JP2006233178A - Polyvinyl alcohol-based film for optical use and polarizing film, polarizing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyvinyl alcohol-based film for optical use for producing polarizing film with high polarizing performance over the whole visible light region, especially near wavelength 460 mn. <P>SOLUTION: The polyvinyl alcohol-based film for optical use comprises a polyvinyl alcohol-based resin(A) containing 1,2-glycol linkages on the side chain and another polyvinyl alcohol-based resin(B) and meets the following relationship(1):0.01≤A×G/(A+B)≤6 ( wherein, A is the proportion(weight ratio) of the resin A to the total of the resins A and B; B is the proportion(weight ratio) of the resin B; and G is the amount(mol%) of the 1,2-glycol linkages on the side chain ). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical polyvinyl alcohol-based film, and more particularly to an optical polyvinyl alcohol-based film for producing a polarizing film having excellent polarization performance in the entire visible light region, particularly in the vicinity of a wavelength of 460 nm.

Conventionally, a polyvinyl alcohol film is prepared by dissolving a polyvinyl alcohol resin in a solvent such as water to prepare a stock solution, then forming a film by a solution casting method (casting method), and drying using a metal heating roll or the like. It is manufactured by doing. The polyvinyl alcohol film thus obtained is used for many applications as a film having excellent transparency, and one of its useful applications is a polarizing film. Such a polarizing film is used as a basic component of a liquid crystal display, and in recent years, its use has been expanded to a device requiring high quality and high reliability.
Under such circumstances, with the increase in brightness and definition of screens of liquid crystal televisions and the like, there is a demand for a polarizing film that is further superior in optical properties than conventional products.

In response to such demands, the polarizing film obtained by improving the polyvinyl alcohol resin is, for example, a polyvinyl alcohol type in which the amount of 1,2-glycol bonded directly to the main chain is 1.8 mol% or more. A polarizing film (for example, refer to Patent Document 1) based on a uniaxially stretched film made of a polymer, or an α-olefin having a cationic group-containing unit of 0.01 to 20 mol% and having 4 or less carbon atoms. A polarizing film made of a polyvinyl alcohol film made of a vinyl alcohol polymer containing 0.5 to 24 mol% of a unit (see, for example, Patent Document 2) has been proposed. In addition, as a means for improving the polarization performance in the vicinity of a wavelength of 400 to 500 nm, cleaning with a 0.8% or more potassium iodide aqueous solution in a cleaning process that is a manufacturing process of a polarizing film (for example, see Patent Document 3). Proposed.
JP-A-8-136728 JP 2003-248123 A JP 2004-341503 A

However, in the disclosed technologies of Patent Document 1 and Patent Document 2, the polarizing film made of the obtained polyvinyl alcohol-based film has insufficient polarization performance in the vicinity of 460 nm, which is the wavelength range of visible light. There is a problem that the gradation display performance and contrast are not improved, and further improvement is desired. In addition, although the disclosed technique of Patent Document 3 can improve the polarization performance in the vicinity of 400 to 500 nm, since the film is washed with water mixed with an inorganic substance, foreign matters (optical defects) are present on the film. We have problems such as increasing.
Therefore, in the present invention, under such a background, an optical polyvinyl alcohol film for producing a polarizing film having excellent polarization performance in the entire visible light region, particularly in the vicinity of a wavelength of 460 nm even under the manufacturing conditions of the conventional polarizing film. Is intended to provide.

However, as a result of intensive studies by the present inventors to solve the above problems, polyvinyl alcohol resins (A) and polyvinyl alcohol resins (B) containing 1,2-glycol bonds in the side chains (polyvinyl alcohol). The present invention has been completed by finding that an optical polyvinyl alcohol film that contains a resin (A) is satisfied and satisfies the following formula (1).
0.01 ≦ A × G / (A + B) ≦ 6 (1)
Here, A is the content ratio (weight ratio) of the polyvinyl alcohol resin (A) to the total of the polyvinyl alcohol resin (A) and the polyvinyl alcohol resin (B), and B is the polyvinyl alcohol resin (B). Content ratio (weight ratio), G represents the amount of 1,2-glycol bonds (mol%) in the side chain.

Moreover, in this invention, it is preferable that the 1, 2- glycol bond amount of the side chain of a polyvinyl alcohol-type resin (A) is 0.01-20 mol%.
In this invention, it is preferable to contain a plasticizer (C) and surfactant (D) further.
Furthermore, in the present invention, the film width is preferably 2 m or more, and the film thickness is preferably 30 to 70 μm.
The present invention also provides a polarizing film comprising the optical polyvinyl alcohol film, and a polarizing plate comprising a protective film on at least one surface of the polarizing film.

  The optical polyvinyl alcohol film of the present invention has an effect of obtaining a polarizing film having excellent polarization performance in the entire visible light region, particularly in the vicinity of a wavelength of 460 nm, and is used for polarized sunglasses, liquid crystal display devices, and the like. It is very useful as an original film for a film, an original film used for a half-wave plate or a quarter-wave plate, and an original film for a retardation film used for a liquid crystal display device.

The polyvinyl alcohol film for optics of the present invention has a polyvinyl alcohol resin (A) and a polyvinyl alcohol resin (B) containing a 1,2-glycol bond in the side chain (excluding the polyvinyl alcohol resin (A)). It contains.
The polyvinyl alcohol resin (A) used in the present invention contains a polyvinyl alcohol resin having a 1,2-glycol bond in the side chain, that is, a 1,2-glycol structural unit represented by the general formula (1). If it is a polyvinyl alcohol-type resin, it will not specifically limit.

（ここで、Ｒ¹、Ｒ²、Ｒ³はそれぞれ独立して水素又はアルキル基である。）

(Here, R ¹ , R ² and R ³ are each independently hydrogen or an alkyl group.)

Such a polyvinyl alcohol resin (A) can be produced, for example, by saponifying a copolymer of (a) a vinyl ester monomer and 3,4-diacetoxy-1-butene.
Such vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valelate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, versatic. Although vinyl acid acid etc. are mentioned, Vinyl acetate is used preferably especially.

（ここで、Ｒはアルキル基で、好ましくはメチル基である。）
なお、上記の（２）式で示される化合物は、イーストマンケミカル社やアクロス社の製品として市場から入手したり、ブタンジオール製造時の中間体を精製して使用することができる。 The 3,4-diacetoxy-1-butene copolymerized with such a vinyl ester monomer is represented by the following chemical formula (2).

(Here, R is an alkyl group, preferably a methyl group.)
In addition, the compound represented by the above formula (2) can be obtained from the market as a product of Eastman Chemical Co. or Acros Co., or can be used by purifying an intermediate during butanediol production.

