JP6604752B2 - Manufacturing method of polarizing film - Google Patents

Description

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

  The polarizing plate is widely used in image display devices such as liquid crystal display devices. As a polarizing plate, the thing of the structure which bonded the protective film to the single side | surface or both surfaces of the polarizing film formed by making a polyvinyl alcohol-type resin film adsorb-orientate dichroic dyes, such as an iodine, is common.

  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 liquid crystal display devices and the advancement of peripheral technology. The polarizing film sometimes has problems such as breakage and dimensional change due to shrinkage caused by environmental changes such as temperature. Japanese Unexamined Patent Publication No. 2009-104062 (Patent Document 1) describes a polarizing film that does not break even when a specific heat cycle test is performed by controlling the boron content in the polarizing film.

JP 2009-104062 A

  An object of the present invention is to provide a new polarizing film in which a shrinkage force caused by a temperature change is suppressed and a method for manufacturing the same. Another object of the present invention is to provide a polarizing plate having excellent dimensional stability.

  The present invention provides a polarizing film, a polarizing plate, and a manufacturing method of the polarizing film shown below.

  [1] A polarizing film comprising a polyvinyl alcohol resin film and containing at least one cyclodextrin selected from the group consisting of α-cyclodextrins and β-cyclodextrins.

[2] The polarizing film according to [1], wherein the thickness is 15 μm or less.
[3] The polarizing film according to [1] or [2];
A protective film laminated on at least one surface of the polarizing film;
A polarizing plate including

[4] A method for producing a polarizing film for producing a polarizing film from a polyvinyl alcohol-based resin film,
A polarizing film comprising a treatment step of bringing the polyvinyl alcohol resin film into contact with a treatment solution containing at least one cyclodextrin selected from the group consisting of α-cyclodextrins and β-cyclodextrins. Manufacturing method.

  [5] The method for producing a polarizing film according to [4], wherein the concentration of the cyclodextrins in the treatment liquid is 0.1 to 10% by weight.

  [6] 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 crosslinking treatment process using a crosslinking liquid as the treatment liquid. [4] Or the manufacturing method of the polarizing film as described in [5].

  ADVANTAGE OF THE INVENTION According to this invention, the new polarizing film by which the shrinkage force produced by a temperature change was suppressed can be provided.

It is a schematic sectional drawing which shows an example of the laminated constitution of the polarizing plate which concerns on this invention. It is a schematic sectional drawing which shows another example of the laminated constitution of the polarizing plate which concerns on this invention. It is sectional drawing which shows typically an example of the polarizing film manufacturing apparatus which concerns on this invention.

<Polarizing film>
The polarizing film which concerns on this invention consists of a polyvinyl alcohol-type resin film, and contains cyclodextrins. The cyclodextrins contained in the polarizing film of the present invention are at least one selected from the group consisting of α-cyclodextrins and β-cyclodextrins. The polarizing film of this invention can suppress the shrinkage force produced by a temperature change. Therefore, the polarizing film of the present invention is excellent in dimensional stability. Moreover, if the polarizing film concerning this invention is used, since it is excellent in dimensional stability of itself, the polarizing plate excellent in dimensional stability can be provided.

  The polarizing film according to the present invention is obtained by adsorbing and orienting a dichroic dye on a polyvinyl alcohol resin film, and more specifically, iodine or dichroic dye on a uniaxially stretched polyvinyl alcohol resin film. A dichroic dye is adsorbed and oriented.

  Although the thickness of a polarizing film can be 30 micrometers or less, for example, Furthermore, it can be 20 micrometers or less, but it is preferable that it is 15 micrometers or less from a viewpoint of thickness reduction of a polarizing plate, and it is more preferable that it is 10 micrometers or less. The thickness of the polarizing film is usually 2 μm or more.

  As a polyvinyl alcohol-type resin which comprises a polarizing film, what saponified polyvinyl acetate type-resin can be used. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers 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.

  What formed the said polyvinyl alcohol-type resin into a film comprises a polarizing film. The method for forming a polyvinyl alcohol-based resin is not particularly limited, and 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%, preferably in the range of 90.0 to 100.0 mol%, more preferably 98.0. It is the range of -100.0 mol%. When the saponification degree is less than 80.0 mol%, the water resistance of the obtained polarizing film tends to be lowered.

