TW201509957A - Vinyl-alcohol-based polymer film - Google Patents

Abstract

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. 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 DEG 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 method for producing an optical film which is used as a vinyl alcohol polymer film for producing a green film for an optical film, and a polarizing film using the same.

A polarizing plate having a light transmitting and shading function is a basic constituent element of a liquid crystal display (LCD) as a liquid crystal that changes a polarized state of light. Most of the polarizing plates have a structure in which a protective film such as a cellulose triacetate (TAC) film is bonded to the surface of the polarizing film, and in the case of a polarizing film, a vinyl alcohol polymer film (hereinafter, sometimes "ethylene" The alcohol-based polymer is called "PVA". The uniaxially stretched matrix is adsorbed with an iodine dye (I ₃ ^- or I ₅ ^- ) or a dichroic dye such as a dichroic organic dye. .

LCDs are widely used in small computers such as computers and watches, mobile phones, notebook computers, LCD screens, liquid crystal color projectors, LCD TVs, car navigation systems, and measuring instruments used inside and outside the home. In recent years, In particular, the display quality is required to be advanced. Accordingly, the polarizing film is required to have high performance, and specifically, a polarizing film which is required to have high degree of polarization or transmittance, excellent optical characteristics, and excellent hue or durability.

In addition, several types of structures are known to be modified. A blank film for the production of optical films for PVA. For example, a polyvinyl alcohol film for a billet comprising a specific PVA polarizing film containing a hydrophilic functional group such as a carboxylic acid group of 0.01 to 1 mol% or a hydrophilic functional group such as an ω-hydroxy-α-olefin group is known. The handleability and the dichroic substance are excellent in the adsorption treatment property (see Patent Document 1). Further, a specific optical PVA film comprising a PVA in which a side chain contains a 1,2-glycol bond is known, and is excellent in optical properties and extensibility (see Patent Document 2). In addition, it is known that the use of a film containing PVA having a saponification degree of 92 to 98.5 mol% can shorten the dyeing time when a polarizing film is produced (see Patent Document 3).

Prior technical literature Patent literature

Patent Document 1 Japanese Patent Publication No. 8-201626

Patent Document 2 Japanese Patent Laid-Open Publication No. 2009-24076

Patent Document 3 Japanese Patent Laid-Open Publication No. 2012-68609

However, when a conventionally known PVA film is used, there is still room for further improvement in obtaining an optical film excellent in optical characteristics, hue, and durability.

Accordingly, the present invention provides a PVA film which can easily produce an optical film excellent in optical characteristics, hue and durability, and a method of producing an optical film using the same.

In order to achieve the above-mentioned object, the inventors of the present invention have made it possible to solve the above problems by solving the above-mentioned problems, and it is found that the above-mentioned problems can be solved by making the ratio of the amount of the crystal component and the total amount of the amorphous component in the PVA film to a specific range. The present invention was completed by repeating the study.

That is, the present invention relates to: [1] a PVA film in which a spin-spin relaxation time T ₂ obtained by performing pulse NMR measurement (observation of nuclei: ¹ H) after one hour of treatment by 60 ° C, When the amount of crystal component (a ₁ ), the amount of amorphous component (a ₂ ), and the amount of amorphous component (a ₃ ) are determined, the amount of amorphous component (a ₂ ) is limited with respect to the amount of crystal component (a ₁ ) And the total amount of the amorphous component (a ₃ ), the ratio of the total amount of the crystal component (a ₁ ) and the amount of the amorphous component (a ₂ ) is 10 to 32%; [2] as described in [1] above. PVA film, wherein an amount of the crystalline component (a _1), to limit the amount of amorphous component (a _2), and the amount of amorphous component (a ₃₎ of the total, limit the amount of amorphous component (a ₂₎ the proportion of 5 [3] The PVA film according to the above [1] or [2], wherein the PVA film contained in the PVA film contains a structural unit (1) selected from the following formula (1), and the following formula ( 2) at least one structural unit of the group of structural units (2) and structural units (3) represented by the following formula (3), when the content ratio of the structural units (1) to (3) is When n ₁ to n ₃ mol % is used, and the content ratio of the vinyl ester unit is n ₄ mol %, Foot 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 1 or more hydroxyl groups];

[In the formula, X ³ and X ⁴ each independently represent a hydroxyalkyl group having 1 or more carbon atoms and having 1 or more carbon atoms]; [4] The PVA film according to [3] above, wherein the PVA film contained in the PVA film contains The PVA film of any one of the above [1] to [4], wherein the PVA film is contained in the PVA film. PVA does not contain the structural unit (3) represented by the following formula (3);

In the formula, X ³ and X ⁴ each independently represent a hydroxyalkyl group having 1 or more carbon atoms and having a carbon number of 1 or more; [6] A PVA film according to any one of the above [1] to [5], wherein PVA The PVA film of any one of the above [1] to [6], wherein the PVA film contains a PVA having a molecular weight distribution of 2.0 to 4.0; [8] The PVA film according to any one of the above [1] to [7], which has a degree of swelling of 160 to 240%; [9] the PVA film according to any one of the above [1] to [8], which is an optical film. [10] A PVA film according to the above [9], which is a raw material film for producing a polarizing film; [11] a manufacturing method using the PVA film according to [9] or [10] above. A method of producing an optical film having a step of performing uniaxial stretching.

According to the present invention, there is provided a PVA film which can easily produce an optical film excellent in optical characteristics, hue and durability, and a method for producing an optical film using the same.

[Formation of the Invention]

In the PVA film of the present invention, the spin-spin relaxation time T ₂ obtained by pulse NMR measurement (observation of the core: ¹ H) after one hour of treatment at 60 ° C is used to obtain the amount of crystal component (a ₁ ), When the amount of amorphous component (a ₂ ) and the amount of amorphous component (a ₃ ) are limited, the amount of amorphous component (a ₁ ), the amount of amorphous component (a ₂ ), and the amount of amorphous component (a ₃ ) are limited. In total, the ratio of the total amount of the crystal component (a ₁ ) and the amount of the amorphous component (a ₂ ) is in the range of 10 to 32%.

Pulse NMR is different from high-resolution NMR, which is widely used in structural identification of organic compounds, etc., and is a mitigation time for measuring ¹ H nucleus related to molecular mobility in a system, and can be utilized for high quantitativeity. An analytical method for determining the proportion of each motion component in the system. In the present invention, in order to obtain the amount of crystal component (a ₁ ), the amount of amorphous component (a ₂ ), and the amount of amorphous component (a ₃ ) in the PVA film, a spin-spin relaxation of ¹ H is used. Time T ₂ . Specifically, the free induction attenuation (FID) signal obtained by measuring the spin-spin relaxation time T ₂ of ¹ H is similarly fitted to the following formula (4), Positive values a ₁ , a ₂ , a ₃ , a ₄ , c ₁ , c ₂ and c ₃ . This nesting (fitting) is preferably performed using a linear least squares method. Among the obtained values, a ₁ belongs to the above-mentioned crystal component amount (a ₁ ), a ₂ belongs to the above-mentioned limited amorphous component amount (a ₂ ), and a ₃ belongs to the above-described amorphous component amount (a ₃ ). For each of the specific conditions in the case of performing pulse NMR measurement, each of the conditions described later in the examples can be used.

In the case of pulse NMR measurement, the PVA film to be measured was previously treated at 60 ° C for 1 hour. By calculating the ratio of the amount of crystal component (a ₁ ) and the amount of amorphous component (a ₂ ) after one hour of treatment at 60 ° C, it is possible to obtain the above-described effects more closely related to the effects (durability, etc.) of the present invention. component ratio. Since the treatment can be carried out in a state where the PVA film to be measured is immersed in water, in particular, the treated PVA film can be directly subjected to pulse NMR measurement, and therefore it is preferable to impregnate the PVA film in an NMR tube or the like. It is carried out in the state of cerium oxide. For a more specific treatment method or condition of the treatment, the method described later in the examples can be employed.