  In the present invention, in addition to the above copolymerization component, other monomers can be copolymerized within a range not inhibiting the purpose of the present invention. For example, ethylene, propylene, isobutylene, α-octene, α- Olefins such as dodecene and α-octadecene, unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride and itaconic acid or salts thereof, mono- or dialkyl esters, nitriles such as acrylonitrile and methacrylonitrile Amides such as diacetone acrylamide, acrylamide and methacrylamide, olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid and methallyl sulfonic acid or salts thereof, glycerol monoallyl ether, alkyl vinyl ethers, dimethylallyl vinyl Luketone, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, polyoxyethylene (meth) allyl ether, polyoxyalkylene (meth) allyl ether such as polyoxypropylene (meth) allyl ether, polyoxyethylene (meth) acrylate, poly Polyoxyalkylene (meth) acrylates such as oxypropylene (meth) acrylate, polyoxyethylene (meth) acrylamide, polyoxyalkylene (meth) acrylamides such as polyoxypropylene (meth) acrylamide, polyoxyethylene (1- (meth) (Acrylamide-1,1-dimethylpropyl) ester, polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, polyoxyethylene allylamine, polyoxypropylene allyla Emissions, polyoxyethylene vinyl amine, polyoxypropylene vinyl amine, ethylene carbonate, allyl acetate, and the like.

  Furthermore, N-acrylamidomethyltrimethylammonium chloride, N-acrylamidoethyltrimethylammonium chloride, N-acrylamidopropyltrimethylammonium chloride, 2-acryloxyethyltrimethylammonium chloride, 2-methacryloxyethyltrimethylammonium chloride, 2-hydroxy-3- Cationic group-containing monomers such as methacryloyloxypropyltrimethylammonium chloride, allyltrimethylammonium chloride, methallyltrimethylammonium chloride, 3-butenetrimethylammonium chloride, dimethyldiallylammonium chloride, diethyldiallylammonium chloride, acetoacetyl group-containing monomers And so on.

  There are no particular restrictions on the copolymerization of the above vinyl ester monomer and 3,4-diacetoxy-1-butene (and other monomers), and there are no block polymerization, bulk polymerization, solution polymerization, suspension polymerization, dispersion polymerization, or emulsion. Although known methods such as polymerization can be employed, solution polymerization is usually performed.

  The method for charging the monomer component at the time of copolymerization is not particularly limited, and any method such as batch charging, split charging, continuous charging, etc. is adopted, but 3,4-diacetoxy-1-butene is a molecule of a polyvinyl ester polymer. Drop polymerization is preferred from the standpoint of physical properties such as uniform distribution in the chain and a decrease in the melting point of polyvinyl alcohol, and a polymerization method based on the HANNA method is particularly preferred.

Examples of the solvent used in such copolymerization include usually lower alcohols such as methanol, ethanol, propanol and butanol, ketones such as acetone and methyl ethyl ketone, and industrially, methanol is preferably used.
The amount of the solvent used may be appropriately selected in consideration of the chain transfer constant of the solvent in accordance with the degree of polymerization of the target copolymer. For example, when the solvent is methanol, S (solvent) / M ( Monomer) = 0.01 to 10 (weight ratio), preferably 0.05 to 3 (weight ratio).

For the copolymerization, a polymerization catalyst is used. Examples of the polymerization catalyst include known radical polymerization catalysts such as azobisisobutyronitrile, acetyl peroxide, benzoyl peroxide, lauryl peroxide, azobisdimethylvaleronitrile, azo Examples include low-temperature active radical polymerization catalysts such as bismethoxydimethylvaleronitrile, and the amount of polymerization catalyst used varies depending on the type of catalyst and cannot be determined unconditionally, but is arbitrarily selected according to the polymerization rate. For example, when azoisobutyronitrile or acetyl peroxide is used, 0.01 to 0.2 mol% is preferable with respect to the vinyl ester monomer, and 0.02 to 0.15 mol% is particularly preferable.
Moreover, it is preferable that the reaction temperature of a copolymerization reaction shall be about 40 degreeC-about a boiling point by the solvent and pressure to be used.

  In the present invention, the copolymerization ratio of 3,4-diacetoxy-1-butene is not particularly limited, but the copolymerization ratio may be determined in accordance with the amount of 1,2-glycol bond introduced below.

  The obtained copolymer is then saponified. In such saponification, the above-obtained copolymer is dissolved in an alcohol or a hydrous alcohol, and an alkali catalyst or an acid catalyst is used. . Examples of the alcohol include methanol, ethanol, propanol, tert-butanol and the like, and methanol is particularly preferably used. The concentration of the copolymer in the alcohol is appropriately selected depending on the viscosity of the system, but is usually selected from the range of 10 to 60% by weight. Catalysts used for saponification include alkali catalysts such as alkali metal hydroxides and alcoholates such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate, potassium methylate, lithium methylate, etc., sulfuric acid, Examples include acid catalysts such as hydrochloric acid, nitric acid, metasulfonic acid, zeolite, and cation exchange resin.

The amount of the saponification catalyst used is appropriately selected depending on the saponification method, the target degree of saponification, and the like. Usually, when an alkali catalyst is used, a vinyl ester monomer and 3,4-diacetoxy-1- A suitable amount is 0.1 to 30 mmol, preferably 2 to 17 mmol, based on 1 mol of butene.
Moreover, although the reaction temperature of saponification reaction is not specifically limited, 10-60 degreeC is preferable, More preferably, it is 20-50 degreeC.
The polyvinyl alcohol resin (A) is produced by simultaneously converting the ester portion of the vinyl ester monomer and the acetoxy portion of 3,4-diacetoxy-1-butene into hydroxyl groups during saponification as described above.

  Thus, a polyvinyl alcohol resin (A) containing a 1,2-glycol bond in the side chain is obtained. In the present invention, the saponification degree of the polyvinyl alcohol resin (A) is 90 mol% or more. In particular, it is preferably 95 mol% or more, more preferably 98 mol% or more. If the degree of saponification is less than the lower limit, the water resistance at the time of forming the polarizing film is not preferred.

  The saponification degree in the present invention is expressed by the rate of change (mol%) of the total amount of the ester portion of the vinyl ester monomer and the acetoxy portion of 3,4-diacetoxy-1-butene to the hydroxyl group (saponification). In the reaction, the acetoxy part of 3,4-diacetoxy-1-butene is almost completely saponified).

