Polarizing plate and image display device

Abstract

To provide a polarizing plate in which a decrease in transmittance in a high temperature environment is suppressed.SOLUTION: Disclosed a polarizing plate which includes: a polarizing element in which a dichroic dye is adsorbed and aligned on a polyvinyl alcohol resin layer; a first transparent protective film laminated on one surface of the polarizing element; and a second transparent protective film laminated on the other surface of the polarizing element. The polarizing element and the transparent protective film are bonded together by a first adhesive layer formed of a first adhesive containing a first compound. The polarizing element and the second transparent protective film are bonded together by a second adhesive layer formed of a second adhesive containing a second compound. The first compound is at least one kind selected from the group consisting of urea, urea derivative, thiourea and thiourea derivative, and the second compound has a nitroxy radical or a nitroxide group.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Liquid crystal display devices (LCDs) are widely used not only in LCD televisions but also in personal computers, mobile devices such as mobile phones, and in-vehicle applications such as car navigation systems. Typically, LCD displays have a liquid crystal panel with polarizing plates attached to both sides of a liquid crystal cell with an adhesive, and display images by controlling the light from a backlight with the liquid crystal panel. In recent years, organic electroluminescence (EL) display devices, like LCD displays, have also been widely used in televisions, mobile devices such as mobile phones, and in-vehicle applications such as car navigation systems. In organic EL display devices, a circular polarizer (a laminate including a polarizing element and a λ / 4 plate) may be placed on the viewing-side surface of the image display panel to prevent external light from being reflected by the metal electrode (cathode) and appearing as a mirror.

[0003] As mentioned above, polarizing plates are increasingly being installed in vehicles as components of image display devices such as liquid crystal display devices and organic EL display devices. Polarizing plates used in in-vehicle image display devices are more likely to be exposed to high-temperature environments than those used in mobile applications such as televisions and mobile phones, and therefore are required to have small changes in properties at higher temperatures (high-temperature durability).

[0004] On the other hand, in order to prevent damage to the image display panel due to impact from the outer surface, a configuration in which a front panel (also called a "window layer") such as a transparent resin plate or glass plate is provided on the viewing side of the image display panel is becoming more common. In image display devices equipped with a touch panel, a configuration in which the touch panel is provided on the viewing side of the image display panel and a front panel is provided further on the viewing side of the touch panel is widely adopted.

[0005] In such a configuration, if an air gap exists between the image display panel and a transparent member such as a front panel or touch panel, light reflection at the interface of the air gap can cause external light to be reflected, reducing the visibility of the screen. Therefore, there is a growing trend to adopt a configuration in which the space between the polarizing plate and the transparent member arranged on the viewing side of the image display panel is filled with a layer other than the air gap, typically a solid layer (hereinafter, sometimes referred to as an "interlayer filler") (hereinafter, sometimes referred to as an "interlayer filler configuration"). The interlayer filler is preferably a material with a refractive index close to that of the polarizing plate or the transparent member. Pressure-sensitive adhesives or UV-curable adhesives are used as interlayer fillers to prevent a reduction in visibility due to reflection at the interface and to bond and fix the various members together (see, for example, Patent Document 1).

[0006] The interlayer filling structure is being widely adopted in mobile applications such as mobile phones, which are often used outdoors. In addition, due to the increasing demand for visibility in recent years, the adoption of an interlayer filling structure in which a front transparent plate is placed on the surface of an image display panel and an adhesive layer or the like is filled between the panel and the front transparent plate is being considered for in-vehicle applications such as car navigation systems.

[0007] However, it has been reported that when such a configuration is adopted, the transmittance of the polarizing plate significantly decreases in a high-temperature environment. As a solution to this problem, Patent Document 2 proposes a method of suppressing the decrease in transmittance by setting the moisture content per unit area of ​​the polarizing plate to a predetermined amount or less and setting the saturated water absorption amount of a transparent protective film adjacent to the polarizing element to a predetermined amount or less. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 11-174417 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-102353 Summary of the Invention [Problem to be solved by the invention]

[0009] However, even such polarizing plates have not been effective in suppressing deterioration in durability in a high-temperature environment. An object of the present invention is to provide a novel polarizing plate that can suppress deterioration in transmittance even when exposed to a high-temperature environment, and an image display device using the polarizing plate. [Means for solving the problem]

[0010] The present invention provides the following polarizing plate and image display device. [1] A polarizing plate comprising 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 surface of the polarizing element, and a second transparent protective film laminated on the other surface of the polarizing element, the polarizing element and the first transparent protective film are bonded together by 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 by a second adhesive layer formed from a second adhesive containing a second compound; the first compound is at least one selected from the group consisting of urea, urea derivatives, thiourea, and thiourea derivatives; A polarizing plate, wherein the second compound is a compound having a nitroxy radical or a nitroxide group. [2] The polarizing plate according to [1], wherein the second compound is an N-oxyl compound. [3] The polarizing plate according to [1] or [2], wherein the first compound is at least one urea-based compound selected from the group consisting of urea derivatives and thiourea derivatives. [4] The polarizing plate according to any one of [1] to [3], wherein the first adhesive and the second adhesive contain a polyvinyl alcohol-based resin. [5] The polarizing plate according to [4], wherein the content of the first compound in the first adhesive is 0.1 parts by mass or more and 400 parts by mass or less with respect to 100 parts by mass of the polyvinyl alcohol-based resin. [6] The polarizing plate according to [4] or [5], wherein the content of the second compound in the second adhesive is 0.1 parts by mass or more and 400 parts by mass or less per 100 parts by mass of the polyvinyl alcohol-based resin. [7] The polarizing plate according to any one of [1] to [6], wherein the first adhesive layer and the second adhesive layer have a thickness of 0.01 μm or more and 7 μm or less. [8] The polarizing plate is used in an image display device, The polarizing plate according to any one of [1] to [7], wherein in the image display device, solid layers are provided on both sides of the polarizing plate in contact with each other. [9] An image display device comprising: an image display cell; a first pressure-sensitive adhesive layer laminated on the viewing-side surface of the image display cell; and the polarizing plate according to any one of [1] to [8] laminated on the viewing-side surface of the first pressure-sensitive adhesive layer.

[10] The image display device described in [9], further comprising a second adhesive layer laminated on the viewing side surface of the polarizing plate, and a transparent member laminated on the viewing side surface of the second adhesive layer.

[11] The image display device according to

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

[12] The image display device according to

[10] , wherein the transparent member is a touch panel. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a polarizing plate having improved high-temperature durability and suppressing a decrease in transmittance even when used in an image display device with an interlayer filling structure and exposed to a high-temperature environment. Furthermore, by using the polarizing plate according to the present invention, it is possible to provide an image display device having suppressed a decrease in transmittance even when exposed to a high-temperature environment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments.

[0013] [Polarizing plate] A polarizing plate according to an embodiment of the present invention includes a polarizing element having a dichroic dye adsorbed and aligned in a layer containing a polyvinyl alcohol-based resin, a first transparent protective film laminated on one surface of the polarizing element, and a second transparent protective film laminated on the other surface of the polarizing element. The polarizing element and the first transparent protective film are bonded together by 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 by a second adhesive layer formed from a second adhesive containing a second compound.

[0014] The first compound is at least one selected from the group consisting of urea, urea derivatives, thiourea, and thiourea derivatives, and the second compound is a compound having a nitroxy radical or a nitroxide group.

[0015] Conventional polarizing plates with excellent high-temperature durability are known, for example, to exhibit minimal transmittance degradation even when left alone at 95°C for 1,000 hours. However, even such polarizing plates, when used in an interlayer filling configuration, can exhibit a significant decrease in transmittance in the central area of ​​the polarizing plate after being left in a 95°C environment for 200 hours. Furthermore, if the moisture content of the polarizing plate or polarizing element is outside a specific range, a significant decrease in transmittance or polarization degree can be observed in the central area of ​​the polarizing plate. The significant decrease in transmittance of polarizing plates in high-temperature environments is thought to be particularly likely to occur when image display devices employing an interlayer filling configuration in which one side of the polarizing plate is bonded to an image display cell and the other side is bonded to a transparent member such as a touch panel or front panel are exposed to high-temperature environments.

