TW202221092A - Polarizing plate and image display device - Google Patents

Abstract

The present invention provides a polarizing plate capable of suppressing transmittance in high temperature environment from decreasing. The polarizing plate of the present invention has a polarizing element in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin layer, and a transparent protective film laminated on at least one surface of the polarizing element; wherein the polarizing element and the transparent protective film are bonded to each other by an adhesive layer formed of an adhesive containing a urea-based compound and a reducing agent, the urea-based compound is at least one selected from the group consisting of urea, urea derivatives, thiourea and thiourea derivatives, and the water content of the polarizing element is equal to or higher than the equilibrium water content at a temperature of 20 DEG C and a relative humidity of 30%, and equal to or lower than the equilibrium water content at a temperature of 20 DEG C and a relative humidity of 50%.

Description

Polarizing plate and image display device

The present invention relates to a polarizing plate and an image display device.

Liquid crystal display devices (LCDs) are widely used not only for liquid crystal televisions, but also for mobile devices such as personal computers and mobile phones, and in-vehicle applications such as car navigation. Generally, a liquid crystal display device has a liquid crystal panel on both sides of a liquid crystal cell with a polarizer attached with an adhesive, and displays by using the liquid crystal panel to control light from a backlight. In recent years, like liquid crystal display devices, organic EL display devices have also been widely used for mobile devices such as televisions and mobile phones, and in-vehicle applications such as car navigation. In the organic EL display device, in order to prevent the external light from being reflected by the metal electrode (cathode) and be seen as a mirror, a circular polarizer (including a laminate of a polarizing element and a λ/4 plate) is arranged on the visible side surface of the image display panel. body) situation.

As described above, polarizing plates are more likely to be mounted on vehicles as components of image display devices such as liquid crystal display devices and organic EL display devices. Compared with mobile applications such as televisions and mobile phones, polarizers used in image display devices for in-vehicles are more exposed to high temperature environments, and therefore require less characteristic change at higher temperatures (high temperature durability).

On the other hand, in order to prevent damage to the image display panel due to impact from the outer surface, etc., a front panel such as a transparent resin plate or a glass plate (also referred to as "" The composition of the "window layer") is increased. In an image display device with a touch panel, it is widely used in A touch panel is disposed on the visual side more than the image display panel, and a front panel is provided on the visual side more than the touch panel.

In such a configuration, if there is an air layer between the image display panel and the transparent member such as the front panel or the touch panel, the reflection of the light at the interface of the air layer will cause the reflection of external light, and the visual recognition of the screen will occur. Tendency to decrease sexuality. Therefore, the space between the polarizing plate and the transparent member disposed on the visible side surface of the image display panel is filled with a layer other than the air layer, usually a solid layer (hereinafter, sometimes referred to as an "interlayer filler"). (Hereinafter, sometimes referred to as "interlayer filling structure") behavior is expanded. The interlayer filler is preferably a material with 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 in order to suppress deterioration of visibility due to reflection at the interface and to fix each member indirectly (for example, refer to Patent Document 1).

The interlayer filling structure is widely used in mobile applications such as mobile phones that are mostly used outdoors. In addition, due to the increasing demand for visibility in recent years, in vehicle applications such as car navigation devices, it has also been studied to arrange the front surface transparent plate on the surface of the image display panel and fill the gap between the panel and the front surface transparent plate with an adhesive layer or the like. Filling between layers.

However, in the case of adopting such a configuration, it is reported that the transmittance of the polarizing plate is significantly reduced in a high temperature environment. In Patent Document 2, as a solution to this problem, a method is proposed in which the water content per unit area of the polarizing plate is set to a predetermined amount or less, and the saturated water absorption amount of the transparent protective film adjacent to the polarizing element is reduced. The reduction of the penetration rate is suppressed by setting it as a specific amount or less.

[Prior Art Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Application Laid-Open No. 11-174417

[Patent Document 2] Japanese Patent Laid-Open No. 2014-102353

However, even with such a polarizing plate, the effect of suppressing the decrease in transmittance in a high temperature environment is insufficient. An object of the present invention is to provide a novel polarizing plate capable of suppressing a decrease in transmittance in a high temperature environment, and an image display device using the polarizing plate.

The present invention provides a polarizing plate and an image display device exemplified below.

[1] A polarizing plate comprising a polarizing element obtained by adsorbing and aligning a dichroic dye on a polyvinyl alcohol-based resin layer, and a transparent protective film laminated on at least one side of the polarizing element; wherein,

The above-mentioned polarizing element and the above-mentioned transparent protective film are bonded together by an adhesive layer, and the above-mentioned adhesive layer is formed by an adhesive containing a urea-based compound and a reducing agent,

The above-mentioned urea-based compound is at least one selected from the group consisting of urea, urea derivatives, thiourea and thiourea derivatives,

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

[2] A polarizing plate comprising a polarizing element obtained by adsorbing and aligning a dichroic dye on a polyvinyl alcohol-based resin layer, and a transparent protective film laminated on at least one side of the polarizing element; wherein,

The above-mentioned polarizing element and the above-mentioned transparent protective film are bonded together by an adhesive layer, and the above-mentioned adhesive layer is formed by an adhesive containing a urea-based compound and a reducing agent,

The above-mentioned urea-based compound is at least one selected from the group consisting of urea, urea derivatives, thiourea and thiourea derivatives,

The moisture content of the polarizing plate is equal to or higher than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and equal to or less than an equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%.

[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 urea derivatives and thiourea derivatives.

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

[5] The polarizing plate according to [4], wherein, in the adhesive, the content of the urea-based compound is 0.1 parts by mass or more and 400 parts by mass or less with respect to 100 parts by mass of the polyvinyl alcohol-based resin.

[6] The polarizing plate according to [4] or [5], wherein, in the adhesive agent, the content of the reducing agent is 1 part by mass or more and 50 parts by mass relative to 100 parts by mass of the polyvinyl alcohol-based resin the following.

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

[8] The polarizing plate according to any one of [1] to [7], wherein the reducing agent is selected from the group consisting of ascorbic acid, erythorbic acid, thiosulfuric acid, sulfurous acid and salts thereof at least one of them.

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

In the above image display device, the solid layers are provided on both sides of the polarizing plate in contact with each other.

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

[11] The image display device according to [10], further comprising: a second adhesive layer laminated on the visible side surface of the polarizing plate; and a transparent member laminated on the second adhesive layer. Visually recognize the lateral surface.

[12] The image display device according to [11], wherein the transparent member is a glass plate or a transparent resin plate.

[13] The image display device according to [11], wherein the transparent member is a touch panel.

According to the present invention, it is possible to provide a polarizing plate whose high-temperature durability is improved, and which can suppress a decrease in transmittance caused by high temperature even when used in an image display device having an interlayer filling structure. Furthermore, by using the polarizing plate of the present invention, it is possible to provide an image display device that suppresses the decrease in transmittance in a high temperature environment.

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

[Polarizer]

The polarizing plate of this embodiment has the polarizing element which made the dichroic dye adsorb|suck and align the layer containing a polyvinyl alcohol-type resin, and a transparent protective film. The polarizing element and the transparent protective film are bonded together by an adhesive layer formed of an adhesive containing a urea-based compound and a reducing agent. The polarizing plate of this embodiment has the characteristic of at least one of the following (a) and (b).

(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%.

(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%.

As a conventional polarizing plate excellent in high-temperature durability, for example, a polarizing plate is known to be left alone in an environment with a temperature of 95° C. for 1000 hours, and a decrease in transmittance is also suppressed. However, even if it is such a polarizing plate, when it is used for interlayer filling structure, if it is left for 200 hours in an environment with a temperature of 95° C., a marked decrease in transmittance may be seen in the central part of the polarizing plate surface. It is considered that the significant decrease in the transmittance of the polarizing plate in a high temperature environment is due to the use of a polarizing plate that is attached to the image display unit on one side, and the other side of the polarizing plate is attached to a transparent member such as a touch panel or a front panel. The problem is especially caused when the display device is exposed to a high temperature environment.

