Polarizing plate with retardation layer

Abstract

To suppress unevenness of reflection light to improve visibility.SOLUTION: A polarizing plate 10 with a retardation layer comprises a polarizer 1, a first retardation layer 2, and a second retardation layer 3 in this sequence. The polarizer 1 and the first retardation layer 2 are laminated through a first adhesive layer 4, and the first retardation layer 2 and the second retardation layer 3 are laminated through a second adhesive layer 5. The first retardation layer 2 and the second retardation layer 3 are 5 μm or less in thickness. The second adhesive layer 5 has an average refractive index of 1.55 or more, and also an average refractive index difference between itself and the first retardation layer 2 and an average refractive index difference between itself and the second retardation layer 3 are less than 0.08.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a polarizing plate with a retardation layer. [Background technology]

[0002] In order to improve poor visibility caused by reflection of external light and glare of the background on the display screen of a display device, a display device in which a circular polarizer is arranged on the viewing side of the display panel is known. Patent documents 1 and 2 propose a polarizer that reduces reflection of incident light from an oblique direction in black display and achieves excellent reflection hue in an oblique direction, and a display device equipped with the polarizer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-111236 A [Patent Document 2] JP 2015-210459 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the display devices using the polarizing plates described in Patent Documents 1 and 2 have problems in that the reflected light is uneven and visibility is insufficient.

[0005] The present invention has been made in view of the above problems, and an object of the present invention is to provide a polarizing plate with a retardation layer capable of suppressing unevenness in reflected light and improving visibility. [Means for solving the problem]

[0006] The polarizing plate with a retardation layer of the present invention comprises a polarizer, a first retardation layer, and a second retardation layer in this order, the polarizer and the first retardation layer are bonded together via a first adhesive layer, the first retardation layer and the second retardation layer are bonded together via a second adhesive layer, the first retardation layer and the second retardation layer have thicknesses of 5 μm or less, and the second adhesive layer has an average refractive index of 1.55 or more, and the difference between the average refractive index of the second adhesive layer and that of the first retardation layer and the average refractive index of the second retardation layer is less than 0.08. In one embodiment, the difference between the average refractive index of the first adhesive layer and the average refractive index of the polarizer and the average refractive index of the first retardation layer is 0.06 or less. In one embodiment, the first adhesive layer and the second adhesive layer have a thickness of 6 μm or less. In one embodiment, the first retardation layer and the second retardation layer are each a layer in which a liquid crystal compound is aligned and fixed. In one embodiment, the first retardation layer is a λ / 2 plate, and the second retardation layer is a λ / 4 plate. In one embodiment, the polarizer has a thickness of 12 μm or less. In one embodiment, the thickness from the polarizer to the second retardation layer is 35 μm or less. According to another aspect of the present invention, there is provided an organic EL display device, the organic EL display device including the above-mentioned retardation layer-attached polarizing plate. Effect of the Invention

[0007] According to the present invention, it is possible to provide a retardation layer-attached polarizing plate capable of suppressing unevenness in reflected light and improving visibility. [Brief description of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view of a retardation layer-attached polarizing plate according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

[0010] (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. Re(λ) is calculated by the formula: Re=(nx-ny)×d, where d(nm) is the thickness of the layer (film). For example, "Re(550)" is the in-plane retardation measured with light of wavelength 550 nm at 23°C. (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=(nx-nz)×d, where d(nm) is the thickness of the layer (film).

[0011] A. Polarizing plate with retardation layer 1 is a 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 10 includes a polarizer 1, a first retardation layer 2, and a second retardation layer 3 in this order.

