JP2013079361A - Acrylic pressure-sensitive adhesive tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acrylic pressure-sensitive adhesive tape with improved adhesion to a low polarity adherend.SOLUTION: The acrylic pressure-sensitive adhesive tape includes a core layer 20; a surface layer 30a placed on one side of the core layer 20; and a surface layer 30b placed on the other side of the core layer 20. The core layer 20 contains an acrylic polymer (A). The surface layers 30a and 30b contain 100 pts.mass of acrylic polymer (B), and 1-70 pts.mass of a (meth)acrylic polymer (C) having a weight average molecular weight of ≥1,000 to <30,000 and having a terpene backbone in the side chain. The (meth)acrylic polymer (C) is a polymer having a smaller weight average molecular weight than the acrylic polymer (B) as a pressure-sensitive adhesive composition, and functions as a tackifier resin.

Description

  The present invention relates to an acrylic pressure-sensitive adhesive tape having an acrylic pressure-sensitive adhesive layer.

  Conventionally, an acrylic pressure-sensitive adhesive tape having an acrylic pressure-sensitive adhesive layer has excellent adhesive properties such as adhesive strength, repulsion resistance, and retention properties (cohesive strength), and has heat resistance, light resistance, weather resistance, oil resistance, etc. Widely used because of its excellent aging resistance. In particular, acrylic pressure-sensitive adhesive tapes having such characteristics are widely used as bonding materials in various industrial fields such as home appliances, building materials, and automobile interior / exterior materials. Therefore, various adhesive materials such as metal materials such as stainless steel and aluminum, various plastic materials such as polyethylene, polypropylene, polystyrene, ABS, (meth) acrylic resin, polycarbonate resin, and glass materials are applied to the acrylic adhesive tape. It is required to adhere to the body (joining object) with high reliability.

  As a technique for improving the adhesion of an acrylic pressure-sensitive adhesive tape to an adherend, a method of adding a tackifier resin (tackifier) to the acrylic pressure-sensitive adhesive composition constituting the acrylic pressure-sensitive adhesive layer is known. Patent Documents 1 and 2 disclose an acrylic pressure-sensitive adhesive composition in which rosin or hydrogenated petroleum resin is added as a tackifier resin to an acrylic polymer.

JP-A-6-207151 Japanese National Patent Publication No. 11-504054

  Acrylic adhesive tapes are always required to have improved adhesion to adherends, especially for polyolefin resins such as polyethylene and polypropylene, which are often used in home appliances, building materials, automotive interior and exterior materials, etc. There is a strong demand for improvement in adhesion to representative low-polar adherends. On the other hand, when the above-mentioned acrylic pressure-sensitive adhesive composition to which a tackifying resin such as rosin is added does not sufficiently meet the demand for improving the adhesion of the acrylic pressure-sensitive adhesive tape to the low-polar adherend. was there. Moreover, although terpene resin is also used as tackifying resin, terpene resin has inadequate compatibility with an acrylic polymer, and may have poor adhesion reliability.

  This invention is made | formed in view of such a subject, The objective provides the technique which can improve adhesiveness, such as the adhesive force of an acrylic adhesive tape, repulsion resistance, and a retention characteristic (cohesive force). There is to do.

  An embodiment of the present invention includes a core layer and a surface layer provided on one or both sides of the core layer. The core layer includes an acrylic polymer (A), and the surface layer includes an acrylic polymer ( B) 100 parts by mass and 1 to 70 parts by mass of a (meth) acrylic polymer (C) having a weight average molecular weight of 1000 or more and less than 30000 and having a terpene skeleton in the side chain.

  According to the acrylic pressure-sensitive adhesive tape of this aspect, it is possible to improve the adhesive strength to adherends including low-polar adherends.

  In the acrylic pressure-sensitive adhesive tape of the above aspect, the core layer may further include fine particles (D) and / or bubbles (E).

一般式（１）式中、Ｒ^１は、２価の有機基である。 The glass transition temperature of the (meth) acrylic polymer (C) may be 0 ° C. or higher and 300 ° C. or lower. The (meth) acrylic polymer (C) may contain, as a monomer unit, a (meth) acrylic monomer having a terpene skeleton of 10% by mass to 100% by mass in all monomers. The acrylic polymer (B) contains, as a monomer unit, at least one monomer selected from the group consisting of N-vinyl cyclic amide represented by acrylic (1) described in the following general formula and a carboxyl group-containing monomer. May be.

In the general formula (1), R ¹ is a divalent organic group.

  Further, the surface layer may contain 40 to 90% by mass of a solvent-insoluble component.

  ADVANTAGE OF THE INVENTION According to this invention, adhesiveness, such as the adhesive force of an acrylic adhesive tape, repulsion resistance, and a retention characteristic (cohesion force), can be improved.

It is a schematic sectional drawing which shows the structure of the acrylic adhesive tape which concerns on embodiment.

  Drawing 1 is an outline sectional view showing the composition of the acrylic adhesive tape concerning an embodiment. The acrylic pressure-sensitive adhesive tape 10 includes a core layer 20, a surface layer 30 a provided on one surface of the core layer 20, and a surface layer 30 b provided on the other surface of the core layer 20. Hereinafter, the surface layer 30a and the surface layer 30b are collectively referred to as a surface layer 30 as appropriate.

(Core layer)
The core layer 20 includes an acrylic polymer (A), fine particles (D), and bubbles (E) as necessary. Hereinafter, each component of the core layer 20 will be described in detail.

[Acrylic polymer (A)]
The acrylic polymer (A) which is an adhesive composition constituting the core layer 20 is, for example, a monomer unit of (meth) acrylic acid alkyl ester having a linear or branched alkyl group having 1 to 20 carbon atoms. Is contained in an amount of 50% by mass or more. Moreover, the acrylic polymer (A) can be configured such that the (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms is singly or in combination of two or more. The acrylic polymer (A) can be obtained by polymerizing (for example, solution polymerization, emulsion polymerization, UV polymerization) (meth) acrylic acid alkyl ester together with a polymerization initiator.

  The proportion of the (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms is 50% by mass or more and 99.9% by mass or less, preferably based on the total amount of monomer components for preparing the acrylic polymer (A). Is 60 mass% or more and 98 mass% or less, More preferably, it is 70 mass% or more and 95 mass% or less.

  Examples of the (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, Butyl (meth) acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, (meth) acryl Hexyl acid, heptyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, (meth) Decyl acrylate, Isodecyl (meth) acrylate, Unde (meth) acrylate , Dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate (Meth) acrylic acid C1-20 alkyl esters such as (meth) acrylic acid nonadecyl, (meth) acrylic acid eicosyl [preferably (meth) acrylic acid C2-14 alkyl ester, more preferably (meth) acrylic acid C2- 10 alkyl ester] and the like. In addition, (meth) acrylic acid alkyl ester means acrylic acid alkyl ester and / or methacrylic acid alkyl ester, and “(meth)...” Has the same meaning.

  The acrylic polymer (A) may contain other monomer components that can be copolymerized with the (meth) acrylic acid alkyl ester, if necessary, for the purpose of modifying cohesion, heat resistance, crosslinkability, and the like. A copolymerizable monomer). Therefore, the acrylic polymer (A) may contain a copolymerizable monomer together with the (meth) acrylic acid alkyl ester as the main component. As the copolymerizable monomer, a monomer having a polar group can be suitably used.

As a specific example of the copolymerizable monomer,
Carboxyl group-containing monomers such as acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid;
Hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, hydroxyhexyl (meth) acrylate, hydroxyoctyl (meth) acrylate, hydroxydecyl (meth) acrylate, (meta ) Hydroxyl-containing monomers such as hydroxyalkyl (meth) acrylates such as hydroxylauryl acrylate and (4-hydroxymethylcyclohexyl) methyl methacrylate;
Acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride;
Sulphonic acid groups such as styrene sulfonic acid, allyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate, (meth) acryloyloxynaphthalene sulfonic acid Containing monomers;
Phosphate group-containing monomers such as 2-hydroxyethylacryloyl phosphate;
(Meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dipropyl (meth) acrylamide, N, N-diisopropyl (meth) acrylamide, N, N-di N, N-dialkyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-isopropyl (meth) such as (n-butyl) (meth) acrylamide, N, N-di (t-butyl) (meth) acrylamide Acrylamide, N-butyl (meth) acrylamide, Nn-butyl (meth) acrylamide, N-methylol (meth) acrylamide, N-ethylol (meth) acrylamide, N-methylolpropane (meth) acrylamide, N-methoxymethyl ( (Meth) acrylamide, N-methoxyethyl (meta) Acrylamide, N- butoxymethyl (meth) acrylamide, N- acryloyl morpholine, etc. (N- substituted) amide monomers;
Succinimide monomers such as N- (meth) acryloyloxymethylenesuccinimide, N- (meth) acryloyl-6-oxyhexamethylenesuccinimide, N- (meth) acryloyl-8-oxyhexamethylenesuccinimide;
Maleimide monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N-phenylmaleimide;
Itaconimides such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, N-laurylitaconimide System monomers;
N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N- Vinyloxazole, N- (meth) acryloyl-2-pyrrolidone, N- (meth) acryloylpiperidine, N- (meth) acryloylpyrrolidine, N-vinylmorpholine, N-vinyl-2-piperidone, N-vinyl-3-morpholinone N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisoxazole, N-vinylthiazole, Contains nitrogen such as N-vinylisothiazole and N-vinylpyridazine Ring-based monomer;
N-vinylcarboxylic acid amides;
Lactam monomers such as N-vinylcaprolactam;
Cyanoacrylate monomers such as acrylonitrile and methacrylonitrile;
(Meth) acrylic such as aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, and t-butylaminoethyl (meth) acrylate Acid aminoalkyl monomers;
(Meth) acrylic acid alkoxyalkyl monomers such as (meth) acrylic acid methoxyethyl, (meth) acrylic acid ethoxyethyl, (meth) acrylic acid propoxyethyl, (meth) acrylic acid butoxyethyl, (meth) acrylic acid ethoxypropyl ;
Styrene monomers such as styrene and α-methylstyrene;
Epoxy group-containing acrylic monomers such as (meth) glycidyl acrylate;
Glycol-based acrylic ester monomers such as (meth) acrylic acid polyethylene glycol, (meth) acrylic acid polypropylene glycol, (meth) acrylic acid methoxyethylene glycol, (meth) acrylic acid methoxypolypropylene glycol;
(Meth) acrylic acid tetrahydrofurfuryl, fluorine atom-containing (meth) acrylate, silicone (meth) acrylate and other heterocyclic rings, halogen atoms, silicon atoms and the like, acrylic ester monomers;
Olefin monomers such as isoprene, butadiene, isobutylene;
Vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether;
Vinyl esters such as vinyl acetate and vinyl propionate;
Aromatic vinyl compounds such as vinyltoluene and styrene;
Olefins or dienes such as ethylene, butadiene, isoprene, isobutylene;
Vinyl ethers such as vinyl alkyl ethers;
Vinyl chloride;
Sulfonic acid group-containing monomers such as sodium vinyl sulfonate;
Imide group-containing monomers such as cyclohexylmaleimide and isopropylmaleimide;
Isocyanate group-containing monomers such as 2-isocyanatoethyl (meth) acrylate;
(Meth) acrylic acid ester having an alicyclic hydrocarbon group such as cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate;
(Meth) acrylic acid ester having an aromatic hydrocarbon group such as phenyl (meth) acrylate;
(Meth) acrylic acid ester obtained from terpene compound derivative alcohol;
Etc. These copolymerizable monomers can be used alone or in combination of two or more.

