Polarizing plate and image display device

Abstract

Provided is a polarizing plate in which the decrease in transmittance in a high-temperature environment is suppressed. A polarizing plate has a polarizing element in which a dichroic dye is adsorbed and oriented in a polyvinyl alcohol-based resin layer, a first transparent protective film laminated on one face of the polarizing element, and a second transparent protective film laminated on the other face of the polarizing element, the polarizing element and the transparent protective films being bonded with a first adhesive layer formed from a first adhesive containing a first compound, the polarizing element and the second transparent protective film being bonded with a second adhesive layer formed from a second adhesive containing a second compound, the first compound being at least one selected from the group consisting of urea, a urea derivative, thiourea, and a thiourea derivative, and the second compound being a compound having a nitroxyl radical or a nitroxide radical.

Description

Technical Field

[0001] This invention relates to polarizing plates and image display devices. Background Technology

[0002] Liquid crystal displays (LCDs) are not only used in LCD televisions, but also widely used in personal computers, mobile devices such as mobile phones, and automotive applications such as navigation systems. Typically, an LCD has a liquid crystal panel formed by bonding polarizing plates to both sides of liquid crystal cells with adhesive. The display is achieved by controlling the light from the backlight using the liquid crystal panel. In recent years, organic EL displays have also been widely used, similarly to LCDs, in televisions, mobile devices such as mobile phones, and automotive applications such as navigation systems. In organic EL displays, to suppress the reflection of external light from the metal electrode (cathode) that results in a mirror-like appearance, a circular polarizing plate (a laminate containing polarizing elements and a λ / 4 plate) is sometimes placed on the viewing side surface of the image display panel.

[0003] The use of polarizing plates in automotive image display devices, such as liquid crystal displays and organic EL displays, as described above, is increasing. Compared to applications in mobile devices like televisions and mobile phones, polarizing plates used in automotive image display devices are frequently exposed to high temperatures, thus requiring less change in properties at high temperatures (high-temperature durability).

[0004] On the other hand, to prevent damage to the image display panel from impacts from external surfaces, there is an increasing trend of constructing a front panel (also known as a "window layer") on the viewing side relative to the image display panel, such as a transparent resin plate or glass plate. In image display devices equipped with touch panels, a configuration is widely adopted where a touch panel is positioned on the viewing side relative to the image display panel, and a front panel is then positioned on the viewing side relative to the touch panel.

[0005] In this configuration, if an air layer exists between the image display panel and transparent components such as the front panel and touch panel, glare from reflected light at the air layer interface will occur, leading to a decrease in image visibility. Therefore, there is a growing trend towards a configuration (hereinafter sometimes referred to as an "interlayer filling configuration") where the space between the polarizer disposed on the viewing side surface of the image display panel and the transparent component is filled with a layer other than the air layer, typically a solid layer (hereinafter sometimes referred to as an "interlayer filler"). The interlayer filler is preferably a material with a refractive index close to that of the polarizer or the transparent component. As the interlayer filler, adhesives and UV-curable adhesives (see, for example, Patent Document 1) are used to suppress the decrease in visibility caused by reflection at the interface and to bond and fix the components together.

[0006] The use of interlayer filling structures in mobile devices such as cell phones, which are frequently used outdoors, is expanding. In addition, due to the increasing demand for visibility in recent years, research is underway on the use of interlayer filling structures in automotive applications such as navigation devices, in which a front transparent panel is placed on the surface of the image display panel and the space between the panel and the front transparent panel is filled with an adhesive layer or the like.

[0007] However, according to the report, with this configuration, the transmittance of the polarizing plate decreases significantly at high temperatures. Patent Document 2 proposes a solution to this problem by setting the water content per unit area of ​​the polarizing plate to a predetermined amount or less, and setting the saturated water absorption of the transparent protective film adjacent to the polarizing element to a predetermined amount or less, thereby suppressing the decrease in transmittance.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 11-174417

[0011] Patent Document 2: Japanese Patent Application Publication No. 2014-102353 Summary of the Invention

[0012] The problem that the invention aims to solve

[0013] However, even with this type of polarizing plate, the effect of suppressing the reduction in durability under high-temperature environments is not sufficient. The object of this invention is to provide a novel polarizing plate that can suppress the reduction in transmittance even when exposed to high-temperature environments, and an image display device using this polarizing plate.

[0014] Methods for solving problems

[0015] The present invention provides a polarizing plate and an image display device as illustrated below.

[0016] [1] A polarizing plate comprising a polarizing element formed by adsorbing and oriented dichroic pigments on a polyvinyl alcohol-based resin layer, a first transparent protective film laminated on one side of the polarizing element, and a second transparent protective film laminated on the other side of the polarizing element.

[0017] The aforementioned polarizing element and the aforementioned first transparent protective film are bonded together using a first adhesive layer formed from a first adhesive containing a first compound.

[0018] The aforementioned polarizing element and the aforementioned second transparent protective film are bonded together using a second adhesive layer formed from a second adhesive containing the second compound.

[0019] The first compound mentioned above is selected from at least one of urea, urea derivatives, thiourea, and thiourea derivatives.

[0020] The second compound mentioned above is a compound containing nitryl radicals or nitroxy radicals.

[0021] [2] According to the polarizing plate described in [1], the second compound mentioned above is an N-oxygen free radical compound.

[0022] [3] According to the polarizing plate described in [1] or [2], wherein the first compound is at least one urea compound selected from urea derivatives and thiourea derivatives.

[0023] [4] The polarizing plate described in any one of [1] to [3], wherein the first adhesive and the second adhesive comprise a polyvinyl alcohol resin.

[0024] [5] According to the polarizing plate described in [4], in the first adhesive, the content of the first compound is 0.1 parts by mass or more and 400 parts by mass or less relative to 100 parts by mass of the polyvinyl alcohol resin.

[0025] [6] According to the polarizing plate described in [4] or [5], wherein in the second adhesive, the content of the second compound is 0.1 parts by mass or more and 400 parts by mass or less relative to 100 parts by mass of the polyvinyl alcohol resin.

[0026] [7] The polarizing plate described in any one of [1] to [6], wherein the thickness of the first adhesive layer and the second adhesive layer is 0.01 μm or more and 7 μm or less.

[0027] [8] The polarizing plate described in any one of [1] to [7], wherein the polarizing plate is used in an image display device,

[0028] In the above-mentioned image display device, a solid layer is provided in contact with both sides of the polarizing plate.

[0029] [9] An image display device having an image display unit, a first adhesive layer laminated on the observation side surface of the image display unit, and a polarizing plate described in any one of [1] to [8] laminated on the observation side surface of the first adhesive layer.

[0030]

[10] The image display device described in [9] further includes a second adhesive layer laminated on the observation side surface of the polarizing plate and a transparent component laminated on the observation side surface of the second adhesive layer.

[0031]

[11] According to the image display device described in

[10] , the transparent component is a glass plate or a transparent resin plate.

[0032]

[12] According to the image display device described in

[10] , the transparent component is a touch panel.

[0033] Invention Effects

[0034] According to the present invention, a polarizing plate with improved high-temperature durability can be provided, which can suppress the decrease in transmittance even when exposed to high-temperature environments, even when used in image display devices with interlayer filling structures. Furthermore, by using the polarizing plate of the present invention, an image display device that can suppress the decrease in transmittance even when exposed to high-temperature environments can be provided. Detailed Implementation

[0035] The embodiments of the present invention will be described below; however, the present invention is not limited to the following embodiments.

[0036] [Polarizing plate]

[0037] The polarizing plate of this embodiment includes a polarizing element formed by adsorbing and oriented a dichroic pigment onto a layer containing a polyvinyl alcohol-based resin, a first transparent protective film laminated on one side of the polarizing element, and a second transparent protective film laminated on the other side of the polarizing element. The polarizing element and the first transparent protective film are bonded together using a first adhesive layer formed from a first adhesive containing a first compound. The polarizing element and the second transparent protective film are bonded together using a second adhesive layer formed from a second adhesive containing a second compound.

[0038] The first compound is selected from at least one of urea, urea derivatives, thiourea, and thiourea derivatives. The second compound is a compound having a nitryl radical or a nitroxide radical.

[0039] Conventional polarizing plates known for their excellent high-temperature durability include those that, when used alone, can suppress transmittance reduction even after 1000 hours at 95°C. However, even with such polarizing plates, when used in interlayer filling configurations, a significant decrease in transmittance is observed in the central portion of the polarizing plate after 200 hours at 95°C. Furthermore, when the moisture content of the polarizing plate or polarizing element is outside a specific range, a significant decrease in transmittance or polarization degree is observed in the central portion of the polarizing plate. This significant decrease in transmittance of polarizing plates at high temperatures is considered a problem that is particularly likely to occur when image display devices using interlayer filling configurations are exposed to high temperatures. These interlayer filling configurations involve bonding one side of the polarizing plate to the image display unit and the other side to transparent components such as a touch panel or front panel.

