JP2020196886A - Adhesive tape - Google Patents

Abstract

To provide an adhesive tape having a foam substrate excellent in resistance to the sebum.SOLUTION: There is provided an adhesive tape having a foam substrate and an adhesive layer formed on at least one surface of the foam substrate, wherein the foam substrate contains a (meth)acrylic copolymer containing 30 wt.% or more of a constitutional unit derived from a fluoroalkyl (meth)acrylate in which some or all of hydrogen atoms of an alkyl group are substituted with fluorine.SELECTED DRAWING: None

Description

The present invention relates to an adhesive tape.

Adhesive tapes are used for assembly in portable electronic devices (for example, mobile phones, personal digital assistants, etc.) equipped with an image display device or an input device. Specifically, for example, a double-sided adhesive tape is used to bond a cover panel for protecting the surface of a portable electronic device to a touch panel module or a display panel module, or to bond a touch panel module and a display panel module. Has been done. Such a double-sided adhesive tape is used, for example, by being punched into a shape such as a frame shape and arranged around a display screen (for example, Patent Documents 1 and 2). Double-sided adhesive tape is also used for fixing vehicle parts (for example, in-vehicle panels) to the vehicle body.

In addition, a foam base material may be used for the double-sided adhesive tape used for fixing the parts of the portable electronic device. For example, 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 is a cross-linked polyolefin resin having a specific degree of cross-linking and an aspect ratio of bubbles. What is a foam sheet is disclosed.

JP-A-2009-242541 JP-A-2009-258274

In recent years, due to the miniaturization, weight reduction, and cost reduction of electronic devices, electronic devices such as mobile phones, smartphones, and wearable terminals that are always worn or kept at hand have become widespread. Such portable electronic devices are frequently used and are operated with bare hands using a touch panel or the like. Frequent touching also exposes the adhesive tape used to secure parts of electronic devices to sebum, but the foam substrate used in conventional adhesive tape swells due to sebum. There was a risk that it would end up.

An object of the present invention is to provide an adhesive tape having a foam base material having excellent resistance to sebum.

The present invention is an adhesive tape having a foam base material and an adhesive layer formed on at least one surface of the foam base material, and the foam base material is a part of hydrogen atoms of an alkyl group. Alternatively, it is an adhesive tape containing a (meth) acrylic copolymer containing 30% by weight or more of a structural unit derived from a fluoroalkyl (meth) acrylate which is entirely fluorinated.
The present invention will be described in detail below.

The adhesive tape of the present invention has a foam base material. By using a foam base material as the base material of the adhesive tape, it is possible to exhibit high flexibility to follow the unevenness and curved surface of the adherend.

The foam base material contains a structural unit derived from a fluoroalkyl (meth) acrylate in which a part or all of hydrogen atoms of an alkyl group are fluorinated (hereinafter, also simply referred to as “fluoroalkyl (meth) acrylate”). Contains a (meth) acrylic copolymer (hereinafter, also referred to as "(meth) acrylic copolymer for a foam base material").
In the conventional foam base material, by absorbing sebum, the strength of the foam base material itself is lowered and damaged, or the elasticity of the foam base material is lost, or the base material side. It is also probable that the resistance to sebum was reduced because the deterioration of the pressure-sensitive adhesive layer due to sebum was promoted by the contact with sebum.
On the other hand, the foam base material containing the (meth) acrylic copolymer for the foam base material containing the structural unit derived from the above fluoroalkyl (meth) acrylate has high water and oil repellency of fluorine itself and fluorine. The dense packing of atoms suppresses the infiltration of sebum into the molecular chain of the (meth) acrylic copolymer. Since the foam base material does not easily absorb sebum, the adhesive tape of the present invention using the foam base material can exhibit excellent resistance to sebum.

The fluoroalkyl (meth) acrylate is not particularly limited, and for example, 2,2,2-trifluoroethyl (meth) acrylate, 1H, 1H, 3H-tetrafluoropropyl (meth) acrylate, 2,2,3. 3,3-Pentafluoropropyl (meth) acrylate, 2- (perfluorohexyl) ethyl (meth) acrylate, 1H-1- (trifluoromethyl) trifluoroethyl (meth) acrylate, 1H, 1H, 3H-hexafluoro Examples thereof include butyl (meth) acrylate, 1,2,2,2-tetrafluoro-1- (trifluoromethyl) ethyl acrylate, and 2- (perfluorobutyl) ethyl (meth) acrylate. These fluoroalkyl (meth) acrylates may be used alone or in combination of two or more. Among them, 2,2,2-trifluoroethyl (meth) acrylate, 2,2,3,3,3-pentafluoropropyl (meth) acrylate, 2- (perfluorobutyl) ethyl (meth) acrylate and 2- At least one selected from the group consisting of (perfluorohexyl) ethyl (meth) acrylate is preferable, and these acrylates are more preferable. 2- (Perfluorohexyl) ethyl acrylate is particularly preferred because of its particularly high resistance to sebum.

In the (meth) acrylic copolymer for a foam base material, the lower limit of the content of the structural unit derived from the fluoroalkyl (meth) acrylate is 30% by weight. When the content is 30% by weight or more, the infiltration of sebum into the molecular chain of the (meth) acrylic copolymer for the foam base material is suppressed, and the resistance of the adhesive tape to sebum is improved. The preferred lower limit of the content is 40% by weight, the more preferable lower limit is 45% by weight, and the particularly preferable lower limit is 50% by weight. The upper limit of the content is not particularly limited, but from the viewpoint that the foam base material does not become too hard and exhibits sufficient impact resistance, a preferable upper limit is 90% by weight, a more preferable upper limit is 80% by weight, and a further preferable upper limit is further exhibited. Is 70% by weight.

The (meth) acrylic copolymer for a foam base material preferably further contains a structural unit derived from an alkyl (meth) acrylate having an alkyl group having 2 or less carbon atoms. When the (meth) acrylic copolymer contains a structural unit derived from the alkyl (meth) acrylate having an alkyl group having 2 or less carbon atoms, the cohesive force of the foam base material is increased, and sebum is formed. Improves resistance.

Examples of the alkyl (meth) acrylate having an alkyl group having 2 or less carbon atoms include methyl (meth) acrylate and ethyl (meth) acrylate. These alkyl (meth) acrylates having an alkyl group having 2 or less carbon atoms may be used alone or in combination of two or more. Of these, methyl acrylate is preferable because it exhibits high cohesive force.

