Phase difference layer-equipped polarizing plate and image display device

Abstract

To provide a polarizing plate with a retardation layer that has superior visibility through polarizing sunglasses and also has superior bending properties although having simple composition.SOLUTION: A polarizing plate with a retardation layer is used for a bendable image display device. The polarizing plate with the retardation layer has: a polarizing plate including a polarizer and a protective layer at least on one side of the polarizer; and the retardation layer provided on the opposite side from a view side of the polarizing plate and having a circular polarizing function or elliptic polarizing function, wherein the total thickness is 80 μm or less, the angle that an axis of bending of the image display device and an axis of absorption of the polarizer contain is 30 to 60°, and the protective layer has an elastic modulus of 5,000 MPa or less.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a polarizing plate with a retardation layer and an image display device.

Background Art

[0002] In recent years, image display devices represented by liquid crystal display devices and electroluminescence (EL) display devices (for example, organic EL display devices, inorganic EL display devices) have been rapidly spreading. Typically, a polarizing plate and a retardation plate are used in image display devices. Practically, a polarizing plate with a retardation layer in which a polarizing plate and a retardation plate are integrated is widely used (for example, Patent Document 1). Recently, as the demand for thinning of image display devices has increased, the demand for thinning of the polarizing plate with a retardation layer has also increased. Furthermore, as the applications of image display devices expand, the demands for image display devices are diversifying. For example, in smartphones, the ability to be foldable and the improvement of visibility through polarized sunglasses are required. Therefore, a polarizing plate with a retardation layer that can realize such an image display device is strongly demanded.

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-described conventional problems, and its main object is to provide a polarizing plate with a retardation layer that has excellent visibility through polarized sunglasses and excellent foldability while having a simple configuration.

Means for Solving the Problems

[0005] The polarizing plate with a phase difference layer of the present invention is used in a flexible image display device. The polarizing plate with a phase difference layer includes a polarizer and a protective layer on at least one side of the polarizer; a phase difference layer having a circular polarization function or an elliptical polarization function provided on the side opposite to the viewing side of the polarizing plate; and has a total thickness of 80 μm or less, the angle formed by the bending axis of the image display device and the absorption axis of the polarizer is 30° to 60°, and the elastic modulus of the protective layer is 5000 MPa or less. In one embodiment, the total thickness of the polarizing plate with a phase difference layer is 60 μm or less. In one embodiment, the thickness of the polarizer is 10 μm or less. In one embodiment, the polarizing plate includes a protective layer only on the side opposite to the phase difference layer of the polarizer. In one embodiment, the elastic modulus of the protective layer is 4000 MPa or less. In one embodiment, the thickness of the protective layer is 45 μm or less. In one embodiment, the angle formed by the bending axis and the absorption axis of the polarizer is 40° to 50°. In one embodiment, the phase difference layer is an alignment cured layer of a liquid crystal compound. In one embodiment, the phase difference layer is a single layer, Re(550) of the phase difference layer is 100 nm to 190 nm, Re(450) / Re(550) of the phase difference layer is 0.8 or more and less than 1, and the angle formed by the slow axis of the phase difference layer and the absorption axis of the polarizer is 40° to 50°. In one embodiment, the polarizing plate with a phase difference layer further has another phase difference layer outside the phase difference layer, and the refractive index characteristics of the another phase difference layer show a relationship of nz>nx=ny. In one embodiment, the phase difference layer has a laminated structure of an alignment cured layer of a first liquid crystal compound and an alignment cured layer of a second liquid crystal compound; Re(550) of the alignment cured layer of the first liquid crystal compound is 200 nm to 300 nm, and the angle formed by its slow axis and the absorption axis of the polarizer is 10° to 20°; Re(550) of the alignment cured layer of the second liquid crystal compound is 100 nm to 190 nm, and the angle formed by its slow axis and the absorption axis of the polarizer is 70° to 80°. According to another aspect of the present invention, an image display device is provided. This image display device includes the above-mentioned polarizing plate with a retardation layer.

Effects of the Invention

[0006] According to an embodiment of the present invention, in the polarizing plate with a retardation layer, by optimizing the angle between the bending axis and the absorption axis of the polarizer when applied to a bendable image display device, and by optimizing the elastic modulus of the protective layer, it is possible to realize a polarizing plate with a retardation layer that has a simple configuration, excellent visibility through polarized sunglasses, and excellent bendability.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

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

[0009] (Definitions of Terms and Symbols) The definitions of terms and symbols 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 orthogonal 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 Retardation (Re) "Re(λ)" is the in-plane retardation measured with light of wavelength λ nm at 23°C. For example, "Re(550)" is the in-plane retardation measured with light of wavelength 550 nm at 23°C. When the thickness of the layer (film) is d (nm), Re(λ) is obtained by the formula: Re(λ) = (nx - ny) × d. (3) Retardation in the thickness direction (Rth) "Rth(λ)" is the retardation in the thickness direction measured with light of wavelength λ nm at 23°C. For example, "Rth(550)" is the retardation in the thickness direction measured with light of wavelength 550 nm at 23°C. When the thickness of the layer (film) is d (nm), Rth(λ) is obtained by the formula: Rth(λ) = (nx - nz) × d. (4) Nz coefficient The Nz coefficient is obtained by Nz = Rth / Re. (5) Angle When referring to an angle in this specification, the angle includes both clockwise and counterclockwise directions with respect to the reference direction. Thus, for example, "45°" means ±45°; and for example, "30° to 60°" means +30° to +60° or -30° to -60°.

[0010] A. Overall configuration of the polarizing plate with a retardation layer FIG. 1 is a schematic perspective view showing a bent state of an image display device to which a polarizing plate with a retardation layer according to an embodiment of the present invention is applied; FIG. 2 is a schematic plan view of a polarizing plate with a retardation layer according to one embodiment of the present invention; FIG. 3 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to one embodiment of the present invention; FIG. 4 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to another embodiment of the present invention. The polarizing plate with a retardation layer 100 in the example shown in FIG. 3 typically has a polarizing plate 10 and a retardation layer 20 in this order from the viewing side. In the illustrated example, the polarizing plate 10 includes a polarizer 11 and protective layers 12 and 13 on both sides of the polarizer 11. Depending on the purpose, one of the protective layers 12 and 13 may be omitted. In one embodiment, the polarizing plate 10 has a protective layer 12 only on the viewing side (opposite side to the retardation layer 20) of the polarizer 11. The components of the polarizing plate with a retardation layer are typically bonded via an arbitrary suitable adhesive layer (adhesive layer or pressure-sensitive adhesive layer: not shown). Practically, a pressure-sensitive adhesive layer (not shown) is provided on the side of the retardation layer 20 opposite to the polarizing plate 10 (i.e., as the outermost layer on the side opposite to the viewing side), and the polarizing plate with a retardation layer can be attached to the image display panel. Further, it is preferable that a release film (not shown) is temporarily attached to the surface of the pressure-sensitive adhesive layer until the polarizing plate with a retardation layer is put into use. By temporarily attaching the release film, the pressure-sensitive adhesive layer is protected and the polarizing plate with a retardation layer can be formed into a roll.

