WO2017126135A1

WO2017126135A1 - Double-sided adhesive tape

Info

Publication number: WO2017126135A1
Application number: PCT/JP2016/059895
Authority: WO
Inventors: 徳之内田; 勇樹岩井
Original assignee: 積水化学工業株式会社
Priority date: 2016-01-21
Filing date: 2016-03-28
Publication date: 2017-07-27
Also published as: CN107709495A; JPWO2017126135A1; KR20180101316A; JP6687515B2

Abstract

The purpose of the present invention is to provide a double-sided adhesive tape of excellent shear adhesive strength to be used for adhesion and fixing of parts configuring portable electronic devices, adhesion and fixing of car components, etc. The present invention is a double-sided adhesive tape with an acrylic adhesive layer on both surfaces of a substrate, wherein: the substrate is made of foam and the interlayer strength thereof is 10 N/5 mm to 30 N/5 mm; and for at least one of the acrylic adhesive layers, storage modulus G' at 20°C is at least 2.5 × 10⁵ Pa and the loss modulus G" at 20°C is at least 2 × 10⁵ Pa.

Description

Double-sided adhesive tape

The present invention relates to a double-sided pressure-sensitive adhesive tape excellent in shearing adhesive force, which is used for adhesive fixing of parts constituting portable electronic devices, adhesive fixing of automobile members, and the like.

Mobile electronic devices such as mobile phones and personal information terminals (Personal Digital Assistants, PDAs) are designed so that they do not come off or break even if an impact is applied in consideration of falling from the user's hand to the foot. Fixed arrangements or device body designs are being considered. Therefore, a double-sided pressure-sensitive adhesive tape that is used for fixing the component to the main body of the device is desired to prevent the component from coming off even when an impact is applied, and not to apply a strong shock to the component. ing.

For example, a double-sided pressure-sensitive adhesive tape having a base material made of a polyolefin foam has been studied as an impact absorbing tape for fixing a component constituting a portable electronic device to the device body.
In

Patent Documents

1 and 2, an acrylic pressure-sensitive adhesive layer is laminated and integrated on at least one surface of a base material layer, and the base material layer has a specific cross-linking degree and a foam aspect ratio. A shock absorbing tape is described.

In addition, double-sided pressure-sensitive adhesive tapes are also used for fixing automobile members (for example, in-vehicle panels) to the automobile body, and as such double-sided pressure-sensitive adhesive tapes, a base made of a polyolefin foam having excellent shock absorbing performance is also used. A double-sided adhesive tape having a material is used.

In recent years, in applications such as adhesive fixing of parts in large-sized portable electronic devices and adhesive fixing of automobile members, it is necessary to bond heavy parts or members, and the load on the double-sided adhesive tape in the shearing direction has increased. ing. For this reason, the conventional double-sided pressure-sensitive adhesive tape has a problem that it cannot withstand such a large load in the shearing direction and peels off.

JP 2009-242541 A JP 2009-258274 A

An object of this invention is to provide the double-sided adhesive tape excellent in the shear adhesive force used for the adhesion fixation of the components which comprise a portable electronic device, the adhesion fixation of a motor vehicle member, etc.

The present invention is a double-sided pressure-sensitive adhesive tape having an acrylic pressure-sensitive adhesive layer on both surfaces of a substrate, wherein the substrate is made of a foam, and has an interlayer strength of 10 N / 5 mm or more and 30 N / 5 mm or less. The acrylic pressure-sensitive adhesive layer is a double-sided pressure-sensitive adhesive tape having a storage elastic modulus G ′ at 20 ° C. of 2.5 × 10 ⁵ Pa or more and a loss elastic modulus G ″ at 20 ° C. of 2 × 10 ⁵ Pa or more.
The present invention is described in detail below.

In the double-sided pressure-sensitive adhesive tape having the acrylic pressure-sensitive adhesive layer on both surfaces of the substrate, the inventors adjusted the storage elastic modulus G ′ and loss elastic modulus G ″ of the acrylic pressure-sensitive adhesive layer at 20 ° C. to a specific range, It has been found that the acrylic pressure-sensitive adhesive layer has an appropriate hardness, and an excellent shear adhesive strength can be obtained.However, when the base material is a foam, the base material can withstand a load in the shear direction. On the other hand, the inventor of the present invention prevents such interlayer breakdown of the base material by adjusting the interlayer strength of the base material to a specific range. The present inventors have found that the present invention can be accomplished and have completed the present invention.

The double-sided pressure-sensitive adhesive tape of the present invention has a base material made of a foam. Although the said foam will not be specifically limited if it is a foam in which the bubble exists in resin, A polyolefin foam is preferable.

The base material has an interlayer strength of 10 N / 5 mm or more and 30 N / 5 mm or less.
By adjusting the interlaminar strength of the base material to the above range, the double-sided adhesive tape that prevents the base material from being able to withstand the load in the shearing direction and causing fracture (interlaminar fracture) and having excellent shear adhesive strength Can be obtained.

When the interlayer strength of the substrate is less than 10 N / 5 mm, when a load in a large shearing direction is applied to the double-sided pressure-sensitive adhesive tape, the interlayer fracture of the substrate occurs. The interlayer strength of the substrate is preferably 15 N / 5 mm or more.
When the interlayer strength of the substrate exceeds 30 N / 5 mm, the flexibility of the substrate is impaired. The interlayer strength of the substrate is preferably 20 N / 5 mm or less.
The interlayer strength of the substrate can be measured as follows. In FIG. 1, the schematic diagram which shows the measuring method of the interlayer intensity | strength of a base material is shown.
As shown in FIG. 1, an adhesive (not shown) is applied to both sides of a substrate (width 5 mm) 1 to a thickness of 50 μm, and one side of this substrate is lined with a PET film having a thickness of 23 μm (illustration). No), the other surface is bonded to the SUS plate 2 and cured for 48 hours to prepare a test sample. Next, the base material 1 is peeled off at a speed of 100 m / min in the 180 ° direction at 23 ° C. and 50% RH, and the peel strength when the base material 1 causes interlaminar fracture is defined as the interlayer strength.
The interlayer strength of the base material can be adjusted to a desired range by the density of the base material, the expansion ratio, the degree of crosslinking, and the stretch ratio.

