JP7579710B2 - Polarizer manufacturing method and manufacturing apparatus - Google Patents

Description

The present invention relates to a method and an apparatus for manufacturing a polarizer. In particular, the present invention relates to a method and an apparatus for manufacturing a polarizer by placing nip rollers in a treatment bath and treating an original film in the treatment bath while transporting the original film with the nip rollers, and the method and apparatus can suppress breakage of the original film in the treatment bath.

Conventionally, polarizing films containing polarizers have been used as a constituent material for liquid crystal display devices, organic EL display devices, and the like. Polarizing films are composed of, for example, a polarizer dyed with a dichroic substance such as iodine and a protective film that protects the polarizer. Long strip polarizing films are usually manufactured by laminating a long strip protective film to at least one side of a long strip polarizer using a roll-to-roll method. The manufactured long strip polarizing film is cut into a size and shape according to the application and used in liquid crystal display devices, etc.

Polarizers are manufactured by treating a raw film, which is a long strip of polymer film, with various treatments by immersing the raw film in various treatment baths while transporting it in the longitudinal direction. Examples of treatment tanks that store the treatment baths include, in order from the upstream side in the transport direction of the raw film, a swelling treatment tank that performs a swelling treatment on the raw film, a dyeing treatment tank that performs a dyeing treatment with a dichroic substance such as iodine on the raw film that has been subjected to the swelling treatment, a crosslinking treatment tank that performs a crosslinking treatment on the raw film that has been subjected to the crosslinking treatment, and a cleaning treatment tank that performs a cleaning (water washing) treatment on the raw film that has been subjected to the stretching treatment (see, for example, Patent Document 1).

Generally, a guide roller placed in the treatment bath is used to transport the raw film through the treatment bath, but a nip roller placed in the treatment bath may also be used (see, for example, Patent Document 2). The guide roller is a roller that comes into contact with one side of the raw film. The nip roller is composed of a drive roller that is rotated by a drive source such as a motor, and a driven roller that rotates with the rotation of the drive roller and conveys the raw film by sandwiching it between the drive roller and the nip roller.

However, it was found that when the raw film is transported using nip rollers placed in the treatment bath, the raw film may break during stretching, resulting in so-called stretch breakage.

JP 2004-341515 A JP 2014-142392 A

The present invention has been made to solve the problems of the conventional technology described above, and aims to provide a method and apparatus for producing a polarizer that can suppress stretching breakage of the original film in the treatment bath, in a method and apparatus for producing a polarizer by placing nip rollers in a treatment bath and treating the original film in the treatment bath while transporting the original film with the nip rollers.

In order to solve the above problems, the inventors conducted extensive research and discovered that one of the reasons why the original film breaks during stretching is that when the surface hardness (outer surface hardness) of the drive roller and driven roller that make up the nip roller is high, the linear pressure acting on the original film from the nip roller becomes large when the original film is nipped (when the original film is sandwiched between the drive roller and driven roller while being pressed against them).
In order to reduce the linear pressure acting on the raw film from the nip roller, it is possible to reduce the surface hardness of both the drive roller and the driven roller. However, reducing the surface hardness is not preferable because the durability of the nip roller decreases when immersed in the bath liquid. Therefore, it has been found that by reducing the surface hardness of only one of the drive roller and the driven roller, the linear pressure acting on the raw film from the nip roller is reduced, preventing the raw film from being cut in the stretched state, and the durability of the nip roller can be maintained to an unobstructed level.
The present invention has been completed based on the above findings of the present inventors.

That is, in order to solve the above-mentioned problems, the present invention provides a method for producing a polarizer by placing nip rollers in a treatment bath and treating a raw film in the treatment bath while transporting the raw film with the nip rollers, the nip rollers being composed of a drive roller and a driven roller that transports the raw film while nipping it between the drive roller, the nip rollers being placed such that a portion of the drive roller is located above the liquid level of the treatment bath and the driven roller is immersed in the treatment bath, and the drive roller has a surface hardness of less than 80 on the Asker C hardness scale, and the driven roller has a surface hardness of 80 or more on the Asker C hardness scale .

In the present invention, "disposing the nip roller in the treatment bath" means disposing the nip roller in a state where at least a part of the nip roller is immersed in the treatment bath.
According to the present invention, the drive roller and the driven roller constituting the nip rollers arranged in the treatment bath have different surface hardnesses. In other words, the surface hardness of one of the drive roller and the driven roller is high and the surface hardness of the other roller is low. Specifically, the surface hardness of the drive roller is lower than that of the driven roller, the surface hardness of the drive roller is less than 80 in Asker C hardness, and the surface hardness of the driven roller is 80 or more in Asker C hardness. Therefore , as the inventors have found, the linear pressure acting on the original film from the nip roller is reduced, preventing the original film from being broken in stretching, and the durability of the nip roller can be maintained to an unobstructed level.

According to the present invention, the nip roller is positioned so that a portion of the drive roller is located above the liquid level of the treatment bath and the driven roller is immersed in the treatment bath, and the surface hardness of the drive roller is lower than the surface hardness of the driven roller.

