CN116367994A

CN116367994A - Adhesive tape

Info

Publication number: CN116367994A
Application number: CN202180070684.0A
Authority: CN
Inventors: 堀尾明史; 石堂泰志; 福山诚; 安田妃那; 西垣达哉
Original assignee: Sekisui Chemical Co Ltd
Current assignee: Sekisui Chemical Co Ltd
Priority date: 2020-10-28
Filing date: 2021-10-28
Publication date: 2023-06-30
Also published as: JPWO2022092199A1; WO2022092199A1; KR20230093413A

Abstract

The purpose of the present invention is to provide an adhesive tape having excellent repeated impact resistance. The adhesive tape of the present invention is an adhesive tape comprising: the multilayer substrate comprises a substrate layer and a resin layer laminated on at least one side of the substrate layer, wherein the storage elastic modulus E ' of the substrate layer in dynamic viscoelasticity measurement at 10 ℃ is 2.0-21 MPa, the Young ' of the resin layer at 23 ℃ is 500MPa or more, the elongation at break of the adhesive layer in shear adhesion measurement at 23 ℃ is 30-30%, and the storage elastic modulus G ' of the adhesive layer in dynamic viscoelasticity measurement at 10 ℃ is 0.13-7.0 MPa.

Description

Adhesive tape

Technical Field

The present invention relates to an adhesive tape.

Background

In portable electronic devices such as mobile phones and portable information terminals (Personal Digital Assistants, PDA), an adhesive tape is used for assembly (for example, patent documents 1 and 2). In addition, an adhesive tape is also used for fixing in-vehicle electronic equipment components such as in-vehicle panels to a vehicle body.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 2009-242541

Patent document 2: japanese patent laid-open No. 2009-258274

Disclosure of Invention

Problems to be solved by the invention

An adhesive tape for fixing portable electronic device components, in-vehicle electronic device components, and the like is required to have high adhesive strength and impact resistance that is not easily peeled off even when subjected to an impact. On the other hand, in recent years, portable electronic devices, in-vehicle electronic devices, and the like have tended to have a more complicated shape with higher functionality, and therefore, adhesive tapes may be used by being attached to uneven portions, corners, non-planar portions, and the like. In such a case, the pressure-sensitive adhesive tape is required to have excellent flexibility capable of following the shape of the adherend.

As an adhesive tape excellent in flexibility and impact resistance, for example, an adhesive tape using a foamed substrate obtained by foaming a polyolefin resin or the like is known. However, in recent years, electronic devices are required to be resistant to repeated impacts (continuous impacts) due to severe and diversified use conditions, and the like, and conventional pressure-sensitive adhesive tapes using foam substrates have the following problems: even if the adhesive is not peeled off by a single impact, the adhesive will peel off or the adhesive will be damaged when the impact such as dropping is repeatedly applied.

The purpose of the present invention is to provide an adhesive tape having excellent repeated impact resistance.

Means for solving the problems

The present invention relates to an adhesive tape, which has: the multilayer substrate comprises a substrate layer and a resin layer laminated on at least one surface of the substrate layer, wherein the storage elastic modulus E ' of the substrate layer in dynamic viscoelasticity measurement at 10 ℃ is 2.0-21 MPa, the Young ' of the resin layer at 23 ℃ is 500MPa or more, the elongation at break of the adhesive layer in shear adhesion measurement at 23 ℃ is 30-30%, and the storage elastic modulus G ' of the adhesive layer in dynamic viscoelasticity measurement at 10 ℃ is 0.13-7.0 MPa.

The present invention will be described in detail below.

The present inventors have found that by using a multilayer substrate having a substrate layer and a resin layer laminated on at least one surface of the substrate layer in an adhesive tape having a substrate and an adhesive layer laminated on at least one surface of the substrate layer, the resin layer can exert a stress-dispersing effect when an impact is applied, and can improve the repeated impact resistance of the adhesive tape.

The present inventors have further analyzed factors that affect the repetition impact resistance of such an adhesive tape. As a result, the present inventors found that: the storage elastic modulus E ' in the dynamic viscoelasticity measurement at 10 ℃ of the base material layer, the Young's modulus at 23 ℃ of the resin layer, the elongation at break in the shear adhesion measurement at 23 ℃ of the adhesive layer, and the storage elastic modulus G ' in the dynamic viscoelasticity measurement at 10 ℃ are adjusted to specific ranges, whereby the adhesive tape can be further greatly improved in the repeated impact resistance. Thus, the present invention has been completed.

The adhesive tape of the present invention comprises: a multilayer substrate, and an adhesive layer laminated on at least one side of the multilayer substrate.

The multilayer substrate comprises: a base material layer and a resin layer laminated on at least one surface of the base material layer. By providing such a multilayer substrate, the resin layer plays a role of dispersing stress when receiving an impact, and the adhesive tape of the present invention can have excellent repeated impact resistance. The resin layer may be laminated on only one side of the base material layer, or may be laminated on both sides, and is preferably laminated on only one side of the base material layer.

The lower limit of the storage elastic modulus E' in the dynamic viscoelasticity measurement at 10 ℃ of the substrate layer is 2.0MPa, and the upper limit thereof is 21MPa.

By setting the storage elastic modulus E' at 10 ℃ to 2.0MPa or more, the base material layer can have a moderate hardness, and the adhesive tape of the present invention can have excellent repeated impact resistance. By setting the storage elastic modulus E' at 10 ℃ to 21MPa or less, the flexibility of the base material layer is improved, and when an impact is applied, the base material layer can be prevented from being too hard to disperse stress, and the adhesive tape of the present invention can have excellent repeated impact resistance. The storage elastic modulus E' at 10℃is preferably 2.1MPa, the upper limit is preferably 12.0MPa, the lower limit is more preferably 2.2MPa, the upper limit is more preferably 11.5MPa, the lower limit is more preferably 2.5MPa, and the upper limit is more preferably 9.6MPa.

The storage elastic modulus E' of the substrate layer in the dynamic viscoelasticity measurement at 10 ℃ can be obtained as follows: the dynamic viscoelasticity spectrum at-40 to 140℃was measured using a viscoelasticity spectrometer (for example, manufactured by IT meter control Co., ltd., DVA-200, etc.) under conditions of 5℃per minute, strain 0.1% and frequency 10Hz in a constant temperature rise stretching mode, and the dynamic viscoelasticity spectrum was obtained as a storage elastic modulus E' at 10 ℃.

The method of adjusting the storage elastic modulus E' at 10 ℃ to the above range is not particularly limited, and examples thereof include: a method for adjusting the gel fraction of the base material layer; a method of adjusting the type or amount of the foaming particles when the substrate layer is a foam substrate layer; the base material layer may be formed by a method of using a copolymer having a structure derived from a vinyl aromatic monomer and a structure derived from a (meth) acrylic monomer, as described later.

The base material layer is not particularly limited as long as the storage elastic modulus E' at 10 ℃ satisfies the above range, and preferably contains a copolymer having a structure derived from a (meth) acrylic monomer, more preferably contains a copolymer having a structure derived from a vinyl aromatic monomer and a structure derived from a (meth) acrylic monomer. By containing these copolymers in the base material layer, the storage elastic modulus E' at 10 ℃ can be easily adjusted to the above range, and the adhesive tape can further improve the impact resistance at repetition.

