KR102607190B1 - Optical film, manufacturing method thereof, polarizer, and liquid crystal display device - Google Patents

Abstract

A process of coextruding resin A and resin B to obtain a laminated film having a core layer made of resin A and a surface layer made of resin B formed on the surface of the core layer, and peeling the surface layer from the laminated film. A method of manufacturing an optical film obtained through a process; And, optical films containing specific block copolymers. The optical film has an absolute value of retardation in the in-plane direction of 5 nm or less, an absolute value of retardation in the thickness direction of 10 nm or less, and a water vapor transmission rate of 20 g/(m ² ·day) or less.

Description

Optical film, manufacturing method thereof, polarizer, and liquid crystal display device

The present invention relates to an optical film, a method of manufacturing the same, a polarizing plate, and a liquid crystal display device.

A polarizing plate installed in a liquid crystal display device usually includes a polarizer and a protective film to protect the polarizer. In many cases, polarizing plate protective films are required to have small retardation and low water vapor transmission rate. From this viewpoint, a polarizer protective film with small retardation has been proposed (see Patent Document 1). Additionally, the polarizing plate is required to exhibit durability in the environment during production and use of the display device. For example, when a polarizer is shrunk during rework during the manufacture of a display device or when the display device is used, the protective film in the polarizing plate may be required to have high peel strength.

Japanese Patent Publication No. 2011-013378

The polarizer protective film proposed in Patent Document 1 is obtained using a resin containing a block copolymer containing a block of an aromatic vinyl compound hydride and a block of a diene compound hydride. According to this polarizer protective film, retardation in the in-plane direction can be reduced. However, when this polarizer protective film is used, the polymer molecules contained in the polarizer protective film are oriented and entanglement between molecules decreases, which causes cohesive failure near the surface layer, reducing the peeling strength of the protective film in the polarizing plate. There was a problem that could arise due to a lack of .

Therefore, an object of the present invention is to provide an optical film with high adhesion to a polarizer, low retardation, and low water vapor transmission rate, a method for manufacturing an optical film that can easily obtain such an optical film, and the optical film. and to provide a polarizing plate and a liquid crystal display device having the above-mentioned performance.

As a result of examining the problems with the conventional polarizer protective film mentioned above, it was thought that it was caused by a strong orientation layer being formed on the surface of the protective film during the process of molding the protective film by the melt extrusion method.

Accordingly, the present inventor conducted intensive studies to solve the above problems. As a result, the present inventor produced a laminated film having a core layer and a surface layer formed on the surface by coextrusion of resin A and resin B, and peeled and removed the surface layer from the laminated film to improve adhesion to the object. It was found that an optical film with high retardation and low water vapor transmission rate could be obtained, and the present invention was completed.

That is, the present invention is as follows.

[1] a block [Da] having a cyclic hydrocarbon group-containing compound unit,

A block having a chain hydrocarbon compound unit, or a chain hydrocarbon compound unit and a cyclic hydrocarbon group-containing compound unit [Ea]

Contains a block copolymer containing,

The difference between the composition ratio of the volume of the block [Da] and the volume of the block [Ea] at the surface and the center is 0 to 10%,

The absolute value of retardation in the in-plane direction is 5 nm or less,

The absolute value of retardation in the thickness direction is 10 nm or less, and

An optical film having a water vapor transmission rate of 20 g/(m ² ·day) or less.

[2] The optical film according to [1], which is formed by extrusion film formation of a resin containing the block copolymer.

[3] The block copolymer is:

As the block [Da], it contains two or more polymer blocks [Db] per molecule having a cyclic hydrocarbon group-containing compound hydride unit,

As the block [Ea], at least one polymer block [Eb] per molecule having a chain hydrocarbon compound hydride unit, or a chain hydrocarbon compound or its hydride unit, and a cyclic hydrocarbon-containing compound or its hydride unit. The optical film according to [1] or [2], which is a copolymer comprising:

[4] A polarizing plate comprising the optical film according to any one of [1] to [3] and a polarizer.

[5] A liquid crystal display device comprising the polarizing plate described in [4].

[6] A process of co-extruding resin A and resin B to obtain a laminated film having a core layer made of resin A and a surface layer made of resin B formed on the surface of the core layer;

A method of manufacturing an optical film comprising a step of peeling the surface layer from the laminated film,

The optical film is,

The absolute value of retardation in the in-plane direction is 5 nm or less,

The absolute value of retardation in the thickness direction is 10 nm or less, and

A method for producing an optical film having a water vapor transmission rate of 20 g/(m ² ·day) or less.

[7] The method for producing the optical film according to [6], wherein the absolute value of the retardation in the in-plane direction of the optical film is 2 nm or less, and the absolute value of the retardation in the thickness direction of the optical film is 2 nm or less. .

[8] The method for producing an optical film according to [6] or [7], wherein the resin B contains an alicyclic structure-containing polymer.

[9] The above resin A,

Two or more polymer blocks [D] per molecule having a cyclic hydrocarbon group-containing compound hydride unit,

At least one polymer block per molecule having chain hydrocarbon compound hydride units, or chain hydrocarbon compound units and cyclic hydrocarbon-containing compound hydride units [E]

The method for producing an optical film according to any one of [6] to [8], comprising a hydrogenated block copolymer containing.

[10] The above resin A,

A block having a compound unit containing a cyclic hydrocarbon group,

A block having a chain hydrocarbon compound unit, or a chain hydrocarbon compound unit and a cyclic hydrocarbon group-containing compound unit.

It is made of a block copolymer containing,

In the optical film, the difference in composition ratio between the surface and the central portion is 0 to 10%,

The method for producing an optical film according to any one of [6] to [8].

The optical film of the present invention can be made into an optical film with high adhesion to an object, low retardation, and low water vapor transmission rate. According to the method for manufacturing an optical film of the present invention, an optical film with high adhesion to an object, small retardation, and low water vapor transmission rate can be easily obtained. According to the polarizing plate of the present invention, it is possible to provide a polarizing plate having the performance described above. According to the liquid crystal display device of the present invention, a liquid crystal display device having the above-described performance can be provided.

1 is a cross-sectional view schematically showing an example of a laminated film production process in the manufacturing method of the present invention.
Figure 2 is a cross-sectional view schematically showing an example of a peeling process in the manufacturing method of the present invention.
Figure 3 is a cross-sectional view schematically showing a sample used in the evaluation test in the Example.

Hereinafter, the present invention will be described in detail by showing embodiments and examples. However, the present invention is not limited to the embodiments and examples shown below, and may be implemented with any modification without departing from the scope of the claims and equivalents of the present invention.

In the following description, a cyclic hydrocarbon group is a hydrocarbon group containing a cyclic structure such as an aromatic ring, cycloalkane, or cycloalkene. Additionally, a chain hydrocarbon compound is a hydrocarbon compound that does not contain such a cyclic hydrocarbon group.

In the following description, the retardation Re in the in-plane direction of the optical film is a value expressed as Re = (nx - ny) × d, unless otherwise specified. In addition, the retardation Rth in the thickness direction of the optical film is a value expressed as Rth = {(nx + ny)/2 - nz} × d, unless otherwise specified. Here, nx represents the refractive index in the direction that provides the maximum refractive index in the direction perpendicular to the thickness direction of the optical film (in-plane direction). ny represents the refractive index of the direction orthogonal to the direction of nx as the in-plane direction of the optical film. nz represents the refractive index in the thickness direction of the optical film. d represents the thickness of the optical film. The measurement wavelength for retardation is 590 nm, unless otherwise specified.

In the following description, unless otherwise specified, the term “polarizing plate” includes not only rigid members but also flexible members such as, for example, resin films.

In the following description, a “long” film refers to a film having a length of 5 times or more relative to the width, preferably 10 times or more, and specifically, the degree to which it is wound into a roll and stored or transported. refers to a film with a length of The upper limit of the length of the long film is not particularly limited, and can be, for example, 100,000 times or less relative to the width.

〔One. [Method for producing optical film of the present invention]

In one aspect of the present invention, the method for producing an optical film includes a core layer made of resin A, and a resin formed on the surface of the core layer by coextruding resin A forming the core layer and resin B forming the surface layer. It includes a step of obtaining a laminated film having a surface layer made of B (laminated film production step) and a step of peeling the surface layer from the laminated film (peeling step).

