JP2022109995A - Polarizer protection resin composition and polarizing plate with protective layer made of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizer protection resin composition which offers superior adhesion with a polarizer and may prevent troubles such as color loss from edges, and a polarizing plate with a protective layer containing the resin composition.

SOLUTION: A polarizer protection resin composition of the present invention contains a polymer obtained by polymerizing more than 50 pts. wt. of an acrylic monomer and 0 to 50 pts. wt., non-inclusive, of a comonomer represented by a formula (1) below, the polymer having a glass transition temperature of 50°C or higher. (In the formula, X represents a functional group having at least one reactive group selected from a group consisting of a vinyl group, a (meth)acryl 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.)

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2022,JPO&INPIT

Description

TECHNICAL FIELD The present invention relates to a resin composition for protecting a polarizer and a polarizing plate having a protective layer formed from the composition.

A polarizer is typically produced by dyeing a polyvinyl alcohol (PVA) resin film with a dichroic substance such as iodine (for example, Patent Documents 1 and 2). It is known that the polarizer breaks down the iodine complex due to moisture absorption in a moist and heat environment, and iodine is eluted, resulting in a decrease in the degree of polarization and an increase in transmittance (color loss). Since water enters from the edges of the polarizing plate, color loss tends to be noticeable at the edges of the polarizer.

A polarizer is typically used as a polarizing plate including a polarizer and protective layers provided on both sides of the polarizer. In recent years, there have been proposals for thinner polarizers and protective layers, and polarizing plates having a protective layer on only one side of the polarizer due to the demand for thinner thickness. With such a configuration, the absorption of moisture from the edges is faster, and color loss at the edges can be more pronounced. Moreover, when the thickness of the protective layer is thin, the durability may be lowered, and the polarizer may not be protected appropriately.

Japanese Patent No. 5048120 JP 2013-156391 A

The present invention has been made to solve the above-mentioned conventional problems, and its main purpose is to provide a polarizer-protecting polarizer that has excellent adhesion to a polarizer and can prevent problems such as color loss from the edges. An object of the present invention is to provide a resin composition and a polarizing plate comprising a protective layer formed from the resin composition.

（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）。
１つの実施形態においては、上記重合体の重量平均分子量は１０，０００以上である。
１つの実施形態においては、上記反応性基は（メタ）アクリル基および（メタ）アクリルアミド基からなる群より選択される少なくとも１種である。
本発明の別の局面においては、偏光板が提供される。この偏光板は、偏光子と、該偏光子の少なくとも一方の面に、上記偏光子保護用樹脂組成物から形成された保護層と、を備える。
１つの実施形態においては、上記保護層の厚みは０．１μｍ～８μｍである。
１つの実施形態においては、上記偏光子のヨウ素含有量は２重量％～２５重量％である。
１つの実施形態においては、上記偏光子の厚みは８μｍ以下である。 The resin composition for protecting a polarizer of the present invention contains more than 50 parts by weight of an acrylic monomer and more than 0 parts by weight and less than 50 parts by weight of a copolymer represented by formula (1). A polymer obtained by polymerization, wherein the glass transition temperature of the polymer is 50° C. or higher:

(Wherein, X is a vinyl group, a (meth)acryl 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. Represents a selected functional group containing at least one reactive group, and R ¹ and R ² each independently represent a hydrogen atom, an optionally substituted aliphatic hydrocarbon group, or a substituted or an optionally substituted heterocyclic group, and R ¹ and R ² may be linked together to form a ring).
In one embodiment, the polymer has a weight average molecular weight of 10,000 or more.
In one embodiment, the reactive group is at least one selected from the group consisting of (meth)acryl groups and (meth)acrylamide groups.
A polarizing plate is provided in another situation of this invention. This polarizing plate includes a polarizer and a protective layer formed on at least one surface of the polarizer from the resin composition for protecting the polarizer.
In one embodiment, the protective layer has a thickness of 0.1 μm to 8 μm.
In one embodiment, the iodine content of the polarizer is 2% to 25% by weight.
In one embodiment, the thickness of the polarizer is 8 μm or less.

（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）。
本発明の偏光子保護用樹脂組成物から形成された層（保護層）は、偏光子と十分に密着し、浮き、剥がれ等の外観不良の発生を防止し得る。また、端部からの水分の侵入を防止し、偏光子の端部からの色抜けを防止し得る。さらに、上記樹脂組成物から形成された保護層は優れた耐クラック性を有する。そのため、保護層の厚みが薄い場合であっても偏光子を適切に保護し得る。また、上記保護層は粘着剤層との投錨力にも優れるため、例えば、画像表示装置の他の構成部材との積層状態を良好に維持し得る。 ADVANTAGE OF THE INVENTION According to this invention, it is equipped with the resin composition for polarizer protection which is excellent in adhesiveness with a polarizer and can prevent defects, such as color loss from an edge part, and the protective layer formed from this resin composition. A polarizer is provided. Specifically, the resin composition for protecting a polarizer of the present invention comprises more than 50 parts by weight of an acrylic monomer and more than 0 parts by weight and less than 50 parts by weight of a copolymer represented by formula (1). including a polymer obtained by polymerizing a monomer and having a glass transition temperature of 50° C. or higher:

(Wherein, X is a vinyl group, a (meth)acryl 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. Represents a selected functional group containing at least one reactive group, and R ¹ and R ² each independently represent a hydrogen atom, an optionally substituted aliphatic hydrocarbon group, or a substituted or an optionally substituted heterocyclic group, and R ¹ and R ² may be linked together to form a ring).
The layer (protective layer) formed from the resin composition for protecting a polarizer of the present invention adheres sufficiently to the polarizer, and can prevent appearance defects such as lifting and peeling. In addition, it is possible to prevent moisture from entering from the ends of the polarizer and to prevent color loss from the ends of the polarizer. Furthermore, the protective layer formed from the resin composition has excellent crack resistance. Therefore, even when the thickness of the protective layer is thin, the polarizer can be appropriately protected. In addition, since the protective layer has excellent anchoring force with the pressure-sensitive adhesive layer, it can maintain a good lamination state with other constituent members of the image display device, for example.

1 is a schematic cross-sectional view of a polarizer according to one embodiment of the invention; FIG.

Preferred embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

（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）。 A. Polarizer-Protecting Resin Composition The polarizer-protecting resin composition of the present invention is represented by the formula (1) containing more than 50 parts by weight of an acrylic monomer and more than 0 parts by weight and less than 50 parts by weight. including a polymer obtained by polymerizing a comonomer, wherein the glass transition temperature of the polymer is 50° C. or higher:

(Wherein, X is a vinyl group, a (meth)acryl 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. Represents a selected functional group containing at least one reactive group, and R ¹ and R ² each independently represent a hydrogen atom, an optionally substituted aliphatic hydrocarbon group, or a substituted or an optionally substituted heterocyclic group, and R ¹ and R ² may be linked together to form a ring).

