JP4800269B2 - Polyvinyl alcohol film for polarizing film, polarizing film, and polarizing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyvinyl alcohol-based film for an optical use, used for producing polarizing film excellent in optical properties and also stretching property, and without breaking even on stretching by a high stretching magnitude so as to improve productivity. <P>SOLUTION: This polyvinyl alcohol-based film for the optical use obtained by film-forming a material for film-forming, and containing a polyvinyl alcohol-based resin is provided with that the polyvinyl alcohol-based resin consists of the polyvinyl alcohol-based resin (X) (provided that a polyvinyl alcohol-based resin (Y) is excluded) and the polyvinyl alcohol-based resin (Y) containing 1,2-diol bonds in its side chains, and has 0.01 to 0.55 ratio (y/x) of the viscosity of 4 wt.% aqueous solution (y) of the polyvinyl alcohol-based resin (Y) at 20&deg;C to the viscosity of 4 wt.% aqueous solution (x) of the polyvinyl alcohol-based resin (X) at 20&deg;C. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

The present invention relates to a polyvinyl alcohol film for polarizing film, more particularly, after having excellent optical properties, excellent in stretchability, the polarizing film be subjected to stretching at a high draw ratio in order to improve the productivity of the film is not broken The present invention relates to a polyvinyl alcohol film for use.

  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 order to improve the compounding property, that is, the polarization performance, the polarizing film is obtained by orienting the polyvinyl alcohol film, which is a raw material, with a dichroic dye such as iodine and stretching the dichroic dye. It was necessary to increase the draw ratio.

In response to such a requirement, the polarizing film obtained by improving the polyvinyl alcohol resin has, for example, a syndiotacticity of 55% or more, and an ω-hydroxy-α-olefin group, an oxyalkylene group, and an amide group. A polyvinyl alcohol film for a polarizing film made of a polyvinyl alcohol polymer containing 0.01 to 1 mol% of one or more hydrophilic functional groups selected from among them has been proposed (for example, Patent Documents). 1).
In addition, in order to improve the polarization performance in the entire visible light range, particularly in the vicinity of a wavelength of 460 nm, optical polyvinyl containing a polyvinyl alcohol resin having a 1,2-diol bond in the side chain and other polyvinyl alcohol resins. Alcohol-based films have been proposed (see, for example, Patent Document 2).

JP-A-8-201626 JP 2006-233178 A

However, in the disclosed technique of Patent Document 1, the obtained polyvinyl alcohol film can obtain a polarizing film excellent in stretchability, but the stretching temperature is limited to 20 to 40 ° C., and the substantial maximum stretching is achieved. The magnification was about 5.3 times.
Usually, from the viewpoint of improving the productivity of the polarizing film, the line speed during the production of the polarizing film is increased, but if the stretching ratio is increased to increase the stretching speed or the final line speed, the film There is a problem that the film breaks, and there is a demand for a polyvinyl alcohol film having more excellent stretchability.

  Further, in the disclosed technique of Patent Document 2, when a polyvinyl alcohol resin having a 1,2-diol bond in the side chain and another polyvinyl alcohol resin are used in combination, the viscosity of the 4 wt% aqueous solution of both is determined as the side chain. In addition, the polyvinyl alcohol resin having a 1,2-diol bond is larger than the other polyvinyl alcohol resins, which is still not satisfactory in terms of optical properties.

Therefore, in the present invention, under such a background, the polyvinyl alcohol film for a polarizing film is excellent in optical characteristics, excellent in stretchability, and does not break even when stretched at a high stretch ratio to improve productivity. And a polarizing film and a polarizing plate using the same.

However, as a result of intensive studies by the present inventors to solve the above problems, in a polyvinyl alcohol film for a polarizing film formed by forming a film forming material containing a polyvinyl alcohol resin, , Polyvinyl alcohol resin (X) (except for polyvinyl alcohol resin (Y) described later) and polyvinyl alcohol resin (Y) containing a 1,2-diol bond in the side chain, By making the molecular weight of the alcohol resin (Y) smaller than the molecular weight of the polyvinyl alcohol resin (X), it is excellent in optical properties, stretchable, and stretched at a high stretch ratio to improve productivity. It found that a polarizing film for polyvinyl alcohol-based film also film is not broken is obtained, the onset It was completed.

