TWI805849B - Polyvinyl alcohol film and method for producing polarizing film using same - Google Patents

Abstract

[式(I)中，苯乙烯單元數(m)為2～3，聚氧乙烯鏈數(n)為12～30。]

[式(II)中，苯乙烯單元數(m)為2～3，聚氧乙烯鏈數(n)與聚氧丙烯鏈數(l)的合計(n＋l)為12～30。]A PVA (A), characterized in that it contains at least one surfactant (B) selected from styryl ether type surfactants represented by the following formula (I) or (II), and a surfactant selected from sulfuric acid PVA of at least one surfactant (C) of ester salt type or sulfonate type; and relative to 100 parts by mass of PVA (A), the content of surfactant (B) is 0.04 to 0.4 parts by mass, and relative to 100 parts by mass of PVA (A), the content of the surfactant (C) is 0.04 to 0.4 parts by mass. The PVA film-based active agent aggregates are small, and the peelability and film surface quality are good. Therefore, a polarizing film with good optical performance can be obtained by using the PVA film as an original sheet.

[In the formula (I), the number of styrene units (m) is 2-3, and the number of polyoxyethylene chains (n) is 12-30. ]

[In the formula (II), the number of styrene units (m) is 2-3, and the total (n+l) of the number of polyoxyethylene chains (n) and the number of polyoxypropylene chains (l) is 12-30. ]

Description

Polyvinyl alcohol film and method for producing polarizing film using same

The present invention relates to a polyvinyl alcohol film (hereinafter, "polyvinyl alcohol" is sometimes abbreviated as "PVA") with a small number of active agent aggregates and good peelability and film surface quality, and a polarizing film using the same Manufacturing method.

PVA films are used in various applications utilizing unique properties such as transparency, optical properties, mechanical strength, and water solubility. In particular, taking advantage of its excellent optical properties, PVA film is used as a polarizing film manufacturing raw material (original film) of a polarizing plate constituting a basic component of a liquid crystal display (LCD), and its use is expanding. Polarizing plates for LCDs require high optical performance, and high optical performance is also required for polarizing films that are components thereof.

In general, polarizing plates are produced by dyeing the original PVA film, uniaxially stretching, and fixing the polarizing film through boron compounds as needed, etc., and then adding triacetate fiber A protective film such as a clear (TAC) film is bonded to the surface of the polarizing film. The original PVA film is generally produced by drying a film-forming stock solution containing PVA by casting a film-making method or the like.

Many technologies are known so far regarding PVA films and their manufacturing methods. Patent Document 1 describes that an aqueous PVA resin solution containing polyoxyethylene laurylamine having a polyoxyethylene chain number of 2 is prepared as a surfactant, and the aqueous PVA resin solution is brought into contact with a drum-type roller for a contact time of 30 to 120 seconds. On the other hand, film formation was performed by a casting method, and the evaporation rate of water in the aforementioned PVA aqueous solution was set at 15 to 30% by weight/minute, whereby a PVA film with a water content of 5% by weight or less was obtained. From the foregoing, it is considered that a PVA film having excellent handling performance and no optical defects can be obtained.

Also, Patent Document 2 has been described: a PVA film comprising: PVA resin, sodium lauryl sulfate as a sulfate ester type anionic surfactant (a), sodium lauryl sulfate as an ether type nonionic surfactant (b ) polyoxyethylene lauryl ether, and lauric acid diethanolamide as the nitrogen-containing nonionic surfactant (c). Based on the above, it is considered that it has excellent optical characteristics such as no optical streaks and optical color unevenness, and can exert an excellent effect of blocking resistance.

In addition, Patent Document 3 has described: a PVA film containing: PVA resin, polyoxyethylene lauryl ether as an ether-type nonionic surfactant (a), and two types of nitrogen-containing nonionic surfactants. The surfactant (b) is polyoxyethylene laurylamine and lauric acid diethanolamide. According to the above, it is considered that it has excellent optical characteristics such as no optical streaks, and can exert the effect of excellent sticking resistance. However, for the PVA films obtained by using Patent Documents 1 to 3, active agent aggregates are formed, and improvement is required. [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]

The present invention was written to solve the above-mentioned problems, and its object is to provide a PVA film with a small number of activator aggregates and good peelability and film surface quality, and a method for producing a polarizing film using the same. [Means to solve the problem]

As a result of intensive studies by the present inventors in order to achieve the above object, it was found that by adding a predetermined amount: polyvinyl alcohol (A) (hereinafter sometimes referred to as "PVA (A)"), selected from the following At least one kind of surfactant (B) (hereinafter sometimes referred to as "surfactant (B)") of the styryl ether type surfactant represented by formula (I) or (II), and styrene At least one surfactant (C) selected from sulfate ester type or sulfonate type (hereinafter sometimes referred to as "surfactant (C)") dispersed in ether-based active agents, although the PVA before film formation The aqueous solution is cloudy, but a PVA film having a small number of active agent aggregates and good peelability and film surface quality can be obtained, and the present invention has been accomplished.