Examples of the vinyl aromatic monomer include: styrene, alpha-methylstyrene, o-methylstyrene, p-methylstyrene, divinylbenzene, 1-diphenylethylene, 1-ethyl-2-vinylbenzene, 1-ethyl-3-vinylbenzene, vinylnaphthalene, chlorostyrene and the like. These vinyl aromatic monomers may be used alone or in combination of two or more. Among them, styrene is preferable from the viewpoint of further improving the repeating impact resistance of the adhesive tape. In the present specification, the structure derived from a vinyl aromatic monomer means a structure represented by the following general formulae (1) and (2).

[ chemical formula 1]

In the general formulae (1) and (2), R ¹ Represents a substituent having an aromatic ring. As substituent R having aromatic ring ¹ Examples thereof include phenyl, methylphenyl, chlorophenyl and the like.

In the copolymer having a structure derived from a vinyl aromatic monomer and a structure derived from a (meth) acrylic monomer, the content of the structure derived from a vinyl aromatic monomer is not particularly limited, and is preferably 1% by weight or more and 30% by weight or less. By setting the content of the structure derived from the vinyl aromatic monomer to the above range, the adhesive tape is further improved in the impact resistance at repetition. The lower limit of the content of the structure derived from the vinyl aromatic monomer is more preferably 1.5 wt%, the lower limit is more preferably 2 wt%, the lower limit is more preferably 3 wt%, the lower limit is more preferably 3.5 wt%, the upper limit is more preferably 15 wt%, and the upper limit is more preferably 8 wt%.

The copolymer having a structure derived from a vinyl aromatic monomer and a structure derived from a (meth) acrylic monomer preferably further has a structure derived from a monomer having a crosslinkable functional group.

If the copolymer having a structure derived from a vinyl aromatic monomer and a structure derived from a (meth) acrylic monomer has a crosslinkable functional group, the rubber elasticity of the copolymer is improved by crosslinking, and therefore, the storage elastic modulus E' at 10℃is easily adjusted to the above range, and the adhesive tape is further improved in the repeated impact resistance. The crosslinkable functional group may be crosslinked or uncrosslinked, but is more preferably crosslinked. However, even when the uncrosslinked structure is maintained, the cohesive force in the hard block or soft block (particularly, the hard block) described later is improved by the interaction between functional groups, and the storage elastic modulus E' at 10 ℃ is easily adjusted to the above range, so that the adhesive tape is further improved in the impact resistance at repetition. In the present specification, the structure derived from a monomer having a crosslinkable functional group means a structure represented by the following general formulae (3) and (4).

[ chemical formula 2]

In the general formulae (3) and (4), R ² Represents a substituent comprising at least one functional group. Examples of the functional group include: carboxyl, hydroxyl, epoxy, double bond, triple bond, amino, amide, nitrile, etc. The substituent R containing at least one functional group ² An alkyl group, an ether group, a carbonyl group, an ester group, a carbonate group, an amide group, a urethane group, or the like may be contained as a constituent thereof.

The monomer having a crosslinkable functional group is not particularly limited, and examples thereof include: carboxyl group-containing monomers, hydroxyl group-containing monomers, epoxy group-containing monomers, double bond-containing monomers, triple bond-containing monomers, amino group-containing monomers, amide group-containing monomers, nitrile group-containing monomers, and the like. These monomers having a crosslinkable functional group may be used alone or in combination of two or more. Among them, at least one selected from the group consisting of carboxyl group-containing monomers, hydroxyl group-containing monomers, epoxy group-containing monomers, double bond-containing monomers, triple bond-containing monomers and amide group-containing monomers is preferable from the viewpoint of further improving the repeating impact resistance of the adhesive tape.

Examples of the carboxyl group-containing monomer include (meth) acrylic monomers such as (meth) acrylic acid. Examples of the hydroxyl group-containing monomer include 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, and the like. Examples of the epoxy group-containing monomer include glycidyl (meth) acrylate. Examples of the double bond-containing monomer include allyl (meth) acrylate and hexanediol di (meth) acrylate. Examples of the monomer containing a triple bond include propargyl (meth) acrylate. Examples of the amide group-containing monomer include (meth) acrylamide and the like. Among them, carboxyl group-containing monomers and hydroxyl group-containing monomers are preferable from the viewpoint of further improving the repeating impact resistance of the adhesive tape. Further, a (meth) acrylic monomer containing a carboxyl group and a (meth) acrylic monomer containing a hydroxyl group are more preferable, and a (meth) acrylic acid, 4-hydroxybutyl (meth) acrylate, and 2-hydroxyethyl (meth) acrylate are more preferable.

In the copolymer having a structure derived from a vinyl aromatic monomer and a structure derived from a (meth) acrylic monomer, the content of the structure derived from a monomer having a crosslinkable functional group is not particularly limited, and is preferably 0.1% by weight or more and 30% by weight or less. By setting the content of the structure derived from the monomer having a crosslinkable functional group to the above range, the adhesive tape is further improved in the impact resistance at repetition. The lower limit of the content of the structure derived from the monomer having a crosslinkable functional group is more preferably 0.5 wt%, the lower limit is more preferably 1 wt%, the upper limit is more preferably 25 wt%, and the upper limit is more preferably 20 wt%.

The (meth) acrylic monomer may be a single monomer or a plurality of monomers may be used. In the present specification, the structure derived from a (meth) acrylic monomer means a structure represented by the following general formulae (5) and (6).

[ chemical formula 3]

In the general formulae (5) and (6), R ³ Representing a side chain. As side chain R ³ Examples thereof include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl, dodecyl, lauryl, isostearyl and the like.

Examples of the (meth) acrylic monomer include: methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, lauryl (meth) acrylate, isostearyl (meth) acrylate, and the like. These (meth) acrylic monomers may be used alone or in combination of two or more. Among them, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate are preferable, and methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate are more preferable from the viewpoint of further improving the repeating impact resistance of the adhesive tape.

Further, as the (meth) acrylic monomer, a (meth) acrylic monomer having 2 or less carbon atoms in the side chain is preferably used. When the (meth) acrylic monomer having 2 or less carbon atoms in the side chain is used, entanglement of the obtained copolymer chains increases, the cohesive force increases, the storage elastic modulus E' at 10℃is easily adjusted to the above range, and the adhesive tape is further improved in the impact resistance at repetition and also improved in the heat resistance.

The (meth) acrylic monomer having 2 or less carbon atoms in the side chain includes methyl (meth) acrylate and ethyl (meth) acrylate, and methyl acrylate and ethyl acrylate are particularly preferable.

In the copolymer having a structure derived from a vinyl aromatic monomer and a structure derived from a (meth) acrylic monomer, the content of the structure derived from a (meth) acrylic monomer is not particularly limited as long as the effect of the present invention is exhibited, and is preferably 30% by weight or more and 99% by weight or less. The content of the structure derived from the (meth) acrylic monomer is more preferably 40% by weight or more and 98% by weight or less, and still more preferably 50% by weight or more and 97% by weight or less.

