JP5779696B2 - Adhesive tape - Google Patents

Description

The present invention relates to a pressure-sensitive adhesive tape that is difficult to peel off even if it is a thin pressure-sensitive adhesive tape and can exhibit high constant load peelability to a low-polar adherend such as a polypropylene (PP) plate.

Adhesive tapes are used in various industrial fields because they can be easily joined. Temporary fixing of curing sheets and bonding of interior materials in the construction field, fixing of interior parts such as seats and sensors, fixing of exterior parts such as side moldings and side visors in the automotive field, module assembly in the electrical and electronic field, Adhesive tape is used for attaching the module to the housing.

In recent years, there has been a demand for adhesive tapes that are thinner than conventional ones in accordance with the increasing needs for miniaturization, thinning or lightening of parts, and resource saving. However, there is a problem that a thin adhesive tape cannot provide sufficient adhesive force and is easily peeled off when a constant load is applied. Among them, sufficient adhesive force cannot be obtained or a load is applied to low polarity adherends such as polypropylene (PP) resin and cycloolefin polymer resin used for automobile parts or parts of electrical and electronic equipment. There was a problem that sometimes it was easy to peel off.

On the other hand, polymers obtained by polymerizing radically polymerizable monomers such as vinyl monomers and acrylic monomers are frequently used as adhesives for adhesive tapes. As a type of radical polymerization, free radical polymerization is common. However, free radical polymerization cannot sufficiently control the molecular weight, molecular weight distribution, copolymer composition, etc., and low molecular weight components are produced, and even in the case of copolymerization, homopolymers are produced. This component has disadvantages such as lowering the heat resistance and cohesive strength of the pressure-sensitive adhesive tape, and making it easier to peel off the pressure-sensitive adhesive tape.

On the other hand, living radical polymerization has been studied as a more controlled radical polymerization. Living radical polymerization is a polymerization in which a molecular chain grows without being hindered by a side reaction such as a termination reaction or a chain transfer reaction, so that it is easy to control the molecular weight and molecular weight distribution, copolymer composition, etc. Generation of low molecular weight components and the like can be suppressed.

Patent Document 1 describes a pressure-sensitive adhesive containing a copolymer obtained by copolymerizing monomers by a living radical polymerization method using an organic tellurium compound as a polymerization initiator. It describes that it exhibits an excellent effect.
However, it is difficult to obtain sufficient adhesive strength, particularly sufficient adhesion to low-polar adherends such as polypropylene (PP) plates, with a thin adhesive tape as requested in recent years, and further improvements are required. Yes.

Japanese Patent No. 5256515

An object of the present invention is to provide a pressure-sensitive adhesive tape that is difficult to peel off even if it is a thin pressure-sensitive adhesive tape and that can exhibit high constant load peelability on a low-polar adherend such as a polypropylene (PP) plate.

The present invention is a polymer component containing 60 wt% or more of an acrylic polymer obtained by living radical polymerization and having a weight average molecular weight of 300,000 to 2,000,000 and a molecular weight distribution (Mw / Mn) of 1.05 to 2.5; It is an adhesive tape having an adhesive layer containing a rosin-based tackifier resin or a terpene-based tackifier resin.
The present invention is described in detail below.

The present inventors obtained a polymer component mainly composed of an acrylic polymer having a weight average molecular weight of 300,000 to 2,000,000 and a molecular weight distribution (Mw / Mn) of 1.05 to 2.5 obtained by living radical polymerization. By blending a rosin-based tackifier resin or a terpene-based tackifier resin, even a thin adhesive tape is difficult to peel off, and a high constant load peelability can be exerted on a low-polar adherend such as a polypropylene (PP) plate. The inventors have found that an adhesive tape can be obtained and have completed the present invention.

The pressure-sensitive adhesive tape of the present invention is an acrylic polymer obtained by living radical polymerization and having a weight average molecular weight of 300,000 to 2,000,000 and a molecular weight distribution (Mw / Mn) of 1.05 to 2.5 (in this specification, “living radical A pressure-sensitive adhesive layer containing a polymer component containing 60% by weight or more of a polymerized acrylic polymer) and a rosin-based tackifier resin or a terpene-based tackifier resin.
When the pressure-sensitive adhesive layer contains the living radical polymerization acrylic polymer and the rosin-based tackifying resin or the terpene-based tackifying resin, the pressure-sensitive adhesive tape of the present invention is hardly peeled even if it is a thin pressure-sensitive adhesive tape, A high constant load peelability can be exhibited with respect to a low polarity adherend such as a polypropylene (PP) plate.

