JP7137120B2 - ADHESIVE COMPOSITION, ADHESIVE USING SAME, ADHESIVE FOR POLARIZING PLATE, AND IMAGE DISPLAY DEVICE - Google Patents

Description

The present invention relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive using the same, a pressure-sensitive adhesive for polarizing plates, and an image display device, and more specifically, a pressure-sensitive adhesive that can achieve both high antistatic performance and durability even in a high-temperature environment. The present invention relates to a pressure-sensitive adhesive composition forming an agent, a pressure-sensitive adhesive using the same, a pressure-sensitive adhesive for polarizing plates, and an image display device.

Conventionally, a polarizing plate, which is a polarizer made of a polyvinyl alcohol-based film or the like with polarizing properties and coated with protective films on both sides, is laminated on the surface of a liquid crystal cell in which an oriented liquid crystal component is sandwiched between two glass plates. Liquid crystal display devices are manufactured. Lamination of the polarizing plate on the surface of the liquid crystal cell is usually carried out by contacting and pressing an adhesive layer provided on the surface of the polarizing plate against the surface of the liquid crystal cell.

The pressure-sensitive adhesive used for bonding the polarizing plate (protective film) and the liquid crystal cell (glass) is required to have durability such that it does not float or peel off from the substrate in a high-temperature environment.

In addition, since the liquid crystal cell is driven by controlling the voltage, static electricity causes problems such as display unevenness and failure. Since static electricity is generated when adhesive films are attached or peeled off, the adhesive is required to have antistatic properties as a countermeasure against static electricity.

For example, it has been proposed to add an ionic compound to the pressure-sensitive adhesive for the purpose of imparting antistatic performance (see, for example, Patent Document 1).

In addition, it has been proposed to use an ionic compound in an adhesive layer for the purpose of preventing malfunction in a touch panel-mounted display (see, for example, Patent Document 2). In particular, in vehicle displays, static electricity is likely to be generated by steering operation or the like, so that the pressure-sensitive adhesive layer is required to have even higher antistatic performance.

JP 2009-79205 A JP 2017-67942 A

However, in the techniques disclosed in Patent Documents 1 and 2, in order to further improve the antistatic performance of the adhesive, it is necessary to contain a large amount of an ionic compound in the adhesive layer. Agents tend to be less durable in high temperature or high humidity environments. For this reason, the durability is still not satisfactory, and there is a problem that the adhesive film is lifted or peeled off.

Therefore, in the present invention, under such a background, for example, when a metal such as a glass or a conductive layer used for an image display member such as a liquid crystal cell is used as an adherend, it has high antistatic performance even in a high temperature environment. An object of the present invention is to provide a pressure-sensitive adhesive composition that forms a pressure-sensitive adhesive that can achieve both durability and durability, a pressure-sensitive adhesive using the same, a pressure-sensitive adhesive for polarizing plates, and an image display device.

However, in the process of earnestly researching in view of such circumstances, the present inventors have found that in a pressure-sensitive adhesive composition containing an acrylic resin (A) and an ionic compound (B), in order to improve durability, it is difficult to bleed. If an ionic compound that is highly compatible with acrylic resin is used, it will be difficult for the ionic compound to segregate on the surface, resulting in a decrease in antistatic performance. I ran into a problem that it became easy to wear and the durability decreased. Therefore, in order to solve this problem, as a result of further research on ionic compounds, among pyridinium-based ionic compounds, in particular, ionic compounds that are salts composed of pyridinium-based cations and bisoxalatoborate anions are used. This product has good compatibility with acrylic resins, does not easily bleed, and has excellent antistatic performance. completed the invention.

That is, the gist of the present invention is a pressure-sensitive adhesive composition containing an acrylic resin (A) and an ionic compound (B), wherein the ionic compound (B) is composed of a pyridinium-based cation and a bisoxalatoborate anion. It relates to a pressure-sensitive adhesive composition that is a salt of

Furthermore, the present invention relates to a pressure-sensitive adhesive, a pressure-sensitive adhesive for polarizing plates, and an image display device using the pressure-sensitive adhesive composition.

The pressure-sensitive adhesive obtained using the pressure-sensitive adhesive composition of the present invention can achieve both high antistatic performance and high durability even in a high-temperature environment. And, the pressure-sensitive adhesive composition of the present invention can be used as a pressure-sensitive adhesive suitable for various uses, especially for polarizing plates.

Further, in the pressure-sensitive adhesive composition of the present invention, if the melting point of the ionic compound (B) is 30 to 200° C., a pressure-sensitive adhesive with more excellent durability can be obtained.

Furthermore, in the pressure-sensitive adhesive composition of the present invention, when the pyridinium-based cation of the ionic compound (B) is an N-alkylpyridinium cation, the compatibility with the acrylic resin is further improved, and the ionic compound ( B) is less likely to bleed, and a more durable pressure-sensitive adhesive can be obtained.

Then, in the adhesive composition of the present invention, the content of the ionic compound (B) is 3 to 30 parts by weight with respect to 100 parts by weight of the acrylic resin (A), antistatic performance and durability A more excellent pressure-sensitive adhesive can be obtained by the balance of

Further, in the adhesive composition of the present invention, the acrylic resin (A) is an acrylic resin obtained by polymerizing a polymerizable component containing an alkyl (meth)acrylate monomer (a1) and a polar group-containing monomer (a2). Then, it is possible to obtain a pressure-sensitive adhesive with even better durability.

Furthermore, in the pressure-sensitive adhesive composition of the present invention, when the polar group-containing monomer (a2) is at least one selected from hydroxyl group-containing monomers and carboxy group-containing monomers, it is possible to obtain a pressure-sensitive adhesive with even better durability. can.

When the pressure-sensitive adhesive composition of the present invention contains the cross-linking agent (C), a cross-linked structure can be formed and a pressure-sensitive adhesive with more excellent durability can be obtained.

Moreover, when the pressure-sensitive adhesive composition of the present invention contains a silane coupling agent (D), a pressure-sensitive adhesive having even more excellent durability can be obtained.

Furthermore, since the pressure-sensitive adhesive of the present invention uses the pressure-sensitive adhesive composition of the present invention, it has both excellent antistatic performance and durability. , when used as an adhesive for bonding image display members such as polarizing plates (protective films) and liquid crystal cells (glass) and metal surfaces (conductive layers), it exhibits good antistatic performance and high durability. It is very useful as an adhesive for polarizing plates and conductive layers.

