Adhesive tapes, articles, and electronic devices

Abstract

The present invention provides an adhesive tape, an article, and an electronic device. The adhesive tape provided by the present invention has an adhesive layer directly or through another layer on at least one surface of a foam substrate, wherein the foaming density of the foam substrate is 0.25 g / cm 3 ~0.75g / cm 3 The adhesive layer contains an acrylic adhesive composition comprising an acrylic copolymer and a cross-linking agent, wherein the acrylic copolymer contains as constituent components: (A) a carboxyl group-containing monomer in an amount within a range of 2% to 30% by mass; (B) an alkoxyalkyl (meth)acrylate in an amount within a range of 10% to 70% by mass; and (C) one or more types selected from the group consisting of alkyl (meth)acrylate monomers other than the monomers (A) and (B), wherein the average number of carbon atoms in the saturated hydrocarbon group of the monomers (B) and (C) is less than 4.

Description

Technical Field

[0001] The present invention relates to an adhesive tape and an electronic device that can be used to fix members constituting an article, for example, to fix parts constituting an electronic device such as a portable electronic terminal, and more particularly to an adhesive tape, an article, and an electronic device. Background Art

[0002] Adhesive tapes are widely used to secure components of articles, for example, electronic devices. Specifically, they are used to secure protective panels and housings of image displays in small electronic devices such as portable electronic terminals, cameras, and computers, and to secure rigid components such as exterior parts and batteries to these small electronic devices.

[0003] The adhesive tape is required to have a level of impact resistance such that even when an item such as a portable electronic terminal is dropped, the impact does not cause parts to fall off or peel off. As such double-sided adhesive tapes, for example, those having adhesive layers on both sides of a flexible foam substrate are known as thin, excellent in adherence to adherends, and capable of absorbing shock (see, for example, Patent Document 1).

[0004] On the other hand, adhesive tapes used to secure components require weather resistance appropriate to the environments in which they are used. For example, electronic devices, such as portable electronic terminals, are used in a wide variety of applications. Therefore, adhesive tapes used to secure components of these electronic devices are generally required to maintain excellent adhesion over long periods of time, unaffected by moisture, heat, and other factors. In particular, adhesive tapes used in the manufacture of portable electronic devices, where they are frequently touched, or for securing automotive interior components, are required to maintain excellent adhesion even in the presence of sweat and sebum, known as oil resistance.

[0005] As an adhesive tape having excellent oil resistance, for example, there is known an adhesive tape obtained using an adhesive composition containing an acrylic copolymer (A) having hydroxyl groups and carboxyl groups and a crosslinking agent (B), wherein the acrylic copolymer (A) comprises, as constituent components, 50% to 90% by mass of an alkyl (meth)acrylate (A1) having an alkyl group having 4 to 12 carbon atoms, 3% to 20% by mass of a carboxyl group-containing monomer (A2), 3% to 20% by mass of a hydroxyl group-containing monomer (A3), and 3% to 15% by mass of an alkyl (meth)acrylate (A4) having an alkyl group having 1 to 3 carbon atoms, and has a weight average molecular weight of 700,000 to 2,000,000 and a theoretical Tg of -40°C or lower (see, for example, Patent Document 2).

[0006] [Prior art literature]

[0007] [Patent Document]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-260880

[0009] [Patent Document 2] International Publication No. 2014 / 002203 Handbook Summary of the Invention

[0010] [Problems to be solved by the invention]

[0011] As the use environments and conditions of articles become more diverse, adhesive tapes used to secure components are required to exhibit enhanced resistance to oils such as sweat and sebum, as well as improved resistance to impacts caused by drops and the like. In particular, the increasing number of times electronic devices such as portable electronic devices come into contact with people, coupled with the increasing size and thickness of portable electronic devices, has led to a desire for adhesive tapes that can be applied in a smaller area and exhibit superior oil resistance and impact resistance while maintaining a narrower width.

[0012] The present invention has been made in view of the above-mentioned actual situation, and an object of the present invention is to provide an adhesive tape having better oil resistance and impact resistance, and an article and an electronic device using the adhesive tape.

[0013] [Technical means to solve the problem]

[0014] The present inventors have discovered that the above-mentioned problems can be solved by providing an adhesive tape in which an adhesive layer comprising an acrylic adhesive composition is provided on a foam base material having a foam density within a specific range. The acrylic adhesive composition contains an acrylic copolymer and a crosslinking agent, wherein the acrylic copolymer contains a specific content of a carboxyl group-containing monomer, a specific content of an alkoxyalkyl (meth)acrylate, and one or more alkyl (meth)acrylate monomers as constituent components, and the average number of carbon atoms of the alkoxyalkyl (meth)acrylate and the alkyl (meth)acrylate monomers is within a specified range.

[0015] That is, the present invention provides an adhesive tape having an adhesive layer directly or through another layer on at least one surface of a foam substrate, wherein the foam density of the foam substrate is 0.25 g / cm 3 ~0.75g / cm 3 The adhesive layer contains an acrylic adhesive composition comprising an acrylic copolymer and a cross-linking agent, wherein the acrylic copolymer contains as a constituent component:

[0016] (A) a carboxyl group-containing monomer in an amount ranging from 2% to 30% by mass;

[0017] (B) an alkoxyalkyl (meth)acrylate in an amount ranging from 10% to 70% by mass; and

[0018] (C) one or more selected from the group consisting of alkyl (meth)acrylate monomers other than the monomers of (A) and (B), and

[0019] The average number of carbon atoms in the saturated hydrocarbon groups of the monomers (B) and (C) is less than 4.

