Polarizing plate and image display device

Abstract

The present application provides a polarizing plate capable of inhibiting the decrease in transmittance in a high-temperature environment and having excellent water resistance. Provided is 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 being bonded by an adhesive layer formed of an adhesive containing a urea-based compound and a dialdehyde, the urea compound being at least one selected from the group consisting of urea, a urea derivative, thiourea, and a thiourea derivative, and the water content of the polarizing element being 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 obtained by adhering polarizing plates 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 for 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 the case where extraneous light is reflected by a metal electrode (cathode) and observed as a mirror surface, 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] Polarizing plates are increasingly mounted in vehicles as a component of image display devices such as liquid crystal display devices and organic EL display devices, as described above. In comparison with television and mobile device uses, the polarizing plate used in an image display device for a car-mounted use is often exposed to a high-temperature environment, and thus is required to have a small change in characteristics at a higher temperature (high-temperature durability).

[0004] On the other hand, a 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 an image display panel for the purpose of preventing breakage of the image display panel due to an impact from the outside surface and the like is increasing. In an image display device equipped with a touch panel, a configuration in which a touch panel is provided on the visible side of an image display panel, and a front panel is further 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 extraneous light due to reflection of light at the interface of the air layer occurs, and there is a tendency that the visibility of the picture decreases. Therefore, a trend of adopting a configuration (hereinafter sometimes referred to as an "interlayer filling configuration") in which a 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 expanding. 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 a decrease in visibility due to reflection at the interface and fixing 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 being studied for adoption in car-mounted applications such as navigation devices.

[0007] However, according to reports, in the case of adopting such a configuration, the transmittance of the polarizing plate significantly decreases in a high-temperature environment. Patent Literature 2 proposes a method in which the amount of moisture per unit area of the polarizing plate is set to be equal to or less than a given 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 given amount, thereby suppressing the decrease in transmittance.

[0008] However, even with such a measure, the suppression effect on the decrease in transmittance in the high-temperature durability test is not sufficient.

[0009] Prior Art Documents

[0010] Patent Literature

[0011] Patent Literature 1: Japanese Patent Application Laid-Open No. 11-174417

[0012] Patent Literature 2: Japanese Patent Application Laid-Open No. 2014-102353 SUMMARY

[0013] Problems to be Solved by the Invention

[0014] An object of the present application is to provide a novel polarizing plate in which the decrease in transmittance in a high-temperature environment can be suppressed and which has excellent water resistance, and an image display device using the polarizing plate.

[0015] Means for Solving the Problems

[0016] The present application provides the following exemplified polarizing plate and image display device.

[0017] [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,

[0018] the polarizing element and the transparent protective film are attached by an adhesive layer formed of an adhesive containing a urea-based compound and a dialdehyde,

[0019] the urea compound is at least one selected from the group consisting of urea, a urea derivative, thiourea, and a thiourea derivative,

[0020] 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.

[0021] [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 surface of the polarizing element,

[0022] 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 dialdehyde,

[0023] The urea compound is at least one selected from the group consisting of urea, a urea derivative, thiourea, and a thiourea derivative,

[0024] 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.

[0025] [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.

[0026] [4] The polarizing plate according to any one of [1] to [3], wherein the adhesive contains a polyvinyl alcohol-based resin.

[0027] [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.

[0028] [6] The polarizing plate according to any one of [1] to [5], wherein the content of the dialdehyde in the adhesive is 0.03 parts by mass or more and 20 parts by mass or less with respect to 1 part by mass of the urea-based compound.

[0029] [7] The polarizing plate according to any one of [1] to [6], wherein the dialdehyde is glyoxal.

[0030] [8] The polarizing plate according to any one of [1] to [7], wherein the thickness of the adhesive layer is 0.01 μm or more and 7 μm or less.

[0031] [9] The polarizing plate according to any one of [1] to [8], wherein the polarizing plate is used for an image display device,

[0032] In the image display device, a solid layer is provided in contact with both surfaces of the polarizing plate.

[0033]

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

[0034]

[11] The image display device described in

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

[0035]

[12] The image display device described in

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

[0036]

[13] The image display device described in

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

[0037] Effects of the Invention

[0038] According to the present application, a polarizing plate having improved high-temperature durability and water resistance can be provided, and even when used in an image display device in which an interlayer filling structure is employed, the decrease in transmittance and degree of polarization due to high temperature can be suppressed, and the image display device has excellent water resistance. Furthermore, by using the polarizing plate of the present application, an image display device in which the decrease in transmittance and degree of polarization under high-temperature environments is suppressed, and which has excellent water resistance, can be provided. DETAILED DESCRIPTION

[0039] Hereinafter, embodiments of the present application will be described, however the present application is not limited to the following embodiments.

[0040] [Polarizing plate]

[0041] The polarizing plate of the present embodiment has a polarizing element in which a dichroic dye is adsorbed 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 attached by an adhesive layer formed by an adhesive containing a urea-based compound and a dialdehyde. The polarizing plate of the present embodiment has at least one of the following features (a) and (b).

[0042] (a) The water content of the polarizing element is equal to or higher than the equilibrium water content at a temperature of 20°C and a relative humidity of 30% and equal to or lower than the equilibrium water content at a temperature of 20°C and a relative humidity of 50%.

[0043] (b) The water content of the polarizing plate is equal to or higher than the equilibrium water content at a temperature of 20°C and a relative humidity of 30% and equal to or lower than the equilibrium water content at a temperature of 20°C and a relative humidity of 50%.

[0044] As a conventional polarizing plate excellent in high-temperature durability, for example, there is known a polarizing plate which can suppress a decrease in transmittance even when left in an environment at a temperature of 95°C for 1000 hours in the case of a single polarizing plate. However, even such a polarizing plate, when used in a layer-filling configuration, if left in an environment at a temperature of 95°C for 200 hours, there are cases where a significant decrease in transmittance is observed in the central portion in the plane of the polarizing plate. The significant decrease in transmittance of a polarizing plate in a high-temperature environment is considered to be a problem that particularly easily occurs when an image display device employing a layer-filling configuration in which one face of a polarizing plate is attached to an image display unit and the other face is attached to a transparent member such as a touch panel or a front panel is exposed to a high-temperature environment.

