TW202219563A - Retardation-layer-equipped polarizing plate, and image display device - Google Patents

Abstract

Provided is a retardation layer-equipped polarizing plate which exhibits excellent bendability and provides excellent visibility through polarized sunglasses while having a simple configuration. A retardation layer-equipped polarizing plate according to an embodiment of the present invention is to be used in a bendable image display device. A retardation layer-equipped polarizing plate having a polarizing plate which includes a polarizer and a protective layer on one or more sides of the polarizer, and also having a retardation layer which has a circular polarization function or an elliptical polarization function and is provided on the side of the polarizing plate opposite the visible side thereof, wherein the total thickness thereof is no more than 80[mu]m, the angle between the axis of bending of the image display device and the axis of absorption of the polarizer is 30-60 DEG, and the elasticity of the protective layer is no more than 5,000MPa.

Description

Polarizing plate with retardation layer and image display device

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

In recent years, image display devices represented by liquid crystal display devices and electroluminescence (EL) display devices (eg, organic EL display devices, inorganic EL display devices) have rapidly spread. A polarizing plate and a retardation plate are typically used in image display devices. In practical use, a polarizing plate with a retardation layer formed by integrating a polarizing plate and a retardation plate is widely used (for example, Japanese Patent Document 1), but recently, the demand for thinner image display devices has increased. The demand for thinning of the polarizing plate with retardation layer has also become strong. Furthermore, the use of the image display device has expanded, and the requirements for the image display device have been diversified along with this. For example, with regard to smart phones, it is required to be able to fold and improve visibility through polarized sunglasses. Therefore, a polarizing plate with retardation layer capable of realizing such an image display device is strongly demanded. prior art literature Patent Literature

Patent Document 1: Japanese Patent No. 3325560

[Problems to be Solved by Invention]

The present invention has been made to solve the above-mentioned problems, and its main object is to provide a polarizing plate with a retardation layer having a simple structure, excellent visibility through polarized sunglasses, and excellent flexibility. [Technical means to solve problems]

The polarizing plate with retardation layer of the present invention is used in a bendable image display device. The polarizing plate with the retardation layer has: a polarizing plate comprising a polarizing element and a protective layer on at least one side of the polarizing element; and a retardation layer disposed on the opposite side of the polarizing plate to the visible side, It has the function of circularly polarized light or elliptically polarized light; and the total thickness of the polarizing plate with the retardation layer is 80 μm or less, and the angle formed by the bending axis of the image display device and the absorption axis of the polarizing element is 30 °～60°, the elastic modulus of the protective layer is below 5000 MPa. In one embodiment, the total thickness of the polarizing plate with the retardation layer is 60 μm or less. In one embodiment, the thickness of the polarizing element is 10 μm or less. In one embodiment, the polarizing plate includes a protective layer only on the opposite side of the polarizing element to the retardation layer. 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 polarizing element is 40°˜50°. In one embodiment, the retardation layer is an alignment cured layer of a liquid crystal compound. In one embodiment, the retardation layer is a single layer, the Re(550) of the retardation layer is 100 nm to 190 nm, and the Re(450)/Re(550) of the retardation layer is 0.8 or more and less than 1. The angle formed by the retardation axis of the retardation layer and the absorption axis of the polarizing element is 40° to 50°. In one embodiment, the polarizing plate with the retardation layer further has another retardation layer outside the retardation layer, and the refractive index characteristic of the other retardation layer exhibits a relationship of nz>nx=ny. In one embodiment, the retardation layer has a laminated structure of the alignment cured layer of the first liquid crystal compound and the alignment cured layer of the second liquid crystal compound; the Re(550) of the alignment cured layer of the first liquid crystal compound is 200 nm～ 300 nm, the angle formed by the retardation axis and the absorption axis of the above-mentioned polarizing element is 10°～20°; the Re(550) of the alignment cured layer of the second liquid crystal compound is 100 nm～190 nm, and the retardation axis is The angle formed with the absorption axis of the polarizer is 70° to 80°. According to another aspect of the present invention, an image display device is provided. The image display device includes the above-mentioned polarizing plate with a retardation layer. [Effect of invention]

According to the embodiment of the present invention, in the polarizing plate with retardation layer, the angle between the bending axis and the absorption axis of the polarizing element in the case of applying to a bendable image display device is optimized, and the By optimizing the elastic modulus of the protective layer, a polarizing plate with retardation layer can be realized with a simple structure, excellent visibility through polarized sunglasses, and excellent bending properties.

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

(Definition of Terms and Symbols) 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 the largest (ie, the direction of the slow axis), "ny" is the refractive index in the direction orthogonal to the slow axis in the plane (ie, the direction of the advance axis), " nz" is the refractive index in the thickness direction. (2) In-plane phase difference (Re) "Re(λ)" is the in-plane retardation measured with light of wavelength λ nm at 23°C. For example, "Re(550)" is the in-plane retardation measured with light having a wavelength of 550 nm at 23°C. Re(λ) is obtained by the formula: Re(λ)=(nx−ny)×d when the thickness of the layer (film) is d (nm). (3) Phase difference in 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 having a wavelength of 550 nm at 23°C. Rth(λ) is obtained by the formula: Rth(λ)=(nx−nz)×d when the thickness of the layer (film) is d (nm). (4) Nz coefficient The Nz coefficient is obtained by Nz=Rth/Re. (5) Angle In this specification, when referring to an angle, 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°.

A. Overall composition of polarizing plate with retardation layer 1 is a schematic perspective view showing the bending 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 view of a polarizing plate with a retardation layer according to an embodiment of the present invention. Schematic plan view; FIG. 3 is a schematic cross-sectional view of a polarizing plate with retardation layer according to one embodiment of the present invention; FIG. 4 is a schematic cross-sectional view of a polarizing plate with retardation layer according to another embodiment of the present invention. The polarizing plate 100 with the retardation layer in the example shown in FIG. 3 typically has the polarizing plate 10 and the retardation layer 20 in this order from the visible side. In the illustrated example, the polarizing plate 10 includes a polarizing element 11 and protective layers 12 and 13 on both sides of the polarizing element 11 . Depending on the purpose, one of the protective layers 12 and 13 may also be omitted. In one embodiment, the polarizing plate 10 has the protective layer 12 only on the visible side of the polarizing element 11 (the side opposite to the retardation layer 20 ). The components of the polarizing plate with the retardation layer are typically bonded via any appropriate adhesive layer (adhesive layer or adhesive layer: not shown). In terms of practicality, an adhesive layer (not shown) is provided on the opposite side of the retardation layer 20 from the polarizing plate 10 (that is, as the outermost layer on the side opposite to the visible side), and a retardation layer is attached. The polarizing plate can be attached to the image display panel. Furthermore, it is preferable to temporarily adhere a release film (not shown) to the surface of the adhesive layer before using the polarizing plate with the retardation layer for use. By temporarily adhering the release film, the adhesive layer can be protected, and the roll of the polarizing plate with the retardation layer can be formed.

