KR20220149535A - Polarizing film and its manufacturing method - Google Patents

Abstract

[식 (I) 중, R¹ 은 탄소수가 1 ∼ 20 인 1 가의 지방족기이며, R¹ 과 보론산기가 붕소-탄소 결합으로 연결되어 있다.]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, and boric acid ( A polarizing film containing C), wherein the boron element content (b _t ) derived from the boron-containing compound (B) is 0.3 to 2.0 mass%, the total boron element content (T) is 3.0 to 7.0 mass%, and (T ) to (b _t ) has a ratio (b _t /T) of 0.10 to 0.30, and is derived from the boron-containing compound (B) in the range from at least one surface inward to 7.5% of the total thickness. It is a polarizing film whose boron element concentration (bo) is _2.2-10.0 atomic%. The said polarizing film has high polarization performance and also high transmittance|permeability.

[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.]

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 a liquid crystal that changes the polarization state of light. In order to prevent fading of a polarizing film and shrinkage of a polarizing film, most polarizing plates have the structure by which protective films, such as a cellulose triacetate (TAC) film, were bonded together by the surface of a polarizing film. As a polarizing film constituting the polarizing plate, a polyvinyl alcohol film (hereinafter, "polyvinyl alcohol" may be referred to as "PVA") is uniaxially stretched with an iodine-based dye (I ^3- , I ^5- , etc.) ) adsorbed is the mainstream.

BACKGROUND ART LCDs are widely used in 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. In recent years, LCDs, such as 4K and 8K, have been put to practical use, and while high-definition of LCD is progressing, the fall of the light extraction efficiency by the fall of an aperture ratio has become a problem. In this regard, in order to compensate for a decrease in light extraction efficiency due to a decrease in the aperture ratio, a polarizing film having high polarization performance and high transmittance is required.

As a method of obtaining a polarizing film with high polarization performance, the method of using PVA of high polymerization degree is known (for example, patent document 1). However, since the stretchability of a PVA film fell when PVA of high polymerization degree was used, there existed a problem that the yield of a polarizing film fell.

Moreover, the method of decomposing|disassembling an unnecessary iodine-type pigment|dye by treating a polarizing film with a reducing agent is also known (for example, patent document 2). However, if the concentration of the reducing agent is not strictly controlled, the iodine-based dye will be decomposed more than necessary, making industrial implementation difficult.

By the way, in order to bridge|crosslink the PVA molecular chain in a polarizing film in recent years, the method of using the aqueous solution of boronic acid is developed. For example, in Patent Document 3, after uniaxial stretching, the PVA film is immersed in an aqueous solution (fixed treatment bath) containing boronic acid such as methylboronic acid and 1,4-butanediboronic acid and potassium iodide, whereby moisture and heat resistance is improved. It is described that excellent polarizing films are obtained. In addition, in Patent Document 4 or Patent Document 5, it is described that a polarizing film excellent in heat-and-moisture resistance and a polarizing film having high polarization performance and small shrinkage force at high temperature can be obtained by treating the PVA film with monoboronic acid to impart hydrophobicity. .

However, in order to meet the high-definition request|requirement of an electronic device, the polarizing film of patent documents 3-5 still had insufficient polarization performance in some cases.

Japanese Patent Application Laid-Open No. 01-084203 Japanese Patent Laid-Open No. 2013-156621 WO 2018/021274 KR 10-2015-0052777 WO 2019/146677

This invention was made in order to solve the said subject, and aims at providing the polarizing film which is high polarization performance and high transmittance, and its manufacturing method.

As a result of intensive studies by the present inventors, in order to obtain a polarizing film having high polarization performance and high transmittance, the amount and ratio of boric acid (C) and boron-containing compound (B) used for crosslinking of PVA molecular chains in the polarizing film should be adjusted to an appropriate range. It discovered that it was important to adjust to and to make a boron-containing compound (B) exist comparatively much near the surface of a polarizing film.

The present invention is

[1] at least one boron-containing compound (B) selected from the group consisting of PVA (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, and boric acid A polarizing film containing (C), wherein the boron element content (b _t ) derived from the boron-containing compound (B) is 0.3 to 2.0 mass%, the total boron element content (T) is 3.0 to 7.0 mass%, and ( The ratio (b _t /T) of (b _t ) to T) is 0.10 to 0.30, and ranges from at least one surface inward to 7.5% of the total thickness (hereinafter, when the range is referred to as a surface portion) polarizing film whose boron element concentration (bo) derived from a boron-containing compound (B) in ) is _2.2-10.0 atomic%;

[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 boron element concentration derived from the boron-containing compound (B) in the range from the center to the outside of the polarizing film to 7.5% of the total thickness (hereinafter, the range may be referred to as the central portion) ( The polarizing film of [1] whose b _i ) is 0.5-2.0 atomic%, and the boron element concentration (ci) derived from a boric acid (C) is _3.5-8.0 atomic%;

[3] Boron derived from a boron-containing compound (B) with respect to the boron element concentration ( _ci ) derived from boric acid (C) in the range of up to 7.5% of the total thickness from the center to the outside of the polarizing film The polarizing film of [1] or [2] whose ratio ( _bi / _ci ) of element concentration ( _bi ) is 0.01-0.25;

[4] The boron element concentration (co) derived from boric acid (C) in the range up to 7.5% with respect to the total thickness inward from at least one surface of the said polarizing film is _3.3-7.8 atomic%, [ 1] - the polarizing film of any of [3];

[5] The boron element concentration (b _o ) derived from the boron-containing compound (B) in the range of up to 7.5% of the total thickness inward from at least one surface of the polarizing film is at the center of the polarizing film The polarizing film of any of [1]-[4] which is higher than the boron element density|concentration ( _bi ) derived from a boron-containing compound (B) in the range to 7.5% with respect to the total thickness outward from;

[6] The boron element concentration (co) derived from _boric acid (C) in the range of up to 7.5% of the total thickness from the center of the polarizing film to the outside in the at least one surface of the polarizing film The polarizing film of any one of [1]-[5] which is lower than the boron element concentration ( _ci ) derived from boric acid (C) in the range to 7.5% with respect to full thickness;

[7] The polarizing film according to any one of [1] to [6], wherein R ¹ is a saturated aliphatic group;

[8] The polarizing film according to any one of [1] to [7], wherein R ¹ is a linear aliphatic hydrocarbon group;

[9] The polarizing film according to any one of [1] to [8], wherein R ¹ has 2 to 5 carbon atoms;

[10] The polarizing film according to any one of [1] to [9], wherein the transmittance when the polarization degree is 99.9% or more is 42% or more;

[11] 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 film is immersed in an aqueous solution containing a boric acid crosslinking agent After carrying out, it is the manufacturing method of the polarizing film of any one of [1]-[10] which has a process to be immersed in the 35-80 degreeC aqueous solution containing 1.5-5.0 mass % of a boron-containing compound (B).

The polarizing film of the present invention has high polarization performance and high transmittance. According to the manufacturing method of this invention, such a polarizing film can be manufactured simply.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which showed the cross section of the thickness direction of the polarizing film of this invention.
It is ¹ H-NMR chart of the polarizing film obtained in Example 1. FIG.

