KR20220041093A - Polarizing film and its manufacturing method - Google Patents

Abstract

At least one boron-containing compound (B) and boric acid (C) selected from the group consisting of polyvinyl alcohol (A), a predetermined monoboronic acid and a compound that can be converted into the monoboronic acid in the presence of water. As a polarizing film, the boron element density|concentration (alpha) derived from a boron-containing compound (B) in the range from the center of the thickness direction to the outside to 1 micrometer is 0.1-3 atomic%, and is 1 to the outside from the center of the thickness direction. Polarized light having a concentration (β) of elemental boron derived from boric acid (C) of 0.1 to 8 atomic% in the range up to μm, and a ratio (α/β) of the concentration (α) to the concentration (β) of 0.1 or more it's a film The said polarizing film has small shrinkage force under high temperature, and is excellent also in optical performance.

Description

Polarizing film and its manufacturing method

This invention relates to a polarizing film and its manufacturing method.

A polarizing plate having a function of transmitting and shielding light is a basic component of a liquid crystal display (LCD) together with liquid crystal that changes the 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 fading of the polarizing film or to prevent shrinkage of the polarizing film, As a polarizing film constituting the polarizing film, an iodine-based dye (I ^3- or I ^5- , etc.) is added to a matrix formed by uniaxial stretching of a polyvinyl alcohol film (hereinafter, “polyvinyl alcohol” may be referred to as “PVA”). What is adsorbed becomes mainstream.

LCDs are used in a wide range of small devices such as electronic desk calculators and wrist watches, smart phones, notebook computers, liquid crystal monitors, liquid crystal color projectors, liquid crystal televisions, in-vehicle navigation systems, and measuring instruments used indoors and outdoors, etc. These electronic devices are required to be thin and high-definition. With this, thickness reduction of the glass used for LCD and high draw ratio increase of a polarizing film are advancing in recent years, As a result, generation|occurrence|production of the curvature of an LCD panel poses a problem. It is said that the main factor of the curvature of an LCD panel is shrinkage of a polarizing film under high temperature, and it has high optical performance, and the polarizing film with small shrinkage force under high temperature is calculated|required.

By the way, in the manufacturing method of a polarizing film in recent years, in order to bridge|crosslink the PVA molecular chain in a polarizing film, it is known to use the aqueous solution of boronic acid. Specifically, Patent Document 1 describes that a polarizing film excellent in heat-and-moisture resistance was obtained by immersing the polarizing film after uniaxial stretching in an aqueous solution (fixed treatment bath) containing 1,4-butanediboronic acid and potassium iodide. has been Moreover, it is described in patent document 2 that the polarizing film excellent in water resistance and adhesive force was obtained by injecting|throwing-in a boronic acid induced group to a water washing step. Moreover, it is described in patent document 3 that the polarizing film excellent in heat resistance and heat-and-moisture resistance was obtained by using the crosslinking liquid containing the hydrocarbon compound which has an aldehyde group.

WO2018/021274 No. KR10-2016-0054229 No. KR10-2015-0001276

However, the polarizing film of patent documents 1-3 had the large contractile force under high temperature, or the optical performance was inadequate. Therefore, it was not able to meet the request|requirement of thickness reduction and high definition of recent electronic devices.

Then, this invention aims at providing the polarizing film excellent also in optical performance with small shrinkage force under high temperature, and its manufacturing method.

Although the present inventors studied earnestly, in order to reduce the shrinkage force while maintaining the excellent optical performance of a polarizing film, the substitution reaction of substituting boronic acid for the boric acid which bridge|crosslinks the PVA molecular chain in a polarizing film is carried out only in the surface part of a polarizing film Rather, it was discovered that it was important to advance to the center of the thickness direction. Moreover, it was discovered that the contractile force of a polarizing film is further reduced, so that the said substitution reaction advances to the center part of the thickness direction of a polarizing film, ie, the boric acid of the center part of the thickness direction of a polarizing film is substituted with boronic acid. Then, the present inventors completed this invention by making the ratio of the boron element concentration derived from the boronic acid (boron containing compound) and boric acid of the center part of the thickness direction of a polarizing film into a specific range.

Moreover, in order to advance the substitution reaction which substitutes boric acid in a polarizing film with boronic acid to the center part of the thickness direction of a polarizing film, it is important to immerse the boric-acid bridge|crosslinked polarizing film in a comparatively low concentration aqueous solution of boronic acid. Usually, when a polarizing film crosslinked with boric acid is immersed in an aqueous solution of boronic acid, a substitution reaction in which boric acid in the polarizing film is substituted with boronic acid proceeds from the surface portion of the polarizing film. Here, when the concentration of the aqueous solution of boronic acid is relatively high, as a result of excessive adsorption of boronic acid to the surface portion of the polarizing film, it becomes difficult for the substitution reaction to proceed to the central portion in the thickness direction of the polarizing film. Moreover, in such a case, there exists a possibility that the precipitate of a boronic acid may generate|occur|produce in the surface part of a polarizing film. On the other hand, in this invention, the said substitution reaction can advance to the center part of the thickness direction of a polarizing film by immersing the polarizing film crosslinked with boric acid in a comparatively low-concentration aqueous solution of boronic acid.

The present invention is as follows [1] to [7].

[1] at least one boron-containing compound (B) selected from the group consisting of polyvinyl alcohol (A), a monoboronic acid represented by the following formula (I), and a compound that can be converted into the monoboronic acid in the presence of water (B) and boric acid (C), wherein the boron element concentration (α) derived from the boron-containing compound (B) in the range from the center in the thickness direction to the outside to 1 µm is 0.1 to 3 atomic%; The concentration (β) of boron element derived from boric acid (C) in the range from the center in the thickness direction to the outside to 1 µm is 0.1 to 8 atomic%, and the ratio of the concentration (α) to the concentration (β) ( Polarizing film having α/β) of 0.1 or more;

[Formula 1]

[In formula (I), R ¹ is a monovalent aliphatic group having 1 to 20 carbon atoms, and R ¹ and the boronic acid group are connected by a boron-carbon bond.]

[2] The polarizing film according to [1], wherein R ¹ is a saturated aliphatic group;

[3] The polarizing film according to [1] or [2], wherein R ¹ is a linear aliphatic hydrocarbon group;

[4] The polarizing film according to any one of [1] to [3], wherein R ¹ has 2 to 5 carbon atoms;

[5] The polarizing film according to any one of [1] to [4], wherein the transmittance is 42.0% or more and the polarization degree is 99.85% or more;

[6] The polarizing film according to any one of [1] to [5], wherein the shrinkage force in the absorption axis direction per width 1.5 cm and 13 μm in thickness when held at 80° C. for 4 hours is less than 12 N;

[7] A method for producing a polarizing film comprising a dyeing treatment of dyeing a polyvinyl alcohol film with a dichroic dye and a stretching treatment of uniaxially stretching the film, wherein the concentration of the boron-containing compound (B) in the film is The manufacturing method of the polarizing film in any one of [1]-[6] which has a process immersed in the aqueous solution whose temperature is 0.2-5 mass % and is 20-70 degreeC.

