JP2024063648A - Polarizing plate with phase difference layer and image display device having the polarizing plate with phase difference layer - Google Patents

Abstract

[Problem] To provide a polarizing plate with a retardation layer in which discoloration of the edge of a polarizer, particularly discoloration due to sweat, is suppressed. [Solution] A polarizing plate with a retardation layer according to an embodiment of the present invention comprises, in this order, a polarizing plate including a polarizer, a first pressure-sensitive adhesive layer, a first retardation layer, a second retardation layer, and a second pressure-sensitive adhesive layer. The first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer are layers formed from a pressure-sensitive adhesive composition containing a base polymer obtained by polymerizing a monomer component containing acrylic acid. [Selected Figure] Figure 1

Description

The present invention relates to a polarizing plate with a retardation layer and an image display device having a polarizing plate with a retardation layer.

In recent years, image display devices such as liquid crystal display devices and electroluminescence (EL) display devices (e.g., organic EL display devices, inorganic EL display devices) have rapidly become widespread. A polarizing plate and a retardation plate are typically used in image display devices. In practice, a polarizing plate with a retardation layer, which integrates a polarizing plate and a retardation plate, is widely used (e.g., Patent Document 1). In recent years, with the improvement in design, bezel-less image display devices with narrower bezel portions have been proposed. In bezel-less image display devices, the human body may come into contact with the end of the polarizer, causing discoloration due to sweat at the end of the polarizer. Furthermore, discoloration may reach the image display section, resulting in a deterioration in image display characteristics.

Japanese Patent No. 3325560

The present invention has been made to solve the above-mentioned problems of the conventional art, and its main objective is to provide a polarizing plate with a retardation layer in which discoloration of the edge of the polarizer, particularly discoloration due to sweat, is suppressed.

1. The retardation layer-attached polarizing plate according to an embodiment of the present invention includes a polarizing plate including a polarizer, a first pressure-sensitive adhesive layer, a first retardation layer, a second retardation layer, and a second pressure-sensitive adhesive layer in this order, and the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer are layers formed from a pressure-sensitive adhesive composition including a base polymer obtained by polymerizing a monomer component including acrylic acid.
2. In the retardation layer-attached polarizing plate according to 1 above, the second pressure-sensitive adhesive layer may have a storage modulus at 23° C. of 1.0×10 ⁵ Pa or more.
3. In the retardation layer-attached polarizing plate according to the above 1 or 2, the base polymer may be a polymer obtained by polymerizing a monomer component containing 1 part by weight to 10 parts by weight of acrylic acid with respect to 100 parts by weight of the total monomer components.
4. In the retardation layer-attached polarizing plate according to any one of the above items 1 to 3, the polarizing plate may further include at least one protective layer.
5. In the retardation layer-attached polarizing plate according to any one of 1 to 4 above, the first retardation layer may function as a λ/4 plate, have an in-plane retardation Re(550) of 100 nm to 190 nm, and satisfy Re(450)/Re(550)<1.
6. In the retardation layer-attached polarizing plate according to any one of the above items 1 to 5, the first retardation layer may have a thickness of 40 μm or less.
7. In the retardation layer-attached polarizing plate according to any one of the above items 1 to 6, the refractive index characteristic of the second retardation layer may satisfy nz>nx=ny.
8. In the retardation layer-attached polarizing plate according to any one of the above items 4 to 7, the protective layer may be a solidified or cured layer of a coating film of a solution of a resin in an organic solvent.
9. In another aspect of an embodiment of the present invention, there is provided an image display device, the image display device including the retardation layer-attached polarizing plate according to any one of 1 to 8 above.

According to an embodiment of the present invention, it is possible to provide a polarizing plate with a retardation layer in which discoloration of the polarizer edge, particularly discoloration due to sweat, is suppressed. Therefore, it can be suitably used in image display devices with high design quality, such as bezel-less image display devices.

1 is a schematic cross-sectional view of a retardation layer-attached polarizing plate according to one embodiment of the present invention.

The following describes embodiments of the present invention, but the present invention is not limited to these embodiments.

(Definition of terms and symbols)
The definitions of terms and symbols used in this specification are as follows.
(1) Refractive index (nx, ny, nz)
"nx" is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., the slow axis direction), "ny" is the refractive index in the direction perpendicular to the slow axis in the plane (i.e., the fast axis direction), and "nz" is the refractive index in the thickness direction.
(2) In-plane retardation (Re)
"Re(λ)" is the in-plane retardation measured with light having a wavelength of λ nm at 23° C. For example, "Re(550)" is the in-plane retardation measured with light having a wavelength of 550 nm at 23° C. Re(λ) is calculated by the formula: Re(λ)=(nx−ny)×d, where d (nm) is the thickness of the layer (film).
(3) Retardation in the thickness direction (Rth)
"Rth(λ)" is the retardation in the thickness direction measured with light having a wavelength of λ nm at 23° C. For example, "Rth(550)" is the retardation in the thickness direction measured with light having a wavelength of 550 nm at 23° C. Rth(λ) is calculated by the formula: Rth(λ)=(nx-nz)×d, where d (nm) is the thickness of the layer (film).
(4) Nz Coefficient The Nz coefficient is calculated by Nz=Rth/Re.
(5) Angle When referring to an angle in this specification, the angle includes both clockwise and counterclockwise angles with respect to a reference direction. Thus, for example, "45°" means ±45°.

A. Overall configuration of retardation layer-attached polarizing plate FIG. 1 is a schematic cross-sectional view of a retardation layer-attached polarizing plate according to one embodiment of the present invention. The retardation layer-attached polarizing plate 100 of the illustrated example has a polarizing plate 10, a first adhesive layer 20, a first retardation layer 30, a second retardation layer 40, and a second adhesive layer 50 in this order from the viewing side. The polarizing plate 10 typically includes a polarizer 11 and protective layers 12 and 13 arranged on both sides of the polarizer 11. The protective layer 13 may be omitted. For example, when the first retardation layer 30 can also function as a protective layer, the protective layer 13 may be omitted. Each member constituting the retardation layer-attached polarizing plate may be laminated via any appropriate adhesive layer (not shown). Specific examples of the adhesive layer include an adhesive layer and an adhesive layer. The first retardation layer 30 and the second retardation layer 40 are preferably laminated via an adhesive layer (not shown). The first pressure-sensitive adhesive layer 20 and the second pressure-sensitive adhesive layer 50 are layers formed from a pressure-sensitive adhesive composition containing a base polymer (hereinafter also referred to as a base polymer containing acrylic acid) obtained by polymerizing a monomer component containing acrylic acid. If the pressure-sensitive adhesive composition containing a base polymer containing acrylic acid is used as the pressure-sensitive adhesive composition forming the first pressure-sensitive adhesive layer 20 and the second pressure-sensitive adhesive layer 50, a retardation layer-attached polarizing plate in which discoloration of the edge of the polarizer, particularly discoloration due to sweat, is suppressed can be provided.

The retardation layer-attached polarizing plate 100 has the second adhesive layer 50 as the outermost layer, and can be attached to an image display device (essentially, an image display cell). For practical purposes, it is preferable that a release liner is temporarily attached to the surface of the second adhesive layer 50 until the retardation layer-attached polarizing plate is used. By temporarily attaching the release liner, the adhesive layer is protected until actual use, and the retardation layer-attached polarizing plate can be rolled.

The polarizing plate with a retardation layer may be in the form of a sheet or a long sheet. In this specification, "long sheet" means a long and narrow shape whose length is sufficiently longer than its width, and includes, for example, a long and narrow shape whose length is 10 times or more, preferably 20 times or more, than its width. In the case of a long polarizing plate with a retardation layer, it is possible to laminate the retardation layer produced by oblique stretching and the plate by roll-to-roll, which simplifies the manufacturing process. A long polarizing plate with a retardation layer can be wound into a roll.

The thickness of the polarizing plate with a retardation layer can be set to any appropriate value. In one embodiment, the total thickness of the polarizing plate with a retardation layer is preferably 40 μm to 200 μm, more preferably 50 μm to 150 μm, and even more preferably 90 μm to 110 μm. The total thickness of the polarizing plate with a retardation layer refers to the sum of the thicknesses of the polarizing plate, the retardation layer (the first retardation layer and the second retardation layer), the adhesive layer for laminating them, and the second adhesive layer provided as the outermost layer (i.e., the total thickness of the polarizing plate with a retardation layer does not include the thickness of the release liner that may be temporarily attached to the surface of the second adhesive layer provided as the outermost layer).

The components of the retardation layer-attached polarizing plate are described in more detail below.

B. Polarizing Plate B-1. Polarizer The polarizer is typically composed of a resin film containing a dichroic material (typically, iodine). As the resin film, any appropriate resin film that can be used as a polarizer can be adopted. The resin film is typically a polyvinyl alcohol-based resin (hereinafter, referred to as "PVA-based resin") film. The resin film may be a single-layer resin film or a laminate of two or more layers.