[0012] The thickness of each of the first retardation layer 2 and the second retardation layer 3 is 5 μm or less. The first retardation layer 2 typically functions as a λ / 2 plate, and the second retardation layer 3 typically functions as a λ / 4 plate. The first retardation layer 2 has a slow axis. In one embodiment, the angle between the slow axis of the first retardation layer 2 and the absorption axis of the polarizer 1 is, for example, 5° to 25°, preferably 10° to 20°, more preferably 10° to 17°, and even more preferably about 15°. The second retardation layer 3 also has a slow axis. The angle between the slow axis of the second retardation layer 3 and the absorption axis of the polarizer 1 is, for example, 60° to 90°, preferably 65° to 85°, more preferably 70° to 78°, and even more preferably about 75°. The angle between the slow axis of the first retardation layer 2 and the slow axis of the second retardation layer 3 is, for example, 50° to 70°, preferably 52° to 65°, more preferably 55° to 65°, and further preferably about 60°. In another embodiment, the angle between the slow axis of the first retardation layer 2 and the absorption axis of the polarizer 1 is, for example, -5° to -25°, preferably -10° to -20°, more preferably -10° to -17°, and further preferably about -15°. The second retardation layer 3 also has a slow axis. The angle between the slow axis of the second retardation layer 3 and the absorption axis of the polarizer 1 is, for example, -60° to -90°, preferably -65° to -85°, more preferably -70° to -78°, and further preferably about -75°. The angle between the slow axis of the first retardation layer 2 and the slow axis of the second retardation layer 3 is, for example, 50° to 70°, preferably 52° to 65°, more preferably 55° to 65°, and further preferably about 60°. In yet another embodiment, the angle between the slow axis of the first retardation layer 2 and the absorption axis of the polarizer 1 is, for example, 60° to 90°, preferably 65° to 85°, more preferably 70° to 78°, and even more preferably about 75°. The second retardation layer 3 also has a slow axis. The angle between the slow axis of the second retardation layer 3 and the absorption axis of the polarizer 1 is, for example, 5° to 25°, preferably 10° to 20°, more preferably 10° to 17°, and even more preferably about 15°. The angle between the slow axis of the first retardation layer 2 and the slow axis of the second retardation layer 3 is, for example, 50° to 70°, preferably 52° to 65°, more preferably 55° to 65°, and even more preferably about 60°. In yet another embodiment, the angle between the slow axis of the first retardation layer 2 and the absorption axis of the polarizer 1 is, for example, -60° to -90°, preferably -65° to -85°, more preferably -70° to -78°, and even more preferably about -75°. The second retardation layer 3 also has a slow axis. The angle between the slow axis of the second retardation layer 3 and the absorption axis of the polarizer 1 is, for example, -5° to -25°, preferably -10° to -20°, more preferably -10° to -17°, and even more preferably about -15°. The angle between the slow axis of the first retardation layer 2 and the slow axis of the second retardation layer 3 is, for example, 50° to 70°, preferably 52° to 65°, more preferably 55° to 65°, and even more preferably about 60°.

[0013] The polarizer 1 and the first retardation layer 2 are bonded together via a first adhesive layer 4, and the first retardation layer 2 and the second retardation layer 3 are bonded together via a second adhesive layer 5. The thicknesses of the first adhesive layer 4 and the second adhesive layer 5 are typically 6 μm or less. The difference between the average refractive index of the first adhesive layer 4 and the average refractive index of the layers adjacent to the first adhesive layer 4 (the polarizer 1 and the first retardation layer 2) is typically less than 0.12. The difference between the average refractive index of the first adhesive layer 4 and the average refractive index of the adjacent layers is preferably less than 0.10, more preferably less than 0.08, and even more preferably 0.06 or less. The average refractive index of the second adhesive layer 5 is 1.55 or more, and the difference between the average refractive index of the layers adjacent to the second adhesive layer 5 (the first retardation layer 2 and the second retardation layer 3) is less than 0.08. The difference between the average refractive index of the second adhesive layer 5 and the average refractive index of the adjacent layers is preferably 0.06 or less, more preferably 0.01 or less. By using the above-mentioned retardation layer-attached polarizing plate 10 in a display device, it is possible to suppress unevenness in reflected light of the display device and improve visibility. Note that the retardation layer-attached polarizing plate 10 may have a protective film (not shown) on the opposite side of the polarizer 1 to the first retardation layer 2.

[0014] The thickness of the retardation layer-attached polarizing plate 10 (total thickness of polarizer 1 / first adhesive layer 4 / first retardation layer 2 / second adhesive layer 5 / second retardation layer 3) is preferably 4 μm to 35 μm, and more preferably 6 μm to 20 μm.

[0015] B. Polarizer Any appropriate polarizer can be adopted as the polarizer 1. For example, the resin film forming the polarizer may be a single-layer resin film or a laminate of two or more layers.

[0016] Specific examples of polarizers made of a single-layer resin film include hydrophilic polymer films such as polyvinyl alcohol (PVA) films, partially formalized PVA films, and partially saponified ethylene-vinyl acetate copolymer films that have been dyed with iodine or a dichroic substance such as a dichroic dye and stretched, and polyene-based oriented films such as dehydrated PVA films and dehydrochlorinated polyvinyl chloride films. A polarizer obtained by dyeing a PVA film with iodine and uniaxially stretching it is preferably used because of its excellent optical properties.

