WO2015020046A1

WO2015020046A1 - Vinyl-alcohol-based polymer film

Info

Publication number: WO2015020046A1
Application number: PCT/JP2014/070605
Authority: WO
Inventors: 勝啓高藤; 磯▲ざき▼　孝徳
Original assignee: 株式会社クラレ
Priority date: 2013-08-09
Filing date: 2014-08-05
Publication date: 2015-02-12
Also published as: KR20160041922A; TWI639618B; JPWO2015020046A1; JP6420153B2; KR102216810B1; CN105431751A; TW201509957A; CN105431751B

Abstract

　[Problem] To provide a PVA film whereby an optical film having excellent optical characteristics, hue, and durability can easily be manufactured, and to provide a method for manufacturing an optical film using the PVA film. [Solution] A PVA film in which the ratio of the sum of the crystal component amount (ａ₁) and the restricted amorphous component amount (ａ₂) with respect to the sum of the crystal component amount (ａ₁), the restricted amorphous component amount (ａ₂), and the amorphous component amount (ａ₃) is 10-32% when the crystal component amount (ａ₁), the restricted amorphous component amount (ａ₂), and the amorphous component amount (ａ₃) are calculated from the spin-spin relaxation time (T)₂ obtained by pulse NMR measurement (observed nucleus: ¹H) after one hour of treatment at 60°C; and a method for manufacturing an optical film using the PVA film, the method having a uniaxial drawing step.

Description

Vinyl alcohol polymer film

The present invention relates to a vinyl alcohol polymer film useful as a raw film for producing an optical film, and a method for producing an optical film such as a polarizing film using the same.

A polarizing plate having a light transmission and shielding function is a basic component of a liquid crystal display (LCD) together with a liquid crystal that changes a polarization state of light. Many polarizing plates have a structure in which a protective film such as a cellulose triacetate (TAC) film is bonded to the surface of a polarizing film. As a polarizing film, a vinyl alcohol polymer film (hereinafter referred to as “vinyl alcohol-based heavy film”) is used. iodine based dye coalescing "the may be referred to as" PVA ") in a matrix formed by uniaxial stretching (I ₃ ^- and I ₅ ^-, etc.) or a dichroic dye such as dichroic organic dyes which are adsorbed Has become the mainstream.

LCDs have come to be used in a wide range of small devices such as calculators and watches, mobile phones, notebook computers, liquid crystal monitors, liquid crystal color projectors, liquid crystal televisions, in-vehicle navigation systems, and measurement devices used indoors and outdoors. In recent years, there has been a demand for higher display quality. Along with this, high performance is also demanded for polarizing films. Specifically, there is a demand for polarizing films that have high degree of polarization and transparency, excellent optical properties, and excellent hue and durability. ing.

By the way, some raw film films for producing optical films containing PVA with various structures changed are known. For example, a polyvinyl alcohol film for a polarizing film made of a specific PVA containing 0.01 to 1 mol% of a hydrophilic functional group such as a carboxylic acid group or an ω-hydroxy-α-olefin group is stretched and oriented. It is known that the processability and the adsorption processability of the dichroic substance are excellent (see Patent Document 1). In addition, it is known that a specific optical PVA film containing PVA containing a 1,2-glycol bond in the side chain is excellent in optical properties and stretchability (see Patent Document 2). Furthermore, it is known that the dyeing time for producing a polarizing film can be shortened by using a film made of PVA having a saponification degree of 92 to 98.5 mol% (see Patent Document 3).

JP-A-8-201626 JP 2009-24076 A JP 2012-68609 A

However, when a conventionally known PVA film is used, there is room for further improvement in that an optical film having excellent optical properties, hue, and durability is obtained.

Therefore, an object of the present invention is to provide a PVA film capable of easily producing an optical film excellent in any of optical properties, hue and durability, and a method for producing an optical film using the PVA film.

As a result of intensive studies by the present inventors to achieve the above object, the above problem is solved if the total ratio of the amount of crystal components and the amount of constrained amorphous components in the PVA film is within a specific range. The present invention was completed through further studies based on the finding and the findings.

That is, the present invention
[1] From the spin-spin relaxation time T ₂ obtained by performing pulse NMR measurement (observation nucleus: ¹ H) after processing at 60 ° C. for 1 hour, the amount of crystal component (a ₁ ), the amount of constrained amorphous component (a ₂ ) And the amount of amorphous component (a ₃ ), the amount of crystal component (a ₁ ) relative to the sum of the amount of crystal component (a ₁ ), the amount of constrained amorphous component (a ₂ ), and the amount of amorphous component (a ₃ ) (a ₁ ) and a PVA film in which the total proportion of the constrained amorphous component amount (a ₂ ) is 10 to 32%;
[2] crystalline component amount _(a 1), are constrained amorphous component amount _{(a 2)} and amorphous component amount _{(a 3)} restraining amorphous component amount to the sum of _{(a 2)} the proportion of 5% or more The PVA film of [1] above;
[3] The PVA contained in the PVA film is a structural unit (1) represented by the following formula (1), a structural unit (2) represented by the following formula (2), and a structural unit represented by the following formula (3) ( 3) at least one structural unit selected from the group consisting of 3), the content of structural units (1) to (3) is n ₁ to n ₃ mol%, respectively, and the content of vinyl ester units is n ₄ mol% The PVA film according to [1] or [2], which satisfies 0.6 ≦ n ₁ + n ₂ + 2 × n ₃ + n ₄ ≦ 1.4.

[Wherein, R ¹ represents a hydrogen atom, a methyl group or an ethyl group. ]

[Wherein R ² represents a hydrogen atom, a methyl group or an ethyl group, and X ² represents a hydroxyalkyl group having 2 or more carbon atoms having one or more hydroxyl groups. ]

[Wherein, X ³ and X ⁴ each independently represent a hydroxyalkyl group having 1 or more carbon atoms having one or more hydroxyl groups. ]

[4] The PVA film of the above [3], wherein the PVA contained in the PVA film contains at least one structural unit selected from the group consisting of the structural unit (1) and the structural unit (2);
[5] The PVA film according to any one of the above [1] to [4], wherein the PVA contained in the PVA film does not contain the structural unit (3) represented by the following formula (3):

[6] The PVA film according to any one of the above [1] to [5], wherein the polymerization degree of PVA contained in the PVA film is 3,000 or less;
[7] The PVA film of any one of [1] to [6] above, wherein the molecular weight distribution of PVA contained in the PVA film is 2.0 to 4.0;
[8] The PVA film according to any one of the above [1] to [7], having a swelling degree of 160 to 240%;
[9] The PVA film of any one of [1] to [8], which is a raw film for producing an optical film;
[10] The PVA film of the above [9], which is a raw film for producing a polarizing film;
[11] A method for producing an optical film using the PVA film of the above [9] or [10], comprising a step of uniaxial stretching;
About.

According to the present invention, a PVA film capable of easily producing an optical film excellent in any of optical properties, hue and durability, and a method for producing an optical film using the PVA film are provided.

The PVA film of the present invention is processed at 60 ° C. for 1 hour and then subjected to pulsed NMR measurement (observation nucleus: ¹ H). From the spin-spin relaxation time T ₂ obtained, the crystal component amount (a ₁ ), constrained amorphous component When the amount (a ₂ ) and the amount of amorphous component (a ₃ ) are determined, the crystal with respect to the sum of the amount of crystal component (a ₁ ), the amount of restrained amorphous component (a ₂ ) and the amount of amorphous component (a ₃ ) The total proportion of the component amount (a ₁ ) and the constrained amorphous component amount (a ₂ ) is in the range of 10 to 32%.

