TW201710355A - Polarizing film, polarizing plate, and method for producing polarizing film - Google Patents

Abstract

A polarizing film comprising a polyvinyl alcohol-based resin film, and containing a cyclodextrin in which the inner diameter of an intramolecular cavity thereof is 0.6nm or higher, wherein the cyclodextrin is, for example, a [beta]-cyclodextrin or a [gamma]-cyclodextrin.

Description

Polarizing film, polarizing plate and method for manufacturing polarizing film

The present invention relates to a method of producing a polarizing film, a polarizing plate, and a polarizing film.

The polarizing plate is widely used for an image display device such as a liquid crystal display device. In the polarizing plate, a protective film is bonded to one or both sides of a polarizing film in which a dichroic dye such as iodine is adsorbed to a polyvinyl alcohol-based resin film.

In recent years, due to the expansion of the field of use of liquid crystal display devices and advances in peripheral technologies, the requirements for the performance of polarizing films have become stricter. It is known that when the polarizing film is placed in a high-temperature environment, the polarizing performance tends to decrease, and it is known that the smaller the thickness of the polarizing film is, the more the tendency of the polarizing performance to decrease is. In addition, in this specification, the resistance to the deterioration of the polarizing performance by the high temperature environment is called "heat resistance."

A polarizing film which improves heat resistance by containing an oligosaccharide is described in Japanese Patent Laid-Open Publication No. 2005-266048 (Patent Document 1).

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2005-266048

An object of the present invention is to provide a polarizing film which further improves heat resistance and a method for producing the same. Further, another object of the present invention is to provide a polarizing plate which is excellent in heat resistance.

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

[1] A polarizing film comprising a polyvinyl alcohol-based resin film and comprising a cyclodextrin having an inner diameter of the 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] A polarizing film according to any one of [1] to [3], wherein a polarizing film according to any one of [1] to [3], and a protective film laminated on at least one surface of the polarizing film.

[5] A method for producing a polarizing film, comprising: forming a polarizing film from a polyvinyl alcohol resin film; and providing a treatment liquid containing a cyclodextrin having an inner diameter of the inner cavity portion of 0.6 nm or more. The treatment step of treating the polyvinyl alcohol-based resin film.

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

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

[8] The method for producing a polarizing film according to any one of [5], wherein the processing step is a swelling treatment using a swelling liquid as a swelling treatment step of the treatment liquid, and a dyeing liquid is used as a dyeing treatment of the treatment liquid. The step or the use of a cross-linking liquid is used as a cross-linking treatment step of the above-mentioned treatment liquid.

According to the present invention, it is possible to provide a polarizing film excellent in heat resistance, a method for producing the same, and a polarizing plate.

1‧‧‧Polar plate

2‧‧‧Polar plate

5‧‧‧ polarizing film

6‧‧‧1st adhesive layer

7‧‧‧1st protective film

8‧‧‧2nd adhesive layer

9‧‧‧2nd protective film

10‧‧‧ Original film containing polyvinyl alcohol resin

11‧‧‧ original film reel

13‧‧‧Swelling bath

15‧‧‧dye bath

17‧‧‧Cross-link bath

19‧‧‧ Washing bath

21‧‧‧ drying oven

23‧‧‧ polarizing film

30‧‧‧guide roller

31‧‧‧guide roller

32‧‧‧guide roller

33‧‧‧guide roller

34‧‧‧guide roller

35‧‧‧guide roller

36‧‧‧guide roller

37‧‧‧guide roller

38‧‧‧guide roller

39‧‧‧guide roller

40‧‧‧guide roller

41‧‧‧guide roller

50‧‧‧ nip rollers

51‧‧‧ nip rollers

52‧‧‧ nip rollers

53‧‧‧ nip rollers

54‧‧‧ nip rollers

55‧‧‧Pinch roller

60‧‧‧guide roller

61‧‧‧guide roller

Fig. 1 is a schematic cross-sectional view showing an example of a layer configuration of a polarizing plate of the present invention.

Fig. 2 is a schematic cross-sectional view showing another example of the layer configuration of the polarizing plate of the present invention.

Fig. 3 is a cross-sectional view schematically showing an example of a polarizing film manufacturing apparatus of the present invention.

Fig. 4 is a graph showing Py before and after the heat resistance test of Examples 1 and 2 and Comparative Examples 1 and 2.

Fig. 5 is a graph showing Py before and after the heat resistance test of Examples 3 to 7 and Comparative Example 3.

<polarized film>

The polarizing film of the present invention contains a polyvinyl alcohol-based resin film and contains a cyclodextrin 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 inner cavity portion of 0.6 nm or more is excellent in heat resistance, and can suppress a decrease in polarizing performance even when placed in a high temperature environment. When the polarizing film of the present invention is used, since it has excellent heat resistance, it is possible to provide a polarizing plate excellent in heat resistance.

When the polarizing performance of the polarizing film is described in more detail, the polarizing performance is generally evaluated based on two parameters called "visibility correction single transmittance Ty" and "visual correction corrected polarization Py". These parameters are the transmittance and the degree of polarization under the corrected visible light range (wavelength 380 to 780 nm) in such a manner that the weighting around the 550 nm, which is the highest sensitivity of the human eye, is maximized. Light with a wavelength of less than 380 nm is not visible to the human eye, so Ty and Py are not considered.

The transmittance correction single transmittance Ty of the polarizing film of the present invention may be a value generally required in an image display device such as a liquid crystal display device to which the polarizing film or the polarizing plate including the polarizing film is applied, and specifically, preferably Within the range of 40 to 47%. The Ty is 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 falls and the display quality of the image display device decreases. When Ty is too low, the brightness of the image display device is lowered to deteriorate the display quality, or the input power must be increased in order to sufficiently increase the brightness.

In the case where the illuminance-corrected monomer transmittance Ty of the polarizing film of the present invention is 43% or less, it is preferably 99.95% or more, and more preferably 99.99% or more. The Py after the heat resistance test described below is preferably 99.93% or more, and more preferably 99.95% or more from the viewpoint of maintaining the display quality of the image display device after the test. Further, the amount of change Py before and after the heat resistance test "Py (before heat resistance test) - Py (after heat resistance test)" is preferably 0.055% or less.

