WO2008032762A1 - Adhesive composition and adhesive sheet - Google Patents

Abstract

Disclosed is an adhesive composition which has an excellent antistatic property, and is reduced in the variance in adhesivity to an object depending on the condition of the object or the peeling speed. The adhesive composition comprises the following components (A) to (C): (A) a (meth)acylic polymer produced by copolymerizing the following monomers (a1) to (a4) (provided that the total amount of the monomers (a1) to (a4) is 100 mass%): 10 to 70 mass% of a (meth)acrylic monomer having an alkylene oxide structure, (a2) 1 to 8 mass% of a monomer having a hydroxy group, (a3) 0.05 to 0.5 mass% of a monomer having one functional group selected from a carboxyl group, an amide group or an amino group, and (a4) 25 to 85 mass% of a (meth)acrylic acid alkyl ester; (B) a liquid ionic salt composed of an organic cation and an inorganic anion; and (C) an isocyanate crosslinking agent.

Description

 Specification

 Adhesive composition and adhesive sheet

 Technical field

 [0001] The present invention relates to a pressure-sensitive adhesive composition, and more specifically, is used for a pressure-sensitive adhesive layer in a surface protective sheet of an optical member such as a polarizing plate, and has excellent antistatic properties and a surface shape of an adherend. The present invention relates to a pressure-sensitive adhesive composition capable of reducing a difference in adhesive strength depending on polarity and peeling speed.

 Background art

 Conventionally, as an adhesive sheet to be affixed to an electronic device or the like, an antistatic adhesive sheet in which a base material, release paper or the like is subjected to an antistatic treatment or an antistatic layer is laminated as an undercoat layer of an adhesive layer has been used. ing.

 In recent years, there has been an increasing demand for imparting an antistatic function to the pressure-sensitive adhesive layer itself, and an antistatic pressure-sensitive adhesive in which an antistatic agent is added to the pressure-sensitive adhesive layer has been developed. For example, a pressure-sensitive adhesive composition containing an ionic liquid and a (meth) acrylic polymer having an alkylene oxide (meth) acrylate has been reported! (See Patent Document 1).

 [0004] However, the pressure-sensitive adhesive sheet using the pressure-sensitive adhesive composition is applied to, for example, a low-polarity anti-glare (AG) polarizing plate having irregularities on the surface, and a high-polarity and smooth surface. Since the adhesive force differs depending on the surface shape and polarity when applied to the polarizing plate, it is necessary to use an adhesive sheet designed for the type of polarizing plate. It was. This means that a line that handles both electronic equipment using AG polarizing plates and electronic equipment using plain polarizing plates must use an adhesive sheet suitable for both. There was a problem in terms of work efficiency.

[0005] On the other hand, the pressure-sensitive adhesive sheet that has finished its role of protecting the surface is peeled off and discarded. However, if this peeling is performed at a high speed, the force required for peeling increases due to the pressure-sensitive adhesive force, resulting in a decrease in work efficiency. There is a problem that contamination occurs, and there is a problem that if the adhesive strength is kept low in order to improve these, the adhesiveness of the member becomes poor and if it floats on the adhesive sheet, peeling will occur [0006] In order to solve this problem, by using an acrylic copolymer containing a hydroxyl group and a carboxyl group and having a glass transition temperature in a specific range and an aromatic polyfunctional isocyanate compound, a peeling force is obtained. A pressure-sensitive adhesive composition with reduced speed dependency has been reported! (See Patent Document 2).

 [0007] However, the adhesive composition does not have an antistatic function, and furthermore, it has a force that cannot reduce the difference in adhesive force caused by the difference in surface shape and polarity of the adherend.

 Patent Document 1: Japanese Patent Application Laid-Open No. 2004-263084

 Patent Document 2: JP 2001-123136 A

 Disclosure of the invention

 Problems to be solved by the invention

[0009] Accordingly, the pressure-sensitive adhesive has excellent antistatic properties, can reduce the difference in adhesive force due to the difference in the surface state of the adherend, and also has a small difference in adhesive force between high-speed peeling and low-speed peeling. Development of a composition is required, and the present invention has an object to provide such a pressure-sensitive adhesive composition.