The degree of saponification is the unit ratio (mol%) of the proportion of acetate groups (acetoxy groups: —OCOCH ₃ ) contained in polyvinyl acetate resin, which is a raw material for polyvinyl alcohol resins, changed to hydroxyl groups by the saponification step. The following formula:
Saponification degree (mol%) = 100 × (number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetate groups)
Defined by The saponification degree can be determined according to JIS K 6726 (1994). The higher the degree of saponification, the higher the proportion of hydroxyl groups, and thus the lower the proportion of acetate groups that inhibit crystallization.

  The polyvinyl alcohol-based resin may be a modified polyvinyl alcohol partially modified. For example, polyvinyl alcohol resins modified with olefins such as ethylene and propylene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; alkyl esters of unsaturated carboxylic acids, (meth) acrylamide, and the like. The proportion of modification is preferably less than 30 mol%, and more preferably less than 10%. When the modification exceeding 30 mol% is performed, it becomes difficult to adsorb the dichroic dye, and it tends to be difficult to obtain a polarizing film having sufficient polarization performance. In the present 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 100 to 10,000, more preferably 1500 to 8000, and further preferably 2000 to 5000. The average degree of polymerization of the polyvinyl alcohol resin can also be determined according to JIS K 6726 (1994).

  The polarizing film of the present invention contains at least one cyclodextrin selected from the group consisting of α-cyclodextrins and β-cyclodextrins. Cyclodextrins are non-reducing cyclic oligosaccharides in which glucose is cyclically linked with α-1,4 bonds, α-cyclodextrins are hexameric cyclodextrins, β-cyclodextrins are Hexameric cyclodextrins. The α-cyclodextrin or β-cyclodextrin is not limited as long as it has 6 or 7 glucoses. For example, α-cyclodextrin (or β-cyclodextrin), α-cyclodextrin (Or β-cyclodextrin) is a branched cyclodextrin having an oligosaccharide such as glucose or maltose in the branched sugar chain, and further, an alkyl group such as methyl, 2-hydroxyethyl, 2-hydroxypropyl, etc. , Cyclodextrin derivatives to which hydroxyalkyl groups such as 2,3-dihydroxypropyl and 2-hydroxybutyl are bonded.

  Although content of the said cyclodextrins in a polarizing film will not be limited if it is the quantity which can suppress the shrinkage force which arises by a temperature change, For example, it can be 0.01-5 weight%. Such a content can be measured by analyzing a polarizing film dissolved in a solvent by liquid chromatography (LC).

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

  In addition, the polarizing plate according to the present invention may be obtained by further bonding a protective film to the other surface of the polarizing film 5, and specifically, as in the polarizing plate 2 shown in FIG. 5 and a polarizing plate with a double-sided protective film comprising a first protective film 7 laminated on one surface thereof, and a second protective film 9 laminated on the other surface thereof. The second protective film 9 can be laminated on the polarizing film 5 via the second adhesive layer 8.

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

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

(3) 1st protective film The 1st protective film 7 is a thermoplastic resin which has translucency (preferably optically transparent), for example, chain polyolefin resin (polypropylene resin etc.), cyclic polyolefin 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; or a mixture thereof And a film made 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 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 preferable to select a low protective film.

  The first protective film 7 can also be a protective film having an optical function 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 (uniaxial stretching or biaxial stretching) or by forming a liquid crystal layer or the like on the film. It can be.

  Examples of the chain polyolefin-based 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.

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

  The cellulose ester 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. Moreover, these copolymers and those in which a part of the hydroxyl group is modified with other substituents can also be used. Among these, cellulose triacetate (triacetyl cellulose: TAC) is particularly preferable.

  The polyester-based resin is a resin having an ester bond other than the cellulose ester-based resin, and generally includes 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. A diol can be used as the polyhydric alcohol, 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, polycyclohexanedimethyl terephthalate, and polycyclohexanedimethyl 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 copolymer polycarbonate, or the like.

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

  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 on the surface of the first protective film 7 opposite to the polarizing film 5. You can also. 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 do.

  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 thinning the polarizing plate. The thickness of the 1st protective film 7 is normally 5 micrometers or more from a viewpoint of intensity | strength and a 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 forming the first adhesive layer 6 is an active energy ray-curable adhesive containing a curable compound that is cured by irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays. It can be an aqueous adhesive in which an adhesive component such as an alcohol resin is dissolved or dispersed in water. Especially, it is preferable to use an active energy ray-curable adhesive from the viewpoint of improving the water resistance of the polarizing plate. A suitable example of the active energy ray curable adhesive is an ultraviolet curable adhesive.

