JP2016221797A - Laminated film and method for producing laminated film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such problems that end parts of a laminate film in a width direction cannot be used for a polarizing plate because uneven dyeing is caused in the width direction by wrinkles or sagging and that if a polarizing laminate film obtained after a dyeing process has wrinkles or sagging, a protective film cannot be laminated, which makes stable production of a polarizing plate impossible.SOLUTION: A laminate film is provided, which has a substantially unstretched polyvinyl alcohol resin layer on at least one surface of a long base film. When the polyvinyl alcohol resin layer is equally divided into 9 regions in a width direction, the laminate film satisfies a formula of D1e-D1c≤-0.3 μm, where D1e represents an average film thickness in the outermost region and D1c represents an average film thickness in the center region.SELECTED DRAWING: Figure 2

Description

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

  Conventional polarizers are manufactured by stretching and dyeing a polyvinyl alcohol-based resin film (usually about 30 to 75 μm), and the thickness of the stretched film is usually about 12 to 30 μm. . When a film of 30 μm or less is used as the original film of polyvinyl alcohol resin for thinning, there is a problem of productivity such that the film is easily broken during stretching.

  Therefore, in order to cope with the recent thinning of the polarizing plate, 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 resin layer is formed by coating an aqueous solution containing a polyvinyl alcohol resin on a base film to obtain a laminated film, and then the laminated film is stretched and dyed. Thus, a polarizing layer is obtained by imparting a polarizing function to the polyvinyl alcohol-based resin layer (Patent Document 1).

JP 2009-0986653 A

  When obtaining a polarizing laminated film by a method of coating an aqueous solution containing a polyvinyl alcohol-based resin, the polarizing laminated film is generally produced 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, when a stretched laminated film is wound up in a roll after the stretching step to obtain a stretched laminated film roll, and the stretched laminated film is unwound from the stretched laminated film roll to carry out the dyeing step, the width in the unrolled long film Wrinkles and slack may occur at both ends of the direction. After winding the film into a roll, wrinkles and slacks that occur at both ends of the unwound film are also generated in the laminated film, and unevenness of dyeing occurs in the width direction due to these wrinkles and slacks. There arises a problem that both end portions in the width direction cannot be used for the polarizing plate. Moreover, when wrinkles and slack have arisen in the polarizing laminated film obtained after a dyeing process, there existed a problem that a polarizing plate could not be manufactured stably, without bonding of a protective film.

The present invention includes the following.
[1] A laminated film comprising a substantially unstretched polyvinyl alcohol-based resin layer on at least one surface of a long base film, wherein the polyvinyl alcohol-based resin layer is divided into nine regions in the width direction. When equally divided, an average film thickness D1e in the outermost region and an average film thickness D1c in the central region satisfy the following formula.
D1e-D1c ≦ −0.3 μm
The average film thickness D1e in the outermost region is the average film thickness having the larger difference from the average film thickness D1c in the central region among the average film thicknesses in the two outermost regions.
[2] The laminated film according to [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] A stretched laminated film comprising a stretched polyvinyl alcohol-based resin layer on at least one surface of a long base film, wherein the stretched polyvinyl alcohol-based resin layer has 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 formula when equally divided into two.
D2e-D2c ≦ 0.25 μm
The average film thickness D2e in the outermost region is the average film thickness that has a larger difference from the average film thickness D2c in the central region among the average film thicknesses in the two outermost regions.
[4] The stretched laminated film according to [3], wherein the average value of the thickness in the width direction of the stretched polyvinyl alcohol resin layer is 7 μm or less.
[5] When the base film is equally 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 formula [3] or [ 4].
D3e-D3c ≦ 1.0 μm
The average film thickness D3e in the outermost region is the average film thickness in which the difference between the average film thickness D3c in the central region and the average film thickness in the two outermost regions is larger.
[6] When the stretched laminated film is equally 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 equations [3] to [5 ] The stretched laminated film in any one of.
D4e-D4c ≦ 1.5 μm
The average film thickness D4e in the outermost region is the average film thickness that has a larger difference from the average film thickness D4c in the central region among the average film thicknesses in the two outermost regions.
[7] A polarizing laminated film including a polarizer layer on at least one surface of a long base film, and the outermost region when the polarizer layer is equally divided into nine regions in the width direction. A polarizing laminate film in which the average film thickness D5e and the average film thickness D5c of the central region satisfy the following formula.
D5e-D5c ≦ 0.25 μm
The average film thickness D5e in the outermost region is the average film thickness in which the difference between the average film thickness D5c in the central region and the average film thickness in the two outermost regions is larger.
[8] The polarizing laminated film according to [7], wherein the average thickness in the width direction of the polarizer layer is 7 μm or less.
[9] When the base film is equally 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 formula [7] or [ 8].
D6e-D6c ≦ 1.0 μm
The average film thickness D6e in the outermost region is the average film thickness in which the difference between the average film thickness D6c in the center region and the average film thickness in the two outermost regions is larger.
[10] When the polarizing laminated film is equally 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] The polarizing laminated film according to any one of [9].
D7e-D7c ≦ 1.5 μm
The average film thickness D7e in the outermost region is the average film thickness in which the difference between the average film thickness D7c in the center region and the average film thickness in the two outermost regions is larger.
[11] 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 of the polarizer layer are expressed by the following equations: The polarizing laminated film according to any one of [7] to [10], which is satisfied.
| Tye-Tyc | ≦ 0.40%
It should be noted that the visibility corrected single transmittance Tye measured at a position 25 mm from the edge is the visibility corrected single transmittance with the larger difference between the two measured values and the visibility corrected single transmittance Tyc measured at the center. To do.
[12] An aqueous solution containing a polyvinyl alcohol-based resin is applied to at least one surface of the long base film so that the central portion is thicker than both ends in the width direction of the coating layer. The manufacturing method of a laminated film including the process of forming a layer, and the process of drying a coating layer and forming the resin layer which consists of polyvinyl alcohol-type resin.
[13] A method for producing a stretched laminated film, comprising a step of uniaxially stretching the laminated film according to [12] more than 5 times to obtain a stretched laminated film.
[14] A method for producing a stretched laminated film roll, comprising a step of winding the stretched laminated film according to [13] around a roll to obtain a stretched laminated film roll.
[15] Production of a polarizing laminated film including a step of obtaining a polarizing laminated film by dyeing the stretched laminated film according to [13] or the drawn laminated film rolled out from the stretched laminated film roll according to [14] Method.
[16] A laminating process for obtaining a multilayer film by laminating a protective film on a surface opposite to the base film side in the polarizer layer of the polarizing laminated film according to [15], and the base from the multilayer film The manufacturing method of a polarizing plate including the peeling process which peels a material film.

  According to the present invention, wrinkles and slack are less likely to occur at both ends in the width direction of the long laminated film, and the area of a portion that does not become a product can be reduced. In addition, a polarizing plate having uniform optical characteristics in the width direction can be obtained. Furthermore, since a protective film can be easily bonded to a polarizing laminated film, a polarizing plate can be produced stably.