Although the thickness of the said base material is not specifically limited, A preferable minimum is 80 micrometers and a preferable upper limit is 300 micrometers. When the thickness of the base material is less than 80 μm, the strength of the base material may be reduced, and the base material may be easily broken between layers, or the impact resistance of the double-sided pressure-sensitive adhesive tape may be reduced. If the thickness of the base material exceeds 300 μm, the flexibility of the base material may be reduced and the impact resistance of the double-sided pressure-sensitive adhesive tape may be reduced, and the total thickness of the double-sided pressure-sensitive adhesive tape may be increased. It may not be suitable for applications such as adhesive fixing of components to be configured, and adhesive fixing of automobile members. The minimum with more preferable thickness of the said base material is 100 micrometers, and a more preferable upper limit is 200 micrometers.

The density of the base material is preferably 0.35 g / cm ³ or more and 0.7 g / cm ³ or less. When the density of the base material is 0.35 g / cm ³ or more, even when a load in a large shear direction is applied to the double-sided pressure-sensitive adhesive tape, interlaminar fracture of the base material hardly occurs. Density is more preferably 0.45 g / cm ³ or more of the substrate, 0.5 g / cm ³ or more is more preferable.
When the density of the substrate is 0.7 g / cm ³ or less, the impact resistance of the double-sided pressure-sensitive adhesive tape can be further increased. A more preferable upper limit of the density of the base material is 0.6 g / cm ³ .
The density of the substrate can be measured and calculated using an electronic hydrometer (trade name “ED120T”) manufactured by Mirage in accordance with JISK-6767.

As for the foaming ratio of the base material, a preferable lower limit is 1.2 times and a preferable upper limit is 2.8 times. When the expansion ratio of the base material is 1.2 times or more, the flexibility and impact resistance of the double-sided pressure-sensitive adhesive tape can be improved. Since the foaming ratio of the base material is 2.8 times or less, the base material can not withstand a load in the shearing direction and is prevented from being broken (interlaminar fracture), and both surfaces have excellent shear adhesive strength. An adhesive tape can be obtained. The more preferable lower limit of the foaming ratio of the substrate is 1.4 times, the more preferable upper limit is 2.2 times, the more preferable lower limit is 1.7 times, and the more preferable upper limit is 2 times.
The expansion ratio of the substrate can be calculated from the reciprocal of the density of the substrate.

As a method for producing a base material made of a foam having an interlayer strength of 10 N / 5 mm or more and 30 N / 5 mm or less, a conventionally known method such as foaming after crosslinking a resin composition as a raw material as necessary The method can be used.
Specifically, for example, when the substrate is a polyolefin resin composition, it can be produced by a method having the following steps (1) to (3).
Step (1): Polyolefin resin composition, which is made into a sheet by supplying a polyolefin resin, a pyrolytic foaming agent, and other additives to an extruder, melt-kneading, and extruding the sheet from the extruder Step (2) for obtaining a product Step (3) for crosslinking the sheet-shaped polyolefin resin composition Step (3): Heating the cross-linked sheet-shaped polyolefin resin composition to foam a pyrolytic foaming agent And a step of stretching in either or both of the MD direction and the TD direction. In addition to this method, the method described in International Publication No. 2005/007731 is a method for producing a crosslinked polyolefin resin foam. Can also be manufactured.

Examples of the polyolefin resin in the step (1) include a polyethylene resin, a polypropylene resin, or a mixture thereof.
The polyethylene resin may be an ethylene homopolymer, but is preferably a polyethylene-α-olefin copolymer obtained by copolymerizing ethylene and a small amount of α-olefin, and among them, Linear low density polyethylene is more preferable. By making the polyethylene resin a copolymer of ethylene and a small amount of α-olefin, the flexibility of the foam can be increased and the impact resistance can be further improved.

Examples of the α-olefin in the polyethylene-α-olefin copolymer include propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, and 1-octene. Can be mentioned. Of these, α-olefins having 4 to 10 carbon atoms are preferable.
The preferable lower limit of the α-olefin in the polyethylene-α-olefin copolymer is 30% by weight, and the more preferable lower limit is 10% by weight.

As the polyethylene resin, an ethylene-vinyl acetate copolymer is also preferable. The ethylene-vinyl acetate copolymer is a copolymer containing 50% by weight or more of a structural unit derived from ethylene.

The polyethylene-based resin preferably has a low density from the viewpoint of enhancing the flexibility of the foam and enhancing the impact resistance. The density of the polyethylene resin is preferably from 0.920 g / cm ³ or less, more preferably 0.880 ~ 0.915g / cm ^3, more preferably 0.885 ~ 0.910g / cm ^3.
The density is a value measured according to ASTM D792.

Examples of the polypropylene resin include a propylene homopolymer, a propylene-α-olefin copolymer containing 50% by weight or more of a structural unit derived from propylene, and the like. These may be used alone or in combination of two or more.
Examples of the α-olefin in the propylene-α-olefin copolymer include ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene and the like. It is done. Among these, α-olefins having 6 to 12 carbon atoms are preferable.

From the viewpoint of improving flexibility and impact absorption, the polyolefin resin is a polyethylene resin, a polypropylene resin polymerized by using a metallocene compound, a Ziegler-Natta compound, a chromium oxide compound or the like as a catalyst, or these Preferably, it is a linear low density polyethylene.

The metallocene compound is preferably a compound such as a bis (cyclopentadienyl) metal complex having a structure in which a transition metal is sandwiched between π-electron unsaturated compounds. Specifically, for example, a tetravalent transition metal such as titanium, zirconium, nickel, palladium, hafnium, and platinum has one or more cyclopentadienyl rings or analogs thereof as a ligand (ligand). The compound which exists is mentioned.
Such metallocene compounds have uniform active site properties and each active site has the same activity. As a result, the polymer synthesized using the above metallocene compound has high uniformity in molecular weight, molecular weight distribution, composition, composition distribution, etc., and thus when a sheet containing a polymer synthesized using the above metallocene compound is crosslinked. In this case, the crosslinking proceeds uniformly. Since the uniformly crosslinked sheet is easily stretched uniformly, the thickness of the crosslinked polyolefin resin foam is easily uniformed.

Examples of the ligand include cyclic compounds such as a cyclopentadienyl ring and an indenyl ring. The cyclic compound may have a substituent such as a hydrocarbon group, a substituted hydrocarbon group, or a hydrocarbon-substituted metalloid group. Examples of the hydrocarbon group include a methyl group, an ethyl group, various propyl groups, various butyl groups, various amyl groups, various hexyl groups, 2-ethylhexyl groups, various heptyl groups, various octyl groups, various nonyl groups, and various decyl groups. Groups, various cetyl groups, phenyl groups and the like. Here, “various” means various isomers such as n-, sec-, tert-, iso- and the like.
Moreover, what polymerized the said cyclic compound as an oligomer may be used as a ligand.
In addition to π-electron unsaturated compounds, monovalent anion ligands such as chlorine and bromine, divalent anion chelate ligands, hydrocarbons, alkoxides, arylamides, aryloxides, amides, arylamides, phosphides, aryls Phosphide or the like may be used.