Regarding Ty and Py of the polarizing film, when it exists as a monomer (in the case of being alone), it is measured as itself as a measurement sample. On the other hand, when a polarizing plate in which a protective film is bonded to a polarizing film is present, the protective film and the adhesive layer are removed from the polarizing plate, and the polarizing film contained in the polarizing plate is separated from the polarizing film. The sample was measured, or Ty and Py were measured using the polarizing plate itself as a measurement sample, and these were used as Ty and Py of the polarizing film. The Ty and Py measured by using the polarizing plate as a measurement sample are substantially the same as the Ty and Py measured by using the polarizing film which is separated from each other as a measurement sample.

In the polarizing film of the present invention, the iodine which is a dichroic dye is adsorbed to the polyvinyl alcohol-based resin film, and more specifically, the iodine is adsorbed to the uniaxially stretched polyvinyl alcohol-based resin film. Adult.

The thickness of the polarizing film is, for example, 30 μm or less, and may be 20 μm or less. From the viewpoint of reducing the thickness of the polarizing plate, it is preferably 15 μm or less, and more preferably 10 μm or less. The thickness of the polarizing film is usually 2 μm or more. When the thickness is smaller, the heat resistance is more likely to be lowered. According to the present invention, it is possible to provide a polarizing film which is excellent in heat resistance even when the thickness is 15 μm or less.

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

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

The degree of saponification of the polyvinyl alcohol-based resin may range from 80.0 to 100.0 mol%, preferably from 90.0 to 100.0 mol%, more preferably from 98.0 to 100.0 mol%. If the degree of saponification is less than 80.0 mol%, the water resistance of the obtained polarizing film is liable to lower.

The degree of saponification is represented by a saponification step in which the acetic acid group (acetoxy group: -OCOCH ₃ ) contained in the polyvinyl acetate-based resin of the raw material of the polyvinyl alcohol-based resin is represented by a unit ratio (mol%). The ratio of the hydroxyl group is based on the following formula: degree of saponification (% by mole) = 100 × (number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetate groups)

And define it. The degree of saponification can be determined in accordance with JIS K 6726 (1994). The higher the degree of saponification, the higher the ratio of hydroxyl groups, and therefore the lower the ratio of the acetate groups which inhibit crystallization.

The polyvinyl alcohol-based resin may also be a part of the modified modified polyvinyl alcohol. For example, the polyvinyl alcohol-based resin may be subjected to 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 or a (meth)acrylamide; Sexuality. The ratio of modification is preferably less than 30 mol%, more preferably less than 10%. When the modification is performed in excess of 30 mol%, it is difficult to adsorb the dichroic dye, and it is difficult to obtain a polarizing film having sufficient polarizing performance. In the present specification, the term "(meth)acrylic acid" means at least one selected from the group consisting of acrylic acid and methacrylic acid. "(Meth)acrylonitrile" is also the same.

The average degree of polymerization of the polyvinyl alcohol-based resin is preferably from 100 to 10,000, more preferably from 1,500 to 8,000, still more preferably from 2,000 to 5,000. The average degree of polymerization of the polyvinyl alcohol-based resin can also be determined in accordance with 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. The cyclodextrin is a non-reducing cyclic oligosaccharide in which glucose is bonded to the ring by α-1,4 bonds, and the more the number of glucoses is, the larger the inner diameter of the intramolecular cavity portion is. Big. It is known that the inner diameter of the intramolecular cavity portion of the β-cyclodextrin which is a heptamer is 0.6 to 0.8 nm, and therefore the inner diameter of the intramolecular cavity portion used in the present invention is 0.6 nm or more. The sperm is not limited as long as the number of glucose components is 7 or more, and includes, for example, β, γ, and δ-cyclodextrin which constitute 7, 8, and 9 glucose groups, respectively; β, γ, δ-cyclodextrin has a branched cyclodextrin of oligosaccharides such as glucose or maltose on a branched sugar chain; an alkyl group such as methyl or 2-hydroxyethyl, 2-hydroxypropyl, 2,3- A cyclodextrin derivative obtained by binding a hydroxyalkyl group such as a dihydroxypropyl group or a 2-hydroxybutyl group to the cyclodextrin or a branched cyclodextrin.

In the present invention, a remarkable effect of improving the heat resistance of the polarizing film is confirmed by the cyclodextrin having an inner diameter of the intramolecular cavity portion of the polarizing film of 0.6 nm or more. It is presumed that the remarkable effect of improving the heat resistance of the polarizing film is that the intramolecular cavity portion of the cyclodextrin having an inner diameter of the inner cavity portion having a diameter of 0.6 nm or more and the polyiodide ion (I ₃ ^- contained in the polarizing film) ^. The result of the interaction of I ₅ ^- ). It is presumed that this interaction depends on the size of the intramolecular cavity portion of the cyclodextrin, and it is presumed that it is a molecule having a cyclodextrin which is larger than the heptamer or octamer which has a remarkable effect of improving heat resistance. The cyclodextrin in the inner cavity portion, that is, the cyclodextrin having an inner diameter of the inner cavity portion of 0.6 nm or more, exhibits the same effect. Furthermore, in order to further enhance the interaction between the intramolecular cavity portion of the cyclodextrin and the polyiodide ion (I ₃ ^- , I ₅ ^- ), the inner diameter of the intramolecular cavity portion of the cyclodextrin is more Preferably, it is 0.8 nm or more. Further, the inner diameter of the intramolecular cavity portion of the cyclodextrin is preferably 1.2 nm or less.

The content of the cyclodextrin having an inner diameter of the intramolecular cavity portion of the polarizing film of 0.6 nm or more is not limited as long as it can increase the heat resistance, and can be, for example, 0.01 to 5% by weight. This content can be measured by analyzing the polarizing film in a solvent by liquid chromatography (LC). Further, it is presumed that the stoichiometric ratio of iodine (I ₂ ) in the polarizing film to the cyclodextrin having an inner diameter of the inner cavity portion of the intramolecular cavity of 0.6 nm or more affects the degree of interaction. In the present invention, the stoichiometric ratio of the iodine (I ₂ ) in the polarizing film to the cyclodextrin having an inner diameter of the inner cavity portion of the intramolecular cavity of 0.6 nm or more is preferably in the range of 1.5:1 to 1500:1. Preferably, it is in the range of 2.5:1 to 1000:1, and more preferably 2.5:1 to 500:1.

