TW202134325A - Polyvinyl alcohol film - Google Patents

Abstract

Provided is a PVA film containing PVA (A), a nonionic surfactant (B), an anionic surfactant (C), and a chelating agent (D), characterized in that: the nonionic surfactant (B) is alkanol amide; the amount of the nonionic surfactant (B) is 0.01 to 0.20 parts by mass relative to 100 parts by mass of the PVA (A); the amount of the anionic surfactant (C) is 0.01 to 0.20 parts by mass relative to 100 parts by mass of the PVA (A); the chelating agent (D) is at least one compound selected from the group consisting of organic carboxylic acid compounds, amino carbonate compounds, and hydroxyamino carbonate compounds; and the amount of the chelating agent (D) is 0.005 to 0.20 parts by mass relative to 100 parts by mass of the PVA (A). This configuration can eliminate contaminations occurring in the manufacturing process, hence making the PVA film easy to peel and have less optical defects while also making the manufacture of the film satisfactory.

Description

Polyvinyl Alcohol Film

The present invention relates to a polyvinyl alcohol film containing polyvinyl alcohol (A), nonionic surfactant (B), anionic surfactant (C), and chelating agent (D).

Polyvinyl alcohol (hereinafter abbreviated as PVA) films are used in various applications using unique properties such as transparency, optical properties, mechanical strength, and water solubility. In particular, using its excellent optical properties, PVA films are used as raw materials (raw films) for the production of polarizing films of polarizing plates, which are the basic constituent elements of liquid crystal displays (LCDs), and their uses are expanding. The polarizing plate for LCD requires high optical performance, and high optical performance is also required for the polarizing film of its constituent elements.

Generally speaking, the polarizing plate is made by dyeing the raw material PVA film, uniaxially stretching, and fixing treatment with boron compound if necessary, etc., and then the triacetate cellulose (TAC) film It is manufactured by bonding a protective film such as the like to the surface of the polarizing film. Moreover, generally, the raw material PVA film is manufactured by the method of drying the film-forming solution containing PVA, such as a casting film-making method.

Many technologies regarding PVA films and their manufacturing methods have been known so far. Patent Document 1 describes a kind of containing sodium lauryl sulfate as a sulfate type anionic surfactant (a), polyoxyethylene lauryl ether as an ether type nonionic surfactant (b), and as A PVA film of lauric acid diethanolamide containing nitrogen-type nonionic surfactant (c). According to this, it has excellent optical characteristics such as no optical streaks, optical color unevenness, and the like, and can exhibit excellent anti-blocking effects.

In addition, Patent Document 2 describes a polyoxyethylene lauryl ether containing PVA resin as an ether-type nonionic surfactant (a), and a combination of two nitrogen-containing nonionic surfactants (b) Polyoxyethylene dodecylamine and lauric acid diethanolamide PVA film. According to this, it has excellent optical characteristics without optical streaks, etc., and can exhibit excellent anti-blocking effects. [Prior Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Application Publication No. 2005-206809 Patent Document 2: Japanese Patent Application Publication No. 2005-206810

[The problem to be solved by the invention]

However, as in Patent Document 1, when a sulfate type anionic surfactant such as sodium lauryl sulfate and a nitrogen-containing nonionic surfactant such as diethanolamide laurate are used, due to these water resistance The decomposability (heat resistance) is low and the blending amount needs to be increased, and there is still room for improvement from an economic point of view. In addition, if these surfactants are blended in large amounts, their decomposition products are likely to stay and contamination in the production step is likely to occur, and there is room for improvement from the viewpoint of productivity. Also, as in Patent Document 2, when a nitrogen-containing non-ionic surfactant is used instead of an anionic surfactant as the surfactant, in addition to the above-mentioned economic and productivity problems, there is also a problem in the PVA film. Many optical defects are such problems.

The present invention was made to solve the above-mentioned problems, and its object is to provide a PVA film that has excellent productivity, few optical defects, and good peelability because it can prevent the occurrence of contamination in the production process. [Means to solve the problem]

The above-mentioned problem can be solved by providing a polyvinyl alcohol film. The polyvinyl alcohol film is a polyvinyl alcohol film containing polyvinyl alcohol (A), nonionic surfactant (B), anionic surfactant (C), and chelating agent (D), wherein the nonionic interface The active agent (B) is an alkanol amide, the content of the nonionic surfactant (B) is 0.01 to 0.20 parts by mass relative to 100 parts by mass of the polyvinyl alcohol (A), and the anionic surfactant ( The content of C) is 0.01 to 0.20 parts by mass relative to 100 parts by mass of polyvinyl alcohol (A), and the chelating agent (D) is selected from organic carboxylic acid-based compounds, amino carbonate-based compounds, and hydroxylamines The content of (D) of the chelating agent in at least one compound of the group of base carbonate-based compounds is 0.005 to 0.20 parts by mass relative to 100 parts by mass of polyvinyl alcohol (A).

At this time, the ratio of the number of moles of the chelating agent (D) to the number of moles of the iron element in the polyvinyl alcohol film is preferably 50 times or more. The content of iron in the polyvinyl alcohol film is also preferably 0.05 ppm to 1.5 ppm.

In addition, at this time, the film width is preferably 1.5 m or more. The length of the film is also preferably 3000 m or more. The thickness of the film is also preferably 10 to 70 μm. [Effects of Invention]

According to the present invention, it is possible to provide a PVA film that has excellent productivity, few optical defects, and good peelability because it can prevent the occurrence of contamination in the production step.