 Means for solving the problem

 [0010] As a result of intensive studies to solve the above problems, the present inventor has found that a (meth) acrylic monomer having an alkylene oxide structure, two types of monomers having a specific functional group, and (meth) acrylic The pressure-sensitive adhesive composition obtained by blending a liquid ionic salt composed of an organic cation and an inorganic anion and an isocyanate cross-linking agent into a (meth) acrylic polymer obtained by copolymerizing an acid alkyl ester has an excellent antistatic effect. In addition, the present inventors have found that the difference in adhesive force due to the difference in surface shape and polarity of the adherend can be reduced regardless of the peeling speed, and that the difference in adhesive force due to the peeling speed can be reduced. It came to complete.

 [0011] That is, the present invention provides:

 Next ingredients (A) to (C)

 (A) The following component (al) is not! /, And (meth) acrylic polymer obtained by copolymerizing (a4) (however, the total of (al) to (a4) is 100% by mass)

(al) (Meth) acrylic monomer having alkylene oxide structure 10-70% by mass

(a2) Hydroxyl-containing monomer;! ~ 8% by mass

(a3) a carboxyl group, model Nomar 0.05 to 0 containing any of the functional groups of the amide group, or amino group. 5 mass ^_0/0

 (a4) (Meth) acrylic acid alkyl ester 25-85% by mass

(B) Liquid ion salt comprising an organic cation and an inorganic anion

 (C) Isocyanate crosslinking agent

 It is an adhesive composition characterized by containing.

Furthermore, the present invention is a pressure-sensitive adhesive sheet obtained by crosslinking the above pressure-sensitive adhesive composition.

 The invention's effect

 [0013] The pressure-sensitive adhesive composition of the present invention has an excellent antistatic effect and can reduce the difference in adhesive force caused by the shape and polarity of the surface of the adherend and the peeling speed, and therefore can be applied. It has excellent mechanical properties with a wide range of adherends and can improve work efficiency.

 BEST MODE FOR CARRYING OUT THE INVENTION

[0014] The pressure-sensitive adhesive composition of the present invention comprises (meth) acrylic polymer (component (A)) obtained by copolymerizing components (al) to (a4) described below as constituent components, an organic cation and an inorganic anion. Liquid ion salt (component (B)) and isocyanate cross-linking agent (component (C)).

 [0015] The components constituting the (meth) acrylic polymer are (meth) acrylic monomers having an alkylene oxide structure (component (al)), hydroxyl group-containing monomers (component (a2)), carboxyl groups, These are monomers (component (a3)) and (meth) acrylic acid alkyl esters (component (a4)) containing amide groups or amino groups!

[0016] The component (al) constituting the component (A) has an alkylene oxide structure in the molecule, and examples of the alkylene oxide structure include an oxymethylene group, an oxyshethylene group, an oxypropylene group, and an oxybutylene group. The number of moles of the alkylene oxide structure added to (meth) acrylic acid is not particularly limited; [0017] Specific examples of the (meth) acrylic monomer having an alkylene oxide structure are as follows.

, Methoxy polyethylene glycol (meth) acrylate, such as methoxydiethylene glycol (meth) acrylate, methoxy triethylene glycol (meth) acrylate; ethoxy such as ethoxyethylene glycol (meth) acrylate, ethoxy triethylene glycol (meth) acrylate Polyethylene glycol (meth) acrylate; Butoxy diethylene glycol (meth) acrylate, butoxypolyethylene glycol (meth) acrylate, such as butoxy triethylene glycol (meth) acrylate; Phenoxy diethylene glycol (meth) acrylate

And phenoxypolyethylene glycol (meth) acrylate, such as phenoxytriethylene glycol (meth) acrylate; methoxy polypropylene glycol (meth) acrylate, such as methoxydipropylene glycol (meth) acrylate. Of these, ethoxydiethylene glycol acrylate, methoxyethyl acrylate and the like are preferably used.

[0018] The (meth) acrylic monomer having an alkylene oxide structure as the component (al) may be used alone or in admixture of two or more. is a monomeric component 10 to 70 mass _^0/0 (meth) acrylic polymer component (a), preferably 20 to 60 wt%. When the content is less than 10% by mass or greater than 70% by mass, the difference in the adhesive force due to the surface shape and polarity of the adherend becomes large, and the adherend is not contaminated during peeling. May occur.