The living radical polymerization acrylic polymer is obtained by living radical polymerization using an acrylic monomer such as (meth) acrylic acid ester or (meth) acrylic acid as a raw material, preferably living radical polymerization using an organic tellurium polymerization initiator. Acrylic polymer.
Living radical polymerization is polymerization in which molecular chains grow without the polymerization reaction being hindered by side reactions such as termination reactions or chain transfer reactions. According to living radical polymerization, for example, a polymer having a more uniform molecular weight and composition than that of free radical polymerization can be obtained, and the generation of low molecular weight components and the like can be suppressed. The constant load peelability to a low polarity adherend such as a (PP) plate is improved.
Among them, living radical polymerization using an organic tellurium polymerization initiator differs from other living radical polymerizations in that radical polymerizable monomers having polar functional groups such as carboxyl group, hydroxyl group, amino group, amide group and nitrile group are used. Without protecting either, it is possible to obtain a polymer having a uniform molecular weight and composition by polymerization with the same initiator. For this reason, the radically polymerizable monomer having a polar functional group can be easily copolymerized.

The organic tellurium polymerization initiator is not particularly limited as long as it is generally used for living radical polymerization, and examples thereof include organic tellurium compounds and organic telluride compounds.
Examples of the organic tellurium compound include (methylterranyl-methyl) benzene, (1-methylterranyl-ethyl) benzene, (2-methylterranyl-propyl) benzene, 1-chloro-4- (methylterranyl-methyl) benzene, 1-hydroxy- 4- (methylterranyl-methyl) benzene, 1-methoxy-4- (methylterranyl-methyl) benzene, 1-amino-4- (methylterranyl-methyl) benzene, 1-nitro-4- (methylterranyl-methyl) benzene, 1- Cyano-4- (methylterranyl-methyl) benzene, 1-methylcarbonyl-4- (methylterranyl-methyl) benzene, 1-phenylcarbonyl-4- (methylterranyl-methyl) benzene, 1-methoxycarbonyl-4- (methylterranyl-methyl) ) Benzene, 1- Enoxycarbonyl-4- (methylterranyl-methyl) benzene, 1-sulfonyl-4- (methylterranyl-methyl) benzene, 1-trifluoromethyl-4- (methylterranyl-methyl) benzene, 1-chloro-4- (1 -Methyl terranyl-ethyl) benzene, 1-hydroxy-4- (1-methyl terranyl-ethyl) benzene, 1-methoxy-4- (1-methyl teranyl-ethyl) benzene, 1-amino-4- (1-methyl terranyl-ethyl) Benzene, 1-nitro-4- (1-methylterranyl-ethyl) benzene, 1-cyano-4- (1-methylterranyl-ethyl) benzene, 1-methylcarbonyl-4- (1-methylterranyl-ethyl) benzene, 1- Phenylcarbonyl-4- (1-methylterranyl-ethyl) benzene, 1-meth Sicarbonyl-4- (1-methylterranyl-ethyl) benzene, 1-phenoxycarbonyl-4- (1-methylterranyl-ethyl) benzene, 1-sulfonyl-4- (1-methylterranyl-ethyl) benzene, 1-trifluoromethyl -4- (1-methylteranyl-ethyl) benzene, 1-chloro-4- (2-methylterranyl-propyl) benzene, 1-hydroxy-4- (2-methylterranyl-propyl) benzene, 1-methoxy-4- (2 -Methyl teranyl-propyl) benzene, 1-amino-4- (2-methyl teranyl-propyl) benzene, 1-nitro-4- (2-methyl teranyl-propyl) benzene, 1-cyano-4- (2-methyl teranyl-propyl) Benzene, 1-methylcarbonyl-4- (2-methylterranyl-propyl ) Benzene, 1-phenylcarbonyl-4- (2-methylterranyl-propyl) benzene, 1-methoxycarbonyl-4- (2-methylterranyl-propyl) benzene, 1-phenoxycarbonyl-4- (2-methylterranyl-propyl) benzene 1-sulfonyl-4- (2-methylterranyl-propyl) benzene, 1-trifluoromethyl-4- (2-methylterranyl-propyl) benzene, 2- (methylterranyl-methyl) pyridine, 2- (1-methylterranyl-ethyl) ) Pyridine, 2- (2-methylterranyl-propyl) pyridine, 2-methylterranyl-methyl ethanoate, methyl 2-methylterranyl-propionate, methyl 2-methylterranyl-2-methylpropionate, 2-methylterranyl-ethyl ethanoate, 2 -Methylterranil Ethyl propionate, 2-Mechiruteraniru -2-methylpropionic acid ethyl, 2-methyl-Terra alkylsulfonyl acetonitrile, 2-methyl-Terra sulfonyl propionitrile, 2-methyl-2-methyl-Terra sulfonyl propionitrile, and the like. The methyl terranyl group in these organic tellurium compounds may be an ethyl terranyl group, n-propyl terranyl group, isopropyl terranyl group, n-butyl terranyl group, isobutyl terranyl group, t-butyl terranyl group, phenyl terranyl group, etc. These organic tellurium compounds may be used alone or in combination of two or more.

