WO2020209222A1 - Laminate for polarizer protection, and polarizing plate using said laminate - Google Patents

Abstract

Provided is a laminate which is for polarizer protection, makes it possible to obtain a polarizing plate having excellent thinness and durability, and suppresses cracks and/or breaks. The laminate for polarizer protection according to the present invention comprises: a first layer formed from the solidified product of a coating film from an organic solvent solution of a thermoplastic acrylic resin having a glass transition temperature of at least 95°C; and a second layer formed from the cured product of a curable resin and having a thickness of at least 1.0μm.

Description

A laminate for protecting a polarizer and a polarizing plate using the laminate

The present invention relates to a laminate for protecting a polarizer and a polarizing plate using the laminate.

In an image display device (for example, a liquid crystal display device or an organic EL display device), a polarizing plate is often arranged on at least one side of a display cell due to the image forming method. In recent years, image display devices have become thinner and more flexible, and along with this, there is a strong demand for thinner polarizing plates and their constituent films (for example, polarizing element protective films). However, the thinner the polarizing element protective film, the more remarkable the problem of durability that the optical characteristics of the polarizing plate deteriorate in a heating and humidifying environment. As a polarizer protective film capable of realizing a thin and highly durable polarizing plate, a polarizer protective film composed of a solidified coating film of a predetermined resin solution has been studied. Such technologies are in the early stages of development, leaving much room for consideration.

JP-A-2015-210474

The present invention has been made to solve the above-mentioned conventional problems, and its main purpose is to realize a thin and highly durable polarizing plate, and further, cracks and / or cracks are suppressed. It is an object of the present invention to provide a laminate for protecting a polarizer.

The laminate for protecting a polarizer of the present invention comprises a first layer composed of a solidified coating film of an organic solvent solution of a thermoplastic acrylic resin having a glass transition temperature of 95 ° C. or higher, and a cured product of a curable resin. It has a configured second layer, and the thickness of the second layer is 1.0 μm or more.
In one embodiment, the elastic modulus of the second layer is 50 MPa or more, and the elongation rate is 2% or more. In one embodiment, the pencil hardness of the second layer is 2H or more.
In one embodiment, the thickness of the first layer is 10 μm or less.
In one embodiment, the in-plane retardation Re (550) of the first layer is 0 nm to 10 nm, and the thickness direction retardation Rth (550) is −20 nm to +10 nm.
According to another aspect of the present invention, a polarizing plate is provided. The polarizing plate has a polarizing element and the above-mentioned laminate for protecting the polarizer arranged on one side of the polarizing element. The first layer of the laminate for protecting the polarizer is arranged so that the first layer is on the polarizer side.
In one embodiment, the polarizing plate is arranged on the viewing side of the image display device, and the second layer of the polarizing element protection laminate is arranged on the viewing side.

According to the present invention, the polarizer protective film has a first layer composed of a solidified coating film of an organic solvent solution of a thermoplastic acrylic resin having a glass transition temperature of 95 ° C. or higher, and a curable resin (typically). , Active energy ray-curable resin) can be laminated with a second layer composed of a cured product to realize a thin and durable polarizing plate, and further crack and / or crack. It is possible to realize a polarizer protective film (laminated body for protecting a polarizer) in which the amount is suppressed.

It is the schematic sectional drawing of the laminate for protecting a polarizer according to one Embodiment of this invention. It is the schematic sectional drawing of the polarizing plate by one Embodiment of this invention. It is a schematic diagram which shows an example of the drying shrinkage treatment using a heating roll in the manufacturing method of the polarizing plate by one Embodiment of this invention.

A. Laminater for protector protection A-1. Schematic FIG. 1 of a laminate for protecting a polarizer is a schematic cross-sectional view of a laminate for protecting a polarizer according to one embodiment of the present invention. The polarizing element protection laminate 100 of the illustrated example has a first layer 10 and a second layer 20. The first layer 10 is composed of a solidified coating film of an organic solvent solution of a thermoplastic acrylic resin having a glass transition temperature of 95 ° C. or higher. The second layer 20 is composed of a cured product of a curable resin. In the embodiment of the present invention, the thickness of the second layer is 1.0 μm or more. Hereinafter, the first layer and the second layer will be specifically described.

A-2. First Layer The first layer can typically function as a protective layer for the polarizer. As described above, the first layer is composed of a solidified coating film of an organic solvent solution of a thermoplastic acrylic resin (hereinafter, simply referred to as an acrylic resin). Hereinafter, the constituent components of the first layer will be specifically described, and then the characteristics of the first layer will be described.

A-2-1. Acrylic resin The acrylic resin has a glass transition temperature (Tg) of 95 ° C. or higher as described above. As a result, the Tg of the first layer becomes 95 ° C. or higher. When the Tg of the acrylic resin is 95 ° C. or higher, the polarizing plate containing the first layer obtained from such a resin tends to have excellent durability. The Tg of the acrylic resin is typically 100 ° C. or higher, preferably 110 ° C. or higher, more preferably 115 ° C. or higher, still more preferably 120 ° C. or higher, and particularly preferably 125 ° C. or higher. On the other hand, the Tg of the acrylic resin is preferably 300 ° C. or lower, more preferably 250 ° C. or lower, still more preferably 200 ° C. or lower, and particularly preferably 160 ° C. or lower. When the Tg of the acrylic resin is in such a range, the moldability can be excellent.

As the acrylic resin, any suitable acrylic resin can be adopted as long as it has Tg as described above. Acrylic resins typically contain an alkyl (meth) acrylate as a main component as a monomer unit (repeating unit). As used herein, the term "(meth) acrylic" means acrylic and / or methacrylic. Examples of the alkyl (meth) acrylate constituting the main skeleton of the acrylic resin include those having a linear or branched alkyl group having 1 to 18 carbon atoms. These can be used alone or in combination. Further, any suitable copolymerization monomer may be introduced into the acrylic resin by copolymerization. The repeating unit derived from alkyl (meth) acrylate is typically represented by the following general 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 an aliphatic or alicyclic hydrocarbon group having 1 to 6 carbon atoms which may be substituted. Shown. Examples of the substituent include halogens and hydroxyl groups. Specific examples of alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, and t-butyl (meth) acrylate. Butyl, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, benzyl (meth) acrylate, dicyclopentanyloxyethyl (meth) acrylate, (meth) acrylic Dicyclopentanyl acid, chloromethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2, (meth) acrylate 2, 3,4,5,6-pentahydroxyhexyl, (meth) acrylate 2,3,4,5-tetrahydroxypentyl, methyl 2- (hydroxymethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, 2 -Methyl (hydroxyethyl) acrylate can be mentioned. In the general formula (1), R ⁵ is preferably a hydrogen atom or a methyl group. Therefore, a particularly preferred alkyl (meth) acrylate is methyl acrylate or methyl methacrylate.

Acrylic resins may also include only a single alkyl (meth) acrylate units, even if R ⁴ and R ⁵ include a plurality of different alkyl (meth) acrylate unit in the above general formula (1) Good.