  When the acrylic polymer (A) contains a copolymerizable monomer together with a (meth) alkyl acid alkyl ester as a main component, a carboxyl group-containing monomer can be suitably used. Among these, acrylic acid can be preferably used. The amount of the copolymerizable monomer used is not particularly limited, but is usually 0.1 to 40% by mass of the copolymerizable monomer with respect to the total amount of monomer components for preparing the acrylic polymer (A), preferably May be contained in an amount of 0.5 to 30% by mass, more preferably 1 to 20% by mass.

  By containing 0.1% by mass or more of the copolymerizable monomer, it is possible to prevent the cohesive force of the acrylic pressure-sensitive adhesive constituting the core layer 20 from being lowered and to obtain a high shearing force. Moreover, by making content of a copolymerizable monomer into 40 mass% or less, it prevents that the cohesion force of the acrylic adhesive which comprises the core layer 20 becomes high too much, and tack feeling at normal temperature (25 degreeC). Can be improved.

  Moreover, in order to adjust the cohesion force of an acrylic adhesive tape, you may contain a polyfunctional monomer in an acrylic polymer (A) as needed.

  Examples of the polyfunctional monomer include (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol di (meth) acrylate, and pentaerythritol. Tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,2-ethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,12-dodecanediol di (meth) acrylate , Trimethylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, allyl (meth) acrylate, vinyl (meth) acrylate, divinylbenzene, epoxy acrylate, poly Ester acrylate, urethane acrylate, butyl di (meth) acrylate, hexyl di (meth) acrylate. Among these, trimethylolpropane tri (meth) acrylate, hexanediol di (meth) acrylate, and dipentaerythritol hexa (meth) acrylate can be preferably used. Polyfunctional (meth) acrylate can be used individually or in combination of 2 or more types.

  The amount of the polyfunctional monomer used varies depending on the molecular weight, the number of functional groups, and the like, but is 0.01 to 3.0% by mass, preferably based on the total amount of monomer components for preparing the acrylic polymer (A). It is added to 0.02 to 2.0% by mass, and more preferably 0.03 to 1.0% by mass.

  When the amount of the polyfunctional monomer used exceeds 3.0% by mass with respect to the total amount of monomer components for preparing the acrylic polymer (A), for example, the cohesive strength of the acrylic pressure-sensitive adhesive constituting the core layer 20 May become too high and the adhesive strength may decrease. On the other hand, if it is less than 0.01% by mass, for example, the cohesive force of the acrylic pressure-sensitive adhesive constituting the core layer 20 may be reduced.

<Polymerization initiator>
In the preparation of the acrylic polymer (A), the acrylic polymer (A) is obtained by utilizing a curing reaction by heat or ultraviolet rays using a polymerization initiator such as a thermal polymerization initiator or a photopolymerization initiator (photoinitiator). It can be formed easily. In particular, a photopolymerization initiator can be preferably used because of the advantage that the polymerization time can be shortened. A polymerization initiator can be used individually or in combination of 2 or more types.

  Examples of the thermal polymerization initiator include azo polymerization initiators (for example, 2,2′-azobisisobutyronitrile, 2,2′-azobis-2-methylbutyronitrile, 2,2′-azobis ( 2-methylpropionic acid) dimethyl, 4,4'-azobis-4-cyanovaleric acid, azobisisovaleronitrile, 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis [2 -(5-Methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobis (2-methylpropionamidine) disulfate, 2,2'-azobis (N, N'-dimethylene) Isobutylamidine) dihydrochloride, etc.); peroxide-based polymerization initiators (for example, dibenzoyl peroxide, t-butylpermaleate, lauroyl peroxide) ); Redox polymerization initiators, and the like.

  The amount of the thermal polymerization initiator used is not particularly limited as long as it can be conventionally used as a thermal polymerization initiator.

  Although it does not restrict | limit especially as a photoinitiator, For example, a benzoin ether type photoinitiator, an acetophenone type photoinitiator, an alpha-ketol type photoinitiator, an aromatic sulfonyl chloride type photoinitiator, photoactivity Oxime photopolymerization initiator, benzoin photopolymerization initiator, benzyl photopolymerization initiator, benzophenone photopolymerization initiator, ketal photopolymerization initiator, thioxanthone photopolymerization initiator, acylphosphine oxide photopolymerization initiator An agent or the like can be used.

  Specifically, examples of the benzoin ether photopolymerization initiator include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethane- 1-one [trade name: Irgacure 651, manufactured by BASF Corporation], anisole methyl ether and the like can be mentioned. Examples of the acetophenone photopolymerization initiator include 1-hydroxycyclohexyl phenyl ketone [trade name: Irgacure 184, manufactured by BASF Corp.], 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, 1- [4- ( 2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one [trade name: Irgacure 2959, manufactured by BASF Corp.], 2-hydroxy-2-methyl-1-phenyl-propane- 1-one [trade name: Darocur 1173, manufactured by BASF Corporation], methoxyacetophenone, and the like can be given. Examples of the α-ketol photopolymerization initiator include 2-methyl-2-hydroxypropiophenone, 1- [4- (2-hydroxyethyl) -phenyl] -2-hydroxy-2-methylpropane-1- ON etc. are mentioned. Examples of the aromatic sulfonyl chloride-based photopolymerization initiator include 2-naphthalene sulfonyl chloride. Examples of the photoactive oxime photopolymerization initiator include 1-phenyl-1,1-propanedione-2- (o-ethoxycarbonyl) -oxime.

  The benzoin photopolymerization initiator includes, for example, benzoin. Examples of the benzyl photopolymerization initiator include benzyl and the like. Examples of the benzophenone-based photopolymerization initiator include benzophenone, benzoylbenzoic acid, 3,3′-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α-hydroxycyclohexyl phenyl ketone, and the like. Examples of the ketal photopolymerization initiator include benzyl dimethyl ketal. Examples of the thioxanthone photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, dodecylthioxanthone and the like are included.

  Examples of the acylphosphine photopolymerization initiator include bis (2,6-dimethoxybenzoyl) phenylphosphine oxide, bis (2,6-dimethoxybenzoyl) (2,4,4-trimethylpentyl) phosphine oxide, bis ( 2,6-dimethoxybenzoyl) -n-butylphosphine oxide, bis (2,6-dimethoxybenzoyl)-(2-methylpropan-1-yl) phosphine oxide, bis (2,6-dimethoxybenzoyl)-(1- Methylpropan-1-yl) phosphine oxide, bis (2,6-dimethoxybenzoyl) -t-butylphosphine oxide, bis (2,6-dimethoxybenzoyl) cyclohexylphosphine oxide, bis (2,6-dimethoxybenzoyl) octylphosphine Oxide, bis (2- Toxibenzoyl) (2-methylpropan-1-yl) phosphine oxide, bis (2-methoxybenzoyl) (1-methylpropan-1-yl) phosphine oxide, bis (2,6-diethoxybenzoyl) (2-methyl Propan-1-yl) phosphine oxide, bis (2,6-diethoxybenzoyl) (1-methylpropan-1-yl) phosphine oxide, bis (2,6-dibutoxybenzoyl) (2-methylpropane-1- Yl) phosphine oxide, bis (2,4-dimethoxybenzoyl) (2-methylpropan-1-yl) phosphine oxide, bis (2,4,6-trimethylbenzoyl) (2,4-dipentoxyphenyl) phosphine oxide Bis (2,6-dimethoxybenzoyl) benzylphosphine oxide, bis 2,6-dimethoxybenzoyl) -2-phenylpropylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2-phenylethylphosphine oxide, bis (2,6-dimethoxybenzoyl) benzylphosphine oxide, bis (2,6 -Dimethoxybenzoyl) -2-phenylpropylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2-phenylethylphosphine oxide, 2,6-dimethoxybenzoylbenzylbutylphosphine oxide, 2,6-dimethoxybenzoylbenzyloctylphosphine oxide Bis (2,4,6-trimethylbenzoyl) -2,5-diisopropylphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -2-methylphenylphosphine oxide, bis (2 4,6-trimethylbenzoyl) -4-methylphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -2,5-diethylphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -2, 3,5,6-tetramethylphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -2,4-di-n-butoxyphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, bis (2,4,6-trimethylbenzoyl) isobutylphosphine oxide, 2,6-dimethoxybenzoyl-2,4,6-trimethyl Benzoyl-n-butylphosphine oxide, bis (2,4,4 -Trimethylbenzoyl) phenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -2,4-dibutoxyphenylphosphine oxide, 1,10-bis [bis (2,4,6-trimethylbenzoyl) phosphine oxide] Examples include decane and tri (2-methylbenzoyl) phosphine oxide.

  Although the usage-amount of a photoinitiator is not restrict | limited in particular, For example, 0.01-5 mass parts with respect to 100 mass parts of monomer components which prepare an acrylic polymer (A), Preferably 0.05-3 mass parts It is blended in an amount within the range.

  Here, when the usage-amount of a photoinitiator is less than 0.01 mass part, a polymerization reaction may become inadequate. When the usage-amount of a photoinitiator exceeds 5 mass parts, an ultraviolet-ray may not reach the inside of an adhesive layer because a photoinitiator absorbs an ultraviolet-ray. In this case, the polymerization rate is lowered, or the molecular weight of the produced polymer is reduced. As a result, the cohesive force of the acrylic pressure-sensitive adhesive constituting the core layer 20 is reduced, and when the film is peeled off from the core layer 20, a part of the acrylic pressure-sensitive adhesive remains on the film, and the film can be reused. It may not be possible. In addition, a photopolymerization initiator can be used individually or in combination of 2 or more types.

  In order to adjust the cohesion force, it is also possible to use a crosslinking agent in addition to the above-mentioned polyfunctional monomer. As the crosslinking agent, a commonly used crosslinking agent can be used. For example, epoxy crosslinking agent, isocyanate crosslinking agent, silicone crosslinking agent, oxazoline crosslinking agent, aziridine crosslinking agent, silane crosslinking agent, alkyl etherification A melamine type crosslinking agent, a metal chelate type crosslinking agent, etc. can be mentioned. In particular, an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent can be preferably used.

  Specifically, examples of isocyanate-based crosslinking agents include tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene. Examples include diisocyanate, triphenylmethane triisocyanate, polymethylene polyphenyl isocyanate, and adducts of these with polyols such as trimethylolpropane. Alternatively, a compound having at least one isocyanate group and one or more unsaturated bonds in one molecule, specifically, 2-isocyanatoethyl (meth) acrylate or the like may be used as an isocyanate-based crosslinking agent. Can do.

