Polarizing plate with optical compensation layer and organic EL panel using the same

Abstract

To provide a polarizing plate with an optical compensation layer that maintains excellent anti-reflective properties in the forward direction, also exhibits excellent anti-reflective properties in the oblique direction, and has a neutral hue in the oblique direction. [Solution] The polarizing plate with optical compensation layer of the present invention is used in organic EL panels. This polarizing plate with optical compensation layer comprises a polarizer, a first optical compensation layer, and a second optical compensation layer in that order. The first optical compensation layer exhibits a refractive index characteristic of nx>nz>ny, and Re(550) is 220nm to 300nm. The second optical compensation layer exhibits a refractive index characteristic of nx>nz>ny, and Re(550) is 90nm to 170nm. The Re(450) and Re(550) of the first and second optical compensation layers are substantially equal.

Description

Technical Field

[0001] The present invention relates to a polarizing plate with an optical compensation layer and an organic EL panel using the same.

Background Art

[0002] In recent years, with the spread of thin displays, displays (organic EL display devices) equipped with organic EL panels have been proposed. Since an organic EL panel has a highly reflective metal layer, problems such as external light reflection and background reflection are likely to occur. Therefore, it is known to provide a circular polarizing plate on the viewing side to prevent these problems. As a general circular polarizing plate, a retardation film (typically, a λ / 4 plate) laminated such that its slow axis forms an angle of about 45° with respect to the absorption axis of the polarizer is known. In addition, in order to further improve the antireflection characteristics, attempts have been made to laminate retardation films (optical compensation layers) having various optical characteristics. As such a retardation film, for example, those satisfying Re(550)>Re(450) are known. A circular polarizing plate using such a retardation film is expected to improve the viewing angle characteristics of an organic EL panel. However, such a retardation film is expensive, and there is a problem that the cost of manufacturing a circular polarizing plate is high.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present invention has been made to solve the above conventional problems, and its main object is to provide a polarizing plate with an optical compensation layer that can realize an organic EL panel that is inexpensive, maintains excellent antireflection characteristics in the front direction, is also excellent in antireflection characteristics in the oblique direction, and has a neutral hue in the oblique direction. [Means for solving the problem]

[0005] The polarizing plate with optical compensation layer of the present invention is used in organic EL panels. This polarizing plate comprises a polarizer, a first optical compensation layer, and a second optical compensation layer in that order. The first optical compensation layer and the second optical compensation layer each exhibit refractive index characteristics of nx>nz>ny. Furthermore, the Re(450) and Re(550) of the first optical compensation layer and the second optical compensation layer are substantially equal. In one embodiment, Re(550) is 220nm to 300nm, the Nz coefficient is 0.4 to 0.8, and the angle between the absorption axis direction of the polarizer and the slow axis direction of the first optical compensation layer is 5° to 25°. Furthermore, the Re(550) of the second optical compensation layer is 90 nm to 170 nm, the Nz coefficient is 0.4 to 0.8, and the angle between the absorption axis direction of the polarizer and the slow axis direction of the second optical compensation layer is 65° to 85°. Here, Re(450) and Re(550) represent the in-plane phase difference measured with light of wavelengths 450 nm and 550 nm at 23°C, respectively. In one embodiment, the Re(550) of the first optical compensation layer is 280 nm to 360 nm, the Nz coefficient is 0.5 to 0.9, and the angle between the absorption axis direction of the polarizer and the slow axis direction of the first optical compensation layer is substantially parallel. Furthermore, the Re(550) of the second optical compensation layer is 100 nm to 180 nm, the Nz coefficient is 0.2 to 0.6, and the angle between the absorption axis direction of the polarizer and the slow axis direction of the second optical compensation layer is 35° to 55°. According to another aspect of the present invention, an organic EL panel is provided. This organic EL panel comprises a polarizing plate with the optical compensation layer described above. [Effects of the Invention]

[0006] According to the present invention, in a polarizing plate with an optical compensation layer, a first optical compensation layer exhibiting refractive index characteristics nx>nz>ny and having a predetermined in-plane phase difference, and a second optical compensation layer exhibiting refractive index characteristics nx>nz>ny and having a predetermined in-plane phase difference are arranged in this order from the polarizer side, and both the first and second optical compensation layers are composed of flat dispersion phase difference films, thereby providing an inexpensive polarizing plate with an optical compensation layer that maintains excellent anti-reflective properties in the front direction, also exhibits excellent anti-reflective properties in the oblique direction, and furthermore, enables the realization of an organic EL panel with neutral hue in the oblique direction. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic cross-sectional view of a polarizing plate with an optical compensation layer according to one embodiment of the present invention. [Modes for carrying out the invention]