<polarizing film>

The polarizing film of the present invention contains at least one boron-containing compound ( B) and a polarizing film containing boric acid (C), wherein the boron element content (b _t ) derived from the boron-containing compound (B) is 0.3 to 2.0 mass%, and the total boron element content (T) is 3.0 to 7.0 mass% and a ratio (b _t /T) of (b _t ) to (T) is 0.10 to 0.30, from at least one surface inward to 7.5% of the total thickness of the boron-containing compound The boron element concentration (b _o ) derived from (B) is 2.2-10.0 atomic%.

[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.]

Thus, the total boron element content (T) in the polarizing film, the boron element content (b _t ) of the boron-containing compound (B), and their ratios are set to a specific range, and further derived from the boron-containing compound (B) of the polarizing film surface part By setting the boron element concentration (b _o ) of , into a specific range, a thing with high polarization performance and high transmittance is obtained. For that reason, the elution of the boric acid (C) from the inside is suppressed because a boron-containing compound (B) exists comparatively much in the surface part of a polarizing film. Thereby, while the relaxation of the orientation of PVA of a polarizing film center part is suppressed, it is thought that it is based on the unnecessary iodine-type pigment|dye of a polarizing film surface part being removed with a boron-containing compound (B).

Usually, when a boric-acid bridge|crosslinked PVA film is immersed in the aqueous solution of a boron-containing compound (B), the reaction in which a boric acid (C) is replaced with a boron-containing compound (B) advances from the surface part of a PVA film. Here, in order to have a relatively large amount of the boron-containing compound (B) in the surface portion of the PVA film, the PVA film is immersed in a relatively high-concentration and high-temperature aqueous solution of the boron-containing compound (B), as described later, so that the boric acid ( It is important to accelerate the substitution reaction between C) and the boron-containing compound (B). When the concentration of the boron-containing compound (B) is low, the elution of the boric acid (C) takes precedence over the adsorption of the boron-containing compound (B). In this case, since it elutes to the boric acid (C) of the central part of a PVA film and the orientation of PVA is relieve|moderated, it becomes difficult to obtain the polarizing film which is high polarization performance and high transmittance|permeability. Moreover, the rigidity of a polarizing film may also fall and there exists a possibility that wrinkles may arise. When the aqueous solution of a boron-containing compound (B) is low temperature, since boric acid (C) is hard to elute, a boron-containing compound (B) is not adsorbed. In this case, since the polarization|polarized-light performance improvement effect by addition of a boron-containing compound (B) is insufficient, the polarizing film which is high polarization performance and high transmittance|permeability cannot be obtained. On the other hand, when the boric acid crosslinked PVA film is immersed in a relatively high concentration and high temperature aqueous solution of the boron-containing compound (B), the substitution reaction proceeds rapidly in the surface portion of the PVA film. As a result, while the relaxation of the orientation of PVA in the central part of a PVA film is suppressed, since the unnecessary iodine-type pigment|dye of the PVA film surface part is removed by the boron-containing compound (B), a polarizing film with high polarization performance and high transmittance is obtained It is thought to be

The boron-containing compound (B) in the polarizing film of the present invention is at least one selected from the group consisting of the monoboronic acid represented by the 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 aliphatic group, R< ¹ > and the boronic acid group are connected by the 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 by a boron-carbon bond. In boric acid [B(OH) ₃ ], the boron atom is different from the bond with three hydroxyl groups in that the boronic acid group has a boron-carbon bond. Representative 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.

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 3]

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 4]

Monoboronic acid has two hydroxyl groups capable of reacting with the hydroxyl group of PVA to form ester, and the PVA chain is appropriately crosslinked. Although the reason is not clear, the polarization performance of the polarizing film is improved because the orientation of the PVA is increased by this crosslinking, or the unnecessary iodine-based dye is destabilized and reduced, so that it becomes a polarizing film with high transmittance with high polarization performance. I think.

In formula (I), R< ¹ > is a C1-C20 monovalent|monohydric 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 more preferable that it is 5 or less from a viewpoint that the adsorption property to a polarizing film becomes favorable and the polarizing film excellent also in optical performance is obtained. 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 a 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. R ¹ may be a saturated aliphatic group or an unsaturated aliphatic group, but 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, an 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 refers to an aliphatic group having a structure containing, and a saturated aliphatic group refers to an aliphatic group having only a single bond structure. Examples of the monoboronic acid 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-decanyl Boronic 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 their isomers, 2-thia-propylboronic acid, 2-thia-butylboronic acid, 2-thia-hexylboronic acid, 2-thia-heptylboronic acid, 2-thia-octyl Boronic 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 be converted into 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 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 with respect 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 be converted into the boronic acid illustrated in 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 preferable, and n-propylboronic acid and n-butylboronic acid are preferable. Acid is more preferred. Moreover, as a compound which can be converted into these exemplified boronic acids in the presence of water, a salt of the said boronic acid etc. are mentioned.

The boron element content (b _t ) derived from the boron-containing compound (B) in the polarizing film of this invention needs to be 0.3-2.0 mass %. When ( _bt ) is less than 0.3 mass %, since bridge|crosslinking by a boron-containing compound (B) becomes inadequate, a polarizing film with high transmittance|permeability with high polarization performance cannot be obtained. For this reason, as for (b _t ), 0.5 mass % or more is preferable. On the other hand, when (b _t ) exceeds 2.0 mass%, the reaction of the boron-containing compound (B) and PVA proceeds excessively, inhibits the formation of an iodine-based dye, and a polarizing film with high transmittance with high polarization performance is obtained. can't For this reason, (b _t ) is preferably 1.8 mass % or less, more preferably 1.6 mass % or less, still more preferably 1.4 mass % or less, particularly preferably 1.3 mass % or less, and most preferably 1.2 mass % or less. do. The boron element content (b _t ) derived from the boron-containing compound (B) in the polarizing film can be obtained by a method combining ¹ H-NMR measurement and ICP emission analysis, specifically, the method described in Examples. As a sample for the measurement of boron element content (bt) and all boron element content ( _T ) mentioned later, the polarizing film which humidity-controlled at 23 degreeC and 50 %RH for 16 hours is used.

Total boron element content (T) of a polarizing film needs to be 3.0-7.0 mass %. When total boron element content (T) in a polarizing film is less than 3.0 mass %, the number of crosslinking points becomes inadequate, the orientation of PVA is disturbed, and a polarizing film with high transmittance|permeability cannot be obtained by high polarization performance. (T) is preferably 3.5 mass% or more, more preferably 4.1 mass% or more, and still more preferably 4.2 mass% or more. On the other hand, when total boron element content (T) in a polarizing film exceeds 7.0 mass %, since an iodine-type pigment|dye is adsorb|sucked excessively in a polarizing film, polarization|polarized-light performance falls. Moreover, it becomes easy to generate|occur|produce the fracture|rupture of a PVA film in the drying process or extending process mentioned later, and productivity of a polarizing film falls. It is preferable that all boron element content (T) in a polarizing film is 6.5 mass % or less, It is more preferable that it is 5.5 mass % or less, It is still more preferable that it is 5.0 mass % or less, It is especially preferable that it is 4.8 mass % or less. Total boron element content (T) in a polarizing film can be calculated|required by ICP emission analysis etc. Specifically, it can be obtained by the method described in Examples.

