TW202032174A - Polarizing plate and polarizing plate roll - Google Patents

Abstract

Provided is a polarizing plate having excellent durability although being extremely thin. This polarizing plate comprises a polarizer, a first protective layer disposed on one side of the polarizer, and a second protective film disposed on the other side of the polarizer. The first protective layer comprises a solidified product of a coating film of an organic solvent solution of a thermoplastic acrylic resin, and the glass transition temperature of the first protective layer is 95 DEG C or higher. The second protective film comprises a resin film. In one embodiment, the thickness of the first protective layer is 10 [mu]m or less.

Description

Polarizing plate and polarizing plate coil

The invention relates to a polarizing plate and a polarizing plate coil.

Background of the invention In image display devices (such as liquid crystal display devices, organic EL display devices), in most cases, a polarizing plate is arranged on at least one side of the display unit due to the image forming method. In recent years, with the development of thinner and flexible image display devices, there is also a strong demand for thinner polarizers. However, the thinner the polarizing plate, the more significant the durability problem of reduced optical properties under heating and humidifying environments.

Prior art literature Patent literature Patent Document 1: Japanese Patent Laid-Open No. 2015-210474

Problems to be solved by the invention The present invention was made in order to solve the above-mentioned conventional problems, and its main purpose is to provide a polarizing plate that has good durability even if it is very thin.

Means to solve the problem The polarizer of the present invention has a polarizer, a first protective layer arranged on one side of the polarizer, and a second protective layer arranged on the other side of the polarizer. The first protective layer is composed of a cured product of a coating film of an organic solvent solution of a thermoplastic acrylic resin, and the glass transition temperature of the first protective layer is 95°C or higher. The second protective layer is composed of a resin film. In one embodiment, the thickness of the first protective layer is 10 μm or less. In one embodiment, the iodine adsorption amount of the first protective layer is 4.0% by weight or less. In one embodiment, the thermoplastic acrylic resin has one selected from the group consisting of lactone ring units, glutaric anhydride units, glutaric anhydride units, maleic anhydride units, and maleimine units. At least one. In one embodiment, the in-plane retardation Re (550) of the first protective layer is 0 nm to 10 nm, and the thickness direction retardation Rth (550) is -20 nm to +10 nm. In one embodiment, the first protective layer is arranged on the display unit side of the image display device, and the second protective layer is arranged on the opposite side of the display unit. In one embodiment, the above-mentioned polarizing plate is arranged on the viewing side of the image display device. According to another aspect of the present invention, a polarizing plate coil is provided. The polarizing plate coil is formed by winding the aforementioned polarizing plate into a roll.

Invention effect According to the present invention, one of the protective layers disposed on both sides of the polarizer is formed by a cured product of a coating film of a thermoplastic acrylic resin in an organic solvent solution, and the glass transition temperature is set to be higher than a predetermined value , It is possible to obtain a polarizing plate with excellent durability even if it is very thin.

A. Overview of polarizer Fig. 1 is a schematic cross-sectional view of a polarizing plate according to an embodiment of the present invention. The polarizing plate 100 of the illustrated example has a polarizer 10, a first protective layer 20 arranged on one side of the polarizer 10, and a second protective layer 30 arranged on the other side of the polarizer 10. The thickness of the polarizer 10 is preferably 8 μm or less. When the polarizing plate 100 is applied to a liquid crystal display device, it can be arranged on the viewing side of the display unit or on the side opposite to the viewing side (back side). In either case, the first protective layer 20 may be arranged on the side of the display unit or on the side (outer side) opposite to the display unit. In one embodiment, the polarizing plate 100 is arranged on the viewing side of the display unit (the image display device as a result), and the first protective layer 20 is arranged on the side of the display unit. By disposing the first protective layer 20 on the side of the display unit, a polarizing plate having both excellent optical characteristics and excellent durability can be realized.

The polarizing plate can be elongated or flake-shaped. When the polarizing plate is long, it is suitable to be wound into a roll to make a polarizing plate coil.

Representatively, the polarizing plate can have an adhesive layer as the outermost layer on one side (the display unit side on the representative) and can be attached to the display unit. The surface protection film and/or carrier film can be temporarily adhered to the polarizing plate in a peelable manner as required to reinforce and/or support the polarizing plate. When the polarizing plate includes an adhesive layer, a separation member is temporarily attached to the surface of the adhesive layer in a peelable state, so as to protect the adhesive layer before actual use, and the polarizing plate can be rolled.

In the embodiment of the present invention, the first protective layer 20 is composed of a cured product of a coating film of an organic solvent solution of a thermoplastic acrylic resin. With this configuration, the protective layer can be made very thin (for example, the thickness is 10 μm or less). In addition, the protective layer can be directly formed on the polarizer (that is, not through the adhesive layer or the adhesive layer). According to the embodiment of the present invention, as described above, the polarizer and the first protective layer are very thin, and the adhesive layer or the adhesive layer can be omitted, so the total thickness of the polarizer can be very thin. The second protective layer is composed of a resin film. By forming the second protective layer with a resin film, the positioning of the polarizing plate (for example, roller transportability) can be ensured.

The total thickness of the polarizing plate is, for example, 50 μm or less, preferably 45 μm or less, and preferably 40 μm or less, and more preferably 35 μm or less. The lower limit of the total thickness of the polarizing plate may be 25 μm, for example.

In addition, in the embodiment of the present invention, the glass transition temperature (Tg) of the first protective layer 20 is 95°C or higher, preferably 100°C or higher, and preferably 105°C or higher, more preferably 110°C or higher, and particularly preferably 115°C the above. As long as the Tg of the first protective layer is within the above range, it is brought about by the formation of the protective layer on both sides of the polarizer and the cured product of the first protective layer with a coating film of a thermoplastic acrylic resin in an organic solvent solution. The multiplied effect of this effect can realize a polarizing plate with excellent durability even if it is very thin. Specifically, it is possible to realize a polarizing plate whose optical characteristics are suppressed even in a heated and humidified environment. On the other hand, the Tg of the first protective layer is preferably 300°C or lower, preferably 250°C or lower, more preferably 200°C or lower, and particularly preferably 160°C or lower. As long as the Tg of the first protective layer is within the above range, the formability is good.

As described above, according to the embodiment of the present invention, it is possible to realize a polarizing plate whose optical characteristics are suppressed even in a heated and humidified environment. After placing this polarizing plate in an environment of 85°C and 85%RH for 48 hours, the change ΔTs of the monomer transmittance Ts and the change ΔP of the polarization degree P are very small. The monomer transmittance Ts is measured using, for example, an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, product name "V7100"). The degree of polarization P is calculated from the monomer transmittance (Ts), parallel transmittance (Tp), and orthogonal transmittance (Tc) measured using an ultraviolet-visible spectrophotometer, using the following formula. Polarization (P)(%)={(Tp-Tc)/(Tp+Tc)} ^1/2 ×100 In addition, the above-mentioned Ts, Tp and Tc are measured with JIS Z 8701 2 degree field of view (C light source) And perform the Y value obtained by visual sensitivity calibration. In addition, Ts and P are essentially the characteristics of the polarizer. ΔTs and ΔP can be obtained by the following equations. ΔTs(%)=Ts ₄₈ -Ts ₀ ΔP(%)=P ₄₈ -P ₀ Here, Ts ₀ is the transmittance of the monomer before placement (initial), Ts ₄₈ is the transmittance of the monomer after placement, P ₀ It is the degree of polarization before placement (initial), and P ₄₈ is the degree of polarization after placement. The ΔTs is preferably 3.0% or less, and preferably 2.7% or less, and more preferably 2.4% or less. ΔP should be -0.05%~0%, and should be -0.03%~0%, more preferably -0.01%~0%.

