JP6636729B2 - Polarizing film, polarizing plate, and method for manufacturing polarizing film - Google Patents

Description

  The present invention relates to a polarizing film, a polarizing plate, and a method for manufacturing a polarizing film.

  2. Description of the Related Art Polarizing plates are widely used in image display devices such as liquid crystal display devices. The polarizing plate generally has a structure in which a protective film is stuck on one or both sides of a polarizing film obtained by adsorbing and orienting a dichroic dye such as iodine on a polyvinyl alcohol-based resin film.

  In recent years, the demand for the performance of the polarizing film has become more severe due to the expansion of the application field of the liquid crystal display device and the advance of peripheral technology. It is known that a polarizing film tends to cause a decrease in polarizing performance when placed in a high-temperature environment, and it is known that such a tendency of the decrease in polarizing performance increases as the thickness of the polarizing film decreases. ing. In this specification, resistance to deterioration of polarization performance due to being placed in a high-temperature environment is referred to as “heat resistance”.

  Japanese Patent Application Laid-Open Publication No. 2005-266048 (Patent Document 1) describes a polarizing film having improved heat resistance by containing an oligosaccharide.

JP 2005-266048 A

  An object of the present invention is to provide a polarizing film with further improved heat resistance and a method for producing the same. Another object of the present invention is to provide a polarizing plate having excellent heat resistance.

  The present invention provides a polarizing film, a polarizing plate, and a method for manufacturing a polarizing film described below.

  [1] A polarizing film comprising a polyvinyl alcohol-based resin film and containing a cyclodextrin having an inner diameter of an intramolecular cavity of 0.6 nm or more.

  [2] The polarizing film according to [1], wherein the cyclodextrin is a β-cyclodextrin or a γ-cyclodextrin.

[3] The polarizing film according to [1] or [2], which has a thickness of 15 μm or less.
[4] The polarizing film according to any one of [1] to [3],
A protective film laminated on at least one surface of the polarizing film.

[5] A method for producing a polarizing film for producing a polarizing film from a polyvinyl alcohol-based resin film,
A method for producing a polarizing film, comprising a treatment step of bringing a treatment liquid containing a cyclodextrin having an inner diameter of an intramolecular cavity of 0.6 nm or more into contact with the polyvinyl alcohol-based resin film for treatment.

  [6] The method for producing a polarizing film according to [5], wherein the cyclodextrin is a β-cyclodextrin or a γ-cyclodextrin.

  [7] The method for producing a polarizing film according to [5] or [6], wherein the concentration of the cyclodextrin in the treatment liquid is 0.1 to 10% by weight.

  [8] The treatment step is a swelling treatment step using a swelling liquid as the treatment liquid, a dyeing treatment step using a staining liquid as the treatment liquid, or a cross-linking treatment step using a cross-linking liquid as the treatment liquid. The method for producing a polarizing film according to any one of [7] to [7].

  ADVANTAGE OF THE INVENTION According to this invention, the polarizing film excellent in heat resistance, its manufacturing method, and a polarizing plate can be provided.

FIG. 2 is a schematic sectional view illustrating an example of a layer configuration of a polarizing plate according to the present invention. It is a schematic sectional drawing which shows another example of the layer structure of the polarizing plate which concerns on this invention. It is a sectional view showing typically an example of a polarizing film manufacturing device concerning the present invention. It is a graph which shows Py before and after the heat resistance test of Examples 1 and 2, and Comparative Examples 1 and 2. It is a graph which shows Py before and after heat resistance test of Examples 3-7 and Comparative Example 3.

<Polarizing film>
The polarizing film according to the present invention is made of a polyvinyl alcohol-based resin film, and contains cyclodextrins having an inner diameter of the intramolecular cavity of 0.6 nm or more. The polarizing film of the present invention containing a cyclodextrin having an inner diameter of the intramolecular cavity of 0.6 nm or more has excellent heat resistance, and can suppress a decrease in polarizing performance even when placed in a high-temperature environment. . By using the polarizing film according to the present invention, a polarizing plate having excellent heat resistance can be provided because the polarizing film itself is excellent in heat resistance.

  To describe the polarization performance of the polarizing film in more detail, the polarization performance is usually evaluated by two parameters called “visibility correction single transmittance Ty” and “visibility correction polarization degree Py”. These parameters are the transmittance and the degree of polarization in the visible region (wavelength 380 to 780 nm) corrected so that the weighting around 550 nm where the sensitivity of the human eye is highest is the largest. Since light having a wavelength of less than 380 nm cannot be visually recognized by human eyes, it is not considered in Ty and Py.

  The visibility correction single transmittance Ty of the polarizing film of the present invention can be a value usually required in an image display device such as a liquid crystal display device to which the polarizing film or a polarizing plate including the same is applied. Is preferably in the range of 40 to 47%. Ty is more preferably in the range of 41 to 45%, and in this case, the balance between Ty and Py becomes better. If Ty is too high, Py decreases and the display quality of the image display device deteriorates. When Ty is excessively low, the brightness of the image display device is reduced to lower the display quality, or it is necessary to increase the input power in order to sufficiently increase the brightness.

  The visibility correction polarization degree Py of the polarizing film of the present invention is preferably 99.95% or more, more preferably 99.99% or more when the visibility correction single transmittance Ty is 43% or less. Py after the heat resistance test described later is preferably 99.93% or more, more preferably 99.95% or more, from the viewpoint of maintaining the display quality of the image display device even after the test. Further, the amount of change in Py before and after the heat resistance test “Py (before the heat resistance test) −Py (after the heat resistance test)” is preferably 0.055% or less.

  When Ty and Py of the polarizing film exist as a single substance (when they exist alone), they are measured as a measurement sample. On the other hand, when the protective film is present on the polarizing film as a laminated polarizing plate, the protective film and the adhesive layer are removed from the polarizing plate, and the polarizing film contained in the polarizing plate is isolated and measured. Ty and Py are measured as a sample or the polarizing plate itself as a measurement sample, and these are defined as Ty and Py of the polarizing film. Ty and Py measured using a polarizing plate as a measurement sample are substantially the same as Ty and Py measured using an isolated polarizing film as a measurement sample.

  The polarizing film according to the present invention is obtained by adsorbing and orienting iodine as a dichroic dye on a polyvinyl alcohol-based resin film, and more specifically, adsorbing and orienting iodine on a uniaxially stretched polyvinyl alcohol-based resin film. It is a thing.