It is a figure explaining the manufacturing method of the laminated film which concerns on one Embodiment of this invention. It is a schematic sectional drawing which shows an example of the base film which has a coating layer obtained by one Embodiment of this invention. It is a schematic sectional drawing which shows an example of the laminated | multilayer film obtained by one Embodiment of this invention. It is a schematic sectional drawing which shows an example of the extending | stretching laminated | multilayer film obtained by one Embodiment of this invention. It is a schematic sectional drawing which shows an example of the light-polarizing laminated film obtained by one Embodiment of this invention. It is a schematic sectional drawing which shows the position of the outermost area | region and center area | region in the coating layer obtained by one Embodiment of this invention. It is a schematic sectional drawing of the extending | stretching laminated | multilayer film in case the extending | stretched polyvinyl alcohol-type resin layer does not satisfy | fill the prescription | regulation of this invention.

  When a polarizer layer is obtained by a method of coating an aqueous solution containing a polyvinyl alcohol-based resin, a polarizing laminate film is usually produced by a method including the following steps.

(Coating process) The process of applying the aqueous solution containing a polyvinyl alcohol-type resin to the at least one surface of a elongate base film, and obtaining a coating layer.
(Drying process) The process of obtaining a laminated film by drying a coating layer and forming a polyvinyl alcohol-type resin layer (it may only be called a resin layer).
(Extension process) The process of extending | stretching a laminated film and obtaining a stretched laminated film.
(Dyeing step) A step of immersing the stretched laminated film in a dyeing solution containing iodine to obtain a polarizing laminated film.

  In order to suppress the occurrence of wrinkles and slack at both ends in the width direction of the polarizing laminated film, the inventor should manufacture the following intermediate product in each step of manufacturing the polarizing plate. I found it. The length in the longitudinal direction of the intermediate product (laminate film, stretched laminate film and polarizing laminate film) of the present invention may be 100 m or more, or 500 m or more. When the length of the film is 100 m or more, the winding diameter becomes large, so that usually tightening tends to occur. However, the present invention can effectively prevent wrinkles and slack from occurring at both ends in the width direction. Usually, the length of the film is 10,000 m or less.

[Intermediate product: Laminated film]
In a laminated film having a polyvinyl alcohol resin layer on a long substrate film, when the polyvinyl alcohol resin layer is equally divided into nine regions in the width direction, the average film thickness D1e and the center of the outermost region It is important that the average film thickness D1c of the region satisfies the following formula (1-1), and it is preferable to satisfy the formula (1-2). D1e-D1c is preferably −0.4 μm or less, more preferably −1.5 μm or more, and even more preferably −1.3 μm or more. The average film thickness D1e in the outermost region is the average film thickness having the larger difference from the average film thickness D1c in the central region among the average film thicknesses in the two outermost regions.
D1e-D1c ≦ −0.3 μm (1-1)
D1e-D1c ≧ −2.0 μm (1-2)

  When the laminated film includes a polyvinyl alcohol-based resin layer on both sides of the base film, it is sufficient that the polyvinyl alcohol-based resin layer disposed on at least one surface of the base film satisfies the formula (1-1). It is preferable that any polyvinyl alcohol-type resin layer arrange | positioned on the surface of a base film satisfy | fills Formula (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 outline of the film thickness distribution in the width direction. And that a polyvinyl alcohol-type resin layer satisfy | fills Formula (1-1) represents that the polyvinyl alcohol-type resin layer whose film thickness distribution of the width direction is convex is arrange | positioned on a base film. In this way, when 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), Compared with the case where the film thickness distribution is concave, the tension applied to the end in the width direction of the laminated film roll can be reduced. As a result, it is considered that winding tightening is less likely to occur at both ends in the width direction of the laminated film roll, and wrinkles and slack can be suppressed from occurring at both ends in the width direction of the unrolled laminated film.

  In addition, although wrinkles and slack may arise in the width direction center part of the laminated | multilayer film unwound from the laminated film roll, wrinkles and slack of the width direction center part can be eliminated by the extending process of a post process. On the other hand, it is difficult to eliminate wrinkles and slacks generated at both ends in the width direction by the stretching process. It is preferable that the polyvinyl alcohol-based resin layer satisfies formula (1-2) in that wrinkles and slack in the central portion in the width direction can be easily eliminated.

  Since the laminated film is a film before being subjected to a stretching process or a dyeing process, the polyvinyl alcohol-based resin layer is substantially unstretched. “Unstretched” means that the draw ratio in the drawing direction is 0.99 to 1.01.

  In this specification, the width direction means a direction perpendicular to the longitudinal direction of the long laminated film and parallel to the laminated film surface. When the laminated film is produced by a roll-to-roll method, the width direction is perpendicular to the laminated film transport direction (MD direction) and coincides with the direction parallel to the laminated film surface (TD direction). Of course, the longitudinal direction coincides with the MD direction. Further, when the laminated film of the present invention is subjected to a longitudinal stretching process to obtain a stretched laminated film, and further to a process including a dyeing process to obtain a polarizing laminated film, the normal stretching direction is the longitudinal direction of the laminated film. The absorption axis direction of the polarizing laminated film coincides with the longitudinal direction of the laminated film. This relationship is the same even in a polarizing plate in which a transparent protective film is bonded to a polarizing laminated film and a base film is peeled off, and the same is true even in a single wafer cut into a predetermined size. It is.

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

[Intermediate product: Stretched laminated film]
The stretched laminated film includes a stretched polyvinyl alcohol-based resin layer on at least one surface of a long base film. The stretched laminated film is a film that can also be obtained by stretching the laminated film. The draw ratio of a polyvinyl alcohol-type resin layer can be 5-17 times, for example, and can also be 5-8 times. When the stretched polyvinyl alcohol-based resin layer is equally 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 are expressed by the following equation (2-1): It is important to satisfy the condition, and it is preferable to satisfy the formula (2-2). D2e-D2c is preferably 0.20 μm or less, more preferably 0.15 μm or less, and preferably −1.0 μm or more. The average film thickness D2e in the outermost region is the average film thickness that has a larger difference from the average film thickness D2c in the central region among the average film thicknesses in the two outermost regions.
D2e-D2c ≦ 0.25 μm (2-1)
D2e-D2c ≧ −1.2 μm (2-2)

  When the polyvinyl alcohol resin layer stretched on both surfaces of the base film is provided, the polyvinyl alcohol resin layer disposed on at least one surface of the base film only needs to satisfy the formula (2-1). It is preferable that any polyvinyl alcohol-type resin layer arrange | positioned on the surface of a base film satisfy | fills Formula (2-1).

  When the stretched polyvinyl alcohol-based resin layer satisfies the formula (2-1), when the stretched laminated film is wound into a stretched laminated film roll, both ends in the width direction for the same reason as the laminated film. It is considered that it is possible to suppress the occurrence of wrinkles and slack at both ends in the width direction.

