Polarizing plate and image display device

Abstract

To provide a polarizing plate that can be suitably used for bendable or foldable image display devices, and to provide an image display device.SOLUTION: A polarizing plate according to an embodiment of the present invention comprises a polarizer and a protective layer. The protective layer is provided at least on one surface of the polarizer. The protective layer has a breaking elongation of 20 mm or more.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Image display devices typified 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 including a polarizer and a protective layer is used in an image display device (see, for example, Patent Document 1). In recent years, the uses of image display devices have diversified, and flexibility and foldability of image display devices have been studied. However, when the polarizing plate described in Patent Document 1 is applied to a bendable or foldable image display device, the bendability of the image display device may be insufficient.

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 a main object thereof is to provide a polarizing plate and an image display device that can be suitably applied to a bendable or foldable image display device.

Means for Solving the Problems

[0005] [1] A polarizing plate according to one embodiment of the present invention includes a polarizer and a protective layer. The protective layer is disposed on at least one side of the polarizer. The elongation at break of the protective layer at 25°C is 20 mm or more. [2]An image display device according to another aspect of the present invention includes the polarizing plate described in [1] above and a bendable image display panel in this order. [3]In the image display device described in [2] above, the thickness ratio of the protective layer to the thickness of the image display panel may be 1 to 2.

Effects of the Invention

[0006] According to an embodiment of the present invention, a polarizing plate and an image display device that can be suitably applied to a bendable or foldable image display device can be realized.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0008] Hereinafter, representative embodiments of the present invention will be described, but the present invention is not limited to these embodiments. In addition, for the purpose of making the description clearer, the drawings may schematically show the width, thickness, shape, etc. of each part compared to the embodiments, but this is merely an example and does not limit the interpretation of the present invention.

[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 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 of wavelength 550 nm at 23°C. Re(λ) can be obtained by the formula: Re(λ) = (nx - ny) × d, where d (nm) is the thickness of the layer (film). (3) Retardation in the thickness direction (Rth) "Rth(λ)" is the retardation in the thickness direction measured with light of wavelength λ nm at 23°C. For example, "Rth(550)" is the retardation in the thickness direction measured with light of wavelength 550 nm at 23°C. Rth(λ) can be obtained by the formula: Rth(λ) = (nx - nz) × d, where d (nm) is the thickness of the layer (film).

[0010] A. Overall configuration of the polarizing plate FIG. 1 is a schematic cross-sectional view of a polarizing plate according to one embodiment of the present invention. As shown in FIG. 1, the polarizing plate 100 includes a polarizer 2 and a protective layer 1. The protective layer 1 is disposed on at least one side of the polarizer 2. The protective layer 1 typically has flexibility. The elongation at break of the protective layer 1 at 25°C is 20 mm or more. The elongation at break can be measured, for example, in accordance with JIS K 7127. When the elongation at break of the protective layer is 20 mm or more, sufficient bending durability can be imparted to the polarizing plate including the protective layer and the polarizer. With such a polarizing plate, it can be applied to a bendable (vendable) image display device (e.g., a liquid crystal display device, an organic EL display device, an inorganic EL display device), preferably a foldable (foldable) image display device, more preferably a foldable (foldable) organic EL display device.

[0011] The elongation at break of the protective layer 1 is preferably 25 mm or more, more preferably 30 mm or more. If the elongation at break of the protective layer is above such a lower limit, the bending durability of the polarizing plate can be further improved. On the other hand, the elongation at break of the protective layer 1 is, for example, 150 mm or less, preferably 130 mm or less, more preferably 100 mm or less, and even more preferably 50 mm or less. If the elongation at break of the protective layer is below such an upper limit, deformation of the protective layer can be suppressed.

[0012] The loss tangent tanδ of the protective layer 1 at 85°C and 85% RH (relative humidity) is, for example, 15×10 -2 or less, preferably 13×10 -2 or less, more preferably 10×10 -2 or less, and even more preferably 7.0×10 -2 or less. On the other hand, the lower limit of the loss tangent tanδ of the protective layer 1 at 85°C and 85% RH (relative humidity) is typically 4.0×10 -2 . The loss tangent tanδ of the protective layer 1 at 100°C is, for example, 15×10 -2 or less, preferably 13×10 -2 or less, more preferably 10×10 -2 or less, even more preferably 8.0×10 -2 or less, and particularly preferably 6.0×10 -2 or less. On the other hand, the lower limit of the loss tangent tanδ of the protective layer 1 at 100°C is typically 3.0×10 -2 . Note that the tanδ of the protective layer is observed, for example, by measuring the dynamic viscoelasticity in a tensile mode at a measurement frequency of 5 Hz. If the tanδ of the protective layer is above such a lower limit, stress relaxation occurs during bending, and failure modes such as cracks due to residual stress and the like can be improved. If the tanδ of the protective layer is below such an upper limit, good image display can be maintained without creases even after bending multiple times.

