TW201819193A - Polarizing plate with high durability and image display device using the same, and method for manufacturing polarizing plate - Google Patents

Abstract

Objects of this invention are providing a high-performance polarizing plate showing high transmittance, high degree of polarization and high contrast and exhibiting high thermal durability, especially high wet heat durability, an image display device including the same, and a method for manufacturing the polarizing plate. This invention provides a polarizing plate comprising: a polarizer element film which is a stretched film of a hydrophilic polymer adsorbing a dichroic dye, a transparent protective layer provided on both sides or one side of the polarizer element film, and at least one acrylic resin layer between the polarizer element film and the protective layer, Wherein the acrylic resin layer is obtained by curing a polymerizable resin composition and has a thickness of 5 to 10 [mu]m after curing, the polymerizable resin composition containing a (meth) acrylate component containing a (meth) acrylate (A) having hydroxyl group, and a photopolymerization initiator, the (meth) acrylate component having a total hydroxyl value of 95 to 120 mg KOH/g.

Description

 High-durability polarizing plate and image display device using the same, and manufacturing method of polarizing plate  

The present invention relates to a polarizing plate having improved durability, an image display device using the same, and a method of manufacturing a polarizing plate.

The polarizing element film is usually produced by adsorbing/aligning a dichroic dye and/or iodine belonging to a dichroic dye to a polyvinyl alcohol-based resin film. At least one surface of the polarizing element film is bonded to a protective film made of triethyl fluorenyl cellulose or the like via an adhesive layer to form a polarizing plate, and is used in a liquid crystal display device or the like.

A polarizing plate having iodine is called an iodine-based polarizing plate. On the other hand, a polarizing plate using a dichroic dye is referred to as a dye-based polarizing plate. Compared with dye-based polarizers, iodine-based polarizers have high transmittance and high degree of polarization, which means high contrast, so they are widely used in general LCD screens, LCD TVs, smart phones, mobile phones, tablet terminals, etc. . However, although the iodine-based polarizing plate is superior to the dye-based polarizing plate in terms of optical characteristics, it is inferior to the dye-based polarizing plate in terms of optical durability, for example, if the iodine-based polarizing plate is placed at a high temperature When wet, there are problems such as discoloration and a large decrease in the degree of polarization. Moreover, even a dye-based polarizing plate is expected to have higher durability depending on the use.

It has been described that a protective film is used in order to improve the durability of the iodine polarizing plate (for example, Patent Documents 1 and 2); in order to improve dry heat durability and wet heat durability, the adhesive of the triethylenesulfonyl cellulose protective film is changed. Quality (for example, Patent Documents 3 and 4). As described above, a technique for improving dry heat durability and wet heat durability of a polarizing plate by a protective film or an adhesive is known.

 [Previous Technical Literature]    [Patent Literature]  

[Patent Document 1] Japanese Patent Laid-Open No. Hei 8-5836

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2001-272534

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2004-12578

[Patent Document 4] Japanese Patent Laid-Open Publication No. 2001-166139

[Patent Document 5] Japanese Patent Laid-Open Publication No. 2003-185842

[Patent Document 6] Japanese Patent Laid-Open Publication No. 2004-77579

However, the improvement in the wet heat durability obtained by these techniques is still insufficient, and an improvement in the wet heat durability of the inexpensive and simple polarizing plate is highly desired.

In addition, a polarizing plate having a protective layer formed of an energy ray-polymerizable compound on one surface of a polarizing element film is known (for example, Patent Documents 5 and 6). However, as in the case of Patent Documents 5 and 6, only the protective layer formed of the energy ray polymerizable compound is provided on one surface of the polarizing element film, the wet heat durability is insufficient, and depending on the film thickness of the protective layer, polymerization may occur. The increase in the uncured monomer of the compound, the moist heat durability and the dry heat durability are rather reduced, and the adhesion is insufficient. Further, although there is a polarizing plate having a resin hardened layer such as a hard coat layer according to a known technique, if a resin layer such as a hard coat layer is provided, the wet heat durability is not necessarily highly improved, and it becomes a discoloration in the dry heat durability test. Such as the highly polarized polarizing plate.

Accordingly, an object of the present invention is to provide a polarizing plate, an image display device including the polarizing plate, and a method of manufacturing a polarizing plate, which is a novel polarizing plate, and preferably exhibits high transmittance, high polarization, and/or Or high contrast, better system exhibits high thermal durability, especially high wet heat durability.

In order to achieve the above object, the inventors of the present invention have intensively reviewed the results and found that the above object can be attained by providing a low-cost and simple method of providing a specific acrylic resin layer between the polarizing element film and the protective layer. invention.

That is, the present invention relates to the following (1) to (10).

(1) A polarizing plate comprising: a polarizing element film which is a stretching film of a hydrophilic polymer having a dichroic dye adsorbed thereon; and a transparent protective layer provided on both sides or a single side of the polarizing element film; And at least one layer of an acrylic resin layer which is between the polarizing element film and the protective layer; wherein the acrylic resin layer is a layer obtained by curing the polymerizable resin composition, and the thickness after hardening The polymerizable resin composition includes a (meth) acrylate component containing a hydroxyl group-containing (meth) acrylate (A) and a photopolymerization initiator, and the aforementioned (meth) acrylate component is 5 to 10 μm. The full hydroxyl number is 95 to 120 mg KOH/g.

(2) A polarizing plate comprising: a polarizing element film which is a stretching film of a hydrophilic polymer having a dichroic dye adsorbed thereon; and a transparent protective layer provided on both sides or a single side of the polarizing element film; And at least one layer of an acrylic resin layer which is between the polarizing element film and the protective layer; wherein the acrylic resin layer is a layer obtained by curing the polymerizable resin composition, and the thickness after hardening The polymerizable resin composition includes a (meth) acrylate component containing a hydroxyl group-containing (meth) acrylate (A) and a photopolymerization initiator, and the aforementioned (meth) acrylate component is 5 to 10 μm. The total hydroxyl number is from 100 to 120 mg KOH/g.

(3) The polarizing plate according to (1) or (2), wherein the (meth) acrylate (A) having a hydroxyl group has three or more (meth) acrylonitrile groups, and/or the foregoing ( The (meth) acrylate component further contains (meth) acrylate (B) having three or more (meth) acrylonitrile groups, and the (meth) acrylate group in the entire (meth) acrylate component The average number of the numbers is 3 or more.

(4) The polarizing plate according to (3), wherein the (meth) acrylate (B) has a pentaerythritol skeleton.

(5) The polarizing plate according to any one of (1) to (4) wherein the protective layer is a triethylenesulfonated cellulose film.

(6) The polarizing plate according to (5), wherein the triethylenesulfonated cellulose film contains a polyester triethylenesulfonated cellulose film.

(7) The polarizing plate according to (6), wherein the in-plane phase difference of the polyester-containing triethylenesulfonated cellulose film is 0 and the phase difference in the thickness direction is 0. Here, the phase difference of 0 means a range including an in-plane phase difference of -10 nm to +10 nm and a phase difference in the thickness direction of -10 nm to +10 nm.

(8) An image display device comprising the polarizing plate according to any one of (1) to (7).

