CN116096829A

CN116096829A - Adhesive tape

Info

Publication number: CN116096829A
Application number: CN202180058188.3A
Authority: CN
Inventors: 石堂泰志; 福山诚; 堀尾明史; 安田妃那; 中岛奈未
Original assignee: Sekisui Chemical Co Ltd
Current assignee: Sekisui Chemical Co Ltd
Priority date: 2020-10-28
Filing date: 2021-10-28
Publication date: 2023-05-09
Also published as: WO2022092201A1; JPWO2022092201A1; KR20230092862A

Abstract

The purpose of the present invention is to provide an adhesive tape having excellent heat-resistant retention properties, which is less likely to peel off when a load is applied at high temperatures. The present invention relates to an adhesive tape, which has: base material, and adhesive layer laminated on at least one surface of the base material, relaxation time (T) of L component measured by Haen echo method at 25 ℃ using pulse NMR _L25 ) Is less than 0.9 ms. In addition, the present invention relates to an adhesive tape, which has: base material, and adhesive layer laminated on at least one surface of the base material, relaxation time (T) of L component measured by Haen echo method at 85 ℃ using pulse NMR _L85 ) Is less than 3.3 milliseconds.

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, due to the severe use conditions, the application to the automotive electronics field, and the like, there has been an increase in the cases of use at higher temperatures for a longer period of time than in the past, and there has been a problem that an adhesive tape using a conventional foam base material is easily peeled off when a load is applied in a shearing direction or the like at a high temperature.

The purpose of the present invention is to provide an adhesive tape having excellent heat-resistant retention properties, which is less likely to peel off when a load is applied at high temperatures.

Means for solving the problems

The present invention relates to an adhesive tape, which has: base material and adhesive layer laminated on at least one surface of the base material, and relaxation time (T) of L component obtained by measuring by Hahn Echo (Hahn Echo) method at 25 ℃ using pulse NMR _L25 ) Is less than 0.9 ms. In addition, the present invention relates to an adhesive tape, which has: base material and adhesive layer laminated on at least one surface of the base material, relaxation time (T) of L component measured by haen echo method at 85 ℃ using pulse NMR _L85 ) Is less than 3.3 milliseconds.

The present invention will be described in detail below.

The present inventors have found that an adhesive tape comprising a base material and an adhesive layer laminated on at least one surface of the base material can be used ¹ Pulse NMR where H nuclei were measured was analyzed. In pulse NMR, the resulting product can be obtained by ¹ The free induction decay curve waveform of the spin-spin relaxation of the H nuclei is separated into a plurality of components, and the "relaxation time" of each component is obtained, whereby the molecular mobility of the component is evaluated.

The inventors of the present invention found that the relaxation time (T) of the L component obtained by measuring by the Haen echo method at 25℃using pulse NMR _L25 ) By adjusting the temperature to a specific value or less, an adhesive tape having excellent heat-resistant retention, which is less likely to be peeled off when a load is applied at a high temperature, is obtained. The inventors of the present invention found that the relaxation time (T) of the L component obtained by measuring the L component by the Haen echo method at 85℃using pulse NMR _L85 ) When the temperature is not higher than a predetermined value, an adhesive tape having excellent heat-resistant retention, which is hardly peeled off even when a load is applied at a high temperature, can be obtained, and the present invention has been completed.

The adhesive tape of the present invention comprises: a base material, and an adhesive layer laminated on at least one surface of the base material.

The adhesive tape of the present invention was prepared by measuring the relaxation time (T _L25 ) The upper limit of (2) is 0.9 milliseconds. Alternatively, the adhesive tape of the present invention may be used to measure the relaxation time of the L component obtained by the Haen echo method at 85℃using pulse NMR(T _L85 ) The upper limit of (2) is 3.3 milliseconds.

Here, "the L component measured by the haen echo method at 25 ℃ using pulse NMR" means: the free induction decay curve of spin-spin relaxation of 1H nuclei, which was measured by the haen echo method at 25 ℃ using pulse NMR, was separated into 3 components according to a sequential waveform of the relaxation time from short to long, with the longest relaxation time. Waveform separation into 3 components (S, M, and L components in order of short relaxation time) is performed by analyzing the free induction decay curve by the least square method.