In the (meth) acrylic copolymer for a foam base material, the content of the structural unit derived from the alkyl (meth) acrylate having an alkyl group having 2 or less carbon atoms is not particularly limited, but the preferable lower limit is 10 weight by weight. %, The preferred upper limit is 40% by weight. When the content is within this range, the cohesive force of the foam base material becomes higher and the resistance to sebum is improved, while the foam base material does not become too hard and has sufficient impact resistance. Can be demonstrated. The more preferable lower limit of the content is 15% by weight, and the more preferable upper limit is 30% by weight.

The (meth) acrylic copolymer for a foam base material preferably further contains a structural unit derived from a monomer having a crosslinkable functional group. Since the (meth) acrylic copolymer for a foam substrate contains a structural unit derived from the monomer having a crosslinkable functional group, the interchains of the (meth) acrylic copolymer when a crosslinking agent is used in combination. Is cross-linked. At that time, the gel fraction of the foam base material can be adjusted by adjusting the degree of cross-linking.

Examples of the crosslinkable functional group include a hydroxyl group, a carboxyl group, a glycidyl group, an amino group, an amide group, a nitrile group and the like. Of these, a hydroxyl group or a carboxyl group is preferable, and a hydroxyl group is more preferable, because the gel fraction of the foam base material can be easily adjusted.
Examples of the monomer having a hydroxyl group include (meth) acrylate having a hydroxyl group such as 4-hydroxybutyl (meth) acrylate and 2-hydroxyethyl (meth) acrylate.
Examples of the monomer having a carboxyl group include (meth) acrylic acid.
Examples of the monomer having a glycidyl group include glycidyl (meth) acrylate.
Examples of the monomer having an amide group include hydroxyethyl acrylamide, isopropyl acrylamide, dimethylamino propyl acrylamide and the like.
Examples of the monomer having a nitrile group include acrylonitrile.
The monomers having these crosslinkable functional groups may be used alone or in combination of two or more.

In the (meth) acrylic copolymer for a foam base material, the content of the structural unit derived from the monomer having a crosslinkable functional group is not particularly limited, but the preferable lower limit is 0.05% by weight and the preferable upper limit is 10. By weight%, the more preferred lower limit is 1% by weight and the more preferred upper limit is 5% by weight. When the content is within the above range, it becomes easy to adjust the gel fraction of the foam base material.

The (meth) acrylic copolymer for a foam base material may further contain a structural unit derived from another monomer as long as the effect of the present invention is not impaired. The other monomers are not particularly limited, and for example, propyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, and the like. Examples thereof include isobornyl (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, vinyl acetate and the like.

When the (meth) acrylic copolymer for the foam base material is prepared by the ultraviolet polymerization method, the (meth) acrylic copolymer for the foam base material is further divided into divinylbenzene and trimethylolpropane. It preferably contains a structural unit derived from a polyfunctional monomer such as (meth) acrylate.

The weight average molecular weight of the (meth) acrylic copolymer for the foam base material is not particularly limited, but the preferable lower limit is 400,000 and the preferable upper limit is 2 million. When the weight average molecular weight of the (meth) acrylic copolymer for the foam base material is within this range, the resistance of the foam base material to sebum can be improved and high impact resistance can be exhibited. it can. The more preferable lower limit of the weight average molecular weight is 500,000, the more preferable upper limit is 1.5 million, the more preferable lower limit is 600,000, and the further preferable upper limit is 1.2 million.
The weight average molecular weight is a polystyrene-equivalent molecular weight obtained by GPC measurement, and can be adjusted according to the polymerization conditions (for example, the type or amount of the polymerization initiator, the polymerization temperature, the monomer concentration, etc.). In the GPC measurement, for example, column LF-804 (manufactured by Showa Denko KK) can be used as the column, tetrahydrofuran can be used as the solvent, and 40 ° C. and a flow rate of 0.5 mL / min can be adopted as the measurement conditions. ..

In order to synthesize the (meth) acrylic copolymer for the foam base material, the monomer from which the structural unit is derived may be radically reacted in the presence of a polymerization initiator.
The radical reaction method is not particularly limited, and examples thereof include living radical polymerization and free radical polymerization. According to the living radical polymerization, a copolymer having a more uniform molecular weight and composition as compared with the free radical polymerization can be obtained, the formation of low molecular weight components and the like can be suppressed, and the cohesive force of the foam substrate can be increased. It gets higher.
The polymerization method is not particularly limited, and conventionally known methods can be used. For example, solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, bulk polymerization and the like can be mentioned. Of these, solution polymerization is preferable because it is easy to synthesize.

When solution polymerization is used as the polymerization method, examples of the reaction solvent include ethyl acetate, toluene, methyl ethyl ketone, methyl sulfoxide, ethanol, acetone, diethyl ether and the like. These reaction solvents may be used alone or in combination of two or more.

The above-mentioned polymerization initiator is not particularly limited, and examples thereof include organic peroxides and azo compounds. Examples of the organic peroxide include 1,1-bis (t-hexyl peroxy) -3,3,5-trimethylcyclohexane, t-hexyl peroxypivalate, t-butylperoxypivalate, 2,5. -Dimethyl-2,5-bis (2-ethylhexanoylperoxy) hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxy Examples thereof 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.
In the case of living radical polymerization, examples of the above-mentioned polymerization initiator include organic tellurium polymerization initiators. The organic telluride polymerization initiator is not particularly limited as long as it is generally used for living radical polymerization, and examples thereof include an organic telluride compound and an organic telluride compound. In the living radical polymerization, in addition to the organic tellurium polymerization initiator, an azo compound may be used as the polymerization initiator for the purpose of promoting the polymerization rate.

The foam base material is preferably crosslinked with a crosslinking agent.
The above-mentioned cross-linking agent is not particularly limited, and examples thereof include isocyanate-based cross-linking agents, aziridine-based cross-linking agents, epoxy-based cross-linking agents, and metal chelate-type cross-linking agents. Of these, isocyanate-based cross-linking agents and epoxy-based cross-linking agents are preferable.
The blending amount of the cross-linking agent is not particularly limited, but the preferable lower limit is 0.01 parts by weight and the preferable upper limit is 10 parts by weight with respect to 100 parts by weight of the (meth) acrylic copolymer for the foam base material, which is a more preferable lower limit. Is 0.1 parts by weight, and a more preferable upper limit is 5 parts by weight.

