Polarizing plate with phase difference layer and image display device

Abstract

Provided is a retardation-layer-equipped polarizing plate in which traces of damage are suppressed. This retardation-layer-equipped polarizing plate has: a polarization plate 10 including a polarizer 11 and a protective layer 12 disposed at least on a viewing side of the polarizer 11; and a retardation layer 30 that is affixed, via a pressure-sensitive adhesive layer 20, to the side of the polarization plate 10 opposite the viewing side. The thickness of the polarizer is 12 μm or less, and the depth of the pressure-sensitive adhesive layer remaining when a load of 3N is loaded is 11 μm or less.

Description

[Technical field]

[0001] The present invention relates to a retardation layer-attached polarizing plate and an image display device. [Background technology]

[0002] In image display devices (e.g., liquid crystal display devices, organic EL display devices, quantum dot display devices), a polarizing plate is often arranged on at least one side of an image display cell due to its image formation method. A retardation film may be laminated on the image display cell side of the polarizing plate arranged on the viewing side of the image display device for the purpose of preventing external light reflection and background reflection, improving color tone, etc. (polarizing plate with retardation layer). As image display devices become thinner, there is a strong demand for thinner polarizing plates with retardation layers. In order to meet such demands, efforts are being made to make polarizers thinner. However, polarizing plates with retardation layers, including thin polarizers, are difficult to handle, and damage marks (typically, many fine cracks in a certain area) may occur due to external forces caused by handling errors by workers, for example. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-200445 A Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention has been made to solve the above problems, and a main object of the present invention is to provide a polarizing plate with a retardation layer in which damage marks are suppressed. [Means for solving the problem]

[0005] The polarizing plate with a retardation layer according to the embodiment of the present invention includes a polarizing plate including a polarizer and a protective layer on at least the viewing side of the polarizer, and a retardation layer attached to the opposite side of the polarizing plate from the viewing side via an adhesive layer, the polarizer having a thickness of 12 μm or less, and the adhesive layer having a remaining depth of 11 μm or less when a load of 3 N is applied. In one embodiment, the pressure-sensitive adhesive layer has a thickness of 6 μm to 15 μm. In one embodiment, the thickness of the protective layer on the viewing side is 30 μm or more. In one embodiment, the retardation layer exhibits refractive index characteristics of nx>nz>ny. In one embodiment, the retardation layer has an Nz coefficient of 0.3 to 0.7. In one embodiment, the retardation layer has an in-plane retardation Re(550) of 250 nm to 350 nm, a thickness of 150 μm or less, and a photoelastic coefficient of 1.0×10 -12 m 2 / N or more. In one embodiment, the retardation layer contains a cyclic olefin resin. In one embodiment, the angle between the slow axis of the retardation layer and the absorption axis of the polarizer is substantially perpendicular or substantially parallel. According to another aspect of the present invention, there is provided an image display device, the image display device including the above-mentioned retardation layer-attached polarizing plate. Effect of the Invention

[0006] According to an embodiment of the present invention, in a polarizing plate with a retardation layer including a thin polarizer, by using an adhesive layer having a specific remaining depth, it is possible to realize a polarizing plate with a retardation layer in which damage marks are suppressed. [Brief description of the drawings]

[0007] [Figure 1] 1 is a schematic cross-sectional view of a retardation layer-attached polarizing plate according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

[0009] (Definition of terms and symbols) The definitions of terms and symbols used in this specification are as follows. (1) Refractive index (nx, ny, nz) "nx" is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., the slow axis direction), "ny" is the refractive index in the direction perpendicular to the slow axis in the plane (i.e., the fast axis direction), and "nz" is the refractive index in the thickness direction. (2) In-plane phase difference (Re) "Re(λ)" is the in-plane retardation measured with light of wavelength λ nm at 23° C. For example, "Re(550)" is the in-plane retardation measured with light of wavelength 550 nm at 23° C. Re(λ) is calculated by the formula: Re(λ)=(nx-ny)×d, where d(nm) is the thickness of the layer (film). (3) Retardation in the thickness direction (Rth) "Rth(λ)" is the retardation in the thickness direction measured with light of wavelength λ nm at 23° C. For example, "Rth(550)" is the retardation in the thickness direction measured with light of wavelength 550 nm at 23° C. Rth(λ) is calculated by the formula: Rth(λ)=(nx-nz)×d, where d(nm) is the thickness of the layer (film). (4) Nz coefficient The Nz coefficient is calculated by Nz=Rth / Re. (5)Angle When angles are referred to herein, the angles include both clockwise and counterclockwise angles relative to a reference direction, so for example, "45°" means ±45°. (6) Substantially perpendicular or substantially parallel In this specification, the expressions "substantially orthogonal" and "approximately orthogonal" include the case where the angle between two directions is 90°±7°, preferably 90°±5°, and more preferably 90°±3°. The expressions "substantially parallel" and "approximately parallel" include the case where the angle between two directions is 0°±7°, preferably 0°±5°, and more preferably 0°±3°. Furthermore, in this specification, when simply referring to "orthogonal" or "parallel," it is understood that this can include a substantially orthogonal or substantially parallel state.