That is, the gist of the present invention is that a polyvinyl alcohol-based film for a polarizing film obtained by forming a film-forming material containing a polyvinyl alcohol-based resin, wherein the polyvinyl alcohol-based resin is a polyvinyl alcohol-based resin (X) (provided that And a polyvinyl alcohol resin (Y) containing a 1,2-diol bond in the side chain, and 4 of the polyvinyl alcohol resin (Y) at 20 ° C. the ratio of the weight% aqueous solution viscosity (y) and polyvinyl alcohol 4 wt% aqueous solution viscosity at 20 ° C. of the resin (X) (x) (y / x) is Ri der 0.01 to 0.55, a polyvinyl alcohol resin Polyvinyl relative to the total amount of (X) and the polyvinyl alcohol resin (Y) containing a 1,2-diol bond in the side chain The content of alcohol-based resin (Y) is related to the polyvinyl alcohol film for polarizing Ru 1-50 wt% der.

The present invention also provides a polarizing film comprising the polyvinyl alcohol film for the polarizing film, and further a polarizing plate comprising a protective film on at least one surface of the polarizing film.

The polyvinyl alcohol-based film for polarizing film of the present invention is excellent in optical properties, excellent in stretchability, and has an effect that the film does not break even when stretched at a high stretch ratio to improve productivity. . Such a polyvinyl alcohol film for a polarizing film is an original film for a polarizing film, a half-wave plate or a quarter-wave plate used for a liquid crystal display device such as polarizing sunglasses or a liquid crystal television. It is very useful as an original film of a retardation film used in a liquid crystal display device.

The present invention is described in detail below.
The polyvinyl alcohol film for polarizing film of the present invention has a polyvinyl alcohol resin (X) (except for the polyvinyl alcohol resin (Y) described later) and 1,2- in the side chain as a polyvinyl alcohol resin. It is composed of a mixed polyvinyl alcohol resin with a polyvinyl alcohol resin (Y) containing a diol bond.

Conventionally, as in Patent Document 1, the viscosity of each 4 wt% aqueous solution of the polyvinyl alcohol resin (X) and the polyvinyl alcohol resin (Y) containing a 1,2-diol bond in the side chain is equivalent, Alternatively, the polyvinyl alcohol resin (Y) containing a 1,2-diol bond in the side chain tends to use a resin having a viscosity higher than that of the polyvinyl alcohol resin (X). The polyvinyl alcohol resin (Y) containing a 1,2-diol bond in the side chain is characterized by using a resin having a smaller viscosity than the polyvinyl alcohol resin (X). A film excellent in both stretchability can be obtained.

The polyvinyl alcohol resin (X) used in the present invention is not particularly limited as long as it is conventionally used as a film for a polarizing film . Usually, the average saponification degree is 90 mol% or more. Is preferably 95 mol% or more, more preferably 98 mol% or more.

  Further, the viscosity of the polyvinyl alcohol resin (X) is preferably 8 to 500 mPa · s, particularly 20 to 400 mPa · s, and more preferably 40 to 400 mPa · s, as a 4 wt% aqueous solution viscosity at 20 ° C. -S is preferable. If the 4% by weight aqueous solution viscosity is too small, the stretchability at the time of forming the polarizing film tends to be insufficient, and if too large, the flatness and transparency of the film tend to be lowered.

The polyvinyl alcohol-based resin (X) is usually unmodified polyvinyl alcohol, but in some cases, a small amount of unsaturated carboxylic acid (including salt, ester, amide, nitrile, etc.), 2 to 2 carbon atoms. It may be a polyvinyl alcohol resin containing a component copolymerizable with vinyl acetate such as 30 olefins (ethylene, propylene, n-butene, isobutene, etc.), vinyl ethers, unsaturated sulfonates and the like.
In addition, the polyvinyl alcohol-based resin (X) may be a mixture of two or more kinds having different average saponification degrees and viscosities.

  The polyvinyl alcohol resin (Y) having a 1,2-diol bond in the side chain used in the present invention is usually a polyvinyl alcohol resin containing a 1,2-diol structural unit represented by the general formula (1). Can be mentioned.

（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-based resin (Y) itself is known and is usually obtained by saponifying a copolymer of (a) a vinyl ester monomer and, for example, 3,4-diacetoxy-1-butene. Can be manufactured.
Such vinyl ester monomers are usually vinyl formate, vinyl acetate, vinyl propionate, vinyl valelate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate. , Vinyl versatate, etc., among which vinyl acetate is preferred.