[式(I)中，苯乙烯單元數(m)為2～3，聚氧乙烯鏈數(n)為12～30]

[式(II)中，苯乙烯單元數(m)為2～3，聚氧乙烯鏈數(n)與聚氧丙烯鏈數(l)的合計(n＋l)為12～30]。 [2]如[1]記載之聚乙烯醇薄膜，其中界面活性劑(B)與界面活性劑(C)的質量比率(B：C)為1：0.2～1：10； [3]如[1]或[2]記載之聚乙烯醇薄膜，其中薄膜的寬度為1.5m以上； [4]如[1]～[3]中任一項記載之聚乙烯醇薄膜，其中薄膜的長度為3000m以上； [5]如[1]～[4]中任一項記載之聚乙烯醇薄膜，其中薄膜的厚度為10～70μm； [6]一種偏光薄膜的製造方法，其具有將如[1]～[5]中任一項記載之聚乙烯醇薄膜進行染色的步驟及進行拉伸的步驟。 [發明之效果]That is, the present invention relates to the following: [1] A polyvinyl alcohol film comprising: polyvinyl alcohol (A), styryl ether type A polyvinyl alcohol film of at least one surfactant (B) and at least one surfactant (C) selected from sulfate ester salt type or sulfonate type; and relative to 100 parts by mass of polyethylene Alcohol (A), the content of surfactant (B) is 0.04-0.4 parts by mass, and relative to 100 parts by mass of polyvinyl alcohol (A), the content of surfactant (C) is 0.04-0.4 parts by mass;

[In the formula (I), the number of styrene units (m) is 2 to 3, and the number of polyoxyethylene chains (n) is 12 to 30]

[In the formula (II), the number of styrene units (m) is 2 to 3, and the total (n+l) of the number of polyoxyethylene chains (n) and the number of polyoxypropylene chains (l) is 12 to 30]. [2] The polyvinyl alcohol film as described in [1], wherein the mass ratio (B:C) of the surfactant (B) to the surfactant (C) is 1:0.2 to 1:10; [3] Such as [ 1] or the polyvinyl alcohol film described in [2], wherein the width of the film is 1.5 m or more; [4] the polyvinyl alcohol film described in any one of [1] to [3], wherein the film length is 3000 m Above; [5] The polyvinyl alcohol film as described in any one of [1] to [4], wherein the thickness of the film is 10 to 70 μm; [6] A method of manufacturing a polarizing film, which has the following steps as in [1] A step of dyeing the polyvinyl alcohol film described in any one of [5] and a step of stretching it. [Effect of Invention]

The PVA film of the present invention has few active agent aggregates, and has good peelability and film surface quality. Therefore, by using this PVA film as an original film, a polarizing film with good optical performance can be obtained.

[Mode for Carrying Out the Invention]

[式(I)中，苯乙烯單元數(m)為2～3，聚氧乙烯鏈數(n)為12～30。]

[式(II)中，苯乙烯單元數(m)為2～3，聚氧乙烯鏈數(n)與聚氧丙烯鏈數(l)的合計(n＋l)為12～30]。The PVA film of the present invention contains: PVA (A), at least one surfactant (B) selected from styryl ether type surfactants represented by the following formula (I) or (II), and at least one surfactant (C) of sulfate ester salt type or sulfonate type,

[In the formula (I), the number of styrene units (m) is 2-3, and the number of polyoxyethylene chains (n) is 12-30. ]

[In the formula (II), the number of styrene units (m) is 2 to 3, and the total (n+l) of the number of polyoxyethylene chains (n) and the number of polyoxypropylene chains (l) is 12 to 30].

In the PVA film of the present invention, it is important to use at least one kind of styryl ether type surfactants represented by the above-mentioned formula (I) or (II) with respect to PVA (A) at a predetermined content. Surfactant (B), at least one kind of surfactant (C) selected from sulfate ester type or sulfonate type. The inventors of the present invention have confirmed that the film surface quality of the obtained PVA film deteriorates compared to the case where the surfactant (B) is used alone for PVA (A). Also, the inventors of the present invention have confirmed that when the surfactant (C) is used alone with respect to PVA (A), the peelability and film surface quality of the obtained PVA film deteriorate.