The foam base material further contains additives such as an antistatic agent, a mold release agent, an antioxidant, a weather resistant agent, and a crystal nucleating agent, and a resin modifier such as polyolefin, polyester, polyamide, and elastomer. May be.

The foam base material has a preferable lower limit of apparent density of 0.5 g / cm ³ and a preferred upper limit of 0.95 g / cm ³ . By setting the apparent density of the foam base material in the above range, it is possible to obtain an adhesive tape having more flexibility and impact resistance while maintaining strength. From the viewpoint of further enhancing the strength, flexibility and impact resistance of the adhesive tape, the more preferable lower limit of the apparent density of the foam base material is 0.6 g / cm ³ , and the more preferable upper limit is 0.93 g / cm ³ . A more preferable lower limit is 0.7 g / cm ³ , and a more preferable upper limit is 0.9 g / cm ³ .
Here, the apparent density is represented by 1-Vp / Va when the total volume including the voids of the foam base material is Va and the volume of the bubble portion is Vp. Va is in the x, y, and z directions when the foam base material is taken out as a rectangular parallelepiped of an arbitrary size, the thickness direction is the z direction, the short axis in the plane direction is the x axis, and the long axis is the y axis. It is the product of lengths. For Vp, a 3D image of the target area of the sample is taken with a CT scan (for example, TDM1000H-II (2K) manufactured by Yamato Scientific Co., Ltd.), and structural analysis is performed with analysis software (for example, VGSstudio manufactured by Volume Graphics Co., Ltd.). Therefore, it can be obtained as the total volume of each bubble.

In the foam base material, the preferable lower limit of the average major axis of the bubbles is 10 μm, and the preferable upper limit is 500 μm. By setting the average major axis within the above range, the adhesive tape of the present invention can exhibit higher impact resistance. The more preferable lower limit of the average major axis is 20 μm, and the more preferable upper limit is 150 μm.
When a heat-expandable microcapsule is used as a foaming agent as described later, the average major axis of the inner pores of the thermal-expandable microcapsule after thermal expansion becomes the average major axis of the bubbles.

The average major axis of the bubbles in the foam base material can be measured by the following method.
First, the foam base material is cut into 50 mm squares, immersed in liquid nitrogen for 1 minute, and then cut with a razor blade on a plane parallel to the MD direction and perpendicular to the plane formed by the MD and TD directions. Next, using a digital microscope (for example, "VHX-900" manufactured by KEYENCE CORPORATION), a magnified photograph of the cut surface was taken at a magnification of 200 times, and a range of 2 mm (thickness x 2 mm range) in the MD direction. The bubble diameter in the MD direction is measured for all the cells existing in. This operation is repeated 5 times, and the average cell diameter in the MD direction is calculated by averaging all the obtained cell diameters. Next, the average cell diameter in the TD direction is obtained by the same method except that the foam base material is cut in a plane parallel to the TD direction and perpendicular to the plane formed by the MD direction and the TD direction. Of the obtained average cell diameters in the MD and TD directions, the larger one is the average major axis of the bubbles, and the shorter one is the average minor axis of the bubbles.
The MD (Machine Direction) refers to the extrusion direction when the foam base material is extruded into a sheet, and the TD (Transverse Direction) refers to the direction perpendicular to the MD.

The foam base material preferably has a gel fraction of 95% by weight or less. When the gel fraction of the foam base material is 95% by weight or less, the impact resistance of the obtained adhesive tape can be further enhanced. From the viewpoint of further enhancing the impact resistance of the adhesive tape, the more preferable upper limit of the gel fraction is 80% by weight. The lower limit of the gel fraction is not particularly limited, but is preferably 10% by weight or more, and more preferably 20% by weight or more.
The gel fraction of the foam base material can be adjusted by cross-linking the (meth) acrylic copolymer for the foam base material.
The gel fraction of the foam base material can be measured by the following method. That is, 0.1 g of only the foam base material is taken out from the adhesive tape, immersed in 50 ml of ethyl acetate, and shaken with a shaker at a temperature of 23 ° C. and 120 rpm for 24 hours. After shaking, a metal mesh (opening # 200 mesh) is used to absorb ethyl acetate and ethyl acetate and separate the swollen foam substrate. The separated foam substrate is dried under the condition of 110 ° C. for 1 hour. The weight of the foam base material including the metal mesh after drying is measured, and the gel fraction of the foam base material is calculated using the following formula.
Gel fraction (% by weight) = 100 x (W _1- W ₂ ) / W ₀
(W ₀ : weight of initial foam base material, W ₁ : weight of foam base material including dried metal mesh, W ₂ : initial weight of metal mesh)

The 25% compressive strength of the foam base material is not particularly limited, but a preferable lower limit is 1 kPa and a preferable upper limit is 2000 kPa. By setting the 25% compressive strength of the foam base material within the above range, excellent flexibility and impact resistance can be exhibited while maintaining the strength of the adhesive tape. From the viewpoint of further improving the strength, flexibility and impact resistance of the adhesive tape, the more preferable lower limit of the 25% compressive strength of the foam base material is 20 kPa, the more preferable upper limit is 300 kPa, the further preferable lower limit is 50 kPa, and further. The preferred upper limit is 200 kPa.
The 25% compression strength can be determined by measuring in accordance with JIS K 6254.

The thickness of the foam base material is not particularly limited, but a preferable lower limit is 40 μm and a preferable upper limit is 2900 μm. By setting the thickness of the foam base material within the above range, the adhesive tape of the present invention can be suitably used for fixing portable electronic device parts, in-vehicle electronic device parts, and the like. From the viewpoint that the parts and the like can be more preferably used, the more preferable lower limit of the thickness of the foam base material is 60 μm, the more preferable upper limit is 1900 μm, the further preferable lower limit is 80 μm, the further preferable upper limit is 1400 μm, and the particularly preferable lower limit. Is 100 μm, and a particularly preferable upper limit is 1000 μm.

