TW201837072A - Optical film, method for producing same, polarizing plate and liquid crystal display device - Google Patents

Abstract

Provided is a method for producing an optical film, which comprises: a step wherein a multilayer film, which comprises a core layer that is formed from a resin A and a surface layer that is formed from a resin B and is arranged on a surface of the core layer, is obtained by co-extruding the resin A and the resin B; and a step wherein the surface layer is separated from the multilayer film. Also provided is an optical film which contains a specific block copolymer. The optical film has an absolute value of the retardation in the in-plane direction of 5 nm or less, an absolute value of the retardation in the thickness direction of 10 nm or less, and a water vapor transmission rate of 20 g/(m2·day) or less.

Description

Optical film, manufacturing method thereof, polarizing plate and liquid crystal display device

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

A polarizing plate provided in a liquid crystal display device usually includes a polarizer and a protective film for protecting the polarizer. In a polarizing plate protective film, a small retardation and a low water vapor transmission rate are required in most cases. From such a viewpoint, a polarizer protective film with a small retardation has been proposed (see Patent Document 1). In addition, the polarizing plate is required to exhibit durability in the environment at the time of manufacture and use of the display device. For example, the protective film of a polarizing plate sometimes requires a high peeling strength during secondary processing during the manufacturing of a display device, and when the polarizer shrinks during use of the display device.

"Patent Literature" "Patent Literature 1" Japanese Patent Publication No. 2011-013378

The polarizer protective film proposed in Patent Document 1 is obtained by 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 such a polarizer protective film, the retardation in the in-plane direction can be reduced. However, if the polarizer protective film is used, the peeling strength of the protective film of the polarizer may be insufficient. This is because the intermolecular entanglement is reduced due to the alignment of the polymer molecules contained in the polarizer protective film. Agglutination near the surface.

Therefore, an object of the present invention is to provide an optical film with high adhesion to a polarizer, a small delay, and a low water vapor transmission rate; a method for manufacturing an optical film capable of easily obtaining such an optical film; and an optical film including the same A polarizing plate and a liquid crystal display device having the aforementioned performance.

As a result of studying the problems of the conventional polarizer protective film described above, it is thought that the reason is that in the step of forming the protective film by the melt extrusion method, a strong alignment layer was formed on the surface of the protective film.

Here, the present inventors conducted intensive studies in order to solve the above problems. As a result, the inventors have found that a stacked film having a core layer and a surface layer provided on the surface is produced by coextrusion of resin A and resin B, and the surface layer can be removed by peeling from the stacked film to obtain a target layer. An optical film with high adhesiveness, small retardation, and low water vapor transmission rate has completed the present invention.

That is, the present invention is as follows.

[1] An optical film comprising a block copolymer comprising: a block [Da] having a cyclic hydrocarbon group-containing compound unit; and a chain hydrocarbon compound unit or a chain hydrocarbon compound unit and a cyclic hydrocarbon group The block [Ea] of the compound unit, wherein the difference between the composition ratio of the volume of the block [Da] on the surface and the central portion and the volume of the block [Ea] is 0 to 10%, and the retardation in the in-plane direction is The absolute value is 5 nm or less, the absolute value of the retardation in the thickness direction is 10 nm or less, and the water vapor transmission rate is 20 g / (m2.day) or less.

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

[3] The optical film according to [1] or [2], wherein the block copolymer contains two or more polymer blocks per molecule [Db] as the block [Da] and each molecule A copolymer containing one or more polymer blocks [Eb] as the block [Ea], the polymer block [Db] has a cyclic hydrocarbon group-containing compound hydride unit, and the polymer block [Eb] has a chain hydrocarbon compound A hydride unit, or a chain hydrocarbon compound or a hydride unit thereof and a cyclic hydrocarbon compound or a hydride unit thereof.

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

[5] A liquid crystal display device including the polarizing plate according to [4].

[6] A method for manufacturing an optical film, comprising: co-extruding resin A and resin B to obtain a core layer made of resin A and a resin layer B provided on a surface of the core layer. A step of stacking a film on the surface layer; and a step of peeling the surface layer from the stacked film; wherein the absolute value of the retardation in the in-plane direction of the optical film is 5 nm or less, the absolute value of the retardation in the thickness direction is 10 nm or less, and the water The vapor transmission rate is below 20 g / (m ² .day).

[7] The method for producing an 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 includes an alicyclic structure-containing polymer.

[9] The method for producing an optical film according to any one of [6] to [8], wherein the resin A includes a hydrogenated block copolymer, and the hydrogenated block copolymer contains two or more polymerizations per molecule. Polymer block [D] and one or more polymer blocks [E] per molecule, the polymer block [D] has a cyclic hydrocarbon group-containing compound hydride unit, and the polymer block [E] has a chain hydrocarbon compound A hydride unit or a chain hydrocarbon compound unit and a cyclic hydrocarbon compound-containing hydride unit.

[10] The method for producing an optical film according to any one of [6] to [8], wherein the resin A is made of a block copolymer, and the block copolymer includes: A block; and a block having a chain hydrocarbon compound unit or a chain hydrocarbon compound unit and a cyclic hydrocarbon group-containing compound unit, in the optical film, the difference between the composition ratios of the surface and the central portion is 0 to 10%.

The optical film of the present invention can be made into an optical film with high adhesion to an object, small retardation, and low water vapor transmission rate. According to the method for producing an optical film of the present invention, an optical film having high adhesion to a target, a small retardation, and a low water vapor transmission rate can be easily obtained. According to the polarizing plate of the present invention, a polarizing plate having the aforementioned performance can be provided. According to the liquid crystal display device of the present invention, a liquid crystal display device having the aforementioned performance can be provided.

The embodiments and examples are disclosed below to explain the present invention in detail. However, the present invention is not limited to the implementation modes and examples disclosed below, and can be implemented with arbitrary changes without departing from the scope of the patent application of the present invention and its equivalent scope.

In the following description, a cycloalkyl group is a group containing a cyclic structure such as an aromatic ring, a cycloalkane, or a cycloalkene. In addition, a so-called chain hydrocarbon compound is a hydrocarbon compound which does not contain such a cyclic hydrocarbon group.

In the following description, unless otherwise noted, the retardation Re in the in-plane direction of the optical film is a value represented by Re = (nx−ny) × d. In addition, unless otherwise noted, the retardation Rth in the thickness direction of the optical film is a value represented by Rth = [(nx + ny) / 2-nz] × d. Here, nx is a refractive index in a direction (in-plane direction) perpendicular to the thickness direction of the optical film and in a direction giving the maximum refractive index. ny is the refractive index of the optical film in the aforementioned in-plane direction and a direction orthogonal to the direction of nx. nz represents the refractive index in the thickness direction of the optical film. d represents the thickness of the optical film. The retardation measurement wavelength is 590 nm unless otherwise noted.

In the following description, unless otherwise noted, the so-called "polarizing plate" includes not only rigid members but also members having flexibility such as a resin film.