Ratio (b _t /T) of boron element content (b _t ) (mass %) derived from a boron-containing compound (B) with respect to all boron element content (T) (mass %) in the said polarizing film needs to be 0.10-0.30 there is When ratio (b _t /T) is less than 0.10, among all the crosslinking points of PVA in a polarizing film, since the ratio of the crosslinking point derived from a boron-containing compound (B) is too low, polarization performance by a boron-containing compound (B) The improvement effect becomes insufficient. 0.12 or more is preferable and, as for ratio (bt/ _T ), 0.15 or more is more preferable. On the other hand, when the ratio (b _t /T) exceeds 0.30, among all the cross-linking points of PVA in the polarizing film, the ratio of the cross-linking points derived from the boron-containing compound (B) is too high. A polarizing film with a high transmittance|permeability may not be obtained by high polarization performance. The ratio (b _t /T) is preferably 0.27 or less, more preferably 0.25 or less, still more preferably 0.23 or less, and particularly preferably 0.18 or less.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which showed the cross section of the thickness direction of the polarizing film of this invention. The said polarizing film is further demonstrated using FIG. From the at least one surface 1 of the said polarizing film inward, the range to 7.5% with respect to the total thickness t _t (the surface part 2, the thickness t _o of the surface part 2, and the total thickness t _t of the polarizing film) satisfies "t _o = t _t x 0.075"), the boron element concentration ( _bo ) derived from the boron-containing compound (B) needs to be 2.2 to 10.0 atomic%. When (b _o ) is less than 2.2 atomic %, the elution inhibitory effect of the boric acid by the boron-containing compound (B) in the polarizing film surface becomes insufficient, and since the polarization performance improvement effect becomes small, polarized light with high transmittance|permeability with high polarization performance No film is obtained. It is preferable that it is 2.4 atomic% or more, and, as for (b _o ), it is more preferable that it is 2.8 atomic% or more. On the other hand, when ( _bo ) exceeds 10.0 atomic%, there is no problem with respect to polarization|polarized-light performance, but productivity of a polarizing film falls because deposits of a boron-containing compound (B) generate|occur|produce on the polarizing film surface. (b _o ) is preferably 8 atomic % or less, more preferably 6 atomic % or less, still more preferably 5 atomic % or less, and particularly preferably 4 atomic % or less. It is preferable that the boron element concentration ( _bo ) derived from the boron-containing compound (B) in the surface parts (2) of both sides of the said polarizing film is the said range.

The boron element concentration (b _o ) can be calculated|required using the X-ray photoelectron spectroscopy with a gas cluster ion beam gun (GCIB XPS). By repeating an etching and a measurement using GCIB XPS, the boron element density|concentration derived from a boron-containing compound (B) is measured at regular intervals inward from the surface of a polarizing film. And let the average value of the boron element concentration derived from the boron-containing compound (B) in the said range (surface part 2) be boron element concentration ( _bo ). Specifically, it can obtain|require by the method described in the Example mentioned later. The boron element concentrations (b _i ), (c _o ), and (c _i ), which will be described later, are also obtained by the same method as (b _o ).

From the center (3) of the polarizing film to the outside, the range up to 7.5% of the total thickness t _t (the thickness t _i of the central portion 4 and the central portion 4 and the total thickness t _t of the polarizing film is “t _i = t _t × 0.15”), the boron element concentration ( _bi ) derived from the boron-containing compound (B) is preferably 0.5 to 2.0 atomic%. Moreover, it is also preferable that the boron element concentration (ci) derived from boric acid (C) in the said range (central part 4) is _3.5-8.0 atomic%. Moreover, in the said range (central part 4), it is more preferable that (bi) is 0.5-2.0 atomic%, and ( _ci ) is _3.5-8.0 atomic%.

When the boron element concentration ( _bi ) derived from the boron-containing compound (B) in the above range (central part (4)) exceeds 2.0 atomic%, the boron-containing compound (B) present inside the polarizing film is excessive Therefore, the formation of the iodine-based dye may be inhibited, which is not preferable. (b _i ) is more preferably 1.8 atomic % or less, further preferably 1.5 atomic % or less, and particularly preferably 1.3 atomic % or less. On the other hand, when ( _bi ) is less than 0.5 atomic%, the boron-containing compound (B) inside a polarizing film runs short, and the polarization|polarized-light performance improvement effect may become inadequate. (b _i ) is more preferably 0.8 atomic % or more, and still more preferably 0.9 atomic % or more.

When the boron element concentration ( _ci ) derived from boric acid (C) in the above range (central part (4)) exceeds 8.0 atomic%, adsorption of the boron-containing compound (B) to the inside of the polarizing film is inhibited It is not preferable because (c _i ) is more preferably 7.0 atomic % or less, and still more preferably 6.0 atomic % or less. On the other hand, when ( _ci ) is less than 3.5 atomic%, there exists a possibility that the number of crosslinking points becomes inadequate, PVA is not maintained in the orientated state, and there exists a possibility that the polarizing film which is high polarization performance may not be obtained. (c _i ) is more preferably 4.0 atomic % or more, still more preferably 4.5 atomic % or more, and particularly preferably 5.0 atomic % or more.

The ratio (b _i /c ) of the elemental boron concentration (b _i ) derived from the boron-containing compound (B) to the boron element concentration (c _i ) derived from boric acid (C) in the above range (central part (4)) It is preferable that _i ) is 0.01-0.25. Since the ratio of the boron-containing compound (B) to the boric acid (C) inside the polarizing film is low when the ratio (b _i /c _i ) is less than 0.01, the polarization performance is improved by the addition of the boron-containing compound (B) There is a possibility that the effect may be insufficient. The ratio (b _i /c _i ) is more preferably 0.08 or more, still more preferably 0.10 or more, particularly preferably 0.12 or more, and most preferably 0.15 or more. On the other hand, when ratio (b _i /c _i ) exceeds 0.25, since formation of an iodine-type pigment|dye is inhibited, it is unpreferable. The ratio (b _i /c _i ) is more preferably 0.20 or less.

The boron element concentration (co) derived from _boric acid (C) in the range (surface part (2)) to 7.5% with respect to the total thickness t _t inside from the at least one surface (1) of the said polarizing film is preferably 3.3 to 7.8 atomic%. When (c _o ) is less than 3.3 atomic%, boric acid is eluting excessively from the said polarizing film in many cases. When boric acid elutes excessively, the polarizing film which is high polarization performance may not be obtained. (c _o ) is more preferably 4.0 atomic % or more, and still more preferably 4.5 atomic % or more. On the other hand, when ( _co ) exceeds 7.8 atomic%, there exists a possibility that a flaw may become easy to produce in the surface 1 of a polarizing film, and there exists a possibility that adsorption|suction of the boron-containing compound (B) with respect to a PVA film may be inhibited. . (c _o ) is more preferably 7.0 atomic % or less, still more preferably 6.5 atomic % or less, particularly preferably 5.5 atomic % or less, and most preferably 4.8 atomic % or less. It is more preferable that the boron element concentration (co) derived from _boric acid (C) in the surface parts 2 of both sides of the said polarizing film is the said range.