[0011] The retardation film - attached polarizing plate is used for a bendable image display device as shown in FIG. 1. As shown in FIGS. 1 and 2, for the retardation film - attached polarizing plate, the angle formed by the bending axis F of the image display device and the absorption axis A of the polarizer 11 is 30° to 60°, preferably 35° to 55°, more preferably 40° to 50°, still more preferably 42° to 48°, and particularly preferably about 45°. With such a configuration, without forming a specific layer (typically, a layer imparting an (elliptical) polarization function such as a λ / 4 plate, an ultra - high retardation layer with an in - plane retardation Re(550) exceeding 1000 nm) on the viewing side of the retardation film - attached polarizing plate, excellent visibility can be realized when viewing through polarized sunglasses. Therefore, the retardation film - attached polarizing plate according to the embodiment of the present invention is simple and low - cost because of the small number of layers, and as a result, it is thin. Further, with such a configuration, an excellent bending property (flexibility) can be realized due to a synergistic effect with the effect of optimizing the elastic modulus of the protective layer. More specifically, when the bending axis is parallel to the absorption axis of the polarizer, the retardation film - attached polarizing plate (substantially, the polarizing plate) is very likely to crack. On the other hand, when the bending axis is perpendicular to the absorption axis of the polarizer, it is less likely to crack, but the visibility when viewing through polarized sunglasses is extremely poor. By optimizing so that the bending axis and the absorption axis of the polarizer form the above - mentioned predetermined angle, it is possible to achieve both excellent bending property (flexibility) and excellent visibility when viewing through polarized sunglasses. In the illustrated example, the bending axis F is in the short - side direction of the image display device, but the bending axis F may be in the long - side direction or in a direction having a predetermined angle with respect to the long - side direction or the short - side direction (diagonal direction). By defining the absorption axis direction with respect to the bending axis direction, the above - mentioned effects can be obtained even when the retardation film - attached polarizing plate is applied to an image display device having a non - rectangular irregular shape (for example, circular, elliptical, triangular, irregular).

[0012] The polarizing plate with a retardation layer has a total thickness (the total thickness of the polarizing plate, the retardation layer, and the adhesive layer laminating these) of 80 μm or less, preferably 70 μm or less, more preferably 60 μm or less, still more preferably 50 μm or less, and particularly preferably 40 μm or less. The total thickness of the polarizing plate with a retardation layer can be, for example, 25 μm or more. According to an embodiment of the present invention, even with such a very small total thickness, excellent visibility can be realized when viewed through polarized sunglasses. In other words, the polarizing plate with a retardation layer can have a very small total thickness even when used for applications such as viewing through polarized sunglasses. As a result, the second moment of area at the time of bending becomes small, and the stress applied to each component (layer) becomes small. Therefore, in addition to the excellent visibility when viewed through sunglasses, excellent bendability (flexibility) can be realized.

[0013] In an embodiment of the present invention, the elastic modulus of the protective layer 12 and / or 13 is 5000 MPa or less, preferably 4500 MPa or less, more preferably 4000 MPa or less, and still more preferably 3500 MPa or less. The lower limit of the elastic modulus of the protective layer can be, for example, 2000 MPa. Preferably, the polarizing plate with a retardation layer (substantially, the polarizing plate) has only the protective layer 12, and the elastic modulus of the protective layer 12 is within the above range. When the elastic modulus of the protective layer is too large, the compressive stress applied to the protective layer becomes large when the strain at the time of bending is the same. As a result, cracks are likely to occur in the protective layer when bending is repeated. By optimizing the elastic modulus of the protective layer within the above range, cracks during bending can be suppressed, and excellent bendability (flexibility) can be realized. The elastic modulus can be measured in accordance with JIS Z 2284.

[0014] The retardation layer 20 has a circular polarization function or an elliptical polarization function. The retardation layer 20 is typically an alignment and solidification layer (liquid crystal alignment and solidification layer) of a liquid crystal compound. By using a liquid crystal compound, the difference between nx and ny of the obtained retardation layer can be made significantly larger than that of a non-liquid crystal material, so that the thickness of the retardation layer for obtaining a desired in-plane retardation can be significantly reduced. Therefore, a significant thinning of the polarizing plate with a retardation layer can be realized. As a result, the excellent foldability (bendability) as described above can be realized. In this specification, the "alignment and solidification layer" refers to a layer in which a liquid crystal compound is aligned in a predetermined direction within the layer and the alignment state is fixed. Note that the "alignment and solidification layer" is a concept that includes an alignment and curing layer obtained by curing a liquid crystal monomer as described later. In the retardation layer 20, typically, rod-shaped liquid crystal compounds are aligned in a state aligned in the slow axis direction of the retardation layer (homogeneous alignment). The retardation layer 20 may be a single layer as shown in FIG. 3, or may have a laminated structure of two or more layers as shown in FIG. 4.

[0015] The polarizing plate with a retardation layer may further include other optical function layers. The type, characteristics, number, combination, arrangement position, etc. of the optical function layers that can be provided on the polarizing plate with a retardation layer can be appropriately set according to the purpose. For example, the polarizing plate with a retardation layer may further have a conductive layer or an isotropic substrate with a conductive layer (both not shown). The conductive layer or the isotropic substrate with a conductive layer is typically provided outside the second retardation layer 22 (on the side opposite to the polarizing plate 10). The conductive layer or the isotropic substrate with a conductive layer is typically an arbitrary layer provided as needed and may be omitted. When the conductive layer or the isotropic substrate with a conductive layer is provided, the polarizing plate with a retardation layer can be applied to a so-called inner touch panel type input display device in which a touch sensor is incorporated between an image display cell (for example, an organic EL cell) and the polarizing plate. Also, for example, the polarizing plate with a retardation layer may further include other retardation layers. The optical characteristics (for example, refractive index characteristics, in-plane retardation, Nz coefficient, photoelastic coefficient), thickness, arrangement position, etc. of the other retardation layers can be appropriately set according to the purpose.

