JP7348986B2 - Polarizing plate comprising a resin composition for protecting a polarizer and a protective layer formed from the composition - Google Patents

Description

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

Polarizers are typically manufactured 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 in a moist heat environment, the iodine complex of a polarizer is destroyed due to moisture absorption, and iodine is eluted, resulting in a decrease in the degree of polarization and an increase in transmittance (color loss). Since moisture enters from the ends of the polarizing plate, color loss tends to become noticeable at the ends of the polarizer.

A polarizer is typically used as a polarizing plate that includes a polarizer and protective layers provided on both sides of the polarizer. In recent years, due to the demand for thinner polarizers and protective layers, proposals have been made for thinning polarizers and protective layers, and for polarizing plates having a protective layer only on one side of the polarizer. In such a configuration, moisture is absorbed from the edges more quickly, and color loss at the edges may become more noticeable. Moreover, when the thickness of the protective layer is thin, durability may be reduced and the polarizer may not be properly protected.

Patent No. 5048120 Japanese Patent Application Publication No. 2013-156391

The present invention has been made to solve the above-mentioned conventional problems, and its main purpose is to provide a polarizer protector that has excellent adhesion to the polarizer and can prevent problems such as color fading from the edges. An object of the present invention is to provide a polarizing plate including a resin composition and 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 copolymerized monomer represented by formula (1). Contains a polymer obtained by polymerization, and the glass transition temperature of the polymer is 50°C or higher:

(wherein, Represents a functional group containing at least one selected reactive group, and R ¹ and R ² each independently represent a hydrogen atom, an aliphatic hydrocarbon group that may have a substituent, or a functional group containing a substituent. represents an aryl group which may have a substituent or a heterocyclic group which may have a substituent, and R ¹ and R ² may be connected to each other to form a ring).
In one embodiment, the weight average molecular weight of the polymer is 10,000 or more.
In one embodiment, the reactive group is at least one selected from the group consisting of (meth)acrylic group and (meth)acrylamide group.
In another aspect of the invention, a polarizing plate is provided. This polarizing plate includes a polarizer and a protective layer formed from the above-mentioned polarizer protective resin composition on at least one surface of the polarizer.
In one embodiment, the thickness of the protective layer is 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。 According to the present invention, there is provided a polarizer protective resin composition that has excellent adhesion to a polarizer and can prevent problems such as color fading from the edges, and a protective layer formed from the resin composition. A polarizing plate is provided. Specifically, the polarizer protecting resin composition 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). It includes a polymer obtained by polymerizing with a monomer, and the glass transition temperature of the polymer is 50°C or higher:

(wherein, Represents a functional group containing at least one selected reactive group, and R ¹ and R ² each independently represent a hydrogen atom, an aliphatic hydrocarbon group that may have a substituent, or a functional group containing a substituent. represents an aryl group which may have a substituent or a heterocyclic group which may have a substituent, and R ¹ and R ² may be connected to each other to form a ring).
The layer (protective layer) formed from the resin composition for protecting a polarizer of the present invention can sufficiently adhere to the polarizer and prevent appearance defects such as lifting and peeling. In addition, it is possible to prevent moisture from entering from the ends and to prevent color fading from the ends of the polarizer. Furthermore, the protective layer formed from the resin composition has excellent crack resistance. Therefore, even if the protective layer is thin, the polarizer can be appropriately protected. Further, since the protective layer has excellent anchoring power with the adhesive layer, it is possible to 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 polarizing plate according to one embodiment of the present invention.

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. Resin composition for protecting a polarizer 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 represented by formula (1). Including a polymer obtained by polymerizing with a comonomer, the glass transition temperature of the polymer is 50 ° C. or higher:

(wherein, Represents a functional group containing at least one selected reactive group, and R ¹ and R ² each independently represent a hydrogen atom, an aliphatic hydrocarbon group that may have a substituent, or a functional group containing a substituent. represents an aryl group which may have a substituent or a heterocyclic group which may have a substituent, and R ¹ and R ² may be connected to each other to form a ring).