[0040] For polarizing plates whose transmittance is significantly reduced due to interlayer filling, this can be attributed to the fact that, during Raman spectroscopy measurements at 1100 cm⁻¹... -1 Nearby (from =CC= key) and 1500cm -1 The presence of peaks near the -C=C- bond results in a polyene structure (-C=C). n - It is speculated that the polyene structure is produced by polyeneification of the polyvinyl alcohol constituting the polarization element through dehydration (Patent Document 2,

[0012] paragraph).

[0041] The polarizing plate of the present invention further improves high-temperature durability. When the polarizing plate of the present invention is incorporated into an image display device composed of interlayer fillers, it can suppress the decrease in transmittance even when exposed to high-temperature environments, such as 105°C. This effect is presumably due to the synergistic effect of the polyvinyl alcohol constituting the polarizing element and the polyvinyl alcohol polyol present in the adhesive layer, which inhibits the polyvinyl alcohol polyol ...

[0042] The polarizing plate of this embodiment may have at least one of the features of (a) and (b) below.

[0043] (a) The moisture content of the polarizing element is above the equilibrium moisture content of 30% relative humidity at 20°C and below the equilibrium moisture content of 80% relative humidity at 20°C.

[0044] (b) The moisture content of the polarizing plate is above the equilibrium moisture content of 30% relative humidity at 20°C and below the equilibrium moisture content of 80% relative humidity at 20°C.

[0045] Even when the polarizing plate of this embodiment has features that further define the features of (a) or (b) above as described below (a1) or (b1), it can still improve high-temperature durability.

[0046] (a1) The moisture content of the polarization element is greater than the equilibrium moisture content at 20°C and relative humidity of 45% or 50%, and is less than the equilibrium moisture content at 20°C and relative humidity of 80% or 70%.

[0047] (b1) The moisture content of the polarizing plate is greater than the equilibrium moisture content at 20°C and relative humidity of 45% or 50%, and is less than the equilibrium moisture content at 20°C and relative humidity of 80% or 70%.

[0048] Even without the step of adjusting the moisture content of the polarizing plate, it is highly likely that it will have the features described in (a) and (b) above. In this embodiment, it may have a step of adjusting the moisture content in a manner that has at least one of the features described in (a) or (b) above, or it may not have a step of adjusting the moisture content.

[0049] <Polarization element>

[0050] As a polarizing element formed by adsorbing and oriented a dichroic dye onto a layer containing a polyvinyl alcohol (hereinafter also referred to as "PVA")-based resin (hereinafter also referred to as "PVA-based resin layer"), a known polarizing element can be used. Examples of polarizing elements include a stretched film obtained by dyeing a PVA-based resin film with a dichroic dye and then uniaxially stretching it; and a stretched layer obtained by using a laminated film having a coating layer formed on a substrate film coated with a coating liquid containing a PVA-based resin, dyeing the coating layer with a dichroic dye, and then uniaxially stretching the laminated film. Stretching can be performed after dyeing with the dichroic dye, or during dyeing, or after stretching.

[0051] PVA-based resins can be obtained by saponifying polyvinyl acetate-based resins. Besides polyvinyl acetate as a homopolymer of vinyl acetate, copolymers of vinyl acetate with other monomers that can be copolymerized can also be mentioned as polyvinyl acetate-based resins. Examples of other monomers that can be copolymerized include unsaturated carboxylic acids, olefins such as ethylene, vinyl ethers, and unsaturated sulfonic acids.

[0052] The degree of saponification of the PVA-based resin is preferably about 85 mol% or more, more preferably about 90 mol% or more, and even more preferably about 99 mol% or more and 100 mol% or less. The degree of polymerization of the PVA-based resin is, for example, 1000 or more and 10000 or less, preferably 1500 or more and 5000 or less. The PVA-based resin can be modified, for example, it can be aldehyde-modified polyvinyl formal, polyvinyl acetal, polyvinyl butyral, etc.

[0053] The thickness of the polarizing element is preferably 3 μm or more and 35 μm or less, more preferably 4 μm or more and 30 μm or less, and even more preferably 5 μm or more and 25 μm or less. By making the thickness of the polarizing element 35 μm or less, the effect of polyolefination of PVA-based resin on the reduction of optical properties under high-temperature conditions can be suppressed. By making the thickness of the polarizing element 3 μm or more, it is easy to manufacture a configuration that achieves the desired optical properties.

[0054] The polarizing element preferably comprises a first compound and a second compound. In this embodiment, since the polarizing element is bonded to the first transparent protective film using a first adhesive layer formed by a first adhesive containing the first compound, and the polarizing element is bonded to the second transparent protective film using a second adhesive layer formed by a second adhesive containing the second compound, it is presumed that a portion of the first compound migrating from the first adhesive layer and a portion of the second compound migrating from the second adhesive layer are contained in the polarizing element. The first compound and the second compound in the polarizing element may include the first compound and the second compound added during the manufacturing process of the polarizing element. By having a first adhesive layer containing the first compound and a second adhesive layer containing the second compound, the transmittance is less likely to decrease even when the polarizing plate is exposed to a high-temperature environment. Furthermore, by having a first adhesive layer containing the first compound and a second adhesive layer containing the second compound, the decrease in polarization degree can be suppressed even when the polarizing plate is exposed to a high-temperature environment. When two polarizers are configured to form orthogonal Nicol prisms, light leakage (hereinafter also referred to as "orthogonal light leakage") is easily generated if the polarization degree of the polarizers decreases. However, according to the present invention, the polarization degree does not easily decrease even when exposed to high temperature environments, and therefore orthogonal light leakage is easily suppressed. This is presumably because the polyolefination of the PVA-based resin is suppressed due to the synergistic effect of the first and second compounds contained in the polarization element.

[0055] As a method for incorporating the first compound and the second compound during the manufacture of polarizing elements, examples include immersing a PVA-based resin layer in a processing solvent containing the first compound and / or the second compound, or spraying, flowing down, or dripping the processing solvent onto the PVA-based resin layer. The method of immersing the PVA-based resin layer in a processing solvent containing both the first compound and the second compound is preferred. Specific examples of the first compound and the second compound include those exemplified as compounds contained in the adhesive described later.

[0056] The process of immersing the PVA-based resin layer in a treatment solvent containing the first and second compounds can be performed simultaneously with the swelling, stretching, dyeing, crosslinking, and cleaning processes described later in the polarization element manufacturing method, or it can be performed separately from these processes. The process of introducing the first and second compounds into the PVA-based resin layer is preferably performed after dyeing the PVA-based resin layer with iodine, and more preferably simultaneously with the crosslinking process after dyeing. According to this method, the color tone variation is small, and the impact on the optical properties of the polarization element can be reduced.

[0057] To make the polarizing element contain both the first compound and the second compound, both can be added during the manufacturing process of the polarizing element and added to the adhesive. Alternatively, the polarizing element can contain only one of the first compound and the second compound during manufacturing, and the adhesive can contain both.

[0058] (Compound 1)

[0059] The first compound is selected from at least one of urea, urea derivatives, thiourea, and thiourea derivatives. The first compound can be used alone or in combination of two or more. The first compound can be either water-soluble or poorly water-soluble; either type of first compound may be used. When using a poorly water-soluble first compound in a water-soluble adhesive, it is preferable to design a dispersion method that prevents haze increase or other issues after the adhesive layer is formed.

[0060] (Urea derivatives)

[0061] Urea derivatives are compounds in which at least one of the four hydrogen atoms of a urea molecule is substituted with a substituent. In this case, there are no particular restrictions on the substituent, but substituents containing carbon, hydrogen, and oxygen atoms are preferred.

[0062] Specific examples of urea derivatives, in terms of monosubstituted ureas, include methylurea, ethylurea, propylurea, butylurea, isobutylurea, N-octadecylurea, 2-hydroxyethylurea, hydroxyurea, acetylurea, allylurea, 2-propynylurea, cyclohexylurea, phenylurea, 3-hydroxyphenylurea, (4-methoxyphenyl)urea, benzylurea, benzoylurea, o-tolylurea, and p-tolylurea.

[0063] Examples of disubstituted ureas include 1,1-dimethylurea, 1,3-dimethylurea, 1,1-diethylurea, 1,3-diethylurea, 1,3-di(hydroxymethyl)urea, 1,3-tert-butylurea, 1,3-dicyclohexylurea, 1,3-diphenylurea, 1,3-di(4-methoxyphenyl)urea, 1-acetyl-3-methylurea, 2-imidazolidineone (ethylidene urea), and tetrahydro-2-pyrimidinone (propylidene urea).

[0064] Examples of tetrasubstituted ureas include tetramethylurea, 1,1,3,3-tetraethylurea, 1,1,3,3-tetrabutylurea, 1,3-dimethoxy-1,3-dimethylurea, 1,3-dimethyl-2-imidazolidineone, and 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone.

[0065] (Thiocarbamide derivatives)

[0066] Thiourea derivatives are compounds in which at least one of the four hydrogen atoms of a thiourea molecule is substituted by a substituent. In this case, there are no particular restrictions on the substituent, but substituents containing carbon, hydrogen, and oxygen atoms are preferred.

