TWI869481B - Polarizing plate and image display device using the polarizing plate - Google Patents

Abstract

An object of the present invention is to provide a polarizing plate in which a decrease in transmittance is suppressed in a high temperature environment even when used in an image display device having an interlayer filling configuration. The present invention provides a polarizing plate having a polarizing element in which iodine is adsorbed and oriented on a polyvinyl alcohol-based resin layer, and a transparent protective film, wherein the polarizing plate has a urea-based compound-containing layer containing at least one urea-based compound selected from the group consisting of urea, urea derivatives, thiourea and thiourea derivatives, the water content of the polarizing element is equal to or greater than the equilibrium moisture content of a temperature of 20℃ and a relative humidity of 30%, and equal to or less than the equilibrium moisture content of a temperature of 20℃ and a relative humidity of 50%.

Description

Polarizing plate and image display device using the same

The present invention relates to a polarizing plate. Furthermore, the present invention relates to an image display device, wherein one side of the polarizing plate is bonded to an image display unit, and the other side is bonded to a transparent component such as a touch panel or a front panel.

Liquid crystal display devices (LCD) are not only used in LCD TVs, but also widely used in portable devices such as personal computers and mobile phones, and in-vehicle applications such as car navigation. Generally speaking, a liquid crystal display device has a liquid crystal panel component with polarizing plates attached to both sides of a liquid crystal unit with an adhesive, and displays by modulating light from a backlight component with the liquid crystal panel component. In addition, in recent years, organic EL display devices have also been widely used in portable devices such as TVs and mobile phones, and in-vehicle applications such as car navigation, just like liquid crystal display devices. In an organic EL display device, in order to prevent external light from being reflected by the metal electrode (cathode) and being viewed as a mirror, a circular polarizer (a laminate including a polarizing element and a λ/4 plate) is sometimes arranged on the viewing side surface of the image display panel.

As mentioned above, the chances of polarizing plates being installed in cars as components of liquid crystal display devices and organic EL display devices are increasing. Compared with portable applications other than car use, such as TVs and mobile phones, polarizing plates used in car image display devices are more often exposed to high temperature environments, and require smaller changes in characteristics at higher temperatures (high temperature durability).

On the other hand, in order to prevent damage to the image display panel caused by impact from the outer surface, there is an increase in structures in which a transparent resin plate, glass plate or other front panel (also called a "window layer") is provided on the visual side of the image display panel closer to the polarizing plate. Moreover, in image display devices with a touch panel, a structure in which a touch panel is provided on the visual side closer to the polarizing plate of the image display panel and a front panel is provided on the visual side closer to the touch panel is widely used.

In such a structure, when an air layer exists between the image display panel and transparent components such as the front panel and the touch panel, the reflection of light at the interface of the air layer causes the specular reflection of external light, and the visibility of the screen tends to be reduced. Therefore, a structure in which the space between the polarizing plate arranged on the viewing side surface of the image display panel and the transparent component is filled with a layer other than the air layer (hereinafter referred to as an "interlayer filler") (hereinafter referred to as an "interlayer filling structure") is widely adopted, and preferably a structure in which the space is filled with a material having a refractive index close to that of these materials. As an interlayer filler, an adhesive or UV curing adhesive is used for the purpose of suppressing the reduction of visibility due to reflection at the interface and bonding and fixing the components together (for example, refer to Patent Document 1).

The above-mentioned interlayer filling structure is widely used in portable applications such as mobile phones that are often used outdoors. In addition, due to the increasing demand for visibility in recent years, even in vehicle-mounted applications such as navigation devices, the use of an interlayer filling structure in which a front panel is arranged on the surface of the image display panel and an adhesive layer is filled between the image display panel and the front panel is examined.

However, in the case of adopting such a structure, there are reports that the results of the heat durability test (95°C, 200 hours, etc.) show that the transmittance in the center of the polarizing plate surface is significantly reduced, while on the other hand, even if the polarizing plate is alone at 95°C for 1000 hours, no significant reduction in transmittance is observed; and there are also reports that according to these results, the significant reduction in the transmittance of the polarizing plate in a high temperature environment is a problem unique to the image display device that adopts "an interlayer filling structure in which one side of the polarizing plate is bonded to the image display unit and the other side is bonded to a transparent component such as a touch panel or front panel" when exposed to a high temperature environment (Patent Document 2).

Furthermore, in the above-mentioned Patent Document 2, the polarizing plate having an interlayer filling structure and significantly reduced transmittance has spectral peaks near 1100 cm ^-1 (originating from =CC= bond) and near 1500 cm ^-1 (originating from -C=C- bond) when measured by Raman spectroscopy. Therefore, it is believed that a polyene structure (-C=C) _n is formed, and it is speculated that the polyvinyl alcohol constituting the polarizing element is polyene-formed due to dehydration (Patent Document 2, paragraph [0012]).

In Patent Document 2, as a solution to this problem, it is proposed to set the moisture content per unit area of the polarizing plate to below the prescribed amount, and to set the saturated water absorption of the transparent protective film adjacent to the polarizing element to below the prescribed amount, thereby suppressing the reduction in transmittance.

However, even with this method, the effect of suppressing the decrease in penetration rate in the high-temperature durability test is still insufficient.

[Prior Art Literature]

[Patent Literature]

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

[Patent Document 2] Japanese Patent Publication No. 2014-102353

The present invention provides the following polarizing plate, image display device and method for manufacturing the polarizing plate.

[1] A polarizing plate having a polarizing element formed by iodine adsorption and orientation on a polyvinyl alcohol resin layer and a transparent protective film, wherein:

It has a urea compound-containing layer, which contains at least one urea compound selected from the group consisting of urea, urea derivatives, thiourea and thiourea derivatives;

The moisture content of the polarizing element is above the equilibrium moisture content of 30% at a temperature of 20°C and a relative humidity, and below the equilibrium moisture content of 50% at a temperature of 20°C and a relative humidity.

[2] A polarizing plate having a polarizing element formed by iodine adsorption and orientation on a polyvinyl alcohol resin layer and a transparent protective film, wherein:

It has a urea compound-containing layer, which contains at least one urea compound selected from the group consisting of urea, urea derivatives, thiourea and thiourea derivatives;

The moisture content of the aforementioned polarizing plate is above the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, and below the equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%.

[3] A polarizing plate as described in [1] or [2], wherein the urea compound-containing layer contains at least one urea compound selected from the group consisting of urea derivatives and thiourea derivatives.

[4] A polarizing plate as described in any one of [1] to [3], wherein the urea-containing compound is layered on the polarizing element.

[5] A polarizing plate as described in any one of [1] to [4], wherein the urea compound-containing layer is a pressure-sensitive adhesive layer.

[6] The polarizing plate described in [5], wherein the urea compound-containing layer comprises a polyvinyl alcohol resin.

