WO2023026687A1 - Adhesive composition, polarizing plate, and image display device using same - Google Patents

Abstract

Provided are: an adhesive composition that has a low resistance and excellent reworkability, and can inhibit the occurrence of dents; and a polarizing plate using the adhesive composition. The adhesive composition according to an embodiment of the present invention comprises: a base polymer containing an alkoxy group-containing monomer as a monomer component; an antistatic agent; and a polyoxyethylene sorbitan fatty acid ester. The number of carbon atoms in an aliphatic hydrocarbon group and the sum of the average numbers of added ethylene oxide moieties in the polyoxyethylene sorbitan fatty acid ester, satisfy the following formula:　the sum of the average numbers of added ethylene oxide moieties/ number of carbon atoms in aliphatic hydrocarbon group ≥ 0.4.

Description

Adhesive composition, polarizing plate and image display device using the same

The present invention relates to a pressure-sensitive adhesive composition, a polarizing plate and an image display device using the same.

Image display devices represented by liquid crystal display devices and electroluminescence (EL) display devices (eg, organic EL display devices and inorganic EL display devices) are rapidly spreading. In an image display device, a polarizing plate is typically attached to a display panel via an adhesive layer. 2. Description of the Related Art In recent years, along with the narrowing of frames of image display devices and the development of so-called in-cell image display devices in which a conductive layer for a touch panel is incorporated in the display panel, there is a demand for improvement in antistatic performance of image display devices. Therefore, it is desired to improve the antistatic performance of the pressure-sensitive adhesive layer and to reduce the resistance. However, in a polarizing plate using such an adhesive layer, there is a problem that the durability of the polarizing plate is lowered by adding a large amount of antistatic agent. It is also required that the antistatic function of the pressure-sensitive adhesive layer be stable under heating and humidification tests.

In addition, a polarizing plate having an adhesive layer (hereinafter also referred to as a polarizing plate with an adhesive layer) may be required to have reworkability in the manufacturing process as well as adhesion to the adherend. In recent years, along with the thinning of image display devices, thinning of polarizers, protective layers, and the like is underway. In such a polarizing plate, the polarizer may be damaged during rework, and the yield may decrease. Moreover, through holes may be provided depending on the application in which the polarizing plate is used. For example, a polarizing plate used for applications such as smartphones may have a through hole provided in a portion corresponding to a camera section. This through hole partially reduces the area of the polarizing plate around the through hole. Therefore, stress tends to concentrate on that portion during rework, and the polarizing plate may be damaged. The thinner the polarizing plate, the greater the tendency.

JP 2015-193371 A

The present invention has been made to solve the above-mentioned conventional problems, and the main purpose thereof is to provide a pressure-sensitive adhesive composition that has low resistance, excellent reworkability, and can suppress the occurrence of dents, and An object of the present invention is to provide a polarizing plate using the adhesive composition.

A pressure-sensitive adhesive composition according to an embodiment of the present invention includes a base polymer containing an alkoxy group-containing monomer as a monomer component, an antistatic agent, and a polyoxyethylene sorbitan fatty acid ester. The total average number of ethylene oxide additions contained in this polyoxyethylene sorbitan fatty acid ester and the number of carbon atoms in the aliphatic hydrocarbon group satisfy the following formula:
Total average addition number of ethylene oxide/carbon number of aliphatic hydrocarbon group≧0.4.
In one embodiment, the sum of the average number of ethylene oxide additions is an integer of 1 or greater.
In one embodiment, the aliphatic hydrocarbon group is a monovalent aliphatic hydrocarbon group having 5 to 20 carbon atoms.
In one embodiment, the content of the polyoxyethylene sorbitan fatty acid ester is 0.005 to 5 parts by weight with respect to 100 parts by weight of the base polymer.
In one embodiment, the base polymer contains 20 to 99 parts by weight of the alkoxy group-containing monomer with respect to 100 parts by weight of all monomer components.
In one embodiment, the content of the antistatic agent in the pressure-sensitive adhesive composition is 10 parts by weight or less with respect to 100 parts by weight of the base polymer.
In one embodiment, the alkoxy group-containing monomer is represented by the formula:

(wherein R ¹ is an alkyl group and n is an integer from 1 to 15).
In one embodiment, the base polymer further contains a hydroxyl group-containing monomer as a monomer component.
In one embodiment, the weight average molecular weight of the base polymer is 1-3 million.
In one embodiment, the antistatic agent comprises lithium bis(trifluoromethanesulfonyl)imide, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide or tributylmethylammonium bis(trifluoromethanesulfonyl)imide.
In one embodiment, the pressure-sensitive adhesive composition further contains a silane coupling agent.
A polarizing plate is provided in another situation of this invention. This polarizing plate includes a polarizer, a protective layer, and an adhesive layer formed using the adhesive composition in this order. The pressure-sensitive adhesive layer has a surface resistance value of 5.0×10 ⁹ Ω/□ or less.
In one embodiment, the polarizing plate has a resistance value increase rate of 4000% or less in a humidification test represented by the following formula:
Resistance value increase rate = (resistance value after humidification reliability test/initial resistance value) x 100
Here, the humidification test is performed for 240 hours under conditions of a temperature of 60° C. and a humidity of 95% RH.
In one embodiment, the protective layer is a solidified layer or hardened layer of a coating film of an organic solvent solution.
In one embodiment, the protective layer has through holes.
In still another aspect of the present invention, an image display device is provided. This image display device includes the polarizing plate.

According to an embodiment of the present invention, a pressure-sensitive adhesive composition having low resistance, excellent reworkability, and capable of suppressing the occurrence of dents, and a polarizing plate using the pressure-sensitive adhesive composition are provided. can be done. Furthermore, according to the embodiments of the present invention, it is possible to provide a pressure-sensitive adhesive composition in which change in resistance due to the influence of humidification is suppressed, and a polarizing plate using the pressure-sensitive adhesive composition.

1 is a schematic cross-sectional view of a polarizer according to one embodiment of the invention; FIG. 1 is a schematic cross-sectional view of an image display device according to one embodiment of the present invention; FIG.

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

A. Adhesive Composition The adhesive composition of the embodiment of the present invention contains a base polymer containing an alkoxy group-containing monomer as a monomer component, an antistatic agent, and a polyoxyethylene sorbitan fatty acid ester. The total average number of additions of ethylene oxide contained in this polyoxyethylene sorbitan fatty acid ester and the number of carbon atoms in the aliphatic hydrocarbon group satisfy the following formula. By containing such a polyoxyethylene sorbitan fatty acid ester, it is possible to provide a pressure-sensitive adhesive composition that has low resistance, excellent reworkability, and can suppress the occurrence of dents. Furthermore, the change in resistance value due to the influence of humidification can also be suppressed.
Total average number of additions of ethylene oxide/carbon number of aliphatic hydrocarbon group ≥ 0.4

A-1. Base Polymer As the base polymer, any suitable base polymer used as a base polymer for adhesives can be used. Examples thereof include (meth)acrylic polymers, urethane polymers, silicone polymers, and rubber polymers. A (meth)acrylic polymer is preferred. In this specification, a (meth)acrylic polymer as a base polymer may be referred to as a (meth)acrylic base polymer.

The glass transition temperature (Tg) of the base polymer is preferably -50°C or lower, more preferably -52°C or lower, and still more preferably -55°C or lower. The Tg of the base polymer can be, for example, -75°C or higher. By using such a base polymer, a pressure-sensitive adhesive layer having a low surface resistance can be realized without using a large amount of antistatic agent. The Tg of the base polymer can be calculated as the Tg of the polymer converted from the Tg of each monomer component using the polymerization ratio.

The dielectric constant at 100 kHz of the base polymer is preferably 5.0 or higher, more preferably 5.5 or higher, still more preferably 6.0 or higher, particularly preferably 6.5 or higher, and more particularly Preferably it is 7.0 or more. The dielectric constant of the base polymer can be, for example, 10.0 or less. By using such a base polymer, a pressure-sensitive adhesive layer having a low surface resistance can be realized without using a large amount of antistatic agent.

The base polymer contains an alkoxy group-containing monomer as a monomer component. By using an alkoxy group-containing monomer as a monomer component, a base polymer having the above Tg and dielectric constant can be obtained. As a result, it is possible to realize a pressure-sensitive adhesive layer having a small surface resistance value in spite of a small content of the antistatic agent. Any appropriate monomer having an alkoxy group can be used as the alkoxy group-containing monomer. Alkoxy group-containing monomers may be used alone or in combination of two or more.