  The 4% by weight aqueous solution viscosity of the polyvinyl alcohol resin (A) is preferably 8 to 400 mPa · s, particularly preferably 40 to 300 mPa · s, and more preferably 50 to 270 mPa · s. If it is less than the range, the stretchability at the time of forming the polarizing film is insufficient, and if it exceeds the upper limit, the flatness and transmittance of the film are undesirably lowered.

  Furthermore, the amount of 1,2-glycol bond introduced into the side chain of the polyvinyl alcohol-based resin (A) needs to be 0.01 to 20 mol%, preferably 0.01 to 15 mol%, Especially preferably, it is less than 0.01-10 mol%. If the amount of bonding is less than the lower limit, the effect of the present invention cannot be obtained. Conversely, if the amount exceeds the upper limit, the production of the polyvinyl alcohol resin becomes difficult, which is not preferable.

  In addition, as a method for producing the polyvinyl alcohol-based resin (A) used in the present invention, a method for saponifying the copolymer of the above (a) vinyl ester-based monomer and 3,4-diacetoxy-1-butene was described in detail. However, without being limited to such a method, for example, (a) a method of saponifying and decarboxylating a copolymer of a vinyl ester monomer and a vinyl ethylene carbonate represented by the general formula (3), (c) vinyl A method of saponifying and deketalizing a copolymer of an ester monomer and a 2,2-dialkyl-4-vinyl-1,3-dioxolane represented by the general formula (4), and (d) a vinyl ester monomer A method of saponifying a copolymer with glycerin monoallyl ether, and the like are also exemplified and are not particularly limited. Vinyl ethylene carbonate can be obtained from the market as a product of Eastman Chemical Company.

但し、Ｒ¹、Ｒ²、Ｒ³はそれぞれ独立して水素又はアルキル基である。

However, R ¹ , R ² and R ³ are each independently hydrogen or an alkyl group.

但し、Ｒ¹、Ｒ²、Ｒ³、Ｒ⁴、Ｒ⁵はそれぞれ独立して水素又はアルキル基である。

However, R ¹ , R ² , R ³ , R ⁴ and R ⁵ are each independently hydrogen or an alkyl group.

  In addition, in the present invention, in addition to the polyvinyl alcohol resin (A), it contains a polyvinyl alcohol resin (B) (excluding the polyvinyl alcohol resin (A)), and thereby stretched. And dyeability are further improved.

  The polyvinyl alcohol resin (B) used in the present invention is not particularly limited, but the saponification degree is preferably 90 mol% or more, particularly preferably 95 mol% or more, and more preferably 98 mol% or more. . If the degree of saponification is less than the lower limit, the water resistance at the time of preparing the polarizing film is insufficient, which is not preferable.

  Further, the viscosity of the 4% by weight aqueous solution of the polyvinyl alcohol resin (B) is preferably 8 to 500 mPa · s, particularly preferably 20 to 400 mPa · s, and more preferably 40 to 400 mPa · s. If the viscosity of the 4% by weight aqueous solution is less than the lower limit value, the stretchability at the time of forming the polarizing film tends to be insufficient, and if the upper limit value is exceeded, the flatness and transparency of the film tend to decrease, which is not preferable.

  The polyvinyl alcohol-based resin (B) is not particularly limited as long as it is a polyvinyl alcohol-based resin other than the polyvinyl alcohol-based resin (A), and an unmodified polyvinyl alcohol-based resin or a small amount of unsaturated carboxylic acid (salt) , Esters, amides, nitriles, etc.), olefins having 2 to 30 carbon atoms (ethylene, propylene, n-butene, isobutene, etc.), vinyl ethers, unsaturated sulfonates, and other components that are copolymerizable with vinyl acetate It may be a polyvinyl alcohol-based resin containing

In the present invention, when the polyvinyl alcohol-based resin (A) and the polyvinyl alcohol-based resin (B) are contained, it is preferable to satisfy the following formula (1), and it is particularly preferable to satisfy the following formula (2).
0.01 ≦ A × G / (A + B) ≦ 6 (1)
0.05 ≦ A × G / (A + B) ≦ 4 (2)
Here, A is the content ratio (weight ratio) of the polyvinyl alcohol resin (A) to the total of the polyvinyl alcohol resin (A) and the polyvinyl alcohol resin (B), and B is the polyvinyl alcohol resin (B). Content ratio (weight ratio), G represents the amount of 1,2-glycol bonds (mol%) in the side chain.
In the above formula (1), if it is less than the lower limit, the effect of the present invention cannot be obtained. Conversely, if it exceeds the upper limit, the water resistance at the time of forming the polarizing film tends to be insufficient.

  In addition, when the polyvinyl alcohol resin (A) and the polyvinyl alcohol resin (B) are contained, the difference in the saponification degree between the polyvinyl alcohol resin (A) and the polyvinyl alcohol resin (B) is 6 mol% or less. Is preferable from the viewpoint of transparency of the film, and is particularly 3 mol% or less. If the difference in the degree of saponification exceeds the upper limit value, the transmittance of the film is lowered, which is not preferable.

  Furthermore, in this invention, it is preferable to contain a plasticizer (C) and surfactant (D) other than polyvinyl alcohol-type resin (A) and polyvinyl alcohol-type resin (B).

  The plasticizer (C) used in the present invention effectively contributes to stretchability when producing a polarizing film, and includes, for example, ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, triethylene glycol. Examples include ethylene glycol, tetraethylene glycol, trimethylolpropane, and polyhydric alcohols such as polyethylene glycol having a polymerization degree of 300 or less. These polyhydric alcohols can be used alone or in combination of two or more. Among them, particularly preferred are glycerin alone, or a combination of glycerin and diglycerin or glycerin and trimethylolpropane.

  The content of the plasticizer (C) is preferably 1 to 20 parts by weight, particularly 3 to 15 parts by weight, and more preferably 7 to 13 parts by weight with respect to 100 parts by weight of the total polyvinyl alcohol resin used. Preferably there is. If the content of the plasticizer (C) is less than the lower limit value, the stretchability tends to decrease when the polarizing film is formed, and if the content exceeds the upper limit value, the temporal stability of the optical polyvinyl alcohol film obtained tends to decrease. It is not preferable.

  In addition, the surfactant (D) used in the present invention functions to suppress film surface smoothness and adhesion between films when wound into a roll when the optical polyvinyl alcohol film is formed. Yes, for example, anionic surfactants and nonionic surfactants can be used singly or in combination of two or more, but in particular, an anionic surfactant and a nonionic surfactant can be used in combination. It is preferable in terms of transparency.

