JP2021018300A - Manufacturing method of laminated polarization film, drier for polarizer and manufacturing apparatus of polarizer - Google Patents

Abstract

To prevent fine bubbles from occurring between layers of a polarizer and a film, when bonding the polarizer and the film interposing an adhesive pair, after drying the polarizer produced through a wet process.SOLUTION: A manufacturing method includes: a polarizer manufacturing process of manufacturing a long-sized belt-like polarizer 1b through dyeing a long-sized belt-like hydrophilic polymer film 1a with a dyeing process liquid and drawing thereof; a drying process of drying the polarizer 1b; and a laminate process of obtaining a laminated polarization film 1 through bonding the polarizer 1c after the drying and a film 12 using an adhesive agent. In the drying process, the polarizer is dried so that a contraction coefficient in a width direction of the polarizer becomes 15% to 20%.SELECTED DRAWING: Figure 5

Description

The present invention relates to a method for producing a laminated polarizing film by drying a polarizing element produced by a wet stretching method and adhering the dried polarizer to an arbitrary film such as a protective film.

Conventionally, a laminated polarizing film containing a polarizer has been used as a constituent material of a liquid crystal display device, polarized sunglasses, and the like. As the laminated polarizing film, for example, a laminated film containing a polarizing element dyed with a dichroic substance such as iodine and a protective film for protecting the polarizing element is used.
Such a laminated polarizing film can be obtained, for example, by adhering a protective film to one side or both sides of a polarizer with a specific adhesive, as described in Patent Document 1.
Specifically, a step of producing a polarizer by stretching a polyvinyl alcohol-based resin film while dyeing it with an iodine solution and washing it with water, a step of drying the polarizing element after washing with water, and adhering it to the dried polarizer. A laminated polarizing film is obtained through a step of laminating a protective film via an agent.

Japanese Unexamined Patent Publication No. 2012-041533

However, when the polarizer obtained by the wet treatment of dyeing and stretching is dried and then attached to a protective film, air enters between the layers, and as a result, fine bubbles are generated between the polarizer and the protective film. In some cases. The laminated polarizing film is required to have high optical characteristics. Therefore, it is required to bond the polarizer and the film so as not to generate fine bubbles.

A first object of the present invention is a method of producing a laminated polarizing film by adhering a polarizing element and a film via an adhesive after drying a polarizing element produced by a wet treatment. This is to suppress the generation of fine bubbles between layers.
A second object of the present invention is for a polarizer capable of drying a polarizing element so that air does not easily enter when the polarizing element and the film are adhered to each other in a drying device for drying the polarizer manufactured by a wet treatment. It is to provide a drying apparatus and a polarizer manufacturing apparatus.

A long strip-shaped polarizer produced by a wet treatment using a hydrophilic polymer film as a raw material film is stretched in the longitudinal direction (MD direction of the production line). Therefore, when the polarizer produced by the wet treatment is dried by a drying device, it often shrinks in the width direction (TD direction of the production line).
The present inventors have found that when the shrinkage of the polarizer in the width direction is large, fine wrinkles are formed on the polarizer during the drying process. It has been found that when a polarizing element having fine wrinkles formed in the drying step is attached to a film, air enters due to the wrinkles, and fine bubbles are likely to be generated between the polarizer and the film. The present invention was completed based on such findings.

The method for producing a laminated polarizing film of the present invention is a polarizer manufacturing step of producing a long strip-shaped polarizing element by dyeing and stretching a long strip-shaped hydrophilic polymer film with a dyeing treatment solution, wherein the polarizing element is used. It has a drying step of drying and a laminating step of obtaining a laminated polarizing film by adhering a polarizing element after drying and a film with an adhesive, and in the drying step, the shrinkage rate of the polarizer in the width direction. The polarizer is dried so that the ratio is 15% to 20%.

In the preferred production method of the present invention, in the drying step, the polarizer is dried so that the moisture content of the polarizer is 18% by weight or less.
In the preferred production method of the present invention, in the drying step, the polarizing element is dried while being conveyed by a plurality of guide rolls including a rough surface guide roll having a roughened surface.
In the preferred production method of the present invention, the surface roughness of the rough surface guide roll is 1 μm to 20 μm in terms of ten-point average roughness Rz.
In the preferred production method of the present invention, an active energy ray-curable adhesive is used as the adhesive in the laminating step.

According to another aspect of the present invention, there is provided a drying device for a polarizer.
The drying device of the present invention is a drying device that dries a long strip-shaped polarizing element obtained by dyeing and stretching a long strip-shaped hydrophilic polymer film with a dyeing treatment solution, and the polarizing element is used. It has a transport unit including a plurality of guide rolls to be transported and a heating unit for heating a polarizer conveyed by the transport unit, and at least one of the plurality of guide rolls has a surface surface. It is a roughened surface guide roll. Preferably, the surface roughness of the rough surface guide roll is 1 μm to 20 μm in terms of ten-point average roughness Rz.

According to another aspect of the present invention, there is provided an apparatus for producing a polarizer.
The polarizing element manufacturing apparatus of the present invention includes a wet treatment apparatus for producing a long strip-shaped polarizer by dyeing and stretching a long strip-shaped hydrophilic polymer film with a dyeing treatment liquid, and the wet treatment apparatus. It has the drying device for drying the produced polarizing element.

According to the production method of the present invention, it is possible to produce an optically good laminated polarizing film in which fine bubbles are less likely to be generated between the polarizer and the film.
Further, according to the drying apparatus of the present invention, it is possible to obtain a polarizer having an appropriate moisture content after drying, which can suppress the shrinkage of the polarizer during drying.

Sectional drawing of the laminated polarizing film which concerns on one Embodiment of this invention. Sectional drawing of the laminated polarizing film which concerns on other embodiment of this invention. Sectional drawing of the laminated polarizing film which concerns on other embodiment of this invention. Sectional drawing of the laminated polarizing film which concerns on other embodiment of this invention. The schematic which shows the manufacturing apparatus of the laminated polarizing film of this invention. An enlarged schematic view of the drying apparatus of the present invention. (A) is a perspective view of a rough surface guide roll used in a drying device, and (b) is a perspective view of a mirror surface guide roll.

In the present specification, the numerical range represented by "lower limit value X to upper limit value Y" means a lower limit value X or more and an upper limit value Y or less. When a plurality of the numerical range are described separately, it is possible to select an arbitrary lower limit value and an arbitrary upper limit value and set "arbitrary lower limit value to arbitrary upper limit value".
Please note that each figure is for reference only, and the dimensions, scale and shape of the members shown in each figure may differ from the actual ones.

[Laminated polarizing film]
The laminated polarizing film obtained by the production method of the present invention has a polarizer and a film bonded to one side of the polarizer using an adhesive layer. This film is a separate film from the polarizer.
1 to 4 show a configuration example of the laminated polarizing film 1 obtained by the production method of the present invention.
In FIG. 1, in the laminated polarizing film 1 of one embodiment of the present invention, the first film 12, the adhesive layer 31, the polarizer 11, the adhesive layer 32, and the second film 13 are in this order. It is laminated with.
In FIG. 2, the laminated polarizing film 1 of another embodiment of the present invention includes a first film 12, an adhesive layer 31, a polarizer 11, an adhesive layer 32, a second film 13, and an adhesive layer. 33 and the third film 14 are laminated in this order.
In FIG. 3, in the laminated polarizing film 1 of another embodiment of the present invention, the polarizer 11, the adhesive layer 31, the first film 12, the adhesive layer 32, and the second film 13 are in this order. It is laminated with.
In FIG. 4, in the laminated polarizing film 1 of another embodiment of the present invention, the polarizer 11, the adhesive layer 31, and the first film 12 are laminated in this order.
However, the laminated polarizing film of the present invention is not limited to the configuration examples of FIGS. 1 to 4, and can be appropriately changed.
For example, one or more arbitrary other films such as the fourth film may be further laminated on the laminated polarizing film of each of the above-mentioned configuration examples.

