JP6915713B2 - Laminated film with controlled thickness retardation (Rth) and its manufacturing method - Google Patents

Description

The present invention relates to a film, and more particularly to a laminated film having a controlled thickness phase difference (Rth), which can be expected to be applied to various optical compensating films and the like. The present invention also relates to a method for producing the laminated film.

In recent years, liquid crystal displays have been widely used as display devices for televisions, personal computers, digital cameras, mobile phones and the like. One or more retardation films may be placed for the purpose of compensating for distortion of images viewed from various viewing angles due to the phase difference of polarized light passing through the liquid crystal cell. This retardation film is also called an optical compensation film, and can also serve as a protective film for a polarizing plate by being directly attached to a polarizing film.

The liquid crystal display is turned on and off depending on the orientation state of the liquid crystal molecules, and is displayed as TN (Twisted Nematic), IPS (In-Plane Switching), OCB (Optical Optical Compensatory Bend), VA (Vertical Element There is a display mode of, and an optical compensation film suitable for these is required.

Here, the anisotropy of the retardation film can be expressed by a refractive index ellipsoid (nx, ny, nz) showing the three-dimensional refractive index as a sphere. It is well known that nx and ny can be continuously controlled by uniaxial stretching or biaxial stretching, but for nz, for example, in Patent Documents 1 and 2, a heat-shrinkable film is adhered to one or both sides of the film. A manufacturing method in which the laminate is heat-stretched to apply a shrinking force in the thickness direction of the polymer film is disclosed. Here, nx indicates the maximum refractive index in the film surface, ny indicates the minimum refractive index in the film surface, and nz indicates the refractive index outside the film surface (thickness direction).

The optical compensation film is sometimes used as a single film, but as a method for controlling optical anisotropy, for example, in Patent Documents 3 and 4, a film having a positive birefringence and a film having a negative intrinsic birefringence can be laminated. It is disclosed.

Japanese Patent No. 2818983 JP-A-2002-207123 Japanese Unexamined Patent Publication No. 2008-268913 JP-A-2009-223163

However, the methods disclosed in Patent Documents 1 and 2 require a member such as a heat-shrinkable film, and the characteristics (variation) of the heat-shrinkable film used affect the control of the refractive index. There was a problem that it was not easy to stabilize.
Further, in the methods of Patent Documents 3 and 4, it is possible to control the optical anisotropy by laminating a resin having a positive intrinsic birefringence on a resin having a negative intrinsic birefringence, but there are two or more types. It is necessary to prepare the material of the above, and there is a concern that the difference in refractive index between layers may affect the optical characteristics. Further, the resin constituting each layer usually has low compatibility, and there is also a problem that it is easy to become cloudy when a trimmed member such as a film edge is added to each layer again. Further, the resin having a negative intrinsic birefringence is substantially an acrylic resin or a styrene resin, and is inferior in impact resistance and heat resistance, and there is also a problem that the performance of the obtained laminated film is limited.

Therefore, in particular, there has been a demand for a laminated film having a simple control method of thickness retardation (Rth), control of thickness retardation (Rth), and excellent transparency. In addition, there has been a demand for a configuration in which trimmed members such as film edges can be regenerated and added.

An object of the present invention is to provide a laminated film which can be regenerated and added in view of the above-mentioned problems of the prior art, whose optical characteristics, particularly thickness phase difference (Rth), are controlled, and which is excellent in transparency. , And a method for producing the laminated film.

As a result of diligent studies in view of the above circumstances, the present inventors have found that the above-mentioned problems can be solved by stacking layers in which the intrinsic birefringence value is positive and the thickness phase difference (Rth) value is positive or negative. The findings led to the completion of the present invention.

That is, according to the present invention, the layer (I) and the layer (II) are composed of a composition containing a resin having a glass transition temperature of 80 ° C. or higher and a positive natural birefringence as a main component. The main component of the layer (I) and the layer (II) is the same resin, and the layer (I) having a negative thickness retardation (Rth) value and the layer (II) having a positive thickness retardation (Rth) value. ) And a laminated film is provided.

According to the present invention, if the same material is used, a trimming member or the like can be regenerated and added, optical characteristics, particularly thickness phase difference (Rth) can be controlled, and a laminated film having excellent transparency can be provided. It can be expected to be applied to optical films, especially various optical compensation films. Further, it is possible to provide a continuous manufacturing method of the laminated film, and its industrial value is high.

Hereinafter, embodiments of the present invention will be described in detail. However, the content of the present invention is not limited to the embodiments described below.

The laminated film of the present invention (hereinafter sometimes referred to as "the present film") is a resin in which the layer (I) and the layer (II) have a glass transition temperature of 80 ° C. or higher and a positive intrinsic birefringence. It is composed of a composition containing a main component, and has a layer (I) having a negative thickness retardation (Rth) value and a layer (II) having a positive thickness retardation (Rth) value.

This film is a laminated film that combines a layer with a negative thickness retardation and a layer with a positive thickness retardation, and the thickness retardation can be controlled by selecting the type of resin, layer composition, and layer thickness. It becomes. In particular, if the same material is used, it is possible to regenerate and add a trimming member or the like.

Hereinafter, the laminated film of the present invention will be described.

(1) Laminated structure The laminated film of the present invention may have a layer (I) and a layer (II)), and the other layers are not particularly limited. Here, an adhesive layer (S) or another layer (Q) can be arranged between the layer (I) and the layer (II)). It is preferable not to arrange the adhesive layer (S) and the other layer (Q) as much as possible because they have an influence on optical characteristics such as light reflection and refraction at the interface of each layer.
Specifically, a two-layer structure of layer (I) / layer (II), layer (I) / layer (II) / layer (I), layer (II) / layer (I) / layer (II), layer (I) / adhesive layer (S) / layer (II) three-layer structure, layer (I) / adhesive layer (S) / layer (II) / adhesive layer (S) / layer (I), layer (II) ) / Adhesive layer (S) / Layer (I) / Adhesive layer (S) / Layer (II), Layer (I) / Other layer (Q) / Layer (II) / Adhesive layer (S) / Layer (I) ), Layer (I) / other layer (Q) / layer (II) / other layer (Q) / layer (I), and the like.
In the present invention, from the viewpoint of curl suppression of the laminated film, optical characteristics, ease of manufacture, etc., a two-layer structure of layer (I) / layer (II) or layer (I) / layer (II) / layer (I) , A three-layer structure of layer (II) / layer (I) / layer (II) is preferable.

