TWI679118B - Laminated film and method for producing the same - Google Patents

Abstract

The problem of the present invention is that the laminated film has wrinkles and sags, and there are problems that color spots are generated in the width direction and that both ends in the width direction cannot be used in a polarizing plate. Furthermore, another problem of the present invention is that when the polarizing laminated film obtained after the dyeing step has wrinkles and slacks, there is a problem that the protective film cannot be attached and the polarizing plate cannot be stably manufactured.

A solution to the above-mentioned problem is a laminated film having a polyvinyl alcohol-based resin layer in a width direction in a laminated film having a substantially unstretched polyvinyl alcohol-based resin layer on at least one side of a long substrate film. When equally divided into 9 regions, the average film thickness D1e of the outermost region and the average film thickness D1c of the central region satisfy the following formula: D1e-D1c ≦ -0.3 μm.

Description

Laminated film and manufacturing method of laminated film

The present invention relates to a laminated film and a method for manufacturing the laminated film.

Conventional polarizers are manufactured by stretching and dyeing an original sheet film (typically, a thickness of about 30 to 75 μm) of a polyvinyl alcohol resin, and the thickness of the stretched film is usually about 12 to 30 μm. When a film having a thickness of 30 μm or less is used as an original sheet film of a polyvinyl alcohol-based resin for thinning, there are problems in production such as that the film becomes easily cracked when stretched.

Therefore, in order to correspond to the reduction in thickness of today's polarizers, a method has been proposed in which an aqueous solution containing a polyvinyl alcohol-based resin is coated on a base film. In this method, an aqueous solution containing a polyvinyl alcohol-based resin is coated on a base film to form a polyvinyl alcohol-based resin layer to obtain a laminated film, and then an extension and dyeing treatment is applied to the laminated film, thereby giving A polyvinyl alcohol-based resin layer has a polarizing function to obtain a polarizer layer (Patent Document 1).

[Prior technical literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2009-098653

When a polarizing laminated film is obtained by applying an aqueous solution containing a polyvinyl alcohol-based resin, the polarizing laminated film can generally be manufactured by a roll-to-roll method using a long base film. In this method, a plurality of steps such as a step of stretching the polyvinyl alcohol-based resin layer and a step of dyeing with iodine are included, so that each of the long substrate films is wound into a roll shape.

In particular, after the stretching step, the stretched laminated film is rolled into a roll shape to obtain a stretched laminated film roll. When the stretched laminated film is rolled out from the stretched laminated film roll in order to perform the dyeing step, it will be in the width direction of the rolled long film. Wrinkles and sags appear on both ends of the body. After the film is rolled into a reel shape, wrinkles and slacks that occur at both ends of the rolled film will also occur on the laminated film, and there are color spots in the width direction due to such wrinkles and slack. There is a problem that both ends cannot be used in a polarizing plate. In addition, when wrinkles and sags occur in the polarizing laminated film obtained after the dyeing step, there is a problem that a protective film cannot be attached and a polarizing plate cannot be stably manufactured.

The present invention includes the following inventions.

[1] A laminated film which is a laminated film having a substantially unstretched polyvinyl alcohol-based resin layer on at least one side of a long base film, and the polyvinyl alcohol-based resin layer is divided into 9 in a width direction. For each area, the average film thickness D1e of the outermost region and the average film thickness D1c of the central region satisfy the following formula: D1e-D1c ≦ -0.3 μm, wherein the average film thickness D1e of the outermost region is the one having a larger difference between the average film thickness of each of the two outermost regions and the average film thickness D1c of the central region. Average film thickness.

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

[3] An extended build-up film, which is an extended build-up film having an extended polyvinyl alcohol-based resin layer on at least one side of a long substrate film, and which extends the extended polyvinyl alcohol-based resin layer in a width direction. When divided into 9 regions, the average film thickness D2e of the outermost region and the average film thickness D2c of the central region satisfy the following formula: D2e-D2c ≦ 0.25 μm, where the average film thickness D2e of the outermost region is set to the maximum The average film thickness of the one with the larger difference between the average film thickness of each of the two outer regions and the average film thickness D2c of the central region.

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

[5] The stretched laminated film according to [3] or [4], wherein when the substrate film is equally divided into 9 regions in the width direction, the average film thickness D3e of the outermost region and the average of the central region The film thickness D3c satisfies the following formula: D3e-D3c ≦ 1.0 μm, where the average film thickness D3e of the outermost region is set to the average film thickness D3c of the average film thickness of each of the two outermost regions and the central region. The larger the average film thickness.

[6] The stretched laminated film according to any one of [3] to [5], wherein when the stretched laminated film is equally divided into 9 regions in the width direction, the average film thickness D4e of the outermost region and the center The average film thickness D4c of the region satisfies the following formula: D4e-D4c ≦ 1.5 μm, where the average film thickness D4e of the outermost region is set to the average of the average film thickness of each of the two outermost regions and the central region. The average film thickness of the one with a larger difference in film thickness D4c.

[7] A polarizing laminated film, which is a polarizing laminated film having a polarizer layer on at least one side of a long substrate film, and when the polarizer layer is equally divided into 9 regions in the width direction, the outermost region The average film thickness D5e and the average film thickness D5c of the central region satisfy the following formula: D5e-D5c ≦ 0.25 μm, where the average film thickness D5e of the outermost region is the average film of each of the two outermost regions. The average film thickness of the one having a large difference between the average thickness and the average film thickness D5c of the central region.

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

[9] The polarizing laminated film according to the item [7] or [8], wherein when the substrate film is equally divided into 9 regions in the width direction, the average film thickness D6e of the outermost region is equal to that of the central region. The average film thickness D6c satisfies the following formula: D6e-D6c ≦ 1.0 μm, where the average film thickness D6e of the outermost region is set to the average film thickness of each of the two outermost regions and the average film thickness of the central region The average film thickness of the larger D6c difference.

[10] The polarizing laminated film according to any one of [7] to [9], wherein when the polarizing laminated film is equally divided into 9 regions in the width direction, the average film thickness D7e of the outermost region The average film thickness D7c from the central region satisfies the following formula: D7e-D7c ≦ 1.5 μm, where the average film thickness D7e of the outermost region is set to the average film thickness of each of the two outermost regions. The larger the average film thickness D7c, the larger the average film thickness.

[11] The polarizing laminated film according to any one of [7] to [10], wherein the photometric correction monomer transmittance Tye and measured at a position 25 mm from the edge in the width direction of the polarizer layer The photometric correction unit transmittance Tyc measured at the center of the width direction of the polarizer layer satisfies the following formula: | Tye-Tyc | ≦ 0.40%, where the photometric correction unit transmittance measured at a position 25 mm from the edge Tye is the photometric correction unit transmittance having a larger difference between the two measured values and the photometric correction unit transmittance Tyc measured at the center.

[12] A method for producing a laminated film, comprising: coating a polyvinyl alcohol resin-containing resin on at least one side of the long base film so that a central portion in a width direction of the coating layer is thicker than both end portions; An aqueous solution to form a coating layer; and a step of drying the coating layer to form a polyvinyl alcohol-based resin-containing resin layer.

[13] A method for manufacturing an extended laminated film, comprising the step of uniaxially extending the laminated film described in the item [12] to more than 5 times to obtain an extended laminated film.

[14] A method for manufacturing an extended laminated film reel, comprising: rolling the extended laminated film described in item [13] into a roll to obtain an extended laminated film reel.

[15] A method for manufacturing a polarizing laminated film, comprising: dyeing the extended laminated film described in [13] or the extended laminated film rolled from the extended laminated film roll described in [14] to obtain polarized light Steps of sexually laminated film.

[16] A method for manufacturing a polarizing plate, comprising: laminating a protective film on a surface of the polarizer layer of the polarizing laminated film according to [15] on the side opposite to the substrate film side to obtain a multilayer film The bonding step is a peeling step of peeling the base film from the multilayer film.