In contrast, in the present invention, by using the surfactant (B) and the surfactant (C) in combination at a predetermined content relative to PVA (A), the number of aggregates of the active agent is small, and the detachability and PVA film with good film surface quality. Here, as shown in the turbidity evaluation in the examples described later, the present inventors, when preparing a film-forming stock solution that can be used to manufacture PVA films, confirmed that it is considered to be the cause in the film-forming stock solution. White turbidity due to aggregation of active agents. However, as a result of investigation by the present inventors, it is clear that even when a PVA film is produced using this cloudy film-forming stock solution, a PVA film with a small number of active agent aggregates and good peelability and film surface quality can be obtained. This department is amazing.

[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, trimethylvinyl acetate (vinyl pivalate), vinyl versatate (Vinyl versatate), etc. These may be used individually by 1 type, and may use 2 or more types together, but the former is preferable. Vinyl acetate is preferable 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 , n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tertiary butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate and other acrylic acid esters; methacrylic acid or its salts; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, methyl methacrylates such as tertiary butyl acrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, etc.; acrylamide, N-methacrylamide Amine, N-ethylacrylamide, N,N-dimethylacrylamide, diacetoneacrylamide, acrylamidopropanesulfonic acid or its salt, acrylamidopropyldimethylamine or its salt, Acrylamide derivatives such as N-methylolacrylamide or its derivatives; methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamide Propanesulfonic acid or its salts, methacrylamide propyl dimethylamine or its salts, N-methylolmethacrylamide or its derivatives and other methacrylamide derivatives; N-vinylformamide Amine, N-vinyl acetamide, N-vinyl pyrrolidone and other N-vinyl amides; 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; acrylonitrile, methacrylonitrile, etc. Vinyl cyanide; vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride and other halogenated vinyl compounds; allyl compounds such as allyl acetate and allyl chloride; maleic acid or its salt, ester or anhydride; itaconic acid or its salt, ester or anhydride; vinyl silicon-based compounds such as vinyltrimethoxysilane; isopropenyl acetate, etc. These other monomers may be used individually by 1 type, and may use 2 or more types together. Among them, as other monomers, ethylene and olefins having 3 to 30 carbon atoms are preferred, and ethylene is more preferred.

The proportion of structural units derived from the above-mentioned other monomers in the aforementioned vinyl ester polymer is not particularly limited, based on the molar number of all structural units constituting the vinyl ester polymer, it is preferably 15 mole % or less, more preferably It is less than 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 suitably 300 or more, and further suitably 400 or more. Especially suitably, it is 500 or more. Also, if the degree of polymerization is too high, the viscosity of the aqueous solution of PVA (A) or the melted PVA (A) will increase, and film formation will tend to be difficult, so it is preferably 10,000 or less, more preferably 9,000 or less, more suitably 8,000 or less, particularly suitably 7,000 or less. Here, the so-called degree of polymerization of PVA (A) refers to the average degree of polymerization measured in accordance with the records of JIS K6726-1994, which can be measured in water at 30°C after saponification and purification of PVA (A). The limiting viscosity [η] (unit: deciliter/g) is obtained by the following formula. Polymerization degree=([η]×10 ⁴ /8.29) ^(1/0.62)

The degree of saponification of PVA (A) is not particularly limited. For example, PVA (A) of 60 mol% or more can be used. The degree of saponification of (A) is preferably at least 95 mol %, more preferably at least 98 mol %, further preferably at least 99 mol %. Here, the degree of saponification of PVA (A) refers to the structural units (typically vinyl ester monomer units) and ethylene that can be converted into vinyl alcohol units due to saponification of PVA (A). The total number of moles of alcohol units, the ratio of the number of 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: PVA with acidic functional groups such as carboxyl and sulfonic acid groups; PVA with acid anhydride groups; PVA with basic functional groups such as amine groups; such neutralizers, etc., will promote crosslinking reactions. For PVA with functional groups, the secondary processability of the PVA film will sometimes be reduced due to the cross-linking reaction between PVA molecules. Therefore, in the case of requiring excellent secondary processability like the original film for optical film production, among PVA (A), PVA with acidic functional groups, PVA with acid anhydride groups, PVA with basic functional groups The contents of the PVA and the neutralized substances are preferably 0.1% by mass or less, more preferably neither of them is contained.

