JP7177590B2 - Polarizing film manufacturing method and polarizing film manufacturing apparatus - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method and apparatus for manufacturing a polarizing film.

BACKGROUND ART Conventionally, polarizing films have been used as constituent materials for liquid crystal display devices, polarized sunglasses, and the like. As a polarizing film, for example, a film in which a dichroic substance such as iodine is oriented is known.
Such a polarizing film can be obtained, for example, by subjecting a polyvinyl alcohol film to swelling treatment, dyeing treatment, and cross-linking treatment.
Patent Document 1 discloses a method for producing a polarizing film in which a polyvinyl alcohol-based film is uniaxially stretched using a peripheral speed difference between two nip rollers during swelling treatment, dyeing treatment, boric acid treatment, and washing treatment. Immediately before the acid treatment step, in the stretching step in which uniaxial stretching is performed by two nip rollers arranged in the air and in the liquid in this order while being immersed in the boric acid treatment solution, the film width after immersion with respect to the film width immediately before immersion. A method for producing a polarizing film with a reduction rate of 6% or less is disclosed. In addition, in Patent Document 1, in the stretching process, as a guide roller from the time when the film is immersed until it is conveyed to the submerged nip roller, the JIS Shore C hardness is 20 to 60 degrees and the density is 0.4 to 0.6 g. /cm ³ and a guide roller with a surface roughness of 10-30S.
Patent Literature 1 describes that a polarizing film with small variations in absorption axis can be produced by the production method.

JP 2011-215216 A

By the way, the degree of polarization of polarizing films has been considerably improved by technological improvements, but the market demands polarizing films with even better degree of polarization.
Moreover, as the optical properties of the polarizing film, not only the degree of polarization but also the hue is an important factor. However, it is difficult to produce a polarizing film with a relatively large y value (xy chromaticity diagram).

A first object of the present invention is to provide a method for producing a polarizing film having a superior degree of polarization and an apparatus for producing the same.
A second object of the present invention is to provide a method and apparatus for producing a polarizing film having a better degree of polarization and a relatively large y value.

The manufacturing method of the polarizing film of the present invention includes a swelling step in which the film is transported and swollen by guide rollers placed in a swelling tank containing a swelling liquid, and two rollers placed in a dyeing tank containing a dyeing liquid. A dyeing step of transporting the film by the above guide rollers and immersing the film in a dyeing solution, a cross-linking step of transporting and cross-linking the film by guide rollers placed in a cross-linking bath containing a cross-linking solution, and a washing solution. a washing step of conveying and washing the film by guide rollers arranged in a washing tank, wherein at least one of the guide rollers in the dyeing tank is JIS B 0601; 2013 has a surface roughness of 5.0 μm or less in terms of arithmetic mean roughness Ra measured according to JIS B 0601; It has a surface roughness exceeding 5.0 μm in terms of arithmetic mean roughness Ra measured by

In the preferred manufacturing method of the present invention, the guide roller arranged closest to the inlet side and the guide roller arranged closest to the outlet side in the dyeing tank are both measured in accordance with JIS B 0601; It has a surface roughness Ra of 5.0 μm or less.
In a preferred manufacturing method of the present invention, all the guide rollers arranged in the dyeing tank have a surface roughness of 5.0 μm or less in terms of arithmetic mean roughness Ra .
In a preferred manufacturing method of the present invention, the dyeing solution contains iodine and the film contains a polyvinyl alcohol film.

According to another aspect of the present invention, a polarizing film manufacturing apparatus is provided.
The polarizing film manufacturing apparatus of the present invention includes a swelling tank containing a swelling liquid and arranged with guide rollers for conveying the film, and two or more guide rollers containing a dyeing liquid and conveying the film. a dyeing tank containing a cross-linking solution and arranged with guide rollers for conveying the film; a washing tank containing a washing solution and arranged with guide rollers for conveying the film; At least one of the guide rollers of the dyeing tank has a surface roughness of 5.0 μm or less in terms of arithmetic mean roughness Ra measured according to JIS B 0601; 2013, Each of the guide rollers in the swelling tank, cross-linking tank, and cleaning tank has a surface roughness exceeding 5.0 μm in terms of arithmetic mean roughness Ra measured according to JIS B 0601;2013.

According to the manufacturing method and manufacturing apparatus of the polarizing film of the present invention, a polarizing film having a higher degree of polarization can be manufactured.
In addition, according to the preferred method and apparatus for producing a polarizing film of the present invention, it is possible to produce a polarizing film having an excellent degree of polarization and a relatively large y value.

Schematic which shows the manufacturing apparatus of the polarizing film of this invention.

In this specification, terms such as “first” and “second” may be added at the beginning of terms, but the terms “first” and the like are added only for the purpose of distinguishing terms, and the order and superiority thereof are does not have a special meaning such as Further, the numerical range represented by "lower limit value X to upper limit value Y" means the lower limit value X or higher and the upper limit value Y or lower. When a plurality of numerical ranges are described separately, an arbitrary lower limit value and an arbitrary upper limit value can be selected, and "an arbitrary lower limit value to an arbitrary upper limit value" can be set.

In manufacturing a polarizing film, any film is immersed in a treatment liquid containing an active ingredient. Said immersion includes adsorbing, adhering, containing, or binding an active ingredient in a treatment liquid to said optional film. As used herein, the term "active ingredient" refers to an ingredient necessary for the intended use of the treatment liquid.
The method for producing the polarizing film of the present invention usually includes a swelling step of swelling the film before treatment, a dyeing step of dyeing the swollen film, a cross-linking step of cross-linking after dyeing, a washing step of washing the film after cross-linking, and further includes a step of stretching the film. The stretching step may be performed in at least one step selected from the above steps, or may be performed between two steps selected from the above steps.
Moreover, the manufacturing method of the polarizing film of this invention may have processes other than each said process.

