TWI458796B - Adhesive composition and adhesive sheet - Google Patents

Description

Adhesive composition and adhesive sheet

The adhesive composition of the present invention relates to an adhesive layer for a surface protective sheet of an optical member such as a polarizer, and has excellent charge prevention property and can reduce the shape of the surface of the adhered body. And an adhesive composition having a difference in adhesion or adhesion strength caused by adhesive strength.

In the adhesive sheet to which an electronic device or the like is attached, a substrate or a release paper or the like is subjected to a charging prevention treatment, or an undercoat layer as an adhesive is used to prevent adhesion by a laminated charging prevention layer. Sheet.

In recent years, there has been an increasing demand for a charging prevention function for the adhesive layer itself, and a development of a charging preventing adhesive having a charging inhibitor added to the adhesive layer has been induced. For example, there is a report of an adhesive composition containing an ionic liquid and a (meth)acrylic polymer having a (meth)acrylic acid alkylene oxide (refer to Patent Document 1).

However, an adhesive sheet using the above-described adhesive composition, for example, is attached to a low-polarity and anti-glare (AG) polarizer having a rough surface, and is attached to a highly polar surface. In the case of a smooth plane polarizer, since the difference in adhesion between the surface shape and the polarity is caused, it is necessary to separately use the adhesive sheet designed by the type of the polarizing plate. In this way, it means that in the operation of the electronic device using the AG polarizing plate and the electronic device using the planar polarizing plate in parallel, it is necessary to use the adhesive sheet which is suitable for both, and thus there is a cost or work efficiency direction. problem.

On the other hand, the adhesive sheet which has achieved the function of protecting the surface is finally peeled off and discarded. However, when the peeling operation is performed at a high speed, the force required for peeling due to the adhesive force is increased, and there is Problems such as low work efficiency, pollution, etc., such as poor adhesion of components when the adhesion is suppressed to improve these problems, so that there is a problem of relief or peeling of the adhesive sheets. .

In order to solve such a problem, there is a pressure-sensitive adhesive which reduces the rate dependence of peeling force by using an acrylic copolymer having a hydroxyl group and a carboxyl group and having a specific range of glass transition temperatures and an aromatic polyfunctional isocyanate compound. (pressare sensitive adhesive) report of the composition (refer to Patent Document 2).

However, the above-mentioned adhesive composition does not have a charging prevention function, and does not reduce the difference in adhesion due to the shape and polarity of the surface of the adherend.

Patent Document 1: Japanese Patent Laid-Open Publication No. 2004-263084, Patent Document 2: Japanese Patent Laid-Open No. 2001-123136

Therefore, it is necessary to develop an adhesive composition which is excellent in the antistatic property and which can reduce the difference in cohesive force due to the difference in the surface state of the adherend, and which has a small difference in adhesion at the time of high-speed peeling and low-speed peeling. Therefore, an object of the present invention is to provide such an adhesive composition.

The present inventors have found that two types of monomers having a specific functional group and a (meth)acrylic monomer having an alkylene oxide structure and (for the purpose of solving the above problems) have been found. The (meth)acrylic polymer obtained by copolymerizing an alkyl (meth)acrylate is prepared by blending an organic cation with an inorganic anion to form a liquid ionic salt and an isocyanate crosslinking agent, and has an excellent charge prevention effect. At the same time, the difference in the adhesion caused by the shape and polarity of the surface of the adherend can be reduced without being peeled off, and the difference in the adhesion caused by the peeling speed can be reduced, and the present invention is finally completed. .

That is, the present invention is an adhesive composition characterized by containing the following components (A) to (C).

(A) (meth)acrylic polymer obtained by copolymerization of the following components (a1) to (a4) (however, the total of (a1) to (a4) is 100% by mass) (a1) has an alkylation group 10 to 70% by mass of the (meth)acrylic monomer having an oxygen structure (a2) 1 to 8 mass% of the monomer having a hydroxyl group (a3) a monomer having a carboxyl group, a mercaptoamine group, or an amine group 0.05 to 0.5% by mass (a4) alkyl (meth) acrylate 25 to 85% by mass (B) liquid ionic salt (C) isocyanate crosslinking agent formed from organic cations and inorganic anions

Further, the present invention is an adhesive sheet characterized by performing crosslinking of the above-mentioned adhesive composition.

