CN109863428B

CN109863428B - Method for producing optical film, polarizing plate, and display device

Info

Publication number: CN109863428B
Application number: CN201780064980.3A
Authority: CN
Inventors: 摺出寺浩成
Original assignee: Zeon Corp
Current assignee: Zeon Corp
Priority date: 2016-12-28
Filing date: 2017-12-22
Publication date: 2021-07-30
Anticipated expiration: 2037-12-22
Also published as: CN109863428A; JP7036030B2; TW201823011A; JPWO2018123903A1; TWI737873B; KR20190100168A; KR102292450B1; WO2018123903A1

Abstract

A method for manufacturing an optical film, which includes a peeling step of providing a 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) to a peeling treatment including peeling the film (B) from the film (A) with a force applied in a thickness direction of the film (A) at a temperature (Tov) (° C) that satisfies a relationship of Tov ≧ TgA with a glass transition temperature (TgA) (° C) of the film (A), the peeling force of the film (A) and the film (B) at the temperature Tov in the multilayer film being 0.03N/50mm or more and 0.5N/50mm or less.

Description

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

Technical Field

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

Background

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

As such an optical film, a film having an NZ coefficient NZ of 0< NZ <1, preferably 0.4< NZ <1, and more preferably 0.5 is necessary. However, when the film is stretched by a usual method, the value of NZ coefficient becomes a value smaller than 0 or a value larger than 1, and it is difficult to obtain a film with 0< NZ < 1.

As a method for obtaining a film having 0< Nz <1, it is conceivable to use a multilayer film in which a plurality of films are combined. However, it is desirable to achieve a film with 0< Nz <1 with a simpler monolayer structure.

As a method for realizing a film having 0< Nz <1 as 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 resin film is shrunk by shrinking the shrink film, so that 0< Nz <1 is realized.

Documents of the prior art

Patent document

Patent document 1: japanese patent application laid-open No. H08-207119 (corresponding other countries publication: European patent application laid-open No. 0707938).

Disclosure of Invention

Problems to be solved by the invention

However, in the method described in patent document 1, it is difficult to control the shrinking force of the shrink film, and the process of shrinking the shrink film is complicated, and it is difficult to easily produce a film having 0< Nz < 1.

Accordingly, an object of the present invention is to provide a method for manufacturing an optical film, which can easily manufacture an optical film having 0< Nz < 1. It is a further object of the present invention to provide a polarizing plate which can be easily manufactured and has a high optical compensation function, and a display device which can be easily manufactured and has a high optical compensation function.

Means for solving the problems

The present inventors have conducted studies to solve the problems. As a result, the present inventors have found that the above problems can be solved by a method for producing an optical film, which has not been known before, in which a film is stretched in the thickness direction by utilizing the peeling force of the film. Further, it was found that the operation of stretching in the thickness direction can be favorably performed by setting the temperature at which the stretching in the thickness direction is performed and the characteristics of the multilayer film to be peeled to specific parameters. The present invention has been completed based on such knowledge findings.

Namely, the present invention is as follows.

[1] A method for manufacturing an optical film, comprising: a peeling step of providing the multilayer film to a peeling treatment,

the multilayer film is a multilayer film comprising a film (A) composed 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 (. degree. C.) in such a manner that a force is applied in a thickness direction of the film (A),

the temperature Tov and the glass transition temperature TgA (DEG C) of the film (A) satisfy the relationship that Tov is more than or equal to TgA,

in the multilayer film, the peel force Pa of the film (A) and the film (B) at a temperature Tov is 0.03N/50mm or more and 0.5N/50mm or less.

[2] The method for producing an optical film according to [1], wherein,

the thermoplastic resin A contains a polymer having an alicyclic structure.

[3] The method for producing an optical film according to [1] or [2], wherein,

further comprising a stretching step of stretching the multilayer film in the in-plane direction thereof.

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

[5] And a display device comprising the optical film produced by the production method according to any one of [1] to [3 ].

Effects of the invention

According to the present invention, there are provided an optical film and a method for manufacturing the optical film, in which 0< Nz <1 can be easily manufactured; a polarizing plate which can be easily manufactured and has a high optical film compensation function; and a display device which can be easily manufactured and which forms high optical compensation.

Drawings

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

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

Detailed Description

The present invention will be described in detail below with reference to embodiments and examples. However, the present invention is not limited to the embodiments and examples described below, and may be modified and implemented as desired without departing from the scope of the claims and their equivalents.

In the following description, the in-plane retardation Re of the film is a value represented by Re { (nx + ny)/2-nz } × d unless otherwise specified, and the retardation Rth in the thickness direction of the film is a value represented by Rth { (nx + ny)/2-nz } × d unless otherwise specified. In addition, the NZ coefficient of the film is a value represented by NZ ═ (nx-NZ)/(nx-ny), and may also be represented by NZ ═ (Rth/Re) + 0.5. Here, nx represents a refractive index in a direction giving the maximum refractive index in a direction perpendicular to the in-plane direction, that is, the thickness direction of the film. ny represents a refractive index in a direction orthogonal to the direction of nx in the in-plane direction. nz represents a refractive index in the thickness direction. d represents the thickness of the film. The measurement wavelength is 590nm unless otherwise specified.