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

[0009] (Definitions 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 where the refractive index is maximum in the plane (i.e., the slow phase axis direction), "ny" is the refractive index in the direction perpendicular to the slow phase axis in the plane (i.e., the fast phase axis direction), and "nz" is the refractive index in the thickness direction. (2) In-plane phase difference (Re) "Re(λ)" is the in-plane phase difference measured with light of wavelength λnm at 23℃. Re(λ) can be calculated using the formula: Re=(nx-ny)×d, where d(nm) is the thickness of the layer (film). For example, "Re(550)" is the in-plane phase difference measured with light of wavelength 550nm at 23℃. (3) Phase difference in the thickness direction (Rth) "Rth(λ)" is the phase difference in the thickness direction measured with light of wavelength λnm at 23°C. Rth(λ) can be calculated using the formula: Rth = (nx - nz) × d, where d (nm) is the thickness of the layer (film). For example, "Rth(550)" is the phase difference in the thickness direction measured with light of wavelength 550nm at 23°C. (4) Nz coefficient The Nz coefficient is calculated using the formula Nz = Rth / Re. (5) substantially orthogonal or parallel The expressions “substantially orthogonal” and “approximately orthogonal” encompass the case where the angle between the two directions is 90°±10°, preferably 90°±7°, and more preferably 90°±5°. The expressions “substantially parallel” and “approximately parallel” encompass the case where the angle between the two directions is 0°±10°, preferably 0°±7°, and more preferably 0°±5°. Furthermore, when “orthogonal” or “parallel” is used in this specification, it may include substantially orthogonal or substantially parallel conditions.

[0010] A. Overall configuration of polarizing plate with optical compensation layer Figure 1 is a schematic cross-sectional view of a polarizing plate with an optical compensation layer according to one embodiment of the present invention. The polarizing plate 100 with an optical compensation layer of this embodiment comprises a polarizer 10, a first optical compensation layer 30, and a second optical compensation layer 40 in this order. Practically, as shown in the illustrated example, a protective layer 20 may be provided on the polarizer 10 opposite to the first optical compensation layer 30. The polarizing plate with an optical compensation layer may also have another protective layer (also called an inner protective layer) between the polarizer 10 and the first optical compensation layer 30. In the illustrated example, the inner protective layer is omitted. In this case, the first optical compensation layer 30 can also function as an inner protective layer. Furthermore, if necessary, a conductive layer and a substrate may be provided on the second optical compensation layer 40 opposite to the first optical compensation layer 30 (i.e., outside the second optical compensation layer 40) in this order (neither of which are shown). The substrate is closely laminated to the conductive layer. In this specification, "close lamination" means that two layers are directly and firmly laminated without the interposition of an adhesive layer (e.g., an adhesive layer, a tack layer). The conductive layer and the substrate can typically be introduced into the polarizing plate 100 with an optical compensation layer as a laminate of the substrate and the conductive layer. By further providing the conductive layer and the substrate, the polarizing plate 100 with an optical compensation layer can be suitably used in an inner touch panel type input display device. Furthermore / or, if necessary, the polarizing plate with an optical compensation layer (substantially the protective layer 20) may be subjected to a treatment to improve visibility when viewed through polarizing sunglasses (typically, by providing (elliptic) circular polarization function or providing an ultra-high phase difference). By applying such a treatment, excellent visibility can be achieved even when the display screen is viewed through polarizing lenses such as polarizing sunglasses. Therefore, the polarizing plate with an optical compensation layer can also be suitably applied to image display devices that can be used outdoors.

[0011] The first optical compensation layer 30 and the second optical compensation layer 40 each exhibit a refractive index characteristic of nx>nz>ny and have a slow axis. Furthermore, the Re(450) and Re(550) of the first optical compensation layer and the second optical compensation layer are substantially equal. That is, the first optical compensation layer and the second optical compensation layer each have flat dispersion characteristics in which the phase difference value hardly changes with the wavelength of the measured light. In one embodiment, the in-plane phase difference Re(550) of the first optical compensation layer 30 is 220nm to 300nm. In this case, the Nz coefficient of the first optical compensation layer is 0.4 to 0.8, and the angle between the slow axis of the first optical compensation layer 30 and the absorption axis of the polarizer 10 is 5° to 25°, preferably 8° to 22°, more preferably 12° to 18°, and even more preferably about 15°. Furthermore, the in-plane phase difference Re(550) of the second optical compensation layer 40 is 90 nm to 170 nm. In this case, the Nz coefficient of the second optical compensation layer is 0.4 to 0.8, and the angle between the slow axis of the second optical compensation layer 30 and the absorption axis of the polarizer 10 is 65° to 85°, preferably 68° to 82°, more preferably 72° to 78°, and even more preferably about 75°. In another embodiment, the in-plane phase difference Re(550) of the first optical compensation layer 30 is preferably 280 nm to 360 nm. In this case, the Nz coefficient of the first optical compensation layer is preferably 0.5 to 0.9, and the angle between the slow axis of the first optical compensation layer 30 and the absorption axis of the polarizer 10 is preferably substantially parallel. Furthermore, the in-plane phase difference Re(550) of the second optical compensation layer 40 is preferably 100 nm to 180 nm. In this case, the Nz coefficient of the second optical compensation layer is preferably 0.2 to 0.6, and the angle between the slow axis of the second optical compensation layer 30 and the absorption axis of the polarizer 10 is preferably 35° to 55°, more preferably 38° to 52°, even more preferably 42° to 48°, and particularly preferably about 45°. As described above, by arranging a first optical compensation layer exhibiting the refractive index characteristics nx>nz>ny and having a predetermined in-plane phase difference, and a second optical compensation layer exhibiting the refractive index characteristics nx>nz>ny and having a predetermined in-plane phase difference, in this order from the polarizer side, and by constructing both the first and second optical compensation layers as flat dispersion phase difference films, it is possible to maintain excellent anti-reflective properties in the front direction due to excellent circular polarization function, while preventing light leakage due to apparent axial misalignment of the polarizer's absorption axis when viewed from an oblique direction. As a result, when a polarizer with optical compensation layers is applied to an organic EL panel, excellent anti-reflective properties are achieved in the oblique direction, and furthermore, a neutral hue (i.e., without unwanted coloration) can be achieved in the oblique direction.

