JP5975728B2 - Polyvinyl alcohol resin film material, method for producing polyvinyl alcohol resin film material, method for producing polarizing film, and method for producing polarizing film with protective film - Google Patents

Description

  The present invention relates to a polyvinyl alcohol resin film material used for obtaining a polyvinyl alcohol resin film for forming a polarizing film, and a method for producing the polyvinyl alcohol resin film material. Moreover, this invention relates to the polarizing film using this polyvinyl alcohol resin film material, the manufacturing method of a polarizing film, and a polarizing film with a protective film.

  Conventionally, in a liquid crystal display device or the like, a polarizing film formed of a polyvinyl alcohol (hereinafter sometimes referred to as PVA) resin film has been widely used.

  When manufacturing a polarizing film using a PVA resin film, for example, a PVA resin film is uniaxially stretched and then dyed. Thereafter, fixing treatment is performed with a boron compound or the like. Alternatively, the PVA resin film is dyed and then uniaxially stretched, and then fixed with a boron compound or the like.

  Patent Document 1 below discloses a polarizing film using a PVA resin film and a method for producing the same. In Patent Document 1, the film width is 2 m or more, the retardation difference between two points 1 cm apart in the width direction is 5 nm or less, and the retardation difference between two points 1 m apart in the width direction is 50 nm or less. Certain PVA resin films are described.

  In addition, excellent polarizing performance is strongly demanded for polarizing films. Patent Document 1 describes that the degree of saponification of PVA is preferably 95 mol% or more, and most preferably 99.5 mol% or more from the viewpoint of polarization performance and durability.

  Patent Document 2 below describes a polarizing plate obtained by applying PVA on a support film to form a PVA layer, stretching the PVA layer together with the support film, and dyeing it, and a method for producing the same. Patent Document 2 describes that a completely saponified PVA having a saponification degree of 98.0 to 99.9 mol% and a polymerization degree of 1700 to 2600 is used. The PVA layer is formed by applying and drying a solution in which the PVA is dissolved in water.

Japanese Patent No. 3422759 JP 2000-338329 A

  When the polarizing film formed using the conventional PVA resin film as described in Patent Documents 1 and 2 is bonded to the bonding target, the adhesion between the polarizing film and the bonding target may be low. In particular, when a polarizing film is obtained by bonding a polarizing film to a triacetyl cellulose (hereinafter sometimes referred to as TAC) film, the adhesiveness between the polarizing film and the TAC film tends to be low. Moreover, if the polarizing film and the bonding target are exposed to high humidity after bonding, the polarizing film is likely to swell. As a result, the obtained liquid crystal display device has problems such as uneven optical characteristics and a decrease in the degree of polarization. In particular, when the screen size of the liquid crystal display device is large, light leakage tends to occur around the panel.

  An object of the present invention is to produce a polyvinyl alcohol resin film material and a polyvinyl alcohol resin film material that can obtain a polarizing film that can be adhered to an object to be bonded with high adhesion and that can suppress swelling of the polarizing film under high humidity. And a polarizing film using the polyvinyl alcohol resin film material, a method for producing the polarizing film, and a polarizing film with a protective film.

  According to a wide aspect of the present invention, there is provided a polyvinyl alcohol resin film material used for obtaining a polyvinyl alcohol resin film for forming a polarizing film, comprising a plurality of polyvinyl alcohols having different saponification degrees, wherein the polyvinyl alcohol is And a first polyvinyl alcohol having a saponification degree of 97 mol% or more and a second polyvinyl alcohol having a saponification degree of less than 97 mol%, and the average saponification degree of the whole polyvinyl alcohol is 93 mol%. A polyvinyl alcohol resin film material is provided.

  It is preferable that the average saponification degree in the whole polyvinyl alcohol is 98.5 mol% or less. The absolute value of the difference between the saponification degree of the first polyvinyl alcohol and the saponification degree of the second polyvinyl alcohol is preferably 10 mol% or less. The absolute value of the difference between the saponification degree of the first polyvinyl alcohol and the saponification degree of the second polyvinyl alcohol is preferably 1 mol% or more.

  In a specific aspect of the polyvinyl alcohol resin film material according to the present invention, the polyvinyl alcohol resin film material further includes a solvent.

  On the specific situation with the polyvinyl alcohol resin film material which concerns on this invention, the said polarizing film is a polarizing film adhere | attached and used for a protective film. The protective film is preferably a cellulose acylate film.

  According to a wide aspect of the present invention, there is provided a method for producing the polyvinyl alcohol resin film material described above, comprising a step of blending a plurality of polyvinyl alcohols having different saponification degrees, wherein the polyvinyl alcohol has a saponification degree of 97 mol% or more. And a second polyvinyl alcohol having a saponification degree of less than 97 mol%, and a polyvinyl alcohol resin film material having an average saponification degree of more than 93 mol% in the whole polyvinyl alcohol is obtained. A method for producing a polyvinyl alcohol resin film material is provided.

  According to the wide aspect of this invention, the polarizing film obtained by dyeing | staining and extending | stretching the polyvinyl alcohol resin film which made the polyvinyl alcohol resin film material the film form mentioned above is provided.

  According to a wide aspect of the present invention, the above-mentioned polyvinyl alcohol resin film material is formed into a film to obtain a polyvinyl alcohol resin film, a dyeing step for dyeing the polyvinyl alcohol resin film, and the polyvinyl alcohol resin film. The manufacturing method of a polarizing film provided with the extending | stretching process of extending | stretching is provided.

  On the specific situation with the manufacturing method of the polarizing film which concerns on this invention, the manufacturing method of this polarizing film is further equipped with the fixing process which performs a fixing process using a boron compound.

  On the specific situation with the manufacturing method of the polarizing film which concerns on this invention, in the said film-forming process, the said polyvinyl alcohol resin film is obtained by pouring the said polyvinyl alcohol resin film material on a support member, and drying.