The polarizing plate of the present invention is very thin as described above, so it can be suitably used for flexible image display devices. Preferably, the image display device has a curved shape (essentially a curved display screen), and/or can be bent or bent. Specific examples of image display devices include liquid crystal display devices and electroluminescence (EL) display devices (for example, organic EL display devices, inorganic EL display devices). It goes without saying that the polarizing plate of the present invention can be applied to general image display devices without the above description.

The polarizer and the protective layer will be described in detail below.

B. Polarizing parts Any appropriate polarizer can be used as the polarizer. The polarizer can be made by using a laminate of more than two layers. Regarding the manufacturing method of the polarizer, the manufacturing method of the polarizing plate is described in item D.

The thickness of the polarizer is preferably 1 μm to 8 μm, preferably 1 μm to 7 μm, and more preferably 2 μm to 5 μm.

The boric acid content of the polarizer is preferably 10% by weight or more, and preferably 13% to 25% by weight. As long as the boric acid content of the polarizer is within the above range, the additive effect of it and the iodine content described later can maintain the ease of curling adjustment during bonding, suppress curling during heating, and improve the appearance during heating. Durability. The boric acid content can be calculated as the amount of boric acid per unit weight of the polarizer by the neutralization method using the following formula. [Math 1]

The iodine content of the polarizer is preferably 2% by weight or more, preferably 2% to 10% by weight. As long as the iodine content of the polarizer is within the above range, the additive effect of it and the boric acid content can well maintain the ease of curling adjustment during bonding, suppress curling during heating, and improve the appearance during heating. Durability. The "iodine content" in this specification means the total amount of iodine contained in the polarizer (PVA-based resin film). More specifically, the iodine iodide ion (I ^-) is present in the form of a polarizer and the like, and the iodine content of the present specification is meant that molecular iodine (I _2), polyiodide ions _{^{(I 3 - -, I 5}} ) Contains all these forms of iodine. The iodine content can be calculated using the calibration curve method such as fluorescent X-ray analysis. In addition, polyiodide ions are present in the polarizer in a state where PVA-iodine complexes are formed. By forming the complex compound, it is possible to exhibit absorption dichroism in the wavelength range of visible light. Specifically, the complexes (PVA · I ₃ ^-) PVA and tri-iodide ions having a light absorption peak around 470nm; PVA complexes with five iodide ions (PVA · I ₅ ^-) having a light absorption near 600nm peak. As a result, polyiodide ions can absorb light in a wide range of visible light according to their form. On the other hand, an iodide ion (I ^-) having a light absorption peak around 230nm, which absorption of visible light associated with insubstantial. Therefore, the polyiodide ions present in the complex state with PVA are mainly related to the absorption performance of the polarizer.

The polarizer should exhibit absorption dichroism at any wavelength from 380nm to 780nm. The monomer transmittance Ts of the polarizer is preferably 40%~48%, more preferably 41%~46%. The degree of polarization P of the polarizer is preferably 97.0% or more, preferably 99.0% or more, and more preferably 99.9% or more.

C. Protective layer C-1. The first protective layer The first protective layer is composed of a cured product of a coating film of an organic solvent solution of a thermoplastic acrylic resin (hereinafter simply referred to as acrylic resin) as described above. Hereinafter, the constituent components of the first protective layer will be specifically described, and then the characteristics of the first protective layer will be described.

C-1-1. Acrylic resin The Tg of the acrylic resin (as described later, including a mixture of two or more acrylic resins and a mixture of acrylic resins and other resins) is as described in the description of the first protective layer in item A above.

As long as the acrylic resin has the above-mentioned Tg, any appropriate acrylic resin can be used. The acrylic resin typically contains an alkyl (meth)acrylate as a main component as a monomer unit (repeating unit). In this specification, "(meth)acrylic acid" means acrylic acid and/or methacrylic acid. The (meth)acrylic acid alkyl ester constituting the main skeleton of the acrylic resin can be exemplified by linear or branched alkyl having 1 to 18 carbon atoms. These can be used alone or in combination. In addition, any appropriate comonomer can also be introduced by copolymerization with acrylic resin. The repeating unit derived from alkyl (meth)acrylate is represented by the following general formula (1):

[Chemical formula 1]

In the general formula (1), R ⁴ represents a hydrogen atom or a methyl group, and R ⁵ represents a hydrogen atom or a substituted aliphatic or alicyclic hydrocarbon group with 1 to 6 carbon atoms. Examples of the substituent include halogen and hydroxyl. Specific examples of alkyl (meth)acrylates include: methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, (meth) Base) tertiary butyl acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, benzyl (meth)acrylate, (meth)acrylic acid Dicyclopentyloxyethyl, dicyclopentyl (meth)acrylate, chloromethyl (meth)acrylate, 2-chloroethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, ( 3-hydroxypropyl meth)acrylate, 2,3,4,5,6-pentahydroxyhexyl (meth)acrylate, 2,3,4,5-tetrahydroxypentyl (meth)acrylate, 2- Methyl (hydroxymethyl)acrylate, ethyl 2-(hydroxymethyl)acrylate, methyl 2-(hydroxyethyl)acrylate. In the general formula (1), R ^{5 is} preferably a hydrogen atom or a methyl group. Therefore, particularly desirable alkyl (meth)acrylates are methyl acrylate or methyl methacrylate.

The acrylic resin may contain only a single alkyl (meth)acrylate unit, or may contain a plurality of alkyl (meth)acrylate units in which R ⁴ and R ⁵ in the general formula (1) are different from each other.

The content ratio of the alkyl (meth)acrylate unit in the acrylic resin is preferably 50 mol%~98 mol%, more preferably 55 mol%~98 mol%, and more preferably 60 mol%~ 98 mol%, particularly preferably 65 mol%~98 mol%, most preferably 70 mol%~97 mol%. If the content ratio is less than 50 mol%, the effect (for example, high heat resistance, high transparency) that can be exhibited by the alkyl (meth)acrylate unit may not be fully exhibited. If the above-mentioned content ratio is greater than 98 mol%, the resin becomes brittle and easily cracked, and the high mechanical strength cannot be sufficiently exhibited, which may deteriorate the productivity.

The acrylic resin preferably has a repeating unit including a ring structure. The repeating unit containing the ring structure may include a lactone ring unit, a glutaric anhydride unit, a glutaric anhydride unit, a maleic anhydride unit, and a maleimid (N-substituted maleimid) unit. The repeating unit containing the ring structure may be contained in only one type in the repeating unit of the acrylic resin, or two or more types may be contained in it.

