JP4641501B2 - POLYVINYL ALCOHOL POLYMER FILM FOR POLARIZING FILM AND POLARIZING FILM - Google Patents

Description

  The present invention relates to a polyvinyl alcohol polymer film for a polarizing film, a method for producing the same, and a polarizing film produced using the polyvinyl alcohol polymer film. More specifically, the present invention provides a polarizing film that has excellent polarization performance, improved hue, and less leakage of blue light when the two polarizing films are crossed into a crossed Nicols state. The present invention relates to a polyvinyl alcohol polymer film for a polarizing film, a production method thereof, and a polarizing film produced from the polyvinyl alcohol polymer.

  Liquid crystal display devices (LCD) are used in small devices such as calculators and wristwatches in the early stages of development, and in recent years used in notebook computers, liquid crystal monitors, liquid crystal color projectors, liquid crystal televisions, in-vehicle navigation systems, mobile phones, indoors and outdoors. It is used in a wide range of measuring instruments and the like, and the screen size of liquid crystal televisions is increasing. Along with the expansion of applications, liquid crystal display devices are increasingly required to improve display quality and improve color reproducibility. A polarizing plate having a light transmission and shielding function is an important constituent member of a liquid crystal display device together with a liquid crystal having a light switching function. In addition to optical properties such as high polarization degree and high transmittance, improvement in hue is strongly demanded.

  Conventionally used polarizing plates are generally one or both sides of a polarizing film produced by subjecting a polyvinyl alcohol polymer film to uniaxial stretching, dyeing treatment with iodine or a dichroic dye, fixing treatment with a boron compound, or the like. And a protective film such as a cellulose triacetate film or an acetic acid / butyric acid cellulose film.

  The hue of the polarizing film can be adjusted to some extent by devising the dyeing method. For example, when a dichroic dye is used, since dyes having absorption wavelengths of various colors can be used, two or more dichroic dyes, usually about three to four dichroic dyes are used. The hue of the polarizing film can be adjusted to a neutral gray state (for example, see Patent Documents 1 and 2), thereby preventing a phenomenon that light of a specific wavelength leaks. However, a polarizing film dyed with a dichroic dye has a low dichroic ratio, and therefore has low contrast, insufficient light transmittance and degree of polarization, and is not used in ordinary liquid crystal displays.

On the other hand, a polarizing film dyed with iodine has a high light transmittance and degree of polarization, a high dichroic ratio, and a high contrast compared to a polarizing film dyed with a dichroic dye. In producing a polarizing plate for use, a polarizing film dyed with iodine is generally used. However, the polarizing film dyed with iodine, iodine in the polarizing film is generally I ₃ ^- and I ₅ ^- the present in two ionic form, to the three or more types of mixed forms such as in the dichroic dye Therefore, compared to a polarizing film dyed with a dichroic dye, a light leakage phenomenon of a specific wavelength is likely to occur, and in particular, a light leakage phenomenon of blue light is likely to occur. It is difficult to get a complete neutral gray.

  Several methods have been proposed for improving the hue in polarizing films dyed with iodine. For example, a conventional method of adding potassium iodide is used, but the hue improvement effect is not sufficient.

  In addition, in producing a polarizing film dyed with iodine using a polyvinyl alcohol polymer film for the purpose of improving the durability of the polarizing film, when performing a dyeing treatment with iodine and / or subsequent treatment, It has been proposed to introduce a water-soluble acrylic polymer into a polarizing film by dissolving a water-soluble acrylic polymer selected from polyacrylic acid and its derivatives in an aqueous solution for treatment (Patent Literature). 3). However, when the present inventors re-examined this method, it is difficult to uniformly impregnate the polarizing film with the water-soluble acrylic polymer, and accordingly, stains are likely to occur when dyeing with iodine. Met. Moreover, the effect of hue improvement was not seen in the polarizing film obtained by this method. In this method, in order to sufficiently impregnate the polyvinyl alcohol polymer film with the water-soluble acrylic polymer, when the film is immersed in an aqueous solution containing the water-soluble acrylic polymer for a long time, the film may be excessive. It has been found that there is a problem that the control of dyeing becomes difficult due to swelling, the mechanical physical properties of the film itself are lowered, and the process passability in producing a polarizing film is deteriorated.

  Moreover, in uses other than a polarizing film, it is from the mixture of the polyvinyl alcohol film (refer patent document 4) of the cold water soluble packaging which consists of polyvinyl alcohol and polyacrylic acid with low polymerization degree (refer patent document 4), and polyvinyl alcohol and poly (meth) acrylic acid. A gas barrier packaging film (see Patent Document 5) in which the formed film is preferably heat-treated at a high temperature of 160 to 230 ° C. has been proposed. However, the cold water-soluble polyvinyl alcohol film described in Patent Document 4 is a polarizing film because the film dissolves in the aqueous solution during processing steps such as uniaxial stretching and iodine staining in the aqueous solution when the polarizing film is produced. It cannot be used for manufacturing. In addition, the film described in Patent Document 5 needs to be heat-treated at a high temperature in order to improve the gas barrier property. Therefore, the water swellability and dyeability are greatly inferior. It cannot be used for.