[Form to implement the invention]

The PVA film of the present invention contains a certain amount of PVA (A), a specific nonionic surfactant (B), an anionic surfactant (C), and a specific chelating agent (D), respectively. The inventors of the present invention found that PVA films containing a certain amount of PVA (A), non-ionic surfactant (B), anionic surfactant (C), and chelating agent (D) have few optical defects and peelability. For good.

Conventionally, as nonionic surfactants, alkanolamides such as lauric acid diethanolamide have been widely used. However, nonionic surfactants such as alkanolamides and anionic surfactants such as sulfate salt type have low heat resistance. Therefore, it is decomposed to generate fatty acids, and the fatty acids combine with the polyvalent metal ions present in the production step to form fatty acid salts. This fatty acid salt becomes one of the causes of pollution generated in the production step, and it is required to be improved. As a result of careful examination, the inventors found that by containing a certain amount of PVA (A), nonionic surfactant (B), and anionic surfactant (C), a certain amount of specific Chelating agent (D) can prevent pollution in the production step. Therefore, as in the present invention, it is important to contain a certain amount of PVA (A), a specific nonionic surfactant (B), an anionic surfactant (C), and a specific chelating agent (D). By satisfying such a configuration, it is possible to obtain a PVA film that has excellent productivity, few optical defects, and good peelability because it can prevent the occurrence of contamination in the production step. In addition, in the present invention, the reason why such a PVA film can be obtained is presumably because the chelating agent (D) captures the polyvalent metal ions represented by iron in the film forming stock solution, and in the film forming step Suppresses the binding reaction of fatty acids (nonionic surfactants or decomposition products of anionic surfactants) and polyvalent metal ions, and suppresses the formation of fatty acid salts.

[PVA(A)] PVA (A) can be manufactured by saponifying a vinyl ester polymer obtained by polymerizing vinyl ester. For vinyl esters, for example, vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl laurate, vinyl stearate, vinyl benzoate, trimethyl vinyl acetate, Vinyl versatate and so on. These may be used individually by 1 type, and may use 2 or more types together, but the former is preferable. From the viewpoints of availability, cost, productivity of PVA (A), etc., vinyl acetate is preferably vinyl acetate.

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, dodecyl acrylate, stearyl acrylate, etc.; methyl Acrylic acid or its salt; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, methacrylic acid tertiary Methacrylates such as butyl ester, 2-ethylhexyl methacrylate, lauryl methacrylate, stearyl methacrylate, etc.; acrylamide, N-methacrylamide, N-ethyl propylene Amide, N,N-dimethyl acrylamide, diacetone acrylamide, acrylamide propane sulfonic acid or its salt, acrylamide propyl dimethyl amine or its salt, N-methylol acrylamide Acrylic amide derivatives such as amines or derivatives thereof; methacrylamide, N-methyl methacrylamide, N-ethyl methacrylamide, methacrylamide propanesulfonic acid or its salt , Methacrylamide, propyldimethylamine or its salt, N-methylolmethacrylamide or its derivatives and other methacrylamide derivatives; N-vinylmethacrylamide, N- N-vinyl amide such as vinyl acetamide and N-vinyl pyrrolidone; 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, vinylidene chloride, vinyl fluoride, vinylidene fluoride and other vinyl halides; allyl compounds such as allyl acetate and allyl chloride; maleic acid or its salts, esters or anhydrides; Iconic acid Or its salts, esters or acid anhydrides; vinyl silyl compounds such as vinyl trimethoxysilane; isopropyl 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-based polymer is not particularly limited, but it is preferably 15 mol% or less according to the number of moles of all structural units constituting the vinyl ester-based polymer , More preferably 5 mol% or less.

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, particularly preferably 500 or more . In addition, if the polymerization is too high, the viscosity of the aqueous solution of PVA (A) or molten PVA (A) tends to increase, and film formation tends to become difficult. Therefore, it is preferably 10,000 or less, more preferably 9,000 or less, and more preferably 8,000 or less, particularly preferably 7,000 or less. The degree of polymerization of PVA (A) here means the average degree of polymerization measured in accordance with the description of JIS K6726-1994. After PVA (A) can be re-saponified and purified, it can be heated at 30°C by the following formula The ultimate viscosity [η] (unit: common/g) measured in the water. Degree of polymerization = ([η]×10 ⁴ /8.29) ^(1/0.62)

The degree of saponification of PVA (A) is not particularly limited. For example, PVA (A) at 60 mol% or more can be used. The saponification degree of) is preferably 95 mol% or more, more preferably 98 mol% or more, and still more preferably 99 mol% or more. The degree of saponification of PVA (A) referred to here refers to structural units (typically vinyl ester monomer units) that can be converted into vinyl alcohol units by saponification and The total moles of vinyl alcohol units, and the ratio of the moles of the vinyl alcohol units (mol%). The degree of saponification of PVA (A) can be measured in accordance with the description of JIS K6726-1994.

PVA (A) may use one type of PVA alone, or two or more types of PVA with different degrees of polymerization, degree of saponification, and degree of modification may be used in combination. However, if the PVA film contains: PVA with acidic functional groups such as carboxyl groups and sulfonic acid groups; PVA with acid anhydride groups; PVA with basic functional groups such as amine groups; these neutralized products have the ability to promote crosslinking The PVA of the reacted functional group may decrease the secondary processability of the PVA film due to the cross-linking reaction between PVA molecules. Therefore, like raw material films for optical film manufacturing, when excellent secondary processability is required, PVA (A) has acidic functional groups, PVA with acid anhydride groups, and basic functional groups. 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 aforementioned PVA film is preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably 85% by mass or more.

