WO2018123912A1

WO2018123912A1 - Method for producing optical film, polarizing plate, and display device

Info

Publication number: WO2018123912A1
Application number: PCT/JP2017/046252
Authority: WO
Inventors: 浩成摺出寺
Original assignee: 日本ゼオン株式会社
Priority date: 2016-12-28
Filing date: 2017-12-22
Publication date: 2018-07-05
Also published as: JP7036031B2; JPWO2018123912A1; KR102287915B1; CN109863429A; KR20190100169A; CN109863429B; TWI736727B; TW201825936A

Abstract

This method for producing an optical film includes a peeling step in which a multilayer film is subjected to peeling processing. The multilayer film is long, and includes: a film (A) comprising a thermoplastic resin A; and a film (B) which is provided to one or both surfaces of film (A). The peeling processing includes peeling film (B) from film (A) at temperature Tov (˚C) such that a force is applied in the thickness direction of film (A). Temperature Tov and the glass transition temperature TgA(˚C) of film (A) satisfy the relationship Tov≥TgA. Film (B) has a shrinkage ratio Xb of at least 0% but less than 4%. The shrinkage ratio Xb is for the width direction of film (B) when film (B) is processed at temperature Tov for 60 seconds. Also provided are a polarizing plate and a display device which use said optical film.

Description

Optical film manufacturing method, polarizing plate, and display device

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

In a display device such as a liquid crystal display device, a resin-made optical film having a phase difference is widely used for the purpose of optical compensation or the like. As a method for imparting a phase difference to a resin film, stretching the film is widely performed.

As such an optical film, a film having an NZ coefficient Nz satisfying 0 <Nz <1, preferably 0.4 <Nz <1, more ideally a film having Nz = 0.5 may be required. . However, when the film is stretched by a usual method, the value of the NZ coefficient becomes a value smaller than 0 or larger than 1, so that it is difficult to obtain a film with 0 <Nz <1.

As a method for obtaining a film of 0 <Nz <1, it is conceivable to employ a multilayer film in which a plurality of films are combined. However, it is required to realize a film of 0 <Nz <1 with a simpler single layer structure.

As a method for realizing a film of 0 <Nz <1 with a single layer film, a method described in Patent Document 1 is known. In Patent Document 1, a shrink film is bonded to a resin film to be processed, and then the shrink film is contracted, thereby contracting the resin film. As a result, 0 <Nz <1 is achieved.

Japanese Patent Application Laid-Open No. 08-207119 (corresponding to other countries: European Patent Application Publication No. 0707938)

However, in the method described in Patent Document 1, it is difficult to control the shrinkage force of the shrink film, and the process of shrinking the shrink film is complicated, and it is easy to produce a film of 0 <Nz <1. Have difficulty.

Therefore, an object of the present invention is to provide an optical film manufacturing method capable of easily manufacturing an optical film of 0 <Nz <1. A further object of the present invention is to provide a polarizing plate that can be easily manufactured and has a high optical compensation function, and a display device that can be easily manufactured and has high optical compensation.

The present inventor has studied to solve the above problems. As a result, the present inventor has found that such a problem can be solved by stretching the film in the thickness direction by utilizing the peeling force of the film as an unprecedented method for producing an optical film. Furthermore, it discovered that the operation of favorable thickness direction extending | stretching can be performed by making the temperature of extending | stretching to this thickness direction, and the characteristic of the film to be peeled into a specific thing. The present invention has been made based on such findings.
That is, the present invention is as follows.

[1] including a peeling step of subjecting the multilayer film to a peeling treatment,
The multilayer film is a long multilayer film including a film (A) made of a thermoplastic resin A, and a film (B) provided on one or both surfaces of the film (A).
The peeling treatment includes peeling the film (B) from the film (A) at a temperature Tov (° C.) so that a force is applied in the thickness direction of the film (A),
The temperature Tov and the glass transition temperature TgA (° C.) of the film (A) satisfy the relationship of Tov ≧ TgA,
The film (B) has a shrinkage rate Xb of 0% or more and less than 4%, and the shrinkage rate Xb is determined when the film (B) is processed under the conditions of a temperature Tov and 60 seconds. B) the shrinkage rate in the width direction,
Manufacturing method of optical film.
[2] The method for producing an optical film according to [1], wherein the thermoplastic resin A includes an alicyclic structure-containing polymer.
[3] The method for producing an optical film according to [1] or [2], further comprising a stretching step of stretching the multilayer film in an in-plane direction.
[4] A polarizing plate comprising an optical film produced by the production method according to any one of [1] to [3] and a polarizer.
[5] A display device comprising an optical film manufactured by the manufacturing method according to any one of [1] to [3].

According to the present invention, an optical film manufacturing method capable of easily manufacturing an optical film of 0 <Nz <1; a polarizing plate that can be easily manufactured and has a high optical compensation function; and easily manufactured A display device capable of performing high optical compensation is provided.

FIG. 1 is a side view schematically showing an example of a peeling apparatus for performing a peeling process in the manufacturing method of the present invention and an operation of the peeling process using the apparatus. FIG. 2 is a side view schematically showing another example of the peeling apparatus for performing the peeling process in the manufacturing method of the present invention and the operation of the peeling process using the apparatus.