  The active energy ray-curable adhesive that forms the first adhesive layer 6 exhibits good adhesiveness, and therefore includes an active energy ray containing a cationic polymerizable curable compound and / or a radical polymerizable curable compound. 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 cationic polymerizable curable compound include an epoxy compound (a compound having one or more epoxy groups in the molecule) and an oxetane compound (one or two or more oxetane rings in the molecule). Or a combination thereof. Examples of the radical polymerizable curable compound include (meth) acrylic compounds (compounds having one or more (meth) acryloyloxy groups in the molecule) and radical polymerizable double bonds. Other vinyl compounds or combinations thereof can be mentioned. A cationic polymerizable curable compound and a radical polymerizable curable compound may be used in combination.

  The active energy ray curable adhesive may be a cationic polymerization accelerator, an ion trap agent, an antioxidant, a chain transfer agent, a tackifier, a thermoplastic resin, a filler, a flow modifier, a plasticizer, Additives such as foaming agents, antistatic agents, leveling agents and solvents can be contained.

  The thickness of the 1st adhesive bond layer 6 is about 0.001-5 micrometers normally, Preferably it is 0.01-3 micrometers.

(5) 2nd protective film The 2nd protective film 9 which the polarizing plate 2 with a double-sided protective film shown by FIG. 2 has is a film which consists of a thermoplastic resin illustrated above similarly to the 1st protective film 7. FIG. And a protective film having both optical functions such as a retardation film and a brightness enhancement film. Regarding the surface treatment layer that the second protective film 9 may have and the thickness of the film, the above description of the first protective film 7 is cited. The first protective film 7 and the second protective film 9 may be protective films made of the same kind of resin or may be protective 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 relatively low moisture permeability 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 preferable to select 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. Regarding the details of the second adhesive layer 8, the 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) 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 in the polarizing plate 2 with a double-sided protective film shown in FIG. On the 2nd protective film 9, you may laminate | stack the adhesive layer for bonding a polarizing plate to another member (for example, liquid crystal cell in the case of applying to a liquid crystal display device). The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is usually a (meth) acrylic resin, styrene resin, silicone resin or the like as a base polymer, and a crosslinking agent such as an isocyanate compound, an epoxy compound or an aziridine compound is added thereto. It consists of an adhesive composition. Furthermore, it can also be set as the adhesive layer which contains fine particle and shows light-scattering property. The thickness of an adhesive layer is 1-40 micrometers normally, Preferably it is 3-25 micrometers.

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

<Production method of 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 (raw material) 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 even more preferably 30 μm or less is used as a starting material for producing a polarizing film. Anti-film) is used. As a result, it is possible to obtain a thin polarizing film whose market demand is increasing. The width of the raw film is not particularly limited and can be, for example, about 400 to 6000 mm. The original fabric film is prepared, for example, as a roll (raw fabric roll) of a long unstretched polyvinyl alcohol resin film.

  The polarizing film, while unwinding the above-described long original film from the original roll, is continuously conveyed along the film conveying path of the polarizing film manufacturing apparatus, and the processing liquid (hereinafter, It can be continuously produced as a long polarizing film by carrying out a drying step after carrying out a predetermined treatment step that is drawn after being immersed in a “treatment bath”. The treatment process is not limited to the method of immersing the film in the treatment bath as long as the treatment solution is brought into contact with the film, and the treatment solution is adhered to the film surface by spraying, flowing down, dropping, or the like. And a method of processing the film.

  Examples of the treatment liquid include swelling liquid, dyeing liquid, crosslinking liquid, and cleaning liquid. And as said process process, the swelling process process which makes a swelling liquid contact a raw fabric film, performs the swelling process, the dyeing process process which makes a dyeing liquid contact the film after swelling process, and a dyeing process Examples include a crosslinking treatment step in which a crosslinking solution is brought into contact with the subsequent film and a washing treatment step in which the washing solution is brought into contact with the film after the crosslinking treatment to perform the washing treatment. In addition, a uniaxial stretching process is performed in a wet or dry manner between these series of processing steps (that is, before and after any one or more processing steps and / or during any one or more processing steps). Other processing steps may be added as necessary.