The adhesive composition of the present invention has an excellent charging prevention effect and can reduce the difference in adhesion due to the shape and polarity of the surface of the adherend or the peeling speed, and can be applied to the adhered body. A wide range of people with excellent mechanical properties and improved work efficiency.

[Best Embodiment of the Invention]

The adhesive composition of the present invention contains, as a constituent component, a (meth)acrylic polymer (component (A)) obtained by copolymerizing components (a1) to (a4) to be described later, and an organic cation and an inorganic anion. A liquid ionic salt (ingredient (B)) and an isocyanate crosslinking agent (ingredient (C)).

The component constituting the (meth)acrylic polymer is a (meth)acrylic monomer (component (a1)) having an alkylene oxide structure, a hydroxyl group-containing monomer (component (a2)), and a carboxyl group. A monomer of any functional group of amidino or an amine group (ingredient (a3)) and an alkyl (meth)acrylate (ingredient (a4)).

The component (a1) constituting the component (A) is a structure having an alkylene oxide structure in the molecule, and the alkylene oxide structure may, for example, be a hydroxymethylene group, a hydroxyethyl group, a hydroxypropyl group or a hydroxy group. The addition molar number of the alkylene oxide structure of (meth)acrylic acid is not limited, but is preferably 1 to 3.

Specific examples of the (meth)acrylic monomer having the above alkylene oxide structure include methoxydiethylene glycol (meth)acrylate, methoxytriethylene glycol (meth)acrylate, and the like. Ethoxy polyethylene glycol (meth) acrylate; ethoxylated polyethylene glycol (meth) acrylate, ethoxylated to ethylene glycol (meth) acrylate, etc. Acrylate; butoxy polyethylene glycol (meth) acrylate such as butoxyethylene glycol (meth) acrylate, butoxy triethylene glycol (meth) acrylate; phenoxy diethylene glycol ( Phenoxypolyethylene glycol (meth) acrylate such as methyl acrylate or phenoxy triethylene glycol (meth) acrylate; methoxypolypropylene glycol such as methoxypropylene glycol (meth) acrylate (A) Base) acrylate and the like. Among them, ethoxydiethylene glycol acrylate, methoxyethyl acrylate and the like are very useful.

The (meth)acrylic monomer having the alkylene oxide structure of the above component (a1) may be used singly or in combination of two or more kinds, but the (meth)acrylic acid having the entire content of the component (A) The monomer component of the polymer is from 10 to 70% by mass, preferably from 20 to 60% by mass. If the content is less than 10% by mass or more than 70% by mass, the difference in adhesion due to the surface shape and polarity of the adherend may increase, or adhesion to the adherend may occur. Pollution.

Further, the hydroxyl group-containing monomer constituting the component (a2) of the component (A) may, for example, be 2-hydroxyethyl (meth) acrylate or 2-hydroxypropyl (meth) acrylate or 6 - alkane such as hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, polypropylene glycol - (meth) acrylate, 1,6-hexane diol - (meth) acrylate a (meth) acrylate of a diol; a (meth) acrylamide such as N-hydroxyethyl (meth) acrylamide or N-hydroxypropyl (meth) acrylamide; 4-Hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, etc. are very useful.

The hydroxyl group-containing monomer of the component (a2) may be used singly or in combination of two or more kinds, and it is preferred that the total content of the monomer component of the (meth)acrylic polymer of the component (A) is 1 to 8 mass%, more preferably 3 to 6 mass%.