Therefore, the image display device of the present invention, which is formed by bonding the polarizing plate and the image display member such as the liquid crystal cell together with the above adhesive, does not cause display unevenness or peeling due to static electricity, and is of excellent quality. Become.

The present invention will be described in detail below.
In the present invention, "(meth)acryl" means acryl or methacryl, and "(meth)acryloyl" means acryloyl or methacryloyl. Moreover, "(meth)acrylate" means acrylate or methacrylate. Furthermore, "acrylic resin" means a resin obtained by polymerizing a polymerizable component containing at least one (meth)acrylate monomer.

The adhesive composition of the present invention contains an acrylic resin (A) and an ionic compound (B).

<Acrylic resin (A)>
The acrylic resin (A) used in the present invention contains an alkyl (meth)acrylate monomer (a1) as a main component and, if necessary, a polar group-containing monomer (a2) and other copolymerizable monomers. An acrylic resin obtained by polymerizing a polymerizable component can be mentioned.
The term "contained as a main component" means that the content is usually 40% by weight or more, preferably 50% by weight or more, and more preferably 60% by weight or more, relative to the total polymerization components.

Examples of the alkyl (meth)acrylate-based monomer (a1) include, for example, monomers in which the number of carbon atoms in the alkyl group is usually 1 to 24, preferably 1 to 18, particularly preferably 1 to 12, and further preferably 1 to 8. includes aliphatic (meth)acrylate monomers, specifically, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-Butyl (meth)acrylate, n-propyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate Acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate and the like. These may be used alone or in combination of two or more.

Among these, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate are preferred in terms of versatility and adhesive properties, and particularly n-butyl (meth) acrylate. is preferred.

The content of the alkyl (meth)acrylate monomer (a1) is preferably 40% by weight or more, particularly preferably 50 to 99% by weight, more preferably 60 to 97% by weight, based on the total polymerization components. is. If it is in the above range, it tends to be excellent in the balance of adhesive physical properties.

Examples of the polar group-containing monomer (a2) include hydroxyl group-containing monomers, carboxy group-containing monomers, and nitrogen-containing monomers. These may be used alone or in combination of two or more.
In the present invention, the acrylic resin (A) uses a polar group-containing monomer as a copolymerization component. It is preferable in terms of increasing the adhesion to the adherend and in terms of wet heat whitening resistance (wet heat whitening: a phenomenon in which the adhesive whitens after being exposed to a constant temperature and humidity environment), especially in terms of wet heat whitening resistance It is preferable to use a hydroxyl group-containing monomer from the

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl ( Hydroxyalkyl (meth)acrylate monomers such as meth)acrylates, caprolactone-modified monomers such as caprolactone-modified 2-hydroxyethyl (meth)acrylate, oxyalkylene-modified (meth)acrylates such as diethylene glycol (meth)acrylate and polyethylene glycol (meth)acrylate Monomers, other primary hydroxyl group-containing (meth)acrylate monomers such as 2-acryloyloxyethyl-2-hydroxyethylphthalic acid, N-methylol (meth)acrylamide, and hydroxyethylacrylamide; 2-hydroxypropyl (meth)acrylate, Secondary hydroxyl group-containing (meth)acrylate monomers such as 2-hydroxybutyl (meth)acrylate and 3-chloro 2-hydroxypropyl (meth)acrylate; Tertiary hydroxyl groups such as 2,2-dimethyl 2-hydroxyethyl (meth)acrylate Included are (meth)acrylate monomers.
These may be used alone or in combination of two or more.

Among the above hydroxyl group-containing monomers, a primary hydroxyl group-containing (meth) acrylate monomer is preferable in terms of excellent reactivity with a cross-linking agent, particularly a nitrogen-containing cross-linking agent described below, and improved wet heat whitening resistance, and further Preferably, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are used. That is, this is because the amount of impurities such as di(meth)acrylates is low and high purity can be obtained when the monomer is prepared.
Further, 4-hydroxybutyl acrylate is preferable in that the monomer preparation contains less acid impurities and suppresses hydrolysis of the base material.

When the hydroxyl group-containing monomer is prepared and used, or when a commercially available product is used, it is also preferable that the content of di(meth)acrylate as an impurity is 0.5% by weight or less, particularly 0. 0.2% by weight or less, more preferably 0.1% by weight or less.

Examples of the carboxy group-containing monomer include dimer acids of (meth)acrylic acid such as (meth)acrylic acid and β-carboxyethyl (meth)acrylate. (Meth)acrylic acid is preferred in terms of stability over time.

Furthermore, examples of the nitrogen-containing monomer include amino group-containing monomers and amide group-containing monomers.
Examples of the amino group-containing monomer include primary amino group-containing (meth)acrylate monomers such as aminoalkyl (meth)acrylates such as aminomethyl (meth)acrylate and aminoethyl (meth)acrylate; t-butylaminoethyl Secondary amino group-containing (meth) acrylate-based monomers such as (meth) acrylate; ) acrylate monomers and the like.

Examples of the amide group-containing monomer include (meth)acrylamide; methoxymethyl (meth)acrylamide, ethoxymethyl (meth)acrylamide, propoxymethyl (meth)acrylamide, isopropoxymethyl (meth)acrylamide, n-butoxymethyl (meth)acrylamide, ) alkoxyalkyl (meth)acrylamide monomers such as acrylamide and isobutoxymethyl (meth)acrylamide; dialkyl (meth)acrylamide monomers such as dimethyl (meth)acrylamide and diethyl (meth)acrylamide; and the like.

Other nitrogen-containing monomers include nitrogen-containing monomers having a cyclic structure such as acryloylmorpholine and vinylimidazole.
These may be used alone or in combination of two or more.

Among the above nitrogen-containing monomers, dialkylacrylamide is preferable because it can suppress hydrolysis of the substrate or adherend, and dimethylacrylamide and diethylacrylamide are preferable because they have high polymerizability and amide group concentration and can suppress hydrolysis.

These polar group-containing monomers (a2) are preferably contained in an amount of 50% by weight or less based on the polymerizable components constituting the acrylic resin (A).

Among the polar group-containing monomers (a2), when a hydroxyl group-containing monomer is used in particular, the content thereof is preferably 0.1 to 50% by weight, particularly preferably 1 to 50% by weight, based on the total polymerization components. 30% by weight, more preferably 5 to 25% by weight. If the content is too small, the resistance to wet heat whitening tends to decrease. There is a tendency that there is no adhesive residue when applying and that the adherend is not damaged).