Alkoxy groups are preferably linear alkoxy groups. If it is a straight-chain alkoxy group, the Tg and dielectric constant of the obtained (meth)acrylic base polymer can be within the above ranges. Alkoxy group-containing monomers preferably include monomers represented by the formula:

(wherein R ¹ is an alkyl group and n is an integer from 1 to 15).

R ¹ above is any suitable alkyl group, preferably a methyl group or an ethyl group.

Specific examples of alkoxy group-containing monomers include methoxyethyl (meth)acrylate, ethoxyethoxyethyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, and methoxypolyethylene glycol (meth)acrylate.

The content of the alkoxy group-containing monomer in the base polymer is preferably 20 parts by weight to 99 parts by weight, more preferably 30 parts by weight to 90 parts by weight, and still more preferably 100 parts by weight of all monomer components. 30 to 60 parts by weight, more preferably 30 to 50 parts by weight. In one embodiment, the content of the alkoxy group-containing monomer in the base polymer is preferably 50 parts by weight to 99 parts by weight, more preferably 60 parts by weight to 99 parts by weight, based on 100 parts by weight of all monomer components. is.

The (meth)acrylic base polymer preferably contains a hydroxyl group-containing monomer as a monomer component. Any suitable monomer having a hydroxyl group can be used as the hydroxyl group-containing monomer. Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl ( meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, (4-hydroxymethylcyclohexyl)-methyl acrylate. From the viewpoint of improving the durability of the adhesive layer, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred, and 4-hydroxybutyl (meth)acrylate is more preferred. Only one hydroxyl group-containing monomer may be used, or two or more thereof may be used in combination.

The content of the hydroxyl group-containing monomer in the base polymer is preferably 1 to 5 parts by weight, more preferably 1 to 3 parts by weight, based on 100 parts by weight of all the monomer components.

The (meth)acrylic base polymer may contain an alkyl (meth)acrylate as a monomer component. Alkyl (meth)acrylates include alkyl (meth)acrylates having a linear or branched alkyl group having 1 to 18 carbon atoms. The number of carbon atoms in the alkyl group is preferably 3-8, more preferably 3-6. Examples of alkyl groups include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, amyl group, hexyl group, cyclohexyl group, heptyl group, 2-ethylhexyl group, isooctyl group, nonyl group and decyl group. , isodecyl group, dodecyl group, isomyristyl group, lauryl group, tridecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group and the like. Only one type of alkyl (meth)acrylate may be used, or two or more types may be used.

The alkyl (meth)acrylate in the base polymer can be used in any suitable amount. For example, the alkoxy group-containing monomer, the hydroxyl group-containing monomer, and any other monomer component may be used so that the total is 100 parts by weight.

The (meth)acrylic base polymer may further contain other monomer components as necessary. Any appropriate monomer component can be used as the other monomer component. Specifically, aromatic hydrocarbon group-containing monomers such as phenyl (meth) acrylate, phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) ) Carboxyl group-containing monomers such as acrylates, itaconic acid, maleic acid, fumaric acid, crotonic acid, amino group-containing monomers such as N,N-dimethylaminoethyl (meth)acrylate, (meth)acrylamide, N,N-dimethyl ( Amide group-containing monomers such as meth)acrylamide and N,N-diethyl (meth)acrylamide, nitrile group-containing monomers such as (meth)acrylonitrile, hexanediol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri Polyfunctional monomers such as (meth)acrylate and dipentaerythritol hexa(meth)acrylate, epoxy group-containing monomers such as glycidyl (meth)acrylate, and heterocyclic ring-containing monomers such as acryloylmorpholine can be used. Other monomer components may be used alone or in combination of two or more. Other monomer components can be used in any suitable amount. For example, the alkoxy group-containing monomer, the hydroxyl group-containing monomer, and any alkyl (meth)acrylate may be used so that the total is 100 parts by weight.

The (meth)acrylic base polymer has a weight average molecular weight Mw of preferably 1 million to 3 million, more preferably 2 million to 3 million, still more preferably 2 million to 2.8 million. If the weight-average molecular weight Mw is less than 1,000,000, the suppression of cracks may be insufficient. If the weight average molecular weight Mw exceeds 3,000,000, viscosity increase and/or gelation during polymer polymerization may occur.

A-2. Antistatic Agent Any appropriate antistatic agent can be used as the antistatic agent. Typical examples include inorganic cation salts and organic cation salts. Only one kind of antistatic agent may be used, or two or more kinds thereof may be used in combination.

An inorganic cation salt is specifically an inorganic cation-anion salt. As cations constituting the cation part of the inorganic cation salt, representative examples thereof include alkali metal ions. Specific examples include lithium ions, sodium ions, and potassium ions. Lithium ion is preferred. A preferred inorganic cation salt is therefore the lithium salt.

Examples of anions constituting the anion portion of the inorganic cation salt include Cl ⁻ , Br ⁻ , I ⁻ , AlCl ₄ ⁻ , Al ₂ Cl ₇ − , BF ₄ ⁻ , PF ₆ ⁻ , ClO ₄ ⁻ , NO ³ ₋ ^, CH ₃ COO ⁻ , CF ₃ COO ⁻ , CH ₃ SO ₃ ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₃ C ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , NbF ₆ ⁻ , TaF ₆ ⁻ , (CN ) ₂ N ⁻ , C ₄ F ₉ SO ₃ ⁻ , C ₃ F ₇ COO ⁻ , (CF ₃ SO ₂ )(CF ₃ CO)N ⁻ , ^—O ₃ S(CF ₂ ) ₃ SO ₃ ⁻ , and General formulas (1) to (4):
(1): (C _n F _2n+1 SO ₂ ) ₂ N ⁻ (n is an integer of 1 to 10),
(2): CF ₂ (C _m F _2m SO ₂ ) ₂ N ⁻ (m is an integer of 1 to 10),
(3): ^- O ₃ S(CF ₂ ) _l SO ₃ ^- (l is an integer from 1 to 10),
(4): (C _p F _2p+1 SO ₂ )N ⁻ (C _q F _2q+1 SO ₂ ), (p and q are integers from 1 to 10),
The anion represented by is mentioned. Fluorine-containing anions are preferred, and fluorine-containing imide anions are more preferred.

Examples of fluorine-containing imide anions include imide anions having a perfluoroalkyl group. Specific examples include (CF ₃ SO ₂ )(CF ₃ CO)N ⁻ described above, and general formulas (1), (2) and (4):
(1): (C _n F _2n+1 SO ₂ ) ₂ N ⁻ (n is an integer of 1 to 10),
(2): CF ₂ (C _m F _2m SO ₂ ) ₂ N ⁻ (m is an integer of 1 to 10),
(4): (C _p F _2p+1 SO ₂ )N ⁻ (C _q F _2q+1 SO ₂ ), (p and q are integers from 1 to 10),
The anion represented by is mentioned. Preferred are (CF ₃ SO ₂ ) ₂ N ⁻ and (C ₂ F ₅ SO ₂ ) ₂ N ^— (perfluoroalkylsulfonyl)imides represented by the general formula (1), more preferably (CF ₃ It is a bis(trifluoromethanesulfonyl)imide represented by SO ₂ ) ₂ ^N- . Accordingly, a preferred inorganic cation salt that may be used in embodiments of the present invention is lithium bis(trifluoromethanesulfonyl)imide.

The organic cation salt is specifically an organic cation-anion salt. As a cation constituting the cation part of the organic cation salt, typically, an organic onium having an onium ion formed by substitution with an organic group can be mentioned. Examples of onium in organic onium include nitrogen-containing onium, sulfur-containing onium, and phosphorus-containing onium. Nitrogen-containing onium and sulfur-containing onium are preferred. Nitrogen-containing oniums include ammonium cations, piperidinium cations, pyrrolidinium cations, pyridinium cations, cations having a pyrroline skeleton, cations having a pyrrole skeleton, imidazolium cations, tetrahydropyrimidinium cations, dihydropyrimidinium cations, Examples include pyrazolium cations and pyrazolinium cations. Examples of sulfur-containing onium include sulfonium cations. Examples of phosphorus-containing onium include phosphonium cations. Examples of organic groups in the organic onium include alkyl groups, alkoxyl groups, and alkenyl groups. Specific examples of preferred organic oniums include tetraalkylammonium cations (eg, tributylmethylammonium cations), alkylpiperidinium cations, and alkylpyrrolidinium cations. The anions constituting the anion portion of the organic cation salt are as described for the anions constituting the anion portion of the inorganic cation salt. Preferred organic cation salts that may be used in embodiments of the present invention are 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide, tributylmethylammonium bis(trifluoromethanesulfonyl)imide.