[0012] The following provides a detailed explanation of each layer and optical film that make up the polarizing plate with an optical compensation layer.

[0013] A-1. Polarizer Any suitable polarizer can be used as the polarizer 10. For example, the resin film forming the polarizer may be a single layer resin film or a laminate of two or more layers.

[0014] Specific examples of polarizers composed of a single layer of resin film include hydrophilic polymer films such as polyvinyl alcohol (PVA) films, partially formalized PVA films, and partially saponified ethylene-vinyl acetate copolymer films, which have been subjected to dyeing and stretching treatments with dichroic substances such as iodine or dichroic dyes, as well as polyene-based oriented films such as dehydrated PVA or dehydrochlorinated polyvinyl chloride. Preferably, polarizers obtained by dyeing a PVA film with iodine and uniaxially stretching are used because they have excellent optical properties.

[0015] The above-mentioned iodine dyeing is carried out, for example, by immersing the PVA film in an iodine aqueous solution. The stretching ratio for the above-mentioned uniaxial stretching is preferably 3 to 7 times. Stretching may be performed after the dyeing treatment, or during the dyeing process. Alternatively, dyeing may be performed after stretching. If necessary, the PVA film may be subjected to swelling, crosslinking, washing, drying, etc. For example, immersing the PVA film in water and washing it before dyeing can not only clean dirt and anti-blocking agents from the surface of the PVA film, but also swell the PVA film to prevent uneven dyeing.

[0016] Specific examples of the polarizer obtained using the laminate 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 formed by coating on the resin substrate. The polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer formed by coating on the resin substrate can be produced, for example, by applying a PVA-based resin solution to the resin substrate and drying it 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 the present embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching it. Further, stretching may further include air-stretching the laminate at a high temperature (for example, 95°C or higher) before stretching in the aqueous boric acid solution as necessary. The obtained laminate of the resin substrate / polarizer may be used as it is (that is, 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 the resin substrate / polarizer, and an arbitrary appropriate protective layer according to the purpose may be laminated on the peeled surface and used. Details of such a method for manufacturing a polarizer are described, for example, in Japanese Patent Application Laid-Open No. 2012-73580 (Patent No. 5414738). The entire description of the publication is incorporated herein by reference.

[0017] The thickness of the polarizer is preferably 25 μm or less, more preferably 1 μm to 12 μm, still more preferably 3 μm to 12 μm, and particularly preferably 3 μm to 8 μm. If the thickness of the polarizer is within such a range, curling during heating can be well suppressed, and good appearance durability during heating can be obtained.

[0018] The polarizer 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%, 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 still more preferably 99.9% or more.

[0019] A-2. First optical compensation layer As described above, the first optical compensation layer 30 exhibits a refractive index characteristic relationship of nx > nz > ny and has a slow axis. Further, the first optical compensation layer exhibits a flat wavelength dispersion characteristic in which the retardation value hardly changes depending on the wavelength of the measurement light. Specifically, Re(450) / Re(550) of the first optical compensation layer is preferably 0.99 to 1.03. Since a retardation film exhibiting a flat wavelength dispersion characteristic is less expensive than a retardation film exhibiting an inverse dispersion characteristic, by adopting a configuration as in the embodiment of the present invention, a polarizing plate with an optical compensation layer that is inexpensive and has excellent optical characteristics can be obtained.

[0020] The in-plane retardation Re(550) of the first optical compensation layer 30 is 220 nm to 300 nm, preferably 230 nm to 290 nm, more preferably 250 nm to 270 nm. If the in-plane retardation of the first optical compensation layer is within such a range, by setting the slow axis direction of the first optical compensation layer to 5° to 25° (particularly, about 15°) with respect to the absorption axis direction of the polarizer as described above, it is possible to prevent a decrease in the anti-reflection function in the oblique direction due to the apparent axis misalignment of the absorption axis of the polarizer. Further, in this case, the Nz coefficient of the first optical compensation layer is, in one embodiment, 0.4 to 0.8, preferably 0.5 to 0.7, more preferably 0.55 to 0.65, and particularly preferably 0.55 to 0.60. If the Nz coefficient is within such a range, by adjusting the angle between the slow axis of the first optical compensation layer and the absorption axis of the polarizer to a predetermined angle, more excellent anti-reflection characteristics in the oblique direction can be achieved.

