Polarizing plate and image display device

Abstract

The present application provides 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 to a polyvinyl alcohol-based resin layer and the dichroic dye is oriented, and a transparent protective film laminated to at least one face of the polarizing element, the polarizing element and the transparent protective film are bonded by an adhesive layer formed by an adhesive containing a urea-based compound and a dicarboxylic acid, the urea-based compound is at least one selected from urea, a urea derivative, thiourea, and a thiourea derivative, and the water content of the polarizing element is equal to or higher than the equilibrium water content at 20°C and 30% RH and equal to or lower than the equilibrium water content at 20°C and 50% RH.

Description

TECHNICAL FIELD

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

[0002] Liquid crystal display devices (LCD) are widely used not only for liquid crystal televisions but also for personal computers, mobile devices such as mobile phones, and car-mounted uses such as car navigation systems. Generally, a liquid crystal display device has a liquid crystal panel in which polarizing plates are attached to both sides of a liquid crystal cell with an adhesive, and displays by controlling light from a backlight with the liquid crystal panel. In recent years, organic EL display devices are also widely used in televisions, mobile devices such as mobile phones, and car-mounted uses such as car navigation systems, as well as liquid crystal display devices. In an organic EL display device, in order to suppress reflection of external light at a metal electrode (cathode) and observation in a mirror-like manner, a circularly polarizing plate (a laminate including a polarizing element and a λ / 4 plate) is sometimes disposed on the visible side surface of an image display panel.

[0003] As described above, polarizing plates are increasingly used as components of image display devices such as liquid crystal display devices and organic EL display devices in cars. The polarizing plates used in image display devices for car-mounted uses are exposed to a high-temperature environment more than those for television and mobile device uses, and thus are required to have less change in characteristics at higher temperatures (high-temperature durability).

[0004] On the other hand, in order to prevent breakage of an image display panel due to impact from the outside surface and the like, the configuration in which a front panel (also referred to as a "window layer") such as a transparent resin plate or a glass plate is provided on the visible side of the image display panel is increasing. In an image display device provided with a touch panel, the configuration in which a touch panel is provided on the visible side of the image display panel, and further a front panel is provided on the visible side of the touch panel is widely adopted.

[0005] In such a configuration, if an air layer exists between the image display panel and the transparent member such as the front panel or the touch panel, reflection glare of external light due to reflection of light at the interface of the air layer tends to decrease the visibility of the image. Thus, an action of adopting a configuration in which the space between the polarizing plate disposed on the visible side surface of the image display panel and the transparent member is filled with a layer other than an air layer, and generally a solid layer (hereinafter sometimes referred to as an "interlayer filler") is being taken (hereinafter sometimes referred to as an "interlayer filling configuration"). The interlayer filler is preferably a material having a refractive index close to that of the polarizing plate or the transparent member. As the interlayer filler, an adhesive or a UV-curable adhesive is used for the purpose of suppressing decrease in visibility due to reflection at the interface and fixing the adhesion between the members (for example, see Patent Document 1).

[0006] The interlayer filling configuration is being increasingly adopted in mobile device applications such as mobile phones that are often used outdoors. In addition, due to the increasing demand for visibility in recent years, the interlayer filling configuration in which a front transparent plate is disposed on the surface of an image display panel and the panel and the front transparent plate are filled with an adhesive layer or the like is also being studied in car-mounted applications such as navigation devices.

[0007] However, in the case of adopting such a configuration, it has been reported that the transmittance of the polarizing plate significantly decreases in a high-temperature environment. In Patent Document 2, as a countermeasure to this problem, a method is proposed in which the amount of moisture per unit area of the polarizing plate is set to be equal to or less than a prescribed amount, and the saturated water absorption amount of the transparent protective film adjacent to the polarizing element is set to be equal to or less than a prescribed amount, thereby suppressing the decrease in transmittance.

[0008] Prior Art Documents

[0009] Patent Documents

[0010] Patent Document 1: Japanese Patent Application Publication No. H11-174417

[0011] Patent Document 2: Japanese Patent Application Publication No. 2014-102353 SUMMARY

[0012] Problems to be Solved by the Invention

[0013] However, even in such a polarizing plate, the suppression effect of the decrease in durability in a high-temperature environment is not sufficient. An object of the present application is to provide a novel polarizing plate capable of suppressing a decrease in transmittance in a high-temperature environment, and an image display device using the same.

[0014] Means for Solving the Problems

[0015] The present application provides the following exemplified polarizing plate and image display device.

[0016] [1] A polarizing plate comprising: a polarizing element in which a dichroic dye is adsorbed to a polyvinyl alcohol-based resin layer and the dichroic dye is oriented, and a transparent protective film laminated to at least one face of the polarizing element,

[0017] the polarizing element and the transparent protective film are attached by an adhesive layer formed from an adhesive containing a urea-based compound and a dicarboxylic acid,

[0018] the urea-based compound is at least one selected from the group consisting of urea, a urea derivative, thiourea, and a thiourea derivative,

[0019] the water content of the polarizing element is equal to or more than the equilibrium water content at a temperature of 20°C and a relative humidity of 30% and equal to or less than the equilibrium water content at a temperature of 20°C and a relative humidity of 50%.

[0020] [2] A polarizing plate having: a polarizing element in which a dichroic dye is adsorbed to a polyvinyl alcohol-based resin layer and the dichroic dye is oriented, and a transparent protective film laminated to at least one face of the polarizing element,

[0021] The polarizing element and the transparent protective film are adhered by an adhesive layer formed by an adhesive containing a urea-based compound and a dicarboxylic acid,

[0022] The urea-based compound is at least one selected from the group consisting of urea, a urea derivative, thiourea, and a thiourea derivative,

[0023] The polarizing plate has a water content rate of 20°C and 30% RH or more and 20°C and 50% RH or less.

[0024] [3] The polarizing plate according to [1] or [2], wherein the adhesive contains at least one urea-based compound selected from the group consisting of a urea derivative and a thiourea derivative.

[0025] [4] The polarizing plate according to any one of [1] to [3], wherein the adhesive contains a polyvinyl alcohol-based resin.

[0026] [5] The polarizing plate according to [4], wherein the content of the urea-based compound in the 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.

[0027] [6] The polarizing plate according to [4] or [5], wherein the content of the dicarboxylic acid in the adhesive is 1 part by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the polyvinyl alcohol-based resin.

[0028] [7] The polarizing plate according to any one of [1] to [6], wherein the thickness of the adhesive layer is 0.01 μm or more and 7 μm or less.

[0029] [8] The polarizing plate according to any one of [1] to [7], wherein the dicarboxylic acid is at least one of maleic acid and phthalic acid.

[0030] [9] The polarizing plate according to any one of [1] to [8], wherein the polarizing plate is used for an image display device, and in the image display device, a solid layer is provided in contact with both faces of the polarizing plate.

[0031]

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

[0032]

[11] The image display device described in

[10] , further having: a second adhesive layer laminated on a visible side surface of the polarizing plate, and a transparent member laminated on a visible side surface of the second adhesive layer.

[0033]

[12] The image display device described in

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

[0034]

[13] The image display device described in

[11] , wherein the transparent member is a touch panel.

[0035] Effects of the Invention

[0036] According to the present application, a polarizing plate having improved high-temperature durability and in which a decrease in transmittance due to high temperature is suppressed even when used in an image display device in which an interlayer filling structure is employed can be provided. Further, by using the polarizing plate of the present application, an image display device in which a decrease in transmittance under a high-temperature environment is suppressed can be provided. DETAILED DESCRIPTION

[0037] Hereinafter, embodiments of the present application will be described, but the present application is not limited to the following embodiments.

[0038] [Polarizing plate]

[0039] The polarizing plate of the present embodiment has: a polarizing element in which a dichroic dye is adsorbed to and oriented in a layer containing a polyvinyl alcohol-based resin, and a transparent protective film. The polarizing element and the transparent protective film are bonded via an adhesive layer formed from an adhesive containing a urea-based compound and a dicarboxylic acid. The polarizing plate of the present embodiment has at least one of the following (a) and (b).

[0040] (a) The moisture content of the polarizing element is equal to or higher than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and equal to or lower than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%.

[0041] (b) The moisture content of the polarizing plate is equal to or higher than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and equal to or lower than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%.

[0042] As for conventional polarizing plates with excellent high-temperature durability, for example, there are known polarizing plates that can suppress the decrease in transmittance even after being placed at 95°C for 1000 hours. However, even with such polarizing plates, when used in an interlayer filling configuration, a significant decrease in transmittance and polarization degree is observed in the central part of the polarizing plate after being placed at 95°C for 200 hours. When an image display device using an interlayer filling configuration is exposed to a high-temperature environment, it is believed that a significant decrease in the transmittance and polarization degree of the polarizing plate under high-temperature conditions is particularly likely to occur. This interlayer filling configuration is a configuration in which one side of the polarizing plate is bonded to the image display unit, and the other side is bonded to transparent components such as a touch panel or front panel.

