JPH07316515A - Acrylic double-sided adhesive tape - Google Patents

Abstract

(57) [Abstract] [Purpose] Initial re-bonding is easy, and it is possible to develop a sufficiently high adhesive strength by curing for a certain period of time, and also high shear strength, especially for automobile parts and building materials. An object is to provide an acrylic double-sided pressure-sensitive adhesive tape suitable for adhesively fixing structures such as. [Structure] Acrylic copolymer obtained by photopolymerizing a photopolymerizable composition in which a tape base material comprises an alkyl (meth) acrylate, a vinyl monomer having a polar group, a photopolymerization initiator, a crosslinking agent and a filler. (A) an alkyl (meth) acrylate having an alkyl group having 15 to 20 carbon atoms on both surfaces of the tape substrate.
1 to 5% by weight, (b) a vinyl monomer 5 having a polar group
From 20% by weight to (c) an acrylic copolymer (B) obtained by copolymerizing a mixed monomer consisting of 75 to 94.9% by weight of (c) an alkyl (meth) acrylate having an alkyl group having 1 to 14 carbon atoms. An acrylic double-sided pressure-sensitive adhesive tape, wherein the acrylic pressure-sensitive adhesive composition is laminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acrylic double-sided pressure-sensitive adhesive tape which can be easily reattached at the initial stage and has a sufficiently high adhesive force after a certain curing time.

[0002]

2. Description of the Related Art Recently, it has been reported that an acrylic double-sided pressure-sensitive adhesive tape using an acrylic sheet as a base material is superior in adhesive strength to those using a polyolefin sheet or a polyurethane sheet as a base material ( Japanese Patent Publication 57-170
No. 30), such an acrylic double-sided adhesive tape,
It is used in the field of adhesion of structures such as fixing of automobile parts and fixing of building materials, which have been generally fixed with adhesives, bolts and screws.

However, since the above-mentioned adhesive tape has a high initial adhesive force, if the tape cannot be accurately attached at a predetermined position, the base material may be deformed or broken if it is forcibly peeled off and reattached. is there.

To solve the above problems, as a method of suppressing the initial adhesive force, for example, an alkyl (meth) acrylate having an alkyl group having 2 to 8 carbon atoms and an alkyl group having 12 to 2 carbon atoms are used.
A pressure-sensitive adhesive comprising a copolymer obtained by copolymerizing the alkyl (meth) acrylate of No. 2 has been reported (JP-A-63-022682), and there is also a description of a pressure-sensitive adhesive tape using the pressure-sensitive adhesive.

However, since this adhesive tape has a low initial adhesive force and a low adhesion progressing property, it has a problem that the finally reaching adhesive force with time is also low, and it cannot be used for applications requiring high adhesive strength. There wasn't.

Therefore, as a method for solving the above problems, non-adhesive solid particles are dispersed in an adhesive layer and projected on the adhesive surface to reduce the adhesive area immediately after application, thereby lowering the initial adhesive force. Finally, there is also reported a pressure-sensitive adhesive tape in which the solid particles are finally embedded in the pressure-sensitive adhesive layer, whereby the adhesive area increases with time, and high adhesive strength with time can be expressed (JP-A-1-118584). .

[0007]

However, in the pressure-sensitive adhesive tape described in JP-A-1-118584, not only the number of steps for dispersing the non-tacky solid particles is increased, but the production efficiency is reduced, and the base material is aggregated. Since the force was low, the shear strength was low, and it could not be used for the adhesive application of structures requiring high adhesive strength.

The present invention has been made in view of the above problems, and its object is to make it easy to re-attach in the initial stage.
Another object of the present invention is to provide an acrylic double-sided pressure-sensitive adhesive tape which has a sufficiently high adhesive strength after a certain curing time and a high shear strength and is particularly suitable for adhesive fixing of structures such as automobile parts and building materials.

[0009]

The tape base material used in the present invention comprises a photopolymerizable composition comprising an alkyl (meth) acrylate, a polar group-containing vinyl monomer, a photopolymerization initiator, a crosslinking agent and a filler. A sheet made of an acrylic copolymer (A) obtained by photopolymerization.

Examples of the alkyl (meth) acrylate include ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, sec-butyl (meth) acrylate, t-butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, n-
Nonyl (meth) acrylate, isononyl (meth) acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, etc. are mentioned. The above alkyl (meth) acrylates may be used alone or in combination of two or more kinds.