  Epoxy crosslinking agents include bisphenol A, epichlorohydrin type epoxy resin, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol glycidyl ether, trimethylolpropane tri Examples include glycidyl ether, diglycidyl aniline, diamine glycidyl amine, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine and 1,3-bis (N, N′-diamine glycidylaminomethyl) cyclohexane. be able to.

  In this embodiment, the acrylic polymer (A) is a partial polymer (acrylic polymer syrup) obtained by irradiating a mixture of the monomer component and the polymerization initiator with ultraviolet rays (UV) to partially polymerize the monomer component. ) Can also be prepared. The weight average molecular weight (Mw) of the acrylic polymer (A) is, for example, 30000 to 5000000.

[Fine particles (D)]
In the present embodiment, fine particles (D) can be added to the acrylic polymer (A) constituting the core layer. Examples of the function and effect of the fine particles (D) include improvement in shear adhesive strength and workability of the acrylic pressure-sensitive adhesive tape.

  As fine particles (D), metal particles such as copper, nickel, aluminum, chromium, iron, stainless steel, or metal oxide particles; carbide particles such as silicon carbide, boron carbide, and nitrogen carbide; aluminum nitride, silicon nitride, boron nitride Nitride particles such as: Ceramic particles typified by oxides such as glass, alumina and zirconium; Inorganic fine particles such as calcium carbide, aluminum hydroxide, glass and silica; Natural raw material particles such as volcanic shirasu and sand; Polystyrene and poly Polymer particles such as methyl methacrylate, phenol resin, benzoguanamine resin, urea resin, silicone resin, nylon, polyester, polyurethane, polyethylene, polypropylene, polyamide, polyimide; organic hollow bodies such as vinylidene chloride and acrylic; nylon beads, acrylic beads, Organic spheres such as corn beads and the like.

  As the fine particles (D), preferably, hollow fine particles can be used. Furthermore, among the hollow fine particles, hollow inorganic fine particles are preferable from the viewpoint of the efficiency and weight of polymerization using an ultraviolet reaction. Examples thereof include glass microspheres such as hollow glass microspheres; hollow balloons made of metal compounds such as hollow alumina microspheres; porcelain hollow microspheres such as hollow ceramic microspheres, and the like. By using the hollow glass microspheres, the high temperature adhesive force of the acrylic pressure-sensitive adhesive tape can be improved without impairing other properties such as shearing force and holding force.

  As hollow glass microspheres, for example, trade name: glass microballoon (manufactured by Fuji Silysia Chemical Co., Ltd.) and trade names: Cell Star Z-20, Cell Star Z-27, Cell Star CZ-31T, Cell Star Z-36, Cell Star Z- 39, Cell Star Z-39, Cell Star T-36, Cell Star PZ-6000 (all manufactured by Tokai Kogyo Co., Ltd.), trade name: Cyrus Fine Balloon (manufactured by Fine Balloon Co., Ltd.), and the like.

  The particle diameter (average particle diameter) of the fine particles (D) is not particularly limited, but can be selected from the range of, for example, 1 to 500 μm, preferably 5 to 200 μm, and more preferably 10 to 150 μm.

The specific gravity of the fine particles (D) is not particularly limited, but is, for example, 0.1 to 1.8 g / cm ³ , preferably 0.2 to 1.5 g / cm ³ , and more preferably 0.2 to 0.5 / It can be selected from the range of cm ³ .

When the specific gravity of the fine particles (D) is smaller than 0.1 g / cm ³ , the fine particles (D) are lifted up when mixed and mixed in the acrylic pressure-sensitive adhesive, and cannot be uniformly dispersed. There is a case. Moreover, the glass strength is low and the glass is easily broken. On the contrary, if it is larger than 1.8 g / cm ³ , the transmittance of ultraviolet rays may be lowered, and the efficiency of ultraviolet reaction may be lowered. Moreover, the acrylic adhesive which comprises the core layer 20 becomes heavy, and workability | operativity falls.

  The amount of the fine particles (D) used is not particularly limited. For example, when the amount used is less than 10% by volume with respect to the total volume of the core layer 20, the effect of adding the fine particles (D) is low, On the other hand, if the amount used exceeds 50% by volume, the adhesive strength of the acrylic pressure-sensitive adhesive constituting the core layer 20 may be reduced.

[Bubble (E)]
In the present embodiment, bubbles (E) can be added to the acrylic polymer (A) constituting the core layer. When the core layer 20 contains air bubbles (E), the acrylic pressure-sensitive adhesive tape 10 can exhibit good adhesion to a curved surface or an uneven surface, and can also exhibit good repulsion resistance. it can.

  It is desirable that the bubbles (E) contained in the core layer 20 are basically closed-cell type bubbles, but closed-cell type bubbles and open-cell type bubbles may be mixed.

  In addition, the bubbles (E) usually have a spherical shape (particularly a true spherical shape), but do not need to be a true spherical shape because the surface has irregularities. The average bubble diameter (diameter) of the bubbles (E) is not particularly limited, but can be selected from the range of, for example, 1 to 1000 μm, preferably 10 to 500 μm, and more preferably 30 to 300 μm.

  The gas component contained in the bubble (E) (gas component forming the bubble (E); hereinafter referred to as a bubble forming gas as appropriate) is not particularly limited, and is inert such as nitrogen, carbon dioxide, or argon. In addition to gas, various gas components such as air can be used. As the gas for forming the bubbles (E), when a polymerization reaction or the like is performed in a state where the bubble forming gas is included, it is important to use a gas that does not inhibit the reaction. As the bubble forming gas, nitrogen can be preferably used from the viewpoint of not inhibiting the polymerization reaction and the like, and from the viewpoint of cost.

  The amount of air bubbles (E) contained in the core layer 20 is not particularly limited and can be appropriately selected depending on the application. The amount of bubbles (E) contained in the core layer 20 is, for example, 5 to 50% by volume, preferably 8 to 40% by volume, based on the total volume of the core layer 20 containing the bubbles (E). When the amount of bubbles mixed is less than 5% by volume, the effect of mixing bubbles (E) cannot be obtained, and when the amount exceeds 50% by volume, the possibility of bubbles penetrating through the core layer 20 increases and the adhesive performance and appearance are deteriorated. There is a case.

  The method for forming the core layer 20 containing the bubbles (E) is not particularly limited. The core layer 20 containing the bubbles (E) may be formed by, for example, (1) using a core layer material in which the bubble forming gas is mixed in advance, or (2) the bubble forming gas is mixed. You may form by mixing a foaming agent with the core layer material which is not. In the case of (2), the foaming agent used is not particularly limited, and can be appropriately selected from known foaming agents, for example. As such a foaming agent, for example, thermally expandable microspheres can be used.

<Other ingredients>
In addition to the above-described components, a thickener, thixotropic agent, extender, etc. may be added to the core layer 20 as necessary. Examples of the thickener include acrylic rubber, epichlorohydrin rubber, butyl rubber and the like. Examples of thixotropic agents include colloidal silica and polyvinyl pyrrolidone. Examples of the bulking agent include calcium carbonate, titanium oxide, and clay. In addition, a plasticizer, an anti-aging agent, an antioxidant, and the like may be appropriately added to the core layer 20.

(Surface)
The surface layer 30 is a (meth) acrylic polymer (B) having a terpene skeleton in the side chain, having a weight average molecular weight of 1000 or more and less than 30000 as a tackifying resin. C) (hereinafter referred to as (meth) acrylic polymer (C) as appropriate).

  The content of each component in the acrylic pressure-sensitive adhesive composition contained in the surface layer 30 is as follows.

Acrylic polymer (B): 100 parts by mass (meth) acrylic polymer (C): 1 to 70 parts by mass Hereinafter, the acrylic polymer (B) and the (meth) acrylic polymer (C) will be described in detail. .

[Acrylic polymer (B)]
The acrylic polymer (B) as the adhesive composition used for the surface layer 30 can be selected from the compounds (various monomer components) exemplified as the acrylic polymer (A) of the core layer 20. The acrylic polymer (B) used for the surface layer 30 may have the same component and composition ratio as the acrylic polymer (A) of the core layer 20, and the acrylic polymer (A) and components and composition of the core layer 20. The ratio may be different.

一般式（１）式中、Ｒ^１は、２価の有機基である。 When the acrylic polymer (B) contains a nitrogen-containing heterocyclic monomer as a constituent unit, a more preferable monomer includes N-vinyl cyclic amide represented by the following general formula (1).

In the general formula (1), R ¹ is a divalent organic group.

  In addition, the glass transition temperature (Tg) of acrylic polymer (B) is less than 0 degreeC, Preferably, it is less than -10 degreeC, and is -80 degreeC or more normally.

  In this embodiment, the acrylic polymer (B) constituting the surface layer is a partially polymerized product in which the monomer component is partially polymerized by irradiating a mixture of the monomer component and the polymerization initiator with ultraviolet rays (UV). (Acrylic polymer syrup). Acrylic polymer syrup is blended with the (meth) acrylic polymer (C) described later to prepare an acrylic pressure-sensitive adhesive composition. This pressure-sensitive adhesive composition is applied to a predetermined substrate and irradiated with ultraviolet rays. To complete the polymerization. The weight average molecular weight (Mw) of the acrylic polymer (B) is, for example, 30000 to 5000000. Moreover, in this embodiment, when preparing the acrylic polymer (B) which comprises a surface layer, the polymerization initiator demonstrated by preparation of an acrylic polymer (A) can be used suitably. Moreover, in order to adjust the cohesion force of the surface layer 30, the crosslinking agent demonstrated by preparation of an acrylic polymer (A) can be used suitably.

[(Meth) acrylic polymer (C)]
The (meth) acrylic polymer (C) is a polymer having a weight average molecular weight smaller than that of the acrylic polymer (B), functions as a tackifying resin, and hardly causes polymerization inhibition during UV polymerization. Have The (meth) acrylic polymer (C) contains, for example, a (meth) acrylic acid ester having a terpene skeleton as a monomer unit. For this reason, the compatibility with the acrylic polymer (B) is not low unlike a normal terpene-based tackifier resin, and since the phase separation is difficult, the adhesion reliability is excellent.

In this specification, the terpene skeleton (terpenes) is a generic name for compounds extracted from plant essential oil components and based on the isoprene rule represented by the molecular formula of C ₅ H ₈ .

  Specifically, monoterpenes such as α-pinene, β-pinene, carene, γ-terpinene, d-limonene, dipinten, terpinolene, β-ferrandlene, pipinalene, camphore, myrcene and the like as terpene skeletons and longifolene And sesquiterpenes. These may be used singly or in combination of two or more.

  The (meth) acrylic acid ester having a terpene skeleton can be obtained by appropriately using a known method without particular limitation. For example, it can be obtained by an esterification reaction between the corresponding terpene alcohol and the above-described (meth) acrylic acid. The (meth) acrylic acid ester containing the terpene skeleton thus obtained can be suitably used as a monomer unit of the (meth) acrylic polymer (C) without particular limitation.