  The thickness of the polarizing film can be, for example, 30 μm or less, and more preferably 20 μm or less, but is preferably 15 μm or less, more preferably 10 μm or less, from the viewpoint of reducing the thickness of the polarizing plate. The thickness of the polarizing film is usually 2 μm or more. Although the heat resistance tends to decrease as the thickness decreases, the present invention can provide a polarizing film having good heat resistance even when the thickness is 15 μm or less.

  As the polyvinyl alcohol-based resin constituting the polarizing film, a polyvinyl acetate-based resin saponified can be used. Examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and a copolymer of vinyl acetate and another monomer copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

  The polarizing film is formed by forming the polyvinyl alcohol-based resin. The method of forming the polyvinyl alcohol-based resin is not particularly limited, and the film can be formed by a known method.

  The degree of saponification of the polyvinyl alcohol-based resin can be in the range of 80.0 to 100.0 mol%, but is preferably in the range of 90.0 to 100.0 mol%, and more preferably 98.0. -100.0 mol%. When the saponification degree is less than 80.0 mol%, the water resistance of the obtained polarizing film tends to decrease.

The degree of saponification is the unit ratio (mol%) of the ratio of acetic acid groups (acetoxy groups: -OCOCH ₃ ) contained in polyvinyl acetate resin, which is a raw material of the polyvinyl alcohol resin, changed to hydroxyl groups in the saponification step. And the following formula:
Degree of saponification (mol%) = 100 × (number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetate groups)
Is defined by The saponification degree can be determined in accordance with JIS K 6726 (1994). The higher the degree of saponification, the higher the proportion of hydroxyl groups, and therefore the lower the proportion of acetate groups that inhibit crystallization.

  The polyvinyl alcohol-based resin may be a partially modified polyvinyl alcohol. For example, those obtained by modifying a polyvinyl alcohol resin with an olefin such as ethylene or propylene; an unsaturated carboxylic acid such as acrylic acid, methacrylic acid, or crotonic acid; an alkyl ester of an unsaturated carboxylic acid, (meth) acrylamide, or the like. The percentage of modification is preferably less than 30 mol%, more preferably less than 10%. When the modification exceeds 30 mol%, the dichroic dye becomes difficult to be adsorbed, and a polarizing film having sufficient polarizing performance tends to be hardly obtained. In this specification, “(meth) acryl” means at least one selected from the group consisting of acryl and methacryl. The same applies to “(meth) acryloyl” and the like.

  The average degree of polymerization of the polyvinyl alcohol-based resin is preferably from 100 to 10,000, more preferably from 1500 to 8,000, and still more preferably from 2,000 to 5,000. The average degree of polymerization of the polyvinyl alcohol-based resin can also be determined according to JIS K 6726 (1994).

  The polarizing film of the present invention contains a cyclodextrin having an inner diameter of the intramolecular cavity of 0.6 nm or more. Cyclodextrin refers to a non-reducing cyclic oligosaccharide in which glucose is cyclically linked by α-1,4 bonds, and the inner diameter of the intramolecular cavity increases as the number of constituent glucoses increases. Since the inner diameter of the intramolecular cavity of β-cyclodextrin, which is a heptamer, is known to be 0.6 to 0.8 nm, the inner diameter of the intramolecular cavity used in the present invention is 0.6 nm. The above cyclodextrins are not limited as long as the number of constituting glucose is 7 or more. For example, β, γ, δ-cyclodextrin in which the number of constituting glucose is 7, 8, 9 respectively, These β, γ, δ-cyclodextrins are branched cyclodextrins having an oligosaccharide such as glucose or maltose as a branched sugar chain, and further, these cyclodextrins or branched cyclodextrins have an alkyl group such as methyl, 2-hydroxyethyl, A hydroxyalkyl group such as hydroxypropyl, 2,3-dihydroxypropyl, 2-hydroxybutyl, etc. is bonded. Cyclodextrin derivatives and the like.

The present invention has been made by confirming a remarkable effect of improving the heat resistance of a polarizing film by including a cyclodextrin having an inner diameter of an intramolecular cavity of 0.6 nm or more in the polarizing film. The remarkable effect of improving the heat resistance of the polarizing film is that the inner cavity of the cyclodextrin having the inner diameter of the inner cavity of 0.6 nm or more and the polyiodide ion (I ₃ ⁻ , I ₃ ⁻ _{5 ^-)} it is estimated to be that provided the results of the interaction of. Since such an interaction is presumed to depend on the size of the intramolecular cavity of the cyclodextrin, a remarkable effect of improving the heat resistance has been confirmed from the 7,8-mer cyclodextrin. It is presumed that a cyclodextrin having a large intramolecular cavity, that is, a cyclodextrin having an inner diameter of the intramolecular cavity of 0.6 nm or more has the same effect. In order to further improve the interaction between the intramolecular cavity of the cyclodextrin and the polyiodide ion (I ₃ ⁻ , I ₅ ⁻ ), the inner diameter of the intramolecular cavity of the cyclodextrin is Preferably it is 0.8 nm or more. The inner diameter of the intramolecular cavity of the cyclodextrin is preferably 1.2 nm or less.

The content of the cyclodextrin having an inner diameter of the intramolecular cavity of 0.6 nm or more in the polarizing film is not limited as long as the heat resistance can be improved, but is, for example, 0.01 to 5% by weight. be able to. Such a content can be measured by analyzing a solution obtained by dissolving a polarizing film in a solvent by liquid chromatography (LC). It is also assumed that the stoichiometric ratio between iodine (I ₂ ) in the polarizing film and cyclodextrins having an inner diameter of the intramolecular cavity of 0.6 nm or more affects the degree of interaction. In the present invention, the stoichiometric ratio between iodine (I ₂ ) in the polarizing film and the cyclodextrin having an inner diameter of the intramolecular cavity of 0.6 nm or more is in the range of 1.5: 1 to 1500: 1. It is more preferably in the range of 2.5: 1 to 1000: 1, and still more preferably in the range of 2.5: 1 to 500: 1.

<Polarizing plate>
(1) Layer Configuration of Polarizing Plate FIG. 1 is a schematic sectional view showing an example of the layer configuration of the polarizing plate according to the present invention. Like the polarizing plate 1 shown in FIG. 1, the polarizing plate of the present invention may be a polarizing plate with a single-sided protective film including a polarizing film 5 and a first protective film 7 laminated on one surface thereof. it can. The first protective film 7 can be laminated on the polarizing film 5 via the first adhesive layer 6.