According to the present invention, it is difficult to cause wrinkles and slacks at both ends in the width direction of the long laminated film, and it is possible to reduce the area of a portion that cannot be used as a product. Further, a polarizing plate having uniform optical characteristics in the width direction can be obtained. In addition, since the protective film can be easily bonded to the polarizing laminated film, a polarizing plate can be manufactured stably.

1‧‧‧ substrate film

2‧‧‧ coated layer

3‧‧‧Polyvinyl alcohol resin layer

4‧‧‧ Stretched polyvinyl alcohol resin layer

5‧‧‧ polarizer layer

9‧‧‧ substrate film with coating layer

10‧‧‧ laminated film

11‧‧‧ stretch laminated film

12‧‧‧Polarized laminated film

30, 32, 34‧‧‧ roll out

42‧‧‧ Surface activation method

44, 48‧‧‧ Coating method

46, 50‧‧‧ Drying method

52‧‧‧Drive roller

31, 33, 35‧‧‧ Take-up Department

100‧‧‧ outermost area

101‧‧‧ central area

[FIG. 1] A diagram illustrating a method for manufacturing a laminated film according to an embodiment of the present invention.

[Fig. 2] A schematic cross-sectional view showing an example of a substrate film having a coating layer obtained by an embodiment of the present invention.

3 is a schematic cross-sectional view showing an example of a multilayer film obtained by an embodiment of the present invention.

4 is a schematic cross-sectional view showing an example of an extended laminated film obtained by an embodiment of the present invention.

5 is a schematic cross-sectional view showing an example of a polarizing laminated film obtained by an embodiment of the present invention.

[FIG. 6] 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] A schematic cross-sectional view of a stretched laminated film when the stretched polyvinyl alcohol-based resin layer does not satisfy the requirements of the present invention.

When a polarizer layer is obtained by applying an aqueous solution containing a polyvinyl alcohol-based resin, a polarizing laminated film can be generally produced by a method including the following steps.

(Coating step) A step of applying an aqueous solution containing a polyvinyl alcohol resin to at least one side of the elongated base film to obtain a coating layer.

(Drying step) A step of obtaining a laminated film by drying the coating layer to form a polyvinyl alcohol-based resin layer (abbreviated as a resin layer).

(Extending step) A step of extending the laminated film to obtain an extended laminated film.

(Dyeing step) A step of immersing the stretched laminated film in a dyeing solution containing iodine to obtain a polarized laminated film.

In order to suppress the occurrence of wrinkles and slacks at both ends in the width direction of the polarizing laminated film, the inventors have found that the following intermediate products can be produced in each step of manufacturing a polarizing plate. The length of the intermediate product (laminated film, stretched laminated film, and polarized laminated film) of the present invention can be It is 100m or more, and may be 500m or more. Since the roll diameter becomes larger when the length of the film is 100 m or more, although the roll tends to be easily generated, the present invention can effectively prevent the occurrence of wrinkles and slack at both ends in the width direction. Generally, the length of the film is 10,000 m or less.

[Intermediate product: laminated film]

In a laminated film including a polyvinyl alcohol-based resin layer on a long substrate film, when the polyvinyl alcohol-based resin layer is equally divided into 9 regions in the width direction, the average film thickness D1e of the outermost region and the central region must be made. The average film thickness D1c satisfies the following formula (1-1), and preferably satisfies the following formula (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. The average film thickness D1e of the outermost region is the average film thickness of the one having the larger difference between the average film thickness of each of the two outermost regions and the average film thickness D1c of the central region.

D1e-D1c ≦ -0.3μm (1-1)

D1e-D1c ≧ -2.0μm (1-2)

For example, when the laminated film is provided with 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 may satisfy the formula (1-1), and may be disposed on It is preferable that all the polyvinyl alcohol-based resin layers on the surface of the substrate film satisfy the formula (1-1).

Among the film thickness distributions in the width direction of the polyvinyl alcohol-based resin layer, D1e-D1c are considered to indicate the uniformity of the film thickness distribution and the approximate shape of the film thickness distribution in the width direction. The so-called polyvinyl alcohol-based resin layer satisfies the formula (1-1), and refers to a polyvinyl alcohol-based resin whose film thickness distribution in the width direction is convex. The layer is arranged on a substrate film. When the film thickness distribution in the width direction is convex, while the tension is applied in the winding direction (MD direction), the laminated film is wound into a reel shape to obtain a laminated film reel. The film thickness distribution in the width direction is Compared with the concave shape, the tension applied to the widthwise end of the laminated film reel can be reduced. As a result, both ends of the width direction of the laminated film reel become difficult to be rolled tightly, and it is possible to suppress the occurrence of wrinkles and slacks in the width direction both ends of the rolled-up laminated film.

In addition, although the laminated film rolled up by the laminated film roll has wrinkles and slacks in the central portion in the width direction, the wrinkles and slacks in the central portion in the width direction can be removed by the extension step of the subsequent step. On the other hand, wrinkles and slacks generated at both ends in the width direction are difficult to be removed by the stretching step. In order to easily remove wrinkles and slack in the central portion in the width direction, the polyvinyl alcohol-based resin layer preferably satisfies the formula (1-2).

Since the laminated film is a film before the stretching step and the dyeing step are performed, the polyvinyl alcohol-based resin layer is substantially unstretched. It is not substantially extended, which means that the stretching ratio in the extending 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 long laminated film and parallel to the surface of the laminated film. When a laminated film is manufactured by a reel-to-reel method, the width direction is perpendicular to the conveying direction (MD direction) of the laminated film and coincides with the direction (TD direction) parallel to the laminated film surface. Of course, the length direction is consistent with the MD direction. Furthermore, when the laminated film of the present invention is subjected to an extension step to obtain an extended laminated film, and when a step including a dyeing step is further performed to obtain a polarized laminated film, the film is usually extended. The direction is the same as the longitudinal direction of the laminated film, and the absorption axis direction of the polarizing laminated film is the same as the longitudinal direction of the laminated film. This relationship is the same even in the case where the transparent protective film is bonded to the polarizing laminated film and the polarizing plate from which the substrate film has been peeled, and the polarizing plate is cut into a blade body having a predetermined size.

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

[Intermediate product: stretch laminated film]

The stretch-laminated film includes a stretched polyvinyl alcohol-based resin layer on at least one side of the elongate base film. The stretched laminated film is a film obtained by extending the above-mentioned laminated film. The stretching ratio of the polyvinyl alcohol-based resin layer may be, for example, 5 to 17 times, or 5 to 8 times. When the extended polyvinyl alcohol-based resin layer is equally divided into 9 regions in the width direction, the average film thickness D2e of the outermost region and the average film thickness D2c of the central region must satisfy the following formula (2-1), and satisfy The following formula (2-2) is preferable. D2e-D2c is preferably 0.20 μm or less, more preferably 0.15 μm or less, and more preferably -1.0 μm or more. The average film thickness D2e of the outermost region is the average film thickness of the one having the larger difference between the average film thickness of each of the two outermost regions and the average film thickness D2c of the central region.

D2e-D2c ≦ 0.25μm (2-1)

D2e-D2c ≧ -1.2μm (2-2)

For example, when both sides of the base film are provided with an extended polyvinyl alcohol-based resin layer, the polyvinyl alcohol-based resin layer disposed on at least one side of the base film may satisfy the formula (2-1) and be disposed on the base. Any side of the film It is preferable that all the polyvinyl alcohol-based resin layers satisfy the formula (2-1).

If the stretched polyvinyl alcohol-based resin layer satisfies the formula (2-1), when the stretched laminated film is wound into a stretched laminated film reel, it is difficult for both ends in the width direction to occur due to the same reason as the above-mentioned laminated film. The curling of the portion is considered to be able to suppress the occurrence of wrinkles and slack at both ends in the width direction.