[Polarizing film manufacturing equipment]
FIG. 1 is a reference diagram showing a polarizing film manufacturing apparatus. The arrows in the drawing indicate the traveling direction (conveying direction) of the film.
The manufacturing apparatus 1 has a front roll section 31 on which the film 2 to be processed is wound and a rear roll section 32 on which the polarizing film 9 is wound. This manufacturing apparatus 1 manufactures a polarizing film by a so-called roll-to-roll method.
Between the front roll portion 31 and the back roll portion 32, from the front roll portion 31, in order, a swelling processing section having a swelling tank 41, a dyeing processing section having a dyeing tank 51, a cross-linking processing section having a cross-linking tank 61, and a washing A cleaning processing section having a bath 81 is arranged. In the manufacturing apparatus 1 of the illustrated example, a stretching processing section having a stretching tank 71 is arranged between the cross-linking processing section and the cleaning processing section.
The film 2 unwound and transported from the front roll unit 31 undergoes a swelling process by a swelling process part, a dyeing process by a dyeing process part, a cross-linking process by a cross-linking process part, a stretching process by a stretching process part, and a washing process by a washing process part. After passing through, it is taken up by the rear roll portion 32 .
In the figure, reference numeral 11 denotes a pair of nip rollers. In order to transport the film 2, some or all of the nip rollers 11 are equipped with a drive (such as a motor, not shown).
Further, each processing section of the manufacturing apparatus is equipped with a rotatable guide roller. The guide roller has a function of guiding the film 2 being transported. The guide rollers are arranged at appropriate positions in the transport path of the film 2 in addition to each processing section such as the swelling processing section, the dyeing processing section, the cross-linking processing section, and the washing processing section.
The diameter and axial length of each guide roller are appropriately set according to the width of the film 2 . For example, each guide roller has a diameter of 100 mm to 1000 mm and an axial length of 1 m to 5 m.

<Film>
The film 2 to be processed has a long strip shape. A long belt shape is a rectangular shape in which the length in the longitudinal direction is sufficiently larger than the length in the lateral direction (direction orthogonal to the longitudinal direction). The longitudinal length of the long strip-shaped film 2 is, for example, 10 m or more, preferably 50 m or more.
The film 2 before processing is wound around the front roll portion 31 .
The film 2 is not particularly limited, but is preferably a film containing a hydrophilic polymer film (for example, a polyvinyl alcohol-based film) because it is excellent in dyeability with a dichroic substance, and more preferably, A hydrophilic polymer film is used. Examples of the film including the hydrophilic polymer film include a film in which a hydrophilic polymer film and a non-hydrophilic polymer film are laminated. In this case, the hydrophilic polymer film is preferably laminated on the surface and/or the back surface of the non-hydrophilic polymer film.

The hydrophilic polymer film is not particularly limited, and conventionally known films can be used. Specifically, examples of hydrophilic polymer films include polyvinyl alcohol (PVA) films, partially formalized PVA films, polyethylene terephthalate (PET) films, ethylene/vinyl acetate copolymer films, and partially saponified films thereof. films and the like. In addition to these, polyene oriented films such as dehydrated PVA and dehydrochlorinated polyvinyl chloride films, stretch-oriented polyvinylene films, and the like can also be used. Among these, a PVA-based polymer film is preferable because it is particularly excellent in dyeability with a dichroic substance.
Examples of the raw material polymer for the PVA-based polymer film include a polymer obtained by polymerizing vinyl acetate and saponifying it, and a copolymerizable monomer such as a small amount of unsaturated carboxylic acid or unsaturated sulfonic acid with respect to vinyl acetate. polymer, and the like. Although the degree of polymerization of the PVA-based polymer is not particularly limited, it is preferably 500 to 10,000, more preferably 1,000 to 6,000 in terms of water solubility. 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 film is not particularly limited, but is, for example, 15 μm to 110 μm, preferably 38 μm to 110 μm, more preferably 50 μm to 100 μm.

<Swelling treatment part>
The swelling treatment section is provided to swell the film 2 before the treatment.
The swelling processing section has a bath 41 (swelling bath 41 ), a swelling liquid 42 put in the swelling bath 41 , and guide rollers 43 arranged in the swelling bath 41 . When a film that swells sufficiently in the dyeing processing section, which will be described later, is used, the swelling processing section may be omitted.
In the illustrated example, only one swelling processing unit is installed, but two or more swelling processing units (two or more swelling tanks) may be arranged in parallel in the direction in which the film advances (not shown).
For example, water can be used as the swelling liquid 42 . Furthermore, water to which an appropriate amount of glycerin, potassium iodide, or the like is added may be used as the swelling liquid. When glycerin is added, its concentration is preferably 5% by weight or less, and when potassium iodide is added, its concentration is preferably 10% by weight or less.

A guide roller 43 is arranged in the swelling tank 41 to guide the transported film. The guide roller 43 is arranged in the swelling tank 41 in a state of being immersed in the swelling liquid 42 .
At least one guide roller 43 of the swelling tank 41 is provided. Preferably, the swelling tank 41 is provided with two or more guide rollers 43 spaced apart in the direction in which the film advances.
In the illustrated example, the swelling tank 41 is provided with two guide rollers 43 .

The surface roughness of one or more guide rollers 43 of the swelling tank 41 is not particularly limited.
For example, in the swelling tank 41, a guide roller having a surface roughness of 5.0 μm or less in terms of arithmetic mean roughness Ra may be arranged, and a guide roller having a surface roughness exceeding 5.0 µm in terms of arithmetic mean roughness Ra may be arranged. Rollers may be arranged. For example, the guide roller 43 of the swelling tank 41 has a surface roughness of 9.0 μm or more in terms of arithmetic mean roughness Ra, and further has a surface roughness of 11.0 μm or more in terms of arithmetic mean roughness Ra. The upper limit of the arithmetic mean roughness Ra of the guide rollers 43 of the swelling tank 41 is, for example, 20 μm, although there is no particular upper limit.
Further, in the swelling tank 41, a guide roller having a surface roughness of 25.0 μm or less in maximum height roughness Rz may be arranged, and a surface roughness exceeding 25.0 μm in maximum height roughness Rz may be arranged. For example, the guide roller 43 of the swelling tank 41 has a maximum height roughness Rz of 40.0 μm or more, and further has a maximum height roughness Rz of 50.0 μm or more. Although there is no particular upper limit for the maximum height roughness Rz of the guide roller 43 of the swelling tank 41, it is, for example, 100 μm.
As for the guide roller having the surface roughness as described above, a commercially available product may be used, or it may be produced individually.