[0013] The thickness of the protective layer 1 is, for example, 10 μm or more, preferably 20 μm or more. If the thickness of the protective layer is equal to or greater than such a lower limit, excellent bending durability can be stably imparted to the polarizing plate. On the other hand, the thickness of the protective layer 1 is, for example, 130 μm or less, preferably 100 μm or less, more preferably 80 μm or less, still more preferably 47 μm or less, particularly preferably 42 μm or less, and most preferably 30 μm or less. If the thickness of the protective layer is equal to or less than such an upper limit, excellent bending durability can be stably imparted to the polarizing plate, and the polarizing plate can be made thinner.

[0014] As shown in FIG. 2, in one embodiment, the protective layer 1 is disposed on both sides of the polarizer 2. Hereinafter, the protective layer 1 disposed on one side of the polarizer 2 may be referred to as the first protective layer 1a, and the protective layer 1 disposed on the other side of the polarizer 2 may be referred to as the second protective layer 1b for distinction.

[0015] Hereinafter, the details of the components of the polarizing plate will be described.

[0016] B. Polarizer As the polarizer 2, any suitable polarizer can be adopted. For example, the resin film forming the polarizer may be composed of a single-layer resin film or may be prepared using a laminate of two or more layers.

[0017] 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 subjected to a dyeing treatment with a dichroic substance such as iodine or a dichroic dye and a stretching treatment, and polyene-based alignment 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.

[0018] Specific examples of the polarizer obtained using the laminate include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer formed by coating on the resin substrate. The polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer formed by coating on the resin substrate can be produced, for example, by applying a PVA-based resin solution to the resin substrate and drying it to form a PVA-based resin layer on the resin substrate to obtain a laminate of the resin substrate and the PVA-based resin layer; stretching and dyeing the laminate to make the PVA-based resin layer a polarizer. In one embodiment of the present invention, 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 one embodiment of the present invention, 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 this embodiment includes subjecting the laminate to an air-assisted stretching treatment, a dyeing treatment, a water stretching treatment, and a drying shrinkage treatment in this order. By introducing the assisted 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 or dissolution when immersed in water in the subsequent dyeing process or stretching process can be prevented, and high 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 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 a water 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 a protective layer for 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 producing a polarizer are described, for example, in JP-A-2012-73580 and Japanese Patent No. 6470455. The entire disclosures of these publications are incorporated herein by reference.

[0019] The above-mentioned iodine staining is performed, for example, by immersing a PVA-based film in an aqueous iodine solution. The draw ratio of the above-mentioned uniaxial drawing is preferably 3 to 7 times. The drawing may be performed after the dyeing treatment, or may be performed while dyeing. Further, dyeing may be performed after drawing. If necessary, the PVA-based film is subjected to a swelling treatment, a crosslinking treatment, a washing treatment, a drying treatment, etc. For example, by immersing the PVA-based film in water and washing it before dyeing, not only can the dirt and anti-blocking agent on the surface of the PVA-based film be washed, but also the PVA-based film can be swollen to prevent uneven dyeing and the like.

[0020] The thickness of the polarizer 2 is, for example, 1 μm to 80 μm, preferably 1 μm to 15 μm, more preferably 1 μm to 12 μm, and still more preferably 3 μm to 12 μm. If the thickness of the polarizer is within such a range, curling during heating can be favorably suppressed, and good appearance durability during heating can be obtained.

[0021] The polarizer 2 typically exhibits absorption dichroism at any wavelength in the wavelength range of 380 nm to 780 nm. The single transmittance of the polarizer 2 is, for example, 41.5% to 46.0%, preferably 43.0% to 46.0%, and more preferably 44.5% to 46.0%. The degree of polarization of the polarizer 2 is preferably 97.0% or more, more preferably 99.0% or more, and still more preferably 99.9% or more.

[0022] C. Protective layer The protective layer 1 is composed of a resin film containing a resin material as a main component. Specific examples of the resin material include cycloolefin (COP) - based such as polynorbornene - based; polyester - based such as polyethylene terephthalate (PET) - based; cellulose - based resins such as triacetyl cellulose (TAC); polycarbonate (PC) - based; (meth)acrylic - based; polyvinyl alcohol - based; polyamide - based; polyimide - based; polyethersulfone - based; polysulfone - based; polystyrene - based; polyolefin - based; acetate - based and other transparent resins. Also, thermosetting resins or ultraviolet - curable resins such as (meth)acrylic - based, urethane - based, (meth)acrylic urethane - based, epoxy - based, silicone - based, etc. are also included. Note that the “(meth)acrylic - based resin” refers to acrylic resin and / or methacrylic resin. In addition, for example, glassy polymers such as siloxane - based polymers are also included. Also, the polymer film described in Japanese Patent Application Laid - Open No. 2001 - 343529 (WO01 / 37007) can also be used. As the material of this film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain can be used. For example, a resin composition having an alternating copolymer composed of isobutene and N - methylmaleimide and an acrylonitrile - styrene copolymer can be mentioned. The polymer film can be, for example, an extruded product of the above resin composition. The materials of the resin film can be used alone or in combination.

