JP7592473B2 - Polarizing plate with optical compensation layer and organic EL panel using same - Google Patents

Description

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

In recent years, displays equipped with organic EL panels (organic EL display devices) have been proposed along with the spread of thin displays. Since organic EL panels have a highly reflective metal layer, they are prone to problems such as reflection of external light and reflection of the background. It is known that these problems can be prevented by providing a circular polarizing plate on the viewing side. A typical circular polarizing plate is one in which a retardation film (typically a λ/4 plate) is laminated so that its slow axis forms an angle of about 45° with respect to the absorption axis of the polarizer. In addition, in order to further improve the anti-reflection properties, attempts have been made to laminate retardation films (optical compensation layers) having various optical properties. However, all conventional circular polarizing plates have the problem of high reflectance in the oblique direction (i.e., insufficient anti-reflection properties in the oblique direction). Furthermore, all conventional circular polarizing plates have the problem of undesirable coloring in the hue in the oblique direction.

Patent No. 3325560

The present invention has been made to solve the above-mentioned problems of the conventional art, and its main objective is to provide a polarizing plate with an optical compensation layer that can realize an organic EL panel that maintains excellent anti-reflection properties in the front direction while also having excellent anti-reflection properties in oblique directions and that has a neutral hue in oblique directions.

The polarizing plate with optical compensation layer of the present invention is used for an organic EL panel. This polarizing plate with optical compensation layer includes a polarizer, a first optical compensation layer, and a second optical compensation layer in this order. The first optical compensation layer exhibits a refractive index characteristic of nx≧nz>ny, Re(550) is 90 nm to 180 nm, the Nz coefficient is 0 to 0.8, the angle between the absorption axis direction of the polarizer and the slow axis direction of the first optical compensation layer is substantially parallel, and Re(450) and Re(550) of the first optical compensation layer are substantially equal. The second optical compensation layer exhibits a refractive index characteristic of nx>ny=nz, Re(550) is 100 nm to 180 nm, 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°, and the second optical compensation layer satisfies Re(550)>Re(450). Here, Re(450) and Re(550) represent in-plane retardations measured at 23° C. using light with wavelengths of 450 nm and 550 nm, respectively.
In one embodiment, the first optical compensation layer exhibits a refractive index characteristic of nx>nz>ny, Re(550) is 90 nm to 170 nm, the Nz coefficient is 0.1 to 0.5, 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°, and Re(450) and Re(550) of the first optical compensation layer are substantially equal. The second optical compensation layer exhibits a refractive index characteristic of nx>ny=nz, Re(550) is 60 nm to 140 nm, the angle between the slow axis direction of the first optical compensation layer and the slow axis direction of the second optical compensation layer is 50° to 70°, and the second optical compensation layer satisfies Re(550)>Re(450). Here, Re(450) and Re(550) represent in-plane retardations measured at 23° C. using light with wavelengths of 450 nm and 550 nm, respectively.
According to another aspect of the present invention, there is provided an organic EL panel, the organic EL panel including the above-mentioned polarizing plate with optical compensation layers.

According to the present invention, in a polarizing plate with an optical compensation layer, a first optical compensation layer exhibiting a refractive index characteristic of nx>nz>ny or nx=nz>ny, having a predetermined in-plane retardation, and exhibiting flat dispersion characteristics, and a second optical compensation layer exhibiting a refractive index characteristic of nx>ny=nz, having a predetermined in-plane retardation, and satisfying Re(550)>Re(450) are arranged in this order from the polarizer side, thereby making it possible to obtain a polarizing plate with an optical compensation layer that maintains excellent anti-reflection properties in the front direction, has excellent anti-reflection properties in oblique directions, and has a neutral hue in the oblique direction.

FIG. 1 is a schematic cross-sectional view of a polarizing plate with optical compensation layers according to one embodiment of the present invention.

The following describes preferred embodiments of the present invention, but the present invention is not limited to these embodiments.

(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 having a wavelength of 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 having a wavelength of 550 nm at 23° C.
(3) Retardation in the thickness direction (Rth)
"Rth(λ)" is the retardation in the thickness direction measured with light having a wavelength of λ 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). For example, "Rth(550)" is the retardation in the thickness direction measured with light having a wavelength of 550 nm at 23° C.
(4) Nz Coefficient The Nz coefficient is calculated by Nz=Rth/Re.
(5) Substantially Orthogonal or Parallel The expressions "substantially orthogonal" and "approximately orthogonal" include the case where the angle between two directions is 90°±10°, preferably 90°±7°, and more preferably 90°±5°. The expressions "substantially parallel" and "approximately parallel" include the case where the angle between two directions is 0°±10°, preferably 0°±7°, and more preferably 0°±5°. Furthermore, when the term "orthogonal" or "parallel" is used herein, it is understood that the term may include a substantially orthogonal or substantially parallel state.

