KR102327242B1 - Polarizing film and its manufacturing method - Google Patents

Abstract

A polarizing film comprising polyvinyl alcohol (A) and a boron-containing compound (B) having at least one functional group selected from the group consisting of a boronic acid group and a boron-containing group that can be converted into a boronic acid group in the presence of water, the polarizing film comprising: It is set as the polarizing film characterized by the boron element content derived from the boron-containing compound (B) in a film being 0.1-3 mass parts with respect to 100 mass parts of polyvinyl alcohol (A). Furthermore, it is preferable that boric acid is contained and that all boron element content in a polarizing film is 0.2-5 mass %. Thereby, the polarizing film excellent in heat-and-moisture resistance performance is provided.

Description

Polarizing film and its manufacturing method

The present invention relates to a polarizing film excellent in heat-and-moisture resistance and a manufacturing method therefor.

A polarizing plate having a function of transmitting and shielding light is a basic component of a liquid crystal display (LCD) together with a liquid crystal that changes the polarization state of light. Most polarizing plates have a structure in which a protective film, such as a cellulose triacetate (TAC) film, is bonded together on the surface of a polarizing film in order to prevent fading of a polarizing film or to prevent shrinkage of a polarizing film, and a polarizing plate As a polarizing film constituting the polyvinyl alcohol film (hereinafter, "polyvinyl alcohol" may be referred to as "PVA"), an iodine-based dye (I ₃ ^- or I ₅ ^- ) is added to a matrix formed by uniaxial stretching. The adsorbed ones are becoming mainstream.

LCDs are used in a wide range of small devices such as electronic tabletop calculators and wrist watches, mobile phones, notebook computers, liquid crystal monitors, liquid crystal color projectors, liquid crystal televisions, in-vehicle navigation systems, and measurement devices used indoors and outdoors. is required to be thinner and lighter. Therefore, although thickness reduction of each member of LCD is also calculated|required, when the protective film of the polarizing plate which is one of the members of LCD is thinned, there is concern that the function which prevents fading of an iodine type polarizing film will fall. Then, the iodine-type polarizing film excellent in what is called heat-and-moisture resistance with little fading under high temperature and high humidity is calculated|required.

By the way, as a method of improving the heat-and-moisture resistance of an iodine-type polarizing film, with respect to a polarizing film, the method of crosslinking-processing with polyhydric aldehyde (patent document 1), and the method of crosslinking-processing with a polyhydric carboxylic acid compound (patent document 2) This is known.

Japanese Patent Laid-Open No. 6-235815 Japanese Laid-Open Patent Publication No. 2011-257756

However, when a polyhydric aldehyde is used, the aldehyde is easily volatilized and the concentration control is difficult, so that industrial implementation has been difficult. Moreover, since the polyhydric carboxylic acid compound had low reactivity and required use of an acid catalyst, a process at high temperature, etc., there existed a problem that a polarizing film was colored.

Then, this invention does not use an acid catalyst, the processing at high temperature is unnecessary, and an object of this invention is to provide the polarizing film excellent in heat-and-moisture-resistance performance which can manufacture easily industrially.

As a result of the present inventors repeating earnest examination in order to achieve the said objective, according to the polarizing film containing polyvinyl alcohol and a specific boron containing organic compound, it discovered that the said subject was solved, and completed this invention.

The above object is a polarized light containing polyvinyl alcohol (A) and a boron-containing compound (B) having at least one functional group selected from the group consisting of a boronic acid group and a boron-containing group that can be converted into a boronic acid group in the presence of water. As a film, 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) It is solved by providing the polarizing film characterized by the above-mentioned.

At this time, it is preferable that boric acid is further contained and that all boron element content in a polarizing film is 0.2-5 mass %. Moreover, it is also preferable that a boron-containing compound (B) has a some said functional group.

Moreover, the said subject is the manufacturing method of a polarizing film containing the dyeing process of dyeing the polyvinyl alcohol film with a dichroic dye, and the extending|stretching process which uniaxially stretches the film. WHEREIN: The film is a boron-containing compound (B) It is also solved by providing the manufacturing method of the said polarizing film characterized by having a process immersed in the aqueous solution of.

ADVANTAGE OF THE INVENTION According to this invention, the polarizing film excellent in heat-and-moisture resistance is provided. Moreover, according to the manufacturing method of this invention, such a polarizing film can be manufactured easily industrially.

^{BRIEF DESCRIPTION OF THE DRAWINGS It is a <1>} H-NMR chart of the polarizing film obtained in Example 1. FIG.

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

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 boronic acid group and a boron-containing group that can be converted into a boronic acid group in the presence of 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 of a boronic acid group is not hydrolyzed, it is stable also in the environment where water exists. Examples of the boron-containing group that can be converted into a boronic acid group in the presence of water include, but are not limited to, the boronic acid ester group described below.

[Formula 1]

The hydroxyl group of a boronic acid group can form ester with alcohol similarly to the hydroxyl group of boric acid. The following structural formula (2) is a boronic acid monoester group in which 1 molecule of alcohol (R-OH) reacted with respect to a boronic acid group. Here, when a boronic acid group couple|bonds with the hydroxyl group of PVA, R in Structural formula (2) is a PVA chain, a carbon-containing group is couple|bonded with a PVA chain via a boron atom, and the heat-and-moisture resistance of a polarizing film improves.

[Formula 2]

The following structural formula (3) is a boronic acid diester group in which two molecules of alcohol (R-OH) react with respect to a boronic acid group. Here, when a boronic acid group couple|bonds with the hydroxyl group of PVA, both two R in Structural formula (3) are PVA chains, a some PVA chain will mutually bridge|crosslink and the heat-and-moisture resistance of the polarizing film obtained improves effectively.

[Formula 3]

Examples of the boron-containing compound (B) used in the present invention include methylboronic acid, ethylboronic acid, propylboronic acid, butylboronic acid, pentylboronic acid, hexylboronic acid, and isomers thereof, and phenylboronic 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 into a boronic acid group in the presence of water in the molecule.

