KR102645997B1 - Laminate film and method for producing laminate film - Google Patents

Abstract

There was a problem that uneven dyeing occurred in the width direction due to wrinkles and loosening, and that both ends in the width direction could not be used as a polarizing plate. Additionally, if wrinkles or loosening occur in the light-polarizing laminated film obtained after the dyeing process, there is a problem in that the protective film cannot be bonded and a polarizing plate cannot be stably manufactured.
In a laminated film having a substantially unstretched polyvinyl alcohol-based resin layer on at least one side of a long base film, when the polyvinyl alcohol-based resin layer is divided into nine regions in the width direction, the outermost region A laminated film in which the average film thickness D1e and the average film thickness D1c of the central region satisfy the following equation.

Description

Laminated film and manufacturing method of laminated film {LAMINATE FILM AND METHOD FOR PRODUCING LAMINATE FILM}

The present invention relates to laminated films and methods for producing laminated films.

Conventional polarizers are manufactured by stretching and dyeing a polyvinyl alcohol-based resin raw film (usually about 30 to 75 μm in thickness), and the thickness of the film after stretching is usually about 12 to 30 μm. When a polyvinyl alcohol-based resin raw film of 30 μm or less was used for thinning, there was a problem with productivity, such as the film becoming prone to breakage during stretching.

Therefore, in order to cope with the recent thinning of polarizing plates, a method of coating an aqueous solution containing a polyvinyl alcohol-based resin on a base film has been proposed. In this method, a polyvinyl alcohol-based resin layer is formed by coating an aqueous solution containing a polyvinyl alcohol-based resin on a base film to obtain a laminated film, and then the laminated film is subjected to stretching and dyeing to form polyvinyl alcohol. A polarizer layer is obtained by imparting a polarizing function to the resin layer (Patent Document 1).

Japanese Patent Publication No. 2009-098653

When obtaining a light-polarizing laminated film by coating an aqueous solution containing a polyvinyl alcohol-based resin, the light-polarizing laminated film is generally manufactured by a roll-to-roll method using a long base film. Since this method includes a plurality of steps, such as a step of stretching the polyvinyl alcohol-based resin layer and a step of dyeing with iodine, a long film may be wound into a roll for each step.

In particular, after the stretching process, the stretched laminated film is wound into a roll to obtain a stretched laminated film roll, and when the stretched laminated film is unwound from the stretched laminated film roll to perform the dyeing process, both ends in the width direction of the unwinded long film are formed. Wrinkles or loosening may occur. After winding the film into a roll, wrinkles and loosening that appear at both ends of the unwinded film also occur in the laminated film, and these wrinkles and loosening cause uneven dyeing in the width direction, causing uneven coloring in the width direction. There was a problem that both ends could not be used as a polarizer. Additionally, if wrinkles or loosening occur in the light-polarizing laminated film obtained after the dyeing process, there is a problem in that the protective film cannot be bonded and a polarizing plate cannot be stably manufactured.

The present invention includes the following.

[1] A laminated film having a substantially unstretched polyvinyl alcohol-based resin layer on at least one side of a long base film, wherein when the polyvinyl alcohol-based resin layer is divided into nine regions in the width direction, the most A laminated film in which the average film thickness D1e of the outer region and the average film thickness D1c of the central region satisfy the following equation:

Additionally, the average film thickness D1e of the outermost region is set to be the average film thickness that has a larger difference from the average film thickness D1c of the central region among the average film thicknesses in the two outermost regions.

[2] The laminated film according to [1], wherein the average thickness of the substantially unstretched polyvinyl alcohol-based resin layer in the width direction is 10 μm or less.

[3] A stretched laminated film having a stretched polyvinyl alcohol-based resin layer on at least one side of a long base film, wherein when the stretched polyvinyl alcohol-based resin layer is divided into nine regions in the width direction, A stretched laminated film in which the average film thickness D2e of the outermost region and the average film thickness D2c of the central region satisfy the following equation:

Additionally, the average film thickness D2e of the outermost region is set to be the average film thickness that has a larger difference from the average film thickness D2c of the central region among the average film thicknesses in the two outermost regions.

[4] The stretched laminated film according to [3], wherein the average thickness of the stretched polyvinyl alcohol-based resin layer in the width direction is 7 μm or less.

[5] When the base film is divided into nine regions in the width direction, the average film thickness D3e of the outermost region and the average film thickness D3c of the central region are described in [3] or [4], where the average film thickness D3c of the central region satisfies the following equation. One stretched laminated film:

Additionally, the average film thickness D3e of the outermost region is set to be the average film thickness that has a larger difference from the average film thickness D3c of the central region among the average film thicknesses in the two outermost regions.

[6] When the stretched laminated film is divided into nine regions in the width direction, the average film thickness D4e of the outermost region and the average film thickness D4c of the central region satisfy the following equation from [3] to [5]. Stretched laminated film according to:

Additionally, the average film thickness D4e of the outermost region is set to be the average film thickness that has a larger difference from the average film thickness D4c of the central region among the average film thicknesses in the two outermost regions.

[7] A polarizing laminated film having a polarizer layer on at least one side of a long base film, wherein when the polarizer layer is divided into nine regions in the width direction, the average film thickness D5e of the outermost region and the average film thickness of the central region are A polarizing laminated film whose average film thickness D5c satisfies the following equation:

Additionally, the average film thickness D5e of the outermost region is set to be the average film thickness that has a larger difference from the average film thickness D5c of the central region among the average film thicknesses in the two outermost regions.

[8] The polarizing laminated film according to [7], wherein the average thickness of the polarizer layer in the width direction is 7 μm or less.

[9] When the base film is divided into nine regions in the width direction, the average film thickness D6e of the outermost region and the average film thickness D6c of the central region are described in [7] or [8], where the average film thickness D6c of the central region satisfies the following equation. Polarizing laminated film:

Additionally, the average film thickness D6e of the outermost region is set to be the average film thickness that has a larger difference from the average film thickness D6c of the central region among the average film thicknesses in the two outermost regions.

[10] When the polarizing laminated film is divided into nine regions in the width direction, the average film thickness D7e of the outermost region and the average film thickness D7c of the central region satisfy the following equations [7] to [9]. Polarizing laminated film according to which:

Additionally, the average film thickness D7e of the outermost region is set to be the average film thickness that has a larger difference from the average film thickness D7c of the central region among the average film thicknesses in the two outermost regions.

[11] [7] ~ where the visibility-corrected single transmittance Tye measured at a position 25 mm from the edge in the width direction of the polarizer layer and the visibility-corrected single transmittance Tyc measured at the center of the width direction of the polarizer layer satisfy the following equation. [10] Polarizing laminated film according to any one of:

Additionally, the visibility corrected single transmittance Tye measured at a position of 25 mm from the edge is taken as the visibility corrected single transmittance that has a larger difference from the visibility corrected single transmittance Tyc measured at the center among the two measured values.

[12] A process of forming a coating layer by coating an aqueous solution containing a polyvinyl alcohol-based resin on at least one side of a long base film so that the central portion is thicker than both ends in the width direction of the coating layer; A method of producing a laminated film including the step of drying to form a resin layer made of polyvinyl alcohol-based resin.

[13] A method for producing a stretched laminated film, comprising the step of obtaining a stretched laminated film by uniaxially stretching the laminated film described in [12] more than 5 times.

[14] A method for producing a stretched laminated film roll, including the step of winding the stretched laminated film described in [13] into a roll to obtain a stretched laminated film roll.

[15] A method for producing a light-polarizing laminated film, comprising the step of obtaining a light-polarizing laminated film by dyeing the stretched laminated film according to [13] or the stretched laminated film unwound from the stretched laminated film roll according to [14]. .

[16] A bonding process for obtaining a multilayer film by bonding a protective film to the side of the polarizer layer of the polarizing laminated film described in [15] opposite to the base film side, and peeling the base film from the multilayer film. A method of manufacturing a polarizer including a peeling process.

According to the present invention, wrinkles and loosening are less likely to occur at both ends in the width direction of a long laminated film, and the area of the portion that does not become a product can be reduced. Additionally, a polarizing plate with uniform optical properties in the width direction can be obtained. Furthermore, since the protective film can be easily bonded to the light-polarizing laminated film, a polarizing plate can be manufactured stably.