In order to more effectively suppress the winding of the stretched film roll, when the base film is divided into 9 regions in the width direction in the stretched film, the average film thickness D3e of the outermost region is equal to that of the central region. The average film thickness D3c preferably satisfies the following formula (3-1), and more preferably satisfies the following formula (3-2). D3e-D3c is preferably 0.8 μm or less, and more preferably −0.8 μm or more. The average film thickness D3e of the outermost region is the average film thickness of the one having the larger difference between the average film thickness of each of the two outermost regions and the average film thickness D3c of the central region.

D3e-D3c ≦ 1.0μm (3-1)

D3e-D3c ≧ -1.0μm (3-2)

It is preferable that the polyvinyl alcohol-based resin layer and the base film can be integrally stretched. At this time, the film thickness distribution in the width direction of the base film tends to reflect the film thickness distribution of the stretched polyvinyl alcohol-based resin layer. That is, not only the film thickness distribution in the width direction of the polyvinyl alcohol resin layer can be changed, but also the film thickness distribution in the width direction of the substrate film can be changed. Therefore, when the film thickness distribution of the stretched polyvinyl alcohol-based resin layer does not satisfy the formula (2-1), for example, as shown in FIG. 7, when the stretched polyvinyl alcohol-based resin layer has a concave film thickness distribution (D2e-D2c> 0.25μm), the film thickness distribution in the width direction of the substrate film can also be deformed into a concave shape by stretching (D3e-D3c> 1.0μm). On the other hand, this In the stretched laminated film of the invention, since the film thickness distribution in the width direction of the stretched polyvinyl alcohol-based resin layer satisfies the formula (2-1) and is approximately smooth, deformation of the base film can be prevented.

Furthermore, when the stretched laminated film is equally divided into 9 regions in the width direction, it is preferable that the average film thickness D4e of the outermost region and the average film thickness D4c of the central region satisfy the following formula (4-1) It is better to satisfy the following formula (4-2). D4e-D4c is preferably -1.0 µm or more, more preferably 0.0 µm or more, and may be 0.5 µm or more. The average film thickness D4e of the outermost region is the average film thickness of the one having the larger difference between the average film thickness of each of the two outermost regions and the average film thickness D4c of the central region.

D4e-D4c ≦ 1.5μm (4-1)

D4e-D4c ≧ -2.0μm (4-2)

The thickness of the stretched laminated film refers to the total thickness, which is the sum of the thickness of the substrate film in the stretched laminated film and the thickness of the stretched resin layer. When a polyvinyl alcohol-based resin layer is provided 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. The thickness is a thickness obtained by adding the thickness of the base film and 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 Formula (4-1) is satisfied, wrinkles and slacks at both ends in the width direction can be more effectively suppressed in the stretch laminated film roll.

As described above, the laminated film satisfies the formula (1-1) and indicates that the cross-sectional shape in the width direction is convex. Compared with the value of formula (1-1), the value of formula (2-1) The larger one is believed to be because the thin-film end portion of the multilayer film will become thicker due to the shrinkage during stretching, and the cross-sectional shape in the width direction will change from convex to flat.

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: Polarized laminated film]

The polarizing laminated film includes a polarizer layer on at least one side of the elongated base film. The polarizing laminated film is a film obtained by performing a step including a dyeing step on the stretched laminated film. The polyvinyl alcohol-based resin layer is a polarizer layer by a step including a dyeing step. Generally, the film thickness distribution in the width direction of each layer (polarizer layer, substrate film) of the polarizing laminated film is a film thickness distribution that reflects the width direction of each layer included in the stretched laminated film.

Therefore, as with the extended laminated film, when the polarizer layer is equally divided into 9 regions in the width direction, the average film thickness D5e of the outermost region and the average film thickness D5c of the central region must satisfy the following formula (5-1), and use It is preferable to satisfy the formula (5-2). D5e-D5c is preferably 0.20 μm or less, and more preferably 0.15 μm or less, and more preferably 0.1 μm or less, and more preferably -0.15 μm or more, and more preferably -0.1 μm or more. The average film thickness D5e of the outermost region is the average film thickness of the one having the larger difference between the average film thickness of each of the two outermost regions and the average film thickness D5c of the central region.

D5e-D5c ≦ 0.25μm (5-1)

D5e-D5c ≧ -0.2μm (5-2)

Polarizing laminated film has polarizers on both sides of the base film As long as the polarizer layer disposed on at least one side of the substrate film satisfies the formula (5-1), and the polarizer layer disposed on the surface of the base film satisfies the formula (5-1) as good.

If the polarizer layer in the width direction satisfies the formula (5-1), when the polarizing laminated film is wound into a polarizing laminated film roll, it is difficult to cause the two ends of the width direction to be tightly tightened. Those with wrinkles and slack at both ends.

In order to more effectively suppress the winding of the polarizing laminated film roll, when the base film is divided into 9 regions in the width direction in the polarizing laminated film, the average film thickness D6e of the outermost region and The average film thickness D6c in the central region preferably satisfies the following formula (6-1), and more preferably satisfies the following formula (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. The average film thickness D6e of the outermost region is the average film thickness of the one having the larger difference between the average film thickness of each of the two outermost regions and the average film thickness D6c of the central region.

D6e-D6c ≦ 1.0μm (6-1)

D6e-D6c ≧ -1.5μm (6-2)

Furthermore, when the polarizing laminated film is divided into 9 regions equally 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 formula (7-1): It is better to satisfy the following formula (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. In addition, the average film thickness D7e of the outermost region is a level having a larger difference between the average film thickness of each of the two outermost regions and the average film thickness D7c of the central region. Uniform film thickness.

D7e-D7c ≦ 1.5μm (7-1)

D7e-D7c ≧ -2.0μm (7-2)

The thickness of the polarizing laminated film refers to the total thickness, which is the sum of the thickness of the base film in the polarizing laminated film and the thickness of the polarizer layer. When a polarizer layer is provided 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. When a polarizer layer is provided on both sides of the base film, the total thickness is the thickness of the base film. Add the thickness of the sum of the thicknesses of a pair of polarizer layers. Therefore, those who have polarizer layers on both sides of the base film and satisfy the formula (7-1) can more effectively suppress wrinkles and slacks at both ends in the width direction in the polarizing laminated film roll.

Furthermore, in terms of a polarizing plate for more uniform polarization performance, the photometric correction unit transmittance Tye measured at a position 25 mm from the edge in the width direction of the polarizer layer and the photometric correction measured at the center in the width direction The monomer transmittance Tyc preferably satisfies the following formula (8-1). | Tye-Tyc | is preferably 0.3% or less, and more preferably 0.2% or less. | Tye-Tyc | Usually 0.00% or more. In addition, the photometric correction unit transmittance Tye measured at a position 25 mm from the edge is determined as the photometric correction unit through which the difference between the two measured values and the photometric correction unit transmittance Tyc measured at the center is larger. Transmission rate.

｜ Tye-Tyc ｜ ≦ 0.40% (8-1)

Transmittance (Ty) of photometric correction monomer can be calculated from the wavelength of 380nm to 780nm in the MD direction (T _MD ) and the TD direction (T _TD ) of the polarized laminated film. The formula (9) shown below is used to calculate the transmittance of the monomer at each wavelength, and it is determined by photometric correction at a 2-degree viewing angle (C light source) of JIS Z 8701.

Cell Transmittance (%) = (T _MD + T _TD ) / 2 (9)

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

Hereinafter, an embodiment of a method for manufacturing a multilayer film, a method for manufacturing a polarizing multilayer film, and a method for manufacturing a polarizing plate of the present invention will be described with reference to the drawings.

