Adhesive composition and adhesive sheet

Abstract

One embodiment of the present invention relates to an adhesive composition or adhesive sheet, comprising a (meth)acrylic acid polymer (A) as a polymer containing specific amounts of at least one (meth)acrylic acid ester selected from alkoxyalkyl (meth)acrylates and specific alkyl (meth)acrylates, a crosslinkable functional group-containing monomer (excluding amino group-containing monomers), and an amino group-containing monomer as a monomer component; an acid-modified polyolefin (B); a specific tackifier resin (C); and a crosslinking agent (D), wherein the adhesive composition satisfies specific requirements (I) to (III).

Description

Technical Field

[0001] One embodiment of the present invention relates to a pressure-sensitive adhesive composition or a pressure-sensitive adhesive sheet. Background Art

[0002] Materials used in automobiles and other applications are shifting from metal to plastic. This is driven by the growing demand for lighter vehicles and the increasing strength of plastic materials.

[0003] However, plastic materials are generally difficult to adhere to compared to metal materials. In particular, polyolefins such as polypropylene and polyethylene, which are inexpensive and versatile, are known to be difficult to adhere to.

[0004] Recently, automotive parts are further required to have high heat resistance. In addition, when using adhesives to bond parts together, the bonding is sometimes performed while heating, and the adhesive is also required to exhibit good adhesion even when exposed to a hot environment.

[0005] Furthermore, a pressure-sensitive adhesive composition has been proposed, comprising a polyisobutylene polymer having a first functional group and an acrylic polymer having a second functional group in its main chain, wherein the first functional group and the second functional group form a hydrogen bond (for example, see Patent Document 1). The pressure-sensitive adhesive composition disclosed in Patent Document 1 is disclosed to have excellent adhesion to various substrates, including low-surface-energy substrates.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Publication No. 2013-511594 Summary of the Invention

[0009] Technical problem to be solved by the invention

[0010] According to the research conducted by the present inventors, it has been found that in conventionally proposed adhesive compositions, the adhesive layer does not have sufficient adhesive strength when exposed to a heat environment.

[0011] One embodiment of the present invention provides a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer that maintains sufficient adhesive strength even when exposed to a heat environment during or after bonding.

[0012] Technical solutions used to solve technical problems

[0013] The present inventors have conducted intensive research to solve the above-mentioned problems and have found that an adhesive composition having the following structure can solve the above-mentioned problems, thereby completing the present invention.

[0014] The embodiments of the present invention are, for example, the following [1] to [7].

[0015] [1] An adhesive composition comprising:

[0016] a (meth)acrylic polymer (A) as a polymer comprising 55 to 99% by mass of at least one (meth)acrylate selected from alkoxyalkyl (meth)acrylates and alkyl (meth)acrylates having an alkyl group with 4 to 12 carbon atoms, 0.5 to 15% by mass of a crosslinkable functional group-containing monomer (excluding an amino group-containing monomer), and 0.01 to 5% by mass of an amino group-containing monomer as monomer components; and

[0017] Acid-modified polyolefin (B), and

[0018] At least one tackifying resin (C) selected from rosin-based tackifying resins (C1) and terpene-phenol-based tackifying resins (C2), and

[0019] Cross-linking agent (D);

[0020] It meets the following requirements (I) to (III):

[0021] (I) A 50 μm-thick PSA layer obtained from the PSA composition has a value of 5 or less in a ball stick test conducted using the J.Dow method.

[0022] (II) The adhesive surface of a 50 μm thick adhesive layer obtained from the adhesive composition was attached to a polypropylene plate and left at 80° C. for 20 minutes. The adhesive strength measured was 10.0 N / 25 mm or more.

[0023] (III) A test piece having an adhesive surface of an adhesive layer having a thickness of 50 μm obtained from the above-mentioned adhesive composition attached to a polypropylene plate with an area of ​​50 mm × 20 mm was placed at 80°C for 20 minutes. A load of 200 g was then applied to one end of the long side of the test piece at 80°C. The amount of adhesive layer peeled off 1 hour after the start of the load application was less than 30 mm.

[0024] [2] The adhesive composition according to [1], wherein the amino group contained in the amino group-containing monomer is a tertiary amino group.

[0025] [3] The adhesive composition according to [1] or [2], wherein the (meth)acrylic polymer (A) is a polymer comprising monomer components of 60 to 94% by mass of an alkyl (meth)acrylate having an alkyl group with 4 to 12 carbon atoms, 0.5 to 15% by mass of a monomer containing a crosslinkable functional group (excluding an amino group-containing monomer), 0.01 to 5% by mass of an amino group-containing monomer, and 5 to 30% by mass of an alkyl (meth)acrylate having an alkyl group with 1 to 3 carbon atoms.

[0026] [4] The adhesive composition according to any one of [1] to [3], wherein the crosslinkable functional group-containing monomer (excluding amino group-containing monomers) is (meth)acrylic acid.

[0027] [5] The adhesive composition according to any one of [1] to [4], comprising 5 to 20 parts by mass of the acid-modified polyolefin (B) and 5 to 50 parts by mass of the tackifier resin (C) per 100 parts by mass of the (meth)acrylic polymer (A).

[0028] [6] The adhesive composition according to any one of [1] to [5], wherein a 50 μm thick adhesive layer obtained from the adhesive composition has a haze of less than 35%.

[0029] [7] A pressure-sensitive adhesive sheet comprising a substrate and a pressure-sensitive adhesive layer provided on the substrate and obtained from the pressure-sensitive adhesive composition according to any one of [1] to [6].

[0030] Effects of the Invention

[0031] According to the embodiment of the present invention, it is possible to provide a pressure-sensitive adhesive composition that can form a pressure-sensitive adhesive layer that maintains sufficient adhesive strength even when exposed to a heat environment during or after bonding. DETAILED DESCRIPTION

[0032] Hereinafter, acrylic acid and methacrylic acid are collectively referred to as "(meth)acrylic acid," and acrylate and methacrylate are collectively referred to as "(meth)acrylate."

[0033] [Adhesive composition]

[0034] The adhesive composition according to one embodiment of the present invention comprises a (meth)acrylic polymer (A), an acid-modified polyolefin (B), a tackifier resin (C), and a crosslinking agent (D), and satisfies the following requirements (I) to (III).

[0035] (I) A 50 μm-thick PSA layer obtained from the PSA composition has a value of 5 or less in a ball stick test conducted using the J.Dow method.

[0036] (II) The adhesive surface of a 50 μm thick adhesive layer obtained from the adhesive composition was attached to a polypropylene plate and left at 80° C. for 20 minutes. The adhesive strength measured was 10.0 N / 25 mm or more.