〔1.1. Overview of the laminated film production process〕

In the laminated film production process, a laminated film is obtained by coextruding resin A for forming the core layer and resin B for forming the surface layer. Coextrusion can be performed using a multilayer extruder.

In the embodiment shown in FIG. 1 , the laminated film 20 has surface layers 11 and 12 on two surfaces of the core layer 10, respectively. In detail, the laminated film 20 has a layer structure of surface layer 11/core layer 10/surface layer 12. M shown in FIG. 1 is an extrusion molding machine. The laminated film may have a surface layer only on one side of the core layer, and the layer structure in this case is surface layer/core layer. From the viewpoint of suppressing film curl, it is preferable that the surface layer is on both sides of the core layer.

〔1.1.1. [Suzy A]

As the resin A forming the core layer, a thermoplastic resin can be used.

The thermoplastic resin forming the core layer (hereinafter also referred to as “thermoplastic resin A”) is not particularly limited, and resins containing various polymers that can provide the desired physical properties as an optical film can be appropriately selected and employed. . Preferred examples of the polymer contained in the thermoplastic resin A include two or more polymer blocks [D] having a cyclic hydrocarbon group-containing compound hydride unit, a chain hydrocarbon compound hydride unit, or a chain hydrocarbon compound unit and a cyclic hydrocarbon compound unit. and hydrogenated block copolymers [G] comprising one or more polymer blocks [E] having hydrocarbon-containing compound hydride units. Since the resin A contains a hydrogenated block copolymer [G], an optical film with a low retardation can be obtained, and therefore, the optical film obtained by the production method of the present invention can be used as a member requiring a low retardation. there is. In addition, an optical film with high light resistance and resistance to yellowing can be obtained.

The cyclic hydrocarbon group-containing compound hydride unit contained in block [D] and block [E] is preferably an aromatic vinyl compound hydride unit. An aromatic vinyl compound hydride unit is a structural unit having a structure formed by further hydrogenating a unit obtained by polymerizing an aromatic vinyl compound. However, the aromatic vinyl compound hydride unit is not limited by its production method.

Examples of aromatic vinyl compounds include styrene; α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 4-t-butylstyrene, 5-t-butyl-2 -Styrenes having an alkyl group of 1 to 6 carbon atoms as a substituent, such as methylstyrene; Styrenes having a halogen atom as a substituent, such as 4-chlorostyrene, dichlorostyrene, and 4-monofluorostyrene; Styrenes having an alkoxy group of 1 to 6 carbon atoms as a substituent, such as 4-methoxystyrene; Styrenes having an aryl group as a substituent, such as 4-phenylstyrene; Vinyl naphthalenes such as 1-vinylnaphthalene and 2-vinylnaphthalene; etc. can be mentioned. These may be used individually, or two or more types may be used in combination at any ratio. Among these, aromatic vinyl compounds that do not contain a polar group, such as styrene and styrenes having an alkyl group of 1 to 6 carbon atoms as a substituent, are preferable because they can lower hygroscopicity, and styrene is especially preferred because of ease of industrial availability. desirable.

The chain-shaped hydrocarbon compound hydride unit contained in block [E] is preferably a chain-shaped conjugated diene compound hydride unit. The chain-shaped conjugated diene compound hydride unit is a structural unit having the structure of a unit obtained by polymerizing a chain-shaped conjugated diene compound, or, when it has a double bond, by hydrogenating part or all of these double bonds. However, the chain-shaped conjugated diene compound hydride unit is not limited by its production method.

Examples of chain conjugated diene compounds include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, and 1,3-pentadiene. These may be used individually, or two or more types may be used in combination at any ratio. Among them, chain-shaped conjugated diene compounds that do not contain a polar group are preferable because they can lower hygroscopicity, and 1,3-butadiene and isoprene are particularly preferable.

The hydrogenated block copolymer [G] preferably has a triblock molecular structure with one block [E] per molecule and two blocks [D] per molecule connected to both ends thereof. That is, the hydrogenated block copolymer [G] contains one block [E] per molecule; One block [D1] per molecule, which is connected to one end of the block [E] and has a cyclic hydrocarbon group-containing compound hydride unit [I]; It is preferably a triblock copolymer containing one block [D2] per molecule, which is connected to the other end of the block [E] and has a cyclic hydrocarbon group-containing compound hydride unit [I].

In the hydrogenated block copolymer [G] as the above-mentioned triblock copolymer, from the viewpoint of easily obtaining a laminated film with desirable characteristics, the weight ratio of the sum of blocks [D1] and blocks [D2] and the block [E] ( It is desirable that D1+D2)/E falls within a specific range. Specifically, the weight ratio (D1+D2)/E is preferably 70/30 or more, more preferably 75/25 or more, preferably 90/10 or less, and more preferably 87/13 or less.

In addition, in the hydrogenated block copolymer [G] as the above-mentioned triblock copolymer, from the viewpoint of easily obtaining a laminated film having the above characteristics, the weight ratio D1/D2 of the block [D1] and the block [D2] is within a specific range. It is desirable to enter . Specifically, the weight ratio D1/D2 is preferably 5 or more, more preferably 5.2 or more, particularly preferably 5.5 or more, and preferably 8 or less, more preferably 7.8 or less, especially preferably 7.5 or less. am.

The weight average molecular weight Mw of the hydrogenated block copolymer [G] is preferably 50,000 or more, more preferably 55,000 or more, particularly preferably 60,000 or more, preferably 80,000 or less, more preferably 75,000 or less. It is less than 70,000. When the weight average molecular weight Mw is within the above range, a laminated film having the above characteristics can be easily obtained. In particular, by reducing the weight average molecular weight, the occurrence of retardation can be effectively reduced.

The molecular weight distribution (weight average molecular weight (Mw)/number average molecular weight (Mn)) of the hydrogenated block copolymer [G] is preferably 2.0 or less, more preferably 1.7 or less, particularly preferably 1.5 or less, and preferably is greater than or equal to 1.0. When the weight average molecular weight Mw is within the above range, the polymer viscosity can be lowered and the moldability can be improved. Additionally, the occurrence of retardation can be effectively reduced.

The weight average molecular weight Mw and number average molecular weight Mn of the hydrogenated block copolymer [G] can be measured as polystyrene conversion values by gel permeation chromatography using cyclohexane as a solvent. In the block copolymer hydrogenated [G], for example, preferably 90% or more, more preferably 97% or more, and even more preferably 99% or more of the carbon-carbon unsaturated bonds of the main chain and side chain are hydrogenated. there is. In addition, in the block copolymer hydrogenated [G], for example, preferably 90% or more, more preferably 97% or more, and even more preferably 99% or more of the carbon-carbon unsaturated bonds of the aromatic ring are hydrogenated. It is done. The higher the hydrogenation rate, which indicates the degree of hydrogenation, the improvement in heat resistance and light resistance is expected.

Block [D1] and block [D2] are each independently preferably composed of only the cyclic hydrocarbon group-containing compound hydride unit [I], but may contain any unit other than the cyclic hydrocarbon group-containing compound hydride unit [I]. It can be included. Examples of arbitrary structural units include structural units based on vinyl compounds other than the cyclic hydrocarbon group-containing compound hydride unit [I]. The content of arbitrary structural units in block [D] is preferably 10% by weight or less, more preferably 5% by weight or less, and particularly preferably 1% by weight or less.

Block [E] is a block consisting only of chain hydrocarbon compound hydride units [II], or a block having chain hydrocarbon compound units [II] and cyclic hydrocarbon-containing compound hydride units [I]. Block [E] may include arbitrary units other than unit [I] and unit [II]. Examples of arbitrary structural units include structural units based on vinyl compounds other than unit [I] and unit [II]. The content of arbitrary structural units in block [E] is preferably 10% by weight or less, more preferably 5% by weight or less, and particularly preferably 1% by weight or less.

The hydrogenated block copolymer [G] as the above-mentioned triblock copolymer has a low incidence of retardation. Therefore, the optical film obtained by peeling the surface layer from the laminate can easily obtain desired characteristics.