Unlike high-resolution NMR, which is widely used in determining the structure of organic compounds, pulsed NMR can measure each relaxation time of ¹ H nuclei associated with molecular mobility in the system and its high quantification. This is an analysis method that can determine the existence ratio of each motion component in the system by using the property. In the present invention, the spin-spin relaxation time T ₂ of ¹ H is used to determine the amount of crystal component (a ₁ ), the amount of constrained amorphous component (a ₂ ) and the amount of amorphous component (a ₃ ) in the PVA film. . Specifically, a ₁ is a positive value so that the free induction decay (FID) signal obtained in the measurement of the spin-spin relaxation time T ₂ of ¹ H approximately fits the following equation (4). , A ₂ , a ₃ , a ₄ , c ₁ , c ₂ and c ₃ are determined. The fitting is preferably performed using a linear least square method. Among the obtained values, a ₁ corresponds to the amount of crystalline component (a ₁ ), a ₂ corresponds to the amount of restrained amorphous component (a ₂ ), and a ₃ corresponds to the amount of amorphous component (a It falls under ₃ ). As specific conditions for the pulsed NMR measurement, conditions described later in the examples can be employed.

In performing the pulse NMR measurement, the PVA film to be measured is previously treated at 60 ° C. for 1 hour. By determining the ratio of the amount of crystal component (a ₁ ) and the amount of constrained amorphous component (a ₂ ) after treatment at 60 ° C. for 1 hour, the above-mentioned component ratio more closely related to the effects (durability, etc.) of the present invention Can be requested. The treatment can be performed in a state in which the PVA film to be measured is immersed in water. In particular, since the treated PVA film can be directly used for pulse NMR measurement, the PVA film is overlapped in an NMR tube or the like. It is preferable to carry out in the state immersed in water. As a more specific processing method or condition of the processing, a method described later in the embodiment can be employed.

The PVA film of the present invention is processed at 60 ° C. for 1 hour and then subjected to pulsed NMR measurement (observation nucleus: ¹ H). From the spin-spin relaxation time T ₂ obtained, the crystal component amount (a ₁ ), constrained amorphous component When the amount (a ₂ ) and the amount of amorphous component (a ₃ ) are determined, the crystal with respect to the sum of the amount of crystal component (a ₁ ), the amount of restrained amorphous component (a ₂ ) and the amount of amorphous component (a ₃ ) The ratio of the total amount of the component amount (a ₁ ) and the constrained amorphous component amount (a ₂ ) needs to be in the range of 10 to 32%. If the proportion is less than 10%, the durability of the optical film obtained using the PVA film is deteriorated. On the other hand, when the ratio exceeds 32%, the hue of the optical film obtained using the PVA film is lowered. Although the present invention is not limited in any way, the reason for this is that the influence on the state of the dichroic dye used may be different for each of the above components, and the ratio may be adjusted. It is estimated that it is extremely important in the effect of the present invention. Total of crystal component amount (a ₁ ), constrained amorphous component amount (a ₂ ), and amorphous component amount (a ₃ ) account for the sum of crystal component amount (a ₁ ) and constrained amorphous component amount (a ₂ ) The ratio is preferably 10.5% or more, more preferably 11% or more, and preferably 31.5% or less from the viewpoint of the hue and durability of the obtained optical film. More preferably, it is 31% or less.

Since the durability of the obtained optical film can be further improved, the PVA film preferably has a constrained amorphous component. In particular, the PVA film has a crystal component amount (a ₁ ) and a constrained amorphous component amount (a ₂ ) and the proportion of the constrained amorphous component amount (a ₂ ) to the total of the amorphous component amount (a ₃ ) is preferably 5% or more, and more preferably 6% or more.

There is no particular limitation on the kind of the PVA contained in the PVA film, since the ratio of the crystalline component amount _{(a 1)} and restraining amorphous component amount _{(a 2)} can be obtained easily PVA film satisfying the above range, PVA The PVA contained in the film is composed of a structural unit (1) represented by the following formula (1), a structural unit (2) represented by the following formula (2), and a structural unit (3) represented by the following formula (3). When the content of the structural units (1) to (3) is n ₁ to n ₃ mol% and the vinyl ester unit content is n ₄ mol%, including at least one structural unit selected from the group 0.6 ≦ n ₁ + n ₂ + 2 × n ₃ + n ₄ ≦ 1.4 is preferably satisfied.

[Wherein, R ¹ represents a hydrogen atom, a methyl group or an ethyl group. ]

In the structural unit represented by the formula (1), R ¹ represents a hydrogen atom, a methyl group or an ethyl group. R ¹ is preferably a methyl group or an ethyl group because the PVA film in which the ratio of the amount of crystalline component (a ₁ ) and the amount of constrained amorphous component (a ₂ ) satisfies the above range can be more easily obtained. More preferred is a methyl group.

In the structural unit represented by the formula (2), R ² represents a hydrogen atom, a methyl group or an ethyl group. R ² is preferably a hydrogen atom or a methyl group because a PVA film in which the ratio of the amount of crystal component (a ₁ ) and the amount of constrained amorphous component (a ₂ ) satisfies the above range can be more easily obtained.

In the structural unit represented by the formula (2), X ² represents a hydroxyalkyl group having 2 or more carbon atoms having one or more hydroxyl groups. The number of carbon atoms of the hydroxyalkyl group is 8 or less because it becomes easier to obtain a PVA film in which the proportion of the amount of crystal component (a ₁ ) and the amount of constrained amorphous component (a ₂ ) satisfy the above range. Is preferably 6 or less, more preferably 4 or less, and the number of hydroxyl groups of the hydroxyalkyl group is preferably 1 or 2. Specific examples of the hydroxyalkyl group include, for example, 2-hydroxyethyl group, 3-hydroxypropyl group, 1-hydroxy-1-methylethyl group, 2-hydroxy-1-methylethyl group, 4-hydroxybutyl group, Examples include 2-hydroxy-2-methylpropyl group, 3-hydroxy-2-methylpropyl group, 5-hydroxypentyl group, 8-hydroxyoctyl group, 1,2-dihydroxyethyl group, 2,3-dihydroxypropyl group, etc. It is done. Among these, a 2-hydroxyethyl group, a 3-hydroxypropyl group, a 4-hydroxybutyl group, a 5-hydroxypentyl group, and a 1,2-dihydroxyethyl group are preferable, and a 1,2-dihydroxyethyl group is more preferable.

In the structural unit represented by the formula (3), X ³ and X ⁴ each independently represent a hydroxyalkyl group having 1 or more carbon atoms having one or more hydroxyl groups. The number of carbon atoms of the hydroxyalkyl group is 8 or less because it becomes easier to obtain a PVA film in which the proportion of the amount of crystal component (a ₁ ) and the amount of constrained amorphous component (a ₂ ) satisfy the above range. It is preferably 6 or less, more preferably 4 or less, and the number of hydroxyl groups of the hydroxyalkyl group is 1 or 2 depending on the number of carbon atoms of the hydroxyalkyl group. It is preferable that it is a piece. Specific examples of the hydroxyalkyl group include hydroxymethyl group, 2-hydroxyethyl group, 3-hydroxypropyl group, 1-hydroxy-1-methylethyl group, 2-hydroxy-1-methylethyl group, 4- Examples thereof include a hydroxybutyl group, a 2-hydroxy-2-methylpropyl group, a 3-hydroxy-2-methylpropyl group, an 8-hydroxyoctyl group, a 1,2-dihydroxyethyl group, and a 2,3-dihydroxypropyl group. Among these, a hydroxymethyl group, a 2-hydroxyethyl group, a 3-hydroxypropyl group, a 4-hydroxybutyl group, and a 1,2-dihydroxyethyl group are preferable, and a hydroxymethyl group is more preferable. X ³ and X ⁴ may be the same or different from each other, and are preferably the same.