The layer (typically, the protective layer) formed using the resin composition for protecting a polarizer of the present invention has excellent adhesion to the polarizer, even when a thin protective layer is formed. , it is possible to prevent poor appearance such as lifting and peeling of the protective layer. Moreover, the layer formed using the resin composition for protecting a polarizer of the present invention can prevent color fading from the ends of the polarizer. Furthermore, the protective layer formed using the resin composition for protecting a polarizer of the present invention also has excellent crack resistance. Therefore, even if the thickness is small, 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 formula (1). Received:

(wherein, Represents a functional group containing at least one selected reactive group, and R ¹ and R ² each independently represent a hydrogen atom, an aliphatic hydrocarbon group that may have a substituent, or a functional group containing a substituent. represents an aryl group which may have a substituent or a heterocyclic group which may have a substituent, and R ¹ and R ² may be connected to each other 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）。
This polymer typically has a structure represented by the following formula. By polymerizing the comonomer represented by formula (1) and the acrylic monomer component, the polymer has a substituent containing boron in the side chain (for example, the repeating unit k in the following formula). have This can improve the adhesion between the polarizer and the layer (protective layer) formed using the polarizer protective resin composition. This boron-containing substituent may be contained continuously or randomly in the polymer.

(In the formula, R ⁶ represents an arbitrary functional group, and j and k represent an integer of 1 or more).

The weight average molecular weight of the above polymer is preferably 10,000 or more, more preferably 20,000 or more, still more preferably 35,000 or more, particularly preferably 50,000 or more. Further, the weight average molecular weight of the above 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, and more preferably 80°C or higher. Further, the glass transition temperature of the polymer is preferably 300°C or lower, more preferably 200°C or lower, and even 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 above polymer contains 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 comonomer represented by formula (1), a polymerization initiator, and an optional It can be obtained by polymerizing a monomer composition containing other monomers using any appropriate polymerization method. As the polymerization method, preferably solution polymerization is used. By polymerizing the above polymer by solution polymerization, a polymer with a higher molecular weight can be obtained.

A-1-1. Acrylic Monomer Any suitable acrylic monomer can be used as the acrylic monomer. Examples include (meth)acrylic acid ester monomers having a linear or branched structure, and (meth)acrylic acid ester monomers having a cyclic structure. In this specification, (meth)acrylic refers to acrylic and/or methacrylic.

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

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-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) Examples include biphenyl group-containing monomers such as 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.

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

As the silsesquioxane compound containing a (meth)acryloyl group, for example, MAC grade and AC grade manufactured by 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.

The acrylic monomer is used in an amount exceeding 50 parts by weight. The acrylic monomer is used so that the total amount together with the copolymerizable monomer described below 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. Copolymerization monomer As the copolymerization monomer, a copolymerization monomer represented by formula (1) is used. By using such a comonomer, a boron-containing substituent is introduced into the side chain of the resulting polymer. Therefore, the adhesion between a polarizer typically made of a PVA-based resin and a layer (protective layer) formed using a polarizer protective resin composition can be improved. Furthermore, the water resistance of the layer itself formed using the polarizer protective resin composition is improved, and color fading from the ends of the polarizer can be prevented. Only one type of copolymerizable monomer may be used, or two or more types may be used in combination.

(wherein, Represents a functional group containing at least one selected reactive group, and R ¹ and R ² each independently represent a hydrogen atom, an aliphatic hydrocarbon group that may have a substituent, or a functional group containing a substituent. represents an aryl group which may have a substituent or a heterocyclic group which may have a substituent, and R ¹ and R ² may be connected to each other to form a ring).

The above-mentioned aliphatic hydrocarbon group includes a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent, and a cyclic alkyl group having 3 to 20 carbon atoms which may have a substituent. , an alkenyl group having 2 to 20 carbon atoms. Examples of the aryl group include a phenyl group having 6 to 20 carbon atoms which may have a substituent, and a naphthyl group having 10 to 20 carbon atoms which may have a substituent. Examples of the heterocyclic group include a 5-membered cyclic group or a 6-membered cyclic group containing at least one heteroatom which may have a substituent. Note that R ¹ and R ² may be connected 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 groups contained in the functional group represented by , and a carboxyl group. Preferably, the reactive groups are (meth)acrylic 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.

(In the formula, Z is from the group consisting of vinyl group, (meth)acrylic group, styryl group, (meth)acrylamide group, vinyl ether group, epoxy group, oxetane group, hydroxyl group, amino group, aldehyde group, and carboxyl group. represents a functional group containing at least one selected 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. 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 0.05 parts by weight to 20 parts by weight. The amount is 5 parts by weight to 5 parts by weight. If the content of the copolymerized monomer exceeds 50 parts by weight, color fading from the edges may easily occur.