  Further, the polarizing plate according to the present invention may be one in which a protective film is further attached to the other surface of the polarizing film 5, and specifically, as in the polarizing plate 2 shown in FIG. 5, a double-sided protective film-equipped polarizing plate comprising: a first protective film 7 laminated on one surface thereof; and a second protective film 9 laminated on the other surface. The second protective film 9 can be laminated on the polarizing film 5 via the second adhesive layer 8.

  When the polarizing plate according to the present invention is incorporated in an image display device such as a liquid crystal display device, the polarizing plate may be a polarizing plate disposed on the visual (front) side of an image display element such as a liquid crystal cell, It may be a polarizing plate disposed on the back side of the display element (for example, on the backlight side of a liquid crystal display device).

(2) Polarizing Film The polarizing plate according to the present invention includes the polarizing film according to the present invention as the polarizing film 5. Therefore, for the details of the polarizing film 5, the above description is cited.

(3) First protective film The first protective film 7 is a translucent (preferably optically transparent) thermoplastic resin, for example, a chain polyolefin-based resin (eg, a polypropylene-based resin) or a cyclic polyolefin-based resin. Polyolefin resins such as (norbornene resins); cellulose ester resins such as cellulose triacetate and cellulose diacetate; polyester resins; polycarbonate resins; (meth) acrylic resins; polystyrene resins; And a film composed of a copolymer or the like. In order to further improve the water resistance of the polarizing plate, the first protective film 7 has a relatively low moisture permeability such as a protective film made of a polyolefin resin, a polyester resin, a (meth) acrylic resin, a polystyrene resin, or the like. It is also preferred to choose a low protective film.

  The first protective film 7 may be a protective film having optical functions such as a retardation film and a brightness enhancement film. For example, a retardation film provided with an arbitrary retardation value by stretching a film made of the thermoplastic resin (such as uniaxial stretching or biaxial stretching) or forming a liquid crystal layer or the like on the film. It can be.

  Examples of the chain polyolefin resin include a homopolymer of a chain olefin such as a polyethylene resin and a polypropylene resin, and a copolymer composed of two or more chain olefins.

  The cyclic polyolefin-based resin is a general term for resins that are polymerized using cyclic olefin as a polymerized unit. Specific examples of the cyclic polyolefin-based resin include a ring-opening (co) polymer of a cyclic olefin, an addition polymer of a cyclic olefin, and a copolymer of a cyclic olefin with a chain olefin such as ethylene and propylene (typically, Are random copolymers), graft polymers obtained by modifying these with unsaturated carboxylic acids and derivatives thereof, and hydrides thereof. Among them, a norbornene-based resin using a norbornene-based monomer such as norbornene or a polycyclic norbornene-based monomer as the cyclic olefin is preferably used.

  The cellulose ester-based resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. In addition, these copolymers and those obtained by modifying a part of hydroxyl groups with other substituents can also be used. Among these, cellulose triacetate (triacetyl cellulose: TAC) is particularly preferred.

  The polyester-based resin is a resin having an ester bond other than the cellulose ester-based resin, and generally comprises a polycondensate of a polyvalent carboxylic acid or a derivative thereof and a polyhydric alcohol. As the polyvalent carboxylic acid or a derivative thereof, a dicarboxylic acid or a derivative thereof can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalenedicarboxylate. As the polyhydric alcohol, a diol can be used, and examples thereof include ethylene glycol, propanediol, butanediol, neopentyl glycol, and cyclohexanedimethanol.

  Specific examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexane dimethyl terephthalate, and polycyclohexane dimethyl naphthalate.

  The polycarbonate resin is composed of a polymer in which monomer units are bonded via a carbonate group. The polycarbonate-based resin may be a resin called a modified polycarbonate having a modified polymer skeleton, a copolymerized polycarbonate, or the like.

The (meth) acrylic resin is a resin having a compound having a (meth) acryloyl group as a main constituent monomer. Specific examples of the (meth) acrylic resin include, for example, poly (meth) acrylates such as polymethyl methacrylate; methyl methacrylate- (meth) acrylic acid copolymer; methyl methacrylate- (meth) acrylic acid Ester copolymer; methyl methacrylate-acrylate- (meth) acrylic acid copolymer; methyl (meth) acrylate-styrene copolymer (MS resin, etc.); methyl methacrylate and alicyclic hydrocarbon group And a copolymer having the compound (e.g., methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-norbornyl (meth) acrylate copolymer). Preferably, a polymer having a poly (meth) acrylate C _1-6 alkyl ester as a main component such as poly (methyl meth) acrylate is used, and more preferably, a methyl methacrylate as a main component (50 to 100). % By weight, preferably 70 to 100% by weight).

  On the surface of the first protective film 7 opposite to the polarizing film 5, a surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, and an antifouling layer is formed. You can also. Further, the first protective film 7 contains one or more additives such as a lubricant, a plasticizer, a dispersant, a heat stabilizer, an ultraviolet absorber, an infrared absorber, an antistatic agent, and an antioxidant. Can be.

  The thickness of the first protective film 7 is preferably 90 μm or less, more preferably 50 μm or less, and still more preferably 30 μm or less, from the viewpoint of reducing the thickness of the polarizing plate. The thickness of the first protective film 7 is usually 5 μm or more from the viewpoint of strength and handleability.

(4) First Adhesive Layer The first adhesive layer 6 is a layer for bonding and fixing the first protective film 7 to one surface of the polarizing film 5. The adhesive that forms the first adhesive layer 6 is an active energy ray-curable adhesive containing a curable compound that is cured by irradiation with an active energy ray such as ultraviolet light, visible light, an electron beam, or X-ray, or polyvinyl. An aqueous adhesive in which an adhesive component such as an alcohol resin is dissolved or dispersed in water can be used. Above all, from the viewpoint of improving the water resistance of the polarizing plate, it is preferable to use an active energy ray-curable adhesive. A preferred example of the active energy ray-curable adhesive is an ultraviolet-curable adhesive.

  Since the active energy ray-curable adhesive forming the first adhesive layer 6 exhibits good adhesiveness, the active energy ray-curable compound containing a cationically polymerizable curable compound and / or a radically polymerizable curable compound is used. A curable adhesive composition can be preferably used. The active energy ray-curable adhesive may further include a cationic polymerization initiator and / or a radical polymerization initiator for initiating a curing reaction of the curable compound.