A layer (typically, a protective layer) formed using the resin composition for protecting a polarizer of the present invention has excellent adhesion to a polarizer, and even when a thin protective layer is formed, , appearance defects such as lifting and peeling of the protective layer can be prevented. In addition, the layer formed using the resin composition for protecting a polarizer of the present invention can prevent color loss from the edges of the polarizer. Furthermore, the protective layer formed using the resin composition for protecting a polarizer of the present invention is also excellent in crack resistance. Therefore, even when the thickness is thin, the polarizer can be appropriately protected.

（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）。 A-1. Polymer The above polymer is obtained by polymerizing more than 50 parts by weight of an acrylic monomer and more than 0 parts by weight and less than 50 parts by weight of a comonomer represented by the formula (1). can be:

(Wherein, X is a vinyl group, a (meth)acryl 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. Represents a selected functional group containing at least one reactive group, and R ¹ and R ² each independently represent a hydrogen atom, an optionally substituted aliphatic hydrocarbon group, or a substituted or an optionally substituted heterocyclic group, and R ¹ and R ² may be linked together to form a ring).

（式中、Ｒ^４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）。 This polymer typically has a structure represented by the following formula. By polymerizing the copolymerizable monomer represented by the formula (1) and the acrylic monomer component, the polymer has a substituent containing boron in the side chain (for example, a repeating unit of k in the following formula). have. This can improve the adhesion between the polarizer and the layer (protective layer) formed using the resin composition for protecting the polarizer. This boron-containing substituent may be included in the polymer continuously or randomly.

(Wherein, ^R4 represents an arbitrary functional group, and j and k represent integers of 1 or more).

The weight average molecular weight of the polymer is preferably 10,000 or more, more preferably 20,000 or more, even more preferably 35,000 or more, and particularly preferably 50,000 or more. The weight average molecular weight of the polymer is preferably 250,000 or less, more preferably 200,000 or less, and even more preferably 150,000 or less. When the weight average molecular weight of the polymer is within the above range, the crack resistance of the layer (protective layer) formed using the resin composition for protecting a polarizer can be improved. The weight average molecular weight can be measured, for example, by GPC (solvent: dimethylformamide (DMF)).

The glass transition temperature of the polymer is 50°C or higher, preferably 60°C or higher, more preferably 80°C or higher. Also, the glass transition temperature of the polymer is preferably 300° C. or lower, more preferably 200° C. or lower, and still more preferably 120° C. or lower. When the glass transition temperature is within the above range, the crack resistance of the layer (protective layer) formed using the resin composition for protecting a polarizer can be improved.

The polymer comprises more than 50 parts by weight of an acrylic monomer, more than 0 parts by weight and less than 50 parts by weight of a copolymer represented by formula (1), a polymerization initiator, and any It is obtained by polymerizing a monomer composition containing other monomers by any appropriate polymerization method. Solution polymerization is preferably used as the polymerization method. By polymerizing the above polymer by solution polymerization, a polymer having a higher molecular weight can be obtained.

A-1-1. Acrylic Monomer Any appropriate acrylic monomer can be used as the acrylic monomer. Examples thereof include (meth)acrylic acid ester-based monomers having a linear or branched structure and (meth)acrylic acid ester-based monomers having a cyclic structure. As used herein, (meth)acryl refers to acryl and/or methacryl.

Examples of (meth)acrylic acid ester-based monomers having a linear or branched structure include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, and (meth)acrylic acid. isopropyl, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, methyl 2-ethylhexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate and the like. . Preferably, methyl (meth)acrylate is used. The (meth)acrylic acid ester-based monomers may be used alone or in combination of two or more.

Examples of the (meth)acrylic ester-based monomer having a cyclic structure include cyclohexyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate, 1-adamantyl (meth)acrylate, ( meth)dicyclopentenyl acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, biphenyl (meth)acrylate, o-biphenyloxyethyl (meth)acrylate, o-biphenyloxyethoxy Ethyl (meth)acrylate, m-biphenyloxyethyl acrylate, p-biphenyloxyethyl (meth)acrylate, o-biphenyloxy-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, biphenyl group-containing monomers such as o-phenylphenol glycidyl ether acrylate, terphenyl (meth)acrylate, o-terphenyloxyethyl (meth)acrylate and the like. Preferably, 1-adamantyl (meth)acrylate and dicyclopentanyl (meth)acrylate are used. A polymer having a high glass transition temperature can be obtained by using these monomers. These monomers may be used alone or in combination of two or more.

A silsesquioxane compound having a (meth)acryloyl group may be used instead of the (meth)acrylic acid ester-based monomer. By using a silsesquioxane compound, an acrylic polymer having a high glass transition temperature can be obtained. Silsesquioxane compounds are known to have various skeleton structures, such as cage structures, ladder structures, and random structures. The silsesquioxane compound may have only one of these structures, or may have two or more. Silsesquioxane compounds may be used alone or in combination of two or more.

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

More than 50 parts by weight of acrylic monomer is used. The acrylic monomer is used so that the total amount of the monomer and the copolymer monomer described later is 100 parts by weight.

（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）。 A-1-2. Comonomer A copolymer represented by formula (1) is used as the copolymerizable monomer. By using such a comonomer, a substituent containing boron is introduced into the side chain of the resulting polymer. Therefore, the adhesion between the polarizer, which is typically made of a PVA-based resin, and the layer (protective layer) formed using the resin composition for protecting the polarizer can be improved. In addition, the water resistance of the layer itself formed using the polarizer-protecting resin composition is improved, and color loss from the edges of the polarizer can be prevented. Comonomers may be used alone or in combination of two or more.

(Wherein, X is a vinyl group, a (meth)acryl 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. Represents a selected functional group containing at least one reactive group, and R ¹ and R ² each independently represent a hydrogen atom, an optionally substituted aliphatic hydrocarbon group, or a substituted or an optionally substituted heterocyclic group, and R ¹ and R ² may be linked together to form a ring).

As the aliphatic hydrocarbon group, an optionally substituted linear or branched C 1-20 alkyl group, an optionally substituted C 3-20 cyclic alkyl group , and alkenyl groups having 2 to 20 carbon atoms. Examples of the aryl group include an optionally substituted phenyl group having 6 to 20 carbon atoms and a naphthyl group having 10 to 20 carbon atoms which may have a substituent. The heterocyclic group includes a 5- or 6-membered ring group containing at least one optionally substituted heteroatom. R ¹ and R ² may be linked together 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, more preferably a hydrogen atom.

The reactive group contained in the functional group represented by X above includes a vinyl group, a (meth)acryl group, a styryl group, a (meth)acrylamide group, a vinyl ether group, an epoxy group, an oxetane group, a hydroxyl group, an amino group, and an aldehyde group. , and at least one selected from the group consisting of a carboxyl group. Preferably, the reactive groups are (meth)acryl and/or (meth)acrylamide groups. By having these reactive groups, the adhesion between the polarizer and the layer (protective layer) formed using the resin composition for protecting the polarizer can be improved.