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 in-plane retardation Re of the film is a value represented by Re = (nx−ny) × d unless otherwise specified, and the retardation Rth in the thickness direction of the film is unless otherwise specified. , Rth = {(nx + ny) / 2−nz} × d. The NZ coefficient Nz of the film is a value represented by Nz = (nx−nz) / (nx−ny), and can also be expressed as Nz = (Rth / Re) +0.5. Here, nx represents the refractive index in the direction that gives the maximum refractive index in the in-plane direction of the film, that is, the direction perpendicular to the thickness direction. ny represents the refractive index in the in-plane direction and orthogonal to the nx direction. nz represents the refractive index in the thickness direction. d represents the thickness of the film. The 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.

In this technical field, “stretching” of a film usually means an operation of deforming the film so as to expand the shape of the film in one or more directions in the in-plane direction of the film. However, in the present application, the “stretching” of the film is not limited thereto, and the film is deformed so as to expand the shape of the film in a direction other than the in-plane direction (a direction non-parallel to the film surface direction, such as a thickness direction). Includes operations. In the following description, when the context clearly shows, the operation of deforming the film so as to expand the shape of the film in one or more normal directions in the in-plane direction of the film is simply referred to as “stretching”. On the other hand, the process of deforming the film so as to expand the shape of the film in a direction other than the in-plane direction is called “thickness direction stretching”, distinguishing from such normal “stretching”, and the film that has undergone such processing Is referred to as a “thickness direction stretched film”.

[1. Manufacturing method of optical film]
The manufacturing method of the optical film of this invention includes the peeling process which uses a specific multilayer film for a specific peeling process.

[1.1. (Multilayer film)
The multilayer film used for the peeling step is a long multilayer film including a film (A) made of the thermoplastic resin A and a film (B) provided on one or both surfaces of the film (A).

[1.1.1. Film (A)]
The thermoplastic resin A constituting the film (A) is not particularly limited, and a resin containing various polymers that can impart desired physical properties as an optical film can be appropriately selected and employed.

Preferable examples of the polymer contained in the thermoplastic resin A 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 can include a crystalline resin and an amorphous polymer. From the viewpoint of obtaining the desired effect of the present invention and the viewpoint of production cost, an amorphous alicyclic structure-containing polymer is preferable.

Examples of the alicyclic structure possessed by the amorphous alicyclic structure-containing polymer include a cycloalkane structure and a cycloalkene structure, and a cycloalkane structure is preferable from the viewpoint of thermal stability and the like.

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 base film can be increased.

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

Examples of the norbornene polymer include a ring-opening polymer of a norbornene monomer, a ring-opening copolymer of a norbornene monomer and another monomer capable of ring-opening copolymerization, and a hydride thereof; an addition polymer of a norbornene monomer, norbornene Examples thereof include addition copolymers with other monomers copolymerizable with the monomers. Among these, a ring-opening polymer hydride of a norbornene monomer is particularly preferable from the viewpoint of transparency.
Examples of the alicyclic structure-containing polymer include polymers disclosed in JP-A No. 2002-332102.

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

Other examples of the polymer contained in the thermoplastic resin A include general-purpose polymers such as triacetyl cellulose and polystyrene polymers. In particular, among polystyrene polymers, polystyrene polymers having a syndiotactic structure can be preferably employed. Examples of the polystyrene-based polymer having a syndiotactic structure include polymers disclosed in JP-A-2014-186273.

The weight average molecular weight of the polymer contained in the thermoplastic resin A is not particularly limited, but is preferably 10,000 or more, more preferably 20,000 or more, and preferably 300,000 or less, more preferably 250,000 or less. When the weight average molecular weight is within such a range, the thermoplastic resin A having excellent mechanical strength and molding processability can be easily obtained.

The thermoplastic resin A may be composed of a polymer as a main component such as those described above, but may contain any compounding agent as long as the effects of the present invention are not significantly impaired. The ratio of the polymer as the main component in the resin is preferably 70% by weight or more, more preferably 80% by weight or more.

As the thermoplastic resin A, various commercially available products having desired characteristics can be appropriately selected and employed. Examples of such commercially available products include the product name “ZEONOR” (manufactured by ZEON Corporation), the product name “TOPAS” (manufactured by Polyplastics Corporation), and the product name “ARTON” (manufactured by JSR Corporation). Is mentioned.

The glass transition temperature TgA of the thermoplastic resin A is preferably 100 ° C. or higher, more preferably 110 ° C. or higher, while preferably 180 ° C. or lower, more preferably 170 ° C. or lower. When TgA is in such a range, a process such as stretching in the thickness direction can be smoothly performed, and an optical film having desired optical properties can be easily obtained.

The thickness of the film (A) is preferably 10 μm or more, more preferably 20 μm or more, while preferably 200 μm or less, more preferably 190 μm or less. When the thickness of the film (A) is within such a range, a process such as stretching in the thickness direction can be smoothly performed, and an optical film having desired optical properties can be easily obtained.

The method for producing the film (A) is not particularly limited, and any production method can be adopted. For example, the film (A) can be produced by molding the thermoplastic resin A into a desired shape. A preferable example of the molding method for molding the resin A is extrusion molding. By performing extrusion molding, a film (A) having a desired dimension can be produced efficiently.