As shown in FIG. 1, a polarizing plate with a retardation layer is used in a bendable image display device. As shown in FIGS. 1 and 2 , in the polarizing plate with retardation layer, the angle formed by the bending axis F of the image display device and the absorption axis A of the polarizing element 11 is 30°˜60°, preferably 35° ~55°, more preferably 40° to 50°, further preferably 42° to 48°, particularly preferably about 45°. With such a configuration, it is not necessary to form a specific layer (typically, a layer that imparts (elliptically) polarized light functions such as a λ/4 plate, a layer such as an in-plane polarizing plate, etc. The retardation Re(550) exceeds the ultra-high retardation layer of 1000 nm), which can realize excellent visibility through polarized sunglasses. Therefore, the polarizing plate with retardation layer according to the embodiment of the present invention is simple and low in cost due to the small number of layers, resulting in a thin type. Furthermore, if it is such a structure, excellent bendability (bendability) can be achieved by the 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 polarizing element, the polarizing plate (substantially a polarizing plate) with a retardation layer becomes very easy to break. On the other hand, when the bending axis is perpendicular to the absorption axis of the polarizing element, it becomes difficult to break, but the visibility when viewed through polarized sunglasses is extremely insufficient. By optimizing such that the bending axis and the absorption axis of the polarizing element form the above-mentioned specific angle, both excellent bending properties (flexibility) and excellent visibility when viewed through polarized sunglasses can be achieved. Furthermore, in the illustrated example, the bending axis F is the short-side direction of the image display device, but the bending axis F may be the long-side direction or a direction having a specific angle with respect to the long-side direction or the short-side direction. (oblique direction). By specifying the direction of the absorption axis with respect to the direction of the bending axis, even if the polarizing plate with the retardation layer is applied to the image display of irregular shapes (for example, circle, ellipse, triangle, indeterminate shape) other than rectangle In the case of the device, the above effects can also be obtained.

The total thickness of the polarizing plate with the retardation layer (the total thickness of the polarizing plate, the retardation layer, and the adhesive layer that is layered equally) is 80 μm or less, preferably 70 μm or less, more preferably 60 μm or less, and further Preferably it is 50 micrometers or less, More preferably, it is 40 micrometers or less. The total thickness of the polarizing plate with the retardation layer may be, for example, 25 μm or more. According to the embodiment of the present invention, even with such a very small total thickness, excellent visibility when viewed through polarized sunglasses can be achieved. In other words, the polarizing plate with the retardation layer can have a very small total thickness even when it is used for the purpose of visual recognition through polarized sunglasses. As a result, the second moment of the cross-section during bending becomes smaller, and the stress applied to each component (layer) becomes smaller. Therefore, not only excellent visibility when viewed through sunglasses, but also excellent bendability (bendability) can be achieved.

In the 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 may be, for example, 2000 MPa. Preferably, the polarizing plate with retardation layer (substantially a polarizing plate) only has the protective layer 12, and the elastic modulus of the protective layer 12 is within the above-mentioned range. When the elastic modulus of the protective layer is too large, the compressive stress applied to the protective layer becomes larger when the strain during bending is the same. As a result, when it is repeatedly folded, the protective layer is likely to be cracked. By optimizing the elastic modulus of the protective layer within the above-mentioned range, cracks at the time of bending can be suppressed, and excellent bendability (bendability) can be realized. In addition, the elastic modulus can be measured based on JIS Z 2284.

The retardation layer 20 has a circularly polarized light function or an elliptically polarized light function. The retardation layer 20 is typically an alignment cured layer (liquid crystal alignment cured 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 significantly larger than that of a non-liquid crystal material, so that the thickness of the retardation layer that can be used to obtain the desired in-plane retardation can be significantly reduced . Therefore, a remarkable thinning of the polarizing plate with the retardation layer can be realized. As a result, excellent bendability (bendability) as described above can be realized. In this specification, the "alignment cured layer" refers to a layer in which the liquid crystal compound is aligned in a specific direction within the layer, and its alignment state is fixed. In addition, the "alignment hardening layer" means the concept containing the alignment hardening layer obtained by hardening a liquid crystal monomer as described below. The retardation layer 20 is typically aligned (horizontal alignment) in a state in which rod-shaped liquid crystal compounds are aligned in the direction of the retardation axis of the retardation layer. 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 .

The polarizing plate with retardation layer can further include other optical functional layers. The type, characteristic, number, combination, arrangement position, and the like of the optical functional layer that can be provided in the polarizing plate with the 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 (not shown). The conductive layer or the isotropic base material with the conductive layer is typically provided on the outer side of the second retardation layer 22 (on the opposite side to the polarizing plate 10 ). The conductive layer or the isotropic substrate with the conductive layer is typically an arbitrary layer provided as needed, and can be omitted. Furthermore, when a conductive layer or an isotropic substrate with a conductive layer is provided, a polarizer with a retardation layer can be used to assemble the touch sensor in an image display unit (eg, an organic EL unit) ) and a polarizing plate, the so-called internal touch panel type input display device. Also, for example, the polarizing plate with the retardation layer may further include other retardation layers. The optical properties (for example, refractive index properties, in-plane retardation, Nz coefficient, photoelastic coefficient), thickness, arrangement position, and the like of the other retardation layers can be appropriately set according to the purpose.

Hereinafter, the constituent elements of the polarizing plate with retardation layer will be described in more detail.

B. Polarizing plate B-1. Polarizing element As the polarizing element 11, any appropriate polarizing element can be used. For example, the resin film forming the polarizing element may be a single-layer resin film, or may be a laminate of two or more layers.

As a specific example of the polarizing element which consists of a single-layer resin film, hydrophilicity for polyvinyl alcohol (PVA) type film, partially formalized PVA type film, ethylene-vinyl acetate copolymer type partially saponified film, etc. can be mentioned. Polymer film, which is obtained by dyeing and stretching treatment with dichroic substances such as iodine or dichroic dyes; polyene-based alignment films such as dehydrogenation-treated products of PVA or dehydrochlorination-treated products of polyvinyl chloride, etc. From the viewpoint of being excellent in optical properties, it is preferable to use a polarizing element obtained by dyeing a PVA-based film with iodine and uniaxially extending it.