[0045] A polarizing plate in which the transmittance significantly decreases due to a layer-filling configuration can be considered to be because, in Raman spectroscopic measurement, a peak is present near 1100 cm -1 (derived from =C-C= bonds) and 1500 cm -1 (derived from -C=C- bonds), and thus a polyene structure (-C=C) n is formed. It is presumed that the polyene structure is a structure that is generated after polyeneization of polyvinyl alcohol constituting a polarizing element by dehydration (Patent Document 2, paragraph

[0012] ).

[0046] The polarizing plate of the present application can improve high-temperature durability and, in addition, can improve water resistance. The polarizing plate of the present application is incorporated into an image display device in a layer-filling configuration, and can suppress a decrease in transmittance even when exposed to a high-temperature environment at a temperature of, for example, 105°C.

[0047] <Polarizing Element>

[0048] As a polarizing element in which a dichroic dye is adsorbed to a layer (hereinafter also referred to as "PVA-based resin layer") containing a polyvinyl alcohol (hereinafter also referred to as "PVA")-based resin and the dichroic dye is oriented, a known polarizing element can be used. As the polarizing element, a stretched film obtained by dyeing a PVA-based resin film with a dichroic dye and uniaxially stretching it; a stretched layer obtained by using a laminate film having a coating layer formed by coating a coating liquid containing a PVA-based resin on a base film, dyeing the coating layer with a dichroic dye, and uniaxially stretching the laminate film. Stretching can be performed after dyeing with a dichroic dye, can be performed while dyeing, or can be performed after stretching.

[0049] 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 be mentioned. As the other monomer copolymerizable, for example, unsaturated carboxylic acids, olefins such as ethylene, vinyl ethers, unsaturated sulfonic acids, and the like can be mentioned.

[0050] The degree of saponification 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 degree of polymerization 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.

[0051] 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, the influence of the decrease in the optical properties of the PVA-based resin due to polyeneization under a high-temperature environment can be suppressed. By making the thickness of the polarizing element 3 μm or more, it is easy to make a constitution that achieves desired optical properties.

[0052] The polarizing element preferably contains a urea-based compound. In the present embodiment, since the polarizing element is attached to the transparent protective film through an adhesive layer formed of an adhesive containing a urea-based compound, it is presumed that a part of the urea-based compound that migrates from the adhesive layer is contained in the polarizing element. The urea-based compound in the polarizing element can contain a urea-based compound added during the manufacturing process of the polarizing element. By having an adhesive layer containing a urea-based compound, even if the polarizing plate is exposed to a high-temperature environment, the transmittance is not easily decreased. It is presumed that this is because the polyeneization of the PVA-based resin is suppressed by the urea-based compound contained in the polarizing element.

[0053] As a method of causing the polarizing element to contain a urea-based compound during the manufacturing process, a method of immersing a PVA-based resin layer in a treatment solvent containing a urea-based compound, or a method of spraying, flowing, or dropping a treatment solvent to a PVA-based resin layer can be mentioned.

[0054] The step of impregnating the PVA-based resin layer in a treatment solvent containing a urea-based compound 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 a urea-based compound 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 color tone changes little, and the influence on the optical characteristics of the polarizing element can be reduced.

[0055] In order to cause the polarizing element to contain a urea-based compound, both the addition during the manufacturing of the polarizing element and the addition to the adhesive can be performed.

[0056] (Urea-based compound)

[0057] 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. There are water-soluble compounds and poorly water-soluble compounds in the urea-based compound, and any urea-based compound can be used. In the case where a poorly water-soluble urea-based compound is used in a water-soluble adhesive, the dispersion method is preferably designed so that turbidity does not increase or the like after the adhesive layer is formed.

[0058] (Urea derivative)

[0059] 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, but is preferably a substituent containing a carbon atom, a hydrogen atom, and an oxygen atom.

[0060] As specific examples of the urea derivative, in the case of a mono-substituted urea, there can be mentioned methylurea, ethylurea, propylurea, butylurea, isobutylurea, N-octadecylurea, 2-hydroxyethylurea, hydroxyurea, acetylurea, allylurea, 2-propynylurea, cyclohexylurea, phenylurea, 3-hydroxyphenylurea, (4-methoxyphenyl)urea, benzylurea, benzoylurea, o-tolylurea, p-tolylurea.

[0061] In the case of a di-substituted urea, there can be mentioned 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), tetrahydro-2-pyrimidinone (propyleneurea).

[0062] 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 given.

[0063] (thiourea derivative)

[0064] The thiourea derivative is a compound in which at least one of the four hydrogen atoms of the thiourea molecule is replaced by a substituent. In this case, the substituent is not particularly limited, however, a substituent containing a carbon atom, a hydrogen atom and an oxygen atom is preferred.

[0065] As the specific examples of 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 given.

[0066] 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 given.

[0067] As the tri-substituted thiourea, trimethyl thiourea can be given, and as the tetra-substituted thiourea, tetramethyl thiourea, 1,1,3,3-tetraethyl thiourea can be given.

[0068] From the viewpoint of suppressing the decrease in the transmittance in a high-temperature environment when used for the interlayer filling of the image display device, among the urea-based compounds, a urea derivative or a thiourea derivative is preferred, and a urea derivative is more preferred. Among the urea derivatives, a mono-substituted urea or a di-substituted urea is preferred, and a mono-substituted urea is more preferred. Among the di-substituted urea, 1,1-substituted urea and 1,3-substituted urea are given, however, 1,3-substituted urea is more preferred.

[0069] (characteristic (a))

[0070] In the case of having the feature (a), 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. The water content of the polarizing element is preferably equal to or lower than the equilibrium water content at 20°C and 45% RH, more preferably equal to or lower than the equilibrium water content at 20°C and 42% RH, and further preferably equal to or lower than the equilibrium water content at 20°C and 38% RH. If the water content of the polarizing element is lower than the equilibrium water content at 20°C and 30% RH, the operability of the polarizing element is reduced, and the polarizing element is easily broken. If the water content of the polarizing element is higher than the equilibrium water 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 water content of the polarizing element is high, the polyene of the PVA-based resin is easily advanced. The water content of the polarizing element is the water content of the polarizing element in the polarizing plate.

[0071] As a method of confirming whether or not 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 regarding that the environment is in equilibrium in the case where there is no change in quality for a certain time; 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 calculated equilibrium water content.