The boron element concentration (b) derived from the boron-containing compound (B) in the range (surface part (2)) up to 7.5% with respect to the total thickness t _t inward from the at least one surface (1) of the said polarizing film _o ) is the boron element concentration (b) derived from the boron-containing compound (B) in the range from the center (3) to the outside of the polarizing film to 7.5% of the total thickness t _t (the center portion (4)) _i ) is preferably higher. When the ratio (b _o /b _i ) of (b _o ) to (b _i ) is 1 or less, the effect of inhibiting the elution of boric acid by the boron-containing compound (B) on the surface of the polarizing film becomes insufficient, and the effect of improving the polarization performance becomes small, there is a fear that a polarizing film having high transmittance with high polarization performance may not be obtained, and since the boron-containing compound (B) present inside the polarizing film becomes excessive, there is a fear that the formation of an iodine-based dye may be inhibited. . The ratio (b _o /b _i ) of (b _o ) to (b _i ) is more preferably 1.1 or more, still more preferably 1.5 or more, particularly preferably 2.0 or more, and most preferably 2.5 or more. On the other hand, 8.0 or less is preferable and, as for ratio (b _o /b _i ), 7.0 or less are more preferable. From the viewpoint of obtaining a polarizing film having very high polarization performance and transmittance, or the productivity of the polarizing film is further improved, the ratio (b _o /b _i ) is preferably 6.0 or less, more preferably 5.0 or less, and further more preferably 4.5 or less. It is preferable, and 4.0 or less is especially preferable. The boron element concentration (bo) derived from the boron-containing compound (B) in the surface portions (2) on both sides of the polarizing film is the boron element concentration (B _o ) derived from the boron-containing compound (B) in the central portion (4) It is more preferable that it is higher than (b _i ).

The boron element concentration (co) derived from _boric acid (C) in the range (surface part (2)) to 7.5% with respect to the total thickness t _t inside from the at least one surface (1) of the said polarizing film is preferably lower than the boron element concentration ( _ci ) derived from boric acid (C) in the range (central part (4)) of up to 7.5% with respect to the total thickness t _t from the center of the said polarizing film to the outside . When the ratio (c _o /c _i ) of (c _o ) to (c _i ) is 1 or more, scratches are likely to occur on the surface (1) of the polarizing film, or adsorption of the boron-containing compound (B) to the PVA film This inhibits or the number of crosslinking points becomes insufficient, and there exists a possibility that the polarizing film which is high polarization performance may not be obtained, without being maintained in the state which PVA orientated. The ratio (c _o / _{ci ) to (c i ) is} more preferably 0.99 or less, still more preferably 0.95 or less, particularly preferably 0.90 or less, and most preferably 0.85 or less. On the other hand, from the viewpoint of obtaining a polarizing film with higher polarization performance or adsorption of the boron-containing compound (B) to the inside of the polarizing film more easily, the ratio ( _co /c _i ) is preferably 0.5 or more. The boron element concentration (c _o ) derived from boric acid (C) in the surface parts (2) of both sides of the said polarizing film is the boron element concentration (c _i ) derived from boric acid (C) in the center part (4) A lower one is more preferable.

As for the thickness of the said polarizing film, 5-60 micrometers is preferable. When the said thickness is less than 5 micrometers, it becomes easy to generate|occur|produce a drawing break at the time of manufacture, and there exists a possibility that productivity may fall. As for the said thickness, 10 micrometers or more are more preferable. On the other hand, when the said thickness exceeds 60 micrometers, there exists a possibility that the performance calculated|required of a polarizing plate, such as thin film reduction and weight reduction, may not be satisfied. For this reason, 45 micrometers or less are more preferable, as for the said thickness, 30 micrometers or less are still more preferable, and 25 micrometers or less are especially preferable.

<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 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(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 the water resistance of the 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) which can be converted into a vinyl alcohol unit (-CH ₂ -CH(OH)-) by saponification which PVA has, and a vinyl 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 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, and the like. 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) acrylate n-propyl, (meth) acrylate i-propyl, (meth) acrylate n-butyl, (meth) acrylate i-butyl, (meth) acrylate 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-vinylamides, 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 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 more preferably 2 mol% or less, with respect to the number of moles of all the structural units constituting the PVA (A). % or less is more preferable.

Ethylene is preferable as a monomer copolymerizable with the vinyl ester monomer in that stretchability is improved, it can be stretched at a higher temperature, and the occurrence of troubles such as stretching break is reduced and the productivity of the polarizing film is further improved. . 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 viewpoints, 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 the said PVA (A). A polyhydric alcohol is mentioned as a preferable plasticizer, ethylene glycol, glycerol, propylene glycol, diethylene glycol, diglycerol, triethylene glycol, tetraethylene glycol, trimethylol propane etc. are mentioned as a specific example. Moreover, 1 type(s) or 2 or more types of these plasticizers may 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 production of the polarizing film of the present invention, further fillers, processing stabilizers such as copper compounds, weathering stabilizers, colorants, ultraviolet absorbers, light stabilizers, antioxidants, antistatic agents, flame retardants, other thermoplastic resins, lubricants, Additives other than PVA (A) and plasticizers, such as a fragrance|flavor, an antifoaming agent, 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 suitably 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 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.

<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, the tendency which drawing nonuniformity becomes easy to generate|occur|produce at the time of the uniaxial stretching process for manufacturing a polarizing film, and since the polarizing film obtained becomes thick, thin and small devices, such as a smart phone and a notebook computer It tends to be difficult to use for

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 which the large-screen-ization of a liquid crystal television and 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 tends to be 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|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 with 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, one or two or more of the above plasticizers, other additives, and surfactants to be described later are dissolved in a liquid medium, PVA (A), And it can be manufactured using the film forming undiluted|stock solution in which PVA (A) is melt|dissolved and contains 1 type or 2 or more types of a plasticizer, another additive, surfactant, a liquid medium, etc. further as needed. 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 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, trimethylolpropane, 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 viewpoints of the load on the environment and the recoverability.

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 during preparation of the film forming undiluted solution are smoothly performed, and the production 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 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 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; Polyoxyethylene lauryl ether sulfate, sodium alkyl sulfate, potassium alkyl sulfate, ammonium alkyl sulfate, triethanolamine alkyl sulfate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxypropylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, octyl sulfate, etc. of sulfuric acid ester; Sodium alkylsulfonate, potassium alkylsulfonate, ammonium alkylsulfonate, triethanolamine alkylsulfonate, sodium alkylbenzenesulfonate, disodium dodecyldiphenyletherdisulfonate, sodium alkylnaphthalenesulfonate, disodium alkylsulfosuccinate, disodium polyoxyethylenealkylsulfosuccinate , sulfonic acid types such as dodecylbenzenesulfonate; Sodium alkyl phosphate, potassium alkyl phosphate, ammonium alkyl phosphate, triethanolamine alkyl phosphate, sodium polyoxyethylene alkyl ether phosphate, sodium polyoxypropylene alkyl ether phosphate, sodium polyoxyethylene alkyl phenyl ether phosphate, etc. Phosphoric acid ester type 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, with respect to 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 parts. 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, it can suppress that surfactant bleeds out on the surface of a PVA film, blocking occurs, and handleability falls.