When a boron-containing compound (B) is an aromatic compound, heat-and-moisture resistance of a polarizing film may improve. Although the reason is not clear, it is estimated that water|moisture content becomes difficult to permeate|transmit by (pi)-(pi) stacking of an aromatic ring, and the heat-and-moisture-resistance improvement effect of a polarizing film becomes high. Examples of the boron-containing compound (B) include phenylboronic acid, 1,4-benzenediboronic acid, 1,3-benzenediboronic acid, and 1,3,5-benzenetriboronic acid.

Further, the boron-containing compound (B) has a plurality of at least one functional group selected from the group consisting of a boronic acid group and a boron-containing group that can be converted into a boronic acid group in the presence of water, so that the heat-and-moisture resistance of the polarizing film is effectively is improved The boron-containing compound (B) in the case of having two boronic acid groups in a molecule|numerator in following structural formula (4) is shown. Here, X is a divalent organic group, and is an alkylene group, an arylene group, etc. In this case, there are four points which react with the hydroxyl group of PVA to form an ester, and the PVA chain is crosslinked more effectively.

[Formula 4]

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

It is necessary that boron element content derived from the boron-containing compound (B) in the polarizing film of this invention is 0.1-3 mass parts with respect to 100 mass parts of polyvinyl alcohol (A). When the boron element content derived from a boron-containing compound (B) is less than 0.1 mass part, there are few crosslinking amounts of polyvinyl alcohol (A), and the effect of improving heat-and-moisture resistance is insufficient. The content of elemental boron 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 content of the boron element derived from the boron-containing compound (B) is more than 3 parts by mass, the film becomes too hard to reduce handleability, and there is a risk of lowering productivity, such as requiring a long treatment time. The content of elemental boron derived from the boron-containing compound (B) is preferably 2 parts by mass or less, and 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 this invention contains boric acid further. Thereby, it is possible to more effectively prevent PVA from eluting into water during wet stretching at high temperature. At this time, it is preferable that all boron element content in a polarizing film is 0.2-5 mass %. Here, total boron element content is the quantity which summed up content of all the boron elements including boron element content derived from a boron-containing compound (B), and boron element content derived from boric acid. When all boron element content in a polarizing film is less than 0.2 mass %, the effect of improving heat-and-moisture resistance falls. It is more preferable that all boron element content in a polarizing film is 1 mass % or more. On the other hand, when there is more total boron element content in a polarizing film than 5 mass %, the dimensional change of the polarizing film at the time of high temperature may become large. It is more preferable that all boron element content in a polarizing film is 4.5 mass % or less. Total boron element content in a polarizing film can be calculated|required by ICP emission analysis etc.

It is preferable to exist in the range of 1,500-6,000, as for the polymerization degree of PVA contained in the polarizing film of this invention, it is more preferable to exist in the range of 1800-5,000, It is more preferable to exist in the range of 2,000-4,000. When the said polymerization degree is 1,500 or more, durability of the polarizing film obtained by uniaxially stretching a film can be improved. On the other hand, when the said polymerization degree is 6,000 or less, a raise of manufacturing cost, the defect of process passability at the time of film forming, etc. can be suppressed. In addition, the polymerization degree of PVA in this specification means the average degree of polymerization measured according to description of JISK6726-1994.

It is preferable that it is 95 mol% or more from the point of the water resistance of the polarizing film obtained by uniaxially stretching a film, as for the saponification degree of PVA contained in the polarizing film of this invention, It is more preferable that it is 96 mol% or more, It is 98 mol% or more more preferably. In addition, the degree of saponification of PVA in the present specification refers to a structural unit (typically a vinyl ester unit) which can be converted into a _{vinyl alcohol unit (-CH 2 -CH(OH)-) by saponification which PVA has, and a vinyl} It means the ratio (mol%) for which the number of moles of the said vinyl alcohol unit occupies with respect to the total number of moles of an alcohol unit. The said saponification degree can be measured according to description of JISK6726-1994.

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, and for example, vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatate, vinyl caproate, caprylic acid Vinyl, vinyl caprate, vinyl laurate, vinyl palmitate, vinyl stearate, vinyl oleate, vinyl benzoate, etc. are mentioned. From an economical viewpoint, vinyl acetate is preferable.

Moreover, PVA used by this invention may convert the vinyl ester unit of the polyvinyl ester copolymer obtained by copolymerizing a vinyl ester monomer and another monomer copolymerizable with it into a vinyl alcohol unit. As another monomer copolymerizable with a vinyl ester monomer, For example, C2-C30 alpha-olefin, such as ethylene, propylene, 1-butene, isobutene; (meth)acrylic acid or its salt; (meth)methyl acrylate, (meth)ethyl acrylate, (meth)acrylic acid n-propyl, (meth)acrylic acid i-propyl, (meth)acrylic acid n-butyl, (meth)acrylic acid i-butyl, (meth)acrylic acid t- (meth)acrylic acid esters, such as butyl, (meth)acrylic-acid 2-ethylhexyl, (meth)acrylic-acid dodecyl, and (meth)acrylic-acid octadecyl; (meth)acrylamide; N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, diacetone (meth) acrylamide, (meth) acrylamide propanesulfonic acid or a salt thereof, (meth) (meth)acrylamide derivatives, such as acrylamide propyl dimethylamine or its salt, N-methylol (meth)acrylamide, or its derivative(s); N-vinylamide, such as N-vinylformamide, N-vinylacetamide, and N-vinylpyrrolidone; Vinyls such as 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, and stearyl vinyl ether ether; Vinyl cyanide, such as (meth)acrylonitrile; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride, and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; Maleic acid or its salt, ester, or acid anhydride; Itaconic acid or its salt, ester, or acid anhydride; vinylsilyl compounds such as vinyltrimethoxysilane; Unsaturated sulfonic acid etc. are mentioned. The said vinyl ester copolymer may have a structural unit derived from 1 type, or 2 or more types of the said other monomer. The said other monomer can be used by making it exist in advance in a reaction container when using a vinyl ester monomer for polymerization reaction, or adding this in a reaction container during advancing of a polymerization reaction. It is preferable that it is 10 mol% or less, and, as for content of the unit derived from another monomer from a viewpoint of polarization|polarized-light performance, it is more preferable that it is 5 mol% or less, It is still more preferable that it is 2 mol% or less.