When the base film is equally divided into nine regions in the width direction in the stretched laminated film, it is possible to more effectively suppress the tightening of the stretched laminated film roll. The average film thickness D3c of the region preferably satisfies the following formula (3-1), and more preferably satisfies the 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 in the outermost region is the average film thickness in which the difference between the average film thickness D3c in the central region and the average film thickness in the two outermost regions is larger.
D3e−D3c ≦ 1.0 μm (3-1)
D3e-D3c ≧ −1.0 μm (3-2)

  The polyvinyl alcohol resin layer and the base film are preferably 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 resin layer. That is, not only the polyvinyl alcohol-based resin layer but also the substrate film can change the film thickness distribution in the width direction. Therefore, when the film thickness distribution in the width direction of the stretched polyvinyl alcohol resin layer does not satisfy the formula (2-1), for example, the stretched polyvinyl alcohol resin layer has a concave film thickness distribution as shown in FIG. (D2e-D2c> 0.25 μm), the film thickness distribution in the width direction of the base film may be deformed into a concave shape (D3e-D3c> 1.0 μm) 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 the formula (2-1) and is nearly smooth, so that deformation of the base film is suppressed. .

In addition, when the stretched laminated film is equally 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 are expressed by the following formula (4-1). It is preferable to satisfy | fill, and it is more preferable to satisfy | fill Formula (4-2) further. 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 in the outermost region is the average film thickness that has a larger difference from the average film thickness D4c in the central region among the average film thicknesses in the two outermost regions.
D4e-D4c ≦ 1.5 μm (4-1)
D4e-D4c ≧ −2.0 μm (4-2)

  The thickness of the stretched laminated film refers to the total thickness, and is the sum of the thickness of the base film in the stretched laminated film and the thickness of the stretched resin layer. When the polyvinyl alcohol 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 polyvinyl alcohol resin layer, and the polyvinyl alcohol resin layer is provided on both sides of the base film. In this case, the total thickness is a thickness obtained by adding the sum of the thicknesses of the pair of polyvinyl alcohol-based resin layers to the thickness of the base film. Therefore, when the polyvinyl alcohol resin layer is provided on both surfaces of the base film and the formula (4-1) is satisfied, the stretched laminated film roll more effectively suppresses wrinkles and slack at both ends in the width direction. be able to.

  When the laminated film satisfies the formula (1-1) as described above, the cross-sectional shape in the width direction is convex. Compared with the value of Formula (1-1), the value of Formula (2-1) is larger because the thin film end in the laminated film becomes thicker due to neck-in during stretching, and the cross section in the width direction This is probably 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.

[Intermediate product: Polarizing laminated film]
The polarizing laminated film includes a polarizer layer on at least one surface of a long base film. The 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 by a process including a dyeing process. The film thickness distribution in the width direction of each layer (polarizer layer, substrate film) provided in the normal polarizing laminate film reflects the film thickness distribution in the width direction of each layer provided in the stretched laminate film.

Therefore, similarly to the stretched laminated film, when the polarizer layer is equally 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 are expressed by the following formula (5- It is important to satisfy 1), and it is preferable to satisfy the formula (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, and preferably −0.15 μm or more, − More preferably, it is 0.1 μm or more. The average film thickness D5e in the outermost region is the average film thickness in which the difference between the average film thickness D5c in the central region and the average film thickness in the two outermost regions is larger.
D5e-D5c ≦ 0.25 μm (5-1)
D5e-D5c ≧ −0.2 μm (5-2)

  When the polarizing laminate film includes a polarizer layer on both surfaces of the base film, the polarizer layer disposed on at least one surface of the base film only needs to satisfy the formula (5-1). It is preferable that any polarizer layer disposed on the surface of the film satisfies the formula (5-1).

  When the polarizer layer satisfies the formula (5-1) in the width direction, when the polarizing laminated film is wound up to become a polarizing laminated film roll, it is difficult to cause tightening at both ends in the width direction. It is considered that wrinkles and slack can be suppressed at both ends in the direction.

When the base film is equally divided into nine areas in the width direction in the polarizing laminated film, the average film thickness D6e of the outermost area can be reduced in that the winding of the polarizing laminated film roll can be more effectively suppressed. It is preferable that the average film thickness D6c of the central region satisfies the following formula (6-1), and it is more preferable to satisfy formula (6-2). D6e-D6c is more preferably 0.9 μm or less, more preferably −1.0 μm or more, and even more preferably −0.8 μm or more. The average film thickness D6e in the outermost region is the average film thickness in which the difference between the average film thickness D6c in the center region and the average film thickness in the two outermost regions is larger.
D6e-D6c ≦ 1.0 μm (6-1)
D6e-D6c ≧ −1.5 μm (6-2)

In addition, when the polarizing laminated film is equally divided into nine regions in the width direction, the average film thickness D7e in the outermost region and the average film thickness D7c in the central region are expressed by the following formula (7− It is preferable to satisfy 1), and it is more preferable to satisfy the formula (7-2). D7e-D7c is preferably 1.3 μm or less, more preferably −1.0 μm or more, and even more preferably 0 μm or more. The average film thickness D7e in the outermost region is the average film thickness in which the difference between the average film thickness D7c in the center region and the average film thickness in the two outermost regions is larger.
D7e-D7c ≦ 1.5 μm (7-1)
D7e-D7c ≧ −2.0 μm (7-2)

  The thickness of the 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 polarizing laminated film. When the 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 the polarizer layer is provided on both sides of the base film, the total thickness is based on The thickness is obtained by adding the sum of the thicknesses of the pair of polarizer layers to the thickness of the material film. Therefore, when the polarizer film is provided on both surfaces of the base film and the formula (7-1) is satisfied, the polarizing laminated film roll more effectively suppresses wrinkles and slack at both ends in the width direction. Can do.

Also, in terms of obtaining a polarizing plate with more uniform polarization performance, the visibility correction single transmittance Tye measured at a position 25 mm from the edge in the width direction of the polarizer layer and the visibility correction measured at the center in the width direction. The single 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 | is usually 0.00% or more. It should be noted that the visibility corrected single transmittance Tye measured at a position 25 mm from the edge is the visibility corrected single transmittance with the larger difference between the two measured values and the visibility corrected single transmittance Tyc measured at the center. To do.
| Tye-Tyc | ≦ 0.40% (8-1)

Visibility correction single transmittance (Ty) at a wavelength 380 nm to 780 nm, determined a polarizing laminate film MD direction of the transmittance _{(T MD)} and TD direction of the transmittance _{(T TD),} wherein represents the following (9 ) To calculate the single transmittance at each wavelength, and further to correct the visibility with a 2 degree visual field (C light source) of JIS Z 8701.
Single transmittance (%) = ( _TMD + _TTD ) / 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.

  Hereinafter, an embodiment is described with reference to drawings about a manufacturing method of a lamination film of the present invention, a manufacturing method of a polarizing lamination film, and a manufacturing method of a polarizing plate.