[7] The polarizing plate as described in [6], wherein in the urea compound-containing layer, the total content of the urea compound is 0.1 parts by mass or more and 400 parts by mass or less relative to 100 parts by mass of the polyvinyl alcohol resin.

[8] A polarizing plate as described in any one of [5] to [7], wherein the thickness of the urea compound-containing layer is 0.01 to 7 μm.

[9] A polarizing plate having a polarizing element formed by iodine adsorption and orientation on a polyvinyl alcohol resin layer and a transparent protective film, wherein:

The aforementioned polarizing element comprises at least one urea compound selected from the group consisting of urea, urea derivatives, thiourea and thiourea derivatives;

The moisture content of the polarizing element is above the equilibrium moisture content of 30% at a temperature of 20°C and a relative humidity, and below the equilibrium moisture content of 50% at a temperature of 20°C and a relative humidity.

[10] A polarizing plate having a polarizing element formed by iodine adsorption and orientation on a polyvinyl alcohol resin layer and a transparent protective film, wherein:

The aforementioned polarizing element comprises at least one urea compound selected from the group consisting of urea, urea derivatives, thiourea and thiourea derivatives;

The moisture content of the aforementioned polarizing plate is above the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, and below the equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%.

[11] A polarizing plate as described in any one of [1] to [10], wherein the polarizing plate is used in an image display device, and in the image display device, a layer other than an air layer is provided on both sides of the polarizing plate in contact with each other.

[12] An image display device comprising: an image display unit, a first adhesive layer laminated on the visual side surface of the image display unit, and a polarizing plate described in any one of [1] to [11] laminated on the visual side surface of the first adhesive layer.

[13] The image display device as described in [12] further comprises: a second adhesive layer laminated on the viewing side surface of the aforementioned polarizing plate, and a transparent component laminated on the viewing side surface of the aforementioned second adhesive layer.

[14] An image display device as described in [13], wherein the transparent component is a glass plate or a transparent resin plate.

[15] An image display device as described in [13], wherein the transparent component is a touch panel.

[16] A method for manufacturing a polarizing plate, which is the method for manufacturing a polarizing plate described in [1] or [9]; wherein,

There is a moisture content adjustment step for adjusting the moisture content of the polarizing element to be above the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, and below the equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%.

[17] A method for manufacturing a polarizing plate, which is the method for manufacturing a polarizing plate described in [2] or [10]; wherein,

There is a moisture content adjustment step for adjusting the moisture content of the polarizing plate to be above the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, and below the equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%.

According to the present invention, a polarizing plate can be provided, which has a small decrease in transmittance in a high temperature environment and excellent high temperature durability even when used in an image display device with an interlayer filling structure; and an image display device can be provided, which suppresses the decrease in transmittance in a high temperature environment by using the polarizing plate of the present invention.

《First Implementation Guide》

The polarizing plate of the first embodiment of the present invention has: a polarizing element formed by iodine adsorption oriented on a polyvinyl alcohol resin layer; a urea compound-containing layer containing at least one urea compound selected from urea, urea derivatives, thiourea and thiourea derivatives; and a transparent protective film. The polarizing plate of this embodiment has at least one of the following characteristics (a) and (b).

(a) The moisture content of the polarizing element is above the equilibrium moisture content of 30% at a temperature of 20°C and a relative humidity, and below the equilibrium moisture content of 50% at a temperature of 20°C and a relative humidity.

(b) The moisture content of the polarizing plate is above the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, and below the equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%.

The polarizing plate of this embodiment has at least one of the above-mentioned properties (a) and (b), and further has a urea-based compound layer, thereby suppressing the decrease in monomer transmittance even when it is exposed to a high temperature environment for a long time as a structural element of an image display device with an interlayer filling structure.

The polarizing plate of this embodiment has a urea-based compound layer, thereby suppressing the decrease in polarization even when the polarizing plate is exposed to a high temperature environment. When two polarizing plates are arranged in a crossed nicol relationship, light leakage (hereinafter referred to as "crossed light leakage") is likely to occur when the polarization of the polarizing plate decreases. However, with the present invention, the polarization is not likely to decrease even when exposed to a high temperature environment, so it is easy to suppress cross light leakage.

[Polarizing element]

As the polarizing element formed by iodine adsorption oriented on the polyvinyl alcohol (hereinafter also referred to as PVA) resin layer of the present invention, a known polarizing element can be used. Such a polarizing element is generally formed by using a PVA resin film, dyeing the PVA resin film with iodine and uniaxially stretching it.

As mentioned above, PVA resins are generally obtained by saponifying polyvinyl acetate resins. The degree of saponification is about 85 mol% or more, preferably about 90 mol% or more, and more preferably about 90 mol% to 100 mol%. As polyvinyl acetate resins, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate, copolymers of vinyl acetate and other monomers copolymerizable with vinyl acetate, such as ethylene-vinyl acetate copolymers, etc. can be listed. As monomers copolymerizable with vinyl acetate, for example, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, etc. can be listed. As for the degree of polymerization of PVA resins, it is 1000 to 10000, preferably 1500 to 5000. The PVA resin can be modified, such as polyvinyl formal, polyvinyl acetal, polyvinyl butyral, etc. modified by aldehydes.

There is no particular restriction on the method for manufacturing the polarizing element. Typical examples include: a method for sending out a polyvinyl alcohol resin film pre-wound into a roll shape and stretching, dyeing, crosslinking, etc.; and a method comprising the steps of "making a laminate of a polyvinyl alcohol resin and a stretching resin substrate, and stretching the laminate in a state". Any method can be used in the present invention. The method for manufacturing such polarizing elements is described in paragraphs [0109] to [0128] of Japanese Patent Publication No. 2014-48497, and this embodiment can use such methods. Moreover, the thickness of the polarizing element of this embodiment is preferably 3 to 35 μm, more preferably 4 to 30 μm, and more preferably 5 to 25 μm.

(Characteristic (a))

In the case of characteristic (a), the moisture content of the polarizing element is above the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, and below the equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%. It is preferably below the equilibrium moisture content at a temperature of 20°C and a relative humidity of 45%, more preferably below the equilibrium moisture content at a temperature of 20°C and a relative humidity of 42%, and most preferably below the equilibrium moisture content at a temperature of 20°C and a relative humidity of 38%. When the moisture content is lower than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, the operability of the polarizing element is reduced and it becomes easy to break. When the moisture content of the polarizing element is higher than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%, the transmittance of the polarizing element is easily reduced. It is speculated that when the water content of the polarizer is high, the polyolefination of the PVA resin will be easier to proceed. The above water content of the polarizer is the water content of the polarizer in the polarizing plate.