ADVANTAGE OF THE INVENTION According to this invention, the shrinkage force under high temperature is small, and the polarizing film excellent also in optical performance, and its manufacturing method can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing when the polarizing film of this invention is cut|disconnected in a perpendicular direction.

<polarizing film>

The polarizing film of this invention contains at least 1 sort(s) of boron selected from the group which consists of polyvinyl alcohol (A), the monoboronic acid represented by following formula (I), and the compound which can be converted into the monoboronic acid in presence of water. It is a polarizing film containing a compound (B) and a boric acid (C), Comprising: The boron element density|concentration (alpha) derived from a boron-containing compound (B) in the range from the center of a thickness direction to the outside to 1 micrometer is 0.1-3 atomic %, the concentration (β) of boron element derived from boric acid (C) in the range from the center in the thickness direction to the outside to 1 µm is 0.1 to 8 atomic%, and the concentration (α) with respect to the concentration (β) ) has a ratio (α/β) of 0.1 or more.

[Formula 2]

[In formula (I), R ¹ is a monovalent aliphatic group having 1 to 20 carbon atoms, and R ¹ and the boronic acid group are connected by a boron-carbon bond.]

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing when the polarizing film of this invention is cut|disconnected in a perpendicular direction. The central portion 3 in the thickness direction of the polarizing film is a range from the center 1 in the thickness direction of the polarizing film to 1 µm in both directions on the surface portion 2 side of the polarizing film, and is the range indicated by the oblique line in FIG. 1 . am. In the polarizing film of this invention, the boron element density|concentration (alpha) derived from the boron-containing compound (B) in the range from the center of the thickness direction of a polarizing film outward to 1 micrometer, the center of the thickness direction of a polarizing film to the outer side Therefore, the concentration (β) of boron element derived from boric acid (C) in the range up to 1 µm and the ratio (α/β) of the concentration (α) to the concentration (β) are in a specific range. When the polarizing film crosslinked with boric acid (C) is immersed in an aqueous solution of the boron-containing compound (B), a substitution reaction between the boron-containing compound (B) and boric acid (C) proceeds from the surface portion of the polarizing film. The fact that α, β and the ratio α/β are within a specific range indicates that the substitution reaction of the boron-containing compound (B) and boric acid (C) has progressed to the central portion of the polarizing film in the thickness direction, whereby the shrinkage force under high temperature is It is small and the polarizing film excellent also in optical performance is obtained.

The boron element density|concentration (alpha) derived from a boron-containing compound (B) in the range from the center of the thickness direction of a polarizing film to 1 micrometer outward needs to be 0.1-3 atomic%. When the boron element concentration (α) is less than 0.1 atomic %, the boron-containing compound (B) of a sufficient amount does not exist to the center of the thickness direction of a polarizing film, but the fall effect of shrinkage force becomes low. On the other hand, when the boron element concentration (α) exceeds 3 atomic %, it is considered that there is no influence on the optical performance and shrinkage force of the polarizing film, but the time of the fixing treatment immersed in the aqueous solution of the boron-containing compound (B) described later is It becomes long and there exists a possibility that productivity of a polarizing film may fall.

The boron element concentration (beta) derived from boric acid (C) in the range from the center of the thickness direction of a polarizing film to 1 micrometer outward needs to be 0.1-8 atomic%. When the boron element concentration (β) is less than 0.1 atomic %, the amount of boric acid (C) in the central portion in the thickness direction of the polarizing film is not sufficient, the orientation state of the PVA molecular chains in the polarizing film is disturbed, and the optical performance decreases. On the other hand, when the boron element concentration (β) exceeds 8 atomic%, the PVA molecular chains oriented by boric acid crosslinking are excessively present in the central portion in the thickness direction of the polarizing film, so the effect of reducing the shrinkage force is not sufficient. there is a fear that it will not

Ratio of the boron element concentration (α) derived from the boron-containing compound (B) to the boron element concentration (β) derived from boric acid (C) in the range from the center of the thickness direction of the polarizing film to the outside to 1 µm ( α/β) needs to be 0.1 or more. When ratio (α/β) of boron element concentration is less than 0.1, it is estimated that there are many quantities of boric acid (C) in the center part of the thickness direction of a polarizing film, and there are few quantities of boron-containing compound (B). In this case, since the PVA molecular chain orientated by boric-acid bridge|crosslinking exists in the center part of the thickness direction of a polarizing film excessively, there exists a possibility that shrinkage force may not fall. On the other hand, even if the ratio (α/β) of the boron element concentration exceeds 3, it is considered that the optical performance and the contractile force of the polarizing film are not affected, but the fixing treatment of immersion in an aqueous solution of the boron-containing compound (B) described later Since time becomes long and there exists a possibility that productivity of a polarizing film may fall, it is preferable that ratio (alpha/beta) of boron element concentration is 3 or less.

The boron element concentration (α) and the boron element concentration (β) in the polarizing film can be determined using an X-ray photoelectron spectrometer with a gas cluster ion beam gun (GCIB XPS). Specifically, it can obtain|require by the method described in the Example mentioned later.

As for the thickness of the said polarizing film, 5-30 micrometers is preferable. 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. The thickness is preferably 10 µm or more. On the other hand, when the said thickness is too thick, there exists a tendency for extending|stretching nonuniformity to become easy to generate|occur|produce at the time of the uniaxial stretching process for manufacturing a polarizing film, and the tendency for the contractile force of the manufactured polarizing film to become large easily.

The boron-containing compound (B) in the present invention is at least one selected from the group consisting of a monoboronic acid represented by the following formula (I) and a compound that can be converted into the monoboronic acid in the presence of water. Here, in formula (I), R< ¹ > is a C1-C20 monovalent|monohydric aliphatic group, R< ¹ > and the boronic acid group are connected by the boron-carbon bond.

[Formula 3]

[In formula (I), R ¹ is a monovalent aliphatic group having 1 to 20 carbon atoms, and R ¹ and the boronic acid group are connected by a boron-carbon bond.]

Monoboronic acid is a compound represented by the said Formula (I), and has one boronic acid group [-B(OH) ₂ ] in 1 molecule. The boronic acid group has a structure in which a boron atom to which two hydroxyl groups are bonded is bonded to a carbon atom, and in the compound represented by the formula (I), R ¹ and the boronic acid group are connected to each other by a boron-carbon bond. In boric acid [B(OH) ₃ ], the boron atom is different from the bonding with three hydroxyl groups in that the boronic acid group has a boron-carbon bond. As a boron-containing group that can be converted into a boronic acid group in the presence of water, a boronic acid ester group described below is exemplified as a representative, but not limited thereto.