[0020] [Effects of the Invention]

[0021] The adhesive tape of the present invention has good initial adhesive strength, is unlikely to swell even when adhered to sweat or sebum, has oil resistance capable of maintaining excellent adhesive strength for a long time, and has excellent impact resistance against being dropped or the like. DETAILED DESCRIPTION

[0022] (Adhesive tape)

[0023] The adhesive tape of the present invention has an adhesive layer on at least one surface of a foam substrate, directly or through another layer, wherein the foam density of the foam substrate is 0.25 g / cm 3 ~0.75g / cm 3 The adhesive layer contains an acrylic adhesive composition comprising an acrylic copolymer and a cross-linking agent, wherein the acrylic copolymer contains as a constituent component:

[0024] (A) a carboxyl group-containing monomer in an amount ranging from 2% to 30% by mass;

[0025] (B) an alkoxyalkyl (meth)acrylate in an amount ranging from 10% to 70% by mass; and

[0026] (C) one or more selected from the group consisting of alkyl (meth)acrylate monomers other than the monomers of (A) and (B), and

[0027] The average number of carbon atoms in the saturated hydrocarbon groups of the monomers (B) and (C) is less than 4.

[0028] The adhesive tape of the present invention achieves both excellent oil resistance and impact resistance by providing an adhesive layer having a predetermined composition on a foam substrate having a predetermined foam density. Specifically, the adhesive tape of the present invention, through the combination of the foam substrate and the adhesive layer, exhibits excellent initial adhesive strength. For example, the adhesive tape is less susceptible to swelling even in the presence of sweat or sebum, exhibiting oil resistance that allows for long-term maintenance of excellent adhesive strength. Furthermore, articles using the adhesive tape of the present invention are less susceptible to peeling off even when subjected to impact, such as when dropped, and exhibit excellent impact resistance.

[0029] As an embodiment of the adhesive tape of the present invention, as long as it has an adhesive layer on at least one side of the foam substrate, either directly or through another layer, it can be a method of having an adhesive layer on a single side of the foam substrate, or a method of having an adhesive layer on each of the two sides of the foam substrate (the first main side and the second main side in a facing relationship). Among them, preferably, an adhesive tape having the adhesive layer on both sides of the foam substrate, either directly or through another layer, can be cited. In particular, when used to fix two or more adherends (parts) constituting an electronic device, it is preferably used in the embodiment of a double-sided adhesive tape having an adhesive layer on each side of the foam substrate.

[0030] The adhesive tape of the present invention may be stored in a state where a release film is laminated on the surface of the adhesive layer. The release film is not particularly limited, and a general-purpose release film can be used.

[0031] In order to achieve superior durability against sweat, sebum, and the like, and excellent impact resistance, the thickness (total thickness) of the adhesive tape of the present invention is preferably in the range of 80 μm to 500 μm, more preferably in the range of 100 μm to 500 μm, further preferably in the range of 150 μm to 400 μm, and particularly preferably in the range of 200 μm to 300 μm. The thickness of the adhesive tape does not include the thickness of the release film.

[0032] (adhesive layer)

[0033] As the adhesive layer constituting the adhesive tape of the present invention, in terms of being able to exert the desired adhesive force, having better durability against sweat and sebum, and contributing to the thinning of electronic devices, it is preferred to use an adhesive layer with a thickness in the range of 5μm to 100μm, more preferably to use an adhesive layer with a thickness in the range of 10μm to 90μm, and even more preferably to use an adhesive layer with a thickness in the range of 30μm to 80μm.

[0034] The acrylic adhesive composition used in the adhesive layer may be an acrylic adhesive composition comprising an acrylic copolymer as a base polymer and optionally blended with additives such as a tackifying resin and a crosslinking agent, wherein the acrylic copolymer comprises the following components:

[0035] (A) a carboxyl group-containing monomer in an amount ranging from 2% to 30% by mass;

[0036] (B) an alkoxyalkyl (meth)acrylate in an amount ranging from 10% to 70% by mass; and

[0037] (C) One or more kinds selected from the group consisting of alkyl (meth)acrylate monomers other than the monomers of (A) and (B).

[0038] <Acrylic acid copolymer>

[0039] The acrylic copolymer may contain, as essential components, a predetermined amount of a carboxyl group-containing monomer (A), a predetermined amount of an alkoxyalkyl (meth)acrylate (B), and an alkyl (meth)acrylate (C) other than the monomers (A) and (B). Specifically, the acrylic copolymer is a polymer containing these monomers in its monomer units.

[0040] <<(A) Carboxyl Group-Containing Monomer>>

[0041] As carboxyl-containing monomers that can be used to produce the acrylic copolymer, acrylic acid, methacrylic acid, itaconic acid, maleic acid, (meth)acrylic acid dimer, crotonic acid, ethylene oxide-modified succinic acid acrylate, etc. can be used. One of the carboxyl-containing monomers can be used alone, or two or more can be used together. Acrylic acid is preferred. In other words, the acrylic copolymer preferably contains acrylic acid in its constituent components (monomer units). Using acrylic acid as a copolymer component is preferred in terms of exhibiting superior durability against sweat, sebum, alcohol, etc.

[0042] The content of the carboxyl group-containing monomer in the total amount of acrylic acid monomers used to produce the acrylic copolymer is within a range of 2% to 30% by mass, more preferably 3% to 20% by mass, even more preferably 5% to 15% by mass, and most preferably 7% to 12% by mass. This range allows for superior durability against sweat, sebum, alcohol, and the like. When two or more carboxyl group-containing monomers are used in combination, their total content is preferably within the above range.

[0043] <<(B) Alkoxyalkyl (meth)acrylate>>

[0044] Alkoxyalkyl (meth)acrylates are (meth)acrylate monomers having an alkoxyalkyl group at the end. By including an alkoxyalkyl (meth)acrylate in the acrylic adhesive composition used in the adhesive layer, the adhesive layer can maintain the flexibility required for impact resistance while also preventing oil from penetrating the adhesive layer.

[0045] The alkoxyalkyl group of the alkoxyalkyl (meth)acrylate preferably has 2 to 16 carbon atoms, more preferably 2 to 14 carbon atoms, and most preferably 2 to 12 carbon atoms. Examples of the alkoxyalkyl (meth)acrylate include methoxymethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, and 4-ethoxybutyl (meth)acrylate. The alkoxyalkyl (meth)acrylates may be used alone or in combination of two or more.

