JP7238520B2 - multilayer laminated film - Google Patents

Description

The present invention relates to multilayer laminated films.

A multi-layered film having a multi-layered structure in which a number of layers with a low refractive index and layers with a high refractive index are alternately laminated is an optical interference film that selectively reflects or transmits light of a specific wavelength by structural optical interference between layers. can do. In addition, such a multi-layer laminated film reflects light over a wide wavelength range by gradually changing the film thickness of each layer along the thickness direction or by bonding films having different reflection peaks. It can be transmitted, and it can also obtain a high reflectance equivalent to a film using metal, and it can also be used as a metallic luster film or a reflective mirror. Furthermore, it is known that by stretching such a multilayer laminated film in one direction, it can be used as a reflective polarizing film that reflects only a specific polarized component, and can be used as a brightness enhancement member for liquid crystal displays and the like. (See Patent Documents 1 to 3, for example).
Especially in mobile phones, tablet PCs, etc., these multi-layer laminated films are widely used to reduce power consumption.

Moreover, such a multilayer laminated film is generally used together with a light-absorbing polarizing plate in a liquid crystal display or the like. However, preparing the multilayer laminate film and the light-absorbing polarizing plate separately and then stacking them together increases the number of steps and increases the thickness and weight of the entire assembly. Therefore, a technique of laminating a polyvinyl alcohol (PVA) film on a multi-layer laminated film and processing the PVA film into a light-absorbing polarizing plate is known (see, for example, Patent Documents 1 to 3).

With such a structure, when these films are incorporated into a large-sized TV or the like, they are difficult to incorporate because they lack rigidity one by one. Combining several films can also reduce the number of steps required for assembly, thus simplifying the process. Furthermore, by pre-adhering the films, it is possible to suppress the optical loss occurring at the interface between the films and the optical loss due to the deviation of the transmission axis, and to prevent the film from warping.

On the other hand, when laminating a PVA film on a multi-layer laminated film, adhesion between these films becomes a problem. In order to improve such adhesion, a technique using an adhesive layer (OCA) (see Patent Document 1, for example) and a technique of bonding with PVA glue (see Patent Document 2, for example) are known.

JP 2013-218316 A JP 2013-218317 A Japanese Patent Publication No. 2017-502330

However, in the above conventional technology, since the number of functional layers to be laminated increases, there is a problem that the thickness and weight of the optical film as a whole increase. If the thickness of the optical film increases, the thickness and weight of the entire backlight unit also increase, which is a problem especially in mobile phones, tablet PCs, etc., for which miniaturization and weight reduction are desired.
An object of the present invention is to provide a multilayer laminated film in which the adhesion of a polyvinyl alcohol-based resin layer is improved while suppressing thickening of the multilayer laminated film.

Means for solving the above problems include the following aspects.
<1>
A multilayer laminate structure in which a first layer mainly composed of resin and a second layer mainly composed of resin are alternately laminated, a multilayer laminate having a support layer mainly composed of resin, and a polyvinyl alcohol-based resin layer wherein the multilayer laminated structure and the support layer are in direct contact, and the support layer and the polyvinyl alcohol-based resin layer are in contact directly or via another layer having a thickness of 1 μm or less wherein the multilayer laminate structure has a layer thickness profile in physical thickness of a repeating unit having at least the first layer and the second layer, the layer thickness profile has a monotonically increasing region of thickness, and the thickness A multi-layer laminate film in which the support layer and the polyvinyl alcohol resin layer are provided on the thin side of the monotonically increasing region.
<2>
The multilayer laminated film according to <1>, wherein the support layer has a thickness of more than 1 μm and not more than 20 μm.
<3>
The multilayer laminated film <4> according to <1> or <2>, wherein the average thickness of the repeating units of 10 pairs from the outermost layer on the thin side of the monotonically increasing region is 80 nm or more and 120 nm or less.
The multilayer laminated film according to any one of <1> to <3>, wherein the first layer is a birefringent layer and the second layer is an isotropic layer.
<5>
The multilayer laminated film according to any one of <1> to <4>, wherein the polyvinyl alcohol-based resin layer has a polarizing function.

ADVANTAGE OF THE INVENTION According to this invention, the multilayer laminated film which improved the adhesiveness of a polyvinyl-alcohol-type resin layer is provided, suppressing film thickening of a multilayer laminated film in the multilayer laminated film.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows an example of the multilayer laminated film of this invention, and a layer thickness profile.

An embodiment that is an example of the present invention will be described below. The present invention is by no means limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention.

[Multilayer laminated film]
The multilayer laminate film of the present invention comprises a multilayer laminate having a multilayer laminate structure in which a first layer mainly composed of resin and a second layer mainly composed of resin are alternately laminated, and a support layer mainly composed of resin; and a polyvinyl alcohol-based resin layer. Also, the multilayer laminate structure, the support layer, and the polyvinyl alcohol-based resin layer are laminated in this order.
Here, the multilayer laminate structure and the support layer are in direct contact. Further, the supporting layer and the polyvinyl alcohol-based resin layer are in direct contact or in contact via another layer, and even if the other layer is interposed, the thickness of the other layer is 1 μm or less.
Each constituent element of the multilayer laminate film of the present invention will be described below.

[Multilayer laminated structure]
The multilayer laminated film of the present invention has a multilayer laminated structure having at least a first layer mainly composed of a resin and a second layer mainly composed of a resin.
It is preferable that the first layer is birefringent and the second layer is isotropic, and due to the light interference effect of the first layer and the second layer, a wide range of visible light with a wavelength of 380 to 780 nm It can be reflective in a wavelength range.

The term "reflectable" as used herein means that the average reflectance of polarized light parallel to the direction perpendicularly incident is 50% or more in at least one arbitrary direction in the plane of the film. Such reflection may be 50% or more as an average reflectance in each wavelength range, preferably 60% or more, and more preferably 70% or more.

Here, the phrase "mainly composed of resin" means that resin accounts for 70% by mass or more in each layer, preferably 80% by mass or more, and more preferably 90% by mass or more.
In order to achieve such reflection characteristics, a birefringent first layer mainly made of resin and having a thickness of 10 to 1000 nm and an isotropic second layer mainly made of resin and having a thickness of 10 to 1000 nm It is preferable to have a structure in which a total of 30 or more layers are alternately laminated in the thickness direction.

The multilayer laminate structure may have a third layer in addition to the first and second layers described above. It preferably has a structure in which repeating units are laminated.

Further, the resin constituting each layer is not particularly limited as long as it can form a birefringent layer and an isotropic layer, although the details will be described later. Thermoplastic resins are preferable for all of them from the viewpoint of easy production of films.
In each layer of the present invention, the film-forming machine axis direction (vertical direction, longitudinal direction, or MD direction), the direction orthogonal to the film-forming machine axis direction in the film plane (horizontal direction, width direction, or the TD direction), the difference between the maximum and minimum refractive indices in the thickness direction is defined as birefringence if it is 0.1 or more, and if it is less than 0.1 as isotropy.