The hydroxyl group in the boronic acid group contained in monoboronic acid can form ester with alcohol similarly to the hydroxyl group in boric acid. The following formula (II) is a monoboronic acid monoester in which one molecule of alcohol (R ² -OH) reacted with boronic acid. Here, when a boronic acid group couple|bonds with the hydroxyl group of PVA(A), R< ² > in Formula (II) is a PVA chain, and a carbon-containing group will couple|bond with PVA chain via a boron atom.

[Formula 4]

The following formula (III) is an example of monoboronic acid diester in which two molecules of alcohol (R ² -OH) reacted with monoboronic acid. Here, when a boronic acid group couple|bonds with the hydroxyl group of PVA, both two R< ² > in Formula (III) are PVA chains.

[Formula 5]

Monoboronic acid has two hydroxyl groups capable of reacting with the hydroxyl group of PVA to form an ester, and the PVA chain is moderately crosslinked. Since this crosslinking is stable to heat, the contractile force under high temperature of a polarizing film becomes small. Thereby, the curvature under the high temperature of the LCD panel using a polarizing film is suppressed. Moreover, it is thought that the orientation state of PVA chain becomes favorable and the optical performance of a polarizing film improves by bridge|crosslinking PVA chain moderately.

In formula (I), R< ¹ > is a C1-C20 monovalent aliphatic group. When R ¹ is an appropriate length, the solubility of the boron-containing compound (B) in water and the reactivity with the hydroxyl group of PVA can be controlled. It is preferable that carbon number of R< ¹ > is 10 or less, It is more preferable that it is 6 or less, It is still more preferable that it is 5 or less. On the other hand, it is preferable that carbon number of R<1> is 2 or more, and, as for carbon number of R< ¹ >, it is more preferable that it is 3 or more from a viewpoint especially excellent in the balance of the optical performance of a polarizing film, and contraction force.

In formula (I), R< ¹ > is a monovalent|monohydric aliphatic group, and R< ¹ > and the boronic acid group should just be connected by the boron-carbon bond. Although a saturated aliphatic group may be sufficient as R< ¹ > or an unsaturated aliphatic group may be sufficient as R<1>, the former is preferable. When R< ¹ > is a saturated aliphatic group, while coloring of the polarizing film obtained is suppressed, durability improves. Moreover, when R< ¹ > is a saturated aliphatic group, the orientation of a dichroic dye improves and optical performance further improves. In addition, the unsaturated aliphatic group refers to a carbon-carbon double bond, a carbon-carbon triple bond, a carbon-oxygen double bond, a carbon-nitrogen double bond, a nitrogen-nitrogen double bond, a carbon-sulfur double bond, and the like. It is an aliphatic group having a structure containing, and a saturated aliphatic group is an aliphatic group having only a single bond structure. Examples of monoboronic acids in which R ¹ is a saturated aliphatic group include methylboronic acid, ethylboronic acid, propylboronic acid, butylboronic acid, pentylboronic acid, hexylboronic acid, heptylboronic acid, octylboronic acid, nonylboronic acid, and decanyl. Boronic acid, undecanylboronic acid, dodecanylboronic acid, tridecanylboronic acid, tetradecanylboronic acid, pentadecanylboronic acid, hexadecanylboronic acid, heptadecanylboronic acid, octadecanylboronic acid, nona Decanylboronic acid, icosanylboronic acid and isomers thereof, cyclopropylboronic acid, cyclobutylboronic acid, cyclopentylboronic acid, cyclohexylboronic acid, cycloheptylboronic acid, cyclooctylboronic acid, cyclononylboronic acid, cyclodeca Nylboronic acid, cycloundecanylboronic acid, cyclododecanylboronic acid, cyclotridecanylboronic acid, cyclotetradecanylboronic acid, cyclopentadecanylboronic acid, cyclohexadecanylboronic acid, cycloheptadecanylboronic acid Acid, cyclooctadecanylboronic acid, cyclononadecanylboronic acid, cycloicosanylboronic acid and their isomers, 2-oxa-propylboronic acid, 2-oxa-butylboronic acid, 2-oxa-hexylboronic acid, 2 -oxa-heptylboronic acid, 2-oxa-octylboronic acid, 2-oxa-nonylboronic acid, 2-oxa-decanylboronic acid, 2-oxa-undecanylboronic acid, 2-oxa-dodecanylboronic acid, 2-oxa-tridecanylboronic acid, 2-oxa-tetradecanylboronic acid, 2-oxa-pentadecanylboronic acid, 2-oxa-hexadecanylboronic acid, 2-oxa-heptadecanylboronic acid, 2-oxa-octadecanylboronic acid, 2-oxa-nonadecanylboronic acid, 2-oxa-icosanylboronic acid and their isomers, 2-aza-propylboronic acid, 2-aza-butylboronic acid, 2- Aza-hexylboronic acid, 2-aza-heptylboronic acid, 2-aza-octylboronic acid, 2-aza-nonylboronic acid, 2-aza-decanylboronic acid, 2-aza-undecanylboronic acid, 2- Aza-dodecanylboronic acid, 2-aza-tridecanylboronic acid, 2-aza-tetradecanylboronic acid, 2-aza-pentadecanylboronic acid, 2-aza-hexadecanylboronic acid, 2-aza -Heptadecanylboronic acid, 2-aza-octadecanylboronic acid, 2-aza-nonadecanylboronic acid, 2-aza-icosanylboronic acid and their isomers, 2-phospha-propylboronic acid, 2- Phospha-butylboronic acid, 2-phospha-hexylboronic acid, 2-phospha-heptylboronic acid, 2-phospha-octylboronic acid, 2-phospha-nonylboronic acid, 2-phospha-deca Nylboronic acid, 2-phospha-undecanylboronic acid, 2-phospha-dodecanylboronic acid, 2-phospha-tridecanylboronic acid, 2-phospha-tetradecanylboronic acid, 2-phospha -Pentadecanylboronic acid, 2-phospha-hexadecanylboronic acid, 2-phospha-heptadecanylboronic acid, 2-phospha-octadecanylboronic acid, 2-phospha-nonadecanylboronic acid , 2-phospha-icosanylboronic acid and isomers thereof, 2-thia-propylboronic acid, 2-thia-butylboronic acid, 2-thia-hexylboronic acid, 2-thia-heptylboronic acid, 2-thia- Octylboronic acid, 2-thia-nonylboronic acid, 2-thia-decanylboronic acid, 2-thia-undecanylboronic acid, 2-thia-dodecanylboronic acid, 2-thia-tridecanylboronic acid, 2 -thia-tetradecanylboronic acid, 2-thia-pentadecanylboronic acid, 2-thia-hexadecanylboronic acid, 2-thia-heptadecanylboronic acid, 2-thia-octadecanylboronic acid, 2 -thia-nonadecanylboronic acid, 2-thia-icosanylboronic acid and their isomers are exemplified. Moreover, as a compound which can convert to the monoboronic acid illustrated in presence of water, the salt of the said monoboronic acid, etc. are mentioned.