The "relaxation time" refers to the time for which the electron spin returns from the excited state to the ground state after the magnetic field is applied, and the longer the "relaxation time" means the higher the molecular mobility. That is, the S component is a hard component having a shortest relaxation time and a comparatively low molecular mobility in which magnetization is immediately attenuated. The M component is a component having a relaxation time intermediate between the S component and the L component and molecular mobility. The L component is a soft component having a longest relaxation time and a relatively high molecular mobility due to a time-consuming decay of magnetization.

Relaxation time (T) of the above-mentioned L component at 25 DEG C _L25 ) When the molecular mobility of the L component is 0.9 milliseconds or less, the adhesive tape of the present invention is suppressed in the molecular mobility at 25℃of the L component, which is relatively high in the molecular mobility, and thus is less likely to peel off when a load is applied at a high temperature. Relaxation time (T) of the above-mentioned L component at 25 DEG C _L25 ) The preferable upper limit of (2) is 0.8 ms, the more preferable upper limit is 0.6 ms, and the more preferable upper limit is 0.4 ms. Relaxation time (T) of the above-mentioned L component at 25 DEG C _L25 ) The lower limit of (2) is not particularly limited, but is preferably 0.05 ms, more preferably 0.1 ms, from the viewpoint of ensuring the flexibility of the adhesive tape.

The relaxation time (T _L25 ) The measurement can be performed by a Hahn echo method at 25℃using a pulse NMR apparatus (for example, the minispec mq20, manufactured by BRUKER Co., ltd.) and analysis software (for example, TD-NMRA, manufactured by BRUKER Co., ltd.) with an adhesive tape as a measurement sample.

The term "L component measured by Haen echo method at 85℃using pulse NMR" as used herein means that the L component is measured by Haen echo method at 85℃using pulse NMR ¹ The free induction decay curve of the spin-spin relaxation of the H nuclei is separated into the L component of the S component and the L component of the 2 components in a sequential waveform from short to long in relaxation time. The waveform separation into 2 components is performed by analyzing the free induction decay curve by the least square method.

Relaxation time (T) of the above-mentioned L component at 85 DEG C _L85 ) When the molecular mobility of the adhesive tape of the present invention is 3.3 milliseconds or less, the molecular mobility of the L component at 85 ℃ which is relatively high in molecular mobility is suppressed, and thus the adhesive tape is less likely to peel when a load is applied at a high temperature. Relaxation time (T) of the above-mentioned L component at 85 DEG C _L85 ) More preferably, the upper limit of (2) is 3 ms, and still more preferably, the upper limit is 2.5 ms. Relaxation time (T) of the above-mentioned L component at 85 DEG C _L85 ) The lower limit of (2) is not particularly limited, but is preferably 0.5 ms, and more preferably 1 ms, from the viewpoint of ensuring the flexibility of the adhesive tape.

The relaxation time (T) of the above-mentioned L component at 25 DEG C _L25 ) And the relaxation time (T) of the above-mentioned L component at 85 DEG C _L85 ) The method of adjusting the temperature to the above range is not particularly limited, and examples thereof include: the base material may be a copolymer having a structure derived from a vinyl aromatic monomer, a structure derived from a (meth) acrylic monomer, or the like as described later. In addition, there may be mentioned: a method of adjusting the weight average molecular weight (Mw) of such copolymers; a method of adjusting the content of the expanded particles in the base material. Further, there may be mentioned: a method for adjusting the composition of the adhesive layer; a method of adjusting the weight average molecular weight (Mw) of the resin constituting the pressure-sensitive adhesive layer.