As a method for producing the foam base material, a conventionally known method such as a method in which a resin composition as a raw material is crosslinked and then foamed can be used. Specifically, for example, it can be produced by a method having the following steps (1) to (3). As a method for producing the foam base material, for example, the method described in International Publication No. 2005/007731 can be mentioned.
Step (1): The (meth) acrylic copolymer for a foam base material, a cross-linking agent, a foaming agent, and other additives are supplied to an extruder, melt-kneaded, and extruded into a sheet from the extruder. Steps to obtain a sheet-shaped resin composition (2): Steps to cross-link the sheet-shaped resin composition (3): Heat the crosslinked sheet-shaped resin composition to form a foaming agent. The process of foaming

The foaming agent to be blended in the (meth) acrylic copolymer for the foam base material is not particularly limited, and for example, Expandel (registered trademark) (manufactured by Nippon Philite), Advancel (manufactured by Sekisui Chemical Co., Ltd.), etc. Examples thereof include heat-expandable microcapsules. Further, thermal decomposition foaming agents such as azodicarbonamide, N, N'-dinitrosopentamethylenetetramine and p-toluenesulfonyl semicarbazide can be mentioned. These foaming agents may be used alone or in combination of two or more.

The blending amount of the foaming agent is not particularly limited, but the preferable lower limit is 0.01 parts by weight and the preferable upper limit is 12 parts by weight with respect to 100 parts by weight of the resin component. When the content of the foaming agent is within the above range, a foam base material having a desired apparent density can be obtained. A more preferable upper limit of the content of the foaming agent is 8 parts by weight.

The adhesive tape of the present invention has an adhesive layer on at least one surface of the foam base material.
The pressure-sensitive adhesive layer is not particularly limited, and examples thereof include a (meth) acrylic pressure-sensitive adhesive layer, a rubber-based pressure-sensitive adhesive layer, a urethane pressure-sensitive adhesive layer, and a silicone-based pressure-sensitive adhesive layer. Among them, a (meth) acrylic copolymer containing 30% by weight or more of a structural unit derived from fluoroalkyl (meth) acrylate in which some or all of the hydrogen atoms of the alkyl group are fluorinated because of its excellent resistance to sebum. A pressure-sensitive adhesive layer made of a pressure-sensitive adhesive containing (hereinafter, also referred to as “(meth) acrylic copolymer for pressure-sensitive adhesive layer”) is preferable.

The fluoroalkyl (meth) acrylate used for the (meth) acrylic copolymer for the pressure-sensitive adhesive layer is not particularly limited, and is, for example, 2,2,2-trifluoroethyl (meth) acrylate, 1H, 1H, 3H-tetrafluoro. Propyl (meth) acrylate, 2,2,3,3,3-pentafluoropropyl (meth) acrylate, 2- (perfluorohexyl) ethyl (meth) acrylate, 1H-1- (trifluoromethyl) trifluoroethyl ( Meta) acrylate, 1H, 1H, 3H-hexafluorobutyl (meth) acrylate, 1,2,2,2-tetrafluoro-1- (trifluoromethyl) ethyl acrylate, 2- (perfluorobutyl) ethyl (meth) Examples include acrylate. These fluoroalkyl (meth) acrylates may be used alone or in combination of two or more. Among them, 2,2,2-trifluoroethyl (meth) acrylate, 2,2,3,3,3-pentafluoropropyl (meth) acrylate, 2- (perfluorobutyl) ethyl (meth) acrylate and 2- At least one selected from the group consisting of (perfluorohexyl) ethyl (meth) acrylate is preferable, and these acrylates are more preferable. 2- (Perfluorohexyl) ethyl acrylate is particularly preferred because of its particularly high resistance to sebum.

In the (meth) acrylic copolymer for the pressure-sensitive adhesive layer, the preferable lower limit of the content of the structural unit derived from the fluoroalkyl (meth) acrylate is 30% by weight. When the content is 30% by weight or more, the infiltration of sebum into the molecular chain of the (meth) acrylic copolymer for the pressure-sensitive adhesive layer is further suppressed, and the resistance of the adhesive tape to the sebum is improved. A more preferable lower limit of the content is 40% by weight, a further preferable lower limit is 45% by weight, and a particularly preferable lower limit is 50% by weight. The upper limit of the content is not particularly limited, but from the viewpoint that the pressure-sensitive adhesive layer does not become too hard and exhibits sufficient adhesive strength, a preferable upper limit is 90% by weight, a more preferable upper limit is 80% by weight, and a further preferable upper limit is 70. By weight%.

The (meth) acrylic copolymer for the pressure-sensitive adhesive layer preferably contains a structural unit derived from an alkyl (meth) acrylate having an alkyl group having 2 or less carbon atoms. When the (meth) acrylic copolymer for the pressure-sensitive adhesive layer contains a structural unit derived from the alkyl (meth) acrylate having an alkyl group having 2 or less carbon atoms, the cohesive force of the pressure-sensitive adhesive layer is increased. As a result, the resistance of the pressure-sensitive adhesive layer to sebum is improved.

Examples of the alkyl (meth) acrylate having an alkyl group having 2 or less carbon atoms include methyl (meth) acrylate and ethyl (meth) acrylate. These alkyl (meth) acrylates having an alkyl group having 2 or less carbon atoms may be used alone or in combination of two or more. Of these, methyl acrylate is preferable because it exhibits high cohesive force.

In the (meth) acrylic copolymer for the pressure-sensitive adhesive layer, the content of the structural unit derived from the alkyl (meth) acrylate having an alkyl group having 2 or less carbon atoms is not particularly limited, but the preferable lower limit is 10% by weight. The preferred upper limit is 40% by weight. When the content is within this range, the cohesive force of the pressure-sensitive adhesive layer becomes higher and the resistance to sebum is improved, while the pressure-sensitive adhesive layer does not become too hard and exhibits sufficient adhesive strength. be able to. The more preferable lower limit of the content is 15% by weight, and the more preferable upper limit is 30% by weight.

The (meth) acrylic copolymer for the pressure-sensitive adhesive layer preferably further contains a structural unit derived from a monomer having a crosslinkable functional group.
Since the (meth) acrylic copolymer for the pressure-sensitive adhesive layer contains a structural unit derived from the monomer having a crosslinkable functional group, the interchains of the (meth) acrylic copolymer can be separated when a crosslinker is used in combination. It is bridged. At that time, the gel fraction of the pressure-sensitive adhesive layer can be adjusted by adjusting the degree of cross-linking.

