JP6893292B1 - Polarizing film manufacturing method and manufacturing equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus for producing a polarizing film capable of producing a polarizing film having a uniform shrinkage force in the width direction. SOLUTION: The method for producing a polarizing film includes a stretching treatment step of performing a stretching treatment between a pair of nip rolls while transporting a polyvinyl alcohol-based resin film, and in the stretching treatment step, a film out of a pair of nip rolls. The width of the nip roll on the upstream side is A [mm] in the transport direction, the width of the nip roll on the downstream side is B [mm] in the film transport direction, and the polyvinyl alcohol-based resin film immediately before contacting the nip roll on the downstream side in the film transport direction. A method for producing a polarizing film, which satisfies 3.0 ≦ Y <7.0 [in the formula, Y = (A + B + C) / C] when the width of is C [mm]. [Selection diagram] None

Description

The present invention relates to a method and an apparatus for producing a polarizing film.

Methods for producing a polarizing film have been proposed, for example, in Patent Document 1 and Patent Document 2.

Japanese Unexamined Patent Publication No. 2017-149052 JP-A-2017-105970

An object of the present invention is to provide a method and an apparatus for producing a polarizing film capable of producing a polarizing film having a uniform shrinkage force in the width direction of the polarizing film.

The present invention provides the following polarizing film manufacturing apparatus and manufacturing method.
[1] A method for producing a polarizing film.
Including a stretching treatment step of performing a stretching treatment between a pair of nip rolls while transporting a polyvinyl alcohol-based resin film.
In the stretching treatment step, the width of the nip roll on the upstream side in the film transport direction is A [mm], the width of the nip roll on the downstream side in the film transport direction is B [mm], and the width of the nip roll on the downstream side is B [mm] in the film transport direction. When the width of the polyvinyl alcohol-based resin film immediately before contacting the nip roll on the downstream side is C [mm], the following formula (1): 3.0 ≦ Y <7.0 (1)
[In the formula, Y = (A + B + C) / C]
A method for producing a polarizing film that satisfies the above conditions.
[2] The A [mm] and the C [mm] are expressed by the following formula (2):
1.0 <A / C <3.0 (2)
The method for producing a polarizing film according to [1], which satisfies the above conditions.
[3] The B [mm] and the C [mm] are expressed by the following formula (3):
1.0 <B / C <3.0 (3)
The method for producing a polarizing film according to [1] or [2], which satisfies the above conditions.
[4] The following steps:
Unwinding process of unwinding a long polyvinyl alcohol-based resin film from a raw roll,
A swelling treatment step of immersing the polyvinyl alcohol-based resin film after the unwinding step in a swelling bath and then pulling it out.
It further includes a dyeing treatment step of immersing the polyvinyl alcohol-based resin film after the swelling treatment step in a dyeing bath and then pulling it out, and a cross-linking treatment step of immersing the polyvinyl alcohol-based resin film after the dyeing treatment in a cross-linking bath and then pulling it out. ,
The method for producing a polarizing film according to [1] to [3], wherein the stretching treatment step is performed in any one or more of the swelling treatment step, the dyeing treatment step, and the cross-linking treatment step.
[5] The method for producing a polarizing film according to [4], wherein the stretching treatment step is performed in the crosslinking treatment step.
[6] In the cross-linking treatment step, the first cross-linking treatment step of immersing the dyed polyvinyl alcohol-based resin film in the first cross-linking bath and then pulling it out, and the polyvinyl alcohol-based resin film after the first cross-linking treatment step are first. (2) The method for producing a polarizing film according to [5], which comprises a second cross-linking treatment step of drawing out after being immersed in a cross-linking bath, and the stretching treatment step is performed in the second cross-linking treatment step.
[7] A polarizing film manufacturing apparatus.
It is equipped with a guide roll that unwinds a long polyvinyl alcohol-based resin film from the original roll and conveys it along the film transport path, and a pair of nip rolls that stretch the unwound polyvinyl alcohol-based resin film.
The width of the nip roll arranged on the upstream side of the film transfer path is A [mm], the width of the nip roll arranged on the downstream side of the film transfer path is B [mm], and the width of the nip roll is arranged on the downstream side of the film transfer path. When the width of the polyvinyl alcohol-based resin film immediately before contacting the nip roll is C [mm], the following formula (4):
3.0 ≤ Y <7.0 (4)
[In the formula, Y = (A + B + C) / C]
A polarizing film manufacturing device that meets the requirements.
[8] The A [mm] and the C [mm] are expressed by the following formula (5):
1.0 <A / C <3.0 (5)
The polarizing film manufacturing apparatus according to [7], which satisfies the above conditions.
[9] The B [mm] and the C [mm] are expressed by the following formula (6):
1.0 <B / C <3.0 (6)
The polarizing film manufacturing apparatus according to [7] or [8], which satisfies the above conditions.
[10] A bathtub for performing a swelling treatment, a bathtub for performing a dyeing treatment, and a bathtub for performing a cross-linking treatment are provided in this order on the film transport path.
The polarizing film manufacturing apparatus according to [7] to [9], wherein the pair of nip rolls is provided at the inlet and outlet of any one or more of the bathtubs.
[11] The polarizing film manufacturing apparatus according to [10], wherein the pair of nip rolls is provided at the inlet and outlet of the bathtub for performing the cross-linking treatment.
[12] The bathtub for performing the cross-linking treatment includes a first cross-linking bathtub and a second cross-linking bathtub in order from the upstream side of the film transport path, and the pair of nip rolls are placed at the inlet and outlet of the second cross-linking bathtub. The apparatus for producing a polarizing film according to [11].

According to the present invention, it is possible to provide a method and an apparatus for producing a polarizing film capable of producing a polarizing film having a uniform shrinkage force in the width direction. Further, the polarizing film obtained by using the method and apparatus for producing a polarizing film of the present invention has good thickness uniformity and optical characteristics.

It is the schematic which shows an example of the manufacturing method of the polarizing film schematically. It is a flowchart which shows the manufacturing method of the polarizing film. It is sectional drawing which shows typically an example of the manufacturing apparatus of a polarizing film. It is sectional drawing which shows typically an example of the crosslinked bathtub in the polarizing film manufacturing apparatus.

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. In all the drawings below, the scale is appropriately adjusted to make it easier to understand each component, and the scale of each component shown in the drawings does not necessarily match the scale of the actual component.

