KR20230122006A - Multi-layer film and manufacturing method thereof - Google Patents

Abstract

A long multilayer film comprising an A layer made of crystalline resin (a) and a B layer made of material (b), wherein either the crystalline resin (a) or the material (b) has a positive intrinsic birefringence. phosphorus material, and the other is a material with negative intrinsic birefringence, and the multilayer film and the B layer satisfy specific requirements with respect to their retardation and refractive index. The multilayer film is preferably a performance product. A method for producing a multilayer film including a step of contacting a specific elongated film (I) with a solvent is also provided.

Description

Multi-layer film and manufacturing method thereof

The present invention relates to a multilayer film that can be usefully used as an optical film, and a method for producing the same.

Conventionally, using a resin film having specific optical properties for an optical purpose has been performed. For example, a film whose Nz coefficient satisfies 0 < Nz < 1 is called a three-dimensional retardation film. It is known that a three-dimensional retardation film can express an effect of reducing coloring of a display surface viewed from an oblique direction when installed in a display device such as a liquid crystal display device. In particular, a three-dimensional retardation film and a so-called reverse wavelength dispersion in which the relationship between retardation and wavelength is obtained can obtain a desired optical effect in a wide wavelength range.

The three-dimensional retardation film has a larger retardation in the z-axis direction (ie, thickness direction) than the retardation in the y-axis direction (ie, the in-plane direction orthogonal to the in-plane slow axis direction). Therefore, it cannot be manufactured by a normal method for producing a retardation film in which a resin for an optical film having a positive intrinsic birefringence is simply stretched. Therefore, manufacturing a three-dimensional retardation film or a film similar thereto by combining a resin having a positive intrinsic birefringence and a resin having a negative intrinsic birefringence has been proposed so far (for example, Patent Documents 1 and 2).

International Publication No. 2019/188205 International Publication No. 2020/137409

Methods for producing a three-dimensional retardation film in which a resin having a positive intrinsic birefringence and a resin having a negative intrinsic birefringence, which have been proposed so far, are combined, require a complicated stretching process, a bonding process after stretching, and require trouble for positioning. There was a problem with a big back. In particular, it is difficult to easily manufacture those having reverse wavelength dispersion. In addition, in such a combination, it is required to increase the ratio of resins with negative intrinsic birefringence to a certain extent or more. However, since many resins with negative intrinsic birefringence generally have low mechanical strength, increasing the ratio of such resins is , a problem of low mechanical strength may occur. Further, in the case where the film is manufactured as a long film and the production includes a step of stretching in the width direction, the problem of easy breakage during conveyance of the long film is remarkable.

Therefore, an object of the present invention is a film that can express good effects as a three-dimensional retardation film in a wide wavelength range and can be easily produced, and a good effect as a three-dimensional retardation film in a wide wavelength range. It is to provide a manufacturing method that can easily manufacture a film having a surface.

This inventor studied in order to solve the said subject. As a result, the present inventors, when a specific material is employed as one of a multilayer film in which a layer of a material having a positive intrinsic birefringence and a layer of a material having a negative intrinsic birefringence are combined, form a three-dimensional retardation film in a wide wavelength range. It was found that a multilayer film that can express favorable effects and can be easily manufactured can be constituted. Based on this knowledge, the inventor completed the present invention.

That is, the present invention includes the following.

[1] A long multilayer film comprising an A layer made of crystalline resin (a) and a B layer made of material (b),

One of the crystalline resin (a) and the material (b) is a material having a positive intrinsic birefringence, and the other is a material having a negative intrinsic birefringence,

The multilayer film satisfies both the following formulas (1) and (2),

The layer B is a multilayer film that satisfies all of the following formulas (3), (4), and (7), or satisfies all of the following formulas (5), (6), and (7):

Re (450) < Re (550) < Re (650) ... (1)

0 < Nz < 1 ... (2)

nx(b) > ny(b) ... (3)

nx(b) > nz(b) ... (4)

nx(b) < ny(b) ...(5)

nx(b) < nz(b) ... (6)

|ny(b) - nz(b)| ≤ 0.003 ... (7)

step,

Re (450), Re (550), and Re (650) are, respectively, the in-plane retardation of the multilayer film at a wavelength of 450 nm, the in-plane retardation of the multilayer film at a wavelength of 550 nm, and the multilayer film In-plane retardation at a wavelength of 650 nm,

Nz is the Nz coefficient of the multilayer film,

nx(b) is the refractive index of the B layer in the in-plane slow axis direction Dx of the multilayer film,

ny (b) is the refractive index of the layer B in a direction Dy orthogonal to the direction Dx as an in-plane direction of the multilayer film,

nz(b) is the refractive index of the layer B in the thickness direction Dz of the multilayer film.

[2] The multilayer film according to [1], which is a new performance product.

[3] The multilayer film according to [2], wherein the new performance product is a new performance product of a raw film which is a co-extruded product.

[4] The multilayer film according to any one of [1] to [3], wherein at least one layer of the A layer is located on the surface of the multilayer film.

[5] The multilayer film according to any one of [1] to [4], wherein an in-plane slow axis of the A layer and an in-plane slow axis of the B layer are orthogonal.

[6] The multilayer film according to any one of [1] to [5], having a layer configuration of (Layer A)/(Layer B)/(Layer A).

[7] The multilayer film according to any one of [1] to [6], wherein the thickness is 40 µm or less.

[8] A method for producing a multilayer film according to any one of [1] to [7],

The pA layer made of the crystalline resin (a) and the pB layer made of the material (b) were formed by co-extrusion film formation of the crystalline resin (a) and the material (b), and the pA layer A step (I) of obtaining a long film (I) in which at least one layer of is located on the surface;

Step of contacting the surface of the film (I) on which the pA layer is located with a solvent to treat the pA layer to form a qA layer, thereby obtaining a long film (II) comprising the qA layer and the pB layer (II) and

Step (III) of obtaining a long film (III) by uniaxially stretching the film (II)

Including, manufacturing method.

[9] The manufacturing method according to [8], wherein the uniaxial stretching in the step (III) is oblique uniaxial stretching.

According to the present invention, a multilayer film capable of exhibiting favorable effects as a three-dimensional retardation film in a wide wavelength range and easily producible, and a multilayer film capable of exhibiting favorable effects as a three-dimensional retardation film in a wide wavelength range A production method capable of easily producing a film is provided.

Hereinafter, the present invention will be described in detail by showing embodiments and examples. However, the present invention is not limited to the embodiments and examples shown below, and can be implemented with arbitrary changes within a range not departing from the scope of the claims of the present invention and their equivalents.

In the following description, the in-plane retardation Re of a layered structure (a film, a layer constituting a part of a multilayer film, etc.) is a value represented by Re = (nx - ny) × d, unless otherwise specified. . The retardation Rth in the thickness direction of the layered structure is a value represented by Rth = [{(nx + ny)/2} - nz] x d unless otherwise specified. The Nz coefficient of the layered structure is a value represented by (nx - nz)/(nx - ny) unless otherwise indicated.

nx represents the refractive index in the direction giving the maximum refractive index as a direction (in-plane direction) perpendicular to the thickness direction of the layered structure. ny represents the refractive index of the direction orthogonal to the direction of nx as the said in-plane direction of a layered structure. nz represents the refractive index of the thickness direction of a layered structure. d represents the thickness of the layered structure. The measurement wavelength is 550 nm unless otherwise noted. However, as the definitions of nx and ny of the layers constituting the multilayer film, as described separately below, definitions different from these definitions are adopted.

In the following description, a material having a positive intrinsic birefringence means a material having a refractive index in a stretching direction greater than a refractive index in a direction perpendicular thereto, unless otherwise specified. In addition, unless otherwise specified, a material with negative intrinsic birefringence means a material whose refractive index in the stretching direction is smaller than the refractive index in the direction perpendicular thereto. The value of intrinsic birefringence can be calculated from the permittivity distribution.

In the following description, unless otherwise specified, the directions of elements are "parallel", "perpendicular", and "orthogonal" within a range that does not impair the effects of the present invention, for example, within a range of ±5°. may contain an error in .

