JPWO2018021274A1 - Polarizing film and method for producing the same - Google Patents

Abstract

Polarized light comprising polyvinyl alcohol (A) and a boron-containing compound (B) having at least one functional group selected from the group consisting of boronic acid groups and boron-containing groups that can be converted to boronic acid groups in the presence of water. It is a film, Comprising: Boron element content derived from the boron containing compound (B) in a polarizing film is 0.1-3 mass parts with respect to 100 mass parts of polyvinyl alcohol (A), The polarizing film characterized by the above-mentioned. And Furthermore, boric acid is contained, and the total boron element content in the polarizing film is preferably 0.2 to 5% by mass. Thereby, the polarizing film excellent in moisture-heat-resistant performance is provided.

Description

  The present invention relates to a polarizing film excellent in wet heat resistance and a method for producing the same.

A polarizing plate having a light transmission and shielding function is a basic component of a liquid crystal display (LCD) together with a liquid crystal that changes a polarization state of light. Many polarizing plates have a structure in which a protective film such as cellulose triacetate (TAC) film is bonded to the surface of the polarizing film in order to prevent the polarizing film from fading or to prevent the polarizing film from shrinking. As a polarizing film constituting the polarizing plate, a iodine-based dye (I ₃ ^- or I ₅ ^- etc.) is formed on a matrix formed by uniaxially stretching a polyvinyl alcohol film (hereinafter, “polyvinyl alcohol” may be referred to as “PVA”). ) Is the mainstream.

  LCDs are used in a wide range of small devices such as calculators and watches, mobile phones, notebook computers, liquid crystal monitors, liquid crystal color projectors, liquid crystal televisions, in-vehicle navigation systems, and measuring devices used indoors and outdoors. These devices are required to be thin and light. Therefore, each member of the LCD is also required to be thinned. However, if the protective film of the polarizing plate, which is one of the LCD members, is thinned, there is a concern that the function of preventing the fading of the iodine polarizing film is deteriorated. ing. Therefore, an iodine-based polarizing film excellent in so-called moist heat resistance with little fading at high temperature and high humidity is required.

  By the way, as a technique for improving the heat-and-moisture resistance of the iodine-based polarizing film, a technique for crosslinking the polarizing film with a polyvalent aldehyde (Patent Document 1) or a method for crosslinking with a polyvalent carboxylic acid compound (Patent Document 2). ) Is known.

JP-A-6-235815 JP 2011-257756 A

  However, when a polyvalent aldehyde is used, industrial implementation is difficult because the aldehyde tends to volatilize and concentration control is difficult. In addition, since the polyvalent carboxylic acid compound has low reactivity and requires use of an acid catalyst or treatment at a high temperature, there is a problem that the polarizing film is colored.

  Therefore, an object of the present invention is to provide a polarizing film excellent in wet heat resistance, which does not use an acid catalyst, does not require treatment at high temperature, and can be easily produced industrially.

  As a result of intensive studies by the present inventors to achieve the above object, the present inventors have found that the above problems can be solved by a polarizing film containing polyvinyl alcohol and a specific boron-containing organic compound, and completed the present invention. It was.

  The subject is a boron-containing compound (B) having at least one functional group selected from the group consisting of polyvinyl alcohol (A) and a boron-containing group that can be converted to a boronic acid group in the presence of a boronic acid group and water. The boron element content derived from the boron-containing compound (B) in the polarizing film is 0.1 to 3 parts by mass with respect to 100 parts by mass of the polyvinyl alcohol (A). This is solved by providing a polarizing film.

  At this time, it is preferable that boric acid is further contained and the total boron element content in the polarizing film is 0.2 to 5% by mass. It is also preferred that the boron-containing compound (B) has a plurality of the functional groups.

  Moreover, the said subject is a manufacturing method of the polarizing film containing the dyeing | staining process which dye | stains a polyvinyl alcohol film with a dichroic dye, and the extending | stretching process which uniaxially stretches this film, This film is made into the aqueous solution of a boron containing compound (B). It is solved also by providing the manufacturing method of the said polarizing film characterized by having the process to immerse.

  According to the present invention, a polarizing film having excellent moisture and heat resistance is provided. Moreover, according to the manufacturing method of this invention, such a polarizing film can be manufactured industrially easily.

¹ H-NMR chart of the polarizing film obtained in Example 1

  The polarizing film of the present invention is a boron-containing compound having at least one functional group selected from the group consisting of polyvinyl alcohol (A) and a boron-containing group that can be converted to a boronic acid group in the presence of a boronic acid group and water. It is a polarizing film containing (B). By cross-linking polyvinyl alcohol with a boron-containing compound (B), the wet heat resistance of the polarizing film is improved.

The boron-containing compound (B) used in the present invention is an organic compound having at least one functional group selected from the group consisting of a boron-containing group that can be converted to a boronic acid group in the presence of a boronic acid group and water. . The boronic acid group is a monovalent substituent represented by the following structural formula (1), and has a structure in which a boron atom is bonded to two hydroxyl groups and a carbon atom (not shown). In boric acid [B (OH) ₃ ], a boron atom is bonded to three hydroxyl groups, whereas boronic acid is different in that it has a boron-carbon bond. And since the boron-carbon bond which a boronic acid group has is not hydrolyzed, it is stable also in the environment where water exists. Examples of boron-containing groups that can be converted to boronic acid groups in the presence of water include, but are not limited to, boronic acid ester groups described below.

  The hydroxyl group of a boronic acid group can form an ester with an alcohol, like the hydroxyl group of boric acid. The following structural formula (2) is a boronic acid monoester group obtained by reacting one molecule of alcohol (R—OH) with a boronic acid group. Here, when the boronic acid group is bonded to the hydroxyl group of PVA, R in the structural formula (2) is a PVA chain, and the carbon-containing group is bonded to the PVA chain via a boron atom, The moisture and heat resistance of the film is improved.

  The following structural formula (3) is a boronic acid diester group obtained by reacting two molecules of alcohol (R—OH) with a boronic acid group. Here, when the boronic acid group is bonded to the hydroxyl group of PVA, two Rs in the structural formula (3) are both PVA chains, and a plurality of PVA chains are cross-linked to each other, and thus obtained. The wet heat resistance of the polarizing film is effectively improved.