<Polarizer>
A polarizer is an optical element that has the property of transmitting light (polarized light) that vibrates in only one specific direction and blocking light that vibrates in the other direction. The polarizer of the present invention is in the form of a flexible film.
Specifically, the polarizer of the present invention is produced by a wet treatment described later. The polarizer consists of a hydrophilic polymer film dyed and stretched with a dichroic substance (for example, a polyvinyl alcohol-based film dyed and stretched with a dichroic substance).

<1st film, 2nd film, 3rd film, etc.>
Other films (films other than the polarizer) such as the first film, the second film, and the third film are all films that do not contain a polarizer.
The first film is adhered to one side of the polarizer via an adhesive layer (see FIGS. 1 to 4).
The second film is adhered to the other side of the polarizer via an adhesive layer, if necessary (see FIGS. 1 and 2).
Another film, such as the third film, is adhered to the second film or the like via an adhesive layer, if necessary (see FIG. 2).

Any optical film can be used as the film such as the first film, the second film, and the third film.
As the optical film, conventionally known ones can be used, and examples thereof include a protective film, a retardation film, an antiglare film, a brightness improving film, a viewing angle improving film, and a transparent conductive film.
Other films such as the first film, the second film and the third film are independently selected from a protective film, a retardation film, an antiglare film, a brightness improving film, a viewing angle improving film, a transparent conductive film and the like. A film can be used.
Above all, it is preferable to use a protective film such as a TAC film as the first film. When the second film is adhered to one side of the polarizer, it is preferable to use a protective film as the second film.

<Adhesive layer>
The adhesive layer is a solidifying layer of an adhesive, which is a layer interposed between two films and adhering the two films.
The adhesive layer between the polarizer and the first film is not particularly limited, and a conventionally known adhesive can be used. Examples of the adhesive include solvent-volatile adhesives, two-component reaction adhesives, and active energy ray-curable adhesives. Preferably, an active energy ray-curable adhesive can be used. The active energy ray-curable adhesive is preferably used at least when adhering the polarizer to the film.
For example, in the case of the laminated polarizing films 1 of FIGS. 1 and 2, it is preferable that the adhesive layers 31 and 32 are all composed of an active energy ray-curable adhesive. In the case of each of the laminated polarizing films 1 of FIGS. 3 and 4, the adhesive layer 31 is preferably composed of an active energy ray-curable adhesive. In the case of the laminated polarizing film 1 of FIG. 2, the adhesive layer 33 may be composed of an active energy ray-curable adhesive or other adhesives, but is preferably composed of other adhesives. It is composed of an active energy ray-curable adhesive. Further, in the case of the laminated polarizing film 1 of FIG. 3, the adhesive layer 32 between the layers of the first film 12 and the second film 13 may be composed of an active energy ray-curable adhesive, or other than that. It may be composed of an adhesive, but is preferably composed of an active energy ray-curable adhesive.

[Manufacturing equipment for polarizers and manufacturing equipment for laminated polarizing films]
The polarizing element manufacturing apparatus of the present invention includes a wet treatment apparatus for producing a long strip-shaped polarizer by dyeing and stretching a long strip-shaped hydrophilic polymer film with a dyeing treatment liquid, and the wet treatment apparatus. It has a drying device for drying the obtained polarizer.
Further, the apparatus for producing a laminated polarizing film of the present invention includes a wet processing apparatus for producing a long strip-shaped polarizing element by dyeing and stretching a long strip-shaped hydrophilic polymer film with a dyeing treatment liquid, and the wet treatment apparatus. It has a drying device for drying the polarizer obtained by the processing device, and a laminating device for laminating the polarizing element with another film.

In the polarizer manufacturing apparatus, a long strip-shaped polarizer is produced from a long strip-shaped hydrophilic polymer film by a wet processing apparatus, and then the polarizer is continuously dried by a drying apparatus. That is, the wet processing device and the drying device are arranged on one production line.
The laminated polarizing film manufacturing apparatus may be of a type in which another film is continuously adhered to the polarizing element dried by the polarizing element manufacturing apparatus by the laminating apparatus. Alternatively, the laminated polarizing film manufacturing apparatus once winds the dried polarizing element into a roll shape in the polarizing element manufacturing apparatus, pulls out the roll-shaped polarizing element, and adheres another film with the laminating apparatus. It may be in the form. The former type is a form in which a series of steps from the production of the polarizer to the bonding of the film to obtain the laminated polarizing film is performed on one production line, and the latter form is the form in which the production of the polarizer is performed in one production. This is a format in which the process of performing on a line and adhering a film to the polarizer to obtain a laminated polarizing film is performed on another production line.
The laminated polarizing film manufacturing apparatus of the present invention is preferably of a roll-to-roll type in which a series of steps from manufacturing a polarizer to adhering the film to obtain a laminated polarizing film is performed on one production line. In the production device for the laminated polarizing film of this type, a polarizer manufacturing device having a wet processing device and a drying device and a laminating device are arranged on one production line.

FIG. 5 shows a preferable configuration example of the laminated polarizing film manufacturing apparatus 2.
With reference to FIG. 5, the laminated polarizing film manufacturing apparatus 2 includes a wet processing apparatus 4, a drying apparatus 5, and a laminating apparatus 6 in this order from the upstream side.
The wet treatment apparatus 4 has a first roll portion 41 around which a long strip-shaped untreated hydrophilic polymer film 1a is wound, a transport portion 42 for transporting the hydrophilic polymer film 1a, and a treatment portion. .. The treated portion is a portion where the untreated hydrophilic polymer film 1a is treated with a dichroic substance to change the hydrophilic polymer film 1a into a polarizer 1b.
The drying device 5 has a transporting unit for transporting a long strip-shaped polarizer and a heating portion for applying heat to the polarizer 1b to dry the polarizer 1b. The transport unit includes a plurality of guide rolls 7, and at least one of the guide rolls 7 is a rough surface guide roll 71 having a roughened surface.
The laminating device 6 has a transport unit 61 for transporting the dried polarizer 1c, the first film 12, and the like, a second roll portion 62 around which the first film 12 is wound, and a second film 13 around which the second film 13 is wound. It has 3 roll portions 63, an adhesive coating portion 64, a bonding portion 65, and a take-up roll portion 67 for winding the manufactured laminated polarizing film.

<Wet processing equipment>
The wet treatment apparatus 4 includes a treatment portion for dyeing and stretching a long strip-shaped hydrophilic polymer film 1a with a dyeing treatment liquid. The wet treatment includes a treatment of stretching the hydrophilic polymer film 1a while allowing a plurality of treatment liquids including a dyeing treatment liquid to act on the hydrophilic polymer film 1a.
The wet processing apparatus is conventionally known, and the conventionally known configuration can be adopted for the wet processing apparatus 4 of the present invention.
The treatment unit includes, for example, a swelling treatment tank 4A, a dyeing treatment tank 4B, a cross-linking treatment tank 4C, a stretching treatment tank 4D, and a cleaning treatment tank 4E in order from the upstream side.
The transport section 42 of the wet treatment device 4 has a plurality of guide rolls and the like, and pulls out the long strip-shaped hydrophilic polymer film 1a wound around the first roll section 41 and transports it to the treatment section.
The white arrows in FIG. 5 indicate the traveling direction (conveying direction) of the film to be conveyed.