The difference (absolute value) in the refractive index (average refractive index) between the layers is not particularly specified, but is preferably 0.1 or less, preferably 0.05 or less, in order to suppress light reflection and refraction at the interface of each layer. More preferably, 0.03 or less is further preferable. Further, although the lower limit of the refractive index difference is not particularly specified, 0.001 or more is preferable, and 0.005 or more is more preferable, in order to measure the thickness of each layer in a non-destructive manner by reflectance spectroscopy.

From the viewpoint of heat resistance, the laminated film of the present invention preferably has a glass transition temperature of either layer (I) or layer (II) of 100 ° C. or higher, more preferably 110 ° C. or higher, and 120 ° C. or higher. Is more preferable, and 130 ° C. or higher is particularly preferable. From the viewpoint of improving heat resistance, it is preferable to set the glass transition temperature of the layer having the thicker total thickness in the above range. Further, 100 ° C. or higher is more preferable for each layer, and 110 ° C. or higher is even more preferable.

(2) Thickness The thickness of the laminated film of the present invention is not particularly limited, but is preferably 100 μm or less, more preferably 80 μm or less, and particularly preferably 60 μm or less from the viewpoint of weight reduction and the like. On the other hand, from the viewpoint of handleability and strength, 5 μm or more is preferable, and 10 μm or more is more preferable.

(3) Lamination ratio In the laminated film of the present invention, the lamination ratio of the layer (I) and the layer (II) is not particularly limited, but the value of the thickness phase difference of the entire laminated film is defined as Rth (lamination). When the absolute value of the total value of the thickness phase difference (Rth) of each layer (I) and layer (II) is | Rth (I) | and | Rth (II) |, respectively, the equations (1) and (2) It is preferable to satisfy. Within this range, it is effective and preferable for improving the image quality of the liquid crystal display.
Equation (1): Rth (lamination) << | Rth (I) |
Equation (2): Rth (lamination) << | Rth (II) |

(4) Phase Difference The thickness retardation (Rth) of the laminated film of the present invention is preferably 30 nm or less, more preferably 10 nm or less, further preferably 5 nm or less, and particularly preferably 3 nm or less. When the thickness retardation (Rth) is 30 nm or less, the optical anisotropy is small, so that it is suitable as an optical film. The in-plane retardation (Ro) of the laminated film of the present invention is preferably 30 nm or less, more preferably 10 nm or less, further preferably 5 nm or less, and particularly preferably 3 nm or less.
The lower limit of the thickness retardation (Rth) and the in-plane retardation (Ro) is not particularly defined, but is preferably -30 nm or more, more preferably -10 nm or more, further preferably -5 nm or more, and particularly preferably -3 nm or more. preferable.
The method for measuring the phase difference is as described in the section of Examples described later.

(5) photoelasticity coefficient of the laminated film of the photoelastic coefficient present invention (absolute value) is preferably ¹⁰ × 10 -12 ^{Pa -1} or less, more preferably 8 × ¹⁰ -12 ^{Pa -1} or less, 5 × 10 ^{- 12} Pa ^-1 or less is particularly preferable. If the photoelastic coefficient is ^{larger than 10 × 10-12} Pa- ¹ , the change in phase difference due to stress becomes large, which may cause light leakage or the like.
The photoelastic coefficient is the stress of the difference in birefringence in a substance that temporarily becomes an optically anisotropic body when an elastic body receives an external force, causes birefringence, and returns to its original state after removing the external force. A constant that represents a dependency. That is, the relationship between the birefringence difference (Δn) and the photoelastic coefficient is expressed by the following equation.
Δn = C · σ (C represents photoelastic coefficient, σ represents stress)

(6) Transparency The total light transmittance of the laminated film of the present invention is preferably 85% or more, more preferably 90% or more, further preferably 91% or more, and particularly preferably 92% or more. The haze is preferably 1% or less, more preferably 0.5% or less, and even more preferably 0.3% or less.

The laminated film of the present invention can be used by cutting out a necessary range by trimming, punching, cutting out, or the like. The laminated film of the present invention may be used as it is, but can be uniaxially stretched or biaxially stretched as needed. In addition, lamination with a layer such as another film can be appropriately performed.

Hereinafter, the resin having a positive intrinsic birefringence as a raw material will be described, and then the method for producing the laminated film of the present invention will be described.

<Resin with positive birefringence>
A resin having a positive intrinsic birefringence is a layer in which the molecular chains of a polymer are uniaxially oriented (for example, a film), and among the light vertically incident on the main surface of the layer, the molecular chains in the layer are oriented. A resin in which the value (n ₁ −n _{2 ) obtained by subtracting the refractive index n 2 of the} layer for the vibration component perpendicular to the orientation axis from _{the refractive index n 1} of the layer for the vibration component parallel to the direction (orientation axis) is positive. be. The value of the intrinsic birefringence can be obtained for each polymer by calculation based on its molecular structure. The positive or negative of the intrinsic birefringence of the resin composition is determined by the total amount of birefringence generated by each polymer contained in the resin composition. Further, in the present invention, the main component means that the composition component in the layer is preferably contained in an amount of 50% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more.

The resin having a positive intrinsic double refraction is not particularly limited as long as the glass transition temperature is 80 ° C. or higher, but specifically, an alicyclic structure-containing polymer resin, polycarbonate, polyarylate, or polyester. Examples thereof include based resins, polyether sulfone, polyphenylene sulfide, polyphenylene oxide, polyallyl sulfone, polyamideimide, polyimide, and cellulose. The polymer may be a copolymer, a derivative thereof, or a blend as long as the intrinsic birefringence is positive. When considering the use of this film as an optical film, especially as a polarizer protective film, an alicyclic structure with excellent transparency, heat resistance, mechanical properties, and surface treatment such as corona treatment provides excellent adhesion to the polarizing film. The containing polymer resin is preferably used.