Among the polar group-containing monomers (a2), when a carboxy group-containing monomer is used, the content thereof is preferably 10% by weight or less, particularly preferably 5% by weight or less, based on the total polymerization components. , more preferably 1% by weight or less, more preferably 0.1% by weight or less. If the content is too high, the hydrolysis of the base material tends to be accelerated and the reworkability tends to decrease.

Furthermore, among the polar group-containing monomers (a2), when a nitrogen-containing monomer is used, the content thereof is preferably 10% by weight or less, particularly preferably 8% by weight or less, based on the total polymerization components. Yes, more preferably 5% by weight or less. If the content is too high, the glass transition temperature of the acrylic resin (A) will be high, and reworkability will be reduced, and zipping (zipping: intermittent change in peeling force to prevent smooth peeling) will easily occur. tend to become

Other copolymerizable monomers that can be used in the acrylic resin (A) of the present invention include, for example, alicyclic structure-containing monomers, aromatic monomers, and alkoxy group-containing monomers. However, when these copolymerizable monomers are used, the content thereof is preferably 5% by weight or less with respect to the total polymerizable components. That is, if the content is too high, the reworkability tends to deteriorate.

Examples of the alicyclic structure-containing monomer include cyclohexyl (meth)acrylate, isobornyl acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, Examples include (meth)acrylates having an alicyclic structure such as dicyclopentenyloxyethyl (meth)acrylate and 2-adamantyl (meth)acrylate. These may be used alone or in combination of two or more.

Examples of the aromatic monomers include phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxypropyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, and phenoxydipropylene glycol (meth)acrylate. , phenoxypolyethylene glycol (meth)acrylate, phenoxypolyethyleneglycol (meth)acrylate, phenoxypolypropylene glycol-(meth)acrylate having one aromatic ring; phenoxybenzyl (meth)acrylate, ethoxylated o-phenyl Examples include (meth)acrylates having two aromatic rings such as phenol (meth)acrylate. These may be used alone or in combination of two or more.

Examples of the alkoxy group-containing monomer include alkoxyalkyl (meth)acrylate such as 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, and 2-butoxyethyl (meth)acrylate. meth)acrylates.

In the present invention, when adjusting the birefringence of the acrylic resin (A) to the positive side, benzyl (meth) acrylate, phenoxy (meth) ethyl acrylate, phenoxybenzyl (meth) acrylate, phenoxy diethylene glycol (meth) It is effective to use aromatic monomers such as acrylates.

Conventionally known methods such as solution radical polymerization, suspension polymerization, bulk polymerization, and emulsion polymerization can be used as the polymerization method for the acrylic resin (A). For example, there is a method in which appropriately selected polymerization components and a polymerization initiator are mixed or added dropwise into an organic solvent and polymerized under predetermined polymerization conditions. Solution radical polymerization is particularly preferred in terms of obtaining an acrylic resin.

Examples of the organic solvent used in the polymerization reaction include aromatic hydrocarbons such as toluene and xylene, aliphatic hydrocarbons such as hexane, esters such as ethyl acetate and butyl acetate, n-propyl alcohol, and isopropyl alcohol. and ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone. These organic solvents can be used alone or in combination of two or more. The amount of these organic solvents to be used is usually 20 to 1000 parts by weight per 100 parts by weight of the polymerizable components.

Among these organic solvents, ethyl acetate, acetone, methyl ethyl ketone, butyl acetate, toluene, and methyl isobutyl are preferred from the standpoints of ease of polymerization reaction, chain transfer effect, ease of drying during adhesive coating, and safety. Ketones are preferred, especially ethyl acetate, acetone and methyl ethyl ketone.

Examples of the polymerization initiator used for such radical polymerization include 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, which are ordinary radical polymerization initiators, Azo polymerization initiators such as 4,4'-azobis (4-cyanovaleric acid), 2,2'-azobis (methylpropionic acid), benzoyl peroxide, lauroyl peroxide, di-t-butyl peroxide, cumene Examples include organic peroxides such as hydroperoxide, which can be appropriately selected and used according to the monomer to be used. These polymerization initiators can be used alone or in combination of two or more. The amount of these polymerization initiators used is usually 0.001 to 5 parts by weight per 100 parts by weight of the polymerization components.

Thus, the acrylic resin (A) used in the present invention is obtained.

The weight average molecular weight of the acrylic resin (A) is preferably 200,000 to 2,500,000, particularly preferably 400,000 to 2,000,000, more preferably 600,000 to 1,800,000, and particularly preferably 1,000,000. ~1.6 million. If the weight-average molecular weight is too small, the components in the hydrolyzed base material migrate quickly, and crystals tend to precipitate easily. is required in large amounts, and the energy required for drying tends to be large.

Further, the degree of dispersion (weight average molecular weight/number average molecular weight) of the acrylic resin (A) is preferably 15 or less, particularly preferably 10 or less, further preferably 7 or less. If the degree of dispersion is too high, the cohesive force tends to decrease, resulting in a decrease in durability and a decrease in reworkability. The lower limit of the degree of dispersion is usually 1.

The weight average molecular weight of the above acrylic resin (A) is the weight average molecular weight in terms of standard polystyrene molecular weight, and high performance liquid chromatography (Japan Waters Co., Ltd., "Waters 2695 (body)" and "Waters 2414 (detection Column: Shodex GPC KF-806L (exclusion limit molecular weight: 2×10 ⁷ , separation range: 100 to 2×10 ⁷ , theoretical plate number: 10,000 plate/column, packing material: styrene-divinyl Benzene copolymer, filler particle size: 10 μm) are connected in series and used, and the number average molecular weight can also be measured by the same method. Further, the dispersity is obtained from the weight average molecular weight and the number average molecular weight.

The glass transition temperature (Tg) of the acrylic resin (A) is preferably -100 to 25°C, particularly preferably -60 to 0°C, and more preferably -55 to -10°C. If the glass transition temperature is too high, the tack tends to be low, making lamination difficult, and zipping tends to occur when reworking from the release film or adherend. Also, if the glass transition temperature is too low, the heat resistance tends to decrease.

The glass transition temperature is calculated from the following Fox formula.