Further, the monomer containing a functional group of a carboxyl group, a mercaptoamine group or an amine group which constitutes the component (a) of the component (A), and a monomer having a hydroxyl group, may be exemplified by (meth) Acrylic acid, β-carboxyethyl (meth)acrylate, itaconic acid, crotonic acid, maleic acid, fumaric acid, etc., and monomers containing amidino group, exemplified by acrylamide, N, N - dimethyl methacrylamide, N-(1,1-dimethyl-3-oxobutyl) acrylamide, tert-butyl propylene decyl sulfonic acid, etc., further, an amine group-containing monomer In other words, N,N-dimethylamine ethyl (meth) acrylate, N,N-diethylamine ethyl (meth) acrylate, N,N-dimethylaminopropyl (methyl) ) acrylate, N,N-diethylaminopropyl (meth) acrylate, and the like. Among them, acrylic acid, acrylamide, and dimethylamine ethyl methacrylate are very useful. Further, the component (a3) may contain two or more monomers having a carboxyl group, a guanamine group or an amine group, such as N-(N',N'-dimethylaminomethyl) acrylamide.

The monomer containing the carboxyl group, the guanamine group, or the amine group of the above component (a3) may be used singly or in combination of two or more kinds, but the total content of the component (A) is The monomer component of the acrylic polymer is preferably from 0.05 to 0.5% by mass, more preferably from 0.1 to 0.3% by mass. If it is in this range, the difference in adhesive force due to the peeling speed can be reduced. For example, when the polymer (a3) is 0.05% by mass or less, it is difficult to reduce the speed dependency of the peeling force, and if it is 0.5% by mass or more, In the case of high-speed peeling, the phenomenon of repeated stop and instantaneous peeling (Zipping) occurs. Further, the (a3) monomer also has an effect of finely adjusting the polarity of the (meth)acrylic polymer.

Further, the (meth)acrylic acid alkyl ester constituting the component (a4) of the component (A) may specifically be methyl (meth)acrylate, ethyl (meth)acrylate or (methyl). N-propyl acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-amyl (meth)acrylate, isoamyl (meth)acrylate, N-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, etc., among these, 2-ethylhexyl (meth)acrylate is preferable.

The (meth)acrylic acid alkyl ester of the component (a4) may be used singly or in combination of two or more kinds, and the total content of the monomer component of the (meth)acrylic polymer is preferably 25 to 85 mass%, more preferably 35 to 75 mass%.

The (meth)acrylic polymer of the component (A) used in the present invention is usually used for a monomer of the above components (a1) to (a4), for example, solution polymerization, emulsion polymerization, bulk polymerization, or the like ( The method of synthesizing a methyl)acrylic polymer can be obtained by copolymerizing it. The molecular weight of the (meth)acrylic polymer of the component (A) is not particularly limited, but is preferably from 200,000 to 700,000.

Further, in the production of the (meth)acrylic polymer of the component (A) used in the present invention, in addition to the above components, it is necessary to use a polymerization initiator or a polymerization regulator.

The polymerization initiator may, for example, be an azo-based polymerization initiator such as azobisisobutyronitrile or a peroxide-based polymerization initiator of a peroxide such as benzamidine peroxide. 100 parts by weight of the mixture of the monomers of the above components (a1) to (a4) is used in the range of 0.01 to 1 part by weight.

On the other hand, the component (B) of the present invention is a liquid ionic salt composed of a combination of an organic cation and an inorganic anion. Here, the liquid ionic salt in the present specification means a salt which is a liquid at room temperature (25 ° C).

The organic cation constituting the above component (B) may, for example, be an imidazolium cation, a pyridinium cation, a piperidinium cation, a pyrrolidinium cation or a tetrahydropyrrolidine. a phosphonium cation, a dihydropyrimidinium cation, a tetraalkylammonium cation, a trialkyl phosphonium cation, or the like. Among them, an imidazolium cation or a pyridinium cation is preferred, and a pyridinium cation is particularly preferred.

Specific examples of the above-mentioned imidazolium cation include 1,3-dimethylimidazolium cation, 1,3-diethylimidazolium cation, 1-ethyl-3-methylimidazolium cation, and 1 -butyl-3-methylimidazolium cation, 1-hexyl-3-methylimidazolium cation, 1-octyl-3-methylimidazolium cation, 1-mercapto-3-methylimidazolium cation, 1-dodecyl-3-methylimidazolium cation, 1-tetradecyl-3-methylimidazolium cation, 1,2-dimethyl-3-propylimidazolium cation, 1-ethyl a 2,3-dimethylimidazolium cation, a 1-butyl-2,3-dimethylimidazolium cation, a 1-hexyl-2,3-dimethylimidazolium cation, etc., among which, 1-butyl-3-methylimidazolium cation, 1-hexyl-3-methylimidazolium cation.

