WO2013146458A1

WO2013146458A1 - Polyvinyl alcohol-type polymer film and polarizing film

Info

Publication number: WO2013146458A1
Application number: PCT/JP2013/057791
Authority: WO
Inventors: 修風藤
Original assignee: 株式会社クラレ
Priority date: 2012-03-30
Filing date: 2013-03-19
Publication date: 2013-10-03
Also published as: TW201734104A; CN104185653B; CN104185653A; TWI602831B; KR102135487B1; JP6100167B2; JP6334748B2; JP2017095729A; JPWO2013146458A1; TWI626261B; KR20140143205A; TW201345930A

Abstract

[Problem] To provide: a PVA film having little disadvantages and good transparency; and a high-quality polarizing film produced from the PVA film and having improved light transmittance. [Solution] A PVA film produced from a PVA composition comprising PVA (A) and a nonionic surfactant (B), wherein the content of the nonionic surfactant (B) is 0.02 to 1 part by mass relative to 100 parts by mass of PVA (A) and the content of at least one metal (C) selected from the group consisting of alkali metals and alkali earth metals is 100 ppm or less relative to the mass of PVA (A) in the PVA composition; and a polarizing film produced from the PVA film.

Description

POLYVINYL ALCOHOL POLYMER FILM AND POLARIZING FILM

The present invention relates to a polyvinyl alcohol polymer film having few defects and good transparency (hereinafter, “polyvinyl alcohol polymer” may be abbreviated as “PVA”), and a polarizing film produced therefrom. .

PVA films are used in various applications by utilizing unique properties such as transparency, optical characteristics, mechanical strength, and water solubility, and recently, liquid crystal displays ( The use as a raw material (raw film) of a polarizing film constituting a polarizing plate which is a basic component of LCD) is expanding. The polarizing plate for LCD is required to have high optical performance, and high optical performance is also required for the polarizing film which is a constituent element thereof.

In general, a polarizing plate is produced by dyeing, uniaxially stretching a PVA film and, if necessary, further applying a fixing treatment with a boron compound or the like to produce a polarizing film, and thereafter, on the surface of the polarizing film, a cellulose triacetate (TAC) film or the like. It is manufactured by laminating a protective film. In many cases, the PVA film is produced by drying a film-forming stock solution containing PVA using a cast film-forming method or the like.

So far, many techniques related to PVA film and its manufacturing method are known. For example, when casting a PVA aqueous solution (film-forming stock solution) using a T-shaped slit die, calcium and silicon are deposited and deposited near the exit of the slit die, and a streak is formed on the resulting film. After the PVA aqueous solution is cast on the surface of the mold roll to form a film, when the film is peeled off from this roll, it becomes difficult to peel off due to the large amount of silicon, and stretching occurs when it is forcibly peeled off. Based on the problem that optical unevenness is formed on the film, the content of calcium or silicon in the PVA film is defined as a specific range for the purpose of obtaining a PVA film in which the occurrence of optical streaks and optical color unevenness is suppressed. There is a known method (see Patent Document 1). The Patent Document 1 specifically describes a PVA film containing about 0.01 parts by mass of a surfactant with respect to 100 parts by mass of PVA. In the PVA film, the content of calcium is about 280 ppm, and the content of silicon It is shown that if the amount is about 70 ppm, the optical streak and optical color unevenness which are problems in Patent Document 1 can be sufficiently reduced.

JP 2007-9056 A

By the way, the inventor of the present invention has deteriorated the transparency of the PVA film obtained when the PVA film is formed by using a relatively large amount of a specific surfactant for the purpose of eliminating the streaky defects in the PVA film. It was recognized that the optical performance of the polarizing film produced using it could be improved by improving the transparency in the PVA film. Particularly in recent years, there has been a strong demand for reducing power consumption in LCDs, and in order to maintain high screen brightness even when the backlight intensity is low, the light transmittance of the polarizing plate and thus the polarizing film must be increased. Although it is desired to improve, if the transparency in a PVA film is improved, it was thought that the polarizing film which improved the light transmittance can be obtained easily.

Therefore, an object of the present invention is to provide a PVA film having few defects and good transparency, and a high-quality polarizing film having an improved light transmittance produced therefrom.

As a result of intensive studies to achieve the above-mentioned object, the present inventor, when a specific surfactant is used in a relatively large amount, forms a film-forming stock solution used in a PVA film or for film formation thereof. It has been found that the transparency of the obtained PVA film deteriorates due to the influence of a specific metal in the inside. And, if the content of the metal in the obtained PVA film is adjusted, for example, by adjusting the content of the metal in the stock solution to a specific range, the PVA film has few defects and good transparency. I found out that The inventor has further studied based on these findings and completed the present invention.

