WO2018181696A1

WO2018181696A1 - Optical film, method for producing same, polarizing plate and liquid crystal display device

Info

Publication number: WO2018181696A1
Application number: PCT/JP2018/013201
Authority: WO
Inventors: 斗馬辻野; 宏晃周
Original assignee: 日本ゼオン株式会社
Priority date: 2017-03-30
Filing date: 2018-03-29
Publication date: 2018-10-04
Also published as: KR102607190B1; KR20190128648A; TWI787246B; TW201837072A; CN110418988A; CN110418988B; JPWO2018181696A1

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.

The polarizing plate provided in the liquid crystal display device usually includes a polarizer and a protective film for protecting the polarizer. In many cases, polarizing plate protective films are required to have low retardation and low water vapor transmission rate. From such a viewpoint, a polarizer protective film having a small retardation has been proposed (see Patent Document 1). Further, the polarizing plate is required to exhibit durability in an environment at the time of manufacturing and using the display device. For example, a high peel strength may be required for the protective film in the polarizing plate, for example, when reworking during manufacturing of the display device and when the polarizer contracts during use of the display device.

JP 2011-013378 A

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, 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 aligned and the entanglement between the molecules decreases, causing cohesive failure near the surface layer, thereby protecting the polarizing plate. There was a problem that the film could have insufficient peel strength.

Accordingly, an object of the present invention is to provide an optical film having high adhesion to a polarizer, low retardation, and low water vapor transmission rate, a method for producing an optical film capable of easily obtaining such an optical film, and An object of the present invention is to provide a polarizing plate and a liquid crystal display device which have the optical film and have the above performance.

As a result of examining the problems in the above-described conventional polarizer protective film, it was considered that a strong alignment layer was formed on the surface of the protective film in the step of forming the protective film by a melt extrusion method.
Therefore, the present inventor has intensively studied to solve the above problems. As a result, the present inventor made a laminated film comprising a core layer and a surface layer provided on the surface thereof by co-extrusion of resin A and resin B, and peeled and removed the surface layer from the laminated film. The present invention was completed by finding that an optical film having high adhesion to a product, low retardation, and low water vapor transmission rate can be obtained.
That is, the present invention is as follows.

[1] A block [Da] having a cyclic hydrocarbon group-containing compound unit;
A block [Ea] having a chain hydrocarbon compound unit, or a chain hydrocarbon compound unit and a cyclic hydrocarbon group-containing compound unit;
A block copolymer comprising
The difference in the composition ratio between the volume of the block [Da] and the volume of the block [Ea] at the surface and the central part is 0 to 10%,
The absolute value of in-plane retardation 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], wherein a resin containing the block copolymer is formed by extrusion.
[3] The block copolymer is
The block [Da] includes two or more polymer blocks [Db] per molecule having a cyclic hydrocarbon group-containing compound hydride unit,
One or more polymers per molecule having a chain hydrocarbon compound hydride unit or a chain hydrocarbon compound or hydride unit thereof and a cyclic hydrocarbon-containing compound or hydride unit thereof as the block [Ea] The optical film according to [1] or [2], which is a copolymer containing a block [Eb].
[4] A polarizing plate comprising the optical film of any one of [1] to [3] and a polarizer.
[5] A liquid crystal display device comprising the polarizing plate according to [4].
[6] A step of obtaining a laminated film including a core layer made of resin A and a surface layer made of resin B provided on the surface of the core layer by co-extruding resin A and resin B;
Peeling the surface layer from the laminated film, and a method for producing an optical film comprising:
The optical film is
The absolute value of in-plane retardation is 5 nm or less,
The absolute value of retardation in the thickness direction is 10 nm or less, and
The manufacturing method of an optical film whose water-vapor-permeation rate is 20 g / (m < ² > * day) or less.
[7] The optical film according to [6], wherein an absolute value of retardation in the in-plane direction of the optical film is 2 nm or less, and an absolute value of retardation in the thickness direction of the optical film is 2 nm or less. Manufacturing method.
[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 resin A is
Two or more polymer blocks [D] per molecule having cyclic hydrocarbon group-containing compound hydride units;
One or more polymer blocks [E] per molecule having a chain hydrocarbon compound hydride unit, or a chain hydrocarbon compound unit and a cyclic hydrocarbon-containing compound hydride unit;
The method for producing an optical film according to any one of [6] to [8], comprising a hydrogenated block copolymer containing.
[10] The resin A is
A block 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;
A block copolymer containing
In the optical film, the difference in composition ratio between the surface and the center is 0 to 10%.
[6] The method for producing an optical film as described in any one of [8].

The optical film of the present invention can be an optical film having high adhesion to an object, low 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 an object, low retardation, and low water vapor transmission rate can be easily obtained. According to the polarizing plate of this invention, the polarizing plate which has the above performances can be provided. According to the liquid crystal display device of the present invention, a liquid crystal display device having the above-described performance can be provided.

FIG. 1 is a cross-sectional view schematically showing an example of a laminated film production process in the production method of the present invention. FIG. 2 is a cross-sectional view schematically showing an example of a peeling step in the production method of the present invention. FIG. 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 with reference to embodiments and examples. However, the present invention is not limited to the following embodiments and exemplifications, and can be implemented with any modifications without departing from the scope of the claims of the present invention and the equivalents thereof.

In the following description, the cyclic hydrocarbon group is a hydrocarbon group containing a cyclic structure such as an aromatic ring, cycloalkane, or cycloalkene. The 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 represented by Re = (nx−ny) × d unless otherwise specified. Further, the retardation Rth in the thickness direction of the optical film is a value represented by Rth = {(nx + ny) / 2−nz} × d unless otherwise specified. Here, nx represents a refractive index in a direction (in-plane direction) perpendicular to the thickness direction of the optical film and giving the maximum refractive index. ny represents the refractive index in the in-plane direction of the optical film and perpendicular to the nx direction. 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 specified.

In the following description, unless otherwise specified, the “polarizing plate” includes not only a rigid member but also a flexible member such as a resin film.