<Dye processing part>
The dyeing processing section is provided for dyeing the film.
The dyeing processing section has a tank 51 (dyeing tank 51 ), a dyeing liquid 52 put in the dyeing tank 51 , and a guide roller 53 arranged in the dyeing tank 51 .
In the illustrated example, only one dyeing processing unit is installed, but two or more dyeing processing units (two or more dyeing tanks) may be arranged in parallel in the direction in which the film advances (not shown).
The dyeing solution 52 is a solution for dyeing the film and contains a dichroic substance as an active ingredient. Dichroic substances include iodine and organic dyes.

Preferably, the staining solution 52 may be a solution in which iodine is dissolved in a solvent. Water is generally used as the solvent, but an organic solvent compatible with water may be added. The concentration of iodine in the dyeing solution is not particularly limited, but is preferably 0.01% to 10% by weight, more preferably 0.02% to 7% by weight, and 0.025% by weight. More preferably ~5% by weight.
Furthermore, it is preferable to add an iodine compound to the dyeing solution in order to further improve the dyeing efficiency. An iodine compound is a compound containing iodine and an element other than iodine in its molecule. Examples of the iodine compound include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, iodide Titanium etc. are mentioned. When an iodine compound is added, its concentration is preferably 0.01 wt % to 10 wt %, more preferably 0.1 wt % to 5 wt %. Among the iodine compounds, it is preferable to add potassium iodide.
When the staining solution contains iodine and an iodine compound, iodine may be the main component of the staining solution, or the iodine compound may be the main component of the staining solution. Usually, a staining solution containing more iodine compounds than iodine is used.

A guide roller 53 is arranged in the dyeing bath 51 to guide the conveyed film. The guide roller 53 is arranged in the dyeing tank 51 while being immersed in the dyeing liquid 52 .
The dyeing tank 51 is provided with two or more guide rollers spaced apart in the film traveling direction, preferably three or more guide rollers spaced in the film traveling direction, more preferably four guide rollers. More than one guide roller is provided, more preferably six or more guide rollers are provided. There is no particular upper limit to the number of guide rollers in the dyeing tank 51, but it is usually 20, preferably 16.
As described above, when two or more dyeing units are arranged side by side, the number of all guide rollers included in the two or more dyeing units is preferably within the above range.

In the illustrated example, ten guide rollers 53 (five pairs of upper and lower guide rollers 53) are arranged in one dyeing processing section (one dyeing tank 51).
A first guide roller 531, a second guide roller 532, a third guide roller 533, a fourth guide roller 534, a fifth guide roller 535, a sixth guide roller 536, a seventh guide roller 537, a 8 guide roller 538 , 9th guide roller 539 , and 10th guide roller 530 .
In FIG. 1, the first guide roller 531 is the guide roller closest to the entrance of the dyeing tank 51 (the guide roller closest to the entrance of the dyeing tank 51), and the tenth guide roller 530 is the guide roller located closest to the exit side of the dyeing tank 51 (the guide roller located closest to the exit of the dyeing tank 51).
The film passes from the first guide roller 531 on the entrance side while being in contact with the second guide roller 532, the third guide roller 533, . be done.

At least one of the plurality of guide rollers 53 of the dyeing tank 51 has a surface roughness of 5.0 μm or less in terms of arithmetic mean roughness Ra. In this specification, "surface roughness with an arithmetic mean roughness Ra of 5.0 μm or less" may be referred to as "surface roughness with a specific Ra".
By using the guide roller having the surface roughness of the specific Ra in the dyeing bath 51, a polarizing film with excellent polarization degree can be produced.
For example, among the plurality of guide rollers 53 of the dyeing tank 51, the guide roller 531 arranged closest to the inlet side of the dyeing tank 51 and/or the guide roller 530 arranged closest to the exit side of the dyeing tank 51 have a specific Ra. It has surface roughness. In addition, of the plurality of guide rollers 53 of the dyeing tank 51, more than half of the guide rollers 531 arranged on the most inlet side of the dyeing tank 51 and/or the guide rollers 530 arranged on the most exit side of the dyeing tank 51 The guide roller 53 has a surface roughness of specific Ra.
Preferably, all the guide rollers 53 of the dyeing bath 51 have a surface roughness of specific Ra. A polarizing film having a relatively large y value can be manufactured by using guide rollers having a surface roughness of a specific Ra as all the guide rollers 53 of the dyeing bath 51 .

The guide roller having the surface roughness of the specific Ra preferably has an arithmetic mean roughness Ra of 4.0 μm or less, more preferably an arithmetic mean roughness Ra of 3.0 μm or less. The lower limit of the arithmetic mean roughness Ra of the guide rollers 53 of the dyeing tank 51 is theoretically zero, but realistically it is 0.01 μm, preferably 0.1 μm.