[1.1.2. Film (B)]
The material constituting the film (B) is not particularly limited, and resins containing various polymers suitable for the practice of the present invention can be appropriately selected and employed. Hereinafter, this resin is simply referred to as “resin B”.

As the resin B, a thermoplastic resin can be used. Examples of the polymer contained in the resin B and the preferred range of the molecular weight thereof include the same examples as those given above as examples of the alicyclic structure-containing polymer and other polymers contained in the thermoplastic resin A. sell.

Further examples of the alicyclic structure-containing polymer contained in the resin B include two or more polymer blocks having a cyclic hydrocarbon group-containing compound hydride unit [I], and a chain hydrocarbon compound hydride. Mention may be made of hydrogenated block copolymers comprising units [II] or one or more polymer blocks having a combination of units [I] and units [II]. Specific examples of such a hydrogenated block copolymer include polymers disclosed in International Publication No. WO2016 / 152871.

Further examples of the polymer contained in the resin B include general-purpose polymers such as polypropylene, (meth) acrylate polymer, and polyimide. As the resin B, among various commercially available products, those having desired characteristics can be appropriately selected and employed. Examples of such commercially available products include self-adhesive stretched polypropylene films (for example, trade name “FSA 010M # 30” manufactured by Futamura Chemical Co., Ltd.).

The film (B) in the multilayer film has a shrinkage rate Xb within a specific range. The shrinkage rate Xb is a shrinkage rate in the width direction of the film (B) when the film (B) is processed under the conditions of the temperature Tov and 60 seconds. Here, the temperature Tov is the temperature of the film in the peeling step of the production method of the present invention.

The shrinkage rate Xb is 0% or more, preferably 0.3% or more, more preferably 0.5% or more, and even more preferably 1.4% or more, while less than 4%, preferably 3.9% or less. More preferably, it is 3.8% or less. When the shrinkage rate Xb is in such a range, the generation of wrinkles in the process up to the peeling process is suppressed, and the unintentional peeling of the film (B) in the stage before the peeling process is suppressed. A force can be applied to the film (A). The shrinkage rate Xb can be obtained by heat-treating a sample of the film (B) at a temperature Tov for 60 seconds, measuring dimensions before and after the heat treatment, and calculating a ratio thereof.

The thickness of the film (B) is preferably 10 μm or more, more preferably 15 μm or more, while preferably 100 μm or less, more preferably 90 μm or less. When the thickness of the film (B) is within such a range, a treatment such as stretching in the thickness direction can be performed smoothly, and an optical film having desired optical properties can be easily obtained.

The method for producing the film (B) is not particularly limited, and any production method can be adopted. For example, the film (B) can be produced by molding the resin B into a desired shape. A preferable example of the molding method for molding the resin B is extrusion molding. By performing extrusion molding, a film (B) having a desired dimension can be efficiently produced.

[1.1.3. Other layers]
The multilayer film can include an arbitrary layer in addition to the films (A) and (B). For example, an adhesive layer can be included. As the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer, various commercially available pressure-sensitive adhesives can be used. Specifically, an adhesive containing an acrylic polymer can be used as the polymer as the main component. For example, a pressure-sensitive adhesive layer is transferred to a film (A) or a film (B) from a film having a commercially available pressure-sensitive adhesive layer (for example, “Mastuck Series” manufactured by Fujimori Kogyo Co., Ltd.), and the pressure-sensitive adhesive layer in a multilayer film It can be used as

When a multilayer film has an adhesive layer between film (A) and (B), it is preferable that the adhesive force with respect to the film (B) of this adhesive layer is higher than the adhesive force with respect to a film (A). By having such a difference in adhesive strength, adhesive residue on the optical film can be reduced, and a high-quality optical film can be easily obtained. Such a difference in adhesive strength can be obtained by appropriately selecting the material of the pressure-sensitive adhesive layer and applying an appropriate surface treatment to the surfaces of the films (A) and (B) as necessary.

[1.1.4. Preparation method of multilayer film]
The method of preparing the multilayer film used for the production method of the present invention is not particularly limited, and any method can be adopted. Such preparation can be performed, for example, by laminating the film (A) and the film (B). Prior to the bonding, the film (A) and / or the film (B) may be subjected to a surface treatment such as a corona treatment, if necessary. Moreover, prior to bonding, an adhesive layer can be formed on the surface of the film (A) and / or the film (B) as necessary, and bonding can be performed via this adhesive layer. Pasting can be performed by laminating a long film (A) and a long film (B) with a roll-to-roll with the longitudinal direction aligned.

[1.2. (Peeling process)
In the peeling step in the production method of the present invention, the multilayer film is subjected to a peeling treatment. The peeling treatment includes peeling the film (B) from the film (A). By performing such a peeling treatment, a force for pulling the film (A) in the thickness direction can be applied, and as a result, stretching in the thickness direction of the film (A) can be achieved. When the multilayer film has a plurality of films (B), the multilayer film (B) usually peels off at the same time.

FIG. 1 is a side view schematically showing an example of a peeling apparatus for performing a peeling process in the manufacturing method of the present invention and an operation of the peeling process using the apparatus. In FIG. 1, a long multilayer film 100 is conveyed in the direction of arrow A <b> 11, and is then subjected to a peeling process in the peeling region P.

