TWI649360B - Polarizing film manufacturing apparatus and manufacturing method, and polarizing film - Google Patents

Abstract

An object of the present invention is to provide a device and method for manufacturing a polarizing film that is less likely to cause bright spots (light leakage) when applied to a liquid crystal display device.

The solution to the above-mentioned problem is to provide a manufacturing apparatus which is a manufacturing apparatus for manufacturing a polarizing film from a polyvinyl alcohol-based resin film, and the manufacturing apparatus includes a plurality of rollers constituting a transport path of the polyvinyl alcohol-based resin film And arranged so as to be in contact with the surface of the polyvinyl alcohol-based resin film; the wet processing section is arranged on the conveying path and includes one or more processing tanks containing a processing solution impregnated with the polyvinyl alcohol-based resin film; and The drying processing section is arranged on the conveying path to dry the polyvinyl alcohol-based resin film after wet processing; wherein the plurality of rollers include a low rotation resistance roller having a rotation resistance of 0.025N or less; A method for manufacturing the device; and a specific polarizing film having a density of 20 unevenness / m ² or less.

Description

Apparatus and method for manufacturing polarizing film, and polarizing film

This invention relates to the manufacturing apparatus and manufacturing method of a polarizing film which can be used as a structural member of a polarizing plate, for example. And this invention relates to a polarizing film.

As for the polarizing film, conventionally, a polyvinyl alcohol-based resin film after uniaxial stretching is used to adsorb and align a dichroic dye such as iodine or a dichroic dye. Generally, a polarizing film is sequentially performed: a dyeing process of dyeing a polyvinyl alcohol-based resin film with a dichroic dye, a crosslinking process of treating with a crosslinking agent, and a film drying process, and the process is performed between manufacturing steps. It is manufactured by uniaxial stretching (for example, Japanese Patent Application Laid-Open No. 2001-141926 (Patent Document 1)).

A manufacturing apparatus of a polarizing film generally has a processing tank such as a dyeing processing tank, a cross-linking processing tank, and a conveyance path of a polyvinyl alcohol-based resin film through a drying device or the like. The polyvinyl alcohol-based resin film conveyed along this path is supported by a roll such as a guide roll or a roll holding a film.

[Prior technical literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2001-141926

One of the main uses of a polarizing film is the use of a polarizing plate as a necessary component of a liquid crystal display device. A polarizing plate refers to an optical member in which a protective layer (protective film, etc.) is typically laminated and bonded on one or both sides of a polarizing film using an adhesive. In recent years, the visibility (brightness) of liquid crystal display devices has been gradually improved. With this requirement, liquid crystal display devices have been gradually used with backlights having higher brightness.

Based on this situation, the inventor faces a new problem: if the brightness of the backlight is increased to a certain level or higher, the brightness of the backlight will not be recognized on the screen of the liquid crystal display device without causing problems. Point-like bright spots (light leakage) are recognized. For example, in a liquid crystal panel, when an air bubble is mixed between the adhesive layer of the liquid crystal cell and the polarizing plate, the air bubble will become the main part and the bright spot (light leakage) is known, although several types have been proposed. The technology for suppressing the incorporation of air bubbles, but the above-mentioned bright spot that the inventors have faced again, it is clear that it is not caused by air bubbles mixed between the adhesive layer and the liquid crystal cell. In addition, the inventors have discovered that the main cause of the above-mentioned bright spots lies on the polarizing film constituting the polarizing plate.

An object of the present invention is to provide a device and method for manufacturing a polarizing film that is less likely to produce bright spots (light leakage) that the present inventors faced again as described above when applied to a liquid crystal display device. Moreover, other objects of the present invention The system provides a polarizing film that is less prone to the above-mentioned bright spots (light leakage).

The present inventors discovered that the main cause of the above-mentioned bright spots (light leakage) is the specific uneven defects (hereinafter also referred to as "specific uneven defects") generated on the surface of the polyvinyl alcohol-based resin film during the production of the polarizing film, and by the following The manufacturing apparatus and manufacturing method of the polarizing film of the present invention as shown can effectively suppress specific unevenness defects and even bright spots (light leakage) of the polarizing film.

That is, this invention provides the manufacturing apparatus and manufacturing method of a polarizing film shown below, and a polarizing film.

[1] A manufacturing apparatus, which is a manufacturing apparatus for manufacturing a polarizing film from a polyvinyl alcohol-based resin film, and includes a plurality of rollers constituting a conveying path of the polyvinyl alcohol-based resin film, and is arranged to be the same as the foregoing The surfaces of the polyvinyl alcohol-based resin film are in contact with each other; the wet processing section is disposed on the conveying path and includes one or more processing tanks containing a processing solution impregnated with the polyvinyl alcohol-based resin film; and a drying processing section Is arranged on the conveying path to dry the polyvinyl alcohol-based resin film after the wet treatment; wherein the plurality of rollers include a low rotation resistance roller having a rotation resistance of 0.025N or less.

[2] The manufacturing apparatus according to [1], wherein the low rotation resistance roller is arranged on a conveying path from the wet processing section to the drying processing section. Either position.

[3] The manufacturing apparatus according to [2], wherein the wet processing unit sequentially includes: a dyeing treatment tank containing a dyeing treatment liquid containing a dichroic pigment; and a crosslinking treatment containing a crosslinking agent. Liquid cross-linking treatment tank; the low-rotation resistance roller is arranged behind the cross-linking treatment tank.

[4] The manufacturing apparatus according to any one of [1] to [3], wherein the low rotation resistance roller has a surface having a contact angle with water of 60 degrees or more.

[5] The manufacturing apparatus according to [4], wherein the surface is made of a fluorine-based resin, a resin containing silicon atoms, carbon, or diamond-like carbon.

[6] The manufacturing device according to any one of [1] to [5], wherein the weight per unit volume of the low rotation resistance roller is 1500 kg / m ³ or less.

[7] The manufacturing apparatus according to any one of [1] to [6], wherein the low rotation resistance roller is a guide roller.

[8] The manufacturing apparatus according to any one of [1] to [7], wherein a thickness of the polyvinyl alcohol-based resin film in contact with the low rotation resistance roller is 15 μm or less.

[9] A manufacturing method for manufacturing a polarizing film from a polyvinyl alcohol-based resin film The method includes the following steps: a wet processing step of conveying the polyvinyl alcohol-based resin film along a conveying path constituted by a plurality of rollers arranged to contact the surface of the polyvinyl alcohol-based resin film While being immersed in one or more treatment liquids; and a drying treatment step, the polyvinyl alcohol-based resin film is transported along the transportation path, and the polyvinyl alcohol-based resin film after the wet treatment is dried ; Wherein the plurality of rollers include a low rotation resistance roller having a rotation resistance of 0.025N or less.

[10] The manufacturing method according to [9], wherein the low rotation resistance roller is arranged at any position on a conveying path from the wet processing step to the drying processing step.

[11] The manufacturing method according to [10], wherein the wet processing step includes: a step of immersing in a dyeing treatment liquid containing a dichroic dye; and a crosslinking treatment containing a crosslinking agent. The step of the liquid; the aforementioned low rotation resistance roller is arranged on the conveying path after the step of being immersed in the crosslinking treatment liquid.

[12] The manufacturing method according to any one of [9] to [11], wherein the low rotation resistance roller has a surface having a contact angle with water of 60 degrees or more.

[13] The manufacturing method according to [12], wherein the surface is made of a fluorine-based resin, a resin containing silicon atoms, carbon, or diamond-like carbon.

[14] The manufacturing method according to any one of [9] to [13], wherein the weight per unit volume of the low rotation resistance roller is 1500 kg / m ³ or less.

[15] The manufacturing method according to any one of [9] to [14], wherein the low rotation resistance roller is a guide roller.

[16] The manufacturing method according to any one of [9] to [15], wherein a thickness of the polyvinyl alcohol-based resin film in contact with the low rotation resistance roller is 15 μm or less.

[17] A polarizing film, which is a dichroic pigment adsorbed and aligned on a polyvinyl alcohol resin film, wherein the density of unevenness on at least one side is 20 / m ² or less, and the unevenness is composed of one convex It is composed of a combination of a recessed part and a recessed part, and the length is within a range of 0.5 to 5 mm. The one protruding part is based on a polarizing film surface other than the aforementioned unevenness defect, and is more prominent than the reference. The one recessed part system It sinks in more than the said reference | standard, and adjoins the said convex part.

According to the present invention, even when applied to a liquid crystal display device using a high-brightness backlight, it is possible to provide a polarizing film that is unlikely to generate bright spots (light leakage) due to specific irregularities on the film surface.

1a, 1b, 1c, 1d, 1e, 1f, 1g, 1h, 1i, 1j, 1k, 1l, 1m, 1n, 1o, 1p, 1q, 1r, 1s‧‧‧guide roller

2a, 2b, 2c, 2d, 2e, 2f

10‧‧‧Polyvinyl alcohol resin film (PVA resin film)

11‧‧‧ unwinding roller

13‧‧‧Swelling tank

15‧‧‧dyeing treatment tank

17‧‧‧ Cross-linking treatment tank

19‧‧‧washing treatment tank

20‧‧‧ Wet processing department

21‧‧‧ drying furnace

22‧‧‧Drying Department

25‧‧‧ polarizing film

27‧‧‧ take-up roller

FIG. 1 is a schematic cross-sectional view showing an example of a polarizing film manufacturing apparatus of the present invention.

FIG. 2 is an enlarged cross-sectional view schematically showing a drying process section included in the polarizing film manufacturing apparatus shown in FIG. 1.

Fig. 3 is a flowchart showing an example of a method for producing a polarizing film of the present invention.