 [0019] The hydroxyl group-containing monomer of the component (a2) constituting the component (A) includes, for example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 6-hydride Monomers of alkylene diols such as xyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, polypropylene glycol mono (meth) acrylate, 1,6-hexanediol mono (meth) acrylate (Meth) atarylates; N-hydroxyethyl (meth)

Among them, 4-hydroxybutyl (meth) acrylate and 2-hydroxyethyl (meth) acrylate are preferably used.

[0020] The hydroxyl group-containing monomer of the above component (a2) may be used alone or in combination of two or more, but the total content is component (A). of (meth) the gesture et preferred that 1 to 8% by weight in a monomer component of the acrylic polymer, it is 3 to 6 mass _^0/0 Is more preferable.

 [0021] Furthermore, the monomer containing any functional group of carboxyl group, amide group or amino group of component (a3) constituting component (A) is, for example, (meth) as a carboxyl group-containing monomer. Acrylic acid, (meth) acrylic acid / 3carboxyethyl, itaconic acid, crotonic acid, maleic acid, fumaric acid, etc. can be mentioned, and amide group-containing monomers include attalinoleamide, N, N-dimethyl Examples include acrylamide, N- (1,1-dimethyl-3-oxobutyl) acrylamide, and tert-butylacrylamide sulfonic acid, and examples of the amino group-containing monomer include N, N-dimethylaminoethyl (meth) acrylate, N , N—Detylaminoethyl (meth) acrylate, N, N—Dimethylaminopropyl (meth) acrylate, N, N—Jet Such Aminopuropiru (meth) Atari rate can be exemplified. Of these, acrylic acid, acrylamide, dimethylaminoethyl methacrylate and the like are preferably used. The component (a3) also includes a monomer having two or more carboxyl groups, amide groups or amino groups, such as N- (Ν ′, N′-dimethylenoreaminomethinole) atalinoleamide.

 [0022] Monomers having a carboxyl group, amide group, or amino group! /, Or any functional group of component (a3) may be used alone or in combination of two or more. However, the total content is preferably 0.05 to 0.5% by mass in the monomer component of the (meth) acrylic polymer of component (A). 3 mass% is more preferable. Within this range, the difference in the adhesive force due to the peeling speed can be reduced. When the monomer (a3) is less than 0.05% by mass, it is difficult to reduce the speed dependence of the peeling force. When the content is higher than mass%, a phenomenon (stopping) that alternately stops and instantaneously peels during high-speed peeling occurs. The (a3) monomer also has the effect of finely adjusting the polarity of the (meth) acrylic polymer.

[0023] Furthermore, specific examples of the (meth) acrylic acid alkyl ester of component (a4) constituting component (A) include methyl (meth) acrylate, ethyl (meth) acrylate, (meth ) Atalinoleate n-propyl, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, n-pentyl (meth) acrylate, isopentyl (meth) acrylate, (meth) Examples include n-hexyl acrylate, 2-ethylhexyl (meth) acrylate, and n-octyl (meth) acrylate. Of these, 2-methyhexyl (meth) acrylate is preferred. Used.

 [0024] The (meth) acrylic acid alkyl ester of component (a4) may be used alone,

It may be used as a mixture of two or more, but preferred that total content of which is 25 to 85 mass _^0/0 in monomer component (meth) acrylic polymer one gesture, et al., 35 to 75 and more preferably the mass is a ^_0/0.

 [0025] The (meth) acrylic polymer of component (A) used in the present invention is a monomer of the above components (al) to (a4) such as solution polymerization, emulsion polymerization, bulk polymerization, etc. (meth) acrylic polymer It can be obtained by copolymerization by a method usually used for polymer synthesis. The molecular weight of the component (A) (meth) acrylic polymer is not particularly limited, but is preferably 200,000 to 700,000.

 [0026] In addition to the above-described components, a polymerization initiator and a polymerization regulator can be used as necessary in producing the (meth) acrylic polymer of component (A) used in the present invention.

 [0027] Examples of the polymerization initiator include azo polymerization initiators such as azobisisoptyronitrile, peroxide polymerization initiators such as benzoyl peroxide, and the like. Using 100 parts by weight of the monomer mixture of (a4), use in the range of 0.01 to;! Parts by weight.

 On the other hand, component (B) of the present invention is a liquid ion salt comprising a combination of an organic cation and an inorganic anion. In this specification, the liquid ion salt means a salt that is liquid at room temperature (25 ° C.).