JP 62-123405 A JP 62-156602 A JP 2004-294808 A Japanese Patent Application No. 61-204254 JP-A-6-220221 “Journal of Applied Polymer Science” 1994, Vol. 51, p. 613-618

  The object of the present invention is high light transmittance and polarization degree, excellent polarization performance, excellent hue, and less light leakage of blue light when two polarizing films are crossed into a crossed Nicols state, It is providing the original film for high performance polarizing films, its manufacturing method, and the polarizing film produced from the said original film.

  The present inventors have intensively studied to achieve the above object. As a result, a polyvinyl alcohol polymer having a high polymerization degree of 2000 or more and a high saponification degree of 99 mol% or more, and a polyvinyl alcohol-containing polymer containing a carboxyl group-containing polymer in a specific amount. When a film is produced from an alcohol-based polymer composition and a polarizing film is produced by performing the same processing operation as in the conventional method using the film, the film has a high light transmittance and a degree of polarization and has a dichroic ratio. The present invention was completed by finding that a high-performance polarizing film with high polarization performance, excellent hue, and low leakage of blue light can be obtained when two polarizing films are crossed into a crossed Nicol state. did.

That is, the present invention
(1) A carboxyl group-containing polymer comprising at least one of polyacrylic acid and a neutralized product of polyacrylic acid with respect to 100 parts by mass of a polyvinyl alcohol polymer having a polymerization degree of 2000 or more and a saponification degree of 99 mol% or more. Polyvinyl alcohol which is contained in a proportion of 1 to 30 parts by mass and is uniformly mixed with a polyvinyl alcohol polymer and a carboxyl group-containing polymer comprising at least one of polyacrylic acid and a neutralized product of polyacrylic acid A polyvinyl alcohol polymer film for a polarizing film , characterized in that it is formed from a polymer polymer composition.

Furthermore, the present invention provides
( 2 ) A carboxyl group-containing polymer consisting of at least one of polyacrylic acid and a neutralized product of polyacrylic acid is uniformly mixed while dissolving a polyvinyl alcohol polymer having a polymerization degree of 2000 or more and a saponification degree of 99 mol% or more. A stock solution containing 1 to 30 parts by mass of a carboxyl group-containing polymer composed of at least one of polyacrylic acid and a neutralized product of polyacrylic acid with respect to 100 parts by mass of the polyvinyl alcohol polymer. (1) The method for producing a polyvinyl alcohol polymer film for a polarizing film according to the above (1).

And this invention,
( 3 ) A polarizing film produced using the polyvinyl alcohol polymer film for polarizing film of (1) .
Furthermore, the present invention provides
( 4 ) The polarizing film of ( 3 ), which is produced by subjecting the polyvinyl alcohol polymer film for polarizing film of (1) to uniaxial stretching, dyeing with iodine, and treatment with a boron compound.

By producing a polarizing film using the polyvinyl alcohol polymer film for polarizing film of the present invention, it has high light transmittance and degree of polarization, high dichroic ratio, excellent polarization performance, and hue. The high-performance polarizing film of the present invention, which is excellent and has little leakage of blue light when the two polarizing films are crossed in a crossed Nicol state, can be obtained smoothly.
By the production method of the present invention, a polyvinyl alcohol polymer film for a polarizing film capable of producing a polarizing film having the above-described excellent characteristics can be obtained smoothly.
The polarizing film of the present invention makes use of the above-mentioned excellent characteristics, such as calculators, watches, notebook computers, liquid crystal monitors, liquid crystal color projectors, liquid crystal televisions, in-vehicle navigation systems, mobile phones, measuring instruments used indoors and outdoors, etc. It can be effectively used for producing a polarizing plate which is a component part of a liquid crystal display device, and is particularly useful as a polarizing plate for a liquid crystal monitor or a liquid crystal television requiring high contrast and high color reproducibility.

The present invention is described in detail below.
First, the polyvinyl alcohol-type polymer which comprises the polyvinyl-alcohol-type polymer film for polarizing films of this invention is demonstrated (Hereinafter, polyvinyl alcohol may be called "PVA.").
The PVA polymer used for the production of the PVA polymer film for polarizing film of the present invention (hereinafter, the PVA polymer film for polarizing film may be simply referred to as “PVA polymer film”) is vinyl acetate, Polyvinyl obtained by polymerization using one or two vinyl esters such as vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl benzoate A PVA polymer obtained by saponifying an ester polymer is preferably used from the viewpoint of ease of production, availability, cost and the like.

A typical example of the PVA polymer that can be used in the PVA polymer film of the present invention is a saponified product (PVA homopolymer) of a vinyl ester homopolymer. However, the PVA polymer used for the PVA polymer film in the present invention is not limited to the saponified vinyl ester homopolymer, and if the effect of the present invention is not impaired, the modified PVA polymer is used as the PVA polymer. A polymer, a saponified product of a copolymer of vinyl ester and a small amount of another copolymerizable monomer, a polyvinyl acetal polymer obtained by crosslinking a part of hydroxyl groups of a PVA polymer, and the like can also be used.
Among them, examples of the modified PVA polymer include graft copolymerization of unsaturated carboxylic acid or a derivative thereof, unsaturated sulfonic acid or a derivative thereof, an α-olefin having 2 to 30 carbon atoms, and the like at a ratio of less than 5 mol%. Examples thereof include a modified PVA polymer produced by saponifying a modified polyvinyl ester, and an unmodified or modified PVA polymer.