Further, specific examples of the pyridinium cation include 1-ethylpyridinium cation, 1-butylpyridinium cation, 1-hexylpyridinium cation, and 1-butyl-3-methylpyridinium. Cation, 1-butyl-4-methylpyridinium cation, 1-hexyl-3-methylpyridinium cation, 1-hexyl-4-methylpyridinium cation, 1-butyl-3,4-dimethyl A pyridinium cation or the like, in which a 1-hexyl-4-methylpyridinium cation is used well.

Further, the inorganic anion constituting the component (B) may, for example, be Cl ^- , Br ^- , I ^- , AlCl ₄ ^- , Al ₂ Cl ₇ ^- , BF ₄ ^- , PF ₆ ^- , ClO ₄ ^- , NO ₃ ^- AsF ₆ ^- , SbF ₆ ^- , NbF ₆ ^- , TaF ₆ ^- , F(HF) _n ^- etc., in which PF ₆ ^- , BF ₄ ^-, etc. are very useful.

The component (B) of the present invention is a salt which is suitably selected from the combination of the above organic cation and an inorganic anion, and specifically, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1 -ethyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylpyridinium tetrafluoroborate, 1-butyl-3-methylpyridinium hexafluorophosphate, 1- Hexyl-3-methylimidazolium tetrafluoroborate, 1-hexyl-3-methylimidazolium hexafluorophosphate, 1-octyl-3-methylimidazolium tetrafluoroborate, 1-octyl 3-methylimidazolium hexafluorophosphate, 1-hexyl-3-methylimidazolium bromide, 1-hexyl-3-methylimidazolium chloride, 1-hexyl-2,3-dimethyl Imidazolium tetrafluoroborate, 1-hexyl-2,3-dimethylimidazolium hexafluorophosphate; 1-butylpyridinium tetrafluoroborate, 1-butylpyridinium hexafluorophosphate, 1 -hexylpyridinium tetrafluoroborate, 1-hexylpyridinium hexafluorophosphate, 1-butyl-3-methylpyridinium tetrafluoroborate, 1-butyl-3-methylpyridinium hexafluorophosphate Phosphate ester, 1-hexyl-4-methyl Pyridinium tetrafluoroborate, 1-hexyl-4-methylpyridinium hexafluorophosphate, etc., wherein 1-butyl-3-methylimidazolium hexafluorophosphate, 1-hexyl-3-methyl Imidazolium tetrafluoroborate, 1-hexyl-4-methylpyridinium hexafluorophosphate, etc. are very useful.

The compounding amount of the component (B) is usually in the range of 0.05 to 3 parts by weight, preferably 0.3 to 1.5 parts by weight, per 100 parts by weight of the component (A).

Further, the isocyanate crosslinking agent of the component (C) of the present invention is a compound having an isocyanate group capable of crosslinking with a hydroxyl group in a molecule, and specific examples thereof include methylphenyl diisocyanate and phenylphenyl chloride. Or isocyanate monomer such as diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, isophorone diisocyanate, xylene diisocyanate, hydrogenated xylene diisocyanate, or the like An isocyanate compound and an iso-trimeric isocyanate compound which are subjected to an addition reaction to an alcohol compound of two or more members such as trimethylolpropane. Further, a polyamine ester which is subjected to an addition reaction of an isocyanate compound, such as a polyether polyol or a polyester polyol, an acrylic polyol, a polybutene polyol, or a polypentadiene polyol, which are well-known, may also be mentioned. Prepolymer and the like. Among them, hexamethylene diisocyanate is very useful.

The compounding amount of the component (C) is usually in the range of 0.5 to 10 parts by weight, preferably 2 to 5 parts by weight, based on 100 parts by weight of the component (A).