The maximum height roughness Rz of the guide roller having a surface roughness of specific Ra is not particularly limited, but is, for example, 25.0 μm or less, preferably 22.0 μm or less, more preferably 20.0 μm or less, more preferably 18.0 μm or less. Theoretically, the lower limit of the maximum height roughness Rz is zero, but the practical numerical value is 0.01 μm, preferably 0.1 μm. In this specification, "surface roughness of 25.0 μm or less at maximum height roughness Rz" may be referred to as "surface roughness of specific Rz". A surface roughness having an arithmetic mean roughness Ra of 5.0 μm or less and a maximum height roughness Rz of 25.0 μm or less” is sometimes referred to as “a surface roughness of specific Ra and Rz”.
By using the guide roller having the surface roughness of the specific Rz in the dyeing tank 51, a polarizing film having an excellent degree of polarization can be produced.
In this specification, the arithmetic mean roughness Ra and the maximum height roughness Rz (surface roughness) of the guide roller refer to values measured according to JIS B 0601;2013. As the measuring instrument, for example, a surface roughness meter (manufactured by Mitutoyo Co., Ltd., trade name "SJ-310") can be used.

Guide rollers having surface roughnesses of specific Ra and Rz may be commercially available products or individually produced. Further, a guide roller having a surface roughness of specific Ra and Rz can be produced by subjecting a guide roller which does not satisfy the above surface roughness to a mirror-finishing treatment such as polishing.

<Cross-linking treatment part>
The cross-linking section is provided for cross-linking the film to which the dichroic substance is adsorbed.
The cross-linking processing section has a bath 61 (cross-linking bath 61), a cross-linking liquid 62 placed in the cross-linking bath 61, and a guide roller 63 arranged in the cross-linking bath.
In the illustrated example, only one cross-linking processing section is provided, but two or more cross-linking processing sections (two or more cross-linking tanks) may be provided side by side in the direction in which the film advances (not shown).
The cross-linking liquid 62 is a solution for cross-linking the film, and a solution containing a boron compound as an active ingredient can be used. For example, as the cross-linking liquid 62, 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 added. Boron compounds include boric acid and borax. Among them, it is preferable to use boric acid. The concentration of the boron compound in the cross-linking solution is not particularly limited, but is preferably 1% to 10% by weight, more preferably 2% to 7% by weight, and 2% to 6% by weight. is more preferred. Moreover, glyoxal, glutaraldehyde, or the like may be added to the cross-linking solution, if necessary.

Further, it is preferable to add an iodine compound to the cross-linking liquid, since the polarizing film 9 having uniform optical properties can be obtained. The iodine compound is not particularly limited, and examples thereof include those exemplified in the staining liquid 52 described above. Among them, potassium iodide is preferred. Although the concentration of the iodine compound is not particularly limited, it is preferably 0.05% to 15% by weight, more preferably 0.5% to 8% by weight. When an iodine compound is added, the weight ratio of the boron compound (preferably boric acid) and the iodine compound (preferably potassium iodide) is preferably in the range of 1:0.1 to 1:6. , 1:0.5 to 1:3.5, more preferably 1:1 to 1:2.5.
When the cross-linking solution contains a boron compound and an iodine compound, the boron compound may be the main component of the solution, or the iodine compound may be the main component of the solution.

A guide roller 63 is arranged in the cross-linking tank 61 to guide the conveyed film. The guide roller 63 is arranged in the cross-linking tank 61 while being immersed in the cross-linking liquid 62 .
At least one guide roller 63 is provided in the bridging bath 61 . Preferably, the cross-linking bath 61 is provided with two or more guide rollers 63 spaced apart in the direction in which the film advances.
In the illustrated example, the bridging tank 61 is provided with two guide rollers 63 .

The surface roughness of one or more guide rollers 63 of the bridging tank 61 is not particularly limited.
For example, in the cross-linking tank 61, a guide roller having a surface roughness of 5.0 μm or less in terms of arithmetic mean roughness Ra may be arranged, and a guide roller having a surface roughness exceeding 5.0 µm in terms of arithmetic mean roughness Ra may be arranged. Rollers may be arranged. For example, the guide roller of the cross-linking tank 61 has a surface roughness of 5.5 μm or more in terms of arithmetic mean roughness Ra, and the guide roller of the cross-linking tank 61 has a surface roughness of 7.0 µm or more in terms of arithmetic mean roughness Ra. have roughness. Although there is no particular upper limit for the arithmetic mean roughness Ra of the guide rollers of the bridging tank 61, it is, for example, 15 μm.
In addition, in the cross-linking tank 61, a guide roller having a surface roughness of 25.0 μm or less in maximum height roughness Rz may be arranged, and a surface roughness exceeding 25.0 μm in maximum height roughness Rz may be arranged. For example, the guide roller of the cross-linking tank 61 has a maximum height roughness Rz of 26.0 μm or more, and the guide roller of the cross-linking tank 61 has a maximum height roughness Rz of 40.0 μm or more. has a surface roughness of Although there is no particular upper limit for the maximum height roughness Rz of the guide rollers of the bridging tank 61, it is, for example, 100 μm.

<Stretching part>
The stretching section is provided for orienting the film that adsorbs the dichroic substance and is crosslinked.
The stretching section has a bath 71 (stretching bath 71 ), a stretching treatment liquid 72 placed in the stretching bath 71 , and guide rollers 73 arranged in the stretching bath 71 .
In the illustrated example, only one stretching processing section is installed, but two or more stretching processing sections (two or more stretching tanks) may be installed in parallel in the direction in which the film advances (not shown).
In addition, since the film can be stretched in the dyeing processing section, the cross-linking processing section, and the like, the stretching processing section can be omitted.
Although the stretching treatment liquid 72 is not particularly limited, for example, a solution containing a boron compound as an active ingredient can be used. As the stretching treatment liquid 72, for example, a boron compound and, if necessary, a solution in which an iodide compound, various metal salts, a zinc compound, 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 added. Examples of the boron compound include boric acid and borax, among which boric acid is preferably used. The concentration of the boron compound in the stretching treatment liquid is not particularly limited, but is preferably 1 wt % to 10 wt %, more preferably 2 wt % to 7 wt %.
Furthermore, from the viewpoint of suppressing the elution of iodine adsorbed on the film, it is preferable to add an iodine compound to the stretching treatment liquid. The iodine compound is not particularly limited, and examples thereof include those exemplified in the staining liquid 52 described above. Among them, potassium iodide is preferred. Although the concentration of the iodine compound in the stretching treatment liquid 72 is not particularly limited, it is preferably 0.05 wt % to 15 wt %, more preferably 0.5 wt % to 8 wt %.
When the stretching treatment liquid contains a boron compound and an iodine compound, the boron compound may be the main component of the solution, or the iodine compound may be the main component of the solution. Ordinarily, a drawing treatment liquid containing more iodine compounds than boron compounds is used.