また、（メタ）アクリル系重合体（Ｂ）は、テルペン骨格を有する（メタ）アクリル酸エステル成分単位のほかに、テルペン骨格を有する（メタ）アクリル酸エステルと共重合可能な他のモノマー成分（共重合性モノマー）を共重合させて得ることも可能である。 Further, as the (meth) acrylic acid ester having a terpene skeleton, those having a glass transition temperature (Tg) of the homopolymer of 0 ° C. or lower, or those having a temperature of 0 ° C. or higher may be used. Use of the monomer having a glass transition temperature (Tg) of 0 ° C. or lower of the homopolymer is effective in improving the tackiness of the pressure-sensitive adhesive layer, while the glass transition temperature (Tg) of the homopolymer is 0 ° C. Use of an excess monomer is effective in improving durability (particularly heat resistance). Moreover, the upper limit of the glass transition temperature (Tg) of the (meth) acrylic acid ester homopolymer having a terpene skeleton is about 180 ° C., and it is preferable to use a glass having a temperature of about 150 ° C. or less. When the glass transition temperature (Tg) of the homopolymer exceeds 180 ° C., it is necessary to reduce the amount used in order to bring the total glass transition temperature (Tg) of the base polymer to 0 ° C. or less. It may be difficult to improve the adhesiveness of the tape. An example (the following formulas (2) to (5)) of a (meth) acrylic acid ester having a terpene skeleton is shown below.

In addition to the (meth) acrylic acid ester component unit having a terpene skeleton, the (meth) acrylic polymer (B) is a monomer component that can be copolymerized with a (meth) acrylic acid ester having a terpene skeleton ( It is also possible to obtain it by copolymerizing a copolymerizable monomer).

As other monomers copolymerizable with (meth) acrylic acid ester having a terpene skeleton,
(Meth) acrylic acid ester having an alkyl group having 1 to 20 carbon atoms such as methyl (meth) acrylate,
(Meth) acrylic acid ester having an alicyclic hydrocarbon group such as cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate;
(Meth) acrylic acid ester having an aromatic hydrocarbon group such as phenyl (meth) acrylate;
Alkoxyalkyl (meth) acrylates such as methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, propoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, ethoxypropyl (meth) acrylate monomer;
(Meth) acrylic acid alkali metal salts and the like;
Di (meth) acrylic acid ester of ethylene glycol, di (meth) acrylic acid ester of diethylene glycol, di (meth) acrylic acid ester of triethylene glycol, di (meth) acrylic acid ester of polyethylene glycol, di (meta) of propylene glycol ) Di (meth) acrylate monomers of (poly) alkylene glycols such as acrylate esters, di (meth) acrylate esters of dipropylene glycol, di (meth) acrylate esters of tripropylene glycol;
Polyvalent (meth) acrylate monomers such as trimethylolpropane tri (meth) acrylate;
Vinyl esters such as vinyl acetate and vinyl propionate;
Vinyl halide compounds such as vinylidene chloride and 2-chloroethyl (meth) acrylate;
An oxazoline group-containing polymerizable compound such as 2-vinyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline;
Aziridine group-containing polymerizable compounds such as (meth) acryloylaziridine, (meth) acrylic acid-2-aziridinylethyl;
Epoxy group-containing vinyl monomers such as allyl glycidyl ether, (meth) acrylic acid glycidyl ether, (meth) acrylic acid-2-ethylglycidyl ether;
(Meth) acrylic acid-2-hydroxyethyl, (meth) acrylic acid-2-hydroxypropyl, monoester of (meth) acrylic acid and polypropylene glycol or polyethylene glycol, lactones and (meth) acrylic acid-2-hydroxy Hydroxyl group-containing vinyl monomers such as adducts with ethyl;
Fluorine-containing vinyl monomers such as fluorine-substituted (meth) acrylic acid alkyl esters;
Acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride;
Aromatic vinyl compound monomers such as styrene, α-methylstyrene, vinyltoluene;
Reactive halogen-containing vinyl monomers such as 2-chloroethyl vinyl ether and monochloro vinyl acetate;
(Meth) acrylamide, N-isopropyl (meth) acrylamide, N-butyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-methylol (meth) acrylamide, N An amide group-containing vinyl monomer such as ethylol (meth) acrylamide, N-methylolpropane (meth) acrylamide, N-methoxyethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N-acryloylmorpholine;
Succinimide monomers such as N- (meth) acryloyloxymethylenesuccinimide, N- (meth) acryloyl-6-oxyhexamethylenesuccinimide, N- (meth) acryloyl-8-oxyhexamethylenesuccinimide;
Maleimide monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N-phenylmaleimide;
Itaconimides such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, N-laurylitaconimide System monomers;
N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N- Vinyloxazole, N- (meth) acryloyl-2-pyrrolidone, N- (meth) acryloylpiperidine, N- (meth) acryloylpyrrolidine, N-vinylmorpholine, N-vinylpyrazole, N-vinylisoxazole, N-vinylthiazole Nitrogen-containing heterocyclic monomers such as N-vinylisothiazole and N-vinylpyridazine;
N-vinylcarboxylic acid amides;
Lactam monomers such as N-vinylcaprolactam;
Cyanoacrylate monomers such as (meth) acrylonitrile;
(Meth) acrylic such as aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, and t-butylaminoethyl (meth) acrylate Acid aminoalkyl monomers;
Imide group-containing monomers such as cyclohexylmaleimide and isopropylmaleimide;
Isocyanate group-containing monomers such as 2-isocyanatoethyl (meth) acrylate;
Organosilicon-containing vinyl monomers such as vinyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, allyltrimethoxysilane, trimethoxysilylpropylallylamine, 2-methoxyethoxytrimethoxysilane;
Hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, hydroxyhexyl (meth) acrylate, hydroxyoctyl (meth) acrylate, hydroxydecyl (meth) acrylate, (meta ) Hydroxyl-containing monomers such as hydroxyalkyl (meth) acrylates such as hydroxylauryl acrylate and (4-hydroxymethylcyclohexyl) methyl methacrylate;
(Meth) acrylic acid tetrahydrofurfuryl, fluorine atom-containing (meth) acrylate, silicone (meth) acrylate and other heterocyclic rings, halogen atoms, silicon atoms and the like, acrylic ester monomers;
Olefin monomers such as isoprene, butadiene, isobutylene;
Vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether;
Olefins or dienes such as ethylene, butadiene, isoprene, isobutylene;
Vinyl ethers such as vinyl alkyl ethers;
Vinyl chloride;
Other examples include macromonomers having a radical polymerizable vinyl group at the terminal of a monomer obtained by polymerizing a vinyl group. These monomers can be copolymerized alone or in combination with a (meth) acrylic acid ester having a terpene skeleton.

  More specifically, in the acrylic pressure-sensitive adhesive composition of this embodiment, examples of the (meth) acrylic polymer (C) include (meth) acrylic acid ester having a terpene skeleton and dicyclopenta Nyl methacrylate (DCPMA), cyclohexyl methacrylate (CHMA), isobornyl methacrylate (IBXMA), isobornyl acrylate (IBXA), dicyclopentanyl acrylate (DCPA), 1-adamantyl methacrylate (ADMA), 1-adamantyl acrylate ( ADA), CHA (cyclohexyl acrylate), isobutyl methacrylate (IBMA), and a copolymer with methyl methacrylate (MMA).

  Further, a functional group having reactivity with an epoxy group or an isocyanate group may be introduced into the (meth) acrylic polymer (C). Examples of such functional groups include a hydroxyl group, a carboxyl group, an amino group, an amide group, and a mercapto group, and a monomer having such a functional group when producing a (meth) acrylic polymer (C). Is preferably used (copolymerized).

  When the (meth) acrylic polymer (C) is a copolymer of a (meth) acrylic acid ester containing a terpene skeleton and another (meth) acrylic acid ester monomer or a copolymerizable monomer The content ratio of the (meth) acrylic acid ester containing a terpene skeleton is 10% by mass to 100% by mass, preferably 20% by mass to 100% by mass in the total monomers constituting the (meth) acrylic polymer (C). %, More preferably 25% by mass to 100% by mass. If the (meth) acrylic acid ester containing a terpene skeleton is contained in an amount of 10% by mass or more, the adhesive force of the acrylic pressure-sensitive adhesive tape to the adherend including the low-polar adherend can be improved.

  The weight average molecular weight of the (meth) acrylic polymer (C) is 1000 or more and less than 30000, preferably 1500 or more and less than 20000, and more preferably 2000 or more and less than 10,000. When the molecular weight is 30000 or more, the effect of improving the adhesive strength of the adhesive tape may not be sufficiently obtained. Moreover, since it becomes low molecular weight as it is less than 1000, the adhesive force of an adhesive tape and the fall of a retention characteristic may be caused.

  The measurement of the weight average molecular weight of acrylic polymer (A), (B) and (meth) acrylic polymer (C) can be calculated | required in polystyrene conversion by GPC method. Specifically, TSKgelGMH-H (20) × 2 columns are used in HPLC 8020 manufactured by Tosoh Corporation, and the measurement is performed with a tetrahydrofuran solvent at a flow rate of about 0.5 ml / min.

  As described above, the content of the (meth) acrylic polymer (C) is 1 to 70 parts by mass, preferably 2 to 50 parts by mass with respect to 100 parts by mass of the acrylic polymer (B). More preferably, it is 3 to 40 parts by mass. When the (meth) acrylic polymer (C) is added in excess of 70 parts by mass, the elastic modulus of the pressure-sensitive adhesive layer formed from the acrylic pressure-sensitive adhesive composition according to this embodiment is increased, and the adhesiveness at low temperature is poor. Or may not develop adhesive force even at room temperature. Moreover, the effect may not be acquired when the addition amount of a (meth) acrylic-type polymer (C) is less than 1 mass part.

  The (meth) acrylic polymer (C) has a glass transition temperature (Tg) of 0 ° C. or higher and 300 ° C. or lower, preferably 20 ° C. or higher and 300 ° C. or lower, more preferably 40 ° C. or higher and 300 ° C. or lower. By setting the glass transition temperature (Tg) to 20 ° C. or higher, the cohesive force of the pressure-sensitive adhesive layer at room temperature or higher can be improved, and the holding characteristics and adhesiveness at high temperatures can be improved. Table 1 shows glass transition temperatures of typical materials that can be used as the (meth) acrylic polymer (C) in the present embodiment. The glass transition temperature shown in Table 1 is a nominal value described in literatures, catalogs, or the like, or a value calculated based on the following formula (6) (Fox formula). In addition, as above-mentioned, the (meth) acrylic-type polymer (C) contains the (meth) acrylic acid ester which has a terpene skeleton as a monomer.

_{1 / Tg = W 1 / Tg} 1 + W 2 / Tg 2 + ··· + Wn / Tg n (6)
[In the formula (6), Tg is the glass transition temperature (unit: K) of the (meth) acrylic polymer (C), and Tg _i (i = 1, 2,... N) is the monomer i is a homopolymer. When formed, the glass transition temperature (unit: K), W _i (i = 1, 2,... N) represents the mass fraction of all monomer components of monomer i. ]
The above formula (6) is a calculation formula in the case where the (meth) acrylic polymer (C) is composed of n types of monomer components of the monomer 1, the monomer 2,.