Examples of the metallocene compound containing the tetravalent transition metal and the ligand include, for example, cyclopentadienyl titanium tris (dimethylamide), methylcyclopentadienyl titanium tris (dimethylamide), and bis (cyclopentadienyl) titanium dichloride. And dimethylsilyltetramethylcyclopentadienyl-t-butylamidozirconium dichloride.

The said metallocene compound exhibits the effect | action as a catalyst in the case of superposition | polymerization of various olefins by combining with a specific cocatalyst (promoter). Examples of the cocatalyst include methylaluminoxane (MAO) and boron compounds. The use ratio of the cocatalyst to the metallocene compound is preferably 100,000 to 1,000,000 mole times, more preferably 50 to 5,000 mole times.

When a polyethylene resin obtained by using the metallocene compound as a catalyst, an ethylene-vinyl acetate copolymer, or a mixture thereof is used, the content is preferably 40% by weight or more of the total polyolefin resin, % By weight or more is more preferable, 60% by weight or more is more preferable, and 100% by weight is particularly preferable. When the polyolefin foam is thin because the content of the polyethylene resin, ethylene-vinyl acetate copolymer, or mixture thereof obtained by using the metallocene compound as a catalyst is 40% by weight or more Even so, a high compressive strength can be obtained.

The Ziegler-Natta compound is a triethylaluminum-titanium tetrachloride solid composite, which is obtained by reducing titanium tetrachloride with an organoaluminum compound and then treating with various electron donors and electron acceptors. A method of combining a titanium composition, an organoaluminum compound and an aromatic carboxylic acid ester (see JP-A 56-1000080, JP-A 56-120712, JP-A 58-104907), Method of supported catalyst in which titanium tetrachloride and various electron donors are brought into contact with magnesium halide (see JP-A-57-63310, JP-A-63-43915, JP-A-63-83116) It is preferable to use what was manufactured by the above.

The said polyolefin resin composition may contain arbitrary components, such as resin other than the polyolefin resin mentioned above.
As said arbitrary component, resin other than polyolefin resin and rubber | gum are mentioned. The total content of these optional components is preferably less than that of the polyolefin resin. Specifically, the content is preferably 50 parts by weight or less and 100 parts by weight or less with respect to 100 parts by weight of the polyolefin resin. Is more preferable.

The pyrolytic foaming agent is not particularly limited, and examples thereof include azodicarbonamide, N, N′-dinitrosopentamethylenetetramine, p-toluenesulfonyl semicarbazide, and among them, azodicarbonamide is preferable. The said thermal decomposition type foaming agent may be used independently and may be used in combination of 2 or more type.

The content of the pyrolytic foaming agent is preferably 1 to 12 parts by weight, more preferably 1 to 8 parts by weight, based on 100 parts by weight of the polyolefin resin. When the content of the pyrolytic foaming agent is within the above range, the foamability of the polyolefin resin composition is improved, and it becomes easier to obtain a polyolefin resin foam having a desired expansion ratio and interlayer strength. , Tensile strength and compression recovery can be improved.

Examples of the other additives include a decomposition temperature adjusting agent, a crosslinking aid, and an antioxidant.
The said decomposition temperature regulator is mix | blended as what adjusts the surface state etc. of a foam by lowering | hanging the decomposition temperature of a thermal decomposition type foaming agent, or accelerating | stimulating a decomposition speed. Examples of the decomposition temperature adjusting agent include zinc oxide, zinc stearate, urea and the like.
The content of the decomposition temperature adjusting agent with respect to 100 parts by weight of the polyolefin resin is preferably 0.01 to 5 parts by weight.

The crosslinking aid is added to the polyolefin resin to reduce the amount of ionizing radiation irradiated in the crosslinking of the polyolefin resin, which will be described later, and to prevent the resin molecules from being cut and deteriorated by the irradiation of the ionizing radiation. Is blended into.
As said crosslinking adjuvant, a polyfunctional monomer etc. are mentioned, for example. Specifically, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, trimellitic acid triallyl ester, 1,2,4-benzenetricarboxylic acid triallyl ester, triallyl isocyanurate, etc. Compounds having functional groups and compounds having two functional groups in one molecule such as 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, 1,10-decanediol dimethacrylate, divinylbenzene, etc. , Diallyl phthalate, diallyl terephthalate, diallyl isophthalate, ethyl vinyl benzene, neopentyl glycol dimethacrylate, lauryl methacrylate, stearyl methacrylate and the like.
These crosslinking aids may be used alone or in combination of two or more.

The addition amount of the crosslinking aid is preferably 0.2 to 10 parts by weight, more preferably 0.3 to 5 parts by weight, and still more preferably 0.5 to 5 parts by weight with respect to 100 parts by weight of the polyolefin resin. When the addition amount of the crosslinking aid is 0.2 parts by weight or more, a foam having a desired degree of crosslinking can be stably obtained. When the addition amount of the crosslinking aid is 10 parts by weight or less, the degree of crosslinking of the foam can be easily controlled.

The antioxidant is blended to prevent oxidative deterioration due to heat. Examples of the antioxidant include phenolic antioxidants such as 2,6-di-t-butyl-p-cresol.

In the step (2), examples of the method of crosslinking the polyolefin resin composition include a method of irradiating the polyolefin resin composition with ionizing radiation such as electron beam, α ray, β ray, γ ray, Examples include a method in which an organic peroxide is blended in advance when forming the resin composition, and then the organic peroxide is decomposed by heating the polyolefin resin composition. These methods may be used alone or in combination of two or more. From the viewpoint of homogeneous crosslinking, a method of irradiating ionizing radiation is preferable.

The dose of ionizing radiation in the method of irradiating with ionizing radiation is preferably adjusted so that the gel fraction is 5 to 45% by weight. A specific irradiation amount is preferably 0.5 to 20 Mrad, and more preferably 3 to 12 Mrad.

Examples of the organic peroxide in the method of previously blending the organic peroxide with the resin composition include 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, 1,1- Examples thereof include bis (t-butylperoxy) cyclohexane. These may be used alone or in combination of two or more.
The amount of the organic peroxide added 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 polyolefin resin. When the addition amount of the organic peroxide is within the above range, the crosslinking of the resin composition is likely to proceed, and the amount of decomposition residue of the organic peroxide present in the obtained polyolefin foam is suppressed. be able to.