In the copolymer having a structure derived from a vinyl aromatic monomer and a structure derived from a (meth) acrylic monomer, the content of the (meth) acrylic monomer having 2 or less carbon atoms in the side chain is not particularly limited, but the lower limit is preferably 5% by weight, and the upper limit is preferably 90% by weight. When the content of the (meth) acrylic monomer having 2 or less carbon atoms in the side chain is 5 wt% or more, the effect of improving the cohesive force is easily exhibited. When the content of the (meth) acrylic monomer having 2 or less carbon atoms in the side chain is 90 wt% or less, the cohesive force becomes too high and the flexibility becomes low, so that the adhesive tape becomes less flexible. The content of the (meth) acrylic monomer having 2 or less carbon atoms in the side chain is more preferably 10 wt%, still more preferably 20 wt%, still more preferably 25 wt%, particularly preferably 30 wt%, yet more preferably 85 wt%, still more preferably 80 wt%, still more preferably 75 wt%, and particularly preferably 70 wt%.

The copolymer having a structure derived from a vinyl aromatic monomer and a structure derived from a (meth) acrylic monomer is not particularly limited as long as it has the respective structures described above, and may be a random copolymer or a block copolymer. The random copolymer is preferable from the viewpoint of further improving the flexibility of the base material layer, and the block copolymer is preferable from the viewpoint of further improving the balance between the hardness and flexibility of the base material layer.

The block copolymer is a copolymer having a rigid structure (hereinafter also referred to as "hard block") and a soft structure (hereinafter also referred to as "soft block").

The two blocks of the block copolymer are not easily compatible, and may have a heterogeneous phase separation structure in which islands formed by aggregation of the hard blocks are dispersed in the sea of the soft block. Further, since the islands serve as suspected crosslinking points (Japanese: suspected shelf points), rubber elasticity can be imparted to the block copolymer, and thus the adhesive tape is further improved in repeated impact resistance. By introducing the crosslinkable functional group described above into the hard block, the adhesive tape has further improved impact resistance at repetition.

Even when the copolymer having a structure derived from a vinyl aromatic monomer and a structure derived from a (meth) acrylic monomer is a random copolymer, the adhesive tape can have excellent repeated impact resistance. This is thought to be probably because: at the very small scale, at the nano-level and at the molecular level, the same interactions as in the above-described phase separation structure are functioning.

In the block copolymer, it is preferable that the vinyl aromatic monomer-derived structure is contained in the hard block, and the (meth) acrylic monomer-derived structure is contained in the soft block.

The hard block is not particularly limited as long as it has a rigid structure, and may have a structure derived from, for example, a compound having a cyclic structure, a compound having a short side chain substituent, or the like, in addition to the structure derived from the vinyl aromatic monomer. The soft block may have a structure derived from a monomer other than the (meth) acrylic monomer, within a range where the effect of the present invention is not lost.

The block copolymer may have any structure such as a diblock structure or a triblock structure, and preferably has a triblock structure having the soft block between the hard blocks, in view of further improving the repeated impact resistance of the adhesive tape.

The block copolymer may be a graft copolymer in which the hard block and the soft block are present in the main chain and the side chain separately. Examples of the graft copolymer include: styrene macromer- (meth) acrylic monomer copolymers, and the like.

The content of the hard block in the block copolymer is not particularly limited, but is preferably 1% by weight or more and 40% by weight or less. By setting the content of the hard block within the above range, the adhesive tape is further improved in the repeated impact resistance and also improved in the heat resistance. The lower limit of the content of the hard block is more preferably 2% by weight, still more preferably 2.5% by weight, and particularly preferably 3% by weight, from the viewpoint of further improving the impact resistance and heat resistance. The more preferable upper limit of the content of the hard block is 35 wt%, the more preferable upper limit is 30 wt%, the more preferable upper limit is 26 wt%, the more preferable upper limit is 20 wt%, the particularly preferable upper limit is 17 wt%, and the particularly preferable upper limit is 8 wt%.

The weight average molecular weight (Mw) of the copolymer having a structure derived from a vinyl aromatic monomer and a structure derived from a (meth) acrylic monomer is not particularly limited, but is preferably 5 to 80 tens of thousands. When the weight average molecular weight is within the above range, the adhesive tape is further improved in repeated impact resistance and also improved in heat resistance. The more preferable lower limit of the weight average molecular weight is 75000, and the more preferable upper limit is 60 ten thousand.

The weight average molecular weight can be obtained by, for example, GPC (Gel Permeation Chromatography: gel permeation chromatography) and conversion to standard polystyrene. More specifically, for example, measurement can be performed using "2690Separations Module" manufactured by Waters corporation as a measurement device, using "GPC KF-806L" manufactured by Showa electric corporation as a chromatographic column, using ethyl acetate as a solvent, and under conditions of a sample flow rate of 1mL/min and a column temperature of 40 ℃.

In order to obtain the copolymer having a structure derived from a vinyl aromatic monomer and a structure derived from a (meth) acrylic monomer, the raw material monomers of the hard block and the soft block may be subjected to a radical reaction in the presence of a polymerization initiator to obtain the hard block and the soft block, respectively, and then the hard block and the soft block may be reacted or copolymerized. After the hard block is obtained, the raw material monomer of the soft block may be continuously charged to perform copolymerization. In the case of a random copolymer, the solution in which the raw material monomers are mixed may be subjected to radical reaction in the presence of a polymerization initiator.

As a method for conducting the radical reaction, that is, a polymerization method, conventionally known methods may be used, and examples thereof include solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, bulk polymerization, and the like.

The base layer may contain additives such as antistatic agents, mold release agents, antioxidants, weather-proofing agents, and crystallization nucleating agents, and resin modifiers such as polyolefin, polyester, polyamide, and elastomer.

The substrate layer preferably has at least one peak in each of a region at 10 ℃ or lower and a region at 50 ℃ or higher when DSC measurement (differential scanning calorimetry) is performed in the atmosphere at a temperature rise rate of 10 ℃/min.

When the substrate layer has at least one peak in each of a region of 10 ℃ or lower and a region of 50 ℃ or higher in DSC measurement, it can be said that the substrate layer contains the block copolymer having two blocks as described above. From the viewpoint of further improving the balance between the hardness and flexibility of the base material layer, it is preferable that the base material layer contains the block copolymer, as described above. In the present invention, the peak in the region at 10℃or lower in DSC measurement may be referred to as a peak derived from the soft block, and the peak in the region at 50℃or higher may be referred to as a peak derived from the hard block. The peak region can be adjusted by the kind of the raw material monomer of the hard block and the soft block.

The DSC measurement of the base material layer may be performed using a differential scanning calorimeter (for example, DSC 2920, manufactured by TA Instruments Co., ltd.) under conditions of a temperature range of-100 to 200℃and a heating rate of 10℃per minute, and a cycle number of 1.

The substrate layer may have a single-layer structure or a multilayer structure.

The substrate layer is preferably a foam substrate layer. By making the base material layer be the foam base material layer, flexibility is improved, and when an impact is applied, the base material layer can be prevented from being too hard to disperse stress. Thereby, the repeated impact resistance of the adhesive tape is further improved. The foam base material layer may have an open cell structure or an independent cell structure, but preferably has an independent cell structure.

The foaming ratio of the foam base layer is not particularly limited, but the lower limit is preferably 1.1 times, and the upper limit is preferably 10 times. When the expansion ratio is in the above range, the balance between the hardness and flexibility of the foam base material layer can be further improved, and therefore, the adhesive tape can be further improved in terms of impact resistance at repetition. From the viewpoint of further improving the repetition impact resistance, the lower limit of the expansion ratio is more preferably 1.3 times, the upper limit is more preferably 7 times, the lower limit is more preferably 1.5 times, and the upper limit is more preferably 5 times.