In the following description, unless otherwise specified, the "polarizing plate" includes not only a rigid member but also a member having flexibility such as a resin film.

In the following description, a "long film" is a film having a length of 5 times or more, preferably 10 times or more, with respect to the width, and more specifically, a film having a length of a degree of being wound in a roll shape for storage or transportation. The upper limit of the length of the long film is not particularly limited, and may be, for example, 10 ten thousand times or less with respect to the width.

In this technical field, "stretching" of a film means an operation of deforming the film so as to expand the shape of the film in one or more directions, which are in the in-plane direction of the film in general. However, in the present application, "stretching" of the film is not limited thereto, and includes an operation of deforming the film so that the shape of the film is expanded in a direction other than the in-plane direction (a direction non-parallel to the in-plane direction of the film, for example, a thickness direction or the like). In the following description, a general operation of deforming a film so as to expand the shape of the film in one or more directions in the in-plane direction of the film will be simply referred to as "stretching" in the case where the context is clear. On the other hand, unlike such a general "stretching", a process of deforming a film so as to expand the shape of the film in a direction other than the in-plane direction is referred to as "thickness direction stretching", and a film subjected to such a process is referred to as "thickness direction stretched film".

[1. method for producing optical film ]

The method for producing an optical film of the present invention includes a peeling step of supplying a specific multilayer film to a specific peeling treatment.

[1.1 multilayer film ]

The multilayer film provided to the peeling step is a multilayer film including a film (a) composed of a 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 resins containing various polymers which impart desired physical properties as an optical film can be selected as appropriate.

Preferable examples of the polymer contained in the thermoplastic resin a include polymers having alicyclic structures.

The alicyclic structure-containing polymer is a polymer having an alicyclic structure in a repeating unit, and any of a polymer having an alicyclic structure in a main chain and a polymer having an alicyclic structure in a side chain can be used. The alicyclic structure-containing polymer includes a crystalline resin and an amorphous polymer. From the viewpoint of obtaining the desired effects of the present invention and the viewpoint of production cost, the amorphous alicyclic structure-containing polymer is preferable.

Examples of the alicyclic structure of 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 of the repeating unit constituting 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 depending on the purpose of use, and is usually 50% by weight or more, preferably 70% by weight or more, and more preferably 90% by weight or more. By increasing the number of the repeating units having an alicyclic structure as described above, the heat resistance of the base film can be improved.

Specific examples of the alicyclic structure-containing polymer include: (1) norbornene polymer, (2) monocyclic cyclic olefin polymer, (3) cyclic conjugated diene polymer, (4) vinyl alicyclic hydrocarbon polymer, and hydrogenated products thereof. Among these, norbornene polymers and hydrogenated products thereof are more preferable from the viewpoint of transparency and moldability.

Examples of the norbornene polymer include: a ring-opened polymer of a norbornene monomer, a ring-opened copolymer of a norbornene monomer and another monomer capable of ring-opening copolymerization, and a hydride thereof; addition polymers of norbornene monomers, addition copolymers of norbornene monomers and other monomers copolymerizable therewith, and the like. Among these, the hydrogenated ring-opening polymers of norbornene monomers are particularly preferable from the viewpoint of transparency.

Examples of the above-mentioned alicyclic structure-containing polymer include polymers disclosed in Japanese patent laid-open publication No. 2002-321302.

Further, examples of the crystalline alicyclic structure-containing polymer include polymers disclosed in japanese patent application laid-open No. 2016-26909.

Other examples of the polymer contained in the thermoplastic resin a include: and general-purpose polymers such as triacetyl cellulose and polystyrene-based polymers. Among the polystyrene-based polymers, polystyrene-based polymers having a syndiotactic structure are particularly preferably used. An example of a polystyrene-based polymer having a syndiotactic structure is disclosed in Japanese patent laid-open publication No. 2014-186273. The weight average molecular weight of the polymer contained in the thermoplastic resin a is not particularly limited, but is preferably 10000 or more, more preferably 20000 or more, and on the other hand is preferably 300000 or less, more preferably 250000 or less. When the weight average molecular weight is within this range, the thermoplastic resin a excellent in mechanical strength and molding processability can be easily obtained.

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

As the thermoplastic resin a, a thermoplastic resin having desired characteristics among various commercially available products can be appropriately selected and used. Examples of such commercially available products include: a product group having a trade name of "ZEONOR" (manufactured by Nippon Rakikusho Co., Ltd.) and a trade name of "TOPAS" (manufactured by polyplasics Co., Ltd.) and a trade name of "ARTON" (manufactured by JSR Corporation).