The hydrophilic polymer film 1a has a long strip shape. In the present specification, the long strip shape means a rectangular shape whose length in the longitudinal direction is sufficiently larger than the length in the width direction (the width direction is a direction orthogonal to the longitudinal direction). The length of the long strip in the longitudinal direction is, for example, 10 m or more, preferably 50 m or more.
The hydrophilic polymer film 1a is not particularly limited, and conventionally known films can be used. Specifically, examples of the hydrophilic polymer film 1a include polyvinyl alcohol (PVA) -based films, partially formalized PVA-based films, polyethylene terephthalate (PET) films, ethylene / vinyl acetate copolymer films, and partial kens thereof. Examples include chemical films. In addition to these, a polyene-oriented film such as a dehydrated product of PVA or a dehydrochlorinated product of polyvinyl chloride, a stretch-oriented polyvinylene-based film, or the like can also be used. Among these, a PVA-based polymer film is particularly preferable because it is excellent in dyeability with a dichroic substance.
As the raw material polymer of the PVA-based polymer film, for example, a polymer obtained by polymerizing vinyl acetate and then saponified, or a copolymerizable monomer such as a small amount of unsaturated carboxylic acid or unsaturated sulfonic acid is copolymerized with vinyl acetate. Polymers, etc. The degree of polymerization of the PVA-based polymer is not particularly limited, but is preferably 500 to 10000, more preferably 1000 to 6000, from the viewpoint of solubility in water and the like. The degree of saponification of the PVA-based polymer is preferably 75 mol% or more, more preferably 98 mol% to 100 mol%.
The thickness of the untreated hydrophilic polymer film 1a is not particularly limited, but is, for example, 15 μm to 110 μm.

The swelling treatment tank 4A is a treatment tank containing a swelling treatment liquid. The swelling treatment liquid swells the hydrophilic polymer film 1a. As the swelling treatment liquid, for example, water can be used. Further, water obtained by adding an appropriate amount of an iodine compound such as glycerin or potassium iodide to water may be used as the swelling treatment liquid. When glycerin is added, the concentration is preferably 5% by weight or less, and when an iodine compound such as potassium iodide is added, the concentration is preferably 10% by weight or less.

The dyeing treatment tank 4B is a treatment tank containing a dyeing treatment liquid. The dyeing solution dyes the hydrophilic polymer film 1a. Examples of the dyeing solution include a solution containing a dichroic substance as an active ingredient. Examples of the dichroic substance include iodine and organic dyes. Preferably, a solution in which iodine is dissolved in a solvent can be used as the dyeing treatment solution. Water is generally used as the solvent, but an organic solvent compatible with water may be further added. The concentration of iodine in the dyeing solution is not particularly limited, but is preferably 0.01% by weight to 10% by weight, more preferably 0.02% by weight to 7% by weight, and 0.025% by weight. It is more preferably% to 5% by weight. If necessary, an iodine compound may be added to the dyeing solution in order to further improve the dyeing efficiency. Iodine compounds are compounds containing iodine and elements other than iodine in the molecule, for example, potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, iodine. Examples thereof include barium iodide, calcium iodide, tin iodide, and titanium iodide.

The cross-linking treatment tank 4C is a treatment tank containing a cross-linking treatment liquid. The cross-linking treatment liquid cross-links the dyed hydrophilic polymer film 1a. As the cross-linking treatment liquid, a solution containing a boron compound as an active ingredient can be used. For example, as the cross-linking treatment liquid, a solution in which a boron compound is dissolved in a solvent can be used. Water is generally used as the solvent, but an organic solvent compatible with water may be further added. Examples of the boron compound include boric acid and borax. The concentration of the boron compound in the cross-linking treatment liquid is not particularly limited, but is preferably 1% by weight to 10% by weight, more preferably 2% by weight to 7% by weight, and 2% by weight to 6% by weight. Is even more preferable. Further, since a polarizer having uniform optical characteristics can be obtained, an iodine compound may be added to the cross-linking treatment liquid, if necessary.

The stretching treatment tank 4D is a treatment tank containing the stretching treatment liquid.
The stretching treatment liquid is not particularly limited, but for example, a solution containing a boron compound as an active ingredient can be used. As the stretching treatment liquid, for example, a solution in which a boron compound and, if necessary, various metal salts, zinc compounds and the like are dissolved in a solvent can be used. Water is generally used as the solvent, but an organic solvent compatible with water may be further added. The concentration of the boron compound in the stretching treatment liquid is not particularly limited, but is preferably 1% by weight to 10% by weight, more preferably 2% by weight to 7% by weight. From the viewpoint of suppressing the elution of iodine adsorbed on the film, an iodine compound may be added to the stretching treatment liquid, if necessary.

The cleaning treatment tank 4E is a treatment tank in which the cleaning treatment liquid is stored. The cleaning treatment liquid cleans the hydrophilic polymer film 1a after stretching. The cleaning treatment liquid is a treatment liquid for cleaning the treatment liquid such as the dyeing treatment liquid and the cross-linking treatment liquid adhering to the hydrophilic polymer film 1a. As the cleaning treatment liquid, water such as ion-exchanged water, distilled water, and pure water is typically used.
In the illustrated example, the treatment unit has a swelling treatment tank 4A, a dyeing treatment tank 4B, a cross-linking treatment tank 4C, a stretching treatment tank 4D, and a cleaning treatment tank 4E, provided that the treatment unit has the dyeing treatment tank 4B. One or two of the treatment tanks may be omitted. On the other hand, the processing unit may further have an adjustment processing tank (not shown). The adjustment treatment tank is a treatment tank in which the adjustment treatment liquid is stored. Although not shown in FIG. 5, this adjustment treatment tank is provided between the cross-linking treatment tank 4C and the stretching treatment tank 4D, or between the stretching treatment tank 4D and the cleaning treatment tank 4E. The adjusting treatment solution is a solution for adjusting the hue of a film, and a solution containing an iodine compound as an active ingredient can be used.

<Drying device (drying device for polarizer)>
The drying device 5 is provided on the downstream side of the wet processing device 4 and on the upstream side of the laminating device 6. In the illustrated example, the drying device 5 is provided on the downstream side of the cleaning treatment tank 4E.
One drying device 5 may be provided, or two or more drying devices 5 may be provided side by side in the conveying direction of the polarizer. In the illustrated example, for example, two drying devices 5 are provided side by side in the conveying direction of the polarizer. Hereinafter, one drying device 5 is referred to as a "first drying device 5A", the other is referred to as a "second drying device 5B", and one or more drying devices 5 are collectively referred to as a "drying device 5". That is.
With reference to FIGS. 5 and 6, the first and second drying devices 5A and 5B each carry a transport section for transporting the long strip-shaped polarizer 1b manufactured by the wet processing device 4 and the transport unit. It has a heating unit that applies heat to the polarizing element 1b conveyed in the longitudinal direction (MD direction) and dries it.
The heating unit has, for example, a chamber 521 and a heat source (not shown). The chamber 521 has a space 522 inside which the polarizer can be conveyed. As the heat source, for example, warm air can be used. A duct 523 for sending warm air is arranged on the inner wall of the chamber 521. A plurality of air outlets 524 are opened in the duct 523. Air (warm air) heated by a heat source (not shown) is sent out from the air outlet 524 into the chamber 521 through the duct 523. The arrow in FIG. 6 indicates the delivery of warm air.
In the chamber 521, a transport unit for transporting the polarizer 1b is arranged. The transport unit has a plurality of guide rolls 7.

Specifically, in each chamber 521 of the first and second drying devices 5A and 5B, two or more guide rolls 7 are spaced in the traveling direction of the long strip-shaped polarizer as a transporting unit of the drying device. It is open and provided. The guide rolls 7 of the transport section are preferably provided with three or more, and more preferably four or more. The upper limit of the number of guide rolls 7 is not particularly limited, but is usually 20 and preferably 16.
In the illustrated example, in each of the first and second drying devices 5A and 5B, a transport portion having eight guide rolls 7 is arranged in the chamber 521.

The plurality of guide rolls 7 of the drying device 5 (drying device 5 including the first and second drying devices 5A and 5B) have a roughened surface guide roll 71 (in the present specification, the surface is roughened). The provided guide roll is referred to as "rough surface guide roll 71"). Further, the plurality of guide rolls 7 may include a guide roll 72 having a mirrored surface (in the present specification, the guide roll 7 having a mirrored surface is referred to as a "mirror surface guide roll 72").