Specific examples of polarizers made of a single-layer resin film include a PVA-based resin film that has been dyed with iodine and stretched (typically uniaxially stretched). The above-mentioned dyeing with iodine is performed, for example, by immersing the PVA-based resin film in an aqueous iodine solution. The stretching ratio of the above-mentioned uniaxial stretching is preferably 3 to 7 times. The stretching may be performed after the dyeing process or while dyeing. Alternatively, the film may be stretched and then dyed. If necessary, the PVA-based resin film may be subjected to a swelling process, a crosslinking process, a cleaning process, a drying process, or the like. For example, by immersing the PVA-based resin film in water and washing it before dyeing, it is possible to clean off dirt and antiblocking agents on the surface of the PVA-based resin film, and also to swell the PVA-based resin film to prevent uneven dyeing, etc.

Specific examples of polarizers obtained using a laminate include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate. A polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate can be produced, for example, by applying a PVA-based resin solution to a resin substrate and drying the resin substrate to form a PVA-based resin layer on the resin substrate to obtain a laminate of the resin substrate and the PVA-based resin layer; stretching and dyeing the laminate to make the PVA-based resin layer into a polarizer. In this embodiment, a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin is preferably formed on one side of the resin substrate. The stretching typically includes immersing the laminate in an aqueous boric acid solution to stretch it. Furthermore, the stretching may further include stretching the laminate in air at a high temperature (e.g., 95°C or higher) before stretching in the aqueous boric acid solution, as necessary. In addition, in this embodiment, the laminate is preferably subjected to a drying shrinkage treatment in which the laminate is heated while being transported in the longitudinal direction to shrink the laminate by 2% or more in the width direction. Typically, the manufacturing method of this embodiment includes subjecting the laminate to an auxiliary air stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment in this order. By introducing the auxiliary stretching, even when PVA is applied onto a thermoplastic resin, it is possible to increase the crystallinity of PVA and achieve high optical properties. In addition, by simultaneously increasing the orientation of PVA in advance, problems such as a decrease in the orientation or dissolution of PVA when immersed in water in the subsequent dyeing step or stretching step can be prevented, and high optical properties can be achieved. Furthermore, when the PVA-based resin layer is immersed in a liquid, the orientation disorder and the decrease in the orientation of polyvinyl alcohol molecules can be suppressed compared to when the PVA-based resin layer does not contain a halide. This can improve the optical properties of a polarizer obtained through a treatment step in which the laminate is immersed in a liquid, such as a dyeing treatment and an underwater stretching treatment. Furthermore, the optical properties can be improved by shrinking the laminate in the width direction by the drying shrinkage treatment. The obtained resin substrate/polarizer laminate may be used as is (i.e., the resin substrate may be used as a protective layer for the polarizer), or the resin substrate may be peeled off from the resin substrate/polarizer laminate, and any suitable protective layer may be laminated on the peeled surface depending on the purpose. Details of the method for producing such a polarizer are described in, for example, JP-A-2012-73580 (Patent No. 5414738) and Japanese Patent No. 6470455. The entire disclosures of these publications are incorporated herein by reference.

The thickness of the polarizer is preferably 1 μm to 25 μm, more preferably 1 μm to 15 μm, even more preferably 1 μm to 10 μm, even more preferably 1 μm to 8 μm, and particularly preferably 2 μm to 5 μm. In the embodiment of the present invention, even when a polarizer having the above thickness is used, the retardation unevenness and color unevenness of the retardation layer-attached polarizing plate can be suppressed in a harsh high-temperature environment and a high-temperature and high-humidity environment.

The polarizer preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The single transmittance Ts of the polarizer is preferably 40% to 48%, more preferably 41% to 46%. The degree of polarization P of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and even more preferably 99.9% or more. The single transmittance is typically a Y value measured using an ultraviolet-visible spectrophotometer and subjected to luminosity correction. The degree of polarization is typically calculated by the following formula based on the parallel transmittance Tp and crossed transmittance Tc measured using an ultraviolet-visible spectrophotometer and subjected to luminosity correction.
Degree of polarization (%)={(Tp−Tc)/(Tp+Tc)} ^1/2 ×100

B-2. Protective layer The protective layers 12 and 13 are formed of any suitable film that can be used as a protective layer for a polarizer. Specific examples of materials that are the main components of the film include cellulose-based resins such as triacetyl cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, polysulfone-based, polystyrene-based, polynorbornene-based, polyolefin-based, (meth)acrylic-based, acetate-based, and other transparent resins. In addition, examples include thermosetting resins or ultraviolet-curing resins such as (meth)acrylic-based, urethane-based, (meth)acrylic urethane-based, epoxy-based, and silicone-based resins. In addition, examples include glassy polymers such as siloxane-based polymers. In addition, the polymer films described in JP-A-2001-343529 (WO01/37007) can also be used. As the material for this film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain can be used, for example, a resin composition containing an alternating copolymer of isobutene and N-methylmaleimide, and an acrylonitrile-styrene copolymer. The polymer film can be, for example, an extrusion molded product of the above resin composition.

The polarizing plate with a retardation layer is typically placed on the viewing side of the image display device, and the protective layer 12 is typically placed on the viewing side. Therefore, the protective layer 12 may be subjected to surface treatments such as hard coat treatment, anti-reflection treatment, anti-sticking treatment, and anti-glare treatment, as necessary.

The thickness of the protective layer is preferably 10 μm to 50 μm, and more preferably 10 μm to 30 μm. If a surface treatment has been applied, the thickness of the outer protective layer (protective layer 12) includes the thickness of the surface treatment layer.

In one embodiment, the protective layer may be a solidified or cured layer of a coating film of an organic solvent solution containing a resin. If the protective layer is a solidified or cured layer of a coating film of an organic solvent solution containing a resin, adhesion to the polarizer may be improved. The organic solvent solution is prepared using any appropriate resin. Any appropriate resin can be used as the resin (base polymer for the protective layer). Only one type of resin may be used, or two or more types may be used in combination.

In one embodiment, a resin having a glass transition temperature (Tg) of, for example, 85° C. or more and a weight average molecular weight Mw of, for example, 25,000 or more is preferably used. If the Tg and Mw of the resin are in such ranges, excellent durability can be achieved in a high temperature and high humidity environment despite the very thin thickness. The Tg of the resin is preferably 90° C. or more, more preferably 100° C. or more, even more preferably 110° C. or more, and particularly preferably 120° C. or more. The Tg can be, for example, 200° C. or less. The Mw of the resin is preferably 30,000 or more, more preferably 35,000 or more, and even more preferably 40,000 or more. The Mw can be, for example, 150,000 or less.

As the resin, any suitable thermoplastic resin or thermosetting resin can be used as long as it can form a solidified or cured product (e.g., a thermoset product) of the coating film of the organic solvent solution and has the above-mentioned Tg and Mw. Thermoplastic resins are preferable. Examples of thermoplastic resins include acrylic resins and epoxy resins. Acrylic resins and epoxy resins may be used in combination.

Acrylic resins typically contain repeating units derived from (meth)acrylic acid ester monomers having a linear or branched structure as the main component. In this specification, (meth)acrylic refers to acrylic and/or methacrylic. Acrylic resins may contain repeating units derived from any appropriate copolymerization monomer depending on the purpose. Examples of copolymerization monomers (copolymerization monomers) include carboxyl group-containing monomers, hydroxyl group-containing monomers, amide group-containing monomers, aromatic ring-containing (meth)acrylates, and heterocycle-containing vinyl monomers. By appropriately setting the type, number, combination, and copolymerization ratio of the monomer units, an acrylic resin having the above-mentioned specified Mw can be obtained.

（式中、Ｘはビニル基、（メタ）アクリル基、スチリル基、（メタ）アクリルアミド基、ビニルエーテル基、エポキシ基、オキセタン基、ヒドロキシル基、アミノ基、アルデヒド基、および、カルボキシル基からなる群より選択される少なくとも１種の反応性基を含む官能基を表し、Ｒ^１およびＲ^２はそれぞれ独立して、水素原子、置換基を有していてもよい脂肪族炭化水素基、置換基を有していてもよいアリール基、または、置換基を有していてもよいヘテロ環基を表し、Ｒ^１およびＲ^２は互いに連結して環を形成してもよい）。 <Boron-containing acrylic resin>
In one embodiment, the acrylic resin includes a copolymer (hereinafter, may be referred to as a boron-containing acrylic resin) obtained by polymerizing a monomer mixture containing more than 50 parts by weight of a (meth)acrylic monomer and more than 0 part by weight and less than 50 parts by weight of a monomer represented by formula (1) (hereinafter, may be referred to as a copolymerization monomer):

(In the formula, X represents a functional group containing at least one reactive group selected from the group consisting of a vinyl group, a (meth)acrylic group, a styryl group, a (meth)acrylamide group, a vinyl ether group, an epoxy group, an oxetane group, a hydroxyl group, an amino group, an aldehyde group, and a carboxyl group; R ¹ and R ² each independently represent a hydrogen atom, an optionally substituted aliphatic hydrocarbon group, an optionally substituted aryl group, or an optionally substituted heterocyclic group; and R ¹ and R ² may be linked together to form a ring).

（式中、Ｒ^６は任意の官能基を表し、jおよびｋは１以上の整数を表す）。 The boron-containing acrylic resin typically has a repeating unit represented by the following formula. By polymerizing a monomer mixture containing a copolymerization monomer represented by formula (1) and a (meth)acrylic monomer, the boron-containing acrylic resin has a boron-containing substituent (e.g., a repeating unit k in the following formula) in the side chain. This can improve the adhesion between the polarizer and the protective layer. The boron-containing substituent may be contained continuously (i.e., in a block shape) or randomly in the boron-containing acrylic resin.

