KR20240023418A - Polarizer and image display device using the polarizer - Google Patents

Abstract

The purpose of the present invention is to provide a novel polarizing plate that has an adhesive layer formed of an adhesive having a sufficient pot life in production and in which a decrease in transmittance when exposed to a high temperature environment is suppressed. The present invention is a polarizing plate having 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 side of the polarizing element, wherein the polarizing element and the transparent protective film include: They are bonded together by an adhesive layer formed of an adhesive containing a first compound, a second compound and a third compound, wherein the first compound is at least one selected from the group consisting of urea, urea derivatives, thiourea and thiourea derivatives. species, the second compound is dialdehyde, and the third compound is a dicarboxylic acid.

Description

Polarizer and image display device using the polarizer

The present invention relates to polarizers and image display devices.

Liquid crystal displays (LCDs) are widely used not only in liquid crystal televisions but also in vehicle applications such as personal computers, mobile phones such as mobile phones, and car navigation systems. Usually, a liquid crystal display device has a liquid crystal panel in which a polarizing plate is bonded to both sides of a liquid crystal cell with an adhesive, and display is performed by controlling light from a backlight to the liquid crystal panel. In recent years, organic EL display devices, like liquid crystal display devices, have been widely used for vehicle applications such as televisions, mobile phones such as cell phones, and car navigation systems. In an organic EL display device, a circularly polarizing plate (a laminate including a polarizing element and a λ/4 plate) is placed on the viewing side surface of the image display panel to prevent external light from being reflected from the metal electrode (cathode) and viewed as a mirror surface. There are cases where this is arranged.

In a polarizing plate, a polyvinyl alcohol-based resin adhesive is used to bond the polarizing element and the protective film because it provides good adhesiveness. However, Patent Document 1 (Japanese Patent Application Laid-Open No. 2005-189615) points out that sufficient pot life cannot be obtained with a polyvinyl alcohol-based resin adhesive. The fact that pot life is not obtained means that the adhesive has a short shelf life. Patent Document 2 (Japanese Patent Application Laid-Open No. 2010-276673) describes that sufficient pot life can be obtained in terms of production by using an adhesive containing maleic acid along with a crosslinking agent.

As mentioned above, a polarizer is a member of an image display device such as a liquid crystal display device or an organic EL display device, and the opportunities for its installation in cars are increasing. Polarizers used in in-vehicle image display devices are often exposed to high-temperature environments compared to those used in mobile applications such as televisions and mobile phones, so they are required to have less change in properties at high temperatures (high-temperature durability).

On the other hand, for the purpose of preventing damage to the image display panel due to impact from the outer surface, a front plate such as a transparent resin plate or glass plate (also called a "window layer") is provided on the viewing side of the image display panel. This is increasing. In an image display device equipped with a touch panel, a configuration in which the touch panel is provided on the viewer's side of the image display panel and the front plate is provided on the viewer's side further than the touch panel is widely adopted.

In this configuration, if an air layer exists between the image display panel and a transparent member such as a front panel or a touch panel, glare of external light occurs due to reflection of light at the air layer interface, and the visibility of the screen tends to decrease. Therefore, the space between the polarizing plate disposed on the viewing side surface of the image display panel and the transparent member is filled with a layer other than the air layer, usually a solid layer (hereinafter sometimes referred to as an “interlayer filler”) ( The movement to adopt this (hereinafter sometimes referred to as “interlayer charging configuration”) is expanding. The interlayer filler is preferably a material with a refractive index close to that of the polarizer or transparent member. As an interlayer filler, an adhesive or a UV curable adhesive is used for the purpose of preventing a decrease in visibility due to reflection at the interface and adhering and fixing each member (for example, Japanese Patent Application Laid-Open No. 11-174417 (Patent Document 3) ) reference).

Interfloor charging configurations are increasingly being adopted for mobile applications such as mobile phones that are often used outdoors. In addition, due to the recent increase in the demand for visibility, even in vehicle applications such as car navigation devices, an interlayer filling configuration in which a front transparent plate is placed on the surface of the image display panel and the space between the panel and the front transparent plate is filled with an adhesive layer, etc. Recruitment is being considered.

However, when this configuration is adopted, it has been reported that the transmittance of the polarizing plate significantly decreases in a high temperature environment. In Japanese Patent Laid-Open No. 2014-102353 (Patent Document 4), as a solution to the problem, the moisture content per unit area of the polarizing plate is set to a predetermined amount or less, and the saturated absorption amount of the transparent protective film adjacent to the polarizing element is set to a predetermined amount. A method of suppressing the decrease in transmittance is proposed by doing the following.

Patent Document 1: Japanese Patent Publication No. 2005-189615 Patent Document 2: Japanese Patent Publication No. 2010-276673 Patent Document 3: Japanese Patent Publication No. Heisei 11-174417 Patent Document 4: Japanese Patent Publication No. 2014-102353

The present invention provides a novel polarizing plate having an adhesive layer formed of an adhesive having a sufficient pot life in production and suppressing a decrease in transmittance when exposed to a high temperature environment, an image display device using the polarizing plate, and an adhesive. The purpose is to

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

[1] A polarizing plate having 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,

The polarizing element and the transparent protective film are bonded together by an adhesive layer formed of an adhesive containing a first compound, a second compound, and a third compound,

The first compound is at least one selected from the group consisting of urea, urea derivatives, thiourea, and thiourea derivatives,

The second compound is dialdehyde,

The third compound is a dicarboxylic acid.

[2] The polarizing plate according to [1], wherein the adhesive contains a polyvinyl alcohol-based resin.

[3] The polarizing plate according to [2], in which the content of the third compound in the adhesive is 0.01 part by mass or more and 400 parts by mass or less with respect to 100 parts by mass of the polyvinyl alcohol-based resin.

[4] In the adhesive, the polarizing plate according to [2] or [3], wherein the content of the first compound is 0.1 part by mass or more and 400 parts by mass or less with respect to 100 parts by mass of the polyvinyl alcohol-based resin.

[5] The polarizing plate according to any one of [2] to [4], wherein in the adhesive, the content of the second compound is 0.03 parts by mass or more and 20 parts by mass or less with respect to 1 part by mass of the first compound.

[6] The polarizing plate according to any one of [1] to [5], wherein the dialdehyde is glyoxal.

[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 polarizer is used in an image display device,

In the image display device, the polarizing plate according to any one of [1] to [7], wherein solid layers are provided in contact with both surfaces of the polarizing plate.

[9] An image display cell, a first adhesive layer laminated on the viewing side surface of the image display cell, and a device according to any one of [1] to [8] laminated on the viewing side surface of the first adhesive layer. An image display device having a polarizing plate.

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

[11] The image display device according to [10], wherein the transparent member is a glass plate or a transparent resin plate.

[12] The image display device according to [10], wherein the transparent member is a touch panel.

[13] Contains a first compound, a second compound and a third compound,

The first compound is at least one selected from the group consisting of urea, urea derivatives, thiourea, and thiourea derivatives,

The second compound is dialdehyde,

The adhesive wherein the third compound is a dicarboxylic acid.

According to the present invention, it becomes possible to provide a polarizing plate that has an adhesive layer formed of an adhesive having a sufficient pot life in production, and in which a decrease in transmittance when exposed to a high temperature environment is suppressed. Furthermore, by using the polarizing plate according to the present invention, it becomes possible to provide an image display device in which a decrease in transmittance is suppressed even when exposed to a high temperature environment.

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

[Polarizer]

A polarizing plate according to an embodiment of the present invention has a polarizing element in which a dichroic dye is adsorbed and oriented in a layer containing a polyvinyl alcohol-based resin, and a transparent protective film. The polarizing element and the transparent protective film are bonded together by an adhesive layer formed from an adhesive containing the first compound, the second compound, and the third compound.

The first compound is at least one selected from the group consisting of urea, urea derivatives, thiourea, and thiourea derivatives. The second compound is dialdehyde. The third compound is a dicarboxylic acid.