  In this embodiment, the α-cyclodextrins and β-cyclodextrins according to the present invention are added by adding the cyclodextrins to at least one of the swelling liquid, the dyeing liquid, and the crosslinking liquid. A polarizing film containing at least one cyclodextrin selected from the group consisting of can be produced. In addition, the said cyclodextrins added to a process liquid are not limited to 1 type, 2 or more types may be added simultaneously, and both (alpha) -cyclodextrin and (beta) -cyclodextrin are added. May be. The density | concentration of the said cyclodextrins in swelling liquid, dyeing | staining liquid, and crosslinking liquid can be 0.1 weight%-10 weight%, for example, Preferably it is 0.8 weight%-5.0 weight%.

  Hereinafter, the manufacturing method of the polarizing film of this embodiment is demonstrated in detail, referring FIG. FIG. 3 is a cross-sectional view schematically showing an example of the polarizing film manufacturing method of the present embodiment and a polarizing film manufacturing apparatus used therefor. The polarizing film manufacturing apparatus shown in FIG. 3 has a film (unstretched) film 10 made of polyvinyl alcohol resin conveyed along the film conveyance path while being continuously unwound from the original film roll 11. A swelling bath (swelling liquid accommodated in the swelling tank) 13, a dyeing bath (staining liquid accommodated in the dyeing tank) 15, and a crosslinking bath (crosslinking liquid accommodated in the crosslinking tank) 17 provided on the conveyance path. , And a cleaning bath (cleaning liquid contained in a cleaning tank) 19 are sequentially passed, and finally, a drying furnace 21 is passed. The obtained polarizing film 23 can be conveyed, for example, to the next polarizing plate production step (step of bonding a protective film on one or both sides of the polarizing film 23) as it is. The arrow in FIG. 3 has shown the conveyance direction of the film.

  FIG. 3 shows an example in which one swelling bath 13, one dyeing bath 15, one crosslinking bath 17 and one washing bath 19 are provided. If necessary, one or more treatment baths are provided in two or more treatment baths. It may be provided. In the description of FIG. 1, “treatment tank” is a generic name including a swelling tank, a dyeing tank, a crosslinking tank, and a washing tank, and “treatment liquid” is a generic name that includes a swelling liquid, a staining liquid, a crosslinking liquid, and a washing liquid. The “treatment bath” is a generic 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, 61 that can support the film to be transported or can further change the film transport direction in addition to the processing bath, and the film to be transported. Can be constructed by placing nip rolls 50 to 55 at appropriate positions, which can press and hold the film and apply a driving force by rotation thereof to the film, or can further change the film conveyance direction. Guide rolls and nip rolls can be arranged before and after each treatment bath or in the treatment bath, whereby the film can be introduced and immersed in the treatment bath and drawn 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 these guide rolls, the film can be immersed in each treatment bath.

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

(Swelling process)
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 easy dyeability, and plasticizing the original film 10. The processing conditions are determined within a range in which the object can be achieved and within a range in which problems such as extreme dissolution and devitrification of the raw film 10 do not occur.

  Referring to FIG. 3, in the swelling treatment step, the raw film 10 is continuously unwound from the raw roll 11 and conveyed along the film conveying path, and the original film 10 is immersed in the swelling bath 13 for a predetermined time. And then withdrawing. In the example of FIG. 3, the raw film 10 is conveyed along the film conveyance path constructed by the guide rolls 60 and 61 and the nip roll 50 until the original film 10 is unwound and immersed in the swelling bath 13. Is done. In the swelling process, the film is conveyed along the film conveyance path constructed by the guide rolls 30 to 32.

  As the swelling liquid of the swelling bath 13, in addition to pure water, boric acid (JP-A-10-153709), chloride (JP-A-06-281816), inorganic acid, inorganic salt, water-soluble organic solvent, alcohol It is also possible to use an aqueous solution to which a kind or the like is 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 the cyclodextrins 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. Moreover, when the raw fabric film 10 is a polyvinyl alcohol-based resin film previously stretched in 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 original film 10 swells in the width direction and the film is wrinkled easily occurs. As one means for conveying the film while removing the wrinkles, a roll having a widening function such as an expander roll, a spiral roll, or a crown roll is used for the guide rolls 30, 31 and / or 32, a cross guider, a bend bar. Or using other widening devices such as tenter clips. Another means for suppressing the generation of wrinkles is to perform stretching. For example, the uniaxial stretching process can be performed in the swelling bath 13 by utilizing the peripheral speed difference between the nip roll 50 and the nip roll 51.