<Manufacturing device and manufacturing method of polarizing film>

The present invention relates to a manufacturing apparatus and a manufacturing method for manufacturing a polarizing film from a polyvinyl alcohol-based resin film (hereinafter also referred to as a "PVA-based resin film"). The polarizing film is produced by subjecting a PVA-based resin film to a series of processes including a dipping process (wet process) and a drying process in a processing tank. The polarizing film is based on a stretched PVA-based resin film that adsorbs and aligns dichroic pigments.

An example of the polarizing film manufacturing apparatus of this invention is shown in FIG. FIG. 2 is a schematic cross-sectional view showing an enlarged drying process section included in the polarizing film manufacturing apparatus shown in FIG. 1. The polarizing film manufacturing apparatus shown in FIGS. 1 and 2 is an apparatus for continuously manufacturing a long polarizing film 25 from a long PVA-based resin film 10 as a raw material film. The arrows in Figs. 1 and 2 indicate the transport direction of the film. In the production of the polarizing film 25 using the manufacturing apparatus shown in FIGS. 1 and 2, the PVA-based resin film 10 is continuously rolled out from the unwinding roller 11, and is sequentially immersed in a swelling place The polarizing film 25 is obtained by performing a drying treatment on the physical treatment tank 13, the dyeing treatment tank 15, the cross-linking treatment tank 17, and the cleaning treatment tank 19, and finally passing through the drying furnace 21. The polarizing film 25 that is made into a long strip can be sequentially taken up by a take-up roll 27.

In a polarizing film manufacturing apparatus, a wet processing area is used in one or more processing tanks, such as a swelling processing tank 13, a dyeing processing tank 15, a cross-linking processing tank 17, and a cleaning processing tank 19, which contain a processing solution impregnated with a film. In this specification, it is called "wet processing part" (wet processing part 20 shown in FIG. 1). In addition, as in the drying furnace 21, an area where the wet-processed film is dried is referred to as a "drying section" (the drying processing section 22 shown in Figs. 1 and 2) in this specification. The polarizing film manufacturing apparatus of the present invention includes a transport path of the PVA-based resin film 10 including a wet processing section and a drying processing section. The PVA-based resin film 10 is transported along this transport path, and a series of processes can be performed to obtain the polarizing film 25. The conveyance speed of the PVA-based resin film 10 conveyed along the conveyance path is usually 10 to 50 m / min, and from the viewpoint of production efficiency, it is preferably 15 m / min or more.

As shown in FIG. 1, the above-mentioned conveying path is a plurality of rollers that support and guide a moving film (PVA-based resin film 10 and polarizing film 25) so as to pass through the wet processing section 20 and the drying processing section 22. And build into. The plurality of rollers are composed of a guide roller belonging to a free roller and / or a pair of rollers (usually a driving roller) supporting one side of the film, and may include a double-rolled film or a roll pressed after being sandwiched. . In the examples shown in FIGS. 1 and 2, the manufacturing apparatus includes guide rollers 1 a to 1 s and rolls 2 a to 2 f. The plurality of rollers defining the conveyance path may include one type of suction roller (suction roller), which is a driving roller. Usually, these rollers are connected to one of the films in the conveying path. The surface or both surfaces (primary surfaces) meet to support the film. These rollers may be arranged at appropriate positions such as before and after each processing tank and drying means (drying furnace), or inside the processing tank and drying means (drying furnace).

The driving roller refers to a roller that can give a driving force for film transportation to a film in contact with the film, and may be a roller or the like directly or indirectly connected to a roller driving source such as a motor. Free rollers are rollers that only support the film in motion and cannot give driving force for film transportation.

A flowchart of an example of a method for producing a polarizing film of the present invention is shown in FIG. 3. Referring to FIG. 3, the method for manufacturing a polarizing film of the present invention includes the following steps: a wet processing step S101, which is along a conveying path constituted by a plurality of rollers arranged to contact the surface of a polyvinyl alcohol-based resin film While immersing the PVA-based resin film in one or more treatment liquids; and the drying process step S102, the PVA-based resin film is transported along the above-mentioned conveying path, and the PVA-based resin after wet processing is transported The resin film is dry.

The wet processing step S101 is a process performed in the above-mentioned wet processing section 20, and the dry processing step S102 is a process performed in the above-mentioned drying processing section 22.

The obtained polarizing film 25 is subjected to a stretching process (usually a uniaxial stretching process). Therefore, the manufacturing apparatus of the polarizing film of the present invention may include a stretching means (wet stretching means) of the PVA-based resin film 10, and the manufacturing method of the polarizing film of the present invention may include a stretching processing step (wet-type) of the PVA-based resin film Extended processing steps).

(1) PVA resin film

The PVA-based resin film 10 introduced into the wet processing section 20 (supplied to the wet processing step S101) is a film made of a polyvinyl alcohol-based resin. As the polyvinyl alcohol-based resin, a polyvinyl acetate-based resin can be used for saponification. As the polyvinyl acetate-based resin, in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate, copolymers of vinyl acetate and other monomers copolymerizable with the vinyl acetate can also be exemplified. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, (meth) acrylamidoamines having an ammonium group, and the like. In addition, "(meth) acrylic acid" means at least one selected from the group consisting of acrylic acid and methacrylic acid. The same applies to other terms with "(methyl)".

The degree of saponification of the polyvinyl alcohol resin may be in a range of 80.0 to 100.0 mol%, but a range of 90.0 to 100.0 mol% is more preferable, a range of 94.0 to 100.0 mol% is more preferable, and a range of 98.0 to 100.0 mol% is more preferable. 100.0 mol% range. When the degree of saponification is less than 80.0 mol%, the water resistance and humidity and heat resistance of the polarizing plate containing the obtained polarizing film 25 are reduced.

The degree of saponification refers to the ratio of the acetic acid group (acetoxy: -OCOCH ₃ ) contained in the polyvinyl acetate-based resin, which is a raw material of the polyvinyl alcohol-based resin, to a hydroxyl group by a saponification step, and the unit The ratio (mol%) is defined by the following formula: degree of saponification (mol%) = 100 × (hydroxyl number) / (hydroxyl number + acetic acid number)

The degree of saponification can be determined in accordance with JIS K 6726 (1994).

The average degree of polymerization of the polyvinyl alcohol-based resin is preferably 100 To 10,000, more preferably 1500 to 8000, and even more preferably 2000 to 5000. The average degree of polymerization of the polyvinyl alcohol-based resin can also be determined in accordance with JIS K 6726 (1994). When the average degree of polymerization is less than 100, it is difficult to obtain a polarizing film 25 having better polarizing performance. When it exceeds 10,000, the solubility in a solvent is deteriorated, and it becomes difficult to form (film-form) the PVA-based resin film 10.

An example of the PVA-based resin film 10 is an unstretched thin film made of the aforementioned polyvinyl alcohol-based resin. The film forming method is not particularly limited, and known methods such as a melt extrusion method and a solvent casting method can be adopted. Another example of the PVA-based resin film 10 is a stretched thin film obtained by stretching the unstretched thin film described above. The extension is usually a uniaxial extension, preferably a longitudinal uniaxial extension. Longitudinal extension refers to the mechanical flow direction (MD) of the film, that is, to the length of the film. The extension is preferably a dry extension. Dry extension refers to extension in air, usually longitudinal uniaxial extension. In terms of dry stretching, heat roller stretching is used to pass the film through a heated heat roller whose surface is heated, and between a guide roller (or a heat roller) whose rotation speed is different from that of the heat roller. Longitudinal stretching under heating; stretching between rolls is to stretch the film through heating means (oven, etc.) between the two sets of rolls located at a maintaining distance, and longitudinally stretch by the difference in peripheral speed between the two sets of rolls; Web extension; compression extension, etc. The elongation temperature (surface temperature of the heat roller, temperature in the oven, etc.) is, for example, 80 to 150 ° C, and preferably 100 to 135 ° C.

The stretching magnification of the above-mentioned stretching depends on whether wet stretching is performed in the wet processing step S101 described later and the stretching magnification during the wet stretching, but it is usually 1.1 to 8 times, preferably 2.5 to 5 times. .

The PVA-based resin film 10 may contain additives such as a plasticizer. Preferable examples of the plasticizer are polyhydric alcohols, and specific examples thereof include ethylene glycol, glycerol, propylene glycol, diethylene glycol, diglycerol, triethylene glycol, triglycerol, tetraethylene glycol, trimethylolpropane, Polyethylene glycol, etc. The PVA-based resin film 10 may contain one or two or more plasticizers. The content of the plasticizer is usually 5 to 20 parts by weight, and preferably 7 to 15 parts by weight, based on 100 parts by weight of the polyvinyl alcohol-based resin constituting the PVA-based resin film 10.

Although the thickness of the PVA-based resin film 10 introduced into the wet processing section 20 (supplied to the wet-processing step S101) depends on whether or not the PVA-based resin film 10 is stretched, it is usually 10 to 150 μm. From the viewpoint of thinning the polarizing film 25, the thickness is preferably 100 μm or less, more preferably 65 μm or less, still more preferably 50 μm or less, and particularly preferably 35 μm or less (for example, 30 μm or less, or even 20 μm or less). The smaller the thickness of the PVA-based resin film 10 is, the smaller the thickness of the polarizing film 25 is. Therefore, the smaller the thickness of the polarizing film, the less likely it is to cause specific unevenness defects. Therefore, in the present invention, when a PVA-based resin film 10 having a small thickness (for example, 65 μm or less, or even 50 μm or less, and 35 μm or less) is used, or a polarizing film 25 (for example, 20 μm or less, or even 15 μm or less) having a small thickness is manufactured. , And more than 10 μm) is particularly advantageous.