 [0029] Examples of the organic cation constituting the component (B) include imidazolium cation, pyridinium cation, piperidinium cation, pyrrolidinium cation, tetrahydropyrimidinium cation, dihydropyrimidium. Powers including cations, tetranolequinoleum ammonium cation, trialkylsulfoium cation, etc. Of these, imidazolium cation and pyridinium cation are preferably used, and pyridinium cation is particularly preferable.

[0030] Specific examples of the imidazolium cation include, for example, 1,3-dimethylimidazolium mucachi, 1,3-jetylimidazolium cation, 1-ethyl-3-methylimidazolium cation, 1-butyl-3-methyl. Imidazolium cation, 1-hexyl Tyrimidazolium cation, 1-octyl- 3-methyl imidazolium cation, 1-deciru 3-methyl imidazolium cation, 1 dodecyl 3-methyl imidazolium cation, 1-tetradecyl 3-methyl imidazolium cation, 1, 2 dimethyl 3-p Oral pyrimidazolium cation, 1-ethyl-2-, 3-dimethylimidazolium cation, 1-butyl-2,3 dimethylimidazolium cation, 1 monohexyl 2,3 dimethylimidazolium cation, etc., 1-butyl-3 —Methylimidazolium cation, 1-hexylru 3-methylimidazolium cation, etc. are preferably used

Yes

 [0031] Specific examples of the pyridinium cation include, for example, 1-ethylpyridinium cation, 1-butylpyridinium cation, 1-hexylpyridinium cation, 1-butyl-3- Methylpyridinium cation, 1-Butyl-4 Methylpyridinium cation, 1-Hexylur 3—Methylpyridinium cation, 1-Hexylru 4 Methylpyridinium cation, 1-Butyl-3,4-Dimethylpyridinium Among them, 1-hexyl 4-methylpyridinium cation and the like are preferably used.

 [0032] In addition, examples of inorganic anions constituting the component (B) include Cl_, Br_, Γ, A1C 1 Al CI BF PF CIO NO AsF SbF NbF TaF F (

4 2 7 4 6 4 3 6 6 6 6

 HF) — and the like, and among them, PF_, BF— and the like are preferably used.

 n 6 4

[0033] Component (B) of the present invention is a salt composed of a combination appropriately selected from the above organic cations and inorganic anions, specifically, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl 3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylpyridinium tetrafluoroborate, 1-butyl-3-methylpyridinium hexafluorophosphate, 1-hexylol 3-methylimidazolium Tetrafluoroborate, 1-hexyluro 3-methylimidazole hexaphosphate, 1-octyl 3-methyl imidazole tetrafluoroborate, 1-octyl 3-methyl imidazole hexa Fluorophosphate, 1 monohexyl 3-methylimidazolium bromide, 1 monohexyl -3-methylimidazolium chloride, 1-hexyluro 2, 3 dimethylimidazolium tetrafluoroborate, 1-1-hexyluro 2, 3-dimethylimidazole hexafluorphosphate; 1 butylpyridinium tetra Fluoroborate, 1 Butylpyridinium hexafluorophosphate, 1-hexylpyridinium tetraf-noreloborate, 1-hexinorepyridinium hexafnoreophosphate phosphate, 1-butynoret 3-methylpyridinium tetrafluoroborate 1-Butyl 3-methylpyridinium hexafluorophosphate, 1 hexyluro 4 Methylpyridinium tetrafluoroborate, 1 1 hexilu 4 methylpyridinium hexafluoro Among them, 1-butyl-3-methylimidazole hexafluorophosphate, 1-hexyl 3-methylimidazole tetrafluoroborate, 1-hexyl 4-methylpyridinium Xafluorophosphate and the like are preferably used.

 [0034] The amount of component (B) is usually in the range of 0.05 to 3 parts by weight, preferably 0.3 to 1.5 parts by weight, relative to 100 parts by weight of component (A). Part range.

 [0035] Furthermore, the isocyanate cross-linking agent of component (C) of the present invention is a compound having an isocyanate group capable of cross-linking with a hydroxyl group in the molecule, and specifically, tolylene diisocyanate, chlorophenol dirange. Isocyanate monomers such as isocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, Examples thereof include isocyanate compounds or isocyanurate compounds obtained by subjecting these to addition reaction with bivalent or higher alcohol compounds such as trimethylolpropane. In addition, urethane prepolymer type isocyanates obtained by adding an isocyanate compound to known polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, polyisoprene polyols, and the like are also included. Of these, hexazimethylene isocyanate is preferably used.