  Examples of the cationically polymerizable curable compound include an epoxy compound (a compound having one or more epoxy groups in a molecule) and an oxetane compound (one or two or more oxetane rings in a molecule). Or a combination thereof. Examples of the radical polymerizable curable compound include a (meth) acrylic compound (compound having one or more (meth) acryloyloxy groups in a molecule) and a radical polymerizable double bond. Other vinyl compounds or combinations thereof can be mentioned. A cationically polymerizable curable compound and a radically polymerizable curable compound may be used in combination.

  The active energy ray-curable adhesive may be, if necessary, a cationic polymerization accelerator, an ion trapping agent, an antioxidant, a chain transfer agent, a tackifier, a thermoplastic resin, a filler, a flow regulator, a plasticizer, Additives such as a foaming agent, an antistatic agent, a leveling agent, and a solvent can be contained.

  The thickness of the first adhesive layer 6 is generally about 0.001 to 5 μm, and preferably 0.01 to 3 μm.

(5) Second protective film Like the first protective film 7, the second protective film 9 included in the polarizing plate 2 with a double-sided protective film shown in FIG. 2 may be a film made of the thermoplastic resin exemplified above. Alternatively, a protective film having an optical function such as a retardation film and a brightness enhancement film may be used. For the surface treatment layer and the thickness of the film that the second protective film 9 may have, the above description of the first protective film 7 is cited. The first protection film 7 and the second protection film 9 may be protection films made of the same kind of resin, or may be protection films made of different kinds of resins. In order to further improve the water resistance of the polarizing plate, the second protective film 9 has a relatively low moisture permeability such as a protective film made of a polyolefin resin, a polyester resin, a (meth) acrylic resin, a polystyrene resin, or the like. It is also preferred to choose a low protective film.

(6) Second adhesive layer The second adhesive layer 8 is a layer for bonding and fixing the second protective film 9 to the other surface of the polarizing film 5. For the details of the second adhesive layer 8, the above description of the first adhesive layer 6 is cited. From the viewpoint of improving the water resistance of the polarizing plate, the second adhesive layer 8 is preferably formed from an active energy ray-curable adhesive. The adhesive forming the second adhesive layer 8 may have the same composition as the adhesive forming the first adhesive layer 6, or may have a different composition.

(7) Pressure-sensitive adhesive layer On the polarizing film 5 or the first protective film 7 in the polarizing plate 1 with a single-sided protective film shown in FIG. 1, or the first protective film 7 or in the polarizing plate 2 with a double-sided protective film shown in FIG. On the second protective film 9, an adhesive layer for bonding the polarizing plate to another member (for example, a liquid crystal cell when applied to a liquid crystal display device) may be laminated. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is usually made of a (meth) acrylic resin, a styrene-based resin, a silicone-based resin, or the like as a base polymer, to which a crosslinking agent such as an isocyanate compound, an epoxy compound, or an aziridine compound is added. It consists of an adhesive composition. Further, a pressure-sensitive adhesive layer having light scattering properties can be obtained by incorporating fine particles. The thickness of the pressure-sensitive adhesive layer is usually from 1 to 40 μm, preferably from 3 to 25 μm.

(8) Other Optical Layer The polarizing plate according to the present invention can further include another optical layer laminated on the first and / or second protective films 7 and 9 and the polarizing film 5. Other optical layers include a reflective polarizing film that transmits a certain kind of polarized light and reflects polarized light having the opposite property; a film with an antiglare function having an uneven surface; a film with a surface antireflection function A reflective film having a reflective function on its surface; a transflective reflective film having both a reflective function and a transmissive function; a viewing angle compensation film, and the like.

<Method for manufacturing polarizing film>
One embodiment of the method for producing a polarizing film of the present invention will be described. In this embodiment, an unstretched polyvinyl alcohol-based resin film (original) having a thickness of 65 μm or less (for example, 60 μm or less), preferably 50 μm or less, more preferably 35 μm or less, and still more preferably 30 μm or less is used as a starting material for polarizing film production. Anti-film). This makes it possible to obtain a thin polarizing film, which is increasingly required in the market. The width of the raw film is not particularly limited, and may be, for example, about 400 to 6000 mm. The raw film is prepared, for example, as a roll of a long unstretched polyvinyl alcohol-based resin film (raw roll).

  The polarizing film, while unwinding the long raw film from the raw roll, continuously transported along the film transport path of the polarizing film manufacturing apparatus, the processing liquid contained in the processing tank (hereinafter, referred to as After performing a predetermined processing step of drawing out after being immersed in a “processing bath”, a drying step is performed, whereby a long polarizing film can be continuously manufactured. The processing step is not limited to a method of immersing the film in a processing bath as long as the processing liquid is brought into contact with the processing liquid, and the processing liquid is attached to the film surface by spraying, flowing down, dropping, or the like. Alternatively, a method of processing the film by using the method may be used.

  Examples of the treatment liquid include a swelling liquid, a dyeing liquid, a crosslinking liquid, and a cleaning liquid. As the above-mentioned treatment steps, a swelling treatment step of bringing a swelling solution into contact with the raw film and performing a swelling treatment, a dyeing treatment step of bringing a swelling film into contact with a staining liquid to carry out a staining treatment, A cross-linking treatment step in which a cross-linking solution is brought into contact with a subsequent film to perform a cross-linking treatment, and a cleaning treatment step in which a cleaning liquid is brought into contact with the film after the cross-linking treatment to perform a cleaning treatment are exemplified. Further, between these series of processing steps (that is, before or after any one or more processing steps and / or during any one or more processing steps), a uniaxial stretching treatment is performed by a wet or dry method. Other processing steps may be added as needed.

  In the present embodiment, the swelling solution, the staining solution, and the crosslinking solution, according to the present invention, by adding a cyclodextrin having an inner diameter of the intramolecular cavity of 0.6 nm or more to at least one of the treatment solutions. It is possible to produce a polarizing film containing a cyclodextrin having an inner diameter of the intramolecular cavity of 0.6 nm or more. The concentration of cyclodextrins having an inner diameter of the intramolecular cavity of 0.6 nm or more in the swelling solution, the staining solution, and the crosslinking solution can be, for example, 0.1% by weight to 10% by weight, and preferably 0.8% by weight. % To 5.0% by weight, and more preferably 2.0% to 5.0% by weight.

