JPWO2019013130A1 - Adhesive composition and adhesive sheet - Google Patents

Abstract

Provided is a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer having blister resistance and whitening resistance even under high durability conditions. A pressure-sensitive adhesive composition containing a (meth)acrylic copolymer (A) having a glass transition temperature (Tg) of less than 0° C., an olefin polymer (B), and a crosslinking agent (C). A pressure-sensitive adhesive composition in which the viscosity of the olefin polymer (B) at 25° C. is 0.5 to 30.0 Pa·s.

Description

  The present invention relates to an adhesive composition and an adhesive sheet.

  In recent years, the market of smartphones and tablet computers has been rapidly expanding, and these are equipped with touch panels. The touch panel is a laminated body of various materials, and an adhesive is used for bonding the various materials (for example, see Patent Document 1).

  Polycarbonate, for example, is used as the material for the support and cover member (surface support) of the touch panel, but the polycarbonate contains water for the reason of its manufacturing process. When put into a durability test, foaming due to this moisture occurs. As described above, blistering may occur due to foaming due to outgas generated from the laminated material.

  Further, although the development of touch panels for automobiles has been expanding, automobiles are required to have higher durability than general use because of high temperatures in summer and the like. However, conventional pressure-sensitive adhesives have not been able to meet the high durability conditions intended for automobiles.

JP, 2013-018892, A

  An object of the present invention is to provide a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer having excellent blister resistance even under high durability conditions.

The present inventors have diligently studied to solve the above problems. As a result, they have found that a pressure-sensitive adhesive composition having the following constitution can solve the above problems, and completed the present invention.
The present invention relates to, for example, the following [1] to [4].

  [1] A pressure-sensitive adhesive composition containing a (meth) acrylic copolymer (A) having a glass transition temperature (Tg) of less than 0 ° C., an olefin polymer (B), and a crosslinking agent (C). The viscosity of the olefin polymer (B) at 25 ° C. is 0.5 to 30.0 Pa · s.

  [2] The pressure-sensitive adhesive composition according to [1], wherein the olefin polymer (B) does not have a crosslinkable functional group.

  [3] Copolymer weight of the monomer component in which the (meth) acrylic copolymer (A) contains 50 to 99 mass% of alkoxyalkyl (meth) acrylate and 0.5 to 20 mass% of a crosslinkable functional group-containing monomer. The pressure-sensitive adhesive composition according to the above [1] or [2], which is a united body.

  [4] A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of [1] to [3].

  According to the present invention, it is possible to provide a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer having excellent blister resistance even under high durability conditions.

Hereinafter, the pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet of the present invention will be described.
In the present specification, acryl and methacryl are collectively referred to as “(meth) acryl”, and acrylates and methacrylates are collectively referred to as “(meth) acrylate”. The term "polymer" is used to include a homopolymer and a copolymer, and the term "polymerization" is used to include a homopolymer and a copolymer.

[Adhesive composition]
The pressure-sensitive adhesive composition of the present invention contains a (meth) acrylic copolymer (A) described below, an olefin polymer (B), and a crosslinking agent (C). The pressure-sensitive adhesive composition of the present invention may contain an additive (D) if necessary.

<< (meth) acrylic copolymer (A) >>
The (meth) acrylic copolymer (A) has a glass transition temperature (Tg) of less than 0 ° C.
The Tg of the (meth) acrylic copolymer (A) can be determined, for example, by the Fox equation.

  The Tg of the (meth) acrylic copolymer (A) is less than 0 ° C, preferably -80 to -10 ° C, more preferably -70 to -30 ° C. When the Tg is within the above range, it is preferable from the viewpoint of the adhesiveness of the pressure-sensitive adhesive layer to the adherend. Further, when Tg is not less than the lower limit value, the cohesive force of the pressure-sensitive adhesive layer is excellent, which is preferable from the viewpoint of improving durability.

  The (meth) acrylic copolymer (A) has a weight average molecular weight (Mw) measured by gel permeation chromatography (GPC method) in terms of polystyrene, preferably 200,000 to 1,000,000, and more preferably Is 250,000 to 800,000, and more preferably 300,000 to 700,000. When the Mw is in the above range, a sufficient cohesive force is imparted to the pressure-sensitive adhesive layer obtained from the pressure-sensitive adhesive composition, which is preferable from the viewpoint of improving durability under high temperature conditions or high temperature and high humidity conditions.