<Polarizing plate>

(1) Layer composition of polarizing plate

Fig. 1 is a schematic cross-sectional view showing an example of a layer configuration of a polarizing plate of the present invention. The polarizing plate of the present invention may have a polarizing film 5 as shown in FIG. 1 and a polarizing plate with a single-sided protective film attached to the first protective film 7 laminated on one surface thereof. The first protective film 7 can be laminated on the polarizing film 5 via the first adhesive layer 6 .

Further, the polarizing plate of the present invention may be formed by bonding a protective film to the other surface of the polarizing film 5, and specifically, a polarizing film 5 may be provided as in the polarizing plate 2 shown in FIG. A polarizing plate with a double-sided protective film attached to the first protective film 7 laminated on one surface and the 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 of the present invention is incorporated in an image display device such as a liquid crystal display device, it may be a polarizing plate disposed on the visual (front surface) side of the image display element such as a liquid crystal cell, or may be configured. A polarizing plate on the back side of the image display element (for example, the backlight side of the liquid crystal display device).

(2) polarizing film

The polarizing plate of the present invention comprises the above-described polarizing film of the present invention as the polarizing film 5. Therefore, the details of the polarizing film 5 are cited above.

(3) First protective film

The first protective film 7 may be a thermoplastic resin containing light transmissive (preferably optically transparent), for example, a chain polyolefin resin (such as a polypropylene resin) or a cyclic polyolefin resin. a polyolefin-based resin such as an olefin resin; a cellulose ester resin such as cellulose triacetate or cellulose diacetate; a polyester resin; a polycarbonate resin; Acrylic resin; polystyrene resin; or a film of such a mixture, copolymer or the like. In order to further improve the water resistance of the polarizing plate, the first protective film 7 preferably contains a protective film such as a polyolefin resin, a polyester resin, a (meth)acrylic resin, or a polystyrene resin. A protective film that has a relatively low moisture permeability.

The first protective film 7 may be a protective film having an optical function such as a retardation film or a brightness enhancement film. For example, by stretching a film containing the thermoplastic resin (uniaxial stretching or biaxial stretching or the like), or forming a liquid crystal layer or the like on the film, a retardation film having an arbitrary retardation value can be obtained.

In addition to the homopolymer of a chain olefin such as a polyethylene resin or a polypropylene resin, a copolymer containing two or more kinds of chain olefins may be mentioned as the chain polyolefin resin.

The cyclic polyolefin resin is a general term for a resin obtained by polymerizing a cyclic olefin as a polymerization 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 copolymerization of a cyclic olefin with a chain olefin such as ethylene or propylene. The product (represented as a random copolymer) and a graft polymer obtained by modifying the unsaturated carboxylic acid or a derivative thereof, and the like, and the like. Among them, the use can be preferably used Alkene or polycyclic drop Ethylene monomer The olefinic monomer is reduced as a cyclic olefin An olefinic resin.

The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester-based resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Further, it is also possible to use such a copolymer or to modify a part of a hydroxyl group with another substituent. Among these, cellulose triacetate (triacetyl cellulose: TAC) is particularly preferred.

The polyester resin is a resin other than the above cellulose ester resin having an ester bond, and is usually a polycondensate comprising 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 naphthalene dicarboxylate. As the polyhydric alcohol, a diol can be used, and examples thereof include ethylene glycol, propylene glycol, butanediol, neopentyl glycol, and cyclohexane dimethanol.

Specific examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, and polytrimethylene 1,3 - propylene glycol ester, 1,3-propane dicarboxylate, dimethyl dimethyl terephthalate, cyclohexane dimethyl phthalate.

The polycarbonate-based resin contains a polymer in which a monomer unit is bonded via a carbonate group. The polycarbonate resin may be a resin called a modified polycarbonate or a copolymerized polycarbonate or the like which modifies a polymer skeleton.

The (meth)acrylic resin is a resin having a compound having a (meth)acryl fluorenyl group as a main constituent monomer. Specific examples of the (meth)acrylic resin include, for example, poly(meth)acrylate such as polymethyl methacrylate; methyl methacrylate-(meth)acrylic acid copolymer; methyl methacrylate- (meth) acrylate copolymer; methyl methacrylate-acrylate-(meth)acrylic acid copolymer; methyl (meth) acrylate-styrene copolymer (MS resin, etc.); methyl methacrylate and a copolymer of a compound having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-(meth)acrylic acid lowering Ester copolymers, etc.). It is preferred to use a polymer having a poly(meth)acrylic acid C _1-6 alkyl ester such as poly(methyl) acrylate as a main component, and it is more preferred to use methyl methacrylate as a main component ( 50 to 100% by weight, preferably 70 to 100% by weight, of a methyl methacrylate-based resin.

A surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, or an antifouling layer may be formed on the surface of the first protective film 7 opposite to the polarizing film 5. Further, the first protective film 7 may contain one or more kinds of lubricants, plasticizers, dispersants, heat stabilizers, ultraviolet absorbers, infrared absorbers, antistatic agents, and antioxidants.

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 the reduction in 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) The first adhesive layer

The first adhesive layer 6 is a layer for subsequently fixing the first protective film 7 to one surface of the polarizing film 5. The adhesive forming the first adhesive layer 6 may be an active energy ray-curable adhesive containing a curable compound which is cured by irradiation with an active energy ray such as ultraviolet light, visible light, electron beam or X-ray, or may be used for polymerization. A water-based adhesive in which an adhesive component such as a vinyl alcohol resin is dissolved or dispersed in water. Among them, from the viewpoint of improving the water resistance of the polarizing plate, it is preferred to use an active energy ray-curable adhesive. A preferred example of the active energy ray-curable adhesive is an ultraviolet curable adhesive.

As the active energy ray-curable adhesive forming the first adhesive layer 6, it is preferable to use a curable compound containing a cationic polymerizable property and/or a radical polymerizable hardening property in terms of exhibiting good adhesion. An active energy ray-curable adhesive composition of a compound. The active energy ray-curable adhesive may further contain a cationic polymerization initiator and/or a radical polymerization initiator for starting the curing reaction of the curable compound.