Examples of such anionic surfactants include:
(1) aliphatic alkyl sulfonates,
(2) alkyl sulfate ester salt,
(3) polyoxyethylene alkyl ether sulfate,
(4) polyoxyethylene alkylphenyl ether sulfate,
(5) higher fatty acid alkanolamide sulfate and the like.

(1) Specific examples of the aliphatic alkyl sulfonate include, for example, sodium hexyl sulfonate, sodium heptyl sulfonate, sodium octyl sulfonate, sodium nonyl sulfonate, sodium decyl sulfonate, sodium dodecyl sulfonate, tetradecyl sulfone. And sodium dodecyl sulfonate, sodium tetradecyl sulfonate, sodium hexadecyl sulfonate, sodium hexadecyl sulfonate, sodium octadecyl sulfonate, sodium octadecyl sulfonate, sodium alkyldecyl sulfonate A sodium sulfonate, a mixture of a secondary alkyl sodium sulfonate having 10 to 18 carbon atoms and the like are used. The counter cation of the aliphatic alkyl sulfonate is not particularly limited, and examples thereof include Na ⁺ , Ca ²⁺ , NH ₄ ⁺ , or a mixture thereof, and among these, Na ⁺ is particularly preferable.

(2) Specific examples of the alkyl sulfate ester salt include, for example, sodium hexyl sulfate, sodium heptyl sulfate, sodium octyl sulfate, sodium nonyl sulfate, sodium decyl sulfate, sodium dodecyl sulfate, sodium tetradecyl sulfate, sodium hexadecyl sulfate, and sodium octadecyl sulfate. , Sodium eicosyl sulfate, alkali metal salts such as potassium salts thereof, alkaline earth metal salts such as calcium salts, and organic amine salts such as ammonium salts, preferably sodium dodecyl sulfate, sodium octadecyl sulfate, etc. Is done. Further, the counter cation is not particularly limited, and Na ⁺ , Ca ²⁺ , NH ₄ ⁺ , or a mixture thereof may be mentioned, and among these, Na ⁺ is particularly preferable.

(3) Specific examples of 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, Sodium polyoxyethylene 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 organic amine salts such as alkali metal salts and ammonium salts of these potassium salts. , Preferably polyoxyethylene dodecyl ether sulfate or the like is used. Further, the counter cation is not particularly limited, and Na ⁺ , Ca ²⁺ , NH ₄ ⁺ , or a mixture thereof may be mentioned, and among these, Na ⁺ is particularly preferable.

(4) Specific examples of polyoxyethylene alkyl phenyl ether sulfate include, for example, sodium polyoxyethylene hexyl phenyl ether sulfate, sodium polyoxyethylene heptyl phenyl ether sulfate, sodium polyoxyethylene octyl phenyl ether sulfate, polyoxyethylene nonyl Sodium phenyl ether sulfate, sodium polyoxyethylene decyl phenyl ether sulfate, sodium polyoxyethylene dodecyl phenyl ether sulfate, sodium polyoxyethylene tetradecyl phenyl ether sulfate, sodium polyoxyethylene hexadecyl phenyl ether sulfate, polyoxyethylene octadecyl phenyl ether sulfate Sodium, sodium polyoxyethylene eicosyl phenyl ether sulfate , Or alkali metal salts such as the potassium salts, and organic amine salts such as ammonium salts, the use of polyoxyethylene nonylphenyl ether sulfate is preferable. Further, the counter cation is not particularly limited, and Na ⁺ , Ca ²⁺ , NH ₄ ⁺ , or a mixture thereof may be mentioned, and among these, Na ⁺ is particularly preferable.

(5) Specific examples of the higher fatty acid alkanolamide sulfate include, for example, sodium caproic acid ethanolamide sulfate, sodium caprylic acid ethanolamide sulfate, sodium capric acid ethanolamide sulfate, sodium lauric acid ethanolamide sulfate, and palmitic acid ethanolamide sulfate. Sodium, stearic acid ethanolamide sodium sulfate, oleic acid ethanolamide or potassium salts thereof, and propanolamide and butanolamide instead of these ethanolamides may be mentioned. Further, the counter cation is not particularly limited, and Na ⁺ , Ca ²⁺ , NH ₄ ⁺ , or a mixture thereof may be mentioned, and among these, Na ⁺ is particularly preferable.

  In addition to the anionic surfactants (1) to (5) above, sulfate ester salts such as sulfated oil, higher alcohol ethoxy sulfate, monoglyculate, fatty acid soap, N-acyl amino acid and salts thereof , Carboxylate types such as polyoxyethylene alkyl ester carboxylates and acylated peptides, alkylbenzene sulfonates, alkyl naphthalene sulfonates, salt formalin polycondensates of naphthalene sulfonic acid, salt formalin condensates of melamine sulfonic acid, Dialkyl sulfosuccinic acid ester salt, sulfosuccinic acid alkyl di-salt, polyoxyethylene alkyl sulfosuccinic acid di-salt, alkyl sulfoacetate, α-olefin sulfonate, N-acylmethyl taurate, dimethyl-5-sulfoisophthalate sodium salt, etc. Sulfonate Can polyoxyethylene alkyl ether phosphates, polyoxyethylene alkyl phenyl ether phosphates, also it is used an anionic surfactant phosphate ester salt type such as alkyl phosphates.

On the other hand, as a nonionic surfactant, for example,
(7) General formula R—O (C ₂ H ₄ O) _n H
(Here, R is an alkyl group or an alkenyl group, and its carbon number is 6-22, preferably 8-18. These may be a single alkyl group or a mixed alkyl group. (Also, an alkyl group having an alkyl distribution obtained from palm oil, palm oil, palm kernel oil, beef tallow, etc. can be used.)
A polyoxyethylene alkyl ether represented by

(8) General formula R—X—O (C ₂ H ₄ O) _n H
(Here, R is an alkyl group or an alkenyl group, and its carbon number is 6-22, preferably 8-18. These may be a single alkyl group or a mixed alkyl group. It is also possible to use an alkyl group having an alkyl distribution obtained from palm oil, palm oil, palm kernel oil, beef tallow, etc. X is a phenylene group, n is 1 to 20, preferably 2 to 10. Is shown.)
A polyoxyethylene alkylphenyl ether represented by

(9) General formula RCONH-R'-OH or RCON- (R'-OH) ₂
(Here, R is an alkyl group or an alkenyl group, and its carbon number is 6-22, preferably 8-18. These may be a single alkyl group or a mixed alkyl group. It is also possible to use an alkyl group having an alkyl distribution obtained from palm oil, palm oil, palm kernel oil, beef tallow, etc. R ′ is —C ₂ H ₄ —, —C ₃ H ₆ —, — C ₄ H ₈ - is either).
A higher fatty acid mono- or dialkanolamide represented by

(10) General formula RCONH ₂
(Here, R is an alkyl group or an alkenyl group, and its carbon number is 6-22, preferably 8-18. These may be a single alkyl group or a mixed alkyl group. (Also, an alkyl group having an alkyl distribution obtained from palm oil, palm oil, palm kernel oil, beef tallow, etc. can be used.)
Higher fatty acid amide represented by

(11) In 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
(Here, R is an alkyl group, and its carbon number is 6-22, preferably 8-18. These may be a single alkyl group or a mixed alkyl group. An alkyl group having an alkyl distribution obtained from palm oil, palm oil, palm kernel oil, beef tallow, etc. can also be used.x and y represent an integer of 1 to 30, preferably 3 to 15.)
A polyoxyethylene alkylamine represented by

(12) Polyoxyethylene higher fatty acid amide (13) Amine oxide and the like.