A. Overall configuration of a polarizing plate with an optical compensation layer FIG. 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 with an optical compensation layer 100 of this embodiment includes a polarizer 10, a first optical compensation layer 30, and a second optical compensation layer 40 in this order. In practical terms, as in the illustrated example, a protective layer 20 may be provided on the polarizer 10 opposite the first optical compensation layer 30. The polarizing plate with an optical compensation layer may also include another protective layer (also referred to as 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 may also function as the inner protective layer. Furthermore, if necessary, a conductive layer and a base material may be provided in this order on the side of the second optical compensation layer 40 opposite the first optical compensation layer 30 (i.e., outside the second optical compensation layer 40) (neither is shown). The base material is laminated in close contact with the conductive layer. In this specification, "adhesion lamination" means that two layers are directly and firmly laminated without an adhesive layer (e.g., an adhesive layer, a pressure-sensitive adhesive layer). The conductive layer and the substrate can be typically introduced into the polarizing plate 100 with an optical compensation layer as a laminate of a substrate and a conductive layer. By further providing a conductive layer and a substrate, the polarizing plate 100 with an optical compensation layer can be suitably used in an inner touch panel type input display device. Furthermore, if necessary, the polarizing plate with an optical compensation layer (substantially, the protective layer 20) may be subjected to a treatment for improving visibility when viewed through polarized sunglasses (typically, imparting an (elliptical) polarizing function or imparting an ultra-high phase difference). By performing such a treatment, excellent visibility can be achieved even when the display screen is viewed through a polarizing lens such as polarized sunglasses. Therefore, the polarizing plate with an optical compensation layer can also be suitably applied to an image display device that can be used outdoors.

In one embodiment, the first optical compensation layer 30 has a slow axis and has a refractive index characteristic of nx≧nz>ny. The in-plane retardation Re(550) of the first optical compensation layer 30 is 90 nm to 180 nm. In this case, the Nz coefficient of the first optical compensation layer is 0 to 0.8, the angle between the slow axis of the first optical compensation layer 30 and the absorption axis of the polarizer 10 is substantially parallel, and the Re(450) and Re(550) of the first optical compensation layer are substantially equal. That is, the retardation value has a flat dispersion characteristic that hardly changes depending on the wavelength of the measurement light. Furthermore, the second optical compensation layer 40 has a refractive index characteristic of nx>ny=nz and has a slow axis. The in-plane retardation Re(550) of the second optical compensation layer 40 is 100 nm to 180 nm. In this case, the angle between the slow axis of the second optical compensation layer 30 and the absorption axis of the polarizer 10 is 35° to 55°, preferably 38° to 52°, more preferably 42° to 48°, and even more preferably about 45°. Furthermore, the second optical compensation layer satisfies Re(550)>Re(450). That is, it has an inverse dispersion characteristic in which the retardation value increases according to the wavelength of the measurement light. In another embodiment, the first optical compensation layer 30 has a slow axis and has a refractive index characteristic of nx>nz>ny. The in-plane retardation Re(550) of the first optical compensation layer 30 is preferably 90 nm to 170 nm. In this case, the Nz coefficient of the first optical compensation layer is preferably 0.1 to 0.5, and the angle between the slow axis of the first optical compensation layer 30 and the absorption axis of the polarizer 10 is preferably 5° to 25°, more preferably 8° to 22°, even more preferably 10° to 20°, and particularly preferably about 13°. Furthermore, the second optical compensation layer 40 has a slow axis, and the refractive index characteristic shows a relationship of nx>ny=nz. The in-plane retardation Re(550) of the second optical compensation layer 40 is 60 nm to 140 nm. In this case, the angle between the slow axis of the second optical compensation layer 30 and the absorption axis of the polarizer 10 is preferably 50° to 70°, more preferably 53° to 67°, even more preferably 55° to 65°, and particularly preferably about 58°. By arranging the first optical compensation layer, which exhibits the above-mentioned refractive index characteristics, has a predetermined in-plane retardation, and exhibits flat dispersion characteristics, and the second optical compensation layer, which exhibits the above-mentioned refractive index characteristics, has a predetermined in-plane retardation, and exhibits reverse dispersion characteristics, in this order from the polarizer side, it is possible to prevent light leakage due to the apparent axial misalignment of the absorption axis of the polarizer when viewed from an oblique direction while maintaining excellent anti-reflection characteristics in the front direction due to excellent circular polarization function. As a result, when a polarizing plate with an optical compensation layer is applied to an organic EL panel, it is possible to realize excellent anti-reflection characteristics in oblique directions and further realize a neutral hue (i.e., without undesired coloring) in oblique directions.