[0067] Specific examples of thiourea derivatives, in terms of monosubstituted thioureas, include N-methylthiourea, ethylthiourea, propylthiourea, isopropylthiourea, 1-butylthiourea, cyclohexylthiourea, N-acetylthiourea, N-allylthiourea, (2-methoxyethyl)thiourea, N-phenylthiourea, (4-methoxyphenyl)thiourea, N-(2-methoxyphenyl)thiourea, N-(1-naphthyl)thiourea, (2-pyridyl)thiourea, o-tolylthiourea, and p-tolylthiourea.

[0068] Examples of disubstituted thioureas include 1,1-dimethylthiourea, 1,3-dimethylthiourea, 1,1-diethylthiourea, 1,3-diethylthiourea, 1,3-dibutylthiourea, 1,3-diisopropylthiourea, 1,3-dicyclohexylthiourea, N,N-diphenylthiourea, N,N'-diphenylthiourea, 1,3-di(o-tolyl)thiourea, 1,3-di(p-tolyl)thiourea, 1-benzyl-3-phenylthiourea, 1-methyl-3-phenylthiourea, N-allyl-N'-(2-hydroxyethyl)thiourea, and ethylidene thiourea.

[0069] Examples of trisubstituted thioureas include trimethylthiourea, and examples of tetrasubstituted thioureas include tetramethylthiourea and 1,1,3,3-tetraethylthiourea.

[0070] From the perspective of suppressing the decrease in transmittance under high-temperature environments and minimizing the decrease in polarization degree (in terms of suppressing orthogonal light leakage) when used in image display devices with interlayer filling, the first compound is preferably a urea derivative or a thiourea derivative, more preferably a urea derivative. Among the urea derivatives, monosubstituted urea or disubstituted urea is preferred, more preferably a monosubstituted urea. Disubstituted ureas include 1,1-substituted ureas and 1,3-substituted ureas, however, 1,3-substituted ureas are more preferred.

[0071] (Compound 2)

[0072] The second compound is a compound containing a nitryl radical or a nitroxy radical. From the viewpoint of having a relatively stable free radical at room temperature and in air, an N-oxygen radical compound (with CN(-C)-O as its functional group) can be cited as the second compound. · Compound (O) ·This represents an oxygen radical, bonded to nitrogen (N). Known N-oxygen radical compounds can be used. Examples of N-oxygen radical compounds include compounds with organic groups having the following structures. The aforementioned compounds having nitryl or nitroxy radicals can be used alone or in combination of two or more.

[0073] [Chemistry 1]

[0074]

[0075] (In general formula (1), R) 1 R represents an oxygen radical. 2 To R 5 (Independently representing hydrogen atoms or alkyl groups having 1 to 10 carbon atoms, where n represents 0 or 1.) It should be noted that the left side of the dashed part in general formula (1) represents any organic group. Any organic group includes hydrogen atoms.

[0076] Examples of compounds having the above-mentioned organic groups include compounds with the following general formulas (2) to (5).

[0077] [Chemistry 2]

[0078]

[0079] (In general formula (2), R) 1 To R 5 And n is the same as above, R 6 (This represents a hydrogen atom, or an alkyl, acyl, or aryl group with 1 to 10 carbon atoms; n represents 0 or 1.)

[0080] [Chemistry 3]

[0081]

[0082] (In general formula (3), R) 1 To R 5 And n is the same as above, R 7 and R 8 (Independently representing a hydrogen atom, or an alkyl, acyl, or aryl group having 1 to 10 carbon atoms.)

[0083] [Chemistry 4]

[0084]

[0085] (In general formula (4), R) 1 To R 5 And n is the same as above, R 9 To R 11Independently representing a hydrogen atom, or an alkyl, acyl, amino, alkoxy, hydroxyl, or aryl group having 1 to 10 carbon atoms.

[0086] [Chemistry 5]

[0087]

[0088] (In general formula (5), R) 1 To R 5 And n is the same as above, R 12 (This refers to a hydrogen atom, or an alkyl, amino, alkoxy, hydroxyl, or aryl group having 1 to 10 carbon atoms.)

[0089] In the above general formulas (1) to (5), from the point of view of accessibility, R 2 To R 5 Preferably, it is an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms. Furthermore, in the above general formula (2), from the viewpoint of availability, R... 6 Preferably, it is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, more preferably a hydrogen atom. Furthermore, in the above general formula (3), from the viewpoint of availability, R... 7 and R 8 Preferably, it is an alkyl group that is independently composed of hydrogen atoms or has 1 to 10 carbon atoms, and more preferably, it is composed of hydrogen atoms. Furthermore, in the above general formula (4), from the viewpoint of availability, R... 9 To R 11 Preferably, it is an alkyl group having 1 to 10 hydrogen atoms. Furthermore, from the viewpoint of availability, R in the above general formula (5) is preferred. 12 Preferably, it is hydroxyl, amino, or alkoxy. In the above general formulas (1) to (5), from the viewpoint of availability, n is preferably 1.

[0090] Furthermore, examples of the aforementioned N-oxygen free radical compounds include those described in Japanese Patent Application Publication No. 2003-64022, Japanese Patent Application Publication No. 11-222462, Japanese Patent Application Publication No. 2002-284737, and International Patent Publication No. 2016 / 047655. Among these N-oxygen free radical compounds, 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxygen free radical is preferred.

[0091] In addition, the following compounds can be cited as examples of second compounds.

[0092] [Chemistry 6]

[0093]

[0094] (In general formula (6), R represents a hydrogen atom, or an alkyl, acyl, or aryl group having 1 to 10 carbon atoms.)

[0095] [Chemistry 7]

[0096]

[0097] [Chemistry 8]

[0098]

[0099] Furthermore, from the viewpoint of efficiently capturing free radicals generated during the polyene reaction, the molecular weight of the second compound is preferably 1000 or less, more preferably 500 or less, and even more preferably 300 or less. The lower limit of the molecular weight is not particularly limited; for example, it can be 80.

[0100] (Feature(a))

[0101] In the case of feature (a), the moisture content of the polarizing element is above the equilibrium moisture content of 30% relative humidity at 20°C and below the equilibrium moisture content of 80% relative humidity at 20°C. The moisture content of the polarizing element may also be greater than the equilibrium moisture content of 45% or 50% relative humidity at 20°C and below the equilibrium moisture content of 80% or 70% relative humidity at 20°C. If the moisture content of the polarizing element is less than the equilibrium moisture content of 30% relative humidity at 20°C, the operability of the polarizing element decreases, and it is prone to breakage. If the moisture content of the polarizing element is high enough to exceed the equilibrium moisture content of 45% or 50% relative humidity at 20°C, it is presumed that polyolefination of the PVA-based resin is easily promoted. However, in this embodiment, since an adhesive layer containing both the first compound and the second compound is provided, the polyolefination of the PVA-based resin can be suppressed.

[0102] As a method to confirm whether the moisture content of a polarizing element is within the range of equilibrium moisture content above 30% relative humidity at 20°C and below 80% relative humidity at 20°C, examples include storing the element in an environment adjusted to the aforementioned temperature and relative humidity range, and considering it to have reached equilibrium with the environment if there is no change in mass over a certain period of time; or pre-calculating the equilibrium moisture content of the polarizing element in an environment adjusted to the aforementioned temperature and relative humidity range, and confirming it by comparing the moisture content of the polarizing element with the pre-calculated equilibrium moisture content.

[0103] There are no particular limitations on the method for manufacturing a polarizing element with an equilibrium moisture content of 30% or higher at a temperature of 20°C and a relative humidity of 80% or lower at a temperature of 20°C. However, for example, a method can be given by storing the polarizing element in an environment adjusted to the above temperature and relative humidity range for 10 minutes or more and 3 hours or less; or a method of heat treatment at 30°C or higher and 90°C or lower.

[0104] As another preferred method for manufacturing polarizing elements with the aforementioned moisture content, examples include storing a laminate in which a protective film is deposited on at least one side of the polarizing element, or a polarizing plate made using the polarizing element, in an environment adjusted to the aforementioned temperature and relative humidity range for 10 minutes to 120 hours; or performing a heat treatment at 30°C to 90°C. In manufacturing an image display device using interlayer filling, the front panel can be bonded after storing the image display panel with a polarizing plate deposited on the image display unit in an environment adjusted to the aforementioned temperature and relative humidity range for 10 minutes to 3 hours, or after heating at 30°C to 90°C.

[0105] (Feature (b))

[0106] In the case of feature (b), the moisture content of the polarizing plate is above the equilibrium moisture content of 30% relative humidity at 20°C and below the equilibrium moisture content of 80% relative humidity at 20°C. The moisture content of the polarizing plate may also be greater than the equilibrium moisture content of 45% or 50% relative humidity at 20°C and below the equilibrium moisture content of 80% or 70% relative humidity at 20°C. If the moisture content of the polarizing plate is less than the equilibrium moisture content of 30% relative humidity at 20°C, the operability of the polarizing plate decreases, and it is prone to breakage. If the moisture content of the polarizing plate is high enough to exceed the equilibrium moisture content of 45% or 50% relative humidity at 20°C, it is presumed that polyolefination of the PVA-based resin is easily promoted. However, in this embodiment, since an adhesive layer containing both the first compound and the second compound is provided, the polyolefination of the PVA-based resin can be suppressed.