As a conventional polarizing plate with excellent high-temperature durability, for example, a polarizing plate is known in which the decrease in transmittance is suppressed even when the polarizing plate alone is left in an environment at a temperature of 95° C. for 1000 hours. However, when even such a polarizing plate is used in an interlayer filling configuration, if left in an environment with a temperature of 105° C., a significant decrease in transmittance may be observed in the central portion of the plane of the polarizing plate. A significant decrease in the transmittance of the polarizing plate in a high temperature environment is caused by adopting an interlayer filling configuration in which one side of the polarizing plate is bonded to the image display cell and the other side is bonded to a transparent member such as a touch panel or front plate. It is thought that this problem is particularly likely to occur when the image display device is exposed to a high temperature environment.

The polarizer, which has a significantly reduced transmittance due to the interlayer filling structure, has peaks around 1100 cm ^-1 (derived from =CC= bond) and around 1500 cm ^-1 (derived from -C=C- bond) in Raman spectroscopy measurement. Therefore, it is thought that it forms a polyene structure (-C=C) _n -. It is presumed that the polyene structure is formed when the polyvinyl alcohol constituting the polarizing element is polyeneized by dehydration (Patent Document 4, paragraph [0012]).

The polarizing plate according to the present invention can further improve high temperature durability. The polarizing plate according to the present invention can suppress a decrease in transmittance even when mounted on an image display device with an interlayer filling configuration and exposed to a high temperature environment, for example, at a temperature of 105°C. It is presumed that this effect is due to the polyenylation of the polyvinyl alcohol constituting the polarizing element being suppressed by the synergistic action of the first compound, second compound, and third compound present in the adhesive layer. This effect is not limited to cases where the moisture content of the polarizing plate is low, and is exhibited even when the moisture content of the polarizing plate is high.

The polarizing plate according to the present invention preferably has at least one of the following characteristics (a) and (b).

(a) The water content of the polarizing element is greater than or equal to the equilibrium water content at a temperature of 20°C and a relative humidity of 30%, and less than or equal to an equilibrium water content of 70% relative humidity at a temperature of 20°C.

(b) The water content of the polarizing plate is greater than or equal to the equilibrium water content at a temperature of 20°C and a relative humidity of 30%, and less than or equal to the equilibrium water content at a temperature of 20°C and a relative humidity of 70%.

<Polarizing element>

As a polarizing element in which a dichroic dye is adsorbed and oriented on a layer containing 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. You can. As a polarizing element, a stretched film obtained by dyeing a PVA-based resin film with a dichroic dye and uniaxially stretching it, or a laminated film having an application layer formed by applying a coating liquid containing PVA-based resin onto a base film is used. , a stretched layer obtained by dyeing the application layer with a dichroic dye and uniaxially stretching the laminated film. Stretching may be performed after dyeing with a dichroic dye, may be stretched while dyeing, or may be dyed after stretching.

PVA-based resin is obtained by saponifying polyvinyl acetate-based resin. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as copolymers of vinyl acetate and other monomers copolymerizable therewith. Other copolymerizable monomers include, for example, unsaturated carboxylic acids, olefins such as ethylene, vinyl ethers, and unsaturated sulfonic acids.

The PVA-based resin layer is preferably formed of PVA-based resin with a boron adsorption rate of 5.70 mass% or more. That is, the boron adsorption rate of the PVA-based resin in the raw material stage before dyeing or stretching is 5.70% by mass or more. By using such a PVA-based resin, the transmittance becomes less likely to decrease even when exposed to a high temperature environment, for example, at a temperature of 105°C. Additionally, the boron adsorption rate of the PVA-based resin is preferably 10% by mass or less. By producing a polarizing element using such a PVA-based resin, the boric acid concentration in the boric acid treatment tank does not have to be high, and the processing time by boric acid treatment can also be shortened, making it easier to obtain a desired polarizing element, The productivity of polarizing elements can also be increased. If the boron adsorption rate of the PVA-based resin is 10% by mass or less, the PVA-based resin layer contains an appropriate amount of boron, and the shrinkage force of the polarizing element is likely to be reduced. As a result, when mounted on an image display device, problems such as peeling between the polarizing plate and other members such as the front plate are less likely to occur. The boron adsorption rate of the PVA-based resin can be measured by the method described in the Examples described later.

The boron adsorption rate of PVA-based resin is a characteristic that reflects the spacing between molecular chains and the crystal structure in the PVA-based resin. Compared to PVA-based resins with a boron adsorption rate of less than 5.70 mass%, the PVA-based resin with a boron adsorption rate of 5.70 mass% or more has a wider gap between molecular chains, and it is believed that there are fewer crystals in the PVA-based resin. Therefore, it is presumed that boron, first metal ions, and second metal ions are likely to enter the PVA-based resin layer, and polyenization is likely to be prevented in a high-temperature environment.

The boron adsorption rate of the PVA-based resin can be adjusted, for example, by performing pretreatment such as hydrothermal treatment, acidic solution treatment, ultrasonic irradiation treatment, or radiation irradiation treatment on the PVA-based resin in the stage before manufacturing the polarizing element. These treatments can widen the gap between molecular chains in the PVA-based resin or destroy the crystal structure. Hydrothermal treatment includes, for example, immersion in pure water at 30°C to 100°C for 1 to 90 seconds and drying. The acidic solution treatment includes, for example, immersion in an aqueous solution of boric acid with a concentration of 10% by mass to 20% by mass for 1 to 90 seconds and drying. Examples of ultrasonic treatment include treatment in which ultrasonic waves at a frequency of 20 to 29 kc are irradiated at an output of 200 W to 500 W for 30 seconds to 10 minutes. Ultrasonic treatment can be performed in a solvent such as water.

The saponification degree of the PVA-based resin is preferably 85 mol% or more, more preferably 90 mol% or more, and even more preferably 99 mol% or more and 100 mol% or less. The degree of polymerization of the PVA-based resin is, for example, 1,000 to 10,000, and preferably 1,500 to 5,000. The PVA-based resin may be modified, and may be, for example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral, etc. modified with 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 polyenization of the PVA-based resin on the deterioration of optical properties in a high temperature environment can be suppressed. When the thickness of the polarizing element is 3 μm or more, it becomes easy to create a configuration that achieves desired optical characteristics.

The polarizing element preferably includes a first compound, a second compound, and a third compound. In this embodiment, since the polarizing element and the transparent protective film are bonded together by an adhesive layer formed of an adhesive containing the first compound, the second compound, and the third compound, the first compound transferred from the adhesive layer It is presumed that part of the second compound and part of the third compound are contained in the polarizing element. The first compound, second compound, and third compound in the polarizing element may include those added during the manufacturing process of the polarizing element. By providing an adhesive layer containing the first compound, the second compound, and the third compound, the transmittance becomes less likely to decrease even when the polarizing plate is exposed to a high temperature environment. In addition, by providing an adhesive layer containing the first compound, the second compound, and the third compound, a decrease in the degree of polarization can be suppressed even when the polarizing plate is exposed to a high temperature environment. When two polarizers are used by arranging them in a cross nicol relationship, if the polarization degree of the polarizer decreases, light loss (hereinafter also referred to as “cross loss”) is likely to occur. However, according to the present invention, even when exposed to a high temperature environment, the polarization degree is reduced. Since it becomes difficult for it to deteriorate, it becomes easier to suppress missing crosses. It is presumed that this is because polyenization of the PVA-based resin is suppressed by the synergistic effect of the first compound, second compound, and third compound contained in the polarizing element.

When manufacturing a polarizing element, a method of containing the first compound, the second compound and the third compound includes adding a PVA-based resin layer to a processing solvent containing the first compound and/or the second compound and/or the third compound. A method of immersing, or a method of spraying, dripping, or dripping a treatment solvent onto the PVA-based resin layer. Among these, a method of immersing the PVA-based resin layer in a treatment solvent containing all of the first compound, second compound, and third compound is preferably used. Specific examples of the first compound, second compound, and third compound include those that are included in the adhesive described later.

The step of immersing the PVA-based resin layer in a treatment solvent containing the first compound, the second compound, and the third compound includes steps such as swelling, stretching, dyeing, crosslinking, and washing in the method for manufacturing a polarizing element described later. It may be performed simultaneously, or may be provided separately from these processes. The step of making the PVA-based resin layer contain the first compound, second compound, and third compound is preferably performed after dyeing the PVA-based resin layer with iodine, and is more preferably performed simultaneously with the crosslinking step after dyeing. According to this method, the color change is small and the influence on the optical characteristics of the polarizing element can be reduced.