The content ratio of the alkyl (meth) acrylate unit in the acrylic resin is preferably 50 mol% to 98 mol%, more preferably 55 mol% to 98 mol%, still more preferably 60 mol% to 98 mol%, and particularly preferably. It is 65 mol% to 98 mol%, most preferably 70 mol% to 97 mol%. If the content ratio is less than 50 mol%, the effects expressed from the alkyl (meth) acrylate unit (for example, high heat resistance and high transparency) may not be sufficiently exhibited. If the content ratio is more than 98 mol%, the resin is brittle and easily cracked, high mechanical strength cannot be sufficiently exhibited, and productivity may be inferior.

The acrylic resin may have a repeating unit including a ring structure. Examples of the repeating unit including the ring structure include a lactone ring unit, a glutaric anhydride unit, a glutarimide unit, a maleic anhydride unit, and a maleimide (N-substituted maleimide) unit. Only one type of the repeating unit including the ring structure may be contained in the repeating unit of the acrylic resin, or two or more types may be contained.

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

In the general formula (2), R ¹ , R ² and R ³ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue may contain an oxygen atom. The acrylic resin may be contained only a single lactone ring units may be R ^1, R ² and R ³ in the general formula (2) is contains different lactone ring unit .. Acrylic resins having a lactone ring unit are described in, for example, Japanese Patent Application Laid-Open No. 2008-181078, and the description in this publication is incorporated herein by reference.

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

In the general formula (3), R ¹¹ and R ¹² independently represent hydrogen or an alkyl group having 1 to 8 carbon atoms, and R ¹³ is an alkyl group having 1 to 18 carbon atoms and 3 to 12 carbon atoms. The cycloalkyl group of the above, or an aryl group having 6 to 10 carbon atoms is shown. In the general formula (3), preferably R ¹¹ and R ¹² are independently hydrogen or methyl groups, and R ¹³ is a hydrogen, methyl group, butyl group or cyclohexyl group, respectively. More preferably, R ¹¹ is a methyl group, R ¹² is a hydrogen, and R ¹³ is a methyl group. The acrylic resin may contain only a single glutarimide unit, or may contain a plurality of glutarimide units having different R ¹¹ , R ¹² and R ¹³ in the above general formula (3). .. Acrylic resins having a glutarimide unit are, for example, JP-A-2006-309033, JP-A-2006-317560, JP-A-2006-328334, JP-A-2006-337491, JP-A-2006-337492. It is described in Japanese Patent Application Laid-Open No. 2006-337493 and Japanese Patent Application Laid-Open No. 2006-337569, and the description of the relevant publication is incorporated herein by reference. Note that the glutaric anhydride units, nitrogen atom substituted by R ¹³ in the general formula (3), except that the oxygen atom, the above description is applied about the glutarimide units.

The structure of the maleic anhydride unit and the maleimide (N-substituted maleimide) unit is specified from the name, so specific description thereof will be omitted.

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

The acrylic resin may contain a repeating unit other than the alkyl (meth) acrylate unit and the repeating unit including the ring structure. Examples of such a repeating unit include a repeating unit derived from a vinyl-based monomer copolymerizable with the monomer constituting the above unit (another vinyl-based monomer unit). Examples of other vinyl-based monomers include acrylic acid, methacrylic acid, crotonic acid, 2- (hydroxymethyl) acrylic acid, 2- (hydroxyethyl) acrylic acid, acrylonitrile, methacrylonitrile, etacrylonitrile, and allyl. Glycidyl ether, maleic anhydride, itaconic anhydride, N-methylmaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, aminoethyl acrylate, propylaminoethyl acrylate, dimethylaminoethyl methacrylate, ethylaminopropyl methacrylate, methacryl Cyclohexylaminoethyl acid, N-vinyldiethylamine, N-acetylvinylamine, allylamine, metaallylamine, N-methylallylamine, 2-isopropenyl-oxazoline, 2-vinyl-oxazoline, 2-acroyl-oxazoline, N-phenylmaleimide, Examples thereof include phenylaminoethyl methacrylate, styrene, α-methylstyrene, p-glycidylstyrene, p-aminostyrene, and 2-styryl-oxazoline. These may be used alone or in combination. The type, number, combination, content ratio, etc. of other vinyl-based monomer units can be appropriately set according to the purpose.

The weight average molecular weight of the acrylic resin is preferably 1,000,000 to 2000000, more preferably 5000 to 1,000,000, further preferably 10000 to 500000, particularly preferably 50,000 to 500000, and most preferably 60000 to 150,000. The weight average molecular weight can be determined by polystyrene conversion using, for example, a gel permeation chromatograph (GPC system, manufactured by Tosoh). Tetrahydrofuran can be used as the solvent.

The acrylic resin can be polymerized by any suitable polymerization method using the above-mentioned monomer units in an appropriate combination.

In the embodiment of the present invention, the acrylic resin and another resin may be used in combination. That is, the monomer component constituting the acrylic resin and the monomer component constituting the other resin may be copolymerized, and the copolymer may be used for molding the first layer described later; the acrylic resin and the other resin. The blend with may be subjected to the molding of the first layer. Examples of other resins include thermoplastic resins such as styrene resin, polyethylene, polypropylene, polyamide, polyphenylene sulfide, polyether ether ketone, polyester, polysulfone, polyphenylene oxide, polyacetal, polyimide, and polyetherimide. The type and blending amount of the resin to be used in combination can be appropriately set according to the purpose and the properties desired for the obtained film. For example, a styrene resin (preferably an acrylonitrile-styrene copolymer) can be used in combination as a retardation control agent.

When the acrylic resin and other resin are used in combination, the content of the acrylic resin in the blend of the acrylic resin and the other resin is preferably 50% by weight to 100% by weight, more preferably 60% by weight to 100% by weight. By weight%, more preferably 70% by weight to 100% by weight, particularly preferably 80% by weight to 100% by weight. If the content is less than 50% by weight, the high heat resistance and high transparency inherent in the acrylic resin may not be sufficiently reflected.

A-2-2. Structure and Characteristics of First Layer As described above, the first layer is composed of a solidified coating film of an organic solvent solution of an acrylic resin having a glass transition temperature of 95 ° C. or higher. With such a solidified coating film, the thickness can be significantly reduced as compared with the extrusion-molded film. The thickness of the first layer is, for example, 10 μm or less, preferably 7 μm or less, more preferably 5 μm or less, and further preferably 3 μm or less. The lower limit of the thickness of the first layer can be, for example, 1 μm. Further, although it is not theoretically clear, such a solidified coating film is compared with a cured product of a thermosetting resin or an active energy ray-curable resin (for example, an ultraviolet curable resin) at the time of film molding. Since the shrinkage is small and the residual monomer or the like is not contained, the deterioration of the film itself can be suppressed, and the adverse effect on the polarizing plate (polarizer) caused by the residual monomer or the like can be suppressed. Further, it has an advantage that it is excellent in humidification durability because it has low hygroscopicity and moisture permeability as compared with a solidified water-based coating film such as an aqueous solution or an aqueous dispersion. As a result, it is possible to realize a polarizing plate having excellent durability that can maintain the optical characteristics even in a heating and humidifying environment.