[0016] The polarizer with a significantly reduced transmittance due to the interlayer filling structure was measured by Raman spectroscopy at 1100cm -1 near (derived from the C-C bond) and 1500 cm -1 Since there is a peak near the -C=C- bond, it is believed to have a polyene structure (-C=C). nThe polyene structure is presumably formed when polyvinyl alcohol constituting the polarizing element is dehydrated to form a polyene structure (Patent Document 2, paragraph

[0012] ).

[0017] The polarizing plate according to the present invention can further improve high-temperature durability. When incorporated into an image display device with an interlayer filling configuration, the polarizing plate according to the present invention can suppress a decrease in transmittance even when exposed to a high-temperature environment, such as a temperature of 105°C. It is believed that this effect is due to the synergistic action of the first compound and the second compound present in the adhesive layer, which suppresses the polyenization of the polyvinyl alcohol constituting the polarizing element. It has been confirmed that this effect is not limited to a specific range of water content in the polarizing plate or polarizing element, but is achieved regardless of whether the water content of the polarizing plate or polarizing element is low or high. It is believed that this is because the effect of the first compound in suppressing the polyenization of the polyvinyl alcohol is more pronounced when the water content of the polarizing plate or polarizing element is low, while the effect of the second compound in suppressing the polyenization of the polyvinyl alcohol is more pronounced when the water content of the polarizing plate or polarizing element is high.

[0018] The polarizing plate according to this embodiment can have at least one of the following characteristics (a) and (b). (a) The moisture content of the polarizing element is equal to or greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 80%. (b) The moisture content of the polarizing plate is equal to or greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 80%. The polarizing plate of this embodiment can achieve the effect of improving high-temperature durability even when it has a more limited feature than the feature (a) or (b) described above, such as the feature (a1) or (b1) described below. (a1) The moisture content of the polarizing element is greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 45% or 50% and is equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 80% or 70%. (b1) The moisture content of the polarizing plate is greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 45% or 50% and is equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 80% or 70%. Even if a polarizing plate does not have a step of adjusting the moisture content, it is usually highly likely to have the above characteristics (a) and (b). In this embodiment, a step of adjusting the moisture content may be included so that the polarizing plate has at least one of the above characteristics (a) and (b), or the step of adjusting the moisture content may not be included.

[0019] <Polarizing element> Known polarizing elements can be used as the polarizing element in which a dichroic dye is adsorbed and aligned in a layer containing a polyvinyl alcohol (hereinafter also referred to as "PVA")-based resin (hereinafter also referred to as a "PVA-based resin layer"). Examples of polarizing elements include a stretched film obtained by dyeing a PVA-based resin film with a dichroic dye and uniaxially stretching it, and a stretched layer obtained by using a laminated film having a coating layer formed by applying a coating liquid containing a PVA-based resin onto a base film, dyeing the coating layer with a dichroic dye, and uniaxially stretching the laminated film. Stretching may be performed after dyeing with the dichroic dye, or may be performed while dyeing, or may be performed after stretching and then dyeing.

[0020] PVA resins are obtained by saponifying polyvinyl acetate resins. Examples of polyvinyl acetate resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate with other copolymerizable monomers. Examples of other copolymerizable monomers include unsaturated carboxylic acids, olefins such as ethylene, vinyl ethers, and unsaturated sulfonic acids.

[0021] The saponification degree of the PVA 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 polymerization degree of the PVA resin is, for example, 1,000 to 10,000, preferably 1,500 to 5,000. The PVA resin may be modified, and may be, for example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral, or the like, modified with aldehydes.

[0022] 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 influence of polyenation of the PVA resin on the deterioration of optical properties in a high-temperature environment can be suppressed. By making the thickness of the polarizing element 3 μm or more, it becomes easy to configure the polarizing element to achieve the desired optical properties.

[0023] The polarizing element preferably contains a first compound and a second compound. In this embodiment, the polarizing element and the first transparent protective film are bonded together using a first adhesive layer formed from a first adhesive containing the first compound, and the polarizing element and the second transparent protective film are bonded together using a second adhesive layer formed from a second adhesive containing the second compound. Therefore, it is presumed that the polarizing element contains a portion of the first compound migrated from the first adhesive layer and a portion of the second compound migrated from the second adhesive layer. The first compound and the second compound in the polarizing element may contain compounds added during the manufacturing process of the polarizing element. By providing a first adhesive layer containing the first compound and a second adhesive layer containing the second compound, the transmittance of the polarizing plate is less likely to decrease even when exposed to a high-temperature environment. Furthermore, by providing a first adhesive layer containing the first compound and a second adhesive layer containing the second compound, the degree of polarization of the polarizing plate can be suppressed from decreasing even when exposed to a high-temperature environment. When two polarizing plates are arranged in a crossed Nicol relationship, a decrease in the degree of polarization of the polarizing plates tends to cause light leakage (hereinafter also referred to as "cross leakage"). However, according to the present invention, the degree of polarization is less likely to decrease even when exposed to a high-temperature environment, and therefore cross leakage is also easily suppressed. This is presumably because the synergistic effect of the first compound and the second compound contained in the polarizing element suppresses the polyenization of the PVA-based resin.

[0024] The first compound and the second compound can be contained in the polarizing element during production by immersing the PVA resin layer in a treatment solvent containing the first compound and / or the second compound, or by spraying, pouring, or dripping the treatment solvent onto the PVA resin layer. Among these, the method of immersing the PVA resin layer in a treatment 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 below.

[0025] The step of immersing the PVA-based resin layer in a treatment solvent containing the first and second compounds may be performed simultaneously with or separately from the swelling, stretching, dyeing, crosslinking, washing, and other steps in the method for producing a polarizing element described below. The step of incorporating 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 step after dyeing. This method results in minimal hue change and minimizes the impact on the optical properties of the polarizing element.

[0026] In order to incorporate the first compound and the second compound into the polarizing element, they may be added both during the production of the polarizing element and to the adhesive. Alternatively, one of the first compound and the second compound may be incorporated during the production of the polarizing element, and both may be incorporated into the adhesive.

[0027] (1st compound) The first compound is at least one selected from the group consisting of urea, urea derivatives, thiourea, and thiourea derivatives. The first compound can be used alone or in combination of two or more. There are water-soluble and poorly water-soluble first compounds, and either type of first compound can be used. When a poorly water-soluble first compound is used in a water-soluble adhesive, it is preferable to devise a dispersion method to prevent an increase in haze after forming the adhesive layer.

[0028] (urea derivative) A urea derivative is a compound in which at least one of the four hydrogen atoms of a urea molecule is substituted with a substituent. In this case, the substituent is not particularly limited, but is preferably a substituent consisting of carbon, hydrogen, and oxygen atoms.

[0029] Specific examples of the urea derivatives include mono-substituted ureas such as 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.

[0030] Examples of disubstituted ureas include 1,1-dimethylurea, 1,3-dimethylurea, 1,1-diethylurea, 1,3-diethylurea, 1,3-bis(hydroxymethyl)urea, 1,3-tert-butylurea, 1,3-dicyclohexylurea, 1,3-diphenylurea, 1,3-bis(4-methoxyphenyl)urea, 1-acetyl-3-methylurea, 2-imidazolidinone (ethyleneurea), and tetrahydro-2-pyrimidinone (propyleneurea).

[0031] Examples of 4-substituted ureas include tetramethylurea, 1,1,3,3-tetraethylurea, 1,1,3,3-tetrabutylurea, 1,3-dimethoxy-1,3-dimethylurea, 1,3-dimethyl-2-imidazolidinone, and 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone.

[0032] (thiourea derivatives) A thiourea derivative is a compound in which at least one of the four hydrogen atoms of a thiourea molecule is substituted with a substituent. In this case, the substituent is not particularly limited, but is preferably a substituent consisting of carbon, hydrogen, and oxygen atoms.

[0033] Specific examples of the thiourea derivatives include mono-substituted thioureas such as 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.

[0034] 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 ethylenethiourea.

[0035] An example of the 3-substituted thiourea is trimethylthiourea, and an example of the 4-substituted thiourea is tetramethylthiourea or 1,1,3,3-tetraethylthiourea.