An aliphatic hydrocarbon group may be sufficient as R< ¹ >, and even if it contains hetero atoms, such as oxygen, nitrogen, sulfur, and a halogen, it is not cared about. Considering the ease of availability, etc., it is preferable that R< ¹ > is an aliphatic hydrocarbon group which does not contain a hetero atom. As an aliphatic hydrocarbon group, it is preferable that it is a straight-chain aliphatic hydrocarbon group which does not have a branch. Thereby, the adsorption property to a polarizing film becomes favorable, and the effect of improving optical performance becomes high. Further, as the boronic acid in which R ¹ is a linear aliphatic hydrocarbon group, specifically, methylboronic acid, ethylboronic acid, n-propylboronic acid, n-butylboronic acid, n-pentylboronic acid, n-hexylboronic acid, n -Heptylboronic acid, n-octylboronic acid, n-nonylboronic acid, n-decanylboronic acid, n-undecanylboronic acid, n-dodecanylboronic acid, n-tridecanylboronic acid, n-tetradeca Nylboronic acid, n-pentadecanylboronic acid, n-hexadecanylboronic acid, n-heptadecanylboronic acid, n-octadecanylboronic acid, n-nonadecanylboronic acid, n-icosanylboronic acid etc. are exemplified. Moreover, as a compound which can convert to boronic acid in the presence of water, the salt of the said boronic acid, etc. are mentioned.

Specifically, as the monoboronic acid represented by the formula (I), ethylboronic acid, n-propylboronic acid, n-butylboronic acid, and n-pentylboronic acid are particularly preferable. Moreover, as a compound which can convert to these boronic acid in presence of water, the said boronic acid salt etc. are mentioned.

<PVA (A)>

PVA(A) in this invention is a polymer which has a vinyl alcohol unit (-CH2 _- CH(OH)-) as a main structural unit.

It is preferable to exist in the range of 1,500-6,000, as for the polymerization degree of PVA(A) contained in the polarizing film of this invention, it is more preferable to exist in the range of 1,800-5,000, 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(A) in this specification means the average degree of polymerization measured according to description of JISK6726-1994.

The degree of saponification of PVA (A) 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 a polarizing film obtained by uniaxially stretching the film, 98 It is more preferable that it is mol% or more. Incidentally, the degree of saponification of PVA in the present specification refers to a structural unit (typically a vinyl ester unit) that can be converted into a vinyl alcohol unit (-CH ₂ -CH(OH)-) by saponification that PVA has, and a vinyl The ratio (mol%) to which the number of moles of the said vinyl alcohol unit occupies with respect to the total number of moles of an alcohol unit is said. The said saponification degree can be measured according to description of JISK6726-1994.

The manufacturing method of PVA (A) used by this invention is not specifically limited. For example, the method of converting the vinyl ester unit of the polyvinyl ester obtained by superposing|polymerizing a vinyl ester monomer into a vinyl alcohol unit is mentioned. The vinyl ester monomer used for the production of PVA (A) is not particularly limited, and for example, vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatate, vinyl caproate, Vinyl caprylate, 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 (A) used by this invention may convert the vinyl ester unit of the vinyl 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, and 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 (meth)acrylamide derivatives, such as its salt, (meth)acrylamide propyldimethylamine 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. Said vinyl ester copolymer may have a structural unit derived from 1 type(s) or 2 or more types of 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 a polymerization reaction, or adding this in a reaction container during advancing of a polymerization reaction. From the viewpoint of optical performance, the content of units derived from other monomers is preferably 10 mol% or less, more preferably 5 mol% or less, and 2 mols or less with respect to the number of moles of all the structural units constituting the PVA (A). % or less is more preferable.

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 breakage in the production of a polarizing film is reduced, so that the productivity of the polarizing film is further improved , ethylene is preferred. When PVA(A) contains an ethylene unit, the content rate of an ethylene unit is 1-10 with respect to the mole number of all the structural units which comprise PVA(A) from a viewpoint, such as above-mentioned stretchability, a stretchable temperature, etc. mol% is preferable, and 2-6 mol% is more preferable.

The PVA film used for manufacture of the polarizing film of this invention can contain a plasticizer other than said PVA (A). 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, 1 type(s) or 2 or more types of these plasticizers can be included. Among these, the point of the improvement effect of a stretchability to glycerol is preferable.

It is preferable that content of the plasticizer in the PVA film used for manufacture of the polarizing film of this invention exists in the range of 1-20 mass parts with respect to 100 mass parts of PVA(A), It is more in the range of 3-17 mass parts It is preferable, and it is still 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. 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 the PVA film used for manufacture of the polarizing film of this invention, further, a filler, processing stabilizers, such as 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 , perfume, antifoaming agent, deodorant, extender, release agent, mold release agent, reinforcing agent, crosslinking agent, fungicide, preservative, crystallization rate retardant, etc. Other additives other than PVA (A) and plasticizer may be appropriately blended as needed. Content of the other additive in the said PVA film is 10 mass % or less normally, Preferably it is 5 mass % or less.

It is preferable to exist in the range of 160 to 240% of swelling degree of the PVA film used for manufacture of the polarizing film of this invention, 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 the swelling degree is 160 % or more, it can suppress that crystallization progresses extremely, and it 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. The degree of swelling of the PVA film was measured by the method described in the Examples.

<The manufacturing method of a polarizing film>

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, Preferably it is 5-60 micrometers, Especially preferably, it is 10-45 micrometers. When the said PVA film 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 PVA film is too thick, there exists a tendency for extending|stretching nonuniformity to become easy to generate|occur|produce at the time of the uniaxial stretching process for manufacturing a polarizing film, and the tendency for the contractile force of the manufactured polarizing film to become large easily.

The width 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 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 in 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, if the width of the PVA film used for the production of the polarizing film is too large, it tends to be difficult to uniformly perform uniaxial stretching when the polarizing film is manufactured with an apparatus that is put into practical use, so it is used for the production of the polarizing film It is preferable that the width|variety of the PVA film used is 10 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 uniform is employ|adopted preferably. For example, PVA (A) and, if necessary, a film forming stock solution in which one or two or more of the above-mentioned plasticizer, the above-mentioned other additives, and surfactants mentioned later are dissolved in a liquid medium, or PVA (A) , and, if necessary, one or more of a plasticizer, another additive, a surfactant, a liquid medium, and the like, and can be produced using a film forming stock solution in which PVA (A) is melted. When the said film forming undiluted|stock solution contains at least 1 sort(s) of a plasticizer, another additive, and surfactant, it is preferable that those components are mixed uniformly.

As said liquid medium used for preparation of the 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, 1 type(s) or 2 or more types of these can be used. Among them, water is preferable from the viewpoint of the load on the environment and the recovery properties.