[0010] A. Overall structure of the polarizing plate with a retardation layer FIG. 1 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to one embodiment of the present invention. The polarizing plate with a retardation layer 100 in the illustrated example has a polarizing plate 10 and a retardation layer 30. The polarizing plate 10 includes a polarizer 11 and a protective layer (viewing-side protective layer) 12 on at least the viewing side of the polarizer 11. In the illustrated example, only the viewing-side protective layer 12 is provided, but another protective layer (inner protective layer) may be provided on the opposite side to the viewing side. The retardation layer 30 is attached to the opposite side to the viewing side of the polarizing plate 10 via an adhesive layer 20. The retardation layer 30 has an in-plane retardation and therefore has a slow axis. The angle between the slow axis of the retardation layer 30 and the absorption axis of the polarizer 11 is typically substantially perpendicular or substantially parallel. For practical purposes, another adhesive layer (not shown) is provided on the side of the retardation layer 30 opposite the polarizing plate 10 (i.e., as the outermost layer on the side opposite the viewing side), so that the retardation layer-attached polarizing plate can be attached to an image display cell. Furthermore, it is preferable that a separator (not shown) is temporarily attached to the surface of the another adhesive layer until the retardation layer-attached polarizing plate is used. By temporarily attaching the separator, the another adhesive layer is protected and the retardation layer-attached polarizing plate can be formed into a roll.

[0011] In an embodiment of the present invention, the adhesive layer 20 has a remaining depth of 11 μm or less, preferably 10.8 μm or less, when a load of 3 N is applied. The smaller the remaining depth, the more preferable it is, and the lower limit thereof may be, for example, 10 μm. The remaining depth can be measured, for example, as follows: (1) the adhesive sheet is attached onto a glass plate; (2) the surface of the adhesive sheet is scratched while increasing the load using a microload automatic scratch tester. (3) The indentation depth when scratched with a load of 3 N is measured using a displacement sensor, and this is taken as the remaining depth. By optimizing the remaining depth of the adhesive layer, damage marks (typically, numerous fine cracks within a certain area) can be significantly suppressed. Damage marks are typically caused by external factors (e.g., impact and / or pressing force) resulting from handling errors by workers. Furthermore, in a retardation layer-attached polarizing plate having an adhesive layer on one side of a polarizer, damage marks typically occur on the polarizer. Damage marks are prominent in thin polarizers, and are even more prominent in polarizing plates with retardation layers for large image display devices (e.g., televisions) that are more difficult to handle. The present inventors have found that damage marks, which appear to be a collection of fine cracks at first glance, have a completely different cause from cracks, and therefore damage marks cannot be suppressed by crack suppression measures (e.g., adjusting the storage modulus of the adhesive layer). Through trial and error, they have found that optimizing the remaining depth (i.e., the degree of return after applying an external force to the adhesive layer) is effective. In other words, the effect of suppressing damage marks by optimizing the remaining depth solves the newly discovered problem of damage marks, and is an unexpectedly excellent effect obtained through trial and error in response to the problem.

[0012] In the embodiment of the present invention, the thickness of the polarizer 11 is 12 μm or less. As described above, damage marks are prominent in thin polarizers and are essentially a problem specific to thin polarizers, but according to the embodiment of the present invention, such a problem can be solved.

[0013] The retardation layer-attached polarizing plate 100 may further have any appropriate functional layer depending on the purpose on the side of the retardation layer 30 opposite to the polarizer 10 (on the image display cell side) (not shown). Representative examples of the functional layer include another retardation layer and a conductive layer. The type, number, combination, arrangement position, and characteristics of the functional layer (for example, the optical characteristics of the other retardation layer: specifically, the refractive index characteristics, in-plane retardation, thickness direction retardation, and Nz coefficient) can be appropriately set depending on the purpose. When the retardation layer-attached polarizing plate further has a conductive layer, the retardation layer-attached polarizing plate can be suitably used in an inner touch panel type input display device.

[0014] The components of the retardation layer-attached polarizing plate will be described in more detail below.

[0015] B. Polarizing plate B-1.Polarizer The polarizer 11 is typically made of a resin film containing a dichroic material.

[0016] As the resin film, any appropriate resin film that can be used as a polarizer can be adopted. The resin film is typically a polyvinyl alcohol-based resin (hereinafter, referred to as "PVA-based resin") film.

[0017] Any appropriate resin can be used as the PVA-based resin forming the PVA-based resin film. Examples include polyvinyl alcohol and ethylene-vinyl alcohol copolymer. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. Ethylene-vinyl alcohol copolymer is obtained by saponifying ethylene-vinyl acetate copolymer. The saponification degree of the PVA-based resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, and more preferably 99.0 mol% to 99.93 mol%. The saponification degree can be determined in accordance with JIS K 6726-1994. By using a PVA-based resin having such a saponification degree, a polarizer having excellent durability can be obtained. If the saponification degree is too high, gelation may occur.

[0018] The average degree of polymerization of the PVA resin can be appropriately selected depending on the purpose. The average degree of polymerization is usually 1000 to 10000, preferably 1200 to 4500, and more preferably 1500 to 4300. The average degree of polymerization can be determined in accordance with JIS K 6726-1994.

