Waters) ・Mobile phase: Mixture of 5mM IPC-DBAA aqueous solution and methanol ・Gradient time and methanol concentration of mobile phase: [Table 2 ] time (minutes) 0 10 15 16 25 Methanol concentration (%) 50 95 95 50 stop ・Flow rate: 1ml/min ・Column: TSKgel ODS-80-Ts (4.6×150mm, 5μm, TOSOH) ・Temperature: 40℃ ・Injection volume: 20μL ・Detector: ELSD (Gain100, gas40, Neb12℃, D. Tube45℃)

(HPLC measurement conditions for sodium alkyl sulfonate) ・Device: AQUITY UPLC (Waters) ・Mobile phase: Mixture of 100mM ammonium acetate aqueous solution and acetonitrile, 20:80 ・Flow rate: 1ml/min ・Column: Acclaim Surfactant Plus (4.6×150mm, 5μm, Thermo) ・Temperature: 30°C ・Injection volume: 20μL ・Detector: ELSD (Gain100, gas40, Neb12°C, D.Tube45°C)

[Quality of PVA film] (Measurement method of haze) A 10-m area was cut out from the surface layer side of the PVA film roll to be measured, and three sample pieces of MD50mm×TD50mm square (thickness 60μm) were collected from arbitrary positions. Using the haze meter "HZ-2" manufactured by Suga Test Instruments Co., Ltd., the collected samples were measured according to JIS K7136 for the haze of the central part of the PVA film three times each, and the average value was obtained.

(Method for measuring the number of active agent aggregates) A region of 10 m was cut out from the surface layer side of the PVA film roll to be measured, and a sample piece of MD50 mm×TD50 mm (thickness 60 μm) was collected from an arbitrary position. The collected samples were taken with a microscope VHX6000 (magnification: 1000 times) manufactured by KEYENCE Co., Ltd. to take images at intervals of about 1 μm in the thickness direction of the film, and the number of active agent aggregates captured in the images was counted. number.

(Evaluation method for optical defects) Visually observe and evaluate rib-like defects and shark-skin-like defects that are parallel to the flow direction (MD direction) during film formation on the PVA film. Specifically, the sample piece cut out by the PVA film obtained in the following examples and comparative examples is suspended in a vertical manner in the MD direction, and a 30W straight tube-shaped fluorescent lamp is placed vertically behind it and turned on. Ribbon-shaped defects shall be evaluated according to the following criteria. A: There are no tendon-like and shark-skin-like defects at all, and it is the most suitable grade for finished products. B: Although there are several tendon-like or shark-skin-like defects, it is a grade that can be used as a finished product. C: There are many tendon-like or shark-skin-like defects, which are not suitable for products.

(Determination of ultimate elongation ratio) A sample was taken from the PVA film roll as a measurement object in the size of MD100mm×TD50mm, and a marking line with a length of 50mm was drawn in the center of the sample. Install the 4 pieces of the marked sample on the extension jig, and uniaxially extend the sample in the longitudinal direction (MD) to 2.0 times the original length ( Phase 1 extension). Next, the sample was uniaxially stretched in the longitudinal direction (MD) to 2.5 times the original length (2nd stage extension).

Next, the sample was uniaxially stretched in the longitudinal direction (MD) to 3.6 times the original length while being immersed in a cross-linking bath at a temperature of 32°C containing boric acid at a concentration of 2.6% by mass for 2 minutes (the third stage stretching ). Furthermore, this sample was uniaxially stretched (fourth stage stretching) while being immersed in a stretching bath at a temperature of 57° C. containing boric acid at a concentration of 2.8% by mass and potassium iodide at a concentration of 5.0% by mass. The time point at which 2 pieces broke was taken out from the extension bath. Measure the distance between the marking lines of two unbroken samples, divide the distance between the marking lines after stretching by the distance between marking lines before stretching (50mm), and use it as the ultimate elongation ratio at the stretching temperature of 57°C .