[0046] Among them, it is preferred that 2-methoxyethyl (meth)acrylate be included as the alkoxyalkyl (meth)acrylate. In other words, it is preferred that the acrylic copolymer include 2-methoxyethyl (meth)acrylate as a constituent component (monomer unit).

[0047] The content of the alkoxyalkyl (meth)acrylate in the total amount of acrylic acid monomers is within a range of 10% to 70% by mass, preferably 10% to 50% by mass, more preferably 15% to 40% by mass, even more preferably 15% to 30% by mass, and most preferably 20% to 30% by mass. Adjusting the content within this range facilitates achieving both excellent durability against sweat, sebum, and the like, and impact resistance. When two or more alkoxyalkyl (meth)acrylates are used in combination, the total content is preferably within the above range.

[0048] <<(C) Alkyl (meth)acrylate monomers other than (A) and (B)>>

[0049] The alkyl (meth)acrylate monomer is a (meth)acrylate monomer having an alkyl group at the end of the ester. The alkyl group in the alkyl (meth)acrylate monomer may be a linear alkyl group or a branched alkyl group.

[0050] Examples of the alkyl (meth)acrylate monomer include (meth)acrylates having an alkyl group with 1 to 18 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isostearyl (meth)acrylate. One or more of these can be used, and preferably two or more can be used.

[0051] Among these, it is preferred to use a (meth)acrylate monomer having an alkyl group with 1 to 12 carbon atoms, and more preferably to use a (meth)acrylate monomer having 1 to 10 carbon atoms. It is particularly preferred to use at least one (meth)acrylate monomer having 1 to 4 carbon atoms because it is easy to adjust the average number of carbon atoms in the alkyl group of the (meth)acrylate monomer to less than 4.

[0052] The content of one or more of the (C) alkyl (meth)acrylate monomers selected from the group consisting of alkyl (meth)acrylate monomers is preferably in the range of 20% to 80% by mass, more preferably in the range of 25% to 75% by mass, even more preferably in the range of 30% to 70% by mass, and most preferably in the range of 40% to 70% by mass, of the total amount of acrylic monomers that can be used to produce the acrylic copolymer. When two or more alkyl (meth)acrylate monomers (C) are used in combination, their total content is preferably within the above range.

[0053] <<Other monomers other than the monomers (A) to (C)>>

[0054] The acrylic copolymer may contain one or more other monomers (D) other than the monomers (A) to (C). As other monomers (D), for example, monomers containing polar groups can be cited. Specifically, monomers containing sulfonic acid groups, monomers containing cyano groups, monomers containing amide groups, monomers containing hydroxyl groups, monomers containing amino groups, monomers containing imide groups, monomers containing epoxy groups, monomers containing isocyanate groups, etc. can be cited. By making the acrylic copolymer contain monomers containing polar groups as constituents, crosslinking points can be introduced into the acrylic polymer or the cohesive force of the acrylic polymer can be improved. Among them, in terms of the cohesive force required for the adhesive layer of the present invention to easily ensure the desired functions such as oil resistance and impact resistance, the acrylic copolymer preferably contains one or more hydroxyl-containing monomers as constituents.

[0055] As the hydroxyl group-containing monomer, for example, a hydroxyl group-containing (meth)acrylate such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, or 6-hydroxyhexyl (meth)acrylate can be used.

[0056] The content of the hydroxyl group-containing monomer in the total amount of the acrylic monomers is preferably 1.0% by mass or less, preferably 0.01% by mass to 0.85% by mass, preferably 0.02% by mass to 0.7% by mass, more preferably 0.03% by mass to 0.5% by mass, more preferably 0.04% by mass to 0.3% by mass, and particularly preferably 0.05% by mass to 0.2% by mass in terms of exhibiting better durability against sweat, sebum, etc.

[0057] In addition, as the other monomer (D), the acrylic copolymer may contain, in addition to the polar group-containing monomer, aromatic vinyl compounds such as styrene and substituted styrene; olefins such as ethylene, propylene, butadiene; vinyl esters such as vinyl acetate; vinyl chloride, etc.

[0058] <Acrylic acid copolymer>

[0059] In the acrylic copolymer, the average number of carbon atoms in the saturated hydrocarbon groups of the monomers selected from the group consisting of the monomers (B) and (C), i.e., the alkoxyalkyl (meth)acrylate monomer (B) and the alkyl (meth)acrylate monomer (C), is less than 4. The average number of carbon atoms in the saturated hydrocarbon groups of the monomers selected from the group consisting of the monomers (B) and (C) is more preferably 2.0 to 3.9, more preferably 2.9 to 3.7, more preferably 3.1 to 3.6, and even more preferably 3.3 to 3.6. By setting the range to this, it is easy to achieve both excellent durability against sweat, sebum, and the like and impact resistance.

[0060] Furthermore, the average number of carbon atoms in the saturated hydrocarbon groups of the alkoxyalkyl (meth)acrylate (B) and one or more of the alkyl (meth)acrylate monomers (C) can be calculated by adding the product of the number of carbon atoms of each saturated hydrocarbon group and its molar concentration (mol%), and dividing the sum by the total molar concentration (mol%) of all the alkoxyalkyl (meth)acrylate monomers (B) and one or more of the alkyl (meth)acrylate monomers (C). For example, if the alkoxyalkyl (meth)acrylate monomer with carbon number A contains a (mol%), the acrylic acid ester monomer with carbon number B contains b (mol%), and the acrylic acid ester monomer with carbon number C contains c (mol%), the average number of carbon atoms can be calculated as (A×a+B×b+C×c) / (a+b+c).

[0061] Acrylic copolymers can be obtained by copolymerization using known polymerization methods such as solution polymerization, bulk polymerization, suspension polymerization, and emulsion polymerization. Solution polymerization or bulk polymerization is preferred in terms of water resistance of the adhesive layer. The polymerization initiation method can be selected from the following: thermal initiation using a peroxide-based initiator such as benzoyl peroxide or lauroyl peroxide, or an azo-based initiator such as azobisisobutyronitrile; ultraviolet irradiation using a photopolymerization initiator such as an acetophenone-based initiator, a benzoin ether-based initiator, a benzyl ketal-based initiator, an acylphosphine oxide-based initiator, a benzoin-based initiator, or a benzophenone-based initiator; or electron beam irradiation.

