JP2005206810A - Polyvinyl alcohol-based film and use of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prepare a polyvinyl alcohol-based film having excellent uniformity in thickness of the film, having a uniform optical performance, without having defects, such as optical streaks, and having an extremely excellent external appearance of the film, without causing blocking of the films with each other, even when the film in continuous length is wound in a roll state and then stored for a long period, and especially useful as a raw film for obtaining a polarizing film having the excellent optical external appearance, without having disorder, such as optical unevenness. <P>SOLUTION: This polyvinyl alcohol-based film contains a polyvinyl alcohol-based resin, an ether-type nonionic surfactant (a), and at least two kinds of nitrogen containing-type nonionic surfactants (b). The polarizing film is obtained by using the same. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is uniform in optical performance without defects such as uneven film thickness and optical streaks, and even when a long film is wound up in a roll state and stored for a long period of time, the films cause blocking. In particular, it relates to a polyvinyl alcohol film having a very excellent film appearance, and particularly to a polyvinyl alcohol film useful as a raw film for obtaining a polarizing film having an excellent optical appearance without any obstacles such as optical color unevenness. is there.

Conventionally, a polyvinyl alcohol film is prepared by dissolving a polyvinyl alcohol resin in a solvent, defoaming to prepare a stock solution, and then using a metal heating roll or the like to form the film formed by the solution casting method (casting method). It is manufactured by drying.
The polyvinyl alcohol film thus obtained is used in many applications as a film having excellent shape stability, and one of its useful applications is an optical film, particularly a polarizing film.
Such a polarizing film is a film obtained by uniaxially stretching and dyeing the polyvinyl alcohol film, and is used as a basic component of a liquid crystal display. In recent years, applications for high-quality and high-reliability devices, especially large-screen liquid crystal displays, etc., have been developed, and associated physical properties such as increased size, in-plane uniformity, and wide viewing angle are high. There is a strong demand for improvement in quality.

Under such circumstances, when producing a polarizing film using a polyvinyl alcohol film as an original film, in order to have excellent optical characteristics, for example, the generation of optical streaks in the polyvinyl alcohol film is suppressed, or the film thickness is reduced. , Making the in-plane retardation (Rd) value uniform, preventing the films from blocking each other during storage of the wound film roll, and damaging its appearance, or unwinding during the production of a polarizing film Various measures are required such as not reducing the efficiency.
As such countermeasures, many proposals have been made. For example, as a method for obtaining the thickness uniformity of a polyvinyl alcohol film, a stock solution for film formation is cast on a metal surface having a surface roughness of 3S or less. A method for forming a film has been proposed (see Patent Document 1).
JP 2001-315138 A

However, although the technique disclosed in this publication can provide film thickness uniformity in terms of physical properties, it is still not satisfactory with respect to the suppression of optical streaks and the improvement of optical color unevenness. Further improvement is required in order to exhibit optical characteristics.
In particular, the generation of optical streaks may be a fatal defect in producing a polarizing film having higher quality and higher optical properties.

  On the other hand, recently, in order to improve the productivity of polarizing film, the original film is often stored and transported as a roll of film wound around a core tube in a long state of 1000 m to 4000 m. There is a strong demand for film rolls that exceed, but since the rolls of such long films inevitably have a large thickness, blocking between films is more likely to occur, which not only impairs the appearance of the film, but also the polarization film. Since film breakage occurs when the film is unwound from the film roll during production, or the unwinding speed is lowered and productivity is lowered, improvement is definitely required.

  In the present invention, it is an object of the present invention to provide a polyvinyl alcohol film having no blocking and excellent optical properties, particularly a polyvinyl alcohol film for a polarizing film, and a polarizing film obtained therefrom. is there.

  However, as a result of intensive studies by the present inventors to solve the above-mentioned problems, polyvinyl alcohol resin, ether type nonionic surfactant (a) and at least two types of nitrogen-containing nonionic surfactant (b The present invention has been completed by finding that a polyvinyl alcohol film containing) and a polarizing film obtained from the film satisfy the purpose.

  Since the polyvinyl alcohol film of the present invention contains a polyvinyl alcohol resin, an ether type nonionic surfactant (a) and at least two types of nitrogen-containing nonionic surfactant (b), It has excellent optical properties and the like, and can exhibit an excellent effect of blocking resistance, and is particularly useful for a polyvinyl alcohol film for polarizing film and a polarizing film obtained therefrom.

Hereinafter, the present invention will be specifically described.
First, the polyvinyl alcohol-based resin that is the main component of the polyvinyl alcohol-based film of the present invention is usually produced by saponifying polyvinyl acetate obtained by polymerizing vinyl acetate, but the present invention is not necessarily limited to this. A small amount of unsaturated carboxylic acid (including salts, esters, amides, nitriles, etc.), olefins having 2 to 30 carbon atoms (ethylene, propylene, n-butene, isobutene, etc.), vinyl ethers, unsaturated sulfonates For example, a modified polyvinyl alcohol resin containing a component copolymerizable with vinyl acetate may be used.

  In addition to this modification, a polyvinyl alcohol-based resin containing a silyl group may be used. Polyvinyl alcohol may be post-modified using a silylating agent, or a silyl group-containing olefinically unsaturated monomer and vinyl acetate may be used together. Examples thereof include a method of saponifying a copolymer obtained by polymerization. Examples of the silyl group-containing olefinically unsaturated monomer include vinyl silane and (meth) acrylamide-alkyl silane.