Among the monomers copolymerizable with the vinyl ester monomer, stretchability is improved and it can be stretched at a higher temperature, and the occurrence of troubles such as stretch breakage during optical film production is reduced, so that the productivity of the optical film is further improved , ethylene is preferred. When the PVA contains an ethylene unit, the content of the ethylene unit is preferably from 1 to 4 mol% with respect to the number of moles of all the structural units constituting the PVA from the viewpoints of stretchability and stretchable temperature as described above, 2-3 mol% is more preferable.

The polymerization method when polymerizing the vinyl ester monomer may be any method such as batch polymerization, semi-batch polymerization, continuous polymerization, and semi-continuous polymerization. As the polymerization method, block polymerization method, solution polymerization method, suspension polymerization method, emulsion polymerization method A well-known method, such as a polymerization method, can be applied. A bulk polymerization method or a solution polymerization method in which polymerization proceeds without a solvent or in a solvent such as alcohol is usually employed. When obtaining polyvinyl ester of high polymerization degree, an emulsion polymerization method is also preferable. Although the solvent in particular of the solution polymerization method is not limited, For example, it is alcohol. The alcohol used for the solvent of the solution polymerization method is a lower alcohol, such as methanol, ethanol, and a propanol, for example. The amount of the solvent used in the polymerization solution may be selected in consideration of the chain transfer of the solvent according to the desired degree of polymerization of the PVA. For example, when the solvent is methanol, the mass ratio of the solvent to all monomers (solvent/total monomers) As such, it 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, for example, azo initiators, peroxide initiators, and redox initiators according to the polymerization method. The azo initiator is, for example, 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(4-methoxy -2,4-dimethylvaleronitrile). A peroxide type initiator, For example, Percarbonate type compounds, such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, and diethoxyethyl peroxydicarbonate; perester compounds such as t-butyl peroxyneodecanate and α-cumylperoxyneodecanate; Acetylcyclohexylsulfonyl peroxide; 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate; It is acetyl peroxide. It is good also as a polymerization initiator combining potassium persulfate, ammonium persulfate, hydrogen peroxide, etc. with the said initiator. The redox-based initiator is, for example, a polymerization initiator obtained by combining the above-mentioned peroxide-based initiator with a reducing agent such as sodium hydrogensulfite, sodium hydrogencarbonate, tartaric acid, L-ascorbic acid or longalite. The amount of the polymerization initiator to be used varies depending on the kind of the polymerization initiator and cannot be determined uniformly, but may be selected according to the polymerization rate. For example, when using 2,2'- azobisisobutyronitrile or acetyl peroxide for a polymerization initiator, 0.01-0.2 mol% is preferable with respect to a vinyl ester monomer, and 0.02-0.15 mol% is more preferable. Although polymerization temperature is not specifically limited, About room temperature - 150 degreeC is suitable, Preferably it is 40 degreeC or more and below the boiling point of the solvent to be used.

You may perform superposition|polymerization of a vinyl ester monomer in presence of a chain transfer agent. The chain transfer agent includes, for example, aldehydes such as acetaldehyde and propionaldehyde; Ketones, such as acetone and methyl ethyl ketone; Mercaptans, such as 2-hydroxyethanethiol; and phosphinic acid salts such as sodium phosphinate monohydrate. Among them, aldehydes and ketones are preferably used. Although the usage-amount of a chain transfer agent can be determined according to the chain transfer coefficient of the chain transfer agent to be used and the degree of polymerization of PVA made into the objective, 0.1-10 mass parts is generally preferable with respect to 100 mass parts of vinyl ester monomers.

Saponification of polyvinyl ester can be performed in the state which the said polyvinyl ester melt|dissolved in alcohol or hydrous alcohol, for example. Examples of the alcohol used for saponification include lower alcohols such as methanol and ethanol, and preferably methanol. The alcohol used for saponification may contain other solvents, such as acetone, methyl acetate, ethyl acetate, benzene, in the ratio of 40 mass % or less of the mass, for example. The catalyst used for saponification is, for example, a hydroxide of alkali metals, such as potassium hydroxide and sodium hydroxide, alkali catalysts, such as sodium methylate, and acid catalysts, such as a mineral acid. Although the temperature at which saponification is performed is not limited, The inside of the range of 20-60 degreeC is preferable. When a gel-like product precipitates with advancing of saponification, after grind|pulverizing a product, it washes and dries, and PVA can be obtained. The saponification method is not limited to the method mentioned above, A well-known method can be applied.

The PVA film used for manufacture of the polarizing film of this invention can contain a plasticizer other than the said PVA. Preferred plasticizers include polyhydric alcohols, and specific examples thereof include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, and trimethylolpropane. Moreover, it can contain 1 type, or 2 or more types of these plasticizers. Among these, glycerol is preferable from the point of the improvement effect of a stretchability.

It is preferable to exist in the range of 1-20 mass parts with respect to 100 mass parts of PVA, as for content of the plasticizer in the PVA film used for manufacture of the polarizing film of this invention, It is more preferable to exist in the range of 3-17 mass parts, It is more preferable to exist in the range of 5-15 mass parts. When the said content is 1 mass part or more, the ductility of a film improves more. On the other hand, when the said content is 20 mass parts or less, it can suppress that a film becomes soft too much and handleability falls.

In addition to the PVA film used for manufacture of the polarizing film of this invention, processing stabilizers, such as a filler and a copper compound, a weather resistance stabilizer, a colorant, a ultraviolet absorber, a light stabilizer, antioxidant, antistatic agent, a flame retardant, another thermoplastic resin, a lubricant Additives, such as a fragrance|flavor, an antifoamer, a deodorant, an extender, a release agent, a mold release agent, a reinforcing agent, a crosslinking agent, a mold inhibitor, a preservative, and a crystallization rate retarder, can be mix|blended suitably as needed.