[0037] (III) A test piece having an adhesive surface of an adhesive layer having a thickness of 50 μm obtained from the above-mentioned adhesive composition attached to a polypropylene plate with an area of ​​50 mm × 20 mm was placed at 80°C for 20 minutes. A load of 200 g was then applied to one end of the long side of the test piece at 80°C. The amount of adhesive layer peeled off 1 hour after the start of the load application was less than 30 mm.

[0038] In the above (I) to (III), the adhesive composition was applied to a 25 μm thick polyethylene terephthalate (PET) film so that the thickness after degassing and drying was 50 μm. The film was dried at 90°C for 3 minutes to remove the solvent and form a coating film. A release-treated PET film was then attached to the surface of the coating film (adhesive layer) opposite to the surface in contact with the PET film. The film was then left to age at 23°C / 50% RH for 7 days to produce an adhesive sheet having a 50 μm thick adhesive layer (layer structure: PET film / adhesive layer / release-treated PET film). The release-treated PET film was peeled off from the adhesive sheet, and the physical properties of (I) to (III) were measured using the exposed adhesive layer as the adhesive surface. Furthermore, the haze described below can be measured using a laminate consisting of the PET film / adhesive layer, obtained by peeling off the release-treated PET film from the adhesive sheet obtained by the above method.

[0039] The above-mentioned physical properties (I) to (III) can be measured by the methods described in the Examples.

[0040] In the above-mentioned adhesive composition, (I) a 50 μm thick adhesive layer obtained using the above-mentioned adhesive composition has a ball adhesion test value of 5 or less, preferably 4 or less, and more preferably 3 or less, according to the J.Dow method. If the ball adhesion value falls within the above-mentioned range, even if the adhesive sheet is attached to an adherend in the wrong position, it can be easily peeled off and reattached to the desired position, which is preferred.

[0041] In the above-mentioned adhesive composition, (II) the adhesive surface of the adhesive layer having a thickness of 50 μm obtained from the above-mentioned adhesive composition is affixed to a polypropylene plate, and the adhesive strength measured after being left at 80°C for 20 minutes is 10.0 N / 25 mm or greater, preferably 13.0 N / 25 mm or greater, and more preferably 15.0 N / 25 mm or greater. Within the above-mentioned range, good adhesive strength is achieved after heat lamination, which is preferred. The higher the adhesive strength, the more preferred it is. There is no particular upper limit, but it is generally 50.0 N / 25 mm or less.

[0042] In the above-mentioned adhesive composition, (III) a test piece having the adhesive surface of an adhesive layer having a thickness of 50 μm obtained by attaching the above-mentioned adhesive composition to a polypropylene plate in an area of ​​50 mm × 20 mm is placed in an environment at 80°C for 20 minutes, and then a load of 200 g is applied to one end of the longitudinal direction of the test piece in an environment at 80°C. The amount of peeling of the adhesive layer one hour after the start of the load application is 30 mm or less, preferably 28 mm or less, and more preferably 25 mm or less. If it is within the above range, sufficient adhesive strength can be exerted even in a hot environment, and thus it is preferred. As for the peeling amount, the smaller the amount, the more preferred, and there is no particular lower limit.

[0043] The adhesive composition according to one embodiment of the present invention satisfies the above-mentioned conditions (I) to (III) by using a (meth)acrylic polymer (A) and an acid-modified polyolefin (B) in combination as specific monomer components, and contains a specific tackifier resin (C) and a crosslinking agent (D). The adhesive layer formed from the adhesive composition can maintain sufficient adhesive strength even when exposed to a heat environment during or after bonding.

[0044] Since the adhesive composition according to one embodiment of the present invention has such characteristics, it is suitable for applications requiring bonding under a hot environment, such as forming an adhesive layer of a decorative film.

[0045] Furthermore, in the adhesive composition of one embodiment of the present invention, the haze of a 50 μm thick adhesive layer obtained from the adhesive composition is preferably less than 35%, more preferably less than 25%. A haze within this range is preferred because the components in the adhesive composition tend to be uniformly mixed. A lower haze is more preferred; while its lower limit is not particularly limited, it is typically 0.5% or greater. The haze can be measured using the method described in the Examples.

[0046] ((Meth)acrylic acid polymer (A))

[0047] The (meth)acrylic polymer (A) included in the adhesive composition is a polymer comprising 55 to 99% by mass of at least one (meth)acrylate selected from alkoxyalkyl (meth)acrylates and alkyl (meth)acrylates having an alkyl group with 4 to 12 carbon atoms, 0.5 to 15% by mass of a crosslinkable functional group-containing monomer (excluding amino group-containing monomers), and 0.01 to 5% by mass of an amino group-containing monomer. The amount (mass %) of each monomer represents the amount per 100% by mass of the monomer component.

[0048] The weight-average molecular weight (Mw) of the (meth)acrylic polymer (A) is typically 150,000 to 1.8 million, preferably 200,000 to 1.5 million, and more preferably 400,000 to 1.3 million. The weight-average molecular weight is determined by gel permeation chromatography (GPC) using standard polystyrene conversion and can be measured using the methods described in the Examples. A weight within this range is preferred because the adhesive composition exhibits excellent coatability and the resulting adhesive layer exhibits excellent durability.

[0049] Examples of the alkyl (meth)acrylates having an alkyl group with 4 to 12 carbon atoms include n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, and lauryl (meth)acrylate.

[0050] The carbon number of the alkyl group and the alkoxy group in the alkoxyalkyl (meth)acrylate is not particularly limited, but is preferably 1 to 12.

[0051] Examples of the alkoxyalkyl (meth)acrylate include methoxymethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, and 4-ethoxybutyl (meth)acrylate.

[0052] As the at least one (meth)acrylate selected from the above-mentioned alkoxyalkyl (meth)acrylates and alkyl (meth)acrylates having an alkyl group with 4 to 12 carbon atoms, n-butyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, and 2-ethylhexyl acrylate are preferred, and n-butyl acrylate (BA) and 2-methoxyethyl acrylate (MEA) are more preferred. As the at least one (meth)acrylate selected from the above-mentioned alkoxyalkyl (meth)acrylates and alkyl (meth)acrylates having an alkyl group with 4 to 12 carbon atoms, one species may be used alone, or two or more species may be used.

[0053] The monomer component contains 55 to 99% by mass, preferably 60 to 94% by mass, and more preferably 65 to 90% by mass of at least one (meth)acrylate selected from the above-mentioned alkoxyalkyl (meth)acrylates and alkyl (meth)acrylates having an alkyl group with 4 to 12 carbon atoms, based on 100% by mass of the monomer component.

[0054] Examples of the crosslinkable functional group-containing monomer include carboxyl group-containing monomers and hydroxyl group-containing monomers. In the present invention, the crosslinkable functional group-containing monomer does not include amino group-containing monomers.

