(Meth)acrylic acid-based copolymer, adhesive composition containing the same, and adhesive sheet

Abstract

The present invention is a (meth)acrylic copolymer (A) having a mass average molecular weight of 50,000 to 1,000,000 obtained by polymerizing a monomer mixture containing a macromonomer (a) having a number average molecular weight of 500 or more and less than 6,000 and a vinyl monomer (b), preferably a (meth)acrylic copolymer (A) containing 7 to 40% by mass of repeating units derived from the macromonomer (a), and the prepared adhesive composition has sufficient coating workability, adhesive retention and adhesiveness.

Description

[0001] This application is a divisional application of the following application.

[0002] Invention Title: (Meth) acrylic acid-based copolymer, adhesive composition containing the (meth) acrylic acid-based copolymer, and adhesive sheet

[0003] Application date: November 28, 2014

[0004] Application number: 201480065130.1 (PCT / JP2014 / 081523) Technical Field

[0005] The present invention relates to a (meth)acrylic acid-based copolymer obtained by copolymerizing a macromonomer, and a PSA composition and a PSA sheet containing the (meth)acrylic acid-based copolymer. Background Art

[0006] In the past, various copolymers with different physical properties were synthesized by polymerizing a single vinyl monomer or copolymerizing a plurality of vinyl monomer mixtures. Since the polymer using a single vinyl monomer cannot meet the various physical property requirements, a method of copolymerizing a mixture containing two or more vinyl monomers or mixing different copolymers is usually used. However, when simply copolymerizing a plurality of vinyl monomer mixtures, the properties possessed by each monomer unit tend to be averaged.

[0007] Furthermore, simply mixing two or more copolymers does not mix with each other, and the properties of the copolymers are often inferior to those of the individual monomer units.

[0008] In order to solve these problems, research on copolymers using macromonomers has been conducted. Macromonomers refer to high molecular weight monomers having polymerizable functional groups. Copolymers obtained by copolymerizing macromonomers have the characteristic of being able to show their respective properties without damaging the respective properties of the macromonomer part and the monomer units copolymerized with the macromonomer. Therefore, for example, in the field of adhesives, various schemes of copolymers using such macromonomers have been proposed.

[0009] For example, Patent Document 1 discloses a binder composition comprising a copolymer obtained by copolymerizing a macromonomer having a number average molecular weight of 2000 g / mol to 50,000 g / mol with an ethylenically unsaturated monomer, thereby being dispersed in an aqueous medium having a specific solid content.

[0010] Furthermore, Patent Document 2 discloses a resin composition for an adhesive obtained by copolymerizing an alkyl (meth)acrylate monomer with a macromonomer having a number average molecular weight of 1000 to 200,000 and a glass transition temperature of 30 to 150°C.

[0011] Prior art literature

[0012] Patent Literature

[0013] Patent Document 1: International Publication No. 2002 / 022755 Pamphlet

[0014] Patent Document 2: Japanese Patent Laid-Open No. 11-158450 Summary of the invention

[0015] Problems to be solved by the invention

[0016] However, the copolymers of Patent Documents 1 and 2 have problems such as insufficient coating workability in various coating methods because the obtained copolymers have too large molecular weights or inappropriate copolymerization ratios with macromonomers, and the obtained adhesives do not have sufficient holding power.

[0017] Means for solving problems

[0018] The present invention relates to a (meth)acrylic copolymer (A) having a weight average molecular weight of 50,000 to 1,000,000, which is obtained by polymerizing a monomer mixture containing a macromonomer (a) having a number average molecular weight of 500 or more and less than 6,000 and a vinyl monomer (b).

[0019] Furthermore, the present invention relates to a pressure-sensitive adhesive composition containing the (meth)acrylic copolymer (A).

[0020] Furthermore, the present invention relates to an adhesive sheet using the adhesive composition.

[0021] Effects of the Invention

[0022] The (meth)acrylic copolymer (A) of the present invention has the properties of the macromonomer part and the monomer unit polymerized with the macromonomer, and therefore the adhesive composition using the (meth)acrylic copolymer (A) can be applied by various coating methods, such as a hot melt method in which the resin composition is directly heated and applied, or a solution coating method in which a solvent is added and then applied. In addition, the obtained adhesive has sufficient adhesive force and holding power. DETAILED DESCRIPTION

[0023] Hereinafter, the present invention will be described based on examples of embodiments. However, the present invention is not limited to the embodiments described below.

[0024] <Macromeremonomer (a)>

[0025] A macromonomer generally refers to a polymer compound having a polymerizable group introduced into the terminal of the polymer. The number average molecular weight of the macromonomer (a) in the present invention is 500 or more and less than 6000. From the perspective of the balance between adhesive strength and coating properties, the number average molecular weight is preferably 800 to 5500, and more preferably 1000 to 4500.