It is preferable that it is 80 mass % or more based on the mass of a PVA film, and, as for the ratio which the sum total of PVA and a plasticizer in the PVA film used for manufacture of the polarizing film of this invention occupies, it is more preferable that it is 90 mass % or more, It is more preferable that it is 95 mass % or more.

It is preferable that the swelling degree of the PVA film used for manufacture of the polarizing film of this invention exists in 160 to 240% of range, It is more preferable to exist in 170 to 230% of range, It is especially preferable to exist in 180 to 220% of range. . When a swelling degree is 160 % or more, it can suppress that crystallization progresses extremely, and can extend|stretch to a high magnification stably. On the other hand, when a swelling degree is 240 % or less, melt|dissolution at the time of extending|stretching is suppressed, and it becomes possible to extend|stretch also under high temperature conditions.

Although the thickness in particular of the PVA film used for manufacture of the polarizing film of this invention is not restrict|limited, Generally, it is 1-100 micrometers, Furthermore, it is 5-60 micrometers, It is preferable that it is especially about 10-45 micrometers. When the said thickness is too thin, there exists a tendency for extending|stretching break to become easy to generate|occur|produce at the time of the uniaxial stretching process for manufacturing a polarizing film. Moreover, when the said thickness is too thick, it will become easy to generate|occur|produce extending|stretching nonuniformity at the time of the uniaxial stretching process for manufacturing a polarizing film.

The width of the PVA film used for manufacturing the polarizing film of the present invention is not particularly limited, and may be determined according to the use of the polarizing film to be manufactured. In recent years, when the width|variety of the PVA film used for manufacture of a polarizing film shall be 3 m or more at the point which the large-screen-ization of a liquid crystal television or a liquid crystal monitor is advancing, it is preferable for these uses. On the other hand, when the width of the PVA film used for the production of the polarizing film is too large, it becomes difficult to uniformly perform uniaxial stretching when the polarizing film is manufactured with an apparatus that is put into practical use. It is preferable that the width of the PVA film to be used is 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 with which the thickness and width|variety of the film after film forming become more uniform is employable preferably, For example, manufacture of a polarizing film The above-described PVA constituting the PVA film used for It can be manufactured using the film forming undiluted|stock solution in which PVA is melt|melted and containing 1 type(s) or 2 or more types of a plasticizer, an additive, surfactant, and a liquid medium, etc. further as needed. When the said film forming undiluted|stock solution contains at least 1 sort(s) of a plasticizer, an additive, and surfactant, it is preferable that those components are mixed uniformly.

As said liquid medium used for preparation of a film forming undiluted|stock solution, For example, water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerol, propylene glycol, diethylene glycol, Triethylene glycol, tetraethylene glycol, trimethylol propane, ethylenediamine, diethylenetriamine, etc. are mentioned, Among these, 1 type, or 2 or more types can be used. Especially, water is preferable from the point of the load given to an environment, and a recovery property.

The volatile fraction of the film forming undiluted solution (the content ratio in the film forming undiluted solution of volatile components such as a liquid medium that is removed by volatilization or evaporation during film forming) also varies depending on the film forming method, film forming conditions, etc., but generally 50 to It is preferable to exist in the range of 95 mass %, and it is more preferable to exist in the range which is 55-90 mass %. When the volatile fraction of the film forming undiluted solution is 50 mass % or more, the viscosity of the film forming undiluted solution does not become excessively high, filtration and defoaming at the time of preparing the film forming undiluted solution are performed smoothly, and the manufacture of a film with few foreign substances and defects becomes easy. On the other hand, when the volatile fraction of the film-forming undiluted solution is 95 mass % or less, the density|concentration of the film-forming undiluted|stock solution does not become low too much, and manufacture of an industrial film becomes easy.

It is preferable that the film forming undiluted|stock solution contains surfactant. By containing surfactant, while film forming property improves and generation|occurrence|production of the thickness nonuniformity of a film is suppressed, peeling of the film from the metal roll or belt used for film forming becomes easy. When a PVA film is prepared from a film forming stock solution containing a surfactant, a surfactant may be contained in the film. Although the kind of said surfactant is not specifically limited, From a viewpoint of peelability from a metal roll or a belt, etc., an anionic surfactant or a nonionic surfactant is preferable.

As anionic surfactant, For example, Carboxylic acid types, such as potassium laurate; sulfuric acid ester types such as polyoxyethylene lauryl ether sulfate and octyl sulfate; Sulfonic acid types, such as dodecylbenzenesulfonate, etc. are preferable.

As a nonionic surfactant, 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; Alkylamine types, such as polyoxyethylene laurylamino ether; alkylamide types such as polyoxyethylene lauric acid amide; polypropylene glycol ether types such as polyoxyethylene polyoxypropylene ether; Alkanolamide types, such as lauric-acid diethanolamide and oleic-acid diethanolamide; Allylphenyl ether types, such as polyoxyalkylene allylphenyl ether, etc. are preferable.

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

When the film forming undiluted solution contains a surfactant, its content is preferably in the range of 0.01 to 0.5 parts by mass, more preferably in the range of 0.02 to 0.3 parts by mass, based on 100 parts by mass of PVA contained in the film forming undiluted solution, and 0.05 It is especially preferable to exist in the range of -0.2 mass part. When the said content is 0.01 mass part or more, film forming property and peelability improve more. On the other hand, when the said content is 0.5 mass part or less, it can suppress that surfactant bleeds out on the surface of a PVA film, blocking generate|occur|produces, and handleability falls.