Specific examples and production methods of the hydrogenated block copolymer [G] include, for example, specific examples and production methods disclosed in International Publication No. WO2016/152871.

The thermoplastic resin A may consist only of the hydrogenated block copolymer [G] described above, or may contain any component other than the hydrogenated block copolymer [G].

Optional components include, for example, inorganic fine particles; Stabilizers such as antioxidants, heat stabilizers, ultraviolet ray absorbers, and near-infrared absorbers; Resin modifiers such as lubricants and plasticizers; Colorants such as dyes and pigments; and antistatic agents. As these optional components, one type may be used individually, and two or more types may be used in combination at an arbitrary ratio. However, from the viewpoint of significantly exhibiting the effects of the present invention, it is preferable that the content ratio of any component is small. For example, the ratio of the total of arbitrary components is preferably 10 parts by weight or less, more preferably 7 parts by weight or less, and even more preferably 5 parts by weight or less, based on 100 parts by weight of hydrogenated block copolymer [G]. do.

Thermoplastic resin A has a glass transition temperature of preferably 110°C or higher, more preferably 120°C or higher, preferably 180°C or lower, and more preferably 170°C or lower. Thermoplastic resin A, which has a glass transition temperature in this range, is excellent in dimensional stability and molding processability.

〔1.1.2. [Suzy B]

As the resin B that forms the surface layer, a resin that can form a surface layer that can be peeled from the core layer made of resin A is used. A thermoplastic resin can be used as resin B. In the following description, in order to distinguish between the resins B for forming the two surface layers, they may be referred to as resin B1 and resin B2. Resin B1 and Resin B2 may be the same or different.

The thermoplastic resin forming the surface layer (hereinafter also referred to as “thermoplastic resin B”) is not particularly limited as long as it is a resin that can form a surface layer that can be peeled from the core layer, and resins containing various polymers can be appropriately selected and employed. there is.

Preferred examples of the polymer contained in the thermoplastic resin B include alicyclic structure-containing polymers. The alicyclic structure-containing polymer is a polymer having an alicyclic structure in the repeating unit, and either a polymer containing an alicyclic structure in the main chain or a polymer containing an alicyclic structure in the side chain can be used. The alicyclic structure-containing polymer includes crystalline resin and amorphous resin, but amorphous resin is preferred from the viewpoint of surface smoothness.

Examples of the alicyclic structure include a cycloalkane structure and a cycloalkene structure, but a cycloalkane structure is preferable from the viewpoint of thermal stability and the like.

There is no particular limitation on the number of carbon atoms constituting the repeating unit of one alicyclic structure, but it is usually 4 to 30, preferably 5 to 20, and more preferably 6 to 15.

The proportion of repeating units having an alicyclic structure in the alicyclic structure-containing polymer is appropriately selected depending on the purpose of use, but is usually 50% by weight or more, preferably 70% by weight or more, and more preferably 90% by weight or more. By increasing the number of repeating units having an alicyclic structure in this way, the heat resistance of the surface layer can be improved.

The alicyclic structure-containing polymer specifically includes (1) norbornene-based polymer, (2) monocyclic olefin polymer, (3) cyclic conjugated diene polymer, (4) vinyl alicyclic hydrocarbon polymer, and these. Hydrogen, etc. can be mentioned. Among these, from the viewpoint of moldability, norbornene-based polymers and their hydrides are more preferable.

Examples of the norbornene-based polymer include ring-opened polymers of norbornene-based monomers, ring-opened copolymers of norbornene-based monomers with other monomers capable of ring-opening copolymerization, and hydrides thereof; Examples include addition polymers of norbornene-based monomers and addition copolymers of other monomers that can be copolymerized with norbornene-based monomers. Among these, from the viewpoint of moldability, ring-opened polymer hydrides of norbornene-based monomers are particularly preferable.

The above-described alicyclic structure-containing polymer is selected, for example, from polymers disclosed in Japanese Patent Application Laid-Open No. 2002-321302.

In addition, examples of crystalline alicyclic structure-containing polymers include, for example, polymers disclosed in Japanese Patent Application Publication No. 2016-26909.

The weight average molecular weight of the alicyclic structure-containing polymer is polyisoprene, measured by gel permeation chromatography (hereinafter abbreviated as “GPC”) using cyclohexane (toluene if the resin does not dissolve) as a solvent. The weight average molecular weight (Mw) in conversion (when the solvent is toluene, polystyrene conversion) is usually 10,000 to 100,000, preferably 25,000 to 80,000, more preferably 25,000 to 50,000. When the weight average molecular weight is in this range, the mechanical strength and molding processability of the surface layer are highly balanced.

The molecular weight distribution (weight average molecular weight (Mw)/number average molecular weight (Mn)) of the alicyclic structure-containing polymer is usually 1 to 10, preferably 1 to 4, and more preferably 1.2 to 3.5.

Thermoplastic resin B has a glass transition temperature of preferably 110°C or higher, more preferably 120°C or higher, preferably 180°C or lower, and more preferably 170°C or lower. Thermoplastic resin B with a glass transition temperature in this range is excellent in molding processability.

The thermoplastic resin B may consist only of an alicyclic structure-containing polymer, but may also contain arbitrary components as long as the effect of the present invention is not significantly impaired. As an optional component, the same thing as the arbitrary component of thermoplastic resin A can be used. The proportion of the alicyclic structure-containing polymer in the thermoplastic resin B is preferably 70% by weight or more, more preferably 80% by weight or more.

As a resin containing an alicyclic structure-containing polymer, various products are commercially available. Among them, one having the desired properties can be appropriately selected and used as the thermoplastic resin B. Examples of such commercial products include the product line under the brand name "ZEONOR" (manufactured by Nippon Zeon Co., Ltd.).

〔1.2. Laminated film production process]

In the laminated film production process, a laminated film can be produced by preparing Resin A, Resin B1, and Resin B2, respectively, and performing melt extrusion molding by co-extrusion of these resins. By performing such melt extrusion molding, a laminated film having each desired layer thickness can be efficiently manufactured. Moreover, according to melt extrusion molding, a long laminated film can be obtained.

Examples of the resin extrusion method in the coextrusion method include the coextrusion T-die method, the coextrusion inflation method, and the coextrusion lamination method. Among them, the coextrusion T-die method is preferable. There are a feedblock method and a multi-manifold method in the coextrusion T-die method, and the multi-manifold method is particularly preferable because it can reduce thickness variation.

The temperature of the resin (hereinafter sometimes arbitrarily referred to as “extrusion temperature”) when performing melt extrusion molding by co-extrusion is not particularly limited, and is a temperature that can melt each resin, and is suitable for molding. The temperature can be set appropriately. Specifically, it can be set based on the higher temperature (Ts[H]) of the heat softening temperature of resin A forming the core layer and the heat softening temperature of resin B forming the surface layer. More specifically, it is preferably (Ts[H] + 70)°C or higher, more preferably (Ts[H] + 80)°C or higher, while preferably (Ts[H] + 180)°C or higher. , more preferably (Ts[H] + 150)°C or lower.

The heat softening temperature of Resin A is preferably 110°C or higher, more preferably 120°C or higher, preferably 180°C or lower, and more preferably 170°C or lower. The heat softening temperature of Resin B is preferably 110°C or higher, more preferably 120°C or higher, preferably 180°C or lower, and more preferably 170°C or lower.

The heat softening temperature Ts of each resin can be measured by TMA (thermomechanical analysis) measurement. For example, the layer to be measured was cut into a shape of 5 mm In this state, the temperature can be changed and the temperature (°C) when the linear expansion changes by 3% can be measured as the softening temperature.

Additionally, the arithmetic mean roughness Ra of the dice lip of the die is preferably 0 μm to 1.0 μm, more preferably 0 μm to 0.7 μm, and particularly preferably 0 μm to 0.5 μm. Here, the arithmetic mean roughness Ra can be measured based on JIS B0601:1994 using a surface roughness meter.

In the coextrusion method, the film-shaped molten resin extruded from the die lip is usually cooled and hardened by bringing it into close contact with a cooling roll. At this time, examples of methods for bringing the molten resin into close contact with the cooling roll include the air knife method, vacuum box method, and electrostatic adhesion method.