[0043] The polarizing plate, whose transmittance is significantly reduced due to its interlayer filling structure, showed poor performance in Raman spectrometry at 1100 cm⁻¹. -1 Nearby (from =CC= key) and 1500cm -1 The presence of a peak near the -C=C- bond suggests the formation of a polyene structure (-C=C)n-. It is speculated that the polyene structure is a result of the polyene formation of the polyvinyl alcohol constituting the polarization element due to dehydration (Patent Document 2,

[0012] paragraph).

[0044] The polarizing plate of the present invention can further improve high-temperature durability. When the polarizing plate of the present invention is incorporated into an image display device composed of interlayer filler, it can suppress the decrease in transmittance and polarization degree even when exposed to a high-temperature environment of 105°C.

[0045] <Polarization element>

[0046] Well-known polarizing elements can be used as polarizing elements in which dichroic pigments are adsorbed onto a layer containing polyvinyl alcohol (hereinafter also referred to as "PVA")-based resin (hereinafter also referred to as "PVA-based resin layer") and the dichroic pigments are oriented. Examples of polarizing elements include a stretched film obtained by dyeing a PVA-based resin film with a dichroic pigment and then uniaxially stretching it; and a stretched layer obtained by using a laminated film having a coating layer formed by coating a substrate film with a coating liquid containing a PVA-based resin, dyeing the coating layer with a dichroic pigment, and then uniaxially stretching the laminated film. Stretching can be performed after dyeing with the dichroic pigment, or while dyeing, or after stretching.

[0047] The PVA-based resin can be obtained by saponifying a polyvinyl acetate-based resin. As the polyvinyl acetate-based resin, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate, a copolymer of vinyl acetate and another monomer copolymerizable therewith can also be used. As the other monomer copolymerizable, for example, unsaturated carboxylic acids, olefins such as ethylene, vinyl ethers, unsaturated sulfonic acids, and the like can be given.

[0048] The saponification degree of the PVA-based resin is preferably about 85 mol% or more, more preferably about 90 mol% or more, and further preferably about 99 mol% or more and 100 mol% or less. The polymerization degree of the PVA-based resin is, for example, 1000 or more and 10000 or less, and is preferably 1500 or more and 5000 or less. The PVA-based resin can be modified, and for example, can be polyvinyl formal, polyvinyl acetal, polyvinyl butyral, or the like modified with an aldehyde.

[0049] 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 further preferably 5 μm or more and 25 μm or less. By making the thickness of the polarizing element 35 μm or less, it is possible to suppress the influence of the decrease in the optical properties of the PVA-based resin due to polyeneization in a high-temperature environment. By making the thickness of the polarizing element 3 μm or more, it is easy to make a constitution that achieves desired optical properties.

[0050] The polarizing element preferably contains a urea-based compound and a dicarboxylic acid. In the present embodiment, since the polarizing element is attached to the transparent protective film with an adhesive layer formed of an adhesive containing a urea-based compound and a dicarboxylic acid, it is presumed that a part of the urea-based compound and a part of the dicarboxylic acid transferred from the adhesive layer are contained in the polarizing element. The urea-based compound and the dicarboxylic acid in the polarizing element can also be the urea-based compound and the dicarboxylic acid added in the process of manufacturing the polarizing element. By having the adhesive layer containing a urea-based compound and a dicarboxylic acid, even if the polarizing plate is exposed to a high-temperature environment, the transmittance is less likely to decrease. In addition, by having the adhesive layer containing a urea-based compound and a dicarboxylic acid, even if the polarizing plate is exposed to a high-temperature environment, it is possible to suppress the decrease in the degree of polarization. In the case where two polarizing plates are used in a manner to be arranged so as to form a right-angle Nicol prism, if the degree of polarization of the polarizing plate decreases, it is easy to cause light leakage (hereinafter also referred to as "right-angle light leakage"), however according to the present embodiment, even if exposed to a high-temperature environment, the degree of polarization is less likely to decrease, and thus it is also easy to suppress the right-angle light leakage. It is presumed that the reason for exerting such an effect is that the urea-based compound and the dicarboxylic acid contained in the polarizing element suppress the polyeneization of the PVA-based resin.

[0051] As a method of causing the polarizing element to contain the urea-based compound and the dicarboxylic acid, there are a method of immersing the PVA-based resin layer in a treatment solvent containing the urea-based compound and / or the dicarboxylic acid, or a method of spraying, flowing, or dripping the treatment solvent to the PVA-based resin layer. Among them, a method of immersing the PVA-based resin layer in a treatment solvent containing both the urea-based compound and the dicarboxylic acid is preferable. Specific examples of the urea-based compound and the dicarboxylic acid can be exemplified by the urea-based compounds and the dicarboxylic acids exemplified as the substances contained in the adhesive described later.

[0052] The step of immersing the PVA-based resin layer in the treatment solvent containing the urea-based compound and the dicarboxylic acid can be performed simultaneously with the swelling, stretching, dyeing, cross-linking, cleaning, and the like in the manufacturing method of the polarizing element described later, or can be provided separately from these steps. The step of causing the PVA-based resin layer to contain the urea-based compound and the dicarboxylic acid is preferably performed after dyeing the PVA-based resin layer with iodine, and more preferably simultaneously with the cross-linking step after dyeing. According to this method, the hue change is small, and the influence on the optical characteristics of the polarizing element can be reduced.

[0053] In order to cause the polarizing element to contain the urea-based compound and the dicarboxylic acid, both the addition at the time of manufacturing the polarizing element and the addition to the adhesive can be performed. Alternatively, one of the urea-based compound and the dicarboxylic acid can be contained at the time of manufacturing the polarizing element, and both can be contained in the adhesive.

[0054] (Urea-based compound)

[0055] The urea-based compound is at least one selected from the group consisting of urea, a urea derivative, thiourea, and a thiourea derivative. The urea-based compound can be used alone or in combination with two or more. The urea-based compound includes a water-soluble compound and a water-insoluble compound, and any urea-based compound can be used. In the case where a water-insoluble urea-based compound is used in a water-soluble adhesive, the dispersion method is preferably designed so as not to cause an increase in turbidity and the like after the adhesive layer is formed.

[0056] (Urea derivative)

[0057] The urea derivative is a compound in which at least one of the four hydrogen atoms of the urea molecule is substituted with a substituent. In this case, the substituent is not particularly limited, and is preferably a substituent containing a carbon atom, a hydrogen atom, and an oxygen atom.

[0058] As specific examples of the urea derivative, in the case of a monosubstituted urea, there are 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.

[0059] As the di-substituted urea, 1,1-dimethyl urea, 1,3-dimethyl urea, 1,1-diethyl urea, 1,3-diethyl urea, 1,3-bis(hydroxymethyl) urea, 1,3-tert-butyl urea, 1,3-biscyclohexyl urea, 1,3-diphenyl urea, 1,3-bis(4-methoxyphenyl) urea, 1-acetyl-3-methyl urea, 2-imidazolidinone (ethylene urea), tetrahydro-2-pyrimidinone (propylene urea) can be mentioned.

[0060] As the tetra-substituted urea, tetramethyl urea, 1,1,3,3-tetraethyl urea, 1,1,3,3-tetrabutyl urea, 1,3-dimethoxy-1,3-dimethyl urea, 1,3-dimethyl-2-imidazolidinone, 1,3-dimethyl-3,4,5,6-tetrahydro-2(lH)-pyrimidinone can be mentioned.

[0061] (thiourea derivative)

[0062] The thiourea derivative is a compound in which at least one of the four hydrogen atoms of the thiourea molecule is substituted with a substituent. In this case, the substituent is not particularly limited, and a substituent containing a carbon atom, a hydrogen atom, and an oxygen atom is preferred.

[0063] As the thiourea derivative, as the mono-substituted thiourea, N-methyl thiourea, ethyl thiourea, propyl thiourea, isopropyl thiourea, 1-butyl thiourea, cyclohexyl thiourea, N-acetyl thiourea, N-allyl thiourea, (2-methoxyethyl) thiourea, N-phenyl thiourea, (4-methoxyphenyl) thiourea, N-(2-methoxyphenyl) thiourea, N-(l-naphthyl) thiourea, (2-pyridyl) thiourea, o-tolyl thiourea, p-tolyl thiourea can be mentioned.

[0064] As the di-substituted thiourea, 1,1-dimethyl thiourea, 1,3-dimethyl thiourea, 1,1-diethyl thiourea, 1,3-diethyl thiourea, 1,3-dibutyl thiourea, 1,3-diisopropyl thiourea, 1,3-dicyclohexyl thiourea, N,N-diphenyl thiourea, N,N'-diphenyl thiourea, 1,3-di(o-tolyl) thiourea, 1,3-di(p-tolyl) thiourea, 1-benzyl-3-phenyl thiourea, 1-methyl-3-phenyl thiourea, N-allyl-N'-(2-hydroxyethyl) thiourea, ethylene thiourea can be mentioned.