(In the formula, ^R6 represents any functional group, and j and k represent integers of 1 or more).

<(Meth)acrylic monomer>
As the (meth)acrylic monomer, any appropriate (meth)acrylic monomer can be used, for example, a (meth)acrylic acid ester monomer having a linear or branched structure, and a (meth)acrylic acid ester monomer having a cyclic structure.

Examples of (meth)acrylic acid ester monomers having a linear or branched structure include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, methyl 2-ethylhexyl (meth)acrylate, and 2-hydroxyethyl (meth)acrylate. Methyl (meth)acrylate is preferably used. Only one type of (meth)acrylic acid ester monomer may be used, or two or more types may be used in combination.

Examples of (meth)acrylic acid ester monomers having a cyclic structure include cyclohexyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate, 1-adamantyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, biphenyl (meth)acrylate, o-biphenyloxyethyl (meth)acrylate, o-biphenyloxyethoxyethyl (meth)acrylate, m-biphenyloxyethyl acrylate, p-biphenyloxyethyl (meth)acrylate, o-biphenyloxyethyl (meth)acrylate, Examples of the monomers include biphenyl group-containing monomers such as oxy-2-hydroxypropyl (meth)acrylate, p-biphenyloxy-2-hydroxypropyl (meth)acrylate, m-biphenyloxy-2-hydroxypropyl (meth)acrylate, N-(meth)acryloyloxyethyl-o-biphenyl=carbamate, N-(meth)acryloyloxyethyl-p-biphenyl=carbamate, N-(meth)acryloyloxyethyl-m-biphenyl=carbamate, and o-phenylphenol glycidyl ether acrylate, terphenyl (meth)acrylate, and o-terphenyloxyethyl (meth)acrylate. Preferably, 1-adamantyl (meth)acrylate and dicyclopentanyl (meth)acrylate are used. By using these monomers, a polymer with a high glass transition temperature can be obtained. These monomers may be used alone or in combination of two or more.

Instead of the above (meth)acrylic acid ester monomer, a silsesquioxane compound having a (meth)acryloyl group may be used. By using a silsesquioxane compound, an acrylic polymer having a high glass transition temperature can be obtained. Silsesquioxane compounds are known to have various skeletal structures, such as a cage structure, a ladder structure, and a random structure. The silsesquioxane compound may have only one of these structures, or may have two or more of them. Only one type of silsesquioxane compound may be used, or two or more types may be used in combination.

As silsesquioxane compounds containing (meth)acryloyl groups, for example, the MAC grade and AC grade of the SQ series from Toagosei Co., Ltd. can be used. The MAC grade is a silsesquioxane compound containing a methacryloyl group, and specific examples include MAC-SQ TM-100, MAC-SQ SI-20, and MAC-SQ HDM. The AC grade is a silsesquioxane compound containing an acryloyl group, and specific examples include AC-SQ TA-100 and AC-SQ SI-20.

The (meth)acrylic monomer is used in an amount of more than 50 parts by weight per 100 parts by weight of the monomer mixture.

<Comonomer>
As the copolymerization monomer, a monomer represented by the above formula (1) is used. By using such a copolymerization monomer, a boron-containing substituent is introduced into the side chain of the obtained polymer. Only one type of copolymerization monomer may be used, or two or more types may be used in combination.

The aliphatic hydrocarbon group in the above formula (1) may be a linear or branched alkyl group having 1 to 20 carbon atoms, which may have a substituent, a cyclic alkyl group having 3 to 20 carbon atoms, which may have a substituent, or an alkenyl group having 2 to 20 carbon atoms. The aryl group may be a phenyl group having 6 to 20 carbon atoms, which may have a substituent, or a naphthyl group having 10 to 20 carbon atoms, which may have a substituent. The heterocyclic group may be a 5-membered or 6-membered ring group containing at least one heteroatom, which may have a substituent. R ¹ and R ² may be linked to each other to form a ring. R ¹ and R ² are preferably a hydrogen atom or a linear or branched alkyl group having 1 to 3 carbon atoms, and more preferably a hydrogen atom.

The reactive group contained in the functional group represented by X is at least one selected from the group consisting of a vinyl group, a (meth)acrylic group, a styryl group, a (meth)acrylamide group, a vinyl ether group, an epoxy group, an oxetane group, a hydroxyl group, an amino group, an aldehyde group, and a carboxyl group. Preferably, the reactive group is a (meth)acrylic group and/or a (meth)acrylamide group. By having these reactive groups, the adhesion between the polarizer and the protective layer can be further improved.

In one embodiment, the functional group represented by X is preferably a functional group represented by Z-Y-, where Z represents a functional group containing at least one reactive group selected from the group consisting of a vinyl group, a (meth)acrylic group, a styryl group, a (meth)acrylamide group, a vinyl ether group, an epoxy group, an oxetane group, a hydroxyl group, an amino group, an aldehyde group, and a carboxyl group, and Y represents a phenylene group or an alkylene group.

Specifically, the following compounds can be used as the copolymerization monomer.

The copolymerization monomer is used in an amount of more than 0 parts by weight and less than 50 parts by weight per 100 parts by weight of the monomer mixture. The amount is preferably 0.01 parts by weight or more and less than 50 parts by weight, more preferably 0.05 parts by weight to 20 parts by weight, even more preferably 0.1 parts by weight to 10 parts by weight, and particularly preferably 0.5 parts by weight to 5 parts by weight.

<Acrylic resin containing lactone ring, etc.>
In another embodiment, the acrylic resin has a repeating unit containing a ring structure selected from a lactone ring unit, a glutaric anhydride unit, a glutarimide unit, a maleic anhydride unit, and a maleimide (N-substituted maleimide) unit. The repeating unit of the acrylic resin may contain only one type of repeating unit containing a ring structure, or may contain two or more types of repeating units containing a ring structure.

The lactone ring unit is preferably represented by the following general formula (2):

一般式（２）において、Ｒ^３、Ｒ^４およびＲ^５は、それぞれ独立して、水素原子または炭素数１～２０の有機残基を表す。なお、有機残基は酸素原子を含んでいてもよい。アクリル系樹脂には、単一のラクトン環単位のみが含まれていてもよく、上記一般式（２）におけるＲ^３、Ｒ^４およびＲ^５が異なる複数のラクトン環単位が含まれていてもよい。ラクトン環単位を有するアクリル系樹脂は、例えば特開２００８－１８１０７８号公報に記載されており、当該公報の記載は本明細書に参考として援用される。

In the general formula (2), R ³ , R ⁴ and R ⁵ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue may contain an oxygen atom. The acrylic resin may contain only a single lactone ring unit, or may contain a plurality of lactone ring units in which R ³ , R ⁴ and R ⁵ in the general formula (2) are different. An acrylic resin having a lactone ring unit is described, for example, in JP 2008-181078 A, and the description of this publication is incorporated herein by reference.

The glutarimide unit is preferably represented by the following general formula (3):

In the general formula (3), R ¹¹ and R ¹² each independently represent hydrogen or an alkyl group having 1 to 8 carbon atoms, and R ¹³ represents an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an aryl group having 6 to 10 carbon atoms. In the general formula (3), preferably, R ¹¹ and R ¹² each independently represent hydrogen or a methyl group, and R ¹³ represents hydrogen, a methyl group, a butyl group, or a cyclohexyl group. More preferably, R ¹¹ represents a methyl group, R ¹² represents hydrogen, and R ¹³ represents a methyl group. The acrylic resin may contain only a single glutarimide unit, or may contain a plurality of glutarimide units in which R ¹¹ , R ¹² , and R ¹³ in the general formula (3) are different. Acrylic resins having glutarimide units are described, for example, in JP-A-2006-309033, JP-A-2006-317560, JP-A-2006-328334, JP-A-2006-337491, JP-A-2006-337492, JP-A-2006-337493, and JP-A-2006-337569, the disclosures of which are incorporated herein by reference. Note that, for the glutaric anhydride unit, the above description of the glutarimide unit applies, except that the nitrogen atom substituted with R ¹³ in the above general formula (3) becomes an oxygen atom.

The structures of maleic anhydride units and maleimide (N-substituted maleimide) units are specified by their names, so a detailed explanation is omitted.

The content of repeating units containing a ring structure in the acrylic resin is preferably 1 mol% to 50 mol%, more preferably 10 mol% to 40 mol%, and even more preferably 20 mol% to 30 mol%. The acrylic resin contains repeating units derived from the above (meth)acrylic monomer as the main repeating units.

<Epoxy resin>
As the epoxy resin, an epoxy resin having an aromatic ring is preferably used. By using an epoxy resin having an aromatic ring as the epoxy resin, the adhesion between the protective layer and the polarizer can be improved. Furthermore, when a pressure-sensitive adhesive layer is disposed adjacent to the protective layer, the anchoring force of the pressure-sensitive adhesive layer can be improved. Examples of the epoxy resin having an aromatic ring include bisphenol-type epoxy resins such as bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, and bisphenol S-type epoxy resins; novolac-type epoxy resins such as phenol novolac epoxy resins, cresol novolac epoxy resins, and hydroxybenzaldehyde phenol novolac epoxy resins; polyfunctional epoxy resins such as glycidyl ether of tetrahydroxyphenylmethane, glycidyl ether of tetrahydroxybenzophenone, and epoxidized polyvinylphenol, naphthol-type epoxy resins, naphthalene-type epoxy resins, and biphenyl-type epoxy resins. Preferably, bisphenol A-type epoxy resins, biphenyl-type epoxy resins, and bisphenol F-type epoxy resins are used. Only one type of epoxy resin may be used, or two or more types may be used in combination.