[0023] Among such resin materials, preferably, PC - based resins are included.

[0024] The PC - based resin is produced by reacting a dihydroxy compound containing at least a structural unit derived from a dihydroxy compound having a bonding structure represented by the following structural formula (1) and containing at least one dihydroxy compound having a bonding structure - CH2 - O - in the molecule with a carbonic acid diester in the presence of a polymerization catalyst. In other words, the PC - based resin contains a structural unit derived from a dihydroxy compound and a carbonate group derived from a carbonic acid diester. [Chemical formula]

[0025] Here, as the dihydroxy compound having the bonding structure represented by the structural formula (1), any compound having a structure containing two alcoholic hydroxyl groups and a linking group -CH2-O- in the molecule and capable of reacting with a diester carbonate to produce a polycarbonate in the presence of a polymerization catalyst can be used, and a plurality of types can be used in combination.

[0026] In addition, a dihydroxy compound having no bonding structure represented by the above structural formula (1) may be used in combination as the dihydroxy compound used in the PC-based resin. Hereinafter, the dihydroxy compound having the bonding structure represented by the structural formula (1) may be abbreviated as dihydroxy compound (A), and the dihydroxy compound having no bonding structure represented by the structural formula (1) may be abbreviated as dihydroxy compound (B).

[0027] (Dihydroxy compound (A)) The "linking group -CH2-O-" in the dihydroxy compound (A) means a structure that combines with an atom other than a hydrogen atom to form a molecule. In this linking group, as the atom to which at least an oxygen atom can be bonded or the atom to which a carbon atom and an oxygen atom can be simultaneously bonded, a carbon atom is preferable. The number of "linking group -CH2-O-" in the dihydroxy compound (A) is preferably 1 or more, more preferably 2 to 4.

[0028] As the dihydroxy compound (A), specifically, compounds having an aromatic group in the side chain and an ether group bonded to the aromatic group in the main chain, such as 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-methylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-isopropylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-isobutylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-tert-butylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-cyclohexylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-phenylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3,5-dimethylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-tert-butyl-6-methylphenyl)fluorene, 9,9-bis(4-(3-hydroxy-2,2-dimethylpropoxy)phenyl)fluorene;Bis[4-(2-hydroxyethoxy)phenyl]methane, bis[4-(2-hydroxyethoxy)phenyl]diphenylmethane, 1,1-bis[4-(2-hydroxyethoxy)phenyl]ethane, 1,1-bis[4-(2-hydroxyethoxy)phenyl]-1-phenylethane, 2,2-bis[4-(2-hydroxyethoxy)phenyl]propane, 2,2-bis[4-(2-hydroxyethoxy)-3-methylphenyl]propane, 2,2-bis[3,5-dimethyl-4-(2-hydroxyethoxy)phenyl]propane, 1,1-bis[4-(2-hydroxyethoxy)phenyl]-3,3,5-trimethylcyclohexane, 1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, 1,4-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, 1,3-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, 2,2-bis[4-(2-hydroxyethoxy)-3-phenylphenyl]propane, 2,2-bis[(2-hydroxyethoxy)-3-isopropylphenyl]propane, 2,2-bis[3-tert-butyl-4-(2-hydroxyethoxy)phenyl]propane, 2,2-bis[4-(2-hydroxyethoxy)phenyl]butane, 2,2-bis[4-(2-hydroxyethoxy)phenyl]-4-methylpentane, 2,2-bis[4-(2-hydroxyethoxy)phenyl]octane, 1,1-bis[4-(2-hydroxyethoxy)phenyl]decane, 2,2-bis[3-bromo-4-(2-hydroxyethoxy)phenyl]propane, 2,2-bis[3-cyclohexyl-4-(2-hydroxyethoxy)phenyl]propane, such as bis(hydroxyalkoxyaryl)alkanes; 1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, 1,1-bis[3-cyclohexyl-4-(2-hydroxyethoxy)phenyl]cyclohexane, 1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclopentane, such as bis(hydroxyalkoxyaryl)cycloalkanes;Dihydroxyalkoxydiaryl ethers such as exemplified by 4,4'-bis(2-hydroxyethoxy)diphenyl ether and 4,4'-bis(2-hydroxyethoxy)-3,3'-dimethyldiphenyl ether; bis-hydroxyalkoxyaryl sulfides such as exemplified by 4,4'-bis(2-hydroxyethoxyphenyl) sulfide and 4,4'-bis[4-(2-dihydroxyethoxy)-3-methylphenyl] sulfide; bis-hydroxyalkoxyaryl sulfoxides such as exemplified by 4,4'-bis(2-hydroxyethoxyphenyl) sulfoxide and 4,4'-bis[4-(2-dihydroxyethoxy)-3-methylphenyl] sulfoxide; bis-hydroxyalkoxyaryl sulfones such as exemplified by 4,4'-bis(2-hydroxyethoxyphenyl) sulfone and 4,4'-bis[4-(2-dihydroxyethoxy)-3-methylphenyl] sulfone; bis-hydroxyalkoxybenzenes such as exemplified by 1,4-bis-hydroxyethoxybenzene; 1,3-bis[2-[4-(2-hydroxyethoxy)phenyl]propyl]benzene; 1,4-bis[2-[4-(2-hydroxyethoxy)phenyl]propyl]benzene; 4,4'-bis(2-hydroxyethoxy)biphenyl; 1,3-bis[4-(2-hydroxyethoxy)phenyl]-5,7-dimethyladamantane; sugar alcohols such as exemplified by the dihydroxy compound represented by the following formula (2); and compounds having a cyclic ether structure such as exemplified by the spiro glycol represented by the following general formula (3). The dihydroxy compound (A) can be used alone or in combination.;