According to the present invention , the nip rollers are arranged such that a portion of the drive roller is located above the liquid level of the treatment bath (in other words, the remaining portion of the drive roller is immersed in the treatment bath) and the driven roller (the entire driven roller) is immersed in the treatment bath. Therefore, it is not necessary to immerse a drive source such as a motor required to rotate the drive roller in the treatment bath (waterproofing equipment for the drive source is not required), and a polarizer can be manufactured with fewer equipment constraints.
According to the present invention , the surface hardness of the drive roller, a part of which is located above the liquid level of the treatment bath, is lower than the surface hardness of the driven roller which is immersed in the treatment bath. In other words, the drive roller, which has a lower surface hardness and therefore is less durable than the driven roller, is not immersed in the treatment bath in its entirety at all times, but is only immersed partially and intermittently as it rotates, so that deterioration of the drive roller can be suppressed.

Preferably, the drive roller and/or the driven roller comprises a core material and multiple layers of elastic members wound around the core material, and the multiple layers of elastic members have a surface hardness of the elastic member of the inner layer that is higher than the surface hardness of the elastic member of the outer layer.

In the above preferred method, "the surface hardness of the elastic member of the inner layer is higher than that of the elastic member of the outer layer" means that, when the elastic member wound around the core is three or more layers, the surface hardness of the elastic member of the inner layer is higher than that of the elastic member of the outer layer when comparing any two layers of elastic members adjacent to each other in the radial direction of the core (the radial direction of the driving roller and the driven roller). For example, when the elastic member wound around the core is three layers, the surface hardness of the elastic member of the innermost layer is the highest, the surface hardness of the elastic member of the intermediate layer is the next highest, and the surface hardness of the elastic member of the outermost layer is the lowest.
In the above preferred method, the surface hardness of the elastic member of each layer means the surface hardness when the elastic member is wound around the core from the inside, and the elastic member of each layer is located on the outermost side. For example, when the elastic member wound around the core is three layers, the surface hardness of the elastic member of the innermost layer means the surface hardness measured when only the elastic member is wound around the core and the elastic member is located on the outermost side (the elastic member of the outermost layer and the elastic member of the intermediate layer among the three layers of elastic members are not wound). In addition, the surface hardness of the elastic member of the intermediate layer means the surface hardness measured when the elastic member of the innermost layer is wound around the core, and the elastic member of the intermediate layer is further wound around the core and the elastic member is located on the outermost side (the elastic member of the outermost layer is not wound around the three layers of elastic members). In addition, the surface hardness of the elastic member of the outermost layer means the surface hardness measured when the elastic member of the innermost layer and the elastic member of the intermediate layer are wound around the core, and the elastic member of the outermost layer is further wound around the core.
According to the above-mentioned preferred method, the core material is sufficiently protected by the elastic member of the innermost layer (elastic member with the highest surface hardness), and the adhesive strength when bonding the core material and the elastic member can be increased. In addition, since the elastic member of the outermost layer (elastic member with the lowest surface hardness) contacts the raw film, the linear pressure acting on the raw film is reduced, and stretching breakage of the raw film is suppressed.

In the above preferred method, more preferably, the multi-layer elastic member is a three-layer elastic member.

According to the above-mentioned more preferred method, the core material is adequately protected by the elastic member (elastic member with the highest surface hardness) of the innermost layer of the three elastic members, and the adhesive strength when bonding the core material and the elastic member can be increased. In addition, since the elastic member of the outermost layer (elastic member with the lowest surface hardness) comes into contact with the original film, the linear pressure acting on the original film is reduced, and stretching and breaking of the original film is suppressed. Furthermore, the surface hardness of the elastic member of the outermost layer can be adjusted by the surface hardness of the elastic member of the intermediate layer (elastic member with an intermediate surface hardness value).

Preferably, the outer diameter of the drive roller is greater than the outer diameter of the driven roller.

According to the above-mentioned preferred method , the nip rollers are arranged so that a portion of the driving roller having a lower surface hardness is located above the liquid level of the treatment bath and the driven roller having a higher surface hardness is immersed in the treatment bath, and since the outer diameter of the driving roller having a lower surface hardness is large, it is easy to position a portion of the driving roller above the liquid level of the treatment bath, thereby making it possible to suppress deterioration of the driving roller.

The method according to the present invention can prevent the original film from breaking during stretching, and is therefore suitable for use when the treatment bath is a treatment bath that applies a stretching treatment to the original film.

In order to solve the above-mentioned problems, the present invention also provides an apparatus for producing a polarizer, the apparatus comprising: a treatment tank for storing a treatment bath; and nip rollers disposed in the treatment bath, and for treating a raw film in the treatment bath while transporting the raw film with the nip rollers, the nip rollers being composed of a drive roller and a driven roller for transporting the raw film while sandwiching it between the drive roller, the nip rollers being disposed such that a portion of the drive roller is located above the liquid level of the treatment bath and the driven roller is immersed in the treatment bath, and the surface hardness of the drive roller is less than 80 in Asker C hardness, and the surface hardness of the driven roller is 80 or more in Asker C hardness .