[Non-ionic surfactant (B)] The content of the nonionic surfactant (B) is 0.01 to 0.20 parts by mass relative to 100 parts by mass of PVA (A). When the content of the nonionic surfactant (B) is less than 0.01 parts by mass, many optical defects are generated in the PVA film and the releasability deteriorates. The content of the nonionic surfactant (B) is preferably 0.02 parts by mass or more, more preferably 0.04 parts by mass or more. On the other hand, when the content of the nonionic surfactant (B) is more than 0.20 parts by mass, the generation of pollution in the production step cannot be prevented, and the productivity is reduced. The content of the nonionic surfactant (B) is preferably 0.16 parts by mass or less, more preferably 0.12 parts by mass or less.

The nonionic surfactant (B) used in the present invention is an alkanolamide. The type of alkanolamide is not particularly limited, but suitable aliphatic alkanolamides such as lauric acid diethanolamide, oleic acid diethanolamide, and lauric acid monoethanolamide. As for the aliphatic alkanol amines, aliphatic alkanol amides of tertiary amide type and aliphatic alkanol amides of secondary amide type can be used.

In addition, as the nonionic surfactant (B), aliphatic alkanolamine having a polyoxyethylene group can also be suitably used. The aforementioned alkanol amides include aliphatic alkanol amines of the secondary amide type represented by the following formula (I), and aliphatic amines of the tertiary amide type represented by the following formula (II) Alkanol amines.

[式(I)中，R為碳數8～18之烷基，聚氧乙烯鏈數(n)為2～10。]

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

[式(II)中，R為碳數8～18之烷基，聚氧乙烯鏈數(n)為2～10。]

[In formula (II), R is an alkyl group having 8 to 18 carbon atoms, and the number of polyoxyethylene chains (n) is 2-10. ]

In the above formulas (I) and (II), R is an alkyl group having 8 to 18 carbon atoms. The aforementioned alkyl group may be linear or branched, but is preferably linear. When the carbon number (alkyl chain length) of R is less than 8, there is a concern that many optical defects will occur 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 carbon number (alkyl chain length) of R is more than 18, the number of aggregates of the active agent may increase and the haze value may increase. The carbon number (alkyl chain length) of R is preferably 15 or less, more preferably 13 or less.

In the above formulas (I) and (II), the number of polyoxyethylene chains (n) is 2-10. When the number of polyoxyethylene chains (n) is less than 2, the number of aggregates of the active agent may increase, and the haze value may increase. The number of polyoxyethylene chains (n) is preferably 4 or more. On the other hand, when the number of polyoxyethylene chains (n) is greater than 10, there is a concern that many optical defects will occur in the PVA film. The number of polyoxyethylene chains (n) is preferably 8 or less.

[Anionic Surfactant (C)] The content of the anionic surfactant (C) is 0.01 to 0.20 parts by mass relative to 100 parts by mass of PVA (A). If the content of the anionic surfactant (C) is out of this range, optical defects increase. The content of the anionic surfactant (C) is preferably 0.02 parts by mass or more, more preferably 0.04 parts by mass or more. On the other hand, the content of the anionic surfactant (C) is preferably 0.16 parts by mass or less, and more preferably 0.12 parts by mass or less.

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

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

As for the aforementioned sulfonate type, sodium alkyl sulfonate, potassium alkyl sulfonate, ammonium alkyl sulfonate, triethanolamine alkyl sulfonate, sodium alkylbenzene sulfonate, dodecyl diphenyl ether Disodium disulfonate, sodium alkylnaphthalene sulfonate, disodium alkylsulfosuccinate, disodium polyoxyethylene alkylsulfosuccinate, etc. The aforementioned alkyl group is preferably an alkyl group having 8 to 20 carbon atoms, and more preferably an alkyl group having 10 to 16 carbon atoms.

The said surfactant may be used individually by 1 type, and may use 2 or more types together. Among them, from the viewpoint of reducing optical defects, the anionic surfactant (C) is preferably a sulfate salt type.

[Chelating Agent (D)] The content of the chelating agent (D) is 0.005 to 0.20 parts by mass relative to 100 parts by mass of PVA (A). In the present invention, the chelating agent (D) captures the polyvalent metal ions represented by iron in the film-forming stock solution, and inhibits fatty acid (nonionic surfactant (B) or anionic interfacial activity) in the film-forming step. The combination reaction of the decomposition product of the agent (C) and the polyvalent metal ion suppresses the formation of fatty acid salt. When the content of the chelating agent (D) is less than 0.005 parts by mass, the generation of contamination in the production step (film forming step) cannot be prevented, and productivity is reduced. The content of the chelating agent (D) is preferably 0.007 parts by mass or more, more preferably 0.01 parts by mass or more. On the other hand, when the content of the chelating agent (D) exceeds 0.20 parts by mass, optical defects increase. The content of the chelating agent (D) is preferably 0.15 parts by mass or less, more preferably 0.1 parts by mass or less.

In addition, the ratio of the number of moles of the chelating agent (D) to the number of moles of the iron element in the PVA film is preferably 50 times or more. With the ratio being 50 times or more, the generation of pollution in the production step can be sufficiently prevented. The ratio is more preferably 80 times or more, and still more preferably 100 times or more. On the other hand, the ratio is usually 500 times or less.