(layer thickness profile)
The multi-layer laminate structure in the present invention has a layer thickness profile at the physical thickness of the repeating unit having at least the first layer and the second layer. Also, such a layer thickness profile has a monotonically increasing region.
Even when the multi-layer laminate structure has a third layer, it also has a layer thickness profile at the physical thickness of the repeating unit, and the layer thickness profile has a monotonically increasing region.

By appropriately distributing repeating units having a refractive index and a thickness corresponding to each reflection wavelength in such a monotonically increasing region, the first layer and the second layer have a wide optical thickness, and light in a wide wavelength range is obtained. It is possible to reflect.
This is because the reflected wavelength is due to the optical thickness of each layer constituting the multilayer laminated film. Generally, the reflection wavelength of a multilayer laminated film is shown by the following (Formula 1).
λ=2(n1×d1+n2×d2) (Formula 1)
(In the above formula, λ is the reflected wavelength (nm), n1 and n2 are the refractive indices of the respective layers, and d1 and d2 are the physical thicknesses (nm) of the respective layers.)

Also, the optical thickness λM (nm) is represented by the product of the refractive index nk and the physical thickness dk (nm) of each layer, as shown in Equation 2 below. The physical thickness here can be obtained from a photograph taken using a transmission electron microscope.
λM (nm)=nk×dk (Formula 2)

In view of the above, a layer thickness profile capable of broadly reflecting light having a wavelength of 380 to 780 nm can be obtained. For example, the thickness range in the monotonically increasing region described later can be widened to reflect light in a wide wavelength range. It is also possible to design the region to reflect light other than the specific wavelength range, and to reflect light in a wide wavelength range as a whole.

In the present invention, the physical thickness of the repeating unit is represented by the following (Formula 3).
dp=d1+d2 (Formula 3)
In the above formula, dp represents the physical thickness (nm) of the repeating unit, and d1 and d2 represent the physical thicknesses (nm) of the first layer and the second layer constituting the repeating unit, respectively.
The physical thickness here can be obtained from a photograph taken using a transmission electron microscope.

The physical thickness of the repeating unit is preferably 60 nm or more and preferably 350 nm or less. This makes it easier to widely reflect light having a wavelength of 380 to 780 nm. If the physical thickness of the repeating unit is too thin, optical properties will not be exhibited. tend to become From such a viewpoint, the lower limit of the physical thickness of the repeating unit is more preferably 70 nm, more preferably 80 nm, and even more preferably 95 nm, and the upper limit is more preferably 330 nm, even more preferably 310 nm, and even more preferably 300 nm.

(monotonically increasing region)
In the present invention, "monotonic increase" preferably means that the thicker side layer is thicker than the thinner side layer in all of the multilayer laminated structures in the multilayer laminated film, but is not limited thereto. All that is necessary is to see a tendency that the thickness increases from the thinner side to the thicker side as a whole. Specifically, when the layers are numbered from the thinner side to the thicker side, plotted on the horizontal axis and the thickness of each layer on the vertical axis, the film thickness shows an increasing tendency. The number of layers in each layer within the range is equally divided into five, and if the average value of the film thickness in each equally divided area increases in the direction of increasing the film thickness, it is monotonically increasing. If not, it is not monotonically increasing.

FIG. 1 is a schematic diagram showing an example of the multilayer laminate film and layer thickness profile of the present invention. For example, as shown in FIG. 1, the multilayer laminate structure of the present invention has a monotonically increasing region. In the layer thickness profile 14P graphically shown in the multilayer laminate structure 14 of FIG.
The multilayer laminated film 30 shown in FIG. 1 has a multilayer laminated structure 14, which is an alternately laminated structure of first and second layers, laminated in two layers via an intermediate layer 16, and a support layer ( A polyvinyl alcohol-based resin layer 22 is adhered to a multilayer laminate 10 in which an outermost layer 12 and an outermost layer 18 are formed. That is, the laminated structure of the multilayer laminated film 30 shown as an example is polyvinyl alcohol-based resin layer 22/support layer (outermost layer) 12/multilayer laminated structure 14/intermediate layer 16/multilayer laminated structure 14/outermost layer 18. .

Regarding the above monotonous increase, it is preferable that the monotonous increase occurs in all of the layers from one outermost layer to the other outermost layer in the multilayer laminated structure. In the multilayer laminated structure, the number of layers is 80% or more, preferably The thickness may monotonically increase in 90% or more, more preferably 95% or more, and the thickness may be constant or decrease in the remaining portion.
For example, Example 1 of the present invention is an aspect that monotonically increases in the 100% portion, but an aspect in which a region that does not monotonically increase is provided on the side of the thickness profile with a small layer number and / or on the side with a large layer number may be

-Construction of multi-layer laminated structure-
[First layer]
The first layer constituting the multilayer laminate structure of the present invention is preferably a birefringent layer, that is, the resin constituting this is preferably capable of forming a birefringent layer. Therefore, a resin with oriented crystallinity is preferable as the resin constituting the first layer, and polyester is particularly preferable as such a resin with oriented crystallinity. The polyester preferably contains ethylene terephthalate units and/or ethylene naphthalate units, more preferably ethylene naphthalate units, in the range of 80 mol% or more and 100 mol% or less based on the repeating units constituting it. This is preferable because it is easy to form a layer with a higher refractive index, thereby easily increasing the difference in refractive index from the second layer. Here, in the case of combined use of resin, it refers to the total content.

(Resin of first layer)
As the resin of the first layer, polyester is preferable, and the polyester contains a naphthalene dicarboxylic acid component as a dicarboxylic acid component, and the content thereof is 80 mol% or more and 100 mol% or less based on the dicarboxylic acid component constituting the polyester. is preferably Such naphthalenedicarboxylic acid components include 2,6-naphthalenedicarboxylic acid components, 2,7-naphthalenedicarboxylic acid components, components derived from combinations thereof, or derivative components thereof, particularly 2,6- A naphthalenedicarboxylic acid component or a derivative component thereof is preferably exemplified. The content of the naphthalenedicarboxylic acid component is preferably 85 mol% or more, more preferably 90 mol% or more, and is preferably less than 100 mol%, more preferably 98 mol% or less, and still more preferably 95 mol% or less. is.

As the dicarboxylic acid component constituting the polyester of the first layer, in addition to the naphthalene dicarboxylic acid component, a terephthalic acid component, an isophthalic acid component, etc. may be contained within a range that does not impair the object of the present invention. It is preferable to contain. The content is preferably in the range of over 0 mol % and 20 mol % or less. The content of the second dicarboxylic acid component is more preferably 2 mol % or more, still more preferably 5 mol % or more, and more preferably 15 mol % or less, still more preferably 10 mol % or less.