The glass transition temperature TgA of the thermoplastic resin A is preferably 100 ℃ or higher, more preferably 110 ℃ or higher, and on the other hand, preferably 180 ℃ or lower, more preferably 170 ℃ or lower. When TgA is within this range, a treatment such as stretching in the thickness direction is smoothly performed, and an optical film having desired optical bulk properties can be easily obtained.

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

The method for producing the film (a) is not particularly limited, and any production method can be employed. 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 the extrusion molding, the film (a) having a desired size can be efficiently produced.

[1.1.2. film (B) ]

The material constituting the film (B) is not particularly limited, and resins containing various polymers suitable for the examples of the present invention can be appropriately selected and used. 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 preferred ranges of the molecular weight thereof include: the same examples as those given above as examples of the alicyclic group-containing polymer and other polymers contained in the thermoplastic resin A are given.

Further examples of the alicyclic structure-containing polymer contained in the resin B include hydrogenated block copolymers comprising 2 or more polymer blocks having a cyclic hydrocarbon group-containing compound hydride unit [ I ] and one or more polymer blocks having a chain hydrocarbon compound hydride unit [ II ] or a combination of the unit [ I ] and the unit [ II ]. Specific examples of such hydrogenated block copolymers include polymers disclosed in International publication No. WO 2016/152871.

Further examples of the polymer contained in the resin B include general-purpose polymers such as polypropylene, (meth) acrylate polymers, and polyimide. As the resin B, a resin having desired characteristics among various commercially available products can be appropriately selected and used. An example of such a commercially available product is a self-adhesive stretched polypropylene film (for example, manufactured by Futamura Chemical co., Ltd, trade name "FSA 010M # 30").

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

The method for producing the film (B) is not particularly limited, and any production method can be employed. For example, the film (B) is 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 the extrusion molding, the film (B) having a desired size can be efficiently produced.

[1.1.3. other layers ]

The multilayer film may contain any layer in addition to the film (a) and the film (B). For example, an adhesive layer may be included. As the adhesive constituting the adhesive layer, various commercially available adhesives can be used. Specifically, as the polymer as a main component, a binder containing an acryl polymer may be used. For example, an adhesive layer may be transferred from a film having a commercially available adhesive layer (e.g., "Master stack series" manufactured by the rattan industry) to film (a) or film (B), which is used as an adhesive layer in a multilayer film.

In the case where the multilayer film has an adhesive layer between the film (a) and the film (B), the adhesive force to the film (B) of such an adhesive layer is preferably higher than the adhesive force to the film (a). By having such a difference in adhesive force, the adhesive residue on the optical film can be reduced, and a high-quality optical film can be easily obtained. Such a difference in adhesive force can be obtained by appropriately selecting the material of the adhesive layer or by performing appropriate surface treatment on the surfaces of the film (a) and the film (B) as needed.

[1.1.4 peeling Strength ]

In the production method of the present invention, as the multilayer film, a multilayer film in which the peeling force Pa of the film (a) and the film (B) at the temperature Tov is a value within a specific range is used. Here, the temperature Tov is a temperature of the film in the peeling step in the production method of the present invention.

The peel force Pa is 0.03N/50mm or more, preferably 0.035N/50mm or more, more preferably 0.04N/50mm, and on the other hand is 0.5N/50mm or less, preferably 0.4N/50mm or less, more preferably 0.3N/50mm or less. When the peeling force is within such a range, the occurrence of wrinkles in the steps up to the peeling step can be suppressed, the peeling of the unintended film (B) in the step before the peeling step can be suppressed, and the excellent peeling on the surface of the film (a) can be realized, and the optical film of excellent quality can be manufactured smoothly.

The peel force Pa can be obtained by subjecting the multilayer film to a 180 ° peel test. The 180 ° peel test can be performed as follows: the multilayer film was cut into a 300mm × 50mm long section, and the cut section was put into a tensile tester (model 5564, manufactured by instron corporation, for example) with a constant temperature and humidity chamber and subjected to Tov. Specifically, the film (A) was held by a chuck on the measuring apparatus side, and the film (B) was held by another chuck, and a peeling test was carried out at a stretching speed of 300 mm/min.

[1.1.5. method for producing multilayer film ]

The method for producing the multilayer film provided for the production method of the present invention is not particularly limited, and any method can be used. This production can be performed by, for example, laminating the film (a) and the film (B). Before the lamination, the film (a) and/or the film (B) may be subjected to surface treatment such as corona treatment, if necessary. Before the lamination, an adhesive layer is formed on the surface of the film (a) and/or the film (B) as needed, and the lamination is performed via the adhesive layer. The lamination can be performed by aligning the long film (a) and the long film (B) in the longitudinal direction and laminating them by roll-to-roll.

[1.2 peeling Process ]

In the peeling step in the production method of the present invention, a multilayer film is provided for the peeling treatment. The peeling treatment includes a step of peeling the film (B) from the film (a). By performing such a peeling process, a force that pulls the film (a) in the thickness direction can be applied, and as a result, the film (a) can be completely stretched in the thickness direction. In the case where the multilayer film has a plurality of films (B), the plurality of films (B) are usually peeled off at the same time.

