WO2019124310A1

WO2019124310A1 - Polyvinyl alcohol film, film roll, and method for producing film roll

Info

Publication number: WO2019124310A1
Application number: PCT/JP2018/046358
Authority: WO
Inventors: 涼平梅本; 鳥越　信一; 勝啓高藤
Original assignee: 株式会社クラレ
Priority date: 2017-12-22
Filing date: 2018-12-17
Publication date: 2019-06-27
Also published as: TW201930422A; KR102627531B1; JP7223709B2; TWI770337B; CN111712533A; JPWO2019124310A1; CN111712533B; KR20200102461A

Abstract

[Problem] Provided are a polyvinyl alcohol film, a film roll, and a method for producing a film roll, wherein aggregates originating from an activator present within the film, which cause deterioration in the polarizing plate performance, are reduced. [Solution] Disclosed is a polyvinyl alcohol film including a polyvinyl alcohol (A), a nonionic surfactant (B), an anionic surfactant (C1), and a sulfonic acid-based anionic surfactant (C2) that is different from said C1, wherein: the polyvinyl alcohol (A) has an average degree of polymerization of from 500 to 7000 and a degree of saponification of 99.0 mol% or greater; the content of each of the nonionic surfactant (B), the anionic surfactant (C1), and the sulfonic acid-based anionic surfactant (C2) to 100 parts by mass of the polyvinyl alcohol (A) is from 0.001 to 1 part by mass; the ratio [(C1+C2)/B] of the total mass of the anionic surfactant (C1) and the sulfonic acid-based anionic surfactant (C2) to the nonionic surfactant (B) is from 1 to 10; and the mass ratio (C2/C1) of the sulfonic acid-based anionic surfactant (C2) to the anionic surfactant (C1) is from 0.1 to 10.

Description

Polyvinyl alcohol film, film roll and method for producing film roll

The present invention is a polyvinyl alcohol film (hereinafter referred to as "polyvinyl alcohol") which is excellent in surface smoothness and reduced in active agent-derived aggregates which are present inside the film and which cause the deterioration of polarizing plate performance. It may be abbreviated as "PVA"), relates to a method of producing a film roll.

PVA films are used in various applications by taking advantage of unique properties such as transparency, optical properties, mechanical strength, water solubility and the like. In particular, a PVA film is used as a raw material (raw film) for producing a polarizing film constituting a polarizing plate which is a basic component of a liquid crystal display (LCD) by utilizing its excellent optical properties. Applications are expanding. The polarizing plate for LCD is required to have high optical performance, and the polarizing film as a component thereof is also required to have high optical performance.

Generally, a polarizing plate is uniaxially stretched after dyeing, uniaxially stretched while dyeing, or uniaxially stretched after dyeing, to form a dyed uniaxially drawn film, which is fixed with a boron compound. After manufacturing a polarizing film by the method of fixing, or the method of performing fixation processing with a boron compound simultaneously with dyeing at the time of the above-mentioned uniaxial stretching / dying processing, a cellulose triacetate (TAC) film, acetic acid · It is manufactured by laminating together a protective film such as a cellulose butyrate (CAB) film.

Up to now, many techniques related to PVA film and its production method are known. Patent Document 1 describes that it is preferable to add one or two or more kinds of alkanolamide-type surfactants excellent in the effect of reducing film surface abnormalities at the time of film production. In the past, the quality was satisfied with a polarizing plate using a film described in Patent Document 1, but in recent years, the demand for higher definition of the LCD and sharpening of the image has become higher, and along with that, the polarizing film Cracks and voids on the surface are often regarded as problems. When the polarizing film contains many cracks and voids, the haze of the film is increased, and such polarizing film can not be used for applications requiring high definition and clear images.

International Publication No. 2013/146533

The present invention has been made to solve the above problems, and a PVA film with few defects on the film surface and reduced aggregates derived from the active agent present inside the film causing a reduction in the polarizing plate performance Intended to be provided.

The inventors of the present invention conducted intensive studies to achieve the above object, and as a result, nonionic surfactant (B), anionic surfactant (C1) and sulfonic acid based anionic surfactant (C2) were used. A PVA film composed of an aqueous solution of PVA contained in a predetermined ratio has few defects on the film surface, and while the conventional surface smoothness is maintained, it originates from the active agent present inside the film causing the deterioration of the polarizing plate performance. The inventors have found that a PVA film with reduced agglomerates can be obtained and completes the present invention.