[0016] The components of the retardation film - attached polarizing plate will be described in more detail below.

[0017] B. Polarizing plate B-1. Polarizer As the polarizer 11, any appropriate polarizer can be adopted. For example, the resin film forming the polarizer may be a single-layer resin film or a laminate of two or more layers.

[0018] Specific examples of polarizers composed of a single-layer resin film include hydrophilic polymer films such as polyvinyl alcohol (PVA)-based films, partially formalized PVA-based films, and ethylene-vinyl acetate copolymer-based partially saponified films, which are dyed and stretched with dichroic substances such as iodine and dichroic dyes, and polyene-based oriented films such as dehydrated products of PVA and dehydrochlorinated products of polyvinyl chloride. Preferably, a polarizer obtained by dyeing a PVA-based film with iodine and uniaxially stretching it is used because of its excellent optical properties.

[0019] The above-mentioned dyeing with iodine is performed, for example, by immersing the PVA-based film in an iodine aqueous solution. The stretching ratio of the above-mentioned uniaxial stretching is preferably 3 to 7 times. The stretching may be performed after the dyeing treatment, during the dyeing, or after the stretching and then the dyeing. If necessary, the PVA-based film is subjected to swelling treatment, cross-linking treatment, washing treatment, drying treatment, etc. For example, by immersing the PVA-based film in water and washing it before dyeing, not only can the dirt and blocking inhibitor on the surface of the PVA-based film be washed away, but also the PVA-based film can be swollen to prevent uneven dyeing.

[0020] As specific examples of the polarizer obtained using the laminate, there may be mentioned 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, preferably, a PVA-based resin layer containing a halide and a polyvinyl alcohol-based resin is formed on one side of the resin substrate. Stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching it. Further, stretching may further include, if necessary, air stretching the laminate at a high temperature (for example, 95° C. or higher) before stretching in the aqueous boric acid solution. In addition, in the present embodiment, preferably, the laminate is subjected to a drying shrinkage treatment in which it is heated while being conveyed in the longitudinal direction to shrink by 2% or more in the width direction. Typically, the manufacturing method of the present embodiment includes subjecting the laminate to an air-assisted stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment in this order. By introducing the auxiliary stretching, even when PVA is applied on a thermoplastic resin, it becomes possible to enhance the crystallinity of PVA and achieve high optical properties. At the same time, by enhancing the orientation of PVA in advance, problems such as a decrease in the orientation of PVA and dissolution when immersed in water in the subsequent dyeing process and stretching process can be prevented, and high optical properties can be achieved. Further, when the PVA-based resin layer is immersed in a liquid, compared with the case where the PVA-based resin layer does not contain a halide, the disturbance of the orientation of polyvinyl alcohol molecules and the decrease in the orientation can be suppressed. Thereby, the optical properties of the polarizer obtained through a treatment step such as a dyeing treatment and an underwater stretching treatment, in which the laminate is immersed in a liquid, can be improved. Furthermore, by shrinking the laminate in the width direction by the drying shrinkage treatment, the optical properties can be improved.The obtained resin substrate / polarizer laminate may be used as it is (i.e., the resin substrate may be used as the protective layer of the polarizer), or the resin substrate may be peeled off from the resin substrate / polarizer laminate, and any 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 JP-A-2012-73580 and Japanese Patent No. 6470455. The entire descriptions of these publications are incorporated herein by reference.

[0021] The thickness of the polarizer is preferably 15 μm or less, more preferably 12 μm or less, still more preferably 10 μm or less, particularly preferably 3 μm to 10 μm, and especially preferably 3 μm to 8 μm. If the thickness of the polarizer is within such a range, the above-described desired total thickness can be achieved, and excellent bendability can be achieved.

[0022] The polarizer preferably exhibits absorption dichroism at any wavelength in the wavelength range of 380 nm to 780 nm. The single transmittance of the polarizer is preferably 41.5% to 46.0%, more preferably 43.0% to 46.0%, and still 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.

[0023] B-2. Protective Layer The protective layers 12 and 13 are each formed of any appropriate film that can be used as the protective layer of the polarizer as long as the above-described elastic modulus can be satisfied. Specific examples of the material that is the main component of the film include cellulose-based resins such as triacetyl cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyether sulfone-based, polysulfone-based, polystyrene-based, cyclic olefin-based (e.g., polynorbornene-based), polyolefin-based, (meth)acrylic-based, acetate-based, and other transparent resins.

[0024] The retardation layer - attached polarizing plate is typically disposed on the viewing side of the image display device, and the protective layer 12 is disposed on its viewing side. Therefore, the protective layer 12 may be subjected to surface treatments such as hard coat treatment, antireflection treatment, anti - sticking treatment, antiglare treatment, etc., as necessary.

[0025] The thicknesses of the protective layers 12 and 13 are each preferably 60 μm or less, more preferably 45 μm or less, and still more preferably 10 μm to 40 μm. When surface treatment is performed, the thickness of the protective layer 12 is the thickness including the thickness of the surface treatment layer.

[0026] C. Retardation layer As described above, the retardation layer 20 may be a single layer or may have a laminated structure of two or more layers.

[0027] When the retardation layer 20 is a single layer, the retardation layer can typically function as a λ / 4 plate. Specifically, Re(550) of the retardation layer is preferably 100 nm to 180 nm, more preferably 110 nm to 170 nm, and still more preferably 110 nm to 160 nm. The thickness of the retardation layer can be adjusted so as to obtain a desired in - plane retardation of the λ / 4 plate. The thickness of the retardation layer can be, for example, 1.0 μm to 2.5 μm. In this embodiment, the angle formed by the slow axis of the retardation layer and the absorption axis of the polarizer is preferably 40° to 50°, more preferably 42° to 48°, and still more preferably 44° to 46°. In this embodiment, the retardation layer - attached polarizing plate may further have a retardation layer (not shown) having a refractive index characteristic of nz>nx = ny outside the retardation layer 20. When the retardation layer is a single layer, the retardation layer preferably exhibits an inverse - dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light. In this case, Re(450) / Re(550) of the retardation layer is preferably 0.8 or more and less than 1, more preferably 0.8 to 0.95.