That is, it is a value calculated by applying the glass transition temperature and the weight fraction of a homopolymer of each monomer constituting the acrylic resin to the Fox formula.
The glass transition temperature of a homopolymer of the monomers constituting the acrylic resin is usually measured by a differential scanning calorimeter (DSC), and is in accordance with JIS K7121-1987 and JIS K 6240. method can be measured.

The viscosity of the acrylic resin (A) is adjusted with a solvent or the like, and the acrylic resin (A) solution is used in the pressure-sensitive adhesive composition of the present invention. The viscosity of the acrylic resin (A) solution is preferably 500 to 20,000 mPa s, particularly preferably 1,000 to 18,000 mPa s, more preferably 2,000 mPa s from the viewpoint of ease of handling. ~15,000 mPa·s.
If the viscosity is too high, the fluidity tends to be low and handling tends to be difficult.

The viscosity of the acrylic resin (A) solution is measured at 25° C. by a rotational viscometer method using a Brookfield viscometer.

Thus, the acrylic resin (A) used in the present invention is obtained.

<Ionic compound (B)>
In the present invention, the ionic compound (B) used together with the acrylic resin (A) is a compound consisting of a cation and an anion. A salt consisting of the latoborate anion is used.

The above-mentioned "pyridinium-based cation" is intended to include not only the pyridinium cation itself, but also pyridinium derivatives obtained by, for example, introducing a substituent to the pyridinium skeleton of the pyridinium cation.

Examples of pyridinium-based cations include 1-ethylpyridinium cation, 1-propylpyridinium cation, 1-butylpyridinium cation, 1-hexylpyridinium cation, 1-ethyl-3-methylpyridinium cation, 1-butyl-3-methyl pyridinium cation, 1-hexyl-3-methylpyridinium cation, 1-butyl-4-methylpyridinium cation, 1-octyl-3-methylpyridinium cation, 1-octyl-4-methylpyridinium cation, 1-butyl-3, Alkylpyridinium cations such as 4-dimethylpyridinium cations and 1,1-dimethylpyridinium cations can be mentioned.

The length of each alkyl group of the alkylpyridinium cation is generally 1 to 20 carbon atoms, preferably 1 to 8 carbon atoms. Within the above range, the balance between compatibility and antistatic performance tends to be excellent. Among these, 1-octyl-3-methylpyridinium cation is particularly preferred.

Furthermore, the melting point of the ionic compound (B) used in the present invention is preferably 25°C or higher, particularly preferably 30°C to 200°C, further preferably 40°C to 150°C. If the melting point is too low, the resulting pressure-sensitive adhesive tends to be plasticized, resulting in reduced durability.
The melting point of the ionic compound (B) is usually measured with a differential scanning calorimeter (DSC).

The content of the ionic compound (B) is preferably 3 to 30 parts by weight, particularly preferably 3 to 10 parts by weight, more preferably 3 to 10 parts by weight, with respect to 100 parts by weight of the acrylic resin (A). 5 to 8 parts by weight. If the content is too small, the antistatic performance tends to decrease, and if it is too large, the substrate tends to be susceptible to hydrolysis when used as a pressure-sensitive adhesive.

<Optional component: Crosslinking agent (C)>
The adhesive composition of the present invention preferably contains a cross-linking agent (C) together with the acrylic resin (A) and the ionic compound (B).
The cross-linking agent (C) is preferable in terms of improving the adhesion to the substrate and improving the durability of the pressure-sensitive adhesive.

Examples of the cross-linking agent (C) include isocyanate-based cross-linking agents, epoxy-based cross-linking agents, aziridine-based cross-linking agents, melamine-based cross-linking agents, aldehyde-based cross-linking agents, amine-based cross-linking agents, chelate-based cross-linking agents, and carbodiimide-based cross-linking agents. etc. Among these, it is preferable to use an isocyanate-based cross-linking agent from the viewpoint of improving the adhesiveness to the substrate and having excellent reactivity with the acrylic resin (A).
The cross-linking agent (C) may be used alone or in combination of two or more.

Examples of the isocyanate-based cross-linking agents include tolylene diisocyanate-based cross-linking agents such as 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, xylylene diisocyanate-based cross-linking agents such as 1,3-xylylene diisocyanate, Aromatic isocyanate cross-linking agents such as diphenylmethane-based cross-linking agents such as diphenylmethane-4,4-diisocyanate and naphthalene diisocyanate-based cross-linking agents such as 1,5-naphthalenediisocyanate; isophorone diisocyanate, 1,4-cyclohexane diisocyanate, 4,4 Alicyclic isocyanate cross-linking agents such as '-dicyclohexylmethane diisocyanate, methylcyclohexane diisocyanate, isopropylidene dicyclohexyl-4,4'-diisocyanate, 1,3-diisocyanatomethylcyclohexane, norbornane diisocyanate; hexamethylene diisocyanate, trimethylhexa Aliphatic isocyanate-based cross-linking agents such as methylene diisocyanate; and adducts, burettes, and isocyanurates of the above isocyanate-based compounds.

Among these isocyanate-based cross-linking agents, tolylene diisocyanate-based cross-linking agents are preferable in terms of pot life and durability, and xylylene diisocyanate-based cross-linking agents or isocyanurate skeleton-containing isocyanate-based cross-linking agents are preferable in terms of shortening the aging time. A ring-free isocyanate-based cross-linking agent is preferred from the standpoint of yellowing resistance. Specifically, among these, tolylene diisocyanate, xylylene diisocyanate, adducts of hexamethylene diisocyanate and trimethylolpropane, and nurates are excellent in the balance of durability, pot life, and crosslinking speed. Preferred, particularly preferred is an adduct of tolylene diisocyanate and trimethylolpropane.

Examples of the epoxy-based cross-linking agent include bisphenol A/epichlorohydrin type epoxy resin, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol diol. glycidyl ether, trimethylolpropane triglycidyl ether, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidylerythritol, diglycerol polyglycidyl ether and the like.

Examples of the aziridine-based cross-linking agent include tetramethylolmethane-tri-β-aziridinylpropionate, trimethylolpropane-tri-β-aziridinylpropionate, N,N'-diphenylmethane-4,4 '-bis(1-aziridinecarboxamide), N,N'-hexamethylene-1,6-bis(1-aziridinecarboxamide) and the like.

Examples of the melamine-based cross-linking agent include hexamethoxymethylmelamine, hexaethoxymethylmelamine, hexapropoxymethylmelamine, hexaptoxymethylmelamine, hexapentyloxymethylmelamine, hexahexyloxymethylmelamine, and melamine resins. .