It is considered that the polarizing plate whose transmittance is significantly reduced in the interlayer filling structure has peaks in the vicinity of 1100 cm ^-1 (derived from the =CC= bond) and around 1500 cm ^-1 (derived from the -C=C- bond) in the Raman spectrometry , thus forming the polyene structure (-C=C) _n -. The polyene structure is presumed to be produced by dehydration of polyvinyl alcohol constituting the polarizing element and polyene (Patent Document 2, paragraph [0012]).

The polarizing plate of the present invention can further improve high temperature durability. The polarizing plate of the present invention is incorporated into an image display device composed of interlayer filling, and even if exposed to a high temperature environment such as a temperature of 105° C., the decrease in transmittance can be suppressed.

<Polarizing element>

As a polarizing element in which a dichroic dye is adsorbed and aligned in a layer containing a polyvinyl alcohol (hereinafter, also referred to as "PVA")-based resin (hereinafter, also referred to as "PVA-based resin layer"), 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, or a coating liquid containing a PVA-based resin applied to a base film can be used. The laminated film of the formed coating layer is formed by dyeing the coating layer with a dichroic dye and forming the laminated film A stretched layer obtained by uniaxial stretching. The stretching may be carried out after dyeing with a dichroic dye, or may be carried out while dyeing, or may be dyed after stretching.

PVA-based resins are obtained by saponifying polyvinyl acetate-based resins. As the polyvinyl acetate-based resin, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate, copolymers of vinyl acetate and other monomers which can be copolymerized therewith can be mentioned. Examples of other copolymerizable monomers include unsaturated carboxylic acids, olefins such as ethylene, vinyl ethers, and unsaturated sulfonic acids.

The degree of saponification of the PVA-based resin is preferably about 85 mol % or more, more preferably about 90 mol % or more, and even more preferably about 99 mol % or more and 100 mol % or less. The degree of polymerization of the PVA-based resin is, for example, 1,000 or more and 10,000 or less, or preferably 1,500 or more and 5,000 or less. PVA-based resins can also be modified, for example, polyvinyl formaldehyde, polyvinyl acetal, polyvinyl butyral, etc., which are modified by aldehydes.

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 still more preferably 5 μm or more and 25 μm or less. When the thickness of the polarizing element is 35 μm or less, the influence of the polyolefinization of the PVA-based resin on the degradation of the optical properties in a high temperature environment can be suppressed. When the thickness of the polarizing element is 3 μm or more, it is easy to achieve the desired optical characteristics.

The polarizing element preferably contains a urea-based compound and a reducing agent. In this embodiment, the polarizing element and the transparent protective film are bonded together by an adhesive layer, and since the adhesive layer is formed by an adhesive containing a urea-based compound and a reducing agent, it is presumed to migrate from the adhesive layer. A part of the urea-based compound and a part of the reducing agent are contained in the polarizing element. The urea-based compound and the reducing agent in the polarizing element may also be included in those added during the manufacturing process of the polarizing element. By having the adhesive layer containing the urea-based compound and the reducing agent, the transmittance is not easily reduced even if the polarizing plate is exposed to a high temperature environment. Moreover, by having the adhesive layer containing a urea type compound and a reducing agent, even if a polarizing plate is exposed to a high temperature environment, the fall of the degree of polarization can be suppressed. It is used by arranging two polarizing plates so as to have a relationship of orthogonal polarization. In this case, if the degree of polarization of the polarizing plate decreases, light leakage (hereinafter, also referred to as "cross-light leakage") is likely to occur, but according to the present invention, the degree of polarization is not easily reduced even when exposed to a high temperature environment, so it is easy to suppress Orthogonal light leakage. The reason for this is presumed to be that the polyolefination of the PVA-based resin is suppressed by the urea-based compound and the reducing agent contained in the polarizer.

As a method of containing a urea-based compound and a reducing agent in a polarizing element, a method of immersing a PVA-based resin layer in a treatment solvent containing a urea-based compound and/or a reducing agent, or spraying, flowing, or dropping the treatment solvent into Method of PVA-based resin layer. Among them, a method of immersing the PVA-based resin layer in a treatment solvent containing both a urea-based compound and a reducing agent is preferably used. Specific examples of the urea-based compound and the reducing agent include those included in the adhesive agent described later.

The step of immersing the PVA-based resin layer in a treatment solvent containing a urea-based compound and a reducing agent can be performed simultaneously with the steps of swelling, stretching, dyeing, cross-linking, and washing in the following manufacturing method of polarizing elements, or it can be combined with the following steps. These steps are set separately. The step of making the PVA-based resin layer contain the urea-based compound and the reducing agent is preferably carried out after the PVA-based resin layer is dyed with iodine, and more preferably carried out simultaneously with the cross-linking step after dyeing. According to this method, the hue change is small, and the influence on the optical characteristics of the polarizing element can be reduced.

In order to contain a urea compound and a reducing agent in a polarizing element, both addition at the time of manufacture of a polarizing element and addition of an adhesive agent may be performed. In addition, when manufacturing a polarizing element, both of the urea compound and the reducing agent may be contained in the adhesive containing either one of the urea compound and the reducing agent.

(urea compound)

The urea-based compound is at least one selected from the group consisting of urea, urea derivatives, thiourea, and thiourea derivatives. A urea-type compound can be used individually by 1 type or in combination of 2 or more types. The urea-based compound has a water-soluble one and a poorly water-soluble one, and either of the urea-based compounds can be used. For the use of poorly water-soluble urea-based compounds in water-soluble In the case of a flexible adhesive, it is preferable to design a dispersion method so as not to cause a rise in haze or the like after the adhesive layer is formed.

(urea derivative)

The urea derivative is a compound in which at least one of the four hydrogen atoms of the urea molecule is substituted as 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.

Specific examples of urea derivatives include methyl urea, ethyl urea, propyl urea, butyl urea, isobutyl urea, N-octadecyl urea, and 2-hydroxyethyl urea as mono-substituted urea. Urea, hydroxyurea, acetylurea, allylurea, 2-propynylurea, cyclohexylurea, phenylurea, 3-hydroxyphenylurea, (4-methoxyphenyl)urea, benzyl Urea, benzyl urea, o-tolyl urea, p-tolyl urea.

As the disubstituted urea, 1,1-dimethylurea, 1,3-dimethylurea, 1,1-diethylurea, 1,3-diethylurea, 1,3-bis( Hydroxymethyl) urea, 1,3-tertiary butylurea, 1,3-dicyclohexylurea, 1,3-diphenylurea, 1,3-bis(4-methoxyphenyl)urea, 1-Acetyl-3-methylurea, 2-imidazolidinone (ethylidene urea), tetrahydro-2-pyrimidinone (propylidene urea).

As tetra-substituted urea, tetramethylurea, 1,1,3,3-tetraethylurea, 1,1,3,3-tetrabutylurea, 1,3-dimethoxy-1, 3-dimethylurea, 1,3-dimethyl-2-imidazolidinone, 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone.

(thiourea derivatives)

The thiourea derivative is a compound in which at least one of the four hydrogen atoms of the thiourea molecule is substituted as 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.

Specific examples of thiourea derivatives include N-methylthiourea, ethylthiourea, propylthiourea, isopropylthiourea, 1-butylthiourea, and cyclohexyl thiourea as monosubstituted thiourea. Thiourea, N-Acetyl sulfide Urea, N-allylthiourea, (2-methoxyethyl)thiourea, N-phenylthiourea, (4-methoxyphenyl)thiourea, N-(2-methoxybenzene) base) thiourea, N-(1-naphthyl) thiourea, (2-pyridyl) thiourea, o-tolyl thiourea, p-tolyl thiourea.