The following method can be used to confirm whether the moisture content of the polarizing element is above the equilibrium moisture content of 30% at a temperature of 20°C and a relative humidity of 20%, and below the equilibrium moisture content of 50% at a temperature of 20°C and a relative humidity of 50%. The polarizing element is stored in an environment adjusted to the above temperature and relative humidity range, and when there is no mass change for a certain period of time, it can be considered to be in equilibrium with the environment. Alternatively, the equilibrium moisture content of the polarizing element in the environment adjusted to the above temperature and relative humidity range can be calculated in advance, and the moisture content of the polarizing element can be compared with the pre-calculated equilibrium moisture content for confirmation.

There is no particular limitation on the method for manufacturing a polarizing element having a moisture content of at least 30% at a temperature of 20°C and a relative humidity and at least 50% at a temperature of 20°C and a relative humidity. Examples of the method include: storing the polarizing element in an environment adjusted to the above temperature and relative humidity range for at least 10 minutes and at most 3 hours; or performing a heat treatment at a temperature of at least 30°C and at most 90°C.

As for other preferred methods for manufacturing polarizing elements with the above-mentioned moisture content, it is possible to list a method of storing a laminate having a protective film laminated on at least one side of the polarizing element or a polarizing plate formed by the polarizing element in an environment adjusted to the above-mentioned temperature and relative humidity range for more than 10 minutes and less than 120 hours, or a method of performing a heat treatment at a temperature of more than 30°C and less than 90°C. When manufacturing an image display device using an interlayer filling structure, an image display panel having a polarizing plate laminated on an image display unit can be stored in an environment adjusted to the above-mentioned temperature and relative humidity range for more than 10 minutes and less than 3 hours, or heated at a temperature of more than 30°C and less than 90°C, and then a front panel can be attached.

The moisture content of the polarizing element is preferably adjusted to the above-mentioned numerical range at the stage of forming the material for the polarizing plate, which is the polarizing element alone or the laminate of the polarizing element and the protective film. In the case of adjusting the moisture content after forming the polarizing plate, the warp will become too large, and there is a possibility of causing problems when it is attached to the image display unit. By forming the polarizing plate using the polarizing element whose moisture content is adjusted to the above-mentioned moisture content at the material stage before forming the polarizing plate, a polarizing plate having a polarizing element whose moisture content satisfies the above-mentioned numerical range can be easily formed. Alternatively, the moisture content of the polarizing element in the polarizing plate can be adjusted to the above-mentioned numerical range when the polarizing plate is attached to the image display unit. In this case, since the polarizing plate is attached to the image display unit, it is not easy to cause warping.

(Characteristic (b))

In the case of characteristic (b), the moisture content of the polarizing plate is higher than the equilibrium moisture content of 30% at a temperature of 20°C and a relative humidity and lower than the equilibrium moisture content of 50% at a temperature of 20°C and a relative humidity. The moisture content of the polarizing plate is preferably lower than the equilibrium moisture content of 45% at a temperature of 20°C and a relative humidity, more preferably lower than the equilibrium moisture content of 42% at a temperature of 20°C and a relative humidity, and even more preferably lower than the equilibrium moisture content of 38% at a temperature of 20°C and a relative humidity. When the moisture content of the polarizing plate is lower than the equilibrium moisture content of 30% at a temperature of 20°C and a relative humidity, the operability of the polarizing plate is reduced and it becomes easy to break. When the moisture content of the polarizing plate is higher than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%, the transmittance of the polarizing element will tend to decrease. It is speculated that this is because when the moisture content of the polarizing plate is high, the polyolefination of the PVA resin is easier to proceed.

As for the method of confirming whether the moisture content of the polarizing plate is above the equilibrium moisture content of 30% at a temperature of 20°C and a relative humidity of 30%, and below the equilibrium moisture content of 50% at a temperature of 20°C and a relative humidity of 50%, the following method can be exemplified. When the polarizing plate is stored in an environment adjusted to the above temperature and relative humidity range and there is no mass change for a certain period of time, it can be considered to be in equilibrium with the environment. Alternatively, the equilibrium moisture content of the polarizing plate in an environment adjusted to the above temperature and relative humidity range can be calculated in advance, and the moisture content of the polarizing plate can be compared with the pre-calculated equilibrium moisture content for confirmation.

There is no particular limitation on the method of manufacturing a polarizing plate having a moisture content above the equilibrium moisture content of 30% at a temperature of 20°C and a relative humidity and below the equilibrium moisture content of 50% at a temperature of 20°C and a relative humidity. For example, the polarizing plate may be stored in an environment adjusted to the above temperature and relative humidity range for 10 minutes to 3 hours, or subjected to a heat treatment at 30°C to 90°C.

When manufacturing an image display device using an interlayer filling structure, the image display panel having a polarizing plate laminated on the image display unit can be stored in an environment adjusted to the above temperature and relative humidity range for more than 10 minutes and less than 3 hours, or heated at more than 30°C and less than 90°C, and then the front panel can be attached.

[Urea compound containing layer]

The polarizing plate of the present invention has a urea compound-containing layer, which contains at least one urea compound selected from urea, urea derivatives, thiourea and thiourea derivatives. The urea compound-containing layer is not particularly limited as long as it is a layer containing a urea compound, and examples thereof include: a bonding agent layer and a curing layer. The urea compound-containing layer may be connected to a polarizing element or not, but from the perspective of further suppressing the decrease in transmittance in a high temperature environment, it is better to connect to a polarizing element.

From the perspective of productivity, in the present invention, it is preferred that the adhesive layer is a urea-containing compound layer. The adhesive layer is formed by the following adhesive. As an adhesive layer containing a urea-containing compound layer, an adhesive layer for bonding a polarizing element and a protective film can be exemplified. Furthermore, the structure of the case where the urea-containing compound layer is other than the adhesive layer is described below.

〈Next layer〉

Any suitable adhesive can be used as the adhesive layer for bonding the protective film to the polarizing element. Specifically, the adhesive can be a water-based adhesive, a solvent-based adhesive, an active energy ray-curing adhesive, etc., preferably a water-based adhesive.

When the adhesive layer is a urea compound-containing layer, the adhesive contains at least one urea compound selected from urea, urea derivatives, thiourea and thiourea derivatives.

The thickness of the adhesive when applied can be set to any suitable value. For example, it can be set in a way that an adhesive layer with a desired thickness can be obtained after curing or heating (drying). The thickness of the adhesive layer is preferably 0.01μm to 7μm, more preferably 0.01μm to 5μm, more preferably 0.01μm to 2μm, and most preferably 0.01μm to 1μm.

(Water-based adhesive)

Moreover, the above-mentioned water-based adhesive can adopt any suitable water-based adhesive. Among them, it is particularly preferred to use a water-based adhesive containing a PVA-based resin (PVA-based adhesive). In terms of adhesion, the average polymerization degree of the PVA-based resin contained in the water-based adhesive is preferably about 100 to 5500, and more preferably 1000 to 4500. In terms of adhesion, the average saponification degree is preferably about 85 mol% to 100 mol%, and more preferably 90 mol% to 100 mol%.