Examples of the PVA include those containing the structural unit (1) but not the structural units (2) and (3); those containing the structural unit (2) and not containing the structural units (1) and (3) Including structural unit (3) and not including structural units (1) and (2); including structural units (1) and (2) but not including structural unit (3); structural units (1) and ( 3) including structural unit (2); including structural units (2) and (3) but not including structural unit (1); including any of structural units (1) to (3) In consideration of the ease of production, the structural unit (1) and the structural unit (2) and (3) are excluded; the structural unit (2) and the structural unit (1) and (3) ); Or including structural unit (3) and structural unit (1) and (2) it does not include those are preferred.

Further, from the viewpoint of availability of raw materials, the PVA contained in the PVA film preferably does not contain the structural unit (3). From such a viewpoint, the PVA exemplified above includes the structural unit (1) but does not include the structural units (2) and (3); the structural unit (2) includes the structural unit (1) and (3). ); Or those containing the structural units (1) and (2) but not the structural unit (3) are preferred.

The exemplified PVA may or may not contain a vinyl ester unit, but it is preferable to contain a vinyl ester unit in consideration of ease of production. The vinyl ester unit typically includes a structural unit derived from a vinyl ester monomer used for the production of PVA as described later.

The PVA exemplified above has 0.6 ≦ n when the content of the structural units (1) to (3) is n ₁ to n ₃ mol% and the content of the vinyl ester unit is n ₄ mol%. ₁ + n ₂ + 2 × n ₃ + n ₄ ≦ 1.4 is satisfied. When the value of n ₁ + n ₂ + 2 × n ₃ + n ₄ is 0.6 mol% or more, the hue of the optical film obtained using the PVA film containing the PVA is improved. On the other hand, when the value of n ₁ + n ₂ + 2 × n ₃ + n ₄ is 1.4 mol% or less, the durability of the optical film obtained using the PVA film containing the PVA is improved. From the viewpoint of the hue and durability of the obtained optical film, the value of n ₁ + n ₂ + 2 × n ₃ + n ₄ is preferably 0.63 mol% or more, and more preferably 0.65 mol% or more. Moreover, it is more preferable that it is 1.38 mol% or less, and it is further more preferable that it is 1.35 mol% or less. In the present specification, the structural unit means a repeating unit constituting the polymer, and the content of the structural units (1) to (3) is relative to the number of moles of all the structural units constituting the PVA. The proportion of the number of moles of the structural units (1) to (3) is meant, and the content of vinyl ester units means the proportion of the number of moles of vinyl ester units to the number of moles of all structural units constituting the PVA.

In the exemplified PVA, the content of vinyl ester units is not particularly limited as long as the value of n ₁ + n ₂ + 2 × n ₃ + n ₄ is in the above range, but the amount of crystal component (a ₁ ) and the amount of restrained amorphous component Considering that it becomes easier to obtain a PVA film in which the proportion of (a ₂ ) satisfies the above range, ease of production, etc., it is preferably 1.35 mol% or less, and 1.3 mol% or less. More preferably, it is 1 mol% or less, more preferably 0.5 mol% or less, furthermore 0.3 mol% or less, and preferably 0.01 mol% or more. 0.05 mol% or more is more preferable, and 0.1 mol% or more is more preferable.

The method for producing the PVA exemplified above is not particularly limited. For example, a vinyl ester monomer is copolymerized with an unsaturated monomer that can be copolymerized therewith and can be converted into at least one structural unit selected from the group consisting of structural units (1) to (3). Then, the vinyl ester unit of the obtained vinyl ester copolymer is converted into a vinyl alcohol unit, and further unsaturated that can be converted into at least one structural unit selected from the group consisting of structural units (1) to (3) Examples thereof include a method of converting a structural unit derived from a monomer into at least one structural unit selected from the group consisting of structural units (1) to (3). Examples of the unsaturated monomer that can be converted into the structural unit (1) include an unsaturated monomer represented by the following formula (5). As an unsaturated monomer which can be converted into a structural unit (2), the unsaturated monomer shown by following formula (6) is mentioned, for example. As an unsaturated monomer which can be converted into a structural unit (3), the unsaturated monomer shown by following formula (7) is mentioned, for example.

[Wherein, R ¹ represents a hydrogen atom, a methyl group or an ethyl group, and Y ¹ represents a hydromethyl group or a group having a structure in which a hydroxyl group of the hydroxymethyl group is protected by a protecting group. ]

[Wherein R ² represents a hydrogen atom, a methyl group or an ethyl group, and Y ² represents a hydroxyalkyl group having 2 or more carbon atoms having one or more hydroxyl groups or a hydroxyl group of the hydroxyalkyl group depending on a protecting group. A group having a protected structure is shown. ]

[Wherein Y ³ and Y ⁴ are each independently a hydroxyalkyl group having 1 or more carbon atoms having one or more hydroxyl groups, or a group having a structure in which the hydroxyl groups of the hydroxyalkyl groups are protected by protecting groups. Indicates. ]

In the formula (5), description of R ¹ are the same as those of R ¹ in the formula (1) are omitted, wherein the overlapping here.

In Formula (5), when Y ¹ represents a group having a structure in which the hydroxyl group of the hydroxymethyl group is protected by a protecting group, the protecting group includes an acyl group such as an acetyl group or a propionyl group; an acetal group; A carbonate group etc. are mentioned, Among these, since the said protective group can be removed when converting a vinyl ester unit into a vinyl alcohol unit, an acyl group is preferable and an acetyl group is more preferable. In view of easy production of the exemplified PVA, Y ¹ is preferably a group having a structure in which a hydroxyl group of a hydroxymethyl group is protected by a protecting group.

In the formula (6), description of R ² are the same as those of R ² in the formula (2) are omitted, wherein the overlapping here.

In the formula (6), description of the number 2 or more hydroxyalkyl group having a carbon having one or more hydroxyl groups represented by Y ² has the formula (2) in the X ² number of 2 or more carbons with one or more hydroxyl groups shown This is the same as the description regarding the hydroxyalkyl group, and redundant description is omitted here. When Y ² represents a group having a structure in which the hydroxyl group of the hydroxyalkyl group is protected by a protecting group, the protecting group may be an acyl group such as an acetyl group or a propionyl group; an acetal such as an isopropylidene group; Examples include a carbonate group and the like. Among these, an acyl group is preferable and an acetyl group is more preferable because the protective group can be removed when the vinyl ester unit is converted to a vinyl alcohol unit. When Y ² represents a group having a structure in which the hydroxyl group of the hydroxyalkyl group is protected by a protecting group, specific examples thereof include, for example, 2-acetoxyethyl group, 3-acetoxypropyl group, 1-acetoxy- 1-methylethyl group, 2-acetoxy-1-methylethyl group, 4-acetoxybutyl group, 2-acetoxy-2-methylpropyl group, 3-acetoxy-2-methylpropyl group, 8-acetoxyoctyl group, 1, Examples include 2-diacetoxyethyl group and 2,3-diacetoxypropyl group. Y ² is a group having a structure in which a hydroxyl group of a hydroxyalkyl group having 2 or more carbon atoms having one or more hydroxyl groups is protected by a protecting group because the exemplified PVA can be easily produced. Is preferred.

Examples of the unsaturated monomer represented by the formula (6) include 4-acetoxy-1-butene, 5-acetoxy-1-pentene, 6-acetoxy-1-hexene, 7-acetoxy-1-heptene, 3 4,4-diacetoxy-1-butene, and 3,4-diacetoxy-1-butene is preferred.