FIG. 7A shows one rough surface guide roll 71, and FIG. 7B shows one mirror surface guide roll 72.
As shown in FIG. 7A, the surface (outer peripheral surface) of the rough surface guide roll 71 is a fine uneven surface. The surface (outer peripheral surface) of the mirror surface guide roll 72 is a mirror surface having substantially no uneven surface.
The material of the surface of the rough surface guide roll 71 and the surface of the mirror surface guide roll 72 is not particularly limited, and examples thereof include metals such as aluminum and iron, rubber, and hard synthetic resin, respectively. The diameter and axial length of the rough surface guide roll 71 and the mirror surface guide roll 72 can be set to the same dimensions as those of the conventionally known guide rolls.

The unevenness of the surface of the rough surface guide roll 71 may be such that convex and concave are regularly arranged, or convex and concave may be irregularly arranged.
The degree of roughening of the surface of the rough surface guide roll 71 is not particularly limited, but if the degree of roughening is too low, the effect of suppressing fine bubbles may not be sufficiently obtained, and the surface is made too rough. If the degree of is high, the polarizer may be finely scratched.
From this point of view, the surface roughness of the rough surface guide roll 71 is preferably 1 μm to 20 μm in terms of ten-point average roughness Rz, and more preferably 2 μm to 15 μm in terms of ten-point average roughness Rz. The ten-point average roughness Rz is particularly preferably 3 μm to 12 μm.
By drying while transporting the polarizer 1b on the rough surface guide roll 71 having a surface roughness of 1 μm to 20 μm at the ten-point average roughness Rz, the polarizer is suppressed from shrinking in the width direction while being suppressed. The polarizer can be dried to an appropriate moisture content.
The surface roughness of the mirror surface guide roll 72 is, for example, less than 1 μm in 10-point average roughness Rz, and preferably 0.5 μm or less in 10-point average roughness Rz.
In the present specification, the ten-point average roughness Rz means Rz _jis94 (former JIS B 0601: 1994 ten-point average roughness) referred to in Annex JA of JIS B 0601: 2013.

Of the plurality of guide rolls 7 of the drying device 5, at least any one is a rough surface guide roll 71.
Assuming that the total number of guide rolls 7 used in the drying device 5 (drying device 5 including the first and second drying devices 5A and 5B) is 100%, 30% to 100% is the rough surface guide roll 71. More preferably, 40% to 100% is a rough surface guide roll 71, and further preferably 50% to 100% is a rough surface guide roll 71. For example, when the 30% is the rough surface guide roll 71, 30% of the guide roll 7 of the drying device 5 (the drying device 5 including the first and second drying devices 5A and 5B) is the rough surface guide roll 71. This means that 70% is a guide roll other than the rough surface guide roll 71 (for example, a mirror surface guide roll 72). When the 100% is a rough surface guide roll 71, it means that all the guide rolls 7 of the drying device 5 are rough surface guide rolls 71.

In one embodiment, for example, the drying device 5 includes a first drying device 5A and a second drying device 5B, and a rough surface guide roll 71 is used as all the guide rolls 7.
In another embodiment, for example, as shown in FIG. 6, the drying device 5 includes the first drying device 5A and the second drying device 5B, and the rough surface guide roll 71 is used as all the guide rolls 7 of the first drying device 5A. The mirror surface guide roll 72 is used as all the guide rolls 7 of the second drying device 5B.
In another embodiment, for example, the drying device 5 includes a first drying device 5A and a second drying device 5B, and a mirror surface guide roll 72 is used as all the guide rolls 7 of the first drying device 5A, and the second drying device 5B. A rough surface guide roll 71 is used as all the guide rolls 7.
In another embodiment, for example, the drying device 5 includes the first drying device 5A and the second drying device 5B, and the rough surface guide roll 71 and the mirror surface guide roll 72 are alternately used as the guide roll 7 of the first drying device 5A. The rough surface guide roll 71 and the mirror surface guide roll 72 are alternately used as the guide roll 7 of the second drying device 5B.
In another embodiment, for example, the drying device 5 includes a first drying device 5A and a second drying device 5B, and one or two or more rough surface guide rolls 71 and 1 as guide rolls 7 of the first drying device 5A. A book or two or more mirror surface guide rolls 72 are randomly used, and one or two or more rough surface guide rolls 71 and one or more mirror surface guide rolls 72 are used as the guide roll 7 of the second drying device 5B. Is used randomly.

<Laminating device>
The transport unit 61 of the laminating device 6 includes a guide roll and the like. The transport section 61 transports the long strip-shaped polarizer 1c dried by the drying device 5 to the downstream side of the bonding section 65 or the like. Further, the transport unit 61 transports the long strip-shaped first film 12 or the like laminated on the polarizer 1c to the downstream side of the bonding portion 65 or the like.
In the laminated polarizing film manufacturing apparatus 2 of the illustrated example, the first film 12 and the second film 13 can be laminated on both sides of the polarizer 1c, respectively. According to this apparatus, a laminated polarizing film 1 having a layer structure of a first film 12 / an adhesive layer 31 / a polarizer 11 / an adhesive layer 32 / a second film 13 as shown in FIG. 1 can be obtained.

Such a manufacturing apparatus 2 has a second roll portion 62 around which the long strip-shaped first film 12 is wound, and a third roll portion 63 around which the long strip-shaped second film 13 is wound. The first film 12 of the second roll portion 62 and the second film 13 of the third roll portion 63 are independently conveyed from the roll portions 62 and 63 to the downstream side such as the bonding portion 65 by the conveying portion 61, respectively. Will be done.

The adhesive coating unit 64 applies the adhesive to the film by, for example, the gravure roll 641. The adhesive coating portion 64 is arranged on the upstream side of the bonding portion 65.
In the laminating device 6 of the illustrated example, the adhesive coating portion 64 is the one-sided side of the polarizer 1c, the other one-sided side of the polarizer 1c, the one-sided side of the first film 12, and the one-sided side of the second film 13. Are placed in each.
An adhesive is applied to one side of the polarizing element 1c by the adhesive coating unit 64, and an adhesive is applied to one side of the first film 12, so that both adhesive layers face each other. By laminating the 1 film 12, it is possible to effectively prevent the formation of air bubbles between the polarizer and the first film 12. Similarly, the adhesive coating unit 64 applies an adhesive to one side of the polarizer 1c and an adhesive to one side of the second film 13, so that the two adhesive layers face each other. By adhering the child 1c and the second film 13, it is possible to effectively prevent the formation of air bubbles between the polarizer 1c and the second film 13.

However, since the polarizer 1c and the first film 12 can be adhered by applying an adhesive to at least one side of the polarizer 1c and the first film 12, the adhesive arranged on one side of the polarizer 1c. Either one of the coating portion 64 and the adhesive coating portion 64 arranged on one side of the first film 12 may be omitted. Similarly, if an adhesive is applied to at least one of the polarizer 1c and the second film 13, the polarizer 1c and the second film 13 can be adhered to each other. Therefore, the adhesion arranged on one side of the polarizer 1c Either one of the agent coating portion 64 and the adhesive coating portion 64 arranged on one side of the second film 13 may be omitted.

The adhesive coating unit 64 has a gravure roll 641, a backup roll 642 arranged to face the gravure roll 641, a container 643 in which the adhesive is stored, and a doctor blade 644. Note that the backup rolls are omitted for the adhesive coating portion 64 arranged on one side and the other side of the polarizer 1c, and the gravure rolls 641 are arranged facing each other with the polarizer 1c in between.
The gravure roll 641 has a plurality of cells (recesses for entering an adhesive) formed on the surface thereof. The gravure roll 641 rotates about an axis so that its surface contacts the adhesive stored in the container 643 (the direction of rotation of the gravure roll 641 is indicated by an arrow). As the rotation proceeds, the adhesive adheres to the surface of the gravure roll 641 containing the cells, and the excess adhesive is scraped off into the container 643 by the doctor blade 644. When the gravure roll 641 containing the adhesive in the cell comes into contact with the polarizer 1c or the like, the adhesive in the cell is transferred to one side of the polarizer 1c or the like. In this way, the adhesive is applied to one side of each film such as the gravure roll 641 to the polarizer 1c in a solid shape.