When the content of the alkyl (meth) acrylate is small, the cohesive force becomes high and it becomes difficult to obtain sufficient pressure-sensitive adhesiveness. When the content is large, the cohesive force becomes low and it becomes difficult to obtain sufficient shear strength. Therefore, it is preferably 50 to 99% by weight, and more preferably 80 to 95% by weight in the total constituent monomer composition.

Examples of the vinyl monomer having a polar group include carboxyl group-containing vinyl monomers such as (meth) acrylic acid, itaconic acid, crotonic acid, (anhydrous) maleic acid, (anhydrous) fumaric acid, and carboxyethyl acrylate. 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4
-Hydroxybutyl (meth) acrylate, caprolactone-modified (meth) acrylate, polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate and other vinyl monomers having a hydroxyl group, (meth) acrylonitrile, N-vinylpyrrolidone, N-vinylcaprolactam , N-vinyl lauryl lactam, (meth) acryloylmorpholine, (meth) acrylamide, dimethyl (meth) acrylamide, N-
Methylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide, dimethylaminopropyl (meth) acrylamide, dimethylaminomethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, diethylaminoethyl ( Examples thereof include monomers such as (meth) acrylate. The above-mentioned vinyl monomer having a polar group may be used alone or in combination of two or more kinds.

When the content of the vinyl monomer having a polar group is small, the cohesive force is low and it is difficult to obtain sufficient shear strength, and when it is large, the cohesive force is high and it is difficult to obtain sufficient pressure-sensitive adhesiveness. Therefore, it is preferably 1 to 50% by weight, and more preferably 5 to 20% by weight in the total composition of the constituent monomers.

Other than the above-mentioned alkyl (meth) acrylate and vinyl monomer having a polar group, other vinyl monomers may be copolymerized. Examples of the vinyl monomer include vinyl monomers such as vinyl acetate, vinyl pivalate, vinyl propionate, styrene, and isobornyl (meth) acrylate. The above vinyl monomers may be used alone or in combination of two or more kinds.

When the content of the vinyl monomer increases, the cohesive force increases and it becomes difficult to obtain sufficient pressure-sensitive adhesiveness. Therefore, the content of the vinyl monomer is preferably 30% by weight or less in the total constituent monomer composition.

Examples of the above photopolymerization initiator include 4-
(2-Hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone [Ciba Geigy, trade name "Darocurer 2959"], 1-hydroxycyclohexyl phenyl ketone [Ciba Geigy, trade name "Irgacure 184"], 2-hydroxy-2,2-dimethylacetophenone [Ciba Geigy, trade name "Darocur 1173"], methoxyacetophenone,
Acetophenone initiators such as 2,2-dimethoxy-2-phenylacetophenone [manufactured by Ciba-Geigy, trade name "Irgacure 651"], benzoin ethyl ethers, benzoin ether initiators such as benzoin propyl ether, benzyl dimethyl ketal, etc. Other examples include ketal-based initiators, halogenated ketones, acylphosphine oxides, and acylphosphinates. The above photopolymerization initiators may be used alone or in combination of two or more kinds.

When the amount of the photopolymerization initiator added is small, the polymerization is not completed and the polymer has a strong monomer odor. When the amount is large, the amount of radicals generated is large, and it is difficult to obtain a sufficient cohesive force due to a decrease in the molecular weight. Therefore, it is preferably 0.01 to 5 with respect to 100 parts by weight of the monomer composition.
Parts by weight, and more preferably 0.05 to 3 parts by weight.

The cross-linking agent is an acrylic copolymer (A).
It is added for the purpose of improving the cohesive force by cross-linking the sheet consisting of, and thereby obtaining a shear strength sufficient for adhesively fixing the structure.

The gel fraction of the acrylic copolymer (A) of the present invention is 70% by weight or more in order to achieve the above object. The gel fraction is an index of the degree of crosslinking of the polymer and does not include fillers. The gel fraction is measured by immersing the acrylic copolymer (A) in a good solvent such as ethyl acetate, toluene, tetrahydrofuran (THF), filtering the insoluble matter as a crosslinked polymer, and measuring the weight fraction. It can be easily measured by determining

In the case of photopolymerization, by adding a polyfunctional (meth) acrylate in advance, polymerization and crosslinking can be carried out simultaneously. Further, in addition to the polyfunctional (meth) acrylate, by adding a cross-linking agent capable of reacting with the polar group in the copolymer used for a general solvent-based adhesive, by curing after photopolymerization, It is also possible to promote the crosslinking between the produced polymer chains.