(7) Specific examples of polyoxyethylene alkyl ether include, for example, polyoxyethylene hexyl ether, polyoxyethylene heptyl ether, polyoxyethylene octyl ether, polyoxyethylene nonyl ether, polyoxyethylene decyl ether, polyoxyethylene dodecyl Examples include ether, polyoxyethylene tetradecyl ether, polyoxyethylene hexadecyl ether, polyoxyethylene octadecyl ether, polyoxyethylene oleyl ether, and polyoxyethylene eicosyl ether. In particular, polyoxyethylene dodecyl ether, polyoxyethylene octadecyl ether, and the like are preferable.

(8) Specific examples of 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 Examples include ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene tetradecyl phenyl ether, polyoxyethylene hexadecyl phenyl ether, polyoxyethylene octadecyl phenyl ether, polyoxyethylene eicosyl phenyl ether, and the like. In particular, polyoxyethylene nonylphenyl ether is suitable.

(9) Specific examples of higher fatty acid mono- or dialkanolamide 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- or diethanolamide, oleic acid mono- or diethanolamide, coconut oil fatty acid mono- or diethanolamide, or propanolamide or butanolamide instead of these ethanolamides may be mentioned. 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.

(10) 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 amide is preferred.

(11) Specific examples of polyoxyethylene alkylamine include, for example, polyoxyethylene hexylamine, polyoxyethylene heptylamine, polyoxyethylene octylamine, polyoxyethylene nonylamine, polyoxyethylene decylamine, polyoxyethylene dodecyl Examples include amine, polyoxyethylene tetradecylamine, polyoxyethylene hexadecylamine, polyoxyethylene octadecylamine, polyoxyethyleneeicosylamine, and among them, polyoxyethylene dodecylamine is preferable.

(12) Specific examples of polyoxyethylene higher fatty acid amides include, for example, polyoxyethylene caproic acid amide, polyoxyethylene caprylic acid amide, polyoxyethylene capric acid amide, polyoxyethylene lauric acid amide, polyoxyethylene myristic acid. Examples include amides, polyoxyethylene palmitic acid amides, polyoxyethylene stearic acid amides, polyoxyethylene oleic acid amides, among which polyoxyethylene lauric acid amides and polyoxyethylene stearic acid amides are suitable.

(13) Specific examples of amine oxides include, for example, dimethyl lauryl amine oxide, dimethyl stearyl oxide, dihydroxyethyl lauryl amine oxide, etc. Among them, dimethyl lauryl amine oxide is preferable.

  In addition to the nonionic surfactants of the above (7) to (13), ethylene oxide derivatives of alkylphenol formalin condensate, polyoxyethylene polyoxypropylene block polymer, polyoxyethylene glycerin fatty acid ester, polyoxyethylene castor Oil and hydrogenated castor oil, polyoxyethylene sorbitan fatty acid ester, ether ester type nonionic surfactant such as polyoxyethylene sorbitol fatty acid ester, polyethylene glycol fatty acid ester, sorbitan fatty acid ester, fatty acid monoglyceride, propylene glycol fatty acid ester, sucrose fatty acid ester Ester type surfactants such as can also be used in combination.

  The surfactant (D) content is preferably 0.01 to 1 part by weight, particularly 0.02 to 0.5 part by weight, based on 100 parts by weight of the total polyvinyl alcohol resin used. Furthermore, it is preferable that it is 0.03-0.2 weight part. If the content of the surfactant (D) is less than the lower limit, it is difficult to obtain an anti-blocking effect.

  When an anionic surfactant and a nonionic surfactant are used in combination, the anionic surfactant is 0.01 to 1 part by weight, particularly 0.02 to the total polyvinyl alcohol resin used. 0.2 part by weight, further 0.03 to 0.1 part by weight, 0.01 to 1 part by weight of the nonionic surfactant, particularly 0.02 to 0.2 part by weight, and more preferably 0. It is preferable that it is 03-0.1 weight part. If the anionic surfactant is less than the lower limit value, the dispersibility of the dye at the time of forming the polarizing film tends to decrease and dyeing spots tend to increase, and if the upper limit value is exceeded, foaming is severe when dissolving the polyvinyl alcohol resin, and in the film It is difficult to use as an optical film because air bubbles are likely to be mixed in, and if the nonionic surfactant is less than the lower limit, it is difficult to obtain an anti-blocking effect, and if it exceeds the upper limit, the transparency and flatness of the film are lowered. This is not preferable.

  In the present invention, it is also useful to add an antioxidant in order to prevent yellowing of the film. Examples of the antioxidant include phenolic antioxidants, and 2,6-di- T-butyl-p-cresol, 2,2'-methylenebis (4-methyl-6-t-butylphenol), 4,4'-butylidenebis (3-methyl-6-t-butylphenol) and the like are preferable. The antioxidant is used in the range of about 2 to 100 ppm with respect to the polyvinyl alcohol resin.

Thus, in the present invention, the polyvinyl alcohol resin (A) and the polyvinyl alcohol resin (B) (excluding the polyvinyl alcohol resin (A)) containing a 1,2-glycol bond in the above side chain, preferably further. A polyvinyl alcohol film is formed using the plasticizer (C) and the surfactant (D).
Hereinafter, the manufacturing method of the polyvinyl alcohol-type film of this invention is demonstrated concretely. The polyvinyl alcohol resin (A) and the polyvinyl alcohol resin (B) may be expressed together as “polyvinyl alcohol resin”.