That is, the present invention
[1] A PVA film comprising a PVA composition containing PVA (A) and a nonionic surfactant (B), wherein in the PVA composition, the content of the nonionic surfactant (B) is PVA ( A) The content of at least one metal (C) selected from the group consisting of alkali metals and alkaline earth metals in PVA (A) is 0.02 to 1 parts by mass with respect to 100 parts by mass. PVA film that is 100 ppm or less on a mass basis,
[2] The PVA film of the above [1], wherein the nonionic surfactant (B) is a nonionic surfactant having an alkyl chain having 9 or more carbon atoms,
[3] The PVA film of [1] or [2] above, wherein the nonionic surfactant (B) is an alkanolamide type nonionic surfactant,
[4] The PVA film according to any one of the above [1] to [3], wherein the metal (C) is an alkaline earth metal,
[5] The PVA film according to any one of the above [1] to [3], wherein the metal (C) is calcium,
[6] The PVA film according to any one of the above [1] to [5], wherein the content of the metal (C) is 0.2 ppm or more based on mass with respect to the PVA (A),
[7] The PVA film according to any one of the above [1] to [6], wherein the content of the metal (C) is 60 ppm or less based on mass relative to the PVA (A),
[8] A polarizing film produced from the PVA film of any one of [1] to [7] above,
About.

According to the present invention, there are provided a PVA film with few defects and good transparency, and a high-quality polarizing film with improved light transmittance produced therefrom.

The present invention is described in further detail below.
The PVA film of the present invention comprises a PVA composition containing PVA (A) and a nonionic surfactant (B). In the PVA composition, the content of the nonionic surfactant (B) is 0.02 to 1 part by mass with respect to 100 parts by mass of PVA (A), and alkali metal and alkaline earth metal. The content of at least one metal (C) selected from the group consisting of is 100 ppm or less on a mass basis with respect to PVA (A).

As the above PVA (A), one produced by saponifying a vinyl ester polymer obtained by polymerizing a vinyl ester monomer can be used. Examples of vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, vinyl versatate, and the like. Among these, vinyl acetate is preferable from the viewpoints of availability, cost, and productivity of PVA (A).

The vinyl ester polymer is preferably obtained by using only one or two or more vinyl ester monomers as a monomer, and using only one vinyl ester monomer as a monomer. Although what was obtained is more preferable, the copolymer of 1 type, or 2 or more types of vinyl-ester type monomers and the other monomer copolymerizable with this may be sufficient.

Other monomers copolymerizable with such vinyl ester monomers include, for example, ethylene; olefins having 3 to 30 carbon atoms such as propylene, 1-butene and isobutene; acrylic acid or salts thereof; methyl acrylate, acrylic Such as ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, etc. Acrylic acid ester; methacrylic acid or salt thereof; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, methacrylic acid 2-ethylhexyl, dodecyl methacrylate Methacrylic acid esters such as octadecyl methacrylate; acrylamide, N-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, diacetone acrylamide, acrylamide propanesulfonic acid or salt thereof, acrylamidopropyldimethylamine or salt thereof, N Acrylamide derivatives such as methylolacrylamide or derivatives thereof; methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid or salts thereof, methacrylamidepropyldimethylamine or salts thereof, N-methylolmethacrylamide or Methacrylamide derivatives such as derivatives thereof; N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone, etc. Vinyl amides; vinyl ethers such as methyl 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, stearyl vinyl ether; acrylonitrile, methacrylonitrile, etc. Vinyl cyanide; 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 , Esters or acid anhydrides; vinylsilyl compounds such as vinyltrimethoxysilane; isopropenyl acetate and the like. The vinyl ester polymer can have a structural unit derived from one or more of these other monomers.

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

The degree of polymerization of PVA (A) is not necessarily limited, but is preferably 200 or more, more preferably 300 or more, more preferably 400 or more, because the film strength tends to decrease as the degree of polymerization decreases. Particularly preferred is 500 or more. Further, if the degree of polymerization is too high, the viscosity of the aqueous solution or molten PVA (A) tends to be high, and film formation tends to be difficult, and therefore it is preferably 10,000 or less, more preferably 9,000. Hereinafter, it is more preferably 8,000 or less, and 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 K6726-1994. After re-saponifying and purifying PVA (A), it is measured in water at 30 ° C. The intrinsic viscosity [η] (unit: deciliter / g) is obtained by the following formula.
Degree of polymerization = ([η] × 10 ³ /8.29) ^{(1 / 0.62)}

There is no restriction | limiting in particular in the saponification degree of PVA (A), For example, 60 mol% or more of PVA (A) can be used, However, PVA film is used especially as raw film films for optical film manufacture, such as a polarizing film. In some cases, the saponification degree of PVA (A) is preferably 95 mol% or more, more preferably 98 mol% or more, and even 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 into vinyl alcohol units by saponification, and vinyl alcohol units, which PVA (A) has. Is the ratio (mol%) occupied by the number of moles of the vinyl alcohol unit. The degree of saponification of PVA (A) can be measured according to the description of JIS K6726-1994.