The layers and optical films that make up the polarizing plate with optical compensation layers are described in detail below.

A-1. Polarizer Any appropriate polarizer can be adopted 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.

Specific examples of polarizers made of a single-layer resin film include hydrophilic polymer films such as polyvinyl alcohol (PVA)-based films, partially formalized PVA-based 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 and dehydrochlorinated polyvinyl chloride. Preferably, a polarizer obtained by dyeing a PVA-based film with iodine and stretching it uniaxially is used because of its excellent optical properties.

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 process or while dyeing. Alternatively, the film may be stretched and then dyed. If necessary, the PVA-based film may be subjected to a swelling process, a crosslinking process, a washing process, a drying process, 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.

Specific examples of polarizers obtained using a 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 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, for example, by applying a PVA-based resin solution to a resin substrate and drying the substrate to form a PVA-based resin layer on the resin substrate to obtain a laminate of a resin substrate and a PVA-based resin layer; and stretching and dyeing the laminate to make the PVA-based resin layer into a polarizer. In this embodiment, stretching typically includes immersing the laminate in an aqueous solution of boric acid and stretching it. Furthermore, stretching may further include air-stretching the laminate at a high temperature (e.g., 95°C or higher) before stretching in the aqueous solution of boric acid, as necessary. The obtained resin substrate/polarizer laminate may be used as 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 resin substrate/polarizer laminate, and any suitable protective layer may be laminated on the peeled surface depending on the purpose. Details of the method for producing such a polarizer are described, for example, in JP-A-2012-73580 (Patent No. 5414738). The entire disclosure of this publication is incorporated herein by reference.

The thickness of the polarizer is preferably 25 μm or less, more preferably 1 μm to 12 μm, even more preferably 3 μm to 12 μm, and particularly preferably 3 μm to 8 μm. If the thickness of the polarizer is within this range, curling during heating can be effectively suppressed, and good appearance durability during heating can be obtained.

The polarizer preferably exhibits absorption dichroism at any wavelength between 380 nm and 780 nm. The single transmittance of the polarizer is preferably between 42.0% and 46.0%, and more preferably between 44.5% and 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.

A-2. First optical compensation layer The first optical compensation layer 30 has a refractive index characteristic of nx>nz>ny or nx=nz>ny, and has a slow axis. Furthermore, the first optical compensation layer 30 exhibits flat wavelength dispersion characteristics in which the retardation value hardly changes depending on the wavelength of the measuring light. Specifically, the Re(450)/Re(550) of the first optical compensation layer is preferably 0.99 to 1.03.

In one embodiment, the first optical compensation layer 30 has a refractive index characteristic of nx≧nz>ny, and an in-plane retardation Re(550) of 90 nm to 180 nm. If the in-plane retardation of the first optical compensation layer is in this range, the slow axis direction of the first optical compensation layer is substantially parallel to the absorption axis direction of the polarizer, thereby preventing a decrease in the anti-reflection function in oblique directions due to the apparent axial misalignment of the absorption axis of the polarizer. Furthermore, in this case, the Nz coefficient of the first optical compensation layer is 0 to 0.8 in one embodiment. If the Nz coefficient is in this range, the angle between the slow axis of the first optical compensation layer and the absorption axis of the polarizer can be adjusted to a predetermined angle to achieve better anti-reflection properties in oblique directions.

In another embodiment, the first optical compensation layer 30 has a refractive index characteristic of nx>nz>ny, and the in-plane retardation Re(550) is preferably 90 nm to 170 nm, more preferably 100 nm to 160 nm, and even more preferably 120 nm to 140 nm. If the in-plane retardation of the first optical compensation layer is in such a range, the slow axis direction of the first optical compensation layer can be set to an angle of 5° to 25° (particularly, about 13°) with respect to the absorption axis direction of the polarizer as described above, thereby preventing a decrease in the anti-reflection function in the oblique direction due to the apparent axial misalignment of the absorption axis of the polarizer. Furthermore, in this case, the Nz coefficient of the first optical compensation layer is preferably 0.1 to 0.5, more preferably 0.15 to 0.45, and even more preferably 0.2 to 0.4. If the Nz coefficient is within this range, better anti-reflection properties in oblique directions can be achieved 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.

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

Cyclic olefin resin is a general term for resins polymerized with cyclic olefins as polymerization units, and examples of such resins include those described in JP-A-1-240517, JP-A-3-14882, and JP-A-3-122137. Specific examples include ring-opening (co)polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers (typically random copolymers) of cyclic olefins with α-olefins such as ethylene and propylene, and graft modified products obtained by modifying these with unsaturated carboxylic acids and their derivatives, as well as hydrogenated products thereof. Specific examples of cyclic olefins include norbornene monomers. Examples of norbornene monomers include those described in JP-A-2015-210459. Various products of the above cyclic olefin resins are commercially available. Specific examples include Zeon Corporation's product names "ZEONEX" and "ZEONOR", JSR Corporation's product name "Arton", TICONA Corporation's product name "TOPUS", and Mitsui Chemicals' product name "APEL".