A-1-3. Polymerization Initiator Any suitable polymerization initiator can be used as the polymerization initiator. Examples include peroxides such as benzoyl peroxide, lauroyl peroxide, and sodium peroxide; hydroperoxides such as t-butyl hydroperoxide and cumene hydroperoxide; and azo compounds such as azobisisobutyronitrile. These may be used alone or in combination of two or more.

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

As mentioned above, the polymer is preferably obtained by solution polymerizing the above-mentioned monomers and comonomers. As the solvent that can be used in solution polymerization, any suitable solvent can be used. For example, water; alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol; aromatic or aliphatic hydrocarbons such as benzene, toluene, xylene, cyclohexane, n-hexane; ester compounds such as ethyl acetate; ketones such as acetone and methyl ethyl ketone. Compounds include cyclic ether compounds such as tetrahydrofuran and dioxane. These solvents may be used alone or in combination of two or more. Further, an organic solvent and water may be used in combination.

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

The resin composition for protecting a polarizer of the present invention includes, for example, the above polymer and a solvent. The content of the polymer in the resin composition for protecting a polarizer is preferably 1% to 30% by weight, more preferably 5% to 20% by weight. 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 a resin composition for protecting a polarizer In one embodiment, the resin composition for protecting a polarizer of the present invention is a polymer solution obtained by solution polymerizing a monomer and a comonomer. In another embodiment of the invention, it is obtained by mixing the above polymer and any suitable solvent by any suitable method. As the solvent, the solvent used in the solution polymerization described above may be used, or other solvents may be used. Ethyl acetate, toluene, methyl ethyl ketone, and cyclopentanone are preferably used as the solvent. These solvents may be used alone or in combination of two or more.

Moreover, the resin composition for protecting a polarizer may further contain any appropriate additives in addition to the above-mentioned polymer and solvent, if necessary. Only one type of additive may be used, or two or more types may be used in combination. 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 from the above resin composition for protecting the polarizer on at least one surface of the polarizer. The protective layer formed from the above resin composition for protecting a polarizer has excellent adhesion to the polarizer. Therefore, even if the polarizer is thin, poor appearance such as lifting or peeling of the protective layer from the polarizer can be prevented. It is also possible to prevent color loss from the ends of the polarizer. Furthermore, this protective layer also has excellent crack resistance. Therefore, even if the thickness is small, the polarizer can be appropriately protected.

B-1. Outline 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 above resin composition for protecting a polarizer. By forming the protective layer from the above resin composition for protecting a polarizer, the adhesion between the protective layer and the polarizer is improved. Therefore, moisture can be prevented from entering from the ends of the polarizing plate, and color fading from the ends can be prevented. Moreover, since the protective layer 20 has excellent 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 the polarizer from discoloring from the end. Therefore, it can also contribute to making the polarizing plate 100 thinner. In the illustrated example, the protective layer 20 is formed only on one side of the polarizer 10, but the protective layer 20 may be formed on both sides of the polarizer 10. Further, 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. The protective layer 20 is typically formed directly on the 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. Further, 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. Examples of the functional layer include a retardation layer, a light diffusion layer, an antireflection layer, and a reflective polarizer. The functional layer may be laminated on the polarizer 10 side, or may be laminated on the protective layer 20 side. Further, it may include a plurality of functional layers.

B-2. Polarizer A polarizer is typically a resin film containing a dichroic substance. Examples of dichroic substances include iodine and organic dyes. Only one type of dichroic substance may be used, or two or more types may be used in combination. Preferably it contains iodine.