That is, the present invention
[1] A polyvinyl alcohol film containing a polyvinyl alcohol (A), a nonionic surfactant (B), an anionic surfactant (C1) and a sulfonic acid based anionic surfactant (C2) different from the above C1. The polyvinyl alcohol (A) has an average degree of polymerization of 500 to 7,000, a degree of saponification of 99.0 mol% or more, and a nonionic surfactant (B) with an anionic property relative to 100 parts by mass of the polyvinyl alcohol (A). The content of each of the surfactant (C1) and the sulfonic acid-based anionic surfactant (C2) is 0.001 to 1 parts by mass, and the anionic surfactant (B) to the nonionic surfactant (B) The total mass ratio [(C1 + C2) / B] of C1) and the sulfonic acid type anionic surfactant (C2) is 1 to 10, and the anionic group is Polyvinyl alcohol film wherein the sulfonate anionic surfactant to active agent (C1) weight ratio of (C2) (C2 / C1) is 0.1 to 10,
[2] The total content (B + C1 + C2) of the nonionic surfactant (B), the anionic surfactant (C1) and the sulfonic acid based anionic surfactant (C2) relative to 100 parts by mass of the polyvinyl alcohol (A) The polyvinyl alcohol film according to the above [1], which is 0.1 to 1 part by mass,
[3] The plasticizer according to the above [1] or [2], further comprising a plasticizer (D), wherein the content of the plasticizer (D) is 1 to 20 parts by mass with respect to 100 parts by mass of the polyvinyl alcohol (A) Polyvinyl alcohol film,
[4] The polyvinyl alcohol film according to any one of the above [1] to [3], wherein the thickness of the film is 10 to 80 μm.
[5] The polyvinyl alcohol film according to any one of the above [1] to [4], which has a film width of 3 m or more.
[6] A film roll in which the polyvinyl alcohol film according to any one of the above [1] to [5] is wound around a core,
[7] A method for producing a film roll, comprising winding the polyvinyl alcohol film according to any one of the above [1] to [6] on a core, which is produced by an extrusion film forming method,
About.

The PVA film of the present invention is excellent in transparency because there are few defects on the surface of the film and there are few aggregates derived from the active agent present inside the film which causes the deterioration of the polarizing plate performance. Therefore, by using the said PVA film as a raw fabric, the optical film with high transparency, especially a polarizing film is obtained.

The PVA film of the present invention comprises a PVA (A), a nonionic surfactant (B), an anionic surfactant (C1) and a resin composition containing a sulfonic acid-based anionic surfactant (C2) different from C1. It consists of things.

As PVA (A), what was manufactured by saponifying the vinyl-ester type polymer obtained by superposing | polymerizing a vinyl ester can be used. Examples of the vinyl ester include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, and vinyl versatate. One of these may be used alone, or two or more may be used in combination, but the former is preferred. From the viewpoint of availability, cost, productivity of PVA (A) and the like, vinyl acetate is preferable as the vinyl ester.

Other monomers copolymerizable with vinyl ester include, for example, ethylene; olefins having 3 to 30 carbon atoms such as propylene, 1-butene and isobutene; acrylic acid or a salt thereof; methyl acrylate, ethyl acrylate, acrylic acid Acrylic acid esters such as n-propyl, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, etc .; methacrylic Acid or its salt; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethyl methacrylate , Dodecyl methacrylate, methacrylic acid oc Methacrylic acid esters such as tadecyl; acrylamide, N-methyl acrylamide, N-ethyl acrylamide, N, N-dimethyl acrylamide, diacetone acrylamide, acrylamidopropane sulfonic acid or salts thereof, acrylamidopropyldimethylamine or salts thereof, N-methylol acrylamide Or acrylamide derivatives such as derivatives thereof; methacrylamide, N-methyl methacrylamide, N-ethyl methacrylamide, methacrylamidopropane sulfonic acid or salts thereof, methacrylamidopropyldimethylamine or salts thereof, N-methylol methacrylamide or derivatives thereof Methacrylamide derivatives of N-vinylamide such as N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone and the like; Vinyl ethers such as vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether and stearyl vinyl ether; vinyl cyanides such as acrylonitrile and methacrylonitrile Vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; maleic acid or its salt, ester or acid anhydride; itaconic acid or its salt, ester or Acid anhydrides; vinylsilyl compounds such as vinyltrimethoxysilane; and isopropenyl acetate. One of these other monomers may be used alone, or two or more thereof may be used in combination. Among them, ethylene and olefins having 3 to 30 carbon atoms are preferable as the other monomer, and ethylene is more preferable.

The proportion of the structural unit derived from the other monomer in the vinyl ester polymer is not particularly limited, but is 15 mol% or less based on the number of moles of all structural units constituting the vinyl ester polymer. Is preferable, and 5 mol% or less is more preferable.

The degree of polymerization of PVA (A) is not necessarily limited, but is preferably 200 or more, more preferably 300 or more, and even more preferably 400 or more because the film strength tends to decrease as the degree of polymerization decreases. Particularly preferably, it is 500 or more. If the degree of polymerization is too high, the viscosity of the aqueous solution or the molten PVA (A) tends to be high, and film formation tends to be difficult, so it is preferably 10,000 or less, more preferably 9,000. The following is more preferably 8,000 or less, particularly preferably 7,000 or less. Here, the degree of polymerization of PVA (A) means the average degree of polymerization measured according to the description of JIS K 6726-1994, and it is measured in water at 30 ° C. after re-saponifying PVA (A) and purification. It is obtained by the following equation from the intrinsic viscosity [η] (unit: deciliter / g).
Degree of polymerization = ([η] × 10 ³ /8.29) ^{(1 / 0.62)}

The degree of saponification of PVA (A) is not particularly limited, and for example, 60 mol% or more of PVA (A) can be used, but when using a PVA film as a raw film for producing an optical film such as a polarizing film In and the like, the degree of saponification of PVA (A) is preferably 95 mol% or more, more preferably 98 mol% or more, and still more preferably 99 mol% or more. Here, the degree of saponification of PVA (A) is the total number of moles of structural units (typically vinyl ester monomer units) that can be converted to vinyl alcohol units by saponification and the number of vinyl alcohol units that PVA (A) has. It means a ratio (mol%) of the number of moles of the vinyl alcohol unit with respect to. The degree of saponification of PVA (A) can be measured according to the description of JIS K 6726-1994.