The protective layer can be formed by applying an organic solvent solution of the above resin to form a coating film, and then solidifying or thermally curing the coating film. Any suitable organic solvent capable of dissolving or uniformly dispersing the acrylic resin or epoxy resin can be used as the organic solvent. Specific examples of organic solvents include ethyl acetate, toluene, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), cyclopentanone, and cyclohexanone. The resin concentration of the solution is preferably 3 to 20 parts by weight per 100 parts by weight of the solvent. With such a resin concentration, a uniform coating film can be formed.

The solution may be applied to any suitable substrate or to a polarizer. When the solution is applied to a substrate, the solidified coating film (resin layer) formed on the substrate is transferred to the polarizer. When the solution is applied to a polarizer, the coating film is dried (solidified) to form a protective layer directly on the polarizer. Preferably, the solution is applied to a polarizer, and a protective layer is formed directly on the polarizer. With this configuration, the adhesive layer or pressure-sensitive adhesive layer required for transfer can be omitted, so that the polarizing plate can be made even thinner. Any suitable method can be used as a method for applying the solution. Specific examples include roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, and knife coating (comma coating, etc.).

A protective layer can be formed by solidifying or heat-curing the coating film of the solution. The heating temperature for solidification or heat-curing is preferably 100°C or less, and more preferably 50°C to 70°C. If the heating temperature is within this range, adverse effects on the polarizer can be prevented. The heating time can vary depending on the heating temperature. The heating time can be, for example, 1 minute to 10 minutes.

The protective layer in this embodiment (essentially, the organic solvent solution of the resin) may contain any suitable additive depending on the purpose. Specific examples of additives include ultraviolet absorbers; leveling agents; antioxidants such as hindered phenols, phosphorus, and sulfur; stabilizers such as light stabilizers, weather stabilizers, and heat stabilizers; reinforcing materials such as glass fibers and carbon fibers; near-infrared absorbers; flame retardants such as tris(dibromopropyl)phosphate, triallyl phosphate, and antimony oxide; antistatic agents such as anionic, cationic, and nonionic surfactants; colorants such as inorganic pigments, organic pigments, and dyes; organic or inorganic fillers; resin modifiers; organic or inorganic fillers; plasticizers; lubricants; antistatic agents; and flame retardants. The type, number, combination, and amount of additives can be appropriately set depending on the purpose.

In one embodiment, the thickness of the protective layer is preferably 0.05 μm to 10 μm, more preferably 0.08 μm to 5 μm, even more preferably 0.1 μm to 1 μm, and particularly preferably 0.2 μm to 0.7 μm. If the protective layer is a solidified or hardened layer of a coating film of an organic solvent solution, the thickness can be made very thin (for example, 10 μm or less).

C. First Retardation Layer The first retardation layer 30 may have any suitable optical and/or mechanical properties depending on the purpose. The first retardation layer 30 typically has a slow axis. In one embodiment, the angle θ between the slow axis of the first retardation layer 30 and the absorption axis of the polarizer 11 is preferably 40° to 50°, more preferably 42° to 48°, and even more preferably about 45°. If the angle θ is in such a range, if the first retardation layer is a λ/4 plate as described later, a retardation layer-attached polarizing plate having very excellent circular polarization properties (as a result, very excellent antireflection properties) can be obtained.

The first retardation layer preferably has a refractive index characteristic that satisfies nx>ny, and more preferably has a refractive index characteristic that satisfies the relationship of nx>ny≧nz. The first retardation layer is typically provided to impart anti-reflection properties to the polarizing plate, and in one embodiment, can function as a λ/4 plate. In this case, the in-plane retardation Re(550) of the first retardation layer is preferably 100 nm to 190 nm, more preferably 110 nm to 170 nm, and even more preferably 130 nm to 160 nm. Note that here, "ny=nz" includes not only the case where ny and nz are completely equal, but also the case where they are substantially equal. Therefore, there may be cases where ny<nz within a range that does not impair the effects of the present invention.

The Nz coefficient of the first retardation layer is preferably 0.9 to 3, more preferably 0.9 to 2.5, even more preferably 0.9 to 1.5, and particularly preferably 0.9 to 1.3. If such a relationship is satisfied, when the obtained polarizing plate with a retardation layer is used in an image display device, an extremely excellent reflection hue can be achieved.

The first retardation layer may exhibit an inverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light, may exhibit a positive wavelength dispersion characteristic in which the retardation value decreases according to the wavelength of the measurement light, or may exhibit a flat wavelength dispersion characteristic in which the retardation value hardly changes according to the wavelength of the measurement light. In one embodiment, the first retardation layer exhibits an inverse dispersion wavelength characteristic. In this case, Re(450)/Re(550) of the retardation layer is preferably less than 1, more preferably 0.8 or more and less than 1, and even more preferably 0.8 or more and 0.95 or less. With such a configuration, it is possible to realize very excellent anti-reflection properties.

The first retardation layer contains a resin having an absolute value of a photoelastic coefficient of preferably 2×10 ⁻¹¹ m ² /N or less, more preferably 2.0×10 ⁻¹³ m ² /N to 1.5×10 ⁻¹¹ m ² /N, and even more preferably 1.0×10 ⁻¹² m ^{2 /} N to 1.2× ^{10 −11} m ² /N. If the absolute value of the photoelastic coefficient is in such a range, a change in retardation is unlikely to occur when shrinkage stress occurs during heating. As a result, thermal unevenness in the obtained image display device can be effectively prevented.

As the material for forming the first retardation layer, any appropriate material may be adopted as long as the above-mentioned characteristics are obtained. Specifically, the first retardation layer may be a layer of a liquid crystal compound with a solidified orientation (liquid crystal alignment solidified layer) or a retardation film (a stretched film of a polymer film). The first retardation layer is preferably a retardation film (a stretched film of a polymer film).

As described above, the first retardation layer is preferably a stretched polymer film. Specifically, by appropriately selecting the type of polymer, stretching conditions (e.g., stretching temperature, stretching ratio, stretching direction), stretching method, etc., a first retardation layer having the desired optical properties (e.g., refractive index characteristics, in-plane retardation, retardation in the thickness direction) can be obtained. More specifically, the stretching temperature is preferably 110°C to 170°C, more preferably 130°C to 150°C. The stretching ratio is preferably 1.37 times to 1.67 times, more preferably 1.42 times to 1.62 times. An example of the stretching method is uniaxial transverse stretching.

Any suitable resin may be used as the resin forming the polymer film. Specific examples include resins that form positive birefringence films, such as norbornene-based resins, polycarbonate-based resins, cellulose-based resins, polyvinyl alcohol-based resins, and polysulfone-based resins. Of these, norbornene-based resins and polycarbonate-based resins are preferred.

The norbornene-based resin is a resin polymerized using norbornene-based monomers as polymerization units. Examples of the norbornene-based monomers include norbornene and its alkyl and/or alkylidene substituted derivatives, such as 5-methyl-2-norbornene, 5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-ethylidene-2-norbornene, and polar group substituted derivatives thereof, such as halogen; dicyclopentadiene, 2,3-dihydrodicyclopentadiene, and the like; dicyclopentadiene, 2,3-dihydrodicyclopentadiene, and the like; Octahydronaphthalene, its alkyl and/or alkylidene substituted derivatives, and polar group substituted derivatives such as halogen, for example, 6-methyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-ethyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-ethylidene-1,4:5,8-dimethano-1,4,4a,5,6,7 ,8,8a-octahydronaphthalene, 6-chloro-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-cyano-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-pyridyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-methoxycarbonyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene norbornene-1,4,4a,5,6,7,8,8a-octahydronaphthalene, etc.; trimers and tetramers of cyclopentadiene, such as 4,9:5,8-dimethano-3a,4,4a,5,8,8a,9,9a-octahydro-1H-benzoindene, 4,11:5,10:6,9-trimethano-3a,4,4a,5,5a,6,9,9a,10,10a,11,11a-dodecahydro-1H-cyclopentaanthracene, etc. The norbornene-based resin may be a copolymer of a norbornene-based monomer and another monomer.

As the polycarbonate resin, an aromatic polycarbonate is preferably used. Aromatic polycarbonate can be obtained, typically, by reacting a carbonate precursor with an aromatic dihydric phenol compound. Specific examples of carbonate precursors include phosgene, bischloroformates of dihydric phenols, diphenyl carbonate, di-p-tolyl carbonate, phenyl-p-tolyl carbonate, di-p-chlorophenyl carbonate, dinaphthyl carbonate, and the like. Among these, phosgene and diphenyl carbonate are preferred. Specific examples of aromatic dihydric phenol compounds include 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)butane, 2,2-bis(4-hydroxy-3,5-dipropylphenyl)propane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, and the like. These may be used alone or in combination of two or more. Preferably, 2,2-bis(4-hydroxyphenyl)propane, 1,1-bis(4-hydroxyphenyl)cyclohexane, and 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane are used. In particular, it is preferable to use 2,2-bis(4-hydroxyphenyl)propane and 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane together.