In one embodiment, polarizer 10 preferably has an iodine content of 2% to 25% by weight. In another embodiment of the invention, polarizer 10 preferably has an iodine content of 10% to 25% by weight, more preferably 15% to 25% by weight. In a polarizer with a high iodine content, color loss may become more noticeable in a humid heat environment. Therefore, the effect of forming a protective layer using the above resin composition for protecting a polarizer can be more effectively exhibited. As used herein, "iodine content" means the total amount of iodine contained in the polarizer (PVA resin film). More specifically, in the polarizer, iodine exists in the form of iodine ions (I ⁻ ), iodine molecules (I ₂ ), polyiodine ions (I ₃ ⁻ , I ₅ ⁻ ), etc.; 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. Note that polyiodine ions exist in a state of forming a PVA-iodine complex in the polarizer. By forming such a complex, absorption dichroism can be exhibited in the wavelength range of visible light. Specifically, the complex of PVA and triiodide ion (PVA・I ₃ ⁻ ) has an absorption peak around 470 nm, and the complex of PVA and pentaiodide ion (PVA・I ₅ ⁻ ) has an absorption peak around 600 nm. It has an absorption peak at As a result, polyiodine ions can absorb light in a wide range of visible light depending on their form. On the other hand, iodine ion (I ⁻ ) has an absorption peak around 230 nm and does not substantially participate 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, even more preferably 18 μm or less, particularly preferably 12 μm or less, and even more preferably less than 8 μm. It 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, 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. Note that the theoretical upper limit of the single transmittance is 50%, and the practical upper limit is 46%. In addition, the single transmittance (Ts) is a Y value measured using a 2-degree field of view (C light source) according to JIS Z8701 and subjected to visibility correction.For example, a spectrophotometer with an integrating sphere (made by JASCO Corporation, Product name: V7100).

Further, the degree of polarization of the polarizer is, for example, 99.0% or more, preferably 99.5% or more, and 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 if the degree of polarization of the polarizer is high, the degree of polarization can be maintained favorably.

B-2-1. Method for manufacturing a polarizer A polarizer can be manufactured by any suitable method. For example, a PVA-based resin film can be manufactured by subjecting it to a swelling process, a dyeing process, a crosslinking 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 base material. The laminate of the base material and the resin layer can be obtained, for example, by a method of applying a coating liquid containing the PVA-based resin to the base material, a method of laminating a PVA-based resin film on the base material, or the like. Any suitable resin base material can be used as the base material, for example, a thermoplastic resin base material can be used.

B-2-1-1. PVA Resin Film Examples of the PVA resin forming the PVA resin film include polyvinyl alcohol and ethylene-vinyl alcohol copolymer. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. Ethylene-vinyl alcohol copolymer can be obtained by saponifying ethylene-vinyl acetate copolymer. The degree of saponification of the PVA 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, and more preferably 1,500 to 4,300. Note that 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 depending on the desired thickness of the polarizer. The thickness of the PVA resin film is, for example, 0.5 μm to 200 μm. By using the dyeing solution described below, for example, even if the PVA-based resin film is less than 10 μm, it can be sufficiently dyed in a short time, and it can be given characteristics that allow it to function satisfactorily as a polarizer.

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

B-2-1-2. Stretching In the stretching process, the PVA 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 preferred because the stretching process can be performed in a wider temperature range. The temperature during 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. Note that the stretching direction may correspond to the absorption axis direction of the obtained polarizer.

B-2-1-3. Dyeing The dyeing process is a process of dyeing the PVA resin film with a dichroic substance. Preferably, this is carried out by adsorbing a dichroic substance. The adsorption method includes, for example, immersing the PVA resin film in a dye solution containing a dichroic substance, coating the PVA resin film with the dye solution, and spraying the dye solution onto the PVA resin film. Examples include a method to do so. Preferably, the method involves immersing the PVA resin film in a dyeing solution. This is because dichroic substances can be adsorbed well.

As mentioned above, the dichroic substances include iodine and dichroic dyes. Preferably it is iodine. When using iodine as the dichroic substance, an iodine aqueous solution is preferably used as the staining solution. The iodine content of the iodine aqueous solution is preferably 0.04 parts by weight to 5.0 parts by weight based on 100 parts by weight of water. In one embodiment, the content of iodine in the iodine aqueous solution is preferably 0.3 parts by weight or more based on 100 parts by weight of water. In order to increase the solubility of iodine in water, it is preferable to add iodide to the iodine aqueous solution. As the iodide, potassium iodide is preferably used. The iodide content is preferably 0.3 to 15 parts by weight per 100 parts by weight of water.