[0029]

Chemical formula

[0030]

Chemical formula

[0031] Among these dihydroxy compounds (A), preferably, the dihydroxy compound represented by the above formula (2) is mentioned. Examples of the dihydroxy compound represented by the above formula (2) include isosorbide, isomannide, and isoidide, which are in a stereoisomeric relationship. These may be used alone or in combination of two or more. Among the dihydroxy compounds (A), isosorbide obtained by dehydrative condensation of sorbitol, which is abundantly present as a resource and easily available, and is produced from various starches, is most preferable in terms of ease of availability and production, optical properties, and moldability.

[0032] The proportion of the structural unit derived from the dihydroxy compound (A) with respect to the structural units derived from all the dihydroxy compounds contained in the PC-based resin is, for example, 10 mol% or more, preferably 40 mol% or more, more preferably 60 mol% or more. On the other hand, the proportion of the structural unit derived from the dihydroxy compound (A) is, for example, 100 mol% or less, preferably 90 mol% or less, more preferably 80 mol% or less, and even more preferably 70 mol% or less. When the proportion of the dihydroxy compound (A) is within the above range, the elongation at break of the protective layer can be stably adjusted within the above range.

[0033] (Dihydroxy compound (B)) As the dihydroxy compound that becomes the structural unit of the PC-based resin, a dihydroxy compound (B) can be used together with the dihydroxy compound (A). When the dihydroxy compounds (A) and (B) are used in combination, the elongation at break of the protective layer can be more stably adjusted within the above range.

[0034] The dihydroxy compound (B) is typically a dihydroxy compound other than the dihydroxy compound (A). Examples of the dihydroxy compound (B) include alicyclic dihydroxy compounds, aliphatic dihydroxy compounds, oxyalkylene glycols, aromatic dihydroxy compounds, and diols having a cyclic ether structure. The dihydroxy compound (B) can be used alone or in combination. Among the dihydroxy compounds (B), preferably, alicyclic dihydroxy compounds are mentioned.

[0035] Although the alicyclic dihydroxy compound is not particularly limited, compounds containing a 5-membered ring structure or a 6-membered ring structure are preferably mentioned. Further, the 6-membered ring structure may be fixed in a chair form or a boat form by a covalent bond. By the alicyclic dihydroxy compound having a 5-membered ring or 6-membered ring structure, the heat resistance of the resulting PC-based resin can be improved. The number of carbon atoms contained in the alicyclic dihydroxy compound is, for example, 70 or less, preferably 50 or less, more preferably 30 or less.

[0036] Specific examples of the alicyclic dihydroxy compound containing a 5-membered ring structure or a 6-membered ring structure include alicyclic dihydroxy compounds represented by the following general formula (I) or (II). HOCH2-R 1 -CH2OH (I) HO-R 2 -OH (II) (In formula (I) and (II), R 1 and R 2 each represent a cycloalkylene group having 4 to 20 carbon atoms.)