The thickness of the first retardation layer can be set so as to obtain the desired optical characteristics. When the first retardation layer is a liquid crystal alignment solidified layer, the thickness is preferably 0.5 μm to 10 μm, more preferably 0.5 μm to 8 μm, and even more preferably 0.5 to 5 μm. When the first retardation layer is a stretched polymer film, the thickness is preferably 5 μm to 55 μm, more preferably 10 μm to 50 μm, and even more preferably 15 μm to 45 μm. In one embodiment, the thickness of the first retardation layer is preferably 40 μm or less.

D. Second retardation layer Any suitable retardation layer is used as the second retardation layer. In one embodiment, the second retardation layer may be a so-called positive C plate whose refractive index characteristics show the relationship nz>nx=ny. By using a positive C plate as the other retardation layer, it is possible to effectively prevent reflection in an oblique direction, and it is possible to widen the viewing angle of the anti-reflection function. In this case, the retardation Rth(550) in the thickness direction of the other retardation layer is preferably -50 nm to -300 nm, more preferably -70 nm to -250 nm, even more preferably -90 nm to -200 nm, and particularly preferably -100 nm to -180 nm. Here, "nx=ny" includes not only the case where nx and ny are strictly equal, but also the case where nx and ny are substantially equal. That is, the in-plane retardation Re(550) of the other retardation layer may be less than 10 nm.

The separate retardation layer having the refractive index characteristic of nz>nx=ny may be formed of any suitable material. The separate retardation layer is preferably made of a film containing a liquid crystal material fixed in homeotropic alignment. The liquid crystal material (liquid crystal compound) that can be homeotropically aligned may be a liquid crystal monomer or a liquid crystal polymer. Specific examples of the liquid crystal compound and the method of forming the retardation layer include the liquid crystal compound and the method of forming the retardation layer described in [0020] to [0028] of JP-A-2002-333642. In this case, the thickness of the separate retardation layer is preferably 0.5 μm to 10 μm, more preferably 0.5 μm to 8 μm, and even more preferably 0.5 μm to 5 μm.

E. Adhesive layer Typically, the first retardation layer and the second retardation layer are laminated via an adhesive layer. Preferably, the first retardation layer and the second retardation layer are laminated via an adhesive layer. By laminating via an adhesive layer, the expansion of the first retardation layer, which is a stretched film of a polycarbonate-based resin film, due to heat and water absorption can be further suppressed. Any suitable adhesive can be used as the adhesive for forming the adhesive layer, and for example, an ultraviolet-curing adhesive can be used. By using an ultraviolet-curing adhesive, an adhesive layer having high hardness and a thin thickness can be formed.

F. Adhesive Layer The retardation layer-attached polarizing plate of the embodiment of the present invention includes a first adhesive layer and a second adhesive layer. The first adhesive layer and the second adhesive layer are layers formed from an adhesive composition containing a base polymer obtained by polymerizing a monomer component containing acrylic acid. Sweat usually has a weak acidic property (pH 5.7 to 6.5 or so). However, when a large amount of sweat is secreted and when moisture evaporates from sweat, the pH of sweat may increase. Therefore, as an evaluation condition under more severe conditions, an alkaline sweat solution is prepared and brought into contact with a retardation-attached polarizing plate to evaluate the decolorization of the polarizer. In addition, when the evaluation is performed as an actual module configuration, the pH of the sweat solution may increase due to the influence of the end sealant, and the sweat solution may become alkaline. When more alkaline sweat comes into contact with a retardation layer-attached polarizing plate, the decolorization of the polarizer may become more noticeable. When the base polymer contained in the adhesive composition forming the adhesive layer contains a monomer unit derived from acrylic acid, the monomer unit derived from acrylic acid (e.g., a carboxyl group) can neutralize the alkaline component contained in sweat. As a result, it is possible to provide a polarizing plate with a retardation layer in which edge discoloration of the polarizer, particularly edge discoloration due to sweat, is suppressed. The first adhesive layer and the second adhesive layer may be formed of the same adhesive composition or different adhesive compositions.

The thickness of the first adhesive layer is preferably 1 μm to 50 μm, more preferably 2 μm to 30 μm, and even more preferably 3 μm to 10 μm. If the thickness of the first adhesive layer is within the above range, it is possible to provide a polarizing plate with a retardation layer in which end discoloration of the polarizer, particularly end discoloration due to sweat, is suppressed. Furthermore, the laminated state between the polarizing plate and the retardation layer can be maintained.

The storage modulus of the second pressure-sensitive adhesive layer at 23° C. is preferably at least 1.0×10 ⁵ Pa, more preferably at least 1.2×10 ⁵ Pa, and even more preferably at least 1.5×10 ⁵ Pa. When the storage modulus of the second pressure-sensitive adhesive layer at 23° C. is within the above range, the storage modulus of the second pressure-sensitive adhesive layer at 23° C. is preferably no greater than 1.9×10 ⁵ Pa. The storage modulus at 23° C. can be measured using a dynamic viscoelasticity measuring device.

The thickness of the second adhesive layer is preferably 1 μm to 100 μm, more preferably 2 μm to 50 μm, and even more preferably 10 μm to 30 μm. If the thickness of the second adhesive layer is within the above range, it is possible to provide a polarizing plate with a retardation layer in which discoloration of the polarizer edge, particularly discoloration of the edge due to sweat, is suppressed. Furthermore, the laminated state between the polarizing plate and the retardation layer can be maintained.

E-1. Pressure-sensitive adhesive composition As described above, the pressure-sensitive adhesive composition is a pressure-sensitive adhesive composition containing a base polymer obtained by polymerizing a monomer component containing acrylic acid, that is, a so-called acrylic pressure-sensitive adhesive. Acrylic pressure-sensitive adhesives are preferred because they have excellent optical transparency, exhibit appropriate adhesive properties (adhesion, cohesion, and adhesion), and are excellent in durability (weather resistance and heat resistance).

The adhesive composition contains, as a base polymer, a polymer obtained by polymerizing a monomer component that preferably contains 1 to 10 parts by weight of acrylic acid relative to 100 parts by weight of the total monomer components. The monomer component preferably contains 1.2 to 8 parts by weight of acrylic acid relative to 100 parts by weight of the total monomer components, more preferably 1.5 to 7 parts by weight, and even more preferably 2 to 6 parts by weight. If the content of acrylic acid is within the above range, a retardation layer-attached polarizing plate in which edge discoloration is further suppressed can be provided.

The base polymer typically has a main skeleton of a structural unit derived from an alkyl (meth)acrylate ester. Examples of the alkyl (meth)acrylate ester include C1 to C20 alkyl esters of (meth)acrylic acid. Specific examples include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, isomyristyl (meth)acrylate, and lauryl (meth)acrylate. Preferably, the average number of carbon atoms in the alkyl group is 3 to 9. The alkyl (meth)acrylate esters may be used alone or in combination. The content of the structural unit derived from an alkyl (meth)acrylate ester is preferably 60 parts by weight or more, more preferably 80 parts by weight or more, and even more preferably 90 to 99 parts by weight, based on 100 parts by weight of the total monomer components. In this specification, (meth)acrylic acid alkyl ester refers to acrylic acid alkyl ester and/or methacrylic acid alkyl ester.

The base polymer may contain, as necessary, a structural unit derived from another monomer component that is copolymerizable with the above-mentioned (meth)acrylic acid alkyl ester. Examples of such monomer components (copolymerization components) include hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)-methyl acrylate; (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, and the like. Examples of the monomers include carboxyl group-containing monomers such as acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid; acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride; caprolactone adducts of acrylic acid; sulfonic acid group-containing monomers such as styrene sulfonic acid, allyl sulfonic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acrylamide propanesulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid; and phosphoric acid group-containing monomers such as 2-hydroxyethyl acryloyl phosphate. Further, (N-substituted) amide monomers such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, and N-methylolpropane(meth)acrylamide; alkylaminoalkyl(meth)acrylate monomers such as aminoethyl(meth)acrylate, N,N-dimethylaminoethyl(meth)acrylate, and t-butylaminoethyl(meth)acrylate; alkoxyalkyl(meth)acrylate monomers such as methoxyethyl(meth)acrylate and ethoxyethyl(meth)acrylate; N-(meth)acryloyloxymethylene succinimide and N-(meth)acryloyloxymethylene succinimide; Succinimide monomers such as acryloyl-6-oxyhexamethylene succinimide, N-(meth)acryloyl-8-oxyoctamethylene succinimide, and N-acryloylmorpholine; maleimide monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide; and itaconimide monomers such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, and N-laurylitaconimide can also be used as copolymerization components for the purpose of modification. Furthermore, vinyl monomers such as vinyl acetate, vinyl propionate, N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, N-vinyl carboxylic acid amides, styrene, α-methylstyrene, and N-vinylcaprolactam; cyanoacrylate monomers such as acrylonitrile and methacrylonitrile; epoxy group-containing acrylic monomers such as glycidyl (meth)acrylate; glycol-based acrylic ester monomers such as polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate, and methoxypolypropylene glycol (meth)acrylate; tetrahydrofurfuryl (meth)acrylate, fluorine (meth)acrylate, silicone (meth)acrylate, and 2-methoxyethyl acrylate can also be used as copolymerization components for the purpose of modification.