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

[1. Method for producing optical film of the present invention]
In one embodiment of the present invention, the method for producing an optical film comprises: coextruding a resin A that forms a core layer and a resin B that forms a surface layer; It includes a step of obtaining a laminated film having a surface layer made of the provided resin B (laminated film production step) and a step of peeling the surface layer from the laminated film (peeling step).

[1.1. Overview of laminated film production process]
In the laminated film production step, a laminated film is obtained by co-extruding 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 includes surface layers 11 and 12 on two surfaces of the core layer 10, respectively. Specifically, the laminated film 20 has a layer configuration 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 surface of the core layer, and the layer structure in this case is a surface layer / core layer. From the viewpoint of curling suppression of the film, the surface layer is preferably on both sides of the core layer.

[1.1.1. Resin 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 a resin containing various polymers that can impart desired physical properties as an optical film is appropriately selected. And can be adopted. Preferable 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. And a hydrogenated block copolymer [G] comprising one or more polymer blocks [E] having a hydrated hydrocarbon compound unit and a cyclic hydrocarbon-containing compound hydride unit. When the resin A contains the hydrogenated block copolymer [G], an optical film having a low retardation can be obtained. Therefore, an optical film obtained by the production method of the present invention is required to have a low retardation. It can be used as a member. In addition, it is possible to obtain an optical film that has high light resistance and hardly yellows.

The cyclic hydrocarbon group-containing compound hydride unit contained in the block [D] and the block [E] is preferably an aromatic vinyl compound hydride unit. The 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 depending on the production method.

Examples of aromatic vinyl compounds include styrene; α-methyl styrene, 2-methyl styrene, 3-methyl styrene, 4-methyl styrene, 2,4-dimethyl styrene, 2,4-diisopropyl styrene, 4-t-butyl. Styrenes having an alkyl group having 1 to 6 carbon atoms as a substituent, such as styrene and 5-t-butyl-2-methylstyrene; as substituents such as 4-chlorostyrene, dichlorostyrene, 4-monofluorostyrene Styrenes having a halogen atom; styrenes having an alkoxy group having 1 to 6 carbon atoms as a substituent such as 4-methoxystyrene; styrenes having an aryl group as a substituent such as 4-phenylstyrene; 1-vinyl And vinyl naphthalenes such as naphthalene and 2-vinylnaphthalene. One of these may be used alone, or two or more of these 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 having 1 to 6 carbon atoms as a substituent, are preferable because they can reduce hygroscopicity, and are easily available industrially. Therefore, styrene is particularly preferable.

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

Examples of the chain conjugated diene compound include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene and the like. One of these may be used alone, or two or more of these may be used in combination at any ratio. Among these, a chain conjugated diene compound not containing a polar group is preferable because 1,2 can be reduced hygroscopicity, 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] per molecule linked to both ends thereof. That is, the hydrogenated block copolymer [G] has one block [E] per molecule; and one end of the block [E] and has a cyclic hydrocarbon group-containing compound hydride unit [I]. One block [D1] per molecule; one block [D2] per molecule having a cyclic hydrocarbon group-containing compound hydride unit [I] connected to the other end of the block [E]; It is preferable that it is a triblock copolymer containing.

In the hydrogenated block copolymer [G] as the triblock copolymer described above, the total of the block [D1] and the block [D2] and the block [E] from the viewpoint of easily obtaining a laminated film having preferable characteristics. ] And the weight ratio (D1 + D2) / E are preferably 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, more preferably 87/13 or less.

Further, in the hydrogenated block copolymer [G] as the triblock copolymer described above, the weight ratio D1 of the block [D1] and the block [D2] is obtained from the viewpoint of easily obtaining a laminated film having the above characteristics. / D2 is preferably within a specific range. Specifically, the weight ratio D1 / D2 is preferably 5 or more, more preferably 5.2 or more, particularly preferably 5.5 or more, preferably 8 or less, more preferably 7.8 or less, particularly preferably. Is 7.5 or less.

The weight average molecular weight Mw of the hydrogenated block copolymer [G] is preferably 50000 or more, more preferably 55000 or more, particularly preferably 60000 or more, preferably 80000 or less, more preferably 75000 or less, and particularly preferably 70000. It is as follows. When the weight average molecular weight Mw is in the above range, a laminated film having the above characteristics can be easily obtained. In particular, by reducing the weight average molecular weight, the 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, and particularly preferably 1.5. Or less, preferably 1.0 or more. When the weight average molecular weight Mw is in the above range, the polymer viscosity can be lowered and the moldability can be improved. Moreover, the expression of retardation can be effectively reduced.

The weight average molecular weight Mw and the number average molecular weight Mn of the hydrogenated block copolymer [G] can be measured as values in terms of polystyrene by gel permeation chromatography using cyclohexane as a solvent. In the block copolymer hydride [G], for example, the main chain and side chain carbon-carbon unsaturated bonds are preferably 90% or more, more preferably 97% or more, and still more preferably 99% or more. ing. The block copolymer hydride [G] is, for example, preferably 90% or more, more preferably 97% or more, and still more preferably 99% or more of the carbon-carbon unsaturated bond of the aromatic ring. Yes. The higher the hydrogenation rate indicating the degree of hydrogenation, the better the heat resistance and light resistance.

It is preferable that the block [D1] and the block [D2] each independently comprise only the cyclic hydrocarbon group-containing compound hydride unit [I], but other than the cyclic hydrocarbon group-containing compound hydride unit [I]. May contain any unit. Examples of arbitrary structural units include structural units based on vinyl compounds other than cyclic hydrocarbon group-containing compound hydride units [I]. The content of any 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 the chain hydrocarbon compound hydride unit [II], or has the chain hydrocarbon compound unit [II] and the cyclic hydrocarbon-containing compound hydride unit [I]. It is a block. The block [E] can include any unit other than the unit [I] and the unit [II]. Examples of arbitrary structural units include structural units based on vinyl compounds other than the units [I] and [II]. The content of any 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 hydrogenated block copolymer [G] as the above-described triblock copolymer has low 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 of only the hydrogenated block copolymer [G] described above, but 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 absorbers, near infrared absorbers; resin modifiers such as lubricants and plasticizers; colorants such as dyes and pigments And antistatic agents. As these arbitrary components, one type may be used alone, or two or more types may be used in combination at an arbitrary ratio. However, from the viewpoint of remarkably exhibiting the effects of the present invention, it is preferable that the content of any component is small. For example, the total ratio of the arbitrary components is preferably 10 parts by weight or less, more preferably 7 parts by weight or less, and still more preferably 5 parts by weight or less with respect to 100 parts by weight of the hydrogenated block copolymer [G].