According to the present invention, in a method and apparatus for manufacturing a polarizer by disposing a nip roller in a treatment bath and treating the original film in the treatment bath while transporting the original film with the nip roller, the linear pressure acting on the original film from the nip roller is reduced, preventing the original film from being cut in the stretched state, and the durability of the nip roller can be maintained to an unobstructed level.

1 is a diagram illustrating a schematic configuration of a polarizer manufacturing apparatus according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a schematic configuration of a drive roller according to an embodiment of the present invention. FIG. 2 is a diagram showing a schematic configuration of a driven roller according to an embodiment of the present invention;

The following describes a method and apparatus for manufacturing a polarizer according to one embodiment of the present invention, with reference to the attached drawings. Please note that each figure is for reference only, and the dimensions, scale, and shapes of the components shown in each figure may differ from the actual ones.

Fig. 1 is a diagram showing a schematic configuration of a polarizer manufacturing apparatus according to the present embodiment. Fig. 1(a) is a side view showing a schematic configuration of the entire manufacturing apparatus 100 (viewed from a horizontal direction perpendicular to the conveying direction of the raw film F0 and the polarizer F1), and Fig. 1(b) is an enlarged view of the stretching treatment tank 14 shown in Fig. 1(a). The thick arrow in Fig. 1 indicates the conveying direction of the raw film F0 and the polarizer F1.
As shown in FIG. 1, the manufacturing apparatus 100 of this embodiment includes a plurality of treatment tanks 1 each storing a treatment bath L (the area hatched in FIG. 1 in a dotted pattern), and nip rollers 2 arranged in a predetermined treatment bath L (in this embodiment, a stretching treatment bath L4). The manufacturing apparatus 100 manufactures a polarizer F1 by treating an original film F0 in the treatment bath L (L1 to L5) while transporting the original film F0 by the nip rollers 2 or the like.
In addition to the processing tank 1 and the nip roller 2, the manufacturing apparatus 100 is equipped with a pay-out roller FR around which a long length of raw film F0 is wound, a nip roller NR and a guide roller GR for transporting the raw film F0 paid out from the pay-out roller FR, and an oven 3 for drying the raw film F0.
After that, a protective film is attached to at least one surface of the polarizer F1 manufactured by the manufacturing apparatus 100 via an ultraviolet-curable adhesive, and the adhesive is cured by an ultraviolet irradiation device, thereby manufacturing a polarizing film. Furthermore, a surface protective film is attached to one surface of the polarizing film, thereby manufacturing a polarizing plate.

As the raw film F0, a long strip-shaped polymer film is used.
The polymer film forming the raw film F0 is not particularly limited and various types can be used. For example, hydrophilic polymer films such as polyvinyl alcohol (PVA)-based films, polyethylene terephthalate (PET)-based films, ethylene-vinyl acetate copolymer-based films, partially saponified films thereof, cellulose-based films, and polyene-based oriented films such as dehydrated PVA and dehydrochlorinated polyvinyl chloride are listed. Among these, it is preferable to use PVA-based films, which have excellent dyeability with iodine.

The degree of polymerization of the polymer that is the material of the polymer film is generally 500 to 10,000, preferably in the range of 1,000 to 6,000, and more preferably in the range of 1,400 to 4,000. Furthermore, when the polymer film is a saponified film, the degree of saponification is preferably 75 mol% or more, more preferably 98 mol% or more, and more preferably in the range of 98.3 to 99.8 mol%, from the viewpoint of solubility in water, for example.

When a PVA-based film is used as the polymer film, any method can be used for producing the PVA-based film, such as a casting method in which a stock solution dissolved in water or an organic solvent is cast into a film, a casting method, an extrusion method, or the like. The retardation value of the PVA-based film is preferably 5 nm to 100 nm. In order to obtain a polarizer F1 with in-plane uniformity, it is preferable that the in-plane retardation variation of the PVA-based film is as small as possible, and the in-plane retardation variation of the PVA-based film as the raw film F0 is preferably 10 nm or less at a measurement wavelength of 1000 nm, and more preferably 5 nm or less.

The raw film F0 described above is wound around the pay-out roller FR and disposed on the most upstream side (the most upstream side in the conveying direction of the raw film F0) of the manufacturing apparatus 100. Then, while conveying the raw film F0 paid out from the pay-out roller FR, the raw film F0 is immersed in the processing bath L (L1 to L5) in the processing tank 1 for processing.
The manufacturing apparatus 100 of this embodiment is equipped with, as the treatment tank 1, in order from the upstream side in the transport direction of the raw film F0, a swelling treatment tank 11 for performing a swelling treatment, a dyeing treatment tank 12 for performing a dyeing treatment, a crosslinking treatment tank 13 for performing a crosslinking treatment, a stretching treatment tank 14 for performing a stretching treatment, and a cleaning treatment tank 15 for performing a cleaning treatment.
The order, number of times, and whether or not each of the swelling, dyeing, crosslinking, stretching, and washing processes in each treatment tank 1 is not particularly limited, and some processes may be performed simultaneously in a single treatment tank 1, or some processes may not be performed. For example, the stretching process may be performed immediately after the dyeing process, or may be performed simultaneously with the swelling process or the dyeing process. Also, the dyeing process may be performed after the stretching process.