1 is a diagram illustrating a method of manufacturing a laminated film according to an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view showing an example of a base film with a coating layer obtained by one embodiment of the present invention.
Figure 3 is a schematic cross-sectional view showing an example of a laminated film obtained by one embodiment of the present invention.
Figure 4 is a schematic cross-sectional view showing an example of a stretched laminated film obtained by one embodiment of the present invention.
FIG. 5 is a schematic cross-sectional view showing an example of a light-polarizing laminated film obtained by one embodiment of the present invention.
Fig. 6 is a schematic cross-sectional view showing the positions of the outermost region and the central region in the coating layer obtained by one embodiment of the present invention.
Fig. 7 is a schematic cross-sectional view of a stretched laminated film when the stretched polyvinyl alcohol-based resin layer does not satisfy the provisions of the present invention.

When obtaining a polarizer layer by coating an aqueous solution containing a polyvinyl alcohol-based resin, the light-polarizing laminated film is usually manufactured by a method including the following steps.

(Coating process) A process of applying an aqueous solution containing a polyvinyl alcohol-based resin to at least one side of a long base film to obtain a coating layer.

(Drying process) A process of obtaining a laminated film by drying the coating layer and forming a polyvinyl alcohol-based resin layer (sometimes simply referred to as a resin layer).

(Stretching process) A process of obtaining a stretched laminated film by stretching the laminated film.

(Dyeing process) A process of obtaining a light-polarizing laminated film by immersing the stretched laminated film in a dyeing solution containing iodine.

The inventor found that in order to suppress wrinkles and loosening from occurring at both ends of the light polarizing laminated film in the width direction, the following intermediate products can be manufactured in each process of manufacturing a polarizing plate. The longitudinal length of the intermediate product (laminated film, stretched laminated film, and light-polarizing laminated film) of the present invention may be 100 m or more, or 500 m or more. When the length of the film exceeds 100 m, the winding diameter increases, so tight wrapping is usually likely to occur, but the present invention can effectively prevent wrinkles and looseness from forming at both ends in the width direction. Typically, the length of the film is 10000 m or less.

[Intermediate product: laminated film]

In a laminated film having a polyvinyl alcohol-based resin layer on a long base film, when the polyvinyl alcohol-based resin layer is divided into nine regions in the width direction, the average film thickness D1e of the outermost region and the average of the central region are It is essential that the film thickness D1c satisfies the following equation (1-1), and it is also desirable to satisfy the equation (1-2). D1e-D1c is preferably -0.4 μm or less, more preferably -1.5 μm or more, and more preferably -1.3 μm or more. Additionally, the average film thickness D1e of the outermost region is set to be the average film thickness that has a larger difference from the average film thickness D1c of the central region among the average film thicknesses in the two outermost regions.

When the laminated film has a polyvinyl alcohol-based resin layer on both sides of the base film, the polyvinyl alcohol-based resin layer disposed on at least one side of the base film needs only satisfy the formula (1-1), and the base film It is preferable that any polyvinyl alcohol-based resin layer disposed on the surface satisfies equation (1-1).

In the film thickness distribution in the width direction of the polyvinyl alcohol-based resin layer, D1e-D1c is considered to represent the uniformity of the film thickness distribution and the approximate shape of the film thickness distribution in the width direction. The fact that the polyvinyl alcohol-based resin layer satisfies the formula (1-1) indicates that the polyvinyl alcohol-based resin layer with a convex film thickness distribution in the width direction is disposed on the base film. In this way, since the film thickness distribution in the width direction is convex, when the laminated film is wound into a roll shape while applying tension in the winding direction (MD direction) to obtain a laminated film roll, the film thickness distribution in the width direction is concave. Compared to , the tension applied to the width direction end portion of the laminated film roll can be reduced. As a result, it is thought that it becomes difficult for tight wrapping to occur at both ends in the width direction of the laminated film roll, and it is possible to suppress wrinkles and loosening at both ends in the width direction of the unwound laminated film.

In addition, wrinkles or loosening may occur in the width direction central portion of the laminated film unwound from the laminated film roll, but wrinkles or loosening in the width direction center portion can be eliminated by a subsequent stretching process. On the other hand, it is difficult to eliminate wrinkles or loosening formed at both ends in the width direction through a stretching process. It is preferable that the polyvinyl alcohol-based resin layer satisfies the formula (1-2) in that wrinkles and loosening in the central portion in the width direction can be easily eliminated.

Since the laminated film is a film before the stretching process or dyeing process, the polyvinyl alcohol-based resin layer is substantially unstretched. Substantially unstretched means that the stretch ratio in the stretching direction is 0.99 to 1.01 times.

In this specification, the width direction refers to a direction perpendicular to the longitudinal direction of the elongated laminated film and parallel to the plane of the laminated film. When manufacturing a laminated film by a roll-to-roll method, the width direction is perpendicular to the conveyance direction (MD direction) of the laminated film and coincides with the direction parallel to the plane of the laminated film (TD direction). Of course, the longitudinal direction coincides with the MD direction. In addition, when the laminated film of the present invention is subjected to a longitudinal stretching process to obtain a stretched laminated film, and when a process including a dyeing process is further performed to obtain a light polarizing laminated film, the stretching direction is usually the length of the laminated film. direction, and the absorption axis direction of the polarizing laminated film coincides with the longitudinal direction of the laminated film. This relationship is the same for a polarizing plate in which a transparent protective film is bonded to a light-polarizing laminated film and the base film is peeled off, and the same holds true even if the polarizing plate is a sheet material cut into a predetermined size.

For example, the laminated film of the present invention has a convex width-direction film thickness distribution as shown in FIG. 3.

[Intermediate product: stretched laminated film]

A stretched laminated film has a polyvinyl alcohol-based resin layer stretched on at least one side of a long base film. A stretched laminated film is a film that can also be obtained by stretching the above-described laminated film. The stretch ratio of the polyvinyl alcohol-based resin layer may be, for example, 5 to 17 times, or 5 to 8 times. When the stretched polyvinyl alcohol-based resin layer is divided into nine regions in the width direction, it is essential that the average film thickness D2e of the outermost region and the average film thickness D2c of the central region satisfy the following equation (2-1). And it is also desirable to satisfy equation (2-2). D2e-D2c is preferably 0.20 μm or less, more preferably 0.15 μm or less, and further preferably -1.0 μm or more. Additionally, the average film thickness D2e of the outermost region is set to be the average film thickness that has a larger difference from the average film thickness D2c of the central region among the average film thicknesses in the two outermost regions.

When having a polyvinyl alcohol-based resin layer stretched on both sides of the base film, the polyvinyl alcohol-based resin layer disposed on at least one side of the base film just needs to satisfy equation (2-1), and It is preferable that any polyvinyl alcohol-based resin layer disposed on top satisfies equation (2-1).

If the stretched polyvinyl alcohol-based resin layer satisfies the formula (2-1), when the stretched laminated film is wound to form a stretched laminated film roll, tight wrapping of both ends in the width direction becomes difficult for the same reason as the above laminated film, It is thought that it is possible to suppress the formation of wrinkles or loosening at both ends in the width direction.

Since the tight wrapping of the stretched laminated film roll can be suppressed more effectively, when the base film in the stretched laminated film is divided into nine regions in the width direction, the average film thickness D3e of the outermost region and the average of the central region are It is preferable that the film thickness D3c satisfies the following equation (3-1), and more preferably it satisfies the equation (3-2). D3e-D3c is preferably 0.8 μm or less, and is preferably -0.8 μm or more. Additionally, the average film thickness D3e of the outermost region is set to be the average film thickness that has a larger difference from the average film thickness D3c of the central region among the average film thicknesses in the two outermost regions.

It is preferable that the polyvinyl alcohol-based resin layer and the base film are stretched integrally. At this time, the film thickness distribution in the width direction of the base film may reflect the tendency of the film thickness distribution of the stretched polyvinyl alcohol-based resin layer. That is, the film thickness distribution in the width direction may change not only for the polyvinyl alcohol-based resin layer but also for the base film. Therefore, when the film thickness distribution in the width direction of the stretched polyvinyl alcohol-based resin layer does not satisfy equation (2-1), for example, as shown in FIG. 7, the stretched polyvinyl alcohol-based resin layer has a concave shape. In the case of having a film thickness distribution (D2e-D2c>0.25 ㎛), the film thickness distribution in the width direction of the base film may also be deformed into a concave shape (D3e-D3c>1.0 ㎛) by stretching. On the other hand, in the stretched laminated film of the present invention, the film thickness distribution in the width direction of the stretched polyvinyl alcohol-based resin layer satisfies equation (2-1) and is close to smooth, so deformation of the base film is suppressed.