（式中、Ｚ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、Ｙはフェニレン基またはアルキレン基を表す）。 In one embodiment, the functional group represented by X is preferably a functional group represented by the following formula.

(Wherein Z is a vinyl group, a (meth)acryl 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 group consisting of a carboxyl group represents a selected functional group containing at least one reactive group, and Y represents a phenylene group or an alkylene group).

Further, as the copolymerizable monomer represented by the general formula (1), specifically, the following compounds can be used.

The comonomer represented by Formula (1) is used in a content of more than 0 parts by weight and less than 50 parts by weight. It is preferably 0.01 to 50 parts by weight, more preferably 0.05 to 20 parts by weight, even more preferably 0.1 to 10 parts by weight, and particularly preferably 0.1 part by weight to 10 parts by weight. 5 to 5 parts by weight. If the content of the comonomer exceeds 50 parts by weight, color loss from the edges may easily occur.

A-1-3. Polymerization Initiator Any appropriate polymerization initiator can be used as the polymerization initiator. Examples thereof include peroxides such as benzoyl peroxide, lauroyl peroxide and sodium peroxide; hydroperoxides such as t-butyl hydroperoxide and cumene hydroperoxide; azo compounds such as azobisisobutyronitrile; These may use only 1 type and may use 2 or more types.

Any appropriate amount can be used as the content of the polymerization initiator. The content of the polymerization initiator is preferably 0.1 to 5 parts by weight, more preferably 0.3 to 2 parts by weight.

As described above, the polymer is preferably obtained by solution polymerizing the above monomers and comonomers. Any appropriate solvent can be used as a solvent that can be used in solution polymerization. For example, water; alcohols such as methyl alcohol, ethyl alcohol and isopropyl alcohol; aromatic or aliphatic hydrocarbons such as benzene, toluene, xylene, cyclohexane and n-hexane; ester compounds such as ethyl acetate; ketones such as acetone and methyl ethyl ketone. Compound; Cyclic ether compounds such as tetrahydrofuran and dioxane. These solvents may be used alone or in combination of two or more. Moreover, you may use together an organic solvent and water.

The polymerization reaction can be conducted at any suitable temperature and time. For example, the polymerization reaction can be carried out in the range of 50°C to 100°C, preferably 60°C to 80°C. The reaction time is, for example, 1 to 8 hours, preferably 3 to 5 hours.

The resin composition for protecting a polarizer of the present invention contains, for example, the above polymer and solvent. The content of the polymer in the polarizer-protecting resin composition is preferably 1 wt % to 30 wt %, more preferably 5 wt % to 20 wt %. When the content of the polymer in the resin composition for protecting a polarizer is within the above range, a desired protective layer can be satisfactorily formed by coating.

A-2. Method for Preparing Polarizer-Protecting Resin Composition In one embodiment, the polarizer-protecting resin composition of the present invention is a polymerization solution obtained by solution polymerization of a monomer and a comonomer. In another embodiment of the present invention, it is obtained by mixing the above polymer and any suitable solvent by any suitable method. As the solvent, the solvent used for the solution polymerization may be used, or another solvent may be used. Ethyl acetate, toluene, methyl ethyl ketone, and cyclopentanone are preferably used as solvents. These solvents may be used alone or in combination of two or more.

Moreover, the resin composition for polarizer protection may further contain arbitrary suitable additives other than the said polymer and solvent as needed. Additives may be used alone or in combination of two or more. These additives can be used in any suitable amount.

B. Polarizing Plate The polarizing plate of the present invention includes a polarizer and a protective layer formed on at least one surface of the polarizer from the resin composition for protecting the polarizer. The protective layer formed from the resin composition for protecting a polarizer has excellent adhesion to the polarizer. Therefore, even when the thickness of the polarizer is small, it is possible to prevent appearance defects such as floating and peeling of the protective layer from the polarizer. In addition, it is possible to prevent color loss from the edge of the polarizer. Furthermore, this protective layer is also excellent in crack resistance. Therefore, even when the thickness is thin, the polarizer can be properly protected.

B-1. Overview of Polarizing Plate FIG. 1 is a schematic cross-sectional view of a polarizing plate according to one embodiment of the present invention. The illustrated polarizing plate 100 includes a polarizer 10 and a protective layer 20 formed on at least one surface of the polarizer. This protective layer 20 is a layer formed from the resin composition for protecting a polarizer. By forming the protective layer from the resin composition for protecting the polarizer, the adhesion between the protective layer and the polarizer is improved. Therefore, it is possible to prevent moisture from entering from the edges of the polarizing plate and to prevent color loss from the edges. Moreover, since the protective layer 20 is also excellent in crack resistance, it can appropriately protect the polarizer 10 . Furthermore, even when the protective layer 20 is formed only on one side of the polarizer 10, it is possible to prevent color loss of the polarizer from the edges. Therefore, it can contribute to making the polarizing plate 100 thinner. Although the protective layer 20 is formed only on one surface of the polarizer 10 in the illustrated example, the protective layer 20 may be formed on both sides of the polarizer 10 . Alternatively, the protective layer 20 may be formed on one surface of the polarizer 10 and another protective layer may be formed on the other surface of the polarizer 10 . Protective layer 20 is typically formed directly on polarizer 10 (without an adhesive layer or adhesive layer). Forming the protective layer directly on the polarizer can contribute to making the polarizing plate thinner. Also, by directly forming the protective layer, the adhesion between the polarizer and the protective layer can be improved.

The polarizing plate 100 may further include any appropriate functional layer other than the protective layer 20 depending on the purpose. Functional layers include a retardation layer, a light diffusion layer, an antireflection layer, a reflective polarizer, and the like. The functional layer may be laminated on the polarizer 10 side or may be laminated on the protective layer 20 side. It may also include multiple functional layers.

B-2. Polarizer A polarizer is typically a resin film containing a dichroic material. Dichroic substances include, for example, iodine and organic dyes. Dichroic substances may be used alone or in combination of two or more. It preferably contains iodine.

In one embodiment, polarizer 10 preferably has an iodine content of 2% to 25% by weight. In another embodiment of the present invention, polarizer 10 preferably has an iodine content of 10% to 25% by weight, more preferably 15% to 25% by weight. With a polarizer having a high iodine content, color loss may become more pronounced in a moist and hot environment. Therefore, the effect by forming a protective layer using the resin composition for protecting a polarizer can be more exhibited. As used herein, "iodine content" means the total amount of iodine contained in the polarizer (PVA-based resin film). More specifically, iodine exists in the form of iodine ions (I ⁻ ), iodine molecules (I ₂ ), polyiodine ions (I ₃ ⁻ , I ₅ ⁻ ) and the like in the polarizer. The iodine content means the amount of iodine including all these forms. The iodine content can be calculated, for example, by a calibration curve method of fluorescent X-ray analysis. The polyiodine ions are present in the polarizer in the form of a PVA-iodine complex. Absorption dichroism can be expressed in the visible light wavelength range by forming such a complex. Specifically, the complex of PVA and triiodide ion (PVA·I ₃ ⁻ ) has an absorption peak near 470 nm, and the complex of PVA and pentaiodide ion (PVA·I ₅ ⁻ ) has an absorption peak near 600 nm. has an absorption peak at As a result, polyiodine ions can absorb light in a wide range of visible light, depending on their morphology. On the other hand, iodine ions (I ⁻ ) have an absorption peak near 230 nm and are not substantially involved in the absorption of visible light. Therefore, polyiodine ions present in a complex with PVA may be primarily responsible for the absorption performance of the polarizer.