  On the specific situation with the manufacturing method of the polarizing film which concerns on this invention, in the said dyeing | staining process, the said polyvinyl alcohol resin film is dye | stained in the state which laminated | stacked the said polyvinyl alcohol resin film on the said supporting member.

  On the specific situation with the manufacturing method of the polarizing film which concerns on this invention, the said extending process is performed after the said dyeing process.

  According to a wide aspect of the present invention, a protection comprising a polarizing film obtained by dyeing and stretching a polyvinyl alcohol resin film obtained by forming a polyvinyl alcohol resin film material into a film, and a protective film bonded to the polarizing film, A polarizing film with a film is provided. The protective film is preferably a cellulose acylate film.

  The polyvinyl alcohol resin film material according to the present invention includes a plurality of polyvinyl alcohols having different saponification degrees, and the polyvinyl alcohol is a first polyvinyl alcohol having a saponification degree of 97 mol% or more and a saponification degree of less than 97 mol%. Since the average saponification degree in the whole said polyvinyl alcohol is 93 mol% or more, the polarizing film which can be adhere | attached with high adhesiveness can be obtained. Moreover, swelling of the polarizing film under high humidity can be suppressed.

  In the polarizing film and the manufacturing method of the polarizing film according to the present invention, since the above-described polyvinyl alcohol resin film material is used, it can be bonded to an object to be bonded with high adhesiveness. Moreover, swelling of the polarizing film under high humidity can be suppressed.

  Details of the present invention will be described below.

(Polyvinyl alcohol resin film material)
The polyvinyl alcohol (hereinafter sometimes referred to as PVA) resin film material according to the present invention is used to obtain a PVA resin film. The PVA resin film is used for forming a polarizing film. The PVA resin film material according to the present invention includes PVA. The PVA includes a plurality of PVA having different degrees of saponification. The PVA contains a first PVA having a saponification degree of 97 mol% or more and a second PVA having a saponification degree of less than 97 mol%. The average saponification degree in the whole PVA exceeds 93 mol%.

  The manufacturing method of the PVA resin film material which concerns on this invention comprises the process of mix | blending several PVA from which a saponification degree differs. In the method for producing a PVA resin film material according to the present invention, the PVA contains a first PVA having a saponification degree of 97 mol% or more and a second PVA having a saponification degree of less than 97 mol%. In the method for producing a PVA resin film material according to the present invention, a PVA resin film material having an average saponification degree exceeding 93 mol% in the whole PVA is obtained.

  By adopting the above-described configuration in the PVA resin film material according to the present invention and the method for producing the PVA resin film material according to the present invention, a polarizing film that can be bonded to an object to be bonded with high adhesion can be obtained. For example, the polarizing film can be bonded to the protective film with high adhesiveness. Moreover, swelling of the polarizing film under high humidity can be suppressed. As a result, in the obtained liquid crystal display device, unevenness in optical characteristics hardly occurs, and the degree of polarization hardly decreases. Therefore, even if the screen size of the liquid crystal display device is large, it is possible to suppress light leakage around the panel.

  The present inventor said that the PVA resin film material includes a plurality of PVA having different saponification degrees, and the PVA has a saponification degree of less than 97 mol% with the first PVA having a saponification degree of 97 mol% or more. By containing the second PVA and the average saponification degree of the whole PVA exceeds 93 mol%, a polarizing film that can be bonded with high adhesion to the object to be bonded can be obtained and bonded to the object to be bonded. It was found that the swelling of the polarizing film under high humidity can be suppressed in such a state.

  When a PVA having a saponification degree of 98 mol% or less is used alone, particularly when a PVA having a saponification degree of less than 97 mol% is used alone, the adhesiveness between the polarizing film and the object to be bonded is low. Tend to be lower. On the other hand, in the present invention, despite the use of PVA having a saponification degree of less than 97 mol%, the adhesion between the polarizing film and the bonding object is sufficiently high.

  In the PVA resin film material according to the present invention, the polarizing film is preferably a polarizing film that is used by being bonded to a protective film. The protective film is preferably a cellulose acylate film. The protective film is particularly preferably a triacetylcellulose (hereinafter sometimes referred to as TAC) film. When a polarizing film is produced using the PVA resin film according to the present invention, the polarizing film can be satisfactorily bonded to a protective film such as a cellulose acylate film, and is adhered to the cellulose acylate film. The swelling of the polarizing film under high humidity can be suppressed. In addition, when a polarizing film is produced using the PVA resin film according to the present invention, the polarizing film can be satisfactorily adhered to the TAC film, and is adhered to the TAC film under high humidity. Swelling of the polarizing film can be sufficiently suppressed.

  Hereinafter, the detail of each component used for the PVA resin film material which concerns on this invention is demonstrated.

(Polyvinyl alcohol (PVA))
The PVA contains a first PVA having a saponification degree of 97 mol% or more and a second PVA having a saponification degree of less than 97 mol%.

  The PVA can be obtained by polymerizing a vinyl ester to obtain a polymer according to a conventionally known method, and then saponifying, ie, hydrolyzing the polymer. In general, alkali or acid is used for saponification. An alkali is preferably used for saponification.

  Examples of the vinyl ester include vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatate, vinyl laurate, vinyl stearate and vinyl benzoate.

  The method for polymerizing the vinyl ester is not particularly limited. Examples of the polymerization method include a solution polymerization method, a bulk polymerization method, and a suspension polymerization method.

  Examples of the polymerization catalyst used when polymerizing the vinyl ester include 2-ethylhexyl peroxydicarbonate (“TrigonoxEHP” manufactured by Tianjin McEIT), 2,2′-azobisisobutyronitrile (AIBN), t-butyl. Peroxyneodecanoate, bis (4-t-butylcyclohexyl) peroxydicarbonate, di-n-propylperoxydicarbonate, di-n-butylperoxydicarbonate, di-cetylperoxydicarbonate and di-s-butylperoxy Examples include dicarbonate. As for the said polymerization catalyst, only 1 type may be used and 2 or more types may be used together.