Examples of the organic telluride compound include dimethyl ditelluride, diethyl ditelluride, di-n-propyl ditelluride, diisopropyl ditelluride, dicyclopropyl ditelluride, di-n-butyl ditelluride, di-sec-butyl ditelluride. , Di-tert-butyl ditelluride, dicyclobutyl ditelluride, diphenyl ditelluride, bis- (p-methoxyphenyl) ditelluride, bis- (p-aminophenyl) ditelluride, bis- (p-nitrophenyl) ditelluride, bis -(P-cyanophenyl) ditelluride, bis- (p-sulfonylphenyl) ditelluride, dinaphthyl ditelluride, dipyridyl ditelluride and the like can be mentioned. These organic telluride compounds may be used alone or in combination of two or more. Of these, dimethyl ditelluride, diethyl ditelluride, di-n-propyl ditelluride, di-n-butyl ditelluride and diphenyl ditelluride are preferable.

In addition, within the range which does not impair the effect of this invention, in addition to the said organic tellurium polymerization initiator, you may use an azo compound as a polymerization initiator for the purpose of acceleration | stimulation of a polymerization rate.
The azo compound is not particularly limited as long as it is generally used for radical polymerization. For example, 2,2′-azobis (isobutyronitrile), 2,2′-azobis (2-methylbutyronitrile) ), 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 1,1-azobis (cyclohexane-1-carbonitrile) ), 1-[(1-cyano-1-methylethyl) azo] formamide, 4,4′-azobis (4-cyanovaleric acid), dimethyl-2,2′-azobis (2-methylpropionate), Dimethyl-1,1′-azobis (1-cyclohexanecarboxylate), 2,2′-azobis {2-methyl-N- [1,1′-bis (hydroxymethyl) -2-hydroxyethyl Propionamide}, 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propionamide], 2,2′-azobis [N- (2-propenyl) -2-methylpropionamide], 2 , 2′-azobis (N-butyl-2-methylpropionamide), 2,2′-azobis (N-cyclohexyl-2-methylpropionamide), 2,2′-azobis [2- (2-imidazoline-2 -Yl) propane] dihydrochloride, 2,2'-azobis {2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl] propane} dihydrochloride, 2,2'-azobis [2 -(2-imidazolin-2-yl) propane], 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis [N- (2-carboxyethyl) -2-methylpropionami Tetrahydrate, 2,2′-azobis (1-imino-1-pyrrolidino-2-methylpropane) dihydrochloride, 2,2′-azobis (2,4,4-trimethylpentane) and the like. It is done. These azo compounds may be used alone or in combination of two or more.

The acrylic monomer that is polymerized in the living radical polymerization is not particularly limited, and is an acrylic monomer having a polar functional group such as a carboxyl group, a hydroxyl group, an amino group, an amide group, and a nitrile group by using an organic tellurium polymerization initiator. Any of them can be used without protection, and examples thereof include (meth) acrylic acid esters and (meth) acrylic acid. In addition to the acrylic monomer, a vinyl compound may be used as a monomer.

The (meth) acrylic acid ester is not particularly limited, and methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, tert-butyl (meth) acrylate, 2-ethylhexyl (Meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, isomyristyl (meth) acrylate, stearyl (meth) acrylate and other (meth) acrylic acid alkyl esters, 4- (Meth) acrylic acid ester having a hydroxyl group such as hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, benzyl (meth) Acrylate, 2-butoxyethyl (meth) acrylate, 2-phenoxyethyl (meth) acrylate, glycidyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, polypropylene glycol mono (meth) acrylate. These (meth) acrylic acid esters may be used alone or in combination of two or more.

When the (meth) acrylic acid ester having a hydroxyl group is used, the content is not particularly limited, but a preferable upper limit in the radical polymerizable monomer is 30% by weight. When the content exceeds 30% by weight, the gel fraction of the pressure-sensitive adhesive layer becomes too high and the pressure-sensitive adhesive tape is easily peeled off, and the constant load peelability to the adherend may be lowered.