In the following description, the so-called "long-shaped" film refers to a film having a length of 5 times or more with respect to the width, and preferably a length of 10 times or more, and specifically means having a roll Film that is roll-shaped to the extent of storage or transport. The upper limit of the length of the elongated film is not particularly limited, and may be set to, for example, 100,000 times or less with respect to the width.

[1. Manufacturing method of optical film of the present invention]

In a certain aspect of the present invention, the method for manufacturing an optical film includes "the resin A forming the core layer and the resin B forming the surface layer are co-extruded to obtain a core layer made of resin A and a core layer provided on the core layer. Step of stacking film of surface layer made of resin B on the surface (stack film production step) "and" step of peeling surface layer from stack film (peeling step) ".

[1.1. Overview of the manufacturing process of the stacked film]

In the manufacturing process of the stacked film, the resin A used to form the core layer and the resin B used to form the surface layer are co-extruded to obtain a stacked film. Coextrusion is performed using a multi-layer extruder.

In the embodiment shown in FIG. 1, the stacked film 20 is provided with surface layers 11 and 12 on both sides of the core layer 10. Specifically, the stacked film 20 has a layer structure of a surface layer 11 / a core layer 10 / a surface layer 12. The M system shown in Fig. 1 is an extruder. The stacked film may have a surface layer only on one side of the core layer. In this case, the layer structure is a surface layer / core layer. From the viewpoint of suppressing film warpage, the surface layer is preferably located on both sides of the core layer.

[1.1.1. Resin A]

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

The thermoplastic resin forming the core layer (hereinafter also referred to as "thermoplastic resin A") is not particularly limited, and a resin containing various polymers that impart desired physical properties as an optical film may be appropriately selected and used. Preferable examples of the polymer included in the thermoplastic resin A include a polymer block [D] having two or more "having a cyclic hydrocarbon group-containing compound hydride unit" and one or more "having a hydrocarbon compound. A hydrogenated block copolymer [G] of a hydride unit or a polymer block [E] "having a chain hydrocarbon compound unit and a cyclic hydrocarbon compound-containing hydride unit. The resin A includes a hydrogenated block copolymer [G], and can obtain an optical film having a low retardation. Therefore, the optical film obtained by the production method of the present invention can be used as a component requiring a low retardation. In addition, an optical film having high light resistance and less yellowing can be obtained.

The cyclic hydrocarbon group-containing compound hydride unit included in the block [D] and the block [E] is preferably an aromatic vinyl compound hydride unit. The aromatic vinyl compound hydride unit has a structural unit of "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 the production method.

Examples of the aromatic vinyl compound include styrene; α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, and 2,4-dimethyl Styrene, 2,4-diisopropylstyrene, 4-tert-butylstyrene, 5-tert-butyl-2-methylstyrene, and the like having alkyl groups having 1 to 6 carbon atoms as substituents Styrene; styrenes with halogen atoms as substituents, such as 4-chlorostyrene, dichlorostyrene, and 4-monofluorostyrene; 4-methoxystyrene and other alkoxy groups with 1 to 6 carbon atoms Styrenes having a substituent as a substituent; styrenes having an aryl group as a substituent such as 4-phenylstyrene; vinylnaphthalenes such as 1-vinylnaphthalene and 2-vinylnaphthalene; and the like. These can be used alone or in combination of two or more at any ratio. Among these, in terms of reducing hygroscopicity, aromatic vinyl compounds which do not contain a polar group, such as styrene, styrenes having an alkyl group having 1 to 6 carbon atoms as substituents, are preferred. In terms of ease of acquisition, styrene is particularly preferred.

The chain hydrocarbon compound hydride unit contained in the block [E] is preferably a chain conjugated diene compound hydride unit. A chain conjugated diene compound hydride unit is a unit obtained by polymerizing a chain conjugated diene compound, or a unit obtained by hydrogenating a part or all of this double bond when it has a double bond. The structural unit of the structure. However, the chain-like conjugated diene compound hydride unit is not limited by the method for producing the same.

Examples of the chain conjugated diene compound include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, and 1,3-pentadiene. Wait. These can be used alone or in combination of two or more at any ratio. Among them, since the hygroscopicity can be reduced, a chain conjugated diene compound not containing a polar group is preferable, and 1,3-butadiene and isoprene are particularly preferable.

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

In the above-mentioned hydrogenated block copolymer [G], which is a triblock copolymer, from the viewpoint of easily obtaining a stacked film having better characteristics, the total of the block [D1] and the block [D2] and the block The weight ratio of [E] (D1 + D2) / E is preferably in a specific range. Specifically, the weight ratio (D1 + D2) / E is preferably 70/30 or more, more preferably 75/25 or more, more preferably 90/10 or less, and most preferably 87/13 or less.

In addition, in the hydrogenated block copolymer [G], which is a triblock copolymer, from the viewpoint of easily obtaining a stacked film having the above characteristics, the weight ratio D1 of the block [D1] to the block [D2] / D2 is preferably in a specific range. Specifically, the weight ratio D1 / D2 is preferably 5 or more, more preferably 5.2 or more, more preferably 5.5 or more, and 8 or less, more preferably 7.8 or less, and even more preferably 7.5 or less.

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, and more preferably 80,000 or less, more preferably 75,000 or less, and especially 70,000. The following is better. When the weight average molecular weight Mw is in the aforementioned range, a stacked film having the above characteristics can be easily obtained. In particular, by reducing the weight-average molecular weight, the appearance 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 more than 1.0 Better. When the weight average molecular weight Mw is in the aforementioned range, the viscosity of the polymer can be reduced and the moldability can be improved. In addition, the visibility of the delay can be effectively reduced.

The weight-average molecular weight Mw and the number-average molecular weight Mn of the hydrogenated block copolymer [G] were measured by gel permeation chromatography using cyclohexane as a solvent, and the values were converted into polystyrene values. The aforementioned block copolymer hydride [G], for example, the carbon-carbon unsaturated bonds of its main chain and side chain are preferably hydrogenated at 90% or more, more preferably 97% or more, and 99% or more For the better. In addition, the block copolymer hydride [G], for example, preferably has a carbon-carbon unsaturated bond whose aromatic ring is hydrogenated at 90% or more, more preferably 97% or more, and 99% or more. Better. The higher the hydrogenation rate, which indicates the degree of hydrogenation, the more expected improvement in heat resistance and light resistance.

The block [D1] and the block [D2] are preferably each independently composed only of the cyclic hydrocarbon group-containing compound hydride unit [I]. However, any unit other than the cyclic hydrocarbon group-containing compound hydride unit [I] can be obtained. Examples of the arbitrary structural unit include a structural unit based on an ethylene compound other than the cyclic hydrocarbon group-containing compound hydride unit [I]. The content of the arbitrary structural unit in the block [D] is preferably 10% by weight or less, more preferably 5% by weight or less, and particularly preferably 1% by weight or less.