As the polycarbonate resin, any suitable polycarbonate resin can be used as long as the effects of the present invention can be obtained. Preferably, the polycarbonate resin contains a structural unit derived from an isosorbide-based dihydroxy compound and a structural unit derived from at least one dihydroxy compound selected from the group consisting of an alicyclic diol, an alicyclic dimethanol, a di-, tri- or polyethylene glycol, and an alkylene glycol or a spiro glycol. More preferably, the polycarbonate resin contains a structural unit derived from an isosorbide-based dihydroxy compound and a structural unit derived from an alicyclic dimethanol and/or a structural unit derived from a di-, tri- or polyethylene glycol. The polycarbonate resin may contain a structural unit derived from another dihydroxy compound as necessary. Details of the polycarbonate resin and the method for producing the retardation film that can be suitably used in the present invention are described, for example, in International Publication No. 2011/062239, and the description is incorporated herein by reference.

The first optical compensation layer can be formed, for example, by applying a coating liquid in which the resin is dissolved or dispersed in any suitable solvent to a shrinkable film to form a coating film, and then shrinking the coating film. Typically, the coating film is shrunk by heating a laminate of the shrinkable film and the coating film to shrink the shrinkable film, and the coating film is shrunk by the shrinkage of the shrinkable film. The shrinkage ratio 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 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 times to 3.0 times, more preferably 1.05 times to 2.0 times, and even more preferably 1.10 times to 1.50 times. Specific examples of materials constituting the shrinkable film include polyolefin, polyester, acrylic resin, polyamide, polycarbonate, norbornene resin, polystyrene, polyvinyl chloride, polyvinylidene chloride, cellulose resin, polyethersulfone, polysulfone, polyimide, polyacrylic, acetate resin, polyarylate, polyvinyl alcohol, and liquid crystal polymer. These may be used alone or in combination. The shrinkable film is preferably a stretched film formed from these materials.

The thickness of the first 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 a thickness, the desired in-plane retardation and Nz coefficient can be obtained.

A-3. Second optical compensation layer The second optical compensation layer 40 has a refractive index characteristic of nx>ny=nz, and has a slow axis. Furthermore, the second optical compensation layer exhibits a reverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light. That is, it satisfies Re(550)>Re(450). By satisfying such a relationship, it is possible to achieve an excellent reflection hue.

The second optical compensation layer 40 has an in-plane retardation Re(550) of 100 nm to 180 nm, preferably 110 nm to 170 nm, and more preferably 130 nm to 150 nm. If the in-plane retardation of the second optical compensation layer is in this range, excellent anti-reflection properties can be achieved by setting the slow axis direction of the second optical compensation layer to form an angle of 35° to 55° (particularly, about 45°) with respect to the absorption axis direction of the polarizer as described above.

In another embodiment, the second optical compensation layer 40 has a refractive index characteristic of nx>ny=nz, as described above. The in-plane retardation Re(550) of the second optical compensation layer is preferably 90 nm to 170 nm, more preferably 90 nm to 120 nm, and even more preferably 90 nm to 100 nm. If the in-plane retardation of the second optical compensation layer is in this range, the slow axis direction of the second optical compensation layer can be set to form an angle of preferably 50° to 70° (particularly preferably about 58°) with respect to the absorption axis direction of the polarizer, as described above, thereby achieving excellent anti-reflection properties.

The second optical compensation layer is typically a retardation film made of any suitable resin that can achieve the above characteristics. The resin that forms this retardation film is preferably a polycarbonate resin.

As the polycarbonate resin, any suitable polycarbonate resin can be used as long as the effects of the present invention can be obtained. Preferably, the polycarbonate resin contains a structural unit derived from a fluorene-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, and a structural unit derived from at least one dihydroxy compound selected from the group consisting of alicyclic diol, alicyclic dimethanol, di-, tri- or polyethylene glycol, and alkylene glycol or spiro glycol. Preferably, the polycarbonate resin contains a structural unit derived from a fluorene-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, a structural unit derived from an alicyclic dimethanol and/or a structural unit derived from a di-, tri- or polyethylene glycol; more preferably, it contains a structural unit derived from a fluorene-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, and a structural unit derived from a di-, tri- or polyethylene glycol. The polycarbonate resin may contain a structural unit derived from another dihydroxy compound as necessary. Details of polycarbonate resins that can be suitably used in the present invention are described, for example, in JP 2014-10291 A and JP 2014-26266 A (Patent No. 5,528,606), and the descriptions therein are incorporated by reference into this specification.