  Examples of other copolymerizable monomers that can be used for the production of a saponified product of a copolymer of vinyl ester and a small amount of other copolymerization monomers include, for example, ethylene, propylene, 1-butene, isobutene, and others. (Meth) acrylic acid and its salt; methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, (meth) acrylic acid i -Propyl, n-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, (meta ) (Meth) acrylic acid esters such as octadecyl acrylate; (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N N-dimethyl (meth) acrylamide, diacetone (meth) acrylamide, (meth) acrylamide propane sulfonic acid and its salt, (meth) acrylamide propyldimethylamine and its salt, N-methylol (meth) acrylamide and its derivatives (meta) ) Acrylamide derivatives; N-vinylamides such as N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether , Vinyl ethers such as t-butyl vinyl ether, dodecyl vinyl ether and stearyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile Vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; maleic acid and salts thereof or esters thereof; itaconic acid and salts thereof or esters thereof; vinyl Examples thereof include vinylsilyl compounds such as trimethoxysilane; isopropenyl acetate; unsaturated sulfonic acid and the like. The PVA polymer can have a structural unit derived from one or more of the other polymerizable monomers described above.

When the PVA polymer is a saponified product of a copolymer of vinyl ester and another copolymerizable monomer, the proportion of the structural unit derived from the other copolymerizable monomer is the PVA polymer. Is preferably 15 mol% or less, more preferably 10 mol% or less, and even more preferably 5 mol% or less based on the total structural units constituting the.
In particular, when the other copolymerizable monomer is a monomer that promotes water solubility of the PVA polymer, such as (meth) acrylic acid or sulfonic acid, the PVA polymer film is used. In order to prevent the film from being dissolved or blown during the treatment in an aqueous solution when producing a polarizing film, the PVA polymerization ratio is preferably 5 mol% or less, particularly 3 mol% or less.

  As an example of the case where the PVA polymer is a polyvinyl acetal polymer in which a part of the hydroxyl group is crosslinked, a polyvinyl acetal system in which a part of the hydroxyl group is crosslinked with aldehydes such as formalin, butyraldehyde, and benzaldehyde. A polymer can be mentioned.

The degree of polymerization of the PVA polymer used for the PVA polymer film of the present invention is required to be 2000 or more from the viewpoint of the polarization performance and durability of the polarizing film. When the degree of polymerization of the PVA polymer used for the PVA polymer film is less than 2000, the polarizing performance and durability of the polarizing film obtained from the PVA polymer film are not improved, and the object of the present invention is achieved. It becomes difficult. The higher the degree of polymerization of the PVA polymer, the better the polarizing performance and durability of the resulting polarizing film. However, if the degree of polymerization of the PVA polymer is too high, the production cost of the PVA polymer increases, Since it tends to cause poor processability during film formation, the degree of polymerization of the PVA polymer is preferably 2000 to 10000, more preferably 2000 to 8000, and more preferably 2200 to 5000. Further preferred.
In addition, the polymerization degree of the PVA polymer referred to in this specification means a polymerization degree measured according to JIS K 6726.

Furthermore, the saponification degree of the PVA polymer used for the PVA polymer film of the present invention is to improve the polarization performance, hue and durability of the polarizing film obtained from the PVA polymer film. 99.9 mol% or more, and 99.9 mol% or more is preferable from the viewpoint of polarization performance and durability of the obtained polarizing film, and more preferably 99.95 mol% or more. When the saponification degree of the PVA polymer is less than 99.0 mol, a polarizing film excellent in polarizing performance and durability cannot be obtained, and the effect of improving the hue in the polarizing film is small.
In this specification, the degree of saponification of the PVA polymer is the total of units (typically vinyl ester units) that can be converted into vinyl alcohol units by saponification among the structural units constituting the polymer. The ratio (mol%) of the unit actually saponified to the vinyl alcohol unit with respect to the number of moles. The degree of saponification can be measured according to the method described in JIS K 6726.

It is important that the PVA polymer film for the polarizing film of the present invention is formed from a PVA polymer composition containing a carboxyl group-containing polymer together with the PVA polymer.
As the carboxyl group-containing polymer, any polymer containing a carboxyl group can be used as long as the effects of the present invention are not impaired. Specific examples include acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid. , Itaconic acid, glyoxylic acid, 2- (meth) acryloyloxyethylmaleic acid, 2- (meth) acryloyloxyethylphthalic acid, 2- (meth) acryloyloxyethylhexahydrophthalic acid And a carboxyl group-containing polymer obtained. In the present invention, only one kind of carboxyl group-containing polymer may be used as the carboxyl group-containing substance, or two or more kinds of carboxyl group-containing polymers may be used in combination.

The carboxyl group in the carboxyl group-containing polymer may not be neutralized, or may be partially or wholly neutralized, and neutralized with the carboxyl group-containing polymer in which the carboxyl group is not neutralized. You may use together the carboxyl group containing polymer currently made.
When the carboxyl group in the carboxyl group-containing polymer is neutralized, the carboxyl group is preferably in the form of a metal salt such as sodium, calcium or magnesium.

When using a carboxyl group-containing polymer in which some or all of the carboxyl groups are neutralized, use a carboxyl group-containing polymer in which some or all of the carboxyl groups are neutralized together with the PVA polymer. A PVA polymer film may be produced, or a PVA polymer film may be produced after a PVA polymer film is produced using a carboxyl group-containing polymer in which carboxyl groups are not neutralized together with the PVA polymer. The carboxyl group of the carboxyl group-containing polymer contained in the film may be neutralized by swelling in a water bath containing a metal compound for neutralization such as calcium nitrate or calcium acetate. In that case, the neutralization degree of a carboxyl group is controllable by adjusting the quantity of the metal compound contained in a water bath.