(9) A method for producing a polarizing plate, comprising the steps of: mixing a solvent in a polymerizable resin composition to prepare a coating liquid, the polymerizable resin composition comprising: a (meth) acrylate having a hydroxyl group ( A) a (meth) acrylate component and a photopolymerization initiator; the (meth) acrylate component has a total hydroxyl value of 95 to 120 mg KOH / g; and the coating liquid is applied to a transparent protective layer to a step of drying to form a coating film; a step of curing the coating film under an inert gas atmosphere or a low oxygen atmosphere to form an acrylic resin layer; and a step of laminating a polarizing element film on the acrylic resin layer, The polarizing element film is a stretching film of a hydrophilic polymer in which a dichroic dye is adsorbed; wherein the solvent is a mixture containing a solvent I and a solvent II in a mass ratio of the solvent I/solvent II of 60/40 to 90/10. The solvent I does not dissolve the protective layer, and the solubility parameter according to Fedors is 10 or more, and the boiling point is 100 ° C or higher. The solvent II dissolves the protective layer and has a boiling point of 100 ° C or higher.

(10) The method according to (9), wherein the step of forming the acrylic resin layer and the step of laminating the polarizing element film further comprises: treating the acrylic resin layer with an aqueous alkaline solution; a step of neutralizing with water or an acidic aqueous solution and drying, and a step of applying a water-based adhesive to the acrylic resin layer and/or the protective layer after drying.

The present invention can provide a high-performance polarizing plate, an image display device including the same, and a method for manufacturing a polarizing plate, which exhibit high transmittance, high polarization, high contrast, and exhibit high heat durability, especially It is high in damp heat durability. According to the polarizing plate of the present invention, even when an iodine-based polarizing element film which is weak in a high-temperature and high-humidity environment is provided as a polarizing element film, in a humid heat environment, for example, at a temperature of 60 ° C and a relative humidity of 90%, the polarizing element The film is also less discolored, and the transmittance change and the degree of polarization are also reduced. Further, the polarizing plate of the present invention also has a property that the acrylic resin layer does not cause discoloration due to heat or humidity.

 [Polarizer]  

The polarizing plate of the present invention comprises a polarizing element film, a transparent protective layer provided on one or both sides of the polarizing element film, and at least one acrylic resin layer provided between the polarizing element film and the protective layer.

The polarizing element film is a polarizing element film obtained by adsorbing a dichroic dye and extending the hydrophilic polymer. The hydrophilic polymer film may, for example, be a polyvinyl alcohol resin, an amylose resin, a starch resin, a cellulose resin or a polyacrylate resin, and these resins may be used for casting or the like. The filmmaker. The type of the polarizing element film may be a dichroic dye such as iodine or a dichroic dye, which is obtained by a one-axis extension, a dehydrated material of polyvinyl alcohol, a dehydrochlorinated product of polyvinyl chloride, or the like. Polyene oriented film. Among these, a polarizing element film composed of a polyvinyl alcohol resin film and a dichroic dye such as iodine or a dichroic dye is preferable. The thickness of the polarizing element film is not particularly limited, but is usually about 5 to 80 μm.

The polyvinyl alcohol-based resin constituting the polarizing element film can be produced by a known method, and is not particularly limited. The polyvinyl alcohol-based resin can be obtained, for example, by saponifying a polyvinyl acetate-based resin. The polyvinyl acetate-based resin may be a copolymer of vinyl acetate and another monomer copolymerizable with vinyl acetate, in addition to polyvinyl acetate of a homopolymer of vinyl acetate. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The degree of saponification of the polyvinyl alcohol-based resin is usually preferably from 85 to 100 mol%, more preferably 95 mol% or more. The polyvinyl alcohol-based resin can be further modified, and for example, an aldehyde-modified polyethylene formal, a polyvinyl acetal or the like can be used. The degree of polymerization of the polyvinyl alcohol-based resin is usually preferably from 1,000 to 10,000, more preferably from 1,500 to 5,000. A film made of a polyvinyl alcohol-based resin can be used as a polyvinyl alcohol-based film.

The obtained polyvinyl alcohol-based film is dyed with a dichroic dye such as iodine or a dichroic dye, and is stretched in one axis to prepare a polarizing element film. The polarizing element film can be produced by, for example, immersing a polyvinyl alcohol resin film in an aqueous solution of iodine and dyeing it, and extending it to 2 to 7 times its original length. The polyvinyl alcohol-based film may be immersed in an aqueous solution of boric acid or potassium iodide as needed. For example, it is preferred to swell the polyvinyl alcohol-based film and then immerse it in a solution containing iodine, potassium iodide and boric acid while maintaining the film, and further extend it to 5 times in an aqueous solution of 50 ° C containing about 3% of boric acid. Further, if necessary, the polyvinyl alcohol-based film may be immersed in water and washed with water before dyeing. By washing the polyvinyl alcohol-based film with water, it is possible to remove not only the stain on the surface of the polyvinyl alcohol-based film, the plasticizer, but also the effect of preventing unevenness in dyeing unevenness due to swelling of the polyvinyl alcohol-based film. The extension may be carried out after dyeing with iodine, or may be carried out while dyeing, and may be extended and then stained with iodine. It may also be extended in an aqueous solution of boric acid, potassium iodide or the like.

The polyvinyl alcohol-based film may contain, in addition to the dichroic dye, boron compounds such as boric acid, borax, and ammonium borate; polyaldehydes such as glyoxal, glutaraldehyde, and dialdehyde starch; biuret type and trimerization. A polyisocyanate compound such as an isocyanate type or a blocked type; a titanium compound such as titanyl sulfate; ethylene glycol epoxidized propyl ether, polyamido epichlorohydrin, peroxy succinic acid, ammonium persulfate, calcium perchlorate, and benzene At least one or more crosslinking agents such as acenaphthyl ether, ethylene glycol diepoxypropyl ether, and glycerol diepoxypropyl ether, or a water resistance agent. For example, when boric acid is used as the crosslinking agent, the content of boric acid is preferably from 10 to 33% by weight, preferably from 18 to 30% by weight, more preferably from 20 to 26% by weight, based on the polyvinyl alcohol-based film.

The polyvinyl alcohol-based film may contain an alkali metal, an alkaline earth metal, a halide, or an inorganic metal. For example, potassium iodide, sodium iodide, ammonium iodide, cobalt iodide, zinc iodide, zinc chloride, potassium chloride, sodium chloride, zinc fluoride tetrahydrate, aluminum chloride, aluminum fluoride, fluorine Ammonium, potassium fluoride, potassium zirconium fluoride, potassium fluoride titanium, calcium fluoride, chromium fluoride trihydrate, potassium zirconium fluoride, ammonium hydrogen fluoride, sodium hydrogen fluoride, potassium hydrogen fluoride, hydrofluoric acid, tin fluoride, Barium fluoride, barium fluoride, lead fluoride, barium fluoride, magnesium fluoride, barium fluoride, ammonium chloride and magnesium chloride are not particularly limited. The polyvinyl alcohol-based film may contain one or more kinds of halogen ions or inorganic metal ions contained in the above-described substances.

A transparent protective layer may be disposed on both sides or one side of the polarizing element film. The transparent protective layer may be formed by coating a layer of a polymer or as a layer of a film. For the transparent polymer or film forming the transparent protective layer, a transparent polymer or film having high mechanical strength and good thermal stability is preferred. The substance to be used as the transparent protective layer is, for example, preferably triethyl fluorenyl cellulose.