In addition, for the stretched laminated film, when the stretched laminated film is divided into nine regions in the width direction, the average film thickness D4e of the outermost region and the average film thickness D4c of the central region satisfy the following equation (4-1). It is preferable, and it is more preferable that equation (4-2) is satisfied. D4e-D4c is preferably -1.0 μm or more, more preferably 0.0 μm or more, and may be 0.5 μm or more. Additionally, the average film thickness D4e of the outermost region is set to be the average film thickness that has a larger difference from the average film thickness D4c of the central region among the average film thicknesses in the two outermost regions.

The thickness of the stretched laminated film refers to the total thickness and is the sum of the thickness of the base film and the thickness of the stretched resin layer in the stretched laminated film. When having a polyvinyl alcohol-based resin layer on one side of the base film, the total thickness is the sum of the thickness of the base film and the thickness of the polyvinyl alcohol-based resin layer, and when having a polyvinyl alcohol-based resin layer on both sides of the base film, The total thickness is the thickness of the base film plus the sum of the thicknesses of a pair of polyvinyl alcohol-based resin layers. Therefore, when a polyvinyl alcohol-based resin layer is provided on both sides of the base film and Equation (4-1) is satisfied, wrinkling and loosening at both ends in the width direction can be more effectively suppressed in the stretched laminated film roll.

As described above, the fact that the laminated film satisfies equation (1-1) indicates that the cross-sectional shape in the width direction is convex. Compared to the value of equation (1-1), the value of equation (2-1) is larger because the end portion of the laminated film, where the film thickness is thinner, becomes thicker due to neck-in during stretching, and the cross section in the width direction It is thought that this is because the shape changes from a convex shape to a flat shape.

For example, the stretched laminated film of the present invention has a film thickness distribution in the width direction as shown in FIG. 4.

[Intermediate product: Polarizing laminated film]

A light-polarizing laminated film has a polarizer layer on at least one side of a long base film. The light-polarizing laminated film is a film that can also be obtained by subjecting the stretched laminated film to a process including a dyeing process. The polyvinyl alcohol-based resin layer becomes a polarizer layer through a process including a dyeing process. Usually, the film thickness distribution in the width direction of each layer (polarizer layer, base film) included in the light-polarizing laminated film reflects the film thickness distribution in the width direction of each layer included in the stretched laminated film.

Therefore, like a stretched laminated film, when the polarizer layer is divided into nine regions in the width direction, the average film thickness D5e of the outermost region and the average film thickness D5c of the central region satisfy the following equation (5-1). It is essential, and it is desirable to satisfy equation (5-2). D5e-D5c is preferably 0.20 μm or less, more preferably 0.15 μm or less, further preferably 0.1 μm or less, further preferably -0.15 μm or more, and more preferably -0.1 μm or more. Additionally, the average film thickness D5e of the outermost region is set to be the average film thickness that has a larger difference from the average film thickness D5c of the central region among the average film thicknesses in the two outermost regions.

When the light-polarizing laminated film has a polarizer layer on both sides of the base film, the polarizer layer disposed on at least one side of the base film just needs to satisfy equation (5-1), and any polarizer disposed on the side of the base film It is desirable to satisfy the layer or equation (5-1).

If the polarizer layer satisfies equation (5-1) in the width direction, when the polarizing laminated film is wound to form a polarizing laminated film roll, tight wrapping at both ends in the width direction is unlikely to occur, and wrinkles or wrinkles appear at both ends in the width direction. It is thought that this can suppress the occurrence of loosening.

Since the tight wrapping of the polarizing laminated film roll can be suppressed more effectively, when the base film in the polarizing laminated film is divided into nine regions in the width direction, the average film thickness D6e of the outermost region and the central region are It is preferable that the average film thickness D6c satisfies the following equation (6-1), and more preferably satisfies equation (6-2). D6e-D6c is more preferably 0.9 μm or less, more preferably -1.0 μm or more, and more preferably -0.8 μm or more. Additionally, the average film thickness D6e of the outermost region is set to be the average film thickness that has a larger difference from the average film thickness D6c of the central region among the average film thicknesses in the two outermost regions.

In addition, when the polarizing laminated film is divided into nine regions in the width direction, the average film thickness D7e of the outermost region and the average film thickness D7c of the central region satisfy the following equation (7-1). It is preferable to do so, and it is more preferable to satisfy equation (7-2). D7e-D7c is preferably 1.3 μm or less, more preferably -1.0 μm or more, and more preferably 0 μm or more. Additionally, the average film thickness D7e of the outermost region is set to be the average film thickness that has a larger difference from the average film thickness D7c of the central region among the average film thicknesses in the two outermost regions.

The thickness of the light-polarizing laminated film refers to the total thickness and is the sum of the thickness of the base film and the thickness of the polarizer layer in the light-polarizing laminated film. In the case of having a polarizer layer on one side of the base film, the total thickness is the sum of the thickness of the base film and the thickness of the polarizer layer, and in the case of having a polarizer layer on both sides of the base film, the total thickness is the thickness of the base film plus the thickness of the polarizer layer. It is the thickness obtained by adding the sum of the thicknesses of the polarizer layers. Therefore, when polarizer layers are provided on both sides of the base film and Equation (7-1) is satisfied, wrinkles and loosening at both ends in the width direction can be more effectively suppressed in the polarizing laminated film roll.

In addition, in that a polarizer with more uniform polarization performance can be obtained, the visibility-corrected single transmittance Tye measured at a position 25 mm from the edge in the width direction of the polarizer layer and the visibility-corrected single transmittance Tyc measured at the center in the width direction are , it is desirable to satisfy the following equation (8-1). |Tye-Tyc| is preferably 0.3% or less, and more preferably 0.2% or less. |Tye-Tyc| is usually 0.00% or more. Additionally, the visibility corrected single transmittance Tye measured at a position of 25 mm from the edge is taken as the visibility corrected single transmittance that has a larger difference from the visibility corrected single transmittance Tyc measured at the center among the two measured values.

The visibility corrected single transmittance (Ty) is obtained by determining the transmittance (T _MD ) in the MD direction of the polarizing laminated film and the transmittance (T _TD ) in the TD direction at a wavelength of 380 nm to 780 nm, and using the equation (9) shown below. Based on this, the single transmittance at each wavelength is calculated, and it can be obtained by further performing visibility correction using the 2-degree field of view (C light source) of JIS Z 8701.

For example, the light-polarizing laminated film of the present invention has a film thickness distribution in the width direction as shown in FIG. 5.

Hereinafter, one embodiment will be described with reference to the drawings regarding the manufacturing method of the laminated film, the manufacturing method of the light-polarizing laminated film, and the manufacturing method of the polarizing plate of the present invention.

(Method for manufacturing laminated film)

1 is a flowchart showing a method for manufacturing a laminated film according to an embodiment of the present invention.

(Base film)

First, a long base film 1 is prepared. The base film 1 may be made of a thermoplastic resin. Examples of thermoplastic resins include polyolefin resins such as chain polyolefin resins and cyclic polyolefin resins (norbornene resins, etc.); Polyester resins such as polyethylene terephthalate; (meth)acrylic resin; Cellulose ester-based resins such as cellulose triacetate and cellulose diacetate; polycarbonate-based resin; polyvinyl alcohol-based resin; Polyvinyl acetate-based resin, polyarylate-based resin; polystyrene-based resin; polyethersulfone-based resin; polysulfone-based resin; polyamide resin; It is a polyimide-based resin.

The base film may have a single-layer structure consisting of one resin layer made of one or two or more types of thermoplastic resins, or may have a multilayer structure in which multiple resin layers made of one or two or more types of thermoplastic resins are laminated.

In addition, the base film may be a stretched product or may be unstretched. In the case of a stretched product, either uniaxial stretching or biaxial stretching may be used.

Examples of the linear polyolefin resin include homopolymers of linear olefins such as polyethylene resin and polypropylene resin, as well as copolymers of two or more types of linear olefins. A base film made of chain polyolefin resin is preferable because it can be stably stretched at a high magnification. Among them, the base film is polypropylene-based resin (polypropylene resin, which is a homopolymer of propylene, copolymer mainly made of propylene, etc.), polyethylene-based resin (polyethylene resin, which is a homopolymer of ethylene, or copolymer mainly made of ethylene). etc.), etc., is more preferable.