In the formula (7), the description regarding the hydroxyalkyl group having 1 or more carbon atoms having one or more hydroxyl groups represented by Y ³ and / or Y ⁴ is the one represented by X ³ and / or X ⁴ in the formula (3). This is the same as the above description regarding a hydroxyalkyl group having 1 or more carbon atoms having a hydroxyl group, and redundant description is omitted here. Further, when Y ³ and / or Y ⁴ represents a group having a structure in which the hydroxyl group of the hydroxyalkyl group is protected by a protecting group, the protecting group may be an acyl group such as an acetyl group or a propionyl group; An acetal group such as a redene group; a carbonate group, and the like. Among these, an acyl group is preferable and an acetyl group is more preferable because the protective group can be removed when converting a vinyl ester unit to a vinyl alcohol unit. preferable. When Y ³ and / or Y ⁴ represents a group having a structure in which the hydroxyl group of the hydroxyalkyl group is protected by a protecting group, specific examples thereof include, for example, an acetoxymethyl group, a 2-acetoxyethyl group, 3 -Acetoxypropyl group, 1-acetoxy-1-methylethyl group, 2-acetoxy-1-methylethyl group, 4-acetoxybutyl group, 2-acetoxy-2-methylpropyl group, 3-acetoxy-2-methylpropyl group , 8-acetoxyoctyl group, 1,2-diacetoxyethyl group, 2,3-diacetoxypropyl group and the like. Y ³ and / or Y ⁴ has a structure in which the hydroxyl group of a hydroxyalkyl group having 1 or more carbon atoms having one or more hydroxyl groups is protected by a protective group because the production of the exemplified PVA is easy. It is preferable that both Y ³ and Y ⁴ are groups having a structure in which the hydroxyl group of the hydroxyalkyl group having 1 or more carbon atoms having one or more hydroxyl groups is protected by a protecting group. More preferred.

Examples of the unsaturated monomer represented by the formula (7) include 1,3-diacetoxy-2-methylenepropane, 1,3-dipropionyloxy-2-methylenepropane, and 1,3-dibutyryloxy-2. -Methylenepropane and the like, and 1,3-diacetoxy-2-methylenepropane is preferred.

The vinyl ester monomer used for the production of the above-mentioned PVA is not particularly limited. For example, vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatate, caproic acid Vinyl, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl palmitate, vinyl stearate, vinyl oleate, vinyl benzoate, etc. From the viewpoint of ease of production, availability, cost, etc. of PVA Vinyl acetate is preferred.

When copolymerizing a vinyl ester monomer and an unsaturated monomer copolymerizable therewith and convertible to at least one structural unit selected from the group consisting of structural units (1) to (3) The polymerization method may be any of batch polymerization, semi-batch polymerization, continuous polymerization, semi-continuous polymerization, etc., and the polymerization method is known as bulk polymerization method, solution polymerization method, suspension polymerization method, emulsion polymerization method, etc. The method can be applied. A bulk polymerization method or a solution polymerization method in which polymerization proceeds in a solvent-free or solvent such as alcohol is usually employed. In order to obtain a vinyl ester copolymer having a high degree of polymerization, an emulsion polymerization method is also preferred. Although the solvent of the solution polymerization method is not particularly limited, for example, alcohol. The alcohol used as the solvent for the solution polymerization method is, for example, a lower alcohol such as methanol, ethanol, or propanol. The amount of solvent used in the polymerization system may be selected in consideration of the chain transfer of the solvent according to the degree of polymerization of the target PVA. For example, when the solvent is methanol, the solvent and all monomers contained in the polymerization system The mass ratio {= (solvent) / (total monomer)} is preferably within the range of 0.01 to 10, more preferably within the range of 0.05 to 3.

Used for copolymerization of a vinyl ester monomer and an unsaturated monomer copolymerizable therewith and convertible to at least one structural unit selected from the group consisting of structural units (1) to (3) The polymerization initiator to be used may be selected from known polymerization initiators such as azo initiators, peroxide initiators, and redox initiators according to the polymerization method. Examples of the azo initiator include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (4-methoxy-2,4- Dimethylvaleronitrile). Examples of the peroxide initiator include percarbonate compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, and diethoxyethyl peroxydicarbonate; t-butyl peroxyneodecanate, α- Perester compounds such as cumylperoxyneodecanate; acetylcyclohexylsulfonyl peroxide; 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate; acetyl peroxide. Potassium persulfate, ammonium persulfate, hydrogen peroxide, or the like may be combined with the above initiator to form a polymerization initiator. The redox initiator is, for example, a polymerization initiator in which the peroxide initiator is combined with a reducing agent such as sodium hydrogen sulfite, sodium hydrogen carbonate, tartaric acid, L-ascorbic acid, or longalite. The amount of the polymerization initiator used varies depending on the type of the polymerization initiator and cannot be determined unconditionally, but may be selected according to the polymerization rate. For example, when 2,2′-azobisisobutyronitrile or acetyl peroxide is used as the polymerization initiator, 0.01 to 0.2 mol% is preferable with respect to the vinyl ester monomer, and 0.02 to 0 More preferred is 15 mol%.

Copolymerization of a vinyl ester monomer with an unsaturated monomer that can be copolymerized therewith and can be converted into at least one structural unit selected from the group consisting of structural units (1) to (3), You may carry out in presence of a chain transfer agent. Examples of the chain transfer agent include aldehydes such as acetaldehyde and propionaldehyde; ketones such as acetone and methyl ethyl ketone; mercaptans such as 2-hydroxyethanethiol; and phosphinic acid salts such as sodium phosphinate monohydrate. Of these, aldehydes and ketones are preferably used. The amount of chain transfer agent used can be determined according to the chain transfer coefficient of the chain transfer agent to be used and the degree of polymerization of the target PVA. 1 to 10 parts by mass is preferred.

Obtained by copolymerization of a vinyl ester monomer and an unsaturated monomer copolymerizable therewith and convertible to at least one structural unit selected from the group consisting of structural units (1) to (3) The PVA exemplified above can be obtained by saponifying the vinyl ester copolymer obtained. By saponifying the vinyl ester copolymer, the vinyl ester unit in the vinyl ester copolymer is converted to a vinyl alcohol unit. Further, for example, in the unsaturated monomer represented by the formula (3), when Y ¹ is a group having a structure in which the hydroxyl group of the hydroxymethyl group is protected by an acyl group, When the unsaturated monomer that can be copolymerized and is converted into at least one structural unit selected from the group consisting of structural units (1) to (3) has a hydroxyl group protected by an acyl group, the unsaturated monomer The ester bond of the acyl group portion in the structural unit derived from the monomer is also saponified to produce a hydroxyl group. Therefore, the PVA can be produced without further reaction such as hydrolysis after saponification.

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

The exemplified PVA can further include other structural units other than the structural units (1) to (3), the vinyl alcohol unit, and the vinyl ester unit. Examples of the other structural unit include a structural unit derived from an ethylenically unsaturated monomer copolymerizable with a vinyl ester monomer. Also, a structure derived from an unsaturated monomer that can be copolymerized with the above-described vinyl ester monomer and can be converted into at least one structural unit selected from the group consisting of structural units (1) to (3) Units (structural units that have not been converted into at least one structural unit selected from the group consisting of structural units (1) to (3) in the deprotection process) can also be included.

The proportion of the total of the structural units (1) to (3), the vinyl alcohol unit and the vinyl ester unit in the PVA exemplified above is 90 mol%, where the number of moles of all structural units constituting the PVA is 100 mol%. Preferably, it is 98 mol% or more, more preferably 99 mol% or more, 99.5 mol% or more, 99.8 mol% or more, 99.9 mol% or more, Furthermore, 100 mol% may be sufficient.