  In the present invention, the copolymerization ratio of 3,4-diacetoxy-1-butene is determined in accordance with the amount of 1,2-diol bond introduced later.

  The amount of 1,2-diol bond introduced into the side chain of the polyvinyl alcohol resin (Y) is preferably 0.1 to 20 mol%, particularly preferably 0.2 to 15 mol%, and still more preferably Is 0.5 to 12 mol%, and if the amount of the bond is too small, it is difficult to obtain the effect of the present invention, whereas if the amount is too large, it tends to be difficult to produce a polyvinyl alcohol-based resin.

  In addition, the copolymer may be copolymerized in a small amount, for example, 10 mol% or less, preferably 5 mol% or less of other monomers, as long as the purpose of the present invention other than the above-described copolymer components is not impaired. It may be a

In copolymerizing the above vinyl ester monomer and 3,4-diacetoxy-1-butene (and other monomers), the same polymerization conditions and polymerization methods as those of known vinyl ester monomers should be employed. Can do.
As a polymerization method, for example, a known method such as bulk polymerization, solution polymerization, suspension polymerization, dispersion polymerization, or emulsion polymerization can be employed, but solution polymerization is usually performed.

  In addition, the charging method of 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 polyvinyl ester polymer. Drop polymerization is preferred from the viewpoint of physical properties such as uniform distribution in the molecular 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).

  In the copolymerization, a polymerization catalyst is used. Examples of the polymerization catalyst include an azo catalyst, a peroxide catalyst, a redox catalyst, and the like. Specifically, azobisisobutyronitrile, peroxide is used. Examples include known radical polymerization catalysts such as acetyl, benzoyl peroxide, and lauryl peroxide, and low-temperature active radical polymerization catalysts such as azobisdimethylvaleronitrile and azobismethoxydimethylvaleronitrile.

The amount of the 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.

  The obtained copolymer is then saponified, and this saponification reaction is basically the same as the saponification conditions of known polyvinyl alcohol resins. That is, usually, the copolymer obtained above is dissolved or dispersed in an alcohol or hydrous alcohol, and the saponification 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. Examples of saponification catalysts include alkali catalysts such as alkali metal hydroxides and alcoholates such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate, potassium methylate and lithium methylate, sulfuric acid, hydrochloric acid, Examples include acid catalysts such as 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.

  By the saponification, the ester portion of the vinyl ester monomer and the acetoxy portion of 3,4-diacetoxy-1-butene are simultaneously converted into hydroxyl groups, whereby the polyvinyl alcohol resin (Y) can be produced.

  Thus, a polyvinyl alcohol resin (Y) containing a 1,2-diol bond in the side chain is obtained. In the present invention, the average saponification degree of the polyvinyl alcohol resin (Y) is relatively high. Higher ones are preferable, usually 90 mol% or more, particularly 95 mol% or more, and more preferably 98 mol% or more. If the average degree of saponification is too low, the water resistance tends to be insufficient when forming a polarizing film. The saponification degree is preferably about the same as the saponification degree of the aforementioned polyvinyl alcohol resin (X).

  The average degree of saponification in the present invention is expressed as 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 into hydroxyl groups (ken%). In the conversion reaction, the acetoxy part of 3,4-diacetoxy-1-butene is almost completely saponified).

  The viscosity of the polyvinyl alcohol resin (Y) is usually 8 to 400 mPa · s, particularly 10 to 300 mPa · s, more preferably 10 to 150 mPa · s, as a 4 wt% aqueous solution viscosity at 20 ° C., If the 4% by weight aqueous solution viscosity is too small, the stretchability at the time of forming the polarizing film tends to be insufficient, and if too large, the flatness and transmittance of the film tend to be lowered.

  In the present invention, as the polyvinyl alcohol resin (Y), two or more kinds of polyvinyl alcohol resins different in 1,2-diol bond amount, average saponification degree, viscosity and the like may be used in combination.

  In addition, as a manufacturing method of the polyvinyl alcohol-type resin (Y) used by this invention, the method of saponifying the copolymer of the said (a) vinyl ester-type monomer and 3, 4- diacetoxy-1-butene was explained in full detail. However, without being limited to such a method, for example, (i) a method of saponifying and decarboxylating a copolymer of a vinyl ester monomer and a vinyl ethylene carbonate represented by the general formula (2), (c) vinyl A method of saponifying and deketalizing a copolymer of an ester-based monomer and a 2,2-dialkyl-4-vinyl-1,3-dioxolane represented by the general formula (3), and (d) a vinyl ester-based monomer A method of saponifying a copolymer with glycerin monoallyl ether, and the like are also exemplified and are not particularly limited.