[0036] The amount of component (C) to be added is usually 0.5 to 10 parts by weight, preferably 2 to 5 parts by weight, relative to 100 parts by weight of component (A). .

[0037] The pressure-sensitive adhesive composition of the present invention can be obtained by adding other additives to the components (A) to (C) as necessary and mixing them by a conventional method. 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 preferable to mix without using a solvent.

[0038] The antistatic pressure-sensitive adhesive composition of the present invention impairs the effects of the present invention in addition to the components described above. If necessary, add a tackifier, plasticizer, antioxidant, preservative, etc. as necessary.

 [0039] The pressure-sensitive adhesive composition of the present invention obtained as described above can be applied to the surface of a support by a conventional method and dried to obtain the pressure-sensitive adhesive sheet of the present invention.

 [0040] In the production of the pressure-sensitive adhesive sheet, as the support, for example, a resin film such as polyester and polyethylene can be used, and the coating thickness of the pressure-sensitive adhesive composition is usually 2 to 30 to 111. Yes, preferably 10 to 20 111.

 [0041] The pressure-sensitive adhesive sheet of the present invention obtained as described above has a pressure-sensitive adhesive force when affixed to an adherend having a different surface shape and polarity, such as an AG polarizing plate or a plain polarizing plate, regardless of the peeling speed. The difference between the adhesive force at low speed peeling and the adhesive force at high speed peeling is also small.

 Example

 Next, the present invention will be described in more detail with reference to production examples and examples, but the present invention is not limited to these examples and the like.

 [0043] Manufacturing Example 1

 60 parts by weight of ethoxydiethylene glycol acrylate (ECA, manufactured by Kyoeisha) as component (al), 5 parts by weight of 4-hydroxybutyl acrylate (4HBA) as component (a2), 0.15 parts by weight of acrylic acid as component (a3) As a component (a4), 2-ethyl hexyl acrylate (2EΗΑ) 34 · 85 parts by weight, ethyl acetate 120 parts by weight and azobisisobutyronitrile (ΑΙΒ Ν) 0.1 part by weight are put in a reaction vessel. The air in the reaction vessel was replaced with nitrogen gas. Thereafter, while stirring in a nitrogen atmosphere, the reaction vessel was heated to 70 ° C. and reacted for 6 hours. After completion of the reaction, the reaction mixture was diluted with ethyl acetate to obtain an acrylic polymer solution A1 having a molecular weight of 500,000.

 [0044] Manufacturing examples 2 to 3

 Atalyl polymer solutions A2 and A3 were obtained in the same manner as in Production Example 1 except that the components (al) to (a4) were changed as shown in Table 2 below. The molecular weight is also shown in Table 1.

 [0045] Production Comparative Examples 1 to 15;

Atari is the same as Production Example 1 except that components (al) to (a4) are changed as shown in Table 2 below. A polymer solution Bl to Bl 5 was obtained. The molecular weight is also shown in Table 1.

[0046] [Table 1]

[0047] Abbreviations in the table are as follows.

 MEA: Methoxyethyl Atylate

 ECA: Ethoxydiethylene dalcol acrylate

 4HBA: 4-hydroxybutyl acrylate

 2HEA: 2-hydroxyethyl acrylate

 AA: Acrylic acid

 AM: acrylamide

 DM: Dimethylaminoethyl methacrylate

 2EHA: 2-Ethylhexyl acrylate

[0048] Example 1

For 100 parts by weight of the solid content of the acrylic polymer solution A1 obtained in Production Example 1, as a liquid ionic salt, 1 part by weight of 1-hexylru 4 methylpyridinium hexafluorophosphate, and as an isocyanate cross-linking agent 3 parts of hexamethylene diisocyanate (HMDI) was added and mixed to obtain a pressure-sensitive adhesive composition. [0049] This pressure-sensitive adhesive composition was coated on a polyester film so that the thickness after drying was 20 m, dried at 80 ° C for 2 minutes, and then peeled off to the pressure-sensitive adhesive layer side. A polyester film (PET3811, manufactured by Lintec) was attached and aged for 7 days at 23 ° C and 65% humidity to obtain an adhesive sheet.