[0017] The dyeing with iodine is carried out, 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 carried out after the dyeing treatment, or may be carried out while dyeing. Alternatively, the film may be stretched and then dyed. If necessary, the PVA-based film may be subjected to a swelling treatment, a crosslinking treatment, a washing treatment, a drying treatment, or the like. For example, by immersing the PVA-based film in water and washing it with water before dyeing, it is possible to wash off dirt and antiblocking agents on the surface of the PVA-based film, and also to swell the PVA-based film and prevent uneven dyeing.

[0018] 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 such a method for producing a polarizer are described in, for example, JP2012-73580A. The entire disclosure of this publication is incorporated herein by reference.

[0019] The thickness of the polarizer 1 is preferably 12 μm or less, more preferably 1 μm to 10 μm, further preferably 3 μm to 8 μm, and particularly preferably 3 μm to 5 μm. When the thickness of the polarizer 1 is within such a range, the entire retardation layer-attached polarizing plate 10 can be made thin. By using a laminate of a resin substrate and a PVA-based resin layer formed by coating on the resin substrate, the above-mentioned thin polarizer 1 can be produced.

[0020] The polarizer 1 preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The single transmittance of the polarizer is preferably 42.0% 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.

[0021] The average refractive index of the polarizer 1 is preferably 1.48 to 1.65, typically 1.55. When the average refractive index of the polarizer 1 is within the above range, the difference between the average refractive index of the polarizer 1 and the average refractive index of the first adhesive layer 4 can be easily adjusted.

[0022] C. First retardation layer and second retardation layer As described above, in one embodiment of the present invention, the first retardation layer 2 can function as a λ / 2 plate, and the second retardation layer 3 can function as a λ / 4 plate. By the first retardation layer 2 functioning as a λ / 2 plate, the retardation can be appropriately adjusted with respect to the wavelength dispersion characteristics (particularly, the wavelength range in which the retardation is out of λ / 4) after lamination with the second retardation layer 3 functioning as a λ / 4 plate, and the circular polarization function can be exhibited in a wide wavelength range.

[0023] The in-plane retardation Re(550) of such a first retardation layer 2 is 180 nm to 320 nm, preferably 200 nm to 300 nm, and more preferably 200 nm to 280 nm. The first retardation layer 2 typically has an index ellipsoid of nx>ny=nz or nz=nx>ny. The in-plane retardation Re(550) of such a second retardation layer 3 is 80 nm to 180 nm, preferably 90 nm to 170 nm, and more preferably 100 nm to 150 nm. The second retardation layer 3 typically has an index ellipsoid of nx>ny=nz or nz=nx>ny.

[0024] The average refractive index of the first retardation layer 2 is preferably 1.50 to 1.70, typically 1.59 or 1.60. If the average refractive index of the first retardation layer 2 is within the above range, the difference between the average refractive index of the first adhesive layer 4 and / or the second adhesive layer 5 can be less than 0.12 (even less than or equal to 0.06). The thickness of the first retardation layer 2 is preferably 1 μm to 5 μm, more preferably 1 μm to 3 μm, and particularly preferably 2 μm.

[0025] The average refractive index of the second retardation layer 3 is preferably 1.50 to 1.70, typically 1.59 or 1.60. When the average refractive index of the second retardation layer 3 is within the above range, the difference from the average refractive index of the second adhesive layer 5 can be less than 0.08. The thickness of the second retardation layer 3 is preferably 1 μm to 5 μm, more preferably 1 μm to 3 μm, and particularly preferably 1 μm.

[0026] In one embodiment, the first retardation layer 2 and / or the second retardation layer 3 may be an alignment-fixed layer of a liquid crystal compound. By using a liquid crystal compound, the difference between nx and ny of the obtained first retardation layer 2 and / or the second retardation layer 3 can be significantly larger than that of a non-liquid crystal material, so that the thickness of the first retardation layer and / or the second retardation layer for obtaining a desired in-plane retardation can be significantly reduced. As a result, the retardation layer-attached polarizing plate 10 (ultimately, the organic EL display device) can be further thinned. In this specification, the "alignment-fixed layer" refers to a layer in which a liquid crystal compound is aligned in a predetermined direction within the layer and the alignment state is fixed.