The adhesive for adhering the polarizer 1c to another film (first film 12 and second film 13 in the illustrated example) is not particularly limited, but it is preferable to use an active energy ray-curable adhesive as described above. .. As the active energy ray-curable adhesive, conventionally known ones can be used. The active energy ray-curable adhesive generally contains an active energy ray-curable component and a polymerization initiator, and if necessary, contains various additives.
The active energy ray-curable component can be roughly classified into electron beam curability, ultraviolet curability, and visible light curability. Further, the active energy ray-curable component can be roughly classified into a radical-polymerizable compound and a cationically polymerizable compound from the viewpoint of the curing mechanism.

Examples of the radically polymerizable compound include compounds having a radically polymerizable functional group of a carbon-carbon double bond such as a (meth) acryloyl group and a vinyl group. Moreover, either a monofunctional radical polymerizable compound or a bifunctional or higher functional radical polymerizable compound can be used. Further, these radically polymerizable compounds may be used alone or in combination of two or more. The radically polymerizable compound is preferably a compound having a (meth) acryloyl group, and examples thereof include a (meth) acrylamide derivative having a (meth) acrylamide group and a (meth) acrylate having a (meth) acryloyloxy group. ..
When a radically polymerizable compound is used as the active energy ray-curable adhesive, the polymerization initiator is appropriately selected according to the active energy ray. When the adhesive is cured by ultraviolet rays or visible light, an ultraviolet cleaving or visible light cleaving polymerization initiator is used. Examples of such a polymerization initiator include benzophenone compounds, aromatic ketone compounds, acetophenone compounds, aromatic ketal compounds, aromatic sulfonyl chloride compounds, and thioxanthone compounds.

Examples of the cationically polymerizable compound include a monofunctional cationically polymerizable compound having one cationically polymerizable functional group in the molecule, a polyfunctional cationically polymerizable compound having two or more cationically polymerizable functional groups in the molecule, and the like. Examples of the cationically polymerizable functional group include an epoxy group, an oxetanyl group, and a vinyl ether group. Examples of the cationically polymerizable compound having an epoxy group include an aliphatic epoxy compound, an alicyclic epoxy compound, and an aromatic epoxy compound. Examples of the cationically polymerizable compound having an oxetanyl group include 3-ethyl-3-hydroxymethyloxetane, 1,4-bis [(3-ethyl-3-oxetanyl) methoxymethyl] benzene, and 3-ethyl-3- (phenoxymethyl). ) Oxetane and the like. Examples of the cationically polymerizable compound having a vinyl ether group include 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, and 4-hydroxybutyl vinyl ether.
When a cationically polymerizable compound is used as the active energy ray-curable adhesive, a cationic polymerization initiator is blended. This cationic polymerization initiator generates a cationic species or Lewis acid by irradiation with active energy rays such as visible light, ultraviolet rays, and electron beams, and initiates a polymerization reaction with an epoxy group of a cationically polymerizable compound. As the cationic polymerization initiator, a photoacid generator and a photobase generator can be used.

In the present invention, an active energy ray-curable adhesive that cures with light containing visible light of 380 nm to 450 nm can also be used. In this case, it is preferable to use an active energy ray-curable adhesive containing a radically polymerizable compound and a polymerization initiator.
Such an active energy ray-curable adhesive is disclosed in, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2018-092186), and the activity described in Patent Document 1 as the active energy ray-curable adhesive of the present invention. An energy ray-curable adhesive can be used. In the present specification, the description of the above-mentioned Patent Document 1 is omitted for the convenience of space, but the description of the adhesive of the above-mentioned Patent Document 1 can be incorporated into the present specification as it is.

The bonding portion 65 is provided with a pair of nip rolls 651 and 651.
The laminate composed of the polarizer 1c and the first film 12 and the like bonded via the adhesive layer is inserted into the nip rolls 651 and 651 and pressed.
When an active energy ray-curable adhesive is used as the adhesive, the curing device 66 is arranged on the downstream side of the bonding portion 65.
The curing device 66 is a device that irradiates the laminated body with active energy rays. The active energy ray is appropriately selected depending on the curability of the active energy ray-curable adhesive. For example, as described in Patent Document 1, a curing device 66 capable of irradiating visible light of 380 nm to 450 nm can be used.
Further, as shown in FIG. 5, it is preferable that the curing device 66 for irradiating the active energy rays is arranged on both side surfaces of the laminated body so that the active energy rays can be irradiated from both side surfaces of the laminated body.
The two curing devices 66 arranged on both sides may be arranged facing each other with the laminate interposed therebetween, or as shown in FIG. 5, one curing device 66 is arranged on the upstream side. One curing device 66 may be arranged on the downstream side thereof. In the illustrated example, the curing device 66 on the first film side is arranged on the upstream side of the curing device 66 on the second film side. By arranging in this way, it is possible to cure the adhesive that adheres the first film 12 to the polarizer 1c, and then cure the adhesive that adheres the second film 13 to the polarizer 1c.

[Manufacturing method of polarizer and manufacturing method of laminated polarizing film]
<Manufacturing process of polarizer>
With reference to FIG. 5, the untreated hydrophilic polymer film 1a is pulled out from the first roll portion 41, and the hydrophilic polymer film 1a is conveyed to the swelling treatment tank 4A by the conveying portion 42. The hydrophilic polymer film 1a is swollen by immersing the hydrophilic polymer film 1a in the swelling treatment liquid while transporting the hydrophilic polymer film 1a by the guide roll 42 in the swelling treatment tank 4A. The temperature of the swelling treatment liquid is not particularly limited, but is, for example, 20 ° C to 45 ° C. The time for immersing the hydrophilic polymer film 1a in the swelling treatment liquid is not particularly limited, but is, for example, 5 seconds to 300 seconds. Next, by immersing the swelled hydrophilic polymer film 1a in the dyeing solution in the dyeing tank 4B, the hydrophilic polymer film 1a is dyed with a dichroic substance. The temperature of the dyeing solution is not particularly limited, but is, for example, 20 ° C to 50 ° C. The time for immersing the hydrophilic polymer film 1a in the dyeing treatment liquid is not particularly limited, but is, for example, 5 seconds to 300 seconds. By immersing the dyed hydrophilic polymer film 1a in the cross-linking treatment liquid in the cross-linking treatment tank 4C, the bicolor substance of the hydrophilic polymer film 1a is cross-linked. The temperature of the cross-linking treatment liquid is not particularly limited, but is, for example, 25 ° C. or higher, preferably 40 ° C. to 70 ° C. The time for immersing the hydrophilic polymer film 1a in the cross-linking treatment liquid is not particularly limited, but is, for example, 5 seconds to 800 seconds.

The crosslinked hydrophilic polymer film 1a is stretched while being conveyed by a guide roll 42 in the stretching treatment liquid of the stretching treatment tank 4D. The temperature of the stretching treatment liquid is not particularly limited, but is, for example, 40 ° C. to 90 ° C. The draw ratio can be appropriately set depending on the intended purpose, but the total draw ratio is, for example, 2 to 7 times, preferably 4.5 to 6.8 times. The total draw ratio means the final draw ratio of the hydrophilic polymer film 1a. The hydrophilic polymer film 1a is washed by immersing the stretched hydrophilic polymer film 1a in the washing treatment liquid in the washing treatment tank 4E. The temperature of the cleaning treatment liquid is, for example, 5 ° C to 50 ° C. The cleaning time is, for example, 1 second to 300 seconds.
The hydrophilic polymer film after washing becomes the polarizer 1b. The obtained polarizer 1b is continuously conveyed to the drying device 5.