Examples of the di-substituted thiourea include 1,1-dimethylthiourea, 1,3-dimethylthiourea, 1,1-diethylthiourea, 1,3-diethylthiourea, 1,3-dimethylthiourea, ,3-dibutylthiourea, 1,3-diisopropylthiourea, 1,3-dicyclohexylthiourea, N,N-diphenylthiourea, N,N'-diphenylthiourea , 1,3-bis(o-tolyl)thiourea, 1,3-bis(p-tolyl)thiourea, 1-benzyl-3-phenylthiourea, 1-methyl-3-phenylthiourea , N-allyl-N'-(2-hydroxyethyl) thiourea, ethylene thiourea.

Trimethyl thiourea is mentioned as a 3-substituted thiourea, and tetramethyl thiourea and 1,1,3,3- tetraethylthiourea are mentioned as 4-substituted thiourea.

Among the urea-based compounds, when used in an image display device composed of interlayer filling, in terms of suppressing a decrease in transmittance under a high temperature environment and reducing a decrease in polarization degree (suppressing cross light leakage), the preferred Urea derivatives or thiourea derivatives, more preferably urea derivatives. Among the urea derivatives, mono-substituted urea or di-substituted urea is preferred, and mono-substituted urea is more preferred. The 2-substituted urea includes 1,1-substituted urea and 1,3-substituted urea, but 1,3-substituted urea is more preferred.

(reducing agent)

Examples of the reducing agent include ascorbic acid (vitamin C), erythorbic acid, thiosulfuric acid, sulfurous acid, chlorogenic acid, citric acid, rosmarinic acid, and salts thereof. Examples of the salt include alkali metal salts such as sodium salts and potassium salts. Among these, preferred are ascorbic acid, erythorbic acid, thiosulfuric acid, sulfurous acid, and salts of these. These reducing agents may be used alone or in combination of two or more. In addition, the reducing agent added in the manufacturing process of the polarizing element or the adhesive is contained in the polarizing plate (in the polarizing element or the adhesive layer) as the reducing agent or an oxidizing agent derived from the reducing agent. In the present invention, even if the polarizing plate contains only In the case of the oxidizing agent of the reducing agent, the reducing agent is also included. For example, ascorbic acid is present in polarizing plates as dehydroascorbic acid which is an oxidizing agent.

(feature (a))

In the case of feature (a), the moisture content of the polarizing element is equal to or higher than the equilibrium moisture content at a temperature of 20°C and relative humidity of 30% and below the equilibrium moisture content at a temperature of 20°C and relative humidity of 50%. The moisture content of the polarizing element is preferably below the equilibrium moisture content of 45% relative humidity at a temperature of 20°C, more preferably below an equilibrium moisture content of 42% relative humidity at a temperature of 20°C, and even more preferably a balance of 38% relative humidity at a temperature of 20°C below the moisture content. If the moisture content of the polarizing element is lower than the equilibrium moisture content of 30% relative humidity at a temperature of 20°C, the operability of the polarizing element will be reduced and it will be easy to break. If the moisture content of the polarizing element exceeds the equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%, the transmittance of the polarizing element is likely to decrease. It is presumed that the reason for this is that when the moisture content of the polarizing element is high, the polyolefinization of the PVA-based resin tends to proceed. The moisture content of the polarizing element is the moisture content of the polarizing element in the polarizing plate.

As a method of confirming whether the moisture content of the polarizing element is within the range of the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% or more and below the equilibrium moisture content at a temperature of 20°C and a relative humidity of 50% or less, there are: It is stored in an environment within the range of the above-mentioned relative humidity, and if there is no change in quality for a certain period of time, it is considered to have reached equilibrium with the environment, or the equilibrium moisture content of the polarizing element is pre-calculated and adjusted to the environment within the range of the above-mentioned temperature and relative humidity. , and is confirmed by comparing the moisture content of the polarizing element with the pre-calculated equilibrium moisture content.

There is no particular limitation on the method of manufacturing a polarizing element whose moisture content is equal to or higher than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and equal to or less than an equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%. It is a method of storing in an environment within the range of the above temperature and relative humidity for 10 minutes or more and 3 hours or less, or a method of heat treatment at 30°C or more and 90°C or less.

Another preferable method for producing the polarizing element with the above-mentioned moisture content includes: adjusting the temperature so that the above-mentioned temperature is opposite to the above-mentioned laminated body with a protective film layered on at least a single area of the polarizing element, or a polarizing plate formed by using the polarizing element. The method of storing in the environment of humidity range for 10 minutes to 120 hours; or the method of heat treatment at 30℃ or more and 90℃ or less. In the production of the image display device with the interlayer filling structure, the image display panel with the polarizing plate laminated in the image display unit can also be stored for more than 10 minutes in the environment adjusted to the range of the above temperature and the above relative humidity. 3 After heating at 30°C or more and 90°C or less for 1 hour or less, the front panel is bonded.

The moisture content of the polarizing element is preferably adjusted so that the moisture content falls within the above-mentioned numerical range at the stage of the material used to constitute the polarizing plate in the polarizing element alone or in the laminate of the polarizing element and the protective film. When the moisture content is adjusted after the polarizing plate is constructed, the curl is too large, and a defect is likely to occur when it is attached to the image display unit. By forming the polarizing plate using the polarizing element adjusted to the above-mentioned moisture content at the material stage prior to constructing the polarizing plate, the polarizing plate having the polarizing element whose moisture content satisfies the above-mentioned numerical range can be easily constructed. In the state where the polarizing plate is attached to the image display unit, the water content of the polarizing element in the polarizing plate can also be adjusted so that the water content is within the above-mentioned numerical range. At this time, since the polarizing plate is attached to the image display unit, curling is unlikely to occur.

(feature (b))

In the case of feature (b), the moisture content of the polarizing plate is above the equilibrium moisture content at a temperature of 20°C and relative humidity of 30% and below the equilibrium moisture content at a temperature of 20°C and relative humidity of 50%. The moisture content of the polarizing plate is preferably below the equilibrium moisture content of 45% relative humidity at a temperature of 20°C, more preferably below the equilibrium moisture content of 42% relative humidity at a temperature of 20°C, and even more preferably a balance of 38% relative humidity at a temperature of 20°C below the moisture content. If the moisture content of the polarizing plate is lower than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, the operability of the polarizing plate will decrease and it will be easy to break. If the moisture content of the polarizing plate exceeds the equilibrium moisture content of 50% relative humidity at a temperature of 20°C, Then the transmittance of the polarizing element is easily reduced. It is presumed that the reason for this is that when the moisture content of the polarizing plate is high, the polyolefinization of the PVA-based resin tends to proceed.

As a method of confirming whether the moisture content of the polarizing plate is within the range of the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% or more and below the equilibrium moisture content at a temperature of 20°C and a relative humidity of 50% or not, there are: When stored in an environment within the range of the above-mentioned relative humidity, if there is no change in quality for a certain period of time, it is regarded as a method to achieve equilibrium with the environment, or pre-calculated and adjusted to the environment within the above-mentioned temperature and relative humidity. The method is confirmed by comparing the moisture content of the polarizing plate with the pre-calculated equilibrium moisture content.

There is no particular limitation on the method for producing a polarizing plate whose moisture content is equal to or higher than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and equal to or less than an equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%. A method of storing the polarizing plate for 10 minutes or more and 3 hours or less in an environment within the range of the above relative humidity, or a method of heat treatment at 30°C or more and 90°C or less.

In the production of the image display device with the interlayer filling structure, the image display panel with the polarizing plate laminated in the image display unit can also be stored for more than 10 minutes in the environment adjusted to the range of the above temperature and the above relative humidity. 3 After heating at 30°C or more and 90°C or less for 1 hour or less, the front panel is bonded.