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

In one embodiment, the dye bath is a solution containing iodide and an oxidizing agent for iodide ions. This oxidizing agent is an ionic compound consisting of a cation and an anion. In this dyeing solution, polyiodine ions are formed by oxidizing iodine ions. As a result, the content of polyiodine ions contained in the dyeing solution increases, and the PVA resin film can be dyed efficiently. Furthermore, the content of polyiodine ions in the dyeing solution can be increased with a smaller amount of iodine than when the dyeing solution is prepared by adding iodine to water or an aqueous solution containing iodide. Further, 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 polyiodine 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, based on 100 parts by weight of the solvent. If the iodide content is within the above range, sufficient polyiodine 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 a cation and an anion is used as an oxidizing agent for iodine ions. Examples of the anions or cations include cations such as Fe ³⁺ , Ag ⁺ , Ag ²⁺ , Au ⁺ , Au ³⁺ , Co 3+ , Cu ²⁺ , Mn ³⁺ , Pt ²⁺ , Br ^{3- , ClO 3 - ,} _{ClO 2} ^- , ClO ⁻ , Cr ₂ O ₇ ²⁻ , NO ₃ ⁻ , MnO ₄ ⁻ and the like. Preferably it is trivalent iron ion (Fe ³⁺ ). Trivalent iron ions are present in the dyeing solution as divalent iron ions after oxidizing iodine 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 suppress the effect of polyiodine ions coming out of 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.

The oxidizing agent may be any ionic compound that causes the desired electrode reaction in the dyeing solution, and any suitable compound can be used. 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. Examples include compounds containing 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 type of oxidizing agent may be used, or two or more types 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 even more preferably 0. .5 to 4 parts by weight. The content of the oxidizing agent in the dyeing solution can be determined depending on the iodide content contained in the dyeing solution.

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

Iodide and oxidizing agent can be used in any suitable combination. For example, a combination of using 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 suitable solvent can be used as the solvent for the dyeing solution, and water is usually used.

In addition to iodide and oxidizing agents, the dyeing solution may also contain any other suitable compounds. 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 A swelling step is usually carried out before the dyeing step. In one embodiment, the swelling step may be performed together 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 suitable liquid can be used as the swelling bath, and 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, and iodides. Examples of iodides include those listed above. Preferably potassium iodide is used. The temperature of the swelling bath is, for example, 20°C to 45°C. Further, the immersion time is, for example, 10 seconds to 300 seconds.

B-2-1-5. Crosslinking In the crosslinking step, a boron compound is usually used as a crosslinking agent. Examples of the boron compound include boric acid and borax. Preferred is boric acid. In the crosslinking step, the boron compound is usually used in the form of an aqueous solution.

When using a boric acid aqueous solution, the boric acid concentration of the boric acid aqueous 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, zinc chloride, etc.

The crosslinking 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 a PVA-based resin film, or a method of spraying an aqueous solution containing a boron compound onto a PVA-based resin film. It will be done. It is preferable to immerse it in an aqueous solution containing a boron compound.

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 above-mentioned iodide. Typically, this is carried out by immersing a PVA resin film in an aqueous potassium iodide solution. 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. Examples include natural drying, blow drying, reduced pressure drying, heat drying, etc., and heat drying is preferably used. When drying by heating, the heating temperature is, for example, 30°C to 100°C. Further, 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 above resin composition for protecting a polarizer.

The thickness of the protective layer 20 can be set to any appropriate 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 making the polarizing plate thinner. As described above, even if the protective layer 20 is thin, it can appropriately protect the polarizer 10 and prevent color fading from the edges. When the thickness of the protective layer 20 exceeds 8 μm, the adhesion between the polarizer and the protective layer may decrease.

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 can be prevented from occurring in the protective layer. Therefore, even when the thickness is small, the polarizer can be appropriately protected. In this specification, the elastic modulus of the cross section of the protective layer can be measured by the method described in the 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, and even more preferably 150 g/m 2.24 h. ^2.24h to 1500g/m ^2.24h . When the moisture permeability is within the above range, it is possible to prevent moisture from entering and causing color loss in the polarizer.

The above-mentioned protective layer can be formed by any suitable method. For example, it can be formed by applying the polarizer protecting resin composition to the polarizer. There are various coating methods such as 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. Further, the surface of the polarizer to which the polarizer protecting resin composition is applied may be subjected to any appropriate surface modification treatment.