  Although the molecular weight of the carboxyl group-containing polymer is not particularly limited, it is generally possible to use a carboxyl group-containing polymer having a weight average molecular weight of 500 to 100,000, more preferably 1000 to 50000, and particularly 3000 to 25000. From the point that the effect of improving the hue of the polarizing film is increased.

  The PVA polymer film of the present invention needs to be formed from a PVA polymer composition containing a carboxyl group-containing polymer in a proportion of 1 to 30 parts by mass with respect to 100 parts by mass of the PVA polymer. It is. When the proportion of the carboxyl group-containing polymer is less than 1 part by mass relative to 100 parts by mass of the PVA polymer, the hue of the polarizing film obtained from the PVA polymer film is not improved, and blue light in a crossed Nicol state Leakage increases. On the other hand, when the proportion of the carboxyl group-containing polymer is more than 30 parts by mass with respect to 100 parts by mass of the PVA polymer, the crystallinity of the PVA polymer film itself decreases, and the water solubility of the PVA polymer film increases. Even if it is difficult to produce a polarizing film, or even when a polarizing film can be produced, the process passability at the time of producing the polarizing film is deteriorated and the polarizing performance of the resulting polarizing film is deteriorated. The PVA polymer film of the present invention is a carboxyl group-containing polymer with respect to 100 parts by mass of the PVA polymer from the viewpoints of improvement in processability when producing a polarizing film, and further improvement in polarization performance and hue. Is preferably formed from a PVA polymer composition containing 1 to 20 parts by mass, particularly 3 to 10 parts by mass.

The reason why the polarizing film produced using the PVA polymer film of the present invention is not only excellent in polarization performance but also excellent in hue is not clear, but is estimated as follows.
That is, the hue of a polarizing film dyed with iodine generally depends on the absorbance ratio (I ₃ ⁻ / I ₅ ⁻ ) between the absorbance of I ₃ ⁻ ions and the absorbance of I ₅ ⁻ ions present as polyiodine in the polarizing film. It is said that. The I ₃ ⁻ ions present in the polarizing film mainly absorb light in the blue wavelength region, and the I ₅ ⁻ ions mainly absorb light in the red wavelength region. A conventional PVA polarizing film has a large absorption of light in the red wavelength region (that is, absorbance of I ₅ ⁻ ions), while a small absorption of light in the blue wavelength region (that is, absorbance of I ₃ ⁻ ions). In the crossed Nicols state in which two polarizing films are orthogonal, it is ideal that light in the entire wavelength region of visible light is shielded (no light leakage occurs). It becomes insufficient. The above-mentioned polyiodine ion species are known to be affected by the matrix structure of the polymer that includes them. For example, in the case of a PVA polymer, it is formed by the hydroxyl group of the PVA polymer. It is known that hydrogen bonding plays an important role (see, for example, Non-Patent Document 1). From this point, in the conventional PVA polarizing film, the action of I ₅ ⁻ ions that mainly absorb light in the red wavelength range is likely to be strong, thereby weakening the absorption of light in the blue wavelength range and reducing the hue. It is thought to have invited.

  The inventors of the present invention have focused on the above-mentioned hydrogen bond, tried to control the structure of the PVA polymer that includes polyiodine ion species, and finally completed the present invention as a result of various studies. . That is, in the PVA polymer film formed from the composition containing the PVA polymer and the carboxyl group-containing polymer, a hydrogen bond group is formed between the hydroxyl group of the PVA polymer and the carboxyl group of the carboxyl group-containing polymer. The change occurs, and the polymer structure that includes polyiodine can be greatly changed when a polarizing film is formed. In order to eliminate local structural spots that cause dyeing spots, it is necessary that recombination of hydrogen bonds occurs throughout the PVA polymer film. To achieve this, PVA for polarizing films is required. In the polymer film, the PVA polymer and the carboxyl group-containing polymer must be uniformly mixed in the film. In the PVA polymer film of the present invention, recombination of hydrogen bonds occurs between the hydroxyl group in the PVA polymer and the carboxyl group in the carboxyl group-containing polymer in the film, and the PVA polymer and carboxyl group-containing polymer are produced. The polymer is uniformly mixed in the film, so that dyeing spots are not generated, and the hue is improved, so that blue light does not leak in a crossed Nicol state in which two polarizing films are orthogonal to each other. It is estimated that

  The composition of the PVA polymer forming the PVA polymer film of the present invention preferably contains a plasticizer together with the PVA polymer and carboxyl group-containing polymer, and contains a plasticizer. By doing it, the improvement of the drawability at the time of manufacturing a polarizing film from a PVA polymer film can be aimed at. As the plasticizer, polyhydric alcohol is preferably used, and specific examples include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, trimethylolpropane, and the like. 1 type (s) or 2 or more types can be contained. Among these, glycerin is more preferably used from the viewpoint that the stretchability of the PVA polymer film becomes better.

  The addition amount of the plasticizer is preferably 3 to 20 parts by mass, more preferably 5 to 15 parts by mass, and particularly preferably 7 to 12 parts by mass with respect to 100 parts by mass of the PVA polymer. If the added amount of the plasticizer is small, the stretchability of the PVA polymer film becomes poor and it becomes difficult to produce the polarizing film smoothly. On the other hand, if the added amount of the plasticizer is too large, the surface of the PVA polymer film is plasticized. The agent bleeds out and the handleability of the PVA polymer film is lowered.