Guide rollers 73 are arranged in the stretching bath 71 to guide and stretch the conveyed film. The guide rollers 73 are arranged in the drawing tank 71 while being soaked in the drawing treatment liquid 72 .
The stretching tank 71 is provided with two or more guide rollers 73 spaced apart in the direction in which the film advances.
In the illustrated example, the drawing tank 71 is provided with two guide rollers 73 .

The surface roughness of the two or more guide rollers 73 of the drawing bath 71 is not particularly limited.
For example, the stretching tank 71 may be provided with a guide roller having a surface roughness of 5.0 μm or less in terms of arithmetic mean roughness Ra, and a guide roller having a surface roughness of more than 5.0 μm in terms of arithmetic mean roughness Ra. Rollers may be arranged. For example, the guide roller of the drawing tank 71 has a surface roughness of 5.5 μm or more in terms of arithmetic mean roughness Ra, and the guide roller of the drawing tank 71 has a surface roughness of 7.0 µm or more in terms of arithmetic mean roughness Ra. have roughness. Although there is no particular upper limit for the arithmetic mean roughness Ra of the guide rollers of the drawing tank 71, it is, for example, 15 μm.
Further, in the stretching tank 71, a guide roller having a surface roughness of 25.0 μm or less in maximum height roughness Rz may be arranged, and a surface roughness exceeding 25.0 μm in maximum height roughness Rz may be arranged. For example, the guide roller of the drawing tank 71 has a surface roughness of 26.0 μm or more in maximum height roughness Rz, and further, the guide roller of the drawing tank 71 has a maximum height roughness Rz of 40.0 μm or more. has a surface roughness of Although there is no particular upper limit for the maximum height roughness Rz of the guide rollers of the drawing tank 71, it is, for example, 100 μm.

<Washing section>
The cleaning processing section is provided for cleaning processing liquids such as the dyeing liquid 52 and the cross-linking liquid 62 adhering to the film.
The cleaning processing section has a bath 81 (cleaning bath 81 ), a cleaning liquid 82 put in the cleaning bath 81 , and guide rollers 83 arranged in the cleaning bath 81 .
In the illustrated example, only one cleaning processing unit is installed, but two or more cleaning processing units (two or more cleaning tanks) may be arranged in parallel in the direction in which the film advances (not shown).
As the cleaning liquid 82, water such as ion-exchanged water, distilled water, or pure water is typically used.

A guide roller 83 is arranged in the washing tank 81 to guide the conveyed film.
At least one guide roller 83 is provided for the cleaning tank 81 . Preferably, the washing tank 81 is provided with two or more guide rollers 83 spaced apart in the direction in which the film advances.
In the illustrated example, the cleaning tank 81 is provided with two guide rollers 83 .

The surface roughness of one or more guide rollers 83 of the cleaning tank 81 is not particularly limited.
For example, the cleaning tank may be provided with a guide roller having a surface roughness of 5.0 μm or less in terms of arithmetic mean roughness Ra, or a guide roller having a surface roughness exceeding 5.0 μm in terms of arithmetic mean roughness Ra. may be placed. For example, the guide roller of the cleaning tank has a surface roughness of 9.0 μm or more in terms of arithmetic mean roughness Ra, and the guide roller of the cleaning tank has a surface roughness of 11.0 µm or more in terms of arithmetic mean roughness Ra. have Although there is no particular upper limit for the arithmetic mean roughness Ra of the guide rollers of the cleaning tank, it is, for example, 20 μm.
In addition, a guide roller having a surface roughness of 25.0 μm or less in maximum height roughness Rz may be arranged in the washing tank, and a surface roughness of more than 25.0 μm in maximum height roughness Rz may be disposed. You may arrange|position the guide roller which has. For example, the guide roller of the cleaning tank has a surface roughness of 40.0 μm or more in maximum height roughness Rz, and the guide roller of the cleaning tank has a surface roughness of 50.0 μm or more in maximum height roughness Rz. have roughness. Although there is no particular upper limit for the maximum height roughness Rz of the guide rollers in the cleaning tank, it is, for example, 100 μm.

<Adjustment processing part>
The adjustment processor is provided to adjust the hue of the film. Although not shown in FIG. 1, the adjustment processing section is provided between the cross-linking processing section and the stretching processing section or between the stretching processing section and the cleaning processing section.
The adjustment processing section (not shown) includes a tank (adjustment tank), an adjustment liquid placed in the adjustment tank, and a guide roller disposed in the adjustment tank.
The adjustment liquid is a solution for adjusting the hue of the film, and a solution containing an iodine compound as an active ingredient can be used. For example, a solution in which an iodine compound is dissolved in a solvent can be used as the adjustment liquid. Water is generally used as the solvent, but an organic solvent compatible with water may be added. The iodine compound is not particularly limited, and examples thereof include those exemplified in the staining liquid 52. Among them, potassium iodide is preferable. The concentration of the iodine compound in the adjustment liquid is not particularly limited, but is preferably 0.5 wt % to 20 wt %, more preferably 1 wt % to 15 wt %.

A guide roller is arranged in the adjustment tank.
The guide rollers of the adjustment tank are the same as the guide rollers of the cleaning tank, so description thereof is omitted here.
Note that the adjustment process and the cleaning process can be used together. In this case, adjustment processing and cleaning processing are performed in the cleaning processing unit without providing a separate adjustment processing unit.