  The polymer obtained by polymerizing the vinyl ester is preferably a polyvinyl ester. The polymer obtained by polymerizing the vinyl ester may be a copolymer of the vinyl ester and another monomer. That is, the PVA may be formed using a copolymer of a vinyl ester and another monomer. Examples of the other monomers, that is, comonomers to be copolymerized, include olefins, (meth) acrylic acid and salts thereof, (meth) acrylic acid esters, (meth) acrylamide derivatives, N-vinylamides, vinyl ethers, and nitriles. , Vinyl halides, allyl compounds, maleic acid and salts thereof, maleic acid esters, itaconic acid and salts thereof, itaconic acid esters, vinylsilyl compounds, and isopropynyl acetate. As for the other monomer, only one kind may be used, or two or more kinds may be used in combination.

  Examples of the olefins include ethylene, propylene, 1-butene and isobutene. Examples of the (meth) acrylic acid esters include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, and (meth) acrylic acid n-. Examples include butyl and 2-ethylhexyl (meth) acrylate. Examples of the (meth) acrylamide derivative include acrylamide, n-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, and (meth) acrylamidepropanesulfonic acid and salts thereof. Examples of the N-vinyl amides include N-vinyl pyrrolidone. Examples of the vinyl ethers include methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, and n-butyl vinyl ether. Examples of the nitriles include (meth) acrylonitrile. Examples of the vinyl halides include vinyl chloride and vinylidene chloride. Examples of the allyl compound include allyl acetate and allyl chloride. Examples of the vinylsilyl compound include vinyltrimethoxysilane.

  When the PVA and the other monomer are copolymerized to obtain a modified PVA, the modification amount is preferably 15 mol% or less, more preferably 5 mol% or less. That is, in the total 100 mol% of the structural unit derived from the vinyl ester in the modified PVA and the structural unit derived from the other monomer, the structural unit derived from the vinyl ester is preferably 85 mol% or more, more preferably 95 mol. %, And the structural unit derived from the other monomer is preferably 15 mol% or less, more preferably 5 mol% or less. In this specification, modified polyvinyl alcohol (modified PVA) is included in polyvinyl alcohol (PVA).

  The average saponification degree in the whole PVA exceeds 93 mol%. From the viewpoint of further improving the adhesion of the polarizing film to the object to be bonded and further suppressing the swelling of the polarizing film under high humidity, the average saponification degree of the whole PVA is preferably 93.5 mol% or more. More preferably 94 mol% or more, still more preferably 95 mol% or more, preferably 99.9 mol% or less, more preferably 98.5 mol% or less, still more preferably less than 98.5 mol%, particularly preferably 98. It is less than mol%, most preferably less than 98 mol%. When the average saponification degree is not less than the above lower limit and not more than the above upper limit, the adhesion of the polarizing film to the object to be bonded is further enhanced, the swelling of the polarizing film under high humidity is further suppressed, and the polarizing film is stuck. The entrapment of bubbles during application is further suppressed, and the uniformity of the entire polarizing film is further enhanced. Moreover, the polarizing performance of a polarizing film becomes it still higher that the said average saponification degree is more than the said minimum. When the degree of saponification is not more than the above upper limit, dyeing can be performed in a short time, and the productivity of the polarizing film is further increased.

The average saponification degree is measured as follows. DMSO is used so that a plurality of PVA (first and second PVA, etc.) contained in the PVA resin film material have a weight ratio in the PVA resin film material and the concentration of the entire PVA is 3% by weight. In addition to -d6 (dimethyl sulfoxide-d6), it is heated at 80 ° C. for 90 minutes to obtain a DMSO-d6 solution containing 3% by weight of PVA. As a standard substance, 0.1 part by weight of tetramethylsilane is added to 100 parts by weight of the DMSO-d6 solution, and ¹ H-NMR measurement is performed at 25 ° C. The average saponification degree in the whole PVA is calculated from the integration ratio of peaks derived from acetyl groups with respect to the main chain.

  The saponification degree of the first PVA (referred to as saponification degree as distinguished from the average saponification degree) is 97 mol% or more. From the viewpoint of further improving the adhesion of the polarizing film to the object to be bonded and further suppressing the swelling of the polarizing film under high humidity, the saponification degree of the first PVA is preferably 99.9 mol% or less. More preferably, it is 99.5 mol% or less.

  The saponification degree of the second PVA (referred to as saponification degree as distinguished from the average saponification degree) is less than 97 mol%. From the viewpoint of further improving the adhesion of the polarizing film to the object to be bonded and further suppressing the swelling of the polarizing film under high humidity, the saponification degree of the second PVA is preferably 80 mol% or more, more Preferably it is 85 mol% or more, More preferably, it is 90 mol% or more.

  The saponification degree is measured according to JIS K6726. The saponification degree indicates the proportion of units that are actually saponified to vinyl alcohol units among the units converted to vinyl alcohol units by saponification.

  The method for adjusting the saponification degree is not particularly limited. The degree of saponification can be appropriately adjusted according to the saponification conditions, that is, the hydrolysis conditions.

  The absolute value of the difference between the saponification degree of the first PVA and the saponification degree of the second PVA is preferably 10 mol% or less, more preferably 8 mol% or less, still more preferably 6 mol% or less, Most preferably, it is 5.5 mol% or less. When the absolute value of the difference is not more than the above upper limit, the adhesiveness of the polarizing film to the adhesion target is further increased, the swelling of the polarizing film under high humidity is further suppressed, and the polarizing film to the adhesion target is The adhesiveness is further increased, and the swelling of the polarizing film under high humidity is further suppressed.