The adhesive composition of the present invention can be obtained by adding other additives to the above components (A) to (C) as needed, and mixing them according to a usual method. Further, in this case, a solvent such as an organic solvent may be contained in order to dissolve or disperse the above components, but it is preferred to directly mix them without using a solvent.

In the charge-preventing adhesive composition of the present invention, in addition to the above-described respective components, a cosmetically-adjustable adhesive-imparting agent, a plasticizer, an oxidation preventive agent, a preservative, and the like are required within a range that does not impair the effects of the present invention.

The adhesive sheet of the present invention obtained as described above is applied to the surface of the support by a usual method and dried to obtain the adhesive sheet of the present invention.

In the production of the adhesive sheet, for example, a resin sheet such as polyester or polyethylene can be used as the support, and the thickness of the adhesive composition is usually 2 to 30 μm, preferably 10 to 20 Mm.

The adhesive sheet of the present invention obtained as described above has a small difference in adhesion force when attached to a surface shape such as an AG polarizing plate or a planar polarizing plate and a very different adherend, regardless of the peeling speed, and The difference between the adhesion at the time of low-speed peeling and the adhesion at the time of high-speed peeling is also small.

[Examples]

The present invention will be described in more detail by way of the examples and examples, but the invention is not limited thereto.

[Manufacturing Example 1]

60 parts by weight of ethoxydiethylene glycol acrylate (ECA, manufactured by Kyoeisha Co., Ltd.) as component (a1) and 5 parts by weight of 4-hydroxybutyl acrylate (4HBA) as component (a2) were placed in the reaction container. 0.15 parts by weight of acrylic acid as component (a3), 34.85 parts by weight of 2-ethylhexyl acrylate (2EHA) as component (a4), 120 parts by weight of ethyl acetate, and 0.1 weight of azobisisobutyronitrile (AIBN) And replace the air in the reaction vessel with nitrogen. Then, the reaction vessel was heated to 70 ° C and reacted for 6 hours while stirring under a nitrogen atmosphere. After completion of the reaction, it was diluted with ethyl acetate to obtain an acrylic polymer solution A1 having a molecular weight of 500,000.

[Manufacturing Examples 2 to 3]

The acrylic polymer solutions A2 and A3 were obtained in the same manner as in Production Example 1 except that the components (a1) to (a4) were changed to the following Table 1. The molecular weight thereof is also shown in Table 1.

[Manufacturing Comparative Examples 1 to 15]

The acrylic polymer solutions B1 and B15 were obtained in the same manner as in Production Example 1 except that the components (a1) to (a4) were changed to the following Table 1. The molecular weight thereof is also shown in Table 1.

Here, the abbreviation in the table means the following meaning.

MEA: methoxyethyl acrylate ECA: ethoxydiethylene glycol acrylate 4HBA: 4-hydroxybutyl acrylate 2HEA: 2-hydroxyethyl acrylate AA: acrylic acid AM: acrylamide DM: dimethylamine B Dimethacrylate 2EHA: 2-ethylhexyl acrylate

[Example 1]

To 100 parts by weight of the solid content of the acrylic polymer solution A1 obtained in Production Example 1, 1 part by weight of 1-hexyl-4-methylpyridinium hexafluorophosphate as a liquid ion salt was added, and crosslinked as an isocyanate The binder was mixed with hexamethylene diisocyanate (HMDI) in an amount of 3 parts by weight to prepare an adhesive composition.

The adhesive composition was applied to a polyester film so as to have a thickness of 20 μm after drying, and after drying at 80 ° C for 2 minutes, the peeled polyester film was attached to the adhesive layer side ( PET3811, manufactured by Lintek Co., Ltd., was aged for 7 days at 23 ° C and a humidity of 65% to obtain an adhesive sheet.

[Examples 2 to 3]

The adhesive composition and the adhesive sheet were prepared in the same manner as in Example 1 except that the acrylic polymer solution and the liquid ion salt were changed to the following Table 2. Here, Table 2 describes the case where the cation and the anion of the liquid ionic salt are organic or inorganic.