The lactone ring unit is preferably represented by the following general formula (2):

通式(2)中，R¹ 、R² 及R³ 分別獨立表示氫原子或碳數1~20之有機殘基。此外，有機殘基亦可含有氧原子。丙烯酸系樹脂中可僅含有單一的內酯環單元，亦可含有多個上述通式(2)中之R¹ 、R² 及R³ 互異的內酯環單元。具有內酯環單元之丙烯酸系樹脂已載於譬如日本專利特開2008-181078號公報中，而本說明書即援用該公報之記載作為參考。[Chemical formula 2]

In the general formula (2), R ¹ , R ² and R ³ each independently represent a hydrogen atom or an organic residue with 1 to 20 carbon atoms. In addition, organic residues may also contain oxygen atoms. The acrylic resin may contain only a single lactone ring unit, or may contain multiple lactone ring units in which R ¹ , R ² and R ³ in the general formula (2) are different from each other. The acrylic resin having a lactone ring unit has been described in, for example, Japanese Patent Laid-Open No. 2008-181078, and the description in the publication is used as a reference in this specification.

The glutarimide unit is preferably represented by the following general formula (3):

[Chemical formula 3]

In the general formula (3), R ¹¹ and R ¹² each independently represent hydrogen or an alkyl group with 1 to 8 carbons, and R ¹³ represents an alkyl group with 1 to 18 carbons, a cycloalkyl group with 3 to 12 carbons, or 6 to 10 carbons. Aryl. In the general formula (3), it is desirable that R ¹¹ and R ¹² are each independently hydrogen or methyl, and R ¹³ is hydrogen, methyl, butyl, or cyclohexyl. More preferably, R ¹¹ is methyl, R ¹² is hydrogen, and R ¹³ is methyl. The acrylic resin may contain only a single glutarimide unit, or may contain multiple glutarimide units in which R ¹¹ , R ¹² and R ¹³ in the general formula (3) are mutually different. Acrylic resins having pentadiimide units are described in, for example, Japanese Patent Application Publication No. 2006-309033, Japanese Patent Application Publication No. 2006-317560, Japanese Patent Application Publication No. 2006-328334, Japanese Patent Application Publication No. 2006-337491 , Japanese Patent Application Publication No. 2006-337492, Japanese Patent Application Publication No. 2006-337493, Japanese Patent Application Publication No. 2006-337569, and this specification refers to the description of the publication as a reference. In addition, for the glutaric anhydride unit, except that the nitrogen atom substituted by R ¹³ in the general formula (3) is changed to an oxygen atom, the above description of the glutarimide unit applies.

The maleic anhydride unit and the maleimidine (N-substituted maleimidine) unit can specify the structure by the name, so the specific description is omitted.

The content ratio of the repeating unit containing the ring structure in the acrylic resin is preferably 1 mol%~50 mol%, more preferably 10 mol%~40 mol%, more preferably 20 mol%~30 mol% . When the content ratio is too small, the Tg may be lower than 110°C, and the heat resistance, solvent resistance, and surface hardness of the obtained first protective layer may be insufficient. When the content ratio is too high, the moldability and transparency may be insufficient.

唑啉、2-乙烯基-

唑啉、2-丙烯醯基-

唑啉、N-苯基馬來醯亞胺、甲基丙烯酸苯基胺乙酯、苯乙烯、α-甲基苯乙烯、對環氧丙基苯乙烯、對胺基苯乙烯、2-苯乙烯基-

唑啉等。該等可單獨使用亦可併用。其他乙烯基系單體單元之種類、數量、組合、含有比率等可按目的適當設定。The acrylic resin may also contain repeating units other than the alkyl (meth)acrylate unit and the repeating unit including a ring structure. The repeating unit may be a repeating unit derived from a vinyl-based monomer copolymerizable with the monomer constituting the unit (other vinyl-based monomer unit). Examples of other vinyl monomers include acrylic acid, methacrylic acid, crotonic acid, 2-(hydroxymethyl)acrylic acid, 2-(hydroxyethyl)acrylic acid, acrylonitrile, methacrylonitrile, ethacrylonitrile ( Ethacrylonitrile), allyl glycidyl ether, maleic anhydride, itaconic anhydride, N-methylmaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, Amino ethyl acrylate, propyl amine ethyl acrylate, dimethyl amine ethyl methacrylate, ethyl amine propyl methacrylate, cyclohexyl amine ethyl methacrylate, N-vinyl diethyl amine, N -Acetyl vinylamine, allylamine, methallylamine, N-methallylamine, 2-isopropenyl-

Oxazoline, 2-vinyl-

Oxazoline, 2-propenyl-

Oxazoline, N-phenylmaleimide, phenylaminoethyl methacrylate, styrene, α-methylstyrene, p-glycidyl styrene, p-aminostyrene, 2-styrene base-

Oxazoline etc. These can be used alone or in combination. The type, number, combination, content ratio, etc. of other vinyl monomer units can be appropriately set according to the purpose.

The weight average molecular weight of the acrylic resin is preferably 1,000 to 2,000,000, and preferably 5,000 to 1,000,000, more preferably 10,000 to 500,000, particularly preferably 50,000 to 500,000, and most preferably 60,000 to 150,000. The weight average molecular weight can be calculated in terms of polystyrene using gel permeation chromatography (GPC system, manufactured by Tosoh Co., Ltd.). In addition, tetrahydrofuran can be used as a solvent.

The acrylic resin can be used in appropriate combination of the above-mentioned monomer units, and polymerized by any appropriate polymerization method. It is also possible to mix two or more types of acrylic resins having different monomer units.

In the embodiment of the present invention, acrylic resin and other resins may be used in combination. That is, the monomer components constituting the acrylic resin can be copolymerized with the monomer components constituting other resins, and the copolymer can be used for the molding of the first protective layer described later; the mixture of acrylic resin and other resins can also be used for The formation of the first protective layer. Other resins include, for example, styrene resin, polyethylene, polypropylene, polyamide, polyphenylene sulfide, polyether ether ketone, polyester, polysulfide, polyphenylene ether, polyacetal, and polyimide , Polyether imine and other thermoplastic resins. The type and blending amount of the resin to be used in combination can be appropriately set according to the purpose and desired characteristics of the resulting film. For example, a styrene resin (preferably an acrylonitrile-styrene copolymer) can be used in combination as a phase difference control agent.

When acrylic resin and other resins are used in combination, the content of acrylic resin in the mixture of acrylic resin and other resins is preferably 50% by weight to 100% by weight, preferably 60% by weight to 100% by weight, and more preferably 70% by weight ~100% by weight, particularly preferably 80% by weight to 100% by weight. When the content is less than 50% by weight, there is a possibility that the high heat resistance and high transparency inherent in acrylic resin may not be fully exhibited.

C-1-2. The composition and characteristics of the first protective layer The first protective layer is composed of the cured product of the coating film of the organic solvent solution of the acrylic resin as described above. As long as it is a cured product of the coating film, the thickness can be much thinner than that of an extruded film. The thickness of the first protective layer is 10 μm or less as described above, preferably 7 μm or less, preferably 5 μm or less, and more preferably 3 μm or less. The lower limit of the thickness of the first protective layer may be, for example, 1 μm. In addition, although it is not clear in theory, the cured product of such a coating film shrinks during film formation smaller than that of thermosetting resin or active energy ray-curable resin (for example, ultraviolet curable resin). And because it does not contain residual monomers, it has the advantages of suppressing the deterioration of the film itself and preventing the residual monomers from adversely affecting the polarizing plate (polarizer). In addition, since its hygroscopicity and moisture permeability are smaller than the cured product of an aqueous coating film such as an aqueous solution or a water dispersion, it has an advantage of excellent humidification durability. As a result, it is possible to realize a polarizing plate that can maintain optical characteristics and has good durability even in a heated and humidified environment.

The Tg of the first protective layer is as described in item A above.