[Polarizing performance of polarizing film] (a) Production of polarizing film The PVA film obtained in the examples and comparative examples was stretched to the ultimate stretching ratio in the same way as the above-mentioned "measurement of the ultimate stretching ratio", and the unbroken 2 The sheet sample was dried at 60° C. for 1 minute to form a polarizing film. At this time, the iodine concentration in the dyeing bath was changed in the range of 0.02 to 0.05%, and 10 polarizing films with different amounts of iodine were produced, and the light transmittance Ts and polarization degree V were obtained by the following method. (b) The mensuration of transmittance Ts is taken the square sample of 2 pieces of MD20mm * TD20mm by using the polarizing film that the PVA film that gains in the example or comparative example is made, uses the spectrophotometer (Japan Spectroscopic Co., Ltd. with integrating sphere) "V7100" manufactured by the company), according to JIS Z8722:2009 (measurement method of object color), perform C light source, 2° field of view in the visible light region, and measure the sensitivity when the longitudinal direction is inclined at 45° for one sample. The transmittance of light and the transmittance of light at an inclination of -45°, and their average value Ts1 (%) is obtained. For the other sample, the transmittance of light at an inclination of 45° and the transmittance of light at an inclination of -45° were measured in the same manner, and their average value Ts2 (%) was obtained. Ts1 and Ts2 were averaged according to the following formula (1) to obtain the transmittance Ts (%) of the polarizing film. Ts=(Ts1+Ts2)/2...(1) (c) Measurement of polarization V Measure the transmittance T in the same manner as in the above "(b) Measurement of transmittance Ts" ∥ (%) and the transmittance T⊥(%), and obtain the degree of polarization V(%) according to the following formula (2), where the transmittance T ∥ (%) is the 2 taken in the measurement of the above transmittance Ts The transmittance of light when the sample pieces are overlapped in parallel in the longitudinal direction, and the transmittance T⊥ (%) is the two samples taken in the measurement of the above transmittance Ts in the longitudinal direction The penetration rate of the light when overlapped in an orthogonal manner. V = {(T ∥ -T⊥)/(T ∥ +T⊥)} ^1/2 ×100…(2) (d) Calculation of light transmittance The value of transmittance Ts for the polarizing film produced, Then draw a graph of the value of the degree of polarization V to obtain an approximate formula. Then, the transmittance Ts when the degree of polarization V is 99.995% is calculated from the approximate formula, and used as an index of light transmittance.

Example 1 As PVA (A), chips of PVA (a saponified product of a homopolymer of vinyl acetate) having a degree of polymerization of 2400 and a degree of saponification of 99.9 mol % were used. After immersing 100 parts by mass of the chips of PVA in 2500 parts by mass of distilled water at 35° C., centrifugal dehydration was performed to obtain water-containing chips of PVA with a volatile content of 60 mass %.

For 250 parts by mass of the PVA hydrous chips (100 parts by mass of PVA), 25 parts by mass of distilled water, 12 parts by mass of glycerin, 0.03 parts by mass of a nonionic surfactant (B), and 0.04 parts by mass of an anionic surfactant (C) were mixed. After mass parts, the obtained mixture was heated and melted with a twin-screw extruder (maximum temperature 130° C.) to prepare a film-forming stock solution. The nonionic surfactant (B) used at this time is that the carbon number of R (alkyl) in the above formula (I) is 12, and the number of polyoxyethylene chains in the above formula (I) (n ) is a secondary amide type aliphatic alkanolamide of 6. Also, the anionic surfactant (C) is sodium polyoxyethylene alkyl ether sulfate (the number of polyoxyethylene chains is 3, and the number of carbon atoms in the alkyl chain is 12).

After the film-making stock solution is cooled to 100°C by a heat exchanger, it is extruded from a 180cm-wide hanger die onto a drum with a surface temperature of 90°C to form a film, and then dried with a hot air drying device, and then cut off the Both ends of the film were necked and thickened during film formation, thereby continuously producing a PVA film with a film thickness of 60 μm and a width of 165 cm. Among the produced PVA films, the amount having a length of 4000 m was wound up on a cylindrical core to obtain a film roll. For the obtained PVA film, the heat resistance, optical defect, haze, number of active agent aggregates, ultimate elongation ratio and polarizing performance of the polarizing film of the nonionic surfactant (B) were evaluated according to the above method. The results are shown in Table 3.