  Hereinafter, the method for manufacturing the polarizing film of the present embodiment will be described in detail with reference to FIG. FIG. 3 is a cross-sectional view schematically illustrating an example of a method for manufacturing a polarizing film of the present embodiment and a polarizing film manufacturing apparatus used for the method. The polarizing film manufacturing apparatus shown in FIG. 3 transports a raw (unstretched) film 10 made of a polyvinyl alcohol-based resin along a film transport path while continuously unwinding it from a raw roll 11. Swelling bath (swelling solution accommodated in swelling tank) 13 provided on the transport path, dyeing bath (staining solution accommodated in staining tank) 15, crosslinking bath (crosslinking solution accommodated in crosslinking tank) 17 , And a cleaning bath (cleaning liquid contained in the cleaning tank) 19, and finally through a drying furnace 21. The obtained polarizing film 23 can be conveyed, for example, as it is to the next polarizing plate manufacturing step (the step of bonding a protective film to one or both sides of the polarizing film 23). The arrow in FIG. 3 indicates the transport direction of the film.

  FIG. 3 shows an example in which each of the swelling bath 13, the dyeing bath 15, the cross-linking bath 17, and the washing bath 19 is provided one by one. If necessary, one or more treatment baths may be provided in two or more baths. It may be provided. In the description of FIG. 1, “treatment tank” is a general term including a swelling tank, a dyeing tank, a cross-linking tank, and a cleaning tank, and “treatment liquid” is a general term including a swelling liquid, a dyeing liquid, a cross-linking liquid, and a cleaning liquid. , "Treatment bath" is a general term including a swelling bath, a dyeing bath, a crosslinking bath, and a washing bath.

  The film transport path of the polarizing film manufacturing apparatus includes guide rolls 30 to 41, 60, and 61 that support the transported film or can further change the film transport direction, in addition to the processing bath described above, and the transported film. Nip rolls 50 to 55, which can apply a driving force to the film by pressing and holding the film, or further change the film transport direction, can be constructed at appropriate positions. The guide roll and the nip roll can be arranged before and after each processing bath or in the processing bath, so that the film can be introduced and dipped into the processing bath and drawn out of the processing bath (see FIG. 3). For example, a film can be immersed in each processing bath by providing one or more guide rolls in each processing bath and conveying the film along these guide rolls.

  In the polarizing film manufacturing apparatus shown in FIG. 3, nip rolls are arranged before and after each processing bath (nip rolls 50 to 54), whereby nip rolls are arranged before and after any one or more processing baths. It is possible to perform inter-roll stretching in which longitudinal uniaxial stretching is performed with a peripheral speed difference therebetween. Hereinafter, each step will be described.

(Swelling process)
The swelling process is performed for the purpose of removing foreign substances on the surface of the raw film 10, removing a plasticizer in the raw film 10, imparting easy dyeability, plasticizing the raw film 10, and the like. The processing conditions are determined within a range in which the object can be achieved and a range in which problems such as extreme melting and devitrification of the raw film 10 do not occur.

  Referring to FIG. 3, in the swelling process, the raw film 10 is conveyed along the film conveying path while being continuously unwound from the raw roll 11, and the raw film 10 is immersed in the swelling bath 13 for a predetermined time. And then withdrawing. In the example of FIG. 3, during the period from unwinding the raw film 10 to immersion in the swelling bath 13, the raw film 10 is transported along the film transport path constructed by the guide rolls 60 and 61 and the nip roll 50. Is done. In the swelling process, the film is transported along the film transport path constructed by the guide rolls 30 to 32.

  Examples of the swelling liquid in the swelling bath 13 include pure water, boric acid (JP-A-10-153709), chloride (JP-A-06-281816), inorganic acids, inorganic salts, water-soluble organic solvents, and alcohols. It is also possible to use an aqueous solution to which compounds and the like are added in the range of about 0.01 to 10% by weight. Further, as described above, in the swelling treatment step, it is also possible to use a swelling liquid to which cyclodextrins having an inner diameter of the intramolecular cavity of 0.6 nm or more are added.

  The temperature of the swelling bath 13 is, for example, about 10 to 50 ° C, preferably about 10 to 40 ° C, and more preferably about 15 to 30 ° C. The immersion time of the raw film 10 is preferably about 10 to 300 seconds, more preferably about 20 to 200 seconds. When the raw film 10 is a polyvinyl alcohol-based resin film stretched in advance in a gas, the temperature of the swelling bath 13 is, for example, about 20 to 70 ° C, preferably about 30 to 60 ° C. The immersion time of the raw film 10 is preferably about 30 to 300 seconds, more preferably about 60 to 240 seconds.

  In the swelling treatment, the problem that the raw film 10 swells in the width direction and wrinkles are apt to occur. As one means for transporting the film while removing the wrinkles, a roll having a widening function such as an expander roll, a spiral roll, or a crown roll may be used for the guide rolls 30, 31, and / or 32, a cross guider, a bend bar, or the like. And other widening devices such as tenter clips. Another means for suppressing the generation of wrinkles is to perform a stretching treatment. For example, a uniaxial stretching process can be performed in the swelling bath 13 by utilizing a peripheral speed difference between the nip roll 50 and the nip roll 51.

  In the swelling process, the film expands and swells also in the transport direction of the film. Therefore, when the film is not actively stretched, in order to eliminate the slack of the film in the transport direction, for example, it is disposed before and after the swelling bath 13. It is preferable to take measures such as controlling the speed of the nip rolls 50 and 51. In order to stabilize the film transport in the swelling bath 13, the water flow in the swelling bath 13 is controlled by a submerged shower, or an EPC device (Edge Position Control device: detects the end of the film and meanders the film). It is also useful to use an apparatus for preventing the above.

  In the example shown in FIG. 3, the film drawn from the swelling bath 13 passes through the guide roll 32 and the nip roll 51 in order and is introduced into the dyeing bath 15.