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.

ここで、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。

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

  In the present invention, as described above, the polyvinyl alcohol resin (X) and the polyvinyl alcohol resin (Y) are used in combination as the polyvinyl alcohol resin, but the combined use improves stretchability and dyeability. To do.

  In the present invention, when the polyvinyl alcohol-based resin (X) and the polyvinyl alcohol-based resin (Y) are contained as a film forming material, the viscosity of the 4% by weight aqueous solution of the polyvinyl alcohol-based resin (Y) at 20 ° C. It is necessary to make it smaller than the 4 wt% aqueous solution viscosity of the resin (X) at 20 ° C., and the 4 wt% aqueous solution viscosity (y) of the polyvinyl alcohol resin (Y) at 20 ° C. and the polyvinyl alcohol resin (X) of 20 ° C. It is necessary that the ratio (y / x) of the 4 wt% aqueous solution viscosity (x) is 0.01 to 0.55, preferably 0.03 to 0.5, and more preferably 0.04 to 0.00. 3. If it exceeds this range, the polarizing performance will be reduced, and if it is less than the above range, the stretchability during the production of the polarizing film will be reduced.

In addition, when the polyvinyl alcohol-based resin (X) and the polyvinyl alcohol-based resin (Y) are contained as the film forming material, the polyvinyl alcohol-based resin (X) and the polyvinyl having a 1,2-diol bond in the side chain are used. the total amount of the alcohol-based resin (Y), it is preferable that the content of the polyvinyl alcohol-based resin (Y) is from 1 to 50 wt%, preferably especially in terms of stretchability and optical performance 2-40 % By weight, and more practically 3-20% by weight. If the content of the polyvinyl alcohol-based resin (Y) is too small or too large, the stretchability tends to decrease during the production of the polarizing film.

In the present invention, when the polyvinyl alcohol-based resin (X) and the polyvinyl alcohol-based resin (Y) are contained, it is preferable to satisfy the following formula (1), and it is particularly preferable to satisfy the following formula (2), Furthermore, it is preferable to satisfy the following formula (3).
0.1 ≦ Y × G / (X + Y) ≦ 1 (1)
0.2 ≦ Y × G / (X + Y) ≦ 0.8 (2)
0.3 ≦ Y × G / (X + Y) ≦ 0.7 (3)

  Here, X is the content ratio (weight ratio) of the polyvinyl alcohol resin (X) to the total amount of the polyvinyl alcohol resin (X) and the polyvinyl alcohol resin (Y), and Y is the polyvinyl alcohol resin (X). And the content ratio (weight ratio) of the polyvinyl alcohol-based resin (Y) with respect to the total amount of the polyvinyl alcohol-based resin (Y), and G represents the amount of 1,2-diol bonds (mol%) in the side chain. In the above formula (1), if it is too small, it is difficult to obtain the effect of the present invention. Conversely, if it is too large, the polarizing performance of the polarizing film tends to deteriorate.

  Moreover, in containing polyvinyl alcohol-type resin (X) and polyvinyl alcohol resin (Y), the difference of the average saponification degree of polyvinyl alcohol-type resin (X) and polyvinyl alcohol-type resin (Y) is 6 mol% or less. Is preferable from the viewpoint of transparency of the film, and particularly preferably 3 mol% or less. If the difference in average saponification degree is too large, the transmittance of the film tends to decrease.

  In the present invention, an optical polyvinyl alcohol film is produced from the above resin mixture. For film production, for example, a known compounding agent such as a plasticizer (C) or a surfactant (D) is blended. Manufacturing.

  The plasticizer (C) generally contributes effectively to stretchability when producing a polarizing film. For example, glycerins such as glycerin, diglycerin, triglycerin, ethylene glycol, diethylene glycol, triglycerin. Examples thereof include alkylene glycols or polyalkylene glycols such as ethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylin glycol and polypropylene glycol, and trimethylolpropane. These plasticizers (C) can be used alone or in combination of two or more. Among them, particularly preferred are glycerin alone, glycerin and diglycerin, or a combination of glycerin and trimethylolpropane.