A copolymer mainly composed of propylene is a copolymer of propylene and other monomers that can be copolymerized with it. Other monomers copolymerizable with propylene include, for example, ethylene and α-olefin. As the α-olefin, α-olefins having 4 or more carbon atoms are preferable, and α-olefins having 4 to 10 carbon atoms are more preferable. Specific examples of α-olefins having 4 to 10 carbon atoms include linear monoolefins such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, and 1-decene; Branched monoolefins such as 3-methyl-1-butene, 3-methyl-1-pentene, and 4-methyl-1-pentene; Includes vinylcyclohexane, etc. The copolymer of propylene and other monomers copolymerizable therewith may be a random copolymer or a block copolymer. The content of the other monomers is, for example, 0.1 to 20% by weight, preferably 0.5 to 10% by weight, in the copolymer.

Among the above, as the polypropylene resin, propylene homopolymer, propylene-ethylene random copolymer, propylene-1-butene random copolymer, or propylene-ethylene-1-butene random copolymer are preferably used.

Cyclic polyolefin resin is a general term for resins polymerized using cyclic olefins as polymerization units, and includes ring-opening (co)polymers of cyclic olefins, addition polymers of cyclic olefins, and copolymers of cyclic olefins and chain olefins such as ethylene and propylene ( Representative examples include random copolymers, graft polymers modified with unsaturated carboxylic acids or their derivatives, and hydrides thereof. Among them, norbornene-based resins using norbornene-based monomers such as norbornene and polycyclic norbornene-based monomers as cyclic olefins are preferably used.

The base film may be composed of one type of cyclic polyolefin-based resin, may be composed of a mixture of two or more types of cyclic polyolefin-based resin, or may be composed of a copolymer of two or more types of cyclic polyolefin-based resin.

Polyester resin is a resin having an ester bond, and is generally composed of a polycondensate of a polyhydric carboxylic acid or its derivative and a polyhydric alcohol. As the polyvalent carboxylic acid or its derivative, a divalent dicarboxylic acid or a derivative thereof can be used, and examples include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalenedicarboxylate. As the polyhydric alcohol, a diol can be used, and examples include ethylene glycol, propanediol, butanediol, neopentyl glycol, and cyclohexanedimethanol.

Specific examples of polyester resins include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexanedimethyl terephthalate, and polycyclohexanedimethyl. Naphthalate, etc. can be mentioned. In the case of polyester resin films such as polyethylene terephthalate, they can be stretched in advance to increase the elastic modulus. The stretching may be uniaxial stretching or biaxial stretching.

The base film may be comprised of one type of polyester resin, may be comprised of a mixture of two or more types of polyester resins, or may be comprised of a copolymer of two or more types of polyester resins.

Examples of (meth)acrylic resins include poly(meth)acrylic acid esters such as polymethyl methacrylate, methyl methacrylate-(meth)acrylic acid copolymer, methyl methacrylate-(meth)acrylic acid ester copolymer, and methacrylic acid. Methyl acid-acrylic acid ester-(meth)acrylic acid copolymer, methyl (meth)acrylate-styrene copolymer (MS resin, etc.), polymers having an alicyclic hydrocarbon group (e.g., methyl methacrylate cyclohexyl methacrylate copolymer, meta methyl acrylate-norbornyl (meth)acrylate copolymer, etc.). Preferably, _{C 1-6} alkyl poly(meth)acrylate such as methyl poly(meth)acrylate is used, and more preferably, methyl methacrylate is used as the main component (50 to 100% by weight, preferably 70 to 100% by weight ₎ . A methyl methacrylate-based resin (% by weight) is used.

The base film may be composed of one type of (meth)acrylic resin, may be composed of a mixture of two or more types of (meth)acrylic resin, or may be composed of a copolymer of two or more types of (meth)acrylic resin. .

Cellulose ester-based resin is an ester of cellulose and fatty acids. Specific examples of cellulose ester resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, cellulose dipropionate, etc. Among these, cellulose triacetate (triacetylcellulose) is particularly preferable.

The base film may be composed of one type of cellulose ester-based resin, may be composed of a mixture of two or more types of cellulose ester-based resin, or may be composed of a copolymer of two or more types of cellulose ester-based resin.

Polycarbonate-based resin is made of a polymer in which monomer units are bonded through carbonate groups. The polycarbonate-based resin may be a resin called modified polycarbonate in which the polymer skeleton has been modified to lower the photoelastic coefficient, or a copolymerized polycarbonate in which wavelength dependence is improved.

The base film may be composed of one type of polycarbonate-based resin, may be composed of a mixture of two or more types of polycarbonate-based resin, or may be composed of a copolymer of two or more types of polycarbonate-based resin.

In addition to the thermoplastic resin described above, any appropriate additive may be added to the base film. Examples of such additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, anti-color agents, flame retardants, nucleating agents, anti-static agents, pigments and colorants. The content of the thermoplastic resin in the base film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, further preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. If the content of the thermoplastic resin in the base film is less than 50% by weight, there is a risk that the original high transparency of the thermoplastic resin may not be sufficiently expressed.

The thickness of the base film 1 can be determined appropriately, but generally, from the viewpoint of workability such as strength and handleability, 1 to 500 μm is preferable, 1 to 300 μm is more preferable, and further, 5 to 200 μm is preferable. It is preferred, and 5 to 150 ㎛ is most preferred.

The width of the base film 1 can be determined appropriately, but may be 500 mm or more, and may be 1000 mm or more. In the laminated film of the present invention, wrinkles and loosening at both ends in the width direction can be effectively suppressed even if the width is 500 mm or more. Additionally, the length of the base film 1 may be longer than the width, but can be 100 m or more, and is preferably 500 m or more.

The base film may have a tensile modulus of elasticity at 80°C of 140 MPa or more, and is more preferably 180 MPa or more, from the viewpoint of suppressing defects such as wrinkles or indentations during the drying process and drying defects in the coating layer. It is more preferable that it is 200 Pa or more.

Moreover, the tensile elastic modulus of the base film at 80°C is usually 1000 MPa or less, preferably 800 MPa or less, and more preferably 600 MPa or less. If the tensile modulus of elasticity at 80°C of the base film exceeds 1000 MPa, a large force is required in the stretching process, so the device may become large.

(Pretreatment of base film)

In order to improve adhesion to the polyvinyl alcohol-based resin layer, the surface of the base film 1 can be pretreated using a pretreatment means as needed.

(Surface Activation)

For example, as shown in FIG. 1(a), the surface of the base film 1 supplied from the unwinding unit 30 is treated with a surface activation means 42 such as corona treatment, plasma treatment, or flame treatment. Activation treatment can be performed on the surface of the film 1.

(Formation of primer layer)

In addition, in order to improve adhesion with the polyvinyl alcohol-based resin layer, a primer layer may be formed on the surface of the base film 1, preferably on the surface on which the surface activation treatment has been performed, by a primer layer forming means. .

For example, as shown in FIG. 1(b), after the coating liquid for forming a primer layer is applied to the surface of the base film 1 supplied from the unwinding portion 32 by the coating means 44, the drying means By drying the coating layer through (46), a base film having a primer layer can be obtained, and this base film (1) can then be wound by the winding unit (33). The coating liquid for forming the primer layer may contain a resin component and a solvent. As the resin component, a thermoplastic resin having excellent transparency, thermal stability, elongation, etc. is preferably used, and examples include (meth)acrylic resin and polyvinyl alcohol-based resin. As a solvent, a general organic solvent or an aqueous solvent such as water that can dissolve the resin component is usually used.

In order to increase the strength of the primer layer, a crosslinking agent may be added to the coating solution for forming the primer layer. The crosslinking agent is appropriately selected from known ones, such as organic or inorganic, depending on the type of thermoplastic resin used. As a crosslinking agent, the crosslinking agent described in Publication WO2013/146644 can be used. The primer coating solution preferably has a solid content concentration of about 1 to 25% by weight.

The thickness of the primer layer is preferably 0.05 to 1 μm, and more preferably 0.1 to 0.4 μm.

The example of the coating means 44 for applying the coating liquid for forming a primer layer to the base film 1 may be the same as or different from the coating means 48 for forming a polyvinyl alcohol-based resin layer described later.

(Coating of polyvinyl alcohol-based resin solution)

After pretreatment, for example, as shown in Figure 1 (c), a solution of polyvinyl alcohol-based resin is applied to the surface of the base film 1 supplied from the unwinding unit 34 by the coating means 48. Thus, the coating layer 2 is formed. A solution of polyvinyl alcohol-based resin can be obtained by dissolving powder of polyvinyl alcohol-based resin in an aqueous solvent such as water.

Examples of polyvinyl alcohol-based resins are polyvinyl alcohol resins and their derivatives. Examples of derivatives of polyvinyl alcohol resin include polyvinyl formal; polyvinyl acetal; Polyvinyl alcohol resin is modified with olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, alkyl esters of unsaturated carboxylic acids, and acrylamide.