<Drying process>
Since the polarizer 1b obtained by the wet treatment contains a relatively large amount of water, it is dried by the drying device 5.
The long strip-shaped polarizer 1b is conveyed by the conveying portion of the drying device 5 including the guide roll 7. While the polarizer 1b passes through the chamber 521 of the drying device 5, it is dried by the heating unit.
In the wet treatment, since the hydrophilic polymer film 1a is stretched in the longitudinal direction (MD direction), the polarizer 1b shrinks in the width direction (TD direction) while being dried by the drying device 5. Will come to do.
In the present invention, it is important that the shrinkage rate of the polarizer in the width direction in the drying step is 15% to 20%. By setting the shrinkage ratio of the polarizer in the drying step to 15% to 20%, it becomes difficult for air to enter when the polarizer 1c and the film 12 after drying are adhered to each other. Preferably, the polarizer is dried so that the shrinkage rate is 16% to 19%.
Here, the shrinkage ratio of the polarizer in the width direction is the length in the width direction of the polarizer 1b immediately before entering the drying device 5 (the length before drying) and the length of the polarizer 1c immediately after leaving the drying apparatus 5. The length in the width direction (length after drying) is measured and substituted into the following equation to obtain the value.
Shrinkage rate (%) = {(length in the width direction before drying-length in the width direction after drying) / length in the width direction before drying} × 100.

Further, it is preferable to dry the polarizer 1b so that the moisture content of the polarizer 1c after drying is as small as possible. For example, the moisture content of the polarizer 1c after drying (after drying in the drying step) is preferably 18% by weight or less, more preferably 17% by weight or less, still more preferably 16% by weight or less. Since the water content is preferably as small as possible, the lower limit is not particularly limited, but since it is practically difficult to dry until the water content becomes zero, the water content of the polarizer 1c after drying is determined to be. For example, it is 10% by weight or more, and further, 12% by weight or more.
The moisture content refers to the proportion of moisture contained in the polarizer 1c after drying. The water content is the weight of the polarizer 1c after drying in the drying step (the weight of the polarizer 1c after drying) and the weight of the polarizer after substantially removing water from the dried polarizer 1c. (Weight of the polarizer after complete drying) and, respectively, are measured and substituted into the following equations to obtain the results.
Moisture content (% by weight) = {(weight of polarizer after drying-weight of polarizer after complete drying) / weight of polarizer after drying} x 100.

The drying temperature in the drying step is preferably set so that the shrinkage rate of the polarizer 1c after drying is in the above range and the moisture content of the polarizer 1c after drying is in the above range. For example, when the drying device 5 having the chamber 521 is used as described above, the temperature of the space 522 of the chamber 521 (atmospheric temperature in the chamber 521) is, for example, 40 ° C to 100 ° C, preferably 50 ° C to 90. Set to ° C. Further, in the case of the drying device 5 using warm air as described above, the wind speed of the warm air is set to, for example, 1 m / sec to 30 m / sec, preferably 2 m / sec to 20 m / sec.

The path length in the drying step is preferably set so that the shrinkage rate of the polarizer 1c after drying is in the above range and the moisture content of the polarizer 1c after drying is in the above range. For example, the path length in the drying step is set to 15 m to 45 m, preferably 20 m to 40 m. The path length in the drying step refers to the transport length of the polarizer from the first guide roll 7 (guide roll on the inlet side) to the last guide roll 7 (guide roll on the outlet side) of the drying device 5. As shown in FIG. 6, in the drying device 5 including the first and second drying devices 5A and 5B, the path length is from the guide roll 7 at the left end of the paper surface of the first drying device 5A to the right end of the paper surface of the second drying device 5B. Refers to the transport length of the polarizer up to the guide roll 7.
Further, the transport speed of the polarizer in the drying step is not particularly limited, and is, for example, 15 m / min to 40 m / min, preferably 20 m / min to 35 m / min. The drying time can be obtained from the path length and the transport speed.

<Laminating process>
The dried long strip-shaped polarizer 1c is conveyed to the bonding portion 65 by the conveying portion 61. In the transfer process, an adhesive such as an active energy ray-curable adhesive is applied to both surfaces of the polarizer 1c by the adhesive coating unit 64. By applying the adhesive, adhesive layers are formed on both sides of the polarizer 1c. On the other hand, the long strip-shaped first film 12 is pulled out from the second roll portion 62 and is conveyed to the bonding portion 65 by the conveying portion 61. Similarly, the long strip-shaped second film 13 is pulled out from the third roll portion 63 and conveyed to the bonding portion 65 by the conveying portion 61. In each transfer process, an adhesive such as an active energy ray-curable adhesive is applied to one side of the first film 12 and one side of the second film 13 by the adhesive coating unit 64. By applying the adhesive, an adhesive layer is formed on one side of the first film 12 and one side of the second film 13, respectively.

The coating thickness of the adhesive layer is not particularly limited, but if it is too small, the adhesive strength is lowered, and if it is too large, the thickness of the laminated polarizing film becomes relatively large. From this point of view, the coating thickness of the adhesive layer formed on the polarizer 1c, the first film 12 and the second film 13 is preferably 0.1 μm to 5 μm, respectively.

Further, the viscosity of the adhesive at the time of coating is not particularly limited, but if it is too small or too large, coating spots of the adhesive may occur. From this point of view, the viscosity of the adhesive at 25 ° C. is preferably adjusted to 10 mPa · s to 50 mPa · s, and the viscosity at 25 ° C. is adjusted to 15 mPa · s to 45 mPa · s. More preferred. The viscosity can be measured at 25 ° C. using a viscometer.
Further, the transport speeds (line speeds) of the polarizer, the first film 12 and the second film 13 at the time of coating are not particularly limited, but if they are too fast, bubbles may be generated, and if they are too slow, the laminated polarized light may be generated. Film production efficiency is reduced. From this point of view, the transport speed of the polarizer 1c, the first film 12 and the second film 13 at the time of coating is preferably 15 m / min to 40 m / min, and more preferably 20 m / min to 35 m / min.

The polarizer 1c, the first film 12, and the second film 13 on which the adhesive layer (uncured adhesive) is formed are independently conveyed to the bonding portion 65. The adhesive layer formed on the polarizer 1c and the adhesive layer formed on the first film 12 face each other, and the adhesive layer formed on the polarizer 1c and the adhesive layer formed on the second film 13 face each other. These films are inserted between the nip rolls 651 and 651 while facing each other. By passing through the nip rolls 651 and 651, the polarizer 1c, the first film 12 and the second film 13 are bonded to each other, and the first film 12 / uncured adhesive layer / polarizer 1c / uncured adhesive layer / A laminate made of the second film 13 is obtained.
When an active energy ray-curable adhesive is used, the active energy ray-curable adhesive is cured by irradiating the laminated body with active energy rays by the curing device 66, and the first film 12 A laminated polarizing film 1 composed of / an adhesive layer after curing / a polarizer 1c / an adhesive layer after curing / a second film 13 can be obtained. The thickness of the adhesive layer made of the active energy ray-curable adhesive is substantially the same as the thickness before curing (at the time of coating) and after curing.
The obtained laminated polarizing film is wound around the winding roll portion 67.

<Modification example>
In the above, the case of producing a laminated polarizing film (laminated polarizing film 1 shown in FIG. 1) including a first film / an adhesive layer after curing / a polarizer / an adhesive layer after curing / a second film has been illustrated. , Not limited to this. For example, an adhesive coating portion is arranged on the downstream side of the laminated polarizing film, and an adhesive is applied to one side of the laminated polarizing film and / or one side of the third film to bond and cure the adhesive layer. As a result, for example, the first film 12 / the cured adhesive layer 31 / the polarizer 11 / the cured adhesive layer 32 / the second film 13 / the cured adhesive layer 33 / the third film as shown in FIG. It is also possible to obtain a laminated polarizing film 1 made of 14. Further, by omitting the bonding of the second film to the polarizer in the above manufacturing method, a laminated polarizing film 1 in which no other film is laminated on one side of the polarizer as shown in FIGS. 3 and 4 can be obtained. Can be done.