The content of the plasticizer (C) is preferably 1 to 35 parts by weight, particularly 3 to 30 parts by weight, and more preferably 7 to 25 parts by weight with respect to 100 parts by weight of the total polyvinyl alcohol resin used. It is preferable that When the content of the plasticizer (C) is too small, the stretchability tends to be reduced when the polarizing film is formed, and when it is too much, the temporal stability of the obtained polyvinyl alcohol film for polarizing film tends to be lowered.

  In addition, the surfactant (D) generally has a function of suppressing film surface smoothness and adhesion between films when wound into a roll, for example, an anionic surfactant or a nonionic interface. The activity can be used singly or in combination of two or more. In particular, it is preferable to use an anionic surfactant and a nonionic surfactant in view of the transparency of the film.

  Examples of the anionic surfactant include (1) aliphatic alkyl sulfonate, (2) alkyl sulfate ester salt, (3) polyoxyethylene alkyl ether sulfate, and (4) polyoxyethylene alkyl phenyl ether sulfate. Salts, (5) higher fatty acid alkanolamide sulfates, etc. In addition to the above anionic surfactants (1) to (5), sulfated oils, higher alcohol ethoxy sulfates, monoglycolates Sulfate salts such as fatty acid soaps, N-acyl amino acids and salts thereof, polyoxyethylene alkyl ester carboxylates, carboxylate types such as acylated peptides, alkylbenzene sulfonates, alkyl naphthalene sulfonates, naphthalene sulfones Acid salt formalin polycondensate, melamine sulfonic acid salt Lumarin condensate, dialkyl sulfosuccinic acid ester salt, sulfosuccinic acid alkyl disalt, polyoxyethylene alkyl sulfosuccinic acid disalt, alkyl sulfoacetate, α-olefin sulphonate, N-acylmethyl taurate, dimethyl-5-sulphoiso Use in combination with anionic surfactants such as sulfonate salts such as sodium phthalate, phosphate esters such as polyoxyethylene alkyl ether phosphate, polyoxyethylene alkylphenyl ether phosphate, and alkyl phosphate You can also

  On the other hand, examples of the nonionic surfactant include (7) polyoxyethylene alkyl ether, (8) polyoxyethylene alkyl phenyl ether, (9) higher fatty acid mono- or dialkanol amide, higher fatty acid amide, polyoxyethylene alkyl. Amines, (12) polyoxyethylene higher fatty acid amides, (13) amine oxides, and the like. In addition to the nonionic surfactants of (7) to (13) above, ethylene oxide derivatives of alkylphenol formalin condensates , Polyoxyethylene polyoxypropylene block polymer, polyoxyethylene glycerin fatty acid ester, polyoxyethylene castor oil and hydrogenated castor oil, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, etc. Glycol ester type nonionic surfactants, polyethylene glycol fatty acid esters, sorbitan fatty acid esters, fatty acid monoglycerides, propylene glycol fatty acid esters, may be used in combination of ester type surfactants such as sucrose fatty acid esters.

  The surfactant (D) content is preferably 0.01 to 1 part by weight, particularly preferably 0.02 to 0.5 part by weight, based on 100 parts by weight of the total polyvinyl alcohol resin used. More preferably, it is 0.03 to 0.2 parts by weight. When the content of the surfactant (D) is too small, it is difficult to obtain an anti-blocking effect, and when it is too large, the transparency of the film tends to be lowered.

  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, relative to 100 parts by weight of the total polyvinyl alcohol resin used. 0.02 to 0.2 parts by weight, preferably 0.03 to 0.1 parts by weight, and nonionic surfactant is 0.01 to 1 part by weight, particularly 0.02 to 0.2 parts by weight. Parts, more preferably 0.03 to 0.1 parts by weight. If the amount of the anionic surfactant is too small, the dispersibility of the dye at the time of forming the polarizing film tends to decrease, and the dyeing spots tend to increase.If the amount is too large, foaming occurs when the polyvinyl alcohol resin is dissolved, and bubbles are generated in the film. It tends to be mixed and cannot be used as an optical film. If the nonionic surfactant is too small, it is difficult to obtain an anti-blocking effect, and if it is too much, the transparency and flatness of the film tend to be lowered.