[0036] Among the first compounds, urea derivatives or thiourea derivatives are preferred, and urea derivatives are more preferred, because when used in an image display device with an interlayer filling configuration, the decrease in transmittance in a high-temperature environment is suppressed and the decrease in polarization degree is small (the cross-drop loss is suppressed). Among urea derivatives, mono-substituted ureas or di-substituted ureas are preferred, and mono-substituted ureas are more preferred. Di-substituted ureas include 1,1-substituted ureas and 1,3-substituted ureas, with 1,3-substituted ureas being more preferred.

[0037] (Second compound) The second compound is a compound having a nitroxy radical or a nitroxide group. As the second compound, an N-oxyl compound (having a functional group of CN(-C)-O) is used from the viewpoint of having a relatively stable radical at room temperature in air. · Compounds having the formula (O · represents an oxy radical and is bonded to N. )) and known compounds can be used. Examples of N-oxyl compounds include compounds having an organic group with the following structure. The compounds having a nitroxy radical or nitroxide group may be used alone or in combination of two or more. [ka] (In general formula (1), R 1 represents an oxy radical, R 2 From R 5 are independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and n is 0 or 1.) In general formula (1), the left side of the dotted line represents an optional organic group. The optional organic group contains a hydrogen atom.

[0038] Examples of the compound having the organic group include compounds represented by the following general formulas (2) to (5). [ka] (In general formula (2), R 1 From R 5 , and n are the same as above, and R 6 represents a hydrogen atom, or an alkyl group, acyl group, or aryl group having 1 to 10 carbon atoms, and n represents 0 or 1. [ka] (In general formula (3), R 1 From R 5 , and n are the same as above, and R 7 and R 8each independently represents a hydrogen atom, or an alkyl group, acyl group, or aryl group having 1 to 10 carbon atoms. [ka] (In general formula (4), R 1 From R 5 , and n are the same as above, and R 9 From R 11 are independently a hydrogen atom, or an alkyl group having 1 to 10 carbon atoms, an acyl group, an amino group, an alkoxy group, a hydroxy group, or an aryl group. [ka] (In general formula (5), R 1 From R 5 , and n are the same as above, and R 12 represents a hydrogen atom, or an alkyl group having 1 to 10 carbon atoms, an amino group, an alkoxy group, a hydroxy group, or an aryl group.

[0039] In the general formulas (1) to (5), R 2 From R 5 From the viewpoint of availability, R is preferably an alkyl group having 1 to 6 carbon atoms, and more preferably an alkyl group having 1 to 3 carbon atoms. 6 is preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and more preferably a hydrogen atom. 7 and R 8 are preferably independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and more preferably a hydrogen atom. 9 From R 11 is preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. 12is preferably a hydroxy group, an amino group, or an alkoxy group. In the general formulae (1) to (5), n is preferably 1 from the viewpoint of availability.

[0040] Examples of the N-oxyl compound include those described in JP 2003-64022 A, JP 11-222462 A, JP 2002-284737 A, and WO 2016 / 047655. 4-Hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl is preferably used as the N-oxyl compound.

[0041] Examples of the second compound include the following compounds: [ka] (In general formula (6), R represents a hydrogen atom, or an alkyl group, acyl group, or aryl group having 1 to 10 carbon atoms.) [ka] [ka]

[0042] From the viewpoint of efficiently capturing radicals generated in the polyenation reaction, the second compound preferably has a molecular weight of 1,000 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, but can be, for example, 80.

[0043] (Feature (a)) When characteristic (a) is present, the moisture content of the polarizing element is equal to or greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 80%. The moisture content of the polarizing element may be greater than the equilibrium moisture content at a temperature of 45% or 50% at a temperature of 20°C and a relative humidity of 80% or 70% at a temperature of 20°C. If the moisture content of the polarizing element is lower than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, the polarizing element becomes less easy to handle and more likely to crack. If the moisture content of the polarizing element is high, such as exceeding the equilibrium moisture content at a temperature of 20°C and a relative humidity of 45% or 50%, it is thought that polyenization of the PVA-based resin is more likely to occur. However, in this embodiment, the adhesive layers containing the first compound and the second compound are provided, thereby suppressing polyenization of the PVA-based resin.

[0044] To confirm whether the moisture content of a polarizing element is within the range of above the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and below the equilibrium moisture content at a temperature of 20°C and a relative humidity of 80%, it can be stored in an environment adjusted to the above temperature and relative humidity ranges, and if there is no change in mass for a certain period of time, it can be assumed that equilibrium with the environment has been reached. Alternatively, the equilibrium moisture content of the polarizing element in an environment adjusted to the above temperature and relative humidity ranges can be calculated in advance, and the moisture content of the polarizing element can be confirmed by comparing the pre-calculated equilibrium moisture content.

[0045] Methods for producing a polarizing element having a moisture content equal to or greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 80% are not particularly limited, but include, for example, storing the polarizing element in an environment adjusted to the above temperature and relative humidity ranges for 10 minutes to 3 hours, or heat treating the polarizing element at a temperature of 30°C to 90°C.

[0046] Another preferred method for producing a polarizing element having the above moisture content includes storing a laminate in which a protective film is laminated on at least one surface of a polarizing element, or a polarizing plate constructed using a polarizing element, in an environment adjusted to the above temperature and relative humidity ranges for 10 minutes to 120 hours, or heat-treating at 30° C. to 90° C. When producing an image display device employing an interlayer filling configuration, an image display panel in which a polarizing plate is laminated on an image display cell may be stored in an environment adjusted to the above temperature and relative humidity ranges for 10 minutes to 3 hours, or heated at 30° C. to 90° C., and then a front panel may be attached thereto.

[0047] (Feature (b)) When characteristic (b) is present, the moisture content of the polarizing plate is equal to or greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 80%. The moisture content of the polarizing plate may be greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 45% or 50% and equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 80% or 70%. If the moisture content of the polarizing plate is lower than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, the polarizing plate becomes less easy to handle and more likely to crack. If the moisture content of the polarizing plate is high, such as exceeding the equilibrium moisture content at a temperature of 20°C and a relative humidity of 45% or 50%, it is thought that polyenization of the PVA-based resin is likely to proceed. However, in this embodiment, the adhesive layers containing the first compound and the second compound are provided, thereby suppressing polyenization of the PVA-based resin.

[0048] To confirm whether the moisture content of a polarizing plate is within the range of above the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and below the equilibrium moisture content at a temperature of 20°C and a relative humidity of 80%, the polarizing plate can be stored in an environment adjusted to the above temperature and relative humidity ranges, and if there is no change in mass for a certain period of time, it can be considered to have reached equilibrium with the environment. Alternatively, the equilibrium moisture content of the polarizing plate in an environment adjusted to the above temperature and relative humidity ranges can be calculated in advance, and the moisture content of the polarizing plate can be confirmed by comparing the pre-calculated equilibrium moisture content.

[0049] Methods for producing a polarizing plate having a moisture content equal to or greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 80% are not particularly limited, but include, for example, a method in which the polarizing plate is stored in an environment adjusted to the above temperature and relative humidity range for 10 minutes to 3 hours, or a method in which the polarizing plate is heated at 30°C to 90°C.

[0050] When manufacturing an image display device employing an interlayer filling configuration, an image display panel in which a polarizing plate is laminated on an image display cell may be stored in an environment adjusted to the above temperature and relative humidity range for 10 minutes to 3 hours or heated at 30°C to 90°C, and then a front panel may be attached thereto.

[0051] (Method of manufacturing a polarizing element) The method for producing a polarizing element is not particularly limited, but typical examples include a method in which a pre-wound PVA-based resin film is fed out and stretched, dyed, crosslinked, etc. (hereinafter referred to as "production method 1"), and a method in which a coating liquid containing a PVA-based resin is applied to a substrate film to form a PVA-based resin layer as a coating layer, and the resulting laminate is stretched (hereinafter referred to as "production method 2").