In the following description, the slow axis of a layered structure is an in-plane slow axis unless otherwise specified.

[Multilayer Film: Optical Properties]

The multilayer film of the present invention includes an A layer made of crystalline resin (a) and a B layer made of material (b).

One of the crystalline resin (a) and material (b) is a material having a positive intrinsic birefringence, and the other is a material having a negative intrinsic birefringence. From the viewpoint of ease of availability of the material, etc., it is preferable that the crystalline resin (a) is a material having a positive intrinsic birefringence and the material (b) is a material having a negative intrinsic birefringence.

The multilayer film satisfies both of the following formulas (1) and (2).

Re450 < Re550 < Re650 ... (1)

0 < Nz < 1 ... (2)

Re(450), Re(550), and Re(650) are in-plane retardation at a wavelength of 450 nm of the multilayer film, in-plane retardation at a wavelength of 550 nm of the multilayer film, and wavelength 650 nm of the multilayer film, respectively. is the in-plane retardation of Nz is the Nz factor of the multilayer film.

A film satisfying Formula (1) is called a reverse wavelength dispersive film. A film satisfying Formula (1) can obtain a desired optical effect in a wide wavelength range. In addition, a film that satisfies Expression (2) is called a three-dimensional retardation film. A film that satisfies Expression (2) can exhibit an effect of reducing coloration of a display surface viewed from an oblique direction when installed in a display device. A film satisfying both formulas (1) and (2) had to be manufactured in a complicated process in the prior art, but the multilayer film of the present invention is easily manufactured by adopting a crystalline resin as the A layer. You can do it with a film that can do it.

Regarding equation (1), Re(550)/Re(450) is greater than 1, preferably equal to or greater than 1.005. The upper limit of Re(550)/Re(450) can be, for example, 1.5 or less. Re(650)/Re(550) is larger than 1, preferably 1.002 or higher. The upper limit of Re(650)/Re(550) can be, for example, 1.5 or less.

The values of Re(450), Re(550), and Re(650) can be adjusted to values suitable for the use of the multilayer film. In any example, the preferred range of Re(550) is 137.5 nm or a value close thereto, specifically preferably 127.5 to 147.5 nm, more preferably 130.5 to 144.5 nm. By setting the value of Re (550) within the range, the multilayer film can be used as a λ/4 wave plate. In another example, the preferred range of Re(550) is 275 nm or a value close thereto, specifically preferably 265 to 285 nm, more preferably 268 to 282 nm. By setting the value of Re (550) within the range, the multilayer film can be used as a λ/2 wave plate.

Regarding equation (2), Nz is larger than 0, preferably 0.2 or more, while smaller than 1, preferably 0.8 or less.

The angle formed by the in-plane slow axis Dx of the multilayer film and the longitudinal direction of the multilayer film can be adjusted to an angle suitable for the purpose of the multilayer film, but from the viewpoint of ease of manufacture, Dx is an angle close to or in the longitudinal direction of the multilayer film it is desirable In one example, the angle formed by the in-plane slow axis Dx and the longitudinal direction is 0° or an angle close thereto, specifically preferably 0° to 5°, more preferably 0° to 3°. By setting the angle formed between the in-plane slow axis Dx and the longitudinal direction within the range, the production of the multilayer film becomes particularly easy, and the transportability of the multilayer film during production becomes particularly good. In another example, the angle formed by the in-plane slow axis Dx and the longitudinal direction may be 45° or an angle close thereto, specifically preferably 40° to 50°, more preferably 42° to 48°. By setting the angle formed between the in-plane slow axis Dx and the longitudinal direction within the range, the yield can be high when the multilayer film is used for a rectangular display screen, and the transportability of the multilayer film at the time of production is also improved.

The B layer in the multilayer film satisfies all of the following formulas (3), (4) and (7), or satisfies all of the following formulas (5), (6) and (7).

nx(b) > ny(b) ... (3)

nx(b) > nz(b) ... (4)

nx(b) < ny(b) ...(5)

nx(b) < nz(b) ... (6)

|ny(b) - nz(b)| ≤ 0.003 ... (7)

Unlike general definitions of principal refractive indices nx and ny, nx(b) and ny(b) are defined based on the in-plane slow axis direction of the multilayer film. That is, nx (b) is the refractive index of layer B in the in-plane slow axis direction Dx of the multilayer film, and ny (b) is the in-plane direction of the multilayer film, in the direction Dy orthogonal to the direction Dx, is the refractive index of layer B. nz(b) is the refractive index of the layer B in the thickness direction Dz of the multilayer film.

If layer B satisfies all of equations (3), (4), and (7), it is called a positive A plate, and layer B satisfies all of equations (5), (6), and (7). What it does is what is called a negative A plate. In the case where the B layer is a material with a positive intrinsic birefringence, the B layer can satisfy all of Expressions (3), (4) and (7). When the layer B is a material having a negative intrinsic birefringence, the layer B can satisfy all of the equations (5), (6) and (7).

Regarding equations (3) and (4), the ratio of nx (b) to the larger of ny (b) and nz (b) (i.e., nx (b) / ny (b) and nx (b) / nz The smaller one of (b)) is larger than 1, and is preferably 1.0005 or more. The upper limit of the ratio can be, for example, 1.002 or less. Regarding equations (5) and (6), the ratio of the smaller of ny(b) and nz(b) to nx(b) (i.e., ny(b)/nx(b) and nz(b)/nx The smaller one of (b)) is larger than 1, and is preferably 1.0005 or more. The upper limit of the ratio can be, for example, 1.002 or less.

The refractive indices nx(a), ny(a), and nz(a) of the layer A in the multilayer film can be appropriately adjusted so that the optical properties of the multilayer film become desired values. Here, nx (a) is the refractive index of layer A in the in-plane slow axis direction Dx of the multilayer film, and ny (a) is the in-plane direction of the multilayer film, in the direction Dy orthogonal to the direction Dx, is the refractive index of layer A. nz(a) is the refractive index of the layer A in the thickness direction Dz of the multilayer film. For example, when the crystalline resin (a) is a material with a positive intrinsic birefringence value, nx(a), ny(a), and nz(a) are nx(a) > nz(a) > ny(a ) or a relationship of nx(a) > nz(a) = ny(a).

The slow axis direction of each of the A layer and the B layer can be appropriately adjusted so that the optical properties of the multilayer film have a desired value, but usually, the slow axis direction of the layer of the material having the positive intrinsic birefringence value among the A layer and the B layer. This is parallel to the slow axis direction of the multilayer film, and the slow axis direction of the other layer forms an angle perpendicular to or close to the slow axis direction of the multilayer film. Therefore, the direction of the slow axis of layer A and the direction of the slow axis of layer B are orthogonal or form an angle close thereto. Specifically, the angle between the slow axis direction of layer A and the slow axis direction of layer B is preferably 85 to 90°, more preferably 88 to 90°.

[Multilayer Film: Other Features]

The multilayer film of the present invention is a long film. A "long" film refers to a film having a length of 5 times or more of the width, preferably a film having a length of 10 times or more, and specifically, a film having a length that is wound up in a roll shape and stored or transported. say There is no particular limitation on the upper limit of the length, but it is usually less than 100,000 times the width.

The multilayer film of this invention can be equipped with A layer and B layer one by one. The multilayer film of this invention may further be equipped with two or more layers of A layers, and may be equipped with two or more layers of B layers.

When a plurality of A layers are provided, the optical properties of those in a state of overlapping them in the same relationship as their planar positional relationship in the multilayer film can be used as the optical properties of the A layer described above. Similarly, when a plurality of B layers are provided, the optical properties of those in a state of overlapping them in the same relationship as their planar positional relationship in the multilayer film can be used as the optical properties of the B layer described above. For example, in an example in which a multilayer film includes two A layers and their slow axes are in the same direction in the multilayer film, the optical properties of the state in which the two A layers are overlapped by aligning the slow axes are the A layer described above. It can be done with the optical properties of Further, for example, in the case where the multilayer film includes a plurality of A layers, they are made of the same material, and the optical properties are constantly expressed, the optical properties independent of the thickness (nx (a), ny (a), and nz(a), etc.), the result of measuring one layer among them can be used as the optical characteristic for the A layer.