In the step (3), the method of foaming the polyolefin resin composition is not particularly limited. For example, the method of heating the polyolefin resin composition with hot air, the method of heating with infrared rays, the method of heating with a salt bath, the oil bath The method of heating by, etc. are mentioned, These may be used together.
In addition, the foaming method of a polyolefin-type resin composition is not limited to the method of using a thermal decomposition type foaming agent, You may use physical foaming by a butane gas etc.

In the step (3), as a method of stretching the polyolefin resin composition, the polyolefin resin composition is foamed to obtain a foam, and then stretched, or the polyolefin resin composition is stretched while being foamed. Methods and the like. In addition, when foaming a polyolefin-based resin composition to obtain a foam, it is preferable to stretch the foam while maintaining the molten state at the time of foaming without cooling the foam. However, the foam may be stretched after the cooled foam is heated again to a molten or softened state.

The draw ratio in the MD direction of the polyolefin-based resin composition is preferably 1.1 to 3.0 times, and more preferably 1.7 to 2.8 times. By setting the draw ratio in the MD direction of the polyolefin resin composition to the above lower limit value or more, the flexibility and tensile strength of the polyolefin resin composition are likely to be good. Further, by setting the draw ratio to the upper limit value or less, it is possible to prevent the base material from being broken during the drawing, or the foaming gas to escape from the foaming resin composition and the foaming ratio to be lowered. Flexibility and tensile strength are improved, and quality is easily uniform. In addition, the polyolefin resin composition may be stretched in the TD direction at a stretching ratio in the above range. Here, the MD direction (Machine Direction) is used when extruding a polyolefin foam into a sheet shape. The direction of extrusion refers to the TD direction (Transverse Direction) refers to the direction perpendicular to the MD direction.

Among the acrylic pressure-sensitive adhesive layers, at least one acrylic pressure-sensitive adhesive layer has a storage elastic modulus G ′ at 20 ° C. of 2.5 × 10 ⁵ Pa or more and a loss elastic modulus G ″ at 20 ° C. of 2 × 10 ⁵ Pa or more. It is.
By adjusting the storage elastic modulus G ′ and loss elastic modulus G ″ at 20 ° C. of the acrylic pressure-sensitive adhesive layer to the above ranges, the acrylic pressure-sensitive adhesive layer has an appropriate hardness, and has excellent shear adhesive strength. In the double-sided pressure-sensitive adhesive tape of the present invention, if at least one acrylic pressure-sensitive adhesive layer has a storage elastic modulus G ′ and a loss elastic modulus G ″ within the above range, double-sided acrylic pressure-sensitive adhesive is used. The layers may have the same composition or different compositions.

When the storage elastic modulus G ′ at 20 ° C. is less than 2.5 × 10 ⁵ Pa, the shear adhesive strength of the double-sided pressure-sensitive adhesive tape decreases, and when a large load in the shear direction is applied, the double-sided pressure-sensitive adhesive tape peels off. The storage elastic modulus G ′ at 20 ° C. is preferably 4.0 × 10 ⁵ Pa or more, and more preferably 6.0 × 10 ⁵ Pa or more.
The upper limit of the storage elastic modulus G ′ at 20 ° C. is not particularly limited, but if it is too high, the tackiness of the acrylic pressure-sensitive adhesive layer may be lost, and the initial adhesiveness may be lowered. 10 ⁶ Pa, and a more preferable upper limit is 3.0 × 10 ⁶ Pa.

When the loss elastic modulus G ″ at 20 ° C. is less than 2 × 10 ⁵ Pa, the shear adhesive strength of the double-sided pressure-sensitive adhesive tape decreases, and the double-sided pressure-sensitive adhesive tape peels off when a large load in the shear direction is applied. The loss elastic modulus G ″ at ° C. is preferably 4.0 × 10 ⁵ Pa or more, and more preferably 6.0 × 10 ⁵ Pa or more.
The upper limit of the loss elastic modulus G ″ at 20 ° C. is not particularly limited. However, if it is too high, the tackiness of the acrylic pressure-sensitive adhesive layer is lost and the initial adhesiveness may be lowered. 10 ⁶ Pa, and a more preferable upper limit is 3.0 × 10 ⁶ Pa.

The storage elastic modulus G ′ and loss elastic modulus G ″ at 20 ° C. were measured using a dynamic viscoelasticity measuring device (for example, DVA-200 manufactured by IT Measurement Control Co., Ltd.) at a frequency of 10 Hz and a heating rate of 3 ° C. It can be obtained by measuring from −40 ° C. to 140 ° C. at / min and reading storage elastic modulus G ′ and loss elastic modulus G ″ at 20 ° C.

As a method for adjusting the storage elastic modulus G ′ and loss elastic modulus G ″ at 20 ° C. of the acrylic pressure-sensitive adhesive layer to the intended ranges, for example, the composition, weight average molecular weight, molecular weight distribution, etc. of the acrylic copolymer are adjusted. Methods, methods of mixing acrylic copolymers of different compositions, weight average molecular weight, molecular weight distribution, etc., methods of adjusting the softening point, content, etc. of tackifying resins, methods of adjusting the degree of crosslinking of the acrylic pressure-sensitive adhesive layer, etc. Is mentioned.

The acrylic copolymer constituting the acrylic pressure-sensitive adhesive layer is preferably obtained by copolymerizing a monomer mixture containing butyl acrylate and 2-ethylhexyl acrylate.
The preferred content of butyl acrylate in the total monomer mixture is 40 to 80% by weight. When the content of butyl acrylate is less than 40% by weight, the acrylic pressure-sensitive adhesive layer becomes too soft and the cohesive force may be reduced, and the shear adhesive force of the double-sided pressure-sensitive adhesive tape may be reduced. When the content of butyl acrylate exceeds 80% by weight, the acrylic pressure-sensitive adhesive layer becomes hard and the adhesive strength or tack may decrease, and the shear adhesive strength of the double-sided adhesive tape may decrease.
The preferred content of 2-ethylhexyl acrylate in the total monomer mixture is 10 to 40% by weight. If the content of 2-ethylhexyl acrylate is less than 10% by weight, the adhesive strength of the acrylic pressure-sensitive adhesive layer may be reduced, and the shear adhesive strength of the double-sided pressure-sensitive adhesive tape may be reduced. When the content of 2-ethylhexyl acrylate exceeds 40% by weight, the acrylic pressure-sensitive adhesive layer becomes too soft and the cohesive strength is lowered, and the shear pressure-sensitive adhesive strength of the double-sided pressure-sensitive adhesive tape may be lowered.