As a film forming method at the time of forming into a film the PVA film used for manufacture of a polarizing film using the above-mentioned film forming undiluted|stock solution, for example, a cast film forming method, an extrusion film forming method, a wet film forming method, a gel film forming method, etc. are mentioned. . These film forming methods may employ|adopt only 1 type, or may employ|adopt them in combination of 2 or more type. Among these film forming methods, the cast film forming method and the extrusion film forming method are preferable at the point from which the PVA film used for manufacture of the polarizing film with uniform thickness and width|variety and a physical property is favorable. Drying or heat processing can be performed to the PVA film formed into a film as needed.

As an example of the specific manufacturing method of the PVA film used for manufacture of the polarizing film of this invention, for example, using a T-type slit die, a hopper plate, an I-die, a lip coater die, etc., the said film forming undiluted|stock solution is placed upstream A volatile component from one side of a film that is uniformly discharged or cast on the peripheral surface of a rotating heated roll (or belt) positioned in the is evaporated to dryness, and then further dried on the circumferential surface of one or a plurality of rotating heated rolls disposed downstream thereof, or further dried by passing through a hot air drying device, and then added to the winding device. The method of winding by means of a method can be industrially preferably employed. You may perform drying by a heated roll and drying by a hot-air drying apparatus combining suitably.

The method in particular at the time of manufacturing the polarizing film of this invention is not restrict|limited. A preferable manufacturing method is the manufacturing method of a polarizing film containing the dyeing process of dyeing a polyvinyl alcohol film with a dichroic dye, and the extending|stretching process of uniaxially stretching the film. It is a manufacturing method of the polarizing film which has the process to be immersed in aqueous solution. With respect to the PVA film used for the production of the polarizing film of the present invention, dyeing treatment, uniaxial stretching treatment, and if necessary, further swelling treatment, boric acid crosslinking treatment, fixing treatment, washing treatment, drying treatment, heat treatment, etc. method can be found. In this case, the order in particular of each process, such as a swelling process, a dyeing process, a boric acid crosslinking process, a uniaxial stretching process, a fixation process, is not restrict|limited, One or two or more processes may be implemented simultaneously. Moreover, one or two or more of each process can also be performed twice or more.

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

A dyeing process can be performed by making a dichroic dye contact with respect to a PVA film. As the dichroic dye, it is common to use an iodine-based dye. As a timing of a dyeing|staining process, any stage after a uniaxial stretching process before a uniaxial stretching process, at the time of a uniaxial stretching process, may be sufficient. The dyeing treatment is generally performed by immersing the PVA film in a solution (especially aqueous solution) containing iodine-potassium iodide as a dyeing bath. It is preferable that the density|concentration of the iodine in a dyeing bath exists in the range of 0.01-0.5 mass %, and it is preferable that the density|concentration of potassium iodide exists in the range of 0.01-10 mass %. Moreover, it is preferable that the temperature of a dyeing bath shall be 20-50 degreeC, especially 25-40 degreeC. A preferred dyeing time is 0.2 to 5 minutes.

By giving a boric-acid crosslinking process with respect to a PVA film, when carrying out wet extending|stretching at high temperature, it can prevent more effectively that PVA elutes to water. From this viewpoint, it is preferable to perform a boric acid crosslinking process before a uniaxial stretching process. A boric-acid crosslinking process can be performed by making a PVA film immerse in the aqueous solution containing a boric-acid crosslinking agent. As the said boric acid crosslinking agent, 1 type, or 2 or more types of boron containing inorganic compounds, such as boric acid salts, such as boric acid and borax, can be used. It is preferable to exist in the range of 1-15 mass %, and, as for the density|concentration of the boric-acid crosslinking agent in the aqueous solution containing a boric acid crosslinking agent, it is more preferable to exist in the range of 2-7 mass %. When the density|concentration of a boric-acid crosslinking agent exists in the range of 1-15 mass %, sufficient stretchability is maintainable. The aqueous solution containing a boric acid crosslinking agent may contain adjuvants, such as potassium iodide. It is preferable to carry out the temperature of the aqueous solution containing a boric-acid crosslinking agent in the range of 20-50 degreeC, especially 25-40 degreeC. A boric-acid bridge|crosslinking can be efficiently carried out by carrying out the said temperature in the range of 20-50 degreeC.

You may perform a uniaxial stretching process by either a wet stretching method or a dry stretching method. In the case of the wet stretching method, it can also carry out in the aqueous solution containing boric acid, and can also carry out in the above-mentioned dyeing bath or the fixed treatment bath mentioned later. In addition, 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 may be performed in air using the PVA film after water absorption. Among these, the wet stretching method is preferable, and it is more preferable to perform a uniaxial stretching process in the aqueous solution containing boric acid. It is preferable to exist in the range of 0.5-6 mass %, and, as for the density|concentration of the boric acid in boric-acid aqueous solution, it is more preferable to exist in the range of 1-5 mass %. Moreover, boric-acid aqueous solution may contain potassium iodide, and it is preferable to carry out the density|concentration in the range of 0.01-10 mass %. It is preferable to exist in the range of 30-90 degreeC, as for the extending|stretching temperature in a uniaxial stretching process, it is more preferable to exist in the range of 40-80 degreeC, It is especially preferable to exist in the range of 50-70 degreeC. Moreover, it is preferable that it is 5 times or more from the point of the polarization performance of the polarizing film obtained, and, as for the draw ratio (total draw ratio from the PVA film which is a raw material) in a uniaxial stretching process, it is more preferable that it is 5.5 times or more. Although the upper limit in particular of a draw ratio is not restrict|limited, It is preferable that a draw ratio is 8 times or less.

There is no restriction|limiting in particular in the direction of the uniaxial stretching process in the case of giving a uniaxial stretching process to a long PVA film, A uniaxial stretching process in a long direction, a transverse uniaxial stretching process, or so-called oblique stretching treatment is adopted. Although it can do it, the uniaxial stretching process to a long direction is preferable at the point from which the polarizing film excellent in polarization performance is obtained. The uniaxial stretching process to a long direction can be performed by changing the peripheral speed between each roll using the extending|stretching apparatus provided with the some roll mutually parallel. On the other hand, the transverse uniaxial stretching process can be performed using a tenter type stretching machine.