Examples of the cationically polymerizable curable compound include an epoxy compound (a compound having one or two or more epoxy groups in the molecule) and an oxetane compound (one or two in the molecule). More than one oxetane ring compound) or a combination of these. Examples of the radically polymerizable curable compound include a (meth)acrylic compound (a compound having one or two or more (meth)acryloxy groups in the molecule) or a radical polymerizable double. Other vinyl compounds of the bond or combinations thereof. A cationically polymerizable curable compound and a radically polymerizable curable compound may also be used in combination.

The active energy ray-curable adhesive may optionally contain a cationic polymerization accelerator, an ion scavenger, an antioxidant, a chain transfer agent, an adhesion-imparting agent, a thermoplastic resin, a filler, a flow regulator, a plasticizer, an antifoaming agent, and an antistatic agent. Additives such as agents, leveling agents, solvents, etc.

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

(5) 2nd protective film

The second protective film 9 of the polarizing plate 2 having the double-sided protective film shown in FIG. 2 is the same as the first protective film 7 and may be a film containing the thermoplastic resin exemplified above, or may be a retardation film. A protective film that combines optical brightness and other optical functions. The thickness of the surface treatment layer and the film which the second protective film 9 can have is described above with respect to the first protective film 7. The first protective film 7 and the second protective film 9 may be protective films containing resins of the same type, or may be protective films containing different types of resins. In order to further improve the water resistance of the polarizing plate, the second protective film 9 preferably contains a protective film such as a polyolefin resin, a polyester resin, a (meth)acrylic resin, or a polystyrene resin. A protective film that has a relatively low moisture permeability.

(6) 2nd adhesive layer

The second adhesive layer 8 is a layer for subsequently fixing the second protective film 9 to the other surface of the polarizing film 5 . The details of the second adhesive layer 8 are described with respect to the first adhesive layer 6 described above. From the viewpoint of improving the water resistance of the polarizing plate, the second adhesive layer 8 is preferably formed of 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) Adhesive layer

The first protection in 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 in the polarizing plate 2 with the double-sided protective film shown in FIG. 2 On the film 7 or the second protective film 9, an adhesive layer for bonding the polarizing plate to another member (for example, a liquid crystal cell used in the case of a liquid crystal display device) may be laminated. The adhesive forming the pressure-sensitive adhesive layer usually contains a (meth)acrylic resin, a styrene resin, a polyoxymethylene resin, or the like as a base polymer, and an isocyanate compound, an epoxy compound, or an aziridine compound is added thereto. An adhesive composition formed by a cross-linking agent. It is also possible to form an adhesive layer which further contains fine particles and exhibits light scattering properties. The thickness of the adhesive layer is usually from 1 to 40 μm, preferably from 3 to 25 μm.

(8) Other optical layers

The polarizing plate of the present invention may further include other optical layers laminated on the first and/or second protective films 7, 9 or the polarizing film 5. Examples of the other optical layer include a reflective polarizing film that transmits light of a certain polarized light and reflects polarized light having a property opposite thereto, and a film having an anti-glare function having a concave-convex shape on the surface; Anti-reflective film; reflective film with reflective function on the surface; semi-transmissive reflective film with both reflective and transmissive functions; viewing angle compensation film.

<Method of Manufacturing Polarized Film>

An embodiment of a method for producing a polarizing film of the present invention will be described. In the present embodiment, as the starting material for producing the polarizing film, an unstretched poly 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. A vinyl alcohol resin film (original film). Thereby, it is possible to obtain a polarizing film of a film which is increasingly required in the market. The width of the original film is not particularly limited, and may be, for example, about 400 to 6000 mm. The original film film is prepared in the form of, for example, a roll of an unstretched polyvinyl alcohol-based resin film (original film roll).

The polarizing film can be continuously produced as a long polarizing film by continuously ejecting the long original film from the original film roll while being conveyed along the film transport path of the polarizing film manufacturing apparatus, and performing impregnation. The drying step is carried out after a specific treatment step in which the treatment liquid (hereinafter also referred to as "treatment bath" contained in the treatment tank is pulled out. Further, the treatment step is not limited to a method of immersing the membrane in the treatment bath as long as the treatment liquid is brought into contact with the membrane, and the treatment liquid may be attached to the treatment liquid by spraying, flowing, dripping or the like. A method of treating a film on the surface of a film.

Examples of the treatment liquid include a swelling liquid, a dyeing liquid, a cross-linking liquid, and a washing liquid. In addition, as the processing step, a swelling treatment step of causing the swelling liquid to contact the original sheet film to perform a swelling treatment, a dyeing treatment step of bringing the dyeing liquid into contact with the film after the swelling treatment, and performing a dyeing treatment, and a crosslinking liquid can be exemplified. Contact with the film after dyeing The cross-linking treatment step of the joint treatment and the washing treatment step of bringing the washing liquid into contact with the membrane after the cross-linking treatment to perform a washing treatment. Further, the uniaxial stretching treatment is performed in a wet or dry manner between the series of processing steps (that is, before and after any one or more processing steps and/or in any one or more processing steps). Additional processing steps can be added as needed.

In the present embodiment, by adding a cyclodextrin having an inner diameter of the intramolecular cavity portion of 0.6 nm or more to at least one of the swelling liquid, the dyeing liquid, and the crosslinking liquid, the molecule of the present invention can be produced. A cyclodextrin-based polarizing film having an inner diameter of the inner cavity portion of 0.6 nm or more. The concentration of the cyclodextrin having an inner diameter of the intramolecular cavity portion of the swelling liquid, the dyeing liquid, and the cross-linking liquid of 0.6 nm or more can be, for example, 0.1% by weight to 10% by weight, preferably 0.8% by weight to 5.0%. The weight % is further preferably 2.0% by weight to 5.0% by weight.