<Manufacturing method of polarizing film>
The method for producing a polarizing film according to one aspect of the present invention includes a stretching treatment step of performing a stretching treatment between a pair of nip rolls while transporting a polyvinyl alcohol-based resin film.

[Polyvinyl alcohol-based resin film]
As the polyvinyl alcohol-based resin constituting the polyvinyl alcohol-based resin film, a saponified polyvinyl acetate-based resin can be used. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and a copolymer of vinyl acetate and another monomer copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth) acrylamides having an ammonium group. The saponification degree of the polyvinyl alcohol-based resin is usually about 85 mol% or more, preferably about 90 mol% or more, and more preferably about 99 mol% or more. As used herein, the term "(meth) acrylic" means at least one selected from acrylic and methacryl. The same applies to "(meth) acryloyl".

The polyvinyl alcohol-based resin may be modified, and for example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral, etc. modified with aldehydes can also be used.

The average degree of polymerization of the polyvinyl alcohol-based resin is preferably 100 or more and 10000 or less, more preferably 1500 or more and 8000 or less, and further preferably 2000 or more and 5000 or less. The average degree of polymerization of the polyvinyl alcohol-based resin can be determined in accordance with JIS K 6726 (1994). If the average degree of polymerization is less than 100, it is difficult to obtain preferable polarization performance, and if it exceeds 10,000, the film processability may be inferior.

The width of the polyvinyl alcohol-based resin film, which is the raw film, is, for example, 300 mm or more and 5000 mm or less.

The thickness of the polyvinyl alcohol-based resin film, which is the raw film, is, for example, about 10 μm or more and 50 μm or less, and is preferably 40 μm or less, more preferably 30 μm or less, from the viewpoint of making the thickness of the polarizing film 15 μm or less.

[Stretching process]
The stretching treatment step is a step of performing a stretching treatment between a pair of nip rolls while transporting a polyvinyl alcohol-based resin film. The stretching treatment can be a uniaxial stretching treatment. The stretching treatment may be either dry stretching in which stretching is performed in the air or wet stretching in which stretching is performed in a treatment bath described later, or both of these may be performed. The stretching treatment can be inter-roll stretching in which a peripheral speed difference is provided between a pair of nip rolls and uniaxial stretching is performed in the film transport direction.

The draw ratio based on the raw film (when the draw treatment is performed in two or more stages, the cumulative draw ratio thereof) is about 3 times or more and 8 times or less. In order to impart good polarization characteristics, the draw ratio is preferably 4 times or more, more preferably 5 times or more.

FIG. 1 is a schematic view showing a stretching process. Of the nip rolls 1 and 2 constituting a pair of nip rolls, the width of the nip roll 1 on the upstream side in the film transport direction is A [mm] (hereinafter, also referred to as the upstream nip roll width A), and the nip roll 2 on the downstream side in the film transport direction. The width of the polyvinyl alcohol-based resin film 3 is B [mm] (hereinafter, also referred to as downstream nip roll width B), and the width of the polyvinyl alcohol-based resin film 3 immediately before contacting the downstream nip roll 2 in the film transport direction is C [mm] (hereinafter, PVA). Width C), the following equation (1):
3.0 ≤ Y <7.0 (1)
[In the formula, Y = (A + B + C) / C]
Meet.
Nip rolls are usually composed of two rolls. In FIG. 1, the nip roll 1 is composed of two rolls 1a and 1b, and the nip roll 2 is composed of two rolls 2a and 2b. The widths of the two rolls that make up the nip roll may be the same or different from each other.

By satisfying the above formula (1) in the stretching treatment step, the deviation of the shrinkage force and the thickness in the width direction of the obtained polarizing film becomes small, and the excellent visibility correction single transmittance Ty (hereinafter, also referred to as transmittance Ty). ) And the luminous efficiency correction unit polarization degree Py (hereinafter, also referred to as polarization degree Py) tend to be easily obtained. In the present specification, the width direction of the polarizing film is a direction perpendicular to the film transport direction and a direction perpendicular to the absorption axis of the polarizing film.

Y in the above formula (1) is preferably 3.1 or more, more preferably 3.3 or more, and further preferably 3.5 or more. Y in the above formula (1) is preferably 6.9 or less, more preferably 6.7 or less, still more preferably 6.5 or less, and particularly preferably 6.3 or less.

The upstream nip roll width A is, for example, 300 mm or more and 3600 mm or less. In the upstream nip roll, when the widths of the two rolls constituting the nip roll are different from each other, the shorter roll width is defined as the upstream nip roll width A.

The downstream nip roll width B is, for example, 300 mm or more and 3100 mm or less. In the downstream nip roll, when the widths of the two rolls constituting the nip roll are different from each other, the shorter roll width is referred to as the downstream nip roll width B.

The upstream nip roll width A [mm] and the downstream nip roll width B [mm] may be the same or different.

The PVA width C is, for example, 300 mm or more and 3000 mm or less.

The upstream nip roll width A and the PVA width C are preferably the following formula (2): from the viewpoint of shrinkage force and thickness uniformity in the width direction of the polarizing film.
1.0 <A / C <3.0 (2)
Can be further satisfied.

The A / C in the above formula (2) is preferably 1.1 or more, more preferably 1.2 or more. The A / C in the above formula (2) is preferably 2.9 or less, more preferably 2.7 or less, still more preferably 2.6 or less, and particularly preferably 2.5 or less.

The upstream nip roll width B and the PVA width C are preferably the following formula (3): from the viewpoint of shrinkage force and thickness uniformity in the width direction of the polarizing film.
1.0 <B / C <3.0 (3)
Can be further satisfied.

The B / C in the above formula (3) is preferably 1.1 or more, more preferably 1.2 or more. The B / C in the above formula (3) is preferably 2.9 or less, more preferably 2.7 or less, still more preferably 2.6 or less, and particularly preferably 2.5 or less.

Although not shown in FIG. 1, one or more guide rolls may be used between the pair of nip rolls 1 and 2 to support the film.