[0052] Production method 1 can be carried out through the steps of uniaxially stretching a PVA-based resin film, dyeing the PVA-based resin film with a dichroic dye such as iodine to adsorb the dichroic dye, treating the PVA-based resin film with the adsorbed dichroic dye with an aqueous boric acid solution, and washing the film with water after the treatment with the aqueous boric acid solution.

[0053] The swelling step is a treatment step in which the PVA-based resin film is immersed in a swelling bath. The swelling step not only removes dirt and blocking agents from the surface of the PVA-based resin film, but also suppresses uneven dyeing by swelling the PVA-based resin film. A medium mainly composed of water, distilled water, pure water, or the like, is typically used for the swelling bath. The swelling bath may contain appropriate additives such as surfactants and alcohols, according to conventional methods. Potassium iodide may be used in the swelling bath to control the potassium content of the polarizing element. 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.

[0054] The temperature of the swelling bath is preferably about 10°C to 60°C, more preferably about 15°C to 45°C, and even more preferably about 18°C ​​to 30°C. The immersion time in the swelling bath cannot be determined in general because the degree of swelling of the PVA resin film is affected by the temperature of the swelling bath, but is preferably about 5 seconds to 300 seconds, more preferably about 10 seconds to 200 seconds, and even more preferably about 20 seconds to 100 seconds. The swelling step may be carried out only once, or may be carried out multiple times as necessary.

[0055] The dyeing process is a treatment process in which a PVA-based resin film is immersed in a dye bath (iodine solution), which allows a dichroic dye such as iodine to be adsorbed and oriented in the PVA-based resin film. The iodine solution is typically an aqueous iodine solution, preferably containing iodine and an iodide as a solubilizing 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 preferred from the viewpoint of controlling the potassium content in the polarizing element.

[0056] The iodine concentration in the dye bath is preferably about 0.01% to 1% by mass, more preferably about 0.02% to 0.5% by mass. The iodide concentration in the dye bath is preferably about 0.01% to 10% by mass, more preferably about 0.05% to 5% by mass, and even more preferably about 0.1% to 3% by mass.

[0057] The temperature of the dye bath is preferably about 10°C to 50°C, more preferably about 15°C to 45°C, and even more preferably about 18°C ​​to 30°C. The immersion time in the dye bath cannot be determined in general because the degree of dyeing of the PVA resin film is affected by the temperature of the dye bath, but is preferably about 10 seconds to 300 seconds, and more preferably about 20 seconds to 240 seconds. The dyeing step may be carried out only once, or may be carried out multiple times as necessary.

[0058] The crosslinking step is a treatment step in which the PVA-based resin film dyed in the dyeing step is immersed in a treatment bath (crosslinking bath) containing a boron compound. The boron compound crosslinks the polyvinyl alcohol-based resin film, allowing iodine molecules or dye molecules to be adsorbed to the crosslinked structure. Examples of boron compounds include boric acid, borate salts, and borax. The crosslinking bath is generally an aqueous solution, but may also be a mixed solution of water and an organic solvent miscible with water. The crosslinking bath preferably contains potassium iodide in order to control the potassium content in the polarizing element.

[0059] The concentration of the boron compound in the crosslinking bath is preferably about 1% by mass to 15% by mass, more preferably about 1.5% by mass to 10% by mass, and even more preferably about 2% by mass to 5% by mass. When potassium iodide is used in the crosslinking bath, the concentration of potassium iodide in the crosslinking bath is preferably about 1% by mass to 15% by mass, more preferably about 1.5% by mass to 10% by mass, and even more preferably about 2% by mass to 5% by mass.

[0060] The temperature of the crosslinking bath is preferably about 20°C or higher and 70°C or lower, and more preferably about 30°C or higher and 60°C or lower. The immersion time in the crosslinking bath cannot be determined in general because the degree of crosslinking of the PVA resin film is affected by the temperature of the crosslinking bath, but is preferably about 5 seconds or higher and 300 seconds or lower, and more preferably about 10 seconds or higher and 200 seconds or lower. The crosslinking step may be carried out only once, or may be carried out multiple times as necessary.

[0061] The stretching step is a treatment step in which a PVA-based resin film is stretched at least in one direction to a predetermined stretching ratio. Generally, the PVA-based resin film is uniaxially stretched in the conveying direction (longitudinal direction). There are no particular limitations on the stretching method, and either wet stretching or dry stretching can be used. The stretching step may be carried out only once, or may be carried out multiple times as necessary. The stretching step may be carried out at any stage in the production of a polarizing element.

[0062] The treatment bath (stretching bath) used in the wet stretching method can typically contain a solvent such as water or a mixture of water and a water-miscible organic solvent. The stretching bath preferably contains potassium iodide to control the potassium content in the polarizing element. When potassium iodide is used in the stretching bath, the concentration of potassium iodide in the stretching bath is preferably from 1 to 15% by mass, more preferably from 2 to 10% by mass, and even more preferably from 3 to 6% by mass. The treatment bath (stretching bath) can contain a boron compound to prevent film breakage during stretching. When a boron compound is contained, the concentration of the boron compound in the stretching bath is preferably from 1 to 15% by mass, more preferably from 1.5 to 10% by mass, and even more preferably from 2 to 5% by mass.

[0063] The temperature of the stretching bath is preferably about 25°C to 80°C, more preferably about 40°C to 75°C, and even more preferably about 50°C to 70°C. The immersion time in the stretching bath cannot be determined in general because the degree of stretching of the PVA resin film is affected by the temperature of the stretching bath, but is preferably about 10 seconds to 800 seconds, and more preferably about 30 seconds to 500 seconds. The stretching treatment in the wet stretching method may be carried out together with one or more of the following treatment steps: swelling step, dyeing step, crosslinking step, and washing step.

[0064] Examples of the dry stretching method include a roll-to-roll stretching method, a heated roll stretching method, a compression stretching method, etc. The dry stretching method may be carried out together with a drying step.

[0065] The total stretching ratio (cumulative stretching ratio) applied to the polyvinyl alcohol-based resin film can be set appropriately depending on the purpose, but is preferably about 2 to 7 times, more preferably about 3 to 6.8 times, and even more preferably about 3.5 to 6.5 times.

[0066] The cleaning step is a treatment step in which the polyvinyl alcohol-based resin film is immersed in a cleaning bath, and foreign matter remaining on the surface of the polyvinyl alcohol-based resin film can be removed. The cleaning bath typically uses a medium whose main component is water, such as distilled water or pure water. To control the potassium content in the polarizing element, it is preferable to use potassium iodide in the cleaning bath. In this case, the concentration of potassium iodide in the cleaning bath is preferably about 1% by mass or more and 10% by mass or less, more preferably about 1.5% by mass or more and 4% by mass or less, and even more preferably about 1.8% by mass or more and 3.8% by mass or less.

[0067] The temperature of the cleaning bath is preferably about 5°C to 50°C, more preferably about 10°C to 40°C, and even more preferably about 15°C to 30°C. The immersion time in the cleaning bath cannot be determined in general because the degree of cleaning of the PVA resin film is affected by the temperature of the cleaning bath, but is preferably about 1 second to 100 seconds, more preferably about 2 seconds to 50 seconds, and even more preferably about 3 seconds to 20 seconds. The cleaning step may be carried out only once, or may be carried out multiple times as necessary.

[0068] The drying step is a step of drying the PVA resin film washed in the washing step to obtain a polarizing element. Drying can be carried out by any appropriate method, such as natural drying, air drying, or heat drying.

[0069] Production method 2 can be achieved by applying a coating liquid containing a PVA resin onto a substrate film, uniaxially stretching the resulting laminated film, dyeing the PVA resin layer of the uniaxially stretched laminated film with a dichroic dye to adsorb it and form a polarizing element, treating the film with the adsorbed dichroic dye with an aqueous boric acid solution, and washing with water after the treatment with the aqueous boric acid solution. The substrate film used to form the polarizing element may also be used as a protective layer for the polarizing element. If necessary, the substrate film may be peeled off and removed from the polarizing element.

[0070] <Transparent protective film> The first transparent protective film used in this embodiment is attached to one surface of the polarizing element via a first adhesive layer, and the second transparent protective film is attached to the other surface of the polarizing element via a second adhesive layer. Hereinafter, when the term is not limited to either the first transparent protective film or the second transparent protective film, it may be simply referred to as a "protective film."