(Manufacturing method of laminated film)

FIG. 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 formed of a thermoplastic resin. Examples of thermoplastic resins include polyolefin resins such as chain polyolefin resins and cyclic polyolefin resins (such as norbornene-based resins); polyester resins such as polyethylene terephthalate; (meth) acrylic acid Resins; cellulose triacetate, cellulose diacetate and other cellulose ester resins; polycarbonate resins; polyvinyl alcohol resins; polyvinyl acetate resins, polyarylate resins; polybenzene Ethylene resin; Polyether fluorene resin; Polyfluorene resin; Polyamine resin; Polyimide resin.

The base film may have a single-layer structure formed of one resin layer containing one or two or more thermoplastic resins, or may include a single-layer structure A multilayer structure in which resin layers of one or more thermoplastic resins are laminated.

The base film may be an extended or unstretched product. When it is an extension, it may be uniaxial or biaxial.

The chain polyolefin-based resin includes, in addition to homopolymers of chain olefins such as polyethylene resins and polypropylene resins, copolymers including two or more types of chain olefins. In terms of being easily and stably stretched at a high magnification, a base film containing a chain olefin-based resin is preferred. Among them, the base film is made of polypropylene resin (polypropylene resin of homopolymer of propylene, copolymer mainly composed of propylene, etc.), polyethylene resin (polyethylene resin of homopolymer of ethylene, ethylene Copolymers, etc.) are more preferred.

A propylene-based copolymer is a copolymer of propylene and other monomers copolymerizable with propylene. Examples of other monomers copolymerizable with propylene include ethylene and α-olefin. The α-olefin is preferably an α-olefin having 4 or more carbon atoms, and more preferably an α-olefin having 4 to 10 carbon atoms. 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 Classes; 3-methyl-1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene and other branched monoolefins; ethylene cyclohexane and the like. The copolymer of propylene and other monomers copolymerizable with propylene may be a random copolymer or a block copolymer.

The content of the other monomers in the copolymer is, for example, 0.1 to 20% by weight, and preferably 0.5 to 10% by weight.

Among the above, polypropylene resin is based on the use of propylene Homopolymer, propylene-ethylene random copolymer, propylene-1-butene random copolymer or propylene-ethylene-1-butene random copolymer are preferred.

Cyclic polyolefin resins are collectively referred to as resins that polymerize cyclic olefins as polymerization units. They include: ring-opened (co) polymers of cyclic olefins, addition polymers of cyclic olefins, and cyclic olefins and ethylene. Copolymers of chain olefins such as propylene and propylene (typically random copolymers), graft polymers modified with unsaturated carboxylic acids or their derivatives, and hydrides such as these. Among them, norbornene-based resins using norbornene-based monomers such as norbornene and polycyclic norbornene-based monomers as cyclic olefins are preferred.

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

The polyester resin is a resin having an ester bond, and is generally a polycondensate containing a polycarboxylic acid or a derivative thereof and a polyhydric alcohol. As the polycarboxylic acid or its derivative, a divalent dicarboxylic acid or its derivative can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalene dicarboxylic acid. Esters, etc. As the polyhydric alcohol, a divalent diol can be used, and examples thereof include ethylene glycol, propylene glycol, butanediol, neopentyl glycol, and cyclohexanedimethanol.

Specific examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, and polyterephthalate. Trimethylene formate, polytrimethylene naphthalate, cyclohexane dimethyl terephthalate, cyclohexane dimethyl polynaphthalate, and the like. For polyester resin films such as polyethylene terephthalate, Extend to increase elasticity. Extension can be uniaxial or biaxial.

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

Examples of the (meth) acrylic resin include poly (meth) acrylates such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic copolymer, and methyl methacrylate- (methyl ) Acrylate copolymer, methyl methacrylate-acrylate- (meth) acrylic copolymer, methyl (meth) acrylate-styrene copolymer (MS resin, etc.), polymer with alicyclic hydrocarbon group ( For example, methyl methacrylate cyclohexyl methacrylate copolymer, methyl methacrylate-norbornyl (meth) acrylate copolymer, etc.). It is preferable to use poly (meth) acrylate C _1-6 alkyl esters such as poly (meth) acrylate, and to use methyl methacrylate as the main component (50 to 100% by weight, and 70 to 100). Methyl methacrylate resin is more preferred.

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

Cellulose ester resin is an ester of cellulose and fatty acid. Specific examples of the cellulose ester-based resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Among these resins, cellulose triacetate (cellulose triacetate) is particularly preferred.

The base film may be composed of one cellulose ester resin, a mixture of two or more cellulose ester resins, or a copolymer of two or more cellulose ester resins.

The polycarbonate resin is a polymer containing a monomer unit bonded via a carbonate group. The polycarbonate-based resin may be, for example, a resin called modified polycarbonate modified with a polymer skeleton in order to reduce the photoelastic coefficient, a copolymerized polycarbonate with improved wavelength dependence, and the like.

The base film may be composed of one polycarbonate resin, a mixture of two or more polycarbonate resins, or a copolymer of two or more polycarbonate resins.

Any appropriate additives may be added to the base film in addition to the above-mentioned thermoplastic resin. Examples of such additives include ultraviolet absorbers, antioxidants, smoothing agents, plasticizers, release agents, anti-colorants, flame retardants, nuclear agents, antistatic agents, pigments, and coloring agents. The content of the thermoplastic resin in the base film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, and even more preferably 60 to 98% by weight, and even more 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 possibility that the high transparency and the like originally possessed by the thermoplastic resin may not be sufficiently expressed.

Although the thickness of the substrate film 1 can be appropriately determined, generally, in terms of operability such as strength and handling, it is preferably 1 to 500 μm, more preferably 1 to 300 μm, and 5 to 200 μm. Even more preferred is 5 to 150 μm.

The width of the base film 1 can be appropriately determined, and may be 500 mm or more, or 1,000 mm or more. In the laminated film of the present invention, even if the width is 500 mm or more, wrinkles and slacks at both ends in the width direction can be effectively suppressed. The length of the base film 1 is longer than the width. Yes, it may be 100 m or more, and 500 m or more is suitable.

From the viewpoint of suppressing defects such as wrinkles and wrinkles in the drying step and poor drying of the coating layer, the tensile modulus of the base film at 80 ° C may be 140 MPa or more, preferably 180 MPa or more, and 200 MPa or more Better. Moreover, the tensile modulus of the base film at 80 ° C. is generally 1,000 MPa or less, preferably 800 MPa or less, and more preferably 600 MPa or less. If the tensile elastic modulus of the base film at 80 ° C exceeds 1,000 MPa, a large force is required in the stretching step, and the device becomes huge.

(Pretreatment of substrate film)

In order to improve the adhesion with the polyvinyl alcohol-based resin layer, if necessary, a pretreatment is performed on the surface of the base film 1 by a pretreatment method.

(Surface activation)

For example, as shown in FIG. 1 (a), on the surface of the substrate film 1 supplied from the unwinding section 30, the substrate film 1 may be subjected to a surface activation method 42 such as corona treatment, plasma treatment, or flame treatment. Surface activation treatment.

(Primer layer formation)

In addition, in order to improve the adhesion with the polyvinyl alcohol-based resin layer, the primer layer may be formed on the surface of the base film 1 by a primer layer forming method, and preferably the primer layer is formed by a primer layer forming method. The lacquer layer is formed on the surface subjected to the surface activation treatment.

For example, as shown in Fig. 1 (b), After the coating liquid for forming a primer layer is coated on the surface of the base film 1 supplied from the unwinding section 32, the coating layer is dried by the drying method 46 to obtain a base film having a primer layer. The base film 1 can be wound by the winding unit 33. The coating liquid for forming a primer layer may contain a resin component and a solvent. The resin component is preferably a thermoplastic resin excellent in transparency, heat stability, elongation, and the like, and examples thereof include (meth) acrylic resins and polyvinyl alcohol resins. As the solvent, a general organic solvent that can dissolve the resin component described above, and an aqueous solvent such as water can be used.