The triethylenesulfonyl cellulose film is usually added with various plasticizers in order to impart film toughness or adjust hardness. For example, a phosphate-based plasticizer, a benzoate-based plasticizer, a polyester-based plasticizer, and the like are preferable, and a benzoate-based plasticizer is preferred from the viewpoint of durability. Polyester plasticizer. The plasticizer can also be used by mixing various plasticizers. Further, an ultraviolet absorber may be added in order to impart light resistance. As the ultraviolet absorber, for example, a benzotriazole-based ultraviolet absorber or the like is preferable.

The protective layer may be, in addition to the triethylenesulfonated cellulose film, a cellulose acetate resin such as diethyl cellulose or a film thereof, an acrylic resin or a film thereof, a polyvinyl chloride resin or a film thereof, or a polyester resin. Or a film thereof, a polyarylate resin or a film thereof, a cyclic polyolefin resin or a film thereof having a cyclic olefin such as norbornene as a monomer, a polyethylene, a polypropylene, a ring system or a polyolefin having a norbornene skeleton The resin, the main chain or the side chain thereof is a resin or polymer of ruthenium and/or guanamine or a film thereof. A resin having a liquid crystal property or a film thereof or the like may be provided as a protective layer.

The thickness of the protective layer is, for example, about 0.5 to 200 μm, preferably 10 to 100 μm.

At least one acrylic resin layer is provided between the polarizing element film and the protective layer. When a protective layer is provided on both sides of the polarizing element film, two or only one between one side of the polarizing element film and the first protective layer, and between the other side of the polarizing element film and the second protective layer An acrylic resin layer is provided at the place. Specifically, it may be composed of any one of a protective layer/acrylic resin layer/polarizing element film/protective layer and a protective layer/acrylic resin layer/polarizing element film/acrylic resin layer/protective layer. An adhesive layer formed of an adhesive may be disposed between the layers. The polarizing plate of the present invention is improved in durability by providing at least one layer of an acrylic resin layer.

The acrylic resin layer is obtained by curing a polymerizable resin composition containing at least a (meth) acrylate component and a photopolymerization initiator. The (meth) acrylate component contains a (meth) acrylate (A) having a hydroxyl group, and optionally further contains a (meth) acrylate (B) having three or more (meth) acrylonitrile groups. In the present specification, the (meth) acrylate means acrylate and/or methacrylate. Similarly, the (meth) acrylonitrile group means an acryl fluorenyl group and/or a methacryl fluorenyl group.

The (meth) acrylate component (excluding the solvent) has a total hydroxyl value of 95 to 120 mgKOH/g, preferably 100 to 120 mgKOH/g, more preferably 100 to 110 mgKOH/g, most preferably 105 to 110 mgKOH/g. When the hydroxyl value of the (meth) acrylate component in the polymerizable resin composition is suppressed within this range, the adhesion of the acrylic resin layer to the protective film and the adhesion to the polarizing element film can be exhibited. Since the adhesion between the acrylic resin layer and the protective film side and the polarizing element film side is good, excellent durability of the polarizing plate can be imparted. When the hydroxyl value of the entire (meth) acrylate component is in the above range, the (meth) acrylate component may further contain a (meth) acrylate compound having no hydroxyl group.

The hydroxyl value in terms of the solid content of the polymerizable resin composition can be determined by the following formula (I).

In the formula (I), the average molecular weight of the resin means the average molecular weight of the (meth) acrylate mixture calculated from the molecular weight of each of the (meth) acrylates contained in the (meth) acrylate component and the compounding ratio. For example, when a (meth) acrylate component contains X _A molecular wt% of (meth) acrylate (A), X _B wt% of the molecular weight M _B of the (meth) acrylate component (B) M _A of The average molecular weight M of the resin is represented by M = M _A × X _A / 100 + M _B × X _B / 100. When the (meth) acrylate component contains another (meth) acrylate, the average molecular weight can be calculated similarly according to the compounding ratio.

The (meth) acrylate (A) having a hydroxyl group may, for example, be an EHC-modified butyl acrylate (DENACOL DA-151 manufactured by Nagase Co., Ltd.) or glyceryl methacrylate (Nippon Oil Co., Ltd.) Company's BLEMMER GLM), 2-hydroxy-3-methylpropenyloxypropyltrimethylammonium chloride (BLEMMER QA, manufactured by Nippon Oil Co., Ltd.), EO-modified phosphate acrylate (Kyoeisha Chemical Co., Ltd.) LIGHTESTER PA), EO modified phthalic acid acrylate (VISCOAT 2308 manufactured by Osaka Organic Chemical Industry Co., Ltd.), EO, PO modified phthalic acid methacrylate (manufactured by Kyoeisha Chemical Co., Ltd.) LIGHTESTER HO), acrylylated trimeric isocyanate (ARONIX M-215 manufactured by Toagosei Co., Ltd.), EO modified bisphenol A diacrylate (EPOXYESTER 3000A manufactured by Kyoeisha Chemical Co., Ltd.), and two new pentylenes Alcohol monohydroxypentaacrylate (SR-399, manufactured by Sartomer Co., Ltd.), glyceryl dimethacrylate (DENACOL DM-811, manufactured by Nagase Industries Co., Ltd.), glycerin acrylate (BLEMMER GAM, manufactured by Nippon Oil Co., Ltd.), Glycerol methacrylate BLEMMER GMR), ECH modified glyceryl triacrylate (DENACOL DA-314, manufactured by Nagase Industries Co., Ltd.), ECH modified 1,6-hexanediol diacrylate (manufactured by Nippon Kayaku Co., Ltd.) KAYARAD R-167), pentaerythritol triacrylate (KAYARAD PET-30 manufactured by Nippon Kayaku Co., Ltd.), stearic acid modified pentaerythritol diacrylate (ARONIX M-233 manufactured by Toagosei Co., Ltd.) ), ECH modified phthalic acid diacrylate (DENACOL DA-721 manufactured by Nagase Industry Co., Ltd.), triglyceride diacrylate (EPOXYESTER 80 MFA manufactured by Kyoeisha Chemical Co., Ltd.), (meth)acrylic acid 2-hydroxyethyl ester, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and the like.

Among these compounds, the (meth) acrylate (A) having a hydroxyl group is preferably a polyfunctional (meth) acrylate, and more preferably has three or more (meth) acrylonitrile groups in addition to a hydroxyl group. (meth) acrylate. In the case of a (meth) acrylate having a hydroxyl group and 3 or more (meth) acrylonitrile groups, pentaerythritol triacrylate (hydroxyl price = 188 mg KOH/g) and dipentaerythritol pentaacrylic acid are preferred. Ester (107 mg KOH / g).

The content of the polymerizable resin composition having a hydroxyl group (meth) acrylate (A) is preferably from 50 to 99% by weight, more preferably from 70 to 99% by weight, based on the solid content of the polymerizable resin composition. .