In the multilayer film of the present invention, it is preferable that at least one layer of the A layer is located on the surface of the multilayer film. That is, it is preferable that the surface of one or both of a multilayer film is the surface of the state in which A layer was exposed. By having such a structure, manufacture of the multilayer film by the manufacturing method of this invention becomes especially easy. Furthermore, it is more preferable that the multilayer film has a layer configuration of (A layer)/(B layer)/(A layer). More specifically, it is preferable that the multilayer film has the A layer of 2 and the B layer located between them, and the surface of both of the multilayer film is the surface of the state in which A layer was exposed. By having such a structure, in the production of the multilayer film by the production method of the present invention, the desired optical properties by the A layer can be more easily expressed, and in the case where the multilayer film is placed in a high temperature and high humidity environment It is possible to favorably suppress the occurrence of curl.

The multilayer film of this invention can be provided with arbitrary layers other than A layer and B layer. For example, an adhesive layer may be provided between the A layer and the B layer.

In general, an optical film used for devices such as a display device requires a certain thickness or more in order to express optical characteristics, while thinness is required from the request for thinning of the device. The thickness of the multilayer film of the present invention is not particularly limited, but by satisfying the requirements of the present invention, it is possible to obtain a film that satisfies desired optical properties even when the thickness is thin. Specifically, the thickness of the multilayer film of the present invention can be preferably 150 μm or less, more preferably 120 μm or less, even more preferably 100 μm or less, and particularly preferably 40 μm or less. A multilayer film having such a small thickness can be easily manufactured by the manufacturing method of the present invention. Although the lower limit of the thickness of a multilayer film is not specifically limited, For example, it can be 20 micrometers or more.

Each thickness of A layer and B layer can be suitably adjusted so that desired optical characteristics may be obtained. The thickness of layer A is preferably 1 μm or more, more preferably 3 μm or more, while preferably 100 μm or less, more preferably 80 μm or less. The thickness of the B layer is preferably 1 μm or more, more preferably 3 μm or more, while preferably 120 μm or less, more preferably 100 μm or less. In the case where the multilayer film includes a plurality of layers A, the thickness of the total can be adjusted within the above preferred range. Similarly, when a multilayer film includes a plurality of B layers, the total thickness thereof can be adjusted within the above preferred range.

The multilayer film of the present invention is preferably a performance product. That is, it is preferable that the multilayer film of this invention is a film obtained by stretching a raw film provided with a plurality of layers, and thereby provided with a plurality of stretched layers.

Moreover, it is preferable that a raw film is a co-extruded material. That is, it is preferable that the raw film is formed into a film having a plurality of layers by extruding a plurality of types of materials from an extruder for co-extrusion. An extruder for co-extrusion is provided with a member (specifically, a die for co-extrusion) having a plurality of inlets through which each of a plurality of types of materials flows, and one outlet through which those materials flow out in a layered manner. It is a device. Specific examples of such co-extrusion and co-extrusion will be described later.

[Material Constituting Layer A]

The crystalline resin (a) constituting the A layer can be a resin containing a polymer having crystallinity. A "polymer having crystallinity" shows a polymer having a melting point Tm. That is, "a polymer having crystallinity" indicates a polymer whose melting point can be observed with a differential scanning calorimeter (DSC). In the following description, a polymer having crystallinity may be referred to as a "crystalline polymer". The crystalline resin is preferably a thermoplastic resin.

The crystalline polymer preferably has positive intrinsic birefringence. By using a crystalline polymer having positive intrinsic birefringence, a multilayer film satisfying the requirements of the present invention, in particular the requirements of formula (2), can be produced particularly easily.

Examples of the crystalline polymer include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); polyolefins such as polyethylene (PE) and polypropylene (PP); etc. may be sufficient, and it is not specifically limited, but what contains an alicyclic structure is preferable. By using a crystalline polymer containing an alicyclic structure, mechanical properties, heat resistance, transparency, low hygroscopicity, dimensional stability, and lightness of the retardation film can be improved. A polymer containing an alicyclic structure refers to a polymer having an alicyclic structure in a molecule. The polymer containing such an alicyclic structure may be, for example, a polymer obtainable by a polymerization reaction using a cyclic olefin as a monomer or a hydride thereof.

As an alicyclic structure, a cycloalkane structure and a cycloalkene structure are mentioned, for example. Among these, a cycloalkane structure is preferable from the viewpoint of easily obtaining a retardation film having excellent properties such as thermal stability. The number of carbon atoms contained in one alicyclic structure is preferably 4 or more, more preferably 5 or more, preferably 30 or less, more preferably 20 or less, and particularly preferably 15 less than a dog When the number of carbon atoms contained in one alicyclic structure is within the above range, mechanical strength, heat resistance, and formability are highly balanced.

In the crystalline polymer containing an alicyclic structure, the ratio of structural units having an alicyclic structure to all structural units is preferably 30% by weight or more, more preferably 50% by weight or more, and particularly preferably 70% by weight or more. more than % by weight. Heat resistance can be improved by increasing the ratio of structural units having an alicyclic structure as described above. The ratio of the structural unit having an alicyclic structure to all the structural units can be 100% by weight or less. In addition, in the crystalline polymer containing an alicyclic structure, the remainder other than the structural unit having an alicyclic structure is not particularly limited and can be appropriately selected depending on the purpose of use.

As a crystalline polymer containing an alicyclic structure, the following polymer ((alpha)) - polymer ((delta)) are mentioned, for example. Among these, the polymer (β) is preferable from the viewpoint of easily obtaining a retardation film having excellent heat resistance.

Polymer (α): A ring-opening polymer of a cyclic olefin monomer, which has crystallinity.

Polymer (β): A hydride of the polymer (α), which has crystallinity.

Polymer (γ): An addition polymer of a cyclic olefin monomer, which has crystallinity.

Polymer (δ): A hydride of the polymer (γ), which has crystallinity.

Specifically, as the crystalline polymer containing an alicyclic structure, those having crystallinity as a ring-opening polymer of dicyclopentadiene and those having crystallinity as a hydride of the ring-opening polymer of dicyclopentadiene are more preferable. . Especially, what has crystallinity as a hydride of the ring-opening polymer of dicyclopentadiene is especially preferable. Here, the ring-opening polymer of dicyclopentadiene means that the ratio of structural units derived from dicyclopentadiene to all structural units is usually 50% by weight or more, preferably 70% by weight or more, and more preferably 90% by weight or more. , more preferably 100% by weight of the polymer.

The hydride of the ring-opening polymer of dicyclopentadiene preferably has a high ratio of racemo diad. Specifically, the ratio of racemo dyads in repeating units in the hydride of the ring-opening polymer of dicyclopentadiene is preferably 51% or more, more preferably 70% or more, and particularly preferably 85%. More than that. A high ratio of racemo dyad indicates high syndiotactic stereoregularity. Therefore, the melting point of the hydride of the ring-opening polymer of dicyclopentadiene tends to be higher as the ratio of the racemo-dyad is higher.

The ratio of racemo dyad can be determined based on ¹³ C-NMR spectrum analysis described in Examples described later.

As the polymer (α) to the polymer (δ), a polymer obtained by a manufacturing method disclosed in International Publication No. 2018/062067 can be used.

The melting point Tm of the crystalline polymer is preferably 200°C or higher, more preferably 230°C or higher, and preferably 290°C or lower. By using a crystalline polymer having such a melting point Tm, a multilayer film having a more excellent balance between moldability and heat resistance can be obtained.

Usually, a crystalline polymer has a glass transition temperature Tg. The specific glass transition temperature Tg of the crystalline polymer is not particularly limited, but is usually 85°C or higher and usually 170°C or lower.

The glass transition temperature Tg and melting point Tm of a polymer can be measured by the following methods. First, a polymer is melted by heating, and the melted polymer is quenched with dry ice. Subsequently, using this polymer as a test body, the glass transition temperature Tg and melting point Tm of the polymer can be measured using a differential scanning calorimeter (DSC) at a heating rate of 10°C/min (heating mode).

