JP4744868B2 - Polyvinyl alcohol film for polarizing film and use thereof - Google Patents

Description

The present invention is uniform in optical performance without defects such as film thickness unevenness 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 block each other. Polyvinyl alcohol film for a polarizing film useful as an original film for obtaining a polarizing film having an excellent optical appearance with no obstacles such as optical color unevenness, etc. It is about film.

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, for example, 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 detracts from the appearance of the polarizing 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 problems, polyvinyl alcohol resin, sulfate ester type anionic surfactant (a), ether type nonionic surfactant (b) and nitrogen type nonionic surfactant (c) Ri greens contain, and nitrogen-containing type nonionic surface active agent as the (c), higher fatty acid alkanolamides and / or an alkyl group having 6 to 22 carbon atoms in the alkyl group polarizing films containing higher fatty acid amide having a carbon number of 6 to 22 of the obtained from Na Ru polarizing film for polyvinyl alcohol film and the film is found to satisfy the objectives, the present invention has been completed.

The polyvinyl alcohol film for polarizing film of the present invention comprises a polyvinyl alcohol resin, a sulfate ester type anionic surfactant (a), an ether type nonionic surfactant (b) and a specific nitrogen-containing nonionic surfactant. because comprising agent (c), has no excellent optical characteristics such as optical stripes or optical color unevenness, and can be highly effective in blocking resistance, especially Niso Rekara It is useful for the obtained polarizing film.

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 resin contains a sulfate ester type anionic surfactant (a), an ether type nonionic surfactant (b), and a nitrogen-containing nonionic surfactant (c). In other words, the combination of such specific surfactants is included.

As the sulfate ester type anionic surfactant (a), typically,
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
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 20, preferably 1 to 10.

Specific examples of the alkyl group include hexyl, heptyl, octyl, nonyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, eicosyl, oleyl and the like.
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 sodium or alkali metal salts such as potassium salts thereof, alkaline earth metal salts such as calcium salts, and organic amine salts such as ammonium salts. Sodium dodecyl sulfate, sodium octadecyl sulfate and the like are preferably used.

  Specific examples of the polyoxyethylene alkyl ether sulfate include, for example, sodium polyoxyethylene hexyl ether sulfate, sodium polyoxyethylene heptyl ether sulfate, sodium polyoxyethylene octyl ether sulfate, sodium polyoxyethylene nonyl ether sulfate, polyoxyethylene Sodium decyl ether sulfate, sodium polyoxyethylene dodecyl ether sulfate, sodium polyoxyethylene tetradecyl ether sulfate, sodium polyoxyethylene hexadecyl ether sulfate, sodium polyoxyethylene octadecyl ether sulfate, sodium polyoxyethylene eicosyl ether sulfate, or these And organic amine salts such as alkali metal salts and ammonium salts of potassium salts. Polyoxyethylene dodecyl ether sulfate is used for.

  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 Alkali metal salts such as et of potassium salts, and organic amine salts such as ammonium salts, the use of polyoxyethylene nonylphenyl ether sulfate is preferable.

Examples of the higher fatty acid alkanolamide sulfate include caproic acid ethanolamide sodium sulfate, caprylic acid ethanolamide sodium sulfate, capric acid ethanolamide sodium sulfate, lauric acid ethanolamide sodium sulfate, palmitic acid ethanolamide sodium sulfate, stearic acid ethanolamide Sodium sulfate, oleic acid ethanolamide or potassium salts thereof, and in addition to these ethanolamides, propanolamide and butanolamide can be mentioned.
In addition, sulfate ester salts such as sulfated oil, higher alcohol ethoxy sulfate, and monoglyculate can also be used.

  In addition, fatty acid soaps, N-acylamino acids and salts thereof, polyoxyethylene alkyl ester carboxylates, carboxylate types such as acylated peptides, alkylbenzene sulfonates, alkyl naphthalene sulfonic acids, and the like without departing from the spirit of the present invention Salt, naphthalene sulfonic acid salt formalin polycondensate, melamine sulfonic acid salt formalin condensate, dialkyl sulfosuccinic acid ester salt, sulfosuccinic acid alkyl disalt, polyoxyethylene alkyl sulfosuccinic acid disalt, alkyl sulfoacetate, α-olefin Sulfonates such as sulfonate, N-acylmethyl taurate, dimethyl-5-sulfoisophthalate sodium salt, polyoxyethylene alkyl ether phosphate, polyoxyethylene alkyl phenyl ether phosphate, alkyl chloride It may be used together other anionic surfactants of the phosphoric acid ester salt type such as salt.