[One Embodiment of a method for producing a polarizing film]
The method for producing the polarizing film is as follows: a step of unwinding a long polyvinyl alcohol-based resin film from a raw fabric roll, and a swelling step of immersing the polyvinyl alcohol-based resin film after the unwinding step in a swelling bath and then pulling it out. Further, a dyeing treatment step of immersing the polyvinyl alcohol-based resin film after the treatment step and the swelling treatment step in the dyeing bath and then pulling it out, and a cross-linking treatment step of pulling out the polyvinyl alcohol-based resin film after the dyeing treatment after immersing it in the cross-linking bath. Can include.

The stretching treatment step can be performed in any one or more of the swelling treatment step, the dyeing treatment step and the cross-linking treatment step. Further, in addition to the above stretching treatment step, another stretching treatment can be performed. Other stretching treatments can be, for example, inter-roll stretching, thermal roll stretching, tenter stretching, etc. other than the above stretching treatment.

The above step can be continuously carried out by continuously transporting a polyvinyl alcohol-based resin film, which is a raw film, along a film transport path of a polarizing film manufacturing apparatus. The film transport path is provided with equipment (processing tank, furnace, etc.) for carrying out each process in the order of their execution.

The film transport path can be constructed by arranging a guide roll, a nip roll, or the like at an appropriate position in addition to the above equipment. For example, the guide roll can be arranged before and after the treatment tub, which will be described later, or in the treatment tub, whereby the film can be introduced / immersed in the treatment tub and pulled out from the treatment tub. More specifically, by providing two or more guide rolls in each treatment tank and transporting the film along these guide rolls, the film can be immersed in each treatment bath.

The method for producing the polarizing film will be described in more detail with reference to FIG. The production method shown in FIG. 2 includes a winding step S10 of unwinding a long polyvinyl alcohol-based resin film from a raw fabric roll, and a swelling treatment step of immersing the polyvinyl alcohol-based resin film after the unwinding step in a swelling bath and then pulling it out. S20, a dyeing treatment step S30 in which the polyvinyl alcohol-based resin film after the swelling treatment step is immersed in the dyeing bath and then pulled out, and a cross-linking treatment step S40 in which the polyvinyl alcohol-based resin film after the dyeing treatment is pulled out after being immersed in the cross-linking bath. A cleaning step S50 in which the film after the cross-linking treatment step S40 is immersed in the cleaning tank, and a drying step S60 after the cleaning step S50 are included.

As described above, the polyvinyl alcohol-based resin film is stretched at any one or more steps of the polarizing film manufacturing process, more specifically, at any one or more steps from the swelling treatment step S20 to the crosslinking treatment step S40. The processing process can be performed.

[Unwinding process]
The polyvinyl alcohol-based resin film, which is a raw film, can be prepared, for example, as a roll (rolled product) of a long unstretched or stretched polyvinyl alcohol-based resin film. In this case, the polarizing film is also obtained as a long product. In the unwinding step S10, a long polyvinyl alcohol-based resin film can be unwound from the raw fabric roll using an unwinding device. The unwound polyvinyl alcohol-based resin film is continuously transported along the film transport path.

[Swelling process]
The swelling treatment is a treatment carried out as necessary for the purpose of removing foreign matter from the polyvinyl alcohol-based resin film, which is the raw film, removing the plasticizer, imparting easy dyeability, and plasticizing the film. Can be performed by immersing a polyvinyl alcohol-based resin film in a bathtub (hereinafter, also referred to as a swollen bathtub) for performing a swelling treatment containing a treatment liquid containing water. The film may be immersed in one swelling bath or in two or more swelling baths in sequence.

The stretching treatment step can be performed before the swelling treatment, during the swelling treatment, or before the swelling treatment and during the swelling treatment.

The treatment liquid contained in the swelling bath can be water (for example, pure water) or an aqueous solution to which a water-soluble organic solvent such as alcohol is added.

The temperature of the treatment liquid contained in the swelling bath when the film is immersed is usually about 10 to 70 ° C., preferably about 15 to 50 ° C., and the film immersion time is usually about 10 to 600 seconds, preferably about 10 to 600 seconds. It takes about 20 to 300 seconds.

The swelling treatment step may include a tank for performing a water washing treatment for washing the polyvinyl alcohol-based resin film (hereinafter, also referred to as a water washing treatment tank) before the swelling treatment is performed.

[Dyeing process]
The dyeing treatment in this step is a treatment performed for the purpose of adsorbing and orienting the bicolor dye on the polyvinyl alcohol-based resin film. Specifically, a dyeing treatment containing a treatment liquid containing the bicolor dye is performed. This can be done by immersing a polyvinyl alcohol-based resin film in a bathtub for applying (hereinafter, also referred to as a dyeing bathtub). The film may be immersed in one dyeing bath or in two or more dyeing baths in sequence. For example, when the film is sequentially immersed in the dyeing baths of 2, the first dyeing treatment step and the second dyeing treatment step may be performed from the upstream side in the film transport direction.

In order to enhance the dyeability of the dichroic dye, the film subjected to the dyeing treatment step may be subjected to at least a certain degree of stretching treatment. Instead of the stretching treatment before the dyeing treatment, or in addition to the stretching treatment before the dyeing treatment, the stretching treatment step may be performed at the time of the dyeing treatment.

The dichroic dye can be iodine or a dichroic organic dye. Specific examples of the bicolor organic dyes are Red BR, Red LR, Red R, Pink LB, Rubin BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, Green LG, Violet LB, Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Supra Blue G, Supra Blue GL, Supra Orange GL, Direct Includes Sky Blue, Direct First Orange S, and First Black. As the dichroic dye, only one kind may be used alone, or two or more kinds may be used in combination.

When iodine is used as the dichroic dye, an aqueous solution containing iodine and potassium iodide can be used as the treatment liquid contained in the dyeing bath. Instead of potassium iodide, other iodides such as zinc iodide may be used, or potassium iodide and other iodides may be used in combination. Further, compounds other than iodide, for example, boric acid, zinc chloride, cobalt chloride and the like may coexist. When boric acid is added, it is distinguished from the cross-linking treatment described later in that it contains iodine. The iodine content in the aqueous solution is usually 0.01 parts by mass or more and 1 part by mass or less per 100 parts by mass of water. The content of iodide such as potassium iodide is usually 0.5 parts by mass or more and 20 parts by mass or less per 100 parts by mass of water.