The weight average molecular weight (Mw) of the crystalline polymer is preferably 1,000 or more, more preferably 2,000 or more, and is preferably 1,000,000 or less, more preferably 500,000 or less. A crystalline polymer having such a weight average molecular weight is excellent in the balance between molding processability and heat resistance.

The molecular weight distribution (Mw/Mn) of the crystalline polymer is preferably 1.0 or more, more preferably 1.5 or more, and preferably 4.0 or less, more preferably 3.5 or less. Here, Mn represents the number average molecular weight. A crystalline polymer having such a molecular weight distribution is excellent in molding processability.

The weight average molecular weight (Mw) and molecular weight distribution (Mw/Mn) of the polymer can be measured as values in terms of polystyrene by gel permeation chromatography (GPC) using tetrahydrofuran as a developing solvent.

The crystallinity of the crystalline polymer included in the retardation film is not particularly limited, but is usually higher than a certain extent. The specific crystallinity range is preferably 10% or more, more preferably 15% or more, and particularly preferably 30% or more.

The degree of crystallinity of a crystalline polymer can be measured by an X-ray diffraction method.

A crystalline polymer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

The proportion of the crystalline polymer in the crystalline resin (a) is preferably 50% by weight or more, more preferably 70% by weight or more, and particularly preferably 90% by weight or more. When the ratio of the crystalline polymer is equal to or greater than the lower limit, the development of birefringence and heat resistance of the retardation film can be improved. The upper limit of the proportion of the crystalline polymer may be 100% by weight or less.

The crystalline resin (a) may contain an optional component in addition to the crystalline polymer. Examples of the optional component include antioxidants such as phenol-based antioxidants, phosphorus-based antioxidants, and sulfur-based antioxidants; light stabilizers such as hindered amine light stabilizers; waxes such as petroleum wax, Fischer tropsch wax, and polyalkylene wax; nucleating agents such as sorbitol-based compounds, metal salts of organic phosphoric acids, metal salts of organic carboxylic acids, kaolin, and talc; diaminostilbene derivatives, coumarin derivatives, azole derivatives (e.g., benzoxazole derivatives, benzotriazole derivatives, benzoimidazole derivatives, and benzothiazole derivatives), carbazole derivatives, pyridine derivatives, naphthalic acid derivatives, and optical brighteners such as imidazolone derivatives; ultraviolet absorbers such as benzophenone-based ultraviolet absorbers, salicylic acid-based ultraviolet absorbers, and benzotriazole-based ultraviolet absorbers; inorganic fillers such as talc, silica, calcium carbonate, and glass fibers; coloring agent; flame retardants; flame retardant aids; antistatic agent; plasticizer; near-infrared absorbers; lubricant; filler; and any polymers other than crystalline polymers, such as soft polymers; etc. can be mentioned. Arbitrary components may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

[Organic Solvent Contained in Crystalline Resin (a)]

The crystalline resin (a) constituting the layer A may contain an organic solvent. This organic solvent is usually absorbed into the film in step (II) of the production method of the present invention.

In step (II), all or part of the organic solvent absorbed in the film may penetrate into the polymer. Therefore, even if drying is performed above the boiling point of the organic solvent, it is difficult to completely remove the solvent easily. Therefore, it is common that A layer contains an organic solvent.

As an organic solvent, it can be made into what does not dissolve a crystalline polymer. Preferred organic solvents include, for example, hydrocarbon solvents such as toluene, limonene, and decalin; carbon disulfide; can be mentioned. One kind of organic solvent may be sufficient as it, and two or more kinds may be sufficient as it.

The ratio (solvent content) of the organic solvent contained therein relative to 100% by weight of the crystalline resin (a) is preferably 10% by weight or less, more preferably 5% by weight or less, and particularly preferably 0.1% by weight. below

[Materials Constituting Layer B]

The material (b) constituting the layer B preferably has negative intrinsic birefringence. By using a resin having negative intrinsic birefringence as the material (b) and combining this with a crystalline resin (a) having positive intrinsic birefringence, a multilayer satisfying the requirements of the present invention, particularly the requirements of formula (2) The film can be produced particularly easily.

Resins with negative intrinsic birefringence are usually thermoplastic resins, and include polymers with negative intrinsic birefringence. Examples of polymers having negative intrinsic birefringence include polystyrene-based polymers including homopolymers and copolymers of styrene or styrene derivatives, and copolymers of styrene or styrene derivatives and arbitrary monomers; polyacrylonitrile polymers; polymethylmethacrylate polymers; or polycomponent polymers thereof; And cellulose compounds, such as a cellulose ester, etc. are mentioned. Moreover, as said arbitrary monomer which can be copolymerized with styrene or a styrene derivative, acrylonitrile, maleic anhydride, methyl methacrylate, and butadiene are mentioned as preferable examples, for example. Among them, polystyrene-based polymers and cellulose compounds are preferred. In addition, these polymers may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

The proportion of the polymer in the resin having negative intrinsic birefringence is preferably 50% by weight to 100% by weight, more preferably 70% by weight to 100% by weight, and particularly preferably 90% by weight to 100% by weight. When the ratio of the polymer is within the above range, desired optical properties can be easily imparted to the layer B.

It is preferable that material (b) contains a plasticizer. By using a plasticizer, the glass transition temperature of material (b) can be adjusted appropriately. Examples of the plasticizer include phthalic acid esters, fatty acid esters, phosphoric acid esters, and epoxy derivatives. As a specific example of a plasticizer, the thing of Unexamined-Japanese-Patent No. 2007-233114 is mentioned. In addition, a plasticizer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

Among the plasticizers, phosphoric acid esters are preferred in terms of availability and low cost. Examples of phosphoric acid esters include trialkyl phosphates such as triethyl phosphate, tributyl phosphate, and trioctyl phosphate; halogen-containing trialkyl phosphates such as trichloroethyl phosphate; triaryl phosphates such as triphenyl phosphate, tricresyl phosphate, tris (isopropylphenyl) phosphate, and cresyl diphenyl phosphate; alkyl-diaryl phosphates such as octyldiphenyl phosphate; tri(alkoxyalkyl)phosphates such as tri(butoxyethyl)phosphate; etc. can be mentioned.

When material (b) contains a plasticizer, the amount is preferably 0.001% by weight or more, more preferably 0.005% by weight or more, particularly preferably 0.1% by weight or more, based on 100% by weight of material (b) , preferably 20% by weight or less, more preferably 18% by weight or less, particularly preferably 15% by weight or less. When the amount of the plasticizer is within the above range, the glass transition temperature of the material (b) can be appropriately adjusted, so desired optical properties can be easily imparted to the layer B.

The material (b) may further contain arbitrary components other than the polymer and the plasticizer in combination with the polymer and the plasticizer. As an arbitrary component, the same example as the arbitrary component which crystalline resin (a) can contain is mentioned, for example. Arbitrary components may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

The glass transition temperature of the material (b) is preferably 80°C or higher, more preferably 90°C or higher, still more preferably 100°C or higher, especially preferably 110°C or higher, particularly preferably 120°C or higher. . When the glass transition temperature of material (b) is so high, desired optical properties can be easily imparted to layer B. The upper limit of the glass transition temperature of the material (b) is not particularly limited, but is usually 200°C or less.

[Manufacturing method of multilayer film]

The multilayer film of the present invention can be manufactured by a manufacturing method including the following steps (I) to (III).

Step (I): crystalline resin (a) and material (b) are co-extruded into a film to form a pA layer made of crystalline resin (a) and a pB layer made of material (b), and the pA layer A long film (I) in which at least one layer of is located on the surface is obtained.

Step (II): The surface of the film (I) on which the pA layer is located is brought into contact with a solvent, and the pA layer is treated to form a qA layer, thereby obtaining a long film (II) comprising the qA layer and the pB layer.

Step (III): The film (II) is uniaxially stretched to obtain a long film (III).

Below, this manufacturing method is demonstrated as a manufacturing method of the multilayer film of this invention.