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

[1.1.2. Resin B]
As the resin B forming the surface layer, a resin capable of forming a surface layer that can be peeled off from the core layer made of the resin A is used. As the resin B, a thermoplastic resin can be used. In the following description, in order to distinguish resin B for forming two surface layers, it may be expressed as resin B1 and resin B2. 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 off from the core layer, and includes resins containing various polymers. It can be selected and adopted as appropriate.

Preferable 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 a polymer having an alicyclic structure in the main chain and a polymer having an alicyclic structure in the side chain. Any of these can be used. The alicyclic structure-containing polymer includes a crystalline resin and an amorphous resin, and is preferably an amorphous resin from the viewpoint of surface smoothness.

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

The number of carbon atoms constituting the repeating unit of one alicyclic structure is not particularly limited, but 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 according to the purpose of use, but is usually 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight. That's it. By increasing the number of repeating units having an alicyclic structure in this way, the heat resistance of the surface layer can be increased.

Specifically, the alicyclic structure-containing polymer includes (1) a norbornene-based polymer, (2) a monocyclic olefin polymer, (3) a cyclic conjugated diene polymer, and (4) a vinyl alicyclic carbonization. Examples thereof include hydrogen polymers and hydrides thereof. Among these, norbornene polymers and hydrides thereof are more preferable from the viewpoint of moldability.

Examples of the norbornene-based polymer include a ring-opening polymer of a norbornene-based monomer, a ring-opening copolymer of a norbornene-based monomer and another monomer capable of ring-opening copolymerization, and a hydride thereof; Examples thereof include addition polymers and addition copolymers with other monomers copolymerizable with norbornene monomers. Among these, a ring-opening polymer hydride of a norbornene-based monomer is particularly preferable from the viewpoint of moldability.
The above alicyclic structure-containing polymer is selected from, for example, polymers disclosed in JP-A No. 2002-321302.

Further, examples of the crystalline alicyclic structure-containing polymer include polymers disclosed in JP-A-2016-26909.

The weight-average molecular weight of the alicyclic structure-containing polymer was measured by gel permeation chromatography (hereinafter abbreviated as “GPC”) using cyclohexane (toluene when the resin is not dissolved) as a solvent. The weight average molecular weight (Mw) in terms of isoprene (when the solvent is toluene, in terms of polystyrene) is usually 10,000 to 100,000, preferably 25,000 to 80,000, more preferably 25,000 to 50,000. 000. When the weight average molecular weight is in such a range, the mechanical strength and moldability 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 glass transition temperature of the thermoplastic resin B is preferably 110 ° C. or higher, more preferably 120 ° C. or higher, preferably 180 ° C. or lower, more preferably 170 ° C. or lower. The thermoplastic resin B having a glass transition temperature in such a range is excellent in moldability.

The thermoplastic resin B may be composed only of the alicyclic structure-containing polymer, but may contain any component as long as the effects of the present invention are not significantly impaired. As an arbitrary component, the thing similar to the arbitrary components of the thermoplastic resin A can be used. The ratio 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.

Since various products are commercially available as the resin containing the alicyclic structure-containing polymer, those having desired characteristics can be appropriately selected and used as the thermoplastic resin B. Examples of such commercially available products include a product group having a trade name “ZEONOR” (manufactured by Nippon Zeon Co., Ltd.).

[1.2. (Laminated film production process)
In the laminated film production step, a laminated film can be produced by preparing resin A, resin B1, and resin B2 and performing melt extrusion molding of these resins by coextrusion. By performing such melt extrusion molding, a laminated film having a desired thickness can be efficiently produced. Moreover, according to melt extrusion molding, a long laminated film can be obtained.

Examples of the resin extrusion method in the coextrusion method include a coextrusion T-die method, a coextrusion inflation method, and a coextrusion lamination method. Of these, the coextrusion T-die method is preferable. The coextrusion T-die method includes a feed block method and a multi-manifold method, and the multi-manifold method is particularly preferable in that variation in thickness can be reduced.

The temperature of the resin at the time of melt extrusion molding by co-extrusion (hereinafter sometimes referred to as “extrusion temperature” as appropriate) is not particularly limited and is a temperature at which each resin can be melted and is suitable for molding. The temperature can be set as appropriate. Specifically, the higher temperature (Ts [H]) of the heat softening temperature of the resin A forming the core layer and the heat softening temperature of the resin B forming the surface layer can be set as a reference. 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 lower, more preferably It is (Ts [H] +150) degrees C or less.

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

The thermal softening temperature Ts of each resin can be measured by TMA (thermomechanical analysis) measurement. For example, the layer to be measured is cut into a 5 mm × 20 mm shape and used as a sample. Using TMA / SS7100 (manufactured by SII Nano Technology Co., Ltd.), the temperature is adjusted in a state where a tension of 50 mN is applied in the longitudinal direction of the sample. The temperature (° C.) when the linear expansion changes by 3% can be measured as the softening temperature.

Furthermore, the arithmetic average roughness Ra of the die slip 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 average roughness Ra can be measured based on JIS B0601: 1994 using a surface roughness meter.

In the coextrusion method, the film-like molten resin extruded from a die slip is usually brought into close contact with a cooling roll, cooled and cured. At this time, examples of the method for bringing the molten resin into close contact with the cooling roll include an air knife method, a vacuum box method, and an electrostatic contact method.

[1.2.1. Dimensions of each layer in laminated film)
In the laminated film obtained by the laminated film production step, the thickness of the core layer is preferably 20 μm or more, more preferably 25 μm or more, preferably 80 μm or less, more preferably 70 μm or less. The thicknesses of the two surface layers are each preferably 5 μm or more, more preferably 10 μm or more, preferably 30 μm or less, more preferably 25 μm or less.