The chelating agent (D) in the present invention is at least one compound selected from the group consisting of an organic carboxylic acid compound, an amino carbonate compound, and a hydroxyl amino carbonate compound. That is, the so-called chelating agent (D) in this specification is a compound that combines with a polyvalent metal ion to form a chelate compound, and is selected from the group consisting of organic carboxylic acid compounds, amino carbonate compounds, and hydroxyl amino carbonates. At least one compound of the group of ester compounds.

The organic carboxylic acid compound is a compound or a salt thereof having at least one group selected from the group consisting of a carboxyl group and a hydroxyl group, and at least one of the groups is a carboxyl group. Examples of organic carboxylic acid-based compounds include aliphatic, alicyclic, aromatic carboxylic acids, or these salts, and among them, aliphatic carboxylic acids or their salts are suitable. Aliphatic carboxylic acids or their salts include aliphatic dicarboxylic acids or their salts such as oxalic acid, malonic acid, succinic acid, glutaric acid, and adipic acid; lactic acid, tartaric acid, citric acid, gluconic acid, etc. The aliphatic hydroxycarboxylic acid or its salt; the ether-based carboxylic acid or its salt such as sodium hydroxymethyl hydroxymalonate and sodium hydroxymethyloxysuccinate. Among them, from the viewpoints of solubility in the film-forming stock solution and effective capture of polyvalent metal ions bound to fatty acids, aliphatic hydroxycarboxylic acid or its salt is more suitable, citric acid or its salt is more suitable, and more suitable is Sodium citrate.

The term "aminocarbonate-based compound" refers to a compound having 2 to 6 carboxyl groups in the molecule and at least one secondary amine structure or tertiary amine structure, or a salt thereof. Examples of the aforementioned amino carbonate-based compounds having a secondary amine structure include iminodiacetic acid or these salts. Examples of the aforementioned amino carbonate-based compounds having a tertiary amine structure include nitrilotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, or these salts. Among them, the aforementioned amino carbonate-based compound is preferably a compound having 2 to 6 carboxyl groups in the molecule and at least one tertiary amine structure or a salt thereof. From the viewpoints of solubility in the film-forming stock solution and effective capture of polyvalent metal ions bound to fatty acids, sodium nitrotriacetate is more suitable.

The hydroxyaminocarbonate-based compound refers to a compound or a salt thereof in which a part or all of the carboxyl groups of the aforementioned aminocarbonate-based compound are substituted with hydroxyl groups. Regarding hydroxyamino carbonate-based compounds, hydroxyethylglycine, triethanolamine, N-(2-hydroxyethyl)imine diacetic acid, hydroxyethylethylenediaminetetraacetic acid, diethanolamine, or the like Waiting for the salt. Among them, from the viewpoints of solubility in the film-forming stock solution and effective capture of polyvalent metal ions bound to fatty acids, it is suitable that all of the aforementioned amino carbonate-based compounds are substituted with hydroxyl groups or their salts, and more preferably For triethanolamine.

[PVA film] The content of iron in the PVA film is preferably 0.05 ppm to 1.5 ppm. In the present invention, the content of iron in the PVA film is measured by the method described later. Here, the iron element in the PVA film is measured indiscriminately with fatty acids (decomposition products of nonionic surfactants (B) or anionic surfactants (C)) that form salts, and by chelating agents ( D) And both of the captured. Therefore, the content of iron in the PVA film of the present invention is usually the same level as the content of iron in the film-forming stock solution. Therefore, when the iron content in the PVA film is less than 0.05 ppm, the purification of the raw material PVA in the film forming solution requires a huge cost, and there is a concern that the economy will deteriorate. The content is more preferably 0.1 ppm or more. On the other hand, when the content of iron in the PVA film is greater than 1.5 ppm, there is a concern that contamination in the production process cannot be sufficiently prevented. In addition, it is necessary to blend a large amount of chelating agent (D) to capture the iron element in the film-forming stock solution, which is not preferable from an economical point of view. The content is more preferably 1.0 ppm or less.

From the viewpoint that flexibility can be imparted to the PVA film, the PVA film of the present invention preferably contains a plasticizer. Examples of preferable plasticizers include polyhydric alcohols, specifically, ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, and the like. For these, only one type of plasticizer may be used, or two or more types of plasticizer may be used in combination. Among them, from the viewpoint of compatibility with PVA (A), availability, etc., ethylene glycol or glycerin is preferred.

The content of the plasticizer is preferably in the range of 1 to 30 parts by mass relative to 100 parts by mass of PVA (A). If the content of the plasticizer is 1 part by mass or more, problems are unlikely to occur in terms of mechanical properties such as impact strength and process 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 the handling properties are improved.

The PVA film of the present invention may further contain other ingredients other than PVA, surfactants and plasticizers as needed. Such other components include, for example, moisture, antioxidants, ultraviolet absorbers, lubricants, colorants, fillers (inorganic particles, starch, etc.), preservatives, antifungal agents, and polymers other than the above-mentioned components. Compound etc. The content of other components in the PVA film is preferably 10 parts by mass or less.

The width of the PVA film of the present invention is not particularly limited. Since a polarizing film with a wide width is required in recent years, the width is preferably 1.5 m or more. In addition, if the width of the PVA film is too wide, the manufacturing cost of the film forming apparatus for forming the PVA film will increase, and it may even become difficult to stretch evenly when the optical film is manufactured using a practical manufacturing apparatus. Therefore, it is usually The width of the PVA film is 7.5m or less.