The PVA resin included in the above-mentioned water-based adhesive is preferably one containing acetyl acetyl groups, because the PVA resin layer has good adhesion to the protective film and good durability. The PVA resin containing acetyl acetyl groups can be obtained, for example, by reacting the PVA resin with diketene in any method. The degree of modification of the acetyl acetyl groups in the PVA resin containing acetyl acetyl groups is generally 0.1 mol% or more, preferably 0.1 mol% to 20 mol%.

The resin concentration of the above-mentioned water-based adhesive is preferably 0.1% to 15% by weight, and more preferably 0.5% to 10% by weight.

(Crosslinking agent, solvent)

The preferred water-soluble PVA adhesive that can be used in the present invention may contain not only the above-mentioned PVA resin and urea compound, but also a crosslinking agent as needed. As the crosslinking agent, known crosslinking agents can be used. For example, water-soluble epoxy compounds, dialdehydes, isocyanates, etc. can be listed.

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

Furthermore, the water-soluble PVA adhesive of the present invention may also contain an organic solvent. In this case, alcohols are preferred in terms of miscibility with water, and methanol or ethanol is more preferred among alcohols.

Furthermore, in the present invention, some urea derivatives have low solubility in water but sufficient solubility in alcohol. In this case, "after dissolving in alcohol to prepare an alcohol solution of the urea derivative, adding the alcohol solution of the urea derivative to the PVA aqueous solution to prepare an adhesive" is also one of the better embodiments.

(Active energy ray-curing adhesive)

As the above-mentioned active energy ray-curing adhesive, any suitable adhesive can be used as long as it can be cured by irradiation with active energy rays. Examples of active energy ray-curing adhesives include ultraviolet ray-curing adhesives and electron ray-curing adhesives. Specific examples of the curing type of active energy ray-curing adhesives include free radical curing type, cationic curing type, anionic curing type, and combinations thereof (e.g., a mixture of free radical curing type and cationic curing type).

The above-mentioned active energy ray-curable adhesive is, for example, an adhesive containing a compound (e.g., a monomer and/or an oligomer) having a free radical polymerizable group such as a (meth)acrylate group or a (meth)acrylamide group as a curing component. Specific examples of the above-mentioned active energy ray-curable adhesive and its curing method are described in, for example, Japanese Patent Publication No. 2012-144690.

(Urea compounds)

When the adhesive layer is a urea-containing compound layer, the adhesive layer contains at least one urea-containing compound selected from urea, urea derivatives, thiourea and thiourea derivatives.

As for the method of making the adhesive layer contain a urea compound, it is preferred that the above-mentioned adhesive contains a urea compound. Furthermore, in the process of forming the adhesive layer from the adhesive through a drying step, etc., it is not a problem that part of the urea compound moves from the adhesive layer to the polarizing element, etc.

Urea compounds are water-soluble and poorly water-soluble, and any type of urea compound can be used in the present invention. When poorly water-soluble urea compounds are used in water-soluble adhesives, it is better to work on the dispersion method in a way that does not cause a haze increase after the adhesive layer is formed.

When the adhesive contains a water-based adhesive of PVA resin, the amount of urea-based compound added is preferably 0.1 to 400 parts by mass, more preferably 1 to 200 parts by mass, and even more preferably 3 to 100 parts by mass relative to 100 parts by mass of PVA.

(Urea derivative)

Urea derivatives are compounds in which at least one of the four hydrogen atoms in the urea molecule is replaced by a substituent. In this case, the substituent is not particularly limited, and preferably is a substituent composed of a carbon atom, a hydrogen atom, and an oxygen atom.

As specific examples of urea derivatives, monosubstituted urea can be listed as follows: 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.

Disubstituted ureas include: 1,1-dimethylurea, 1,3-dimethylurea, 1,1-diethylurea, 1,3-diethylurea, 1,3-bis(hydroxymethyl)urea, 1,3-tert-butylurea, 1,3-dicyclohexylurea, 1,3-diphenylurea, 1,3-bis(4-methoxyphenyl)urea, 1-acetyl-3-methylurea, 2-imidazolidinone (ethylene urea), tetrahydro-2-pyrimidinone (propylene urea).

Tetrasubstituted ureas include: 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(1H)-pyrimidinone.

(Thiourea derivative)

Thiourea derivatives are compounds in which at least one of the four hydrogen atoms in the thiourea molecule is replaced by a substituent. In this case, the substituent is not particularly limited, and preferably is a substituent composed of a carbon atom, a hydrogen atom, and an oxygen atom.

As specific examples of thiourea derivatives, monosubstituted thiourea can be listed as follows: N-methylthiourea, ethylthiourea, propylthiourea, isopropylthiourea, 1-butylthiourea, cyclohexylthiourea, N-acetylthiourea, N-allylthiourea, (2-methoxyethyl)thiourea, N-phenylthiourea, (4-methoxyphenyl)thiourea, N-(2-methoxyphenyl)thiourea, N-(1-naphthyl)thiourea, (2-pyridyl)thiourea, o-tolylthiourea, p-tolylthiourea.

Disubstituted thioureas include: 1,1-dimethylthiourea, 1,3-dimethylthiourea, 1,1-diethylthiourea, 1,3-diethylthiourea, 1,3-dibutylthiourea, 1,3-diisopropylthiourea, 1,3-dicyclohexylthiourea, N,N-diphenylthiourea, N,N'-diphenylthiourea, 1,3-di(o-tolyl)thiourea, 1,3-di(p-tolyl)thiourea, 1-benzyl-3-phenylthiourea, 1-methyl-3-phenylthiourea, N-allyl-N,-(2-hydroxyethyl)thiourea, ethylenethiourea.

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

When used in an image display device with an interlayer filling structure, the decrease in transmittance in a high temperature environment is suppressed and the decrease in polarization degree is small (the point where orthogonal light leakage is suppressed). Among the urea compounds, urea derivatives or thiourea derivatives are preferred, and urea derivatives are more preferred. Among the urea derivatives, monosubstituted urea or disubstituted urea is particularly preferred, and monosubstituted urea is more preferred. Disubstituted urea includes 1,1-substituted urea and 1,3-substituted urea, but 1,3-substituted urea is more preferred.

[Transparent protective film]

The transparent protective film (hereinafter referred to as "protective film") used in the present invention is bonded to at least one side of the polarizing element via an adhesive layer. The transparent protective film can be bonded to one side or both sides of the polarizing element, and it is more preferable to bond to both sides. In one embodiment, the protective film is bonded to the polarizing element via an adhesive layer belonging to a urea-containing compound layer.