The alicyclic structure-containing polymer resin is a resin having an alicyclic structure in the repeating unit of the polymer. In the present invention, either a polymer resin having an alicyclic structure in the main chain and a polymer resin having an alicyclic structure in the side chain can be used. Further, as the polymer resin having an alicyclic structure in the repeating unit, a crystalline resin and an amorphous resin can be obtained depending on the structure, but in the present invention, the amorphous resin having excellent transparency is used. preferable.

Examples of the alicyclic structure include a cycloalkane structure and a cycloalkene structure, and the cycloalkane structure is preferable from the viewpoint of thermal stability and the like. The number of carbon atoms constituting the alicyclic structure is not particularly limited, but is usually 4 to 30, preferably 5 to 20, and more preferably 6 to 15.

The ratio of the repeating unit having the alicyclic structure in the polymer resin having the alicyclic structure is not particularly limited as long as the glass transition temperature is 80 ° C. or higher, but is usually 30% by weight or more, preferably 30% by weight or more. It is 50% by weight or more. It is preferable to set the repeating unit having an alicyclic structure in the above range because the heat resistance can be improved and the optical characteristics can be adjusted.

Specific examples of the alicyclic structure-containing polymer resin include (1) a copolymer of cyclic ethers and an alicyclic dihydroxy compound, (2) a norbornene polymer, and (3) a monocyclic cyclic olefin polymer. Examples thereof include (4) cyclic conjugated diene polymers, (5) vinyl alicyclic hydrocarbon polymers, and hydrogenated products thereof. Among these, from the viewpoint of transparency and moldability, copolymers and norbornene polymers of cyclic ethers and alicyclic dihydroxy compounds, which will be described later, and hydrogenated products thereof are more preferable.

Examples of the copolymer of the cyclic ethers and the alicyclic dihydroxy compound include isosorbide, isomannide and isoidet as the cyclic ethers. Here, isosorbide can be inexpensively produced by hydrogenating D-glucose obtained from starch and then dehydrating it, and can be abundantly obtained as a resource.
Examples of the alicyclic dihydroxy compound include monomer units derived from the alicyclic dihydroxy compound described in International Publication No. 2007/148604. In the present invention, those containing a 5-membered ring structure or a 6-membered ring structure are preferable from the viewpoint of heat resistance and optical characteristics. The 6-membered ring structure may be fixed in a chair or boat shape by covalent bonds. Among them, cyclohexanedimethanol, tricyclodecanedimethanol, adamantanediol and pentacyclopentadecanedimethanol can be preferably exemplified. Among these, cyclohexanedimethanol or tricyclodecanedimethanol is more preferable from the viewpoint of economy and heat resistance.

As the copolymer of the cyclic ethers and the alicyclic dihydroxy compound, a commercially available product can be used, and specific examples thereof include the trade name "DURABIO" manufactured by Mitsubishi Chemical Corporation. ..

Examples of the norbornene polymer include a ring-opening polymer of a norbornene monomer, a ring-opening copolymer of a norbornene monomer and an arbitrary monomer capable of ring-opening copolymerization, and hydrogenating agents thereof; an addition polymer of a norbornene monomer. Examples thereof include an addition copolymer of a norbornene monomer and an arbitrary monomer copolymerizable. Among these, a ring-opening polymer hydrogenated additive of norbornene monomer is particularly preferable from the viewpoint of transparency.
The alicyclic structure-containing polymer resin can be selected from known polymers disclosed in, for example, JP-A-2002-321302.

As the norbornene polymer, it is also possible to use a commercially available product. Specifically, the trade names "ZEONEX", "ZEONOR", and JSR Corporation manufactured by Nippon Zeon Co., Ltd. The product name "ARTON" and the like can be mentioned.

The glass transition temperature of the resin having a positive intrinsic birefringence used in the present invention is preferably 80 ° C. or higher, more preferably 100 ° C. or higher, further preferably 110 ° C. or higher, and particularly 120 ° C. or higher. The upper limit is usually 250 ° C. or lower, preferably 200 ° C. or lower, and more preferably 180 ° C. or lower. When the glass transition temperature is within this range, it is preferable because it has excellent durability against deformation and stress during use at high temperatures.

The intrinsic birefringence of the resin used in the present invention may be positive, but the intrinsic birefringence is preferably 0.1 or less, more preferably 0.08 or less, and particularly preferably 0.05 or less. The closer the intrinsic birefringence is to zero, the smaller the optical anisotropy of the film, which is preferable.

The above resin contains other polymers for the purpose of improving and adjusting various properties without impairing the effects of the present invention, as well as lubricants, plasticizers, antistatic agents, antioxidants, ultraviolet absorbers, and photostabilizers. Additives such as agents, antistatic agents, flame retardants, fillers and nanofillers can be included. These other polymers and additives may be used alone or in combination of two or more.

<Manufacturing method of this film>
Next, the method for producing the laminated film of the present invention will be described.
In the method for producing a laminated film according to an example of the embodiment of the present invention (hereinafter, may be referred to as "the present film production method"), the layer (I) and the layer (II) have a glass transition temperature of 80 ° C. or higher. The layer (I) is composed of a composition containing a resin having a positive intrinsic compound refraction as a main component, and the layer (I) is a melt extrusion step of heating and melting the composition and extruding it into a sheet, and is specified as a cooling roll (A). A layer (I) having a negative thickness phase difference (Rth) value obtained by a pressing step of sandwiching the extruded sheet-like material with a touch roll (B) and a thickness phase difference (Rth). A method for producing a laminated film in which a layer (II) having a positive value is laminated by an extrusion laminating method, wherein a layer (I) having a negative thickness retardation (Rth) and a thickness retardation (Rth) are laminated. This is a method for producing a laminated film having a layer (II) having a positive value.