The above-mentioned dyeing with iodine can be performed, for example, by immersing the PVA-based film in an aqueous iodine solution. The stretching ratio of the above-mentioned uniaxial stretching is preferably 3 times to 7 times. The extension can be carried out after the dyeing treatment or simultaneously with the dyeing. Moreover, you may dye it after extending|stretching. If necessary, swelling treatment, crosslinking treatment, washing treatment, drying treatment, etc. are performed on the PVA-based film. For example, by immersing the PVA film in water and washing it before dyeing, not only the stains and anti-blocking agents on the surface of the PVA film can be removed, but also the PVA film can be swelled to prevent uneven dyeing.

As a specific example of the polarizing element obtained by using the laminate, a laminate using a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a resin substrate and coating A polarizing element obtained by a laminate of PVA-based resin layers formed on the resin substrate. A polarizing element obtained by using a laminate of a resin substrate and a PVA-based resin layer formed on the resin substrate can be produced, for example, by the following steps: coating a PVA-based resin solution on the resin substrate, This is dried to form a PVA-based resin layer on a resin substrate to obtain a laminate of the resin substrate and the PVA-based resin layer; and the laminate is stretched and dyed to make the PVA-based resin layer a polarizer. In this embodiment, it is preferable to form the polyvinyl-alcohol-type resin layer containing a halide and a polyvinyl-alcohol-type resin on one side of a resin base material. The stretching is typically performed by immersing the layered body in a boric acid aqueous solution. Further, the stretching may further include a step of stretching the laminate in air at a high temperature (eg, 95° C. or higher) before stretching in a boric acid aqueous solution, if necessary. Moreover, in this embodiment, it is preferable to subject a laminated body to the drying shrinkage process which shrinks 2% or more in the width direction by heating while conveying in the longitudinal direction. Typically, the manufacturing method of the present embodiment includes the steps of sequentially performing an air-assisted stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment on the laminate. By introducing the auxiliary extension, when the PVA is coated on the thermoplastic resin, the crystallinity of the PVA can also be improved, and higher optical properties can be achieved. In addition, by simultaneously improving the orientation of PVA in advance, when immersed in water in the subsequent dyeing step or stretching step, problems such as decrease in the orientation of PVA or dissolution can be prevented, and higher optical properties can be achieved. Furthermore, 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 alignment disorder of the polyvinyl alcohol molecules and the decrease in the alignment property can be suppressed. Thereby, the optical characteristics of the polarizing element obtained by the process step of immersing a laminated body in liquid, such as dyeing process and an underwater extension process, can be improved. Furthermore, optical properties can be improved by shrinking the laminate in the width direction by drying shrinkage treatment. The obtained laminate of resin substrate/polarizing element can be used as it is (that is, the resin substrate can be used as a protective layer of the polarizing element), or the resin substrate can be peeled off from the laminate of resin substrate/polarizing element, and placed in the This peeling surface can be used by laminating any appropriate protective layer as needed. Details of the manufacturing method of such a polarizing element are described in, for example, Japanese Patent Laid-Open No. 2012-73580 and Japanese Patent No. 6470455 . All the descriptions of these publications are incorporated herein by reference.

The thickness of the polarizing element is preferably 15 μm or less, more preferably 12 μm or less, further preferably 10 μm or less, particularly preferably 3 μm to 10 μm, particularly preferably 3 μm to 8 μm. If the thickness of the polarizing element is within such a range, the above-mentioned desired total thickness can be achieved, and excellent bendability can be achieved.

The polarizing element preferably exhibits absorption dichroism at any wavelength from 380 nm to 780 nm. The single transmittance of the polarizing element is preferably 41.5% to 46.0%, more preferably 43.0% to 46.0%, and still more preferably 44.5% to 46.0%. The polarization degree of the polarizing element is preferably 97.0% or more, more preferably 99.0% or more, and still more preferably 99.9% or more.

B-2. Protective layer The protective layers 12 and 13 may be formed of any appropriate film that can be used as a protective layer of a polarizing element as long as the above-mentioned elastic modulus can be obtained, respectively. Specific examples of the material used as the main component of the film include cellulose-based resins such as triacetyl cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, and polyamide-based resins. , polyimide series, polyether series, polyether series, polystyrene series, cyclic olefin series (eg, polynorene series), polyolefin series, (meth)acrylic series, acetate series and other transparent resins.

The polarizing plate with the retardation layer is typically arranged on the visible side of the image display device, and the protective layer 12 is arranged on the visible side. Therefore, the protective layer 12 may also be subjected to surface treatments such as hard coating treatment, anti-reflection treatment, anti-sticking treatment, and anti-glare treatment as required.

The thicknesses of the protective layers 12 and 13 are respectively preferably 60 μm or less, more preferably 45 μm or less, and still more preferably 10 μm to 40 μm. Furthermore, when the surface treatment is performed, the thickness of the protective layer 12 is the thickness including the thickness of the surface treatment layer.

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.

When the retardation layer 20 is a single layer, the retardation layer can typically function as a λ/4 plate. Specifically, the 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 may be adjusted so that the desired in-plane retardation of the λ/4 plate can be obtained. The thickness of the retardation layer may be, for example, 1.0 μm to 2.5 μm. In this embodiment, the angle formed by the retardation axis of the retardation layer and the absorption axis of the polarizing element is preferably 40°˜50°, more preferably 42°˜48°, and more preferably 44°˜46° . In this embodiment, the polarizing plate with the retardation layer 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 wavelength dispersion 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.

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 from the polarizing plate side as shown in FIG. 4 . The H layer typically functions as a λ/2 plate, and the Q layer typically functions as a λ/4 plate. Specifically, the Re(550) of the H layer is preferably 200 nm to 300 nm, more preferably 220 nm to 290 nm, and more preferably 230 nm to 280 nm; the 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 in such a way that the desired in-plane retardation of the λ/2 plate can be obtained. When the H layer is a liquid crystal alignment cured layer, its thickness may be, for example, 2.0 μm˜4.0 μm. The thickness of the Q layer can be adjusted in such a way that the desired in-plane retardation of the λ/4 plate can be obtained. When the Q layer is a liquid crystal alignment cured layer, its thickness may be, for example, 1.0 μm˜2.5 μm. In this embodiment, the angle formed by the retardation axis of the H layer and the absorption axis of the polarizing element is preferably 10°-20°, more preferably 12°-18°, and more preferably 12°-16°; The angle formed between the retardation axis of the Q layer and the absorption axis of the polarizing element is preferably 70° to 80°, more preferably 72° to 78°, and further preferably 72° to 76°. Furthermore, the arrangement order of the H layer and the Q layer may be reversed, and the angle formed by the retardation axis of the H layer and the absorption axis of the polarizer and the angle formed by the retardation axis of the Q layer and the absorption axis of the polarizer may also be on the contrary. When the retardation layer has a laminated structure, each layer (for example, the H layer and the Q layer) may exhibit inverse wavelength dispersion characteristics in which the retardation value increases according to the wavelength of the measurement light, and may also exhibit the retardation value according to the wavelength of the measurement light. The positive chromatic dispersion characteristic that the wavelength decreases, and the flat chromatic dispersion characteristic that the retardation value is basically unchanged regardless of the wavelength of the measurement light.