As a film forming method at the time of forming a PVA film into a film using said 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 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 volatile component from one side of the film discharged or cast uniformly on the peripheral surface of a rotating heated roll (or belt) or cast on the peripheral surface of this first roll (or belt), located on the is evaporated to dryness, and then further dried on the circumferential 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, followed by further drying by a winding device The winding-up method can be suitably employ|adopted industrially. You may perform drying by a 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 preferable manufacturing method is the manufacturing method of a polarizing film including the dyeing process which dyes a PVA film with a dichroic dye, and the extending|stretching process which uniaxially stretches the film. WHEREIN: The film is immersed in the aqueous solution containing a boric acid crosslinking agent. After carrying out, it is the manufacturing method of the polarizing film which has a process immersed in the aqueous solution containing a boron-containing compound (B). In addition to the said dyeing process and an extending|stretching process, you may perform a swelling process, a boric-acid crosslinking process, a fixing process, a washing process, a drying process, heat processing, etc. further with respect to a PVA film as needed. The order of each treatment is not particularly limited, and one or two or more treatments may be performed simultaneously. In addition, one or two or more of each treatment may 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, 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. You may perform a dyeing|staining process at any stage after an extending|stretching process before an extending|stretching process, at the time of an extending|stretching process. It is common to perform a dyeing process by immersing a PVA film in the solution (especially aqueous solution) containing iodine-potassium iodide as a dyeing bath, or the solution (especially aqueous solution) containing several dichroic dyes. 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, a dyeing aid may be used as needed, and inorganic salts, such as sodium sulfate, surfactant, etc. may be used. When using sodium sulfate, 0.1-10 mass % is preferable. As for the dyeing|staining temperature, 30-80 degreeC is preferable. As a specific dichroic dye, C. Child. Direct Yellow 28, Mr. Child. Direct Orange 39, Mr. Child. Direct Yellow 12, Mr. Child. Direct Yellow 44, Mr. Child. Direct Orange 26, Mr. Child. Direct Orange 71, Mr. Child. Direct Orange 107, Mr. Child. Direct Red 2, Mr. Child. Direct Red 31, Mr. Child. Direct Red 79, Mr. Child. Direct Red 81, Mr. Child. Direct Red 247, Mr. Child. Direct Green 80, Mr. Child. Direct Green 59 etc. are mentioned, The dichroic dye developed for manufacture of a polarizing plate is preferable.

A boric acid crosslinking process can be performed by immersing a PVA film in the aqueous solution containing a boric acid crosslinking agent. By performing a boric acid crosslinking process with respect to a PVA film, a PVA molecular chain 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. As said boric acid crosslinking agent, 1 type, or 2 or more types of boron containing inorganic compounds, such as borate salts, such as boric acid and borax, can be used, From the point of easy handling, it is preferable that boric acid crosslinking agent is 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 at the point which can maintain sufficient stretchability, it is more preferable that it is 2-7 mass %. When the density|concentration of a boric-acid crosslinking agent exceeds 10 mass %, bridge|crosslinking may advance excessively, and there exists a possibility that ductility may fall. Moreover, when the density|concentration of a boric-acid crosslinking agent is less than 1 mass %, the orientation of the dichroic dye adsorbed to the PVA film does not fully improve, but there exists a possibility that the polarization|polarized-light performance of the polarizing film obtained may not fully improve. The aqueous solution containing a boric acid crosslinking agent may contain adjuvants, such as potassium iodide. The concentration of the boron-containing compound (B) in the aqueous solution containing the boric acid crosslinking agent is preferably 2.0 mass% or less, more preferably 0.5 mass% or less, still more preferably 0.1 mass%, and the aqueous solution contains the boron-containing compound (B) It is particularly preferred that it is substantially free of Moreover, in the aqueous solution containing a boric acid crosslinking agent, the ratio of the concentration (mass %) of the boron-containing compound (B) to the concentration (mass %) of the boric acid crosslinking agent [boron-containing compound (B)/boric acid crosslinking agent] is 1 Less than is preferable, 0.5 or less is more preferable, 0.25 or less is still more preferable, 0.1 or less is especially preferable. From the point which can crosslink boric acid efficiently, 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.

In the manufacturing method of this invention, although immersion with respect to the aqueous solution containing a boric-acid crosslinking agent of a PVA film may be performed in any process, it is preferable to perform in a boric-acid crosslinking process. Moreover, you may perform immersion with respect to the aqueous solution containing the boric-acid crosslinking agent of a PVA film in a some process.

Separately from the extending|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 of the pre-stretching performed before the extending|stretching process (the magnification which multiplied the draw ratio in each 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 are more preferable, and 2.5 times or more are 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 boron crosslinking process, 1.1-2.5 times are preferable.

You may perform an extending|stretching process by either a wet extending|stretching method or a dry extending|stretching method. In the case of the wet stretching method, stretching is performed in an aqueous solution. It can also be extended|stretched in the said dyeing bath, a boric acid aqueous solution, etc. Moreover, in the case of the dry extending|stretching method, the extending|stretching process may be performed at room temperature, the extending|stretching process may be performed while heating, and the extending|stretching process can also be performed in air using the PVA film after water absorption. Among these, the wet extending|stretching method is preferable, and it is more preferable to perform an extending|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 an extending|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 70 degrees C or less is still more preferable. Moreover, as a draw ratio in an extending|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 from the point of the optical performance of the polarizing film obtained, 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 . 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 uniaxial stretching in the case of applying a stretching treatment to a long PVA film, and uniaxial stretching in the long direction, uniaxial stretching in the transverse direction, so-called oblique stretching can be adopted, but the optical performance is poor. From the viewpoint of obtaining an excellent polarizing film, uniaxial stretching in a long direction is preferable. Uniaxial stretching 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, transverse uniaxial stretching can be performed using a tenter type stretching machine.

In manufacturing 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 an extending|stretching process. As a fixed treatment bath used for a fixed treatment, Preferably, the aqueous solution containing a boron-containing compound (B) is used. Moreover, you may further add boric acid, an iodine compound, a metal compound, etc. into a fixed treatment bath as needed. It is preferable that the temperature of a fixed treatment bath is 35 degreeC - 80 degreeC. On the other hand, when the temperature of a fixed process bath exceeds 80 degreeC, a polarizing film may melt|dissolve in a fixed process bath, or wrinkles may arise in a polarizing film, and polarization|polarized-light performance may fall. As for the said temperature, 75 degrees C or less is more preferable, and 70 degrees C or less is still more preferable. 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.

If it is after immersing a PVA film in the aqueous solution containing a boric acid crosslinking agent, you may make a PVA film adsorb|suck a boron-containing compound (B) in any process of a dyeing process, an extending|stretching process, and a fixed process. From the viewpoints that unnecessary iodine-based dyes are efficiently removed and the PVA film is suppressed from being cut during the stretching treatment, the fixing treatment after the stretching treatment WHEREIN: It is preferable to make the PVA film adsorb|suck the boron-containing compound (B). A boron-containing compound (B) may be used individually by 1 type, or may be used in mixture of 2 or more types. The concentration of the boron-containing compound (B) in the aqueous solution used for adsorption of the boron-containing compound (B) is 1.5 to It needs to be 5.0 mass %. When the said density|concentration is lower than 1.5 mass %, adsorption|suction with respect to the surface part of a PVA film of a boron-containing compound (B) becomes slow. It is preferable that it is 2.0 mass % or more, and, as for the said density|concentration, it is more preferable that it is 2.5 mass % or more. On the other hand, when the said density|concentration is higher than 5.0 mass %, a boron-containing compound (B) adsorb|sucks excessively to the surface part of a PVA film, and it becomes difficult to advance the substitution reaction of a boron-containing compound (B) and boric acid (C). Moreover, there exists a possibility that the precipitate of a boron-containing compound (B) may generate|occur|produce in the surface part of the polarizing film obtained, and optical performance may fall. For this reason, it is preferable that it is 4.5 mass % or less, and, as for the density|concentration of a boron containing compound (B), it is more preferable that it is 4.0 mass % or less. The concentration of the boric acid crosslinking agent in the aqueous solution containing the boron-containing compound (B) is preferably 1.5 mass% or less, more preferably 1.0 mass% or less, still more preferably 0.5 mass% or less, and particularly preferably 0.1 mass% or less. Preferably, the aqueous solution is most preferably substantially free of the boric acid crosslinking agent. Further, in the aqueous solution containing the boron-containing compound (B), the ratio of the concentration (mass%) of the boric acid crosslinking agent to the concentration (mass%) of the boron-containing compound (B) [boronic acid crosslinking agent/boron-containing compound (B) )] is preferably less than 1, more preferably 0.5 or less, still more preferably 0.25 or less, and particularly preferably 0.1 or less.