The thickness of the polarizer is preferably 8 μm or less, more preferably 0.6 μm or more and less than 8 μm. In one embodiment, the thickness of the polarizer is preferably 30 μm or less, more preferably 25 μm or less, still more preferably 18 μm or less, particularly preferably 12 μm or less, and even more preferably less than 8 μm. is. The thickness of the polarizer is preferably 1 μm or more. In another embodiment, the thickness of the polarizer is preferably 5 μm or less, more preferably 2.5 μm or less, even more preferably 2 μm or less, and particularly preferably 1.5 μm or less. On the other hand, the thickness of the polarizer is preferably 0.6 μm or more, more preferably 1.0 μm or more.

The single transmittance of the polarizer is, for example, 30% or more. The theoretical upper limit of single transmittance is 50%, and the practical upper limit is 46%. In addition, the single transmittance (Ts) is a Y value measured with a 2-degree field of view (C light source) of JIS Z8701 and corrected for visibility. product name: V7100).

Further, the polarization degree of the polarizer is, for example, 99.0% or more, preferably 99.5% or more, more preferably 99.9% or more. As described above, the polarizing plate of the present invention can prevent color loss from the edges. Therefore, even when the degree of polarization of the polarizer is high, the degree of polarization can be favorably maintained.

B-2-1. Method for Producing Polarizer The polarizer can be produced by any appropriate method. For example, a PVA-based resin film can be produced by subjecting it to a swelling process, a dyeing process, a cross-linking process, a stretching process, a washing process, and a drying process. In one embodiment, the PVA-based resin film may be a PVA-based resin layer formed on a substrate. A laminate of a base material and a resin layer can be obtained, for example, by a method of coating a base material with a coating liquid containing the PVA-based resin, a method of laminating a PVA-based resin film on a base material, or the like. Any suitable resin substrate can be used as the substrate, for example, a thermoplastic resin substrate can be used.

B-2-1-1. PVA-based resin film Examples of PVA-based resins that form the PVA-based resin film include polyvinyl alcohol and ethylene-vinyl alcohol copolymers. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. An ethylene-vinyl alcohol copolymer is obtained by saponifying an ethylene-vinyl acetate copolymer. The saponification degree of the PVA-based resin is usually 85 mol% or more and less than 100 mol%, preferably 95.0 mol% to 99.99 mol%, more preferably 99.0 mol% to 99.99 mol%. be. The degree of saponification can be determined according to JIS K 6726-1994. By using a PVA-based resin having such a degree of saponification, a polarizer with excellent durability can be obtained.

The average degree of polymerization of the PVA-based resin can be appropriately selected depending on the purpose. The average degree of polymerization is usually 1,000 to 10,000, preferably 1,200 to 4,500, more preferably 1,500 to 4,300. The average degree of polymerization can be determined according to JIS K 6726-1994.

The thickness of the PVA-based resin film can be set according to the desired thickness of the polarizer. The thickness of the PVA-based resin film is, for example, 0.5 μm to 200 μm. By using the dyeing solution described later, for example, even if the PVA-based resin film has a thickness of less than 10 μm, it can be sufficiently dyed in a short time, and can be imparted with properties capable of sufficiently functioning as a polarizer.

As described above, the polarizer can be produced, for example, by subjecting a PVA-based resin film to a swelling process, a dyeing process, a cross-linking process, a stretching process, a washing process, and a drying process. Each step is performed at any appropriate timing. Also, if necessary, any step other than the dyeing step may be omitted, a plurality of steps may be performed simultaneously, or each step may be performed a plurality of times. Each step will be described below.

B-2-1-2. Stretching In the stretching treatment, the PVA-based resin film is typically uniaxially stretched 3 to 7 times its original length. The PVA-based resin film is subjected to dry stretching. Dry stretching is preferable because the stretching process can be performed in a wider temperature range. The temperature for dry stretching is, for example, 50°C to 200°C, preferably 80°C to 180°C, more preferably 90°C to 160°C. The stretching direction may be the longitudinal direction (MD direction) of the film or the width direction (TD direction) of the film. The stretching direction can correspond to the absorption axis direction of the resulting polarizer.

B-2-1-3. Dyeing The dyeing step is a step of dyeing the PVA-based resin film with a dichroic substance. It is preferably carried out by adsorbing a dichroic substance. Examples of the adsorption method include a method of immersing the PVA-based resin film in a dyeing solution containing a dichroic substance, a method of coating the PVA-based resin film with the dyeing solution, and a method of spraying the dyeing solution onto the PVA-based resin film. and the like. A preferred method is to immerse the PVA-based resin film in a dyeing solution. This is because the dichroic substance can be well adsorbed.

Examples of the dichroic substance include iodine and dichroic dyes, as described above. Iodine is preferred. When iodine is used as the dichroic substance, an aqueous iodine solution is preferably used as the staining solution. The iodine content of the aqueous iodine solution is preferably 0.04 to 5.0 parts by weight per 100 parts by weight of water. In one embodiment, the content of iodine in the aqueous iodine solution is preferably 0.3 parts by weight or more with respect to 100 parts by weight of water. In order to increase the solubility of iodine in water, it is preferable to add an iodide to the iodine aqueous solution. Potassium iodide is preferably used as the iodide. The content of iodide is preferably 0.3 to 15 parts by weight with respect to 100 parts by weight of water.

The temperature of the staining solution during staining can be set to any appropriate value. For example, 20°C to 50°C. When the PVA-based resin film is immersed in the dyeing solution, the immersion time is, for example, 1 second to 1 minute.

In one embodiment, the dyeing bath is a solution containing iodide and an oxidizing agent for iodide ions. This oxidizing agent is an ionic compound consisting of cations and anions. In this staining solution, polyiodine ions are formed by oxidation of iodine ions. As a result, the content of polyiodine ions contained in the dyeing solution is increased, and the PVA-based resin film can be efficiently dyed. Furthermore, the content of polyiodine ions in the dyeing solution can be increased with a smaller amount of iodine than in the case where the dyeing solution is prepared by adding iodine to water or an aqueous solution containing iodide. Also, in this embodiment, the iodine content in the dyeing solution can be adjusted by adding an oxidizing agent for iodine ions to the dyeing solution. Therefore, the content of polyiodide ions in the dyeing solution can be adjusted more easily.