In order to contain the first compound, second compound, and third compound in the polarizing element, both addition during production of the polarizing element and addition to the adhesive may be performed. For example, an adhesive containing the first compound, second compound, and third compound is used, and at the time of manufacturing a polarizing element, at least one of the first compound, second compound, and third compound may be added.

(First compound)

The first compound is at least one selected from the group consisting of urea, urea derivatives, thiourea, and thiourea derivatives. The first compound can be used individually or in combination of two or more types. The first compounds include those that are water-soluble and those that are poorly water-soluble, but either first compound can be used. When using the poorly water-soluble first compound in a water-soluble adhesive, it is desirable to devise a dispersion method to prevent haze from increasing after forming the adhesive layer.

(urea derivative)

A urea derivative is a compound in which at least one of the four hydrogen atoms of the urea molecule is replaced with a substituent. In this case, there is no particular limitation on the substituent, but it is preferable that it is a substituent containing a carbon atom, a hydrogen atom, and an oxygen atom.

Specific examples of urea derivatives include 1-substituted urea, methylurea, ethylurea, propylurea, butylurea, isobutylurea, N-octadecylurea, 2-hydroxyethylurea, hydroxyurea, acetylurea, and allylurea. , 2-propynylurea, cyclohexylurea, phenylurea, 3-hydroxyphenylurea, (4-methoxyphenyl)urea, benzylurea, benzoylurea, o-tolylurea, and p-tolylurea.

2 As a substitution element, 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-imida Zolidinone (ethylene urea) and tetrahydro-2-pyrimidinone (propylene urea) can be mentioned.

4 As a substitution element, tetramethylurea, 1,1,3,3-tetraethylurea, 1,1,3,3-tetrabutylurea, 1,3-dimethoxy-1,3-dimethylurea, 1,3 -dimethyl-2-imidazolidinone and 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone.

(thiourea derivative)

A thiourea derivative is a compound in which at least one of the four hydrogen atoms of the thiourea molecule is replaced with a substituent. In this case, there is no particular limitation on the substituent, but it is preferable that it is a substituent containing a carbon atom, a hydrogen atom, and an oxygen atom.

Specific examples of thiourea derivatives include 1-substituted thiourea, 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-naph) Examples include thiourea (tyl)thiourea, (2-pyridyl)thiourea, o-tolylthiourea, and p-tolylthiourea.

2 As substituted thiourea, 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 3-substituted thiourea include trimethylthiourea, and examples of 4-substituted thiourea include tetramethylthiourea and 1,1,3,3-tetraethylthiourea.

Among the first compounds, when used in an image display device with an interlayer filling configuration, a decrease in transmittance under a high temperature environment is suppressed and a decrease in polarization degree is small (cross-out is suppressed), so urea derivatives or thiourea are used. Derivatives are preferred, and urea derivatives are more preferred. Among urea derivatives, mono-substituted urea or di-substituted urea is preferable, and mono-substituted urea is more preferable. Bi-substitution elements include 1,1-substitution elements and 1,3-substitution elements, but 1,3-substitution elements are more preferred.

(second compound)

The second compound is dialdehyde. Examples of dialdehydes include glyoxal, propanedial (malondialdehyde), butanedial (succinaldehyde), and the like. In particular, glyoxal, which has a simple structure and is highly reactive, is preferred. Hereinafter, glyoxal may be explained, but as the dialdehyde, conventionally known ones can be used as described above, and it is not limited to glyoxal.

(Third compound)

The third compound is a dicarboxylic acid. Examples of dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, tartaric acid, glutamic acid, malic acid, and maleic acid. Acid, fumaric acid, itaconic acid, muconic acid, 1,4-cyclohexanedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid , 4,4'-biphenyldicarboxylic acid, 2,5-pyridinedicarboxylic acid, 3,5-pyridinedicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenylmethanedicarboxylic acid, jade Saloacetic acid, methyl fumaric acid, 2,6-pyridinedicarboxylic acid, etc. can be mentioned. Among these, it is preferable to use citric acid, malic acid, maleic acid, or tartaric acid. These dicarboxylic acids can be used individually or in combination of two or more types.

The polarizing element usually contains potassium ions (also referred to as “first metal ions”) and preferably contains metal ions other than potassium ions (also referred to as “second metal ions”). The content of the second metal ion in the polarizing element is preferably 0.05 mass% or more and 10.0 mass% or less, more preferably 0.05 mass% or more and 8.0 mass% or less, and even more preferably 0.1 mass% or more and 6.0 mass%. % or less. When the second metal ion content of the polarizing element exceeds 10.0% by mass, the degree of polarization may decrease in a high temperature and high humidity environment. Additionally, when the content of the second metal ion is less than 0.05% by mass, the effect of improving durability in a high temperature environment may not be sufficient. In addition, the content of the second metal ion in the polarizing element is calculated as the mass fraction (% by mass) of the metal element relative to the mass of the polarizing element by, for example, high-frequency inductively coupled plasma (ICP) emission spectroscopy. can do. It is believed that the metal element exists in the polarizing element as a metal ion or in a cross-linked structure formed with a component of the polyvinyl alcohol resin. However, the content of the second metal ion referred to here is the value of the metal atom.

The second metal ion is not limited as long as it is a metal ion other than potassium ion, and is preferably an ion of a metal other than an alkali metal. In particular, from the viewpoint of color tone adjustment and durability, it is cobalt, nickel, zinc, chromium, aluminum, and copper. It is preferable that it contains at least one type of metal ion of a transition metal such as , manganese, or iron. Among these metal ions, zinc ions are preferable in terms of color tone adjustment and imparting heat resistance.

The boron content of the polarizing element is preferably 2.4% by mass or more. Furthermore, the boron content is preferably 3.9 mass% or more and 8.0 mass% or less, more preferably 4.2 mass% or more and 7.0 mass% or less, and further preferably 4.4 mass% or more and 6.0 mass% or less. If the boron content of the polarizing element exceeds 8.0% by mass, the shrinkage force of the polarizing element increases, and problems such as peeling between other members such as the front plate to which the polarizing element is bonded when mounted on an image display device may occur. there is. Additionally, when the boron content is less than 2.4% by mass, desired optical properties may not be achieved. In addition, the content of boron in the polarizing element can be calculated as the mass fraction (% by mass) of boron relative to the mass of the polarizing element by, for example, high-frequency inductively coupled plasma (ICP) emission spectroscopy. Boron is thought to exist in the polarizing element in a cross-linked structure with boric acid or a component of the polyvinyl alcohol resin. However, the content of boron referred to here is the value as a boron atom (B).

When the boron content of the polarizing element is 2.4% by mass or more and 8.0% by mass or less, the decrease in transmittance is further suppressed even when exposed to a high temperature environment as a component of an image display device with an interlayer filling configuration. This is presumed to be because, in the case where the boron content of the polarizing element is 2.4 mass% or more and 8.0 mass% or less, polyenization is less likely to occur even in a high temperature environment, and a decrease in transmittance is suppressed.

The potassium ion content in the polarizing element is preferably 0.28 mass% or more, more preferably 0.32 mass% or more, and 0.34 mass% or more from the viewpoint of suppressing deterioration of the optical properties of the polarizing element in a high temperature environment. It is more preferable, and from the viewpoint of suppressing color change in a high temperature environment, it is preferably 0.60 mass% or less, more preferably 0.55 mass% or less, and even more preferably 0.50 mass% or less. The content of potassium ions can be measured in the same way as the content of second metal ions, and the content of potassium ions referred to here is the value as a potassium atom.

(Method for manufacturing polarizing element)

The manufacturing method of the polarizing element is not particularly limited, but may include a method of producing a PVA-based resin film previously wound into a roll and performing stretching, dyeing, cross-linking, etc. (hereinafter referred to as “manufacturing method 1”), or a PVA-based resin. A typical method is a method (hereinafter referred to as “manufacturing method 2”) that includes the step of applying a coating liquid containing the product on a base film to form a PVA-based resin layer as an application layer and stretching the obtained laminate.