Fig. 1 is a side view schematically showing an example of an operation of a peeling apparatus for performing a peeling step in a manufacturing method of the present invention and a peeling step using the apparatus. In fig. 1, a long multilayer film 100 is conveyed in the direction of arrow a11, and then supplied to a peeling step in a 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)112 provided on the other surface of the film (a) 131. The laminated film 100 further includes

adhesive layers

121 and 122 interposed between the films (a) and (B). The thickness of film (a)131 in the multilayer film is shown by arrow a 14.

The peeling treatment in the peeling step is performed by pulling the film (B) in a direction different from the in-plane direction of the film (a) being conveyed. In the example of fig. 1, in the peeling region P, the film (B)111 is pulled in the arrow a12 direction along its long dimension direction, and the film (B)112 is pulled in the arrow a13 direction along its long dimension direction. This allows the films (B)111 and 112 to be peeled off so as to apply a force in the thickness direction of the film (a)131 by peeling from the downstream side toward the upstream side in the conveyance direction of the multilayer film. The force in the thickness direction of the film as used herein means a force in a direction nonparallel to the in-plane direction of the film, and preferably in a direction close to the direction perpendicular to the surface of the film. As a result of such a peeling step, the optical film 132 stretched in the thickness direction can be obtained. Further, by balancing the pulling force in the arrow a12 direction and the pulling force in the arrow a13 direction, it is possible to perform these pulling without applying an undesired in-plane tension to the multilayer film 100 and the optical film 132.

In the example of FIG. 1, the thickness of optical film 132 is represented by arrow A15. As a result of stretching the optical film 132 in the thickness direction, it has a thickness thicker than the film (a)131 in the multilayer film 100. But the manufacturing method of the present invention is not limited thereto. For example, in the case where the peeling step is accompanied by stretching in the in-plane direction, the thickness of the optical film is not necessarily thicker than the thickness of the film (a), and even in such a case, an optical film of 0< Nz <1 may be obtained.

The optical film 132 obtained as a result of the peeling process in the peeling region P is further conveyed in the direction of the arrow a 11. The multilayer film 100 and the optical film 132 are conveyed in a state of being held by the

pressing rollers

151 and 152 upstream of the peeling area and the

pressing rollers

161 and 162 downstream of the peeling area. The conveying speed is adjusted by appropriately adjusting the peripheral speed of these press rolls.

Further, the peripheral speed of the downstream press roll may be adjusted to a speed higher than that of the upstream press roll as necessary. By performing such adjustment, a desired tension can be applied to the multilayer film 100 and the optical film 132. If necessary, by adjusting such tension, a stretching step in the film longitudinal direction accompanying the peeling step can be performed. Further, stretching in any direction within the film surface may be performed upstream or downstream of the peeling region P, together with the peeling step, as necessary.

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 the stretching in the thickness direction can be appropriately adjusted in accordance with the desired optical performance to be imparted to the optical film. The specific stretching ratio is preferably 1 time or more, more preferably 1.01 time or more, and on the other hand, preferably 2 times or less, more preferably 1.8 times or less. When the in-plane direction stretch ratio is in such a range, desired optical performance can be easily obtained.

When the peeling step is continuously performed on a long multilayer film in the peeling device, the peeling region P can be set at a position having the peeling device by balancing the conveyance speed of the multilayer film and the peeling speed. In this case, the conveying speed of the multilayer film becomes the peeling speed. The peeling speed can be appropriately adjusted in accordance with the desired optical properties required to be imparted to the optical film. The specific peeling speed is preferably 1m/min or more, more preferably 2 m/min or more, and on the other hand, preferably 50 m/min or less, more preferably 40 m/min or less. When the peeling speed is in 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 (. degree. C.). The temperature Tov and the glass transition temperature TgA (DEG C) of the film (A) satisfy the relationship that Tov is not less than TgA. Tov is preferably (TgA +3) ° C or more, and more preferably (TgA +5) ° C or more. By adjusting the Tov in such a range, desired optical characteristics such as NZ coefficient can be easily imparted to the optical film. The upper limit of Tov is not particularly limited, and may be, for example, (TgA + 40). degree.C.or less. The temperature Tov in the peeling process can be adjusted by heating the temperature in an oven (not shown) surrounding the region including the peeling region in the peeling device by an appropriate heating device.

Fig. 2 is a side view schematically showing another example of the operation of a peeling apparatus for performing a peeling step in the manufacturing method of the present invention and the peeling step using the apparatus. In fig. 2, a long multilayer film 200 is conveyed in the direction of arrow a21, and then supplied to a peeling step in a peeling region P. The laminated film 200 includes a film (a)231 and a film (B)211 provided on one surface of the film (a)231, and the other surface of the film (a)231 is not provided with the film (B). The laminated film 200 further includes an adhesive layer 221 interposed between the films (a) and (B). The thickness of film (a)231 in the multilayer film is shown by arrow a 24.