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

[1.3. (Peeling process)
The peeling process in the manufacturing method of the optical film of the present invention is a process of peeling the surface layer from the laminated film. An optical film can be obtained through this peeling process. The two surface layers peel at the same time in the embodiment described below, but 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 laminated film conveyed from the extruder M (the laminated film 20 described with reference to FIG. 1) is conveyed downward in the drawing and is then subjected to a peeling process.

The peeling treatment in the peeling step can be performed by pulling the surface layers 11 and 12 in a direction different from the in-plane direction of the laminated film 20 to be conveyed. In the example of FIG. 2, the two

surface layers

11 and 12 are pulled in directions (directions indicated by arrow Y and arrow Z) in which the angles with respect to the two

surfaces

100A and 100B of the optical film 100 are θ1 and θ2, respectively. Thus, 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, while preferably 135 ° or less, more preferably 125 ° or less.

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

[1.4. Other process (stretching process)]
The manufacturing method of the optical film of this invention may include the extending | stretching process process. The stretching treatment step may be performed in the laminated film production step, may be performed after the laminated film production step and before the peeling step, may be performed in the peeling step, or may be performed after the peeling step. Also good.

When performing the stretching treatment step, it may be stretching in the thickness direction or stretching in the in-plane direction, and 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 in the case of stretching in the in-plane direction in addition to stretching in the thickness direction can be appropriately adjusted according to the desired optical performance required to be imparted to the optical film. . The specific draw ratio is preferably 1.0 times or more, more preferably 1.05 times or more, and preferably 1.5 times or less, more preferably 1.4 times or less. When the draw ratio in the in-plane direction is within such a range, 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 in 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, and other oblique directions. The angle formed by the two stretching directions when biaxial stretching is performed can usually be an angle orthogonal to each other, but is not limited thereto, and may be an arbitrary angle. Biaxial stretching may be sequential biaxial stretching or simultaneous biaxial stretching.

[1.5. Dimensions and characteristics of 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 water vapor transmission. The rate is 20 g / (m ² · day) or less.

The absolute value of the in-plane retardation Re 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, ideally 0 nm.

The absolute value of 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 permeability 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 may be, for example, 1 g / (m ² · day) or more.

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, 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 production 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 said measuring apparatus, the retardation of the in-plane direction and thickness direction of an optical film is computed using the average refractive index of the said optical film. Here, the average refractive index refers to the refractive index in two directions perpendicular to each other in the in-plane direction of the optical film and the average value of 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, for example, a temperature of 40 ° C. and a humidity of 90% RH in accordance with JIS K 7129 B method using a water vapor transmission rate measuring device (“PERMATRAN-W” manufactured by MOCON). It can be measured under the following conditions.

The thickness of the optical film obtained by the production method of the present invention can be measured by microscopic observation in the same manner as the thickness of each layer. Specifically, the optical film can be sliced using a microtome, and the cut surface can be observed, for example, with a polarizing microscope (for example, “BX51” manufactured by Olympus).

An optical film obtained by the method for producing an optical film of the present invention is an optical film obtained by peeling a surface layer from a laminated film comprising a core layer made of resin A and a surface layer made of resin B. By making the absolute value of the retardation Re and the absolute value of the retardation Rth in the thickness direction 2 nm or less and the water vapor transmission rate 20 g / (m ² · day) or less, the adhesion with the object is high, An optical film having a small retardation and a low water vapor transmission rate can be obtained. 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 method for producing an optical film of the present invention is usually a transparent layer and transmits visible light. The specific light transmittance can be appropriately selected according to the use of the optical film. For example, the light transmittance at a wavelength of 420 nm to 780 nm is preferably 85% or more, more preferably 88% or more. By adopting such a configuration having 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 decrease in luminance particularly during long-term use.

[2. Optical film of the present invention]
In another certain aspect of the present invention, the optical film comprises 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. The block copolymer containing the block [Ea] which has a compound unit is included. 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, a unit obtained by hydrogenating a unit having an unsaturated bond may be used, or a unit which is not hydrogenated and has an unsaturated bond may be used. When the optical film contains such a block copolymer, an optical film having a low retardation can be obtained, and therefore the optical film of the present invention can be used as a member that requires a low retardation. In addition, it is possible to obtain an optical film that has high light resistance and hardly yellows.

As a preferable example of the block copolymer, the block [Da] includes two or more polymer blocks [Db] each having a cyclic hydrocarbon group-containing compound hydride unit, and the block [Ea] 1 or more of a polymer block [Eb] having a chain hydrocarbon compound hydride unit, or a chain hydrocarbon compound or hydride unit thereof and a cyclic hydrocarbon-containing compound or hydride unit thereof. A copolymer is mentioned.

Specific examples of the material constituting the optical film of the present invention include the resin A described above. Moreover, as an example of the block copolymer contained in it, the same example as the example of the hydrogenated block copolymer [G] described above is mentioned. Furthermore, examples of the blocks [Da] and [Ea] constituting the block copolymer and examples of the blocks [Db] and [Eb] as specific examples thereof include the blocks [D] and [E] described above. The same example as above is given. Examples of units constituting the block [Da] and the block [Ea] include the same examples as the units constituting the blocks [D] and [E]; and an aromatic vinyl compound unit and a chain conjugated diene compound unit Is mentioned. 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. is there. However, these are not limited by the manufacturing method. Examples of the aromatic vinyl compound and the chain conjugated diene compound mentioned here are the same as those mentioned above.

Examples of block copolymers other than hydrogenated block copolymers [G] include aromatic vinyl compounds as hydride precursors described in International Publication No. WO2016 / 1528771 / Conjugated diene compound block 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] 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 central part" here is the central part in the thickness direction of the film. However, in the case of the 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 the same composition ratio as 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 replaced with the value of the composition ratio at the center.

The composition ratio between the volume of the block [Da] and the volume of the block [Ea] can be obtained 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, in the surface and cross section of the optical film, the area ratio of the phase derived from each block is obtained, and the ratio of the areas can be obtained to obtain the composition ratio of the block [Da] and the block [Ea]. .