The laminated film 100 includes a film (A) 131, a film (B) 111 provided on one surface of the film (A) 131, and a film (B) provided on the other surface of the film (A) 131. 112. The laminated film 100 further includes pressure-sensitive

adhesive layers

121 and 122 interposed between the films (A) and (B). The thickness of the film (A) 131 in the multilayer film is indicated by an arrow A14.

The peeling process in the peeling step can be performed by pulling the film (B) in a direction different from the in-plane direction of the film (A) to be conveyed. In the example of FIG. 1, in the peeling region P, the film (B) 111 is pulled in the direction of the arrow A12 along the longitudinal direction, and the film (B) 112 is pulled in the direction of the arrow A13 along the longitudinal direction. ing. Thereby, peeling progresses toward the upstream from the downstream of the conveyance direction of a multilayer film, and can peel films (B) 111 and 112 so that force may be applied to the thickness direction of film (A) 131. Here, the force in the thickness direction of the film is a force in a direction not parallel to the in-plane direction of the film, and is preferably a direction close to a direction perpendicular to the surface of the film. As a result of such a peeling step, an optical film 132 stretched in the thickness direction is obtained. Further, by balancing the traction force in the direction of arrow A12 and the traction force in the direction of arrow A13, the traction is performed without applying undesired in-plane tension to the multilayer film 100 and the optical film 132. be able to.

In the example of FIG. 1, the thickness of the optical film 132 is indicated by an arrow A15. The optical film 132 has a thickness larger than the film (A) 131 in the multilayer film 100 as a result of stretching in the thickness direction. However, the manufacturing method of the present invention is not limited to this. For example, when the peeling process also involves stretching in the in-plane direction, the thickness of the optical film is not necessarily larger than the thickness of the film (A). A film may be obtained.

The optical film 132 obtained as a result of the peeling process in the peeling area P is further conveyed in the direction of arrow A11. The multilayer film 100 and the optical film 132 are conveyed while being gripped by the nip rolls 151 and 152 upstream of the peeling area and the nip rolls 161 and 162 downstream of the peeling area. The conveyance speed can be adjusted by appropriately adjusting the peripheral speed of these nip rolls.

Also, if necessary, the peripheral speed of the downstream nip roll can be adjusted to be higher than the peripheral speed of the upstream nip roll. By performing such adjustment, a desired tension can be applied to the multilayer film 100 and the optical film 132. If necessary, by adjusting the tension, a stretching process in the film longitudinal direction accompanying the peeling process can be performed. Furthermore, you may extend | stretch to the arbitrary directions in a film surface with a peeling process or in the upstream or downstream of the peeling area | region P as needed.

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 time or more, more preferably 1.01 time or more, while preferably 2 times or less, more preferably 1.8 times or less. When the draw ratio in the in-plane direction is within such a range, desired optical performance can be easily obtained.

In the peeling apparatus, when the peeling process is continuously performed for a long multilayer film, the peeling area P can be set at a position where the peeling apparatus is located by balancing the transport speed of the multilayer film and the peeling speed. it can. In that case, the conveyance speed of a multilayer film becomes a peeling speed. The peeling speed can be appropriately adjusted according to desired optical performance required to be imparted to the optical film. The specific peeling rate is preferably 1 m / min or more, more preferably 2 m / min or more, while preferably 50 m / min or less, more preferably 40 m / min or less. When the peeling rate is within such a range, desired optical performance can be easily obtained.

In the method for producing an optical film of the present invention, the peeling step is performed at a temperature Tov (° C.). The temperature Tov and the glass transition temperature TgA (° C.) of the film (A) satisfy the relationship of Tov ≧ TgA. Tov is preferably (TgA + 3) ° C. or higher, more preferably (TgA + 5) ° C. or higher. By adjusting Tov within such a range, it is possible to easily impart desired optical characteristics such as a NZ coefficient to the optical film. The upper limit of Tov is not particularly limited, but may be, for example, (TgA + 40) ° C. or lower. The temperature Tov in the peeling step can be adjusted by heating the temperature in an oven (not shown) surrounding the region including the peeling region in the peeling device with an appropriate heating device.

FIG. 2 is a side view schematically showing another example of a peeling apparatus for performing the peeling process in the manufacturing method of the present invention and an operation of the peeling process using the apparatus. In FIG. 2, the long multilayer film 200 is conveyed in the direction of the arrow A <b> 21, and then subjected to a peeling process in the peeling region P. The multilayer film 200 includes a film (A) 231 and a film (B) 211 provided on one surface of the film (A) 231, but the other surface of the film (A) 231 has a film ( B) is not provided. The laminated film 200 further includes an adhesive layer 221 interposed between the films (A) and (B). The thickness of the film (A) 231 in the multilayer film is indicated by an arrow A24.