[0071] The protective film may also have other optical functions and may be formed into a laminated structure in which multiple layers are laminated. A thin protective film is preferable from the viewpoint of optical properties, but if it is too thin, the strength decreases and processability becomes poor. The appropriate 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.

[0072] The protective film may be a cellulose acylate film, a film made of a polycarbonate resin, a film made of a cycloolefin resin such as norbornene, a (meth)acrylic polymer film, a polyester resin film such as polyethylene terephthalate, etc. When protective films are attached to both sides of a polarizing element using a water-based adhesive such as a PVA adhesive, it is preferable that the protective film on at least one side be either a cellulose acylate film or a (meth)acrylic polymer film in terms of moisture permeability, and of these, a cellulose acylate film is preferred.

[0073] At least one of the protective films may have a retardation function for the purpose of viewing angle compensation, etc. In this case, the protective film itself may have a retardation function, may have a separate retardation layer, or may be a combination of both. The film having a retardation function may be directly attached to the polarizing element via an adhesive, or may be attached via a pressure-sensitive adhesive or adhesive via another protective film attached to the polarizing element.

[0074] <Adhesive layer> An adhesive containing a first compound is used as a first adhesive constituting a first adhesive layer for bonding a first transparent protective film to a polarizing element. An adhesive containing a second compound is used as a second adhesive constituting a second adhesive layer for bonding a second transparent protective film to a polarizing element. Hereinafter, when not limited to either the first adhesive or the second adhesive, it may be simply referred to as an "adhesive." Furthermore, when not limited to either the first adhesive layer or the second adhesive layer, it may be simply referred to as an "adhesive layer." The adhesive may be a water-based adhesive, a solvent-based adhesive, an active energy ray-curable adhesive, or the like, but is preferably a water-based adhesive and preferably contains a PVA-based resin. By using a first adhesive containing a first compound and a second adhesive containing a second compound, it is possible to suppress a decrease in transmittance of the polarizing plate in a high-temperature environment.

[0075] The thickness of the adhesive when applied can be set to any value, for example, so that an adhesive layer having a desired thickness is obtained after curing or heating (drying). The thickness of the adhesive layer made 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, even more preferably 0.01 μm or more and 2 μm or less, and most preferably 0.01 μm or more and 1 μm or less.

[0076] The following description of the adhesive describes the preferred range for the case where the first compound and the second compound are not contained in the polarizing element during production of the polarizing element. When the first compound and the second compound are contained in the polarizing element, the following values ​​may be adjusted appropriately. Specific examples of the first compound and the second compound are as described above. During the process of forming an adhesive layer after the drying step when adhering the polarizing element and the protective film, it is acceptable if a portion of the first compound and a portion of the second compound migrate from the adhesive layer to the polarizing element, etc.

[0077] When the first adhesive is an aqueous adhesive containing a PVA-based resin, the content of the first compound is preferably 0.1 to 400 parts by mass, more preferably 1 to 200 parts by mass, and even more preferably 3 to 100 parts by mass, per 100 parts by mass of the PVA-based resin. If the content is less than 0.1 part by mass, the effect of suppressing polyenization of the polarizing element in a high-temperature environment may be insufficient. On the other hand, if the content exceeds 400 parts by mass, urea may precipitate after the polarizing plate is produced, resulting in an increase in haze.

[0078] When the second adhesive is an aqueous adhesive containing a PVA-based resin, the content of the second compound is preferably 0.1 to 400 parts by mass, more preferably 1 to 200 parts by mass, and even more preferably 3 to 100 parts by mass, per 100 parts by mass of the PVA-based resin. If the content is less than 0.1 part by mass, the effect of suppressing polyenization of the polarizing element in a high-temperature environment may be insufficient. On the other hand, if the content exceeds 400 parts by mass, the second compound may precipitate after the polarizing plate is produced.

[0079] (water-based adhesive) Any suitable aqueous adhesive can be used as the aqueous adhesive, but preferably an aqueous adhesive containing a PVA resin (PVA adhesive) is used. From the viewpoint of adhesiveness, the average polymerization degree of the PVA resin contained in the aqueous adhesive is preferably about 100 to 5500, more preferably 1000 to 4500. From the viewpoint of adhesiveness, the average saponification degree is preferably about 85 mol% to 100 mol%, more preferably 90 mol% to 100 mol%.

[0080] The PVA resin contained in the aqueous adhesive preferably contains an acetoacetyl group, because it has excellent adhesion between the PVA resin layer and the protective film and excellent durability. The acetoacetyl group-containing PVA resin can be obtained, for example, by reacting a PVA resin with diketene using any method. The degree of acetoacetyl group modification of the acetoacetyl group-containing PVA resin is typically 0.1 mol% or more, preferably about 0.1 mol% to 20 mol%. The resin concentration of the aqueous adhesive is preferably 0.1 mass% to 15 mass%, more preferably 0.5 mass% to 10 mass%.

[0081] The water-based adhesive may contain a crosslinking agent. Known crosslinking agents can be used. Examples of crosslinking agents include water-soluble epoxy compounds, dialdehydes, and isocyanates.

[0082] When the PVA-based resin is an acetoacetyl group-containing PVA-based resin, the crosslinking agent is preferably any one of glyoxal, glyoxylate, or methylolmelamine, more preferably any one of glyoxal or glyoxylate, and particularly preferably glyoxal.

[0083] The aqueous adhesive may also contain an organic solvent. Alcohols are preferred as organic solvents because they are miscible with water, and among alcohols, methanol or ethanol is more preferred. The methanol concentration 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. A methanol concentration of 10% by mass or more can more easily suppress polyenation of the PVA resin in a high-temperature environment. Furthermore, a methanol content of 70% by mass or less can suppress deterioration of color. Some urea derivatives have low solubility in water, but sufficient solubility in alcohol. In this case, one preferred embodiment is to dissolve the first compound in alcohol to prepare an alcohol solution of the first compound, and then add the alcohol solution of the first compound to the PVA aqueous solution to prepare the first adhesive.

[0084] (Active energy ray curing adhesive) The active energy ray-curable adhesive is an adhesive that cures upon irradiation with active energy rays such as ultraviolet rays, and examples thereof include adhesives containing a polymerizable compound and a photopolymerization initiator, adhesives containing a photoreactive resin, and adhesives containing a binder resin and a photoreactive crosslinking agent. Examples of the polymerizable compound 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 the photopolymerization initiator include compounds containing substances that generate active species such as neutral radicals, anion radicals, and cation radicals upon irradiation with active energy rays such as ultraviolet rays.

[0085] <Urea-based compound-containing layer> The first compound and the second compound are not limited to being contained in the adhesive layer as described above, and may be contained in layers other than the adhesive layer from the viewpoint of improving the high-temperature durability of the polarizing plate. A cured layer may be laminated on the first compound and the second compound from the viewpoint of improving the physical strength of the polarizing plate.

[0086] In this embodiment, such a cured layer may contain a first compound and a second compound to form a layer containing a urea-based compound. Typically, such a cured layer is formed from a curable composition containing an organic solvent. However, paragraphs

[0020] to

[0042] of JP 2017-075986 A describe a method for forming such a cured layer from an aqueous solution of an active energy ray-curable polymer composition. Water-soluble first and second compounds may be contained in such a composition.

[0087] The urea compound-containing layer preferably contains at least one first compound, at least one second compound, and a binder, such as a polymer binder, a thermosetting resin binder, or an active energy ray-curable resin binder, and any of these binders can be preferably used.

[0088] The thickness of the urea compound-containing 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.

[0089] [Polarizing plate manufacturing method] The manufacturing method of a polarizing plate of this embodiment includes a lamination step. The manufacturing method of a polarizing plate of this embodiment may also include a moisture content adjusting step. In the moisture content adjusting step, when manufacturing a polarizing plate having feature (a), the moisture content of the polarizing element is adjusted so that the moisture content of the polarizing element is equal to or greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 80%. The moisture content of the polarizing element can be adjusted according to the description of the moisture content of polarizing elements above. In the moisture content adjusting step, when manufacturing a polarizing plate having feature (b), the moisture content of the polarizing element is adjusted so that the moisture content of the polarizing element is equal to or greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 80%. The moisture content of the polarizing plate can be adjusted according to the description of the moisture content of polarizing plates above. In the lamination step, the polarizing element and the transparent protective film are laminated via the adhesive layer. In the lamination step, for example, a polarizing element that has not been treated to contain the first compound and the second compound is bonded to a transparent protective film using an adhesive containing the first compound and the second compound. The order of the moisture content adjusting step and the lamination step is not limited, and the moisture content adjusting step and the lamination step may be performed in parallel.