[0055] Examples of the carboxyl group-containing monomer include carboxyl group-containing (meth)acrylates such as (meth)acrylic acid, β-carboxyethyl (meth)acrylate, 5-carboxypentyl (meth)acrylate, mono(meth)acryloyloxyethyl succinate, and ω-carboxypolycaprolactone mono(meth)acrylate; and itaconic acid, crotonic acid, fumaric acid, and maleic acid.

[0056] 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 (meth)acrylate.

[0057] As the crosslinkable functional group-containing monomer, one type may be used alone, or two or more types may be used in combination.

[0058] When the crosslinkable functional group-containing monomer is (meth)acrylic acid, the heat resistance after the adherend and the pressure-sensitive adhesive layer are bonded together tends to be further improved, which is preferred.

[0059] The monomer component contains 0.5 to 15 mass%, preferably 0.8 to 15 mass%, and more preferably 1 to 13 mass% of the crosslinkable functional group-containing monomer, based on 100 mass% of the monomer component. When the content of the crosslinkable functional group-containing monomer is within the above range, a pressure-sensitive adhesive sheet can be obtained that does not exhibit poor curing and exhibits an excellent balance of adhesive properties.

[0060] The amino group-containing monomer is a monomer having an amino group in its molecule. The amino group-containing monomer may have one amino group in one molecule or two or more amino groups in one molecule. The amino group-containing monomer preferably has one to three amino groups in one molecule, and more preferably has one amino group in one molecule.

[0061] If the amino group of the amino group-containing monomer is a primary or secondary amino group, it is possible that the amino group reacts chemically with the acid-modified site of the acid-modified polyolefin, crosslinks the (meth)acrylic polymer component and the modified polyolefin component, and causes gelation. Therefore, a tertiary amino group is preferred.

[0062] 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. Preferred amino group-containing monomers include N,N-dimethylaminoethyl methacrylate (DM) and N,N-diethylaminoethyl methacrylate (DE). These amino group-containing monomers may be used alone or in combination of two or more.

[0063] The monomer components contain 0.01 to 5 mass % of the amino group-containing monomer, preferably 0.01 to 3 mass % of the amino group-containing monomer, based on 100 mass % of the monomer components. If the content of the amino group-containing monomer is within the above range, an adhesive composition having excellent compatibility with the acid-modified polyolefin (B) described below and excellent coating properties can be obtained.

[0064] The above-mentioned monomer components may include at least one (meth)acrylate selected from the above-mentioned alkoxyalkyl (meth)acrylates and (meth)alkyl (meth)acrylates having an alkyl group with 4 to 12 carbon atoms, a monomer containing a crosslinkable functional group (excluding an amino group-containing monomer), an amino group-containing monomer, and monomers other than these monomers (hereinafter also referred to as "other monomers").

[0065] Examples of such other monomers include (meth)acrylates having an alkyl group with 1 to 3 carbon atoms, (meth)acrylates containing an alicyclic hydrocarbon group, and (meth)acrylates containing an aromatic hydrocarbon group.

[0066] The above-mentioned other monomers may be used alone or in combination of two or more.

[0067] Examples of the (meth)acrylic acid alkyl ester having an alkyl group with 1 to 3 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, and isopropyl (meth)acrylate. Methyl acrylate (MA) is preferred as the (meth)acrylic acid alkyl ester having an alkyl group with 1 to 3 carbon atoms. A single type of (meth)acrylic acid alkyl ester having an alkyl group with 1 to 3 carbon atoms may be used alone, or two or more types may be used. It is preferred that the monomer component contain an (meth)acrylic acid alkyl ester having an alkyl group with 1 to 3 carbon atoms, because the heat resistance and durability of the resulting adhesive sheet are improved.

[0068] Examples of the alicyclic hydrocarbon group-containing (meth)acrylate include cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and adamantyl (meth)acrylate.

[0069] Examples of the aromatic hydrocarbon group-containing (meth)acrylate include benzyl (meth)acrylate, phenyl (meth)acrylate, and phenoxyethyl (meth)acrylate.

[0070] The monomer component preferably comprises 60 to 94% by mass of an alkyl (meth)acrylate having an alkyl group with 4 to 12 carbon atoms, 0.5 to 15% by mass of a crosslinkable functional group-containing monomer (excluding an amino group-containing monomer), 0.01 to 5% by mass of an amino group-containing monomer, and 5 to 30% by mass of an alkyl (meth)acrylate having an alkyl group with 1 to 3 carbon atoms. More preferably, the monomer component comprises 65 to 90% by mass of an alkyl (meth)acrylate having an alkyl group with 4 to 12 carbon atoms, 0.8 to 15% by mass of a crosslinkable functional group-containing monomer (excluding an amino group-containing monomer), 0.01 to 3% by mass of an amino group-containing monomer, and 8 to 25% by mass of an alkyl (meth)acrylate having an alkyl group with 1 to 3 carbon atoms.

[0071] When an alicyclic hydrocarbon group-containing (meth)acrylate or an aromatic hydrocarbon group-containing (meth)acrylate is used as the other monomer, the total content of these monomers is preferably 0.5 to 15% by mass relative to 100% by mass of the monomer component.

[0072] (Production Conditions of (Meth)Acrylic Polymer (A))

[0073] The (meth)acrylic polymer (A) can be obtained by copolymerizing the above-mentioned monomer components.

[0074] Examples of the copolymerization method include production by conventionally known polymerization methods such as solution polymerization, bulk polymerization, emulsion polymerization, and suspension polymerization. Among these, solution polymerization is preferred.

[0075] For example, a polymerization solvent and monomer components are placed in a reaction vessel, a polymerization initiator is added under an inert gas atmosphere such as nitrogen, the reaction starting temperature is set to generally 40 to 100° C., preferably 50 to 90° C., the reaction system is maintained at a temperature generally 50 to 90° C., preferably 60 to 90° C., and the reaction is carried out for 3 to 20 hours to obtain a (meth)acrylic polymer (A).

[0076] Examples of the polymerization initiator include peroxide-based polymerization initiators and azo-based initiators.

[0077] Examples of the peroxide-based polymerization initiator include tert-butyl hydroperoxide, cumyl hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, hexanoyl peroxide, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, tert-butyl peroxypivalate, 2,2-bis(4,4-di-tert-butylperoxycyclohexyl)propane, 2,2-bis(4,4-di-tert-amylperoxycyclohexyl)propane, 2,2-bis(4,4-di-tert-octylperoxycyclohexyl)propane, 2,2-bis(4,4-di-α-cumylperoxycyclohexyl)propane, 2,2-bis(4,4-di-tert-butylperoxycyclohexyl)butane, and 2,2-bis(4,4-di-tert-octylperoxycyclohexyl)butane.