 [0050] Examples 2 to 3

 A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were obtained in the same manner as in Example 1 except that the acrylic polymer solution and the liquid ion salt were changed as shown in Table 2 below. Table 2 shows whether the cation and anion of the liquid ion salt are organic or inorganic, respectively.

 [0051] Comparison example;! ~ 15

 A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were obtained in the same manner as in Example 1 except that the acrylic polymer solution and the ionic liquid were changed as shown in Table 2 below. The force that the cation and anion of the ionic salt are either organic or inorganic, and the state of the ionic salt at room temperature are also shown.

[0052] [Table 2]

Acrylic series. Limaric acid salt Cation Anion State Example 1 A1 1-Hexyl-4-methylpyricinium hexafluorofluoro organic inorganic liquid

 Sufu I

 Example 2 A2 1-Fu "til-3-methylimita" ', Lium hexafluoro Organic Inorganic Liquid Phosph I-to

 Example 3 A3 卜 hexyl-3-methylimita 'so'lium terrafluo □ Organic Inorganic Liquid Formate

 Comparative Example 1 B1--

 Comparative Example 2 B2-Ichi Comparative Example 3 B3-Ichi

 Comparative Example 4 B4 1-Hexyl-4-Methylpyrici Nyhexafluoro Organic Inorganic Liquid Sulf I -To

 Comparative Example 5 B5 1-7 "til-3-methylimita 'so'lium hexafluoro organic inorganic liquid wood suf I-to

 Comparative Example 6 B6 Trityl Methyl Pyramonium Bis (Trifluoro Organic Organic Liquid Methanesulfonyl)

 COMPARATIVE EXAMPLE 7 B7 Trimethylph 'mouth pyrammonium bis (trifluoro organic organic liquid methanesulfonyl) imito'

 Comparative Example 8 B8 1-Hexyl-3-methylimita "so" lium trifluoro organic organic liquid methanesulfonate

 Comparative Example 9 B9 Lithium /, '-Chlorate Inorganic Inorganic Solid Comparative Example 10 B10 Lithium', — -Chlorine- 卜 Inorganic Inorganic Solid Comparative Example 1 1 B1 1 Lithium-urolate Inorganic Inorganic Solid Comparative Example 12 B12 1- Hexyl-4- (Chirch'Rishi'Nyhexafluorolo Organic Inorganic Liquid

 Sufu I

 Comparative Example 13 B13 1-Futyl-3-methylimitaso 'hexahexafluoro Organic Inorganic Liquid Phosphate

 Comparative Example 14 B14 1-Futhyl-3-methylimitasolium hexafluoro Organic Inorganic Liquid Phosph I-to

 Comparative Example 15 B15 1-Hexyl-3-Methylimiline "So" lium Trifluoro Organic Organic Liquid Methanesulfonate

[0053] The adhesive sheet obtained in Example 1! /, 3 and Comparative Example 1! /, 15 were evaluated for peeling force and antistatic property by the following evaluation methods and criteria. did. The results are shown in Table 3.

Yes

 [0054] (Evaluation method and criteria)

 <Peeling force>

After the adhesive sheet was cut into a size of 150 mm × 250 mm, the peeled polyester film was peeled off and transferred to one side of the AG polarizing plate and the Plane polarizing plate, respectively. After leaving at 23 ° C and 65% for 1 day, measure the adhesive strength when peeling off the attached adhesive sheet in the 180 ° direction at a peeling speed of 300mm / min (low speed) and 30m / min (high speed). The low-speed peel force and the high-speed peel force were used respectively. [0055] <Antistatic property>

 (Evaluation methods)

 Create a laminate that combines an acrylic plate (70 mm x 150 mm x lmm) and a polarizing plate (AG polarizing plate, plain polarizing plate) so that the AG and plain surfaces of the polarizing plate are on the outside. Static elimination was performed using SJ-F300).

 The pressure-sensitive adhesive sheets obtained in the above Examples and Comparative Examples were cut into 40 mm × 150 mm, and then pressure-bonded to the AG surface and plain surface of the laminate that had been neutralized with a 2 kg rubber roller. After leaving at 25 ° C and 65% for 1 day, the charge is removed again, and the surface potential of the polarizing plate when peeled at a peeling speed of 30m / min and peeling angle of 180 ° is measured using a potential meter (SK manufactured by KEYEN CE). ).