[0028] When the retardation layer 20 has a laminated structure, the retardation layer typically has a two-layer structure of an H layer 21 and a Q layer 22 in this order from the polarizer side as shown in FIG. 4. The H layer can typically function as a λ / 2 plate, and the Q layer can typically function as a λ / 4 plate. Specifically, Re(550) of the H layer is preferably 200 nm to 300 nm, more preferably 220 nm to 290 nm, and still more preferably 230 nm to 280 nm; Re(550) of the Q layer is preferably 100 nm to 180 nm, more preferably 110 nm to 170 nm, and still more preferably 110 nm to 150 nm. The thickness of the H layer can be adjusted so as to obtain a desired in-plane retardation of the λ / 2 plate. When the H layer is a liquid crystal alignment solidification layer, its thickness can be, for example, 2.0 μm to 4.0 μm. The thickness of the Q layer can be adjusted so as to obtain a desired in-plane retardation of the λ / 4 plate. When the Q layer is a liquid crystal alignment solidification layer, its thickness can be, for example, 1.0 μm to 2.5 μm. In the present embodiment, the angle formed by the slow axis of the H layer and the absorption axis of the polarizer is preferably 10° to 20°, more preferably 12° to 18°, and still more preferably 12° to 16°; the angle formed by the slow axis of the Q layer and the absorption axis of the polarizer is preferably 70° to 80°, more preferably 72° to 78°, and still more preferably 72° to 76°. Note that the arrangement order of the H layer and the Q layer may be reversed, and the angle formed by the slow axis of the H layer and the absorption axis of the polarizer and the angle formed by the slow axis of the Q layer and the absorption axis of the polarizer may also be reversed. When the retardation layer has a laminated structure, each layer (for example, the H layer and the Q layer) may exhibit an inverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light, a positive wavelength dispersion characteristic in which the retardation value decreases according to the wavelength of the measurement light, or a flat wavelength dispersion characteristic in which the retardation value hardly changes according to the wavelength of the measurement light.

[0029] The retardation layer (each layer in the case of a laminated structure) typically exhibits a refractive index characteristic of the relationship nx > ny = nz. Note that "ny = nz" includes not only the case where ny and nz are exactly equal but also the case where they are substantially equal. Therefore, within a range that does not impair the effects of the present invention, ny > nz or ny < nz may occur. The Nz coefficient of the retardation layer is preferably 0.9 to 1.5, more preferably 0.9 to 1.3.

[0030] The retardation layer is typically a liquid crystal alignment solidified layer as described above. Examples of the liquid crystal compound include a liquid crystal compound (nematic liquid crystal) having a nematic liquid crystal phase. As such a liquid crystal compound, for example, a liquid crystal polymer or a liquid crystal monomer can be used. The mechanism for the expression of liquid crystallinity of the liquid crystal compound may be either lyotropic or thermotropic. The liquid crystal polymer and the liquid crystal monomer may be used alone or in combination.

[0031] When the liquid crystal compound is a liquid crystal monomer, the liquid crystal monomer is preferably a polymerizable monomer and a crosslinkable monomer. This is because the alignment state of the liquid crystal monomer can be fixed by polymerizing or crosslinking (i.e., curing) the liquid crystal monomer. After the liquid crystal monomer is aligned, for example, by polymerizing or crosslinking the liquid crystal monomers with each other, the alignment state can be fixed thereby. Here, a polymer is formed by polymerization and a three-dimensional network structure is formed by crosslinking, but these are non-liquid crystalline. Therefore, in the formed retardation layer, for example, a transition from a liquid crystal phase, a glass phase, or a crystal phase due to a temperature change peculiar to the liquid crystalline compound does not occur. As a result, the retardation layer becomes an extremely stable retardation layer that is not affected by temperature changes.

[0032] The temperature range in which the liquid crystal monomer exhibits liquid crystallinity varies depending on its type. Specifically, the temperature range is preferably 40°C to 120°C, more preferably 50°C to 100°C, and most preferably 60°C to 90°C.

[0033] As the above liquid crystal monomer, any suitable liquid crystal monomer can be adopted. For example, polymerizable mesogenic compounds described in JP-T-2002-533742 (WO00 / 37585), EP358208 (US5211877), EP66137 (US4388453), WO93 / 22397, EP0261712, DE19504224, DE4408171, GB2280445, etc. can be used. Specific examples of such polymerizable mesogenic compounds include, for example, LC242 with the trade name of BASF, E7 with the trade name of Merck, and LC-Sillicon-CC3767 with the trade name of Wacker-Chem. As the liquid crystal monomer, for example, a nematic liquid crystal monomer is preferred.

[0034] D. Image display device The retardation layer-containing polarizing plate described in Items A to C above can be applied to an image display device. Therefore, an image display device including a retardation layer-containing polarizing plate is also included in the embodiments of the present invention. An image display device typically includes an image display cell and a retardation layer-containing polarizing plate bonded to the image display cell via an adhesive layer. Representative examples of the image display device include a liquid crystal display device and an electroluminescence (EL) display device (for example, an organic EL display device and an inorganic EL display device). The image display device is bendable as described above and is preferably foldable. In such an image display device, the effect of the retardation layer-containing polarizing plate according to the embodiments of the present invention becomes remarkable.