[0037] Cyclohexanedimethanol, which is an alicyclic dihydroxy compound represented by the above general formula (I), in general formula (I), R 1 is represented by the following general formula (Ia) (wherein R 3 represents an alkyl group having 1 to 12 carbon atoms or a hydrogen atom.) and includes various isomers. Specific examples of such compounds include 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol.

[0038]

Chemical formula

[0039] Tricyclodecanedimethanol or pentacyclopentadecanedimethanol, which is an alicyclic dihydroxy compound represented by the above general formula (I), in general formula (I), R1 includes various isomers represented by the following general formula (Ib) (wherein n represents 0 or 1).

[0040]

Chemical formula

[0041] Decalin dimethanol, which is an alicyclic dihydroxy compound represented by the above general formula (I), or tricyclotetradecane dimethanol, in the general formula (I), R 1 includes various isomers represented by the following general formula (Ic) (wherein m represents 0 or 1). Specific examples of such compounds include 2,6-decalin dimethanol, 1,5-decalin dimethanol, and 2,3-decalin dimethanol.

[0042]

Chemical formula

[0043] Norbornane dimethanol, which is an alicyclic dihydroxy compound represented by the above general formula (I), in the general formula (I), R 1 includes various isomers represented by the following general formula (Id). Specific examples of such compounds include 2,3-norbornane dimethanol and 2,5-norbornane dimethanol.

[0044]

Chemical formula

[0045] Adamantane dimethanol, which is an alicyclic dihydroxy compound represented by the general formula (I), in the general formula (I), R 1 includes various isomers represented by the following general formula (Ie). Specific examples of such compounds include 1,3-adamantane dimethanol.

[0046]

Chemical formula

[0047] The cyclohexanediol, which is an alicyclic dihydroxy compound represented by the above general formula (II), in the general formula (II), R 2 represents various isomers represented by the following general formula (IIa) (wherein, R 3 represents an alkyl group having 1 to 12 carbon atoms or a hydrogen atom). Specific examples thereof include 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, and 2-methyl-1,4-cyclohexanediol.

[0048]

Chemical formula

[0049] The tricyclodecanediol or pentacyclopentadecanediol, which is an alicyclic dihydroxy compound represented by the above general formula (II), in the general formula (II), R 2 represents various isomers represented by the following general formula (IIb) (wherein, n represents 0 or 1).

[0050]

Chemical formula

[0051] The decahydroxy compound or tricyclotetradecanediol, which is an alicyclic dihydroxy compound represented by the above general formula (II), in the general formula (II), R 2 represents various isomers represented by the following general formula (IIc) (wherein, m represents 0 or 1). Specific examples thereof include 2,6-decahydroxy compound, 1,5-decahydroxy compound, and 2,3-decahydroxy compound.

[0052]

Chemical formula

[0053] The norbornanediol, which is an alicyclic dihydroxy compound represented by the above general formula (II), in the general formula (II), R 2 includes various isomers represented by the following general formula (IId). Specific examples of such compounds include 2,3-norbornanediol and 2,5-norbornanediol.

[0054]

Chemical formula

[0055] The adamantanediol, which is an alicyclic dihydroxy compound represented by the above general formula (II), in the general formula (II), R 2 includes various isomers represented by the following general formula (IIe). Specific examples of such compounds include 1,3-adamantanediol.

[0056]

Chemical formula

[0057] Among the specific examples of the above-mentioned alicyclic dihydroxy compounds, preferably, cyclohexanedimethanols, tricyclodecanedimethanols, adamantanediols, pentacyclopentadecanedimethanols are included. From the viewpoints of easy availability and easy handling, more preferably, 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, tricyclodecanedimethanol are included. Even more preferably, tricyclodecanedimethanol is included.

[0058] Regarding the structural unit derived from the total dihydroxy compounds contained in the PC-based resin, the proportion of the structural unit derived from the dihydroxy compound (B) is, for example, 0 mol% or more, preferably 10 mol% or more, more preferably 20 mol% or more, still more preferably 30 mol% or more. On the other hand, the proportion of the structural unit derived from the dihydroxy compound (B) is, for example, 90 mol% or less, preferably 60 mol% or less, more preferably 40 mol% or less.

[0059] Details of these PC-based resins are described, for example, in JP-A-2012-31370 (Patent No. 5448264). The description of the patent document is incorporated herein by reference.

[0060] In one embodiment, the PC-based resin contains a structural unit derived from the dihydroxy compound (A) represented by the above formula (2), a structural unit derived from the alicyclic dihydroxy compound (B) represented by the above general formula (I), and a carbonate group connecting them. When the PC-based resin containing these structural units is applied to a resin film, the elongation at break of the protective layer can be more stably adjusted within the above range. In such a PC-based resin, the molar ratio (A:B) of the structural unit derived from the dihydroxy compound (A) represented by the above formula (2) to the structural unit derived from the alicyclic dihydroxy compound (B) represented by the above general formula (I) is, for example, 5:5 to 9:1, preferably 6:4 to 8:2. In such a PC-based resin, the combination of the dihydroxy compound (A) represented by the above formula (2) and the alicyclic dihydroxy compound (B) represented by the above general formula (I) is preferably a combination of isosorbide and tricyclodecane dimethanol.