  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 (X) and the polyvinyl alcohol resin (Y) containing a 1,2-diol bond in the side chain, preferably a plasticizer (C) and / or a surfactant. Using (D), a film-forming material is prepared, and the film-forming material is formed to obtain a polyvinyl alcohol film.

  Hereinafter, the manufacturing method of the polyvinyl alcohol-type film of this invention is demonstrated concretely. When the polyvinyl alcohol resin (X) and the polyvinyl alcohol resin (Y) are expressed together, they may be expressed as “polyvinyl alcohol resin”.

  In the present invention, the polyvinyl alcohol resin (X) and the polyvinyl alcohol resin (Y) containing a 1,2-diol bond in the side chain, preferably a plasticizer (C) and / or a surfactant (D). Is used to prepare a film-forming material, and an aqueous solution of the film-forming material is cast on a drum-type roll or an endless belt, preferably a drum-type roll, to form, dry, and heat-treat a polyvinyl alcohol 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 is too high, it tends to be difficult to obtain a desired aqueous solution concentration.

  Next, an aqueous solution of a film forming material used for forming a polyvinyl alcohol film is prepared by adding water, water-containing polyvinyl alcohol resin wet cake after dehydration, a plasticizer (C), and a surfactant (D) to the dissolution tank. Etc. are prepared, heated, stirred and dissolved. 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 too low, the load on the motor increases, and if it is too high, the polyvinyl alcohol resin tends to be hardened and cannot be uniformly dissolved. Furthermore, it is also preferable to pressurize the inside of the can when water vapor is blown and the resin temperature is normally 90 to 100 ° C., preferably 95 to 100 ° C., from the viewpoint of uniform dissolution. If the resin temperature is too low, undissolved products tend to be formed. 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 film-forming material thus obtained is usually preferably 10 to 50% by weight, more preferably 15 to 40% by weight, particularly preferably 20 to 30% by weight. If the concentration is too small, the drying load tends to be large and the production capacity tends to be inferior. If it is too large, the viscosity becomes too high and uniform dissolution becomes difficult.

  Next, the aqueous solution of the obtained film forming material 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 film forming material discharged from the multi-screw extruder is introduced into a T-type slit die by a certain amount and cast onto a drum-type roll or an endless belt to form a film, Dry and heat treated.
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-type slit die is usually 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 too low, flow failure occurs, and if it is too high, foaming tends to occur.

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.
When 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 too low, drying will be poor, and if it is too large, foaming tends to occur.

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, Usually, it is preferable that it is 60-100 degreeC, Furthermore, it is 65-90 degreeC. When the surface temperature is too low, drying is poor, and when the surface temperature is too high, the surface is excessively dried, which tends to cause poor appearance.
In the present invention, heat treatment is performed after drying.

  About heat processing, it is preferable to heat-process at the temperature of 70-150 degreeC normally, and 80-140 degreeC is especially preferable. If the heat treatment temperature is too low, the water resistance is insufficient, or heat treatment spots increase, which tends to cause optical spots. If it is too high, the stretchability during the production of the polarizing film tends to decrease. Moreover, as a heat processing method, for example, (1) The method of passing the roll (1-30 rolls) 0.2-2m in diameter which carried out the hard chrome plating process or the mirror surface process, (2) Floating type dryer (length) : 2 to 30 m).

The polyvinyl alcohol film of the present invention thus obtained has a light transmittance of 90% or more in the entire visible light region, and is very useful as a polyvinyl alcohol film for a polarizing film .
Therefore, the polyvinyl alcohol film for polarizing film of the present invention is particularly preferably used as a raw film for the polarizing film.

Hereinafter, the production method of the polarizing film described in the present invention using the polarizing film for polyvinyl alcohol-based film of the present invention.

  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 immersed in a solution of iodine or dichroic dye and dyed, and then treated with a boron compound. After stretching and dyeing are performed simultaneously, a boron compound is treated. 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.

  Stretching is preferably performed 2.5 to 10 times, preferably 2.8 to 7 times in a uniaxial direction. 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., particularly 45 to 55 ° C., and the treatment time is preferably about 3 to 20 minutes, and 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 clock, a word processor, a personal computer, a TV, 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, LCD, etc.) for reflection reduction layer, 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-diol bond amount in the side chain (mol%)
It was calculated by measuring with ¹ H-NMR (internal standard substance: tetramethylsilane, solvent: d ₆ -DMSO).

(2) Average saponification degree (mol%) of polyvinyl alcohol resin
The analysis was carried out with the alkali consumption required for hydrolysis of the residual vinyl acetate units.