The temperature of the treatment liquid contained in the dyeing bath when the film is immersed is usually 10 ° C. or higher and 45 ° C. or lower, preferably 10 ° C. or higher and 40 ° C. or lower, more preferably 20 ° C. or higher and 35 ° C. or lower, and the film. The immersion time of the film is usually 30 seconds or more and 600 seconds or less, preferably 60 seconds or more and 300 seconds or less.

When a dichroic organic dye is used as the dichroic dye, an aqueous solution containing the dichroic organic dye can be used as the treatment liquid contained in the dyeing bath. The content of the dichroic organic dye in the aqueous solution is usually 1 × 10 ^-4 parts by mass or more and 10 parts by mass or less, preferably 1 × 10 ^-3 parts by mass or more and 1 part by mass or less per 100 parts by mass of water. .. A dyeing aid or the like may coexist in the dyeing bath, and for example, an inorganic salt such as sodium sulfate or a surfactant may be contained. Only one type of dichroic organic dye may be used alone, or two or more types may be used in combination. The temperature of the treatment liquid contained in the dyeing bath when the film is immersed is, for example, 20 ° C. or higher and 80 ° C., preferably 30 ° C. or higher and 70 ° C. or lower, and the film immersion time is usually 30 seconds or longer and 600 seconds or lower. It is preferably 60 seconds or more and 300 seconds or less.

[Crossing process]
The cross-linking treatment of treating the polyvinyl alcohol-based resin film with a cross-linking agent after the dyeing treatment step is a treatment performed for the purpose of making the polyvinyl alcohol-based resin film water-resistant by cross-linking, adjusting the hue, etc. Specifically, the cross-linking treatment containing a cross-linking agent is performed. This can be a process of immersing the film after the dyeing treatment step in the treatment liquid contained in the bath (hereinafter, also referred to as a crosslinked bath). The film may be immersed in one crosslinked bath or may be sequentially immersed in two or more crosslinked baths. The stretching treatment step may be performed at the time of the cross-linking treatment. For example, when the film is sequentially immersed in the cross-linking bath of 2, the first cross-linking treatment step and the second cross-linking treatment step may be performed from the upstream side in the film transport direction.

Examples of the cross-linking agent include boric acid, glyoxal, glutaraldehyde and the like, and boric acid is preferably used. Two or more kinds of cross-linking agents can also be used in combination. The content of boric acid in the treatment liquid contained in the cross-linked bath is usually 0.1 parts by mass or more and 15 parts by mass or less, preferably 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of water. When the dichroic dye is iodine, the treatment liquid contained in the cross-linked bath preferably contains iodide in addition to boric acid. The content of iodide in the treatment liquid contained in the crosslinked bath is usually 0.1 parts by mass or more and 15 parts by mass or less, preferably 5 parts by mass or more and 12 parts by mass or less per 100 parts by mass of water. Examples of the iodide include potassium iodide and zinc iodide. Further, compounds other than iodide, for example, zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate and the like may coexist in the cross-linked bath.

The temperature of the treatment liquid contained in the cross-linking bath when the film is immersed is usually 50 ° C. or higher and 85 ° C. or lower, preferably 50 ° C. or higher and 70 ° C. or lower, and the film immersion time is usually 10 seconds or longer and 600 seconds or lower. It is preferably 20 seconds or more and 300 seconds or less.

When the cross-linked bath is composed of two or more baths, the composition and temperature of the treatment liquid contained in each cross-linked bath may be the same or different. The treatment liquid contained in the cross-linking bath may have a concentration and temperature of a cross-linking agent, iodide, etc., depending on the purpose of immersing the polyvinyl alcohol-based resin film. The cross-linking treatment for water resistance by cross-linking and the cross-linking treatment for hue adjustment (complementary color) may be performed in a plurality of steps (for example, a plurality of tanks).

Generally, when both the cross-linking treatment for water resistance by cross-linking and the cross-linking treatment for hue adjustment (complementary color) are carried out, the tank (complementary color tank) for carrying out the cross-linking treatment for hue adjustment (complementary color) is in the subsequent stage. Be placed. The temperature of the treatment liquid contained in the complementary color tank is, for example, 10 ° C. or higher and 55 ° C. or lower, preferably 20 ° C. or higher and 50 ° C. or lower. The content of the cross-linking agent in the treatment liquid contained in the complementary color tank is, for example, 1 part by mass or more and 5 parts by mass or less per 100 parts by mass of water. The content of iodide in the treatment liquid contained in the complementary color tank is, for example, 3 parts by mass or more and 30 parts by mass or less per 100 parts by mass of water.

The stretching treatment step is preferably performed in the cross-linking treatment step from the viewpoint of shrinkage force and uniformity of thickness in the width direction of the polarizing film, and is performed in both the swelling treatment step and the line color treatment step in addition to the cross-linking treatment step. Is more preferable. In the cross-linking treatment step, the first cross-linking treatment step of immersing the dyed polyvinyl alcohol-based resin film in the first cross-linking bath and then pulling it out, and the polyvinyl alcohol-based resin film after the first cross-linking treatment step are used in the second cross-linking bath. When the second cross-linking treatment step of drawing out after immersion is included, the stretching treatment step is preferably performed in the second cross-linking treatment step.

[Washing process]
The cleaning treatment in this step is a treatment carried out as necessary for the purpose of removing excess cross-linking agent, dichroic dye, and other chemicals adhering to the polyvinyl alcohol-based resin film, and a cleaning liquid containing water is used. This is a process for cleaning the polyvinyl alcohol-based resin film after the cross-linking treatment step. Specifically, it can be a process of immersing the polyvinyl alcohol-based resin film after the crosslinking treatment step in the treatment liquid (cleaning liquid) contained in the cleaning tank. The film may be immersed in one cleaning tank or in two or more cleaning tanks in sequence. Alternatively, the cleaning treatment may be a treatment of spraying the cleaning liquid as a shower on the polyvinyl alcohol-based resin film after the crosslinking treatment step, or the above-mentioned immersion and spraying may be combined.

The cleaning liquid may be water (for example, pure water) or an aqueous solution to which a water-soluble organic solvent such as alcohol is added. The temperature of the cleaning liquid can be, for example, about 5 ° C. or higher and 40 ° C. or lower.

The cleaning step S50 is an arbitrary step and may be omitted, or a cleaning process may be performed during the drying step S60 as described later. Preferably, the drying step S60 is performed on the film after the cleaning step S50.