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

[Styryl ether type surfactant (B)] The styryl ether type surfactant (B) that can be used in the present invention is represented by the following formula (I) or (II).

[式(I)中，苯乙烯單元數(m)為2～3，聚氧乙烯鏈數(n)為12～30。]

[In the formula (I), the number of styrene units (m) is 2-3, and the number of polyoxyethylene chains (n) is 12-30. ]

[式(II)中，苯乙烯單元數(m)為2～3，聚氧乙烯鏈數(n)與聚氧丙烯鏈數(l)的合計(n＋l)為12～30。]

[In the formula (II), the number of styrene units (m) is 2-3, and the total (n+l) of the number of polyoxyethylene chains (n) and the number of polyoxypropylene chains (l) is 12-30. ]

In the above formulas (I) and (II), the number of styrene units (m) is 2-3. When the number of styrene units (m) is less than 2, the surfactant does not sufficiently seep out to the interface between the PVA film and the drum when the PVA aqueous solution is discharged from a die and dried on the drum surface. As a result, the surfactant remaining in the PVA film will be observed as the number of aggregates. In addition, the peelability and film surface quality of the PVA film will deteriorate. On the other hand, when the number of styrene units (m) exceeds 3, the ability to lower the surface tension is insufficient and the film surface quality deteriorates.

In the above formula (I), the number of polyoxyethylene chains (n) is 12 to 30, and in the above formula (II), the total (n+l) of the number of polyoxyethylene chains (n) and the number of polyoxypropylene chains (l) is 12 to 30. By setting the number of (n) and the number of (n+l) in this range, when used in combination with the surfactant (C) described later, it is possible to obtain a low number of active agent aggregates, and the peelability and film surface quality Good PVA film.

In the above-mentioned formula (I), when the number of polyoxyethylene chains (n) is lower than 12, or in the above-mentioned formula (II), the sum of the number of polyoxyethylene chains (n) and the number of polyoxypropylene chains (l) ( When n+l) is less than 12, the ability to reduce the surface tension is insufficient and the film surface quality deteriorates.

On the other hand, in the above formula (I), when the number of polyoxyethylene chains (n) exceeds 30, or in the above formula (II), the number of polyoxyethylene chains (n) and the number of polyoxypropylene chains (l) When the total (n+l) exceeds 30, the hydrophilicity of the surfactant becomes too high, and because the surfactant is stabilized in the PVA aqueous solution, when the film is formed on the surface of the drum, the surfactant becomes It is not easy to seep out to the interface between the PVA film and the roller. As a result, problems such as peelability and deterioration of film surface quality occur. In the above formula (I), the polyoxyethylene chain number (n) is preferably 25 or less, more preferably 20 or less. In the above formula (II), the total (n+l) of the number of polyoxyethylene chains (n) and the number of polyoxypropylene chains (l) is preferably 25 or less, more preferably 20 or less.

The content of the styryl ether type surfactant (B) that can be used in the present invention is 0.04 to 0.4 parts by mass relative to 100 parts by mass of PVA (A). When the content of the styryl ether type surfactant (B) is less than 0.04 parts by mass, the peelability and surface quality of the obtained PVA film will deteriorate. The content of the styryl ether type surfactant (B) is preferably at least 0.1 parts by mass, more preferably at least 0.2 parts by mass. On the other hand, when the content of the styryl ether type surfactant (B) exceeds 0.4 parts by mass, the film surface quality of the obtained PVA film will deteriorate. The content of the styryl ether type surfactant (B) is preferably at most 0.38 parts by mass, more preferably at most 0.3 parts by mass. The styryl ether type surfactant (B) which can be used in this invention may be used individually by 1 type, and may use 2 or more types together.

[Surfactant (C)] The surfactant (C) that can be used in the present invention is at least one kind of surfactant selected from sulfate ester type or sulfonate type. The content of the surfactant (C) that can be used in the present invention is 0.04 to 0.4 parts by mass relative to 100 parts by mass of PVA (A). When the content of the surfactant (C) is less than 0.04 parts by mass, the surface quality of the obtained PVA film will deteriorate. The content of the surfactant (C) is preferably at least 0.05 parts by mass, more preferably at least 0.06 parts by mass. On the other hand, when the content of the surfactant (C) exceeds 0.4 parts by mass, pyrolyzed products of the surfactant (C) are observed as aggregates in the PVA film. Also, the surface quality of the obtained PVA film deteriorates. The content of the surfactant (C) is preferably at most 0.3 parts by mass, more preferably at most 0.2 parts by mass, further preferably at most 0.1 parts by mass.