(2) Wet processing section and wet processing step S101

The wet processing unit 20 is a region arranged on the conveyance path of the PVA-based resin film 10 and includes one or more processing tanks that contain a processing solution impregnated with the PVA-based resin film 10. In the wet processing unit 20, it is carried out: while conveying The PVA-based resin film 10 is wet-processed in step S101 by immersing the PVA-based resin film 10 in one or more of the above-mentioned processing liquids. As described above, the conveyance path is constituted by a plurality of rollers supporting and guiding the film in motion, and a part of the plurality of rollers is usually arranged in the wet processing unit 20.

The wet processing unit 20 is the above-mentioned processing tank, and generally includes a dyeing processing tank 15 and a cross-linking processing tank 17, and preferably further includes a swelling processing tank 13 and a washing processing tank 19. These processing tanks are usually arranged in the order of the swelling processing tank 13, the dyeing processing tank 15, the cross-linking processing tank 17, and the washing processing tank 19 in this order from the upstream side of the conveying path (see FIG. 1). In addition, although the figure 1 shows an example in which the swelling treatment tank 13, the dyeing treatment tank 15, the cross-linking treatment tank 17, and the washing treatment tank 19 are each provided with one tank, two or more tanks may be provided as necessary. A dyeing treatment tank 15 or a cross-linking treatment tank 17 having two or more tanks. The same applies to the swelling treatment tank 13 and the washing treatment tank 19.

The processing liquid contained in the swelling processing tank 13 may be, for example, water (pure water, etc.), or an aqueous solution to which a water-soluble organic solvent such as an alcohol is added. The treatment liquid (swelling bath) may contain boric acid, chlorides, inorganic acids, inorganic salts, and the like. The swelling treatment can be performed by immersing the PVA-based resin film 10 in a swelling bath. The swelling treatment is based on the purpose of removing foreign matter, plasticizer removal, imparting easy dyeability, and plasticizing the film of the PVA-based resin film 10 as needed. In the swelling process, the PVA-based resin film 10 may be subjected to a wet stretching process (usually a uniaxial stretching process). The stretching ratio at this time is usually 1.2 to 3 times, preferably 1.3 to 2.5 times. The temperature of the swelling bath is usually 10 to 70 ° C, preferably 15 to 50 ° C. The immersion time (residence time in the swelling bath) of the PVA-based resin film 10 is usually 10 to 600 seconds, preferably 20 to 300 seconds.

The processing liquid contained in the dyeing processing tank 15 is a dyeing processing liquid containing a dichroic pigment. The dyeing treatment can be performed by immersing the PVA-based resin film 10 in the dyeing treatment liquid. This makes it possible to adsorb the dichroic dye to the PVA-based resin film 10. The dichroic pigment may be iodine or a dichroic organic dye, and it is preferably iodine. The dichroic pigment may be used alone or in combination of two or more.

When using iodine as a dichroic dye, an aqueous solution containing iodine and potassium iodide can be used in the dyeing treatment liquid. Instead of potassium iodide, other iodides such as zinc iodide may be used, and potassium iodide may be used in combination with other iodides. In addition, compounds other than iodide, such as boric acid, zinc chloride, and cobalt chloride, may also coexist. When boric acid is added, it differs from the crosslinking treatment liquid mentioned later at the point containing iodine. The content of iodine in the dyeing treatment liquid usually ranges from 0.003 to 1 part by weight per 100 parts by weight of water. The content of iodide such as potassium iodide in the dyeing treatment liquid is usually 0.1 to 20 parts by weight per 100 parts by weight of water. The temperature of the dyeing treatment liquid is usually 10 to 45 ° C, preferably 10 to 40 ° C, and more preferably 20 to 35 ° C. The immersion time (residence time in the dyeing treatment liquid) of the PVA-based resin film 10 is usually 20 to 600 seconds, and preferably 30 to 300 seconds.

When a dichroic organic dye is used as the dichroic dye, an aqueous solution containing a dichroic organic dye can be used in the dyeing treatment liquid. The content of the dichroic organic dye in the dyeing treatment liquid usually ranges from 1 × 10 ^-4 to 10 parts by weight, preferably 1 × 10 ^-3 to 1 part by weight, per 100 parts by weight of water. The dyeing treatment liquid may coexist with a dyeing auxiliary agent, and may contain, for example, an inorganic salt such as sodium sulfate or a surfactant. The dichroic organic dye may be used alone or in combination of two or more. The temperature of the dyeing treatment liquid containing a dichroic organic dye is, for example, 20 to 80 ° C, and preferably 30 to 70 ° C. The immersion time of the PVA-based resin film 10 is usually 30 to 600 seconds, and preferably 60 to 300 seconds.

In order to improve the dyeability of the dichroic pigment, the PVA-based resin film 10 supplied to the dyeing treatment is preferably subjected to at least a certain degree of stretching treatment (usually a uniaxial stretching treatment). Instead of the stretching treatment before the dyeing treatment, or in addition to the stretching treatment before the dyeing treatment, the stretching treatment may be performed while performing the dyeing treatment. The cumulative stretch ratio up to the dyeing process (the stretch ratio in the dyeing process when the unstretching step has not been performed up to the dyeing process) is usually 1.6 to 4.5 times, preferably 1.8 to 4 times.

The processing liquid contained in the crosslinking processing tank 17 is a crosslinking processing liquid containing a crosslinking agent. The crosslinking treatment can be performed by dipping the PVA-based resin film 10 after the dyeing treatment in the crosslinking treatment solution. This makes it possible to perform water resistance, hue adjustment, and the like using the crosslinked PVA-based resin film 10. It is also possible to perform a stretching treatment (normally a uniaxial stretching treatment) while performing a crosslinking treatment.

Examples of the crosslinking agent include boric acid, glyoxal, and glutaraldehyde. Boric acid is preferably used. Two or more types of crosslinking agents may be used in combination. The content of the crosslinking agent in the crosslinking treatment liquid is usually 0.1 to 15 parts by weight, preferably 1 to 12 parts by weight, per 100 parts by weight of water. When the dichroic pigment is iodine, The crosslinking treatment liquid preferably contains an iodide in addition to the crosslinking agent. The content of the iodide in the crosslinking treatment liquid is usually 0.1 to 20 parts by weight, preferably 5 to 15 parts by weight, per 100 parts by weight of water. Examples of the iodide include potassium iodide and zinc iodide. The crosslinking treatment liquid may contain compounds other than iodide, such as zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate, and the like. The temperature of the crosslinking treatment liquid is usually 50 to 85 ° C, and preferably 50 to 70 ° C. The four-immersion time (residence time in the crosslinking treatment liquid) of the PVA-based resin film 10 is usually 10 to 600 seconds, and preferably 20 to 300 seconds.

The treatment liquid contained in the cleaning treatment tank 19 may be, for example, water (pure water) or an aqueous solution to which a water-soluble organic solvent such as an alcohol is added. The cleaning treatment can be performed by immersing the PVA-based resin film 10 after the cross-linking treatment in the treatment liquid (washing bath). The cleaning treatment is a treatment performed for the purpose of removing unnecessary cross-linking agents, dichroic dyes, and other agents attached to the PVA-based resin film 10 as needed. The temperature of the washing bath is, for example, 2 to 40 ° C. It is also possible to perform an elongation process (normally a uniaxial elongation process) while performing a washing process.

The washing treatment may be a treatment in which a washing liquid is sprayed on the PVA-based resin film 10 after the cross-linking treatment, or a combination of the immersion in the washing bath and the spraying of the washing liquid may be combined. FIG. 1 shows an example when the PVA-based resin film 10 is immersed in water in a washing treatment tank 19 to perform a washing treatment.

As described above, in the wet processing step S101, the PVA-based resin film 10 may be subjected to wet stretching. Wet extension is usually uniaxial It may be stretched and subjected to any one of a swelling treatment, a dyeing treatment, a crosslinking treatment, and a washing treatment, or a treatment selected from two or more of these. The wet-stretching is preferably performed at the crosslinking treatment step or at one or more stages before it. As described above, in order to improve the dyeability of the dichroic dye and obtain a polarizing film 25 having good polarizing characteristics, the PVA-based resin film 10 is supplied to the dyeing treatment, and more preferably, it has been subjected to at least a certain degree of extension treatment. From the viewpoint of the polarization characteristics of the obtained polarizing film 25, the stretching ratio of the wet stretching is preferably such that the final cumulative stretching ratio of the polarizing film 25 is obtained (when the PVA-based resin film 10 supplied to the wet processing is a stretched one) , Also including the extension of the cumulative extension magnification) to adjust to 3 to 8 times.

When the wet stretching process step is performed, the polarizing film manufacturing apparatus is a wet stretching means including the PVA-based resin film 10. The wet stretching means is preferably a stretching means for stretching between rolls. In the case where the roll-to-roll stretching is performed in a wet manner during the cross-linking treatment, the roll-to-roll stretching means are two rolls 2 c and 2 d arranged before and after the cross-linking treatment tank 17. The same can be done when stretching is performed in other wet processes, and two sets of rolls that are separately arranged can be used as a wet stretching method.

(3) Drying processing section and drying processing step S102

The drying processing section 22 is an area located on the conveyance path of the PVA-based resin film 10 and is disposed on the downstream side of the wet processing section 20 to dry the PVA-based resin film 10 after the wet processing step S101. While continuing to transport the PVA-based resin film 10 after the wet processing step S101, The thin film is introduced into the drying treatment section 22, and a drying treatment can be performed, whereby a polarizing film 25 can be obtained.

The drying processing unit 22 includes a means (heating means) for drying the film. A suitable example of the drying means is a drying furnace. The drying furnace is preferably one capable of controlling the temperature in the furnace. The drying furnace is, for example, a hot air oven that can increase the temperature in the furnace by supplying hot air. In addition, the drying process by the drying means may be a process in which one or two or more types of heating bodies having convex curved surfaces are brought into close contact with the PVA-based resin film 10 after the wet processing step S101, or heating may be performed using a heater. Processing of the film.