[0026] Various monomers can be used as the monomer constituting the macromonomer, but in the present invention, a monomer having a structure represented by the following formula (1) in which a polymerizable group is introduced at the end of a poly(meth)acrylate segment is preferred. In the present invention, "(meth)acrylic acid" means "acrylic acid" or "methacrylic acid".

[0027] [Chemistry 1]

[0028]

[0029] N is a natural number ranging from 4 to 5999.

[0030] In formula (1), R and R 1 ~R n are each independently a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group or a heterocyclic group. The alkyl group, the cycloalkyl group, the aryl group or the heterocyclic group may be substituted or unsubstituted.

[0031] As R or R 1 ~R n The alkyl group includes, for example, branched or straight-chain alkyl groups having 1 to 20 carbon atoms. Specific examples of branched or straight-chain alkyl groups having 1 to 20 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, isobutyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, and eicosyl. Among them, from the perspective of ease of acquisition, methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, pentyl, hexyl, heptyl, and octyl are preferred, and methyl, ethyl, n-propyl, isopropyl, n-butyl, and tert-butyl are more preferred.

[0032] As R or R 1 ~R n The cycloalkyl group may be, for example, a cycloalkyl group having 3 to 20 carbon atoms. Specific examples of the cycloalkyl group having 3 to 20 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl and adamantyl. In terms of availability, cyclopropyl, cyclobutyl and adamantyl are preferred.

[0033] As R or R 1~R n The aryl group includes, for example, an aryl group having 6 to 18 carbon atoms. Specific examples of the aryl group having 6 to 18 carbon atoms include phenyl and naphthalene.

[0034] As R or R 1 ~R n Examples of the heterocyclic group include heterocyclic groups having 5 to 18 carbon atoms. 1 ~R n Specific examples of the heterocyclic group include a γ-butyrolactone group and an ε-caprolactone group.

[0035] As R or R 1 ~R n The substituents that each group may have include alkyl, aryl, carboxyl, alkoxycarbonyl (-COOR'), cyano, hydroxyl, amino (-NR'R"), amide (-CONR'R"), halogen, allyl, epoxy, alkoxy (-OR'), siloxy, or a group or atom selected from the group consisting of hydrophilic or ionic groups. In addition, R' or R" may be independently a hydrogen atom, an alkyl, a cycloalkyl, or an aryl group that is the same as R.

[0036] Examples of the alkoxycarbonyl group as the substituent include a methoxycarbonyl group.

[0037] Examples of the amino group as the substituent include amino, monomethylamino, and dimethylamino. For example, N-methylcarbamoyl and N,N-dimethylcarbamoyl can be mentioned.

[0038] Examples of the amide group as the substituent include carbamoyl (-CONH 2 ), N-methylcarbamoyl (-CONHMe), N,N-dimethylcarbamoyl (dimethylamide: -CONMe 2 ).

[0039] Examples of the halogen as the substituent include fluorine, chlorine, bromine and iodine.

[0040] Examples of the alkoxy group as the substituent include alkoxy groups having 1 to 12 carbon atoms, and a specific example thereof includes a methoxy group.

[0041] Examples of the substituents showing hydrophilicity or ionicity include cationic substituents such as alkali salts of carboxyl groups or alkali salts of sulfoxyl groups, poly(alkylene oxide) groups such as polyoxyethylene groups and polyoxypropylene groups, and quaternary ammonium salt groups.

[0042] R and R 1 ~R nIt is preferably at least one selected from an alkyl group and a cycloalkyl group, and more preferably an alkyl group.

[0043] X 1 ~X n are each independently a hydrogen atom or a methyl group.

[0044] From the viewpoint of the ease of synthesis of the macromonomer (a), X 1 ~X n Preferred X 1 ~X n More than half of them are methyl groups.

[0045] Z is a terminal group of the macromonomer (a). Examples of the terminal polymerizable functional group of the macromonomer include a methacryloyl group, an acryloyl group, a vinyl group, and a terminal polymerizable functional group represented by the following formula (2).

[0046] [Chemistry 2]

[0047]

[0048] (In formula (2), R Z It represents the same as R and R in formula (1). 1 ~R n Same meaning.)