  Examples of the boron-containing compound (B) used in the present invention include methyl boronic acid, ethyl boronic acid, propyl boronic acid, butyl boronic acid, pentyl boronic acid, hexyl boronic acid, and isomers thereof, and phenyl boronic acid. . These have at least one functional group selected from the group consisting of a boronic acid group and a boron-containing group that can be converted to a boronic acid group in the presence of water in the molecule.

  When the boron-containing compound (B) is an aromatic compound, the heat and humidity resistance of the polarizing film may be improved. The reason for this is not clear, but it is presumed that π-π stacking of aromatic rings makes it difficult for moisture to permeate, and the effect of improving the heat and humidity resistance of the polarizing film is enhanced. Examples of such a boron-containing compound (B) include phenylboronic acid, 1,4-benzenediboronic acid, 1,3-benzenediboronic acid, 1,3,5-benzenetriboronic acid, and the like.

  In addition, the boron-containing compound (B) has a plurality of at least one functional group selected from the group consisting of boron-containing groups that can be converted into boronic acid groups in the presence of boronic acid groups and water in the molecule. The wet heat resistance of the polarizing film is effectively improved. The following structural formula (4) shows the boron-containing compound (B) in the case where the molecule has two boronic acid groups. Here, X is a divalent organic group, such as an alkylene group or an arylene group. In this case, there are four points that react with the hydroxyl group of PVA to form an ester, and the PVA chain is more effectively cross-linked.

  Examples of the boron-containing compound (B) having a plurality of functional groups include methanediboronic acid, ethanediboronic acid, propanediboronic acid, butanediboronic acid, pentanediboronic acid, hexanediboronic acid, and isomers thereof, and 1,4 -Benzenediboronic acid, 1,3-benzenediboronic acid, 1,3,5-benzenetriboronic acid and the like.

The boron element content derived from the boron-containing compound (B) in the polarizing film of the present invention needs to be 0.1 to 3 parts by mass with respect to 100 parts by mass of the polyvinyl alcohol (A). When the boron element content derived from the boron-containing compound (B) is less than 0.1 parts by mass, the crosslinking amount of the polyvinyl alcohol (A) is small, and the effect of improving the heat and moisture resistance is insufficient. The boron element content derived from the boron-containing compound (B) is preferably 0.2 parts by mass or more, more preferably 0.3 parts by mass or more. On the other hand, if the boron element content derived from the boron-containing compound (B) is to be increased from 3 parts by mass, the film becomes too hard and the handleability is lowered, and the productivity is lowered because a long processing time is required. There is also a risk. The boron element content derived from the boron-containing compound (B) is preferably 2 parts by mass or less, particularly preferably 1 part by mass or less. The boron element content derived from the boron-containing compound (B) can be obtained by ¹ H-NMR measurement.

  It is preferable that the polarizing film of the present invention further contains boric acid. Thereby, it is possible to more effectively prevent PVA from eluting into water when wet-stretching at a high temperature. At this time, it is preferable that total boron element content in a polarizing film is 0.2-5 mass%. Here, the total boron element content is an amount obtained by totaling the contents of all boron elements including the boron element content derived from the boron-containing compound (B) and the boron element content derived from boric acid. When the total boron element content in the polarizing film is less than 0.2% by mass, the effect of improving the heat and moisture resistance is lowered. The total boron element content in the polarizing film is more preferably 1% by mass or more. On the other hand, when the total boron element content in the polarizing film is more than 5% by mass, the dimensional change of the polarizing film at high temperatures may increase. The total boron element content in the polarizing film is more preferably 4.5% by mass or less. The total boron element content in the polarizing film can be determined by ICP emission analysis or the like.

  The polymerization degree of PVA contained in the polarizing film of the present invention is preferably in the range of 1,500 to 6,000, more preferably in the range of 1,800 to 5,000, and 2,000. More preferably, it is in the range of ˜4,000. When the polymerization degree is 1,500 or more, the durability of the polarizing film obtained by uniaxially stretching the film can be improved. On the other hand, when the degree of polymerization is 6,000 or less, it is possible to suppress an increase in manufacturing cost, poor process passability during film formation, and the like. In addition, the polymerization degree of PVA in this specification means the average degree of polymerization measured according to description of JIS K6726-1994.

The saponification degree of PVA contained in the polarizing film of the present invention is preferably 95 mol% or more, more preferably 96 mol% or more from the viewpoint of water resistance of the polarizing film obtained by uniaxially stretching the film. Preferably, it is 98 mol% or more. In this specification, the degree of saponification of PVA refers to the structural units (typically vinyl ester units) that can be converted into vinyl alcohol units (—CH ₂ —CH (OH) —) by saponification, which PVA has, and vinyl. The ratio (mol%) which the number-of-moles of the said vinyl alcohol unit occupies with respect to the total number-of-moles with an alcohol unit. The saponification degree can be measured according to the description of JIS K6726-1994.

  The manufacturing method of PVA used by this invention is not specifically limited. For example, the method of converting the vinyl ester unit of polyvinyl ester obtained by polymerizing a vinyl ester monomer into a vinyl alcohol unit is mentioned. The vinyl ester monomer used for the production of PVA is not particularly limited. For example, vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatate, vinyl caproate, caprylic acid Examples thereof include vinyl, vinyl caprate, vinyl laurate, vinyl palmitate, vinyl stearate, vinyl oleate, and vinyl benzoate. From the economical viewpoint, vinyl acetate is preferred.