[0061] In addition to the resin material described above, the protective layer 1 may contain any suitable additive. Examples of the additive include antioxidants, ultraviolet absorbers, light stabilizers, nucleating agents, fillers, pigments, surfactants, and antistatic agents. An optional suitable surface treatment layer may be provided on the surface of the protective layer 1 (the surface opposite to the polarizer 2). Examples of the surface treatment layer include a hard coat layer, an easy adhesion layer, an easy sliding layer, an antiblocking layer, an antistatic layer, an antireflection layer, and an oligomer prevention layer.

[0062] Typically, the protective layer 1 is optically isotropic. As used herein, "optically isotropic" means that the in-plane retardation Re(550) and the retardation in the thickness direction Rth(550) are within the following ranges. The in-plane retardation Re(550) of the protective layer 1 is, for example, 10 nm or less, preferably 5 nm or less, more preferably 3 nm or less. On the other hand, the lower limit of the in-plane retardation Re(550) of the protective layer 1 is typically 0 nm. The retardation in the thickness direction Rth(550) of the protective layer 1 is, for example, -10 nm to +10 nm, preferably -5 nm to +5 nm.

[0063] The total light transmittance of the protective layer 1 is, for example, 80% or more, preferably 85% or more, more preferably 90% or more, and even more preferably 95% or more. The haze value of the protective layer 1 is, for example, 2.0% or less, preferably 1.5% or less, more preferably 1.0% or less, even more preferably 0.7% or less, particularly preferably 0.5% or less, and especially preferably 0.3% or less. The lower limit of the haze value of the protective layer 1 is typically 0.05%. If the total light transmittance and / or the haze value of the protective layer are within such ranges, it is possible to suppress the influence of the protective layer on the optical properties of the polarizer.

[0064] D. Adhesive layer (adhesive layer or bonding agent layer) Although not shown in the figure, the protective layer 1 is typically attached to the polarizer 2 via an adhesive layer (adhesive layer or bonding agent layer).

[0065] Examples of the pressure-sensitive adhesive that constitutes the pressure-sensitive adhesive layer include (meth)acrylic pressure-sensitive adhesives, rubber-based pressure-sensitive adhesives, vinyl alkyl ether-based pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, polyester-based pressure-sensitive adhesives, polyamide-based pressure-sensitive adhesives, urethane-based pressure-sensitive adhesives, fluorine-based pressure-sensitive adhesives, epoxy-based pressure-sensitive adhesives, and polyether-based pressure-sensitive adhesives. The pressure-sensitive adhesive may be used alone or in combination of two or more. Among the pressure-sensitive adhesives, preferably (meth)acrylic pressure-sensitive adhesives are mentioned.

[0066] The thickness of the pressure-sensitive adhesive layer is typically 10 μm to 250 μm, preferably 10 μm to 150 μm. The pressure-sensitive adhesive layer may be a single layer or may have a laminated structure.

[0067] The storage elastic modulus (G') of the pressure-sensitive adhesive layer at 25°C is, for example, 0.01 MPa to 1.00 MPa, preferably 0.05 MPa to 0.50 MPa. If the storage elastic modulus of the pressure-sensitive adhesive layer is within such a range, a polarizing plate having very excellent flexibility can be realized, and as a result, a bendable or foldable image display device (particularly an organic EL display device) can be realized.

[0068] Examples of the adhesive that constitutes the adhesive layer include thermosetting adhesives and active energy ray-curing adhesives, and preferably ultraviolet-curing adhesives. The thickness of the adhesive layer is, for example, 0.4 μm or more and 3.0 μm or less. Among these adhesive layers, preferably the adhesive layer is mentioned.

[0069] E. Image display device In one embodiment, the polarizing plate described in the above items A to D is used by being attached to a bendable image display panel. FIG. 3 is a schematic cross-sectional view of an image display device including the polarizing plate of FIG. 2. The image display device 200 in the illustrated example includes a polarizing plate 100 and a bendable image display panel 5 in this order.