[0072] As a method of producing the polarizing element having the water content 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 is no particular limitation, and there can be mentioned, for example, 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 more and 90°C or less.

[0073] As another preferable method of producing the 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 on at least one side 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 more and 90°C or less. In the production of an image display device using an interlayer filling, an image display panel in which a polarizing plate is laminated on 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 heated at 30°C or more and 90°C or less, and then a front panel is attached.

[0074] The water content of the polarizing element is preferably adjusted as shown below, that is, in a material stage used for constituting a polarizing plate as a single polarizing element or as a laminate of a polarizing element and a protective film, the water content is in the above numerical range. In the case where the water content is adjusted after constituting the polarizing plate, curling becomes too large, and there is a case where poor conditions are easily caused at the time of attaching to an image display unit. By constituting the polarizing plate using a polarizing element whose water content is adjusted to the above water content in the material stage before constituting the polarizing plate, it is possible to easily constitute a polarizing plate having a polarizing element whose water content satisfies the above numerical range. It is also possible to adjust the water content of the polarizing element in the polarizing plate to the above numerical range in a state where the polarizing plate is attached to an image display unit. In this case, the polarizing plate is attached to the image display unit, and thus curling is not easily caused.

[0075] (characteristic (b))

[0076] In the case of having characteristic (b), 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. The water content of the polarizing plate is preferably equal to or lower than the equilibrium water content at 20°C and 45% RH, more preferably equal to or lower than the equilibrium water content at 20°C and 42% RH, and further preferably equal to or lower than the equilibrium water content at 20°C and 38% RH. If the water content of the polarizing plate is lower than the equilibrium water content at 20°C and 30% RH, the operability of the polarizing plate is reduced, and breakage is easily caused. If the water content of the polarizing plate is higher than the equilibrium water 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 water content of the polarizing plate is high, polyene of the PVA-based resin is easily advanced.

[0077] As a method of confirming whether or not the water content of the polarizing plate 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 temperature and the above relative humidity, and considering that the environment is in equilibrium in the case where there is no change in quality for a certain time; or a method of calculating in advance the equilibrium water content of the polarizing plate in an environment adjusted to the above temperature and the above relative humidity, and confirming by comparing the water content of the polarizing plate with the calculated equilibrium water content.

[0078] As a method of producing a polarizing plate 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, and there can be mentioned, for example, a method of storing the polarizing plate in an environment adjusted to the above temperature and the above relative humidity for 10 minutes or more and 3 hours or less; or a method of performing a heat treatment at 30°C or higher and 90°C or lower.

[0079] In the production of the image display device configured by the interlayer filling, the image display panel in which the polarizing plate is laminated to the image display unit can be 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 heated at 30°C or more and 90°C or less, and then the front panel is attached.

[0080] (Method for manufacturing polarizing element)

[0081] The method for manufacturing the polarizing element is not particularly limited, however, typical methods are: a method (hereinafter, referred to as "manufacturing method 1") in which a PVA-based resin film that is wound in a roll shape in advance is sent out and then stretched, dyed, cross-linked, and the like to produce; and a method (hereinafter, referred to as "manufacturing method 2") including a step of forming a PVA-based resin layer as a coating layer by applying a coating liquid containing a PVA-based resin onto a base film, and a step of stretching the obtained laminate.

[0082] The manufacturing method 1 can be manufactured by a step of uniaxially stretching the PVA-based resin film, a step of dyeing the PVA-based resin film with a dichroic dye such as iodine to adsorb the dichroic dye, a step of treating the PVA-based resin film on which the dichroic dye is adsorbed with an aqueous boric acid solution, and a step of washing with water after the treatment based on the aqueous boric acid solution.

[0083] The swelling step is a treatment step in which the PVA-based resin film is immersed in a swelling bath. By the swelling step, in addition to the removal of dirt, an adhesive agent, or the like from the surface of the PVA-based resin film, dyeing unevenness can be suppressed 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 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 the 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. The immersion time in the swelling bath cannot be determined in general because the degree of swelling of the PVA-based resin film is affected by the temperature of the swelling bath, however, it is preferably 5 seconds or more and 300 seconds or less, more preferably 10 seconds or more and 200 seconds or less, and further preferably 20 seconds or more and 100 seconds or less. The swelling step can be performed only once, or can be performed multiple times as necessary.

[0085] The dyeing step is a treatment step in which the PVA-based resin film is immersed in a dyeing bath (iodine solution), and can cause the PVA-based resin film to adsorb a dichroic coloring agent such as iodine and orient it. The iodine solution is preferably generally an aqueous iodine solution, and contains iodine and an iodide as a dissolution aid. As the iodide, 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 can be given. Among these, from the viewpoint of controlling the content of potassium 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, 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 more and 300 seconds or less, and more preferably 20 seconds or more and 240 seconds or less. The dyeing step can be performed only once, or can be performed a plurality of times as necessary.

[0088] The cross-linking step is a treatment step in which the PVA-based resin film dyed in the dyeing step 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 are adsorbed to the cross-linked structure. As the boron compound, boric acid, a boric acid salt, borax, and 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] The concentration of the boron compound in the cross-linking bath is preferably 1% by mass or more and 15% by mass or less, more preferably 1.5% by mass or more and 10% by mass or less, and further preferably 2% by mass or more and 5% by mass or less. In the case where 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 more and 15% by mass or less, more preferably 1.5% by mass or more and 10% by mass or less, and further preferably 2% by mass or more and 5% by mass or less.

[0090] The temperature of the cross-linking bath is preferably 20°C or higher and 70°C or lower, more preferably 30°C or higher and 60°C or lower. The immersion time in the 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, more preferably 10 seconds or longer and 200 seconds or shorter.

[0091] The cross-linking process can be performed only once, or can be performed multiple times as necessary.

[0092] The stretching process is a process in which the PVA-based resin film is stretched at a given 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 either of a wet stretching method and a dry stretching method can be employed. The stretching process can be performed only once, or can be performed multiple times as necessary. The stretching process can be performed at any stage in the production of the polarizing element.

[0093] 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 higher and 15% by mass or lower, more preferably 2% by mass or higher and 10% by mass or lower, and further preferably 3% by mass or higher and 6% by mass or lower. 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 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.