The average degree of polymerization of the polyvinyl alcohol-based resin is preferably 100 to 10,000, and more preferably 1,000 to 10,000. In particular, 1500 to 8000 is more preferable, and furthermore, 2000 to 5000 is most preferable. The average degree of polymerization is a value obtained by the method established by JIS K 6726 (1994). If the average degree of polymerization is less than 100, it is difficult to obtain desirable optical properties. If it exceeds 10000, solubility in water deteriorates and formation of a resin layer becomes difficult.

It is preferable that the polyvinyl alcohol-based resin is a saponified product. The range of saponification degree is preferably 80.0 to 100.0 mol%, more preferably 90.0 to 99.5 mol%, and even more preferably 93.0 to 99.5 mol%. For example, a polyvinyl alcohol-based resin with a saponification degree of 98.0 to 99.5 mol% can be used.

If the degree of saponification is less than 80.0 mol%, it is difficult to obtain desirable optical properties. The degree of saponification refers to the rate at which the acetic acid group contained in the polyvinyl acetate resin, which is the raw material of the polyvinyl alcohol resin, is changed to a hydroxyl group through the saponification process, expressed in unit ratio (mol%).

Saponification degree (mol%) = (number of hydroxyl groups)/(number of hydroxyl groups + number of acetic acid groups) × 100

It is a value defined as , and can be obtained by the method specified in JIS K 6726 (1994).

The solid content concentration in the solution is preferably 5% by weight or more, more preferably 5 to 15% by weight, and still more preferably 5 to 10% by weight. If it is less than 5% by weight, moisture increases and drying efficiency deteriorates. If it exceeds 15% by weight, the viscosity tends to increase and handling becomes difficult.

The viscosity of the solution at the time of coating is preferably 500 to 10,000 cps, more preferably 1,000 to 7,000 cps, and even more preferably 1,000 to 5,000 cps. If the viscosity is less than 500 cps, control of the film thickness tends to be difficult, and if it exceeds 10,000 cps, liquid feeding tends to be difficult. Additionally, the viscosity of the solution can also be adjusted by heating or cooling the solution, in addition to the composition of the solution.

Examples of aqueous solvents are water and alcohols such as methanol.

The solution may contain additives such as plasticizers and surfactants as needed. As the plasticizer, polyol or its condensate can be used, and examples include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. It is appropriate that the mixing amount of the additive is 20% by weight or less of the polyvinyl alcohol-based resin.

Examples of the coating means 48 include roll coating methods such as wire bar coating, reverse coating, and gravure coating; die coating method; Comma coating method; lip coating method; Spin coating method; Knife coating method; screen coating method; Fountain coating method; dipping method; It can be appropriately selected from known methods such as spray method. In the coating process of the polyvinyl alcohol-based resin solution, the solution is continuously applied while conveying the base film 1 in its longitudinal direction. The longitudinal direction may not necessarily be horizontal. Coating is preferably performed on the upper surface of the base film 1.

The average film thickness (WET film thickness) of the polyvinyl alcohol-based resin solution to be coated can be, for example, 50 to 200 μm. The coating width of the solution can be made to match the overall width of the base film 1, but may be narrower than the overall width of the base film 1.

As shown in Fig. 2(a), in the present invention, the coated layer 2 is formed by applying a polyvinyl alcohol-based resin solution so that the central portion is thicker than both ends in the width direction of the coated layer 2. Such coating methods include, for example, the gravure coating method, which uses a doctor blade with a curved blade tip and makes the amount of solution scraped off small at the center and large at both ends; In the die coating method, the gap between the slit for discharging the coating liquid formed between the front edge and the doctor edge and the liquid pool is widened at the center and narrowed at both ends; In the knife coating method, a knife with a curved blade tip is used, and the gap between the base film and the blade tip is widened at the center and narrowed at both ends; In the comma coating method, a thin film is wound around both ends of a backup roll, and the gap between the comma roll and the base film is widened at the center and narrowed at both ends.

In the coating layer 2 (the layer before drying to obtain the polyvinyl alcohol-based resin layer), the film thickness measured at the center in the width direction is the film thickness measured at a position of 50 mm from the edge in the width direction of the coating layer. Compared to , it is preferable to coat 2.5% or more thickly, and it is preferable to coat 3.0% or more thickly.

Usually, coating about 5.0% thick is sufficient. Additionally, the film thickness measured at a position of 50 mm from the edge is taken as the film thickness that has the larger difference from the film thickness measured at the center among the two measured values.

In this way, the polyvinyl alcohol-based resin solution is applied to obtain a coated layer (2), and this coated layer (2) is dried to form a polyvinyl alcohol-based resin layer (3) that satisfies the above-mentioned formula (1-1). can be formed.

(drying process)

Next, the coated solution is dried by the drying means 50 while transporting the base film 1 coated with the solution in its longitudinal direction, and as shown in FIG. 3(a), the coated solution is dried on the base film 1. The laminated film 10 of the present invention having the polyvinyl alcohol-based resin layer 3 is obtained.

In the drying process, the conveyance direction of the base film 1 is preferably horizontal, but may be conveyed in a direction inclined to the horizontal as long as it is approximately 45° with respect to the horizontal.

Examples of the drying means 50 include a floating dryer that supplies hot air from both sides of the base film to dry the base film 1 while holding it in the air in a non-contact manner, and an infrared dryer that irradiates infrared rays to the base film 1 transported in the air. It is a dryer and a microwave dryer.

The drying temperature, for example, the temperature of the resin layer during drying or the temperature of hot air when applying hot air to the base film 1, can be, for example, 50 to 200 ° C., and is preferably 60 to 150 ° C. , it is more preferable that it is 80°C or higher. When the solution contains water, it is desirable for these temperatures to be 80°C or higher. The drying time, that is, the time during which the transport film travels inside the drying means, can be set to 2 to 20 minutes. Moreover, in the drying process, it is preferable that the solution is applied to the upper surface of the base film 1.

Through this drying process, a laminated film 10 having a polyvinyl alcohol-based resin layer 3 is formed on one side of the base film 1, as shown in Fig. 3(a). Since good polarization performance and durability can be provided, the average thickness of the polyvinyl alcohol-based resin layer 3 after drying is usually 20 μm or less, and preferably 10 μm or less. Additionally, the average thickness of the polyvinyl alcohol-based resin layer 3 is usually 2 μm or more.

In addition, the above-mentioned pretreatment of the surface of the base film 1, solution coating, and drying processes as necessary are performed again on the opposite side of the base film, and as shown in FIG. 3(b), the base film 1 A laminated film 10 having a polyvinyl alcohol-based resin layer 3 may be formed on both sides.

Additionally, pretreatment and solution coating may be performed on both sides of the base film 1, and the coated layers formed on both sides of the base film 1 may be dried simultaneously.

In addition, in the above embodiment, each process of pretreatment, primer layer formation, and resin layer formation (coating and drying) is performed in a batch manner, that is, a roll of film is obtained after each process, and in the next process, Although the method of processing the film by unwinding it from the roll has been shown, any two or more of these processes may be performed continuously, that is, without winding the film onto a roll.

(Method for manufacturing stretched laminated film)

Next, the obtained laminated film 10 (may have the polyvinyl alcohol-based resin layer 3 on only one side of the base film 1, or have the polyvinyl alcohol-based resin layer 3 on both sides of the base film 1) (optional) is unwound from the roll and stretched to obtain the stretched laminated film of the present invention. Additionally, the dyeing process may be performed before the stretching process, or the stretching process and dyeing process may be performed simultaneously. Additionally, stretching may be performed in the air or in water. It is preferable to wind the stretched laminated film into a roll to obtain a stretched laminated film roll. The storage period of the stretched laminated film roll is preferably within 2 years, and more preferably within 1 year. If the roll transfer time from the stretching process to the next process is also considered a storage period, the storage period is usually 30 minutes or more. In order to prevent curling and deterioration of the surface condition due to movement of moisture, it is desirable to take moisture-proof measures such as covering the stretched laminated film roll with an aluminum retort film before storing it.

In this way, by rolling the film once after completing each process, the loss when a problem occurs in one process or when starting the process is reduced compared to the case where each process is performed continuously. Storage of rolls other than stretched laminated film rolls can also be carried out in the same manner as above.