[0062] The weight average molecular weight of the acrylic copolymer, as measured by gel permeation chromatography (GPC), is preferably 500,000 or more, more preferably 700,000 to 1.2 million, and more preferably 900,000 to 1.1 million in terms of exhibiting superior durability against sweat, sebum, alcohol, and the like.

[0063] Here, the weight average molecular weight by the GPC method is a standard polystyrene-equivalent value measured using a GPC apparatus (HLC-8329GPC) manufactured by Tosoh Corporation. The measurement conditions are as follows.

[0064] Sample concentration: 0.5 mass% (tetrahydrofuran (THF) solution)

[0065] Sample injection volume: 100 μL

[0066] Eluent: THF

[0067] Flow rate: 1.0 mL / min

[0068] Measurement temperature: 40°C

[0069] Official column: TSKgel GMHXL 4 pieces

[0070] Guard column: TSKgel HXL-H

[0071] Detector: Differential refractometer

[0072] Standard polystyrene molecular weight: 10,000 to 20,000,000 (manufactured by Tosoh Corporation)

[0073] Cross-linking agent

[0074] Examples of the crosslinking agent contained in the acrylic adhesive composition include isocyanate crosslinking agents, epoxy crosslinking agents, metal chelate crosslinking agents, and aziridine crosslinking agents. Among these, the crosslinking agent is preferably one that is easily mixed with the acrylic copolymer or its solution and rapidly undergoes a crosslinking reaction. Specifically, an isocyanate crosslinking agent or an epoxy crosslinking agent is more preferred, and an isocyanate crosslinking agent is even more preferred.

[0075] Examples of the isocyanate crosslinking agent include toluene diisocyanate, naphthylene-1,5-diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, xylene diisocyanate, and trimethylolpropane-modified toluene diisocyanate. Toluene diisocyanate and trimethylolpropane-modified toluene diisocyanate are preferred.

[0076] As the epoxy crosslinking agent, for example, TETRAD X or TETRAD C manufactured by Mitsubishi Gas Chemical Co., Ltd., or E-05X manufactured by Soken Chemical Co., Ltd. can be used.

[0077] The crosslinking agent is preferably contained in an amount such that the gel fraction of the adhesive layer relative to toluene falls within the range described below. Specifically, in terms of achieving durability against sweat, sebum, etc., the crosslinking agent content is preferably in the range of 0.2 to 2.5 parts by mass per 100 parts by mass of the resin solids content in the acrylic adhesive composition. In terms of achieving even better durability against sweat, sebum, etc., the crosslinking agent content is preferably in the range of 0.4 to 2.3 parts by mass, more preferably in the range of 0.6 to 2.2 parts by mass, and even more preferably in the range of 0.9 to 1.8 parts by mass. Furthermore, the resin solids content in the acrylic adhesive composition refers to the solids content of the acrylic copolymer when the acrylic adhesive composition contains only the acrylic copolymer, and refers to the sum of the solids content of the acrylic copolymer and the solids content of the adhesive resin other than the acrylic copolymer, such as the tackifier resin, when the acrylic adhesive composition contains, in addition to the acrylic copolymer, an adhesive resin other than the acrylic copolymer, such as a tackifier resin.

[0078] <Other ingredients>

[0079] As the acrylic adhesive composition of the present invention, an acrylic adhesive composition containing a tackifier resin can be used in order to obtain an adhesive sheet having more excellent adhesiveness.

[0080] Examples of the tackifier resin include rosin-based tackifier resins, polymerized rosin-based tackifier resins, polymerized rosin ester-based tackifier resins, rosin phenol-based tackifier resins, stabilized rosin ester-based tackifier resins, disproportionated rosin ester-based tackifier resins, hydrogenated rosin ester-based tackifier resins, terpene-based tackifier resins, terpene phenol-based tackifier resins, petroleum resin-based tackifier resins, and (meth)acrylate resin-based tackifier resins.

[0081] When the acrylic adhesive composition contains a tackifier resin, the content of the tackifier resin is preferably in the range of 10 to 50 parts by mass relative to 100 parts by mass of the acrylic copolymer. In order to obtain an adhesive tape with high adhesive strength, the content is more preferably in the range of 15 to 30 parts by mass.

[0082] The softening point of the tackifying resin is not particularly limited.

[0083] In addition, the acrylic adhesive composition may also contain additives such as plasticizers, softeners, antioxidants, flame retardants, glass or plastic fibers or balloons, beads, fillers such as metals, metal oxides, and metal nitrides, colorants such as pigments and dyes, leveling agents, thickeners, water repellents, and defoaming agents.

[0084] <Adhesive layer>

[0085] The gel fraction of the adhesive layer in the adhesive tape of the present invention is preferably in the range of 40% to 80% by mass, more preferably in the range of 40% to 70% by mass, further preferably in the range of 40% to 65% by mass, and particularly preferably in the range of 40% to 65% by mass. By keeping the gel fraction of the adhesive layer within this range, it is easy to obtain an adhesive sheet that has both excellent adhesion to an adherend or foam substrate and excellent conformability. Furthermore, if the gel fraction is too low, oil resistance will be affected, while if it is too high, impact resistance will be affected. Therefore, in order for the adhesive tape to exhibit good oil resistance and impact resistance, it is preferably within this range.

[0086] The gel fraction of the adhesive layer refers to the gel fraction relative to toluene, and is a value measured by the method described below.

[0087] The acrylic adhesive composition is applied to the release-treated surface of the release liner in a manner such that the thickness after drying becomes 50 μm, and after drying it at 100°C for 3 minutes, it is aged for two days at 40°C to form an adhesive layer. The adhesive layer is cut into squares of 50 mm in length and 50 mm in width as test pieces, and the mass (G1) of the test piece is measured. Then, the test piece is immersed in toluene at 23°C for 24 hours. After immersion, the mixture of the test piece and toluene is filtered using a 300-mesh metal mesh to extract the insoluble components in toluene. The mass (G2) of the substance obtained by drying the insoluble components at 110°C for 1 hour is measured, and its gel fraction is calculated based on the mass (G1), mass (G2) and the following formula.