〔1.2.1. [Dimensions of each layer in laminated film]

In the laminated film obtained by the laminated film production process, the thickness of the core layer is preferably 20 μm or more, more preferably 25 μm or more, preferably 80 μm or less, and more preferably 70 μm or less. The thickness of the two surface layers is each preferably 5 μm or more, more preferably 10 μm or more, preferably 30 μm or less, and more preferably 25 μm or less.

The thickness of each layer can be measured by microscopic observation. Specifically, the laminated film can be sliced using a microtome and the thickness of each layer can be measured by observing the cut surface. Observation of the cut surface can be performed, for example, using a polarizing microscope (for example, “BX51” manufactured by Olympus Corporation).

〔1.3. Peeling process]

The peeling step in the optical film manufacturing method of the present invention is a step of peeling the surface layer from the laminated film. By going through this peeling process, an optical film can be obtained. The two surface layers are peeled off simultaneously in the embodiment described below, but they may be peeled off one layer at a time.

Figure 2 is a cross-sectional view schematically showing an example of a peeling process in the optical film manufacturing method of the present invention. The laminated film (laminated film 20 explained in FIG. 1) conveyed from the extrusion molding machine M is conveyed downward in the figure, and is then subjected to a peeling process.

The peeling process in the peeling process can be performed by pulling the surface layers 11 and 12 in a direction different from the in-plane direction of the conveyed laminated film 20. In the example of FIG. 2, the two surface layers 11 and 12 are oriented in directions (arrows Y) at angles of θ1 and θ2 with respect to the two surfaces 100A and 100B of the optical film 100, respectively. and the direction indicated by arrow Z), the surface layers 11 and 12 are peeled from the laminated film 20. θ1 and θ2 may be the same or different. The range of θ1 and θ2 is preferably 45° or more, more preferably 55° or more, and preferably 135° or less, and more preferably 125° or less.

The temperature of the peeling process is not particularly limited, but from the viewpoint of transportability, it is preferably 5°C or higher, more preferably 15°C or higher, and from the viewpoint of peelability, it is preferably 60°C or lower, and more preferably 50°C. It is as follows. The peeling temperature can be adjusted by heating the peeling area P of the laminated film with an appropriate heating device.

〔1.4. Other processes (stretching process)]

The method for producing an optical film of the present invention may include a stretching treatment step. The stretching treatment process may be performed in the laminated film production process, may be performed after the laminated film production process and before the peeling process, may be performed in the peeling process, or may be performed after the peeling process.

When performing the stretching treatment step, stretching may be performed in the thickness direction, stretching may be performed in the in-plane direction, or stretching in the in-plane direction may be performed in addition to stretching in the thickness direction. In the method for producing an optical film of the present invention, the stretch ratio when stretching in the in-plane direction in addition to stretching in the thickness direction is performed can be adjusted appropriately in accordance with the desired optical performance required to be provided to the optical film. The specific draw ratio is preferably 1.0 times or more, more preferably 1.05 times or more, while preferably 1.5 times or less, and more preferably 1.4 times or less. When the draw ratio in the in-plane direction is within this range, the desired optical performance can be easily obtained.

The stretching performed in the stretching treatment step can be uniaxial stretching, biaxial stretching, or other stretching. The stretching direction can be set to any direction. For example, when the film before stretching is a long film, the stretching direction may be any of the longitudinal direction of the film, the width direction, or any other oblique direction. When performing biaxial stretching, the angle formed by the two stretching directions can usually be an angle orthogonal to each other, but is not limited to that and can be any angle. Biaxial stretching may be sequential biaxial stretching or simultaneous biaxial stretching.

〔1.5. [Dimensions and characteristics of optical films obtained by the manufacturing method of the present invention]

The optical film obtained by the optical film manufacturing method of the present invention has an absolute value of retardation Re in the in-plane direction of 5 nm or less, an absolute value of retardation Rth in the thickness direction of 10 nm or less, and a water vapor transmission rate of It is less than 20 g/(m ² ·day).

The absolute value of the retardation Re in the in-plane direction of the optical film obtained by the production method of the present invention is preferably 3 nm or less, more preferably 2 nm or less, and ideally 0 nm.

The absolute value of the retardation Rth in the thickness direction of the optical film obtained by the production method of the present invention is preferably 3 nm or less, more preferably 2 nm or less, and ideally 0 nm.

The water vapor transmission rate of the optical film obtained by the production method of the present invention is preferably 18 g/(m ² ·day) or less, more preferably 15 g/(m ² ·day) or less. On the other hand, the lower limit is ideally 0 g/(m ² ·day), but can be set to 1 g/(m ² ·day) or more, for example.

The thickness of the optical film obtained by the production method of the present invention is preferably 20 μm or more, more preferably 25 μm or more, preferably 70 μm or less, and more preferably 80 μm or less.

The retardation in the in-plane direction and the retardation in the thickness direction of the optical film obtained by the manufacturing method of the present invention can be measured at a measurement wavelength of 590 nm using “AxoScan” manufactured by AXOMETRICS as a measuring device. When using the above measuring device, the retardation in the in-plane direction and thickness direction of the optical film is calculated using the average refractive index of the optical film. Here, the average refractive index refers to the average value of the refractive index in two directions perpendicular to each other as the in-plane direction of the optical film and the refractive index in the thickness direction of the optical film.

The water vapor transmission rate of the optical film obtained by the production method of the present invention is measured according to JIS K 7129 B method using a water vapor transmission rate measuring device (“PERMATRAN-W” manufactured by MOCON) at, for example, a temperature of 40°C and a humidity of 90%. It can be measured under the condition of %RH.

The thickness of the optical film obtained by the manufacturing method of the present invention can be measured by microscopic observation similar to the thickness of each layer. Specifically, it can be performed by slicing the optical film using a microtome and observing the cut surface with, for example, a polarizing microscope (for example, "BX51" manufactured by Olympus Corporation).

The optical film obtained by the method for producing an optical film of the present invention is an optical film obtained by peeling the surface layer from a laminated film having a core layer made of resin A and a surface layer made of resin B, and has a retardation Re in the in-plane direction. By setting the absolute value of and the absolute value of the retardation Rth in the thickness direction to 2 nm or less, and the water vapor permeability to 20 g/(m ² ·day) or less, adhesion to the object is high and retardation is small. , it is also possible to obtain an optical film with low water vapor transmission rate. As a result, according to the present invention, an optical film that can be usefully used as a polarizer protective film can be obtained.

The optical film obtained by the optical film manufacturing method of the present invention is usually a transparent layer and transmits visible light. The specific light transmittance can be appropriately selected depending on the purpose of the optical film. For example, the light transmittance in the wavelength range of 420 nm to 780 nm is preferably 85% or more, and more preferably 88% or more. By constructing a structure having such a high light transmittance, when the optical film is mounted on a display device such as a liquid crystal display device, a decrease in luminance can be suppressed, especially during long-term use.

〔2. Optical film of the present invention]

In any other aspect of the present invention, the optical film has a block [Da] having a cyclic hydrocarbon group-containing compound unit, a chain hydrocarbon compound unit, or a chain hydrocarbon compound unit and a cyclic hydrocarbon group-containing compound unit. Includes block copolymers containing block [Ea]. The cyclic hydrocarbon group-containing compound unit and the chain hydrocarbon compound unit may or may not have an unsaturated bond, and are not limited by the production method. Therefore, for example, it may be a unit formed by hydrogenating a unit having an unsaturated bond, or it may be a unit that is not hydrogenated and has an unsaturated bond. When the optical film contains such a block copolymer, an optical film with a low retardation can be obtained, and therefore, the optical film of the present invention can be used as a member requiring a low retardation. Additionally, an optical film with high light resistance and resistance to yellowing can be obtained.

Preferred examples of the block copolymer include, as a block [Da], two or more polymer blocks [Db] having cyclic hydrocarbon group-containing compound hydride units per molecule, and as a block [Ea], a chain hydrocarbon Examples include copolymers containing at least one polymer block [Eb] per molecule having a compound hydride unit, a chain hydrocarbon compound or its hydride unit, and a cyclic hydrocarbon-containing compound or its hydride unit.