In the swelling treatment tank 11, for example, water is used as the treatment bath L (swelling treatment bath L1). By immersing the raw film F0 in this swelling treatment bath L1, the raw film F0 is washed with water, and dirt and blocking inhibitors on the surface of the raw film F0 can be washed off. Furthermore, by swelling the raw film F0, it is expected that unevenness such as uneven dyeing can be prevented. Glycerin, potassium iodide, etc. may be added appropriately to the swelling treatment bath L1, and the concentration of glycerin added is preferably 5% by weight or less, and potassium iodide is preferably 10% by weight or less. The temperature of the swelling treatment bath L1 is preferably in the range of 20 to 45°C, and more preferably 25 to 40°C. The immersion time of the raw film F0 in the swelling treatment bath L1 is preferably 2 to 180 seconds, more preferably 10 to 150 seconds, and particularly preferably 60 to 120 seconds. The raw film F0 may also be stretched in this swelling treatment bath L1, with the stretching ratio being approximately 1.1 to 3.5 times, including the extension due to swelling.

In the dyeing process tank 12, a process bath containing a dichroic substance such as iodine is used as the process bath L (dyeing process bath L2), and the original film F0 is immersed in this dyeing process bath L2 to cause the dichroic substance to be adsorbed onto the original film F0.

As the dichroic material, conventionally known substances can be used, such as iodine and organic dyes. As organic dyes, for example, 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, Spra Blue G, Spra Blue GL, Spra Orange GL, Direct Sky Blue, Direct Fast Orange S, Fast Black, etc. can be used.

These dichroic substances may be used alone or in combination of two or more. When the organic dyes are used, it is preferable to combine two or more organic dyes, for example, from the viewpoint of neutralizing the visible light region. Specific examples include a combination of Congo Red and Supra Blue G, a combination of Supra Orange GL and Direct Sky Blue, or a combination of Direct Sky Blue and Fast Black.

As the dyeing treatment bath L2, a solution in which the dichroic material is dissolved in a solvent can be used. Water is generally used as the solvent, but an organic solvent compatible with water may also be added. The concentration of the dichroic material is preferably in the range of 0.010 to 10% by weight, more preferably in the range of 0.020 to 7% by weight, and particularly preferably in the range of 0.025 to 5% by weight.

When iodine is used as the dichroic substance, it is preferable to further add an iodide since this can further improve the dyeing efficiency. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. The ratio of these iodides added in the dyeing treatment bath L2 is preferably 0.010 to 10% by weight, and more preferably 0.10 to 5% by weight. Among these, it is preferable to add potassium iodide, and the ratio (weight ratio) of iodine to potassium iodide is preferably in the range of 1:5 to 1:100, more preferably in the range of 1:6 to 1:80, and particularly preferably in the range of 1:7 to 1:70.

The immersion time of the original film F0 in the dyeing bath L2 is not particularly limited, but is preferably in the range of 1 to 20 minutes, and more preferably 2 to 10 minutes. The temperature of the dyeing bath L2 is preferably in the range of 5 to 42°C, and more preferably in the range of 10 to 35°C. The original film F0 may be stretched in the dyeing bath L2, and the accumulated total stretch ratio at this time is about 1.1 to 4.0 times.

In addition to the above-mentioned method of immersing in the dyeing bath L2, the dyeing process may be carried out by, for example, applying or spraying an aqueous solution containing a dichroic substance onto the original film F0, or by premixing the dichroic substance into the original film F0 during film formation.

In the crosslinking treatment tank 13, the raw film F0 is crosslinked by immersing it in a treatment bath L (crosslinking treatment bath L3) containing a crosslinking agent. As the crosslinking agent, a conventionally known substance can be used, for example, boron compounds such as boric acid and borax, glyoxal, glutaraldehyde, etc. These may be used alone or in combination of two or more. When two or more types are used in combination, for example, a combination of boric acid and borax is preferred, and the addition ratio (molar ratio) is preferably in the range of 4:6 to 9:1, more preferably in the range of 5.5:4.5 to 7:3, and most preferably 6:4.

The crosslinking treatment bath L3 can be a solution in which the crosslinking agent is dissolved in a solvent. The solvent can be, for example, water, but may also contain an organic solvent that is compatible with water. The concentration of the crosslinking agent in the solution is not limited to this, but is preferably in the range of 1 to 10% by weight, and more preferably 2 to 6% by weight.