(Dyeing process)
The dyeing process is performed for the purpose of, for example, adsorbing and orienting the dichroic dye on the polyvinyl alcohol-based resin film after the swelling process. The processing conditions are determined within a range in which the object can be achieved and a range in which problems such as extreme dissolution and devitrification of the film do not occur. Referring to FIG. 3, in the dyeing process, the film after the swelling process is transported along the film transport path constructed by the guide rolls 33 to 35 and the nip roll 51, and the swelling process is performed. Liquid) for a predetermined time and then withdrawn. In order to enhance the dyeability of the dichroic dye, the film subjected to the dyeing process is preferably a film that has been subjected to at least some uniaxial stretching, or, instead of the uniaxial stretching before the dyeing, Alternatively, in addition to the uniaxial stretching treatment before the dyeing treatment, it is preferable to perform the uniaxial stretching treatment during the dyeing treatment.

  In the present embodiment, iodine is used as the dichroic dye. As the dyeing solution of the dyeing bath 15, for example, an aqueous solution having a concentration of iodine / potassium iodide / water = about 0.003 to 0.3 / about 0.1 to 10/100 by weight can be used. Instead of potassium iodide, another iodide such as zinc iodide may be used, or potassium iodide and another iodide may be used in combination. Further, a compound other than iodide, for example, boric acid, zinc chloride, cobalt chloride or the like may be allowed to coexist. When boric acid is added, it is distinguished from the crosslinking treatment described below in that it contains iodine. If the aqueous solution contains about 0.003 parts by weight or more of iodine with respect to 100 parts by weight of water, the dyeing bath 15 Can be considered. The temperature of the dye bath 15 when immersing the film is usually about 10 to 45 ° C., preferably 10 to 40 ° C., more preferably 20 to 35 ° C., and the immersion time of the film is usually 30 to 600 seconds. Degree, preferably 60 to 300 seconds.

  As described above, in the staining treatment step, it is also possible to use a staining solution to which cyclodextrins having an inner diameter of the intramolecular cavity of 0.6 nm or more are added.

  As described above, in the dyeing process, the film can be uniaxially stretched in the dyeing bath 15. Uniaxial stretching of the film can be performed by a method such as providing a peripheral speed difference between a nip roll 51 and a nip roll 52 disposed before and after the dyeing bath 15.

  In the dyeing process, as in the case of the swelling process, in order to transport the polyvinyl alcohol-based resin film while removing wrinkles of the film, a widening function such as an expander roll, a spiral roll, and a crown roll is applied to the guide rolls 33, 34 and / or 35. Or other widening devices such as cross guiders, bend bars, tenter clips, etc. can be used. Another means for suppressing the generation of wrinkles is to apply a stretching treatment as in the case of the swelling treatment.

  In the example shown in FIG. 3, the film drawn from the dyeing bath 15 passes through the guide roll 35 and the nip roll 52 in order and is introduced into the crosslinking bath 17.

(Cross-linking process)
The cross-linking process is a process performed for the purpose of, for example, making the film water-resistant and adjusting the hue (preventing the film from becoming bluish) by cross-linking. Referring to FIG. 3, the cross-linking treatment is carried out along a film conveyance path constructed by guide rolls 36 to 38 and nip roll 52, and after dyeing treatment in cross-linking bath 17 (cross-linking solution contained in the cross-linking bath). It can be carried out by immersing the film for a predetermined time and then withdrawing the film.

  The crosslinking solution for the crosslinking bath 17 may be an aqueous solution containing, for example, about 1 to 10 parts by weight of boric acid with respect to 100 parts by weight of water. When the dichroic dye used in the dyeing treatment is iodine, the crosslinking solution preferably contains iodide in addition to boric acid, and the amount thereof is, for example, 1 to 30 parts by weight with respect to 100 parts by weight of water. It can be. Examples of the iodide include potassium iodide, zinc iodide and the like. Further, a compound other than iodide, for example, zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate and the like may coexist.

  In the crosslinking treatment, the concentration of boric acid and iodide and the temperature of the crosslinking bath 17 can be appropriately changed depending on the purpose. For example, when the purpose of the cross-linking treatment is water resistance by cross-linking, and the polyvinyl alcohol-based resin film is subjected to a swelling treatment, a dyeing treatment, and a crosslinking treatment in this order, the concentration of the cross-linking agent-containing liquid in the cross-linking bath is determined by weight. It can be a cross-linking solution of boric acid / iodide / water = 3 to 10/1 to 20/100. If necessary, another crosslinking agent such as glyoxal or glutaraldehyde may be used instead of boric acid, or boric acid and another crosslinking agent may be used in combination. The temperature of the crosslinking bath when immersing the film is usually about 50 to 70 ° C., preferably 53 to 65 ° C., and the immersion time of the film is usually about 10 to 600 seconds, preferably 20 to 300 seconds, more preferably Is 20 to 200 seconds. When the dyeing treatment and the crosslinking treatment are performed in this order on the polyvinyl alcohol-based resin film stretched in advance before the swelling treatment, the temperature of the crosslinking bath 17 is usually about 50 to 85 ° C, preferably 55 to 80 ° C. .

  In the crosslinking treatment for the purpose of adjusting the hue, for example, when iodine is used as the dichroic dye, a crosslinking solution having a concentration of boric acid / iodide / water = 1 to 5/3 to 30/100 by weight is used. Can be used. The temperature of the crosslinking bath when immersing the film is usually about 10 to 45 ° C., and the immersion time for the film is usually about 1 to 300 seconds, preferably 2 to 100 seconds.

  As described above, in the crosslinking treatment step, it is also possible to use a crosslinking liquid to which cyclodextrins having an inner diameter of the intramolecular cavity of 0.6 nm or more are added.

  The crosslinking treatment may be performed a plurality of times, and is usually performed 2 to 5 times. In this case, the composition and temperature of each crosslinking bath used may be the same or different as long as they are within the above ranges. Cross-linking treatment for water resistance by cross-linking and cross-linking treatment for hue adjustment may be performed in a plurality of steps.

  A uniaxial stretching treatment can be performed in the crosslinking bath 17 by utilizing a peripheral speed difference between the nip roll 52 and the nip roll 53.

  In the cross-linking treatment, the guide rolls 36, 37 and / or 38 have a widening function such as an expander roll, a spiral roll, or a crown roll in order to transport the polyvinyl alcohol-based resin film while removing wrinkles of the film, similarly to the swelling treatment. Or other widening devices such as cross guiders, bend bars, tenter clips, etc. can be used. Another means for suppressing the generation of wrinkles is to apply a stretching treatment as in the case of the swelling treatment.

  In the example shown in FIG. 3, the film drawn from the crosslinking bath 17 passes through the guide roll 38 and the nip roll 53 in order and is introduced into the cleaning bath 19.