  In the swelling treatment, the film swells and expands in the film conveyance direction. Therefore, when the film is not actively stretched, for example, it is disposed before and after the swelling bath 13 in order to eliminate the sag of the film in the conveyance direction. It is preferable to take measures such as controlling the speed of the nip rolls 50 and 51. In addition, for the purpose of stabilizing the film transport in the swelling bath 13, the water flow in the swelling bath 13 is controlled by an underwater shower, or an EPC device (Edge Position Control device: detecting the edge of the film to meander the film. It is also useful to use a device for preventing the above in combination.

  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 this order and is introduced into the dyeing bath 15.

(Dyeing process)
The dyeing treatment step is performed for the purpose of adsorbing and orienting the dichroic dye on the polyvinyl alcohol resin film after the swelling treatment. The processing conditions are determined within a range in which the object can be achieved and in a range in which defects such as extreme dissolution and devitrification of the film do not occur. With reference to FIG. 3, the dyeing treatment step is carried along the film carrying path constructed by the guide rolls 33 to 35 and the nip roll 51, and the film after the swelling treatment is treated with the dyeing bath 15 (the treatment accommodated in the dyeing tank). (Liquid) for a predetermined time and then withdrawing. In order to enhance the dyeability of the dichroic dye, the film subjected to the dyeing treatment step is preferably a film subjected to at least some uniaxial stretching treatment, or instead of the uniaxial stretching treatment before the dyeing treatment, Alternatively, in addition to the uniaxial stretching process before the dyeing process, it is preferable to perform the uniaxial stretching process during the dyeing process.

  When iodine is used as the dichroic dye, the concentration of the dyeing solution in the dyeing bath 15 is, for example, iodine / potassium iodide / water = about 0.003 to 0.3 / about 0.1 to 10 in weight ratio. / 100 aqueous solution can be used. Instead of potassium iodide, other iodides such as zinc iodide may be used, or potassium iodide and other iodides may be used in combination. In addition, compounds other than iodide, for example, boric acid, zinc chloride, cobalt chloride and the like may coexist. When boric acid is added, it is distinguished from the crosslinking treatment described later in terms of containing 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 dyeing bath 15 when dipping the film is usually about 10 to 45 ° C., preferably 10 to 40 ° C., more preferably 20 to 35 ° C., and the dipping time of the film is usually 30 to 600 seconds. Degree, preferably 60 to 300 seconds.

  When a water-soluble dichroic dye is used as the dichroic dye, the concentration of the dyeing solution in the dyeing bath 15 is, for example, dichroic dye / water by weight ratio of about 0.001 to 0.1 / 100. An aqueous solution can be used. This dyeing bath 15 may contain a dyeing assistant or the like, and may contain, for example, an inorganic salt such as sodium sulfate or a surfactant. Only one dichroic dye may be used alone, or two or more dichroic dyes may be used in combination. The temperature of the dyeing bath 15 when dipping the film is, for example, about 20 to 80 ° C., preferably 30 to 70 ° C., and the dipping time of the film is usually about 30 to 600 seconds, preferably about 60 to 300 seconds. is there.

  As described above, in the dyeing process, it is also possible to use a dyeing solution to which the cyclodextrins 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 of making a peripheral speed difference between the nip roll 51 and the nip roll 52 arranged before and after the dyeing bath 15.

  Also in the dyeing process, the widening function such as an expander roll, a spiral roll, or a crown roll is provided on the guide rolls 33, 34 and / or 35 in order to convey the polyvinyl alcohol resin film while removing the wrinkles of the film as in the swelling process. Can be used, or other widening devices such as cross guiders, bend bars, tenter clips can be used. Another means for suppressing the generation of wrinkles is to perform a stretching process as in the swelling process.

  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 this order and is introduced into the crosslinking bath 17.

(Crosslinking process)
The crosslinking treatment step is a treatment performed for the purpose of water resistance and hue adjustment (such as preventing the film from being bluish) by crosslinking. Referring to FIG. 3, the crosslinking treatment is carried along the film conveyance path constructed by the guide rolls 36 to 38 and the nip roll 52, and is subjected to the dyeing treatment in the crosslinking bath 17 (crosslinking liquid accommodated in the crosslinking tank). It can be carried out by immersing the film for a predetermined time and then withdrawing it.