Hereinafter, a method of manufacturing the polarizing film of the present embodiment will be described in detail with reference to Fig. 3 . Fig. 3 is a cross-sectional view schematically showing an example of a method for producing a polarizing film of the embodiment and a polarizing film manufacturing apparatus used therefor. The polarizing film manufacturing apparatus shown in Fig. 3 is configured such that a film 10 (unstretched) containing a polyvinyl alcohol-based resin is continuously drawn from the original roll 11 while being along the film. The transfer path is carried, and the swelling bath (swelling liquid accommodated in the swelling tank) 13 provided in the film transport path, the dye bath (dyeing liquid contained in the dyeing tank) 15, and the cross-linking bath are accommodated in order. The cross-linking liquid 17 in the cross-linking tank and the washing bath (washing liquid contained in the washing tank) 19 are finally passed through the drying furnace 21. The obtained polarizing film 23 can be directly transferred to the next polarizing plate producing step (step of bonding the protective film to one side or both sides of the polarizing film 23), for example. The arrows in Fig. 3 indicate the direction in which the film is conveyed.

In addition, FIG. 3 shows an example in which one tank is provided for each of the swelling bath 13, the dye bath 15, the crosslinking bath 17, and the washing bath 19, and two or more tanks may be provided in any one or more processing baths as needed. In the description of Fig. 1, the "treatment tank" is a general term for a swelling tank, a dyeing tank, a crosslinking tank, and a washing tank. The "treatment liquid" is a general term for a swelling liquid, a dyeing liquid, a crosslinking liquid, and a washing liquid. The "treatment bath" is a general term for a swelling bath, a dye bath, a cross-linking bath, and a washing bath.

The film transport path of the polarizing film manufacturing apparatus can be configured to support the transported film or the guide rollers 30 to 41, 60, and 61 that change the film transport direction in addition to the above-described processing bath, or can be transported The film is pressed and held, and the driving force generated by the rotation is applied to the film or the nip rollers 50 to 55 which change the film conveying direction are disposed at appropriate positions. The guide roller or the nip roller can be disposed before or after each treatment bath, whereby the film can be introduced, immersed in the treatment bath, and pulled out from the treatment bath [see FIG. 3]. For example, by providing one or more guide rolls in each treatment bath and transporting the film along the guide rolls, the film can be immersed in each treatment bath.

The polarizing film manufacturing apparatus shown in FIG. 3 is provided with nip rolls (nip rolls 50 to 54) before and after each processing bath, whereby the nip rolls disposed before and after the processing can be disposed in any one or more of the processing baths. The circumferential speed difference is used to extend the roll between the longitudinal uniaxial extensions. Hereinafter, each step will be described.

(swelling treatment step)

The swelling treatment step is performed for the purpose of removing foreign matter on the surface of the original film 10, removing the plasticizer in the original film 10, imparting dyeability, and plasticizing the original film 10. The treatment conditions are determined within a range in which such an object can be achieved without causing extreme problems such as dissolution or devitrification of the original film 10 .

Referring to Fig. 3, the swelling treatment step can be carried out by continuously ejecting the original film 10 from the original film roll 11 along the film transport path, and immersing the original film 10 in the swelling bath 13 At a specific time, then pull out. In the example of FIG. 3, the original film 10 is carried out along the film transport path constructed by the guide rolls 60, 61 and the nip rolls 50 after the original film 10 is wound up and before being immersed in the swelling bath 13. Transfer. In the swelling treatment, the film is conveyed along the film transport path constructed by the guide rolls 30 to 32.

As the swelling liquid of the swelling bath 13, in addition to the pure water, boric acid may be added in the range of about 0.01 to 10% by weight (Japanese Patent Laid-Open No. Hei 10-153709), and chloride (Japanese Patent Laid-Open No. 06- Bulletin No. 281816), inorganic acid, inorganic salt, water-soluble organic solvent An aqueous solution of a reagent, an alcohol or the like. Further, as described above, in the swelling treatment step, a swelling liquid to which a cyclodextrin having an inner diameter of the intramolecular cavity portion of 0.6 nm or more is added may be used.

The temperature of the swelling bath 13 is, for example, about 10 to 50 ° C, preferably about 10 to 40 ° C, more preferably about 15 to 30 ° C. The immersion time of the original film 10 is preferably about 10 to 300 seconds, more preferably about 20 to 200 seconds. Further, when the original film 10 is a polyvinyl alcohol-based resin film which is extended 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 original film 10 is preferably about 30 to 300 seconds, more preferably about 60 to 240 seconds.

In the swelling treatment, problems such as swelling of the original film 10 in the width direction and wrinkles of the film are likely to occur. As a method for conveying the film while removing the wrinkles, a guide roll 30, 31, and/or 32 may be used as a roll having a widening function such as a spreader roll, a spiral roll, or a medium-high roll, or a guide. Other expansion devices such as cloth rolls, bending rolls, tenter clips. Another method for suppressing the generation of wrinkles is to perform an extension process. For example, the uniaxial stretching treatment can be performed in the swelling bath 13 by the circumferential speed difference between the nip roller 50 and the nip roller 51.

In the swelling treatment, the film is swollen and expanded in the direction in which the film is transported. Therefore, when the film is not actively extended, in order to eliminate the slack of the film in the transport direction, for example, it is preferable to control the separator before and after the swelling bath 13 A method such as the speed of the rolls 50, 51. Further, in order to stabilize the film transport in the swelling bath 13, the water flow in the swelling bath 13 is controlled by spraying in water, or an EPC device (Edge Position Control) device is used in combination to detect the end portion of the film and prevent the film from being formed. Bending devices, etc. are also useful.

In the example shown in FIG. 3, the film drawn from the swelling bath 13 is sequentially introduced into the dyeing bath 15 by the guide rolls 32 and the nip rolls 51.

(dye processing step)

The dyeing treatment step is carried out for the purpose of adsorbing the dichroic dye, or aligning the polyvinyl alcohol-based resin film after the swelling treatment. The treatment conditions are determined within a range in which such an object can be achieved without causing extreme dissolution or devitrification of the membrane. Referring to Figure 3, dyeing The color processing step is carried out by transporting along the film transport path constructed by the guide rolls 33 to 35 and the nip rolls 51, and the film after the swelling treatment is applied to the dye bath 15 (contained in the dye bath) The liquid is immersed for a specific time and then pulled out. In order to improve the dyeability of the dichroic dye, the film to be subjected to the dyeing treatment step is preferably a film which has been subjected to at least a certain degree of uniaxial stretching treatment, or preferably to replace the uniaxial stretching treatment or the dyeing treatment before the dyeing treatment. In addition to the previous uniaxial stretching process, uniaxial stretching is performed during the dyeing process.