  Although the weight average molecular weight of a polyvinyl alcohol-type resin is not specifically limited, Preferably it is 120,000-300000, More preferably, it is 140000-26000. When the weight average molecular weight is less than 120,000, sufficient optical performance cannot be obtained when the polyvinyl alcohol resin is used as an optical film, and when it exceeds 300,000, when the film is used as a polarizing film, stretching becomes difficult and industrial production is difficult. Is difficult and undesirable. In addition, the weight average molecular weight of polyvinyl alcohol-type resin is measured by GPC-LALLS method.

  Furthermore, the saponification degree of the polyvinyl alcohol-based resin is preferably 80 mol% or more, particularly 85 to 100 mol%, more preferably 98 to 100 mol%. When the saponification degree is less than 80 mol%, it is not preferable because sufficient optical performance may not be obtained when an optical film is used.

  A feature of the present invention is that the polyvinyl alcohol-based resin contains an ether-type nonionic surfactant (a) and at least two types of nitrogen-containing nonionic surfactant (b), that is, such a specific surfactant. Is to combine and blend.

As such an ether type nonionic surfactant (a), typically,
General formula R—O (C ₂ H ₄ O) _n H
A polyoxyethylene alkyl ether represented by
General formula R—X—O (C ₂ H ₄ O) _n H
And polyoxyethylene alkylphenyl ether represented by the formula:
Here, R is an alkyl group or an alkenyl group, and the carbon number thereof is 6 to 22, preferably 8 to 18. These may be a single alkyl group or a mixed alkyl group. Moreover, the alkyl group which has an alkyl distribution obtained from palm oil, palm oil, palm kernel oil, beef tallow, etc. can also be used. X represents a phenylene group, and n represents an integer of 1 to 70, preferably 10 to 30.

  Specific examples of the polyoxyethylene alkyl ether include, for example, polyoxyethylene hexyl ether, polyoxyethylene heptyl ether, polyoxyethylene octyl ether, polyoxyethylene nonyl ether, polyoxyethylene decyl ether, polyoxyethylene dodecyl ether, polyoxyethylene Oxyethylene tetradecyl ether, polyoxyethylene hexadecyl ether, polyoxyethylene octadecyl ether, polyoxyethylene eicosyl ether, polyoxyethylene oleyl ether, palm oil reduced alcohol ethylene oxide adduct, beef tallow reduced alcohol ethylene oxide adduct, etc. Among them, polyoxyethylene dodecyl ether, polyoxyethylene octadecyl ether, coconut oil reductant Call ethylene oxide adduct, it is advantageous use of such beef tallow reducing alcohol ethylene oxide adducts.

  Specific examples of the polyoxyethylene alkyl phenyl ether include, for example, polyoxyethylene hexyl phenyl ether, polyoxyethylene heptyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene decyl phenyl ether, polyoxyethylene decyl phenyl ether, Examples include oxyethylene dodecyl phenyl ether, polyoxyethylene tetradecyl phenyl ether, polyoxyethylene hexadecyl phenyl ether, polyoxyethylene octadecyl phenyl ether, and polyoxyethylene eicosyl phenyl ether. desirable.

In addition, ethylene oxide derivatives of alkylphenol formalin condensates, polyoxyethylene polyoxypropylene block polymers, and the like can also be used.
In addition, polyoxyethylene glycerin fatty acid ester, polyoxyethylene castor oil and hydrogenated castor oil, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, and other ether ester type nonionic surfactants within the scope of the present invention. An ester type surfactant such as an agent, polyethylene glycol fatty acid ester, sorbitan fatty acid ester, fatty acid monoglyceride, propylene glycol fatty acid ester, sucrose fatty acid ester may be used in combination.

Nitrogen-containing type nonionic surface active agents as (b), a representative formula ^RCONH-R '-OH or RCON- ^(R' is the _{-OH) 2}
A higher fatty acid mono- or dialkanolamide represented by
General formula RCONH ₂
A higher fatty acid amide represented by
Formula _{RNH (C 2 H 4 O)} x H or _{H (C 2 H 4 O)} y N (R) (C 2 H 4 O) x H
The polyoxyethylene alkylamine shown by these is mentioned, It uses in combination of 2 or more types. It is essential to use different types of nitrogen-containing nonionic surfactants (b) together, and even if the same type is used in the same amount, it is difficult to obtain the effects of the present invention.
Here, R is the same as that of the ether type nonionic surfactant, and R ^′ is any one of —C ₂ H ₄ —, —C ₃ H ₆ —, and —C ₄ H ₈ —. . x and y are integers of 1-20.
In the present invention, when two or more types of nitrogen-containing nonionic surfactants (b) are used, polyoxyethylene alkylamine is particularly essential to improve optical color unevenness and to suppress generation of optical streaks. Further, it is preferable to use polyoxyethylene alkylamine and a higher fatty acid mono- or dialkanolamide in view of suppression of blocking property.

Specific examples of higher fatty acid alkanolamides include, for example, caproic acid mono or diethanolamide, caprylic acid mono or diethanolamide, capric acid mono or diethanolamide, lauric acid mono or diethanolamide, palmitic acid mono or diethanolamide, stearic acid mono Alternatively, diethanolamide, oleic acid mono- or diethanolamide, coconut oil fatty acid mono- or diethanolamide, or propanolamide and butanolamide may be used instead of these ethanolamides. Of these, alkyldiethanolamide is preferred, and specifically, lauric acid diethanolamide and palm oil fatty acid diethanolamide are preferably used. Particularly, the diethanolamide and diethanolamine [NH- (C ₂ H ₄ The use of a mixture of adducts with (OH) ₂ ] (1: 2 molar form) is advantageous in terms of water solubility.