The content of the antistatic agent in the pressure-sensitive adhesive composition is preferably 10 parts by weight or less, more preferably 7 parts by weight or less, and still more preferably 5 parts by weight or less with respect to 100 parts by weight of the base polymer. , particularly preferably 3 parts by weight or less. According to an embodiment of the present invention, an adhesive capable of forming an adhesive layer having a small surface resistance value (for example, 5.0×10 ⁹ Ω/□ or less) despite a low antistatic agent content. A composition can be provided. In addition, the use of a large amount of antistatic agent can suppress the occurrence of dents due to softening of the pressure-sensitive adhesive composition (resultingly formed pressure-sensitive adhesive layer). The content of the antistatic agent may be, for example, 0.5 parts by weight or more. If the content of the antistatic agent is too small, the surface resistance value may not be lowered sufficiently.

A-3. Polyoxyethylene Sorbitan Fatty Acid Ester The adhesive composition comprises a polyoxyethylene sorbitan fatty acid ester. Polyoxyethylene sorbitan fatty acid ester has a polyethylene glycol structure in at least part of the hydroxyl group of sorbitan such as 1,4-anhydrosorbitol, 1,5-anhydrosorbitol and 1,4,3,6-dianhydrosorbitol. It refers to an ester of a terminal hydroxyl group of an ether obtained by introducing and a fatty acid. As described above, the total average number of ethylene oxide additions contained in the polyoxyethylene sorbitan fatty acid ester and the number of carbon atoms in the aliphatic hydrocarbon group satisfy the following formula. By including such a polyoxyethylene sorbitan fatty acid ester as a rework improver, it is possible to provide a pressure-sensitive adhesive composition that has low resistance, excellent reworkability, and can suppress the occurrence of dents.
Total average number of additions of ethylene oxide/carbon number of aliphatic hydrocarbon group ≥ 0.4

　Polyoxyethylene sorbitan fatty acid ester can function as a surfactant. In the adhesive layer formed using the above adhesive composition, the hydrophilic group of the polyoxyethylene sorbitan fatty acid ester is on the adherend side and the hydrophobic group is on the adhesive layer side at the interface with the adherend (e.g., glass). It can be unevenly distributed in a state where As a result, excessive increase in the adhesive strength of the adhesive layer can be suppressed, and reworkability can be improved.

In the polyoxyethylene sorbitan fatty acid ester, the total average number of additions of ethylene oxide/the number of carbon atoms in the aliphatic hydrocarbon group is 0.4 or more, preferably 0.5 or more, more preferably 0.8 as described above. more preferably 1.0 or more, more preferably 1.2 or more, and particularly preferably 1.5 or more. The total average number of additions of ethylene oxide/the number of carbon atoms of the aliphatic hydrocarbon group is, for example, 2.0 or less.

Polyoxyethylene sorbitan fatty acid esters of 1,4-anhydrosorbitol and/or 1,5-anhydrosorbitol are preferably used as polyoxyethylene sorbitan fatty acid esters. Specifically, polyoxyethylene sorbitan fatty acid esters represented by the following formulas (A) and (B) can be used.

(wherein, x1, y1, z1, x2, y2, and z2 each independently represent an integer of 0 or greater, and R represents a monovalent aliphatic hydrocarbon group).

The above x1, y1, z1, x2, y2, and z2 each independently represent an integer of 0 or more. x1, y1, z1, x2, y2, and z2 can be set to any suitable values such that the sum of the average number of additions of ethylene oxide/the number of carbon atoms in the aliphatic hydrocarbon group is 0.4 or more. x1, y1, z1, x2, y2, and z2 are, for example, integers of 1 or more, preferably 2 or more. The upper limits of x1, y1, z1, x2, y2, and z2 are not particularly limited, and the total average number of additions of ethylene oxide (for example, the above x1 + y1 + z1 or x2 + y2 + z2) is the total average number of additions of ethylene oxide/aliphatic hydrocarbon group may be any value as long as the value of the number of carbon atoms is within the above range.

The total average number of additions of ethylene oxide contained in the polyoxyethylene sorbitan fatty acid ester (for example, x1 + y1 + z1 or x2 + y2 + z2 above) is the total number of average additions of ethylene oxide / any number of aliphatic hydrocarbon groups having 0.4 or more carbon atoms can be set to an appropriate value of The total average number of ethylene oxide additions is preferably 1 or more, more preferably 7 or more, still more preferably 10 or more, even more preferably 15 or more, and particularly preferably 20 or more. The upper limit of the total average addition number of ethylene oxide contained in the polyoxyethylene sorbitan fatty acid ester is not particularly limited, and is, for example, 50 or less, preferably 25 or less.

R represents a monovalent aliphatic hydrocarbon group. The monovalent aliphatic hydrocarbon group includes any appropriate aliphatic hydrocarbon group such that the average number of additions of ethylene oxide/the number of carbon atoms in the aliphatic hydrocarbon group is 0.4 or more. For example, a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms can be used, preferably a monovalent aliphatic hydrocarbon group having 2 to 20 carbon atoms, more preferably a monovalent aliphatic hydrocarbon group having 3 to 20 carbon atoms. can be used, more preferably a monovalent aliphatic hydrocarbon group having 4 to 20 carbon atoms.

Specific examples of polyoxyethylene sorbitan fatty acid esters include polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, and polyoxyethylene sorbitan monostea. rate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan triisostearate, and the like.

The content of polyoxyethylene sorbitan fatty acid ester can be set to any appropriate amount. It is preferably 0.005 to 5 parts by weight, more preferably 0.01 to 3 parts by weight, still more preferably 0.02 to 1 part by weight, based on 100 parts by weight of the base polymer. is. If the content of the polyoxyethylene sorbitan fatty acid ester is within the above range, the reworkability of the pressure-sensitive adhesive composition can be improved. If the content of the polyoxyethylene sorbitan fatty acid ester is less than 0.005 parts by weight, there is a possibility that sufficient reworkability cannot be obtained. If the content of the polyoxyethylene sorbitan fatty acid ester exceeds 5 parts by weight, there is a possibility that sufficient adhesive strength cannot be exhibited.

A-4. Additives The adhesive composition may further contain additives. Specific examples of additives include powders such as silane coupling agents, cross-linking agents, antioxidants, colorants and pigments, dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, Softeners, anti-aging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, inorganic or organic fillers, metal powders, particles, and foils. Also, a redox system with a reducing agent added may be employed within a controllable range. The type, number, combination, content, etc. of additives can be set to any appropriate value depending on the purpose.

Any appropriate silane coupling agent can be used as the silane coupling agent. The following advantages can be obtained by including a silane coupling agent. A pressure-sensitive adhesive composition using a base polymer containing an alkoxy group-containing monomer has a high polarity, which may result in insufficient pressure-sensitive adhesiveness to a non-polar adherend. By containing a silane coupling agent, sufficient adhesion to various adherends can be obtained, and peeling can be suppressed. Silane coupling agents typically include functional group-containing silane coupling agents. Functional groups include, for example, epoxy group, mercapto group, amino group, isocyanate group, isocyanurate group, vinyl group, styryl group, acetoacetyl group, ureido group, thiourea group, (meth)acrylic group, heterocyclic group, acid Anhydride groups and combinations thereof are included. Silane coupling agents may be used alone or in combination of two or more.

Examples of cross-linking agents include isocyanate-based cross-linking agents and peroxide-based cross-linking agents. Only one kind of the crosslinking agent may be used, or two or more kinds thereof may be used in combination.

Any appropriate antioxidant can be used as the antioxidant. Antioxidants may be used alone or in combination of two or more. Inclusion of antioxidants may provide the following benefits. Base polymers containing alkoxy group-containing monomers have a lower Tg and are softer. By containing an antioxidant, it is possible to suppress shrinkage due to oxidative deterioration from the end surfaces of the polarizing plate and the adhesive layer.

B. Polarizing plate B-1. Overall Configuration of Polarizing Plate A polarizing plate according to an embodiment of the present invention includes a polarizer, a protective layer, and an adhesive layer formed using the adhesive composition in this order. FIG. 1 is a schematic cross-sectional view of a polarizing plate according to one embodiment of the invention. The polarizing plate 100 typically includes a polarizer 10, a protective layer 20 provided on one side of the polarizer 10 (hereinafter also referred to as a first protective layer), and the polarizer 10 of the protective layer 20. It has an adhesive layer 40 provided on the opposite side and a protective layer 30 (hereinafter also referred to as a second protective layer) provided on the other side of the polarizer 10 . Depending on the purpose, the protective layer 30 may be omitted. The pressure-sensitive adhesive layer 40 is provided as the outermost layer, and the polarizing plate can be attached to an image display device (substantially, an image display panel). Practically, it is preferable that a release film is temporarily attached to the surface of the adhesive layer 40 until the polarizing plate is used. By temporarily attaching the release film, it is possible to protect the pressure-sensitive adhesive layer and to form a roll of the polarizing plate.