Examples of the aldehyde cross-linking agent include glyoxal, malondialdehyde, succindialdehyde, maleinedialdehyde, glutaredialdehyde, formaldehyde, acetaldehyde, and benzaldehyde.

Examples of the amine cross-linking agent include hexamethylenediamine, triethyldiamine, polyethyleneimine, hexamethylenetetramine, diethylenetriamine, triethyltetramine, isophoronediamine, amino resins, and polyamides.

Examples of the metal chelate-based cross-linking agents include acetylacetone and acetoacetyl ester coordination compounds of polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, panadium, chromium, and zirconium. mentioned.

Examples of the carbodiimide-based cross-linking agent include polyfunctional carbodiimide compounds and polymer-type carbodiimide compounds.

When such a cross-linking agent (C) is used, its content is preferably 0.01 to 20 parts by weight with respect to 100 parts by weight of the acrylic resin (A) from the viewpoint of durability and the like. More preferably 0.05 to 10 parts by weight. If the content is too small, the durability tends to be lowered, and adhesive residue tends to occur during rework. On the other hand, if the amount is too large, the stress relaxation property tends to decrease, and an adherend such as a liquid crystal cell tends to warp, and display unevenness tends to occur in an image display device.

<Optional component: silane coupling agent (D)>
Moreover, it is preferable to further add a silane coupling agent (D) to the pressure-sensitive adhesive composition of the present invention in order to improve the durability in a high-temperature and high-humidity environment.
Such a silane coupling agent (D) is an organosilicon compound containing in its structure at least one reactive functional group and at least one alkoxy group bonded to a silicon atom.

Examples of the reactive functional groups include epoxy groups, (meth)acryloyl groups, mercapto groups, hydroxyl groups, carboxy groups, amino groups, amide groups, and isocyanate groups. A mercapto group and an epoxy group are preferable from the point of balance.

From the standpoint of durability and storage stability, the silicon-bonded alkoxy group preferably contains an alkoxy group having 1 to 8 carbon atoms, and particularly preferably a methoxy group or an ethoxy group.

The content of the silicon-bonded alkoxy groups in the silane coupling agent (D) is preferably 1 to 80% by weight, particularly preferably 5 to 60% by weight, based on the total amount of the silane coupling agent (D). %, more preferably 7.5 to 30% by weight. If the content of the silicon-bonded alkoxy group is too low, the adhesion to the adherend tends to be low and the durability tends to be low.

The reactive functional group equivalent weight of the silane coupling agent (D) is preferably 50-1000 g/mol, particularly preferably 200-800 g/mol, further preferably 300-600 g/mol. If the reactive functional group equivalent is too small, the reworkability tends to be lowered, and if it is too large, the durability under wet heat conditions tends to be lowered.

The silane coupling agent (D) may have a reactive functional group and an organic substituent other than the silicon-bonded alkoxy group, such as an alkyl group or a phenyl group.

The weight average molecular weight of the silane coupling agent (D) is preferably 2,000 or more, particularly preferably 2,500 to 25,000, further preferably 5,000 to 20,000. If the weight-average molecular weight is too small, the long-term reworkability tends to be deteriorated.

The above weight average molecular weight is a weight average molecular weight in terms of standard polystyrene molecular weight, and is measured by the following method.
Apparatus: Gel permeation chromatography Detector: Differential refractive index detector RI (RI-8020 type manufactured by Tosoh Corporation, sensitivity 32)
Column: TSKguardcolumn HHR-H (1 piece) (φ6 mm × 4 cm) manufactured by Tosoh Corporation, TSKgelGMHHR-N (2 pieces) (φ7.8 mm × 30 cm)
Filler material: Styrene-divinylbenzene copolymer Solvent: Tetrahydrofuran (THF)
Column temperature: 23°C Flow rate: 1.0 mL/min

Examples of the silane coupling agent (D) used in the present invention include
3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2-(3,4 epoxycyclohexyl) A monomer type epoxy group-containing silane coupling agent that is a silane compound such as ethyltrimethoxysilane, an oligomer type epoxy group-containing silane coupling agent that is a silane compound obtained by hydrolytic condensation polymerization of a part of the silane compound, and the above Oligomeric epoxy group-containing silane coupling agents, which are silane compounds obtained by cocondensation of a silane compound and an alkyl group-containing silane compound such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, and ethyltrimethoxysilane;
Monomeric mercapto group-containing silane coupling agents that are silane compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, γ-mercaptopropyldimethoxymethylsilane, 3-mercaptopropylmethyldimethoxysilane, and the above Oligomer-type mercapto group-containing silane coupling agents, which are silane compounds in which a part of the silane compound is hydrolytically polycondensed, and the above silane compounds and methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, etc. an oligomeric mercapto group-containing silane coupling agent, which is a silane compound obtained by cocondensation of an alkyl group-containing silane compound of
(Meth), such as 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, etc. acryloyl group-containing silane coupling agent;
N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, amino group-containing silane coupling agents such as N-phenyl-3-aminopropyltrimethoxysilane;
an isocyanate group-containing silane coupling agent such as 3-isocyanatopropyltriethoxysilane;
vinyl group-containing silane coupling agents such as vinyltrimethoxysilane and vinyltriethoxysilane;
etc.
These may be used independently and may use 2 or more types together.

Among these, epoxy group-containing silane coupling agents and mercapto group-containing silane coupling agents are preferably used from the viewpoint of excellent balance between durability and reworkability, and epoxy group-containing silane coupling agents and mercapto group-containing silane coupling agents Combined use of an agent is also preferable from the viewpoint of improving wet heat durability and preventing excessive increase in adhesive strength.

The silane coupling agent (D) may be a monomer type silane coupling agent or a partially hydrolyzed and polycondensed oligomer type silane coupling agent. It is preferable to use an oligomeric silane coupling agent because it is less likely to volatilize during drying after coating.