EXAMPLES Hereinafter, the present invention will be specifically explained 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 base material, an amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 μm) with a water absorption rate of 0.75% and a Tg of 75°C was used. Using. Corona treatment was applied to one side of the base material, and polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetoacetyl-modified PVA (degree of polymerization 1200, degree of acetoacetyl modification 4.6) was applied to the corona-treated surface. %, saponification degree of 99.0 mol% or more, manufactured by Nippon Gosei Kagaku Kogyo Co., Ltd., trade name "Gosefimer Z200") in a ratio of 9:1 was applied and dried at 25°C to form a 5 μm thick film. A PVA-based resin layer was formed to produce a laminate.
The obtained laminate was stretched in the air by 4.5 times in a direction perpendicular to the longitudinal direction of the laminate at 140° C. using a tenter stretching machine (stretching treatment).
Next, the laminate was immersed for 30 seconds in an insolubilization 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. (insolubilization treatment).
Next, the laminate was treated with an iodide dyeing solution at 30°C (an aqueous solution containing 24.0 parts by weight of potassium iodide and 2.8 parts by weight of ferric sulfate n-hydrate per 100 parts by weight of water). It was dyed by immersing it in a molar ratio of 21.0/1 to the oxidizing agent for 6 seconds (staining treatment).
Next, it was immersed in a crosslinking bath (boric acid aqueous 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) at a liquid temperature of 60°C for 35 seconds. (Crosslinking treatment).
Thereafter, the laminate was immersed for 10 seconds in a cleaning bath (an 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. (cleaning treatment).
Thereafter, 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 base material, a long, amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 μm) with a water absorption rate of 0.75% and a Tg of 75°C was used. ) was used. Corona treatment was applied to one side of the base material, and polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetoacetyl-modified PVA (degree of polymerization 1200, degree of acetoacetyl modification 4.6) was applied to the corona-treated surface. %, saponification degree of 99.0 mol% or more, manufactured by Nippon Gosei Kagaku Kogyo Co., Ltd., trade name "Gosefimer Z200") in a ratio of 9:1 was coated and dried at 25°C to form a 11 μm thick film. A PVA-based resin layer was formed to produce a laminate.
The obtained laminate was uniaxially stretched free end to 2.0 times in the longitudinal direction (longitudinal direction) between rolls having different circumferential speeds in an oven at 120° C. (in-air assisted stretching).
Next, the laminate was immersed for 30 seconds in an insolubilization 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. (insolubilization treatment).
Next, the polarizing plate was immersed in a dyeing bath at a liquid temperature of 30° C. while adjusting the iodine concentration and immersion time so that the polarizing plate had a predetermined transmittance. In this example, 100 parts by weight of water was mixed with 0.2 parts by weight of iodine and 1.5 parts by weight of potassium iodide. .
Next, it was immersed for 30 seconds in a crosslinking bath (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) at a liquid temperature of 30°C. (Crosslinking treatment).
Thereafter, the laminate was immersed in an aqueous boric acid solution (an aqueous solution obtained by blending 4 parts by weight of boric acid and 5 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 70°C. However, uniaxial stretching was performed between rolls having different circumferential speeds in the longitudinal direction (longitudinal direction) so that the total stretching ratio was 5.5 times (underwater stretching).
Thereafter, the laminate was immersed in a cleaning bath (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 30° C. (cleaning treatment).
Next, it was dried in an oven at 60° C. for 60 seconds to obtain a laminate 2 having a PVA 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 introduction 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 . Furthermore, to 100 parts by weight of the above monomer mixture (solid content), 0.1 parts by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator was charged together with ethyl acetate, and nitrogen gas was introduced while stirring gently. After introducing the flask and purging it with nitrogen, the temperature of the liquid in the flask was maintained at around 60° C. and a polymerization reaction was carried out for 7 hours. Thereafter, ethyl acetate was added to the obtained reaction solution to adjust the solid content concentration to 30%. In this way, a solution of an acrylic polymer (base polymer) having a weight average molecular weight of 1.4 million was prepared.
To 100 parts by weight of the solid content of the above acrylic polymer solution, 0.095 parts by weight of trimethylolpropane xylylene diisocyanate (manufactured by Mitsui Chemicals, trade name: Takenate D110N) as a crosslinking agent and 0.3 parts by weight of dibenzoyl peroxide. 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 0.2 parts by weight of a thiol group-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: X41-1810). 2 parts by weight and 0.3 parts by weight of an antioxidant (trade name: Irganox 1010, manufactured by BASF) were blended to obtain an acrylic adhesive (solution).