As PVA (A), one type of PVA may be used alone, or two or more types of PVA having different degrees of polymerization, saponification degree, modification degree, etc. may be used in combination. However, PVA film has an acidic functional group such as a carboxyl group and a sulfonic acid group; PVA having an acid anhydride group; PVA having a basic functional group such as an amino group; crosslinking products such as neutralized products thereof When the PVA having a functional group that promotes H 2 is contained, the secondary processability of the PVA film may be reduced due to the crosslinking reaction between PVA molecules. Therefore, when excellent secondary processability is required as in the raw film for optical film production, PVA having an acidic functional group, PVA having an acid anhydride group, basicity in PVA (A) It is preferable that content of PVA which has a functional group, and these neutralized products is 0.1 mass% or less, respectively, and it is more preferable not to contain any.

The content of PVA (A) in the resin composition is preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably 85% by mass or more.

As the nonionic surfactant (B) used in the present invention, for example, alkyl ether type such as polyoxyethylene oleyl ether; alkyl phenyl ether type such as polyoxyethylene octyl phenyl ether; alkyl such as polyoxyethylene laurate Ester type; Alkylamine type such as polyoxyethylene lauryl aminoether; Alkylamide type such as polyoxyethylene lauric acid amide; Polypropylene glycol ether type such as polyoxyethylene polyoxypropylene ether; Lauric acid diethanolamide, oleic acid diethanolamide Alkanolamide type such as, for example, allyl phenyl ether type such as polyoxyalkylene allyl phenyl ether and the like. One of these may be used alone, or two or more may be used in combination.

The nonionic surfactant (B) preferably includes a nonionic surfactant having an alkyl chain (alkyl group) having 9 or more carbon atoms. Such nonionic surfactants are easily aggregated in the PVA film, and easily deteriorate the transparency of the PVA film. On the other hand, in the present invention, a PVA film having high transparency is obtained by using an anionic surfactant (C1) in combination with a nonionic surfactant having an alkyl chain (alkyl group) having 9 or more carbon atoms. be able to. And, by using a nonionic surfactant having an alkyl chain having 9 or more carbon atoms as the nonionic surfactant (B), the occurrence of streak defects during film formation can be further reduced. . From the above viewpoint, the carbon number (alkyl chain length) of the alkyl chain is more preferably 10 or more. On the other hand, the carbon number of the alkyl chain is preferably 30 or less, more preferably 22 or less, still more preferably 16 or less, and particularly preferably 12 or less. The alkyl chain may be linear or branched, but is preferably linear. The alkyl chain is preferably contained in the main chain (longest chain) of the nonionic surfactant (B). The content of the nonionic surfactant having the alkyl chain in the nonionic surfactant (B) is preferably 90% by mass or more, and the nonionic surfactant (B) substantially has the alkyl chain. It is more preferable to contain only nonionic surfactant.

Moreover, it is preferable that the nonionic surfactant (B) which has the said alkyl chain contains the nonionic surfactant of an alkanolamide type, and it is more preferable that the dialkanolamide of a fatty acid is included. The content of the alkanolamide type nonionic surfactant in the nonionic surfactant (B) is preferably 90% by mass or more, and the nonionic surfactant (B) is substantially an alkanolamide type nonionic surfactant. It is particularly preferred to contain only a surfactant.

Examples of the anionic surfactant (C1) used in the present invention include coconut oil fatty acid triethanolamine, triethanolamine laurate, lauroyl sarcosine sodium, coconut oil fatty acid sarcosine sodium, coconut oil fatty acid sarcosine triethanolamine, etc. Carboxylic acid type; sodium lauryl sulfate, ammonium lauryl sulfate, triethanolamine lauryl sulfate, sodium polyoxyethylene lauryl ether sulfate, polyoxyethylene alkyl (12, 13) ether sodium sulfate, polyoxyethylene alkyl ether sulfate, polyoxyethylene lauryl Sulfuric acid ester type such as sodium ether sulfate, polyoxyethylene coconut oil fatty acid monoethanolamide sodium sulfate, etc .; lauryl phosphoric acid, polyoxyethylene Phosphoric ester type such as lauryl ether phosphoric acid, polyoxyethylene oleyl ether phosphoric acid, polyoxyethylene oleyl ether sodium phosphate, polyoxyethylene stearyl ether phosphoric acid, polyoxyethylene alkyl (12 to 15) ether phosphoric acid, alkyl benzene Sodium sulfonate, sodium alkyl sulfonate, sodium alkyl naphthalene sulfonate, sodium naphthalene sulfonate, sodium diphenylether sulfonate, triethanolamine dodecylbenzene sulfonate, dioctyl sulfosuccinate, disodium lauryl polyoxyethylene sulfosuccinate, lauryl sulfosuccinate Disodium, polyoxyethylene alkyl (12-14) sulfosodium disuccinate, coconut oil fatty acid Chill taurine sodium, coconut oil fatty acid methyl taurine sodium, a sulfonic acid type, such as coconut oil fatty acid taurine sodium. In these, only one anionic surfactant may be used alone, or two or more anionic surfactants may be used in combination.