[0070] The polarizing plate 100 is typically disposed on the viewing side with respect to the image display panel 5. In one embodiment, the polarizing plate 100 is attached to the image display panel 5 via an arbitrary suitable adhesive layer (adhesive layer or bonding agent layer). The bendable image display panel 5 typically includes an image display cell. Examples of the bendable image display panel 5 include a liquid crystal display panel, an organic EL panel, and an inorganic EL panel, and preferably, an organic EL panel. The bendable image display panel 5 is described, for example, in Japanese Patent Application Laid-Open No. 2017-126061. The entire disclosures of these publications are incorporated herein by reference. As the adhesive layer for attaching the polarizing plate 100 to the image display panel 5, preferably, the above-described adhesive layer is mentioned, and more preferably, an adhesive layer composed of an acrylic adhesive is mentioned.

[0071] In one embodiment, the thickness of the protective layer 1 included in the polarizing plate 100 is, for example, 0.6 to 2.2, preferably 1.0 to 2.0, with respect to the thickness of the image display panel 5. If the thickness ratio between the protective layer and the image display panel is within such a range, suitable flexibility can be stably imparted to the image display device.

[0072] Such an image display device 200 is bendable or foldable as described above. Note that the image display device may be referred to as an optical display device, the image display panel may be referred to as an optical display panel, and the image display cell may be referred to as an optical display cell.

Examples

[0073] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. The measurement methods for each characteristic are as follows.

[0074] (1) Elongation at break of the protective layer (resin film) In the examples and comparative examples, the resin film serving as the protective layer was cut into a dumbbell shape (width 10 mm, length 100 mm) to obtain test samples. Next, using an Autograph AGS-50D type (manufactured by Shimadzu Corporation) as a tensile testing machine, a tensile test was conducted on the test samples at a tensile speed of 60 mm / min with a distance of 10 mm between chucks to obtain a stress-strain curve. Also, the stress at the time when the test sample broke was determined as the breaking strength, and the strain (elongation rate) at the time when the test sample broke was determined as the elongation at break. The results are shown in Table 1.

[0075] (2) Loss tangent tanδ of the protective layer (resin film) The loss tangent tanδ of the resin films used in the examples and comparative examples was measured under the following conditions using a dynamic viscoelasticity measuring device (manufactured by IT Measurement & Control Co., Ltd.). The results are shown in Table 1. <Measurement conditions> Measurement temperature: 85°C or 100°C Measurement humidity: 85 RH% (relative humidity) *85℃の場合のみ Mode: Tension Frequency: 5 Hz Sample width: 5 mm Distance between chucks: 20 mm

[0076] (3) Flexibility of the organic EL display device The polarizing plates obtained in the examples and comparative examples were used as dummies for a flexible organic EL panel, and a transparent polyimide film (manufactured by KOLON, thickness 25 μm) was used and attached with an acrylic-based adhesive (thickness 15 μm). The thickness ratio of the protective layer to the thickness of the organic EL panel is shown in Table 1. Next, the obtained evaluation samples were cut into a strip shape of 100 mm × 20 mm with the direction of the absorption axis of the polarizer as the long side. The cut samples were set in a non-load U-shaped expansion and contraction testing machine (manufactured by Yuasa System Devices Co., Ltd., "Small desktop durability tester DLMD111LHA" and "U-shaped expansion and contraction test jig") with the polarizer side on the inner side of the bend, and a bending test was conducted under the following conditions. Environmental conditions: 25°C, 55% RH Test speed: 60 rpm Bending radius: R3 Number of bending cycles: 100,000 times Subsequently, the flexibility of the organic EL display device was evaluated according to the following criteria. The results are shown in Table 1. 〇: No crack in the polarizing plate. ×: Crack in the polarizing plate.

[0077] <<Preparation Example 1: PC-based resin film>> To 81.98 parts by mass of isosorbide (ISB), 47.19 parts by mass of tricyclodecane dimethanol (TCDDM), 175.1 parts by mass of diphenyl carbonate (DPC), and 0.979 parts by mass of a 0.2 mass% aqueous solution of cesium carbonate as a catalyst were charged into a reaction vessel. Under a nitrogen atmosphere, as the first stage of the reaction, the temperature of the heating bath was heated to 150 °C, and the raw materials were dissolved (about 15 minutes) while stirring as necessary. Next, the pressure was changed from normal pressure to 13.3 kPa, and while raising the temperature of the heating bath to 190 °C over 1 hour, the generated phenol was extracted out of the reaction vessel. After holding the entire reaction vessel at 190 °C for 15 minutes, as the second stage of the reaction, the pressure inside the reaction vessel was set to 6.67 kPa, the temperature of the heating bath was raised to 230 °C in 15 minutes, and the generated phenol was extracted out of the reaction vessel. Since the stirring torque of the stirrer increased, the temperature was raised to 250 °C in 8 minutes, and in order to further remove the generated phenol, the pressure inside the reaction vessel was made to reach 0.200 kPa or less. After reaching a predetermined stirring torque, the reaction was terminated, and the generated reaction product was extruded into water to obtain pellets of the PC-based resin. After vacuum-drying the obtained PC-based resin at 100 °C for 12 hours, a film-forming apparatus equipped with a single-screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder set temperature: 250 °C), a T-die (width 1700 mm, set temperature: 250 °C), a casting roll (set temperature: 60 °C), and a winder was used to produce a PC-based resin film with a thickness of 25 μm. The in-plane retardation Re(550) of the PC-based resin film was 3.0 nm.