The manufacturing method of each of the layer (I) and the layer (II) will be described. Here, the layer (II) having a positive value of intrinsic birefringence and a positive value of thickness phase difference (Rth) can be produced by a known method such as a normal melt extrusion method or a solution casting method. ..
Here, the in-plane phase difference (Ro) is Ro = (nx−) when the refractive indexes in the slow axis direction and the phase advance axis direction of the film are nx and ny, respectively, and d (nm) is the thickness of the film. It is obtained by ny) × d. The slow-phase axis refers to the direction in which the in-plane refractive index is maximized. Further, the thickness phase difference (Rth) is obtained by Rth = {(nx + ny) /2-nz} × d, where nz is the refractive index in the thickness direction.

On the other hand, the layer (I) in which the value of the intrinsic birefringence is positive and the value of the thickness phase difference (Rth) is negative is the most important part in the present invention. In the present invention, the layer (I) is a melt extrusion step in which a composition containing a resin having a glass transition temperature of 80 ° C. or higher and a positive intrinsic compound refraction as a main component is heated and melted and extruded into a sheet. It can be obtained by a film manufacturing method including a pressing step of sandwiching a sheet-like material extruded in a melt extrusion step between a cooling roll (A) and a specific touch roll (B). Since the manufacturing method may include the above steps, it may further include other steps and treatments.

In the present invention, the touch roll (B) is deformed from a perfect circle when the sheet-like material extruded by heating and melting the resin composition is pressed with the cooling roll (A) as shown in FIG. Therefore, it is considered that the narrow pressure state of the sheet-like material changes from the linear pressure state to the surface pressure state, and the so-called pressing effect is exhibited. It is considered that this makes it possible to collect a film having a negative thickness retardation (Rth) despite the resin having a positive intrinsic birefringence.

<Melting extrusion process>
In this step, a resin having a glass transition temperature of 80 ° C. or higher and a positive natural birefringence and other raw materials are preblended with a mixer such as a tumbler mixer or an omni mixer, and then obtained as necessary. The resulting mixture may be extruded and kneaded to prepare a resin composition.

The raw materials may be heat-dried in an oven, a vacuum dryer, or the like in a state of being separated or mixed. It is preferable that the conditions are such that the components do not deteriorate or fuse during drying.

The equipment used when kneading the resin composition is not particularly limited. For example, a known extruder such as a single-screw extruder, a twin-screw extruder, or a multi-screw extruder can be used.
Further, depending on the equipment structure and necessity, a decompressor may be connected to the vent port to remove water and low molecular weight substances.

The L / D value of the extruder (L is the length of the cylinder of the extruder and D is the inner diameter of the cylinder) is 10 to 80 or less in order to sufficiently plasticize the resin composition and obtain a good kneading state. Is preferable. When the L / D value is 10 or more, the resin composition can be sufficiently plasticized, and a good kneading state can be obtained. On the other hand, when the L / D value is 80 or less, it is possible to prevent the resin composition from being thermally decomposed due to excessive shear heat generation. From this point of view, the L / D value of the extruder is preferably 10 to 80 or less, and more preferably 15 or more or 60 or less.

The melting temperature when the resin composition is heated and melted, for example, when the T-die method is adopted, the temperature of the T-die is + 50 ° C. to + 200 ° C., that is, Tg + 50 ° C. to the glass transition temperature (Tg) of the resin composition. It is preferably Tg + 200 ° C., more preferably Tg + 70 ° C. or higher or Tg + 180 ° C. or lower, and more preferably Tg + 100 ° C. or higher or Tg + 150 ° C. or lower. The glass transition temperature (Tg) can be measured by differential scanning calorimetry (DSC).

The T-die may have a single-layer structure or a laminated structure. The interval (lip gap) of the discharge portions in the T-die is preferably 10 to 1500 μm, more preferably 50 μm or more or 1000 μm or less, and more preferably 100 μm or more or 800 μm or less.

Further, a constant flow rate equipment such as a gear pump, a foreign matter removing equipment such as a filter pack, a thermogenizer, or the like may be installed between the extruder and the T-die for processing.

<Pressure process>
In this step, the sheet-like material extruded in the melt extrusion step is sandwiched between the cooling roll (A) and the specific touch roll (B), and is taken out while being in close contact with the cooling roll to be formed into a continuous sheet-like material. Is preferable. FIG. 1 shows a schematic configuration diagram of a manufacturing apparatus prepared for manufacturing the layer (I) (film) in which the value of the thickness retardation (Rth) of the present invention is negative. Further, FIG. 2 shows a schematic cross-sectional view of the touch roll (B) according to the embodiment of the present invention.

First, the cooling roll (A) is not particularly limited, but is usually a metal roll. By using a metal mirror surface roll made of stainless steel or the like as the cooling roll (A), the metal mirror surface can be transferred to the film and the surface appearance can be improved.

The surface shape of the cooling roll (A) may be appropriately selected according to the desired surface characteristics of the film, but if a mirror surface appearance is required, the maximum height measured in accordance with JIS-B0601 (2001). (Rz) is preferably 0.3 μm or less, more preferably 0.2 μm or less.
The size of the cooling roll (A) is not particularly limited, but usually, the diameter is 100 mm to 2500 mm, preferably 200 mm to 1000 mm, and more preferably 250 mm to 600 mm. In addition, the width is usually 5000 mm or less, preferably 800 mm to 2500 mm, more preferably 1000 to 1800 mm.
In FIG. 1, a second cooling roll 5 is further arranged after the cooling roll 4. The number of cooling rolls may be appropriately selected according to the material of the film to be sampled, the molding temperature, the thickness, and the like.

Next, the touch roll (B) has a structure including a shaft body and a base layer formed along the outer periphery of the shaft body, and the base layer is an inner layer (B-1) and an outer layer (B-1). It is important that it has at least two layers of B-2) and its storage elastic modulus satisfies the relationship of the formula (3).
Equation (3): 100 MPa ≧ E'(B-2)>E'(B-1)
Here, E'(B-1) is the storage elastic modulus (MPa) of the inner layer (B-1) at 20 ° C., and E'(B-2) is the storage elastic modulus of the outer layer (B-2) at 20 ° C. It shows the rate (MPa). The storage elastic modulus is a value measured using a viscoelasticity measuring device at a vibration frequency of 10 Hz, a strain of 0.1%, and a heating rate of 3 ° C./min.