The Tg of the first layer is as described in Section A-2-1 above regarding the acrylic resin.

The first layer is preferably substantially optically isotropic. In the present 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. Say something. The in-plane retardation Re (550) is more preferably 0 nm to 5 nm, further preferably 0 nm to 3 nm, and particularly preferably 0 nm to 2 nm. The phase difference Rth (550) in the thickness direction is more preferably −5 nm to + 5 nm, further preferably -3 nm to + 3 nm, and particularly preferably -2 nm to + 2 nm. When Re (550) and Rth (550) of the first layer are in such a range, it is possible to prevent an adverse effect on the display characteristics when the polarizing plate including the first layer is applied to an image display device. Re (550) is an in-plane phase difference of the film measured with light having a wavelength of 550 nm at 23 ° C. Re (550) is calculated by the formula: Re (550) = (nx-ny) × d. Rth (550) is a phase difference in the thickness direction of the film measured with light having a wavelength of 550 nm at 23 ° C. Rth (550) is calculated by the formula: Rth (550) = (nx-nz) × d. Here, nx is the refractive index in the direction in which the in-plane refractive index is maximized (that is, the slow-phase axis direction), and ny is the in-plane direction orthogonal to the slow-phase axis (that is, the phase-advancing axis direction). It is the refractive index, nz is the refractive index in the thickness direction, and d is the thickness (nm) of the film.

The higher the light transmittance at 380 nm when the thickness of the first layer is 3 μm, the more preferable. Specifically, the light transmittance is preferably 85% or more, more preferably 88% or more, still more preferably 90% or more. When the light transmittance is in such a range, the desired transparency can be ensured. The light transmittance can be measured, for example, by a method according to ASTM-D-1003.

The lower the haze of the first layer, the more preferable. Specifically, the haze is preferably 5% or less, more preferably 3% or less, still more preferably 1.5% or less, and particularly preferably 1% or less. When the haze is 5% or less, a good clear feeling can be given to the film. Further, even when the polarizing plate on the visual side of the image display device is used, the displayed contents can be visually recognized satisfactorily.

The YI of the first layer at a thickness of 3 μm is preferably 1.27 or less, more preferably 1.25 or less, still more preferably 1.23 or less, and particularly preferably 1.20 or less. If the YI exceeds 1.3, the optical transparency may be insufficient. YI is obtained from, for example, the tristimulus values (X, Y, Z) of the color obtained by measurement using a high-speed integrating sphere type spectral transmittance measuring machine (trade name: DOT-3C: manufactured by Murakami Color Technology Research Institute). , Can be calculated by the following equation.
YI = [(1.28X-1.06Z) / Y] x 100

The b value (a measure of hue according to the hunter's color system) at a thickness of 3 μm of the first layer is preferably less than 1.5, more preferably 1.0 or less. When the b value is 1.5 or more, an undesired color may appear. For the b value, for example, a sample of the film constituting the first layer is cut into 3 cm squares, and a high-speed integrating sphere type spectral transmittance measuring machine (trade name: DOT-3C: manufactured by Murakami Color Technology Laboratory) is used. It can be obtained by measuring the hue and evaluating the hue according to the hunter's color system.

The first layer (solidified coating film) may contain any suitable additive depending on the purpose. Specific examples of the additives include ultraviolet absorbers; leveling agents; antioxidants such as hindered phenol-based, phosphorus-based and sulfur-based; stabilizers such as light-resistant stabilizers, weather-resistant stabilizers and heat stabilizers; glass fibers, Reinforcing materials such as carbon fibers; Near infrared absorbers; Flame retardants such as tris (dibromopropyl) phosphate, triallyl phosphate, antimony oxide; Antistatic agents such as anionic, cationic and nonionic surfactants; Inorganic pigments , Organic pigments, colorants such as dyes; organic fillers or inorganic fillers; resin modifiers; organic fillers and inorganic fillers; plasticizers; lubricants; antistatic agents; flame retardants; and the like. The additive may be added at the time of polymerization of the acrylic resin, or may be added to the solution at the time of film formation. The type, number, combination, amount of additive, etc. of the additive can be appropriately set according to the purpose.

An easy-adhesion layer may be formed on the side of the first layer opposite to the second layer (typically, the polarizer side when used for a polarizing plate). The easy-adhesion layer contains, for example, an aqueous polyurethane and an oxazoline-based cross-linking agent. By forming such an easy-adhesion layer, the adhesion between the first layer and the polarizer can be improved.

A-3. Second layer The second layer can typically function as a hard coat layer. By providing the second layer, cracks and / or cracks in the first layer can be maintained while maintaining the excellent characteristics of the first layer (a polarizing plate having excellent durability despite being extremely thin) can be realized. Cracking can be suppressed. As described above, the second layer is composed of a cured product of a curable resin. Although not theoretically clear, it is presumed that the three-dimensional crosslinked structure of the cured product suppresses cracking and / or cracking. The curable resin may be an active energy ray-curable resin or a thermosetting resin. It is preferably an active energy ray-curable resin. The active energy ray-curable resin has the advantages that the reaction can be easily controlled and the operability is excellent.

In the embodiment of the present invention, the thickness of the second layer is 1.0 μm or more, preferably 2.0 μm or more, and more preferably 2.5 μm or more as described above. By setting the thickness of the second layer to a predetermined value or more, desired rigidity can be obtained and cracks can be suppressed. The upper limit of the thickness of the second layer can be, for example, 5.0 μm. If the thickness of the second layer is too small, the curing reaction may be insufficient and layer formation may be difficult, and the rigidity of the formed layer may be insufficient. If the thickness of the second layer is too large, the flexibility may be insufficient and cracks may easily occur.

Preferably, the elastic modulus of the second layer is 50 MPa or more, and the elongation rate is 2% or more. By providing such a second layer, cracks and / or cracks in the first layer (as a result, the laminate for protecting the polarizer) can be remarkably suppressed. The elastic modulus of the second layer is more preferably 500 MPa or more, further preferably 1000 MPa or more, particularly preferably 2800 MPa or more, and particularly preferably 2900 MPa or more. The upper limit of the elastic modulus of the second layer can be, for example, 7000 MPa. If the elastic modulus of the second layer is too high, it becomes brittle and may not function as a protective layer. The elongation rate of the second layer is more preferably 5% or more, further preferably 10% or more, particularly preferably 20% or more, and particularly preferably 40% or more. The upper limit of the second layer can be, for example, 300%. When the elastic modulus of the second layer is large, the elongation rate can be small, and when the elastic modulus of the second layer is small, the elongation rate can be large. The elastic modulus and elongation can be measured according to, for example, JIS K 7161.

The pencil hardness of the second layer is preferably 2H or more, more preferably 3H or more, and further preferably 4H or more. The upper limit of the pencil hardness of the second layer can be, for example, 6H. When the pencil hardness of the second layer is in such a range, cracks and / or cracks of the first layer can be further suppressed. Pencil hardness can be measured according to, for example, JIS K 5400.