In the PVA film of the present invention, the spin-spin relaxation time T ₂ obtained by pulse NMR measurement (observation of the core: ¹ H) after one hour of treatment at 60 ° C is used to obtain the amount of crystal component (a ₁ ), When the amount of amorphous component (a ₂ ) and the amount of amorphous component (a ₃ ) are limited, the total amount of amorphous component (a ₁ ), the amount of amorphous component (a ₂ ), and the amount of amorphous component (a3) are limited. It is necessary that the ratio of the total amount of the crystal component (a ₁ ) and the amount of the amorphous component (a ₂ ) is in the range of 10 to 32%. When the ratio is less than 10%, the durability of the optical film obtained by using the PVA film is deteriorated. On the other hand, when the ratio is more than 32%, the hue of the optical film obtained by using the PVA film is lowered. For this reason, although it is not limited to the present invention, it is considered that the influence on the state of the dichroic dye to be used is different depending on the above components, and it is presumed that the adjustment of the above ratio is The effects of the invention are extremely important. With respect to the amount of crystalline component (a _1), to limit the amount of amorphous component (a _2), and the amount of amorphous component (a ₃₎ the total amount of crystalline component (a ₁₎ and limit the amount of amorphous component (a ₂₎ Total The proportion is preferably 10.5% or more, more preferably 11% or more, still more preferably 31.5% or less, and still more preferably 31% or less, from the viewpoint of the hue or durability of the obtained optical film.

In order to further improve the durability of the obtained optical film, etc., it is preferable that the PVA film has a limited amorphous component, in particular, a PVA film system: the amount of amorphous component (a ₂ ) relative to the amount of the crystalline component (a ₂ ) The total amount of the amorphous component (a ₃ ) is preferably 5% or more, and more preferably 6% or more, based on the amount of the amorphous component (a ₂ ).

The type of PVA contained in the PVA film is not particularly limited, but the PVA film contained in the PVA film is a PVA film having a ratio of the amount of the crystal component (a ₁ ) and the amount of the amorphous component (a ₂ ) which are easily obtained. It is preferable to contain a structural unit (2) selected from the structural unit (1) represented by the following formula (1), the structural unit (2) represented by the following formula (2), and the structural unit (3) represented by the following formula (3). At least one structural unit in the group, and the content ratios of the structural units (1) to (3) are respectively set to n ₁ to n ₃ mol %, and the content ratio of the vinyl ester unit is set to n ₄ When Moer%, satisfy 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 1 or more hydroxyl groups];

In the formula, X ³ and X ⁴ each independently represent a hydroxyalkyl group having 1 or more carbon atoms and having 1 or more carbon atoms.

In the structural unit represented by the formula (1), R ¹ represents a hydrogen atom, a methyl group or an ethyl group. In the PVA film or the like in which the ratio of the amount of the crystal component (a ₁ ) and the amount of the amorphous component (a ₂ ) are more easily obtained, R ^{1 is} preferably a methyl group or an ethyl group, more preferably 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. In the PVA film or the like in which the ratio of the amount of the crystal component (a ₁ ) and the amount of the amorphous component (a ₂ ) are more easily obtained, the R ^{2 is} preferably a hydrogen atom or a methyl group.

In the structural unit represented by the formula (2), X ² represents a hydroxyalkyl group having 2 or more carbon atoms and having 2 or more carbon atoms. The PVA film or the like in which the ratio of the amount of the crystal component (a ₁ ) and the amount of the amorphous component (a ₂ ) are more easily obtained, the hydroxyalkyl group has a carbon number of preferably 8 or less, more preferably 6 or less. In the following, it is 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 2-hydroxyethyl, 3-hydroxypropyl, 1-hydroxy-1-methylethyl, 2-hydroxy-1-methylethyl, 4-hydroxybutyl Base, 2-hydroxy-2-methylpropyl, 3-hydroxy-2-methylpropyl, 5-hydroxypentyl, 8-hydroxyoctyl, 1,2-dihydroxyethyl, 2,3-di Hydroxypropyl and the like. Among these, 2-hydroxyethyl, 3-hydroxypropyl, 4-hydroxybutyl, 5-hydroxypentyl, 1,2-dihydroxyethyl, and more preferably 1,2-dihydroxyethyl, are preferred. base.

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 and having 1 or more carbon atoms. The PVA film or the like in which the ratio of the amount of the crystal component (a ₁ ) and the amount of the amorphous component (a ₂ ) are more easily obtained, the hydroxyalkyl group has a carbon number of preferably 8 or less, more preferably 6 or less. In the following, it is preferably 4 or less, and the number of hydroxyl groups of the hydroxyalkyl group varies depending on the carbon number of the hydroxyalkyl group, and is preferably one or two. Specific examples of the hydroxyalkyl group include a methylol group, a 2-hydroxyethyl group, a 3-hydroxypropyl group, a 1-hydroxy-1-methylethyl group, and a 2-hydroxy-1-methylethyl group. 4-hydroxybutyl, 2-hydroxy-2-methylpropyl, 3-hydroxy-2-methylpropyl, 8-hydroxyoctyl, 1,2-dihydroxyethyl, 2,3-dihydroxypropyl Base. Among these, a hydroxymethyl group, a 2-hydroxyethyl group, a 3-hydroxypropyl group, a 4-hydroxybutyl group, a 1,2-dihydroxyethyl group is preferred, and a hydroxymethyl group is more preferred. X ³ and X ⁴ may be the same or different from each other, and are preferably the same.

Examples of the PVA listed above include those including structural unit (1) and structural units (2) and (3), and structural unit (2) and structural units (1) and (3); Containing structural unit (3) without structural unit (1) and (2); containing structural unit (1) and (2) without structural unit (3); containing structural unit (1) and (3) Those without structural unit (2); those containing structural units (2) and (3) without structural unit (1); structural units (1) to (3) are all included, such as ease of manufacture, etc. Preferably, the structural unit (1) is contained without the structural unit (2) and (3); the structural unit (2) is contained without the structural unit (1) and (3); or the structural unit is included (3) ) without structural units (1) and (2).

Further, the PVA contained in the PVA film is preferably one containing no structural unit (3) from the viewpoint of the availability of the raw material and the like. Based on this point of view, it is preferable that the PVA listed above contains the structural unit (1) and does not contain the structural units (2) and (3); and contains the structural unit (2) without the structural unit (1) And (3); or those containing structural units (1) and (2) without structural unit (3).

Further, the PVA listed above may or may not contain a vinyl ester unit, and it is preferable to contain a vinyl ester unit in consideration of ease of production and the like. The vinyl ester unit is typically a structural unit derived from a vinyl ester monomer used for the production of a PVA to be described later.

The PVA listed above satisfies 0.6 when the content ratio of the structural units (1) to (3) is n ₁ to n ₃ mol% and the vinyl ester unit content is n ₄ mol %. ≦n ₁ +n ₂ +2×n ₃ +n ₄ ≦1.4. 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 by using the PVA-containing PVA film can be 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 by using the PVA-containing PVA film can be improved. The value of n ₁ + n ₂ + 2 × n ₃ + n ₄ is preferably 0.63 mol% or more, more preferably 0.65 mol% or more, and still more preferably 1.38, from the viewpoints of hue or durability of the obtained optical film. Moer% or less, and then preferably 1.35 mol% or less. Further, in the present specification, the structural unit refers to a repeating unit constituting a polymer, and the content ratios of the structural units (1) to (3) respectively mean a structural unit (1) with respect to the molar number of the total structural unit constituting the PVA. The ratio of the molar number of ~(3), the content of the vinyl ester unit means the ratio of the molar number of the vinyl ester unit relative to the molar number of the total structural unit constituting the PVA.