  In the present specification, “glass transition temperature when homopolymer is formed” means “glass transition temperature of homopolymer of the monomer”, and may be referred to as a certain monomer (“monomer X”). ) Is the glass transition temperature (Tg) of a polymer formed using only the monomer component. Specifically, “Polymer Handbook” (3rd edition, John Wiley & Sons, Inc, 1989) lists numerical values. In addition, the glass transition temperature (Tg) of the homopolymer which is not described in the said literature says the value obtained by the following measuring methods, for example. That is, in a reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube and a reflux condenser, 100 parts by mass of monomer X, 0.2 parts by mass of 2,2′-azobisisobutyronitrile and ethyl acetate 200 as a polymerization solvent. Stirring is performed for 1 hour while introducing nitrogen gas. After removing oxygen in the polymerization system in this way, the temperature is raised to 63 ° C. and the reaction is carried out for 10 hours. Subsequently, it cools to room temperature and the homopolymer solution with a solid content concentration of 33 mass% is obtained. Next, this homopolymer solution is cast-coated on a release liner and dried to prepare a test sample (sheet-like homopolymer) having a thickness of about 2 mm. Then, about 1 to 2 mg of this test sample was weighed in an aluminum open cell, and a nitrogen atmosphere of 50 ml / min was used using a temperature modulation DSC (trade name “Q-2000”, manufactured by TA Instruments). Under the temperature rising rate of 5 ° C./min, the reversing heat flow (specific heat component) behavior of the homopolymer is obtained. Referring to JIS-K-7121, the low temperature side baseline of the obtained Reversing Heat Flow and the straight line that is equidistant from the straight line extending the high temperature side base line, and the stepwise change of the glass transition The temperature at the point where the curve of the part intersects is the glass transition temperature (Tg) when the homopolymer is used.

表１中の略語は以下の化合物を示す。
ＤＣＰＭＡ：ジシクロペンタニルメタクリレート
ＤＣＰＡ：ジシクロペンタニルアクリレート
ＩＢＸＭＡ：イソボルニルメタクリレート
ＩＢＸＡ：イソボルニルアクリレート
ＣＨＭＡ：シクロヘキシルメタクリレート
ＣＨＡ：シクロヘキシルアクリレート
ＩＢＭＡ：イソブチルメタクリレート
ＭＭＡ：メチルメタクリレート
ＡＤＭＡ：１―アダマンチルメタクリレート
ＡＤＡ：１―アダマンチルアクリレート
ＨＣＰＡ：水添テルペンアクリレート
ＨＣＰＭＡ：水添テルペンメタクリレート

Abbreviations in Table 1 indicate the following compounds.
DCPMA: dicyclopentanyl methacrylate DCPA: dicyclopentanyl acrylate IBXMA: isobornyl methacrylate IBXA: isobornyl acrylate CHMA: cyclohexyl methacrylate CHA: cyclohexyl acrylate IBMA: isobutyl methacrylate MMA: methyl methacrylate ADMA: 1-adamantyl methacrylate ADA: 1-adamantyl acrylate HCPA: hydrogenated terpene acrylate HCPMA: hydrogenated terpene methacrylate

<Method for producing (meth) acrylic polymer (C)>
The (meth) acrylic polymer (C) is obtained by, for example, polymerizing a (meth) acrylic monomer having the above-described structure by a solution polymerization method, a bulk polymerization method, an emulsion polymerization method, a suspension polymerization, a bulk polymerization, or the like. Can be produced.

<Method for adjusting molecular weight of (meth) acrylic polymer (C)>
In order to adjust the molecular weight of the (meth) acrylic polymer (C), a chain transfer agent can be used during the polymerization. Examples of chain transfer agents used include compounds having a mercapto group such as octyl mercaptan, dodecyl mercaptan, t-dodecyl mercaptan, mercaptoethanol; thioglycolic acid, methyl thioglycolate, ethyl thioglycolate, propyl thioglycolate, Butyl thioglycolate, t-butyl thioglycolate, 2-ethylhexyl thioglycolate, octyl thioglycolate, isooctyl thioglycolate, decyl thioglycolate, dodecyl thioglycolate, 3-mercapto-1-propanol, 3-mercapto- 1,3-propanediol, ethylene glycol thioglycolate, neopentyl glycol thioglycolate, pentaerythritol thioglycolate

  Although it does not restrict | limit especially as the usage-amount of a chain transfer agent, Usually, 0.1-20 mass parts of chain transfer agents with respect to 100 mass parts of (meth) acrylic-type monomers, Preferably, 0.2-15 masses Part, more preferably 0.3 to 10 parts by mass. Thus, the (meth) acrylic-type polymer (C) of a suitable molecular weight can be obtained by adjusting the addition amount of a chain transfer agent. In addition, a chain transfer agent can be used individually or in combination of 2 or more types.

  The acrylic pressure-sensitive adhesive composition according to this embodiment contains the above-mentioned acrylic polymer (B) and (meth) acrylic polymer (C) as essential components, and is common in the field of pressure-sensitive adhesive compositions. Various additives may be contained as optional components. Examples of such optional components include tackifier resins, plasticizers, softeners, fillers, colorants (pigments, dyes, etc.), antioxidants, leveling agents, stabilizers, preservatives, and the like. Conventionally known additives can be used as such additives.

  An acrylic pressure-sensitive adhesive comprising an acrylic polymer (B) as a pressure-sensitive adhesive composition, and a (meth) acrylic polymer (C) having a terpene skeleton in the side chain and having a weight average molecular weight of 1000 or more and less than 30000 The layer has a solvent-insoluble component ratio of 40 to 90% by mass, preferably 45 to 85% by mass. When the solvent-insoluble component ratio is less than 40% by mass, the cohesive force may be insufficient and the retention characteristics may not be satisfied. When the solvent-insoluble component rate exceeds 90% by mass, the cohesive force becomes too high, May be inferior to repulsion resistance test. In addition, the evaluation method of a solvent insoluble component rate is mentioned later.

(Layer thickness ratio)
The ratio of the thickness of the surface layer 30a (or surface layer 30b) to the total thickness of the thickness of the core layer 20 and the thickness of the surface layer 30a (or surface layer 30b) is preferably 3 to 70%. If the ratio is less than 3%, desired adhesion may not be obtained. Moreover, when the said ratio becomes higher than 70%, the effect expected when it has the core layer 20 containing a bubble (E), such as stress relaxation property and level | step difference absorbability as an adhesive tape, may not be acquired. Although not particularly limited, the total thickness of the acrylic pressure-sensitive adhesive tape 10 (the sum of the thickness of the core layer 20 and the thickness of the surface layer 30) is 0.4 mm to 4.0 mm, preferably 0.5 mm to 2.5 mm.

(Multilayering method)
Although the method of laminating | stacking the core layer 20 and the surface layer 30 is not specifically limited, For example, the method shown below is applicable.

  (1) A method of multilayering by separately curing the core layer 20 and the surface layer 30 and then laminating the surface layer 30 a on one surface of the core layer 20 and laminating the surface layer 30 b on the other surface of the core layer 20. : This method has the advantage that the thickness accuracy of each layer can be increased.

  (2) After applying the core layer 20 to the previously cured surface layer 30a (or surface layer 30b), the core layer 20 is cured, and subsequently the surface layer 30b (or surface layer 30a) is applied to the core layer 20, A method of curing the surface layer 30b (or the surface layer 30a), or after coating the surface layer 30a (or the surface layer 30b on the other surface) on one surface of the core layer 20 previously cured, the surface layer 30a (or the surface layer 30b) Next, after the surface layer 30b (or the surface layer 30a on one surface) is applied to the other surface of the core layer 20, the surface layer 30b (or the surface layer 30a) is cured: In this method, the surface layer 30b is cured. Since another layer is applied to the layer, the thickness accuracy of each layer can be increased. Moreover, since another layer can be collectively coated on the cured layer, the manufacturing process can be simplified and the manufacturing time can be shortened.

  (3) A method in which the core layer 20 (or the surface layer 30) is applied to the applied surface layer 30 (or the core layer 20) sequentially or simultaneously and cured: In this method, the surface layer 30 and the core layer 20 can be applied together. It is.

  As a method for forming each layer, a coating roll such as a roll coater or a comma coater may be used, or a slot die may be used. In particular, in the method (3), a multilayer slot die for applying each layer may be used.

(Acrylic adhesive tape production method as an example)
[Preparation of composition for core layer]
The (meth) acrylic acid alkyl ester, copolymerizable monomer, and polymerization initiator described above are mixed to partially polymerize the (meth) acrylic acid alkyl ester and the copolymerizable monomer. Thereby, a partial polymer (acrylic polymer syrup) having a predetermined polymerization rate is produced. Next, a predetermined amount of hollow glass microspheres (trade name: Cellstar Z-27, manufactured by Tokai Kogyo Co., Ltd.) is added to the acrylic polymer syrup. A fluorosurfactant (trade name: Surflon S-393, manufactured by Sey Chemical Co., Ltd .; acrylic copolymer having a polyoxyethylene group and a fluorinated hydrocarbon group in the side chain, to a syrup to which hollow glass microspheres are added Mw = 8300, 0.5 parts by mass) is added to prepare a composition precursor for the core layer. In the core layer composition precursor, the volume of the hollow glass microspheres in the total volume of the core layer composition precursor is, for example, about 1.5% by volume.

  An apparatus is provided that includes a stator having a large number of fine teeth on a disk having a through-hole in the center, and a rotor facing the stator and having fine teeth similar to the stator on the disk. Then, the core layer composition precursor is introduced between the teeth on the stator and the teeth on the rotor in the apparatus, and nitrogen gas is passed through the through hole while rotating the rotor at a high speed. To introduce. Thereby, a bubble is mixed with the composition precursor for core layers, and the composition for core layers is obtained. For example, the bubbles are mixed so as to be about 20% by volume with respect to the total volume of the core layer composition.

[Preparation of composition for surface layer]
The (meth) acrylic monomer (C) for the surface layer is prepared by blending the above-mentioned (meth) acrylic monomer, chain transfer agent, polymerization initiator, and, if necessary, a copolymerizable monomer into a predetermined solvent. To do. Next, the above-mentioned acrylic polymer syrup (partial polymer) and the obtained (meth) acrylic polymer (C) are mixed to obtain a composition for the surface layer.

[Preparation of core layer]
The composition for a core layer is applied onto the release-treated surface of a polyester film (release liner) that has been subjected to a single-side release treatment using, for example, a roll coater. Next, the same type of release liner is bonded to the other surface of the coated core layer composition. At this time, the both surfaces are bonded together so that the release-treated surface of the release liner faces the other surface of the core layer composition. Next, ultraviolet irradiation is performed using, for example, a black light lamp. The core layer 20 is produced by the above procedure.

[Production of surface layer]
The surface layer composition is applied onto the release-treated surface of a polyester film (release liner) that has been subjected to a single-side release treatment using, for example, a roll coater. Next, the same type of release liner is bonded to the other surface of the applied surface layer composition. At this time, both surfaces are bonded together so that the release-treated surface of the release liner faces the other surface of the surface layer composition. Next, ultraviolet irradiation is performed using, for example, a black light lamp. The surface layer 30 is produced by the above procedure.