[0094] The temperature of the stretching bath is preferably 25°C or higher and 80°C or lower, more preferably 40°C or higher and 75°C or lower, and 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 longer and 800 seconds or shorter, and more preferably 30 seconds or longer and 500 seconds or shorter. The stretching process in the wet stretching method can be performed together with any one or more of the swelling process, the dyeing process, the cross-linking process, and the cleaning process.

[0095] As the dry stretching method, for example, roll-to-roll stretching, heated roll stretching, compression stretching, or the like can be given. Note that the dry stretching method can be performed together with the drying process.

[0096] The total stretching ratio (cumulative stretching ratio) applied to the polyvinyl alcohol-based resin film can be appropriately set according to the purpose, and 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.

[0097] The cleaning step is a treatment step 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 as a medium having water as a main component. In addition, from the viewpoint of controlling the content of potassium in the polarizing element, it is preferable to use potassium iodide 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.

[0098] The temperature of the cleaning bath is preferably 5°C or more and 50°C or less, more preferably 10°C or more and 40°C or less, further preferably 15°C or more and 30°C or less. As for the immersion time in the cleaning bath, since the degree of cleaning of the PVA-based resin film is affected by the temperature of the cleaning bath, it cannot be determined in general, but is preferably 1 second or more and 100 seconds or less, more preferably 2 seconds or more and 50 seconds or less, further preferably 3 seconds or more and 20 seconds or less. The cleaning step can be performed only once, or can be performed a plurality of times as needed.

[0099] The drying step is a step of drying the PVA-based resin film cleaned in the cleaning step to obtain a polarizing element. Drying can be performed by any appropriate method, and for example, natural drying, air blowing drying, and heating drying can be given.

[0100] The production method 2 can be produced by a step of applying a coating liquid containing a PVA-based resin to a base film, a step of uniaxially stretching the obtained laminated film, a step of producing a polarizing element by dyeing the PVA-based resin layer of the uniaxially stretched laminated film with a dichroic dye to adsorb the dichroic dye, a step of treating the film having adsorbed the dichroic dye with an aqueous boric acid solution, and a step of performing water washing after the treatment based on the aqueous boric acid solution. The base film used for forming the polarizing element can be used as a protective layer of the polarizing element. The base film can be peeled off and removed from the polarizing element as needed.

[0101] <Transparent protective film>

[0102] 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 is attached to one side or both sides of the polarizing element, but is preferably attached to both sides.

[0103] The protective film can have other optical functions, and can be formed in a laminated structure with multiple layers. From the viewpoint of optical properties, the film thickness of the protective film is preferably thin, but if it is too thin, the strength decreases and the processability is poor. As a suitable film thickness, it is 5 μm or more and 100 μm or less, preferably 10 μm or more and 80 μm or less, more preferably 15 μm or more and 70 μm or less.

[0104] 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, or the like. In the case where a water-based adhesive such as a PVA adhesive is used to adhere the protective film to both sides of the polarizing element, the protective film on at least one side is preferably either a cellulose acylate film or a (meth)acrylic polymer film from the viewpoint of moisture permeability, with the cellulose acylate film being preferred.

[0105] The protective film on at least one side can have a phase difference function for the purpose of view angle compensation or the like. In this case, the protective film itself can have a phase difference function, or a phase difference layer can be separately provided, or a combination of both can be used. The film having a phase difference function can be directly adhered to the polarizing element via an adhesive, but can also be adhered via an adhesive or an adhesive layer with another protective film interposed between the film and the polarizing element.

[0106] <Adhesive Layer>

[0107] An adhesive containing a urea compound and a dialdehyde is used as an adhesive for forming an adhesive layer for adhering a protective film to a polarizing element. The adhesive can use 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 an adhesive containing a urea compound and a dialdehyde, the decrease in transmittance of the polarizing plate under a high-temperature environment can be suppressed, and the water resistance can be improved. In addition, by using an adhesive containing a urea compound and a dialdehyde, even if the polarizing plate is exposed to a high-temperature environment, the decrease in degree of polarization can be suppressed. In the case where two polarizing plates are used in a manner to be arranged so as to form a cross-Nicol prism, if the degree of polarization of the polarizing plate decreases, light leakage (hereinafter also referred to as "cross light leakage") easily occurs, but according to the present application, the degree of polarization is not easily decreased even if it is exposed to a high-temperature environment, and thus the cross light leakage is easily suppressed.

[0108] As the dialdehyde, for example, glyoxal, malondialdehyde, succinaldehyde, or the like can be given. Glyoxal is particularly preferred because of its simple structure and high reactivity. Glyoxal is described below, but a dialdehyde known in the art can be used as the dialdehyde as described above, and is not limited to glyoxal.

[0109] The thickness of the adhesive at the time of application can be set to an arbitrary value, for example, can be set in a manner that an adhesive layer having a desired thickness is obtained after curing or after heating (drying). The thickness of the adhesive layer composed of the adhesive is preferably 0.01 μm or more and 7 μm or less, more preferably 0.01 μm or more and 5 μm or less, further preferably 0.01 μm or more and 2 μm or less, most preferably 0.01 μm or more and 1 μm or less.

[0110] The following description of the adhesive is set as a description of a preferable range in the case where the polarizing element does not contain a urea-based compound at the time of manufacturing the polarizing element. In the case where the polarizing element contains a urea-based compound, the following values can be appropriately adjusted. For specific examples of the urea-based compound, the above-described examples of the urea-based compound contained in the polarizing element can be applied as they are. 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 can move from the adhesive layer to the polarizing element or the like.

[0111] 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 part by mass or more and 200 parts by mass or less, 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 less than 0.1 parts by mass, there is a case where the inhibitory effect on the polyene of the polarizing element in 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, and there is a case where an undesirable condition such as an increase in turbidity occurs.

[0112] In the case where the adhesive is a water-based adhesive containing a PVA-based resin, the content of the dialdehyde is preferably 1 part by mass or more and 60 parts by mass or less, more preferably 1.5 parts by mass or more and 50 parts by mass or less, further preferably 2 parts by mass or more and 45 parts by mass or less, with respect to 100 parts by mass of the PVA-based resin. If less than 1 part by mass, there is a case where the effect of improving water resistance is not sufficient. On the other hand, in the case where it is more than 60 parts by mass, there is a case where the liquid stability of the adhesive is reduced.