In this example, since the multilayer film 200 has the film (B)211 only on one surface thereof, the peeling treatment in the peeling step is performed by pulling the film (B)211 in the direction of the arrow a22 which is a direction different from the in-plane direction of the conveyed film (a). Therefore, tension is given to the multilayer film 200 and the optical film 232 after the peeling process by the

pressure rollers

151 and 152 upstream of the peeling region and the

pressure rollers

161 and 162 downstream of the peeling region, and the drawing of the film (B)211 is resisted by the tension. As a result of such a peeling step, the film (a)231 is stretched in the thickness direction to obtain the optical film 232. Optical film 232 has a thickness, indicated by arrow a25, that is thicker than 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 preferably 0.4< Nz <1, ideally 0.5. An optical film having such an NZ coefficient is difficult to manufacture by stretching a normal film in an in-plane direction, but can be effectively used for the purpose of optical compensation of a display device or the like. Therefore, the production method of the present invention exhibits a high effect in that a product which is difficult to produce and useful can be easily produced.

The in-plane retardation Re of the optical film is preferably 100nm or more, more preferably 120nm or more, and on the other hand, is preferably 350nm or less, more preferably 300nm or less. When Re is in such a range, an optical film which is effectively used for optical compensation or the like can be formed. The retardation Rth in the thickness direction of the optical film is preferably-80 nm or more, more preferably-70 nm or more, and on the other hand, is preferably 80nm or less, more preferably 70nm or less. When Re is in such a range, an optical film having desired characteristics such as an Nz coefficient and being effectively used for applications such as optical compensation can be formed.

[3] use 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 component such as a polarizing plate may be configured by combining an optical film with another member.

The polarizing plate of the present invention includes an optical film and a polarizer manufactured by the manufacturing method of the present invention. The polarizing plate of the present invention can be produced by laminating an optical film and a polarizer.

Before the optical film is attached to the polarizing plate, an optional layer may be provided on the surface of the optical film. Examples of the optional layer include: a hard coat layer for increasing the surface hardness of the film, a mat (mat) layer for improving the smoothness of the film, and an antireflection layer.

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

The polarizer is not particularly limited, and any polarizer may be used. Examples of the polarizer include polarizers obtained by adsorbing a material such as iodine or a dichroic dye to a polyvinyl alcohol film and then stretching the polyvinyl alcohol film. Examples of the binder constituting the binder layer include binders containing various polymers as a base polymer. Examples of such a base polymer include acrylic polymers, silicone polymers, polyesters, polyurethanes, polyethers, and synthetic rubbers.

The polarizing plate may have a protective film. The number of polarizers and protective films which the polarizing plate has is arbitrary, but the polarizing plate of the present invention may generally have a polarizer of 1 layer, and protective films of 2 layers provided on both surfaces thereof. Both of the 2-layer protective films may be films cut from the optical film of the present invention, or only one of the films may be a film cut from the optical film of the present invention.

The display device of the present invention may have an optical film manufactured by the manufacturing method of the present invention. The display device of the present invention preferably has the polarizing plate of the present invention. The display device of the present invention can be suitably configured by combining the optical film of the present invention with other constituent elements 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 liquid crystal display devices having liquid crystal cells of a driving system such as an in-plane switching (IPS) mode, a Vertical Alignment (VA) mode, a multi-domain vertical alignment (MVA) mode, a continuous fireworks alignment (CPA) mode, a Hybrid Alignment Nematic (HAN) mode, a Twisted Nematic (TN) mode, a Super Twisted Nematic (STN) mode, and an Optically Compensated Bend (OCB) mode.

In the case where the display device of the present invention is a liquid crystal display device, the polarizing plate may be provided as a layer for transmitting only desired specific polarized light from among light incident to the liquid crystal cell and light emitted from the liquid crystal cell. The polarizing plate is also provided as a part of a constituent element for preventing reflection of external light.

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

Examples

The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the examples described below, and can be modified and implemented as desired within a range not departing from the scope of the claims of the present invention and the equivalent thereof.

In the following description, "%" and "part" representing amounts are based on weight unless otherwise specified. Unless otherwise specified, the operations described below are performed under normal temperature and normal pressure conditions.

[ evaluation method ]

(method of measuring glass transition temperature of resin)

The glass transition temperature of resin particles to be measured was measured by a differential scanning calorimeter (Seiko Instruments [ DSC6220 ]). The conditions were 10mg of the sample weight and 20 ℃ per minute of the temperature increase rate.

(method of measuring phase difference and NZ coefficient)

Re and Rth were measured using a phase difference measuring apparatus (product name "Axoscan" manufactured by Axometric Co., Ltd.) having a wavelength of 590nm, and the NZ coefficient was determined based on these measurements.