[0021] In another embodiment, the in-plane phase difference Re(550) of the first optical compensation layer is preferably 280 nm to 360 nm, more preferably 290 nm to 350 nm, and even more preferably 310 nm to 330 nm. If the in-plane phase difference of the first optical compensation layer is within this range, the reduction in oblique anti-reflection function due to apparent misalignment of the polarizer's absorption axis can be prevented by preferably making the slow phase axis direction of the first optical compensation layer substantially parallel to the polarizer's absorption axis direction. Furthermore, in this case, the Nz coefficient is preferably 0.5 to 0.9, more preferably 0.6 to 0.8, even more preferably 0.7 to 0.8, and particularly preferably 0.72 to 0.78 in another embodiment. If the Nz coefficient is within this range, better oblique anti-reflection characteristics can be achieved by adjusting the angle between the slow phase axis of the first optical compensation layer and the polarizer's absorption axis to a predetermined angle.

[0022] The first optical compensation layer is typically formed from a resin film made of any suitable resin capable of achieving the above characteristics. Examples of resins used to form this resin film include polycarbonate resins, cyclic olefin resins, cellulose resins, polyester resins, polyvinyl alcohol resins, polyamide resins, polyimide resins, polyether resins, polystyrene resins, acrylic resins, and polyester carbonate resins. Among these, cyclic olefin resins or polycarbonate resins can be preferably used.

[0023] Cyclic olefin resins are a general term for resins polymerized using cyclic olefins as polymerization units. Examples include resins described in Japanese Patent Publication No. 1-240517, Japanese Patent Publication No. 3-14882, and Japanese Patent Publication No. 3-122137. Specific examples include ring-opening (co)polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins with α-olefins such as ethylene and propylene (typically random copolymers), graft-modified products obtained by modifying these with unsaturated carboxylic acids and their derivatives, and their hydrides. Specific examples of cyclic olefins include norbornene monomers. Examples of norbornene monomers include those described in Japanese Patent Publication No. 2015-210459, etc. Various products of the above-mentioned cyclic olefin resins are commercially available. Specific examples include the product names "Zeonex" and "Zeonor" manufactured by Nippon Zeon Corporation, "Arton" manufactured by JSR Corporation, "Topas" manufactured by TICONA Corporation, and "APEL" manufactured by Mitsui Chemicals Corporation.

[0024] As the polycarbonate resin, any suitable polycarbonate resin can be used as long as the effects of the present invention are obtained. Preferably, the polycarbonate resin comprises structural units derived from isosorbide-based dihydroxy compounds and structural units derived from at least one dihydroxy compound selected from the group consisting of alicyclic diols, alicyclic dimethanol, di, tri, or polyethylene glycol, and alkylene glycol or spiroglycol. More preferably, the polycarbonate resin comprises structural units derived from isosorbide-based dihydroxy compounds and structural units derived from alicyclic dimethanol and / or structural units derived from di, tri, or polyethylene glycol. The polycarbonate resin may optionally contain structural units derived from other dihydroxy compounds. Details of polycarbonate resins and methods for producing phase difference films that can be suitably used in the present invention are described, for example, in International Publication No. 2011 / 062239, which is incorporated herein by reference.

[0025] The first optical compensation layer can be formed, for example, by applying a coating solution obtained by dissolving or dispersing the above resin in any suitable solvent to a shrinkable film to form a coating film, and then shrinking the coating film. Typically, the shrinkage of the coating film is caused by heating the laminate of the shrinkable film and the coating film to shrink the shrinkable film, and this shrinkage of the shrinkable film causes the coating film to shrink. The shrinkage rate of the coating film is preferably 0.50 to 0.99, more preferably 0.60 to 0.98, and even more preferably 0.70 to 0.95. The heating temperature is preferably 130°C to 170°C, and even more preferably 150°C to 160°C. In one embodiment, when shrinking the coating film, the laminate may be stretched in a direction perpendicular to the shrinkage direction. In this case, the stretching ratio of the laminate is preferably 1.01 to 3.0, more preferably 1.05 to 2.0, and even more preferably 1.10 to 1.50. Specific examples of materials that constitute a shrinkable film include polyolefins, polyesters, acrylic resins, polyamides, polycarbonates, norbornene resins, polystyrenes, polyvinyl chlorides, polyvinylidene chlorides, cellulose resins, polyethersulfones, polysulfones, polyimides, polyacrylics, acetate resins, polyarylates, polyvinyl alcohols, and liquid crystal polymers. These may be used individually or in combination. Preferably, the shrinkable film is a stretched film formed from these materials.

[0026] The thickness of the first optical compensation layer is preferably 10 μm to 200 μm, more preferably 20 μm to 150 μm, and even more preferably 20 μm to 60 μm. With such thicknesses, the desired in-plane phase difference and Nz coefficient can be obtained.