The iodine adsorption amount of the first protective layer is preferably 4.0% by weight or less, and preferably 3.0% by weight or less, more preferably 2.0% by weight or less, particularly preferably 1.0% by weight or less, and particularly preferably 0.5% by weight or less. The smaller the iodine adsorption amount, the better, and the lower limit thereof may be, for example, 0.1% by weight. As long as the iodine adsorption amount is in the above range, a polarizing plate having more excellent durability can be obtained. The iodine adsorption content can be measured by the method described in the following examples.

Preferably, the first protective layer is substantially optically isotropic. In this specification, "substantially optically isotropic" means that the in-plane retardation Re (550) is 0 nm to 10 nm, and the thickness direction retardation Rth (550) is -20 nm to +10 nm. The in-plane phase difference Re(550) is preferably 0nm~5nm, more preferably 0nm~3nm, and particularly preferably 0nm~2nm. The phase difference Rth(550) in the thickness direction is preferably -5nm~5nm, more preferably -3nm~3nm, especially -2nm~2nm. As long as the Re (550) and Rth (550) of the first protective layer are within the above range, when the polarizing plate including the first protective layer is applied to an image display device, it can prevent adverse effects on the display characteristics. In addition, Re(550) is the in-plane retardation of the film measured at 23°C with light with a wavelength of 550 nm. Re(550) can be obtained by the formula: Re(550)=(nx-ny)×d. Rth(550) is the retardation in the thickness direction of the film measured with light with a wavelength of 550nm at 23°C. Rth(550) can be obtained by formula: Rth(550)=(nx-nz)×d. Here, nx is the refractive index in the direction where the in-plane refractive index is the largest (ie the slow axis direction), ny is the refractive index in the direction orthogonal to the slow axis in the plane (ie the fast axis direction), and nz is the thickness The refractive index in the direction, d is the thickness of the film (nm).

The light transmittance of the first protective layer at a thickness of 3 µm at 380 nm is as high as possible. Specifically, the light transmittance is preferably 85% or more, more preferably 88% or more, and more preferably 90% or more. As long as the light transmittance is within the range, the desired transparency can be ensured. The light transmittance can be measured according to the method of ASTM-D-1003, for example.

The lower the haze of the first protective layer, the better. Specifically, it is preferably 5% or less, preferably 3% or less, more preferably 1.5% or less, and particularly preferably 1% or less. As long as the haze is 5% or less, good transparency can be imparted to the film. Moreover, even when it is used in the viewing side polarizer of an image display device, the display content can still be viewed well.

The YI of the first protective layer with a thickness of 3 µm is preferably 1.27 or less, preferably 1.25 or less, more preferably 1.23 or less, and particularly preferably 1.20 or less. When YI is greater than 1.3, there may be insufficient optical transparency. In addition, YI can be obtained, for example, from the color tristimulus values (X, Y, Z) measured by using a high-speed integrating sphere spectroscopic transmittance measuring machine (trade name DOT-3C: manufactured by Murakami Color Technology Laboratory) by the following formula Out. YI=[(1.28X-1.06Z)/Y]×100

The b value (the hue scale based on the Hunter color system) of the first protective layer at a thickness of 3 μm is preferably less than 1.5, and preferably less than 1.0. When the b value is 1.5 or more, an undesirable hue sometimes appears. In addition, the b value can be obtained, for example, by cutting a sample of the film constituting the first protective layer into 3 cm squares, and using a high-speed integrating sphere spectroscopic transmittance measuring machine (trade name DOT-3C: Murakami Color (Institute of Technology) measured the hue, and evaluated the hue according to the Hunter color system.

The first protective layer (cured product of the coating film) may contain any appropriate additives according to the purpose. Specific examples of additives include ultraviolet absorbers; leveling agents; hindered phenol, phosphorus, sulfur and other antioxidants; stabilizers such as light stabilizers, weather stabilizers, and heat stabilizers; reinforcing materials such as glass fiber and carbon fiber; Near-infrared absorbent; ginseng (dibromide propyl) phosphate, triallyl phosphate, antimony oxide and other flame retardants; anionic, cationic, non-ionic surfactants and other antistatic agents; inorganic pigments, Organic pigments, dyes and other colorants; organic or inorganic fillers; resin modifiers; organic or inorganic fillers; plasticizers; slip agents; antistatic agents; flame retardants, etc. The additives may be added when the acrylic resin is polymerized, or may be added to the solution when the film is formed. The type, quantity, combination, and amount of additives can be appropriately set according to the purpose.

唑啉系交聯劑。藉由形成所述易接著層，可提升第1保護層與偏光件之密著性。An easy bonding layer may also be formed on the polarizer side of the first protective layer. The easy-to-bond layer includes, for example, water-based polyurethane and

Oxazoline-based crosslinking agent. By forming the easy bonding layer, the adhesion between the first protective layer and the polarizer can be improved.

C-2. The second protective layer The second protective layer is composed of a resin film as described above. Specific examples of the material that becomes the main component of the film include cellulose resins such as cellulose triacetate (TAC), polyester resins such as polyethylene terephthalate (PET), and polyvinyl alcohol resins. , Polycarbonate resins, polyamide resins, polyimide resins, polyether sulfide resins, poly sulfide resins, polystyrene resins, polynorbornene resins and other cycloolefin resins, poly Transparent resins such as olefin resins, (meth)acrylic resins and acetate resins. In addition, thermosetting resins such as (meth)acrylic type, urethane type, (meth)acrylate urethane type, epoxy type, and polysilicon type resin, or ultraviolet curing type resin, etc. may also be mentioned. Other examples include glassy polymers such as silicone polymers. In addition, the polymer film described in JP 2001-343529 A (WO01/37007) can also be used. As the material of the film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted amide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain can be used, for example, Examples include resin compositions having alternating copolymers composed of isobutylene and N-methylmaleimide and acrylonitrile-styrene copolymers. The polymer film may be, for example, an extruded product of the above-mentioned resin composition.

When the polarizing plate of the present invention is arranged on the viewing side of the image display device and the second protective layer 30 is arranged on the opposite side of the image display device from the display unit (viewing side), the second protective layer 30 can be hard-coated as needed Fabric treatment, anti-reflection treatment, anti-adhesion treatment, anti-glare treatment and other surface treatments. And/or, the second protective layer 30 can also be processed as needed to improve the visibility through polarized sunglasses (representatively, imparting (elliptical) circular polarization function and ultra-high phase difference). By performing the above processing, even when the displayed image is visualized through a polarized lens such as polarized sunglasses, excellent visibility can still be achieved. Therefore, the polarizing plate can also be suitably used for image display devices that can be used outdoors.

The thickness of the second protective layer is preferably 10 μm to 50 μm, more preferably 10 μm to 30 μm. In addition, when the surface treatment is applied, the thickness of the outer protective layer includes the thickness of the surface treatment layer.