The block [E] is a block composed of only chain hydrogenated hydrocarbon hydride units [II] or a block having a chain hydrocarbon compound unit [II] and a cyclic hydrocarbon compound hydride unit [I]. The block [E] may include any unit other than the unit [I] and the unit [II]. Examples of the arbitrary structural unit include a structural unit based on an ethylene compound other than the unit [I] and the unit [II]. The content of the arbitrary structural unit in the 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 above-mentioned hydrogenated block copolymer [G], which is a triblock copolymer, has a small retardation display property. Therefore, the optical film obtained by peeling the surface layer from the stacked body 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 Patent Publication No. WO2016 / 152871.

The thermoplastic resin A may be composed only of the hydrogenated block copolymer [G] described above, but may include any component other than the hydrogenated block copolymer [G].

Examples of the optional component include inorganic fine particles; stabilizers such as antioxidants, heat stabilizers, ultraviolet absorbers, and near-infrared absorbers; resin modifiers such as lubricants and plasticizers; colorants such as dyes and pigments; and Antistatic agent. These arbitrary components can be used individually by 1 type, and can also be used combining two or more types by arbitrary ratios. However, from the viewpoint of making the effects of the present invention apparent, it is preferable that the content ratio of any component is small. For example, the total ratio of any component 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 with respect to 100 parts by weight of the hydrogenated block copolymer [G].

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

[1.1.2. Resin B]

As the resin B for forming the surface layer, a resin for forming a surface layer capable of peeling off the core layer formed by the free resin A is used. As the resin B, a thermoplastic resin must be used. In the following description, in order to distinguish the resin B used for the two surface layers, resin B1 and resin B2 may be expressed. The resin B1 and the resin B2 may be the same or different.

The thermoplastic resin that forms 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 a resin containing various polymers can be appropriately selected and used. .

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 a repeating unit, and any of a polymer containing an alicyclic structure in a main chain and a polymer containing an alicyclic structure in a side chain can be used. Although the alicyclic structure-containing polymer includes a crystalline resin and an amorphous resin, an amorphous resin is preferred from the viewpoint of surface smoothness.

Examples of the alicyclic structure include a cycloalkane structure and a cycloalkene structure. From the viewpoint of thermal stability and the like, a cycloalkane structure is preferred.

The carbon number of the repeating unit constituting one alicyclic structure is not particularly limited, but it is usually 4 to 30, preferably 5 to 20, and more preferably 6 to 15.

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

Specific examples of the alicyclic structure-containing polymer include: (1) a norbornene polymer, (2) a monocyclic cyclic olefin polymer, (3) a cyclic conjugated diene polymer, and (4) ethylene alicyclic hydrocarbon polymerization. And these hydrides. Among these, from the viewpoint of moldability, a norbornene-based polymer and these hydrides are preferable.

Examples of the olefin-reducing polymer include ring-opening polymers of the olefin-reducing monomer, ring-opening copolymers of the olefin-reducing monomer and other monomers capable of ring-opening copolymerization, and hydrides thereof. ; Addition polymers of norylene monomers, addition copolymers of norylene monomers and other monomers that can be copolymerized. Among these, a ring-opening polymer hydride of a norbornene-based monomer is particularly preferred from the viewpoint of moldability.

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

Examples of the crystalline alicyclic structure-containing polymer include polymers disclosed in Japanese Patent Laid-Open No. 2016-26909.

The weight average molecular weight of the alicyclic structure-containing polymer is measured by gel permeation chromatography (hereinafter abbreviated to "GPC") using cyclohexane (toluene is used when the resin is not dissolved) as a solvent. The weight average molecular weight (Mw) of pentadiene conversion (polystyrene conversion when the solvent is toluene) is usually 10,000 to 100,000, preferably 25,000 to 80,000, and most preferably 25,000 to 50,000. When the weight average molecular weight is in this range, the mechanical strength and formability 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.

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

The thermoplastic resin B may be composed only of an alicyclic structure-containing polymer, but may also contain an arbitrary component as long as the effect of the present invention is not significantly impaired. As an arbitrary component, the same as the arbitrary component of the 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, and more preferably 80% by weight or more.

As a resin containing an alicyclic structure-containing polymer, various products are commercially available, and those having desired characteristics among them may be appropriately selected and used as the thermoplastic resin B. As an example of such a commercially available product, a product series with a brand name "ZEONOR" (manufactured by Japan's Rui On Co., Ltd.) can be cited.

[1.2. Manufacturing process for stacked films]

In the stacked film manufacturing process, a resin A, a resin B1, and a resin B2 are prepared, respectively, and a stacked film can be manufactured by performing melt extrusion molding of these resins by co-extrusion. By performing this melt extrusion molding, a stacked film having a desired thickness of each layer can be efficiently produced. In addition, a long stack film can be obtained by melt extrusion molding.

Examples of the resin extrusion method in the coextrusion method include a coextrusion T-die method, a coextrusion inflation method, and a coextrusion stack method. Among them, the co-extrusion T-die method is preferable. The co-extrusion T-die method includes the feeding head method and the branch pipe die method. In terms of reducing the thickness variation, the branch pipe die method is particularly preferred.

The temperature of the resin at the time of melt-extrusion molding by coextrusion (hereinafter may be appropriately referred to as "extrusion temperature") is not particularly limited, and may be appropriately set to a temperature at which the respective resins melt and are suitable for molding temperature. Specifically, a higher temperature (Ts [H]) between the thermal softening temperature of the resin A forming the core layer and the thermal softening temperature of the resin B forming the surface layer must be set as a reference. More specifically, it is preferably (Ts [H] +70) ° C or higher, and more preferably (Ts [H] +80) ° C or higher. On the other hand, it is preferably (Ts [H] +180) ° C or lower. (Ts [H] +150) ° C or lower is preferred.

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

The thermal softening temperature Ts of each resin was measured by TMA (thermo-mechanical analysis) measurement. For example, it is necessary to cut the measurement target layer into a shape of 5mm × 20mm to make a sample, and use TMA / SS7100 (manufactured by SII NANO TECHNOLOGY Co., Ltd.) to apply a temperature of 50mN to the length of the sample to make the temperature The change is measured by measuring the temperature (° C) at which the linear expansion changes by 3% as the softening temperature.

The arithmetic mean roughness Ra of the die lip 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 average roughness Ra can be measured using a surface roughness meter in accordance with JIS B0601: 1994.

In the co-extrusion method, a film-like molten resin extruded from a die lip is usually brought into close contact with a cooling roll and cooled to be solidified. In this case, examples of the method for bringing the molten resin into close contact with the cooling roll include a pneumatic blade method, a vacuum box method, and an electrostatic adhesion method.

[1.2.1. Size of each layer in the stacked film]

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

The thickness of each layer must be measured by microscope observation. Specifically, it is necessary to measure the thickness of each layer by slicing a stacked film using a microtome and observing a cross section. Observation of the cross section is performed by, for example, a polarizing microscope (for example, "BX51" manufactured by Olympus Corporation).