[0027] A-3. Second optical compensation layer As described above, the second optical compensation layer 40 exhibits a refractive index characteristic of nx>nz>ny and has a slow axis. Furthermore, the second optical compensation layer exhibits flat wavelength dispersion characteristics in which the phase difference value hardly changes with the wavelength of the measured light. Specifically, the Re(450) / Re(550) of the second optical compensation layer is preferably 0.99 to 1.03. Since a phase difference film exhibiting flat wavelength dispersion characteristics is less expensive than a phase difference film exhibiting inverse dispersion characteristics, by adopting a configuration like that of the embodiment of the present invention, an inexpensive polarizing plate with an optical compensation layer having excellent optical properties can be obtained.

[0028] The second optical compensation layer 40 has an in-plane phase difference Re(550) of 90 nm to 170 nm, preferably 100 nm to 160 nm, and more preferably 120 nm to 140 nm, as described above. If the in-plane phase difference of the second optical compensation layer is within this range, excellent anti-reflective properties can be achieved by setting the slow axis direction of the second optical compensation layer to an angle of 65° to 85° (particularly about 75°) with respect to the absorption axis direction of the polarizer, as described above. Furthermore, in this case, the Nz coefficient of the second optical compensation layer is 0.4 to 0.8, preferably 0.5 to 0.7, more preferably 0.55 to 0.65, and particularly preferably 0.57 to 0.63 in one embodiment. This can achieve even better reflective hue.

[0029] In another embodiment, the second optical compensation layer 40 has an in-plane phase difference Re(550) of preferably 100 nm to 180 nm, more preferably 110 nm to 170 nm, and even more preferably 130 nm to 150 nm, as described above. If the in-plane phase difference of the second optical compensation layer is within this range, excellent anti-reflective properties can be achieved by setting the lagging axis direction of the second optical compensation layer to an angle of preferably 35° to 55° (particularly preferably about 45°) with respect to the absorption axis direction of the polarizer, as described above. Furthermore, in this case, the Nz coefficient is preferably 0.2 to 0.6, more preferably 0.3 to 0.5, even more preferably 0.35 to 0.45, and particularly preferably 0.37 to 0.42. A better reflective hue can be achieved.

[0030] The material for forming the second optical compensation layer and the method for forming the second optical compensation layer are the same as those for the first optical compensation layer.

[0031] The thickness of the second optical compensation layer is preferably 10 μm to 150 μm, more preferably 10 μm to 100 μm, and even more preferably 10 μm to 30 μm. With such thicknesses, the desired in-plane phase difference and Nz coefficient can be obtained.

[0032] By combining the first optical compensation layer described in A-2. above with the second optical compensation layer described in A-3., it is possible to obtain an optical compensation layer polarizing plate that is inexpensive, maintains excellent anti-reflective properties in the forward direction, also exhibits excellent anti-reflective properties in the oblique direction, and further enables the realization of an organic EL panel with neutral hue in the oblique direction.

[0033] A-4.Protective layer The protective layer 20 is formed from any suitable film that can be used as a protective layer for the polarizer. Specific examples of materials that make up the main component of the film include cellulosic resins such as triacetylcellulose (TAC), and transparent resins such as polyester, polyvinyl alcohol, polycarbonate, polyamide, polyimide, polyethersulfone, polysulfone, polystyrene, polynorbornene, polyolefin, (meth)acrylic, and acetate. Thermosetting resins or UV-curing resins such as (meth)acrylic, urethane, (meth)acrylic urethane, epoxy, and silicone can also be used. In addition, glassy polymers such as siloxane polymers can also be used. Polymer films described in Japanese Patent Application Publication No. 2001-343529 (WO01 / 37007) can also be used. As materials for this film, for example, a resin composition containing a thermoplastic resin having substituted or unsubstituted imide groups in its side chains, and a thermoplastic resin having substituted or unsubstituted phenyl groups and nitrile groups in its side chains can be used. Examples include a resin composition having an alternating copolymer of isobutene and N-methylmaleimide, and an acrylonitrile-styrene copolymer. The polymer film may be, for example, an extruded product of the above resin composition.

[0034] The protective layer 20 may be subjected to surface treatments such as hard coating, anti-reflective coating, anti-sticking coating, and anti-glare coating, as needed.

[0035] The thickness of the protective layer 20 is typically 5 mm or less, preferably 1 mm or less, more preferably 1 μm to 500 μm, and even more preferably 5 μm to 150 μm. If a surface treatment is applied, the thickness of the protective layer includes the thickness of the surface treatment layer.

[0036] When an inner protective layer is provided between the polarizer 10 and the first optical compensation layer 30, it is preferable that the inner protective layer is optically isotropic. In this specification, "optically isotropic" means that the in-plane phase difference Re(550) is 0 nm to 10 nm and the phase difference Rth(550) in the thickness direction is -10 nm to +10 nm. The inner protective layer can be composed of any suitable material as long as it is optically isotropic. The material can be appropriately selected, for example, from the materials described above for the protective layer 20.