  The (meth) acrylic copolymer (A) has a molecular weight distribution (Mw / Mn) measured by GPC method of preferably 2.0 to 15.0, more preferably 2.5 to 13.0. , And more preferably 2.8 to 10.0. When Mw / Mn is within the above range, a pressure-sensitive adhesive layer having excellent durability can be obtained, which is preferable.

  The total content of the (meth) acrylic copolymer (A), the olefin polymer (B) and the crosslinking agent (C) described below in the pressure-sensitive adhesive composition is 100% by mass of the solid content of the pressure-sensitive adhesive composition. The content is usually 60% by mass or more, preferably 65% by mass or more, more preferably 70% by mass or more. The solid content is a component excluding the solvent.

  Examples of the monomer component forming the (meth) acrylic copolymer (A) include (meth) acrylic acid alkyl ester, (meth) acrylic acid alkoxyalkyl ester and alkoxypolyalkylene glycol mono (meth) acrylate described below. Examples include at least one selected monomer (a1), a crosslinkable functional group-containing monomer (a2), and another monomer (a3). Hereinafter, these are also simply referred to as “monomers (a1) to (a3)”.

<Monomer (a1)>
Examples of the monomer (a1) include at least one monomer selected from (meth) acrylic acid alkyl ester, (meth) acrylic acid alkoxyalkyl ester and alkoxypolyalkylene glycol mono (meth) acrylate.

  Examples of the (meth) acrylic acid alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth). Acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, n-heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) Acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isostearyl (Meth) acrylate may be mentioned.

  Examples of the (meth) acrylic acid alkoxyalkyl ester include methoxymethyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 3-methoxypropyl (meth) acrylate, and 3-ethoxy. Examples thereof include propyl (meth) acrylate, 4-methoxybutyl (meth) acrylate and 4-ethoxybutyl (meth) acrylate.

Examples of the alkoxypolyalkylene glycol mono (meth) acrylate include methoxydiethylene glycol mono (meth) acrylate, methoxydipropylene glycol mono (meth) acrylate, ethoxytriethylene glycol mono (meth) acrylate, ethoxydiethylene glycol mono (meth) acrylate, Methoxytriethylene glycol mono (meth) acrylate may be mentioned.
The monomer (a1) may be used alone or in combination of two or more.

  The content of the monomer (a1) in 100% by mass of the monomer component used for forming the (meth) acrylic copolymer (A) is usually 50 to 99% by mass, and preferably 60 to 98% by mass. It is preferably 65 to 95% by mass. Such an embodiment is preferable because the obtained adhesive layer has excellent adhesive strength and cohesive strength. The content can be grasped, for example, from the charged amount of the monomer component.

  Especially when the content of the (meth) acrylic acid alkoxyalkyl ester as the monomer (a1) is 50% by mass or more in 100% by mass of the monomer component used for forming the (meth) acrylic copolymer (A). It is possible to efficiently disperse the water that has penetrated into the obtained pressure-sensitive adhesive layer, and to obtain a pressure-sensitive adhesive layer that is excellent not only in blister resistance but also in whitening resistance.

<Monomer (a2)>
The monomer (a2) is a crosslinkable functional group-containing monomer, and examples thereof include a hydroxyl group-containing monomer and an acid group-containing monomer.

  Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, and 8-hydroxyoctyl ( Examples thereof include hydroxyl group-containing (meth) acrylates such as hydroxyalkyl (meth) acrylates such as (meth) acrylate.

  Examples of the acid group include a carboxy group, an acid anhydride group, a phosphoric acid group, and a sulfuric acid group. Examples of the carboxy group-containing monomer include (meth) acrylic acid, β-carboxyethyl (meth) acrylate, 5-carboxypentyl (meth) acrylic acid, mono (meth) acryloyloxyethyl succinate, and ω-carboxypolyester. Examples include caprolactone mono (meth) acrylate, itaconic acid, crotonic acid, fumaric acid, maleic acid and the like. Examples of the acid group-containing monomer other than the carboxy group include phthalic anhydride, maleic anhydride, phosphoric acid group-containing monomer, and sulfuric acid group-containing monomer.

Among the monomers (a2), a hydroxyl group-containing monomer and a carboxy group-containing monomer are preferable. At least a part of the crosslinkable functional group derived from the monomer (a2) becomes a crosslinking point in the (meth) acrylic copolymer (A), and reacts with a crosslinking agent (C) described later to form a crosslinked structure. can do.
The monomer (a2) may be used alone or in combination of two or more.