[0090] [Configuration of image display device] The polarizing plate of this embodiment is used in various image display devices such as liquid crystal display devices and organic electroluminescence (EL) display devices. When an image display device has an interlayer filling configuration in which both surfaces 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 is likely to decrease in a high-temperature environment. Even with an interlayer filling configuration, an image display device using the polarizing plate of this embodiment can suppress a decrease in the transmittance of the polarizing plate in a high-temperature environment. An example of an image display device includes an image display cell, a first adhesive layer laminated on the viewing-side surface of the image display cell, and a polarizing plate laminated on the viewing-side surface of the first adhesive layer. Such an image display device may further include a second adhesive layer laminated on the viewing-side surface of the polarizing plate and a transparent member laminated on the surface of the second adhesive layer. In particular, the polarizing plate of this embodiment is suitable for use in an image display device having an interlayer filling configuration in which a transparent member is disposed on the viewing side of the image display device, the polarizing plate and the image display cell are bonded together by the first adhesive layer, and the polarizing plate and the transparent member are bonded together by the second adhesive layer. In this specification, either or both of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer may be simply referred to as the “pressure-sensitive adhesive layer.” Note that the member used to bond the polarizing plate to the image display cell and the member used to bond the polarizing plate to the transparent member are not limited to a pressure-sensitive adhesive layer and may be an adhesive layer.

[0091] <Image display cell> Examples of image display cells include liquid crystal cells and organic EL cells. The liquid crystal cell may be a reflective liquid crystal cell that uses external light, a transmissive liquid crystal cell that uses light from a light source such as a backlight, or a semi-transmissive semi-reflective liquid crystal cell that uses both external light and light from the light source. When the liquid crystal cell uses light from a light source, the image display device (liquid crystal display device) has a polarizing plate disposed on the opposite side of the image display cell (liquid crystal cell) from the viewing side, and further has a light source disposed thereon. The polarizing plate on the light source side and the liquid crystal cell are preferably bonded together via an appropriate adhesive layer. The liquid crystal cell may be driven in any type of mode, such as VA mode, IPS mode, TN mode, STN mode, or bend orientation (π type).

[0092] As the organic EL cell, a light-emitting body (organic electroluminescence light-emitting body) formed by sequentially laminating a transparent electrode, an organic light-emitting layer, and a metal electrode on a transparent substrate is preferably used. The organic light-emitting layer is a laminate of various organic thin films, and various layer configurations can be adopted, such as a laminate of a hole-injection layer made of a triphenylamine derivative or the like and a light-emitting layer made of a fluorescent organic solid such as anthracene, a laminate of such a light-emitting layer and an electron-injection layer made of a perylene derivative or the like, or a laminate of a hole-injection layer, a light-emitting layer, and an electron-injection layer.

[0093] <Laminating the image display cell and polarizing plate> A pressure-sensitive adhesive layer (pressure-sensitive adhesive sheet) is preferably used to bond the image display cell to the polarizing plate. Among these, a method of bonding a polarizing plate with a pressure-sensitive adhesive layer, in which a pressure-sensitive adhesive layer is attached to one side of the polarizing plate, to the image display cell is preferred from the viewpoint of workability, etc. The pressure-sensitive adhesive layer can be attached to the polarizing plate by any suitable method. Examples of such methods include a method in which a pressure-sensitive adhesive solution of about 10% by mass to 40% by mass is prepared by dissolving or dispersing a base polymer or a composition thereof in a solvent consisting of a single or mixture of suitable solvents such as toluene or ethyl acetate, and then applying the solution directly to the polarizing plate by a suitable spreading method such as a casting method or a coating method, and a method in which a pressure-sensitive adhesive layer is formed on a separator and then transferred to the polarizing plate.

[0094] <Adhesive layer> The pressure-sensitive adhesive layer may consist of one layer or two or more layers, but preferably consists of one layer. The pressure-sensitive adhesive layer can be composed of a pressure-sensitive adhesive composition whose main component is a (meth)acrylic resin, a rubber resin, a urethane resin, an ester resin, a silicone resin, or a polyvinyl ether resin. Among these, a pressure-sensitive adhesive composition whose base polymer is a (meth)acrylic resin, which is excellent in transparency, weather resistance, heat resistance, etc., is preferred. The pressure-sensitive adhesive composition may be of an active energy ray-curable type or a thermosetting type.

[0095] The (meth)acrylic resin (base polymer) used in the pressure-sensitive adhesive composition is preferably a polymer or copolymer containing one or more (meth)acrylic acid esters as monomers, such as butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. A polar monomer is preferably copolymerized into the base polymer. Examples of polar monomers include monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, or an epoxy group, such as a (meth)acrylic acid compound, a 2-hydroxypropyl (meth)acrylate compound, a hydroxyethyl (meth)acrylate compound, a (meth)acrylamide compound, an N,N-dimethylaminoethyl (meth)acrylate compound, or a glycidyl (meth)acrylate compound.

[0096] The pressure-sensitive adhesive composition may contain only the base polymer, but usually further contains a crosslinking agent. Examples of crosslinking agents include divalent or higher metal ions that form metal carboxylates with carboxyl groups, polyamine compounds that form amide bonds with carboxyl groups, polyepoxy compounds or polyols that form ester bonds with carboxyl groups, and polyisocyanate compounds that form amide bonds with carboxyl groups. Among these, polyisocyanate compounds are preferred.

[0097] The active energy ray-curable pressure-sensitive adhesive composition has the property of being cured by irradiation with active energy rays such as ultraviolet rays or electron beams, and has adhesive properties even before irradiation with active energy rays, allowing it to adhere to an adherend such as a film, and has the property of being cured by irradiation with active energy rays, allowing the adhesive strength to be adjusted. The active energy ray-curable pressure-sensitive adhesive composition is preferably ultraviolet-curable. The active energy ray-curable pressure-sensitive adhesive composition further contains an active energy ray-polymerizable compound in addition to a base polymer and a crosslinking agent. If necessary, it may contain a photopolymerization initiator, a photosensitizer, etc.

[0098] The pressure-sensitive adhesive composition may contain additives such as fine particles for imparting light scattering properties, beads (resin beads, glass beads, etc.), glass fibers, resins other than the base polymer, tackifiers, fillers (metal powders and other inorganic powders, etc.), antioxidants, UV absorbers, dyes, pigments, colorants, defoamers, corrosion inhibitors, and photopolymerization initiators.

[0099] The pressure-sensitive adhesive layer can be formed by applying an organic solvent diluted solution of the pressure-sensitive adhesive composition to the surface of a substrate film, an image display cell, or a polarizing plate, and drying the applied solution. The substrate film is generally a thermoplastic resin film, and a typical example thereof is a release-treated separate film. The separate film can be, for example, a film made of a resin such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, or polyacrylate, and the surface on which the pressure-sensitive adhesive layer is to be formed is subjected to a release treatment such as silicone treatment.

[0100] The pressure-sensitive adhesive composition may be directly applied to the release-treated surface of a separate film to form a pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer with the separate film may then be laminated on the surface of a polarizer.The pressure-sensitive adhesive composition may be directly applied to the surface of a polarizing plate to form a pressure-sensitive adhesive layer, and a separate film may then be laminated on the outer surface of the pressure-sensitive adhesive layer.

[0101] When providing the adhesive layer on the surface of the polarizing plate, it is preferable to subject the bonding surface of the polarizing plate and / or the bonding surface of the adhesive layer to a surface activation treatment such as plasma treatment or corona treatment, and it is more preferable to subject the layer to corona treatment.