Specific examples of the material constituting the optical film of the present invention include the above-mentioned resin A. In addition, examples of the block copolymer contained therein include the same examples as those of the above-mentioned hydrogenated block copolymer [G]. In addition, examples of blocks [Da] and [Ea] constituting the block copolymer, and examples of blocks [Db] and [Eb], which are specific examples thereof, are the same as the examples of blocks [D] and [E] described above. I can hear it. Examples of units constituting blocks [Da] and blocks [Ea] include the same examples as examples of units constituting blocks [D] and [E]; and aromatic vinyl compound units and chain-type conjugated diene compound units. An aromatic vinyl compound unit is a structural unit having a structure obtained by polymerizing an aromatic vinyl compound, and a chain-shaped conjugated diene compound unit is a structural unit having a structure obtained by polymerizing a chain-shaped conjugated diene compound. However, these are not limited by the manufacturing method. Examples of aromatic vinyl compounds and chain-type conjugated diene compounds mentioned herein include the same ones as mentioned above.

Examples of block copolymers other than hydrogenated block copolymer [G] include aromatic vinyl compound/conjugated diene compound block copolymers as precursors of hydrides, which are described in International Publication No. WO2016/152871. there is.

In the block copolymer constituting the optical film of the present invention, the difference in composition ratio between the volume of the block [Da] and the volume of the block [Ea] between the surface and the central portion is 0 to 10%. The difference in composition ratio is preferably 8% or less, more preferably 5% or less.

The “center portion” referred to here is the central portion in the thickness direction of the film. However, in the case of a film manufactured by the optical film manufacturing method of the present invention described above, the position at a depth of about 5 μm in the thickness direction usually has a composition ratio equivalent to the central portion in the thickness direction. Therefore, when the thickness of the optical film exceeds 10 μm, the value obtained by observing the composition at a depth of about 5 μm in the thickness direction can be changed to the value of the composition ratio in the central portion.

The composition ratio of the volume of the block [Da] and the volume of the block [Ea] can be determined by observing the cross section of the optical film. That is, since the area ratio of the cross section is usually proportional to the volume ratio, the volume ratio can be obtained by measuring the area ratio of the surface and the cross section. Specifically, on the surface and cross section of the optical film, the area of the phase originating from each block is determined, and the ratio of these areas is determined to obtain the composition ratio of the block [Da] and the block [Ea]. You can.

The area of each phase can be measured using an atomic force microscope (for example, an atomic force microscope Dimension Fast Scan Icon manufactured by Bruker). Using an atomic force microscope, an image of the adhesion force of the optical film can be obtained, and the area ratio of the phase originating from each block in the image can be measured. Additionally, from information about the adhesive force of the observed phase, the observed phase can be attributed to the phase of the block [Da] and the phase of the block [Ea].

By setting the sum of the areas of the two types of phases to 100% and calculating the percentage of the area of the phase belonging to the block [Da], the block [Da] ratio in each of the surface and central products can be calculated. The difference in composition ratio between the volume of the block [D] and the volume of the block [E] at the surface and the center can be calculated using the following equation.

Difference in composition ratio = |(Block[D] ratio in the center) - (Block[D] ratio on the surface)|

The value of (block [D] ratio of central part) - (block [D] ratio of surface) may be positive or negative.

The optical film of the present invention can be manufactured by extrusion film forming of a resin containing a block copolymer. By performing extrusion film forming, efficient manufacturing becomes possible. However, according to what the present inventor found, when extrusion film forming is performed, the difference in composition ratio between the volume of the block [D] and the volume of the block [E] at the surface and the center increases. Here, the above [1. By employing the manufacturing method described in [Method for manufacturing an optical film of the present invention], a film with a small difference in such composition ratios can be easily obtained.

The dimensions and characteristics of the optical film of the present invention are [1.5. Dimensions and characteristics of optical films obtained by the manufacturing method of the present invention].

〔3. Polarizer and its manufacturing method]

Above [1. An optical film obtained by the manufacturing method described in [Method for producing an optical film of the present invention], and the above [2. The optical film of the present invention (hereinafter simply referred to as “the optical film of the present invention”) described in “Optical film of the present invention” is used as a protective film that protects other layers in a display device such as a liquid crystal display device. It can be used conveniently. Among them, the optical film of the present invention is suitable as a polarizer protective film and is particularly suitable as an inner polarizer protective film of a display device.

The polarizing plate of the present invention includes the optical film and polarizer of the present invention described above. In the present invention, the optical film can function as a polarizer protective film. The polarizing plate of the present invention may further include an adhesive layer between the optical film and the polarizer for adhering them together.

The polarizing plate of the present invention may be provided with an arbitrary layer in addition to the optical film and polarizer. Optional layers include a hard coat layer that increases surface hardness, a mat layer that improves the slipperiness of the film, and an anti-reflection layer.

The polarizer is not particularly limited, and any polarizer can be used. Examples of polarizers include those that adsorb materials such as iodine and dichroic dye to a polyvinyl alcohol film, and then carry out stretching processing. Adhesives constituting the adhesive layer include those using various polymers as base polymers. Examples of such base polymers include, for example, acrylic polymers, silicone polymers, polyesters, polyurethanes, polyethers, and synthetic rubbers.

Although the number of polarizers and protective films provided in the polarizing plate is arbitrary, in the present invention, it can usually be provided with one layer of polarizer and two layers of protective films provided on both sides. Among these two layers of protective films, both may be the optical films of the present invention, and only one may be the optical film of the present invention. In particular, in a liquid crystal display device comprising a light source and a liquid crystal cell and having a polarizing plate on both the light source side and the display surface side of the liquid crystal cell, the present invention is a protective film used at a position on the light source side rather than the polarizer on the display surface side, comprising: It is particularly desirable to provide an optical film. By having this configuration, it is possible to easily construct a liquid crystal display device with excellent durability and good display quality with little color unevenness.

The polarizing plate of the present invention can be manufactured by any manufacturing method. For example, the polarizing plate of the present invention can be manufactured by bonding the optical film obtained by the above manufacturing method and the polarizer. This bonding can be done by bonding these layers in direct contact, or bonding through an adhesive layer.

〔4. Liquid crystal display device and manufacturing method thereof]

The liquid crystal display device of the present invention includes the polarizing plate of the present invention.

Liquid crystal display devices suitable for installing the polarizer of the present invention include, for example, in-plane switching (IPS) mode, vertical alignment (VA) mode, multi-domain vertical alignment (MVA) mode, and continuous pinwheel alignment (CPA). A liquid crystal display device having a liquid crystal cell in a driving mode such as hybrid alignment nematic (HAN) mode, twisted nematic (TN) mode, super twisted nematic (STN) mode, and optical compensated bend (OCB) mode. can be mentioned. Among these, a liquid crystal display device provided with an IPS mode liquid crystal cell is particularly preferable because the optical film of the present invention has excellent durability and a remarkable effect of suppressing color unevenness.

The liquid crystal display device of the present invention can be manufactured by any manufacturing method. For example, the liquid crystal display device of the present invention can be manufactured by combining the polarizing plate obtained by the above manufacturing method with other members constituting the liquid crystal display device, such as a liquid crystal cell. For example, a liquid crystal display device can be manufactured by bonding a liquid crystal cell and a polarizing plate directly or through an adhesive layer, and installing this in a display device. Alternatively, a liquid crystal display device can be manufactured by simply overlapping the liquid crystal cell and the polarizing plate and installing them in the display device.

[Example]

Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited to the examples shown below, and may be implemented with any modification without departing from the scope of the claims and equivalents of the present invention.

In the following description, “%” and “part” indicating amounts are based on weight, unless otherwise specified. In addition, the operations described below were performed under conditions of room temperature and pressure, unless otherwise specified.

A specific example that can be used as a specific example of the block [D] in the above description or a specific example of the block [Da] in the above description is simply referred to as “block [D]” in the following description. It is said that In addition, specific examples that can be used as specific examples of the block [E] in the above description or as specific examples of the block [Ea] in the above description are simply referred to as “block [E]” in the following description. ]”.