[0088] Gel fraction (mass %) = (G2 / G1) × 100

[0089] The adhesive layer of the adhesive tape of the present invention preferably exhibits a peak loss tangent (tan δ) at a frequency of 1 Hz at a temperature within the range of -40°C to 10°C. By setting the peak loss tangent of the adhesive layer within this range, good adhesion to the adherend at room temperature is easily achieved. Furthermore, from the perspective of improving drop impact resistance, the temperature is more preferably within the range of -35°C to 0°C, even more preferably within the range of -35°C to -10°C, and most preferably within the range of -35°C to -20°C.

[0090] The loss tangent (tanδ) of the adhesive layer at a frequency of 1 Hz can be calculated from the storage elastic coefficient (G') and the loss elastic coefficient (G") obtained by dynamic viscoelasticity measurement using temperature dispersion, according to the formula tanδ = G" / G'. In the measurement of dynamic viscoelasticity, a viscoelasticity testing machine (manufactured by TA Instrument Japan, trade name: ARES G2) is used. An adhesive layer having a thickness of approximately 2 mm is formed, and a test piece is sandwiched between parallel discs with a diameter of 8 mm, which serve as the measuring part of the testing machine. The storage elastic coefficient (G') and the loss elastic coefficient (G") are measured from -50°C to 150°C at a frequency of 1 Hz.

[0091] Described adhesive layer can be formed by the acrylic acid-based adhesive composition that at least comprises described acrylic copolymer and cross-linking agent.When forming described adhesive layer, about described adhesive composition, with regard to aspects such as maintaining its good coating workability, it is preferably to use the adhesive composition that contains solvent and makes the solution (adhesive solution) that comprises adhesive composition.As described solvent, for example, toluene, xylene, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, hexane etc. can be used.In addition, when described adhesive composition is made into water-based adhesive, water or water-based aqueous solvent can be used.

[0092] (Foam base material)

[0093] The adhesive tape of the present invention has a foam base material.

[0094] In order to achieve both impact resistance and excellent adhesion to the adherend, the density of the foam substrate is 0.25 g / cm 3 ~0.75g / cm 3 In the range of 0.3 g / cm 3 ~0.7g / cm 3 More preferably, it is within the range of 0.35 g / cm 3 ~0.65g / cm 3 The most preferred range is 0.5 g / cm 3~0.65g / cm 3 within the range.

[0095] The density of the foam substrate is measured according to Japanese Industrial Standards (JIS) K6767. Specifically, it refers to the following value, that is, prepare a foam substrate of about 15 cm 3 The foam substrate was cut into a rectangular shape of 4 cm x 5 cm, and its mass was measured to determine the apparent density.

[0096] The foam substrate preferably has a 25% compressive strength of 30 kPa or greater, more preferably 50 kPa to 1000 kPa, more preferably 120 kPa to 800 kPa, and even more preferably 150 kPa to 700 kPa. By setting the 25% compressive strength within this range, suitable adhesive strength can be achieved for adherends having uneven shapes or rough surfaces.

[0097] The 25% compressive strength is measured in accordance with JIS K6767. Specifically, a sample of foam substrates cut into 25 squares (250 mm x 250 mm) is stacked together to a thickness of approximately 10 mm. The sample is then clamped between stainless steel plates larger in area than the sample. The strength of the sample is measured when it is compressed by approximately 2.5 mm (25% of its original thickness) at a rate of 10 mm / min at 23°C.

[0098] As the foam substrate, it is preferred to use a foam substrate having an interlayer strength of 4 N / cm or more, preferably in the range of 6 N / cm to 150 N / cm, more preferably in the range of 10 N / cm to 100 N / cm, and more preferably in the range of 20 N / cm to 60 N / cm. By using a foam having an interlayer strength in the above range, good followability to the adherend and excellent impact resistance can be achieved. Furthermore, even when the adhesive tape or parts are peeled off (reprocessed) from the semi-finished product in order to improve the yield rate during the manufacture of portable electronic devices, or when the frame or parts are separated, decomposed, or disassembled in order to repair, regenerate, or reuse the finished product, and interlayer cracks of the foam substrate are generated, the adhesive tape can be easily peeled off.

[0099] The interlayer strength is measured by the following method. After a 50 μm thick strong adhesive layer (not peeling from the adherend and the foam substrate during the high-speed peel test described below) is attached to each side of the foam substrate for evaluating the interlayer strength, the tape is aged at 40°C for 48 hours to prepare a double-sided adhesive tape for interlayer strength measurement. Next, at 23°C and 50% RH, a 2 kg roller is moved back and forth once to pressurize a 1 cm wide and 15 cm long double-sided adhesive tape with a single adhesive surface lined with a 25 μm thick polyester film to a 50 μm thick, 3 cm wide, 20 cm long polyester film, and allowed to stand at 60°C for 48 hours. After standing at 23°C for 24 hours, the side bonded to the 50 μm thick polyester film was fixed to the mounting fixture of a high-speed peel tester at 23°C and 50% RH, and the maximum strength when the 25 μm thick polyester film was stretched in a 90-degree direction at a tensile speed of 15 m / min and the foam was torn was measured.