The content of iodide contained in the dyeing solution is preferably 1 to 40 parts by weight, more preferably 3 to 30 parts by weight, per 100 parts by weight of the solvent. If the iodide content is within the above range, sufficient polyiodide ions can be formed in the dyeing solution. Examples of iodides include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. etc. Potassium iodide is preferred.

In one embodiment, an ionic compound consisting of cations and anions is used as an oxidizing agent for iodide ions. Examples of the anion or cation include Fe ³⁺ , Ag ⁺ , Ag ²⁺ , Au ⁺ , Au ³⁺ , Co ³⁺ , Cu ²⁺ , Mn ³⁺ , Pt ²⁺ cations, Br ^3- , ClO ₃ ^- , ClO ₂ ^- , ClO ⁻ , Cr ₂ O ₇ ²⁻ , NO ₃ ⁻ , MnO ₄ ^{− and} the like. Trivalent iron ions (Fe ³⁺ ) are preferred. Trivalent iron ions are present in the staining solution as divalent iron ions after oxidation of the iodide ions. Trivalent iron ions and divalent iron ions can be incorporated into the PVA-based resin film during the dyeing process. These iron ions have the effect of dehydrating PVA. Therefore, it is possible to prevent the polyiodine ions from escaping from the PVA-based resin film in subsequent steps. As a result, the dyeability of the PVA-based resin film can be further improved, which is preferable.

As the oxidizing agent, any appropriate compound can be used as long as it is an ionic compound in which the desired electrode reaction occurs in the dyeing solution. For example, compounds containing Fe ³⁺ as a cation such as ferric sulfate, ferric chloride, and ferric nitrate; compounds containing MnO ₄ ⁻ as an anion such as potassium permanganate; and Cu ²⁺ such as copper chloride and copper sulfate. as a cation. Since it contains Fe ³⁺ , it is preferable to use at least one compound selected from the group consisting of ferric sulfate, ferric chloride, and ferric nitrate. Only one kind of oxidizing agent may be used, or two or more kinds may be used in combination.

The content of the oxidizing agent in the dyeing solution is preferably 0.1 parts by weight to 10 parts by weight, more preferably 0.5 parts by weight to 10 parts by weight, and still more preferably 0 parts by weight with respect to 100 parts by weight of the solvent. .5 to 4 parts by weight. The content of the oxidizing agent in the dyeing solution can be determined according to the content of iodide contained in the dyeing solution.

The molar ratio of iodide to oxidizing agent can be set to any suitable value, for example 2/1 to 50/1, preferably 10/1 to 50/1. If the molar ratio between iodide and oxidizing agent is within the above range, the oxidizing agent can sufficiently function as an oxidizing agent for iodide ions.

Iodides and oxidizing agents can be used in any suitable combination. For example, a combination of potassium iodide as the iodide and ferric sulfate as the oxidizing agent is preferable because a polarizer having excellent properties such as durability can be obtained.

Any appropriate solvent can be used as the solvent for the dyeing solution, and water is usually used.

The dyeing solution may contain any suitable other compound besides iodide and oxidizing agent. For example, the staining solution may further contain iodine. When the dyeing solution further contains iodine, the iodine content in the dyeing solution is, for example, 1 part by weight or less per 100 parts by weight of the solvent.

B-2-1-4. Swelling The swelling step is usually performed before the dyeing step. In one embodiment, the swelling step may be performed with the dyeing step in the same immersion bath. The swelling step is performed, for example, by immersing the PVA-based resin film in a swelling bath. Any appropriate liquid can be used as the swelling bath, for example, water such as distilled water or pure water is used. The swelling bath may contain any suitable other ingredients besides water. Other components include solvents such as alcohols, additives such as surfactants, iodides, and the like. Examples of iodides include those exemplified above. Potassium iodide is preferably used. The temperature of the swelling bath is, for example, 20°C to 45°C. Also, the immersion time is, for example, 10 seconds to 300 seconds.

B-2-1-5. Cross-linking In the cross-linking step, a boron compound is usually used as a cross-linking agent. Boron compounds include, for example, boric acid and borax. Boric acid is preferred. In the cross-linking step, the boron compound is usually used in the form of an aqueous solution.

When an aqueous boric acid solution is used, the concentration of boric acid in the aqueous boric acid solution is, for example, 2% to 15% by weight, preferably 3% to 13% by weight. The boric acid aqueous solution may further contain iodides such as potassium iodide, zinc compounds such as zinc sulfate and zinc chloride.

The cross-linking step can be performed by any suitable method. Examples include a method of immersing a PVA-based resin film in an aqueous solution containing a boron compound, a method of applying an aqueous solution containing a boron compound to the PVA-based resin film, or a method of spraying an aqueous solution containing a boron compound onto the PVA-based resin film. be done. Immersion in an aqueous solution containing a boron compound is preferred.

The temperature of the solution used for crosslinking is, for example, 25°C or higher, preferably 30°C to 85°C, more preferably 40°C to 70°C. The immersion time is, for example, 5 seconds to 800 seconds, preferably 8 seconds to 500 seconds.

B-2-1-6. Washing The washing step is performed using water or an aqueous solution containing the iodide. Typically, it is carried out by immersing the PVA-based resin film in an aqueous solution of potassium iodide. The temperature of the aqueous solution in the washing step is, for example, 5°C to 50°C. The immersion time is, for example, 1 second to 300 seconds.

B-2-1-7. Drying The drying step can be performed by any suitable method. For example, natural drying, air drying, reduced pressure drying, heat drying, etc. can be mentioned, and heat drying is preferably used. When heat drying is performed, the heating temperature is, for example, 30°C to 100°C. Also, the drying time is, for example, 10 seconds to 10 minutes.

B-3. Protective Layer The protective layer 20 is formed on at least one surface of the polarizer 10 . The protective layer 20 is formed using the resin composition for protecting a polarizer.

The thickness of the protective layer 20 can be set to any suitable value depending on the thickness of the polarizer and the glass transition temperature of the polymer. In one embodiment, the thickness of the protective layer is preferably 0.1 μm to 8 μm, more preferably 0.2 μm to 3 μm, even more preferably 0.5 μm to 1 μm. When the thickness of the protective layer is within the above range, it can contribute to thinning of the polarizing plate. As described above, even if the protective layer 20 is thin, it can adequately protect the polarizer 10 and prevent color loss from the edges. If the thickness of the protective layer 20 exceeds 8 μm, the adhesion between the polarizer and the protective layer may deteriorate.

The cross-sectional elastic modulus of the protective layer 20 is preferably 4 GPa to 8 GPa, more preferably 5 GPa to 6 GPa. When the elastic modulus is within the above range, cracks in the protective layer can be prevented. Therefore, even when the thickness is thin, the polarizer can be properly protected. In the present specification, the elastic modulus of the cross section of the protective layer can be measured by the method described in Examples below.