  The content of the monomer (a2) is usually 0.5 to 20% by mass, preferably 0.8 to 100% by mass of the monomer component used for forming the (meth) acrylic copolymer (A). -18 mass%, more preferably 1-15 mass%. In such an embodiment, the crosslinked structure of the (meth) acrylic copolymer (A) is appropriately formed, and an adhesive layer having appropriate flexibility can be obtained. The content can be grasped, for example, from the charged amount of the monomer component.

<Monomer (a3)>
Examples of the monomer (a3) include monomers other than the above-mentioned monomers (a1) and (a2), and examples thereof include alicyclic hydrocarbon group- or aromatic hydrocarbon group-containing (meth) acrylate, styrene-based monomer, and amide group-containing. Examples thereof include monomers, amino group-containing monomers, cyano group-containing monomers, vinyl acetate, and polymerizable macromonomers.

  Examples of the alicyclic hydrocarbon group- or aromatic hydrocarbon group-containing (meth) acrylate include cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, adamantyl (meth) acrylate, benzyl (meth) acrylate, and phenyl (meth) acrylate. Acrylate and phenoxyethyl (meth) acrylate are mentioned.

  Examples of the styrene-based monomer include styrene; alkylstyrene such as methylstyrene, dimethylstyrene, trimethylstyrene, propylstyrene, butylstyrene, hexylstyrene, heptylstyrene, and octylstyrene; fluorostyrene, chlorostyrene, bromostyrene, dibromostyrene. And halogenated styrenes; functionalized styrenes such as nitrostyrene, acetylstyrene, and methoxystyrene.

  Examples of the amide group-containing monomer include N-alkyl such as (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide and N-hexyl (meth) acrylamide. N, N-dialkyl (meth) acrylamides such as (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide; N-vinylpyrrolidone, N-vinylcaprolactam, (meth) acryloyl Examples include nitrogen-based heterocycle-containing monomers such as morpholine.

Examples of the amino group-containing monomer include N, N-dialkylaminoalkyl (meth) acrylates such as N, N-dimethylaminoethyl (meth) acrylate and N, N-diethylaminoethyl (meth) acrylate.
Examples of the cyano group-containing monomer include cyano (meth) acrylate and (meth) acrylonitrile.

  Examples of the monomer of the polymer chain (main chain) part constituting the polymerizable macromonomer include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate and t-. Examples thereof include alkyl (meth) acrylates such as butyl (meth) acrylate, and the alkyl group preferably has 1 to 20 carbon atoms, and (meth) acrylonitrile; styrenes such as styrene and α-methylstyrene. Monomers are also included.

The macromonomer is preferably, for example, a (meth) acrylic macromonomer, a (meth) acrylonitrile-based macromonomer, or a styrene-based macromonomer, which can be produced according to various known methods, for example, JP2013-018227A. It can be produced by the method described in paragraph [0039] of the publication.
As the macromonomer, a commercially available product may be used, for example, a macromonomer whose main chain constituent monomer is methyl methacrylate (product name: 45% AA-6 (AA-6S), AA-6; manufactured by Toagosei) , A macromonomer whose main chain is a styrene / acrylonitrile copolymer (product name: AN-6S; manufactured by Toagosei), a macromonomer whose main chain constituent monomer is butyl acrylate (product name: AB-6; manufactured by Toagosei) And these are terminated with methacryloyl groups.
The monomer (a3) may be used alone or in combination of two or more.

  The content of the monomer (a3) is 20 mass% or less, preferably 15 mass% or less, more preferably 100 mass% of the monomer component used for forming the (meth) acrylic copolymer (A). Is 10% by mass or less.

<Method for producing (meth) acrylic copolymer (A)>
The (meth) acrylic copolymer (A) can be produced by a known method, but it is preferably produced by solution polymerization. Specifically, a monomer component and a polymerization solvent are charged into a reaction vessel, a polymerization initiator is added under an inert gas atmosphere such as nitrogen gas, and the reaction temperature is heated to about 50 to 90 ° C. and reacted for 4 to 20 hours. Let In addition, a polymerization initiator, a chain transfer agent, a monomer component, and a polymerization solvent may be appropriately added during the polymerization reaction.

  Examples of the polymerization initiator include ordinary organic polymerization initiators, and specific examples thereof include peroxides such as benzoyl peroxide and lauroyl peroxide, and 2,2′-azobisisobutyronitrile. Azo compounds may be mentioned. Among these, azo compounds are preferable.