  Moreover, the PVA polymer film of the present invention may contain an antioxidant, an antifreezing agent, a pH adjusting agent, a concealing agent, an anti-coloring agent, an oil agent, and the like, if necessary.

  The thickness of the PVA polymer film of the present invention is not particularly limited, but is generally 20 to 120 μm, more preferably 30 to 100 μm, and particularly preferably about 40 to 80 μm. When the PVA polymer film is too thin, stretching breakage is likely to occur during uniaxial stretching treatment for producing a polarizing film, and it becomes difficult to obtain a polarizing film having excellent polarization performance. On the other hand, if the PVA polymer film is too thick, stretch spots are likely to occur during the uniaxial stretching process for producing the polarizing film.

  The width of the PVA polymer film of the present invention is not particularly limited, and can be determined according to the use of a polarizing film produced from the PVA polymer film. In recent years, the enlargement of screens of liquid crystal televisions and monitors has progressed. From this point of view, it is preferable that the width of the PVA polymer film is 2 m or more. On the other hand, if the width of the PVA polymer film is too large, it is difficult to uniformly perform uniaxial stretching itself when manufacturing a polarizing plate using a practical device. It is preferable that it is 6 m or less.

  The production method of the PVA polymer film of the present invention is not particularly limited, and the PVA polymer and the carboxyl group-containing polymer are uniformly mixed in the PVA polymer composition constituting the PVA polymer film, When a plasticizer and other additives are contained, these components are also mixed uniformly, and the thickness and width are uniform, and a method for producing a PVA polymer film that can be suitably used for producing a polarizing film Any method may be used.

  Among them, a PVA polymer having a polymerization degree of 2000 or more and a saponification degree of 99 mol% or more is dissolved in a solvent, a carboxyl group-containing polymer is uniformly mixed or dissolved, preferably a plasticizer is added, and further required Accordingly, a method of preparing a stock solution by adding other components and forming a film using the stock solution to produce a PVA polymer film is preferably employed.

  The method for preparing the stock solution used for film formation is not particularly limited. For example, a solution in which a PVA polymer is dissolved and a solution in which a carboxyl group-containing polymer is dissolved are separately prepared, and both solutions are mixed at an appropriate ratio. A method for preparing and dissolving a PVA polymer and a carboxyl group-containing polymer in a solvent for a stock solution, and a PVA polymer and a carboxyl group-containing polymer in a solvent for a stock solution. You may prepare by any methods, such as the method of dissolving the remaining polymer after making it melt | dissolve.

  Examples of the solvent used for preparing the stock solution include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, An ethylenediamine, a diethylenetriamine, etc. can be mentioned, Among these, 1 type (s) or 2 or more types can be used. Among these, water, dimethyl sulfoxide, a mixed solvent of water and dimethyl sulfoxide, and a mixed solvent of water and glycerin are preferably used from the viewpoints of environmental load and recoverability.

  The volatile fraction of the stock solution containing the PVA polymer and the carboxyl group-containing polymer (content ratio of volatile components such as a solvent removed by volatilization or evaporation during film formation) is determined by the weight of the PVA polymer and the carboxyl group-containing polymer. Although it may vary depending on the molecular weight of the coalescence (degree of polymerization), the blending ratio of both polymers, the film forming method, the film forming conditions, etc., it is generally 50 to 95% by mass, more preferably 55 to 90% by mass, especially 60 to 85% by mass. % Is preferred. If the volatile content of the stock solution is too low, the viscosity of the film-forming stock solution becomes too high, making filtration and defoaming difficult when preparing the stock solution, and making it difficult to produce a PVA polymer film free from foreign matter and defects There is. On the other hand, when the volatile fraction of the stock solution is too high, the viscosity of the film-forming stock solution becomes too low, and it tends to be difficult to produce a PVA polymer film having the desired thickness and thickness accuracy.

  Moreover, it is preferable to add a surfactant to the stock solution for producing the PVA polymer film, and the addition of the surfactant improves the film forming property and suppresses the occurrence of uneven thickness of the film. In addition, peeling of the film from the metal roll or belt used for film formation becomes easy. The type of the surfactant is not particularly limited, but an anionic or nonionic surfactant is preferable from the viewpoint of releasability from a metal roll or belt, and a nonionic surfactant is particularly preferable. As the anionic surfactant, for example, a carboxylic acid type such as potassium laurate, a sulfate type such as octyl sulfate, and a sulfonic acid type anionic surfactant such as dodecylbenzene sulfonate are suitable. Nonionic surfactants include, for example, alkyl ether types such as polyoxyethylene oleyl ether, alkylphenyl ether types such as polyoxyethylene octylphenyl ether, alkyl ester types such as polyoxyethylene laurate, and polyoxyethylene laurylamino. Alkylamine type such as ether, alkylamide type such as polyoxyethylene lauric acid amide, polypropylene glycol ether type such as polyoxyethylene polyoxypropylene ether, alkanolamide type such as oleic acid diethanolamide, polyoxyalkylene allyl phenyl ether, etc. Nonionic surfactants such as allyl phenyl ether type are preferred. These surfactants can be used alone or in combination of two or more.