[Drying process]
The drying step S60 is a zone for drying the polyvinyl alcohol-based resin film after the washing step S50. While the polyvinyl alcohol-based resin film after the washing step S50 is continuously conveyed, the drying treatment can be performed by introducing the film into the drying step S60, whereby a polarizing film can be obtained.

The drying treatment is performed by using a film drying means (heating means). A preferred example of a drying means is a drying oven. The drying furnace is preferably one in which the temperature inside the furnace can be controlled. The drying furnace is, for example, a hot air oven in which the temperature inside the furnace can be raised by supplying hot air or the like. Further, the drying treatment by the drying means may be a treatment in which the polyvinyl alcohol-based resin film after the cleaning step S50 is brought into close contact with one or more heated bodies having a convex curved surface, or a treatment in which the film is heated by using a heater. Good.

Examples of the heating body include a roll (for example, a guide roll that also serves as a heat roll) that is provided with a heat source (for example, a heat medium such as hot water or an infrared heater) and can raise the surface temperature. Examples of the heater include an infrared heater, a halogen heater, a panel heater and the like.

The temperature of the drying treatment (for example, the temperature inside the drying furnace, the surface temperature of the heat roll, etc.) is usually 30 ° C. or higher and 100 ° C. or lower, and preferably 50 ° C. or higher and 90 ° C. or lower. The drying time is not particularly limited, but is, for example, 30 seconds or more and 600 seconds or less.

[Other processing processes]
The other treatment step may be, for example, a complementary color treatment step of immersing in an aqueous iodide solution containing no boric acid, which is performed after the cross-linking treatment.

Through the above steps, a polarizing film in which the dichroic dye is adsorbed and oriented on the uniaxially stretched polyvinyl alcohol-based resin film can be obtained.

The obtained polarizing film can be directly conveyed to, for example, the next polarizing plate manufacturing step (step of laminating a thermoplastic resin film on one side or both sides of the polarizing film).

[Polarizing film]
The thickness of the polarizing film may be, for example, 4 μm or more and 40 μm or less, preferably 4 μm or more and 30 μm or less, and more preferably 4 μm or more and 24 μm or less.

The shrinkage force of the polarizing film may be, for example, 1.0 N or more and 10.0 N or less, preferably 1.0 N or more and 5.0 N or less, and more preferably 1.0 N or more and 4.0 N or less.

The deviation of the shrinkage force in the width direction of the polarizing film may be, for example, 0.3 N or less, preferably 0.25 N or less. In the present specification, the deviation of the contraction force in the width direction means the difference in the contraction force between the central portion and the end portion in the width direction.

The polarizing film may have a transmittance Ty of, for example, 40% or more, usually 50.0% or less, for example, less than 50.0%, or 49.0% or less.

In the polarizing film, the deviation of the transmittance Ty in the width direction may be, for example, 2.0% or less, preferably 1.0% or less. In the present specification, the deviation of the transmittance Ty in the width direction means the difference between the maximum value and the minimum value of the transmittance Ty in the width direction.

The polarizing film may have a degree of polarization Py of, for example, 99.00% or more, preferably 99.90% or more, usually 100% or less, and may be, for example, less than 100%.

In the polarizing film, the deviation of the degree of polarization Py in the width direction may be, for example, 0.1% or less, preferably 0.01% or less. In the present specification, the deviation of the degree of polarization Py in the width direction means the difference between the maximum value and the minimum value of the degree of polarization Py in the width direction.

The thickness, shrinkage force, transmittance Ty and degree of polarization Py of the polarizing film can be measured according to the method described in the column of Examples described later.

<Polarizing film manufacturing equipment>
The polarizing film manufacturing apparatus according to another embodiment of the present invention includes a guide roll for transporting a long polyvinyl alcohol-based resin film from the raw fabric roll along the film transport path, and the unwound polyvinyl alcohol. It is provided with a pair of nip rolls for stretching an alcohol-based resin film. As for the explanation of the polyvinyl alcohol-based resin film, the raw fabric roll, the film transport path, the guide roll, the stretching treatment, and the pair of nip rolls, the above-mentioned description in the method for producing a polarizing film is applied.

The width of the nip roll arranged on the upstream side of the film transport path is A [mm] (hereinafter, also referred to as the upstream nip roll width A), and the width of the nip roll arranged on the downstream side of the film transport path is B [mm] (hereinafter, also referred to as B [mm]). , Also referred to as downstream nip roll width B), when the width of the polyvinyl alcohol-based resin film immediately before contacting the nip roll arranged on the downstream side of the film transport path is C [mm] (hereinafter, also referred to as PVA width C). , The following formula (4):
3.0 ≤ Y <7.0 (4)
[In the formula, Y = (A + B + C) / C]
Meet.

By satisfying the above formula (4) in the polarizing film manufacturing apparatus, the deviation of the shrinkage force and the thickness in the width direction of the obtained polarizing film becomes small, and the excellent transmittance Ty and the degree of polarization Py tend to be easily obtained. It is in.

In the above formula (4), Y is preferably 3.1 or more, more preferably 3.3 or more, and further preferably 3.5 or more. In the above formula (4), Y is preferably 6.9 or less, more preferably 6.7 or less, still more preferably 6.5 or less, and particularly preferably 6.3 or less.

The upstream nip roll width A is, for example, 300 mm or more and 3600 mm or less. In the upstream nip roll, when the widths of the two rolls constituting the nip roll are different from each other, the shorter roll width is defined as the upstream nip roll width A.

The downstream nip roll width B is, for example, 300 mm or more and 3100 mm or less. In the downstream nip roll, when the widths of the two rolls constituting the nip roll are different from each other, the shorter roll width is referred to as the downstream nip roll width B.

The upstream nip roll width A [mm] and the downstream nip roll width B [mm] may be the same or different.

The PVA width C is, for example, 300 mm or more and 3000 mm or less.

The upstream nip roll width A and PVA width C are preferably the following formula (5): from the viewpoint of contraction force.
1.0 <A / C <3.0 (5)
Can be further satisfied.

In the above formula (5), the A / C is preferably 1.1 or more, more preferably 1.2 or more. The right side of the above formula (5) is preferably 2.9 or less, more preferably 2.7 or less, still more preferably 2.6 or less, and particularly preferably 2.5 or less.