(Manufacturing method of polarizing element)

The manufacturing method of the polarizing element is not particularly limited, but is typically a method including the following steps: a method of producing a PVA-based resin film that is pre-wound in a roll shape, and then stretched, dyed, cross-linked, etc. (hereinafter referred to as "Manufacturing method 1"); or a step of applying a coating solution containing a PVA-based resin on a substrate film to form a PVA-based resin layer belonging to the coating layer, and extending the resulting laminate (hereinafter referred to as the step "Manufacturing method 2").

Manufacturing method 1 can be performed through the step of uniaxially extending the PVA-based resin film, the step of dyeing the PVA-based resin film with a dichroic dye such as iodine to adsorb the dichroic dye, and the PVA-based resin film to which the dichroic dye has been adsorbed It is produced by the step of treating with boric acid aqueous solution and the step of washing with water after treatment with boric acid aqueous solution.

The swelling step is a treatment step of immersing the PVA-based resin film in a swelling bath. By the swelling step, in addition to removing dirt, caking agents, etc. on the surface of the PVA-based resin film, uneven dyeing can be suppressed by swelling the PVA-based resin film. The swelling bath usually uses water, distilled water, pure water and other media with water as the main component. A surfactant, an alcohol, etc. may be appropriately added to the swelling bath according to a conventional method. From the viewpoint of controlling the potassium content of the polarizing element, potassium iodide may also be used in the swelling bath. In this case, the concentration of potassium iodide in the swelling bath is preferably 1.5 mass % or less, more preferably 1.0 mass % or less, and More preferably, it is 0.5 mass % or less.

The temperature of the swelling bath is preferably 10°C or higher and 60°C or lower, more preferably 15°C or higher and 45°C or lower, and even more preferably 18°C or higher and 30°C or lower. The time of immersion in the swelling bath cannot be determined universally because the degree of swelling of the PVA-based resin film is affected by the temperature of the swelling bath, but it is preferably 5 seconds or more and 300 seconds or less, more preferably 10 seconds or more and 200 seconds or less, and more Preferably, it is 20 seconds or more and 100 seconds or less. The swelling step may be carried out only once, or may be carried out a plurality of times if necessary.

The dyeing step is a treatment step in which the PVA-based resin film is immersed in a dyeing bath (iodine solution), so that dichroic dyes such as iodine can be adsorbed and aligned on the PVA-based resin film. The iodine solution is usually preferably an aqueous iodine solution containing iodine and iodide as a dissolution aid. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Among these, potassium iodide is preferable from the viewpoint of controlling the content rate of potassium in the polarizing element.

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

The temperature of the dyeing bath is preferably 10°C or higher and 50°C or lower, more preferably 15°C or higher and 45°C or lower, and even more preferably 18°C or higher and 30°C or lower. The time of immersion in the dyeing bath cannot be determined universally because the degree of dyeing of the PVA-based resin film is affected by the temperature of the dyeing bath, but it is preferably 10 seconds or more and 300 seconds or less, more preferably 20 seconds or more and 240 seconds or less. The dyeing step may be carried out only once, or may be carried out a plurality of times if necessary.

The cross-linking step is a treatment step of immersing the PVA-based resin film dyed in the dyeing step in a treatment bath (cross-linking bath) containing a boron compound. The polyvinyl alcohol-based resin film is cross-linked by the boron compound, iodine molecules or dye molecules. can be adsorbed on the cross-linked structure. As a boron compound, boric acid, borate, borax, etc. are mentioned, for example. The crosslinking bath is generally an aqueous solution, but it can also be a mixed solution of an organic solvent and water miscible with water. From the viewpoint of controlling the content rate of potassium in the polarizing element, the crosslinking bath preferably contains potassium iodide.

In the crosslinking bath, the concentration of the boron compound is preferably 1 mass % or more and 15 mass % or less, more preferably 1.5 mass % or more and 10 mass % or less, and even more preferably 2 mass % or more and 5 mass % or less. When potassium iodide is used in the cross-linking bath, the concentration of potassium iodide in the cross-linking bath is preferably 1 mass % or more and 15 mass % or less, more preferably 1.5 mass % or more and 10 mass % or less, still more preferably 2 mass % More than 5 mass % or less.

The temperature of the crosslinking bath is preferably 20°C or higher and 70°C or lower, more preferably 30°C or higher and 60°C or lower. The time of immersion in the cross-linking bath is affected by the temperature of the cross-linking bath due to the degree of cross-linking of the PVA-based resin film. Therefore, it cannot be determined universally, but it is preferably not less than 5 seconds and not more than 300 seconds, and more preferably not less than 10 seconds and not more than 200 seconds. The cross-linking step may be carried out only once, or may be carried out a plurality of times if necessary.

The extending step is a processing step of extending the PVA-based resin film to a predetermined magnification in at least one direction. Generally, the PVA-type resin film is uniaxially stretched in the conveyance direction (longitudinal direction). The method of stretching is not particularly limited, and either a wet stretching method or a dry stretching method can be used. The extension step may be performed only once, or may be performed multiple times as required. The extending step can be performed at any stage in the manufacture of the polarizer.

As the treatment bath (stretching bath) in the wet stretching method, a solvent such as water or a water-miscible organic solvent and a mixed solution of water can be generally used. From the viewpoint of controlling the content rate of potassium in the polarizing element, the stretching bath preferably contains potassium iodide. When potassium iodide is used in the stretching bath, the concentration of potassium iodide in the stretching bath is preferably 1 mass % or more and 15 mass % or less, more preferably 2 mass % or more and 10 mass % or less, still more preferably 3 mass % or more6 mass % or less. The treatment bath (stretching bath) may contain a boron compound from the viewpoint of suppressing film breakage during stretching. When a boron compound is contained, the concentration of the boron compound in the stretching bath is preferably 1 mass % or more and 15 mass % or less, more preferably 1.5 mass % or more and 10 mass % or less, still more preferably 2 mass % or more and 5 mass % %the following.

The temperature of the stretching bath is preferably 25°C or higher and 80°C or lower, more preferably 40°C or higher and 75°C or lower, and even more preferably 50°C or higher and 70°C or lower. The immersion time in the stretching bath cannot be uniformly determined because the degree of stretching of the PVA-based resin film is affected by the temperature of the stretching bath, but is preferably 10 seconds or more and 800 seconds or less, more preferably 30 seconds or more and 500 seconds or less. The stretching treatment in the wet stretching method may be carried out together with any one or more treatment steps of the swelling step, the dyeing step, the cross-linking step, and the washing step.

Examples of the dry stretching method include a roll-to-roll stretching method, a heated roll stretching method, a compression stretching method, and the like. Furthermore, the dry stretching method may be implemented together with the drying step.

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, and still more preferably 3.5 times. More than 6.5 times less.

The cleaning step is a treatment step in which the polyvinyl alcohol-based resin film is immersed in a cleaning bath, and foreign matter remaining on the surface of the polyvinyl alcohol-based resin film and the like can be removed. The cleaning bath usually uses a medium mainly composed of water, such as water, distilled water, and pure water. In addition, from the viewpoint of controlling the potassium content in the polarizing element, potassium iodide is preferably used in the cleaning bath, and in this case, the concentration of potassium iodide in the cleaning bath is preferably 1 mass % or more and 10 mass % % or less, more preferably 1.5 mass % or more and 4 mass % or less, still more preferably 1.8 mass % or more and 3.8 mass % or less.