[0102] Alternatively, a pressure-sensitive adhesive sheet may be prepared by applying a pressure-sensitive adhesive composition to a second separate film to form a pressure-sensitive adhesive layer, laminating a separate film on the formed pressure-sensitive adhesive layer, peeling the second separate film from the pressure-sensitive adhesive sheet, and laminating the resulting pressure-sensitive adhesive layer with the separate film on a polarizing plate. The second separate film used has weaker adhesion to the pressure-sensitive adhesive layer than the separate film and is therefore easier to peel off.

[0103] The thickness of the pressure-sensitive adhesive layer is not particularly limited, but is preferably, for example, from 1 μm to 100 μm, more preferably from 3 μm to 50 μm, and may be 20 μm or more.

[0104] <Transparent materials> Examples of transparent members arranged on the viewing side of an image display device include a transparent plate (window layer) and a touch panel. A transparent plate having appropriate mechanical strength and thickness is used as the transparent plate. Examples of such transparent plates include transparent resin plates such as polyimide resin, acrylic resin, and polycarbonate resin, and glass plates. A functional layer such as an anti-reflection layer may be laminated on the viewing side of the transparent plate. Furthermore, when the transparent plate is a transparent resin plate, a hard coat layer may be laminated to increase physical strength, or a low-moisture permeability layer may be laminated to reduce moisture permeability. Examples of touch panels include various touch panels such as resistive, capacitive, optical, and ultrasonic touch panels, as well as glass or transparent resin plates equipped with touch sensor functions. When a capacitive touch panel is used as the transparent member, it is preferable to provide a transparent plate made of glass or a transparent resin plate on the viewing side of the touch panel.

[0105] <Bonding polarizing plate and transparent material> A pressure-sensitive adhesive or an active energy ray-curable adhesive is preferably used to bond the polarizing plate and the transparent member. When a pressure-sensitive adhesive is used, the pressure-sensitive adhesive can be applied by an appropriate method. Specific application methods include, for example, the application method of the pressure-sensitive adhesive layer used in bonding the image display cell and the polarizing plate described above.

[0106] When an active energy ray-curable adhesive is used, a method is preferably used in which a dam material is provided around the periphery of the image display panel to prevent the adhesive solution from spreading before curing, a transparent member is placed on the dam material, and the adhesive solution is then poured in. After the adhesive solution is poured, alignment and degassing are performed as necessary, and then active energy rays are irradiated to cause curing. [Example]

[0107] The present invention will be specifically described below based on examples. The materials, reagents, amounts and proportions of substances, procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the present invention is not limited to or by the following examples.

[0108] <Fabrication of Polarizing Element A> A 40 μm-thick PVA film made of PVA with an average degree of polymerization of approximately 2400 and a saponification degree of 99.9 mol% or greater was dry-stretched uniaxially approximately 5 times. While still under tension, it was immersed in pure water at 60°C for 1 minute, then immersed in an aqueous solution of iodine / potassium iodide / water in a weight ratio of 0.05 / 5 / 100 at 28°C for 60 seconds. It was then immersed in an aqueous solution of potassium iodide / boric acid / water in a weight ratio of 8.5 / 8.5 / 100 at 72°C for 300 seconds. It was then washed in pure water at 26°C for 20 seconds and dried at 65°C to obtain a 15 μm-thick polarizing element A in which iodine was adsorbed and aligned in the PVA. The thickness of the polarizing element was measured using a Nikon MH-15M digital micrometer.

[0109] <Preparation of adhesive> (Preparation of PVA solution A for adhesive) 50 g of a modified PVA resin containing acetoacetyl groups ("Gohsenex Z-410" manufactured by Mitsubishi Chemical Corporation) was dissolved in 950 g of pure water, heated at 90°C for 2 hours, and then cooled to room temperature to obtain a PVA solution for adhesive (hereinafter referred to as "PVA solution A").

[0110] (Preparation of Adhesives 1a, 1b, 1c, 2a, 2b, 2c, and 3) Each adhesive was prepared by blending PVA solution A, urea as the first compound, 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (hereinafter also referred to as "TEMPOL") as the second compound, and pure water so that PVA solution A was 3.0 mass % and the contents of the first compound and second compound were as shown in Table 1.

[0111] [Table 1]

[0112] <Preparing transparent protective film A> A commercially available cellulose acylate film TD40 (manufactured by Fujifilm Corporation, film thickness 40 μm) was immersed in a 1.5 mol / L NaOH aqueous solution (saponification solution) maintained at 55°C for 2 minutes, and then washed with water. The film was then immersed in a 0.05 mol / L sulfuric acid aqueous solution at 25°C for 30 seconds, and then passed through a water washing bath under running water for 30 seconds to neutralize the film. The film was then drained three times with an air knife to remove the water, and then allowed to dry in a drying zone at 70°C for 15 seconds to produce a saponified film, designated Transparent Protective Film A.

[0113] <Preparation of Polarizing Plates 1 to 8> Transparent protective film A was laminated to both sides of polarizing element A via adhesive 3 using a roll laminator, and then dried at 80°C for 5 minutes to obtain polarizing plate 1. The adhesive layer was adjusted so that the thickness of each side after drying was 50 nm. The adhesive layer used to laminate transparent protective film A to one side of polarizing element A is referred to as the first adhesive layer, and the adhesive layer used to laminate transparent protective film A to the other side is referred to as the second adhesive layer.

[0114] In polarizing plate 1, adhesive 3 used on both sides was changed to each adhesive listed in Table 2, and polarizing plates 2 to 8 were obtained.

[0115] (Adjusting the moisture content of polarizing plates (polarizing elements)) The polarizing plates 1 to 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 measured using the Karl Fischer method after 66, 69, and 72 hours of storage. The moisture content values ​​remained unchanged under all humidity conditions. Therefore, the moisture content of polarizing plates 1 to 8 can be considered to be the same as the equilibrium moisture content in the 72-hour storage environment used in this experimental example. When the moisture content of a polarizing plate reaches equilibrium in a certain storage environment, the moisture content of the polarizing elements in the polarizing plate can also be considered to have reached equilibrium in that storage environment. Furthermore, when the moisture content of the polarizing elements in a polarizing plate reaches equilibrium in a certain storage environment, the moisture content of the polarizing plate can also be considered to have reached equilibrium in that storage environment.

[0116] <Optical laminate 1~8> Optical laminates 1 to 8 were produced using any one of polarizing plates 1 to 8 shown in Table 2. Optical laminates 1 to 8 were stored for 72 hours at a temperature of 20°C and a relative humidity of 30%, 45%, or 55% so that the moisture content of the polarizing plate (polarizing element) used would be the equilibrium moisture content in the environment shown in Table 2, and were subjected to the following high-temperature durability evaluation at each moisture content.

[0117] <High temperature durability evaluation> (Preparation of evaluation samples) For the optical laminates 1 to 8 at each moisture content, an acrylic adhesive (manufactured by Lintec Corporation, product number: #7) was applied to both sides, and the laminates were cut into pieces measuring 50 mm x 100 mm so that the absorption axis was parallel to the long side. Evaluation samples were then prepared by laminating alkali-free glass ("EAGLE XG" manufactured by Corning Incorporated) to the adhesive surface of each piece. In order to evaluate the cross-over of the evaluation sample, an acrylic adhesive (manufactured by Lintec Corporation, product number: #7) was applied to only one side of the polarizing plate 1 in order to create a cross-Nicol state by overlapping it with the evaluation sample.The polarizing plate was then cut to a size of 50 mm x 100 mm so that the absorption axis was parallel to the short side, and alkali-free glass ("EAGLE XG" manufactured by Corning Incorporated) was attached to the adhesive surface to produce an optical laminate R to be used for cross-over evaluation.

[0118] The evaluation samples of the optical laminates 1 to 8 were subjected to a temperature of 50°C and a pressure of 5 kgf / cm 2 (490.3 kPa) for 1 hour, and then left to stand for 24 hours in an environment at a temperature of 23°C and a relative humidity of 55%. Thereafter, the evaluation samples of optical laminates 1 to 8 in each moisture content state were evaluated for high-temperature durability as follows.