The shape of the PVA film of the present invention is not particularly limited, but from the point of view that a more uniform PVA film can be manufactured continuously and smoothly, and the point of continuous use when manufacturing an optical film, etc., a long film is preferred. The length of the long film (the length in the flow direction) is not particularly limited, and can be set appropriately. The length of the film is preferably 3000 m or more. On the other hand, the length of the film is preferably 30000 m or less. The long film is preferably wound on a core or the like to make 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 material film for the production of optical films such as polarizing films, the thickness of the film is preferably 10 to 70 μm. In addition, the thickness of the PVA film can be obtained as the average value of the values measured at any 10 locations.

The manufacturing method of the PVA film of the present invention is not particularly limited, but a suitable manufacturing method contains polyvinyl alcohol (A), nonionic surfactant (B), anionic surfactant (C), and chelating agent (D). ) A method for producing a polyvinyl alcohol film, which comprises blending polyvinyl alcohol (A), a nonionic surfactant (B), an anionic surfactant (C), and a chelating agent (D) to prepare a film-forming stock solution And the step of using the film-forming stock solution to form a film, the nonionic surfactant (B) is an alkanolamide, and the chelating agent (D) is selected from the group consisting of organic carboxylic acid-based compounds and amino carbonate-based At least one compound of the group of the compound and the hydroxylamino carbonate-based compound, and the blending amount of the nonionic surfactant (B) in the film forming stock solution is relative to 100 parts by mass of polyvinyl alcohol (A) It is 0.01 to 0.20 parts by mass, and the blending amount of the anionic surfactant (C) in the film-forming stock solution is 0.01 to 0.20 parts by mass relative to 100 parts by mass of polyvinyl alcohol (A). The blending amount of the chelating agent (D) in the film forming stock solution is 0.005 to 0.20 parts by mass relative to 100 parts by mass of polyvinyl alcohol (A).

In the step of preparing the film-forming stock solution, a liquid medium may be further blended. As for the liquid medium at this time, for example, water, dimethyl sulfide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethyl Diol, triethylene glycol, tetraethylene glycol, trimethylolpropane, ethylenediamine, diethylenetriamine, etc., one or more of these can be used. Among them, water is preferred from the viewpoint of low load on the environment and recyclability.

In the manufacturing method of the PVA film of the present invention, for example, PVA (A), nonionic surfactant (B), anionic surfactant (C), chelating agent (D), liquid medium, and further response can be used. The film-forming stock solution of the above-mentioned plasticizer or other components required is a well-known method such as a cast film-making method and a melt-extrusion film-making 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 fraction of the film-forming stock solution (the ratio of the volatile components of the liquid medium removed by volatilization and evaporation during film-making in the film-forming stock solution) varies depending on the film forming method, film forming conditions, etc., but it is more It is preferably in the range of 50 to 90% by mass, and more preferably in the range of 55 to 80% by mass. Since the volatile fraction 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 the film formation becomes easy. On the other hand, since the volatile fraction of the film-forming dope is 90% by mass or less, the viscosity of the film-forming dope does 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 0.20 parts by mass relative to 100 parts by mass of the polyvinyl alcohol (A). When the blending amount of the nonionic surfactant (B) is less than 0.01 parts by mass, many optical defects are generated in the PVA film, and the peelability may be deteriorated. The blending amount of the nonionic surfactant (B) is more preferably 0.02 parts by mass or more, and still more preferably 0.04 parts by mass or more. On the other hand, when the blending amount of the nonionic surfactant (B) is more than 0.20 parts by mass, there is a concern that the generation of contamination in the production step cannot be prevented. The blending amount of the nonionic surfactant (B) is more preferably 0.16 parts by mass or less, and still more preferably 0.12 parts by mass or less. The nonionic surfactant (B) used in the present invention may be used singly or in combination of two or more kinds.

The blending amount of the anionic surfactant (C) in the aforementioned film forming stock solution is preferably 0.01 to 0.20 parts by mass relative to 100 parts by mass of polyvinyl alcohol (A). If the blending amount of the anionic surfactant (C) is out of this range, there is a concern that optical defects will increase. The blending amount of the anionic surfactant (C) is more preferably 0.02 parts by mass or more, and still more preferably 0.04 parts by mass or more. On the other hand, the blending amount of the anionic surfactant (C) is more preferably 0.16 parts by mass or less, and still more preferably 0.12 parts by mass or less. The anionic surfactant (C) used in the present invention may be used singly or in combination of two or more kinds.

The blending amount of the chelating agent (D) in the aforementioned film forming stock solution is preferably 0.005 to 0.20 parts by mass relative to 100 parts by mass of polyvinyl alcohol (A). When the blending amount of the chelating agent (D) is less than 0.005 parts by mass, there is a concern that contamination in the production step cannot be prevented. The blending amount of the chelating agent (D) is more preferably 0.007 parts by mass or more, and still more preferably 0.01 parts by mass or more. On the other hand, when the blending amount of the chelating agent (D) exceeds 0.20 parts by mass, there is a concern that optical defects may increase. The blending amount of the chelating agent (D) is more preferably 0.15 parts by mass or less, and still more preferably 0.1 parts by mass or less. The chelating agent (D) used in this invention may be used individually by 1 type, and may use 2 or more types together.

Next, the steps of forming a film will be described. The PVA film of the present invention preferably uses the above-mentioned film-forming stock solution, and is manufactured by a cast film-forming method and a melt-extrusion film-forming method. The specific production method at this time is not particularly limited. For example, the film-forming stock solution can be cast or discharged into a film on a support such as a drum or a belt, and the film can be applied on the support. It is obtained by drying. The obtained film may be further dried by a drying roller or a hot air drying device, heat-treated by a heat treatment device, or humidity controlled by a humidity control device as needed. The manufactured 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 manufactured PVA film may be cut off.