The measurement of the area of each phase can be performed with an atomic force microscope (for example, an atomic force microscope manufactured by Bruker, Dimension Fast Scan Icon). An adhesion force image of the optical film can be obtained by an atomic force microscope, and the area ratio of phases derived from each block in the image can be measured. Moreover, the observed phase can be attributed to the phase of the block [Da] and the phase of the block [Ea] from the information regarding the adhesion force of the observed phase.

The block [Da] ratio in each of the surface and the central object can be calculated by calculating the percentage of the area of the phase belonging to the block [Da] out of the total area of the two types of phase as 100%. . The difference in composition ratio between the volume of the block [D] and the volume of the block [E] at the surface and the central part can be calculated by the following equation.
Difference in composition ratio = | (block [D] ratio in the center) − (block [D] ratio in the surface) |

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

The optical film of the present invention can be produced by extrusion film formation of a resin containing a block copolymer. By performing extrusion film formation, efficient production becomes possible. However, according to what the present inventors have found, when extrusion film formation is performed, the difference in the composition ratio between the volume of the block [D] and the volume of the block [E] at the surface and the central portion becomes large. Here, [1. By adopting the production method described in [Production method of optical film of the present invention], a film having a small difference in composition ratio can be easily obtained.

The dimensions and characteristics of the optical film of the present invention are described in [1.5. The dimensions and characteristics of the optical film obtained by the production method of the present invention] are the same as those described above.

[3. Polarizing plate and manufacturing method thereof]
[1. The optical film obtained by the production method described in [Production method of optical film of the present invention], and [2. The optical film of the present invention described below in the optical film of the present invention (hereinafter simply referred to as “optical film of the present invention”) is a protective film for protecting other layers in a display device such as a liquid crystal display device. Can be suitably used. Especially, the optical film of this invention is suitable as a polarizer protective film, and is especially suitable as an inner side polarizer protective film of a display apparatus.

The polarizing plate of the present invention includes the above-described optical film of the present invention and a polarizer. 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 for bonding these between the optical film and the polarizer.

The polarizing plate of the present invention can include an arbitrary layer in addition to the optical film and the polarizer. Examples of the optional layer include a hard coat layer that increases the surface hardness, a mat layer that improves the slipperiness of the film, and an antireflection layer.

The polarizer is not particularly limited, and any polarizer can be used. Examples of the polarizer include those obtained by adsorbing a material such as iodine or a dichroic dye on a polyvinyl alcohol film and then stretching the material. Examples of the adhesive constituting the adhesive layer include those using various polymers as a base polymer. Examples of such base polymers include 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, usually, a single-layer polarizer and two-layer protective films provided on both sides thereof can be provided. Of these two protective films, both may be the optical film of the present invention, and only one of them may be the optical film of the present invention. In particular, in a liquid crystal display device having a light source and a liquid crystal cell and having polarizing plates on both the light source side and the display surface side of the liquid crystal cell, the present invention is used as a protective film used at a position closer to the light source side than a polarizer on the display surface side. It is particularly preferred to provide the inventive optical film. By having such a configuration, a liquid crystal display device having excellent display quality with excellent durability and small color unevenness can be easily configured.

The polarizing plate of the present invention can be manufactured by any manufacturing method. For example, the polarizing plate of this invention can be manufactured by bonding the optical film obtained by the said manufacturing method, and a polarizer. Such pasting may be pasting in which these layers are brought into direct contact or pasting via 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.
Examples of the liquid crystal display device suitable for providing the polarizing plate of the present invention include an in-plane switching (IPS) mode, a vertical alignment (VA) mode, a multi-domain vertical alignment (MVA) mode, and a continuous spin wheel alignment (CPA). ) Mode, hybrid alignment nematic (HAN) mode, twisted nematic (TN) mode, super twisted nematic (STN) mode, optically compensated bend (OCB) mode, etc. . Among these, a liquid crystal display device including an IPS mode liquid crystal cell is particularly preferable because the optical film of the present invention is excellent in durability and the effect of suppressing color unevenness is remarkable.

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 another member constituting the liquid crystal display device such as a liquid crystal cell. For example, a liquid crystal display device can be manufactured by laminating a liquid crystal cell and a polarizing plate directly or via an adhesive layer, and placing this in a display device. Alternatively, a liquid crystal display device can be manufactured by simply stacking a liquid crystal cell and a polarizing plate and placing them in the display device.

Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples, and can be implemented with any modifications without departing from the scope of the claims of the present invention and the equivalents thereof.
In the following description, “%” and “part” representing amounts are based on weight unless otherwise specified. In addition, the operations described below were performed under normal temperature and normal pressure conditions unless otherwise specified.

The specific example of the block [D] in the above description and the specific example of the block [Da] in the above description are simply referred to as “block [D]” in the following description. The specific example of the block [E] in the above description and the specific example of the block [Ea] in the above description are simply referred to as “block [E]” in the following description.

〔Evaluation 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 equivalent values using a gel permeation chromatography (GPC) system (“HLC-8320” manufactured by Tosoh Corporation). In the measurement, an H type column (manufactured by Tosoh Corporation) was used as the column, and cyclohexane was used as the solvent. Moreover, the temperature at the time of measurement was 40 degreeC.

[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 containing hydrogenated block copolymer [G1] or the like) was press-molded to prepare a test piece having a length of 50 mm, a width of 10 mm, and a thickness of 1 mm. Using this test piece, based on JIS-K7244-4 method, using a viscoelasticity measuring device (product name “ARES”, manufactured by T.A. Instruments Japan Co., Ltd.), −100 ° C. to + 150 ° C. The dynamic viscoelastic properties were measured at a temperature rising rate of 5 ° C./min. The glass transition temperature Tg ₂ was calculated from the peak top temperature of the loss tangent tan δ (when a plurality of peaks are observed, the peak temperature on the high temperature side).

[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 30 ° C. higher than the glass transition temperature, and then cooled at −10 ° C. / After cooling to room temperature in minutes, the temperature was increased at a rate of temperature increase of 10 ° C./min, thereby measuring the thermal softening temperature.