Moreover, it is also preferable to use (meth) acrylic acid, and the content thereof is not particularly limited, but a preferable lower limit in the radical polymerizable monomer is 0.1% by weight, and a preferable upper limit is 10% by weight. When the content is less than 0.1% by weight, the pressure-sensitive adhesive layer becomes too soft and heat resistance may be lowered. When the content exceeds 10% by weight, the pressure-sensitive adhesive layer may become too hard and the pressure-sensitive adhesive tape may be easily peeled off.

The vinyl compound is not particularly limited, and examples thereof include (meth) acrylamide compounds such as N, N-dimethylacrylamide, N, N-diethylacrylamide, N-isopropylacrylamide, N-hydroxyethylacrylamide, and acrylamide, N-vinylpyrrolidone, N-vinylcaprolactam, N-vinylacetamide, N-acryloylmorpholine, acrylonitrile, styrene, vinyl acetate and the like can be mentioned. These vinyl compounds may be used alone or in combination of two or more.

In the living radical polymerization, a dispersion stabilizer may be used. Examples of the dispersion stabilizer include polyvinyl pyrrolidone, polyvinyl alcohol, methyl cellulose, ethyl cellulose, poly (meth) acrylic acid, poly (meth) acrylic acid ester, and polyethylene glycol.
As the living radical polymerization method, conventionally known methods are used, and examples thereof include solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, bulk polymerization and the like.
When a polymerization solvent is used in the living radical polymerization, the polymerization solvent is not particularly limited. For example, a nonpolar solvent such as hexane, cyclohexane, octane, toluene, xylene, water, methanol, ethanol, propanol, butanol, acetone, Highly polar solvents such as methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, dioxane, N, N-dimethylformamide can be used. These polymerization solvents may be used alone or in combination of two or more.
The polymerization temperature is preferably 0 to 110 ° C. from the viewpoint of the polymerization rate.

The living radical polymerization acrylic polymer has a lower limit of 300,000 and an upper limit of 2 million for the weight average molecular weight (Mw). When the weight average molecular weight is less than 300,000, the pressure-sensitive adhesive layer becomes too soft and heat resistance is lowered. If the weight average molecular weight exceeds 2,000,000, the viscosity at the time of coating becomes too high to be applied, which may cause uneven thickness of the pressure-sensitive adhesive layer. The minimum with a preferable weight average molecular weight (Mw) of the said living radical polymerization acrylic polymer is 400,000, and a preferable upper limit is 1.3 million.

The living radical polymerization acrylic polymer has a molecular weight distribution (Mw / Mn) of 1.05 to 2.5. When the molecular weight distribution exceeds 2.5, the low molecular weight components and the like generated in the living radical polymerization increase, so that the pressure-sensitive adhesive tape is easily peeled off and the constant load peelability to the adherend is lowered. A preferable upper limit of the molecular weight distribution is 2.0, a more preferable upper limit is 1.8, and a further preferable upper limit is 1.7.

The molecular weight distribution (Mw / Mn) is a ratio between the weight average molecular weight (Mw) and the number average molecular weight (Mn).
A weight average molecular weight (Mw) and a number average molecular weight (Mn) are measured as a polystyrene conversion molecular weight by the gel permeation chromatography (GPC) method. Specifically, the weight average molecular weight (Mw) and the number average molecular weight (Mn) are obtained by filtering a diluted solution obtained by diluting a living radical polymerization acrylic polymer with tetrahydrofuran (THF) 50 times through a filter. It is measured as a polystyrene equivalent molecular weight by the GPC method using the filtrate obtained. In the GPC method, for example, 2690 Separations Model (manufactured by Waters) or the like can be used.

The polymer component may contain a polymer other than the living radical polymerization acrylic polymer, for example, a polymer obtained by free radical polymerization.
However, the lower limit of the content of the living radical polymerization acrylic polymer in the polymer component is 60% by weight, and the total amount (100% by weight) of the polymer component is preferably the living radical polymerization acrylic polymer. By making the content of the above-mentioned living radical polymerization acrylic polymer in the polymer component 60% by weight or more, it is difficult to peel off even if it is thin, and has high constant load peelability for low polarity adherends such as polypropylene (PP) plates. An adhesive tape that can be exhibited can be obtained.
The rosin tackifier resin or terpene tackifier resin is not included in the polymer component.

The rosin-based tackifier resin or terpene-based tackifier resin has a preferred lower limit of hydroxyl value of 25 and a preferred upper limit of 55. When the hydroxyl value is out of the above range, the constant load peelability of low pressure adherends such as a polypropylene (PP) plate of the adhesive tape may be lowered. A more preferred lower limit of the hydroxyl value is 30, and a more preferred upper limit is 50.
The hydroxyl value can be measured by JIS K1557 (phthalic anhydride method).