  The PVA used in the present invention is obtained by converting a vinyl ester unit of a polyvinyl ester copolymer obtained by copolymerizing a vinyl ester monomer and another monomer copolymerizable therewith into a vinyl alcohol unit. It may be a thing. Examples of other monomers copolymerizable with the vinyl ester monomer include α-olefins having 2 to 30 carbon atoms such as ethylene, propylene, 1-butene, and isobutene; (meth) acrylic acid or a salt thereof; Methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, (Meth) acrylic acid esters such as t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, octadecyl (meth) acrylate; (meth) acrylamide; N-methyl (Meth) acrylamide, N-ethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, diacetone (meth) acryl (Meth) acrylamide derivatives such as amide, (meth) acrylamide propanesulfonic acid or salts thereof, (meth) acrylamidepropyldimethylamine or salts thereof, N-methylol (meth) acrylamide or derivatives thereof; N-vinylformamide, N-vinyl N-vinylamides such as acetamide and N-vinylpyrrolidone; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether, etc. Vinyl ether; vinyl cyanide such as (meth) acrylonitrile; halogenated vinyl such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride; vinegar Allyl compounds such as allyl acid and allyl chloride; maleic acid or its salt, ester or acid anhydride; itaconic acid or its salt, ester or acid anhydride; vinylsilyl compound such as vinyltrimethoxysilane; unsaturated sulfonic acid be able to. The vinyl ester copolymer can have a structural unit derived from one or more of the other monomers described above. The other monomer may be pre-existed in the reaction vessel when the vinyl ester monomer is subjected to the polymerization reaction, or may be added to the reaction vessel during the polymerization reaction. Can be used. From the viewpoint of polarization performance, the content of units derived from other monomers is preferably 10 mol% or less, more preferably 5 mol% or less, and more preferably 2 mol% or less. Further preferred.

  Among the monomers copolymerizable with the above vinyl ester monomer, the stretchability is improved and the film can be stretched at a higher temperature. Ethylene is preferred because the productivity of the film is further improved. When PVA contains an ethylene unit, the content of the ethylene unit is 1 to 4 mol% with respect to the number of moles of all structural units constituting the PVA, from the viewpoints of stretchability and stretchable temperature as described above. Preferably, 2-3 mol% is more preferable.

  The polymerization method for polymerizing the vinyl ester monomer may be any of batch polymerization, semi-batch polymerization, continuous polymerization, semi-continuous polymerization, etc., and polymerization methods include bulk polymerization, solution polymerization, suspension Known methods such as a polymerization method and an emulsion polymerization method can be applied. A bulk polymerization method or a solution polymerization method in which polymerization is allowed to proceed in a solvent-free or solvent such as alcohol is usually employed. In the case of obtaining a polyvinyl ester having a high degree of polymerization, an emulsion polymerization method is also preferable. Although the solvent of the solution polymerization method is not particularly limited, for example, alcohol. The alcohol used as the solvent for the solution polymerization method is, for example, a lower alcohol such as methanol, ethanol, or propanol. The amount of solvent used in the polymerization solution may be selected in consideration of the chain transfer of the solvent in accordance with the degree of polymerization of the target PVA. For example, when the solvent is methanol, the mass ratio of the solvent to all monomers ( Solvent / total monomer) is preferably selected within the range of 0.01 to 10, more preferably within the range of 0.05 to 3.

  The polymerization initiator used for polymerization of the vinyl ester monomer may be selected from known polymerization initiators such as azo initiators, peroxide initiators, and redox initiators according to the polymerization method. Examples of the azo initiator include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (4-methoxy-2,4- Dimethylvaleronitrile). Examples of the peroxide initiator include percarbonate compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, and diethoxyethyl peroxydicarbonate; t-butyl peroxyneodecanate, α- Perester compounds such as cumylperoxyneodecanate; acetylcyclohexylsulfonyl peroxide; 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate; acetyl peroxide. Potassium persulfate, ammonium persulfate, hydrogen peroxide, or the like may be combined with the above initiator to form a polymerization initiator. The redox initiator is, for example, a polymerization initiator in which the peroxide initiator is combined with a reducing agent such as sodium hydrogen sulfite, sodium hydrogen carbonate, tartaric acid, L-ascorbic acid, or longalite. The amount of the polymerization initiator used varies depending on the type of the polymerization initiator and cannot be determined unconditionally, but may be selected according to the polymerization rate. For example, when 2,2′-azobisisobutyronitrile or acetyl peroxide is used as a polymerization initiator, 0.01 to 0.2 mol% is preferable with respect to the vinyl ester monomer, and 0.02 to 0.02%. 15 mol% is more preferable. The polymerization temperature is not particularly limited, but is suitably about room temperature to 150 ° C, preferably 40 ° C or higher and lower than the boiling point of the solvent used.

  The polymerization of the vinyl ester monomer may be performed in the presence of a chain transfer agent. Examples of the chain transfer agent include aldehydes such as acetaldehyde and propionaldehyde; ketones such as acetone and methyl ethyl ketone; mercaptans such as 2-hydroxyethanethiol; phosphinic acid salts such as sodium phosphinate monohydrate and the like. Of these, aldehydes and ketones are preferably used. The amount of the chain transfer agent used can be determined according to the chain transfer coefficient of the chain transfer agent to be used and the polymerization degree of the target PVA, but is generally 0.1% with respect to 100 parts by mass of the vinyl ester monomer. -10 mass parts is preferable.

  The saponification of the polyvinyl ester can be performed, for example, in a state where the polyvinyl ester is dissolved in an alcohol or a hydrous alcohol. Examples of the alcohol used for saponification include lower alcohols such as methanol and ethanol, preferably methanol. The alcohol used for saponification may contain other solvents such as acetone, methyl acetate, ethyl acetate, and benzene at a ratio of 40% by mass or less of the mass, for example. The catalyst used for saponification is, for example, an alkali metal hydroxide such as potassium hydroxide or sodium hydroxide, an alkali catalyst such as sodium methylate, or an acid catalyst such as mineral acid. The temperature at which saponification is performed is not limited, but is preferably in the range of 20 to 60 ° C. When a gel-like product precipitates as saponification progresses, the product is pulverized, washed and dried to obtain PVA. The saponification method is not limited to the method described above, and a known method can be applied.

  The PVA film used for production of the polarizing film of the present invention can contain a plasticizer in addition to the above PVA. Preferred plasticizers include polyhydric alcohols, and specific examples include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, trimethylolpropane, and the like. Furthermore, 1 type, or 2 or more types of these plasticizers can be included. Among these, glycerin is preferable in terms of the effect of improving stretchability.

  The content of the plasticizer in the PVA film used for the production of the polarizing film of the present invention is preferably in the range of 1 to 20 parts by mass, and in the range of 3 to 17 parts by mass with respect to 100 parts by mass of PVA. More preferably, it is still more preferably in the range of 5 to 15 parts by mass. When the content is 1 part by mass or more, the stretchability of the film is further improved. On the other hand, when the content is 20 parts by mass or less, it is possible to prevent the film from becoming too flexible and handling properties from being lowered.