At the time of manufacture of a polarizing film, in order to strengthen adsorption|suction of the dichroic dye (iodine dye etc.) with respect to a PVA film, it is preferable to perform a fixation process after a uniaxial stretching process. As the fixed treatment bath used for the fixed treatment, an aqueous solution containing the 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 process bath as needed. The temperature of the fixed 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 steps of dyeing treatment, boric acid crosslinking treatment, uniaxial stretching treatment, and fixing treatment. It is especially preferable at the point which does not give. Moreover, you may use not only one type, but a mixture of two or more types of a boron containing compound (B). 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 concentration of the aqueous solution of the boron-containing compound (B) is lower than 0.05 mass %, adsorption may become slow, and when the aqueous solution concentration is higher than 15 mass %, a precipitate of the boron-containing compound (B) is formed on the surface of the polarizing film There are cases. Moreover, it is preferable that aqueous solution containing a boron-containing compound (B) contains adjuvants, such as potassium iodide, from the point of a polarization|polarized-light performance improvement. Moreover, as for the temperature of a process bath, it is preferable that it is 10-70 degreeC, It is more preferable to set it as 20-60 degreeC, It is especially preferable to set it as 20-50 degreeC. When the temperature is too low, the boron-containing compound (B) may precipitate in the treatment bath. Moreover, when temperature is too high, it will become difficult to manufacture easily industrially on comparatively mild conditions.

A preferable manufacturing method in the case of making a polarizing film adsorb|suck a boron containing compound (B) at the time of a fixed process is to perform a swelling process, a boric-acid crosslinking process, a uniaxial stretching process, and a fixation process in this order. Thereafter, if necessary, one or more treatments selected from a washing treatment, a drying treatment, and a heat treatment may be performed in this order.

The washing process is generally performed by immersing the film in water, distilled water, pure water, or the like. At this time, it is preferable that the aqueous solution used for a washing process from the point of a polarization performance improvement contains iodide, such as potassium iodide, as an auxiliary agent, and it is preferable that the density|concentration of this iodide shall be 0.5-10 mass %. Moreover, the temperature of the aqueous solution in a washing process is 5-50 degreeC generally, Preferably it is 10-45 degreeC, More preferably, it is 15-40 degreeC. From an economical point of view, it is not preferable that the temperature of the aqueous solution is too low, and when the temperature of the aqueous solution is too high, the polarization performance may be deteriorated.

Although the conditions in particular of a drying process are not restrict|limited, It is preferable to dry at the temperature within the range of 30-150 degreeC, especially 50-130 degreeC. A polarizing film excellent in dimensional stability is easy to be obtained by drying at the temperature within the range of 30-150 degreeC.

By heat-processing after a drying process, the polarizing film further excellent in dimensional stability can be obtained. Here, a heat treatment heats the polarizing film after the drying process whose moisture content is 5 % or less further, and says the process which improves the dimensional stability of a polarizing film. Although the conditions in particular of heat processing are not restrict|limited, It is preferable to heat-process within the range of 60 degreeC - 150 degreeC, especially within the range of 70 degreeC - 150 degreeC. When heat treatment is performed at a temperature lower than 60° C., the dimensional stabilization effect by heat treatment is insufficient, and when heat treatment is performed at a temperature higher than 150° C., red discoloration of the polarizing film may occur severely.

The heat-and-moisture-resistance performance of the polarizing film obtained as mentioned above can be evaluated using discoloration of the color derived from the PVA- iodine complex under high temperature and high humidity as an index|index. Specifically, the absorbance D (610 nm) after fading to the absorbance C (610 nm) before fading when two polarizing films are superimposed on cross nicol can be evaluated as a percentage (absorbance residual rate). The absorbance residual ratio after making it fade at 60 degreeC/90%RH for 8 hours becomes like this. Preferably it is 22 % or more, More preferably, it is 25 % or more.

A polarizing film is normally used as a polarizing plate by bonding together the protective film which is optically transparent and has mechanical strength on the both surfaces or single side|surface. As the protective film, a cellulose triacetate (TAC) film, a cellulose acetate/butyrate (CAB) film, an acrylic film, a polyester film, or the like is used. Moreover, although a PVA type adhesive agent, a urethane type adhesive agent, etc. are mentioned as an adhesive agent for bonding, Especially, a PVA type adhesive agent is preferable.

After coating adhesives, such as an acrylic type, the polarizing plate obtained by making it above can be bonded together to a glass substrate, and can be used as a component of LCD. Simultaneously, you may bond together retardation film, a viewing angle improvement film, a brightness improvement film, etc.

Example

Hereinafter, the present invention will be described in more detail by way of Examples, but the present invention is not limited by these Examples. In addition, each measurement or evaluation method employ|adopted in the following Example and a comparative example is shown below.

[Swelling degree of PVA film]

The PVA film was cut into 5 cm x 10 cm, and it was made to immerse in 1000 ml of 30 degreeC distilled water for 30 minutes. Then, the PVA film was taken out, the water|moisture content on the surface of a PVA film was wiped off with filter paper, and the PVA film mass (mass E) after immersion was measured. Then, after putting a PVA film into a 105 degreeC dryer and drying it for 16 hours, the PVA film mass (mass F) after drying was measured. The swelling degree of the PVA film was calculated by substituting the values of the mass E and the mass F in 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 portion of the polarizing film obtained in the following examples or comparative examples, two samples of 4 cm in the stretching direction and 2 cm in the width direction of the polarizing film were taken, and a spectrophotometer with an integrating sphere (“Nippon Spectroscopy Co., Ltd.” V7100"), in accordance with JIS Z 8722 (Method for measuring object color), C light source, visibility correction in the visible light region of 2 ° field of view, for one sample, +45 ° tilted with respect to the longitudinal direction The transmittance of light in this case and the transmittance of light when inclined at -45° were measured, and their average value Ts1 (%) was obtained. In the same manner for the other sample, the transmittance of light when tilted at +45° and transmittance of light when tilted at -45° were measured, and their average value Ts2 (%) was obtained. Ts1 and Ts2 were averaged by following formula (6), and it was set as the transmittance|permeability Ts (%) of a polarizing film.