Iodides may be added to the crosslinking treatment bath L3 in order to obtain uniform characteristics within the plane of the polarizer F1. Examples of iodides include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide, and the content is 0.05 to 15% by weight, more preferably 0.5 to 8% by weight. Among these, a combination of boric acid and potassium iodide is preferred, and the ratio (weight ratio) of boric acid to potassium iodide is preferably in the range of 1:0.1 to 1:3.5, and more preferably in the range of 1:0.5 to 1:2.5.

The temperature of the crosslinking bath L3 is usually in the range of 20 to 70°C, and the immersion time of the raw film F0 is usually in the range of 1 second to 15 minutes, preferably 5 seconds to 10 minutes. As with the dyeing process, the crosslinking process may also be performed by applying or spraying a solution containing a crosslinking agent. Furthermore, the raw film F0 may be stretched in the crosslinking bath L3, and the accumulated total stretch ratio at this time is about 1.1 to 4.0 times.

In the stretching tank 14, the raw film F0 is stretched while immersed in the treatment bath L (stretching bath L4) so that the cumulative total stretch ratio is approximately 2 to 7 times.

The stretching bath L4 is not particularly limited to this, but may be, for example, a solution containing various metal salts or compounds of iodine, boron, or zinc. As the solvent for this solution, water, ethanol, or various organic solvents are appropriately used. Among these, it is preferable to use a solution containing approximately 2 to 18% by weight of boric acid and/or potassium iodide. When using boric acid and potassium iodide simultaneously, it is preferable to use them at a content ratio (weight ratio) of approximately 1:0.1 to 1:4, more preferably approximately 1:0.5 to 1:3.

The temperature of the stretching bath L4 is preferably in the range of, for example, 40 to 67°C, and more preferably 50 to 62°C.

In the cleaning bath 15, for example, the raw film F0 is immersed in a treatment bath L (cleaning bath L5) which is an aqueous solution, and thus unnecessary residues such as boric acid attached to the raw film F0 in the previous treatment can be washed away. An iodide may be added to the aqueous solution, and for example, sodium iodide or potassium iodide is preferably used as the iodide. When potassium iodide is added to the cleaning bath L5, the concentration is usually 0.1 to 10% by weight, and preferably 3 to 8% by weight. Furthermore, the temperature of the cleaning bath L5 is preferably 10 to 60°C, and more preferably 15 to 40°C. The number of cleaning treatments is not particularly limited, and may be performed multiple times. In this case, the type and concentration of additives in each cleaning bath L5 may be changed.

In this embodiment, a nip roller NR is disposed on the exit side of each processing tank 1, preventing dripping when the raw film F0 is pulled up from each processing tank 1.

The raw film F0 that has been treated in the treatment bath L of each treatment tank 1 described above is subjected to a drying process. As the drying process, any suitable method such as natural drying, air drying, or heat drying can be used, but heat drying is usually used preferably. In the manufacturing apparatus 100 of this embodiment, heat drying is performed using an oven 3. In the oven 3, for example, it is preferable that the heating temperature is about 20 to 80°C and the drying time is about 1 to 10 minutes. Furthermore, regardless of the method, it is preferable to keep the drying temperature as low as possible from the viewpoint of preventing deterioration of the polarizer F1. It is more preferable that the temperature is 60°C or less, and particularly preferable that the temperature is 45°C or less.

The final total stretch ratio of the polarizer F1 produced in the above manner is preferably 3.0 to 7.0 times, and more preferably 5.5 to 6.2 times, relative to the original film F0 before processing. If the final total stretch ratio is less than 3.0 times, it is difficult to obtain a polarizer F1 with a high degree of polarization, and if it exceeds 7.0 times, the original film F0 becomes prone to breakage.

The manufacturing apparatus 100 according to this embodiment includes nip rollers 2 arranged in a treatment bath L. In this embodiment, the nip rollers 2 are arranged in a stretching bath L4 stored in a stretching tank 14 of the treatment tank 1. In this embodiment, two pairs of nip rollers 2 (2a, 2b) are arranged along the transport direction of the raw film F0. As shown in FIG. 1(b), the nip rollers 2 are composed of a drive roller 21 and a driven roller 22 that transports the raw film F0 by nipping it between the drive roller 21. The configuration of the nip rollers 2 according to this embodiment will be described in more detail below.

The nip roller 2 of this embodiment is characterized in that the surface hardness of the drive roller 21 is different from the surface hardness of the driven roller 22. In this embodiment, the surface hardness of the drive roller 21 is set to be lower than the surface hardness of the driven roller 22.
1(b), in this embodiment, the nip roller 2 is arranged so that the drive roller 21 and the driven roller 22 face each other vertically, and the drive roller 21 is located above the driven roller 22. The nip roller 2 is arranged so that a portion of the drive roller 21 is located above the liquid level of the stretching bath L4, and the driven roller 22 is immersed in the stretching bath L4. Specifically, the drive roller 21 is arranged so that the shaft portion 211a is located above the liquid level of the stretching bath L4.