 (Evaluation criteria)

 Evaluation Stripping voltage

 〇: Less than ± 0.5kV

 △: ± 0.5 ~ 1. OkV

 X: ± 1. OkV or more

[0056] [Table 3]

Low speed peel force (300mm / m i n) High speed peel force (30m / m i n) Antistatic property Unit: / 150mm Table position: g / 150mm

 AG① Fu. Lane ② ① ー ② AG③ Fu. Lane ④ ③ ー ④

Example 1 42 42 0 650 650 0 〇 Example 2 42 42 0 650 650 0 Ο Example 3 43 43 0 650 650 0 〇 Comparative example 1 42 36 6 650 600 50 X Comparative example 2 36 43 7 600 650 50 X Comparative Example 3 32 48 16 550 750 200 X Comparative Example 4 Contamination Contamination Undecided Comparative Example 5 36 47 11 600 750 150 ○ Comparative Example 6 41 36 7 650 600 50 ○ Comparative Example 1 36 42 6 600 650 50 ○ Comparative Example 8 32 48 16 550 750 200 〇 Comparative Example 9 Contaminated Stain; t = Not determined Comparative Example 10 Contaminated Contaminated Not determined Comparative Example 1 1 33 47 14 550 750 200 Δ Comparative Example 12 54 48 6 900 750 50 〇 Comparative Example 13 53 52 1 δθθζ ί ρ ^ ¹ δθθζ ί ρ '^' 0 X Comparative Example 14 Unmeasurable * ² Unmeasurable * ² Undecided Comparative Example 15 53 47 6 900 750 150 〇

* 丄 Deformation of the pressure-sensitive adhesive layer could not follow the peeling speed, and a phenomenon was observed in which stopping and instantaneous peeling were repeated alternately.

 *? Breakage occurred in the pressure-sensitive adhesive layer at the time of peeling, and accurate measurement could not be performed.

 As is apparent from the results, the pressure-sensitive adhesive tape produced using the pressure-sensitive adhesive composition of the present invention is excellent in antistatic property, and in both high-speed peeling and low-speed peeling, is an AG polarizing plate. The adhesive strength was equivalent to that of a plain polarizing plate, and the difference between the adhesive strength at high speed peeling and the adhesive strength at low speed peeling was small.

[0058] On the other hand, in the comparative example in which the monomer composition and the ionic salt of the acrylic polymer are different from those of the present invention, there is a large difference in adhesive force between the AG polarizing plate and the plain polarizing plate. As a result, contamination with sufficient performance could not be obtained. For example, an acrylic polymer having the same monomer composition as the acrylic polymer used in Example 1 of Patent Document 1 (Japanese Patent Laid-Open No. 2006-63311), and a liquid ionic salt comprising the same organic cation and organic anion are used. In Comparative Example 15 used, the difference in adhesive strength between the AG polarizing plate and the plain polarizing plate is large in both low-speed peeling and high-speed peeling, and the difference in adhesive strength in low-speed peeling and in high-speed peeling is also large. Larger than Examples 1 to 3. there were.

 Action

 [0059] The reason why the pressure-sensitive adhesive sheet of the present invention exhibits the same adhesive strength with either an AG polarizing plate or a plain polarizing plate is not clear, but is considered as follows. In other words, the AG polarizing plate has low polarity and unevenness on the surface, whereas the plain polarizing plate is high polarity and smooth. The content of functional group-containing monomers such as (meth) acrylic monomers having an alkylene oxide structure and other hydroxyl group-containing monomers is high, and the (meth) acrylic polymer of component (A) becomes more polar and (meth) The higher the polarity of the acrylic polymer, the lower the adhesion to the low-polarity AG polarizing plate and the higher the adhesion to the high-polarity plain polarizing plate.

 [0060] On the other hand, since the gap between the irregularities on the surface of the AG polarizing plate is small, the adhesive usually does not adhere to the entire surface and does not contact the concave portions. Therefore, if the affinity of the (meth) acrylic polymer to the AG polarizing plate and that of the plain polarizing plate are the same, the adhesive strength to the (meth) acrylic polymer is smaller for the plain polarizing plate because of the smaller contact area. It is larger than the polarizing plate.