The rosin-based tackifier resin or terpene-based tackifier resin has a preferred softening temperature lower limit of 70 ° C. and a preferred upper limit of 170 ° C. When the softening temperature is less than 70 ° C., the rosin-based tackifier resin or terpene-based tackifier resin is too soft and the constant load peelability to a low-polar adherend such as a polypropylene (PP) plate may decrease. . When the softening temperature exceeds 170 ° C., the pressure-sensitive adhesive layer becomes too hard, the pressure-sensitive adhesive tape is easily peeled off, and the constant load peelability to a low-polar adherend such as a polypropylene (PP) plate may be lowered. . A more preferable lower limit of the softening temperature is 120 ° C.
The softening temperature is a softening temperature measured by the JIS K2207 ring and ball method.

The rosin tackifier resin or terpene tackifier resin is not particularly limited, and examples thereof include rosin ester resins and terpene phenol resins, and rosin ester resins are preferable.
The above-mentioned rosin ester resins are rosin resins mainly composed of abietic acid, disproportionated rosin resins and hydrogenated rosin resins, dimers of polymer acids such as abietic acid (polymerized rosin resins), etc. It is the resin obtained by making it. A part of the hydroxyl group of the alcohol used for esterification is contained in the resin without being used for esterification, so that the hydroxyl value is adjusted to the above range. Examples of the alcohol include polyhydric alcohols such as ethylene glycol, glycerin, and pentaerythritol.
Resin esterified rosin resin is rosin ester resin, disproportionated rosin resin esterified disproportionated rosin ester resin, hydrogenated rosin resin esterified resin is hydrogenated rosin ester resin, polymerized rosin A resin obtained by esterifying the resin is a polymerized rosin ester resin.
The terpene phenol resin is a resin obtained by polymerizing terpene in the presence of phenol.

Examples of the disproportionated rosin ester resin include Superester A75 (hydroxyl value 23, softening temperature 75 ° C.) manufactured by Arakawa Chemical Industries, Superester A100 (hydroxyl value 16, softening temperature 100 ° C.) manufactured by Arakawa Chemical Co., Ltd. Examples thereof include ester A115 (hydroxyl value 19, softening temperature 115 ° C.), super ester A125 (hydroxyl value 15, softening temperature 125 ° C.) manufactured by the same company. Examples of the hydrogenated rosin ester resin include Pine Crystal KE-359 (hydroxyl value 42, softening temperature 100 ° C.) manufactured by Arakawa Chemical Industries, and ester gum H (hydroxyl value 29, softening temperature 70 ° C.) manufactured by the same company. It is done. Examples of the polymerized rosin ester resin include Pencel D135 (Hydroxyl value 45, softening temperature 135 ° C.) manufactured by Arakawa Chemical Industries, Pencel D125 (Hydroxyl value 34, softening temperature 125 ° C.) manufactured by Arakawa Chemical Co., Ltd. 42, softening temperature 160 ° C.) and the like.
Examples of the terpene-based tackifier resin include YS Polystar G150 (softening point 150 ° C.) manufactured by Yasuhara Chemical, YS Polystar T100 (softening point 100 ° C.) manufactured by Yasuhara Chemical, YS Polystar G125 (softening point 125 ° C.) manufactured by the company Examples thereof include YS Polystar T115 (softening point 115 ° C.), YS Polystar T130 (softening point 130 ° C.) manufactured by the same company.
These rosin-based tackifier resins or terpene-based tackifier resins may be used alone or in combination of two or more.

The content of the rosin-based tackifier resin or terpene-based tackifier resin is preferably 5 parts by weight with respect to 100 parts by weight of the living radical polymerization acrylic polymer, and 40 parts by weight with a preferable upper limit. When the content is less than 5 parts by weight, the pressure-sensitive adhesive tape is easily peeled off, and the constant load peelability to a low-polar adherend such as a polypropylene (PP) plate may be lowered. Even if the content exceeds 40 parts by weight, the pressure-sensitive adhesive layer may become too hard due to an increase in the glass transition temperature (Tg), and the pressure-sensitive adhesive tape may be easily peeled off.

The pressure-sensitive adhesive layer may contain other resins such as additives such as a plasticizer, an emulsifier, a softener, a filler, a pigment, a dye, a silane coupling agent, and an antioxidant, if necessary. Good.