The retardation film (i.e., the second optical compensation layer) is typically produced by stretching a resin film in at least one direction.

Any suitable method may be used to form the resin film. Examples include melt extrusion (e.g., T-die molding), cast coating (e.g., casting), calendar molding, heat pressing, co-extrusion, co-melting, multi-layer extrusion, and inflation molding. Preferably, the T-die molding, casting, and inflation molding methods are used.

The thickness of the resin film (unstretched film) can be set to any appropriate value depending on the desired optical properties, the stretching conditions described below, etc. It is preferably 50 μm to 300 μm.

The above stretching may be performed using any suitable stretching method and conditions (e.g., stretching temperature, stretching ratio, stretching direction). Specifically, various stretching methods such as free end stretching, fixed end stretching, free end shrinkage, and fixed end shrinkage may be used alone, simultaneously, or sequentially. Stretching may be performed in various directions or dimensions, such as horizontal, vertical, thickness direction, and diagonal direction. The stretching temperature is preferably Tg-30°C to Tg+60°C relative to the glass transition temperature (Tg) of the resin film, and more preferably Tg-10°C to Tg+50°C.

By appropriately selecting the above-mentioned stretching method and stretching conditions, it is possible to obtain a retardation film (i.e., a second optical compensation layer) having the above-mentioned desired optical properties (e.g., refractive index properties, in-plane retardation, Nz coefficient).

The thickness of the retardation film (stretched film, i.e., the second optical compensation layer) is preferably 20 μm to 100 μm, more preferably 20 μm to 80 μm, and even more preferably 20 μm to 65 μm. With such a thickness, the desired in-plane retardation and thickness direction retardation can be obtained.

By combining the first optical compensation layer described in A-2. above with the second optical compensation layer described in A-3. above, it is possible to obtain a polarizing plate with an optical compensation layer that maintains excellent anti-reflection properties in the front direction while also exhibiting excellent anti-reflection properties in oblique directions, and that can realize an organic EL panel with a neutral hue in oblique directions.

A-4. Protective layer The protective layer 20 is formed of any suitable film that can be used as a protective layer for a polarizer. Specific examples of materials that are the main components of the film include cellulose-based resins such as triacetyl cellulose (TAC), and transparent resins such as polyesters, polyvinyl alcohols, polycarbonates, polyamides, polyimides, polyethersulfones, polysulfones, polystyrenes, polynorbornenes, polyolefins, (meth)acrylics, and acetates. Other examples include thermosetting resins or ultraviolet-curing resins such as (meth)acrylics, urethanes, (meth)acrylic urethanes, epoxys, and silicones. Other examples include glassy polymers such as siloxane polymers. Polymer films described in JP-A-2001-343529 (WO01/37007) can also be used. As the material for this film, 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 can be used, for example, a resin composition containing an alternating copolymer of isobutene and N-methylmaleimide, and an acrylonitrile-styrene copolymer. The polymer film can be, for example, an extrusion molded product of the above resin composition.

If necessary, the protective layer 20 may be subjected to surface treatments such as hard coat treatment, anti-reflection treatment, anti-sticking treatment, and anti-glare treatment.

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. Note that if a surface treatment has been applied, the thickness of the protective layer includes the thickness of the surface treatment layer.

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

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.

A-5. Others The layers constituting the polarizing plate with an optical compensation layer are bonded together via any appropriate pressure-sensitive adhesive layer or adhesive layer.

Although not shown, an adhesive layer may be provided on the second optical compensation layer 40 side of the polarizing plate with optical compensation layer 100. By providing the adhesive layer in advance, it is possible to easily attach it to other optical members (e.g., an organic EL panel). It is preferable that a release film is attached to the surface of this adhesive layer until it is used. Temporarily attaching the release film protects the adhesive layer and enables roll formation.

B. Organic EL Panel The organic EL panel of the present invention includes an organic EL cell and, on the viewing side of the organic EL cell, the polarizing plate with an optical compensation layer described in the above item A. The polarizing plate with an optical compensation layer is laminated so that the second optical compensation layer is on the organic EL cell side (so that the polarizer is on the viewing side).

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 each characteristic are as follows.