The PVA composition may contain one type of PVA alone as PVA (A), and one or more of the degree of polymerization, the degree of saponification, the degree of modification, etc. are different from each other. The PVA may be contained. However, in the case where excellent secondary processability is required for the PVA film of the present invention, such as when used as a raw film for optical film production, the PVA composition has an acidic functional group such as a carboxyl group or a sulfonic acid group. PVA having a group; PVA having an acid anhydride group; PVA having a basic functional group such as an amino group; and neutralizing these PVA having a functional group that promotes a crosslinking reaction. The secondary processability of the PVA film may decrease due to the crosslinking reaction. Therefore, in the above case, it is preferable that the PVA composition does not contain any of PVA having an acidic functional group, PVA having an acid anhydride group, PVA having a basic functional group, and neutralized products thereof. PVA (A) produced by saponifying a vinyl ester polymer obtained by using only a vinyl ester monomer as a monomer, and / or a vinyl ester monomer and ethylene and / or It is more preferable to contain only PVA produced by saponifying a vinyl ester polymer obtained by using only an olefin having 3 to 30 carbon atoms as a monomer. As PVA (A), a vinyl ester PVA produced by saponifying a vinyl ester polymer obtained using only monomers as monomers, Preliminary / or, more preferably containing only PVA produced by saponifying a vinyl ester based polymer obtained by using only the vinyl ester monomer and ethylene monomer.

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

The PVA composition further contains a nonionic surfactant (B) in addition to the above PVA (A). Examples of the nonionic surfactant (B) include alkyl ether types such as polyoxyethylene oleyl ether; alkylphenyl ether types such as polyoxyethylene octylphenyl ether; alkyl ester types such as polyoxyethylene laurate; polyoxy Alkylamine types such as ethylene lauryl amino ether; Alkylamides type such as polyoxyethylene lauric acid amide; Polypropylene glycol ether types such as polyoxyethylene polyoxypropylene ether; Alkanolamide types such as lauric acid diethanolamide and oleic acid diethanolamide An allyl phenyl ether type such as polyoxyalkylene allyl phenyl ether. The PVA composition may contain only one kind of nonionic surfactant, or may contain two or more kinds of nonionic surfactant.

The nonionic surfactant (B) is preferably a nonionic surfactant having an alkyl chain (alkyl group) having 9 or more carbon atoms. Such a nonionic surfactant is likely to deteriorate in transparency in a PVA film due to low polarity or the like depending on the prior art. Therefore, when the nonionic surfactant is used, the nonionic surfactant is related to transparency. The effect of the present invention is more remarkable. In addition, when the nonionic surfactant (B) is a nonionic surfactant having an alkyl chain having 9 or more carbon atoms, the occurrence of streak-like defects can be further reduced when a PVA film is formed. From the above viewpoints, the number of carbon atoms (alkyl chain length) of the alkyl chain is more preferably 10 or more, preferably 30 or less, more preferably 22 or less, and 16 or less. More preferably, it is 12 or less. The alkyl chain may be linear or branched, and is preferably linear. Moreover, it is preferable that said alkyl chain is contained in the principal chain part (longest chain) of nonionic surfactant (B).

The nonionic surfactant (B) is preferably an alkanolamide type nonionic surfactant, and more preferably a fatty acid dialkanolamide. Depending on the prior art, such nonionic surfactants are likely to interact with the metal (C), which will be described later, and the transparency in the PVA film is likely to deteriorate. When the nonionic surfactant is used, the effect of the present invention relating to transparency is more remarkably exhibited. Further, when the nonionic surfactant (B) is an alkanolamide type nonionic surfactant, the occurrence of streak-like defects can be further reduced when a PVA film is formed.

The content of the nonionic surfactant (B) in the PVA composition needs to be in the range of 0.02 to 1 part by mass with respect to 100 parts by mass of PVA (A). When the content is less than 0.02 parts by mass with respect to 100 parts by mass of PVA (A), streaky defects are likely to occur when a PVA film is formed. On the other hand, when the content exceeds 1 part by mass with respect to 100 parts by mass of PVA (A), the PVA film moves to the surface and blocking is likely to occur, resulting in poor handling. From the above viewpoint, the content is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and 0.2 parts by mass with respect to 100 parts by mass of PVA (A). More preferably, it is 0.7 mass parts or less, and more preferably 0.5 mass parts or less.

The PVA composition may further contain a surfactant other than the nonionic surfactant (B). Examples of such other surfactants include anionic surfactants. Examples of the anionic surfactant include carboxylic acid types such as potassium laurate; sulfate ester types such as octyl sulfate; sulfonic acid types such as dodecylbenzene sulfonate and the like.

In using the nonionic surfactant (B) and other surfactants other than that, it is preferable to use them in the form of a mixture containing these surfactants because they are easily available and inexpensive. . The surfactant content in the mixture is preferably 70% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more. Moreover, as an upper limit of the content rate of surfactant in the said mixture, 99.99 mass% is mentioned, for example. There are no particular restrictions on the components other than the surfactant contained in the mixture. For example, raw materials, catalysts, and solvents used in the production of the surfactant; decomposition products generated by the decomposition of the surfactant; And a stabilizer added to improve the stability of the surfactant. More specifically, when the surfactant is an alkanolamide-type nonionic surfactant, a corresponding alkanolamine is exemplified.