In the present embodiment, iodine is used as the dichroic dye. For the dyeing liquid of the dyeing bath 15, for example, an aqueous solution having a concentration by weight of iodine/potassium iodide/water = about 0.003 to 0.3/about 0.1 to 10/100 can be used. Other iodides such as zinc iodide may be used instead of potassium iodide, and potassium iodide and other iodides may be used in combination. Further, a compound other than the iodide such as boric acid, zinc chloride, cobalt chloride or the like may be allowed to coexist. In the case of adding boric acid, the crosslinking treatment is different from the following in that iodine is contained, and the aqueous solution can be regarded as the dyeing bath 15 as long as it contains about 0.003 parts by weight or more of iodine per 100 parts by weight of water. The temperature of the dye bath 15 when the film is impregnated 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 about 30 to 600 seconds, preferably 60 to 60. 300 seconds.

As described above, in the dyeing treatment step, a dyeing liquid to which a cyclodextrin having an inner diameter of the intramolecular cavity portion of 0.6 nm or more is added may be used.

As described above, in the dyeing treatment step, the uniaxial stretching of the film can be carried out in the dyeing bath 15. The uniaxial stretching of the film can be carried out by a method such as setting a peripheral speed difference between the nip roller 51 and the nip roller 52 disposed before the dyeing bath 15.

In the dyeing treatment, the polyvinyl alcohol-based resin film is conveyed while removing the wrinkles of the film in the same manner as the swelling treatment, and the dancer rolls 33, 34, and/or 35 may use a wide-rolling roll, a spiral roll, or a medium-high roll. Rollers with a widening function, or other expansion devices such as a guide roller, a bending roller, and a tenter clip. Another method for suppressing the generation of wrinkles is to carry out the stretching treatment in the same manner as the swelling treatment.

In the example shown in FIG. 3, the film pulled out from the dyeing bath 15 is sequentially passed through the guide rolls 35 and the clips. The roller 52 is introduced into the crosslinking bath 17.

(cross-linking processing steps)

The crosslinking treatment step is carried out for the purpose of performing water resistance or hue adjustment (preventing the film from being bluish, etc.) by crosslinking. Referring to Fig. 3, the cross-linking treatment can be carried out by transporting along the film transport path constructed by the guide rolls 36 to 38 and the nip rolls 52, and the dyed film is placed in the cross-linking bath 17 (accommodating It is immersed in the cross-linking liquid in the cross-linking tank for a specific time and then pulled out.

The cross-linking liquid of the cross-linking bath 17 may be an aqueous solution containing, for example, about 1 to 10 parts by weight of boric acid per 100 parts by weight of water. When the dichroic dye used in the dyeing treatment is iodine, the cross-linking liquid preferably contains iodide in addition to boric acid, and the amount thereof is, for example, 1 to 30 parts by weight based on 100 parts by weight of water. Examples of the iodide include potassium iodide, zinc iodide, and the like. Further, a compound other than the iodide such as zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate or the like may be allowed to 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 crosslinking treatment is to achieve water resistance by crosslinking, and the polyvinyl alcohol-based resin film is sequentially subjected to swelling treatment, dyeing treatment, and cross-linking treatment, the crosslinking agent-containing liquid of the crosslinking bath may be in a concentration. The cross-linking liquid of boric acid/iodide/water=3~10/1~20/100 by weight ratio. Other crosslinking agents such as glyoxal or glutaraldehyde may be used instead of boric acid, and boric acid and other crosslinking agents 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 20 to 20 200 seconds. Further, in the case where the polyvinyl alcohol-based resin film which has been previously stretched before the swelling treatment is subjected to the dyeing treatment and the crosslinking treatment in this order, the temperature of the crosslinking bath 17 is usually about 50 to 85 ° C, preferably 55 to 80 ° C. .

In the cross-linking treatment for the purpose of hue adjustment, for example, when iodine is used as the dichroic dye, the concentration can be used in terms of weight ratio, boric acid/iodide/water = 1 to 5/3 to 30/100. Liquid. The temperature of the crosslinking bath when immersing the film is usually about 10 to 45 ° C, and the film The immersion time is usually about 1 to 300 seconds, preferably 2 to 100 seconds.

As described above, in the crosslinking treatment step, a crosslinking liquid to which a cyclodextrin having an inner diameter of the intramolecular cavity portion of 0.6 nm or more is added may be used.

The cross-linking treatment can be carried out plural times, usually 2 to 5 times. In this case, the composition and temperature of each of the crosslinking baths used may be the same or different as long as they are within the above range. The crosslinking treatment for water resistance by crosslinking and the crosslinking treatment for hue adjustment can also be carried out in a plurality of steps, respectively.

The uniaxial stretching treatment may be performed in the crosslinking bath 17 by the circumferential speed difference between the nip roller 52 and the nip roller 53.

In the cross-linking treatment, the polyvinyl alcohol-based resin film is conveyed while removing the wrinkles of the film in the same manner as the swelling treatment, and the dancer rolls 36, 37, and/or 38 may use a wide-rolling roll, a spiral roll, or a medium-high roll. Rollers having a widening function, or other expanding devices such as a guide roll, a bending roll, and a tenter clip. Another method for suppressing the generation of wrinkles is to carry out the stretching treatment in the same manner as the swelling treatment.

In the example shown in FIG. 3, the film drawn from the crosslinking bath 17 is sequentially introduced into the washing bath 19 by the guide rolls 38 and the nip rolls 53.

(washing process step)

In the example shown in FIG. 3, the washing treatment step after the crosslinking treatment step is included. The washing treatment is carried out in order to remove excess boric acid or iodine adhering to the polyvinyl alcohol-based resin film. The washing treatment step is performed, for example, by immersing the crosslinked polyvinyl alcohol resin film in the washing bath 19. Further, the washing treatment step may be carried out by spraying the film with a washing liquid as a shower instead of immersing the film in the washing bath 19, or by immersing in the washing bath 19 and spraying. Clean liquid.