(Laminated film manufacturing method)
FIG. 1 is a flowchart showing a method for producing 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 can 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 resins; cellulose triacetate, cellulose diester Cellulose ester resins such as acetate; polycarbonate resins; polyvinyl alcohol resins; polyvinyl acetate resins, polyarylate resins; polystyrene resins; polyethersulfone resins; polysulfone resins; polyamide resins; .

  The base film may have a single-layer structure composed of one resin layer composed of one or two or more thermoplastic resins, or a plurality of resin layers composed of one or two or more thermoplastic resins are laminated. It may be a multilayer structure.

  Further, the base film may be a stretched product or may be unstretched. In the case of a stretched product, it may be uniaxial stretching or biaxial stretching.

  Examples of the chain polyolefin-based resin include homopolymers of chain olefins such as polyethylene resins and polypropylene resins, and copolymers composed of two or more chain olefins. A base film made of a chain polyolefin-based resin is preferable in that it is easily stretched stably at a high magnification. Among them, the base film is composed mainly of polypropylene resin (polypropylene resin which is a propylene homopolymer, copolymer mainly composed of propylene, etc.), polyethylene resin (polyethylene resin which is a homopolymer of ethylene or ethylene). And the like.

  The copolymer mainly composed of propylene is a copolymer of propylene and another monomer copolymerizable therewith. Examples of other monomers copolymerizable with propylene include ethylene and α-olefin. As the α-olefin, an α-olefin having 4 or more carbon atoms is preferable, and an α-olefin having 4 to 10 carbon atoms is more preferable. Specific examples of the α-olefin having 4 to 10 carbon atoms include linear monoolefins such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene and 1-decene; 3-methyl Branched monoolefins such as -1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene; and vinylcyclohexane. The copolymer of propylene and other monomers copolymerizable therewith may be a random copolymer or a block copolymer. Content of the said other monomer is 0.1-20 weight% in a copolymer, for example, Preferably it is 0.5-10 weight%.

  Among these, as the polypropylene resin, a propylene homopolymer, a propylene-ethylene random copolymer, a propylene-1-butene random copolymer or a propylene-ethylene-1-butene random copolymer is preferably used.

  Cyclic polyolefin resin is a general term for resins that are polymerized using cyclic olefins as polymerization units, and cyclic olefin ring-opening (co) polymers, cyclic olefin addition polymers, cyclic olefins and chain olefins such as ethylene and propylene. Copolymers (typically random copolymers), graphene polymers obtained by modifying these with unsaturated carboxylic acids or derivatives thereof, and hydrides thereof. Among these, norbornene resins using norbornene monomers such as norbornene and polycyclic norbornene monomers as cyclic olefins are preferably used.

  The base film may be composed of one kind of cyclic polyolefin-based resin, may be composed of a mixture of two or more kinds of cyclic polyolefin-based resins, or may be composed of two or more kinds of cyclic polyolefin-based resins. It may be composed of a polymer.

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

  Specific examples of polyester resins include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, poly (ethylene methylene terephthalate), poly (ethylene methylene naphthalate), polycyclohexane dimethyl terephthalate, polycyclohexane dimethyl naphthalate, etc. Can be mentioned. In the case of a polyester resin film such as polyethylene terephthalate, it can be stretched in advance to increase the elastic modulus. Stretching may be uniaxial stretching or biaxial stretching.

  The base film may be composed of one kind of polyester resin, may be composed of a mixture of two or more kinds of polyester resins, or may be composed of a copolymer of two or more kinds of polyester resins. It may be configured.

Examples of (meth) acrylic resins include poly (meth) acrylic esters such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymers, methyl methacrylate- (meth) acrylic acid ester copolymers , Methyl methacrylate-acrylic acid ester- (meth) acrylic acid copolymer, (meth) methyl acrylate-styrene copolymer (MS resin, etc.), polymer having an alicyclic hydrocarbon group (for example, methacrylic acid) Methyl methacrylic acid cyclohexyl copolymer, methyl methacrylate- (meth) acrylic acid norbornyl copolymer, etc.). Preferably, poly (meth) acrylate C _1-6 alkyl such as methyl poly (meth) acrylate is used, more preferably methyl methacrylate as the main component (50 to 100% by weight, preferably 70 to 100% by weight). %) Is used.

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

  The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, cellulose dipropionate, and the like. Among these, cellulose triacetate (triacetyl cellulose) is particularly preferable.

  The base film may be composed of one kind of cellulose ester resin, may be composed of a mixture of two or more kinds of cellulose ester resins, or may be composed of two or more kinds of cellulose ester resins. It may be composed of a polymer.

  The polycarbonate resin is made of a polymer in which monomer units are bonded via a carbonate group. The polycarbonate-based resin may be a resin called a modified polycarbonate in which the polymer skeleton is modified in order to lower the photoelastic coefficient, or a copolymerized polycarbonate having a modified wavelength dependency.

  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 resins, or may be composed of a copolymer of two or more types of polycarbonate-based resins. It may be configured.

  Arbitrary appropriate additives other than said thermoplastic resin may be added to the base film. Examples of such additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, anti-coloring agents, flame retardants, nucleating 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, still more 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, the high transparency inherent in the thermoplastic resin may not be sufficiently exhibited.

  Although the thickness of the base film 1 can be determined as appropriate, it is generally preferably 1 to 500 μm, more preferably 1 to 300 μm, even more preferably 5 to 200 μm from the viewpoint of workability such as strength and handleability. Most preferred is ˜150 μm.

  Although the width | variety of the base film 1 can be determined suitably, it can be 500 mm or more, and can also be 1000 mm or more. In the laminated film of the present invention, even if the width is 500 mm or more, wrinkles and slack at both ends in the width direction can be effectively suppressed. Moreover, although the length of the base film 1 should just be longer than a width | variety, it can be set to 100 m or more, and it is suitable to set it as 500 m or more.

  From the viewpoint of suppressing defects such as wrinkles or folds in the drying process and poor drying of the coating layer, the base film can have a tensile elastic modulus at 80 ° C. of 140 MPa or more, and can be 180 MPa or more. More preferably, it is more preferably 200 Pa or more. Moreover, the tensile elasticity modulus in 80 degreeC of a base film is 1000 MPa or less normally, it is preferable that it is 800 MP or less, and it is more preferable that it is 600 MPa or less. If the tensile modulus of elasticity of the base film at 80 ° C. exceeds 1000 MPa, a large force is required in the stretching process, and the apparatus may become huge.

(Pretreatment of base film)
In order to improve the adhesion to the polyvinyl alcohol-based resin layer, the surface of the base film 1 can be pretreated by pretreatment means as necessary.
(Surface activation)
For example, as shown in FIG. 1A, the surface of the base film 1 supplied from the unwinding section 30 is applied to the surface of the base film 1 by surface activation means 42 such as corona treatment, plasma treatment or flame treatment. Surface activation treatment can be performed.

(Primer layer formation)
Moreover, in order to improve adhesiveness with a polyvinyl alcohol-type resin layer, a primer layer may also be formed on the surface of the base film 1, preferably on the surface subjected to the surface activation treatment by a primer layer forming means. it can.