Examples of the ethylenically unsaturated monomer include α-olefins such as ethylene, propylene, n-butene, isobutylene and 1-hexene; acrylic acid and salts thereof; unsaturated monomer having an acrylate group. Body; methacrylic acid and salts thereof; unsaturated monomer having methacrylic ester group; acrylamide; N-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, diacetoneacrylamide, acrylamidepropanesulfonic acid and salts thereof Acrylamide derivatives such as acrylamidepropyldimethylamine and salts thereof (for example, quaternary salts); methacrylamide; N-methyl methacrylamide, N-ethyl methacrylamide, methacrylamide propane sulfonic acid and salts thereof, methacrylamide propylene Methacrylamide derivatives such as dimethylamine and its salts (eg quaternary salts); 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 , Vinyl ethers such as stearyl vinyl ether and 2,3-diacetoxy-1-vinyloxypropane; vinyl cyanides such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride and vinyl fluoride; vinylidene chloride and fluoride Vinylidene halides such as vinylidene; allyl compounds such as 2,3-diacetoxy-1-allyloxypropane and allyl chloride; unsaturated dicarbonates such as maleic acid, itaconic acid and fumaric acid Rubonic acid and salts or esters thereof; vinylsilyl compounds such as vinyltrimethoxysilane; isopropenyl acetate.

There is no particular limitation on the arrangement order of at least one structural unit selected from the group consisting of structural units (1) to (3) in the above exemplified PVA, a vinyl alcohol unit, and any other structural unit, and it is random, block, alternating Any of these may be used.

The degree of polymerization of the exemplified PVA can be obtained more easily by obtaining a PVA film in which the ratio of the amount of crystal component (a ₁ ) and the amount of constrained amorphous component (a ₂ ) satisfies the above range. From the viewpoint of improving the hue of the optical film obtained, it is preferably 3,000 or less, more preferably 2,900 or less, and even more preferably 2,800 or less. On the other hand, the degree of polymerization is preferably more than 2,000, more preferably more than 2,100, because the durability of the optical film obtained using the PVA film containing PVA is improved. More preferably, it exceeds 200. In this specification, the degree of polymerization of PVA means an average degree of polymerization measured according to the description of JIS K6726-1994.

In addition, the molecular weight distribution of the above exemplified PVA is such that the PVA film in which the ratio of the crystal component amount (a ₁ ) and the constrained amorphous component amount (a ₂ ) satisfies the above range is more easily obtained. The molecular weight distribution is preferably 2.2 or more, more preferably 2.4 or more, and even more preferably 3.8 or less. More preferably, it is as follows. In addition, the molecular weight distribution of PVA in this specification is a value calculated by mass average molecular weight (Mw) / number average molecular weight (Mn). The weight average molecular weight (Mw) and number average molecular weight (Mn) were obtained by using monodisperse polymethyl methacrylate as a standard, hexafluoroisopropanol containing 20 mmol / L sodium trifluoroacetate as a mobile phase, 40 ° C., flow rate 0 It can be determined by measuring gel permeation chromatography (manufactured by Tosoh Corporation, apparatus: HLC-8220GPC, column: GMHHR-H (S)) at 2 mL / min.

The PVA film of the present invention can contain a plasticizer in addition to the above PVA. Preferred plasticizers include polyhydric alcohols, and specific examples include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, trimethylolpropane, and the like. The PVA film of the present invention can contain one or more of these plasticizers. Among these, glycerin is preferable in terms of the effect of improving stretchability.

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

The PVA film of the present invention further includes a filler, a processing stabilizer such as a copper compound, a weather resistance stabilizer, a colorant, an ultraviolet absorber, a light stabilizer, an antioxidant, an antistatic agent, a flame retardant, Additives such as thermoplastic resins, lubricants, fragrances, defoamers, deodorants, extenders, release agents, mold release agents, reinforcing agents, crosslinking agents, fungicides, preservatives, crystallization rate retarders These can be blended as needed.

The proportion of the total of PVA and plasticizer in the PVA film of the present invention is preferably 80% by mass or more, more preferably 90% by mass or more, and 95% by mass or more based on the mass of the PVA film. More preferably.

The degree of swelling of the PVA film of the present invention is preferably in the range of 160 to 240%, more preferably in the range of 170 to 230%, and particularly preferably in the range of 180 to 220%. . When the degree of swelling is 160% or more, it is more effective that the total ratio of the amount of crystal component (a ₁ ) and the amount of constrained amorphous component (a ₂ ) after treatment at 60 ° C. for 1 hour becomes too high. The hue of the optical film obtained using the PVA film can be prevented. On the other hand, when the degree of swelling is 240% or less, it is more effective that the total ratio of the amount of crystal component (a ₁ ) and the amount of constrained amorphous component (a ₂ ) after treatment at 60 ° C. for 1 hour becomes too low. Therefore, the durability of the optical film obtained using the PVA film is improved. In this specification, the degree of swelling of the PVA film is obtained by dividing the mass when the PVA film is immersed in distilled water at 30 ° C. for 30 minutes by the mass after drying at 105 ° C. for 16 hours. It means the percentage of the value, and specifically can be measured by the method described later in the examples. The degree of swelling can be adjusted, for example, by changing the conditions for heat treatment, and the degree of swelling can usually be lowered by increasing the heat treatment temperature and lengthening the heat treatment time.

Since the PVA film of the present invention can easily produce an optical film excellent in all of optical properties, hue and durability, it can be used particularly effectively when the thickness is thinner than the conventional one. The thickness of the PVA film is preferably 1 to 60 μm, more preferably 5 to 55 μm, and particularly preferably 10 to 50 μm. When the thickness is less than 1 μm, stretch breakage tends to occur during uniaxial stretching treatment for producing an optical film such as a polarizing film. Moreover, when the said thickness is too thick, there exists a tendency for a stretch spot to generate | occur | produce at the time of the uniaxial stretching process for manufacturing an optical film.

The width of the PVA film of the present invention is not particularly limited, and can be determined according to its use. In recent years, when the screen size of liquid crystal televisions and liquid crystal monitors has been increasing, it is preferable that the width of the PVA film is 3 m or more for use as an end product. On the other hand, if the width of the PVA film is too large, problems such as difficulty in uniformly performing uniaxial stretching itself may occur when an optical film is produced with a practical device. The width of the film is preferably 7 m or less.

The production method of the PVA film of the present invention is not particularly limited, and a production method in which the thickness and width of the film after film formation are more uniform can be preferably adopted. For example, the above-described PVA constituting the PVA film and necessary Depending on the film forming stock solution in which one or more of the plasticizers, additives and surfactants described later are dissolved in a liquid medium, PVA and, if necessary, further plasticizers, additions It can be manufactured using a film-forming stock solution containing one or more of an agent, a surfactant, a liquid medium, and the like, in which PVA is melted. When the film-forming stock solution contains at least one of a plasticizer, an additive, and a surfactant, it is preferable that these components are uniformly mixed.

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

The volatile fraction of the film-forming stock solution (content ratio in the film-forming stock solution of volatile components such as liquid media removed by volatilization or evaporation during film formation) varies depending on the film-forming method, film-forming conditions, etc. Specifically, it is preferably in the range of 50 to 95% by mass, more preferably in the range of 55 to 90% by mass, and still more preferably in the range of 60 to 85% by mass. The film-forming stock solution has a volatile content of 50% by mass or more, so that the viscosity of the film-forming stock solution does not become too high, and filtration and defoaming are smoothly performed during the preparation of the film-forming stock solution, and there are few foreign substances and defects. Is easy to manufacture. On the other hand, when the volatile fraction of the film-forming stock solution is 95% by mass or less, the concentration of the film-forming stock solution does not become too low, and industrial film production is facilitated.

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

As the anionic surfactant, for example, a carboxylic acid type such as potassium laurate; a sulfuric acid ester type such as polyoxyethylene lauryl ether sulfate and octyl sulfate; and a sulfonic acid type such as dodecylbenzene sulfonate are suitable.