(Washing process)
The example shown in FIG. 3 includes a cleaning step after the crosslinking step. The cleaning treatment is performed for the purpose of removing excess chemicals such as boric acid and iodine attached to the polyvinyl alcohol-based resin film. The cleaning process is performed, for example, by immersing the crosslinked polyvinyl alcohol-based resin film in the cleaning bath 19. The cleaning process is performed by spraying the film with a cleaning liquid as a shower instead of the step of immersing the film in the cleaning bath 19, or by using both the immersion in the cleaning bath 19 and the spraying of the cleaning liquid. You can do it too.

  FIG. 3 shows an example in which a polyvinyl alcohol-based resin film is immersed in a cleaning bath 19 to perform a cleaning process. The temperature of the washing bath 19 in the washing treatment is usually about 2 to 40 ° C., and the immersion time of the film is usually about 2 to 120 seconds.

  In the cleaning treatment, rolls having a widening function such as an expander roll, a spiral roll, and a crown roll are used as guide rolls 39, 40, and / or 41 for the purpose of transporting the polyvinyl alcohol-based resin film while removing wrinkles. Alternatively, other widening devices such as cross guiders, bend bars, tenter clips, etc. can be used. Further, in the film washing process, a stretching process may be performed to suppress generation of wrinkles.

(Stretching process)
As described above, the raw film 10 is uniaxially stretched in a wet or dry manner between the above series of processing steps (that is, before and after one or more processing steps and / or during one or more processing steps). It is processed. A specific method of the uniaxial stretching treatment is, for example, a method in which a circumferential speed difference is applied between two nip rolls (for example, two nip rolls disposed before and after a treatment bath) constituting a film transport path to perform longitudinal uniaxial stretching. Stretching, hot roll stretching, tenter stretching and the like as described in Japanese Patent No. 2731813 can be used, and inter-roll stretching is preferable. The uniaxial stretching process can be performed a plurality of times until the polarizing film 23 is obtained from the raw film 10. As described above, the stretching treatment is also advantageous in suppressing the occurrence of wrinkles in the film.

  The final cumulative stretch ratio of the polarizing film 23 based on the raw film 10 is usually about 4.5 to 7 times, and preferably 5 to 6.5 times. The stretching treatment step may be performed in any of the treatment steps. Even when the stretching treatment is performed in two or more treatment steps, the stretching treatment may be performed in any of the treatment steps.

(Drying process)
After the washing process, it is preferable to perform a process of drying the polyvinyl alcohol-based resin film. The drying of the film is not particularly limited, but can be performed using a drying furnace 21 as in the example shown in FIG. The drying temperature is, for example, about 30 to 100 ° C., and the drying time is, for example, about 30 to 600 seconds. The thickness of the polarizing film 23 obtained as described above is, for example, about 5 to 30 μm.

(Other processing steps for polyvinyl alcohol-based resin film)
Processing other than the processing described above can be added. Examples of treatments that may be added include immersion treatment in a boric acid-free aqueous iodide solution (complementary color treatment), immersion treatment in an aqueous solution containing boric acid and containing zinc chloride or the like, which is performed after the crosslinking treatment step. Zinc treatment).

  By the above manufacturing method, a polarizing film containing a cyclodextrin having an inner diameter of the intramolecular cavity of 0.6 nm or more can be manufactured. The cyclodextrin having an inner diameter of the intramolecular cavity of 0.6 nm or more is subjected to a process of incorporating the cyclodextrin into a polarizing film by including the same in a processing solution, and a processing step using a processing solution containing the same is performed at a later stage. To some extent, the effect of improving the heat resistance of the polarizing film is high. Therefore, in the above production method, it is most preferable that the polarizing film is added to the cross-linking solution, and then it is added to the dyeing solution, and then swells. It is preferably added to the liquid. Cyclodextrins having an inner diameter of the intramolecular cavity of 0.6 nm or more may be added to all of the crosslinking solution, the staining solution, and the swelling solution.

  In the above, the method of manufacturing a polarizing film by performing a predetermined treatment on a single-layer film that is a polyvinyl alcohol-based resin film has been described, but the manufacturing method of the polarizing film is not limited to such a method, After forming a polyvinyl alcohol-based resin layer by applying a coating solution containing a polyvinyl alcohol-based resin on at least one surface of the film, the obtained laminated film is subjected to a stretching treatment, a dyeing treatment, and a crosslinking treatment, so that polyvinyl alcohol is formed. A method in which the system resin layer is a polarizing film may be used. Also in this method, according to the present invention, by using a treatment liquid to which a cyclodextrin having an inner diameter of an intramolecular cavity of 0.6 nm or more is added as a staining liquid used in the staining treatment or a crosslinking liquid used in the crosslinking treatment. A polarizing film containing a cyclodextrin having an inner diameter of the intramolecular cavity of 0.6 nm or more can be produced. Further, in this method, the inner diameter of the intramolecular cavity is 0.6 nm or more by adding cyclodextrins having the inner diameter of the intramolecular cavity of 0.6 nm or more to the coating liquid containing the polyvinyl alcohol-based resin. A polarizing film containing the cyclodextrins can also be produced.

<Manufacturing method of polarizing plate>
A polarizing plate can be obtained by laminating a protective film on at least one side of the polarizing film manufactured as described above via an adhesive. The adhesive and the protective film are as described above.

  In addition, in order to improve the adhesion between the polarizing film and the protective film, a corona treatment, a flame treatment, a plasma treatment, an ultraviolet ray irradiation, a primer coating treatment, a saponification treatment, etc. May be applied.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In Evaluation Tests 1 and 2, polarizing films of Examples and Comparative Examples were manufactured by the following methods. The presence / absence and concentration of cyclodextrin in the treatment liquid used in each treatment step, and the type of cyclodextrin added, were as shown in Tables 1 and 2.

<Manufacture of polarizing film>
(1) Swelling treatment step A 30 µm thick polyvinyl alcohol film [Kuraray Co., Ltd. product name “Kuraray Poval Film VF-PE # 3000”, polymerization degree 2400, saponification degree 99.9 mol% or more] was treated at 30 ° C. The film was immersed in a swelling bath containing pure water for 31 seconds while maintaining the tension state so as not to loosen the film. In this swelling treatment, 2.47 times longitudinal uniaxial stretching was performed.