FIG. 3 shows an example in which a polyvinyl alcohol-based resin film is immersed in the washing bath 19 and washed. 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.

Further, in the cleaning treatment, the polyvinyl alcohol-based resin film is conveyed while removing the wrinkles, and the guide rolls 39, 40, and/or 41 may be expanded by using a wide-rolling roll, a spiral roll, a medium-high roll, or the like. The function of the roller, or other expansion devices such as a guide roller, a bending roller, and a tenter clip can be used. Further, in the film cleaning treatment, in order to suppress the occurrence of wrinkles, an extension treatment may be performed.

(Extension processing step)

As described above, the original film 10 is uniaxially stretched in a wet or dry manner between the series of processing steps (i.e., before any one or more of the processing steps and/or in any one or more of the processing steps). deal with. The specific method of the uniaxial stretching process may be performed by providing a circumferential speed difference between two nip rolls (for example, two nip rolls disposed before the processing bath) constituting the film transport path, and performing longitudinal uniaxial stretching between the rolls. The heat roller extension, the tenter stretching, and the like described in Japanese Patent No. 2731813 are preferably extended between rolls. The uniaxial stretching treatment step can be performed plural times from the original film 10 to the obtained polarizing film 23. As described above, the stretching treatment is also advantageous for suppressing the generation of wrinkles of the film.

The final cumulative stretching ratio of the polarizing film 23 based on the original film 10 is usually about 4.5 to 7 times, preferably 5 to 6.5 times. The stretching treatment step can be carried out in any processing step, and in the case where the stretching treatment is performed in two or more processing steps, the stretching processing can also be performed in any processing step.

(drying process step)

After the washing treatment step, it is preferred to carry out a treatment for drying the polyvinyl alcohol-based resin film. The drying of the film is not particularly limited, and it can be carried out using the drying oven 21 as in the example shown in Fig. 1 . 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 in the above manner is, for example, about 5 to 30 μm.

(Other processing steps for the polyvinyl alcohol resin film)

Processing other than the above processing may be added. Examples of the treatment that can be added include immersion treatment in an aqueous solution of boric acid-free iodide after the crosslinking treatment step (complement) Color treatment), immersion treatment (zinc treatment) in an aqueous solution containing no boric acid and containing zinc chloride or the like.

According to the above production method, a polarizing film containing a cyclodextrin having an inner diameter of the intramolecular cavity of 0.6 nm or more can be produced. Further, the cyclodextrin having an inner diameter of the inner cavity portion of 0.6 nm or more is introduced into the polarizing film by being contained in the treatment liquid, and the treatment step using the treatment liquid containing the same is performed. In the latter stage, the effect of improving the heat resistance of the polarizing film is higher. Therefore, in the above production method, it is preferably added to the cross-linking liquid, preferably added to the dyeing liquid, and more preferably added to the swelling liquid. . A cyclodextrin having an inner diameter of the intramolecular cavity portion of 0.6 nm or more may be added to the cross-linking liquid, the dyeing liquid, and the swelling liquid.

In the above, a method of producing a polarizing film by performing a specific treatment on a single layer film of a polyvinyl alcohol resin film has been described. However, the method of producing the polarizing film is not limited to this method, and may be performed by a substrate film. After the coating liquid containing a polyvinyl alcohol-based resin is applied to at least one surface to form a polyvinyl alcohol-based resin layer, the obtained laminated film is subjected to elongation treatment, dyeing treatment, and crosslinking treatment to form a polyvinyl alcohol-based resin layer. A method of forming a polarizing film. In the method, the treatment liquid used in the dyeing liquid used in the dyeing treatment or the crosslinking treatment used in the crosslinking treatment is also used by using a treatment liquid containing a cyclodextrin having an inner diameter of 0.6 nm or more added to the intramolecular cavity portion. As the liquid, a polarizing film of the present invention comprising a cyclodextrin having an inner diameter of 0.6 nm or more in the intramolecular cavity portion can be produced. Further, in this method, by adding a cyclodextrin having an inner diameter of the intramolecular cavity portion of 0.6 nm or more to the coating liquid containing the polyvinyl alcohol-based resin, it is possible to manufacture the intramolecular cavity portion. A cyclodextrin-based polarizing film having a diameter of 0.6 nm or more.

<Method of Manufacturing Polarizing Plate>

A polarizing plate can be obtained by bonding a protective film to at least one surface of the polarizing film manufactured as described above via an adhesive. The subsequent agent and protective film are as described above.

Furthermore, in order to improve the adhesion between the polarizing film and the protective film, the polarizing film and/or the polarizing film and/or The bonding surface of the protective film is subjected to surface treatment such as corona treatment, flame treatment, plasma treatment, ultraviolet irradiation, primer treatment, and saponification treatment.

[Examples]

Hereinafter, the present invention will be specifically described by way of examples and comparative examples, but the present invention is not limited by the examples. In the evaluation tests 1 and 2, the polarizing films of the examples and the comparative examples were produced by the methods shown below. The presence or absence of the addition of the cyclodextrin in the treatment liquid used in each treatment step, and the type of the added cyclodextrin are shown in Tables 1 and 2.

<Manufacture of polarizing film>

(1) Swelling treatment steps

A polyvinyl alcohol film having a thickness of 30 μm [Kuraray Poval Film VF-PE #3000, manufactured by Kuraray Co., Ltd., a polymerization degree of 2400, and a saponification degree of 99.9 mol% or more] is kept in a state in which the film is not slackened. The mixture was directly immersed in a swelling bath having 30 ° C of pure water for 31 seconds. In the swelling treatment, 2.47 times of longitudinal uniaxial stretching was performed.

(2) Dyeing process steps

Next, the film was left in a dye bath having an iodine/potassium iodide/boric acid/water (weight ratio) of 0.15/2/0.3/100 at a temperature of 30 ° C for 122 seconds while maintaining the tension without loosening. In the dyeing treatment, a longitudinal uniaxial stretching of 1.12 times was performed.

(3) Cross-linking processing steps

Next, in order to carry out the crosslinking treatment for the purpose of hydration resistance, the membrane was directly impregnated in a crosslinking bath of potassium iodide/boric acid/water (weight ratio) of 12/4.05/100 at 56 ° C in a state where the membrane was not relaxed. 70 seconds. In the cross-linking treatment, 2.06 times of longitudinal uniaxial stretching was also performed. The cumulative stretching ratio based on the original film 10 was 5.70 times.