 However, when the compatibility of the liquid ionic salt of component (B) with the acrylic polymer is appropriate (not completely compatible and slightly localized), the liquid ionic salt is Adhesive strength increases because it is slightly localized on the surface of the adhesive without bleed and fills the concave and convex surfaces of the AG polarizing plate.

 [0062] The compatibility of the liquid ion salt and the (meth) acrylic polymer is related to the combination of the cation and anion of the liquid ion salt and the content of the monomer having an alkylene oxide structure in the (meth) acrylic polymer. First, the ionic bond strength of the liquid ion salt is the combined force of caton / ayuon, in the order of inorganic / inorganic, organic / inorganic, and organic / organic, so the (meth) acrylic polymer of component (A) that is highly polar Compatibility with organic / organic

It becomes higher in the order of organic / inorganic and inorganic / inorganic. On the other hand, the higher the content of the monomer having an alkylene oxide structure, the higher the polarity and the higher the compatibility with the liquid ion salt.

[0063] Therefore, a combination of an organic cation and an inorganic anion is selected as the liquid ion salt,

Content of monomer having alkylene oxide structure in (meth) acrylic polymer By setting the content to 10 to 70% by mass, the compatibility becomes moderate without being too high, and the effect of filling the uneven surface is obtained. The difference in surface shape and polarity between the AG polarizing plate and the plain polarizing plate Regardless of this, an adhesive composition having the same adhesive strength can be obtained. In contrast, when the monomer having an alkylene oxide structure is contained in an amount of 70% by mass or more, or when a combination of an organic cation and an organic anion is used as the liquid ion salt, the polarity of the pressure-sensitive adhesive composition increases. Adhesive strength to AG polarizing plate due to poor adhesion to AG polarizing plate with low surface polarity, and high compatibility between acrylic polymer and liquid ionic salt, which does not cause localization of ionic salt. Will remain low.

 [0064] As described above, for the AG polarizing plate, by reducing the polarity of the (meth) acrylic polymer, a liquid ion salt of a combination of an organic cation and an inorganic anion having a high filling effect is selected. On the other hand, for the plain polarizing plate, on the other hand, the force that increases the adhesive strength when the polarity of the (meth) acrylic polymer is increased. In the present invention, the polarity of the (meth) acrylic polymer By adjusting both the filling effect and the hole filling effect, it is possible to obtain a pressure-sensitive adhesive composition that exhibits the same adhesive strength to polarizing plates having different surface states.

 Industrial applicability

[0065] The pressure-sensitive adhesive composition of the present invention is excellent in an antistatic effect and has a small difference in adhesive force due to the difference in shape and polarity of the adherend surface at both low speed and high speed peeling. Since the difference in adhesive strength depending on the peeling speed is small, it has excellent mechanical properties and can improve work efficiency.

 Therefore, the pressure-sensitive adhesive sheet using the pressure-sensitive adhesive composition of the present invention is advantageously used as a pressure-sensitive adhesive sheet for protecting the surface of optical members such as polarizing plates.

Claims

The scope of the claims  [1] Next component (A) to (C)  (A) The following component (al)! /, (Meth) acrylic polymer obtained by copolymerizing (a4) (however, the total of (al) to (a4) is 100% by mass)  (al) (Meth) acrylic monomer having alkylene oxide structure  10-70% by mass  (a2) Hydroxyl-containing monomer;! ~ 8% by mass (a3) a carboxyl group, model Nomar 0.05 to 0 containing any of the functional groups of the amide group, or amino group. 5 mass ^_0/0  (a4) (Meth) acrylic acid alkyl ester 25-85% by mass (B) Liquid ion salt comprising an organic cation and an inorganic anion  (C) Isocyanate crosslinking agent  A pressure-sensitive adhesive composition comprising: [2] Component (A) (meth) acrylic polymer 100 parts by weight of component (B) of organic cation and inorganic ionic liquid ion salt content 0.05 to 3 parts by weight, component (C) The pressure-sensitive adhesive composition according to claim 1, wherein the content of the isocyanate cross-linking agent is from 0.5 to 10 parts by weight.  [3] The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the organic cation power of component (B) is an imidazolium cation or a pyridinium cation. [4] The inorganic canyon force of component (B) is PF— or BF—.  6 4  The pressure-sensitive adhesive composition according to item.  [5] A pressure-sensitive adhesive sheet obtained by crosslinking the pressure-sensitive adhesive composition according to claim 1!