[0065] As the tri-substituted thiourea, trimethyl thiourea can be mentioned, and as the tetra-substituted thiourea, tetramethyl thiourea, 1,1,3,3-tetraethyl thiourea can be mentioned.

[0066] Among the urea-based compounds, from the viewpoint of being able to suppress the decrease in transmittance in a high-temperature environment and the decrease in degree of polarization (the viewpoint of suppressing orthogonal light leakage), preferably, a urea derivative or a thiourea derivative, more preferably a urea derivative. Among the urea derivatives, preferably, a mono-substituted urea or a di-substituted urea, more preferably a mono-substituted urea. Among the di-substituted ureas, 1,1-substituted urea and 1,3-substituted urea, more preferably 1,3-substituted urea.

[0067] (di-carboxylic acid)

[0068] As the di-carboxylic acid, for example, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, tartaric acid, glutamic acid, malic acid, maleic acid, fumaric acid, itaconic acid, muconic acid, 1,4-cyclohexane dicarboxylic acid, 1,4-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, 2,7-naphthalene dicarboxylic acid, 4,4-biphenyl dicarboxylic acid, 2,5-pyridine dicarboxylic acid, 3,5-pyridine dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl methane dicarboxylic acid, oxalacetic acid, methyl fumaric acid, 2,6-pyridine dicarboxylic acid, and the like can be given. Among them, it is preferable to use citric acid, malic acid, maleic acid, or tartaric acid. These di-carboxylic acids can be used alone or two or more can be used in combination.

[0069] (characteristic (a))

[0070] When having the characteristic (a), the moisture content of the polarizing element is equal to or higher than the equilibrium moisture content at 20°C and 30% RH and equal to or lower than the equilibrium moisture content at 20°C and 50% RH. The moisture content of the polarizing element is preferably equal to or lower than the equilibrium moisture content at 20°C and 45% RH, more preferably equal to or lower than the equilibrium moisture content at 20°C and 42% RH, and further preferably equal to or lower than the equilibrium moisture content at 20°C and 38% RH. If the moisture content of the polarizing element is lower than the equilibrium moisture content at 20°C and 30% RH, the operability of the polarizing element decreases and it is easily broken. If the moisture content of the polarizing element exceeds the equilibrium moisture content at 20°C and 50% RH, the transmittance of the polarizing element easily decreases. It is presumed that this is because if the moisture content of the polarizing element is high, the polyene of the PVA-based resin easily progresses. The moisture content of the polarizing element is the moisture content of the polarizing element in the polarizing plate.

[0071] As a method of confirming whether the water content of the polarizing element is in the range of equal to or higher than the equilibrium water content at 20°C and 30% RH and equal to or lower than the equilibrium water content at 20°C and 50% RH, there can be mentioned a method of storing in an environment adjusted to the above-mentioned temperature and the above-mentioned relative humidity range, and when there is no change in quality for a certain period of time, it is considered that the environment has reached equilibrium; or a method of calculating in advance the equilibrium water content of the polarizing element in an environment adjusted to the above-mentioned temperature and the above-mentioned relative humidity range, and confirming by comparing the water content of the polarizing element with the equilibrium water content calculated in advance.

[0072] As a method of manufacturing a polarizing element having a water content equal to or higher than the equilibrium water content at 20°C and 30% RH and equal to or lower than the equilibrium water content at 20°C and 50% RH, there is no particular limitation, but for example, there can be mentioned a method of storing the polarizing element in an environment adjusted to the above-mentioned temperature and the above-mentioned relative humidity range for 10 minutes or more and 3 hours or less; or a method of performing heat treatment at 30°C or higher and 90°C or lower.

[0073] As another preferable method of manufacturing a polarizing element having the above-mentioned water content, there can be mentioned a method of storing a laminate in which a protective film is laminated to at least one surface of the polarizing element, or a polarizing plate using the polarizing element, in an environment adjusted to the above-mentioned temperature and the above-mentioned relative humidity range for 10 minutes or more and 120 hours or less; or a method of performing heat treatment at 30°C or higher and 90°C or lower. In the production of an image display device using an interlayer filling, an image display panel obtained by laminating the polarizing plate to an image display unit can be stored in an environment adjusted to the above-mentioned temperature and the above-mentioned relative humidity range for 10 minutes or more and 3 hours or less, or can be heat-treated at 30°C or higher and 90°C or lower, and then the front panel can be attached.

[0074] As for the water content of the polarizing element, it is preferable to adjust the water content to the above-mentioned numerical range in the stage of the material alone, or in the stage of the laminate of the polarizing element and the protective film, and in the stage of the material used for constituting the polarizing plate. In the case of adjusting the water content after constituting the polarizing plate, the curl becomes too large, and there is a case where the attachment to the image display unit is likely to be in a poor condition. By using the polarizing element adjusted to the above-mentioned water content in the stage of the material before constituting the polarizing plate, it is possible to easily constitute the polarizing plate having the polarizing element having a water content satisfying the above-mentioned numerical range. It is also possible to adjust the water content of the polarizing element in the polarizing plate to the above-mentioned numerical range in the state where the polarizing plate is attached to the image display unit. In this case, since the polarizing plate is attached to the image display unit, the curl is less likely to occur.

[0075] (Characteristics (b))

[0076] When the feature (b) is satisfied, the moisture content of the polarizing plate is equal to or higher than the equilibrium moisture content at 20°C and 30% RH and equal to or lower than the equilibrium moisture content at 20°C and 50% RH. The moisture content of the polarizing plate is preferably equal to or lower than the equilibrium moisture content at 20°C and 45% RH, more preferably equal to or lower than the equilibrium moisture content at 20°C and 42% RH, and further preferably equal to or lower than the equilibrium moisture content at 20°C and 38% RH. If the moisture content of the polarizing plate is lower than the equilibrium moisture content at 20°C and 30% RH, the handling property of the polarizing plate is reduced and the polarizing plate is easily broken. If the moisture content of the polarizing plate exceeds the equilibrium moisture content at 20°C and 50% RH, the transmittance of the polarizing element is easily reduced. It is presumed that this is because if the moisture content of the polarizing plate is high, the polyene of the PVA-based resin is easily advanced.

[0077] As a method for confirming whether the moisture content of the polarizing plate is within the range of equal to or higher than the equilibrium moisture content at 20°C and 30% RH and equal to or lower than the equilibrium moisture content at 20°C and 50% RH, there can be mentioned a method in which storage is performed in an environment adjusted to the above-mentioned temperature and the above-mentioned relative humidity, and when there is no change in quality for a certain period of time, it is considered that the environment has reached equilibrium; or a method in which the equilibrium moisture content of the polarizing plate in an environment adjusted to the above-mentioned temperature and the above-mentioned relative humidity is calculated in advance, and confirmation is made by comparing the moisture content of the polarizing plate with the calculated equilibrium moisture content.

[0078] As a method for producing a polarizing plate having a moisture content equal to or higher than the equilibrium moisture content at 20°C and 30% RH and equal to or lower than the equilibrium moisture content at 20°C and 50% RH, there is no particular limitation, but for example, there can be mentioned a method in which the polarizing plate is stored in an environment adjusted to the above-mentioned temperature and the above-mentioned relative humidity for 10 minutes or more and 3 hours or less; or a method in which heat treatment is performed at 30°C or higher and 90°C or lower.

[0079] In the production of an image display device configured by interlayer filling, the image display panel obtained by laminating the polarizing plate to the image display unit is stored in an environment adjusted to the above-mentioned temperature and the above-mentioned relative humidity for 10 minutes or more and 3 hours or less, or is heated at 30°C or higher and 90°C or lower, and then the front panel is attached.

[0080] (Method for producing polarizing element)

[0081] The method for producing the polarizing element is not particularly limited, and typical methods are a method in which a PVA-based resin film that has been previously wound in a roll shape is fed out and stretched, dyed, crosslinked, and the like to produce (hereinafter referred to as "production method 1"); or a method including a step of applying a coating liquid containing a PVA-based resin onto a base film to form a PVA-based resin layer as a coating layer, and stretching the obtained laminate (hereinafter referred to as "production method 2").

[0082] The production method 1 can produce the PVA-based resin film by a process of uniaxially stretching the PVA-based resin film, a process of dyeing the PVA-based resin film with a dichroic dye such as iodine to adsorb the dichroic dye, a process of treating the PVA-based resin film having adsorbed the dichroic dye with an aqueous boric acid solution, and a process of washing with water after the treatment with the aqueous boric acid solution.