  The absolute value of the difference between the saponification degree of the first PVA and the saponification degree of the second PVA is more than 0 mol%, preferably 0.1 mol% or more, more preferably 0.5 mol%. As mentioned above, More preferably, it is 1 mol% or more. When the absolute value of the difference is not less than the above lower limit, the adhesive property of the polarizing film to the adhesion target is further increased, the swelling of the polarizing film under high humidity is further suppressed, and the polarizing film to the adhesion target The adhesiveness is further increased, and the swelling of the polarizing film under high humidity is further suppressed.

  The average degree of polymerization in the whole PVA is preferably 2000 or more, and preferably 3500 or less. From the viewpoint of suppressing the entrapment of bubbles at the time of attaching the polarizing film and further improving the uniformity of the entire polarizing film, the average degree of polymerization of the entire PVA is more preferably 2500 or more, and further preferably 2600 or more. Especially preferably, it is 2700 or more, More preferably, it is 3000 or less, More preferably, it is 2900 or less. Further, when the average degree of polymerization is not less than the above lower limit, dissolution of the PVA resin film is suppressed during the dyeing step, and the optical properties of the polarizing film are further improved. When the average degree of polymerization is less than or equal to the above upper limit, partial gelation is less likely to occur in the immobilization process, the coating property of the PVA resin film material is increased, and air bubbles are trapped when the PVA resin film is applied. It becomes difficult, the thickness of the PVA resin film tends to be uniform, and the optical properties of the polarizing film are further improved.

  The average degree of polymerization is measured as follows. A plurality of PVA contained in the PVA resin film material is added to water so that the concentration of the whole PVA is 1% by weight in the PVA resin film material, and heated at 95 ° C. for 2 hours. Thus, an aqueous solution of 1% by weight of PVA is obtained. Using the obtained aqueous solution, the degree of polymerization is measured according to JIS K6726, and the obtained degree of polymerization is defined as the average degree of polymerization.

  The degree of polymerization (referred to as the degree of polymerization in distinction from the average degree of polymerization) of each of the plurality of PVAs (such as the first and second PVAs) contained in the whole PVA is not particularly limited. The degree of polymerization of the PVA is preferably 1000 or more, more preferably 1500 or more, still more preferably 1800 or more, particularly preferably 2000 or more, preferably 4000 or less, more preferably 3500 or less, and still more preferably 3000 or less. The polymerization degree of the PVA is more preferably 2500 or more, further preferably 2600 or more, particularly preferably 2700 or more, more preferably 3000 or less, and further preferably 2900 or less. When the polymerization degree is not less than the above lower limit, dissolution of the PVA resin film is suppressed during the dyeing step, and the optical properties of the polarizing film are further improved. When the degree of polymerization is less than or equal to the above upper limit, partial gelation is less likely to occur in the immobilization step, the coating property of the PVA resin film material is increased, and bubbles are less likely to be encapsulated during the application of the PVA resin film. Thus, the thickness of the PVA resin film tends to be uniform, and the optical properties of the polarizing film are further improved. The degree of polymerization is measured according to JIS K6726.

  From the viewpoint of further improving the moisture resistance of the PVA resin film, the degree of polymerization of the plurality of PVA (first and second PVA, etc.) contained in the whole PVA is preferably 2000 or more, more preferably Is 2500 or more, more preferably 2700 or more, and preferably 3000 or less. When the degree of polymerization is within this range, the PVA resin film is not easily deformed even when the PVA resin film is exposed to a high humidity environment. For this reason, it is possible to obtain a PVA resin film suitable for processing and use in a high humidity environment.

  The absolute value of the difference between the degree of polymerization of the first PVA and the degree of polymerization of the second PVA is preferably 2000 or less, more preferably 1000 or less, and even more preferably 300 or less. When the absolute value of the difference is not more than the above upper limit, the entrapment of bubbles at the time of attaching the polarizing film is further suppressed, and the uniformity of the entire polarizing film is further enhanced.

  The total content of the first PVA and the second PVA is preferably 20% by weight or more, more preferably 30% by weight or more, still more preferably 40% by weight or more, in 100% by weight of the whole PVA. Especially preferably, it is 50 to 100 weight%. When the total content is not less than the above lower limit and not more than the above upper limit, the adhesiveness of the polarizing film to the object to be bonded is further enhanced. Only two types of the first PVA and the second PVA may be used. Other PVA may be used together with the first PVA and the second PVA. However, when other PVA is used, the average saponification degree of the entire PVA is set to satisfy a predetermined range.

  The PVA resin film material preferably contains the first PVA and the second PVA in a weight ratio of 1:99 to 99: 1, more preferably 5:95 to 95: 5. More preferably, it is included at 10:90 to 90:10, particularly preferably 20:80 to 80:20, and particularly preferably 30:70 to 70:30. When the content of the first PVA is increased, the adhesion between the protective film and the object to be bonded is further increased. When the content of the second PVA is increased, the average degree of saponification is easily controlled, partial gelation is less likely to occur in the immobilization process, and the coating property of the PVA resin film material is increased. Bubbles are less likely to be encapsulated during film coating, the PVA resin film is likely to have a uniform thickness, and the optical properties of the polarizing film are further improved.

  When the PVA resin film material contains a solvent, the total content of the PVA is preferably 1% by weight or more, more preferably 5% by weight or more, preferably 100% by weight in total of the whole PVA and the solvent. It is 65% by weight or less, more preferably 55% by weight or less. When the content of the entire PVA is not less than the above lower limit, the drying time is further shortened, and a PVA resin film with better quality can be obtained. When the content of the entire PVA is less than or equal to the above upper limit, the fluentness of the PVA resin film material becomes easy.