Specific examples of the silane coupling agent (D) that can be used in the present invention include the following commercially available products.
For example, Shin-Etsu Chemical Co., Ltd., "X-41-1059A" (weight average molecular weight: 2,270, containing functional group: epoxy group, containing silicon atom-bonded alkoxy group: methoxy group and ethoxy group, containing silicon atom-bonded alkoxy group amount: 42% by weight, functional group equivalent: 350 g/mol), "X-41-1805" (weight average molecular weight: 3,450, contained functional group: mercapto group, contained silicon atom-bonded alkoxy group: methoxy group and ethoxy group , containing silicon atom-bonded alkoxy group content: 50% by weight, functional group equivalent: 800 g / mol), "X-24-9579A" (weight average molecular weight: 2,370, containing functional group: mercapto group, containing silicon atom-bonded alkoxy Group: methoxy group, functional group equivalent: 510 g / mol), "X-24-9589" (weight average molecular weight: 4,700, containing functional group: epoxy group, containing silicon atom-bonded alkoxy group: ethoxy group, functional group equivalent : 680 g/mol), "X-24-9590" (weight average molecular weight: 13,700, contained functional group: epoxy group, contained silicon atom-bonded alkoxy group: methoxy group, amount of silicon atom-bonded alkoxy group contained: 9.5 % by weight, functional group equivalent: 592 g/mol), "X-41-1818" (weight average molecular weight: 2,350, containing functional group: mercapto group, containing silicon atom-bonded alkoxy group: ethoxy group, containing silicon atom-bonded alkoxy base weight: 60% by weight, functional group equivalent: 850 g/mol) and the like. Among these, "X-41-1059A", "X-24-9579A" and "X-24-9590" are preferable from the viewpoint of durability.

When the silane coupling agent (D) is used, its content is preferably 0.001 to 2 parts by weight, particularly preferably 0.005, with respect to 100 parts by weight of the acrylic resin (A). ~1 part by weight, more preferably 0.01 to 0.5 part by weight, and most preferably 0.015 to 0.3 part by weight. If the content is too low, the reworkability tends to deteriorate, and if it is too high, the silane coupling agent tends to bleed, resulting in a deterioration in durability.

<Other optional ingredients>
Furthermore, the pressure-sensitive adhesive composition of the present invention may contain, as other optional components, a resin component, an acrylic monomer, a polymerization inhibitor, an antioxidant, a corrosion inhibitor, a cross-linking accelerator, as long as the effects of the present invention are not impaired. Radical generators, peroxides, radical scavengers, ultraviolet absorbers, antioxidants, plasticizers, pigments, stabilizers, various additives such as fillers, metals, resin particles and the like can be blended. In addition to the above, it may contain a small amount of impurities contained in raw materials for manufacturing constituent components of the pressure-sensitive adhesive composition.

When the other optional components are used, the content thereof is preferably 5 parts by weight or less, particularly preferably 1 part by weight or less, more preferably 0.5 parts by weight, based on 100 parts by weight of the acrylic resin (A). Part by weight or less. If the content is too large, the compatibility with the acrylic resin (A) tends to decrease, resulting in a decrease in durability.

Thus, by mixing the acrylic resin (A) and the ionic compound (B), optionally the cross-linking agent (C), the silane coupling agent (D), and other optional components, the present An inventive pressure-sensitive adhesive composition can be obtained.

The method of mixing these components is not particularly limited, and there are various methods such as a method of mixing each component at once, a method of mixing an arbitrary component and then mixing the remaining components all at once or sequentially. method can be adopted.

The pressure-sensitive adhesive composition of the present invention can be made into a pressure-sensitive adhesive by curing (crosslinking). An optical member with an adhesive layer can be obtained.
It is preferable to further provide a release sheet on the surface of the pressure-sensitive adhesive layer opposite to the optical member surface of the pressure-sensitive adhesive layer-attached optical member.

As a method for manufacturing the optical member with the pressure-sensitive adhesive layer,
[1] An optical member is coated with a pressure-sensitive adhesive composition, dried, and then laminated with a release sheet. how to process by aging in
[2] A method of coating a release sheet with a pressure-sensitive adhesive composition, drying the adhesive composition, laminating an optical member, and subjecting the composition to aging at least one of normal temperature and heated conditions;
etc.
Among these methods, the method [2], in which aging is performed at room temperature, is preferable because the optical member is not damaged and the adhesion to the optical member is excellent.
In the above, the optical member is particularly effective when it is a polarizing plate, but the above method can also be used when forming a pressure-sensitive adhesive layer on an adherend other than an optical member.

Such aging treatment is carried out in order to balance the adhesive physical properties as reaction time for chemical cross-linking of the adhesive, and the aging conditions are temperature of 20 to 70° C. and time of usually 1 to 30 days. Specifically, the conditions may be, for example, 23° C. for 1 to 20 days, 23° C. for 3 to 10 days, and 40° C. for 1 to 7 days.

When applying the pressure-sensitive adhesive composition, it is preferable to apply the pressure-sensitive adhesive composition after diluting it with a solvent. 30% by weight.

The solvent is not particularly limited as long as it dissolves the pressure-sensitive adhesive composition. Ketone solvents such as isobutyl ketone, aromatic solvents such as toluene and xylene, and alcohol solvents such as methanol, ethanol and propyl alcohol can be used. Among these, ethyl acetate and methyl ethyl ketone are preferably used in terms of solubility, drying property, price, and the like.
These can be used alone or in combination of two or more.

In addition, application of the pressure-sensitive adhesive composition is carried out by conventional methods such as roll coating, die coating, gravure coating, comma coating and screen printing.

The gel fraction of the pressure-sensitive adhesive layer produced by the above method is preferably 30 to 97% by weight, particularly preferably 35 to 95% by weight, and more preferably 50%, from the viewpoint of durability performance and suppression of decrease in degree of polarization. ~90% by weight. If the gel fraction is too low, foaming will tend to occur in a high-temperature environment, and if it is too high, lifting and peeling will tend to occur.

The gel fraction is a measure of the degree of cross-linking (degree of curing), and is calculated, for example, by the following method. That is, the adhesive is collected by picking from an adhesive film in which an adhesive layer is formed on a base material such as an optical member, especially a polarizing plate, wrapped in a 200-mesh SUS wire net, and acetic acid adjusted to 23 ° C. After immersion in ethyl for 24 hours, the weight percentage of the undissolved adhesive component remaining in the wire mesh with respect to the weight of the adhesive layer before immersion in ethyl acetate is defined as the gel fraction.

The pressure-sensitive adhesive layer produced by the above method tends to have good wettability when actually applied to an adherend and improve workability when it has a moderate tackiness when touched with a finger. preferred.