Manufacturing method 1 is a process of uniaxially stretching a PVA-based resin film, a process of dyeing the PVA-based resin film with a dichroic dye such as iodine and adsorbing the dichroic dye, and soaking the PVA-based resin film with the dichroic dye adsorbed in an aqueous solution of boric acid. It can be manufactured through a process of treatment with an aqueous solution of boric acid and then a process of washing with water.

The swelling process is a treatment process in which the PVA-based resin film is immersed in a swelling bath. Through the swelling process, not only can dirt and blocking agents on the surface of the PVA-based resin film be removed, but also dyeing unevenness can be suppressed by swelling the PVA-based resin film. For the swelling bath, a medium containing water as a main component, such as water, distilled water, or pure water, is usually used. A surfactant, 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 be used in the swelling bath. In this case, the concentration of potassium iodide in the swelling bath is preferably 1.5% by mass or less, and more preferably 1.0% by mass or less. And, it is more preferable that it is 0.5% by 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 immersion time in the swelling bath cannot be uniformly determined because the degree of swelling of the PVA-based resin film is affected by the temperature of the swelling bath, but is preferably 5 seconds to 300 seconds, and more preferably 10 seconds to 200 seconds. It is preferable, and it is more preferable that it is 20 seconds or more and 100 seconds or less. The swelling process may be performed only once, or may be performed multiple times as needed.

The dyeing process is a treatment process in which the PVA-based resin film is immersed in a dyeing bath (iodine solution), and a dichroic dye such as iodine can be adsorbed and oriented on the PVA-based resin film. The iodine solution is usually preferably an iodine aqueous solution, and contains iodine and iodide as a dissolution aid. Examples of 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 suitable from the viewpoint of controlling the potassium content in the polarizing element.

The concentration of iodine in the dyeing bath is preferably 0.01 mass% or more and 1 mass% or less, and more preferably 0.02 mass% or more and 0.5 mass% or less. The concentration of 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 immersion time in the dyeing bath cannot be uniformly determined because the degree of dyeing of the PVA-based resin film is affected by the temperature of the dyeing bath, but is preferably 10 seconds to 300 seconds, and more preferably 20 seconds to 240 seconds. desirable. The dyeing process may be performed only once, or may be performed multiple times as needed.

The crosslinking process is a treatment process in which the PVA-based resin film dyed in the dyeing process is immersed in a treatment bath (crosslinking bath) containing a boron compound, and the polyvinyl alcohol-based resin film is crosslinked by the boron compound to form iodine molecules or Dye molecules can adsorb to the cross-linked structure. Examples of boron compounds include boric acid, borate, and borax. The crosslinking bath is generally an aqueous solution, but may also be a mixed solution of water and an organic solvent miscible with water. The crosslinking bath preferably contains potassium iodide from the viewpoint of controlling the potassium content in the polarizing element.

The concentration of the boron compound in the crosslinking bath is preferably 1 mass% or more and 15 mass% or less, more preferably 1.5 mass% or more and 10 mass% or less, and 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% to 15 mass%, more preferably 1.5 mass% to 10 mass%, and 2 mass% to 5 mass%. It is more preferable that it is % or less.

The temperature of the crosslinking bath is preferably 20°C or higher and 70°C or lower, and more preferably 30°C or higher and 60°C or lower. The immersion time in the crosslinking bath cannot be uniformly determined because the degree of crosslinking of the PVA-based resin film is affected by the temperature of the crosslinking bath, but is preferably 5 seconds to 300 seconds, and more preferably 10 seconds to 200 seconds. desirable. The crosslinking process may be performed only once, or may be performed multiple times as needed.

The stretching process is a treatment process in which the PVA-based resin film is stretched at a predetermined magnification in at least one direction. Generally, the PVA-based resin film is uniaxially stretched in the conveyance direction (longitudinal direction). The stretching method is not particularly limited, and either a wet stretching method or a dry stretching method can be employed. The stretching process may be performed only once, or may be performed multiple times as needed. The stretching process may be performed at any stage in the production of the polarizing element.

The treatment bath (stretching bath) in the wet stretching method can usually use a solvent such as water or a mixed solution of water and an organic solvent miscible with water. The stretching bath preferably contains potassium iodide from the viewpoint of controlling the potassium content in the polarizing element. When using potassium iodide in a 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, and 3 mass% or more and 6 mass%. It is more preferable that it is % or less. The treatment bath (stretching bath) may contain a boron compound from the viewpoint of suppressing film breakage during stretching. When containing a boron compound, 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, and 2 mass% or more and 5 mass% or less. It is more desirable.

The temperature of the stretching bath is preferably 25 to 80°C, more preferably 40 to 80°C, further preferably 50 to 75°C, and particularly preferably 65 to 75°C. 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 to 800 seconds, and more preferably 30 seconds to 500 seconds. desirable. The stretching treatment in the wet stretching method may be performed together with any one or more of the swelling process, dyeing process, crosslinking process, and washing process.

Examples of dry stretching methods include roll-to-roll stretching methods, heated roll stretching methods, and compression stretching methods. Additionally, the dry stretching method may be performed together with the drying process.

The total stretch ratio (cumulative stretch ratio) applied to the polyvinyl alcohol-based resin film can be set appropriately depending on the purpose, but is preferably between 2 and 7 times, and more preferably between 3 and 6.8 times, It is more preferable that it is 3.5 times or more and 6.5 times or less.

The cleaning process is a treatment process in which the polyvinyl alcohol-based resin film is immersed in a washing bath, and foreign substances remaining on the surface of the polyvinyl alcohol-based resin film can be removed. As a washing bath, a medium containing water as a main component, such as water, distilled water, or pure water, is usually used. In addition, from the viewpoint of controlling the potassium content in the polarizing element, it is preferable to use potassium iodide in the washing bath. In this case, the concentration of potassium iodide in the washing bath is preferably 1% by mass or more and 10% by mass or less. , it is more preferable that it is 1.5 mass% or more and 4 mass% or less, and it is still more preferable that it is 1.8 mass% or more and 3.8 mass% or less.

The temperature of the washing 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 immersion time in the washing bath cannot be uniformly determined because the degree of cleaning of the PVA-based resin film is affected by the temperature of the washing bath, but is preferably 1 second to 100 seconds, and more preferably 2 seconds to 50 seconds. It is preferable, and it is more preferable that it is 3 seconds or more and 20 seconds or less. The cleaning process may be performed only once, or may be performed multiple times as needed.

Additionally, it is preferable to have a metal ion treatment process among the above processes or as a separate process from the above processes. The metal ion treatment step is performed by immersing the polyvinyl alcohol-based resin film in an aqueous solution containing a metal salt of the second metal ion. Through the metal ion treatment process, the second metal ion is contained in the polyvinyl alcohol-based resin film.

The second metal ion is not limited as long as it is a metal ion other than potassium ion, and is preferably an ion of a metal other than an alkali metal. In particular, from the viewpoint of color adjustment and durability, it is cobalt, nickel, zinc, chromium, aluminum, and copper. It is preferable that it contains at least one type of metal ion of a transition metal such as , manganese, or iron. Among these metal ions, zinc ions are preferable in terms of color tone adjustment and imparting heat resistance. Examples of zinc salts include zinc halides such as zinc chloride and zinc iodide, zinc sulfate, and zinc acetate.

In the metal ion treatment process, a metal salt solution is used. Hereinafter, among the metal ion treatment processes, immersion treatment in a zinc-containing solution will be described as a representative example when an aqueous zinc salt solution is used.

The concentration of zinc ions in the aqueous zinc salt solution is in the range of 0.1 to 10 mass%, preferably 0.3 to 7 mass%. Additionally, as the zinc salt solution, it is preferable to use an aqueous solution containing potassium ions and iodine ions using potassium iodide or the like because it is easy to impregnate the zinc ions. The potassium iodide concentration in the zinc salt solution is preferably 0.1 to 10 mass%, and preferably 0.2 to 5 mass%.