[0049] Examples of the monomer for obtaining the macromonomer (a) include (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, hexadecyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, cyclohexyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, 3,5,5-trimethylcyclohexyl (meth)acrylate, dicyclopentyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, and the like. Ester, terpene acrylate and its derivatives, hydrogenated rosin acrylate and its derivatives, behenyl (meth)acrylate, glycidyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, n-butoxyethyl (meth)acrylate, isobutoxyethyl (meth)acrylate, tert-butoxyethyl (meth)acrylate, phenoxyethyl (meth)acrylate, nonylphenoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, (meth)acryloylmorpholine, "PLACCEL "FM" (a monomer of caprolactone addition manufactured by Daicel Chemical Co., Ltd., a trade name), "BLEMMER PME-100" (a methoxy polyethylene glycol methacrylate (two ethylene glycol chains) manufactured by NOF Corporation, a trade name), "BLEMMER PME-200" (a methoxy polyethylene glycol methacrylate (four ethylene glycol chains) manufactured by NOF Corporation, a trade name), "BLEMMER PME-400" (trade name of methoxy polyethylene glycol methacrylate (9 ethylene glycol chains), manufactured by NOF Corporation), "BLEMMER 50POEP-800B" (trade name of octyloxy polyethylene glycol-polypropylene glycol-methacrylate (8 diethanol chains and 6 propylene glycol chains), manufactured by NOF Corporation), and "BLEMMER 20ANEP-600" (trade name of nonylphenoxy (ethylene glycol-polypropylene glycol) monoacrylate), "BLEMMER AME-100" (trade name of NOF Corporation), and "BLEMMER AME-200" (trade name of NOF Corporation)."Trade name") and "BLEMMER50AOEP-800B" (manufactured by NOF Corporation, trade name) SILAPLANE FM-0711 (manufactured by JNC Corporation, trade name), SILAPLANE FM-0721 (manufactured by JNC Corporation, trade name), SILAPLANE FM-0725 (manufactured by JNC Corporation, trade name), SILAPLANE TM-0701 (manufactured by JNC Corporation, trade name), SILAPLANE TM-0701T (manufactured by JNC Corporation, trade name) X-22-174DX (manufactured by Shin-Etsu Chemical Co., Ltd., trade name), X-22-2426 (manufactured by Shin-Etsu Chemical Co., Ltd., trade name), X-22-2475 (manufactured by Shin-Etsu Chemical Co., Ltd., trade name). ,

[0050] Among them, methacrylate is preferred from the perspective of glass transition temperature, ease of polymerization, and improved holding power. Methyl methacrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, hydroxyethyl (meth)acrylate, and hydroxypropyl (meth)acrylate are further preferred.

[0051] Glass transition temperature (Tga)

[0052] In the present invention, the glass transition temperature (Tga) of the macromonomer (a) is preferably 0 to 120° C. From the viewpoint of exhibiting sufficient holding power when used as a binder, it is more preferably 10 to 110° C., and further preferably 30 to 100° C.

[0053] In addition, Tga can be measured by differential scanning calorimetry (DSC).

[0054] Method for producing macromonomer (a)

[0055] The macromonomer (a) can be produced by a known method. Examples of the method for producing the macromonomer (a) include a method using a cobalt chain transfer agent, a method using an α-substituted unsaturated compound such as α-methylstyrene dimer as a chain transfer agent, a method of chemically bonding a polymerizable group, and a method utilizing thermal decomposition.

[0056] Among them, as a method for producing the macromonomer (a), a method using a cobalt chain transfer agent is preferred from the viewpoint of having a small number of production steps and using a catalyst with a high chain transfer constant. In addition, when a cobalt chain transfer agent is used for production, the terminal polymerizable functional group of the macromonomer (a) has the structure of the above formula (2).

[0057] Examples of methods for producing the macromonomer (a) using a cobalt chain transfer agent include bulk polymerization, solution polymerization, and aqueous dispersion polymerization such as suspension polymerization and emulsion polymerization. Aqueous dispersion polymerization is preferred from the viewpoint of simplicity of the recovery step.

[0058] 〈Monomer mixture〉

[0059] The monomer mixture comprises a macromonomer (a) and a vinyl monomer (b).

[0060] In the monomer mixture, the content of the macromonomer (a) is preferably 7 to 40% by mass. When the content of the macromonomer (a) is 7% by mass or more, the holding power when used as an adhesive tends to become good. When it is below 40% by mass, the coating property tends to become good. From the viewpoint of the holding power and coating property of the adhesive, the content of the macromonomer (a) is preferably 8 to 30% by mass, and more preferably 9 to 20% by mass.

[0061] <(Meth)acrylic acid-based copolymer (A)>

[0062] The (meth)acrylic copolymer (A) is a copolymer obtained by polymerizing a monomer mixture containing the above-mentioned macromonomer (a) and a vinyl monomer (b). As a production method, it can be produced by known polymerization methods such as solution polymerization, suspension polymerization, and emulsion polymerization. Since it is used as an adhesive composition in the present invention, solution polymerization is preferred.

[0063] In the present invention, the (meth)acrylic copolymer (A) may contain at least one selected from a polymer having only repeating units derived from a macromonomer (a), a polymer having one or more repeating units derived from a vinyl monomer (b), an unreacted macromonomer (a), and an unreacted vinyl monomer (b).

[0064] Furthermore, the (meth)acrylic copolymer (A) includes at least one selected from a block copolymer having repeating units derived from a macromonomer (a) and a vinyl monomer (b) and a graft copolymer of a vinyl monomer having repeating units derived from the macromonomer (a) in a side chain.