The second layer can be typically composed of any suitable active energy ray-curable resin that can satisfy the above characteristics. Examples of the active energy ray-curable resin include an ultraviolet curable resin and an electron beam-curable resin. UV curable resin is preferable. This is because the second layer can be efficiently formed by a simple processing operation. Examples of the ultraviolet curable resin include various resins such as polyester-based, acrylic-based, urethane-based, amide-based, silicone-based, and epoxy-based resins. In one embodiment, the UV curable resin is a urethane acrylate resin. The details of the ultraviolet curable resin are described, for example, in Japanese Patent No. 6199605 as an organic component of the hard coat layer. The description of this publication is incorporated herein by reference.

B. Polarizing plate The laminate for protecting a polarizer according to the above item A can be applied to a polarizing plate as a polarizing element protecting film. Therefore, embodiments of the present invention also include such polarizing plates. FIG. 2 is a schematic cross-sectional view of a polarizing plate according to one embodiment of the present invention. The polarizing plate 200 of the illustrated example has a polarizer 120 and a polarizing element protection laminate 100 arranged on one side of the polarizer 120. The polarizer 100 is a laminate for protecting a polarizer according to the embodiment of the present invention according to the above item A. The laminate 100 for protecting the polarizer is arranged so that the first layer 10 is on the side of the polarizer 120. When the polarizing plate 200 is applied to an image display device, the polarizing plate 200 is typically located on the visible side of the display cell. Be placed. In this case, typically, the second layer 20 of the polarizing element protection laminate 100 is arranged on the viewing side.

If necessary, another protective layer (not shown) may be provided on the opposite side of the polarizer 120 from the polarizer protecting laminate 100. Typically, the polarizing plate has an adhesive layer as the outermost layer on one side (typically, the side opposite to the polarizing element protection laminate 100 of the polarizer 120), and is bonded to the display cell. Is possible. If necessary, a surface protective film and / or a carrier film may be temporarily attached to the polarizing plate so as to reinforce and / or support the polarizing plate. When the polarizing plate contains a pressure-sensitive adhesive layer, a separator is temporarily attached to the surface of the pressure-sensitive adhesive layer so that the pressure-sensitive adhesive layer can be protected and the polarizing plate can be rolled until actual use.

The polarizing plate may be long or single-wafered. When the polarizing plate has a long shape, the polarizing plate can be wound preferably in a roll shape.

In the embodiment of the present invention, the thickness of the polarizer protective film can be made very thin by adopting the laminate for protecting the polarizer according to the above item A. Further, such a polarizer protective laminate can be formed directly on the polarizer (ie, without the intervention of an adhesive layer or an adhesive layer). As a result, the total thickness of the polarizing plate can be made extremely thin. The total thickness of the polarizing plate is, for example, 40 μm or less, preferably 30 μm or less, more preferably 25 μm or less, and further preferably 15 μm or less. The lower limit of the total thickness of the polarizing plate can be, for example, 10 μm.

Further, by adopting the laminate for protecting the polarizer according to the above item A, it is possible to realize a polarizing plate having excellent durability even though it is very thin. Specifically, it is possible to realize a polarizing plate in which deterioration of optical characteristics is suppressed even in a heating and humidifying environment. In the polarizing plate of the present invention, the amount of change ΔTs of the simple substance transmittance Ts and the amount of change ΔP of the degree of polarization P after being left in an environment of 85 ° C. and 85% RH for 48 hours are very small, respectively. The simple substance transmittance Ts can be measured using, for example, an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, product name "V7100"). The degree of polarization P is calculated by the following equation from the simple substance transmittance (Ts), the parallel transmittance (Tp) and the orthogonal transmittance (Tc) measured by using an ultraviolet-visible spectrophotometer.
Polarization degree (P) (%) = {(Tp-Tc) / (Tp + Tc)} ^1/2 × 100
The Ts, Tp, and Tc are Y values measured by the JIS Z 8701 2 degree field of view (C light source) and corrected for luminosity factor. Also, Ts and P are substantially properties of the polarizer. ΔTs and ΔP are calculated by the following formulas, respectively.
ΔTs (%) = Ts ₄₈ -Ts ₀
ΔP (%) = P ₄₈ −P ₀
Here, Ts ₀ is the single transmittance before leaving (initial), Ts ₄₈ is the single transmittance after leaving, P ₀ is the degree of polarization before leaving (initial), and P ₄₈ is after leaving. The degree of polarization. ΔTs is preferably 3.0% or less, more preferably 2.7% or less, still more preferably 2.4% or less. ΔP is preferably −0.05% to 0%, more preferably −0.03% to 0%, and even more preferably −0.01% to 0%.

Since the polarizing plate of the present invention is extremely thin as described above, it can be suitably applied to a flexible image display device. More preferably, the image display device has a curved shape (substantially a curved display screen) and / or is bendable or bendable. Specific examples of the image display device include a liquid crystal display device and an electroluminescence (EL) display device (for example, an organic EL display device and an inorganic EL display device). Needless to say, the above description does not prevent the polarizing plate of the present invention from being applied to a normal image display device.

B-1. Polarizer As the polarizer, any suitable polarizer can be adopted. The polarizer can typically be made using a laminate of two or more layers. The method for manufacturing the polarizer will be described later in Section B-2 as the method for manufacturing the polarizing plate.

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

The boric acid content of the polarizer is preferably 10% by weight or more, more preferably 13% by weight to 25% by weight. When the boric acid content of the polarizer is in such a range, the ease of curl adjustment at the time of bonding is well maintained due to the synergistic effect with the iodine content described later, and the curl at the time of heating is maintained. It is possible to improve the appearance durability at the time of heating while satisfactorily suppressing the above. The boric acid content can be calculated as the amount of boric acid contained in the polarizer per unit weight, for example, by using the following formula from the neutralization method.

The iodine content of the polarizer is preferably 2% by weight or more, more preferably 2% by weight to 10% by weight. When the iodine content of the polarizer is in such a range, the ease of curl adjustment at the time of bonding is well maintained due to the synergistic effect with the above boric acid content, and the curl at the time of heating is maintained. It is possible to improve the appearance durability at the time of heating while satisfactorily suppressing the above. As used herein, the term "iodine content" means the amount of all iodine contained in the polarizer (PVA-based resin film). More specifically, iodine during polarizers iodide ion (I ^-), molecular iodine (I _2), polyiodine ion _{^{(I 3 -, I 5 -}} ) where present in the form of such, herein Iodine content means the amount of iodine that includes all of these forms. The iodine content can be calculated, for example, by the calibration curve method of fluorescent X-ray analysis. The polyiodine ion exists in a state in which a PVA-iodine complex is formed in the polarizer. By forming such a complex, absorption dichroism can be exhibited in the wavelength range of visible light. Specifically, a complex of PVA and tri-iodide ion (PVA · _{I 3} ^-) has a light absorption peak around 470 nm, a complex of PVA and five iodide ion (PVA · _{I 5} ^-) is 600nm near Has an absorptive peak. As a result, polyiodine ions can absorb light in a wide range of visible light, depending on their morphology. On the other hand, iodine ion (I ⁻ ) has an absorption peak near 230 nm and is not substantially involved in the absorption of visible light. Therefore, polyiodine ions present in the form of a complex with PVA may be mainly involved in the absorption performance of the polarizer.