Examples of the azo compound include 2,2′-azobisisobutyronitrile, 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile) and 2,2′-azobis (2-cyclopropyl). Propionitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2-methylbutyronitrile), 1,1'-azobis (cyclohexane-1-carbonitrile) , 2- (carbamoylazo) isobutyronitrile, 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis ( N, N'-dimethyleneisobutylamidine), 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) -propionamide], 2,2'-azobis (isobutylamide) dihydrate, 4,4 '-Azobis (4-cyanopentanoic acid), 2,2'-azobis (2-cyanopropanol), dimethyl-2,2'-azobis (2-methylpropionate), 2,2'-azobis [2- Methyl-N- (2-hydroxyethyl) propionamide].
The polymerization initiator may be used alone or in combination of two or more.

  The amount of the polymerization initiator used is usually 0.01 to 5 parts by mass with respect to 100 parts by mass of the monomer component. With such a mode, the Mw of the (meth) acrylic copolymer (A) can be adjusted within an appropriate range.

  In the solution polymerization, examples of the polymerization solvent include aromatic hydrocarbons such as benzene, toluene and xylene; aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane and n-octane; cyclopentane and cyclohexane. Alicyclic hydrocarbons such as cycloheptane and cyclooctane; ethers such as diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, dibutyl ether, tetrahydrofuran, dioxane, anisole, phenylethyl ether and diphenyl ether; chloroform, carbon tetrachloride , Halogenated hydrocarbons such as 1,2-dichloroethane and chlorobenzene; esters such as ethyl acetate, propyl acetate, butyl acetate and methyl propionate; ketones such as acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone and cyclohexanone; N, N Examples include amides such as dimethylformamide, N, N-dimethylacetamide and N-methylpyrrolidone; nitriles such as acetonitrile and benzonitrile; and sulfoxides such as dimethyl sulfoxide and sulfolane. The polymerization solvent may be used alone or in combination of two or more.

<< Olefin-based polymer (B) >>
It is considered that the olefin polymer (B) is unevenly distributed at the interface with the adherend when the pressure-sensitive adhesive sheet is produced from the pressure-sensitive adhesive composition and attached to the adherend. Since the olefin polymer (B) is unevenly distributed on the interface of the adherend, the outgas generated from the adherend can be suppressed from proceeding to the pressure-sensitive adhesive layer, and a pressure-sensitive adhesive sheet having excellent blister resistance can be obtained.

  The viscosity of the olefin polymer (B) at 25 ° C. measured by the method described in Examples is 0.5 to 30.0 Pa · s, preferably 0.8 to 28.0 Pa · s, and more preferably Is 1.0 to 25.0 Pa · s. When the viscosity is within the above range, when the pressure-sensitive adhesive sheet is attached to an adherend, it is likely to be unevenly distributed at the adherend interface, which is preferable from the viewpoint of blister resistance.

  The weight average molecular weight (Mw) of the olefin polymer (B) measured by the gel permeation chromatography method (GPC method) is, in terms of polystyrene, 1000 to 15000, preferably 2000 to 13000, more preferably 2500 to 12000. Is. When the Mw is within the above range, it is easy to migrate to the interface between the pressure-sensitive adhesive layer and the adherend, which is preferable from the viewpoint of blister resistance.

  The olefin polymer (B) may or may not have a polar functional group, but in the case of having a polar functional group, the above-mentioned ( A cross-linking reaction occurs between the (meth) acrylic copolymer (A) or between the olefin polymers (B), and it becomes difficult for the olefin polymer (B) to move to the interface between the pressure-sensitive adhesive layer and the adherend. Therefore, it is preferable that the olefin polymer (B) does not have a polar functional group.

  In the pressure-sensitive adhesive composition of the present invention, the content of the olefin polymer (B) is preferably 0.5 to 15 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer (A). It is more preferably 0.7 to 12 parts by mass, further preferably 1.0 to 10 parts by mass. When the content of the olefin polymer (B) is at least the lower limit, it is possible to impart blister resistance to the pressure-sensitive adhesive layer, and when it is at most the upper limit, problems such as clouding of the pressure-sensitive adhesive layer occur. Unlikely to occur.

  Examples of the olefin polymer (B) include Lucant LX004 (1.0 Pa · s), Lucant LX010 (2.9 Pa · s), Lucant LX020 (4.0 Pa · s), Lucant LX100 (24.2 Pa · s). ) (All manufactured by Mitsui Chemicals), B-1000 (1.0 Pa · s), B-2000 (7.0 Pa · s) (all manufactured by Nippon Soda) and the like. Among the above-mentioned olefin-based polymers, it is preferable to use Lucant LX010 and Lucant LX100 from the viewpoint of the presence or absence of a functional group and the viscosity.