  Specific examples of higher fatty acid amides include caproic acid amide, caprylic acid amide, capric acid amide, lauric acid amide, palmitic acid amide, stearic acid amide, oleic acid amide, and the like. Are advantageously used.

  Specific examples of the polyoxyethylene alkylamine include, for example, polyoxyethylene hexylamine, polyoxyethylene heptylamine, polyoxyethylene octylamine, polyoxyethylene nonylamine, polyoxyethylene decylamine, polyoxyethylene dodecylamine, polyoxyethylene Examples thereof include oxyethylene tetradecylamine, polyoxyethylene hexadecylamine, polyoxyethylene octadecylamine, polyoxyethylene oleylamine, polyoxyethylene eicosylamine, and polyoxyethylene dodecylamine is advantageously used. Moreover, it is preferable that the condensation degree of a polyoxyethylene unit is 1-30, and 1-20 are more preferable.

  In addition to the above, polyoxyethylene higher fatty acid amides and amine oxides can also be used. Specific examples of polyoxyethylene higher fatty acid amides include, for example, polyoxyethylene caproic acid amide, polyoxyethylene caprylic acid amide, polyoxyethylene Examples include ethylene capric acid amide, polyoxyethylene lauric acid amide, polyoxyethylene palmitic acid amide, polyoxyethylene stearic acid amide, polyoxyethylene oleic acid amide, among others, polyoxyethylene lauric acid amide, polyoxyethylene stearic acid Amides are advantageously used, and specific examples of amine oxides include, for example, dimethyl lauryl amine oxide, dimethyl stearyl oxide, dihydroxyethyl lauryl amine oxide, and the like. Methyl lauryl amine oxide it is preferably used.

In the present invention, a surfactant other than the ether type nonionic surfactant (a) and the nitrogen-containing type nonionic surfactant (b), for example, sulfate ester type anionic interface, without departing from the gist of the present invention. An active agent can be used in combination. Typically, the general formula ROSO ₃ ⁻
Alkyl sulfate salt represented by
Formula R—O (C ₂ H ₄ O) _n SO ₃ ^—
A polyoxyethylene alkyl ether sulfate represented by
General formula R—X—O (C ₂ H ₄ O) _n SO ₃ ^—
A polyoxyethylene alkylphenyl ether sulfate represented by
Formula _{RCONH- (C 2 H 4 O)} n SO 3 -
And higher fatty acid alkanolamide sulfates represented by the formula:
Here, R and X are the same as in the above case. n represents an integer of 1 to 20, preferably 1 to 10.

  Specific examples of the alkyl sulfate ester salt include sodium hexyl sulfate, sodium heptyl sulfate, sodium octyl sulfate, sodium nonyl sulfate, sodium decyl sulfate, sodium dodecyl sulfate, sodium tetradecyl sulfate, sodium hexadecyl sulfate, sodium octadecyl sulfate, and eicosyl sulfate. Examples thereof include alkali metal salts such as sodium or potassium salts thereof, alkaline earth metal salts such as calcium salts, and organic amine salts such as ammonium salts.

  Specific examples of the polyoxyethylene alkyl ether sulfate include, for example, polyoxyethylene hexyl ether sodium, polyoxyethylene heptyl ether sodium, polyoxyethylene octyl ether sodium, polyoxyethylene nonyl ether sodium, polyoxyethylene decyl ether sodium, Organic amines such as polyoxyethylene dodecyl ether sodium, polyoxyethylene tetradecyl ether sodium, polyoxyethylene hexadecyl ether sodium, polyoxyethylene octadecyl ether sodium, polyoxyethylene eicosyl ether sodium, or potassium salts and ammonium salts thereof Examples include salts.

  Examples of the polyoxyethylene alkylphenyl ether sulfate include sodium polyoxyethylene hexylphenyl ether sulfate, sodium polyoxyethylene heptylphenyl ether sulfate, sodium polyoxyethylene octylphenyl ether sulfate, sodium polyoxyethylene nonylphenyl ether sulfate, poly Sodium oxyethylene decyl phenyl ether sulfate, sodium polyoxyethylene dodecyl phenyl ether sulfate, sodium polyoxyethylene tetradecyl phenyl ether sulfate, sodium polyoxyethylene hexadecyl phenyl ether sulfate, sodium polyoxyethylene octadecyl phenyl ether sulfate, polyoxyethylene eico Sodium silphenyl ether sulfate or this Et potassium salts, organic amine salts such as ammonium salts.

Specific examples of higher fatty acid alkanolamide sulfate ester salts include, for example, sodium caproic acid ethanolamide sulfate, sodium caprylic acid ethanolamide sulfate, sodium capric acid ethanolamide sulfate, sodium lauric acid ethanolamide sulfate, sodium palmitate ethanolamide sulfate, Sodium stearic acid ethanolamide sulfate, oleic acid ethanolamide sodium sulfate or potassium salts thereof, and propanolamide, butanolamide and the like instead of these ethanolamides may be mentioned.
In addition, sulfate ester salts such as sulfated oil, higher alcohol ethoxy sulfate, and monoglyculate can also be used.

  Of course, fatty acid soaps other than the sulfate ester salt type, N-acyl amino acids and salts thereof, polyoxyethylene alkyl ester carboxylates, carboxylate types such as acylated peptides, alkyl benzene sulfonates, alkyl naphthalene sulfonates, Naphthalene sulfonic acid salt formalin polycondensate, melamine sulfonic acid salt formalin condensate, dialkyl sulfosuccinic acid ester salt, sulfosuccinic acid alkyl di salt, polyoxyethylene alkyl sulfosuccinic acid di salt, alkyl sulfoacetic acid salt, α-olefin sulfonic acid Sulfonates such as salts, N-acylmethyl taurate, dimethyl-5-sulfoisophthalate sodium salt, polyoxyethylene alkyl ether phosphate, polyoxyethylene alkylphenyl ether phosphate, alkyl phosphorus May be used together other anionic surfactants of the phosphoric acid ester salt type such as salt.