  The PVA film used for the production of the polarizing film of the present invention further includes a filler, a processing stabilizer such as a copper compound, a weather resistance stabilizer, a colorant, an ultraviolet absorber, a light stabilizer, an antioxidant, and an antistatic agent. , Flame retardants, other thermoplastic resins, lubricants, fragrances, antifoaming agents, deodorants, extenders, release agents, mold release agents, reinforcing agents, crosslinking agents, fungicides, preservatives, crystallization rate delay An additive such as an agent can be appropriately blended as necessary.

  The proportion of the total of PVA and plasticizer in the PVA film used for producing the polarizing film of the present invention is preferably 80% by mass or more, more preferably 90% by mass or more based on the mass of the PVA film. Preferably, it is 95 mass% or more.

  The swelling degree of the PVA film used for producing the polarizing film of the present invention is preferably in the range of 160 to 240%, more preferably in the range of 170 to 230%, and in the range of 180 to 220%. It is particularly preferred that When the degree of swelling is 160% or more, the crystallization can be prevented from proceeding extremely, and the film can be stably stretched to a high magnification. On the other hand, when the degree of swelling is 240% or less, dissolution during stretching is suppressed, and stretching is possible even under higher temperature conditions.

  The thickness of the PVA film used for the production of the polarizing film of the present invention is not particularly limited, but is generally 1 to 100 μm, more preferably 5 to 60 μm, and particularly preferably about 10 to 45 μm. When the thickness is too thin, there is a tendency that stretching breakage is likely to occur during the uniaxial stretching process for producing the polarizing film. Moreover, when the said thickness is too thick, it will become easy to generate | occur | produce a stretching spot at the time of the uniaxial stretching process for manufacturing a polarizing film.

  The width | variety in particular of the PVA film used for manufacture of the polarizing film of this invention is not restrict | limited, It can determine according to the use etc. of the polarizing film manufactured. In recent years, since the enlargement of screens of liquid crystal televisions and liquid crystal monitors has progressed, the width of the PVA film used for the production of the polarizing film is preferably 3 m or more, which is suitable for these applications. On the other hand, if the width of the PVA film used for the production of the polarizing film is too large, it is difficult to perform uniaxial stretching uniformly when the polarizing film is produced with a device that has been put to practical use. The width of the PVA film to be used is preferably 7 m or less.

  The manufacturing method of the PVA film used for manufacture of the polarizing film of this invention is not specifically limited, The manufacturing method from which the thickness and width | variety of the film after film forming become more uniform can be employ | adopted preferably, for example, manufacture of a polarizing film The above-mentioned PVA constituting the PVA film used in the above, and if necessary, one or more of the above-described plasticizers, additives, and surfactants described later are dissolved in a liquid medium. Use a membrane forming solution in which PVA is melted, including one or more of a membrane stock solution, PVA, and, if necessary, a plasticizer, an additive, a surfactant, and a liquid medium. Can be manufactured. When the film-forming stock solution contains at least one of a plasticizer, an additive, and a surfactant, it is preferable that these components are uniformly mixed.

  Examples of the liquid medium used for the preparation of the membrane forming stock solution include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, and tetraethylene glycol. , Trimethylolpropane, ethylenediamine, diethylenetriamine and the like, and one or more of them can be used. Among these, water is preferable from the viewpoint of environmental load and recoverability.

  The volatile fraction of the film-forming stock solution (content ratio in the film-forming stock solution of volatile components such as liquid media removed by volatilization or evaporation during film formation) varies depending on the film-forming method, film-forming conditions, etc. Specifically, it is preferably in the range of 50 to 95% by mass, and more preferably in the range of 55 to 90% by mass. The film-forming stock solution has a volatile content of 50% by mass or more, so that the viscosity of the film-forming stock solution does not become too high, and filtration and defoaming are smoothly performed during the preparation of the film-forming stock solution, and there are few foreign substances and defects. Is easy to manufacture. On the other hand, when the volatile fraction of the film-forming stock solution is 95% by mass or less, the concentration of the film-forming stock solution does not become too low, and industrial film production is facilitated.

  The film-forming stock solution preferably contains a surfactant. By including the surfactant, the film-forming property is improved and the occurrence of uneven thickness of the film is suppressed, and the film is easily peeled off from the metal roll or belt used for film formation. When a PVA film is produced from a film-forming stock solution containing a surfactant, the film may contain a surfactant. Although the kind of said surfactant is not specifically limited, From a viewpoint of the peelability from a metal roll or a belt, an anionic surfactant or a nonionic surfactant is preferable.

  Suitable examples of the anionic surfactant include carboxylic acid types such as potassium laurate; sulfate ester types such as polyoxyethylene lauryl ether sulfate and octyl sulfate; and sulfonic acid types such as dodecylbenzene sulfonate.

  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; 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 lauric acid diethanolamide and oleic acid diethanolamide; polyoxy An allyl phenyl ether type such as alkylene allyl phenyl ether is preferred.

  These surfactants can be used individually by 1 type or in combination of 2 or more types.

  When the film-forming stock solution contains a surfactant, the content thereof is preferably in the range of 0.01 to 0.5 parts by weight with respect to 100 parts by weight of PVA contained in the film-forming stock solution, and 0.02 More preferably, it is in the range of -0.3 parts by mass, and particularly preferably in the range of 0.05-0.2 parts by mass. When the said content is 0.01 mass part or more, film forming property and peelability improve more. On the other hand, when the content is 0.5 parts by mass or less, it is possible to suppress that the surfactant bleeds out to the surface of the PVA film to cause blocking, and the handleability is deteriorated.

  Examples of the film forming method for forming a PVA film used for the production of a polarizing film using the above-described film forming stock solution include a cast film forming method, an extrusion film forming method, a wet film forming method, a gel film forming method, and the like. Is mentioned. These film forming methods may be used alone or in combination of two or more. Among these film forming methods, the cast film forming method and the extrusion film forming method are preferable because a PVA film used for manufacturing a polarizing film having uniform thickness and width and good physical properties can be obtained. The formed PVA film can be dried or heat-treated as necessary.