In the PVA composition, the content of at least one metal (C) selected from the group consisting of alkali metals and alkaline earth metals is based on mass relative to PVA (A) (that is, metal relative to the mass of PVA (A)) The ratio of the mass of (C) is required to be 100 ppm or less. When the PVA film contains the nonionic surfactant (B) in a relatively large amount as described above, the content of the metal (C) is in the above range, so that there are few defects and the transparency is good. Become a film. From the above viewpoint, the content of the metal (C) is preferably 60 ppm or less, more preferably 50 ppm or less, and further preferably 30 ppm or less, based on mass with respect to PVA (A). It is particularly preferably 10 ppm or less. On the other hand, if the content of the metal (C) is too small, wrinkles tend to occur when the formed PVA film is wound on a film roll, so the content is relative to PVA (A). It is preferably 0.2 ppm or more on a mass basis, more preferably 0.4 ppm or more, further preferably 0.5 ppm or more, and particularly preferably 0.7 ppm or more. In addition, when several types of metals are contained as a metal (C), the sum total of content of each metal should just be in the said range. The content of metal (C) can be determined by ICP-MS analysis.

Examples of the metal (C) include lithium, sodium, potassium, rubidium and the like as the alkali metal, and magnesium and calcium as the alkaline earth metal. Among these, when the PVA film contains a nonionic surfactant (B) in a relatively large amount as described above, it has a strong influence on the transparency of the PVA film, so that the metal (C) is an alkaline earth. A metal is preferable, and calcium is more preferable. In addition, although there is no restriction | limiting in particular in the form of a metal (C), Since the effect of this invention is show | played more notably, it is preferable that it is a form of a metal salt.

The PVA composition preferably contains a plasticizer because it can impart flexibility to the PVA film. Preferred plasticizers include polyhydric alcohols, and specific examples include ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and trimethylolpropane. The PVA composition may contain only one kind of plasticizer or may contain two or more kinds of plasticizers. Among these plasticizers, ethylene glycol or glycerin is preferable from the viewpoint of compatibility with PVA (A) and availability.

The content of the plasticizer in the PVA composition is preferably in the range of 1 to 30 parts by mass with respect to 100 parts by mass of PVA (A).

The PVA composition further contains other components other than the above-mentioned surfactants such as PVA (A) and nonionic surfactant (B), metal (C), and plasticizer as necessary. Also good. Examples of such other components include water, antioxidants, ultraviolet absorbers, lubricants, colorants, fillers (inorganic particles, starch, etc.), preservatives, antifungal agents, and other components other than those described above. Examples thereof include polymer compounds.

The thickness of the PVA film of the present invention is not particularly limited, and can be set as appropriate according to the use of the PVA film. For example, the thickness can be 300 μm or less. The PVA film of the present invention is an optical film such as a polarizing film. When used as a raw film for production, the thickness is preferably in the range of 5 to 150 μm. In addition, the thickness of a PVA film can be calculated | required as an average value of the value measured in arbitrary 10 places.

The shape of the PVA film of the present invention is not particularly limited, but a more uniform PVA film can be produced continuously and smoothly, and it can be continuously produced even when an optical film such as a polarizing film is produced using the PVA film. It is preferable that the film is a long film. The length of the long film (the length in the flow direction) is not particularly limited, and can be set as appropriate according to the application, for example, within a range of 5 to 30,000 m. The long film is preferably wound around a core to form a film roll.

There is no restriction | limiting in particular in the width | variety of the PVA film of this invention, For example, although it can be 0.5 m or more, Since the wide polarizing film is calculated | required in recent years, the said width is preferably 1 m or more, and 3 m More preferably, it is 4.5 m or more, more preferably 5.0 m or more, 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 increases, and further, it is uniform in the case of manufacturing an optical film with a manufacturing apparatus that has been put to practical use. The width of the PVA film is preferably 7.5 m or less, more preferably 7.0 m or less, and 6.5 m or less. Further preferred.

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. For example, the haze value of the PVA film is preferably 3.0% or less, more preferably 2.5% or less, and 2.0% More preferably, it is more preferably 1.5% or less. Thus, according to the PVA film having good transparency, an optical film such as a polarizing film having improved light transmittance can be easily obtained. In addition, the haze value of the PVA film was determined at 10 measurement points arbitrarily per 50 cm in the width direction over the entire width direction of the PVA film, and individual haze values were measured at the measurement points, as described later in Examples. In this case, the average value of the measured individual haze values can be obtained. Here, each haze value is represented by the following formula showing the ratio of the diffuse transmittance (Td) to the total light transmittance (Tt) when the film is irradiated with visible light.
Individual haze value (%) = 100 × Td / Tt

According to the present invention, in addition to obtaining a PVA film with good transparency, a PVA film with little variation in transparency in the width direction can be obtained. Thus, according to the PVA film having little variation in transparency in the width direction, it is possible to easily obtain an optical film such as a polarizing film with little unevenness in light transmittance over the entire film surface. The PVA film of the present invention was measured when 10 measurement points were arbitrarily determined per 50 cm in the width direction over the entire width direction of the PVA film as described above, and individual haze values were measured at the measurement points. The maximum value among the individual haze values is preferably 3.5% or less, more preferably 3.0% or less, further preferably 2.5% or less, and 2.0% or less. It is particularly preferred that

For the same reason, the difference between the maximum value and the minimum value among the individual haze values is preferably 0.8% or less, more preferably 0.6% or less, and It is more preferably 3% or less, and particularly preferably 0.2% or less.