As the ether type nonionic surfactant (b), 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
The polyoxyethylene alkyl phenyl ether shown by these is mentioned.
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 20, preferably 2 to 10.

  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 Examples thereof include oxyethylene tetradecyl ether, polyoxyethylene hexadecyl ether, polyoxyethylene octadecyl ether, polyoxyethylene oleyl ether, and polyoxyethylene eicosyl ether. In particular, use of polyoxyethylene dodecyl ether, polyoxyethylene octadecyl ether, or the like is advantageous.

  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 thereof include oxyethylene dodecyl phenyl ether, polyoxyethylene tetradecyl phenyl ether, polyoxyethylene hexadecyl phenyl ether, polyoxyethylene octadecyl phenyl ether, and polyoxyethylene eicosyl phenyl ether. In particular, the use of polyoxyethylene nonyl phenyl ether is desirable.

In addition, ethylene oxide derivatives of alkylphenol formalin condensates, polyoxyethylene polyoxypropylene block polymers, and the like can also be used.
Further, ether ester type nonionic surfactants such as polyoxyethylene glycerin fatty acid ester, polyoxyethylene castor oil and hardened castor oil, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester and the like are 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 agent as a (c),
One general formula ^RCONH-R '-OH or RCON- ^(R' _{-OH) 2}
A higher fatty acid mono- or dialkanolamide represented by
General formula RCONH ₂
Are used, respectively.
Here, R is an alkyl group or an alkenyl group, and the carbon number thereof is 6-22, preferably 8-18. 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. R ^′ is any of —C ₂ H ₄ —, —C ₃ H ₆ —, and —C ₄ H ₈ —.
Also,
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
And polyoxyethylene alkylamines, polyoxyethylene higher fatty acid amides, and amine oxides.
In the above general formula, R is an alkyl group, and the same alkyl group as described above can be used. x and y represent an integer of 1 to 30, preferably 3 to 15.

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. Among these, alkyldiethanolamide is preferable, and specifically, lauric acid diethanolamide and palm oil fatty acid diethanolamide are preferably used. In particular, the diethanolamide and diethanolamine [NH- (C ₂ The use of a mixture of adducts with (H ₄ OH) ₂ ] (1: 2 molar form) is advantageous in terms of water solubility.

  Specific examples of higher fatty acid amides include, for example, caproic acid amide, caprylic acid amide, capric acid amide, lauric acid amide, palmitic acid amide, stearic acid amide, oleic acid amide, etc., among them palmitic acid amide, stearic acid Amides 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 eicosylamine, and among them, polyoxyethylene dodecylamine is advantageously used.
Specific examples of the polyoxyethylene higher fatty acid amide include, for example, polyoxyethylene caproic acid amide, polyoxyethylene caprylic acid amide, polyoxyethylene capric acid amide, polyoxyethylene lauric acid amide, polyoxyethylene myristic acid amide, Examples thereof include oxyethylene palmitic acid amide, polyoxyethylene stearic acid amide, polyoxyethylene oleic acid amide, etc. Among them, polyoxyethylene lauric acid amide and polyoxyethylene stearic acid amide are advantageously used.
Specific examples of the amine oxide include, for example, dimethyl lauryl amine oxide, dimethyl stearyl oxide, dihydroxyethyl lauryl amine oxide, and the like. Among them, dimethyl lauryl amine oxide is advantageously used.

  The surfactants may be used in combination of at least one or more of them, and there may be used two or more of them. The addition amount is not particularly limited, but the contents of the sulfate ester type anionic surfactant (a), the ether type nonionic surfactant (b) and the nitrogen-containing type nonionic surfactant (c) are: 5 to 5000 ppm (preferably 50 to 3000 ppm, particularly preferably 100 to 2000 ppm) of the sulfate ester type anionic surfactant (a) and the ether type nonionic surfactant (b) with respect to the polyvinyl alcohol resin. From 50 to 1000 ppm (preferably 100 to 800 ppm, particularly preferably 200 to 700 ppm) and nitrogen-containing nonionic surfactant (c) from 50 to 5000 ppm (preferably 200 to 3000 ppm, particularly preferably 300 to 2000 ppm). It is practical to choose.

If the content of the sulfate ester type anionic surfactant (a) is less than 5 ppm, optical color unevenness may occur. If it exceeds 5000 ppm, corrosion of the production apparatus may occur, which is not preferable.
Furthermore, if the content of the ether type nonionic surfactant (b) is less than 50 ppm, optical streaks may occur, and if it exceeds 1000 ppm, the transmittance tends to be significantly lowered, which is not preferable.
Further, when the content of the nitrogen-containing nonionic surfactant (c) is less than 50 ppm, optical streaks and long run properties may be deteriorated, and when long winding is performed, wrinkles may be caused. Is not preferable. On the other hand, if it exceeds 5000 ppm, there is a risk of blocking, which is not preferable.