The retardation layer (in the case of having a laminated structure, each layer) typically exhibits a relationship of nx>ny=nz in refractive index characteristics. Furthermore, "ny=nz" includes not only the case where ny and nz are completely equal, but also the case where they are substantially equal. Therefore, within the range that does not impair the effect of the present invention, there may be cases where ny>nz or ny<nz. The Nz coefficient of the retardation layer is preferably 0.9 to 1.5, more preferably 0.9 to 1.3.

The retardation layer is typically a liquid crystal alignment cured layer as described above. As a liquid crystal compound, the liquid crystal compound (nematic liquid crystal) whose liquid crystal phase is a nematic phase is mentioned, for example. As such a liquid crystal compound, for example, a liquid crystal polymer or a liquid crystal monomer can be used. The expression mechanism of the liquid crystallinity of the liquid crystal compound may be liquid tropism or thermotropism. The liquid crystal polymer and the liquid crystal monomer may be used alone or in combination.

When the liquid crystal compound is a liquid crystal monomer, the liquid crystal monomer is preferably a polymerizable monomer and a crosslinkable monomer. The reason for this is that, by polymerizing or crosslinking (ie, hardening) the liquid crystal monomer, the alignment state of the liquid crystal monomer can be fixed. After aligning the liquid crystal monomers, for example, as long as the liquid crystal monomers can be polymerized or crosslinked, the above-mentioned alignment state can be fixed. Here, a polymer is formed by polymerization, and a three-dimensional network structure is formed by crosslinking, but these are non-liquid crystalline. Therefore, the formed retardation layer, for example, does not undergo transition to a liquid crystal phase, a glass phase, or a crystal phase under the influence of a temperature change, which is peculiar to a liquid crystal compound. As a result, the retardation layer becomes a retardation layer which is not affected by temperature changes and has extremely excellent stability.

The temperature range in which the liquid crystal monomer exhibits liquid crystallinity varies depending on its kind. 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.

As the above-mentioned liquid crystal monomer, any appropriate liquid crystal monomer can be used. For example, polymeric mesogen compounds described in Japanese Patent Application Laid-Open No. 2002-533742 (WO00/37585), EP358208 (US5211877), EP66137 (US4388453), WO93/22397, EP0261712, DE19504224, DE4408171, GB2280445 and the like can be used. Specific examples of such a polymerizable mesogen compound include, for example, a product named LC242 from BASF, a product named E7 from Merck, and a product named LC-Silicon-CC3767 from Wacker-Chem. . As a liquid crystal monomer, for example, a nematic liquid crystal monomer is preferable.

D. Image Display Device The polarizing plate with retardation layer described in the above items A to C can be applied to an image display device. Therefore, an image display device including a polarizing plate with a retardation layer is also included in the embodiments of the present invention. The image display device typically includes an image display unit and a polarizing plate with a retardation layer attached to the image display unit via an adhesive layer. Typical examples of image display devices include liquid crystal display devices and electroluminescence (EL) display devices (eg, organic EL display devices, inorganic EL display devices). The image display device can be bent as described above, and preferably can be folded. In such an image display device, the effect of the polarizing plate with the retardation layer according to the embodiment of the present invention becomes remarkable. [Example]

Hereinafter, the present invention will be specifically described using examples, but the present invention is not limited to these examples. The measurement method of each characteristic is as follows. In addition, unless otherwise stated, "parts" and "%" in Examples and Comparative Examples are based on weight. (1) Thickness The thickness of 10 μm or less was measured using an interference film thickness meter (product named “MCPD-3000” manufactured by Otsuka Electronics Co., Ltd.). Thicknesses exceeding 10 μm were measured using a digital micrometer (a product named “KC-351C” manufactured by Amway Corporation). (2) Elastic modulus The measurement was carried out according to JIS Z 2284. Specifically, it is as follows. A short 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 a continuous autostereograph (manufactured by Shimadzu Corporation) corresponding to high speed was used under the following conditions The sample piece was stretched in the longitudinal direction, and the elastic modulus was calculated from the obtained S-S (Stress-Strain, stress-strain) curve. As measurement conditions, the stretching speed was 50 mm/min, the distance between the chucks was 100 mm, and the measurement temperature was normal temperature (25° C.). The method of calculating the elastic modulus from the S-S curve is as follows. Draw a tangent at the initial rise of the S-S curve, read the strength at the position where the extension of the tangent becomes 100% elongation, and divide it by the cross-sectional area of the sample sheet (thickness × sample width (10 mm)) where this value was measured, The obtained value was taken as the modulus of elasticity. (3) Bending test The polarizing plates with retardation layers obtained in Examples and Comparative Examples were cut out to a size of 100 mm×55 mm, and used as measurement samples. Here, cutting is performed so that the bending axis becomes the short-side direction of the measurement data. The measurement sample was subjected to a continuous bending test using a bending tester (product named "CL09 Type D01" manufactured by Yuasa System Machinery Co., Ltd.). The bending was performed at room temperature so that the protective layer on the viewing side became the inner side. The radius of curvature of the bend is 3 mm. The presence or absence of cracks was visually observed when folded 500,000 times, and evaluated according to the following criteria. ○: No cracks confirmed ×: Cracks confirmed (4) Visual recognition through polarized sunglasses The polarizing plate on the visible side of the commercially available liquid crystal display device was removed, the surface after removing the polarizing plate was washed, and the polarizing plate with the retardation layer obtained in the Examples and Comparative Examples was pasted on the washed surface. . The angle between the absorption axis of the polarizing element of the polarizing plate with the retardation layer and the short side of the liquid crystal display device is 0°, 30°, 40°, 45°, 50°, 60°, and 90°. . The liquid crystal display device obtained in this way is made to display specific characters, and the display screen is observed by wearing polarized sunglasses. Here, the direction of the absorption axis of the polarized sunglasses and the short-side direction and the long-side direction of the image display device were respectively aligned and observed, and the evaluation was performed according to the following criteria. ○: When the absorption axis direction of polarized sunglasses is aligned with either the short side direction or the long side direction, the content of the display screen can be recognized to an intelligible level ×: When the absorption axis direction of polarized sunglasses is aligned with at least one of the short side direction or the long side direction, the content of the display screen cannot be recognized