  In the present invention, the addition amount of the surfactant is not particularly limited, but the content of the ether type nonionic surfactant (a) and the nitrogen-containing type nonionic surfactant (b) is in the polyvinyl alcohol resin. On the other hand, the ether type nonionic surfactant (a) is 5 to 1500 ppm (preferably 50 to 1000 ppm, particularly preferably 100 to 900 ppm), and the nitrogen-containing nonionic surfactant (b) is 5 to 5000 ppm (preferably It is practical to select from the range of 50 to 4000 ppm, particularly preferably 100 to 3000 ppm.

  If the content of the ether type nonionic surfactant (a) is less than 5 ppm, optical streaks may occur, and if it exceeds 1500 ppm, the transmittance is remarkably lowered, which is not preferable. Furthermore, when the content of the nitrogen-containing nonionic surfactant (b) is less than 5 ppm, optical streaks and long run properties may be deteriorated, and wrinkles may be caused when performing long winding. Is not preferable. On the other hand, if it exceeds 5000 ppm, there is a risk of blocking, which is not preferable.

And about the weight ratio (a: b) of content of ether type nonionic surfactant (a) and nitrogen-containing type nonionic surfactant (b), it is 1: 1-20 (preferably 1: 1-1). 15 and particularly preferably 1: 1 to 10) is advantageous in that a high-quality, high-optical and long-winding film can be stably produced. If the ratio of the nitrogen-containing nonionic surfactant (b) is less than 1, optical color unevenness or optical streaks may occur, and if it exceeds 20, the blocking may occur, which is not preferable.
Further, the mixing ratio of the nitrogen-containing nonionic surfactants (b) is not particularly limited, but when two types are used, for example, with respect to 100 parts by weight of polyoxyethylene alkylamine, higher fatty acid alkano- 5 to 100 parts by weight, preferably 10 to 90 parts by weight of ruamide is practical. When polyoxyethylene alkylamine and higher fatty acid amide are used, 1 to 50 parts by weight of higher fatty acid amide is practical with respect to 100 parts by weight of polyoxyethylene alkylamine. When three types are used, for example, 100 to 100 parts by weight of polyoxyethylene alkylamine, 10 to 100 parts by weight of higher fatty acid alkanolamide, preferably 20 to 80 parts by weight, 1 to 40 parts by weight of higher fatty acid amide, preferably 5 to 30 parts by weight is practical.

  In the present invention, in order to prevent yellowing of the film, the addition of an antioxidant is also useful, and an arbitrary antioxidant such as a phenolic antioxidant is exemplified, and 2,6-di-t-butyl is exemplified. -P-cresol, 2,2'-methylenebis (4-methyl-6-t-butylphenol), 4,4'-butylidenebis (3-methyl-6-t-butylphenol) and the like are useful. The antioxidant is used in the range of about 2 to 100 ppm with respect to the polyvinyl alcohol resin.

  In the polyvinyl alcohol-based resin, one or more commonly used plasticizers such as glycerin, diglycerin, triglycerin, ethylene glycol, triethylene glycol, polyethylene glycol, etc. are added to the polyvinyl alcohol-based resin as necessary. On the other hand, it can be contained in an amount of 30% by weight or less, preferably 3 to 25% by weight, more preferably 5 to 20% by weight. When the content of the plasticizer exceeds 30% by weight, the film strength is inferior, which is not preferable.

  More preferably, in order to improve the peelability of the film from the film forming apparatus, one or more of the various release agents are 5% by weight or less, preferably 0.001 to 3% by weight based on the polyvinyl alcohol resin. %, More preferably 0.001 to 2% by weight. If the release agent exceeds 5% by weight, film surface appearance defects or film blocking may occur, which is not preferable.

  Thus, in the present invention, a polyvinyl alcohol-based resin aqueous solution is prepared using the polyvinyl alcohol-based resin composition, and the aqueous solution is cast on a drum-type roll to form a film and then dried to form a polyvinyl alcohol-based film. To manufacture.

In preparing the polyvinyl alcohol resin solution, water alone or water and dimethyl sulfoxide (DMSO), N-methylpyrrolidone, glycerin, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylol Mixtures with polyhydric alcohols such as propane and amines such as ethylenediamine and diethylenetriamine are used.
The concentration of the polyvinyl alcohol resin in the aqueous polyvinyl alcohol resin solution is practically 5 to 50% by weight.

Next, the aqueous polyvinyl alcohol resin solution is cast from a T-type slit die onto a drum-type roll to form a film.
The material of such a drum-type roll is not particularly limited, but usually stainless steel is preferably used, and the surface of the roll is preferably metal-plated to prevent damage. As the type of metal plating, for example, chrome plating, nickel plating, galvanization, etc. are suitably used, which can be used alone or in combination of two or more kinds of multilayers, particularly the ease of surface smoothing and its durability. From this point, the outermost surface is preferably chrome plating. The surface of the drum is desirably kept smooth, and the surface roughness is desirably 3S or less, particularly 0.5S or less.