[0078] Examples of the azo initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2-(carbamoyl azo)isobutyronitrile, 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, 2,2'-azobis(2 Azo compounds such as 2,4-dimethylaminopropane) 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-cyanovaleric acid), 2,2'-azobis(2-cyanopropanol), 2,2'-azobis(2-methylpropionic acid) dimethyl ester, and 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)propionamide).

[0079] The polymerization initiator may be used alone or in combination of two or more. There is no limitation on the number of times the polymerization initiator is added during polymerization.

[0080] The polymerization initiator is generally used in an amount within the range of 0.01 to 5 parts by mass, preferably 0.005 to 3 parts by mass, relative to 100 parts by mass of the monomer components forming the (meth)acrylic polymer (A). Furthermore, during the above-mentioned polymerization reaction, additional polymerization initiators, chain transfer agents, polymerizable monomers, and polymerization solvents may be added as appropriate.

[0081] Examples of the polymerization solvent for solution polymerization include aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane, and n-octane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, cycloheptane, and cyclooctane; diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, dibutyl ether, tetrahydrofuran, dimethoxyethane ... Ethers such as alkanes, anisole, phenethyl ether, and diphenyl ether; halogenated hydrocarbons such as chloroform, carbon tetrachloride, 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; amides such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; nitriles such as acetonitrile and benzonitrile; and sulfoxides such as dimethyl sulfoxide and sulfolane.

[0082] The polymerization solvent may be used alone or in combination of two or more.

[0083] (Acid-modified polyolefin (B))

[0084] The acid-modified polyolefin (B) contained in the adhesive composition is not particularly limited as long as it is a polymer obtained by modifying a polyolefin with an acid.

[0085] The acidic groups of the acid-modified polyolefin (B) interact with the amino groups of the (meth)acrylic polymer (A), thereby suppressing phase separation between the (meth)acrylic polymer (A) and the acid-modified polyolefin (B) even after mixing them. Furthermore, it is believed that the acid-modified polyolefin (B) is unevenly distributed on the surface of the adhesive sheet obtained from the adhesive composition containing the acid-modified polyolefin (B), forming a sea-island structure. It is believed that this uneven distribution can reduce the ball adhesion of the adhesive layer to less than 5.

[0086] Examples of the acid-modified polyolefin (B) include carboxylic anhydride-modified polyolefins. Examples of the carboxylic anhydride-modified polyolefins include maleic anhydride-modified polyolefins, itaconic anhydride-modified polyolefins, and aconitic anhydride-modified polyolefins. Among these, maleic anhydride-modified polyolefins using maleic anhydride as the carboxylic anhydride are preferred from the perspective of ease of industrial product availability.

[0087] The polyolefin before modification is preferably a polymer of an olefin having 2 to 4 carbon atoms, and may be a homopolymer or a copolymer. The polyolefin is preferably polyethylene (including ethylene homopolymers and copolymers containing ethylene as a main component) or polypropylene (including propylene homopolymers and copolymers containing propylene as a main component).

[0088] The weight average molecular weight (Mw) of the acid-modified polyolefin (B) measured by GPC is usually in the range of 10,000 to 300,000, preferably in the range of 20,000 to 200,000, and more preferably in the range of 50,000 to 100,000.

[0089] The acid-modified polyolefin (B) may be used alone or in combination of two or more.

[0090] The amount of the acid-modified polyolefin (B) in the adhesive composition is generally 5 to 20 parts by mass, preferably 6 to 18 parts by mass, and more preferably 7 to 16 parts by mass, relative to 100 parts by mass of the (meth)acrylic polymer (A). When the amount of the acid-modified polyolefin (B) is within this range, it tends to produce an adhesive sheet that exhibits high adhesiveness even after heating, which is preferred.

[0091] (Adhesion-imparting resin (C))

[0092] The tackifier resin (C) contained in the adhesive composition is at least one tackifier resin (C) selected from rosin-based tackifier resins (C1) and terpene-phenol-based tackifier resins (C2).

[0093] The weight average molecular weight (Mw) of the tackifying resin (C) is usually 500 to 5000, preferably 600 to 5000, and more preferably 1000 to 4500. The weight average molecular weight is a molecular weight determined by gel permeation chromatography (GPC) in terms of standard polystyrene and can be measured by the method described in Examples.

[0094] The hydroxyl value of the tackifying resin (C) is usually 10 to 200 mgKOH / g, preferably 15 to 150 mgKOH / g, and more preferably 20 to 150 mgKOH / g. The hydroxyl value can be measured by the method described in the Examples.

[0095] When the Mw and hydroxyl value of the tackifying resin (C) are within the above ranges, it is preferred from the viewpoint of excellent compatibility with the (meth)acrylic polymer (A) and suppression of a decrease in the adhesive strength of the resulting adhesive sheet after aging.

[0096] The rosin-based tackifying resin (C1) is not particularly limited as long as it is a rosin-based tackifying resin, but preferably has a softening point of 100°C or higher. From the viewpoint of imparting stress relaxation properties under high temperature environments, the softening point is preferably 100 to 200°C, more preferably 120 to 160°C.

[0097] Examples of the rosin-based tackifying resin (C1) include PENSEL C (softening point 120°C), PENSEL D-125 (softening point 125°C), PENSEL D-135 (softening point 135°C), and PENSEL D-160 (softening point 160°C), SUPER ESTER A-100 (SEA-100) (softening point 100°C), SUPER ESTER A-115 (softening point 115°C), and SUPER ESTER A-125 (softening point 125°C) manufactured by Arakawa Chemical Industries, Ltd.; and HARITACK PCJ (softening point 123°C), HARITACK DP-2669 (softening point 135°C), and HARITACK FK125 (softening point 125°C) manufactured by Harima Chemicals Co., Ltd.

[0098] The terpene-phenol-based adhesion-imparting resin (C2) is not particularly limited. For example, a resin obtained by polymerizing terpene in the presence of phenol can be used. Preferably, a terpene-phenol-based adhesion-imparting resin having a softening point of 100°C or higher is used. From the viewpoint of imparting stress relaxation properties under high temperature environments, the softening point is preferably 100 to 200°C, more preferably 120 to 160°C.

[0099] Examples of the terpene phenol-based tackifying resin (C2) include YS POLYSTAR G150 (softening point 150°C), YS POLYSTAR T100 (softening point 100°C), YS POLYSTAR G125 (softening point 125°C), YS POLYSTART 115 (softening point 115°C), YS POLYSTAR T145 (softening point 145°C), YS POLYSTAR T130 (softening point 130°C), and YS POLYSTAR U130 (softening point 130°C). These products are manufactured by Yasuhara Chemical Co., Ltd.

[0100] The tackifier resin (C) may be used alone or in combination of two or more.