More specifically, as a method for shortening the relaxation time, there is given: a method of introducing a structure derived from a vinyl aromatic monomer into the substrate or the pressure-sensitive adhesive layer; a method of increasing the content of a hard block to be described later in the block copolymer; a method of introducing a crosslinked structure or increasing the degree of crosslinking. Further, there may be mentioned: a method of increasing intermolecular entanglement (i.e., increasing a monomer having a short side chain or a monomer having a reduced side chain length) in the above-mentioned substrate or the above-mentioned adhesive layer; a method of reducing the mobility of a molecular chain (for example, introducing an alicyclic structure); methods of increasing polar interactions (e.g., introducing an acid or hydroxyl group, or increasing the amount thereof), and the like. Further, there may be mentioned: a method of selecting a raw material monomer so that the glass transition temperature (Tg) of the substrate or the adhesive layer becomes higher; a method of increasing molecular weight; and a method of adding a filler.

The base material is not particularly limited, and preferably contains a copolymer having a structure derived from a vinyl aromatic monomer and a structure derived from a (meth) acrylic monomer. By incorporating such a copolymer into the base material, the relaxation time (T) of the L component at 25℃can be easily reduced _L25 ) And the relaxation time (T) of the above-mentioned L component at 85 DEG C _L85 ) When the pressure-sensitive adhesive tape is adjusted to the above range, the pressure-sensitive adhesive tape is less likely to peel off when a load is applied at a high temperature.

Examples of the vinyl aromatic monomer include: styrene, alpha-methylstyrene, p-methylstyrene, chlorostyrene, and the like. These vinyl aromatic monomers may be used alone or in combination of two or more. Among them, styrene is preferable in view of less easy detachment of the adhesive tape when a load is applied at a high temperature. 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 less likely to peel off when a load is applied at a high temperature. 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 2.5 wt%, the lower limit is particularly preferably 3 wt%, the lower limit is particularly preferably 4 wt%, the upper limit is more preferably 25 wt%, the upper limit is more preferably 20 wt%, and the upper limit is particularly preferably 15 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 cohesive force of the copolymer is improved by crosslinking, and therefore the relaxation time (T) of the L component at 25℃can be easily increased _L25 ) And the relaxation time (T) of the above-mentioned L component at 85 DEG C _L85 ) The adjustment is made to the above range. Thus, the adhesive tape is less likely to peel off when a load is applied at a high temperature. 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 increased by the interaction between functional groups, and the adhesive tape is less likely to peel off when a load is applied at a high temperature. 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 its constituent elements.

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 in view of the fact that the adhesive tape is less likely to peel off when a load is applied at a high temperature.

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 in that the adhesive tape is less likely to peel off when a load is applied at a high temperature. 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 less likely to peel off when a load is applied at a high temperature. 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, 2-ethylhexyl (meth) acrylate are preferable, and methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate are more preferable, from the viewpoint that the adhesive tape is less likely to peel off when a load is applied at a high temperature.

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, cohesive force increases, and relaxation time (T) of the L component at 25℃is easily increased _L25 ) And the relaxation time (T) of the above-mentioned L component at 85 DEG C _L85 ) When the pressure-sensitive adhesive tape is adjusted to the above range, the pressure-sensitive adhesive tape is less likely to peel off when a load is applied at a high temperature.

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, and the block copolymer is preferable from the viewpoint of further improving the balance between the heat resistance retention and the flexibility of the base material.

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, the islands serve as pseudo-crosslinking points (Japanese: pseudo-orange points), and thus the block copolymer can be imparted with rubber elasticity, so that the adhesive tape is less likely to peel off when a load is applied at a high temperature. By introducing the crosslinkable functional group described above into the hard block, the adhesive tape is less likely to peel off when a load is applied at a high temperature.

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 pressure-sensitive adhesive tape is excellent in heat resistance retention, which is not easily peeled off when a load is applied at a high temperature. This is thought to be 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, or may have a structure derived from the (meth) acrylic monomer, within a range in which the effect of the present invention is not lost. 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, since the adhesive tape is less likely to be peeled off when a load is applied at a high temperature.