The temperature of the drum-type roll during film formation is practically 50 to 120 ° C., and the film is peeled off from the roll when the water content of the film reaches about 5 to 30% by weight. Subsequently, drying is performed using a single or multi-stage roll, and preferably alternate drying of the front and back surfaces of the film is continued using a multi-stage roll. After drying, an unstretched polyvinyl alcohol film is formed.
If necessary, after drying, heat treatment and humidity control are performed, and the core tube is wound into a roll state to obtain the polyvinyl alcohol film of the present invention.

  Steam, a heating medium, hot water, an electric heater, or the like is employed as the drum or roll heating means. Also, it is possible to install an auxiliary device for blowing warm air, cold air, or the like, or sucking air or steam around the device. The width of the film is arbitrary, but in the case of a wide film, which has recently been strongly demanded by the market, 2 m or more, preferably 2.5 m or more, particularly 3 m or more is useful.

  In the present invention, it is important that the length of the polyvinyl alcohol film is 2000 m to 15000 m. The length of the film is preferably from 4000 m to 15000 m, and the feature of the present invention is particularly prominent in the production of a long film of 6000 m to 15000 m.

  The film thickness of the polyvinyl alcohol film is not particularly limited, but is preferably 30 to 100 μm, more preferably 30 to 70 μm, and particularly preferably 40 to 60 μm. If the film thickness is less than 30 μm, stretching is difficult, while if it exceeds 100 μm, the film thickness accuracy is lowered, which is not preferable. Moreover, when using for optical uses, such as the polarizing film mentioned later, the film thickness of a polyvinyl-alcohol-type film has a preferable viewing angle of 70 micrometers or less at the point from which a viewing angle is wider and a favorable visibility is obtained.

The polyvinyl alcohol film obtained above is useful as an original film for optical use, particularly for polarizing film.
Hereinafter, a method for producing a polarizing film will be described.

  As a method for producing a polarizing film, such a polyvinyl alcohol film is stretched and immersed in an iodine or dichroic dye solution for dyeing, or stretching and dyeing are performed simultaneously, or dyed with iodine or a dichroic dye. A method of treating with a boron compound after stretching may be mentioned. There is also a method of drawing in a solution of a boron compound after dyeing, etc., which can be appropriately selected and used.

  In the stretching and dyeing of the polyvinyl alcohol film (unstretched film) and the boron compound treatment, the stretching and dyeing and the boron compound treatment may be performed separately or simultaneously. In the present invention, the dyeing step and the boron compound treatment are performed. It is desirable to carry out uniaxial stretching during at least one of the steps.

  The stretching is desirably performed in a uniaxial direction by 3 to 10 times, preferably 3.5 to 6 times. At this time, the film may be slightly stretched in the direction perpendicular to the above (stretching to prevent shrinkage in the width direction or more). The temperature condition during stretching is desirably selected from 40 to 170 ° C. Furthermore, the draw ratio may be finally set in the above range, and the drawing operation may be performed not only in one stage but also in any stage of the manufacturing process.

The film is dyed by bringing the film into contact with a liquid containing iodine or a dichroic dye.
Usually, an aqueous solution of iodine-potassium iodide is used, the concentration of iodine is 0.1 to 20 g / l, the concentration of potassium iodide is 10 to 70 g / l, and the weight ratio of potassium iodide / iodine is 10 to 100. Is appropriate. The dyeing time is practically about 30 to 500 seconds. The temperature of the treatment bath is preferably 5 to 60 ° C. In addition to the water solvent, a small amount of an organic solvent compatible with water may be used.
Any means such as dipping, coating, spraying, etc. can be applied as the contact means.

The dyed film is then treated with a boron compound. As the boron compound, boric acid and borax are practical. The boron compound is used in the form of an aqueous solution or a water-organic solvent mixture at a concentration of about 0.3 to 2 mol / l, and it is practically desirable for a small amount of potassium iodide to coexist in the solution.
The treatment method is preferably an immersion method, but of course, a coating method and a spraying method can also be implemented. The temperature during the treatment is preferably about 40 to 70 ° C., and the treatment time is preferably about 2 to 20 minutes. If necessary, the stretching operation may be performed during the treatment.

The polarizing film thus obtained can also be used by laminating and bonding an optically isotropic polymer film or sheet as a protective film on one or both sides thereof.
Examples of the protective film include films or sheets of cellulose triacetate, cellulose diacetate, polycarbonate, polymethyl methacrylate, polystyrene, polyethersulfone, polyarylene ester, poly-4-methylpentene, polyphenylene oxide, and the like.

  In addition, instead of the protective film, such a polarizing film can be laminated by applying a curable resin such as a urethane resin, an acrylic resin, or a urea resin on one or both sides instead of the protective film.

  Such a polarizing film (or a laminate of a protective film or a curable resin on at least one surface thereof) has a transparent pressure-sensitive adhesive layer formed on a surface of the polarizing film as required by a generally known method. In some cases, it may be put to practical use. Examples of the pressure-sensitive adhesive layer include acrylic esters such as butyl acrylate, ethyl acrylate, methyl acrylate, 2-ethylhexyl acrylate, and α-monoolefin carboxylic acids such as acrylic acid, maleic acid, itaconic acid, methacrylic acid. Copolymers with acids, crotonic acid, etc. (including those added with vinyl monomers such as acrylonitrile, vinyl acetate and styrene) do not interfere with the polarization characteristics of the polarizing film. However, the present invention is not particularly limited to this, and any pressure-sensitive adhesive having transparency can be used. For example, polyvinyl ether or rubber may be used.