[Example 1-1] 1. Production of polarizing plate As the thermoplastic resin substrate, a long amorphous isophthalic acid copolymerized polyethylene terephthalate film (thickness: 100 μm) with Tg of about 75°C was used. Perform corona treatment. It is prepared by mixing polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetylacetate modified PVA (product called "GOHSEFIMER" manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) at a ratio of 9:1. To 100 parts by weight of the PVA-based resin, 13 parts by weight of potassium iodide was added, and the resultant was dissolved in water to prepare an aqueous PVA solution (coating liquid). The above-mentioned PVA aqueous solution was coated on 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 layered body was uniaxially stretched to 2.4 times in the longitudinal direction (longitudinal direction) in an oven at 130° C. (assisted stretching treatment in air). Next, the layered body was immersed for 30 seconds in an insolubilization bath (a boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40°C (insolubilization treatment). Then, in a dyeing bath (with respect to 100 parts by weight of water, an iodine aqueous solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7) in a dyeing bath with a liquid temperature of 30° C., the monomer transmittance of the polarizing element finally obtained is determined. (Ts) was immersed for 60 seconds while adjusting the density so that it became a specific value (dyeing treatment). Next, it was immersed for 30 seconds in a crosslinking bath (a boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40°C (crosslinking treatment). After that, the layered body was immersed in a boric acid aqueous solution (boric acid concentration of 4 wt %, potassium iodide concentration of 5 wt %) at a liquid temperature of 70°C, and the longitudinal extension ratio was 5.5 in the longitudinal direction (longitudinal direction) between rolls with different peripheral speeds. Uniaxial stretching is carried out in a multi-fold way (underwater stretching treatment). Then, the layered body was immersed in a cleaning bath (aqueous solution obtained by mixing 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). Then, while drying in the oven maintained at about 90 degreeC, it contacted with the heating roll made of SUS (Steel Special Use Stainless, stainless steel) maintained at the surface temperature of about 75 degreeC (drying shrinkage treatment). In this way, a polarizing element having a thickness of about 5 μm was formed on the resin substrate, and a polarizing plate having a resin substrate/polarizing element configuration was obtained.

Furthermore, an HC-TAC film was attached to the surface of the obtained polarizer (the surface opposite to the resin substrate) via an ultraviolet curable adhesive (thickness 1.0 μm) to serve as a protective substrate (protective layer). Furthermore, the HC-TAC film is a film in which a hard coat (HC) layer (thickness 7 μm) is formed on a triacetate cellulose (TAC) film (thickness 25 μm), and the TAC film becomes the polarizer side. fit. In this way, a polarizing plate having a protective layer/polarizing element configuration is obtained. The elastic modulus of the protective layer is 3872 MPa.

使用磨擦布對聚對苯二甲酸乙二酯(PET)膜(厚度38 μm)表面進行磨擦，實施配向處理。配向處理之方向設為於貼合於偏光板時，相對於偏光元件之吸收軸之方向自視認側觀察時成為15°方向。利用棒式塗佈機對該配向處理表面塗佈上述液晶塗佈液，於90℃下加熱乾燥2分鐘，藉此使液晶化合物配向。使用金屬鹵化物燈，對以此方式形成之液晶層照射1 mJ/cm ²之光，使該液晶層硬化，藉此於PET膜上形成液晶配向固化層A。液晶配向固化層A之厚度為2 μm，面內相位差Re(550)為270 nm。進而，液晶配向固化層A具有nx＞ny＝nz之折射率分佈。使用液晶配向固化層A作為W層。 變更塗佈厚度，以及使配向處理方向相對於偏光元件之吸收軸之方向自視認側觀察時成為75°方向，除此之外，與上述同樣地於PET膜上形成液晶配向固化層B。液晶配向固化層B之厚度為1 μm，面內相位差Re(550)為140 nm。進而，液晶配向固化層B具有nx＞ny＝nz之折射率分佈。使用液晶配向固化層B作為Q層。 2. Preparation of retardation layer 10 g of a polymerizable liquid crystal exhibiting a nematic liquid crystal phase (manufactured by BASF: a product named "Paliocolor LC242", represented by the following formula), and 3 g of the polymerizable liquid crystal compound. A photopolymerization initiator (manufactured by BASF: commercial product named "Irgacure 907") was dissolved in 40 g of toluene to prepare a liquid crystal composition (coating liquid). [hua 1]

The surface of the polyethylene terephthalate (PET) film (thickness 38 μm) was rubbed with a rubbing cloth to perform alignment treatment. The direction of the alignment treatment was set to be a 15° direction when viewed from the visual side with respect to the direction of the absorption axis of the polarizing element when it was bonded to a polarizing plate. The above-mentioned liquid crystal coating liquid was applied to the alignment-treated surface by a bar coater, and the liquid crystal compound was aligned by heating and drying at 90° C. for 2 minutes. The liquid crystal layer formed in this way was irradiated with light of 1 mJ/cm ² using a metal halide lamp to harden the liquid crystal layer, thereby forming a liquid crystal alignment cured layer A on the PET film. The thickness of the liquid crystal alignment cured layer A is 2 μm, and the in-plane retardation Re(550) is 270 nm. Furthermore, the liquid crystal alignment cured layer A has a refractive index distribution of nx>ny=nz. The liquid crystal alignment cured layer A was used as the W layer. The liquid crystal alignment cured layer B was formed on the PET film in the same manner as above except that the coating thickness was changed and the alignment treatment direction was 75° when viewed from the visible side with respect to the direction of the absorption axis of the polarizer. The thickness of the liquid crystal alignment cured layer B is 1 μm, and the in-plane retardation Re(550) is 140 nm. Furthermore, the liquid crystal alignment cured layer B has a refractive index distribution of nx>ny=nz. The liquid crystal alignment cured layer B was used as the Q layer.

3. Production of polarizing plate with retardation layer The liquid crystal alignment cured layer A (W layer) and the liquid crystal alignment cured layer B (Q layer) obtained in 2. above were sequentially transferred to the polarizer surface of the polarizing plate obtained in 1. above. At this time, the angle formed by the absorption axis of the polarizing element and the retardation axis of the alignment cured layer A is 15°, and the angle formed by the absorption axis of the polarizing element and the retardation axis of the alignment cured layer B is 75°. Transfer (lamination). In addition, each transfer (bonding) was performed via an ultraviolet curable adhesive (thickness 1.0 μm). In this way, a polarizing plate with retardation layer having a configuration of protective layer/adhesive/polarizing element/adhesive/W layer/adhesive/Q layer was obtained. The obtained polarizing plate with retardation layer had a thickness of 43 μm. The polarizing plate with the retardation layer is punched out into a rectangle of a specific size corresponding to a bendable image display device having a bending axis in the short-side direction. Here, punching is performed so that the absorption axis of the polarizing element becomes 30° with respect to the bending axis. The obtained polarizing plate with retardation layer was used for the evaluation of the above (3) and (4). The results are shown in Table 1.