  When a surfactant is added to the stock solution for film formation, the addition amount is 0.01 to 0.5 parts by mass, and further 0.02 to 0.03 parts by mass with respect to 100 parts by mass of the PVA polymer. Parts, particularly 0.05 to 0.1 parts by weight. When the addition amount of the surfactant is less than 0.01 parts by mass, the effect of improving the film-forming property and the releasability due to the addition of the surfactant is difficult to appear, while when it exceeds 0.5 parts by mass, The surfactant may bleed out on the surface of the PVA polymer film to cause blocking, and the handleability may be reduced.

  The method for forming a PVA polymer film using the stock solution described above is not particularly limited, and a conventionally known method can be employed. For example, using the above-described stock solution, a casting film-forming method, a wet film-forming method (discharging into a poor solvent), a gel film-forming method (the solvent after the stock solution containing the PVA polymer is once cooled and gelled) And a method of obtaining a PVA polymer film by extracting and removing them), a combination of these, and the like. Among these, the casting film forming method is preferably employed because a PVA polymer film having a uniform film thickness and width and good physical properties can be obtained. The PVA polymer film is dried or heat-treated as necessary.

In film formation, a T-type slit die, a hopper plate, an I-die, a lip coater die, or the like is used, or the film-forming stock solution is heated and rotated at the most upstream side by casting or the like. The film is uniformly discharged (cast) on the peripheral surface of the roll, the volatile matter is evaporated and dried from one surface of the film discharged (cast) on the first heating roll, and then discharged ( One or a plurality of rotating heating rolls disposed on the downstream side of the second heated roll (drying roll) that passes through the other surface of the film that has been cast and dried on the peripheral surface of the second heating roll. A method of further drying on the peripheral surface or passing through a hot air drying apparatus and drying the wound around a winding apparatus is preferably employed industrially. Roll drying and hot air drying can be performed in combination as appropriate.
In order to adjust the PVA polymer film to an appropriate state, it is desirable to provide a heat treatment device, a humidity control device, and a speed adjusting mechanism such as a motor and a transmission for driving each roll.
When the polarizing film is produced, the drying treatment from the discharge of the stock solution to the production of the dried PVA polymer film is generally performed at a drying temperature of 50 to 150 ° C., particularly 60 to 140 ° C. It is preferable from the viewpoint that the stretchability and dyeability of the polarizing film are excellent and the polarizing performance of the obtained polarizing film is improved.

The manufacturing method of the polarizing film at the time of manufacturing a polarizing film from the PVA polymer film of this invention is not specifically limited, It is employ | adopted conventionally when manufacturing a polarizing film using a PVA polymer film as a raw fabric film. Any method may be adopted.
In order to produce a polarizing film from the PVA polymer film of the present invention, for example, moisture adjustment of the PVA polymer film, dyeing, uniaxial stretching, fixing treatment, drying treatment, and further heat treatment as necessary, The order of operation of dyeing, uniaxial stretching, and fixing treatment is not particularly limited. Further, uniaxial stretching may be performed in multiple stages of two or more stages.

Dyeing is preferably performed using iodine, and the dyeing time may be any stage before uniaxial stretching, during uniaxial stretching, or after uniaxial stretching. Usually, the dyeing is generally performed by immersing the PVA polymer film in a solution (particularly an aqueous solution) containing iodine-potassium iodide. In the present invention, the dye contains iodine and potassium iodide. A dyeing method using an aqueous solution is preferably employed. It is preferable that the concentration of iodine in the aqueous dyeing solution is 0.01 to 0.5% by mass and the concentration of potassium iodide is 0.01 to 10% by mass. Moreover, it is preferable that the temperature of a dyeing bath shall be 20-50 degreeC, especially 25-40 degreeC.
In some cases, iodine and potassium iodide may be mixed into a stock solution for producing a PVA polymer film without using a dyeing bath, and the treatment conditions and treatment method are particularly limited. Not. Further, a film may be formed by adding a boron compound such as boric acid or borax as a crosslinking agent.

Uniaxial stretching may be performed by either a wet stretching method or a dry heat stretching method. In the case of the wet stretching method, uniaxial stretching in an aqueous solution containing a dye, uniaxial stretching in warm water composed of an aqueous solution containing a dye and boric acid, uniaxial stretching in a fixed treatment bath after dyeing, the above-mentioned steps Can be carried out by multi-stage stretching over the substrate, uniaxial stretching in the air using the PVA polymer film after water absorption, or the like.
The stretching temperature is not particularly limited, but is preferably 30 to 90 ° C. when the PVA polymer film is wet-stretched in warm water, and preferably 50 to 180 ° C. when dry-heat stretching.
In addition, the stretching ratio of uniaxial stretching (total stretching ratio in the case of uniaxial stretching in multiple stages) is preferably 4 times or more, particularly 5 times or more from the viewpoint of the polarizing performance of the obtained polarizing film. The upper limit of the stretching ratio is not particularly limited, but is preferably 8 times or less from the viewpoint of uniform stretching.

  In the production of the polarizing film, in order to strengthen the adsorption of the dye to the PVA polymer film, a fixing treatment is often performed. In the present invention, the fixing treatment is preferably performed in the production of the polarizing film. As the treatment bath used for the fixing treatment, an aqueous solution to which one or more of boron compounds such as boric acid and borax are added is usually used. Moreover, you may add an iodine compound and a metal compound in the processing bath for fixing processes as needed. The concentration of the boron compound in the treatment bath for fixing treatment is generally about 2 to 15% by mass, particularly about 3 to 10% by mass. The temperature of the treatment bath during the fixing treatment is preferably 15 to 60 ° C, particularly 25 to 40 ° C.