[0107] As a method to confirm whether the moisture content of the polarizing plate is within the range of equilibrium moisture content above 30% relative humidity at 20°C and below 80% relative humidity at 20°C, one can cite the method of storing the plate in an environment adjusted to the above temperature and relative humidity range, and considering it to have reached equilibrium with the environment if there is no change in mass over a certain period of time; or a method of pre-calculating the equilibrium moisture content of the polarizing plate in an environment adjusted to the above temperature and relative humidity range, and confirming it by comparing the moisture content of the polarizing plate with the pre-calculated equilibrium moisture content.

[0108] There are no particular limitations on the method for manufacturing a polarizing plate with an equilibrium moisture content of 30% or higher at 20°C and 80% or lower at 20°C. However, for example, a method can be given by storing the polarizing plate in an environment adjusted to the above temperature and relative humidity range for 10 minutes or more and 3 hours or less; or a method of heat treatment at 30°C or higher and 90°C or lower.

[0109] When manufacturing an image display device using interlayer filling, the front panel can be attached after the image display panel with the polarizing plate stacked on the image display unit is kept in an environment adjusted to the above-mentioned temperature and relative humidity range for 10 minutes to 3 hours or heated to 30°C to 90°C.

[0110] (Manufacturing method of polarization element)

[0111] There is no particular limitation on the manufacturing method of polarizing elements; however, typical methods include: a method of producing a PVA-based resin film pre-wound into a roll and then stretching, dyeing, cross-linking, etc. (hereinafter referred to as "manufacturing method 1"); and a method including a process of coating a coating liquid containing PVA-based resin onto a substrate film to form a PVA-based resin layer as a coating layer, and stretching the resulting laminate (hereinafter referred to as "manufacturing method 2").

[0112] Manufacturing method 1 can be carried out by a process of uniaxially stretching a PVA-based resin film, dyeing the PVA-based resin film with dichroic pigments such as iodine to adsorb dichroic pigments, treating the PVA-based resin film with adsorbed dichroic pigments with a boric acid aqueous solution, and washing with water after treatment with boric acid aqueous solution.

[0113] The swelling process involves immersing a PVA-based resin film in a swelling bath. Besides removing surface contaminants and adhesives from the PVA-based resin film, the swelling process also helps suppress uneven dyeing by causing the film to swell. The swelling bath typically uses a water-based medium, such as water, distilled water, or pure water. Surfactants, alcohols, etc., can be appropriately added to the swelling bath using conventional methods. From the viewpoint of controlling the potassium content of the polarizing element, potassium iodide can be used in the swelling bath. In this case, the concentration of potassium iodide in the swelling bath is preferably 1.5% by mass or less, more preferably 1.0% by mass or less, and even more preferably 0.5% by mass or less.

[0114] The temperature of the swelling bath is preferably 10°C or higher and 60°C or lower, more preferably 15°C or higher and 45°C or lower, and even more preferably 18°C ​​or higher and 30°C or lower. Regarding the immersion time in the swelling bath, since the degree of swelling of the PVA-based resin film is affected by the temperature of the swelling bath, it cannot be fixed indefinitely; however, it is preferably 5 seconds or higher and 300 seconds or lower, more preferably 10 seconds or higher and 200 seconds or lower, and even more preferably 20 seconds or higher and 100 seconds or lower. The swelling process can be performed only once or multiple times as needed.

[0115] The dyeing process involves immersing a PVA-based resin film in a dyeing bath (iodine solution), which allows dichroic pigments such as iodine to be adsorbed and oriented on the PVA-based resin film. The iodine solution is typically an aqueous solution containing iodine and iodides as a dissolving agent. Examples of iodides include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Among these, potassium iodide is suitable from the viewpoint of controlling the potassium content in the polarization element.

[0116] The concentration of iodine in the staining bath is preferably 0.01% by mass or more and 1% by mass or less, more preferably 0.02% by mass or more and 0.5% by mass or less. The concentration of iodide in the staining bath is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.05% by mass or more and 5% by mass or less, and even more preferably 0.1% by mass or more and 3% by mass or less.

[0117] The temperature of the dyeing bath is preferably 10°C or higher and 50°C or lower, more preferably 15°C or higher and 45°C or lower, and even more preferably 18°C ​​or higher and 30°C or lower. The immersion time in the dyeing bath cannot be fixed because the degree of dyeing of the PVA-based resin film is affected by the temperature of the dyeing bath; however, it is preferably 10 seconds or higher and 300 seconds or lower, more preferably 20 seconds or higher and 240 seconds or lower. The dyeing process can be performed only once or multiple times as needed.

[0118] The crosslinking process involves immersing the dyed PVA-based resin film from the dyeing process in a treatment bath (crosslinking bath) containing a boron compound. The boron compound crosslinks the polyvinyl alcohol-based resin film, allowing iodine or dye molecules to adsorb onto the crosslinked structure. Examples of boron compounds include boric acid, borates, and borax. The crosslinking bath is generally an aqueous solution; however, it can also be a mixture of an organic solvent miscible with water and water. From the viewpoint of controlling the potassium content in the polarizing element, the crosslinking bath preferably contains potassium iodide.

[0119] In the crosslinking bath, the concentration of the boron compound is preferably 1% by mass or more and 15% by mass or less, more preferably 1.5% by mass or more and 10% by mass or less, and even more preferably 2% by mass or more and 5% by mass or less. When potassium iodide is used in the crosslinking bath, the concentration of potassium iodide in the crosslinking bath is preferably 1% by mass or more and 15% by mass or less, more preferably 1.5% by mass or more and 10% by mass or less, and even more preferably 2% by mass or more and 5% by mass or less.

[0120] The temperature of the crosslinking bath is preferably 20°C or higher and 70°C or lower, more preferably 30°C or higher and 60°C or lower. The immersion time in the crosslinking bath cannot be fixed because the degree of crosslinking of the PVA resin film is affected by the temperature of the crosslinking bath; however, it is preferably 5 seconds or higher and 300 seconds or lower, more preferably 10 seconds or higher and 200 seconds or lower. The crosslinking process can be performed only once or multiple times as needed.

[0121] The stretching process is a procedure in which a PVA-based resin film is stretched at least in one direction at a specified ratio. Generally, the PVA-based resin film is uniaxially stretched along the transport direction (length direction). There are no particular restrictions on the stretching method; either wet stretching or dry stretching can be used. The stretching process can be performed once or multiple times as needed. The stretching process can be performed at any stage of the manufacturing of polarizing elements.

[0122] The treatment bath (stretching bath) in the wet stretching process can typically be water or a solvent such as an organic solvent miscible with water and a mixture of water. From the viewpoint of controlling the potassium content in the polarization element, the stretching bath preferably contains potassium iodide. When potassium iodide is used in the stretching bath, the concentration of potassium iodide in the stretching bath is preferably 1% by mass or more and 15% by mass or less, more preferably 2% by mass or more and 10% by mass or less, and even more preferably 3% by mass or more and 6% by mass or less. From the viewpoint of suppressing film breakage during stretching, the treatment bath (stretching bath) may contain a boron compound. When a boron compound is included, the concentration of the boron compound in the stretching bath is preferably 1% by mass or more and 15% by mass or less, more preferably 1.5% by mass or more and 10% by mass or less, and even more preferably 2% by mass or more and 5% by mass or less.

[0123] The temperature of the stretching bath is preferably 25°C or higher and 80°C or lower, more preferably 40°C or higher and 75°C or lower, and even more preferably 50°C or higher and 70°C or lower. The immersion time in the stretching bath cannot be fixed because the degree of stretching of the PVA-based resin film is affected by the temperature of the stretching bath; however, it is preferably 10 seconds or higher and 800 seconds or lower, more preferably 30 seconds or higher and 500 seconds or lower. The stretching treatment in the wet stretching method can be performed together with any one or more of the following processing steps: swelling, dyeing, crosslinking, and cleaning.

[0124] Examples of dry stretching methods include inter-roll stretching, heated roll stretching, and compression stretching. It should be noted that dry stretching can be performed concurrently with the drying process.

[0125] The total stretch ratio (cumulative stretch ratio) applied to the polyvinyl alcohol-based resin film can be appropriately set according to the purpose, preferably 2 times or more and 7 times or less, more preferably 3 times or more and 6.8 times or less, and even more preferably 3.5 times or more and 6.5 times or less.

[0126] The cleaning process involves immersing the polyvinyl alcohol (PVA) resin film in a cleaning bath to remove foreign matter remaining on the surface of the PVA resin film. The cleaning bath typically uses a water-based medium, such as water, distilled water, or pure water. Furthermore, from the viewpoint of controlling the potassium content in the polarization element, potassium iodide is preferably used in the cleaning bath. In this case, the concentration of potassium iodide in the cleaning bath is preferably 1% by mass or more and 10% by mass or less, more preferably 1.5% by mass or more and 4% by mass or less, and even more preferably 1.8% by mass or more and 3.8% by mass or less.