[0101] The amount of the tackifier resin (C) incorporated into the adhesive composition is generally 5 to 50 parts by mass, preferably 6 to 40 parts by mass, and more preferably 7 to 30 parts by mass, relative to 100 parts by mass of the (meth)acrylic polymer (A). The amount of the tackifier resin (C) incorporated within the above range is preferred because it maintains the balance of adhesive properties and allows the production of an adhesive sheet having excellent heat resistance.

[0102] (Crosslinking agent (D))

[0103] The crosslinking agent (D) contained in the adhesive composition is not particularly limited as long as it can crosslink the (meth)acrylic polymer (A). Examples of the crosslinking agent (D) include isocyanate compounds (D1), epoxy compounds (D2), and metal chelate compounds (D3) that react with the crosslinkable functional groups of the polymer.

[0104] Since the adhesive composition contains the crosslinking agent (D), a crosslinked body is formed in the adhesive layer bonded to the adherend by pressure bonding, thermoforming, etc., and thus the adhesive composition has excellent adhesive strength and heat resistance.

[0105] The cross-linking agent (D) may be used alone or in combination of two or more.

[0106] (Isocyanate compound (D1))

[0107] As the isocyanate compound, for example, one having 2 or more isocyanate groups per molecule is generally used, and the number of isocyanate groups per molecule is preferably 2 to 8, more preferably 3 to 6. When the number of isocyanate groups is within the above range, it is preferred from the perspective of improving the efficiency of the cross-linking reaction between the (meth)acrylic polymer (A) or the acid-modified polyolefin (B) and the isocyanate compound, and from the perspective of maintaining the flexibility of the adhesive layer.

[0108] Examples of the diisocyanate compound having two isocyanate groups in one molecule include aliphatic diisocyanates, alicyclic diisocyanates and aromatic diisocyanates.

[0109] Examples of the aliphatic diisocyanate include aliphatic diisocyanates having 4 to 30 carbon atoms, such as ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2-methyl-1,5-pentamethylene diisocyanate, 3-methyl-1,5-pentamethylene diisocyanate, and 2,2,4-trimethyl-1,6-hexamethylene diisocyanate.

[0110] Examples of the alicyclic diisocyanate include alicyclic diisocyanates having 7 to 30 carbon atoms, such as isophorone diisocyanate, cyclopentyl diisocyanate, cyclohexyl diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated toluene diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogenated tetramethylxylylene diisocyanate.

[0111] Examples of the aromatic diisocyanate include aromatic diisocyanates having 8 to 30 carbon atoms, such as phenylene diisocyanate, toluene diisocyanate, xylylene diisocyanate, naphthalene diisocyanate, diphenyl ether diisocyanate, diphenylmethane diisocyanate and diphenylpropane diisocyanate.

[0112] Examples of isocyanate compounds having three or more isocyanate groups per molecule include aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. Specific examples include 2,4,6-toluene triisocyanate, 1,3,5-benzene triisocyanate, and 4,4',4"-triphenylmethane triisocyanate.

[0113] Examples of isocyanate compounds include polymers (e.g., dimers, trimers, biuret forms, isocyanurate forms) of the aforementioned isocyanate compounds having two or more isocyanate groups, derivatives (e.g., addition reaction products of polyols with two or more diisocyanate molecules), and polymers. Examples of the polyols in these derivatives include low-molecular-weight polyols such as trimethylolpropane, glycerin, and pentaerythritol, and high-molecular-weight polyols such as polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, and polyisoprene polyols.

[0114] Examples of such isocyanate compounds include trimers of diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanates, biuret forms or isocyanurate forms of hexamethylene diisocyanate or toluene diisocyanate, reaction products of trimethylolpropane with toluene diisocyanate or xylylene diisocyanate (e.g., trimerized adducts of toluene diisocyanate or xylylene diisocyanate), reaction products of trimethylolpropane with hexamethylene diisocyanate (e.g., trimerized adducts of hexamethylene diisocyanate), polyether polyisocyanates, and polyester polyisocyanates.

[0115] Among isocyanate compounds, from the perspective of yellowing resistance, xylylene diisocyanate and hexamethylene diisocyanate crosslinking agents are preferred, while from the perspective of stress relaxation properties, toluene diisocyanate crosslinking agents are preferred. Examples of xylylene diisocyanate crosslinking agents include xylylene diisocyanate and its multimers, derivatives, and polymers; examples of hexamethylene diisocyanate crosslinking agents include hexamethylene diisocyanate and its multimers, derivatives, and polymers; and examples of toluene diisocyanate crosslinking agents include toluene diisocyanate and its multimers, derivatives, and polymers.

[0116] (Epoxy compound (D2))

[0117] Examples of the epoxy compound include compounds having two or more epoxy groups in the molecule, such as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diamine glycidyl amine, N,N,N',N'-tetraglycidyl-m-xylenediamine, and 1,3-bis(N,N'-diamine glycidylaminomethyl).

[0118] (Metal chelate compound (D3))

[0119] Examples of metal chelate compounds include compounds obtained by coordinating a polyvalent metal such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, or zirconium with an alkoxide, acetylacetone, or ethyl acetoacetate. Specific examples include aluminum isopropoxide, aluminum sec-butyrate, aluminum ethyl acetoacetate / diisopropyl ester, aluminum triethylacetoacetate, and aluminum triacetylacetonate.

[0120] The amount of the crosslinking agent (D) in the pressure-sensitive adhesive composition is generally 0.01 to 5 parts by mass, preferably 0.02 to 4 parts by mass, and more preferably 0.03 to 3 parts by mass, relative to 100 parts by mass of the (meth)acrylic polymer (A).

[0121] (Organic solvent (E))

[0122] The pressure-sensitive adhesive composition may contain an organic solvent (E) in order to adjust coating properties.

[0123] Examples of the organic solvent (E) include the same organic solvents as those described in the section "Production Conditions for (Meth)Acrylic Polymer (A)." The polymerization solvent used in the production of the (meth)acrylic polymer (A) and the organic solvent contained in the PSA composition may be of the same type or different types. The organic solvent may be used alone or in combination of two or more.

[0124] When the pressure-sensitive adhesive composition contains an organic solvent (E), the content of the organic solvent (E) is usually 30 to 90% by mass, preferably 40 to 90% by mass, relative to 100% by mass of the pressure-sensitive adhesive composition.

[0125] (Additive (F))

[0126] The adhesive composition may contain an additive (F) in addition to the components (A) to (E) as long as the effects of the present invention are not impaired.