The monomer mixture may contain other copolymerizable monomers other than butyl acrylate and 2-ethylhexyl acrylate as necessary.
Examples of other polymerizable monomers that can be copolymerized include, for example, carbon number of alkyl groups such as methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, and isopropyl (meth) acrylate. (Meth) acrylic acid alkyl ester having 1 to 3 carbon atoms, such as (meth) acrylic acid alkyl ester, tridecyl methacrylate, stearyl (meth) acrylate, and the like, and (meth) acrylic acid hydroxyalkyl And functional monomers such as glycerin dimethacrylate, glycidyl (meth) acrylate, 2-methacryloyloxyethyl isocyanate, (meth) acrylic acid, itaconic acid, maleic anhydride, crotonic acid, maleic acid and fumaric acid.

In order to copolymerize the monomer mixture to obtain the acrylic copolymer, the monomer mixture may be radically reacted in the presence of a polymerization initiator. As a method of radical reaction of the monomer mixture, that is, a polymerization method, a conventionally known method is used, and examples thereof include solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, bulk polymerization and the like.
The said polymerization initiator is not specifically limited, For example, an organic peroxide, an azo compound, etc. are mentioned. Examples of the organic peroxide include 1,1-bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane, t-hexylperoxypivalate, t-butylperoxypivalate, 2,5 -Dimethyl-2,5-bis (2-ethylhexanoylperoxy) hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxy Examples include isobutyrate, t-butylperoxy-3,5,5-trimethylhexanoate, and t-butylperoxylaurate. Examples of the azo compound include azobisisobutyronitrile and azobiscyclohexanecarbonitrile. These polymerization initiators may be used alone or in combination of two or more.

As for the weight average molecular weight (Mw) of the said acrylic copolymer, a preferable minimum is 400,000 and a preferable upper limit is 1 million. When the weight average molecular weight is less than 400,000, the cohesive force of the acrylic pressure-sensitive adhesive layer may be reduced, and the shear adhesive force of the double-sided pressure-sensitive adhesive tape may be reduced. When a weight average molecular weight exceeds 1 million, the adhesive force of the said acrylic adhesive layer may fall, and the shear adhesive force of a double-sided adhesive tape may fall. A more preferable lower limit of the weight average molecular weight is 500,000, and a more preferable upper limit is 700,000.
In order to adjust the weight average molecular weight within the above range, polymerization conditions such as a polymerization initiator and a polymerization temperature may be adjusted.
In addition, a weight average molecular weight (Mw) is a weight average molecular weight of standard polystyrene conversion by GPC (Gel Permeation Chromatography: gel permeation chromatography).

The acrylic pressure-sensitive adhesive layer may contain a tackifier resin.
Examples of the tackifier resins include rosin ester resins, hydrogenated rosin resins, terpene resins, terpene phenol resins, coumarone indene resins, alicyclic saturated hydrocarbon resins, C5 petroleum resins, and C9 resins. Examples include petroleum resins and C5-C9 copolymer petroleum resins. These tackifying resins may be used alone or in combination of two or more.

Although content of the said tackifying resin is not specifically limited, The preferable minimum with respect to 100 weight part of said acrylic copolymers is 10 weight part, and a preferable upper limit is 60 weight part. When the content of the tackifying resin is less than 10 parts by weight, the adhesive strength of the acrylic pressure-sensitive adhesive layer may be reduced, and the shear adhesive strength of the double-sided pressure-sensitive adhesive tape may be reduced. When the content of the tackifying resin exceeds 60 parts by weight, the acrylic pressure-sensitive adhesive layer is hardened, the adhesive strength or tack may be reduced, and the shear adhesive strength of the double-sided adhesive tape may be reduced.

In the acrylic pressure-sensitive adhesive layer, a crosslinking structure is formed between the main chains of the resin (the acrylic copolymer and / or the tackifying resin) constituting the acrylic pressure-sensitive adhesive layer by adding a crosslinking agent. It is preferable.
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. Of these, isocyanate-based crosslinking agents are preferred. By adding an isocyanate-based crosslinking agent to the acrylic pressure-sensitive adhesive layer, the isocyanate group of the isocyanate-based cross-linking agent reacts with the alcoholic hydroxyl group in the resin constituting the acrylic pressure-sensitive adhesive layer, and the acrylic pressure-sensitive adhesive layer. The cross-linking becomes loose. Accordingly, the acrylic pressure-sensitive adhesive layer can disperse the intermittently applied peeling stress, and the shear adhesive strength of the double-sided pressure-sensitive adhesive tape is further improved.
The addition amount of the crosslinking agent is preferably 0.01 to 10 parts by weight and more preferably 0.1 to 3 parts by weight with respect to 100 parts by weight of the acrylic copolymer.

The degree of cross-linking of the acrylic pressure-sensitive adhesive layer is preferably 5 to 40% by weight, because it may be easily peeled off from the adherend when a load in a large shear direction is applied, whether it is too high or too low. More preferred is 40% by weight, and particularly preferred is 15 to 35% by weight.
The degree of cross-linking of the acrylic pressure-sensitive adhesive layer was determined by taking W1 (g) of the acrylic pressure-sensitive adhesive layer and immersing this acrylic pressure-sensitive adhesive layer in ethyl acetate at 23 ° C. for 24 hours to make the insoluble matter 200 mesh wire mesh. The residue on the wire mesh is vacuum-dried, and the weight W2 (g) of the dried residue is measured, and calculated by the following formula (1).
Crosslinking degree (% by weight) = 100 × W2 / W1 (1)

The thickness of the acrylic pressure-sensitive adhesive layer is not particularly limited, but the thickness of the single-sided acrylic pressure-sensitive adhesive layer is preferably 10 to 100 μm. When the thickness of the acrylic pressure-sensitive adhesive layer is less than 10 μm, the impact resistance or shear adhesive strength of the double-sided pressure-sensitive adhesive tape may be lowered. When the thickness of the acrylic pressure-sensitive adhesive layer exceeds 100 μm, the reworkability or removability of the double-sided pressure-sensitive adhesive tape may be impaired.

The double-sided pressure-sensitive adhesive tape of the present invention preferably has a total thickness of 50 to 400 μm. If the total thickness of the double-sided pressure-sensitive adhesive tape is less than 50 μm, the impact resistance or shear adhesive strength of the double-sided pressure-sensitive adhesive tape may be lowered. If the total thickness of the double-sided pressure-sensitive adhesive tape exceeds 400 μm, it may not be suitable for applications such as adhesive fixing of parts constituting portable electronic devices and adhesive fixing of automobile members. The minimum with more preferable total thickness of a double-sided adhesive tape is 100 micrometers, and a more preferable upper limit is 300 micrometers.