The pressure-sensitive adhesive layer has a preferred lower limit of the gel fraction of 1% by weight and a preferred upper limit of 70% by weight. When the gel fraction is less than 1% by weight, the pressure-sensitive adhesive layer becomes too soft and heat resistance may be lowered. When the gel fraction exceeds 70% by weight, the cross-linking density of the pressure-sensitive adhesive layer becomes too high, the pressure-sensitive adhesive tape is easily peeled off, and the constant load peelability to a low polarity adherend such as a polypropylene (PP) plate is obtained. May decrease. A more preferable lower limit of the gel fraction is 10% by weight, and a more preferable upper limit is 60% by weight.
The gel fraction is measured as follows. First, the adhesive tape was cut into a flat rectangular shape of 50 mm × 100 mm to prepare a test piece. After the test piece was immersed in ethyl acetate at 23 ° C. for 24 hours, the test piece was taken out from ethyl acetate and subjected to a condition of 110 ° C. For 1 hour. The weight of the test piece after drying is measured, and the gel fraction is calculated using the following formula (1). In addition, the release film for protecting an adhesive layer shall not be laminated | stacked on the test piece.
Gel fraction (% by weight) = 100 × (W2-W0) / (W1-W0) (1)
(W0: weight of substrate, W1: weight of test piece before immersion, W2: weight of test piece after immersion and drying)

As a method for obtaining a pressure-sensitive adhesive layer having a gel fraction in the above range, a method of adding a crosslinking agent to form a crosslinked structure between the main chains of the resin constituting the pressure-sensitive adhesive layer is preferable. By appropriately adjusting the type or amount of the crosslinking agent, the gel fraction of the pressure-sensitive adhesive layer can be easily adjusted to the above range.

The said crosslinking agent is not specifically limited, For example, an isocyanate type crosslinking agent, an aziridine type crosslinking agent, an epoxy-type crosslinking agent, a metal chelate type crosslinking agent etc. are mentioned. Especially, since it is excellent in the adhesive stability with respect to a base material, an isocyanate type crosslinking agent is preferable. Examples of the isocyanate-based crosslinking agent include Coronate HX (manufactured by Nippon Polyurethane Industry Co., Ltd.), Coronate L (manufactured by Nippon Polyurethane Industry Co., Ltd.), and Mytec NY260A (manufactured by Mitsubishi Chemical Corporation).
The blending amount of the crosslinking agent is preferably 0.01 to 5 parts by weight and more preferably 0.1 to 3 parts by weight with respect to 100 parts by weight of the living radical polymerization acrylic polymer.

Since the pressure-sensitive adhesive tape of the present invention is difficult to peel off even if it is a thin pressure-sensitive adhesive tape, the pressure-sensitive adhesive layer and the substrate described later can be made thin according to the application.
The thickness of the pressure-sensitive adhesive layer is not particularly limited because it is set depending on the application, but a preferred lower limit is 1 μm and a preferred upper limit is 100 μm. When the thickness is less than 1 μm, the pressure-sensitive adhesive tape is easily peeled off, and the constant load peelability to a low-polar adherend such as a polypropylene (PP) plate may be lowered. When the said thickness exceeds 100 micrometers, a thin adhesive tape may not be obtained. The more preferable lower limit of the thickness is 15 μm, and the more preferable upper limit is 75 μm.

The pressure-sensitive adhesive tape of the present invention may be a support type having a base material or a non-support type having no base material. In the case of the support type, the pressure-sensitive adhesive layer may be formed on one side of the substrate, or the pressure-sensitive adhesive layer may be formed on both sides.

Although the said base material is not specifically limited, A resin film, a resin foam, paper, a nonwoven fabric, a yarn cloth cloth etc. are mentioned.
Examples of the resin film include polyolefin resin films such as polyethylene films and polypropylene films, polyester resin films such as PET films, and modified olefins such as ethylene-vinyl acetate copolymers and ethylene-acrylic acid ester copolymers. Examples thereof include a resin film, a polyvinyl chloride resin film, a polyurethane resin film, and a cycloolefin polymer resin film.
Examples of the resin foam include polyethylene foam, polypropylene foam, acrylic foam, urethane foam, and ethylene propylene rubber foam.
Examples of the yarn cloth cloth include a woven polyethylene flat yarn and a laminate of a resin film on the surface thereof.
Especially in the case of double-sided tapes used in the assembly of display modules, black-printed substrates to prevent light transmission, white-printed substrates to improve light reflectivity, metal-deposited film substrates, etc. Can also be used.

The thickness of the substrate is not particularly limited because it is set depending on the application, but for example, in the case of a film substrate, 1 to 100 μm is preferable, and 5 to 75 μm is more preferable. When the thickness of the substrate is less than 1 μm, the mechanical strength of the adhesive tape may be lowered. If the thickness of the base material exceeds 100 μm, the adhesive tape may become too stiff and it may be difficult to adhere and adhere together along the shape of the adherend.