(1) Thickness: The thickness was measured using a dial gauge (manufactured by PEACOCK, product name "DG-205" and a dial gauge stand (product name "pds-2")).
(2) Retardation A sample of 50 mm x 50 mm was cut out from the retardation film constituting each of the optical compensation layers of the polarizing plates with optical compensation layers of the Examples and Comparative Examples to prepare a measurement sample, and was measured using an Axoscan manufactured by Axometrics, Inc. The measurement wavelengths were 450 nm and 550 nm, and the measurement temperature was 23°C.
In addition, the average refractive index was measured using an Abbe refractometer manufactured by Atago Co., Ltd., and the refractive indexes nx, ny, and nz were calculated from the obtained retardation value.
(3) Front Reflection Brightness The polarizing plates with optical compensation layers obtained in the Examples and Comparative Examples were attached to the viewing side of an organic EL panel of an organic EL display device (LG Display, product name "55C7P") via a pressure-sensitive adhesive layer so that the optical compensation layer was on the organic EL side, thereby obtaining an organic EL display device.
A black image was displayed on the organic EL, and the front reflection luminance was measured using a spectrophotometer manufactured by Konica Minolta (product name "CM-2600D").
(4) Reflection characteristics in oblique directions Simulation was performed using the characteristics of the polarizing plates with optical compensation layers obtained in the examples and comparative examples. Evaluation was performed in an oblique direction (polar angle 60°). For the simulation, "LCD MASTER Ver. 6.084" manufactured by Shintech Co., Ltd. was used. The reflection characteristics were simulated using the extended function of LCD Master.

[Example 1]
(i) Preparation of the first optical compensation layer A commercially available cyclic olefin resin film (manufactured by JSR Corporation, trade name "Arton (R5000)") was used as the resin film. The thickness was 130 μm, and the Tg was 137 ° C. A shrinkable film (manufactured by Toray Industries, Inc., trade name "Trefan BO2873") having a thickness of 60 μm was attached to both sides of the film via an acrylic adhesive layer (thickness 15 μm), and subjected to free end uniaxial stretching to obtain a retardation film constituting the first optical compensation layer. The stretching temperature was 165 ° C., and the stretching ratio was 1.14 times. The Re (550) of the obtained first optical compensation layer was 101 nm, and the Nz coefficient was 0. Re (450) / Re (550) was 1.00.

(ii) Preparation of the second optical compensation layer (ii-1) Preparation of a polycarbonate resin film Polymerization was carried out using a batch polymerization apparatus consisting of two vertical reactors equipped with stirring blades and a reflux condenser controlled at 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 x 10-5. After the inside of the reactor was sufficiently replaced with nitrogen (oxygen concentration 0.0005 to 0.001 vol%), heating was carried out with a heat medium, and stirring was started when the internal temperature reached 100°C. The internal temperature was allowed to reach 220° C. 40 minutes after the start of the temperature rise, and while controlling to maintain this temperature, pressure reduction was started, and the pressure was reduced to 13.3 kPa 90 minutes after reaching 220° C. Phenol vapor by-produced during the polymerization reaction was guided to a reflux condenser at 100° C., and a small amount of monomer components contained in the phenol vapor was returned to the reactor, and uncondensed phenol vapor was guided to a condenser at 45° C. and recovered.

Nitrogen was introduced into the first reactor to restore the pressure to atmospheric pressure, and the oligomerized reaction liquid in the first reactor was then transferred to the second reactor. Next, heating and decompression in the second reactor were started, and the internal temperature was 240°C and the pressure was 0.2 kPa in 50 minutes. Polymerization was then allowed to proceed until a predetermined stirring power was reached. When the predetermined power was reached, nitrogen was introduced into the reactor to restore the pressure, and the reaction liquid was extracted in the form of strands and pelletized with 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.

(ii-2) Preparation of second optical compensation layer The obtained polycarbonate resin was vacuum-dried at 80°C for 5 hours, and then a polycarbonate resin film having a thickness of 130 μm was produced using a film-forming device equipped with a single-screw extruder (manufactured by Isuzu Chemical Engineering Co., Ltd., screw diameter 25 mm, cylinder set temperature: 220°C), a T-die (width 900 mm, set temperature: 220°C), a chill roll (set temperature: 125°C) and a winder. The water absorption rate of the obtained polycarbonate resin film was 1.2%.

The polycarbonate resin film obtained as described above was obliquely stretched according to Example 1 of JP 2014-194483 A to obtain a retardation film constituting the second optical compensation layer. The obtained retardation film (i.e., the second optical compensation layer) had an Re(550) of 137 nm, an Nz coefficient of 1.0, and an Re(450)/Re(550) of 0.89.