Nonionic surfactants include, for example, alkyl ether types such as polyoxyethylene oleyl ether; alkylphenyl ether types such as polyoxyethylene octylphenyl ether; alkyl ester types such as polyoxyethylene laurate; polyoxyethylene laurylamino Alkylamine type such as ether; alkylamide type such as polyoxyethylene lauric acid amide; polypropylene glycol ether type such as polyoxyethylene polyoxypropylene ether; alkanolamide type such as lauric acid diethanolamide and oleic acid diethanolamide; polyoxy An allyl phenyl ether type such as alkylene allyl phenyl ether is preferred.

These surfactants can be used alone or in combination of two or more.

When the film-forming stock solution contains a surfactant, the content thereof is preferably in the range of 0.01 to 0.5 parts by weight with respect to 100 parts by weight of PVA contained in the film-forming stock solution, and 0.02 It is more preferably in the range of -0.3 parts by mass, and particularly preferably in the range of 0.05-0.1 parts by mass. When the said content is 0.01 mass part or more, film forming property and peelability improve more. On the other hand, when the content is 0.5 parts by mass or less, it is possible to suppress that the surfactant bleeds out to the surface of the PVA film to cause blocking, and the handleability is deteriorated.

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

As an example of a specific method for producing the PVA film of the present invention, for example, a T-type slit die, a hopper plate, an I-die, a lip coater die or the like is used, and the above film forming stock solution is positioned on the most upstream side. It discharges or casts uniformly on the peripheral surface of the rotating heated first roll (or belt), and volatilizes from one surface of the film discharged or cast on the peripheral surface of the first roll (or belt). Evaporate and dry the sexual components, and then further dry on the circumference of one or more rotating heated rolls located downstream, or pass through a hot air dryer to further dry Then, the method of winding with a winding device can be preferably employed industrially. Drying with a heated roll and drying with a hot air dryer may be performed in an appropriate combination.

Although there is no restriction | limiting in particular in the use of the PVA film of this invention, According to the PVA film of this invention, since an optical film excellent in all of an optical characteristic, a hue, and durability can be manufactured easily, an optical film is used. It is preferable to use it as a raw film for manufacturing. Examples of such an optical film include a polarizing film and a retardation film, and a polarizing film is preferable. Such an optical film can be produced, for example, by a method using the PVA film of the present invention as a raw film for producing an optical film and having a step of uniaxial stretching. The PVA film itself, or the PVA film derived from the PVA film of the present invention produced by applying the swelling treatment described later (hereinafter referred to as “the PVA film of the present invention” and “the PVA film derived from the PVA film of the present invention”). ”May be collectively referred to as“ PVA film according to the present invention ”).

The method for producing a polarizing film using the PVA film of the present invention is not particularly limited, and any method conventionally employed may be employed. Examples of such a method include a method of dyeing and uniaxially stretching a PVA film based on the present invention, or uniaxially stretching a PVA film based on the present invention containing a dye. As a more specific method for producing the polarizing film, the PVA film based on the present invention is subjected to swelling, dyeing, uniaxial stretching, and, if necessary, crosslinking treatment, fixing treatment, drying, heat treatment, etc. The method of giving is mentioned. In this case, the order of each treatment such as swelling, dyeing, crosslinking treatment, uniaxial stretching, and fixing treatment is not particularly limited, and one or two or more treatments can be performed simultaneously. Also, one or more of each process can be performed twice or more.

Swelling can be performed by immersing the PVA film according to the present invention in water. The temperature of the water when immersed in water is preferably in the range of 20 to 40 ° C., more preferably in the range of 22 to 38 ° C., and preferably in the range of 25 to 35 ° C. Further preferred. The time for immersion in water is preferably in the range of 0.1 to 5 minutes, for example, and more preferably in the range of 0.5 to 3 minutes. In addition, the water at the time of immersing in water is not limited to pure water, The aqueous solution in which various components melt | dissolved may be sufficient, and the mixture of water and an aqueous medium may be sufficient.

Dyeing can be performed by bringing a dichroic dye into contact with the PVA film according to the present invention. As the dichroic dye, an iodine dye is generally used. The dyeing time may be any stage before uniaxial stretching, during uniaxial stretching, or after uniaxial stretching. Dyeing is generally performed by immersing the PVA film in a solution (particularly an aqueous solution) containing iodine-potassium iodide which is a dyeing bath, and such a dyeing method is also suitably employed in the present invention. The The iodine concentration in the dyeing bath is preferably in the range of 0.01 to 0.5% by mass, and the potassium iodide concentration is preferably in the range of 0.01 to 10% by mass. The temperature of the dyeing bath is preferably 20 to 50 ° C., particularly 25 to 40 ° C.

By subjecting the PVA film according to the present invention to a crosslinking treatment, it is possible to more effectively prevent PVA from eluting into water when wet-stretching at a high temperature. From this viewpoint, the crosslinking treatment is preferably performed after the treatment for bringing the dichroic dye into contact and before the uniaxial stretching. The crosslinking treatment can be performed by immersing the PVA film according to the present invention in an aqueous solution containing a crosslinking agent. As the crosslinking agent, one or more of boron compounds such as boric acid and borate such as borax can be used. The concentration of the crosslinking agent in the aqueous solution containing the crosslinking agent is preferably in the range of 1 to 15% by mass, more preferably in the range of 2 to 7% by mass, and in the range of 3 to 6% by mass. More preferably. Sufficient stretchability can be maintained when the concentration of the crosslinking agent is in the range of 1 to 15% by mass. The aqueous solution containing a crosslinking agent may contain potassium iodide and the like. The temperature of the aqueous solution containing the crosslinking agent is preferably in the range of 20 to 50 ° C., particularly in the range of 25 to 40 ° C. By setting the temperature within the range of 20 to 50 ° C., crosslinking can be performed efficiently.

Uniaxial stretching of the PVA film according to the present invention may be performed by either a wet stretching method or a dry stretching method. In the case of the wet stretching method, it can be carried out in an aqueous solution containing boric acid, or can be carried out in the dyeing bath described above or in a fixing treatment bath described later. In the case of the dry stretching method, the stretching may be performed at room temperature, may be performed while heating, or may be performed in the air using a PVA film after water absorption. Among these, the wet stretching method is preferable because it can be uniformly stretched in the width direction, and uniaxial stretching is more preferable in an aqueous solution containing boric acid. The concentration of boric acid in the boric acid aqueous solution is preferably within the range of 0.5 to 6.0% by mass, more preferably within the range of 1.0 to 5.0% by mass, It is particularly preferably within the range of ˜4.0% by mass. The aqueous boric acid solution may contain potassium iodide, and the concentration of potassium iodide is preferably in the range of 0.01 to 10% by mass.
The stretching temperature in the uniaxial stretching is preferably in the range of 30 to 90 ° C, more preferably in the range of 40 to 80 ° C, and particularly preferably in the range of 50 to 70 ° C.
In addition, the draw ratio in uniaxial stretching is preferably 6.6 times or more, more preferably 6.8 times or more, and 7.0 times or more from the viewpoint of the polarizing performance of the obtained polarizing film. Is particularly preferred. The upper limit of the draw ratio is not particularly limited, but the draw ratio is preferably 8 times or less.

The direction of uniaxial stretching in the case of uniaxially stretching a long PVA film is not particularly limited, and uniaxial stretching or lateral uniaxial stretching in the long direction can be adopted, but a polarizing film having excellent polarization performance can be obtained. To uniaxial stretching in the longitudinal direction. Uniaxial stretching in the longitudinal direction can be performed by changing the peripheral speed between the rolls using a stretching apparatus including a plurality of rolls parallel to each other. On the other hand, lateral uniaxial stretching can be performed using a tenter type stretching machine.