[0127] As additives (F), for example, (meth)acrylic polymers other than (meth)acrylic polymers (A), adhesive imparting resins other than the above-mentioned adhesive imparting resin (C), silane coupling agents, antistatic agents, antioxidants, light stabilizers, metal corrosion inhibitors, plasticizers, crosslinking promoters, surfactants and repair agents can be mentioned. As additives (F), one type can be used alone, or two or more types can be used. In the case where the above-mentioned adhesive composition contains additives (F), the content of additives (F) varies depending on the type of additives (F) and is not particularly limited, but is generally 0.01 to 20% by mass, preferably 0.01 to 15% by mass, relative to 100% by mass of the adhesive composition.

[0128] (Preparation of Adhesive Composition)

[0129] The adhesive composition can be prepared, for example, by mixing the above-mentioned components by a conventionally known method. For example, the adhesive composition can be prepared by mixing a solution containing a (meth)acrylic polymer (A), an acid-modified polyolefin (B), a tackifying resin (C), a crosslinking agent (D), and other components such as additives as needed.

[0130] [Adhesive sheet]

[0131] The pressure-sensitive adhesive sheet according to one embodiment of the present invention includes a substrate and a pressure-sensitive adhesive layer provided on the substrate and obtained from the pressure-sensitive adhesive composition.

[0132] Examples of adhesive sheets include a double-sided adhesive sheet having a substrate and adhesive layers formed on both sides of the substrate, at least one of the adhesive layers being an adhesive layer formed from an adhesive composition according to one embodiment of the present invention; a single-sided adhesive sheet having a substrate and an adhesive layer formed from an adhesive composition according to one embodiment of the present invention on one side of the substrate; and an adhesive sheet having substrates arranged on both sides of an adhesive layer formed from an adhesive composition according to one embodiment of the present invention.

[0133] The substrate is not particularly limited and may include plastic substrates, nonwoven fabrics, woven fabrics, paper, metal, glass, and ceramics. The thickness of the substrate varies depending on its application and is not particularly limited, but is generally 10 to 500 μm.

[0134] Examples of the plastic substrate include substrates made of plastic selected from polyethylene terephthalate (PET), polyvinyl chloride, polyolefins (polypropylene, polyethylene, TPO (thermoplastic olefin elastomer)), polymethyl methacrylate, polycarbonate, polyimide, and ABS.

[0135] The substrate may be a release-treated substrate. In the case where the adhesive sheet is a sheet having substrates disposed on both sides of an adhesive layer formed from an adhesive composition according to one embodiment of the present invention, at least one of the substrates is a release-treated substrate, and the release-treated substrate is removed during bonding to an adherend.

[0136] The thickness of the adhesive layer is usually 5 to 200 μm, preferably 10 to 100 μm, from the viewpoint of maintaining adhesive performance.

[0137] At least a portion of the adhesive layer can be crosslinked by reacting with the (meth)acrylic polymer (A) and the crosslinking agent (D) in the adhesive composition during the production process.

[0138] There are no particular restrictions on the method for producing the adhesive sheet, and for example, it is described as follows. The aforementioned adhesive composition is applied to a substrate. When the adhesive composition contains a solvent, it is usually dried at 50 to 150° C., preferably 60 to 100° C., for 1 to 10 minutes, preferably 2 to 7 minutes to remove the solvent to form a coating film. Then, another substrate is attached to the surface of the coating film (adhesive layer) on the side without a substrate. Then, the adhesive sheet is manufactured by ripening for more than 1 day, preferably 3 to 10 days, at a temperature of usually 5 to 60° C., preferably 15 to 40° C., and usually at 30 to 70% RH, preferably at 40 to 70% RH. The above-mentioned ripening is also referred to as aging. If ripening is carried out under the above conditions, crosslinking can be carried out during ripening to efficiently form a crosslinked body.

[0139] The adhesive composition can be applied by a known method, for example, by applying the composition to a predetermined thickness by spin coating, blade coating, roll coating, bar coating, knife coating, die coating, gravure coating, or doctor blade coating.

[0140] The present inventors believe that in the adhesive layer obtained from the above-mentioned adhesive composition, the acid-modified polyolefin (B) is unevenly present near the surface, resulting in fine unevenness on the surface. It is believed that due to this fine unevenness, the surface of the adhesive layer has excellent reworkability after being attached to the adherend. In addition, it is believed that lamination by pressure bonding or thermoforming can make the adhesive layer firmly attached to the adherend without fine unevenness.

[0141] The adhesive sheet can maintain sufficient adhesive strength even when exposed to a hot environment during or after bonding, and can therefore be used in various applications. For example, the adhesive sheet is suitable for decorative films that are bonded in a hot environment.

[0142] Example

[0143] Hereinafter, an embodiment of the present invention will be described in detail with reference to an example, but the present invention is not limited thereto.

[0144] [Production Example 1]

[0145] In a reaction apparatus equipped with a stirrer, a reflux cooler, a thermometer, and a nitrogen inlet tube, 89.9 parts by mass of n-butyl acrylate (BA), 0.1 parts by mass of N,N-dimethylaminoethyl methacrylate (DM), 10 parts by mass of acrylic acid (AA), and 100 parts by mass of ethyl acetate were placed, and the temperature was raised to 80°C while introducing nitrogen. Subsequently, 0.1 parts by mass of 2,2'-azobisisobutyronitrile was added, and a polymerization reaction was carried out at 80°C under a nitrogen atmosphere for 6 hours to obtain an acrylic polymer (A-1). After the reaction was completed, the mixture was diluted with ethyl acetate to prepare a polymer solution having a solids concentration of 30% by mass.

[0146] [Production Example 2]

[0147] An acrylic polymer (A-2) was produced in the same manner as in Production Example 1 except that the monomer components used were changed to those described in Table 1, thereby preparing a polymer solution having a solid content concentration of 30% by mass.

[0148] In Table 1, MEA represents 2-methoxyethyl acrylate.

[0149] [Production Example 3]

[0150] In a reaction apparatus equipped with a stirrer, a reflux cooler, a thermometer, and a nitrogen inlet tube, 69.9 parts by mass of n-butyl acrylate (BA), 20 parts by mass of methyl acrylate (MA), 0.1 parts by mass of N,N-dimethylaminoethyl methacrylate (DM), 10 parts by mass of acrylic acid (AA), and 100 parts by mass of ethyl acetate were placed, and the temperature was raised to 80°C while introducing nitrogen. Subsequently, 0.1 parts by mass of 2,2'-azobisisobutyronitrile was added, and a polymerization reaction was carried out at 80°C under a nitrogen atmosphere for 6 hours to obtain an acrylic polymer (A-3). After the reaction was completed, the mixture was diluted with ethyl acetate to prepare a polymer solution having a solids concentration of 30% by mass.

[0151] [Production Examples 4 to 13]

[0152] Acrylic polymers (A-4) to (A-10) and (A'-1) to (A'-3) were produced in the same manner as in Production Example 3 except that the monomer components used were changed to those listed in Table 1, and polymer solutions having a solid content concentration of 30% by mass were prepared.