  As an example of a specific production method of the PVA film used for the production of the polarizing film of the present invention, for example, using the T-type slit die, hopper plate, I-die, lip coater die, etc. A film that is uniformly discharged or cast on the peripheral surface of a heated heated first roll (or belt) positioned on the most upstream side, and discharged or cast on the peripheral surface of the first roll (or belt) The volatile components are evaporated and dried from one side of the substrate, and then further dried on the peripheral surface of one or more rotating heated rolls arranged downstream thereof, or in a hot air dryer. After passing through and further drying, a method of winding with a winding device can be preferably employed industrially. Drying with a heated roll and drying with a hot air dryer may be performed in an appropriate combination.

  The method for producing the polarizing film of the present invention is not particularly limited. A preferred production method is a method for producing a polarizing film comprising a dyeing treatment for dyeing a polyvinyl alcohol film with a dichroic dye, and a stretching treatment for uniaxially stretching the film, wherein the film is made into an aqueous solution of a boron-containing compound (B). It is a manufacturing method of the polarizing film which has the process to immerse. The PVA film used for the production of the polarizing film of the present invention is subjected to a dyeing process, a uniaxial stretching process, and, if necessary, a swelling process, a boric acid crosslinking process, a fixing process, a washing process, a drying process, a heat treatment and the like. A method is mentioned. In this case, the order of each treatment such as swelling treatment, dyeing treatment, boric acid crosslinking treatment, uniaxial stretching treatment, and fixing treatment is not particularly limited, and one or two or more treatments can be performed simultaneously. Also, one or more of each process can be performed twice or more.

  The swelling treatment can be performed by immersing the PVA film in water. The temperature of the water when immersed in water is preferably within a range of 20 to 40 ° C, more preferably within a range of 22 to 38 ° C, and within a range of 25 to 35 ° C. Further preferred. Moreover, as time to immerse in water, it is preferable to exist in the range of 0.1 to 5 minutes, for example, and it is more preferable to be in the range of 0.2 to 3 minutes. In addition, the water at the time of immersing in water is not limited to pure water, The aqueous solution in which various components melt | dissolved may be sufficient, and the mixture of water and an aqueous medium may be sufficient.

  The dyeing process can be performed by bringing a dichroic dye into contact with the PVA film. As the dichroic dye, an iodine dye is generally used. The timing of the dyeing process may be any stage before the uniaxial stretching process, at the time of the uniaxial stretching process, or after the uniaxial stretching process. The dyeing treatment is generally performed by immersing the PVA film in a solution (particularly an aqueous solution) containing iodine-potassium iodide as a dyeing bath. The iodine concentration in the dyeing bath is preferably in the range of 0.01 to 0.5% by mass, and the potassium iodide concentration is preferably in the range of 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. The preferred staining time is 0.2 to 5 minutes.

  By performing the boric acid crosslinking treatment on the PVA film, it is possible to more effectively prevent PVA from eluting into water when wet-stretching at a high temperature. From this viewpoint, the boric acid crosslinking treatment is preferably performed before the uniaxial stretching treatment. The boric acid crosslinking treatment can be performed by immersing the PVA film in an aqueous solution containing a boric acid crosslinking agent. As the boric acid crosslinking agent, one or more of boron-containing inorganic compounds such as borates such as boric acid and borax can be used. The concentration of the boric acid crosslinking agent in the aqueous solution containing the boric acid crosslinking agent is preferably in the range of 1 to 15% by mass, and more preferably in the range of 2 to 7% by mass. Sufficient stretchability can be maintained when the concentration of the boric acid crosslinking agent is in the range of 1 to 15% by mass. The aqueous solution containing the boric acid crosslinking agent may contain an auxiliary agent such as potassium iodide. The temperature of the aqueous solution containing the boric acid crosslinking agent is preferably in the range of 20 to 50 ° C, particularly in the range of 25 to 40 ° C. By making the said temperature into the range of 20-50 degreeC, boric acid bridge | crosslinking can be performed efficiently.

  The uniaxial stretching treatment may be performed by either a wet stretching method or a dry stretching method. In the case of the wet stretching method, it can be carried out in an aqueous solution containing boric acid, or can be carried out in the dyeing bath described above or in a fixing treatment bath described later. In the case of the dry stretching method, the uniaxial stretching treatment may be performed at room temperature, the uniaxial stretching treatment may be performed while heating, or the uniaxial stretching treatment is performed in the air using the PVA film after water absorption. You can also. Among these, the wet stretching method is preferable, and it is more preferable to perform the uniaxial stretching process in an aqueous solution containing boric acid. The concentration of boric acid in the boric acid aqueous solution is preferably in the range of 0.5 to 6% by mass, and more preferably in the range of 1 to 5% by mass. Moreover, the boric acid aqueous solution may contain potassium iodide, and the concentration is preferably in the range of 0.01 to 10% by mass. The stretching temperature in the uniaxial stretching treatment is preferably in the range of 30 to 90 ° C, more preferably in the range of 40 to 80 ° C, and particularly preferably in the range of 50 to 70 ° C. The stretching ratio in the uniaxial stretching treatment (total stretching ratio from the raw material PVA film) is preferably 5 times or more from the viewpoint of the polarizing performance of the obtained polarizing film, and more preferably 5.5 times or more. preferable. The upper limit of the draw ratio is not particularly limited, but the draw ratio is preferably 8 times or less.

  There is no particular limitation on the direction of the uniaxial stretching treatment when performing a uniaxial stretching treatment on a long PVA film, and a uniaxial stretching treatment or a lateral uniaxial stretching treatment in the long direction or a so-called oblique stretching treatment can be employed. A uniaxial stretching treatment in the longitudinal direction is preferable because a polarizing film having excellent polarization performance can be obtained. The uniaxial stretching process in the longitudinal direction can be performed by changing the peripheral speed between the rolls using a stretching apparatus including a plurality of rolls parallel to each other. On the other hand, the lateral uniaxial stretching treatment can be performed using a tenter type stretching machine.

  In the production of the polarizing film, it is preferable to perform a fixing process after the uniaxial stretching process in order to strengthen the adsorption of the dichroic dye (iodine dye or the like) to the PVA film. As the fixing treatment bath used for the fixing treatment, an aqueous solution containing a boron-containing compound (B) can be preferably used. Moreover, you may add a boric acid, an iodine compound, a metal compound, etc. in a fixed treatment bath as needed. The temperature of the fixing treatment bath is preferably 15 to 60 ° C, particularly preferably 25 to 40 ° C.