In the PVA listed above, the content of the vinyl ester unit 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 it is considered that the amount of the crystal component is more easily obtained (a) ₁ ) and the PVA film having a ratio of the amount of the amorphous component (a ₂ ) which satisfies the above range, or the ease of production, etc., is preferably 1.35 mol% or less, more preferably 1.3 mol% or less, and further preferably 1 mol. % or less may be 0.5 mol% or less, or even 0.3 mol% or less, and more preferably 0.01 mol% or more, more preferably 0.05 mol% or more, still more preferably 0.1 mol% or more.

The production method of the PVA listed above is not particularly limited. For example, a method in which a vinyl ester monomer and an unsaturated monomer which can be copolymerized therewith and which can be converted into at least one structural unit selected from the group consisting of structural units (1) to (3) can be mentioned. Copolymerization, converting the vinyl ester unit of the obtained vinyl ester copolymer into a vinyl alcohol unit, and then converting from at least one structural unit which can be converted into a group selected from the group consisting of structural units (1) to (3) The structural unit of the unsaturated monomer is converted into at least one structural unit selected from the group consisting of structural units (1) to (3). The unsaturated monomer which can be converted into the structural unit (1) is, for example, an unsaturated monomer represented by the following formula (5). The unsaturated monomer which can be converted into the structural unit (2) is, for example, an unsaturated monomer represented by the following formula (6). The unsaturated monomer which can be converted into the structural unit (3) is, for example, an unsaturated monomer represented by the following formula (7):

Wherein R ¹ represents a hydrogen atom, a methyl group or an ethyl group, and Y ¹ represents a methylol group or a group having a structure in which a hydroxyl group of the methylol group is protected by a protecting group;

In the formula, 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 structure having a hydroxyl group possessed by the hydroxyalkyl group protected by a protective group. Base

In the formula, Y ³ and Y ⁴ each independently represent a hydroxyalkyl group having one or more hydroxyl groups having 1 or more carbon atoms or a group having a structure in which a hydroxyl group of the hydroxyalkyl group is protected by a protective group.

In the formula (5), R is the same system and the instructions of formula (1) description of the R ^{1 1,} where the line will be repeated description is omitted.

In the formula (5), when Y ¹ represents a group having a structure in which the hydroxyl group of the methylol group is protected by a protecting group, examples of the protecting group include a mercapto group such as an ethenyl group or a propyl group; A base group such as a carbonate group or the like, wherein the protecting group is removed based on the conversion of the vinyl ester unit to the vinyl alcohol unit, preferably a mercapto group, more preferably an ethyl group. In order to easily produce the PVA or the like listed above, Y ¹ is preferably a group having a structure in which a hydroxyl group of the methylol group is protected by a protective group.

In the formula (6), the same system and the instructions R R formula (2) Description of the ^{2 2,} where the line will be repeated description is omitted.

In the formula (6), the description of the hydroxyalkyl group having 2 or more carbon atoms and having 2 or more carbon atoms represented by Y ² is a hydroxyl group having 2 or more carbon atoms and having 2 or more hydroxyl groups represented by X ² in the formula (2) The description of the alkyl group is the same, and the description of the duplicate is omitted here. In addition, when Y ² represents a group having a structure in which the hydroxyl group of the hydroxyalkyl group is protected by a protecting group, examples of the protecting group include a fluorenyl group such as an ethyl fluorenyl group and a propyl fluorenyl group; An aldehyde group, a carbonate group or the like, among these, a sulfhydryl group, more preferably an acetamidine group, is preferred because the protective group can be removed when the vinyl ester unit is converted into a vinyl alcohol unit. When Y ² represents a group having a structure in which the hydroxyl group of the above hydroxyalkyl group is protected by a protecting group, examples thereof include, for example, 2-ethenyloxyethyl group, 3-ethyloxypropyl group, and 1-B. Indole-1-methylethyl, 2-ethenyloxy-1-methylethyl, 4-ethenyloxybutyl, 2-ethiono-2-methylpropyl, 3-ethyloxene- 2-methylpropyl, 8-ethionoxyoctyl, 1,2-diethyloxyethyl, 2,3-diethyloxypropyl, and the like. In the case of the above-described PVA or the like, it is preferable that 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 protective group.

As the unsaturated monomer represented by the formula (6), for example, for example, 4-Ethyloxy-1-butene, 5-ethoxyox-1-pentene, 6-ethenoxy-1-hexene, 7-ethenox-1-heptene, 3,4-diethyl Indole-1-butene or the like is preferably 3,4-diethoxyin-1-butene.

In the formula (7), the description of the hydroxyalkyl group having 1 or more carbon atoms and having 1 or more carbon atoms represented by Y ³ and/or Y ⁴ has 1 in the formula (3) and X ¹ and/or X ⁴ The description of the hydroxyalkyl group having 1 or more carbon atoms of the above hydroxyl group is the same, and the description of the same is omitted here. In addition, 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, examples of the protecting group include a fluorenyl group such as an acetamidine group or a propyl group; An acetal group such as an isopropyl group; a carbonate group or the like, and among these, a protecting group can be removed by converting a vinyl ester unit into a vinyl alcohol unit, preferably a mercapto group, more preferably an ethyl group. When Y ³ and/or Y ⁴ represents a group having a structure in which the hydroxyl group of the above hydroxyalkyl group is protected by a protecting group, examples thereof include, for example, acetoxymethyl group and 2-ethyloxyethyl group. , 3-Ethyloxypropyl, 1-ethiono-1-methylethyl, 2-ethenyloxy-1-methylethyl, 4-ethenyloxybutyl, 2-ethyloxene-2 -methylpropyl, 3-ethiono-2-methylpropyl, 8-ethionoxyoctyl, 1,2-diethyloxyethyl, 2,3-diethyloxypropyl, and the like. In the case of the above-described PVA or the like, it is preferable that Y ³ and/or Y ⁴ have a structure in which a hydroxyl group of a hydroxyalkyl group having 1 or more carbon atoms and one or more hydroxyl groups is protected by a protective group. More preferably, both of Y ³ and Y ⁴ are groups having a structure in which a hydroxyl group of a hydroxyalkyl group having 1 or more carbon atoms and having 1 or more hydroxyl groups is protected by a protective group.

As the unsaturated monomer represented by the formula (7), for example, for example, 1,3-Diethoxyoxo-2-methylenepropane, 1,3-dipropionyloxy-2-methylenepropane, 1,3-dibutyloxy-2-methylenepropane, etc. Preferably, it is 1,3-diethoxyox-2-methylenepropane.

The vinyl ester system used in the manufacture of the PVA listed above The monomer is not particularly limited, and examples thereof include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, trimethyl vinyl acetate, vinyl versatate. ), vinyl hexanoate, vinyl octanoate, vinyl decanoate, vinyl laurate, vinyl palmitate, vinyl stearate, vinyl oleate, vinyl benzoate, etc., easy to manufacture by PVA, From the viewpoints of ease of handling, cost, and the like, vinyl acetate is preferred.

a vinyl ester monomer, and can be copolymerized therewith and can be transferred The polymerization method in which the unsaturated monomer is selected from the group consisting of at least one structural unit including the structural units (1) to (3) may be batch polymerization or half. Any one of batch polymerization, continuous polymerization, and semi-continuous polymerization, as the polymerization method, a known method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, or an emulsion polymerization method can be applied. A bulk polymerization method or a solution polymerization method in which polymerization is carried out in a solvent such as a solvent or an 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. The solvent of the solution polymerization method is not particularly limited and is, for example, an alcohol. The alcohol used in the solvent of the solution polymerization method is a lower alcohol such as methanol, ethanol or propanol. The amount of the solvent in the polymerization system may be selected according to the degree of polymerization of the target PVA, considering the chain transfer of the solvent. For example, when the solvent is methanol, the mass ratio of the solvent to the total monomer contained in the polymerization system {= (solvent) And / (total monomer) can be selected from the range of preferably 0.01 to 10, more preferably 0.05 to 3.