Here, it is important that the storage elastic modulus of the inner layer (B-1) is smaller than the storage elastic modulus of the outer layer (B-2) as in the above equation. Due to this relationship, as shown in FIG. 3, when the sheet-like material extruded by heating and melting the resin composition is pressed against the cooling roll (A), the touch roll (B) is deformed from a perfect circle. As a result, it is considered that the narrow pressure state of the sheet-like material changes from the linear pressure state to the surface pressure state, and the so-called pressing effect is exhibited. It is considered that this makes it possible to collect a film having a negative thickness retardation (Rth) despite the resin having a positive intrinsic birefringence.
On the other hand, when the storage elastic modulus of the inner layer (B-1) is larger than the storage elastic modulus of the outer layer (B-2), the outer layer becomes soft, and it is difficult to ensure the flatness of the surface of the produced film. Become. Further, when the soft touch roll outer layer comes into direct contact with the film, the film may be pulled toward the touch roll side, which may cause a trau phenomenon.

As a specific value of the storage elastic modulus, the storage elastic modulus of the outer layer (B-2) at 20 ° C. is preferably 100 MPa or less, more preferably 50 MPa or less, still more preferably 30 MPa or less. The lower limit is usually 5 MPa. The storage elastic modulus of the inner layer (B-1) at 20 ° C. is preferably 10 MPa or less, more preferably 1 MPa or less, and even more preferably 0.5 MPa or less. The lower limit is usually 0.1 MPa. Within this range, when the film is pressed against the cooling roll (A), the touch roll (B) changes from a linear pressure state to a surface pressure state with respect to the film obtained by being deformed from a perfect circle, and a pressing effect is exhibited. It is preferable because it is easy to do.

The difference in storage elastic modulus (E'(B-2) -E'(B-1)) between the outer layer (B-2) and the inner layer (B-1) at 20 ° C. is not particularly limited, but is 1.0 to 1. It is preferably 50 MPa, more preferably 3.0 to 30 MPa, and particularly preferably 5.0 to 20 MPa. Within this range, when the film is pressed against the cooling roll (A), the touch roll (B) changes from a linear pressure state to a surface pressure state with respect to the film obtained by being deformed from a perfect circle, and a pressing effect is exhibited. It is preferable because it is easy to do.

The material of the outer layer and the inner layer is not particularly limited as long as it has the above-mentioned relationship of storage elastic modulus, but the outer layer is made of silicone rubber, and the inner layer is made of silicone-based sponge rubber or urethane-based sponge rubber. Etc. can be preferably used. Further, a heat-dissipating silicone rubber having a thermal conductivity of 0.5 W / m · K or more can also be preferably used for the purpose of improving the peelability and cooling efficiency of the film.

Here, the hardness (JIS-A) of the outer layer is preferably 40 to 90 °, more preferably 50 to 85 °, and even more preferably 60 to 85 °. Within this range, the pressing effect on the obtained film is sufficiently exhibited, and the durability of the touch roll itself is also improved, which is preferable. The surface condition may be appropriately adjusted according to the required characteristics of the obtained film, but in the case of a mirror film, the glossiness (JIS Z8741) is preferably 60 to 80%, more preferably 65 to 75%.

When silicone rubber is used for the outer layer, silicone-based sponge rubber is preferably used as the material of the inner layer from the viewpoint of adhesiveness between layers and heat resistance. As a method for producing a silicone-based sponge rubber, a known method described in JP-A-2011-168728 can be applied.

The thickness of the inner layer (B-1) and the outer layer (B-2) is not particularly limited, but the inner layer (B-1) is preferably 1 mm to 30 mm, more preferably 2 mm to 10 mm. The outer layer (B-2) is preferably 0.5 mm to 10 mm, more preferably 1 mm to 5 mm. When the thickness of the inner layer and the outer layer is within this range, the touch roll (B) changes from a linear pressure state to a surface pressure state with respect to the film obtained by deforming the touch roll (B) from a perfect circle when pressed with the cooling roll (A). It is preferable because the pressing effect is easily exhibited. Further, when the thickness of the outer layer is within the range, the peelability of the film is good, which is preferable. Further, it is preferable that the thickness of the inner layer (B-1) is thicker than the thickness of the outer layer (B-2) because the effect of the present invention is likely to be exhibited.

The base layer of the touch roll (B) may have at least two layers, an inner layer (B-1) and an outer layer (B-2), as described above. Specifically, an adhesive layer or a layer having an elastic modulus between the inner layer and the outer layer may be arranged between the inner layer (B-1) and the outer layer (B-2). Further, even if a layer similar to the outer layer (B-2) or a layer having an elastic modulus intermediate between the inner layer and the outer layer is arranged between the inner layer (B-1) and the shaft body (made of iron, aluminum, etc.). good. Further, the surface of the outer layer (B-2) can be subjected to various surface treatments such as coating and sputtering for the purpose of improving smoothness and surface hardness.

The size of the touch roll (B) is not particularly limited, but usually, the diameter is 50 mm to 500 mm, preferably 100 mm to 400 mm, and more preferably 150 mm to 300 mm. In addition, the width is usually 5000 mm or less, preferably 800 mm to 2500 mm, more preferably 1000 to 1800 mm.

The touch roll (B) used in the present invention may be a drive roll or a free roll that is not driven. Further, a heating / cooling medium such as water or oil can be circulated in the shaft body of the touch roll (B) by a double pipe or a spiral pipe for the purpose of heating / cooling.

In the step of sandwiching the sheet-shaped melt between the cooling roll (A) and the specific touch roll (B) to obtain a film, for example, when a T-die is used, from the lip outlet to the contact of the film with the cooling roll (A). The distance, that is, the air gap is preferably 80 mm or less, and more preferably 70 mm or less. It is preferable to set the air gap in this range because it is easy to suppress the thickness fluctuation due to the shaking of the sheet-shaped melt. Further, in order to suppress the thickness fluctuation, it is preferable that the lip gap is narrow.