The polarizer preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The simple substance transmittance Ts of the polarizer is preferably 40% to 48%, more preferably 41% to 46%. The degree of polarization P of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and further preferably 99.9% or more.

B-2. Method for manufacturing polarizing plate B-2-1. Method for producing a polarizer The method for producing a polarizer according to the above item B-1 is a polyvinyl alcohol containing a halide and a polyvinyl alcohol-based resin (PVA-based resin) on one side of a long thermoplastic resin base material. By forming a based resin layer (PVA-based resin layer) to form a laminated body, and by heating the laminated body while carrying it in the longitudinal direction, an aerial auxiliary stretching treatment, a dyeing treatment, and an underwater stretching treatment. The drying shrinkage treatment of shrinking by 2% or more in the width direction and the drying shrinkage treatment are performed in this order. The content of the halide in the PVA-based resin layer is preferably 5 parts by weight to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin. The drying shrinkage treatment is preferably carried out using a heating roll, and the temperature of the heating roll is preferably 60 ° C. to 120 ° C. According to such a manufacturing method, the above-mentioned polarizer can be obtained. In particular, by preparing a laminate containing a PVA-based resin layer containing a halide, stretching the laminate to multi-step stretching including aerial auxiliary stretching and underwater stretching, and heating the stretched laminate with a heating roll. It is possible to obtain a polarizer having excellent optical characteristics (typically, simple substance transmittance and degree of polarization) and suppressing variation in optical characteristics. Specifically, by using a heating roll in the drying shrinkage treatment step, the laminated body can be uniformly shrunk over the entire laminated body while being conveyed. As a result, not only can the optical characteristics of the obtained polarizer be enhanced, but also a polarizer having excellent optical characteristics can be stably produced, and variations in the optical characteristics of the polarizer (particularly, single transmittance) can be suppressed. can do. Hereinafter, the halide and the drying shrinkage treatment will be described. Details of manufacturing methods other than these are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580. The entire description of the publication is incorporated herein by reference.

B-2-1-1. Halide A PVA-based resin layer containing a halide and a PVA-based resin can be formed by applying a coating liquid containing a halide and a PVA-based resin onto a thermoplastic resin base material and drying the coating film. The coating liquid is typically a solution in which the halide and the PVA-based resin are dissolved in a solvent. Examples of the solvent include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylpropane, and amines such as ethylenediamine and diethylenetriamine. These can be used alone or in combination of two or more. Of these, water is preferred. The PVA-based resin concentration of the solution is preferably 3 parts by weight to 20 parts by weight with respect to 100 parts by weight of the solvent. With such a resin concentration, a uniform coating film that adheres to the thermoplastic resin base material can be formed.

As the halide, any suitable halide can be adopted. For example, iodide and sodium chloride. Examples of iodides include potassium iodide, sodium iodide, and lithium iodide. Of these, potassium iodide is preferred.

The amount of the 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 with respect to 100 parts by weight of the PVA-based resin. If the amount of the halide is too large, the halide may bleed out and the finally obtained polarizer may become cloudy.

Generally, when the PVA-based resin layer is stretched, the orientation of the polyvinyl alcohol molecules in the PVA-based resin is increased. However, when the stretched PVA-based resin layer is immersed in a liquid containing water, the polyvinyl alcohol molecules become more oriented. The orientation may be disturbed and the orientation may decrease. In particular, when the laminate of the thermoplastic resin base material and the PVA-based resin layer is stretched in boric acid water, the laminate is stretched in boric acid water at a relatively high temperature in order to stabilize the stretching of the thermoplastic resin base material. In the case of stretching, the tendency of the degree of orientation to decrease is remarkable. For example, while stretching a PVA film alone in boric acid water is generally performed at 60 ° C., stretching of a laminate of A-PET (thermoplastic resin base material) and a PVA-based resin layer is performed. It is carried out at a high temperature of about 70 ° C., and in this case, the orientation of PVA at the initial stage of stretching may decrease before it is increased by stretching in water. On the other hand, a laminate of a PVA-based resin layer containing a halide and a thermoplastic resin base material is prepared, and the laminate is stretched at a high temperature (auxiliary stretching) in air before being stretched in boric acid water. , Crystallization of the PVA-based resin in the PVA-based resin layer of the laminated body after the auxiliary stretching can be promoted. As a result, when the PVA-based resin layer is immersed in a liquid, the disorder of the orientation of the polyvinyl alcohol molecules and the decrease in the orientation can be suppressed as compared with the case where the PVA-based resin layer does not contain a halide. As a result, the optical characteristics of the polarizer obtained through a treatment step of immersing the laminate in a liquid, such as a dyeing treatment and a stretching treatment in water, can be improved.

B-2-1-2. Dry shrinkage treatment The dry shrinkage treatment may be carried out by heating the entire zone by zone heating, or by heating the transport roll (using a so-called heating roll) (heating roll drying method). Preferably, both are used. By drying using a heating roll, it is possible to efficiently suppress the heating curl of the laminate and produce a polarizer having an excellent appearance. Specifically, by drying the laminate along the heating roll, the crystallization of the thermoplastic resin base material can be efficiently promoted and the crystallinity can be increased, which is relatively low. Even at the drying temperature, the crystallinity of the thermoplastic resin base material can be satisfactorily increased. As a result, the rigidity of the thermoplastic resin base material is increased so that it can withstand the shrinkage of the PVA-based resin layer due to drying, and curling is suppressed. Further, by using the heating roll, the laminated body can be dried while being maintained in a flat state, so that not only curling but also wrinkles can be suppressed. At this time, the laminated body can be improved in optical characteristics by shrinking in the width direction by a drying shrinkage treatment. This is because the orientation of PVA and the PVA / iodine complex can be effectively enhanced. The shrinkage ratio in the width direction of the laminate by the dry shrinkage treatment is preferably 2% to 10%, more preferably 2% to 8%, and particularly preferably 4% to 6%. By using the heating roll, the laminated body can be continuously contracted in the width direction while being conveyed, and high productivity can be realized.

FIG. 3 is a schematic view showing an example of the drying shrinkage treatment. In the drying shrinkage treatment, the laminate 200 is dried while being transported by the transport rolls R1 to R6 heated to a predetermined temperature and the guide rolls G1 to G4. In the illustrated example, the transport rolls R1 to R6 are arranged so as to alternately and continuously heat the surface of the PVA resin layer and the surface of the thermoplastic resin base material. For example, one surface of the laminate 200 (for example, thermoplastic) is arranged. The transport rolls R1 to R6 may be arranged so as to continuously heat only the resin base material surface).