As described above, since the surface hardness of the driving roller 21 and the surface hardness of the driven roller 22 are different (specifically, the surface hardness of the driving roller 21 is lower than that of the driven roller 22), the line pressure acting on the original film F0 from the nip roller 2 is reduced, and the stretching breakage of the original film F0 is suppressed, and the durability of the nip roller 2 can be maintained to a degree that does not cause any problems. In addition, since a part of the driving roller 21 is located above the liquid level of the stretching treatment bath L4, it is not necessary to immerse a driving source such as a motor (not shown) required to rotate the driving roller 21 in the stretching treatment bath L4, and it is possible to manufacture a polarizer F1 with fewer equipment constraints. Furthermore, since a part of the driving roller 21, which has a lower surface hardness than the driven roller 22, is located above the liquid level of the stretching treatment bath L4, the entire driving roller 21 is not constantly immersed in the stretching treatment bath L4, but is only partially and intermittently immersed as it rotates, so that it is possible to suppress deterioration of the driving roller 21.

Fig. 2 is a diagram showing a schematic configuration of the drive roller 21 of this embodiment, in which Fig. 2(a) is a side view (a view seen from a horizontal direction perpendicular to the conveying direction of the original film F0 and the polarizer F1 shown in Fig. 1), and Fig. 2(b) is a front cross-sectional view (a cross-sectional view passing through the center of the drive roller 21 seen from the conveying direction of the original film F0 and the polarizer F1 shown in Fig. 1).
As shown in FIG. 2, the drive roller 21 of this embodiment includes a core material 211 and a multi-layer elastic member 212 wound around the core material 211 .

The core material 211 of this embodiment has a shaft portion 211a with a circular cross section and a tubular portion 211b with a circular cross section. A drive source (not shown) is connected to the shaft portion 211a, and the shaft portion 211a rotates by the rotational driving force supplied from the drive source. The central axis of the shaft portion 211a becomes the central axis of rotation of the drive roller 21. The tubular portion 211b has a hollow portion at its center, and the shaft portion 211a is fitted into this hollow portion to be connected to the shaft portion 211a. When the shaft portion 211a rotates, the tubular portion 211b also rotates integrally with the shaft portion 211a. The materials of the shaft portion 211a and the tubular portion 211b are not particularly limited, but for example, the shaft portion 211a is formed from stainless steel (e.g., SUS316), and the tubular portion 211b is formed from resin (e.g., CFRP). The outer diameter of the core material 211 (outer diameter of the tubular portion 211b) is, for example, 400 to 600 mm.

In this embodiment, the elastic member 212 is formed by wrapping three layers of elastic members 212a, 212b, and 212c around the surface (outer surface) of the tubular portion 211b of the core material 211. The elastic member 212a of the innermost layer is adhered to the surface of the tubular portion 211b with an appropriate adhesive. The elastic member 212b of the intermediate layer is adhered to the surface (outer surface) of the elastic member 212a with an appropriate adhesive. The elastic member 212c of the outermost layer is adhered to the surface (outer surface) of the elastic member 212b with an appropriate adhesive.
The material of the elastic member 212a is not particularly limited, but for example, the elastic member 212a is preferably made of styrene-butadiene rubber (SBR). Alternatively, the elastic member 212a can be made of acrylonitrile-butadiene rubber (NBR) or ethylene-propylene-diene rubber (EPDM). The thickness of the elastic member 212a is not particularly limited, but is preferably 0.5 to 5 mm, and more preferably 1.5 to 2 mm.
The material of the elastic member 212b is not particularly limited, but for example, the elastic member 212b is preferably made of EPDM. Alternatively, the elastic member 212b can be made of NBR or SBR. The thickness of the elastic member 212b is not particularly limited, but is preferably 1 to 10 mm, and more preferably 6 to 6.5 mm.
The material of the elastic member 212c is not particularly limited, but for example, like the elastic member 212b, the elastic member 212c is preferably formed from EPDM. However, in order to reduce the surface hardness of the elastic member 212c, the elastic member 212c is preferably formed from an EPDM foam. The EPDM foam can be manufactured, for example, by foaming EPDM with a foaming agent and crosslinking it with a crosslinking agent. The thickness of the elastic member 212c is not particularly limited, but is preferably 0.5 to 10 mm, more preferably 1 to 5 mm, and particularly preferably 1.5 to 2.5 mm.