  For example, as shown in FIG. 1 (b), after applying the primer layer forming coating liquid onto the surface of the base film 1 supplied from the unwinding section 32 by the coating means 44, the drying means 46 The base material film having the primer layer can be obtained by drying the coating layer, and the base material film 1 can be wound up by the winding unit 33 thereafter. The primer layer forming coating solution may contain a resin component and a solvent. As the resin component, a thermoplastic resin excellent in transparency, thermal stability, stretchability, and the like is preferably used, and examples thereof include (meth) acrylic resins and polyvinyl alcohol resins. As the solvent, a general organic solvent capable of dissolving the resin component and an aqueous solvent such as water are usually used.

  In order to increase the strength of the primer layer, a crosslinking agent may be added to the primer layer forming coating solution. A suitable crosslinking agent is appropriately selected from known ones such as organic and inorganic based on the type of thermoplastic resin used. As a crosslinking agent, the crosslinking agent described in WO2013 / 146644 can be used. The primer coating liquid 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.

  An example of the coating means 44 for applying the primer layer forming coating solution 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. Also good.

(Coating of polyvinyl alcohol resin solution)
After the pretreatment, for example, as shown in FIG. 1 (c), the surface of the base film 1 supplied from the unwinding section 34 is coated with a solution of a polyvinyl alcohol resin by the coating means 48. The coating layer 2 is formed. The polyvinyl alcohol resin solution can be obtained by dissolving polyvinyl alcohol resin powder in an aqueous solvent such as water.

  Examples of polyvinyl alcohol resins are polyvinyl alcohol resins and derivatives thereof. Examples of polyvinyl alcohol resin derivatives include polyvinyl formal; polyvinyl acetal; polyvinyl alcohol resin such as 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. Etc.

  100-10000 are preferable and, as for the average degree of polymerization of polyvinyl alcohol-type resin, 1000-10000 are more preferable. In particular, 1500 to 8000 is more preferable, and 2000 to 5000 is most preferable. The average degree of polymerization is a numerical value obtained by a method defined by JIS K 6726 (1994). If the average degree of polymerization is less than 100, it is difficult to obtain preferable optical characteristics. If it exceeds 10,000, the solubility in water deteriorates and it becomes difficult to form a resin layer.

The polyvinyl alcohol 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 93.0 to 99.5 mol%. Is more preferable. For example, a polyvinyl alcohol resin having a saponification degree of 98.0 to 99.5 mol% can be used. When the degree of saponification is less than 80.0 mol%, it is difficult to obtain preferable optical characteristics. The saponification degree is a unit ratio (mol%) representing the ratio of the acetate group contained in the polyvinyl acetate resin, which is the raw material of the polyvinyl alcohol resin, to the hydroxyl group by the saponification step.
Degree of saponification (mol%) = (number of hydroxyl groups) / (number of hydroxyl groups + number of acetate groups) × 100
It can be obtained by the method defined in JIS K 6726 (1994).

  The solid concentration in the solution is preferably 5% by weight or more, more preferably 5 to 15% by weight, still more preferably 5 to 10% by weight. If it is less than 5% by weight, the amount of water increases and the drying efficiency deteriorates. If it exceeds 15% by weight, the viscosity tends to be high and handling tends to be difficult.

  As for the viscosity of the solution at the time of coating, 500-10000 cps is preferable, 1000-7000 cps is more preferable, 1000-5000 cps is further more preferable. When the viscosity is less than 500 cps, it tends to be difficult to control the film thickness, and when it exceeds 10,000 cps, liquid feeding tends to be difficult. In addition to the composition of the solution, the viscosity of the solution can also be adjusted by heating or cooling the solution.

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

  The solution may contain additives such as a plasticizer and a surfactant as necessary. As the plasticizer, a polyol or a condensate thereof can be used, and examples thereof include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. The blending amount of the additive is preferably 20% by weight or less of the polyvinyl alcohol resin.

  Examples of the coating means 48 are wire bar coating method, roll coating method such as reverse coating, gravure coating, die coating method, comma coating method, lip coating method, spin coating method, knife coating method, screen coating method, fountain coating The method can be appropriately selected from known methods such as a dipping method and a spray method. In the coating step of the polyvinyl alcohol-based resin solution, the solution is continuously applied while the base film 1 is conveyed in the longitudinal direction. The longitudinal direction is not necessarily 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 polyvinyl alcohol-type resin to apply can be 50-200 micrometers, for example. The coating width of the solution can be matched with the full width of the base film 1, but may be narrower than the full width of the base film 1.

  As shown in FIG. 2 (a), in the present invention, a polyvinyl alcohol-based resin solution is applied so that the central portion is thicker than both ends in the width direction of the coating layer 2, and the coating layer 2 is formed. Form. As such a coating method, for example, in the gravure coating method, a doctor blade having a curved blade edge shape is used, and the amount of the solution to be scraped is small in the central portion and large in both end portions; In the die coating method, a method in which the gap between the slit for discharging the coating liquid formed between the front edge and the doctor edge and the liquid reservoir is wide at the center and narrow at both ends; In the knife coating method, using a knife with a curved blade edge shape, the distance between the base film and the blade edge is wide at the center and narrow at both ends; A thin film is wrapped around both ends so that the distance between the comma roll and the base film is in the center. Widely it has, a method to be narrower at the ends.

  In 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 is the film thickness measured at a position 50 mm from the edge in the width direction of the coating layer. In comparison, 2.5% or more thick coating is preferable, and 3.0% or more thick coating is preferable. In general, it is sufficient to apply the coating to a thickness of about 5.0%. The film thickness measured at a position 50 mm from the edge is the film thickness having the larger difference between the film thickness measured at the center of the two measured values.

  Thus, the polyvinyl alcohol-type resin layer 3 which satisfy | fills above-mentioned Formula (1-1) is formed by applying the polyvinyl alcohol-type resin solution, obtaining the coating layer 2, and drying this coating layer 2. can do.

(Drying process)
Subsequently, the coated solution is dried by the drying means 50 while the substrate film 1 coated with the solution is conveyed in the longitudinal direction, and the substrate film 1 as shown in FIG. The laminated film 10 of the present invention having the polyvinyl alcohol resin layer 3 thereon is obtained.

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

  The example of the drying means 50 is a floating dryer which supplies hot air from both sides of the base film and supports the base film 1 in the air without contact, and irradiates the base film 1 conveyed in the air with infrared rays. Infrared dryer and microwave dryer.

  The drying temperature, for example, the temperature of the resin layer at the time of drying, or the temperature of the hot air when hot air is applied to the base film 1 can be, for example, 50 to 200 ° C., and can be 60 to 150 ° C. Preferably, it is 80 ° C. or higher. When the solution contains water, these temperatures are preferably 80 ° C. or higher. The drying time, that is, the time for the transport film to travel in the drying means can be 2 to 20 minutes. In the drying step, the solution is preferably applied to the upper surface of the base film 1.