  Further, various functional layers can be provided on one side of the polarizing plate (the one provided with the pressure-sensitive adhesive) (the side where the pressure-sensitive adhesive is not provided). Antiglare layer, hard coat layer, antireflection layer, half reflection layer, reflection layer, phosphorescent layer, diffusion layer, electroluminescence layer, viewing angle expansion layer, brightness enhancement layer, etc. For example, an antiglare layer and an antireflection layer, a phosphorescent layer and a reflective layer, a phosphorescent layer and a half reflection layer, a phosphorescent layer and a light diffusion layer, a phosphorescent layer and an electroluminescence layer, a half reflection layer and an electroluminescence layer, etc. Combinations are listed. However, it is not limited to these.

Hereinafter, the present invention will be specifically described with reference to examples.
In the examples, “parts” and “%” are based on weight unless otherwise specified.

Weight average molecular weight:
Measurement was performed by the GPC-LALLS method under the following conditions.

1) GPC
Apparatus: Waters type 244 gel permeation chromatograph column: Tosoh TSK-gel-GMPW _XL (inner diameter 8 mm, length 30 cm, 2 pieces)
Solvent: 0.1 M Tris buffer (pH 7.9)
Flow rate: 0.5 ml / min
Temperature: 23 ° C
Sample concentration: 0.040%
Filtration: 0.45 μm Mysori disk W-25-5 made by Tosoh
Injection volume: 0.2ml
Detection sensitivity (differential refractive index detector): 4 times

2) LALLS
Apparatus: Chromatrix KMX-6 type low angle laser light scattering photometer Temperature: 23 ° C
Wavelength: 633nm
Second virial coefficient × concentration: 0 mol / g
Refractive index density change (dn / dc): 0.159 ml / g
Filter: MILLIPORE 0.45 μm filter HAWP01300
Gain: 800mV

[Example 1]
Using a polyvinyl alcohol resin having a weight average molecular weight of 130000 and a saponification degree of 99.8 mol% determined by the GPC-LALLS method, a polyvinyl alcohol resin aqueous solution having a resin concentration of 33% comprising the following component composition was prepared.
・ Water 191 parts ・ Polyvinyl alcohol resin 100 parts ・ Polyoxyethylene dodecyl ether (a) 0.040 parts (10 to 30 centering on polyoxyethylene condensation degree 21)
・ Polyoxyethylene dodecylamine (b) 0.180 parts (3-13 centering on polyoxyethylene condensation degree 7)
-Lauric acid diethanolamide (b) 0.040 parts (mixture with adduct (1: 2 mol type))
・ 12 parts of glycerin The aqueous solution is cast on a drum-type roll heated to 90 ° C from a T-shaped slit die (a stainless steel base material is nickel-plated and further chrome-plated to a mirror finish of 0.5S surface roughness) Filmed, dried to a moisture content of 10%, subsequently heat treated at 120 ° C., and finally conditioned, to a polyvinyl alcohol film having a moisture content of 4%, an average thickness of 75 μm, and a film width of 2 m. The film roll was obtained by winding it around the core tube.
The following measurement was performed on the obtained polyvinyl alcohol film. The results are shown in Table 1.

(Optical streak)
Cut the resulting polyvinyl alcohol film to a total width of 500 mm, place the polyvinyl alcohol film between the white screen and the projector in a dark room, count the number of streaky shadows on the screen, and Evaluated.

(Optical color unevenness)
A light box with a surface illuminance of 14,000 lux after sandwiching a polyvinyl alcohol film between two polarizing plates in a crossed Nicol state (single transmittance: 43.5%, polarization degree: 99.9%) at an angle of 45 ° Was used to observe optical color unevenness in the transmission mode and evaluated according to the following criteria.
A: Nothing is visible and uniform B: Discontinuous shading can be confirmed C: Only streaky shading can be confirmed D: Streaky shading and discontinuous shading can be confirmed

(Blocking property)
100 sheets of polyvinyl alcohol-based film were overlaid, applied with a load of 0.05 kg / cm ² and left in an atmosphere of 65% RH and 25 ° C. for 1 week, and the blocking state of the film was observed and evaluated according to the following criteria. .
Pull out 1/4, 2/4, and 3/4 points from the outermost surface of 100 stacked films, cut out a test piece with a width of 25 mm and a length of 180 mm, and peel the adhered film into a T-shape. Then, the adhesion was measured. For the measurement, an autograph (“AGS-H” manufactured by Shimadzu Corporation) is used, the test speed is 200 mm / min, each three points are measured, and the average value is calculated.

  Next, the polyvinyl alcohol film was unwound and swollen in a water washing tank (24 ° C.), then 1.3 times in a iodine tank (20 ° C., iodine concentration 0.05 g / l), and a boric acid tank (50 ° C. , Uniaxial stretching of 1.7 times at an iodine concentration of 0.0012 g / l, boric acid concentration of 47 g / l), followed by uniaxial stretching and total uniaxial stretching of 6 times, followed by cellulose triacetate film (thickness) 80 μm) was adhered with a polyvinyl alcohol adhesive to obtain a polarizing film.