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 removed by volatilization or evaporation during film forming) also varies depending on the film forming method, film forming conditions, etc., but is 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 too high, filtration and defoaming at the time of preparing the film forming undiluted solution are smoothly performed, and the production of a film with few foreign substances and defects is facilitated. On the other hand, when the volatile fraction of the film forming undiluted solution is 95 mass % or less, the concentration of the film forming undiluted solution does not become too low, and manufacture of an industrial film becomes easy.

It is preferable that the film forming undiluted|stock solution contains surfactant. By including 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 undiluted 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 (A) contained in the film forming undiluted solution. And it is especially preferable that it exists in the range of 0.05-0.2 mass part. When the said content is 0.01 mass part or more, film formability and peelability improve more. On the other hand, when the said content is 0.5 mass part or less, surfactant bleeds out on the surface of a PVA film, blocking arises and it can suppress that handleability falls.

As a film forming method at the time of forming a PVA film into a film using the above-mentioned film forming undiluted|stock solution, the cast film forming method, the extrusion film forming method, the wet film forming method, the gel film forming method etc. are mentioned, for example. 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 thickness and width|variety are uniform and the PVA film used for manufacture of a polarizing film with favorable physical properties is obtained. 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 manufacturing 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., From one side of a film that is uniformly discharged or cast on the main surface of the rotating heated roll (or belt) and is discharged or cast on the main surface of this first roll (or belt) The volatile components are evaporated to dryness, and then further dried on the main surface of one or a plurality of rotating heated rolls arranged on the downstream side thereof, or further dried by passing through a hot air drying device, and then by a winding device The winding-up method can be employ|adopted industrially suitably. You may perform drying by the heated roll and drying by a hot-air drying apparatus combining suitably. Moreover, you may form a multilayer PVA film into a film by forming the layer which consists of PVA (A) in one surface of the base film comprised from a single resin layer.

The method in particular at the time of manufacturing the polarizing film of this invention is not restrict|limited. A preferred production method is a method for producing a polarizing film comprising a dyeing treatment in which the PVA film is dyed with a dichroic dye, and a stretching treatment in which the film is uniaxially stretched. It is a manufacturing method of the polarizing film which has a process to be immersed. At this time, in addition to the dyeing treatment and the uniaxial stretching treatment, if necessary, the PVA film may be further subjected to a swelling treatment, a boric acid crosslinking treatment, a fixing treatment, a washing treatment, a drying treatment, a heat treatment, and the like. . 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 fixed process, is not restrict|limited, Two or more processes may be implemented simultaneously. Moreover, 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 the water which immerses a film, 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 in which the film is immersed is not limited to pure water, The aqueous solution which various components melt|dissolved may be sufficient, and the mixture of water and a hydrophilic 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 or a dichroic dye. As 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. It is common to perform dyeing treatment by immersing a PVA film in the solution (especially aqueous solution) containing an iodine-potassium iodide as a dyeing bath, or the solution containing several dichroic dyes (especially aqueous solution). 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. When a dichroic dye is used, the dichroic dye is preferably an aqueous dye. Moreover, it is preferable that the dye density|concentration in a dyeing bath is 0.001-10 mass %. Moreover, if necessary, a dyeing aid may be used, and inorganic salts, such as sodium sulfate, surfactant, etc. may be used. When using sodium sulfate, 0.1-10 mass % is preferable. As a specific dichroic dye, see Si. Child. Direct Yellow 28, ci. Child. Direct Orange 39, ci. Child. Direct Yellow 12, ci. Child. Direct Yellow 44, ci. Child. Direct Orange 26, ci. Child. Direct Orange 71, ci. Child. direct. Orange 107, Po. Child. Direct Red 2, Poetry. Child. Direct Red 31, ci. Child. direct. Red 79, ci. Child. Direct Red 81, ci. Child. Direct Red 247, ci. Child. Direct Green 80, ci. Child. Although Direct Green 59 etc. are mentioned, A dichroic dye developed for manufacture of a polarizing plate is preferable.

By performing a boric acid crosslinking process with respect to a PVA film, the PVA molecular chain in a PVA film is bridge|crosslinked, and the orientation of a PVA molecular chain improves. As a result, since the orientation of the dichroic dye adsorb|sucked to the PVA film improves, the optical performance of the polarizing film obtained improves. From this viewpoint, it is more preferable to perform a boric-acid crosslinking process after a dyeing process and before an extending|stretching process. A boric acid crosslinking process can be performed by immersing a PVA film in the aqueous solution containing a boric acid crosslinking agent. As the boric acid crosslinking agent, one type or two or more types of boron-containing inorganic compounds such as boric acid salts such as boric acid and borax can be used, and from the viewpoint of ease of handling, the boric acid crosslinking agent is preferably boric acid. It is preferable that it is 1-10 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 that it is 2-7 mass %. When the density|concentration of a boric-acid crosslinking agent is 1-10 mass %, sufficient stretchability is maintainable. When the concentration of the boric acid crosslinking agent exceeds 10% by mass, excessive crosslinking proceeds and extensibility may decrease, or excessive PVA molecular chains orient and contractile force may increase, which is not preferred. Moreover, when the density|concentration of a boric-acid crosslinking agent is less than 1 mass %, since there exists a possibility that the orientation of the dichroic dye adsorbed to the PVA film does not fully improve, and there exists a possibility that the optical performance of the polarizing film obtained may not fully improve, it is unpreferable. The aqueous solution containing a boric-acid crosslinking agent may contain adjuvants, such as potassium iodide. 20-50 degreeC is preferable and, as for the temperature of the aqueous solution containing a boric-acid crosslinking agent, 25-40 degreeC is especially preferable. A boric-acid bridge|crosslinking can be efficiently carried out by making the said temperature into 20-50 degreeC.

Apart from the uniaxial stretching process mentioned later, you may extend|stretch (pre-stretch) a PVA film in each process mentioned above, or between processes. Thus, the total draw ratio (magnification which multiplied the draw ratio in each process) performed before the uniaxial stretching process is the original length of the PVA film of the raw material before extending|stretching from viewpoints, such as optical performance of the polarizing film obtained. Based on this, 1.5 times or more is preferable, 2.0 times or more is more preferable, and 2.5 times or more is still more preferable. On the other hand, 4.0 times or less are preferable and, as for the said total draw ratio, 3.5 times or less are more preferable. As a draw ratio in a swelling process, 1.05-2.5 times are preferable. As a draw ratio in a dyeing process, 1.1-2.5 times are preferable. As a draw ratio in a boric-acid crosslinking process, 1.1-2.5 times are preferable.