The upstream nip roll width B and PVA width C are preferably the following formula (6): from the viewpoint of contraction force.
1.0 <B / C <3.0 (6)
Can be further satisfied.

In the above formula (6), the B / C is preferably 1.1 or more, more preferably 1.2 or more. In the above formula (6), the B / C is preferably 2.9 or less, more preferably 2.7 or less, still more preferably 2.6 or less, and particularly preferably 2.5 or less.

In a polarizing film manufacturing apparatus, a pair of nip rolls treat a polyvinyl alcohol-based resin film provided on a film transport path, such as a swelling bath, a dyeing bath, a cross-linked bath, and a washing bath. The bathtub that houses the treatment liquid to be applied can be arranged at the entrance and the outlet of the treatment bathtub (also collectively referred to as a treatment bathtub). As a result, in one or more treatment baths, inter-roll stretching can be performed by uniaxially stretching in the film transport direction with a peripheral speed difference between the nip rolls arranged before and after the nip rolls.

[One Embodiment of a polarizing film manufacturing apparatus]
The polarizing film manufacturing apparatus includes a bathtub for performing a swelling treatment, a bathtub for performing a dyeing treatment, and a bathtub for performing a cross-linking treatment on the film transport path in this order, and one or more of the above bathtubs. A pair of nip rolls for applying a stretching treatment to the inlet and outlet of the bathtub can be provided. As for the description of the swelling treatment, the dyeing treatment, and the cross-linking treatment, the above-mentioned description in the method for producing a polarizing film is applied.

Hereinafter, the polarizing film manufacturing apparatus of the present invention will be described in more detail with reference to FIG. The polarizing film manufacturing apparatus shown in FIG. 3 transports a raw fabric (unstretched) film 10 made of a polyvinyl alcohol-based resin along a film transport path while continuously unwinding the raw fabric (unstretched) film 10 from the raw fabric roll 11. The swelling bathtub 13, the dyeing bathtub 15, the crosslinked bathtub 17, and the washing tank 19 provided on the transport path are sequentially passed through, and finally the drying furnace 21 is passed through. The obtained polarizing film 23 can be conveyed as it is to, for example, the next polarizing plate manufacturing step (step of laminating a protective film on one side or both sides of the polarizing film 23). The arrows in FIG. 3 indicate the direction in which the film is conveyed.

Note that FIG. 3 shows an example in which one processing bathtub (swelling bathtub 13, dyeing bathtub 15, cross-linked bathtub 17, and cleaning bathtub 19) is provided, but if necessary, one or more treatment bathtubs are provided. May be provided in two or more tanks.

The pair of nip rolls can be, for example, a combination of nip rolls 51 and 52, a combination of nip rolls 52 and 53, a combination of nip rolls 53 and 54, and the like.

In addition to the above-mentioned processing bathtub, the film transport path of the polarizing film manufacturing apparatus includes guide rolls 30 to 50 that can support the film to be transported or further change the film transport direction, and press / hold the film to be transported. However, it can be constructed by arranging nip rolls 51 to 55 capable of applying a driving force due to the rotation to the film or further changing the film conveying direction at appropriate positions. The guide roll and the nip roll can be arranged before and after each treatment bath or in the treatment bath, whereby the film can be introduced and immersed in the treatment bath and pulled out from the treatment bath. For example, by providing one or more guide rolls in each treatment bath and transporting the film along these guide rolls, the film can be immersed in each treatment bath.

In the swelling treatment, the raw fabric film 10 is continuously unwound from the raw fabric roll 11 and conveyed along the film transport path, and the raw fabric film 10 is predetermined in the swelling bathtub 13 (treatment liquid contained in the swelling bathtub). It can be carried out by soaking for hours and then withdrawing. In the swelling treatment, the film is conveyed along the film transfer path constructed by the nip rolls 51 and 52 and the guide rolls 30 to 34.

In the swelling treatment, a problem that the raw film 10 swells in the width direction and the film is wrinkled tends to occur. As one means for transporting the film while removing the wrinkles, a roll having a widening function such as an expander roll, a spiral roll, or a crown roll is used for any one or more of the guide rolls 30 to 34, or a cross guider is used. Other widening devices such as bend bars and tenter clips may be used. Further, when the stretching treatment is performed by the nip rolls 51 and 52, the occurrence of wrinkles tends to be easily suppressed.

When the film is stretched in the swelling bathtub 13, it can be carried out by a method such as providing a peripheral speed difference between the nip rolls 51 and the nip rolls 52 arranged at the inlet and the outlet of the swelling bathtub 13, respectively.

In the swelling treatment, the film swells and expands in the transport direction of the film. Therefore, when the film is not actively stretched, it is arranged in front of and behind the swelling bath 13 in order to eliminate the slack of the film in the transport direction. It is preferable to take measures such as controlling the speeds of the nip rolls 51 and 52. Further, for the purpose of stabilizing the film transfer in the swelling bathtub 13, the water flow in the swelling bathtub 13 is controlled by an underwater shower, and an EPC device (Edge Position Control device: the edge of the film is detected to meander the film. It is also useful to use a device to prevent the above.

In the example shown in FIG. 3, the film drawn from the swelling bath 13 passes through the nip roll 52 and the guide roll 35 in this order and is introduced into the dyeing bath 15.

The dyeing treatment is carried out along the film transport path constructed by the nip rolls 52 and 53 and the guide rolls 35 to 39, and the film after the swelling treatment is immersed in the dyeing bath 15 (treatment liquid contained in the dyeing bath) for a predetermined time. It can then be carried out by pulling it out. In order to improve the dyeability of the bicolor dye, the film to be subjected to the dyeing treatment step is preferably a film that has undergone at least some stretching treatment, or instead of the stretching treatment before the dyeing treatment, or the dyeing treatment. In addition to the previous stretching treatment, it is more preferable to carry out a stretching treatment step during the dyeing treatment.

In the dyeing treatment as well, in order to convey the polyvinyl alcohol-based resin film while removing the wrinkles of the film as in the swelling treatment, widening such as an expander roll, a spiral roll, and a crown roll is performed on any one or more of the guide rolls 35 to 39. Functional rolls can be used, or other widening devices such as cross guiders, bend bars, and tenter clips can be used. Further, when the stretching treatment is performed by the nip rolls 52 and 53, the occurrence of wrinkles tends to be easily suppressed.