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 to the above range, the adhesive tape is less likely to peel off when a load is applied at a high temperature. 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 heat resistance retention and flexibility. The upper limit of the content of the hard block is more preferably 35 wt%, the upper limit is more preferably 30 wt%, the upper limit is more preferably 25 wt%, the upper limit is more preferably 20 wt%, and the upper limit is particularly preferably 15 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 pressure-sensitive adhesive tape is less likely to peel off when a load is applied at a high temperature. 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 Water 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 material may contain additives such as antistatic agents, mold release agents, antioxidants, weather-proofing agents, crystallization nucleating agents, and the like, and resin modifiers such as polyolefin, polyester, polyamide, and elastomer, and the like.

The substrate preferably has at least one peak in each of a region of 10 ℃ or lower and a region of 50 ℃ or higher when DSC measurement (differential scanning calorimetry) is performed at a temperature rise rate of 10 ℃/min and a temperature range of-80 to 200 ℃.

When the substrate 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 contains the block copolymer having two blocks as described above. From the viewpoint of both heat-resistant retention and flexibility, it is preferable that the base material 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 substrate may be performed on 100mg of the substrate using a differential scanning calorimeter (for example, manufactured by Seiko Instruments Co., ltd., 220C, etc.).

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

The substrate is preferably a foam substrate. By making the base material be the foam base material, the relaxation time (T) of the L component at 25℃can be easily set _L25 ) And the relaxation time (T) of the above-mentioned L component at 85 DEG C _L85 ) When the pressure-sensitive adhesive tape is adjusted to the above range, the pressure-sensitive adhesive tape is less likely to peel off when a load is applied at a high temperature.

The foam base material may have an open cell structure or an independent cell structure, but preferably has an independent cell structure.

In the case where the substrate is the foam substrate, the expansion ratio is not particularly limited, and the lower limit is preferably 1.1cm ³ Preferably an upper limit of 5cm per gram ³ And/g. By setting the expansion ratio to the above range, the balance between heat resistance retention and flexibility of the adhesive tape can be further improved. From the viewpoint of further improving the balance between heat resistance retention and flexibility, the lower limit of the expansion ratio is more preferably 1.2cm ³ A more preferable upper limit of the ratio/g is 4.5cm ³ A further preferred lower limit is 1.3cm ³ A further preferred upper limit of the ratio/g is 4cm ³ /g。

The expansion ratio of the base material can be calculated from the inverse number of the density of the base material, and can be measured by using an electronic densitometer (for example, "ED120T" manufactured by the mig company) based on JIS K7222.

In the case where the substrate is the foam substrate, the average cell diameter is not particularly limited, and is preferably 80 μm or less. By setting the average bubble diameter to 80 μm or less, the balance between heat resistance retention and flexibility of the adhesive tape can be further improved. 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 bubble diameter is not particularly limited, but is preferably 10 μm or more, more preferably 20 μm or more, from the viewpoint of securing the flexibility of the adhesive tape.

The average bubble diameter of the substrate can be measured by the following method. First, the substrate was cut into 50mm square pieces, immersed in liquid nitrogen for 1 minute, and then cut off on a surface of the substrate perpendicular to the thickness direction using a razor. 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 material is preferably 90% by weight or less.

By setting the gel fraction of the base material to the above range, the pressure-sensitive adhesive tape can exhibit more excellent flexibility. From the viewpoint of further improving the flexibility of the pressure-sensitive adhesive tape, 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, from the viewpoint that the pressure-sensitive adhesive tape is less likely to peel off when a load is applied at a high temperature. The gel fraction can be adjusted by crosslinking the resin constituting the base material.

The gel fraction of the substrate can be measured by the following method. Only 0.1g of the base material 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 substrate swollen by absorbing ethyl acetate using a metal mesh (mesh # 200). The separated substrate was dried at 110℃for 1 hour. The weight of the dried substrate including the metal mesh was measured, and the gel fraction of the substrate was calculated using the following formula.

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

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

The base material is preferably formed into a crosslinked structure between main chains of resins constituting the base material by adding a crosslinking agent.

By forming a crosslinked structure between the main chains of the resin constituting the base material, the intermittently applied stress can be dispersed, and the adhesive tape is less likely to peel off when a load is applied at a high temperature.