[0065] Vinyl monomer (b)

[0066] The vinyl monomer (b) used in the present invention may be the same monomer as that used to obtain the macromonomer (a). From the viewpoint of being able to exhibit flexibility as an adhesive and being able to suppress water absorption of the (meth)acrylic copolymer (A) due to its hydrophobicity, or being able to adjust the electrical properties such as the dielectric constant of the (meth)acrylic copolymer (A), 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, n-butyl acrylate, ethyl acrylate, etc. are particularly preferred.

[0067] In addition, (meth)acrylic acid, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, methyl (meth)acrylate, styrene, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, and the like are also preferred.

[0068] Weight average molecular weight

[0069] The weight average molecular weight of the (meth)acrylic copolymer (A) is 50,000 to 1,000,000. If it is above 50,000, the durability of the adhesive composition prepared tends to be good. If it is below 1,000,000, the coating property tends to be good. From the viewpoint of coating property, the weight average molecular weight of the (meth)acrylic copolymer (A) is preferably 120,000 to 700,000, more preferably 150,000 to 500,000.

[0070] Glass transition temperature (TgB)

[0071] In the present invention, in order to have the flexibility or appropriate adhesiveness (tackiness) of the adhesive resin composition at room temperature, the glass transition temperature (TgB) of the copolymer (B) obtained by polymerizing the vinyl monomer (b) is preferably -100°C to 10°C. TgB is more preferably -65°C to -0°C. It is particularly preferably -60°C to -10°C or less.

[0072] TgB is a value calculated from the glass transition temperature of a polymer obtained from a homopolymer of the monomer (b) and the constituent ratio by the calculation formula of Fox.

[0073] The calculation formula of Fox refers to a calculated value obtained by the following formula, and can be obtained using the value described in Polymer Handbook [Polymer HandBook, J. Brandrup, Interscience, 1989].

[0074] 1 / (273+Tg)=Σ(Wi / (273+Tgi))

[0075] [Wherein, Wi represents the weight fraction of monomer i, and Tgi represents the Tg (°C) of the homopolymer of monomer i]

[0076] In order to fully express the properties of the macromonomer portion and the monomer unit copolymerized with the macromonomer, it is preferred that the glass transition temperature (Tga) and (TgB) have the relationship represented by the following formula (3).

[0077] Tga>TgB···(3)

[0078] More preferably, Tga-TgB>50°C, and most preferably, Tga-TgB>80°C.

[0079] The (meth)acrylic copolymer (A) of the present invention preferably has a melt viscosity of 20 to 800 Pa·s at 130°C. When the melt viscosity at 130°C is within the above-described range, the resin composition can be directly heated and coated by a hot melt method. In addition, the melt viscosity can be measured using, for example, a viscoelasticity measuring device Rheosol-G5000 manufactured by UBM Co., Ltd. In the present invention, the melt viscosity is measured using The viscosity (η) was measured at 130°C, strain 0.7%, and 0.02 Hz. ＊ ) value is taken as the value of the melt viscosity at 130° C. From the viewpoint of coating properties, it is preferably 20 to 600 Pa·s, more preferably 50 to 600 Pa·s, and further preferably 100 to 500 Pa·s.

[0080] The (meth)acrylic copolymer (A) of the present invention has a holding force X represented by the following formula of 100 or more and a peel strength Y of 3 N / 25 mm or more.

[0081] Holding force X = holding time (40) / holding time (90)

[0082] The holding time (40) and the holding time (90) respectively represent the holding time at 40°C and the holding time at 90°C measured under the conditions of a bonding area of ​​20 mm×20 mm and a load of 0.5 kg in accordance with JIS Z0237.

[0083] The peel strength Y is the peel strength with respect to the glass substrate measured under the conditions of a peel angle of 180° and a tensile speed of 60 mm / min in accordance with JIS Z0237.

[0084] By satisfying the above conditions, when used as an adhesive composition, the composition has excellent adhesive holding power and adhesiveness.

[0085] Examples of the (meth)acrylic copolymer (A) satisfying the above conditions include (meth)acrylic copolymers having a weight average molecular weight of 50,000 to 1,000,000 obtained by polymerizing a monomer mixture containing a macromonomer (a) having a number average molecular weight of 500 to less than 6,000 and a vinyl monomer (b).

[0086] <Adhesive composition>

[0087] The adhesive composition of the present invention contains a (meth)acrylic copolymer (A).

[0088] The adhesive composition of the present invention may contain known components mixed in a conventional adhesive composition. For example, a filler may be added to impart heat resistance, thermal conductivity, flame retardancy, electrical conductivity, and the like. Examples of fillers include metal powders such as zinc oxide powder and titanium oxide powder, carbon black such as acetylene black, talc, glass powder, silica powder, conductive particles, inorganic fillers such as glass powder, and organic fillers such as polyethylene powder, polyester powder, polyamide powder, fluororesin powder, polyvinyl chloride powder, epoxy resin powder, and silicone resin powder. These fillers may be used alone or in combination of two or more.