[0027] In one embodiment, typically, rod-shaped liquid crystal compounds are aligned in the slow axis direction of the first retardation layer 2 (second retardation layer 3) (homogeneous alignment). Examples of the liquid crystal compound include liquid crystal compounds (nematic liquid crystals) whose liquid crystal phase is a nematic phase. Examples of the liquid crystal compound that can be used include liquid crystal polymers and liquid crystal monomers. The mechanism by which the liquid crystal compound exhibits liquid crystallinity may be either lyotropic or thermotropic. The liquid crystal polymer and liquid crystal monomer may be used alone or in combination. Any appropriate liquid crystal monomer may be used as the liquid crystal monomer. For example, the polymerizable mesogen compounds described in JP-A-2002-533742 (WO00 / 37585), EP358208 (US5211877), EP66137 (US4388453), WO93 / 22397, EP0261712, DE19504224, DE4408171, and GB2280445 can be used. Specific examples of such polymerizable mesogen compounds include BASF's product name LC242, Merck's product name E7, and Wacker-Chem's product name LC-Sillicon-CC3767. As the liquid crystal monomer, for example, a nematic liquid crystal monomer is preferable. Specific examples of liquid crystal compounds and details of the method for forming the alignment solidification layer are described in JP-A-2006-163343. The description of the publication is incorporated herein by reference.

[0028] In another embodiment, typically, the discotic liquid crystal compound is aligned in any one of vertical alignment, hybrid alignment, and tilt alignment. Examples of the liquid crystal compound include discotic liquid crystal compounds. Typically, the discotic liquid crystal compound is aligned substantially perpendicular to the film surface of the first retardation layer (second retardation layer). The discotic liquid crystal compound being substantially perpendicular means that the average angle between the film surface and the discotic surface of the discotic liquid crystal compound is within the range of 70° to 90°. More preferably, it is 80° to 90°, and even more preferably, it is 85° to 90°. As the discotic liquid crystal compound, for example, those described in JP-A-2007-108732 and JP-A-2010-244038 can be preferably used, but are not limited thereto.

[0029] D. First adhesive layer As described above, the difference between the average refractive index of the first adhesive layer 4 and the average refractive index of the layer adjacent to the first adhesive layer 4 is less than 0.12. When a thin retardation layer-attached polarizing plate having a thin retardation layer (for example, 5 μm or less) is used in a display device, the thickness unevenness and unevenness of each layer may be visually recognized as interference unevenness due to the refractive index difference between each layer constituting the retardation layer-attached polarizing plate. In contrast, when the difference between the average refractive index of the first adhesive layer 4 and the average refractive index of the layer adjacent to the first adhesive layer 4 is less than 0.12, the above-mentioned interference unevenness can be suppressed, and as a result, visibility can be improved.

[0030] The average refractive index of the first adhesive layer 4 is preferably 1.52 to 1.64, more preferably 1.55 to 1.64. The thickness of the first adhesive layer 4 is preferably 10 nm to 6 μm, more preferably 200 nm to 2 μm.

[0031] The adhesive that can constitute the first adhesive layer 4 preferably has transparency and optical isotropy. As the adhesive, an active energy ray curable adhesive can be typically used. As the active energy ray curable adhesive, radical curable, cationic curable, anionic curable, or other types can be selected as necessary, and it is also possible to use an appropriate combination, such as a hybrid of radical curable and cationic curable types. As the radical curable adhesive, for example, an adhesive containing a compound (e.g., a monomer and / or oligomer) having a radical polymerizable group such as a (meth)acrylate group or a (meth)acrylamide group as a curing component can be mentioned. In addition, "(meth)acrylic" refers to acrylic and / or methacrylic.

[0032] The active energy ray curable adhesive can have desired properties (e.g., refractive index after curing) by adjusting the type, combination, and compounding ratio of double bond-containing monomers and / or oligomers and crosslinking agents. Examples of components that can adjust the refractive index after curing include compounds having aromatic rings, compounds having halogen atoms, compounds having sulfur atoms, and inorganic particles such as titania and zirconia. Examples of compounds having aromatic rings include compounds having a naphthalene skeleton, a phenoxybenzyl skeleton, a fluorene skeleton, and a 9-vinylcarbazole skeleton. In addition, the active energy ray curable adhesive can contain a compound containing a (meth)acryloyl group as a diluent component, an acrylic oligomer as a plasticizer, and a radical photopolymerization initiator as a photopolymerization initiator.

[0033] E. Second adhesive layer The second adhesive layer 5 may be made of any suitable adhesive. As described above, the difference between the average refractive index of the second adhesive layer 5 and the average refractive index of the layer adjacent to the second adhesive layer 5 is less than 0.08. This can suppress the above-mentioned interference unevenness, and as a result, can improve visibility.

[0034] The average refractive index of the second adhesive layer 5 is 1.55 or more, preferably 1.55 to 1.64, and more preferably 1.55 to 1.63. The thickness of the second adhesive layer 5 is preferably 10 nm to 6 μm, and more preferably 200 nm to 2 μm. The adhesive that can constitute the second adhesive layer 5 is the same as the adhesive described for the first adhesive layer 4 in Section D.

[0035] F. Protective film The protective film is formed of any suitable film that can be used as a protective film for the polarizer 1. 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.