In the production of the polarizing film, it is preferable to perform a fixing treatment in order to strengthen the adsorption of the dichroic dye (iodine dye or the like) to the film. As the fixing treatment bath used for the fixing treatment, an aqueous solution containing one or more of boron compounds such as boric acid and borax can be used. Moreover, you may add an iodine compound and a metal compound in a fixed treatment bath as needed. The concentration of the boron compound in the fixing treatment bath is generally about 2 to 15% by mass, particularly about 3 to 10% by mass. By setting the concentration within the range of 2 to 15% by mass, the adsorption of the dichroic dye can be further strengthened. The temperature of the fixing treatment bath is preferably 15 to 60 ° C., particularly 25 to 40 ° C.

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

The polarizing film obtained as described above is usually used as a polarizing plate by attaching an optically transparent protective film having mechanical strength to both sides or one side. As the protective film, a cellulose triacetate (TAC) film, a cycloolefin polymer (COP) film, an acetic acid / cellulose butyrate (CAB) film, an acrylic film, a polyester film, or the like is used. Examples of the adhesive for bonding include PVA adhesives, urethane adhesives, acrylate ultraviolet curable adhesives, and the like.

The polarizing plate obtained as described above can be used as an LCD component after being coated with an acrylic adhesive or the like and bonded to a glass substrate. At the same time, it may be bonded to a retardation film, a viewing angle improving film, a brightness improving film, or the like.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In addition, each measurement or evaluation method employ | adopted in the following examples and comparative examples is shown below.

Primary structure of PVA The primary structure of PVA used in the following examples and comparative examples was analyzed using 400 MHz ¹ H-NMR. Deuterated DMSO was used as a solvent for the ¹ H-NMR measurement.

The degree of swelling of the PVA film The PVA film obtained in Examples or Comparative Examples below was cut to 1.5 g and immersed in distilled water at 30 ° C. for 30 minutes. After immersion for 30 minutes, the film was taken out, the surface water was taken out with a filter paper, and the mass “N” was determined. Subsequently, the film was dried with a dryer at 105 ° C. for 16 hours, and then the mass “M” was determined. From the obtained masses “N” and “M”, the degree of swelling of the PVA film was calculated by the following formula (8).
Swelling degree (%) = 100 × N / M (8)

Crystal component amount (a ₁ ) and constrained amorphous component amount (a ₂ ) in the PVA film
A sample (100 mg) obtained from the PVA film obtained in the following examples or comparative examples was cut into a size of about 5 mm × 5 mm, and then poured into an NMR tube together with 1 mL of heavy water. This NMR tube was immersed in a constant temperature bath at 60 ° C. for 1 hour. Then, it stored at 20 degreeC for 24 hours, and was set as the measurement sample. This measurement sample was measured for ¹ H spin-spin relaxation time T ₂ using pulsed NMR (“minispec mq20 WVT” manufactured by Bruker BioSpin Corporation). The measurement conditions are as follows.
Pulse sequence: Solid-Echo method (90x-τ-90y)
RF pulse width (Pw1): 2.1 μs
・ Pulse interval (Pi1): 1 μs
・ Pulse repetition time: 1s
・ Measurement temperature: 30 ℃
The free induction decay (FID) signal obtained by the above measurement is fitted to the above equation (4) by the linear least square method, and the crystal component amount (a ₁ ) and the constrained amorphous component amount (a ₂ ) and the amount of amorphous component (a ₃ ) were determined, and the ratio of each component to the total amount of these three components was calculated.

Stretchability of PVA film From a central portion in the width direction of the PVA film obtained in the following examples or comparative examples, a sample having a width of 5 cm and a length of 8 cm was cut so that a range of width 5 cm x length 5 cm could be uniaxially stretched. . This sample was uniaxially stretched in the length direction by a factor of 1.5 while being immersed in pure water at 30 ° C. Subsequently, while being immersed in an aqueous solution (dyeing bath) (temperature 30 ° C.) containing 0.03% by mass of iodine and 3.0% by mass of potassium iodide for 60 seconds, the ratio is 1.6 times (2.4 in total). Uniaxially stretching in the length direction to adsorb iodine. Next, the length was 1.1 times (2.6 times in total) while being immersed in an aqueous solution (crosslinking bath) (temperature 30 ° C.) containing 3% by weight of boric acid and 3% by weight of potassium iodide. Uniaxially stretched in the direction. Further, while immersing in an aqueous solution (stretching bath) containing 4% by mass of boric acid and 6% by mass of potassium iodide, the film is uniaxially stretched in the length direction until it is cut, and is relative to the length of the PVA film before stretching. The length ratio at the time of cutting was defined as the limit draw ratio. However, the temperature of the stretching bath was changed by 1 ° C. from an appropriate temperature, the limiting stretching ratio was measured, and the temperature at which the limiting stretching ratio was the highest was selected.

Optical properties of polarizing film (dichroic ratio)
(1) Measurement of transmittance Ts From the central part of the polarizing film obtained in the following examples or comparative examples, two 2 cm samples were taken in the length direction of the polarizing film, and a spectrophotometer with an integrating sphere (Japan) Using “V7100” manufactured by Spectroscopic Co., Ltd., in accordance with JIS Z 8722 (measuring method of object color), the visibility of the visible light region of the C light source and 2 ° field of view is corrected. The light transmittance when tilted by + 45 ° with respect to the vertical direction and the light transmittance when tilted by −45 ° were measured, and an average value Ts1 (%) thereof was obtained. Similarly, with respect to the other sample, the light transmittance when tilted by + 45 ° and the light transmittance when tilted by −45 ° were measured, and an average value Ts2 (%) thereof was obtained. Ts1 and Ts2 were averaged by the following formula (9) to obtain the transmittance Ts (%) of the polarizing film.
Ts = (Ts1 + Ts2) / 2 (9)

(2) Measurement of degree of polarization V Light transmittance T∥ (%) and length direction when two samples collected in the measurement of transmittance Ts are stacked so that their length directions are parallel. Are measured in the same manner as in the case of “(1) Measurement of transmittance Ts”, and the degree of polarization V ( %).
V = {(T∥−T⊥) / (T∥ + T⊥)} ^1/2 × 100 (10)

(3) Calculation of dichroic ratio when transmittance is 44% In each of the following Examples and Comparative Examples, the iodine concentration in the dyeing bath is 0.02 to 0.04% by mass, and the potassium iodide concentration is 2. The same operation was carried out by changing 4 times within the range of 0 to 4.0% by mass (however, the concentration of iodine: concentration of potassium iodide = 1: 100). Four polarizing films having different dichroic dye adsorption amounts were produced. For each of these four polarizing films, the transmittance Ts (%) and the degree of polarization V (%) were determined by the method described above, and the transmittance Ts (%) was plotted on the horizontal axis and the degree of polarization for each example and comparative example. With V (%) as the vertical axis, a total of 5 points including one point based on the transmittance Ts (%) and the degree of polarization V (%) of the polarizing film obtained in each example or comparative example are plotted on a graph. Thus, an approximate curve was obtained, and from the approximate curve, the degree of polarization V ₄₄ (%) when the transmittance Ts (%) was 44% was obtained.
From the obtained degree of polarization V ₄₄ (%), the dichroic ratio at a transmittance of 44% was determined by the following formula (11), and used as an index of polarization performance. In addition, the higher the dichroic ratio, the better the optical properties of the polarizing film. When the dichroic ratio is 66 or more, it is determined as “◯” (good), and when it is less than 66, “X” (defect) It was determined.
Dichroic ratio when the transmittance 44% = log (44 / 100-44 / 100 × V 44/100) / log (44/100 + 44/100 × V 44/100) (11)

Color of polarizing film (parallel b value)
In the above-mentioned “optical properties of the polarizing film (dichroic ratio)”, the transmittance T∥ (%) and the transmittance are obtained when the degree of polarization V of the four polarizing films having different dichroic dye adsorption amounts is obtained. Lab color space is measured when measuring T⊥ (%), b value when measuring transmittance T∥ (%) is a parallel b value, and b value when measuring transmittance T⊥ (%) is an orthogonal b value. It was. For each example and comparative example, including the parallel b value as the horizontal axis and the orthogonal b value as the vertical axis, including one point based on the parallel b value and orthogonal b value of the polarizing film obtained in each example or comparative example A total of 5 points were plotted on a graph to obtain an approximate curve, and a parallel b value when the orthogonal b value was −4 was obtained from the approximate curve. In addition, the hue of the polarizing film is better as the parallel b value is closer to 0, and the case where the parallel b value is less than 2.2 is determined as “◯” (good), and the case where the parallel b value is 2.2 or more is determined as “x”. (Defect) was determined.