Vinyl ester monomer, and copolymerizable with it and convertible An initiator used for copolymerization of an unsaturated monomer selected from at least one structural unit of the group consisting of structural units (1) to (3), as long as a known polymerization initiator is used depending on the polymerization method, For example, an azo initiator, a peroxide initiator, and a redox initiator may be selected. The azo initiator is, for example, 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis (4) -Methoxy-2,4-dimethylvaleronitrile) and the like. The peroxide-based initiator is a peroxycarbonate compound such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate or diethoxyethyl peroxydicarbonate; a peroxy ester compound such as tertiary butyl peroxy neodecanoate or α-cumene peroxy neodecanoate; acetamidine cyclohexylsulfonyl peroxide; 2,4,4-trimethylpentyl -2-peroxyphenoxyacetate; acetoxy peroxide. Can also be potassium persulfate, ammonium persulfate, peroxidation Hydrogen or the like is combined with the above initiator to form a polymerization initiator. The redox-based initiator is, for example, a polymerization initiator obtained by combining the above peroxide initiator with a reducing agent such as sodium hydrogen sulfite, sodium hydrogencarbonate, tartaric acid, L-ascorbic acid, or Rongalit. Since the amount of the polymerization initiator to be used varies depending on the type of the polymerization initiator, it cannot be generally determined, but it may be selected according to the polymerization rate. For example, when 2,2'-azobisisobutyronitrile or ruthenium peroxide is used as the polymerization initiator, it is preferably 0.01 to 0.2 mol%, more preferably 0.02 to 0.15 mol, based on the vinyl ester monomer. %.

Vinyl ester monomer, and copolymerizable with it and convertible The copolymerization of an unsaturated monomer selected from at least one structural unit including a group of structural units (1) to (3) can be carried out in the presence of a chain transfer agent. The chain transfer agent is, for example, an aldehyde such as acetaldehyde or propionaldehyde; a ketone such as acetone or methyl ethyl ketone; a thiol such as 2-hydroxyethanethiol; or a phosphinate such as sodium phosphinate monohydrate. Among them, aldehydes and ketones can be suitably used. The amount of the chain transfer agent can be determined depending on the chain transfer constant of the chain transfer agent to be used and the polymerization degree of the target PVA. Generally, it is preferably 0.1 to 10 mass based on 100 parts by mass of the vinyl ester monomer. Share.

Ethylene obtained by copolymerization of a vinyl ester-based monomer and an unsaturated monomer copolymerizable therewith and convertible into an unsaturated monomer selected from the group consisting of at least one structural unit of the structural unit (1) to (3) The ester copolymer is saponified to obtain the PVA listed above. By saponifying the vinyl ester copolymer, the vinyl ester unit in the vinyl ester copolymer is converted into a vinyl alcohol unit. Further, as an example, in the unsaturated monomer represented by the formula (3), Y ¹ is a group having a structure in which a hydroxyl group has a hydroxyl group protected by a mercapto group, and when it is copolymerizable with a vinyl ester monomer Polymerized and convertible into an unsaturated monomer selected from at least one structural unit including a group of structural units (1) to (3), and a structural unit derived from the unsaturated monomer when having a hydroxyl group protected by a mercapto group The ester bond of the thiol moiety in the thiol moiety is also saponified to form a hydroxyl group. Therefore, the PVA can be produced after the saponification, even if the hydrolysis or the like is not further carried out.

Saponification of a vinyl ester copolymer can be, for example, the ethylene The ester copolymer is dissolved in an alcohol or an aqueous alcohol. The alcohol to be used for the saponification may, for example, be a lower alcohol such as methanol or ethanol, and is preferably methanol. The alcohol to be used for the saponification may contain, for example, another solvent such as acetone, methyl acetate, ethyl acetate or benzene in a proportion of 40% by mass or less based on the mass. The catalyst used for the saponification is, for example, a hydroxide of an alkali metal such as potassium hydroxide or sodium hydroxide, an alkali catalyst such as sodium methoxide, or an acid catalyst such as mineral acid. The temperature at which saponification is carried out is not limited, and is preferably in the range of 20 to 60 °C. When the gelatinous product is precipitated as the saponification progresses, the product is pulverized, washed, and dried to obtain PVA. The saponification method is not limited to the aforementioned method, and a well-known method can be applied.

The PVA listed above may further contain a structure list Other structural units other than the elements (1) to (3), vinyl alcohol units, and vinyl ester units. The other structural unit may, for example, be a structural unit derived from an ethylenically unsaturated monomer copolymerizable with a vinyl ester monomer. Further, it may contain: a structural unit derived from the above-mentioned unsaturated monomer copolymerizable with a vinyl ester monomer and convertible into at least one structural unit selected from the group consisting of structural units (1) to (3) (The process of deprotection is not converted into a structural unit selected from at least one structural unit including a group of structural units (1) to (3)).

Let the number of moles constituting the total structural unit of the PVA be 100. In the case of mol%, the proportion of the structural units (1) to (3), the vinyl alcohol unit, and the vinyl ester unit in the PVA listed above is preferably 90 mol% or more, more preferably 98 m. More than %, more preferably 99% by mole or more, and may be 99.5 % by mole or more, 99.8 % by mole or more, 99.9 % by mole or more, or even 100 % by mole.

As the above ethylenically unsaturated monomer, for example, B Alpha-olefins such as olefin, propylene, n-butene, isobutylene and 1-hexene; acrylic acid and salts thereof; unsaturated monomers having acrylate groups; methacrylic acid and salts thereof; Saturated monomer; acrylamide, N-methyl acrylamide, N-ethyl acrylamide, N,N-dimethyl decylamine, diacetone acrylamide, acrylamide propylene sulfonic acid and salts thereof a acrylamide derivative such as acrylamidopropyl dimethylamine and a salt thereof (for example, a quaternary salt); methacrylamide, N-methylmethacrylamide, N-ethyl methacrylamide a methacrylamide derivative such as methacrylamide amide sulfonic acid and its salt, methacrylamide propyl dimethylamine and a salt thereof (for example, a quaternary salt); methyl vinyl ether, ethyl vinyl Ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, tert-butyl vinyl ether, dodecyl vinyl ether, octadecyl ethylene Vinyl ethers such as alkyl ethers, 2,3-diethyloxy-1-vinyloxypropane, vinyl cyanide such as acrylonitrile and methacrylonitrile, and halogenated vinyls such as vinyl chloride and vinyl fluoride. Divinylidene halides such as dichloroethylene and difluoroethylene; allylic compounds such as 2,3-diethyloxy-1-allyloxypropane and allyl chloride; An unsaturated dicarboxylic acid such as an acid, itaconic acid or fumaric acid or a salt thereof or an ester thereof; a vinyl sulfonyl compound such as vinyltrimethoxyoxane; an isopropenyl acetate or the like.

The PVA listed above is selected from the group consisting of structural units The order of arrangement of at least one structural unit, vinyl alcohol unit, and any other constituent unit in the group of (1) to (3) is not particularly limited, and may be random, block, or alternate.