<< Crosslinking agent (C) >>
The crosslinking agent (C) is not particularly limited as long as it is a component capable of causing a crosslinking reaction with the (meth) acrylic copolymer (A). For example, an isocyanate type crosslinking agent (C1), an epoxy type crosslinking agent (C2), and a metal chelate crosslinking agent (C3) are mentioned.
As the crosslinking agent (C), one type may be used alone, or two or more types may be used.

  In the pressure-sensitive adhesive composition of the present invention, the total content of the cross-linking agent (C) is 0.01 to 8 parts by mass, preferably 0.1 part by mass with respect to 100 parts by mass of the (meth) acrylic copolymer (A). 05 to 5 parts by mass, more preferably 0.1 to 3 parts by mass. In such an embodiment, a crosslinked structure is sufficiently and appropriately formed, a cohesive force is high, a balance of physical properties of the adhesive is excellent, and an adhesive having excellent durability can be obtained.

<Isocyanate cross-linking agent (C1)>
The isocyanate crosslinking agent (C1) is, for example, an isocyanate compound having two or more isocyanate groups in one molecule. The number of isocyanate groups in one molecule of the isocyanate cross-linking agent (C1) is preferably 2-8, more preferably 2-5. When the number of isocyanate groups is within the above range, it is preferable in terms of the efficiency of crosslinking reaction and availability.

  Examples of the diisocyanate compound having two isocyanate groups in one molecule include aliphatic diisocyanate, alicyclic diisocyanate, and aromatic diisocyanate. Examples of the aliphatic diisocyanate include ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate and 2,2,4-trimethyl. Aliphatic diisocyanates having 4 to 30 carbon atoms such as -1,6-hexamethylene diisocyanate can be mentioned. Examples of the alicyclic diisocyanate include isophorone diisocyanate, cyclopentyl diisocyanate, cyclohexyl diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethyl xylylene diisocyanate, and the like having 7 to 30 carbon atoms. Group diisocyanates are mentioned. Examples of aromatic diisocyanates include aromatic diisocyanates having 8 to 30 carbon atoms such as phenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, naphthylene diisocyanate, diphenyl ether diisocyanate, diphenylmethane diisocyanate and diphenylpropane diisocyanate.

  Examples of the isocyanate compound having 3 or more isocyanate groups in one molecule include aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. Specific examples include 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, and 4,4 ', 4 "-triphenylmethane triisocyanate.

  Examples of the isocyanate compound include, for example, a multimer (for example, a dimer or trimer, a biuret body, an isocyanurate body) or a derivative (for example, a polyhydric alcohol) of the above isocyanate compound having 2 or 3 or more isocyanate groups. Addition reaction products with two or more molecules of a diisocyanate compound) and polymers. Examples of the polyhydric alcohol in the derivative include low molecular weight polyhydric alcohols, for example, trihydric or higher alcohols such as trimethylolpropane, glycerin, and pentaerythritol; examples of high molecular weight polyhydric alcohols include polyether polyols Examples thereof include polyester polyol, acrylic polyol, polybutadiene polyol, and polyisoprene polyol.

Examples of such isocyanate compounds include diphenylmethane diisocyanate trimer, polymethylene polyphenyl polyisocyanate, hexamethylene diisocyanate or tolylene diisocyanate biuret or isocyanurate, trimethylolpropane and tolylene diisocyanate or xylylene diisocyanate. A reaction product with (for example, a three-molecule adduct of tolylene diisocyanate or xylylene diisocyanate), a reaction product of trimethylolpropane and hexamethylene diisocyanate (for example, a three molecule adduct of hexamethylene diisocyanate), polyether polyisocyanate, Examples include polyester polyisocyanates.
The isocyanate crosslinking agent (C1) may be used alone or in combination of two or more.

<Epoxy cross-linking agent (C2)>
As the epoxy-based cross-linking agent (C2), an epoxy compound having two or more epoxy groups in one molecule is usually used. For example, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N, N ′, N ′. -Tetraglycidyl-m-xylylenediamine, N, N, N ', N'-tetraglycidylaminophenylmethane, triglycidyl isocyanurate, m-N, N-diglycidylaminophenylglycidyl ether, N, N-diglycidyl Examples include toluidine and N, N-diglycidylaniline.
The epoxy-based crosslinking agent (C2) may be used alone or in combination of two or more.