In an embodiment of the present invention, the polarizing plate has a resistance value increase rate of 4000% or less, more preferably 2000% or less, and still more preferably 1000% or less in a humidification test represented by the following formula. , particularly preferably 500% or less.
Resistance value increase rate = resistance value after humidification reliability test / initial resistance value x 100
Here, the humidification test is performed for 240 hours under conditions of a temperature of 60° C. and a humidity of 95% RH.
In the polarizing plate according to the embodiment of the present invention, a polarizing plate having excellent durability can be realized by setting the rate of increase in resistance value of the polarizing plate within such a range.

The polarizing plate according to the embodiment of the present invention may further contain other functional layers. A representative example of such a functional layer is a retardation layer. The optical properties (for example, refractive index properties, in-plane retardation, Nz coefficient, photoelastic coefficient), thickness, arrangement position, etc. of the retardation layer can be appropriately set according to the purpose.

The polarizing plate according to the embodiment of the present invention may be sheet-shaped or elongated. As used herein, the term "long shape" means an elongated shape whose length is sufficiently long relative to its width, for example, an elongated shape whose length is 10 times or more, preferably 20 times or more, its width. include. A long polarizing plate can be wound into a roll.

In one embodiment, the polarizing plate has through holes. For example, the shape of the through hole may be circular, elliptical, triangular, quadrangular, pentagonal, hexagonal, or octagonal. Also, the through holes are provided at any appropriate positions depending on the purpose. The through-holes may be provided substantially in the center of the longitudinal ends of the rectangular polarizing plate, may be provided at predetermined positions of the longitudinal ends, or may be provided at the corners of the polarizing plate. It may be provided at the ends of the rectangular polarizing plate in the short direction; it may be provided at the central portion of the polarizing plate having an irregular shape as a whole.

The thickness of the polarizing plate can be set to any appropriate value. The thickness of the polarizing plate is, for example, 30 μm to 150 μm, preferably 40 μm to 100 μm, more preferably 50 μm to 80 μm.

The constituent elements of the polarizing plate will be described in more detail below.

B-2. Polarizer A polarizer is typically composed of a resin film containing a dichroic substance (typically iodine). Any appropriate resin film that can be used as a polarizer can be adopted as the resin film. The resin film is typically a polyvinyl alcohol-based resin (hereinafter referred to as "PVA-based resin") film. The resin film may be a single-layer resin film or a laminate of two or more layers.

A specific example of a polarizer composed of a single-layer resin film is a PVA-based resin film that has been dyed with iodine and stretched (typically, uniaxially stretched). The dyeing with iodine is performed by, for example, immersing the PVA-based film in an aqueous iodine solution. The draw ratio of the uniaxial drawing is preferably 3 to 7 times. Stretching may be performed after the dyeing treatment, or may be performed while dyeing. Moreover, you may dye after extending|stretching. If necessary, the PVA-based resin film is subjected to swelling treatment, cross-linking treatment, washing treatment, drying treatment, and the like. For example, by immersing the PVA-based resin film in water and washing it with water before dyeing, it is possible not only to wash away stains and anti-blocking agents on the surface of the PVA-based film, but also to swell the PVA-based resin film to prevent uneven dyeing. etc. can be prevented.

Specific examples of the polarizer obtained using a laminate include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a resin substrate and the resin A polarizer obtained by using a laminate with a PVA-based resin layer formed by coating on a substrate can be mentioned. A polarizer obtained by using a laminate of a resin base material and a PVA-based resin layer formed by coating on the resin base material is obtained, for example, by applying a PVA-based resin solution to the resin base material and drying the resin base material. forming a PVA-based resin layer thereon to obtain a laminate of a resin substrate and a PVA-based resin layer; stretching and dyeing the laminate to use the PVA-based resin layer as a polarizer; obtain. In this embodiment, preferably, a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin is formed on one side of the resin substrate. Stretching typically includes immersing the laminate in an aqueous boric acid solution for stretching. Furthermore, stretching may further include stretching the laminate in air at a high temperature (eg, 95° C. or higher) before stretching in an aqueous boric acid solution, if necessary. In addition, in the present embodiment, the laminate is preferably subjected to drying shrinkage treatment in which the laminate is heated while being conveyed in the longitudinal direction to shrink the laminate by 2% or more in the width direction. Typically, the manufacturing method of the present embodiment includes subjecting the laminate to an in-air auxiliary stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment in this order. By introducing auxiliary stretching, it is possible to improve the crystallinity of PVA and achieve high optical properties even when PVA is coated on a thermoplastic resin. At the same time, by increasing the orientation of PVA in advance, it is possible to prevent problems such as deterioration of orientation and dissolution of PVA when immersed in water in the subsequent dyeing process or stretching process, resulting in high optical properties. can be achieved. Furthermore, when the PVA-based resin layer is immersed in a liquid, disturbance of the orientation of the polyvinyl alcohol molecules and deterioration of the orientation can be suppressed as compared with the case where the PVA-based resin layer does not contain a halide. This can improve the optical properties of the polarizer obtained through treatment steps such as dyeing treatment and underwater stretching treatment in which the laminate is immersed in a liquid. Furthermore, the optical properties can be improved by shrinking the laminate in the width direction by drying shrinkage treatment. The obtained resin substrate/polarizer laminate may be used as it is (that is, the resin substrate may be used as a protective layer for the polarizer), or the resin substrate may be peeled off from the resin substrate/polarizer laminate. Then, any appropriate protective layer may be laminated on the release surface according to the purpose. Details of such a polarizer manufacturing method are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580 (Patent No. 5414738) and Japanese Patent No. 6470455. These publications are incorporated herein by reference in their entirety.

The thickness of the polarizer is preferably 1 μm to 15 μm, more preferably 1 μm to 10 μm, even more preferably 1 μm to 8 μm, and particularly preferably 2 μm to 5 μm.

The polarizer preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The single transmittance of the polarizer is preferably 41.5% to 46.0%, more preferably 43.0% to 46.0%, still more preferably 44.5% to 46.0%. be. The degree of polarization of the polarizer is preferably 97.0% or higher, more preferably 99.0% or higher, still more preferably 99.9% or higher.

B-3. First Protective Layer Protective layer 20 may be composed of any suitable resin. For example, it may be any suitable resin film, or it may be a solidified layer or a cured layer of a coating film of an organic solvent solution containing a resin. The protective layer 20 is preferably a solidified layer or hardened layer of a coating film of an organic solvent solution containing a resin. When the protective layer 20 is a solidified layer or a cured layer of a coating film of a solvent-containing solution containing a resin, the adhesion to the polarizer can be improved. Organic solvent solutions are prepared using any suitable resin. Any appropriate resin can be used as the resin (base polymer). Only one type of resin may be used, or two or more types may be used in combination.

In one embodiment, a resin having a glass transition temperature (Tg) of, for example, 85°C or higher and a weight average molecular weight Mw of, for example, 25000 or higher is used. By setting the Tg and Mw of the resin within such ranges, it is possible to achieve excellent durability in a high-temperature, high-humidity environment despite the fact that the thickness is very thin. The Tg of the resin is preferably 90° C. or higher, more preferably 100° C. or higher, even more preferably 110° C. or higher, and particularly preferably 120° C. or higher. Tg can be, for example, 200° C. or less. Also, the Mw of the resin is preferably 30,000 or more, more preferably 35,000 or more, and still more preferably 40,000 or more. Mw can be, for example, 150,000 or less.

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

Acrylic resins typically contain, as a main component, repeating units derived from (meth)acrylic acid ester-based monomers having a linear or branched structure. As used herein, (meth)acryl refers to acryl and/or methacryl. The acrylic resin may contain repeating units derived from any appropriate comonomers depending on the purpose. Examples of copolymerizable monomers (copolymerizable monomers) include carboxyl group-containing monomers, hydroxyl group-containing monomers, amide group-containing monomers, aromatic ring-containing (meth)acrylates, and heterocyclic ring-containing vinyl monomers. By appropriately setting the type, number, combination and copolymerization ratio of the monomer units, an acrylic resin having the predetermined Mw can be obtained.