The temperature of the cleaning bath is preferably 5°C or higher and 50°C or lower, more preferably 10°C or higher and 40°C or lower, and even more preferably 15°C or higher and 30°C or lower. The time of immersion in the cleaning bath cannot be determined uniformly because the degree of cleaning of the PVA-based resin film is affected by the temperature of the cleaning bath, but it is preferably 1 second or more and 100 seconds or less, more preferably 2 seconds or more and 50 seconds or less. More preferably, it is 3 seconds or more and 20 seconds or less. The washing step may be carried out only once, or may be carried out a plurality of times if necessary.

The drying step is a step of drying the PVA-based resin film washed in the washing step to obtain a polarizing element. Drying can be performed by any appropriate method, and examples thereof include natural drying, air drying, and heat drying.

Manufacturing method 2 can be manufactured through the following steps: a step of applying a coating liquid containing a PVA-based resin on a base film; a step of uniaxially extending the obtained laminated film; by using a dichroic dye The step of dyeing the PVA-based resin layer of the uniaxially stretched laminate film to make it adsorb to form a polarizing element; the step of treating the film having the dichroic dye adsorbed with an aqueous solution of boric acid; and the step of using After the treatment of the boric acid aqueous solution, the step of washing with water is performed. The base film used to form the polarizer can also be used as a protective layer for the polarizer. If necessary, the base film may be peeled off and removed from the polarizer.

<Transparent protective film>

The transparent protective film (hereinafter, also simply referred to as "protective film") used in the present embodiment is bonded 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, preferably attached to both sides.

The protective film may have other optical functions at the same time, and may be formed into a laminated structure in which a plurality of layers are laminated. 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 workability is poor. As a suitable film thickness, it is 5 micrometers or more and 100 micrometers or less, Preferably it is 10 micrometers or more and 80 micrometers or less, More preferably, it is 15 micrometers or more and 70 micrometers or less.

As the protective film, a cellulose-based film, a film composed of a polycarbonate-based resin, a film composed of a cycloolefin-based resin such as norbornene, a (meth)acrylic-based polymer film, and a polyparaphenylene can be used. Films such as polyester resin-based films such as ethylene diformate. In the case where the protective film is attached to both sides of the polarizing element using a water-based adhesive such as PVA adhesive, the protective film on at least one side is preferably a cellulose-based film or (methyl) in terms of moisture permeability. ) any of acrylic polymer films, among which carboxylated cellulose films are preferred.

For the purpose of viewing angle compensation and the like, at least one protective film may also have a retardation function. In this case, the protective film itself may have a retardation function, may additionally have a retardation layer, or may be a combination of the two. The film having the retardation function may be directly bonded to the polarizer via an adhesive, or may be bonded via an adhesive or an adhesive via another protective film bonded to the polarizer.

<Adhesive layer>

An adhesive containing a urea-based compound and a reducing agent is used as the adhesive constituting the adhesive layer for bonding the protective film to the polarizing element. Water-based adhesives, solvent-based adhesives, active energy adhesives can be used as adhesives The line hardening type adhesive or the like is preferably a water-based adhesive, and preferably contains a PVA-based resin. By using an adhesive containing a urea-based compound and a reducing agent, the decrease in the transmittance of the polarizing plate in a high temperature environment can be suppressed.

The thickness of the adhesive during coating can be set to any value, for example, after hardening or heating (drying), it can be set so as to obtain an adhesive layer with a desired thickness. 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, still more preferably 0.01 μm or more and 2 μm or less, and most preferably 0.01 μm or more and 1 μm or less.

The description about the following adhesive agent describes the preferable range about the case where a urea-type compound and a reducing agent are not contained in a polarizing element at the time of manufacture of a polarizing element. When the polarizing element contains a urea-based compound and a reducing agent, the following values may be appropriately adjusted. Regarding the specific examples of the urea-based compound and the reducing agent, the examples of the urea-based compound and the reducing agent contained in the above-mentioned polarizing element can be directly applied. In the process of forming the adhesive layer through the drying step of bonding the polarizer and the protective film, a part of the urea compound and a part of the reducing agent may also move from the adhesive layer to the polarizer and the like.

When the adhesive is a water-based adhesive containing a PVA-based resin, the content of the urea-based compound is preferably 0.1 part by mass or more and 400 parts by mass or less, more preferably 1 part by mass or more and 200 parts by mass relative to 100 parts by mass of the PVA-based resin. It is not more than 3 parts by mass, and more preferably not less than 3 parts by mass and not more than 100 parts by mass. If it is less than 0.1 part by mass, the effect of suppressing polyolefination of the polarizing element in a high temperature environment may be insufficient. On the other hand, when it exceeds 400 mass parts, urea may precipitate, and troubles, such as a haze rise, may arise.

When the adhesive is a water-based adhesive containing a PVA-based resin, the content of the reducing agent is preferably 1 part by mass or more and 50 parts by mass or less, more preferably 1.5 parts by mass or more and 40 parts by mass relative to 100 parts by mass of the PVA-based resin. parts or less, more preferably not less than 2 parts by mass and not more than 35 parts by mass, and may be 20 parts by mass or less. If it is less than 1 part by mass, the effect of suppressing polyolefination of the polarizing element in a high temperature environment may be insufficient. On the other hand, when it exceeds 50 mass parts, the iodine complex in a polarizing element is reduced, and the polarization degree may fall.

In the structure in which the two sides of the polarizing element are laminated with the transparent protective film through the adhesive layer, the adhesive layer on both sides of the polarizing element may only be a layer containing a urea compound and a reducing agent on one side of the adhesive layer. Preferably, the adhesive layers on both sides are layers containing a urea-based compound and a reducing agent.

In order to meet the requirement of thinning polarizers, polarizers with transparent protective film only on one side of the polarizer have been developed. In this configuration, the transparent protective film is laminated through the adhesive layer containing the urea-based compound and the reducing agent. As a method for producing such a polarizing plate with a transparent protective film only on one side of the polarizing element, it can be considered to first produce a polarizing plate with a transparent protective film attached to both sides through an adhesive layer, and then peel off one transparent protective film. method. In the case of using such a production method, the urea-based compound and the reducing agent may be contained only in the adhesive layer on either side, but it is preferable that the adhesive layers on both sides contain the urea-based compound and the reducing agent. When only the adhesive layer on one side contains the urea-based compound and the reducing agent, it is preferable that the adhesive layer on the non-peeling film side contains the urea-based compound and the reducing agent.

(Water based adhesive)

As the water-based adhesive, any appropriate water-based adhesive can be used, and it is preferable to use a water-based adhesive (PVA-based adhesive) containing a PVA-based resin. In terms of adhesiveness, the average degree of polymerization of the PVA-based resin contained in the water-based adhesive is preferably 100 or more and 5,500 or less, more preferably 1,000 or more and 4,500 or less. In terms of adhesion, the average saponification degree is preferably 85 mol% or more and 100 mol% or less, more preferably 90 mol% or more and 100 mol% or less.

As the PVA-based resin contained in the water-based adhesive, those containing an acetyl acetyl group are preferable because the PVA-based resin layer and the protective film have excellent adhesion and durability. Acetyl Acetyl-based PVA-based resins can be obtained, for example, by reacting PVA-based resins with diketene by any method. The degree of modification of the acetoacetyl group of the PVA-based resin containing an acetoacetyl group is typically 0.1 mol % or more, preferably 0.1 mol % or more and 20 mol % or less. The resin concentration of the water-based adhesive is preferably 0.1 mass % or more and 15 mass % or less, more preferably 0.5 mass % or more and 10 mass % or less.

The water-based adhesive may contain a crosslinking agent. As the crosslinking agent, a known crosslinking agent can be used. As a crosslinking agent, a water-soluble epoxy compound, a dialdehyde, an isocyanate, etc. are mentioned, for example.

In the case where the PVA-based resin is a PVA-based resin containing an acetoacetyl group, the crosslinking agent is preferably any one of glyoxal, glyoxalate, and methylol melamine, more preferably Any of glyoxal and glyoxalate, particularly preferably glyoxal.