In the immersion treatment in a zinc-containing solution, the temperature of the zinc salt solution is usually 15 to 85°C, preferably 25 to 70°C. The immersion time is usually in the range of 1 to 120 seconds, preferably 3 to 90 seconds. In the immersion treatment in the zinc-containing solution, the zinc content in the polyvinyl alcohol-based resin film is adjusted by adjusting conditions such as the concentration of the zinc salt solution, the immersion temperature of the polyvinyl alcohol-based resin film into the zinc salt solution, and the immersion time. Adjust so that it falls within the above range. There is no particular limitation on when the immersion treatment in the zinc-containing solution is performed. The immersion treatment in the zinc-containing solution may be performed alone, or the zinc salt may be coexisted in a dyeing bath, a crosslinking bath, or a stretching bath, and may be performed simultaneously with at least one of the dyeing process, the crosslinking process, and the stretching process.

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

Manufacturing method 2 is a process of applying a coating liquid containing a PVA-based resin onto a base film, a process of uniaxially stretching the obtained laminated film, and adsorbing the PVA-based resin layer of the uniaxially stretched laminated film by dyeing it with a dichroic dye. It can be manufactured through a step of forming a polarizing element, a step of treating a film with an adsorbed dichroic dye with an aqueous boric acid solution, and a step of washing with water after treatment with an aqueous boric acid solution. The base film used to form the polarizing element may be used as a protective layer of the polarizing element. If necessary, the base film may be peeled and removed from the polarizing element.

<Transparent protective film>

The transparent protective film (hereinafter also simply referred to as “protective film”) used in this embodiment is bonded to at least one side of the polarizing element through an adhesive layer. This transparent protective film is bonded to one side or both sides of the polarizing element, but is preferably bonded to both sides.

The protective film may have different optical functions at the same time, and may be formed in a laminated structure in which a plurality of layers are laminated. The thickness of the protective film is preferably thin from the viewpoint of optical properties, but if it is too thin, the strength decreases and processability is poor. An appropriate film thickness is 5 μm or more and 100 μm or less, preferably 10 μm or more and 80 μm or less, and more preferably 15 μm or more and 70 μm or less.

The protective film includes films such as cellulose acylate-based films, films made of polycarbonate-based resins, films made of cycloolefin-based resins such as norbornene, (meth)acrylic polymer films, and polyester resin-based films such as polyethylene terephthalate. Available. When bonding a protective film to both sides of a polarizing element using a water-based adhesive such as PVA adhesive, it is preferable that the protective film on at least one side is either a cellulose acylate-based film or a (meth)acrylic-based polymer film in terms of moisture permeability. , Among them, cellulose acylate film is preferable.

At least one protective film may have a phase difference function for purposes such as viewing angle compensation. In that case, the protective film itself may have a phase difference function, may have a separate phase difference layer, or may be a combination of both. The film with a retardation function may be bonded directly to the polarizing element through an adhesive, or may be bonded to the polarizing element through a separate protective film through an adhesive or adhesive.

<Adhesive layer>

The adhesive layer for bonding the protective film to the polarizing element is formed from the following adhesive.

(glue)

The adhesive contains a first compound, a second compound, and a third compound. The adhesive may be, but is not limited to, a water-based adhesive, a solvent-based adhesive, an active energy ray-curable adhesive, etc., but is preferably a water-based adhesive and preferably contains a PVA-based resin. By forming an adhesive layer for bonding a polarizing element and a protective film using an adhesive containing the first compound, second compound, and third compound, a decrease in the transmittance of the polarizing plate in a high-temperature environment can be suppressed. Furthermore, by using an adhesive having the second compound and the third compound, an adhesive having a sufficient pot life can be obtained in terms of production. The use of the adhesive according to the present invention is not limited, and is suitably used in optical elements, for example, in the use of bonding a polarizing element and a protective film.

The thickness when applying the adhesive can be set to an arbitrary value, for example, so that an adhesive layer with a desired thickness can be obtained after curing or heating (drying). The thickness of the adhesive layer made of adhesive is preferably 0.01 ㎛ or more and 7 ㎛ or less, more preferably 0.01 ㎛ or more and 5 ㎛ or less, further preferably 0.01 ㎛ or more and 2 ㎛ or less, and most preferably 0.01 ㎛ or more. It is ㎛ or more and 1 ㎛ or less.

When the adhesive is a water-based adhesive containing a PVA-based resin, the content of the third compound is, for example, 0.01 parts by mass or more and 400 parts by mass or less, preferably 0.05 parts by mass or more and 50 parts by mass, based on 100 parts by mass of the PVA-based resin. or less, and more preferably 0.1 parts by mass or more and 10 parts by mass or less. If it is less than 0.01 parts by mass, the effect of improving pot life may not be sufficient or the effect of suppressing polyenylation of the polarizing element in a high temperature environment may not be sufficient. On the other hand, when it exceeds 400 parts by mass, the third compound may precipitate after production of the polarizing plate.

When the adhesive is a water-based adhesive containing a PVA-based resin, the content of the first 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, based on 100 parts by mass of the PVA-based resin. It is 200 parts by mass or less, more preferably 3 parts by mass or more and 100 parts by mass or less. If it is less than 0.1 part by mass, the effect of suppressing polyenylation of the polarizing element in a high temperature environment may not be sufficient. On the other hand, when it exceeds 400 parts by mass, the first compound may precipitate after production of the polarizing plate, and the haze may increase.

When the adhesive is a water-based adhesive containing a PVA-based resin, the content of the second compound is preferably 1 part by mass or more and 60 parts by mass or less, more preferably 1.5 parts by mass or more, based on 100 parts by mass of the PVA-based resin. It is 50 parts by mass or less, more preferably 2 parts by mass or more and 45 parts by mass or less. If it is less than 1 part by mass, the effect of improving water resistance may not be sufficient. On the other hand, when it exceeds 60 parts by mass, the stability of the adhesive preparation solution may decrease.

In the adhesive, the content of dialdehyde, which is the second compound, is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, with respect to 1 part by mass of the urea-based compound, which is the first compound. It is 10 parts by mass or less, and the lower limit is not limited, but is, for example, 0.03 parts by mass or more. When the content ratio of the urea-based compound and dialdehyde in the adhesive is within the above-mentioned range, it becomes easy to achieve both the effect of improving high temperature durability by the urea-based compound and the effect of improving adhesiveness by dialdehyde. It is understood that the effect of improving water resistance is obtained by the effect of improving adhesion by dialdehyde. When dialdehyde is contained in more than 20 parts by mass relative to 1 part by mass of the urea-based compound, the effect of improving high temperature durability by the urea-based compound may not be sufficiently exhibited. The content ratio of the urea-based compound and dialdehyde in the adhesive can be considered to be the same as the content ratio of the urea-based compound and dialdehyde in the adhesive layer.

In the adhesive, the content of dicarboxylic acid, which is the third compound, is preferably 0.001 parts by mass or more and 100 parts by mass or less, and preferably 0.01 parts by mass or more and 80 parts by mass, based on 1 part by mass of dialdehyde, which is the second compound. It is below wealth. If it is less than 0.001 parts by mass, the effect of improving pot life may not be sufficient. On the other hand, when it exceeds 100 parts by mass, the third compound may precipitate after production of the polarizing plate.

Regarding the above adhesive, when used to form an adhesive layer for bonding a polarizing element and a protective film, the first compound, the second compound, and the third compound are included in the polarizing element to be bonded, and the case is not included. Accordingly, the amount of these compounds contained in the adhesive may be adjusted appropriately.

In a configuration in which a transparent protective film is bonded to both sides of the polarizing element through an adhesive layer, only the adhesive layer on one side may be a layer containing the first compound, the second compound, and the third compound among the adhesive layers on both sides of the polarizing element. , it is preferable that the adhesive layers on both sides are layers containing the first compound, the second compound, and the third compound.

In order to meet the demand for thinner polarizing plates, polarizing plates having a transparent protective film on only one side of the polarizing element have been developed. In this configuration as well, a transparent protective film is laminated through an adhesive layer containing the first compound, second compound, and third compound. As a method of manufacturing a polarizing plate having a transparent protective film on only one side of such a polarizing element, a method of first manufacturing a polarizing plate in which a transparent protective film is bonded to both sides through an adhesive layer and then peeling off the transparent protective film on one side is considered. When such a manufacturing method is used, only one adhesive layer may contain the first compound, the second compound, and the third compound, but the adhesive layers on both sides may contain the first compound, the second compound, and the third compound. It is preferable that it is a layer containing 3 compounds. When only one adhesive layer contains the first compound, the second compound, and the third compound, it is preferable that the adhesive layer on the film side that is not peeled contains the first compound, the second compound, and the third compound.