Examples

[0035] Hereinafter, the present invention will be specifically described by examples, but the present invention is not limited by these examples. The measurement methods for each property are as follows. Unless otherwise specified, "parts" and "%" in the examples and comparative examples are based on weight. (1) Thickness For a thickness of 10 μm or less, it was measured using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name "MCPD-3000"). For a thickness exceeding 10 μm, it was measured using a digital micrometer (manufactured by Anritsu Corporation, product name "KC-351C"). (2) Elastic modulus Measurement was carried out in accordance with JIS Z 2284. Specifically, it was as follows. A strip-shaped sample piece with a width of 10 mm and a length of 100 mm was cut out from the protective layer used in the examples and comparative examples, and using a high-speed compatible single-type autograph (manufactured by Shimadzu Corporation), the sample piece was pulled in the longitudinal direction under the following conditions, and the elastic modulus was determined from the obtained S-S (Stress-Strain) curve. As the measurement conditions, the tensile speed was 50 mm / min, the distance between chucks was 100 mm, and the measurement temperature was normal temperature (25 °C). The method for obtaining the elastic modulus from the S-S curve was as follows. A tangent was drawn at the initial rising part of the S-S curve, and the strength at the position where the extension line of the tangent reached a 100% elongation rate was read, and the value obtained by dividing this value by the cross-sectional area of the measured sample piece (thickness × sample width (10 mm)) was taken as the elastic modulus. (3) Bending test The retardation layer-attached polarizing plates obtained in the examples and comparative examples were cut out to a size of 100 mm × 55 mm and used as measurement samples. Here, they were cut out so that the bending axis was in the short side direction of the measurement material. For this measurement sample, a continuous bending test was carried out using a bending tester (manufactured by Yuasa System Devices Co., Ltd., product name "CL09 Type D01"). Bending was carried out at room temperature with the viewing-side protective layer on the inside. The bending radius of curvature was 3 mm. The presence or absence of cracks after 500,000 bends was visually observed and evaluated according to the following criteria. ○: No cracks were observed ×: Cracks were observed (4) Visibility when viewed through polarized sunglasses The polarizing plate on the viewing side of a commercially available liquid crystal display device was removed, the surface from which the polarizing plate was removed was cleaned, and the retardation layer-attached polarizing plates obtained in the examples and comparative examples were bonded to the cleaned surface. They were bonded so that the angle between the absorption axis of the polarizer of the retardation layer-attached polarizing plate and the short side of the liquid crystal display device was 0°, 30°, 40°, 45°, 50°, 60°, and 90°. A predetermined character was displayed on the liquid crystal display device thus obtained, and the display screen was observed through polarized sunglasses. Here, the display screen was observed with the absorption axis direction of the polarized sunglasses aligned with the short side direction and the long side direction of the image display device respectively, and evaluated according to the following criteria. ○: Regardless of whether the absorption axis direction of the polarized sunglasses is aligned with the short side direction or the long side direction, the content of the display screen could be recognized and understood clearly. ×: When the absorption axis direction of the polarized sunglasses was aligned with at least one of the short side direction or the long side direction, the content of the display screen could not be recognized.

[0036] [Example 1-1] 1. Preparation of Polarizer As a thermoplastic resin substrate, an amorphous isophthalic copolyethylene terephthalate film (thickness: 100 μm) in a long strip shape with a Tg of about 75 °C was used, and one side of the resin substrate was subjected to corona treatment. 13 parts by weight of potassium iodide was added to 100 parts by weight of a PVA-based resin obtained by mixing polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosefimer") in a ratio of 9:1, and the mixture was dissolved in water to prepare a PVA aqueous solution (coating solution). The above PVA aqueous solution was applied to the corona-treated surface of the resin substrate and dried at 60 °C to form a PVA-based resin layer with a thickness of 13 μm, thereby producing a laminate. The obtained laminate was uniaxially stretched 2.4 times in the longitudinal direction (longitudinal direction) in an oven at 130 °C (air-assisted stretching treatment). Next, the laminate was immersed in an insolubilization bath at a liquid temperature of 40 °C (an aqueous boric acid solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds (insolubilization treatment). Next, the laminate was immersed in a dyeing bath at a liquid temperature of 30 °C (an iodine aqueous solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 with 100 parts by weight of water) for 60 seconds while adjusting the concentration so that the single transmittance (Ts) of the finally obtained polarizer became a predetermined value (dyeing treatment). Next, the laminate was immersed in a crosslinking bath at a liquid temperature of 40 °C (an aqueous boric acid solution obtained by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds (crosslinking treatment). Thereafter, while immersing the laminate in an aqueous boric acid solution (boric acid concentration: 4% by weight, potassium iodide concentration: 5% by weight) at a liquid temperature of 70°C, uniaxial stretching was performed in the longitudinal direction (lengthwise direction) between rolls with different peripheral speeds so that the total draw ratio became 5.5 times (stretching treatment in water). Thereafter, the laminate was immersed in a cleaning bath (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 20°C (cleaning treatment). Thereafter, while drying in an oven maintained at about 90°C, it was brought into contact with a SUS heating roll whose surface temperature was maintained at about 75°C (dry shrinkage treatment). In this way, a polarizer with a thickness of about 5 μm was formed on the resin substrate, and a polarizing plate having a resin substrate / polarizer structure was obtained.

[0037] Furthermore, an HC-TAC film was laminated as a protective substrate (protective layer) on the surface of the obtained polarizer (the surface opposite to the resin substrate) via an ultraviolet curable adhesive (thickness: 1.0 μm). The HC-TAC film is a film in which a hard coat (HC) layer (thickness: 7 μm) is formed on a triacetyl cellulose (TAC) film (thickness: 25 μm), and it was laminated so that the TAC film faced the polarizer side. In this way, a polarizing plate having a protective layer / polarizer structure was obtained. The elastic modulus of the protective layer was 3872 MPa.

[0038] 2. Preparation of the retardation layer 10 g of a polymerizable liquid crystal (manufactured by BASF: trade name "Paliocolor LC242", represented by the following formula) showing a nematic liquid crystal phase and 3 g of a photopolymerization initiator (manufactured by BASF: trade name "Irgacure 907") for the polymerizable liquid crystal compound were dissolved in 40 g of toluene to prepare a liquid crystal composition (coating liquid).

Chemical formula

[0039] 3. Fabrication of a Polarizing Plate with a Retardation Layer On the polarizer surface of the polarizing plate obtained in 1. above, the liquid crystal alignment cured layer A (W layer) and the liquid crystal alignment cured layer B (Q layer) obtained in 2. above were transferred in this order. At this time, the transfer (lamination) was performed so that the angle formed by the absorption axis of the polarizer and the slow axis of the alignment cured layer A was 15°, and the angle formed by the absorption axis of the polarizer and the slow axis of the alignment cured layer B was 75°. Each transfer (lamination) was performed via an ultraviolet curable adhesive (thickness: 1.0 μm). In this way, a polarizing plate with a retardation layer having a structure of protective layer / adhesive / polarizer / adhesive / W layer / adhesive / Q layer was obtained. The thickness of the obtained polarizing plate with a retardation layer was 43 μm. This polarizing plate with a retardation layer was punched into a rectangle of a predetermined size corresponding to a bendable image display device having a bending axis in the short side direction. Here, it was punched so that the absorption axis of the polarizer was 30° with respect to the bending axis. The obtained polarizing plate with a retardation layer was subjected to the evaluations in (3) and (4) above. The results are shown in Table 1.

[0040] [Example 1-2] to [Example 1-5] and [Comparative Example 1-1] to [Comparative Example 1-2] A polarizing plate with a retardation layer was obtained in the same manner as in Example 1-1, except that it was punched so that the angle between the absorption axis of the polarizer and the bending axis was the angle shown in Table 1. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in Example 1-1. The results are shown in Table 1.