<Metal chelate cross-linking agent (C3)>
Examples of the metal chelate crosslinking agent (C3) include polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium and zirconium, alkoxides, acetylacetone, ethyl acetoacetate and the like. A compound in which is coordinated. Specific examples include aluminum isopropylate, aluminum secondary butyrate, aluminum ethyl acetoacetate diisopropylate, aluminum trisethyl acetoacetate, and aluminum tris acetylacetonate.
The metal chelate crosslinking agent (C3) may be used alone or in combination of two or more.

<< Additive (D) >>
The pressure-sensitive adhesive composition of the present invention includes, in addition to the above components, an organic solvent, an antistatic agent, a silane coupling agent, an ultraviolet absorber, an antioxidant, a tackifying resin, and a plasticizer, as long as the effects of the present invention are not impaired. , An antifoaming agent, a filler, a stabilizer, a softening agent, and a wettability adjusting agent may be contained.

  Examples of the organic solvent include the polymerization solvents described in the description of the method for producing the (meth) acrylic copolymer (A). For example, a polymer solution containing a (meth) acrylic copolymer (A) and a polymerization solvent, an olefin polymer (B), and a crosslinking agent (C) are mixed to prepare a pressure-sensitive adhesive composition. You can In the pressure-sensitive adhesive composition of the present invention, the content of the organic solvent is usually 0 to 90% by mass, preferably 10 to 80% by mass.

[Adhesive sheet]
The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer formed from the above-mentioned pressure-sensitive adhesive composition. The pressure-sensitive adhesive layer can be obtained by crosslinking the above-mentioned pressure-sensitive adhesive composition, specifically, by crosslinking the (meth) acrylic copolymer (A) with the crosslinking agent (C).

  Examples of the pressure-sensitive adhesive sheet include a double-sided pressure-sensitive adhesive sheet having only the pressure-sensitive adhesive layer, a base material, and a double-sided pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer formed on both surfaces of the base material, the base material, and one of the base materials. Examples thereof include a single-sided pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer formed on its surface, and a pressure-sensitive adhesive sheet having a release-treated separator attached to the surface of these pressure-sensitive adhesive layers that is not in contact with other layers.

  The conditions for forming the pressure-sensitive adhesive layer are as follows, for example. The composition is applied onto a separator or a substrate and dried at usually 60 to 120 ° C, preferably 70 to 110 ° C, usually 1 to 5 minutes, preferably 2 to 4 minutes to form a coating film. Then, when applied to the separator, the substrate or the separator is attached to the coating film on the side without the separator, and when applied on the substrate, the separator is attached to the coating film. Then, it is usually cured for 1 day or longer, preferably 3 to 10 days, usually 5 to 60 ° C., preferably 15 to 40 ° C., usually 30 to 70% RH, preferably 40 to 70% RH. (Age). Crosslinking under the aging conditions as described above enables efficient formation of a crosslinked body (network polymer). In the case of a coating film sandwiched by separators, one of the separators is peeled off after aging and the substrate is attached to the exposed pressure-sensitive adhesive layer.

  As the base material and the separator, for example, polyester (eg: polyethylene terephthalate, polyethylene naphthalate), polyethylene, polypropylene, polycarbonate, polymethyl methacrylate, acrylonitrile-butadiene-styrene copolymer, ethylene-vinyl acetate copolymer, polyamide, Plastic films such as polyurethane and polyvinyl chloride; woven fabrics, non-woven fabrics; paper, glass and the like. The surface of each of the base material and the separator may be subjected to a release treatment.

The thickness of the pressure-sensitive adhesive layer is usually 3 to 1000 μm, preferably 5 to 500 μm. The thickness of the base material and the separator is usually 10 to 1000 μm.
The pressure-sensitive adhesive layer has a gel fraction of preferably 40 to 90% by mass, more preferably 50 to 80% by mass, and further preferably 60 to 70% by mass, from the viewpoint of improving cohesive force, adhesive force and removability. Is.

The gel fraction of the pressure-sensitive adhesive layer can be obtained as follows. About 0.1 g of the adhesive was collected from the adhesive layer into a sampling bottle, 30 mL of ethyl acetate was added, and the mixture was shaken for 4 hours. Then, the contents of the sample bottle were filtered through a 200-mesh stainless steel wire net and remained on the wire net. The product is dried at 100 ° C. for 2 hours and the dry mass is measured. The gel fraction of the pressure-sensitive adhesive layer is calculated by the following formula.
Gel fraction (mass%) = (dry mass / adhesive agent mass) × 100 (%)

  The pressure-sensitive adhesive sheet of the present invention has a highly durable pressure-sensitive adhesive layer. Particularly, when tested under severe conditions of 90 ° C./95% RH, excellent blister resistance, whitening resistance and substrate adhesion are exhibited. As described above, the pressure-sensitive adhesive sheet of the present invention having high durability under high temperature and high humidity conditions such as automobile applications can be widely used as an industrial pressure-sensitive adhesive sheet or for application of various resin films.