[0089] The (meth)acrylic copolymer (A) and the crosslinking agent in the adhesive composition may also be crosslinked by ultraviolet irradiation to form an adhesive sheet. For example, the following methods may be mentioned: a method in which a crosslinking agent capable of chemically bonding to reactive groups such as hydroxyl groups introduced into the (meth)acrylic copolymer (A) is added and reacted by heating or aging, or a method in which a multifunctional (meth)acrylate having two or more (meth)acryloyl groups or an acrylate having nitrogen atoms introduced therein is added as a crosslinking agent and a reaction initiator such as a photopolymerization initiator is reacted.

[0090] Furthermore, a functional group may be introduced into the (meth)acrylic copolymer (A) to prepare an adhesive composition mixed with a crosslinking agent or a polymerization initiator to prepare an adhesive sheet obtained by crosslinking. As the crosslinking method, for example, isocyanate-based, epoxy-based, metal chelate-based, photocurable, melamine-based, aziridine-based, etc. may be cited, and they may be used in combination.

[0091] Examples of the isocyanate crosslinking agent include aromatic polyisocyanates such as xylylene diisocyanate, diphenylmethane diisocyanate, triphenylmethane triisocyanate, and benzal diisocyanate; aliphatic or alicyclic polyisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, and hydrogenated products of the above aromatic polyisocyanates; dimers or trimers of these polyisocyanates; and adducts of these polyisocyanates with polyols such as trimethylolpropane. These substances may be used alone or in combination of two or more.

[0092] Examples of epoxy crosslinking agents include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, bisphenol A type epoxy resin, N,N,N',N'-tetraglycidyl-m-xylene diamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N-diglycidyl aniline, and N,N-diglycidyl toluidine.

[0093] Examples of metal chelate compounds include compounds obtained by covalently or coordinately bonding a polyvalent metal to an organic compound. Examples of polyvalent metals include aluminum, nickel, chromium, copper, iron, tin, titanium, zinc, cobalt, manganese, and zirconium.

[0094] Examples of the covalently bonded or coordinately bonded organic compound include organic compounds having oxygen, such as ketone compounds such as acetylacetone, alkyl esters, alcohol compounds, carboxylic acid compounds, and ether compounds.

[0095] Regarding the photocuring system, a multifunctional (meth)acrylate having two or more (meth)acryloyl groups and a reaction initiator such as a photopolymerization initiator can be added as a crosslinking agent, and crosslinking can be achieved by ultraviolet irradiation or the like. Examples of such a crosslinking agent include a multifunctional (meth)acrylate having two or more (meth)acryloyl groups, or a multifunctional organic functional group resin having two or more organic functional groups such as isocyanate groups, epoxy groups, melamine groups, glycol groups, siloxane groups, and amine groups, or a metal having zinc, aluminum, sodium, zirconium, calcium, and the like. Organic metal compounds belonging to complexes, triethylene glycol diacrylate, polyalkylene glycol diacrylate, bisphenol A-EO / PO modified diacrylate, alkoxylated hexanediol diacrylate, polyisobutylene diacrylate, alkoxylated trimethylolpropane triacrylate, alkoxylated pentaerythritol triacrylate, alkoxylated pentaerythritol tetraacrylate, alkoxylated dipentaerythritol pentaacrylate, caprolactone modified dipentaerythritol pentaacrylate and caprolactone modified dipentaerythritol hexaacrylate and other multifunctional (meth) acrylates, etc.

[0096] In addition, various additives such as tackifier resin, antioxidant, light stabilizer, metal deactivator, anti-aging agent, moisture absorbent, rust inhibitor, anti-hydrolysis agent, etc. may be appropriately contained as needed. Reaction catalysts (tertiary amine compounds, quaternary ammonium compounds, tin laurate compounds, etc.) may also be appropriately contained.

[0097] As the type of antioxidant, for example, phenolic, phosphorus, hydroxylamine, sulfur, etc. can be cited. Among them, phenolic and phosphoric acid antioxidants are preferred because they cause less coloring of the resin after heating. They can be used alone or in combination. The mixing amount of the above antioxidant is preferably in the range of 0.1 to 5 parts by mass relative to the (meth)acrylic copolymer.

[0098] The adhesive resin composition can be formed into a sheet and used as an adhesive sheet.

[0099] The adhesive sheet can be applied in a solution state using a solvent, or can be prepared as a hot melt adhesive composition without using a solvent. If a hot melt adhesive composition without using a solvent is prepared, it can have a thicker thickness than an adhesive composition using a solvent, and therefore, for example, it can have a sufficient thickness to fill the gap between the components of the image display device.