Furthermore, in the structure where the protective film is laminated on both sides of the polarizing element via the adhesive layer, it is not a problem that only one side of the adhesive layer on both sides of the polarizing element is a urea-containing compound layer, but it is more preferable that both sides of the adhesive layer are urea-containing compound layers.

In recent years, in order to meet the demand for thinner polarizing plates, polarizing plates with a protective film only on one side of the polarizing element have been developed. In this structure, it is also preferred to laminate the protective film via an adhesive layer containing the urea compound layer of the present invention.

As a method for manufacturing a polarizing plate having a protective film only on one side of a polarizing element, a method of "first manufacturing a polarizing plate having protective films bonded to both sides via adhesive layers, and then peeling off one protective film" can be considered. When such a manufacturing method is used, only one adhesive layer may be the urea-containing compound layer of the present invention. It is more preferable to use the urea-containing compound layer of the present invention on both sides of the polarizing element.

Furthermore, when the urea-containing compound layer of the present invention is applied only to one side of the polarizing element as an adhesive layer, it is preferred that the adhesive layer on the film side that is not peeled off is the urea-containing compound layer of the present invention.

The protective film can have other optical functions at the same time, and can also form a layered structure with other layers stacked on top.

From the perspective of optical properties, the thickness of the protective film is preferably thinner, but if it is too thin, the strength will be reduced and the processability will be poor. The suitable film thickness is 5 to 100μm, preferably 10 to 80μm, and more preferably 15 to 70μm.

The protective film may be made of acetylated cellulose resin films, polycarbonate resin films, cycloolefin resin films such as norbornene, (meth)acrylic polymer films, polyester resin films such as polyethylene terephthalate, etc.

When the polarizing element has a protective film on both sides, when a water-based adhesive such as PVA adhesive is used for bonding, it is preferred that the protective film on at least one side is either an acetylated cellulose resin film or a (meth) acrylic polymer film in terms of moisture permeability, and the acetylated cellulose resin film is particularly preferred.

As a protective film on at least one side, it can have a phase difference function for the purpose of viewing angle compensation, etc. In this case, the film itself can have a phase difference function, it can also have a phase difference layer separately, or it can be a combination of the two.

Furthermore, although the structure in which the film having a phase difference function is directly bonded to the polarizing element via an adhesive is described, a structure in which the film is bonded via an adhesive or an adhesive via another protective film already bonded to the polarizing element is also acceptable.

[Polarizing plate manufacturing method]

The manufacturing method of the polarizing plate of the present embodiment comprises a lamination step and a moisture content adjustment step, wherein the lamination step is to laminate a polarizing element and a urea-containing compound layer, and the urea-containing compound layer comprises at least one urea-containing compound selected from the group consisting of urea, urea derivatives, thiourea and thiourea derivatives. When manufacturing a polarizing plate having characteristic (a), in the moisture content adjustment step, the moisture content of the polarizing element is adjusted so that the moisture content of the polarizing element is above the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and below the equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%. The moisture content of the polarizing element can be adjusted according to the description of the moisture content of the polarizing element. When manufacturing a polarizing plate having characteristic (b), in the moisture content adjustment step, the moisture content of the polarizing element is adjusted so that the moisture content of the polarizing plate is above the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and below the equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%. The moisture content of the polarizing plate can be adjusted according to the description of the moisture content of the polarizing plate described above. The order of the lamination step and the moisture content adjustment step is not limited, and the lamination step and the moisture content adjustment step can also be performed simultaneously.

[Structure of image display device]

The polarizing plate of the present invention can be used in various image display devices such as liquid crystal display devices and organic EL display devices. Regarding the image display device, when the interlayer filling structure is a structure in which both sides of the polarizing plate are in contact with a layer other than an air layer, the transmittance is easily reduced in a high temperature environment. In an image display device using the polarizing plate of the present invention, even if it is an interlayer filling structure, the transmittance of the polarizing plate in a high temperature environment can be suppressed from being reduced. As an image display device, there can be exemplified a structure 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. Such an image display device may further include a second adhesive layer laminated on the viewing side surface of the polarizing plate, and a transparent member laminated on the surface of the second adhesive layer. In particular, the polarizing plate of the present invention is suitable for use in an image display device having an interlayer filling structure, wherein the interlayer filling structure is formed by arranging a transparent member on the viewing side of the image display device, bonding the polarizing plate and the image display unit via the first adhesive layer, and bonding the polarizing plate and the transparent member via the second adhesive layer. In this specification, one or both of the first adhesive layer and the second adhesive layer may be referred to as "adhesive layer". Furthermore, the components used for laminating the polarizing plate to the image display unit and laminating the polarizing plate to the transparent component are not limited to adhesive layers, but may also be bonding agent layers.

〈Image display unit〉

As image display units, liquid crystal units and organic EL units can be listed. As liquid crystal units, any of "reflective liquid crystal units using external light", "transmissive liquid crystal units using light from a light source such as a backlight", and "semi-transmissive and semi-reflective liquid crystal units using both light from the outside and light from the light source" can be used. When the liquid crystal unit uses light from the light source, the image display device (liquid crystal display device) is configured with polarizing plates on both the viewing side and the opposite side of the image display unit (liquid crystal unit), and a light source is configured. The polarizing plate on the light source side and the liquid crystal unit are preferably bonded with a suitable adhesive layer. As for the driving method of the liquid crystal unit, any type such as VA mode, IPS mode, TN mode, STN mode, bent orientation (π type) can be used.

As an organic EL unit, it is suitable for use in a transparent substrate where a transparent electrode, an organic light-emitting layer and a metal electrode are sequentially stacked to form a light-emitting body (light-emitting body of organic electroluminescence). The organic light-emitting layer is a laminate of various organic thin films, and various layer structures can be adopted, for example: a laminate of a hole injection layer formed by triphenylamine derivatives and a light-emitting layer formed by fluorescent organic solids such as anthracene; a laminate of these light-emitting layers and an electron injection layer formed by perylene derivatives; or a laminate of a hole injection layer, a light-emitting layer and an electron injection layer, etc.

〈Attachment of image display unit and polarizing plate〉

The image display unit and the polarizing plate can be bonded using an adhesive layer (adhesive sheet). From the perspective of operability, it is preferred to bond the polarizing plate with an adhesive layer attached to one side of the polarizing plate and the image display unit. The polarizing plate can be bonded using an appropriate method. For example, the following methods can be cited: dissolving or dispersing the matrix polymer or its components in a suitable solvent such as toluene, ethyl acetate, or a mixture thereof, preparing an adhesive solution of about 10 to 40% by weight, and directly attaching the adhesive solution to the polarizing plate in a suitable extending manner such as flowing or coating; or forming an adhesive layer on a separator as described above, and then transferring the adhesive layer to the polarizing plate, etc.