Examples of the polyfunctional (meth) acrylates include 1.4 butanediol di (meth) acrylate, 1.6 hexanediol di (meth) acrylate, 1.9 nonanediol di (meth) acrylate,
(Poly) ethylene glycol di (meth) acrylate,
(Poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate,
Examples thereof include pentaerythritol di (meth) acrylate, glycerin methacrylate acrylate, pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, allyl (meth) acrylate, vinyl (meth) acrylate, and divinylbenzene. Besides, epoxy (meth) acrylate, polyester (meth) acrylate, urethane (meth) acrylate and the like can be mentioned. The above polyfunctional (meta)
The acrylates may be used alone or in combination of two or more.

If the amount of the polyfunctional (meth) acrylate added is too small, a sufficient degree of crosslinking cannot be obtained, so that the cohesive force is reduced, and it becomes difficult to obtain sufficient heat resistance and shear strength. The crosslinking density becomes high, the flexibility is impaired, and it becomes difficult to obtain sufficient pressure-sensitive adhesiveness. Therefore, it is preferably 0.0 with respect to 100 parts by weight of the monomer composition.
1 to 1 part by weight, more preferably 0.02 to 0.8
Parts by weight.

Examples of the cross-linking agent capable of reacting with the polar group include toluylene diisocyanate (TDI),
Naphthylene-1,5-diisocyanate, diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HMDI), isophorone diisocyanate (IPDI), xylene diisocyanate (XD)
I), an isocyanate-based crosslinking agent such as trimethylolpropane modified TDI, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether,
Examples thereof include epoxy crosslinking agents such as 1,6-hexanediol diglycidyl ether and aziridine crosslinking agents such as N, N-hexamethylene-1,6-bis (1-aziridinecarboxamide). The above crosslinking agents may be used alone or in combination of two or more.

If the amount of the cross-linking agent capable of reacting with the polar group is too small, a sufficient degree of cross-linking cannot be obtained, so that the cohesive force decreases and it becomes difficult to obtain sufficient heat resistance and shear strength. When it is too large, the crosslink density becomes high, the flexibility is impaired, and it becomes difficult to obtain sufficient pressure-sensitive adhesiveness. Therefore, it is preferably 0.0 based on 100 parts by weight of the monomer composition.
It is 1 to 5 parts by weight, and more preferably 0.05 to 3 parts by weight.

It is also possible to use the above-mentioned polyfunctional (meth) acrylate in combination with a crosslinking agent capable of reacting with a polar group.

The above-mentioned filler is added for the purpose of improving the stress relaxation property of the tape base material. For example, inorganic hollow fine particles such as glass balloons, alumina balloons, shirasu balloons and fly ash balloons, glass beads, silica beads, silica gel. , Alumina silica, fly ash, inorganic fine particles such as synthetic mica, diatomaceous earth, porous fillers such as porous silica, polymethylmethacrylate, acrylonitrile-vinylidene chloride copolymer, polystyrene, organic hollow consisting of phenolic resin, etc. Fine particles, polymethylmethacrylate beads, polystyrene beads, nylon beads, styrene acrylic beads, urethane beads, silicone beads, polyethylene beads, polypropylene beads, EVA beads, organic fine particles such as poly (ethyl acrylate), cube-shaped particles Minashirika, glass flakes, glass fibers, chain clay minerals, and the like. You may use the said filler individually or in combination of 2 or more types.

The average particle size of the filler is preferably 0.2 to 200 μm, more preferably 10 to 200 μm.
It is 100 μm.

A tackifier resin may be added to the above-mentioned photopolymerizable composition, if necessary, within a range that does not impair the photopolymerizability.

When the photopolymerizable composition is formed into a sheet and the thickness is 100 μm or less, 1,000 cp
s, TI value (thixotropic index) can be applied even if it is about 1.5, but when forming a sheet having a thickness larger than that, it is difficult to control to a constant thickness because it will flow at low viscosity. It is preferable to adjust the viscosity with a thickener.

Examples of the thickener include acrylic rubber, nitrile rubber, epichlorohydrin rubber, isoprene rubber, butyl rubber, elastomers such as styrene-isoprene-styrene (SIS), thermoplastic resins such as polymethylmethacrylate and polystyrene, Alternatively, inorganic particles such as hydrophobic silica and alumina having an average particle diameter of 5 μm or less can be used. When inorganic particles are added, it is preferable that the particles are hydrophobized because the dispersion up to the primary particles is fast.

If the amount of the thickener added is increased, the cohesive force of the acrylic copolymer (A) becomes low, and it becomes difficult to obtain sufficient shear strength.
It is preferably 20 parts by weight or less, more preferably 10 parts by weight or less, still more preferably 5 parts by weight or less, based on parts by weight.