  The above-described uniaxial stretching, dyeing treatment, fixing treatment and the like are performed, and then the obtained polarizing film is dried. It is preferable to perform the drying process of the obtained polarizing film at 30-150 degreeC, especially 50-100 degreeC.

  In the polarizing film of the present invention obtained using the PVA polymer film of the present invention, the b value obtained by the method described in the following examples is generally in the range of 4.0 to 5.6 and excellent in hue. In addition, there is little light leakage in the blue wavelength region in the crossed Nicols state of the conventional PVA polarizing film.

  The polarizing film obtained as described above is usually used as a polarizing plate by bonding a protective film having optical transparency and mechanical strength on both sides or one side. As the protective film, a cellulose triacetate (TAC) film, an acetic acid / cellulose butyrate (CAB) film, an acrylic film, a polyester film, or the like is used. Examples of the adhesive for bonding include PVA adhesives and urethane adhesives. Among them, PVA adhesives are preferable.

  The polarizing plate obtained as described above is used as a component of a liquid crystal display device after being coated with an acrylic-based pressure-sensitive adhesive and then bonded to a glass substrate. At the same time, it may be bonded to a retardation film, a viewing angle improving film, a brightness improving film, or the like.

  The present invention will be specifically described below with reference to examples and the like, but the present invention is not limited to the following examples. In the following examples, the degree of polarization and hue were evaluated by the following methods.

(1) Polarization degree of polarizing film:
(I) Transmittance Two square samples measuring 4 cm × 4 cm in parallel to the alignment direction of the polarizing film were collected from the central portion in the width direction of the polarizing film obtained in the following examples or comparative examples. Using a spectrophotometer U-4100 (attached to integrating sphere) manufactured by Seisakusho, in accordance with JIS Z 8722 (measuring method of object color), the visibility of the visible light region of the C light source and the 2-degree visual field is corrected. About the polarizing film sample of 1 sheet, the transmittance | permeability of the light at the time of inclining 45 degree | times with respect to the extending | stretching axis direction and the light transmittance at the time of inclining -45 degree | times were measured, and those average values (Y1) were calculated | required. .
For the other polarizing film sample, the light transmittance when tilted by 45 degrees and the light transmittance when tilted by -45 degrees were measured in the same manner as described above, and the average value (Y2) was calculated. Asked.
Y1 and Y2 obtained above were averaged to obtain the transmittance (Y) (%) of the polarizing film.

(Ii) Polarization degree:
The light transmittance (Y で) when the two polarizing films collected in (i) above are stacked so that their orientation directions are parallel, and the light when they are stacked so that their orientation directions are orthogonal to each other. The transmittance (Y⊥) was measured by the same method as the transmittance measuring method, and the degree of polarization was determined from the following equation.
Polarization degree (V /%) = {(Y‖−Y⊥) / (Y‖ + Y⊥)} ^1/2 × 100

(2) Color of polarizing film:
In order to evaluate the presence or absence of blue light leakage of the polarizing film, b value was calculated and evaluated by Hunter Lab color system. The two polarizing film samples collected in (i) of (1) above were overlapped so that the b value (b‖) when the stretching axis directions were parallel and the stretching axis directions were orthogonal to each other. In this case, the b value (b⊥) was measured by the same method as the transmittance measuring method, and the b value was obtained from the following equation.

b value = b‖−b⊥

Example 1
(1) 100 parts by mass of a PVA polymer having an average polymerization degree of 2400 and a saponification degree of 99.9 mol% or more, and 10 parts by mass of polyacrylic acid having a weight average molecular weight of 5000 (manufactured by Wako Pure Chemical Industries, Ltd.) A PVA-based aqueous solution of 12 parts by mass of glycerin as a plasticizer was dried on a metal roll at 60 ° C. to obtain a PVA-based film having a thickness of 75 μm. Furthermore, the obtained film was fixed to a frame and heat-treated at 120 ° C. for 3 minutes.
(2) After immersing the PVA polymer film obtained in (1) above in 30 ° C. pure water for 30 seconds, 0.04% by mass of iodine, 4% by mass of potassium iodide and 4% by mass of boric acid % Was immersed for 1 minute in an aqueous solution (dye bath) containing 30% (temperature 30 ° C.) to adsorb iodine. Subsequently, after uniaxially stretching six times in a boric acid aqueous solution (boric acid concentration: 4% by mass, 50 ° C.), an aqueous solution further containing 4% by mass of potassium iodide and 4% by mass of boric acid (35 ° C. ) For 4 minutes. Then, it dried at 50 degreeC for 4 minute (s), and obtained the polarizing film.
About the polarizing film obtained by this, the polarization degree and the hue were evaluated by the method described above. The results are shown in Table 1.
(3) As shown in Table 1 below, the transmittance of the polarizing film obtained in Example 1 was 44.0%, the degree of polarization was 99.71%, and the b value was 4.7. There was no appearance defect such as the above, and the hue was greatly improved as compared with the PVA polarizing film made of the conventional PVA film.