Embodiment 2～9, comparative example 1～5 Except that the type and amount of the nonionic surfactant (B) and the anionic surfactant (C) were changed as shown in Table 3, a PVA film was produced and evaluated in the same manner as in Example 1 . In Examples 8 and 9, sodium alkylsulfonate having 15 carbon atoms in the alkyl chain was used as the anionic surfactant (C). In Comparative Example 5, tertiary amide type lauric acid diethanolamide was used as the nonionic surfactant (B). The results are shown in Table 3.

As shown in Table 3, the PVA film-based active agent aggregates of Examples 1 to 9 had few aggregates, and the haze value was also low. Although the PVA films of Example 7 and Example 8 have several defects, they are of a grade that can be used as a product. In addition, the PVA films of Examples 1 to 9 are not easily broken due to the high ultimate elongation ratio, and the polarizing properties are also excellent. On the other hand, the PVA film of Comparative Example 1 that did not use the nonionic surfactant (B) represented by the above formula (I) had a large number of optical defects. The PVA film of Comparative Example 2 in which the anionic surfactant (C) was not used, the PVA film of Comparative Example 3 in which the content of the nonionic surfactant (B) represented by the above formula (I) was large, and the anionic interface The PVA film of Comparative Example 4 in which the added amount of the active agent (C) was large had a large number of active agent aggregates and a high haze value. Furthermore, the PVA films of Comparative Examples 2 to 4 are films with low ultimate elongation ratios and are easily broken, and the polarizing properties are also not good. In Comparative Example 5 using diethanolamide laurate as the nonionic surfactant, the heat resistance of the nonionic surfactant was low, the number of active agent aggregates was large, and the haze value was also high. In addition, the PVA film of Comparative Example 5 is a film with a low ultimate elongation ratio and is easily broken, and its polarizing performance is also not good.

[table 3] Non-ionic surfactant (B) Anionic Surfactant (C) Total content (B+C) Containing mass ratio (B): (C) Heat resistance of nonionic surfactant (B) The quality of PVA film Alkyl carbon number Polyoxyethylene side chain number (n) Blending amount ^*1) (parts by mass) Content ^*2) (parts by mass) type Blending amount ^*1) (parts by mass) Content ^*2) (parts by mass) Content in film ^*3) / blending amount optical defect Haze Active agent condensate (unit) Ultimate elongation ratio Polarizing performance of polarizing film [transmittance (%)] Example 1 12 6 0.030 0.029 Sodium Polyoxyethylene Alkyl Ether Sulfate 0.040 0.032 0.061 48:52 0.98 A 0.10 50 6.36 43.6 Example 2 12 6 0.030 0.029 Sodium Polyoxyethylene Alkyl Ether Sulfate 0.080 0.065 0.094 31:69 0.98 A 0.18 123 6.36 43.6 Example 3 12 6 0.030 0.030 Sodium Polyoxyethylene Alkyl Ether Sulfate 0.120 0.095 0.125 24:76 0.99 A 0.21 147 6.36 43.6 Example 4 12 6 0.050 0.048 Sodium Polyoxyethylene Alkyl Ether Sulfate 0.040 0.031 0.079 61:39 0.96 A 0.24 176 6.36 43.6 Example 5 12 6 0.050 0.048 Sodium Polyoxyethylene Alkyl Ether Sulfate 0.080 0.065 0.113 42:58 0.96 A 0.39 331 6.34 43.5 Example 6 12 6 0.070 0.068 Sodium Polyoxyethylene Alkyl Ether Sulfate 0.040 0.033 0.101 67:33 0.97 A 0.36 390 6.35 43.5 Example 7 12 6 0.070 0.067 Sodium Polyoxyethylene Alkyl Ether Sulfate 0.180 0.145 0.212 32:68 0.96 B 0.50 550 6.34 43.5 Example 8 12 6 0.030 0.029 Sodium alkyl sulfonate 0.040 0.038 0.067 44:56 0.98 B 0.14 69 6.36 43.6 Example 9 12 6 0.050 0.049 Sodium alkyl sulfonate 0.080 0.077 0.126 39:61 0.98 A 0.17 90 6.36 43.6 Comparative example 1 - - - - Sodium Polyoxyethylene Alkyl Ether Sulfate 0.080 0.062 0.062 0:100 - C 0.10 38 6.36 43.6 Comparative example 2 12 6 0.070 0.069 - - - 0.069 100:0 0.98 B 0.55 646 6.33 43.4 Comparative example 3 12 6 0.130 0.127 Sodium Polyoxyethylene Alkyl Ether Sulfate 0.040 0.032 0.159 80:20 0.98 B 0.75 940 6.32 43.4 Comparative example 4 12 6 0.070 0.069 Sodium Polyoxyethylene Alkyl Ether Sulfate 0.300 0.241 0.310 22:78 0.98 B 0.55 620 6.33 43.4 Comparative Example 5 Diethanolamide Laurate 0.100 0.072 Sodium Polyoxyethylene Alkyl Ether Sulfate 0.080 0.063 0.135 53:47 0.72 A 0.90 1350 6.30 43.3 *1): The blending amount of surfactant (B) or (C) relative to 100 parts by mass of PVA at the time of PVA film production. *2): The content of the surfactant (B) in the PVA film relative to 100 parts by mass of PVA. *3): The ratio of the surfactant (B) remaining in the PVA film after manufacturing the PVA film.