[0041] [Example 2-1] In the same manner as in Example 1-1, a polarizing plate having a structure of protective layer / polarizer was produced. On the other hand, a retardation layer (a single retardation layer showing inverse dispersion wavelength dependence and capable of functioning as a λ / 4 plate) and another retardation layer (positive C plate) were produced as follows. 55 parts of the compound represented by formula (II), 25 parts of the compound represented by formula (III), and 20 parts of the compound represented by formula (IV) were added to 400 parts of cyclopentanone (CPN). After that, the mixture was heated to 60 °C, stirred and dissolved. After dissolution was confirmed, it was returned to room temperature, and 3 parts of Irgacure 907 (manufactured by BASF Japan Ltd.), 0.2 part of Megafac F-554 (manufactured by DIC Corporation), and 0.1 part of p-methoxyphenol (MEHQ) were added, and stirring was further carried out to obtain a solution. The solution was transparent and homogeneous. The obtained solution was filtered through a 0.20 μm membrane filter to obtain a polymerizable composition. On the other hand, a polyimide solution for an alignment film was applied to a glass substrate with a thickness of 0.7 mm by a spin coating method, dried at 100 °C for 10 minutes, and then fired at 200 °C for 60 minutes to obtain a coating film. The obtained coating film was subjected to a rubbing treatment to form an alignment film. The rubbing treatment was performed using a commercially available rubbing apparatus. The polymerizable composition obtained above was applied to the substrate (substantially the alignment film) by a spin coating method and dried at 100 °C for 2 minutes. After the obtained coating film was cooled to room temperature, it was irradiated with ultraviolet rays at an intensity of 30 mW / cm 2 for 30 seconds using a high-pressure mercury lamp to obtain a liquid crystal alignment cured layer C. The thickness of the liquid crystal alignment cured layer was 3.0 μm, and the in-plane retardation Re(550) was 130 nm. Also, Re(450) / Re(550) of the liquid crystal alignment cured layer was 0.851, showing an inverse dispersion wavelength characteristic. This liquid crystal alignment cured layer was used as a retardation layer.

Chemical formula

Chemical formula

[0042] 20 parts by weight of a side-chain liquid crystal polymer represented by the following chemical formula (I) (the numbers 65 and 35 in the formula represent mol% of monomer units, and are represented as a block polymer for convenience: weight average molecular weight 5000), 80 parts by weight of a polymerizable liquid crystal showing 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 solution. 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 then heated and dried at 80 °C for 4 minutes to align the liquid crystal. The liquid crystal layer was irradiated with ultraviolet rays to cure the liquid crystal layer, thereby forming a liquid crystal alignment cured layer (positive C plate, thickness 3 μm) serving as another retardation layer on the substrate. Re(590) of this layer was 0 nm, Rth(590) was -100 nm, and it showed a refractive index characteristic of nz > nx = ny. [Chemical formula]

[0043] The liquid crystal alignment cured layer C was transferred onto the surface of the polarizer of the polarizing plate obtained above via an adhesive layer (thickness 5 μm), and further, a positive C plate was transferred onto the surface of the liquid crystal alignment cured layer C. In this way, a polarizing plate with a retardation layer having a structure of protective layer / adhesive / polarizer / adhesive layer / retardation layer / adhesive / positive C plate was obtained. The thickness of the obtained polarizing plate with a retardation layer was 49 μm. This polarizing plate with a retardation layer was punched out into a rectangle of a predetermined size corresponding to a bendable image display device having a bending axis in the short side direction. Here, it was punched out so that the absorption axis of the polarizer was 30° with respect to the bending axis. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in Example 1-1. The results are shown in Table 1.

[0044] [Example 2-2] to [Example 2-5] and [Comparative Example 2-1] to [Comparative Example 2-2] A retardation film - attached polarizing plate was obtained in the same manner as in Example 2 - 1, except that the punching was performed such that the angle between the absorption axis and the bending axis of the polarizer was the angle shown in Table 1. The obtained retardation film - attached polarizing plate was subjected to the same evaluation as in Example 1 - 1. The results are shown in Table 1.

[0045] [Example 3 - 1] A retardation film - attached polarizing plate was obtained in the same manner as in Example 1 - 1, except that an acrylic resin film (thickness: 20 μm) was used instead of the HC - TAC film as the protective layer. The elastic modulus of the protective film was 2881 MPa. Also, the thickness of the obtained retardation film - attached polarizing plate was 31 μm. This retardation film - attached polarizing plate was punched into a rectangle of a predetermined size corresponding to a bendable image display device having a bending axis in the short - side direction. Here, the punching was performed such that the absorption axis of the polarizer was 30° with respect to the bending axis. The obtained retardation film - attached polarizing plate was subjected to the same evaluation as in Example 1 - 1. The results are shown in Table 1.

[0046] [Examples 3 - 2] to [Examples 3 - 5] and [Comparative Examples 3 - 1] to [Comparative Examples 3 - 2] A retardation film - attached polarizing plate was obtained in the same manner as in Example 3 - 1, except that the punching was performed such that the angle between the absorption axis and the bending axis of the polarizer was the angle shown in Table 1. The obtained retardation film - attached polarizing plate was subjected to the same evaluation as in Example 1 - 1. The results are shown in Table 1.

[0047] [Example 4 - 1] A retardation film - attached polarizing plate was obtained in the same manner as in Example 1 - 1, except that an acrylic resin film (thickness: 40 μm) was used instead of the HC - TAC film as the protective layer. The elastic modulus of the protective film was 3066 MPa. Also, the thickness of the obtained retardation film - attached polarizing plate was 51 μm. This retardation film - attached polarizing plate was punched into a rectangle of a predetermined size corresponding to a bendable image display device having a bending axis in the short - side direction. Here, the punching was performed such that the absorption axis of the polarizer was 30° with respect to the bending axis. The obtained retardation film - attached polarizing plate was subjected to the same evaluation as in Example 1 - 1. The results are shown in Table 1.

[0048] [Examples 4 - 2] to [Examples 4 - 5] and [Comparative Examples 4 - 1] to [Comparative Examples 4 - 2] A retardation film - attached polarizing plate was obtained in the same manner as in Example 4 - 1, except that the punching was performed such that the angle between the absorption axis and the bending axis of the polarizer was the angle shown in Table 1. The obtained retardation film - attached polarizing plate was subjected to the same evaluation as in Example 1 - 1. The results are shown in Table 1.