When the film is stretched in the dyeing bath 15, it can be carried out by a method such as providing a peripheral speed difference between the nip roll 52 and the nip roll 53 arranged at the inlet and the outlet of the dyeing bath 15, respectively.

The film drawn from the dyeing bath 15 passes through the nip roll 53 and the guide roll 40 in this order and is introduced into the crosslinked bath 17.

In the cross-linking treatment, the film is conveyed along the film transport path constructed by the nip rolls 53 and 54 and the guide rolls 40 to 44, and the dyed film is immersed in the cross-linking bathtub 17 (treatment liquid contained in the cross-linking bathtub) for a predetermined time. It can then be carried out by pulling it out.

Stretching treatment can also be performed in the cross-linking bathtub 17 by utilizing the difference in peripheral speed between the nip roll 53 and the nip roll 54 arranged at the inlet and the outlet of the bathtub for performing the cross-linking treatment. From the viewpoint of shrinkage force and uniformity of thickness in the width direction of the polarizing film, the stretching treatment step is preferably performed in the crosslinked bathtub 17.

As shown in FIG. 4, the crosslinked bathtub 17 can be composed of the first crosslinked bathtub 17a and the second crosslinked bathtub 17b in order from the upstream side of the film transport path. When the cross-linked bathtub 17 is composed of the first cross-linked bathtub 17a and the second cross-linked bathtub 17b, it is preferable to perform the stretching treatment with a pair of nip rolls 56 and 57 arranged at the inlet and the outlet of the second cross-linked bathtub 17b. In FIG. 4, the nip roll 56 serves as the inlet side nip roll, and the nip roll 57 serves as the outlet side nip roll.

In the cross-linking treatment as well, in order to convey the polyvinyl alcohol-based resin film while removing the wrinkles of the film as in the swelling treatment, widening such as an expander roll, a spiral roll, and a crown roll is performed on any one or more of the guide rolls 40 to 44. Functional rolls can be used, or other widening devices such as cross-guiders, bend bars, and tenter clips can be used. Further, when the stretching treatment is performed by the nip rolls 53 and 54, the occurrence of wrinkles tends to be easily suppressed.

The film drawn from the crosslinked bathtub 17 passes through the nip roll 54 and the guide roll 45 in this order and is introduced into the washing tank 19. Also in the cleaning treatment, for the purpose of transporting the polyvinyl alcohol-based resin film while removing wrinkles, a roll having a widening function such as an expander roll, a spiral roll, or a crown roll may be used for any one or more of the guide rolls 45 to 49. , Cross guiders, bend bars, tenter clips and other widening devices can be used.

After the cleaning treatment, it is preferable to carry out a treatment of drying the polyvinyl alcohol-based resin film. Drying of the film is not particularly limited, but can be performed using, for example, a drying oven 21 as shown in FIG.

The method for producing the polarizing film may include other processing baths. Examples of other treatment baths include complementary color treatment baths for treating with an aqueous iodide solution containing no boric acid, which is performed after the cross-linking treatment.

Hereinafter, the present invention will be described in more detail with reference to Examples. Unless otherwise specified, "%" and "part" in the example are mass% and parts by mass.

(1) Shrinkage force of polarizing film Supercutter (Co., Ltd.) makes the polarizing film into a rectangle with a short side of 2 mm and a long side of 50 mm from the center and edges in the width direction so that the slow axis of the polarizing film coincides with the long side. It was cut out by Ogino Seiki Seisakusho Co., Ltd.) and used as a test piece. The contraction force of the test piece was measured using a thermomechanical analyzer (manufactured by SII Nanotechnology Co., Ltd., model TMA / 6100). This measurement was carried out in a constant dimensional mode (distance between chucks was 10 mm), the test piece was left in a room at 20 ° C. for a sufficient time, and then the temperature in the sample room was set from 20 ° C. to 80 ° C. in 10 minutes. The temperature was raised, and after the temperature was raised, the temperature inside the sample chamber was set to be maintained at 80 ° C. After the temperature was raised and left for another 4 hours, the contraction force in the long side direction of the test piece was measured in an environment of 80 ° C. In this measurement, the static load was 0 mN, and a SUS probe was used as the jig. The difference in contraction force between the central part and the end part was calculated as a deviation.

(2) Luminosity factor correction single transmittance Ty and luminous efficiency correction polarization degree Py of polarizing film
A non-alkali glass plate (trade name "EAGLE XG" manufactured by Corning Inc., thickness 0.7 mm) was attached to the polarizing film via a (meth) acrylic pressure-sensitive adhesive layer to obtain a measurement sample. This measurement sample was set in a spectrophotometer with an integrating sphere (“V7100” manufactured by JASCO Corporation, 2 degree field; C light source), and the transmittance Ty and the degree of polarization Py were measured. The measurement sample was set so that the incident light was incident from the side opposite to the non-alkali glass plate.
The transmittance Ty and the degree of polarization Py are expressed by the following formulas, respectively:
Transmittance (λ) = 0.5 × (Tp (λ) + Tc (λ))
Degree of polarization (λ) = 100 × (Tp (λ) -Tc (λ)) / (Tp (λ) + Tc (λ))
Defined in. Tp (λ) is the transmittance (%) when measured in the relationship between the incident linearly polarized light with a wavelength of λ nm and parallel Nicol, and Tc (λ) is the relationship between the incident linearly polarized light with a wavelength of λ nm and cross Nicol. It is the transmittance (%) when measured.
The transmittance Ty and the degree of polarization Py are those obtained by correcting the luminosity factor (λ) and the degree of polarization (λ) obtained for each wavelength with a two-degree field of view (C light source) of JlS Z 8701. Is. Ty and Py were measured in the wavelength range of 380 to 780 nm in 5 nm increments.