[Process (I)]

Step (I) can be performed by co-extruding the crystalline resin (a) and the material (b) with an extrusion apparatus equipped with a die for normal co-extrusion molding. In the case of producing a multilayer film having a layer configuration of (Layer A)/(Layer B)/(Layer A) as a preferred embodiment, using a film forming apparatus equipped with a die for coextrusion molding of two types and three layers, , Film (I) having a layer configuration of (pA layer)/(pB layer)/(pA layer) can be manufactured. By forming the film (I) by co-extrusion, a multilayer film having good adhesion between the A layer and the B layer can be easily produced. When the adhesiveness of A-layer and B-layer is favorable, generation|occurrence|production of the shift|offset|difference between layers in a case where a multilayer film is put|placed in a high-temperature, high-humidity environment can be suppressed satisfactorily.

[Process (II)]

In step (II), the surface of the film (I) where the pA layer is located is brought into contact with a solvent. As the solvent, a solvent capable of penetrating into the resin without dissolving the crystalline resin (a) can be appropriately selected. As a solvent, an organic solvent is usually used. Examples of the organic solvent include hydrocarbon solvents such as toluene, limonene, and decalin; and carbon disulfide. One type of solvent may be sufficient as it, and two or more types may be sufficient as it.

The contact in step (II) can be achieved by any operation. Examples of the operation of the contact include a spray method of spraying a solvent on the surface of the pA layer; a coating method of applying a solvent to the surface of the pA layer; and an immersion method in which the film (I) is immersed in a solvent. From the viewpoint of being able to easily perform continuous contact, an immersion method is preferable. In particular, when both sides of the film (I) are pA layers, efficient treatment can be performed by the immersion method. However, when one surface of the film (I) is a pB layer, the pB layer may be dissolved by contact with a solvent. Therefore, when one surface of the film (I) is a pB layer, an operation capable of achieving contact of the solvent with only one side of the film (I) is preferable, and this operation is an operation other than the immersion method. Specifically, It can be done by a spray method and a coating method.

The temperature of the solvent at the time of contact in step (II) is arbitrary within the range in which the solvent can maintain a liquid state, and therefore can be set within the range of not less than the melting point of the solvent and not more than the boiling point of the solvent.

When contacting the film (I) and the solvent by immersion, the contact time is preferably 0.5 seconds or more, more preferably 1.0 seconds or more, particularly preferably 5.0 seconds or more, and preferably 120 seconds or less, more Preferably it is 80 seconds or less, Especially preferably, it is 60 seconds or less. When contact time is more than the said lower limit, adjustment of the Nz coefficient of A-layer by contact with a solvent can be performed effectively. On the other hand, even if the contact time is lengthened, the adjustment amount of the Nz coefficient tends not to change significantly. Therefore, when contact time is below the said upper limit, productivity can be improved, without impairing the quality of A-layer.

As a result of the contact with the solvent in step (II), the refractive index of the pA layer changes, resulting in a qA layer. Such a change caused by contact with a solvent is difficult to obtain by a conventional method for producing a retardation film in which a resin for an optical film is simply stretched. Thus, as a result of these changes, easy production of the multilayer film of the present invention is possible.

[Process (III)]

In step (III), the film (II) obtained in step (II) is uniaxially stretched. By stretching the film (II), the qA layer and the pB layer of the film (II) are co-stretched. By this stretching, the polymer molecules included in these layers are oriented in a direction along the stretching direction. Since the film (II) has passed through the step (II), as a result of the step (III), the film (III) having optical properties that are difficult to obtain with the ordinary method of manufacturing a retardation film in which resin for optical films is simply stretched. ) can be easily obtained.

There is no limitation on the stretching direction in step (III), and examples thereof include a longitudinal direction, a width direction, and an oblique direction. Here, the inclination direction is a direction perpendicular to the thickness direction, and indicates a direction in which the angle formed with the width direction is neither 0° nor 90° (that is, a direction in which the angle formed with the width direction exceeds 0° and is less than 90°).

When it is intended to manufacture a film having optical properties equivalent to those of the multilayer film of the present invention by a production method not involving step (II), a plurality of complicated stretching steps are usually required. In the case of expressing optical properties by stretching, it is necessary to strictly control the stretching conditions, so the disadvantage in terms of manufacturing efficiency is large if there are many stretching steps. In addition, stretching in the width direction is often required as one of such a plurality of stretching steps, and stretching in the width direction lowers the strength in the longitudinal direction of the film and may cause breakage during conveyance. In contrast, in the production method of the present invention, since the multilayer film of the present invention can be obtained only by uniaxial stretching, it is advantageous from the viewpoint of production efficiency. In addition, since the stretching process can be completed only by stretching in the longitudinal direction or stretching in the oblique direction without stretching in the width direction, the possibility of breakage during transport of the film can be reduced.

The draw ratio is preferably 1.1 times or more, more preferably 1.2 times or more, preferably 20.0 times or less, more preferably 10.0 times or less, still more preferably 5.0 times or less, and particularly preferably 2.0 times or less. am. A specific stretch ratio is preferably set appropriately according to factors such as optical properties, thickness, and strength of the multilayer film as a product. When the stretching ratio is equal to or greater than the lower limit, the birefringence can be greatly changed by stretching. In addition, when the draw ratio is equal to or less than the above upper limit, the direction of the slow axis can be easily controlled or breakage of the film can be effectively suppressed.

The stretching temperature is preferably "Tg + 5°C" or higher, more preferably "Tg + 10°C" or higher, preferably "Tg + 100°C" or lower, more preferably "Tg + 90°C" or lower. am. Here, "Tg" represents the glass transition temperature of a crystalline polymer. When the stretching temperature is equal to or higher than the above lower limit, the film is sufficiently softened and the stretching can be performed uniformly. Further, when the stretching temperature is equal to or less than the above upper limit, curing of the film due to the progress of crystallization of the crystalline polymer can be suppressed, so that stretching can be performed smoothly and large birefringence can be developed by stretching. Moreover, transparency can be improved by making the haze of the obtained multilayer film small normally.

Since the birefringence can be changed by step (III), the Nz coefficient can be adjusted. Therefore, film (III) as a film having desired optical properties is obtained by stretching in step (III). The obtained film (III) can be used as a multilayer film of the present invention as it is. Alternatively, the film (III) may be further subjected to an arbitrary treatment to obtain a multilayer film of the present invention. Examples of the optional process include adjustment of birefringence by processing such as heat treatment while maintaining the stretched dimension or relaxation treatment to reduce the stretched dimension.

[Other processes]

The manufacturing method of the multilayer film of this invention can further include arbitrary processes in combination with the process mentioned above. For example, a process of removing the solvent adhering to the film (II) may be included after the process (II). As a method of removing the solvent, drying, wiping, etc. are mentioned, for example.

The method for producing a multilayer film of the present invention may include a preheat treatment step for setting the temperature of the film (II) to a stretching temperature or a temperature close thereto before step (III). Usually, the preheating temperature and the stretching temperature are the same, but may be different. The preheating temperature is preferably T1 - 10°C or higher, more preferably T1 - 5°C or higher, and is preferably T1 + 5°C or lower, more preferably T1 + 2°C or lower relative to the stretching temperature T1. The preheating time is arbitrary, and may be preferably 1 second or more, more preferably 5 seconds or more, and preferably 60 seconds or less, more preferably 30 seconds or less.

The elongated multilayer film obtained by step (III) can be wound up into a roll shape as needed to obtain a film roll.

[Other manufacturing methods]

The multilayer film of the present invention can be produced by methods other than the above-described manufacturing method of the present invention. For example, the multilayer film of this invention can be manufactured also by forming the film for pA layer and the film for pB layer separately, bonding them together, and using instead of film (I).

[Use of multi-layer film]

The multilayer film of the present invention can be used as a component of an optical device such as a display device after being processed into a desired shape such as a rectangle as necessary. When the multilayer film of the present invention is used as a component of a display device, display quality such as viewing angle, contrast, and image quality of an image displayed on the display device can be improved.