[Method for producing polarizing film]
The method for producing a polarizing film of the present invention has a dyeing step of conveying the film by two or more guide rollers arranged in a dyeing bath containing a dyeing solution and immersing the film in the dyeing solution, at least The single guide roller has a surface roughness of 5.0 μm or less in terms of arithmetic mean roughness Ra.
A polarizing film can be manufactured using the manufacturing apparatus 1 described above.
With reference to FIG. 1, the film 2 before treatment is unwound from the front roll portion 31 and conveyed to the swelling tank 41 .
The film 2 is immersed in the swelling liquid 42 while being conveyed by the guide rollers 43 of the swelling bath 41, thereby swelling the film.
Although the temperature of the swelling liquid 42 is not particularly limited, it is, for example, 20°C to 45°C, preferably 25°C to 40°C. The time for immersing the film in the swelling liquid 42 is not particularly limited, but is, for example, 5 seconds to 300 seconds, preferably 8 seconds to 240 seconds.

After the swelling process, the film 2 is pulled out from the swelling tank 41 and transported to the dyeing tank 51 .
The film is dyed with the dichroic substance by immersing the film in the dyeing solution 52 while conveying the film by the guide rollers 53 of the dyeing bath 51 .
The temperature of the dyeing solution 52 is not particularly limited, but is, for example, 20°C to 50°C, preferably 25°C to 40°C. The time for which the film is immersed in the staining solution 52 is not particularly limited, but is, for example, 5 seconds to 300 seconds, preferably 8 seconds to 240 seconds.

After the dyeing process, the film 2 is withdrawn from the dyeing bath 51 and transported to the cross-linking bath 61 .
By immersing the film in the cross-linking liquid 62 while conveying the film with the guide rollers 63 of the cross-linking tank 61, the dichroic substance of the film is cross-linked.
The temperature of the cross-linking liquid 62 is not particularly limited, but is, for example, 25°C or higher, preferably 30°C to 85°C. The time for which the film is immersed in the cross-linking liquid 62 is not particularly limited, but is, for example, 5 seconds to 800 seconds, preferably 6 seconds to 500 seconds.

After the cross-linking process, the film 2 is withdrawn from the cross-linking tank 61 and transported to the stretching tank 71 .
The film is stretched while being conveyed by the guide rollers 73 of the stretching bath 71 . The draw ratio can be appropriately set depending on the purpose, and 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 film.

After the stretching process, the film 2 is transported to an adjustment processing section and immersed in an adjustment liquid, if necessary. The temperature of the adjustment liquid is not particularly limited, but is, for example, 15°C to 40°C. The time for which the film is immersed in the adjustment liquid is not particularly limited, but is, for example, 2 seconds to 20 seconds.

After the stretching process or the adjusting process, the film 2 is conveyed to the washing tank 81 .
The film is washed by immersing the film in the washing liquid 82 while conveying the film with the guide rollers 83 of the washing bath 81 .
The temperature of the cleaning liquid is, for example, 5°C to 50°C, preferably 10°C to 45°C. The cleaning time is, for example, 1 second to 300 seconds, preferably 3 seconds to 240 seconds.
The polarizing film 9 is obtained by drying the film after the washing process as necessary. The manufactured polarizing film 9 is wound around the rear roll section 32 .

By using the manufacturing method and manufacturing apparatus of the present invention, a polarizing film having better polarizing properties can be manufactured.
The polarizing film obtained by the present invention has a high degree of polarization of, for example, 99.992% or more, as is clear from the examples described later. Furthermore, according to the present invention, a polarizing film having a large y value in the xy chromaticity diagram can be obtained. Although the reason why such a polarizing film can be produced is not clear, the present inventors presume as follows.
Generally, in the production of a polarizing film, by stretching a film dyed with a dichroic substance such as iodine, a polymer such as a PVA-based polymer that constitutes the film is oriented, and the dichroic substance is oriented according to the orientation. , exhibiting polarization properties.
For example, in the dyeing process, when a guide roller having a surface with a large arithmetic mean roughness Ra is used, it is presumed that the polymer such as the PVA-based polymer forming the film is partially crystallized . If the polymer is partially crystallized, even if it is stretched after the dyeing process, the polymer in that portion is not sufficiently oriented, and as a result, the dichroic material is also not sufficiently oriented in some portion. In this respect, as in the present invention, a guide roller having a surface roughness of a specific Ra (preferably a guide roller having a surface roughness of specific Ra and Rz) is used as at least one guide roller in the dyeing tank. It is presumed that, in the dyeing process, a polymer such as a PVA-based polymer becomes difficult to crystallize, and as a result, the dichroic substance also becomes sufficiently oriented. Therefore, the polarizing film obtained by the production method and production apparatus of the present invention has excellent polarization degree and large y value.

[Use of polarizing film, etc.]
The polarizing film of the present invention can be used, for example, in lenses such as sunglasses, light control windows, and image display devices such as liquid crystal displays.
The polarizing film of the present invention can also be used as a polarizing plate by laminating a protective film on one side or both sides thereof. When used as a polarizing plate, a retardation film may be further laminated.
As the protective film, for example, a film excellent in transparency, mechanical strength, thermal stability, water barrier properties, etc. can be suitably employed. Specific examples of materials constituting the protective film include cellulose-based resins such as triacetyl cellulose, polyester-based resins, polyethersulfone-based resins, polysulfone-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, and polyolefin-based resins. , (meth)acrylic resins, cyclic polyolefin resins (norbornene resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof.

Hereinafter, the present invention will be described in further detail with reference to Examples. However, the present invention is not limited to the following examples.