Ts = (Ts1 + Ts2)/2 (6)

(2) Measurement of polarization degree V

For the two samples used in the measurement of the transmittance Ts, the transmittance of light T⊥ (%) when superimposed so that the stretching directions are orthogonal to each other and the transmittance of light T// ( %), using a spectrophotometer with an integrating sphere ("V7100" manufactured by Nippon Spectroscopy Co., Ltd.), in accordance with JIS Z 8722 (Method for measuring object color), C light source, visibility correction in the visible light region with a 2° field of view carried out and measured. The measured T// (%) and T⊥ (%) were substituted for the following formula (7), and the polarization degree V (%) was calculated|required.

[Moisture and heat resistance performance]

Each of the two polarizing films was fixed to a metal frame, superposed on cross nicols, and the absorbance C (610 nm) of the initial stage (0 hours) was measured with a spectrophotometer. Moreover, after leaving the polarizing film fixed to the metal frame to stand still in the atmosphere of 60 degreeC/90%RH for 8 hours, it was made to overlap with cross nicol, and the absorbance D (610 nm) after 8 hours was measured with the spectrophotometer. . The value of the absorbance D/absorbance C x 100 was taken as the residual ratio (%), and was used as an index of discoloration 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)]

At 23 ℃ / 50% RH for 16 hours humidity (調濕) was dissolved so that a polarizing film is 0.005 mass% in heavy water (重水) and, by a rotary twofold buffer concentrator a solution was concentrated so that the 0.15 mass% ¹ H-NMR It was set as the measurement sample. ¹ H-NMR: performed (manufactured by Nippon Electronics Co., Ltd. JNM-AL400 of 400 ㎒) is measured at 80 ℃, and use the ALICE2 (manufactured by Nippon Electronics Co., Ltd.) was analyzed by the following method. ^{For the 1} H-NMR chart obtained by measurement, the baseline was automatically corrected by setting the average point to 20 after adjusting the phase so that the baseline was smooth. Next, it was automatically set as a reference so that the peak of heavy water which is a measurement solvent might become the position of 4.65 ppm. Then, as shown in FIG. 1, the hydrogen peak of the hydrocarbon group contained in the boron-containing compound (B) was integrated, and the peak area was calculated|required. At this time, the sum of all the hydrogen peak areas of hydrocarbon groups contained in the boron-containing compound (B) that do not overlap with the PVA-derived hydrogen peak (area G) is used as the peak area, and the boron-containing compound (B) It was set so that the number of hydrogens of the corresponding hydrocarbon group and the value of area G were the same. Next, the hydrogen peak in the range of 1.7 ppm to 2.4 ppm is overlapped with the hydrogen peak derived from the methylene group of PVA and the hydrogen peak derived from the methylene group of PVA. The hydrogen peak of the hydrocarbon group contained in the boron-containing compound (B) overlaps. The peak area (area H) was calculated by taking it as the sum of . Then, the area I obtained by subtracting the number of hydrogens in 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 boron element content derived from the boron-containing compound (B) with respect to 100 mass parts of polyvinyl alcohol (A) was computed by substituting the value calculated|required by these methods into the following formula (8). In addition, X and Y in the following formula (8) are the number of hydrogens of hydrocarbon groups contained in the boron-containing compound (B) that do not overlap the peak of PVA, respectively, and the number of borons per molecule of the boron-containing compound (B). . In addition, formula (8) is an formula used when unmodified PVA is used, When using modified|denatured PVA as a raw material, it is necessary to modify|transform formula (8) suitably.

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)

10.811 is the atomic weight of boron, and 44.0526 is the molecular weight per mole of the repeating unit of PVA without modification. ¹ H-NMR chart of FIG. 1 is a measurement of the polarizing film of Example 1, and the boron element content derived from the boron-containing compound (B) with respect to 100 parts by mass of polyvinyl alcohol (A) is the second decimal place. It was raised to 0.5 mass part.

[Calculation of total boron element content (mass %) in polarizing film]

The mass (J(g)) of the polarizing film controlled at 23 degreeC/50%RH for 16 hours was measured, and it was made to melt|dissolve in 20 ml of distilled water so that a polarizing film might be 0.005 mass %. The aqueous solution in which the polarizing film was dissolved was made into a measurement sample, and the mass (K(g)) was measured. Then, the boron concentration (L (ppm)) of the measurement sample was measured using the Shimadzu Corporation multi-type ICP emission spectrometer (ICP). Then, the value calculated by substituting a value for following formula (9) was made into total boron element content (mass %) in a polarizing film.

Total boron element content in polarizing film (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, an aqueous solution having a content of PVA of 10% by mass was formed into a film Using it as a stock solution, this was dried on a metal roll at 80°C, and the obtained film was heat-treated in a hot air dryer at a temperature of 120°C for 10 minutes to adjust the swelling degree to 200%, and a PVA film having a thickness of 30 µm was produced.

Thus, from the width direction center part of the obtained PVA film, the sample of width 5 cm x length 9 cm was cut so that the range of width 5 cm x length 5 cm could be uniaxially stretched. It uniaxially stretched to 1.1 times longitudinally, and the swelling process was carried out, making this sample immersed in 30 degreeC pure water for 30 second. Subsequently, while immersing in an aqueous solution (dye treatment bath) (temperature 30° C.) containing 0.04 mass% of iodine and 4.0 mass% of potassium iodide for 60 seconds, it is uniaxially stretched in the longitudinal direction at 2.2 times (2.4 times in total) to adsorb iodine. did it Subsequently, uniaxial stretching was carried out in the longitudinal direction at 1.2 times (2.7 times in total) while being immersed in an aqueous solution (boric acid crosslinking treatment bath) (temperature of 30° C.) containing 3% by mass of boric acid and 3% by mass of potassium iodide. . Furthermore, it uniaxially stretched in the longitudinal direction to 6.0 times as a whole, immersing boric acid in the 58 degreeC aqueous solution (uniaxial stretching process bath) containing 4 mass % and potassium iodide in the ratio of 6 mass %. Then, it was made to immerse for 100 second in the aqueous solution (fixed treatment bath) (temperature 30 degreeC) containing 0.5 mass % of 1, 4- butanediboronic acid and potassium iodide in the ratio of 4 mass %. Finally, the polarizing film was prepared by drying at 60° C. for 4 minutes. The absorbance (610 nm) at the time of fixing the polarizing film of 2 sheets after drying to the metal frame, respectively and superimposing it on cross nicol became 3.9.