  The boron-containing compound (B) may be adsorbed to the polarizing film in any of the dyeing process, boric acid crosslinking process, uniaxial stretching process, and fixing process. It is particularly preferable because it does not affect the above. Further, the boron-containing compound (B) is not limited to one type, and two or more types may be mixed and used. 0.05-15 mass% is preferable and, as for the aqueous solution density | concentration of a boron containing compound (B), 0.1 mass%-10 mass% are especially preferable. When the aqueous solution concentration of the boron-containing compound (B) is lower than 0.05% by mass, the adsorption may be slow, and when the aqueous solution concentration is higher than 15% by mass, the boron-containing compound (B) Precipitation may occur. Moreover, it is preferable that the aqueous solution containing a boron containing compound (B) contains adjuvants, such as potassium iodide, from the point of a polarizing performance improvement. The temperature of the treatment bath is preferably 10 to 70 ° C, more preferably 20 to 60 ° C, and particularly preferably 20 to 50 ° C. If the temperature is too low, the boron-containing compound (B) may precipitate in the treatment bath. On the other hand, if the temperature is too high, it is difficult to easily produce industrially under relatively mild conditions.

  In the case of adsorbing the boron-containing compound (B) on the polarizing film during the fixing treatment, a suitable production method is to perform a swelling treatment, a boric acid crosslinking treatment, a uniaxial stretching treatment, and a fixing treatment in this order. Thereafter, if necessary, one or more processes selected from a cleaning process, a drying process, and a heat treatment may be performed in this order.

  The washing treatment is generally performed by immersing the film in water, distilled water, pure water or the like. At this time, the aqueous solution used for the washing treatment preferably contains an iodide such as potassium iodide as an auxiliary from the viewpoint of improving the polarization performance, and the concentration of the iodide is preferably 0.5 to 10% by mass. . Moreover, the temperature of the aqueous solution in the washing treatment is generally 5 to 50 ° C, preferably 10 to 45 ° C, more preferably 15 to 40 ° C. From an economical viewpoint, it is not preferable that the temperature of the aqueous solution is too low. If the temperature of the aqueous solution is too high, the polarization performance may be deteriorated.

  The conditions for the drying treatment are not particularly limited, but it is preferable to perform the drying at a temperature within the range of 30 to 150 ° C, particularly within the range of 50 to 130 ° C. A polarizing film excellent in dimensional stability is easily obtained by drying at a temperature in the range of 30 to 150 ° C.

  By performing the heat treatment after the drying treatment, a polarizing film having further excellent dimensional stability can be obtained. Here, the heat treatment is a treatment for further heating the polarizing film after the drying treatment having a moisture content of 5% or less to improve the dimensional stability of the polarizing film. The conditions for the heat treatment are not particularly limited, but it is preferable to perform the heat treatment within a range of 60 ° C to 150 ° C, particularly within a range of 70 ° C to 150 ° C. When the heat treatment is performed at a temperature lower than 60 ° C., the dimensional stabilization effect by the heat treatment is insufficient, and when the heat treatment is performed at a temperature higher than 150 ° C., the polarizing film may be severely reddened.

  The heat-and-moisture resistance performance of the polarizing film obtained as described above can be evaluated using, as an index, fading of a color derived from the PVA-iodine complex at high temperature and high humidity. Specifically, the evaluation is based on the percentage of absorbance D (610 nm) after fading with respect to absorbance C (610 nm) before fading when two polarizing films are superposed on crossed Nicols. be able to. The absorbance remaining rate after fading for 8 hours at 60 ° C./90% RH is preferably 22% or more, and more preferably 25% or more.

  A polarizing film is usually used as a polarizing plate by attaching a protective film that is optically transparent and has mechanical strength to 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 which PVA adhesives are suitable.

  The polarizing plate obtained as described above can be used as a component of an LCD after being coated with an acrylic adhesive or the like 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.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited at all by these Examples. In addition, each measurement or evaluation method employ | adopted in the following examples and comparative examples is shown below.

[Swelling degree of PVA film]
The PVA film was cut into 5 cm × 10 cm and immersed in 1000 mL of distilled water at 30 ° C. for 30 minutes. Thereafter, the PVA film was taken out, the moisture on the surface of the PVA film was wiped off with filter paper, and the mass (mass E) of the PVA film after immersion was measured. Thereafter, the PVA film was put in a dryer at 105 ° C. and dried for 16 hours, and then the PVA film mass (mass F) after drying was measured. The degree of swelling of the PVA film was calculated by substituting the values of mass E and mass F into the following formula (5).
Swelling degree (%) = (mass E / mass F) × 100 (5)

[Optical properties of polarizing film]
(1) Measurement of transmittance Ts From the central part of the polarizing film obtained in the following examples or comparative examples, two samples of 4 cm in the stretching direction of the polarizing film and 2 cm in the width direction were collected, and spectroscopy with an integrating sphere Using a photometer (“V7100” manufactured by JASCO Corporation), in accordance with JIS Z 8722 (object color measurement method), the visibility correction of the visible light region of the C light source and the 2 ° field of view is performed. About the sample, the light transmittance when tilted by + 45 ° with respect to the length direction and the light transmittance when tilted by −45 ° were measured, and an average value Ts1 (%) thereof was obtained. In the same manner for the other sample, the light transmittance when tilted by + 45 ° and the light transmittance when tilted by −45 ° were measured, and an average value Ts2 (%) thereof was obtained. Ts1 and Ts2 were averaged by the following calculation formula (6) to obtain the transmittance Ts (%) of the polarizing film.
Ts = (Ts1 + Ts2) / 2 (6)

(2) Measurement of polarization degree V With respect to the two samples used in the measurement of the transmittance Ts, the light transmittance T⊥ (%) when the samples are stacked so that the stretching directions are orthogonal to each other, and the stretching Using a spectrophotometer with an integrating sphere (“V7100” manufactured by JASCO Corporation), the light transmittance T // (%) when stacked so that the directions are parallel to each other is JIS Z 8722 (object color In accordance with the measurement method), the measurement was performed by correcting the visibility of the C light source and the visible light region of the 2 ° visual field. The measured degree of polarization V (%) was determined by substituting the measured T // (%) and T⊥ (%) into the following formula (7).
V = {(T‖−T⊥) / (T‖ + T⊥)} ^1/2 × 100 (7)

[Humidity and heat resistance]
Two polarizing films were each fixed to a metal frame, overlapped with crossed Nicols, and the initial absorbance (0 hour) C (610 nm) was measured with a spectrophotometer. Further, the polarizing film fixed to the metal frame was allowed to stand in an atmosphere of 60 ° C./90% RH for 8 hours, and then superimposed on crossed Nicols, and the absorbance D (610 nm) after 8 hours was measured with a spectrophotometer. The value of absorbance D / absorbance C × 100 was defined as the residual rate (%), and was used as an index for fading of the color derived from the PVA-iodine complex.