The crosslinking agent is not particularly limited, and may be appropriately selected according to the functional group of the resin constituting the base material. 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 constituting the base material is crosslinked between the alcoholic hydroxyl group and the carboxyl group 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 constituting the base material 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 constituting the base material.

The thickness of the substrate 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 to the above range, an adhesive tape excellent in flexibility, heat resistance retention, 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 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, 100gm at a particularly preferred lower limit, and 1000 μm at a particularly preferred upper limit.

The method for producing the base material is not particularly limited. Examples of the method for producing the foam base material among the base materials 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 base material produced by the latter method is called a syntactic foam, and the base material is preferably a syntactic foam in view of more excellent strength, flexibility and heat resistance.

By forming the base material as a composite foam, the foam is formed as an independent cell foam having a more uniform size distribution, and therefore the density of the entire base material 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 0.1 part by weight, more preferably 10 parts by weight, still more preferably 0.3 parts by weight, and still more preferably 7 parts by weight, based on 100 parts by weight of the resin constituting the base material, from the viewpoint that the pressure-sensitive adhesive tape is less likely to peel off when a load is applied at a high temperature.

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

The pressure-sensitive adhesive layer may be laminated on only one side of the base material or on both sides. When the adhesive layers are laminated on both surfaces of the base material, the adhesive layers on both surfaces may have the same composition and physical properties, or may have different compositions and physical properties.

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, the upper limit is preferably 100% by weight, the lower limit is more preferably 30% by weight, the upper limit is more preferably 80% by weight, the lower limit is more preferably 50% by weight, and the upper limit is more preferably 60% by weight. 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 monomer include alkyl (meth) acrylates having 1 to 8 carbon atoms in the alkyl group, alkyl (meth) acrylates having 13 to 18 carbon atoms in the alkyl group, and functional monomers.

Examples of the alkyl (meth) acrylate in which the alkyl group has 1 to 8 carbon atoms include: methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, isobutyl (meth) acrylate, pentyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, heptyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, and the like. Examples of the alkyl (meth) acrylate in which the alkyl group has 13 to 18 carbon atoms include: tridecyl methacrylate, stearyl (meth) acrylate, and the like. Examples of the functional monomer include: hydroxyalkyl (meth) acrylates, glycerol dimethacrylate, glycidyl (meth) acrylate, 2-methacryloxyethyl 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. When the weight average molecular weight of the acrylic copolymer is in the above range, the adhesive tape can exhibit high adhesive strength, and is less likely to peel off when a load is applied at a high temperature. The lower limit of the weight average molecular weight is more preferably 50 ten thousand, and the upper limit is more preferably 140 ten thousand from the viewpoint of further improving the adhesive force and heat resistance retention.

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 the low molecular components is suppressed, and the pressure-sensitive adhesive layer is suppressed from softening at high temperature, and the main body strength (Japanese strength) is reduced, and the adhesive strength is reduced, so that the pressure-sensitive adhesive tape is less likely to peel off when a load is applied at high temperature. 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 strength, and the pressure-sensitive adhesive tape is less likely to peel off when a load is applied at a high temperature. 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 main chains of resins (for example, the acrylic copolymer, the tackifying resin, etc.) constituting 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 alcoholic hydroxyl groups in the resin (for example, the acrylic copolymer, the tackifying resin, etc.) constituting 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 constituting the pressure-sensitive adhesive layer, the intermittently applied stress can be dispersed, and the pressure-sensitive adhesive tape is less likely to peel off when a load is applied at a high temperature.

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 lower limit of the gel fraction of the adhesive layer is preferably 10 wt% and the upper limit is preferably 80 wt%. If the gel fraction is in the above range, the adhesive tape is less likely to peel off when a load is applied at a high temperature. The lower limit of the gel fraction is more preferably 20% by weight, and the upper limit is more preferably 70% by weight.