(3) 4% aqueous solution viscosity of polyvinyl alcohol resin (mPa · s)
The water temperature was adjusted to 20 ° C. and measured with a Heppler viscometer.

(4) Optical properties Using a retardation measuring device ("RETS-1100A" manufactured by Otsuka Electronics Co., Ltd.), the polarization degree, transmittance and dichroic ratio of the obtained polarizing film were measured.

Example 1
In a 200-liter tank, 39.9 kg of unmodified polyvinyl alcohol resin (X) having a 4% aqueous solution viscosity of 68 mPa · s and an average saponification degree of 99.8 mol% as a polyvinyl alcohol resin, and a 4% aqueous solution viscosity of 15 mPa · s. 2.1 kg of polyvinyl alcohol resin (Y) having an average degree of saponification of 99.8 mol%, a side chain 1,2-glycol bond amount of 6 mol%, and 100 kg of water, and glycerin (C) as a plasticizer. 2 kg, 21 g of sodium dodecyl sulfonate as surfactant (D) and 8 g of polyoxyethylene dodecylamine were added, heated to 150 ° C. with stirring, dissolved uniformly, and then a film with a concentration of 26% was formed by adjusting the concentration. An aqueous solution of the material was obtained.

Next, an aqueous solution of the film forming material (liquid temperature 147 ° C.) was supplied to a twin screw extruder and defoamed. The defoamed aqueous film-forming material solution was cast from a T-shaped slit die (straight manifold die) onto a cast drum 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: 90 ° 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.

After drying, this film is subjected to heat treatment at 130 ° C. by a floating dryer (length: 18.5 m) that blows hot air from both sides, and the film is 4 m wide, 65 μm thick, and 4000 m long for polarizing film . An alcohol film was obtained.

Using the polyvinyl alcohol film for polarizing film of the present invention obtained above, a polarizing film was obtained in the following manner, and optical characteristics were evaluated. The evaluation results are shown in Table 2.

The obtained polyvinyl alcohol film for polarizing 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. / L was immersed in a boric acid treatment tank (52 ° C.) and boric acid treatment was performed for 6 minutes while uniaxially stretching 2.56 times. Thereafter, it was dried to obtain a polarizing film having a total draw ratio of 5 times.

  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 2.

Separately from this, the film was stretched under the following conditions to determine the limit stretch ratio.
The evaluation results are shown in Table 2.

(Evaluation of limit draw ratio)
The polyvinyl alcohol film was stretched 1.5 times while being immersed in a water bath with a water temperature of 30 ° C. Next, the film was stretched 1.3 times while being immersed for 240 seconds in a dyeing tank (30 ° C.) composed of 0.2 g / L of iodine and 20 g / L of potassium iodide. Furthermore, it is immersed in a boric acid treatment tank (52 ° C.) having a composition of boric acid 50 g / L and potassium iodide 50 g / L, and uniaxially stretching 40% per minute on the film before immersion in the boric acid treatment tank. The total draw ratio with respect to the raw film when it was broken was defined as the limit draw ratio, and evaluation was performed according to the following evaluation criteria.
A: Limit draw ratio 7.0 times or more B: Limit draw ratio 6.3 times or more and less than 7.0 times C: Limit draw ratio 6.0 times or more and less than 6.3 times D: Limit draw ratio 5.7 times or more Less than 6.0 times E: Limit draw ratio less than 5.7 times

Examples 2-4, Comparative Examples 1-3
Except having changed into the film forming material and film forming conditions as shown in Table 1, it carried out similarly to Example 1, the polyvinyl alcohol-type film was obtained, and also the polarizing film was obtained similarly to Example 1. FIG.
Evaluation similar to Example 1 was performed about the obtained polyvinyl alcohol-type film and polarizing film. The evaluation results are shown in Table 2.

From the results of the above Examples and Comparative Examples, for the Example products, it is possible to obtain a polarizing film having excellent optical properties at a draw ratio of 5 times the total draw ratio, and excellent stretchability. Whereas a polarizing film having a stretching ratio can be easily obtained, the comparative example product is inferior to the optical characteristics of the polarizing film when the total stretching ratio is 5 times, and further, the stretching ratio is to increase the optical characteristics. However, in Comparative Examples 2 and 3, the stretchability was poor.