(2) Dyeing Step Next, the iodine / potassium iodide / boric acid / water (weight ratio) is 0.15 / 2 / 0.3 / 100 while maintaining the tension state so that the film is not loosened. C. for 122 seconds. In this dyeing treatment, longitudinal and uniaxial stretching of 1.12 times was performed.

(3) Cross-linking treatment step Next, in order to carry out a cross-linking treatment for the purpose of water resistance, potassium iodide / boric acid / water (weight ratio) is 12/4. It was immersed in a 05/100 56 ° C. crosslinking bath for 70 seconds. In this crosslinking treatment, longitudinal uniaxial stretching of 2.06 times was performed. The cumulative stretch ratio based on the raw film 10 was 5.70 times.

(4) Cleaning Treatment Step The film after the crosslinking treatment was immersed in a cleaning bath containing pure water at 7 ° C. for 3 seconds.

(5) Drying Step The film after the cross-linking treatment was left in a drying furnace at an atmosphere temperature of 60 ° C. for 190 seconds to obtain a polarizing film having a thickness of 14.2 μm.

<Evaluation Test 1: Evaluation of Cyclodextrin Type>
(1) Production of Evaluation Sample The polarizing films of Examples 1 and 2 and Comparative Examples 1 and 2 were produced by the above-described method. The presence or absence and concentration of cyclodextrin in the treatment liquid used in each treatment step, and the type of cyclodextrin added, were as shown in Table 1 below. Examples of the cyclodextrin include β-cyclodextrin (the inner diameter of the intramolecular cavity is 0.6 to 0.8 nm) and γ-cyclodextrin (the inner diameter of the intramolecular cavity is 0.8 to 1.0 nm). In the comparative example, α-cyclodextrin (the inner diameter of the intramolecular cavity was 0.5 nm) was used.

(2) Measurement of Ty and Py The transmittance obtained for the polarizing films of Examples 1 and 2 and Comparative Examples 1 and 2 using an absorptiometer with an integrating sphere (“V7100” manufactured by JASCO Corporation). The luminosity was corrected for the degree of polarization by a two-degree visual field (C light source) according to JIS Z8701, and the luminosity-corrected single transmittance Ty and the luminosity-corrected polarization Py before the heat resistance test were measured. Table 1 shows the results.

(3) Evaluation of Heat Resistance The polarizing films of Examples 1 and 2 and Comparative Examples 1 and 2 were cut into 4 cm squares, allowed to stand in a dry atmosphere at 105 ° C. for 30 minutes, and then allowed to stand at room temperature for about 1 hour. Then, the visibility correction polarization degree Py (after the heat resistance test) was measured by the same method as described above. For the evaluation of heat resistance, “Py (before heat resistance test) −Py (after heat resistance test)” was calculated and defined as ΔPy. Table 1 shows the results.

  FIG. 4 is a graph showing the visibility correction polarization degrees Py before and after the heat test shown in Table 1. As is clear from ΔPy in Table 1 and FIG. 4, the polarizing film containing β, γ-cyclodextrin (Examples 1 and 2) was the same as the polarizing film containing α-cyclodextrin (Comparative Example 2) and the cyclodextrin. Compared with the polarizing film containing no (Comparative Example 1), the decrease in the visibility correction polarization degree Py after the heat resistance test was suppressed, and it was found that the film had high heat resistance.

<Evaluation Test 2: Evaluation of treatment solution and concentration to which cyclodextrin is added>
(1) Production of Evaluation Sample The polarizing films of Examples 3 to 7 and Comparative Example 3 were produced by the above-described method. The presence or absence and concentration of cyclodextrin in the treatment liquid used in each treatment step, and the type of cyclodextrin added, were as shown in Table 2 below.

(2) Measurement of Ty and Py For the polarizing films of Examples 3 to 7 and Comparative Example 3, the visibility correction single transmittance Ty and the visibility correction polarization degree Py before the heat resistance test were measured in the same manner as described above. Table 2 shows the results.

(3) Evaluation of heat resistance The heat resistance test was performed on the polarizing films of Examples 3 to 7 and Comparative Example 3 in the same manner as described above, and the luminosity correction degree of polarization Py after the heat resistance test was measured. For the evaluation of heat resistance, “Py (before heat resistance test) −Py (after heat resistance test)” was calculated and defined as ΔPy. Table 2 shows the results.

  FIG. 5 is a graph showing the visibility correction polarization degree Py before and after the heat test shown in Table 2. As is clear from ΔPy in Table 2 and FIG. 5, the polarizing film containing β-cyclodextrin (Examples 3 to 7) was compared with the polarizing film containing no cyclodextrin (Comparative Example 3) in heat resistance test. The later decrease in the degree of visibility correction polarization degree Py is suppressed, and 1 wt% is obtained when β-cyclodextrin is added to the treatment liquid at a concentration of 3 wt% (Examples 4 and 7). % Heat resistance is higher than that in the case of manufacturing by adding at a concentration of 10% (Examples 3 and 6), and the case of adding to the cross-linking solution (Examples 6 and 7) is the case of adding to the swelling solution and the dyeing solution. It was found that the heat resistance was higher than (Examples 3 to 5).

  1, 2 polarizing plate, 6 first adhesive layer, 7 first protective film, 8 second adhesive layer, 9 second protective film, 10 raw film made of polyvinyl alcohol resin, 11 raw roll, 13 swelling Bath, 15 dyeing bath, 17 crosslinking bath, 19 washing bath, 21 drying furnace, 23 polarizing film, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 60, 61 guide Roll, 50, 51, 52, 53, 54, 55 Nip roll.

Claims (4)

A method for producing a polarizing film for producing a polarizing film from a polyvinyl alcohol-based resin film,
A method for producing a polarizing film, comprising a treatment step of bringing a treatment liquid containing a cyclodextrin having an inner diameter of an intramolecular cavity of 0.6 nm or more into contact with the polyvinyl alcohol-based resin film for treatment. The method for producing a polarizing film according to claim 1 , wherein the cyclodextrin is a β-cyclodextrin or a γ-cyclodextrin. The concentration of the cyclodextrins in the treatment solution is 0.1 to 10 wt%, method for producing a polarizing film according to claim 1 or 2. Said processing step, swelling treatment step using swelling liquid as the treatment liquid, a crosslinking treatment step using a crosslinking solution as dyeing processing step or the treatment liquid, using staining solution as the treatment liquid, according to claim 1 to 3 A method for producing a polarizing film according to any one of the preceding claims.