[0019] Examples of the dichroic material contained in the resin film include iodine, organic dyes, etc. These may be used alone or in combination of two or more. Iodine is preferably used.

[0020] The resin film may be a single-layer resin film or a laminate of two or more layers.

[0021] A specific example of a polarizer composed of a single-layer resin film is a PVA-based resin film that has been subjected to a dyeing treatment with iodine and a stretching treatment (typically, uniaxial stretching). The dyeing with iodine is performed, for example, by immersing the PVA-based film in an aqueous iodine solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. The stretching may be performed after the dyeing treatment or while dyeing. Alternatively, the film may be stretched and then dyed. If necessary, the PVA-based resin film is subjected to a swelling treatment, a crosslinking treatment, a washing treatment, a drying treatment, or the like. For example, by immersing the PVA-based resin film in water and washing it before dyeing, not only can dirt and antiblocking agents on the surface of the PVA-based film be washed off, but also the PVA-based resin film can be swelled to prevent uneven dyeing.

[0022] Specific examples of polarizers obtained using laminates include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate. A polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate can be produced by, for example, applying a PVA-based resin solution to the resin substrate and drying the resin substrate to form a PVA-based resin layer on the resin substrate to obtain a laminate of the resin substrate and the PVA-based resin layer; stretching and dyeing the laminate to make the PVA-based resin layer a polarizer. In this embodiment, stretching typically includes immersing the laminate in an aqueous solution of boric acid to stretch it. Furthermore, stretching may further include, as necessary, stretching the laminate in air at a high temperature (for example, 95°C or higher) before stretching in the aqueous solution of boric acid. The obtained laminate of resin substrate / polarizer may be used as it is (i.e., the resin substrate may be used as a protective layer for the polarizer), or the resin substrate may be peeled off from the laminate of resin substrate / polarizer, and any suitable protective layer may be laminated on the peeled surface depending on the purpose. Details of the method for producing such a polarizer are described in, for example, JP2012-73580A and JP6470455A. The entire disclosures of these publications are incorporated herein by reference.

[0023] As described above, the thickness of the polarizer is 12 μm or less, preferably 1 μm to 12 μm, more preferably 3 μm to 10 μm, and further preferably 3 μm to 8 μm. When the thickness of the polarizer is within this range, curling during heating can be well suppressed, and good appearance durability during heating can be obtained.

[0024] The polarizer preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The single transmittance of the polarizer is, for example, 41.5% to 46.0%, preferably 43.0% to 46.0%, and more preferably 44.5% to 46.0%. The degree of polarization of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and even more preferably 99.9% or more.

[0025] B-2.Protective layer The viewing-side protective layer 12 and the inner protective layer (if present) are each formed of any suitable film that can be used as a protective layer for a polarizer. Specific examples of materials that are the main components of the film include cellulose-based resins such as triacetyl cellulose (TAC), and transparent resins such as polyesters, polyvinyl alcohols, polycarbonates, polyamides, polyimides, polyethersulfones, polysulfones, polystyrenes, polynorbornenes, polyolefins, (meth)acrylics, and acetates. Other examples include thermosetting resins or ultraviolet-curing resins such as (meth)acrylics, urethanes, (meth)acrylic urethanes, epoxys, and silicones. Other examples include glassy polymers such as siloxane polymers. Polymer films described in JP 2001-343529 A (WO01 / 37007) can also be used. The material for this film may be, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain, and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain, such as a resin composition containing an alternating copolymer of isobutene and N-methylmaleimide, and an acrylonitrile-styrene copolymer. The polymer film may be, for example, an extrusion molded product of the above resin composition.

[0026] The polarizing plate with a retardation layer is typically placed on the viewing side of an image display device, and the viewing-side protective layer 12 is typically placed on the viewing side. Therefore, the viewing-side protective layer 12 may be subjected to a surface treatment such as a hard coat treatment, an anti-reflection treatment, an anti-sticking treatment, or an anti-glare treatment, if necessary. In addition, the protective layer 12 may be subjected to a treatment for improving visibility when viewed through polarized sunglasses (typically, imparting an (elliptical) polarization function or imparting an ultra-high phase difference) if necessary. By performing such a treatment, excellent visibility can be achieved even when the display screen is viewed through polarized lenses such as polarized sunglasses. Therefore, the polarizing plate with a retardation layer can be suitably applied to an image display device that can be used outdoors.

[0027] The thickness of the viewer-side protective layer is preferably 30 μm or more, more preferably 30 μm to 100 μm, and even more preferably 30 μm to 60 μm. If the thickness of the protective layer is in such a range, damage marks can be more significantly suppressed due to a synergistic effect with the remaining depth of the pressure-sensitive adhesive layer. In addition, when the viewer-side protective layer is surface-treated to form a surface-treated layer, the thickness of the viewer-side protective layer is the thickness including the surface-treated layer.