Durability of polarizing film (absorbance remaining rate)
For each example or comparative example, the four polarizing films produced in the above-mentioned “Optical characteristics of the polarizing film (dichroic ratio)” with different amounts of adsorption of the dichroic dye, and each example or comparative example were obtained. The absorbance (orthogonal absorbance) at a wavelength of 610 nm obtained when the transmittance was in the range of 44 to 45% and the transmittance T⊥ (%) was measured out of the total of five polarizing films obtained. One polarizing film of 2.95 to 3.05 was selected.
The polarizing film was exposed for 4 hours in an environment of 60 ° C. and 90% RH, and the orthogonal absorbance at an initial wavelength of 610 nm was A _0h and the orthogonal absorbance at a wavelength of 610 nm after exposure for 4 hours was A _4h. The residual rate of orthogonal absorbance (absorbance residual rate) D (%) determined by 12) was evaluated as the durability of the polarizing film. The higher the residual absorbance rate, the better the durability of the polarizing film. When the residual absorbance rate is 20% or more, it is judged as “◯” (good), and when it is less than 20%, “x” (bad). It was determined.
D (%) = 100 × A _4h / A _0h (12)

[Examples 1 to 6 and Comparative Examples 1 to 5]
(1) Copolymer of vinyl acetate and 2-methyl-2-propenyl acetate, 3,4-diacetoxy-1-butene, 7-acetoxy-1-heptene or 1,3-diacetoxy-2-methylenepropane ( In Comparative Example 1, 100 parts by mass of PVA shown in Table 1 obtained by saponifying a vinyl acetate homopolymer), 10 parts by mass of glycerin as a plasticizer, and sodium polyoxyethylene lauryl ether sulfate as a surfactant 0.1 Using an aqueous solution containing 10 parts by mass and containing 10 parts by mass of PVA as a film-forming stock solution, this is dried on a metal roll at 80 ° C., and the resulting film is heated at a predetermined temperature in a hot air dryer. The degree of swelling was adjusted to 200% by heat treatment for 1 minute, and a PVA film having a thickness of 30 μm was produced.
Using the obtained PVA film, the ratio of the crystal component amount (a ₁ ) and the constrained amorphous component amount (a ₂ ) was determined by the above-described method, and the stretchability was evaluated. The results are shown in Table 1.

(2) A sample having a width of 5 cm and a length of 8 cm was cut from the central portion in the width direction of the PVA film obtained in (1) so that a range of width 5 cm × length 5 cm could be uniaxially stretched. This sample was uniaxially stretched in the length direction by a factor of 1.5 while being immersed in pure water at 30 ° C. Subsequently, while being immersed in an aqueous solution (dyeing bath) (temperature 30 ° C.) containing 0.03% by mass of iodine and 3.0% by mass of potassium iodide for 60 seconds, the ratio is 1.6 times (2.4 in total). Uniaxially stretching in the length direction to adsorb iodine. Next, the length was 1.1 times (2.6 times in total) while being immersed in an aqueous solution (crosslinking bath) (temperature 30 ° C.) containing 3% by weight of boric acid and 3% by weight of potassium iodide. Uniaxially stretched in the direction. Further, while dipping in an aqueous solution (stretching bath) containing 4% by mass of boric acid and 6% by mass of potassium iodide (the temperature at which the limiting stretching ratio determined in the above “stretchability of PVA film” is highest). The film was uniaxially stretched in the length direction to a magnification 0.2 times lower than the limit draw ratio. Thereafter, it was immersed in an aqueous solution (cleaning bath) containing 3% by mass of potassium iodide (temperature 30 ° C.) for 5 seconds, and finally dried at 60 ° C. for 4 minutes to produce a polarizing film.
Using the obtained polarizing film, the optical properties (dichroic ratio), hue (parallel b value) and durability of the polarizing film were evaluated by the method described above. The results are shown in Table 1.

As is clear from the above results, it can be seen that according to the PVA films of Examples 1 to 6 that satisfy the regulations of the present invention, an optical film excellent in any of optical characteristics, hue, and durability can be easily produced.

Claims

From the spin-spin relaxation time T 2 obtained by pulsed NMR measurement (observation nucleus: 1 H) after treatment at 60 ° C. for 1 hour, the amount of crystal component (a 1 ), amount of constrained amorphous component (a 2 ), and non- when asked crystallized component amount (a 3), the crystalline component amount (a 1), the crystalline component amount relative to the total weight constraints amorphous component (a 2) and amorphous component amount (a 3) (a 1) and A vinyl alcohol polymer film, wherein the total proportion of the constrained amorphous component amount (a 2 ) is 10 to 32%.
Crystalline component amount (a 1), is constrained amorphous component amount (a 2) and amorphous component amount (a 3) restraining amorphous component amount to the sum of (a 2) the proportion of 5% or more, claim 2. The vinyl alcohol polymer film as described in 1.
The vinyl alcohol polymer contained in the vinyl alcohol polymer film is a structural unit (1) represented by the following formula (1), a structural unit (2) represented by the following formula (2), and the following formula (3). The content of vinyl ester units, including at least one structural unit selected from the group consisting of the structural units (3) shown, wherein the content of structural units (1) to (3) is n 1 to n 3 mol%, respectively. The vinyl alcohol polymer film according to claim 1 or 2, which satisfies 0.6 ≦ n 1 + n 2 + 2 × n 3 + n 4 ≦ 1.4, when n is 4 mol%.

[Wherein, R 1 represents a hydrogen atom, a methyl group or an ethyl group. ]

[Wherein R 2 represents a hydrogen atom, a methyl group or an ethyl group, and X 2 represents a hydroxyalkyl group having 2 or more carbon atoms having one or more hydroxyl groups. ]

[Wherein, X 3 and X 4 each independently represent a hydroxyalkyl group having 1 or more carbon atoms having one or more hydroxyl groups. ]
The vinyl alcohol polymer according to claim 3, wherein the vinyl alcohol polymer contained in the vinyl alcohol polymer film contains at least one structural unit selected from the group consisting of the structural unit (1) and the structural unit (2). Polymer film.
The vinyl alcohol polymer according to any one of claims 1 to 4, wherein the vinyl alcohol polymer contained in the vinyl alcohol polymer film does not contain the structural unit (3) represented by the following formula (3). Combined film.

[Wherein, X 3 and X 4 each independently represent a hydroxyalkyl group having 1 or more carbon atoms having one or more hydroxyl groups. ]
6. The vinyl alcohol polymer film according to claim 1, wherein the degree of polymerization of the vinyl alcohol polymer contained in the vinyl alcohol polymer film is 3,000 or less.
The vinyl alcohol polymer film according to any one of claims 1 to 6, wherein the molecular weight distribution of the vinyl alcohol polymer contained in the vinyl alcohol polymer film is 2.0 to 4.0.
The vinyl alcohol polymer film according to any one of claims 1 to 7, having a swelling degree of 160 to 240%.
The vinyl alcohol polymer film according to any one of claims 1 to 8, which is a raw film for producing an optical film.
The vinyl alcohol polymer film according to claim 9, which is a raw film for producing a polarizing film.
A method for producing an optical film using the vinyl alcohol polymer film according to claim 9 or 10, which comprises a step of uniaxially stretching.