<Boron-containing acrylic resin>
In one embodiment, the acrylic resin is more than 50 parts by weight of a (meth)acrylic monomer and more than 0 parts by weight and less than 50 parts by weight of the monomer represented by formula (1) (hereinafter , may be referred to as a copolymer monomer) and a copolymer obtained by polymerizing a monomer mixture (hereinafter sometimes referred to as a boron-containing acrylic resin) including:

(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 group consisting of 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 boron-containing acrylic resin typically has a repeating unit represented by the following formula. By polymerizing a monomer mixture containing a copolymerizable monomer represented by formula (1) and a (meth)acrylic monomer, the boron-containing acrylic resin has a substituent containing boron in the side chain (e.g., repeating unit k in the following formula). This can improve the adhesion between the polarizer and the protective layer. The boron-containing substituent may be included continuously (that is, in blocks) in the boron-containing acrylic resin, or may be included randomly.

(Wherein, ^R6 represents an arbitrary functional group, and j and k represent integers of 1 or more).

<(Meth) acrylic monomer>
Any appropriate (meth)acrylic monomer can be used as the (meth)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.

Examples of (meth)acrylic 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 (meth)acrylic ester-based monomers 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)acrylate 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 the silsesquioxane compound containing a (meth)acryloyl group, for example, Toagosei Co., Ltd. SQ series MAC grade and AC grade 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 (meth)acrylic monomer is used in an amount exceeding 50 parts by weight with respect to 100 parts by weight of the monomer mixture.

<Comonomer>
A monomer represented by the above formula (1) is used as the comonomer. By using such a comonomer, a substituent containing boron is introduced into the side chain of the resulting polymer. Comonomers may be used alone or in combination of two or more.

As the aliphatic hydrocarbon group in the above formula (1), a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent, 3 to 3 carbon atoms which may have a substituent 20 cyclic alkyl groups 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.

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

In one embodiment, the functional group represented by X is preferably a functional group represented by ZY-. Here, Z is selected from the 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. and Y represents a phenylene group or an alkylene group.

Specifically, the following compounds can be used as the comonomer.

The comonomer is used in a content of more than 0 parts by weight and less than 50 parts by weight with respect to 100 parts by weight of the monomer mixture. 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.

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

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

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

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

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

Regarding the maleic anhydride unit and the maleimide (N-substituted maleimide) unit, the structure is specified from the name, so a specific description is omitted.

The content of repeating units containing a ring structure in the acrylic resin is preferably 1 mol% to 50 mol%, more preferably 10 mol% to 40 mol%, still more preferably 20 mol% to 30 mol%. In addition, acrylic resin contains the repeating unit derived from said (meth)acrylic-type monomer as a main repeating unit.

<Epoxy resin>
As the epoxy resin, an epoxy resin having an aromatic ring is preferably used. Adhesion between the protective layer and the polarizer can be improved by using an epoxy resin having an aromatic ring as the epoxy resin. Furthermore, when the adhesive layer is arranged adjacent to the protective layer, the anchoring force of the adhesive layer can be improved. Examples of epoxy resins having an aromatic ring include bisphenol type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin; phenol novolak epoxy resin, cresol novolak epoxy resin, hydroxybenzaldehyde phenol novolak Novolac type epoxy resins such as epoxy resins; polyfunctional epoxy resins such as glycidyl ether of tetrahydroxyphenylmethane, glycidyl ether of tetrahydroxybenzophenone, epoxidized polyvinylphenol, naphthol type epoxy resin, naphthalene type epoxy resin, biphenyl type epoxy resin and the like. Bisphenol A type epoxy resin, biphenyl type epoxy resin, and bisphenol F type epoxy resin are preferably used. Epoxy resins may be used alone or in combination of two or more.

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

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

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

The first protective layer (substantially an organic solvent solution of the above resin) may contain any appropriate additive depending on the purpose. Specific examples of additives include ultraviolet absorbers; leveling agents; antioxidants such as hindered phenol, phosphorus, and sulfur; stabilizers such as light stabilizers, weather stabilizers, and heat stabilizers; Reinforcing materials such as carbon fiber; near-infrared absorbers; flame retardants such as tris(dibromopropyl) phosphate, triallyl phosphate, and antimony oxide; antistatic agents such as anionic, cationic, and nonionic surfactants; inorganic pigments , organic pigments, colorants such as dyes; organic fillers or inorganic fillers; resin modifiers; organic fillers or inorganic fillers; plasticizers; The type, number, combination, addition amount, etc. of additives can be appropriately set according to the purpose.

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

B-4. Second Protective Layer The second protective layer (protective layer 30) is formed of any suitable film that can be used as a protective layer for a polarizer. Specific examples of the material that is the main component of the film include cellulose resins such as triacetyl cellulose (TAC), polyesters, polyvinyl alcohols, polycarbonates, polyamides, polyimides, polyethersulfones, polysulfones, Examples include transparent resins such as polystyrene, polynorbornene, polyolefin, (meth)acrylic, and acetate. Thermosetting resins such as (meth)acrylic, urethane, (meth)acrylic urethane, epoxy, and silicone, or ultraviolet curable resins may also be used. Further, for example, glassy polymers such as siloxane-based polymers can also be used. Further, polymer films described in JP-A-2001-343529 (WO01/37007) can also be used. Materials for this film include, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in a side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and nitrile group in a side chain. can be used, for example, a resin composition comprising an alternating copolymer of isobutene and N-methylmaleimide and an acrylonitrile/styrene copolymer. The polymer film can be, for example, an extrudate of the resin composition.

When the polarizing plate is arranged on the viewing side of the image display device, the protective layer 30 is typically arranged on the viewing side. In this case, the protective layer 30 may be subjected to surface treatment such as hard coat treatment, anti-reflection treatment, anti-sticking treatment, anti-glare treatment, etc., as required.

The thickness of the second protective layer is preferably 10 µm to 50 µm, more preferably 15 µm to 35 µm. In addition, when the surface treatment is performed, the thickness of the second protective layer is the thickness including the thickness of the surface treatment layer.

C. Adhesive Layer The adhesive layer 40 can be formed using the adhesive composition described in section A above. The surface resistance value of the adhesive layer 40 is 5.0×10 ⁹ Ω/□ or less, preferably 1.0×10 ⁹ Ω/□ or less, more preferably 9.0×10 ⁸ as described above. Ω/□ or less, more preferably 8.0×10 ⁸ Ω/□ or less, even more preferably 7.0×10 ⁸ Ω/□ or less, particularly preferably 6.0×10 ⁸ Ω /□ or less. The surface resistance value can be, for example, 1.0×10 ⁷ Ω/□ or more. According to the embodiment of the present invention, it is possible to realize a pressure-sensitive adhesive layer with a low surface resistance value despite a low antistatic agent content.

The adhesive strength of the adhesive layer to glass is preferably 1.0 N/25 mm or more, more preferably 1.5 N/25 mm or more, and still more preferably 2.0 N/25 mm or more. If the adhesive strength is within such a range, the adhesiveness to the image display panel is excellent and the reworkability is excellent. Adhesion can be, for example, 4.0 N/25 mm or less.

The thickness of the adhesive layer is preferably 2 µm to 55 µm, more preferably 2 µm to 30 µm, still more preferably 5 µm to 25 µm, and particularly preferably 10 µm to 20 µm.

D. Image Display Device An image display device according to an embodiment of the present invention includes the polarizing plate described above. Accordingly, embodiments of the present invention include image display devices using such polarizing plates. Typical examples of image display devices include liquid crystal display devices and electroluminescence (EL) display devices (eg, organic EL display devices and inorganic EL display devices). In one embodiment, the image display device is a narrow frame (preferably bezelless) image display device or an in-cell image display device. In such an image display device, the effects of the embodiments of the present invention are remarkable.

FIG. 2 is a schematic cross-sectional view of an image display device according to an embodiment of the invention. This image display 300 is an in-cell liquid crystal display device. As shown in FIG. 2, the in-cell liquid crystal cell 200 includes a liquid crystal layer 90 containing liquid crystal molecules that are homogeneously aligned in the absence of an electric field, and a first transparent substrate 71 and a second transparent substrate 72 that sandwich the liquid crystal layer 90 on both sides. have A touch sensor section 61 is provided between the liquid crystal layer 90 and the first transparent substrate 71 , and a driving electrode/sensor section 62 is provided between the liquid crystal layer 50 and the second transparent substrate 72 . The in-cell liquid crystal cell has a touch sensor portion 61 and a driving electrode/sensor portion 62 inside the liquid crystal cell, and does not have a touch sensor portion outside the liquid crystal cell. That is, no conductive layer (having a surface resistance of 1×10 ¹³ Ω/□ or less) is provided on the viewing side of the first transparent substrate 41 of the in-cell liquid crystal cell.