[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 the angle between the absorption axis and the bending axis of the polarizing element was punched into the angle shown in Table 1. The obtained polarizing plate with retardation layer was used for the same evaluation as Example 1-1. The results are shown in Table 1.

[化3]

[Example 2-1] In the same manner as in Example 1-1, a polarizing plate having a protective layer/polarizing element configuration was produced. On the other hand, a retardation layer (a single retardation layer that exhibits inverse wavelength dispersion dependence and can function as a λ/4 plate) and another retardation layer (positive C plate) are produced as described below. 55 parts of the compound represented by the formula (II), 25 parts of the compound represented by the formula (III), and 20 parts of the compound represented by the formula (IV) were added to 400 parts of cyclopentanone (CPN), and then heated to 60° C., stir to dissolve, and after confirming dissolution, return to room temperature, and add 3 parts of Irgacure 907 (manufactured by BASF Japan Co., Ltd.), 0.2 parts of MEGAFAC F-554 (manufactured by DIC Co., Ltd.), and 0.1 part of p-methoxyl phenol (MEHQ) was further stirred to obtain a solution. The solution is clear 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 coated on a glass substrate with a thickness of 0.7 mm using a spin coating method, dried at 100° C. for 10 minutes, and then fired at 200° C. for 60 minutes to obtain a coating. membrane. The obtained coating film is subjected to rubbing treatment to form an alignment film. The rubbing treatment was performed using a commercially available rubbing device. The polymerizable composition obtained above was applied to a substrate (substantially an alignment film) by a spin coating method, and dried at 100° C. for 2 minutes. After cooling the obtained coating film to room temperature, a high pressure mercury lamp was used to irradiate ultraviolet rays at an intensity of 30 mW/cm ² for 30 seconds to obtain a liquid crystal alignment cured layer C. The thickness of the liquid crystal alignment cured layer is 3.0 μm, and the in-plane retardation Re(550) is 130 nm. In addition, the Re(450)/Re(550) of the liquid crystal alignment cured layer was 0.851, showing reverse wavelength dispersion characteristics. This liquid crystal alignment cured layer was used as a retardation layer. [hua 2]

[hua 3]

20 parts by weight of the following chemical formula (I) (the numbers 65 and 35 in the formula represent the mole % of the monomer unit, and for convenience are represented in the form of block polymers: the side represented by the weight average molecular weight 5000) A chain liquid crystal polymer, 80 parts by weight of a polymerizable liquid crystal exhibiting a nematic liquid crystal phase (manufactured by BASF: a commodity named Paliocolor LC242), and 5 parts by weight of a photopolymerization initiator (manufactured by Ciba Specialty Chemicals: A product named Irgacure 907) was dissolved in 200 parts by weight of cyclopentanone to prepare a liquid crystal coating liquid. Then, the coating liquid was applied to a base film (nor-alkene-based resin film: a product named "ZEONEX" by Zeon Corporation) using a bar coater, and then heated at 80°C. The liquid crystal was aligned by drying for 4 minutes. The liquid crystal layer was irradiated with ultraviolet rays to harden the liquid crystal layer, thereby forming a liquid crystal alignment cured layer (positive C plate, thickness 3 μm) on the substrate to become another retardation layer. Re(590) of this layer is 0 nm, Rth(590) is -100 nm, showing the refractive index characteristic of nz>nx=ny. [hua 4]

The liquid crystal alignment cured layer C was transferred to the surface of the polarizing element of the polarizing plate obtained above through the adhesive layer (thickness 5 μm), and then the positive C plate was transferred to the surface of the liquid crystal alignment cured layer C. In this way, a polarizing plate with retardation layer having a configuration of protective layer/adhesive/polarizing element/adhesive layer/retardation layer/adhesive/positive C plate is obtained. The obtained polarizing plate with retardation layer had a thickness of 49 μm. The polarizing plate with the retardation layer is punched out into a rectangle of a specific size corresponding to a bendable image display device having a bending axis in the short-side direction. Here, punching is performed so that the absorption axis of the polarizing element becomes 30° with respect to the bending axis. The obtained polarizing plate with retardation layer was used for the same evaluation as Example 1-1. The results are shown in Table 1.

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

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

[Example 3-2] to [Example 3-5] and [Comparative Example 3-1] to [Comparative Example 3-2] A polarizing plate with a retardation layer was obtained in the same manner as in Example 3-1, except that the angle between the absorption axis and the bending axis of the polarizing element was punched into the angle shown in Table 1. The obtained polarizing plate with retardation layer was used for the same evaluation as Example 1-1. The results are shown in Table 1.

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

[Example 4-2] to [Example 4-5] and [Comparative Example 4-1] to [Comparative Example 4-2] A polarizing plate with a retardation layer was obtained in the same manner as in Example 4-1, except that the angle between the absorption axis and the bending axis of the polarizing element was punched to the angle shown in Table 1. The obtained polarizing plate with retardation layer was used for the same evaluation as Example 1-1. The results are shown in Table 1.

[Comparative Example 5-1] A retardation layer (a single retardation layer that exhibits reverse wavelength dispersion dependence and can function as a λ/4 plate) was produced as follows. The polymerization was carried out using a batch polymerization apparatus consisting of two vertical stirring reactors equipped with stirring blades and a reflux condenser. 30.31 parts by mass (0.047 mol) of bis[9-(2-phenoxycarbonylethyl)perpen-9-yl]methane (BPFM) synthesized by the method described in Japanese Patent Laid-Open No. 2015-25111 was added , 39.94 parts by mass (0.273 mol) of isosorbide (ISB, manufactured by Roquette Freres), 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 Co., Ltd.), and 7.88×10 ⁻⁴ parts by mass (4.47×10 ⁻⁶ mol) of calcium acetate monohydrate as a catalyst. After the inside of the reactor was replaced with nitrogen under reduced pressure, it was heated with a heat medium, and stirring was started when the internal temperature reached 100°C. 40 minutes after the start of the temperature increase, the internal temperature was brought to 220°C, and the pressure was reduced while maintaining the temperature. After reaching 220°C, the pressure was reduced to 13.3 kPa over 90 minutes. The phenol vapor by-produced with the polymerization reaction was led to a reflux condenser at 110°C, so that a certain amount of monomer components contained in the phenol vapor was returned to the reactor, and the uncondensed phenol vapor was led to a condenser of 45°C be recycled. Nitrogen gas was introduced into the first reactor, and the pressure was temporarily restored to atmospheric pressure, and then the oligomerized reaction liquid in the first reactor was transferred to the second reactor. Then, the temperature increase and pressure reduction in the second reactor were started, the internal temperature was changed to 240° C. in 40 minutes, and the pressure was changed to 20 kPa. Then, the pressure is further reduced, and polymerization is performed until a specific stirring power is obtained. When a certain power is reached, nitrogen gas is introduced into the reactor for recompression, the resulting polyester carbonate is extruded into water, and the strands are cut to obtain pellets. The ratio of the structural unit derived from each monomer of this resin is BPFM/ISB/SPG/DPC=21.5/39.4/30.0/9.1 mass %. The obtained pellets were vacuum-dried at 100°C for more than 6 hours, and then used a single-screw extruder (screw diameter 25 mm manufactured by ISUZU Chemical Machinery Co., Ltd., set temperature of cylinder: 250°C), T-die ( Width 300 mm, setting temperature: 220°C), cooling roll (setting temperature: 120-130°C), and film-making device of a coiler, to produce a long unstretched film with a length of 3 m, a width of 200 mm, and a thickness of 100 μm. The stretching temperature was set to Tg (139° C.), and the long unstretched film was stretched to obtain a retardation film with a thickness of 37 μm. The obtained retardation film exhibited a refractive index characteristic of nx>ny=nz, Re(550) was 145 nm, and Re(450)/Re(550) was 0.85.