Examples of the crosslinkable functional group include a hydroxyl group, a carboxyl group, a glycidyl group, an amino group, an amide group, a nitrile group and the like. Of these, a hydroxyl group or a carboxyl group is preferable, and a hydroxyl group is more preferable, because the gel fraction of the pressure-sensitive adhesive layer can be easily adjusted.
Examples of the monomer having a hydroxyl group include (meth) acrylate having a hydroxyl group such as 4-hydroxybutyl (meth) acrylate and 2-hydroxyethyl (meth) acrylate.
Examples of the monomer having a carboxyl group include (meth) acrylic acid.
Examples of the monomer having a glycidyl group include glycidyl (meth) acrylate.
Examples of the monomer having an amide group include hydroxyethyl acrylamide, isopropyl acrylamide, dimethylamino propyl acrylamide and the like.
Examples of the monomer having a nitrile group include acrylonitrile.
The monomers having these crosslinkable functional groups may be used alone or in combination of two or more.

In the (meth) acrylic copolymer for the pressure-sensitive adhesive layer, the content of the structural unit derived from the monomer having a crosslinkable functional group is not particularly limited, but the preferable lower limit is 0.05% by weight and the preferable upper limit is 10% by weight. The more preferable lower limit is 1% by weight, and the more preferable upper limit is 5% by weight. When the content is within the above range, it becomes easy to adjust the gel fraction for the pressure-sensitive adhesive layer.

The (meth) acrylic copolymer for the pressure-sensitive adhesive layer may further contain a structural unit derived from another monomer as long as the effect of the present invention is not impaired. The other monomers are not particularly limited, and for example, propyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, and the like. Examples thereof include isobornyl (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, vinyl acetate and the like.

When the (meth) acrylic copolymer for the pressure-sensitive adhesive layer is prepared by an ultraviolet polymerization method, the (meth) acrylic copolymer may be further composed of divinylbenzene, trimethylolpropane tri (meth) acrylate, or the like. It preferably contains a structural unit derived from a polyfunctional monomer.

The weight average molecular weight of the (meth) acrylic copolymer for the pressure-sensitive adhesive layer is not particularly limited, but the preferable lower limit is 300,000. When the weight average molecular weight of the (meth) acrylic copolymer for the pressure-sensitive adhesive layer is 300,000 or more, the resistance of the pressure-sensitive adhesive layer to sebum is improved and foaming generated under high temperature and high humidity is further suppressed. Can be done. The more preferable lower limit of the weight average molecular weight of the (meth) acrylic copolymer is 400,000, the more preferable lower limit is 500,000, and the particularly preferable lower limit is 1 million.
The upper limit of the weight average molecular weight of the (meth) acrylic copolymer is not particularly limited, but the preferable upper limit is 2 million, and the more preferable upper limit is 1.8 million.
The weight average molecular weight is a polystyrene-equivalent molecular weight obtained by GPC measurement, and can be adjusted according to the polymerization conditions (for example, the type or amount of the polymerization initiator, the polymerization temperature, the monomer concentration, etc.). In the GPC measurement, for example, column LF-804 (manufactured by Showa Denko KK) can be used as the column, tetrahydrofuran can be used as the solvent, and 40 ° C. and a flow rate of 0.5 mL / min can be adopted as the measurement conditions. ..

The method for synthesizing the (meth) acrylic copolymer for the pressure-sensitive adhesive layer is not particularly limited, and the same method as the method for synthesizing the (meth) acrylic copolymer for the foam base material can be used.

The pressure-sensitive adhesive layer preferably contains a cross-linking agent in addition to the (meth) acrylic copolymer for the pressure-sensitive adhesive layer.
When the (meth) acrylic copolymer for the pressure-sensitive adhesive layer contains a structural unit derived from the monomer having a crosslinkable functional group, the crosslinker constructs a crosslinked structure between the chains of the (meth) acrylic copolymer. can do. At that time, the gel fraction of the pressure-sensitive adhesive layer can be adjusted by adjusting the degree of cross-linking.

The above-mentioned cross-linking agent is not particularly limited, and examples thereof include isocyanate-based cross-linking agents, aziridine-based cross-linking agents, epoxy-based cross-linking agents, and metal chelate-type cross-linking agents. Of these, isocyanate-based cross-linking agents and epoxy-based cross-linking agents are preferable, and isocyanate-based cross-linking agents are more preferable because the gel fraction of the pressure-sensitive adhesive layer can be easily adjusted.
In the pressure-sensitive adhesive layer, the content of the cross-linking agent is not particularly limited, but the preferable lower limit is 0.01 parts by weight and the preferable upper limit is 10 parts by weight with respect to 100 parts by weight of the (meth) acrylic copolymer for the pressure-sensitive adhesive layer. The more preferable lower limit is 0.1 parts by weight, and the more preferable upper limit is 5 parts by weight.

The pressure-sensitive adhesive layer preferably further contains a silane coupling agent.
When the pressure-sensitive adhesive layer contains the silane coupling agent, the adhesion of the pressure-sensitive adhesive layer to the adherend is improved. As a result, the resistance of the pressure-sensitive adhesive layer to sebum is improved, and foaming that occurs under high temperature and high humidity can be further suppressed.

The silane coupling agent is not particularly limited, and for example, vinyltrimethoxysilane, vinyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane. , 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-amino Propyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethylmethoxysilane, N- (2-aminoethyl) 3-aminopropyltriethoxysilane, N- (2-aminoethyl) 3-aminopropylmethyl Examples thereof include dimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, mercaptobutyltrimethoxysilane, and 3-mercaptopropylmethyldimethoxysilane. Of these, 3-glycidoxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, or a combination thereof is preferable.

In the pressure-sensitive adhesive layer, the content of the silane coupling agent is not particularly limited, but the preferable lower limit is 0.1 parts by weight and the preferable upper limit is 10 parts by weight with respect to 100 parts by weight of the (meth) acrylic copolymer for the pressure-sensitive adhesive layer. It is a department. When the content is 0.1 part by weight or more, the adhesiveness of the pressure-sensitive adhesive layer to the adherend is improved, the resistance to sebum is improved, and the foaming generated under high temperature and high humidity is further suppressed. Can be done. When the content is 10 parts by weight or less, the adhesive residue when the adhesive sheet is peeled off can be suppressed, and the reworkability of the adhesive sheet is improved. The more preferable lower limit of the content is 1 part by weight, and the more preferable upper limit is 5 parts by weight.

The pressure-sensitive adhesive layer contains, if necessary, additives such as plasticizers, emulsifiers, softeners, fillers, pigments and dyes, pressure-sensitive adhesives such as rosin-based resins and terpene-based resins, and other resins. May be.