(method of measuring peeling force Pa between film (A) and film (B))

A long multilayer film to be measured was cut to obtain a cut piece having a length direction × width direction of 300mm × 50 mm. The cut pieces were placed in a tensile tester (model 5564, manufactured by instron corporation) equipped with a constant temperature and humidity chamber, and the temperature was raised to a predetermined oven temperature Tov. While maintaining this temperature, a 180 ° peel test was performed. The 180 DEG peel test was carried out at a drawing speed of 300mm/min by holding the film (A) with a chuck on the measuring apparatus side and the film (B) with another chuck. The average value of the measurement values of the peel force Pa (N/50mm) at a stable stretching distance of 50mm was used as the value of the peel force Pa.

Production example 1 production of film (A) -1

Pellets of a resin containing a polymer having an alicyclic structure (a resin of a norbornene polymer having a glass transition temperature of 126 ℃ C., product name "ZEONOR" available from Nippon Rapule Co., Ltd.) were dried at 100 ℃ for 5 hours. Thereafter, the dried pellets of the resin were supplied to a uniaxial extruder. After the resin was melted in the extruder, it was extruded from the T die onto a casting drum through a polymer tube and a polymer filter into a sheet shape and cooled. Thus, a long film (A) -1 having a thickness of 80 μm and a width of 1000mm was obtained. The produced film (A) -1 was wound up in a roll shape and recovered.

Production example 2 production of film (A) -2

The same operation as in production example 1 was performed except that the opening width of the gate of the T-die was changed. Thus, a long film (A) -2 having a thickness of 185 μm and a width of 1000mm was obtained, and was wound 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 opening width of the gate of the T-die was changed. Thus, a long film (A) -3 having a thickness of 133 μm and a width of 1000mm was obtained and collected in a roll form.

Production example 4 production of film (A) -4

The film (a) -1 obtained in production example 1 was unwound from a roll, and both surfaces of the film (a) -1 were subjected to corona treatment. Thus, film (A) -4 was obtained. The obtained film (a) -4 was collected by winding the corona-treated surface into a roll shape.

Production example 5 production of raw film for film (B)

Pellets of a polyester resin ("PET-G6763" manufactured by Eastman Co.) were dried at 120 ℃ for 5 hours. The dried pellets were fed to an extruder, melted in the extruder, passed through a polymer tube and a polymer filter at a resin temperature of 260 ℃, extruded from a T die onto a casting drum in the form of a sheet, and cooled. Thus, a raw material film having a thickness of 60 μm and a width of 1400mm was obtained.

Production example 6 production of film (B) -1

The raw material film obtained in production example 5 was continuously fed to a tenter type transverse stretching machine. The raw material film was stretched in the width direction at a stretching temperature of 80 ℃ and a stretching ratio of 2 times using the transverse stretcher. Both ends of the stretched film in the width direction were trimmed, and further corona treatment was performed on one surface. Thus, a long film (B) -1 having a thickness of 900mm and a thickness of 42 μm was obtained. The corona-treated surface of the film (B) was turned to the inside of a roll and wound up in a roll shape for recovery.

Production example 7 production of multilayer film (C) -1

The film (B) -1 obtained in production example 6 was unwound from a roll, and an adhesive layer (for example, an adhesive layer of "Master stack series" manufactured by the rattan industry) was transferred to the corona-treated surface of the film (B) -1. Further, the film (B) -1 was laminated to both surfaces of the film (a) -1 obtained in production example 1 via an adhesive layer by a conventional method. Thus, a long multilayer film (C) -1 having a layer structure of (film (B) -1)/(adhesive layer)/(film (a) -1)/(adhesive layer)/(film (B) -1) was obtained. The multilayer film (C) -1 was wound up in a roll form and recovered. 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) -1 obtained in production example 6 was unwound from a roll, and an adhesive layer (for example, an adhesive layer of "Master stack series" manufactured by the rattan industry) was transferred to the corona-treated surface of the film (B) -1. Further, the film (B) -1 was laminated on both surfaces of the film (a) -4 obtained in production example 4 by an adhesive layer in a conventional manner. Thus, a long multilayer film (C) -2 having a layer structure of (film (B) -1)/(adhesive layer)/(film (a) -4)/(adhesive layer)/(film (B) -1) was obtained. The multilayer film (C) -2 was wound up in a roll form and recovered. The thickness of each layer was 42 μm/25 μm/80 μm/25 μm/42 μm.

Production example 9 production of multilayer film (C) -3

As the film (B) -2, a self-adhesive stretched polypropylene film (for example, manufactured by Futamura Chemical co., Ltd, trade name "FSA 010M # 30") was prepared. The film (B) -2 was attached to both surfaces of the film (a) -1 obtained in production example 1 in a conventional manner. Thus, a long multilayer film (C) -3 having a layer structure of (film (B) -2)/(film (a) -1)/(film (B) -2) was obtained. The multilayer film (C) -3 was wound up in a roll form and recovered. The thickness of each layer was 30 μm/80 μm/30 m.