It is preferable that the anionic surfactant (C1) contains an anionic surfactant having an alkyl chain (alkyl group) having 9 or more carbon atoms. Such an anionic surfactant has the effect of dispersing the nonionic surfactant (B), and aggregates of the active agent that cause droplets are less likely to be generated, resulting in a more transparent film. . Furthermore, like the nonionic surfactant (B), when the anionic surfactant (C1) contains an anionic surfactant having an alkyl chain having 9 or more carbon atoms, occurrence of streaky defects during film formation Further reduce. From the above viewpoint, the carbon number (alkyl chain length) of the alkyl chain is more preferably 10 or more. On the other hand, the carbon number of the alkyl chain is preferably 30 or less, more preferably 22 or less, still more preferably 16 or less, and particularly preferably 12 or less. The above alkyl chain may be linear or branched, but is preferably linear. The above alkyl chain is preferably contained in the main chain (longest chain) of the anionic surfactant (C1). The content of the anionic surfactant having an alkyl chain in the anionic surfactant (C1) is preferably 90% by mass or more, and the anionic surfactant (C1) substantially has the alkyl chain. It is more preferable to contain only an anionic surfactant.

It is preferable that the said anionic surfactant (C1) which has an alkyl chain contains the anionic surfactant of a sulfated-ester type. The content of the sulfate ester type anionic surfactant in the anionic surfactant (C1) is preferably 90% by mass or more, and the anionic surfactant (C1) is a substantially sulfate ester type anionic system It is particularly preferred to contain only a surfactant.

The sulfonic acid-based anionic surfactant (C2) different from C1 used in the present invention is, for example, sodium alkyl benzene sulfonate, sodium alkyl sulfonate, sodium alkyl naphthalene sulfonate, sodium naphthalene sulfonate, sodium diphenyl ether sulfonate, Dodecyl benzene sulfonic acid triethanolamine, dioctyl sulfosuccinate, polyoxyethylene sodium sulfosuccinic acid lauryl disodium, sodium lauryl sulfosuccinate disodium, polyoxyethylene alkyl (12 to 14) disodium sulfosuccinic acid sodium, coconut oil fatty acid methyl taurine sodium, coconut Examples include sulfonic acid types such as oil fatty acid methyl taurine sodium and coconut oil fatty acid taurine sodium. In these, only one anionic surfactant may be used alone, or two or more anionic surfactants may be used in combination.

It is preferable that the said sulfonic acid type anionic surfactant (C2) contains the sulfonic acid type anionic surfactant which has a C9 or more alkyl chain (alkyl group). Such a sulfonic acid-based anionic surfactant (C2) has higher heat resistance than the anionic surfactant (C1), and has the effect of dispersing the nonionic surfactant (B) more in the film forming process. Since it becomes difficult to generate aggregates derived from the active agent present inside the film, it becomes a more transparent film. On the other hand, since the sulfonic acid-based anionic surfactant (C2) has a poor ability to reduce the surface tension, and the sulfonic acid-based anionic surfactant (C2) alone causes thickness unevenness during film formation, the anionic surfactant (C2) It is necessary that C1) and the sulfonic acid type anionic surfactant (C2) be a combined system. Furthermore, like the nonionic surfactant (B) and the anionic surfactant (C1), the sulfonic acid-based anionic surfactant (C2) is an anionic surfactant having an alkyl chain having 9 or more carbon atoms. When it contains, generation | occurrence | production of the stripe-like defect at the time of film forming will reduce further. From the above viewpoint, the carbon number (alkyl chain length) of the alkyl chain is more preferably 10 or more. On the other hand, the carbon number of the alkyl chain is preferably 30 or less, more preferably 22 or less, still more preferably 18 or less, and particularly preferably 16 or less. The alkyl chain may be linear or branched, but is preferably linear. The alkyl chain is preferably contained in the main chain (longest chain) of the sulfonic acid anionic surfactant (C2). It is preferable that content of the anionic surfactant which has the said alkyl chain in a sulfonic acid type anionic surfactant (C2) is 90 mass% or more, and a sulfonic acid type anionic surfactant (C2) is substantial. It is more preferable to contain only the anionic surfactant which has the said alkyl chain in.