The water-based adhesive may contain an organic solvent. In terms of being miscible with water, the organic solvent is preferably an alcohol, and among the alcohols, methanol or ethanol is more preferable. The concentration of methanol in the aqueous adhesive is preferably 10 mass % or more and 70 mass % or less, more preferably 15 mass % or more and 60 mass % or less, and even more preferably 20 mass % or more and 60 mass % or less. When the concentration of methanol is 10% by mass or more, it is easier to suppress the polyolefinization of the PVA-based resin in a high temperature environment. Moreover, the deterioration of a hue can be suppressed by the content rate of methanol being 70 mass % or less. Some of the urea derivatives have low solubility in water, but on the other hand, have sufficient solubility in alcohol. At this time, it is also one of preferable aspects to prepare an adhesive by dissolving the urea-based compound in alcohol to prepare an alcohol solution of the urea-based compound, and then adding the alcohol solution of the urea-based compound to the PVA aqueous solution.

(active energy ray hardening adhesive)

Active energy ray-curable adhesives are adhesives that are cured by irradiating active energy rays such as ultraviolet rays, for example, adhesives containing a polymerizable compound and a photopolymerizable initiator, adhesives containing a photoreactive resin, Adhesives including adhesive resins and photoreactive cross-linking agents, etc. As a polymerizable compound, a photocurable epoxy monomer, a photocurable acrylic monomer, a photocurable urethane monomer can be mentioned. Photopolymerizable monomers such as ester-based monomers, and oligomers derived from these monomers. Examples of the photopolymerization initiator include compounds containing substances that generate active species such as neutral radicals, anionic radicals, and cationic radicals by irradiation with active energy rays such as ultraviolet rays.

<Urea-based compound-containing layer>

The urea-based compound and the reducing agent are not limited to being contained in the adhesive layer as described above, and may be contained in layers other than the adhesive layer from the viewpoint of improving the high-temperature durability of the polarizing plate. In a polarizing plate having a transparent protective film only on one side, a hardened layer may be layered on the opposite area of the polarizing element to the transparent protective film from the viewpoint of improvement of physical strength.

In the present embodiment, such a cured layer may be made to contain a urea-based compound and a reducing agent to form a layer containing a urea-based compound. Usually, such a hardened layer is formed of a curable composition containing an organic solvent, but paragraphs [0020] to [0042] of Japanese Patent Laid-Open No. 2017-075986 describe a polymer curable by active energy rays A method of forming such a hardened layer from an aqueous solution of a composition. Water-soluble urea compounds and reducing agents may be contained in these compositions.

The urea-based compound-containing layer preferably includes at least one urea-based compound, at least one reducing agent, and a binder. Examples of the binder include polymer binders, thermosetting resin binders, active energy ray curing resin binders, and the like, and any binder can be preferably used.

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

[Manufacturing method of polarizing plate]

The manufacturing method of the polarizing plate of this embodiment has a moisture content adjustment process and a lamination process. In the moisture content adjustment step, in the case of manufacturing the polarizing plate having the feature (a), the moisture content of the polarizing element is set to be equal to or higher than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and at a temperature of 20°C and a relative humidity of 50%. balance The moisture content of the polarizing element is adjusted below the moisture content. The moisture content of the polarizing element can be adjusted according to the description of the moisture content of the polarizing element above. In the moisture content adjustment step, in the case of manufacturing the polarizing plate having the feature (b), the moisture content of the polarizing plate is set to be equal to or higher than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, and at a temperature of 20°C and a relative humidity of 50%. Adjust the moisture content of the polarizing plate below the equilibrium moisture content. The moisture content of the polarizing plate can be adjusted according to the description of the above-mentioned moisture content of the polarizing plate. In the lamination step, the polarizing element and the transparent protective film are laminated through the adhesive layer. In the lamination step, for example, the polarizing element that has not been treated with the urea-based compound and the reducing agent is bonded to the transparent protective film by an adhesive containing the urea-based compound and the reducing agent. The order of the water content adjustment step and the layering step is not limited, and the water content adjustment step and the layering step may be performed in parallel.

[Configuration of Image Display Device]

The polarizing plate of this embodiment is used in various image display devices such as liquid crystal display devices and organic EL display devices. Regarding the image display device, when both sides of the polarizing plate are filled with layers other than the air layer, specifically, solid layers 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 this embodiment, even if it is an interlayer filling structure, the reduction of the transmittance of the polarizing plate in a high temperature environment can be suppressed. An example of the image display device includes an image display unit, a first adhesive layer laminated on the visible side surface of the image display unit, and a polarizing plate laminated on the visible side surface of the first adhesive layer. The image display device may further include a second adhesive layer laminated on the visible side surface of the polarizing plate, and a transparent member laminated on the surface of the second adhesive layer. In particular, the polarizing plate of this embodiment can be preferably used in an image display device with an interlayer filling structure, and the interlayer filling structure is configured with a transparent member, a polarizing plate and an image display unit on the visible side of the image display device. The polarizing plate and the transparent member are bonded together by the first adhesive layer, and the polarizing plate and the transparent member are bonded together by the second adhesive layer. In this specification, either one of the first adhesive layer and the second adhesive layer or The two are referred to as "adhesive layers" for short. Furthermore, as a member for bonding a polarizing plate and an image display unit, and a member for bonding a polarizing plate and a transparent member, it is not limited to an adhesive layer, but may be an adhesive layer.

<Image Display Unit>

As an image display cell, a liquid crystal cell or an organic EL cell is mentioned. As the liquid crystal cell, a reflective liquid crystal cell using external light, a transmissive liquid crystal cell using light from a light source such as a backlight, and a transflective liquid crystal cell using both external light and light from a light source can be used either. When the liquid crystal cell utilizes light from a light source, the image display device (liquid crystal display device) is also provided with a polarizer and a light source on the opposite side of the image display cell (liquid crystal cell) from the viewing side. The polarizing plate on the light source side and the liquid crystal cell are preferably attached via an appropriate adhesive layer. As the driving method of the liquid crystal cell, for example, any type such as VA mode, IPS mode, TN mode, STN mode, or bend alignment (π type) can be used.

As the organic EL unit, a transparent electrode, an organic light-emitting layer, and a metal electrode are sequentially laminated on a transparent substrate to form a light-emitting body (organic electroluminescent light-emitting body) or the like can be preferably used. The organic light-emitting layer is a layered product of various organic films, for example, a layered product of a hole injection layer composed of a triphenylamine derivative and a light-emitting layer composed of a fluorescent organic solid such as anthracene, or a layered product of these light-emitting layers and a Various layers, such as a laminate of an electron injection layer composed of a perylene derivative, etc., or a laminate of a hole injection layer, a light-emitting layer, and an electron injection layer, etc. are formed.

<The bonding of the image display unit and the polarizing plate>

In the lamination of the image display unit and the polarizing plate, an adhesive layer (adhesive sheet) can be preferably used. Among them, from the viewpoints of workability and the like, a method of laminating the polarizing plate with the adhesive layer on which the adhesive layer is attached on one surface of the polarizing plate and the image display unit is preferred. The adhesive layer of the polarizing plate can be attached by suitable Do it the way it should. As an example, a base polymer or its composition prepared by dissolving or dispersing in a solvent containing an appropriate solvent such as toluene or ethyl acetate or a mixture of a single substance or a mixture of 10% by mass or more and 40% by mass or less can be mentioned. The adhesive solution is directly attached to the polarizing plate by suitable spreading methods such as casting or coating; the method of forming an adhesive layer on the separator and transferring it to the polarizing plate, etc.