[Measurement of boron element content derived from boron-containing compound (B) with respect to 100 parts by mass of polyvinyl alcohol (A)]
A solution obtained by dissolving a polarizing film conditioned at 23 ° C./50% RH for 16 hours with heavy water to 0.005% by mass and concentrating with a rotary evaporator to 0.15% by mass is obtained by ¹ H-NMR. A measurement sample was obtained. ¹ H-NMR (manufactured by JEOL Ltd., JNM-AL400: 400 MHz) was measured at 80 ° C. and analyzed by ALEX2 (manufactured by JEOL Ltd.) by the following method. For the ¹ H-NMR chart obtained by the measurement, the phase was adjusted so that the baseline was smooth, and then the average point was set to 20 and the baseline was automatically corrected. Next, it was automatically set as a reference so that the peak of heavy water as a measurement solvent was at a position of 4.65 ppm. Thereafter, as shown in FIG. 1, the hydrogen peak of the hydrocarbon group contained in the boron-containing compound (B) was integrated to determine the peak area. At this time, the sum of the hydrogen peak areas of the hydrocarbon groups contained in the boron-containing compound (B) that does not overlap with the hydrogen peak derived from PVA (area G) is used as a reference for the peak area, and the boron-containing compound (B) The number of hydrogen of the corresponding hydrocarbon group and the value of the area G were set to be the same. Next, the hydrocarbon peak contained in the boron-containing compound (B) in which the hydrogen peak in the range of 1.7 ppm to 2.4 ppm overlaps the hydrogen peak derived from the methylene group of PVA and the hydrogen peak derived from the methylene group of PVA. The peak area (area H) was determined by regarding the total of the hydrogen peaks. Thereafter, an area I obtained by subtracting the hydrogen number of the hydrocarbon group of the boron-containing compound (B) overlapping the hydrogen peak of the methylene group derived from PVA from the area H was calculated. The values obtained by these methods were substituted into the following formula (8) to calculate the boron element content derived from the boron-containing compound (B) with respect to 100 parts by mass of the polyvinyl alcohol (A). In the following calculation formula (8), X and Y are the number of hydrogen atoms of the hydrocarbon group contained in the boron-containing compound (B) not overlapping the PVA peak, and boron per molecule of the boron-containing compound (B). Is a number. Calculation formula (8) is a formula used when unmodified PVA is used. When modified PVA is used as a raw material, calculation formula (8) needs to be appropriately modified.
Content of boron element derived from boron-containing compound (B) with respect to 100 parts by mass of polyvinyl alcohol (A) (parts by mass) = {(area G / X) / (area I / 2)} × {(10.811 × Y) /44.0526}×100 (8)
10.0.811 is the atomic weight of boron, and 44.0526 is the molecular weight per mole of unmodified PVA repeating units. The ¹ H-NMR chart of FIG. 1 is obtained by measuring the polarizing film of Example 1. The boron element content derived from the boron-containing compound (B) with respect to 100 parts by mass of the polyvinyl alcohol (A) is the second decimal place. To 0.5 parts by mass.

[Calculation of total boron element content (mass%) in polarizing film]
The mass (J (g)) of the polarizing film conditioned at 23 ° C./50% RH for 16 hours was measured, and dissolved in 20 mL of distilled water so that the polarizing film was 0.005% by mass. The aqueous solution in which the polarizing film was dissolved was used as a measurement sample, and its mass (K (g)) was measured. Thereafter, the boron concentration (L (ppm)) of the measurement sample was measured using a multi-type ICP emission analyzer (ICP) manufactured by Shimadzu Corporation. Thereafter, the value calculated by substituting the value into the following formula (9) was defined as the total boron element content (% by mass) in the polarizing film.
Total boron element content in polarizing film (% by mass)
= [(L × 10 ⁻⁶ × K) / J] × 100 (9)

[Example 1]
100 parts by mass of PVA (saponification degree 99.9 mol%, polymerization degree 2400), 10 parts by mass of glycerin as a plasticizer, and 0.1 parts by mass of sodium polyoxyethylene lauryl ether sulfate as a surfactant, the content of PVA Using an aqueous solution of 10% by mass as a film-forming stock solution, this was dried on a metal roll at 80 ° C., and the resulting film was swollen by heat treatment at a temperature of 120 ° C. for 10 minutes in a hot air dryer. The degree was adjusted to 200%, and a PVA film having a thickness of 30 μm was produced.

  A sample having a width of 5 cm and a length of 9 cm was cut from the central portion in the width direction of the PVA film thus obtained so that the range of width 5 cm × length 5 cm could be uniaxially stretched. While immersing this sample in pure water at 30 ° C. for 30 seconds, the sample was uniaxially stretched 1.1 times in the length direction and swelled. Subsequently, while being immersed in an aqueous solution (dyeing bath) containing 0.04% by mass of iodine and 4.0% by mass of potassium iodide (temperature 30 ° C.) for 60 seconds, it is 2.2 times (2.4 times as a whole). The iodine was adsorbed by uniaxial stretching in the length direction. Next, 1.2 times (2.7 times overall) while immersing in an aqueous solution (boric acid crosslinking treatment bath) containing 3% by mass of boric acid and 3% by mass of potassium iodide (temperature 30 ° C.). The film was uniaxially stretched in the length direction. Further, while being immersed in a 58 ° C. aqueous solution (uniaxial stretching treatment bath) containing 4% by mass of boric acid and 6% by mass of potassium iodide, the whole was uniaxially stretched in the length direction up to 6.0 times. Then, it was immersed for 100 seconds in an aqueous solution (fixed treatment bath) (temperature 30 ° C.) containing 0.5% by mass of 1,4-butanediboronic acid and 4% by mass of potassium iodide. Finally, it was dried at 60 ° C. for 4 minutes to produce a polarizing film. When the two polarizing films after drying were each fixed to a metal frame and superimposed on crossed Nicols, the absorbance (610 nm) was 3.9.