  By this drying step, a laminated film 10 having a polyvinyl alcohol-based resin layer 3 on one surface of the base film 1 is formed as shown in FIG. The average value of the thickness of the polyvinyl alcohol-based resin layer 3 after drying is usually 20 μm or less, preferably 10 μm or less in that good polarization performance and durability can be imparted. Moreover, the average value of the thickness of the polyvinyl alcohol-type resin layer 3 is 2 micrometers or more normally.

  In addition, as shown in FIG. 3B, the above-described pretreatment of the surface of the base film 1, application of the solution, and drying are performed again on the opposite surface of the base film as necessary. The laminated film 10 having the polyvinyl alcohol resin layer 3 on both surfaces of the base film 1 may be formed. Further, pretreatment and solution coating may be performed on both surfaces of the base film 1, and the coating layers provided on both surfaces of the base film 1 may be simultaneously dried.

  In the above embodiment, each process of pretreatment, primer layer formation, and resin layer formation (coating and drying) is a batch method, that is, a film roll is obtained after each process, and the next process In the above method, the film is unwound from the roll and processed, but any two or more of these steps are continuously performed, that is, two or more steps are continuously performed without being wound on the roll. Also good.

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

  Thus, after each process is completed, the film is once rolled to reduce loss when trouble occurs in any process or when the process is started up as compared to when each process is performed continuously. . Storage of rolls other than the stretched laminated film roll can be the same as described above.

  Various known methods can be used for stretching. For example, it may be longitudinal stretching that extends in the longitudinal direction of the laminated film 10, transverse stretching that extends in the width direction of the laminated film 10, or oblique stretching. Especially, it is preferable to extend | stretch the laminated | multilayer film 10 longitudinally (uniaxially), conveying in a longitudinal direction. The draw ratio can be appropriately adjusted 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 a single stage or in multiple stages.

  In the stretching step, 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 a polyvinyl alcohol-type resin layer and the draw ratio of a base film are substantially the same. 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 0.0. Preferably there is. Moreover, it is preferable that the extending | stretching direction of a polyvinyl alcohol-type resin layer and the extending | stretching direction of a base film are substantially the same. That the stretching direction is 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 formed is It is preferably less than 1 °.

  The average thickness in the width direction of the stretched polyvinyl alcohol-based resin layer is preferably 10 μm or less, more preferably 7 μm or less, and even more preferably 5.5 μm or less. Moreover, the average value of the thickness of the stretched polyvinyl alcohol-type resin layer in the width direction is 1 micrometer or more normally in the point that favorable durability can be provided, Preferably it is 2 micrometers or more.

(Production method of polarizing laminated film)
Various known methods such as immersing a laminated film or a stretched laminated film in a dyeing tank can be used for the dyeing step. For example, a dichroic dye can be used as the dye. Examples of dichroic pigments are iodine and organic dyes. In dyeing, a crosslinking treatment of polyvinyl alcohol in a resin tank may be performed. After dyeing, the laminated film is preferably washed with water and dried.

  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. Further, the average value of the thickness of the polarizer layer is usually 1 μm or more, preferably 2 μm or more.

(Production method of polarizing plate)
Then, the manufacturing method of a polarizing plate is demonstrated. First, a protective film is stuck on the polarizer layer 5 of the polarizing laminated film 12 via an adhesive to obtain a multilayer film. When the polarizer layer 5 is provided on both surfaces of the base film 1, a protective film is attached on each polarizer layer 5. Then, the base film 1 is peeled from the multilayer film, and two polarizing plates in which the protective film is bonded to the polarizer layer 5 through an adhesive are obtained. When the polarizing laminated film 12 can have the polarizer layer 5 only on one side, one polarizing plate is obtained.

  In the present invention, since slack and wrinkles at both ends in the width direction of the polarizing laminated film are suppressed, a polarizing plate can be stably produced with low yield when the protective film is bonded to the polarizer layer. Can do.

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

  Various known adhesives can be used as the adhesive. 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 around a shaft and stored as a polarizing plate roll, if necessary. The polarizing plate according to the present embodiment stores the polarizing plate as a roll because the thickness of the widthwise end of the polarizer layer 5 is not so thick as compared to the thickness of the central portion of the polarizer 5 in the widthwise direction. Sometimes, the same anti-sagging effect as described above can be exhibited. If necessary, the polarizing plate can be unwound from the roll after storage and cut into a desired size. The obtained polarizing plate can be thinned, can be suitably used as a polarizing material for liquid crystal display elements, and can be incorporated into a liquid crystal display device.

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

[Measurement of coating layer thickness]
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 a central position with a film thickness measuring machine (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 was 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. The measurement was performed while moving the sample with an automatic stage so that the acquisition interval of the film thickness data was 2 mm or less.

[Example 1]
<Preparation of laminated film>
(1) Base 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 at 80 ° C. of this base film was 205 Mpa.

(2) Preparation of coating solution Polyvinyl alcohol resin powder (“Z-200” manufactured by Nippon Synthetic Chemical Industry Co., Ltd., average polymerization degree 1100, average saponification degree 99.5 mol%) was dissolved in 95 ° C. hot water. A polyvinyl alcohol aqueous solution having a concentration of 3% by weight was prepared. The resulting aqueous solution was mixed with 1 part by weight of a crosslinking agent (“SUMIREZ RESIN (registered trademark) 650” manufactured by Sumitomo Chemical Co., Ltd.) with respect to 2 parts by weight of the polyvinyl alcohol resin powder to obtain a primer layer forming coating solution. It was.

  Polyvinyl alcohol resin powder (“PVA124” manufactured by Kuraray Co., Ltd., average polymerization degree 2400, average saponification degree 98.0 to 99.0 mol%) was dissolved in hot water at 95 ° C., and the polyvinyl alcohol concentration was 8% by weight. A coating solution for forming a resin layer, which is an aqueous solution, was prepared.

(3) Application, drying / single-area layer product The corona treatment was applied to one surface of the substrate film while continuously conveying the substrate film. The primer layer-forming coating solution is continuously applied to the corona-treated surface of the base film 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. did. Then, the said coating liquid for resin layer formation was apply | coated continuously on the primer layer by the comma coating method, conveying a base film, and the coating layer was obtained. By winding a polyethylene terephthalate film having a thickness of 20 μm around both ends of the backup roll, the distance between the comma roll and the base film was wide at the center and narrowed at both ends. The coating layer was dried at 80 ° C. for 10 minutes in a drying furnace to form a polyvinyl alcohol (PVA) resin layer having an average thickness in the width direction of 9.7 μm 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 (positions 50 mm from the edge). In addition, the thickness distribution in the width direction of the resin layer was D1e−D1c = −0.54 μm.