Examples of the heating body include a roller (for example, a guide roller that also has a heat roller) that has a heat source (for example, a heating medium such as warm water or an infrared heater) and can increase the surface temperature. Examples of the heater include an infrared heater, a halogen heater, and a flat heater. Figures 1 and 2 show that the PVA-based resin film 10 after the wet processing step S101 is introduced into the drying furnace 21, and the film is conveyed along the guide rollers in the furnace for 1 to 1 s. Examples of drying treatment. As described above, a part (one or two or more) of a plurality of rollers included in the polarizing film manufacturing apparatus and constituting the conveying path of the PVA-based resin film 10 can be disposed in the drying processing section 22 (drying means).

The temperature of the drying treatment (for example, the temperature in the furnace of the drying furnace 21, the surface temperature of the heat roller, etc.) is usually 30 to 100 ° C, preferably 50 to 90 ° C. The drying time is not particularly limited, but is, for example, 30 to 600 seconds.

The moisture content of the film can be reduced by drying. The moisture content of the polarizing film 25 obtained after drying is usually 5 to 20 weight %, Preferably 8 to 15% by weight. When the moisture content is less than 5 wt%, the flexibility of the polarizing film 25 may be excessively reduced, and the polarizing film 25 may be damaged or broken during subsequent transportation or processing. When the water content of the polarizing film 25 is higher than 20% by weight, the thermal stability of the polarizing film 25 is liable to decrease. The water content referred to herein is measured by a dry weight method.

The polarizing film 25 is a film in which a stretched (usually uniaxially stretched) PVA-based resin film adsorbs and aligns a dichroic dye. The thickness of the polarizing film 25 is usually 2 to 40 μm. From the viewpoint of thinning the polarizing plate containing the polarizing film 25, the thickness of the polarizing film 25 is preferably 20 μm or less, more preferably 15 μm or less, and still more preferably 10 μm or less. As described above, the present invention is particularly advantageous when manufacturing a polarizing film 25 having a small thickness (for example, a thickness of 20 μm or less, or even 15 μm or less, and 10 μm or less).

In consideration of the balance with the luminous factor correction polarization degree Py, the luminous factor correction unit transmittance Ty of the obtained polarizing film 25 is preferably 40 to 47%, more preferably 41 to 45%. The luminous factor correction polarization degree Py is preferably 99.9% or more, and more preferably 99.95% or more. The larger the emission factor correction unit Ty of the polarizing film 25 is, the easier it is to recognize the aforementioned bright spots (light leakage) when applied to a liquid crystal display device. Therefore, the present invention is particularly advantageous when manufacturing a polarizing film 25 having a transmittance Ty of 41 or more, or even 42% or more, and 43% or more. Ty and Py are measured based on the description of the examples described later.

The obtained polarizing film 25 can be sequentially wound on the take-up roller 27 to form a roll shape, or it can be directly supplied to the polarizing plate manufacturing step without winding (on the single-sided or double-area protective layer (protection of the polarizing film 25) Film, etc.) step).

(4) Low rotation resistance roller

The plurality of rollers that construct / define the transport path of the polarizing film manufacturing device and are arranged to be in contact with the surface of the PVA-based resin film 10 to be transported include at least one low-rotation resistance roller having a rotation resistance of 0.025N or less. This can suppress specific unevenness defects generated on the surface of the polarizing film 25. From the viewpoint of more effectively suppressing specific unevenness defects, the rotation resistance of the low rotation resistance roller is preferably 0.01 N or less. The rotation resistance of this roller is usually 0.001N or more.

The rotational resistance of the roller referred to herein means a rotational resistance value measured in the following manner. That is, after a thin film is wound around a roller, the outer end of the wound film is fixed to a spring scale, and the load applied to the spring scale when the spring scale is pulled at a constant speed so that the number of rotations of the roller becomes 100 rpm.

The use of a low-rotational resistance roller can suppress specific irregularities, and it is presumed that the tension of the PVA-based resin film 10 during transportation will be reduced when contacting the low-rotational resistance roller, so that the low-rotational resistance roller and the PVA-based resin film 10 in contact therewith will be caused. The adhesion force between them is low. As a result, when the PVA-based resin film 10 leaves the low-rotation resistance roller, the resistance derived from the above-mentioned adhesion force that the PVA-based resin film 10 wants to continue to adhere to the low-rotation resistance roller is accompanied by the resistance. It is possible to suppress deformation of the PVA-based resin film 10.

The type of the low rotation resistance roller is not particularly limited, and may be a free roller such as a guide roller, or a driving roller such as a roll or a suction roller. When a low-rotation resistance roller is applied to a roll, a pair of rolls constituting the roll can be used. Only one of them is a low rotation resistance roller, or both of them are low rotation resistance rollers. When the low rotation resistance roller is a free roller which does not have a driving force for film conveyance, the effect of suppressing specific unevenness defects can be improved, and therefore it is preferably a guide roller.

For example, by reducing the weight per unit volume of the roller or using a bearing with a small frictional torque, the rotation resistance of the roller can be reduced. Among these, a method of reducing the weight per unit volume of the roller is effective in reducing the rotation resistance of the roller. In order to set the rotation resistance of the roller to the above range, the weight per unit volume of the low rotation resistance roller is preferably 1500 kg / m ³ or less, more preferably 1000 kg / m ³ or less, and still more preferably 700 kg / m ³ or less. By using a lightweight material such as carbon or aluminum as the core material (or the material of the entire roller) of the roller, or using a hollow roller, the weight per unit volume of the roller can be reduced. The weight per unit volume of the roller is usually 200 kg / m ³ or more.

As a result of investigations by the present inventors, it has been understood that the low wettability of the surface of the low-rotation resistance roller (the surface in contact with the PVA-based resin film 10 during transportation) is advantageous for suppressing specific uneven defects. This system is presumed to contribute to reducing the above-mentioned adhesion between the low rotation resistance roller and the PVA-based resin film 10 in contact therewith. Therefore, it is preferable that the low rotation resistance roller system has a surface with low wettability (the surface in contact with the PVA-based resin film 10 during conveyance). Specifically, the low rotation resistance roller system has a contact angle with water. The surface contact angle with water is preferably 60 degrees or more, more preferably 80 degrees or more, and even more preferably 100 degrees or more. The maximum value of the contact angle with water is usually about 120 degrees. The contact angle of the surface of the low-rotation resistance roller with respect to water is measured according to the description of the examples described later.

Surfaces with a large contact angle with water as described above The roller may be a surface layer (coating layer) provided on the surface of the roller and made of a material having a large contact angle with water. Specific examples of materials having a large contact angle with water include: fluorine-based resins such as polytetrafluoroethylene; resins containing silicon atoms such as siloxane-based resins; and carbon materials such as carbon and diamond-like carbon (DLC).

The number of the low rotation resistance rollers is not particularly limited, and the low rotation resistance rollers can be arranged at any position on the conveying path provided in the polarizing film manufacturing apparatus. Therefore, two or more low-rotational-resistance rollers can be arranged on the conveying path, and all the rollers that are in contact with the surface of the PVA-based resin film 10 during conveyance can be low-rotational-resistance rollers. Preferably, the low-rotation resistance roller is arranged at any position from the conveying path from the wet processing section 20 (wet processing step S101) to the drying processing section 22 (drying processing step S102). The so-called "from the wet processing unit 20 (wet processing step S101)" refers to the upstream end of the swelling processing tank 13 (the PVA-based resin film 10 is immersed in the swelling bath when the first wet processing is swelling processing) Time point). The "Zidar drying processing unit 22 (drying process step S102)" refers to the downstream end of the drying processing unit 22 (drying means) (at the end of the drying process).

Among them, it is more preferable to select the arrangement position of the low-rotation resistance roller after considering the following points.

[A] The present inventors have confirmed that the PVA-based resin film 10 after the cross-linking treatment tends to be more likely to generate specific uneven defects when it comes into contact with the rollers than before the cross-linking treatment. Therefore, at least one conveying path is arranged after the crosslinking treatment tank 17 (on the downstream side of the crosslinking treatment tank 17 or later). Rotational resistance rollers are preferred. When there are a plurality of rollers in the transport path after the cross-linking treatment tank 17, it is preferable that all of these rollers be low rotation resistance rollers.

[B] The inventors have confirmed that the PVA-based resin film 10 tends to be more likely to generate specific unevenness defects when the PVA-based resin film 10 is in contact with the roller after the wet processing is completed, compared to the wet processing. Therefore, it is better to arrange at least one low-rotation resistance roller in the conveying path downstream of the cross-linking treatment tank 17. When there are a plurality of rolls in the conveying path downstream of the cross-linking treatment tank 17, It is preferable that all of the rollers are low rotation resistance rollers. When performing a wet treatment such as a washing treatment after the cross-linking treatment, it is preferable to arrange at least one low rotation resistance roller in the conveying path downstream of the wet treatment section 20, and in the specific wet treatment section 20 When there are a plurality of rollers on the downstream conveying path, it is preferable that all of the rollers are low-rotation resistance rollers.

[C] It has been confirmed by the present inventors that when the PVA-based resin film 10 having a lower water content than that immediately after the wet processing is completed (immediately after leaving the last wet processing tank) is in contact with a roller, There is a tendency that specific uneven defects easily occur. Therefore, it is also preferable to arrange at least one low-rotation resistance roller in the conveying path further downstream than the wet processing section 20, and when there are a plurality of rollers in the conveying path further downstream than the wet processing section 20, It is preferable that all of these rolls are low rotation resistance rolls. In particular, when the PVA-based resin film 10 in front of the polarizing film 25 having a desired moisture content is brought into contact with a roller immediately after completion of the wet processing, a specific unevenness defect is likely to occur. Therefore, the transport path connecting the wet processing section 20 and the drying processing section 22, Or it is better to arrange at least one low-rotation resistance roller in the conveying path of the first half of the drying processing section 22, and the conveying path connecting the wet processing section 20 and the drying processing section 22 and the conveying in the first half of the drying processing section 22 When there are a plurality of rollers in the path, it is preferable that all of the rollers are low-rotation resistance rollers. The moisture content of the "PVA-based resin film 10 having a moisture content lower than the moisture content immediately after completion of the wet processing (just after leaving the last wet processing tank)" is, for example, 8 to 30% by weight. Even 10 to 25% by weight. The meaning (measurement method) of the water content is the same as described above.