[0049] [Comparative Example 5 - 1] A retardation layer (a single retardation layer showing inverse dispersion wavelength dependence and capable of functioning as a λ / 4 plate) was produced as follows. Polymerization was carried out using a batch polymerization apparatus consisting of two vertical stirring reactors equipped with stirring blades and reflux coolers. 30.31 parts by mass (0.047 mol) of bis[9-(2 - phenoxycarbonylethyl)fluorene - 9 - yl]methane (BPFM) synthesized by the method described in JP - A - 2015 - 25111, 39.94 parts by mass (0.273 mol) of isosorbide (ISB, manufactured by Rocket Fuel Co., Ltd.), 30.20 parts by mass (0.099 mol) of spiroglycol (SPG, manufactured by Mitsubishi Gas Chemical Co., Ltd.), 69.67 parts by mass (0.325 mol) of diphenyl carbonate (DPC, manufactured by Mitsubishi Chemical Corporation), and 7.88×10 -4 parts by mass (4.47×10 -6([number of moles]) was charged. After replacing the inside of the reactor with nitrogen under reduced pressure, it was heated with a heat medium, and stirring was started when the internal temperature reached 100 °C. Forty minutes after the start of temperature increase, the internal temperature reached 220 °C, and while controlling to maintain this temperature, reduced pressure was started and it was made 13.3 kPa in 90 minutes after reaching 220 °C. The phenol vapor by-produced along with the polymerization reaction was led to a reflux condenser at 110 °C, the monomer components contained in a small amount in the phenol vapor were returned to the reactor, and the phenol vapor that did not condense was led to a condenser at 45 °C for recovery. Nitrogen was introduced into the first reactor to once return the pressure to atmospheric pressure, and then the oligomerized reaction solution in the first reactor was transferred to the second reactor. Next, heating and reduced pressure in the second reactor were started, and the internal temperature was made 240 °C and the pressure was made 20 kPa in 40 minutes. Then, while further reducing the pressure, the polymerization was allowed to proceed until a predetermined stirring power was reached. When the predetermined power was reached, nitrogen was introduced into the reactor to return the pressure, and the produced polyester carbonate was extruded into water, and the strands were cut to obtain pellets. The ratio of the structural units derived from each monomer of this resin was BPFM / ISB / SPG / DPC = 21.5 / 39.4 / 30.0 / 9.1 mass%. The obtained pellets were vacuum-dried at 100 °C for 6 hours or more, and then using a film forming apparatus equipped with a single-screw extruder (manufactured by Isuzu Kako Co., Ltd., screw diameter 25 mm, cylinder set temperature: 250 °C), a T-die (width 300 mm, set temperature: 220 °C), a chill roll (set temperature: 120 - 130 °C), and a winder, a long unstretched film with a length of 3 m, a width of 200 mm, and a thickness of 100 μm was produced. This long unstretched film was stretched with the stretching temperature being Tg (139 °C) to obtain a retardation film with a thickness of 37 μm. The obtained retardation film showed a refractive index characteristic of nx > ny = nz, Re(550) was 145 nm, and Re(450) / Re(550) was 0.85.

[0050] The obtained retardation film was used as a retardation layer, the retardation film was bonded to a polarizer via an adhesive layer (thickness: 5 μm) instead of an adhesive layer, and a positive C plate used in Example 2-1 was transferred onto the surface of the retardation layer. Otherwise, in the same manner as in Example 1-1, a polarizing plate with a retardation layer having a structure of protective layer / adhesive / polarizer / adhesive layer / retardation layer (retardation film) / adhesive / positive C plate was obtained. The thickness of the obtained polarizing plate with a retardation layer was 89 μm. This polarizing plate with a retardation layer was punched into a rectangle of a predetermined size corresponding to a bendable image display device having a bending axis in the short side direction. Here, it was punched so that the absorption axis of the polarizer was 0° with respect to the bending axis. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in Example 1-1. The results are shown in Table 1.

[0051] [Comparative Example 5-2] to [Comparative Example 5-7] A polarizing plate with a retardation layer was obtained in the same manner as in Comparative Example 5-1, except that it was punched so that the angle between the absorption axis of the polarizer and the bending axis was the angle shown in Table 1. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in Example 1-1. The results are shown in Table 1.

[0052] [Comparative Example 6-1] A polarizing plate with a retardation layer was obtained in the same manner as in Example 1-1, except that an HC-COP film was used instead of the HC-TAC film as the protective layer. The elastic modulus of the protective film was 1988 MPa. Also, the thickness of the obtained polarizing plate with a retardation layer was 84 μm. This polarizing plate with a retardation layer was punched into a rectangle of a predetermined size corresponding to a bendable image display device having a bending axis in the short side direction. Here, it was punched so that the absorption axis of the polarizer was 30° with respect to the bending axis. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in Example 1-1. The results are shown in Table 1.

[0053] [Comparative Example 6-2] to [Comparative Example 6-7] A polarizing plate with a retardation layer was obtained in the same manner as in Comparative Example 6-1, except that it was punched so that the angle between the absorption axis of the polarizer and the bending axis was the angle shown in Table 1. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in Example 1-1. The results are shown in Table 1.

[0054] [Comparative Example 7-1] A polarizing plate was produced as follows. A polyvinyl alcohol-based resin film having an average degree of polymerization of 2,400, a saponification degree of 99.9 mol%, and a thickness of 30 μm was prepared. The polyvinyl alcohol film was immersed in a swelling bath (water bath) at 20°C for 30 seconds between rolls with different peripheral speed ratios and stretched 2.4 times in the conveying direction while swelling (swelling step). Subsequently, it was immersed in a dyeing bath at 30°C (an aqueous solution with an iodine concentration of 0.03 wt% and a potassium iodide concentration of 0.3 wt%) and stretched 3.7 times in the conveying direction with respect to the original polyvinyl alcohol film (a polyvinyl alcohol film not stretched at all in the conveying direction) while dyeing so that the monomer transmittance after the final stretching became a desired value (dyeing step). The immersion time at this time was about 60 seconds. Next, the dyed polyvinyl alcohol film was immersed in a crosslinking bath at 40°C (an aqueous solution with a boric acid concentration of 3.0 wt% and a potassium iodide concentration of 3.0 wt%) and stretched up to 4.2 times in the conveying direction with respect to the original polyvinyl alcohol film (crosslinking step). Further, the obtained polyvinyl alcohol film was immersed in a stretching bath at 64°C (an aqueous solution with a boric acid concentration of 4.0 wt% and a potassium iodide concentration of 5.0 wt%) for 50 seconds and stretched up to 6.0 times in the conveying direction with respect to the original polyvinyl alcohol film (stretching step), and then immersed in a washing bath at 20°C (an aqueous solution with a potassium iodide concentration of 3.0 wt%) for 5 seconds (washing step). The washed polyvinyl alcohol film was dried at 30°C for 2 minutes to produce a polarizer (thickness 12 μm). An HC-TAC film was laminated on one surface of the obtained polarizer in the same manner as in Example 1-1, and a TAC film with a thickness of 25 μm was laminated on the other surface. In this way, a polarizing plate having a structure of a visible-side protective layer (HC-TAC film) / polarizer / inner protective layer (TAC film) was produced. The elastic modulus of the visible-side protective layer was 3872 MPa as in Example 1-1.