The expansion ratio of the foam base material layer is the inverse number of the density of the foam base material layer, and can be measured by using an electron densitometer (for example, manufactured by MIRAGE Co., ltd., ED120T, etc.) based on JIS K7222.

The average cell diameter of the foam base layer is not particularly limited, but is preferably 80 μm or less. By setting the average cell diameter to 80 μm or less, the balance between the hardness and flexibility of the foam base material layer can be further improved, and therefore, the adhesive tape can be further improved in the impact resistance at repetition. The average bubble diameter is more preferably 60 μm or less, and still more preferably 55 μm or less.

The lower limit of the average cell diameter is not particularly limited, but is preferably 20 μm or more, more preferably 30 μm or more, from the viewpoint of securing flexibility of the foam base material layer.

The average cell diameter of the foam base material layer can be measured by the following method. First, the foam base layer was cut into 50mm square pieces, immersed in liquid nitrogen for 1 minute, and then cut by a razor on a surface perpendicular to the thickness direction of the foam base layer. Next, an enlarged photograph of the cut surface was taken at 200 times magnification using a digital microscope (for example, "VHX-900" manufactured by KEYENCE corporation), and the longest bubble diameter (bubble diameter) was measured for all bubbles present in the range of thickness×2 mm. This operation was repeated 5 times, and the resultant total bubble diameters were averaged, thereby calculating an average bubble diameter.

The gel fraction of the base layer is preferably 90% by weight or less.

By setting the gel fraction of the base material layer to the above range, the adhesive tape is further improved in the repeated impact resistance. From the viewpoint of further improving the repetition impact resistance, the upper limit of the gel fraction is more preferably 85% by weight, and the upper limit is more preferably 80% by weight. The lower limit of the gel fraction is not particularly limited, and is, for example, 10% by weight or more, particularly 20% by weight or more, and particularly 35% by weight or more. The gel fraction can be adjusted by crosslinking the resin forming the base layer.

The gel fraction of the base material layer can be measured by the following method. Only 0.1g of the base layer was taken out from the adhesive tape, immersed in 50mL of ethyl acetate, and shaken by a shaker at a temperature of 23℃and 120rpm for 24 hours. After shaking, ethyl acetate was separated from the base material layer swollen by absorbing ethyl acetate using a metal mesh (mesh # 200). The separated substrate layer was dried at 110℃for 1 hour. The weight of the dried base material layer containing the metal net was measured, and the gel fraction of the base material layer was calculated using the following formula.

Gel fraction (wt%) =100× (W ₁ -W ₂ )/W ₀

(W ₀ : initial substrate layer weight, W ₁ : weight of dried substrate layer containing metal mesh, W ₂ : initial weight of metal mesh

The base material layer preferably has a crosslinked structure formed between the main chains of the resin forming the base material layer by adding a crosslinking agent.

By forming a crosslinked structure between the main chains of the resin forming the base layer, the intermittently applied stress can be dispersed, and the adhesive tape can be further improved in the repeated impact resistance and also in the heat resistance.

The crosslinking agent is not particularly limited, and may be appropriately selected according to the functional group of the resin forming the base layer. Specifically, examples thereof include: isocyanate-based crosslinking agents, aziridine-based crosslinking agents, epoxy-based crosslinking agents, metal chelate-based crosslinking agents, and the like. Among them, epoxy-based crosslinking agents and isocyanate-based crosslinking agents are preferable from the viewpoint of being capable of crosslinking resins having alcoholic hydroxyl groups and carboxyl groups, which can further improve flexibility. When the isocyanate-based crosslinking agent is used, the resin forming the base layer is crosslinked between the alcoholic hydroxyl group and the carboxyl group in the resin and the isocyanate group of the isocyanate-based crosslinking agent. In the case of using the epoxy-based crosslinking agent, the carboxyl group in the resin forming the base layer and the epoxy group of the epoxy-based crosslinking agent are crosslinked.

The amount of the crosslinking agent to be added is not particularly limited, but is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 7 parts by weight, based on 100 parts by weight of the resin forming the base layer.

The thickness of the base material layer is not particularly limited, but is preferably limited to 40 μm at the lower limit and 2900 μm at the upper limit. By setting the thickness of the base material layer to the above range, an adhesive tape excellent in flexibility, repeated impact resistance, heat resistance, handleability, and the like can be produced, and the adhesive tape can be suitably used for fixing electronic device components such as portable electronic device components and vehicle-mounted electronic device components. From the viewpoint of being more suitably used for fixing the above-described member or the like, the thickness of the above-described base material layer is more preferably limited to 60 μm at a lower limit, 1900 μm at a more preferred upper limit, 80 μm at a more preferred lower limit, 1400 μm at a more preferred upper limit, 100 μm at a particularly preferred lower limit, and 1000 μm at a particularly preferred upper limit.

The method for producing the base material layer is not particularly limited. Examples of the method for producing the foam base material layer in the base material layer include: a method of manufacturing by the action of a foaming gas; a method of manufacturing by incorporating hollow spheres into a raw material matrix. Among them, the foam base material layer produced by the latter method is called a syntactic foam, and the foam base material layer is preferably a syntactic foam in view of more excellent strength, flexibility and heat resistance.

By forming the foam base layer as a composite foam, a foam having a uniform size distribution of independent cells is obtained, and therefore, the density of the foam base layer as a whole is more constant, and the strength, flexibility, and heat resistance are further improved. In addition, the syntactic foam is less likely to cause irreversible disintegration at high temperature and high pressure than other foams, and therefore exhibits higher heat resistance. As syntactic foam, there are: a composite foam having a foamed structure containing hollow inorganic particles and a composite foam having a foamed structure containing hollow organic particles are preferred from the viewpoint of flexibility.

Examples of the hollow organic particles include: expancel DU series (manufactured by Japan Fillite Co., ltd.), advanell EM series (manufactured by ponding chemical industries Co., ltd.), and the like. Among them, from the viewpoint of easy design of the bubble diameter after foaming to a region with higher effect, expancel461-DU-20 (average bubble diameter after foaming under optimal conditions of 20 μm), expancel461-DU-40 (average bubble diameter after foaming under optimal conditions of 40 μm), expancel 043-80 (average bubble diameter after foaming under optimal conditions of 80 μm), and advanced EML101 (average bubble diameter after foaming under optimal conditions of 50 μm) are preferable.

The content of the hollow organic particles is not particularly limited, but is preferably limited to 0.1 part by weight, preferably 10 parts by weight, more preferably 0.3 parts by weight, and still more preferably 7 parts by weight, based on 100 parts by weight of the resin forming the foam base layer. By setting the content of the hollow organic particles to the above range, the expansion ratio of the foam base material layer can be adjusted to an appropriate range.

The foaming agent in the case where the foam base layer contains a foam other than the syntactic foam is not particularly limited, and a conventionally known foaming agent such as a thermally decomposable foaming agent can be used.

The lower limit of Young's modulus of the resin layer at 23℃is 500MPa.

By setting the Young's modulus at 23℃to 500MPa or more, the resin layer can disperse stress when an impact is applied thereto, and the adhesive tape of the present invention can have excellent repeated impact resistance. The lower limit of Young's modulus at 23℃is preferably 1000MPa, and more preferably 2000MPa.