The PVA film which satisfies the above range in a ratio in which the amount of the crystal component (a ₁ ) and the amount of the amorphous component (a ₂ ) are more easily obtained, and the color of the optical film obtained by using the PVA film can be improved, the above-mentioned list The degree of polymerization of the PVA is preferably 3,000 or less, more preferably 2,900 or less, and still 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, still more preferably more than 2,200, from the viewpoint of improving the durability of the optical film obtained by using the PVA-containing PVA film. Further, the degree of polymerization of PVA in the present specification means the average degree of polymerization measured in accordance with the description of JIS K6726-1994.

Further, in the PVA film in which the ratio of the crystal component (a ₁ ) and the amount of the amorphous component (a ₂ ) are more easily obtained, the PVA having the above-described PVA has a molecular weight distribution of preferably 2.0 to 4.0. The molecular weight distribution is more preferably 2.2 or more, more preferably 2.4 or more, still more preferably 3.8 or less, and still more preferably 3.6 or less. Further, the molecular weight distribution of PVA in the present specification means a value calculated based on the mass average molecular weight (Mw) / number average molecular weight (Mn). The mass average molecular weight (Mw) and the number average molecular weight (Mn) can be obtained by using monodisperse polymethyl methacrylate as a standard, and hexafluoroisopropanol containing 20 mmol/L of sodium trifluoroacetate is used for the mobile phase. The gel permeation chromatography (manufactured by TOSOH; apparatus: HLC-8220GPC; column: GMHHR-H(S)) was measured at 40 ° C and a flow rate of 0.2 mL/min.

The PVA film of the present invention may contain, in addition to the above PVA Plasticizer. Preferred examples of the plasticizer include polyhydric alcohols, and specific examples thereof include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, and trishydroxyl. Methylpropane, etc. The PVA film of the present invention may contain one or more of these plasticizers. Among these, glycerin is preferred from the viewpoints of the effect of the elongation enhancement and the like.

The content of the plasticizer in the PVA film of the present invention, phase The amount of PVA 100 parts by mass is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, further preferably 20 parts by mass or less, more preferably 17 parts by mass. The amount is preferably 15 parts by mass or less. When the content is 1 part by mass or more, the elongation of the film can be further improved. On the other hand, when the content is 20 parts by mass or less, it is possible to suppress the film from being too soft and to deteriorate the handling property.

In the PVA film of the present invention, it can be further adapted to the needs When blending fillers, processing stabilizers for copper compounds, etc., weathering stabilizers, colorants, UV absorbers, light stabilizers, antioxidants, antistatic agents, flame retardants, other thermoplastic resins, lubricants, perfumes, Additives such as antifoaming agent, deodorant, extender, stripper, mold release agent, reinforcing agent, crosslinking agent, antifungal agent, preservative, and crystallization rate retarder.

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

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, the total amount of the crystal component (a ₁ ) and the amount of the amorphous component (a ₂ ) after the treatment at 60 ° C for one hour can be more effectively prevented, and the use ratio can be improved. The hue of the optical film obtained from the PVA film. On the other hand, when the degree of swelling is 240% or less, the total amount of the crystal component (a ₁ ) and the amount of the amorphous component (a ₂ ) after the treatment at 60 ° C for one hour can be more effectively prevented from being too low. The durability of the optical film obtained by using the PVA film can be improved. Further, in the present specification, the degree of swelling of the PVA film means a percentage of the value obtained by immersing the PVA film in distilled water at 30 ° C for 30 minutes by the mass after drying at 105 ° C for 16 hours, specifically, It can be measured by the method described later in the examples. The degree of swelling can be adjusted by, for example, changing the conditions of the heat treatment. Generally, the degree of swelling can be lowered by increasing the heat treatment temperature and prolonging the heat treatment time.

The PVA film of the present invention can be easily fabricated by optical An optical film excellent in characteristics, hue, and durability can be used particularly effectively when its thickness is thinner than in the past. The thickness of the PVA film is preferably from 1 to 60 μm, more preferably from 5 to 55 μm, particularly preferably from 10 to 50 μm. When the thickness is less than 1 μm, the uniaxial stretching treatment for producing an optical film such as a polarizing film tends to cause elongation fracture. Moreover, if the thickness is too thick, the unevenness tends to occur easily during the uniaxial stretching treatment for producing an optical film.

The width of the PVA film of the present invention is not particularly limited, and It is determined depending on its use and the like. In recent years, when the width of the PVA film is formed to be 3 m or more based on the advancement of the liquid crystal television or the liquid crystal screen, it is suitable for use as a final product. On the other hand, if the width of the PVA film is too large, the optical device is manufactured in a practical device. In the case of a film, problems such as uniform uniaxial stretching itself tend to be more difficult, and thus the width of the PVA film is preferably 7 m or less.

The method for producing the PVA film of the present invention is not particularly limited Preferably, the thickness and width of the film after film formation are preferably more uniform, for example, by using the film forming stock solution described below: the PVA constituting the PVA film, and further a film forming stock solution obtained by dissolving one or more of a plasticizer, an additive, and a surfactant described later in a liquid medium; or containing PVA, and further including a plasticizer, an additive, and an interface activity as needed A film-forming stock solution in which one or two or more kinds of the agent and the liquid medium are melted, and the PVA has been melted. When the film forming stock solution contains at least one of a plasticizer, an additive, and a surfactant, it is preferred to uniformly mix the components.

Examples of the liquid medium used for preparing the film forming stock solution include water, dimethyl hydrazine, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, and C. Triol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, ethylenediamine, diethylenetriamine, etc., one or more of these may be used. Among them, water is preferred in terms of environmental burden or recovery.

The volatilization ratio of the film forming solution (the content of the volatile component in the film forming solution such as the liquid medium removed by volatilization or evaporation during film formation) varies depending on the film forming method, the film forming conditions, and the like, and generally In other words, 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. When the volatilization rate of the film forming solution is 50% by mass or more, the viscosity of the film forming solution is not excessively high, and the filtration or defoaming during the preparation of the film forming solution can be smoothly performed, and it is easy. A film that produces less impurities or defects. On the other hand, when the volatilization rate of the film forming stock solution is 95% by mass or less, the concentration of the film forming raw liquid is not excessively low, and industrial production of the film is easy.

The film forming solution is preferably a surfactant. Through The inclusion of a surfactant enhances the film forming property and suppresses the occurrence of film thickness unevenness, and also facilitates the peeling of the film from the metal roll or tape 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. The type of the above-mentioned surfactant is not particularly limited, and an anionic surfactant or a nonionic surfactant is preferred from the viewpoint of the releasability from a metal roll or a belt.

As an anionic surfactant, suitable for example A carboxylic acid type such as potassium laurate; a sulfate type such as polyoxyethylene lauryl ether sulfate or octyl sulfate; a sulfonic acid type such as dodecylbenzenesulfonate.

As a nonionic surfactant, suitable for example An alkyl ether type such as polyoxyethylene oleyl ether; an alkylphenyl ether type such as polyoxyethylene octyl phenyl ether; an alkyl ester type such as polyoxyethylene laurate; an alkane such as polyoxyethylene lauryl amine ether Alkylamine type; polyalkylene laurate decylamine and other alkylguanamine type; polyoxyethylene polyoxypropylene ether and other polypropylene glycol ether type; lauric acid diethanolamine, oleic acid diethanolamine and other alkanolamine type ; allyl phenyl ether type such as polyoxyalkylene allylic phenyl ether;

These surfactants may 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 mass, more preferably in the range of 0.02 to 0.3 parts by mass, based on 100 parts by mass of the PVA contained in the film forming stock solution. Preferably, it is in the range of 0.05 to 0.1 parts by mass. When the content is 0.01 parts by mass or more, the film formability and the peeling property can be further improved. On the other hand, when the content is 0.5 parts by mass or less, it is possible to suppress the occurrence of adhesion of the surfactant from the surface of the PVA film and cause the handling property to deteriorate.