  And the weight ratio (a: b: c) of the content of the sulfate ester salt type anionic surfactant (a), the ether type nonionic surfactant (b) and the nitrogen-containing nonionic surfactant (c) Is preferably 100: 20 to 500: 100 to 1000 from the viewpoint that optical streaks and optical color unevenness are further eliminated, and is advantageous from the viewpoint that a film with good transparency can be stably produced over a long period of time. If the ratio of the ether type nonionic surfactant (b) is less than 20 with respect to the sulfate ester salt type anionic surfactant (a) 100, there is a risk of optical streaks. It is not preferable because it may cause a decrease. If the content ratio of the nitrogen-containing nonionic surfactant (c) is less than 100 with respect to the sulfate ester salt-type anionic surfactant (a) 100, there is a risk of optical streaks and long-running properties worsening. In addition, when performing long winding, there is a risk of causing wrinkles, and exceeding 1000 is not preferable because it may cause blocking and the like.

  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 may be deteriorated, 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 polyvinyl alcohol resin solution is practically 5 to 50% by weight.

Next, the 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 preferably used, and can be used alone or in combination of two or more kinds of multilayers, and in particular 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 preferably 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, preferably alternating drying of the front and back surfaces of the film is continued using a multi-stage roll, and 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 more 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:
The measurement was carried out under the following conditions by the GPC-LALLS method.

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-based resin 100 parts ・ Sodium dodecyl sulfate (a) 0.02 parts ・ Polyoxyethylene dodecyl ether (b) 0.04 parts (1 to 10 centering on polyoxyethylene condensation degree 4) )
・ 0.07 part of lauric acid diethanolamide (c) (mixture with adduct (1: 2 mol type))
・ 12.0 parts of glycerin A drum-type roll heated at 90 ° C. from a T-type slit die (nickel-plated stainless steel and further chrome-plated, mirror-finished to a surface roughness of 0.5S) The film was cast, dried to a moisture content of 10%, subsequently heat treated at 120 ° C., and finally conditioned to a moisture content of 4%, an average thickness of 75 μm, and a polyvinyl alcohol film having a film width of 2 m of 6000 m. A film roll was obtained on the core tube without winding wrinkles.
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 ・ Sodium dodecyl sulfate (a) 0.005 part ・ Polyoxyethylene dodecyl ether sodium sulfate (a) 0.050 part (1 centering on polyoxyethylene condensation degree 1) -10)
-Polyoxyethylene dodecyl ether (b) 0.040 part (1-10 centering on polyoxyethylene condensation degree 4)
・ 0.100 part of lauric acid diethanolamide (c) (mixture with adduct (1: 2 mol type))
・ 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 ・ Sodium dodecyl sulfate (a) 0.005 part ・ Polyoxyethylene dodecyl ether sodium sulfate (a) 0.050 part (1 centering on polyoxyethylene condensation degree 1) -10)
-Polyoxyethylene dodecyl ether (b) 0.040 part (1-10 centering on polyoxyethylene condensation degree 4)
・ 0.100 part of lauric acid diethanolamide (c) (mixture with adduct (1: 2 mol type))
・ Stearic acid amide (c) 0.001 part ・ Glycerin 12 parts

[Example 4]
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 ・ Sodium dodecyl sulfate (a) 0.005 part ・ Sodium polyoxyethylene dodecyl ether sulfate (a) 0.050 part (1 centering on polyoxyethylene condensation degree 1) -10)
-Polyoxyethylene dodecyl ether (b) 0.040 part (1-10 centering on polyoxyethylene condensation degree 4)
・ 0.100 part of lauric acid diethanolamide (c) (mixture with adduct (1: 2 mol type))
・ Stearic acid amide (c) 0.001 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 without rolling up to 7000 m A film roll was obtained on the core tube.
Hereinafter, the same measurement as in Example 1 was performed. The results are shown in Table 1.