[1.3. Stripping process]

The peeling process in the manufacturing method of the optical film of this invention is a process of peeling a surface layer from a stacked film. Through such a peeling process, an optical film can be obtained. In the embodiment described below, the two surface layers are peeled simultaneously, but a single layer may be peeled one by one.

FIG. 2 is a cross-sectional view schematically showing an example of a peeling step in the method for producing an optical film of the present invention. The stacked film (stacked film 20 illustrated in FIG. 1) transported by the self-extrusion molding machine M is transported to the lower part of the figure, and then supplied to the peeling process.

The peeling process in the peeling process is performed by pulling the surface layers 11 and 12 in a direction different from the in-plane direction of the stacked film 20 being conveyed. In the example of FIG. 2, the two surface layers 11 and 12 are clamped in directions θ1 and θ2 along the angles with respect to the two surfaces 100A and 100B of the optical film 100 (directions indicated by arrows Y and Z) The surface layers 11 and 12 are peeled from the stacked film 20 by pulling. 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 more preferably 135 ° or less, and more preferably 125 ° or less.

The temperature of the peeling step 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, 60 ° C or lower is preferred, and 50 ° C is preferred. Below ℃ is preferred. The peeling temperature is adjusted by heating a peeling region P or the like of the stacked film by an appropriate heating device.

[1.4. Other processes (extension treatment process)]

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

When performing the stretching treatment step, stretching in the thickness direction, stretching in the in-plane direction, or stretching in the upper inward direction in addition to the thickness direction may be performed. In the manufacturing method of the optical film of the present invention, the stretching ratio when extending in addition to the thickness direction and the upper and inner directions is performed, and it is necessary to appropriately adjust according to the desired optical performance required to give the optical film. The specific stretching ratio is preferably 1.0 times or more, more preferably 1.05 times or more, and on the other hand, 1.5 times or less is preferable, and 1.4 times or less is more preferable. When the extension magnification in the in-plane direction is within this range, desired optical performance can be easily obtained.

The stretching performed in the stretching processing step may be uniaxial stretching, biaxial stretching, or other stretching. The extension direction must be set to any direction. For example, in the case where the film before stretching is an elongated film, the stretching direction may be any of the long side direction, the width direction, and other oblique directions of the film. When biaxial stretching is performed, the angle formed by the two extending directions is usually determined as an angle orthogonal to each other, but it is not limited to this and may be set to an arbitrary angle. The biaxial extension may be a sequential biaxial extension or a simultaneous biaxial extension.

[1.5. Dimensions and characteristics of the optical film obtained by the production method of the present invention]

The optical film obtained by the method for producing an optical film 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 20g / (m ^{2 ·} day) or less.

The absolute value of retardation Re in the in-plane direction of the optical film obtained by the manufacturing 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 manufacturing 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 manufacturing method of the present invention is preferably 18 g / (m ² .day) or less, and more preferably 15 g / (m ² .day) or less. On the other hand, the lower limit is ideally 0 g / (m ² .day), but may be set to, for example, 1 g / (m ² .day) or more.

The thickness of the optical film obtained by the manufacturing method of the present invention is preferably at least 20 μm, more preferably at least 25 μm, more preferably at most 70 μm, and most preferably at most 80 μm.

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 Corporation as a measuring device. When the measurement device is used, the retardation in the in-plane direction and the thickness direction of the optical film is calculated using the average refractive index of the optical film. Here, the average refractive index means an average value of the refractive index in the in-plane direction of the optical film and two directions perpendicular to each other and the refractive index in the thickness direction of the optical film.

The water vapor transmission rate of the optical film obtained by the manufacturing method of the present invention can be determined by using a water vapor transmission measuring device ("PERMATRAN-W" manufactured by MOCON Corporation) in accordance with the JIS K 7129 B method at a temperature of 40, for example. Measured at ℃ and 90% RH.

The thickness of the optical film obtained by the manufacturing method of the present invention can be measured through a microscope observation as well as the thickness of each layer. Specifically, it can be performed by slicing an optical film using a microtome and observing a cross section with, for example, a polarizing microscope (for example, "BX51" manufactured by Olympus Corporation).

In the optical film obtained by the method for producing an optical film of the present invention, in an optical film obtained by peeling a surface layer from a stacked film having a core layer made of resin A and a surface layer made of resin B, the optical film is obtained by The absolute value of the retardation Re in the in-plane direction and the absolute value of the retardation Rth in the thickness direction are set to 2 nm or less, and the water vapor transmission rate is set to 20 g / (m ² .day) or less. Optical film with high adhesion, small retardation, and low water vapor transmission rate. As a result, according to the present invention, it is possible to obtain an optical film that is advantageous for use as a protective film for a polarizer.

The optical film obtained by the method for producing an optical film of the present invention is usually a transparent layer and transmits visible light. The specific light transmittance is appropriately selected according to the application of the optical film. For example, the light transmittance at a wavelength of 420nm to 780nm is preferably 85% or more, and more preferably 88% or more. With such 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, it is possible to suppress a drop in luminance during long-term use in particular.

[2. Optical film of the present invention]

In another aspect of the present invention, the optical film includes a block copolymer including: a block [Da] having a cyclic hydrocarbon group-containing compound unit and a chain hydrocarbon compound unit or a chain hydrocarbon compound Block [Ea] of the unit and the cyclic hydrocarbon-containing compound unit. The cyclic hydrocarbon group-containing compound unit and the chain hydrocarbon compound unit may or may not have an unsaturated bond, and they are not limited by the manufacturing method thereof. Therefore, for example, it may be a unit obtained by hydrogenating a unit having an unsaturated bond, or it may be a unit having an unsaturated bond that is not hydrogenated. When the optical film contains such a block copolymer, an optical film having a low retardation can be obtained. Therefore, the optical film of the present invention can be used as a component requiring a low retardation. In addition, an optical film having high light resistance and less yellowing can be obtained.

As a preferable example of the block copolymer, "a polymer block [Db] containing two or more cyclic hydrocarbon group-containing compound hydride units per molecule is used as the block [Da], and A polymer block [Eb] containing at least one "having a alkane compound hydride unit, or having a alkane compound or its hydride unit, and a cyclic hydrocarbon compound or having its hydride unit" as a block [Ea] ”Copolymer.

Specific examples of the material constituting the optical film of the present invention include the resin A described above. In addition, as examples of the block copolymer included therein, the same examples as those of the above-mentioned hydrogenated block copolymer [G] can be cited. In addition, as examples of the blocks [Da] and [Ea] constituting the block copolymer and examples of the blocks [Db] and [Eb] as specific examples thereof, the above-mentioned blocks [D] and The example of [E] is the same. Examples of the unit constituting the block [Da] and the block [Ea] include the same examples as those of the unit constituting the blocks [D] and [E]; and an aromatic vinyl compound unit and a chain shape. Conjugated diene compound unit. The aromatic vinyl compound unit is a structural unit having a structure obtained by polymerizing an aromatic vinyl compound, and the chain conjugated diene compound unit is a structural unit having a structure obtained by polymerizing a chain conjugated diene compound. However, these are not limited by the manufacturing method. Examples of the so-called aromatic vinyl compound and examples of the chain-shaped conjugated diene compound include the same as those exemplified above.