[D] The smaller the thickness of the PVA-based resin film 10 that is in contact with the roller, the more likely it is that specific unevenness defects will occur. Therefore, compared with the thickness of the PVA-based resin film 10 supplied to the wet processing step S101, the thickness of the PVA-based resin film 10 is reduced by the wet stretching process. Rotational resistance rollers are preferable, and when there are a plurality of such rollers, it is preferable that all of the rollers are low rotation resistance rollers. Specifically, conveyance is performed after the dyeing treatment tank 15 (the downstream side of the dyeing treatment tank 15 or the downstream side) or the cross-linking treatment tank 17 (the downstream side of the cross-linking treatment tank 17 or the downstream side) that is often wet-drawn. It is preferable to arrange at least one low rotation resistance roller in the path, and when there are a plurality of rollers in the conveying path, it is preferable to make all of the rollers be low rotation resistance rollers. The thickness of the aforementioned "the PVA-based resin film 10 which is smaller than the thickness of the PVA-based resin film 10 supplied at the time of the wet processing step S101 due to wet stretching treatment" is, for example, 15 μm or less, It is even less than 12 μm, and more preferably less than 10 μm.

[E] Compared with the case where the conveying direction of the PVA-based resin film 10 is not changed compared to before and after the contact with the roll, there is a tendency that specific uneven defects tend to occur when the changing is performed. Therefore, it is preferable that the roller that changes the conveying direction of the PVA-based resin film 10 in contact therewith be a low rotation resistance roller. The conveyance direction vector of the PVA-based resin film 10 before contacting the roller is set to A, and the conveyance direction vector of the PVA-based resin film 10 immediately after leaving the roller is set to B. The PVA-based resin before contacting the roller is When the conveying direction of the film 10 is the same as the conveying direction of the PVA-based resin film 10 immediately after leaving the roller, the angle (the conveying direction change angle) α formed by the vectors A and B is regarded as 0 °, When the conveying direction of the PVA-based resin film 10 before being in contact with the roller is reversed from the conveying direction of the PVA-based resin film 10 immediately after leaving the roller, the angle α formed by the vectors A and B is regarded as 180 ° The present invention is advantageous when the angle α satisfies 30 to 180 °, and further satisfies 45 to 180 °.

(5) Specific unevenness

The specific irregularities referred to in this specification, which are generated on the surface of a polarizing film, are bright spots (light leakage) when the polarizing film is applied to a liquid crystal display device. This bright spot is a defect that can be identified only when the brightness of the backlight is increased to a certain level or more. This spot is a new issue discovered by the inventors for the first time. The above "when the brightness of the backlight is increased to a certain level or more" refers to a time when the brightness of the backlight measured by a brightness meter is about 10,000 cd / m ² or more. If the brightness of the backlight is compared with the brightness of a light emitted from a liquid crystal display device including the backlight and a liquid crystal panel (the liquid crystal panel includes a liquid crystal cell and a polarizing plate arranged on both sides) disposed on the backlight, the brightness is approximately It is equivalent to 500cd / m ² or more.

Regarding the specific unevenness defect, a polarizing film surface other than the unevenness defect is used as a reference, and is typically composed of a combination of a convex portion protruding from the reference and a concave portion which is caught in the reference and is adjacent to the convex portion. Generally, the film conveyance direction has a convex portion on the upstream side and a concave portion on the downstream side. In a conventional polarizing film, a plurality of concave-convex portions composed of the convex portions and the concave portions are spread over almost the entire surface of the polarizing film to form dots randomly. When the polarizing film is viewed from above (when viewed from a direction perpendicular to the film surface), the shape of the uneven portion is, for example, a circular shape, an elliptical shape, or the like, but may be irregular in shape. When the polarizing film is viewed from above (when viewed from a direction perpendicular to the film surface), the major diameter (maximum diameter) of the specific irregularity defect is about 0.5 to 5 mm (for example, 1 to 3 mm). Regarding the specific unevenness defect, the height of the convex portion and the depth of the concave portion are typically about 0.05 to 0.5 μm with respect to the above-mentioned reference. The height difference (the distance in the thickness direction of the film from the top of the convex portion to the bottom of the concave portion) in the specific unevenness is about 0.1 to 1 μm. When the long diameter or the height difference of a specific unevenness defect is outside the above-mentioned range, the unevenness defect does not cause a bright spot, and there is a tendency that it does not easily cause a problem. The presence of a specific uneven defect can be confirmed, for example, with a magnifying glass. The long diameter and the height difference of a specific uneven defect are measured by the method described in the Example item mentioned later.

According to the present invention, it is possible to suppress or prevent the occurrence of specific uneven defects as described above on the surface of the polarizing film. Thereby, even when a polarizing film is applied to a liquid crystal display device using a high-brightness backlight, bright spots (light leakage) can be effectively suppressed or prevented.

The polarizing film of the present invention preferably has a density of specific unevenness on at least one side of 20 / m ² or less, more preferably 15 / m ² or less, and still more preferably 10 / m ² or less. The density of specific unevenness defects on at least one side of the polarizing film is expected to be 0 / m ² , but if it is 20 / m ² or less, the bright spot when viewing the screen of a liquid crystal display device has nothing to do with the size of the screen and hardly Affects the visibility of the picture. On the other hand, when the density of specific uneven defects exceeds 20 pieces / m ² , the visibility is hindered by the size of the screen. The density of the specific unevenness | corrugation defect is measured by the method as described in the Example item mentioned later. In addition, when a specific unevenness defect is found on one side of the polarizing film, a specific unevenness defect where the convex portion and the concave portion are reversed is usually formed at the same position on the other side.

<Polarizer>

By forming a protective layer on one or both sides of the polarizing film 25, a polarizing plate can be obtained. The protective layer may be a protective film made of a thermoplastic resin, or may be a cured product layer of an active energy ray-curable resin composition. When a protective film is used, a polarizing plate can be obtained by bonding a protective film on one or both sides of the polarizing film 25 with an adhesive layer interposed therebetween. When a protective film is bonded to both sides of the polarizing film 25, the thermoplastic resin constituting the protective films may be the same type or different types.

The thermoplastic resin constituting the protective film is a thermoplastic resin having translucency, and is preferably an optically transparent thermoplastic resin. The thermoplastic resin may be, for example, a polyolefin resin such as a chain polyolefin resin (such as a polypropylene resin) or a cyclic polyolefin resin (such as a norbornene resin); such as cellulose triacetate or diacetic acid. A cellulose-based resin; such as a polymer pair. Polyester resins such as polyethylene terephthalate and polybutylene terephthalate; polycarbonate resins; (meth) acrylic resins such as methyl methacrylate resins; polystyrene resins Resin; Polyvinyl chloride resin; Acrylonitrile / butadiene / styrene resin; Acrylonitrile / styrene resin; Polyvinyl acetate resin; Polyvinylidene chloride resin; Polyamide resin; Polyvinyl chloride resin Acetal-based resins; modified polyphenylene ether-based resins; polyfluorene-based resins; polyetherfluorene-based resins; polyacrylate-based resins; polyamidamine-imide-based resins; polyimide-based resins, and the like.

In addition to the homopolymer of a linear olefin such as a polyethylene resin or a polypropylene resin, the chain polyolefin-based resin may be a copolymer composed of two or more kinds of chain olefins. More specific examples include polypropylene resins (polypropylene resins which are homopolymers of propylene, or copolymers mainly composed of propylene), polyethylene resins (polyethylene resins which are homopolymers of ethylene, Or copolymer based on ethylene).

The cyclic polyolefin resin is a general term for a resin polymerized by using a cyclic olefin as a polymerization unit. Specific examples of cyclic polyolefin resins include ring-opened (co) polymers of cyclic olefins, addition polymers of cyclic olefins, and copolymerization of cyclic olefins and chain olefins such as ethylene and propylene. Materials (represented by random copolymers), graft polymers modified with unsaturated carboxylic acids or their derivatives, and hydrides such as these. Among them, norbornene-based resins in which norbornene-based monomers such as norbornene or polycyclic norbornene-based monomers are used as cyclic olefins are preferred.

The cellulose resin refers to the hydroxyl group of cellulose obtained from cellulose such as cotton wool or wood pulp (broadwood pulp, coniferous pulp). A cellulose organic acid ester or a cellulose organic acid mixed ester in which a part or all of the hydrogen atoms are substituted with ethenyl, propionyl and / or butyl fluorenyl. Examples include cellulose acetate, propionate, butyrate, and mixed esters thereof. Among them, cellulose triacetate, cellulose diacetate, cellulose acetate propionate, and cellulose acetate butyrate are preferred.

The polyester-based resin is a resin other than the above-mentioned cellulose-based resin having an ester bond, and is generally composed of a polycondensate of a polycarboxylic acid or a derivative thereof and a polyhydric alcohol. As the polycarboxylic acid or a derivative thereof, a divalent dicarboxylic acid or a derivative thereof can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalate. As the polyhydric alcohol, a divalent diol can be used, and examples thereof include ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, and cyclohexanedimethanol. Examples of suitable polyester-based resins include polyethylene terephthalate.