It is preferable that the sulfonic acid-based anionic surfactant (C2) having an alkyl chain contains an anionic surfactant of alkyl sulfonates. The content of the anionic surfactant of the alkyl sulfonate in the sulfonic acid anionic surfactant (C2) is preferably 90% by mass or more, and the sulfonic acid anionic surfactant (C2) is substantially It is particularly preferable to contain only anionic surfactants of alkyl sulfonates in

The total mass ratio of the anionic surfactant (C1) to the nonionic surfactant (B) and the sulfonic acid-based anionic surfactant (C2) different from the C1 in the resin composition [(C1 + C2) / B It is necessary that the mass ratio (C2 / C1) of the sulfonic acid type anionic surfactant (C2) to the anionic surfactant (C1) is 0.1 to 10. When the total mass ratio [(C1 + C2) / B] is less than 1, the addition amount of the anionic surfactant is too small, so the effect of dispersing the nonionic surfactant is small, and the surfactant derived from the inside of the film is derived And the film is reduced in transparency. When the total mass ratio [(C1 + C2) / B] is 10 or more, the addition amount of the nonionic surfactant is small, the film surface stability is lacking, and streak defects occur. When the mass ratio (C2 / C1) of the sulfonic acid-based anionic surfactant (C2) to the anionic surfactant (C1) is less than 0.1, the sulfonic acid-based anionic surfactant (C2) is used. The addition amount is small, the dispersing effect of the nonionic surfactant is low, and aggregates derived from the active agent are generated to deteriorate the transparency of the film. When the mass ratio (C2 / C1) is 10 or more, the sulfonic acid-based anionic surfactant (C2) has a poor ability to reduce the surface tension, so that the film surface stability is lacking and streak defects occur.

In the resin composition, the total content (B + C1 + C2) of the nonionic surfactant (B), the anionic surfactant (C1) and the sulfonic acid anionic surfactant (C2) relative to 100 parts by mass of PVA (A) Is preferably 0.1 to 1 part by mass. When the total content exceeds 1 part by mass, the addition amount of the nonionic surfactant (B), the anionic surfactant (C1) or the sulfonic acid anionic surfactant (C2) is too large, so the film Droplets may form internally, reducing the transparency of the film. 0.5 mass parts or less are preferable, and, as for the said total content, 0.3 mass parts or less are more preferable. On the other hand, when the said total content is less than 0.1 mass part, while the defect of stripe shape increases in the PVA film obtained, a surface may be roughened and smoothness may become inferior. The total content is preferably 0.1 parts by mass or more.

It is preferable that the PVA film of the present invention further contain a plasticizer (D) from the viewpoint of being able to impart flexibility to the PVA film. Preferred plasticizers (D) include polyhydric alcohols, and specific examples thereof include ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane and the like. One of these may be used alone, or two or more may be used in combination. Among them, ethylene glycol or glycerin is preferable from the viewpoint of compatibility with PVA (A), availability, and the like.

The content of the plasticizer (D) is preferably in the range of 1 to 20 parts by mass with respect to 100 parts by mass of PVA (A).

The said resin composition may further contain other components other than PVA, surfactant, aliphatic monoalcohol, and a plasticizer as needed. As such other components, for example, water, antioxidants, ultraviolet light absorbers, lubricants, colorants, fillers (inorganic particles, starch, etc.), preservatives, fungicides, other than the above-mentioned components A high molecular compound etc. are mentioned. The content of the other components in the resin composition is preferably 10% by mass or less.

The thickness of the PVA film of the present invention is not particularly limited, and can be appropriately set according to the use of the PVA film, and can be, for example, 300 μm or less. When the PVA film of the present invention is used as a raw film for producing an optical film such as a polarizing film, the thickness is preferably in the range of 10 to 80 μm. In addition, the thickness of a PVA film can be calculated | required as an average value of the value measured in arbitrary ten places.

The shape of the PVA film of the present invention is not particularly limited, but it can be continuously used, for example, in the case where an even more uniform PVA film can be produced continuously and smoothly, or when producing an optical film etc. using the obtained PVA film. It is preferable that it is a long film from the point to be carried out. The length (length in the flow direction) of the long film is not particularly limited and can be appropriately set according to the application etc., and can be, for example, in the range of 5 to 30,000 m. The long film is preferably taken as a film roll by winding it around a core.

There is no restriction | limiting in particular in the width | variety of the PVA film of this invention, For example, it can be 0.5 m or more. Since a wide polarizing film is required in recent years, the width is preferably 1 m or more, more preferably 3 m or more, still more preferably 4.5 m or more, and 5.0 m or more. Are particularly preferred, and most preferably 5.5 m or more. On the other hand, 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 furthermore, the optical film can be manufactured uniformly by the manufacturing apparatus put into practical use. The width of the PVA film is preferably 7.5 m or less, more preferably 7.0 m or less, and still more preferably 6.5 m or less because it becomes difficult to stretch the film.

According to the present invention, a PVA film having good surface smoothness can be obtained. The degree of surface smoothness of the PVA film is not particularly limited, but the surface smoothness Ra defined by JIS B0601: 2001 is preferably 2.0 μm or less, more preferably 1.5 μm or less, 1 The thickness is further preferably 0.3 μm or less, particularly preferably 1.0 μm or less, and most preferably 0.5 μm or less. As described above, according to the PVA film having good surface smoothness, it is possible to easily obtain an optical film having high light transmittance and excellent transparency.

According to the present invention, a PVA film having good transparency can be obtained. The degree of transparency of the PVA film is not particularly limited, but the turbidity defined by the color meter is preferably 3.00 or less, more preferably 2.00 or less, and 1.50 or less. Is particularly preferred.