  The crosslinking liquid of the crosslinking bath 17 can 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 liquid preferably contains iodide in addition to boric acid. The amount is, for example, 1 to 30 parts by weight with respect to 100 parts by weight of water. It can be. Examples of iodide include potassium iodide and zinc iodide. In addition, compounds 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 crosslinking treatment is water resistance by crosslinking, and the polyvinyl alcohol resin film is subjected to swelling treatment, dyeing treatment and crosslinking treatment in this order, the crosslinking agent-containing liquid in the crosslinking bath has a concentration by weight ratio. It can be a crosslinking solution of boric acid / iodide / water = 3 to 10/1 to 20/100. As needed, it may replace with boric acid and may use other crosslinking agents, such as a glyoxal or glutaraldehyde, and may use boric acid and another crosslinking agent together. The temperature of the crosslinking bath when dipping the film is usually about 50 to 70 ° C., preferably 53 to 65 ° C., and the dipping time of the film is usually about 10 to 600 seconds, preferably 20 to 300 seconds, more preferably. Is 20 to 200 seconds. Moreover, when performing the dyeing | staining process and the crosslinking process in this order with respect to the polyvinyl alcohol-type resin film previously extended | stretched before the swelling process, the temperature of the crosslinking bath 17 is about 50-85 degreeC normally, Preferably it is 55-80 degreeC. .

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

  As described above, in the cross-linking treatment step, it is possible to use a cross-linking liquid to which the cyclodextrins 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 range. The cross-linking treatment for water resistance by cross-linking and the cross-linking treatment for hue adjustment may be performed in a plurality of steps, respectively.

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

  In the cross-linking treatment, a widening function such as an expander roll, a spiral roll, or a crown roll is provided on the guide rolls 36, 37 and / or 38 in order to convey the polyvinyl alcohol resin film while removing the wrinkles of the film as in the swelling treatment. Can be used, or other widening devices such as cross guiders, bend bars, tenter clips can be used. Another means for suppressing the generation of wrinkles is to perform a stretching process as in the swelling process.

  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 this order and is introduced into the cleaning bath 19.

(Washing process)
The example shown in FIG. 3 includes a cleaning process after the crosslinking process. The washing treatment is performed for the purpose of removing excess chemicals such as boric acid and iodine adhering to the polyvinyl alcohol resin film. The cleaning process is performed, for example, by immersing the crosslinked polyvinyl alcohol resin film in the cleaning bath 19. In addition, instead of the step of immersing the film in the cleaning bath 19, the cleaning treatment step is performed by spraying the cleaning liquid on the film as a shower, or by using both immersion in the cleaning bath 19 and spraying of the cleaning liquid. It can also be done.

  FIG. 3 shows an example in which a cleaning process is performed by immersing a polyvinyl alcohol-based resin film in the cleaning bath 19. 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 process, a roll having a widening function such as an expander roll, a spiral roll, or a crown roll is used for the guide rolls 39, 40 and / or 41 for the purpose of conveying the polyvinyl alcohol resin film while removing wrinkles. Or other widening devices such as cross guiders, bend bars, tenter clips can be used. In the film cleaning process, a stretching process may be performed in order to suppress generation of wrinkles.

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

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

(Drying process)
It is preferable to perform the process which dries a polyvinyl alcohol-type resin film after a washing process process. 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 resin film)
Processing other than the processing described above can also be added. Examples of treatments that can be added include immersion treatment (complementary color treatment) in an aqueous iodide solution that does not contain boric acid, and immersion treatment in an aqueous solution that does not contain boric acid and contains zinc chloride, etc. Zinc treatment).

  By the said manufacturing method, the polarizing film containing the at least 1 sort (s) of cyclodextrin selected from the group which consists of (alpha) -cyclodextrin and (beta) -cyclodextrin can be manufactured. The cyclodextrins are incorporated into the polarizing film by containing them in the treatment liquid. However, the more the treatment step using the treatment liquid containing the cyclodextrins is in the previous stage, the more the cyclodextrins are in the polarizing film. In the manufacturing method, it is preferable to add to the swelling liquid because the effect of suppressing the shrinkage force caused by the temperature change due to the incorporation is high. The cyclodextrins may be added to at least one of the crosslinking liquid, the dyeing liquid, and the swelling liquid, and the cyclodextrins may be added to all of them.