[Example 1] Production of polarizing plate 1 99.9 parts by weight of methyl methacrylate (MMA, manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., trade name: methyl methacrylate monomer), copolymer monomer represented by general formula (1e) 0.1 part by weight of polymer and 0.2 part by weight of a polymerization initiator (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., trade name: 2,2'-azobis(isobutyronitrile)) were dissolved in 100 parts by weight of toluene. Next, 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 content concentration: 50% by weight). The weight average molecular weight of the obtained acrylic polymer was 50,000, and the glass transition temperature was 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 to obtain a polarizing plate 1.

[Example 2] Production of polarizing plate 2 The content of MMA was 99 parts by weight, the content of comonomer was 1 part by weight, and 2 parts by weight of a polymerization initiator was used (set weight average molecular weight An acrylic polymer solution (resin composition for protecting a polarizer) 2 (solid content concentration: 50% by weight) was obtained in the same manner as in Example 1, except that the polymerization conditions were changed. The weight average molecular weight of the obtained acrylic polymer was 10,000, and the glass transition temperature was 50°C.
Polarizing plate 2 was obtained in the same manner as in Example 1 except that acrylic polymer solution 2 was used.

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

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

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

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

[Example 8] Production 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., trade name: FA-513AS) was used as the monomer, Acrylic polymer solution (resin composition for protecting polarizer) 6 (solid content concentration: 30% by weight) was obtained. The weight average molecular weight of the obtained acrylic polymer was 50,000, and the glass transition temperature was 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] Production 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 adamantyl monomer (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name: MADA) was used as the monomer. 7 (resin composition for protecting polarizer) (solid content concentration: 30% by weight) was obtained. The weight average molecular weight of the obtained acrylic polymer was 50,000, and the glass transition temperature was 150°C.
Polarizing plate 9 was obtained in the same manner as in Example 3 except that acrylic polymer solution 7 was used.

[Example 10] Production of polarizing plate 10 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 a protective layer was formed by applying acrylic polymer solution 3 so that the thickness after drying was 10 μm.

(Comparative Example 1) Production of polarizing plate C1 Acrylic polymer solution (resin composition for protecting polarizer) C1 (solid content concentration: 50% by weight). The weight average molecular weight of the obtained acrylic polymer was 50,000, and the glass transition temperature was 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 The acrylic polymer solution (polarizing plate Resin composition for child protection) C2 (solid content concentration: 1% by weight) was obtained. The weight average molecular weight of the obtained acrylic polymer was 50,000, and the glass transition temperature was 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 Acrylic polymer A solution (resin composition for protecting a polarizer) C3 (solid content concentration: 30% by weight) was obtained. The weight average molecular weight of the obtained acrylic polymer was 50,000, and the glass transition temperature was 10°C.
Polarizing plate C3 was obtained in the same manner as in Example 1 except that 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 dissolved in cyclohexane. ) was prepared.
The obtained resin composition for protecting a polarizer was applied to the polarizer of the laminate obtained in Production Example 1 to form a protective layer so that the thickness after drying was 1 μm, and a polarizing plate C4 was obtained.

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

The following evaluations were performed using the resin compositions for protecting polarizers used in Examples and Comparative Examples and the obtained polarizing plates. The results are shown in Table 1.

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

2. Elastic modulus <Sample preparation method>
The polarizing plates obtained in Examples or Comparative Examples were embedded in epoxy resin. The embedded polarizing plate was then cut using 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. For the measurement, a nanoindenter (manufactured by Hysitron Inc., product name: Triboindenter) was used. The measurements were conducted under the following conditions.
Indenter used: Berkovich (triangular pyramid type)
Measurement method: Single indentation measurement Measurement temperature: Room temperature Indentation depth setting: 50nm

3. Adhesion (checkerboard peel test)
The polarizing plates obtained in each Example and Comparative Example were cut into a size of 50 mm x 150 mm, and used as evaluation samples.
Eleven scratches were made vertically and horizontally at 1 mm intervals in the center of the protective layer side of the evaluation sample using an NT cutter and an adhesion test jig. The entry angle was 35°±10°. Next, Sekisui Cellotape (No. 252, 24 mm width) was applied so as to cover the entire wound, and the area to which the tape was applied was evenly rubbed and crimped 10 times using a crimping spatula. Thereafter, the tape was peeled off by hand in a 45° direction at high speed. Pasting and peeling of the tape was repeated twice, and the presence or absence of peeling was visually confirmed.
The case where there was no peeling was rated as ○, the case where 1 to 5 pieces of peeling was confirmed was rated as △, and the case where there were 6 or more pieces of peeling was rated as ×.