(Water-based adhesive)

As the water-based adhesive, any suitable water-based adhesive may be employed, but a water-based adhesive containing a PVA-based resin (PVA-based adhesive) is preferably used. 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 from the viewpoint of adhesiveness. From the viewpoint of adhesiveness, the average degree of saponification is preferably 85 mol% or more and 100 mol% or less, and more preferably 90 mol% or more and 100 mol% or less.

As the PVA-based resin contained in the water-based adhesive, one containing an acetoacetyl group is preferable, because it is excellent in adhesion between the PVA-based resin layer and the protective film and is excellent in durability. PVA-based resin containing an acetoacetyl group is obtained, for example, by reacting PVA-based resin and diketene by an arbitrary method. The acetoacetyl group modification degree of the PVA-based resin containing an acetoacetyl group is typically 0.1 mol% or more, and is preferably 0.1 mol% or more and 20 mol% or less. The resin concentration of the water-based adhesive is preferably 0.1 mass% or more and 15 mass% or less, and more preferably 0.5 mass% or more and 10 mass% or less.

The second compound, dialdehyde, can act as a crosslinking agent. The water-based adhesive may also contain a crosslinking agent other than the second compound. As a crosslinking agent, a known crosslinking agent can be used. Examples of the crosslinking agent include water-soluble epoxy compounds and isocyanates.

When the PVA-based resin is a PVA-based resin containing an acetoacetyl group, the crosslinking agent is preferably either glyoxylate or methylolmelamine, and more preferably either glyoxylate.

Water-based adhesives may contain organic solvents. The organic solvent is preferably alcohol because it is miscible with water, and among alcohols, methanol or ethanol is more preferable. The methanol concentration of the water-based adhesive is preferably 10 mass% or more and 70 mass% or less, more preferably 15 mass% or more and 60 mass% or less, and even more preferably 20 mass% or more and 60 mass% or less. When the concentration of methanol is 10% by mass or more, it becomes easier to suppress polyenization of the PVA-based resin in a high-temperature environment. Additionally, when the methanol content is 70% by mass or less, color deterioration can be suppressed. Some of the urea derivatives have low solubility in water, while others have sufficient solubility in alcohol. In that case, one preferred embodiment is to dissolve the urea-based compound in alcohol to prepare an alcohol solution of the urea-based compound, and then add the alcohol solution of the urea-based compound to the PVA aqueous solution to prepare the adhesive.

(Active energy ray curing adhesive)

Active energy ray-curable adhesives are adhesives that are cured by irradiating active energy rays such as ultraviolet rays, and include, for example, an adhesive containing a polymerizable compound and a photopolymerization initiator, an adhesive containing a photoreactive resin, a binder resin, and a photoreactive crosslinking agent. Adhesives etc. can be mentioned. Examples of the polymerizable compound include photopolymerizable monomers such as photocurable epoxy monomers, photocurable acrylic monomers, and photocurable urethane monomers, and oligomers derived from these monomers. Examples of the photopolymerization initiator include compounds containing a substance that generates active species such as neutral radicals, anion radicals, and cation radicals when irradiated with active energy rays such as ultraviolet rays.

<Layer containing the first compound, second compound, and third compound>

The first compound, second compound, and third compound are not limited to being contained in the adhesive layer as described above, and may be contained in layers other than the adhesive layer from the viewpoint of improving the high-temperature durability of the polarizing plate. In a polarizing plate having a transparent protective film on only one side, from the viewpoint of improving physical strength, a cured layer may be laminated on the side opposite to the transparent protective film of the polarizing element, and this cured layer may contain the first compound and the second compound. and a layer containing a third compound.

The thickness of the layer containing the first compound, second compound and third compound is preferably 0.1 ㎛ or more and 20 ㎛ or less, more preferably 0.5 ㎛ or more and 15 ㎛ or less, and even more preferably 1 ㎛ or more and 10 ㎛ or less. am.

[Configuration of image display device]

The polarizing plate of this embodiment is used in various image display devices, such as a liquid crystal display device and an organic EL display device. Regarding the image display device, in the case of an interlayer filling configuration in which both sides of the polarizing plate are configured to be in contact with a layer other than the air layer, specifically a solid layer such as an adhesive layer, the transmittance is likely 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 configuration, a decrease in the transmittance of the polarizing plate under a high temperature environment can be suppressed. An example of an image display device is a structure having an image display cell, a first adhesive layer laminated on the viewer-side surface of the image display cell, and a polarizing plate laminated on the viewer-side surface of the first adhesive layer. This 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 viewing side surface of the second adhesive layer. In particular, the polarizing plate of this embodiment has a transparent member disposed on the viewing side of the image display device, the polarizing plate and the image display cell are bonded to each other by a first adhesive layer, and the polarizing plate and the transparent member are bonded to each other by a second adhesive layer. It is suitably used in an image display device having an interlayer filling configuration. In this specification, either or both the first adhesive layer and the second adhesive layer may be simply referred to as “adhesive layer.” In addition, the member used for bonding the polarizing plate and the image display cell and the member used for bonding the polarizing plate and the transparent member are not limited to the adhesive layer and may be an adhesive layer.

<Image display cell>

Examples of image display cells include liquid crystal cells and organic EL cells. As the liquid crystal cell, any of a reflective liquid crystal cell using external light, a transmissive liquid crystal cell using light from a light source such as a backlight, or a transflective liquid crystal cell using both light from the outside and light from the light source may be used. good night. When the liquid crystal cell uses light from a light source, the image display device (liquid crystal display device) has a polarizing plate disposed on the side opposite to the viewing side of the image display cell (liquid crystal cell), and a light source is also disposed. It is preferable that the polarizing plate on the light source side and the liquid crystal cell are bonded together through an appropriate adhesive layer. As a driving method for the liquid crystal cell, for example, any type such as VA mode, IPS mode, TN mode, STN mode, or bend orientation (π type) can be used.

As an organic EL cell, one in which a transparent electrode, an organic light-emitting layer, and a metal electrode are stacked in that order on a transparent substrate to form a light emitter (organic electroluminescence light emitter) is suitably used. The organic light-emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer containing a triphenylamine derivative, etc., and a light-emitting layer containing a fluorescent organic solid such as anthracene, or a laminate of these light-emitting layers and a perylene derivative, etc. Various layer configurations may be employed, such as a laminate of an electron injection layer including a hole injection layer, a light emitting layer, and an electron injection layer.

<Combination of image display cell and polarizer>

An adhesive layer (adhesive sheet) is suitably used to bond an image display cell and a polarizing plate. Among them, a method of bonding a polarizing plate having an adhesive layer on one side of the polarizing plate to an image display cell is preferable from the viewpoint of workability and the like. Laying down the adhesive layer on the polarizing plate can be performed in an appropriate manner. As an example, prepare an adhesive solution of 10% by mass or more and 40% by mass or less by dissolving or dispersing the base polymer or its composition in a solvent containing a suitable solvent such as toluene or ethyl acetate alone or in a mixture, and softening it. Appropriate deployment methods such as a coating method or a coating method include laying directly on a polarizing plate, forming an adhesive layer on a separator, and attaching it to a polarizing plate.

<Adhesive layer>

The adhesive layer may consist of one layer or two or more layers, but is preferably comprised of one layer. The adhesive layer can be composed of an adhesive composition containing (meth)acrylic resin, rubber-based resin, urethane-based resin, ester-based resin, silicone-based resin, and polyvinyl ether-based resin as main components. Among them, an adhesive composition containing a (meth)acrylic resin excellent in transparency, weather resistance, heat resistance, etc. as a base polymer is suitable. The adhesive composition may be of an active energy ray curing type or a thermosetting type.