The obtained polarizing film is sandwiched between two polarizing plates in a crossed Nicol state (single transmittance 43.5%, polarization degree 99.9%) at an angle of 45 °, and then a light box having a surface illuminance of 14,000 lux. Was used to observe optical color unevenness in the transmission mode and evaluated according to the following criteria.
○ ・ ・ ・ No color unevenness × ・ ・ ・ Color unevenness

[Example 2]
Except for preparing a polyvinyl alcohol resin aqueous solution having a resin concentration of 30% and comprising the following component composition, using a polyvinyl alcohol resin having a weight average molecular weight of 170000 and a saponification degree of 99.8 mol% determined by the GPC-LALLS method. This was carried out in the same manner as in Example 1, and a film roll was obtained by winding a polyvinyl alcohol film having an average thickness of 70 μm and a film width of 2 m on a core tube without winding 7000 m. The results are shown in Table 1.
・ Water 221 parts ・ Polyvinyl alcohol-based resin 100 parts ・ Polyoxyethylene dodecyl ether (a) 0.040 part (10 to 30 centering on polyoxyethylene condensation degree 21)
・ Polyoxyethylene dodecylamine (b) 0.180 parts (3-13 centering on polyoxyethylene condensation degree 7)
-Lauric acid diethanolamide (b) 0.040 parts (mixture with adduct (1: 2 mol type))
・ Stearic acid amide 0.008 parts ・ Glycerin 12 parts

[Example 3]
A polyvinyl alcohol film having an average thickness of 60 μm and a film width of 3 m is wound up on a core tube without wrinkles at 10000 m, except that the composition of the aqueous polyvinyl alcohol resin solution in Example 2 is changed as follows. Got. The results are shown in Table 1.
Water 221 parts Polyvinyl alcohol-based resin 100 parts Palm oil reduced alcohol ethylene oxide adduct (a) 0.050 parts (10-30 with a polyoxyethylene condensation degree of 21 as the center)
・ Polyoxyethylene dodecylamine (b) 0.100 parts (3-13 centering on polyoxyethylene condensation degree 7)
・ 0.040 parts of lauric acid diethanolamide (b) (mixture with adduct (1: 1 mol type))
・ Stearic acid amide 0.008 parts ・ Glycerin 12 parts

[Example 4]
Except that the composition of the aqueous polyvinyl alcohol resin solution of Example 2 was changed to the following, the same procedure as in Example 1 was carried out. Got. The results are shown in Table 1.
・ Water 221 parts ・ Polyvinyl alcohol-based resin 100 parts ・ Polyoxyethylene dodecyl ether (a) 0.040 part (10 to 30 centering on polyoxyethylene condensation degree 21)
・ Polyoxyethylene dodecylamine (b) 0.200 parts (3-13 centering on polyoxyethylene condensation degree 7)
・ Stearic acid amide 0.010 parts ・ Glycerin 12 parts

[Example 5]
Using a polyvinyl alcohol resin having a weight average molecular weight of 24,000 and a saponification degree of 99.8 mol% determined by the GPC-LALLS method, a polyvinyl alcohol resin aqueous solution having a resin concentration of 25% composed of the following component compositions was prepared.
Water 288 parts Polyvinyl alcohol-based resin 100 parts Palm oil reduced alcohol ethylene oxide adduct (a) 0.050 parts (10 to 30 centering on polyoxyethylene condensation degree 21)
-Polyoxyethylene dodecylamine (b) 0.09 part (3-13 centering on polyoxyethylene condensation degree 7)
-Lauric acid diethanolamide (b) 0.040 parts (mixture with adduct (1: 2 mol type))
・ Stearic acid amide 0.010 part ・ 4,4′-butylidenebis (3-methyl-6 0.001 part-t-butylphenol)
・ 12 parts of glycerin The aqueous solution is cast on a drum-type roll heated to 90 ° C. from a T-type slit die (a stainless steel base material is nickel-plated and further chrome-plated to give a surface finish of 0.3S). Filmed, dried to a moisture content of 10%, subsequently heat treated at 120 ° C., and finally conditioned, to a polyvinyl alcohol film having a moisture content of 4%, an average thickness of 75 μm, and a film width of 3 m. The film roll was obtained by winding it around the core tube. Hereinafter, the same measurement as in Example 1 was performed. The results are shown in Table 1.

[Example 6]
In Example 5, a film roll was obtained in the same manner except that the average film thickness of the film was 50 μm, and a polyvinyl alcohol film having a film width of 3 m was wound around a core tube without wrinkles of 12000 m.
Hereinafter, the same measurement as in Example 1 was performed. The results are shown in Table 1.

[Comparative Example 1]
A polyvinyl alcohol film was obtained in the same manner as in Example 1 except that the composition of the aqueous polyvinyl alcohol resin solution of Example 1 was changed to the following. It was 4000 m that was wound on a film roll without winding wrinkles. Experiments were conducted according to Example 1 using the obtained polyvinyl alcohol film. The results are shown in Table 1.
・ Water 191 parts ・ Polyvinyl alcohol resin 100 parts ・ Polyoxyethylene dodecylamine (b) 0.210 parts (3 to 13 centering on polyoxyethylene condensation degree 7)
-Lauric acid diethanolamide (b) 0.050 part (mixture with adduct (1: 2 mol type))
・ Glycerin 12 parts

[Comparative Example 2]
A polyvinyl alcohol film was obtained in the same manner as in Example 1 except that the composition of the aqueous polyvinyl alcohol resin solution of Example 1 was changed to the following. It was 4000 m that was wound on a film roll without winding wrinkles. Experiments were conducted according to Example 1 using the obtained polyvinyl alcohol film. The results are shown in Table 1.
・ Water 191 parts ・ Polyvinyl alcohol resin 100 parts ・ Polyoxyethylene dodecyl ether (a) 0.130 parts (10 to 30 centering on polyoxyethylene condensation degree 21)
-Lauric acid diethanolamide (b) 0.130 parts (mixture with adduct (1: 2 mol type))
・ Glycerin 12 parts