[0037] The thickness of the inner protective layer is preferably 5 μm to 200 μm, more preferably 10 μm to 100 μm, and even more preferably 15 μm to 95 μm.

[0038] A-5. Others Each layer constituting the polarizing plate with optical compensation layer is bonded together via any suitable adhesive or bonding layer.

[0039] Although not shown in the diagram, an adhesive layer may be provided on the side of the second optical compensation layer 40 of the polarizing plate 100 with an optical compensation layer. The presence of the adhesive layer allows for easy bonding to other optical components (e.g., organic EL panels). Preferably, a release film is bonded to the surface of this adhesive layer until it is put into use. Temporarily bonding the release film protects the adhesive layer and enables roll formation.

[0040] B. Organic EL panel The organic EL panel of the present invention comprises an organic EL cell and a polarizing plate with an optical compensation layer as described in item A above, on the viewing side of the organic EL cell. The polarizing plate with an optical compensation layer is laminated such that the second optical compensation layer is on the organic EL cell side (the polarizer is on the viewing side). [Examples]

[0041] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The measurement methods for each characteristic are as follows.

[0042] (1) Thickness Measurements were taken using a dial gauge (PEACOCK Corporation, product name "DG-205") and a dial gauge stand (product name "pds-2"). (2) Phase difference 50mm x 50mm samples were cut from the phase difference films constituting the optical compensation layer of the optical compensation layer polarizers of the examples and comparative examples, and measured using an Axoscan manufactured by Axometrics. The measurement wavelengths were 450nm and 550nm, and the measurement temperature was 23°C. Furthermore, the average refractive index was measured using an Abbe refractometer manufactured by Atago, and the refractive indices nx, ny, and nz were calculated from the obtained phase difference values. (3) Frontal reflected brightness The polarizing plates with optical compensation layers obtained in the examples and comparative examples were bonded to the viewing side of the organic EL panel of an organic EL display device (LG Display, product name "55C7P") via an adhesive layer, with the optical compensation layer facing the organic EL side, to obtain an organic EL display device. A black image was displayed on an OLED screen, and the frontal reflected luminance was measured using a Konica Minolta spectrophotometer (product name "CM-2600D"). (4) Reflectance characteristics in oblique directions The properties of polarizers with optical compensation layers obtained in the examples and comparative examples were used for simulation. The evaluation was performed in the oblique direction (extreme angle 60°). The simulation was performed using "LCD MASTER Ver. 6.084" from Syntec Corporation. Reflection characteristics were simulated using the extended functions of LCD Master.

[0043] [Example 1] (i) Fabrication of the first optical compensation layer A commercially available cyclic olefin resin film (manufactured by JSR, trade name "Arton (R5000)") was used as the resin film. Its thickness was 130 μm and its Tg was 137°C. A 60 μm thick shrinkable film (manufactured by Toray Industries, trade name "Trefan BO2873") was laminated to both sides of the film via an acrylic adhesive layer (thickness 15 μm), and the free end was subjected to uniaxial stretching to obtain a phase difference film constituting the first optical compensation layer. The stretching temperature was 134°C and the stretching ratio was 1.06 times. The obtained phase difference film (i.e., the first optical compensation layer) had a Re(550) of 257 nm, an Nz coefficient of 0.59, and a Re(450) / Re(550) of 1.00.

[0044] (ii) Fabrication of the second optical compensation layer (i) A phase difference film constituting the second optical compensation layer was fabricated in the same manner as the first optical compensation layer, except that the stretching temperature was set to 135°C and the stretching ratio was set to 1.03 times. The obtained phase difference film (i.e., the second optical compensation layer) had a Re(550) of 130 nm, an Nz coefficient of 0.6, and a Re(450) / Re(550) of 1.00.

[0045] (iii) Fabrication of polarizers A 12 μm thick polarizer was fabricated by uniaxially stretching a 30 μm thick polyvinyl alcohol (PVA) resin film (manufactured by Kuraray, product name "PE3000") in the longitudinal direction using a roll stretching machine to 5.9 times its length, while simultaneously subjecting it to swelling, dyeing, crosslinking, and washing treatments, and finally drying treatment. Specifically, the swelling treatment involved stretching the material 2.2 times while treating it with pure water at 20°C. Next, the dyeing treatment involved stretching the material 1.4 times while treating it in an aqueous solution at 30°C with an iodine-to-potassium iodide weight ratio of 1:7, where the iodine concentration was adjusted so that the resulting polarizer's single-component transmittance was 45.0%. Furthermore, the cross-linking treatment employed a two-stage process. In the first stage, the material was stretched 1.2 times while treating it in an aqueous solution of boric acid and potassium iodide at 40°C. The boric acid content of the aqueous solution for the first stage was 5.0% by weight, and the potassium iodide content was 3.0% by weight. In the second stage, the material was stretched 1.6 times while treating it in an aqueous solution of boric acid and potassium iodide at 65°C. The boric acid content of the aqueous solution for the second stage was 4.3% by weight, and the potassium iodide content was 5.0% by weight. Furthermore, the washing treatment was performed with an aqueous potassium iodide solution at 20°C. The potassium iodide content of the washing solution was 2.6% by weight. Finally, the polarizer was obtained by drying at 70°C for 5 minutes.