[0127] The temperature of the cleaning bath is preferably 5°C or higher and 50°C or lower, more preferably 10°C or higher and 40°C or lower, and even more preferably 15°C or higher and 30°C or lower. Regarding the immersion time in the cleaning bath, since the degree of cleaning of the PVA resin film is affected by the temperature of the cleaning bath, it cannot be fixed in general; however, it is preferably 1 second or higher and 100 seconds or lower, more preferably 2 seconds or higher and 50 seconds or lower, and even more preferably 3 seconds or higher and 20 seconds or lower. The cleaning process can be performed only once or multiple times as needed.

[0128] The drying process is the process of drying the PVA-based resin film cleaned in the cleaning process to obtain the polarizing element. Drying can be carried out using any appropriate method, such as natural drying, forced air drying, or heat drying.

[0129] Manufacturing method 2 can be performed by a process of coating a coating solution containing PVA-based resin onto a substrate film, uniaxially stretching the resulting laminated film, adsorbing dichroic pigments by dyeing the PVA-based resin layer of the uniaxially stretched laminated film with dichroic pigments to form a polarizing element, treating the film adsorbed with dichroic pigments with a boric acid aqueous solution, and washing with water after the boric acid aqueous solution treatment. The substrate film used to form the polarizing element can be used as a protective layer for the polarizing element. The substrate film can be peeled off from the polarizing element as needed.

[0130] <Transparent Protective Film>

[0131] In this embodiment, the first transparent protective film is attached to one side of the polarizing element via a first adhesive layer, and the second transparent protective film is attached to the other side of the polarizing element via a second adhesive layer. Hereinafter, without being limited to either the first transparent protective film or the second transparent protective film, it will sometimes be simply referred to as "protective film".

[0132] The protective film can simultaneously possess other optical functions and can be formed in a laminated structure with multiple layers. From an optical property point of view, a thin protective film is preferred; however, if it is too thin, its strength decreases and its processability suffers. An appropriate film thickness is 5 μm or more and 100 μm or less, preferably 10 μm or more and 80 μm or less, and more preferably 15 μm or more and 70 μm or less.

[0133] The protective film can be made of cellulose acylated film, film containing polycarbonate resin, film containing cyclic olefin resin such as norbornene, (meth)acrylic polymer film, polyester resin such as polyethylene terephthalate, etc. When the protective film is bonded to both sides of the polarizing element using a water-based adhesive such as PVA adhesive, from the perspective of moisture permeability, it is preferable that at least one side of the protective film is either a cellulose acylated film or a (meth)acrylic polymer film, with a cellulose acylated film being preferred.

[0134] At least one of the protective films can have a phase difference function for purposes such as viewing angle compensation. In this case, the protective film itself can have a phase difference function, or it can have a separate phase difference layer, or a combination of both. The film with the phase difference function can be directly attached to the polarizing element via an adhesive, or it can be a structure in which another protective film attached to the polarizing element is sandwiched between the two films and attached via an adhesive or bonding agent.

[0135] <Adhesive layer>

[0136] An adhesive containing a first compound is used as the first adhesive layer constituting the first adhesive layer for bonding the first transparent protective film to the polarizing element. An adhesive containing a second compound is used as the second adhesive layer constituting the second adhesive layer for bonding the second transparent protective film to the polarizing element. Hereinafter, without limitation on either the first adhesive or the second adhesive, it is sometimes simply referred to as "adhesive". Similarly, without limitation on either the first adhesive layer or the second adhesive layer, it is sometimes simply referred to as "adhesive layer". The adhesive can be a water-based adhesive, a solvent-based adhesive, an active energy radiation-curable adhesive, etc., but a water-based adhesive is preferred, and preferably contains a PVA-based resin. By using the first adhesive containing the first compound and the second adhesive containing the second compound, the decrease in transmittance of the polarizing plate under high-temperature conditions can be suppressed.

[0137] The thickness of the adhesive coating can be set to any value, for example, it can be set in such a way that an adhesive layer with a desired thickness is obtained after curing or heating (drying). The thickness of the adhesive layer composed of the adhesive is preferably 0.01 μm or more and 7 μm or less, more preferably 0.01 μm or more and 5 μm or less, further preferably 0.01 μm or more and 2 μm or less, and most preferably 0.01 μm or more and 1 μm or less.

[0138] The following description of the adhesive is based on a preferred range where the polarizing element is manufactured without containing the first and second compounds. If the polarizing element does contain the first and second compounds, the following values ​​can be adjusted appropriately. Specific examples of the first and second compounds are as described above. During the drying process of forming the adhesive layer when bonding the polarizing element to the protective film, a portion of the first and second compounds can migrate from the adhesive layer to the polarizing element, etc.

[0139] When the first adhesive is an aqueous adhesive containing PVA-based resin, the content of the first compound relative to 100 parts by weight of the PVA-based resin is preferably 0.1 parts by weight or more and 400 parts by weight or less, more preferably 1 part by weight or more and 200 parts by weight or less, and even more preferably 3 parts by weight or more and 100 parts by weight or less. If it is less than 0.1 parts by weight, the suppression effect on polyene formation of the polarizing element under high temperature conditions may be insufficient. On the other hand, if it is greater than 400 parts by weight, urea may precipitate after the polarizing plate is manufactured, resulting in an increase in haze.

[0140] When the second adhesive is an aqueous adhesive containing PVA-based resin, the content of the second compound relative to 100 parts by weight of the PVA-based resin is preferably 0.1 parts by weight or more and 400 parts by weight or less, more preferably 1 part by weight or more and 200 parts by weight or less, and even more preferably 3 parts by weight or more and 100 parts by weight or less. If it is less than 0.1 parts by weight, the suppression effect on polyene formation of the polarization element under high temperature conditions may be insufficient. On the other hand, if it is greater than 400 parts by weight, the second compound may precipitate after the polarization plate is manufactured.

[0141] (Water-based adhesive)

[0142] Any suitable aqueous adhesive can be used as the aqueous adhesive; however, it is preferred to use an aqueous adhesive containing PVA-based resin (PVA-based adhesive). From an adhesiveness perspective, the average degree of polymerization of the PVA-based resin contained in the aqueous adhesive is preferably 100 or more and 5500 or less, more preferably 1000 or more and 4500 or less. From an adhesiveness perspective, the average degree of saponification is preferably 85 mol% or more and 100 mol% or less, more preferably 90 mol% or more and 100 mol% or less.

[0143] As the PVA-based resin contained in the water-based adhesive, a resin containing acetyl groups is preferred because it exhibits excellent adhesion and durability to the protective film. For example, a PVA-based resin containing acetyl groups can be obtained by reacting a PVA-based resin with a diene using any method. The degree of acetyl group modification in the PVA-based resin containing acetyl groups is typically 0.1 mol% or more, preferably 0.1 mol% or more and 20 mol% or less. The resin concentration of the water-based adhesive is preferably 0.1% by mass or more and 15% by mass or less, more preferably 0.5% by mass or more and 10% by mass or less.

[0144] Water-based adhesives can also contain crosslinking agents. Known crosslinking agents can be used. Examples of crosslinking agents include water-soluble epoxy compounds, dialdehydes, and isocyanates.

[0145] When the PVA resin is a PVA resin containing acetyl groups, the crosslinking agent is preferably any one of glyoxal, glyoxylate, or hydroxymethyl melamine, more preferably any one of glyoxal or glyoxylate, and particularly preferably glyoxal.

[0146] Aqueous adhesives may also contain organic solvents. From the perspective of miscibility with water, alcohols are preferred organic solvents, and methanol or ethanol are more preferred among alcohols. The concentration of methanol in the aqueous adhesive is preferably 10% by mass or more and 70% by mass or less, more preferably 15% by mass or more and 60% by mass or less, and even more preferably 20% by mass or more and 60% by mass or less. By maintaining a methanol concentration of 10% by mass or more, it is easier to further suppress the polyene formation of PVA-based resins under high-temperature conditions. Furthermore, by maintaining a methanol content of 70% by mass or less, color deterioration can be suppressed. Some urea derivatives are compounds with low solubility relative to water but sufficient solubility relative to alcohols. In this case, it is also a preferred method to prepare the first adhesive by dissolving the first compound in an alcohol to prepare an alcohol solution of the first compound and then adding the alcohol solution of the first compound to an aqueous PVA solution.

[0147] (Active energy radiation curing adhesive)

[0148] Reactive energy radiation-cured adhesives are adhesives that are cured by irradiation with reactive energy rays such as ultraviolet light. Examples include adhesives containing polymerizable compounds and photopolymerization initiators, adhesives containing photoreactive resins, and adhesive resins containing photoreactive crosslinking agents. Examples of polymerizable compounds include photopolymerizable monomers such as photocurable epoxy monomers, photocurable acrylic monomers, and photocurable urethane monomers, as well as oligomers derived from these monomers. Examples of photopolymerization initiators include compounds containing substances that generate reactive species such as neutral free radicals, anionic free radicals, and cationic free radicals upon irradiation with reactive energy rays such as ultraviolet light.