As a manufacturing method of the double-sided adhesive tape of this invention, the following methods are mentioned, for example.
First, a solution of an adhesive A is prepared by adding a solvent to an acrylic copolymer, a tackifier resin, and a cross-linking agent as necessary, and the solution of the adhesive A is applied to the surface of the substrate. The acrylic adhesive layer A is formed by completely removing and removing the solvent. Next, a release film is overlaid on the formed acrylic pressure-sensitive adhesive layer A so that the release treatment surface faces the acrylic pressure-sensitive adhesive layer A.
Next, a release film different from the above release film is prepared, the adhesive B solution is applied to the release treatment surface of the release film, and the solvent in the solution is completely removed by drying, thereby releasing the release film. A laminated film in which the acrylic pressure-sensitive adhesive layer B is formed on the surface of the mold film is produced. The obtained laminated film is superposed on the back surface of the base material on which the acrylic pressure-sensitive adhesive layer A is formed, with the acrylic pressure-sensitive adhesive layer B facing the back surface of the base material to produce a laminate. Then, by pressing the laminate with a rubber roller or the like, a double-sided pressure-sensitive adhesive tape having an acrylic pressure-sensitive adhesive layer on both surfaces of the base material and having the surface of the acrylic pressure-sensitive adhesive layer covered with a release film can be obtained. it can.

In addition, two sets of laminated films are produced in the same manner, and a laminated body is produced by superposing these laminated films on both sides of the base material with the acrylic adhesive layer of the laminated film facing the base material. Then, by pressing this laminate with a rubber roller or the like, a double-sided pressure-sensitive adhesive tape having an acrylic pressure-sensitive adhesive layer on both surfaces of the base material and the surface of the acrylic pressure-sensitive adhesive layer covered with a release film can be obtained. Good.

Although the use of the double-sided pressure-sensitive adhesive tape of the present invention is not particularly limited, it can be used for bonding and fixing parts constituting a portable electronic device to the device main body, and can be used for bonding and fixing an automobile member to the vehicle main body. preferable. Specifically, the double-sided pressure-sensitive adhesive tape of the present invention can be used for adhesive fixing of components in large-sized portable electronic devices, adhesive fixing of automobile members (for example, in-vehicle panels), and the like.
The shape of the double-sided pressure-sensitive adhesive tape of the present invention in these applications is not particularly limited, and examples thereof include a rectangle, a frame shape, a circle, an ellipse, and a donut shape.

ADVANTAGE OF THE INVENTION According to this invention, the double-sided adhesive tape excellent in the shear adhesive force used for the adhesion fixation of the components which comprise a portable electronic device, the adhesion fixation of a motor vehicle member, etc. can be provided.

It is a schematic diagram which shows the measuring method of the interlayer intensity | strength of a base material. It is a schematic diagram which shows the measuring method of the shear adhesive force of a double-sided adhesive tape.

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

(Preparation of adhesive (A))
A reactor equipped with a thermometer, a stirrer, and a condenser tube is 70 parts by weight of butyl acrylate, 27 parts by weight of 2-ethylhexyl acrylate, 3 parts by weight of acrylic acid, 0.2 parts by weight of 2-hydroxyethyl acrylate, and 80 parts by weight of ethyl acetate. After adding nitrogen and replacing with nitrogen, the reactor was heated to start refluxing. Subsequently, 0.1 part by weight of azobisisobutyronitrile was added as a polymerization initiator in the reactor. The solution was refluxed at 70 ° C. for 5 hours to obtain a solution of the acrylic copolymer (a). When the weight average molecular weight of the obtained acrylic copolymer (a) was measured by a GPC method using “2690 Separations Model” manufactured by Water as a column, it was 710,000.
15 parts by weight of a polymerized rosin ester having a softening point of 150 ° C. and a terpene having a softening point of 145 ° C. with respect to 100 parts by weight of the solid content of the acrylic copolymer (a) contained in the resulting solution of the acrylic copolymer (a) 10 parts by weight of phenol, 10 parts by weight of rosin ester having a softening point of 70 ° C., 125 parts by weight of ethyl acetate (Fuji Chemical Co., Ltd.), 2.2 parts of isocyanate crosslinking agent (trade name “Coronate L45” manufactured by Nippon Polyurethane Co., Ltd.) Part was added and stirred to obtain an adhesive (A).

(Preparation of adhesive (B))
Similar to the adhesive (A) except that 15 parts by weight of polymerized rosin ester having a softening point of 130 ° C., 10 parts by weight of terpene phenol having a softening point of 130 ° C., and 10 parts by weight of rosin ester having a softening point of 100 ° C. were used as the tackifier resin. Thus, a pressure-sensitive adhesive (B) was obtained.

(Preparation of adhesive (C))
Similar to the adhesive (A) except that 12 parts by weight of polymerized rosin ester having a softening point of 130 ° C., 10 parts by weight of terpene phenol having a softening point of 150 ° C., and 10 parts by weight of rosin ester having a softening point of 100 ° C. were used as the tackifier resin. Thus, a pressure-sensitive adhesive (C) was obtained.

(Preparation of adhesive (D))
An acrylic copolymer having a weight average molecular weight of 670,000 was changed in the same manner as the acrylic copolymer (a) except that the addition amount of 2-ethylhexyl acrylate was changed to 20 parts by weight and 7 parts by weight of ethyl acrylate was further added. A solution of (c) was obtained.
Use of the resulting acrylic copolymer (c) solution, 15 parts by weight of polymerized rosin ester having a softening point of 150 ° C., 10 parts by weight of terpene phenol having a softening point of 130 ° C., and rosin having a softening point of 70 ° C. A pressure-sensitive adhesive (D) was obtained in the same manner as the pressure-sensitive adhesive (A) except that 10 parts by weight of the ester was used.

(Preparation of adhesive (E))
The weight average molecular weight of 75 was changed in the same manner as in the acrylic copolymer (a) except that the amount of 2-ethylhexyl acrylate was changed to 15 parts by weight and that 7 parts by weight of ethyl acrylate and 5 parts by weight of vinyl acetate were further added. A solution of 10,000 acrylic copolymer (d) was obtained.
Use of the resulting solution of acrylic copolymer (d), 10 parts by weight of polymerized rosin ester having a softening point of 130 ° C., 8 parts by weight of terpene phenol having a softening point of 130 ° C., and rosin having a softening point of 70 ° C. A pressure-sensitive adhesive (E) was obtained in the same manner as the pressure-sensitive adhesive (A) except that 6 parts by weight of ester was used.

(Preparation of adhesive (F))
A pressure-sensitive adhesive (F) was obtained in the same manner as the pressure-sensitive adhesive (A) except that 15 parts by weight of a polymerized rosin ester having a softening point of 150 ° C. was used as the tackifier resin.