In this example, since the multilayer film 200 has the film (B) 211 only on one surface thereof, the peeling process in the peeling step is performed on the surface of the film (A) to be transported. This is done by pulling in the direction of arrow A22, which is a direction different from the inward direction. Therefore, tension is applied to the multilayer film 200 and the optical film 232 after the peeling process by the nip rolls 151 and 152 upstream of the peeling area and the nip rolls 161 and 162 downstream of the peeling area, and the tension of the film (B) 211 is applied by the tension. Confronts towing. As a result of such a peeling step, the film (A) 231 is stretched in the thickness direction, and the optical film 232 is obtained. The optical film 232 has a thickness indicated by an arrow A25 that is thicker than the film (A) 231.

[2. Optical film)
According to the production method of the present invention, an optical film having an NZ coefficient Nz of 0 <Nz <1 can be easily produced. Nz is more preferably 0.4 <Nz <1, ideally Nz = 0.5. While it is difficult to produce an optical film having such an NZ coefficient by stretching the film in a normal in-plane direction, it can be usefully used for the purpose of optical compensation of a display device. Therefore, the production method of the present invention is highly effective from the viewpoint that production is difficult and a useful product can be easily produced.

The in-plane retardation Re of the optical film is preferably 100 nm or more, more preferably 120 nm or more, while it is preferably 350 nm or less, more preferably 300 nm or less. When Re is in this range, an optical film that can be usefully used in applications such as optical compensation can be constructed. The retardation Rth in the thickness direction of the optical film is preferably −80 nm or more, more preferably −70 nm or more, while it is preferably 80 nm or less, more preferably 70 nm or less. When Re is in such a range, an optical film having characteristics such as a desired Nz coefficient and useful for use in optical compensation can be formed.

[3. Application of optical film: polarizing plate and display device]
The optical film obtained by the production method of the present invention can be used as a component of an optical device such as a display device. For example, an optical part such as a polarizing plate can be configured by combining with an optical film and another member.

The polarizing plate of the present invention comprises an optical film produced by the production method of the present invention and a polarizer. The polarizing plate of this invention can be manufactured by bonding an optical film and a polarizer.

Prior to bonding with the polarizing plate, an arbitrary layer can be provided on the surface of the optical film. Examples of optional layers include a hard coat layer that increases the surface hardness of the film, a matte layer that improves the slipperiness of the film, and an antireflection layer.

The polarizing plate of the present invention may further include an adhesive layer for bonding these films between the film cut from the optical film and the polarizer.

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.

The polarizing plate can be provided with a protective film. The number of polarizers and protective films provided in the polarizing plate is arbitrary, but the polarizing plate of the present invention can usually comprise a single layer of polarizer and two layers of protective films provided on both sides thereof. Of these two protective films, both may be films cut from the optical film of the present invention, or only one of them may be a film cut from the optical film of the present invention.

The display device of the present invention includes an optical film manufactured by the manufacturing method of the present invention. The display device of the present invention can preferably include the polarizing plate of the present invention. The display device of the present invention can be appropriately configured by combining the optical film of the present invention with other components of the display device.
The display device of the present invention is preferably a liquid crystal display device. Examples of the liquid crystal display device include an in-plane switching (IPS) mode, a vertical alignment (VA) mode, a multi-domain vertical alignment (MVA) mode, a continuous spin wheel alignment (CPA) mode, a hybrid alignment nematic (HAN) mode, Examples of the liquid crystal display device include a liquid crystal cell of a driving system such as a twisted nematic (TN) mode, a super twisted nematic (STN) mode, and an optically compensated bend (OCB) mode.
When the display device of the present invention is a liquid crystal display device, the polarizing plate can be provided as a layer for transmitting only a specific polarized light out of light incident on the liquid crystal cell and light emitted from the liquid crystal cell. The polarizing plate can also be provided as a part of a component for preventing reflection of external light.

The display device of the present invention may also be an organic electroluminescence display device. In this case, for example, the polarizing plate of the present invention is provided as a part of a component for preventing reflection of external light.

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.

〔Evaluation methods〕
(Measurement method of glass transition temperature of resin)
A pellet of the resin to be measured was prepared, and the glass transition temperature of the resin pellet was measured using a differential scanning calorimeter (“DSC 6220” manufactured by Seiko Instruments Inc.). The conditions were a sample weight of 10 mg and a heating rate of 20 ° C./min.

(Measurement method of phase difference and NZ coefficient)
Re and Rth were measured using a phase difference measuring device (product name “Axoscan” manufactured by Axometric) at a wavelength of 590 nm, and an NZ coefficient was obtained based on them.

(Measurement method of shrinkage rate Xb)
A long film to be measured was cut out to obtain a slice of longitudinal direction × width direction = 120 mm × 120 mm. Marks were drawn with oil-based pens at the four corners of a square 10 mm inside the section. That is, the square had a size of 100 mm × 100 mm and was located at the center of the section, and each side of the square was parallel to the side of the section.
Thereafter, the distance between the four marks was measured using a universal projector (Nikon “V-12BDC”). After that, the sample was put into an oven and heated at a predetermined temperature for 60 seconds. After the heat treatment, the distance between the four marks was measured again. The shrinkage ratio Xb was determined from the ratio of the distance in the width direction before the heat treatment and after the heat treatment. Shrinkage rate Xb (%) = ((distance before treatment−distance after treatment) / distance before treatment) × 100

[Production Example 1. Production of Film (A) -1]
Pellets of a resin containing an alicyclic structure-containing polymer (a norbornene polymer resin having a glass transition temperature of 126 ° C., trade name “ZEONOR”, manufactured by Nippon Zeon Co., Ltd.) were dried at 100 ° C. for 5 hours. Thereafter, the dried resin pellets were fed into a single screw extruder. After the resin was melted in an extruder, the resin was extruded from a T die onto a casting drum through a polymer pipe and a polymer filter, and cooled. As a result, a long film (A) -1 having a thickness of 80 μm and a width of 1000 mm was obtained. The produced film (A) -1 was collected in a roll form.