Of the three layers of elastic member 212, the surface hardness of the elastic member 212 located on the inside is higher than the surface hardness of the elastic member 212 located on the outside. That is, the surface hardness of the elastic member 212a located on the inside is the highest, the surface hardness of the elastic member 212b located in the middle layer is the next highest, and the surface hardness of the elastic member 212c located on the outside is the lowest.
Specifically, the surface hardness (outer surface hardness) of the elastic member 212a is preferably 70 to 100 in Shore A hardness, more preferably 80 to 100, and particularly preferably 90 to 100. The Shore A hardness can be measured using a commercially available durometer (type A) conforming to JIS K6253 (1997). As the durometer (type A), for example, "ASKER-TYPE A" manufactured by Kobunshi Keiki Co., Ltd. can be used.
The surface hardness (outer surface hardness) of the elastic member 212b is preferably 60-99, more preferably 70-90, and particularly preferably 75-85 in Shore A hardness.
The surface hardness (outer surface hardness) of the elastic member 212c is preferably less than 50 in Shore A hardness or less than 80 in Asker C hardness, more preferably 10 to 40 in Shore A hardness or 60 to 79 in Asker C hardness, and particularly preferably 20 to 30 in Shore A hardness and 65 to 75 in Asker C hardness. The Asker C hardness can be measured using a commercially available durometer (type C) conforming to JIS K7312 (1996). As the durometer (type C), for example, "ASKER-TYPE C (Asker C type durometer)" manufactured by Kobunshi Keiki Co., Ltd. can be used.
The surface hardness (outer surface hardness) of the drive roller 21 is represented by the surface hardness of the elastic member 212c, which is the outermost layer. Therefore, the surface hardness of the drive roller 21 is preferably less than 50 in Shore A hardness or less than 80 in Asker C hardness.

As described above, the driving roller 21 of this embodiment has three layers of elastic members 212, in which the surface hardness of the elastic members 212 in the innermost layer is higher than that of the elastic members 212 in the outermost layer. Therefore, the core material 211 is sufficiently protected by the elastic member 212a with a high surface hardness of the innermost layer, and the adhesive force between the core material 211 and the elastic member 212a can be increased. In addition, since the elastic member 212c with a low surface hardness of the outermost layer contacts the original film F0, the linear pressure acting on the original film F0 is reduced, and stretching breakage of the original film F0 is suppressed. Furthermore, the surface hardness of the elastic member 212c in the outermost layer can be adjusted by the surface hardness of the elastic member 212b in the middle layer.

Fig. 3 is a diagram showing a schematic configuration of the driven roller 22 of this embodiment, in which Fig. 3(a) is a side view (a view seen from a horizontal direction perpendicular to the conveying direction of the original film F0 and the polarizer F1 shown in Fig. 1), and Fig. 3(b) is a front cross-sectional view (a cross-sectional view passing through the center of the driven roller 22 seen from the conveying direction of the original film F0 and the polarizer F1 shown in Fig. 1).
As shown in FIG. 3 , the driven roller 22 of this embodiment includes a core material 221 and one layer of an elastic member 222 wound around the core material 221 .

The core material 221 has the same configuration as the core material 211 of the drive roller 21. That is, the core material 221 has a shaft portion 221a having a circular cross section and a tubular portion 221b having a circular cross section. The central axis of the shaft portion 221a becomes the central axis of rotation of the driven roller 22. The tubular portion 221b has a hollow portion at its center, and the shaft portion 221a is fitted into this hollow portion to be connected to the shaft portion 221a. When the shaft portion 221a rotates, the tubular portion 221b also rotates integrally with the shaft portion 221a. The materials of the shaft portion 221a and the tubular portion 221b are not particularly limited, but for example, the shaft portion 221a is formed from stainless steel (e.g., SUS316), and the tubular portion 221b is formed from resin (e.g., CFRP). The outer diameter of the core material 221 (outer diameter of the tubular portion 221b) is, for example, 400 to 500 mm.

The elastic member 222 is adhered to the surface of the tubular portion 221b via a suitable adhesive.
The material of the elastic member 222 is not particularly limited, but for example, the elastic member 222 is preferably made of styrene-butadiene rubber (SBR). Alternatively, the elastic member 222 can be made of NBR or EPDM. The thickness of the elastic member 222 is not particularly limited, but is preferably 5 to 20 mm, more preferably 5 to 15 mm, and particularly preferably 10 mm.
The preferred thickness of the elastic member 222 is the thickness at the axial center of the driven roller 22, and it is preferred to provide a crown on the driven roller 22 so that the thickness is greatest at the center and decreases toward the axial ends. By providing a crown on the driven roller 22, when the drive roller 21 is pressed toward the driven roller 22, a gap larger than the thickness of the original film F0 is unlikely to occur between the drive roller 21 and the driven roller 22, and the original film F0 can be securely sandwiched and transported.

The surface hardness (outer surface hardness) of the driven roller 22 is expressed by the surface hardness (outer surface hardness) of the elastic member 222, and as described above, the surface hardness of the driven roller 22 is higher than the surface hardness of the drive roller 21 (the surface hardness of the elastic member 212c). Therefore, the surface hardness of the elastic member 222 is preferably 50 or more in Shore A hardness.