The gel fraction of the pressure-sensitive adhesive layer is preferably 20% by weight or more. When the gel fraction is 20% by weight or more, the cohesive force of the pressure-sensitive adhesive is in an appropriate range, the adhesion to the adherend is improved, and the sebum resistance is improved. A more preferable lower limit of the gel fraction is 25% by weight. The upper limit of the gel fraction is not particularly limited, but a preferable upper limit is 95% by weight.
The gel fraction of the pressure-sensitive adhesive layer can be measured by the following method. That is, 0.1 g of only the pressure-sensitive adhesive layer is taken out from the adhesive tape, immersed in 50 ml of ethyl acetate, and shaken with a shaker at a temperature of 23 ° C. and 120 rpm for 24 hours. After shaking, a metal mesh (opening # 200 mesh) is used to absorb ethyl acetate and ethyl acetate and separate the swollen pressure-sensitive adhesive layer. The adhesive layer after separation is dried under the condition of 110 ° C. for 1 hour. The weight of the pressure-sensitive adhesive layer containing the metal mesh after drying is measured, and the gel fraction of the foam base material is calculated using the following formula.
Gel fraction (% by weight) = 100 x (W _1- W ₂ ) / W ₀
(W ₀ : Initial weight of adhesive layer, W ₁ : Weight of adhesive layer including dried metal mesh, W ₂ : Initial weight of metal mesh)

The thickness of the pressure-sensitive adhesive layer is not particularly limited, but a preferable lower limit is 5 μm and a preferable upper limit is 150 μm. When the thickness is within the above range, the adhesive strength and workability are improved. The more preferable lower limit of the thickness is 10 μm, and the more preferable upper limit is 100 μm.

The adhesive tape of the present invention preferably has a resin layer on at least one surface of the foam base material.
By having the resin layer, the strength of the obtained adhesive tape is improved, so that the impact resistance can be further improved. The resin layer may be formed on one side of the foam base material or on both sides, but it is preferably formed on one side of the foam base material.

The resin constituting the resin layer preferably has heat resistance. Examples of the resin constituting the heat-resistant resin layer include polyester resins such as polyethylene terephthalate, acrylic resins, silicone resins, phenol resins, polyimides, and polycarbonates. Among them, acrylic resin and polyester resin are preferable, and polyethylene terephthalate is more preferable, because an adhesive tape having excellent flexibility can be obtained.

The resin layer may be colored. By coloring the resin layer, it is possible to impart light-shielding properties to the adhesive tape.
The method of coloring the resin layer is not particularly limited, and for example, a method of kneading particles such as carbon black or titanium oxide or fine bubbles into the resin constituting the resin layer, or applying ink to the surface of the resin layer. The method and the like can be mentioned.

The resin layer may be formed of conventionally known fine particles and additives such as inorganic fine particles, conductive fine particles, plasticizers, tackifiers, ultraviolet absorbers, antioxidants, foaming agents, organic fillers, and inorganic fillers, if necessary. May be contained.

The thickness of the resin layer is not particularly limited, but the preferable lower limit is 5 μm and the preferable upper limit is 100 μm. By setting the thickness of the resin layer within the above range, it is possible to achieve both handleability and impact resistance of the adhesive tape. From the viewpoint of further achieving both handleability and impact resistance, the more preferable lower limit of the thickness of the resin layer is 10 μm, and the more preferable upper limit is 70 μm.

The adhesive tape of the present invention may have a layer other than the foam base material, the pressure-sensitive adhesive layer and the resin layer, if necessary.

The thickness of the adhesive tape of the present invention is not particularly limited, but the preferable lower limit is 0.04 mm, the more preferable lower limit is 0.05 mm, the preferable upper limit is 2 mm, and the more preferable upper limit is 1.5 mm. By setting the thickness of the adhesive tape of the present invention within the above range, it is possible to obtain an adhesive tape having excellent handleability.

The method for producing the adhesive tape of the present invention is not particularly limited, and examples thereof include the following methods. First, a pressure-sensitive adhesive solution is applied to a release film and dried to form a pressure-sensitive adhesive layer, and a second pressure-sensitive adhesive layer is formed in the same manner. Next, the obtained pressure-sensitive adhesive layers are bonded to both sides of the foam base material to produce an pressure-sensitive adhesive tape.

The shape of the adhesive tape of the present invention is not particularly limited, and examples thereof include a rectangle, a frame, a circle, an ellipse, and a donut.

The use of the adhesive tape of the present invention is not particularly limited, but since it is excellent in impact resistance and resistance to sebum, it is resistant to fixing electronic parts such as portable electronic device parts and in-vehicle electronic device parts. It can be suitably used as an impact adhesive tape. Such an adhesive tape of the present invention used for fixing parts of an electronic device is also one of the present inventions.

According to the present invention, it is possible to provide an adhesive tape having a foam base material having excellent resistance to sebum.

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

(Example 1)
(1) Preparation of Foam Base Material Ethyl acetate was added as a polymerization solvent to the reaction vessel, bubbling with nitrogen, and then the reaction vessel was heated while flowing nitrogen to start reflux. Subsequently, a polymerization initiator solution obtained by diluting 0.1 part by weight of azobisisobutyronitrile with ethyl acetate 10 times as a polymerization initiator was put into the reaction vessel, and 67 parts by weight of butyl acrylate, 2,2,2- 30 parts by weight of trifluoroethyl acrylate and 3 parts by weight of acrylic acid were added dropwise over 2 hours. After completion of the dropwise addition, the polymerization initiator solution obtained by diluting 0.1 part by weight of azobisisobutyronitrile with ethyl acetate 10 times as a polymerization initiator was put into the reaction vessel again, and the polymerization reaction was carried out for 4 hours to carry out the polymerization reaction to form a foam group. A (meth) acrylic copolymer-containing solution for materials was obtained.
The polystyrene-equivalent molecular weight of the obtained (meth) acrylic copolymer for a foam substrate was measured by GPC measurement using a gel permeation chromatograph (2690 Separations Model manufactured by Waters) to determine the weight average molecular weight. As a result, it was 1.22 million. In the GPC measurement, a column LF-804 (manufactured by Showa Denko KK) was used as a column, and tetrahydrofuran was used as a solvent, and the measurement was performed under the conditions of 40 ° C. and a flow rate of 0.5 mL / min.