[0046] (iv) Fabrication of polarizing plates A roll-to-roll application of an HC-TAC film (thickness: 32 μm, corresponding to the protective layer) having a hard coat (HC) layer (7 μm) formed on one side of a TAC film (25 μm) by hard coat treatment was applied to one side of the above polarizer via a polyvinyl alcohol-based adhesive, thereby obtaining a long polarizing plate having a protective layer / polarizer configuration.

[0047] (v) Fabrication of polarizing plates with optical compensation layer The polarizing plate, the first optical compensation layer, and the second optical compensation layer obtained above were cut to predetermined sizes. The polarizer surface of the polarizing plate and the first optical compensation layer were bonded together using an acrylic adhesive, and then the first optical compensation layer and the second optical compensation layer were bonded together using an acrylic adhesive. In this way, a polarizing plate with an optical compensation layer having the configuration of a protective layer / polarizer / first optical compensation layer / second optical compensation layer was obtained. The first optical compensation layer was cut so that the angle between the absorption axis of the polarizer and the slow axis of the first optical compensation layer in the polarizing plate with an optical compensation layer was 15°. The second optical compensation layer was cut so that the angle between the absorption axis of the polarizer and the slow axis of the second optical compensation layer in the polarizing plate with an optical compensation layer was 75°. In other words, the number of times the process of cutting and bonding each layer constituting the polarizing plate with an optical compensation layer (RtoS) was performed was 2.

[0048] The obtained polarizing plate with optical compensation layer was used for the evaluation described in (3) above. Furthermore, the reflection characteristics described in (4) above were simulated using the properties of the obtained polarizing plate with optical compensation layer. The results are shown in Table 1.

[0049] [Example 2] A first optical compensation layer and a second optical compensation layer were obtained in the same manner as in Example 1, except that the stretching temperature and stretching ratio listed in Table 1 were used. The obtained first optical compensation layer had a Re(550) of 317 nm, an Nz coefficient of 0.75, and a Re(450) / Re(550) ratio of 1.00. The obtained second optical compensation layer had a Re(550) of 136 nm, an Nz coefficient of 0.41, and a Re(450) / Re(550) ratio of 1.00. The polarizer and the first optical compensation layer were bonded together by roll-to-roll, and the shrinkable film was peeled off to obtain a laminate of protective layer / polarizer / first optical compensation layer. The absorption axis of the polarizer and the slow axis of the first optical compensation layer were substantially parallel. The laminate was cut to a predetermined size, and the second optical compensation layer was cut and bonded so that the angle between the absorption axis of the polarizer and the slow axis of the second optical compensation layer was 45°, thereby obtaining an optical compensation layer polarizer having the configuration of protective layer / polarizer / first optical compensation layer / second optical compensation layer. In other words, the number of cut and bond steps (RtoS) of each layer constituting the optical compensation layer polarizer was one. Furthermore, an organic EL panel was fabricated in the same manner as in Example 1, except that this optical compensation layer polarizer was used. The obtained optical compensation layer polarizer was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0050] [Comparative Example 1] (i) Fabrication of the first optical compensation layer (i-1) Preparation of polycarbonate resin film Polymerization was carried out using a batch polymerization apparatus consisting of two vertical reactors equipped with stirring blades and reflux condensers controlled to 100°C. 9,9-[4-(2-hydroxyethoxy)phenyl]fluorene (BHEPF), isosorbide (ISB), diethylene glycol (DEG), diphenyl carbonate (DPC), and magnesium acetate tetrahydrate were charged in a molar ratio of BHEPF / ISB / DEG / DPC / magnesium acetate = 0.348 / 0.490 / 0.162 / 1.005 / 1.00 × 10⁻⁵. After thoroughly purging the reactor with nitrogen (oxygen concentration 0.0005~0.001 vol%), heating was carried out with a heat transfer medium, and stirring was started when the internal temperature reached 100°C. 40 minutes after the start of heating, the internal temperature was raised to 220°C, and while controlling the pressure to maintain this temperature, the pressure was reduced to 13.3 kPa 90 minutes after reaching 220°C. The phenol vapor produced as a by-product during the polymerization reaction was led to a reflux condenser at 100°C, the monomer components contained in small amounts in the phenol vapor were returned to the reactor, and the uncondensed phenol vapor was led to a condenser at 45°C for recovery.

[0051] Nitrogen was introduced into the first reactor to restore pressure to atmospheric pressure, and then the oligomerized reaction mixture in the first reactor was transferred to the second reactor. Next, heating and depressurization were started in the second reactor, and the internal temperature was raised to 240°C and the pressure to 0.2 kPa in 50 minutes. Polymerization was then allowed to proceed until the predetermined stirring power was reached. Once the predetermined power was reached, nitrogen was introduced into the reactor to restore pressure, the reaction mixture was extracted in strand form, and pelletized using a rotary cutter to obtain a polycarbonate resin with a copolymer composition of BHEPF / ISB / DEG = 34.8 / 49.0 / 16.2 [mol%]. The reduced viscosity of this polycarbonate resin was 0.430 dL / g, and the glass transition temperature was 128°C.