In this embodiment, the outer diameter of the drive roller 21 is larger than the outer diameter of the driven roller 22. For example, the outer diameter of the drive roller 21 is 500 mm (outer diameter of the core material 211 480 mm + thickness of the elastic member 212a 1.5 mm x 2 + thickness of the elastic member 212b 6.5 mm x 2 + thickness of the elastic member 212c 2 mm x 2 = 500 mm), and the outer diameter of the driven roller 22 is 460 mm (outer diameter of the core material 221 440 mm + thickness of the elastic member 222 10 mm x 2 = 460 mm).
In this manner, since the outer diameter of the drive roller 21 is large, it is easy to position a part of the drive roller 21 above the liquid surface of the stretching treatment bath L4, and deterioration of the drive roller 21 can be suppressed.

In the above-described embodiment, the nip roller 2 is arranged so that a part of the driving roller 21 is located above the liquid level of the stretching bath L4 and the driven roller 22 is immersed in the stretching bath L4, but the present invention is not limited to this. It is also possible to adopt a mode in which the nip roller 2 is arranged so that both the driving roller 21 and the driven roller 22 are immersed in the stretching bath L4. It is also possible to adopt a mode in which the vertical positional relationship between the driving roller 21 and the driven roller 22 is reversed. Specifically, it is also possible to adopt a mode in which the nip roller 2 is arranged so that a part of the driven roller 22 is located above the liquid level of the stretching bath L4 and the driving roller 21 is immersed in the stretching bath L4, or a mode in which the nip roller 2 is arranged so that both the driven roller 22 located above and the driving roller 21 located below are immersed in the stretching bath L4.

In addition, in this embodiment, a case has been described in which the surface hardness of the drive roller 21 is lower than the surface hardness of the driven roller 22, but the present invention is not limited to this, and it is also possible to adopt a configuration in which the surface hardness of the driven roller 22 is lower than the surface hardness of the drive roller 21.

In the present embodiment, the driving roller 21 is described as having three layers of elastic members 212, but the present invention is not limited to this, and it is also possible to adopt a mode in which the driving roller 21 has two layers, or four or more layers of multiple elastic members 212. It is also possible to adopt a mode in which the driven roller 22 has multiple layers of elastic members 222 like the driving roller 21 (i.e., a mode in which both the driving roller 21 and the driven roller 22 have multiple layers of elastic members 212, 222, respectively). It is also possible to adopt a mode in which the driven roller 22 has multiple layers of elastic members 222 and the driving roller 21 has one layer of elastic member 212. It is also possible to adopt a mode in which both the driving roller 21 and the driven roller 22 have one layer of elastic members 212, 222, respectively.

Furthermore, in this embodiment, the nip roller 2 is described as being placed in the stretching bath L4 of the stretching bath 14, but the present invention is not limited to this, and it is also possible to place it in any treatment bath L of any treatment bath 1. For example, as described above, the raw film F0 may be stretched in the swelling bath L1 of the swelling bath 11, the dyeing bath L2 of the dyeing bath 12, or the crosslinking bath L3 of the crosslinking bath 13, so when stretching is performed in these treatment baths L, the nip roller 2 of this embodiment may be placed in these treatment baths L. This makes it possible to prevent the raw film F0 from breaking during stretching in each treatment bath L.

Reference Signs List 1: Treatment tank 2: Nip roller 14: Stretching tank 21: Drive roller 22: Driven roller F0: Raw film F1: Polarizer L: Treatment bath L4: Stretching bath 100: Manufacturing apparatus

Claims (6)

A method for producing a polarizer, comprising: disposing nip rollers in a treatment bath; and treating an original film in the treatment bath while transporting the original film by the nip rollers, the method comprising the steps of:
the nip roller is composed of a drive roller and a driven roller that conveys the original film by nipping it between the drive roller and the driven roller,
The nip rollers are disposed so that a portion of the drive roller is located above the liquid level of the treatment bath and the driven roller is immersed in the treatment bath;
The method for producing a polarizer , wherein the drive roller has a surface hardness of less than 80 in Asker C hardness, and the driven roller has a surface hardness of 80 or more in Asker C hardness . The drive roller and/or the driven roller include a core material and a plurality of layers of an elastic member wound around the core material,
The elastic member of the multiple layers has a surface hardness of an inner layer higher than a surface hardness of an outer layer.
A method for producing the polarizer according to claim 1 . The multiple-layer elastic member is a three-layer elastic member.
The method for producing the polarizer according to claim 2 . The outer diameter of the drive roller is larger than the outer diameter of the driven roller.
A method for producing the polarizer according to claim 1 . The treatment bath is a treatment bath for performing a stretching treatment on the raw film.
A method for producing the polarizer according to claim 1 . An apparatus for producing a polarizer, comprising: a treatment tank for storing a treatment bath; and a nip roller disposed in the treatment bath, the apparatus treating a raw film in the treatment bath while transporting the raw film by the nip roller, the apparatus comprising:
the nip roller is composed of a drive roller and a driven roller that conveys the original film by nipping it between the drive roller and the driven roller,
the nip rollers are disposed such that a portion of the drive roller is located above the liquid level of the treatment bath and the driven roller is immersed in the treatment bath;
the drive roller has a surface hardness of less than 80 in Asker C hardness, and the driven roller has a surface hardness of 80 or more in Asker C hardness .

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