The polymerizable resin composition may further contain a (meth) acrylate (B) having three or more (meth) acrylonitrile groups. The (meth) acrylate (B) having three or more (meth) acrylonitrile groups, for example, pentaerythritol triacrylate (KAYARAD PET-30 manufactured by Nippon Kayaku Co., Ltd.), Pentaerythritol tetraacrylate (KAYARAD PET-40 manufactured by Nippon Kayaku Co., Ltd.), pentaerythritol tetramethacrylate (SR-367 manufactured by Sartomer Co., Ltd.), and dipentaerythritol hexaacrylate (Japan) KAYARAD DPHA), Alkyl Modified Dipentaerythritol Pentaacrylate (KAYARAD D-310, manufactured by Nippon Kayaku Co., Ltd.), Alkyl Modified Dipentaerythritol Tetraacrylate (Japan) KAYARAD D-320, manufactured by Pharmaceutical Co., Ltd., alkyl modified dipentaerythritol triacrylate (KAYARAD D-330, manufactured by Nippon Kayaku Co., Ltd.), caprolactone modified dipentaerythritol hexaacrylate (KAYARAD DPCA-20 manufactured by Nippon Kayaku Co., Ltd., KAYARAD DPCA-60 manufactured by Nippon Kayaku Co., Ltd., KAYARAD DPCA-120 manufactured by Nippon Kayaku Co., Ltd.), Trimethylolpropane triacrylate (Japan Chemical) KAYARAD TMPTA), Trimethylolpropane Trimethacrylate (Sartome) R-made SR-350), di-trimethylolpropane tetraacrylate (SR-355, manufactured by Sartomer Co., Ltd.), neopentyl glycol modified trimethylolpropane diacrylate (KAYARAD, manufactured by Nippon Kayaku Co., Ltd.) R-604), EO modified trimethylolpropane triacrylate (SR-450 manufactured by Sartomer Co., Ltd.), PO modified trimethylolpropane triacrylate (KAYARAD TPA-series manufactured by Nippon Kayaku Co., Ltd.) or ECH modified trimethylolpropane triacrylate (DENACOL DA-321 manufactured by Nagase Industry Co., Ltd.), ginseng (propylene oxyethyl) trimeric isocyanate (ARONIX M315 manufactured by Toagosei Co., Ltd.), surface chlorine Alcohol (ECH) modified tris(meth)acrylate, ethylene oxide (EO) modified tris(meth)acrylate, propylene oxide (PO) modified tris(meth)acrylate, EO modified tris(meth)acrylate, caprolactone modified trimethylolpropane tri(meth)acrylate, EO modified trimethylolpropane tri(meth)acrylate, PO modified three Hydroxymethylpropane tri(meth)acrylate, polydecane hexa(meth) acrylate, diol and polyisocyanate and (meth) propylene having hydroxyl group a urethane acrylate of a reactant of an acid ester, a polyfunctional urethane (meth) belonging to a reactant of a polyfunctional (meth) acrylate having an active hydrogen (hydroxyl, amine, etc.) and a polyisocyanate compound Acrylate and the like.

The content of the (meth) acrylate (B) having three or more (meth) acrylonitrile groups in the polymerizable resin composition is preferably from 50 to 99% by weight in the solid content of the polymerizable resin composition. More preferably, it is 70 to 99% by weight.

The average number of (meth) acrylonitrile groups in the entire (meth) acrylate component is preferably from 3 to 6. When the average value of the number of (meth)acryl fluorenyl groups is in the above range, the film has a high hardness, is less likely to cause scratches in the coating step, and can improve the durability of the polarizing plate.

The (meth) acrylate component is a (meth) acrylate (A) having a hydroxyl group and having three or more (meth) acrylonitrile groups as long as the hydroxyl value of the (meth)acrylic component is in the above range. In addition to the (meth) acrylate (B), other (meth) acrylate may be further contained in any ratio.

The photopolymerization initiator may, for example, be a benzoin such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether or benzoin isobutyl ether. Acetophenone, 2,2-diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, 2-hydroxy-2-methyl-phenylpropan-1-one, two Ethyl acetophenone, 1-hydroxycyclohexyl phenyl ketone, and acetophenone such as 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinylpropan-1-one Anthraquinones such as 2-ethyl hydrazine, 2-tert-butyl fluorene, 2-chloroindole and 2-pentyl hydrazine; 2,4-diethyl thianonanone, 2-iso Thiol ketones such as propyl thioxanthone and 2-chlorothiazolone; ketals such as acetophenone dimethyl ketal and benzyl dimethyl ketal; benzophenone, 4- Benzoyl-4'-methyldiphenyl sulfide and benzophenones such as 4,4'-bismethylaminobenzophenone; oxidation of 2,4,6-trimethylbenzhydrazide Diphenylphosphine and oxidized phosphines such as bis(2,4,6-trimethylbenzylidene)-phenylphosphine. These may be used alone or in combination of two or more.

In the polymerizable resin composition, the content of the photopolymerization initiator is preferably from 0.5 to 10% by weight, more preferably from 1 to 7% by weight, based on the solid content of the polymerizable resin composition.

The photopolymerization initiator can be used in combination with a hardening accelerator. Examples of the hardening accelerator which can be used in combination include triethanolamine, diethanolamine, N-methyldiethanolamine, 2-methylaminoethylbenzoate, dimethylaminoacetophenone, and p-pair. Hydrogen donors such as isoamyl methylaminobenzoate, amines such as EPA, and 2-mercaptobenzothiazole. The amount of the hardening accelerator to be used is preferably from 0 to 5% by weight based on the solid content of the polymerizable resin composition.

Since the acrylic resin layer obtained by curing the above-mentioned polymerizable resin composition has a hydroxyl group, the adhesion to the triacetyl cellulose is improved, and the adhesion to the polarizing element film after the saponification treatment is also improved.

The thickness of the acrylic resin layer is 5 to 10 μm, preferably 5 to 8 μm. By making the thickness of the acrylic resin layer to this range, there is an effect of improving the durability of the polarizing plate. When the thickness of the acrylic resin layer exceeds 10 μm, not only the polarizing plate becomes thick, but also the drying failure of the adhesive layer may occur when the acrylic resin layer and the polarizing element are subsequently bonded, which is not preferable.

The polarizing plate of the present invention can suppress the decrease in the degree of polarization of the polarizing element film and suppress the decrease in the concentration of boric acid in a humid heat environment. The wet heat durability is improved by suppressing a decrease in the concentration of boric acid in the polarizing element film in a hot and humid environment.

 [Method of Manufacturing Polarizing Plate]  

The method for producing a polarizing plate includes: (1) preparing a coating liquid in which a solvent is mixed in the polymerizable resin composition to prepare a coating liquid; and (2) applying the coating liquid to a protective layer and drying it to form a coating liquid. a coating film forming step of a coating film; (3) an acrylic resin layer forming step of curing the coating film to form an acrylic resin layer; and (4) the acrylic layer is adsorbed with dichroism A step of laminating a polarizing element film of a stretched film of a hydrophilic polymer of a pigment.

In the coating liquid preparation step (1), a solvent is mixed in the above-mentioned polymerizable resin composition. The solvent is a mixture of the solvent I and the solvent II, wherein the solvent I does not dissolve the protective layer, and the solvent II dissolves the above protection according to the solubility parameter (SP value) of the Fedors of 10 or more and 23 or less, and the boiling point is 100 ° C or more. The layer has a boiling point of 100 ° C or higher, and the mass ratio of the solvent I / solvent II in the mixture is 60/40 to 90/10. Here, the "dissolved protective layer" means that when a solvent is applied to the protective layer, the protective layer is melted, swollen, or whitened, that is, the planarity and optical properties of the protective layer are affected by the solvent, "No. The "dissolved protective layer" means that the protective layer does not melt, swell, or whiten even when the solvent is brought into contact with the protective layer, that is, the solvent does not affect the planarity and optical properties of the protective layer. When the SP value of the solvent I is less than 10, there is a problem that the compatibility with the protective layer is poor, cissing occurs (for example, toluene, xylene), or the film is atomized by etching the substrate (example: Base ethyl ketone: MEK), and problems affecting adhesion (methyl isobutyl ketone: MIBK). Further, when the boiling point of the solvent I and the solvent II is less than 100 ° C, the effect of adhesion to the protective film is not exhibited, or the drying is rapid and good surface properties are not obtained.