There is no restriction | limiting in particular in the manufacturing method of the PVA film of this invention, For example, the sulfonic-acid-type anionic interface different from PVA (A), nonionic surfactant (B), anionic surfactant (C1), and said C1 Manufacture by a known method such as a cast film forming method or a melt extrusion film forming method using a film forming solution containing an activator (C2), a liquid medium, and, if necessary, the above-mentioned plasticizer and other components. can do. The membrane-forming stock solution may be one in which PVA (A) is dissolved in a liquid medium, or one in which PVA (A) is melted.

Examples of the liquid medium in the membrane forming solution include water, dimethylsulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, Ethylenediamine, diethylenetriamine and the like can be mentioned, and one or more of these can be used. Among them, water is preferable from the viewpoint of small impact on the environment and recovery.

Although the volatilization fraction of the membrane-forming solution (the content ratio of volatile components such as liquid media to be removed by volatilization or evaporation in film-forming in the membrane-forming solution) varies depending on the film-forming method, film-forming conditions, etc. It is preferably in the range of 90% by mass, and more preferably in the range of 55 to 80% by mass. When the volatilization fraction of the membrane-forming solution is 50% by mass or more, the viscosity of the membrane-forming solution does not become too high, and film formation becomes easy. On the other hand, when the volatilization fraction of the membrane forming solution is 90% by mass or less, the thickness uniformity of the obtained PVA film is improved without the viscosity of the membrane forming solution becoming too low.

Although there is no restriction | limiting in particular in the specific manufacturing method in the case of manufacturing the PVA film of this invention using said film forming undiluted | stock solution, For example, the said film forming undiluted | stock solution is flowed on supports, such as a metal plate and a glass plate. A cast film-forming method of drying on the support, or an extrusion film-forming method of discharging the film-forming stock solution heated and melted by an extruder onto a support such as a metal drum or metal belt and drying it on the support The law can be adopted. Among them, the extrusion film-forming method is preferable from the viewpoint of continuous production and good production efficiency. The obtained film may be further dried by a drying roll or a hot air drier, heat treated by a heat treatment apparatus, or conditioned by a humidity control apparatus, as necessary. It is preferable that the produced PVA film is wound on a core to form a film roll. Moreover, you may cut off the both ends of the width direction of the manufactured PVA film.

The PVA film of the present invention can be suitably used as a raw film for producing an optical film such as a polarizing film, a retardation film, and a special light collecting film. By using the PVA film of the present invention, an optical film having high light transmittance and high quality can be obtained. The PVA film of the present invention can also be used as a packaging material, a water-soluble film such as a laundry bag, a release film for producing an artificial marble, and the like. Among them, the PVA film of the present invention is suitably used as a raw film for producing a polarizing film.

The manufacturing method of the polarizing film which has the process of dyeing | staining the said PVA film, and the process of extending | stretching is a preferable embodiment of this invention. The manufacturing method may further include a fixing treatment step, a drying treatment step, a heat treatment step and the like. The order of dyeing and drawing is not particularly limited, and dyeing may be carried out before drawing, may be carried out simultaneously with drawing, or may be carried out after drawing. . Further, the steps of stretching, dyeing, etc. may be repeated multiple times. In particular, it is preferable to divide the drawing into two or more stages because uniform drawing can be easily performed.

As dyes used for dyeing of PVA film, iodine or dichroic organic dyes (for example, DirectBlack 17, 19, 154; Direct Brown 44, 106, 195, 210, 223; Direct Red 2, 23, 28, 31, 37, 39 79, 81, 240, 242, 247; DirectBlue 1, 15, 22, 78, 90, 98, 151, 168, 236, 249, 270; Direct Violet 9, 12, 51, 98; DirectGreen 1, 85; DirectYellow 8, 12, 44, 86, 87; dichroic dyes such as DirectOrange 26, 39, 106, 107, etc. can be used. These dyes may be used alone or in combination of two or more. Although dyeing | staining can be normally performed by immersing a PVA film in the solution containing the said dye, the processing conditions and the processing method in particular are not restrict | limited.

As a method of extending | stretching a PVA film, the uniaxial stretching method and the biaxial stretching method are mentioned, The former is preferable. Uniaxial stretching in which the PVA film is stretched in the flow direction (MD) or the like may be performed by either a wet stretching method or a dry heat stretching method, but a wet stretching method from the viewpoint of the performance and quality stability of the obtained polarizing film Is preferred. Examples of the wet stretching method include a method of stretching a PVA film in an aqueous solution containing various components such as pure water, an additive and 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 uniaxially stretching in warm water containing boric acid, and a method of uniaxially stretching in a solution containing the dye or in a fixing treatment bath described later. The film may be uniaxially stretched in air using a PVA film after water absorption, or may be uniaxially stretched by another method.

The stretching temperature in uniaxial stretching is not particularly limited, but in the case of wet stretching, a temperature in the range of preferably 20 to 90 ° C., more preferably 25 to 70 ° C., still more preferably 30 to 65 ° C. is employed. In the case of heat drawing, a temperature in the range of 50 to 180 ° C. is preferably employed.

From the viewpoint of polarization performance, it is preferable that the stretching ratio of the uniaxial stretching process (total stretching ratio when performing uniaxial stretching in multiple stages) be as much as possible until just before the film is cut, specifically 4 times or more Is preferable, 5 times or more is more preferable, and 5.5 times or more is more preferable. The upper limit of the draw ratio is not particularly limited as long as the film does not break, but in order to perform uniform drawing, it is preferably 8.0 times or less.