In the present invention, the mass ratio (B:C) of the styryl ether type surfactant (B) to the surfactant (C) is preferably 1:0.2˜1:10. When the mass ratio (B:C) is lower than 1:0.2, the surface quality of the obtained PVA film may deteriorate. The mass ratio (B:C) is more preferably at least 1:0.25, further preferably at least 1:0.3. On the other hand, when the mass ratio (B:C) exceeds 1:10, the quality of the film surface may deteriorate. The mass ratio (B:C) is preferably at most 1:8, more preferably at most 1:6, further preferably at most 1:4, particularly preferably at most 1:2.

As for the aforementioned sulfate ester salt type, examples include: sodium alkyl sulfate, potassium alkyl sulfate, ammonium alkyl sulfate, triethanolamine alkyl sulfate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxypropylene alkyl ether sulfate , Sodium polyoxyethylene alkylphenyl ether sulfate, etc. The aforementioned alkyl group is preferably an alkyl group having 8 to 20 carbon atoms, more preferably a lauryl group.

As for the aforementioned sulfonate type, examples include: sodium alkyl sulfonate, potassium alkyl sulfonate, ammonium alkyl sulfonate, triethanolamine alkyl sulfonate, sodium alkylbenzene sulfonate, dodecyl diphenyl 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 preferable, and dodecyl group is more preferable among them. These may be used individually by 1 type, and may use 2 or more types together.

Among them, the surfactant (C) is preferably a sulfate ester salt type from the viewpoint of reducing the number of activator aggregates in the obtained PVA film as much as possible.

[PVA film] From the viewpoint of being able to impart flexibility to the PVA film, the PVA film of the present invention preferably contains a plasticizer. In terms of preferred plasticizers, polyhydric alcohols can be mentioned, specifically: ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylol propane, etc. . These may use only 1 type of plasticizer, and may use 2 or more types of plasticizers together. Among them, ethylene glycol or glycerin is preferred from the viewpoints 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, problems with mechanical properties such as impact strength and process passability at the time of secondary processing are less likely to arise. On the other hand, if the content of the plasticizer is 30 parts by mass or less, the film will become moderately soft and handleability will improve.

The PVA film of the present invention may further contain other components other than PVA, surfactant and plasticizer as needed. Such other components include, for example, water, antioxidants, ultraviolet absorbers, lubricants (lubricant), colorants, fillers (inorganic particles, starch, etc.), preservatives, antifungal agents, and ingredients other than the above other polymer compounds, etc. The content of other components in the aforementioned resin composition 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 polarizing film has been demanded. Therefore, the width is preferably more than 1.5m, more preferably more than 3m, further preferably more than 4.5m, and most preferably more than 5.0m. Preferably it is more than 5.5m. On the other hand, if the width of the PVA film is too wide, then or in order to increase the manufacturing cost of the film-forming apparatus of film-forming PVA film, further, under the situation that utilizes the manufacturing apparatus that is put into practical use to manufacture optical film, have When stretching uniformly, it may become difficult, so the width of the PVA film is preferably 7.5 m or less, more preferably 7.0 m or less, further preferably 6.5 m or less.

The shape of the PVA film of the present invention is not particularly limited, and it is preferably a long film from the point of view that a more uniform PVA film can be continuously and smoothly produced, or that it can be used continuously when producing an optical film, etc. . The length (length in the flow direction) of the elongated film is not particularly limited and can be set appropriately. The length of the film is preferably at least 3000 m. On the other hand, the length of the film is preferably 30000 m or less. Preferably, a long film is wound around a core or the like to form a film roll.

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

The number of active agent aggregates in the PVA film of the present invention is measured by the method described in the following examples. The number of such active agent aggregates is preferably 3 or less, more preferably 2 or less, further preferably 1 or less.

The manufacture method of the PVA film of the present invention is not particularly limited, for example, can use and contain: PVA (A), styryl ether type surfactant (B), surfactant (C), liquid medium, and as required further The film-forming stock solution containing the above-mentioned plasticizer and other components is produced by a known method such as a cast film-forming method or a melt-extrusion film-forming method. Furthermore, the film-forming stock solution may be obtained by dissolving PVA(A) in a liquid medium, or may be obtained by melting PVA(A).