Examples of the block copolymer and examples other than the hydrogenated block copolymer [G] include an aromatic vinyl compound / conjugated diene compound as a precursor of a hydride described in WO2016 / 152871. Paragraph copolymer.

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

Here, the "central portion" refers to the central portion in the thickness direction of the film. However, when a film is manufactured by the method for manufacturing an optical film of the present invention described above, a position at a depth of about 5 μm in the thickness direction generally has a composition ratio equivalent to that of 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 may be substituted by the value of the composition ratio at the center.

The composition ratio of the volume of the block [Da] to 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 generally 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 composition of the block [Da] and the block [Ea] can be obtained by determining the area of the phase derived from each block and the ratio of this area. ratio.

The measurement of the area of each phase is performed by an interatomic force microscope (for example, the Dimension Fast Scan Icon made by Bruker). A cohesive force image of the optical film was obtained through an atomic force microscope, and the area ratio of the phases derived from each block in the image was measured. Then, based on the information about the cohesion of the observed phase, the observed phase can be assigned to the phase of the block [Da] and the phase of the block [Ea].

The total area of the two types of phases was set to 100%, and the percentage of the area of the phase allocated to the block [Da] was calculated to calculate the respective block [Da] ratios of the surface and the center. The difference in the composition ratio between the volume of the block [D] and the volume of the block [E] on the surface and the center can be calculated by the following formula. Difference in composition ratio = | (block [D] ratio in the center)-(block [D] ratio on the surface) |

The value of (block [D] ratio in the center)-(block [D] ratio on the surface) may be positive or negative.

The optical film of the present invention can be produced by extrusion film-forming of a resin containing a block copolymer. By performing extrusion film formation, efficient production can be achieved. However, according to the findings of the present inventors, when extrusion filming is performed, the difference in the composition ratio between the volume of the block [D] and the volume of the block [E] on the surface and the central portion becomes large. . Here, by using the production method described in the above [1. Production method of an optical film of the present invention], a film having a small difference in composition ratio can be easily obtained.

The size and characteristics of the optical film of the present invention are the same as those described in [1.5. Size and characteristics of the optical film obtained by the manufacturing method of the present invention].

[3. Polarizing plate and manufacturing method thereof]

The optical film obtained by the production method described in the above [1. Production method of an optical film of the present invention] and the optical film of the present invention described in the above [2. Optical film of the present invention] These are simply referred to as "the optical film of the present invention"), and can be suitably used as a protective film for protecting other layers in a display device such as a liquid crystal display device. Among them, the optical film of the present invention is suitable as a polarizer protective film, and is particularly suitable for use as an inner polarizer protective film of a display device.

A polarizing plate of the present invention includes the optical film and a polarizer of the present invention. In the present invention, the optical film has a function as a protective film for a polarizer. The polarizing plate of the present invention may further include a bonding agent layer for bonding these between the optical film and the polarizer.

The polarizing plate of the present invention may include any layer in addition to the optical film and the polarizer. Examples of the arbitrary layer include a hard coat layer for improving surface hardness, a cushion layer for optimizing film smoothness, and an anti-reflection layer.

The polarizer is not particularly limited, and any polarizer may be used. As an example of a polarizer, the thing which carried out the extending | stretching process after adsorbing materials, such as an iodine and a dichroic dye, to a polyvinyl alcohol film is mentioned. Examples of the adhesive constituting the adhesive layer include those in which various polymers are used as a base polymer. Examples of such a base polymer include acrylic polymers, silicone polymers, polyesters, polyurethanes, polyethers, and synthetic rubbers.

The number of polarizers and protective films included in a polarizing plate is arbitrary, but in the present invention, a polarizer having one layer and a two-layer protective film provided on both sides thereof are usually obtained. Among such two-layer protective films, both of them may be the optical film of the present invention, or only one of them may be the optical film of the present invention. Especially in a liquid crystal display device having a light source and a liquid crystal cell, and both the light source side and the display surface side of the liquid crystal cell have a polarizing plate, it is particularly "equipped with the optical film of the present invention as compared with the display surface. The protective film used in the position where the polarizer on the side is closer to the light source side is preferable. With this structure, a liquid crystal display device having excellent durability, small color unevenness, and good display quality can be easily constructed.

The polarizing plate of the present invention must be manufactured by any manufacturing method. For example, the polarizing plate of the present invention can be manufactured by bonding the optical film and the polarizer obtained by the above-mentioned manufacturing method. This bonding can be a bonding in which these layers are in direct contact, or a bonding in an intervening adhesive layer.

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

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

Examples of the liquid crystal display device suitable for installing the polarizing plate of the present invention include a plane switching mode (IPS), a vertical alignment mode (VA), a multi-region vertical alignment mode (MVA), a continuous firework-like alignment mode (CPA), A liquid crystal display device that mixes liquid crystal cells such as alignment nematic mode (HAN), twisted nematic mode (TN), super twisted nematic mode (STN), and optically compensated bending mode (OCB). Among these, since the optical film of the present invention has excellent durability and the effect of suppressing color unevenness, the liquid crystal display device having a liquid crystal cell having an IPS mode is particularly preferable.

The liquid crystal display device of the present invention must be manufactured by any manufacturing method. For example, a liquid crystal display device of the present invention can be manufactured by combining a polarizing plate obtained through the above-mentioned manufacturing method and other components constituting a liquid crystal display device such as a liquid crystal cell. For example, a liquid crystal display device can be manufactured by directly bonding a liquid crystal cell and a polarizing plate or bonding an intermediary adhesive layer and setting this in a display device. In addition, a liquid crystal display device must be manufactured by simply superposing a liquid crystal cell and a polarizing plate and placing the liquid crystal cell in a display device.

『Examples』

The following examples are disclosed to illustrate the present invention in detail. However, the present invention is not limited to the embodiments disclosed below, and can be implemented with arbitrary changes without departing from the scope of the patent application of the present invention and its equivalent scope.

In the following description, unless otherwise noted, the "%" and "parts" indicating amounts are based on weight. In addition, the operations described below are performed under normal temperature and pressure conditions unless otherwise noted.

Specific examples of the block [D] in the above description and specific examples of the block [Da] in the above description may be made, and are simply referred to as "block [D]" in the following description. In addition, both the specific example of the block [E] in the above description and the specific example of the block [Ea] in the above description may be made, and it is simply referred to as "block [E]" in the following description. ".

[Evaluation method]

[Measurement method of weight average molecular weight and number average molecular weight]

The weight average molecular weight and number average molecular weight of the polymer were measured using a gel permeation chromatography (GPC) system ("HLC-8320" manufactured by Tosoh Corporation) as a polystyrene conversion value. For measurement, an H-shaped column (manufactured by Tosoh Corporation) was used as the column, and cyclohexane was used as the solvent. The temperature during measurement was 40 ° C.