・ Double-sided laminated product Furthermore, the same treatment as that for producing the above single-area layer product was performed on the surface (second coated surface) opposite to the surface (first coated surface) on which the resin layer was formed in the base film. Was applied to form a primer layer having a thickness of 0.2 μm and a polyvinyl alcohol-based resin layer having an average thickness in the width direction of 9.6 μm to produce a double-sided laminate. And the laminated | multilayer film (double-sided laminated product) was wound up in roll shape, and the laminated | multilayer film roll was obtained.

  At this time, in the thickness distribution (WET film thickness) in the width direction of the coating layer on the second coating surface, the center portion was about 3.0% thicker than both end portions (positions at 50 mm from the edge). In addition, the thickness distribution in the width direction of the resin layer was D1e−D1c = −0.40 μm.

<Production of stretched laminated film>
(4) Stretching Up to 2.5 times between the nip rolls at a stretching temperature of 140 ° C. while continuously unwinding the laminated film (double-sided laminated product) from the laminated film roll obtained in (3) above and continuously conveying it. The film was stretched in the machine direction (MD direction) and then stretched in the machine direction at a stretching temperature of 160 ° C. so that the total stretch ratio was 5.8 times to produce a stretched laminated film. Furthermore, the stretched laminated film was wound into a roll to obtain a stretched laminated film roll. When the laminated film was unwound, neither wrinkles nor slack was confirmed at both ends in the width direction of the laminated film, and slack was confirmed at the center in the width direction. However, in the stretched laminated film, neither wrinkles nor slack were observed at the end and 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 film thickness distribution in the width direction 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 provided in the stretched laminated film were peeled and the base film was taken out, the 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.

<Preparation of polarizing laminated film>
(5) Dyeing / Crosslinking The stretched laminated film is unwound from the stretched laminated film roll obtained in (4) above, and the residence time is about 150 seconds in a dyed solution at 30 ° C. containing iodine and potassium iodide. The stretched laminated film was immersed to dye the resin layer, and then the excess dyeing solution was washed away with 10 ° C. pure water. Subsequently, the stretched laminated film was immersed in a 76 ° C. cross-linking solution containing boric acid and potassium iodide so that the residence time was 600 seconds, and a cross-linking treatment was performed to obtain a polarizing laminated film. Thereafter, the polarizing laminated film was washed with pure water at 10 ° C. for 4 seconds and dried at 80 ° C. for 300 seconds. Furthermore, the polarizing laminated film was wound up to produce a polarizing laminated film roll. When the stretched laminated film was unwound, no wrinkles or slack were observed at both ends or 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 polarizing laminated film was 5.8 μm and 5.8 μm, respectively. At this time, the film thickness distribution in the width direction of the polarizer layer on the first coated surface and the second coated surface was D5e−D5c = −0.12 μm and −0.09 μm, respectively. When the two polarizer layers included in the polarizing laminate film were peeled and the base film was taken out, the 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 coating surface side was peeled off and removed to prepare a polarizing laminate film consisting of two layers of substrate / first coating surface side polarizer layer. Both ends and the center of the polarizing laminated film were cut out and used as samples.

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

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

<Preparation of polarizing plate>
(6) Preparation of adhesive solution Polyvinyl alcohol resin powder (“KL-318” manufactured by Kuraray Co., Ltd., average polymerization degree 1800) was dissolved in hot water at 95 ° C. to prepare a 3% by weight polyvinyl alcohol aqueous solution. The resulting aqueous solution was mixed with 1 part by weight of a crosslinking agent (“SUMIREZ RESIN (registered trademark) 650” manufactured by Sumitomo Chemical Co., Ltd.) with respect to 2 parts by weight of the polyvinyl alcohol resin powder to prepare an adhesive solution.

  After the polarizing laminated film is unwound from the polarizing laminated film roll obtained in (5) above, the adhesive solution is applied onto both polarizer layers, and then the saponification treatment is applied to the bonding surface. A film [transparent protective film (“KC4UY” manufactured by Konica Minolta Co., Ltd.) made of triacetylcellulose (TAC), thickness 40 μm] was bonded to each polarizer layer. Bonding having a TAC film / polarizer layer / primer layer / base film / primer layer / polarizer layer / TAC film in this order by pressure bonding the polarizer layer and the TAC film through a pair of bonding rolls. A film was obtained. When the polarizing laminated film was unwound, neither wrinkles nor slack were observed at both ends or the center.

  Two films, a film having a TAC film / polarizer layer / primer layer / base film in this order and a film having a primer layer / polarizer layer / TAC film in this order, are peeled off between the base film and the primer layer in the bonding film. The laminated film was divided into films. Subsequently, the base film was peeled off and a polarizing plate having a TAC film / polarizer layer / primer layer in this order was obtained. No troubles such as film breakage occurred in the peeling step.

[Example 2]
In Example 1, a single-area layer product was produced in the same manner except that the base film was changed to a polyethylene terephthalate (PET) film having a thickness of 38 μm and the primer layer was not formed on the base film. The average thickness in the width direction of the polyvinyl alcohol-based resin layer was 9.5 μm. At this time, in the thickness distribution (WET film thickness) in the width direction of the coating layer, the center portion was about 3.3% thicker than both end portions (positions at 50 mm from the edge). Further, the film thickness distribution in the width direction of the resin layer was D1e−D1c = −0.32 μm.

  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, wrinkles and slack were not confirmed 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 product A single-area layer product was prepared in the same manner as in Example 1 except that the thickness distribution (WET film thickness) of the coating layer was not particularly controlled. At this time, the thickness of the coating layer was almost flat in the width direction. The average thickness in the width direction of the polyvinyl alcohol-based resin layer was 9.7 μm. At this time, the thickness distribution in the width direction of the resin layer was D1e−D1c = 0.68 μm.

・ Double-sided laminated product Furthermore, the film thickness distribution (WET film thickness) of the coating layer particularly on the surface (second coating surface) opposite to the surface (first coating surface) on which the resin layer is formed in the base film The resin layer was formed in the same manner as in Example 1 except that the control of) was not performed, and a laminated film (double-sided laminated product) was produced. And the laminated film was wound up and the laminated film roll was obtained. 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. In addition, the thickness distribution in the width direction of the resin layer was D1e−D1c = 0.64 μm.

  In the same manner as in Example 1, the laminated film was stretched to produce a stretched laminated film. Furthermore, the stretched laminated film was wound up to obtain a stretched laminated film roll. When the laminated film was unwound, looseness 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 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 included in the stretched laminated film were peeled and the base film was taken out, the thickness distribution in the width direction of the base film was D3e−D3c = 1.47 μm. In the thickness distribution of the total thickness in the width direction of the stretched laminated film, D4e−D4c = 2.28 μm.

  Subsequently, in Example 1, except that the residence time of the stretched laminated film in the dyeing solution was about 170 seconds, the stretched laminated film was unwound from the stretched laminated film roll, and the dyeing step and the crosslinking step were performed. A polarizing laminated film was produced. And the polarizing laminated film was wound up and the polarizing laminated film roll was obtained. When the stretched laminated film was unwound, looseness was confirmed only at both ends of the stretched laminated film. The average thickness in the width direction of the polarizer layer on the first coated surface and the second coated surface in the polarizing laminated film was 5.9 μm and 5.9 μm, respectively.