〔Assessment Methods〕

[Method for measuring weight average molecular weight and number average molecular weight]

The weight average molecular weight and number average molecular weight of the polymer were measured as polystyrene conversion values using a gel permeation chromatography (GPC) system (“HLC-8320” manufactured by Tosoh Corporation). During the measurement, an H type column (manufactured by Tosoh Corporation) was used as the column, and cyclohexane was used as the solvent. Additionally, the temperature at the time of measurement was 40°C.

[Method for measuring hydrogenation rate of hydrogenated block copolymer [G]]

The hydrogenation rate of the polymer was calculated by ¹ H-NMR measurement at 145°C using orthodichlorobenzene-d ₄ as a solvent.

[Glass transition temperature of resin A]

Resin A (resin [G1] containing a hydrogenated block copolymer, etc.) was press-molded to produce a test piece with a length of 50 mm, a width of 10 mm, and a thickness of 1 mm. Using this test piece, and based on the JIS-K7244-4 method, using a viscoelasticity measuring device (product name "ARES", manufactured by TA Instrument Japan), in the range of -100°C to +150°C, Dynamic viscoelastic properties were measured at a temperature increase rate of 5°C/min. The glass transition temperature Tg ₂ was calculated from the peak top temperature of the loss tangent tan δ (the peak temperature on the high temperature side when multiple peaks are observed).

[Thermal softening temperature of resin B]

Based on JIS K 7121, using a differential scanning calorimeter (manufactured by Nanotechnology, product name "DSC6220S11"), resin B was heated to a temperature at least 30°C higher than the glass transition temperature, and then cooled at a cooling rate of -10°C/min. It was cooled to room temperature, and then the temperature was raised at a temperature increase rate of 10°C/min, and the heat softening temperature was measured thereby.

[Method for measuring the thickness of each layer and the thickness of the optical film]

The thickness of each layer and the thickness of the optical film were measured as follows.

The film to be measured was sliced using a microtome (“RV-240” manufactured by Yamato Koki Co., Ltd.). The cut surface of the sliced film was observed with a polarizing microscope (“BX51” manufactured by Olympus Corporation), and its thickness was measured.

[Method for measuring heat softening temperature Ts]

The film to be measured was cut into a shape of 5 mm x 20 mm and used as a sample. As a measuring device, TMA/SS7100 (manufactured by SI Nano Technology Co., Ltd.) was used. In the thermomechanical analysis (TMA) measurement, the temperature was changed while a tension of 50 mN was applied in the longitudinal direction of the sample. The temperature (°C) when the linear expansion changed by 3% was taken as the softening temperature.

[Method of measuring retardation in the in-plane direction and retardation in the thickness direction]

The absolute value and thickness of the retardation Re in the in-plane direction of the film of each example (Examples and Comparative Examples) were measured using a phase difference measuring device (product name "Axoscan" manufactured by Axometric) at a wavelength of 590 nm. The absolute value of the direction retardation Rth was obtained.

[Method for measuring peel strength]

As a film instead of a polarizing plate, a test film (glass transition temperature 160°C, thickness 100 μm, manufactured by Nippon Zeon Co., Ltd., unstretched) made of a resin containing a norbornene-based polymer was prepared. Corona treatment was performed on one side of the film obtained in each example and the test film. An adhesive was attached to the corona-treated side of the film of each example and the corona-treated side of the test film, and the sides to which the adhesive had been attached were bonded together. At this time, UV adhesive (CRB series (manufactured by Toyochem) was used as the adhesive. As a result, a sample film (S) including the film 100 and the test film 60 for each example was obtained (see Figure 3). .

Thereafter, as shown in FIG. 3, the sample film S was cut to a width of 15 mm, and the film 100 side of each example was bonded to the surface of the slide glass 80 with an adhesive 70 to form an evaluation sample. got it At this time, as the adhesive 70, a double-sided adhesive tape (manufactured by Nitto Denko, product number “CS9621”) was used. In Figure 3, 50 is an adhesive.

A 90-degree peeling test was performed by placing the test film 60 between the ends of the force gauge and pulling it in the direction normal to the surface of the slide glass 80 (the direction indicated by the arrow (X) in FIG. 3). At this time, the force measured when the test film 60 is peeled off is the force required to peel the film 100 and the test film 60 of each example (Example and Comparative Example), so the force of this force is Size was measured as peel strength. In cases where the force required for peeling was so large that the material was destroyed before the test film was peeled off, it was described as “Measurement not possible due to destruction of the material.”

(Supplement to the measurement method of peel strength)

In the above-mentioned peel strength measuring method, a specific test film is used instead of a polarizing plate. In this way, in order to verify the validity of measuring peel strength using a test film instead of a polarizing plate, the inventor performed the following experiment on the film obtained in Example 1.

Instead of the test film, according to Example 1 of Japanese Patent Application Laid-Open No. 2005-70140, a retardation film laminate is bonded to the surface of one side of the polarizing film, and a triacetylcellulose film is bonded to the surface of the other side of the polarizing film, A 90 degree peel test was performed. That is, first, the polarizing film and adhesive described in Example 1 of Japanese Patent Application Publication No. 2005-70140 were prepared. The corona-treated side of the retardation film laminate was bonded to the surface of one side of the prepared polarizing film through the adhesive described above. Additionally, a triacetylcellulose film was bonded to the surface of the other side of the polarizing film through the adhesive described above. Afterwards, the adhesive was cured by drying at 80°C for 7 minutes to obtain a sample film. A 90 degree peeling test was performed on the obtained sample film.

As a result of the above experiment, the same results were obtained as when a test film was used instead of a polarizing plate. Therefore, the results of the following examples and comparative examples using a test film instead of a polarizing plate are valid.

(Measurement of water vapor transmission rate)

The water vapor transmission rate of the optical film was measured using a water vapor transmission rate measurement device (“PERMATRAN-W” manufactured by MOCON) under the conditions of a temperature of 40°C and a humidity of 90%RH according to the JIS K 7129 B method.

(Measurement of total light transmittance)

The total light transmittance of the optical film was measured in accordance with JIS K 7136 using a haze meter NDH-2000 (manufactured by Nippon Denshoku Industries).

(Measurement of block composition ratio)

To measure the block composition ratio in an optical film, use an atomic force microscope Dimension Fast Scan Icon manufactured by Bruker, obtain an image of the adhesion force of the optical film, and measure the area ratio of the phase originating from each block in the image. This was done by measuring.

As a cantilever for capturing adhesive force images, AC240TS (manufactured by Olympus, spring constant: 1.5 N/m, TIP curvature radius 15 nm) was used. The measurement mode for imaging was ScanAsyst mode, the scan rate was 2 Hz, and adhesion images were measured in an area of 500 nm × 500 nm.

Measurements of the adhesion force images were performed on the film surface and central portion. The measurement of the central portion of the film was performed after forming a cross section of the film, at a position of 5 μm in depth from the film surface in the cross section.

The image of the measurement result of the adhesive force image was analyzed, and a histogram was drawn. In the histogram, the adhesive force measured at each measurement point is taken on the horizontal axis, and the number of measurement points at which the adhesive force was measured is taken on the vertical axis. The area ratio of the two types of phases, which are believed to originate from the two types of blocks, was calculated by fitting a Gaussian function.

In general, adhesion depends on Tg, and it is known that separating the cantilever from the sample surface with a low Tg increases the adhesion. For this reason, it can be determined that the attribute with high adhesion is block [E], and the attribute with low adhesion is block [D].

The area ratio was calculated by taking the sum of the areas of the two types of phases as 100%, and calculating the percentage of the area of the phase belonging to the block [D] as the block [D] ratio.

The difference in composition ratio between block [D] and block [E] at the surface and central portion was calculated using the following equation.

Difference in composition ratio = |(Block[D] ratio in the center) - (Block[D] ratio on the surface)|

[Production Example 1]

(P1-1) Preparation of block copolymer [F1]

270 parts of dehydrated cyclohexane, 75 parts of dehydrated styrene, and 7.0 parts of dibutyl ether were placed in a reactor equipped with a stirring device and the interior of which was sufficiently purged with nitrogen. While stirring the whole at 60°C, 5.6 parts of n-butyllithium (15% cyclohexane solution) was added to initiate polymerization. The whole was then stirred at 60°C for 60 minutes. The reaction temperature was maintained at 60°C until the reaction was stopped. At this point (first stage of polymerization), the reaction solution was analyzed by gas chromatography (hereinafter sometimes referred to as “GC”) and GPC, and the polymerization conversion rate was 99.4%.