Polycarbonate resins are engineering plastics composed of polymers that combine monomer units through carbonate groups. They are resins with high impact resistance, heat resistance, flame resistance, and transparency. The polycarbonate-based resin may be, for example, a resin called modified polycarbonate that has been modified with a polymer skeleton in order to reduce the photoelastic coefficient, or a copolymerized polycarbonate having improved wavelength dependency.

The (meth) acrylic resin is a polymer containing a structural unit derived from a (meth) acrylic monomer. The polymer is typically a polymer containing methacrylate. A polymer containing a methacrylate-derived structural unit at a ratio of 50% by weight or more based on the total structural unit is preferred. The (meth) acrylic resin may be a homopolymer of methacrylate, or It may be a copolymer containing a structural unit derived from another polymerizable monomer. In this case, the ratio of the constituent units derived from other polymerizable monomers is preferably 50% by weight or less based on the total structural units.

The methacrylate that can constitute a (meth) acrylic resin is preferably an alkyl methacrylate. Examples of the alkyl methacrylate include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, and methyl formate. Third butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, and 2-hydroxyethyl methacrylate-like alkyl groups having 1 to 8 carbon atoms. The carbon number of the alkyl group contained in the alkyl methacrylate is preferably 1 to 4. Among (meth) acrylic resins, methacrylates may be used alone or in combination of two or more.

Examples of the other polymerizable monomers that can constitute a (meth) acrylic resin include acrylates and other compounds having a polymerizable carbon-carbon double bond in the molecule. The other polymerizable monomers may be used alone or in combination of two or more. The acrylate is preferably an alkyl acrylate. Examples of the alkyl acrylate include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, third butyl acrylate, 2-ethylhexyl acrylate, and acrylic acid. Cyclohexyl, 2-hydroxyethyl acrylate, alkyl acrylate having 1 to 8 carbon atoms, and the like. The carbon number of the alkyl group contained in the alkyl acrylate is preferably 1 to 4. Among (meth) acrylic resins, acrylates may be used alone or in combination of two or more.

Examples of other compounds having a polymerizable carbon-carbon double bond in the molecule include vinyl compounds such as ethylene, propylene, and styrene, or propylene Acrylonitrile vinyl cyanide compound. Other compounds having a polymerizable polymerizable carbon-carbon double bond in the molecule may be used alone or in combination of two or more.

The protective film may also be a thin film having optical functions such as a retardation film and a brightness enhancement film. For example, a retardation film having an arbitrary retardation value can be formed by extending a film (such as uniaxial stretching or biaxial stretching) of the thermoplastic resin or forming a liquid crystal layer on the film. The protective film may have a surface treatment layer (coating layer) laminated on its surface such as a hard coat layer, an anti-glare layer, an anti-reflection layer, an anti-static layer, and an anti-fouling layer.

The thickness of the protective film is usually 1 to 100 μm, but from the viewpoints of strength, handleability, and thinning of the polarizing plate, the thickness is preferably 5 to 60 μm, and more preferably 5 to 50 μm.

The adhesive used when bonding the polarizing film 25 and the protective film is an aqueous adhesive, an active energy ray-curable adhesive, or a thermosetting adhesive, and is preferably an aqueous adhesive or active energy ray-curable. Then agent. When the protective film is laminated on both sides of the polarizing film 25, the adhesive used to attach the protective films may be the same type of adhesive or different types of adhesives.

The aqueous adhesive is one in which an adhesive component is dissolved or dispersed in water. The water-based adhesive that can be preferably used is, for example, an adhesive composition using a polyvinyl alcohol resin or a urethane resin as a main component.

When a polyvinyl alcohol-based resin is used as the main component of the adhesive, the polyvinyl alcohol-based resin may be, for example, a partially saponified polyvinyl alcohol or a completely saponified polyvinyl alcohol, and may also be a carboxyl group. change Modified polyvinyl alcohol resin based on modified polyvinyl alcohol, acetoacetic acid modified polyvinyl alcohol, methylol modified polyvinyl alcohol, and amino modified polyvinyl alcohol. Polyvinyl alcohol resins are copolymers of vinyl acetate and other monomers copolymerizable with vinyl acetate, in addition to vinyl alcohol homopolymers obtained by saponification of polyvinyl acetate, which is a homopolymer of vinyl acetate. A polyvinyl alcohol copolymer obtained by saponification.

The aqueous adhesive containing a polyvinyl alcohol resin as an adhesive component is usually an aqueous solution of a polyvinyl alcohol resin. The concentration of the polyvinyl alcohol-based resin in the adhesive is usually 1 to 10 parts by weight, and preferably 1 to 5 parts by weight with respect to 100 parts by weight of water.

In order to improve the adhesion, the adhesive composed of an aqueous solution of a polyvinyl alcohol resin preferably contains, for example, polyaldehyde, melamine-based compound, zirconia compound, zinc compound, glyoxal, glyoxal derivative, and water-soluble ring. Hardening component or cross-linking agent of oxygen resin. As the water-soluble epoxy resin, for example, polyamine obtained by reacting a polyalkylene polyamine such as diethylene glycol triamine and triethylene glycol tetraamine with a dicarboxylic acid such as adipic acid can be suitably used. Polyamine polyamine epoxy resin obtained by reacting with epichlorohydrin. Commercially available products of this polyamine polyamine epoxy resin include "Sumirez Resin 650" (manufactured by Taoka Chemical Industry Co., Ltd.), "Sumirez Resin 675" (manufactured by Taoka Chemical Industry Co., Ltd.), and "WS-525" (Japanese PMC (shares) system) and so on. The amount of these hardening components or cross-linking agents (the total amount when they are added together as a hardening component and a cross-linking agent) is usually 1 to 100 parts by weight based on 100 parts by weight of the polyvinyl alcohol resin, preferably It is 1 to 50 parts by weight. The addition amount of the hardening component or the crosslinking agent is less than 1 weight based on 100 weight parts of the polyvinyl alcohol resin. In the case of parts, the effect of improving the adhesiveness tends to be small, and when the added amount exceeds 100 parts by weight based on 100 parts by weight of the polyvinyl alcohol resin, the adhesive layer tends to become brittle.

Moreover, as a suitable example when a urethane resin is used as the main component of an adhesive agent, the mixture of a polyester-type ionic polymer type urethane resin and the compound which has a glycidyloxy group is mentioned. The polyester-based ionic polymer-based urethane resin refers to a urethane resin having a polyester skeleton, and a small amount of an ionic component (hydrophilic component) is introduced into the urethane resin. This ionic polymer-type urethane resin is suitable as an aqueous adhesive because it is emulsified into water directly without using an emulsifier to form an emulsion.

Active energy ray-curable adhesives are adhesives that are hardened by irradiation of active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays. When an active energy ray-curable adhesive is used, the adhesive layer included in the polarizing plate is a cured product layer of the adhesive.

The active energy ray-curable adhesive may be an adhesive containing an epoxy-based compound hardened by cationic polymerization as a hardening component, and is preferably an ultraviolet-curable adhesive containing the epoxy-based compound as a hardening component. The epoxy-based compound herein means a compound having an average of one or more, preferably two or more epoxy groups in the molecule. The epoxy-based compound may be used alone or in combination of two or more.

Specific examples of the epoxy-based compound that can be suitably used include a hydrogenated epoxy-based compound obtained by reacting an alicyclic polyol obtained by hydrogenating an aromatic ring of an aromatic polyol with epichlorohydrin ( Glycidyl ether of a polyhydric alcohol having an alicyclic ring); such as an aliphatic polyhydric alcohol or its Aliphatic epoxy compound of polyglycidyl ether of alkylene oxide adduct; alicyclic epoxy of epoxy compound having one or more epoxy groups bonded to alicyclic ring in the molecule Department of compounds.

The active energy ray hardening adhesive may contain a radically polymerizable (meth) acrylic compound as a hardening component instead of the epoxy compound, or may contain both an epoxy compound and a (meth) acrylic compound . Examples of the (meth) acrylic compound include a (meth) acrylic acid ester monomer having at least one (meth) acryloxy group in the molecule; and a compound obtained by reacting two or more kinds of compounds containing a functional group. A compound containing a (meth) acryloxy group, such as a (meth) acrylate oligomer having at least two (meth) acryloxy groups in the molecule.

When the active energy ray-curable adhesive contains an epoxy-based compound that is cured by cationic polymerization as a curable component, it is preferable to include a photocationic polymerization initiator. Examples of the photocationic polymerization initiator include an onium salt such as an aromatic diazonium salt; an onium salt such as an aromatic sulfonium salt or an aromatic sulfonium salt; an iron-aromatic hydrocarbon complex; and the like. When the active energy ray-curable adhesive contains a radical polymerizable curable component such as a (meth) acrylic compound, it is preferable to include a photoradical polymerization initiator. Examples of the photoradical polymerization initiator include an acetophenone-based initiator, a diphenylketone-based initiator, a benzoin ether-based initiator, a thia anthrone-based initiator, an xanthone, and a fluorenone. , Camphorquinone, benzaldehyde, anthraquinone, etc.

Before the polarizing film is bonded to the protective film, the surface of the polarizing film and / or the protective film can be subjected to surface activation treatments such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame treatment, and saponification treatment. This surface activation treatment can improve the adhesion between the polarizing film and the protective film.

(Example)

Hereinafter, the present invention will be described more specifically by showing examples and comparative examples, but the present invention is not limited to these examples. The measurement or evaluation is based on the following method.

(1) Measurement of film thickness

The measurement was performed using a digital micrometer "MH-15M" manufactured by Nikon.