Using the retardation film obtained above as the retardation layer, instead of the adhesive layer, the retardation film was attached to the polarizing element through the adhesive layer (thickness 5 μm), and the positive film used in Example 2-1 was applied. Except that the C plate was transferred to the surface of the retardation layer, it was carried out in the same manner as in Example 1-1 to obtain a protective layer/adhesive/polarizing element/adhesive layer/retardation layer (retardation film)/adhesive/ Polarizing plate with retardation layer composed of positive C plate. The obtained polarizing plate with retardation layer had a thickness of 89 μm. The polarizing plate with the retardation layer is punched out into a rectangle of a specific size corresponding to a bendable image display device having a bending axis in the short-side direction. Here, punching is performed so that the absorption axis of the polarizing element becomes 0° with respect to the bending axis. The obtained polarizing plate with retardation layer was used for the same evaluation as Example 1-1. The results are shown in Table 1.

[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 the angle between the absorption axis and the bending axis of the polarizing element was punched into the angle shown in Table 1. The obtained polarizing plate with retardation layer was used for the same evaluation as Example 1-1. The results are shown in Table 1.

[Comparative Example 6-1] A polarizing plate with a retardation layer was obtained in the same manner as in Example 1-1, except that the HC-COP film was used as the protective layer instead of the HC-TAC film. The elastic modulus of the protective film is 1988 MPa. In addition, the obtained polarizing plate with retardation layer had a thickness of 84 μm. The polarizing plate with the retardation layer is punched out into a rectangle of a specific size corresponding to a bendable image display device having a bending axis in the short-side direction. Here, punching is performed so that the absorption axis of the polarizing element becomes 30° with respect to the bending axis. The obtained polarizing plate with retardation layer was used for the same evaluation as Example 1-1. The results are shown in Table 1.

[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 the angle between the absorption axis and the bending axis of the polarizing element was punched into the angle shown in Table 1. The obtained polarizing plate with retardation layer was used for the same evaluation as Example 1-1. The results are shown in Table 1.

[Comparative Example 7-1] A polarizing plate was produced in the following manner. A polyvinyl alcohol-based resin film having an average degree of polymerization of 2,400, a degree of saponification 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 to swell, while extending to 2.4 times in the conveying direction (swelling step), and then, at 30°C In a dyeing bath (aqueous solution with an iodine concentration of 0.03% by weight and a potassium iodide concentration of 0.3% by weight), it was immersed in a dyeing bath so that the monomer transmittance after final stretching became a desired value to dye it, and at the same time, the original polyvinyl alcohol film ( The polyvinyl alcohol film that is not stretched at all in the conveying direction) is stretched 3.7 times in the conveying direction based on the reference (dyeing step). The immersion time at this time was about 60 seconds. Next, the dyed polyvinyl alcohol film was immersed in a cross-linking bath at 40° C. (aqueous solution with a boric acid concentration of 3.0 wt % and a potassium iodide concentration of 3.0 wt %), and at the same time, the original polyvinyl alcohol film was used as a reference along the conveying direction. Extension to 4.2-fold (cross-linking step). Further, the obtained polyvinyl alcohol film was immersed in a stretching bath (aqueous solution with a boric acid concentration of 4.0 wt % and a potassium iodide concentration of 5.0 wt %) at 64° C. for 50 seconds, and the original polyvinyl alcohol film was used as a reference in the conveying direction. After stretching to 6.0 times (stretching step), it was immersed for 5 seconds in a cleaning bath (aqueous solution with a potassium iodide concentration of 3.0 wt %) at 20°C (cleaning step). The washed polyvinyl alcohol film was dried at 30° C. for 2 minutes to prepare a polarizing element (thickness: 12 μm). A HC-TAC film was attached to one side of the obtained polarizing element in the same manner as in Example 1-1, and a TAC film having a thickness of 25 μm was attached to the other side. In this way, a polarizing plate having a configuration of the visible-side protective layer (HC-TAC film)/polarizing element/inside protective layer (TAC film) was produced. The elastic modulus of the visible-side protective layer was 3872 MPa as in Example 1-1.

Except having used the polarizing plate obtained above, it carried out similarly to Comparative Example 5-1 to obtain the film having protective layer/adhesive/polarizing element/adhesive/protective layer/adhesive layer/retardation layer (retardation film) A polarizing plate with retardation layer composed of /adhesive/positive C plate. The obtained polarizing plate with retardation layer had a thickness of 116 μm. The polarizing plate with the retardation layer is punched out into a rectangle of a specific size corresponding to a bendable image display device having a bending axis in the short-side direction. Here, punching is performed so that the absorption axis of the polarizing element becomes 0° with respect to the bending axis. The obtained polarizing plate with retardation layer was used for the same evaluation as Example 1-1. The results are shown in Table 1.

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

[Comparative Example 8-1] The single-sided bonding brightness enhancement film of the polarizing element produced in Comparative Example 7-1 (amorphous isophthalic acid copolymerization polyethylene terephthalate with a water absorption rate of 0.75% and a Tg of 75°C) (IPA copolymerized PET) film (thickness: 30 μm)) to produce a polarizing plate with a brightness enhancing film/polarizing element. Regarding the following procedure, a polarizing plate with retardation layer having a configuration of protective layer (brightness enhancement film)/adhesive/polarizing element/adhesive/W layer/adhesive/Q layer was obtained in the same manner as in Example 1-1 . The elastic modulus of the protective layer is 5005 MPa. In addition, the obtained polarizing plate with retardation layer had a thickness of 48 μm. The polarizing plate with the retardation layer is punched out into a rectangle of a specific size corresponding to a bendable image display device having a bending axis in the short-side direction. Here, punching is performed so that the absorption axis of the polarizing element becomes 0° with respect to the bending axis. The obtained polarizing plate with retardation layer was used for the same evaluation as Example 1-1. The results are shown in Table 1.