Next, 15 parts of dehydrated isoprene was continuously added to the reaction solution over 40 minutes, and stirring was continued for 30 minutes after the addition was completed. At this point (second stage of polymerization), the reaction solution was analyzed by GC and GPC, and the polymerization conversion rate was 99.8%.

After that, 10 parts of dehydrated styrene was continuously added to the reaction solution over 30 minutes, and the mixture was stirred for 30 minutes after the addition was completed. At this point (third stage of polymerization), the reaction solution was analyzed by GC and GPC, and the polymerization conversion rate was approximately 100%.

Here, 1.0 parts of isopropyl alcohol was added to stop the reaction, thereby obtaining a polymer solution containing the [D1]-[E]-[D2] type block copolymer [F1]. In the obtained block copolymer [F1], Mw[F1] = 82,400 and Mw/Mn was 1.32.

(P1-2) Preparation of hydrogenated block copolymer [G1]

The polymer solution obtained in (P1-1) was transferred to a pressure-resistant reactor equipped with a stirring device, and as a hydrogenation catalyst, 4.0 parts of a diatomaceous earth-supported nickel catalyst (product name "E22U", nickel supported amount 60%, manufactured by Nikki Catalyst Chemical Company) was used as a hydrogenation catalyst. , and 30 parts of dehydrated cyclohexane were added and mixed. The inside of the reactor was replaced with hydrogen gas, hydrogen was supplied while stirring the solution, and a hydrogenation reaction was performed at a temperature of 190°C and a pressure of 4.5 MPa for 6 hours.

The reaction solution obtained by the hydrogenation reaction contained hydrogenated block copolymer [G1]. The Mw[G1] of the hydrogenated block copolymer was 71,800, the molecular weight distribution Mw/Mn was 1.30, and the hydrogenation rate was approximately 100%.

After completion of the hydrogenation reaction, the reaction solution was filtered to remove the hydrogenation catalyst, and then the phenolic antioxidant pentaerythrityl tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propio Nate] (product name “AO60”, manufactured by ADEKA) was dissolved by adding 2.0 parts of xylene solution in which 0.3 parts were dissolved to obtain a solution.

Next, the solution was treated at a temperature of 260°C and a pressure of 0.001 MPa or less using a cylindrical concentration dryer (product name “Contro”, manufactured by Hitachi Ltd.) to remove cyclohexane, xylene, and other volatile components from the solution. Thus, molten resin was obtained. This was extruded from a die into a strand shape, cooled, and formed into pellets using a pelletizer. In this way, 95 parts of pellets of resin [G1] containing hydrogenated block copolymer [G1] were produced.

The hydrogenated block copolymer [G1] in the obtained resin [G1] was Mw[G1] = 68,500, Mw/Mn = 1.30, Tg ₂ = 140°C, Ts = 139°C, (D1 + D2)/E = 85. /15, D1/D2 = 7.5.

[Production Example 2]

(P2-1) Preparation of block copolymer [F2]

270 parts of dehydrated cyclohexane, 70 parts of dehydrated styrene, and 7.0 parts of dibutyl ether were placed in a reactor equipped with a stirring device and the interior of which was sufficiently purged with nitrogen. While stirring the whole at 60°C, 5.6 parts of n-butyllithium (15% cyclohexane solution) was added to initiate polymerization. The whole was then stirred at 60°C for 60 minutes. The reaction temperature was maintained at 60°C until the reaction was stopped. At this point (first stage of polymerization), the reaction solution was analyzed by GC and GPC, and the polymerization conversion rate was 99.4%.

Next, 20 parts of dehydrated isoprene was continuously added to the reaction solution over 40 minutes, and stirring was continued for 30 minutes after the addition was completed. At this point (second stage of polymerization), the reaction solution was analyzed by GC and GPC, and the polymerization conversion rate was 99.8%.

After that, 10 parts of dehydrated styrene was continuously added to the reaction solution over 30 minutes, and the mixture was stirred for 30 minutes after the addition was completed. At this point (third stage of polymerization), the reaction solution was analyzed by GC and GPC, and the polymerization conversion rate was approximately 100%.

Here, 1.0 parts of isopropyl alcohol was added to stop the reaction, thereby obtaining a polymer solution containing the [D1]-[E]-[D2] type block copolymer [F2]. In the obtained block copolymer [F2], Mw[F2] = 83,400 and Mw/Mn was 1.32.

(P2-2) Preparation of hydrogenated block copolymer [G2]

The polymer solution obtained in (P2-1) was transferred to a pressure-resistant reactor equipped with a stirring device, and as a hydrogenation catalyst, 4.0 parts of a diatomaceous earth-supported nickel catalyst (product name "E22U", nickel supported amount 60%, manufactured by Nikki Catalyst Chemical Company) was used as a hydrogenation catalyst. , and 30 parts of dehydrated cyclohexane were added and mixed. The inside of the reactor was replaced with hydrogen gas, hydrogen was supplied while stirring the solution, and a hydrogenation reaction was performed at a temperature of 190°C and a pressure of 4.5 MPa for 6 hours.

The reaction solution obtained by the hydrogenation reaction contained hydrogenated block copolymer [G2]. The Mw[G2] of the hydrogenated block copolymer [G2] was 72,800, the molecular weight distribution Mw/Mn was 1.30, and the hydrogenation rate was approximately 100%.

After completion of the hydrogenation reaction, the reaction solution was filtered to remove the hydrogenation catalyst, and then the phenolic antioxidant pentaerythrityl tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propio Nate] (product name “AO60”, manufactured by ADEKA) was dissolved by adding 2.0 parts of xylene solution in which 0.3 parts were dissolved to obtain a solution.

Next, the solution was treated at a temperature of 260°C and a pressure of 0.001 MPa or less using a cylindrical concentration dryer (product name “Contro”, manufactured by Hitachi Ltd.) to remove cyclohexane, xylene, and other volatile components from the solution. Thus, molten resin was obtained. This was extruded from a die into a strand shape, cooled, and formed into pellets using a pelletizer. In this way, 95 parts of pellets of resin [G2] containing hydrogenated block copolymer [G2] were produced.

The hydrogenated block copolymer [G2] in the obtained resin [G2] was Mw[G2] = 69,500, Mw/Mn = 1.30, Tg ₂ = 140°C, Ts = 138°C, (D1 + D2)/E = 80. /20, D1/D2 = 7.0.

[Example 1]

(1-1. Manufacturing of optical film)

A double-flight type single-screw extruder (screw diameter D = 50 mm, ratio L/D of the screw length L and screw diameter D = 28) equipped with a leaf disk-shaped polymer filter with a sieve diameter of 3 μm was prepared. The pellet-shaped resin [G1] obtained in Production Example 1 as thermoplastic resin A was introduced into this single-screw extruder, melted, and supplied to a single-layer die through a feed block. Resin A was introduced into the single-screw extruder through a hopper loaded in the single-screw extruder. Additionally, the surface roughness (arithmetic average roughness Ra) of the die lip of the above-described single-layer die was 0.1 μm. Additionally, the extruder outlet temperature of Resin A was 260°C.

Meanwhile, one single-screw extruder (screw diameter D = 50 mm, ratio L/D of the screw length L and screw diameter D = 30) equipped with a leaf disk-shaped polymer filter with a sieve size of 3 μm was prepared. Into this single-screw extruder, resin B (referred to as resin "B-1", manufactured by Nippon Zeon Co., Ltd., heat softening temperature 160°C) containing an amorphous alicyclic structure-containing polymer as thermoplastic resin B is introduced and dissolved. The above single-layer die was fed through a feed block. The extruder outlet temperature of Resin B was 260°C.