When the PVA film is produced by using the above-mentioned film forming stock solution Examples of the film forming method include a cast film forming method, an extrusion film forming method, a wet film forming method, and a gel system film method. These film forming methods may be used alone or in combination of two or more. Among these film forming methods, a cast film forming method and an extrusion film forming method are preferred because of a PVA film having a uniform thickness and width and good physical properties. The finished film can be dried or heat treated as needed.

As a specific manufacturing method of the PVA film of the present invention For example, it is preferable to industrially use, for example, a T-slot die, a hopper plate, an I-die, a lip coater die, etc., to uniformly discharge or cast the above-mentioned film-forming stock solution to On the circumferential surface of the first roller (or belt) that is rotated and heated on the most upstream side, volatile components are evaporated from one side of the film discharged or cast onto the circumferential surface of the first roller (or belt) After drying, it is further dried on the circumferential surface of one or more rotating and heated rolls disposed on the downstream side thereof, or further dried in a hot air drying device, and then wound up by a winding device. It can also be carried out by appropriately combining the drying by the heating roller and the drying by the hot air drying device.

The use of the PVA film of the present invention is not particularly limited, but According to the PVA film of the present invention, an optical film excellent in optical characteristics, hue, and durability can be easily produced as a light for manufacturing It is preferred to use a blank film for film. 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 using the PVA film of the present invention as a film for producing a film for optical film production and having a method of performing a uniaxial stretching step, specifically, by The PVA film from the PVA film of the present invention produced by the PVA film of the present invention or by the swelling treatment described later (hereinafter, the "PVA film of the present invention" and "from this" are sometimes used. The PVA film of the PVA film of the invention is collectively referred to as the "PVA film according to the present invention". The method of performing the uniaxial stretching step.

When a polarizing film is produced using the PVA film of the present invention The method is not particularly limited, and any method conventionally employed may be employed. As such a method, for example, a method of performing dyeing and uniaxial stretching of the PVA film according to the present invention or uniaxial stretching of the PVA film according to the present invention containing a dye can be exemplified. As a more specific method for producing a polarizing film, a method of performing swelling, dyeing, uniaxial stretching, and further performing crosslinking treatment, fixing treatment, drying, heat treatment, and the like on the PVA film according to the present invention may be mentioned. In this case, the order of each treatment such as swelling, dyeing, cross-linking treatment, uniaxial stretching, and fixation treatment is not particularly limited, and one or two or more kinds of treatments may be simultaneously performed. In addition, one or two or more types of each treatment may be performed twice or more.

Swelling can be performed by impregnating a PVA film according to the present invention In the water to carry out. 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. Also, in terms of the time of immersion in water, for example It is preferably in the range of 0.1 to 5 minutes, more preferably in the range of 0.5 to 3 minutes. Further, the water when immersed in water is not limited to pure water, and may be an aqueous solution in which various components are dissolved, or may be a mixture of water and an aqueous medium.

Dyeing can be achieved by contacting the PVA film according to the present invention A dichroic dye is used. As the dichroic dye, an iodine dye is generally used. In terms of the time point of dyeing, it may be any stage before uniaxial stretching, uniaxial stretching, or after uniaxial stretching. The dyeing is generally carried out by immersing the PVA film in a solution (particularly an aqueous solution) containing iodine-potassium iodide as a dye bath, and such a dyeing method is also suitable in the present invention. The concentration of iodine in the dyeing bath is preferably in the range of 0.01 to 0.5% by mass, and the concentration of potassium iodide is preferably in the range of 0.01 to 10% by mass. Further, the temperature of the dyeing bath is preferably 20 to 50 ° C, particularly preferably 25 to 40 ° C.

By performing cross-linking on the PVA film according to the present invention It is more effective to prevent PVA from eluting in water when wet stretching is carried out at high temperatures. From this point of view, the crosslinking treatment is preferably carried out after the treatment of contacting the dichroic dye, that is, before the uniaxial stretching. The crosslinking treatment can be carried out by immersing the PVA film according to the present invention in an aqueous solution containing a crosslinking agent. As the crosslinking agent, one type or two or more types of boron compounds such as a borate such as boric acid or 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, still more preferably in the range of 3 to 6% by mass. When the concentration of the crosslinking agent is in the range of 1 to 15% by mass, sufficient elongation can be maintained. The aqueous solution containing a crosslinking agent may also contain potassium iodide or the like. The temperature of the aqueous solution containing the crosslinking agent is preferably in the range of 20 to 50 ° C, particularly preferably in the range of 25 to 40 ° C. When the temperature is in the range of 20 to 50 ° C, crosslinking can be carried out efficiently.

Uniaxial extension of the PVA film according to the present invention can be wetted Either the stretching method or the dry stretching method is carried out. For example, in the wet-stretching method, it may be carried out in an aqueous solution containing boric acid, or in a dye bath as described above or in a fixed treatment bath to be described later. Further, in the case of the dry stretching method, the stretching may be carried out directly at room temperature, or may be carried out while heating, or may be carried out in the air using a water-absorbent PVA film. Among these, the wet stretching method is preferably carried out by uniformly extending the width direction, and more preferably, the uniaxial stretching is carried out in an aqueous solution containing boric acid. The concentration of boric acid in the aqueous boric acid solution is preferably in the range of 0.5 to 6.0% by mass, more preferably in the range of 1.0 to 5.0% by mass, particularly preferably in the range of 1.5 to 4.0% by mass. Further, 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 of 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.

Moreover, from the viewpoint of the polarizing performance of the obtained polarizing film, the stretching ratio of the uniaxial stretching is preferably 6.6 times or more, more preferably 6.8 times or more, and particularly preferably 7.0 times or more. The upper limit of the stretching ratio is not particularly limited, and the stretching ratio is preferably 8 times or less.

The direction of the uniaxial stretching in the uniaxial stretching of the long-sized PVA film is not particularly limited, and a uniaxial stretching or a lateral uniaxial stretching in the longitudinal direction may be employed, but it is preferably a polarizing film excellent in polarizing performance. It is a single axis extension in the length direction. The uniaxial stretching in the longitudinal direction can be performed by using a stretching device having a plurality of rollers parallel to each other and changing the peripheral speed between the rollers. On the other hand, the lateral uniaxial stretching can be carried out using a tenter type stretcher.

In the production of polarizing film, in order to make dichroic pigment (iodine) It is preferable that the adsorption of the film is stronger, and the fixing treatment is preferred. As the fixed treatment bath used for the fixation treatment, one type or two or more types of aqueous solutions containing a boron compound such as boric acid or borax can be used. Further, an iodine compound or a metal compound may be added to the fixed treatment bath as needed. The concentration of the boron compound in the fixed treatment bath is generally from 2 to 15% by mass, particularly preferably from about 3 to 10% by mass. By making the concentration in the range of 2 to 15% by mass, the adsorption of the dichroic dye can be further enhanced. The temperature of the fixed treatment bath is preferably from 15 to 60 ° C, especially from 25 to 40 ° C.

The drying conditions are not particularly limited, but preferably 30 to 150 Drying is carried out at a temperature in the range of °C, particularly in the range of 50 to 130 °C. By drying at a temperature in the range of 30 to 150 ° C, a polarizing film excellent in dimensional stability can be easily obtained.