[Comparative Example 8-2] to [Comparative Example 8-7] A polarizing plate with a retardation layer was obtained in the same manner as in Comparative Example 8-1, except that the angle between the absorption axis and the bending axis of the polarizing element was punched into the angle shown in Table 1. The obtained polarizing plate with retardation layer was used for the same evaluation as Example 1-1. The results are shown in Table 1.

[Table 1] Total thickness (μm) Elastic modulus of protective layer (MPa) Angle between bending axis and absorption axis (°) bendability Visibility of polarized sunglasses Comparative Example 1-1 43 3872 0 ○ × Example 1-1 30 ○ ○ Example 1-2 40 ○ ○ Examples 1-3 45 ○ ○ Examples 1-4 50 ○ ○ Examples 1-5 60 ○ ○ Comparative Example 1-2 90 ○ × Comparative Example 2-1 49 3872 0 ○ × Example 2-1 30 ○ ○ Example 2-2 40 ○ ○ Example 2-3 45 ○ ○ Example 2-4 50 ○ ○ Example 2-5 60 ○ ○ Comparative Example 2-2 90 ○ × Comparative Example 3-1 31 2881 0 ○ × Example 3-1 30 ○ ○ Example 3-2 40 ○ ○ Example 3-3 45 ○ ○ Example 3-4 50 ○ ○ Example 3-5 60 ○ ○ Comparative Example 3-2 90 ○ × Comparative Example 4-1 51 3066 0 × × Example 4-1 30 ○ ○ Example 4-2 40 ○ ○ Example 4-3 45 ○ ○ Example 4-4 50 ○ ○ Example 4-5 60 ○ ○ Comparative Example 4-2 90 ○ × Comparative Example 5-1 89 3872 0 × × Comparative Example 5-2 30 × ○ Comparative Example 5-3 40 × ○ Comparative Example 5-4 45 × ○ Comparative Example 5-5 50 × ○ Comparative Example 5-6 60 × ○ Comparative Example 5-7 90 × × Comparative Example 6-1 84 1988 0 × × Comparative Example 6-2 30 × ○ Comparative Example 6-3 40 × ○ Comparative Example 6-4 45 × ○ Comparative Example 6-5 50 × ○ Comparative Example 6-6 60 ○ ○ Comparative Example 6-7 90 ○ × Comparative Example 7-1 116 3872 0 × × Comparative Example 7-2 30 × ○ Comparative Example 7-3 40 × ○ Comparative Example 7-4 45 × ○ Comparative Example 7-5 50 × ○ Comparative Example 7-6 60 × ○ Comparative Example 7-7 90 × × Comparative Example 8-1 48 5005 0 × × Comparative Example 8-2 30 × ○ Comparative Example 8-3 40 × ○ Comparative Example 8-4 45 × ○ Comparative Example 8-5 50 × ○ Comparative Example 8-6 60 × ○ Comparative Example 8-7 90 × ×

[Evaluation] As is clear from Table 1, according to the examples of the present invention, a polarizing plate with a retardation layer excellent in both flexibility and visibility through polarized sunglasses can be obtained. [Industrial Availability]

The polarizing plate with retardation layer of the present invention can be suitably used in an image display device, which can be bent and can be visually recognized through polarized sunglasses.

10: Polarizer 11: Polarizing element 12,13: Protective layer 20: retardation layer 21: H floor 22: Q layer 100: polarizer with retardation layer 102: Polarizing plate with retardation layer A: Absorption axis F: Bending shaft

FIG. 1 is a schematic perspective view showing a curved 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. 2 is a schematic plan view of a polarizing plate with a retardation layer according to an embodiment of the present invention. 3 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to an embodiment of the present invention. 4 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to another embodiment of the present invention.

A: Absorption axis

F: Bending shaft

Claims (12)

A polarizing plate with a retardation layer, which is used in a bendable image display device, and has: A polarizing plate, which comprises a polarizing element and a protective layer on at least one side of the polarizing element; and a retardation layer, which is arranged on the opposite side of the polarizing plate to the visible side, and has a circularly polarized light function or an elliptically polarized light function; and The total thickness of the polarizing plate with retardation layer is below 80 μm, The angle formed by the bending axis of the image display device and the absorption axis of the polarizing element is 30° to 60°, The elastic modulus of the protective layer is below 5000 MPa. As claimed in claim 1, the polarizing plate with retardation layer has a total thickness of 60 μm or less. The polarizing plate with retardation layer according to claim 1 or 2, wherein the thickness of the polarizing element is 10 μm or less. The polarizing plate with retardation layer according to any one of claims 1 to 3, wherein the polarizing plate includes a protective layer only on the opposite side of the polarizing element to the retardation layer. The polarizing plate with retardation layer according to claim 4, wherein the elastic modulus of the protective layer is below 4000 MPa. The polarizing plate with retardation layer according to claim 5, wherein the thickness of the protective layer is 45 μm or less. The polarizing plate with retardation layer according to any one of claims 1 to 6, wherein the angle formed by the bending axis and the absorption axis of the polarizing element is 40° to 50°. The polarizing plate with retardation layer according to any one of claims 1 to 7, wherein the retardation layer is an alignment cured layer of a liquid crystal compound. The polarizing plate with retardation layer as claimed in claim 8, wherein the retardation layer is a single layer, the Re(550) of the retardation layer is 100 nm to 190 nm, and the Re(450)/Re of the retardation layer (550) is 0.8 or more and less than 1, and the angle formed by the retardation axis of the retardation layer and the absorption axis of the polarizing element is 40° to 50°. The polarizing plate with retardation layer according to claim 9, wherein the polarizing plate with retardation layer further has another retardation layer outside the retardation layer, and the refractive index characteristic of the other retardation layer shows The relationship of nz>nx=ny. The polarizing plate with retardation layer according to claim 8, wherein the retardation 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, and The Re(550) of the alignment cured layer of the first liquid crystal compound is 200 nm to 300 nm, and the angle formed between the retardation axis and the absorption axis of the polarizing element is 10° to 20°, The Re(550) of the alignment cured layer of the second liquid crystal compound is 100 nm to 190 nm, and the angle formed between the retardation axis and the absorption axis of the polarizer is 70° to 80°. An image display device comprising the polarizing plate with a retardation layer according to any one of claims 1 to 11.

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