The uniaxial stretching process may be performed by either a wet stretching method or a dry stretching method. In the case of the wet stretching method, the PVA film is stretched in an aqueous solution. The PVA film can also be stretched in the above-described dyeing bath or aqueous boric acid solution. 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 %. 30 degreeC or more is preferable, as for the extending|stretching temperature in a uniaxial stretching process, 40 degreeC or more is more preferable, and 50 degreeC or more is still more preferable. On the other hand, 90 degrees C or less is preferable, as for extending|stretching temperature, 80 degrees C or less is more preferable, and its 70 degrees C or less is still more preferable. Moreover, as a draw ratio in a uniaxial stretching process, 2.0-4.0 times are preferable. From viewpoints, such as optical performance of the polarizing film obtained, as for the said draw ratio, 2.2 times or more are more preferable. On the other hand, as for the said draw ratio, 3.5 times or less are more preferable. Moreover, it is preferable that it is 5 times or more based on the original length of the PVA film of a raw material before extending|stretching, and, as for the total draw ratio before the fixing process mentioned later, it is more preferable that it is 5.5 times or more from the point of the optical performance of the polarizing film obtained. . 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 particular limitation on the direction of the uniaxial stretching treatment when the elongated PVA film is subjected to uniaxial stretching treatment, and uniaxial stretching treatment in the long direction, uniaxial stretching treatment in the transverse direction, so-called oblique stretching treatment may be employed. However, from the viewpoint of obtaining a polarizing film excellent in optical performance, the uniaxial stretching treatment in the elongate direction is preferable. 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.

In manufacture of a polarizing film, in order to strengthen adsorption|suction of the dichroic dye (iodine type dye etc.) 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) is preferably used. Moreover, you may further add a boric acid, an iodine compound, a metal compound, etc. in a fixed process bath as needed. From the point of speeding up the substitution reaction of the boron-containing compound (B) and boric acid (C) in the center part of the thickness direction of a polarizing film, it is preferable that a fixed treatment bath does not contain boric acid substantially. It is preferable that the temperature of a fixed treatment bath is 10-80 degreeC. 1.3 times or less are preferable, as for the draw ratio in a fixing process, 1.2 times or less are more preferable, and its less than 1.1 times are still more preferable.

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 cutting|disconnection of the PVA film of is suppressed. Moreover, a boron containing compound (B) may be used not only by 1 type, but in mixture of 2 or more types. From a viewpoint of advancing the substitution reaction of a boron-containing compound (B) and a boric acid (C) to the center part of the thickness direction of a polarizing film, the aqueous solution density|concentration of a boron-containing compound (B) needs to be 0.2-5 mass %. When the concentration of the boron-containing compound (B) in the aqueous solution is lower than 0.2 mass%, the adsorption of the boron-containing compound (B) to the surface portion of the polarizing film becomes slow, and it is more preferably 0.4 mass% or more, and 0.6 mass% or more. more preferably. On the other hand, when the concentration of the boron-containing compound (B) in the aqueous solution is higher than 5.0 mass%, the boron-containing compound (B) is excessively adsorbed to the surface portion of the polarizing film, and the boron-containing compound (B) and boric acid (C) ), the substitution reaction becomes difficult to proceed. Moreover, there exists a possibility that the precipitate of a boron-containing compound (B) may generate|occur|produce in the surface part of a polarizing film. The concentration of the boron-containing compound (B) is more preferably 4.0 mass% or less, still more preferably 2.0 mass% or less, and particularly preferably 1.0 mass% or less.

Moreover, it is preferable that the aqueous solution containing a boron-containing compound (B) contains the adjuvant of iodide, such as potassium iodide, from the point of optical performance improvement, and it is preferable that the density|concentration of an iodide is 0.5-15 mass %. Moreover, the temperature of the aqueous solution containing a boron containing compound (B) needs to be 20-70 degreeC. When the temperature of the aqueous solution containing a boron-containing compound (B) is less than 20 degreeC, it becomes difficult to advance the substitution reaction which substitutes the boric acid in a polarizing film with boronic acid to the center part of the thickness direction of a polarizing film. Moreover, a boron-containing compound (B) may precipitate in the aqueous solution containing a boron-containing compound (B). 23 degreeC or more is preferable and, as for the temperature of the aqueous solution containing a boron-containing compound (B), 25 degreeC or more is more preferable. On the other hand, when the temperature of the aqueous solution containing a boron containing compound (B) is too high, it will become difficult to manufacture a polarizing film easily industrially on comparatively mild conditions. 60 degrees C or less is preferable and, as for the temperature of the aqueous solution containing a boron containing compound (B), 40 degrees C or less is more preferable. As for the time to be immersed in the aqueous solution containing a boron-containing compound (B), 5-400 second is preferable.

As a method of manufacturing a polarizing film by adsorbing a boron-containing compound (B) to a polarizing film at the time of a fixed treatment, a swelling treatment, a uniaxial stretching treatment, performing a fixed treatment in this order, a swelling treatment, a boric acid crosslinking treatment, It is preferable to perform a uniaxial stretching process and a fixed process in this order, and to perform a swelling process, a uniaxial stretching process, a fixed process, and a boric-acid crosslinking process in this order. After performing these treatments, one or more treatments selected from washing treatment, drying treatment and heat treatment may be further performed as needed.

The washing process is generally performed by immersing the PVA film in distilled water, pure water, aqueous solution, or the like. At this time, it is preferable to use the aqueous solution containing iodide, such as potassium iodide, as an auxiliary agent from the point of optical performance improvement, and it is preferable that the density|concentration of the said iodide shall be 0.5-10 mass %. Moreover, the temperature of the aqueous solution in a washing process is 5-50 degreeC generally, 10-45 degreeC is preferable, and 15-40 degreeC is more preferable. From an economical viewpoint, it is not preferable that the temperature of aqueous solution is too low, and when the temperature of aqueous solution is too high, optical performance may fall.

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, heat processing is a process which further heats the polarizing film whose moisture content after a drying process is 5 % or less, and 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 it is lower than 60 degreeC, the dimensional stabilization effect by heat processing is inadequate, and when higher than 150 degreeC, redness may generate|occur|produce severely in a polarizing film.

Thus, it is preferable that the transmittance|permeability of the polarizing film of this invention obtained is 42.0 % or more, and it is preferable that a polarization degree is 99.85 % or more. When the transmittance|permeability of a polarizing film is less than 42.0 %, there exists a possibility that the brightness of LCD obtained may become inadequate. 43.0 % or more is more preferable, and, as for the said transmittance|permeability, 43.5 % or more is still more preferable. On the other hand, the transmittance is usually 45% or less. Moreover, when the polarization degree of a polarizing film is 99.85 % or more, an LCD panel with high image quality is obtained. The transmittance and the degree of polarization of the polarizing film are measured by the method described in Examples to be described later.