Example

Hereinafter, the present invention will be described in detail by showing examples. However, the present invention is not limited to the examples shown below, and can be implemented with arbitrary changes within a range not departing from the scope of the claims of the present invention and their equivalents.

In the following description, "%" and "parts" representing amounts are based on weight unless otherwise specified. In addition, the operation described below was performed under conditions of normal temperature and normal pressure unless otherwise indicated.

In the following description, free-end uniaxial stretching of a film is uniaxial stretching performed in an aspect allowing shrinkage in a direction orthogonal to the stretching direction among in-plane directions. On the other hand, uniaxial stretching performed in an aspect in which dimensions in a direction orthogonal to the stretching direction are fixed and shrinkage in the direction is not allowed is called fixed-end uniaxial stretching. Among the uniaxial stretching of a long film described below, uniaxial stretching other than free end uniaxial stretching in the vertical direction is fixed end uniaxial stretching unless otherwise specified.

[Assessment Methods]

(Measuring Method of Weight Average Molecular Weight Mw and Number Average Molecular Weight Mn of Polymer)

The weight average molecular weight Mw and number average molecular weight Mn of the polymer were measured as values in terms of polystyrene using a gel permeation chromatography (GPC) system ("HLC-8320" manufactured by Tosoh Corporation). In the measurement, an H-type column (manufactured by Tosoh Corporation) was used as a column, and tetrahydrofuran was used as a solvent. In addition, the temperature at the time of measurement was 40 degreeC.

(Method for Measuring Hydrogenation Rate of Polymer)

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

(Method of measuring glass transition temperature Tg and melting point Tm)

The glass transition temperature Tg and melting point Tm of the polymer were measured as follows. First, the polymer was melted by heating, and the melted polymer was quenched with dry ice. Then, using this polymer as a test body, the glass transition temperature Tg and melting point Tm of the polymer were measured using a differential scanning calorimeter (DSC) at a heating rate of 10°C/min (heating mode).

(Method for measuring racemo-dyad ratio of polymer)

The ratio of the racemo-dyad of the polymer was measured as follows. ¹³ C-NMR measurement of the polymer was performed using orthodichlorobenzene-d ⁴ as a solvent and applying an inverse-gated decoupling method at 200°C. In the result of this ¹³ C-NMR measurement, with the peak at 127.5 ppm of orthodichlorobenzene-d ⁴ as the reference shift, a signal of 43.35 ppm derived from meso diad and a signal of 43.43 ppm derived from racemo diad signal was identified. Based on the intensity ratio of these signals, the ratio of racemo-dyads in the polymer was determined.

(measurement of thickness)

The thickness of the film was measured using a contact type thickness meter (Code No. 543-390 manufactured by MITUTOYO). The thickness of each layer in the film composed of a plurality of layers was determined by microscopic observation of a cross section of the film to obtain a thickness ratio, and was calculated from the ratio and the overall thickness of the film.

(measurement of refractive index, in-plane retardation, slow axis angle)

The refractive index and in-plane retardation of the film were performed using an ellipsometer (product name "AxoScan", manufactured by AXOMETRICS). As for the measurement position, 9 measurement points were determined at intervals of 1/10 of the film width on a line parallel to the film width direction, and their average was obtained. At each measurement point, measurement was performed at wavelengths of 450 nm, 550 nm, and 650 nm, in-plane retardation Re450 (unit: nm) at a measurement wavelength of 450 nm, in-plane retardation Re550 (unit: nm) at a measurement wavelength of 550 nm, and measurement In-plane retardation Re650 (unit: nm) at a wavelength of 650 nm and nx, ny, and nz at a measurement wavelength of 550 nm were determined. In the measurement of a film composed of a plurality of layers (the film (II) and the multilayer film, that is, the result obtained in step (III)), the direction of the slow axis of the film is determined by measurement using an ellipsometer, and the The refractive index of the layer was determined based on the direction. In addition, in the measurement of the multilayer film, the NZ coefficient of the multilayer film and the intersection angle of the slow axes of the A layer and the B layer were measured together.

(Measurement of crystallinity)

The crystallinity of layer A was confirmed by X-ray diffraction according to JIS K0131. Specifically, using a wide-angle X-ray diffractometer ("RINT 2000" manufactured by Rigaku Co., Ltd.), the diffracted X-ray intensity from the crystallized portion was obtained, and from the ratio with the overall diffracted X-ray intensity, the following formula (I) was obtained. The crystallinity was obtained by

Xc = K Ic/It (I)

In the formula (I), Xc represents the degree of crystallinity of the test sample, Ic represents the diffracted X-ray intensity from the crystallized portion, It represents the overall diffracted X-ray intensity, and K represents a correction term.

(Evaluation of return property)

The obtained multilayer film (for example, in Examples 1 and 2, immediately after the end of step (III)) is conveyed at a speed of 20 m/min, and the state of conveyance in the step of winding the film roll into a film roll is observed. The presence or absence of problems due to breakage of the film was evaluated.

(Evaluation of shrinkage due to high temperature and high humidity load)

Square samples were cut out one by one from the vicinity of the center and both ends of the elongated film in the width direction. All of the dimensions of the samples were 100 mm × 100 mm. Each side of the sample was set in a direction parallel to the longitudinal direction or width direction of the elongated film. The central sample was cut out from a position whose center coincided with the center of the long film in the width direction. The sample at both ends was cut out from the position where the distance between the side on the side of the end and the end of the long film in the width direction was 10 mm. After maintaining each of the three samples in an environment of 85°C and 85% RH for 200 hours, they were placed on a horizontal surface plate.

The sample was observed from the upper surface, and the difference in dimensional change between one and the other of the two types of layers (A layer and B layer) constituting the sample was evaluated. Specifically, in each of the four sides of the sample, the distance from the side of the layer located on the outer side of the two types of layers to the side of the layer located on the inner side was measured. The case where the maximum value of the four measured values of the three samples was less than 1 mm was evaluated as "good", the case of 1 mm or more and less than 2 mm as "good", and the case of 2 mm or more as "unacceptable".

(Evaluation of curl by high temperature and high humidity load)

In the same procedure as in "Evaluation of shrinkage by high temperature and high humidity load", a sample was cut out from a long film, held for 200 hours in an environment of 85 ° C. and 85% RH, and then left on a platen.

Lifting of four sides of the sample in that state was measured. Specifically, the distance from the surface plate was measured on each of the four sides of the sample. The case where the average value of the four measured values of the three samples was less than 1 mm was evaluated as "good", the case of 1 mm or more and less than 2 mm as "good", and the case of 2 mm or more as "unacceptable".

[Production Example 1: Crystalline Resin (a)]

The metal pressure-resistant reactor was sufficiently dried and then purged with nitrogen. In this metal pressure reactor, 154.5 parts of cyclohexane, 42.8 parts of a 70% concentration of dicyclopentadiene (endo body content of 99% or more) cyclohexane solution (30 parts as the amount of dicyclopentadiene), and 1.9 parts of 1-hexene and warmed to 53°C.

A solution was prepared by dissolving 0.014 part of tetrachlorotungstenphenylimide (tetrahydrofuran) complex in 0.70 part of toluene. To this solution, 0.061 part of a diethylaluminum ethoxide/n-hexane solution having a concentration of 19% was added and stirred for 10 minutes to prepare a catalyst solution. This catalyst solution was added to the mixture in the pressure-resistant reactor to initiate a ring-opening polymerization reaction. Then, it was made to react for 4 hours, maintaining 53 degreeC, and the solution of the ring-opening polymer of dicyclopentadiene was obtained. The number average molecular weight (Mn) and weight average molecular weight (Mw) of the obtained ring-opening polymer of dicyclopentadiene were 8,750 and 28,100, respectively, and the molecular weight distribution (Mw/Mn) determined therefrom was 3.21.