[0153] In Table 1, 2HEA represents 2-hydroxyethyl acrylate.

[0154] In Production Examples 6 to 8, acrylic acid polymers having different molecular weights were produced by adjusting the amount of the solvent (the amount of ethyl acetate) in Production Example 3.

[0155] The weight average molecular weight (Mw) of acrylic polymers (A-1) to (A-10) and (A'-1) to (A'-3) was determined by gel permeation chromatography (GPC) under the following conditions as Mw in terms of standard polystyrene. The Mw of each polymer is shown in Table 1.

[0156] ·Measuring device: HLC-8120GPC (manufactured by Tosoh Corporation)

[0157] GPC column configuration: The following five columns connected in series (all manufactured by Tosoh Corporation)

[0158] (1)TSK-GEL HXL-H (guard column)

[0159] (2)TSK-GEL G7000HXL

[0160] (3)TSK-GEL GMHXL

[0161] (4)TSK-GEL GMHXL

[0162] (5)TSK-GEL G2500HXL

[0163] Sample concentration: Dilute with tetrahydrofuran to reach 1.0 mg / cm 3

[0164] Mobile phase solvent: tetrahydrofuran

[0165] Flow rate: 1.0cm 3 / minute

[0166] Column temperature: 40°C

[0167] [Table 1]

[0168]

[0169] [Examples 1 to 16, Comparative Examples 1 to 6]

[0170] A polymer solution containing acrylic polymers (A-1) to (A-10) and (A'-1) to (A'-3) obtained in Production Examples 1 to 13, an acid-modified polyolefin (B), a tackifier resin (C), and a crosslinking agent (D) were mixed in the amounts (parts by mass) listed in Tables 3 and 4 below to obtain a PSA composition. The values ​​listed in Tables 3 and 4 are solid content ratios, and the amounts of acrylic polymer listed in Tables 3 and 4 refer to the amounts of acrylic polymer, not the amounts of the polymer solution.

[0171] In Examples and Comparative Examples, an isocyanate crosslinking agent L-45 (manufactured by Soken Chemical Co., Ltd.) was used as the crosslinking agent (D).

[0172] Table 2 shows the acid-modified polyolefin (B), tackifier resin (C), and tackifier resins other than tackifier resin (C) used in the Examples and Comparative Examples (abbreviated as "tackifier resins" in the table). The weight-average molecular weight (Mw) in Table 2 was measured under the same conditions as the Mw measurement method for the acrylic polymers obtained in Production Examples 1 to 13. Furthermore, the hydroxyl value was measured in accordance with JIS K0070 by acetylation of the hydroxyl groups of the polymer molecules or (meth)acrylic polymers with acetic anhydride and then neutralization and titration of the excess acetic acid with potassium hydroxide.

[0173] [Table 2]

[0174]

[0175] <Manufacturing of Adhesive Sheet>

[0176] The obtained adhesive composition was defoamed on a polyethylene terephthalate (PET) film (Lumirror #25-T60, manufactured by Toray Industries, Ltd., with a haze of approximately 0.8%) with a thickness of 25 μm, and then coated using a doctor blade so that the thickness after drying reached 50 μm. The film was then dried at 90°C for 3 minutes to remove the solvent and form a coating.

[0177] A release-treated PET film was laminated to the surface of the coating film (adhesive layer) opposite to the surface in contact with the PET film. The film was then left to stand for 7 days under conditions of 23°C / 50% RH to mature, thereby producing an adhesive sheet (1) having an adhesive layer with a thickness of 50 μm.

[0178] <Experiment>

[0179] (Haze)

[0180] The release-treated PET film was peeled off from the pressure-sensitive adhesive sheet (1), and the haze value of the laminate consisting of the PET film / pressure-sensitive adhesive layer was measured as the haze value of the pressure-sensitive adhesive layer.

[0181] The haze was measured using a haze meter (model name HM-150, manufactured by Murakami Color Research Laboratory) in accordance with JIS K7105. The results are shown in Tables 3 and 4.

[0182] (Ball sticky)

[0183] Determined by J.Dow method

[0184] The peelable PET film was peeled off from the adhesive sheet (1) and mounted on an inclined surface at an angle of 30 degrees to expose the adhesive layer. Then, under a 23°C / 50% RH environment, a steel ball was run up from the upper side of the inclined surface and then slid across the adhesive surface (run-up distance 10 cm, sliding distance 10 cm).

[0185] The sliding test was performed while varying the diameter of the steel ball to determine the maximum diameter of the steel ball at which it stopped sliding within the adhesive layer. The diameter of the steel ball used was X / 32 inches (X is an integer in the range of 2 to 32). Tables 3 and 4 show the results of the ball sticking test, representing the maximum diameter of the steel ball, as shown in X. In Tables 3 and 4, examples and comparative examples in which the steel ball did not stop even when X was 2 are marked as "not stopped."

[0186] (Adhesion)

[0187] The above-mentioned adhesive sheet (1) was cut into a size of 25 mm × 100 mm to obtain a test piece. The peeled PET film was peeled off from the obtained test piece, and the exposed adhesive layer was attached to a polypropylene (PP) plate (PP-N-BN (size: 70 mm × 150 mm × 2 mm (thickness)), manufactured by Showa Denko Materials Co., Ltd.). After pressing with a 2 kg roller back and forth three times, the plate was left in an environment of 23°C / 50% RH for 20 minutes. Thereafter, the adhesive force (N / 25 mm) was measured when the end of the test piece was pulled at a speed of 300 mm / min in a direction 180° to the surface of the PP plate. The adhesive force at this time was recorded in Tables 3 and 4 as "initial adhesive force to PP".

[0188] The adhesive sheet (1) was cut into a size of 25 mm x 100 mm to obtain a test piece. The peeled PET film was peeled off from the obtained test piece, and the exposed adhesive layer was attached to the polypropylene (PP) plate. After pressing the sheet with a 2 kg roller back and forth three times, the sheet was placed in an 80°C / dry environment for 20 minutes. After that, the sheet was placed in a 23°C / 50% RH environment for 20 minutes. The adhesive strength was measured when the end of the sheet was pulled in a direction 180° from the surface of the PP plate at a speed of 300 mm / min. The adhesive strength at this time (N / 25 mm) was recorded in Tables 3 and 4 as "Adhesion strength to PP after heating."

[0189] (Adhesion after aging)

[0190] The adhesive sheet (1) was cut into a size of 25 mm x 100 mm to obtain a test piece. The release-treated PET film was peeled from the obtained test piece, and the exposed adhesive layer was attached to a polypropylene (PP) (PP-N-BN) plate. After pressing with a 2 kg roller three times, the plate was left in an 80°C environment for 500 hours. After this, the plate was left in a 50°C relative humidity environment for 20 minutes. The adhesive strength was measured by pulling the end of the test piece at a speed of 300 mm / min in a direction 180° from the surface of the PP plate.