[Comparative Examples 1 to 15]

The adhesive composition and the adhesive sheet were prepared in the same manner as in Example 1 except that the acrylic polymer solution and the ionic liquid were changed to the following Table 2. Here, it is noted that the cation and anion of the ionic salt belong to the state of organic or inorganic, and the ionic salt is at room temperature.

The adhesive sheets obtained in Examples 1 to 3 and Comparative Examples 1 to 15 were evaluated for peeling force and charge prevention in accordance with the following evaluation methods and standards. The results are shown in Table 3.

(Evaluation method and standard) <Peel force> After the adhesive sheet was cut into a size of 150 mm × 250 mm, the peeled polyester film was peeled off and transcribed to an AG polarizing plate or a plane polarizing plate. One side. After being placed at 23 ° C and a humidity of 65% for 1 day, the adhesion of the attached adhesive sheet at a tearing speed of 300 mm/min (low speed) and 30 m/min (high speed) to 180° was measured and respectively As a low speed peeling force, high speed peeling force.

<Electrification prevention property> (Evaluation method) The acrylic plate (70 mm × 150 mm × 1 mm) and the polarizing plate (AG polarizing plate, planar polarizing plate) are attached so that the AG surface of the polarizing plate and the plane surface can be outside. The laminate was subjected to static elimination using a static eliminator (SJ-F300, manufactured by Keyence Corporation).

The adhesive sheets obtained in the above Examples and Comparative Examples were cut into 40 mm × 150 mm, and then pressed against a AG surface and a flat surface of a pre-static-removed laminate using a 2 kg rubber roller. After being placed at 25 ° C and a humidity of 65% for 1 day, the static electricity was removed again, and the surface potential of the polarizing plate at a tearing speed of 30 m/min and a peeling angle of 180° in the peeling direction was measured using a potentiometer (SK, manufactured by Keyence). .

(Evaluation criteria) Evaluation Stripping tape voltage ○: ±0.5kV or less △: ±0.5~1.0kV×: ±1.0kV or more

As a result, it is understood that the adhesive tape manufactured by using the adhesive composition of the present invention is excellent in charge prevention property, and both the high-speed peeling and the low-speed peeling are applied to the AG polarizing plate and the planar polarizing plate. The same adhesion is exhibited, and the difference between the adhesion at the time of high-speed peeling and the adhesion at the time of low-speed peeling is also small.

On the other hand, in the comparative example in which the monomer composition or the ionic salt of the acrylic polymer is different from that of the present inventors, the difference in adhesion between the AG polarizing plate and the planar polarizing plate is large, or adhesion is caused. The body is so contaminated that it cannot produce sufficient performance. For example, the acrylic polymer obtained by the same monomer composition as that of the acrylic polymer used in Example 1 of the above-mentioned Patent Document 1 (Japanese Laid-Open Patent Publication No. 2006-63311) is the same as the organic cation and the organic anion. In Comparative Example 15, which is a liquid ionic salt, the difference in adhesion between the AG polarizing plate and the planar polarizing plate is large at low-speed peeling and high-speed peeling, and the adhesion at low-speed peeling and the adhesion at high-speed peeling are high. The difference is also larger than in Examples 1 to 3.

〔effect〕

The reason why the adhesive sheet of the present invention can exhibit the same adhesive force in the AG polarizing plate or the flat polarizing plate is not known, but it can be presumed as follows. That is, the AG polarizing plate is low in polarity and has irregularities on the surface, and the planar polarizing plate is relatively smooth and highly polarized. The more the content of the functional group-containing monomer having a (meth)acrylic monomer or another hydroxyl group-containing monomer having an alkylene oxide structure, the higher the polarity of the (meth)acrylic polymer of the component (A) However, the higher the polarity of the (meth)acrylic polymer, the lower the adhesion to the low-polarity AG polarizer and the greater the adhesion to the highly polar planar polarizer.

On the other hand, since the gap between the irregularities on the surface of the AG polarizing plate is small, the adhesive is generally not completely adhered, and the concave portion is not in contact. Therefore, when the affinity between the AG polarizing plate and the planar polarizing plate of the (meth)acrylic polymer is the same, the adhesion between the portion having a reduced contact area and the (meth)acrylic polymer is flat. The polarizer is larger than the AG polarizer.