In the step of sandwiching the sheet-shaped melt between the cooling roll (A) and the specific touch roll (B) to obtain a film, the touch pressure (surface pressure) of the touch roll (B) is 0.01 MPa to 2. 0 MPa is preferable, and 0.1 MPa to 1.0 MPa is more preferable. When the touch pressure (surface pressure) of the cooling roll (A) and the touch roll (B) is within this range, the effect of the present invention is sufficiently exhibited, and the durability of the touch roll (B) is also ensured. preferable.

The set temperature of the cooling roll (A) may be appropriately adjusted in consideration of the thickness of the film to be collected, the take-up speed, and the like. As a guide, the Tg of the film to be collected may be set in the range of Tg-50 ° C to Tg + 30 ° C, preferably in the range of Tg-40 ° C to Tg + 10 ° C. The glass transition temperature (Tg) can be measured by differential scanning calorimetry (DSC).

<Laminating process>
Next, a method of laminating the layer (I) and the layer (II) will be described. As described above, it is possible to prepare the films used for each layer separately and laminate them with an adhesive layer or an adhesive, but in the present invention, the film of either layer is prepared in advance in the form of a film roll or the like. A method of forming a laminated film by an extrusion laminating method is preferable from the viewpoints of energy efficiency, productivity and reduction of masking film.

For example, when a film for layer (I) is prepared first and a laminated film is obtained by extrusion lamination, a two-layer structure of layer (I) / layer (II) or layer (I) / layer (II) / A laminated film having a three-layer structure of layer (I) is preferably used. Here, it is preferable that the masking film of the film prepared earlier is laminated as it is without being peeled off, because the masking film can be reduced.

Further, various functional coatings (coatings) may be applied to one side or both sides of the laminated film of the present invention. The functional coating layer includes, for example, an easy-adhesion layer, an antistatic layer, an adhesive layer, an antiglare (non-glare) layer, an antifouling layer such as a photocatalyst layer, an antireflection layer, a hard coat layer, an ultraviolet shielding layer, and a heat ray. Shielding layer, electromagnetic wave shielding layer, gas barrier layer, anti-blocking layer, etc.

<Polarizer>
The use of this film is not particularly limited, but since the optical anisotropy is very small and the mechanical strength such as tear strength is excellent, it is particularly possible to arrange this film on at least one side of the polarizing film. , Can be suitably used as a protective film for the polarizing film of the polarizing plate.

When this film is used, for example, as a protective film for a polarizing film in a polarizing plate, the polarizing film is generally bonded via an adhesive for adhering the polarizing film.
Conventionally known adhesives can be used. For example, water-based adhesives such as polyvinyl alcohol-based and urethane compounds, and active energy ray-curable adhesives such as acrylic compounds, epoxy compounds, and oxazoline compounds can be used. Can be mentioned.

<Liquid crystal display device>
This film has excellent optical properties and mechanical strength such as tear strength, can be adhered to the polarizing film with good adhesion, and has excellent handleability when the polarizing plate is peeled from the liquid crystal. The polarizing plate of the present invention using the present film has excellent protective effect and function retention of the polarizing film, and realizes a high-quality display screen as a polarizing plate of a liquid crystal display device such as a television, a personal computer, a digital camera, and a mobile phone. In addition, it is excellent in workability at the time of manufacturing a liquid crystal display device.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. The various measured values and evaluations displayed in the present specification were performed as follows. Here, the flow direction of the film from the extruder is called the MD direction, and the direction orthogonal to the MD direction is called the TD direction.

(1) Glass transition temperature (Tg)
Using a differential scanning calorimeter manufactured by PerkinElmer Co., Ltd., trade name "Pyris1 DSC", the temperature of about 10 mg of the sample was raised from -40 ° C to 200 ° C at a heating rate of 10 ° C / min according to JIS K7121. After holding at 200 ° C. for 1 minute, the temperature was lowered to −40 ° C. at a cooling rate of 10 ° C./min, and the temperature was raised again to 200 ° C. at a heating rate of 10 ° C./min. ) (° C) was calculated. The Tg value is rounded off to the first minority.

(2) Total light transmittance and haze For the obtained film, use a haze meter (manufactured by Nippon Denshoku Kogyo Co., Ltd., trade name: NDH-5000) according to JIS K7105, and the total light transmittance and haze. Was measured. In addition, the results of judgment based on the following criteria are also described.
(Total light transmittance)
⊚: Total light transmittance is 92% or more ○: Total light transmittance is 90% or more and less than 92% Δ: Total light transmittance is 85% or more and less than 90% ×: Total light transmittance is less than 85% (haze) )
⊚: Haze is 0.3% or less ○: Haze exceeds 0.3% and 1.0% or less ×: Haze exceeds 1.0%

(3) Storage elastic modulus (E')
Using a viscoelasticity measuring device manufactured by IT Measurement Co., Ltd., trade name "Viscoelasticity Spectrometer DVA-200", a sample (MD direction 4 mm, TD direction 60 mm) is heated with a vibration frequency of 10 Hz, strain of 0.1%, and temperature rise. The lateral direction was measured at a speed of 3 ° C./min and a chuck distance of 25 mm from −100 ° C. to 150 ° C., and the storage elastic modulus (E ′) (MPa) at 20 ° C. was determined from the obtained data.