[0149] <Urea compounds contain a layer>

[0150] The first and second compounds are not limited to being contained in the adhesive layer as described above. From the viewpoint of improving the high-temperature durability of the polarizing plate, they can also be contained in other layers besides the adhesive layer. From the viewpoint of improving the physical strength of the polarizing plate, a laminated curing layer can be used.

[0151] In this embodiment, the cured layer may also contain the first compound and the second compound, and be designated as a urea-based compound containing layer. Normally, this type of cured layer is formed from a curable composition containing an organic solvent; however, Japanese Patent Application Publication No. 2017-075986, paragraphs

[0020] to

[0042] , describes a method for forming this type of cured layer from an aqueous solution of an active energy ray curable polymer composition. This composition may contain water-soluble first and second compounds.

[0152] The urea compound containing the layer preferably comprises at least one first compound, at least one second compound, and an adhesive. Examples of adhesives include polymer adhesives, thermosetting resin adhesives, and active energy radiation-cured resin adhesives; any adhesive may be preferred.

[0153] The thickness of the urea compound containing the layer is preferably 0.1 μm or more and 20 μm or less, more preferably 0.5 μm or more and 15 μm or less, and even more preferably 1 μm or more and 10 μm or less.

[0154] [Manufacturing method of polarizing plate]

[0155] The method for manufacturing a polarizing plate according to this embodiment includes a lamination process. The method for manufacturing a polarizing plate according to this embodiment may also include a moisture content adjustment process. In the moisture content adjustment process, when manufacturing a polarizing plate having feature (a), the moisture content of the polarizing element is adjusted such that it is above the equilibrium moisture content of 30% relative humidity at 20°C and below the equilibrium moisture content of 80% relative humidity at 20°C. The moisture content of the polarizing element can be adjusted according to the aforementioned description of the moisture content of the polarizing element. In the moisture content adjustment process, when manufacturing a polarizing plate having feature (b), the moisture content of the polarizing plate is adjusted such that it is above the equilibrium moisture content of 30% relative humidity at 20°C and below the equilibrium moisture content of 80% relative humidity at 20°C. The moisture content of the polarizing plate can be adjusted according to the aforementioned description of the moisture content of the polarizing plate. In the lamination process, the polarizing element and the transparent protective film are laminated via the aforementioned adhesive layer. In the lamination process, for example, a polarizing element that has not undergone treatment containing the first and second compounds is bonded to a transparent protective film using an adhesive containing the first and second compounds. The order of the moisture content adjustment process and the lamination process is not limited, and the moisture content adjustment process and the lamination process can also be performed in parallel.

[0156] [Composition of an image display device]

[0157] The polarizing plate of this embodiment is used in various image display devices such as liquid crystal display devices and organic EL display devices. In image display devices with an interlayer filling configuration where both sides of the polarizing plate are in contact with a layer other than an air layer, specifically a solid layer such as an adhesive layer, the transmittance tends to decrease at high temperatures. In image display devices using the polarizing plate of this embodiment, even with an interlayer filling configuration, the decrease in the transmittance of the polarizing plate at high temperatures can be suppressed. An example of an image display device is a configuration having an image display unit, a first adhesive layer laminated to the viewing-side surface of the image display unit, and a polarizing plate laminated to the viewing-side surface of the first adhesive layer. This image display device may also include a second adhesive layer laminated to the viewing-side surface of the polarizing plate and a transparent member laminated to the surface of the second adhesive layer. In particular, the polarizing plate of this embodiment can be suitably used in image display devices with an interlayer filling configuration where a transparent member is disposed on the viewing side of the image display device, the polarizing plate is bonded to the image display unit using the first adhesive layer, and the polarizing plate is bonded to the transparent member using the second adhesive layer. In this specification, either or both of the first adhesive layer and the second adhesive layer are sometimes referred to simply as "adhesive layer". It should be noted that the components used in bonding the polarizing plate to the image display unit and the components used in bonding the polarizing plate to the transparent component are not limited to adhesive layer, and may also be adhesive layer.

[0158] <Image Display Unit>

[0159] Examples of image display units include liquid crystal cells and organic EL cells. As a liquid crystal cell, one can use a reflective liquid crystal cell that utilizes external light, a transmissive liquid crystal cell that utilizes light from a light source such as a backlight, or a semi-transmissive / semi-reflective liquid crystal cell that utilizes both external light and light from a light source. When the liquid crystal cell utilizes light from a light source, the image display device (liquid crystal display device) also provides a polarizing plate on the side of the image display cell (liquid crystal cell) opposite to the viewing side, and further provides a light source. The polarizing plate on the light source side is preferably bonded to the liquid crystal cell via a suitable adhesive layer. As for the driving method of the liquid crystal cell, any type of driving method can be used, such as VA mode, IPS mode, TN mode, STN mode, or π-type bending orientation.

[0160] As an organic EL unit, an organic EL unit in which a transparent electrode, an organic light-emitting layer, and a metal electrode are sequentially stacked on a transparent substrate to form a light emitter (organic electroluminescent emitter) can be appropriately used. The organic light-emitting layer is a stack of various organic thin films, such as a stack of a hole injection layer containing a triphenylamine derivative and a light-emitting layer containing a fluorescent organic solid such as anthracene, a stack of these light-emitting layers and an electron injection layer containing a perylene derivative, or a stack of a hole injection layer, a light-emitting layer, and an electron injection layer, etc.

[0161] <Attachment of image display unit to polarizing plate>

[0162] In the bonding of the image display unit and the polarizing plate, an adhesive layer (adhesive sheet) can be appropriately used. From an operational perspective, a method of bonding the image display unit to a polarizing plate with an adhesive layer attached to one side of the polarizing plate is preferred. The attachment of the adhesive layer to the polarizing plate can be performed in an appropriate manner. Examples include: preparing an adhesive solution containing 10% by mass or more and 40% by mass or less of a base polymer or a combination thereof dissolved or dispersed in a solvent containing a suitable solvent such as toluene or ethyl acetate, and directly attaching it to the polarizing plate using an appropriate spreading method such as casting or coating; or forming the adhesive layer on a spacer and transferring it to the polarizing plate.

[0163] <Adhesive layer>

[0164] The adhesive layer can be formed in one or more layers, but is preferably formed in one layer. The adhesive layer can be composed of an adhesive composition with (meth)acrylic resin, rubber resin, urethane resin, ester resin, silicone resin, or polyvinyl ether resin as the main component. Among these, adhesive compositions with (meth)acrylic resin as the base polymer are particularly suitable, exhibiting excellent transparency, weather resistance, and heat resistance. The adhesive composition can also be of the active energy radiation curing type or the thermosetting type.

[0165] The (meth)acrylic resin (base polymer) used in the adhesive composition can suitably be a polymer or copolymer with one or more (meth)acrylate monomers such as butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. It is preferable to copolymerize a polar monomer in the base polymer. Examples of polar monomers include (meth)acrylic acid compounds, 2-hydroxypropyl (meth)acrylate compounds, hydroxyethyl (meth)acrylate compounds, (meth)acrylamide compounds, N,N-dimethylaminoethyl (meth)acrylate compounds, and glycidyl (meth)acrylate compounds, which have carboxyl, hydroxyl, amide, amino, or epoxy groups.

[0166] The adhesive composition may contain only the aforementioned base polymer, but typically also contains a crosslinking agent. Examples of crosslinking agents include metal ions with a valence of divalent or higher that form a carboxylic acid metal salt between themselves and a carboxyl group; polyamine compounds that form an amide bond between themselves and a carboxyl group; polyepoxide compounds or polyols that form an ester bond between themselves and a carboxyl group; and polyisocyanate compounds that form an amide bond between themselves and a carboxyl group. Among these, polyisocyanate compounds are preferred.

[0167] The active energy radiation-curing adhesive composition possesses the property of curing upon irradiation by active energy radiation such as ultraviolet rays or electron beams. It also exhibits adhesiveness even before irradiation, enabling it to adhere tightly to substrates such as films, and the ability to adjust the adhesion force upon curing. The active energy radiation-curing adhesive composition is preferably ultraviolet-curing. In addition to containing a base polymer and a crosslinking agent, the active energy radiation-curing adhesive composition also contains an active energy radiation-polymerizing compound. Depending on the requirements, it may contain photopolymerization initiators, photosensitizers, etc.

[0168] The adhesive composition may contain additives such as microparticles, beads (resin beads, glass beads, etc.) for imparting light scattering properties, glass fibers, resins other than the base polymer, tackifiers, fillers (metal powders, other inorganic powders, etc.), antioxidants, ultraviolet absorbers, dyes, pigments, colorants, defoamers, corrosion inhibitors, and photopolymerization initiators.

[0169] The adhesive layer can be formed by applying an organic solvent dilution of the adhesive composition described above to the surface of a substrate film, an image display unit, or a polarizing plate and then drying it. The substrate film is typically a thermoplastic resin film; a typical example is a release film that has undergone a release treatment. The release film can be, for example, a film in which the adhesive layer of a film containing resins such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, or polyarylate has undergone a release treatment such as silicone treatment.