[0083] The swelling process is a treatment process of immersing the PVA-based resin film in a swelling bath. With the swelling process, in addition to being able to remove dirt, anti-blocking agents, and the like from the surface of the PVA-based resin film, it is also possible to suppress dyeing unevenness by swelling the PVA-based resin film. The swelling bath generally uses water, distilled water, pure water, or the like as a main component. The swelling bath can also be appropriately added with a surfactant, an alcohol, or the like in accordance with the usual method. From the viewpoint of controlling the potassium content of the polarizing element, potassium iodide can be used in the swelling bath, in which 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 further preferably 0.5% by mass or less.

[0084] 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 further preferably 18°C or higher and 30°C or lower. With respect to 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 determined in general, but is preferably 5 seconds or longer and 300 seconds or shorter, more preferably 10 seconds or longer and 200 seconds or shorter, and further preferably 20 seconds or longer and 100 seconds or shorter. The swelling process can be performed only once, or can be performed multiple times as necessary.

[0085] The dyeing process is a treatment process of immersing the PVA-based resin film in a dyeing bath (iodine solution), and can cause the PVA-based resin film to adsorb a dichroic dye such as iodine and orient the dichroic dye. The iodine solution is generally preferably an aqueous iodine solution, and contains iodine and an iodide as a dissolution aid. As the iodide, there can be mentioned potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, and the like. Among these, from the viewpoint of controlling the potassium content in the polarizing element, potassium iodide is suitable.

[0086] The concentration of iodine in the dyeing bath is preferably 0.01% by mass or more and 1% by mass or less, and more preferably 0.02% by mass or more and 0.5% by mass or less. The concentration of the iodide in the dyeing 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 further preferably 0.1% by mass or more and 3% by mass or less.

[0087] 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 further preferably 18°C or higher and 30°C or lower. The immersion time in the dyeing bath cannot be determined generally because the degree of dyeing of the PVA-based resin film is affected by the temperature of the dyeing bath, but is preferably 10 seconds or longer and 300 seconds or shorter, and more preferably 20 seconds or longer and 240 seconds or shorter. The dyeing process can be performed only once, or can be performed a plurality of times as necessary.

[0088] The cross-linking process is a treatment process in which the PVA-based resin film dyed in the dyeing process is immersed in a treatment bath (cross-linking bath) containing a boron compound, and the polyvinyl alcohol-based resin film is cross-linked by the boron compound, and iodine molecules or dye molecules can be adsorbed to the cross-linked structure. As the boron compound, for example, boric acid, a boric acid salt, borax, or the like can be given. The cross-linking bath is generally an aqueous solution, but can also be a mixed solution of an organic solvent having miscibility with water and water. From the viewpoint of controlling the content of potassium in the polarizing element, the cross-linking bath preferably contains potassium iodide.

[0089] In the cross-linking bath, the concentration of the boron compound is preferably 1% by mass or higher and 15% by mass or lower, more preferably 1.5% by mass or higher and 10% by mass or lower, and further preferably 2% by mass or higher and 5% by mass or lower. When potassium iodide is used in the cross-linking bath, the concentration of the potassium iodide in the cross-linking bath is preferably 1% by mass or higher and 15% by mass or lower, more preferably 1.5% by mass or higher and 10% by mass or lower, and further preferably 2% by mass or higher and 5% by mass or lower.

[0090] The temperature of the cross-linking bath is preferably 20°C or higher and 70°C or lower, and more preferably 30°C or higher and 60°C or lower. The immersion time in the cross-linking bath cannot be determined generally because the degree of cross-linking of the PVA-based resin film is affected by the temperature of the cross-linking bath, but is preferably 5 seconds or longer and 300 seconds or shorter, and more preferably 10 seconds or longer and 200 seconds or shorter. The cross-linking process can be performed only once, or can be performed a plurality of times as necessary.

[0091] The stretching process is a treatment process in which the PVA-based resin film is stretched to a predetermined ratio in at least one direction. In general, the PVA-based resin film is uniaxially stretched in the conveying direction (lengthwise direction). The method of stretching is not particularly limited, and any of a wet stretching method and a dry stretching method can be adopted. The stretching process can be performed only once, or can be performed a plurality of times as necessary. The stretching process can be performed at any stage in the production of the polarizing element.

[0092] The treatment bath (stretching bath) in the wet stretching method can generally use water or a mixed solution of an organic solvent having miscibility with water and water, or the like. From the viewpoint of controlling the content of potassium in the polarizing element, the stretching bath preferably contains potassium iodide. In the case where 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, further 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) can contain a boron compound. In the case where a boron compound is contained, 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, further preferably 2% by mass or more and 5% by mass or less.

[0093] 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, further preferably 50°C or higher and 70°C or lower. The immersion time in the stretching bath cannot be determined generally because the degree of stretching of the PVA-based resin film is affected by the temperature of the stretching bath, but is preferably 10 seconds or more and 800 seconds or less, more preferably 30 seconds or more and 500 seconds or less. The stretching treatment in the wet stretching method can be performed together with any one or more of the swelling process, the dyeing process, the crosslinking process, and the cleaning process.

[0094] As the dry stretching method, for example, an inter-roller stretching method, a heated roller stretching method, a compression stretching method, or the like can be given. Note that the dry stretching method can be performed together with the drying process.

[0095] The total stretching ratio (cumulative stretching ratio) applied to the polyvinyl alcohol-based resin film can be appropriately set according to the purpose, but is preferably 2 times or more and 7 times or less, more preferably 3 times or more and 6.8 times or less, further preferably 3.5 times or more and 6.5 times or less.

[0096] The cleaning process is a treatment process in which the polyvinyl alcohol-based resin film is immersed in a cleaning bath, and can remove foreign matter remaining on the surface or the like of the polyvinyl alcohol-based resin film. The cleaning bath generally uses water, distilled water, pure water, or the like using water as a main component. In addition, from the viewpoint of controlling the content of potassium in the polarizing element, potassium iodide is preferably used in the cleaning bath, in which 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, further preferably 1.8% by mass or more and 3.8% by mass or less.

[0097] 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 further preferably 15°C or higher and 30°C or lower. The immersion time in the cleaning bath cannot be determined in general because the degree of cleaning of the PVA-based resin film is affected by the temperature of the cleaning bath, but is preferably 1 second or longer and 100 seconds or shorter, more preferably 2 seconds or longer and 50 seconds or shorter, and further preferably 3 seconds or longer and 20 seconds or shorter. The cleaning process can be performed only once, or can be performed a plurality of times as necessary.

[0098] The drying process is a process of drying the PVA-based resin film subjected to the cleaning in the cleaning process to obtain a polarizing element. The drying can be performed by an optional appropriate method, and for example, natural drying, air blowing drying, and heating drying can be given.

[0099] The production method 2 can be produced by the following processes, that is, a process of applying a coating liquid containing a PVA-based resin onto a base film, a process of uniaxially stretching the obtained laminated film, a process of making a polarizing element by dyeing the PVA-based resin layer of the uniaxially stretched laminated film with a dichroic dye and adsorbing the dichroic dye, a process of treating the film adsorbed with the dichroic dye with an aqueous boric acid solution, and a process of performing water washing after the treatment with the aqueous boric acid solution. The base film used for forming the polarizing element can also be used as a protective layer of the polarizing element. The base film can be removed from the polarizing element as necessary by peeling.

[0100] <Transparent protective film>

[0101] The transparent protective film (hereinafter also simply referred to as "protective film") used in the present embodiment is attached to at least one side of the polarizing element via an adhesive layer. The transparent protective film can be attached to one side or both sides of the polarizing element, but is preferably attached to both sides.

[0102] The protective film can have other optical functions and can be made into a laminated structure in which a plurality of layers are laminated. From the viewpoint of optical properties, it is preferable that the film thickness of the protective film be thin, but if it is too thin, the strength is reduced and the processability is poor. As an appropriate film thickness, 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.

[0103] The protective film can use a cellulose acylate film, a film containing a polycarbonate-based resin, a film containing a cyclic olefin-based resin such as norbornene, a (meth)acrylic polymer film, a polyester resin-based film such as polyethylene terephthalate, and the like. In the case where a water-based adhesive such as a PVA adhesive is used to attach the protective film to both sides of the polarizing element, from the viewpoint of moisture permeability, it is preferable that the protective film on at least one side be either a cellulose acylate film or a (meth)acrylic polymer film, of which a cellulose acylate film is preferable.

[0104] For the purpose of view angle compensation or the like, at least one of the protective films can have a phase difference function. In this case, the protective film itself can have the phase difference function, or a phase difference layer can be separately provided, or a combination of both can be used. The film having the phase difference function can be directly attached to the polarizing element via an adhesive, or can be attached via an adhesive or an adhesive while being sandwiched by another protective film attached to the polarizing element.