[0100] The tensile elastic coefficients in the flow direction and the width direction of the foam substrate are not particularly limited, and are preferably 200 N / cm 2 More than 300 N / cm 2 ~1800N / cm 2 In addition, the tensile elastic coefficient in the direction with the lowest tensile elastic coefficient in the flow direction and the width direction is preferably 500N / cm 2 ~800N / cm 2 The range is more preferably 600N / cm 2 ~700N / cm 2 In this case, the tensile elastic coefficient in the high direction is preferably 700N / cm 2 ~1800N / cm 2 The range is more preferably 800N / cm 2 ~1600N / cm 2 The tensile elongation at break during the tensile test is not particularly limited; however, the tensile elongation in the flow direction is preferably within the range of 200% to 1500%, more preferably 400% to 1000%, and even more preferably 450% to 800%. Using a foam substrate with a tensile modulus of elasticity or tensile elongation within the aforementioned ranges can suppress deterioration in the workability of the adhesive tape or a reduction in the ease of application, even with a foamed, flexible substrate. Furthermore, interlayer breakage or fragmentation of the foam is less likely to occur during peeling, allowing for easy peeling of the tape even in the event of interlayer breakage.

[0101] The tensile modulus of elasticity in the flow direction and width direction of the foam substrate is measured in accordance with JIS K6767. Specifically, it is the maximum strength measured using a Tensilon tensile tester at a temperature of 23°C and 50% RH at a tensile speed of 300 mm / min for a foam substrate sample having a gauge length of 2 cm and a width of 1 cm.

[0102] The cell structure of the foam substrate may be a closed cell structure or a continuous cell structure, but a closed cell structure is preferred because it effectively prevents water or oil from entering the cut surface of the foam substrate. Regarding the shape of the cells forming the closed cell structure, it is preferred that the closed cells have an average cell diameter in the flow direction or the width direction, or in both directions, that is longer than the average cell diameter in the thickness direction of the foam, thereby providing appropriate followability and cushioning properties.

[0103] The average cell diameter in the flow and width directions of the foam substrate is within a range of 1.2 μm to 700 μm, preferably 10 μm to 500 μm, more preferably 30 μm to 300 μm, and even more preferably 50 μm to 200 μm. By setting the average cell diameter in the flow and width directions within these ranges, the number of closed cells per unit width increases even when the width of the adhesive tape is narrowed, thereby appropriately blocking water and oil infiltration paths in the cross section of the self-foam substrate.

[0104] The average cell diameter in the thickness direction of the foam substrate is 1 μm to 150 μm, preferably 5 μm to 100 μm, and more preferably 10 μm to 60 μm, depending on the thickness of the foam substrate.

[0105] In the foam substrate, the ratio of the average bubble diameter in the flow direction of the foam substrate to the average bubble diameter in the thickness direction of the foam substrate (average bubble diameter in the flow direction / average bubble diameter in the thickness direction), and the ratio of the average bubble diameter in the width direction of the foam substrate to the average bubble diameter in the thickness direction of the foam substrate (average bubble diameter in the width direction / average bubble diameter in the thickness direction) are both 1.2 to 15, more preferably 1.2 to 10, and even more preferably 2 to 8. If the ratio is 1.2 or more, it is easy to ensure flexibility in the thickness direction, thereby improving followability. In addition, if the ratio is 15 times or less, the durability against interlayer destruction of the foam during drop impact is greatly improved. In addition, it is less likely to produce a deviation in flexibility or tensile strength between the flow direction and the width direction of the foam substrate. The adhesive tape using a foam base material having the above-mentioned ratio of average bubble diameters has preferred followability and cushioning properties in the thickness direction, so the pressure during attachment is concentrated on the joint portion and the air present in the bonding interface is easily squeezed out. Therefore, in the bonding between rigid bodies, excellent adhesion can be achieved without generating gaps into which water or oil can enter.

[0106] Furthermore, the ratio of the average cell diameter in the flow direction to the average cell diameter in the width direction is not particularly limited, but is preferably 0.25 to 4 times, more preferably 0.33 to 3 times, further preferably 0.6 to 1.5 times, and particularly preferably 0.7 to 1.3 times, with the flow direction being 1. Within this ratio range, the foam substrate is less likely to exhibit a deviation in flexibility or tensile strength between the flow direction and the thickness direction.

[0107] The average bubble diameter in the width direction, flow direction, and thickness direction of the foam substrate is measured according to the following method. First, the foam substrate is cut into pieces of approximately 1 cm in both the width direction and the flow direction. Next, a digital microscope (trade name "KH-7700", manufactured by HiROX) is used to magnify the cross-section of the foam substrate 200 times, and the cross-section of the foam substrate in the width direction or the flow direction is photographed. In the resulting magnified image, the bubble diameters of all bubbles present in the cross-section with an actual length of 2 mm before magnification in the flow direction or the width direction are measured, and the average bubble diameter is calculated based on the average value. The average bubble diameter is calculated based on the results measured at any ten locations.

[0108] The interlaminar strength, compressive strength, and tensile modulus of the foam substrate can be appropriately adjusted depending on the raw material and foam structure of the foam substrate used. The material of the foam substrate used in the present invention is not particularly limited as long as it has the aforementioned interlaminar strength, 25% compressive strength, and tensile modulus. Examples include polyolefin resins, polyester resins, polyvinyl chloride resins, polyphenylene sulfide resins, amide resins, polyimide resins, polyetheretherketone (PEEK), styrene resins, polyurethane resins, and rubber resins. Among these, at least one resin selected from the group consisting of polyolefin resins, polyurethane resins, and rubber resins is preferred. Specifically, as the type of the foam substrate, the following can be used: polyolefin foams comprising polyolefin resins such as polyethylene, polypropylene, ethylene-propylene copolymer, and ethylene-vinyl acetate copolymer; polyurethane foams comprising polyurethane resins; rubber foams comprising rubber resins such as acrylic rubber or other elastomers, etc. Among them, in order to easily produce a foam substrate with a thin independent cell structure that has excellent followability to the unevenness of the adherend surface or cushioning absorption properties, polyolefin foams can be preferably used.

[0109] In polyolefin foams using polyolefin resins, polyethylene resins are preferred because they can be easily produced with uniform thickness and impart appropriate flexibility. In particular, the polyethylene resin content in the polyolefin resin is preferably 40% by mass or more, more preferably 50% by mass or more, further preferably 60% by mass or more, and particularly preferably 100% by mass.