The touch sensor section 61 is arranged between the polarizer 10 and the liquid crystal layer 90, and can usually be formed on the first transparent substrate 71 as a transparent electrode pattern. A transparent electrode pattern can also be formed on the drive electrode/sensor portion 62 by any appropriate method. The transparent electrode pattern is normally electrically connected to a lead wire (not shown) formed at the end of the transparent substrate, and the lead wire is connected to a controller IC (not shown). As for the shape of the transparent electrode pattern, any shape such as a stripe shape, a rhombus shape, or the like can be adopted in addition to the comb shape, depending on the application. The height of the transparent electrode pattern is, for example, 10 nm to 100 nm, and the width is 0.1 mm to 5 mm.

In the in-cell liquid crystal panel 300 , a conducting structure 51 can be provided on the side surface of at least one layer of the polarizing plate 100 . The conductive structure 51 connects the side surface of at least one layer of the polarizing plate 100 to another suitable location, thereby suppressing the generation of static electricity. Materials forming the conductive structure 51 include conductive pastes such as silver, gold or other metal pastes, conductive adhesives, or any other suitable conductive material may be used. The conducting structure 51 can also be formed in a linear shape extending from the side surface of at least one layer of the polarizing plate 100 .

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The measurement method of each characteristic is as follows. "Parts" and "%" in Examples and Comparative Examples are by weight unless otherwise specified.

(1) Thickness A thickness of 10 μm or less was measured using an interferometric film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name “MCPD-3000”). A thickness exceeding 10 μm was measured using a digital gauge (manufactured by PEACOCK, trade name “DGN-255”).

(2) Surface resistance value The resistance value of the adhesive layer surface of the polarizing plate (polarizing plate with adhesive layer) obtained in Examples and Comparative Examples was measured using "MCP-HT450" manufactured by Mitsubishi Chemical Analytic Tech. was measured and used as the initial resistance value. Further, the pressure-sensitive adhesive layer-attached polarizing plate was subjected to a reliability test under humidified conditions (at 60° C. and 95% RH for 240 hours), and then the resistance value was measured in the same manner as described above. The resistance value increase rate was calculated by the following formula.
Resistance value increase rate = resistance value after reliability test/initial resistance value x 100

(3) ESD test The polarizing plates (polarizing plates with adhesive layer) obtained in Examples and Comparative Examples were cut into 70 mm x 150 mm pieces, and bonded to a liquid crystal panel via an adhesive layer. Next, a silver paste was applied to the side surface of the bonded polarizing plate with an adhesive layer so as to cover the entire thickness direction of the side surface of the polarizing plate with an adhesive layer, and connected to an external ground electrode. Next, on the surface of the pressure-sensitive adhesive layer-attached polarizing plate, a static electricity generator, ESD (ESD-8012A, manufactured by SANKI) was used (applied voltage 15 kV) to draw a circle every second in the plane of the polarizing plate. A total of 10 times of emission (applying) was performed to cause alignment disturbance of the liquid crystal of the liquid crystal panel. The time until the white spots disappeared due to electricity was measured and evaluated according to the following criteria. In addition, after subjecting the polarizing plate with an adhesive layer to a reliability test under humidified conditions (under an environment of 60°C and 95% RH for 240 hours), similarly, the time until the white spots disappeared by electricity was measured. and evaluated according to the following criteria.
○: White spots disappeared within 1 second △: White spots disappeared within 1 to 5 seconds ×: White spots remained for 5 seconds or more

(4) Non-alkali glass adhesive strength test The prepared polarizing plate (polarizing plate with adhesive layer) was cut into a size of 25 mm × 50 mm so that the absorption axis of the polarizer was parallel to the long side. The polarizing plate was laminated to non-alkaline glass (manufactured by Corning, trade name "EG-XG") having a thickness of 170 mm×50 mm×0.7 mm using a laminator. Then, autoclave treatment was performed at 50° C. and 0.5 MPa for 15 minutes to adhere the adhesive layer to the glass. After that, in accordance with JIS Z 0237, a 90 degree peeling test (temperature: 23 ° C., peeling angle: 90 degrees, peeling speed: 300 mm / min, initial length (chuck interval): 150 mm) was performed. was measured. In addition, the adhesive strength was measured in the same manner for the polarizing plate and the non-alkali glass that were placed in close contact with each other at room temperature for 4 weeks.

(5) Presence or absence of dents A polyethylene terephthalate film (manufactured by Mitsubishi Chemical Polyester Film Co., Ltd., product (named "MRF38", separator film), and crimped using a digital gauge (manufactured by PEACOCK, trade name "DGN-255") (range 25 mm, test force 1.2 N). After 3 minutes, the depth of the depression at the measurement site was measured using the digital gauge.
○: dent depth less than 11 μm (no dents)
×: dent depth of 11 μm or more (with dents)

[Production Example 1: Preparation of (meth)acrylic base polymer A1]
79 parts of butyl acrylate (BA), 20 parts of methoxyethyl acrylate (MEA), and 1 part of 4-hydroxybutyl acrylate (4HBA) are placed in a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser. A monomer mixture containing was charged. Further, 0.1 part of 2,2'-azobisisobutyronitrile as a polymerization initiator was added to 100 parts of this monomer mixture together with 100 parts of ethyl acetate, and nitrogen gas was introduced while gently stirring. After the substitution, the liquid temperature in the flask was maintained at around 55° C., and the polymerization reaction was carried out for 8 hours to prepare a solution of (meth)acrylic base polymer A1. The (meth)acrylic base polymer A1 had a Tg of −53° C. and a dielectric constant of 5.7.

[Production Example 2: Preparation of (meth)acrylic base polymer A2]
A solution of (meth)acrylic base polymer A2 was prepared in the same manner as in Production Example 1 except that a monomer mixture containing 59 parts of BA, 40 parts of MEA and 1 part of 4HBA was used. The (meth)acrylic base polymer A2 had a Tg of −52° C. and a dielectric constant of 6.5.

[Production Example 3: Preparation of (meth)acrylic base polymer A3]
A solution of (meth)acrylic base polymer A3 was prepared in the same manner as in Production Example 1 except that a monomer mixture containing 39 parts of BA, 60 parts of MEA and 1 part of 4HBA was used. The (meth)acrylic base polymer A3 had a Tg of −51° C. and a dielectric constant of 7.3.

[Production Example 4: Preparation of (meth)acrylic base polymer A4]
A solution of (meth)acrylic base polymer A4 was prepared in the same manner as in Production Example 1 except that a monomer mixture containing 19 parts of BA, 80 parts of MEA and 1 part of 4HBA was used. The (meth)acrylic base polymer A4 had a Tg of −50° C. and a dielectric constant of 8.1.

[Production Example 5: Preparation of (meth)acrylic base polymer A5]
A solution of (meth)acrylic base polymer A5 was prepared in the same manner as in Production Example 1 except that a monomer mixture containing 9 parts of BA, 90 parts of MEA and 1 part of 4HBA was used. The (meth)acrylic base polymer A5 had a Tg of −50° C. and a dielectric constant of 8.5.

[Production Example 6: Preparation of (meth)acrylic base polymer A6]
A (meth)acrylic base was prepared in the same manner as in Production Example 3 except that 60 parts of MEA was replaced with 60 parts of methoxytriethylene glycol acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name: Viscoat #MTG). A solution of polymer A6 was prepared.