In the obtained (meth) acrylic copolymer-containing solution for a foam base material, a cross-linking agent (isocyanate-based cross-linking agent, Coronate L, Toso Co., Ltd.) was added to 100 parts by weight of the (meth) acrylic copolymer for a foam base material. 1 part by weight and 0.16 part by weight of Expandel (registered trademark) 461-DU40 (manufactured by Nippon Philite Co., Ltd.) were added to prepare a resin composition solution for a foam substrate. The obtained resin composition solution was applied to a release-treated PET film having a thickness of 75 μm so as to have a thickness of 120 μm after drying and foaming, and then dried at 90 ° C. for 10 minutes. After drying, a release-treated PET film having a thickness of 25 μm was laminated on the surface opposite to the surface on which the PET film was present, and heated at 130 ° C. for 5 minutes for foaming to obtain a foam substrate having a thickness of 120 μm. ..

The obtained foam base material was cut into 5 mm squares to prepare a sample, and the volume (Va) of the entire sample was calculated. In addition, a 3D image of the above sample is taken with a CT scan (manufactured by Yamato Scientific Co., Ltd., TDM1000H-II (2K)), and structural analysis is performed with analysis software (manufactured by Volume Graphics Co., Ltd., VGStudio) to perform structural analysis to obtain the volume of the bubble portion (Vp). ) Was asked. At this time, the imaging interval (slice thickness) of the CT scan was set to 5 μm. The apparent density (1-Vp / Va) of the foam substrate was calculated from Va and Vp.

With respect to the obtained foam base material, the average major axis of bubbles was calculated using a digital microscope (“VHX-900” manufactured by KEYENCE CORPORATION).

0.1 g of the obtained foam substrate was taken out, immersed in 50 ml of ethyl acetate, and shaken with a shaker at a temperature of 23 ° C. and 120 rpm for 24 hours. After shaking, a metal mesh (opening # 200 mesh) was used to absorb ethyl acetate and ethyl acetate to separate the swollen foam substrate. The foam substrate after separation was dried under the condition of 110 ° C. for 1 hour. The weight of the foam base material containing the metal mesh after drying was measured, and the gel fraction of the foam base material was calculated using the above formula.

(2) Preparation of Adhesive Solution After adding ethyl acetate as a polymerization solvent into the reaction vessel and bubbling with nitrogen, the reaction vessel was heated while flowing nitrogen to start reflux. Subsequently, a polymerization initiator solution obtained by diluting 0.1 part by weight of azobisisobutyronitrile with ethyl acetate 10 times as a polymerization initiator was put into the reaction vessel, and 47 parts by weight of butyl acrylate, 2- (perfluorohexyl) was added. ) -50 parts by weight of ethyl acrylate and 3 parts by weight of acrylic acid were added dropwise over 2 hours. After completion of the dropping, the polymerization initiator solution obtained by diluting 0.1 part by weight of azobisisobutyronitrile with ethyl acetate 10 times as a polymerization initiator was put into the reaction vessel again, and the polymerization reaction was carried out for 4 hours to carry out the polymerization reaction, and the pressure-sensitive adhesive layer was carried out. A solution containing the (meth) acrylic copolymer A was obtained.
The polystyrene-equivalent molecular weight of the obtained (meth) acrylic copolymer A for the pressure-sensitive adhesive layer was measured by GPC measurement using a gel permeation chromatograph (2690 Separations Model manufactured by Waters) to determine the weight average molecular weight. As a result, it was 1.2 million.

(3) Production of Adhesive Tape In the obtained (meth) acrylic copolymer A-containing solution for the pressure-sensitive adhesive layer, a cross-linking agent (isocyanate-based cross-linking agent) was added to 100 parts by weight of the (meth) acrylic copolymer A for the pressure-sensitive adhesive layer. , Coronate L-45, manufactured by Toso Co., Ltd.) and 1 part by weight of a silane coupling agent (KBM-403, manufactured by Shin-Etsu Chemical Industry Co., Ltd.) were added to prepare an adhesive solution.
On the release-treated surface of a 75 μm polyethylene terephthalate film (release film) that has been released-treated on one side, the obtained adhesive solution is applied so that the thickness of the dry film is 40 μm, and the temperature is 110 ° C. The coating solution was dried by heating for 5 minutes to obtain a pressure-sensitive adhesive layer. Then, another pressure-sensitive adhesive layer was produced by the same operation to obtain two pressure-sensitive adhesive layers.
Then, the PET film obtained by releasing the mold on both sides of the foam base material obtained above was peeled off, the two obtained adhesive layers were bonded to each other, and a double-sided adhesive tape having both surfaces protected by the release film was applied. Obtained.

(Examples 2 to 9, Comparative Examples 1 and 2)
A double-sided adhesive tape was obtained in the same manner as in Example 1 except that the monomer composition of the foam base material was as shown in Table 1.

(Evaluation)
The double-sided adhesive tapes obtained in Examples and Comparative Examples were evaluated by the following methods.
The results are shown in Table 1.

(1) Evaluation of Oleic Acid Resistance of Foam Base Material The foam base material was cut into a flat rectangular shape of 20 mm × 40 mm to obtain a test piece, and the weight thereof was measured. The test piece was immersed in oleic acid under the conditions of 65 ° C. and 90% humidity for 24 hours, then taken out, the surface was washed with ethanol, and then dried at 110 ° C. for 3 hours. The weight of the test piece after drying was measured, and the oleic acid swelling rate was calculated using the following formula. When the obtained oleic acid swelling rate is less than 120% by weight, it is regarded as "◎", when it is 120% by weight or more and less than 150% by weight, it is regarded as "○", and when it is 150% by weight or more, it is regarded as "x". Oleic acid resistance was evaluated. Oleic acid is the main component of human sebum, and resistance to sebum (suppression of swelling due to sebum) can be confirmed by evaluating the resistance of the foam base material to oleic acid.
Oleic acid swelling rate (% by weight) = 100 x W ₂ / W ₁
(W ₁ : Weight before oleic acid immersion, W ₂ : Weight after oleic acid immersion and drying)

(2) Evaluation of Adhesive Strength The obtained double-sided adhesive tape was cut into strips with a width of 10 mm to prepare test pieces, and one of the release films was peeled off to expose the adhesive layer, and PET with a thickness of 50 μm. The film was pasted. Further, the other release film is peeled off to expose the adhesive layer, and this test piece is placed on a stainless plate so that the adhesive layer faces the stainless plate, and then 300 mm on the test piece. The test piece and the stainless steel plate were bonded to each other by reciprocating a 2 kg rubber roller once at a speed of / minute, and then allowed to stand at 23 ° C. for 24 hours to prepare a test sample.