When the multilayer laminated film of the present invention is used as a brightness improving member or a reflective polarizing plate used in liquid crystal displays and the like, the first layer is a layer having a relatively higher refractive index characteristic than the second layer, and the second layer It is preferred that the layer is a layer having relatively lower refractive index properties than the first layer and is uniaxially stretched.
In this case, in the present invention, the uniaxial stretching direction is the X direction (also referred to as the longitudinal direction), the direction perpendicular to the X direction in the film plane is the Y direction (lateral direction, also referred to as the non-stretching direction), The direction perpendicular to the film surface is sometimes called the Z direction (also referred to as the thickness direction).

By using a polyester containing a naphthalene dicarboxylic acid component as a main component for the first layer as described above, it is possible to exhibit a high refractive index in the X direction and at the same time achieve birefringence characteristics with high uniaxial orientation. The difference in refractive index with respect to the direction of the second layer can be increased, contributing to a high degree of polarization. On the other hand, when the content of the naphthalenedicarboxylic acid component is less than the lower limit, the amorphous property tends to increase, and the difference between the refractive index nX in the X direction and the refractive index nY in the Y direction tends to decrease. In the multi-layer laminate film, it is difficult to obtain sufficient reflection performance for the P-polarized component in the present invention, which is defined as a polarized component parallel to the plane of incidence including the uniaxially stretched direction (X direction), with the film surface as the reflective surface. tend to become
The S-polarized component in the present invention is defined as a polarized component perpendicular to the plane of incidence including the uniaxial stretching direction (X direction) with the film surface as the reflecting surface in the multilayer laminated film.

An ethylene glycol component is used as the diol component that constitutes the preferred polyester of the first layer, and the content thereof is preferably 80 mol % or more and 100 mol % or less based on the diol component that constitutes the polyester. It is more preferably 85 mol % or more and 100 mol % or less, still more preferably 90 mol % or more and 100 mol % or less, and particularly preferably 90 mol % or more and 98 mol % or less. If the ratio of the diol component is less than the lower limit, the uniaxial orientation described above may be impaired.

As the diol component constituting the polyester of the first layer, in addition to the ethylene glycol component, a trimethylene glycol component, a tetramethylene glycol component, a cyclohexanedimethanol component, a diethylene glycol component, etc. are contained within a range that does not impair the object of the present invention. good too.

(Characteristics of the polyester of the first layer)
The melting point of the polyester used in the first layer is preferably in the range of 220-290°C, more preferably in the range of 230-280°C, still more preferably in the range of 240-270°C. The melting point can be determined by measuring with a differential scanning calorimeter (DSC). If the melting point of the polyester exceeds the upper limit, the fluidity of the melt-extruded molding may be poor, and the discharge may become uneven. On the other hand, if the melting point is less than the lower limit, although the film-forming property is excellent, the mechanical properties of polyester are likely to be impaired, and the refractive index when used as a brightness enhancement member for liquid crystal displays or as a reflective polarizing plate. rate characteristics tend to be difficult to develop.

The glass transition temperature (hereinafter sometimes referred to as Tg) of the polyester used in the first layer is preferably 80 to 120° C., more preferably 82 to 118° C., still more preferably 85 to 118° C., particularly preferably It is in the range of 100-115°C. When Tg is within this range, the film is excellent in heat resistance and dimensional stability, and easily develops refractive index characteristics when used as a brightness improving member for liquid crystal displays or as a reflective polarizing plate. The melting point and glass transition temperature can be adjusted by controlling the type and amount of copolymerization components, diethylene glycol as a by-product, and the like.

The polyester used in the first layer preferably has an intrinsic viscosity of 0.50 to 0.75 dl/g, more preferably 0.55 to 0.72 dl, measured at 35°C using an o-chlorophenol solution. /g, more preferably 0.56 to 0.71 dl/g. This tends to make it easier to have moderate oriented crystallinity, and tends to make it easier to develop a refractive index difference with the second layer.

[Second layer]
The second layer constituting the multilayer laminate structure of the present invention is preferably an isotropic layer, that is, the resin constituting it is preferably capable of forming an isotropic layer. Therefore, amorphous resin is preferable as the resin constituting the second layer. Among them, amorphous polyester is preferable. The term "amorphous" as used herein does not exclude extremely slight crystallinity, as long as the second layer can be made isotropic to the extent that the multilayer laminated film of the present invention exhibits the intended function. good.

(Resin of the second layer)
The resin constituting the second layer is preferably a copolymerized polyester, and it is particularly preferable to use a copolymerized polyester containing a naphthalene dicarboxylic acid component, an ethylene glycol component and a trimethylene glycol component as copolymer components. The naphthalenedicarboxylic acid component includes a 2,6-naphthalenedicarboxylic acid component, a 2,7-naphthalenedicarboxylic acid component, a component derived from a combination thereof, or a derivative component thereof, particularly 2, A preferred example is a 6-naphthalenedicarboxylic acid component or a derivative component thereof. Such a naphthalenedicarboxylic acid component, preferably a 2,6-naphthalenedicarboxylic acid component, is preferably 30 mol % or more and 100 mol % or less of the total carboxylic acid components constituting the copolymerized polyester of the second layer, and more preferably. is 30 mol % or more and 80 mol % or less, more preferably 40 mol % or more and 70 mol % or less. Thereby, the adhesion with the first layer can be made higher. If the content of the naphthalene dicarboxylic acid component is less than the lower limit, the adhesion may deteriorate from the viewpoint of compatibility. The upper limit of the content of the naphthalene dicarboxylic acid component is not particularly limited, but if it is too large, it tends to be difficult to develop a refractive index difference with the first layer. In addition, other dicarboxylic acid components may be copolymerized in order to adjust the refractive index relationship with the first layer.

In addition, the copolymerization component in the present invention means any component that constitutes the polyester, and the secondary component (copolymerization amount is less than 50 mol% with respect to the total acid component or the total diol component ), and the main component (50 mol % or more of all acid components or all diol components as a copolymerization amount) is also used.

In the present invention, as described above, it is preferable to use a polyester containing ethylene naphthalate units as a main component as the resin for the first layer. is used, the compatibility with the first layer tends to be high, the interlayer adhesion with the first layer tends to be improved, and delamination is less likely to occur, which is preferable.
In the copolyester of the second layer, the diol component preferably contains at least two components, an ethylene glycol component and a trimethylene glycol component. Among these, the ethylene glycol component is preferably used as the main diol component from the viewpoint of film formability.

The ethylene glycol component is preferably 50 mol% or more and 95 mol% or less, more preferably 50 mol% or more and 90 mol% or less, still more preferably 50 mol % or more and 85 mol % or less, particularly preferably 50 mol % or more and 80 mol % or less. This tends to make it easier to develop a refractive index difference with the first layer.