(3) Thickness of polarizing film Using a digital micrometer "MH-15M" manufactured by Nikon Corporation, the thickness of the polarizing film in the width direction (perpendicular to the film transport direction) was measured at multiple points, and among them, When the difference between the maximum value and the minimum value was taken as the deviation, the improvement rate was calculated according to the following formula.
Improvement rate [%] = [(deviation of Comparative Example 1-deviation of Example) / deviation of Comparative Example 1] × 100

<Example 1>
While continuously transporting a long polyvinyl alcohol-based resin film (raw fabric width: 550 mm, average degree of polymerization: about 2400, saponification degree: 99.9 mol% or more, thickness: 30 μm), the following [1] -[4] was sequentially immersed in the bath while applying tension, and stretched in the film transport direction. Subsequently, the film was washed with pure water and then dried to obtain a long polarizing film in which iodine was adsorbed and oriented on a uniaxially stretched polyvinyl alcohol film.
However, when the stretching treatment is performed between the pair of nip rolls in the second crosslinked bathtub of [4], the width of the nip roll (nip roll width A) on the inlet side (upstream side in the film transport direction) of the second crosslinked bathtub is set. 900 mm, the width of the nip roll (nip roll width B) on the outlet side (downstream side in the film transport direction) is 900 m, and the width (PVA width C) of the polyvinyl alcohol-based resin film immediately before contacting the nip roll width on the outlet side is 355 nm. I made it. It was (A + B + C) / C = 6.1.
[1] Swelling bath: pure water at 40 ° C. [2] Dyeing bath: aqueous solution containing iodine and potassium iodide [3] 1st cross-linking bath: aqueous solution containing potassium iodide and boric acid [4] 2nd cross-linking Bath: Aqueous solution containing potassium iodide and boric acid Table 1 shows the improvement rates of the shrinkage force, optical performance, and thickness deviation of the obtained polarizing film.

<Examples 2 to 5, Comparative Example 1>
A polarizing film was produced in the same manner as in Example 1 except that the original fabric width, nip roll widths A and B, and PVA width C of the long polyvinyl alcohol-based resin film were set to the values shown in Table 1. The results are shown in Table 1.

1, 2 nip rolls, 1a, 1b, 2a, 2b rolls, 3 polyvinyl alcohol-based resin films, 10 raw fabric films, 11 raw fabric rolls, 13 swelling bathtubs, 15 dyeing bathtubs, 17 cross-linked bathtubs, 17a first cross-linked bathtubs, 17b 2nd cross-linked bath, 19 washing tub, 21 drying furnace, 23 polarizing film, 30-50 guide rolls, 51-57 nip rolls.

Claims (12)

It is a method of manufacturing a polarizing film.
Including a stretching treatment step of performing a stretching treatment between a pair of nip rolls while transporting a polyvinyl alcohol-based resin film.
In the stretching treatment step, the width of the nip roll on the upstream side in the film transport direction is A [mm], the width of the nip roll on the downstream side in the film transport direction is B [mm], and the width of the nip roll on the downstream side is B [mm] in the film transport direction. When the width of the polyvinyl alcohol-based resin film immediately before contacting the nip roll on the downstream side is C [mm], the following formula (1): 3.0 ≦ Y <7.0 (1)
[In the formula, Y = (A + B + C) / C]
A method for producing a polarizing film that satisfies the above conditions. The A [mm] and the C [mm] are expressed by the following formula (2):
1.0 <A / C <3.0 (2)
The method for producing a polarizing film according to claim 1, which satisfies the above conditions. The B [mm] and the C [mm] are expressed by the following formula (3):
1.0 <B / C <3.0 (3)
The method for producing a polarizing film according to claim 1 or 2, which satisfies the above conditions. The following steps:
Unwinding process of unwinding a long polyvinyl alcohol-based resin film from a raw roll,
A swelling treatment step of immersing the polyvinyl alcohol-based resin film after the unwinding step in a swelling bath and then pulling it out.
It further includes a dyeing treatment step of immersing the polyvinyl alcohol-based resin film after the swelling treatment step in a dyeing bath and then pulling it out, and a cross-linking treatment step of immersing the polyvinyl alcohol-based resin film after the dyeing treatment in a cross-linking bath and then pulling it out. ,
The method for producing a polarizing film according to any one of claims 1 to 3, wherein the stretching treatment step is performed in any one or more of the swelling treatment step, the dyeing treatment step, and the cross-linking treatment step. The method for producing a polarizing film according to claim 4, wherein the stretching treatment step is performed in the crosslinking treatment step. In the cross-linking treatment step, the first cross-linking treatment step of immersing the dyed polyvinyl alcohol-based resin film in the first cross-linking bath and then pulling it out, and the second cross-linking bath of the polyvinyl alcohol-based resin film after the first cross-linking treatment step. The method for producing a polarizing film according to claim 5, wherein the stretching treatment step includes a second cross-linking treatment step of drawing out after being immersed in the second cross-linking treatment step. It is a polarizing film manufacturing equipment.
It is equipped with a guide roll that unwinds a long polyvinyl alcohol-based resin film from the original roll and conveys it along the film transport path, and a pair of nip rolls that stretch the unwound polyvinyl alcohol-based resin film.
The width of the nip roll arranged on the upstream side of the film transfer path is A [mm], the width of the nip roll arranged on the downstream side of the film transfer path is B [mm], and the width of the nip roll is arranged on the downstream side of the film transfer path. When the width of the polyvinyl alcohol-based resin film immediately before contacting the nip roll is C [mm], the following formula (4):
3.0 ≤ Y <7.0 (4)
[In the formula, Y = (A + B + C) / C]
A polarizing film manufacturing device that meets the requirements. The A [mm] and the C [mm] are expressed by the following formula (5):
1.0 <A / C <3.0 (5)
The polarizing film manufacturing apparatus according to claim 7. The B [mm] and the C [mm] are expressed by the following formula (6):
1.0 <B / C <3.0 (6)
The polarizing film manufacturing apparatus according to claim 7 or 8. A bathtub for performing a swelling treatment, a bathtub for performing a dyeing treatment, and a bathtub for performing a cross-linking treatment are provided in this order on the film transport path.
The polarizing film manufacturing apparatus according to any one of claims 7 to 9, wherein the pair of nip rolls is provided at the inlet and outlet of any one or more of the bathtubs. The polarizing film manufacturing apparatus according to claim 10, further comprising the pair of nip rolls at the inlet and outlet of the bathtub for performing the cross-linking treatment. The bathtub for performing the cross-linking treatment includes a first cross-linked bathtub and a second cross-linked bathtub in this order from the upstream side of the film transport path, and is provided with the pair of nip rolls at the inlet and outlet of the second cross-linked bathtub. Item 11. The apparatus for manufacturing a polarizing film according to Item 11.

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