The PVA film of the present invention can be suitably used as a raw material film for producing polarizing films, retardation films, special light-concentrating films, and the like. According to the present invention, a PVA film with high light permeability and high quality can be obtained. Therefore, the optical PVA film is a suitable embodiment of the present invention.

The manufacturing method of the polarizing film having the step of dyeing the aforementioned PVA film and the step of stretching is a suitable embodiment of the present invention. The 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, the dyeing treatment may be performed simultaneously with the stretching treatment, or the dyeing treatment may be performed after the stretching treatment. In addition, the steps of stretching and dyeing can be repeated multiple times. Particularly, if the stretching is divided into two or more stages, it becomes easy to perform uniform stretching, which is preferable.

Regarding the dyes used in the dyeing of PVA films, iodine or dichroic organic dyes can be used (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) and so on. These dyes can be used individually by 1 type or in combination of 2 or more types. Dyeing can usually be performed by immersing the PVA film in a solution containing the above-mentioned dye, but the treatment conditions and treatment methods are not particularly limited.

As a method of stretching the PVA film, a uniaxial stretching method and a biaxial stretching method are exemplified, and the former is preferred. Uniaxial stretching in which the PVA film is stretched in the flow direction (MD) etc. can be performed by either wet stretching method or dry heat stretching method, but from the viewpoint of the performance and quality stability of the polarizing film obtained The wet stretching method is preferred. The wet stretching method includes a method of stretching the PVA film in pure water, an aqueous solution containing various components such as additives and water-soluble organic solvents, or an aqueous dispersion in which various components are dispersed. Specific examples of the uniaxial stretching method using the wet stretching method include a method of performing uniaxial stretching in warm water containing boric acid, and performing uniaxial stretching in a solution containing the aforementioned dye or in a fixed treatment bath described later. Method and so on. In addition, it is also possible to uniaxially stretch in the air using a PVA film after water absorption, or to perform uniaxial stretching in other methods.

The stretching temperature when performing uniaxial stretching is not particularly limited, but when performing wet stretching, a temperature in the range of preferably 20 to 90°C, more preferably 25 to 70°C, and still more preferably 30 to 65°C is adopted. When performing dry heat stretching, a temperature preferably in the range of 50 to 180°C is used.

The stretching magnification of the uniaxial stretching treatment (the total stretching magnification in the case of multi-stage uniaxial stretching), from the viewpoint of polarization performance, it is preferable to stretch as much as possible before the film is cut. Specifically, it is preferable It is 4 times or more, more preferably 5 times or more, and still more preferably 5.5 times or more. The upper limit of the stretching ratio is not particularly limited as long as the film does not break, but for uniform stretching, it is preferably 8.0 times or less.

In the manufacture of the polarizing film, in order to firmly adsorb the dye to the uniaxially stretched PVA film, it is preferable to perform a fixation treatment. Regarding the fixing treatment, a general method of immersing the PVA film in a treatment bath added with boric acid and/or a boron compound can be adopted. At this time, an iodine compound can be added to the treatment bath as needed.

Preferably, the PVA film subjected to uniaxial stretching treatment, or uniaxial stretching treatment and fixing treatment is subsequently subjected to drying treatment or heat treatment. The temperature of the drying treatment or heat treatment is preferably 30 to 150°C, particularly preferably 50 to 140°C. If the temperature is too low, the dimensional stability of the obtained polarizing film will tend to decrease. On the other hand, if the temperature is too high, the degradation of the polarization performance accompanying the decomposition of the dye or the like easily occurs.

A polarizing plate can be made by bonding an optically transparent and mechanically strong protective film on both sides or one side of the polarizing film obtained as described above. For the protective film at this time, cellulose triacetate (TAC) film, cellulose acetate·butyrate (CAB) film, acrylic film, polyester film, etc. can be used. Moreover, as for the adhesive for bonding the protective film, PVA-based adhesives, urethane-based adhesives, etc. are generally used, and among them, PVA-based adhesives are preferably used.

The polarizing plate obtained as described above can be used as a part of a liquid crystal display device after being coated with an acrylic adhesive or the like, and then bonded to a glass substrate. When bonding the polarizing plate to the glass substrate, it is also possible to bond retardation film, viewing angle enhancement film, brightness enhancement film, etc. at the same time. [Example]

Hereinafter, the present invention will be specifically explained with examples and the like, but the present invention is not limited at all by these examples.

[The content of iron in PVA film] A 0.5 g of PVA film was put into a PTFE pressure vessel, 6 mL of concentrated nitric acid was added thereto, and it was decomposed at room temperature for 30 minutes. After the decomposition, the lid is closed, and the wet decomposition device (ACTAC's "MWS-2") is used to heat at 150°C for 10 minutes, and then at 180°C for 5 minutes to further decompose, and then cool to room temperature. This treatment solution was transferred to a 100 mL measuring flask (manufactured by PMP), and diluted with pure water in the measuring flask to prepare a sample solution for measurement. For this sample solution, the content of iron element was determined by an ICP emission spectrometer ("OPTIMA4300DV" from PerkinElmer).

[The content of chelating agent in PVA film] A 10 m area was cut out from the surface layer side of the PVA film roll to be the measurement target, and a sample piece of MD100mm×TD100mm (thickness 60μm) was further collected from an arbitrary position. Use the following conditions to pre-treat the sample pieces taken.