[Production Example 7: Production of polarizing plate]
1. Production of Polarizer As a thermoplastic resin substrate, a long amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 μm) having a water absorption of 0.75% and a Tg of about 75° C. was used. Corona treatment was applied to one side of the resin substrate.
Polyvinyl alcohol (degree of polymerization: 4,200, degree of saponification: 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOSEFIMER Z410") mixed at 9:1: 100 weight of PVA-based resin 13 parts by weight of potassium iodide was added to parts by weight, and dissolved in water to prepare an aqueous PVA solution (coating solution).
The above PVA aqueous solution was applied to the corona-treated surface of the resin base material and dried at 60° C. to form a PVA-based resin layer having a thickness of 13 μm, thereby producing a laminate.
The obtained laminate was uniaxially stretched 2.4 times at the free end in the machine direction (longitudinal direction) between rolls with different peripheral speeds in an oven at 130° C. (in-air auxiliary stretching treatment).
Next, the laminate was immersed in an insolubilizing bath (an aqueous boric acid solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40° C. for 30 seconds (insolubilizing treatment).
Then, the finally obtained polarizer is added to a dyeing bath (iodine aqueous solution obtained by blending iodine and potassium iodide at a weight ratio of 1:7 with respect to 100 parts by weight of water) at a liquid temperature of 30 ° C. It was immersed for 60 seconds while adjusting the concentration so that the single transmittance (Ts) was a predetermined value (dyeing treatment).
Next, it was immersed for 30 seconds in a cross-linking bath at a liquid temperature of 40°C (an aqueous solution of boric acid obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water). (crosslinking treatment).
After that, while immersing the laminate in an aqueous solution of boric acid (boric acid concentration: 4.0% by weight, potassium iodide concentration: 5% by weight) at a liquid temperature of 70°C, the laminate is placed between rolls having different peripheral speeds in the vertical direction (longitudinal direction). Then, the film was uniaxially stretched so that the total draw ratio was 5.5 times (underwater stretching treatment).
After that, the laminate was immersed in a washing 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 20° C. (washing treatment).
After that, while drying in an oven kept at 90° C., it was brought into contact with a heating roll made of SUS whose surface temperature was kept at 75° C. for about 2 seconds (drying shrinkage treatment). The shrinkage ratio in the width direction of the laminate due to the drying shrinkage treatment was 5.2%.
Thus, a polarizer having a thickness of 7 μm was formed on the resin substrate.

2. Preparation of Polarizing Plate An HC-TAC film (second protective layer) as a protective layer is placed on the surface of the polarizer obtained above (the surface opposite to the resin base material) via an ultraviolet curable adhesive. pasted together. Specifically, the curable adhesive was applied so as to have a total thickness of 1.0 μm, and was bonded using a roll machine. After that, UV rays were applied from the protective layer side to cure the adhesive. The HC-TAC film is a film in which a hard coat (HC) layer (thickness 7 μm) is formed on a triacetyl cellulose (TAC) film (thickness 25 μm), and is attached so that the TAC film faces the polarizer side. Matched.
Methyl methacrylate (MMA, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., trade name "methyl methacrylate monomer") 97.0 parts, 3.0 parts of the copolymerization monomer represented by the above general formula (1e), polymerization initiation In 200 parts of toluene was dissolved 0.2 parts of an agent (trade name “2,2′-azobis(isobutyronitrile)” manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.). Then, a polymerization reaction was carried out for 5.5 hours while heating at 70° C. in a nitrogen atmosphere to obtain a boron-containing acrylic resin solution (solid concentration: 33%). The resulting boron-containing acrylic polymer had a Tg of 110°C and an Mw of 80,000. 20 parts of the obtained boron-containing acrylic resin was dissolved in 80 parts of methyl ethyl ketone to obtain a resin solution (20%). Next, the resin substrate is peeled off, and a resin solution is applied to the surface from which the resin substrate has been peeled off using a wire bar. A protective layer (first protective layer) configured as a solidified product was formed to obtain a polarizing plate.

[Example 1]
1. Preparation of PSA Composition Antistatic agent 1 (lithium bis(trifluoromethanesulfonyl)imide (LiTFSi) , trade name: LiTFSi30EA, manufactured by Mitsubishi Materials Corporation) 3 parts, benzoyl peroxide as a cross-linking agent (trade name: Nyper BMT 40SV, manufactured by NOF Corporation) 0.3 parts, isocyanate-based cross-linking agent (trade name: Takenate D160N, manufactured by Mitsui Chemicals Co., Ltd.) 0.2 parts, polyoxyethylene sorbitan fatty acid ester (trade name: Rhodol TW-L120, manufactured by Kao Corporation) 0.03 parts, antioxidant (trade name: Irganox 1010, Hindered 0.3 part of a phenolic adhesive (manufactured by BASF Japan Ltd.) was blended to prepare a solution of an acrylic pressure-sensitive adhesive composition.

2. Preparation of pressure-sensitive adhesive layer-attached polarizing plate The solution of the acrylic pressure-sensitive adhesive composition obtained above was applied to a polyethylene terephthalate film (manufactured by Mitsubishi Chemical Polyester Film Co., Ltd., trade name "MRF38", separator film) treated with a silicone-based release agent. was applied to one side of the separator film so that the thickness of the adhesive layer after drying was 15 μm, and dried at 155° C. for 1 minute to form an adhesive layer on the surface of the separator film. Next, the adhesive layer formed on the separator film was transferred to the first protective layer of the polarizing plate produced in Production Example 6 to produce a polarizing plate with an adhesive layer. The pressure-sensitive adhesive layer-attached polarizing plate thus obtained was subjected to the above evaluations (2) to (5). Table 1 shows the results.

[Examples 2 and 3]
A polarizing plate with an adhesive layer was produced in the same manner as in Example 1 except that the amount of the antistatic agent added was changed to the amount shown in Table 1. The pressure-sensitive adhesive layer-attached polarizing plate thus obtained was subjected to the above evaluations (2) to (5). Table 1 shows the results.

[Examples 4-6]
A polarizing plate with an adhesive layer was produced in the same manner as in Examples 1 to 3, except that (meth)acrylic base polymer A2 was used instead of (meth)acrylic base polymer A1. The pressure-sensitive adhesive layer-attached polarizing plate thus obtained was subjected to the above evaluations (2) to (5). Table 1 shows the results.

[Examples 7-9]
A polarizing plate with an adhesive layer was produced in the same manner as in Examples 1 to 3, except that (meth)acrylic base polymer A3 was used instead of (meth)acrylic base polymer A1. The pressure-sensitive adhesive layer-attached polarizing plate thus obtained was subjected to the above evaluations (2) to (5). Table 1 shows the results.

[Example 10]
Polarized light with adhesive layer in the same manner as in Example 1 except that (meth)acrylic base polymer A4 was used instead of (meth)acrylic base polymer A1 and the amount of the antistatic agent added was 2 parts. A plate was made. The pressure-sensitive adhesive layer-attached polarizing plate thus obtained was subjected to the above evaluations (2) to (5). Table 1 shows the results.

[Example 11]
The pressure-sensitive adhesive layer was prepared in the same manner as in Example 1 except that the (meth)acrylic base polymer A5 was used in place of the (meth)acrylic base polymer A1 and the amount of the antistatic agent added was 1.5 parts. A polarizing plate was prepared. The pressure-sensitive adhesive layer-attached polarizing plate thus obtained was subjected to the above evaluations (2) to (5). Table 1 shows the results.

[Example 12]
A polarizing plate with an adhesive layer was produced in the same manner as in Example 7, except that the amount of the antistatic agent added was 0.1 parts. The pressure-sensitive adhesive layer-attached polarizing plate thus obtained was subjected to the above evaluations (2) to (5). Table 1 shows the results.

[Example 13]
In the same manner as in Example 12, except that 0.2 parts of silane coupling agent 1 (trade name: A-100, manufactured by Soken Chemical Co., Ltd., an acetoacetyl group-containing silane coupling agent) was further added to the adhesive composition. A polarizing plate with an adhesive layer was produced. The pressure-sensitive adhesive layer-attached polarizing plate thus obtained was subjected to the above evaluations (2) to (5). Table 1 shows the results.

[Example 14]
In the same manner as in Example 7, except that 0.03 parts of silane coupling agent 1 (trade name: A-100, manufactured by Soken Chemical Co., Ltd., an acetoacetyl group-containing silane coupling agent) was further added to the adhesive composition. A polarizing plate with an adhesive layer was produced. The pressure-sensitive adhesive layer-attached polarizing plate thus obtained was subjected to the above evaluations (2) to (5). Table 1 shows the results.

[Example 15]
In the same manner as in Example 7, except that 0.2 parts of silane coupling agent 1 (trade name: A-100, manufactured by Soken Chemical Co., Ltd., an acetoacetyl group-containing silane coupling agent) was further added to the adhesive composition. A polarizing plate with an adhesive layer was produced. The pressure-sensitive adhesive layer-attached polarizing plate thus obtained was subjected to the above evaluations (2) to (5). Table 1 shows the results.

[Example 16]
A polarizing plate with an adhesive layer was prepared in the same manner as in Example 15 except that 0.2 parts of silane coupling agent 2 (trade name: X41-1810, manufactured by Shin-Etsu Chemical Co., Ltd.) was added instead of silane coupling agent 1. was made. The pressure-sensitive adhesive layer-attached polarizing plate thus obtained was subjected to the above evaluations (2) to (5). Table 1 shows the results.