Besides the addition of the above thickener, there is also a thickening method in which the photopolymerizable composition is partially prepolymerized in advance. Such prepolymerization should be carried out before adding the polyfunctional (meth) acrylate to prevent the formation of microgels. This is because when gel is partially generated, it causes defects such as streaks during coating. Further, the polymer obtained by the prepolymerization remains as an uncrosslinked component even in the pressure-sensitive adhesive after crosslinking and causes a decrease in cohesive force. Therefore, the conversion rate with respect to the total constituent monomer composition is preferably 20% or less, and more preferably Is 10% or less, and more preferably 5% or less.

The manufacturing process conditions for the sheet made of the acrylic copolymer (A) will be described. As a basic process, there is a method of applying the above-mentioned photopolymerizable composition onto a release sheet using a coating machine such as a roll coater, and then irradiating with light to polymerize on the release sheet.

As the lamp used for the light irradiation,
Those having an emission distribution at a light wavelength of 400 nm or less are used, and examples thereof include a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excited mercury lamp, and a metal halide lamp. Among the above lamps, a chemical lamp is preferable because it efficiently emits light in a wavelength region (usually 330 to 400 nm) effective for photodecomposition of a polymerization initiator and can efficiently polymerize a thick film sheet.

Further, the irradiation light intensity of the lamp influences the degree of polymerization of the polymer obtained from the photopolymerizable composition, and is appropriately selected depending on the performance of the intended product. For example, in the case of a cleavage-type photopolymerization initiator having a usual acetophenone group, the irradiation light intensity is low, and the time until the reaction starts varies due to polymerization inhibition by oxygen, and a polymer having a constant degree of polymerization is obtained. The range of 0.1 to 100 mW / cm ² is preferable because the cohesive force and the stress relaxation property are difficult to be balanced because the molecular weight decreases and the molecular weight decreases when it increases.

Radical polymerization such as the above-mentioned photopolymerization generally has a polymerization inhibition by oxygen, and the cause thereof is particularly the invasion of oxygen in the air and the dissolved oxygen in the photopolymerizable composition. Therefore, a process capable of removing polymerization inhibition by oxygen is preferable. For example, as a method for suppressing the invasion of oxygen in the air, the surface is covered with a light-transmissive film such as polyethylene terephthalate or Teflon, and the above cover film A method of irradiating the composition via
Examples include a method of carrying out a polymerization reaction in an inert box having a light-transmissive window and having oxygen substituted with an inert gas such as nitrogen gas or carbon dioxide gas.

The thickness of the sheet made of the acrylic copolymer (A) is preferably 50 μm to 5 mm because the unevenness followability decreases as the thickness decreases and the shear strength decreases as the thickness increases.

Next, the acrylic pressure-sensitive adhesive composition used in the present invention will be described. The acrylic copolymer (B) that is the main component of the acrylic pressure-sensitive adhesive composition is (a)
Alkyl (meth) acrylate having 15 to 20 carbon atoms, (b) vinyl monomer having polar group, and (c) alkyl (meth) having 1 to 14 carbon atoms of alkyl group
It is obtained by copolymerizing a mixed monomer composed of acrylate.

Examples of the alkyl (meth) acrylate (a) having 15 to 20 carbon atoms in the alkyl group include, for example, n
-Pentadecyl (meth) acrylate, isopentadecyl (meth) acrylate, cetyl (meth) acrylate, isopalmityl (meth) acrylate, n-heptadecyl (meth) acrylate, isoheptadecyl (meth) acrylate, n-stearyl (meth) acrylate, iso Stearyl (meth) acrylate, n-nonadecyl (meth) acrylate, isononadecyl (meth) acrylate, n-eicosyl (meth) acrylate, isoeicosyl (meth) acrylate, etc. are mentioned.

When the content of the alkyl (meth) acrylate (a) having 15 to 20 carbon atoms in the alkyl group is small, the initial adhesive strength is high, and the removability immediately after application is difficult to obtain, and the content is high. If so, the adhesive strength will be low even after curing, and it will be difficult to use it for the adhesive application of structures requiring high adhesive strength.
It is 1 to 5% by weight, preferably 1 to 3% by weight.

Vinyl monomer (b) having the above polar group
Is contained for the purpose of positively migrating the alkyl group having 15 to 20 carbon atoms in the pressure-sensitive adhesive to the surface of the pressure-sensitive adhesive and, as a result, reducing the initial pressure-sensitive adhesive force. Examples of the vinyl monomer having a polar group (b) include the vinyl monomers having a polar group described above.