[0100] Furthermore, the adhesive sheet obtained by the present invention can be used when bonding various substrates and exhibits very good bonding performance. For example, by being applied to a transparent plastic film or processed into an adhesive film, it can be used for bonding window films for vehicles and buildings, or for bonding labels in label displays. In addition, by being processed into a transparent double-sided adhesive sheet, it can be used for bonding various panels in display displays such as liquid crystal panels, or for bonding transparent plates such as glass.

[0101] Example

[0102] The adhesive resin composition of the present invention is further described in detail by showing the following examples and comparative examples. However, the present invention is not limited to these examples. In addition, the "parts" in the present examples refer to "parts by mass".

[0103] <Synthesis of macromonomer (a-1)>

[0104] <Production of dispersant 1>

[0105] In a polymerization device equipped with a stirrer, a condenser, and a thermometer, 900 parts of deionized water, 60 parts of sodium 2-sulfoethyl methacrylate, 10 parts of potassium methacrylate, and 12 parts of methyl methacrylate (MMA) were added and stirred, and the polymerization device was purged with nitrogen while the temperature was raised to 50°C. 0.08 parts of 2,2'-azobis(2-methylpropionamidine) dihydrochloride as a polymerization initiator was added thereto, and the temperature was further raised to 60°C. After heating, MMA was continuously added dropwise at a rate of 0.24 parts / minute for 75 minutes using a dropping pump. After the reaction solution was kept at 60°C for 6 hours, it was cooled to room temperature to obtain a dispersant 1 having a solid content of 10% by mass in a transparent aqueous solution.

[0106] 145 parts of deionized water, 0.1 parts of sodium sulfate and 0.25 parts of dispersant 1 (solid content 10% by mass) were added to a polymerization apparatus equipped with a stirrer, a condenser and a thermometer, and stirred to prepare a uniform aqueous solution. Then, 100 parts of MMA, 0.008 parts of bis[(difluoroboryl)diphenylglyoxime]cobalt(II) as a chain transfer agent and 0.8 parts of "Parokta" (registered trademark) O (2-ethylperoxyhexanoic acid-1,1,3,3-tetramethylbutyl ester, manufactured by NOF Corporation) as a polymerization initiator were added to prepare an aqueous suspension.

[0107] Next, the polymerization apparatus was purged with nitrogen, the temperature was raised to 80°C for reaction for 1 hour, and further, in order to increase the polymerization rate, the temperature was raised to 90°C and maintained for 1 hour. Then, the reaction solution was cooled to 40°C to obtain an aqueous suspension containing a macromolecular monomer. The aqueous suspension was filtered, the filtrate was washed with deionized water, dehydrated, and dried at 40°C for 16 hours to obtain a macromolecular monomer (a-1). The number average molecular weight of the macromolecular monomer (a-1) was 1400, and the glass transition temperature obtained by DSC measurement was 55°C.

[0108] <Production of macromonomers (a-2) to (a-9)>

[0109] The same method as the macromonomer (a-1) was used to produce the macromonomer (a-1) except that the monomer, polymerization initiator, and chain transfer agent added to the dispersant 1 were changed to the charged amounts (parts) shown in Table 1. The number average molecular weight (Mn) and glass transition temperature (Tga) of the obtained macromonomer (a) are shown in Table 1.

[0110] [Table 1]

[0111]

[0112] MMA: Methyl Methacrylate

[0113] IBXMA: Isobornyl methacrylate

[0114] (Evaluation method)

[0115] Glass transition temperature (Tga) of macromonomer (a)

[0116] The measurement was performed using a differential scanning calorimeter (DSC SmartRoader manufactured by Rigaku) ​​in a nitrogen atmosphere at a temperature increase rate of 5°C / min. Alumina was used as a standard substance.

[0117] Molecular weight of the macromonomer (a) and the acrylic copolymer (A)

[0118] Macromonomer (a)

[0119] The measurement was performed using a gel permeation chromatograph (GPC) (HLC-8320 manufactured by Tosoh Corporation). After preparing a 0.2% by mass tetrahydrofuran solution of the macromonomer (a), 10 μl of the solution was injected into a device equipped with a chromatographic column manufactured by Tosoh Corporation (TSKgelSuperHZM-M×HZM-M×HZ2000, TSKguardcolumn SuperHZ-L), and the measurement was performed under the conditions of a flow rate of 0.35 ml / min, an eluent of tetrahydrofuran (stabilizer BHT), and a column temperature of 40°C. The number average molecular weight (Mn) was calculated by conversion to standard polystyrene.