Thus, it is preferable that the contraction force of the absorption axis direction per width 1.5cm and 13 micrometers in thickness at the time of hold|maintaining at 80 degreeC for 4 hours of the polarizing film of this invention obtained in this way is less than 12N. When LCD is enlarged as the contractile force of a polarizing film is 12 N or more, LCD may bend easily by screen heat_generation|fever, and there exists a possibility that light leakage may arise from an edge part. The shrinkage force of the polarizing film was measured by the method described in Examples.

The polarizing film of this invention is used normally as a polarizing plate by bonding 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, as an adhesive agent for bonding, a PVA type adhesive agent, a UV curing adhesive agent, etc. are mentioned.

You may bond the polarizing plate obtained as mentioned above to retardation film, a viewing angle improvement film, a brightness improvement film, etc. Moreover, after coating adhesives, such as an acrylic type, to a polarizing plate, it can bond with a glass substrate and can use it as a component of LCD.

Example

The present invention will be specifically illustrated by the following examples, but the present invention is not limited at all by these examples. In addition, each evaluation method employ|adopted in the following Example and a comparative example is shown below.

<Optical performance of polarizing film>

A rectangular sample of 4 cm x 2 cm in the longitudinal direction of the polarizing film was collected from the central portion in the width direction and the longitudinal direction of the polarizing film, and a spectrophotometer V-7100 with an integrating sphere (manufactured by Nippon Spectroscopy Co., Ltd.) and a Glan Taylor polarizer The parallel transmittance and cross nicol transmittance of the polarizing film were measured using an automatic polarizing film measuring apparatus VAP-7070S (manufactured by Nippon Spectroscopy Co., Ltd.) equipped with a polarizing film. Here, the measurement wavelength range is set to 380 nm to 780 nm, and the transmittance when the vibration direction of the polarized light incident on the polarizing film through the Glan Taylor polarizer is parallel to the transmission axis of the polarizing film is the parallel transmittance and the transmittance of the polarizing film The case perpendicular to the axis was defined as the cross nicol transmittance. Then, using the "polarizing film evaluation program" (manufactured by Nippon Spectroscopy Co., Ltd.), in accordance with JIS Z 8722 (method for measuring object color), using the above-described parallel transmittance and cross nicol transmittance, C light source, 2 ° field of view Visibility correction of the visible light region was performed, the single transmittance of the polarizing film and the polarization degree were calculated, and these two values were obtained as optical properties of the polarizing film.

<Contraction force of polarizing film>

The contractile force was measured using Shimadzu Corporation autograph "AG-X" with thermostat and video extensometer "TRViewX120S". Since the absorption axis direction and the longitudinal direction (stretching axis direction) of the polarizing film are substantially the same, the contractile force in the absorption axis direction of the polarizing film was determined by measuring the tension in the longitudinal direction (stretching axis direction). For the measurement, a polarizing film (longitudinal direction (stretching axis direction) 15 cm, width direction 1.5 cm) controlled at 20°C/20%RH for 18 hours was attached to a chuck (chuck spacing of 5 cm), and simultaneously with the start of tensioning, 80°C to start the temperature increase of the thermostat. The polarizing film was pulled at a rate of 1 mm/min, the tension was stopped when the tension reached 2N, and the tension until 4 hours later was measured in that state. At this time, since the distance between the chucks changes due to thermal expansion, a marked seal is attached to the chuck, and the distance between the chucks is corrected so that the distance between the chucks becomes constant only as much as the marked seal attached to the chuck moves using a video extensometer “TR VieWX120S”. Measurements were made. In addition, when the minimum value of tension arises in the measurement initial stage (within 10 minutes of measurement start), the minimum value of tension was subtracted from the measured value of the tension 4 hours after, and the difference was made into the contraction force of the stretch axis direction of a polarizing film.

<Swelling degree of PVA film>

The PVA film was cut into 5 cm x 10 cm, and it was immersed 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 H) after immersion was measured. Then, after putting a PVA film into a 105 degreeC dryer and making it dry for 16 hours, the PVA film mass (mass I) after drying was measured. The swelling degree of the PVA film was computed by substituting the values of mass H and mass I in following formula (1).

Swelling degree (%) = (mass H/mass I) × 100 (1)

<Concentration of elemental boron (α) and concentration of elemental boron (β)>

The boron element concentration derived from the boron-containing compound (B) in the polarizing film was measured using an X-ray photoelectron spectrometer with a gas cluster ion beam gun (PHI5000 VersaProbe II manufactured by ULVAC PAI Corporation) (GCIB-XPS). For the measurement, the polarizing film controlled at about 23°C/40%RH for 16 hours or more was used. Under the conditions of a sputtering ion source Ar2500+, an acceleration voltage of 10 keV, and a current value of 30 nA, sputtering was performed in a range of 1 mm × 1 mm while neutralizing, and X-ray photoelectron spectroscopy (XPS measurement) was performed. For XPS measurement, monochromatic Al is used as the X-ray source, the X-ray spot diameter is 200 µm, the X-ray output is 15 kV, and 50 W is set, and the detection elements are 5 of carbon, boron, oxygen, iodine, and potassium. species was selected. Moreover, when using a dichroic dye for a dichroic dye, it is necessary to select suitably also elements, such as nitrogen and sulfur contained in a dichroic dye, as a detection element. Next, using the analysis software "MultiPak" (manufactured by ULVAC PAI Co., Ltd.), based on 284.8 eV, which is the binding energy of CC and CH bonds, the boron element concentration at each depth in the thickness direction of the polarizing film (a, atomic %) was calculated. Then, with respect to the XPS spectrum at each depth, the binding energy resulting from boron of boric acid (C) and the binding energy resulting from boron of the boron-containing compound (B) are appropriately set, and table calculation software "Microsoft Excel 2010" ' (manufactured by Microsoft Corporation), the peak separation was performed by the least squares method using a pseudo Forkt function. In addition, a linear function calculated from the average value of the intensity of the XPS spectrum of 187 to 189 eV and the average value of the XPS spectrum of 195 to 197 was used as the baseline. In this way, the peak area (b, %) of the boron derived from the boron-containing compound (B) with respect to the sum of the boron derived from the boric acid (C) and the boron derived from the boron-containing compound (B) is calculated, and the following formula (2) ), the boron element concentration derived from the boron-containing compound (B) at each depth was calculated.

Concentration of elemental boron derived from boron-containing compound (B) (atomic %)

= a × b × 10 ^-2 (2)

In addition, the binding energy resulting from boron in the boron-containing compound (B) changes depending on the structure of the compound. Therefore, it is necessary to set the said binding energy appropriately according to the kind of boron-containing compound (B). For example, when the boron-containing compound (B) is n-propylboronic acid, it is around 191.5 eV. In addition, when peak separation was performed by the least squares method using the pseudo-Fort function, the Lorentz water ratio of boric acid was set to 0.241, and 2 ^1/2 × σ was set to 0.916. In addition, the Lorentz water content and full width at half maximum of the boron-containing compound (B) also change depending on the structure of the compound. Therefore, it is necessary to appropriately set the Lorentz water content and 2 ^1/2 × σ according to the type of the compound. When the boron-containing compound (B) was n-propylboronic acid, the Lorentz water content was set to 0.000, and 2 ^1/2 × σ was set to 0.769.