  In the present invention, a polyvinyl alcohol resin (A) and a polyvinyl alcohol resin (B) containing a 1,2-glycol bond in the side chain, preferably a plasticizer (C) and a surfactant (D) are used. Then, an aqueous solution of the polyvinyl alcohol-based resin composition is prepared, and the aqueous solution is cast on a drum-type roll or an endless belt, preferably a drum-type roll, and formed into a film and dried to produce a polyvinyl alcohol-based film.

In the production method of the present invention, first, the polyvinyl alcohol resin powder is washed to remove sodium acetate usually contained in the resin. In the washing, washing with methanol or water is performed, but the method of washing with methanol requires solvent recovery, so that the washing method with water is more preferable.
Next, the water-containing polyvinyl alcohol resin wet cake after washing is dissolved to prepare a polyvinyl alcohol resin aqueous solution. When the water-containing polyvinyl alcohol resin wet cake is dissolved in water as it is, a desired high-concentration aqueous solution is obtained. Therefore, it is preferable to perform dehydration once. The dehydration method is not particularly limited, but a method using centrifugal force is common.
By the washing and dehydration, a wet polyvinyl alcohol resin wet cake having a water content of 50% by weight or less, preferably 30 to 45% by weight, is preferable. If the water content exceeds the upper limit, it is difficult to obtain a desired aqueous solution concentration.

  Next, an aqueous solution of the polyvinyl alcohol resin composition used for forming a polyvinyl alcohol film is prepared by adding water, water-containing polyvinyl alcohol resin wet cake after dehydration, plasticizer (C), and surfactant in a dissolution tank. It is prepared by charging (D) and the like, heating, stirring and dissolving. In the production method of the present invention, it is particularly preferable from the viewpoint of solubility that water-containing polyvinyl alcohol resin wet cake is dissolved by blowing water vapor in a dissolution tank equipped with a vertical circulation flow generation type stirring blade.

When the water-containing polyvinyl alcohol resin wet cake is dissolved by blowing water vapor in a dissolving tank equipped with an up-and-down circulating flow generation type stirring blade, water vapor is blown and the resin temperature is 40 to 80 ° C., preferably 45 to 70 ° C. At that point, it is preferable to start stirring because it can be uniformly dissolved. If the resin temperature is less than the lower limit value, the load on the motor increases. If the resin temperature exceeds the upper limit value, the polyvinyl alcohol-based resin can be hardened and cannot be uniformly dissolved. Furthermore, it is also preferable to pressurize the inside of the can at the time when steam is blown and the resin temperature reaches 90 to 100 ° C., preferably 95 to 100 ° C., from the viewpoint of uniform dissolution. If the resin temperature is less than the lower limit, undissolved material is formed, which is not preferable. Then, when the resin temperature reaches 130 to 150 ° C., the blowing of water vapor is finished, and stirring is continued for 0.5 to 3 hours to perform dissolution. After dissolution, the concentration is adjusted so that the desired concentration is obtained.
The concentration of the aqueous solution of the polyvinyl alcohol resin composition thus obtained is preferably 10 to 50% by weight, more preferably 15 to 40% by weight, and particularly preferably 20 to 30% by weight. If the concentration of the aqueous solution is less than the lower limit, the drying load becomes large and the production capacity is inferior.

  Next, the obtained aqueous solution of the polyvinyl alcohol-based resin composition is defoamed. Examples of the defoaming method include stationary defoaming and defoaming with a multi-screw extruder. In the production method of the present invention, from the viewpoint of productivity, there is a method of defoaming using a multi-screw extruder. preferable.

After the defoaming treatment, the aqueous solution of the polyvinyl alcohol-based resin composition discharged from the multi-screw extruder is introduced into the T-type slit die by a certain amount and cast onto a drum-type roll or an endless belt, The film is formed and dried.
As the T-type slit die, a T-type slit die having an elongated rectangle is usually used. The resin temperature at the exit of the T-shaped slit die is preferably 80 to 100 ° C, more preferably 85 to 98 ° C. If the resin temperature at the exit of the T-type slit die is less than the lower limit value, the flow is poor, and if it exceeds the upper limit value, foaming is not preferable.

The casting is performed with a drum-type roll or an endless belt, but it is preferably performed with a drum-type roll in terms of widening, lengthening, film thickness uniformity, and the like.
In casting a film with a drum-type roll, for example, the rotational speed of the drum is preferably 5 to 30 m / min, and particularly preferably 6 to 20 m / min. The surface temperature of the drum roll is preferably 70 to 99 ° C, more preferably 75 to 97 ° C. If the surface temperature of the drum-type roll is less than the lower limit value, drying is poor, and if it exceeds the upper limit value, foaming is not preferable.
Drying of the polyvinyl alcohol film formed by the drum type roll is performed by alternately passing the front and back surfaces of the film through a plurality of drying rolls. Although the surface temperature of a drying roll is not specifically limited, It is preferable that it is 60-100 degreeC, Furthermore, it is 65-90 degreeC. If the surface temperature is less than the lower limit, the drying is poor. If the surface temperature exceeds the upper limit, the surface is excessively dried, resulting in poor appearance. In the present invention, it is preferable to perform heat treatment after drying.
Regarding heat treatment, (1) a method in which the surface is subjected to hard chrome plating treatment or mirror surface treatment, and a roll having a diameter of 0.2 to 2 m (1 to 30 rolls) is adjusted to a temperature of 60 to 180 ° C. and (2) floating Examples include a method using a mold dryer (length: 2 to 30 m, temperature 80 to 180 ° C.).

  The polyvinyl alcohol film of the present invention thus obtained has a light transmittance of 90% or more over the entire visible light range, and is very useful as an optical polyvinyl alcohol film. Accordingly, the optical polyvinyl alcohol film of the present invention is particularly preferably used as an original film of a polarizing film.

Hereinafter, the manufacturing method of the polarizing film of the present invention using the optical polyvinyl alcohol film of the present invention will be described.
The polarizing film of the present invention is produced through processes such as normal dyeing, stretching, boric acid crosslinking and heat treatment. As a method for producing a polarizing film, a polyvinyl alcohol film is stretched and dyed by dipping in an iodine or dichroic dye solution, and then treated with a boron compound. After stretching and dyeing at the same time, a boron compound treatment is performed. There are a method, a method of dyeing with iodine or a dichroic dye and stretching, and then a method of treating with a boron compound, a method of dyeing and then stretching in a solution of a boron compound, etc., which can be appropriately selected and used. As described above, the polyvinyl alcohol film (unstretched film) may be stretched and dyed and further subjected to boron compound treatment separately or simultaneously, but during at least one of the dyeing step and the boron compound treatment step. It is desirable from the viewpoint of productivity to carry out uniaxial stretching.