A crosslinking agent may be added to the coating liquid for forming a primer layer to increase the strength of the primer layer. The crosslinking agent may be appropriately selected from known ones such as organic and inorganic based on the type of thermoplastic resin used. As the cross-linking agent, the cross-linking agent described in WO2013 / 146644 can be used. It is preferable that the primer layer coating liquid 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 method 44 in which the coating liquid for forming a primer layer is applied to the base film 1 may be the same as or different from the coating method 48 for forming a polyvinyl alcohol-based resin layer described later.

(Application of polyvinyl alcohol resin solution)

After the pretreatment, as shown in FIG. 1 (c), for example, a coating layer 2 is formed on the surface of the base film 1 supplied from the unwinding section 34 by a coating method 48 to form a coating layer 2. . Solution of polyvinyl alcohol resin The powder of the polyvinyl alcohol resin is obtained by dissolving it in an aqueous solvent such as water.

Examples of the polyvinyl alcohol-based resin include a polyvinyl alcohol resin and a derivative thereof. Examples of polyvinyl alcohol resin derivatives include polyvinyl formaldehyde; polyvinyl acetal; polyvinyl alcohol resins are olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, and unsaturated carboxylic acids. Alkyl esters, acrylamide and other modified people.

The average degree of polymerization of the polyvinyl alcohol resin is preferably 100 to 10,000, and more preferably 1,000 to 10,000. Especially preferred is 1,500 to 8,000, and most preferred is 2,000 to 5,000. The average degree of polymerization is a value obtained by a method prescribed by JIS K 6726 (1994). If the average degree of polymerization is less than 100, it is difficult to obtain good optical characteristics. When it exceeds 10,000, the solubility with respect to water will deteriorate and it will become difficult to form a resin layer.

The polyvinyl alcohol-based resin is preferably a saponified product. The range of the 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 having a saponification degree of 98.0 to 99.5 mol% can be used.

When the saponification degree is less than 80.0 mol%, it is difficult to obtain good optical characteristics. The degree of saponification is the ratio of the acetic acid group contained in the polyvinyl acetate resin of the raw material of the polyvinyl alcohol resin to the hydroxyl group by the saponification step, which is expressed in unit ratio (mol%) and is defined by the following formula Value: Saponification degree (mol%) = (hydroxyl number) / (hydroxyl number + acetic acid group number) × 100, and can be obtained by a method prescribed by 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 even more preferably 5 to 10% by weight. If it is less than 5% by weight, the moisture content increases and the drying efficiency deteriorates. When it exceeds 15 weight%, viscosity will become high and handling will become difficult.

The viscosity of the solution during 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, it will be difficult to adjust the film thickness, and if it exceeds 10,000 cps, the liquid delivery will become difficult. The viscosity of the solution can be adjusted by heating or cooling the solution, in addition to the composition of the solution.

Examples of the aqueous solvent include alcohols such as water and methanol.

The solution may contain additives such as a plasticizer and a surfactant, if necessary. As the plasticizer, a polyhydric alcohol or a condensate thereof can be used, and examples thereof include glycerol, diglycerol, triglycerol, ethylene glycol, propylene glycol, and polyethylene glycol. The blending amount of the additives is preferably 20% by weight or less of the polyvinyl alcohol-based resin.

As an example of the coating method 48, a roll coating method such as a bar coating method, a reverse coating method, and a gravure coating method may be appropriately selected; a die coating method; a comma coating method; a die lip coating ( Lip coating method; spin coating method; knife coating method; screen coating method; fountain coating method; dip coating method; spray coating method and the like. In the step of applying the polyvinyl alcohol-based resin solution, the solution is continuously applied while the base film 1 is transported to the longitudinal direction thereof. The length direction may not necessarily be horizontal. The coating is preferably performed on the upper surface of the base film 1.

The average film thickness (WET film thickness) of the solution of the applied polyvinyl alcohol-based resin can be, for example, 50 to 200 μm. Solution coating width The degree may be the same as the total width of the base film 1, but may be narrower than the total width of the base film 1.

As shown in FIG. 2 (a), in the present invention, the coating layer 2 is formed by applying a solution of a polyvinyl alcohol-based resin so that the central portion of the coating layer 2 in the width direction becomes thicker than both end portions. . Such coating methods include, for example, a method in which a blade with a curved blade shape is used in the gravure coating method so that the amount of the solution to be scraped is reduced in the central portion and increased in both ends; The coating method is a method in which the gap formed between the leading edge and the blade edge to discharge the coating liquid and the liquid storage portion is wide at the center and narrow at both ends. In the knife coating method, It is a method of using a curved blade with a curved blade shape to make the distance between the base film and the blade edge wider at the center and narrower at both ends. In the comma coating method, the film body of the film is wound on a support. Both ends of a backup roll have a method in which the distance between the comma roll and the base film is wider at the center and narrower at both ends.

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

Usually, a thick coating of about 5.0% is sufficient. In addition, the film thickness measured at a position 50 mm from the edge was defined as the film thickness having a larger difference between the two measured values and the film thickness measured at the center.

The coating layer 2 is obtained by applying the polyvinyl alcohol-based resin solution in this manner, and the coating layer 2 is dried to form a coating layer 2 that satisfies the above formula (1-1). 的 Polyvinyl alcohol-based resin layer 3.

(Drying step)

Next, while the substrate film 1 to which the solution has been applied is transported in its longitudinal direction, the applied solution is dried by the drying method 50, as shown in FIG. 3 (a). The laminated film 10 of the present invention of the polyvinyl alcohol-based resin layer 3.

In the drying step, the transport direction of the base film 1 is preferably horizontal, but as long as it is about 45 ° with respect to the horizontal system, it can be transported in a direction inclined with respect to the horizontal.

As an example of the drying method 50, there is a floating drier that supports the substrate film 1 in the air by supplying hot air from both sides of the substrate film instead of contacting it, and irradiates the substrate film 1 that can be transported in the air with infrared rays. Infrared dryer, microwave dryer.

The drying temperature is, for example, the temperature of the resin layer during drying, or the temperature of the hot air when hot air is supplied to the substrate film 1, and can be set to 50 to 200 ° C, preferably 60 to 150 ° C, and more preferably 80 ° C or more good. When the solution contains water, the temperature is preferably set to 80 ° C or higher. The drying time, that is, the running time for transporting the film in the drying mode can be set to 2 to 20 minutes. In the drying step, it is preferable to apply a solution on the upper surface of the base film 1.

By this drying step, as shown in FIG. 3 (a), a laminated film 10 having a polyvinyl alcohol-based resin layer 3 on one surface of the base film 1 can be formed. In terms of imparting good polarizing performance and durability, after drying, The average value of the thickness of the polyvinyl alcohol-based resin layer 3 is usually 20 μm or less, and preferably 10 μm or less. The average value of the thickness of the polyvinyl alcohol-based resin layer 3 is usually 2 μm or more.

Furthermore, the surface pretreatment, solution coating, and drying steps of the surface of the substrate film 1 may be performed again on the opposite side of the substrate film, as shown in FIG. 3 (b). A laminated film 10 having a polyvinyl alcohol-based resin layer 3 is formed on both sides of the film 1.

In addition, pretreatment and solution application may be performed on both sides of the base film 1, and the coating layers provided on both sides of the base film 1 may be simultaneously dried.

In addition, in the above-mentioned embodiment, the method of performing each step of the pre-treatment, the formation of the primer layer, and the formation (coating and drying) of the resin layer in batches is shown, that is, although it is shown in each step The film reel is obtained afterwards, and the film is unwound from the reel and processed in the next step. However, any two or more steps in these steps may be continuously performed, that is, without rolling into a reel. Perform 2 or more steps in succession.