However, if the compatibility of the acrylic polymer of the liquid ionic salt of the component (B) is moderate (incompletely miscible and slightly localized), the liquid ionic salt does not bleed out (bleeding). After the surface of the adhesive is slightly localized, the adhesion force is increased to fill the uneven surface of the AG polarizing plate.

The compatibility of the liquid ionic salt with the (meth)acrylic polymer is a combination of a cation and an anion of the liquid ionic salt and the content of the monomer having an alkylene oxide structure in the (meth)acrylic polymer. relationship. First, the ionic binding force of the liquid ionic salt is due to the combination of cation/anion in the order of inorganic/inorganic, organic/inorganic, organic/organic, and is itself a highly polar component (A) pair (methyl The compatibility of the acrylic polymer is increased in the order of organic/organic, organic/inorganic, inorganic/inorganic. On the other hand, the more the content of the monomer having an alkylene oxide structure, the higher the polarity, and as a result, the compatibility with the liquid ion salt is increased.

Thus, if a combination of an organic cation and an inorganic anion is selected as a liquid ionic salt and the monomer content of the (meth)acrylic polymer having an alkylene oxide structure is 10 to 70% by mass, the compatibility is not excessive. When the height is low, the effect of filling the above-mentioned uneven surface is obtained. As a result, regardless of the difference in surface shape and polarity of the AG polarizing plate and the planar polarizing plate, an adhesive composition having the same adhesive force can be obtained. On the other hand, in the case where 70% by mass or more of the monomer having an alkylene oxide structure is contained, or a combination of an organic cation or an organic anion is used as the liquid ionic salt, since the polarity of the adhesive composition is increased, The adhesion to the AG polarizer having a low polarity on the surface is deteriorated, and since the compatibility between the acrylic polymer and the liquid ion salt is high, the localization of the ion salt does not occur, and the adhesion to the AG polarizer is still Stay at a low level.

Thus, for the AC polarizing plate, as a result of lowering the polarity of the (meth)acrylic polymer, or selecting a combination of an organic cation having a high hole-filling effect and an inorganic anion, the adhesion is increased. In the case of a polarizing plate, as a result of increasing the polarity of the (meth)acrylic polymer, the adhesion will increase, but in the invention of the present application, for example, the polarity and the pore-filling effect of the (meth)acrylic polymer are adjusted. As a result of both, an adhesive composition capable of exerting the same adhesion to a polarizing plate having a different surface state can be obtained.

[Industrial use possibility]

The adhesive composition of the present invention is excellent in charge prevention effect, and in any case of low speed and high speed peeling, the difference in adhesion due to the difference in shape and polarity of the surface of the adherend is small, and peeling is caused by peeling The difference in adhesion caused by the speed is also small, and it is excellent in mechanical properties, and can improve the efficiency of the pair.

Therefore, the adhesive sheet using the adhesive composition of the present invention is suitable as a user of the surface protective adhesive sheet for an optical member such as a polarizing plate.

Claims (5)

An adhesive composition comprising the following components (A) to (C), (A) a (meth)acrylic polymer obtained by copolymerization of the following components (a1) to (a4) ( However, the total of (a1) to (a4) is 100% by mass) (B) A liquid ionic salt (C) isocyanate crosslinking agent formed from an organic cation and an inorganic anion. The adhesive composition of claim 1, wherein the content of the liquid ionic salt of the organic cation and the inorganic anion of the component (B) is 100 parts by weight of the (meth)acrylic polymer of the component (A). The content of the isocyanate crosslinking agent of the component (C) is from 0.5 to 10 parts by weight, based on 0.05 to 3 parts by weight. An adhesive composition according to claim 1 or 2, wherein the organic cation of the component (B) is an imidazolium cation or a pyridinium cation child. An adhesive composition according to claim 1 or 2, wherein the inorganic anion of the component (B) is PF ₆ ^- or BF ₄ ^- . An adhesive sheet characterized by being obtained by crosslinking an adhesive composition according to any one of claims 1 to 4.