[0028] The inner protective layer (if present) is preferably optically isotropic. In this specification, "optically isotropic" means that the in-plane retardation Re(550) is 0 nm to 10 nm, and the retardation Rth(550) in the thickness direction is -10 nm to +10 nm. The thickness of the inner protective layer is preferably 5 μm to 80 μm, more preferably 10 μm to 40 μm, and further preferably 10 μm to 30 μm. From the viewpoint of thinning, the protective layer may be preferably omitted. In the embodiment of the present invention, the retardation layer 30 preferably doubles as the inner protective layer.

[0029] C.Adhesive layer Any suitable adhesive may be used as the adhesive forming the adhesive layer 20 as long as it realizes the desired remaining depth. Examples of the base resin of the adhesive include acrylic resin, styrene resin, silicone resin, urethane resin, and rubber resin. Acrylic resin is preferable from the viewpoints of chemical resistance, adhesion to prevent the infiltration of the treatment liquid during immersion, and flexibility to the adherend. That is, the adhesive layer 20 may be preferably composed of an acrylic adhesive (acrylic adhesive composition). The acrylic adhesive composition typically contains a (meth)acrylic polymer as a main component. The (meth)acrylic polymer may be contained in the adhesive composition at a ratio of, for example, 50% by weight or more, preferably 70% by weight or more, and more preferably 90% by weight or more of the solid content of the adhesive composition. The (meth)acrylic polymer contains alkyl (meth)acrylate as a monomer unit as a main component. Note that (meth)acrylate refers to acrylate and / or methacrylate. Examples of the alkyl group of the alkyl (meth)acrylate include linear or branched alkyl groups having 1 to 18 carbon atoms. The average number of carbon atoms of the alkyl group is preferably 3 to 9, more preferably 3 to 6. Examples of monomers constituting the (meth)acrylic polymer include, in addition to the alkyl (meth)acrylate, carboxyl group-containing monomers (e.g., (meth)acrylic acid), hydroxyl group-containing monomers (e.g., hydroxyethyl acrylate), amide group-containing monomers (e.g., acrylamide), aromatic ring-containing (meth)acrylates (e.g., benzyl acrylate), heterocyclic ring-containing (meth)acrylates (e.g., acryloylmorpholine), and (meth)acrylates having a bridged ring structure (e.g., dicyclopentanyl (meth)acrylate). The (meth)acrylic polymer preferably has a carboxyl group-containing monomer unit and a hydroxyl group-containing monomer unit. The content of the carboxyl group-containing monomer unit in the (meth)acrylic polymer is preferably 3% by weight to 7% by weight, and the content of the hydroxyl group-containing monomer unit is preferably 0.05% by weight to 0.1% by weight. Adhesive layerThe desired remaining depth can be achieved. The acrylic adhesive composition may preferably contain a silane coupling agent and / or a crosslinking agent. Examples of the silane coupling agent include an epoxy group-containing silane coupling agent. Examples of the crosslinking agent include an isocyanate-based crosslinking agent and a peroxide-based crosslinking agent. By using a suitable combination of a monomer unit of a (meth)acrylic polymer, a silane coupling agent, and a crosslinking agent, an acrylic adhesive (and, as a result, an adhesive layer) having desired properties can be obtained. Details of the adhesive layer or the acrylic adhesive composition are described in, for example, JP 2007-138147 A, JP 2016-190996 A, and JP 2018-028573 A, and the descriptions in these publications are incorporated herein by reference.

[0030] The thickness of the pressure-sensitive adhesive layer 20 is preferably 6 μm to 25 μm, more preferably 6 μm to 15 μm, and further preferably 10 μm to 15 μm. When the thickness of the pressure-sensitive adhesive layer is in such a range, air bubbles can be suppressed when the polarizer and the retardation layer are attached to each other.

[0031] The creep value of the adhesive layer 20 is preferably 30 μm / h to 50 μm / h, more preferably 35 μm / h to 45 μm / h. If the creep value of the adhesive layer is in such a range, damage marks can be significantly suppressed. The creep value can be measured, for example, as follows. An adhesive composition is applied to a protective layer of a polarizing plate including a protective layer and a polarizer to form an adhesive layer, thereby preparing an adhesive layer-attached polarizing plate. The prepared polarizing plate is cut to a width of 10 mm and a length of 50 mm. Of the cut adhesive layer-attached polarizing plate, a portion of width 10 mm and length 10 mm is attached to a stainless steel plate via the adhesive layer, and then the cut plate is treated in an autoclave (50° C., 5 atm) for 15 minutes, and then left at room temperature for 1 hour. After leaving it, a load of 500 g (tensile load) is applied to the end of the adhesive layer-attached polarizing plate on the side that is not attached to the stainless steel plate at 23°C for 1 hour, and the amount of displacement (deformation) of the adhesive layer after the load is applied is measured using a laser creep tester, thereby allowing the creep value of the adhesive layer to be measured.