With regard to the above-mentioned liquid medium in the film-making stock solution, for example: water, dimethylsulfide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, Glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, ethylenediamine, diethylenetriamine, etc., one or more of these can be used . Among these, water is preferable from the viewpoint of a small load on the environment and recyclability.

The volatile component ratio of the film-making stock solution (the proportion of volatile components in the film-making stock solution such as volatile components removed by volatilization or evaporation during film making) will vary depending on the film-making method and film-making conditions, but it is better It exists in the range of 50-90 mass %, More preferably, it exists in the range of 55-80 mass %. Since the volatile component ratio 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 film formation becomes easy. On the other hand, since the volatile component ratio 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 will be improved.

There is no particular limitation on the specific manufacturing method when the PVA film of the present invention is manufactured using the above-mentioned film-making stock solution by casting film-making method or melt-extrusion film-making method. For example, the film-making stock solution can be It is obtained by casting or discharging in a film form onto a support such as a drum or a belt, and drying on the support. The obtained film can also be further dried by a drying roller or a hot air drying device, or heat-treated by a heat treatment device, or conditioned by a humidity control device as needed. The manufactured PVA film is preferably wound around a core or the like to form 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 an original film for manufacturing polarizing films, retardation films, special light-collecting films, and the like. A PVA film with high light transmittance and high quality can be obtained by the present invention. Therefore, a PVA film for optical use is a suitable embodiment of the present invention.

The manufacturing method of the polarizing film which has the process of dyeing the said PVA film and the process of stretching is a suitable embodiment of this invention. This manufacturing method may further have a fixing treatment step, a drying treatment step, a heat treatment step, and the like. The order of dyeing and stretching is not particularly limited, and the dyeing treatment may be performed before the stretching treatment, may be performed simultaneously with the stretching treatment, or may be performed after the stretching treatment. In addition, steps such as stretching and dyeing can also be repeated many times. In particular, when stretching is divided into two or more steps, uniform stretching becomes easy, which is preferable.

As far as the dyes used in the dyeing of PVA films can be used: iodine or dichroic organic dyes (for example: 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 and treatment methods are not particularly limited.

As a method of stretching a PVA film, a uniaxial stretching method and a biaxial stretching method are mentioned, and the former is preferable. The uniaxial stretching of the PVA film in the flow direction (MD), etc., can be carried out by either the wet stretching method or the dry heat stretching method, but from the performance of the obtained polarizing film and From the viewpoint of quality stability, a wet stretching method is preferable. The wet stretching method includes stretching a PVA film in pure water, an aqueous solution containing various components such as additives or a water-soluble organic solvent, 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, a solution containing the aforementioned dye, or a fixation treatment described later. A method of performing uniaxial stretching in a bath, etc. In addition, uniaxial stretching may be performed in air using a PVA film after water absorption, or uniaxial stretching may be performed by another method.

The stretching temperature when performing uniaxial stretching is not particularly limited, but when performing wet stretching, it is preferably 20 to 90°C, more preferably 25 to 70°C, and even more preferably 30 to 65°C. When performing dry heat stretching, it is preferable to use the temperature within the range of 50-180 degreeC.

From the point of view of polarizing performance, the stretching ratio of the uniaxial stretching treatment (in the case of multi-step uniaxial stretching, it is the total stretching ratio) is preferably stretched as far as possible until the film is almost cut. Specifically, it is preferably at least 4 times, more preferably at least 5 times, and even more preferably at least 5.5 times. The upper limit of the stretch 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 consolidate the adsorption of the dye to the uniaxially stretched PVA film, it is preferable to perform a fixation treatment. For the fixation treatment, a method of immersing the PVA film in a treatment bath generally added with boric acid and/or a boron compound, etc. 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 the drying treatment or heat treatment is preferably from 30 to 150°C, particularly preferably from 50 to 140°C. If the temperature is too low, the dimensional stability of the polarizing film obtained will fall easily. On the other hand, if the temperature is too high, the degradation of the polarizing performance due to dye decomposition or the like tends to occur.

A polarizing plate can be produced by bonding an optically transparent and mechanically strong protective film to both surfaces or one surface of the polarizing film obtained as described above. As the protective film in this case, cellulose triacetate (TAC) film, cellulose acetate and butyrate (CAB) film, acrylic film, polyester film, etc. are used. In addition, as an adhesive for attaching a protective film, generally a PVA-based adhesive or a urethane-based adhesive is 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 by being bonded to a glass substrate after being coated with an adhesive such as an acrylic system. When bonding a polarizing plate to a glass substrate, a retardation film, a viewing angle improvement film, a brightness improvement film, etc. may be bonded simultaneously. [Example]

Hereinafter, although an Example etc. demonstrate this invention more concretely, this invention is not limited at all by these Examples.