The copolyester of the second layer in the present invention preferably further contains a trimethylene glycol component as a diol component. By containing the trimethylene glycol component, the effect of supplementing the elasticity of the layer structure and suppressing delamination is enhanced.

The trimethylene glycol component is preferably 3 mol% or more and 50 mol% or less, more preferably 5 mol% or more and 40 mol% or less, of the total diol component constituting the copolyester of the second layer. , more preferably 10 mol % or more and 40 mol % or less, particularly preferably 10 mol % or more and 30 mol % or less. Thereby, the interlayer adhesion with the first layer can be made higher. In addition, there is a tendency that a difference in refractive index from that of the first layer is likely to occur. If the content of the trimethylene glycol component is less than the lower limit, it tends to be difficult to ensure interlayer adhesion, and if it exceeds the upper limit, it becomes difficult to obtain a resin having a desired refractive index and glass transition temperature.
The second layer in the present invention contains a thermoplastic resin other than the copolymerized polyester within a range of 10% by mass or less based on the mass of the second layer as long as it does not impair the object of the present invention. It may be contained as a component.

Specific examples of the copolymerized polyester of the second layer include (1) a copolymerized polyester containing a 2,6-naphthalene dicarboxylic acid component as a dicarboxylic acid component and an ethylene glycol component and a trimethylene glycol component as a diol component; A copolymer polyester containing a 2,6-naphthalenedicarboxylic acid component and a terephthalic acid component as the dicarboxylic acid component and an ethylene glycol component and a trimethylene glycol component as the diol component can be mentioned.

(Characteristics of the copolyester of the second layer)
In the present invention, the copolyester of the second layer described above preferably has a glass transition temperature of 85° C. or higher, more preferably 90° C. or higher and 150° C. or lower, still more preferably 90° C. or higher and 120° C. or lower. Particularly preferably, the temperature is 93°C or higher and 110°C or lower. Thereby, it is excellent in heat resistance. In addition, there is a tendency that a difference in refractive index from that of the first layer is likely to occur. If the glass transition temperature of the copolyester of the second layer is less than the lower limit, sufficient heat resistance may not be obtained. The haze increases due to brittleness and embrittlement, which may be accompanied by a decrease in the degree of polarization when used as a brightness enhancement member or a reflective polarizing plate. In addition, if the glass transition temperature of the copolyester of the second layer is too high, the polyester of the second layer may also have birefringence due to stretching during stretching, and accordingly, the refractive index of the polyester of the second layer is different from that of the first layer in the stretching direction. The index difference becomes small, and the reflection performance may deteriorate.

Among the copolyesters described above, amorphous copolyesters are preferable because they can remarkably suppress the increase in haze due to crystallization by heat treatment at 90° C. for 1000 hours. The term "amorphous" as used herein means that the heat of crystal fusion is less than 0.1 mJ/mg when the temperature is increased at a temperature increase rate of 20°C/min in DSC.

The copolyester of the second layer preferably has an intrinsic viscosity of 0.50 to 0.70 dl/g, more preferably 0.55 to 0.65 dl, measured at 35°C using an o-chlorophenol solution. /g. When the copolyester used in the second layer contains a trimethylene glycol component as a copolymerization component, the film formability may deteriorate. can be further enhanced. In the case of using the above-described copolyester as the second layer, the intrinsic viscosity is preferably higher from the viewpoint of film-forming properties, but in the range exceeding the upper limit, the difference in melt viscosity from the polyester of the second layer increases, The thickness of each layer may be uneven.

[Support layer]
The multilayer laminated film of the present invention has a support layer having a function of supporting the multilayer laminated structure between the multilayer laminated structure and the polyvinyl alcohol-based resin layer. When the multilayer laminate structure has a support layer, the operability of the multilayer laminate structure is improved, and the operability of the finally obtained multilayer laminate film is also improved.
Such a support layer is mainly made of resin. Here, "mainly" means that the resin accounts for 70% by mass or more in the layer, preferably 80% by mass or more, and more preferably 90% by mass or more. In addition, the support layer is preferably an isotropic layer, and from the viewpoint of ease of production, it may be the same resin as the second layer, and is composed of the above-described copolymerized polyester of the second layer. possible, and such an embodiment is preferred.

The thickness of the support layer is preferably greater than 1 μm, more preferably 1.5 μm or more, still more preferably 2 μm or more, still more preferably 3 μm or more, particularly preferably 4 μm or more, and preferably 20 μm or less, more preferably 20 μm or more. is 15 μm or less, more preferably 12 μm or less. Since such a support layer is optically thick, it does not easily affect the optical properties exhibited by the multi-layered structure. Moreover, it excels by the adhesion improvement effect of a polyvinyl-alcohol-type resin layer. If the support layer is too thin, it tends to affect the optical properties, possibly leading to deterioration of the optical properties. In addition, from the viewpoint of the adhesiveness of the polyvinyl alcohol-based resin layer, if it is too thin, stress cannot be relaxed in a well-balanced manner, and if it is too thick, it is too rigid, which tends to reduce the effect of improving adhesion.

[Polyvinyl alcohol resin layer]
The multilayer laminate film of the present invention has a polyvinyl alcohol-based resin layer (hereinafter also referred to as a "PVA-based resin layer"). Moreover, it is preferable that the polyvinyl alcohol-based resin layer has a polarizing function. Here, "having a polarizing function" means that the transmittance of polarized light parallel to the transmission axis of the PVA-based resin layer and the transmittance of polarized light parallel to the axis perpendicular to the transmission axis (absorption axis) is 50%. It means that there are more differences. Such a difference is preferably 60% or more, more preferably 70% or more, even more preferably 80% or more.
Any appropriate resin is used as the polyvinyl alcohol-based resin (hereinafter also referred to as "PVA-based resin") forming the PVA-based resin layer. Examples thereof include polyvinyl alcohol and ethylene-vinyl alcohol copolymer. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. An ethylene-vinyl alcohol copolymer is obtained by saponifying an ethylene-vinyl acetate copolymer. The saponification degree of the PVA-based resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.5 mol%, more preferably 99.0 mol% to 99.93 mol%. . The degree of saponification can be determined according to JIS K 6726-1994. By using a PVA-based resin having such a degree of saponification, it is possible to obtain a polarizing film excellent in durability and optical properties. If the degree of saponification is too high, gelation may occur.

The average degree of polymerization of the PVA-based resin is appropriately selected depending on the purpose. The average degree of polymerization is usually 1,000 to 10,000, preferably 1,200 to 4,500, more preferably 1,500 to 4,300. The average degree of polymerization can be determined according to JIS K 6726-1994.

The PVA-based resin layer may contain a dichroic substance in order to exhibit the polarizing properties necessary for the liquid crystal display. Dichroic substances include, for example, iodine and organic dyes. These are used alone or in combination of two or more. Iodine is preferably used.