[0113] In the adhesive, the content of the dialdehyde is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and further preferably 10 parts by mass or less, relative to 1 part by mass of the urea compound, and the lower limit is not limited, but is, for example, 0.03 parts by mass or more. By having the content ratio of the urea compound to the dialdehyde in the adhesive within the above range, it is easy to achieve both the effect of improving the high-temperature durability based on the urea compound and the effect of improving the adhesion based on the dialdehyde. It is considered that, by the effect of improving the adhesion based on the dialdehyde, the effect of improving the water resistance is obtained. In the case where the dialdehyde is contained in an amount of more than 20 parts by mass relative to 1 part by mass of the urea compound, the effect of improving the high-temperature durability based on the urea compound cannot be sufficiently exerted. The content ratio of the urea compound to the dialdehyde in the adhesive and the content ratio of the urea compound to the dialdehyde in the adhesive layer can be considered to be the same.

[0114] In the configuration in which the transparent protective film is attached to both faces of the polarizing element via the adhesive layer, only one of the adhesive layers on both faces of the polarizing element can be the layer containing the urea compound and the dialdehyde, but preferably both of the adhesive layers are the layers containing the urea compound and the dialdehyde.

[0115] In order to respond to the demand for thinness of the polarizing plate, a polarizing plate having a transparent protective film on only one face of the polarizing element has been developed. 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 where such a production method is used, it is preferable that the adhesive layer on the side from which the film is not peeled off contains the urea compound and the dialdehyde, and both of the adhesive layers can be the layers containing the urea compound and the dialdehyde.

[0116] It is also preferable that the adhesive contains a water-soluble chelate compound. The water-soluble chelate compound can increase the cross-linking degree between the adhesive layer and the transparent protective film such as the polarizing element and the cellulose-based film, the olefin-based film, and the like, and can function as an additive that does not cause a problem in optical durability, and can function to improve the adhesion and the water resistance.

[0117] The water-soluble chelate compound has an effect of promoting the curing of the glyoxal. As the type of the chelate compound, zinc chloride, cobalt chloride, magnesium chloride, magnesium acetate, aluminum nitrate, zinc nitrate, zinc sulfate, and the like can be added. Zinc chloride and aluminum nitrate, which are particularly preferable, are excellent in the action of a cross-linking catalyst.

[0118] The weight ratio of the water-soluble chelate compound contained in the adhesive layer is preferably in the range of 2 to 10 parts by mass relative to 100 parts by mass of the PVA-based resin. In the case where the mass ratio of the water-soluble chelate compound is less than 2 parts by mass based on the above-mentioned criteria, the adhesive layer when the polarizing plate is produced is difficult to sufficiently exhibit water resistance, and in the case where the mass ratio is more than 10 parts by mass, there is a case where the optical properties are reduced.

[0119] (water-based adhesive)

[0120] Any appropriate water-based adhesive can be used as the water-based adhesive, but a water-based adhesive containing a PVA-based resin (PVA-based adhesive) is preferably used. 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 more preferably 1000 or more and 4500 or less, from the viewpoint of adhesiveness. 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, from the viewpoint of adhesiveness.

[0121] In the case where the adhesive is a water-based adhesive containing a PVA-based resin, a resin containing an acetoacetyl group is preferably used as the PVA-based resin, because the effect of improving the adhesion based on a dialdehyde is more remarkable. It is presumed that, for example, in the case where glyoxal is used as the dialdehyde, the aldehyde moiety of the glyoxal and the acetoacetyl group of the acetoacetyl-modified PVA-based resin undergo an addition reaction, and function as a crosslinking agent, thereby improving the adhesion. The PVA-based resin containing an acetoacetyl group can be obtained, for example, by reacting a PVA-based resin with diketene by any method. The degree of acetoacetyl modification of the acetoacetyl-modified PVA-based resin is preferably 0.1 mol% or more, and more preferably 0.1 mol% or more and 20 mol% or less. The concentration of the PVA-based resin in 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.

[0122] The water-based adhesive can also contain other crosslinking agents than dialdehydes. A publicly known crosslinking agent can be used as the crosslinking agent. As the crosslinking agent, for example, water-soluble epoxy compounds, isocyanates, and the like can be given.

[0123] The water-based adhesive can also contain an organic solvent. The organic solvent is preferably an alcohol from the viewpoint of miscibility with water, and more preferably methanol or ethanol. The concentration of methanol in the water-based 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 further preferably 20% by mass or more and 60% by mass or less. By making the concentration of methanol 10% by mass or more, it is easy to further suppress the polyenization of the PVA-based resin in a high-temperature environment. In addition, by making the content of methanol 70% by mass or less, it is possible to suppress the deterioration of the color tone. Some of urea derivatives have a low solubility in water, but a sufficient solubility in alcohol. In this case, it is also one of the preferable methods to prepare an alcohol solution of the urea-based compound by dissolving the urea-based compound in alcohol, and then adding the alcohol solution of the urea-based compound to the PVA aqueous solution to prepare the adhesive.

[0124] (Radiation-curable adhesive)

[0125] The radiation-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.

[0126] (Urea-based compound-containing layer)

[0127] The urea-based compound is not limited to the case where it is contained in the adhesive layer as described above, and can also be contained in other layers other than the adhesive layer from the viewpoint of improving the high-temperature durability of the polarizing plate. 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.

[0128] In the present embodiment, such a cured layer can also contain a urea-based compound, and be provided as a urea-based compound-containing layer. Such a cured layer is generally formed from a curable composition containing an organic solvent, but a method of forming such a cured layer from an aqueous solution of a high-energy radiation-curable polymer composition is described in

[0020] to

[0042] of Japanese Patent Application Publication No. 2017-075986. Such a composition can contain a water-soluble urea-based compound.

[0129] The urea compound-containing layer preferably has at least one urea compound and a binder. As the binder, a polymer binder, a thermally curable resin binder, a radiation curable resin binder, or the like can be given, and any of these can be preferably used.

[0130] 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 further preferably 1 μm or more and 10 μm or less.