[0170] An adhesive composition can be directly applied to the release surface of the release film to form an adhesive layer, and this adhesive layer with the release film can be laminated onto the surface of the polarizing plate. Alternatively, an adhesive composition can be directly applied to the surface of the polarizing plate to form an adhesive layer, and a release film can be laminated on the outer surface of the adhesive layer.

[0171] When the adhesive layer is applied to the surface of the polarizing plate, it is preferable to perform surface activation treatments such as plasma treatment or corona treatment on the bonding surface of the polarizing plate and / or the bonding surface of the adhesive layer, and more preferably to perform corona treatment.

[0172] Alternatively, an adhesive sheet can be prepared by coating an adhesive composition onto a second release liner to form an adhesive layer, and then laminating a release liner onto the formed adhesive layer. The adhesive layer with the release liner, after peeling the second release liner from the adhesive sheet, is then laminated onto a polarizing plate. The second release liner is a membrane with weaker adhesion to the adhesive layer and easier to peel off compared to the release liner.

[0173] The thickness of the adhesive layer is not particularly limited, but it is preferably 1 μm or more and 100 μm or less, more preferably 3 μm or more and 50 μm or less, and may also be 20 μm or more.

[0174] <Transparent Components>

[0175] Examples of transparent components that can be used as the viewing side of an image display device include transparent panels (window layers) and touch panels. A transparent panel with appropriate mechanical strength and thickness is used. Examples of such transparent panels include transparent resin sheets made of polyimide-based resins, acrylic resins, polycarbonate resins, or glass sheets. Functional layers such as anti-reflective layers can also be laminated on the viewing side of the transparent panel. Furthermore, when the transparent panel is a transparent resin sheet, a hard coating can be laminated to improve physical strength, and a low-permeability layer can be laminated to reduce moisture permeability. Various touch panels, such as resistive film, capacitive, optical, and ultrasonic touch panels, as well as glass sheets and transparent resin sheets with touch sensor functionality, can be used as touch panels. When using a capacitive touch panel as the transparent component, it is preferable to provide a transparent panel made of glass or a transparent resin sheet on the viewing side relative to the touch panel.

[0176] <Fitting of polarizing plate with transparent component>

[0177] In bonding the polarizing plate to the transparent component, adhesives or active energy radiation-cured adhesives can be appropriately used. When using adhesives, they can be applied in a suitable manner. For example, the adhesive layer application method used in the aforementioned bonding of the image display unit to the polarizing plate can be cited as a specific application method.

[0178] When using an active energy ray-cured adhesive, to prevent the adhesive solution from spreading before curing, the following method can be appropriately used: a dam material is set up to surround the periphery of the image display panel; a transparent component is placed on the dam material; and the adhesive solution is injected. After the adhesive solution is injected, alignment and degassing are performed as needed, followed by curing by irradiation with active energy rays.

[0179] Example

[0180] The present invention will now be described in detail based on embodiments. The materials, reagents, quantities, proportions, and operations shown in the following embodiments may be appropriately modified without departing from the spirit of the invention.

[0181] Therefore, the present invention is not limited or restricted by the following embodiments.

[0182] <Fabrication of Polarizing Element A>

[0183] A 40 μm thick PVA film, formed from PVA with an average degree of polymerization of approximately 2400 and a saponification degree of 99.9 mol% or higher, was uniaxially stretched to approximately 5 times its original length using a dry method. While maintaining tension, it was then immersed in pure water at 60°C for 1 minute, followed by immersion in an aqueous solution of iodine / potassium iodide / water at a weight ratio of 0.05 / 5 / 100 at 28°C for 60 seconds. Subsequently, it was immersed in an aqueous solution of potassium iodide / boric acid / water at a weight ratio of 8.5 / 8.5 / 100 at 72°C for 300 seconds. After washing with pure water at 26°C for 20 seconds, it was dried at 65°C to obtain a 15 μm thick polarizing element A with iodine adsorbed and oriented in the PVA. The thickness of the polarizing element was measured using a digital micrometer "MH-15M" manufactured by Nikon Corporation.

[0184] <Preparation of Adhesives>

[0185] (Preparation of PVA solution A for adhesives)

[0186] 50g of a modified PVA resin containing acetyl groups (GOHSENX Z-410 manufactured by Mitsubishi Chemical Corporation) was dissolved in 950g of pure water, heated at 90°C for 2 hours, and then cooled to room temperature to obtain a PVA solution for adhesives (hereinafter referred to as "PVA solution A").

[0187] (Preparation of adhesives 1a, 1b, 1c, 2a, 2b, 2c, and 3)

[0188] Adhesives were prepared by combining PVA solution A, urea as compound 1, 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxy radical (hereinafter also referred to as "TEMPOL") as compound 2, and pure water, with PVA at 3.0% by mass, compound 1 and compound 2 as shown in Table 1.

[0189] [Table 1]

[0190]

[0191] <Preparation of Transparent Protective Film A>

[0192] A commercially available cellulose acylated membrane TD40 (manufactured by Fujifilm Corporation, 40 μm thick) was immersed in a 1.5 mol / L NaOH aqueous solution (saponification solution) maintained at 55°C for 2 minutes, followed by washing with water. Then, it was immersed in a 0.05 mol / L sulfuric acid aqueous solution at 25°C for 30 seconds, and then washed under running water for 30 seconds to neutralize the membrane. Afterward, water was removed three times using an air knife, and the membrane was dried in a drying zone at 70°C for 15 seconds to produce a saponified membrane, designated as transparent protective film A.

[0193] <Preparation of Polarizing Plates 1-8>

[0194] A transparent protective film A is bonded to both sides of the polarizing element A using a roller laminator via adhesive 3. After bonding, it is dried at 80°C for 5 minutes to obtain the polarizing plate 1. The adhesive layer is adjusted so that the thickness after drying is 50 nm on both sides. The adhesive layer used to bond the transparent protective film A to one side of the polarizing element A is designated as the first adhesive layer, and the adhesive layer used to bond the transparent protective film A to the other side is designated as the second adhesive layer.

[0195] In polarizing plate 1, the adhesive 3 used on both sides is changed to the adhesives listed in Table 2 to obtain polarizing plates 2 to 8.

[0196] (Adjustment of moisture content in polarizing plate (polarizing element))

[0197] The polarizing plates 1-8 obtained above were stored for 72 hours at a temperature of 20°C and relative humidity of 30%, 35%, 40%, 45%, 50%, or 55%. The moisture content was determined using the Karl Fischer method after 66, 69, and 72 hours of storage. Under any humidity conditions, the moisture content remained unchanged after 66, 69, and 72 hours of storage. Therefore, the moisture content of polarizing plates 1-8 can be considered the same as the equilibrium moisture content under the 72-hour storage environment used in this experimental example. When the moisture content of a polarizing plate reaches equilibrium under a certain storage environment, it can be assumed that the moisture content of the polarizing element in the polarizing plate also reaches equilibrium under that storage environment. Furthermore, when the moisture content of the polarizing element in a polarizing plate reaches equilibrium under a certain storage environment, it can be assumed that the moisture content of the polarizing plate also reaches equilibrium under that storage environment.

[0198] <Optical laminates 1-8>

[0199] Optical laminates 1 to 8 were fabricated using any of the polarizers 1 to 8 shown in Table 2. For optical laminates 1 to 8, the moisture content of the polarizers (polarizing elements) used was kept at an equilibrium moisture content of 30%, 45%, or 55% relative humidity for 72 hours at a temperature of 20°C, relative humidity of 30%, 45%, or 55% as shown in Table 2, and the high-temperature durability was evaluated below under each moisture content condition.

[0200] <High Temperature Durability Evaluation>

[0201] (Preparation of evaluation samples)

[0202] Optical laminates 1 to 8 at various moisture contents were coated with an acrylic adhesive (LINTEC Corporation, model #7) on both sides, and then cut to a size of 50mm × 100mm with the absorption axis parallel to the long side. Alkali-free glass (Corning Corporation, "EAGLE XG") was then bonded to each adhesive surface to produce evaluation samples.

[0203] To evaluate the orthogonal light leakage of the aforementioned evaluation sample, an optical laminate R was fabricated to create an orthogonal Nicol prism state overlapping with the evaluation sample. Specifically, an acrylic adhesive (LINTEC Corporation, model #7) was formed on only one side of the aforementioned polarizer 1, and then it was cut to a size of 50mm × 100mm with the absorption axis parallel to the short side. Alkali-free glass (Corning Corporation, "EAGLE XG") was then bonded to the adhesive surface, thereby fabricating the optical laminate R used in the orthogonal evaluation.

[0204] Evaluation samples of optical laminates 1–8 were tested at a temperature of 50°C and a pressure of 5 kgf / cm². 2After undergoing autoclave treatment at (490.3 kPa) for 1 hour, the samples were placed in an environment with a temperature of 23°C and a relative humidity of 55% for 24 hours. Subsequently, the high-temperature durability of the evaluation samples 1 to 8 at various moisture contents was evaluated as shown below.

[0205] (i) Evaluation samples of the equilibrium moisture content of polarizing plates or polarizing elements at a temperature of 20°C and a relative humidity of 55%.