In the present invention, the thickness of the pressure-sensitive adhesive layer is preferably 5 to 100 μm, particularly preferably 10 to 50 μm, further preferably 10 to 30 μm, from the viewpoint of durability.
If the thickness of the pressure-sensitive adhesive layer is too thin, the pressure-sensitive adhesive layer for a polarizing plate will not have sufficient stress relaxation properties, and the durability will tend to decrease. tend to decline.

As for the electrical properties of the pressure-sensitive adhesive layer obtained using the pressure-sensitive adhesive composition of the present invention, a low surface resistance value is preferable as a countermeasure against static electricity, particularly preferably less than 5.0×10 ¹⁰ Ω/cm ² , more preferably less than 5.0×10 10 Ω/cm 2 . is less than 3.0×10 ⁹ Ω/cm ² , particularly preferably less than 1.0×10 ⁹ Ω/cm ² . Also, the lower limit is usually 1.0×10 ⁷ Ω/cm ² , preferably 5.0×10 ⁷ Ω/cm ² . If the surface resistance value is too high, the pressure-sensitive adhesive tends to be easily charged, and display unevenness due to static electricity tends to occur when the adhesive is used for image display such as display by a liquid crystal cell. On the other hand, if it is too low, malfunction tends to occur when used for touch panel applications.

In the present invention, an optical member with an adhesive layer, particularly a polarizing plate with an adhesive layer, is directly applied or, if a release sheet is provided, after peeling off the release sheet, the adhesive layer surface is bonded to a glass substrate or the like, For example, it is used for an image display device such as a liquid crystal display panel.

The pressure-sensitive adhesive composition of the present invention can be used to obtain a pressure-sensitive adhesive that can achieve both high antistatic performance and durability even in a high-temperature environment. It is useful as an adhesive for polarizing plates to be laminated together.

Examples of the protective film that constitutes the polarizing plate include triacetyl cellulose films, acrylic films, polyethylene films, polypropylene films, cycloolefin films, and the like. In particular, a polarizing plate formed by laminating a cycloolefin film is preferable because the effect of the present invention can be easily obtained.

Further, by using the adhesive, a polarizing plate and a liquid crystal cell or the like can be pasted together to produce an image display device such as a liquid crystal display device. The resulting image display device can be manufactured with high accuracy and has excellent durability.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. In the examples, "parts" and "%" mean weight standards.

<Acrylic resin (A)>
First, an acrylic resin (A) was prepared as follows. The viscosity, weight average molecular weight, and degree of dispersion of the acrylic resin (A) were measured according to the methods described above.

91.3 parts of n-butyl acrylate (a1), 8 parts of 2-hydroxyethyl acrylate (a2), acrylic 0.7 parts of acid (a2), 53 parts of ethyl acetate, 42 parts of acetone, and 0.013 parts of azobisisobutyronitrile (AIBN) as a polymerization initiator were charged, and the internal temperature was raised to the boiling point of the mixture. The reaction was started. Then, 30 parts of an ethyl acetate solution containing 0.04% of AIBN was added dropwise and the mixture was reacted under reflux for 3.25 hours. , viscosity 8,060 mPa·s/25° C., acrylic resin (A): weight average molecular weight 1,120,000, dispersion degree 4.17).

<Ionic compound (B)>
The following were used as the ionic compound (B).
(B-1): 1-octyl-3-methylpyridinium oxalatoborate (B'-1): tributylmethylammonium N,N-bis(trifluoromethanesulfonyl)imide (B'-2): lithium N,N- Bis(trifluoromethanesulfonyl)imide (B'-3): tetraalkylammonium N,N-bis(fluorosulfonyl)imide (B'-4): 1-hexyl-4-methylpyridinium N,N-bis(trifluoromethane sulfonyl)imide (B'-5): dinonyldimethylammonium thiocyanate (B'-6): 1-octyl-3-methylpyridinium nonafluorobutane-1 sulfonate

<Crosslinking agent (C)>
As the cross-linking agent (C), the following were used.
(C): Adduct of tolylene diisocyanate and trimethylolpropane (Coronate L55E manufactured by Tosoh Corporation)

<Silane coupling agent (D)>
The following were used as the silane coupling agent (D).
The weight average molecular weight of the silane coupling agent (D) was measured according to the method described above. As for the content of alkoxy groups, reactive functional groups, epoxy equivalents or mercapto equivalents, and alkoxy groups contained, catalog values were used unless otherwise specified.

(D): 1:1 (weight ratio) mixture of "X-24-9590" and "X-41-1059A"・"X-24-9590": manufactured by Shin-Etsu Chemical Co., Ltd., containing reactive functional group: epoxy Group, functional group equivalent weight: 592 g/mol, alkoxy group content: methoxy group, alkoxy group content: 9.5%, weight average molecular weight: 13,700, degree of dispersion: 3.44
・ “X-41-1059A”: manufactured by Shin-Etsu Chemical Co., Ltd., containing reactive functional group: epoxy group, reactive functional group equivalent: 350 g / mol, containing alkoxy group: methoxy group and ethoxy group, alkoxy group content: 42 %, weight average molecular weight: 2,270, dispersity: 1.86

<Example 1, Comparative Examples 1 to 6>
A pressure-sensitive adhesive composition was obtained by blending the above components according to Table 1 below and adjusting the solid content concentration to 15% using ethyl acetate.

A sample for evaluation was produced using the obtained pressure-sensitive adhesive composition, and its performance was evaluated. The details of each evaluation item are described below. The evaluation results are shown in Table 2 below.

<Durability>
[sample]
The obtained pressure-sensitive adhesive composition was applied to a 38 μm-thick release sheet (Therapeel WZ, manufactured by Toray Industries, Inc.) so that the thickness after drying was 20 μm, dried at 100° C. for 3 minutes, and then triacetyl cellulose (TAC ) system film laminated on both sides of the polarizing plate, the pressure-sensitive adhesive layer surface on the opposite side of the release sheet is attached to the surface of the polarizing plate, and the pressure-sensitive adhesive layer is aged for 7 days in an environment of 23 ° C. × 50% RH. A layered polarizing plate [I] was obtained [layer structure: release sheet/adhesive layer/TAC film 1/polarizing plate/TAC film 2].
The above TAC-based films are triacetyl cellulose-based films, the thickness of TAC-based film 1 is 40 μm, and the thickness of TAC-based film 2 is 40 μm.
The adhesive layer-attached polarizing plate [I] was cut to 165 mm × 95 mm, the release sheet was peeled off, and the adhesive layer surface was pressed against alkali-free glass (manufactured by Corning, Eagle XG, thickness 1.1 mm). The roller was reciprocated twice to bond them together. Then, it was subjected to autoclave treatment (0.5 MPa×50° C.×20 minutes) to obtain a sample for durability test.
[Evaluation method]
After the obtained samples were exposed under the conditions of 105° C. for 250 hours, the following evaluation criteria were used to evaluate whether or not the quality of the polarizing plate was impaired.
[Evaluation criteria]
○: No floatation is observed on the sides of the polarizing plate. △: Bulk is observed on the sides of the polarizing plate.