[0032] D. Retardation layer The retardation layer 30 has an in-plane retardation and a slow axis as described above. As described above, the retardation layer also serves as a protective layer for the polarizer and a retardation layer (or an optical compensation layer). This configuration eliminates the need to provide a protective layer and an optical compensation layer separately, which can greatly contribute to making the image display device thinner. The in-plane retardation Re(550) of the retardation layer is preferably 250 nm to 350 nm, more preferably 270 nm to 330 nm, and even more preferably 290 nm to 310 nm. If the in-plane retardation Re(550) of the retardation layer is in this range, the movement distance on the Poincaré sphere is short, so that excellent hue and luminance characteristics are realized, and the color shift of the image display panel and the deviation due to the retardation component of the TFT are also reduced.

[0033] The retardation layer preferably has a refractive index characteristic that satisfies the relationship of nx>nz>ny. When the retardation layer has such a refractive index characteristic, the hue in the oblique direction of an image display device to which a retardation layer-attached polarizing plate is applied can be improved satisfactorily. Furthermore, such improvement in the hue in the oblique direction can be achieved without separately providing a retardation layer and a layer that performs optical compensation in the oblique direction, which can contribute to making the retardation layer-attached polarizing plate (and thus the image display device) thinner.

[0034] The Nz coefficient of the retardation layer is preferably 0.3 to 0.7, more preferably 0.4 to 0.6, and further preferably 0.45 to 0.55. If the Nz coefficient is within such a range, the hue in the oblique direction can be further improved.

[0035] The retardation layer may exhibit a reverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light, may exhibit a positive wavelength dispersion characteristic in which the retardation value decreases according to the wavelength of the measurement light, or may exhibit a flat wavelength dispersion characteristic in which the retardation value hardly changes depending on the wavelength of the measurement light. The retardation layer typically exhibits a flat wavelength dispersion characteristic.

[0036] The retardation layer preferably has an absolute value of the photoelastic coefficient of 15×10 -12 m 2 / N or less, more preferably 10×10 -12 m 2 / N or less. The lower limit of the absolute value of the photoelastic coefficient is, for example, 1.0 × 10 -12 m 2 When the absolute value of the photoelastic coefficient of the retardation layer is within such a range, display unevenness of the image display device can be suppressed satisfactorily.

[0037] The retardation layer is typically a retardation film formed of any suitable resin that can realize the above-mentioned characteristics.The resin forming this retardation film can be, for example, a cyclic olefin resin, polyarylate, polyamide, polyimide, polyester, polyaryletherketone, polyamideimide, polyesterimide, polyvinyl alcohol, polyfumaric acid ester, polyethersulfone, polysulfone, polycarbonate resin, cellulose resin and polyurethane.These resins can be used alone or in combination.Preferably, it is a cyclic olefin resin.A representative example of a cyclic olefin resin can be a norbornene resin.

[0038] The norbornene resin is a resin polymerized using norbornene monomers as polymerization units. Examples of the norbornene monomer include norbornene and its alkyl and / or alkylidene substituted derivatives, such as 5-methyl-2-norbornene, 5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-ethylidene-2-norbornene, and polar group substituted derivatives thereof, such as halogen; dicyclopentadiene, 2,3-dihydrodicyclopentadiene; dicyclopentadiene, 2,3-dihydrodicyclopentadiene; Octahydronaphthalene, its alkyl and / or alkylidene substituted derivatives, and polar group substituted derivatives such as halogen, for example, 6-methyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-ethyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-ethylidene-1,4:5,8-dimethano-1,4,4a,5,6,7 ,8,8a-octahydronaphthalene, 6-chloro-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-cyano-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-pyridyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-methoxycarbonyl-1,4:5,8-dimethano norbornene-1,4,4a,5,6,7,8,8a-octahydronaphthalene, etc.; trimers and tetramers of cyclopentadiene, for example, 4,9:5,8-dimethano-3a,4,4a,5,8,8a,9,9a-octahydro-1H-benzoindene, 4,11:5,10:6,9-trimethano-3a,4,4a,5,5a,6,9,9a,10,10a,11,11a-dodecahydro-1H-cyclopentaanthracene, etc. The norbornene-based resin may be a copolymer of a norbornene-based monomer and another monomer.

[0039] The retardation layer (retardation film) is a stretched film formed from the above resin. Any suitable method can be adopted as a method for producing the stretched film. A representative example is a method in which a shrinkable film is attached to one or both sides of a resin film and then heated and stretched. The shrinkable film is used to impart a shrinkage force in a direction perpendicular to the stretching direction during heat stretching. By imparting such a shrinkage force, nz can be increased, and as a result, a Z film can be produced. Examples of materials used for the shrinkable film include polyester, polystyrene, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, etc. Polypropylene film is preferably used because of its excellent shrink uniformity and heat resistance.

[0040] As the stretching method, any suitable stretching method can be adopted as long as it can impart tension in the stretching direction of the resin film and a shrinkage force in a direction perpendicular to the stretching direction in the film plane. The stretching temperature is preferably equal to or higher than the glass transition temperature (Tg) of the resin film. This is because the retardation value of the obtained stretched film is likely to be uniform, and the film is unlikely to crystallize (become cloudy). The stretching temperature is more preferably Tg+1°C to Tg+30°C of the polymer film, even more preferably Tg+2°C to Tg+20°C, particularly preferably Tg+3°C to Tg+15°C, and most preferably Tg+5°C to Tg+10°C. By setting the stretching temperature in such a range, uniform heat stretching can be performed. Furthermore, the stretching temperature is preferably constant in the film width direction. This is because a stretched film having good optical uniformity with small variation in retardation value can be produced.