The polyvinyl alcohol-based film for polarizing film of the present invention is a polyvinyl alcohol-based film for polarizing film obtained by forming a film-forming material containing a polyvinyl alcohol-based resin. A polyvinyl alcohol resin (A) containing a glycol bond and a polyvinyl alcohol resin (B) other than the polyvinyl alcohol resin (A), and a 4% by weight aqueous solution of the polyvinyl alcohol resin (A) at 20 ° C. viscosity, 1 / 3-1 / 25 der 4 wt% aqueous solution viscosity at 20 ° C. of the polyvinyl alcohol-based resin (B) is, containing a 1,2-diol-linked polyvinyl alcohol-based resin (X) and in a side chain Polyvinyl alcohol tree relative to the total amount of polyvinyl alcohol resin (Y) Content of 1-50 wt.% Der because of (Y), excellent stretchability, to produce a polarizing film can be obtained even high polarization performance, further, a high stretching ratio in order to improve the productivity It has the effect that the film does not break even when stretched, such as electronic desk calculators, electronic watches, word processors, personal computers, TVs, personal digital assistants, liquid crystal display devices such as cars and machinery instruments, sunglasses, For anti-eye glasses, stereoscopic glasses, reflection reduction layers for display elements (CRT, LCD, etc.), polarizing films used in medical equipment, building materials, toys, etc. It is very useful as an original film used for a retardation film used for a liquid crystal display device.

Claims (9)

In a polyvinyl alcohol film for a polarizing film formed by forming a film forming material containing a polyvinyl alcohol resin, the polyvinyl alcohol resin is a polyvinyl alcohol resin (X) (however, a polyvinyl alcohol resin (Y) described later) And a 4 wt% aqueous solution viscosity (y) at 20 ° C. of the polyvinyl alcohol resin (Y) containing a 1,2-diol bond in the side chain. the ratio of polyvinyl 4 wt% aqueous solution viscosity at 20 ° C. of alcohol resin (X) (x) (y / x) is Ri der from 0.01 to 0.55, a polyvinyl alcohol-based resin (X) and the side chain 1 , Polyvinyl alcohol resin (Y) with respect to the total amount of polyvinyl alcohol resin (Y) containing a 2-diol bond Polarizing a polyvinyl alcohol-based film content and wherein 1 to 50 wt% der Rukoto. Polyvinyl alcohol resins are, polarizing a polyvinyl alcohol film of claim 1 Symbol placement and satisfies the following formula (1).
0.1 ≦ Y × G / (X + Y) ≦ 1 (1)
Here, X is the content ratio (weight ratio) of the polyvinyl alcohol resin (X) to the total amount of the polyvinyl alcohol resin (X) and the polyvinyl alcohol resin (Y), and Y is the polyvinyl alcohol resin (X). And the content ratio (weight ratio) of the polyvinyl alcohol-based resin (Y) with respect to the total amount of the polyvinyl alcohol-based resin (Y), and G represents the amount of 1,2-diol bonds (mol%) in the side chain. The polyvinyl alcohol film for a polarizing film according to claim 1 or 2, wherein the 1,2-diol bond amount of the side chain of the polyvinyl alcohol resin (Y) is 0.1 to 20 mol%. The average saponification degree of the polyvinyl alcohol-based resin (Y) is 90 mol% or more, and the viscosity of a 4% by weight aqueous solution of the polyvinyl alcohol-based resin (Y) at 20 ° C. is 8 to 400 mPa · s. The polyvinyl-alcohol-type film for polarizing films in any one of Claims 1-3 . The average saponification degree of the polyvinyl alcohol resin (X) is 90 mol% or more, and the viscosity of a 4 wt% aqueous solution of the polyvinyl alcohol resin (X) at 20 ° C is 8 to 500 mPa · s. The polyvinyl-alcohol-type film for polarizing films in any one of Claims 1-4 . The polyvinyl alcohol film for a polarizing film according to any one of claims 1 to 5, wherein the difference in the average saponification degree between the polyvinyl alcohol resin (X) and the polyvinyl alcohol resin (Y) is within 6 mol%. The polyvinyl alcohol film for a polarizing film according to any one of claims 1 to 6 , wherein the film width is 2 m or more. Claim 1-7 polarizing a polyvinyl alcohol-based polarizing film comprising a film according to any one. A polarizing plate comprising a protective film on at least one surface of the polarizing film according to claim 8 .