Vinyl monomer (b) having the above polar group
When the content of C is less, not only the cohesive force becomes low and it becomes difficult to obtain sufficient shear strength, but also the carbon number of 15 to 20
Since the alkyl group of is less likely to migrate to the pressure-sensitive adhesive surface, the initial adhesive strength becomes higher, and when it becomes larger, the cohesive strength becomes higher, and it is difficult to obtain sufficient pressure-sensitive adhesiveness, and it becomes difficult for the adhesive to grow over time. It is 5 to 20% by weight, preferably 5 to 15% by weight in the above mixed monomer.

The alkyl (meth) acrylate (c) having 1 to 14 carbon atoms in the above alkyl group has 14 carbon atoms in the above-mentioned alkyl (meth) acrylate.
The following alkyl (meth) acrylates may be mentioned.

When the content of the alkyl (meth) acrylate (c) having 1 to 14 carbon atoms in the alkyl group is small, the cohesive force becomes high, and it becomes difficult to obtain sufficient pressure-sensitive adhesive property. Becomes low and it becomes difficult to obtain sufficient shear strength.
It is 4.9% by weight, preferably 75 to 90% by weight.

Vinyl monomers other than (a), (b) and (C) may be copolymerized in the above copolymer. Examples of the vinyl monomer include vinyl monomers such as vinyl acetate, vinyl pivalate, vinyl propionate, styrene, and isobornyl (meth) acrylate. The above vinyl monomer is used alone or in 2
You may use together more than one kind.

The content of the vinyl monomer is preferably 30 parts by weight or less with respect to 100 parts by weight of the mixed monomer, because when the content of the vinyl monomer increases, the cohesive force increases and it becomes difficult to obtain sufficient pressure-sensitive adhesiveness.

The above acrylic copolymer can be obtained by a solvent polymerization method of polymerizing in a solvent, an emulsion polymerization method of polymerizing in water, a photopolymerization method of polymerizing by irradiating with light (mainly ultraviolet rays), and the like.

For the solvent polymerization method and emulsion polymerization method,
Generally, a thermal polymerization initiator is used. Examples of the thermal polymerization initiator include methyl ethyl ketone peroxide,
Ketone peroxides such as cyclohexanone peroxide, diacyl peroxides such as isobutyryl peroxide, benzoyl peroxide, P-chlorobenzoyl peroxide, and hydroperoxides such as diisopropylbenzene hydroperoxide and t-butyl hydroperoxide. , 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 1,
Dialkyl peroxides such as 3-bis- (t-butylperoxyisopropyl) benzene, 1,1-di (t
-Butylperoxy) -3,3,5-trimethylcyclohexane, peroxyketals such as 1,1-di (t-butylperoxy) cyclohexane, t-butylperoxypivalate, t-butylperoxy-2 -Alkyl peresters such as ethylhexanoate and t-butyl peroxyisobutyrate, percarbonates such as di-2 ethylhexyl peroxydicarbonate and bis- [4- (t-butyl) cyclohexyl] peroxydicarbonate In addition to organic peroxides such as 2,2'-azobis-isobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis-2,4-dimethylvalero Nitrile, 1,1'-azobis-1-cyclohexanecarbonitrile, dimethyl-2,2'-azobisisobutyrate, 4 4'-azobis-4-cyanovaleric acid, 2,2'-azobis - (2-aminopropane) dihydrochloride azobis compounds such as ride like.

Similarly, a photopolymerization initiator is used in the photopolymerization method. Examples of the photopolymerization initiator include the photopolymerization initiators described above.

When the above acrylic copolymer (B) is polymerized, a chain transfer agent is added to the monomer solution for the purpose of suppressing variations in the polymerization reaction and appropriately controlling the molecular weight of the resulting copolymer. May be.

Examples of the chain transfer agent include n-dodecyl mercaptan, 2-mercaptoethanol, β-
Mercaptopropionic acid, octyl β-mercaptopropionate, methoxybutyl β-mercaptopropionate, trimethylolpropane tris (β-thiopropionate), butyl thioglycolate, propanethiols, butanethiols, thiophosphites, etc. Examples thereof include thiol compounds and halogen compounds such as carbon tetrachloride.

The acrylic copolymer (B) may be crosslinked for the purpose of improving cohesive force. As a crosslinking method, there is addition of a crosslinking agent capable of reacting with the polar group in the acrylic copolymer (B). Examples of the cross-linking agent include all cross-linking agents capable of reacting with the polar group in the acrylic copolymer.