There is no restriction | limiting in particular in the manufacturing method of the PVA film of this invention, For example, surfactant, liquid media, such as PVA (A) and nonionic surfactant (B), and the above-mentioned plasticizer and others as needed It can manufacture by employ | adopting well-known methods, such as a casting film forming method and a melt extrusion film forming method, using the film forming stock solution containing these components. At this time, the target PVA film can be easily obtained by adjusting in advance the content of the metal (C) in the stock solution. The adjustment method is not particularly limited. For example, the content of the metal (C) is obtained by using a raw material with a reduced content of the metal (C), or conversely, by adding a salt of the metal (C). And a method of increasing the value. The film-forming stock solution may be one obtained by dissolving PVA (A) in a liquid medium, or one obtained by melting PVA (A).

Examples of the liquid medium in the film-forming stock solution include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, Examples thereof include ethylenediamine and diethylenetriamine, and one or more of these can be used. Among these, water is preferable from the viewpoint of a small environmental load and recoverability. A liquid medium having a reduced metal (C) content, such as a distilled liquid medium, is used as at least a part of the liquid medium in order to bring the metal (C) content in the film-forming stock solution into a desired range. It is preferable.

The volatile fraction of the film-forming stock solution (the content ratio of volatile components such as a liquid medium removed by volatilization or evaporation during film-forming in the film-forming stock 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 55-80% by mass. When 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 film formation becomes easy. On the other hand, when the volatile fraction of the film-forming stock solution is 90% by mass or less, the thickness uniformity of the obtained PVA film is improved without the viscosity of the film-forming stock solution being too low.

There is no particular limitation on the specific production method for producing the PVA film of the present invention by the casting film forming method or the melt extrusion film forming method using the above film forming stock solution. For example, the film forming stock solution is a drum. It is cast or discharged in the form of a film on a support such as a belt or belt, dried on the support, and the resulting film is further dried by a drying roll or hot air drying device, if necessary, or heat-treated. The target PVA film can be manufactured by heat-processing with an apparatus, or adjusting humidity with a humidity control apparatus. The manufactured PVA film is preferably wound into 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 high-quality polarizing film, a retardation film, and a special light collecting film with improved light transmittance. The PVA film of the present invention can also be used for other uses, for example, a packaging material, a water-soluble film such as a laundry bag, a release film for producing artificial marble, and the like. Of these uses, the PVA film of the present invention is particularly preferably used as a raw film for producing a polarizing film.

In order to produce a polarizing film from the PVA film of the present invention, for example, the PVA film may be dyed, uniaxially stretched, fixed, dried, and further heat treated as necessary. The order of dyeing and uniaxial stretching is not particularly limited, and the dyeing process may be performed before the uniaxial stretching process, the dyeing process may be performed simultaneously with the uniaxial stretching process, or the dyeing process may be performed after the uniaxial stretching process. You may go. In addition, steps such as uniaxial stretching and dyeing may be repeated a plurality of times. In particular, it is preferable to divide the uniaxial stretching into two or more stages because uniform stretching is easily performed.

Examples of the dye used for dyeing the PVA film include iodine or a dichroic organic dye (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; Direct Yellow 8, 12, 44, 86, 87; dichroic dyes such as Direct Orange 26, 39, 106, 107) can be used. These dyes can be used alone or in combination of two or more. Dyeing can usually be performed by immersing the PVA film in a solution containing the dye, but the treatment conditions and treatment method are not particularly limited.

Uniaxial stretching for stretching the PVA film in the flow direction (MD) or the like may be performed by either a wet stretching method or a dry heat stretching method, but from the viewpoint of the performance and quality stability of the obtained polarizing film, the wet stretching method. Is preferred. Examples of the wet stretching method include a method of stretching a PVA film in pure water, an aqueous solution containing various components such as an additive and an aqueous medium, or an aqueous dispersion in which various components are dispersed. Uniaxial stretching by a wet stretching method. Specific examples of the method include a method of uniaxially stretching in warm water containing boric acid, a method of uniaxially stretching in a solution containing the above-described dye or a fixing treatment bath described later, and the like. Moreover, you may uniaxially stretch in the air using the PVA film after water absorption, and you may uniaxially stretch by another method.

The stretching temperature for 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, and even more preferably 30 to 65 ° C is adopted. In the case of hot stretching, a temperature within the range of 50 to 180 ° C. is preferably employed.

The stretching ratio of the uniaxial stretching treatment (the total stretching ratio when performing uniaxial stretching in multiple stages) is preferably stretched as much as possible from the point of polarization performance until just before the film is cut, and specifically 4 times or more. Is preferably 5 times or more, more preferably 5.5 times or more. The upper limit of the stretching ratio is not particularly limited as long as the film is not broken, but is preferably 8.0 times or less in order to perform uniform stretching.