(Preservative)
When producing a PVA resin film using PVA, generally, PVA is dissolved in a solvent. Conventionally, a preservative has not been blended in a solution containing PVA and a solvent. Conventionally, it is publicly known that preservatives suppress corrosion itself, but in the solution containing PVA and a solvent for obtaining a PVA resin film for forming a polarizing film, no preservative is added. It was not done. For this reason, if the solution containing the conventional PVA and the solvent is stored for a long period of time or exposed to a high temperature condition or a high humidity condition, there is a problem that the solution is corroded. As a result, a good polarizing film could not be obtained, or the quality of the plurality of polarizing films was likely to vary.

  On the other hand, the corrosion of PVA resin film material can be effectively suppressed by mix | blending PVA and antiseptic | preservative. Furthermore, a favorable and homogeneous PVA resin film and polarizing film can be obtained.

  Examples of the preservative include isothiazolone compounds, glutaraldehyde, and quaternary ammonium compounds. Other preservatives may be used. As for the said preservative, only 1 type may be used and 2 or more types may be used together.

  Since corrosion is more effectively suppressed, the preservative is preferably a compound having a heterocyclic ring. Since the corrosion is further effectively suppressed, the heterocyclic ring preferably contains a nitrogen atom and a sulfur atom in the ring.

  Since the corrosion is further effectively suppressed, the preservative is preferably an isothiazolone compound. Examples of the isothiazolone compounds include 2-methyl-4-isothiazolin-3-one, 2-octyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one, and 5-chloro- Examples include 3-methylisothiazol-3-one and 2-methylisothiazol-3-one. Examples of the quaternary ammonium compound include benzyldecyldimethylammonium chloride, didecyldimethylammonium chloride, and cetylpyridinium chloride.

  In the PVA resin film material, the content of the preservative is preferably 0.03 parts by weight or more, more preferably 0.1 parts by weight or more, preferably 1 part by weight or less with respect to 100 parts by weight of the whole PVA. More preferably, it is 0.3 parts by weight or less. When the content of the entire PVA is not less than the above lower limit and not more than the above upper limit, the corrosion of the PVA resin film material is further suppressed, and a more favorable and uniform polarizing film is obtained.

(solvent)
The PVA resin film material preferably contains a solvent. When the PVA resin film material does not contain a solvent, the PVA resin film material is preferably used with a solvent added. A material containing PVA and a solvent has a problem that corrosion is more likely to occur. In contrast, when the PVA resin film material contains a preservative, even if the PVA resin film contains a solvent, corrosion is effectively suppressed.

  In addition, since the PVA resin film material contains a solvent, the PVA resin film material can be poured on the support member and dried to obtain a PVA resin film.

  The solvent is preferably capable of dissolving PVA. Examples of the solvent include water and organic solvents. As for the said solvent, only 1 type may be used and 2 or more types may be used together.

  Examples of the organic solvent include dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, ethylenediamine, diethylenetriamine, and diglycerin. Etc.

  Since the solubility of the PVA is excellent, the solvent preferably contains water, glycerin or dimethyl sulfoxide. The solvent preferably contains water, preferably contains glycerin, and preferably contains dimethyl sulfoxide. Since the solubility of the PVA is excellent, the solvent is particularly preferably water, a mixed solvent of water and glycerin, or dimethyl sulfoxide.

  The solvent preferably contains a polyhydric alcohol. The polyhydric alcohol also acts as a plasticizer and enhances the stretchability of the PVA resin film material. Examples of the polyhydric alcohol include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, and triethylene glycol. From the viewpoint of further improving the stretchability of the PVA resin film material, the polyhydric alcohol is preferably diglycerin, ethylene glycol or glycerin. The polyhydric alcohol preferably contains diglycerin, preferably contains ethylene glycol, and preferably contains glycerin.

  When the PVA resin film material contains a solvent, the content of the solvent is preferably 10% by weight or more, more preferably 35% by weight or more, and still more preferably, in a total of 100% by weight of the whole PVA and the solvent. It is 45% by weight or more, preferably 99% by weight or less, more preferably 95% by weight or less, and still more preferably 90% by weight or less. When the content of the solvent is equal to or more than the above lower limit, the PVA resin film material can be easily fluent. When the content of the solvent is not more than the above upper limit, the drying time is further shortened, and a PVA resin film with better quality can be obtained.

  In the PVA resin film material, the content of the polyhydric alcohol is preferably 0.1 parts by weight or more, more preferably 1 part by weight or more, preferably 100 parts by weight or less, with respect to 100 parts by weight of the whole PVA. The amount is preferably 25 parts by weight or less. When the content of the polyhydric alcohol is not less than the above lower limit, dyeability and stretchability are further improved. When the content of the polyhydric alcohol is not more than the above upper limit, the flexibility of the PVA resin film becomes appropriate, and the handleability of the PVA resin film in the dyeing process and the stretching process is further enhanced.

(Other ingredients)
The PVA resin film material preferably contains a surfactant. The surfactant imparts a defoaming effect to the PVA resin film material. For this reason, the use of a surfactant provides a good PVA resin film in which the inclusion of bubbles is suppressed. As for the said surfactant, only 1 type may be used and 2 or more types may be used together.

  The surfactant is not particularly limited. Examples of the surfactant include an anionic surfactant and a cationic surfactant. From the viewpoint of more effectively obtaining the defoaming effect, the surfactant is preferably an anionic surfactant or a cationic surfactant. The surfactant is preferably an anionic surfactant and is preferably a cationic surfactant.

(Polarizing film, polarizing film manufacturing method and polarizing film with protective film)
The polarizing film which concerns on this invention is obtained by dyeing | staining and extending | stretching the polyvinyl alcohol resin film which made the polyvinyl alcohol resin film material mentioned above into a film form.