Moreover, it is preferable that the said aqueous solution containing a boron-containing compound (B) contains the auxiliary agent of iodide, such as potassium iodide, from the point of optical performance improvement, and, as for the density|concentration of the said iodide, 0.5-15 mass % is preferable. Moreover, it is also preferable that the temperature of the said aqueous solution containing a boron-containing compound (B) is 35-80 degreeC. When the said temperature is less than 35 degreeC, the substitution rate of a boron-containing compound (B) and a boric acid (C) becomes slow, and there exists a possibility that the polarization|polarized-light performance improvement effect may become inadequate. It is more preferable that the said temperature is 40 degreeC or more, and it is still more preferable that it is 45 degreeC or more. On the other hand, when the said temperature is too high, a PVA film may melt|dissolve in the said aqueous solution, or wrinkles may arise in the polarizing film obtained, and there exists a possibility that polarization|polarized-light performance may fall. For this reason, as for the said temperature, 75 degrees C or less is more preferable, and 70 degrees C or less is still more preferable. As for the time to immerse a PVA film in the said aqueous solution, 5-400 second is preferable. As for the said time, 10 second or more is more preferable, 15 second or more is still more preferable, and 20 second or more is especially preferable. On the other hand, as for the said time, 350 second or less is more preferable, 250 second or less is still more preferable, 150 second or less is especially preferable, and 70 second or less is the most preferable.

As a method for adsorbing the boron-containing compound (B) to the PVA film, (1) a method of immersing the PVA film in an aqueous solution containing the boron-containing compound (B) alone without bonding a base film or the like, (2) fixing After bonding a base film to one side of a PVA film so that generation|occurrence|production of the wrinkles in a process can be reduced, the method of immersing the obtained laminated body in the said aqueous solution, (3) the aqueous solution containing a boron-containing compound (B) is polarized The method of spraying on the film surface, (4) the method of apply|coating the said aqueous solution to the PVA film surface using the roll in which the said aqueous solution was coated, etc. are mentioned, Especially, (1) is preferable. According to the method of (1), since adsorption|suction of the boron-containing compound (B) to the center of a PVA film advances similarly from both sides, it is preferable.

As a method of manufacturing the polarizing film of this invention by adsorbing a boron-containing compound (B) to a PVA film in a fixing process, the method of performing a swelling process, an extending|stretching process, and a fixed process in this order, and a swelling process, boric acid bridge|crosslinking The method of performing a process, an extending|stretching process, and a fixing process in this order is preferable, and the latter is more preferable. After performing these processes, you may perform at least 1 process selected from the group which consists of a washing process, a drying process, and heat processing further as needed. After adsorbing a boron-containing compound (B) to a PVA film, it is preferable not to immerse the said PVA film in the aqueous solution containing a boric-acid crosslinking agent.

The washing process is generally performed by immersing the 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, 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 generally 5-50 degreeC, 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 said range.

By heat-processing after a drying process, the polarizing film further excellent in dimensional stability can be obtained. Here, heat processing heats the polarizing film whose moisture content after a drying process is 5 % or less, 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.

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|luminance 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 48% 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. It is more preferable that the said polarization degree is 99.9 % or more. The transmittance and the degree of polarization of the polarizing film are measured by the method described in Examples to be described later.

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 described with reference to the following examples, but the present invention is not limited by these examples at all. In addition, each evaluation method employ|adopted in the following Example and a comparative example is shown below.

<Calculation of total boron element content (T), etc. in a polarizing film>

The mass [A(g)] of the polarizing film controlled at 23 degreeC and 50%RH for 16 hours was measured, and it melt|dissolved in 20 mL of distilled water so that a polarizing film might be set to 0.005 mass %. The aqueous solution which melt|dissolved the polarizing film was made into the measurement sample, and the mass [B(g)] was measured. The boron concentration [C (ppm)], the potassium concentration [D (ppm)], and the iodine concentration [E (ppm)] of the measurement sample were measured using the Shimadzu Corporation multi-type ICP emission spectrometer (ICP). Then, total boron element content (mass %) in a polarizing film, all potassium element content (mass %), all iodine for the value which substituted and computed the value measured to following formula (1), (2), (3) It was set as elemental content (mass %).

Total boron element content in polarizing film (T, mass %)

= [(C × 10 ^-6 × B)/A] × 100 (1)

Total potassium element content in polarizing film (F, mass %)

= [(D × 10 ^-6 × B)/A] × 100 (2)

Total iodine element content in polarizing film (G, mass %)

= [(E × 10 ^-6 × B)/A] × 100 (3)

<Calculation of moisture content (H, mass %) in polarizing film>

About 0.1 g of the polarizing film whose humidity was controlled at 23 degreeC and 50 %RH for 16 hours was cut out, and the mass [X(g)] was measured. After drying the said polarizing film in a dryer at 105 degreeC for 16 hours, the mass [Y(g)] of the said polarizing film was measured. The obtained value was substituted for following formula (4), and the moisture content in a polarizing film was computed.

Moisture content in polarizing film (H, mass %)

= (X - Y)/X × 100 (4)

<Measurement of boron element content (b _t ) derived from boron-containing compound (B) in polarizing film>

After melt|dissolving a polarizing film so that it might be set to 0.003 mass % in heavy water, the solution which concentrated so that it might be set to 0.15 mass % with a rotary evaporator was made into the measurement sample ^of 1H-NMR. 1H ^- NMR (JNM-AL400 by JEOL Corporation: 400 MHz) measurement was implemented at 80 degreeC, and the number of times of integration was set to 256. It analyzed by the following method using ALICE2 (made by Nippon Electronics Co., Ltd.). With respect to the ¹ H-NMR chart obtained by the measurement, after adjusting the phase so that the baseline was smooth, the average point was set to 20, and the baseline was automatically corrected. Next, it was automatically set as a reference so that the peak of heavy water which is a measurement solvent might become the position of 4.65 ppm. Thereafter, as in FIG. 2 , the hydrogen peak of the hydrocarbon group contained in the boron-containing compound (B) was integrated, and the peak area (area I) was determined. At this time, the sum (area J) of the hydrogen peak derived from PVA and the hydrogen peak area of the hydrocarbon group contained in the boron-containing compound (B) that does not overlap is taken as a reference of the peak area, and of the boron-containing compound (B) It was set so that the number of hydrogens of the corresponding hydrocarbon group and the value of the area J became the same. Next, the hydrogen peak in the range of 1.6 to 2.4 ppm is the sum of the hydrogen peak derived from the methylene group of PVA and the hydrogen peak of the hydrocarbon group contained in the boron-containing compound (B) overlapping the hydrogen peak derived from the methylene group of PVA , and the peak area (area K) was obtained. Then, the area L 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 K was calculated. The value calculated|required by these methods was substituted into following formula (5), and content (M, mass part) of the organic group derived from the boron-containing compound (B) with respect to 100 mass parts of PVA (A) was computed. Moreover, the boron content (N, mass part) derived from the boron-containing compound (B) with respect to 100 mass parts of PVA(A) was calculated|required by substituting a value into following formula (6). In the following formulas (5) and (6), O is the number of hydrogens in the hydrocarbon group contained in the boron-containing compound (B) that does not overlap the peak of PVA, and P is the number of borons per molecule of the boron-containing compound (B) , Q are food for the organic group of the boron-containing compound (B). Then, each value computed in Formula (7) was substituted, and boron element content (b _t , mass %) derived from the boron-containing compound (B) in a polarizing film was computed. In addition, formulas (5), (6), (7) are formulas used when PVA which is not modified|denatured is used, When using modified|denatured PVA as a raw material, Formula (5), (6), (7) needs to be modified appropriately.