Various known methods can be used for stretching. For example, vertical stretching in the longitudinal direction of the laminated film 10 may be sufficient, transverse stretching in the width direction of the laminated film 10 may be sufficient, or diagonal stretching may be used. Among these, it is preferable to longitudinally (uniaxially) stretch the laminated film 10 while conveying it in the longitudinal direction. The stretch ratio can be adjusted appropriately according to the required polarization characteristics, and can be, for example, 5 to 17 times, or 5 to 8 times.

Stretching may be performed in one stage or in multiple stages.

In the stretching process, it is preferable that the base film is also stretched integrally with the stretching of the polyvinyl alcohol-based resin layer. That is, it is preferable that the draw ratio of the polyvinyl alcohol-based resin layer and the draw ratio of the base film are substantially the same. The fact that the draw ratio is substantially the same means that the difference between the draw ratio of the polyvinyl alcohol-based resin layer and the draw ratio of the base film is 0, and the difference is preferably 0.0. Additionally, it is preferable that the stretching direction of the polyvinyl alcohol-based resin layer and the stretching direction of the base film are substantially the same. That the stretching directions are substantially the same means that the angle formed between the stretching direction of the polyvinyl alcohol-based resin layer and the stretching direction of the base film is less than 5°, and the size of the angle is preferably less than 1°.

The average thickness of the stretched polyvinyl alcohol-based resin layer in the width direction is preferably 10 μm or less, more preferably 7 μm or less, and still more preferably 5.5 μm or less. In addition, since good durability can be provided, the average thickness of the stretched polyvinyl alcohol-based resin layer in the width direction is usually 1 μm or more, and preferably 2 μm or more.

(Method for producing polarizing laminated film)

In the dyeing process, various known methods can be used, such as immersing a laminated film or stretched laminated film in a dye bath. For example, a dichroic dye can be used as a dye. Examples of dichroic dyes are iodine or organic dyes. In dyeing, crosslinking treatment of polyvinyl alcohol in a resin bath may be performed. After dyeing, it is preferable to wash the laminated film with water and dry it.

The average thickness of the polarizer layer is preferably 10 μm or less, more preferably 7 μm or less, and even more preferably 5.5 μm or less. Additionally, the average thickness of the polarizer layer is usually 1 μm or more, and preferably 2 μm or more.

(Method of manufacturing polarizer)

Next, the manufacturing method of the polarizing plate is explained. First, a protective film is attached to the polarizer layer 5 of the light-polarizing laminated film 12 using an adhesive to obtain a multilayer film. When the polarizer layer 5 is formed on both sides of the base film 1, a protective film is adhered onto each polarizer layer 5. Next, the base film 1 is peeled from the multilayer film to obtain two polarizing plates in which the protective film is bonded to the polarizer layer 5 via an adhesive. When the light-polarizing laminated film 12 has the polarizer layer 5 only on one side, one polarizing plate can be obtained.

In the present invention, since loosening and wrinkling of both ends in the width direction of the light-polarizing laminated film are suppressed, a polarizing plate can be manufactured stably with low yield when bonding the protective film to the polarizer layer.

As the protective film 3, various known films can be used. For example, the film exemplified as the base film 1 can be used.

As the adhesive, various known adhesives can be used. For example, an active energy ray-curable adhesive such as an ultraviolet ray-curable epoxy resin can be used.

The obtained polarizing plate can be wound around an axis and stored as a polarizing plate roll, as needed. In the polarizing plate according to this embodiment, the thickness of the width direction end portion of the polarizer layer 5 is not very thick compared to the thickness of the width direction center portion of the polarizer layer 5, so even when the polarizing plate is stored as a roll, The above-described loosening prevention effect can be achieved. The polarizing plate can be unwound from the stored roll as needed and cut to a desired size. The obtained polarizing plate can be reduced in thickness, so it can be suitably used as a polarizing material for liquid crystal display elements, etc., and can be set in a liquid crystal display device.

[Example]

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples. In the examples, parts and percentages indicating the usage amount or content are based on weight unless otherwise specified.

[Measurement of film thickness of coating layer]

The film thickness of the coating layer was measured at a position 50 mm from the edge in the width direction of the coating layer and at a position in the center using a film thickness measuring instrument (SI-80T) manufactured by Keyence Corporation. In-line, the film thickness of the coating layer was measured at intervals of 7 mm in the MD direction, and the film thickness data for 10 m were averaged.

[Other film thickness measurements]

The film thickness was measured over the entire width in the width direction using an interference film thickness meter (F20) manufactured by Filmetrics. Measurements were made while moving the sample using an automatic stage so that the acquisition interval of film thickness data was 2 mm or less.

[Example 1]

<Production of laminated film>

(1) Base film

An unstretched polypropylene (PP) film (melting point: 163°C) with a thickness of 90 μm was prepared as a base film. The tensile modulus of elasticity at 80°C of this base film was 205 MPa.

(2) Preparation of coating solution

Polyvinyl alcohol resin powder (“Z-200” manufactured by Nippon Kosei Chemical Co., Ltd., average degree of polymerization 1100, average degree of saponification 99.5 mol%) was dissolved in hot water at 95°C to produce polyvinyl alcohol with a concentration of 3% by weight. An aqueous solution was prepared. The obtained aqueous solution was mixed with 1 part by weight of a crosslinking agent (“Sumirez Resin (registered trademark) 650” manufactured by Sumitomo Chemical Co., Ltd.) based on 2 parts by weight of polyvinyl alcohol resin powder to obtain a coating solution for forming a primer layer.

In addition, polyvinyl alcohol resin powder (“PVA124” manufactured by Kuraray Co., Ltd., average degree of polymerization 2400, average degree of saponification 98.0 to 99.0 mol%) was dissolved in hot water at 95°C to prepare an aqueous polyvinyl alcohol solution with a concentration of 8% by weight. A coating liquid for forming a stratum was prepared.

(3) Application, drying

· Single-sided laminated product

While conveying the base film continuously, corona treatment was performed on one side. The coating solution for forming a primer layer was continuously applied to the corona-treated side of the base film using a microgravure coater and dried at 60°C for 3 minutes to form a primer layer with a thickness of 0.2 μm. Next, the coating liquid for forming a resin layer was continuously applied onto the primer layer by the comma coating method while transporting the base film to obtain a coating layer. By wrapping a 20-μm-thick polyethylene terephthalate film around both ends of the backup roll, the gap between the comma roll and the base film was widened at the center and narrowed at both ends. By drying the coating layer in a drying furnace at 80°C for 10 minutes, a polyvinyl alcohol (PVA)-based resin layer with an average thickness in the width direction of 9.7 μm was formed on the primer layer.

At this time, in the thickness distribution (WET film thickness) in the width direction of the coating layer, the center was about 3.5% thicker than both ends (position 50 mm from the edge). Moreover, in the film thickness distribution in the width direction of the resin layer, D1e-D1c = -0.54 ㎛.

· Double-sided laminated products

Additionally, the same treatment as that used to produce the single-sided laminate was performed on the surface (second coated surface) of the base film opposite to the surface on which the resin layer was formed (first coated surface), so that the thickness was 0.2. A primer layer having a thickness of ㎛ and a polyvinyl alcohol-based resin layer having an average thickness in the width direction of 9.6 ㎛ were formed, and a double-sided laminate was produced. Then, the laminated film (double-sided laminated product) was wound into a roll shape to obtain a laminated film roll.

At this time, in the thickness distribution (WET film thickness) in the width direction of the coating layer on the second coating surface, the central portion was about 3.0% thicker than both ends (50 mm from the edge). Moreover, in the film thickness distribution in the width direction of the resin layer, D1e-D1c = -0.40 ㎛.

<Production of stretched laminated film>

(4) Stretching

A laminated film (double-sided laminated product) is unwound from the laminated film roll obtained in (3) above and continuously conveyed, stretched in the longitudinal direction (MD direction) up to 2.5 times between nip rolls at a stretching temperature of 140°C, and then A stretched laminated film was produced by stretching in the longitudinal direction at a stretching temperature of 160°C so that the total stretching ratio was 5.8 times. Additionally, the stretched laminated film was wound into a roll shape to obtain a stretched laminated film roll. When unwinding the laminated film, no wrinkles or loosening were observed at both ends of the laminated film in the width direction, and loosening was confirmed at the center portion in the width direction. However, in the stretched laminated film, no wrinkling or loosening was observed at either the ends or the center in the width direction.