〈Adhesive layer〉

Regarding the adhesive layer, as described in paragraphs [0103] to [0143] of Japanese Patent Publication No. 2018-025765, such adhesives can be used in the present invention.

〈Transparent components〉

As transparent components arranged on the visual side of the image display device, there can be listed front panels (window layers), touch panels, etc. The front panel can use a front panel with suitable mechanical strength and thickness. Such a front panel can be, for example, a transparent resin plate such as acrylic resin and polycarbonate resin, or a glass plate. It is also possible to laminate functional layers such as anti-reflection layers on the visual side of the front panel. Moreover, when the front panel is a transparent resin plate, it is also possible to laminate a hard coating layer to improve physical strength, and to laminate a low moisture permeability layer to reduce moisture permeability.

The touch panel can be a variety of touch panels such as resistive film, capacitive, optical, and ultrasonic, and a glass plate or transparent resin plate with a touch sensor function. When a capacitive touch panel is used as a transparent component, it is better to set a front panel made of glass or transparent resin plate closer to the viewing side of the touch panel.

〈Bonding of polarizing plate and transparent components〉

In terms of bonding the polarizing plate and the transparent component, it is suitable to use an adhesive or a UV curing adhesive. When using an adhesive, the adhesive can be set in a suitable manner. The specific setting method can be listed as follows: the setting method of the adhesive layer used in the bonding of the aforementioned image display unit and the polarizing plate.

When using a UV curing adhesive, in order to prevent the diffusion of the adhesive solution before curing, it is suitable to use a method in which a dam material is set around the periphery of the image display panel, a transparent component is placed on the dam material, and the adhesive solution is injected. After the adhesive solution is injected, alignment and degassing are performed as needed, and then UV light is irradiated for curing.

Next, the urea-based compound-containing layer other than the adhesive layer is described.

[Urea compound-containing layer (other than adhesive layer)]

The urea compound-containing layer preferably has at least one urea compound and a binder. Examples of binders include polymer binders, thermosetting resin binders, active energy ray-hardening resin binders, etc. Any binder can be used in the present invention.

The thickness of the urea compound layer is preferably 0.1 to 20 μm, more preferably 0.5 to 15 μm, and even more preferably 1 to 10 μm.

The urea compound layer can be directly laminated on the polarizing element or laminated via other layers. However, in terms of easily suppressing the reduction of transmittance in a high temperature environment, it is better to laminate directly and connect to the polarizing element.

In order to improve the physical strength of the polarizing plate, it is preferred that the polarizing plate has a transparent protective film on at least one side of the polarizing element through the adhesive layer. In this case, the adhesive layer may contain a urea compound or not, but it is preferred to contain a urea compound.

As described in the description of the protective film, in recent years, in order to meet the demand for thinner polarizing plates, polarizing plates with a protective film only on one side of the polarizing element have been developed (hereinafter also referred to as "polarizing plates with a single-sided protective film").

For such a structure, attempts have been made to form a hardening layer on the area of the polarizing element without a protective film in order to improve physical strength, etc. (e.g., Japanese Patent Publication No. 2011-221185).

In this embodiment, it is also one of the preferred embodiments to make such a hardening layer contain a urea compound as a structure of a urea compound-containing layer. Generally speaking, such a hardening layer is formed by a hardening composition containing an organic solvent, and paragraphs [0020] to [0042] of Japanese Patent Publication No. 2017-075986 describe a method of forming such a hardening layer by an aqueous solution of an active energy ray-hardening polymer composition. Since urea compounds are mostly water-soluble, it is also one of the preferred embodiments of this embodiment to make such a composition contain a water-soluble urea compound and form a urea compound-containing layer.

《Second Implementation Guide》

The second embodiment of the present invention has a polarizing plate and a transparent protective film. The polarizing plate is formed by iodine adsorption and orientation on a polyvinyl alcohol resin layer, and contains at least one urea compound selected from urea, urea derivatives, thiourea and thiourea derivatives. The polarizing plate of this embodiment has at least one of the following characteristics (a) and (b).

(a) The moisture content of the polarizing element is above the equilibrium moisture content of 30% at a temperature of 20°C and a relative humidity, and below the equilibrium moisture content of 50% at a temperature of 20°C and a relative humidity.

(b) The moisture content of the polarizing plate is above the equilibrium moisture content of 30% at a temperature of 20°C and a relative humidity and below the equilibrium moisture content of 50% at a temperature of 20°C and a relative humidity.

The polarizing plate of this embodiment has at least one of the above-mentioned characteristics (a) and (b), and contains a urea compound in the polarizing element, thereby suppressing the decrease of the monomer transmittance even when used in an image display device with an interlayer filling structure and exposed to a high temperature environment for a long time. The polarizing plate of this embodiment, the polarizing element contains a urea compound, thereby suppressing the decrease of the polarization degree even when the polarizing plate is exposed to a high temperature environment, and it becomes easy to suppress orthogonal light leakage.

The above characteristics (a) and (b) are the same as the characteristics (a) and (b) in the first embodiment.

The method for producing a polarizing element of the present embodiment comprises a step of making the polarizing element contain a urea compound in the method for producing a polarizing element described in the first embodiment. As for the method for making the polarizing element contain a urea compound, the polarizing element can be produced by coating a solution containing a urea compound on at least one side of the polarizing element and drying the solution, thereby obtaining a polarizing element containing a urea compound. Alternatively, in the step of producing the polarizing element, the polarizing element can be made to contain a urea compound by immersing a PVA resin layer in a treatment solution containing a urea compound, or by spraying, flowing, or dripping the treatment solution on the PVA resin layer. Among them, the method of immersing the PVA resin layer in a treatment solution containing a urea compound is particularly preferred.

The step of immersing the PVA resin layer in a treatment solution containing a urea compound can be performed simultaneously with the swelling, stretching, dyeing, crosslinking, and washing steps in the manufacturing method of the polarizing element, or can be set separately from these steps. The step of making the PVA resin layer contain a urea compound is preferably performed after the PVA resin layer is dyed with iodine, and is more preferably performed simultaneously with the crosslinking step after dyeing. By such a method, the color tone change can be reduced and the impact on the optical characteristics of the polarizing element can be reduced.

The type and content of the urea compound contained in the polarizing element of this embodiment can be applied to the description of the urea compound-containing layer of the first embodiment. Furthermore, the polarizing element of this embodiment can also be used as the polarizing element of the polarizing plate of the first embodiment. The other structures of the polarizing plate of this embodiment are the same as those of the first embodiment, except that the urea compound-containing layer of the first embodiment is an arbitrary structural element.

[Urea compound solution]

The solvent of the solution containing urea compounds used in this embodiment is preferably water, an organic solvent or a mixture thereof, and water or a mixed solvent of water and alcohol is more preferred. Moreover, when it is a mixed solvent of water and alcohol, the alcohol is preferably methanol or ethanol. The urea compounds are as described in the first embodiment, but in terms of the fact that the urea compounds are not easily precipitated on the surface of the polarizing element after drying, it is preferred that the urea compounds are water-soluble.