[0120] ·Acrylic copolymer (A)

[0121] The measurement was performed using a gel permeation chromatograph (GPC) (HLC-8120 manufactured by Tosoh Corporation). A 0.3% by mass tetrahydrofuran solution of the acrylic copolymer (A) was prepared, and 20 μl of the solution was injected into a device equipped with a chromatographic column manufactured by Tosoh Corporation (TSKgelSuperHM-H*4, TSKguardcolumn SuperH-H), and the measurement was performed under the conditions of a flow rate of 0.6 ml / min, an eluent of tetrahydrofuran (stabilizer BHT), and a column temperature of 40° C. The weight average molecular weight (Mw) was calculated by conversion to standard polystyrene.

[0122] Transparency

[0123] After the polymerized resin solution was desolventized by drying under reduced pressure, it was measured into a 200 mL transparent wide-mouth screw-top bottle and observed with the naked eye under diffuse natural light. "○" was recorded when it was transparent and no foreign matter or separation was observed, and "×" was recorded when any of turbidity, foreign matter, separation, etc. was observed.

[0124] Evaluation of coating properties (melt viscosity at 130°C)

[0125] The viscoelasticity measuring device Rheosol-G5000 manufactured by UBM Co., Ltd. was used for the measurement. The viscosity (η) when measured under the conditions of a cone plate, a strain of 0.7% at 130°C, and 0.02 Hz ＊ ) value was taken as the value of melt viscosity at 130°C, and coating properties were judged according to the following criteria.

[0126] 500Pa·s or less: ○

[0127] Greater than 500Pa·s and less than 800Pa·s: △

[0128] Greater than 800Pa·s: ×

[0129] Retention test evaluation

[0130] According to JIS Z 0237, the release film on one side of the acrylic copolymer (A) which is sandwiched on both sides with a release film and formed into a sheet is peeled off, and a polyethylene terephthalate film (hereinafter referred to as PET film) is pressed with a 2 kg hand roller as a replacement. It is cut into strips of 20 mm × 100 mm, and the release film on the other side is peeled off. It is horizontally bonded to a 30 mm × 100 mm SUS plate using a 2 kg hand roller, so that the bonding area is 20 × 20 mm. After aging at 40 ° C for 30 minutes, a 0.5 kg weight is added to the end of the PET film, and the holding time is measured in a constant temperature layer at 40 ° C. The holding power is determined according to the following criteria.

[0131] Keep time for

[0132] 30 points or more: ◎

[0133] More than 5 points and less than 30 minutes: ○

[0134] Within 5 minutes: ×

[0135] In addition, the temperature was changed to 90°C (relative humidity 50%) and the retention time was measured in the same manner.

[0136] (holding time at 40°C) / (holding time at 90°C) = X

[0137] The comprehensive holding power was evaluated and judged as follows.

[0138] X≥230:◎

[0139] 230>X≥200:○

[0140] 200>X≥100:△

[0141] 100>X:×

[0142] Adhesion test

[0143] According to JIS Z0237, the peel strength Y relative to the glass substrate was measured under the conditions of a peeling angle of 180° and a tensile speed of 60 mm / min. In addition, the peeled glass substrate surface was visually observed to confirm the presence or absence of residual adhesive. The adhesive strength was determined according to the following criteria.

[0144] Y≥3N / 25mm and no residual paste: ○

[0145] Y≥3N / 25mm and there is residual paste:△

[0146] Y<3N / 25mm:×

[0147] [Production Example 1]

[0148] <Production of (meth)acrylic acid-based copolymer (A-1)>

[0149] In a four-necked flask equipped with a stirring device, a thermometer, a condenser, and a nitrogen inlet, 40 parts of the prepared solvent (Shigomi solvent) ethyl acetate and 10 parts of the macromonomer (a-1) were placed, and the temperature was raised to 85°C under nitrogen ventilation. After reaching 85°C, a mixture consisting of 20 parts of ethyl acetate, 90 parts of n-butyl acrylate, and 0.04 parts of benzoyl peroxide was added dropwise over 4.5 hours. After the addition was completed, it was kept for 1 hour, and then a mixture consisting of 0.5 parts of "Parokta O" and 10 parts of ethyl acetate was added over 1 hour. Then, after keeping it for 2 hours, 0.5 parts of "Ilganox 1010" (manufactured by BASF, trade name) and 20.5 parts of ethyl acetate as an antioxidant were added, and then cooled to room temperature to obtain a (meth)acrylic copolymer (A-1).

[0150] [Production Examples 2 to 21]

[0151] <Production of (meth)acrylic acid-based copolymers (A-2) to (A-21)>

[0152] (Meth)acrylic copolymers (A-2) to (A-21) were obtained in the same manner as in Production Example 1 except that the composition of the monomer mixture (macromonomer (a) and vinyl monomer (b)) and the solvent prepared initially were changed to those shown in Table 2.

[0153] In addition, (A-12) is an example in which the macromonomer (a) is not used.