[0055] A retardation film polarizer having a structure of protective layer / adhesive / polarizer / adhesive / protective layer / adhesive layer / retardation layer (retardation film) / adhesive / positive C plate was obtained in the same manner as in Comparative Example 5-1, except that the polarizer obtained above was used. The thickness of the obtained retardation film polarizer was 116 μm. This retardation film polarizer was punched into a rectangle of a predetermined size corresponding to a bendable image display device having a bending axis in the short side direction. Here, it was punched so that the absorption axis of the polarizer was 0° with respect to the bending axis. The obtained retardation film polarizer was subjected to the same evaluation as in Example 1-1. The results are shown in Table 1.

[0056] [Comparative Example 7-2] to [Comparative Example 7-7] A retardation film polarizer was obtained in the same manner as in Comparative Example 7-1, except that it was punched so that the angle between the absorption axis of the polarizer and the bending axis was the angle shown in Table 1. The obtained retardation film polarizer was subjected to the same evaluation as in Example 1-1. The results are shown in Table 1.

[0057] [Comparative Example 8-1] A brightness enhancement film (an amorphous isophthalic acid copolymer polyethylene terephthalate (IPA copolymer PET) film with a water absorption rate of 0.75% and a Tg of 75 °C (thickness: 30 μm)) was laminated on one side of the polarizer produced in Comparative Example 7-1 to produce a polarizer having a structure of brightness enhancement film / polarizer. In the following procedure, in the same manner as in Example 1-1, a retardation film polarizer having a structure of protective layer (brightness enhancement film) / adhesive / polarizer / adhesive / W layer / adhesive / Q layer was obtained. The elastic modulus of the protective layer was 5005 MPa. Also, the thickness of the obtained retardation film polarizer was 48 μm. This retardation film polarizer was punched into a rectangle of a predetermined size corresponding to a bendable image display device having a bending axis in the short side direction. Here, it was punched so that the absorption axis of the polarizer was 0° with respect to the bending axis. The obtained retardation film polarizer was subjected to the same evaluation as in Example 1-1. The results are shown in Table 1.

[0058] [Comparative Example 8-2] to [Comparative Example 8-7] A retardation layer - attached polarizing plate was obtained in the same manner as in Comparative Example 8 - 1, except that the punching was performed such that the angle between the absorption axis and the bending axis of the polarizer was the angle shown in Table 1. The obtained retardation layer - attached polarizing plate was subjected to the same evaluation as in Example 1 - 1. The results are shown in Table 1.

[0059] [Table 1]

[0060] [Evaluation] As is clear from Table 1, according to the examples of the present invention, it can be seen that a retardation layer - attached polarizing plate excellent in both foldability and visibility when viewed through polarized sunglasses can be obtained. [Industrial Applicability]

[0061] The retardation layer - attached polarizing plate of the present invention can be suitably used for a bendable image display device and an image display device that can be viewed through polarized sunglasses. [Explanation of Reference Numerals]

[0062] 10 Polarizing plate 11 Polarizer 12 Protective layer 20 Retardation layer 21 H layer 22 Q layer 100 Retardation layer - attached polarizing plate 102 Retardation layer - attached polarizing plate

Claims

1. A polarizing plate with a retardation layer used in a bendable image display device, comprising: a polarizer and a protective layer on at least one side of the polarizer; and a retardation layer provided on the side opposite to the viewing side of the polarizer and combined with the polarizer to have a circular polarization function or an elliptical polarization function; having a total thickness of 80 μm or less, the angle between the bending axis of the image display device and the absorption axis of the polarizer being 35° to 55°, the elastic modulus of the protective layer being 5000 MPa or less, the retardation layer being an alignment and curing layer of a liquid crystal compound, the absorption axis of the polarizer extending in one direction throughout the polarizer, a polarizing plate with a retardation layer.

2. The polarizing plate with a retardation layer according to claim 1, having a total thickness of 60 μm or less.

3. The polarizing plate with a retardation layer according to claim 1 or 2, wherein the thickness of the polarizer is 10 μm or less.

4. The polarizing plate with a retardation layer according to any one of claims 1 to 3, wherein the polarizing plate includes a protective layer only on the side opposite to the retardation layer of the polarizer.

5. The polarizing plate with a retardation layer according to claim 4, wherein the elastic modulus of the protective layer is 4000 MPa or less.

6. The polarizing plate with a retardation layer according to claim 5, wherein the thickness of the protective layer is 45 μm or less.

7. The polarizing plate with a retardation layer according to any one of claims 1 to 6, wherein the angle between the bending axis and the absorption axis of the polarizer is 40° to 50°.

8. The polarizing plate with a retardation layer according to any one of claims 1 to 7, wherein the retardation layer is a single layer, Re(550) of the retardation layer is 100 nm to 190 nm, Re(450) / Re(550) of the retardation layer is 0.8 or more and less than 1, and the angle between the slow axis of the retardation layer and the absorption axis of the polarizer is 40° to 50°.

9. The polarizing plate with a retardation layer according to claim 8, further having another retardation layer outside the retardation layer, and the refractive index characteristics of the other retardation layer showing a relationship of nz > nx = ny.

10. The retardation layer has a laminated structure of an alignment and curing layer of a first liquid crystal compound and an alignment and curing layer of a second liquid crystal compound, Re(550) of the alignment and curing layer of the first liquid crystal compound is 200 nm to 300 nm, and the angle between its slow axis and the absorption axis of the polarizer is 10° to 20°, Re(550) of the alignment and curing layer of the second liquid crystal compound is 100 nm to 190 nm, and the angle between its slow axis and the absorption axis of the polarizer is 70° to 80°. A polarizing plate with a retardation layer according to any one of claims 1 to 7. **Claim 11** An image display device comprising the polarizing plate with a retardation layer according to any one of claims 1 to 10.

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