(Pre-treatment conditions) 1. Accurately weigh 0.3g sample in a 50ml sample tube. 2. Add 15 ml of HFIP (hexafluoroisopropanol), and further add 1 ml of 0.01 mol/l hydrochloric acid, and stir to dissolve at 50°C. 3. After dissolving, cool to room temperature, drop into 60 ml of methanol (at room temperature, under stirring) for reprecipitation. 4. Filter with a cotton plug to remove sediment. 5. Concentrate the filtrate with an evaporator (40°C). 6. Add a 4:6 mixture of methanol and water and dilute it to 2 ml in a measuring flask to prepare an analysis sample.

(Quantification of chelating agent) The pre-treated sample was quantified by HPLC to obtain the content of the chelating agent (D). When the signal-to-noise ratio of the chelating agent is inappropriate, the amount of the added liquid in the aforementioned pretreatment condition 6 or the injection amount measured by HPLC is adjusted to quantify the chelating agent.

(HPLC determination conditions of trisodium citrate and sodium nitrilotriacetate) ‧Device: ACQUITY UPLC H-class (made by waters) ‧Column: ACQUITY UPLC BEH Amide 2.1×100mm 1.7μm (made by waters) ‧Mobile phase: Mix a solution of 0.1% trifluoroacetic acid and acetonitrile solution at 4:6 ‧Flow rate: 0.5ml/min ‧Temperature: 40℃ ‧Injection volume: 10μL ‧Detector: ELSD

(HPLC measurement conditions for triethanolamine) ‧Device: LC-20a1 (manufactured by Shimadzu Corporation) ‧Column: TSKgel Amide-80 (4.6×250mm, 5μm) ‧Mobile phase: a mixture of 0.1% formic acid and acetonitrile‧ The gradient time and the acetonitrile concentration of the mobile phase: [Table 1] Time (minutes) 0 5 15 16 20 Acetonitrile concentration (%) 90 20 20 90 STOP ‧Flow rate: 1ml/min ‧Temperature: 40℃ ‧Injection volume: 10μL ‧Detector: corona

[Processability of PVA film manufacturing] (Peelability) In the production of a long film of 4000m or more, when the film is peeled from the casting drum, the one that has no problem but can be peeled is regarded as A, and the one that is partly attached to the drum but easily peels off and there is no problem in productivity is regarded as A B. The person who cannot be peeled off due to adhesion to the drum is regarded as C and evaluated.

[Quality of PVA film] (Evaluation method of optical defect) The evaluation was performed by visually observing the streak-like defects and the scale-like defects that exist in the PVA film parallel to the flow direction (MD direction) during film formation. Specifically, the sample pieces cut from the PVA films obtained in the following examples and comparative examples were hung so that the MD direction became vertical, and a 30W straight tubular fluorescent lamp was placed vertically behind it and lit. Optical defects were evaluated using the following criteria. A: There are no streaks and scale-like defects at all, which is the most suitable degree for products. B: There are streak-like or fish-scale defects in some places, but it is still usable as a product. C: There are many striped or fish-scale defects, which are not suitable for products.

[Mold contamination] The equipment was stopped after 50,000 m of continuous PVA film formation, and the adhesion state of contamination on the raw liquid flow road surface inside the mold was observed, and the following criteria were used for evaluation. A: There is no pollution and it is the most suitable level for products. B: There is pollution in some places, but it can be used to take products. C: There is a lot of pollution, which is not suitable for the use of products.

Example 1 A chip 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% was used as PVA (A). After immersing 100 parts by mass of the PVA sheet in 2500 parts by mass of distilled water at 35° C., centrifugal dehydration was performed to obtain a PVA water-containing sheet with a volatile content of 60% by mass.

For 250 parts by mass of the PVA water-containing sheet (100 parts by mass for dry PVA), 25 parts by mass of distilled water, 12 parts by mass of glycerin, 0.05 parts by mass of nonionic surfactant (B), and 0.05 parts by mass of anion were mixed After the surfactant (C) and 0.03 parts by mass of the chelating agent (D) are used, the resulting mixture is heated and melted (maximum temperature 130°C) with a biaxial extruder to form a film-forming stock solution. The nonionic surfactant (B) used at this time is tertiary amide type diethanolamide laurate, and the anionic surfactant (C) is polyoxyethylene lauric acid ether sodium sulfate (alkyl carbon The number is 12, the addition number of ethylene oxide is 3), and the chelating agent (D) is sodium citrate.

After cooling the film-forming stock solution to 100°C with a heat exchanger, the film is extruded from a 180cm wide hanger-type die on a drum with a surface temperature of 90°C, and then dried with a hot air drying device. Both ends of the film that became thicker than the neck-in at the time of film formation were cut off, and a PVA film with a film thickness of 60 μm and a width of 165 cm was continuously manufactured. The peelability of the PVA film in the manufacturing process was evaluated by the above-mentioned method. Next, a 4000 m long part of the manufactured PVA film was wound on a cylindrical core to form a film roll. The optical defect and the content of iron element were evaluated for the obtained PVA film by the above-mentioned method. In addition, the contamination adhering to the mold during the manufacturing process was evaluated by the above-mentioned method. The results are shown in Table 2.