Production example 10 production of multilayer film (C) -4

A long multilayer film (C) -4 having a layer structure of (film (B) -2)/(film (a) -2)/(film (B) -2) was obtained by the same operation as in production example 9, except that the film (a) -2 obtained in production example 2 was used instead of the film (a) -1. The multilayer film (C) -4 was wound up in a roll form and recovered. The thickness of each layer was 30 μm/185 μm/30 m.

Production example 11 production of multilayer film (C) -5

A long multilayer film (C) -5 having a layer structure of (film (B) -2)/(film (a) -3)/(film (B) -2) was obtained in 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. The multilayer film (C) -5 was wound up in a roll form and recovered. The thickness of each layer was 30 μm/133 μm/30 m.

Production example 12 production of multilayer film (C) -6

The film (B) -6 obtained in production example 6 was unwound from a roll, and an adhesive layer (for example, an adhesive layer of "Master stack series" manufactured by the rattan industry) was transferred to the corona-treated surface of the film (B) -1. Further, corona treatment was performed on the surface of the transferred adhesive layer. On both surfaces of the film (a) -4 obtained in production example 4, the film (B) -1 having an adhesive layer subjected to corona treatment was attached via an adhesive layer in a conventional manner. Thus, a long multilayer film (C) -6 having a layer structure of (film (B) -1)/(adhesive layer)/(film (a) -4)/(adhesive layer)/(film (B) -1) was obtained. The multilayer film (C) -6 was wound up in a roll form and recovered. The thickness of each layer was 42 μm/25 μm/80 μm/25 μm/42 μm.

[ example 1]

A floating type longitudinal stretching machine was prepared. The stretching machine is a stretching machine that stretches a long film conveyed in an oven with a temperature adjusted in the longitudinal direction thereof. The multilayer film (C) -2 obtained in production example 8 was unwound from a roll, conveyed in the film length direction, and supplied to the longitudinal stretching machine. The multilayer film (C) -2 was conveyed in the oven of the longitudinal stretcher. During the conveyance, the temperature Tov in the oven was set at 135 ℃ and the stretching ratio was 1.07 times.

Further, a peeling step is performed near the exit in the oven. The peeling step is performed by: the films (B) -1 on both sides of the multilayer film (C) -2 were pulled, and the films (B) -1 were continuously peeled from the films (A) -4. The direction in which the 2 films (B) -1 were pulled was set to be perpendicular to the surface of the conveyed film (A) -4 and opposite to each other. Thus, peeling was performed by applying a force in the thickness direction of the film (A) -4, and the film (A) -4 was stretched in the thickness direction. The peeling speed was 5 m/min. As a result, a film (A) -4 stretched in the thickness direction was obtained as an optical film.

The in-plane retardation Re, the thickness and the NZ coefficient of the obtained optical film were measured. Further, the peel force Pa between the film (a) and the film (B) within the multilayer film of Tov of this example was measured. The results are shown in table 1. As can be seen from the results in table 1, the NZ coefficient of the obtained optical film was between 0 and 1.

[ example 2]

The multilayer films (C) -3 obtained in production example 9 were unwound from rolls, conveyed in the longitudinal direction, and supplied to the same longitudinal stretching machine as that used in example 1. The multilayer films (C) -3 were conveyed in the oven of the longitudinal stretcher. During the transportation, the oven internal temperature Tov was set to 126 ℃. The stretching ratio was set to 1.00 times, that is, the conveyance without stretching was performed.

Further, a peeling step is performed near the exit in the oven. The peeling step is performed by: the films (B) -2 on both sides of the multilayer film (C) -3 were pulled, and the films (A) -1 and (B) -2 were continuously peeled off. The direction in which the 2 films (B) -2 were pulled was set to be perpendicular to the surface of the conveyed film (A) -1 and opposite to each other. Thus, peeling was performed by applying 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.

[ example 3]

An optical film was obtained and evaluated by the same operation as example 2, except that the oven internal temperature Tov was changed from 126 ℃ to 130 ℃, the stretching magnification was changed from 1.00 times to 1.02 times, and stretching was performed. The peeling speed in the peeling step was 1 m/min. The results are shown in table 1. As can be seen from the results in table 1, the NZ coefficient of the obtained optical film was 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, and supplied to the same longitudinal stretching machine as that used in example 1. The multilayer films (C) -4 were conveyed in the oven of the longitudinal stretcher. During the conveyance, the temperature Tov in the oven was set at 135 ℃ and the stretching ratio was 1.07 times.

Further, a peeling step is performed near the exit in the oven. The peeling step is performed by: the films (B) -2 on both sides of the multilayer film (C) -4 were pulled, and the films (B) -2 were continuously peeled from the films (A) -2. The direction in which the 2 films (B) -2 were pulled was set to be perpendicular to the surface of the conveyed film (A) -2 and opposite to each other. Thus, peeling was performed by applying a 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.