By adjusting the type, combination, and blending ratio of the copolymerization components (and thus the content ratio of the structural units), it is possible to obtain an adhesive with the desired properties. Preferred copolymerization components include hydroxyl group-containing monomers and carboxyl group-containing monomers. These can act as reaction points with the crosslinking agent, making it possible to form an adhesive layer with excellent cohesiveness, heat resistance, etc.

The weight average molecular weight of the base polymer is preferably 300,000 to 3,000,000, more preferably 1,000,000 to 2,800,000, and even more preferably 1,400,000 to 2,500,000. The weight average molecular weight is measured by GPC (gel permeation chromatography; solvent: THF) and calculated in terms of polystyrene.

The adhesive composition may further contain any suitable crosslinking agent. Examples of crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, peroxide-based crosslinking agents, melamine-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, carbodiimide-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, and amine-based crosslinking agents. Isocyanate-based crosslinking agents, epoxy-based crosslinking agents, and peroxide-based crosslinking agents are preferred. Only one type of crosslinking agent may be used, or two or more types may be used in combination.

The content of the crosslinking agent is preferably 40 parts by weight or less, and more preferably 30 parts by weight or less, per 100 parts by weight of the base polymer. By keeping the content of the crosslinking agent within the above range, whitening of the adhesive composition can be suppressed. The content of the crosslinking agent is, for example, 0.01 parts by weight or more.

The adhesive composition may further contain any suitable additive. Specific examples of additives include silane coupling agents, tackifiers, plasticizers, pigments, dyes, fillers, antioxidants, anti-aging agents, conductive materials, UV absorbers, light stabilizers, release regulators, softeners, surfactants, and flame retardants. The types, combinations, amounts, etc. of additives can be appropriately set according to the purpose.

In one embodiment, the second adhesive layer is preferably formed using an adhesive composition containing, as monomer units, a (meth)acrylic polymer (A) containing acrylic acid, an alkyl (meth)acrylate, and an aromatic ring-containing monomer, and a polyether compound (B) having a reactive silyl group. By forming the second adhesive layer using such an adhesive composition, it is possible to suppress the occurrence of color unevenness in a humid environment. In addition, it is possible to suppress the change in phase difference due to the dimensional shrinkage of the polarizing plate in a high-temperature environment, and to provide a polarizing plate with a phase difference layer in which in-plane unevenness in the reflection hue is suppressed.

An aromatic ring-containing monomer is a compound that contains an aromatic group in its structure and a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group. Examples of aromatic groups include a benzene ring, a naphthalene ring, a biphenyl ring, and a heterocyclic ring. Examples of heterocyclic rings include a morpholine ring, a piperidine ring, a pyrrolidine ring, and a piperazine ring. Examples of such compounds include (meth)acrylates that contain an aromatic group. Only one type of aromatic ring-containing monomer may be used, or two or more types may be used in combination.

Specific examples of (meth)acrylates containing an aromatic group include, for example, benzyl (meth)acrylate, phenyl (meth)acrylate, o-phenylphenol (meth)acrylate, phenoxy (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxypropyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, ethylene oxide modified nonylphenol (meth)acrylate, ethylene oxide modified cresol (meth)acrylate, phenol ethylene oxide modified (meth)acrylate, 2 -Hydroxy-3-phenoxypropyl (meth)acrylate, methoxybenzyl (meth)acrylate, chlorobenzyl (meth)acrylate, cresyl (meth)acrylate, polystyryl (meth)acrylate, and other monomers having a benzene ring; hydroxyethylated β-naphthol acrylate, 2-naphthoethyl (meth)acrylate, 2-naphthoxyethyl acrylate, 2-(4-methoxy-1-naphthoxy)ethyl (meth)acrylate, and other monomers having a naphthalene ring; and biphenyl (meth)acrylate, and other monomers having a biphenyl ring. Examples of (meth)acrylates containing a heterocyclic ring include thiol (meth)acrylate, pyridyl (meth)acrylate, and pyrrole (meth)acrylate. Other examples of (meth)acrylic monomers containing a heterocyclic ring include N-acryloylmorpholine, N-acryloylpiperidine, N-methacryloylpiperidine, and N-acryloylpyrrolidine.

Specific examples of vinyl compounds containing an aromatic group include vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, N-vinyl carboxylic acid amides, styrene, and α-methylstyrene.

The aromatic ring-containing monomer may contain a functional group such as sulfonic acid in addition to a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group. Examples of aromatic ring-containing monomers having such a functional group include styrene sulfonic acid and (meth)acryloyloxynaphthalene sulfonic acid.

As the aromatic ring-containing monomer, from the viewpoint of adhesive properties and durability, (meth)acrylates containing aromatic groups are preferred, of which benzyl (meth)acrylate and phenoxyethyl (meth)acrylate are preferred, with benzyl (meth)acrylate being more preferred.

The proportion of aromatic ring-containing monomer in (meth)acrylic polymer (A) is preferably 1 to 50% by weight, more preferably 1 to 35% by weight, even more preferably 1 to 20% by weight, even more preferably 7 to 18% by weight, and particularly preferably 10 to 16% by weight, based on 100% by weight of all constituent monomers of (meth)acrylic polymer (A).

As monomer components other than the aromatic ring-containing monomer in the (meth)acrylic polymer (A), the monomer components exemplified as those used in the above pressure-sensitive adhesive composition can be used.

The content of acrylic acid in (meth)acrylic polymer (A) is as described above.

Any suitable compound having a polyether skeleton can be used as the polyether compound (B). The polyether compound (B) preferably has a polyether skeleton and has a reactive silyl group represented by the general formula: -SiR _a M _3-a at at least one end (wherein R is a monovalent organic group having 1 to 20 carbon atoms which may have a substituent, M is a hydroxyl group or a hydrolyzable group, and a is an integer of 1 to 3. However, when there are multiple Rs, the multiple Rs may be the same or different from each other, and when there are multiple Ms, the multiple Ms may be the same or different from each other).

The polyether skeleton of the polyether compound (B) preferably has a repeating structural unit of a linear or branched oxyalkylene group having 1 to 10 carbon atoms. The structural unit of the oxyalkylene group preferably has 2 to 6 carbon atoms, more preferably 3 carbon atoms. The repeating structural unit of the oxyalkylene group may be a repeating structural unit of one type of oxyalkylene group, or may be a repeating structural unit of a block unit or random unit of two or more types of oxyalkylene groups. Examples of the oxyalkylene group include an oxyethylene group, an oxypropylene group, and an oxybutylene group. Among these oxyalkylene groups, those having a structural unit of an oxypropylene group (particularly, -CH ₂ CH(CH ₃ )O-) are preferred.

In addition to the reactive silyl group, the main chain of the polyether compound (B) preferably consists essentially of a polyether skeleton. Here, the main chain consisting essentially of a polyoxyalkylene chain means that it may contain a small amount of other chemical structures. Examples of other chemical structures include the chemical structure of an initiator when producing a repeating structural unit of an oxyalkylene group related to a polyether skeleton and a linking group with a reactive silyl group. The repeating structural unit of an oxyalkylene group related to a polyether skeleton is preferably 50% by weight or more of the total weight of the polyether compound (B), and more preferably 80% by weight or more.

As the polyether compound (B), a commercially available product may be used. Specific examples of the polyether compound (B) include, for example, MS Polymer S203, S303, S810; SILYL EST250, EST280; SAT10, SAT200, SAT220, SAT350, SAT400 manufactured by Kaneka Corporation, and EXCESTARS S2410, S2420, or S3430 manufactured by Asahi Glass Co., Ltd.

The proportion of the polyether compound (B) in the pressure-sensitive adhesive composition is preferably 0.001 to 20 parts by weight per 100 parts by weight of the (meth)acrylic polymer (A). The content of the polyether compound (B) is more preferably 0.01 parts by weight or more, even more preferably 0.02 parts by weight or more, particularly preferably 0.1 parts by weight or more, and most preferably 0.5 parts by weight or more. The content of the polyether compound (B) is more preferably 10 parts by weight or less, even more preferably 5 parts by weight or less, and particularly preferably 3 parts by weight or less.

A pressure-sensitive adhesive composition containing a (meth)acrylic polymer (A) and a polyether compound (B) is described, for example, in Japanese Patent No. 4,959,014. The disclosure of this publication is incorporated herein by reference.

The second adhesive layer may further contain any suitable crosslinking agent and additive. The types and amounts of the crosslinking agent and additive may be the same as those used in the adhesive composition.

G. Image display device The retardation layer-attached polarizing plate described in the above items A to F can be applied to an image display device. Therefore, the embodiment of the present invention includes an image display device using such a retardation layer-attached polarizing plate. Representative examples of image display devices include liquid crystal display devices and electroluminescence (EL) display devices (e.g., organic EL display devices, inorganic EL display devices). The image display device according to the embodiment of the present invention is provided with the retardation layer-attached polarizing plate described in the above items A to F on the viewing side. The retardation layer-attached polarizing plate is laminated so that the retardation layer is on the image display cell (e.g., liquid crystal cell, organic EL cell, inorganic EL cell) side (so that the polarizer is on the viewing side).