D. Manufacturing method of polarizing plate D-1. Manufacturing method of polarizing parts The method for manufacturing a polarizer described in item B above includes the following steps: forming a polyvinyl alcohol resin layer (PVA resin) containing a halide and a polyvinyl alcohol resin (PVA resin) on one side of a long-form thermoplastic resin substrate. Resin layer) to form a laminated body; and, sequentially perform aerial auxiliary stretching treatment, dyeing treatment, underwater stretching treatment, and drying shrinkage treatment on the laminated body, and the drying and shrinking treatment system transports the laminated body in the longitudinal direction. Heat it to shrink by 2% or more in the width direction. The halide content in the PVA-based resin layer is preferably 5 to 20 parts by weight relative to 100 parts by weight of the PVA-based resin. The drying shrinkage should be treated with a heating roller, and the temperature of the heating roller should be 60℃~120℃. According to the manufacturing method, the polarizer as described above can be obtained. In particular, a polarizer with excellent optical characteristics (representatively, monomer transmittance and polarization degree) and with suppressed optical characteristics can be obtained by the following method: after making a laminate containing a halide-containing PVA-based resin layer, The stretching of the above-mentioned laminated body is subjected to multi-stage stretching including aerial auxiliary stretching and underwater stretching, and then the stretched laminated body is heated by a heating roller. Specifically, by using a heating roller in the drying and shrinking treatment step, the entire layered body can be uniformly shrunk while conveying the layered body. In this way, not only can the optical characteristics of the obtained polarizer be improved, but also the polarizer with excellent optical characteristics can be stably produced, and the variation of the optical characteristics (especially the transmittance of monomer) of the polarizer can be suppressed. The following describes the halide and drying shrinkage treatment. The details of the manufacturing method other than these are described in, for example, Japanese Patent Laid-Open No. 2012-73580. In this manual, the entire record of the bulletin is used as a reference.

D-1-1. Halide The PVA-based resin layer containing the halide and the PVA-based resin can be formed by applying a coating solution containing the halide and the PVA-based resin on a thermoplastic resin substrate and drying the coating film. The coating liquid represents a solution prepared by dissolving the above-mentioned halide and the above-mentioned PVA-based resin in a solvent. As the solvent, for example, water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, trimethylolpropane and other polyols, ethylene oxide Amines such as diamine and diethylenetriamine. These can be used alone or in combination of two or more kinds. Among these, water is better. The concentration of the PVA-based resin of the solution is preferably 3 to 20 parts by weight relative to 100 parts by weight of the solvent. As long as the resin concentration is the above, a uniform coating film that adheres to the thermoplastic resin substrate can be formed.

As the halide, any appropriate halide can be used. Examples include iodide and sodium chloride. Examples of iodides include potassium iodide, sodium iodide, and lithium iodide. Among these, potassium iodide is preferred.

The amount of halide in the coating liquid is preferably 5 parts by weight to 20 parts by weight, and more preferably 10 parts by weight to 15 parts by weight relative to 100 parts by weight of the PVA-based resin. If the amount of halide is too much, the halide may overflow and the resulting polarizer may become cloudy.

Generally speaking, the extension of the PVA resin layer will increase the orientation of the polyvinyl alcohol molecules in the PVA resin layer. However, if the extended PVA resin layer is immersed in a water-containing liquid, there will be polyethylene A situation where the orientation of alcohol molecules is disordered and the orientation is reduced. Especially when the laminate of the thermoplastic resin substrate and the PVA-based resin layer is stretched in boric acid water, in order to stabilize the extension of the thermoplastic resin substrate, the laminate is stretched in boric acid water at a relatively high temperature. The tendency to decrease orientation is obvious. For example, the extension of the PVA film monomer in boric acid water is generally performed at 60°C. In contrast, the extension of the laminate of A-PET (thermoplastic resin substrate) and PVA-based resin layer is performed at 70°C. The temperature before and after is performed at a higher temperature. At this time, the orientation of the PVA at the beginning of the extension will decrease before it rises due to the extension in the water. In this regard, by making a laminate of a halide-containing PVA-based resin layer and a thermoplastic resin substrate, and stretching the laminate in the air before stretching in boric acid water (assisted extension), the post-assisted extension can be promoted The crystallization of the PVA resin in the PVA resin layer of the laminate. As a result, when the PVA-based resin layer is immersed in a liquid, compared to the case where the PVA-based resin layer does not contain a halide, it is possible to suppress the orientation disorder of the polyvinyl alcohol molecules and the decrease in orientation. Thereby, it is possible to improve the optical characteristics of the polarizer obtained by the processing step of immersing the laminate in a liquid through a dyeing process and an underwater stretching process.

D-1-2. Drying shrinkage treatment The drying shrinkage treatment can be performed by heating the area by heating the entire area, or by heating the conveying roller (so-called heating roller) (heat roller drying method). It is preferable to use both. By using a heating roller to dry it, heating and curling of the laminate can be effectively suppressed, and a polarizer with excellent appearance can be manufactured. Specifically, by drying the laminate in a state where the laminate is along the heating roller, the crystallization of the thermoplastic resin substrate can be efficiently promoted to increase the degree of crystallinity, even at a relatively low drying temperature. It can still increase the crystallinity of the thermoplastic resin substrate. As a result, the rigidity of the thermoplastic resin base material is increased and the PVA-based resin layer can withstand the shrinkage of the PVA-based resin layer due to drying, and curling is suppressed. In addition, by using a heating roller, the laminate can be dried while maintaining a flat state. Therefore, not only can the generation of curls be suppressed, but also the generation of wrinkles can be suppressed. In this case, the laminated body can be shrunk in the width direction through a drying shrinkage treatment to improve optical properties. It is because it can effectively improve the orientation of PVA and PVA/iodine complexes. The shrinkage rate of the laminate in the width direction obtained by drying and shrinking is preferably 2%~10%, more preferably 2%~8%, especially 4%~6%. By using heating rollers, the laminate can be continuously shrunk in the width direction while conveying the laminate, thereby achieving high productivity.

Fig. 2 is a schematic diagram showing an example of drying shrinkage treatment. In the drying shrinkage process, the layered body 200 is dried while being conveyed by the conveying rollers R1 to R6 and the guide rollers G1 to G4 heated to a predetermined temperature. In the example of the figure, the conveying rollers R1 to R6 are arranged to alternately and continuously heat the surface of the PVA resin layer and the surface of the thermoplastic resin substrate. However, for example, the conveying rollers R1 to R6 may be arranged to only continuously heat the laminate 200 One side (such as the thermoplastic resin substrate side).

By adjusting the heating temperature of the conveying roller (temperature of the heating roller), the number of heating rollers, and the contact time with the heating roller, the drying conditions can be controlled. The temperature of the heating roller is preferably 60℃~120℃, more preferably 65℃~100℃, especially 70℃~80℃. The degree of crystallinity of the thermoplastic resin can be increased well and curling can be well suppressed, and an optical laminate with extremely excellent durability can be produced. In addition, the temperature of the heating roller can be measured with a contact thermometer. In the example of the figure, there are 6 conveying rollers, but there is no particular limitation as long as there are a plurality of conveying rollers. The number of conveying rollers is usually 2-40, preferably 4-30. The contact time (total contact time) between the laminate and the heating roller is preferably 1 second to 300 seconds, preferably 1 to 20 seconds, and more preferably 1 to 10 seconds.

The heating roller can be installed in a heating furnace (such as an oven), or can be installed in a general manufacturing line (at room temperature). It is suitable to be installed in a heating furnace with air supply mechanism. By combining drying with heating rollers and hot-air drying, rapid temperature changes between heating rollers can be suppressed, and the shrinkage in the width direction can be easily controlled. The temperature of hot air drying should be 30℃~100℃. Moreover, the hot air drying time is preferably 1 second to 300 seconds. The wind speed of the hot air should be about 10m/s~30m/s. In addition, the wind speed is the wind speed in the heating furnace, which can be measured by a mini fan blade type digital anemometer.