[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 as follows.
The film to be measured was sliced using a microtome (“RV-240” manufactured by Daiwa Koki Co., Ltd.). The cut surface of the sliced film was observed with a polarizing microscope (OLYMPUS "BX51"), and the thickness was measured.

[Measurement method of thermal softening temperature Ts]
A film to be measured was cut into a 5 mm × 20 mm shape and used as a sample. As a measuring device, TMA / SS7100 (manufactured by SII Nanotechnology Inc.) was used. In TMA (thermomechanical analysis) measurement, the temperature was changed with a tension of 50 mN applied in the longitudinal direction of the sample. The temperature (° C.) when the linear expansion changed by 3% was defined as the softening temperature.

[Measurement method of in-plane direction retardation and thickness direction retardation]
By measuring the film of each example (Example and Comparative Example) using a retardation measuring device (product name “Axoscan” manufactured by Axometric) at a wavelength of 590 nm, the retardation Re in the in-plane direction of the film of each example is measured. And the absolute value of retardation Rth in the thickness direction were determined.

[Measurement method of 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., which has not been subjected to stretching treatment) made of a resin containing a norbornene-based polymer was prepared. One side of the film obtained in each example and the test film was subjected to corona treatment. An adhesive was attached to the corona-treated surface of the film of each example and the corona-treated surface of the test film, and the surfaces to which the adhesive was attached were bonded together. At this time, a UV adhesive (CRB series (manufactured by Toyochem Co., Ltd.)) was used as the adhesive, thereby obtaining a sample film S including the film 100 and the test film 60 of each example (see FIG. 3).
Thereafter, as shown in FIG. 3, the sample film S was cut into 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 obtain an evaluation sample. At this time, double-sided adhesive tape (manufactured by Nitto Denko Corporation, product number “CS9621”) was used as the adhesive 70. In FIG. 3, 50 is an adhesive.
A 90-degree peel test was performed by sandwiching the test film 60 at the tip of a force gauge and pulling it in the normal direction of 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 a force required to peel off the film 100 of each example (Example and Comparative Example) from the test film 60. The size was measured as peel strength. When the material was destroyed before the test film was peeled off because the force required for peeling was very large, it was described as “impossible to measure due to material destruction”.

(Supplementary method for measuring peel strength)
In the measurement method of the peel strength, a specific test film is used instead of the polarizing plate. Thus, in order to verify the validity of measuring the peel strength using the test film instead of the polarizing plate, the inventor conducted the following experiment on the film obtained in Example 1.
Instead of the test film, according to Example 1 of JP-A-2005-70140, a retardation film laminate is bonded to one surface of the polarizing film, and a triacetyl cellulose film is attached to the other surface of the polarizing film. Bonding and 90 degree peeling test were carried out. That is, first, a polarizing film and an adhesive described in Example 1 of JP-A-2005-70140 were prepared. A surface of the retardation film laminate subjected to corona treatment was bonded to one surface of the prepared polarizing film via the adhesive. In addition, a triacetyl cellulose film was bonded to the other surface of the polarizing film via the adhesive. Then, it was made to dry for 7 minutes at 80 degreeC, the adhesive agent was hardened, and the sample film was obtained. The sample film obtained was subjected to a 90 degree peel test.
As a result of the experiment, the same result as that obtained when the test film was used instead of the polarizing plate was obtained. Therefore, the results of the following examples and comparative examples using test films instead of polarizing plates are reasonable.

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

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

(Measurement of block composition ratio)
In the optical film, the block composition ratio is measured using a Bruker atomic force microscope Dimension Fast Scan Icon to obtain an adhesion force image of the optical film and measure the area ratio of the phase derived from each block in the image. It was done by doing.

AC240TS (Olympus, spring constant: 1.5 N / m, TIP radius of curvature 15 nm) was used as a cantilever for capturing an adhesion force image. The measurement mode for imaging was the Scan Asyst mode, the scan rate was 2 Hz, and the adhesion force image was measured in an area of 500 nm × 500 nm.

The adhesion force image was measured at the film surface and at the center. The measurement of the center of the film was performed at a position of a depth of 5 μm from the film surface in the cross section after the cross section of the film was taken out.

The image of the adhesion force image measurement result was analyzed and a histogram was drawn. In the histogram, the horizontal axis represents the adhesion force measured at each measurement point, and the vertical axis represents the number of measurement points at which the adhesion force was measured. The area ratio of two types of phases considered to be attributable to the two types of blocks was calculated by fitting with a Gaussian function.

Generally, the adhesion force depends on Tg, and it is known that the adhesion force is higher when the cantilever is pulled away from the surface of the low Tg sample. For this reason, it can be determined that the phase having a high adhesive force is the block [E] and the phase having a low adhesive force is the block [D].

The area ratio was calculated by taking the total area 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 the block [D] and the block [E] between the surface and the center was calculated by the following formula.
Difference in composition ratio = | (block [D] ratio in the center) − (block [D] ratio in the surface) |

[Production Example 1]
(P1-1) Production of Block Copolymer [F1] A reactor equipped with a stirrer and sufficiently purged with nitrogen inside was charged with 270 parts of dehydrated cyclohexane, 75 parts of dehydrated styrene and 7.0 parts of dibutyl ether. . While stirring the whole volume at 60 ° C., 5.6 parts of n-butyllithium (15% cyclohexane solution) was added to initiate polymerization. Subsequently, the whole volume was stirred at 60 ° C. for 60 minutes. The reaction temperature was maintained at 60 ° C. until the reaction was stopped. At this time (first stage of polymerization), the reaction solution was analyzed by gas chromatography (hereinafter sometimes referred to as “GC”) and GPC. As a result, 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 as it was after the addition was completed. At this time (second stage of polymerization), the reaction solution was analyzed by GC and GPC. As a result, the polymerization conversion was 99.8%.
Thereafter, 10 parts of dehydrated styrene was continuously added to the reaction solution over 30 minutes, and stirred for 30 minutes as it was after completion of the addition. At this time (the third stage of polymerization), the reaction solution was analyzed by GC and GPC. As a result, the polymerization conversion was almost 100%.