[0036] The (meth)acrylic resin preferably has a Tg (glass transition temperature) of 115° C. or higher, more preferably 120° C. or higher, even more preferably 125° C. or higher, and particularly preferably 130° C. or higher. This is because the resin can have excellent durability. The upper limit of the Tg of the (meth)acrylic resin is not particularly limited, but is preferably 170° C. or lower from the viewpoint of moldability, etc.

[0037] As the (meth)acrylic resin, any appropriate (meth)acrylic resin may be adopted within a range that does not impair the effects of the present invention. For example, poly(meth)acrylic acid ester such as polymethyl methacrylate, methyl methacrylate-(meth)acrylic acid copolymer, methyl methacrylate-(meth)acrylic acid ester copolymer, methyl methacrylate-acrylic acid ester-(meth)acrylic acid copolymer, methyl (meth)acrylate-styrene copolymer (MS resin, etc.), and polymers having alicyclic hydrocarbon groups (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-norbornyl (meth)acrylate copolymer, etc.). Preferably, poly(meth)acrylic acid C1-6 alkyl such as polymethyl (meth)acrylate is used. More preferably, methyl methacrylate resins containing methyl methacrylate as the main component (50 to 100% by weight, preferably 70 to 100% by weight) are used.

[0038] Specific examples of the (meth)acrylic resin include ACRYPET VH and ACRYPET VRL20A manufactured by Mitsubishi Rayon Co., Ltd., (meth)acrylic resins having a ring structure in the molecule described in JP-A-2004-70296, and high Tg (meth)acrylic resins obtained by intramolecular crosslinking or intramolecular cyclization reaction.

[0039] As the (meth)acrylic resin, the (meth)acrylic resin having a lactone ring structure is particularly preferred in terms of having high heat resistance, high transparency, and high mechanical strength.As the (meth)acrylic resin having the lactone ring structure, the (meth)acrylic resin having the lactone ring structure described in JP-A-2000-230016, JP-A-2001-151814, JP-A-2002-120326, JP-A-2002-254544, JP-A-2005-146084, etc. can be mentioned.

[0040] The (meth)acrylic resin having a lactone ring structure has a mass average molecular weight (sometimes referred to as weight average molecular weight) of preferably 1,000 to 2,000,000, more preferably 5,000 to 1,000,000, further preferably 10,000 to 500,000, and particularly preferably 50,000 to 500,000.

[0041] The (meth)acrylic resin having a lactone ring structure has a Tg (glass transition temperature) of preferably 115° C. or higher, more preferably 125° C. or higher, even more preferably 130° C. or higher, particularly preferably 135° C. or higher, and most preferably 140° C. or higher. This is because it can have excellent durability. The upper limit of the Tg of the (meth)acrylic resin having a lactone ring structure is not particularly limited, but is preferably 170° C. or lower from the viewpoint of moldability, etc. In this specification, "(meth)acrylic" refers to acrylic and / or methacrylic.

[0042] The retardation layer-attached polarizing plate 10 of the present invention is typically disposed on the viewing side of an image display device, and the protective film is typically disposed on the viewing side. Therefore, the protective film may be subjected to surface treatment such as hard coat treatment, anti-reflection treatment, anti-sticking treatment, and anti-glare treatment, as necessary.

[0043] The thickness of the protective film may be any appropriate thickness as long as the effects of the present invention are obtained. The thickness of the protective film is, for example, 10 μm to 100 μm, and preferably 12 μm to 90 μm. In addition, when the surface is treated, the thickness of the protective film includes the thickness of the surface treatment layer.

[0044] G.Display device The retardation layer-attached polarizing plate described in the above items A to F can be applied to display devices such as liquid crystal display devices and organic EL display devices. Therefore, the present invention includes a display device using the retardation layer-attached polarizing plate. A display device according to an embodiment of the present invention includes a display element and the retardation layer-attached polarizing plate described in the above items A to F arranged on the viewing side of the display element. The retardation layer-attached polarizing plate is arranged so that the second retardation layer 3 faces the display element. EXAMPLES