(Manufacturing method of stretch laminated film)

Next, the obtained laminated film 10 is unwound from the film roll (the polyvinyl alcohol-based resin layer 3 may be provided on only one side of the base film 1 or the polyvinyl alcohol-based resin layer 3 may be provided on both sides of the base film 1), The stretching is performed to obtain the stretched laminated film of the present invention. In addition, the dyeing step may be performed before the stretching step, or the stretching step and the dyeing step may be performed simultaneously. Moreover, it can be extended in the air or in water. Preferably, the stretched laminated film is wound into a roll to obtain a stretched laminated film reel. The shelf life of stretch laminated film reels is 2 years Within 1 year is preferred, and within 1 year. When the delivery time of the reel from the extending step to the next step is also considered as the storage period, the storage period is usually 30 minutes or more. In order to prevent warpage caused by the movement of water and deterioration of the surface state, it is better to store it by using moisture-proof measures such as covering an extended laminated film roll with an aluminum retort film.

After completing the steps in this manner, the film is temporarily made into a roll shape, so that the loss at the time of a problem in any step or at the start-up step becomes smaller than the loss at the time of successively performing the steps. The storage of the reels other than the stretch laminated film reel may be the same as that described above.

For extension, various known methods can also be used. For example, it may be a longitudinal extension extending in the longitudinal direction of the laminated film 10, a lateral extension extending in the width direction of the laminated film 10, or an oblique extension. Among them, it is preferable to perform longitudinal stretching (uniaxial) stretching while conveying the laminated film 10 in the longitudinal direction. The extension magnification can be appropriately adjusted according to the required polarization characteristics. For example, it can be set to 5 to 17 times and 5 to 8 times.

Extension can be performed in one stage or in multiple stages.

In the stretching step, it is preferable that the base film is also integrally stretched as the polyvinyl alcohol-based resin layer is stretched. That is, it is preferable that the stretching ratio of the polyvinyl alcohol-based resin layer is substantially the same as the stretching ratio of the base film. The stretching ratio is substantially the same, which means that the difference between the stretching ratio of the polyvinyl alcohol-based resin layer and the stretching ratio of the substrate film is 0, and the difference is preferably 0.0. In addition, the extension of the polyvinyl alcohol resin layer The extending direction with the base film is preferably substantially the same. The extending directions are substantially the same, which means that the angle formed by the extending direction of the polyvinyl alcohol-based resin layer and the extending direction of the substrate film is less than 5 °, and the formed 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 even more preferably 5.5 μm or less. Furthermore, in terms of imparting good durability, the average value of the thickness in the width direction of the stretched polyvinyl alcohol-based resin layer is usually 1 μm or more, and preferably 2 μm or more.

(Manufacturing method of polarizing laminated film)

In the dyeing step, various known methods such as immersing a laminated film or an extended laminated film in a dyeing tank can be used. For example, a dichroic pigment can be used as the dye. Examples of dichroic pigments include iodine and organic dyes. During dyeing, a cross-linking treatment of polyvinyl alcohol may be performed in a resin tank. After dyeing, the laminated film is preferably washed with water and dried.

The average value of the 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. In general, the average value of the thickness of the polarizer layer is usually 1 μm or more, and preferably 2 μm or more.

(Manufacturing method of polarizing plate)

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

In the present invention, since sags and wrinkles at both ends in the width direction of the polarizing laminated film can be suppressed, when the protective film is bonded to the polarizer layer, the polarizing plate can be manufactured with high yield and stability.

As the protective film 3, various known films can be used. For example, a 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-curable epoxy resin can be used.

The obtained polarizing plate can be wound on a shaft to form a polarizing plate reel and stored as needed. In the polarizing plate of this embodiment, the thickness in the widthwise end portion of the polarizer layer 5 is not too thick compared to the thickness in the widthwise center portion of the polarizer layer 5. Therefore, even if the polarizer is stored as a roll, it is stored In this case, the same effect of preventing slack as described above can be exhibited. If necessary, roll out the polarizing plate from the roll after storage and cut it to the required size. The obtained polarizing plate can be made thin, can be suitably used as a polarizing material such as a liquid crystal display element, and can be incorporated into a liquid crystal display.

[Example]

Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples. In the example, except Unless otherwise stated, parts and% used amount and content are based on weight.

[Measurement of film thickness of coating layer]

The film thickness of the coating layer was measured by a film thickness measuring machine (SI-80T) manufactured by Keyence Co., Ltd. at a position 50 mm from the edge in the width direction of the coating layer and at the center. The film thickness of the coating layer was measured on the inline at intervals of 7 mm in the MD direction, and the film thickness data of 10 meters (m) minutes were averaged.

[Other film thickness measurement]

The interference film thickness meter (F20) manufactured by Filmetrics was used to measure the film thickness over the entire width in the width direction. The measurement was performed while the sample was moved by the automatic stage so that the acquisition interval of the film thickness data was 2 mm or less.

[Example 1] <Production of laminated film> (1) Substrate film

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

(2) Preparation of coating liquid

Polyvinyl alcohol resin powder ("Z-200" manufactured by Nippon Synthetic Chemical Industry Co., Ltd., with an average degree of polymerization of 1,100 and an average degree of saponification of 99.5 mole%) was dissolved in hot water at 95 ° C to prepare a concentration of 3% by weight. Polyethylene Alcohol solution. A cross-linking agent ("SUMIREZ RESIN (registered trademark) 650" manufactured by Sumitomo Chemical Co., Ltd.) was mixed with 2 parts by weight of the polyvinyl alcohol resin powder in the obtained aqueous solution to obtain a primer layer-forming coating. Cloth fluid.

Then, polyvinyl alcohol resin powder ("PVA124" manufactured by Kuraray Co., Ltd., with an average degree of polymerization of 2400 and an average degree of saponification of 98.0 to 99.0 mole%) was dissolved in hot water at 95 ° C to prepare a polymer having a concentration of 8% by weight. A coating liquid for forming a resin layer of an aqueous vinyl alcohol solution.

(3) Coating and drying ‧Single-area layer

While continuously transporting the base film, corona treatment is applied to one side of the base film. On the corona-treated surface of the base film, the coating liquid for forming the primer layer was continuously applied by a micro gravure coater, and dried at 60 ° C. for 3 minutes to form a primer layer having a thickness of 0.2 μm. . Next, the above-mentioned coating liquid for forming a resin layer was continuously coated on the primer layer by a comma coating method while the base film was being conveyed, thereby obtaining a coating layer. By winding a polyethylene terephthalate film with a thickness of 20 μm around both ends of the support roll, the distance between the comma-type doctor roll and the base film becomes wider at the center and narrow at both ends. By drying the coating layer at 80 ° C. for 10 minutes in a drying furnace, a polyvinyl alcohol (PVA) -based resin layer having 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) of the coating layer in the width direction, the center was about 3.5% thicker than the both end portions (positions 50 mm from the edges). In the film thickness distribution in the width direction of the resin layer, D1e-D1c = -0.54 μm.

‧Two-area layer

In addition, the surface (second coating surface) opposite to the surface (first coating surface) on which the resin layer was formed on the base film was subjected to the same treatment as in the production of the single-area layered product to form a thickness of 0.2. A primer layer of μm and a polyvinyl alcohol-based resin layer having an average thickness in the width direction of 9.6 μm were prepared as a two-area layer. Then, the laminated film (two-area layer) is rolled into a reel shape to obtain a laminated film reel.

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 approximately 3.0% thicker than the both end portions (50 mm from the edge). In the film thickness distribution in the width direction of the resin layer, D1e-D1c = -0.40 μm.