[0041] The stretching ratio during the above stretching can be set to any appropriate value, preferably 1.05 to 2.00 times, more preferably 1.10 to 1.50 times, and particularly preferably 1.20 to 1.40 times. By setting the stretching ratio within such a range, a stretched film with little shrinkage in the film width and excellent mechanical strength can be obtained.

[0042] The thickness of the retardation layer is preferably 80 μm to 200 μm, more preferably 90 μm to 150 μm, and further preferably 110 μm to 150 μm. With such a thickness, a desired in-plane retardation value can be obtained.

[0043] E. Image display device The retardation layer-attached polarizing plate according to the embodiment of the present invention can be applied to an image display device. Typically, the retardation layer-attached polarizing plate is disposed on the viewing side of the image display device so that the polarizing plate is on the viewing side. Representative examples of the image display device include a liquid crystal display device, an organic electroluminescence (EL) display device, and a quantum dot display device. A liquid crystal display device is preferred, and an IPS mode liquid crystal display device is more preferred. This is because the hue improvement in the oblique direction is more significant. The image display device is preferably large (for example, for a television of 27 inches or more). This is because the effect of suppressing damage marks by optimizing the remaining depth of the adhesive layer is significant. EXAMPLES

[0044] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The evaluation methods in the examples are as follows. Unless otherwise specified, "parts" and "%" in the examples are based on weight.

[0045] (1) Remaining depth An adhesive sheet was formed from the adhesive prepared in the manufacturing example. The adhesive sheet obtained was attached to a glass plate, and the surface of the adhesive sheet was scratched with increasing load using a microload automatic scratch tester. The indentation depth when scratched with a load of 3N was measured with a displacement sensor, and this was taken as the remaining depth. (2) Damage marks The retardation layer-attached polarizing plate obtained in the examples and comparative examples was cut into a length of 50 mm and a width of 25 mm to be used as a measurement sample. This measurement sample was attached to a glass plate via a normal acrylic adhesive (corresponding to a different adhesive layer). A guitar pick with a weight attached was pressed against the adhesive sheet of the measurement sample attached to the glass plate with a load of 3N, and in this state, it was moved back and forth in the longitudinal direction using a sliding tester. The number of times of reciprocation was 1, 5, 10, 50, and 70. Then, the measurement sample was placed in an oven at 95°C for 1 hour. The measurement sample taken out of the oven was checked under a microscope for the presence or absence of damage marks, and was evaluated according to the following criteria. Excellent: No damage was observed even after 70 round trips Good: No damage was observed after 50 passes, but was observed after 70 passes. No: No damage was observed after 10 passes, but after 50 passes Poor: Damage marks observed after 1, 5 or 10 passes (3) Appearance For the polarizing plates with retardation layers obtained in the examples and comparative examples, the state of air bubbles between the polarizer and the retardation layer during production (when the polarizer and the retardation layer were bonded together) was visually observed and evaluated according to the following criteria. Good: No bubbles were observed Acceptable: A small amount of air bubbles were observed, but they did not affect the display characteristics. Unacceptable: Air bubbles were found that could affect the display characteristics. The appearance evaluation was carried out as a secondary evaluation.

[0046] [Production Example 1: Preparation of adhesive constituting adhesive layer] A solution was prepared by adding 100 parts of butyl acrylate, 5 parts of acrylic acid, 0.075 parts of 2-hydroxyethyl acrylate, and 0.3 parts of 2,2'-azobisisobutyronitrile together with ethyl acetate to a reaction vessel equipped with a cooling tube, a nitrogen inlet tube, a thermometer, and a stirrer. The solution was then stirred while blowing in nitrogen gas and reacted at 60°C for 4 hours to obtain a solution containing an acrylic polymer with a weight average molecular weight of 2.2 million. Ethyl acetate was further added to the solution containing the acrylic polymer to adjust the solid content to 30%, to obtain an acrylic polymer solution (A1). 100 parts of the solid content of the obtained acrylic polymer solution (A1) was mixed in this order with 0.6 parts of a crosslinking agent mainly composed of a compound having an isocyanate group (manufactured by Nippon Polyurethane Co., Ltd., product name "Coronate L") as a crosslinking agent and 0.075 parts of γ-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KMB-403") as a silane coupling agent to prepare adhesive A. The remaining depth of the adhesive layer (adhesive sheet) formed from adhesive A was 10.7 mm.