  At this time, the film thickness distribution in the width direction of the polarizer layer on the first coated surface and the second coated surface was D5e−D5c = 0.27 μm and 0.28 μm, respectively. When the two polarizer layers included in the polarizing stretched laminated film were peeled and the base film was taken out, the 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 laminate film, D7e−D7c = 2.11 μm.

  The polarizer layer on the second coating surface side was peeled off and removed to prepare a polarizing laminate film consisting of two layers of substrate / first coating surface side polarizer layer. Both ends and the center of the polarizing laminated film were cut out and used as samples.

  In the same manner 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, Tye having a larger difference from Tyc at both ends compared to Tyc at the center is 41.52%, and at this time, polarization degree Py is 99.997%. It was. The Tyc at the center was 41.10% and the degree of polarization Py was 99.998%.

  Further, 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 coating surface side, Tye having a larger difference from Tyc at both ends compared with Tyc at the center is 41.42%, and at this time, polarization degree Py is 99.998%. It was. The Tyc at the center was 40.94%, and the polarization degree 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 polarizing laminate film was unwound from the polarizing laminate film roll, looseness was confirmed at both ends in the width direction. An adhesive solution was applied onto the two polarizer layers in the polarizing laminate film and an attempt was made to bond the protective film. However, the slack portion was wrinkled and the protective film could not be bonded.

  The results of Examples 1 and 2 and Comparative Example 1 are shown in Tables 1-3. The unit of numerical values in the table is μm unless otherwise specified. As described above, in the present invention, slackening is suppressed at both ends in the width direction in the stretching step and the dyeing step, a polarizing plate can be stably produced, and the optical characteristics are uniform in the width direction.

  According to the present invention, wrinkles and slack are less likely to occur at both ends in the width direction of the long laminated film, and the area of a portion that does not become a product can be reduced. In addition, a polarizing plate having uniform optical characteristics in the width direction can be obtained. Furthermore, a protective film can be easily bonded to a polarizing laminated film, and a polarizing plate can be produced stably.

DESCRIPTION OF SYMBOLS 1 Base film, 2 coating layer, 3 polyvinyl alcohol-type resin layer, 4 stretched polyvinyl alcohol-type resin layer, 5 polarizer layer, 9 base film which has 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 roll, 31, 33, 35 rolls Tobe, 100 Outermost area, 101 Center area

Claims (16)

A laminated film having a substantially unstretched polyvinyl alcohol resin layer on at least one surface of a long base film, wherein the polyvinyl alcohol resin layer is equally divided into nine regions in the width direction. When 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
The average film thickness D1e in the outermost region is the average film thickness having the larger difference from the average film thickness D1c in the central region among the average film thicknesses in the two outermost regions. The laminated film according to claim 1, wherein an average value of thicknesses in the width direction of the substantially unstretched polyvinyl alcohol-based resin layer is 10 μm or less. A stretched laminated film comprising a stretched polyvinyl alcohol-based resin layer on at least one surface of a long base film, wherein the stretched polyvinyl alcohol-based resin layer is equally divided into nine regions in the width direction. When the film is stretched, the average film thickness D2e in the outermost region and the average film thickness D2c in the central region satisfy the following formula.
D2e-D2c ≦ 0.25 μm
The average film thickness D2e in the outermost region is the average film thickness that has a larger difference from the average film thickness D2c in the central region among the average film thicknesses in the two outermost regions. The stretched laminated film according to claim 3, wherein an average value of thicknesses in the width direction of the stretched polyvinyl alcohol-based resin layer is 7 µm or less. When the said base film is equally divided into nine area | regions in the width direction, the average film thickness D3e of an outermost area | region and the average film thickness D3c of a center area | region satisfy | fill the following formula | equation. Stretched laminated film.
D3e-D3c ≦ 1.0 μm
The average film thickness D3e in the outermost region is the average film thickness in which the difference between the average film thickness D3c in the central region and the average film thickness in the two outermost regions is larger. When the stretched laminated film is equally 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 formulas: The stretched laminated film described.
D4e-D4c ≦ 1.5 μm
The average film thickness D4e in the outermost region is the average film thickness that has a larger difference from the average film thickness D4c in the central region among the average film thicknesses in the two outermost regions. A polarizing laminated film having a polarizer layer on at least one surface of a long substrate film, and when the polarizer layer is equally divided into nine regions in the width direction, the average film in the outermost region A polarizing laminate film in which a thickness D5e and an average film thickness D5c in a central region satisfy the following formula.
D5e-D5c ≦ 0.25 μm
The average film thickness D5e in the outermost region is the average film thickness in which the difference between the average film thickness D5c in the central region and the average film thickness in the two outermost regions is larger. The polarizing laminated film according to claim 7, wherein an average value of thicknesses in the width direction of the polarizer layer is 7 μm or less. When the base film is equally 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 expressions. Polarizing laminated film.
D6e-D6c ≦ 1.0 μm
The average film thickness D6e in the outermost region is the average film thickness in which the difference between the average film thickness D6c in the center region and the average film thickness in the two outermost regions is larger. When the polarizing laminated film is equally 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 formulas: The polarizing laminated film described in 1.
D7e-D7c ≦ 1.5 μm
The average film thickness D7e in the outermost region is the average film thickness in which the difference between the average film thickness D7c in the center region and the average film thickness in the two outermost regions is larger. 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 of the polarizer layer satisfy the following expression: The polarizing laminated film in any one of 7-10.
| Tye-Tyc | ≦ 0.40%
It should be noted that the visibility corrected single transmittance Tye measured at a position 25 mm from the edge is the visibility corrected single transmittance with the larger difference between the two measured values and the visibility corrected single transmittance Tyc measured at the center. To do. A coating layer is formed by applying an aqueous solution containing a polyvinyl alcohol-based resin on at least one surface of a long base film so that the central portion is thicker than both ends in the width direction of the coating layer. The manufacturing method of a laminated | multilayer film including the process to dry and the process of drying a coating layer and forming the resin layer which consists of polyvinyl alcohol-type resin. The manufacturing method of the extending | stretching laminated | multilayer film including the process of uniaxially stretching the laminated | multilayer film of Claim 12 over 5 times, and obtaining a stretched laminated film. The manufacturing method of the extending | stretching laminated | multilayer film roll including the process of winding up the extending | stretching laminated | multilayer film of Claim 13 on a roll, and obtaining a stretched laminated film roll. The manufacturing method of a polarizing laminated film including the process of dye | staining the extending | stretching laminated | multilayer film of Claim 13, or the extending | stretching laminated | multilayer film unwound from the extending | stretching laminated film roll of Claim 14, and obtaining a polarizing laminated film. A laminating step of laminating a protective film on a surface opposite to the base film side in the polarizer layer of the polarizing laminate film according to claim 15 to obtain a multilayer film, and the base film from the multilayer film. The manufacturing method of a polarizing plate including the peeling process to peel.

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