[0105] <adhesive layer>

[0106] As the adhesive constituting the adhesive layer for attaching the protective film to the polarizing element, an adhesive containing a urea-based compound and a dicarboxylic acid is used. The adhesive can be a water-based adhesive, a solvent-based adhesive, an active energy ray-curable adhesive, or the like, but a water-based adhesive is preferred, and a PVA-based resin is preferably contained. By using an adhesive containing a urea-based compound and a dicarboxylic acid, the decrease in transmittance of the polarizing plate under a high-temperature environment can be suppressed.

[0107] The thickness of the adhesive at the time of application can be set to an optional value, and for example, can be set in such a manner that an adhesive layer having a desired thickness is obtained after curing or after heating (drying). The thickness of the adhesive layer formed 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.

[0108] The following description of the adhesive is described using the preferred range for the case where the urea-based compound and the dicarboxylic acid are not contained in the polarizing element at the time of manufacturing the polarizing element. In the case where the urea-based compound and the dicarboxylic acid are contained in the polarizing element, the values described below can be appropriately adjusted. For specific examples of the urea-based compound and the dicarboxylic acid, the examples of the urea-based compound and the dicarboxylic acid contained in the polarizing element described above can be directly applied. In the process of forming the adhesive layer through a drying process at the time of bonding the polarizing element and the protective film, a part of the urea-based compound and a part of the dicarboxylic acid can move from the adhesive layer to the polarizing element or the like.

[0109] In the case where the adhesive is a water-based adhesive containing a PVA-based resin, the content of the urea-based compound is preferably 0.1 parts by mass or more and 400 parts by mass or less, more preferably 1 parts by mass or more and 200 parts by mass or less, and further preferably 3 parts by mass or more and 100 parts by mass or less, with respect to 100 parts by mass of the PVA-based resin. If it is less than 0.1 parts by mass, the inhibitory effect on the polyene of the polarizing element under a high-temperature environment is not sufficient. On the other hand, in the case where it is more than 400 parts by mass, the urea is precipitated after the polarizing plate is manufactured, and the haze increases.

[0110] In the case where the adhesive is a water-based adhesive containing a PVA-based resin, the content of the dicarboxylic acid is preferably 1 part by mass or more and 50 parts by mass or less, more preferably 1.5 parts by mass or more and 40 parts by mass or less, and further preferably 2 parts by mass or more and 35 parts by mass or less, and can also be 20 parts by mass or less, with respect to 100 parts by mass of the PVA-based resin. If less than 1 part by mass, the inhibitory effect on polyene of the polarizing element in a high-temperature environment is not sufficient. On the other hand, in the case where more than 50 parts by mass, there is a case where the dicarboxylic acid is precipitated after the polarizing plate is produced.

[0111] In the configuration in which transparent protective films are attached to both faces of the polarizing element via adhesive layers, it is possible that only the adhesive layer of one face is a layer containing a urea-based compound and a dicarboxylic acid, but it is preferable that both adhesive layers are layers containing a urea-based compound and a dicarboxylic acid.

[0112] In order to respond to the demand for thin polarizing plates, a polarizing plate having a transparent protective film on only one face of the polarizing element has been developed. In this configuration, the transparent protective film is also laminated via an adhesive layer containing a urea-based compound and a dicarboxylic acid. As a method for producing such a polarizing plate having a transparent protective film on only one face of the polarizing element, a method in which a polarizing plate having transparent protective films attached to both faces via adhesive layers is first produced and then the transparent protective film on one side is peeled off can be considered. In the case of using such a production method, it is possible that the urea-based compound and the dicarboxylic acid are contained in only one of the adhesive layers, but it is preferable that both adhesive layers are layers containing a urea-based compound and a dicarboxylic acid. In the case where the urea-based compound and the dicarboxylic acid are contained in only one of the adhesive layers, it is preferable that the adhesive layer on the side from which the film is not peeled off contains a urea-based compound and a dicarboxylic acid.

[0113] (Water-based adhesive)

[0114] As the water-based adhesive, an optional appropriate water-based adhesive can be used, but it is preferable to use a water-based adhesive containing a PVA-based resin (PVA-based adhesive). The average polymerization degree of the PVA-based resin contained in the water-based adhesive is preferably 100 or more and 5500 or less, and further preferably 1000 or more and 4500 or less, from the viewpoint of adhesion. The average saponification degree is preferably 85 mol% or more and 100 mol% or less, and more preferably 90 mol% or more and 100 mol% or less.

[0115] As the PVA-based resin contained in the water-based adhesive, a resin containing an acetoacetyl group is preferable, for the reason that the adhesion of the PVA-based resin layer to the protective film is excellent, and the durability is excellent. The PVA-based resin containing an acetoacetyl group can be obtained, for example, by reacting a PVA-based resin with a diketene using an optional method. The modification degree of the acetoacetyl group of the PVA-based resin containing an acetoacetyl group is, in a representative case, 0.1 mol% or more, and is preferably 0.1 mol% or more and 20 mol% or less. The resin concentration of the water-based adhesive is preferably 0.1 mass% or more and 15 mass% or less, and more preferably 0.5 mass% or more and 10 mass% or less.

[0116] A crosslinking agent can also be contained in the water-based adhesive. As the crosslinking agent, a publicly known crosslinking agent can be used. As the crosslinking agent, for example, a water-soluble epoxy compound, a dialdehyde, an isocyanate, or the like can be cited.

[0117] In the case where the PVA-based resin is a PVA-based resin containing an acetoacetyl group, as the crosslinking agent, any of glyoxal, glyoxalate, and methylol melamine is preferable, any of glyoxal and glyoxalate is more preferable, and glyoxal is particularly preferable.

[0118] The water-based adhesive can also contain an organic solvent. From the viewpoint of miscibility with water, the organic solvent is preferably an alcohol, and among alcohols, methanol or ethanol is more preferable. The concentration of methanol in the water-based adhesive is preferably 10 mass% or more and 70 mass% or less, more preferably 15 mass% or more and 60 mass% or less, and further preferably 20 mass% or more and 60 mass% or less. By making the concentration of methanol 10 mass% or more, polyene of the PVA-based resin under a high-temperature environment is more easily suppressed. In addition, by making the content of methanol 70 mass% or less, deterioration of the color tone can be suppressed. The solubility of a part of the urea derivative in water is low, but the solubility in alcohol is sufficient. In this case, it is preferable to prepare an alcohol solution of the urea-based compound by dissolving the urea-based compound in alcohol, and then to prepare an adhesive by adding the alcohol solution of the urea-based compound to a PVA aqueous solution.

[0119] (Radiation curable adhesive)

[0120] The active energy ray-curable adhesive is an adhesive that is cured by irradiation of active energy rays such as ultraviolet rays, and examples thereof include an adhesive containing a polymerizable compound and a photopolymerization initiator, an adhesive containing a photoreactive resin, an adhesive containing a binder resin and a photoreactive crosslinking agent, and the like. As the polymerizable compound, there are photocurable epoxy-based monomers, photocurable acrylic-based monomers, photocurable urethane-based monomers, and the like, and oligomers and the like derived from these monomers. As the above-mentioned photopolymerization initiator, there are compounds containing substances that generate active species such as neutral radicals, anionic radicals, and cationic radicals by irradiation of active energy rays such as ultraviolet rays.

[0121] <Layer containing urea-based compound>

[0122] The urea-based compound and the dicarboxylic acid are not limited to the case of being contained in the adhesive layer as described above, and from the viewpoint of improving the high-temperature durability of the polarizing plate, can also be contained in other layers other than the adhesive layer. In a polarizing plate having a transparent protective film on only one side, from the viewpoint of improving the physical strength, a cured layer can be laminated on the side of the polarizing element opposite to the transparent protective film.

[0123] In the present embodiment, the urea-based compound and the dicarboxylic acid can also be contained in such a cured layer, to obtain a layer containing a urea-based compound. Such a cured layer is generally formed from a curable composition containing an organic solvent, and a method of forming such a cured layer from an aqueous solution of an active energy ray-curable polymer composition is described in

[0020] to

[0042] of Japanese Patent Application Publication No. 2017-075986. The aqueous urea-based compound and the dicarboxylic acid can also be contained in such a composition.

[0124] The layer containing a urea-based compound preferably has at least one urea-based compound, at least one dicarboxylic acid, and a binder. As the binder, there are polymer binders, heat-curable resin binders, active energy ray-curable resin binders, and the like, and any of these can be preferably used.

[0125] The thickness of the layer containing a urea-based compound 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 further preferably 1 μm or more and 10 μm or less.