In the production of a polarizing film, fixing treatment is often performed in order to strengthen the adsorption of the dye to the uniaxially stretched film. As the fixing treatment, a method of immersing a film in a treatment bath to which boric acid and / or a boron compound is added is generally widely adopted. In that case, you may add an iodine compound in a processing bath as needed.

It is preferable that the film subjected to the uniaxial stretching treatment or the uniaxial stretching treatment and the fixing treatment is then subjected to a drying treatment (heat treatment). The temperature of the drying treatment (heat treatment) is preferably 30 to 150 ° C., particularly 50 to 140 ° C. If the temperature of the drying treatment (heat treatment) is too low, the dimensional stability of the obtained polarizing film tends to be lowered, while if too high, the polarizing performance is likely to deteriorate due to the decomposition of the dye.

Protective films that are optically transparent and have mechanical strength can be bonded to both sides or one side of the polarizing film obtained as described above to form a polarizing plate. As the protective film in this case, a cellulose triacetate (TAC) film, an acetic acid / cellulose butyrate (CAB) film, an acrylic film, a polyester film, or the like is used. Moreover, as an adhesive for laminating a protective film, a PVA adhesive or a urethane adhesive is generally used, and among them, a PVA adhesive is preferably used.

The polarizing plate obtained as described above can be used as a component of a liquid crystal display device after being coated with an acrylic adhesive or the like and then bonded to a glass substrate. When the polarizing plate is bonded to the glass substrate, a retardation film, a viewing angle improving film, a brightness improving film, or the like may be bonded simultaneously.

Hereinafter, the present invention will be specifically described with reference to examples and the like, but the present invention is not limited to these examples. In addition, each measurement or evaluation method employ | adopted in the following examples and comparative examples is shown below.

[Measuring method of content of metal (C)]
The content of calcium in the PVA film (PVA composition) was determined by ICP-MS analysis (high frequency inductively coupled plasma mass spectrometry). Specifically, first, about 5 g of a sample piece is taken from the PVA film obtained in the following examples or comparative examples, weighed into a platinum crucible, subjected to dry decomposition using nitric acid and sulfuric acid, and ash After adding about 5 mL of hydrochloric acid to the converted sample, it was fixed in a 25 mL “Teflon” volumetric flask and filtered with a PTFE filter having a pore diameter of 0.45 μm to prepare a sample solution. Next, using the obtained sample solution, ICP-MS analysis was performed under the following conditions, and the calcium content in the PVA film (PVA composition) was determined based on the mass of the metal (C) relative to the mass of PVA (A). As a percentage of The calibration curve used to determine the calcium content is SPEX CertiPrep, Inc. It was prepared using a standard solution for preparing a calibration curve prepared by diluting a standard solution “XSTC-622” manufactured by the company.
"Measurement condition"
Equipment: ELAN DRCII manufactured by Perkin-Elmer
Plasma output: 1100W
Nebulizer gas flow rate: 1.01 L / min Auxiliary gas flow rate: 1.10 L / min Plasma gas flow rate: 18.00 L / min

[Evaluation method for streaks]
The streaky defects on the PVA film parallel to the flow direction (MD) during film formation were visually observed and evaluated. Specifically, the sample piece cut out from the PVA film obtained in the following examples or comparative examples is suspended so that the MD is horizontal, and a 30 W straight tube fluorescent lamp is horizontally placed behind and lighted. The streaky defects observed when the fluorescent lamp was viewed through the sample piece were evaluated according to the following criteria.
A: No streak-like defects are observed B: Almost no streak-like defects are observed C: A few streak-like defects are observed D: Many streak-like defects are observed

[Measurement method of haze value]
From the PVA film obtained in the following examples or comparative examples, a strip-like sample having a length of 15 cm in the MD and a full width in the width direction (TD) was taken. This sample was further cut from one end to a width of 50 cm in TD. When a sample piece with a width of less than 50 cm remains (in the following examples and comparative examples, a sample piece with a width of 15 cm remains because a PVA film with a width of 165 cm remains). The width was left as it was.
Ten arbitrary measurement points were selected from the top of the obtained 50 cm wide sample piece, and the haze value at the measurement point was measured using ASTM H100-1 manufactured by Suga Test Instruments Co., Ltd. according to ASTM D1003- Measured according to 61. That is, the number of haze value measurement points is 10 per 50 cm in the width direction. For sample pieces whose width is less than 50 cm, the haze value at the measurement point of a number proportional to the width (that is, the number obtained by dividing the width of the sample piece by 5 cm and rounding up) is obtained. It was measured. The average value of the obtained individual haze values was determined and used as the haze value of the PVA film. Moreover, the maximum value and the minimum value of the obtained individual haze values were obtained, and the difference between them was calculated.

[Method for evaluating blocking in film roll]
The presence or absence of blocking when the PVA film was unwound from the film roll obtained in the following Examples or Comparative Examples was confirmed.