Further, in the above manufacturing method, an adhesive is applied to both sides of the polarizer 1c, and an adhesive is also applied to each side of the first film 12 and the second film 13 so that the adhesive layers face each other. They are pasted together, but not limited to this. For example, an adhesive is applied to only one side of the polarizer 1c or one side of the first film 12 to form an adhesive layer, and the polarizer and the first film 12 are attached through the adhesive layer. You may stick them together. Similarly, an adhesive is applied to only one side of the polarizer 1c or one side of the second film 13 to form an adhesive layer, and the polarizer 1c and the second film are formed through the adhesive layer. 13 may be pasted together.

[Action and effect of the present invention]
According to the production method of the present invention, it is difficult for fine bubbles to be generated between the polarizer and the film, and an optically good laminated polarizing film can be obtained.
According to the research by the present inventors, when the polarizer obtained by the wet treatment is dried, when the polarizer contracts relatively large in the width direction, the polarizer has fine wrinkles (streaks extending in the longitudinal direction). It is known that wrinkles) occur. When the polarizing element having such wrinkles is adhered to the film in the subsequent laminating step, air easily enters between the polarizer and the film. Therefore, fine bubbles are generated between the polarizer of the finally obtained laminated polarizing film and the film, and the bubbles deteriorate the optical characteristics of the laminated polarizing film. Therefore, from the viewpoint of preventing the generation of bubbles, it is desirable to dry the polarizer so that the shrinkage ratio of the polarizer is as small as possible.
On the other hand, according to the research by the present inventors, there is a trade-off relationship between the widthwise shrinkage rate of the polarizer when the polarizer is dried and the moisture content of the polarizer after drying. Specifically, when trying to obtain a polarizer having a low water content, the polarizer tends to shrink during drying (that is, when the polarizer is dried so that a polarizer having a low moisture content can be obtained, it becomes dry. The contraction rate of the polarizer increases). On the contrary, if an attempt is made to suppress the shrinkage of the polarizer during drying, a polarizer having a high water content is obtained after drying (that is, if the polarizer is dried so that the shrinkage ratio is small, the moisture content of the polarizer after drying is obtained. The rate will be higher). As described above, there is a trade-off relationship between the shrinkage rate of the polarizer during drying and the moisture content of the polarizer after drying.

As in the present invention, by drying the polarizing element so that the shrinkage rate in the width direction of the polarizer is 15% to 20%, the polarization having a relatively low moisture content after drying while suppressing the occurrence of wrinkles. You will be able to have children. The laminated polarizing film obtained by the production method of the present invention has good optical characteristics because fine bubbles are suppressed as described above, and further, since the moisture content of the polarizer is in an appropriate range, curling and the like Deformation is unlikely to occur over time.
In particular, by using the rough surface guide roll as the transporting portion of the drying device, it is possible to reduce the shrinkage rate and dry the polarizer, and to obtain a dried polarizer having a low water content. By drying the polarizer using the rough surface guide roll having the above surface roughness, it is possible to suppress the shrinkage of the polarizer during drying to prevent the occurrence of wrinkles and obtain a dried polarizer having a low water content. , This is the first matter discovered by the present inventors.

[Use of laminated polarizing film, etc.]
The laminated polarizing film of the present invention is typically used as an optical film for a display such as a liquid crystal display device or an organic display device.
Further, the laminated polarizing film of the present invention is not limited to the case where it is used for the above-mentioned display, and can be used for applications other than the display. Applications other than displays include optical equipment, buildings, medical / food fields, and the like. When a laminated polarizing film is used in an optical instrument, the laminated polarizing film is processed into, for example, a polarizing lens or a transparent radio wave blocking film. When a laminated polarizing film is used for an electronic device, the laminated polarizing film is processed into, for example, a film for a light control window. When the laminated polarizing film is used in the medical / food field, the laminated polarizing film is processed into, for example, a photodegradation prevention film.

Hereinafter, Examples and Comparative Examples will be described, and the present invention will be described in more detail. However, the present invention is not limited to the following examples.

[Material used]
<Rough surface guide roll A>
A rough surface guide roll A having a surface layer made of aluminum and having a surface roughness (10-point average roughness Rz) of 12 μm was prepared. The diameter of the rough surface guide roll A was about 110 mm, and the axial length was 2000 mm.
<Rough surface guide roll B>
A rough surface guide roll B having a surface layer made of aluminum and having a surface roughness (10-point average roughness Rz) of 3 μm was prepared. The diameter of the rough surface guide roll B was about 110 mm, and the axial length was 2000 mm.
<Mirror surface guide roll C>
A mirror surface guide roll C having a surface layer made of aluminum and having a surface roughness (10-point average roughness Rz) of 0.3 μm was prepared. The diameter of the mirror surface guide roll C was about 110 mm, and the axial length was 2000 mm.
The surface roughness (ten-point average roughness Rz) of the rough surface guide roll and the mirror surface guide roll is based on the ten-point average roughness Rz _jis94 of Annex JA of JIS B 0601: 2013, and is a surface roughness meter (stock). Each measurement was performed using the company Tokyo Seimitsu Co., Ltd. (trade name "Surfcom 130A").

<Active energy ray-curable adhesive D>
28.5% by weight 1,9-nonanediol diacrylate, 38% by weight hydroxyethyl acrylamide and 28.5% by weight acryloylmorpholin (active energy ray-curable component) and 3% by weight IRGACURE 907 and 2 By mixing with wt% KAYACURE DETX-S (polymerization initiator) and stirring for 3 hours, an active energy ray-curable adhesive D was obtained.
The viscosity of this active energy ray-curable adhesive D at 25 ° C. was 40 mPa · s, and the surface tension was 35 mN / m.

<First film E and second film F>
As the first film E, a cyclic polyolefin film (manufactured by Nippon Zeon Corporation) having a thickness of 52 μm was used.
As the second film F, a triacetyl cellulose film (manufactured by FUJIFILM Corporation) having a thickness of 60 μm was used.

[Viscosity measurement method]
The viscosity of the active energy ray-curable adhesive D was measured at 25 ° C. using an E-type rotary viscometer (manufactured by Toki Sangyo Co., Ltd.).
[Measurement method of surface tension]
The surface tension of the active energy ray-curable adhesive D was measured at 25 ° C. by the pendant drop method using Drop Master (manufactured by Kyowa Interface Science Co., Ltd.).

[Manufacturing equipment used]
An existing laminated polarizing film manufacturing apparatus (manufacturing apparatus as shown in FIG. 5) having a wet processing apparatus, a drying apparatus and a laminating apparatus was used. As shown in FIG. 6, the drying device included in the existing manufacturing device is one in which the first drying device and the second drying device are continuously arranged side by side. In both the first drying device and the second drying device, 13 guide rolls were installed in the chamber, and the polarizer was dried by warm air. The path length of this drying device was about 30 m (the path length from the guide roll on the inlet side of the first drying device to the guide roll on the outlet side of the second drying device was about 30 m).
The first drying device and the second drying device are the same devices in terms of the volume of the chamber, the number and arrangement of guide rolls, the number and arrangement of air outlets, and the like.

[Example 1]
The rough surface guide roll A was attached as all the guide rolls of the first drying apparatus of the existing manufacturing apparatus, and the mirror surface guide roll C was attached as all the guide rolls of the second drying apparatus.
Using the manufacturing apparatus of Example 1, a polarizer was produced as follows, and after drying, a first film and a second film were adhered to both sides of the polarizer to prepare a laminated polarizing film. ..