  The stretching is desirably performed in a uniaxial direction by 3 to 10 times, preferably 3.5 to 7 times. At this time, a slight stretching (stretching to prevent shrinkage in the width direction or more) may be performed in a direction perpendicular to the stretching direction. The stretching temperature is preferably selected from 20 to 170 ° C. Furthermore, the draw ratio may be finally set within 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 iodine-potassium iodide aqueous solution is used, the iodine concentration is 0.1 to 2 g / L, the potassium iodide concentration is 10 to 50 g / L, and the potassium iodide / iodine weight ratio is 20 to 100. Is appropriate. The dyeing time is practically about 30 to 500 seconds. The temperature of the treatment bath is preferably 5 to 50 ° C. The aqueous solution may contain a small amount of an organic solvent compatible with water in addition to the aqueous solvent. As the contact means, any means such as dipping, coating, spraying and the like can be applied.

  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 that a small amount of potassium iodide coexists in the solution. The treatment method is preferably an immersion method, but of course, an application method and a spray method can also be carried out. The temperature during the treatment is preferably about 20 to 60 ° C., and the treatment time is preferably about 3 to 20 minutes. If necessary, the stretching operation may be performed during the treatment.

The polarizing film of the present invention thus obtained can be used as a polarizing plate by laminating and bonding an optically isotropic polymer film or sheet as a protective film on one or both surfaces thereof. As a protective film used for the polarizing plate of the present invention, for example, cellulose triacetate, cellulose diacetate, polycarbonate, polymethyl methacrylate, polystyrene, polyethersulfone, polyarylene ester, poly-4-methylpentene, polyphenylene oxide, cyclo type Or a film or sheet of norbornene-based polyolefin or the like can be mentioned.
For the purpose of reducing the thickness of the polarizing film, instead of the protective film, a curable resin such as a urethane resin, an acrylic resin, or a urea resin may be applied and laminated on one or both surfaces.

  A polarizing film (including at least one surface laminated with a protective film or a curable resin) 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 pressure-sensitive adhesive layers include acrylic acid esters such as butyl acrylate, ethyl acrylate, methyl acrylate, 2-ethylhexyl acrylate, and α- such as acrylic acid, maleic acid, itaconic acid, methacrylic acid, and crotonic acid. Since the main component is a copolymer with a monoolefin carboxylic acid (including those added with vinyl monomers such as acrylonitrile, vinyl acetate, and styrene), the polarizing properties of the polarizing film are not impaired. Although it is particularly preferable, the present invention is not limited to this, and any pressure-sensitive adhesive having transparency can be used. For example, polyvinyl ether or rubber may be used.

  The polarizing film of the present invention includes an electronic desk calculator, an electronic watch, a word processor, a personal computer, a portable information terminal, a liquid crystal display device such as an instrument for automobiles and machinery, sunglasses, eye protection glasses, stereoscopic glasses, a display element (CRT, Used for reflection-reducing layers for LCD, etc., medical equipment, building materials, toys and the like.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to a following example, unless the summary is exceeded.
In the examples, “parts” and “%” mean weight basis unless otherwise specified.

About each physical property, it carried out as follows.
(1) 1,2-glycol bond amount of side chain
It was calculated by measuring with ¹ H-NMR (internal standard substance: tetramethylsilane, solvent: d6-DMSO).
(2) Degree of Saponification of Polyvinyl Alcohol Resin The analysis was performed based on alkali consumption required for hydrolysis of residual vinyl acetate units.
(3) Viscosity of 4% aqueous solution of polyvinyl alcohol resin The water temperature was adjusted to 20 ° C. and measured with a Heppler viscometer.
(4) Optical properties Using a high-speed multi-wavelength birefringence measuring apparatus (“RETS-2000” manufactured by Otsuka Electronics Co., Ltd.), the polarization degree, transmittance, and dichroism of the obtained polarizing film at wavelengths of 460 nm, 540 nm, and 640 nm. The ratio was measured.

Example 1
200 kg of water at 5 ° C. is put into a 500 L tank, and while stirring, polyvinyl having a 4% aqueous solution viscosity of 107 mPa · s, a saponification degree of 99.3 mol%, and a side chain 1,2-glycol bond amount of 1.0 mol% 21 kg of alcohol resin (A), 21 kg of 4% aqueous solution viscosity of 64 mPa · s and 21 kg of polyvinyl alcohol resin (B) having a saponification degree of 99.8 mol% were added, and stirring was continued for 15 minutes. Thereafter, after draining water, 200 kg of water was further added and stirred for 15 minutes. The obtained slurry was dehydrated to obtain a polyvinyl alcohol resin wet cake having a water content of 40%.
70 kg (42 kg of resin content) of the obtained polyvinyl alcohol resin wet cake was put in a dissolution tank, 4.2 kg of glycerin as a plasticizer (C), 21 g of sodium dodecyl sulfonate as a surfactant (D), polyoxyethylene dodecylamine 8 g and 10 kg of water were added, and steam was blown from the bottom of the tank. Stirring was performed when the internal resin temperature reached 50 ° C., the system was pressurized when the internal resin temperature reached 100 ° C., and the temperature was raised to 150 ° C., after which the blowing of water vapor was stopped. After stirring for 30 minutes and uniformly dissolving, an aqueous solution of a polyvinyl alcohol resin composition having a concentration of 26% was obtained by adjusting the concentration.

Next, the aqueous solution (liquid temperature 147 degreeC) of the polyvinyl alcohol-type resin composition was supplied to the twin-screw extruder, and it defoamed. An aqueous solution of the defoamed polyvinyl alcohol resin composition was cast on a cast drum from a T-shaped slit die (straight manifold die) to form a film. The conditions for such casting film formation are as follows.
Drum type roll diameter (R1): 3200 mm, width: 4.3 m, rotation speed: 8 m / min, surface temperature: 90 ° C., resin temperature at T-type slit die outlet: 95 ° C.
Drying was performed while the front and back surfaces of the obtained film were alternately passed through a drying roll under the following conditions.
Drying roll diameter (R2): 320 mm, width: 4.3 m, number (n): 10, rotational speed: 8 m / min, surface temperature: 80 ° C.
Continuously, this film is heat-treated at 140 ° C. by a floating dryer (length: 18.5 m) that blows hot air from both sides, and has a width of 4.0 m, a thickness of 50 μm, and a length of 4000 m. Got.