[Example 1]
As PVA (A), PVA (saponified product of homopolymer of vinyl acetate) having a polymerization degree of 2400 and a saponification degree of 99.9 mol% was used, and this PVA chip (calcium content is based on mass relative to PVA). After dipping 100 parts by mass (less than 0.005 ppm) in 2500 parts by mass of distilled water at 35 ° C. for 24 hours, centrifugal dehydration was performed to obtain a PVA water-containing chip. The volatile fraction in the obtained PVA water-containing chip was 70% by mass. 12 parts by mass of glycerin and lauric acid diethanolamide (purity 95% by mass, diethanolamine as an impurity) with respect to 333 parts by mass of the PVA hydrous chip (100 parts by mass of dry PVA) 0.3 parts by weight of the mixture) and 0.0002 parts by weight of calcium chloride dihydrate in terms of calcium, and then mixed well to obtain a mixture. A film forming stock solution was obtained by heating and melting.
After this film-forming stock solution is cooled to 100 ° C. with a heat exchanger, it is formed into a film by extrusion from a coat hanger die having a width of 180 cm onto a drum having a surface temperature of 90 ° C., and further dried through a hot air dryer, and then manufactured. A PVA film having a width of 165 cm was continuously produced by cutting off both ends of the film which became thick due to neck-in at the time of film formation. In addition, a length of 4000 m of the manufactured PVA film was wound around a cylindrical core to obtain a film roll.
The obtained PVA film was measured or evaluated for the content of metal (C) (calcium), streak-like defects and haze value by the method described above, and the blocking was evaluated by the method described above for the obtained film roll. The content of calcium is 1.8 ppm on a mass basis with respect to PVA, the streaky defect is evaluated as “A”, and the haze value is 0.4% (maximum value is 0.5%, minimum value) 0.4% and the difference between the two was 0.1%), and no blocking was observed. In addition, wrinkles particularly conspicuous on the surface of the film roll were not observed. The above results are summarized in Table 1.

[Example 2]
In Example 1, the PVA film (and film roll) was prepared in the same manner as in Example 1 except that the amount of calcium chloride dihydrate added was changed from 0.0002 parts by mass to 0.008 parts by mass in terms of calcium. Manufactured.
The obtained PVA film was measured or evaluated for the content of metal (C) (calcium), streak-like defects and haze value by the method described above, and the blocking was evaluated by the method described above for the obtained film roll. The content of calcium is 78 ppm on a mass basis with respect to PVA, the streaky defect is evaluated as “A”, the haze value is 2.8% (the maximum value is 3.3%, and the minimum value is 2). 0.6% and the difference between the two was 0.7%), and no blocking was observed. In addition, wrinkles particularly conspicuous on the surface of the film roll were not observed. The above results are summarized in Table 1.

[Example 3]
In Example 1, the nonionic surfactant (B) is changed from lauric acid diethanolamide (purity 95% by mass, mixture containing diethanolamine as an impurity) to polyoxyethylene laurylamine (purity 93% by mass, mixture containing impurities). A PVA film (and a film roll) was produced in the same manner as in Example 1 except that the change was made.
The obtained PVA film was measured or evaluated for the content of metal (C) (calcium), streak-like defects and haze value by the method described above, and the blocking was evaluated by the method described above for the obtained film roll. The content of calcium is 1.9 ppm on a mass basis with respect to PVA, the streaky defect is evaluated as “B”, and the haze value is 0.8% (maximum value is 1.0%, minimum value) 0.7% and the difference between the two was 0.3%), and no blocking was observed. In addition, wrinkles particularly conspicuous on the surface of the film roll were not observed. The above results are summarized in Table 1.

[Example 4]
In Example 1, the nonionic surfactant (B) was changed from lauric acid diethanolamide (purity 95 mass%, a mixture containing diethanolamine as an impurity) to stearic acid diethanolamide (purity 95 mass%, a mixture containing impurities). A PVA film (and a film roll) was produced in the same manner as in Example 1 except that.
The obtained PVA film was measured or evaluated for the content of metal (C) (calcium), streak-like defects and haze value by the method described above, and the blocking was evaluated by the method described above for the obtained film roll. The content of calcium is 1.8 ppm on a mass basis with respect to PVA, the streaky defect is evaluated as “B”, and the haze value is 0.6% (maximum value is 0.8%, minimum value) 0.5% and the difference between the two was 0.3%), and no blocking was observed. In addition, wrinkles particularly conspicuous on the surface of the film roll were not observed. The above results are summarized in Table 1.

[Example 5]
In Example 1, a PVA film (and a film roll) was produced in the same manner as in Example 1 except that calcium chloride dihydrate was not added.
The obtained PVA film was measured or evaluated for the content of metal (C) (calcium), streak-like defects and haze value by the method described above, and the blocking was evaluated by the method described above for the obtained film roll. The content of calcium is 0.01 ppm on a mass basis with respect to PVA, the streaky defect is evaluated as “A”, and the haze value is 0.3% (maximum value is 0.3%, minimum value) 0.2%, the difference between the two was 0.1%), and no blocking was observed. However, wrinkles occurred on the surface of the film roll. The above results are summarized in Table 1.