As the solvent I, for example, n-butanol (SP=10.86, BP=117.7 ° C), n-pentanol (SP=10.46, BP=138° C.), 2-ethyl-1-butanol (SP= 10.02, BP=147°C), propylene glycol monomethyl ether (SP=11.35, BP=120°C), ethoxyethanol (SP=11.51, BP=135°C) and diacetone alcohol (SP=11.7, BP=167.9) °C) and so on.

The amount of the solvent I used is preferably from 50 to 90 parts by mass, more preferably from 60 to 80 parts by weight, based on 100 parts by mass of the solid content of the polymerizable resin composition. When the amount of the solvent I used is too large, adhesion to the protective layer cannot be obtained, and when it is too small, adhesion to the polarizing element film may not be obtained. Further, when the boiling point of the solvent I is too low, there is a case where the drying is rapid and good surface properties cannot be obtained.

As the solvent II, for example, n-butyl acetate (SP = 8.42, BP = 126 ° C), diisobutyl ketone (SP = 7.96, BP = 168 ° C), methyl isobutyl ketone (SP = 8.21, BP = 116.7 ° C), cyclopentanone (SP = 9.67, BP = 131 ° C), cyclohexanone (SP = 9.8, BP = 155.7 ° C) and propylene glycol monomethyl ether acetate (SP = 8.7, BP =146 ° C) and so on.

The amount of the solvent II used is 10 to 50 parts by mass, preferably 20 to 40 parts by mass, based on 100 parts by mass of the solid content of the polymerizable resin composition. When the amount of the solvent II used is too large, the corrosion resistance to the protective film is too strong, and there is a case where the peeling from the inside or the adhesion to the polarizing element film is also affected. Further, when the amount of the solvent II used is small, adhesion to the protective film may cause problems.

The coating liquid can be obtained by mixing a polymerizable resin composition in a mixture of the solvent I and the solvent II, dissolving it, and filtering. In the coating liquid, it is important that the total hydroxyl value of 100% of the polymerizable resin component other than the solvent is 100 to 200 mgKOH/g. It is preferable to use a (meth) acrylate having three or more acryl fluorenyl groups as a main component of the polymerizable resin component, and the number of the average functional groups of the (meth) acryl fluorenyl group as a whole of the polymerizable resin component is preferably 3 or more. .

In the coating film forming step (2), the coating liquid is applied to a protective layer and dried to form a coating film. The method of applying the coating liquid to the protective layer is not particularly limited, and examples thereof include a spin coating method, a wire bar (or a wire bar) method, a gravure coating method, a micro gravure method, and a reverse gravure method. The micro gravure method, the mold coating method, the vacuum mold method, the lip mold method, the dipping method, the flow method, and the slit mold method are reversed. The coating film is preferably formed in such a manner that the thickness after drying of the solvent and after hardening is 5 to 10 μm.

The drying system is carried out, for example, at 30 to 100 ° C for 1 to 5 minutes, preferably at 40 to 70 ° C for 1 to 2 minutes. When the drying temperature is low or the drying time is short, the solvent remains in the formed coating film, which may cause a defect and adversely affect the adhesion. Further, when the drying temperature is high, the photopolymerization initiator is volatilized together with the solvent, and the curability is insufficient.

In the acrylic resin layer forming step (3), the coating film is cured to form an acrylic resin layer. By this step, an acrylic resin layer can be formed on the protective layer. The curing is performed by irradiating the coated film after drying with radiation. Examples of the radiation to be used include ultraviolet rays, electron beams, and the like. When curing by ultraviolet light, an ultraviolet irradiation device having a light source such as a xenon lamp, a high pressure mercury lamp, a metal halide lamp, or a super metal halide lamp is used as the light source, and the amount of light, the arrangement of the light source, the number of turns of the lamp, and the like are adjusted as needed. The irradiation amount is, for example, preferably about 100 to 1,500 mJ/cm ² .

The hardening is carried out under an inert gas atmosphere or a low oxygen atmosphere. In the case of an inert gas environment, for example, it is preferably a nitrogen-substituted environment. The oxygen concentration in the inert gas atmosphere and the low oxygen atmosphere is preferably 50 to 10,000 ppm, more preferably 1000 ppm or less, still more preferably 100 ppm or less. If the curing is not performed under an inert gas atmosphere or a low oxygen atmosphere, the adhesion to the polarizing element film is affected. It is predicted that the surface will not be hardened, and the internal low molecular substances will migrate, resulting in poor adhesion.

In the past, depending on the type of the protective film, adhesion to the polarizing element film may not be obtained, and when the polarizing element film is used, even if a general water-based adhesive is used, there is no problem (for example, Japanese Patent No. In the polarizing plate of the present invention, the acrylic resin layer excellent in adhesion to both the protective film and the polarizing element film is provided between the protective layer and the polarizing element film, and is simply provided. Even the protective layer with poor adhesion to this day can be closely connected, or the adhesion can be improved more than ever. Further, the adhesion between the acrylic resin layer and the water-based adhesive was also good.

Further, the acrylic resin layer to be formed is excellent in both the adhesion between the triacetyl cellulose film having a phase difference of 0 and the adhesion to the polarizing element film. The triethylenesulfonyl cellulose film characterized by zero phase difference and the general triacetyl cellulose film have a large difference in the aggressiveness of the solvent, and it is extremely difficult to achieve both films by the common polymerizable resin composition. The adhesion between the substrate and the film adhesion of the polarizing element can be achieved by optimizing the range of the hydroxyl value, the selection of the resin, the solvent, and the curing conditions.

Then, the acrylic resin layer provided on the protective layer is preferably treated with an alkaline aqueous solution. Specifically, it is treated at 40 ° C or higher for 10 minutes or more by an aqueous alkaline solution having a pH of 11 or higher. By this treatment, the adhesion between the acrylic resin layer and the polarizing element film composed of the polyvinyl alcohol film is improved when a water-based adhesive is used. After the treatment with an aqueous alkaline solution, it is preferred to use a neutralization treatment with water or an acidic aqueous solution, followed by drying.

In the lamination step (4), a polarizing element film is laminated on the acrylic resin layer provided on the protective layer. By the lamination step, a polarizing plate in which a protective layer/acrylic resin layer/polarizing element film is sequentially laminated can be obtained.