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

The adhesive layer has a storage elastic modulus G' of 10 in dynamic viscoelasticity measurement at 23 DEG C ⁵ Pa, a preferred upper limit is 10 ⁶ Pa. If the storage elastic modulus G' at 23℃is within the above range, the adhesive tape is less likely to peel off when a load is applied at a high temperature. The lower limit of the storage elastic modulus G' of the adhesive layer at 23 ℃ is more preferably 2X 10 ⁵ Pa, a more preferable upper limit is 8X 10 ⁵ Pa. The storage elastic modulus G' of the adhesive layer at 23 ℃ can be adjusted by the composition of the raw material monomers of the adhesive layer.

The storage elastic modulus G' of the adhesive layer at 23 ℃ can be obtained as follows: the storage elastic modulus at 23℃was measured by using a viscoelasticity spectrometer (for example, manufactured by IT meter control Co., ltd., DVA-200, etc.) under conditions of 10 ℃/min and 10Hz in a constant temperature rise stretching mode, and a dynamic viscoelasticity spectrum at-40 to 140 ℃.

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, heat resistance retention, 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 pressure-sensitive adhesive tape of the present invention may further comprise a resin layer laminated on at least one surface of the base material.

By having the resin layer, the strength and heat-resistant retention of the adhesive tape are further improved. The resin layer may be laminated on only one surface of the base material or may be laminated on both surfaces, but is preferably laminated on only one surface of the base material.

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

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 constituting 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 heat-resistant retention of the adhesive tape can be achieved at the same time. From the viewpoint of further satisfying both of the handleability and the heat-resistant retention property, 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 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 with excellent flexibility, heat-resistant retention, handleability, and the like.

The shape of the adhesive tape of the present invention is not particularly limited, and examples thereof include rectangle, square, 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 substrate is produced, and a resin layer is laminated on the unfoamed substrate to form a laminate. Then, the adhesive layers are bonded to both sides of the obtained laminate, and the unfoamed substrate is foamed to produce a foamed 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 components such as portable electronic equipment components and vehicle-mounted electronic equipment components, since the pressure-sensitive adhesive tape is excellent in heat resistance retention, and is not easily peeled off when a load is applied at a high temperature.

Effects of the invention

According to the present invention, an adhesive tape having excellent heat resistance retention, which is less likely to peel off when a load is applied at a high temperature, can be provided.

Drawings

Fig. 1 is a front view schematically showing a retention test of an adhesive tape.

Fig. 2 is a side view schematically showing a retention test of an adhesive tape.

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

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 to conduct 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 (St, AAc, HEA) 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 monomer (MA, BA, AAc) 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 39.1 ten thousand. The measurement was performed using "2690Separations Module" manufactured by Water 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 0.16 part by weight of tetra C (epoxy cross-linking agent, mitsubishi gas chemical Co., ltd.) as a cross-linking agent were added to 100 parts by weight of the block copolymer in terms of a solid content ratio, and the mixture was further sufficiently stirred to obtain a base material solution. The obtained base material solution was applied to one surface of a 23 μm polyethylene terephthalate (PET) film, which was subjected to corona treatment on both surfaces of the resin layer, and dried at 90 ℃ for 7 minutes, thereby obtaining a laminate of an unfoamed base material and the resin layer.

(2) Production of acrylic copolymer

52 parts by weight of ethyl acetate was charged into a reactor equipped with a thermometer, a stirrer and a condenser, and after nitrogen substitution, the reactor was heated to start reflux. After boiling ethyl acetate for 30 minutes, 0.08 parts by weight of azobisisobutyronitrile as a polymerization initiator was charged. To this was added a monomer mixture containing 70 parts by weight of butyl acrylate, 27 parts by weight of 2-ethylhexyl acrylate, 3 parts by weight of acrylic acid, and 0.2 parts by weight of 2-hydroxyethyl acrylate uniformly and slowly dropwise over 1 hour and 30 minutes to carry out the reaction. After completion of the dropwise addition for 30 minutes, 0.1 part by weight of azobisisobutyronitrile was added, and further polymerization was performed for 5 hours, and the mixture was cooled while ethyl acetate was added to the reactor to dilute the mixture, whereby a solution of an acrylic copolymer having a solid content of 40% by weight was obtained.