(2) Measurement of the moisture content of the film

Using a plurality of polyvinyl alcohol film samples having different moisture contents, the correlation between the moisture content obtained by the dry weight method and the measured value of an infrared absorption moisture meter ("IRMA1100" manufactured by Chino Corporation) was created. Calibration line (conversion formula). The measured value is obtained by using the moisture content meter, and the measured value is substituted into the calibration curve (conversion formula), and converted into a moisture content [wt%] obtained by a dry weight method, and this is used as the moisture content of the film. The moisture content obtained by the dry weight method is that the weight of the polyvinyl alcohol film sample when heat-treated at 105 ° C. for 120 minutes is W1, and the weight of the polyvinyl alcohol film sample before heat treatment is W0, according to the following formula: Determiner: Moisture content [wt%] obtained by dry weight method = {(W0-W1) ÷ W0} × 100

The calibration curve is created according to the thickness of the film to be measured.

(3) Confirmation and evaluation of specific uneven defects

One side of the obtained polarizing film was observed with a magnifying glass (when a specific unevenness defect is found on one side, usually a specific unevenness defect is also formed on the other side), and the presence or absence of the specific unevenness defect is confirmed. As described above, the polarizing film surface other than the unevenness defect is used as a reference, and is composed of a combination of a convex portion that protrudes from the reference and a concave portion that is lower than the reference and is adjacent to the convex portion. When specific irregularities exist, the average length of the specific irregularities (average major diameter) and the average height difference (average elevation difference) of the average irregularities are measured using a white light drying instrument "VertScan" manufactured by Ryoka Systems. (The average distance in the thickness direction of the film from the top of the convex portion to the bottom of the concave portion) (see (4) below). In addition, from the obtained polarizing film, three samples of 200 mm in the transmission axis direction and 300 mm in the absorption axis direction were cut out from random regions, and each of them was observed with a magnifying glass to measure the number of specific irregularities. The density of specific unevenness defects (the number of specific unevenness defects per unit area of the polarizing film, unit: unit / m ² ) was determined. Specifically, the calculation of the density of specific unevenness defects is based on the following formula: The density of specific unevenness defects (pieces / m ² ) = (Total number of specific unevenness defects in three samples) / (of three samples) (Total area)

The results are shown in Table 1. In addition, the above-mentioned confirmation of specific unevenness defects was performed only on one side of the obtained polarizing film, but in the following Examples and Comparative Examples, the confirmation of specific unevenness defects was performed on the same surface of the polarizing film.

(4) Measurement of the average major diameter and average height difference of specific uneven defects

The measurement was performed using a white light dryer "VertScan" made by Ryoka Systems. The so-called long diameter (maximum diameter) refers to the specific unevenness viewed from above In the case of a defect (when viewed from a direction perpendicular to the film surface), the longest distance is from the outer end of the convex portion to the outer end of the concave portion. Ten specific irregularities were randomly selected, and the average of these major diameters was set as the "average major diameter". Further, the step difference was measured for the above-mentioned ten specific uneven defects, and the average value of these was defined as the "average step difference". The results are shown in Table 1. In addition, in the examples and comparative examples, the long diameter of each of the specific irregularities measured was in a range of 0.5 to 5 mm, and the height difference was in a range of 0.1 to 1 μm.

(5) Confirmation and evaluation of bright spots (light leakage)

From the random regions of the obtained polarizing film, three samples of 200 mm in the transmission axis direction and 300 mm in the absorption axis direction were cut out, and bright spots (light leakage) were evaluated for each of them. Specifically, a polarizing plate for inspection is placed on a backlight in a dark room with a brightness of 20,000 cd / m ² (measured using a luminance meter "BM-5A" manufactured by Topcon Technohouse). The above polarizing film sample. At this time, the polarizing plate for inspection and the polarizing film sample are arranged so that the transmission axis of the polarizing film included in the polarizing plate for inspection is orthogonal to the transmission axis of the polarizing film sample. Next, the backlight was turned on, and the presence or absence of dot-like bright spots (light leakage) on the surface of the sample was visually confirmed from the polarizing film sample side. When bright spots are found, measure the number of them and find their density (the number of bright spots per unit area, unit: pcs / m ² ). Specifically, the calculation of the density of bright spots is based on the following formula: Density of bright spots (pieces / m ² ) = (Total number of bright spots in three samples) / (Total area of three samples)

The results are shown in Table 1.

The density of the bright spots was determined in the same manner as described above, except that one of the following conditions (A) or (B) was applied when the brightness was confirmed based on the above conditions. The results are shown in Table 1.

(A) A neutral density filter with an average transmittance of 50% is further arranged between the backlight and the polarizing plate for inspection (in this case, the actual brightness of the backlight is 10,000 cd / m ² ).

(B) A full-wave dimmer with an average transmittance of 3% is further disposed between the backlight and the polarizing plate for inspection (in this case, the substantial brightness of the backlight is 600 cd / m ² ).

(6) Measurement of transmittance Ty and luminous factor correction polarization degree Py

Using a spectrophotometer with an integrating sphere ("V7100" manufactured by JASCO Corporation), the obtained transmittance and polarization were corrected for luminescence factor using a 2-degree viewing angle (C light source) of JIS Z 8701 to measure luminescence. The factor correction unit transmittance Ty and the luminous factor correction polarization degree Py.

(7) Measurement of rotation resistance of guide roller

After winding a thin film (polyethylene terephthalate film with a thickness of 25 μm) on a roll, the outer end of the wound film was fixed to a spring scale, and the spring scale was pulled at a certain speed to make the number of rotations of the roll When the speed reached 100 rpm, the load applied to the spring scale was measured, and this was used as the rotation resistance of the guide roller.

(8) Determination of contact angle (contact angle to water) with water on the surface of the guide roller

The measurement was performed using a contact angle meter (Full-automatic contact angle meter "DM-701" manufactured by Kyowa Interface Science Co., Ltd.) at a temperature of 23 ° C and a relative humidity of 50% by a droplet method.

<Example 1>

The drying process section includes a total of 15 guide rollers (free rollers) (all connected to the film surface), and uses the same polarizing film manufacturing apparatus as in Figs. 1 and 2 to continuously from the long PVA-based resin film 10 A long polarizing film 25 is manufactured. Next, a polarizing plate is produced using the obtained polarizing film 25. The details are as follows.

(1) Preparation of PVA-based resin film 10

As the PVA-based resin film 10, the following PVA-based resin film a was prepared. The PVA-based resin film a is a dry-type uniaxial extension of a polyvinyl alcohol film having a thickness of 30 μm to 4.1 times. The degree of saponification of the polyvinyl alcohol constituting the film is 99.9 mol% or more, and the average degree of polymerization is 2400. A plasticizer is 10 parts by weight based on 100 parts by weight of polyvinyl alcohol constituting the film.

(2) Wet processing step S101

The PVA-based resin film a is unrolled from the unwinding roller 11 while being continuously conveyed while being tensioned, and is dipped in a swelling treatment tank 13 containing pure water at 40 ° C. for a retention time of 60 seconds. On the other hand, the PVA-based resin film a is sufficiently swollen (swelling treatment step). The film pulled out from the swelling treatment tank 13 was immersed in a container containing iodine / potassium iodide / water for a retention time of 60 seconds to re-weight In the dyeing treatment tank 15 of the dyeing treatment liquid having a volume ratio of 0.1 / 6/100 at 30 ° C, uniaxial stretching (stretching between rolls in a bath) was performed at the same time (dyeing processing step). The film pulled out from the dyeing treatment tank 15 was immersed in a crosslinking treatment tank 17 containing a crosslinking treatment solution of 68 ° C of potassium iodide / boric acid / water at a weight ratio of 15 / 5.5 / 100 for a retention time of 130 seconds, and During this period, uniaxial stretching (stretching between rolls in the bath) was performed (crosslinking treatment step). The film pulled out from the crosslinking treatment tank 17 was immersed in a cleaning treatment tank 19 containing pure water at 20 ° C. for a retention time of 3 seconds (washing treatment step). The cumulative stretching ratio based on the PVA-based resin film a was 4.5 times.

(3) Drying step S102

Next, the film pulled out from the washing treatment tank 19 is continuously conveyed, and simultaneously introduced into a drying furnace 21 as a hot-air oven, and subjected to a drying treatment with a retention time of 90 seconds and a temperature of 60 ° C. to obtain a polarizing film 25. The obtained polarizing film 25 had a thickness of 12 μm, a luminosity factor correction monomer transmittance Ty of 42.5%, a luminosity factor correction polarization degree Py of 99.993%, and a water content of 10% by weight. The obtained polarizing film 25 was checked for specific irregularities. The results are shown in Table 1. In addition, the thickness of the film when connected to the first low rotation resistance roller is substantially the same as the thickness of the polarizing film 25.

In Example 1, among the guide rollers for constructing the conveyance path of the thin film provided in the polarizing film manufacturing device, the guide rollers for constructing the conveyance path of the first half of the drying furnace 21 (the upstream of the 15 guide rollers) 8) All were set as low rotation resistance rollers. As these low rotation resistance rollers, the following low rotation resistance rollers I were used. Guide the construction of the conveying path of the first half of the drying furnace 21 As the guide rollers (7 downstream), the following guide rollers II were used. The following guide rollers II were also used as the guide rollers of the wet processing section.

〔Low rotation resistance roller I〕

‧Composition: Guide rollers using carbon for the core material and coated with a fluorine resin layer on the surface

‧Rotational resistance: 0.008N

‧Weight per unit volume: 640kg / m ³

‧Surface water contact angle: 95 degrees

‧The angle α of the film in each of the low rotation resistance rollers (the angle of change in the conveying direction): 90 ° or 180 ° (common to all examples and comparative examples).

[Guiding Roller II]

‧Composition: SUS304 is used as the core material and the surface has been chrome plated.

‧Rotational resistance: 0.03N

‧Weight per unit volume: 1600kg / m ³

‧Surface contact angle with water: 75 degrees

About the obtained polarizing film 25, the specific unevenness | corrugation defect and the bright point (light leakage) were evaluated by the method mentioned above. The results are shown in Table 1.