(iii) Preparation of Polarizer A long roll of a polyvinyl alcohol (PVA)-based resin film (manufactured by Kuraray, product name "PE3000") having a thickness of 30 μm was uniaxially stretched in the longitudinal direction to 5.9 times its length using a roll stretching machine, while simultaneously undergoing swelling, dyeing, crosslinking, and washing treatments, and finally undergoing a drying treatment, to prepare a polarizer having a thickness of 12 μm.
Specifically, the film was stretched 2.2 times while being treated with pure water at 20°C for the swelling treatment. Next, the film was stretched 1.4 times while being treated in an aqueous solution at 30°C in which the weight ratio of iodine to potassium iodide was 1:7, and the iodine concentration was adjusted so that the single transmittance of the resulting polarizer was 45.0%. Furthermore, a two-stage crosslinking treatment was adopted for the crosslinking treatment, and the film was stretched 1.2 times while being treated in an aqueous solution at 40°C in which boric acid and potassium iodide were dissolved. The aqueous solution at the first crosslinking treatment had a boric acid content of 5.0% by weight and a potassium iodide content of 3.0% by weight. The film was stretched 1.6 times while being treated in an aqueous solution at 65°C in which boric acid and potassium iodide were dissolved. The aqueous solution at the second crosslinking treatment had a boric acid content of 4.3% by weight and a potassium iodide content of 5.0% by weight. The cleaning treatment was performed with an aqueous potassium iodide solution at 20° C. The aqueous solution used for the cleaning treatment had a potassium iodide content of 2.6% by weight. Finally, the film was dried at 70° C. for 5 minutes to obtain a polarizer.

(iv) Preparation of Polarizing Plate An HC-TAC film (thickness: 32 μm, corresponding to a 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 bonded to one side of the above polarizer via a polyvinyl alcohol-based adhesive by roll-to-roll method to obtain a long polarizing plate having a protective layer/polarizer configuration.

(v) Preparation of a polarizing plate with an optical compensation layer The polarizing plate (iv), the retardation film (i) (first optical compensation layer), and the retardation film (ii) (second optical compensation layer) were laminated by roll-to-roll to obtain a retardation film laminate. The shrinkable film was peeled off to obtain a polarizing plate with an optical compensation layer having a configuration of protective layer/polarizer/first optical compensation layer/second optical compensation layer. The absorption axis of the polarizer and the slow axis of the first optical compensation layer were substantially parallel, and the angle between the absorption axis of the polarizer and the slow axis of the second optical compensation layer was 45°.

The obtained polarizing plate with an optical compensation layer was subjected to the evaluation of (3) above. Furthermore, the characteristics of the obtained polarizing plate with an optical compensation layer were used to simulate the reflection characteristics of (4) above. The results are shown in Table 1.

[Example 2]
A polarizing plate with an optical compensation layer having a configuration of protective layer/polarizer/first optical compensation layer/second optical compensation layer was obtained in the same manner as in Example 1, except that the stretching temperature and stretching ratio described in Table 1 were adopted. The Re (550) of the first optical compensation layer was 138 nm, the Nz coefficient was 0.5, and Re (450) / Re (550) was 1.00. The Re (550) of the second optical compensation layer was 137 nm, the Nz coefficient was 1.0, and Re (450) / Re (550) was 0.89. Furthermore, an organic EL panel was produced 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 the organic EL panel were subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Example 3]
A polarizing plate with an optical compensation layer having a configuration of protective layer/polarizer/first optical compensation layer/second optical compensation layer was obtained in the same manner as in Example 1, except that the stretching temperature and stretching ratio described in Table 1 were adopted. The Re (550) of the first optical compensation layer was 173 nm, the Nz coefficient was 0.64, and Re (450) / Re (550) was 1.00. The Re (550) of the second optical compensation layer was 137 nm, the Nz coefficient was 1.0, and Re (450) / Re (550) was 0.89. Furthermore, an organic EL panel was produced 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 the organic EL panel were subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Example 4]
The stretching temperature and stretching ratio shown in Table 1 were used. The first optical compensation layer and the second optical compensation layer were laminated together by roll-to-roll to obtain a laminate having a configuration of the first optical compensation layer/second optical compensation layer. The angle between the slow axis of the first optical compensation layer and the slow axis of the second optical compensation layer was 45°. The laminate was cut to a predetermined size, and the polarizing plate was further cut and laminated such that the angle between the absorption axis of the polarizer and the slow axis of the first optical compensation layer was 13°, and the angle between the absorption axis of the polarizer and the slow axis of the second optical compensation layer was 58°, thereby obtaining a polarizing plate with an optical compensation layer having a configuration of the protective layer/polarizer/first optical compensation layer/second optical compensation layer. The number of times of the process (RtoS) of cutting and laminating each layer constituting the polarizing plate with an optical compensation layer was one. The first optical compensation layer had an Re(550) of 133 nm, an Nz coefficient of 0.27, and an Re(450)/Re(550) of 1.00. The second optical compensation layer had an Re(550) of 98 nm, an Nz coefficient of 1.0, and an Re(450)/Re(550) of 0.89. Furthermore, an organic EL panel was produced in the same manner as in Example 1 except that this polarizing plate with optical compensation layer was used. The obtained polarizing plate with optical compensation layer and organic EL panel were subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Comparative Example 1]
(i) Preparation of first optical compensation layer A first optical compensation layer was prepared in the same manner as the second optical compensation layer in Example 1. The first optical compensation layer had Re(550) of 139 nm, an Nz coefficient of 1.10, and Re(450)/Re(550) of 0.89.