The thickness of the PVA-based resin layer is set to any appropriate value. The thickness is preferably 20 µm or less, more preferably 10 µm or less, still more preferably 6 µm or less, and particularly preferably 4 µm or less. The PVA-based resin layer has a large shrinkage force due to heat, and usually depends on the thickness. If the shrinkage force is too large, peeling at the interface or warping of the film will occur, so the thinner the thickness, the better. On the other hand, if the thickness is too thin, sufficient optical properties may not be exhibited, so the thickness is preferably 1.0 μm or more, more preferably 1.5 μm or more, even more preferably 2.0 μm or more, and even more preferably 2.0 μm or more. 4.0 μm or more.

The multilayer laminate film of the present invention comprises a multilayer laminate having a multilayer laminate structure and a support layer, and a polyvinyl alcohol resin layer, and the multilayer laminate structure, the support layer, and the polyvinyl alcohol resin layer are laminated in this order. ing.
This multi-layer laminate structure has a monotonically increasing region of the layer thickness profile, and the support layer and the PVA-based resin layer are on the thin side of the monotonically increasing region. By setting it as such a lamination|stacking structure, it is excellent in the adhesiveness of a PVA-type resin layer.

Although the cause of this is not clear, the following mechanism is conceivable. That is, in the monotonically increasing region of the multilayer structure, the portion where the relatively thin first layers and the second layers are alternately laminated is higher than the portion where the relatively thick first layers and the second layers are alternately laminated. It is considered that the stress from the outside is more likely to be relaxed in the case. When stress is applied from the outside, the stress is relaxed on the side where the thickness of the monotonically increasing region is thin, and cohesive failure of the layers and interfacial peeling between layers are less likely to occur, and as a result, the adhesion of the PVA-based resin layer is improved. Conceivable.
Therefore, it is not necessary to provide a functional layer (e.g., an adhesive layer, etc.) for adhering the PVA-based resin layer, or even if it is provided, a thin layer is sufficient, thereby suppressing the thickening of the multilayer laminated film. be able to.

In the multilayer laminated film of the present invention, the adhesiveness of the polyvinyl alcohol-based resin layer is considered to be related to stress relaxation of the thin layer in the monotonically increasing region of the multilayer laminated structure. From the viewpoint of improving the adhesion of the polyvinyl alcohol-based resin layer, the multilayer laminate structure has an average thickness of up to 10 repeating units along the direction in which the layer number of the repeating unit increases from the end of the thin side of the monotonically increasing region (hereinafter , Also referred to as “minimum 10-point average thickness”) is preferably in the range of 80 nm or more and 120 nm or less, more preferably 85 nm or more and 115 nm or less, even more preferably 90 nm or more and 113 nm or less. .
The minimum 10-point average thickness is calculated by calculating the physical thickness dp of 10 sets of repeating units from the thin side of the multi-layer laminate structure by the above method, and obtaining the average value.

[Middle layer/outermost layer]
The multilayer laminate constituting the multilayer laminate film of the present invention may have an intermediate layer or an outermost layer other than the outermost layer serving as the support layer of the multilayer laminate structure.

The intermediate layer, which may be referred to as an internal thick film layer or the like in the present invention, refers to a thick film layer present inside the alternately laminated structure of the first layer and the second layer. Here, a thick film means an optically thick film. In the present invention, thick layers (sometimes referred to as thickness adjusting layers or buffer layers) are formed on both sides of the alternately laminated structure in the initial stage of manufacturing the multilayer laminated film, and then the number of laminated layers is increased by doubling. In this case, two thick layers are laminated to form an intermediate layer, and the thick layer formed inside becomes the intermediate layer, and the thick layer formed on the outside becomes the intermediate layer. The thick film layer is the outermost layer. That is, the laminated structure is outermost layer/multilayer laminated structure/intermediate layer/multilayer laminated structure/outermost layer. Among these outermost layers, the outermost layer on the side where the PVA-based resin layer is provided becomes the support layer described above.

The intermediate layer preferably has a layer thickness of, for example, 5 μm or more and 100 μm or less, more preferably 50 μm or less. When such an intermediate layer is part of the alternately laminated structure of the first layer and the second layer, the thickness of each layer constituting the first layer and the second layer is adjusted uniformly without affecting the polarizing function. easier. The intermediate layer may have the same composition as either the first layer or the second layer, or a composition partially including these compositions, and does not contribute to the reflection properties due to the thick layer thickness. On the other hand, since it may affect the transmission characteristics, when particles are included in the layer, the particle diameter and particle concentration should be selected in consideration of the light transmittance.

When the thickness of the intermediate layer is 5 μm or more, the layer structure of the multilayer laminated structure is less likely to be disturbed, and there is a tendency to suppress deterioration in reflection performance. In addition, when the thickness of the intermediate layer is 100 μm or less, the thickness of the entire multilayer laminated film can be suppressed, and from the viewpoint of space saving when used as a reflective polarizing plate or a brightness improving member of a thin liquid crystal display. is advantageous from Further, when a plurality of intermediate layers are included in the multilayer laminated film, the thickness of each intermediate layer is preferably at least the lower limit of the above range, and the total thickness of the intermediate layers is at most the upper limit of the above range. is preferably
The polymer used for the intermediate layer may be a resin different from that of the first layer or the second layer, provided that it can be present in the multilayer laminate using the method for producing a multilayer laminate film of the present invention. From the viewpoint of compatibility, it is preferable that the composition is the same as that of either the first layer or the second layer, or a composition that partially contains these compositions.

The method of forming the intermediate layer is not particularly limited. One intermediate layer can be provided by dividing into two in the direction and re-laminating them in the alternate lamination direction. A plurality of intermediate layers can also be provided by dividing into three or four by a similar method.

The outermost layer other than the support layer described above can be provided on the surface of the multilayer laminate opposite to the support layer that supports the multilayer laminate structure. A preferred resin for such another outermost layer is the same as that for the support layer described above, but the thickness is preferably in the range of more than 1 μm, more preferably 3 μm or more, further preferably 5 μm or more, and preferably 100 μm or less. 50 μm or less is more preferable.
When the thickness of such another outermost layer exceeds 1 μm, the layer structure of the multilayer structure is less likely to be disturbed, and there is a tendency to suppress deterioration in reflection performance. In addition, when the thickness of the other outermost layer is 100 μm or less, the thickness of the entire multilayer laminated film can be suppressed, and space can be saved when used as a reflective polarizing plate or a brightness improving member of a thin liquid crystal display. It is advantageous from the viewpoint of

[Other layers]
In the multilayer laminated film of the present invention, the support layer and the polyvinyl alcohol-based resin layer are in direct contact with each other, or are in contact with each other via another layer having a thickness of 1 μm or less.
According to the present invention, since stress is relieved on the thin side of the multilayer laminate structure as described above, even if the supporting layer and the polyvinyl alcohol-based resin layer are in direct contact with each other, the adhesion can be improved.
As another layer, for example, there is a functional layer for improving the adhesion of the polyvinyl alcohol-based resin layer. purpose is not achieved. A functional layer for improving adhesion is usually provided with a thickness exceeding 1 μm to improve adhesion, but according to the present invention, the effect of improving adhesion can be obtained even if the thickness is 1 μm or less. , it is possible to suppress the thickening of the multilayer laminated film. The thickness of the other layers is 1 μm or less, preferably 0.8 μm or less, from the viewpoint of miniaturization and weight reduction.