Using the optical polyvinyl alcohol film of the present invention obtained above, a polarizing film was obtained in the following manner to evaluate the polarization characteristics.
The obtained optical polyvinyl alcohol film was stretched 1.5 times while being immersed in a water bath at a water temperature of 30 ° C. Next, it is stretched 1.3 times while being immersed for 240 seconds in a dyeing tank (30 ° C.) consisting of 0.2 g / L of iodine and 15 g / L of potassium iodide, and further 50 g / L of boric acid and 30 g of potassium iodide. A boric acid treatment was performed for 5 minutes while being uniaxially stretched 2.8 times while being immersed in a boric acid treatment tank (40 ° C.) having a composition of / L. Then, it dried and obtained the polarizing film.
Next, using a polyvinyl alcohol-based aqueous solution as an adhesive on both surfaces of the obtained polarizing film, a 80 μm thick triacetyl cellulose film was bonded and dried at 50 ° C. to obtain a polarizing plate. About this polarizing plate, the polarization degree and the light transmittance were measured. The measurement results are shown in Table 1. As shown in Table 1, a very high polarization performance of 460 nm was obtained.

Example 2
In Example 1, a polyvinyl alcohol resin having a 4% aqueous solution viscosity of 173 mPa · s, a saponification degree of 99.8 mol%, and a side chain 1,2-glycol bond amount of 8.0 mol% (A ) 4 kg and 4% aqueous solution viscosity 64 mPa · s, unmodified polyvinyl alcohol resin (B) having a saponification degree of 99.8 mol% was changed to 38 kg in the same manner, and an optical polyvinyl alcohol film (length 4000 m, Width 4 m, thickness 50 μm).
About the obtained polyvinyl alcohol-type film for optics, it carried out similarly to Example 1, and obtained the polarizing film and the polarizing plate, and measured the polarization degree and the light transmittance. The measurement results are shown in Table 1. As shown in Table 1, a very high polarization performance of 460 nm was obtained.

Comparative Example 1
In Example 1, the same procedure was followed except that the polyvinyl alcohol-based resin was changed to 42 kg of an unmodified polyvinyl alcohol-based resin having a 4% aqueous solution viscosity of 64 mPa · s and a saponification degree of 99.8 mol%. 4000 m, width 4 m, thickness 50 μm).
About the obtained polyvinyl alcohol-type film, it carried out similarly to Example 1, and obtained the polarizing film and the polarizing plate, and measured the polarization degree and the light transmittance. The measurement results are shown in Table 1. As shown in Table 1, the dichroic ratio at 460 nm was 31.72, and sufficient polarization performance was not obtained.

Comparative Example 2
In Example 1, as a polyvinyl alcohol resin, a 4% aqueous solution viscosity of 27 mPa · s, a saponification degree of 99.8 mol%, and a polyvinyl alcohol resin having a 1,2-glycol bond of 1.8 mol% in the main chain of 42 kg Except having changed, it carried out similarly and the polyvinyl-alcohol-type film (length 4000m, width 4m, thickness 50micrometer) was obtained.
About the obtained polyvinyl alcohol-type film, it carried out similarly to Example 1, and obtained the polarizing film and the polarizing plate, and measured the polarization degree and the light transmittance. The measurement results are shown in Table 1. As shown in Table 1, the dichroic ratio at 460 nm was 27.01, and sufficient polarization performance was not obtained.

The polyvinyl alcohol film for optics of the present invention has a polyvinyl alcohol resin (A) and a polyvinyl alcohol resin (B) containing a 1,2-glycol bond in the side chain (excluding the polyvinyl alcohol resin (A)). Therefore, it has the effect of obtaining a polarizing film with excellent polarization performance in the entire visible light range, particularly in the vicinity of a wavelength of 460 nm. Electronic desk calculator, electronic clock, word processor, personal computer, mobile phone Used in information terminals, liquid crystal display devices such as automobile and machinery instruments, sunglasses, eyeglasses, stereoscopic glasses, reflection reduction layers for display elements (CRT, LCD, etc.), medical equipment, building materials, toys, etc. Retardation films used for original films of polarizing films, original films used for half-wave plates and quarter-wave plates, and liquid crystal display devices. It is very useful as a raw film of the beam.

Claims (14)

It contains a polyvinyl alcohol resin (A) and a polyvinyl alcohol resin (B) containing a 1,2-glycol bond in the side chain (excluding the polyvinyl alcohol resin (A)), and the following (1) An optical polyvinyl alcohol film characterized by satisfying the formula:
0.01 ≦ A × G / (A + B) ≦ 6 (1)
Here, A is the content ratio (weight ratio) of the polyvinyl alcohol resin (A) to the total of the polyvinyl alcohol resin (A) and the polyvinyl alcohol resin (B), and B is the polyvinyl alcohol resin (B). Content ratio (weight ratio), G represents the amount of 1,2-glycol bonds (mol%) in the side chain. 2. The polyvinyl alcohol film for optics according to claim 1, wherein the amount of 1,2-glycol bonds in the side chain of the polyvinyl alcohol resin (A) is 0.01 to 20 mol%. The optical polyvinyl alcohol film according to claim 1 or 2, wherein the saponification degree of the polyvinyl alcohol resin (A) is 90 mol% or more. The optical polyvinyl alcohol film according to any one of claims 1 to 3, wherein the viscosity of the 4% by weight aqueous solution of the polyvinyl alcohol resin (A) is 8 to 400 mPa · s. The polyvinyl alcohol film for optics according to any one of claims 1 to 6, wherein the saponification degree of the polyvinyl alcohol resin (B) is 90 mol% or more. The optical polyvinyl alcohol film according to any one of claims 1 to 5, wherein the viscosity of a 4% by weight aqueous solution of the polyvinyl alcohol resin (B) is 8 to 500 mPa · s. The optical polyvinyl alcohol film according to any one of claims 1 to 6, wherein a difference in the degree of saponification between the polyvinyl alcohol resin (A) and the polyvinyl alcohol resin (B) is 6 mol% or less. The optical polyvinyl alcohol film according to any one of claims 1 to 7, further comprising a plasticizer (C). Furthermore, surfactant (D) is contained, The polyvinyl alcohol film for optics in any one of Claims 1-8 characterized by the above-mentioned. The optical polyvinyl alcohol film according to any one of claims 1 to 9, wherein the film width is 2 m or more. The optical polyvinyl alcohol film according to claim 1, wherein the film has a thickness of 30 to 70 μm. The optical polyvinyl alcohol film according to any one of claims 1 to 11, wherein the optical polyvinyl alcohol film is used as a raw film of a polarizing film. A polarizing film comprising the polyvinyl alcohol film for optics according to any one of claims 1 to 12. A polarizing plate comprising a protective film on at least one surface of the polarizing film according to claim 13.