[0206] (Single-cell transmittance evaluation (105℃))

[0207] Transmittance (initial value) was measured for evaluation samples of optical laminates 1–8 with an equilibrium moisture content of 20°C and 55% relative humidity for polarizing plates or polarizing elements. These samples were then stored at 105°C, and transmittance was measured every 24 hours for 48–96 hours. Evaluation was based on the time it took for transmittance to decrease by more than 5% relative to the initial value, according to the following criteria. The results are shown in Table 2.

[0208] Samples whose transmittance decreased by less than 5% after 96 hours: A1

[0209] Samples with a transmittance reduction of more than 5% over 72–96 hours: B1

[0210] Samples with a transmittance reduction of more than 5% over 48–72 hours: C1

[0211] Samples with a transmittance reduction of more than 5% after 48 hours: D1

[0212] (Evaluation of orthogonal light leakage)

[0213] Evaluation samples were prepared after measuring the monomer transmittance after 96 hours in the above-mentioned monomer transmittance evaluation. The optical stack R used for orthogonal Nicol prism evaluation (without heating) and the evaluation samples were arranged in a manner forming an orthogonal Nicol prism and placed on a backlight. With the surrounding light blocked, orthogonal light leakage was evaluated visually according to the following criteria in a 4-level scale. The results are shown in Table 2. It should be noted that evaluation samples with a monomer transmittance rating other than A1 were excluded from the orthogonal light leakage evaluation due to coloration caused by polyolefination.

[0214] Samples with no observable orthogonal light leakage: A1

[0215] Samples with virtually no orthogonal light leakage can be observed: B1

[0216] Slightly observed cross-leaking light in sample C1

[0217] The sample with clearly observed orthogonal light leakage: D1

[0218] (ii) Evaluation samples of polarizing plates or polarizing elements at equilibrium moisture content of 20°C and 45% relative humidity.

[0219] (Single-cell transmittance evaluation (105℃))

[0220] Transmittance (initial value) was measured for evaluation samples of optical laminates 1–8 with an equilibrium moisture content of 20°C and 45% relative humidity for polarizing plates or polarizing elements. These samples were then stored at 105°C for 50 hours, with transmittance measured every 50 hours until 100–200 hours. Evaluation was based on the time it took for the transmittance to decrease by more than 5% relative to the initial value, according to the following criteria. The results are shown in Table 2.

[0221] Samples whose transmittance decreased by less than 5% after 200 hours: A2

[0222] Samples with a transmittance reduction of more than 5% after 150–200 hours: B2

[0223] Samples with a transmittance decrease of more than 5% over 100–150 hours: C2

[0224] Samples with a transmittance reduction of more than 5% after 100 hours: D2

[0225] (Evaluation of orthogonal light leakage)

[0226] Evaluation samples were prepared after 200 hours of monomer transmittance measurement in the aforementioned monomer transmittance evaluation. The optical stack R used for orthogonal Nicol prism evaluation (without heating) and the evaluation samples were arranged in a manner forming an orthogonal Nicol prism and placed on a backlight. With the surrounding light blocked, orthogonal light leakage was evaluated visually according to the following criteria in four grades. The results are shown in Table 2. It should be noted that evaluation samples with a monomer transmittance rating other than A2 were excluded from the orthogonal light leakage evaluation due to coloration caused by polyolefination.

[0227] Samples with no observable orthogonal light leakage: A2

[0228] Samples with virtually no orthogonal light leakage can be observed: B2

[0229] Slightly observed cross-leaking light in sample C2

[0230] The sample with clearly observed orthogonal light leakage: D2

[0231] (iii) Evaluation samples of polarizing plates or polarizing elements at equilibrium moisture content at 20°C and 30% relative humidity.

[0232] (Single-cell transmittance evaluation (105℃))

[0233] Transmittance (initial value) was measured for evaluation samples of optical laminates 1–8 with an equilibrium moisture content of 20°C and 30% relative humidity for polarizing plates or polarizing elements. These samples were then stored at 105°C for 500–800 hours, with transmittance measured every 150 hours. Evaluation was based on the time it took for the transmittance to decrease by more than 5% relative to the initial value, according to the following criteria. The results are shown in Table 2.

[0234] Samples whose transmittance decreased by less than 5% after 800 hours: A3

[0235] Samples with a transmittance reduction of more than 5% over 650–800 hours: B3

[0236] Samples with a transmittance reduction of more than 5% after 500–650 hours: C3

[0237] Samples with a transmittance reduction of more than 5% after 500 hours: D3

[0238] (Evaluation of orthogonal light leakage)

[0239] Evaluation samples were prepared after 800 hours of monomer transmittance measurement in the aforementioned monomer transmittance evaluation. The optical stack R used for orthogonal Nicol prism evaluation (without heating) and the evaluation samples were arranged in a manner forming an orthogonal Nicol prism and placed on a backlight. With the surrounding light blocked, orthogonal light leakage was evaluated visually according to the following criteria in a 4-level scale. The results are shown in Table 2. It should be noted that evaluation samples with a monomer transmittance rating other than A3 were excluded from the orthogonal light leakage evaluation due to coloration caused by polyolefination.

[0240] Samples with no observable orthogonal light leakage: A3

[0241] Samples with virtually no orthogonal light leakage can be observed: B3

[0242] Slightly observed cross-leaking light in sample C3

[0243] The sample with orthogonal light leakage was clearly observed: D3

[0244] [Table 2]

[0245]

[0246] It is known that the polarizing element and the first transparent protective film are bonded together using a first adhesive containing the first compound, and the polarizing element and the second transparent protective film are bonded together using a second adhesive containing the second compound. The polarizing plate (optical laminate 6-8) does not depend on the moisture content of the polarizing plate and the polarizing element. Even when exposed to a high temperature environment of 105°C, the transmittance is not easily reduced. In addition, the evaluation of orthogonal light leakage is excellent, and the high temperature durability is excellent.

Claims

1. A polarizing plate comprising a polarizing element formed by adsorbing and oriented dichroic pigments on a polyvinyl alcohol-based resin layer, a first transparent protective film laminated on one side of the polarizing element, and a second transparent protective film laminated on the other side of the polarizing element. The polarizing element and the first transparent protective film are bonded together using a first adhesive layer formed from a first adhesive containing a first compound. The polarizing element and the second transparent protective film are bonded together using a second adhesive layer formed from a second adhesive containing a second compound. The first adhesive and the second adhesive comprise a polyvinyl alcohol-based resin. In the first adhesive, the content of the first compound is 0.1 parts by weight or more and 400 parts by weight or less relative to 100 parts by weight of the polyvinyl alcohol-based resin. In the second adhesive, the content of the second compound is 0.1 parts by weight or more and 400 parts by weight or less relative to 100 parts by weight of the polyvinyl alcohol-based resin. The first compound is selected from at least one of urea, urea derivatives, thiourea, and thiourea derivatives. The urea derivative is selected from methylurea, ethylurea, propylurea, butylurea, isobutylurea, N-octadecylurea, 2-hydroxyethylurea, hydroxyurea, acetylurea, allylurea, 2-propynylurea, cyclohexylurea, phenylurea, 3-hydroxyphenylurea, (4-methoxyphenyl)urea, benzylurea, benzoylurea, o-tolylurea, p-tolylurea, 1,1-dimethylurea, 1,3-dimethylurea, 1,1-diethylurea, 1,3-diethylurea, 1,3-diethylurea, 1 At least one urea compound selected from the following: 3-bis(hydroxymethyl)urea, 1,3-tert-butylurea, 1,3-dicyclohexylurea, 1,3-diphenylurea, 1,3-bis(4-methoxyphenyl)urea, 1-acetyl-3-methylurea, 2-imidazolidineone (i.e., ethylidene urea), tetrahydro-2-pyrimidinone (i.e., propylidene urea), tetramethylurea, 1,1,3,3-tetraethylurea, 1,1,3,3-tetrabutylurea, and 1,3-dimethoxy-1,3-dimethylurea. The second compound is a compound having a nitryl radical or a nitroxy radical.

2. The polarizing plate according to claim 1, wherein, The second compound is an N-oxygen free radical compound.

3. The polarizing plate according to claim 1 or 2, wherein, The first compound is at least one urea compound selected from urea derivatives and thiourea derivatives.

4. The polarizing plate according to claim 1 or 2, wherein, The thickness of the first adhesive layer and the second adhesive layer is greater than 0.01 μm and less than 7 μm.

5. The polarizing plate according to claim 1 or 2, wherein, The polarizing plate is used in an image display device. In the image display device, a solid layer is provided in contact with both sides of the polarizing plate.

6. An image display device, It comprises an image display unit, a first adhesive layer laminated on the observation side surface of the image display unit, and a polarizing plate as described in any one of claims 1 to 5.

7. The image display device according to claim 6, further comprising a second adhesive layer laminated on the observation-side surface of the polarizing plate and a transparent component laminated on the observation-side surface of the second adhesive layer.

8. The image display device according to claim 7, wherein, The transparent component is a glass plate or a transparent resin plate.

9. The image display device according to claim 7, wherein, The transparent component is a touch panel.

Images