The laminate is preferably an adhesive. As the adhesive, a known adhesive can be used without particular limitation. The subsequent agent, for example, a polyvinyl alcohol-based, urethane-based, acrylic-based, or epoxy-based adhesive is preferably used in an inexpensive manner, and is preferably a polyvinyl alcohol used as a substrate as a polarizing element. A water-based adhesive such as a polyvinyl alcohol having a very high adhesion to a film. The additive of the adhesive agent may contain a zinc compound, a chloride, an iodide or the like at a concentration of about 0.1 to 10% by weight. Examples of the polyvinyl alcohol-based adhesive include GOHSENOL NH-26 (manufactured by Nippon Synthetic Chemical Co., Ltd.), EXCEVAL RS-2117 (manufactured by Kuraray Co., Ltd.), and GOHSEFIMER Z-200 (Japan Synthetic Chemical Industry) Co., Ltd.), etc., but not limited to these. A crosslinking agent such as glyoxal or glutaraldehyde and/or a water resistance agent may be added to the subsequent agent. Further, in the adhesive, an acidic substance such as sulfuric acid, acetic acid, hydrochloric acid, formic acid, aluminum sulfate or aluminum chloride is preferably contained in a concentration of 0.0001 to 20% by weight, more preferably 0.02 to 5% by weight. In the polyvinyl alcohol-based adhesive, a maleic anhydride-isobutylene copolymer may be mixed, and a crosslinking agent may be further mixed. For the maleic anhydride-isobutylene copolymer, for example, ISOBAM #18 (manufactured by Kuraray Co., Ltd.), ISOBAM #04 (manufactured by Kuraray Co., Ltd.), and ammonia modified ISOBAM #104 (kuraray Co., Ltd.) Ammonia-modified ISOBAM #110 (manufactured by kuraray Co., Ltd.), yttrium-imidized ISOBAM #304 (manufactured by Kuraray Co., Ltd.), yttrium-imidized ISOBAM #310 (manufactured by Kuraray Co., Ltd.), and the like. As the crosslinking agent used in combination with the maleic anhydride-isobutylene copolymer, a water-soluble polyvalent epoxy compound can be used. Examples of the water-soluble polyvalent epoxy compound include DENACOL EX-521 (manufactured by Nagase ChemteX Co., Ltd.) and TETRAD-C (manufactured by Mitsubishi Gas Chemical Co., Ltd.). After the polarizing element film and the acrylic resin layer provided on the protective layer are bonded together with an adhesive, the drying or heat treatment is appropriately performed at an appropriate temperature.

After the laminating step (4), it is preferred to further carry out (5a) a step of laminating a protective layer on the polarizing element film, or (5b) a step of laminating an acrylic resin layer provided on the protective layer on the polarizing element film.

In the step (5a), it is preferable to use an adhesive to laminate another protective layer on the polarizing element film in the laminate (protective layer/acrylic resin layer/polarizing element film) obtained in the layering step (4). Thereby, a polarizing plate composed of a layer of a protective layer/acrylic resin layer/(adjacent layer/) polarizing element film/(adjacent layer/) protective layer can be obtained.

In the step (5b), a laminate of the protective layer and the acrylic resin layer obtained in the above steps (1) to (3) is further prepared, and the laminate obtained in the step (4) is laminated (protective layer/acrylic acid) The polarizing element film in the resin layer/polarizing element film is laminated so that the polarizing element film and the acrylic resin layer are adjacent to each other. The laminate is preferably an adhesive. By the step (5b), a polarizing plate having a protective layer/acrylic resin layer/(interlayer/) polarizing element film/(adjacent layer/) acrylic resin layer/protective layer layer structure can be obtained.

For the adhesive used in the steps (5a) and (5b), the same adhesive as described above can be used.

Various functional layers and/or pressure-sensitive adhesive layers may be provided on one surface of the obtained polarizing plate, specifically, the surface of the protective layer which is a non-exposed surface after being attached to the display device. By providing an adhesive layer, a polarizing plate can be attached to display devices such as various functional layers, liquid crystals, or organic electroluminescence. The various functional layers can be layers for regulating the phase difference and the touch panel.

A well-known various functional layers such as an antireflection layer or an antiglare layer, a hard coat layer, a viewing angle improvement, and/or a liquid crystal coating layer for improvement can be laminated on the exposed surface of the protective layer of the polarizing plate. It is preferable to apply various functional layers, but it is also preferable to apply a film having the function via an adhesive or an adhesive.

The polarizing plate of the present invention has a low transmittance change and a decrease in the degree of polarization under a humid heat environment, for example, at a temperature of 60 ° C and a relative humidity of 90% RH, and the reliability is high even under severe conditions. Therefore, the present invention can provide a polarizing plate for a display, particularly a polarizing plate which is suitable for a liquid crystal display, has high transmittance, high contrast, and high wet heat durability. A display using the polarizing plate of the present invention is a display having high reliability, high contrast over a long period of time, and high color reproducibility.

 (Example)  

Hereinafter, the present invention will be described in more detail by way of examples, but the invention is not limited thereto.

 [Production Example 1]  

95 parts by mass of a mixture of pentaerythritol triacrylate and neopentyl alcohol tetraacrylate (KAYARAD PET-30 manufactured by Nippon Kayaku Co., Ltd.), 5 parts by mass of IRGACURE 184 (manufactured by BASF Corporation), propylene glycol monomethyl group 70 parts by mass of ether (SP value: 11.35, boiling point: 120 ° C) and 30 parts by mass of cyclopentanone (SP value: 9.67, boiling point: 131 ° C) were stirred and mixed to obtain an ultraviolet curable coating liquid. The hydroxyl group of the polymerizable component in the coating liquid was 105 mgKOH/g.

The coating liquid was applied to a zero phase difference modified triethylenesulfonated cellulose film (ZRD 60SL, ZTAC, and ZTAC) prepared as a protective layer so as to have a film thickness after hardening of 5 μm. One side of each of an acetaminocellulose film (P960GL, manufactured by TacBright Co., Ltd., below TAC). The solvent was dried at 40 to 70 ° C for 2 minutes, and then cured in a nitrogen atmosphere (oxygen concentration: 1% or less) with a high pressure mercury lamp (accumulated light amount: 500 mJ/cm ² ) to form an acrylic resin layer. After hardening, alkali treatment was carried out for 4 minutes at 30 ° C in a 2N potassium hydroxide aqueous solution, and washed with water and dried.

Then, a polyvinyl alcohol-based film (VF-PE manufactured by Kuraray Co., Ltd.) having a thickness of 45 μm, a polymerization degree of 2400, and a saponification degree of 99% or more was swollen in warm water at 30° C., and then an aqueous solution containing iodine, potassium iodide, and boric acid was used. dyeing. The dyed film was stretched to 5 times in a solution containing 3 wt% of boric acid, and after stretching, it was immersed in an aqueous solution containing 2% by weight of potassium iodide. The film was immersed in an aqueous solution of potassium iodide for 15 seconds, and dried in a dryer at 70 ° C for 10 minutes to obtain a polarizing element film. On both sides of the obtained polarizing element film, the acrylic resin layer-protective layer prepared in advance was laminated with a PVA-based adhesive in the following configuration to obtain a polarizing plate. The layer of the obtained polarizing plate was TAC/resin layer/sublayer/polarizing element film/adhesion layer/resin layer/ZTAC.

 [Production Example 2]  

In addition to using 95 parts by mass of dipentaerythritol monohydroxypentaacrylate (SR399 manufactured by Sartomer Co., Ltd.) in place of a mixture of neopentyl alcohol triacrylate and pentaerythritol tetraacrylate (KAYARAD PET manufactured by Nippon Kayaku Co., Ltd.) -30) The same procedure as in Production Example 1 except that 95 parts by mass was used to obtain a polarizing plate. The hydroxyl group of the polymerizable component in the coating liquid was 107 mgKOH/g.

 [Production Example 3]  

In addition to using a mixture of dipentaerythritol hexaacrylate and dipentaerythritol pentaacrylate (KAYARAD DPHA, manufactured by Nippon Kayaku Co., Ltd.), 48 parts by weight, pentaerythritol triacrylate, and pentaerythritol. 28 parts by mass of acrylate mixture (KAYARAD PET-30 manufactured by Nippon Kayaku Co., Ltd.), 19 parts by mass of tricyclodecane acrylate (FA-513AS manufactured by Hitachi Chemical Co., Ltd.), and IRGACURE 184 (manufactured by BASF Corporation) 5 70 parts by mass of toluene (SP value: 9.1, boiling point: 97 ° C), 30 parts by mass of cyclopentanone (SP value: 9.6, boiling point: 131 ° C), and a coating liquid obtained by stirring and mixing was used instead of the production example 1. A polarizing plate was obtained in the same manner as in Production Example 1 except that the coating liquid was used. The hydroxyl group of the polymerizable component in the coating liquid was 60 mgKOH/g.