  The manufacturing method of the polarizing film which concerns on this invention makes the polyvinyl alcohol resin film material into a film form, the film-forming process which obtains a polyvinyl alcohol resin film, the dyeing | staining process which dye | stains the said polyvinyl alcohol resin film, and the said polyvinyl alcohol A stretching step of stretching the resin film. The stretching step may be performed before the dyeing step, may be performed at the time of the dyeing step, or may be performed after the dyeing step. The stretching process may be performed before the dyeing process or at the time of the dyeing process, or may be performed at the time of the dyeing process or after the dyeing process.

  In the manufacturing method of the polarizing film which concerns on this invention, it is preferable to further provide the fixing process which performs a fixing process. In the immobilization step, it is preferable to use a boron compound. The immobilization process may be performed during the stretching process after the dyeing process, or may be performed after the dyeing process and the stretching process.

  When a PVA resin film is obtained using the PVA resin film material, a method of forming the PVA into a film by an appropriate method is used. A method in which a PVA resin film material containing PVA and a solvent is cast on a support member and dried is preferably used.

  The support member is preferably a support film. The support member is preferably capable of supporting the PVA resin film while maintaining the PVA resin film material on the surface when the PVA resin film material is cast. Examples of the material for the support member include polyolefin, polyethylene terephthalate, acrylic resin, and the like. Examples of the polyolefin include ethylene and polypropylene.

  From the viewpoint of making the thickness suitable for the polarizing film, the thickness of the PVA resin film is a thickness after stretching, and is preferably 10 μm or more, and preferably 200 μm or less.

  An appropriate method can be used as a drying method after casting the PVA resin film on the support member, and it is not particularly limited. Examples of the drying method include a method of natural drying and a method of heat drying at a temperature lower than the glass transition temperature of PVA.

  In order to dye the PVA resin film, an appropriate dye is used. Examples of the dye include iodine-potassium iodide, direct black 17, 19, 154, direct brown 44, 106, 195, 210, 223, direct red 2, 23, 28, 31, 37, 39, 79, 81, 210, 242,247, Direct Blue 1,15,22,78,90,108,151,158,202,236,249,270, Direct Violet 9,12,51,98, Direct Green 1,85, Direct Yellow 8, And dichroic dyes such as 12, 44, 86, 87 and direct orange 26, 39, 106, 107. As for the said dye, only 1 type may be used and 2 or more types may be used together.

  In the dyeing step, the PVA resin film may be immersed in a solution containing the dye. You may apply the solution containing the said dye on a PVA resin film.

  Moreover, in the method of forming a PVA resin film on a support member by casting, the PVA resin film may be peeled off from the support member to dye the PVA resin film. Moreover, you may dye | stain a PVA resin film in the state which laminated | stacked the PVA resin film on the supporting member. When dyeing | staining in the state which laminated | stacked the PVA resin film on the supporting member, it is preferable to perform an extending | stretching process before a dyeing process. When the average saponification degree of the PVA is in the range of 92 to 98.5 mol%, dyeing can be performed quickly and the production efficiency of the polarizing film can be increased.

  In the stretching step, the PVA resin film may be uniaxially stretched or stretched other than uniaxially stretched. It is preferable to uniaxially stretch the PVA resin film. Examples of the stretching method include a wet stretching method and a dry heat stretching method. When the stretching step is performed during the dyeing step, the PVA resin film may be stretched while being immersed in a solution containing the dye.

  The PVA resin film may be stretched in a state where the PVA resin film is laminated on the support member, and after the PVA resin film is peeled off from the support member, the PVA resin film may be stretched.

  When the stretching step is performed before the dyeing step, it is preferable to stretch the PVA resin film in a state where the PVA resin film is laminated on the support member. In this case, the PVA resin film is stretched more uniformly.

  When performing the said extending process after the said dyeing process, you may extend | stretch a PVA resin film in air | atmosphere.

  The stretching temperature is not particularly limited. The stretching temperature is preferably 30 ° C or higher, more preferably 50 ° C or higher, preferably 180 ° C or lower, more preferably 90 ° C or lower. When the PVA resin film is wet-stretched alone, the stretching temperature is preferably 30 ° C or higher, and preferably 90 ° C or lower. When the PVA resin film is stretched by dry heat alone, the stretching temperature is preferably 50 ° C or higher, and preferably 180 ° C or lower. Depending on the type of support member, when the PVA resin film is laminated with the PVA resin film on the support member, the temperature is higher than the temperature at which the support member is stretched, and the PVA resin film does not deteriorate or decompose. The stretching temperature is preferably set below. When the support member is applicable to wet stretching, wet stretching may be performed.

  The draw ratio is preferably 4 times or more, more preferably 5 times or more. When the draw ratio is not less than the above lower limit, the polarizing performance of the polarizing film is further enhanced. The upper limit of the draw ratio is appropriately set so that it can be drawn uniformly. The draw ratio is preferably 15 times or less, more preferably 8 times or less.

  In the fixing step, the dye is fixed to the PVA resin film. A conventionally well-known process is employable as the fixing process in the said fixing process. The fixing treatment can be performed by immersing the PVA resin film in a solution containing boron atoms. The solution containing boron atoms contains, for example, boric acid or a boron compound. The temperature in the fixing process is not particularly limited. The temperature in the fixing treatment is preferably 30 ° C. or higher, preferably 90 ° C. or lower.

  When the average saponification degree of the PVA is in the range of 92 to 98.5 mol%, the fixing treatment can be performed quickly, and the production efficiency of the polarizing film can be increased.

  As described above, it is preferable to dry after passing through the dyeing step, the stretching step, and the fixing step. This drying may be performed by natural drying. In order to increase the drying rate, it is desirable to heat and dry. In the case of drying by heating, the heating temperature is preferably 30 ° C. or higher, more preferably 50 ° C. or higher, preferably 150 ° C. or lower, more preferably 100 ° C. or lower.

  The thickness of the polarizing film is preferably 10 μm or more, and preferably 200 μm or less.