Examples of the (meth)acrylic resin (base polymer) used in the adhesive composition include (meth)acrylic acid esters such as butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. A polymer or copolymer containing one or two or more of the following as monomers is suitably used. It is preferable to copolymerize a polar monomer with the base polymer. As polar monomers, (meth)acrylic acid compounds, (meth)acrylic acid 2-hydroxypropyl compounds, (meth)acrylic acid hydroxyethyl compounds, (meth)acrylamide compounds, and N,N-dimethylaminoethyl (meth)acrylate compounds. , monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, etc., such as a glycidyl (meth)acrylate compound.

The pressure-sensitive adhesive composition may contain only the base polymer, but usually further contains a crosslinking agent. The crosslinking agent is a divalent or higher metal ion, such as a metal ion that forms a carboxylic acid metal salt between carboxyl groups, a polyamine compound that forms an amide bond between carboxyl groups, and a polyepoxy that forms an ester bond between carboxyl groups. Examples include polyisocyanate compounds that form amide bonds between compounds, polyols, and carboxyl groups. Among them, polyisocyanate compounds are preferable.

The active energy ray-curable adhesive composition has the property of curing when irradiated with active energy rays such as ultraviolet rays or electron beams, and has adhesiveness even before irradiation with active energy rays, allowing it to be adhered to an adherend such as a film, and thus irradiated with active energy rays. It has the property of being able to adjust the adhesion by hardening. The active energy ray-curable adhesive composition is preferably of an ultraviolet ray-curable type. The active energy ray curable adhesive composition further contains an active energy ray polymerizable compound in addition to the base polymer and crosslinking agent. If necessary, a photopolymerization initiator, a photosensitizer, etc. may be contained.

The adhesive composition includes fine particles for imparting light scattering properties, beads (resin beads, glass beads, etc.), glass fibers, resins other than the base polymer, tackifiers, fillers (metal powders and other inorganic powders, etc.), antioxidants, and ultraviolet rays. It may contain additives such as absorbents, dyes, pigments, colorants, defoaming agents, corrosion inhibitors, and photopolymerization initiators.

The adhesive layer can be formed by applying an organic solvent dilution of the adhesive composition to the surface of a base film, an image display cell, or a polarizing plate and drying it. The base film is generally a thermoplastic resin film, and a typical example thereof includes a separate film to which release treatment has been performed. The separate film may be a film made of, for example, a resin such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, or polyalate, and the surface on which the adhesive layer is formed may be subjected to release treatment such as silicone treatment.

A pressure-sensitive adhesive composition may be applied directly to the release-treated surface of the separate film to form a pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer having this separate film may be laminated on the surface of the polarizer. The adhesive composition may be applied directly to the surface of the polarizing plate to form an adhesive layer, and a separate film may be laminated on the outer surface of the adhesive layer.

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

Additionally, a pressure-sensitive adhesive composition is applied on the second separate film to form a pressure-sensitive adhesive layer, a pressure-sensitive adhesive sheet is prepared by laminating the separate film on the formed pressure-sensitive adhesive layer, and the second separate film is peeled from the pressure-sensitive adhesive sheet. The pressure-sensitive adhesive layer may be laminated on the polarizing plate. The second separate film is used because it has weaker adhesion to the adhesive layer and is easier to peel than the separate film.

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>

Examples of transparent members disposed on the viewing side of the image display device include a transparent plate (window layer) and a touch panel. As the transparent plate, a transparent plate having appropriate mechanical strength and thickness is used. Examples of such transparent plates include transparent resin plates such as polyimide resin, acrylic resin, and polycarbonate resin, or glass plates. A functional layer such as an antireflection layer may be laminated on the viewing side of the transparent plate. Additionally, when the transparent plate is a transparent resin plate, a hard coat layer may be laminated to increase physical strength or a low moisture permeability layer may be laminated to reduce moisture permeability. As the touch panel, various touch panels such as resistive type, capacitive type, optical type, and ultrasonic type, as well as glass plates and transparent resin plates with a touch sensor function, are used. When a capacitive touch panel is used as a transparent member, it is preferable that a transparent plate made of glass or a transparent resin plate be provided further on the viewing side than the touch panel.

<Combination of polarizer and transparent member>

To bond the polarizing plate and the transparent member, an adhesive or an active energy ray-curable adhesive is suitably used. When an adhesive is used, laying of the adhesive can be done in an appropriate manner. As a specific laying method, for example, the method of laying an adhesive layer used in bonding the image display cell and the polarizing plate described above can be mentioned.

When using an active energy ray-curable adhesive, a dam material is provided to surround the peripheral edge of the image display panel for the purpose of preventing the adhesive solution from spreading before curing, a transparent member is placed on the dam material, and the adhesive solution is injected. This is used appropriately. After injection of the adhesive solution, alignment and defoaming are performed as necessary, and then curing is performed by irradiation of active energy rays.

Example

Hereinafter, the present invention will be described in detail based on examples. Materials, reagents, amounts of substances, ratios, operations, etc. shown in the examples below can be changed appropriately as long as they do not deviate from the spirit of the present invention.

Accordingly, the present invention is not limited to the following examples.

(1) Measurement of the thickness of the polarizing element:

Measurements were made using a digital micrometer "MH-15M" manufactured by Nikon Corporation.

(2) Measurement of visibility-corrected polarization degree, visibility-corrected single transmittance, and color of the polarizer:

Spectrophotometer having an integrating sphere [“V7100” manufactured by Nippon Bunko Co., Ltd., 2-degree field of view; C light source].

(3) Measurement of boron content:

0.2 g of the polarizing element was dissolved in 200 g of a 1.9% by mass mannitol aqueous solution. Subsequently, the obtained aqueous solution was titrated with 1 mol/L aqueous sodium hydroxide solution, and the boron content of the polarizing element was calculated by comparing the amount of aqueous sodium hydroxide solution required for neutralization with a calibration curve.

(4) Measurement of zinc ion content:

Nitric acid was added to the precisely weighed polarizing element, and the solution was subjected to acid decomposition using a microwave sample preparation device (ETHOS D) manufactured by Milestone General, and the obtained solution was used as a measurement solution. The zinc ion content was calculated by quantifying the zinc concentration of the measurement liquid using an ICP emission spectrophotometer (5110 ICP-OES) manufactured by Agilent Technologies and calculating the zinc mass relative to the mass of the polarizing element.

(5) Measurement of boron adsorption rate of PVA-based resin film:

A PVA-based resin film cut into a square with a side of 100 mm was immersed in pure water at 30°C for 60 seconds, and then immersed in an aqueous solution at 60°C containing 5 parts of boric acid for 120 seconds. The PVA-based resin film taken out from the boric acid aqueous solution was dried in an oven at 80°C for 11 minutes. The humidity was controlled in an environment of 23°C and 55% RH for 24 hours to obtain a boron-containing PVA film. 0.2 g of the boron-containing PVA-based resin film obtained in this way was dissolved in 200 g of a 1.9 mass% aqueous mannitol solution. Subsequently, the obtained aqueous solution was titrated with 1 mol/L aqueous sodium hydroxide solution, and the boron content of the PVA-based resin film was calculated by comparing the amount of aqueous sodium hydroxide solution required for neutralization with a calibration curve. The boron content of the PVA-based resin film obtained in this way was used as the boron adsorption rate of the PVA-based resin film.

(Production of Polarizing Element 1)

A 30-μm-thick polyvinyl alcohol-based resin film with a boron adsorption rate of 5.71% by mass is immersed in pure water at 21.5°C for 79 seconds (swelling treatment), and then the mass ratio of potassium iodide/boric acid/water is 2/2/100, It was immersed in an aqueous solution containing 1.0 mM iodine at 23°C for 151 seconds (staining process). Afterwards, it was immersed in an aqueous solution with a mass ratio of potassium iodide/boric acid/water of 2.5/4/100 at 68.5°C for 76 seconds (first crosslinking process). Subsequently, it was immersed in an aqueous solution of potassium iodide/boric acid/zinc chloride/water with a mass ratio of 3/5.5/0.6/100 at 45°C for 11 seconds (second crosslinking step, metal ion treatment step). Afterwards, it was washed by immersing it in a washing bath (washing process) and dried at 38°C (drying process) to obtain a polarizing element with a thickness of 12 μm in which iodine was adsorbed and oriented in polyvinyl alcohol. Stretching was mainly performed in the dyeing process and the first crosslinking process, and the total stretching ratio was 5.85 times. The zinc ion content of the obtained polarizing element was 0.17 mass%, and the boron content was 4.62 mass%.