^{When 1} H-NMR of the obtained polarizing film was measured and analyzed, since the hydrogen peak of 1, 4- butanediboronic acid which does not overlap with the hydrogen peak derived from PVA appeared at 1.0-1.3 ppm, this peak area (area G) was set to 4. Next, the peak area (area H) of hydrogen of the methylene group of PVA in which a peak appears in the range of 1.7-2.4 ppm was computed. Since there was a hydrogen peak of 1,4-butanediboronic acid overlapping with the hydrogen peak of the methylene group of PVA, the area of the hydrogen number 4 of 1,4-butanediboronic acid corresponding to the hydrogen peak overlapping with the methylene group of PVA The area I was calculated by subtracting from H. As a result of substituting these values into calculation formula (8), the boron content derived from the boron-containing compound (B) with respect to 100 mass parts of polyvinyl alcohol (A) became 0.5 mass parts.

Furthermore, 0.00099 g (mass J) of the polarizing film manufactured by the same method was melt|dissolved in 20 ml of distilled water, and the measurement sample for ICP measurement was prepared. As a result of measuring the mass of the prepared sample for measurement, the mass was found to be 20.03 g (mass K). Then, as a result of performing ICP measurement, the boron concentration of the measurement sample was 1.24 ppm (boron concentration L). As a result of substituting these values into calculation formula (9), total boron element content with respect to a polarizing film became 2.5 mass %. Moreover, using the obtained polarizing film, the above method evaluated the optical characteristic and moist-and-heat-resistance performance of a polarizing film. The above results are put together in Table 1, and are shown.

Further, in Examples 2 to 4 and Comparative Examples 1 to 3, while immersing in an aqueous solution (dye treatment bath) (temperature 30° C.) containing 100 parts by mass of potassium iodide in a ratio of 100 parts by mass of potassium iodide to 1 part by mass of iodine for 60 seconds ( iodine was adsorbed by uniaxial stretching in the longitudinal direction with a total of 2.4 times). At this time, the concentration of iodine and potassium iodide in the dyeing treatment bath was adjusted so that the absorbance (610 nm) at the time of fixing two polarizing films after drying to a metal frame, respectively and superimposing them on a cross nicol might be set to 3.6-4.2.

[Example 2]

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

[Example 3]

Except having used the aqueous solution (temperature 30 degreeC) containing phenylboronic acid in the ratio of 1.0 mass % and potassium iodide in the ratio of 2.0 mass % for a fixed treatment bath, it carried out similarly to Example 1, and manufactured a polarizing film, each measurement or Evaluation was performed. The results are shown in Table 1.

[Example 4]

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

[Comparative Example 1]

Except having used the aqueous solution (temperature 30 degreeC) containing 2 mass % of boric acid and potassium iodide in the ratio of 3 mass % for a fixed treatment bath, it carried out similarly to Example 1, manufactures a polarizing film, and each measurement or evaluation carried out. The results are shown in Table 1.

[Comparative Example 2]

Except having used the aqueous solution (temperature 30 degreeC) containing 1.0 mass % of boric acid and potassium iodide in the ratio of 3 mass % for a fixed treatment bath, it carried out similarly to Example 1, manufactures a polarizing film, and each measurement or evaluation carried out. The results are shown in Table 1.

[Comparative Example 3]

Except having used the aqueous solution (temperature 30 degreeC) containing 0.5 mass % of boric acid and potassium iodide in the ratio of 3 mass % for a fixed treatment bath, it carried out similarly to Example 1, and manufactured a polarizing film, and each measurement or evaluation carried out. The results are shown in Table 1.

When Examples 1 and 2 and Comparative Example 2 are compared, it can be seen that the absorbance residual ratio of Examples 1 and 2 is higher than that of Comparative Example 2, although the total boron element content in the polarizing film is equal or less. Moreover, when Examples 3 and 4 and the comparative example 1 are compared, although the total boron element content in a polarizing film is equal or less, it turns out that the absorbance residual rate of Examples 3 and 4 is higher than the comparative example 1. From the above, it turns out that the polarizing film of Examples 1-4 which satisfy|fills the prescription|regulation of this invention is excellent in heat-and-moisture resistance performance.

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

Claims (4)

A polarizing film containing polyvinyl alcohol (A), a boron-containing compound (B) selected from propanediboronic acid or butanediboronic acid, and boric acid, wherein the boron element content derived from the boron-containing compound (B) in the polarizing film is polyvinyl alcohol. It is 0.1-3 mass parts with respect to 100 mass parts of vinyl alcohol (A), and total boron element content in a polarizing film is 0.2-5 mass %, The polarizing film characterized by the above-mentioned. A dyeing treatment of dyeing a polyvinyl alcohol film with a dichroic dye, a boric acid crosslinking treatment of immersing the film in an aqueous solution containing 1 to 15 mass% of a boric acid crosslinking agent, a stretching treatment of uniaxially stretching the film, and a film A method for producing a polarizing film comprising a fixing treatment of immersion in an aqueous solution containing 0.05 to 15% by mass of a boron-containing compound (B), characterized in that the fixing treatment is performed after the boric acid crosslinking treatment. A method of manufacturing a polarizing film according to. delete delete

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