(Preparation of adhesive (G))
Acrylic copolymer except that the addition amount of 2-ethylhexyl acrylate was changed to 20 parts by weight, 7 parts by weight of ethyl acrylate was added, and the addition amount of azobisisobutyronitrile was changed to 0.05 parts by weight. In the same manner as in the union (a), a solution of the acrylic copolymer (f) having a weight average molecular weight of 1,220,000 was obtained.
Use of the resulting acrylic copolymer (f) solution, 15 parts by weight of a polymerized rosin ester having a softening point of 150 ° C., 10 parts by weight of terpene phenol having a softening point of 150 ° C., and rosin having a softening point of 100 ° C. A pressure-sensitive adhesive (G) was obtained in the same manner as the pressure-sensitive adhesive (A) except that 10 parts by weight of the ester was used.

(Preparation of adhesive (H))
A pressure-sensitive adhesive (H) was obtained in the same manner as the pressure-sensitive adhesive (A) except that 10 parts by weight of a polymerized rosin ester having a softening point of 150 ° C. and 8 parts by weight of a rosin ester having a softening point of 100 ° C. were used as the tackifier resin. .

(Preparation of adhesive (I))
The weight average was changed in the same manner as in the acrylic copolymer (a) except that the amount of butyl acrylate was changed to 77 parts by weight and that 20 parts by weight of methyl methacrylate was added instead of 27 parts by weight of 2-ethylhexyl acrylate. A solution of an acrylic copolymer (h) having a molecular weight of 600,000 was obtained.
A pressure-sensitive adhesive (I) was obtained in the same manner as the pressure-sensitive adhesive (A) except that the obtained acrylic copolymer (h) solution was used and no tackifying resin was used.

(Preparation of adhesive (J))
The weight average was changed in the same manner as in the acrylic copolymer (a) except that the amount of butyl acrylate was changed to 77 parts by weight and that 20 parts by weight of methyl acrylate was added instead of 27 parts by weight of 2-ethylhexyl acrylate. A solution of an acrylic copolymer (h) having a molecular weight of 600,000 was obtained.
Use of the resulting solution of acrylic copolymer (h), 15 parts by weight of polymerized rosin ester having a softening point of 150 ° C., 15 parts by weight of terpene phenol having a softening point of 150 ° C., and rosin having a softening point of 100 ° C. A pressure-sensitive adhesive (J) was obtained in the same manner as the pressure-sensitive adhesive (A) except that 15 parts by weight of ester was used.

(Production of polyolefin foam (A))
100 parts by weight of a linear low density polyethylene (exon chemical company, trade name “Exact3027”, density: 0.900 g / cm ³ ) as a polyolefin-based resin, 2 parts by weight of azodicarbonamide as a thermally decomposable foaming agent, 1 part by weight of zinc oxide as a decomposition temperature adjusting agent and 0.5 part by weight of 2,6-di-t-butyl-p-cresol as an antioxidant are supplied to an extruder and melt-kneaded at 130 ° C., A long sheet-like polyolefin resin composition having a thickness of about 0.3 mm was extruded.
Next, the polyolefin resin composition in the form of a long sheet is cross-linked by irradiating 4.5 Mrad of an electron beam with an acceleration voltage of 500 kV on both sides, and then maintained in a foaming furnace maintained at 250 ° C. with hot air and an infrared heater. Polyolefin foam having a thickness of 0.14 mm by continuously feeding to foam and heating and foaming, and by stretching the foam with a stretch ratio of MD of 1.5 times and a stretch ratio of TD of 2.0 times (A) was obtained. The density and interlayer strength of the obtained foam were measured. The density of the polyolefin foam was measured and calculated using an electronic hydrometer (trade name “ED120T”) manufactured by Mirage in accordance with JISK-6767. The interlayer strength of the polyolefin foam was measured by the measurement method shown in FIG. 1 as described above.

(Manufacture of polyolefin foam (B))
A polyolefin foam (B) was obtained in the same manner as in the production of the polyolefin foam (A) except that the draw ratio of TD was 2.2 times. The density and interlayer strength of the obtained foam were measured.

(Manufacture of polyolefin foam (C))
A polyolefin foam (C) was obtained in the same manner as in the production of the polyolefin foam (A) except that the amount of azodicarbonamide to be blended was 2.2 parts by weight and the draw ratio of TD was 1.8 times. The density and interlayer strength of the obtained foam were measured.

(Manufacture of polyolefin foam (D))
A polyolefin foam (D) was obtained in the same manner as in the production of the polyolefin foam (A) except that the amount of azodicarbonamide to be blended was 1.9 parts by weight and the draw ratio of TD was 1.9 times. The density and interlayer strength of the obtained foam were measured.

(Manufacture of polyolefin foam (E))
A polyolefin foam (E) was obtained in the same manner as in the production of the polyolefin foam (A) except that the amount of azodicarbonamide to be blended was 3 parts by weight and the draw ratio of TD was 3 times. The density and interlayer strength of the obtained foam were measured.

(Manufacture of polyolefin foam (F))
A polyolefin foam (F) was obtained in the same manner as in the production of the polyolefin foam (A) except that the amount of azodicarbonamide to be blended was 2.8 parts by weight and the draw ratio of TD was 2.8 times. The density and interlayer strength of the obtained foam were measured.

Example 1
A release paper having a thickness of 150 μm was prepared, an adhesive (J) was applied to the release-treated surface of the release paper, and dried at 100 ° C. for 5 minutes to form an acrylic adhesive layer having a thickness of 50 μm. This acrylic pressure-sensitive adhesive layer was bonded to the surface of the polyolefin foam (A). Next, in the same manner, the same acrylic pressure-sensitive adhesive layer as above was bonded to the opposite surface of the polyolefin foam. Then, curing was performed by heating at 40 ° C. for 48 hours. This obtained the double-sided adhesive tape of the total thickness shown in Table 1 covered with the 150-micrometer-thick release paper.
The acrylic pressure-sensitive adhesive layer was measured from −40 ° C. to 140 ° C. at a frequency of 10 Hz and a temperature increase rate of 3 ° C./min using a dynamic viscoelasticity measuring device (DVA-200 manufactured by IT Measurement Control). The storage elastic modulus G ′ and loss elastic modulus G ″ at 20 ° C. were read and shown in Table 1.

(Example 2)
Example 1 except that the type of the pressure-sensitive adhesive was changed to the pressure-sensitive adhesive (A), and the acrylic pressure-sensitive adhesive layer having a storage elastic modulus G ′ and a loss elastic modulus G ″ at 20 ° C. shown in Table 1 was changed. Similarly, a double-sided adhesive tape was obtained.