[Production Example 2. Production of Film (A) -2]
The same operation as in Production Example 1 was performed except that the size of the opening of the base of the T die was changed. As a result, a long film (A) -2 having a thickness of 185 μm and a width of 1000 mm was obtained and wound up into a roll and collected.

[Production Example 3. Production of Film (A) -3]
The same operation as in Production Example 1 was performed except that the size of the opening of the base of the T die was changed. As a result, a long film (A) -3 having a thickness of 133 μm and a width of 1000 mm was obtained and wound up into a roll and collected.

[Production Example 4. Production of raw film for film (B)]
The pellets of polyester resin (“PET-G 6763” manufactured by Eastman) were dried at 120 ° C. for 5 hours. The dried pellets were supplied to an extruder, melted in the extruder, passed through a polymer pipe and a polymer filter under the condition of a resin temperature of 260 ° C., extruded from a T die onto a casting drum, and cooled. Thereby, a raw material film having a thickness of 60 μm and a width of 1400 mm was obtained.

[Production Example 5. Production of Film (B) -1]
The raw material film obtained in Production Example 4 was continuously supplied to a roll-type longitudinal stretching apparatus. Using this longitudinal stretching machine, the raw material film was stretched in the longitudinal direction under the conditions of a stretching temperature of 80 ° C. and a stretching ratio of 2 times. Both ends of the stretched film in the width direction were trimmed, and a corona treatment was applied to one surface. As a result, a long film (B) -1 having a width of 900 mm and a thickness of 42 μm was obtained. When the shrinkage rate of the film (B) -1 in air at 135 ° C. for 60 seconds was measured, the shrinkage rate Xb in the film width direction was 2%. This film (B) was collected by winding it in a roll shape with the corona-treated surface in the winding.

[Production Example 6. Production of Film (B) -2]
The raw material film obtained in Production Example 4 was continuously supplied to a tenter-type transverse stretching apparatus. Using this transverse stretching machine, the film was stretched in the film width direction under conditions of a stretching temperature of 80 ° C. and a stretching ratio of 2 times. Thereafter, both ends in the film width direction were trimmed and further subjected to corona treatment on one side to obtain a long film (B) -2 having a width of 1000 mm and a thickness of 30 μm. When the shrinkage rate of this film (B) -2 in air at 135 ° C. for 60 seconds was measured, the shrinkage rate Xb in the film width direction was 20%. This film (B) -2 was collected by winding it in a roll shape with the corona-treated surface in the winding.

[Production Example 7. Production of multilayer film (C) -1]
The film (B) -1 obtained in Production Example 5 is unwound from a roll, and the pressure-sensitive adhesive layer (adhesive layer of “Mastuck Series” manufactured by Fujimori Kogyo) is applied to the corona-treated surface of the film (B) -1. Transcribed. Further, the film (B) -1 was bonded to both sides of the film (A) -1 obtained in Production Example 1 through a pressure-sensitive adhesive layer by a conventional method. Thus, a long film having a layer structure of (film (B) -1) / (adhesive layer) / (film (A) -1) / (adhesive layer) / (film (B) -1) A multilayer film (C) -1 was obtained. This multilayer film (C) -1 was collected in a roll form. The thickness of each layer was 42 μm / 25 μm / 80 μm / 25 μm / 42 μm.

[Production Example 8. Production of multilayer film (C) -2]
The film (B) -2 obtained in Production Example 6 is unwound from a roll, and the pressure-sensitive adhesive layer (adhesive layer of “Mastuck Series” manufactured by Fujimori Kogyo) is applied to the corona-treated surface of the film (B) -2. Transcribed. Further, the film (B) -1 was bonded to both sides of the film (A) -1 obtained in Production Example 1 through a pressure-sensitive adhesive layer by a conventional method. Thus, a long film having a layer structure of (film (B) -2) / (adhesive layer) / (film (A) -1) / (adhesive layer) / (film (B) -2) A multilayer film (C) -2 was obtained. This multilayer film (C) -2 was collected in a roll form. The thickness of each layer was 30 μm / 25 μm / 80 μm / 25 μm / 30 μm.

[Production Example 9. Production of multilayer film (C) -3]
As film (B) -3, a self-adhesive stretched polypropylene film (“FSA 010M # 30” manufactured by Futamura Chemical Co., Ltd.) was prepared. Shrinkage in the film width direction of this film (B) -3 in air at 120 ° C. × 60 seconds, 126 ° C. × 60 seconds, 130 ° C. × 60 seconds, 135 ° C. × 60 seconds, 140 ° C. × 60 seconds The rate Xb was 0.9%, 1.4%, 1.6%, 2.5%, and 3.5%. Film (B) -3 was bonded to both sides of film (A) -1 obtained in Production Example 1 by a conventional method. Thus, a long multilayer film (C) -3 having a layer structure of (film (B) -3) / (film (A) -1) / (film (B) -3) was obtained. This multilayer film (C) -3 was collected in a roll form. The thickness of each layer was 30 μm / 80 μm / 30 μm.