<Manufacturing process of polarizer>
Using the wet treatment apparatus of the above manufacturing apparatus, a polyvinyl alcohol film (thickness 45 μm, width 3000 mm) having an average degree of polymerization of 2400 and a saponification degree of 99.9 mol% was immersed in warm water at 30 ° C. for 60 seconds to swell. Then, the film was dyed by immersing it in an aqueous solution having a concentration of iodine / potassium iodide (weight ratio = 0.5 / 8) at a concentration of 0.3% and stretching it up to 3.5 times. Then, it was stretched in a boric acid ester aqueous solution at 65 ° C. so that the total stretching ratio was 6 times, and then washed with water to prepare a long strip-shaped polarizer.
<Polarizer drying process>
Subsequently, the polarizer was conveyed into a drying device and dried. The air velocity of the warm air of the drying device was 3 m / sec, the ambient temperature in the chamber was about 60 ° C., and the polarizer was transported at a transport speed of 25 m / min.
<Laminating process>
Subsequently, while transporting the dried polarizer to the adhesive coating portion of the apparatus at a speed of 25 m / min, the active energy ray-curable adhesive D is coated on both sides of the polarizer with a gravure roll in a solid shape. An adhesive layer having a coating thickness of 1.0 μm was formed. At the same time, one side of the first film E and one side of the second film F are also coated with the active energy ray-curable adhesive D in a solid shape with a gravure roll to form an adhesive layer having a coating thickness of 1.0 μm. Formed. These adhesive layers are overlapped with each other and passed through a nip roll to obtain a laminate of the first film / uncured adhesive layer / polarizer / uncured adhesive layer / second film, and from both sides of the laminate. A laminated polarizing film was continuously produced by irradiating light having a wavelength of 380 nm to 450 nm to cure the adhesive layer.

The shrinkage of the polarizer of Example 1 was 19%, and the moisture content was 15%.
The contraction rate of the polarizer was measured as follows.
Approximately 60 minutes after the device is put into operation, the length in the width direction of the polarizer is measured immediately before entering the drying device (after exiting the wet processing device and before entering the drying device), and immediately after exiting the drying device. The length of the polarizer in the width direction was measured. The measurement was performed on the carried polarizer.
Substitute the length of the polarizer just before entering the drying device (the length in the width direction before drying) and the length of the polarizer immediately after leaving the drying device (the length in the width direction after drying) into the following equation. By doing so, the shrinkage rate of the polarizer was determined.
Shrinkage rate of the polarizer (%) = {(length in the width direction before drying-length in the width direction after drying) / length before drying} × 100.

The water content of the polarizer was measured as follows.
Approximately 60 minutes after the device was put into operation, a sample piece was obtained by cutting an arbitrary portion of the polarizer immediately after leaving the drying device into a square shape. After cutting, the weight of the sample piece was immediately measured under standard conditions. Then, the sample piece was forcibly dried at 120 ° C. for 2 hours using a heating oven, and then the weight of the sample piece was quickly measured under standard conditions. It is considered that the water content in the sample piece is almost eliminated by this forced drying.
By substituting the weight of the sample piece before forced drying (weight of the polarizer after drying) and the weight of the sample piece after forced drying (weight of the polarizer after complete drying) into the following equation, the water content of the polarizer I asked for the rate.
Moisture content of the polarizer (% by weight) = {(weight of the polarizer after drying-weight of the polarizer after complete drying) / weight of the polarizer after drying} × 100.

[Example 2]
A laminated polarizing film was produced in the same manner as in Example 1 except that the rough surface guide roll A was attached as all the guide rolls of the first drying device and all the guide rolls of the second drying device.
The shrinkage ratio of the polarizer in Example 2 was 17%, and the moisture content of the polarizer after drying was 15%.

[Example 3]
A laminated polarizing film was produced in the same manner as in Example 1 except that the rough surface guide roll B was attached as all the guide rolls of the first drying device and all the guide rolls of the second drying device.
The shrinkage ratio of the polarizer in Example 3 was 18%, and the moisture content of the polarizer after drying was 15%.

[Comparison example]
A laminated polarizing film was produced in the same manner as in Example 1 except that the mirror surface guide roll C was attached as all the guide rolls of the first drying device and all the guide rolls of the second drying device.
The shrinkage of the polarizer of the comparative example was 21%, and the moisture content of the polarizer after drying was 15%.

[Check for bubbles]
The presence or absence of air bubbles was confirmed in the laminated polarizing films obtained in each Example and Comparative Example as follows. About 1 hour after the operation of the apparatus, the obtained laminated polarizing film was taken out, and both sides (one side and the other side) of the laminated polarizing film were magnified and observed with an optical microscope to confirm the presence or absence of bubbles. The bubbles were counted in the range of 5 cm × 5 cm, and bubbles on both sides were confirmed. The results are shown in Table 1.
In Table 1, "◎" indicates that there were no bubbles, "○" indicates that fine bubbles could be slightly confirmed, but there was no problem with the quality of the product, and "×" indicates that there were no bubbles. Each indicates that it exists and there is a problem with the quality of the product.

[Evaluation]
Example 1 in which the shrinkage rate of the polarizer during drying is 19%, Example 2 in which the shrinkage rate is 17%, and Example 3 in which the shrinkage rate is 18% are comparative examples having the same shrinkage rate of 21%. In comparison, it can be seen that bubbles are less likely to be generated. From the comparison between each example and the comparative example, when the shrinkage rate of the polarizer during drying is 20% or less, the polarizer and the film can be adhered while suppressing the generation of fine bubbles.
Further, from the comparison between Example 1 and Examples 2 and 3, it can be seen that by using as many rough surface guide rolls as possible, the polarizer and the film can be adhered while suppressing the generation of fine bubbles.

1 Laminated polarizing film 1a Hydrophilic polymer film 1b Polarizer before drying 1c, 11 Polarizer after drying 12, 13, 14 film 2 Laminated polarizing film manufacturing equipment 4 Wet processing equipment 5 Drying equipment for polarizer 6 Laminating equipment 7 Drying device guide roll 71 Drying device rough surface guide roll

Claims (8)

A polarizer manufacturing process for producing a long strip-shaped polarizer by dyeing and stretching a long strip-shaped hydrophilic polymer film with a dyeing treatment solution.
A drying step of drying the polarizer,
It has a laminating step of obtaining a laminated polarizing film by adhering the dried polarizer and a film with an adhesive.
A method for producing a laminated polarizing film, wherein in the drying step, the polarizer is dried so that the shrinkage ratio of the polarizer in the width direction is 15% to 20%. The method for producing a laminated polarizing film according to claim 1, wherein in the drying step, the polarizing element is dried so that the moisture content of the polarizing element is 18% by weight or less. In the drying step
The method for producing a laminated polarizing film according to claim 1 or 2, wherein the polarizing element is dried while being conveyed by a plurality of guide rolls including a rough surface guide roll having a roughened surface. The method for producing a laminated polarizing film according to claim 3, wherein the surface roughness of the rough surface guide roll is 1 μm to 20 μm in terms of ten-point average roughness Rz. In the laminating process
The method for producing a laminated polarizing film according to any one of claims 1 to 4, wherein an active energy ray-curable adhesive is used as the adhesive. A drying device for drying a long strip-shaped polarizer obtained by dyeing and stretching a long strip-shaped hydrophilic polymer film with a dyeing treatment solution.
A transport unit including a plurality of guide rolls for transporting the polarizer,
It has a heating unit that heats the polarizing element transported by the transport unit.
A drying device for a polarizer in which at least one of the plurality of guide rolls is a rough surface guide roll having a roughened surface. The drying apparatus for a polarizer according to claim 6, wherein the surface roughness of the rough surface guide roll is 1 μm to 20 μm in terms of ten-point average roughness Rz. A wet treatment apparatus for producing a long strip-shaped polarizer by dyeing and stretching a long strip-shaped hydrophilic polymer film with a dyeing treatment liquid.
A device for producing a polarizing element, comprising the drying device according to claim 6 or 7, which dries the polarizer manufactured by the wet processing device.

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