 [Production Example 4]  

A polarizing plate was obtained in the same manner as in Production Example 1, except that the coating liquid was applied so that the film thickness after hardening became 3.5 μm.

 [Production Example 5]  

In place of propylene glycol monomethyl ether (SP value), except that 85 parts by mass of methyl ethyl ketone (SP value: 9, boiling point: 79.6 ° C) and 30 parts by mass of cyclopentanone (SP value: 9.6, boiling point: 131 ° C) were used. :11.2, boiling point: 120 ° C) 70 parts by mass and cyclopentanone (SP value: 9.6, boiling point: 131 ° C), except that 30 parts by mass of the solvent of the coating liquid was used, and polarized light was obtained in the same manner as in Production Example 1. board.

 [Production Example 6]  

In addition to the use of a mixture of neopentyl alcohol triacrylate and neopentyl alcohol tetraacrylate (KAYARAD PET-30 manufactured by Nippon Kayaku Co., Ltd.) 85.5 parts by mass and dicyclopentadienyl diacrylate (Nippon Chemical Co., Ltd. limited) 9.5 parts by mass of the company R-684), in place of 95 parts by mass of a mixture of neopentyl alcohol triacrylate and neopentyl alcohol tetraacrylate (KAYARAD PET-30 manufactured by Nippon Kayaku Co., Ltd.) Production Example 1 was operated in the same manner to obtain a polarizing plate. The hydroxyl group of the polymerizable component in the coating liquid was 95 mgKOH/g.

 [Production Example 7]  

In place of pentaerythritol triacrylate and pentaerythritol, 95 parts by mass of a mixture of dipentaerythritol hexaacrylate and dipentaerythritol pentaacrylate (KAYARAD DPHA, manufactured by Nippon Kayaku Co., Ltd.) A polarizing plate was obtained in the same manner as in Production Example 1 except that 95 parts by mass of a mixture of acrylate (KAYARAD PET-30 manufactured by Nippon Kayaku Co., Ltd.) was used. The hydroxyl group of the polymerizable component in the coating liquid was 42 mgKOH/g.

 [Production Example 8]  

A polarizing plate was obtained in the same manner as in Production Example 1 except that it was cured in a nitrogen atmosphere (oxygen concentration: 1% or less) using a high-pressure mercury lamp.

 [Production Example 9]  

A polarizing plate was obtained in the same manner as in Production Example 1 except that the acrylic resin layer was not provided.

 [Evaluation 1]  

With respect to the polarizing plates obtained in Production Examples 1 to 8, the adhesion between the protective layer and the acrylic resin layer and the adhesion between the polarizing element film and the acrylic resin layer were confirmed.

 <Adhesiveness of Protective Layer and Acrylic Resin Layer>  

The adhesion between the protective layer and the acrylic resin layer was evaluated in accordance with Japanese Industrial Standard JIS-K5600-5-6. Specifically, in the acrylic resin layer (hard coat layer) of the polarizing plates obtained in the production examples 1 to 8, 100 checkerboards were produced using a cutter at intervals of 1 mm, and the CELLOTAPE (registered trademark) CT-24 manufactured by Nichiban Co., Ltd. was surely attached. After that, peel off once in the direction of 90 degrees. When 100 of the 100 checkerboards are in good contact, the evaluation is "○", and when the checkerboard is peeled off, the evaluation is "X", which is shown in Table 1.

 <Adhesion of polarizing element film and acrylic resin layer>  

The adhesion between the polarizing element film and the acrylic resin layer was evaluated according to the following test method.

The polarizing plates of Production Examples 1 to 8 were fixed to the glass with an adhesive, and the cutter was inserted between the polarizing element film and the acrylic resin layer from the end portion of the polarizing plate to attempt peeling. When the polarizing element film and the acrylic resin layer were not peeled off or peeled off, it was evaluated as "○", and when the polarizing element film and the acrylic resin layer were easily peeled off, it was evaluated as "x", which is shown in Table 1.

Table 1 shows the results of the adhesion between the two protective layers of the polarizing plates of Examples 1 to 8 and the acrylic resin layer, and the adhesion between the polarizing element film and the acrylic resin layer.

As a result of Table 1, in Production Examples 3 and 7 in which the hydroxyl value was less than 95, the adhesion to the polarizing element film and the adhesion of the protective layer (substrate) were not obtained. In Production Example 4 in which the film thickness was as low as 3.5 μm, there was no problem in adhesion and adhesion. In the production example 5 of the MEK in which the solvent was changed to the substrate, the corrosion of ZTAC was too strong, and the adhesion and the adhesion were poor. In Production Example 9 in which nitrogen substitution was not performed at the time of hardening, the polarizing element film of ZTAC was poor in adhesion.

 [Evaluation 2]  

The dry heat test and the damp heat test were carried out for the production examples 1, 2, 4, 6, 8, and 9 with good adhesion, and the penetration rate before and after the test (monomer penetration rate Ys, parallel position transmittance Yp, orthogonal) was confirmed. The bit penetration rate Yc), the degree of polarization Py, and the change in contrast CR.

 (penetration rates Ts, Tp and Tc)  

For each polarizing plate, a transmittance (T7, Tp, and Tc) at each wavelength was measured using a spectrophotometer ("V7100" manufactured by JASCO Corporation). Here, the transmittance Ts is a measurement of the spectral transmittance of each wavelength at the time of measuring one sample. Further, the transmittance Tp is obtained by superimposing two measurement samples so that the absorption axis directions are parallel, and the transmittance of each wavelength at the time of measurement, and the transmittance Tc are two measurement samples to absorb the axis. The directions in which the directions are orthogonal are overlapped, and the spectral transmittance of each wavelength at the time of measurement is performed.

 (monomer penetration rate Ys, parallel position transmittance Yp and orthogonal position penetration rate Yc)  

For each measurement sample, the monomer transmittance Ys, the parallel position transmittance Yp, and the orthogonal position penetration rate Yc were respectively determined. The monomer transmittance Ys, the parallel position transmittance Yp, and the orthogonal position transmittance Yc are respectively obtained for the wavelength region of 400 to 700 nm with a predetermined wavelength interval d λ (here, 10 nm). The rates Ts, Tp, and Tc are the transmittances corrected for the sensibility according to JIS Z 8722:2009. Specifically, the above-described transmittances Ts, Tp, and Tc are substituted into the following formulas (II) to (IV), and are calculated separately. Further, in the following formulae (II) to (IV), P λ represents a spectral distribution of standard light (C light source), and y λ represents a color matching function of a 2 degree field of view. Further, the monomer permeability Ys is shown in Table 2 as Ys0.

 [Polarization ρ y]  

For each measurement sample, the degree of polarization ρ y was obtained. The degree of polarization ρ y is calculated by substituting the parallel position transmittance Yp and the orthogonal position transmittance Yc into the following formula (V). The results are shown in Table 1.

ρ y = {(Yp-Yc ) / (Yp + Yc)} 1/2 × 100 ...... formula (V)

 (compared to CR)  

The contrast CR system was obtained from the parallel position transmittance Yp and the orthogonal position transmittance Yc by the following formula (VI).