The moisture permeability of the protective layer is preferably 10 g/m ² ·24 h to 2000 g/m ² ·24 h, more preferably 100 g/m ² ·24 h to 1800 g/m ² ·24 h, still more preferably 150 g/m 2 ·24 h. ² ·24h to 1500 g/m ² ·24h. When the moisture permeability is within the above range, it is possible to prevent the polarizer from losing its color due to the penetration of moisture.

The protective layer can be formed by any appropriate method. For example, it can be formed by applying the polarizer-protecting resin composition to the polarizer. Various coating methods include bar coater coating, air knife coating, gravure coating, gravure reverse coating, reverse roll coating, lip coating, die coating, dip coating, offset printing, flexographic printing, and screen printing. method can be adopted. Any appropriate surface modification treatment may be applied to the surface of the polarizer to which the resin composition for protecting the polarizer is applied.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these Examples.

[Production Example 1] Production of Polarizer 1 As a thermoplastic resin substrate, an amorphous isophthalic acid-copolymerized polyethylene terephthalate (IPA-copolymerized PET) film (thickness: 100 µm) having a Tg of 75°C and a water absorption of 0.75% was used. Using. One side of the substrate was subjected to corona treatment, and the corona-treated side was coated with polyvinyl alcohol (degree of polymerization: 4,200, degree of saponification: 99.2 mol%) and acetoacetyl-modified PVA (degree of polymerization: 1,200, degree of acetoacetyl modification: 4.6). %, degree of saponification 99.0 mol% or more, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOSEFIMER Z200") at a ratio of 9:1. A PVA-based resin layer was formed to produce a laminate.
The obtained laminate was stretched 4.5 times in the air at 140° C. in a direction orthogonal to the longitudinal direction of the laminate using a tenter stretching machine (stretching treatment).
Next, the laminate was immersed in an insolubilizing bath (an aqueous boric acid solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 30° C. for 30 seconds (insolubilizing treatment).
Then, the laminated body was dyed with a dyeing solution at 30 ° C. (an aqueous solution in which 24.0 parts by weight of potassium iodide and 2.8 parts by weight of ferric sulfate n-hydrate were added to 100 parts by weight of water, iodide and 21.0/1 molar ratio to oxidizing agent) for 6 seconds for dyeing (dyeing treatment).
Next, it was immersed for 35 seconds in a cross-linking bath at a liquid temperature of 60°C (an aqueous boric acid solution obtained by blending 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with respect to 100 parts by weight of water). (crosslinking treatment).
Thereafter, the laminate was immersed in a cleaning bath (aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 25° C. for 10 seconds (washing treatment).
Then, it was dried in an oven at 60° C. for 60 seconds to obtain a laminate 1 having a PVA-based resin layer (polarizer) with a thickness of 1.2 μm.

[Production Example 2] Production of Polarizer 2 As a substrate, a long amorphous isophthalic acid-copolymerized polyethylene terephthalate (IPA-copolymerized PET) film having a Tg of 75°C and a water absorption of 0.75% (thickness: 100 µm) was used. ) was used. One side of the substrate was subjected to corona treatment, and the corona-treated side was coated with polyvinyl alcohol (degree of polymerization: 4,200, degree of saponification: 99.2 mol%) and acetoacetyl-modified PVA (degree of polymerization: 1,200, degree of acetoacetyl modification: 4.6). %, degree of saponification 99.0 mol% or more, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOSEFIMER Z200") at a ratio of 9:1. A PVA-based resin layer was formed to produce a laminate.
The resulting laminate was uniaxially stretched 2.0 times at the free end in the machine direction (longitudinal direction) between rolls with different peripheral speeds in an oven at 120° C. (in-air auxiliary stretching).
Next, the laminate was immersed in an insolubilizing bath (an aqueous boric acid solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 30° C. for 30 seconds (insolubilizing treatment).
Then, it was immersed in a dyeing bath at a liquid temperature of 30° C. while adjusting the iodine concentration and the immersion time so that the polarizing plate had a predetermined transmittance. In this example, 0.2 parts by weight of iodine was added to 100 parts by weight of water, and 1.5 parts by weight of potassium iodide was added to the resulting iodine aqueous solution for 60 seconds (dyeing treatment). .
Next, it was immersed for 30 seconds in a cross-linking bath at a liquid temperature of 30°C (an aqueous boric acid solution obtained by blending 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with respect to 100 parts by weight of water). (crosslinking treatment).
After that, the laminate is immersed in an aqueous solution of boric acid having a liquid temperature of 70° C. (an aqueous solution obtained by blending 4 parts by weight of boric acid and 5 parts by weight of potassium iodide with respect to 100 parts by weight of water). Meanwhile, the film was uniaxially stretched in the machine direction (longitudinal direction) between rolls with different circumferential speeds so that the total draw ratio was 5.5 (underwater stretching).
After that, the laminate was immersed in a cleaning bath having a liquid temperature of 30° C. (aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) (cleaning treatment).
Then, it was dried in an oven at 60° C. for 60 seconds to obtain a laminate 2 having a PVA-based resin layer (polarizer) with a thickness of 5 μm.

[Production Example 3] Preparation of acrylic adhesive In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser, 99 parts by weight of butyl acrylate and 1 part by weight of 4-hydroxybutyl acrylate were added. A monomer mixture containing was charged. Further, 0.1 part by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator was added to 100 parts by weight of the above monomer mixture (solid content) together with ethyl acetate, and nitrogen gas was introduced while gently stirring. After introducing and purging with nitrogen, the liquid temperature in the flask was kept around 60° C., and polymerization reaction was carried out for 7 hours. After that, ethyl acetate was added to the obtained reaction solution to adjust the solid content concentration to 30%. Thus, a solution of an acrylic polymer (base polymer) having a weight average molecular weight of 1,400,000 was prepared.
Per 100 parts by weight of the solid content of the acrylic polymer solution, 0.095 parts by weight of trimethylolpropane xylylene diisocyanate (manufactured by Mitsui Chemicals, Inc., trade name: Takenate D110N) and 0.3 part of dibenzoyl peroxide are used as a cross-linking agent. Parts by weight, 0.2 parts by weight of organosilane (manufactured by Soken Chemical Co., Ltd., trade name: A100) as a silane coupling agent and a thiol group-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: X41-1810)0. 2 parts by weight and 0.3 parts by weight of an antioxidant (manufactured by BASF, trade name: Irganox 1010) were blended to obtain an acrylic adhesive (solution).

[Example 1] Production of polarizing plate 1 Methyl methacrylate (MMA, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., trade name: methyl methacrylate monomer) 99.9 parts by weight, a copolymer unit represented by general formula (1e) 0.1 parts by weight of the polymer and 0.2 parts by weight of a polymerization initiator (trade name: 2,2'-azobis(isobutyronitrile) manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) were dissolved in 100 parts by weight of toluene. Then, a polymerization reaction was carried out for 5 hours while heating at 70° C. in a nitrogen atmosphere to obtain an acrylic polymer solution (resin composition for protecting a polarizer) 1 (solid concentration: 50% by weight). The obtained acrylic polymer had a weight average molecular weight of 50,000 and a glass transition temperature of 80°C.
The obtained acrylic polymer solution was applied to the polarizer side of the laminate obtained in Production Example 1 so that the thickness after drying was 1 μm to form a protective layer. Next, the thermoplastic resin base material was peeled off from the polarizer, and a polarizing plate 1 was obtained.