The weight average molecular weight of the obtained acrylic copolymer was measured by GPC using a column "2690Separations Model" manufactured by Water company, and found to be 71 ten thousand. The ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) was 5.5.

(3) Production of adhesive tape

15 parts by weight of a polymerized rosin ester having a softening point of 150℃and 10 parts by weight of a terpene phenol having a softening point of 145℃and 10 parts by weight of a rosin ester having a softening point of 70℃were added to 100 parts by weight of the solid content of the obtained acrylic copolymer. Further, 30 parts by weight of ethyl acetate (manufactured by Wako chemical industries, ltd.) and 3.0 parts by weight of an isocyanate-based crosslinking agent (Coronate L45 manufactured by Tosoh Co., ltd.) were added and stirred to obtain a binder solution.

The adhesive solution obtained was applied to a release treated surface of a 50 μm polyethylene terephthalate (PET) film having one surface subjected to a release treatment using a doctor blade so that the thickness of the dried film became 75 μm, and the applied solution was heated at 110 ℃ for 5 minutes, whereby an adhesive layer was obtained. Another adhesive layer was produced by the same operation. Then, an adhesive layer was laminated on each surface of the laminate of the unfoamed base material and the resin layer obtained as described above, to obtain a laminate. After standing at 40℃for 48 hours, the mixture was taken out from the 40℃environment and heated at 130℃for 1 minute to foam the unfoamed substrate, thereby obtaining a foamed substrate (thickness: 127 μm) and obtaining an adhesive tape.

(4) Determination of gel fraction of substrate

Only 0.1g of the base material 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 substrate swollen by absorbing ethyl acetate using a metal mesh (mesh # 200). The separated substrate was dried at 110℃for 1 hour. The weight of the dried substrate including the metal mesh was measured, and the gel fraction of the substrate was calculated using the following formula.

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

(5) Determination of relaxation time of L component of adhesive tape

About 700mg (height about 2 cm) of the adhesive tape was introduced into a glass sample tube (manufactured by BRUKER, product No. 1824511, 10mm diameter, 180mm length, flat bottom) having a diameter of 10mm) Is a kind of medium. Samples were set in a pulse NMR apparatus (the minispec mq20, manufactured by BRUKER) and kept at 25℃or 85℃for 10 minutes, followed by a Haen echo method. The obtained ¹ The free induction decay curve waveform of the spin-spin relaxation of the H nuclei is separated into 3 curves derived from 3 components of the S component, the M component, and the L component, or 2 curves derived from 2 components of the S component and the L component, and the relaxation time of the L component is obtained. Waveform separation is performed by fitting using both gaussian and exponential types.

The analysis software "TD-NMRA (Version 4.3rev 0.8)" manufactured by BRUKER corporation was used, and according to the product manual, the relaxation curve obtained at 25 ℃ was fitted to the S component using gaussian type, the M component and the L component were fitted to each other using exponential type, and the relaxation curve obtained at 85 ℃ was fitted to each other using exponential type. In addition, the following formula was used for fitting at each of 25℃and 85 ℃.

[ mathematics 1]

Y＝A1＊exp(-1/w1＊(t/T2A)^w1)+B1＊exp(-1/w2＊(t/T2B)^w2)+C1＊exp(-1/w3＊(t/T2C)^w3)

[ math figure 2]

Y＝A1＊exp(-1/w1＊(t/T2A)^w1)+B1＊exp(-1/w2＊(t/T2B)^w2)

Wherein w1 to w3 are Weibull coefficients.

At 25 ℃, w1 takes a value of 2, and w2 and w3 take a value of 1. A1 is a component ratio of the S component, B1 is a component ratio of the M component, C1 is a component ratio of the L component, T2A represents a relaxation time of the S component, T2B represents a relaxation time of the M component, and T2C represents a relaxation time of the L component. t is time.