To 200 parts of the obtained solution of the ring-opening polymer of dicyclopentadiene, 0.037 parts of 1,2-ethanediol was added as a terminating agent, heated to 60°C, and stirred for 1 hour to terminate the polymerization reaction. To this, one part of a hydrotalcite-type compound (“Kyoward (registered trademark) 2000” manufactured by Kyowa Chemical Industry Co., Ltd.) was added, heated to 60° C., and stirred for 1 hour. After that, 0.4 part of filter aid (“Radiolite (registered trademark) #1500” manufactured by Showa Chemical Industry Co., Ltd.) was added, and a PP pleat cartridge filter (“TCP-HX” manufactured by ADVANTEC Toyo Co., Ltd.) was used to filter the adsorbent and solution was separated by filtration.

To 200 parts of a ring-opening polymer solution of dicyclopentadiene after filtration (polymer weight: 30 parts), 100 parts of cyclohexane was added, 0.0043 part of chlorohydridecarbonyltris(triphenylphosphine)ruthenium was added, and hydrogen pressure was 6 MPa. , and a hydrogenation reaction was performed at 180°C for 4 hours. As a result, a reaction liquid containing a hydride of a ring-opening polymer of dicyclopentadiene was obtained. Hydride was precipitated in this reaction liquid, and it became a slurry solution.

The hydride and the solution contained in the above reaction liquid were separated using a centrifugal separator and dried under reduced pressure at 60°C for 24 hours to obtain 28.5 parts of a hydride of a crystalline dicyclopentadiene ring-opened polymer. The hydrogenation rate of this hydride was 99% or more, the glass transition temperature Tg was 93°C, the melting point (Tm) was 262°C, and the ratio of racemo dyad was 89%.

To 100 parts of the hydride of the resulting ring-opening polymer of dicyclopentadiene, an antioxidant (tetrakis[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane After mixing 1.1 parts of “Irganox (registered trademark) 1010” manufactured by BASF Japan Co., Ltd., it is introduced into a twin-screw extruder (product name “TEM-37B” manufactured by Toshiba Machinery Co., Ltd.) equipped with four die holes with an inner diameter of 3 mm Φ did A mixture of a hydride of a ring-opening polymer of dicyclopentadiene and an antioxidant is molded into a strand shape by hot-melt extrusion molding, and then cut with a strand cutter to obtain pellets of the crystalline resin COP1 as the crystalline resin (a) got it The operating conditions of the twin-screw extruder were as follows.

Barrel setting temperature = 270 ~ 280℃

Die set temperature = 250℃

·Screw rotation rate = 145 rpm

[Production Example 2: Material (b)]

(2-1. Preparation of styrene-maleic anhydride copolymer)

In an autoclave equipped with a stirrer, 15 parts of methyl ethyl ketone, 10 parts of styrene, and 0.014 part of α-methylstyrene dimer were charged, the inside of the system was purged with nitrogen gas, and then heated to a temperature of 80°C.

A solution was prepared by dissolving 2.2 parts of maleic anhydride and 0.04 part of benzoyl peroxide in 9 parts of methyl ethyl ketone. This solution was added to the mixture in the autoclave 10 hours after the start of the heating. After the addition, the temperature was maintained at 80°C for another 2 hours, and the reaction was continued. As a result, reaction solution 1 was obtained. 20 parts of methyl ethyl ketone was added to the reaction solution 1 and cooled to room temperature. This was poured into 120 parts of methanol while stirring vigorously, separated by filtration, and then dried to obtain a white powdery polymer. The white powdery polymer was extruded with a single screw extruder with a screw diameter of 40 mm at a cylinder temperature of 220°C and a screw rotation speed of 100 rpm to obtain pellets of styrene-maleic anhydride copolymer PS1 as material (b). The glass transition temperature of PS1 was 128°C.

[Example 1]

(1-1. Process (I): Film before stretching)

Equipped with a single-screw extruder with a double-flight type screw, a film forming device for co-extrusion molding of two types and three layers (a type of molding device capable of forming a film having a three-layer structure using two types of resins) prepared. The pellets of COP1 obtained in Production Example 1 were introduced into one single-screw extruder of the above film forming apparatus and melted. Further, the pellets of PS1 obtained in Production Example 2 were put into the single screw extruder on the other side of the above film forming apparatus and melted.

The molten COP1 at 290°C was supplied to one manifold of a multi-manifold die (surface roughness Ra of die slip: 0.1 μm) through a leaf disk-shaped polymer filter with an eye size of 10 μm. Further, the molten PS1 at 250°C was supplied to the other manifold of the multi-manifold die through a leaf disk-shaped polymer filter having an aperture of 10 µm. COP1 and PS1 were simultaneously extruded from a multi-manifold die at 300° C. and molded into a film.

The molded film-like molten resin was cast on a cast roll adjusted to a surface temperature of 80°C to obtain a long film (I) having a pA layer made of COP1 and a pB layer made of PS1. At this time, the thickness of the film I was adjusted by adjusting the rotational speed of the screw and the rotational speed of the cast roll.

(1-2. Process (II))

The film (I) obtained in (1-1) was conveyed at a speed of 5 m/min, passed through an immersion tank containing toluene, and then passed through an oven at 110°C to dry. By adjusting the transport route, the immersion time was 5 seconds and the drying time was 60 seconds. Thus, the pA layer of the film (I) was treated to obtain a qA layer, and a long film (II) comprising the qA layer and the pB layer was obtained.

A part of the obtained film (II) was cut out, and the thickness and slow axis direction of each layer were measured. In addition, the qA layer and the pB layer were peeled off to make different films, and the slow axis direction and refractive index were measured for each. The refractive indices nx(qa), ny(qa), and nz(qa) of the qA layer and the refractive indices nx(pb), ny(pb), and nz(pb) of the pB layer are in the direction of the slow axis of the film (II) was obtained in the nx direction. The slow axis of the qA layer coincided with the slow axis of the film (II), and they were in a direction parallel to the longitudinal direction of the film (II).

(1-3. Process (III))

The film (II) obtained in (1-2) was uniaxially stretched at the free end in the longitudinal direction of the film with a longitudinal stretching machine, thereby forming the qA layer and the pB layer into the A layer and the B layer to obtain a multilayer film. The stretching ratio was 1.7 times, and the stretching temperature was 140°C.

The conveyance state immediately after step (III) was observed and the conveyance property of the multilayer film was evaluated. A part of the obtained multilayer film was cut out, and the overall thickness of the multilayer film, the thickness of each layer, the slow axis direction, Re(450), Re(550), Re(650), and NZ coefficient were measured. The A layer and the B layer were peeled off to make different films, and the direction of the slow axis and the refractive index were measured for each, and the intersection angle between the slow axis of the A layer and the slow axis of the B layer was determined. The refractive indices nx(a), ny(a), and nz(a) of the layer A and the refractive indices nx(b), ny(b), and nz(b) of the layer B represent the slow axis direction of the multilayer film as nx Retrieved in the direction. The slow axis of layer A coincided with the slow axis of the multilayer film, and they were in a direction parallel to the longitudinal direction of the multilayer film. In addition, the crystallinity of the A layer was measured.

In addition, shrinkage and curling of the obtained multilayer film under high temperature and high humidity load were evaluated.

[Example 2]

Except for the following changes, a multilayer film was obtained and evaluated by the same operation as in Example 1.

(1-1) The thickness of the film (I) was changed by changing the conditions for forming the film (I).

・(1-3) The stretching conditions were changed. Using an oblique stretching machine as a stretching machine, the film was uniaxially stretched in a direction of 45° with respect to the longitudinal direction. However, the stretching ratio and the stretching temperature were set at 1.7 times and 140°C without changing.

The slow axis of the qA layer in the film (II) coincided with the slow axis of the film (II), and they were in a direction parallel to the longitudinal direction of the film (II). The slow axis of the layer A in the multilayer film coincided with the slow axis of the multilayer film, and these were directions forming an angle of 45° with the longitudinal direction of the multilayer film.

[Example 3]

(3-1. film for pA layer)

An extrusion molding apparatus equipped with a leaf disc-shaped polymer filter (filtration accuracy of 10 µm), a single-screw extruder with a screw diameter of 50 mm, and a T-shaped die was prepared. Using this extrusion molding machine, the pellets of COP1 obtained in Production Example 1 were melt-extruded into a film at an extrusion temperature of 300°C. The extruded film-like resin was passed through three cooling drums (diameter: 250 mm, drum temperature: 80° C., take-up speed: 1.0 m/s) to cool, and a transparent film with a thickness of 26 μm and a width of 600 mm was obtained as a film for the pA layer.