[Measurement method of hydrogenation rate of hydrogenated block copolymer [G]]

The hydrogenation rate of the polymer was calculated by ¹ H-NMR measurement at 145 ° C using o-dichlorobenzene-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 having a length of 50 mm, a width of 10 mm, and a thickness of 1 mm. Using this test piece, a viscoelasticity measuring device (product name "ARES", manufactured by TA Instruments Japan) was used in accordance with JIS-K7244-4 method at a temperature range of -100 ° C to + 150 ° C and a temperature increase rate of 5 ° C / min. Measure dynamic viscoelastic properties. The glass transition temperature Tg _{2 was} calculated from the peak top temperature of the loss tangent tanδ (the peak temperature on the high temperature side when multiple peaks were observed).

[Heat softening temperature of resin B]

According to JIS K 7121, using a differential scanning calorimeter (manufactured by Nanotechnology, product name "DSC6220S11"), resin B is heated to a temperature higher than 30 ° C above the glass transition temperature, and then cooled to -10 ° C / min to At room temperature, the temperature was then increased at a rate of 10 ° C / minute, and the thermal softening temperature was measured.

[Measurement method of thickness of each layer and thickness of optical film]

The thickness of each layer and the thickness of the optical film were measured in the following manner.

The film to be measured was sliced using a microtome ("RV-240" manufactured by Yamato Koki Co., Ltd.). The cross section of the sliced film was observed with a polarizing microscope ("BX51" manufactured by Olympus), and the thickness was measured.

[Measurement method of thermal softening temperature Ts]

The film to be measured was cut into a shape of 5 mm × 20 mm to prepare a sample. As the measuring device, TMA / SS7100 (SII NANO TECHNOLOGY Co., Ltd.) was used. In TMA (thermo-mechanical analysis) measurement, the temperature was changed while a tension of 50 mN was applied to the longitudinal direction of the sample. The temperature (° C) at which the linear expansion changed by 3% was set as the softening temperature.

[Measurement method of retardation in the plane direction and retardation in the thickness direction]

The retardation measurement device (manufactured by Axometric Corporation, product name "Axoscan") was used to measure the films of each example (Example and Comparative Example) at a wavelength of 590 nm, and the retardation Re Absolute value and absolute value of retardation Rth in thickness direction.

[Measurement Method of Peel Strength]

A thin film for testing (a glass transition temperature of 160 ° C., a thickness of 100 μm, manufactured by Japan's Ruiwon Co., Ltd. without extension treatment) was prepared as a film instead of a polarizing plate, and was made of a resin containing a norbornene-based polymer. Corona treatment was performed on one side of the film obtained in each example and the aforementioned test film. The adhesive was adhered to the corona-treated surface of each film and the corona-treated surface of the test film, and the surfaces to which the adhesive was adhered were adhered to each other. At this time, a UV adhesive (CRB series (manufactured by TOYOCHEM)) was used as the adhesive. Thereby, a sample film S including a film 100 of each example and a test film 60 (see FIG. 3) was obtained.

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 adhered to the surface of the slide glass 80 with an adhesive 70 to obtain an evaluation sample. At this time, a double-sided adhesive tape (manufactured by Nitto Denko Corporation, product number "CS9621") was used as the adhesive 70. In FIG. 3, 50 is a bonding agent.

The test film 60 was sandwiched between the front ends of the dynamometers, and stretched in the normal direction of the surface of the slide glass 80 (direction indicated by arrow X in FIG. 3), and a 90-degree peel test was performed. At this time, since 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 (examples and comparative examples), the magnitude of this force is measured. As peeling strength. When the force required for peeling is very large and the material is damaged before the test film is peeled off, it is described as "impossible due to material damage".

(Supplement to the measurement method of peel strength)

In the aforementioned measurement method of peel strength, a specific test film is used instead of the polarizing plate. In order to verify the rationality of the measurement of the peeling strength using the test film instead of the polarizing plate in this manner, the inventors performed the following experiments on the film obtained in Example 1.

Instead of the test film, following Example 1 of Japanese Patent Laid-Open No. 2005-70140, a retardation film stack was attached to one surface of the polarizing film, and triethylpyridine was attached to the other surface of the polarizing film. The cellulose film was subjected to a 90-degree peel test. That is, first, a polarizing film and a bonding agent described in Example 1 of Japanese Patent Laid-Open No. 2005-70140 are prepared. The corona-treated surface of the retardation film stack was bonded to the surface of one side of the prepared polarizing film through the aforementioned bonding agent. In addition, a triacetam cellulose film was bonded to the surface of the other side of the polarizing film through the aforementioned bonding agent. Then, it dried at 80 degreeC for 7 minutes, and hardened the adhesive agent, and obtained the sample film. A 90-degree peel test was performed on the obtained sample film.

The results of the foregoing experiments were the same as those obtained when a polarizing plate was used instead of a test film. Therefore, the results of the following examples and comparative examples using a test film in place of the polarizing plate are reasonable.

(Measurement of water vapor transmission rate)

The water vapor transmission rate of the optical film is measured using a water vapor transmission measurement device ("PERMATRAN-W" manufactured by MOCON Corporation) in accordance with JIS K 7129 B method at a temperature of 40 ° C and a humidity of 90% RH. .

(Measurement of total light transmittance)

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

(Measurement of block composition ratio)

The measurement of the composition ratio of the blocks in the optical film is obtained by "using an atomic force microscope Dimension Fast Scan Icon manufactured by Bruker Co., Ltd. to obtain an agglutination force image of the optical film, and measuring the phase derived from each block in the image. Area ratio ".

As a cantilever beam for capturing an agglutination force image, AC240TS (manufactured by Olympus Corporation, spring constant: 1.5 N / m, TIP radius of curvature 15 nm) was used. The measurement mode used for shooting was set to ScanAsyst mode, and the scan rate was set to 2 Hz. The agglutination force image was measured with an area of 500 nm × 500 nm.

The measurement of the agglutination force image was performed on the film surface and the center. The measurement of the central portion of the film was performed at a position having a depth of 5 μm from the surface of the film in the section on the premise that the film section had been performed.

An image of the measurement result of the agglutination force image is analyzed and a histogram is drawn. In the histogram, the agglutination force measured at each measurement point is taken as the horizontal axis, and the number of measurement points through which the agglutination force is measured is taken as the vertical axis. The area ratios of the two types of phases considered to be caused by the two types of blocks were calculated by fitting a Gaussian function.

In general, it is known that the agglutination force depends on Tg, and the agglutination force becomes higher when the sample is pulled away from the cantilever beam from the surface of the low Tg. Therefore, the phase with a high cohesive force is a block [E], and the phase with a low cohesive force is a block [D], and distribution is determined.

The area ratio refers to the total area of the two phases as 100%, and the percentage of the area of the phase allocated to the block [D] is calculated as the block [D] ratio.