The average thickness in the width direction of the resin layer on the first coated surface and the second coated surface in the stretched laminated film was 4.9 μm and 4.9 μm, respectively. At this time, in the width direction film thickness distribution of the stretched polyvinyl alcohol-based resin layer on the first coated surface and the second coated surface, D2e-D2c = 0.07 μm and 0.11 μm, respectively. When the two resin layers included in the stretched laminated film were peeled off and the base film was taken out, the film thickness distribution in the width direction of the base film was D3e-D3c = 0.73 μm. In the film thickness distribution of the total thickness in the width direction of the stretched laminated film, D4e-D4c = 1.48 μm.

<Production of polarizing laminated film>

(5) Dyeing/crosslinking

Unwind the stretched laminated film from the stretched laminated film roll obtained in (4) above, immerse the stretched laminated film in a dyeing solution at 30°C containing iodine and potassium iodide for a residence time of about 150 seconds, and dye the resin layer. treatment, and then the excess dyeing solution was washed away with pure water at 10°C. Subsequently, the stretched laminated film was immersed in a 76°C cross-linking solution containing boric acid and potassium iodide for a residence time of 600 seconds, and cross-linked to obtain a light-polarizing laminated film. Afterwards, the polarizing laminated film was washed with pure water at 10°C for 4 seconds and dried at 80°C for 300 seconds. Additionally, the light-polarizing laminated film was wound up to produce a light-polarizing laminated film roll. Additionally, when unwinding the stretched laminated film, no wrinkles or loosening were observed at either ends or in the center.

The average thickness in the width direction of the polarizer layer on the first coated surface and the second coated surface in the light polarizing laminated film was 5.8 μm and 5.8 μm, respectively. At this time, in the width direction film thickness distribution of the polarizer layer on the first coating surface and the second coating surface, D5e-D5c = -0.12 ㎛ and -0.09 ㎛, respectively. When the two polarizer layers included in the light-polarizing laminated film were peeled off and the base film was taken out, the film thickness distribution in the width direction of the base film was D6e-D6c=0.91 µm. In the film thickness distribution of the total thickness in the width direction of the polarizing laminated film, D7e-D7c = 1.21 μm.

The polarizer layer on the second coated surface side was peeled and removed to produce a light-polarizing laminated film consisting of two layers: a base material/polarizer layer on the first coated surface side. Both ends and the center portion of this light-polarizing laminated film were cut out, respectively, to serve as samples.

The visibility corrected single transmittance Ty of the sample having the polarizer layer on the first coated surface side was measured using a spectrophotometer (V7100, manufactured by Nippon Bunko Co., Ltd.) having an integrating sphere. Incident light was incident from the polarizer layer side. In the polarizer layer on the first coated surface side, among Ty at both ends, the visibility corrected single transmittance Tye with a larger difference compared to the visibility corrected single transmittance Tyc at the center was 42.51%, and at this time, the polarization degree Py was 99.983%. Tyc of the central part was 42.34%, and polarization Py was 99.978%.

Additionally, Ty was measured similarly for the removed polarizer layer on the second coated surface side. In the polarizer layer on the second coated surface side, among Ty at both ends, the visibility corrected single transmittance Tye with a larger difference compared to the visibility corrected single transmittance Tyc at the center was 42.59%, and at this time, the polarization degree Py was 99.980%. Tyc of the central part was 42.52%, and polarization Py was 99.981%.

Therefore, the value of |Tye-Tyc| was 0.17% in the polarizer layer on the first coating surface side, and 0.07% in the polarizer layer on the second coating surface side.

<Production of polarizer>

(6) Adjustment of adhesive solution

Polyvinyl alcohol resin powder (“KL-318” manufactured by Kuraray Co., Ltd., average degree of polymerization 1800) was dissolved in hot water at 95°C to prepare an aqueous polyvinyl alcohol solution with a concentration of 3% by weight. An adhesive solution was prepared by mixing 1 part by weight of a crosslinking agent (“Sumirez Resin (registered trademark) 650” manufactured by Sumitomo Chemical Co., Ltd.) with the obtained aqueous solution based on 2 parts by weight of polyvinyl alcohol resin powder.

A polarizing laminated film was unwound from the polarizing laminated film roll obtained in (5) above, the adhesive solution was applied on both polarizer layers, and the bonding surface was subjected to saponification treatment to form a protective film [triacetylcellulose (TAC)]. A transparent protective film (“KC4UY” manufactured by Konica Minolta Co., Ltd., 40 μm in thickness) consisting of was bonded to each polarizer layer. The polarizer layer and the TAC film were pressed together after passing between a pair of bonding rolls, and a bonding film having TAC film/polarizer layer/primer layer/base film/primer layer/polarizer layer/TAC film in this order was obtained. When unwinding the polarizing laminated film, no wrinkles or loosening were observed at both ends and the center.

By peeling between the base film and the primer layer in the bonding film, two films are formed: a film having TAC film/polarizer layer/primer layer/base film in this order and a film having primer layer/polarizer layer/TAC film in this order. The bonded film was divided into films. Next, the base film was peeled and removed to obtain a polarizing plate having TAC film/polarizer layer/primer layer in this order. Problems such as breakage of the film did not occur in the peeling process.

[Example 2]

A single-sided laminate was produced in the same manner as in Example 1, except that the base film was changed to a polyethylene terephthalate (PET) film with a thickness of 38 μm and a primer layer was not formed on the base film. The average thickness of the polyvinyl alcohol-based resin layer in the width direction was 9.5 μm. At this time, in the thickness distribution (WET film thickness) in the width direction of the coating layer, the central portion was about 3.3% thicker than both ends (50 mm from the edge). Moreover, in the film thickness distribution in the width direction of the resin layer, D1e-D1c = -0.32 ㎛.

The laminated film was wound up to obtain a laminated film roll, and then the laminated film was unwound from the laminated film roll. At this time, no wrinkles or loosening were confirmed at both ends of the laminated film in the width direction, and loosening was confirmed at the center part in the width direction.

[Comparative Example 1]

· Single-sided laminated product

A single-sided laminate was produced in the same manner as in Example 1, except that the film thickness distribution (WET film thickness) of the coating layer was not particularly controlled. At this time, the film thickness of the coating layer became almost uniform in the width direction. The average thickness of the polyvinyl alcohol-based resin layer in the width direction was 9.7 μm.

At this time, the film thickness distribution in the width direction of the resin layer was D1e-D1c = 0.68 μm.

· Double-sided laminated products

In addition, the film thickness distribution (WET film thickness) of the coating layer is not particularly controlled on the surface (second coating surface) of the base film opposite to the surface on which the resin layer is formed (first coating surface). A laminated film (double-sided laminated product) was manufactured by forming a resin layer in the same manner as in Example 1 except that it was not used. Then, the laminated film was wound up to obtain a laminated film roll. At this time, the average thickness in the width direction of the polyvinyl alcohol-based resin layer on the second coated surface was 9.8 μm. Moreover, in the film thickness distribution in the width direction of the resin layer, D1e-D1c = 0.64 ㎛.

As in Example 1, the laminated film was stretched to produce a stretched laminated film. Additionally, the stretched laminated film was wound to obtain a stretched laminated film roll. Additionally, when unwinding the laminated film, loosening was confirmed only at both ends of the laminated film.

The average thickness in the width direction of the resin layer on the first coated surface and the second coated surface in the stretched laminated film was 4.8 μm and 4.8 μm, respectively. At this time, the film thickness distribution in the width direction of the resin layer on the first coated surface and the second coated surface was D2e-D2c = 0.28 μm and 0.37 μm, respectively. When the two resin layers of the stretched laminated film were peeled off and the base film was taken out, the film thickness distribution in the width direction of the base film was D3e-D3c = 1.47 μm. In the film thickness distribution of the total thickness in the width direction of the stretched laminated film, D4e-D4c = 2.28 μm.

Next, the stretched laminated film was unwound from the stretched laminated film roll in the same manner as in Example 1 except that the residence time of the stretched laminated film in the dyeing solution was about 170 seconds, and a dyeing process and a crosslinking process were performed to determine the polarization property. A laminated film was prepared. Then, the light-polarizing laminated film was wound up to obtain a light-polarizing laminated film roll. Additionally, when unwinding the stretched laminated film, it was confirmed that only both ends of the stretched laminated film became loose. The average thickness in the width direction of the polarizer layer on the first coating surface and the second coating surface in the light polarizing laminated film was 5.9 μm and 5.9 μm, respectively.

At this time, in the width direction film thickness distribution of the polarizer layer on the first coating surface and the second coating surface, D5e-D5c = 0.27 μm and 0.28 μm, respectively. When the two polarizer layers included in the stretched light-polarizing laminated film were peeled off and the base film was taken out, the film thickness distribution in the width direction of the base film was D6e-D6c = 1.3 μm. In the film thickness distribution of the total thickness in the width direction of the polarizing laminated film, D7e-D7c = 2.11 μm.