It is advisable to perform a washing treatment after the water extension treatment and before the drying shrinkage treatment. The above-mentioned washing treatment can typically be performed by immersing the PVA-based resin layer in a potassium iodide aqueous solution.

In the above manner, a laminate of a thermoplastic resin substrate/polarizer can be obtained.

D-2. Manufacturing method of polarizing plate A resin film for forming the second protective layer is attached to the surface of the polarizer of the laminate obtained in the above item D-1. Next, the thermoplastic resin substrate is peeled off, and an organic solvent solution of acrylic resin is applied to the peeled surface to form a coating film, and the coating film is cured to form a first protective layer. In the above manner, a polarizing plate having a configuration of the first protective layer (cured product of the coating film)/polarizer/second protective layer (resin film) can be obtained.

The acrylic resin is as described in the above item C-1-1.

The organic solvent can be any suitable organic solvent that can dissolve or uniformly disperse the acrylic resin. Specific examples of organic solvents include ethyl acetate, toluene, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), cyclopentanone, and cyclohexanone.

The acrylic resin concentration of the solution is preferably 3 parts by weight to 20 parts by weight relative to 100 parts by weight of the solvent. As long as the resin concentration is the above, a uniform coating film that adheres to the polarizer can be formed.

The solution can be coated on any suitable substrate, and can also be coated on the polarizer. When the solution is applied to the substrate, the cured product of the coating film formed on the substrate is transferred to the polarizer. When the solution is applied to the polarizer, the coating film is dried (cured) to directly form the first protective layer on the polarizer. Preferably, the solution is coated on the polarizer, and the first protective layer is directly formed on the polarizer. As long as it has the above configuration, the adhesive layer or the adhesive layer required for transfer can be omitted, so the polarizing plate can be made thinner. Any appropriate method can be adopted for the coating method of the solution. Specific examples include a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, a die coating method, a curtain coating method, a spray coating method, and a knife coating method (comma coating method, etc.).

By drying (curing) the coating film of the solution, the first protective layer can be formed. The drying temperature should be below 100℃, more preferably 50℃~70℃. As long as the drying temperature is within the above range, adverse effects on the polarizer can be prevented. The drying time can be changed according to the drying temperature. The drying time can be, for example, 1 minute to 10 minutes.

In the above manner, a polarizing plate having the configuration of the first protective layer (cured product of the coating film)/polarizer/second protective layer (resin film) can be obtained. Alternatively, the thermoplastic resin substrate can be used directly as the second protective layer. At this time, the surface of the polarizer of the laminate of thermoplastic resin substrate/polarizer is coated with an organic solvent solution of acrylic resin to form a coating film, and the coating film is cured to form the first protective layer. The result is A polarizing plate having a first protective layer (cured product of the coating film)/polarizer/second protective layer (thermoplastic resin substrate). Example

Hereinafter, the present invention will be specifically described with examples, but the present invention is not limited by these examples. The measuring methods of each characteristic are as follows. In addition, as long as there is no special note, "parts" and "%" in the examples are the basis of weight.

(1) Glass transition temperature Tg The solution obtained by dissolving the material constituting the first protective layer used in the examples and comparative examples in a predetermined solvent is applied to the substrate (PET film) with a spreader, and dried at 60°C to form a coating film (Thickness 40μm). The obtained coating film was peeled from the base material, and cut into short stick shapes to prepare measurement samples. This measurement sample was subjected to DMA measurement to measure Tg. The measuring device and measuring conditions are as follows. (Measurement device) "DMS6100" manufactured by SII NanoTechnology Inc. (Measurement conditions) ・Measuring temperature range: -80℃~150℃ ・Temperature rise rate: 2℃/min ・Measurement sample width: 10mm ・Distance between clamps: 20mm ・Measurement Frequency: 1Hz ・Strain amplitude: 10μm ・Measuring gas environment: N ₂ (250mL/min) (2) Iodine adsorption amount The material constituting the first protective layer used in the examples and comparative examples is dissolved in a predetermined solvent to obtain a solution using a dispenser It is applied to a substrate (PET film) and dried at 60°C to form a coating film (thickness 40 μm). The obtained coating film was peeled from the substrate and cut into 1 cm×1 cm (1 cm ² ) to prepare a measurement sample. The measurement sample is applied to the combustion IC method, and the amount of iodine in the sample is quantitatively analyzed. The details are as follows. The measurement sample is taken into a headspace vial (20 mL capacity) and weighed. Next, a vial (2 mL capacity) containing 1 mL of an iodine solution (iodine concentration of 1% by weight, potassium iodide concentration of 7% by weight) was placed in the headspace vial and capped tightly. After that, the headspace vial was heated with a dryer at 65°C for 6 hours, and the heated sample was taken into a ceramic boat and burned with an automatic combustion device, and then the generated gas was collected into the absorption liquid. Perform quantitative analysis to obtain the weight% of adsorbed iodine. In addition, the devices used are as follows.・Automatic sample burning device: "AQF-2100H" manufactured by Mitsubishi Chemical Analytech Co., Ltd. ・IC (anion): manufactured by Thermo Fisher Scientific, "ICS-3000" (3) Discoloration cut out from the polarizers obtained in the examples and comparative examples Test piece (50mm×50mm), the test piece is formed on two sides that are perpendicular to the direction of the absorption axis of the polarizer and the direction of the absorption axis, respectively. Put the test piece on the alkali-free glass plate with an adhesive so that the first protective layer is inside to make a test sample, and place the test sample in an oven at 85°C and 85%RH for 48 hours to heat it Humidify, and then when configured to be orthogonal to the standard polarizer, check the fading state of the polarizer after humidification with the naked eye, and evaluate it based on the following criteria. No problem: no discoloration observed. Discoloration: discoloration observed at the end. Overall discoloration: overall polarizing plate discoloration. (4) Monomer transmittance and polarization degree. A test piece (50mm) was cut out from the polarizer obtained in the Examples and Comparative Examples. ×50mm), the test piece is formed on two sides opposite to the direction perpendicular to the absorption axis direction of the polarizer and the absorption axis direction. The test piece was bonded to an alkali-free glass plate with an adhesive so that the protective layer was on the outside to prepare a test sample. For the test sample, an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, product name "V7100") ) The monomer transmittance (Ts), parallel transmittance (Tp), and orthogonal transmittance (Tc) are measured, and the degree of polarization (P) is obtained by the following formula. At this time, the measurement light was made incident from the protective layer side. Polarization (P)(%)={(Tp-Tc)/(Tp+Tc)} ^1/2 ×100 In addition, the above-mentioned Ts, Tp and Tc are measured with JIS Z 8701 2 degree field of view (C light source) And perform the Y value obtained by visual sensitivity calibration. In addition, Ts and P are essentially the characteristics of the polarizer. Then, place the polarizing plate in an oven at 85°C and 85%RH for 48 hours after heating and humidifying (heating test), from the monomer transmittance Ts ₀ before the heating test and the monomer transmittance Ts ₄₈ after the heating test The amount of change in transmittance ΔTs of the monomer is obtained by the following formula. ΔTs(%)=Ts ₄₈ -Ts ₀ Similarly, from the degree of polarization P ₀ before the heating test and the degree of polarization P ₄₈ after the heating test, the amount of change in the degree of polarization ΔP is obtained by the following formula. ΔP(%)=P ₄₈ -P _{0 In} addition, the heating test was performed by making test specimens in the same manner as in the above evaluation of fading.