(Example 3)
A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 2 except that the polyolefin foam (B) was changed to one having the density, thickness and interlayer strength shown in Table 1 by changing the type of the polyolefin foam. It was.

Example 4
In the same manner as in Example 3, except that the polyolefin foam was changed to one having the density, thickness and interlayer strength shown in Table 1 by changing the type of polyolefin foam to polyolefin foam (C). An adhesive tape was obtained.

(Example 5)
Example 4 except that the acrylic adhesive layer having the storage elastic modulus G ′ and the loss elastic modulus G ″ at 20 ° C. shown in Table 1 was changed by changing the type of the adhesive to the adhesive (B). Similarly, a double-sided adhesive tape was obtained.

(Example 6)
Example 4 except that the type of the pressure-sensitive adhesive was changed to the pressure-sensitive adhesive (C), and the acrylic pressure-sensitive adhesive layer having a storage elastic modulus G ′ and a loss elastic modulus G ″ at 20 ° C. shown in Table 1 was changed. Similarly, a double-sided adhesive tape was obtained.

(Example 7)
By changing the type of polyolefin foam to polyolefin foam (D), the polyolefin foam is changed to one having the density, thickness and interlayer strength shown in Table 1, and the type of pressure-sensitive adhesive is changed to pressure-sensitive adhesive (D). A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 3 except that the acrylic pressure-sensitive adhesive layer having a storage elastic modulus G ′ and a loss elastic modulus G ″ at 20 ° C. shown in Table 1 was changed.

(Example 8)
By changing the type of polyolefin foam to polyolefin foam (D), the polyolefin foam is changed to one having the density, thickness and interlayer strength shown in Table 1, and the type of pressure-sensitive adhesive is changed to pressure-sensitive adhesive (E). A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 3 except that the acrylic pressure-sensitive adhesive layer having a storage elastic modulus G ′ and a loss elastic modulus G ″ at 20 ° C. shown in Table 1 was changed.

(Comparative Example 1)
By changing the type of polyolefin foam to polyolefin foam (E), the polyolefin foam is changed to one having the density, thickness and interlayer strength shown in Table 2, and the type of pressure-sensitive adhesive is changed to pressure-sensitive adhesive (F). A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 3 except that the acrylic pressure-sensitive adhesive layer having a storage elastic modulus G ′ and a loss elastic modulus G ″ at 20 ° C. shown in Table 2 was changed.

(Comparative Example 2)
Comparative Example 1 with the exception of changing the adhesive type to an adhesive (G) and changing to an acrylic adhesive layer having a storage elastic modulus G ′ and a loss elastic modulus G ″ at 20 ° C. shown in Table 2 Similarly, a double-sided adhesive tape was obtained.

(Comparative Example 3)
By changing the type of the polyolefin foam to the polyolefin foam (F), the polyolefin foam was changed to one having the density, thickness and interlayer strength shown in Table 2, and the both sides were the same as in Comparative Example 1. An adhesive tape was obtained.

(Comparative Example 4)
Example 4 with the exception that the pressure-sensitive adhesive (H) was changed to an acrylic pressure-sensitive adhesive layer having a storage elastic modulus G ′ and a loss elastic modulus G ″ at 20 ° C. shown in Table 2 by changing the type of the pressure-sensitive adhesive. Similarly, a double-sided adhesive tape was obtained.

(Comparative Example 5)
Comparative Example 3 with the exception of changing the type of adhesive to adhesive (I) to an acrylic adhesive layer having storage elastic modulus G ′ and loss elastic modulus G ″ at 20 ° C. shown in Table 2 Similarly, a double-sided adhesive tape was obtained.

<Evaluation>
The following evaluation was performed about the double-sided adhesive tape obtained by the Example and the comparative example. The results are shown in Tables 1 and 2.

(1) Measurement of shear adhesive strength FIG. 2 is a schematic diagram showing a method for measuring the shear adhesive strength of a double-sided adhesive tape.
As shown in FIG. 2, two 2 mm-thick polycarbonate plates (PC plates) 3 are bonded with double-sided adhesive tape (vertical 1 cm × width 1 cm) 4, pressed with 5 kg for 10 seconds, and then allowed to stand at 23 ° C. for 24 hours. Thus, a test piece was prepared. Next, two 20 mm-thick polycarbonate plates (PC plates) 3 having a thickness of 2 mm are peeled off at a rate of 10 mm / min in the shear direction of the double-sided pressure-sensitive adhesive tape 4 (arrow direction in FIG. 2). The maximum value of force was defined as shear adhesive strength.
Where shear adhesive strength was 175 N / cm ² or more ◎, 100 N / cm ² or more, the case was less than 175 N / cm ² ○, was determined as × when was less than 100 N / cm ^2. Moreover, the peeling state was observed and it was evaluated whether peeling mode was interface peeling or delamination.

1 Base material 2 SUS plate 3 2 mm thick polycarbonate plate (PC plate)
4 Double-sided adhesive tape

Claims

A double-sided adhesive tape having an acrylic adhesive layer on both sides of a substrate,
The base material is made of a foam and has an interlayer strength of 10 N / 5 mm or more and 30 N / 5 mm or less,
At least one of the acrylic pressure-sensitive adhesive layers has a storage elastic modulus G ′ at 20 ° C. of 2.5 × 10 5 Pa or more and a loss elastic modulus G ″ at 20 ° C. of 2 × 10 5 Pa or more. Adhesive tape.
2. The double-sided pressure-sensitive adhesive tape according to claim 1, wherein the total thickness of the double-sided pressure-sensitive adhesive tape is 50 to 400 μm.
The double-sided pressure-sensitive adhesive tape according to claim 1 or 2, wherein the single-sided acrylic pressure-sensitive adhesive layer has a thickness of 10 to 100 µm.
The double-sided pressure-sensitive adhesive tape according to claim 1, 2 or 3, wherein the foam is a polyolefin foam.
5. The double-sided pressure-sensitive adhesive tape according to claim 1, wherein the density of the base material is 0.35 g / cm 3 or more and 0.7 g / cm 3 or less.
6. The double-sided pressure-sensitive adhesive tape according to claim 1, 2, 3, 4 or 5, wherein the double-sided pressure-sensitive adhesive tape is used for bonding and fixing a component constituting a portable electronic device to the device body.
6. The double-sided pressure-sensitive adhesive tape according to claim 1, wherein the double-sided pressure-sensitive adhesive tape is used for adhesively fixing an automobile member to an automobile body.