[0045] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The methods for measuring the various properties are as follows. 1. Refractive index measurement of polarizers Using a prism coupler SPA-4000 (manufactured by Cylon Technology), the in-plane refractive index of the polarizer was measured in the direction perpendicular to the absorption axis, in the absorption axis direction, and in the thickness direction, and the average value of these was taken as the average refractive index of the polarizer. The measurement temperature was 23°C and the measurement wavelength was 532 nm. 2. Refractive index measurement of retardation layer Using a prism coupler SPA-4000 (manufactured by Cylon Technology), the in-plane refractive index of the retardation film was measured in the direction perpendicular to the slow axis, the direction of the slow axis, and the thickness direction, and the average value of these was taken as the average refractive index of the retardation layer. The measurement temperature was 23°C and the measurement wavelength was 532 nm. 3. Refractive index measurement of adhesive layer Using a prism coupler SPA-4000 (manufactured by Cylon Technology), the in-plane refractive index and the refractive index in the thickness direction of the cured adhesive that constitutes the adhesive layer were measured, and the average value of these was taken as the average refractive index of the adhesive layer. The measurement temperature was 23°C and the measurement wavelength was 532 nm. 4. Retardation measurement of retardation layer Measurement was performed using an Axoscan (manufactured by Axometrics) at a measurement temperature of 23° C. and a measurement wavelength of 550 nm.

[0046] (Preparation of polarizer) As the resin substrate, an amorphous polyethylene terephthalate (A-PET) film (manufactured by Mitsubishi Plastics, Inc., trade name "Novaclear", thickness: 100 μm) was used. An aqueous solution of polyvinyl alcohol (PVA) resin (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosenol (registered trademark) NH-26") was applied to one side of the resin substrate at 60 ° C. and dried to form a PVA-based resin layer with a thickness of 7 μm. The laminate thus obtained was immersed for 30 seconds in an insolubilization bath (a boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with respect to 100 parts by weight of water) with a liquid temperature of 30 ° C. (insolubilization step). Next, it was immersed for 60 seconds in a dyeing bath (an iodine aqueous solution obtained by blending 0.2 parts by weight of iodine and 2 parts by weight of potassium iodide with respect to 100 parts by weight of water) with a liquid temperature of 30 ° C. (dyeing step). Next, the laminate was immersed in a crosslinking bath (a boric acid aqueous solution obtained by blending 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 step). Thereafter, the laminate was immersed in a boric acid aqueous solution (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 60°C, while being uniaxially stretched in the longitudinal direction (longitudinal direction) between rolls with different peripheral speeds (step B). The immersion time in the boric acid aqueous solution was 120 seconds, and the laminate was stretched until it was about to break. Thereafter, the laminate was immersed in a cleaning bath (aqueous solution obtained by blending 3 parts by weight of potassium iodide with respect to 100 parts by weight of water), and then dried with hot air at 60°C (cleaning and drying step). In this way, a laminate was obtained in which a polarizer having a thickness of 5 μm was formed on a resin substrate. Next, the resin substrate was peeled off from the polarizer, and an acrylic transparent protective film described in JP 2012-3269 A was attached as a protective film to one surface of the polarizer to obtain a polarizer with a protective film. The above polarizer with a protective film was subjected to a corona treatment before use.

[0047] (Preparation of Retardation Film Constituting Retardation Layer) (Retardation film A) A coating solution containing a rod-shaped polymerizable nematic liquid crystal monomer was applied to a transparent resin substrate for λ / 2 alignment, which had an alignment film that had been subjected to rubbing treatment, and solidified while maintaining the refractive index anisotropy, to produce a retardation film A with a thickness of 2 μm on the transparent resin substrate. The in-plane refractive index of the retardation film A was 1.55 in the fast axis direction, 1.68 in the slow axis direction, and 1.55 in the thickness direction, with an average refractive index of 1.59. The in-plane retardation Re(550) of the retardation film A was 260 nm. The obtained retardation film was subjected to corona treatment before use. (Retardation film B) A coating solution containing a rod-shaped polymerizable nematic liquid crystal monomer was applied to a transparent resin substrate for λ / 4 alignment, which had an alignment film that had been subjected to rubbing treatment, and solidified while maintaining the refractive index anisotropy, to produce a retardation film A with a thickness of 1 μm on the transparent resin substrate. The in-plane refractive index of retardation film B was 1.55 in the fast axis direction, 1.68 in the slow axis direction, and 1.55 in the thickness direction, with an average refractive index of 1.59. The in-plane retardation Re(550) of retardation film B was 120 nm. The obtained retardation film was subjected to corona treatment before use. (Retardation film C) A transparent resin substrate made of cellulose acylate was subjected to an alkali saponification treatment, and then an alignment film coating solution was applied to the surface of the alkali saponification-treated cellulose acylate, followed by drying to perform λ / 2 alignment treatment. Next, a coating solution containing a discotic liquid crystal compound was applied to the alignment-treated surface of the transparent support, and the alignment of the liquid crystal compound was fixed by heating and UV irradiation, thereby producing a retardation film C having a thickness of 2 μm on the transparent resin substrate. The in-plane refractive index of the retardation film C was 1.53 in the fast axis direction, 1.64 in the slow axis direction, and 1.64 in the thickness direction, with the average refractive index being 1.60. The in-plane retardation Re(550) of the retardation film C was 246 nm. The obtained retardation film was subjected to a corona treatment before use. (Retardation film D) A transparent resin substrate made of cellulose acylate was subjected to an alkali saponification treatment, and then an alignment film coating solution was applied to the surface of the alkali saponification-treated cellulose acylate, followed by drying to perform λ / 4 alignment treatment. Next, a coating solution containing a discotic liquid crystal compound was applied to the alignment-treated surface of the transparent support, and the alignment of the liquid crystal compound was fixed by heating and UV irradiation, thereby producing a retardation film D having a thickness of 1 μm on the transparent resin substrate. The in-plane refractive index of the retardation film D was 1.53 in the fast axis direction, 1.64 in the slow axis direction, and 1.64 in the thickness direction, with the average refractive index being 1.60. The in-plane retardation Re(550) of the retardation film D was 123 nm. The obtained retardation film was subjected to a corona treatment before use.