(4) Thickness phase difference (Rth)
The obtained film was measured using a phase difference measuring device (manufactured by Oji Measuring Instruments Co., Ltd., trade name: KOBRA-WR). In addition, the results of judgment based on the following criteria are also described. Rth was calculated from the phase difference between when the incident angle was 0 ° and when the incident angle was 40 °.
⊚: Absolute value of Rth is 3 nm or less ○: Absolute value of Rth exceeds 3 nm and is 10 nm or less ×: Absolute value of Rth is larger than 10 nm

The raw materials used in Examples and Comparative Examples are described below.
(Resin: P-1)
The molar ratio of the monomer unit derived from isosorbide, which is a dihydroxy compound, and the monomer unit derived from tricyclodecanedimethanol, obtained by a method according to JP-A-2008-024919, is isosorbide / tricyclode. Polycarbonate copolymer in which candimethane = 70/30 mol%. Density: 1.36 g / cm ³ , Tg: 130 ° C, MFR (temperature: 230 ° C, load: 37.3 N): 9.6 g / 10 min, average refractive index: 1.5102, intrinsic birefringence: 0.03, Photoelastic coefficient: 12 × ^10-12 Pa ^-1

(Example 1)
(Preparation of layer (I) in which the value of intrinsic birefringence is positive and the value of thickness phase difference (Rth) is negative)
As a resin having a glass transition temperature of 80 ° C. or higher and a positive intrinsic double refraction, 100 parts by mass of resin (P-1) is supplied to a biaxial extruder having a venting function at a resin temperature of 220 to 255 ° C. After melt-kneading, a film-like melt is prepared with a T-die at 255 ° C via a gear pump and a filter pack (leaf disc filter, mesh size 5 μm), and a stainless steel cooling roll (φ300 mm, temperature) with an air gap of 65 mm. 100 ° C.) and a touch roll (φ200 mm, outer layer; mirror surface silicone rubber, E'= 9.0 MPa, thickness 3 mm, inner layer; silicone sponge rubber, E'= 0.26 MPa, thickness 7 mm) to increase the thickness. A 40 μm film is prepared, and a masking film (manufactured by Futamura Chemical Co., Ltd., self-adhesive OPP film, trade name; Taiko FSA, grade; 010M, thickness: 30 μm) is laminated in a subsequent step, and both ends of the film are slit. A film roll (width 1370 mm, length 1100 m) was obtained (hereinafter, may be abbreviated as FR-1). The touch pressure was 0.8 MPa. The obtained film had a good appearance and was also excellent in flatness, and this was used as a film for layer (I). The thickness retardation (Rth) of the film was −7.4 nm.
(Preparation of laminated film)
As a resin having a glass transition temperature of 80 ° C. or higher and a positive intrinsic double refraction, 100 parts by mass of resin (P-1) is supplied to a biaxial extruder having a venting function at a resin temperature of 220 to 255 ° C. After melt-kneading, a film-like melt is prepared with a T-die at 255 ° C. via a gear pump and a filter pack (leaf disc filter, mesh size 5 μm), and is used for the layer (I) prepared in advance. FR-1 is unwound from the touch roll side with the masking film laminated, and a stainless steel cooling roll (φ300 mm, temperature 100 ° C.) and touch roll (φ200 mm, all layers; mirror surface silicone rubber, E'= 9.0 MPa ) To prepare a laminated film having a thickness of 40 μm for each layer (layer (I) / layer (II)), and slit both ends of the film to obtain a film roll (width 1330 mm, length 1000 m). rice field. The results of evaluation using the laminated film are shown in Table 1.

(Example 2)
(Preparation of laminated film)
In the production of the laminated film of Example 1, a laminated film was obtained in the same manner except that a trimming member having slits at both ends of the film was regenerated and added at a ratio of 15 parts by mass with respect to 100 parts by mass of the resin (P-1). rice field. The results of evaluation using the laminated film are shown in Table 1.

(Example 3)
(Preparation of layer (II) in which the value of intrinsic birefringence is positive and the value of thickness phase difference (Rth) is positive)
As a resin having a glass transition temperature of 80 ° C. or higher and a positive intrinsic double refraction, 100 parts by mass of resin (P-1) is supplied to a biaxial extruder having a venting function at a resin temperature of 220 to 255 ° C. After melt-kneading, a film-like melt is prepared with a T-die at 255 ° C via a gear pump and a filter pack (leaf disc filter, mesh size 5 μm), and a stainless steel cooling roll (φ300 mm, temperature) with an air gap of 65 mm. A film having a thickness of 40 μm is produced by sandwiching the film between a touch roll (φ200 mm, all layers; mirror surface silicone rubber, E'= 9.0 MPa) and a masking film (manufactured by Futamura Chemical Co., Ltd.). , Self-adhesive OPP film, trade name; Taiko FSA, grade; 010M, thickness: 30 μm) was laminated, and both ends of the film were slit to obtain a film roll (width 1370 mm, length 1100 m) (hereinafter, FR-2). May be abbreviated as). The touch pressure was 0.8 MPa. The obtained film had a good appearance and was also excellent in flatness, and this was used as a film for layer (II). The thickness retardation (Rth) of the film was 7.2 nm.
(Preparation of laminated film)
As a resin having a glass transition temperature of 80 ° C. or higher and a positive intrinsic double refraction, 100 parts by mass of resin (P-1) is supplied to a biaxial extruder having a venting function at a resin temperature of 220 to 255 ° C. After melt-kneading, a film-like melt is prepared with a T-die at 255 ° C. via a gear pump and a filter pack (leaf disc filter, mesh size 5 μm), and is used for the layer (II) prepared in advance. FR-2 is unwound from the touch roll side with the masking film laminated, and a stainless steel cooling roll (φ300 mm, temperature 100 ° C.) and touch roll (φ200 mm, outer layer; mirror surface silicone rubber, E'= 9.0 MPa, A laminated film having a thickness of 40 μm for each layer (layer (I) / layer (II)) was produced by sandwiching the film with a thickness of 3 mm, an inner layer; a silicone-based sponge rubber, E'= 0.26 MPa, a thickness of 7 mm). Both ends of the film were slit to obtain a film roll (width 1330 mm, length 1000 m). The results of evaluation using the laminated film are shown in Table 1.

(Example 4)
(Preparation of layer (II) in which the value of intrinsic birefringence is positive and the value of thickness phase difference (Rth) is positive)
In Example 3, a film roll with a masking film was obtained in the same manner except that the thickness of the film to be collected was changed from 40 μm to 20 μm and the number of films to be collected was two (hereinafter, abbreviated as FR-3). There is). The obtained film had a good appearance and was also excellent in flatness, and this was used as a film for layer (II). The thickness retardation (Rth) of the film was 3.8 nm.
(Preparation of laminated film)
In the preparation of the laminated film of Example 3, a laminated film was obtained in the same manner except that the layer structure of the film to be collected was changed to layer (II) / layer (I) / layer (II) = 20 μm / 40 μm / 20 μm. rice field. The results of evaluation using the laminated film are shown in Table 1.