[Bonding of core layer / surface layer]
About the core layer 20 and the surface layer 30 obtained by the above-described procedure, the release liner bonded to one surface is peeled off, and the respective adhesive surfaces are bonded together. Thereby, the acrylic adhesive tape 10 which provided the surface layer 30 on both surfaces of the core layer 20 is produced.

  The composition for the surface layer and the composition for the core layer can contain various additives that are common in the field of pressure-sensitive adhesive compositions as optional components. Examples of such optional components include plasticizers, softeners, fillers, colorants (pigments, dyes, etc.), antioxidants, leveling agents, stabilizers, preservatives, and the like. Conventionally known additives can be used as such additives.

In the acrylic pressure-sensitive adhesive tape according to this embodiment, the pressure-sensitive adhesive layer disclosed herein is fixed to one side or both sides of a sheet-like base material (support), that is, without intention to separate the pressure-sensitive adhesive layer from the base material. The provided adhesive tape with a base material may be sufficient. More specifically, as such an adhesive tape, for example,
Composition of sheet-like substrate / core layer / surface layer,
Configuration of sheet-like substrate / surface layer / core layer / surface layer,
Composition of surface layer / core layer / sheet-like substrate / core layer / surface layer,
The structure of surface layer / core layer / surface layer / sheet-like substrate / surface layer / core layer / surface layer can be mentioned. In addition, what is called an adhesive sheet, an adhesive label, an adhesive film etc. may be included by the concept of an adhesive tape here.

As the base material, for example,
Plastic films such as polypropylene film, ethylene-propylene copolymer film, polyester film, polyvinyl chloride film;
Foam substrates such as polyurethane foam and polyethylene foam;
Kraft paper, crepe paper, Japanese paper, etc .;
Cotton, soft cloth, etc .;
Nonwoven fabrics such as polyester nonwoven fabrics and vinylon nonwoven fabrics;
Metal foil such as aluminum foil and copper foil;
Can be appropriately selected and used depending on the application of the adhesive tape. As the plastic film, any of an unstretched film and a stretched (uniaxially stretched or biaxially stretched) film can be used. Further, the surface of the substrate on which the pressure-sensitive adhesive layer is provided may be subjected to surface treatment such as application of a primer and corona discharge treatment. The thickness of the substrate can be appropriately selected according to the purpose, but is generally about 10 μm to 500 μm (typically 10 μm to 200 μm).

  The acrylic adhesive tape according to the present embodiment includes, for example, PE (polyethylene), PP (polypropylene), ABS (acrylonitrile-butadiene-styrene copolymer), SBS (styrene-butadiene-styrene block copolymer), PC ( Polycarbonate), PVC (vinyl chloride), PMMA (polymethyl methacrylate resin) and other resins including acrylic resins, and members made of metals such as SUS and aluminum It can be suitably used for applications where it is bonded (fixed) to the surface of building materials, home appliances and the like.

  Moreover, since the acrylic adhesive tape which concerns on this embodiment is excellent also in transparency, it is used suitably for the use which bonds various optical members, for example to a liquid crystal cell, an optical polyester film, a touch panel member, etc. Therefore, the technique shown here includes a laminate in which an adhesive layer containing an acrylic adhesive composition is provided on an optical member. This laminate typically has a form in which the pressure-sensitive adhesive layer on the optical member is protected by a release liner. The optical member provided with such an adhesive layer can be easily attached to, for example, the surface of a plastic cover lens panel, glass, liquid crystal cell, or the like. The optical member is not particularly limited, and may be a polarizing film, a retardation film, a transparent conductive film (ITO film), or the like. Such an optical member may have a single layer structure made of the same material or a multilayer structure made of a plurality of materials. As a method of forming the pressure-sensitive adhesive layer on the optical member, a method of directly applying or a method of transferring can be appropriately employed as in the case of forming the pressure-sensitive adhesive layer on the substrate. Typically, the pressure-sensitive adhesive layer formed on the release liner is transferred to the base surface of the optical member.

  As described above, the acrylic pressure-sensitive adhesive tape according to the present embodiment includes the core layer 20 and the surface layer 30 provided on one or both sides of the core layer 20. The core layer 20 includes an acrylic polymer (A), and the surface layer 30 has 100 parts by mass of an acrylic polymer (B) as an adhesive composition and a terpene skeleton in a side chain as a tackifier resin. And (meth) acrylic polymer (C) having a weight average molecular weight of 1000 or more and less than 30000. Thereby, the adhesiveness with respect to the low polarity adherend of an acrylic adhesive tape can be improved. As a result, the adhesion reliability of acrylic adhesive tapes to various adherends with different surface polarities, including low-polar adherends, can be improved, and acrylic adhesive tapes can be used in the fields of automobiles, household appliances, etc. It can be used for various joining applications.

  The reason why the adhesiveness of the acrylic pressure-sensitive adhesive tape to the low polarity adherend is improved is that the (meth) acrylic copolymer (C) having a terpene skeleton in the side chain is compatible with the acrylic polymer (B). It is guessed.

  In addition, the surface layer of the acrylic pressure-sensitive adhesive tape according to the present embodiment can be designed so that the monomer constituting the acrylic polymer (B) does not contain an acidic group. In this case, it is possible to obtain an acrylic pressure-sensitive adhesive tape that is less affected by metal corrosion caused by acidic groups. In addition, even if it is a case where the monomer which comprises an acrylic polymer (B) contains an acidic group, the improvement in the adhesive characteristic of an acrylic adhesive tape can be aimed at.

  In the acrylic pressure-sensitive adhesive tape 10 of the above-described embodiment, the surface layers 30a and 30b are provided on both sides of the core layer 20, respectively, but only the surface layer 30a or the surface layer 30b may be provided on the core layer 20. The core layer 20 contains the acrylic polymer (A) as the pressure-sensitive adhesive composition, the fine particles (D), and the bubbles (E), but if it contains at least the acrylic polymer (A). Good.

  EXAMPLES The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

  Table 2 shows components of the composition for the surface layer in the acrylic pressure-sensitive adhesive tapes according to Examples 1 to 10 and Comparative Examples 1 to 7.

Abbreviations in Table 2 indicate the following compounds.
2EHA: 2-ethylhexyl acrylate NVP: N-vinyl-2-pyrrolidone AA: acrylic acid DCPMA: dicyclopentanyl methacrylate CHMA: cyclohexyl methacrylate IBMA: isobutyl methacrylate TMPTA: trimethylolpropane triacrylate HDDA: 1,6-hexanediol Diacrylate HCPMA: Hydrogenated terpene methacrylate HCPA: Hydrogenated terpene acrylate Clearon P135: Terpene hydrogenated resin manufactured by Yashara Chemical

(Measurement of solvent insoluble component ratio)
The solvent-insoluble component ratio was determined by sampling 0.1 g of the surface layer and precisely weighing (mass before immersion), immersing it in 50 ml of ethyl acetate at room temperature (20 to 25 ° C.) for 1 week, Ethyl) Insoluble matter is taken out, and the solvent-insoluble matter is dried at 130 ° C. for 2 hours, and then weighed (mass after soaking and drying), and the solvent-insoluble component rate calculation formula “solvent insoluble component rate (mass%) = [ (Mass after immersion / drying) / (mass before immersion)] × 100 ”.

(Preparation of acrylic polymer syrup 1 (2EHA / NVP = 86/14) as component (B))
86 parts by mass of 2-ethylhexyl acrylate (2EHA), 14 parts by mass of N-vinyl-2-pyrrolidone (NVP), 0.05 parts by mass of a photopolymerization initiator (trade name: Irgacure 184, manufactured by BASF), and photopolymerization start 0.05 parts by mass of an agent (trade name: Irgacure 651, manufactured by BASF) was charged into a four-necked flask. The mixture was exposed to ultraviolet rays under a nitrogen atmosphere and partially photopolymerized to obtain a partially polymerized product (acrylic polymer syrup 1) having a polymerization rate of about 8% by mass.

(Preparation of acrylic polymer syrup 2 (2EHA / AA = 94/6) as component (B))
94 parts by mass of 2-ethylhexyl acrylate (2EHA), 6 parts by mass of acrylic acid (AA), 0.05 parts by mass of a photopolymerization initiator (trade name: Irgacure 184, manufactured by BASF), and a photopolymerization initiator (trade name: 0.05 part by mass (Irgacure 651, manufactured by BASF) was charged into a four-necked flask. The mixture was exposed to ultraviolet light under a nitrogen atmosphere and partially photopolymerized to obtain a partially polymerized product (acrylic polymer syrup 2) having a polymerization rate of about 8% by mass.

(Preparation of acrylic polymer syrup 3 (2EHA / NVP / AA = 84/14/2) as component (B))
84 parts by mass of 2-ethylhexyl acrylate (2EHA), 14 parts by mass of N-vinyl-2-pyrrolidone (NVP), 2 parts by mass of acrylic acid (AA), photopolymerization initiator (trade name: Irgacure 184, manufactured by BASF) 0 0.05 part by mass and 0.05 part by mass of a photopolymerization initiator (trade name: Irgacure 651, manufactured by BASF) were charged into a four-necked flask. The mixture was exposed to ultraviolet light under a nitrogen atmosphere and partially photopolymerized to obtain a partially polymerized product (acrylic polymer syrup 3) having a polymerization rate of about 8% by mass.

(Preparation of acrylic polymer syrup 4 (2EHA / NVP / AA = 85/14/1) as component (B))
85 parts by mass of 2-ethylhexyl acrylate (2EHA), 14 parts by mass of N-vinyl-2-pyrrolidone (NVP), 1 part by mass of acrylic acid (AA), photopolymerization initiator (trade name: Irgacure 184, manufactured by BASF) 0 0.05 part by mass and 0.05 part by mass of a photopolymerization initiator (trade name: Irgacure 651, manufactured by BASF) were charged into a four-necked flask. The mixture was exposed to ultraviolet light under a nitrogen atmosphere and partially photopolymerized to obtain a partially polymerized product (acrylic polymer syrup 4) having a polymerization rate of about 8% by mass.

(Preparation of acrylic polymer syrup 5 (2EHA / AA / HCPA = 78/5/17) as component (B))
78 parts by mass of 2-ethylhexyl acrylate (2EHA), 5 parts by mass of acrylic acid (AA), acrylic acid (AA), 17 parts by mass of hydrogenated terpene methacrylate (the following chemical formula (4), trade name: HCPA, manufactured by Yasuhara Chemical Co., Ltd.) , 0.05 part by mass of a photopolymerization initiator (trade name: Irgacure 184, manufactured by BASF) and 0.05 part by mass of a photopolymerization initiator (trade name: Irgacure 651, manufactured by BASF) are charged into a four-necked flask. did. The mixture was exposed to ultraviolet rays under a nitrogen atmosphere and partially photopolymerized to obtain a partially polymerized product (acrylic polymer syrup 5) having a polymerization rate of about 8% by mass.