[0047] [Production Example 2: Preparation of adhesive constituting adhesive layer] In a reaction vessel equipped with a cooling tube, a nitrogen introduction tube, a thermometer and a stirrer, 99 parts of butyl acrylate, 1.0 parts of 4-hydroxybutyl acrylate and 0.3 parts of 2,2'-azobisisobutyronitrile were added together with ethyl acetate and reacted at 60°C for 4 hours under a nitrogen gas stream. Next, ethyl acetate was added to the reaction liquid to obtain a solution containing an acrylic polymer having a weight average molecular weight of 1.65 million (solid content concentration 30%). 0.15 parts of dibenzoyl peroxide (manufactured by Nippon Oil & Fats Co., Ltd., product name: Niper BO-Y), 0.08 parts of trimethylolpropane xylene diisocyanate (manufactured by Mitsui Takeda Chemical Co., Ltd., product name: Takenate D110N) and 0.2 parts of a silane coupling agent (manufactured by Soken Chemical Industries, Ltd., product name A-100, an acetoacetyl group-containing silane coupling agent) were added to the acrylic polymer solution per 100 parts of solid content of the obtained acrylic polymer solution to prepare adhesive B. The remaining depth of the adhesive layer (adhesive sheet) formed from Adhesive B was 12.5 mm.

[0048] [Example 1] 1. Preparation of Polarizer As the resin substrate, a long amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 μm) with a water absorption rate of 0.75% and a Tg of 75° C. was used. One side of the substrate was subjected to a corona treatment, and an aqueous solution containing polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (polymerization degree 1200, acetoacetyl-modification degree 4.6%, saponification degree 99.0 mol% or more, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., product name "GOHSEFYMER Z200") in a ratio of 9:1 was applied to the corona-treated side and dried at 25° C. to form a PVA-based resin layer with a thickness of 11 μm, and a laminate was produced. The obtained laminate was uniaxially stretched at its free end 2.0 times in the machine direction (longitudinal direction) between rolls with different peripheral speeds in an oven at 120° C. (auxiliary air stretching). Next, the laminate was immersed in an insolubilizing bath (a boric acid aqueous solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 30° C. for 30 seconds (insolubilizing treatment). Next, the polarizing plate was immersed in a dye bath at a liquid temperature of 30° C. while adjusting the iodine concentration and immersion time so that the polarizing plate had a predetermined transmittance. In this example, the polarizing plate was immersed for 60 seconds in an iodine aqueous solution obtained by mixing 0.2 parts by weight of iodine and 1.5 parts by weight of potassium iodide with respect to 100 parts by weight of water (dyeing treatment). Next, the piece was immersed in a crosslinking bath (a boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 30° C. for 30 seconds (crosslinking treatment). Thereafter, the laminate was immersed in an aqueous boric acid solution (an aqueous solution obtained by blending 4 parts by weight of boric acid and 5 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 70°C, and uniaxially stretched in the longitudinal direction (longitudinal direction) between rolls with different peripheral speeds so that the total stretch ratio was 5.5 times (underwater stretching). Thereafter, the laminate was immersed in a cleaning bath (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 30° C. (cleaning treatment). Finally, the laminate was dried to obtain a laminate in which a polarizer was formed on the resin substrate. The polarizer had a thickness of 5 μm and a single transmittance of 42.3%.

[0049] 2. Lamination of protective layer An acrylic resin film (thickness 40 μm) containing a lactone ring structure was attached as a protective layer to the polarizer surface of the laminate obtained in 1 above via an ultraviolet-curable adhesive. Specifically, the curable adhesive was applied so that the total thickness was 1.0 μm, and the layers were attached using a rolling machine. Thereafter, the adhesive was cured by irradiating it from the protective layer side with UV light. Next, the resin substrate was peeled off to obtain a laminate having a configuration of protective layer (acrylic resin film) / polarizer.

[0050] 3. Preparation of retardation layer (retardation film) A 60 μm-thick shrinkable film [manufactured by Toray Industries, Inc., product name "Torayfan BO2873"] was laminated on both sides of a 130 μm-thick norbornene resin film via an acrylic adhesive layer (thickness 15 μm). The film was then held in the longitudinal direction by a roll stretching machine and stretched 1.38 times in an air-circulating oven at 146 °C. After stretching, the shrinkable film was peeled off together with the acrylic adhesive layer to produce a retardation film. The obtained retardation film showed a refractive index characteristic of nx>nz>ny, with Re(550)=280 nm, Nz coefficient=0.52, and photoelastic coefficient of 4.0×10 -12 m 2 / N and the thickness was 138 μm.

[0051] 4. Preparation of polarizing plate with retardation layer The retardation film (retardation layer) obtained in the above 3 is attached to the polarizer surface of the laminate obtained in the above 2. The plates were laminated together via the adhesive A (thickness: 12 μm) obtained in Production Example 1. In this way, a polarizing plate with a retardation layer having a structure of protective layer / polarizer / adhesive layer / retardation layer was obtained. The obtained polarizing plate with a retardation layer was subjected to the above-mentioned evaluations (2) and (3). The results are shown in Table 1.