[0110] Furthermore, polyethylene resins used in the polyolefin foams, obtained using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst, have a narrow molecular weight distribution. In the case of copolymers, the copolymer components are introduced at substantially equal proportions in all molecular weight fractions, allowing the polyolefin foam to be uniformly crosslinked. Consequently, uniform crosslinking of the foam sheet facilitates uniform stretching as needed, making it easier to achieve uniform thickness across the entire polyolefin resin foam, which is preferred.

[0111] Furthermore, the polyethylene resin constituting the polyolefin foam may also contain polyolefin resins other than polyethylene resins obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst. Examples of such polyolefin resins include polyethylene resins other than those mentioned above, polypropylene resins, and the like. In addition, the polyolefin resins may be used alone or in combination of two or more.

[0112] Examples of such polyethylene resins include linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-α-olefin copolymers containing 50% by weight or more of ethylene, and ethylene-vinyl acetate copolymers containing 50% by weight or more of ethylene. These may be used alone or in combination of two or more. Examples of the α-olefins constituting the ethylene-α-olefin copolymers include propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, and 1-octene.

[0113] The polypropylene resin is not particularly limited, and examples thereof include polypropylene and propylene-α-olefin copolymers containing 50% by weight or more of propylene. These may be used alone or in combination of two or more. Examples of the α-olefin constituting the propylene-α-olefin copolymer include ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, and 1-octene.

[0114] The polyolefin foam may be cross-linked. When the expandable polyolefin resin sheet is foamed using a thermally decomposable foaming agent, cross-linking is preferred.

[0115] Next, a method for producing a polyolefin resin foam will be described. The method for producing a polyolefin resin foam is not particularly limited, but an example thereof includes the following method, which comprises: supplying a foamable polyolefin resin composition to an extruder for melt kneading, extruding the composition into a sheet from the extruder, thereby producing a foamable polyolefin resin sheet; the foamable polyolefin resin composition comprising a polyolefin resin, a thermally decomposable foaming agent, a foaming aid, and a colorant for coloring the foam to black or white, wherein the polyolefin resin contains 40% by weight or more of a polyethylene resin obtained using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst; crosslinking the foamable polyolefin resin sheet; foaming the foamable polyolefin resin sheet; and melting or softening the resulting foamed sheet and stretching the sheet in either or both the flow direction and the width direction. The step of stretching the foamed sheet can be repeated as needed and may be repeated multiple times.

[0116] Furthermore, as methods for crosslinking the polyolefin resin foam substrate, for example, there are methods of irradiating a foamable polyolefin resin sheet with ionizing radiation; methods of pre-blending an organic peroxide in a foamable polyolefin resin composition and heating the obtained foamable polyolefin resin sheet to decompose the organic peroxide, and the like. These methods may also be used in combination.

[0117] Examples of ionizing radiation include electron beams, α-rays, β-rays, and γ-rays. The dose of ionizing radiation is appropriately adjusted to achieve a gel fraction within the preferred range described above for the polyolefin resin foam substrate, preferably within a range of 5 kGy to 200 kGy. Furthermore, to facilitate obtaining a uniform foamed state, irradiation with ionizing radiation is preferably performed on both sides of the foamable polyolefin resin sheet, and more preferably, the same dose is applied to both sides.

[0118] Examples of the organic peroxide include 1,1-bis(tert-butylperoxy)3,3,5-trimethylcyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, 2,2-bis(tert-butylperoxy)octane, n-butyl-4,4-bis(tert-butylperoxy)valerate, di-tert-butyl peroxide, tert-butylcumyl peroxide, dicumyl peroxide, α,α′-bis(tert-butylperoxy-m-isopropyl)benzene, 2 ,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3, benzoyl peroxide, cumyl peroxide neodecanoate, tert-butyl peroxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, tert-butyl peroxyisopropyl carbonate, tert-butyl peroxyallyl carbonate, etc., which can be used alone or in combination of two or more.

[0119] The amount of the organic peroxide added is preferably in the range of 0.01 to 5 parts by mass, more preferably in the range of 0.1 to 3 parts by mass, relative to 100 parts by mass of the polyolefin-based resin.

[0120] The amount of the thermally decomposable foaming agent added to the foamable polyolefin resin composition can be appropriately determined depending on the expansion ratio of the polyolefin resin foam substrate. It is preferably in the range of 1 to 40 parts by mass, more preferably in the range of 1 to 30 parts by mass, relative to 100 parts by mass of the polyolefin resin.

[0121] The method for foaming the foamable polyolefin resin sheet is not particularly limited, and examples thereof include methods using hot air heating, infrared heating, salt bath heating, and oil bath heating, and these methods may be used in combination. Of these, methods using hot air heating and infrared heating are preferred because they minimize the difference in appearance between the front and back surfaces of the polyolefin resin foam substrate.

[0122] The foam substrate may be stretched after the foamable polyolefin resin sheet is foamed to obtain the foam substrate, or may be stretched while the foamable polyolefin resin sheet is foamed. Furthermore, when the foam substrate is stretched after the foamable polyolefin resin sheet is foamed to obtain the foam substrate, the foam substrate may be stretched while maintaining the molten state during foaming without cooling the foam substrate. Alternatively, after cooling the foam substrate, the foam sheet may be heated again to a molten or softened state before stretching the foam substrate.

[0123] Here, the molten state of the foam substrate refers to a state in which the foam substrate is heated to a temperature above the melting point of the polyolefin resin constituting the foam substrate. Furthermore, the softened state of the foam substrate refers to a state in which the foam substrate is heated to a temperature above the softening point but below the melting point of the polyolefin resin constituting the foam substrate. By stretching the foam substrate, the cells in the foam substrate are stretched and deformed in a predetermined direction, thereby producing a polyolefin foam having a cell aspect ratio within a predetermined range.

[0124] Furthermore, the foam substrate is extended in the flow direction or width direction of the long foamed polyolefin resin sheet, or in both the flow direction and the width direction. Furthermore, when the foam substrate is extended in both the flow direction and the width direction, the foam substrate may be extended in both the flow direction and the width direction simultaneously, or may be extended in each direction separately.