Example 2
(1) Instead of PVA, an ethylene-modified PVA polymer having an average polymerization degree of 2400, a saponification degree of 99.3 mol%, and an ethylene modification amount (copolymerization ratio) of 2.5 mol% was used as the PVA polymer. Except for this, a PVA polymer film for polarizing film was produced in the same manner as in Example 1.
(2) A polarizing film was obtained in the same manner as (1) of Example 1 using the PVA polymer film obtained in (1) above. About the polarizing film obtained by this, polarization degree and b value were evaluated by the method mentioned above. The results are shown in Table 1.
(3) As shown in Table 1 below, the polarizing film obtained in Example 1 has a transmittance of 44.0%, a degree of polarization of 99.76%, and a b value of 5.6. Thus, it was greatly improved as compared with the conventional PVA polarizing film.

<< Comparative Example 1 >>
(1) A PVA polymer film for a polarizing film was produced in the same manner as in (1) of Example 1 except that polyacrylic acid was not used at the time of preparing the stock solution. ) To prepare a polarizing film.
(2) About the polarizing film obtained by said (1), the polarization degree and the hue were evaluated by the method mentioned above. The results are shown in Table 2 below.
(3) As shown in Table 2 below, the transmittance of the polarizing film obtained in Comparative Example 1 was 44.0%, the degree of polarization was 99.75%, and the b value was 6.0. Compared to 1 and 2, it was inferior in terms of hue.

<< Comparative Example 2 >>
(1) A PVA system for polarizing film in the same manner as in (1) of Example 1, except that polyacrylic acid having a weight average molecular weight of 5000 was blended at a ratio of 40 parts by mass with respect to 100 parts by mass of the PVA polymer. A polymer film was produced.
(2) When an attempt was made to produce a polarizing film in the same manner as in (2) of Example 1 using the PVA polymer film obtained in (1) above, in the aqueous solution when producing the polarizing film Part of the PVA polymer was dissolved during the swelling process, and a polarizing film could not be produced.

<< Comparative Example 3 >>
(1) A PVA polymer film for a polarizing film was produced in the same manner as in Example (1) except that a PVA polymer having an average polymerization degree of 500 and a saponification degree of 99.0 mol% was used.
(2) When an attempt was made to produce a polarizing film in the same manner as in (2) of Example 1 using the PVA polymer film obtained in (1) above, in the aqueous solution when producing the polarizing film Part of the PVA polymer was dissolved during the swelling process, and a polarizing film could not be produced.

  As can be seen from the results in Tables 1 and 2, in Examples 1 and 2, a PVA polymer containing a PVA polymer having a polymerization degree of 2000 or more and a saponification degree of 99 mol% or more and a carboxyl group-containing polymer. By producing a polarizing film using a PVA polymer film produced from the composition, the obtained polarizing film has a low b value indicating leakage of blue light, and the hue is greatly improved.

  On the other hand, the polarizing film of Comparative Example 1 produced from the PVA polymer film produced using only the PVA polymer without containing the carboxyl group-containing polymer has a high b value. It is inferior in terms of hue as compared with the polarizing film of No. 2.

  Moreover, the change film of the comparative example 2 using the PVA-type polymer film which consists of a PVA-type polymer composition which contains a carboxyl group-containing polymer more than 30 mass parts with respect to 100 mass parts of PVA-type polymers, Polymerization The film of Comparative Example 4 produced from a PVA polymer composition comprising a PVA polymer having a degree of less than 2000 (polymerization degree 500) and a carboxyl group-containing polymer is dissolved in an aqueous solution during the production of the polarizing film. Therefore, a polarizing film cannot be produced.

According to the present invention, there is provided a polarizing film having excellent hue and less leakage of blue light in a crossed Nicol state in which two polarizing films are orthogonal to each other, which could not be achieved by the prior art, and the polarizing film. A PVA polymer film (raw film) for production can be provided.
The polarizing film produced using the PVA polymer film for polarizing film of the present invention is particularly suitable for producing a polarizing plate as a member for components of liquid crystal display devices and liquid crystal televisions that require high contrast and high color reproducibility. It can be used effectively.

Claims (4)

1 to 30 carboxyl group-containing polymers comprising at least one of polyacrylic acid and a neutralized product of polyacrylic acid with respect to 100 parts by mass of a polyvinyl alcohol polymer having a polymerization degree of 2000 or more and a saponification degree of 99 mol% or more. A polyvinyl alcohol polymer containing a polyvinyl alcohol polymer in a proportion of parts by mass , and a carboxyl group-containing polymer comprising at least one of polyacrylic acid and a neutralized product of polyacrylic acid. A polyvinyl alcohol polymer film for a polarizing film, which is formed from a composition. A stock solution in which a polyvinyl alcohol polymer having a polymerization degree of 2000 or more and a saponification degree of 99 mol% or more is dissolved and a carboxyl group-containing polymer comprising at least one of polyacrylic acid and a neutralized product of polyacrylic acid is uniformly mixed. And using the stock solution which contains the carboxyl group-containing polymer which consists of at least one of polyacrylic acid and the neutralized product of polyacrylic acid in the ratio of 1-30 mass parts with respect to 100 mass parts of polyvinyl alcohol-type polymers. The method for producing a polyvinyl alcohol polymer film for a polarizing film according to claim 1, wherein the film is formed. A polarizing film produced using the polyvinyl alcohol polymer film for polarizing film according to claim 1 . The polarizing film of Claim 3 produced by giving the polyvinyl alcohol polymer film for polarizing films of Claim 1 uniaxial stretching, the dyeing | staining by an iodine, and the process by a boron compound.