[0131] [Method for manufacturing polarizing plate]

[0132] The method for manufacturing 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 above-described description of the water content of the polarizing element. 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 above-described description of the water content of the polarizing plate. In the laminating step, the polarizing element and the transparent protective film are laminated via the above-described adhesive layer. In the laminating step, for example, the polarizing element, which has not been subjected to the treatment of containing a urea compound, and the transparent protective film are attached using an adhesive containing a urea compound and a dialdehyde. 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.

[0133] [Configuration of image display device]

[0134] The polarizing plate of the present embodiment is used for various image display devices such as liquid crystal display devices, organic EL display devices, and the like. For the image display device, in the case of being configured in a manner in which both surfaces of the polarizing plate contact 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 the image display device using the polarizing plate of the present embodiment, even in the case of being configured in a manner in which both surfaces of the polarizing plate contact a layer other than an air layer, specifically, a solid layer such as an adhesive layer, 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 visual side surface of the image display unit, and a polarizing plate laminated on the visual side surface of the first adhesive layer can be exemplified. The image display device can further have a second adhesive layer laminated on the visual 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 the present embodiment can be suitably used for an image display device configured in a manner in which a transparent member is disposed on the visual side of the image display device, the polarizing plate is attached to the image display unit via the first adhesive layer, and the polarizing plate is attached to the transparent member via the second adhesive layer. In the present specification, either or both of the first adhesive layer and the second adhesive layer are sometimes simply referred to as an "adhesive layer". Note that, as the member used in the attachment of the polarizing plate to the image display unit and the member used in the attachment of the polarizing plate to the transparent member, the adhesive layer is not limited, and a bonding agent layer can also be used.

[0135] <image display unit>

[0136] As the image display unit, a liquid crystal cell, an organic EL cell can be exemplified. As the liquid crystal cell, any one of a reflection type liquid crystal cell using external light, a transmission type liquid crystal cell using light from a light source such as a backlight, and 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, the image display device (liquid crystal display device) is configured to have a polarizing plate on the side opposite to the visual side of the image display unit (liquid crystal cell), and further has a 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, a driving mode of an optional type such as a VA mode, an IPS mode, a TN mode, an STN mode, a bend alignment (pi cell) can be used.

[0137] As the organic EL unit, an organic EL unit in which a transparent electrode, an organic light-emitting layer, and a metal electrode are sequentially stacked on a transparent substrate to form a light emitter (organic electroluminescent light emitter) and the like can be appropriately 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.

[0138] <Attachment of image display unit and polarizing plate>

[0139] In the attachment of the image display unit and the polarizing plate, an adhesive layer (adhesive sheet) can be appropriately used. Among them, from the viewpoint of workability and the like, a method in which a polarizing plate with an adhesive layer to which an adhesive layer is attached to one surface is attached to the image display unit is preferred. The attachment of the adhesive layer to the polarizing plate can be performed by a suitable method. As examples thereof, a method in which an adhesive solution in which 10% by mass or more and 40% by mass or less of a base polymer or a composition thereof is dissolved or dispersed in a solvent of a single substance or a mixture of suitable solvents such as toluene, ethyl acetate, and the like, and is directly attached to the polarizing plate by a suitable 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.

[0140] <Adhesive layer>

[0141] The adhesive layer can be formed of one layer or two or more layers, but is preferably formed of one layer. The adhesive layer can be composed 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, a polyvinyl ether-based resin, or the like is used as a base polymer. Among them, an adhesive composition in which a (meth)acrylic resin is used as a base polymer is suitable in that transparency, weather resistance, heat resistance, and the like are excellent. The adhesive composition can be a type that is cured by active energy rays or a type that is cured by heat.

[0142] As the (meth)acrylic resin (base polymer) used in the adhesive composition, a polymer or a copolymer using one or two or more kinds of (meth)acrylic esters such as butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and the like as monomers can be appropriately used. It is preferable to copolymerize a polar monomer in the base polymer. As the polar monomer, monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, and 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, a glycidyl (meth)acrylate compound, and the like can be exemplified.

[0143] The adhesive composition can contain only the above-described base polymer, but generally also contains a cross-linking agent. As the cross-linking agent, a metal ion of two or more valences that forms a carboxylate metal salt between the carboxyl group and the metal ion; a polyamine compound that forms an amide bond between the carboxyl group and the compound; a polyepoxide compound or a polyhydric alcohol that forms an ester bond between the carboxyl group and the compound; a polyisocyanate compound that forms an amide bond between the carboxyl group and the compound can be exemplified. Among them, the polyisocyanate compound is preferable.

[0144] The active energy ray-curable adhesive composition has a property of being cured by irradiation of an active energy ray such as ultraviolet rays, electron beams, and the like, and has a property of being able to be closely adhered to a film or the like adherend before irradiation of the active energy ray and being able to be cured by irradiation of the active energy ray to achieve adjustment of the adhesion force. The active energy ray-curable adhesive composition is preferably ultraviolet ray-curable. The active energy ray-curable adhesive composition contains, on the basis of a base polymer, a cross-linking agent, and further contains an active energy ray-polymerizable compound. As necessary, a photopolymerization initiator, a photosensitizer, and the like can be contained.

[0145] The adhesive composition can contain a fine particle, a bead (resin bead, glass bead, and the like), a glass fiber, a resin other than the base polymer, a tackifier, a filler (metal powder, other inorganic powder, and the like), an antioxidant, an ultraviolet absorber, a dye, a pigment, a colorant, an antifoaming agent, an anticorrosive agent, a photopolymerization initiator, and the like as an additive for imparting light scattering properties.

[0146] The adhesive layer can be formed by applying an organic solvent diluent of the above-described adhesive composition to the surface of a base film, an image display unit, or a polarizing plate and drying. The base film is generally a thermoplastic resin film, and as a typical example thereof, a release film on which a mold release treatment is performed can be exemplified. The release film can be, for example, a film on which a mold release treatment such as silicone treatment is performed on the surface of a film containing a resin such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, polyarylate, and the like on which an adhesive layer is formed.

[0147] An adhesive composition can be applied directly to the release-treated surface of the release film to form an adhesive layer, and the adhesive layer with the release film can be laminated to the surface of the polarizing body. Alternatively, an adhesive composition can be applied directly to the surface of the polarizing plate to form an adhesive layer, and a release film can be laminated to the outer surface of the adhesive layer.