If the amount of the cross-linking agent capable of reacting with the polar group is small, it becomes difficult to obtain a sufficient degree of cross-linking, and thus the cohesive force is lowered and it becomes difficult to obtain sufficient heat resistance and shear strength. Further, when the amount is too large, the crosslink density becomes high, the flexibility is impaired, and it becomes difficult to obtain sufficient pressure-sensitive adhesiveness. Therefore, it is preferably 0.01 to 5 with respect to 100 parts by weight of the acrylic copolymer (B). Parts by weight, more preferably 0.1 to 3 parts by weight.

When the acrylic copolymer (B) is prepared by a photopolymerization method, a polyfunctional (meth) acrylate can be used as in the method for preparing the acrylic copolymer sheet. Examples of the polyfunctional (meth) acrylate include the above-mentioned polyfunctional (meth) acrylate, and it is also possible to use it in combination with a crosslinking agent capable of reacting with a polar group.

When the amount of the polyfunctional (meth) acrylate added is small, it is difficult to obtain a sufficient degree of cross-linking. Therefore, the cohesive force is lowered and it is difficult to obtain sufficient heat resistance and shear strength. Since the crosslink density becomes high, the flexibility is impaired, and it becomes difficult to obtain sufficient pressure-sensitive adhesiveness, so that it is preferably 0.01 to 1 part by weight, more preferably 0, relative to 100 parts by weight of the mixed monomer. .02
~ 0.8 parts by weight.

When the above acrylic copolymer (B) is obtained by photopolymerization, a thickener may be added for the purpose of improving coatability. Examples of the thickener include the above-mentioned thickeners, and the addition amount is also the same as above. A method of partially prepolymerizing the above-mentioned photopolymerizable composition to increase the viscosity is also applicable, and the addition rate is also the same as above.

To the acrylic pressure-sensitive adhesive composition used in the present invention, a tackifying resin, a filler and an extender may be appropriately added.

Examples of the tackifying resin include C5
-Based and C9 petroleum resin, rosin resin, rosin ester resin, terpene resin, terpene phenol resin, coumarone indene resin, disproportionated rosin resin, disproportionated rosin ester resin, polymerized rosin resin, polymerized rosin ester resin and these Included are all commercially available tackifying resins such as hydrogenates.

In the case of photopolymerization, tackifying resins that do not inhibit photopolymerizability may be mentioned. Examples of tackifying resins having low polymerization inhibiting properties include C5 and C9 hydrogenated petroleum resins and hydrogenated resins. Rosin resin, hydrogenated rosin ester resin, hydrogenated terpene resin, hydrogenated terpene phenol resin, hydrogenated coumarone indene resin, disproportionated rosin resin, disproportionated rosin ester resin, polymerized rosin resin, polymerized rosin ester resin, etc. Resins having relatively few unsaturated bonds are mentioned. The tackifying resins may be used alone or in combination of two or more.

If the amount of the tackifying resin added is too large, the cohesive force of the acrylic pressure-sensitive adhesive composition will be low, and it will be difficult to obtain sufficient shear strength. Therefore, 100 parts by weight of the acrylic copolymer (B) is added. On the other hand, it is preferably 30 parts by weight or less.

Examples of the above-mentioned filler and extender include the above-mentioned filler and extender.

[0062]

The acrylic double-sided pressure-sensitive adhesive tape of the present invention can exhibit sufficient shear strength by using a sheet made of an acrylic polymer as a tape base material. In addition, by copolymerizing a vinyl monomer having a polar group in the acrylic copolymer, which is the main component of the acrylic adhesive of the surface layer, the alkyl group having 15 to 20 carbon atoms is positively transferred to the adhesive interface. By doing so, the initial adhesive strength is reduced. However, with the passage of time, the alkyl group having 15 to 20 carbon atoms is gradually buried, so that the adhesion progresses, and a sufficient adhesive strength with time that can be used for the purpose of adhering a structure can be obtained.

[0063]

EXAMPLES Examples of the present invention will be described below.
In the following, "parts" means "parts by weight". "Preparation of Sheet Composed of Acrylic Copolymer (A)" [Acrylic Copolymer Sheet 1] 850 parts of 2-ethylhexyl acrylate, 50 parts of acrylic acid, 100 parts of N-vinylpyrrolidone, 2,2-dimethoxy-2 -Phenolacetophenone (manufactured by Ciba-Geigy Co., Ltd., trade name "Irgacure 651") (3.0 parts) was stirred and mixed in a separable flask, and then dissolved oxygen was removed from the monomer by purging with nitrogen gas. Then, while stirring, the above monomer composition is irradiated with ultraviolet rays using a black light lamp, and a part thereof is polymerized to increase the viscosity,
A partially polymerized product was obtained (conversion rate 3.7%, viscosity 2,20).
0 cps).