In the production of the polarizing film, it is preferable to perform a fixing treatment in order to strengthen the adsorption of the dye to the uniaxially stretched PVA film. As the fixing treatment, a method of immersing a PVA film in a treatment bath to which a general boric acid and / or a boron compound is added can be adopted. At this time, if necessary, an iodine compound may be added to the treatment bath.

Preferably, the PVA film subjected to uniaxial stretching treatment, or uniaxial stretching treatment and fixation treatment is then 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. When the temperature is too low, the dimensional stability of the obtained polarizing film tends to be reduced. On the other hand, if the temperature is too high, the degradation of polarization performance accompanying the decomposition of the dye is likely to occur.

A protective film which is optically transparent and has mechanical strength can be bonded to both sides or one side of the polarizing film obtained as described above to make a polarizing plate. As a protective film in that case, a cellulose triacetate (TAC) film, a cellulose acetate / butyrate (CAB) film, an acrylic film, a polyester film, etc. are used. Moreover, as an adhesive agent for bonding together a protective film, a PVA-type adhesive agent, a urethane type adhesive agent, etc. are generally used, and even among them, a PVA-type adhesive agent is used preferably.

The polarizing plate obtained as described above can be used as a component of a liquid crystal display device after being coated with an acrylic or other pressure-sensitive adhesive and then bonded to a glass substrate. When bonding a polarizing plate together to a glass substrate, you may bond together a retardation film, a viewing angle improvement film, a brightness improvement film etc. simultaneously.

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

[Method for evaluating rough surface defects]
The rough surface defect is a defect in which unevenness is generated continuously in the flow direction (MD direction) at the time of film formation, and when light transmitted through the film surface is projected onto a white wall using a light source, mottled MD Light and dark patterns of the direction can be confirmed. A film having a rough surface has a height difference of 0.2 μm or more between concave and convex portions on the surface, and is clearly visible as the above-mentioned mottled light and dark pattern. Those in which the light and dark patterns were clearly visible were regarded as rough surface defects having the height difference of 0.2 μm or more, and were visually observed and evaluated by the following method. Specifically, the sample piece cut out of the PVA film obtained in the example or the comparative example is suspended so that the MD direction is vertically up and down, 530-580 lux on the film surface at a position 350 cm away from the film surface. A halogen lamp light source manufactured by S ONE CO., LTD., Having an illuminance of 1, was installed to project light perpendicularly to the film surface. Next, light and dark patterns observed when light transmitted through the film was projected on a white wall 10 cm away from the film were continuously observed for 10 m or more in the length direction, and evaluated as rough surface defects, and the following criteria It judged by.
:: Rough surface defect is only less than 10% in the width direction ○: Rough surface defect is present in a ratio of 10% to less than 50% in the width direction Δ: Rough surface defect is in the width direction 5 Exists at a rate of at least 80% but is at a rate of at least 80% in the width direction

[Method for evaluating streaky defects]
The streak-like defect is a defect in which one continuous line is seen in the flow direction (MD direction) at the time of film formation, and when light transmitted through the film surface is projected onto a white wall using a light source A linear light or dark pattern can be confirmed. The film having a streak defect has a height difference of 0.2 μm or more in the concave or convex portion on the surface, and is clearly visible as the above-mentioned linear bright pattern or dark pattern. Those in which the light or dark pattern was clearly visible were regarded as streak defects having the height difference of 0.2 μm or more. The streak defects were observed and evaluated in the same manner as the method of observing and evaluating the surface rough defects. In the present application, those in which the bright pattern or the dark pattern is continuously present for 10 m or more in the flow direction are counted as streak defects, and judged according to the following criteria.
:: There is no streak defect ○: One streak defect exists in the width direction Δ: Two streak defects exist in the width direction ×: Three streak defects exist in the width direction

[Method of measuring aggregates derived from active agent]
A 1 cm × 1 cm sample was taken from the PVA film obtained in the following example. The measurement of the aggregate derived from the active agent present inside the film was performed by measuring the aggregate derived from the active agent present in the film using a phase contrast microscope “ECLIPSE 80i” manufactured by Nikron Co., Ltd. The magnification is 1000 times, one measurement point is divided into 5 in the thickness direction, and the number and size of active agent-derived aggregates present in the film are observed every one division, and the number average value for each size Calculate It measured at five points of the position which divided this into five equally in the width direction, and the following standard evaluated about the value which averaged the five points.
:: 2 or more droplets of a size of 1.2 μm or more exist on average :: more than 2 droplets of a size of 1.2 μm or more are 5 or less on average Δ: a liquid of 1.2 μm or more Drops are on average more than 5 and less than 10
X: Droplets with a size of 1.2 μm or more exist on average more than 10

Example 1
As the PVA (A), a chip of PVA (saponified homopolymer of vinyl acetate) having a degree of polymerization of 2400 and a degree of saponification of 99.9 mol% was used. After immersing 100 parts by mass of the tip of the PVA in 2500 parts by mass of distilled water at 35 ° C. for 24 hours, centrifugal dehydration was performed to obtain a PVA-containing tip. The volatile fraction in the obtained PVA hydrous chip was 70% by mass. 12 parts by mass of glycerin, 0.04 parts by mass of lauric acid diethanolamide as the nonionic surfactant (B), and an anionic interface with respect to 333 parts by mass of the PVA-containing water-containing chip (100 parts by mass of dry PVA) After mixing 0.1 parts by mass of sodium lauryl sulfate as an activator (C1) and 0.1 parts by mass of sodium alkyl sulfonate as a sulfonic acid-based anionic surfactant (C2), the mixture obtained is subjected to a single-screw extruder The solution was heated and melted (maximum temperature 130 ° C.) to form a film forming solution.