<Antistatic performance>
[sample]
The same pressure-sensitive adhesive layer-attached polarizing plate [I] used for durability evaluation was used as a sample for evaluation of antistatic performance.
[Evaluation method]
First, the sample was allowed to stand in an atmosphere of 23° C.×50% RH for 24 hours, then the release sheet of the adhesive layer was removed and a surface resistivity measuring device (Mitsubishi Chemical Analytic Tech, Hiresta-UP MCP- HT450) was used to measure the surface resistivity (Ω/cm ² ) of the adhesive layer. And it evaluated by the following evaluation criteria.
[Evaluation criteria]
A: Less than 1.0×10 ⁹ Ω/cm ² ◯: 1.0×10 ⁹ Ω/cm ² or more and less than 3.0×10 ⁹ Ω/cm ² Δ: 3.0×10 ⁹ Ω/cm ² or more and less than 5.0×10 ⁹ Ω/cm ² × … 5.0×10 ⁹ Ω/cm ² or more

<Reworkability>
[sample]
The same polarizing plate [I] with an adhesive layer as used for durability evaluation was cut into a width of 25 mm. 1 mm), and pasted together by reciprocating twice with a 2 kg roller. Then, it was subjected to autoclave treatment (0.5 MPa×50° C.×20 minutes) to obtain a sample for durability test.
[Evaluation method]
First, the sample was allowed to stand in an atmosphere of 23° C. and 50% RH for 20 days, and then peeled off at a peeling angle of 180° and a peeling rate of 300 mm/min to measure the adhesive strength. And it evaluated by the following evaluation criteria.
[Evaluation criteria]
○: Less than 15N/25mm and no adhesive residue ×: 15N/25mm or more or adhesive residue

<Gel fraction>
[sample]
The same polarizing plate [I] with an adhesive layer as used for durability evaluation was used as a sample for determining the gel fraction.
[Evaluation method]
First, the release sheet of the above sample was peeled off, the adhesive was picked from the adhesive layer surface, wrapped with a SUS 200-mesh metal mesh, and then immersed in ethyl acetate adjusted to 23° C. for 24 hours. Then, the weight percentage of the undissolved adhesive component remaining in the wire mesh with respect to the weight of the adhesive layer before immersion in ethyl acetate was defined as the gel fraction (%).

From the above results, Example 1 product using a salt composed of a pyridinium-based cation and a bisoxalatoborate anion as the ionic compound (B) has both high durability and antistatic performance in a high-temperature environment. I understand.
On the other hand, Comparative Examples 1 to 6, which used ionic compounds (B) other than the combination of pyridinium-based cations and bisoxalatoborate anions, did not exhibit both high durability and antistatic performance. , the performance of at least one of them is low.

And, since the polarizing plate with an adhesive layer obtained using the adhesive composition which is the example product of the present invention has both high durability and antistatic performance, the polarizing plate is attached to the polarizing plate through the adhesive layer. and an image display member such as a liquid crystal cell are expected to have excellent quality.

When the pressure-sensitive adhesive composition of the present invention is used as a pressure-sensitive adhesive for bonding a polarizing plate (protective film) to a glass surface of a liquid crystal cell, a metal surface of a conductive layer, or the like, even in a high-temperature environment, excellent Due to its durability and excellent antistatic performance, it is used as an adhesive for bonding various displays and image display members that constitute them, especially glass substrates such as polarizing plates and liquid crystal cells, and conductive adhesives. It is useful as a pressure-sensitive adhesive for polarizing plates for laminating a layered substrate or the like.

Claims (11)

A pressure-sensitive adhesive layer using a pressure-sensitive adhesive composition containing an acrylic resin (A) and an ionic compound (B),
The acrylic resin (A) is an acrylic resin obtained by polymerizing a polymerizable component containing 1 to 25% by weight of a polar group-containing monomer (a2),
The ionic compound (B) is a salt composed of a pyridinium-based cation and a bisoxalatoborate anion,
The adhesive layer has a surface resistance value of 1.0×10 ⁷ Ω/cm ² or more and less than 5.0×10 ¹⁰ Ω/cm ² and a gel fraction of 30 to 90% by weight . Characterized adhesive layer . 2. The pressure-sensitive adhesive layer according to claim 1, wherein the ionic compound (B) has a melting point of 30 to 200.degree. 3. The pressure-sensitive adhesive layer according to claim 1, wherein the pyridinium-based cation of the ionic compound (B) is an N-alkylpyridinium cation. The adhesive according to any one of claims 1 to 3, wherein the content of the ionic compound (B) is 3 to 30 parts by weight with respect to 100 parts by weight of the acrylic resin (A). agent layer . The acrylic resin (A) is an acrylic resin obtained by polymerizing a polymerizable component containing an alkyl (meth)acrylate monomer (a1) and a polar group-containing monomer (a2). 5. The pressure-sensitive adhesive layer according to any one of 4. 6. The pressure-sensitive adhesive layer according to claim 5, wherein the polar group-containing monomer (a2) is at least one selected from hydroxyl group-containing monomers and carboxy group-containing monomers. The pressure-sensitive adhesive layer according to any one of claims 1 to 6, wherein the pressure-sensitive adhesive composition further contains a cross-linking agent (C). The pressure-sensitive adhesive layer according to any one of claims 1 to 7, wherein the pressure-sensitive adhesive composition further contains a silane coupling agent (D). 9. A pressure-sensitive adhesive layer , wherein the pressure-sensitive adhesive layer according to any one of claims 1 to 8 is crosslinked with a crosslinking agent (C). A pressure-sensitive adhesive layer for a polarizing plate, comprising the pressure-sensitive adhesive layer according to claim 9 . 10. An image display device comprising a polarizing plate and an image display member laminated together with the pressure-sensitive adhesive layer according to claim 9.