Content of organic group derived from boron-containing compound (B) with respect to 100 parts by mass of PVA (A) (M, parts by mass)

=｛(Area J/O)/(Area L/2) ｝× (Q/44.0526) × 100 (5)

Content of elemental boron derived from boron-containing compound (B) with respect to 100 parts by mass of PVA (A) (N, parts by mass)

=｛(Area J/O)/(Area L/2) ｝× (10.811 × P/44.0526) × 100 (6)

Boron element content (b _t , mass %) derived from the boron-containing compound (B) in a polarizing film

= N × 1/(100 + M) × (100 - T - F - G - H) (7)

In the formula, 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. In addition, the < ¹ >H-NMR chart of FIG. 2 was obtained by measuring the polarizing film of Example 1. FIG.

<Calculation of elemental boron concentration (b _o ), elemental boron concentration (b _i ), elemental boron concentration (c _o ), and elemental boron concentration (c _i )>

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). The polarizing film which the humidity was controlled at about 23 degreeC and 40 %RH for 16 hours or more was used for the measurement. 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. XPS measurement is performed using monochromatic Al 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 analysis software "MultiPak" (manufactured by ULVAC PAI Co., Ltd.), based on 284.8 eV, which is the binding energy of C-C and C-H bonds, the concentration of boron element at each depth of the polarizing film (a, atomic %) was calculated. Thereafter, for the XPS spectrum at each depth, the binding energy due to boron in boric acid (C) and the binding energy due to boron in the boron-containing compound (B) are appropriately set, and table calculation software "Microsoft 2010" (manufactured by Microsoft Corporation), the peak separation was performed by the least squares method using a pseudo Forkt function. In addition, the linear function calculated from the average value of the intensity of the XPS spectrum at 187 to 189 eV and the average value of the XPS spectrum at 195 to 197 was used as the baseline. In this way, the ratio of the peak area of the boron derived from the boron-containing compound (B) to the sum of the peak area of the boron derived from boric acid (C) and the peak area of the boron derived from the boron-containing compound (B) (b, %) By calculating and substituting into the following formula (8), the boron element concentration derived from the boron-containing compound (B) at each depth and the boron element concentration derived from the boric acid (C) at each depth were calculated.

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

= a × b × 10 ^-2 (8)

Concentration of elemental boron derived from boric acid (C) (atomic %)

= a × (100 - b) × 10 ^-2 (9)

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 Laurent water content of boric acid was set to 0.241, and 2 ^1/2 x σ was set to 0.916. In addition, the Laurent water content and full width at half maximum of the boron-containing compound (B) also change depending on the structure of the compound. Accordingly, it is necessary to appropriately set the Laurent 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 Laurent 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 (atomic%) derived from the boron-containing compound (B) in each depth from one surface to the center of a polarizing film, and boron element concentration (atomic%) derived from a boric acid (C) were calculated respectively. It measures 14 times in total, setting an etching range so that an etching rate may be set to about 16-26 nm/min specifically, and etching from one surface of a polarizing film to the center of a polarizing film, in each measurement time, that is, The boron element concentration (atomic%) derived from the boron-containing compound (B) in each depth and the boron element concentration (atomic%) derived from boric acid (C) were computed, respectively. And the same measurement is performed also from the other surface of a polarizing film, and the boron element concentration (atomic%) derived from the boron-containing compound (B) in each depth, and boron element concentration (atomic%) derived from a boric acid (C) (atomic%) ) were calculated respectively. Then, the average value of the boron element concentration derived from the boron-containing compound (B) calculated in the range of up to 7.5% of the total thickness from the surface of the polarizing film to the boron element concentration derived from the boron-containing compound (B) ( b _o , atomic %), and the average value of the boron element concentration (atomic %) derived from boric acid (C) calculated in the said range was made into boron element concentration (co _o , atomic %) derived from boric acid (C).

Moreover, the average value of the boron element concentration derived from the boron-containing compound (B) calculated in the range to 7.5% of the total thickness from the center of the polarizing film to the outside, the boron element concentration (b) derived from the boron-containing compound (B) _i , atomic %), and the average value of the boron element concentration derived from boric acid (C) calculated in the said range was made into boron element concentration ( _ci , atomic %) derived from boric acid (C). In addition, in order to reduce an error, the average concentration (c _o ) and (b _o ) were calculated by excluding the measured value of the outermost surface not subjected to sputtering.

<Optical performance of polarizing film>

A rectangular sample of 4 cm x 2 cm in the longitudinal direction of the polarizing film was taken from the central portion in the width direction and the longitudinal direction of the polarizing film, and a spectrophotometer with an integrating sphere V-7100 (manufactured by Nippon Spectroscopy Co., Ltd.) and a Glan Taylor polarizer The parallel transmittance and cross Nicol transmittance|permeability of a polarizing film were measured using the automatic polarizing film measuring apparatus VAP-7070S (made by Nippon Spectroscopy Co., Ltd.) provided with this. Here, the measurement wavelength range is set to 380 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 axis of the polarizing film. The case perpendicular to the cross nicol transmittance was defined as. 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 of the polarizing film 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.

<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 mass [R(g)] of the PVA film after immersion was measured. Then, after drying a PVA film in a dryer at 105 degreeC for 16 hours, the PVA film mass [S(g)] after drying was measured. The degree of swelling of the PVA film was calculated by substituting a value in the following formula (10).

Swelling degree (%) = (R/S) × 100 (10)

[Example 1]

PVA (saponification degree 99.9%, polymerization degree 2400) 100 parts by mass, 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 PVA content of 10% by mass was prepared did. The film obtained by drying the said PVA aqueous solution on the metal roll of 80 degreeC was heat-processed for 10 minutes in a hot air dryer (120 degreeC), 30 micrometers in thickness, and the swelling degree of 200% PVA film was obtained.

From the width direction central 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. Subsequently, it uniaxially stretched 2.2 times (total 2.4 times) in the longitudinal direction while 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, and made iodine adsorb|suck. Then, it uniaxially stretched in the longitudinal direction at 1.2 times (2.7 times in total), immersing in the 30 degreeC aqueous solution (boric acid crosslinking process bath) containing 3.0 mass % and potassium iodide in the ratio of 3 mass % of boric acid then. 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 % and potassium iodide in the ratio of 6 mass % boric acid. After the stretching treatment, the boron-containing compound (B) was immersed in a 50°C aqueous solution (fixed treatment bath) containing 3.0 mass% of n-propylboronic acid and 3.5 mass% of potassium iodide (fixed treatment bath) for 30 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).