[Use]
The pressure-sensitive adhesive sheet of the present invention can be attached to various members, but is particularly suitable for attaching a member for a touch panel for attaching different types of members. The touch panel is mounted on, for example, an in-vehicle device such as a car navigation device as well as a smartphone and a tablet computer.

  Examples of the touch panel unit include a resistance film type touch panel unit and a capacitance type touch panel unit, both of which are laminated bodies of various materials, and the adhesive of the present invention is used for bonding the various materials. The composition can be used. Examples of the use of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition include a pressure-sensitive adhesive layer for bonding transparent members to each other, and a pressure-sensitive adhesive layer for bonding a transparent member and a transparent conductive film. Be done.

Since the touch panel unit is disposed on the outermost surface of the screen, the pressure-sensitive adhesive used is required to have high transparency, and further required to have high heat resistance and wet heat resistance.
The touch panel unit has, for example, a surface support, a pressure-sensitive adhesive layer, a transparent conductive film made of a metal or a metal oxide, or a transparent conductive film made of a metal with a support or a metal oxide with a support. Examples of metals and metal oxides include indium tin oxide (ITO), antimony tin oxide (ATO), and tin oxide.

  The pressure-sensitive adhesive sheet of the present invention has good adhesiveness to an adherend to a polyolefin such as polypropylene or polyethylene, and has high heat resistance. Further, it has good adhesiveness to adherends such as resins other than polyolefin and glass.

  The pressure-sensitive adhesive sheet of the present invention can be used not only as a member for a touch panel, but also as various members such as various display members, automobile members, aircraft members, marine members, electric appliance members, and building material members.

Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to these examples. In the following description of Examples and the like, "part" means "part by mass" unless otherwise specified.
Each measured value in the examples was obtained by the following method.

[Weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn)]
With respect to the (meth) acrylic copolymer (A), Mw and Mw / Mn in terms of standard polystyrene were determined by the gel permeation chromatography (GPC) method under the following conditions.
・ Measuring device: HLC-8120GPC (manufactured by Tosoh Corporation)
・ GPC column configuration: The following 5 columns (all manufactured by Tosoh)
(1) TSK-GEL HXL-H (guard column)
(2) TSK-GEL G7000HXL
(3) TSK-GEL GMHXL
(4) TSK-GEL GMHXL
(5) TSK-GEL G2500HXL
Sample Concentration: As will be 1.0 mg / cm ^3, diluting and mobile phase solvent with tetrahydrofuran: tetrahydrofuran Flow rate: 1.0 cm ³ / min
・ Column temperature: 40 ℃

[Production Example 1]
In a reactor equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen inlet tube, 85 parts of 2-methoxyethyl acrylate (MEA), 10 parts of n-butyl acrylate (BA), 2-hydroxyethyl acrylate (HEA) 5 Parts, ethyl acetate 80 parts, and methyl ethyl ketone 50 parts were charged, and the temperature was raised to 75 ° C. while introducing nitrogen gas. Next, 0.1 part of 2,2′-azobisisobutyronitrile was added, and a polymerization reaction was carried out at 75 to 76 ° C. for 4 hours under a nitrogen atmosphere. After completion of the reaction, the reaction solution was diluted with ethyl acetate to prepare a polymer solution. The Tg of the obtained (meth) acrylic copolymer (A-1) was -49 ° C, Mw was 300,000, and Mw / Mn was 3.8.

[Production Example 2]
In a reactor equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen inlet tube, 95 parts of n-butyl acrylate (BA), 4 parts of acrylic acid (AA), 1 part of 2-hydroxyethyl acrylate (HEA), and 130 parts of ethyl acetate was charged and the temperature was raised to 75 ° C. while introducing nitrogen gas. Next, 0.1 part of 2,2′-azobisisobutyronitrile was added, and a polymerization reaction was carried out at 75 to 76 ° C. for 4 hours under a nitrogen atmosphere. After completion of the reaction, the reaction solution was diluted with ethyl acetate to prepare a polymer solution. The Tg of the obtained (meth) acrylic copolymer (A-2) was -46 ° C, Mw was 600,000, and Mw / Mn was 4.0.