<Production of stretched laminated film> (4) Extend

While rolling out the laminated film (two-area layer) from the laminated film roll obtained in the above (3) and continuously conveying it, it was extended between the rolls at a stretching temperature of 140 ° C in the longitudinal direction (MD direction) to 2.5 times the original, and then The stretching temperature was 160 ° C in the longitudinal direction until the total stretching ratio became 5.8 times, and a stretched laminated film was produced. The extended laminated film is further wound into a reel shape to obtain an extended laminated film reel. When the laminated film was rolled up, wrinkles and slack were not observed at both ends in the width direction of the laminated film, and slack was observed at the center in the width direction. However, in the stretch-laminated film, it was not possible to confirm at the ends / centers in the width direction at the same time. To wrinkles, sagging.

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

<Production of Polarized Multilayer Film> (5) Dyeing / crosslinking

Extend the extended laminated film from the extended laminated film roll obtained in the above (4), soak the extended laminated film in a dyeing solution containing iodine and potassium iodide at 30 ° C so that the residence time is about 150 seconds, and dye the resin layer Treatment, followed by washing excess dyeing solution with pure water at 10 ° C. Next, the stretched multilayer film was immersed in a cross-linking solution at 76 ° C. containing boric acid and potassium iodide so that the retention time was 600 seconds, and subjected to a crosslinking treatment to obtain a polarizing multilayer film. Then, the polarizing laminated film was washed with pure water at 10 ° C for 4 seconds, and dried at 80 ° C for 300 seconds. The polarizing laminated film was further wound to produce a polarizing laminated film roll. In addition, when the stretch-laminated film was rolled out, no wrinkles or sags were observed at both the end portions and the central portion.

The average thicknesses of the polarizer layers in the width direction of the first coating surface and the second coating surface in the polarizing laminated film are 5.8, respectively. μm and 5.8 μm. At this time, the film thickness distribution in the width direction of the polarizer layer on the first coating surface and the second coating surface is D5e-D5c = -0.12 μm and -0.09 μm, respectively. When the two polarizer layers included in the 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 of the polarizing laminated film in the width direction, D7e-D7c = 1.21 μm.

The polarizer layer on the second coating surface side was peeled off and removed to prepare a polarizing laminated film including two layers of the base material / the polarizer layer on the first coating surface side. Both ends and a central portion of the polarizing laminated film were cut out to prepare samples.

With a integrating sphere spectrophotometer (manufactured by JASCO Corporation, V7100), the light-corrected monomer transmittance Ty of the sample having the polarizer layer on the side of the first coating surface was measured. Incident light is incident from the polarizer layer side. In the polarizer layer on the first coating surface side, within the Ty at both ends, the photocorrection monomer transmittance Tye, which has a large difference from the photocorrection monomer transmittance Tyc in the central portion, is 42.51%. At this time, the polarization degree Py is 99.983%. The Tyc in the center is 42.34%, and the degree of polarization Py is 99.978%.

The polarizer layer on the removed second coating surface side was also measured for Ty in the same manner. In the polarizer layer on the second coating surface side, within the Ty at both ends, the photocorrection monomer transmittance Tye, which has a large difference from the photocorrection monomer transmittance Tyc at the center, is 42.59%. At this time, the polarization degree Py is 99.980%. The central part Tyc is 42.52%, and the degree of polarization Py is 99.981%.

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

<Production of Polarizing Plate> (6) Adjustment of adhesive solution

Polyvinyl alcohol resin powder ("KL-318" manufactured by Kuraray Co., Ltd., average polymerization degree 1,800) was dissolved in hot water at 95 ° C to prepare a polyvinyl alcohol aqueous solution having a concentration of 3% by weight. In the obtained aqueous solution, 1 part by weight of a crosslinking agent ("SUMIREZ RESIN (registered trademark) 650" manufactured by Sumitomo Chemical Co., Ltd.) was mixed with 2 parts by weight of a polyvinyl alcohol resin powder to prepare an adhesive solution.

After the polarized laminated film roll obtained in the above (5) is rolled out, the polarized laminated film is rolled, and after the above-mentioned adhesive solution is coated on the polarized photonic layers of both sides, a saponified protective film is applied to the bonding surface [including A transparent protective film of cellulose triacetate (TAC) ("KC4UY" manufactured by Konica Minolta Co., Ltd.), having a thickness of 40 [mu] m] was bonded to each of the polarizer layers. The polarizer layer is pressed against the TAC film between a pair of laminating rollers to obtain a TAC film, a polarizer layer, a primer layer, a substrate film, a primer layer, a polarizer layer, and a TAC film. Laminating film. When the polarizing laminated film was rolled up, no wrinkles and slack were observed at both the end portions and the central portion.

The bonding film was separated from the base film and the primer layer therein, and the bonding film was divided into the following two films: a film having a TAC film, a polarizer layer, a primer layer, and a base film in this order , And a film having a primer layer, a polarizer layer, and a TAC film in this order. Second, the substrate film is peeled and removed to obtain Sequential polarizer with TAC film / polarizer layer / primer layer. No defects such as cracking of the original sheet film were generated in the aforementioned peeling step.

[Example 2]

Except that the substrate film in Example 1 was changed to a polyethylene terephthalate (PET) film with a thickness of 38 μm, and a primer layer was not formed on the substrate film, the other side was produced in the same operation. Laminates. 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 center was about 3.3% thicker than both end portions (a position 50 mm from the edge). In the film thickness distribution in the width direction of the resin layer, D1e-D1c = -0.32 μm.

Take the laminated film roll to the laminated film roll, and then roll out the laminated film from the laminated film roll. At this time, wrinkles and slack were not recognized at both ends in the width direction of the laminated film, and slack was confirmed at the center in the width direction.

[Comparative Example 1] ‧Single-area layer

Except that the film thickness distribution (WET film thickness) of the coating layer was not specifically controlled, a single-area layered product was produced in the same manner as in Example 1. At this time, the film thickness of the coating layer was almost flat in the width direction. The average thickness of the polyvinyl alcohol-based resin layer in the width direction was 9.7 μm. In the film thickness distribution in the width direction of the resin layer at this time, D1e-D1c = 0.68 μm.

‧Two-area layer

In addition, as for the surface (second coating surface) opposite to the surface (first coating surface) where the resin layer is formed in the base film, the film thickness distribution (WET film thickness) of the coating layer is not specifically implemented. Except for the control of), a resin layer was formed by the same operation as in Example 1 to produce a laminated film (two-area layered product). The laminated film is then 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 coating surface was 9.8 μm. In the film thickness distribution in the width direction of the resin layer, D1e-D1c = 0.64 μm.

The same operation as in Example 1 was performed, and the laminated film was extended to produce an extended laminated film. Then, the extended laminated film is wound to obtain an extended laminated film reel. When the laminated film was rolled up, slack was confirmed only at both end portions of the laminated film.

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

Next, the same operation was performed except that the residence time of the stretched laminated film in the dyeing solution in Example 1 was set to about 170 seconds. The self-stretched laminated film roll was used to roll out the stretched laminated film, and the dyeing step and crosslinking were performed Steps to produce a polarizing laminated film. Then, the polarizing laminated film is wound up to obtain a polarizing laminated film roll. When the stretch laminated film is rolled out, Slack was confirmed only at both ends of the stretched laminated film. The average thicknesses of the polarizer layers in the width direction of the first coated surface and the second coated surface in the polarizing laminated film were 5.9 μm and 5.9 μm, respectively.

At this time, in the film thickness distribution in the width direction 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 polarizing 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 D6e-D6c = 1.3 μm. In the film thickness distribution of the total thickness of the polarizing laminated film in the width direction, D7e-D7c = 2.11 μm.

The polarizer layer on the second coating surface side was peeled off and removed to prepare a polarizing laminated film including two layers of the base material / the polarizer layer on the first coating surface side. Both ends and a central portion of the polarizing laminated film were cut out to prepare samples.