When ¹ H-NMR of the obtained polarizing film was measured and analyzed, a hydrogen peak of 1,4-butanediboronic acid that did not overlap with the hydrogen peak derived from PVA appeared at 1.0 to 1.3 ppm. The area (area G) was set to 4. Next, the hydrogen peak area (area H) of the methylene group of PVA in which a peak appears in the range of 1.7 to 2.4 ppm was calculated. Since there was a hydrogen peak of 1,4-butanediboronic acid that overlapped with the hydrogen peak of the methylene group of PVA, the number of hydrogens of 1,4-butanediboronic acid corresponding to the hydrogen peak that overlapped with the methylene group of PVA was subtracted from area H. Area I was calculated. When these values were substituted into Formula (8), the boron content derived from the boron-containing compound (B) with respect to 100 parts by mass of the polyvinyl alcohol (A) was 0.5 parts by mass.

  Further, 0.00099 g (mass J) of a polarizing film prepared by the same method was dissolved in 20 mL of distilled water to prepare a measurement sample for ICP measurement. When the mass of the produced measurement sample was measured, the mass was 20.03 g (mass K). Then, when ICP measurement was performed, the boron concentration of the measurement sample was 1.24 ppm (boron concentration L). When these values were substituted into the calculation formula (9), the total boron element content with respect to the polarizing film was 2.5% by mass. Moreover, using the obtained polarizing film, the optical characteristics and wet heat resistance performance of the polarizing film were evaluated by the method described above. The above results are summarized in Table 1.

  In Examples 2 to 4 and Comparative Examples 1 to 3, immersion was performed for 60 seconds in an aqueous solution (dyeing bath) (temperature 30 ° C.) containing 100 parts by mass of potassium iodide with respect to 1 part by mass of iodine. However, it was uniaxially stretched in the length direction 2.2 times (total 2.4 times) to adsorb iodine. At this time, the iodine or potassium iodide concentration in the dyeing bath is such that the absorbance (610 nm) when the two polarizing films after drying are fixed to a metal frame and superimposed on crossed Nicols is 3.6 to 4 .2 adjusted.

[Example 2]
Example 1 was used except that an aqueous solution (temperature 30 ° C.) containing 0.5% by mass of 1,3-propanediboronic acid and 3% by mass of potassium iodide was used for the fixing treatment bath. A polarizing film was prepared, and each measurement or evaluation was performed. The results are shown in Table 1.

[Example 3]
A polarizing film in the same manner as in Example 1 except that an aqueous solution (temperature 30 ° C.) containing 1.0% by mass of phenylboronic acid and 2.0% by mass of potassium iodide was used for the fixing treatment bath. And each measurement or evaluation was performed. The results are shown in Table 1.

[Example 4]
Except that an aqueous solution (temperature 30 ° C.) containing 4.0% by mass of n-propylboronic acid and 3.0% by mass of potassium iodide was used for the fixing treatment bath, the same as in Example 1. A polarizing film was produced and each measurement or evaluation was performed. The results are shown in Table 1.

[Comparative Example 1]
A polarizing film was prepared in the same manner as in Example 1 except that an aqueous solution (temperature 30 ° C.) containing 2% by mass of boric acid and 3% by mass of potassium iodide was used in the fixing treatment bath. Each measurement or evaluation was performed. The results are shown in Table 1.

[Comparative Example 2]
A polarizing film was produced in the same manner as in Example 1 except that an aqueous solution (temperature 30 ° C.) containing 1.0% by mass of boric acid and 3% by mass of potassium iodide was used for the fixing treatment bath. Each measurement or evaluation was performed. The results are shown in Table 1.

[Comparative Example 3]
A polarizing film was prepared in the same manner as in Example 1 except that an aqueous solution (temperature 30 ° C.) containing 0.5% by mass of boric acid and 3% by mass of potassium iodide was used for the fixing treatment bath. Each measurement or evaluation was performed. The results are shown in Table 1.

  When Examples 1 and 2 are compared with Comparative Example 2, the residual absorbance of Examples 1 and 2 is higher than that of Comparative Example 2 even though the total boron element content in the polarizing film is equal to or less than that of Comparative Example 2. I understand. Moreover, when Example 3 and 4 and Comparative Example 1 are compared, although the total boron element content in a polarizing film is equivalent or less, the residual absorbance rate of Examples 3 and 4 is higher than that of Comparative Example 1. I understand that it is expensive. As mentioned above, it turns out that the polarizing film of Examples 1-4 which satisfy | fills prescription | regulation of this invention is excellent in heat-and-moisture resistant performance.

1 Hydrogen peak derived from heavy water as measurement solvent 2 Hydrogen peak derived from methine group of PVA 3 Hydrogen peak derived from methylene group of PVA 4 Derived from hydrocarbon group contained in boron-containing compound (B) overlapping with hydrogen peak derived from PVA 5 Hydrogen peak derived from hydrocarbon group contained in boron-containing compound (B) that does not overlap with hydrogen peak derived from PVA

Claims (4)

  Polarized light comprising polyvinyl alcohol (A) and a boron-containing compound (B) having at least one functional group selected from the group consisting of boronic acid groups and boron-containing groups that can be converted to boronic acid groups in the presence of water. It is a film, Comprising: Boron element content derived from the boron containing compound (B) in a polarizing film is 0.1-3 mass parts with respect to 100 mass parts of polyvinyl alcohol (A), The polarizing film characterized by the above-mentioned. .   Furthermore, boric acid is contained, The total boron element content in a polarizing film is 0.2-5 mass%, The polarizing film of Claim 1 characterized by the above-mentioned.   The polarizing film according to claim 1 or 2, wherein the boron-containing compound (B) has a plurality of the functional groups. In the manufacturing method of the polarizing film including the dyeing | staining process which dyes a polyvinyl alcohol film with a dichroic dye, and the extending | stretching process which uniaxially stretches this film, it has a process which immerses this film in the aqueous solution of a boron containing compound (B) The manufacturing method of the polarizing film in any one of Claims 1-3 characterized by these.

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