[Guide roller used]
・Guide roller (1)
A guide roller having a butadiene-acrylonitrile copolymer (NBR) surface layer (manufactured by Kanuki Roller Mfg. Co., Ltd. under the trade name “Black S45”).
・Guide roller (2)
A guide roller having a butadiene-acrylonitrile copolymer (NBR) surface layer (manufactured by Kanuki Roller Mfg. Co., Ltd. under the trade name of "Dyna Roller") whose surface is straight-polished.
・Guide roller (3)
A guide roller having a polyurethane foam surface layer (trade name “Sponge Roller” manufactured by Kanuki Roller Mfg. Co., Ltd.).
・Guide roller (4)
A guide roller having a butadiene-acrylonitrile copolymer (NBR) surface layer (manufactured by Kanuki Roller Mfg. Co., Ltd. under the trade name of "TAFSEL").
・Guide roller (5)
A guide roller having a butadiene-acrylonitrile copolymer (NBR) surface layer (manufactured by Kanuki Roller Mfg. Co., Ltd. under the trade name of "Dyna Roller").
・Guide roller (6)
A guide roller having a butadiene-acrylonitrile copolymer (NBR) surface layer (manufactured by Kanuki Roller Mfg. Co., Ltd. under the trade name of "Dyna Roller") whose surface was slightly polished.
Each of the guide rules (1) to (6) has a cylindrical shape with a diameter of 200 mm and an axial length of 2.5 m.

[Measurement of surface roughness]
The surface roughness of the guide rollers (1) to (6) (guide roller arithmetic mean roughness Ra and maximum height roughness Rz) was measured according to JIS B 0601; Mitutoyo's product name "SJ-310") was used for each measurement.
Table 1 shows the results.

[Example 1]
As shown in FIG. 1, a swelling tank having two guide rollers, a dyeing tank having ten guide rollers, a cross-linking tank having two guide rollers, a drawing tank having two guide rollers, and two A manufacturing apparatus was prepared in which cleaning tanks having guide rollers of 100 mm width were arranged in order.
Also referring to Table 2, the following guide rollers for each tank were selected and installed in the manufacturing apparatus.

<Guide rollers for each tank>
Two guide rollers in the swelling tank: Both guide rollers (4) were used.
10 guide rollers in the dyeing bath: All 10 guide rollers (1) were used.
Two guide rollers in the cross-linking bath: both guide rollers (5) were used.
Two guide rollers in the drawing bath: Both guide rollers (5) were used.
Two guide rollers in the washing tank: Both guide rollers (4) were used.

An unstretched film (manufactured by Kuraray Co., Ltd., trade name “VF-PE6000”) having a thickness of 60 μm and containing a polyvinyl alcohol resin as a main component was set in the front roll section of the manufacturing apparatus. The film is introduced into a swelling tank, a dyeing tank, a cross-linking tank, a stretching tank, and a washing tank in this order, and subjected to each step of swelling, dyeing, cross-linking, stretching, and washing. A polarizing film having a thickness of 30 μm was produced by drying for a second.

<Processing liquid and processing time in each tank>
Swelling step: The swelling liquid is pure water at 25°C. Immersion time is about 10 seconds.
Dyeing process: The dyeing solution is an aqueous solution at 30°C containing 1% by weight of iodine and 7% by weight of potassium iodide. Immersion time is about 10 seconds.
Cross-linking step: The cross-linking solution is an aqueous solution at 40°C containing 3% by weight of potassium iodide and 4.5% by weight of boric acid. Immersion time is about 8 seconds.
Stretching step: The stretching treatment liquid is an aqueous solution at 63°C containing 5% by weight of potassium iodide and 4% by weight of boric acid. Immersion time is about 12 seconds.
Washing step: The washing solution is an aqueous solution containing 5% by weight of potassium iodide at 27°C. Immersion time is about 3 seconds.

[Example 2]
A polarizing film was produced in the same manner as in Example 1, except that all 10 guide rollers (2) were used as the guide rollers of the dyeing bath (see Table 2).

[Example 3]
The guide roller (1) is used as the first guide roller 531, the third guide roller 533, the fifth guide roller 535, the seventh guide roller 537 and the ninth guide roller 539 of the dyeing tank, and the second guide roller 532 and the fourth guide roller 539 are used. A polarizing film was produced in the same manner as in Example 1 except that the guide roller (2) was used as the guide roller 534, the sixth guide roller 536, the eighth guide roller 538 and the tenth guide roller 530, respectively.

[Example 4]
Guide rollers (1) are used as the first guide roller 531, the second guide roller 532, the fifth guide roller 535, the sixth guide roller 536, the ninth guide roller 539 and the tenth guide roller 530 of the dyeing tank, respectively. A polarizing film was produced in the same manner as in Example 1, except that the guide roller (2) was used as the guide roller 535, the fourth guide roller 534, the seventh guide roller 537, and the eighth guide roller 538, respectively.

[Example 5]
Guide roller (1) is used as the first guide roller 531 (the guide roller closest to the entrance) of the dyeing tank, and guide roller (3) is used as the second to tenth guide rollers 532 to 530 (remaining nine guide rollers). A polarizing film was produced in the same manner as in Example 1, except that the was used.

[Example 6]
Guide roller (1) is used as the tenth guide roller 530 (the guide roller closest to the exit side) of the dyeing tank, and guide roller (3) is used as the first to ninth guide rollers 531 to 539 (remaining nine guide rollers). A polarizing film was produced in the same manner as in Example 1, except that the was used.

[Example 7]
Guide roller (1) is used as the fifth guide roller 535 of the dyeing tank, and guide rollers are used as the first to fourth guide rollers 531 to 534 and the sixth to tenth guide rollers 536 to 530 (remaining nine guide rollers). A polarizing film was produced in the same manner as in Example 1, except that (3) was used.

[Comparative Example 1]
A polarizing film was produced in the same manner as in Example 1, except that all 10 guide rollers (4) were used as guide rollers for the dyeing bath.

[Comparative Example 2]
A polarizing film was produced in the same manner as in Example 1, except that all 10 guide rollers (3) were used as the guide rollers of the dyeing bath.

[Comparative Example 3]
A polarizing film was produced in the same manner as in Example 1, except that the ten guide rollers (5) were used as guide rollers for the dyeing tank.