(3-2. film for pB layer)

An extrusion molding apparatus equipped with a leaf disc-shaped polymer filter (filtration accuracy of 10 µm), a single-screw extruder with a screw diameter of 50 mm, and a T-shaped die was prepared. Using this extrusion molding machine, the pellets of PS1 obtained in Production Example 2 were melt-extruded into a film at an extrusion temperature of 250°C. The extruded film-like resin was passed through three cooling drums (diameter: 250 mm, drum temperature: 110° C., take-up speed: 0.3 m/s) to cool, and a transparent film with a thickness of 102 μm and a width of 600 mm was obtained as a film for the pB layer.

(3-3. Film (I'))

The film for pA layer obtained in (3-1) and the film for pB layer obtained in (3-2) were bonded together. For bonding, two pA layer films and one pB layer film are stacked with an adhesive layer interposed therebetween, (pA layer)/(adhesive layer)/(pB layer)/(adhesive layer)/(pA layer) layer It was made to be configurable. Bonding was performed by aligning these films in their longitudinal directions and bonding them together by the roll-to-roll method. As the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer, "CS9621T" manufactured by Nitto Denko was used.

(3-4. Process (II) and (III))

Except for the following changes, a multilayer film was obtained and evaluated by the same operation as (1-2) (step (II)) and (1-3) (step (III)) of Example 1.

· Instead of the film (I) obtained in (1-1), the film (I') obtained in (3-3) was used.

・(1-3) The stretching conditions were changed. Using an oblique stretching machine as a stretching machine, the film was uniaxially stretched in a direction of 45° with respect to the longitudinal direction. However, the stretching ratio and the stretching temperature were set to 1.7 times and 140° C. without changing (the same as in Example 2).

The slow axis of the qA layer in the film (II) coincided with the slow axis of the film (II), and they were in a direction parallel to the longitudinal direction of the film (II). The slow axis of the layer A in the multilayer film coincided with the slow axis of the multilayer film, and these were directions forming an angle of 45° with the longitudinal direction of the multilayer film.

[Comparative Example 1]

(C1-1. Film for layer A')

Amorphous norbornene-type polymer resin (“ZEONOR1420” manufactured by Zeon Corporation, glass transition temperature: 136° C.) was subjected to melt extrusion molding to obtain a long film. The thickness and refractive index of this film were measured as numerical values corresponding to the qA layer thickness, nx(qa), ny(qa), and nz(qa) of Examples.

Further, this film was uniaxially stretched in the film width direction. The stretching ratio and the stretching temperature were 3.0 times and 140°C. In this way, a long film for layer A' was obtained.

(C1-2. Film for layer B')

An acrylic resin (“Smipex HT55X” manufactured by Sumitomo Chemical Co., Ltd., glass transition temperature: 105° C.) was prepared.

PS1 and the acrylic resin obtained in Production Example 2 were co-extruded to obtain a long film having a layer configuration of (acrylic resin layer)/(PS1 layer)/(acrylic resin layer). The thickness and refractive index of this film were measured as numerical values corresponding to the pB layer thickness, nx(pb), ny(pb), and nz(pb) of Examples.

Further, this film was uniaxially stretched in the width direction of the film, and then uniaxially stretched in the longitudinal direction of the film. The stretching ratio was set to 2.0 times for either stretching. As for the extending|stretching temperature, both extending|stretching made it 140 degreeC. In this way, a long film for layer B' was obtained.

(C1-3. Bonding and Evaluation)

The film for layer A' obtained in (C1-1) and the film for layer B' obtained in (C1-2) were bonded together. The bonding was performed by laminating one film for A' layer and one film for B' layer through an adhesive layer so as to form a layer configuration of (A' layer)/(Adhesive layer)/(B' layer). Bonding was performed by aligning these films in their longitudinal directions and bonding them together by the roll-to-roll method. As the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer, "CS9621T" manufactured by Nitto Denko was used. By this bonding, a multilayer film comprising the A' layer and the B' layer was obtained.

The conveyance state immediately after bonding was observed, and conveyability was evaluated. Further, the slow axis direction, Re(450), Re(550), and Re(650) of the obtained multilayer film, and NZ coefficient were measured. In addition, shrinkage and curling of the multilayer film due to high temperature and high humidity load were evaluated.

In addition, a part of the obtained multilayer film was cut out, and the A' layer and the B' layer were peeled off to make different films, and the slow axis direction and refractive index were measured for each. The slow axis of the A' layer coincided with the slow axis of the multilayer film, and they formed an angle of 90° with the longitudinal direction of the multilayer film.

Table 1 shows the outlines and results of Examples and Comparative Examples. In the comparative example, the measurement results for the A' layer and the B' layer are shown in the corresponding rows of the A layer and the B layer.

As is clear from the results of Examples and Comparative Examples, in Examples in which a crystalline resin was employed as the A-layer material, a good effect as a three-dimensional retardation film can be easily expressed in a wide wavelength range by uniaxial stretching. Multilayer films could be made. In addition, the film obtained in the Example had a low degree of curl and shrinkage due to high-temperature, high-humidity load.

Claims (9)

A long multilayer film comprising an A layer made of crystalline resin (a) and a B layer made of material (b),
One of the crystalline resin (a) and the material (b) is a material having a positive intrinsic birefringence, and the other is a material having a negative intrinsic birefringence,
The multilayer film satisfies both the following formulas (1) and (2),
The B layer is a multilayer film that satisfies all of the following formulas (3), (4), and (7), or satisfies all of the following formulas (5), (6), and (7):
Re (450) < Re (550) < Re (650) ... (1)
0 < Nz < 1 ... (2)
nx(b) > ny(b) ...(3)
nx(b) > nz(b) ... (4)
nx(b) < ny(b) ...(5)
nx(b) < nz(b) ... (6)
|ny(b) - nz(b)| ≤ 0.003 ... (7)
step,
Re (450), Re (550), and Re (650) are, respectively, the in-plane retardation of the multilayer film at a wavelength of 450 nm, the in-plane retardation of the multilayer film at a wavelength of 550 nm, and the multilayer film In-plane retardation at a wavelength of 650 nm,
Nz is the Nz coefficient of the multilayer film,
nx(b) is the refractive index of the B layer in the in-plane slow axis direction Dx of the multilayer film,
ny (b) is the refractive index of the layer B in a direction Dy orthogonal to the direction Dx as an in-plane direction of the multilayer film,
nz(b) is the refractive index of the layer B in the thickness direction Dz of the multilayer film. According to claim 1,
A performance new product, a multi-layered film. According to claim 2,
The new performance product is a new performance product of a fabric film, which is a co-extruded product, a multi-layer film. According to any one of claims 1 to 3,
The multilayer film in which at least one layer of the said A-layer is located on the surface of the said multilayer film. According to any one of claims 1 to 4,
The multilayer film in which the in-plane slow axis of the said A layer and the in-plane slow axis of the said B layer are orthogonal. According to any one of claims 1 to 5,
A multilayer film having a layer configuration of (Layer A)/(Layer B)/(Layer A). According to any one of claims 1 to 6,
A multilayer film having a thickness of 40 μm or less. A method for producing the multilayer film according to any one of claims 1 to 7,
A pA layer made of the crystalline resin (a) and a pB layer made of the material (b) were formed by co-extrusion film formation of the crystalline resin (a) and the material (b), and the pA layer A step (I) of obtaining a long film (I) in which at least one layer of is located on the surface;
Step of contacting the surface of the film (I) on which the pA layer is located with a solvent to treat the pA layer to form a qA layer, thereby obtaining a long film (II) comprising the qA layer and the pB layer (II) and
Step (III) of obtaining a long film (III) by uniaxially stretching the film (II)
Including, manufacturing method. According to claim 8,
The manufacturing method in which the said uniaxial stretching in the said process (III) is oblique uniaxial stretching.