[0052] [Example 2] A polarizing plate with a retardation layer was obtained in the same manner as in Example 1, except that the thickness of the adhesive A was changed to 23 μm. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0053] [Example 3] A polarizing plate with a retardation layer was obtained in the same manner as in Example 1, except that the thickness of the adhesive A was changed to 5 μm. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0054] [Comparative Example 1] A polarizing plate with a retardation layer was obtained in the same manner as in Example 1, except that adhesive B (thickness: 12 μm) was used instead of adhesive A. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0055] [Comparative Example 2] A polarizing plate with a retardation layer was obtained in the same manner as in Example 1, except that adhesive B (thickness: 20 μm) was used instead of adhesive A. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0056] [Reference example 1] 1. Preparation of Polarizer A polyvinyl alcohol resin film with an average polymerization degree of 2,400, a saponification degree of 99.9 mol%, and a thickness of 50 μm was prepared. The polyvinyl alcohol film was stretched 2.4 times in the conveying direction while swelling by immersing it in a swelling bath (water bath) at 20 ° C for 30 seconds between rolls with different peripheral speed ratios (swelling step), and then stretched 3.7 times in the conveying direction based on the original polyvinyl alcohol film (polyvinyl alcohol film that was not stretched at all in the conveying direction) while immersing it in a dyeing bath (aqueous solution with an iodine concentration of 0.03 wt% and a potassium iodide concentration of 0.3 wt%) at 30 ° C so that the single-piece transmittance after the final stretching becomes a desired value (dyeing step). The immersion time at this time was about 60 seconds. Next, the dyed polyvinyl alcohol film was stretched in the conveying direction to 4.2 times the original polyvinyl alcohol film while immersed in a 40°C crosslinking bath (aqueous solution with a boric acid concentration of 3.0% by weight and a potassium iodide concentration of 3.0% by weight) (crosslinking step). Furthermore, the obtained polyvinyl alcohol film was immersed in a 64°C stretching bath (aqueous solution with a boric acid concentration of 4.0% by weight and a potassium iodide concentration of 5.0% by weight) for 50 seconds to be stretched in the conveying direction to 6.0 times the original polyvinyl alcohol film (stretching step), and then immersed in a 20°C cleaning bath (aqueous solution with a potassium iodide concentration of 3.0% by weight) for 5 seconds (cleaning step). The washed polyvinyl alcohol film was dried at 30°C for 2 minutes to prepare a polarizer (thickness 20 μm).

[0057] 2. Preparation of polarizing plate and polarizing plate with retardation layer An acrylic resin film (thickness 40 μm) containing a lactone ring structure was attached as a protective layer to the surface of the polarizer obtained in 1 above in the same manner as in Example 1 to obtain a laminate having a configuration of protective layer (acrylic resin film) / polarizer. The procedure below was the same as in Example 1 to obtain a polarizing plate with a retardation layer. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0058] [Table 1]

[0059] [evaluation] As is clear from Table 1, it is understood that the damage marks can be significantly suppressed according to the examples of the present invention. Furthermore, as is clear from the reference examples, it is understood that such damage marks are a problem specific to thin polarizers. [Industrial Applicability]

[0060] The retardation layer-attached polarizing plate of the present invention can be suitably used in image displays such as liquid crystal displays, organic EL displays, and quantum dot displays, and can be particularly suitably used in liquid crystal displays. [Explanation of symbols]

[0061] 10 Polarizing plate 11 Polarizer 12 Protective layer 20 Adhesive layer 30 Retardation layer 100 Polarizing plate with retardation layer

Claims

1. A polarizing plate including a polarizer and a protective layer on at least the viewing side of the polarizer, and a retardation layer attached to the opposite side to the viewing side of the polarizing plate via a pressure-sensitive adhesive layer, The thickness of the polarizer is 3 μm to 8 μm, the pressure-sensitive adhesive layer is made of an acrylic pressure-sensitive adhesive composition, The acrylic pressure-sensitive adhesive composition contains a (meth)acrylic polymer as a main component, the (meth)acrylic polymer contains 3% by weight to 7% by weight of a carboxyl group-containing monomer unit and 0.05% by weight to 0.1% by weight of a hydroxyl group-containing monomer unit; The pressure-sensitive adhesive layer has a residual depth of 11 μm or less when a load of 3 N is applied. Polarizing plate with retardation layer.

2. 2. The retardation layer-attached polarizing plate according to claim 1, wherein the pressure-sensitive adhesive layer has a thickness of 6 μm to 15 μm.

3. 3. The polarizing plate with a retardation layer according to claim 1, wherein the protective layer on the viewing side has a thickness of 30 [mu]m or more.

4. 4. The polarizing plate with a retardation layer according to claim 1, wherein the retardation layer exhibits a refractive index characteristic of nx>nz>ny.

5. 5. The polarizing plate with a retardation layer according to claim 4, wherein the retardation layer has an Nz coefficient of 0.3 to 0.

7.

6. The retardation layer has an in-plane retardation Re(550) of 250 nm to 350 nm, a thickness of 150 μm or less, and a photoelastic coefficient of 1.0×10 －１２ m ２ 6. The retardation layer-attached polarizing plate according to claim 4, wherein the retardation layer-attached polarizing plate has a retardation coefficient of 1:1 or more.

7. The polarizing plate with a retardation layer according to claim 4 , wherein the retardation layer contains a cyclic olefin resin.

8. 8. The polarizing plate with a retardation layer according to claim 1, wherein an angle between a slow axis of the retardation layer and an absorption axis of the polarizer is 90°±7° or 0°±7°.

9. An image display device comprising the retardation layer-attached polarizing plate according to claim 1 .

Images