CR=Yp/Yc...(VI)

 <dry heat test>  

In the dry heat test, the polarizing plate was allowed to stand under dry heat of a temperature of 95 ° C for 500 hours. The penetration rate and degree of polarization before and after the dry heat test were measured. The results are shown in Table 2.

In Table 2, Ys0 indicates the initial transmittance, ρ 0 indicates the initial polarization, Ys-Dry indicates the transmittance after the dry heat test, ρ-Dry indicates the degree of polarization after the dry heat test, and ΔYs The amount of change in the transmittance after the initial heat test is shown, and Δρ indicates the amount of change in the degree of polarization from the initial stage to the dry heat test.

As a result of Table 2, a large change in the transmittance and the degree of polarization after the dry heat test was not confirmed for each of the polarizing plates.

 <Damp heat test>  

In the damp heat test, the polarizing plate was allowed to stand in a hot and humid environment at a temperature of 60 ° C and a relative humidity of 90% for 500 hours. The penetration rate and degree of polarization before and after the damp heat test were measured. The results are shown in Table 3.

In Table 3, Ys0 indicates the initial transmittance, ρ 0 indicates the initial polarization, Ys-Wet indicates the transmittance after the damp heat test, ρ-Wet indicates the degree of polarization after the damp heat test, and ΔYs indicates the The amount of change in the transmittance after the initial wet heat test, Δρ indicates the amount of change in the degree of polarization from the initial stage to the damp heat test.

As a result of Table 3, the changes in the transmittance and the degree of polarization before and after the damp heat test of Production Examples 1, 2, and 8 were small, indicating that deterioration was suppressed. The transmittances before and after the damp heat test of Production Examples 4, 6 and 9 were large, indicating deterioration.

The measurement results of the comparison before and after the dry heat test of Preparation Examples 1, 2, 4, 6, 8, and 9 and before and after the damp heat test are shown in Table 4. In Table 4, Yp indicates initial parallel position transmittance, Yc indicates initial orthogonal position transmittance, CR indicates initial comparison, CR-Dry indicates contrast after dry heat test, and CR-Wet indicates after wet heat test. The contrast.

From the results of Table 4, the overall contrast reduction was confirmed in both the dry heat test and the damp heat test, but the production examples 4, 6, and 9 were found to have a particularly large decrease in the damp heat test. In Production Example 8, although the overall value was large, the adhesion to the polarizing element film of ZTAC was poor, and it was found that there was a difference in the damp heat test.

If the results of Tables 1 to 4 were summarized, the polarizing plates of Production Examples 1 and 2 had little deterioration in the transmittance and the degree of polarization before and after the damp heat test, and the decrease in the contrast after the dry heat test and after the damp heat test was not large. Therefore, the wet heat durability of the polarizing plates of Production Examples 1 and 2 was improved. On the other hand, in Production Examples 4, 6, and 9, the deterioration of the transmittance and the degree of polarization after the damp heat test was large. In Production Example 8, although the deterioration of the transmittance after the damp heat test was not large, the contrast after the damp heat test and after the dry heat test was remarkably lowered.

Further, the triacetyl fluorene-based cellulose film which is characterized by a zero phase difference and the general triethyl fluorenyl cellulose film have a large difference in the etching property of the solvent, and it is extremely difficult to form a film of both of the common polymerizable resin compositions. The substrate adhesion and the polarizing element film adhesion were achieved, but the range of the hydroxyl value, the selection of the resin, the solvent, and the curing conditions were optimized to a specific range. Production examples 1, 2, and 4 were still possible in both films.

Claims (10)

 A polarizing plate comprising: a polarizing element film which is a stretching film of a hydrophilic polymer which adsorbs a dichroic dye; and a transparent protective layer which is provided on both sides or one side of the polarizing element film; and at least 1 The acrylic resin layer of the layer is interposed between the polarizing element film and the protective layer; wherein the acrylic resin layer is a layer obtained by curing the polymerizable resin composition, and the thickness after curing is 5 to 10 μm, the polymerizable resin composition includes a (meth) acrylate component containing a hydroxyl group-containing (meth) acrylate (A) and a photopolymerization initiator, and the total hydroxyl value of the (meth) acrylate component It is 95 to 120 mgKOH/g.    A polarizing plate comprising: a polarizing element film which is a stretching film of a hydrophilic polymer which adsorbs a dichroic dye; and a transparent protective layer which is provided on both sides or one side of the polarizing element film; and at least 1 The acrylic resin layer of the layer is interposed between the polarizing element film and the protective layer; wherein the acrylic resin layer is a layer obtained by curing the polymerizable resin composition, and the thickness after curing is 5 to 10 μm, the polymerizable resin composition includes a (meth) acrylate component containing a hydroxyl group-containing (meth) acrylate (A) and a photopolymerization initiator, and the total hydroxyl value of the (meth) acrylate component It is 100 to 120 mgKOH/g.    The polarizing plate according to claim 1 or 2, wherein the (meth) acrylate having a hydroxyl group (A) has three or more (meth) acrylonitrile groups, and/or the above (methyl group) The acrylate component further contains (meth) acrylate (B) having three or more (meth) acrylonitrile groups, and the number of (meth) acryl oxime groups in the entire (meth) acrylate component is The average value is 3 or more.    The polarizing plate according to claim 3, wherein the (meth) acrylate (B) has a pentaerythritol skeleton.    The polarizing plate according to any one of claims 1 to 4, wherein the protective layer is a triethylenesulfonated cellulose film.    The polarizing plate according to claim 5, wherein the triethylenesulfonated cellulose film contains a polyester triethylenesulfonated cellulose film.    The polarizing plate according to claim 6, wherein the polyester-containing triethylenesulfonated cellulose film has an in-plane retardation of 0 and a phase difference in the thickness direction of 0, wherein the phase difference is 0 It includes a phase difference of -10 nm to +10 nm in the in-plane direction and a phase difference of -10 nm to +10 nm in the thickness direction.    An image display device comprising the polarizing plate according to any one of claims 1 to 7.    A method for producing a polarizing plate, comprising the steps of: mixing a solvent in a polymerizable resin composition to prepare a coating liquid, the polymerizable resin composition comprising: a (meth) acrylate having a hydroxyl group (A) a (meth) acrylate component and a photopolymerization initiator, wherein the (meth) acrylate component has a total hydroxyl value of 95 to 120 mg KOH/g; and the coating liquid is applied to a transparent protective layer and dried to form a step of coating a film; a step of curing the coating film under an inert gas atmosphere or a low oxygen atmosphere to form an acrylic resin layer; and a step of laminating a polarizing element film on the acrylic resin layer, the polarizing element film a stretched film of a hydrophilic polymer having a dichroic dye adsorbed thereon, wherein the solvent is a mixture containing a solvent I and a solvent II in a mass ratio of the solvent I/solvent II of from 60/40 to 90/10. The protective layer is not dissolved, and the solubility parameter according to Fedors is 10 or more, and the boiling point is 100 ° C or higher, and the solvent II dissolves the protective layer and has a boiling point of 100 ° C or higher.    The manufacturing method according to claim 9, wherein the step of forming the acrylic resin layer and the step of laminating the polarizing element film further comprises: treating the acrylic resin layer with an aqueous alkaline solution; a step of neutralizing with water or an acidic aqueous solution and drying, and a step of applying a water-based adhesive to the acrylic resin layer and/or the protective layer after drying.