[0078] <<Preparation Example 2: PC-based resin film>> A PC-based resin film was produced in the same manner as in Preparation Example 1, except that the thickness was changed to 60 μm.

[0079] [Example 1] As the thermoplastic resin substrate, an amorphous isophthal copolymer polyethylene 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 mass of potassium iodide was added to 100 parts by mass of a PVA-based resin in which polyvinyl alcohol (degree of polymerization 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosefimer") were mixed at 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 insolubilizing bath at a liquid temperature of 40°C (an aqueous boric acid solution obtained by blending 4 parts by mass of boric acid with respect to 100 parts by mass of water) for 30 seconds (insolubilizing treatment). Next, the laminate was immersed in a dyeing bath at a liquid temperature of 30°C (an aqueous iodine solution obtained by blending iodine and potassium iodide at a weight ratio of 1:7 with respect to 100 parts by mass of water) for 60 seconds while adjusting the concentration so that the single transmittance (Ts) of the finally obtained polarizer becomes a desired 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 blending 3 parts by mass of potassium iodide and 5 parts by mass of boric acid with respect to 100 parts by mass of water) for 30 seconds (crosslinking treatment). Thereafter, while immersing the laminate in an aqueous boric acid solution at a liquid temperature of 70°C (boric acid concentration 4 wt%, potassium iodide concentration 5 wt%), uniaxial stretching was performed in the longitudinal direction (longitudinal direction) between rolls with different peripheral speeds so that the total stretching ratio becomes 5.5 times (stretching treatment in water). Thereafter, the laminate was immersed in a washing bath at a liquid temperature of 20°C (an aqueous solution obtained by blending 4 parts by mass of potassium iodide with respect to 100 parts by mass of water) (washing 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 laminate having a resin substrate / polarizer structure was obtained. The polarizer surface of the obtained laminate (the surface opposite to the resin substrate) and the PC-based resin film (the first protective layer) obtained in Preparation Example 1 were bonded together using an adhesive (specifically, an active energy ray-curable adhesive), and ultraviolet rays were irradiated to cure the adhesive. Next, the resin substrate was peeled off, and the peeled surface of the resin substrate in the polarizer and the PC-based resin film (the second protective layer) obtained in Preparation Example 1 were bonded together using an adhesive (specifically, an active energy ray-curable adhesive), and ultraviolet rays were irradiated to cure the adhesive. Thus, a polarizing plate having a structure of the first protective layer / polarizer / second protective layer was obtained.

[0080] [Example 2] A polarizing plate was obtained in the same manner as in Example 1, except that the PC-based resin film of Preparation Example 1 was changed to a PET film with a thickness of 40 μm (manufactured by Toray Industries, Inc., product number "50U48").

[0081] [Comparative Example 1] A polarizing plate was obtained in the same manner as in Example 1, except that the PC-based resin film of Preparation Example 1 was changed to a COP-based resin film with a thickness of 50 μm (manufactured by Nippon Zeon Co., Ltd., product number ZF16).

[0082] [Comparative Example 2] A polarizing plate was obtained in the same manner as in Example 1, except that the PC-based resin film of Preparation Example 1 was changed to an acrylic resin film with a thickness of 25 μm (manufactured by Kaneka Corporation, product name "HTX-Z").

[0083] [Comparative Example 3] A polarizing plate was obtained in the same manner as in Example 1, except that the PC-based resin film of Preparation Example 1 was changed to the PC-based resin film of Preparation Example 2.

[0084] [Table 1]

[0085] [Evaluation] As is clear from Table 1, when the elongation at break of the protective layer is 20 mm or more, it can be seen that by applying a polarizing plate having the protective layer to an organic EL display device, excellent flexibility can be imparted to the organic EL display device.

Industrial Applicability

[0086] The polarizing plate of the present invention can be applied to an image display device, and in particular, can be suitably used for a flexible or foldable organic EL display device.

Explanation of Signs

[0087] 1 Protective layer 2 Polarizer 100 Polarizing plate 200 Image display device

Claims

Claim 1 A polarizer and a protective layer disposed on at least one side of the polarizer, wherein the elongation at break of the protective layer at 25°C is 20 mm or more, a polarizing plate.

Images