(Coating layer)
The multilayer laminated film of the present invention can have a coating layer between the support layer and the polyvinyl alcohol-based resin layer as an example of the other layer.
Examples of such a coating layer include a primer layer that improves the adhesion of these layers, but it may also be an easy-to-slip layer for imparting slipperiness.

The coating layer contains a binder component, and may contain, for example, particles in order to impart lubricity. In order to impart easy adhesion, the binder component to be used should be chemically close to the component of the layer to be adhered. In addition, the coating liquid for forming the coating layer is preferably an aqueous coating liquid using water as a solvent from an environmental point of view. Surfactants can be included for enhancement purposes. In addition, a functional agent such as a cross-linking agent may be added to increase the strength of the coating layer.

[Method for producing multilayer laminate and multilayer laminate film]
A method for producing the multilayer laminate film of the present invention will be described in detail. Note that the manufacturing method described below is merely an example, and the present invention is not limited to this. Different aspects can also be obtained by reference to the following.
The multilayer laminate in the multilayer laminate film of the present invention is obtained by alternately superimposing the resin constituting the first layer and the resin constituting the second layer in a molten state using a multilayer feed block apparatus, for example, in total An alternately laminated structure of 30 or more layers is created, buffer layers are provided on both sides thereof, and then an apparatus called layer doubling is used to divide the alternately laminated structure having the buffer layers into, for example, 2 to 4, and alternately having the buffer layers. It can be obtained by increasing the number of layers by stacking again so that the number of layers (doubling number) of the block becomes 2 to 4 times with the layered structure as one block. According to this method, it is possible to obtain a multilayer laminate having an intermediate layer in which two buffer layers are laminated inside the multilayer laminate and an outermost layer consisting of a single buffer layer on both sides.

Such alternate lamination structure is laminated so that the thickness of each layer of the first layer and the second layer has a desired gradient structure. This can be achieved, for example, by varying the spacing and length of the slits in a multi-layer feedblock device.
After laminating the desired number of layers by the method described above, the laminate is extruded through a die and cooled on a casting drum to obtain a multilayer unstretched body. A PVA-based resin layer is formed on this multilayer unstretched body, and then a multilayer laminate film is obtained by stretching as described below. Any appropriate method can be adopted for forming the PVA-based resin layer. Preferably, a PVA-based resin layer is formed by applying a coating liquid containing a PVA-based resin onto the multilayer laminate and drying the coating liquid.

The coating liquid is typically a solution obtained by dissolving the PVA-based resin in a solvent. Examples of the solvent include water, dimethylsulfoxide, dimethylformamide, dimethylacetamide, various glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine. These can be used alone or in combination of two or more. Among these, water is preferred. The concentration of the PVA-based resin in the solution is preferably 3 to 20 parts by weight with respect to 100 parts by weight of the solvent. With such a resin concentration, it is possible to form a uniform coating film with good adhesion to the multilayer laminate. Further, the coating liquid may contain additives.

Any appropriate method can be employed as the coating method of the coating liquid, and examples thereof include roll coating, wire bar coating, die coating, spray coating, and the like.

In addition, the drying temperature after coating in the above coating method is lower than the glass transition temperature (Tg) of the resins constituting each layer of the multilayer laminate (for example, in the present invention, preferably the glass transition temperature of the resin constituting the second layer is temperature (Tg)), and more preferably Tg-20°C or less. By drying the coating solution at such a temperature, it is possible to prevent deformation of the multilayer laminate before forming the PVA-based resin layer, and obtain a good multilayer laminate film.

The multi-layer unstretched body and the PVA-based resin layer obtained by the above method are aligned in at least one axial direction of the film-forming machine axis direction or a direction perpendicular to it in the film plane (transverse direction, width direction, or TD). (The uniaxial direction is the direction along the film plane.). The stretching temperature is preferably in the range of the glass transition temperature (Tg) of the resin of the first layer to (Tg+20)°C. By stretching at a temperature lower than conventional, the orientation properties of the film can be more highly controlled.

The multi-layer unstretched body and the PVA-based resin layer are preferably stretched at a magnification of 2.0 to 7.0, more preferably 4.5 to 6.5. The larger the draw ratio within this range, the smaller the variation in the refractive index in the plane direction of the individual layers in the first layer and the second layer due to the thinning due to stretching, and the optical interference of the multilayer laminate is uniform in the plane direction. It is preferable because the difference in refractive index between the first layer and the second layer in the stretching direction becomes large. As the stretching method at this time, a known stretching method such as heating stretching with a rod-shaped heater, roll heating stretching, and tenter stretching can be used. preferable.

In addition, in the case where the film is stretched in a direction perpendicular to the film plane (Y direction) and biaxially stretched, although it depends on the application, if the film is desired to have reflective polarizing properties, 1. It is preferable to limit the draw ratio to about 01 to 1.20 times. If the draw ratio in the Y direction is made higher than this, the polarizing performance may deteriorate.
Further, after the stretching, the orientation characteristics of the multilayer laminated film obtained by toe-out (re-stretching) in the stretching direction in the range of 5 to 15% while heat setting at a temperature of (Tg) to (Tg + 30) ° C. can be highly controlled.
When a coating layer is provided as another layer, it can be provided by coating and drying before coating the multilayer laminate with a coating liquid containing a PVA-based resin in the film manufacturing process.
Thus, the multilayer laminate film of the present invention is obtained.

- Optical Properties of Multilayer Laminate and Multilayer Laminate Film -
In the present invention, the multilayer laminate preferably has an average transmittance on the transmission axis at a wavelength of 380 to 780 nm of 70% or more, more preferably 80% or more, and most preferably 85% or more. The average transmittance along the axis of reflection is preferably 30% or less, more preferably 20% or less, and most preferably 15% or less.

In addition, as a multi-layer laminate film in which the PVA-based resin layer is dyed, the average transmittance on the transmission axis at a wavelength of 380 to 780 nm is preferably 60% or more, more preferably 70% or more, and most preferably 75% or more. The average transmittance on the reflection axis (or the absorption axis for the PVA-based resin layer) at 380 to 780 nm is preferably less than 5%, more preferably less than 1%, and most preferably less than 0.5%.

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to the examples shown below. Physical properties and characteristics in the examples were measured or evaluated by the following methods.