[Example 1]
Olefin polymer Lucant LX004 (manufactured by Mitsui Chemicals, viscosity (25 ° C.) 1 Pa · s, weight average molecular weight 3000: effective with respect to 100 parts of solid content of the (meth) acrylic copolymer (A-1). Component 100%), and an isocyanate-based cross-linking agent Y-75 (manufactured by Soken Chemical Co., Inc., hexamethylene diisocyanate isocyanurate: solid content 75% ethyl acetate solution) in an amount such that the solid content is 0.6 part. An adhesive composition was obtained by adding to the above solution.

  The obtained pressure-sensitive adhesive composition was applied onto a polyethylene terephthalate (PET) film that had been subjected to a release treatment so that the thickness after drying was 50 μm, and dried at 80 ° C. for 3 minutes to remove the solvent, The agent layer was formed. The release-treated PET film was attached to the surface of the pressure-sensitive adhesive layer opposite to the surface in contact with the PET film. Then, it was aged for 7 days in an environment of 23 ° C. and 65% RH to obtain an adhesive sheet having an adhesive layer with a thickness of 50 μm.

[Examples 2 to 7, Comparative Examples 1 to 5]
A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive composition was prepared using the components shown in Table 1.

<Evaluation>
[Blister resistance test]
After peeling off the release-treated PET film from the pressure-sensitive adhesive sheet, and attaching the exposed pressure-sensitive adhesive layer to a PET film (base material) having a thickness of 100 μm, it is cut into a size of 60 mm × 50 mm, and the other release treatment is performed. The exposed PET layer is peeled off, the exposed adhesive layer is attached to a polycarbonate plate (PC plate, adherend), and then held in an autoclave adjusted to 50 ° C. and 5 atm for 20 minutes to prepare a test plate. did. After the test plate was left under the condition of 90 ° C./95% RH for 72 hours, the blister resistance was evaluated according to the following criteria.
⊚: No appearance defects such as foaming and blown air were observed at all ○: Very few appearance defects such as foaming and blown air were observed, but there was no problem in actual use △: Poor appearances such as foaming and blown air were observed Poor: Defects such as foaming and fluff were observed in a wide range

[Whitening resistance test]
After peeling off the release-treated PET film from the pressure-sensitive adhesive sheet, and attaching the exposed pressure-sensitive adhesive layer to a PET film (base material) having a thickness of 100 μm, it is cut into a size of 60 mm × 50 mm, and the other release treatment is performed. The exposed PET layer is peeled off, the exposed adhesive layer is attached to a polycarbonate plate (PC plate, adherend), and then held in an autoclave adjusted to 50 ° C. and 5 atm for 20 minutes to prepare a test plate. did. After the test plate was left under the condition of 90 ° C./95% RH for 100 hours, the presence or absence of whitening was visually confirmed according to the following criteria.
◯: No bleaching appearance defect was observed at all ∆: Very few bleaching appearance defect was observed, but it was within a range where there was no problem in actual use ×: Blushing appearance defect was observed over a wide range

Lucant LX004 (Mitsui Chemicals, viscosity 1.0 Pa · s, Mw 3000)
Lucant LX010 (Mitsui Chemicals, viscosity 2.9 Pa · s, Mw 5000)
Lucant LX100 (Mitsui Chemicals, viscosity 24.2 Pa · s, Mw 10000)
Lucant LX200 (Mitsui Chemicals, viscosity 57.0 Pa · s, Mw 12000)
B-1000 (manufactured by Nippon Soda, viscosity 1.0 Pa · s, Mw 4000)
G-1000 (manufactured by Nippon Soda, viscosity 77.2 Pa · s, Mw 5600)
IR2200 (made by JSR, solid)
* The viscosity of olefin polymers is the value at 25 ° C, and the active ingredient is 100%.

Claims (4)

A (meth) acrylic copolymer (A) having a glass transition temperature (Tg) of less than 0 ° C.,
An olefin polymer (B),
A pressure-sensitive adhesive composition containing a cross-linking agent (C),
The viscosity of the olefin polymer (B) at 25 ° C. is 0.5 to 30.0 Pa · s, which is a pressure-sensitive adhesive composition.   The pressure-sensitive adhesive composition according to claim 1, wherein the olefin polymer (B) does not have a crosslinkable functional group.   The (meth) acrylic copolymer (A) is a copolymer of monomer components containing 50 to 99% by mass of an alkoxyalkyl (meth) acrylate and 0.5 to 20% by mass of a crosslinkable functional group-containing monomer. The pressure-sensitive adhesive composition according to claim 1 or 2, characterized in that.   A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to claim 1.