[Example 2] Preparation of polarizing plate 2 The content of MMA was 99 parts by weight, the content of the copolymerization monomer was 1 part by weight, and the polymerization initiator was 2 parts by weight (set weight average molecular weight to obtain an acrylic polymer solution (polarizer-protecting resin composition) 2 (solid concentration: 50% by weight) in the same manner as in Example 1, except that the polymerization conditions were changed by changing The obtained acrylic polymer had a weight average molecular weight of 10,000 and a glass transition temperature of 50°C.
A polarizing plate 2 was obtained in the same manner as in Example 1 except that the acrylic polymer solution 2 was used.

[Example 3] Preparation of polarizing plate 3 The acrylic polymer solution (polarizer Protective resin composition) 3 (solid concentration: 50% by weight) was obtained. The obtained acrylic polymer had a weight average molecular weight of 50,000 and a glass transition temperature of 80°C.
A polarizing plate 3 was obtained in the same manner as in Example 1 except that the acrylic polymer solution 3 was used.

[Example 4] Preparation of polarizing plate 4 In the same manner as in Example 1, except that the content of MMA was 99 parts by weight, the copolymerization monomer was 1 part by weight, and the polymerization initiator was 0.1 parts by weight. An acrylic polymer solution (resin composition for protecting a polarizer) 4 (solid concentration: 50% by weight) was obtained. The obtained acrylic polymer had a weight average molecular weight of 100,000 and a glass transition temperature of 90°C.
A polarizing plate 4 was obtained in the same manner as in Example 1 except that the acrylic polymer solution 4 was used.

[Example 5] Production of polarizing plate 5 A polarizing plate 5 was obtained in the same manner as in Example 3, except that the acrylic polymer solution 3 was applied so that the thickness after drying was 0.2 µm.

[Example 6] Preparation of polarizing plate 6 A polarizing plate 6 was obtained in the same manner as in Example 3, except that the acrylic polymer solution 3 was applied so that the thickness after drying was 5 µm.

[Example 7] Preparation of polarizing plate 7 The acrylic polymer solution (polarizer protective resin Composition) 5 (solid concentration: 10% by weight) was obtained. The obtained acrylic polymer had a weight average molecular weight of 50,000 and a glass transition temperature of 80°C.
A polarizing plate 7 was obtained in the same manner as in Example 1 except that the acrylic polymer solution 5 was used.

[Example 8] Preparation of polarizing plate 8 In the same manner as in Example 3, except that 99 parts by weight of dicyclopentanyl acrylate (DCPA, manufactured by Hitachi Chemical Co., Ltd., product name: FA-513AS) was used as a monomer. An acrylic polymer solution (resin composition for protecting a polarizer) 6 (solid concentration: 30% by weight) was obtained. The obtained acrylic polymer had a weight average molecular weight of 50,000 and a glass transition temperature of 150°C.
A polarizing plate 8 was obtained in the same manner as in Example 3 except that the acrylic polymer solution 6 was used.

[Example 9] Preparation of polarizing plate 9 An acrylic polymer solution was prepared in the same manner as in Example 3 except that 99 parts by weight of an adamantyl-based monomer (trade name: MADA, manufactured by Osaka Organic Chemical Industry Co., Ltd.) was used as a monomer. 7 (resin composition for protecting a polarizer) (solid concentration: 30% by weight) was obtained. The obtained acrylic polymer had a weight average molecular weight of 50,000 and a glass transition temperature of 150°C.
A polarizing plate 9 was obtained in the same manner as in Example 3 except that the acrylic polymer solution 7 was used.

[Example 10] Production of polarizing plate 10 A polarizing plate 10 was obtained in the same manner as in Example 3, except that the laminate 2 obtained in Production Example 2 was used as the polarizer.

[Example 11] Production of polarizing plate 11 Polarizing plate 11 was obtained in the same manner as in Example 3, except that acrylic polymer solution 3 was applied to form a protective layer so that the thickness after drying was 10 µm.

(Comparative Example 1) Preparation of polarizing plate C1 Acrylic polymer solution (polarizer-protecting resin composition) C1 (solid content concentration: 50% by weight). The obtained acrylic polymer had a weight average molecular weight of 50,000 and a glass transition temperature of 80°C.
A polarizing plate C1 was obtained in the same manner as in Example 1, except that the acrylic polymer solution C1 was used.

(Comparative Example 2) Production of polarizing plate C2 An acrylic polymer solution (polarizing A child-protecting resin composition) C2 (solid concentration: 1% by weight) was obtained. The obtained acrylic polymer had a weight average molecular weight of 50,000 and a glass transition temperature of 80°C.
A polarizing plate C2 was obtained in the same manner as in Example 1, except that the acrylic polymer solution C2 was used.

(Comparative Example 3) Preparation of polarizing plate C3 An acrylic polymer solution was prepared in the same manner as in Example 1 except that methacrylic acid (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., trade name: methyl acrylate) was used as a monomer. (Resin composition for protecting a polarizer) C3 (solid concentration: 30% by weight) was obtained. The obtained acrylic polymer had a weight average molecular weight of 50,000 and a glass transition temperature of 10°C.
A polarizing plate C3 was obtained in the same manner as in Example 1, except that the acrylic polymer solution C3 was used.

(Comparative Example 4) Preparation of polarizing plate C4 A cycloolefin film (manufactured by Nippon Zeon Co., Ltd., product name: Zeonor, thickness: 25 µm) was dissolved in cyclohexane, and a resin composition for protecting a polarizer (solid content concentration: 5% by weight) was prepared. ) was prepared.
The obtained resin composition for protecting a polarizer was applied to the polarizer of the laminate obtained in Production Example 1 so as to have a thickness of 1 μm after drying to form a protective layer, thereby obtaining a polarizing plate C4.

(Comparative Example 5) Preparation of polarizing plate C5 A triacetyl cellulose (TAC) film (manufactured by Konica Corporation, trade name: KC4UYW, thickness 40 μm) was dissolved in dichloromethane, and a resin composition for protecting a polarizer (solid concentration: 5 weight) was prepared. %) were prepared.
The obtained resin composition for protecting a polarizer was applied to the polarizer of the laminate obtained in Production Example 1 so as to have a thickness of 1 μm after drying to form a protective layer, thereby obtaining a polarizing plate C5.

The following evaluations were performed using the polarizer-protecting resin compositions used in Examples and Comparative Examples and the obtained polarizing plates. Table 1 shows the results.