The upper limit of the Young's modulus at 23℃is not particularly limited, but from the viewpoint of securing flexibility, the upper limit is preferably 4000MPa, and more preferably 3000MPa.

The Young's modulus of the resin layer at 23℃can be measured by using a bench-type precision universal tester (for example, autograph AGS-X series, manufactured by Shimadzu corporation) based on JIS-K-7161. More specifically, for example, a test piece cut into a width of 10mm and a length of 100mm is held at intervals of 50mm, a stress-strain curve at a speed of 200mm/min is measured, and an average slope from 1% to 5% of strain is calculated to obtain Young's modulus.

The method of adjusting the Young's modulus at 23℃to the above range is not particularly limited, and examples thereof include a method of selecting a resin for forming the resin layer. More specifically, a resin having a rigid component such as an aromatic ring in the main chain is preferably selected.

The resin forming the resin layer preferably has heat resistance. Examples of the resin having heat resistance and forming the resin layer include: polyester resins such as polyethylene terephthalate, acrylic resins, silicone resins, phenolic resins, polyimides, polycarbonates, polyolefin resins, and the like. Among them, from the viewpoint of further improving the repeating impact resistance of the adhesive tape, polyester-based resins, polyimide and polyolefin resins are preferable, polyester-based resins are more preferable, and polyethylene terephthalate is still more preferable.

The resin layer may be colored. By coloring the resin layer, light shielding properties can be imparted to the pressure-sensitive adhesive tape.

The method for coloring the resin layer is not particularly limited, and examples thereof include: a method of mixing particles or fine bubbles such as carbon black and titanium oxide into the resin forming the resin layer; a method of applying an ink to the surface of the resin layer.

The resin layer may contain conventionally known particles and additives such as inorganic particles, conductive particles, plasticizers, tackifiers, ultraviolet absorbers, antioxidants, foaming agents, organic fillers, and inorganic fillers, as needed.

The thickness of the resin layer is not particularly limited, but is preferably 5 μm in lower limit and 100 μm in upper limit. By setting the thickness of the resin layer to the above range, the handleability and the repeated impact resistance of the adhesive tape can be achieved at the same time. From the viewpoint of further satisfying both of handling properties and repeated 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 pressure-sensitive adhesive layer may be laminated on only one side of the multilayer substrate, or may be laminated on both sides. When the adhesive layers are laminated on both surfaces of the multilayer substrate, the adhesive layers on both surfaces may have the same composition and physical properties, or may have different compositions and physical properties.

The lower limit of the elongation at break in the shear adhesion measurement at 23℃of the adhesive layer was 30%. By setting the elongation at break at 23 ℃ to 30% or more, breakage due to deformation of the adhesive layer upon receiving an impact is less likely to occur, and the adhesive tape of the present invention can have excellent repeated impact resistance. The preferable lower limit of the elongation at break at 23℃is 35%.

The upper limit of the elongation at break at 23℃is not particularly limited, but from the viewpoint of securing strength, the upper limit is preferably 80%, and more preferably 70%.

The elongation at break in the measurement of the shear adhesion force of the adhesive layer at 23℃can be calculated as described below based on JIS-Z-0237 using a bench-type precision universal tester (for example, autograph AGS-X series, manufactured by Shimadzu corporation).

Test pieces obtained by cutting the adhesive tape into pieces having a length of 5 mm. Times.35 mm in width were prepared. Then, two polycarbonate plates 55mm×65mm×1mm thick were adhered to both sides of the test piece, and the two polycarbonate plates were adhered by pressing with 10kg for 10 seconds. Then, the mixture was allowed to stand at 23℃for 3 hours to obtain a test sample. By the above-mentioned apparatus, the test specimen was stretched in the longitudinal direction of the test piece at a speed of 500mm/min in an atmosphere of 23 ℃, the stretching elongation at break of the test piece was recorded, and the elongation at break in the shear adhesion measurement of the adhesive layer at 23 ℃ was calculated as the elongation relative to the length of the test piece.

In the case of using the laminate as a measurement object, the elongation at break in the shear adhesion measurement is dominant in the influence of the layer that is most likely to extend. Even if the laminate to be measured contains a layer having a small elongation due to a shearing force, the presence of the layer having a small elongation due to a shearing force does not greatly affect the overall value. Therefore, when the adjustment of the test piece is difficult, the elongation at break of the layer which is most easily stretched can be estimated by performing the same measurement on the laminate itself.

The lower limit of the gel fraction of the adhesive layer is preferably 10 wt% and the upper limit is preferably 90 wt%. If the gel fraction is 10% by weight or more, the pressure-sensitive adhesive layer is less likely to deform when subjected to impact, and the adhesive tape further improves in the repeated impact resistance. If the gel fraction is 90 wt% or less, the flexibility of the pressure-sensitive adhesive layer is improved, and the pressure-sensitive adhesive layer can be prevented from being too hard to disperse stress when an impact is applied. Thereby, the repeated impact resistance of the adhesive tape is further improved. The lower limit of the gel fraction is more preferably 20% by weight, and the upper limit is more preferably 80% by weight.

The gel fraction of the adhesive layer can be measured by the same method as the gel fraction of the base material layer.

The lower limit of the storage elastic modulus G' in the dynamic viscoelasticity measurement at 10 ℃ of the adhesive layer is 0.13MPa, and the upper limit thereof is 7.0MPa. If the storage elastic modulus G' at 10℃is 0.13MPa or more, the pressure-sensitive adhesive layer is less likely to deform when subjected to an impact, and the adhesive tape is further improved in the repeated impact resistance. If the storage elastic modulus G' at 10 ℃ is 7.0MPa or less, the flexibility of the pressure-sensitive adhesive layer is improved, and the pressure-sensitive adhesive layer can be prevented from being too hard to disperse stress when an impact is applied. Thereby, the repeated impact resistance of the adhesive tape is further improved. The lower limit of the storage elastic modulus G' of the adhesive layer at 10℃is preferably 0.25MPa, the upper limit is preferably 5.0MPa, the lower limit is more preferably 0.3MPa, and the upper limit is more preferably 4.0MPa.

The storage elastic modulus G 'of the adhesive layer at 10 ℃ can be measured by the same method as the storage elastic modulus of the base material layer, except that the storage elastic modulus G' is measured in the constant temperature rise shear mode.

The method of adjusting the elongation at break at 23℃and the gel fraction and the storage elastic modulus G' at 10℃to the above ranges is not particularly limited, and examples thereof include a method of selecting a resin and an additive for forming the adhesive layer. More specifically, as the pressure-sensitive adhesive layer, an acrylic pressure-sensitive adhesive layer containing an acrylic copolymer, a tackifying resin, and a crosslinking agent as described below is preferably used.

The pressure-sensitive adhesive layer is not particularly limited, and examples thereof include an acrylic pressure-sensitive adhesive layer, a rubber pressure-sensitive adhesive layer, a urethane pressure-sensitive adhesive layer, a silicone pressure-sensitive adhesive layer, and the like. Among them, an acrylic pressure-sensitive adhesive layer containing an acrylic copolymer is preferable in that it has excellent heat resistance and can be adhered to a wide variety of adherends.

The acrylic copolymer is preferably obtained by copolymerizing a monomer mixture containing butyl acrylate and/or 2-ethylhexyl acrylate, from the viewpoint that the adhesion at low temperature becomes good due to the improvement of the initial tackiness. Of these, a monomer mixture containing butyl acrylate and 2-ethylhexyl acrylate is more preferable to be copolymerized.