1,6 hexanediol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name "AH"
D ”) 0.2 part of the photopolymerizable composition obtained is applied to a 38 μm PET film having a release treatment on one side, and the release treatment surface of the PET film is adhered to the coated surface. Covered to do. An acrylic copolymer sheet having a thickness of 1.0 ± 0.1 mmmm at the end of the polymerization is obtained by irradiating ultraviolet rays having an intensity of ² mW / cm ² from the PET film cover surface with a chemical lamp for 8 minutes. (The residual monomer amount was 0.1% or less, and the gel fraction was 95%). [Acrylic Copolymer Sheet 2] The above acrylic copolymer sheet 1 except that 1,6 hexanediol diacrylate was not added to the partial polymer when the acrylic copolymer sheet 1 was prepared. Acrylic copolymer sheet 2 was obtained by the same method as described above (the amount of residual monomer was 0.2.
1% or less, gel fraction 0%). [Acrylic Copolymer Sheet 3] 850 parts of 2-ethylhexyl acrylate, 50 parts of acrylic acid, 100 parts of N-vinylpyrrolidone, 30 parts of hydrophilic silica (manufactured by Nippon Aerosil Co., Ltd., trade name "Aerosil 200") After that, using a dissolver type stirrer, the rotation speed is 1,00.
A mixed composition was obtained by stirring at 0 rpm for 4 hours.

2,2-dimethoxy-2 was added to the above mixed composition.
-Acrylic copolymer sheet 3 was obtained in the same manner as acrylic copolymer sheet 1 by adding 3.0 parts of phenylacetophenone and 0.2 part of 1,6 hexanediol diacrylate (the residual monomer amount is 0.1% or less, gel fraction 95%).

[Preparation of Acrylic Adhesive Composition] [Adhesive A] A 2-ethylhexyl acrylate 690 was placed in a separable flask equipped with a cooling tube, a thermometer and a stirrer.
Parts, n-butyl acrylate 250 parts, acrylic acid 50
Department, Stearyl acrylate (Osaka Organic Co., Ltd.) 1
0 part, 0.2 part of n-dodecyl mercaptan was charged together with 900 parts of ethyl acetate, the temperature was raised under reflux in a nitrogen gas atmosphere until reflux started, and then maintained for 20 minutes, and 1.0 part of benzoyl peroxide was added to 50 parts of ethyl acetate. The initiator solution dissolved in was added dropwise and reacted for 4 hours. After that, an initiator solution prepared by dissolving 1.0 part of benzoyl peroxide in 50 parts of ethyl acetate was further added dropwise and reacted for 3 hours. After the reaction, 500 parts of toluene was stirred and mixed to obtain an acrylic copolymer solution (solid content: 39.5%, viscosity: 12,000 cps). Furthermore, the solid content of the acrylic copolymer solution is 100
Based on parts by weight, N, N-hexamethylene-1,6-bis (1-aziridinecarboxamide) (Mutual Yakuhin Co., Ltd.)
A solution of the pressure-sensitive adhesive A was obtained by adding and mixing 0.1 part of "HDU" (trade name, manufactured by the company). [Adhesive B] 2-Ethylhexyl acrylate 690
Parts, n-butyl acrylate 250 parts, acrylic acid 50
Department, cetyl acrylate (Osaka Organic Co., Ltd.) 10
Parts, n-dodecyl mercaptan was added in the same manner as for the pressure-sensitive adhesive A except that it was 0.2 part (solid content was 39.
8%, viscosity 14,200 cps). [Adhesive C] 2-Ethylhexyl Acrylate 848
Parts, N-vinylpyrrolidone 100 parts, stearyl acrylate 10 parts, 2-hydroxyethyl methacrylate 2
Parts, n-dodecyl mercaptan was used in the same manner as for the pressure-sensitive adhesive A except that it was 0.2 parts.
9.8%, viscosity 12,200 cps). [Adhesive D] 2-ethylhexyl acrylate 920
Parts, acrylic acid 30 parts, cetyl acrylate 50 parts, n
-Adhesive A except that 0.2 parts of dodecyl mercaptan was used.
A solution of adhesive D (solid content: 40.0%, viscosity: 12,000 cps) was obtained in the same manner as in. [Adhesive E] 2-ethylhexyl acrylate 798
Parts, N-vinylpyrrolidone 100 parts, stearyl acrylate 100 parts, 2-hydroxyethyl methacrylate 2 parts, and n-dodecyl mercaptan 0.2 parts except that the solution of the adhesive E (solid content Is 3
9.8%, viscosity 14,200 cps). [Adhesive F] 2-Ethylhexyl acrylate 950
Parts, acrylic acid 50 parts, n-dodecyl mercaptan 0.
A solution of adhesive F (solid content 40.0%, viscosity 12,000 cps) was prepared in the same manner as adhesive A except that 2 parts were used.
Got [Adhesive G] 2-ethylhexyl acrylate 740
Parts, acrylic acid 250 parts, stearyl acrylate 10
Part, n-dodecyl mercaptan, except that 0.2 part of n-dodecyl mercaptan was used.
8%, viscosity 14,000 cps). [Adhesive H] 2-ethylhexyl acrylate 960
Parts, acrylic acid 30 parts, stearyl acrylate 10
Part, n-dodecyl mercaptan was used in the same manner as the pressure-sensitive adhesive A except that it was 0.2 part.
8%, viscosity 14,000 cps).