[Example 5]
In Example 4, a film roll was obtained in the same manner except that the average film thickness was 50 μm, and a polyvinyl alcohol film having a film width of 3 m was wound on 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-based resin 100 parts ・ Polyoxyethylene dodecyl ether (b) 0.05 part (1-10 centering on polyoxyethylene condensation degree 4)
・ 0.08 parts of lauric acid diethanolamide (c) (mixture with adduct (1: 2 mol type))
・ Glycerin 12.0 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. An experiment was 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 Sodium dodecyl sulfate (a) 0.03 parts Lauric acid diethanolamide (c) 0.10 parts (mixture with adduct (1: 2 mol type))
・ Glycerin 12.0 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. An experiment was 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 ・ Sodium dodecyl sulfate (a) 0.04 parts ・ Polyoxyethylene dodecyl ether (b) 0.09 parts (1 to 10 centering on polyoxyethylene condensation degree 4) )
・ Glycerin 12.0 parts

[Comparative Example 4]
In Example 5, a film roll was obtained by winding a polyvinyl alcohol film having a film width of 3 m on a core tube without wrinkles of 7000 m, except that the average film thickness was 20 μm. 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 5 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 5 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 with 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. 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 Example 2, the visibility was good up to 44 degrees in the left-right direction. Display inversion occurred at a degree, and in Examples 3 and 5, the visibility was good up to 48 degrees in the left-right direction, 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 for polarizing film of the present invention is excellent in film thickness uniformity, has excellent optical properties without optical streaks, and exhibits an excellent blocking resistance effect. Electronic desk calculators, electronic clocks, word processors, personal computers, monitors, liquid crystal televisions, personal digital assistants, liquid crystal display devices such as automobile and machinery instruments, sunglasses, anti-glare glasses, stereoscopic glasses, display elements (CRT, LCD, etc.) It is very useful as an original film of a polarizing film used in a reflection reducing 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)

Polyvinyl alcohol, sulfuric ester salt type anionic surfactant (a), Ri greens contain ether type nonionic surfactant (b) and nitrogen-containing type nonionic surface active agent (c), and containing nitrogen-type nonionic surfactant (c), and wherein Rukoto such contain higher fatty acid amide having a carbon number of 6 to 22 of the higher fatty acid alkanolamides and / or an alkyl group having 6 to 22 carbon atoms in the alkyl group Polyvinyl alcohol film for polarizing film. The polyvinyl alcohol film for polarizing film according to claim 1, wherein the sulfate ester type anionic surfactant (a) is an alkyl sulfate ester salt and / or a polyoxyethylene alkyl ether sulfate. The polyvinyl alcohol film for polarizing film according to claim 2, wherein the alkyl group of the alkyl sulfate ester salt has 6 to 22 carbon atoms. The polyvinyl alcohol film for polarizing film according to claim 2, wherein the polyoxyethylene alkyl ether sulfate has an alkyl group having 6 to 22 carbon atoms and a polyoxyethylene unit condensation degree of 1 to 20. 2. The polyvinyl alcohol film for polarizing film according to claim 1, wherein the ether type nonionic surfactant (b) is polyoxyethylene alkyl ether. 6. The polyvinyl alcohol film for polarizing film according to claim 5, wherein the polyoxyethylene alkyl ether has an alkyl group having 6 to 22 carbon atoms and a polyoxyethylene unit condensation degree of 1 to 20. Polarizing film for polyvinyl alcohol film of claim 1, wherein the higher fatty acid alkanolamides wherein the alkyl diethanolamides. The content of the sulfate ester type anionic surfactant (a), the ether type nonionic surfactant (b) and the nitrogen-containing type nonionic surfactant (c) is 5 for each polyvinyl alcohol resin. The polyvinyl alcohol film for a polarizing film according to any one of claims 1 to 7 , wherein the polyvinyl alcohol film is ˜5000 ppm, 50˜1000 ppm, and 50˜5000 ppm. The weight ratio (a: b: c) of the sulfate ester type anionic surfactant (a), the ether type nonionic surfactant (b) and the nitrogen-containing nonionic surfactant (c) is from 100: 20 to It is 500: 100-1000, The polyvinyl alcohol-type film for polarizing films in any one of Claims 1-8 characterized by the above-mentioned. Furthermore, antioxidant is contained , The polyvinyl-alcohol-type film for polarizing films in any one of Claims 1-9 characterized by the above-mentioned. Polarizing film for polyvinyl alcohol-based film according to any one of claims 1 to 10, wherein the thickness of the film is 30 to 70 .mu.m. The polyvinyl alcohol-based film for polarizing film according to any one of claims 1 to 11, wherein the polyvinyl alcohol-based resin has a weight average molecular weight of 120,000 to 300,000. Polarizing film for polyvinyl alcohol-based film according to any one of claims 1 to 12, wherein the width of the film is not less than 2m. The polyvinyl alcohol film for polarizing film according to any one of claims 1 to 13 , wherein the length of the film is 4000 m or more. Polarizing film, wherein it was prepared using a claims 1-14 polarizing film for polyvinyl alcohol-based film according to any one.