As described above, the polarizing plate with a retardation layer according to the embodiment of the present invention can provide a polarizing plate with a retardation layer in which discoloration of the polarizer edge, particularly discoloration due to sweat, is suppressed. Therefore, the polarizing plate can be suitably used in image display devices with high design quality, such as bezel-less image display devices.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The methods for measuring each property are as follows. Unless otherwise specified, "parts" and "%" in the examples and comparative examples are by weight.

(1) Thickness Thicknesses of 10 μm or less were measured using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name "MCPD-3000"), and thicknesses of more than 10 μm were measured using a digital micrometer (manufactured by Anritsu Co., Ltd., product name "KC-351C").

(2) Artificial Sweat Test The polarizing plate with the adhesive layer and the retardation layer obtained in the examples or comparative examples (protective film/adhesive/polarizer/protective layer/first adhesive layer/first retardation layer/second retardation layer/second adhesive layer/separator) was cut into a square of 50 mm x 50 mm. Then, the separator was peeled off, and the polarizing plate with the retardation layer was attached to alkali-free glass via the adhesive layer. Next, a separate adhesive (adhesive not containing acrylic acid as a monomer component) was transferred to the protective film side, and then attached to alkali-free glass (alkali-free glass/adhesive/protective film/adhesive/polarizer/protective layer/adhesive/alkali-free glass). The polarizing plate sandwiched between the alkali-free glass was wrapped with a nonwoven fabric soaked in 1 mL of artificial sweat, put into a vinyl bag, sealed, and left under conditions of temperature 55°C and relative humidity (RH) 95% for 48 hours. Thereafter, the four corners of the sample were checked with an optical microscope (Olympus, product name: MX61L). The bleached width was measured in the MD direction and the TD direction, and the average value was calculated. If the average value of the bleached width of all four corners was 1000 μm or less, it was judged as ◯ (good), and if the average value of the bleached width of even one corner exceeded 1500 μm, it was judged as × (bad).
The artificial sweat solution was prepared by dissolving 2.5 g of sodium chloride, 19 g of ammonium chloride, 0.63 g of urea, 1.88 g of lactic acid, and 0.32 g of acetic acid in 125 g of pure water, adding sodium hydroxide, and adjusting the pH to 9.5 using a pH meter (HORIBA portable pH ORP meter D-72).

(3) Storage Modulus The storage modulus was measured using a dynamic viscoelasticity device (a viscoelasticity spectrometer, manufactured by Rheometric Scientific, Inc., "ARES device").

<Production Example 1: Preparation of Pressure-Sensitive Adhesive Composition 1>
A monomer mixture containing 91.5 parts by weight of butyl acrylate (BA), 3 parts by weight of acrylic acid (AA), 0.5 parts by weight of 4-hydroxybutyl acrylate (HBA), and 5 parts by weight of acryloylmorpholine (ACMO) was charged into a four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a cooler. Further, 0.1 parts by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator was charged together with 100 parts by weight of ethyl acetate for 100 parts by weight of this monomer mixture, and nitrogen gas was introduced while gently stirring to replace the atmosphere with nitrogen. The liquid temperature in the flask was kept at around 55°C, and a polymerization reaction was carried out for 8 hours to prepare a solution of an acrylic polymer (base polymer A) having a weight average molecular weight (Mw) of 2.5 million.
0.2 parts by weight of an isocyanate crosslinking agent (trimethylolpropane/tolylene diisocyanate adduct, Tosoh Corporation, product name "Coronate L"), 0.3 parts by weight of a peroxide crosslinking agent, benzoyl peroxide (NOF Corporation, product name: Niper BMT), and 0.1 parts by weight of a silane coupling agent (Shin-Etsu Chemical Co., Ltd., product name: KBM403), were blended with 100 parts by weight of the solid content of the obtained solution of base polymer A to prepare adhesive composition 1. The content of acrylic acid in the monomer components used in the polymerization of the base polymer was 3 parts by weight with respect to 100 parts by weight of the total monomer components.

<Production Example 2: Preparation of Pressure-Sensitive Adhesive Composition 2>
A solution of an acrylic polymer (base polymer B) having a weight average molecular weight (Mw) of 2,300,000 was prepared in the same manner as in Production Example 1, except that the monomers used were changed to 74.9 parts by weight of butyl acrylate (BA), 20.0 parts by weight of benzyl acrylate (BzA), 5.0 parts by weight of acrylic acid (AA), and 0.1 parts by weight of 4-hydroxybutyl acrylate (HBA), and the reaction time was changed to 7 hours.
12 parts by weight of an isocyanate-based crosslinking agent (trimethylolpropane/tolylene diisocyanate adduct, manufactured by Tosoh Corporation, product name "Coronate L"), 0.1 parts by weight of a silane coupling agent (product name: KBM403, manufactured by Shin-Etsu Chemical Co., Ltd.), and 1 part by weight of a polyether compound having a reactive silyl group (manufactured by Kaneka Corporation, product name "Silyl SAT10") were mixed with 100 parts by weight of the solid content of the obtained solution of base polymer B to prepare adhesive composition 2. The content of acrylic acid in the monomer components used for polymerization of the base polymer was 5 parts by weight with respect to 100 parts by weight of the total monomer components.

<Production Example 3: Preparation of Pressure-Sensitive Adhesive Composition 3>
A solution of an acrylic polymer (base polymer C) having a weight average molecular weight (Mw) of 2,000,000 was prepared in the same manner as in Production Example 2, except that the monomers used were changed to 94.9 parts by weight of BA, 5 parts by weight of AA, and 0.1 parts by weight of HEA.
0.6 parts by weight of an isocyanate crosslinking agent (trimethylolpropane/tolylene diisocyanate adduct, manufactured by Tosoh Corporation, product name "Coronate L") and 0.1 parts by weight of a silane coupling agent (product name: KBM403, manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed with 100 parts by weight of the solid content of the obtained solution of base polymer C to prepare adhesive composition 3. The content of acrylic acid in the monomer components used in the polymerization of the base polymer was 5 parts by weight with respect to 100 parts by weight of the total monomer components.

<Production Example 4: Preparation of Pressure-Sensitive Adhesive Composition 4>
A solution of an acrylic polymer (base polymer D) having a weight average molecular weight (Mw) of 1,600,000 was prepared in the same manner as in Production Example 1, except that the monomers used were changed to 99 parts by weight of BA and 1 part by weight of HBA.
0.6 parts by weight of an isocyanate-based crosslinking agent (trimethylolpropane/tolylene diisocyanate adduct, manufactured by Tosoh Corporation, product name "Coronate L") and 0.1 parts by weight of a silane coupling agent (product name: KBM403, manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed with 100 parts by weight of the solid content of the obtained solution of base polymer D to prepare adhesive composition 4.

<Production Example 5: Preparation of first retardation layer>
1. Polymerization of polyester carbonate resin Polymerization was carried out using a batch polymerization apparatus consisting of two vertical reactors equipped with stirring blades and a reflux condenser controlled at 100 ° C. Bis[9-(2-phenoxycarbonylethyl)fluoren-9-yl]methane 29.60 parts by mass (0.046 mol), isosorbide (ISB) 29.21 parts by mass (0.200 mol), spiroglycol (SPG) 42.28 parts by mass (0.139 mol), diphenyl carbonate (DPC) 63.77 parts by mass (0.298 mol), and calcium acetate monohydrate 1.19 × 10 ^-2 parts by mass (6.78 × 10 ^-5 mol) as a catalyst were charged. After the inside of the reactor was replaced with nitrogen under reduced pressure, it was heated with a heat medium, and stirring was started when the internal temperature reached 100 ° C. The internal temperature was allowed to reach 220°C 40 minutes after the start of the temperature rise, and the pressure was simultaneously reduced to 13.3 kPa in 90 minutes after the temperature reached 220°C. Phenol vapor by-produced during the polymerization reaction was led to a reflux condenser at 100°C, a small amount of monomer components contained in the phenol vapor were returned to the reactor, and uncondensed phenol vapor was led to a condenser at 45°C and recovered. Nitrogen was introduced into the first reactor to restore the pressure to atmospheric pressure, and the oligomerized reaction liquid in the first reactor was transferred to the second reactor. Next, the temperature rise and pressure reduction in the second reactor were started, and the internal temperature was set to 240°C and the pressure to 0.2 kPa in 50 minutes. Thereafter, polymerization was allowed to proceed until a predetermined stirring power was reached. When the predetermined power was reached, nitrogen was introduced into the reactor to restore the pressure, and the polyester carbonate resin produced was extruded into water, and the strands were cut to obtain pellets.

2. Preparation of Retardation Film The obtained polyester carbonate resin (pellets) was vacuum-dried at 80 ° C. for 5 hours, and then a long resin film having a thickness of 130 μm was produced using a film-forming device equipped with a single-screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder setting temperature: 250 ° C.), a T-die (width 200 mm, setting temperature: 250 ° C.), a chill roll (setting temperature: 120 ° C. to 130 ° C.) and a winder. The obtained polycarbonate resin film was obliquely stretched by a method according to Example 2 of JP-A-2014-194483 to obtain a retardation film having a thickness of 47 μm. The Re (550) of the obtained retardation film was 144 nm, Re (450) / Re (550) was 0.86, the Nz coefficient was 1.21, and the orientation angle (direction of the slow axis) was 45 ° with respect to the longitudinal direction.