(ii) Preparation of the second optical compensation layer 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 mol% of the monomer unit, 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 (manufactured by BASF: trade name Paliocolor LC242) and 5 parts by weight of a photopolymerization initiator (manufactured by Ciba Specialty Chemicals: trade name Irgacure 907) were dissolved in 200 parts by weight of cyclopentanone to prepare a liquid crystal coating liquid. Then, the coating liquid was applied to a substrate film (norbornene-based resin film: manufactured by Nippon Zeon Co., Ltd., trade name "Zeonex") by a bar coater, and the liquid crystal was aligned by heating and drying at 80°C for 4 minutes. The liquid crystal layer was irradiated with ultraviolet light to harden the liquid crystal layer, thereby forming a liquid crystal solidified layer (thickness: 0.58 μm) to be the second optical compensation layer on the substrate. The obtained second optical compensation layer had Re(550) of 0 nm and Rth(550) of −71.

A polarizing plate with optical compensation layers having a configuration of protective layer/polarizer/first optical compensation layer/second optical compensation layer was obtained in the same manner as in Example 1, except that the first optical compensation layer and the second optical compensation layer obtained in (i) and (ii) above were used, and the angle between the absorption axis of the polarizer and the slow axis of the first optical compensation layer was set to 45°. Furthermore, an organic EL panel was produced in the same manner as in Example 1, except that this polarizing plate with optical compensation layers was used. The obtained polarizing plate with optical compensation layers and organic EL panel were subjected to evaluation in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 2]
A polarizing plate with an optical compensation layer having a configuration of protective layer/polarizer/first optical compensation layer/second optical compensation layer 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. The Re(550) of the first optical compensation layer was 139 nm, the Nz coefficient was 1.00, and Re(450)/Re(550) was 1.00. The Re(550) of the second optical compensation layer was 0 nm, and Rth(550) was −54. Furthermore, an organic EL panel was produced 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 the organic EL panel were subjected to the same evaluation as in Example 1. The results are shown in Table 1.

* indicates retardation (Rth) in the thickness direction.

[evaluation]
As is clear from Table 1, the polarizing plate with an optical compensation layer according to the embodiment of the present invention can have excellent antireflection properties in an oblique direction while maintaining excellent antireflection properties in a front direction. Furthermore, it was confirmed that the embodiment can make the hue in an oblique direction neutral.

The polarizing plate with optical compensation layer of the present invention is suitable for use in organic EL panels.

REFERENCE SIGNS LIST 10 Polarizer 20 Protective layer 30 First optical compensation layer 40 Second optical compensation layer 100 Polarizing plate with optical compensation layer

Claims (3)

a polarizer, a first optical compensation layer, and a second optical compensation layer in this order;
the first optical compensation layer exhibits refractive index characteristics of nx≧nz>ny, Re(550) is 90 nm to 180 nm, an Nz coefficient is 0 to 0.8, and an angle between an absorption axis direction of the polarizer and a slow axis direction of the first optical compensation layer is 0°±10° ,
the second optical compensation layer exhibits refractive index characteristics of nx>ny=nz, Re(550) is 100 nm to 180 nm, 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°,
the first optical compensation layer has an Re(450)/Re(550) of 0.99 to 1.03 , and the second optical compensation layer satisfies Re(550)>Re(450);
Used in organic EL panels,
Polarizing plate with optical compensation layer:
Here, Re(450) and Re(550) represent in-plane retardations measured at 23° C. using light with wavelengths of 450 nm and 550 nm, respectively. a polarizer, a first optical compensation layer, and a second optical compensation layer in this order;
the first optical compensation layer exhibits refractive index characteristics of nx>nz>ny, has Re(550) of 90 nm to 170 nm, has an Nz coefficient of 0.1 to 0.5, and an angle between an absorption axis direction of the polarizer and a slow axis direction of the first optical compensation layer is 5° to 25°,
the second optical compensation layer exhibits refractive index characteristics of nx>ny=nz, Re(550) is 60 nm to 140 nm, and the angle between the absorption axis direction of the polarizer and the slow axis direction of the second optical compensation layer is 50° to 70°,
the first optical compensation layer has an Re(450)/Re(550) of 0.99 to 1.03 , and the second optical compensation layer satisfies Re(550)>Re(450);
Used in organic EL panels,
Polarizing plate with optical compensation layer:
Here, Re(450) and Re(550) represent in-plane retardations measured at 23° C. using light with wavelengths of 450 nm and 550 nm, respectively. An organic EL panel comprising a polarizing plate with an optical compensation layer according to claim 1 or 2.

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