1. Moisture permeability (Mocon measurement method)
A 25 μm-thick TAC film was coated with the polarizer-protecting resin composition used in each example or comparative example so that the thickness after drying was 1 μm, to prepare a laminate for evaluation. The moisture permeability of this laminate was measured according to JIS K7129-2:2019 under conditions of temperature of 40° C. and humidity of 90%. For the measurement, a MOCON water vapor transmission rate measuring device (manufactured by MOCON, product name: PERMATRAN-W) was used.

2. Elastic modulus <Sample preparation method>
A polarizing plate obtained in an example or a comparative example was embedded in an epoxy resin. The embedded polarizer was then cut with an ultramicrotome. Next, the cut sample was fixed to a predetermined support, and the elastic modulus of the cut surface (side surface) of the protective layer was measured. A nanoindenter (manufactured by Hysitron Inc., product name: Triboindenter) was used for the measurement. Measurement was performed under the following conditions.
Indenter used: Berkovich (triangular pyramid type)
Measurement method: single indentation measurement Measurement temperature: room temperature Indentation depth setting: 50 nm

3. Adhesion (cross-cut peeling test)
The polarizing plate obtained in each example and comparative example was cut into a size of 50 mm×150 mm and used as an evaluation sample.
Using an NT cutter and an adhesion testing jig, eleven vertical and horizontal scratches were made at intervals of 1 mm in the central portion of the evaluation sample on the side of the protective layer. The incision angle was 35°±10°. Next, Sekisui Sellotape (No. 252, width of 24 mm) was applied so as to cover the entire wound, and a spatula for pressure application was used to evenly rub the taped portion 10 times and pressure. After that, the tape was manually peeled off at a high speed in the direction of 45°. The application and peeling of the tape were repeated twice, and the presence or absence of peeling was visually confirmed.
A case where there was no peeling was evaluated as ◯, a case where 1 to 5 peelings were observed was evaluated as Δ, and a case where 6 or more peelings were observed was evaluated as X.

4. Edge Color Loss The acrylic pressure-sensitive adhesive composition obtained in Production Example 3 was evenly applied with a fountain coater to the surface of a polyethylene terephthalate film (separator) treated with a silicone release agent, and then heated at 155°C. It was dried in an air circulation type constant temperature oven for 2 minutes to form an adhesive layer with a thickness of 20 μm on the surface of the separator. Then, this pressure-sensitive adhesive layer was transferred to the polarizer protective layer surface side of the polarizing plate obtained in Examples or Comparative Examples. Also, an adhesive was applied to the polarizer-side surface of the polarizing plate, and a (meth)acrylic resin film A (thickness: 40 μm) having a lactone ring structure was attached to obtain a polarizing plate with an adhesive layer.
The obtained polarizing plate with an adhesive layer (optical film/(adhesive)/polarizer/protective layer/adhesive/separator) was cut into a size (50 mm×50 mm). Then, the separator was peeled off and attached to non-alkali glass via the pressure-sensitive adhesive layer. Then, it was placed under conditions of a temperature of 60°C and a humidity of 90% for 72 hours. After that, the presence or absence of color omission of the polarizer was confirmed with an optical microscope (manufactured by Olympus, product name: MX61L). The amount of color loss was measured from an image of the length of color loss from the edge of the polarizer taken with an optical microscope at a magnification of 10 times. The length of the color loss portion of the polarizer having the longest length (μm) was defined as the length of the color loss portion.
Separately, for Polarizer 1 obtained in Production Example 1 and Polarizer 2 obtained in Production Example 2, the presence or absence of color loss was measured under the same conditions. Based on the color loss of the polarizer alone (polarizer 1: 450 μm, polarizer 2: 150 μm), ◯ if the color loss is less than 45% of the case of the polarizer only, 45% or more and less than 60% was rated as Δ, and those exceeding 60% were rated as x.

5. Weight-average molecular weight of acrylic polymer Using the acrylic polymer obtained in Examples or Comparative Examples, a 0.5% by weight N,N-dimethylformamide (DMF) (salt added) solution was prepared and heated at room temperature. was allowed to stand overnight. Next, the prepared liquid was filtered through a membrane filter (pore size: 0.45 μm), and the filtrate was subjected to GPC measurement. The measurement was performed using the following equipment under the following conditions.
GPC: Agilent, 1200 (manufactured by Agilent Technologies)
<Measurement conditions>
Column temperature: 40°C
Eluent: DMF (with salt added)
Flow rate: 0.4 mL/min Injection volume: 40 μL
Detector: differential refractometer (RI)
Standard sample: polystyrene conversion (PS)

6. Glass Transition Temperature About 5 mg of the acrylic polymer obtained in Examples or Comparative Examples was sampled and subjected to DSC measurement under the following conditions.
Measuring device: manufactured by TA Instruments, product name: Q-2000
<Measurement conditions>
Temperature program: 0℃→150℃→0℃→150℃
Atmospheric gas: N ₂ (50 mL/min)
Measurement speed: 10°C/min

In the polarizing plates obtained in Examples 1 to 11, even when the thickness of the protective layer was thin, color loss from the edges of the polarizer was prevented. In addition, the adhesiveness to the polarizer was excellent, and the polarizer could be protected without being peeled off.

INDUSTRIAL APPLICABILITY The resin composition for protecting a polarizer of the present invention has excellent adhesion to a polarizer, and can provide a thin polarizing plate that prevents color loss at the edges. The polarizing plate of the present invention can be widely applied to liquid crystal panels of liquid crystal televisions, liquid crystal displays, mobile phones, digital cameras, video cameras, portable game machines, car navigation systems, copiers, printers, facsimiles, clocks, microwave ovens, and the like. can.

REFERENCE SIGNS LIST 10 polarizer 20 protective layer 100 polarizing plate

Claims (7)

A polymer obtained by polymerizing more than 50 parts by weight of an acrylic monomer and more than 0 parts by weight and less than 50 parts by weight of a comonomer represented by formula (1), A resin composition for protecting a polarizer, wherein the polymer has a glass transition temperature of 50° C. or higher:

(Wherein, X is a vinyl group, a (meth)acryl 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. Represents a selected functional group containing at least one reactive group, and R ¹ and R ² each independently represent a hydrogen atom, an optionally substituted aliphatic hydrocarbon group, or a substituted or an optionally substituted heterocyclic group, and R ¹ and R ² may be linked together to form a ring). The resin composition for protecting a polarizer according to claim 1, wherein the polymer has a weight average molecular weight of 10,000 or more. The resin composition for protecting a polarizer according to claim 1 or 2, wherein the reactive group is at least one selected from the group consisting of (meth)acryl groups and (meth)acrylamide groups. a polarizer;
A polarizing plate comprising, on at least one surface of the polarizer, a protective layer formed from the resin composition for protecting a polarizer according to any one of claims 1 to 3. 5. The polarizing plate according to claim 4, wherein the protective layer has a thickness of 0.1 μm to 8 μm. 6. The polarizing plate according to claim 4, wherein the iodine content of said polarizer is 2% to 25% by weight. The polarizing plate according to any one of claims 4 to 6, wherein the polarizer has a thickness of 8 µm or less.

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