Drying conditions can be controlled by adjusting the heating temperature of the transport roll (temperature of the heating roll), the number of heating rolls, the contact time with the heating roll, and the like. The temperature of the heating roll is preferably 60 ° C. to 120 ° C., more preferably 65 ° C. to 100 ° C., and particularly preferably 70 ° C. to 80 ° C. The crystallinity of the thermoplastic resin can be satisfactorily increased, curling can be satisfactorily suppressed, and an optical laminate having extremely excellent durability can be produced. The temperature of the heating roll can be measured with a contact thermometer. In the illustrated example, six transport rolls are provided, but there is no particular limitation as long as there are a plurality of transport rolls. The number of transport rolls is usually 2 to 40, preferably 4 to 30. The contact time (total contact time) between the laminate and the heating roll is preferably 1 second to 300 seconds, more preferably 1 to 20 seconds, and further preferably 1 to 10 seconds.

The heating roll may be provided in a heating furnace (for example, an oven) or in a normal production line (in a room temperature environment). Preferably, it is provided in a heating furnace provided with a blowing means. By using both drying with a heating roll and hot air drying together, a steep temperature change between the heating rolls can be suppressed, and shrinkage in the width direction can be easily controlled. The temperature of hot air drying is preferably 30 ° C to 100 ° C. The hot air drying time is preferably 1 second to 300 seconds. The wind speed of hot air is preferably about 10 m / s to 30 m / s. The wind speed is the wind speed in the heating furnace and can be measured by a mini-vane type digital anemometer.

Preferably, a washing treatment is performed after the underwater stretching treatment and before the drying shrinkage treatment. The cleaning treatment is typically performed by immersing a PVA-based resin layer in an aqueous potassium iodide solution.

In this way, a laminate of a thermoplastic resin base material / polarizer can be obtained.

B-2-2. Method for manufacturing polarizing plate A coating film is formed by applying an organic solvent solution of an acrylic resin to the surface of the laminate obtained in Section B-2-1 above, and the coating film is solidified to protect a polarizer. The first layer of the laminate is formed.

The acrylic resin is as described in Section A-2-1 above.

As the organic solvent, any suitable organic solvent capable of dissolving or uniformly dispersing the acrylic resin can be used. Specific examples of the organic solvent 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 with respect to 100 parts by weight of the solvent. With such a resin concentration, a uniform coating film in close contact with the polarizer can be formed.

The solution may be applied to any suitable substrate or to a polarizer. When the solution is applied to the base material, the solidified material of the coating film formed on the base material is transferred to the polarizer. When the solution is applied to the polarizer, the first layer is directly formed on the polarizer by drying (solidifying) the coating film. Preferably, the solution is applied to the polarizer and a first layer is formed directly on the polarizer. With such a configuration, the adhesive layer or the adhesive layer required for transfer can be omitted, so that the polarizing plate can be further thinned. Any suitable method can be adopted as the method for applying 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.).

The first layer can be formed by drying (solidifying) the coating film of the solution. The drying temperature is preferably 100 ° C. or lower, more preferably 50 ° C. to 70 ° C. When the drying temperature is in such a range, it is possible to prevent an adverse effect on the polarizer. The drying time can vary depending on the drying temperature. The drying time can be, for example, 1 to 10 minutes.

Next, the second layer is formed by applying an active energy ray-curable resin to the surface of the first layer and curing it. The method for applying the active energy ray-curable resin is as described above for the first layer. The active energy ray-curable resin (resin composition) may contain a leveling agent. Examples of the leveling agent include a fluorine-based leveling agent and a silicone-based leveling agent. Further, the active energy ray-curable resin (resin composition) may contain an additive. Examples of the additive include fine particles, fillers, dispersants, plasticizers, ultraviolet absorbers, surfactants, antioxidants, thixotropy agents and the like. The curing conditions can be appropriately set according to the type of the active energy ray-curable resin.

In this way, the laminate for protecting the polarizer is formed. In the above description, the embodiment in which the laminate for protecting the polarizer is directly formed on the polarizer has been described, but the laminate for protecting the polarizer may be transferred to the polarizer. For example, a second layer and a first layer are formed in this order on an arbitrary suitable base material to prepare a laminated body having a base material / polarizer protection laminate (second layer / first layer). The laminate for protecting the polarizer may be transferred from this laminate to the polarizer.

As a result of the above, it is possible to obtain a laminate having a structure of a thermoplastic resin base material / a polarizer / a laminate for protecting a polarizer. By peeling the thermoplastic resin base material from this laminate, a polarizing plate 200 having a polarizing element 120 and a polarizing element protection laminate 100 as shown in FIG. 2 can be obtained. Alternatively, a resin film forming another protective layer is attached to the polarizing element surface of the thermoplastic resin base material / polarizer laminate, then the thermoplastic resin base material is peeled off, and the polarizer protective laminate is laminated on the peeled surface. You may form a body. In this case, a polarizing plate having another protective layer can be obtained.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. The measurement method of each characteristic is as follows. Unless otherwise specified, "parts" and "%" in the examples are based on weight.

(1) Glass transition temperature Tg
The film constituting the first layer of the polarizing element protection laminate used in Examples and Comparative Examples was measured using a heated TMA analyzer (manufactured by Hitachi High-Tech Science Corporation, product name “TMA-7100C”). The measurement conditions were as follows: load 2 g; nitrogen atmosphere (200 ml / min); temperature rise from 25 ° C to 150 ° C, held at 150 ° C for 5 minutes, then lowered to 25 ° C and again to 150 ° C. Heat up and hold at 150 ° C. for 5 minutes; temperature rise rate 2 ° C./min.
(2) Elastic modulus and elongation The films constituting the second layer of the polarizer protective laminate used in Examples and Comparative Examples were measured in accordance with JIS K 7161 and JIS K 7113.
(3) Cracks From the polarizing plates obtained in Examples and Comparative Examples, test pieces (50 mm × 50 mm) having two sides facing each other in the direction orthogonal to the absorption axis direction of the polarizer and the absorption axis direction were cut out. The test piece was attached to a glass plate with an adhesive so that the laminate for protecting the polarizer or the protective layer was on the outside to form a test sample, and the test sample was left in an oven at 85 ° C. and 85% RH for 48 hours. The state of the laminate for protecting the polarizer or the protective layer on the polarizing plate after heating and humidifying was examined visually or microscopically, and evaluated according to the following criteria.
〇: No cracks were observed Δ: Some cracks were observed ×: Cracks were prominent and cracks were also observed (4) Single transmittance and degree of polarization Polarized light obtained in Examples and Comparative Examples For the plate, the single transmittance (Ts), parallel transmittance (Tp) and orthogonal transmittance (Tc) were measured using an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, product name "V7100"), and the degree of polarization was measured. (P) was calculated by the following equation.
Polarization degree (P) (%) = {(Tp-Tc) / (Tp + Tc)} ^1/2 × 100
The Ts, Tp, and Tc are Y values measured by the JIS Z 8701 2 degree field of view (C light source) and corrected for luminosity factor. Also, Ts and P are substantially properties of the polarizer.
Next, the polarizing plate was left in an oven at 85 ° C. and 85% RH for 48 hours to heat and humidify (heating test), and from the simple substance transmittance Ts ₀ before the heating test and the simple substance transmittance Ts ₄₈ after the heating test, The amount of change in single transmittance ΔTs was determined using 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 degree of polarization ΔP was determined using the following formula.
ΔP (%) = P ₄₈ −P ₀
The heating test was carried out by preparing a test sample in the same manner as in the case of the above-mentioned crack.