<Adhesive layer>

The adhesive layer may be composed of one layer or two or more layers, preferably one layer. The adhesive layer may be composed of an adhesive composition mainly composed of (meth)acrylic resin, rubber-based resin, urethane-based resin, ester-based resin, polysiloxane-based resin, and polyvinyl ether-based resin. Among them, an adhesive composition having a (meth)acrylic resin excellent in transparency, weather resistance, heat resistance, etc. as a base polymer is preferable. The adhesive composition may be of an active energy ray hardening type or a thermosetting type.

As the (meth)acrylic resin (base polymer) used in the adhesive composition, butyl (meth)acrylate, ethyl (meth)acrylate, and isopropyl (meth)acrylate can be preferably used. A polymer or copolymer of one or more of (meth)acrylates such as octyl ester and 2-ethylhexyl (meth)acrylate as monomers. In the base polymer, it is preferable to copolymerize polar monomers. Examples of polar monomers include (meth)acrylic acid compounds, 2-hydroxypropyl (meth)acrylate compounds, hydroxyethyl (meth)acrylate compounds, (meth)acrylamide compounds, and (meth)acrylate compounds. Monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, etc., such as N,N-dimethylaminoethyl acrylate compounds and glycidyl (meth)acrylate compounds.

The adhesive composition may contain only the above-mentioned base polymer, but usually further contains a crosslinking agent. Examples of the crosslinking agent include a metal ion having a valence of at least two and forming a metal carboxylate with a carboxyl group, a polyamine compound forming an amide bond with a carboxyl group, and a polyamine compound forming an ester bond with the carboxyl group. Polyepoxy compounds or polyols, and polyisocyanate compounds that form amide bonds with carboxyl groups. Among them, polyisocyanate compounds are preferred.

The active energy ray hardening type adhesive composition has the property of being hardened by irradiation with active energy rays such as ultraviolet rays or electron beams, and has the property of being adhesive even before the irradiation of the active energy rays and being in close contact with adherends such as films. , and has the property that it can be hardened and adjusted by the irradiation of active energy rays. The active energy ray-curable adhesive composition is preferably an ultraviolet-curable type. The active energy ray curable adhesive composition further contains an active energy ray polymerizable compound in addition to the base polymer and the crosslinking agent. A photopolymerization initiator, a photosensitizer, etc. may be contained as needed.

The adhesive composition may include microparticles, beads (resin beads, glass beads, etc.) for imparting light scattering properties, glass fibers, resins other than base polymers, adhesion imparting agents, fillers (metal powder or other Inorganic powder, etc.), antioxidants, ultraviolet absorbers, dyes, pigments, colorants, defoaming agents, anti-corrosion agents, photopolymerization initiators and other additives.

The adhesive layer can be formed by applying the organic solvent dilution of the above-mentioned adhesive composition on the surface of the base film, the image display unit or the polarizing plate and drying it. The base film is generally a thermoplastic resin film, and a typical example thereof includes a release film subjected to mold release treatment. For the separation membrane, for example, the surface of the membrane containing resins such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, polyarylate, etc., on which the adhesive layer is formed, may be subjected to silicone treatment or the like. Mold processed.

The adhesive composition can also be directly coated on the release treatment surface of the separation film to form an adhesive layer, and the adhesive layer with the separation film is laminated on the surface of the polarizer. The adhesive composition can also be directly coated on the surface of the polarizing plate to form an adhesive layer, and a separation film is formed on the outer surface of the adhesive layer.

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

Furthermore, an adhesive layer may be prepared by applying an adhesive composition on the second separation film, and an adhesive sheet obtained by laminating a separation film on the formed adhesive layer may be prepared, and the second separation film may be peeled off from the adhesive sheet. After the separation film, the adhesive with the separation film is laminated on the polarizing plate. For the second separation membrane, the adhesive force with the adhesive layer is weaker than that of the separation membrane, and it is easy to peel off.

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 may be 20 μm or more.

<Transparent member>

As a transparent member arrange|positioned at the viewing side of an image display apparatus, a transparent plate (window layer), a touch panel, etc. are mentioned. As the transparent plate, a transparent plate having appropriate mechanical strength and thickness can be used. As such a transparent plate, for example, a transparent resin plate of a polyimide resin, an acrylic resin, or a polycarbonate resin, a glass plate, etc. are mentioned. Functional layers such as anti-reflection layers can also be laminated on the visible side of the transparent plate. In addition, when the transparent plate is a transparent resin plate, a hard coat layer for improving physical strength or a low moisture permeability layer for reducing moisture permeability may be laminated. As the touch panel, various touch panels such as a resistive film method, a capacitive method, an optical method, and an ultrasonic method, or a glass plate or a transparent resin plate having a touch sensor function can be used. When a capacitive touch panel is used as a transparent member, it is preferable to provide a transparent plate including glass or a transparent resin plate on the visible side of the touch panel.

<Lamination of polarizer and transparent member>

In the lamination of the polarizing plate and the transparent member, it is preferable to use an adhesive or an active energy ray hardening adhesive. In the case of using an adhesive, the attachment of the adhesive can be carried out in a suitable manner. as a specific As an attachment method, the attachment method of the adhesive layer used for the lamination of the said image display unit and a polarizing plate is mentioned, for example.

In the case of using an active energy ray hardening type adhesive, in order to prevent the adhesive solution from spreading before hardening, it is preferable to use the following method. A transparent member is placed thereon, and an adhesive solution is injected. After injection of the adhesive solution, if necessary, alignment and defoaming are performed, and then active energy rays are irradiated for curing.

[Example]

Hereinafter, the present invention will be specifically described based on examples. The materials, reagents, amounts of substances and their ratios, operations, etc. shown in the following examples can be appropriately changed as long as they do not depart from the gist of the present invention. Therefore, the present invention is not limited to the following examples.

<Production of polarizing element A>

A PVA film with a thickness of 40 μm composed of PVA with an average degree of polymerization of about 2,400 and a degree of saponification of 99.9 mol% or more was uniaxially stretched to about 5 times in a dry manner, and further maintained in a taut state, immersed in pure water at 60°C for 1 minute Then, it was immersed for 60 second in the aqueous solution whose weight ratio of iodine/potassium iodide/water is 0.05/5/100 at 28 degreeC. Then, the weight ratio of potassium iodide/boric acid/water was immersed at 72 degreeC for 300 second in the aqueous solution of 8.5/8.5/100. Then, after washing with pure water at 26° C. for 20 seconds, it was dried at 65° C. to obtain a polarizer A with a thickness of 15 μm in which iodine was adsorbed and aligned on PVA. The thickness of the polarizing element was measured using a digital micrometer "MH-15M" manufactured by Nikon Co., Ltd.

<Preparation of Adhesives 1 to 11>

(Preparation of PVA solution A for adhesive)

50 g of a modified PVA-based resin containing an acetyl acetyl group (“GOHSENEX Z-410” manufactured by Mitsubishi Chemical Co., Ltd.) was dissolved in 950 g of pure water, heated at 90°C for 2 hours, and then cooled to room temperature to obtain an adhesive for PVA solution (hereinafter referred to as "PVA solution A").

(Preparation of Adhesives 1 to 11)

PVA solution A, a urea-type compound, a reducing agent, and pure water were prepared so that PVA was 3.0 mass %, and a urea-type compound and a reducing agent became the content shown in Table 1, and the adhesive agent 1-11 was prepared.

[Table 1]

<Preparation of transparent protective film A>

A commercially available cellulose cellulose film TD40 (manufactured by Fujifilm Co., Ltd., film thickness 40 μm) was immersed in a 1.5 mol/L NaOH aqueous solution (saponified solution) maintained at 55° C. for 2 minutes, and then the film was washed with water. Then, after immersing in 0.05 mol/L sulfuric acid aqueous solution of 25 degreeC for 30 second, the water bath was further made to pass under running water for 30 second, and the film was brought into a neutral state. Then, after repeating 3 times of draining with an air knife to remove water, it was made to stay in a drying zone of 70 degreeC for 15 seconds, and it dried, and the film which saponified process was produced, and the transparent protective film A was produced.