At 85 ℃, w1 and 2 take the value of 1. A1 is a component ratio of the S component, B1 is a component ratio of the L component, T2A represents a relaxation time of the S component, and T2B represents a relaxation time of the L component. t is time.

[ measurement conditions ]

Scans：16

Recycle Deray：1sec

First 90-180Pulse Separation：0.0082

Final Pulse Separation(ms)：5(25℃)、50(85℃)

Number of Data Points for Fitting：100

Examples 2 to 9 and comparative examples 1 to 2

An adhesive tape was obtained in the same manner as in example 1, except that the base material and the resin layer were changed as shown in table 1. In examples 8 to 9, copolymers were obtained by a one-stage synthesis reaction (random copolymerization) using only ABN-E without using RAFT agent. In comparative example 2, a 30% toluene solution of Cepton 2063 (styrene-ethylene-propylene-styrene block polymer resin, manufactured by Coleus) was used, and tetra C (epoxy-based crosslinking agent, manufactured by Mitsubishi gas chemical Co., ltd.) was not added as a crosslinking agent. The raw materials in the table are as follows.

Foaming agent (foaming particles)

Advanwell EML101 (heating foaming Process of unfoamed substrate at 150 ℃ C. For 1 minute manufactured by Water chemical industry Co., ltd.)

Raw material monomer of substrate

2EHA (2-ethylhexyl acrylate)

AS-6S (styrene macromer, manufactured by Toyama Synthesis Co., ltd.)

Olefin (Cepton 2063, styrene-ethylene-propylene-styrene block polymer resin, manufactured by Coleus Co., ltd.)

< evaluation >

The adhesive tapes obtained in examples and comparative examples were evaluated as follows. The results are shown in Table 1.

(1) Evaluation of Heat-resistant Retention (Retention force test)

Fig. 1 and 2 are diagrams schematically showing a retention test of an adhesive tape.

As shown in fig. 1 (front view) and fig. 2 (side view), one surface (front surface) of a test piece 1 having a size of 25mm×25mm of an adhesive tape was bonded to the SUS plate 2, and a rubber roller of 2kg was reciprocated once at a speed of 300 mm/min from the other surface (back surface) side of the test piece 1. Next, an aluminum plate 3 was bonded to the back surface of the test piece 1, and after pressing the test piece by pressing the test piece with a weight of 0.5kg for 10 seconds from the aluminum plate 3 side, the test piece was left to stand in an environment at 23 ℃ and a relative humidity of 50% for 24 hours, to prepare a sample for a retention force test.

For the sample for retention test, a 1kg weight 4 was attached to one end of the aluminum plate 3 at 85℃so as to apply a load in the horizontal direction to the test piece 1 and the aluminum plate 3, and the amount of deflection (deflection length) of the weight after 1 hour was measured. The case where the offset amount was 0mm (no offset) was regarded as excellent, the case where the offset amount was more than 0mm and less than 1mm was regarded as o, and the case where the offset amount was 1mm or more or the adhesive tape was peeled and dropped was regarded as x.

Industrial applicability

Description of the reference numerals

1 test piece (adhesive tape)

2SUS plate

3 aluminum plate

4 weight (1 kg)

Claims

1. An adhesive tape, characterized by comprising:

substrate and method for producing the same

An adhesive layer laminated on at least one surface of the base material,

relaxation time T of L component measured by Haen echo method at 25 ℃ by pulse NMR _L25 Is less than 0.9 ms.

2. An adhesive tape, characterized by comprising:

substrate and method for producing the same

An adhesive layer laminated on at least one surface of the base material,

relaxation time T of L component measured by Haen echo method at 85 ℃ by pulse NMR _L85 Is less than 3.3 milliseconds.

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

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

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

the copolymer having a structure derived from a vinyl aromatic monomer and a structure derived from a (meth) acrylic monomer is a block copolymer.

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

the substrate is a foam substrate.

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

the adhesive layer is laminated on both sides of the base material.

7. The adhesive tape of claim 1, 2, 3, 4, 5 or 6, wherein the adhesive tape is used for assembly or fixation of electronic device parts.