[0048] (Preparation of adhesive that constitutes adhesive layer) (Adhesive A) 50 parts of Plaxel FA1DDM (manufactured by Daicel Corporation), 40 parts of acryloylmorpholine (ACMO: registered trademark) (manufactured by Kojinsha), 10 parts of ARFON UP-1190 (manufactured by Toagosei Co., Ltd.), 3 parts of a photopolymerization initiator (product name "KAYACURE DETX-S", manufactured by Nippon Kayaku Co., Ltd.), and 3 parts of IRGACURE 907 (manufactured by BASF Japan Ltd.) were mixed to prepare adhesive A. The obtained adhesive A was photocured (300 mJ / cm 2 The cured product obtained by this process had an in-plane refractive index of 1.52, a refractive index in the thickness direction of 1.52, and an average refractive index of these of 1.52. (Adhesive B) Adhesive B was prepared by mixing 40 parts of Light Acrylate POB-A (Kyoeisha Chemical), 10 parts of Plaxel FA1DDM (Daicel), 40 parts of Acryloyl Morpholine (ACMO: registered trademark) (Kojinsha), 10 parts of ARFON UP-1190 (Toagosei), 3 parts of a photopolymerization initiator (product name "KAYACURE DETX-S", Nippon Kayaku), and 3 parts of IRGACURE907 (BASF Japan). The resulting adhesive B was photocured (300 mJ / cm 2 The cured product obtained by this step had an in-plane refractive index of 1.55, a refractive index in the thickness direction of 1.55, and an average refractive index of 1.55. (Adhesive C) 70 parts of OGSOL EA-F5710 (Osaka Gas Chemicals), 10 parts of PLAXEL FA1DDM (Daicel), 18 parts of acryloylmorpholine (ACMO: registered trademark) (Kojinsha), 5 parts of ARFON UP-1190 (Toagosei), and 3 parts of a photopolymerization initiator (product name "DAROCUR1173", BASF Japan) were mixed to prepare adhesive C. The obtained adhesive C was photocured (300 mJ / cm 2 The cured product obtained by this process had an in-plane refractive index of 1.60, a refractive index in the thickness direction of 1.60, and an average refractive index of these of 1.60. (Adhesive D) 35 parts of 9-vinylcarbazole (Tokyo Chemical Industry Co., Ltd.), 40 parts of OGSOL EA-F5710 (Osaka Gas Chemicals Co., Ltd.), 20 parts of acryloylmorpholine (ACMO: registered trademark), 5 parts of ARFON UP-1190 (Toagosei Co., Ltd.), and 3 parts of a photopolymerization initiator (product name "DAROCUR1173", BASF Japan Ltd.) were mixed to prepare adhesive D. The obtained adhesive D was photocured (300 mJ / cm 2 The cured product obtained by this process had an in-plane refractive index of 1.64, a refractive index in the thickness direction of 1.64, and an average refractive index of these of 1.64.

[0049] <Example 1> The adhesive A constituting the first adhesive layer was applied to the polarizer, and the retardation film A constituting the first retardation layer was transferred from the transparent resin substrate to the adhesive A-coated surface so that the angle between the absorption axis of the polarizer and the slow axis of the retardation film A was 15°. Then, the film was irradiated with UV (300 mJ / cm 2 ) to cure the adhesive A. Next, adhesive B constituting a second adhesive layer was applied to the surface of retardation film A opposite to the polarizer, and retardation film D constituting a second retardation layer was transferred from the transparent resin substrate to the adhesive B-coated surface so that the angle between the absorption axis of the polarizer and the slow axis of retardation film D was 75° and the angle between the slow axis of retardation film A and the slow axis of retardation film D was 60°. Then, the adhesive B was irradiated with UV (300 mJ / cm 2) and curing adhesive B to obtain a polarizing plate with a retardation layer. The cured adhesive A (first adhesive layer) had a thickness of 1 μm, and the cured adhesive B (second adhesive layer) had a thickness of 1 μm.