The film-forming stock solution was cooled to 100 ° C. with a heat exchanger, and then discharged from a 390 cm wide coat hanger die onto a drum having a surface temperature of 90 ° C. for extrusion film formation. Furthermore, the film was dried using a hot-air drying apparatus, and then both ends of the film thickened by neck-in during film formation were cut off to continuously produce a PVA film with a film thickness of 60 μm and a width of 300 cm. Of the produced PVA film, a length of 10000 m was wound around a cylindrical core to obtain a film roll. Table 1 shows the results of evaluation of surface rough defects, streak defects and droplets by the method described above for the obtained PVA film.

Examples 2 to 5 and Comparative Examples 1 to 6
The same as Example 1, except that the amounts used of the nonionic surfactant (B), the anionic surfactant (C1) and the sulfonic acid anionic surfactant (C2) are changed as shown in Table 1. Production and evaluation of the PVA film (and film roll). The results are shown in Table 1. In addition, since it was visually confirmed that the film of Comparative Example 3 was significantly inferior in surface property, the evaluation of the surface rough defect was omitted.

As shown in Table 1, the nonionic surfactant (B), the anionic surfactant (C1) and the sulfonic acid-based anionic surfactant (C2) are each 0.001 to 100 parts by weight of PVA (A). It is 1 part by mass, the mass ratio [(C1 + C2) / B] of them is in the range of 1 to 10, and the mass ratio of the sulfonic acid based anionic surfactant (C2) to the anionic surfactant (C1) ( Examples 1 to 3 in which C2 / C1) is in the range of 0.1 to 10 have few surface rough defects, streak defects, and few large activator aggregates having a size of 1.2 μm or more. The PVA film (comparative examples 3 to 6) in which the mass ratio [(C1 + C2) / B] is out of the range of 1 to 10 is at least one of evaluation of rough surface defects and streak defects or activator aggregates. It was inferior. Furthermore, the PVA film (comparative examples 4 to 6) in which the total content (B + C1 + C2) deviates from 0.1 to 1 part by mass has many aggregates derived from the active agent present in the film inside, and the transparency of the film is reduced. did.

As shown in the above examples, the PVA film of the present invention is excellent in transparency because it has few rough surface and streak defects and the dispersibility of the active agent inside the film is good. By using such a PVA film as a raw film, an optical film having high light transmittance and high quality, in particular, a polarizing film can be obtained. Moreover, it becomes possible to manufacture an optical film etc. by a high yield by using the PVA film of this invention as a raw film, and cost is reduced.

Claims

It is a polyvinyl alcohol film containing a polyvinyl alcohol (A), a nonionic surfactant (B), an anionic surfactant (C1), and a sulfonic acid based anionic surfactant (C2) different from the C1. The polyvinyl alcohol (A) has an average polymerization degree of 500 to 7,000, a saponification degree of 99.0 mol% or more, and a nonionic surfactant (B) and an anionic surfactant based on 100 parts by mass of the polyvinyl alcohol (A) The content of each of (C1) and the sulfonic acid-based anionic surfactant (C2) is 0.001 to 1 parts by mass, and the anionic surfactant (C1) for the nonionic surfactant (B) and The total mass ratio [(C1 + C2) / B] of the sulfonic acid based anionic surfactant (C2) is 1 to 10, and the anionic surfactant is Polyvinyl alcohol film wherein the sulfonate anionic surfactant weight ratio of (C2) (C2 / C1) is from 0.1 to 10 to the agent (C1).
The total content (B + C1 + C2) of the nonionic surfactant (B), the anionic surfactant (C1) and the sulfonic acid based anionic surfactant (C2) relative to 100 parts by mass of the polyvinyl alcohol (A) is 0.1 The polyvinyl alcohol film according to claim 1, which is 1 to 1 part by mass.
The polyvinyl alcohol film according to claim 1, further comprising a plasticizer (D), wherein the content of the plasticizer (D) is 1 to 20 parts by mass with respect to 100 parts by mass of the polyvinyl alcohol (A).
The polyvinyl alcohol film according to any one of claims 1 to 3, wherein the thickness of the film is 10 to 80 μm.
The polyvinyl alcohol film according to any one of claims 1 to 4, wherein the film width is 3 m or more.
A film roll comprising the polyvinyl alcohol film according to any one of claims 1 to 5 wound around a core.
The method for producing a film roll according to any one of claims 1 to 5, wherein the polyvinyl alcohol film is wound around a core.