  The polarizing film with a protective film according to the present invention includes a polarizing film obtained by dyeing and stretching a polyvinyl alcohol resin film obtained by forming a polyvinyl alcohol resin film material into a film, and a protective film adhered to the polarizing film. . The polarizing film is used in various optical devices and display devices such as polarizing plates of liquid crystal display devices. The polarizing film is preferably used to obtain a polarizing plate by laminating protective films (protective films) on both sides or one side of the polarizing film. The polarizing film with a protective film is preferably a polarizing plate.

  Examples of the protective film include a cellulose acylate film, an acrylic film, and a polyester film. Of these, a cellulose acylate film is preferable. By using the PVA resin film material according to the present invention, the polarizing film can be satisfactorily adhered to the cellulose acylate film, and the swelling of the polarizing film is further suppressed under high humidity while being adhered to the cellulose acylate film. it can. Moreover, when a polarizing film is bonded to a cellulose acylate film to obtain a polarizing plate, excellent optical characteristics can be obtained, high polarization can be obtained in a wide wavelength range, and the contrast of the liquid crystal display device can be increased.

  Examples of the cellulose acylate film include a triacetyl cellulose (TAC) film and an acetic acid / cellulose butyrate (CEB) film. Of these, a triacetyl cellulose (TAC) film is preferable. By using the PVA resin film material according to the present invention, the polarizing film can be satisfactorily adhered to the TAC film, and the swelling of the polarizing film under high humidity can be suppressed while being adhered to the TAC film.

  Examples of the adhesive used for adhesion when obtaining a polarizing plate include a PVA adhesive and a urethane adhesive.

  Hereinafter, the present invention will be clarified by giving specific examples and comparative examples of the present invention. The present invention is not limited to the following examples.

  The following PVA was prepared.

PVA1 (degree of polymerization 2500, degree of saponification 99 mol%, synthesized in Synthesis Example 1 below)
(Synthesis Example 1)
In a reactor equipped with a thermometer, a stirrer, and a cooling tube, 2000 parts by weight of vinyl acetate monomer and 200 parts by weight of methanol were added, nitrogen gas was blown for 30 minutes to replace the nitrogen, and then the reactor was heated at 60 ° C. for 30 minutes. Heated. Next, 0.4 part by weight of 2,2′-azobisisobutyronitrile as a polymerization initiator was added, followed by reaction at 60 ° C. for 4 hours. After completion of the reaction time, the reaction solution was cooled. When the polymerization rate was measured after cooling, the polymerization rate was 29%. Subsequently, the operation of removing the remaining vinyl acetate monomer together with methanol under reduced pressure was performed while adding methanol to obtain a methanol solution containing 50% by weight of polyvinyl acetate. A part of this methanol solution was taken, a methanol solution of sodium hydroxide was added so that the amount of sodium hydroxide was 0.07 mol% with respect to vinyl acetate, and saponification was performed at 40 ° C. The obtained solid was pulverized, washed with methanol, and dried to obtain PVA1.

PVA2 (degree of polymerization 2530, degree of saponification 96 mol%, synthesized in Synthesis Example 2 below)
(Synthesis Example 2)
PVA2 was obtained in the same manner as in Synthesis Example 1 except that a methanol solution of sodium hydroxide was added so that the amount of sodium hydroxide was 0.035 mol% with respect to vinyl acetate during saponification.

PVA3 (degree of polymerization 2570, degree of saponification 83.5 mol%, synthesized in Synthesis Example 3 below)
(Synthesis Example 3)
During the saponification, PVA3 was obtained in the same manner as in Synthesis Example 1 except that a methanol solution of sodium hydroxide was added so that the amount of sodium hydroxide was 0.02 mol% relative to vinyl acetate.

Example 1
PVA1 (polymerization degree 2500, saponification degree 99 mol%, synthesized in Synthesis Example 1) 50 parts by weight, PVA2 (polymerization degree 2530, saponification degree 96 mol%, synthesized in Synthesis Example 2) 50 parts by weight, and glycerin 10 parts by weight And a preservative isothiazolone compound (“San-I-Back IT-20P” manufactured by Sanai Oil Co., Ltd.) 0.15 part by weight, water is added and heated at 95 ° C. for 90 minutes, resulting in a mixture concentration of 40 wt. % PVA resin film material (aqueous solution) was prepared.

  The obtained PVA resin film material was apply | coated on the polypropylene film (thickness 60 micrometers) which is a supporting member, it was made to dry, and the PVA resin film was obtained.

  The laminate in which the PVA resin film was laminated on the supporting member was uniaxially stretched at a free end in a constant temperature bath maintained at 110 ° C. at a draw ratio of 5.5 times. Next, the stretched laminate is immersed in an aqueous solution containing iodine and potassium iodide at a concentration of 0.4 g / L of iodine and 40 g / L of potassium iodide at a temperature of 30 ° C. for 120 seconds (dying time), and dyeing is performed. did. Next, a laminate obtained by laminating a PVA resin film on a supporting member in an aqueous solution containing boric acid and potassium iodide at a concentration of boric acid 60 g / L and potassium iodide 30 g / L is formed at 60 ° C. for 2 minutes. (Boric acid treatment time) Dipped. Then, it washed with water and dried and obtained the polarizing film.

  The thickness of the obtained polarizing film was 20 μm. A polarizing plate was obtained by adhering a triacetyl cellulose film having a thickness of 80 μm to this polarizing film using an aqueous PVA solution (containing 5% by weight of PVA (polymerization degree 1700, saponification degree 99.8 mol%)).

(Examples 2 and 3 and Comparative Examples 1 and 2)
Except having changed the kind and compounding quantity of PVA as shown in following Table 1, it carried out similarly to Example 1, and obtained the PVA resin film material, the polarizing film, and the polarizing plate.