[Active agent aggregate number] A region of 10 m was cut from the surface layer side of the PVA film roll to be measured, and a square sample having a width of 1.5 cm, a length of 1.5 cm, and a thickness of 60 μm was cut. Thereafter, an image of the central portion in the thickness direction of the film was taken at a magnification of 1000 using a differential interference microscope. The captured image was analyzed using image analysis software "ImagePro" manufactured by Nippon Roper Co., Ltd., and the number of active agent aggregates in a region of 135 μm×100 μm was measured.

[peelability] In the film forming of a long film of 4000 m or more, when the film was peeled from the casting drum, those that could not be peeled due to adhesion to the drum were rated as x, and those that could be peeled without any problem were rated as ○.

[Membrane Quality] The cut PVA film was arranged between the white screen and the projector in the dark room, and the shadow reflected on the screen was observed. If discontinuous shading or stripe-like shading can be confirmed, it was rated as ×, and if the aforementioned shading was not seen and uniform, it was rated as ◯. Furthermore, at the time of observation, the distance between the screen and the projector was set to 360 cm, and the distance between the screen and the PVA film was set to 10 cm.

[Evaluation of Turbidity] The film-forming stock solution was drawn out from the discharge port at the outlet of the twin-screw extruder, and the white turbidity of the solution was visually evaluated. If the liquid was transparent, it was set to ◯, if it was slightly cloudy, it was set to △, and if it was strongly cloudy, it was set to ×.

Example 1 After immersing 100 parts by mass of PVA sheets with a degree of polymerization of 2400 and a degree of saponification of 99.9 mol% in 2500 parts by mass of distilled water at 35°C for 24 hours, centrifugal dehydration was performed to obtain a PVA water-containing sheet with a volatile component ratio of 70% by mass. With respect to 333 parts by mass of this PVA water-containing sheet (100 parts by mass of dry PVA), 10 parts by mass of glycerin, 0.27 parts by mass of styrene units (m) of 2, and polyoxyethylene chains (n) of 13 or more were mixed. After the activator is used as the styryl ether type surfactant (B), and 0.08 parts by mass of polyoxyethylene lauryl ether sodium sulfate as the surfactant (C), the obtained The mixture was heated and melted (maximum temperature 130°C) to make a film-forming stock solution.

After cooling the film-making stock solution to 100°C with a heat exchanger, it is extruded from a clothes hanger die with a width of 180cm to a drum with a surface temperature of 90°C to form a film, and is further dried with a hot air drying device, and then cut through A PVA film having a film thickness of 60 μm and a width of 165 cm was continuously produced at both ends of the film thickened by neck in during film formation. This PVA film was wound around a cylindrical core with a middle length of 4000 m to prepare a film roll. The number of active agent aggregates, detachability, film surface quality, and turbidity of the film-forming stock solution were evaluated for the obtained PVA film by the above-mentioned method. The results are shown in Table 1.

Embodiment 2～5, comparative example 1～9 Except that the kind and usage amount of styryl ether type surfactant (B) and surfactant (C) were changed as shown in Table 1, it was carried out in the same manner as in Example 1, and the production of PVA film was carried out. manufacture and evaluation. The results are shown in Table 1.