The difference between the composition ratios of the block [D] and the block [E] on the surface and the center is calculated by the following formula. Difference in composition ratio = | (block [D] ratio in the center)-(block [D] ratio on the surface) |

[Manufacturing example 1]

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

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

Subsequently, 15 parts of dehydrated isoprene was continuously added to the reaction liquid over 40 minutes, and after the addition was completed, stirring was continued for 30 minutes. As a result of analyzing the reaction liquid by GC and GPC at this time point (the second stage of polymerization), the polymerization conversion rate was 99.8%.

Thereafter, 10 parts of dehydrated styrene was continuously added to the reaction solution over 30 minutes, and stirring was continued for 30 minutes directly after the addition was completed. As a result of analyzing the reaction liquid by GC and GPC at this time point (the third stage of polymerization), the polymerization conversion rate was almost 100%.

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

(P1-2) Production 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 a diatomite-supported nickel catalyst (product name "E22U" was added, and the nickel bearing capacity was 60%. 4.0 parts of the company) and 30 parts of dehydrated cyclohexane were mixed as a hydrogenation catalyst. The inside of the reactor was replaced with hydrogen, and 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 contains a 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 almost 100%.

After the completion of the hydrogenation reaction, the reaction solution was filtered to remove the hydrogenation catalyst, and then 3- [3,5-di (tributyl) -4-hydroxyphenyl] propanoic acid, which was a phenolic antioxidant, was added. Neopentyl tetraester (product name "AO60", manufactured by ADEKA) 0.3 parts of xylene solution and 2.0 parts were dissolved to make a solution.

Next, the above-mentioned solution was treated at a temperature of 260 ° C and a pressure of 0.001 MPa or less using a cylindrical-type concentration dryer (product name "Kontro", manufactured by Hitachi, Ltd.), and cyclohexane, xylene, and other volatile components were removed from the solution to obtain Molten resin. This was extruded from a die into strands and cooled, and formed into granules by a granulator. Thereby, 95 parts of pellets of the resin [G1] containing the hydrogenated block copolymer [G1] were produced.

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

[Manufacture example 2]

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

270 parts of dehydrated cyclohexane, 70 parts of dehydrated styrene, and 7.0 parts of dibutyl ether were added to a reactor equipped with a stirring device and the inside was sufficiently replaced with nitrogen. While stirring the whole at 60 ° C, 5.6 parts of n-butyllithium (15% cyclohexane solution) was added to start polymerization. Subsequently, the whole was stirred at 60 ° C for 60 minutes. The reaction temperature was maintained at 60 ° C until the reaction stopped. As a result of analyzing the reaction liquid by GC and GPC at this time point (the first stage of polymerization), the polymerization conversion rate was 99.4%.

Subsequently, 20 parts of dehydrated isoprene was continuously added to the reaction solution over 40 minutes, and after the addition was completed, stirring was continued for 30 minutes. As a result of analyzing the reaction liquid by GC and GPC at this time point (the second stage of polymerization), the polymerization conversion rate was 99.8%.

Thereafter, 10 parts of dehydrated styrene was continuously added to the reaction solution over 30 minutes, and stirring was continued for 30 minutes directly after the addition was completed. As a result of analyzing the reaction liquid by GC and GPC at this time point (the third stage of polymerization), the polymerization conversion rate was almost 100%.

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

(P2-2) Production 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 diatomite-supported nickel catalyst (product name "E22U" was added, and the nickel bearing capacity was 60%. 4.0 parts of the company) and 30 parts of dehydrated cyclohexane were mixed as a hydrogenation catalyst. The inside of the reactor was replaced with hydrogen, and 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 contains a hydrogenated block copolymer [G2]. The Mw [G2] of the hydrogenated block copolymer was 72,800, the molecular weight distribution Mw / Mn was 1.30, and the hydrogenation rate was almost 100%.

After the completion of the hydrogenation reaction, the reaction solution was filtered to remove the hydrogenation catalyst, and then 3- [3,5-di (tertiarybutyl) -4-hydroxyphenyl｝ propionate｝ was added as a phenolic antioxidant. Neopentyl tetraester (product name "AO60", manufactured by ADEKA) 0.3 parts of xylene solution and 2.0 parts were dissolved to make a solution.

Next, the above-mentioned solution was treated at a temperature of 260 ° C and a pressure of 0.001 MPa or less using a cylindrical-type concentration dryer (product name "Kontro", manufactured by Hitachi, Ltd.), and cyclohexane, xylene and other volatile components were removed from the solution to obtain Molten resin. This was extruded from a die into strands and cooled, and formed into granules by a granulator. Thereby, 95 parts of pellets of the resin [G2] containing the hydrogenated block copolymer [G2] were produced.

Hydrogenated block copolymer [G2] in the obtained resin [G2], 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 twin-screw single-shaft extruder equipped with a polymer filter with a leaf disc shape with a mesh size of 3 μm was prepared (the ratio of the diameter L of the screw D to 50 mm and the diameter L of the screw L / D = 28) . The pelletized resin [G1] obtained in Production Example 1 was introduced into this uniaxial extruder as the thermoplastic resin A, melted, and fed to a single-layer mold through a feed head. The introduction of the resin A to the uniaxial extruder was performed through a hopper mounted on the uniaxial extruder. The surface roughness (arithmetic average roughness Ra) of the lip of the single-layer mold was 0.1 μm. The extruder exit temperature of the resin A was 260 ° C.

On the other hand, a single-shaft extruder equipped with a polymer filter with a leaf disc shape with a mesh size of 3 μm (screw diameter D = 50 mm, and the ratio L / D of the length L of the screw to the diameter D of the screw) was prepared. = 30). In this uniaxial extruder, a resin B containing an amorphous alicyclic structure-containing polymer was introduced as a thermoplastic resin B (made of resin "B-1", manufactured by Japan's Ruiwon Corporation, with a heat softening temperature of 160 ° C) and This is dissolved and supplied to the aforementioned single-layer mold through a feed head. The extruder exit temperature of resin B was 260 ° C.

The resin A and the resin B were discharged from a single-layer mold of an extrusion molding machine in a molten state at 260 ° C. Thereby, a three-layer film-shaped resin having 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 is continuously formed (coextrusion molding step). The discharged film-like resin is poured onto a cooling roller. During the pouring, the widthwise end of the film-like resin was fixed to the edge of the cooling roller, and the air gap was set to 50 mm. Thereby, the film-like resin was cooled, and a three-layer structured stacked film was obtained. The obtained stacked film is a three-layer stacked film made of two kinds of resins, and the three-layer stacked film made of two kinds of resins is provided with a surface layer made of resin B and a core made of resin A in this order. Layer and surface layer made of resin B.

(1-2. Manufacturing and Evaluation of Optical Films)

The peeling step of peeling the surface layer from the three-layered stacked film obtained in (1-1) was performed. The peeling process is performed by pulling the surface layers on both sides of the stacked film and continuously peeling the surface layers from the core layer. The direction of pulling the two surface layers was a direction with 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 having a thickness of 40 μm where the surface layer was peeled off was obtained.