Resin A and Resin B were discharged from a single-layer die of an extrusion molding machine in a molten state at 260°C. As a result, a film-like resin was continuously formed including three layers in this order: a surface layer made of resin B, a core layer made of resin A, and a surface layer made of resin B (co-extrusion molding process). The discharged film-like resin was cast on a cooling roll. At the time of casting, edge peening was performed to fix the width direction end portion of the film-like resin to a cooling roll, and the air gap amount was set to 50 mm. In this way, the film-like resin was cooled, and a laminated film with a three-layer structure was obtained. The obtained laminated film was a three-layer laminated film made of two types of resins, including a surface layer made of resin B, a core layer made of resin A, and a surface layer made of resin B in this order.

(1-2. Manufacturing and evaluation of optical films)

A peeling process was performed to peel the surface layer from the 3-layer structure laminated film obtained in (1-1). The peeling process was performed by pulling the surface layers on both sides of the laminated film and continuously peeling the surface layers from the core layer. The direction in which the surface layer of the second layer was pulled was at an angle of 60° with respect to the surface of the core layer, and the peeling speed was 5 m/min. As a result, a single-layer film 1 with a peeled surface layer and a thickness of 40 μm was obtained.

The obtained film 1 was evaluated, and the results are shown in Table 1. In evaluating the peel strength, the peel strength could not be measured because material destruction occurred before peeling of the test film. This means that the peel strength is high.

[Example 2]

A laminated film was produced in the same manner as in Example 1, except that the pellet-shaped resin [G2] obtained in Production Example 2 was used instead of the pellet-shaped resin [G1] obtained in Production Example 1, and then the surface layer was peeled to obtain a thickness. A monolayer film 2 with a thickness of 40 μm was obtained. The obtained film 2 was evaluated in the same manner as in Example 1, and the results are shown in Table 1. In evaluating the peel strength, the peel strength could not be measured because material destruction occurred before peeling of the test film. This means that the peel strength is high.

[Comparative Example 1]

A double-flight type single-screw extruder (screw diameter D = 50 mm, ratio L/D of the screw length L and screw diameter D = 28) equipped with a leaf disk-shaped polymer filter with a sieve diameter of 3 μm was prepared. The pellet-shaped resin [G1] obtained in Production Example 1 was introduced into this single-screw extruder, melted, and supplied to a single-layer die. Resin [G1] was introduced into the single-screw extruder through a hopper loaded in the single-screw extruder. Additionally, the surface roughness (arithmetic average roughness Ra) of the die lip of the above-described single-layer die was 0.1 μm. Additionally, the extruder outlet temperature of resin [G1] was 260°C.

Resin [G1] was discharged from a single-layer die in a molten state at 260°C. As a result, a film-like resin consisting only of a layer made of resin [G1] was continuously formed. The discharged film-like resin was cast on a cooling roll. At the time of casting, edge peening was performed to fix the width direction end portion of the film-like resin to a cooling roll, and the air gap amount was set to 50 mm. In this way, the film-like resin was cooled, and film C1 with a single-layer structure made of resin [G1] and having a thickness of 40 μm was obtained. The obtained resin film C1 was evaluated in the same manner as the film in Example 1, and the results are shown in Table 1.

[Comparative Example 2]

Thickness of a single-layer structure made of resin [G2] by the same operation as Comparative Example 1, except that instead of the pellet-shaped resin [G1] obtained in Production Example 1, the pellet-shaped resin [G2] obtained in Production Example 2 was used. Film C2 with a thickness of 40 μm was prepared. This film C2 was evaluated in the same manner as the film in Example 1, and the results are shown in Table 1.

[Comparative Example 3]

Optical film E (Fuji Film Co., Ltd., "Fujitac", thickness 40 μm) was evaluated in the same manner as the film in Example 1, and the results are shown in Table 1. For the measurement of peel strength, a film subjected to saponification treatment was used.

The results of the examples and comparative examples are summarized in Table 1.

The meanings of the symbols in the table are as follows.

G1: Hydrogenated block copolymer [G1] prepared in Preparation Example 1.

G2: Hydrogenated block copolymer [G2] prepared in Preparation Example 2.

B-1: Resin containing an alicyclic structure-containing polymer, heat softening temperature of 160°C, one of the “ZEONOR” product lines manufactured by Nippon Zeon Corporation.

E: Optical film, “Fujitag” manufactured by Fuji Film Co., Ltd.

|Re|: Absolute value of retardation in in-plane direction

|Rth|: Absolute value of retardation in the thickness direction

As is clear from the results of the examples and comparative examples, the film obtained by the method for producing an optical film of the present invention can be an optical film with high adhesion to an object, small retardation, and low water vapor transmission rate.

10···Core layer
11, 12···Surface layer
12···Surface layer
20···Laminated film
50···UV adhesive
60···Test film
70···Adhesive
80···slide glass
100···Optical film
100A, 100B...side of optical film
M···Extrusion Molding Machine
P···Peeling area
S···Sample film

Claims (10)

A block [Da] having a cyclic hydrocarbon group-containing compound unit,
A block having a chain hydrocarbon compound unit, or a chain hydrocarbon compound unit and a cyclic hydrocarbon group-containing compound unit [Ea]
Contains a block copolymer containing,
The block copolymer includes a triblock copolymer,
wherein the triblock copolymer has a chain hydrocarbon compound hydride unit, or a chain hydrocarbon compound hydride unit and a cyclic hydrocarbon-containing compound hydride unit, one block [E] per molecule; One block [D1] per molecule, which is connected to one end of the block [E] and has a cyclic hydrocarbon group-containing compound hydride unit; It is connected to the other end of the block [E] and has a cyclic hydrocarbon group-containing compound hydride unit, one block [D2] per molecule,
The weight ratio D1/D2 of the block [D1] and the block [D2] is 5 or more and 8 or less,
The weight ratio (D1+D2)/E of the sum of the block [D1] and the block [D2] and the block [E] is 70/30 or more and 80/20 or less,
The difference between the composition ratio of the volume of the block [Da] and the volume of the block [Ea] at the surface and the center is 0 to 10%,
The absolute value of retardation in the in-plane direction is 2 nm or less,
The absolute value of retardation in the thickness direction is 10 nm or less, and
An optical film having a water vapor transmission rate of 20 g/(m ² ·day) or less. According to paragraph 1,
An optical film formed by extrusion film formation of a resin containing the block copolymer. A polarizing plate comprising the optical film according to claim 1 or 2 and a polarizer. A liquid crystal display device comprising the polarizing plate according to claim 3. A method for producing the optical film according to claim 1, comprising:
A step of co-extruding resin A and resin B to obtain a laminated film having a core layer made of resin A and a surface layer made of resin B formed on the surface of the core layer;
Comprising a step of peeling the surface layer from the laminated film,
When the higher temperature of the heat softening temperature of resin A and the heat softening temperature of resin B is (Ts[H]), the extrusion temperature of coextrusion is (Ts[H] + 70)°C or higher, (Ts [H] + 180) ℃ or less,
The optical film is,
The absolute value of retardation in the in-plane direction is 2 nm or less,
The absolute value of retardation in the thickness direction is 10 nm or less, and
A method for producing an optical film having a water vapor transmission rate of 20 g/(m ² ·day) or less. According to clause 5,
A method for producing an optical film, wherein the absolute value of the retardation in the in-plane direction of the optical film is 2 nm or less, and the absolute value of the retardation in the thickness direction of the optical film is 2 nm or less. According to claim 5 or 6,
A method for producing an optical film, wherein the resin B contains an alicyclic structure-containing polymer. According to claim 5 or 6,
The resin A is,
Two or more polymer blocks [D] per molecule having a cyclic hydrocarbon group-containing compound hydride unit,
At least one polymer block per molecule having chain hydrocarbon compound hydride units, or chain hydrocarbon compound units and cyclic hydrocarbon-containing compound hydride units [E]
A method for producing an optical film comprising a hydrogenated block copolymer comprising a. According to claim 5 or 6,
The resin A is,
A block having a compound unit containing a cyclic hydrocarbon group,
A block having a chain hydrocarbon compound unit, or a chain hydrocarbon compound unit and a cyclic hydrocarbon group-containing compound unit.
It is made of a block copolymer containing,
In the optical film, the difference in composition ratio between the surface and the central portion is 0 to 10%,
Method for manufacturing optical films. delete