[0119] (i) Evaluation sample of a polarizing plate or polarizing element with an equilibrium moisture content at a temperature of 20°C and a relative humidity of 55% (Single unit transmittance evaluation (105℃)) For evaluation samples of Optical Laminates 1 to 8, in which the moisture content of the polarizing plate or polarizing element was the equilibrium moisture content at a temperature of 20°C and a relative humidity of 55%, the transmittance was measured (initial value), and the samples were stored in a heated environment at a temperature of 105°C, with the transmittance measured every 24 hours for 48 to 96 hours. Evaluation was performed according to the following criteria, based on the time at which the transmittance had decreased by 5% or more from the initial value. The results are shown in Table 2. Transmittance reduction of 5% or less after 96 hours: A1 Transmittance reduction of 5% or more after 72 to 96 hours: B1 Transmittance reduction of 5% or more after 48 to 72 hours: C1 Transmittance decreases by 5% or more after 48 hours: D1

[0120] (Cross-out evaluation) An evaluation sample was prepared after measuring the single-piece transmittance after 96 hours in the above-described evaluation of single-piece transmittance. The optical laminate R for crossed-Nicol evaluation, which had not been placed in a heated environment, and the evaluation sample were arranged in a crossed-Nicol relationship and placed on a backlight. The surrounding area was shielded from light, and cross-missing was visually observed and evaluated on a four-point scale according to the following criteria. The results are shown in Table 2. Evaluation samples with a single-piece transmittance evaluation other than A1 were excluded from the evaluation of cross-missing because they had coloration due to polyenation. No cross-cuts are visible: A1 Almost no cross-cuts are visible: B1 Slight cross-cut defects: C1 Clearly missing crosses: D1

[0121] (ii) An evaluation sample in which the moisture content of a polarizing plate or polarizing element is the equilibrium moisture content at a temperature of 20°C and a relative humidity of 45%. (Single unit transmittance evaluation (105℃)) For evaluation samples of Optical Laminates 1 to 8, in which the moisture content of the polarizing plate or polarizing element was the equilibrium moisture content at a temperature of 20°C and a relative humidity of 45%, the transmittance was measured (initial value), and the samples were stored in a heated environment at a temperature of 105°C, with the transmittance measured every 50 hours for 100 to 200 hours. Evaluation was performed according to the following criteria, based on the time at which the transmittance had decreased by 5% or more from the initial value. The results are shown in Table 2. Transmittance reduction of 5% or less after 200 hours: A2 Transmittance reduction of 5% or more after 150 to 200 hours: B2 Transmittance reduction of 5% or more after 100 to 150 hours: C2 Transmittance reduction of 5% or more after 100 hours: D2

[0122] (Cross-out evaluation) An evaluation sample was prepared after measuring the single-piece transmittance after 200 hours in the above-described evaluation of single-piece transmittance. The optical laminate R for crossed-Nicol evaluation, which had not been placed in a heated environment, and the evaluation sample were arranged in a crossed-Nicol relationship and placed on a backlight. The surrounding area was shielded from light, and cross-missing was visually observed and rated on a four-point scale according to the following criteria. The results are shown in Table 2. Evaluation samples with a single-piece transmittance rating other than A2 were excluded from the evaluation of cross-missing because they had coloration due to polyenation. No cross-linking is visible: A2 Almost no cross-cuts are visible: B2 Slight cross-cutting: C2 Clearly missing crosses: D2

[0123] (iii) An evaluation sample in which the moisture content of a polarizing plate or polarizing element is the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%. (Single unit transmittance evaluation (105℃)) For evaluation samples of Optical Laminates 1 to 8, whose polarizing plates or polarizing elements had an equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, the transmittance was measured (initial value), and the samples were stored in a heated environment at a temperature of 105°C, with the transmittance measured every 150 hours for 500 to 800 hours. Evaluation was performed according to the following criteria, based on the time at which the transmittance had decreased by 5% or more from the initial value. The results are shown in Table 2. Transmittance reduction of 5% or less after 800 hours: A3 Transmittance reduction of 5% or more after 650 to 800 hours: B3 Transmittance reduction of 5% or more after 500 to 650 hours: C3 Transmittance reduction of 5% or more after 500 hours: D3

[0124] (Cross-out evaluation) An evaluation sample was prepared after measuring the single-piece transmittance after 800 hours in the above-described evaluation of single-piece transmittance. The optical laminate R for crossed Nicols evaluation, which had not been placed in a heated environment, and the evaluation sample were arranged in a crossed Nicols relationship and placed on a backlight. The surrounding area was shielded from light, and cross-missing was visually observed and rated on a four-point scale according to the following criteria. The results are shown in Table 2. Evaluation samples with a single-piece transmittance rating other than A3 were excluded from the evaluation of cross-missing because they had coloration due to polyenation. No cross-cuts are visible: A3 Almost no cross-cuts are visible: B3 Slight cross-cutting: C3 Clear crossover: D3

[0125] [Table 2]

[0126] Polarizing plates (optical laminates 6 to 8) in which a polarizing element and a first transparent protective film are bonded together with a first adhesive containing a first compound, and a polarizing element and a second transparent protective film are bonded together with a second adhesive containing a second compound, are less likely to experience a decrease in transmittance even when exposed to a high-temperature environment of 105°C, regardless of the moisture content of the polarizing plate and polarizing element, and also have excellent evaluations of cross-stripping, indicating that they have excellent high-temperature durability.

Claims

1. A polarizing plate comprising: a polarizing element having a polyvinyl alcohol-based resin layer in which a dichroic dye is adsorbed and oriented; a first transparent protective film laminated on one surface of the polarizing element; and a second transparent protective film laminated on the other surface of the polarizing element, the polarizing element and the first transparent protective film are bonded together by a first adhesive layer formed from a first adhesive containing a first compound but not a second compound; the polarizing element and the second transparent protective film are bonded together by a second adhesive layer formed from a second adhesive containing a second compound but not the first compound; the first compound is urea; the second compound is a compound having a nitroxy radical or a nitroxide group, the polarizing element includes the first compound and the second compound, The polarizing plate, wherein the first adhesive and the second adhesive contain a polyvinyl alcohol-based resin.

2. 2. The polarizing plate according to claim 1, wherein the second compound is an N-oxyl compound.

3. 3 . The polarizing plate according to claim 1 , wherein the content of the first compound in the first adhesive is 0.1 parts by mass or more and 400 parts by mass or less with respect to 100 parts by mass of the polyvinyl alcohol-based resin.

4. The polarizing plate according to any one of claims 1 to 3, wherein the content of the second compound in the second adhesive is 0.1 parts by mass or more and 400 parts by mass or less with respect to 100 parts by mass of the polyvinyl alcohol-based resin.

5. 5. The polarizing plate according to claim 1, wherein the first adhesive layer and the second adhesive layer have a thickness of 0.01 μm or more and 7 μm or less.

6. The polarizing plate is used in an image display device, 6. The polarizing plate according to claim 1, wherein in the image display device, solid layers are provided on both sides of the polarizing plate in contact with each other.

7. An image display device comprising: an image display cell; a first pressure-sensitive adhesive layer laminated on a viewing-side surface of the image display cell; and the polarizing plate according to any one of claims 1 to 6 laminated on the viewing-side surface of the first pressure-sensitive adhesive layer.

8. The image display device according to claim 7 , further comprising: a second adhesive layer laminated on the viewer-side surface of the polarizing plate; and a transparent member laminated on the viewer-side surface of the second adhesive layer.

9. 9. The image display device according to claim 8, wherein the transparent member is a glass plate or a transparent resin plate.

10. The image display device according to claim 8 , wherein the transparent member is a touch panel.

11. A method for producing a polarizing plate having 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 surface of the polarizing element, and a second transparent protective film laminated on the other surface of the polarizing element, a lamination step of bonding the polarizing element and the first transparent protective film with a first adhesive containing a first compound but not a second compound; a lamination step of bonding the polarizing element and the second transparent protective film with a second adhesive containing a second compound but not the first compound, the first compound is urea; the second compound is a compound having a nitroxy radical or a nitroxide group, In the polarizing plate, the polarizing element includes the first compound and the second compound, The manufacturing method, wherein the first adhesive and the second adhesive contain a polyvinyl alcohol-based resin.

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