[Production Example 10. Production of multilayer film (C) -4]
(Film (B) -3) / (Film (A)-), except that the film (A) -2 obtained in Production Example 2 was used instead of the film (A) -1 in the same manner as in Production Example 9. A long multilayer film (C) -4 having a layer structure of 2) / (film (B) -3) was obtained. This multilayer film (C) -4 was collected in a roll form. The thickness of each layer was 30 μm / 185 μm / 30 μm.

[Production Example 11. Production of multilayer film (C) -5]
(Film (B) -3) / (Film (A)-) by the same operation as in Production Example 9 except that the film (A) -3 obtained in Production Example 3 was used instead of the film (A) -1. A long multilayer film (C) -5 having a layer structure of 3) / (film (B) -3) was obtained. This multilayer film (C) -5 was collected by winding it into a roll. The thickness of each layer was 30 μm / 133 μm / 30 μm.

[Example 1]
A floating type longitudinal stretching machine was prepared. This stretching machine is a stretching machine capable of stretching a long film to be conveyed in the longitudinal direction thereof in an oven whose temperature is controlled. The multilayer film (C) -1 obtained in Production Example 7 was unwound from a roll, conveyed in the longitudinal direction of the film, and supplied to the longitudinal stretching machine. The multilayer film (C) -1 was conveyed in an oven of a longitudinal stretching machine. During the transport, the oven internal temperature Tov was set to 135 ° C., and the film was stretched at a stretching ratio of 1.07.

Furthermore, the peeling process was performed near the exit in the oven. The peeling step was performed by pulling the film (B) -1 on both sides of the multilayer film (C) -1 and continuously peeling the film (B) -1 from the film (A) -1. The direction of pulling the two films (B) -1 was a direction perpendicular to the surface of the film (A) -1 to be conveyed and directions opposite to each other. As a result, peeling was applied with a force in the thickness direction of the film (A) -1, and the film (A) -1 was stretched in the thickness direction. The peeling speed was 5 m / min. As a result, a film (A) -1 stretched in the thickness direction was obtained as an optical film.
In-plane retardation Re, thickness, and NZ coefficient of the obtained optical film were measured. The results are shown in Table 1. As can be seen from the results in Table 1, the obtained optical film had an NZ coefficient between 0 and 1.

[Example 2]
The multilayer film (C) -3 obtained in Production Example 9 was unwound from a roll, transported in the longitudinal direction of the film, and supplied to the same longitudinal stretching machine used in Example 1. The multilayer film (C) -3 was conveyed in an oven of a longitudinal stretching machine. During the transport, the oven internal temperature Tov was set to 126 ° C. Further, the draw ratio was 1.00 times, that is, transport without stretching was performed.

Furthermore, the peeling process was performed near the exit in the oven. The peeling process was performed by pulling the film (B) -3 on both sides of the multilayer film (C) -3 and continuously peeling the film (B) -3 from the film (A) -1. The direction of pulling the two films (B) -3 was a direction perpendicular to the surface of the film (A) -1 to be conveyed and directions opposite to each other. As a result, peeling was applied with a force in the thickness direction of the film (A) -1, and the film (A) -1 was stretched in the thickness direction. The peeling speed was 1 m / min. As a result, a film (A) -1 stretched in the thickness direction was obtained as an optical film.
In-plane retardation Re, thickness, and NZ coefficient of the obtained optical film were measured. The results are shown in Table 1. As can be seen from the results in Table 1, the obtained optical film had an NZ coefficient between 0 and 1.

Example 3
An optical film was obtained and evaluated in the same manner as in Example 2, except that the oven internal temperature Tov was changed from 126 ° C. to 130 ° C. and the draw ratio was changed from 1.00 times to 1.02 times. did. The peeling speed in the peeling process was 1 m / min. The results are shown in Table 1. As can be seen from the results in Table 1, the obtained optical film had an NZ coefficient between 0 and 1.

Example 4
The multilayer film (C) -4 obtained in Production Example 10 was unwound from a roll, conveyed in the longitudinal direction of the film, and supplied to the same longitudinal stretching machine used in Example 1. The multilayer film (C) -4 was conveyed in an oven of a longitudinal stretching machine. During the transport, the oven internal temperature Tov was set to 135 ° C., and the film was stretched at a stretching ratio of 1.07.

Furthermore, the peeling process was performed near the exit in the oven. The peeling process was performed by pulling the film (B) -3 on both sides of the multilayer film (C) -4 and continuously peeling the film (B) -3 from the film (A) -2. The direction of pulling the two films (B) -3 was a direction perpendicular to the surface of the film (A) -2 to be conveyed and directions opposite to each other. As a result, peeling was applied with force in the thickness direction of the film (A) -2, and the film (A) -2 was stretched in the thickness direction. The peeling speed was 1 m / min. As a result, a film (A) -2 stretched in the thickness direction was obtained as an optical film.
In-plane retardation Re, thickness, and NZ coefficient of the obtained optical film were measured. The results are shown in Table 1. As can be seen from the results in Table 1, the obtained optical film had an NZ coefficient between 0 and 1.