Examples 2-7, Comparative Examples 1-6 Except that the types and amounts of nonionic surfactant (B), anionic surfactant (C), and chelating agent (D) were changed as shown in Table 2, the same procedure as in Example 1 was carried out to produce a PVA film , And evaluate it. In addition, the chelating agent (D) used in Example 3 was triethanolamine, the chelating agent (D) used in Example 4 was sodium nitrotriacetate, and the nonionic surfactant (B) used in Example 5 The anionic surfactant (C) is respectively polyoxyethylene lauric acid monoethanolamide (polyoxyethylene chain number is 6) and sodium alkyl sulfonate (alkyl group carbon number is 15).

As shown in Table 2, the PVA film systems of Examples 1 to 7 have excellent releasability, few optical defects, and good quality. In addition, since there is no mold contamination, the mold cleaning frequency can be reduced, and the productivity is excellent. On the other hand, the PVA film of Comparative Example 1 with a large amount of nonionic surfactant (B) caused a lot of mold contamination. The PVA film of Comparative Example 2 with a large amount of anionic surfactants (C) and Comparative Example 3 with a large amount of chelating agents (D) had many optical defects. The PVA film of Comparative Example 4 without the nonionic surfactant (B) had poor releasability and many optical defects. The PVA film of Comparative Example 5 without the anionic surfactant (C) had many optical defects. The PVA film of Comparative Example 6 without the chelating agent (D) produced a lot of mold contamination. In addition, as shown in Table 2, the value of the blending amount of the nonionic surfactant (B) and the anionic surfactant (C) in the film-forming stock solution of the PVA film is related to the nonionic interface in the PVA film The content of the active agent (B) and the anionic surfactant (C) are the same. This is due to the decomposition of the nonionic surfactant (B) and the anionic surfactant (C) blended in the film-forming stock solution The fatty acid produced is very small, so it is impossible to measure the difference between the value of the blending amount and the value of the content.

[Table 2] Surfactant Chelating agent (D) The content of non-ionic surfactant (B) [%/PVA] Anionic surfactant (C) content [%/PVA] The content of chelating agent (D) [%/PVA] Iron element content [ppm] Ratio ^{* 1)} [times] Processability The quality of PVA film Mold contamination Non-ionic surfactant (B) Anionic surfactant (C) Peelability Optical defect Example 1 Lauric acid diethanolamide Sulfate salt type Sodium citrate 0.05 0.05 0.030 0.4 171 A A A Example 2 Lauric acid diethanolamide Sulfate salt type Sodium citrate 0.10 0.10 0.030 0.5 137 A A A Example 3 Lauric acid diethanolamide Sulfate salt type Triethanolamine 0.05 0.05 0.030 0.4 296 A A A Example 4 Lauric acid diethanolamide Sulfate salt type Sodium Nitrotriacetate 0.05 0.05 0.030 0.4 172 A A A Example 5 Polyoxyethylene lauric acid monoethanolamide Sulfonate type Sodium citrate 0.05 0.05 0.030 0.4 171 A B A Example 6 Lauric acid diethanolamide Sulfate salt type Sodium citrate 0.05 0.05 0.006 0.4 34 A A B Example 7 Lauric acid diethanolamide Sulfate salt type Sodium citrate 0.05 0.05 0.030 1.7 40 A A B Comparative example 1 Lauric acid diethanolamide Sulfate salt type Sodium citrate 0.25 0.05 0.030 0.3 228 A A C Comparative example 2 Lauric acid diethanolamide Sulfate salt type Sodium citrate 0.05 0.25 0.030 0.4 171 A C A Comparative example 3 Lauric acid diethanolamide Sulfate salt type Sodium citrate 0.05 0.05 0.250 0.3 1900 A C A Comparative example 4 - Sulfate salt type Sodium citrate - 0.05 0.030 0.3 228 C C A Comparative example 5 Lauric acid diethanolamide - Sodium citrate 0.05 - 0.030 0.3 228 B C A Comparative example 6 Lauric acid diethanolamide Sulfate salt type - 0.05 0.05 - 0.4 - A A C *1) The ratio of the number of moles of the chelating agent (D) to the number of moles of iron in the PVA film

without.

without.

without.

Claims (6)

A polyvinyl alcohol film, which is a polyvinyl alcohol film containing polyvinyl alcohol (A), a nonionic surfactant (B), an anionic surfactant (C), and a chelating agent (D), wherein The nonionic surfactant (B) is alkanolamide, The content of the nonionic surfactant (B) is 0.01 to 0.20 parts by mass relative to 100 parts by mass of polyvinyl alcohol (A), The content of the anionic surfactant (C) is 0.01 to 0.20 parts by mass relative to 100 parts by mass of polyvinyl alcohol (A), The chelating agent (D) is at least one compound selected from the group consisting of an organic carboxylic acid compound, an amino carbonate compound, and a hydroxyl amino carbonate compound, The content of (D) of the chelating agent is 0.005 to 0.20 parts by mass relative to 100 parts by mass of polyvinyl alcohol (A). The polyvinyl alcohol film of claim 1, wherein the ratio of the number of moles of the chelating agent (D) to the number of moles of iron in the polyvinyl alcohol film is 50 times or more. Such as the polyvinyl alcohol film of claim 1 or 2, wherein the content of iron in the polyvinyl alcohol film is 0.05 ppm to 1.5 ppm. Such as the polyvinyl alcohol film of claim 1 or 2, wherein the film width is 1.5m or more. Such as the polyvinyl alcohol film of claim 1 or 2, wherein the length of the film is more than 3000m. Such as the polyvinyl alcohol film of claim 1 or 2, wherein the film thickness is 10 to 70 μm.