[ example 5]

An optical film was obtained and evaluated by the same operation as example 2, except that the oven internal temperature Tov was changed from 126 ℃ to 135 ℃, the stretch magnification was changed from 1.00 times to 1.07 times, and stretching was performed. The peeling speed in the peeling step was 5 m/min. The results are shown in table 1. As can be seen from the results in table 1, the NZ coefficient of the obtained optical film was between 0 and 1.

[ example 6]

The multilayer films (C) -5 obtained in production example 11 were unwound from rolls, conveyed in the longitudinal direction, and supplied to the same longitudinal stretching machine as that used in example 1. The multilayer films (C) -5 were conveyed in the oven of the longitudinal stretcher. During the conveyance, the temperature inside the oven Tov was set at 140 ℃, and the stretching was performed at a stretching ratio of 1.07 times.

Further, a peeling step is performed near the exit in the oven. The peeling step is performed by: the films (B) -2 on both sides of the multilayer film (C) -5 were pulled, and the films (B) -2 were continuously peeled from the films (A) -3. The direction of pulling 2 films (B) -2 was set to be perpendicular to the surface of the conveyed film (A) -3 and opposite to each other. Thus, peeling was performed in which a force was applied 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, film (A) -3 stretched in the thickness direction was obtained as an optical film.

Comparative example 1

The multilayer film (C) -1 obtained in production example 7 was unwound from a roll, conveyed in the longitudinal direction, and supplied to the same longitudinal stretching machine as that used in example 1. The multilayer film (C) -1 was conveyed in the oven of the longitudinal stretcher. During the conveyance, the temperature Tov in the oven was set at 135 ℃ and the stretching ratio was 1.07 times.

Further, although an attempt was made to carry out the peeling step in the vicinity of the exit in the oven, peeling of the film (B) -1 occurred in the multilayer film (C) -1 reaching the vicinity of the exit in the oven, wrinkles occurred on the entire surface of the film (a) -1, and the peeling step could not be carried out.

Further, the peel force Pa between the film (a) and the film (B) within the multilayer film of Tov of this example was measured. The results are shown in table 1.

Comparative example 2

The multilayer films (C) -6 obtained in production example 12 were unwound from rolls, conveyed in the longitudinal direction, and supplied to the same longitudinal stretching machine as that used in example 1. The multilayer films (C) -6 were conveyed in the oven of the longitudinal stretcher. During the conveyance, the temperature inside the oven Tov was set at 135 ℃, and the stretching was performed at a stretching ratio of 1.07 times.

Further, although an attempt was made to perform the peeling step near the exit in the oven, peeling was not smoothly performed at the boundary between the film (a) and the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive remained on the surface of the peeled film (a), and thus a satisfactory optical film could not be produced.

Comparative example 3

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 ℃ to 120 ℃. The peeling speed in the peeling step was 5 m/min. The results are shown in table 1. As is clear from the results in table 1, the NZ coefficient of the obtained optical film was 1.6, which is a value exceeding 1.

The results of the examples and comparative examples are collectively shown in table 1.

[ Table 1]

TABLE 1

The abbreviations in the tables have the following meanings.

COP: a resin containing a polymer having an alicyclic structure (a resin of a norbornene polymer having a glass transition temperature of 126 ℃, trade name "ZEONOR", manufactured by japan ruing corporation).

PET: polyester resin ("PET-G6763" manufactured by Eastman).

OPP: a self-adhesive stretched polypropylene film (Futamura Chemical Co., Ltd., product name "FSA 010M # 30" by Ltd.).

As is clear from the results of table 1, in the examples of the present application in which stretching was performed under the condition that the relationship between Tov and TgA and the value of Pa satisfy the requirements of the present application, an optical film of 0< Nz <1 could be easily produced.

Description of the reference numerals

100: a multilayer film;

111: a film (B);

112: a film (B);

121: an adhesive layer;

122: an adhesive layer;

131: a film (A);

132: an optical film;

151: a pressure roller upstream of the stripping zone;

152: a pressure roller upstream of the stripping zone;

161: a pressure roller downstream of the stripping zone;

162: a pressure roller downstream of the stripping zone;

200: a multilayer film;

231: a film (A);

211: a film (B);

221: an adhesive layer;

232: an optical film;

p: and (4) stripping the area.

Claims

1. A method for manufacturing an optical film includes a peeling step of providing a multilayer film to a peeling treatment,

the multilayer film is a multilayer film comprising a film A composed of a thermoplastic resin 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 with a force applied in a thickness direction of the film a at a temperature Tov in units of,

the temperature Tov and the glass transition temperature TgA of the film A meet the relationship that Tov is more than or equal to TgA, the unit of the temperature TgA is,

in the multilayer film, the peel force Pa of the film A and the film B at the temperature Tov is 0.03N/50mm or more and 0.5N/50mm or less.

2. The method for manufacturing an optical film according to claim 1,

the thermoplastic resin contains a polymer containing an alicyclic structure.

3. The method for manufacturing an optical film according to claim 1 or 2,