[0126] [Method for manufacturing polarizing plate]

[0127] The manufacturing method of the polarizing plate of the present embodiment has a water content adjusting step and a laminating step. In the water content adjusting step, in the case of manufacturing the polarizing plate having the feature (a), the water content of the polarizing element is adjusted so as to be equal to or higher than the equilibrium water content at 20°C and 30% RH and equal to or lower than the equilibrium water content at 20°C and 50% RH. The water content of the polarizing element can be adjusted in accordance with the description of the water content of the polarizing element described above. In the water content adjusting step, in the case of manufacturing the polarizing plate having the feature (b), the water content of the polarizing plate is adjusted so as to be equal to or higher than the equilibrium water content at 20°C and 30% RH and equal to or lower than the equilibrium water content at 20°C and 50% RH. The water content of the polarizing plate can be adjusted in accordance with the description of the water content of the polarizing plate described above. In the laminating step, the polarizing element and the transparent protective film are laminated via the adhesive layer described above. In the laminating step, for example, the polarizing element which has not been subjected to the treatment of containing the urea-based compound and the dicarboxylic acid is attached to the transparent protective film using the adhesive containing the urea-based compound and the dicarboxylic acid. The order of the water content adjusting step and the laminating step is not limited, and the water content adjusting step and the laminating step can be performed in parallel.

[0128] [Configuration of image display device]

[0129] The polarizing plate of the present embodiment can be used for various image display devices such as liquid crystal display devices and organic EL display devices. In the case of an image display device configured in such a manner that 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 tends to decrease in a high-temperature environment. In an image display device using the polarizing plate of the present embodiment, even in the case of an interlayer-filling configuration, the decrease in the transmittance of the polarizing plate in a high-temperature environment can be suppressed. As the image display device, a configuration having an image display unit, a first adhesive layer laminated on the visible side surface of the image display unit, and a polarizing plate laminated on the visible side surface of the first adhesive layer can be exemplified. The image display device can further have a second adhesive layer laminated on the visible side surface of the polarizing plate, and a transparent member laminated on the visible side surface of the second adhesive layer. In particular, the polarizing plate of the present embodiment can be suitably used for an image display device having an interlayer-filling configuration in which a transparent member is disposed on the visible side of the image display device, the polarizing plate is attached to the image display unit by the first adhesive layer, and the polarizing plate is attached to the transparent member by the second adhesive layer. In the present specification, either one or both of the first adhesive layer and the second adhesive layer are sometimes referred to simply as an "adhesive layer". Note that, as the member used in the attachment of the polarizing plate to the image display unit and the attachment of the polarizing plate to the transparent member, the member is not limited to the adhesive layer, but can be an adhesive layer.

[0130] [Image display unit]

[0131] As the image display unit, a liquid crystal cell, an organic EL cell can be given. As the liquid crystal cell, any one of a reflection type liquid crystal cell using extraneous light, a transmission type liquid crystal cell using light from a light source such as a backlight, a semi-transmission semi-reflection type liquid crystal cell using both light from the outside and light from a light source can be used. In the case where the liquid crystal cell is a liquid crystal cell using light from a light source, a polarizing plate is also disposed on the side of the image display unit (liquid crystal cell) opposite to the visible side, in addition to the light source. The polarizing plate on the light source side is preferably attached to the liquid crystal cell via a proper adhesive layer. As the driving mode of the liquid crystal cell, for example, any optional type of driving mode such as a VA mode, an IPS mode, a TN mode, an STN mode, a bend alignment (pi type) and the like can be used.

[0132] As the organic EL cell, an organic EL cell 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 electroluminescence light emitter) and the like can be suitably used. The organic light emitting layer is a laminate of various organic thin films, and for example, a laminate of a hole injection layer containing a triphenylamine derivative or the like and a light emitting layer containing a fluorescent organic solid such as anthracene, a laminate of these light emitting layers and an electron injection layer containing a perylene derivative or the like, or a laminate of a hole injection layer, a light emitting layer and an electron injection layer and the like can be used.

[0133] <Attachment of the image display unit to the polarizing plate>

[0134] In the attachment of the image display unit to the polarizing plate, an adhesive layer (adhesive sheet) can be suitably used. Among them, from the viewpoint of operability and the like, a method in which a polarizing plate with an adhesive layer to which an adhesive layer is attached to one face is attached to the image display unit is preferred. The attachment of the adhesive layer to the polarizing plate can be performed by a proper method. As examples thereof, a method in which an adhesive solution in which 10 mass% or more and 40 mass% or less of a base polymer or a composition thereof is dissolved or dispersed in a solvent formed of a single substance or a mixture of proper solvents such as toluene, ethyl acetate and the like is prepared, and is directly attached to the polarizing plate using a proper spreading method such as a casting method, a coating method and the like; a method in which an adhesive layer is formed on a spacer and is transferred to the polarizing plate; and the like can be given.

[0135] <Adhesive layer>

[0136] The adhesive layer can be formed of one layer or two or more layers, and is preferably formed of one layer. The adhesive layer can be formed of an adhesive composition in which a (meth)acrylic resin, a rubber-based resin, a urethane-based resin, an ester-based resin, a silicone-based resin, or a polyvinyl ether-based resin is used as a main component. Among these, an adhesive composition in which a (meth)acrylic resin is used as a base polymer is suitable because of its excellent transparency, weather resistance, heat resistance, and the like. The adhesive composition can be either a radiation-curable type or a heat-curable type.

[0137] As the (meth)acrylic resin (base polymer) used in the adhesive composition, a polymer or a copolymer in which one or two or more kinds of (meth)acrylate such as butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, or 2-ethylhexyl (meth)acrylate is used as a monomer can be appropriately used. It is preferable that a polar monomer be copolymerized in the base polymer. As the polar monomer, a monomer having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, or the like 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 can be exemplified.

[0138] The adhesive composition can contain only the above-described base polymer, but generally contains a crosslinking agent as well. As the crosslinking agent, a metal ion that forms a carboxylate metal salt between itself and a carboxyl group, a polyamine compound that forms an amide bond between itself and a carboxyl group, a polyepoxide compound or a polyhydric alcohol that forms an ester bond between itself and a carboxyl group, or a polyisocyanate compound that forms an amide bond between itself and a carboxyl group can be exemplified. Among these, a polyisocyanate compound is preferable.

[0139] The radiation-curable adhesive composition has a property of being cured by irradiation with active energy rays such as ultraviolet rays or electron beams, and has a property of being able to be closely adhered to a film or the like before irradiation with active energy rays and of being able to be cured by irradiation with active energy rays to adjust the adhesion force. The radiation-curable adhesive composition is preferably ultraviolet-curable. The radiation-curable adhesive composition contains, on the basis of a base polymer and a crosslinking agent, a radiation-polymerizable compound. If necessary, a photopolymerization initiator, a photosensitizer, or the like can be contained.

[0140] The adhesive composition can contain a particulate, a bead (resin bead, glass bead, or the like), a glass fiber, a resin other than the base polymer, a tackifier, a filler (metal powder, other inorganic powder, or the like), an antioxidant, an ultraviolet absorber, a dye, a pigment, a colorant, an antifoaming agent, an anticorrosive agent, a photopolymerization initiator, or the like as an additive.

[0141] The adhesive layer can be formed by applying the organic solvent dilution of the above-mentioned adhesive composition to the surface of the base film, the image display unit, or the polarizing plate and drying. The base film is usually a thermoplastic resin film, and as typical examples thereof, a release film subjected to a mold release treatment can be mentioned. The release film can be, for example, a film subjected to a mold release treatment such as silicone treatment on the surface of the film formed of a resin such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, polyarylate, or the like.

[0142] The adhesive layer can be formed by applying the organic solvent dilution of the above-mentioned adhesive composition to the surface of the base film, the image display unit, or the polarizing plate and drying. The base film is usually a thermoplastic resin film, and as typical examples thereof, a release film subjected to a mold release treatment can be mentioned. The release film can be, for example, a film subjected to a mold release treatment such as silicone treatment on the surface of the film formed of a resin such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, polyarylate, or the like.

[0143] In the case where the adhesive layer is provided to the surface of the polarizing plate, it is preferable that the surface of the polarizing plate and / or the surface of the adhesive layer be subjected to a surface activation treatment such as plasma treatment or corona treatment, and more preferably, the surface be subjected to corona treatment.

[0144] In addition, an adhesive sheet in which the adhesive layer is formed by applying the adhesive composition to the second release film and the release film is laminated on the formed adhesive layer can be prepared, and the adhesive layer with the release film peeled off from the adhesive sheet can be laminated on the polarizing plate. The second release film is a film which has a weaker adhesion to the adhesive layer than the release film and is easily peeled off.

[0145] The thickness of the adhesive layer is not particularly limited, and for example, it is preferably 1 μm or more and 100 μm or less, more preferably 3 μm or more and 50 μm or less, and can also be 20 μm or more.