The obtained thin film 1 was evaluated, and the results are shown in Table 1. In the evaluation of the peel strength, since material damage occurred before the test film was peeled, the peel strength was not measurable. This means that the peel strength is high.

[Example 2]

Except that the granular resin [G2] obtained in Manufacturing Example 2 was used instead of the granular resin [G1] obtained in Manufacturing Example 1, the rest was peeled off from the surface layer after preparing a stacked film according to Example 1 to obtain a single unit having a thickness of 40 μm.层 的 膜 2。 Thin film 2. The obtained film 2 was evaluated in the same manner as in Example 1. The results are shown in Table 1. In the evaluation of the peel strength, since material damage occurred before the test film was peeled, the peel strength was not measurable. This means that the peel strength is high.

[Comparative Example 1]

A twin-screw single-shaft extruder equipped with a polymer filter with a leaf disc shape with a mesh size of 3 μm was prepared (the ratio of the screw diameter L = 50 mm and the length L of the screw to the diameter D of the screw L / D = 28) . The pelletized resin [G1] obtained in Production Example 1 was introduced into this uniaxial extruder, melted, and supplied to a single-layer mold. The resin [G1] for the uniaxial extruder is introduced through the hopper loaded on the uniaxial extruder. The surface roughness (arithmetic average roughness Ra) of the lip of the single-layer mold was 0.1 μm. The extruder exit temperature of the resin [G1] was 260 ° C.

The resin [G1] was discharged from the single-layer mold in a molten state at 260 ° C. As a result, a thin-film resin consisting only of the "layer made of resin [G1]" is continuously formed. The discharged film-like resin is poured onto a cooling roller. During the pouring, the widthwise end of the film-like resin was fixed to the edge of the cooling roller, and the air gap was set to 50 mm. Thereby, the film-shaped resin was cooled, and a film C1 having a single-layer structure made of the 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 of Example 1. The results are shown in Table 1.

[Comparative Example 2]

Except that the granular resin [G2] obtained in Manufacturing Example 2 was used instead of the granular resin [G1] obtained in Manufacturing Example 1, the resin [G2] was manufactured by the same operation as in Comparative Example 1. The film C2 has a single-layer structure with a thickness of 40 μm. This film C2 was evaluated in the same manner as the film of Example 1. The results are shown in Table 1.

[Comparative Example 3]

The optical film E ("FUJITAC" manufactured by FUJI FILM Co., Ltd., thickness: 40 μm) was evaluated in the same manner as the film of Example 1. The results are shown in Table 1. The measurement of the peeling strength uses a saponified film.

The results of Examples and Comparative Examples are summarized and shown in Table 1.

"Table 1"

The meanings of the abbreviations in the table are as follows. G1: The hydrogenated block copolymer [G1] produced in Production Example 1. G2: The hydrogenated block copolymer [G2] produced in Production Example 2. B-1: Resin containing alicyclic structure polymer, heat softening temperature of 160 ° C, one of the products of "ZEONOR" made by Japan's Rui Weng Company. E: Optical film, "FUJITAC" manufactured by FUJI FILM Co., Ltd. | Re |: Absolute value of retardation in plane direction | Rth |: Absolute value of retardation in thickness direction

From the results of the examples and comparative examples, it can be seen that the film obtained by the method for producing an optical film of the present invention can be made into an optical film with high adhesion to an object, small retardation, and low water vapor transmission rate.

10‧‧‧ Core Layer

11, 12‧‧‧ surface

20‧‧‧ stacked film

50‧‧‧UV bonding agent

60‧‧‧Test film

70‧‧‧Adhesive

80‧‧‧Slides

100‧‧‧ Optical Film

100A, 100B‧‧‧face of optical film

M‧‧‧ Extrusion Forming Machine

P‧‧‧ Stripped area

S‧‧‧Sample film

FIG. 1 is a cross-sectional view schematically showing an example of a manufacturing process of a stacked film in the manufacturing method of the present invention. 2 is a cross-sectional view schematically showing an example of a peeling step in the manufacturing method of the present invention. FIG. 3 is a schematic cross-sectional view of a sample used in an evaluation test in an example.

Claims (10)

An optical film comprising a block copolymer comprising: a block [Da] having a cyclic hydrocarbon group-containing compound unit; and a block having a chain hydrocarbon compound unit or a chain hydrocarbon compound unit and a cyclic hydrocarbon group-containing compound unit Block [Ea], wherein the difference between the composition ratio of the volume of the block [Da] on the surface and the central portion and the volume of the block [Ea] is 0 to 10%, and the absolute value of the retardation in the in-plane direction is The thickness is 5 nm or less, the absolute value of the retardation in the thickness direction is 10 nm or less, and the water vapor transmission rate thereof is 20 g / (m ² .day) or less. The optical film according to claim 1, which is formed by extruding a resin containing the aforementioned block copolymer into a film. The optical film according to claim 1 or 2, wherein the aforementioned block copolymer contains at least two polymer blocks [Db] per molecule as the aforementioned block [Da] and contains more than one per molecule A polymer block [Eb] is a copolymer of the foregoing block [Ea], the polymer block [Db] has a cyclic hydrocarbon group-containing compound hydride unit, and the polymer block [Eb] has a chain hydrocarbon compound hydride unit Or has a hydrocarbon compound or a hydride unit thereof and a cyclic hydrocarbon compound or a hydride unit thereof. A polarizing plate comprising the optical film and the polarizer according to any one of claims 1 to 3. A liquid crystal display device includes the polarizing plate according to claim 4. An optical film manufacturing method comprising: by co-extruding resin A and resin B, obtaining a stack including a core layer made of resin A and a surface layer made of resin B provided on the surface of the core layer A film step; and a step of peeling the surface layer from the stacked film, wherein the absolute value of the retardation in the in-plane direction of the optical film is 5 nm or less, the absolute value of the retardation in the thickness direction is 10 nm or less, and water vapor transmission The rate is below 20g / (m ^{2 ·} day). The method for manufacturing an optical film according to claim 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. The method for producing an optical film according to claim 6 or 7, wherein the resin B contains an alicyclic structure-containing polymer. The method for manufacturing an optical film according to claim 6 or 7, wherein the resin A includes a hydrogenated block copolymer, and the hydrogenated block copolymer contains 2 or more polymer blocks [D] per molecule and 1 The molecule contains more than one polymer block [E], the polymer block [D] has a cyclic hydrocarbon compound-containing hydride unit, and the polymer block [E] has a hydrocarbon compound hydride unit, or has a chain Hydrocarbon compound units and cyclic hydrocarbon compound hydride units. The method for manufacturing an optical film according to claim 6 or 7, wherein the resin A is made of a block copolymer including: a block having a cyclic hydrocarbon group-containing compound unit; and a chain hydrocarbon compound unit In the optical film, the difference between the composition ratio between the surface and the central portion of the block having a chain hydrocarbon compound unit and a cyclic hydrocarbon group-containing compound unit is 0 to 10%.