The polarizing film obtained as above is usually on both sides or A single-sided optically transparent protective film having mechanical strength is used as a polarizing plate. As the protective film, a cellulose triacetate (TAC) film, a cycloolefin polymer (COP) film, and acetic acid can be used. A cellulose butyrate (CAB) film, an acrylic film, a polyester film, or the like. In addition, examples of the adhesive for bonding include a PVA-based adhesive, a urethane-based adhesive, and an acrylate-based ultraviolet-curable adhesive.

The polarizing plate obtained as above can be coated with acrylic or the like The adhesive is then applied to a glass substrate to form a part of the LCD. At the same time, it can also be bonded to a retardation film, a viewing angle lifting film, a brightness enhancement film, and the like.

[Examples]

Hereinafter, the present invention will be described in more detail based on the examples, but the present invention is not limited to these examples. In addition, each measurement or evaluation method used in the following examples and comparative examples is shown below.

Primary structure of PVA

The primary structure of the PVA used in the following examples and comparative examples was analyzed by 400 MHz ¹ H-NMR. The solvent used in the ¹ H-NMR measurement used deuterated DMSO.

Swelling degree of PVA film

The PVA film obtained in the following examples or comparative examples was cut into 1.5 g, and immersed in distilled water at 30 ° C for 30 minutes. After immersing for 30 minutes, the film was taken out, and water on the surface was taken up with a filter paper to obtain a mass "N". Then, the film was dried in a dryer at 105 ° C for 16 hours, and then the mass "M" was obtained. From the obtained masses "N" and "M", the degree of swelling of the PVA film was calculated according to the following formula (8).

Degree of swelling (%) = 100 × N / M (8)

Amount of crystalline component in PVA film (a ₁ And limiting the amount of amorphous components (a ₂ )

A sample (100 mg) of the PVA film obtained in the following examples or comparative examples was cut into a size of about 5 mm × 5 mm, and then placed in an NMR tube together with 1 mL of cerium oxide. The NMR tube was immersed in a thermostat at 60 ° C for 1 hour. Thereafter, the sample was stored at 20 ° C for 24 hours to prepare a measurement sample. For the measurement sample, the spin-spin relaxation time T ₂ of ¹ H was measured by pulse NMR ("minispec mq20 WVT" manufactured by Bruker BIOSPIN Co., Ltd.). The measurement conditions are as follows:

‧ Pulse series: Solid-Echo method (90x-τ-90y)

‧RF pulse width (Pw1): 2.1 microseconds

‧ Pulse interval (Pi1): 1 microsecond

‧ Pulse repetition time: 1 second

‧Measurement temperature: 30 ° C

The free induction attenuation (FID) signal obtained by the above measurement is fitted to the above formula (4) by a linear least squares method to obtain a total positive crystal component amount (a ₁ ) and a limited amorphous component amount (a ₂ ). And the amount of the amorphous component (a ₃ ), the ratio of each component to the total amount of the three components is calculated.

Extensibility of PVA film

From the 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 × a length of 8 cm was cut out so that a range of 5 cm in width × 5 cm in length was uniaxially stretchable. The sample was immersed in pure water at 30 ° C while being uniaxially stretched by 1.5 times in the longitudinal direction. Then, it was immersed in an aqueous solution (dyeing bath) (temperature: 30 ° C) containing iodine and potassium iodide at a ratio of 0.03 mass% and 3.0 mass% for 60 seconds while uniaxially extending 1.6 times in the longitudinal direction (2.4 times as a whole) ) while iodine is adsorbed. Next, it is immersed in an aqueous solution (cross-linking bath) containing 30% by mass and 3% by mass of boric acid and potassium iodide (temperature: 30 ° C), and uniaxially stretched by 1.1 times in the longitudinal direction (2.6 times as a whole) ). Further, it is immersed in a water-soluble solution containing boric acid and potassium iodide in a ratio of 4% by mass and 6% by mass. The liquid (extension bath) is uniaxially stretched in the longitudinal direction until it is broken, and the magnification at the time of breaking with respect to the length of the PVA film before stretching is taken as the limit stretching ratio. However, in terms of the temperature of the stretching bath, the limit stretching ratio is measured every 1 °C from an appropriate temperature, and the temperature at which the limit stretching ratio is maximized is selected.

Optical properties of polarizing film (dichroic ratio) (1) Determination of penetration rate Ts

From the center of the polarizing film obtained in the following examples or comparative examples, two 2 cm samples were taken along the longitudinal direction of the polarizing film, and a spectrophotometer with an integrating sphere ("V7100" manufactured by JASCO Corporation) was used based on JIS. Z 8722 (measurement method of object color), the visibility of the visible light region of the C light source and the 2° field of view is corrected, and the light transmittance and the inclination of -45° when tilting +45° with respect to the longitudinal direction are measured for one sample. The light transmittance at the time is obtained as the average value Ts1 (%) of them. Similarly, the light transmittance at a tilt of +45° and the light transmittance at a tilt of -45° were measured for the other sample, and the average value Ts2 (%) thereof was determined. Ts1 and Ts2 are averaged according to the following formula (9), which is the transmittance Ts (%) of the polarizing film.

Ts=(Ts1+Ts2)/2 (9)

(2) Determination of the degree of polarization V

In the same manner as in the case of the above-described "(1) Measurement of the transmittance Ts", the light penetration when the two samples taken in the measurement of the transmittance Ts were overlapped so that the longitudinal directions thereof were parallel were measured. The transmittance T//(%) and the light transmittance T⊥(%) when the longitudinal directions are orthogonal to each other, and the degree of polarization V(%) is obtained by the following formula (10): V={ (T//-T⊥)/(T//+T⊥)} ^1/2 ×100 (10)

(3) Calculation of dichroic ratio when the penetration rate is 44%

In each of the following examples and comparative examples, the concentration of iodine in the dyeing bath and the concentration of potassium iodide were changed four times in each of 0.02 to 0.04% by mass and 2.0 to 4.0% by mass (however, the concentration of iodine was set: The same operation was carried out by the concentration of potassium iodide = 1:100, and four polarizing films having different amounts of adsorption of the dichroic dye and the polarizing film produced in each of the examples or the comparative examples were prepared. For each of the four polarizing films, the transmittance Ts (%) and the degree of polarization V (%) were determined by the above method, and according to the respective examples and comparative examples, the transmittance Ts (%) was plotted on the horizontal axis. The degree of polarization V (%) is plotted on the vertical axis, and is also plotted as a total of 5 points based on the transmittance Ts (%) and the degree of polarization V (%) of the polarizing film obtained in each of the examples or the comparative examples. Then, an approximate curve was obtained, and from this approximation curve, the degree of polarization V ₄₄ (%) at which the transmittance Ts (%) was 44% was obtained.

From the obtained degree of polarization V ₄₄ (%), the dichroic ratio at a transmittance of 44% was obtained by the following formula (11), and this was used as an index of the polarizing performance. In addition, the higher the dichroic ratio, the better the optical characteristics of the polarizing film, and the case where the dichroic ratio is 66 or more is judged as "○" (good), and the case where the dichroic ratio is less than 66 is judged as "x" (defective). .