[Table 1] Styryl ether type surfactant (B) Surfactant (C) mass ratio Evaluation of Membrane Stock Solution film evaluation Number of styrene units (m) Polyoxyethylene chain number (n) The sum of polyoxyethylene chain number (n) and polyoxypropylene chain number (l) (n+l) Content ^a (parts by mass) active agent type Content ^a (parts by mass) Turbidity Evaluation The number of active agent aggregates (pieces) Stripping Film quality Example 1 2 13 - 0.27 Sodium polyoxyethylene lauryl ether sulfate 0.08 1:0.3 x 2 ○ ○ Example 2 3 20 - 0.27 Sodium polyoxyethylene lauryl ether sulfate 0.08 1:0.3 △ 2 ○ ○ Example 3 3 - 12 0.27 Sodium polyoxyethylene lauryl ether sulfate 0.08 1:0.3 x 1 ○ ○ Example 4 3 12 - 0.27 sodium lauryl sulfonate 0.08 1:0.3 x 3 ○ ○ Example 5 3 12 - 0.27 Sodium Lauryl Benzene Sulfonate 0.08 1:0.3 x 2 ○ ○ Comparative example 1 3 12 - 0.27 - - - x 3 ○ x Comparative example 2 - - - - Sodium polyoxyethylene lauryl ether sulfate 0.08 - ○ 2 x x Comparative example 3 3 12 - 0.5 Sodium polyoxyethylene lauryl ether sulfate 0.08 1:0.16 x 2 ○ x Comparative example 4 3 12 - 0.02 Sodium polyoxyethylene lauryl ether sulfate 0.08 1:4 △ 2 x x Comparative Example 5 1 12 - 0.27 Sodium polyoxyethylene lauryl ether sulfate 0.08 1:0.3 △ 20 x x Comparative example 6 3 - 5 0.27 Sodium polyoxyethylene lauryl ether sulfate 0.08 1:0.3 x 5 ○ x Comparative Example 7 3 31 - 0.27 Sodium polyoxyethylene lauryl ether sulfate 0.08 1:0.3 ○ 2 x x Comparative Example 8 3 12 - 0.27 Sodium polyoxyethylene lauryl ether sulfate 0.5 1:1.9 x twenty three ○ x Comparative Example 9 3 12 - 0.27 Sodium polyoxyethylene lauryl ether sulfate 0.02 1:0.07 x 1 ○ x Content ^a ... content relative to 100 parts by mass of PVA(A)

As shown in Table 1, for the PVA films of Examples 1 to 5, although the PVA aqueous solution (film-making stock solution) was cloudy, the number of active agent aggregates in the obtained PVA film was 3 or less, and The peelability and film surface quality are also good.

On the other hand, for Comparative Example 1 where no surfactant (C) was used, the surface quality of the obtained PVA film was not good. In Comparative Example 2 where no surfactant (B) was used, the peelability and surface quality of the obtained PVA film were not good. In Comparative Example 3 in which the content of the surfactant (B) exceeds 0.4 parts by mass, the surface quality of the obtained PVA film is not good. In Comparative Example 4 in which the content of the surfactant (B) is lower than 0.04, the peelability and surface quality of the obtained PVA film are not good. In Comparative Example 5 using a surfactant (B) with a styrene unit number (m) of 1, the obtained PVA film had a large number of activator aggregates, and the detachability and film surface quality were not good. In Comparative Example 6 using a surfactant (B) in which the total (n+l) of polyoxyethylene chain number (n) and polyoxypropylene chain number (l) was 5, the film surface quality of the obtained PVA film Not good. In Comparative Example 7 using a surfactant (B) with a polyoxyethylene chain number (n) of 31, the peelability and surface quality of the obtained PVA film were not good. In Comparative Example 8 in which the content of the surfactant (C) exceeded 0.4 parts by mass, the obtained PVA film had a large number of aggregates of the active agent, and the quality of the film surface was not good. For the comparative example 9 in which the content of the surfactant (C) is lower than 0.04 mass, the film surface quality of the obtained PVA film is not good.

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Claims (5)

A polyvinyl alcohol film comprising polyvinyl alcohol (A), at least one surfactant (B) selected from styryl ether type surfactants represented by the following formula (I) or (II), And a polyvinyl alcohol film of at least one surfactant (C) selected from sulfate ester salt type or sulfonate type, wherein relative to 100 parts by mass of polyvinyl alcohol (A), the content of surfactant (B) is 0.04～0.4 mass parts, relative to 100 mass parts polyvinyl alcohol (A), the content of surfactant (C) is 0.04～0.4 mass parts, the mass ratio of surfactant (B) and surfactant (C) ( B:C) is 1:0.2~1:10,

[In the formula (I), the number of styrene units (m) is 2~3, and the number of polyoxyethylene chains (n) is 12~30]

[In the formula (II), the number of styrene units (m) is 2 to 3, and the total (n+1) of the number of polyoxyethylene chains (n) and the number of polyoxypropylene chains (1) is 12 to 30]. The polyvinyl alcohol film as claimed in claim 1, wherein the width of the film is more than 1.5m. The polyvinyl alcohol film as claimed in claim 1, wherein the length of the film is more than 3000m. Such as the polyvinyl alcohol film of claim 1, wherein the thickness of the film is 10-70 μm. A method for manufacturing a polarizing film, comprising the steps of dyeing and stretching the polyvinyl alcohol film according to any one of claims 1 to 4.