4. Edge discoloration The acrylic pressure-sensitive adhesive composition obtained in Production Example 3 was uniformly applied to the surface of a polyethylene terephthalate film (separator) treated with a silicone release agent using a fountain coater, and then heated at 155°C. It was dried in an air circulating constant temperature oven for 2 minutes to form an adhesive layer with a thickness of 20 μm on the surface of the separator. Next, this adhesive layer was transferred to the surface side of the polarizer protective layer of the polarizing plate obtained in the example or comparative example. Further, 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 thereto to obtain a polarizing plate with an adhesive layer.
The obtained polarizing plate with adhesive layer (optical film/(adhesive)/polarizer/protective layer/adhesive/separator) was cut into pieces (50 mm x 50 mm). Next, the separator was peeled off and bonded to alkali-free glass via an adhesive layer. Then, it was left at a temperature of 60 degrees and a humidity of 90% for 72 hours. Thereafter, the presence or absence of color loss in the polarizer was confirmed using an optical microscope (manufactured by Olympus, product name: MX61L). The length of color loss from the end of the polarizer was measured from an image taken with an optical microscope at a magnification of 10 times. Among the discolored portions, the longest one was defined as the length (μm) of the discolored portion of the polarizer.
Separately, the presence or absence of color fading was also measured for Polarizer 1 obtained in Production Example 1 and Polarizer 2 obtained in Production Example 2 under the same conditions. Based on the color loss of the polarizer only (Polarizer 1: 450 μm, Polarizer 2: 150 μm), the color loss is less than 45% of the polarizer only, ○, and the color loss is 45% or more and less than 60%. △, and those exceeding 60% were rated ×.

5. Weight average molecular weight of acrylic polymer Using the acrylic polymer obtained in the example or comparative example, a 0.5% by weight N,N-dimethylformamide (DMF) (salt added) solution was prepared, and the solution was heated to room temperature. It was left undisturbed overnight. Next, the prepared solution was filtered through a membrane filter (pore size: 0.45 μm), and the filtrate was used for GPC measurement. The measurements were performed using the following equipment under the following conditions.
GPC: Agilent, 1200 (manufactured by Agilent Technologies)
<Measurement conditions>
Column temperature: 40℃
Eluent: DMF (salt added)
Flow rate: 0.4mL/min Injection volume: 40μL
Detector: Differential refractometer (RI)
Standard sample: polystyrene equivalent (PS)

6. Glass Transition Temperature About 5 mg of the acrylic polymer obtained in the example or comparative example 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℃
Atmosphere gas: _N2 (50mL/min)
Measurement speed: 10℃/min

In the polarizing plates obtained in Examples 1 to 11, color fading from the ends of the polarizer was prevented even when the protective layer was thin. It also had excellent adhesion to the polarizer, making it possible to protect the polarizer without peeling it off.

The resin composition for protecting a polarizer of the present invention has excellent adhesion to a polarizer, and even if it is thin, it can provide a polarizing plate that is prevented from discoloring 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 consoles, car navigation systems, copy machines, printers, faxes, watches, microwave ovens, etc. can.

10 Polarizer 20 Protective layer 100 Polarizing plate

Claims (3)

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 copolymerizable monomer represented by formula ( 1) A resin composition for protecting a polarizer, which does not contain a fluorine-containing monomer as a polymer , and has a glass transition temperature of 50° C. or higher:

(wherein, Represents a functional group containing at least one selected reactive group, and R ¹ and R ² each independently represent a hydrogen atom, an aliphatic hydrocarbon group that may have a substituent, or a functional group containing a substituent. represents an aryl group which may have a substituent or a heterocyclic group which may have a substituent, and R ¹ and R ² may be connected to each other 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 a (meth)acrylic group and a (meth)acrylamide group.

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