(Example 5)
A laminated film was obtained in the same manner except that the layer structure of the film collected in Example 4 was changed to layer (II) / layer (I) / layer (II) = 10 μm / 40 μm / 10 μm. The results of evaluation using the laminated film are shown in Table 1.

(Comparative Example 1)
(Preparation of layer (II) in which the value of intrinsic birefringence is positive and the value of thickness phase difference (Rth) is positive)
Similar to the method described in Example 3, a film roll for layer (II) having a positive value of intrinsic birefringence and a positive value of thickness phase difference (Rth) was obtained (hereinafter, FR-). It may be abbreviated as 2).
(Preparation of laminated film)
As a resin having a glass transition temperature of 80 ° C. or higher and a positive intrinsic double refraction, 100 parts by mass of resin (P-1) is supplied to a biaxial extruder having a venting function at a resin temperature of 220 to 255 ° C. After melt-kneading, a film-like melt is prepared with a T-die at 255 ° C. via a gear pump and a filter pack (leaf disc filter, mesh size 5 μm), and is used for the layer (II) prepared in advance. FR-2 is unwound from the touch roll side with the masking film laminated, and a stainless steel cooling roll (φ300 mm, temperature 100 ° C.) and touch roll (φ200 mm, all layers; mirror surface silicone rubber, E'= 9.0 MPa ) To produce a laminated film having a thickness of 40 μm for each layer (layer (II) / layer (II ′)), and slit both ends of the film to form a film roll (width 1330 mm, length 1000 m). Obtained. The results of evaluation using the laminated film are shown in Table 1.

Since the same material is used for all the layers constituting the laminated films of Examples 1 to 5 and no difference in refractive index is generated between the layers, the obtained laminated film has excellent transparency, which means that the total light transmittance is excellent. , Can be confirmed from haze. Further, by comparing Examples 1 to 5 with Comparative Example 1, a layer having a positive thickness retardation (Rth) value and a layer having a negative thickness retardation value (Rth) are laminated to form a laminated film thickness retardation (Rth). It can be confirmed that the absolute value of) is small and can be controlled. Therefore, the laminated films of Examples 1 to 5 in which the thickness retardation is controlled can be suitably used for a polarizer protective film application or the like.
Examples of the resin having a negative intrinsic compound refraction include acrylic resins and styrene resins. When a layer having a negative thickness phase difference from these resins is produced, a laminate having inferior impact resistance and heat resistance is obtained. However, the film of the present invention is highly useful because it is a film that can control the thickness phase difference and has excellent transparency without using an acrylic resin or a styrene resin.
Further, it can be confirmed that the transparency is hardly lowered even if the trimming member having slits at both ends of the film is regenerated (Example 2).

It is a schematic block diagram of the manufacturing apparatus prepared for manufacturing the layer (I) (film) which has a negative thickness phase difference (Rth) value of this invention. It is sectional drawing of the touch roll (B) which is one Embodiment of this invention. It is a photograph which showed the state of the cooling roll (A) and touch roll (B) which are one Embodiment of this invention.

1 ... Extruder 1a ... Filter pack 1b ... T die 2 ... Film 3 ... Touch rolls 4, 5 ... Cooling rolls 6 ... Shaft body 7 ... Inner layer (B) -1)
8 ... Outer layer (B-2)

Claims (7)

The layer (I) and the layer (II) are composed of a composition containing a resin having a glass transition temperature of 80 ° C. or higher and a positive intrinsic birefringence as a main component, and the layer (I) and the layer (II). A laminated film having the same resin as the main components of the above, and having a layer (I) having a negative thickness retardation (Rth) value and a layer (II) having a positive thickness retardation (Rth) value. The total value of the thickness retardation of the laminated film is Rth (laminated), and the absolute value of the total thickness retardation (Rth) of each layer (I) and layer (II) is | Rth (I) | and | Rth (, respectively. II) The laminated film according to claim 1, wherein when | is satisfied, the formulas (1) and (2) are satisfied.
Equation (1): Rth (lamination) << | Rth (I) |
Equation (2): Rth (lamination) << | Rth (II) | The laminated film according to claim 1 or 2, wherein the layer (I) and the layer (II) are in direct contact with each other. The laminated film according to any one of claims 1 to 3 , wherein the glass transition temperature of either the layer (I) or the layer (II) is 100 ° C. or higher. The laminated film according to any one of claims 1 to 4 , wherein the absolute value of the thickness retardation (Rth) is 30 nm or less. The laminated film according to any one of claims 1 to 5 , wherein the absolute value of the photoelastic coefficient is 10 × 10 ^-12 Pa ^{-1 or less.} The layer (I) and the layer (II) are composed of a composition containing a resin having a glass transition temperature of 80 ° C. or higher and a positive intrinsic birefringence as a main component, and the layer (I) and the layer (II). The main components of are the same resin,
The layer (I) is subjected to a melt extrusion step of heating and melting the composition and extruding it into a sheet, and a pressing step of sandwiching the extruded sheet with a cooling roll (A) and a touch roll (B). Obtained,
The touch roll (B) has a structure including a shaft body and a base layer formed along the outer periphery of the shaft body, and the base layer is an inner layer (B-1) and an outer layer (B-2). It has at least two layers, and the storage elastic moduli E'(B-1) and E'(B-2) of the inner layer and the outer layer at 20 ° C. satisfy the relationship of the formula (3).
A method for producing a laminated film in which a layer (I) having a negative thickness retardation (Rth) value and a layer (II) having a positive thickness retardation (Rth) value are laminated by an extrusion lamination method. ,
A method for producing a laminated film having a layer (I) having a negative thickness retardation (Rth) value and a layer (II) having a positive thickness retardation (Rth) value.
Equation (3): 100 MPa ≧ E'(B-2)>E'(B-1)

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