[Comparative Example 1]
In Example 1, the addition amount of lauric acid diethanolamide (purity 95% by mass, a mixture containing diethanolamine as an impurity) was changed from 0.3 parts by mass to 0.01 parts by mass, and addition of calcium chloride dihydrate A PVA film (and a film roll) was produced in the same manner as in Example 1 except that the amount was changed from 0.0002 parts by mass to 0.015 parts by mass in terms of calcium.
The obtained PVA film was measured or evaluated for the content of metal (C) (calcium), streak-like defects and haze value by the method described above, and the blocking was evaluated by the method described above for the obtained film roll. The content of calcium is 148 ppm on a mass basis with respect to PVA, the streak-like defect is evaluated as “D”, and the haze value is 0.4% (maximum value is 0.5%, minimum value is 0). 4% and the difference between the two was 0.1%), and no blocking was observed. In addition, wrinkles particularly conspicuous on the surface of the film roll were not observed. The above results are summarized in Table 1.

[Comparative Example 2]
In Example 1, except that the addition amount of lauric acid diethanolamide (purity 95% by mass, mixture containing diethanolamine as an impurity) was changed from 0.3 parts by mass to 0.01 parts by mass, the same as in Example 1 PVA films (and film rolls) were produced.
The obtained PVA film was measured or evaluated for the content of metal (C) (calcium), streak-like defects and haze value by the method described above, and the blocking was evaluated by the method described above for the obtained film roll. The content of calcium is 2.0 ppm on a mass basis with respect to PVA, the streaky defect is evaluated as “D”, and the haze value is 0.4% (the maximum value is 0.4%, the minimum value) 0.3% and the difference between the two was 0.1%), and no blocking was observed. In addition, wrinkles particularly conspicuous on the surface of the film roll were not observed. The above results are summarized in Table 1.

[Comparative Example 3]
In Example 1, the PVA film (and film roll) was prepared in the same manner as in Example 1 except that the amount of calcium chloride dihydrate added was changed from 0.0002 parts by mass to 0.015 parts by mass in terms of calcium. Manufactured.
The obtained PVA film was measured or evaluated for the content of metal (C) (calcium), streak-like defects and haze value by the method described above, and the blocking was evaluated by the method described above for the obtained film roll. The content of calcium is 152 ppm on a mass basis with respect to PVA, the streaky defect is evaluated as “A”, and the haze value is 3.3% (maximum value is 5.0%, minimum value is 3). 0.0% and the difference between the two was 2.0%), and no blocking was observed. In addition, wrinkles particularly conspicuous on the surface of the film roll were not observed. The above results are summarized in Table 1.

[Comparative Example 4]
In Example 1, the addition amount of lauric acid diethanolamide (purity 95% by mass, a mixture containing diethanolamine as an impurity) is changed from 0.3 parts by mass to 2.0 parts by mass (1.9 parts by mass as lauric acid diethanolamide). A PVA film (and a film roll) was produced in the same manner as in Example 1 except that the change was made.
The obtained PVA film was measured or evaluated for the content of metal (C) (calcium) and streak-like defects by the method described above, and blocking was evaluated by the method described above for the obtained film roll. The content of is 1.8 ppm on a mass basis with respect to PVA, and the streak-like defect was evaluated as “A”, but blocking was seen, and an original film for producing an optical film such as a polarizing film was obtained. As a film, it was unbearable. In addition, wrinkles particularly conspicuous on the surface of the film roll were not observed. The above results are summarized in Table 1.

According to the present invention, since a PVA film with few defects and good transparency is provided, if the PVA film is used as a raw film, for example, a high-quality polarizing film with improved light transmittance, etc. An optical film can be manufactured at a low cost with a high product yield.

Claims

A polyvinyl alcohol polymer film comprising a polyvinyl alcohol polymer composition containing a polyvinyl alcohol polymer (A) and a nonionic surfactant (B), wherein the polyvinyl alcohol polymer composition comprises: The content of the system surfactant (B) is 0.02 to 1 part by mass with respect to 100 parts by mass of the polyvinyl alcohol polymer (A), and is selected from the group consisting of alkali metals and alkaline earth metals The polyvinyl alcohol-type polymer film whose content of at least 1 sort (s) of metal (C) is 100 ppm or less on a mass basis with respect to a polyvinyl alcohol-type polymer (A).
The polyvinyl alcohol polymer film according to claim 1, wherein the nonionic surfactant (B) is a nonionic surfactant having an alkyl chain having 9 or more carbon atoms.
The polyvinyl alcohol polymer film according to claim 1 or 2, wherein the nonionic surfactant (B) is an alkanolamide type nonionic surfactant.
The polyvinyl alcohol polymer film according to any one of claims 1 to 3, wherein the metal (C) is an alkaline earth metal.
The polyvinyl alcohol polymer film according to any one of claims 1 to 3, wherein the metal (C) is calcium.
The polyvinyl alcohol polymer film according to any one of claims 1 to 5, wherein the content of the metal (C) is 0.2 ppm or more based on mass with respect to the polyvinyl alcohol polymer (A).
The polyvinyl alcohol polymer film according to any one of claims 1 to 6, wherein the content of the metal (C) is 60 ppm or less on a mass basis with respect to the polyvinyl alcohol polymer (A).
A polarizing film produced from the polyvinyl alcohol polymer film according to any one of claims 1 to 7.