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Claims (8)

A kind of polyvinyl alcohol film, it contains polyvinyl alcohol (A), nonionic surfactant (B) and anionic surfactant (C), wherein, nonionic surfactant (B) is following formula ( For the secondary amide type aliphatic alkanolamide shown in I), the content of the nonionic surfactant (B) is 0.01 to 0.12 parts by mass relative to 100 parts by mass of polyvinyl alcohol (A), and the content of the anionic surfactant is 0.01 to 0.12 parts by mass. The content of the surfactant (C) is 0.01-0.24 parts by mass relative to 100 parts by mass of polyvinyl alcohol (A);

[In the formula (I), R is an alkyl group with 8 to 18 carbon atoms, and the polyoxyethylene chain number (n) is 2 to 10]. Such as the polyvinyl alcohol film of claim 1, wherein the total content (B+C) of the nonionic surfactant (B) and the anionic surfactant (C) is relative to 100 parts by mass of the polyvinyl alcohol (A) It is 0.05 to 0.24 parts by mass. The polyvinyl alcohol film according to claim 1 or 2, wherein the mass ratio (B:C) of the nonionic surfactant (B) to the anionic surfactant (C) is 20:80 to 80:20. The polyvinyl alcohol film as claimed in claim 1 or 2, which is a film width of 1.5m or more. The polyvinyl alcohol film as claimed in claim 1 or 2, the film length is more than 3000m. As the polyvinyl alcohol film of claim 1 or 2, the thickness of the film is 10-70 μm. A method for manufacturing a polarizing film, which has the step of dyeing the polyvinyl alcohol film according to any one of claims 1-6 and the step of stretching. A kind of production method, it is the production method of the polyvinyl alcohol film that contains polyvinyl alcohol (A), nonionic surfactant (B) and anionic surfactant (C), and it has mixing polyvinyl alcohol (A ), a nonionic surfactant (B) and an anionic surfactant (C) to prepare a film-forming stock solution, and a step of using the film-forming stock solution to form a film, wherein the nonionic surfactant (B ) is the secondary amide type aliphatic alkanolamide shown in the following formula (I), and the blending amount of the nonionic surfactant (B) in the film-making stock solution is relative to polyvinyl alcohol (A ) is 0.01 to 0.12 parts by mass for 100 parts by mass, and the blending amount of the anionic surfactant (C) in the film-forming stock solution is 0.01 to 0.24 parts by mass relative to 100 parts by mass of polyvinyl alcohol (A) ;

[In the formula (I), R is an alkyl group with 8 to 18 carbon atoms, and the polyoxyethylene chain number (n) is 2 to 10].