As a result of measuring all boron element content in the obtained polarizing film, total potassium element content, and total iodine element content, they were 4.3 mass %, 1.0 mass %, and 5.0 mass %, respectively. Next, when the moisture content in a polarizing film was computed, it was 10.0 mass %. And as a result of measuring and analyzing ¹ H-NMR of the polarizing film, the hydrogen peak of n-propylboronic acid which does not overlap with the hydrogen peak derived from PVA at 1.1-1.3 ppm appeared, this peak area (area J) 5 was set. Next, the peak area (area K) of hydrogen of the methylene group of PVA in which a peak appears in the range of 1.6-2.4 ppm was computed. Since the hydrogen peak of the methylene group of PVA and the hydrogen peak of the C2 hydrocarbon group of n-propylboronic acid overlapped, the area L is obtained by subtracting the number of hydrogens 2 of the C2 hydrocarbon group of n-propylboronic acid from the area K. saved As a result of substituting these values into said Formula (5), (6), (7), boron element content derived from the boron containing compound (B) in a polarizing film was 0.7 mass %. As a result of measuring and analyzing the XPS spectrum of a polarizing film, the boron element concentration ( _bo ) was 3.1 atomic%, and the boron element concentration (co) derived from _boric acid (C) in the surface part was 4.6 atomic%. Moreover, the boron element density|concentration ( _bi ) derived from the boron-containing compound (B) in the range (central part) to 7.5% with respect to the whole thickness from the center to the outer side of a polarizing film is 1.1 atomic%, and it is 1.1 atomic% in a central part. The boron element concentration ( _ci ) derived from boric acid (C) was 5.7 atomic%.

As a result of evaluating the optical characteristic of a polarizing film by said method, the single transmittance at the time of polarization degree 99.9% was 44.85 %.

[Examples 2 and 3, Comparative Examples 1 to 5]

Except having changed the composition of a fixed process bath, temperature, and immersion time like Table 1, it carried out similarly to Example 1, the polarizing film was produced, and each measurement and evaluation were performed. In Comparative Example 4, in the measurement of ¹ H-NMR, the boron-containing compound (B) could not be detected when the number of integrations was 256 times, so the number of integrations was changed to 4096 times.

[Comparative Example 6]

It is an example of the polarizing film which does not contain a boron containing compound (B). Using the aqueous solution (temperature 30 degreeC) containing potassium iodide in the ratio of 2 mass % as a fixed treatment bath, except having changed the time to be immersed in a fixed treatment bath into 20 seconds, it carried out similarly to Example 1, and a polarizing film produced, and each measurement and evaluation were performed.

[Comparative Example 7]

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

In Examples 2 to 3 and Comparative Examples 1 to 7, in the same manner as in Example 1, an aqueous solution (dyeing bath) containing 100 parts by mass of potassium iodide in a ratio of 100 parts by mass to 1 part by mass of iodine (temperature: 30°C) for 60 seconds The iodine was adsorbed by uniaxial stretching in the longitudinal direction at 2.2 times (2.4 times in total) while immersed. At this time, the iodine density|concentration and potassium iodide density|concentration of a dyeing process bath were adjusted so that the polarization degree of the polarizing film after drying might be set to 99.9 %. Moreover, in any of Examples 1-3 and Comparative Examples 1-7, although each measurement and evaluation were performed about the surface of both sides of a polarizing film, all brought the same result. About the reason which became the same result in the surface of both sides of a polarizing film, it is a fixed process WHEREIN: It is estimated because adsorption|suction of the boron-containing compound (B) to the center from the surface of a PVA film advanced similarly from both sides.

As shown in Table 1, the polarizing film of this invention of Examples 1-3 has high polarization|polarized-light performance, and a single transmittance is also high, and it can respond to the request|requirement of high definition of an electronic device in recent years.

1: surface
2: surface part
3: center
4: central part
5: Hydrogen peak derived from heavy water as a measurement solvent
6: Hydrogen peak derived from the methine group of PVA
7: Hydrogen peak derived from the methylene group of PVA
8: A hydrogen peak derived from a hydrocarbon group contained in the boron-containing compound (B) overlapping with a hydrogen peak derived from PVA
9: 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
t _o , t _i , t _t : thickness

Claims (11)

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, and boric acid ( C) as a polarizing film comprising:
The boron element content (b _t ) derived from the boron-containing compound (B) is 0.3 to 2.0 mass %, the total boron element content (T) is 3.0 to 7.0 mass %, and the ratio of (b _t ) to (T) (b _t /T) is 0.10 to 0.30,
The polarizing film whose boron element density|concentration (bo) derived from a boron-containing compound (B) in the range to 7.5% of the total thickness is _2.2-10.0 atomic% inward from at least one surface.

[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 boron element concentration ( _bi ) derived from the boron-containing compound (B) in the range to 7.5% of the total thickness from the center to the outside of the said polarizing film is 0.5-2.0 atomic%, and a boric acid (C) The polarizing film whose derived boron element concentration ( _ci ) is 3.5-8.0 atomic%. 3. The method according to claim 1 or 2,
The boron element concentration derived from the boron-containing compound (B) with respect to the boron element concentration ( _ci ) derived from boric acid (C) in the range from the center to the outside of the polarizing film to 7.5% of the total thickness ( The polarizing film whose ratio (b _i /c _i ) of b _i ) is 0.01-0.25. 4. The method according to any one of claims 1 to 3,
The polarizing film whose boron element density|concentration (co) derived from boric acid (C) in the range to 7.5% with respect to full thickness is _3.3-7.8 atomic% inward from the at least one surface of the said polarizing film. 5. The method according to any one of claims 1 to 4,
The boron element concentration (b _o ) derived from the boron-containing compound (B) in the range to 7.5% of the total thickness inward from the at least one surface of the polarizing film is from the center of the polarizing film to the outside , A polarizing film higher than the boron element concentration ( _bi ) derived from the boron-containing compound (B) in the range to 7.5% of the total thickness. 6. The method according to any one of claims 1 to 5,
The boron element concentration (co) derived from _boric acid (C) in the range up to 7.5% with respect to the total thickness inward from the at least one surface of the said polarizing film from the center of the said polarizing film to the outside, the whole A polarizing film lower than the boron element concentration ( _ci ) derived from boric acid (C) in the range to 7.5% with respect to thickness. 7. The method according to any one of claims 1 to 6,
The polarizing film in which R< ¹ > is a saturated aliphatic group. 8. The method according to any one of claims 1 to 7,
The polarizing film whose R< ¹ > is a linear aliphatic hydrocarbon group. 9. The method according to any one of claims 1 to 8,
The polarizing film whose carbon number of R< ¹ > is 2-5. 10. The method according to any one of claims 1 to 9,
The polarizing film whose transmittance|permeability in case a polarization degree is 99.9 % or more is 42 % or more. 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,
After immersing the film in the aqueous solution containing a boric-acid crosslinking agent, it has the process of immersing in the 35-80 degreeC aqueous solution containing 1.5-5.0 mass % of a boron-containing compound (B), in Claims 1-10. The manufacturing method of the polarizing film in any one of Claims.

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