[0191] (Constant load peeling)

[0192] The adhesive sheet (1) was cut into a size of 80 mm × 20 mm. The peeling-treated PET film was peeled off from the cut adhesive sheet (1), and the exposed adhesive layer was attached to a polypropylene (PP) plate (PP-N-BN) so that the attached area was 50 mm × 20 mm. The adhesive layer was pressed by reciprocating a 2 kg roller three times to obtain a test piece. The obtained test piece was then arranged so that the main surface was approximately perpendicular to gravity, and the adhesive layer was arranged on the lower side of the PP plate under gravity. The test piece was allowed to stand for 20 minutes in an 80°C / dry environment. Under the same environment, a load of 200 g was applied to one end of the longitudinal direction of the test piece (the end of one end of the longitudinal direction of the laminate composed of the PET film / adhesive layer attached to the test piece). The amount of peeling (mm) of the adhesive layer from the PP plate was measured one hour after the start of the load application [the length from the end of the side on which the load was applied to the point where the adhesive layer peeled from the PP plate]. The results are shown in Tables 3 and 4.

[0193] In addition, the phrase "falling off in ∼ minutes" in Table 4 means that the adhesive layer completely peeled off from the PP plate and fell off in ∼ minutes from the start of load application.

[0194] (Compatibility)

[0195] Acrylic polymers (A-1) to (A-10), (A'-1) to (A'-3), acid-modified polyolefin (B), and tackifier resin (C) were placed in a container in the amounts (parts by mass) listed in Tables 3 and 4. Ethyl acetate was then added and mixed to a solids concentration of 30% by mass. After mixing, the mixture was allowed to stand for 24 hours, and compatibility was evaluated according to the following criteria. No crosslinking agent was used in the compatibility evaluation.

[0196] AA: No phase separation was confirmed

[0197] BB: Confirm phase separation

[0198] [Table 3]

[0199]

[0200] [Table 4]

[0201]

[0202] Tables 3 and 4 show that the adhesive sheets obtained from the adhesive compositions described in Examples 1 to 16 exhibited low ball adhesion values, with post-heat adhesion to polypropylene (post-heat adhesion to PP) exceeding 10.0 N / 25 mm, and constant-load peel strength to polypropylene exceeding 30 mm. Comparative Example 1, which used an acrylic polymer (A'-1) without copolymerization of an amino group-containing monomer, exhibited poor evaluation in the constant-load peel test and poor compatibility between the acrylic polymer, the acid-modified polyolefin (B), and the adhesion-imparting resin (C).

[0203] Comparative Example 4 using an acrylic polymer (A'-2) copolymerized with a crosslinkable functional group-containing monomer in a predetermined amount or more and Comparative Example 5 using an acrylic polymer (A'-3) without copolymerizing a crosslinkable functional group-containing monomer gave poor results in the constant load peel test.

[0204] The PSA sheet obtained from the PSA composition not containing the acid-modified polyolefin (B) (Comparative Example 2) had a high ball tack value and low adhesive strength after heating.

[0205] The results of the constant load peel test of the adhesive sheet (Comparative Example 3) obtained from the adhesive composition that does not contain the adhesion-imparting resin (C) are poor. Compared with the adhesive sheets (Examples 3, 4, 14-16) obtained from the adhesive composition having the same composition as Comparative Example 6 except for the type of adhesion-imparting resin, the adhesive strength of the adhesive sheet (Comparative Example 6) obtained from the adhesive composition that does not contain (C1) or (C2) and contains adhesion-imparting resins other than (C1) and (C2) after pasting aging is poor.

Claims

1. An adhesive composition comprising: A (meth)acrylic polymer (A) comprising a monomer component comprising 55 to 99% by mass of at least one (meth)acrylate selected from alkoxyalkyl (meth)acrylates and alkyl (meth)acrylates having an alkyl group with 4 to 12 carbon atoms, 0.5 to 15% by mass of a crosslinkable functional group-containing monomer other than an amino group-containing monomer, and 0.01 to 5% by mass of an amino group-containing monomer, and Acid-modified polyolefin (B), and At least one tackifying resin (C) selected from rosin-based tackifying resins (C1) and terpene-phenol-based tackifying resins (C2), having a weight average molecular weight of 500 to 4500 and a hydroxyl value of 15 to 150 mgKOH / g, and Cross-linking agent (D); It meets the following requirements (I) to (III): (I) A 50 μm thick adhesive layer obtained from the adhesive composition has a ball adhesion test value of 5 or less according to the J.Dow method, (II) the adhesive surface of a 50 μm thick adhesive layer obtained from the adhesive composition is attached to a polypropylene plate, and the adhesive strength measured after standing at 80° C. for 20 minutes is 10.0 N / 25 mm or more; (III) A test piece having an adhesive surface of an adhesive layer having a thickness of 50 μm obtained from the adhesive composition and attached to a polypropylene plate with an area of ​​50 mm × 20 mm is placed at 80° C. for 20 minutes. A load of 200 g is then applied to one end of the long side of the test piece at 80° C., and the amount of adhesive layer peeled off 1 hour after the start of the load application is less than 30 mm.

2. The adhesive composition according to claim 1, wherein The amino group contained in the amino group-containing monomer is a tertiary amino group.

3. The adhesive composition according to claim 1 or 2, wherein The (meth)acrylic polymer (A) is a polymer comprising monomer components of 60 to 94% by mass of an alkyl (meth)acrylate having an alkyl group with 4 to 12 carbon atoms, 0.5 to 15% by mass of a monomer containing a crosslinkable functional group other than the amino group-containing monomer, 0.01 to 5% by mass of the amino group-containing monomer, and 5 to 30% by mass of an alkyl (meth)acrylate having an alkyl group with 1 to 3 carbon atoms.

4. The adhesive composition according to claim 1 or 2, wherein The crosslinkable functional group-containing monomer other than the amino group-containing monomer is (meth)acrylic acid.

5. The adhesive composition according to claim 1 or 2, wherein The acid-modified polyolefin (B) and the tackifier resin (C) are contained in an amount of 5 to 20 parts by mass based on 100 parts by mass of the (meth)acrylic polymer (A).

6. The adhesive composition according to claim 1 or 2, wherein A 50 μm-thick PSA layer obtained from the PSA composition had a haze of less than 35%. 7 . A pressure-sensitive adhesive sheet comprising a substrate and a pressure-sensitive adhesive layer provided on the substrate and obtained from the pressure-sensitive adhesive composition according to claim 1 .

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