(Preparation of acrylic polymer syrup 6 (2EHA / NVP / HCPA = 72/11/17) as component (B))
78 parts by mass of 2-ethylhexyl acrylate (2EHA), 11 parts by mass of N-vinyl-2-pyrrolidone (NVP), hydrogenated terpene acrylate (the above chemical formula (4), glass transition temperature (Tg): 65 ° C., manufactured by Yasuhara Chemical Co., Ltd., HCPA) 17 parts by mass, photopolymerization initiator (trade name: Irgacure 184, manufactured by BASF) 0.05 part by mass, and photopolymerization initiator (trade name: Irgacure 651, manufactured by BASF) 0.05 part by mass Charged to a necked flask. The mixture was exposed to ultraviolet light under a nitrogen atmosphere and partially photopolymerized to obtain a partially polymerized product (acrylic polymer syrup 6) having a polymerization rate of about 8% by mass.

(Preparation of (meth) acrylic polymer 1 (HCPMA) as component (C))
4-neck flask containing 100 parts by mass of toluene, 100 parts by mass of hydrogenated terpene methacrylate (the following chemical formula (5), trade name: HCPMA, manufactured by Yasuhara Chemical Co., Ltd.), and 3 parts by mass of thioglycolic acid (GSH acid) as a chain transfer agent It was thrown into. Then, after stirring at 70 ° C. for 1 hour in a nitrogen atmosphere, 0.2 part by mass of azobisisobutyronitrile as a thermal polymerization initiator is added and reacted for 2 hours at 70 ° C., followed by 2 at 80 ° C. Reacted for hours. Thereafter, the reaction solution was put in a temperature atmosphere of 130 ° C., and toluene, the chain transfer agent, and the unreacted monomer were removed by drying to obtain a solid (meth) acrylic polymer 1. The obtained (meth) acrylic polymer 1 had a glass transition temperature of 115 ° C. and a weight average molecular weight of 3,500.

(Preparation of (meth) acrylic polymer 2 (HCPMA / DCPMA = 50/50) as component (C))
100 parts by mass of toluene, hydrogenated terpene methacrylate (the above chemical formula (5), trade name: HCPMA, manufactured by Yasuhara Chemical Co., Ltd.), 50 parts by mass, dicyclopentanyl methacrylate (DCPMA) (trade name: FA-513M, Hitachi Chemical Co., Ltd.) 50 parts by mass) and 3 parts by mass of thioglycolic acid (GSH acid) as a chain transfer agent were charged into a four-necked flask. Then, after stirring at 70 ° C. for 1 hour in a nitrogen atmosphere, 0.2 part by mass of azobisisobutyronitrile as a thermal polymerization initiator is added and reacted for 2 hours at 70 ° C., followed by 2 at 80 ° C. Reacted for hours. Thereafter, the reaction solution was put in a temperature atmosphere of 130 ° C., and toluene, the chain transfer agent, and the unreacted monomer were removed by drying to obtain a solid (meth) acrylic polymer 2. The obtained (meth) acrylic polymer 2 had a glass transition temperature of 143 ° C. and a weight average molecular weight of 3400.

(Preparation of (meth) acrylic polymer 3 (HCPA / DCPMA = 50/50) as component (C))
100 parts by mass of toluene, hydrogenated terpene methacrylate (the above chemical formula (4), trade name: HCPA, manufactured by Yasuhara Chemical Co., Ltd.), 50 parts by mass, dicyclopentanyl methacrylate (DCPMA) (trade name: FA-513M, Hitachi Chemical Co., Ltd.) 50 parts by mass) and 3 parts by mass of thioglycolic acid (GSH acid) as a chain transfer agent were charged into a four-necked flask. Then, after stirring at 70 ° C. for 1 hour in a nitrogen atmosphere, 0.2 part by mass of azobisisobutyronitrile as a thermal polymerization initiator is added and reacted for 2 hours at 70 ° C., followed by 2 at 80 ° C. Reacted for hours. Thereafter, the reaction solution was put in a temperature atmosphere of 130 ° C., and toluene, the chain transfer agent, and the unreacted monomer were removed by drying to obtain a solid (meth) acrylic polymer 1. The obtained (meth) acrylic polymer 3 had a glass transition temperature of 112 ° C. and a weight average molecular weight of 3400.

(Preparation of (meth) acrylic polymer 4 (CHMA / IBMA = 60/40) as component (C))
After compounding cyclohexyl methacrylate (CHMA, 60 parts by mass), isobutyl methacrylate (IBMA, 40 parts by mass) and thioglycolic acid (4.0 parts by mass), nitrogen gas was blown to remove dissolved oxygen. Next, when the temperature was raised to 90 ° C., perhexyl O (manufactured by NOF Corporation, 0.005 parts by mass) and perhexyl D (manufactured by NOF Corporation, 0.01 parts by mass) were mixed. Furthermore, after stirring at 90 ° C. for 1 hour, the temperature was raised to 150 ° C. over 1 hour and stirred at 150 ° C. for 1 hour. Subsequently, it heated up to 170 degreeC over 1 hour, and stirred for 60 minutes at 170 degreeC.

  Next, the pressure was reduced at 170 ° C., and the mixture was stirred for 1 hour to remove the residual monomer, thereby obtaining (meth) acrylic polymer 4. The obtained (meth) acrylic polymer 1 had a glass transition temperature (calculated from the Fox equation) of 59 ° C. and a weight average molecular weight of 4000.

Example 1
(Preparation of composition for surface layer)
After adding 20 parts by mass of the above-mentioned (meth) acrylic polymer 1 and 0.12 parts by mass of trimethylolpropane triacrylate to 100 parts by mass of the above-described acrylic polymer syrup 2, they are mixed uniformly. Thus, a surface layer composition was prepared.

(Production of surface layer)
The surface layer composition described above was applied to the release surface of a 38 μm thick polyester film (trade name: Diafoil MRF, manufactured by Mitsubishi Plastics Co., Ltd.) having one surface peeled with silicone so that the final thickness was 50 μm. Thus, a coating layer was formed. Next, a 38 μm thick polyester film (trade name: Diafoil MRN, manufactured by Mitsubishi Plastics Co., Ltd.) having one surface peeled with silicone on the surface of the applied surface layer composition, the peel-treated surface of the film is a coating layer. Covered side by side. Thereby, the coating layer (surface adhesive layer) of the surface layer composition was shielded from oxygen. The surface pressure-sensitive adhesive layer sheet thus obtained was irradiated with ultraviolet rays having an illuminance of 5 mW / cm ² (measured with Topcon UVR-T1 having a maximum sensitivity of about 350 nm) using a black light lamp (manufactured by Toshiba Corporation). Irradiated for 360 seconds. In this way, a surface layer composed of an acrylic pressure-sensitive adhesive layer having a thickness of 50 μm was obtained. The solvent insoluble component ratio of the surface pressure-sensitive adhesive layer was 66.3% by mass. The polyester film coated on both sides of the pressure-sensitive adhesive layer functions as a release liner.

(Preparation of composition for core layer)
After adding 0.08 parts by mass of 1,6-hexanediol diacrylate to 100 parts by mass of the acrylic polymer syrup 2 described above, hollow glass microspheres are further added to 9.5 parts with respect to the syrup. (Product name: Cellstar Z-27, manufactured by Tokai Kogyo Co., Ltd.) was added.

  Fluorosurfactant (trade name: Surflon S-393, manufactured by Sey Chemical Co., Ltd .; acrylic copolymer having polyoxyethylene group and fluorinated hydrocarbon group in the side chain) in syrup after addition of hollow glass microspheres Mw = 8300, 0.5 parts by mass) was added to prepare a core layer composition precursor. In the core layer composition precursor, the volume of the hollow glass microspheres in the total volume of the core layer composition precursor was about 26% by volume.

  Teeth on the stator in a device comprising a stator having a large number of fine teeth on a disk having a through hole in the center, and a rotor facing the stator and having fine teeth similar to the stator on the disk; The obtained core layer composition precursor was introduced between the teeth on the rotor. And while rotating a rotor at high speed, nitrogen gas was introduce | transduced into the composition precursor for core layers through the through-hole, and the bubble was mixed with the composition precursor for core layers. Thereby, the composition for core layers was obtained. In addition, it mixed so that a bubble might be about 20 volume% with respect to the whole volume of the composition for core layers.

(Preparation of core layer)
The resulting core layer composition was applied to a thickness of 1.2 mm on the release-treated surface of a 38 μm-thick polyester film (polyester release liner) having one surface peel-treated by a roll coater. Next, the same type of polyester release liner was bonded to the surface of the applied core layer composition so that the release treatment surface of the release liner was on the core layer composition side. Next, ultraviolet rays with an illuminance of 5 mW / cm ² were irradiated from both sides for 3 minutes using a black light lamp. Thus, the core layer which consists of a 1.2-mm-thick acrylic adhesive layer was obtained.

(Bonding of core layer / surface layer)
Regarding the core layer and the surface layer obtained by the above-described procedure, each of the release liners bonded to one surface is peeled off, and the respective adhesive surfaces are bonded to each other, and the surface layer / core layer / surface layer according to Example 1 is configured. An acrylic adhesive tape was obtained.

(Example 2)
The same as Example 1 except that 20 parts by mass of the (meth) acrylic polymer 2 described above and 0.08 parts by mass of trimethylolpropane triacrylate were added to 100 parts by mass of the acrylic polymer syrup 2 described above. Thus, an acrylic pressure-sensitive adhesive tape was obtained. The solvent-insoluble component ratio of the obtained pressure-sensitive adhesive layer for the surface layer was 51.4% by mass.

(Example 3)
The same as Example 1 except that 20 parts by mass of the above-mentioned (meth) acrylic polymer 3 and 0.08 parts by mass of trimethylolpropane triacrylate were added to 100 parts by mass of the acrylic polymer syrup 2 described above. Thus, an acrylic pressure-sensitive adhesive tape was obtained. The solvent-insoluble component ratio of the obtained adhesive layer for surface layers was 63.3 mass%.

Example 4
The same as Example 1 except that 20 parts by mass of the (meth) acrylic polymer 1 described above and 0.14 parts by mass of trimethylolpropane triacrylate were added to 100 parts by mass of the acrylic polymer syrup 1 described above. Thus, an acrylic pressure-sensitive adhesive tape was obtained. The solvent-insoluble component ratio of the obtained pressure-sensitive adhesive layer for the surface layer was 74.5% by mass.

(Example 5)
The same as Example 1 except that 20 parts by mass of the above-mentioned (meth) acrylic polymer 1 and 0.06 parts by mass of trimethylolpropane triacrylate were added to 100 parts by mass of the acrylic polymer syrup 3 described above. Thus, an acrylic pressure-sensitive adhesive tape was obtained. The solvent-insoluble component ratio of the obtained pressure-sensitive adhesive layer for the surface layer was 58.5% by mass.

(Example 6)
The same as Example 1 except that 20 parts by mass of the above-mentioned (meth) acrylic polymer 2 and 0.10 parts by mass of trimethylolpropane triacrylate were added to 100 parts by mass of the above-mentioned acrylic polymer syrup 1. Thus, an acrylic pressure-sensitive adhesive tape was obtained. The solvent-insoluble component ratio of the obtained pressure-sensitive adhesive layer for the surface layer was 66.7% by mass.