<Example 1>
1. 1. Fabrication of Laminate of Polarizer / Resin Base Material As a resin base material, an amorphous isophthal copolymer polyethylene terephthalate film (thickness: 100 μm) having a long shape, a water absorption rate of 0.75%, and a Tg of about 75 ° C. Was used. One side of the resin base material was corona-treated.
100 weight of PVA-based resin in which polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosefimer Z410") are mixed at a ratio of 9: 1. 13 parts by weight of potassium iodide was added to the part to prepare a PVA aqueous solution (coating liquid).
A PVA-based resin layer having a thickness of 13 μm was formed by applying the above PVA aqueous solution to the corona-treated surface of the resin base material and drying at 60 ° C. to prepare a laminate.
The obtained laminate was uniaxially stretched at the free end 2.4 times in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds in an oven at 130 ° C. (aerial auxiliary stretching treatment).
Next, the laminate was immersed in an insolubilizing bath at a liquid temperature of 40 ° C. (an aqueous boric acid solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds (insolubilization treatment).
Next, in a dyeing bath having a liquid temperature of 30 ° C. (an aqueous iodine solution obtained by mixing iodine and potassium iodide in a weight ratio of 1: 7 with respect to 100 parts by weight of water), the polarizer finally obtained Immersion was carried out for 60 seconds while adjusting the concentration so that the simple substance transmittance (Ts) was 41.5% ± 0.1% (staining treatment).
Next, it was immersed in a cross-linked bath at a liquid temperature of 40 ° C. (an aqueous boric acid solution obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds. (Crossing treatment).
Then, while immersing the laminate in a boric acid aqueous solution (boric acid concentration 4.0% by weight, potassium iodide 5.0% by weight) at a liquid temperature of 62 ° C., the rolls having different peripheral speeds are subjected to the longitudinal direction (longitudinal direction). ) Was uniaxially stretched so that the total stretching ratio was 5.5 times (underwater stretching treatment).
Then, the laminate was immersed in a washing bath at a liquid temperature of 20 ° C. (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) (cleaning treatment).
Then, while drying in an oven kept at 90 ° C., it was brought into contact with a heating roll made of SUS whose surface temperature was kept at 75 ° C. for about 2 seconds (dry shrinkage treatment). The shrinkage rate in the width direction of the laminated body by the dry shrinkage treatment was 5.2%.
In this way, a polarizer having a thickness of 5 μm was formed on the resin substrate to prepare a laminate of the polarizer / resin substrate.

2. Fabrication of Polarizing Plate A cycloolefin-based film (Zeon Corporation, ZT-12, thickness 23 μm) as a film constituting another protective layer is applied to the surface of the polarizing element obtained above via an ultraviolet curable adhesive. And pasted together. Specifically, the curable adhesive was coated so as to have a total thickness of 1.0 μm, and bonded using a roll machine. Then, a UV ray was irradiated from the film side to cure the adhesive. Then, the resin base material was peeled off to obtain a polarizing plate having another protective layer (ZT-12) / polarizer configuration.

20 parts of an acrylic resin having a methyl methacrylate unit (manufactured by Kusumoto Kasei Co., Ltd., product name "B728") was dissolved in 80 parts of methyl ethyl ketone to obtain an acrylic resin solution (20%). This acrylic resin solution is applied to the surface of the polarizer of the polarizing plate obtained above using a wire bar, and the coating film is dried at 60 ° C. for 5 minutes to form a polarizing element formed as a solidified product of the coating film. The first layer of the protective laminate was formed. The thickness of the first layer was 2 μm, and the Tg was 116 ° C. Further, the composition for forming the second layer was applied to the surface of the first layer. The composition for forming the second layer is 100 parts of an ultraviolet curable urethane acrylate resin for a hard coat layer (manufactured by DIC, product name "Unidic 17-806"), a leveling agent (manufactured by DIC, product name "GRANDIC PC4100"). ) 0.01 part and 3 parts of a photopolymerization initiator (manufactured by IGM Resins B.V., product name "Omnirad 907"). The coating film is dried at 90 ° C. for 1 minute, and then irradiated with ultraviolet rays having an integrated light intensity of 200 mW / cm ^{2 with} a high-pressure mercury lamp to form a cured product of the coating film. Was formed. The thickness of the second layer was 3 μm, the elastic modulus was 5000 MPa, and the elongation rate was larger than 3%. In this way, a polarizing plate having a structure of a laminate for protecting a polarizer (second layer / first layer) / a polarizer / another protective layer (ZT-12) was obtained. The obtained polarizing plate was used for the evaluation of (3) and (4) above. The results are shown in Table 1.

<Example 2>
Same as Example 1 except that the second layer was formed by using "Unidic ELS-888" (manufactured by DIC) instead of "Unidic 17-806" as the ultraviolet curable urethane acrylate resin for the hard coat layer. Then, a polarizing plate having a structure of a laminate for protecting a polarizer (second layer / first layer) / a polarizer / another protective layer (ZT-12) was obtained. The thickness of the second layer was 3 μm, the elastic modulus was 3000 MPa, and the elongation rate was 40%.
The obtained polarizing plate was used for the evaluation of (3) and (4) above. The results are shown in Table 1.

<Example 3>
Same as Example 1 except that the second layer was formed by using "Unidic V-4221" (manufactured by DIC) instead of "Unidic 17-806" as the ultraviolet curable urethane acrylate resin for the hard coat layer. Then, a polarizing plate having a structure of a laminate for protecting a polarizer (second layer / first layer) / a polarizer / another protective layer (ZT-12) was obtained. The thickness of the second layer was 3 μm, the elastic modulus was 60 MPa, and the elongation rate was 200%.

<Example 4>
For protecting the polarizer in the same manner as in Example 1 except that the first layer was formed by using a copolymer of methyl acrylate / butyl acrylate (molar ratio 80/20) instead of "B728" as the acrylic resin. A polarizing plate having a structure of a laminate (second layer / first layer) / polarizer / another protective layer (ZT-12) was obtained. The thickness of the first layer was 2 μm, and the Tg was 95 ° C.
The obtained polarizing plate was used for the evaluation of (3) and (4) above. The results are shown in Table 1.

<Example 5>
Same as Example 4 except that the second layer was formed by using "Unidic ELS-888" (manufactured by DIC) instead of "Unidic 17-806" as the ultraviolet curable urethane acrylate resin for the hard coat layer. Then, a polarizing plate having a structure of a laminate for protecting a polarizer (second layer / first layer) / a polarizer / another protective layer (ZT-12) was obtained. The thickness of the second layer was 3 μm, the elastic modulus was 3000 MPa, and the elongation rate was 40%.
The obtained polarizing plate was used for the evaluation of (3) and (4) above. The results are shown in Table 1.