[0050] <Example 2> A polarizing plate with a retardation layer was produced in the same manner as in Example 1, except that adhesive B was used as the adhesive constituting the first adhesive layer.

[0051] <Example 3> A polarizing plate with a retardation layer was produced in the same manner as in Example 2, except that adhesive C was used as the adhesive constituting the second adhesive layer.

[0052] <Example 4> A polarizing plate with a retardation layer was produced in the same manner as in Example 1, except that adhesive C was used as the adhesive constituting the first adhesive layer and adhesive D was used as the adhesive constituting the second adhesive layer.

[0053] <Example 5> The adhesive B constituting the first adhesive layer is applied to the polarizer, and the retardation film C constituting the first retardation layer is transferred from the transparent resin substrate to the adhesive B-coated surface so that the angle between the absorption axis of the polarizer and the slow axis of the retardation film C is 75°. Then, the film is irradiated with UV (300 mJ / cm 2 ) to cure the adhesive B. Next, the adhesive B constituting the second adhesive layer was applied to the surface of the retardation film C opposite to the polarizer, and the retardation film B constituting the second retardation layer was transferred from the transparent resin substrate to the adhesive B-coated surface so that the angle between the absorption axis of the polarizer and the slow axis of the retardation film B was 15° and the angle between the slow axis of the retardation film C and the slow axis of the retardation film B was 60°. The adhesive B was then irradiated with UV (300 mJ / cm 2 ) and curing the adhesive B to obtain a polarizing plate with a retardation layer. The cured adhesive B (first adhesive layer) had a thickness of 1 μm, and the cured adhesive B (second adhesive layer) had a thickness of 1 μm.

[0054] <Example 6> A polarizing plate with a retardation layer was prepared in the same manner as in Example 2, except that retardation film C was used as the retardation film constituting the first retardation layer and retardation film D was used as the retardation film constituting the second retardation layer.

[0055] <Example 7> A polarizing plate with a retardation layer was produced in the same manner as in Example 2, except that the retardation film B was used as the retardation film constituting the second retardation layer.

[0056] <Comparative Example 1> A polarizing plate with a retardation layer was produced in the same manner as in Example 1, except that adhesive A was used as the adhesive constituting the second adhesive layer.

[0057] <Comparative Example 2> A polarizing plate was produced in the same manner as in Comparative Example 1, except that adhesive B was used as the adhesive constituting the first adhesive layer.

[0058] (evaluation) The retardation layer-attached polarizing plate of each of the Examples and Comparative Examples was attached to a reflector via an acrylic adhesive, and the appearance was visually observed under a three-wavelength tube. The results were evaluated according to the following criteria and are shown in Table 1. No visible unevenness was observed... Virtually no visible unevenness (no problems in actual use) Unevenness was visible... × [Table 1] [Industrial Applicability]

[0059] The retardation layer-attached polarizing plate of the present invention is preferably used for, for example, image display devices. Specifically, it is preferably used as a liquid crystal panel for liquid crystal televisions, liquid crystal displays, mobile phones, digital cameras, video cameras, portable game machines, car navigation systems, copy machines, printers, fax machines, clocks, microwave ovens, etc., an antireflection plate for organic EL devices, etc. [Explanation of symbols]

[0060] 1 Polarizer 2 First retardation layer 3 Second retardation layer 4 First adhesive layer 5 Second adhesive layer 10 Retardation film polarizer

Claims

【Claim 1】 A polarizer, a first retardation layer, and a second retardation layer are provided in this order, the polarizer and the first retardation layer are bonded via a first adhesive layer, the first retardation layer and the second retardation layer are bonded via a second adhesive layer, the thicknesses of the first retardation layer and the second retardation layer are 5 μm or less, the average refractive indices of the first retardation layer and the second retardation layer are 1.50 to 1.70, the average refractive index of the second adhesive layer is 1.55 or more, and the absolute value of the difference from the average refractive index of the first retardation layer and the absolute value of the difference from the average refractive index of the second retardation layer are 0.06 or less, the thickness of the polarizer is 1 μm to 8 μm, the thickness from the polarizer to the second retardation layer is 35 μm or less, A polarizing plate with a retardation layer.

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