[Comparative Example 4]
A polarizing film was produced in the same manner as in Example 1, except that all 10 guide rollers (6) were used as guide rollers for the dyeing bath.

[Comparative Example 5]
A polarizing film was produced in the same manner as in Example 1, except that all 10 guide rollers (3) were used as guide rollers in the dyeing tank, and two guide rollers (1) were used as guide rollers in the cross-linking tank. .

[Evaluation of optical properties of polarizing film]
On one side of the polarizing film obtained in each example and comparative example, a 40 μm thick acrylic resin film (manufactured by Kaneka Co., Ltd., trade name “HTX”, Re=0 nm, Rth=0 nm) was applied via an adhesive. On the other side of the polarizing film, a 52 μm-thick norbornene-based resin film (manufactured by Nippon Zeon Co., Ltd., trade name “Zeonor”, transversely stretched film, Re=55 nm, Rth=130 nm) is laminated via an adhesive. By doing so, a polarizing plate having a thickness of 152 μm was produced. Single transmittance, degree of polarization, etc. were measured for each polarizing plate. Table 3 shows the results.
The single transmittance T, parallel transmittance Tp, orthogonal transmittance Tc, and orthogonal transmittance Tc430 at 430 nm of the polarizing plate were measured using an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, trade name "V7100"). . These T, Tp, Tc, and Tc430 are Y values measured with a 2-degree field of view (C light source) according to JIS Z 8701 and subjected to visibility correction. The degree of polarization P was obtained from the following equation using the above transmittance.
Degree of polarization P (%) = {(Tp-Tc)/(Tp+Tc)} ^1/2 × 100

In addition, two polarizing plates superimposed at right angles (crossed nicols) were measured, and the x value and y value according to the xy chromaticity diagram were measured according to JIS Z 8722; 2009. A spectrophotometer (manufactured by JASCO Corporation, trade name "V7100") was used as a measuring instrument. Table 3 shows the results.

From Table 3, it can be seen that the polarizing plates having the polarizing films obtained in Examples 1 to 7, in which guide rollers having specific Ra and Rz surface roughness were used in the dyeing bath, had a high degree of polarization of 99.992% or more. Was. In particular, the polarizing plate having the polarizing film obtained in Examples 1 to 4 in which all the guide rollers in the dyeing bath have specific Ra and Rz surface roughness has a very high degree of polarization of 99.994% or more. Was. Furthermore, the polarizing plates having the polarizing films obtained in Examples 1 to 4 had large x and y values, which are numerical values representing hue. A polarizing plate with large x and y values can be produced using a polarizing film with large x and y values. Although it is generally difficult to produce a polarizing film with a large y value, according to the present invention, a polarizing film with a large y value can be produced. For example, polarizing plates comprising the polarizing films obtained in Examples 1-4 have x values of 0.27 or greater and y values of 0.23 or greater.
On the other hand, the polarizing plates having the polarizing films obtained in Comparative Examples 1 to 4 had a low degree of polarization and a small y value. Also, the polarizing plate having the polarizing film obtained in Comparative Example 5, in which guide rollers having specific Ra and Rz surface roughness were used in the cross-linking tank, also had a low degree of polarization and a small y value. From this, it can be seen that a polarizing film having a better degree of polarization can be produced by using guide rollers having specific Ra and Rz surface roughness in the dyeing tank.

1 Manufacturing apparatus for polarizing film 2 Film before treatment 41 Swelling tank 51 Dyeing tank 53, 531, 532, 533, 534, 535, 536, 537, 538, 539, 530 Guide roller of dyeing tank 61 Cross-linking tank 71 Stretching tank 81 cleaning tank

Claims (5)

A swelling step in which the film is transported and swelled by guide rollers arranged in a swelling tank containing a swelling liquid, and the film is transported by two or more guide rollers arranged in a dyeing tank containing a dyeing liquid. , a dyeing step of immersing the film in a dyeing solution, a cross-linking step of conveying and cross-linking the film by guide rollers placed in a cross-linking bath containing a cross-linking solution, and a washing bath containing a washing solution a cleaning step of conveying and cleaning the film by guide rollers ,
At least one of the guide rollers of the dyeing tank has a surface roughness of 5.0 μm or less in terms of arithmetic mean roughness Ra measured according to JIS B 0601; 2013,
Each guide roller of the swelling tank, cross-linking tank, and washing tank has a surface roughness exceeding 5.0 μm in terms of arithmetic mean roughness Ra measured according to JIS B 0601; 2013. Production method. Both guide rollers arranged on the most inlet side in the dyeing tank and guide rollers arranged on the most outlet side have an arithmetic mean roughness Ra measured according to JIS B 0601; 2013 of 5.0 μm or less. The method for producing a polarizing film according to claim 1, having a surface roughness of . 3. The method for producing a polarizing film according to claim 1, wherein all the guide rollers arranged in the dyeing bath have a surface roughness of 5.0 [mu]m or less in terms of arithmetic mean roughness Ra. The method for producing a polarizing film according to any one of claims 1 to 3, wherein the dyeing solution contains iodine, and the film contains a polyvinyl alcohol-based film. A swelling tank containing a swelling liquid and arranged with guide rollers for conveying the film, a dyeing tank containing a dyeing liquid and containing two or more guide rollers for conveying the film, and a cross-linking liquid. a bridging tank containing guide rollers for conveying the film, and a cleaning tank containing a cleaning liquid and containing guide rollers for conveying the film,
At least one of the guide rollers of the dyeing tank has a surface roughness of 5.0 μm or less in terms of arithmetic mean roughness Ra measured according to JIS B 0601; 2013,
Each guide roller of the swelling tank, cross-linking tank, and washing tank has a surface roughness exceeding 5.0 μm in terms of arithmetic mean roughness Ra measured according to JIS B 0601; 2013. manufacturing device.

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