[0148] When the adhesive layer is provided to the surface of the polarizing plate, it is preferable to perform a surface activation treatment such as a plasma treatment or a corona treatment on the adherend surface of the polarizing plate and / or the adherend surface of the adhesive layer, and more preferably, a corona treatment.

[0149] Alternatively, an adhesive sheet in which an adhesive composition is applied to a second release film to form an adhesive layer, and a release film is laminated to the formed adhesive layer can be prepared, and the adhesive layer with the release film after the second release film is peeled from the adhesive sheet can be laminated to the polarizing plate. The second release film is a film that has a weaker adhesion to the adhesive layer than the release film and is easily peeled.

[0150] The thickness of the adhesive layer is not particularly limited, but 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.

[0151] <Transparent member>

[0152] 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 given. A transparent plate having an appropriate mechanical strength and thickness is used as the transparent plate. 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 given. A functional layer such as an antireflection layer can be laminated on the visual side of the transparent plate. 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 permeation. As the touch panel, various touch panels such as a resistance film method, an electrostatic capacity method, an optical method, an ultrasonic wave 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 to provide a transparent plate formed of a glass or a transparent resin plate on the visual side with respect to the touch panel.

[0153] <Lamination of polarizing plate and transparent member>

[0154] In the lamination of the polarizing plate and the transparent member, an adhesive or a active energy ray-curable adhesive can be appropriately used. In the case where an adhesive is used, the attachment of the adhesive can be performed by an appropriate method. As a specific attachment method, for example, the attachment method of the adhesive layer used in the lamination of the image display unit and the polarizing plate described above can be given.

[0155] In the case of using the active energy ray-curable adhesive, a method of disposing a coffer material so as to surround the peripheral portion on the image display panel, loading the transparent member on the coffer material, and injecting the adhesive solution can be appropriately used for the purpose of preventing the spread of the adhesive solution before curing. After the injection of the adhesive solution, the position alignment and the defoaming are performed as necessary, and then the active energy ray is irradiated to perform the curing.

[0156] Example

[0157] Hereinafter, the present application will be specifically described based on examples. The materials, reagents, substances, and their proportions, operations, and the like 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.

[0158] Production of Polarizing Element A

[0159] 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 maintaining the tension state. Subsequently, 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. Then, the PVA film was washed with pure water at 26°C for 20 seconds, and then dried at 65°C to obtain a polarizing element A having a thickness of 15 μm, in which iodine was adsorbed to and oriented in the PVA. In the measurement of the thickness of the polarizing element, a digital micrometer "MH-15M" manufactured by Nikon Corporation was used.

[0160] Preparation of Adhesives 1 to 8

[0161] (Preparation of PVA Solution A for Adhesive)

[0162] A modified PVA-based resin (GOHSENX Z-410 manufactured by Mitsubishi Chemical Corporation) containing acetoacetyl groups, 50 g, 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").

[0163] (Preparation of Urea Compound Solution 1)

[0164] Urea, 10 g, was added to 90 g of pure water to obtain an aqueous solution in which urea was 10 mass% (urea compound solution 1).

[0165] (Preparation of Adhesives 1 to 8)

[0166] The adhesive agent 1 to 8 was prepared by mixing the PVA solution A, the urea compound solution 1, a commercially available 40 mass% glyoxal solution, and pure water in such a manner that the PVA was 3.0 mass%, and the urea compound and the glyoxal were in the amounts shown in Table 1.

[0167] [Table 1]

[0168]

[0169] <Preparation of transparent protective film A>

[0170] A commercially available cellulose acylate film TD40 (manufactured by FUJIFILM Corporation, 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, the film was immersed in a 0.05 mol / L aqueous sulfuric acid solution at 25°C for 30 seconds, and then washed with water under a running water stream for 30 seconds to neutralize the film. Thereafter, 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 saponification-treated film, which was used as the transparent protective film A.

[0171] <Production of polarizing plates 1 to 8>

[0172] The transparent protective film A was attached to both surfaces of the polarizing element A using a roll laminator via the adhesive agent 1. After the attachment, the film was dried at 80°C for 5 minutes to obtain the polarizing plate 1. The thickness of the adhesive agent layer was adjusted so that the thickness after drying was 100 nm on both surfaces.

[0173] In the polarizing plate 1, the adhesive agent 1 was changed to the adhesive agents 2 to 8 to obtain the polarizing plates 2 to 8.

[0174] (Adjustment of water content of polarizing plate (polarizing element))

[0175] The polarizing plates 1 to 8 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 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 8 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 element in the polarizing plate reaches equilibrium under a certain storage environment, it can be regarded that the water content of the polarizing plate also reaches equilibrium under the same storage environment. In addition, when the water content of the polarizing element in the polarizing plate reaches equilibrium under a certain storage environment, it can be regarded that the water content of the polarizing plate also reaches equilibrium under the same storage environment.

[0176] <Optical laminates 1 to 10>

[0177] Using any of the polarizing plates 1 to 8 shown in Table 2, optical laminates 1 to 10 were produced in such a manner that the polarizing plate (polarizing element) used was stored at a temperature of 20°C and a relative humidity of 35%, 45% or 55% for 72 hours in an environment having a balanced moisture content shown in Table 2.

[0178] <High-temperature durability evaluation>

[0179] (Production of evaluation samples)

[0180] To the optical laminates 1 to 10, an acrylic adhesive (LINTEC Corporation, Type: #7) was applied to both surfaces, and then cut into a size of 50 mm x 100 mm in such a manner that the absorption axis was parallel to the long side. To the respective adhesive surfaces, an alkali-free glass (Corning Company, "EAGLE XG") was attached, thereby producing evaluation samples.

[0181] In order to evaluate the cross leakage of the above evaluation samples, an optical laminate R was produced for the purpose of producing a cross-Nicol prism state by overlapping the evaluation samples. Specifically, to the above polarizing plate 8, an acrylic adhesive (LINTEC Corporation, Type: #7) was applied to one surface, and then cut into a size of 50 mm x 100 mm in such a manner that the absorption axis was parallel to the short side. To the adhesive surface, an alkali-free glass (Corning Company, "EAGLE XG") was attached, thereby producing the optical laminate R used in the cross evaluation.