  In the above, the method for producing a polarizing film by subjecting a single-layer film, which is a polyvinyl alcohol resin film, to a predetermined treatment has been described. However, the method for producing a polarizing film is not limited to such a method, After forming a polyvinyl alcohol-based resin layer by applying a coating liquid containing a polyvinyl alcohol-based resin on at least one surface of the film, the resulting laminated film is subjected to stretching treatment, dyeing treatment, and crosslinking treatment to obtain polyvinyl alcohol. The method which uses a system resin layer as a polarizing film may be sufficient. Also in this method, the α-cyclodextrin and β-cyclodextrin according to the present invention can be obtained by using the treatment liquid to which the above cyclodextrins are added as a dyeing liquid used in the dyeing process or a crosslinking liquid used in the crosslinking process. A polarizing film comprising at least one cyclodextrin selected from the group consisting of can be produced. Further, in this method, at least one selected from the group consisting of α-cyclodextrins and β-cyclodextrins is obtained by adding the cyclodextrins to a coating liquid containing a polyvinyl alcohol resin. A polarizing film containing cyclodextrins can also be produced.

<Production method of polarizing plate>
A polarizing plate can be obtained by bonding a protective film via an adhesive on at least one surface of the polarizing film produced as described above. The adhesive and the protective film are as described above.

  In order to improve the adhesion between the polarizing film and the protective film, the bonding surface of the polarizing film and / or protective film is subjected to corona treatment, flame treatment, plasma treatment, ultraviolet irradiation, primer coating treatment, saponification treatment, etc. The surface treatment may be performed.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited by these examples. The polarizing films of Examples 1 to 5 and Comparative Example 1 were produced by the following method. The presence / absence and concentration of cyclodextrin in the treatment solution used in each treatment step were as shown in Table 1.

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

(2) Dyeing step Next, iodine / potassium iodide / boric acid / water (weight ratio) is 0.15 / 2 / 0.3 / 100 while maintaining the tension state so that the film does not loosen. It was immersed in a dyeing bath at ° C for 122 seconds. In this dyeing process, 1.12 times of longitudinal uniaxial stretching was performed.

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

(4) Washing treatment process The film after the crosslinking treatment was immersed in a washing bath containing 7 ° C. pure water for 3 seconds.

(5) Drying process The film after the crosslinking treatment was allowed to stand in a drying furnace having an atmospheric temperature of 60 ° C. for 190 seconds to obtain a polarizing film having a thickness of 14.2 μm.

<Evaluation test: Evaluation of MD contraction force>
From the polarizing films of Examples 1 to 5 and Comparative Example 1, a measurement sample having a width of 2 mm and a length of 10 mm with the MD direction (absorption axis direction, stretching direction) as the long side was cut out. When this measurement sample is set in a thermomechanical analyzer (TMA) “product name: EXSTAR-6000” manufactured by SII Nanotechnology, and kept at 80 ° C. for 4 hours while keeping the dimensions constant. The contraction force (MD contraction force) in the generated long side direction (MD direction) was measured. Table 1 shows the results.

  As is clear from the results shown in Table 1, the polarizing films containing α-cyclodextrin or β-cyclodextrin (Examples 1 to 5) were compared with the polarizing films not containing cyclodextrin (Comparative Example 1). MD contraction force is suppressed.

  DESCRIPTION OF SYMBOLS 1, 2 Polarizing plate, 6 1st adhesive layer, 7 1st protective film, 8 2nd adhesive layer, 9 2nd protective film, 10 Original fabric film which consists of polyvinyl alcohol-type resin, 11 Original fabric roll, 13 Swelling Bath, 15 Dye bath, 17 Cross-linking bath, 19 Washing bath, 21 Drying oven, 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 treatment step of contacting the polyvinyl alcohol-based resin film with a treatment liquid containing at least one cyclodextrin selected from the group consisting of α-cyclodextrins and β-cyclodextrins ;
The said process process is a manufacturing method of a polarizing film which is a swelling process process which uses a swelling liquid as the said process liquid . 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. The manufacturing method of the polarizing film of Claim 1 or 2 which further has the dyeing | staining process process which makes the dyeing liquid containing iodine contact the said polyvinyl alcohol-type resin film. The said swelling process process is a manufacturing method of the polarizing film of Claim 3 made | formed upstream from the said dyeing | staining process process.

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