"Production of Acrylic Double-sided Adhesive Tape" (Examples 1 to 8 and Comparative Examples 1 to 12) According to Tables 1 and 2, the solutions of the above-mentioned adhesives A to H were coated on 95 μm release paper, respectively. , A pressure-sensitive adhesive layer of 50 μm obtained by drying in an oven at 120 ° C. for 5 minutes (each gel fraction is 9
0%) was laminated on both sides of the acrylic cross-linked pressure-sensitive adhesive sheets 1 to 3 to obtain an acrylic double-sided pressure-sensitive adhesive tape.

"Evaluation of performance of pressure-sensitive adhesive" Evaluation items and evaluation methods are shown below. (Initial T-type Peeling Force Test) 2 on both sides of the double-sided adhesive tape of size 20 mm × 40 mm obtained in Examples and Comparative Examples.
5mm x 100mm x 0.05mm stainless steel foil "S
US-304 "[manufactured by Nippon Test Panel Co., Ltd., JIS
G4305 standard product] at 23 ° C,
It was pressure-bonded by reciprocating a pressure roller of 2 kg twice. After leaving it at 23 ° C for 5 minutes, JI under the same condition
Based on SK6854, a T-type peel test was performed at a speed of 200 mm / min to measure the peel strength. (T-Type Peeling Force Test with Time) A test sample was prepared by the same operation as the initial T-type peeling force test, left at 72 ° C. for 72 hours, and then the peel strength was measured in the same manner. The results are shown in Tables 1 and 2.

[0069]

[Table 1]

[0070]

[Table 2]

[0071]

The acrylic double-sided pressure-sensitive adhesive tape of the present invention is
Acrylic copolymer having sufficient shear strength by using an acrylic polymer sheet as a base material, and an acrylic (meth) acrylate having a long-chain alkyl group having been copolymerized on the surface of the acrylic pressure-sensitive adhesive layer. By using the coalescence, the initial adhesive strength is suppressed to a low level, and yet the long-chain alkyl group is gradually buried with the lapse of time to accelerate the adhesion and increase the temporal adhesive strength. As a result, it is easy to re-paste immediately after pasting, yet sufficient adhesive strength over time can be developed and high shear strength is retained, so the conventional method of fixing with adhesives, bolts, or screws is generally used. It is suitable for applications such as fixing automobile parts and building materials, and for adhering structures that require high shear strength.

Claims (1)

[Claims] 1. A tape substrate comprising an alkyl (meth) acrylate, a polar group-containing vinyl monomer, a photopolymerization initiator,
A sheet made of an acrylic copolymer (A) having a gel fraction of 70% by weight or more, which is obtained by photopolymerizing a photopolymerizable composition composed of a cross-linking agent and a filler. (A) 0.1 to 5% by weight of alkyl (meth) acrylate having 15 to 20 carbon atoms in the alkyl group, (b) 5 to 20% by weight of vinyl monomer having a polar group, and (c) 1 to 1 carbon atoms in the alkyl group. 14. An acrylic pressure-sensitive adhesive composition comprising an acrylic copolymer (B) obtained by copolymerizing a mixed monomer consisting of 75 to 94.9% by weight of 14 alkyl (meth) acrylate is laminated. Double sided acrylic adhesive tape.