[Example 17]
A polarizing plate with an adhesive layer was prepared in the same manner as in Example 15 except that 0.2 parts of silane coupling agent 3 (trade name: X41-1056, manufactured by Shin-Etsu Chemical Co., Ltd.) was added instead of silane coupling agent 1. was made. The pressure-sensitive adhesive layer-attached polarizing plate thus obtained was subjected to the above evaluations (2) to (5). Table 1 shows the results.

[Example 18]
Example 15 except that 0.2 parts of silane coupling agent 4 (trade name: KBM403, manufactured by Shin-Etsu Silicone Co., Ltd., a silane coupling agent having an epoxy group as an organic functional group) was added instead of silane coupling agent 1. A polarizing plate with an adhesive layer was produced in the same manner as in the above. The pressure-sensitive adhesive layer-attached polarizing plate thus obtained was subjected to the above evaluations (2) to (5). Table 1 shows the results.

[Example 19]
A polarizing plate with an adhesive layer was produced in the same manner as in Example 7 except that 3 parts of antistatic agent 2 (trade name: Elexel AS110, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used instead of antistatic agent 1. The pressure-sensitive adhesive layer-attached polarizing plate thus obtained was subjected to the above evaluations (2) to (5). Table 1 shows the results.

[Example 20]
Implemented except that 8.5 parts of antistatic agent 3 (tributylmethylammonium bis(trifluoromethanesulfonyl)imide (TBMA-TFSI), trade name: FC-4400, manufactured by Orwell) was used instead of antistatic agent 1. A polarizing plate with an adhesive layer was produced in the same manner as in Example 7. The pressure-sensitive adhesive layer-attached polarizing plate thus obtained was subjected to the above evaluations (2) to (5). Table 1 shows the results.

[Example 21]
The pressure-sensitive adhesive layer was prepared in the same manner as in Example 1 except that the (meth)acrylic base polymer A6 was used instead of the (meth)acrylic base polymer A1 and the amount of the antistatic agent added was 0.8 parts. A polarizing plate was prepared. The pressure-sensitive adhesive layer-attached polarizing plate thus obtained was subjected to the above evaluations (2) to (5). Table 1 shows the results.

(Comparative example 1)
Using an acrylic adhesive (trade name: SK2137, manufactured by Soken Kagaku Co., Ltd.) instead of the (meth)acrylic base polymer A3, adding 7 parts of the antistatic agent, and polyoxyethylene sorbitan A polarizing plate with an adhesive layer was produced in the same manner as in Example 13, except that 0.03 part of rework improver 1 (trade name: Silyl SAT10, manufactured by Kaneka Corporation) was used instead of the fatty acid ester. The pressure-sensitive adhesive layer-attached polarizing plate thus obtained was subjected to the above evaluations (2) to (5). Table 1 shows the results.

(Comparative example 2)
Example 7 except that an acrylic adhesive (trade name: SK2137, manufactured by Soken Kagaku Co., Ltd.) was used instead of the (meth)acrylic base polymer A3, and that the amount of the antistatic agent added was 12 parts. A polarizing plate with an adhesive layer was produced in the same manner as in the above. The pressure-sensitive adhesive layer-attached polarizing plate thus obtained was subjected to the above evaluations (2) to (5). Table 1 shows the results.

(Comparative Example 3)
A polarizing plate with an adhesive layer was produced in the same manner as in Comparative Example 1, except that 24 parts of Antistatic Agent 3 was used instead of Antistatic Agent 1. The pressure-sensitive adhesive layer-attached polarizing plate thus obtained was subjected to the above evaluations (2) to (5). Table 1 shows the results.

(Comparative Example 4)
A polarizing plate with an adhesive layer was produced in the same manner as in Example 13, except that 0.03 part of rework improver 1 (trade name: Silyl SAT10, manufactured by Kaneka Corporation) was used instead of polyoxyethylene sorbitan fatty acid ester. . The pressure-sensitive adhesive layer-attached polarizing plate thus obtained was subjected to the above evaluations (2) to (5). Table 1 shows the results.

(Comparative Example 5)
A polarizing plate with an adhesive layer was produced in the same manner as in Comparative Example 4, except that 0.03 part of rework improver 2 (trade name: Rheodol O-106V, manufactured by Kao Corporation) was used instead of rework improver 1. . The pressure-sensitive adhesive layer-attached polarizing plate thus obtained was subjected to the above evaluations (2) to (5). Table 1 shows the results.

(Comparative Example 6)
A polarizing plate with an adhesive layer was produced in the same manner as in Comparative Example 4, except that the amount of rework improver 2 added was changed to 1 part. The pressure-sensitive adhesive layer-attached polarizing plate thus obtained was subjected to the above evaluations (2) to (5). Table 1 shows the results.

(Comparative Example 7)
A pressure-sensitive adhesive layer-attached polarizing plate was produced in the same manner as in Comparative Example 6, except that Rework Improver 3 (trade name: Rhodol SP-L110, manufactured by Kao Corporation) was used instead of Rework Improver 2. The pressure-sensitive adhesive layer-attached polarizing plate thus obtained was subjected to the above evaluations (2) to (5). Table 1 shows the results.

[evaluation]
As is clear from Table 1, the polarizing plates of Examples of the present invention showed good results in the ESD test and maintained low surface resistance values even after the humidification reliability test. Furthermore, the reworkability was excellent, and the formation of dents was suppressed.

The polarizing plate of the present invention is suitably used for image display devices such as liquid crystal display devices, organic EL display devices and inorganic EL display devices.

REFERENCE SIGNS LIST 10 polarizer 20 protective layer 30 protective layer 40 adhesive layer 100 polarizing plate

Claims (16)

1. A pressure-sensitive adhesive composition comprising a base polymer containing an alkoxy group-containing monomer as a monomer component, an antistatic agent, and a polyoxyethylene sorbitan fatty acid ester,
   A pressure-sensitive adhesive composition in which the total average number of ethylene oxide additions contained in the polyoxyethylene sorbitan fatty acid ester and the number of carbon atoms in the aliphatic hydrocarbon group satisfy the following formula:
   Total average number of additions of ethylene oxide/carbon number of aliphatic hydrocarbon group ≥ 0.4
2. The pressure-sensitive adhesive composition according to claim 1, wherein the total average addition number of ethylene oxide is an integer of 1 or more.
3. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the aliphatic hydrocarbon group is a monovalent aliphatic hydrocarbon group having 5 to 20 carbon atoms.
4. The pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the content of said polyoxyethylene sorbitan fatty acid ester is 0.005 to 5 parts by weight with respect to 100 parts by weight of said base polymer.
5. The pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the base polymer contains 20 to 99 parts by weight of the alkoxy group-containing monomer with respect to 100 parts by weight of all monomer components.
6. The pressure-sensitive adhesive composition according to any one of claims 1 to 5, wherein the content of the antistatic agent in the pressure-sensitive adhesive composition is 10 parts by weight or less with respect to 100 parts by weight of the base polymer.
7. The pressure-sensitive adhesive composition according to any one of claims 1 to 6, wherein the alkoxy group-containing monomer is represented by the following formula:
   

   

   (wherein R ¹ is an alkyl group and n is an integer from 1 to 15).
8. The pressure-sensitive adhesive composition according to any one of claims 1 to 7, wherein the base polymer further contains a hydroxyl group-containing monomer as a monomer component.
9. The pressure-sensitive adhesive composition according to any one of claims 1 to 8, wherein the base polymer has a weight average molecular weight of 1,000,000 to 3,000,000.
10. 10. Any of claims 1 to 9, wherein the antistatic agent comprises lithium bis(trifluoromethanesulfonyl)imide, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide or tributylmethylammonium bis(trifluoromethanesulfonyl)imide. The pressure-sensitive adhesive composition according to 1.
11. The pressure-sensitive adhesive composition according to any one of claims 1 to 10, further comprising a silane coupling agent.
12. A polarizing plate comprising a polarizer, a protective layer, and a pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition according to any one of claims 1 to 11 in this order,
    A polarizing plate, wherein the pressure-sensitive adhesive layer has a surface resistance value of 5.0×10 ⁹ Ω/□ or less.
13. The polarizing plate according to claim 12, wherein the resistance value increase rate in the humidification test represented by the following formula is 4000% or less;
    Resistance value increase rate = (resistance value after humidification reliability test/initial resistance value) x 100
    Here, the humidification test is performed for 240 hours under conditions of a temperature of 60° C. and a humidity of 95% RH.
14. The polarizing plate according to claim 12 or 13, wherein the protective layer is a solidified layer or a cured layer of a coating film of an organic solvent solution.
15. The polarizing plate according to any one of claims 12 to 14, which has through holes.
16. An image display device comprising the polarizing plate according to any one of claims 12 to 15.

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