[0182] <Monomer transmittance evaluation (105°C)>

[0183] After the evaluation samples of the optical laminates 1 to 10 were subjected to autoclave treatment at a temperature of 50°C and a pressure of 5 kgf / cm 2 (490.3 kPa) for 1 hour, they were left to stand in an environment at a temperature of 23°C and a relative humidity of 55% for 24 hours. Thereafter, the transmittance (initial value) of the evaluation samples of the optical laminates 1 to 10 was measured, and they were stored in a heating environment at a temperature of 105°C until 100 to 200 hours, and the transmittance was measured every 50 hours. Based on the time at which the decrease in the transmittance with respect to the initial value was 5% or more, the evaluation was performed in accordance with the following criteria. The results obtained are shown in Table 2.

[0184] Samples in which the decrease in the transmittance after 200 hours was 5% or less: A

[0185] Samples in which the decrease in the transmittance at 150 to 200 hours was 5% or more: B

[0186] Samples in which the decrease in transmittance reached 5% or more at 100 to 150 hours: C

[0187] Samples in which the decrease in transmittance was 5% or more at 100 hours after the start: D

[0188] <Orthogonal light leakage after high-temperature durability test>

[0189] The evaluation sample after the measurement of the monomer transmittance at 200 hours in the above-described evaluation of the monomer transmittance was prepared. The optical laminate R for the evaluation of the orthogonal Nicol prism without being put into the heating environment and the evaluation sample were arranged in a manner that the optical laminate R and the evaluation sample were related to form an orthogonal Nicol prism, and were placed on a backlight. The surroundings were shielded from light, and the orthogonal light leakage was evaluated in 4 ranks by visual observation in accordance with the following criteria. The results obtained are shown in Table 2. Note that the evaluation sample other than A was excluded from the evaluation of the orthogonal light leakage because of coloring due to polyene formation.

[0190] Samples in which the orthogonal light leakage was not observed at all: A

[0191] Samples in which the orthogonal light leakage was not observed substantially: B

[0192] Samples in which the orthogonal light leakage was observed slightly: C

[0193] Samples in which the orthogonal light leakage was observed clearly: D

[0194] <Water resistance evaluation (warm water immersion test)>

[0195] The water resistance test of the present example was performed in accordance with the water resistance test described in Japanese Patent Application Publication No. 2009-025728

[0060] .

[0196] The polarizing plate produced above was formed with an acrylic-based adhesive (manufactured by LINTEC Corporation, type: #7) on one side, and was cut into a strip shape with the size of 50 mm x 20 mm with the absorption axis (stretching direction) of the polarizing plate as the long side, and the dimension of the long side direction was accurately measured. Here, the evaluation sample exhibited a unique color uniformly over the entire surface due to adsorption of iodine in the polarizing element.

[0197] One short side of the sample was held with a holding jig, and about 8% of the length direction was immersed in a water tank at 60°C for 4 hours. Thereafter, the sample was taken out of the water tank, and the moisture was wiped off. Due to the immersion in the warm water, the polarizing plate was shrunk. The degree of shrinkage of the polarizing element was evaluated in 3 ranks in accordance with the above criteria by measuring the distance from the end of the sample (the end of the protective film) to the end of the polarizing element that was shrunk at the center of the short side of the sample.

[0198] Samples where the distance from the end of the sample to the end of the polarizer is less than 1 mm: A

[0199] Samples where the distance from the end of the sample to the end of the polarizer is greater than 1 mm but less than 3 mm: B

[0200] Samples where the distance from the end of the sample to the end of the polarizer is greater than 3 mm: C

[0201] [Table 2]

[0202]

[0203] It can be seen that the polarizer containing urea in the adhesive (optical laminate 8) exhibits superior high-temperature durability compared to the polarizer without urea in the adhesive (optical laminates 9 and 10), even when exposed to a high-temperature environment of 105°C, as its transmittance is not easily reduced. It can also be seen that by using an adhesive that contains both urea and glyoxal, water resistance can be improved. Furthermore, even when exposed to high-temperature environments, orthogonal light leakage is less likely to occur (comparison of optical laminates 2 and 8).

Claims

1. A polarizing plate, It comprises: a polarizing element on which a dichroic pigment is adsorbed and oriented in a polyvinyl alcohol-based resin layer, and a transparent protective film laminated on at least one side of the polarizing element. The polarizing element and the transparent protective film are bonded together by an adhesive layer formed of an adhesive containing urea compounds and dialdehyde. In the adhesive, the content of the dialdehyde is 0.03 parts by weight or more and 0.75 parts by weight or less relative to 1 part by weight of the urea compound. The urea compound is selected from at least one of urea, urea derivatives, thiourea, and thiourea derivatives. The moisture content of the polarizing element is above the equilibrium moisture content of 30% relative humidity at 20°C and below the equilibrium moisture content of 50% relative humidity at 20°C.

2. A polarizing plate, It comprises: a polarizing element on which a dichroic pigment is adsorbed and oriented in a polyvinyl alcohol-based resin layer, and a transparent protective film laminated on at least one side of the polarizing element. The polarizing element and the transparent protective film are bonded together by an adhesive layer formed of an adhesive containing urea compounds and dialdehyde. In the adhesive, the content of the dialdehyde is 0.03 parts by weight or more and 0.75 parts by weight or less relative to 1 part by weight of the urea compound. The urea compound is selected from at least one of urea, urea derivatives, thiourea, and thiourea derivatives. The moisture content of the polarizing plate is above the equilibrium moisture content at 20°C and 30% relative humidity and below the equilibrium moisture content at 20°C and 50% relative humidity.

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

4. The polarizing plate according to claim 1 or 2, wherein, The adhesive comprises a polyvinyl alcohol-based resin.

5. The polarizing plate according to claim 4, wherein, In the adhesive, the content of the urea compound is 0.1 parts by weight or more and 400 parts by weight or less relative to 100 parts by weight of the polyvinyl alcohol resin.

6. The polarizing plate according to claim 1 or 2, wherein, The dialdehyde is glyoxal.

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

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

9. An image display device, comprising: Image display unit The first adhesive layer laminated on the visible side surface of the image display unit and the polarizing plate laminated on the visible side surface of the first adhesive layer, as described in any one of claims 1 to 8.

10. The image display device according to claim 9, further comprising 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.

11. The image display device according to claim 10, wherein, The transparent component is a glass plate or a transparent resin plate.

12. The image display device according to claim 10, wherein, The transparent component is a touch panel.

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