This test sample is heated in an oven at 60 ° C. and 90% humidity for 100 hours, allowed to stand at 23 ° C. for 24 hours, and then subjected to a tensile test in the 180 ° direction at a peeling speed of 300 mm / min according to JIS Z0237. The 180 ° peeling adhesive strength (N / mm) before soaking in acid was measured.

The test sample was immersed in a bath of oleic acid at 60 ° C. and a humidity of 90% for 100 hours, taken out, washed with water, and allowed to stand for 24 hours. Then, according to JIS Z0237, a tensile test in the 180 ° direction was performed at a peeling speed of 300 mm / min, and the 180 ° peeling adhesive strength (N / mm) after immersion in oleic acid was measured.

The residual rate of adhesive force before and after immersion in oleic acid (adhesive force after immersion in oleic acid / adhesive force before immersion in oleic acid x 100) was calculated, and when the residual rate was 30% or more, "◎", 15% or more. , The case of less than 30% was evaluated as "◯", and the case of less than 15% was evaluated as "x".

(3) Evaluation of Impact Resistance The obtained double-sided adhesive tape was punched into a square shape having an outer diameter of 24 mm × 24 mm and a width of 2 mm. One side of the punched double-sided adhesive tape was attached to the center of a square-shaped stainless steel plate having a hole of 20 mm × 20 mm in the center and having a thickness of 40 mm × 40 mm and a thickness of 2 mm. Next, a 20 mm × 20 mm, 2 mm thick square stainless steel plate is attached to the other side of the double-sided adhesive tape, crimped with a 5 kg weight for 10 seconds, and allowed to stand at 23 ° C for 24 hours for testing. A laminate was obtained. The obtained laminate was fixed to a stainless steel frame-shaped body (inner diameter 30 mm × 30 mm) so that a square stainless steel plate was on the lower surface. After that, a 100 g iron ball was dropped toward the center of the square stainless steel plate. The height at which the iron ball was dropped was increased, and the height of the iron ball when the square-shaped stainless steel plate was peeled off from the square-shaped stainless steel plate was measured. The potential energy (mJ) was calculated from the height of the iron ball when the tempered glass plate was peeled off from the stainless steel plate, and used as the shock absorption energy. The impact resistance was evaluated as "⊚" when the impact absorption energy was 550 mJ or more, "◯" when it was 300 mJ or more and less than 550 mJ, and "Δ" when it was less than 300 mJ.

(Reference example 1)
(1) Preparation of Adhesive Solution After adding ethyl acetate as a polymerization solvent to the reaction vessel and bubbling with nitrogen, the reaction vessel was heated while flowing nitrogen to start reflux. Subsequently, a polymerization initiator solution obtained by diluting 0.1 part by weight of azobisisobutyronitrile with ethyl acetate 10 times as a polymerization initiator was put into the reaction vessel, and 97 parts by weight of butyl acrylate and 3 parts by weight of acrylic acid were added. It was added dropwise over 2 hours. After completion of the dropping, the polymerization initiator solution obtained by diluting 0.1 part by weight of azobisisobutyronitrile with ethyl acetate 10 times as a polymerization initiator was put into the reaction vessel again, and the polymerization reaction was carried out for 4 hours to carry out the polymerization reaction, and the pressure-sensitive adhesive layer was carried out. A solution containing the (meth) acrylic copolymer B was obtained.
The polystyrene-equivalent molecular weight of the obtained (meth) acrylic copolymer B for the pressure-sensitive adhesive layer was measured by GPC measurement using a gel permeation chromatograph (2690 Separations Model manufactured by Waters) to determine the weight average molecular weight. As a result, it was 1.2 million.

(2) Production of Adhesive Tape A double-sided adhesive tape was obtained in the same manner as in Example 2 except that the obtained (meth) acrylic copolymer B-containing solution for the pressure-sensitive adhesive layer was used.

(3) Evaluation of Adhesive Strength When the adhesive strength of the obtained double-sided adhesive tape was evaluated by the same method as in the example, the 180 ° peeling adhesive strength before and after oleic acid immersion was 1. It was 33 N / mm and 0.10 N / mm.

(Reference example 2)
When the resin composition solution is applied and foamed in the preparation of the foam base material, the resin composition solution is applied using a corona-treated PET film having a thickness of 23 μm instead of the release-treated PET film having a thickness of 75 μm. Worked. After that, when the two pressure-sensitive adhesive layers and the foam base material were bonded to each other in the production of the adhesive tape, the PET film treated with corona having a thickness of 23 μm was foamed in the same manner as in Example 7 except that the PET film was not peeled off. A double-sided adhesive tape having a resin layer on one surface of the body base material and an adhesive layer on both surfaces was obtained.
When the impact resistance of the obtained double-sided adhesive tape was evaluated by the same method as in the examples, the impact absorption energy was 588 mJ.

According to the present invention, it is possible to provide an adhesive tape having a foam base material having excellent resistance to sebum.

Claims (6)

An adhesive tape having a foam base material and an adhesive layer formed on at least one surface of the foam base material, and the foam base material has a part or all of hydrogen atoms of an alkyl group that are fluorine. An adhesive tape containing a (meth) acrylic copolymer containing 30% by weight or more of a structural unit derived from a modified fluoroalkyl (meth) acrylate. The adhesive tape according to claim 1, wherein the foam base material has an apparent density of 0.5 g / cm ³ or more and 0.95 g / cm ³ or less. The adhesive tape according to claim 1 or 2, wherein the foam base material has an average major axis of bubbles of 10 μm or more and 500 μm or less. The pressure-sensitive adhesive layer comprises a pressure-sensitive adhesive containing a (meth) acrylic copolymer containing 30% by weight or more of a structural unit derived from a fluoroalkyl (meth) acrylate in which a part or all of hydrogen atoms of an alkyl group are fluorinated. , The adhesive tape according to any one of claims 1 to 3. The adhesive tape according to any one of claims 1 to 4, which has a resin layer on at least one surface of the foam base material. The adhesive tape according to any one of claims 1 to 5, which is used for fixing a component of an electronic device.