[0154] [Table 2]

[0155]

[0156] AA-6: Macromonomer manufactured by East Asia Synthetics, trade name, Mn = 6000

[0157] MMA: Methyl Methacrylate

[0158] n-BA: n-butyl acrylate

[0159] 2-EHA: 2-Ethylhexyl acrylate

[0160] CHMA: Cyclohexyl methacrylate

[0161] AA: Acrylic acid

[0162] 2-HEMA: 2-Hydroxyethyl Methacrylate

[0163] EtOAc: ethyl acetate

[0164] IPA: Isopropyl alcohol

[0165] [Examples 1 to 19, Comparative Examples 1 to 3]

[0166] The melt viscosity, transparency, holding power and adhesive force of the (meth)acrylic copolymer (A-1) produced in Production Example 1 were measured at 130°C. The results are shown in Table 3. The (meth)acrylic copolymers (A-2 to A-21) of Production Examples 2 to 21 were also measured in the same manner (Table 3 and Table 4). In addition, Example 11 shows an example in which the coating method was changed to a hot melt method using the (meth)acrylic copolymer (A-4).

[0167] [Table 3]

[0168]

[0169] [Table 4]

[0170]

[0171] [Example 1] to [Example 19] show good coating properties and holding power as adhesives. On the other hand, in [Comparative Example 1], the commercially available (meth)acrylic copolymer (A-11) having a number average molecular weight of 6000 using a macromonomer (a) has a high melt viscosity at 130°C and poor coating properties. In addition, it has poor transparency and poor adhesiveness. [Comparative Example 2] uses a (meth)acrylic copolymer (A-12) without using a macromonomer (a). In [Comparative Example 3], the number average molecular weight of the macromonomer (a) is as large as 7000, and the comprehensive evaluation of the holding power of the (meth)acrylic polymer (A-13) using this macromonomer decreases slightly, and the adhesiveness further deteriorates.

[0172] [Examples 20 to 23]

[0173] The adhesive composition having the composition shown in Table 5 was cured or crosslinked by ultraviolet irradiation or the like. In this case, the adhesive composition also had good holding power and adhesive strength.

[0174] [Curing conditions]

[0175] Device: 2P curing device, light source: metal halide, irradiation intensity: 100mW / cm 2 , irradiation dose: 3000mJ / cm 2

[0176] [Table 5]

[0177]

[0178] ACMO: Acryloylmorpholine

[0179] NK-A-600: "NK Esther 600" manufactured by Shin-Nakamura Chemical Co., Ltd. (Polyethylene glycol #600 diacrylate)

[0180] IRG184: "IRGACURE184" BASF manufactured trade name (1-hydroxy-cyclohexyl-phenyl-ketone)

[0181] TPA-100: "DURANATE TPA-100" Asahi Kasei product name (polyisocyanurate)

Claims

1. A (meth)acrylic acid copolymer A, It is characterized in that The (meth)acrylic copolymer A has a mass average molecular weight of 120,000 to 1,000,000 and is obtained by polymerizing a monomer mixture containing a macromonomer a having a number average molecular weight of 500 or more and less than 6,000 and a vinyl monomer b. The macromonomer a has a terminal polymerizable functional group, and the vinyl monomer b contains acrylic acid. The (meth)acrylic copolymer A contains 20% by mass or less of repeating units derived from the macromonomer a, The macromonomer a is represented by the following formula (1): In formula (1), n ​​is a natural number from 4 to 5999; R and R 1 ~R n are independently a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group or a heterocyclic group, and the alkyl group, the cycloalkyl group, the aryl group or the heterocyclic group may be substituted; X 1 ~X n are independently a hydrogen atom or a methyl group, and Z is the terminal group of the macromonomer a.

2. The (meth)acrylic acid copolymer A according to claim 1, in, The repeating unit derived from the macromonomer a is contained in an amount of 7 to 20% by mass.

3. The (meth)acrylic acid copolymer A according to claim 1 or 2, in, The glass transition temperature Tga of the macromonomer a is 30-120°C.

4. The (meth)acrylic acid copolymer A according to claim 1 or 2, in, The melt viscosity at 130°C is 20 to 800 Pa·s.

5. The (meth)acrylic acid copolymer A according to claim 1 or 2, It is characterized in that The holding force X expressed by the following formula is greater than 100, and the peel strength Y is greater than 3N / 25mm. Holding force X = holding time at 40°C / holding time at 90°C The holding time at 40°C and the holding time at 90°C respectively refer to the holding time at 40°C and the holding time at 90°C measured under the conditions of a bonding area of ​​20 mm×20 mm and a load of 0.5 kg according to JIS Z0237. The peel strength Y is the peel strength with respect to the glass substrate measured under the conditions of a peel angle of 180° and a tensile speed of 60 mm / min in accordance with JIS Z0237.

6. An adhesive composition, It is characterized in that The copolymer comprises the (meth)acrylic acid-based copolymer A according to any one of claims 1 to 4.

7. An adhesive sheet, It is characterized in that The adhesive composition according to claim 6 is used.

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