>Example 1> 1. The laminated resin substrate of the polarizer/resin substrate is made of a long strip of amorphous isophthalic acid copolymer polyethylene terephthalate with a water absorption rate of 0.75% and a Tg of about 75°C Diester film (thickness: 100μm). And applied corona treatment to one side of the resin substrate. In a 9:1 mixture of polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetyl acetyl modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER Z410"). To 100 parts by weight of the resin, 13 parts by weight of potassium iodide was added to prepare a PVA aqueous solution (coating liquid). The above-mentioned PVA aqueous solution was applied to the corona-treated surface of the resin substrate and dried at 60° C. to form a PVA-based resin layer with a thickness of 13 μm to produce a laminate. The obtained laminate was subjected to uniaxial extension of the free end 2.4 times in the longitudinal direction (long side direction) between rollers at different peripheral speeds in an oven at 130°C (air-assisted extension treatment). Next, the layered body was immersed in an insoluble bath (a boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40°C for 30 seconds (insoluble treatment). Next, while adjusting the concentration of a dye bath (an iodine aqueous solution obtained by mixing iodine and potassium iodide at a weight ratio of 1:7 with respect to 100 parts by weight of water) at a liquid temperature of 30°C, the concentration of the resulting polarizer The volume transmittance (Ts) becomes 41.5%±0.1% while being immersed therein for 60 seconds (dyeing treatment). Next, it was immersed in a cross-linking bath (a boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water with a liquid temperature of 40°C) for 30 seconds (cross-linking treatment) . Then, while immersing the layered body in a boric acid aqueous solution (boric acid concentration 4.0% by weight) at a liquid temperature of 70°C, uniaxial stretching was performed in the longitudinal direction (longitudinal direction) between rolls with different peripheral speeds to achieve the total stretching ratio Up to 5.5 times (extension treatment in water). After that, the layered body was immersed in a washing bath (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with respect to 100 parts by weight of water with a liquid temperature of 20°C) (washing treatment). After that, while drying in an oven maintained at 90°C, the contact surface temperature was maintained at 75°C with a heating roller made of SUS for about 2 seconds (drying shrinkage treatment). The shrinkage rate in the width direction of the laminate after drying and shrinking was 5.2%. In the above-mentioned manner, a polarizer with a thickness of 5 μm was formed on the resin substrate to produce a laminate of polarizer/resin substrate. The monomer transmittance (initial monomer transmittance) Ts ₀ of the polarizer is 41.5, and the polarization degree (initial polarization degree) P ₀ is 99.996%.

2. Making polarizer A cycloolefin-based film (ZT-12, 23 μm thick, manufactured by Zeon Co., Ltd., Japan) was used as a film constituting the second protective layer to be bonded to the surface of the polarizer obtained above through an ultraviolet curable adhesive. Specifically, it is applied so that the total thickness of the hardening adhesive becomes 1.0 μm, and is bonded using a rolling mill. After that, UV rays were irradiated from the film side to harden the adhesive. Next, the resin substrate was peeled off, and a polarizing plate having a second protective layer (ZT-12)/polarizer configuration was obtained.

20 parts of acrylic resin of polymethyl methacrylate having lactone ring units (30 mol% of lactone ring units) was dissolved in 80 parts of methyl ethyl ketone to obtain an acrylic resin solution (20%) . The acrylic resin solution was coated on the surface of the polarizer of the polarizer obtained above using a wire rod, and the coating film was dried at 60°C for 5 minutes to form the first protective layer as a cured product of the coating film . The thickness of the first protective layer is 3 μm, the Tg is 119°C, and the iodine adsorption amount is 0.25% by weight. In the above manner, a polarizing plate having a configuration of the first protective layer (cured product of the coating film)/polarizer/second protective layer (ZT-12) was obtained. The obtained polarizing plate was used for the evaluation of (3) and (4) above. Also, the presence or absence of shrinkage after the formation of the protective layer was observed with the naked eye. The results are listed in Table 1.

>Example 2> In addition to using an acrylic resin with maleic anhydride unit of polymethyl methacrylate (maleic anhydride unit 7 mol%) to replace the acrylic resin with lactone ring unit of polymethyl methacrylate, according to In the same manner as in Example 1, the first protective layer was formed. The thickness of the first protective layer was 3 μm, and the Tg was 115°C. Except for using this first protective layer, a polarizing plate was produced in the same manner as in Example 1. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are listed in Table 1.

>Example 3> In addition to using 100% polymethyl methacrylate acrylic resin (manufactured by Kusumoto Chemical Co., Ltd., product name "B-728") to replace the polymethyl methacrylate acrylic resin with lactone ring units, according to In the same manner as in Example 1, the first protective layer was formed. The thickness of the first protective layer was 3 μm, the Tg was 116° C., and the iodine adsorption amount was 0.34% by weight. Except for using this first protective layer, a polarizing plate was produced in the same manner as in Example 1. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are listed in Table 1.

>Example 4> Except for the use of acrylic resin of polymethyl methacrylate with glutarimide ring unit (4 mol% of glutarimide ring unit) to replace acrylic acid with lactone ring unit of polymethyl methacrylate Except for the resin, a first protective layer was formed in the same manner as in Example 1. The thickness of the first protective layer was 3 μm, the Tg was 103° C., and the iodine adsorption amount was 2.3% by weight. Except for using this first protective layer, a polarizing plate was produced in the same manner as in Example 1. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are listed in Table 1.

>Example 5> The first protective layer was formed in the same manner as in Example 1, except that an acrylic resin (lactone ring unit 20 mol%) having a different polymethyl methacrylate different from the lactone ring unit was used. The thickness of the first protective layer was 3 μm, the Tg was 104° C., and the iodine adsorption amount was 2.8% by weight. Except for using this first protective layer, a polarizing plate was produced in the same manner as in Example 1. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are listed in Table 1.

>Example 6> In addition to using the acrylic resin of a copolymer of methyl methacrylate/butyl methacrylate (mole ratio 80/20) to replace the acrylic resin of polymethyl methacrylate with lactone ring units, according to In the same manner as in Example 1, the first protective layer was formed. The thickness of the first protective layer was 3 μm, the Tg was 95° C., and the iodine adsorption amount was 3.8% by weight. Except for using this first protective layer, a polarizing plate was produced in the same manner as in Example 1. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are listed in Table 1.

>Comparative Example 1> Except for the use of methyl methacrylate/ethyl acrylate (mole ratio 55/45) copolymer acrylic resin (manufactured by Kusumoto Chemical Co., Ltd., product name "B-722") to replace the polymethylmethacrylate with lactone ring unit Except for the acrylic resin of methyl acrylate, the first protective layer was formed in the same manner as in Example 1. The thickness of the first protective layer was 3 μm, the Tg was 39° C., and the iodine adsorption amount was 1.7% by weight. Except for using this first protective layer, a polarizing plate was produced in the same manner as in Example 1. After the obtained polarizer was subjected to the evaluation of fading, the result was bad ("overall fading"), so the evaluation of monomer transmittance and polarization degree was not performed. The results are listed in Table 1.