(Evaluation)
(1) Average degree of saponification DMSO-d6 (dimethyl sulfoxide-d6) so that the concentration of PVA used in the PVA resin film material is 3% by weight in terms of weight ratio in the PVA resin film material. ) And heated at 80 ° C. for 90 minutes to obtain a DMSO-d6 solution containing 3% by weight of PVA. As a standard substance, 0.1 part by weight of tetramethylsilane was added to 100 parts by weight of the DMSO-d6 solution, and ¹ H-NMR measurement was performed at 25 ° C. The average saponification degree in the whole PVA was calculated from the integration ratio of peaks derived from acetyl groups with respect to the main chain.

(2) Measurement of polarization degree Polarization degree P of the obtained polarizing plate was obtained by measuring cross transmittance and parallel transmittance using a spectrophotometer UV-3101PC apparatus manufactured by Shimadzu Corporation. The degree of polarization was determined according to the following criteria. When the cross transmittance is YC and the parallel transmittance is YP, the polarization degree P is expressed by the following equation. In addition, when the adhesiveness with respect to the protective film of a polarizing film is high, a polarization degree will also become high.

Polarization degree P = {(YP−YC) / (YP + YC)} ^1/2
[Judgment criteria for degree of polarization]
○: Polarization degree is 99 or more Δ: Polarization degree is 90 or more and less than 99 ×: Polarization degree is less than 90

(3) Change in adhesiveness of polarizing film to protective film under high humidity The obtained polarizing plate was left in an environment of 85% humidity and 85 ° C. for 500 hours. The degree of polarization in the polarizing plate after standing was measured. The change in the adhesiveness of the polarizing film to the protective film under high humidity was determined according to the following criteria. In addition, when the amount of change of the polarization degree was small before and after being left, it was confirmed that the swelling of the polarizing film was suppressed after being left.

Change in polarization degree = (polarization degree in polarizing plate before leaving) − (degree of polarization in polarizing plate after leaving)
[Criteria for changes in adhesion of polarizing film to protective film under high humidity]
○: Change in polarization degree is less than 3 Δ: Change in polarization degree is 3 or more and less than 5 ×: Change in polarization degree is 5 or more

  The results are shown in Table 1 below.

Claims (15)

A polyvinyl alcohol resin film material used to obtain a polyvinyl alcohol resin film for forming a polarizing film,
Including a plurality of polyvinyl alcohols having different saponification degrees,
The polyvinyl alcohol contains a first polyvinyl alcohol having a saponification degree of 97 mol% or more and a polymerization degree of 1000 or more, and a second polyvinyl alcohol having a saponification degree of less than 97 mol% and a polymerization degree of 2000 or more. And
The absolute value of the difference between the saponification degree of the first polyvinyl alcohol and the saponification degree of the second polyvinyl alcohol is 1 mol% or more,
The polyvinyl alcohol resin film material whose average saponification degree in the whole said polyvinyl alcohol exceeds 93 mol%.   The polyvinyl alcohol resin film material according to claim 1, wherein the average saponification degree of the whole polyvinyl alcohol is 98.5 mol% or less.   The polyvinyl alcohol resin film material according to claim 1 or 2, wherein an absolute value of a difference between the saponification degree of the first polyvinyl alcohol and the saponification degree of the second polyvinyl alcohol is 10 mol% or less. The first polymerization degree of polyvinyl alcohol is on the 2000 or more, a polyvinyl alcohol resin film material according to any one of claims 1 to 3.   The polyvinyl alcohol resin film material according to any one of claims 1 to 4, further comprising a solvent.   The polyvinyl alcohol resin film material according to any one of claims 1 to 5, wherein the polarizing film is a polarizing film used by being bonded to a protective film.   The polyvinyl alcohol resin film material according to claim 6, wherein the protective film is a cellulose acylate film. It is a manufacturing method of the polyvinyl alcohol resin film material according to any one of claims 1 to 7,
Comprising a step of blending a plurality of polyvinyl alcohols having different saponification degrees,
The polyvinyl alcohol contains a first polyvinyl alcohol having a saponification degree of 97 mol% or more and a polymerization degree of 1000 or more, and a second polyvinyl alcohol having a saponification degree of less than 97 mol% and a polymerization degree of 2000 or more. And
The absolute value of the difference between the saponification degree of the first polyvinyl alcohol and the saponification degree of the second polyvinyl acetal resin is 1 mol% or more,
The manufacturing method of the polyvinyl alcohol resin film material which obtains the polyvinyl alcohol resin film material in which the average saponification degree in the said whole polyvinyl alcohol exceeds 93 mol%. Making the polyvinyl alcohol resin film material according to any one of claims 1 to 7 into a film shape, and forming a polyvinyl alcohol resin film;
A dyeing step of dyeing the polyvinyl alcohol resin film;
The manufacturing method of a polarizing film provided with the extending process which extends | stretches the said polyvinyl alcohol resin film.   The manufacturing method of the polarizing film of Claim 9 further equipped with the fixing process which performs a fixing process using a boron compound.   The manufacturing method of the polarizing film of Claim 9 or 10 which obtains the said polyvinyl alcohol resin film by pouring the said polyvinyl alcohol resin film material on a supporting member in the said film-forming process, and drying.   The manufacturing method of the polarizing film of Claim 11 which dye | stains the said polyvinyl alcohol resin film in the said dyeing process in the state which laminated | stacked the said polyvinyl alcohol resin film on the said supporting member.   The manufacturing method of the polarizing film of any one of Claims 9-12 which performs the said extending process after the said dyeing process.   The manufacturing method of a polarizing film with a protective film provided with the process of adhere | attaching a protective film on the polarizing film obtained by the manufacturing method of the polarizing film of any one of Claims 9-13.   The manufacturing method of the polarizing film with a protective film of Claim 14 whose said protective film is a cellulose acylate film.