<Example 6>
Same as Example 4 except that the second layer was formed by using "Unidic V-4221" (manufactured by DIC) instead of "Unidic 17-806" as the ultraviolet curable urethane acrylate resin for the hard coat layer. Then, a polarizing plate having a structure of a laminate for protecting a polarizer (second layer / first layer) / a polarizer / another protective layer (ZT-12) was obtained. The thickness of the second layer was 3 μm, the elastic modulus was 60 MPa, and the elongation rate was 200%.
The obtained polarizing plate was used for the evaluation of (3) and (4) above. The results are shown in Table 1.

<Comparative example 1>
In the same manner as in Example 1 except that the first layer was formed by using "B734" (manufactured by Kusumoto Kasei Co., Ltd.) instead of "B728" as the acrylic resin, the laminate for protecting the polarizer (second layer / A polarizing plate having a structure of (first layer) / polarizer / another protective layer (ZT-12) was obtained. The thickness of the first layer was 2 μm, and the Tg was 71 ° C.
The obtained polarizing plate was used for the evaluation of (3) and (4) above. The results are shown in Table 1.

<Comparative example 2>
Similar to Comparative Example 1 except that the second layer was formed by using "Unidic ELS-888" (manufactured by DIC) instead of "Unidic 17-806" as the ultraviolet curable urethane acrylate resin for the hard coat layer. Then, a polarizing plate having a structure of a laminate for protecting a polarizer (second layer / first layer) / a polarizer / another protective layer (ZT-12) was obtained. The thickness of the second layer was 3 μm, the elastic modulus was 3000 MPa, and the elongation rate was 40%.
The obtained polarizing plate was used for the evaluation of (3) and (4) above. The results are shown in Table 1.

<Comparative example 3>
Similar to Comparative Example 1 except that the second layer was formed by using "Unidic V-4221" (manufactured by DIC) instead of "Unidic 17-806" as the ultraviolet curable urethane acrylate resin for the hard coat layer. Then, a polarizing plate having a structure of a laminate for protecting a polarizer (second layer / first layer) / a polarizer / another protective layer (ZT-12) was obtained. The thickness of the second layer was 3 μm, the elastic modulus was 60 MPa, and the elongation rate was 200%.
The obtained polarizing plate was used for the evaluation of (3) and (4) above. The results are shown in Table 1.

<Comparative example 4>
A laminate for protecting a polarizer (second layer / A polarizing plate having a structure of (first layer) / polarizer / another protective layer (ZT-12) was obtained. The thickness of the first layer was 2 μm, and the Tg was 39 ° C.
The obtained polarizing plate was used for the evaluation of (3) and (4) above. The results are shown in Table 1.

<Comparative example 5>
Similar to Comparative Example 4 except that the second layer was formed by using "Unidic ELS-888" (manufactured by DIC) instead of "Unidic 17-806" as the ultraviolet curable urethane acrylate resin for the hard coat layer. Then, a polarizing plate having a structure of a laminate for protecting a polarizer (second layer / first layer) / a polarizer / another protective layer (ZT-12) was obtained. The thickness of the second layer was 3 μm, the elastic modulus was 3000 MPa, and the elongation rate was 40%.
The obtained polarizing plate was used for the evaluation of (3) and (4) above. The results are shown in Table 1.

<Comparative Example 6>
Similar to Comparative Example 4 except that the second layer was formed by using "Unidic V-4221" (manufactured by DIC) instead of "Unidic 17-806" as the ultraviolet curable urethane acrylate resin for the hard coat layer. Then, a polarizing plate having a structure of a laminate for protecting a polarizer (second layer / first layer) / a polarizer / another protective layer (ZT-12) was obtained. The thickness of the second layer was 3 μm, the elastic modulus was 60 MPa, and the elongation rate was 200%.
The obtained polarizing plate was used for the evaluation of (3) and (4) above. The results are shown in Table 1.

<Comparative Example 7>
A polarizing plate was produced in the same manner as in Example 1 except that the second layer was not formed (that is, the protective layer was formed only by the first layer). The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Comparative Example 8>
A polarizing plate was produced in the same manner as in Example 4 except that the second layer was not formed (that is, the protective layer was formed only by the first layer). The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Comparative Example 9>
A polarizing plate was produced in the same manner as in Comparative Example 1 except that the second layer was not formed (that is, the protective layer was formed only by the first layer). The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Comparative Example 10>
A polarizing plate was produced in the same manner as in Comparative Example 4 except that the second layer was not formed (that is, the protective layer was formed only by the first layer). The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Evaluation>
As is clear from Table 1, the laminate for protecting the polarizer of the embodiment of the present invention is suppressed from cracking even in a heating and humidifying environment. By using such a laminate for protecting a polarizer, it is possible to realize a polarizing plate having excellent durability by suppressing deterioration of optical characteristics even in a heating and humidifying environment, even though it is very thin.

The polarizing plate of the present invention is suitably used for an image display device. Examples of image display devices include portable devices such as mobile information terminals (PDAs), smartphones, mobile phones, clocks, digital cameras, and portable game machines; OA devices such as personal computer monitors, laptop computers, and copiers; video cameras and televisions. , Household electrical equipment such as microwave ovens; In-vehicle equipment such as back monitors, car navigation system monitors, car audio; Exhibition equipment such as digital signage and commercial store information monitors; Security equipment such as monitoring monitors; Nursing care Nursing care / medical equipment such as monitors for medical use and monitors for medical use;

10 1st layer 20 2nd layer 100 Polarizer protection laminate 120 Polarizer 200 Polarizing plate

Claims (7)

1. It has a first layer composed of a solidified coating film of an organic solvent solution of a thermoplastic acrylic resin having a glass transition temperature of 95 ° C. or higher, and a second layer composed of a cured product of a curable resin. ,
   The thickness of the second layer is 1.0 μm or more.
   Laminated body for protector protection.
2. The laminate for protecting a polarizer according to claim 1, wherein the elastic modulus of the second layer is 50 MPa or more and the elongation rate is 2% or more.
3. The laminate for protecting a polarizer according to claim 2, wherein the pencil hardness of the second layer is 2H or more.
4. The laminate for protecting a polarizer according to any one of claims 1 to 3, wherein the thickness of the first layer is 10 μm or less.
5. The polarizer according to any one of claims 1 to 4, wherein the in-plane retardation Re (550) of the first layer is 0 nm to 10 nm, and the retardation Rth (550) in the thickness direction is −20 nm to +10 nm. Protective laminate.
6. It has a polarizer and a laminate for protecting a polarizer according to any one of claims 1 to 5, which is arranged on one side of the polarizer.
   The laminate for protecting the polarizer is arranged so that the first layer is on the polarizer side.
   Polarizer.
7. The polarizing plate according to claim 6, wherein the second layer of the polarizing element protection laminate is arranged on the visual side of the image display device.
   

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