Here, 1.0 part of isopropyl alcohol was added to stop the reaction, thereby obtaining a polymer solution containing a block copolymer [F1] of [D1]-[E]-[D2] type. 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) is transferred to a pressure-resistant reactor equipped with a stirrer, and diatomaceous earth-supported nickel is used as a hydrogenation catalyst. 4.0 parts of a catalyst (product name “E22U”, nickel loading 60%, manufactured by JGC Catalysts & Chemicals Co., Ltd.) and 30 parts of dehydrated cyclohexane were added and mixed. The inside of the reactor was replaced with hydrogen gas, and hydrogen was supplied while stirring the solution. 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 the hydrogenated block copolymer [G1]. The hydrogenated block copolymer had a Mw [G1] of 71,800, a molecular weight distribution Mw / Mn of 1.30, and a hydrogenation rate of almost 100%.

After completion of the hydrogenation reaction, the reaction solution is filtered to remove the hydrogenation catalyst, and then the phenol-based antioxidant pentaerythrityl tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) ) Propionate] (product name “AO60”, manufactured by ADEKA) 2.0 parts of xylene solution in which 0.3 part was dissolved was added and dissolved to obtain a solution.
Next, the above solution is treated at a temperature of 260 ° C. and a pressure of 0.001 MPa or less using a cylindrical concentrating dryer (product name “Contro”, manufactured by Hitachi, Ltd.), and cyclohexane, xylene and other volatile components are removed from the solution. And a molten resin was obtained. This was extruded from a die into a strand, cooled, and formed into pellets by a pelletizer. As a result, 95 parts of a pellet of the resin [G1] containing the hydrogenated block copolymer [G1] was produced.
The obtained hydrogenated block copolymer [G1] in the resin [G1] has Mw [G1] = 68,500, Mw / Mn = 1.30, Tg ₂ = 140 ° C., Ts = 139 ° C., (D1 + D2) / E = 85/15 and D1 / D2 = 7.5.

[Production Example 2]
(P2-1) Production of block copolymer [F2] A reactor equipped with a stirrer and sufficiently purged with nitrogen inside was charged with 270 parts of dehydrated cyclohexane, 70 parts of dehydrated styrene and 7.0 parts of dibutyl ether. . While stirring the whole volume at 60 ° C., 5.6 parts of n-butyllithium (15% cyclohexane solution) was added to initiate polymerization. Subsequently, the whole volume was stirred at 60 ° C. for 60 minutes. The reaction temperature was maintained at 60 ° C. until the reaction was stopped. As a result of analyzing the reaction solution by GC and GPC at this time (first stage of polymerization), 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 as it was after the addition was completed. At this time (second stage of polymerization), the reaction solution was analyzed by GC and GPC. As a result, the polymerization conversion was 99.8%.
Thereafter, 10 parts of dehydrated styrene was continuously added to the reaction solution over 30 minutes, and stirred for 30 minutes as it was after completion of the addition. At this time (the third stage of polymerization), the reaction solution was analyzed by GC and GPC. As a result, the polymerization conversion was almost 100%.

Here, 1.0 part of isopropyl alcohol was added to stop the reaction to obtain a polymer solution containing a block copolymer [F2] of [D1]-[E]-[D2] type. 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) is transferred to a pressure resistant reactor equipped with a stirrer, and diatomaceous earth-supported nickel is used as a hydrogenation catalyst. 4.0 parts of a catalyst (product name “E22U”, nickel loading 60%, manufactured by JGC Catalysts & Chemicals Co., Ltd.) and 30 parts of dehydrated cyclohexane were added and mixed. The inside of the reactor was replaced with hydrogen gas, and hydrogen was supplied while stirring the solution. 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 the hydrogenated block copolymer [G2]. 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 almost 100%.

After completion of the hydrogenation reaction, the reaction solution is filtered to remove the hydrogenation catalyst, and then the phenol-based antioxidant pentaerythrityl tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) ) Propionate] (product name “AO60”, manufactured by ADEKA) 2.0 parts of xylene solution in which 0.3 part was dissolved was added and dissolved to obtain a solution.
Next, the above solution is treated at a temperature of 260 ° C. and a pressure of 0.001 MPa or less using a cylindrical concentrating dryer (product name “Contro”, manufactured by Hitachi, Ltd.), and cyclohexane, xylene and other volatile components are removed from the solution. And a molten resin was obtained. This was extruded from a die into a strand, cooled, and formed into pellets by a pelletizer. As a result, 95 parts of a pellet of the resin [G2] containing the hydrogenated block copolymer [G2] was produced.
The obtained hydrogenated block copolymer [G2] in the resin [G2] has Mw [G2] = 69,500, Mw / Mn = 1.30, Tg ₂ = 140 ° C., Ts = 138 ° C., (D1 + D2) / E = 80/20 and D1 / D2 = 7.0.

[Example 1]
(1-1. Production of optical film)
A double flight type single screw extruder (screw diameter D = 50 mm, screw length L to screw diameter D ratio L / D = 28) equipped with a leaf disk-shaped polymer filter with a mesh opening of 3 μm was prepared. . Into this single-screw extruder, the pellet-shaped resin [G1] obtained in Production Example 1 was introduced as the thermoplastic resin A, melted, and supplied to the single-layer die through the feed block. The introduction of the resin A into the single screw extruder was performed through a hopper loaded in the single screw extruder. Moreover, the surface roughness (arithmetic mean roughness Ra) of the die slip of the single-layer die was 0.1 μm. Furthermore, the extruder A exit temperature of the resin A was 260 ° C.

On the other hand, a single-screw extruder (screw diameter D = 50 mm, screw length L / screw diameter D ratio L / D = 30) having a leaf disk-shaped polymer filter with a mesh opening of 3 μm was prepared. . Into this single screw extruder, as thermoplastic resin B, resin B containing an amorphous alicyclic structure-containing polymer (resin “B-1”, manufactured by Nippon Zeon Co., Ltd., heat softening temperature: 160 ° C.) The solution was introduced, dissolved, and supplied to the single-layer die through a feed block. The extruder B temperature of resin B was 260 ° C.