Example 5
An optical film was obtained and evaluated in the same manner as in Example 2, except that the oven internal temperature Tov was changed from 126 ° C. to 135 ° C. and the draw ratio was changed from 1.00 times to 1.07 times. did. The peeling speed in the peeling process was 5 m / min. The results are shown in Table 1. As can be seen from the results in Table 1, the obtained optical film had an NZ coefficient between 0 and 1.

Example 6
The multilayer film (C) -5 obtained in Production Example 11 was unwound from a roll, transported in the longitudinal direction of the film, and supplied to the same longitudinal stretching machine used in Example 1. The multilayer film (C) -5 was conveyed in an oven of a longitudinal stretching machine. During the transport, the oven internal temperature Tov was set to 140 ° C., and the film was stretched at a stretching ratio of 1.07.

Furthermore, the peeling process was performed near the exit in the oven. The peeling process was performed by pulling the film (B) -3 on both sides of the multilayer film (C) -5 and continuously peeling the film (B) -3 from the film (A) -3. The direction of pulling the two films (B) -3 was a direction perpendicular to the surface of the film (A) -3 to be conveyed and directions opposite to each other. As a result, peeling was applied with a force in the thickness direction of the film (A) -3, and the film (A) -3 was stretched in the thickness direction. The peeling speed was 1 m / min. As a result, a film (A) -3 stretched in the thickness direction was obtained as an optical film.
In-plane retardation Re, thickness, and NZ coefficient of the obtained optical film were measured. The results are shown in Table 1. As can be seen from the results in Table 1, the obtained optical film had an NZ coefficient between 0 and 1.

[Comparative Example 1]
The multilayer film (C) -2 obtained in Production Example 8 was unwound from a roll, conveyed in the longitudinal direction of the film, and supplied to the same longitudinal stretching machine used in Example 1. The multilayer film (C) -2 was conveyed in an oven of a longitudinal stretching machine. During the transport, the oven internal temperature Tov was set to 135 ° C., and the film was stretched at a stretching ratio of 1.07.

Furthermore, an attempt was made to perform a peeling step in the vicinity of the outlet in the oven, but in the multilayer film (C) -2 that reached the vicinity of the outlet in the oven, peeling of the film (B) -2 occurred, and the film ( A) -1 was wrinkled on the entire surface, and the peeling process could not be performed.

[Comparative Example 2]
An optical film was obtained and evaluated by the same operation as in Example 2 except that the oven internal temperature Tov was changed from 126 ° C. to 120 ° C. The peeling speed in the peeling process was 5 m / min. The results are shown in Table 1. As can be seen from the results in Table 1, the obtained optical film had a NZ coefficient of 1.6, which was a value exceeding 1.

Table 1 summarizes the results of Examples and Comparative Examples.

The meanings of the abbreviations in the table are as follows.
COP: a resin containing an alicyclic structure-containing polymer (a resin of a norbornene polymer having a glass transition temperature of 126 ° C., trade name “ZEONOR”, manufactured by ZEON CORPORATION).
PET: Polyester resin ("PET-G 6763" manufactured by Eastman).
OPP: Self-adhesive stretched polypropylene film ("FSA 010M # 30" manufactured by Futamura Chemical Co., Ltd.).

As is clear from the results in Table 1, in the present example in which the relationship between Tov and TgA and the value of Xb were stretched under the conditions satisfying the requirements of the present application, an optical film of 0 <Nz <1 was easily manufactured. Can do.

100: Multilayer film 111: Film (B)
112: Film (B)
121: Adhesive layer 122: Adhesive layer 131: Film (A)
132: optical film 151: nip roll upstream of the peeling area 152: nip roll upstream of the peeling area 161: nip roll downstream of the peeling area 162: nip roll downstream of the peeling area 200: multilayer film 231: film (A)
211: Film (B)
221: Adhesive layer 232: Optical film P: Release area

Claims

Including a peeling step for subjecting the multilayer film to a peeling treatment,
The multilayer film is a long multilayer film including a film (A) made of a thermoplastic resin A, and a film (B) provided on one or both surfaces of the film (A).
The peeling treatment includes peeling the film (B) from the film (A) at a temperature Tov (° C.) so that a force is applied in the thickness direction of the film (A),
The temperature Tov and the glass transition temperature TgA (° C.) of the film (A) satisfy the relationship of Tov ≧ TgA,
The film (B) has a shrinkage rate Xb of 0% or more and less than 4%, and the shrinkage rate Xb is determined when the film (B) is processed under the conditions of a temperature Tov and 60 seconds. B) the shrinkage rate in the width direction,
Manufacturing method of optical film.
The method for producing an optical film according to claim 1, wherein the thermoplastic resin A includes an alicyclic structure-containing polymer.
The method for producing an optical film according to claim 1 or 2, further comprising a stretching step of stretching the multilayer film in an in-plane direction.
A polarizing plate comprising an optical film produced by the production method according to any one of claims 1 to 3 and a polarizer.
A display device comprising an optical film produced by the production method according to any one of claims 1 to 3.