-Measurement of thickness of each layer-
The multilayer laminated film was cut into a lengthwise direction of 2 mm and a width direction of 2 cm, fixed in an embedding capsule, and then embedded in an epoxy resin (Epomount manufactured by Refinetech Co., Ltd.). The embedded sample was cut perpendicular to the width direction with a microtome (ULTRACUT UCT manufactured by LEICA) to obtain thin slices with a thickness of 50 nm. Observation and photographing were performed using a transmission electron microscope (Hitachi S-4300) at an accelerating voltage of 100 kV, and the thickness (physical thickness) of each layer was measured from the photographs.
Regarding layers with a thickness exceeding 1 μm, those existing inside the multilayer structure are defined as intermediate layers, and those existing on the outermost layer are defined as outermost layers (those on the PVA-based resin layer side are support layers). thickness was measured.
Whether the layer is the first layer or the second layer can be determined based on the refractive index, but if this is difficult, it can be determined based on the electronic state obtained by NMR analysis or TEM analysis.

-Measurement of refractive index after stretching-
A two-layer laminated film having a layer thickness ratio of 1:1 was prepared under the same conditions as the manufacturing conditions of the obtained multilayer laminated structure, and the refractive indices of the first and second layers of the multilayer laminated structure were the same. The refractive indices of the first layer and the second layer measured using are obtained as the refractive indices of the first layer and the second layer of the multilayer structure, respectively.
For example, in the present embodiment, a film having a total thickness of 75 μm was prepared under the same conditions as in Example 1 described later, except that a two-layer laminated film having a thickness ratio of 1st layer: 2nd layer = 1:1 was used. , for each of the first layer and the second layer, the respective refractive indices (respectively nX, nY, nZ) in the stretching direction (X direction), the orthogonal direction (Y direction), and the thickness direction (Z direction) are , the refractive index at a wavelength of 633 nm was measured using a prism coupler manufactured by Metricon, and the refractive index after stretching of each of the first layer and the second layer was obtained.

- Judgment of monotonous increase -
Determination of monotonic increase of the multi-layer laminated structure is performed by setting the combination of the first layer and the second layer as one repeating unit, entering the value of the physical thickness of the repeating unit on the vertical axis, and calculating the layer number (thin In an arbitrary region of the layer thickness profile when the number attached from the side) is input on the horizontal axis, the number of layer repeating units within the range where the film thickness shows an increasing tendency is divided into 5 equal parts, and the direction in which the film thickness increases In addition, when the average value of the film thickness in each equally divided area is all increasing, it is assumed that the increase is monotonous, and if not, it is assumed that the increase is not monotonous.

- Adhesion evaluation (cross-cut test) -
Adhesion of the PVA-based resin layer was evaluated by the following method. Twenty-five 4 mm ² cross-cuts were made on the surface of the PVA-based resin layer of the multi-layer laminate film having the PVA-based resin layer formed thereon, and these were performed at four locations (100 cross-cuts in total). A cellophane tape (manufactured by Nichiban Co., Ltd.) was adhered thereon, strongly pressed with a finger, peeled off in the 90° direction, and evaluated as follows based on the number of remaining PVA-based resin layers.
A: 90<remaining number ≤ 100: very good adhesion B: 80 <remaining number ≤ 90: good adhesion C: 70 <remaining number ≤ 80: somewhat good adhesion D: remaining number ≤ 70・・・Poor adhesion

-Evaluation of transmittance-
Using a polarizing film measurement device (“VAP7070S” manufactured by JASCO Corporation), the transmission spectra of the obtained multilayer laminate and multilayer laminate film were measured.
For measurement, a Glan-Taylor prism, a spot diameter adjustment mask Φ1.4, and a deflection angle stage were used, and the incident angle of the measurement light was set to 0 degrees. The average transmittance in the wavelength range of 380 to 780 nm of the transmission axis of the film and the axis (reflection axis) orthogonal to the transmission axis (also referred to as "transmission axis average transmittance" and "reflection axis average transmittance"), Measurements were taken at intervals of 5 nm.
The transmission axis average transmittance and reflection axis average transmittance of each of the multilayer laminate and the multilayer laminate film were evaluated according to the following criteria.

・Evaluation of transmission axis average transmittance of multilayer laminate A: 80% or more B: 70% or more and less than 80% C: less than 70%

・ Evaluation of reflection axis average transmittance of multilayer laminate A: 20% or less B: over 20% and 30% or less C: over 30%

・ Evaluation of transmission axis average transmittance of multilayer laminated film A: 70% or more B: 60% or more and less than 70% C: less than 60%

・ Evaluation of reflection axis average transmittance of multilayer laminated film A: less than 1% B: 1% or more and less than 5% C: 5% or more

-Evaluation of polarizing function of PVA-based resin layer-
From the obtained multilayer laminated film, the PVA-based resin layer is peeled off by making a notch with a needle or the like at the interface with the PVA-based resin layer at the end face of the film, and the transmission axis average The transmittance and the average transmittance along the absorption axis were measured, the difference between them (average transmittance along the transmission axis−average transmittance along the absorption axis) was obtained, and the deflection function of the PVA-based resin layer was evaluated. In this evaluation, the axis orthogonal to the transmission axis is called the absorption axis, and the absorption axis average transmittance is measured in the same manner as the reflection axis average transmittance in the above "evaluation of transmittance".
A: The difference is 80% or more B: The difference is 70% or more and less than 80% C: The difference is 50% or more and less than 70% D: The difference is less than 50%

[Production Example 1] Polyester A
Dimethyl 2,6-naphthalenedicarboxylate, dimethyl terephthalate, and ethylene glycol as the polyester for the first layer were subjected to transesterification reaction in the presence of titanium tetrabutoxide, followed by polycondensation reaction to obtain an acid component. Copolyester (intrinsic viscosity 0.64 dl/g) (o-chlorophenol , 35° C., hereinafter the same) were prepared.

[Production Example 2] Polyester B
As the polyester for the second layer, dimethyl 2,6-naphthalenedicarboxylate, dimethyl terephthalate, and ethylene glycol and trimethylene glycol are subjected to transesterification reaction in the presence of titanium tetrabutoxide, followed by polycondensation reaction. 50 mol% of the acid component is 2,6-naphthalene dicarboxylic acid component, 50 mol% of the acid component is terephthalic acid component, 85 mol% of the glycol component is ethylene glycol component, and 15 mol% of the glycol component is trimethylene glycol. A copolyester component (intrinsic viscosity of 0.63 dl/g) was prepared.

[Manufacturing Example 3] PVA-based resin VP18 manufactured by Nippon Acetate & Poval Co., Ltd. was used as the PVA-based resin, water was used as the solvent, and a PVA aqueous solution diluted to 8% by weight was prepared. A dyeing solution was prepared by dissolving 0.4 g of iodine and 1.0 g of potassium iodide in 1000 ml of a 4% by weight boric acid aqueous solution. A coating solution A was prepared by mixing the obtained PVA aqueous solution and the staining solution at a ratio of 1000:1.