<Production Example 6: Preparation of a positive C plate serving as a liquid crystal alignment solidified layer>
20 parts by weight of a side-chain liquid crystal polymer represented by the following chemical formula (the numbers 65 and 35 in the formula indicate the mole percent of the monomer unit, and are conveniently expressed as a block polymer: weight average molecular weight 5000), 80 parts by weight of a polymerizable liquid crystal exhibiting a nematic liquid crystal phase (manufactured by BASF: trade name Paliocolor LC242), and 5 parts by weight of a photopolymerization initiator (manufactured by Ciba Specialty Chemicals: trade name Irgacure 907) were dissolved in 200 parts by weight of cyclopentanone to prepare a liquid crystal coating liquid. Then, the coating liquid was applied to a PET substrate that had been subjected to a vertical alignment treatment by a bar coater, and then the liquid crystal was aligned by heating and drying at 80°C for 4 minutes. This liquid crystal layer was irradiated with ultraviolet light to harden the liquid crystal layer, thereby forming a retardation layer (thickness 4 μm) exhibiting a refractive index characteristic of nz>nx=ny on the substrate.

[Example 1]
1. Preparation of Polarizer As a thermoplastic resin substrate, a long amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 μm) having a Tg of about 75° C. was used. One surface of the resin substrate was subjected to a corona treatment.
A PVA aqueous solution (coating solution) was prepared by adding 13 parts by weight of potassium iodide to 100 parts by weight of a PVA-based resin prepared by mixing polyvinyl alcohol (polymerization degree 4,200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., product name "GOHSEFFIMER Z410") in a ratio of 9:1.
The above PVA aqueous solution was applied to the corona-treated surface of a resin substrate and dried at 60° C. to form a PVA-based resin layer having a thickness of 13 μm, thereby producing a laminate.
The obtained laminate was uniaxially stretched at its free end to 2.4 times its original size in the machine direction (longitudinal direction) between rolls having different peripheral speeds in an oven at 130° C. (auxiliary air stretching treatment).
Next, the laminate was immersed in an insolubilizing bath (a boric acid aqueous solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40° C. for 30 seconds (insolubilizing treatment).
Next, the film was immersed in a dye bath (an aqueous iodine solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 with 100 parts by weight of water) having a liquid temperature of 30° C. for 60 seconds while adjusting the concentration so that the single transmittance (Ts) of the finally obtained polarizer would be 43% (dyeing treatment).
Next, the plate was immersed in a crosslinking bath (a boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40° C. for 30 seconds (crosslinking treatment).
Thereafter, the laminate was immersed in an aqueous boric acid solution (boric acid concentration: 4.0% by weight, potassium iodide concentration: 5.0% by weight) at a liquid temperature of 70° C., and uniaxially stretched in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds to a total stretch ratio of 5.5 times (underwater stretching treatment).
Thereafter, the laminate was immersed in a cleaning bath (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 20° C. (cleaning treatment).
Thereafter, while drying in an oven maintained at 90° C., the laminate was brought into contact with a SUS heated roll having a surface temperature maintained at 75° C. for about 2 seconds (drying shrinkage treatment). The shrinkage rate of the laminate in the width direction due to the drying shrinkage treatment was 2%.
In this manner, a polarizer having a thickness of 5.0 μm was formed on the resin substrate.

2. Preparation of Polarizing Plate An HC-TAC film was attached to the polarizer surface of the resin substrate/polarizer laminate obtained above via a UV-curable adhesive. The HC-TAC film was a triacetyl cellulose (TAC) film (thickness 25 μm) with a hard coat (HC) layer (thickness 7 μm) formed thereon, and the TAC film was attached to the polarizer side.
Separately, 97.0 parts by weight of methyl methacrylate (MMA, Fujifilm Wako Pure Chemical Industries, Ltd., trade name "methyl methacrylate monomer"), 3.0 parts by weight of the copolymerization monomer represented by the above general formula (1e), and 0.2 parts by weight of a polymerization initiator (Fujifilm Wako Pure Chemical Industries, Ltd., trade name "2,2'-azobis (isobutyronitrile)") were dissolved in 200 parts by weight of toluene. Next, a polymerization reaction was carried out for 5.5 hours while heating to 70 ° C. under a nitrogen atmosphere to obtain a boron-containing acrylic resin solution (solid content concentration: 33%). The obtained boron-containing acrylic polymer had a Tg of 110 ° C. and a Mw of 80,000. 20 parts by weight of the obtained boron-containing acrylic resin was dissolved in 80 parts by weight of methyl ethyl ketone to obtain a resin solution (20%). Next, the resin substrate was peeled off, and a resin solution was applied to the surface from which the resin substrate was peeled off using a wire bar. The coating film was then dried at 60°C for 5 minutes to form a protective layer (first protective layer) constituted as a solidified coating film of the resin in an organic solvent solution, thereby obtaining a polarizing plate.
Separately, the adhesive composition 1 obtained in Production Example 1 was uniformly applied to the surface of a 38 μm thick polyethylene terephthalate film (PET film) treated with a silicone-based release agent using a fountain coater, and dried for 2 minutes in an air-circulating thermostatic oven at 155 ° C. to form an adhesive layer 1 (first adhesive layer) having a thickness of 5 μm on the surface of the PET film. The formed adhesive layer 1 was transferred to the first protective layer side of the polarizing plate, and the PET film was peeled off. Next, the first retardation film obtained in Production Example 5 was laminated via the first adhesive layer. At this time, the absorption axis of the polarizer and the slow axis of the first retardation film were laminated at an angle of 45 °. Next, the first retardation layer and the second retardation layer obtained in Production Example 6 were laminated via an ultraviolet-curable adhesive (thickness 1 μm after curing) to obtain a retardation layer-attached polarizing plate (thickness: 85 μm) having a configuration of protective layer (HC layer / TAC film) / adhesive layer / polarizer / first protective layer / first pressure-sensitive adhesive layer / first retardation layer / adhesive layer / second retardation layer. Thereafter, the pressure-sensitive adhesive composition 2 (thickness 20 μm) obtained in Production Example 2 was applied to the surface of the second retardation layer that was not in contact with the first retardation layer to form a second pressure-sensitive adhesive layer. The obtained retardation layer-attached polarizing plate was subjected to the above evaluation. The results are shown in Table 1.

[Example 2]
A polarizing plate with a retardation layer was obtained in the same manner as in Example 1, except that the adhesive composition 3 obtained in Production Example 3 was used instead of the adhesive composition 1 and the adhesive composition 2. The obtained polarizing plate with a retardation layer was subjected to the above-mentioned evaluation. The results are shown in Table 1.

(Comparative Example 1)
A polarizing plate with a retardation layer was obtained in the same manner as in Example 1, except that the adhesive composition 4 obtained in Production Example 4 was used instead of the adhesive composition 1 and the adhesive composition 2. The obtained polarizing plate with a retardation layer was subjected to the above-mentioned evaluation. The results are shown in Table 1.

[evaluation]
As is clear from Table 1, in the retardation layer-attached polarizing plates of the examples of the present invention, discoloration due to artificial sweat was suppressed.

The polarizing plate with a retardation layer according to the embodiment of the present invention can be suitably used in image display devices such as liquid crystal display devices, organic EL display devices, and inorganic EL display devices.

REFERENCE SIGNS LIST 10 Polarizing plate 11 Polarizer 12 Protective layer 13 Protective layer 20 First pressure-sensitive adhesive layer 30 First retardation layer 40 Second retardation layer 50 Second pressure-sensitive adhesive layer 100 Retardation layer-attached polarizing plate

Claims (9)

A polarizing plate including a polarizer, a first pressure-sensitive adhesive layer, a first retardation layer, a second retardation layer, and a second pressure-sensitive adhesive layer, in this order;
The first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer are layers formed from a pressure-sensitive adhesive composition containing a base polymer obtained by polymerizing a monomer component containing acrylic acid. The retardation layer-attached polarizing plate according to claim 1 , wherein the second pressure-sensitive adhesive layer has a storage modulus at 23° C. of 1.0×10 ⁵ Pa or more. The polarizing plate with a retardation layer according to claim 1, wherein the base polymer is a polymer obtained by polymerizing a monomer component containing 1 to 10 parts by weight of acrylic acid per 100 parts by weight of the total monomer components. The polarizing plate with a retardation layer according to claim 1, wherein the polarizing plate further includes at least one protective layer. The polarizing plate with a retardation layer according to claim 1, wherein the first retardation layer functions as a λ/4 plate, the in-plane retardation Re(550) is 100 nm to 190 nm, and Re(450)/Re(550)<1 is satisfied. The polarizing plate with a retardation layer according to claim 1, wherein the thickness of the first retardation layer is 40 μm or less. The polarizing plate with a retardation layer according to claim 1, wherein the refractive index characteristic of the second retardation layer satisfies nz>nx=ny. The polarizing plate with a retardation layer according to claim 4, wherein the protective layer is a solidified or hardened layer of a coating film of a resin in an organic solvent. An image display device comprising a polarizing plate with a retardation layer according to any one of claims 1 to 8.

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