(Preparation of PVA solution for adhesive)

50 g of modified PVA-based resin containing an acetoacetyl group (manufactured by Mitsubishi Chemical Corporation: Gosenex Z-410) was dissolved in 950 g of pure water, heated at 90°C for 2 hours, and then cooled to room temperature to obtain a PVA solution for adhesives. got it

(Preparation of adhesives 1 to 3 for polarizing plates)

Adhesives 1 to 3 were prepared by mixing the PVA solution, urea, a commercially available 40 mass% solution of glyoxal, maleic acid, and pure water so that the contents of PVA, urea, glyoxal, and maleic acid were as shown in Table 1. did. In addition, the adhesive was used 3 days after preparation.

(Saponification of cellulose acylate film)

A commercially available cellulose acylate film TJ40UL (manufactured by Fuji Film Co., Ltd.; film thickness 40 μm) was immersed in a 1.5 mol/L NaOH aqueous solution (saponification solution) maintained at 55°C for 2 minutes, and the film was washed with water. After that, the film was immersed in a 0.05 mol/L sulfuric acid aqueous solution at 25°C for 30 seconds, and then passed through a water washing bath under running water for 30 seconds to bring the film into a neutral state. Then, water removal using an air knife was repeated three times. After removing the moisture, the film was dried by remaining in a drying zone at 70°C for 15 seconds to produce a saponified film.

(Production of polarizers 1 to 3)

The saponified cellulose acylate film was bonded to both sides of the polarizing element 1 using the adhesive 1 prepared above and stored for 3 days using a roll bonding machine, and then dried at 80°C for 5 minutes to form the polarizing plate 1. got it The adhesive layer was adjusted so that the thickness after drying was 50 nm on both sides.

In the production of polarizing plate 1, adhesive 1 was changed to adhesives 2 to 3, and polarizing plates 2 to 3 were obtained.

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

The polarizing plates 1 to 3 obtained above were stored at a temperature of 20°C and a relative humidity of 30%, 35%, 40%, 45%, 50%, or 55% for 72 hours. Moisture content was measured using the Karl Fischer method at 66, 69, and 72 hours of storage. Under any humidity condition, the moisture content value did not change at 66 hours, 69 hours, and 72 hours of storage. Therefore, the water content of polarizers 1 to 3 can be considered to be the same as the equilibrium water content of the 72-hour storage environment used in this experimental example. When the water content of the polarizing plate reaches equilibrium in a certain storage environment, the water content of the polarizing element in the polarizing plate can be considered to have similarly reached equilibrium in that storage environment. Additionally, when the water content of the polarizing element in the polarizing plate reaches equilibrium in a certain storage environment, the water content of the polarizing plate can be considered to have similarly reached equilibrium in that storage environment.

(Adjustment of moisture content of polarizers 1 to 3)

The moisture content of polarizers 1 to 3 was adjusted by storing them for 72 hours at a temperature of 20°C and a relative humidity of 55% so that the moisture content of the polarizers 1 to 3 was 55% at 20°C.

<High temperature durability evaluation>

(Production of samples for evaluation)

For polarizers 1 to 3 with adjusted moisture content, an acrylic adhesive (manufactured by Lintech Co., Ltd., product number: #7) is formed on both sides, and the absorption axis is parallel to the long side, with a size of 50 mm x 100 mm. Evaluation samples were produced by cutting and bonding alkali-free glass (“EAGLE XG” manufactured by Corning) to the surface of each adhesive.

<Evaluation of group transmittance (105℃)>

The evaluation samples of polarizers 1 to 3 were autoclaved at a temperature of 50°C and a pressure of 5 kgf/cm2 (490.3 kPa) for 1 hour, and then left in an environment of a temperature of 23°C and a relative humidity of 55% for 24 hours. Thereafter, the transmittance of the evaluation samples of polarizers 1 to 3 was measured (initial value), stored in a heating environment at a temperature of 105°C, and the transmittance was measured at 50-hour intervals for 100 to 200 hours. Evaluation was made using the following criteria based on the time at which the transmittance decrease reached 5% or more relative to the initial value. The obtained results are shown in Table 2.

A decrease in transmittance of 5% or less after 200 hours: A

Transmittance decline reaches 5% or more after 150 to 200 hours: B

Transmittance decline reaches 5% or more in 100 to 150 hours: C

Transmittance decline of 5% or more after 100 hours: D

<Water resistance evaluation (hot water immersion test)>

The water resistance test in this example was conducted in accordance with the water resistance test described in Japanese Patent Application Laid-Open No. 2009-025728 [0060]. An acrylic adhesive (manufactured by Lintech Co., Ltd., product number: #7) is formed on one side of the polarizing plate prepared above, and a strip-like shape of 50 mm x 20 mm is formed with the absorption axis (stretching direction) of the polarizing plate as the long side. It was cut and the dimensions of the long side were accurately measured. Here, the evaluation sample shows a unique color uniformly over the entire surface due to iodine adsorbed on the polarizing element.

One short side of this sample was held with a gripper, and approximately 80% of the sample in the longitudinal direction was immersed in a water bath at 60°C and held for 4 hours. After that, the sample was taken out from the water bath and the moisture was wiped off. The polarizing element of the polarizing plate shrinks when immersed in hot water. The degree of shrinkage of this polarizing element was evaluated in three stages based on the following criteria by measuring the distance from the tip of the sample (end of the protective film) at the center of the short side of the sample to the tip of the shrunken polarizing element. The results are shown in Table 2.

The distance from the tip of the sample to the tip of the polarizing element is 1 mm or less: A

The distance from the tip of the sample to the tip of the polarizing element exceeds 1 mm and is less than 3 mm: B

The distance from the tip of the sample to the tip of the polarizing element is greater than 3 mm: C

A polarizing plate containing a first compound (urea), a second compound (glyoxal), and a third compound (maleic acid) in the adhesive is exposed to a high temperature environment of 105°C compared to a polarizing plate not containing urea in the adhesive. It was found that the transmittance was unlikely to decrease even if the material was used and the high temperature durability was excellent. In addition, it was found that for any adhesive, even a polarizing plate produced after being stored for 3 days, was excellent in water resistance and had a sufficient pot life in terms of productivity.

Claims (13)

A polarizing plate having 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,
The polarizing element and the transparent protective film are bonded together by an adhesive layer formed of an adhesive containing a first compound, a second compound, and a third compound,
The first compound is at least one selected from the group consisting of urea, urea derivatives, thiourea, and thiourea derivatives,
The second compound is dialdehyde,
The third compound is a dicarboxylic acid. The polarizing plate of claim 1, wherein the adhesive includes a polyvinyl alcohol-based resin. The polarizing plate according to claim 2, wherein in the adhesive, the content of the third compound is 0.01 part 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 2 or 3, wherein in the adhesive, the content of the first compound is 0.1 part 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 any one of claims 2 to 4, wherein in the adhesive, the content of the second compound is 0.03 parts by mass or more and 20 parts by mass or less with respect to 1 part by mass of the first compound. The polarizing plate according to any one of claims 1 to 5, wherein the dialdehyde is glyoxal. 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 method according to any one of claims 1 to 7, wherein the polarizing plate is used in an image display device,
In the image display device, a polarizing plate is provided on both sides of the polarizing plate in contact with a solid layer. It has an image display cell, a first adhesive layer laminated on a viewing side surface of the image display cell, and the polarizing plate according to any one of claims 1 to 8 laminated on a viewing side surface of the first adhesive layer. Image display device. The image display device according to claim 9, further comprising a second adhesive layer laminated on a viewing side surface of the polarizing plate, and a transparent member laminated on a viewing side surface of the second adhesive layer. The image display device according to claim 10, wherein the transparent member is a glass plate or a transparent resin plate. The image display device according to claim 10, wherein the transparent member is a touch panel. Containing a first compound, a second compound and a third compound,
The first compound is at least one selected from the group consisting of urea, urea derivatives, thiourea, and thiourea derivatives,
The second compound is dialdehyde,
The adhesive wherein the third compound is a dicarboxylic acid.