The same operation as in Example 1 was performed to measure Ty of a sample having a polarizer layer on the first application surface side.

In the polarizer layer on the first application surface side, within the Ty at both ends, the Tye having the larger difference compared with the Tyc at the center is 41.52%, and the polarization degree Py is 99.997%. The central part Tyc is 41.10%, and the degree of polarization Py is 99.998%.

Further, the same measurement as in Example 1 was performed on the polarizer layer on the second coated surface side that was removed.

In the polarizer layer on the second coating surface side, within the Ty at both ends, the Tye having a larger difference from the Tyc at the center is 41.42%, and the polarization degree Py at this time is 99.998%. The Tyc in the center is 40.94%, and the polarization Py is 99.998%.

Therefore, the value of | Tye-Tyc | is 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 polarizing laminated film was rolled out from the self-polarizing laminated film roll, it was confirmed that the both ends in the width direction were loosened. Although the adhesive solution was applied to the two polarizer layers in the polarizing laminated film and the protective film was bonded, the slack portion became wrinkles 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. Unless otherwise stated, the unit of numerical values in the table is μm. Therefore, in the extending step and the dyeing step of the present invention, both ends in the width direction are suppressed from being loosened, a polarizing plate can be stably manufactured, and the optical characteristics in the width direction are uniform.

[Industrial availability]

According to the present invention, it is difficult to cause wrinkles and slack at both ends in the width direction of the long laminated film, and it is possible to reduce the number of parts that cannot be used as a product. Percent area. Moreover, a polarizing plate with uniform optical characteristics in the width direction can be obtained. In addition, the protective film can be easily bonded to a polarizing laminated film, and a polarizing plate can be stably manufactured.

Claims (16)

A laminated film is a laminated film having a substantially unstretched polyvinyl alcohol-based resin layer on at least one side of a long substrate film, and when the polyvinyl alcohol-based resin layer is equally divided into 9 regions in the width direction , The average film thickness D1e of the outermost region and the average film thickness D1c of the central region satisfy the following formulae (1-1) and (1-2): D1e-D1c ≦ -0.3 μm (1-1) D1e-D1c ≧ -2.0 μm (1-2) Among them, the average film thickness D1e of the outermost region is an average film having a larger difference between the average film thickness of each of the two outermost regions and the average film thickness D1c of the central region. thick. The laminated film according to item 1 of the scope of patent application, wherein the average value of the thickness in the width direction of the substantially unstretched polyvinyl alcohol-based resin layer is 10 μm or less. An extended laminated film is an extended laminated film having an extended polyvinyl alcohol-based resin layer on at least one side of a long substrate film, and the extended polyvinyl alcohol-based resin layer is divided into 9 in the width direction. In each region, the average film thickness D2e of the outermost region and the average film thickness D2c of the central region satisfy the following equations (2-1) and (2-2): D2e-D2c ≦ 0.25 μm (2-1) D2e-D2c ≧ -1.2 μm (2-2), where the average film thickness D2e of the outermost region is the one having the larger difference between the average film thickness of each of the two outermost regions and the average film thickness D2c of the central region Average film thickness. The stretched laminated film according to item 3 of the scope of patent application, wherein the average thickness of the stretched polyvinyl alcohol-based resin layer in the width direction is 7 μm or less. The extended laminated film according to item 3 or item 4 of the scope of patent application, wherein when the substrate film is equally divided into 9 regions in the width direction, the average film thickness D3e of the outermost region and the average film of the central region The thickness D3c satisfies the following formula: D3e-D3c ≦ 1.0 μm, wherein the average film thickness D3e of the outermost region is the difference between the average film thickness of each of the two outermost regions and the average film thickness D3c of the central region. The larger is the average film thickness. The stretched laminated film according to item 3 or 4 of the scope of patent application, wherein when the stretched laminated film is equally divided into 9 regions in the width direction, the average film thickness D4e of the outermost region and the average film thickness of the central region D4c satisfies the following formula: D4e-D4c ≦ 1.5 μm, where the average film thickness D4e of the outermost region is set to be the difference between the average film thickness of each of the two outermost regions and the average film thickness D4c of the central region. The larger is the average film thickness. A polarizing laminated film is a polarizing laminated film having a polarizer layer on at least one side of a long substrate film. When the polarizer layer is divided into 9 regions in the width direction, the average film in the outermost region The thickness D5e and the average film thickness D5c in the central region satisfy the following equations (5-1) and (5-2): D5e-D5c ≦ 0.25 μm (5-1) D5e-D5c ≧ -0.2 μm (5-2) Among them, The average film thickness D5e of the outermost region is the average film thickness of the one having the larger difference between the average film thickness of each of the two outermost regions and the average film thickness D5c of the central region. The polarizing laminated film according to item 7 of the scope of patent application, wherein the average thickness of the polarizer layer in the width direction is 7 μm or less. The polarizing laminated film according to item 7 or item 8 of the scope of patent application, wherein when the substrate film is equally divided into 9 regions in the width direction, the average film thickness D6e of the outermost region and the average of the central region The film thickness D6c satisfies the following formula: D6e-D6c ≦ 1.0 μm, wherein the average film thickness D6e of the outermost region is set to be the average film thickness of each of the two outermost regions and the average film thickness D6c of the central region. The larger the average film thickness. The polarizing laminated film according to item 7 or 8 of the scope of patent application, wherein when the polarizing laminated film is equally divided into 9 regions in the width direction, the average film thickness D7e of the outermost region and the average of the central region The film thickness D7c satisfies the following formula: D7e-D7c ≦ 1.5 μm, where the average film thickness D7e in the outermost region is set to be the average film thickness of each of the two outermost regions and the average film thickness D7c in the central region The larger the average film thickness. The polarizing laminated film according to item 7 or item 8 of the patent application scope, wherein the photometric correction monomer transmittance Tye measured at a position 25 mm from the widthwise edge of the polarizer layer and the The photometric correction unit transmittance Tyc measured in the center of the width direction satisfies the following formula: | Tye-Tyc | ≦ 0.40%, where the photometric correction unit transmittance Tye measured at a position 25 mm from the edge is set to two The photometric correction cell transmittance having the larger difference between the measured value and the photometric correction cell transmittance Tyc measured at the center. A method for producing a laminated film, comprising: applying an aqueous solution containing a polyvinyl alcohol-based resin to at least one side of a long base film so that a central portion in a width direction of a coating layer is thicker than both end portions; Forming a coating layer; and drying the coating layer to form a polyvinyl alcohol resin-containing resin layer satisfying the following formulae (1-1) and (1-2); D1e-D1c ≦ -0.3 μm (1-1) D1e-D1c ≧ -2.0 μm (1-2). A method for manufacturing an stretched laminated film, comprising the steps of obtaining a stretched laminated film by uniaxially extending the laminated film obtained by the manufacturing method described in item 12 of the application for a patent to more than 5 times. A method for manufacturing an extended laminated film reel includes the steps of: winding the extended laminated film obtained by the manufacturing method described in item 13 of the patent application into a roll to obtain an extended laminated film reel. A method for manufacturing a polarizing laminated film, comprising: an extended laminated film obtained by the manufacturing method described in item 13 of the patent application scope or an extended laminated film obtained by the manufacturing method described in item 14 of the patent application scope Step of dyeing an extended laminated film rolled out of a laminated film roll to obtain a polarized laminated film. A method for manufacturing a polarizing plate, comprising: attaching and protecting a surface on a side opposite to a substrate film side of a polarizer layer of a polarizing laminated film obtained by the manufacturing method described in Item 15 of a patent application scope; A step of laminating a film to obtain a multilayer film; and a peeling step of peeling the substrate film from the multilayer film.