The preferable lower limit of the content of the butyl acrylate in the whole monomer mixture is 40% by weight, and the preferable upper limit is 80% by weight. By setting the content of butyl acrylate to the above range, both high adhesion and tackiness can be achieved.

The content of 2-ethylhexyl acrylate in the whole monomer mixture is preferably 10% by weight at the lower limit and 100% by weight at the upper limit. By setting the content of 2-ethylhexyl acrylate to the above range, high adhesion can be exhibited.

The above monomer mixture may contain other copolymerizable polymerizable monomers other than butyl acrylate and 2-ethylhexyl acrylate as required. Examples of the other copolymerizable polymerizable monomer include alkyl (meth) acrylates having 1 to 18 carbon atoms in the alkyl group, functional monomers, and the like.

Examples of the alkyl (meth) acrylate in which the alkyl group has 1 to 18 carbon atoms include: methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, tridecyl (meth) acrylate, stearyl (meth) acrylate, and the like. Examples of the functional monomer include: hydroxyalkyl (meth) acrylates, alkoxyalkyl (meth) acrylates, glycerol dimethacrylate, glycidyl (meth) acrylate, 2-methacryloyloxyethyl isocyanate, (meth) acrylic acid, itaconic acid, maleic anhydride, crotonic acid, maleic acid, fumaric acid, and the like.

In order to obtain the acrylic copolymer by copolymerizing the monomer mixture, the monomer mixture may be subjected to a radical reaction in the presence of a polymerization initiator. As a method for causing the above monomer mixture to undergo a radical reaction, that is, a polymerization method, conventionally known methods may be used, and examples thereof include solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, bulk polymerization, and the like.

The weight average molecular weight (Mw) of the acrylic copolymer is not particularly limited, but is preferably 40 tens of thousands as a lower limit and 150 tens of thousands as an upper limit. By setting the weight average molecular weight of the acrylic copolymer to the above range, high adhesion can be exhibited. From the viewpoint of further improving the adhesive force, the more preferable lower limit of the weight average molecular weight is 50 ten thousand, and the more preferable upper limit is 140 ten thousand.

The preferable upper limit of the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the acrylic copolymer is 10.0. When the Mw/Mn is 10.0 or less, the ratio of low molecular components is suppressed, and the pressure-sensitive adhesive layer is prevented from softening at high temperature, and the bulk strength (Japanese strength) and the adhesive strength are prevented from decreasing. From the same viewpoint, the more preferable upper limit of Mw/Mn is 5.0, and the more preferable upper limit is 3.0.

The adhesive layer may contain a tackifying resin.

Examples of the tackifying resin include rosin ester resins, hydrogenated rosin resins, terpene phenol resins, coumarone indene resins, alicyclic saturated hydrocarbon resins, C5 petroleum resins, C9 petroleum resins, and C5-C9 copolymerized petroleum resins. These tackifying resins may be used alone or in combination of two or more.

The content of the tackifying resin is not particularly limited, but is preferably 10 parts by weight at the lower limit and 60 parts by weight at the upper limit, relative to 100 parts by weight of the resin (for example, acrylic copolymer) that is the main component of the adhesive layer. When the content of the tackifier resin is 10 parts by weight or more, the pressure-sensitive adhesive layer can exhibit high adhesive force. When the content of the tackifying resin is 60 parts by weight or less, a decrease in adhesion or tackiness due to hardening of the adhesive layer can be suppressed.

The pressure-sensitive adhesive layer preferably has a crosslinked structure between the main chains of the resin (for example, the acrylic copolymer, the tackifying resin, etc.) forming the pressure-sensitive adhesive layer by adding a crosslinking agent.

The crosslinking agent is not particularly limited, and examples thereof include isocyanate-based crosslinking agents, aziridine-based crosslinking agents, epoxy-based crosslinking agents, metal chelate-based crosslinking agents, and the like. Among them, an isocyanate-based crosslinking agent is preferable. By adding an isocyanate-based crosslinking agent to the pressure-sensitive adhesive layer, the isocyanate groups of the isocyanate-based crosslinking agent react with the alcoholic hydroxyl groups in the resin (for example, the acrylic copolymer, the tackifying resin, etc.) forming the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer is crosslinked. By forming a crosslinked structure between the main chains of the resin forming the pressure-sensitive adhesive layer, the intermittently applied stress can be dispersed, and the pressure-sensitive adhesive tape can be further improved in terms of impact resistance and heat resistance.

The amount of the crosslinking agent to be added is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 7 parts by weight, based on 100 parts by weight of the resin (for example, the acrylic copolymer) which is the main component of the pressure-sensitive adhesive layer.

The adhesive layer may contain a silane coupling agent for the purpose of improving the adhesive force. The silane coupling agent is not particularly limited, and examples thereof include epoxy silanes, acrylic silanes, methacrylic silanes, amino silanes, isocyanate silanes, and the like.

The pressure-sensitive adhesive layer may contain a coloring material for the purpose of imparting light-shielding property. The coloring material is not particularly limited, and examples thereof include carbon black, nigrosine, titanium oxide, and the like. Among them, carbon black is preferable in terms of relatively low cost and chemical stability.

The pressure-sensitive adhesive layer may contain conventionally known particles such as inorganic particles, conductive particles, antioxidants, foaming agents, organic fillers, and inorganic fillers, and additives, as required.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, but is preferably 0.01mm in lower limit, 0.1mm in upper limit, 0.015mm in lower limit, and 0.09mm in upper limit. By setting the thickness of the pressure-sensitive adhesive layer to the above range, an adhesive tape excellent in flexibility, repeated impact resistance, heat resistance, handleability, and the like can be produced, and the adhesive tape can be suitably used for fixing electronic device components such as portable electronic device components and vehicle-mounted electronic device components.

The lower limit of the elongation at break in the shear adhesion measurement at 23℃of the adhesive tape of the present invention is preferably 30%. The elongation at break of the adhesive tape of the present invention in the shear adhesion measurement at 23 ℃ can be adjusted by, for example, changing the elongation at break of the adhesive layer in the shear adhesion measurement at 23 ℃.

The thickness of the whole adhesive tape of the present invention is not particularly limited, but is preferably 0.04mm in lower limit, more preferably 0.05mm in lower limit, and preferably 2mm in upper limit, more preferably 1.5mm in upper limit. When the thickness of the entire pressure-sensitive adhesive tape of the present invention is in the above range, the pressure-sensitive adhesive tape can be produced which is excellent in flexibility, repeated impact resistance, heat resistance, handleability and the like.

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

The method for producing the pressure-sensitive adhesive tape of the present invention is not particularly limited, and examples thereof include the following methods. First, an adhesive solution is coated on a release film and dried to form an adhesive layer. Next, an unfoamed base material layer is produced, and a resin layer is laminated on the unfoamed base material layer to form a laminate. Then, the adhesive layers were bonded to both sides of the obtained laminate, and the foam substrate layer was produced by foaming the unfoamed substrate by heating, thereby producing an adhesive tape.

The use of the pressure-sensitive adhesive tape of the present invention is not particularly limited, and is preferably used for assembling or fixing electronic equipment parts such as portable electronic equipment parts and in-vehicle electronic equipment parts because of its excellent repetition impact resistance.