>Comparative Example 2> In addition to the use of methyl methacrylate/butyl methacrylate (mole ratio 35/65) copolymer acrylic resin (manufactured by Kusumoto Chemical Co., Ltd., product name "B-734") instead of the lactone ring unit Except for the acrylic resin of polymethyl methacrylate, the first protective layer was formed in the same manner as in Example 1. The thickness of the first protective layer was 3 μm, the Tg was 71° C., and the iodine adsorption amount was 12% by weight. Except for using this first protective layer, a polarizing plate was produced in the same manner as in Example 1. After the obtained polarizer was subjected to the evaluation of fading, the result was bad ("overall fading"), so the evaluation of monomer transmittance and polarization degree was not performed. The results are listed in Table 1.

>Comparative Example 3> Except for using UV-curable acrylic resin (manufactured by Kyoeisha Chemical Co., Ltd., product name "LIGHT ACRYLATE HPP-A", neopentyl glycol acrylate adduct of hydroxytrimethylacetate) The first protective layer (cured product) was formed in the same manner as in Example 1. Specifically, a composition obtained by blending 97% by weight of the acrylic resin and 3% by weight of a photopolymerization initiator (IRGACURE 907, manufactured by BASF Corporation) was applied to the polarizer, and a high pressure was used in a nitrogen environment. The mercury lamp irradiates ultraviolet rays with a cumulative light quantity of 300 mJ/cm ² to form a hardened layer (first protective layer). The thickness of the first protective layer was 3 μm, the Tg was 83° C., and the iodine adsorption amount was 6.6% by weight. Except for using this first protective layer, a polarizing plate was produced in the same manner as in Example 1. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are listed in Table 1.

>Comparative Example 4> In addition to using UV-curable acrylic resin (manufactured by Toagosei Co., Ltd., product name "ARONIX M-402"), dineopentylene pentaerythritol penta and hexaacrylate (pentaacrylate is 30%-40%)), according to In the same manner as in Example 1, the first protective layer (cured product) was formed. The method of forming the first protective layer is the same as that of Comparative Example 3. The thickness of the first protective layer is 3 μm. Except for using this first protective layer, a polarizing plate was produced in the same manner as in Example 1. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are listed in Table 1.

>Comparative Example 5> A first protective layer (cured product) was formed in the same manner as in Example 1, except that an ultraviolet curing epoxy resin (manufactured by DAICEL, product name "CELLOXIDE 2021P") was used. Specifically, a composition prepared by mixing 95% by weight of the epoxy resin and 5% by weight of a photopolymerization initiator (CPI-100P, manufactured by San-Apro) was applied to the polarizer and applied to the air Under the environment, a high-pressure mercury lamp was used to irradiate ultraviolet rays with a cumulative light amount of 500 mJ/cm ² to form a hardened layer (first protective layer). The thickness of the first protective layer is 3 μm, the Tg is 95° C., and the iodine adsorption capacity is 9% by weight. Except for using this first protective layer, a polarizing plate was produced in the same manner as in Example 1. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are listed in Table 1.

>Comparative Example 6> The first protective layer (cured product of the coating film) was formed in the same manner as in Example 1, except that an aqueous polyester resin (manufactured by Nippon Synthetic Chemical Co., Ltd., product name "POLYESTER WR905") was used. The thickness of the first protective layer was 3 μm, and the iodine adsorption amount was 12% by weight. Except for using this first protective layer, a polarizing plate was produced in the same manner as in Example 1. After the obtained polarizer was subjected to the evaluation of fading, the result was bad ("overall fading"), so the evaluation of monomer transmittance and polarization degree was not performed. The results are listed in Table 1.

>Comparative Example 7> The first protective layer (cured product of the coating film) was formed in the same manner as in Example 1, except that an aqueous polyurethane resin (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd., product name "SUPERFLEX SF210") was used. The thickness of the first protective layer was 3 μm, the Tg was 107°C, and the iodine adsorption amount was 19% by weight. Except for using this first protective layer, a polarizing plate was produced in the same manner as in Example 1. After the obtained polarizer was subjected to the evaluation of fading, the result was bad ("overall fading"), so the evaluation of monomer transmittance and polarization degree was not performed. The results are listed in Table 1.

>Comparative Example 8> Except that an aqueous polyurethane resin (manufactured by Unitika, product name "ARROW BASE SE1200") was used, the first protective layer (cured product of the coating film) was formed in the same manner as in Example 1. The thickness of the first protective layer is 3 μm, and the iodine adsorption capacity is 15% by weight. Except for using this first protective layer, a polarizing plate was produced in the same manner as in Example 1. After the obtained polarizer was subjected to the evaluation of fading, the result was bad ("overall fading"), so the evaluation of monomer transmittance and polarization degree was not performed. The results are listed in Table 1.

[Table 1]

>Evaluation> It can be seen from Table 1 that although the polarizing plate of the embodiment of the present invention is very thin, it can suppress the degradation of optical properties in a heated and humidified environment, and has excellent durability. At the same time, it does not shrink after the protective layer is formed, and is resistant Polarizing plate for practical application.

Industrial availability The polarizing plate of the present invention can be suitably used in image display devices. Examples of image display devices include portable information terminals (PDAs), smart phones, mobile phones, clocks, digital cameras, and portable game consoles; OA devices such as computer screens, notebook computers, and copiers; video Home appliances such as cameras, TVs, and microwave ovens; rear monitors, monitors for car navigation systems, car stereos, and other in-vehicle devices; display devices such as digital signage and information guide screens for commercial stores; security devices such as monitors ; Nursing medical equipment such as nursing monitors and medical monitors.

10: Polarizing parts 20: The first protective layer 30: The second protective layer 100: Polarizing plate 200: layered body G1~G4: guide roller R1~R6: conveyor roller

Fig. 1 is a schematic cross-sectional view of a polarizing plate according to an embodiment of the present invention. 2 is a schematic diagram showing an example of drying and shrinking treatment using a heating roller in the manufacturing method of a polarizing plate according to an embodiment of the present invention.

10: Polarizing parts

20: The first protective layer

30: The second protective layer

100: Polarizing plate

Claims (8)

A polarizing plate having a polarizing element, a first protective layer arranged on one side of the polarizing element, and a second protective layer arranged on the other side of the polarizing element; The first protective layer is composed of a cured product of a coating film of an organic solvent solution of a thermoplastic acrylic resin, and the glass transition temperature of the first protective layer is 95°C or higher; The second protective layer is composed of a resin film. The polarizing plate of claim 1, wherein the thickness of the first protective layer is 10 μm or less. The polarizing plate of claim 1 or 2, wherein the iodine adsorption amount of the first protective layer is 4.0% by weight or less. The polarizing plate according to any one of claims 1 to 3, wherein the aforementioned thermoplastic acrylic resin is selected from the group consisting of lactone ring unit, glutaric anhydride unit, glutaric anhydride unit, maleic anhydride unit and maleic acid At least one of the group consisting of imine units. The polarizing plate of any one of claims 1 to 4, wherein the in-plane phase difference Re(550) of the first protective layer is 0nm~10nm, and the thickness direction phase difference Rth(550) is -20nm~+10nm. According to the polarizing plate of any one of claims 1 to 5, wherein the first protective layer is arranged on the side of the display unit of the image display device, and the second protective layer is arranged on the opposite side of the display unit. Such as the polarizing plate of claim 6, which is arranged on the viewing side of the image display device. A polarizing plate coil is formed by winding the polarizing plate of any one of claims 1 to 7 into a roll.

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