By such a method, the boron element concentration ((alpha), atomic%) derived from the boron containing compound (B) from the center of the thickness direction of a polarizing film to the outer side 1 micrometer was calculated|required. Moreover, the boron element density|concentration ((beta), atomic%) derived from the boric acid to the outer side 1 micrometer from the center of the thickness direction of a polarizing film was calculated|required.

<Example 1>

100 parts by mass of PVA (a degree of saponification of 99.9%, a degree of polymerization of 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, a PVA aqueous solution having a content of PVA of 10% by mass is prepared did The film obtained by drying the said PVA aqueous solution on an 80 degreeC metal roll was heat-processed in (120 degreeC) for 10 minutes in a hot-air dryer, 30 micrometers in thickness and the swelling degree obtained the PVA film of 200%.

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, immersing this sample in 30 degreeC pure water for 30 second. Then, it uniaxially stretched 2.2 times (total 2.4 times) in the longitudinal direction, and iodine was adsorbed, immersing in 30 degreeC aqueous solution (dye treatment bath) containing 0.035 mass % of iodine and 3.5 mass % of potassium iodide for 60 second. Subsequently, it uniaxially stretched in the longitudinal direction at 1.1 times (2.7 times as a whole), immersing in the 30 degreeC aqueous solution (boric acid crosslinking treatment bath) containing 3.0 mass % of boric acid and potassium iodide in the ratio of 3 mass %. Furthermore, it uniaxially stretched in the longitudinal direction to 6.0 times as a whole, immersing in the 60 degreeC aqueous solution (stretching process bath) containing 4.0 mass % of boric acid and potassium iodide in the ratio of 6 mass %. After the uniaxial stretching treatment, the boron-containing compound (B) was immersed in an aqueous solution (fixed treatment bath) at 30°C containing 0.7% by mass of n-propylboronic acid and 2 to 5% by mass of potassium iodide for 100 seconds. . In the fixing treatment, the PVA film was not stretched (draw ratio 1.0 times). Finally, it dried at 60 degreeC for 240 second, and produced the polarizing film (13 micrometers in thickness).

When the XPS spectrum of the polarizing film was measured and analyzed, the boron element concentration (α) derived from the boron-containing compound (B) in the range of 1 µm from the center in the thickness direction of the polarizing film was 1.4 atomic%, The boron element concentration (beta) derived from boric acid in the range of 1 micrometer from the center was 1.5 atomic%. Although the above method evaluated the optical characteristic and contractile force of a polarizing film, it was 44.18% of transmittance|permeability, 99.89% of polarization degree, and it was 0.6 N of contractility.

<Examples 2 to 4>

Except having changed the time and aqueous solution density|concentration to be immersed in a fixed process bath like Table 1, it carried out similarly to Example 1, the polarizing film was produced, and each measurement and evaluation were performed.

<Comparative Example 1>

It is an example of the polarizing film which does not contain a boron containing compound (B). As a fixed process bath, it carried out similarly to Example 1, except having used the aqueous solution (temperature 30 degreeC) containing potassium iodide in the ratio of 2 mass %, and having been immersed in the fixed process bath into 20 second, it carried out similarly to Example 1, and a polarizing film was produced, and each measurement and evaluation were performed. Although the boron element concentration ((beta)) derived from boric acid (C) was low and the contractile force of a polarizing film became low to 6.4 N, the polarization degree was insufficient at less than 99.85 %.

<Comparative Example 2>

It is an example of the polarizing film which does not contain a boron containing compound (B). As a fixed treatment bath, the aqueous solution (temperature 30 degreeC) containing potassium iodide in the ratio of 2 mass % was used, except having changed the time to be immersed in the fixed treatment bath into 5 seconds, it carried out similarly to Example 1, and a polarizing film was produced, and each measurement and evaluation were performed. At this time, the contractile force of the polarizing film exceeded 12 N, and the contractile force was not sufficiently reduced.

In Examples 2 to 4 and Comparative Example 1, similarly to Example 1, while immersing in an aqueous solution (dye treatment bath) (temperature of 30° C.) containing 100 parts by mass of potassium iodide in a ratio of 100 parts by mass of iodine for 60 seconds, The iodine was adsorbed by uniaxial stretching in the longitudinal direction at 2.2 times (total 2.4 times). At this time, the iodine and potassium iodide density|concentration of a dyeing process bath were adjusted so that the transmittance|permeability of the polarizing film after drying might be set to 43.8-44.2%.

As shown in Table 1, it turns out that the polarizing film of Examples 1-4 has small shrinkage force under high temperature, and is excellent also in optical performance.

As shown in Examples, the polarizing film of the present invention has a low shrinkage force while having high optical performance. Therefore, it can meet the request|requirement of thinning and high definition of the recent electronic device.

1: center of thickness direction of polarizing film
2: the surface of the polarizing film
3: center of thickness direction of polarizing film

Claims (7)

At least one boron-containing compound (B) and boric acid ( A polarizing film containing C), wherein the boron element concentration (α) derived from the boron-containing compound (B) in the range from the center in the thickness direction to the outside to 1 µm is 0.1 to 3 atomic %, in the thickness direction The concentration (β) of boron element derived from boric acid (C) in the range from the center to 1 µm outward is 0.1 to 8 atomic%, and the ratio of the concentration (α) to the concentration (β) (α/β) ) is 0.1 or more, the polarizing film.

[In formula (I), R ¹ is a monovalent aliphatic group having 1 to 20 carbon atoms, and R ¹ and the boronic acid group are connected by a boron-carbon bond.] The method of claim 1,
The polarizing film in which R< ¹ > is a saturated aliphatic group. 3. The method of claim 1 or 2,
The polarizing film whose R< ¹ > is a linear aliphatic hydrocarbon group. 4. The method according to any one of claims 1 to 3,
The polarizing film whose carbon number of R< ¹ > is 2-5. 5. The method according to any one of claims 1 to 4,
A polarizing film having a transmittance of 42.0% or more and a polarization degree of 99.85% or more. 6. The method according to any one of claims 1 to 5,
The polarizing film whose contraction force in the absorption axis direction per width 1.5cm and 13 micrometers in thickness at the time of hold|maintaining at 80 degreeC for 4 hours is less than 12N. In the manufacturing method of a polarizing film including the dyeing process of dyeing a polyvinyl alcohol film with a dichroic dye, and the extending|stretching process which uniaxially stretches the film WHEREIN: The density|concentration of the boron-containing compound (B) of the film is 0.2-5 It is mass % and the manufacturing method of the polarizing film in any one of Claims 1-6 which has a process immersed in the aqueous solution whose temperature is 20-70 degreeC.

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