Effects of the invention

According to the present invention, an adhesive tape excellent in repeated impact resistance can be provided.

Detailed Description

The following examples illustrate the mode of the present invention in more detail, but the present invention is not limited to these examples.

Example 1

(1) Manufacture of unfoamed substrate layers

Into a 2-necked flask, 0.902g of 1, 6-hexanedithiol, 1.83g of carbon disulfide and 11mL of dimethylformamide were charged, and the mixture was stirred at 25 ℃. 2.49g of triethylamine was added dropwise thereto over 15 minutes, and the mixture was stirred at 25℃for 3 hours. Next, 2.75g of methyl-. Alpha. -bromophenylacetic acid was added dropwise over 15 minutes, followed by stirring at 25℃for 4 hours. Thereafter, 100mL of an extraction solvent (n-hexane: ethyl acetate=50:50) and 50mL of water were added to the reaction solution, followed by liquid-separation extraction. The organic layers obtained by the first and second liquid-phase extractions were mixed and washed successively with 50mL of 1M hydrochloric acid, 50mL of water, and 50mL of saturated brine. After drying the washed organic layer by adding sodium sulfate, sodium sulfate was filtered, and the filtrate was concentrated by an evaporator to remove the organic solvent. The resulting concentrate was purified by silica gel column chromatography, whereby a RAFT agent was obtained.

93 parts by weight of styrene (St), 6 parts by weight of acrylic acid (AAc), 1 part by weight of hydroxyethyl acrylate (HEA), 2.8 parts by weight of RAFT agent, and 0.35 part by weight of 2,2' -azobis (2-methylbutyronitrile) (ABN-E) were charged into a 2-necked flask, and the inside of the flask was replaced with nitrogen gas, and the temperature was raised to 85 ℃. Then, the mixture was stirred at 85℃for 6 hours to carry out a polymerization reaction (first-stage reaction).

After completion of the reaction, 4000 parts by weight of n-hexane was charged into the flask, the reaction mixture was stirred to precipitate a reaction product, and then unreacted monomer and RAFT agent were filtered, and the reaction product was dried under reduced pressure at 70 ℃.

A mixture comprising 49.5 parts by weight of Methyl Acrylate (MA), 49.5 parts by weight of Butyl Acrylate (BA), 1 part by weight of acrylic acid (AAc), 0.058 parts by weight of ABN-E and 50 parts by weight of ethyl acetate, and the copolymer (hard block) obtained above were put into a 2-necked flask, and the inside of the flask was purged with nitrogen gas and then heated to 85 ℃. Then, the mixture was stirred at 85℃for 6 hours, and polymerization reaction (second stage reaction) was carried out to obtain a reaction solution containing a block copolymer composed of a hard block and a soft block. The blending amount of the mixture was adjusted so that the hard block content and the soft block content of the obtained block copolymer became 3% by weight and 97% by weight, respectively.

A part of the reaction solution was taken, 4000 parts by weight of n-hexane was added thereto, and after the reaction was precipitated by stirring, unreacted monomers and a solvent were filtered, and the reaction was dried under reduced pressure at 70℃to obtain a block copolymer.

The weight average molecular weight of the obtained block copolymer was measured by GPC and found to be 39 ten thousand. The measurement was performed using "2690Separations Module" manufactured by Waters corporation as a measurement device, using "GPC KF-806L" manufactured by Showa electric corporation as a chromatographic column, using ethyl acetate as a solvent, and under conditions of a sample flow rate of 1mL/min and a column temperature of 40 ℃.

The obtained block copolymer was dissolved in ethyl acetate so that the solid content was 35%. 3.3 parts by weight of Expancel 461-DU-40 (461 DU 40) (manufactured by Japan filler Co., ltd.) as a foaming agent (expanded particles) and 0.15 part by weight of tetra C (manufactured by Mitsubishi gas chemical Co., ltd.) as a crosslinking agent were added to 100 parts by weight of the block copolymer, and the mixture was further sufficiently stirred to obtain a foam base material layer solution. The obtained foam base material layer solution was applied to a corona-treated surface of a resin film (a polyethylene terephthalate (PET) film having a thickness of 23 μm after corona treatment on one surface, a young's modulus of 2026MPa at 23 ℃) as a resin layer I, and dried at 90 ℃ for 7 minutes, thereby obtaining a laminate of an unfoamed base material layer a and the resin layer I. The thickness of the unfoamed base material layer a was adjusted so that the unfoamed base material layer a after standing at 40 ℃ for 48 hours became 127 μm when heated at 130 ℃ for 1 minute.

(2) Preparation of binder solution

78 parts by weight of Butyl Acrylate (BA), 19 parts by weight of 2-ethylhexyl acrylate (2 EHA), 3 parts by weight of acrylic acid (AAc), 0.2 part by weight of 2-hydroxyethyl acrylate (HEA) and 80 parts by weight of ethyl acetate were added to a reactor equipped with a thermometer, a stirrer and a condenser, and after replacing with nitrogen, the reactor was heated to start reflux. Next, 0.1 part by weight of azobisisobutyronitrile as a polymerization initiator was added to the above reactor. Reflux was carried out for 5 hours to obtain a solution of an acrylic copolymer (random copolymer). The weight average molecular weight of the obtained acrylic copolymer was measured by GPC using a column "2690Separations Model" manufactured by Waters corporation, and found to be 91 ten thousand.

15 parts by weight of a polymerized rosin ester resin having a softening point of 135 ℃, 10 parts by weight of a terpene-phenol resin having a softening point of 160 ℃, and 10 parts by weight of a rosin ester resin having a softening point of 75 ℃ were added to 100 parts by weight of the solid content of the acrylic copolymer contained in the obtained acrylic copolymer solution. 125 parts by weight of ethyl acetate (manufactured by Wako chemical industries, ltd.) and 2.2 parts by weight of an isocyanate-based crosslinking agent (manufactured by Tosoh corporation, coronate L45) were further added and stirred to obtain a solution of the adhesive (1).

(3) Production of adhesive tape

The release treated surface of a 50 μm polyethylene terephthalate (PET) film having one surface subjected to release treatment was coated with the solution of the obtained adhesive (1) using a doctor blade so that the thickness of the dried film became 75 μm, and the coated solution was heated at 110℃for 5 minutes, whereby the adhesive layer (1) was obtained. Then, another adhesive layer was produced by the same procedure, and two adhesive layers (1) were obtained. Then, two adhesive layers (1) were laminated on both sides of the laminate of the unfoamed base material layer a and the resin layer I, and the laminate was left standing at 40 ℃ for 48 hours. After 48 hours, the adhesive tape was obtained by taking out from the 40℃environment and heating at 130℃for 1 minute to foam the unfoamed base material layer A, thereby producing a foamed base material layer A.

(4) Preparation of sample for measuring elongation at break of adhesive layer

A sample for measuring elongation at break of the adhesive layer was obtained in the same manner as in (3) above except that the adhesive layer (1) was bonded to both surfaces of a polyethylene terephthalate (PET) film having a thickness of 50 μm instead of the laminate of the unfoamed base material layer a and the resin layer I.