(4) Fabrication of polarizing plate

The obtained polarizing film 25 was continuously conveyed, and at the same time, the first protective film [TAC film "KC2UAW" made by Konica Minolta Opto (strand) was used, and the thickness was: 25 μm] and the second protective film [is a cyclic polyolefin resin film made by JSR (stock), trade name "FEKB015D3", thickness: 15 μm] are continuously conveyed, between the polarizing film 25 and the first protective film, and An aqueous adhesive is injected between the polarizing film 25 and the second protective film, and at the same time, it is passed between the laminating rollers to form a first protective film / aqueous adhesive layer / polarizing film 25 / aqueous adhesive layer / second protective film. Composition of the laminated film.

The above-mentioned aqueous adhesive is an aqueous solution obtained by dissolving polyvinyl alcohol powder [trade name "Gohsefimer" manufactured by Nippon Synthetic Chemical Industry Co., Ltd., average polymerization degree: 1100] in hot water at 95 ° C. In the obtained polyvinyl alcohol aqueous solution having a concentration of 3% by weight, a cross-linking agent [sodium glyoxylate manufactured by Japan Synthetic Chemical Industry Co., Ltd.] was obtained at a ratio of 1 part by weight to 10 parts by weight of the polyvinyl alcohol powder. Aqueous solution.

Next, the obtained laminated film was conveyed and passed through a hot-air drier to perform a heat treatment at 80 ° C. for 300 seconds, thereby drying the aqueous adhesive layer to obtain a polarizing plate.

<Example 2>

A polarizing film 25 (thickness: 12 μm) was produced in the same manner as in Example 1 except that the following low rotation resistance roller III was used, and then a polarizing plate was produced. Table 1 shows the evaluation results of specific uneven defects and bright spots (light leakage).

[Low Rotational Resistance Roller III]

‧Composition: Guide using carbon for core material and diamond-like carbon layer coated on the surface Roller

‧Rotational resistance: 0.008N

‧Weight per unit volume: 640kg / m ³

‧Surface contact angle with water: 105 degrees

<Example 3>

All the guide rollers that construct the conveyance path of the first half of the drying furnace 21 and all the guide rollers that construct the conveyance path connecting the cleaning treatment tank 19 and the drying furnace 21 are set as low-rotation resistance rollers I. A polarizing film 25 (thickness: 12 μm) was produced in the same manner as in Example 1, and a polarizing plate was produced next. Table 1 shows the evaluation results of specific uneven defects and bright spots (light leakage).

<Examples 4 to 6>

A polarizing film was produced in the same manner as in Examples 1 to 3 except that a PVA-based resin film b obtained by uniaxially extending a polyvinyl alcohol film having a thickness of 20 μm to 4.1 times was used as the PVA-based resin film 10. 25 (thickness 7 μm), and a polarizing plate was produced next. Table 1 shows the evaluation results of specific uneven defects and bright spots (light leakage).

<Comparative example 1>

A polarizing film 25 was produced in the same manner as in Example 1 except that the guide rollers constituting the transport path of the film included in the polarizing film manufacturing apparatus were not used, and the low-rotation resistance roller I was not used. thickness 12 μm), and a polarizing plate was produced next. Table 1 shows the evaluation results of specific uneven defects and bright spots (light leakage).

<Comparative example 2>

A polarizing film 25 was produced in the same manner as in Comparative Example 1 except that a PVA-based resin film b obtained by uniaxially extending a polyvinyl alcohol film having a thickness of 20 μm to 4.1 times was used as the PVA-based resin film 10. Thickness is 7 μm), and a polarizing plate is produced next. Table 1 shows the evaluation results of specific uneven defects and bright spots (light leakage).

Claims (18)

A manufacturing device for manufacturing a polarizing film from a polyvinyl alcohol-based resin film and comprising a plurality of rollers constituting a conveying path of the polyvinyl alcohol-based resin film and configured to be in contact with the polyvinyl alcohol-based resin The surfaces of the films are in contact with each other; the wet processing section is disposed on the conveying path and includes one or more processing tanks containing a processing solution impregnated with the polyvinyl alcohol-based resin film; and the drying processing section is disposed on the foregoing On the conveying path, the polyvinyl alcohol-based resin film is dried after being wet-processed; wherein the plurality of rollers include a low rotation resistance roller having a rotation resistance of 0.025N or less, and the low rotation resistance roller has a contact angle with water For surfaces above 100 degrees. A manufacturing device for manufacturing a polarizing film from a polyvinyl alcohol-based resin film and comprising a plurality of rollers constituting a conveying path of the polyvinyl alcohol-based resin film and configured to be in contact with the polyvinyl alcohol-based resin The surfaces of the films are in contact with each other; the wet processing section is disposed on the conveying path and includes one or more processing tanks containing a processing solution impregnated with the polyvinyl alcohol-based resin film; and the drying processing section is disposed on the foregoing The conveying path is used to dry the polyvinyl alcohol-based resin film after the wet treatment; wherein the plurality of rollers include low-rotation resistance rollers having a rotation resistance of 0.025N or less, and the wet processing unit sequentially includes: A dyeing treatment tank containing a dichroic dye-containing dyeing treatment solution and a cross-linking treatment tank containing a cross-linking agent-containing cross-linking treatment solution. The low-rotation resistance roller is disposed on a downstream side of the cross-linking treatment tank. Path, the aforementioned low rotation resistance roller is a guide roller. The manufacturing apparatus according to item 1 of the scope of patent application, wherein the low-rotation resistance roller is arranged at any position on a conveying path from the wet processing section to the drying processing section. The manufacturing apparatus according to item 3 of the scope of patent application, wherein the wet processing section sequentially includes: a dyeing treatment tank containing a dyeing treatment liquid containing a dichroic pigment; and a crosslinking treatment containing a crosslinking agent. Liquid cross-linking treatment tank; the low-rotation resistance roller is arranged behind the cross-linking treatment tank. The manufacturing apparatus according to item 2 of the scope of patent application, wherein the low rotation resistance roller has a surface having a contact angle of 60 degrees or more with respect to water. The manufacturing device according to item 1 or 5 of the scope of the patent application, wherein the surface is made of a fluorine-based resin, a resin containing silicon atoms, carbon, or diamond-like carbon. The manufacturing device according to any one of claims 1 to 5, wherein the weight per unit volume of the aforementioned low rotation resistance roller is 1500 kg / m ³ or less. The manufacturing apparatus according to item 1, 3, or 4 of the scope of patent application, wherein the aforementioned low rotation resistance roller is a guide roller. The manufacturing apparatus according to any one of claims 1 to 5, wherein the thickness of the polyvinyl alcohol-based resin film in contact with the low rotation resistance roller is 15 μm or less. A manufacturing method, which is a method of manufacturing a polarizing film from a polyvinyl alcohol-based resin film, and includes the following steps: a wet processing step, which is arranged along a plurality of layers so as to be in contact with the surface of the aforementioned polyvinyl alcohol-based resin film A conveying path constituted by a roller conveys the polyvinyl alcohol-based resin film while immersing the polyvinyl alcohol-based resin film in one or more treatment liquids; and a drying process step conveys the polyvinyl alcohol-based resin along the conveying path. While drying the polyvinyl alcohol-based resin film after wet processing; wherein the plurality of rollers include a low rotation resistance roller having a rotation resistance of 0.025N or less, and the low rotation resistance roller has a contact angle with water of 100 degrees Above the surface. A manufacturing method, which is a method of manufacturing a polarizing film from a polyvinyl alcohol-based resin film, and includes the following steps: a wet processing step, which is arranged along a plurality of layers so as to be in contact with the surface of the aforementioned polyvinyl alcohol-based resin film A conveying path constituted by a roller conveys the polyvinyl alcohol-based resin film while immersing the polyvinyl alcohol-based resin film in one or more treatment liquids; and a drying process step conveys the polyvinyl alcohol-based resin along the conveying path. Film, the polyvinyl alcohol resin film after the wet treatment is dried; wherein the plurality of rollers include a low rotation resistance roller having a rotation resistance of 0.025N or less, and the wet treatment step includes: A step of dyeing a coloring dye solution and a step of immersing in a crosslinking treatment solution containing a crosslinking agent contained in a crosslinking treatment tank, the low-rotation resistance roller system is disposed further downstream than the crosslinking treatment tank The conveying path of the low rotation resistance roller is a guide roller. The manufacturing method according to item 10 of the scope of patent application, wherein the low-rotation resistance roller is arranged at any position on the conveying path from the wet processing step to the drying processing step. The manufacturing method according to item 12 of the scope of patent application, wherein the aforementioned wet processing step includes sequentially: a step of immersing in a dyeing treatment liquid containing a dichroic pigment; and a crosslinking treatment of immersing in a crosslinking agent. Step of liquid; the aforementioned low rotation resistance roller is arranged on the conveying path after the step of immersing in the crosslinking treatment liquid. The manufacturing method according to item 11 of the patent application range, wherein the low rotation resistance roller has a surface having a contact angle of 60 degrees or more with respect to water. The manufacturing method according to item 10 or 14 of the scope of patent application, wherein the surface is made of a fluorine-based resin, a resin containing silicon atoms, carbon, or diamond-like carbon. The manufacturing method according to any one of claims 10 to 14, in which the weight per unit volume of the aforementioned low rotation resistance roller is 1500 kg / m ³ or less. The manufacturing method according to item 10, 12 or 13 of the scope of the patent application, wherein the aforementioned low rotation resistance roller is a guide roller. The manufacturing method according to any one of claims 10 to 14, wherein the thickness of the polyvinyl alcohol-based resin film in contact with the low rotation resistance roller is 15 μm or less.