The production method of the pressure-sensitive adhesive tape of the present invention is not particularly limited. For example, the living radical polymerization acrylic polymer and the rosin-based tackifier resin or the terpene-based tackifier resin may be used as required, and the others such as the crosslinking agent. Are mixed together and stirred to prepare an adhesive solution, and then this adhesive solution is applied to a release-treated PET film and dried to form an adhesive layer. The resulting adhesive layer And the like, and a method of coating and drying the substrate directly on one side or both sides of the substrate. The pressure-sensitive adhesive layer formed by coating and drying the PET film obtained by releasing the pressure-sensitive adhesive solution may be used as a non-support type pressure-sensitive adhesive tape without a substrate.

The use of the adhesive tape of the present invention is not particularly limited, but it is used for assembling an electronic device (for example, a mobile phone, a portable information terminal, etc.) equipped with an image display device or an input device, assembling and fixing automobile parts, and the like. Is preferred. More specifically, for example, for low-polar adherends such as polypropylene (PP) resin used for automobile parts or parts of electric and electronic equipment, cycloolefin polymer resin used for display modules, etc. It is preferable that they are bonded together.

ADVANTAGE OF THE INVENTION According to this invention, even if it is a thin adhesive tape, it is hard to peel and can provide the adhesive tape which can exhibit high constant load peelability with respect to low polar adherends, such as a polypropylene (PP) board.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

(Radical polymerization polymer)
(Synthesis 1)
(Synthesis 1-1)
Tellurium (40 mesh, metal tellurium, manufactured by Aldrich) 6.38 g (50 mmol) was suspended in tetrahydrofuran (THF) 50 mL, and 1.6 mol / L n-butyllithium / hexane solution (Aldrich) 34 was added thereto. 4 mL (55 mmol) was slowly added dropwise at room temperature. The reaction solution was stirred until the metal tellurium disappeared completely. To this reaction solution, 10.7 g (55 mmol) of ethyl-2-bromo-isobutyrate was added at room temperature and stirred for 2 hours. After completion of the reaction, the solvent was concentrated under reduced pressure, followed by distillation under reduced pressure to obtain a yellow oily ethyl 2-methyl-2-n-butylteranyl-propionate.

(Synthesis 1-2)
In a glove box substituted with argon, 38 μL of ethyl 2-methyl-2-n-butylterranyl-propionate prepared in Synthesis 1-1, V-60 (2,2′-azobisisobutyronitrile) was prepared in a reaction vessel. 2.8 mg, manufactured by Wako Pure Chemical Industries, Ltd.) and 1 mL of ethyl acetate were added, the reaction vessel was sealed, and the reaction vessel was taken out of the glove box. Subsequently, while flowing argon gas into the reaction vessel, a total of 100 g of the monomers (BA: butyl acrylate, Aac: acrylic acid, HEA: 2-hydroxyethyl acrylate) shown in Table 1 was added into the reaction vessel, and acetic acid as the polymerization solvent. 66.5 g of ethyl was added, and a polymerization reaction was performed at 60 ° C. for 20 hours to obtain a living radical polymerization acrylic polymer-containing solution.
The obtained living radical polymerization acrylic polymer was diluted 50-fold with tetrahydrofuran (THF) and the resulting diluted solution was filtered with a filter (material: polytetrafluoroethylene, pore size: 0.2 μm), and the resulting filtrate was obtained. Is supplied to a gel permeation chromatograph (Waters, 2690 Separations Model), GPC measurement is performed under the conditions of a sample flow rate of 1 ml / min and a column temperature of 40 ° C., and the molecular weight of the polymer in terms of polystyrene is measured. Average molecular weight (Mw) and molecular weight distribution (Mw / Mn) were determined. GPC KF-806L (Showa Denko) was used as the column, and a differential refractometer was used as the detector.

(Synthesis 2)
58 μL of ethyl 2-methyl-2-n-butylterranyl-propionate prepared in Synthesis 1-1, 4.2 mg of V-60 (2,2′-azobisisobutyronitrile, manufactured by Wako Pure Chemical Industries, Ltd.) A living radical polymerization acrylic polymer-containing solution was obtained in the same manner as in Synthesis 1-2 except that the weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) were determined.

(Synthesis 3)
17 μL of ethyl 2-methyl-2-n-butylterranyl-propionate produced in Synthesis 1-1, 1.2 mg of V-60 (2,2′-azobisisobutyronitrile, manufactured by Wako Pure Chemical Industries, Ltd.) A living radical polymerization acrylic polymer-containing solution was obtained in the same manner as in Synthesis 1-2 except that the weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) were determined.