[0146] <Transparent member>

[0147] As the transparent member disposed on the visual side of the image display device, a transparent plate (window layer), a touch panel, or the like can be mentioned. As the transparent plate, a transparent plate having an appropriate mechanical strength and thickness is used. As such a transparent plate, for example, a transparent resin plate such as a polyimide-based resin, an acrylic-based resin, a polycarbonate-based resin, or a glass plate, or the like can be mentioned. A functional layer such as an antireflection layer can also be laminated on the visual side of the transparent plate. In addition, in the case where the transparent plate is a transparent resin plate, a hard coat layer can be laminated in order to improve the physical strength, and a low moisture permeation layer can be laminated in order to reduce the moisture permeability. As the touch panel, various touch panels such as a resistance film method, an electrostatic capacity method, an optical method, an ultrasonic method, a glass plate having a touch sensor function, a transparent resin plate, or the like can be used. In the case where the touch panel of the electrostatic capacity method is used as the transparent member, it is preferable that a transparent plate formed of a glass or a transparent resin plate be provided on the visual side with respect to the touch panel.

[0148] <Conjunction of Polarizing Plate and Transparent Member>

[0149] In the conjunction of the polarizing plate and the transparent member, an adhesive or a radiation-curable adhesive can be suitably used. In the case of using an adhesive, the attachment of the adhesive can be performed in an appropriate manner. As a specific attachment method, for example, the attachment method of the adhesive layer used in the conjunction of the aforementioned image display unit and the polarizing plate can be cited.

[0150] In the case of using a radiation-curable adhesive, for the purpose of preventing the spread of the adhesive solution before curing, a method in which a cofferdam material is disposed so as to surround the peripheral portion on the image display panel, the transparent member is loaded on the cofferdam material, and the adhesive solution is injected can be suitably used. After the injection of the adhesive solution, the position alignment and the degassing are performed as necessary, and then the curing is performed by irradiation of the radiation.

[0151] Example

[0152] Hereinafter, the present application will be specifically described based on examples. The materials, reagents, substances, and the proportions thereof, and the operations shown in the following examples can be appropriately changed as long as the gist of the present application is not deviated. Thus, the present application is not limited or restricted by the following examples.

[0153] <Manufacture of Polarizing Element A>

[0154] A PVA film having a thickness of 40 μm, which was formed of PVA having an average polymerization degree of about 2400 and a saponification degree of 99.9 mol% or more, was uniaxially stretched in a dry manner to about 5 times, and then immersed in pure water at 60°C for 1 minute while the tension was maintained. Thereafter, the PVA film was immersed in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.05 / 5 / 100 at 28°C for 60 seconds. Thereafter, the PVA film was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 8.5 / 8.5 / 100 at 72°C for 300 seconds. Subsequently, after washing with pure water at 26°C for 20 seconds, drying was performed at 65°C, and a polarizing element A having a thickness of 15 μm, in which iodine was adsorbed to PVA and oriented, was obtained. In the measurement of the thickness of the polarizing element, a digital micrometer "MH-15M" manufactured by Nikon Corporation was used.

[0155] <Preparation of Adhesives 1 to 11>

[0156] (Preparation of PVA Solution A for Adhesive)

[0157] A modified PVA-based resin (Mitsubishi Chemical Corporation, "GOHSENX XZ-410") containing acetoacetyl group, 50 g, was dissolved in 950 g of pure water, and after heating at 90°C for 2 hours, it was cooled to room temperature to obtain a PVA solution for adhesive (hereinafter, referred to as "PVA solution A").

[0158] (Preparation of Adhesives 1 to 11)

[0159] The PVA solution A, the urea-based compound, the dicarboxylic acid, and pure water were mixed so that the PVA was 3.0 mass%, and the urea-based compound and the dicarboxylic acid were contained in the amounts shown in Table 1, to prepare Adhesives 1 to 11.

[0160] [Table 1]

[0161]

[0162] <Preparation of Transparent Protective Film A>

[0163] A commercially available cellulose acylate film TD40 (Fuji Photo Film Co., Ltd., film thickness 40 μm) was immersed in a 1.5 mol / L aqueous NaOH solution (saponification solution) maintained at 55°C for 2 minutes, and then washed with water. Thereafter, it was immersed in a 0.05 mol / L aqueous sulfuric acid solution at 25°C for 30 seconds, and then washed with water for 30 seconds under running water to neutralize the film. Then, the film was dried by being held in a drying zone at 70°C for 15 seconds after removing water by air blowing three times, to produce a saponified film, which was set as Transparent Protective Film A.

[0164] <Production of Polarizing Plates 1 to 11>

[0165] Transparent Protective Film A was attached to both sides of Polarizing Element A via Adhesive 1 using a roll laminator. After attachment, it was dried at 80°C for 5 minutes to obtain Polarizing Plate 1. The adhesive layer was adjusted so that the thickness after drying was 50 nm on both sides.

[0166] In Polarizing Plate 1, Adhesive 1 was changed to Adhesives 2 to 11 to obtain Polarizing Plates 2 to 11.

[0167] (Adjustment of Moisture Content of Polarizing Plate (Polarizing Element))

[0168] The polarizing plates 1 to 11 obtained above were stored under conditions of a temperature of 20°C and a relative humidity of 30%, 35%, 40%, 45%, 50%, or 55% for 72 hours. The water content was measured using the Karl-Fischer method at 66 hours, 69 hours, and 72 hours of storage. The value of the water content did not change at 66 hours, 69 hours, and 72 hours of storage under any of the humidity conditions. Thus, the water content of the polarizing plates 1 to 11 can be regarded as the same as the equilibrium water content under the storage environment of 72 hours used in this experimental example. When the water content of the polarizing plate reaches equilibrium under a certain storage environment, the water content of the polarizing element in the polarizing plate can likewise be regarded as reaching equilibrium under the storage environment. In addition, when the water content of the polarizing element in the polarizing plate reaches equilibrium under a certain storage environment, the water content of the polarizing plate can likewise be regarded as reaching equilibrium under the storage environment.

[0169] <Optical laminates 1 to 14>

[0170] For the optical laminates 1 to 14, any of the polarizing plates 1 to 11 shown in Table 2 was used, and stored under conditions of a temperature of 20°C and a relative humidity of 35%, 40%, 45%, or 55% for 72 hours to allow the water content of the used polarizing plate (polarizing element) to reach the equilibrium water content of the environment shown in Table 2, thereby producing.

[0171] <High-temperature durability evaluation>

[0172] (Production of evaluation samples)

[0173] For the optical laminates 1 to 14, an acrylic adhesive (LINTEC Corporation, Type #7) was formed on both surfaces, and then cut to a size of 50 mm x 100 mm in a manner such that the absorption axis was parallel to the long side. A non-alkali glass (Corning Company, "EAGLE XG") was attached to the respective adhesive surfaces, thereby producing evaluation samples.

[0174] In order to evaluate the orthogonal light leakage of the above evaluation samples, an optical laminate R was produced for the purpose of overlapping the evaluation samples to produce an orthogonal Nicol prism state. Specifically, for the above polarizing plate 9, an acrylic adhesive (LINTEC Corporation, Type #7) was formed on only one surface, and then cut to a size of 50 mm x 100 mm in a manner such that the absorption axis was parallel to the short side. A non-alkali glass (Corning Company, "EAGLE XG") was attached to the adhesive surface, thereby producing the optical laminate R used in the orthogonal evaluation.

[0175] (Single transmittance evaluation (105°C))

[0176] The evaluation sample of the optical laminate 1 to 14 was subjected to autoclave treatment at a temperature of 50°C, a pressure of 5 kgf / cm 2 (490.3 kPa) for 1 hour, and then left to stand in an environment at a temperature of 23°C and a relative humidity of 55% for 24 hours. Thereafter, the evaluation sample of the optical laminate 1 to 14 was measured for transmittance (initial value), and stored in a heating environment at a temperature of 105°C until 100 to 200 hours. The transmittance was measured every 50 hours. The time at which the transmittance decreased by 5% or more with respect to the initial value was used as a basis for evaluation using the following criteria. The results obtained are shown in Table 2.

[0177] The sample in which the decrease in transmittance after 200 hours was 5% or less: A

[0178] The sample in which the decrease in transmittance from 150 to 200 hours was 5% or more: B

[0179] The sample in which the decrease in transmittance from 100 to 150 hours was 5% or more: C

[0180] The sample in which the decrease in transmittance after 100 hours was 5% or more: D

[0181] (Evaluation of orthogonal light leakage)

[0182] The evaluation sample after the measurement of monomer transmittance at 200 hours in the above-described evaluation of monomer transmittance was prepared. The optical laminate R for orthogonal Nicol prism evaluation, which was not subjected to the heating environment, was arranged in relation to the evaluation sample as an orthogonal Nicol prism, and placed on a backlight. The surroundings were shielded from light, and the orthogonal light leakage was evaluated visually in 4 stages according to the following criteria. The results obtained are shown in Table 2. Note that the evaluation sample other than A in the evaluation of monomer transmittance was excluded from the evaluation of orthogonal light leakage because of coloring due to polyene.