(5) Determination of gel fraction of substrate layer

Only 0.1g of the base material layer (foam base material layer a) was taken out from the adhesive tape, immersed in 50mL of ethyl acetate, and shaken by a shaker at a temperature of 23℃and 120rpm for 24 hours. After shaking, ethyl acetate was separated from the base material layer swollen by absorbing ethyl acetate using a metal mesh (mesh # 200). The separated substrate layer was dried at 110℃for 1 hour. The weight of the dried base material layer containing the metal net was measured, and the gel fraction of the base material layer was calculated using the following formula.

Gel fraction (wt%) =100× (W ₁ -W ₂ )/W ₀

(6) Determination of storage elastic modulus E' and expansion ratio of substrate layer at 10 DEG C

A dynamic viscoelasticity spectrum at-40 to 140℃in a constant temperature rise stretching mode of 5℃per minute, a strain of 0.1% and a frequency of 10Hz was obtained by using a viscoelasticity spectrometer (DVA-200, manufactured by IT meter control Co.), and the storage elastic modulus E' of the base material layer (foam base material layer A) at 10℃was measured.

The expansion ratio of the base material layer (foam base material layer a) was measured by using an electronic densitometer (ED 120T, manufactured by MIRAGE corporation) based on JIS K7222.

(7) Determination of elongation at break of adhesive layer at 23 DEG C

The measurement was performed in accordance with JIS-Z-0237 using a bench-type precision universal tester (Autograph AGS-X series, manufactured by Shimadzu corporation) as follows.

A test piece obtained by cutting a sample for measuring elongation at break of an adhesive layer into pieces having a length of 5 mm. Times.35 mm was prepared, and then two polycarbonate plates having a thickness of 55 mm. Times.65 mm. Times.1 mm were bonded to both sides of the test piece, and the two polycarbonate plates were bonded by pressing with 10kg for 10 seconds. Then, the mixture was allowed to stand at 23℃for 3 hours to obtain a test sample. By the above-mentioned apparatus, the test specimen was stretched in the longitudinal direction of the test piece at a speed of 500mm/min in an atmosphere of 23 ℃, the stretching elongation at break of the test piece was recorded, and the elongation at break in the shear adhesion measurement of the adhesive layer at 23 ℃ was calculated as the elongation relative to the length of the test piece.

(8) Determination of gel fraction of adhesive layer

From the pressure-sensitive adhesive tape, only 0.1g of the pressure-sensitive adhesive layer (1)) was removed, and the gel fraction was measured by the same method as that of the base layer.

(9) Determination of storage elastic modulus G' of adhesive layer at 10 DEG C

The storage elastic modulus G 'was measured by the same method as the storage elastic modulus E' of the base material layer (foam base material layer a) at 10 ℃.

Examples 2 to 20 and comparative examples 1 to 7

An adhesive tape was obtained in the same manner as in example 1, except that the base material layer (foam base material layer), the adhesive layer, and the resin layer were changed as shown in tables 4 to 5. Details of the base material layer (foam base material layer) are shown in table 1, details of the adhesive layer are shown in table 2, and details of the resin layer are shown in table 3.

The AS-6S (styrene macromer solution (50% toluene solution) manufactured by Toyama Synthesis Co., ltd.) of the base material layer (foam base material layer R) used in comparative example 7 was adjusted so that the styrene macromer solid amount became the value shown in the table. The raw materials in the table are as follows.

Foaming agent (foaming particles)

Expancel 461-DU-40 (461 DU 40) (manufactured by Japan Fillite Co., ltd.)

Expancel 461-DU-20 (461 DU 20) (manufactured by Japan Fillite Co., ltd.)

Advance ll EML101 (manufactured by Water chemical industry Co., ltd.)

Raw material monomer of substrate layer

AS-6S (styrene macromer solution (50% toluene solution) manufactured by east Asia Synthesis Co., ltd.)

2EHA (2-ethylhexyl acrylate)

Resin for forming resin layer

OPP (polyolefin resin film, thickness 25 μm, young's modulus at 23 ℃ C. 689 MPa)

PI (polyimide film, thickness 25 μm, young's modulus 2110MPa at 23 ℃ C.)

Acrylic resin film (thickness 23 μm, young's modulus at 23 ℃ C. 1.3MPa, preparation method is shown below)

(method for producing acrylic resin film as resin layer IV)

An acrylic resin film was obtained in the same manner as in the method for producing the unfoamed substrate layer a of example 1, except that the composition was changed as described below, and a resin solution was applied to the release treated surface of a polyethylene terephthalate (PET) film having a thickness of 50 μm without adding foaming particles and a curing agent.

Content ratio of each block: hard block 20 wt%, soft block 80 wt%

Hard block composition (weight ratio): st 93%, AAc 12%, HEA 1%

Soft block composition (weight ratio): MA 50%, BA 50%

Weight average molecular weight: 40 ten thousand (40)

< evaluation >

The adhesive tapes obtained in examples and comparative examples were evaluated as follows. The results are shown in tables 4 to 5.

(1) Repeated impact test

Two pieces of adhesive tape cut into 1mm by 70mm were prepared. Next, the adhesive tape was attached to each short side of a polycarbonate plate having a thickness of 1mm and a longitudinal direction of 72mm and a lateral direction of 135 mm. The polycarbonate sheets were bonded by overlapping the side of the polycarbonate sheet to which the adhesive tape was attached with the polycarbonate sheet having a longitudinal direction of 77mm, a transverse direction of 150mm and a thickness of 4mm such that the short sides and the long sides of the two polycarbonate sheets were opposed to each other and pressing at 0.7MPa for 15 seconds. Then, the mixture was allowed to stand at 23℃for 24 hours, whereby a test sample was obtained.

The test sample was placed in a TD-1000A drum-type spin drop tester (manufactured by Xinrong electronic measuring instruments Co., ltd.) and was spun at a speed of 12 revolutions per minute while being maintained in a room temperature environment at 23℃to thereby repeatedly drop the test sample from a height of 1 m.

The number of times of dropping when the polycarbonate plate was peeled off was set to be excellent, the number of times of dropping was set to be more than 1000 times and not more than 1500 times was set to be o, and the number of times of dropping was set to be not more than 1000 times was set to be x.

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TABLE 3

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TABLE 5

Industrial applicability

Claims

1. An adhesive tape, characterized by comprising:

multilayer substrate, and

an adhesive layer laminated on at least one side of the multilayer substrate,

the multilayer substrate has a substrate layer and a resin layer laminated on at least one surface of the substrate layer,

the storage elastic modulus E' of the substrate layer in dynamic viscoelasticity measurement at 10 ℃ is 2.0MPa or more and 21MPa or less,

the Young's modulus of the resin layer at 23 ℃ is 500MPa or more,

the adhesive layer has an elongation at break of 30% or more in shear adhesion measurement at 23 ℃ and a storage elastic modulus G' of 0.13MPa or more and 7.0MPa or less in dynamic viscoelasticity measurement at 10 ℃.

2. The adhesive tape according to claim 1, wherein,

the base material layer contains a copolymer having a structure derived from a vinyl aromatic monomer and a structure derived from a (meth) acrylic monomer.

3. The adhesive tape according to claim 2, wherein,

the content of the structure derived from the vinyl aromatic monomer in the copolymer is 1.5% by weight or more and 15% by weight or less.

4. An adhesive tape according to claim 1, 2 or 3, wherein,

the substrate layer is a foam substrate layer.

5. The adhesive tape according to claim 1, 2, 3 or 4, wherein,

the adhesive layer is laminated on both sides of the multilayer substrate.