(Example 7)
The same as Example 1 except that 20 parts by mass of the above-mentioned (meth) acrylic polymer 2 and 0.10 parts by mass of trimethylolpropane triacrylate were added to 100 parts by mass of the above-mentioned acrylic polymer syrup 3. Thus, an acrylic pressure-sensitive adhesive tape was obtained. The solvent-insoluble component ratio of the obtained pressure-sensitive adhesive layer for the surface layer was 65.7% by mass.

(Example 8)
The same as Example 1 except that 20 parts by mass of the (meth) acrylic polymer 3 and 0.10 parts by mass of trimethylolpropane triacrylate were added to 100 parts by mass of the acrylic polymer syrup 1 described above. Thus, an acrylic pressure-sensitive adhesive tape was obtained. The solvent-insoluble component ratio of the obtained pressure-sensitive adhesive layer for the surface layer was 73.3% by mass.

Example 9
The same as Example 1 except that 20 parts by mass of the (meth) acrylic polymer 2 described above and 0.08 parts by mass of trimethylolpropane triacrylate were added to 100 parts by mass of the acrylic polymer syrup 4 described above. Thus, an acrylic pressure-sensitive adhesive tape was obtained. The solvent-insoluble component ratio of the obtained pressure-sensitive adhesive layer for the surface layer was 58.1% by mass.

(Example 10)
The same as Example 1 except that 20 parts by mass of the above-mentioned (meth) acrylic polymer 3 and 0.06 parts by mass of trimethylolpropane triacrylate were added to 100 parts by mass of the acrylic polymer syrup 4 described above. Thus, an acrylic pressure-sensitive adhesive tape was obtained. The solvent-insoluble component ratio of the obtained pressure-sensitive adhesive layer for the surface layer was 61.4% by mass.

(Comparative Example 1)
An acrylic pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that 0.045 parts by mass of 1,6-hexanediol diacrylate was added to 100 parts by mass of the acrylic polymer syrup 1 described above. The solvent-insoluble component ratio of the obtained pressure-sensitive adhesive layer for the surface layer was 77.4% by mass.

(Comparative Example 2)
An acrylic pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that 0.07 part by mass of 1,6-hexanediol diacrylate was added to 100 parts by mass of the acrylic polymer syrup 2 described above. The solvent-insoluble component ratio of the obtained pressure-sensitive adhesive layer for the surface layer was 75.2% by mass.

(Comparative Example 3)
The same as Example 1 except that 20 parts by mass of the above-mentioned (meth) acrylic polymer 4 and 0.12 parts by mass of trimethylolpropane triacrylate were added to 100 parts by mass of the acrylic polymer syrup 1 described above. Thus, an acrylic pressure-sensitive adhesive tape was obtained. The solvent-insoluble component ratio of the obtained pressure-sensitive adhesive layer for the surface layer was 73.4% by mass.

(Comparative Example 4)
Except that 20 parts by mass of the above-mentioned (meth) acrylic polymer 4 and 0.14 parts by mass of trimethylolpropane triacrylate were added to 100 parts by mass of the above-mentioned acrylic polymer syrup 2, the same manner as in Example 1 was performed. Thus, an acrylic adhesive tape was obtained. The solvent-insoluble component ratio of the obtained adhesive layer for surface layers was 67.3 mass%.

(Comparative Example 5)
Example 1 with the exception that 20 parts by mass of Clearon P135 (terpene-based hydrogenated resin manufactured by Yashara Chemical Co., Ltd.) and 0.20 parts by mass of trimethylolpropane triacrylate were added to 100 parts by mass of the acrylic polymer syrup 2 described above. Similarly, an acrylic pressure-sensitive adhesive tape was obtained. The solvent-insoluble component ratio of the obtained pressure-sensitive adhesive layer for the surface layer was 49.1% by mass.

(Comparative Example 6)
An acrylic pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that 0.04 parts by mass of trimethylolpropane triacrylate was added to 100 parts by mass of the acrylic polymer syrup 5 described above. The solvent-insoluble component ratio of the obtained pressure-sensitive adhesive layer for the surface layer was 67.2% by mass.

(Comparative Example 7)
An acrylic pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that 0.06 parts by mass of trimethylolpropane triacrylate was added to 100 parts by mass of the acrylic polymer syrup 6 described above. The solvent-insoluble component ratio of the obtained pressure-sensitive adhesive layer for the surface layer was 72.4% by mass.

(Test method)
[180 ° peel adhesion test]
One of the release liners (polyester film) in the acrylic pressure-sensitive adhesive tape according to each example and each comparative example was peeled off, a polyethylene terephthalate film having a thickness of 50 μm was bonded, and the test piece was cut into 25 mm width. . In addition, a 2 mm thick polypropylene plate (Part No. 1600, manufactured by Takiron Co., Ltd.) and an acrylic plate (Acrylite, manufactured by Mitsubishi Rayon Co., Ltd.) cleaned with isopropyl alcohol were prepared. Then, the other release liner (polyester film) of the pressure-sensitive adhesive layer sheet was peeled off, and a 2 kg roller was reciprocated to attach the pressure-sensitive adhesive surface of the acrylic pressure-sensitive adhesive tape to the polypropylene plate and the acrylic plate.

  After attaching an acrylic adhesive tape to a polypropylene plate and an acrylic plate, the mixture was allowed to stand for 48 minutes in an environment at 40 ° C. and then left for 30 minutes in an environment at 23 ° C. And the other end of the acrylic adhesive tape was peeled in the peeling direction of 180 degrees at a speed of 50 mm / min, and the adhesive force (resistance force) (unit: N / 25 mm) to the adherend at that time was measured. In each of the polypropylene plate and the acrylic plate, the case where the adhesive strength was 40 N / 25 mm or more was judged good, and the case where it was less than 40 N / 25 mm was judged as bad. It was confirmed whether the fracture mode at the time of peeling was an interface fracture or a cohesive fracture of the core layer. Table 3 shows the measurement results.

[Repulsion resistance test]
The acrylic pressure-sensitive adhesive tape according to each example and each comparative example was cut into a width of 10 mm and a length of 90 mm, and bonded to a clean aluminum plate having a thickness of 0.5 mm, a width of 10 mm, and a length of 90 mm. A test piece was obtained. Next, the test piece was curved so that the curvature would be R50 mm by placing the aluminum plate side of the test piece along the cylinder. Then, the other release liner (polyester film) of the acrylic pressure-sensitive adhesive tape was peeled off and laminated on the above polypropylene plate. The distance from which the pressure-sensitive adhesive layer sheet floats after passing 24 hours at room temperature (25 ° C.) with the test piece laminated on the polypropylene plate, that is, the distance from the surface of the polypropylene plate to the pressure-sensitive adhesive layer (height of both ends Average) (unit: mm). A case where the floating distance was 5 mm or less was determined to be good, and a case where the floating distance exceeded 5 mm was determined to be defective. Table 3 shows the measurement results. In addition, the numerical value shown in Table 3 is an average value about arbitrary plural points.

[Retention characteristics test]
One release liner (polyester film) of the acrylic pressure-sensitive adhesive tape according to each example and each comparative example was peeled off, a 50 μm thick polyethylene terephthalate film was bonded, and the test piece was cut to a width of 10 mm. . The adhesive surface of the test piece was bonded to a bakelite plate cleaned with toluene in an area of 10 mm in width and 20 mm in length, and left in an environment at 60 ° C. for 30 minutes. Thereafter, a weight was hung at one end of the test piece so that a load of 500 g was applied in the shear direction, and the weight was left suspended in an environment of 60 ° C. for 1 hour to evaluate the holding characteristics. The case where the test piece did not fall was evaluated as good (◯), and the case where it dropped was regarded as defective (x). Table 3 shows the measurement results.

  As shown in Table 3, Comparative Examples 1-4, 6, and 7 had poor adhesion to the polypropylene plate. Further, Comparative Example 1 had poor adhesion to the acrylic plate. On the other hand, Examples 1-10 had favorable adhesive force in both a polypropylene board and an acrylic board. In Example 3, the failure mode at the time of peeling from the polypropylene plate and the acrylic plate is the cohesive failure of the core layer. In all examples, the failure mode at the time of peeling from the acrylic plate is the cohesive failure of the core layer. Thus, it was confirmed that the surface pressure-sensitive adhesive exhibits very high adhesion to the adherend. That is, it was confirmed that the adhesiveness to the low-polar adherend was improved in any of the Examples as compared with Comparative Examples 1-4, 6, and 7.

  In Comparative Examples 1 to 6, the repulsion resistance of the polypropylene plate was poor. In Comparative Example 5, the repulsion resistance of the acrylic plate was poor. On the other hand, in all the examples, the repulsion resistance was good in both the polypropylene plate and the acrylic plate.

  Moreover, in all Examples and Comparative Examples, good holding characteristics (cohesive force) were observed. Therefore, it was confirmed that Examples 1 to 10 had excellent adhesive strength, excellent repulsion resistance, and excellent retention characteristics.

  To summarize the above results, the surface layer of the acrylic pressure-sensitive adhesive tape has a terpene skeleton in the side chain as the tackifier resin added to the acrylic polymer (A) as the pressure-sensitive adhesive composition, and the weight average molecular weight is 1000 Conventionally, by including the (meth) acrylic polymer (B) of less than 30000, it is possible to improve the adhesive strength, repulsion resistance, and retention characteristics for adherends including low-polar adherends. It was confirmed that an effect that is not present can be obtained.

  10 Acrylic adhesive tape, 20 core layer, 30, 30a, 30b surface layer

Claims (6)

A core layer;
A surface layer provided on one or both sides of the core layer;
With
The core layer includes an acrylic polymer (A),
The surface layer includes 100 parts by mass of an acrylic polymer (B),
1 to 70 parts by mass of a (meth) acrylic polymer (C) having a weight average molecular weight of 1000 or more and less than 30000 and having a terpene skeleton in the side chain;
An acrylic pressure-sensitive adhesive tape comprising:   The acrylic pressure-sensitive adhesive tape according to claim 1, wherein the core layer further includes fine particles (D) and / or bubbles (E).   The acrylic pressure-sensitive adhesive tape according to claim 1 or 2, wherein the glass transition temperature of the (meth) acrylic polymer (C) is 0 ° C or higher and 300 ° C or lower.   The (meth) acrylic polymer (C) includes any (meth) acrylic monomer having a terpene skeleton of 10% by mass or more and 100% by mass or less as a monomer unit in all monomers. Acrylic adhesive tape described in 1. The acrylic polymer (B) contains, as a monomer unit, at least one monomer selected from the group consisting of N-vinyl cyclic amide represented by acrylic (1) described in the following general formula and a carboxyl group-containing monomer. The acrylic adhesive tape according to any one of claims 1 to 4.

In the general formula (1), R ¹ is a divalent organic group.   The acrylic pressure-sensitive adhesive tape according to any one of claims 1 to 4, wherein the surface layer contains 40 to 90% by mass of a solvent-insoluble component.

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