<Production of Polarizing Plates 1 to 11>

Through the adhesive agent 1, the transparent protective film A was bonded to both surfaces of the polarizer A using a roll bonding machine. After bonding, it dried at 80 degreeC for 5 minutes, and the polarizing plate 1 was obtained. The adhesive layer was adjusted so that the thickness after drying was 50 nm on both sides.

In polarizing plate 1, adhesive agent 1 was changed into adhesive agent 2-11, and polarizing plate 2-11 was obtained.

(Moisture content adjustment of polarizing plate (polarizing element))

The polarizing plates 1 to 11 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 water content was measured using the Karl Fischer method at storage for 66 hours, 69 hours and 72 hours. Under any humidity condition, the value of moisture content did not change in storage for 66 hours, 69 hours and 72 hours. Therefore, the moisture content of the polarizing plates 1 to 11 can be regarded as the same as the equilibrium moisture content of the 72-hour storage environment used in this experimental example. When the moisture content of the polarizing plate reaches equilibrium under a certain storage environment, the moisture content of the polarizing element in the polarizing plate can also be regarded as being balanced under its storage environment. In addition, when the moisture content of the polarizing element in the polarizing plate reaches equilibrium under a certain storage environment, the moisture content of the polarizing plate can also be regarded as being balanced under the storage environment.

<Optical Laminates 1 to 13>

The optical laminates 1 to 13 use any one of the polarizing plates 1 to 11 shown in Table 2, so that the moisture content of the polarizing plate (polarizing element) used becomes the equilibrium moisture content of the environment shown in Table 2 Produced by storing at 20°C and relative humidity of 35%, 45% or 55% for 72 hours.

<High temperature durability evaluation>

(Preparation of samples for evaluation)

The optical layered bodies 1 to 13 were formed with acrylic adhesives (manufactured by LINTEC Co., Ltd., model number: #7) on both surfaces, and cut into a size of 50 mm×100 mm so that the absorption axis was parallel to the long side. An evaluation sample was prepared by attaching an alkali-free glass (“EAGLE XG” manufactured by Corning Corporation) to the surface of each adhesive.

In order to evaluate the cross-light leakage of the above-mentioned evaluation sample, the optical layered body R was produced for the purpose of creating a cross-polarized light state by overlapping with the evaluation sample. Specifically, an acrylic adhesive (manufactured by LINTEC Co., Ltd., model number: #7) was formed on only one side of the polarizing plate 9, and cut into a size of 50 mm×100 mm so that the absorption axis was parallel to the short side. The optical layered body R for the evaluation of orthogonal light leakage was produced by attaching an alkali-free glass (“EAGLE XG” manufactured by Corning Co., Ltd.) to the surface of the adhesive.

<Evaluation of monomer penetration rate (105°C)>

The evaluation samples of optical laminates 1 to 13 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, and then left at a temperature of 23° C. and a relative humidity of 55% for 24 hours. Then, the transmittance (initial value) of the evaluation samples of the optical layered bodies 1 to 13 was measured, and the transmittance was measured every 50 hours until 100 to 200 hours in a heating environment with a temperature of 105°C. Based on the time when the penetration rate decreased by 5% or more from the initial value, it was evaluated by the following criteria. The obtained results are shown in Table 2.

After 200 hours, the decrease in penetration rate is less than 5%: A

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

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

100 hours after the decrease in penetration rate of 5% or more: D

<Evaluation of Orthogonal Light Leakage>

An evaluation sample after the measurement of the monomer penetration rate at the time of 200 hours was prepared in the above-mentioned evaluation of the monomer penetration rate. The optical layered body R for cross-polarized light evaluation and the evaluation sample, which were not put into a heating environment, were arranged so as to have a relationship of crossed polarized light, and were placed on a backlight. The surrounding area was shielded from light, and orthogonal light leakage was visually observed, and four-stage evaluation was performed based on the following criteria. The obtained results are shown in Table 2. In addition, the evaluation samples whose monomer transmittance was evaluated as other than A were excluded from the evaluation of orthogonal light leakage due to the presence of coloration due to polyolefination.

Can't see orthogonal light leaks at all: A

Barely visible orthographic leakers: B

Slightly sees orthographic light leaks: C

Clearly see the orthogonal light leak :D

[Table 2]

It can be seen that the polarizing plates (optical laminates 1 to 9) formed by laminating the polarizing element and the transparent protective film with an adhesive containing a urea compound and a reducing agent are difficult to transmit even when exposed to a high temperature environment of 105°C. It has excellent high temperature durability, wherein the polarizing plate has a polarizing element and a transparent Protector. It turned out that the optical layered bodies 1 to 9 are also excellent in the orthogonal light leakage evaluation, and the degree of polarization is not easily reduced even when exposed to a high temperature environment of 105° C., and in this regard, the high temperature durability is also excellent.

Claims (13)

A polarizing plate comprising a polarizing element obtained by adsorbing and aligning a dichroic dye on a polyvinyl alcohol-based resin layer, and a transparent protective film laminated on at least one side of the polarizing element; wherein, The above-mentioned polarizing element and the above-mentioned transparent protective film are bonded together by an adhesive layer, and the above-mentioned adhesive layer is formed by an adhesive containing a urea-based compound and a reducing agent, The above-mentioned urea-based compound is at least one selected from the group consisting of urea, urea derivatives, thiourea and thiourea derivatives, The moisture content of the above polarizing element is above the equilibrium moisture content of 30% relative humidity at a temperature of 20°C and below the equilibrium moisture content of 50% relative humidity at a temperature of 20°C. A polarizing plate comprising a polarizing element obtained by adsorbing and aligning a dichroic dye on a polyvinyl alcohol-based resin layer, and a transparent protective film laminated on at least one side of the polarizing element; wherein, The above-mentioned polarizing element and the above-mentioned transparent protective film are bonded together by an adhesive layer, and the above-mentioned adhesive layer is formed by an adhesive containing a urea-based compound and a reducing agent, The above-mentioned urea-based compound is at least one selected from the group consisting of urea, urea derivatives, thiourea and thiourea derivatives, The moisture content of the polarizing plate is equal to or higher than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and equal to or less than an equilibrium moisture content at a temperature of 20°C and a relative humidity of 50%. The polarizing plate according to claim 1 or 2, wherein the adhesive comprises at least one urea-based compound selected from the group consisting of urea derivatives and thiourea derivatives. The polarizing plate according to any one of claims 1 to 3, wherein the adhesive contains a polyvinyl alcohol-based resin. The polarizing plate according to claim 4, wherein, in the adhesive, the content of the urea-based compound 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. The polarizing plate according to claim 4 or 5, wherein, in the adhesive, the content of the reducing agent is 1 part by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the polyvinyl alcohol-based resin. The polarizing plate according to any one of claims 1 to 6, wherein the adhesive layer has a thickness of 0.01 μm or more and 7 μm or less. The polarizing plate according to any one of claims 1 to 7, wherein the reducing agent is at least one selected from the group consisting of ascorbic acid, erythorbic acid, thiosulfuric acid, sulfurous acid and salts thereof. The polarizing plate according to any one of claims 1 to 8, wherein the polarizing plate is used in an image display device, In the above-mentioned image display device, the solid layers are provided on both sides of the above-mentioned polarizing plate in contact with each other. An image display device comprising: an image display unit; a first adhesive layer laminated on a visible side surface of the image display unit; and the polarizing plate according to any one of claims 1 to 9, It is laminated|stacked on the visible side surface of the said 1st adhesive bond layer. The image display device according to claim 10, 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 . The image display device according to claim 11, wherein the transparent member is a glass plate or a transparent resin plate. The image display device according to claim 11, wherein the transparent member is a touch panel.