[Comparative Example 3]
A polyvinyl alcohol film was obtained in the same manner as in Example 1 except that the composition of the aqueous polyvinyl alcohol resin solution of Example 1 was changed to the following. It was 4000 m that was wound on a film roll without winding wrinkles. Experiments were conducted according to Example 1 using the obtained polyvinyl alcohol film. The results are shown in Table 1.
・ Water 191 parts ・ Polyvinyl alcohol resin 100 parts ・ Polyoxyethylene dodecyl ether (a) 0.050 parts (10 to 30 centering on the degree of condensation of polyoxyethylene 21)
・ Polyoxyethylene dodecylamine (b) 0.210 parts (3-13 centering on polyoxyethylene condensation degree 7)
・ Glycerin 12 parts

[Comparative Example 4]
In Example 5, a film roll was obtained in the same manner except that the average film thickness was 20 μm, and a polyvinyl alcohol film having a film width of 3 m was wound on a core tube with no wrinkles of 6000 m. An attempt was made to produce a polarizing film using the obtained polyvinyl alcohol film in the same manner as in Example 1. However, the film was cut frequently, and a polarizing film could not be obtained.

※延伸時に切断多発のため、偏光フイルムが得られなかった。

* Polarized film could not be obtained due to frequent cutting during stretching.

From the results of Table 1 above, the polyvinyl alcohol films of the present invention obtained in Examples 1 to 6 are excellent in optical streaks, optical color unevenness, and blocking resistance. The polyvinyl alcohol film of Comparative Examples 1 to 4 was not excellent in target color unevenness, but none of the above performances were satisfied.
Furthermore, in the polarizing film obtained from the polyvinyl alcohol film obtained in Examples 1 to 6 and Comparative Examples 1 to 3, an acrylic pressure-sensitive adhesive layer (25 μm thickness) was provided on one side, and a liquid crystal display element (13. 3 inches, TFT type, XGA) were bonded to crossed Nicols at an absorption axis angle of 45 degrees, and the visibility of the liquid crystal display was observed in the left-right direction, and the visibility was evaluated. Example 1, Example 5 In Comparative Examples 1 to 3, the visibility was good up to 40 degrees in the left-right direction and the display was reversed at 42 degrees, whereas in Examples 2 and 4, the visibility was good up to 44 degrees in the left-right direction. The display was reversed at 46 degrees, and in Examples 3 and 6, the visibility was good up to 48 degrees in the left and right directions, and the display was reversed at 50 degrees. That is, when the film thickness of the polyvinyl alcohol film was 30 to 70 μm, a polarizing film with better visibility was obtained.

  The polyvinyl alcohol film of the present invention is excellent in film thickness uniformity, has excellent optical characteristics such as no optical streaks, and exhibits an effect of excellent blocking resistance. , Electronic clocks, word processors, personal computers, monitors, liquid crystal televisions, personal digital assistants, liquid crystal display devices such as cars and machinery instruments, sunglasses, anti-glare glasses, stereoscopic glasses, reflection for display elements (CRT, LCD, etc.) It is very useful as an original film of a polarizing film used for a reduction layer, medical equipment, building materials, toys and the like. Of course, it is also useful for applications such as packaging film, peelable film, agricultural film, and building material film.

Claims (15)

  A polyvinyl alcohol film comprising a polyvinyl alcohol resin, an ether type nonionic surfactant (a) and at least two types of nitrogen-containing nonionic surfactant (b).   2. The polyvinyl alcohol film according to claim 1, wherein the ether type nonionic surfactant (a) is a polyoxyethylene alkyl ether.   The polyvinyl alcohol film according to claim 2, wherein the polyoxyethylene alkyl ether has an alkyl group having 6 to 22 carbon atoms and a polyoxyethylene unit condensation degree of 1 to 70.   The polyvinyl alcohol film according to claim 1, wherein the nitrogen-containing nonionic surfactant (b) is selected from higher fatty acid alkanolamides, higher fatty acid amides and polyoxyethylene alkylamines.   5. The polyvinyl alcohol film according to claim 4, wherein the higher fatty acid alkanolamide is alkyldiethanolamide.   The higher fatty acid alkanolamide, the higher fatty acid amide and the polyoxyethylene alkylamine have an alkyl group having 6 to 22 carbon atoms, and the polyoxyethylene alkylamine has a polyoxyethylene unit condensation degree of 1 to 30. The polyvinyl alcohol film according to claim 4.   The content of the ether type nonionic surfactant (a) and the nitrogen-containing type nonionic surfactant (b) is 5 to 1500 ppm and 5 to 5000 ppm, respectively, with respect to the polyvinyl alcohol resin. The polyvinyl alcohol film according to any one of claims 1 to 6.   The weight ratio (a: b) of the content of the ether type nonionic surfactant (a) and the nitrogen-containing type nonionic surfactant (b) is from 1: 1 to 20. The polyvinyl alcohol-type film in any one of -7.   Furthermore, an antioxidant is contained, The polyvinyl alcohol-type film in any one of Claims 1-8 characterized by the above-mentioned.   The polyvinyl alcohol film according to claim 1, wherein the film has a thickness of 30 to 70 μm.   The polyvinyl alcohol film according to any one of claims 1 to 10, wherein the polyvinyl alcohol resin has a weight average molecular weight of 120,000 to 300,000.   The polyvinyl alcohol film according to any one of claims 1 to 11, wherein the width of the film is 2 m or more.   The length of a film is 4000 m or more, The polyvinyl alcohol-type film in any one of Claims 1-12 characterized by the above-mentioned.   The polyvinyl alcohol film according to any one of claims 1 to 13, which is used as an original film of a polarizing film. A polarizing film produced using the polyvinyl alcohol film for polarizing film according to claim 14.