The polarizer layer on the second coated surface side was peeled and removed to produce a light-polarizing laminated film consisting of two layers: a base material/polarizer layer on the first coated surface side. Both ends and the center portion of this light-polarizing laminated film were cut out, respectively, to serve as samples.

As in Example 1, Ty of the sample having the polarizer layer on the first coating surface side was measured.

In the polarizer layer on the first coating surface side, among Ty at both ends, Tye at the side with a larger difference compared to Tyc at the center was 41.52%, and at this time, the polarization degree Py was 99.997%. Tyc of the central part was 41.10%, and polarization Py was 99.998%.

Additionally, Ty was measured in the same manner as in Example 1 for the removed polarizer layer on the second coated surface side.

In the polarizer layer on the second coated surface side, among Ty at both ends, Tye at the side with a larger difference compared to Tyc at the center was 41.42%, and at this time, the polarization degree Py was 99.998%. Tyc of the central part was 40.94%, and polarization Py was 99.998%.

Therefore, the value of |Tye-Tyc| was 0.42% in the polarizer layer on the first coating surface side, and 0.48% in the polarizer layer on the second coating surface side.

When the light-polarizing laminated film was unwound from the light-polarizing laminated film roll, it was confirmed that it was loosened at both ends in the width direction. An attempt was made to bond the protective film by applying an adhesive solution onto the two polarizer layers in the light-polarizing laminated film, but the loose portion became wrinkled and the protective film could not be bonded.

The results of Examples 1 and 2 and Comparative Example 1 are shown in Tables 1 to 3. Additionally, the numerical unit in the table is ㎛ unless otherwise specified. In this way, in the present invention, loosening is suppressed at both ends in the width direction in the stretching process and dyeing process, so that a polarizing plate can be stably manufactured and the optical properties are uniform in the width direction.

According to the present invention, wrinkles and loosening are less likely to occur at both ends in the width direction of a long laminated film, and the area of the portion that does not become a product can be reduced. Additionally, a polarizing plate with uniform optical properties in the width direction can be obtained. Moreover, the protective film can be easily bonded to the polarizing laminated film, and a polarizing plate can be manufactured stably.

1: Base film, 2: Coating layer, 3: Polyvinyl alcohol-based resin layer, 4: Stretched polyvinyl alcohol-based resin layer, 5: Polarizer layer, 9: Base film with coating layer, 10: Laminated film, 11 : Stretched laminated film, 12: Polarizing laminated film, 30, 32, 34: Unwinding part, 42: Surface activation means, 44: Coating means, 46: Drying means, 48: Coating means, 50: Drying means, 52: Driving Rolls, 31, 33, 35: winding section, 100: outermost area, 101: central area.

Claims (21)

A laminated film comprising an unstretched polyvinyl alcohol-based resin layer on at least one side of a long base film, wherein when the polyvinyl alcohol-based resin layer is divided into nine regions in the width direction, the average of the outermost region is The film thickness D1e and the average film thickness D1c in the central region satisfy the following equation,
A laminated film in which the average thickness of the polyvinyl alcohol-based resin layer in the width direction is 10 μm or less.

Additionally, the average film thickness D1e of the outermost region is set to be the average film thickness that has a larger difference from the average film thickness D1c of the central region among the average film thicknesses in the two outermost regions. The laminated film according to claim 1, wherein D1e and D1c satisfy the following equation.
A stretched laminated film comprising a polyvinyl alcohol-based resin layer stretched in the longitudinal direction on at least one side of a long base film, when the stretched polyvinyl alcohol-based resin layer is divided into nine regions in the width direction. , the average film thickness D2e of the outermost region and the average film thickness D2c of the central region satisfy the following equation,
A stretched laminated film wherein the average thickness of the stretched polyvinyl alcohol-based resin film in the width direction is 7 μm or less.

Additionally, the average film thickness D2e of the outermost region is set to be the average film thickness that has a larger difference from the average film thickness D2c of the central region among the average film thicknesses in the two outermost regions. The stretched laminated film according to claim 3, wherein D2e and D2c satisfy the following equation.
Stretch lamination according to claim 3 or 4, wherein when the base film is divided into nine regions in the width direction, the average film thickness D3e of the outermost region and the average film thickness D3c of the central region satisfy the following equation. film.

Additionally, the average film thickness D3e of the outermost region is set to be the average film thickness that has a larger difference from the average film thickness D3c of the central region among the average film thicknesses in the two outermost regions. The stretched laminated film according to claim 5, wherein D3e and D3c satisfy the following equation.
The stretched laminated film according to claim 3 or 4, wherein when the stretched laminated film is divided into nine regions in the width direction, the average film thickness D4e of the outermost region and the average film thickness D4c of the central region satisfy the following equation. film.

Additionally, the average film thickness D4e of the outermost region is set to be the average film thickness that has a larger difference from the average film thickness D4c of the central region among the average film thicknesses in the two outermost regions. The stretched laminated film according to claim 7, wherein D4e and D4c satisfy the following equation.
A light-polarizing laminated film comprising a polarizer layer on at least one side of a long base film and having an absorption axis in the longitudinal direction, wherein when the polarizer layer is divided into nine regions in the width direction, the average film of the outermost region is A light polarizing laminated film in which the thickness D5e and the average film thickness D5c in the central region satisfy the following equation, and the average value of the width direction thickness of the polarizer layer is 7 μm or less.

Additionally, the average film thickness D5e of the outermost region is set to be the average film thickness that has a larger difference from the average film thickness D5c of the central region among the average film thicknesses in the two outermost regions. The light polarizing laminated film according to claim 9, wherein D5e and D5c satisfy the following equation.
The polarization property according to claim 9 or 10, wherein when the base film is divided into nine regions in the width direction, the average film thickness D6e of the outermost region and the average film thickness D6c of the central region satisfy the following equation. Laminated film.

Additionally, the average film thickness D6e of the outermost region is set to be the average film thickness that has a larger difference from the average film thickness D6c of the central region among the average film thicknesses in the two outermost regions. The light polarizing laminated film according to claim 11, wherein D6e and D6c satisfy the following equation.
The method of claim 9 or 10, wherein when the polarizing laminated film is divided into nine regions in the width direction, the average film thickness D7e of the outermost region and the average film thickness D7c of the central region satisfy the following equation: Photosensitive laminated film.

Additionally, the average film thickness D7e of the outermost region is set to be the average film thickness that has a larger difference from the average film thickness D7c of the central region among the average film thicknesses in the two outermost regions. The light polarizing laminated film according to claim 13, wherein D7e and D7c satisfy the following equation.
The method of claim 10, wherein the visibility corrected single transmittance Tye measured at a position 25 mm from the edge in the width direction of the polarizer layer and the visibility corrected single transmittance Tyc measured at the center of the width direction of the polarizer layer satisfy the following equation: Photosensitive laminated film.

Additionally, the visibility corrected single transmittance Tye measured at a position of 25 mm from the edge is taken as the visibility corrected single transmittance that has a larger difference from the visibility corrected single transmittance Tyc measured at the center among the two measured values. A step of forming a coating layer by coating an aqueous solution containing a polyvinyl alcohol-based resin on at least one side of a long base film so that the central portion is thicker than both ends in the width direction of the coating layer, and drying the coating layer to form a polyvinyl alcohol-based resin. The method for producing a laminated film according to claim 1, comprising the step of forming a resin layer made of vinyl alcohol-based resin. delete A method for producing a stretched laminated film, comprising the step of obtaining a laminated film by the manufacturing method according to claim 16, and uniaxially stretching the obtained laminated film in the longitudinal direction more than 5 times to obtain a stretched laminated film. A method for producing a stretched laminated film roll, comprising the steps of obtaining a stretched laminated film by the manufacturing method according to claim 18, winding the obtained stretched laminated film into a roll, and obtaining a stretched laminated film roll. A process of obtaining a light polarizing laminated film by dyeing the stretched laminated film obtained by the manufacturing method according to item 18 or by dyeing the stretched laminated film unwound from the stretched laminated film roll obtained by the manufacturing method according to item 19. A method of producing a polarizing laminated film comprising: A bonding step of obtaining a light-polarizing laminated film by the manufacturing method according to claim 20, bonding a protective film to the surface of the obtained light-polarizing laminated film opposite to the base film side of the polarizer layer to obtain a multilayer film, and obtaining a multilayer film, A method of manufacturing a polarizing plate including a peeling process of peeling the base film from the multilayer film.

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