[0052] (i-2) Fabrication of the first optical compensation layer The obtained polycarbonate resin was vacuum-dried at 80°C for 5 hours. Then, a 130 μm thick polycarbonate resin film was produced using a film-making apparatus equipped with a single-screw extruder (manufactured by Isuzu Chemical Machinery Co., Ltd., screw diameter 25 mm, cylinder setting temperature: 220°C), a T-die (width 900 mm, setting temperature: 220°C), a chill roll (setting temperature: 125°C), and a winding machine. The water absorption rate of the obtained polycarbonate resin film was 1.2%.

[0053] The polycarbonate resin film obtained as described above was obliquely stretched in accordance with Example 1 of Japanese Patent Application Publication No. 2014-194483 to obtain a first optical compensation layer. The obtained first optical compensation layer had a Re(550) of 139 nm, an Nz coefficient of 1.10, and a Re(450) / Re(550) of 0.89.

[0054] (ii) Fabrication of the second optical compensation layer A liquid crystal coating solution was prepared by dissolving 20 parts by weight of a side-chain liquid crystal polymer represented by the following chemical formula (II) (the numbers 65 and 35 in the formula indicate the mole percent of monomer units and are conveniently represented as a block polymer: weight-average molecular weight 5000), 80 parts by weight of a polymerizable liquid crystal exhibiting a nematic liquid crystal phase (BASF: trade name Paliocolor LC242), and 5 parts by weight of a photopolymerization initiator (Ciba Specialty Chemicals: trade name Irgacure 907) in 200 parts by weight of cyclopentanone. Then, the coating solution was applied to a substrate film (norbornene-based resin film: manufactured by Nippon Zeon Co., Ltd., trade name "Zeonex") using a bar coater, and the liquid crystal was oriented by heating and drying at 80°C for 4 minutes. By irradiating this liquid crystal layer with ultraviolet light and curing the liquid crystal layer, a liquid crystal solidification layer (thickness: 0.58 μm), which serves as a second optical compensation layer, was formed on the substrate. The obtained second optical compensation layer had a Re(550) of 0 nm and a Rth(550) of -71.

[0055] [ka]

[0056] The polarizing plate and the first optical compensation layer and the second optical compensation layer obtained in (i) and (ii) above were bonded together by roll-to-roll bonding, and the substrate was peeled off to obtain a polarizing plate with an optical compensation layer having the configuration of protective layer / polarizer / first optical compensation layer / second optical compensation layer. The angle between the absorption axis of the polarizer and the slow axis of the first optical compensation layer was 45°. Furthermore, an organic EL panel was fabricated in the same manner as in Example 1, except that this polarizing plate with an optical compensation layer was used. The obtained polarizing plate with an optical compensation layer and organic EL panel were subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0057] [Comparative Example 2] An optical compensation layer polarizer was obtained in the same manner as in Comparative Example 1, except that the thickness of the second optical compensation layer was 0.44 μm, and the configuration was that of a protective layer / polarizer / first optical compensation layer / second optical compensation layer. The Re(550) of the first optical compensation layer was 139 nm, the Nz coefficient was 1.00, and the Re(450) / Re(550) was 0.89. The Re(550) of the second optical compensation layer was 0 nm, and the Rth(550) was -54. Furthermore, an organic EL panel was fabricated in the same manner as in Example 1, except that this optical compensation layer polarizer was used. The obtained optical compensation layer polarizer and organic EL panel were subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0058] [Table 1] * indicates the phase difference (Rth) in the thickness direction.

[0059] [evaluation] As is clear from Table 1, the polarizing plate with an optical compensation layer according to the embodiment of the present invention can maintain excellent anti-reflective properties in the forward direction while also achieving excellent anti-reflective properties in the oblique direction. Furthermore, according to the embodiment, it was confirmed that the hue in the oblique direction can be made neutral. [Industrial applicability]

[0060] The polarizing plate with an optical compensation layer of the present invention is suitably used in organic EL panels. [Explanation of Symbols]

[0061] 10 Polarizers 20 protective layer 30 First optical compensation layer 40 Second optical compensation layer 100 Polarizing plate with optical compensation layer

Claims

1. The polarizer, the first optical compensation layer, and the second optical compensation layer are provided in this order. The first optical compensation layer exhibits a refractive index characteristic nx > nz > ny, The second optical compensation layer exhibits a refractive index characteristic nx > nz > ny, The slow axis of the first optical compensation layer and the slow axis of the second optical compensation layer intersect, The Re(450) / Re(550) ratio of the first optical compensation layer and the second optical compensation layer is 0.99 to 1.

03. Polarizing plate with optical compensation layer: Here, Re(450) and Re(550) represent the in-plane phase differences measured with light at wavelengths of 450 nm and 550 nm at 23°C, respectively.

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