(Synthesis 4)
230 μL of ethyl 2-methyl-2-n-butylterranyl-propionate prepared in Synthesis 1-1 and 17 mg of V-60 (2,2′-azobisisobutyronitrile, manufactured by Wako Pure Chemical Industries, Ltd.) were changed. Otherwise, a living radical polymerization acrylic polymer-containing solution was obtained in the same manner as in Synthesis 1-2, and the weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) were determined.

(Synthesis 5)
50 g of ethyl acetate was added as a polymerization solvent in the reaction vessel, and after bubbling with nitrogen, the reaction vessel was heated while flowing nitrogen and refluxing was started. Subsequently, a polymerization initiator solution in which 0.15 g of V-60 (2,2′-azobisisobutyronitrile, manufactured by Wako Pure Chemical Industries, Ltd.) as a polymerization initiator was diluted 10-fold with ethyl acetate was placed in the reaction vessel. A total of 100 g of the monomers shown in Table 1 was added dropwise over 2 hours. After completion of dropping, a polymerization initiator solution in which 0.15 g of V-60 (2,2′-azobisisobutyronitrile, manufactured by Wako Pure Chemical Industries, Ltd.) as a polymerization initiator was diluted 10 times with ethyl acetate was added to the reaction vessel. The polymerization reaction was carried out for 4 hours to obtain a free radical polymerization polymer-containing solution.
In the same manner as in Synthesis 1, the weight average molecular weight (Mw) and the molecular weight distribution (Mw / Mn) were determined.

(Tackifying resin)
The tackifying resin shown in Table 2 was used.

(Examples 1-8, Comparative Examples 1-6)
To the radical polymerization polymer-containing solution obtained above, a predetermined amount of tackifying resin shown in Tables 3 and 4 is added to 100 parts by weight of the nonvolatile content, ethyl acetate is added and stirred, and a crosslinking agent ( IPDI: isophorone diisocyanate) and a tackifying resin were added in predetermined amounts shown in Tables 3 and 4 and stirred to obtain a pressure-sensitive adhesive solution having a nonvolatile content of 30% by weight. The obtained pressure-sensitive adhesive solution was applied to a 50 μm-thick release PET film so as to have the tape thicknesses shown in Tables 3 and 4 after drying, and then dried at 70 ° C. for 10 minutes to obtain a pressure-sensitive adhesive tape. It was. In addition, the release film for protecting an adhesive layer was laminated | stacked on the surface of the both sides of an adhesive layer.
The obtained adhesive tape was cut into a flat rectangular shape of 50 mm × 100 mm to prepare a test piece, and the release film was peeled off. The test piece was immersed in ethyl acetate at 23 ° C. for 24 hours, then taken out from the ethyl acetate and dried at 110 ° C. for 1 hour. The weight of the test piece after drying was measured, and the gel fraction was calculated using the following formula (1).
Gel fraction (% by weight) = 100 × (W2-W0) / (W1-W0) (1)
(W0: weight of substrate, W1: weight of test piece before immersion, W2: weight of test piece after immersion and drying)

(Evaluation)
The following evaluation was performed about the adhesive tape obtained by the Example and the comparative example. The results are shown in Tables 3 and 4.

(1) Constant load peelability for polypropylene (PP) plate Affixed to a polypropylene (PP) plate with a backing adhesive tape with a width of 20 mm x 50 mm, cured at 23 ° C and 50% humidity overnight, and then at 60 ° C and 90 ° direction A 50 g load was applied to the film, and the peel distance after 30 minutes was measured.
A: Peeling distance is 5 mm or less B: Peeling distance exceeds 5 mm but 10 mm or less Δ: Peeling distance exceeds 10 mm but 15 mm or less X: Peeling distance exceeds 15 mm

ADVANTAGE OF THE INVENTION According to this invention, even if it is a thin adhesive tape, it is hard to peel and can provide the adhesive tape which can exhibit high constant load peelability with respect to low polar adherends, such as a polypropylene (PP) board.

Claims (1)

A polymer component containing 60% by weight or more of an acrylic polymer containing a hydroxyl group having a weight average molecular weight of 300,000 to 2,000,000 and a molecular weight distribution (Mw / Mn) of 1.05 to 2.5, obtained by living radical polymerization; A pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing a rosin-based tackifying resin or a terpene-based tackifying resin having a hydroxyl group and a crosslinking agent ,
The rosin-based tackifier resin or terpene-based tackifier resin having a hydroxyl group has a softening temperature of 70 to 170 ° C. and a hydroxyl value of 25 to 55,
The pressure-sensitive adhesive tape, wherein the pressure-sensitive adhesive layer has a gel fraction of 1 to 70% by weight .