The dichroic ratio at a transmittance of 44% = log (44/100-44/100 × V ₄₄ /100) / log (44 / 100 + 44 / 100 × V ₄₄ / 100) (11)

Hue of polarizing film (parallel b value)

In the above-mentioned "optical characteristics (dichroic ratio) of the polarizing film", when the polarization degree V of four polarizing films having different amounts of adsorption of the dichroic dye is obtained, the transmittance is T//( When measuring the penetration rate T⊥(%), the b value when the transmittance T//(%) is measured is parallel b value, and the transmittance T⊥ (%) is measured. The b value is an orthogonal b value. According to each of the examples and the comparative examples, the parallel b value is the horizontal axis and the orthogonal b value is the vertical axis, and the parallel b value and the orthogonal b value of the polarizing film obtained from each of the examples or the comparative examples are also included. The total of 5 points is plotted as a graph to obtain an approximate curve, and from this approximate curve, a parallel b value when the orthogonal b value is -4 is obtained. Further, the closer the parallel b value is to 0, the better the hue of the polarizing film, and the case where the parallel b value is less than 2.2 is judged as "○" (good), and the case where 2.2 or more is judged as "x" (bad).

Durability of polarizing film (absorbance residual ratio)

According to each of the examples and the comparative examples, four polarizing films having different amounts of adsorption of the dichroic dye produced in the above-mentioned "optical characteristics (dichroic ratio) of the polarizing film" and the respective examples or comparative examples were obtained. Among the five polarizing films, the absorbance (orthogonal absorbance) at a wavelength of 610 nm obtained by measuring the transmittance T⊥ (%) is selected in the range of 44 to 45%. 2.95~3.05 polarizing film.

The polarizing film was exposed to an environment of 60 ° C and 90% RH for 4 hours, and the orthogonal absorbance at the 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 ratio (absorbance residual ratio) D (%) of the orthogonal absorbance obtained by the following formula (12) is taken as the durability of the polarizing film. In addition, the higher the residual ratio of the absorbance, the better the durability of the polarizing film, and the case where the residual ratio of the absorbance is 20% or more is judged as "○" (good), and the case where the residual ratio is less than 20% is judged as "x" (defect). .

D(%)=100×A _4h /A _0h (12)

[Examples 1 to 6 and Comparative Examples 1 to 5]

(1) will contain: 100 parts by mass of vinyl acetate with 2-methyl-2-propenyl acetate, 3,4-diethoxy-1-butene, 7-acetoxy-1- a copolymer of heptene or 1,3-diethoxyindol-2-methylenepropane (a homopolymer of vinyl acetate in Comparative Example 1) obtained by saponification of PVA shown in Table 1 and 10 parts by mass as a plastic A glycerin of the chemical agent and 0.1 part by mass of a polyoxyethylene lauryl ether sulfate as a surfactant, and an aqueous solution having a PVA content of 10% by mass, used as a film forming solution, and passed through at 80 ° C The metal roll was dried, and the obtained film was subjected to heat treatment at a predetermined temperature for 1 minute in a hot air dryer to adjust the degree of swelling to 200% to prepare a PVA film having a thickness of 30 μm.

Using the obtained PVA film, the ratio of the amount of crystal component (a ₁ ) to the amount of amorphous component (a ₂ ) was determined by the above method and the elongation 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 out from the central portion in the width direction of the PVA film obtained in the above (1) so that the range of 5 cm in width × 5 cm in length was uniaxially stretchable. Immerse the sample in pure water at 30 ° C while facing the length The direction is uniaxially extended by a factor of 1.5. Then, it was immersed in an aqueous solution (dyeing bath) (temperature: 30 ° C) containing iodine and potassium iodide at a ratio of 0.03 mass% and 3.0 mass% for 60 seconds while uniaxially extending 1.6 times in the longitudinal direction (2.4 times as a whole) ) while iodine is adsorbed. Next, it is immersed in an aqueous solution (cross-linking bath) containing 30% by mass and 3% by mass of boric acid and potassium iodide (temperature: 30 ° C), and uniaxially stretched by 1.1 times in the longitudinal direction (2.6 times as a whole) ). Furthermore, it is immersed in an aqueous solution (extension bath) containing boric acid and potassium iodide in a ratio of 4% by mass and 6% by mass (the temperature at which the ultimate stretching ratio is maximized as determined in the "Extensibility of PVA film"). At the same time, the uniaxial extension is performed in the longitudinal direction to a magnification which is 0.2 times lower than the limit extension ratio. Thereafter, the mixture was immersed in an aqueous solution (cleaning bath) containing potassium iodide at a ratio of 3 mass% (temperature: 30 ° C) for 5 seconds, and finally dried at 60 ° C for 4 minutes to prepare a polarizing film.

Using the obtained polarizing film, the optical characteristics (dichroicity ratio), hue (parallel b value), and durability of the polarizing film were evaluated by the above method. The results are shown in Table 1.

It is clear from the above results that according to the present invention is satisfied The PVA film of Examples 1 to 6 can easily produce an optical film excellent in optical characteristics, hue, and durability.

Claims (11)

A vinyl alcohol-based polymer film obtained by taking a spin-spin relaxation time T ₂ obtained by pulse NMR measurement (observation nucleus: ¹ H) after treatment for 1 hour at 60 ° C to obtain a crystal component amount (a _1), to limit the amount of amorphous component (a _2), and the amount of amorphous component _{(a. 3)} on the occasion, the amount of the crystalline component (a _1), to limit the amount of amorphous component (a _2), and the amount of amorphous component (a _In the total of ₃ ), the ratio of the total amount of the crystal component (a ₁ ) and the amount of the amorphous component (a ₂ ) is 10 to 32%. The vinyl alcohol polymer film of claim 1, wherein the amount of the amorphous component is limited with respect to the total amount of the crystal component (a ₁ ), the amount of the amorphous component (a ₂ ), and the amount of the amorphous component (a ₃ ). a ₂ ) The proportion is 5% or more. The vinyl alcohol polymer film according to claim 1 or 2, wherein the vinyl alcohol polymer contained in the vinyl alcohol polymer film contains a structural unit (1) selected from the group consisting of the following formula (1) At least one structural unit in the group of the structural unit (2) represented by the formula (2) and the structural unit (3) represented by the following formula (3), when the structural unit (1) to (3) The content ratio is set to n ₁ to n ₃ mol %, and when the content ratio of the vinyl ester unit is n ₄ mol %, 0.6 ≦ n ₁ + n ₂ + 2 × n ₃ + n ₄ ≦ 1.4 is satisfied; Wherein R ¹ represents a hydrogen atom, a methyl group or an ethyl group; In the formula, R ² represents a hydrogen atom, a methyl group or an ethyl group, and X ² represents a hydroxyalkyl group having a carbon number of 2 or more having one or more hydroxyl groups; In the formula, X ³ and X ⁴ each independently represent a hydroxyalkyl group having 1 or more carbon atoms and having 1 or more carbon atoms. The vinyl alcohol polymer film of claim 3, wherein the vinyl alcohol polymer contained in the vinyl alcohol polymer film contains at least 1 selected from the group consisting of structural unit (1) and structural unit (2). a structural unit. The vinyl alcohol polymer film 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); In the formula, X ³ and X ⁴ each independently represent a hydroxyalkyl group having 1 or more carbon atoms and having 1 or more carbon atoms. The vinyl alcohol polymer film according to any one of claims 1 to 5, wherein the vinyl alcohol polymer contained in the vinyl alcohol polymer film has a degree of polymerization of 3,000 or less. The vinyl alcohol polymer film according to any one of claims 1 to 6, wherein the vinyl alcohol polymer contained in the vinyl alcohol polymer film has a molecular weight distribution of 2.0 to 4.0. The vinyl alcohol polymer film according to any one of claims 1 to 7, which has a degree of swelling of 160 to 240%. The vinyl alcohol polymer film according to any one of claims 1 to 8, which is a material film for optical film production. The vinyl alcohol-based polymer film of claim 9 which is a raw material film for producing a polarizing film. A manufacturing method which is a method of producing an optical film using the vinyl alcohol-based polymer film of claim 9 or 10, which has a step of performing uniaxial stretching.