Resin A and Resin B were discharged from a single layer die of an extruder in a molten state at 260 ° C. Thereby, a film-like resin including three layers of 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 was formed (coextrusion molding step). The discharged film-like resin was cast on a cooling roll. In casting, edge pinning was performed to fix the widthwise end of the film-like resin to the cooling roll, and the air gap amount was set to 50 mm. Thereby, the film-like resin was cooled to obtain a laminated film having a three-layer structure. The obtained laminated film was a three-layer laminated film made of two kinds of resins provided with 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. Production and evaluation of optical film)
A peeling step for peeling the surface layer from the laminated film having the three-layer structure obtained in (1-1) was performed. The peeling process was performed by pulling the surface layer on both sides of the laminated film and continuously peeling the surface layer from the core layer. The direction of pulling the two surface layers was such that the angle with respect to the surface of the core layer was 60 °, and the peeling speed was 5 m / min. As a result, a single-layer film 1 having a thickness of 40 μm from which the surface layer was peeled was obtained.
The obtained film 1 was evaluated and the results are shown in Table 1. In the evaluation of peel strength, the peel strength was not measurable 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. Later, the surface layer was peeled off to obtain a single-layer film 2 having a thickness of 40 μm. The obtained film 2 was evaluated in the same manner as in Example 1, and the results are shown in Table 1. In the evaluation of peel strength, the peel strength was not measurable 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, screw length L to screw diameter D ratio L / D = 28) equipped with a leaf disk-shaped polymer filter with a mesh opening 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 the single-layer die. The resin [G1] was introduced into the single screw extruder through a hopper loaded in the single screw extruder. Moreover, the surface roughness (arithmetic mean roughness Ra) of the die slip of the single-layer die was 0.1 μm. Furthermore, 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. Thereby, a film-like resin consisting only of the layer made of the resin [G1] was continuously formed. The discharged film-like resin was cast on a cooling roll. In casting, edge pinning was performed to fix the widthwise end of the film-like resin to the cooling roll, and the air gap amount was set to 50 mm. Thereby, the film-like resin was cooled to obtain a film C1 having a single-layer structure made of resin [G1] and having a thickness of 40 μm. The obtained resin film C1 was evaluated in the same manner as the film of Example 1, and the results are shown in Table 1.

[Comparative Example 2]
From the resin [G2], the same operation as in Comparative Example 1 was used 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. A film C2 having a single layer structure and a thickness of 40 μm was manufactured. This film C2 was evaluated in the same manner as the film of Example 1, and the results are shown in Table 1.

[Comparative Example 3]
Optical film E (“Fujitack”, manufactured by Fuji Film Co., Ltd., thickness 40 μm) was evaluated in the same manner as the film of Example 1, and the results are shown in Table 1. For the measurement of peel strength, a saponified film was used.

Table 1 summarizes the results of Examples and Comparative Examples.

The meanings of the abbreviations in the table are as follows.
G1: Hydrogenated block copolymer [G1] produced in Production Example 1.
G2: Hydrogenated block copolymer [G2] produced in Production Example 2.
B-1: A resin containing an alicyclic structure-containing polymer, a heat softening temperature of 160 ° C., one of the “ZEONOR” product group manufactured by Nippon Zeon.
E: Optical film, “Fujitack” manufactured by FUJIFILM Corporation
| Re |: Absolute value of retardation in in-plane direction | Rth |: Absolute value of retardation in thickness direction

As is apparent from the results of the examples and comparative examples, the film obtained by the method for producing an optical film of the present invention has high adhesion to an object, low retardation, and low optical permeability. can do.

DESCRIPTION OF SYMBOLS 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 ... Optical film surface M ... Extrusion molding Machine P ... Peeling area S ... Sample film

Claims

A block [Da] having a cyclic hydrocarbon group-containing compound unit;
A block [Ea] having a chain hydrocarbon compound unit, or a chain hydrocarbon compound unit and a cyclic hydrocarbon group-containing compound unit;
A block copolymer comprising
The difference in the composition ratio between the volume of the block [Da] and the volume of the block [Ea] at the surface and the central part is 0 to 10%,
The absolute value of in-plane retardation 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.
The optical film according to claim 1, wherein the resin containing the block copolymer is formed by extrusion.
The block copolymer is
The block [Da] includes two or more polymer blocks [Db] per molecule having a cyclic hydrocarbon group-containing compound hydride unit,
One or more polymers per molecule having a chain hydrocarbon compound hydride unit or a chain hydrocarbon compound or hydride unit thereof and a cyclic hydrocarbon-containing compound or hydride unit thereof as the block [Ea] The optical film of Claim 1 or 2 which is a copolymer containing block [Eb].
A polarizing plate comprising the optical film according to any one of claims 1 to 3 and a polarizer.
A liquid crystal display device comprising the polarizing plate according to claim 4.
By coextruding resin A and resin B to obtain a laminated film comprising a core layer made of resin A, and a surface layer made of resin B provided on the surface of the core layer;
Peeling the surface layer from the laminated film, and a method for producing an optical film comprising:
The optical film is
The absolute value of in-plane retardation is 5 nm or less,
The absolute value of retardation in the thickness direction is 10 nm or less, and
The manufacturing method of an optical film whose water-vapor-permeation rate is 20 g / (m < 2 > * day) or less.
The method for producing an optical film according to claim 6, wherein an absolute value of retardation in the in-plane direction of the optical film is 2 nm or less, and an absolute value of 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 resin A is
Two or more polymer blocks [D] per molecule having cyclic hydrocarbon group-containing compound hydride units;
One or more polymer blocks [E] per molecule having a chain hydrocarbon compound hydride unit, or a chain hydrocarbon compound unit and a cyclic hydrocarbon-containing compound hydride unit;
The method for producing an optical film according to any one of claims 6 to 8, comprising a hydrogenated block copolymer comprising
The resin A is
A block 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;
A block copolymer containing
In the optical film, the difference in composition ratio between the surface and the center is 0 to 10%.
The method for producing an optical film according to any one of claims 6 to 8.