[0183] The sample in which the orthogonal light leakage was not observed at all: A

[0184] The sample in which the orthogonal light leakage was basically not observed: B

[0185] The sample in which the orthogonal light leakage was observed slightly: C

[0186] The sample in which the orthogonal light leakage was observed clearly: D

[0187] [Table 2]

[0188]

[0189] It is known that the polarizing plate (optical laminate 1 to 10) in which the polarizing element and the transparent protective film having an equilibrium moisture content higher than the equilibrium moisture content at 20°C and 30% RH and lower than the equilibrium moisture content at 20°C and 50% RH, and the polarizing element and the transparent protective film are bonded by the adhesive containing the urea-based compound and the dicarboxylic acid, is not easily reduced in transmittance even when exposed to a high-temperature environment of 105°C, and is excellent in high-temperature durability. The optical laminate 1 to 10 is also excellent in evaluation of orthogonal light leakage, and is not easily reduced in degree of polarization even when exposed to a high-temperature environment of 105°C, and is excellent in high-temperature durability from this point.

Claims

1. A polarizing plate having: a polarizing element in which a dichroic dye is adsorbed to a polyvinyl alcohol-based resin layer and the dichroic dye is oriented, and a transparent protective film laminated to at least one face of the polarizing element, the polarizing element and the transparent protective film are bonded by an adhesive layer formed from an adhesive containing a urea-based compound and a dicarboxylic acid, the urea-based compound is at least one selected from the group consisting of a urea derivative, thiourea, and a thiourea derivative, the urea derivative is methyl urea, ethyl urea, propyl urea, butyl urea, isobutyl urea, N-octadecyl urea, 2-hydroxyethyl urea, hydroxy urea, acetyl urea, allyl urea, 2-propynyl urea, cyclohexyl urea, phenyl urea, 3-hydroxyphenyl urea, (4-methoxyphenyl) urea, benzyl urea, benzoyl urea, o-tolyl urea, p-tolyl urea, 1,1-dimethyl urea, 1,3-dimethyl urea, 1,1-diethyl urea, 1,3-diethyl urea, 1,3-bis(hydroxymethyl) urea, 1,3-t-butyl urea, 1,3-biscyclohexyl urea, 1,3-diphenyl urea, 1,3-bis(4-methoxyphenyl) urea, 1-acetyl-3-methyl urea, 2-imidazolidinone (ethylene urea), tetrahydro-2-pyrimidinone (propylene urea), tetramethyl urea, 1,1,3,3-tetraethyl urea, 1,1,3,3-tetrabutyl urea, 1,3-dimethoxy-1,3-dimethyl urea, 1,3-dimethyl-2-imidazolidinone, or 1,3-dimethyl-3,4,5,6-tetrahydro-2(lH)-pyrimidinone, and the moisture content of the polarizing element is equal to or higher than the equilibrium moisture content at 20°C and 30% RH and equal to or lower than the equilibrium moisture content at 20°C and 50% RH.

2. A polarizing plate having: a polarizing element in which a dichroic dye is adsorbed to a polyvinyl alcohol-based resin layer and the dichroic dye is oriented, and a transparent protective film laminated to at least one face of the polarizing element, the polarizing element and the transparent protective film are bonded by an adhesive layer formed from an adhesive containing a urea-based compound and a dicarboxylic acid, the urea-based compound is at least one selected from the group consisting of a urea derivative, thiourea, and a thiourea derivative, ​ ​ ​ ​ ​ ​ The urea derivative is methyl urea, ethyl urea, propyl urea, butyl urea, isobutyl urea, N-octadecyl urea, 2-hydroxyethyl urea, hydroxy urea, acetyl urea, allyl urea, 2-propynyl urea, cyclohexyl urea, phenyl urea, 3-hydroxyphenyl urea, (4-methoxyphenyl) urea, benzyl urea, benzoyl urea, o-tolyl urea, p-tolyl urea, 1,1-dimethyl urea, 1,3-dimethyl urea, 1,1-diethyl urea, 1,3-diethyl urea, 1,3-bis(hydroxymethyl) urea, 1,3-tert-butyl urea, 1,3-biscyclohexyl urea, 1,3-diphenyl urea, 1,3-bis(4-methoxyphenyl) urea, 1-acetyl-3-methyl urea, 2-imidazolidinone (ethylene urea), tetrahydro-2-pyrimidinone (propylene urea), tetramethyl urea, 1,1,3,3-tetraethyl urea, 1,1,3,3-tetrabutyl urea, 1,3-dimethoxy-1,3-dimethyl urea, 1,3-dimethyl-2-imidazolidinone, or 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone, The water content of the polarizing plate is equal to or higher than the equilibrium water content at 20°C and 30% RH and equal to or lower than the equilibrium water content at 20°C and 50% RH.

3. The polarizing plate according to claim 1 or 2, wherein The adhesive contains at least one urea-based compound selected from a urea derivative and a thiourea derivative.

4. The polarizing plate according to any one of claims 1 to 3, wherein The adhesive contains a polyvinyl alcohol-based resin.

5. The polarizing plate according to claim 4, wherein The content of the urea-based compound in the 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 claim 4 or 5, wherein The content of the dicarboxylic acid in the adhesive is 1 part by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the polyvinyl alcohol-based resin.

7. A polarizing plate having: a polarizing element in which a dichroic dye is adsorbed to a polyvinyl alcohol-based resin layer and the dichroic dye is oriented, and a transparent protective film laminated to at least one face of the polarizing element, The polarizing element and the transparent protective film are bonded by an adhesive layer formed by an adhesive containing a urea-based compound and a dicarboxylic acid, The adhesive contains a polyvinyl alcohol-based resin, the content of the urea-based compound is 30 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the polyvinyl alcohol-based resin, The urea-based compound is at least one selected from urea and monosubstituted urea, The monosubstituted urea is selected from methyl urea, ethyl urea, propyl urea, butyl urea, isobutyl urea, N-octadecyl urea, 2-hydroxyethyl urea, hydroxy urea, acetyl urea, allyl urea, 2-propynyl urea, cyclohexyl urea, phenyl urea, 3-hydroxyphenyl urea, (4-methoxyphenyl) urea, benzyl urea, benzoyl urea, o-tolyl urea, p-tolyl urea, The water content of the polarizing element is equal to or higher than the equilibrium water content at 20°C and 30% RH and equal to or lower than the equilibrium water content at 20°C and 50% RH.

8. A polarizing plate, comprising: a polarizing element in which a dichroic dye is adsorbed to a polyvinyl alcohol-based resin layer and the dichroic dye is oriented, and a transparent protective film laminated to at least one face of the polarizing element, the polarizing element and the transparent protective film are bonded by an adhesive layer formed from an adhesive containing a urea-based compound and a dicarboxylic acid, the adhesive contains a polyvinyl alcohol-based resin, the content of the urea-based compound is 30 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the polyvinyl alcohol-based resin, the urea-based compound is at least one selected from the group consisting of urea and monosubstituted urea, the monosubstituted urea is selected from the group consisting of methyl urea, ethyl urea, propyl urea, butyl urea, isobutyl urea, N-octadecyl urea, 2-hydroxyethyl urea, hydroxy urea, acetyl urea, allyl urea, 2-propynyl urea, cyclohexyl urea, phenyl urea, 3-hydroxyphenyl urea, (4-methoxyphenyl) urea, benzyl urea, benzoyl urea, o-tolyl urea, p-tolyl urea, the polarizing plate has a moisture content of 20°C and 30% RH or more and 20°C and 50% RH or less.

9. The polarizing plate according to claim 7 or 8, wherein In the adhesive, the content of the dicarboxylic acid is 1 part by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the polyvinyl alcohol-based resin.

10. The polarizing plate according to any one of claims 1 to 9, wherein the thickness of the adhesive layer is 0.01 μm or more and 7 μm or less.

11. The polarizing plate according to any one of claims 1 to 10, wherein the dicarboxylic acid is at least one of maleic acid or phthalic acid.

12. The polarizing plate according to any one of claims 1 to 11, wherein the polarizing plate is used for an image display device, in the image display device, a solid layer is provided in contact with both faces of the polarizing plate.

13. An image display device, comprising: an image display unit, a first adhesive layer laminated to a visual side surface of the image display unit, and a polarizing plate according to any one of claims 1 to 12 laminated to a visual side surface of the first adhesive layer.

14. The image display device according to claim 13, further comprising: a second adhesive layer laminated to a visual side surface of the polarizing plate, and a transparent member laminated to a visual side surface of the second adhesive layer.

15. The image display device according to claim 14, wherein the transparent member is a glass plate or a transparent resin plate.

16. The image display device according to claim 14, wherein the transparent member is a touch panel. ​ ​ ​ ​ ​

Images