(4) Washing process steps

The film after the crosslinking treatment was immersed in a washing bath to which pure water of 7 ° C was added for 3 seconds.

(5) Drying step

The film after the crosslinking treatment was allowed to stand in a drying oven at an ambient temperature of 60 ° C for 190 seconds to obtain a polarizing film having a thickness of 14.2 μm.

<Evaluation Test 1: Evaluation of Types of Cyclodextrin>

(1) Production of evaluation samples

The polarizing films of Examples 1 and 2 and Comparative Examples 1 and 2 were produced by the above methods. The presence or absence of the addition of the cyclodextrin in the treatment liquid used in each treatment step, and the type of the added cyclodextrin are shown in Table 1 below. As the cyclodextrin, in the examples, β-cyclodextrin (the inner diameter of the intramolecular cavity portion is 0.6 to 0.8 nm) and γ-cyclodextrin (the inner diameter of the intramolecular cavity portion is 0.8 to 1.0) is used. In the comparative example, α-cyclodextrin (the inner diameter of the intramolecular cavity portion was 0.5 nm) was used.

(2) Determination of Ty and Py

For the polarizing films of Examples 1 and 2 and Comparative Examples 1 and 2, an absorption sphere photometer ("V7100" manufactured by JASCO Corporation) was used, and the obtained transmittance and polarization degree were measured by JIS. The 2D field of view (C light source) of Z 8701 was subjected to visual sensitivity correction, and the visual sensitivity correction single transmittance Ty and the visual sensitivity corrected polarization Py before the heat resistance test were measured. The results are shown in Table 1.

(3) Heat resistance evaluation

The polarizing films of Examples 1 and 2 and Comparative Examples 1 and 2 were cut into 4 cm squares and allowed to stand in a dry environment at 105 ° C for 30 minutes, and then allowed to stand at room temperature for about 1 hour, by using the above. The visual sensitivity correction polarization Py (after the heat resistance test) was measured by the same method. Moreover, in order to evaluate heat resistance, "Py (before heat resistance test) - Py (after heat resistance test)" was calculated, and this was made into ΔPy. The results are shown in Table 1.

Fig. 4 is a graph showing the visual sensitivity correcting polarization Py before the heat resistance test shown in Table 1 and after the heat resistance test. It can be seen from ΔPy in Table 1 and FIG. 4 that β-, γ-cyclodide is contained in comparison with a polarizing film containing α-cyclodextrin (Comparative Example 2) and a polarizing film containing no cyclodextrin (Comparative Example 1). The fine polarizing film (Examples 1 and 2) suppressed the decrease in the visibility correction correcting degree Py after the heat resistance test, and had high heat resistance.

<Evaluation Test 2: Evaluation of Treatment Liquid and Concentration of Adding Cyclodextrin>

(1) Production of evaluation samples

The polarizing films of Examples 3 to 7 and Comparative Example 3 were produced by the above methods. The presence or absence of the addition of the cyclodextrin in the treatment liquid used in each treatment step, and the type of the added cyclodextrin are shown in Table 2 below.

(2) Determination of Ty and Py

With respect to the polarizing films of Examples 3 to 7 and Comparative Example 3, the luminosity-corrected monomer transmittance Ty and the opacity-corrected polarization degree Py before the heat resistance test were measured by the same method as described above. The results are shown in Table 2.

(3) Heat resistance evaluation

With respect to the polarizing films of Examples 3 to 7 and Comparative Example 3, the heat resistance test was carried out in the same manner as above, and the visibility correction polarization Py after the heat resistance test was measured. Moreover, in order to evaluate heat resistance, "Py (before heat resistance test) - Py (after heat resistance test)" was calculated, and this was made into ΔPy. The results are shown in Table 2.

Fig. 5 is a graph showing the visual sensitivity correcting polarization Py before the heat resistance test shown in Table 2 and after the heat resistance test. As can be seen from ΔPy in Table 2 and FIG. 5, the polarizing film containing β-cyclodextrin (Examples 3 to 7) was suppressed from the heat-resistant test as compared with the polarizing film containing no cyclodextrin (Comparative Example 3). When the sensitivity correction correction Py is decreased, and β-cyclodextrin is added in a concentration of 3% by weight in the treatment liquid, (Examples 4 and 7) and a concentration of 1% by weight are added and produced (implementation) In the case of Examples 3 and 6), the heat resistance was higher, and the case where it was added to the cross-linking liquid (Examples 6, 7) was compared with the case where it was added to the swelling liquid and the dyeing liquid (Examples 3 to 5). , high heat resistance.

1‧‧‧Polar plate

5‧‧‧ polarizing film

6‧‧‧1st adhesive layer

7‧‧‧1st protective film

Claims (8)

A polarizing film comprising a polyvinyl alcohol-based resin film and containing a cyclodextrin having an inner diameter of the intramolecular cavity of 0.6 nm or more. The polarizing film of claim 1, wherein the cyclodextrin is a β-cyclodextrin or a γ-cyclodextrin. The polarizing film of claim 1 or 2 has a thickness of 15 μm or less. A polarizing plate comprising: the polarizing film of claim 1 or 2; and a protective film laminated on at least one side of the polarizing film. A method for producing a polarizing film, comprising: forming a polarizing film from a polyvinyl alcohol resin film; and providing the cyclodextrin having an inner diameter of 0.6 nm or more in contact with the polyvinyl alcohol resin film in the intramolecular cavity portion; The processing step of processing the treatment liquid. The method for producing a polarizing film according to claim 5, wherein the cyclodextrin is a β-cyclodextrin or a γ-cyclodextrin. The method for producing a polarizing film according to claim 5, wherein the concentration of the cyclodextrin in the treatment liquid is 0.1 to 10% by weight. The method for producing a polarizing film according to claim 5, wherein the treatment step is a swelling treatment using the swelling liquid as a swelling treatment step of the treatment liquid, a dyeing liquid as a dyeing treatment step of the treatment liquid, or a crosslinking liquid as the treatment liquid. Cross-linking processing steps.