[Polarizing plate manufacturing method]

The manufacturing method of the polarizing plate of this embodiment has a moisture content adjustment step. The moisture content adjustment step is the same as the manufacturing method of the polarizing plate of the first embodiment.

(Implementation example)

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

(Production of polarizing element 1)

A 40μm thick polyvinyl alcohol film made of polyvinyl alcohol with an average polymerization degree of about 2,400 and a saponification degree of more than 99.9 mol% was stretched uniaxially by about 5 times in a dry manner, and then immersed in pure water at 60°C for 1 minute while being tightly stretched, and then immersed in an aqueous solution of iodine/potassium iodide/water with a weight ratio of 0.05/5/100 at 28°C for 60 seconds. Then, it was immersed in an aqueous solution of potassium iodide/boric acid/water with a weight ratio of 8.5/8.5/100 at 72°C for 300 seconds. Then, it was washed with pure water at 26°C for 20 seconds and dried at 65°C to obtain a polarizing element with a thickness of 15μm with iodine adsorbed and oriented on polyvinyl alcohol.

(Then prepare the PVA solution)

Dissolve 50 g of modified PVA resin containing acetyl group (Gohsenx Z-410 manufactured by Mitsubishi Chemical Co., Ltd.) in 950 g of pure water, heat at 90°C for 2 hours, and then cool to room temperature to obtain a PVA solution for adhesive.

(Preparation of urea compound solution)

10 g of urea was added to 90 g of pure water to obtain a 10 wt% urea aqueous solution (solution 1). Similarly, according to Table 1, urea solutions 2 to 4 were prepared by replacing urea with the urea compounds listed in Table 1.

The urea, methyl urea, ethyl urea, and tetrahydro-2-pyrimidinone used above are all reagents from Tokyo Chemical Industry Co., Ltd.

(Preparation of adhesive 1 for polarizing plate)

The prepared adhesive PVA solution, urea solution 1, pure water and methanol were mixed in such a way that the PVA concentration was 3.0%, the methanol concentration was 20% and the urea concentration was 0.5%, and the adhesive 1 for polarizing plate was obtained.

(Preparation of adhesive 2 for polarizing plate)

Similarly, the adhesive PVA solution, urea solution 2 listed in Table 1, pure water and methanol were mixed to obtain an adhesive 2 for polarizing plates with a PVA concentration of 3.0%, a methanol concentration of 20% and a methyl urea concentration of 0.7%.

(Preparation of adhesive 3 for polarizing plate)

Similarly, the adhesive PVA solution, urea solution 3 listed in Table 1, pure water and methanol were mixed to obtain an adhesive 3 for polarizing plates with a PVA concentration of 3.0%, a methanol concentration of 20% and an ethyl urea concentration of 1.0%.

(Preparation of adhesive 4 for polarizing plate)

Similarly, the adhesive PVA solution, urea solution 4 listed in Table 1, pure water and methanol were mixed to obtain an adhesive 4 for polarizing plates with a PVA concentration of 3.0%, a methanol concentration of 20% and a tetrahydro-2-pyrimidinone concentration of 1.5%.

(Preparation of adhesive 5 for polarizing plate)

Similarly, the adhesive PVA solution, pure water and methanol were mixed to obtain an adhesive 5 for polarizing plates with a PVA concentration of 3.0% and a methanol concentration of 20%.

(Saponification of acetylated cellulose membrane)

The commercially available acetylated cellulose membrane TD40 (manufactured by FUJI FILM Co., Ltd.: membrane thickness 40μm) was immersed in a 1.5 mol/L NaOH aqueous solution (saponification solution) maintained at 55°C for 2 minutes, then washed with water, and then immersed in a 0.05 mol/L sulfuric acid aqueous solution at 25°C for 30 seconds, and then passed through a water bath under running water for 30 seconds to make the membrane neutral. Then, water was removed three times with an air knife, and after the water was removed, it was dried in a drying zone at 70°C for 15 seconds to produce a saponified membrane.

(Production of polarizing plate 1)

On both sides of the polarizing element 1, the saponified acetylated cellulose film prepared above is placed through the polarizing plate adhesive 1, and the thickness of the adhesive layer after drying is adjusted to be 100nm on both sides. After laminating using a roller laminating machine, it is dried at 60°C for 10 minutes to obtain a polarizing plate 1 with acetylated cellulose films on both sides.

(Production of polarizing plates 2 to 5)

Polarizing plates 2 to 5 are manufactured in the same manner as polarizing plate 1, except that polarizing plate adhesives 2 to 5 are used instead of polarizing plate adhesive 1.

(Adjustment of moisture content of polarizing plate (polarizing element))

The polarizing plates 1 to 5 obtained above were stored for 72 hours at a temperature of 20°C and a relative humidity of 30%, 35%, 40%, 45%, 50% or 55%. The moisture content was measured using the Karl Fischer method after 66 hours, 69 hours and 72 hours of storage. Under all humidity conditions, the moisture content values after 66 hours, 69 hours and 72 hours of storage did not change. Therefore, the moisture content of the polarizing plates 1 to 5 can be regarded as the same as the equilibrium moisture content of the 72-hour storage environment adopted in this experimental example. When the moisture content of the polarizing plate reaches equilibrium in a certain storage environment, the moisture content of the polarizing element in the polarizing plate can also be regarded as reaching equilibrium with the storage environment. Furthermore, when the moisture content of the polarizing element in the polarizing plate reaches a balance with a certain storage environment, the moisture content of the polarizing plate can also be considered to be in balance with the storage environment.

(Fabrication of optical layer 1)

Referring to the embodiment of Japanese Patent Publication No. 2018-025765, an acrylic adhesive (manufacturer: LINTEC (Co., Ltd.), product number: #7) is applied on both sides of the polarizing plate 1 prepared above, thereby preparing an optical laminate 1 having adhesive layers (first adhesive layer and second adhesive layer) with a thickness of 25 μm on both sides.

(Fabrication of optical layers 2 to 5)

Optical laminates 2 to 5 are manufactured in the same manner as optical laminate 1, except that polarizing plates 2 to 5 are used instead of polarizing plate 1.

[Examples 1 to 9, Comparative Examples 1 to 6]

Examples 1 to 9 and Comparative Examples 1 to 6 use the optical laminate shown in Table 2, and store the optical laminate for 72 hours at a temperature of 20°C and a relative humidity of 30%, 35%, 40%, 45%, 50% or 55% in such a manner that the moisture content of the optical laminate becomes the equilibrium moisture content of the environment shown in Table 2. The moisture content of the optical laminate can be considered to be in equilibrium with the moisture content of the storage environment, and the moisture content of the polarizer and polarizing element in the optical laminate can also be considered to be the same as the moisture content of the optical laminate.