<Example 1>
After drying polyester A for the first layer at 170° C. for 5 hours, polyester B for the second layer was dried at 85° C. for 8 hours, then supplied to the first and second extruders, respectively, and heated to 300° C. After heating to a molten state and branching the polyester for the first layer into 139 layers and the polyester for the second layer into 138 layers, the first layer and the second layer are alternately laminated, and the composition shown in Table 1 is obtained. Using a multi-layer feedblock device equipped with comb teeth to provide a layer thickness profile, a total of 277 layers of the melt were laminated and extruded from the third extruder to the second on both sides while maintaining the laminated state. The same polyester as the polyester for the layers was led to a three-layer feed block, and buffer layers were further laminated on both sides of the melt in the laminated state of 277 layers (both surface layers were the first layers) in the lamination direction. The feed rate of the third extruder was adjusted so that the sum of the buffer layers on both sides was 47% of the total. The laminated state is further bifurcated with a layer doubling block and laminated at a ratio of 1:1 to create an unstretched multi-layer laminated structure with a total of 557 layers, including an intermediate layer inside and two outermost layers as the outermost layer. made.
The coating liquid A obtained above was applied by a roll coater to the thin side of the monotonically increasing region in the unstretched multilayer structure to obtain an unstretched laminate. The coating was applied to a thickness of 3 μm after drying and uniaxial stretching.
This unstretched multilayer laminate was stretched 5.9 times in the width direction at a temperature of 130°C. The thickness of the obtained uniaxially stretched multilayer laminate film was 78 μm.
This multilayer laminated film was evaluated by the evaluation method described above when the layer number of the repeating unit of the multilayer laminated film was given from the thin side, and the results are shown in Table 1.
Moreover, it was confirmed from the above-described refractive index after stretching that the first layer was birefringent and the second layer was isotropic.

<Examples 2 and 3>
The multilayer laminate films of Examples 2 and 3 were produced in the same manner as in Example 1, except that the thickness profile of the multilayer laminate structure was produced so as to have the values shown in Table 1.
Table 1 shows the evaluation results of the multilayer laminate films obtained in Examples 2 and 3.

<Examples 4 and 5>
In Examples 4 and 5, the thickness of the support layer and the thickness profile of the multi-layer laminate structure were adjusted to the values shown in Table 1, and along with this, a buffer layer was formed by a third extruder to adjust the thickness of the intermediate layer and the outermost layer. A multilayer laminated film was produced in the same manner as in Example 1, except that the supply amount of was adjusted.
Table 1 shows the evaluation results of the multilayer laminate films obtained in Examples 4 and 5.

<Examples 6 and 7>
In Examples 6 and 7, multilayer laminate films were produced in the same manner as in Example 1, except that the thickness of the PVA-based resin layer was set to the thickness shown in Table 1.
Table 1 shows the evaluation results of the multilayer laminate films obtained in Examples 6 and 7.

<Examples 8 and 9>
In Examples 8 and 9, the thickness of the support layer was set to the value shown in Table 1, and accordingly, the amount of buffer layer supplied by the third extruder was adjusted in order to adjust the thickness of the intermediate layer and the outermost layer. produced a multilayer laminated film in the same manner as in Example 1.
Table 1 shows the evaluation results of the multilayer laminate films obtained in Examples 8 and 9.

In all the films obtained in Examples 2 to 9, it was confirmed from the above-described evaluation of the refractive index after stretching that the first layer was birefringent and the second layer was isotropic.

<Comparative Example 1>
In Comparative Example 1, except that the multilayer laminated structure did not have a monotonically increasing region, that is, the thickness of one set of repeating units of the first layer and the second layer was constant (125 μm). A multilayer laminated film was obtained in the same manner as above.
Table 1 shows the evaluation results of the multilayer laminated film obtained in Comparative Example 1.

<Comparative Example 2>
In Comparative Example 2, a multilayer laminated film was obtained in the same manner as in Example 1, except that the supporting layer and the PVA-based resin layer were provided on the thicker side of the monotonically increasing thickness region of the multilayer laminated structure.
Table 1 shows the evaluation results of the multilayer laminated film obtained in Comparative Example 2.

<Comparative Example 3>
In Comparative Example 3, a multilayer laminated film was obtained in the same manner as in Example 8, except that the supporting layer and the PVA-based resin layer were provided on the thicker side of the monotonically increasing thickness region of the multilayer laminated structure.
Table 1 shows the evaluation results of the multilayer laminated film obtained in Comparative Example 3.

<Comparative Example 4>
In Comparative Example 4, a multilayer laminated film was obtained in the same manner as in Example 9, except that the supporting layer and the PVA-based resin layer were provided on the thicker side of the monotonically increasing thickness region of the multilayer laminated structure.
Table 1 shows the evaluation results of the multilayer laminated film obtained in Comparative Example 4.

As can be seen from Table 1, the multilayer laminate films of Examples were excellent in adhesion of the PVA-based resin layer. On the other hand, in the multilayer laminated film of the comparative example, the adhesion of the PVA-based resin layer did not satisfy the evaluation criteria.

Therefore, in the multilayer laminated films of Examples, the adhesion improving layer having a thickness of more than 1 μm for preventing the peeling of the PVA-based resin layer from the multilayer laminate can be omitted. For example, when it is applied to a liquid crystal display and a device including the same, it can contribute to the miniaturization and weight reduction thereof.

10 multilayer laminate 12 support layer (outermost layer)
14 Multilayer laminated structure 16 Intermediate layer 18 Outermost layer 22 Polyvinyl alcohol resin layer 30 Multilayer laminated film

Claims (4)

A multilayer laminate having a multilayer laminate structure in which a first layer mainly composed of resin and a second layer mainly composed of resin are alternately laminated, and a support layer mainly composed of resin;
a polyvinyl alcohol-based resin layer;
A multilayer laminated film having
The multilayer laminated structure and the support layer are in direct contact,
The support layer and the polyvinyl alcohol-based resin layer are in direct contact ,
The multilayer laminated structure has a layer thickness profile in physical thickness of a repeating unit having at least the first layer and the second layer, the layer thickness profile has a monotonically increasing thickness region,
The average thickness of 10 sets of repeating units from the outermost layer on the thin side of the monotonically increasing region is 80 nm or more and 120 nm or less,
A multi-layer laminated film, wherein the support layer and the polyvinyl alcohol-based resin layer are provided on the thinner side of the monotonically increasing thickness region. 2. The multilayer laminated film according to claim 1, wherein the support layer has a thickness of more than 1 [mu]m and 20 [mu]m or less. 3. The multilayer laminate film according to claim 1, wherein the first layer is a birefringent layer and the second layer is an isotropic layer. 4. The multilayer laminated film according to any one of claims 1 to 3 , wherein the polyvinyl alcohol-based resin layer has a polarizing function.

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