(Polarizing plate for inspection 1)

An acrylic adhesive (manufacturer: LINTEC (Co., Ltd., product number: #7) is layered only on one surface of the polarizing plate 1 to produce a test polarizing plate 1. The test polarizing plate 1 produced in this way is cut into a size of 50 mm × 100 mm in such a way that the short side is parallel to the absorption axis, and the surface of the adhesive layer is bonded to an alkali-free glass (trade name "EAGLE XG", manufactured by Corning Incorporated) to produce a cross-evaluation sample 1.

[Evaluation of single body penetration after high temperature durability test (105℃)]

The optical laminates 1 to 5 prepared above were cut into a size of 50 mm × 100 mm with the long sides parallel to the absorption axis, and the surfaces of the first adhesive layer and the second adhesive layer were respectively adhered to alkali-free glass (trade name "EAGLE XG", manufactured by Corning Incorporated) to prepare evaluation samples.

The evaluation sample was subjected to an autoclave treatment at a temperature of 50°C and a pressure of 5kgf/ ^cm2 (490.3kPa) for 1 hour, and then placed in an environment at a temperature of 23°C and a relative humidity of 55% for 24 hours. Then, the transmittance (initial value) was measured, and the transmittance was measured every 50 hours from 100 to 200 hours after being stored in a heated environment at a temperature of 105°C. The evaluation was performed using the following criteria based on the time when the transmittance decreased by 5% or more relative to the initial value. The results are shown in Table 2.

After 200 hours, the penetration rate decreases by less than 5%: A

After 150 to 200 hours, the penetration rate decreases by more than 5%: B

After 100 to 150 hours, the penetration rate decreases by more than 5%: C

After 100 hours, the penetration rate decreases by more than 5%: D

[Evaluation of orthogonal light leakage after high temperature durability test]

After the single body transmittance evaluation sample after the high temperature durability test was evaluated after 200 hours, the above optical laminate and the cross evaluation sample 1 that was not placed in the heating environment were arranged in a state of orthogonal polarizers and placed on a backlight. The surrounding light was shielded and the orthogonal light leakage was evaluated visually according to the following standards. In addition, samples with a single body transmittance reduction of more than 5% were excluded from the evaluation of orthogonal light leakage due to coloring caused by polyolefination.

Those who did not observe any orthogonal light leakage at all: A

Almost no orthogonal light leakage was observed: B

Some orthogonal light leaks observed: C

Obvious orthogonal light leakage was observed: D

Claims (17)

A polarizing plate, which has a polarizing element formed by iodine adsorption and orientation on a polyvinyl alcohol resin layer and a transparent protective film, wherein the layer has a urea compound layer, and the urea compound layer contains at least one urea compound selected from the group consisting of urea, urea derivatives, thiourea and thiourea derivatives; the water content of the polarizing element is above the equilibrium water content of 30% at a temperature of 20°C and a relative humidity, and below the equilibrium water content of 38% at a temperature of 20°C and a relative humidity. A polarizing plate, which has a polarizing element formed by iodine adsorption and orientation on a polyvinyl alcohol resin layer and a transparent protective film, wherein the polarizing plate has a urea compound layer, and the urea compound layer contains at least one urea compound selected from the group consisting of urea, urea derivatives, thiourea and thiourea derivatives; the moisture content of the polarizing plate is above the equilibrium moisture content of 30% at a temperature of 20°C and a relative humidity, and below the equilibrium moisture content of 38% at a temperature of 20°C and a relative humidity. The polarizing plate as described in claim 1 or 2, wherein the urea compound-containing layer contains at least one urea compound selected from the group consisting of urea derivatives and thiourea derivatives. The polarizing plate as described in claim 1 or 2, wherein the urea-containing compound layer is connected to the polarizing element. The polarizing plate as described in claim 1 or 2, wherein the aforementioned urea compound-containing layer is an adhesive layer. The polarizing plate as described in claim 5, wherein the urea-containing compound layer comprises a polyvinyl alcohol-based resin. The polarizing plate as described in claim 6, wherein in the aforementioned urea compound-containing layer, the total content of the aforementioned urea compound is 0.1 parts by mass or more and 400 parts by mass or less relative to 100 parts by mass of the aforementioned polyvinyl alcohol resin. The polarizing plate as described in claim 5, wherein the thickness of the urea compound layer is 0.01 to 7 μm. A polarizing plate, which has a polarizing element formed by iodine adsorption and orientation on a polyvinyl alcohol resin layer and a transparent protective film, wherein the polarizing element contains at least one urea compound selected from the group consisting of urea, urea derivatives, thiourea and thiourea derivatives; the water content of the polarizing element is above the equilibrium water content of 30% at a temperature of 20°C and a relative humidity, and below the equilibrium water content of 38% at a temperature of 20°C and a relative humidity. A polarizing plate, which has a polarizing element formed by iodine adsorption and orientation on a polyvinyl alcohol resin layer and a transparent protective film, wherein the polarizing element contains at least one urea compound selected from the group consisting of urea, urea derivatives, thiourea and thiourea derivatives; the moisture content of the polarizing plate is above the equilibrium moisture content of 30% at a temperature of 20°C and a relative humidity, and below the equilibrium moisture content of 38% at a temperature of 20°C and a relative humidity. A polarizing plate as described in any one of claim 1, 2, 9, and 10, wherein the polarizing plate is used in an image display device, and in the image display device, a layer other than an air layer is provided in contact with both surfaces of the polarizing plate. An image display device comprises an image display unit, a first adhesive layer laminated on the visual side surface of the image display unit, and a polarizing plate as described in any one of claims 1 to 11 laminated on the visual side surface of the first adhesive layer. The image display device as described in claim 12 further comprises: a second adhesive layer laminated on the viewing side surface of the aforementioned polarizing plate, and a transparent component laminated on the viewing side surface of the aforementioned second adhesive layer. An image display device as described in claim 13, wherein the transparent component is a glass plate or a transparent resin plate. An image display device as described in claim 13, wherein the transparent component is a touch panel. A method for manufacturing a polarizing plate, which is the method for manufacturing a polarizing plate as described in claim 1 or 9, wherein the method comprises a moisture content adjustment step of adjusting the moisture content of the polarizing element so that the moisture content is above the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, and below the equilibrium moisture content at a temperature of 20°C and a relative humidity of 38%. A method for manufacturing a polarizing plate, which is the method for manufacturing a polarizing plate as described in claim 2 or 10, wherein the method comprises a moisture content adjustment step of adjusting the moisture content of the polarizing plate so that the moisture content is above the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, and below the equilibrium moisture content at a temperature of 20°C and a relative humidity of 38%.