[0125] As methods for extending the foam substrate in the flow direction, for example, there can be listed: a method for extending the foam substrate in the flow direction by winding the long foam sheet after foaming (winding speed) faster than the speed (feeding speed) at which the long foamed polyolefin resin sheet is supplied to the foaming step while cooling; a method for extending the foam substrate in the flow direction by winding the foam substrate (winding speed) faster than the speed (feeding speed) at which the obtained foam substrate is supplied to the stretching step, etc.

[0126] In addition, in the former method, since the foamable polyolefin resin sheet expands in the flow direction due to its own foaming, when the foam substrate is extended in the flow direction, it is necessary to adjust the supply speed and winding speed of the foam substrate based on the amount of expansion in the flow direction caused by the foaming of the foamable polyolefin resin sheet so that the foam substrate is extended in the flow direction to a degree greater than its expansion amount.

[0127] Furthermore, as a method for extending the foam substrate in the width direction, it is preferred to use a pair of gripping members to grip both ends of the foam substrate in the width direction, and then slowly move the pair of gripping members in a direction away from each other, thereby extending the foam substrate in the width direction. Furthermore, since the foamable polyolefin resin sheet expands in the width direction due to its own foaming, when extending the foam substrate in the width direction, it is necessary to adjust the width direction of the foam substrate to a value greater than the amount of expansion caused by the foaming of the foamable polyolefin resin sheet, taking into account the amount of expansion in the width direction caused by the foaming of the foamable polyolefin resin sheet.

[0128] Here, the stretching ratio of the polyolefin foam substrate in the flow direction is preferably in the range of 1.1 to 2.0 times, and more preferably in the range of 1.2 to 1.5 times.

[0129] The stretching ratio of the polyolefin foam substrate in the width direction is preferably in the range of 1.2 to 4.5 times, and more preferably in the range of 1.5 to 3.5 times.

[0130] The foam substrate may be colored to impart design, light-shielding or concealing properties, light reflectivity, or light resistance to the adhesive tape. Colorants may be used alone or in combination of two or more.

[0131] When imparting light-shielding or concealing properties, or light resistance, to the adhesive tape of the present invention, the foam substrate is preferably colored black. Examples of black colorants for the black foam substrate include carbon black, graphite, copper oxide, manganese dioxide, aniline black, perylene black, titanium black, cyanine black, activated carbon, ferrite, magnetite, chromium oxide, iron oxide, molybdenum disulfide, chromium complexes, composite oxide-based black pigments, and anthraquinone-based organic black pigments. Carbon black is preferred from the perspectives of cost, availability, insulation, and heat resistance to withstand the temperatures encountered during the extrusion or heating steps of the foaming polyolefin resin composition.

[0132] In the case of imparting design or light reflectivity to the adhesive tape of the present invention, the foam substrate is preferably colored white. As the white colorant contained in the white foam substrate, inorganic white colorants such as titanium oxide, zinc oxide, aluminum oxide, silicon oxide, magnesium oxide, zirconium oxide, calcium oxide, tin oxide, barium oxide, cesium oxide, yttrium oxide, magnesium carbonate, calcium carbonate, barium carbonate, zinc carbonate, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, zinc hydroxide, aluminum silicate, calcium silicate, barium sulfate, calcium sulfate, barium stearate, zinc white, talc, silicon dioxide, aluminum oxide, clay, kaolinite, titanium phosphate, mica, gypsum, white carbon, diatomaceous earth, bentonite, lithopone, zeolite, and sericite, and organic white colorants such as silicone resin particles, acrylic resin particles, urethane resin particles, and melamine resin particles can be used. Among these, aluminum oxide or zinc oxide is preferred from the viewpoints of cost, availability, color tone, and heat resistance to withstand the temperature of the step of extruding the foamable polyolefin-based resin composition or the step of heating and foaming.

[0133] In addition, the foamable polyolefin resin composition may optionally contain, as needed, known substances such as plasticizers, antioxidants, foaming aids such as zinc oxide, cell nucleation modifiers, heat stabilizers, flame retardants such as aluminum hydroxide or magnesium hydroxide, antistatic agents, glass or plastic hollow spheres or microspheres, fillers such as metal powders or metal compounds, conductive fillers, and thermally conductive fillers, within a range that does not impair the physical properties of the polyolefin resin foam substrate. The polyolefin resin foam substrate used in the adhesive sheet of the present invention preferably contains 0.1% to 10% by mass, more preferably 1% to 7% by mass, relative to the polyolefin resin, in order to maintain appropriate followability and cushioning properties.

[0134] Furthermore, when the colorant, pyrolyzable foaming agent, or foaming aid is formulated in a foamable polyolefin resin composition, it is preferred to prepare a masterbatch using the foamable polyolefin resin composition or a thermoplastic resin highly compatible with the foamable polyolefin resin composition before supplying the composition to the extruder from the viewpoint of preventing color unevenness or partial excess or insufficient foaming.

[0135] In order to improve the adhesion with the adhesive layer or other layers, the foam substrate may also be subjected to surface treatments such as corona treatment, flame treatment, plasma treatment, hot air treatment, ozone or ultraviolet treatment, and coating of an easy-adhesion treatment agent. The surface treatment is performed so that the wettability index obtained by utilizing a wetting agent is 36 mN / m or more, preferably 40 mN / m or more, and further preferably 48 mN / m or more, thereby obtaining good adhesion with the adhesive layer. The foam substrate with improved adhesion can be laminated with the adhesive layer in a continuous step or temporarily wound. In the case of temporarily winding the foam substrate, in order to prevent the adhesion of the foam substrates with improved adhesion to each other, it is preferred to wind the foam substrate together with a backing paper such as a film of paper or polyethylene or polypropylene, polyester, etc., preferably a polypropylene film or polyester film with a thickness of 25 μm or less.

[0136] The thickness of the foam substrate is preferably in the range of 50 μm to 400 μm, more preferably in the range of 50 μm to 300 μm, even more preferably in the range of 100 μm to 300 μm, and most preferably in the range of 100 μm to 200 μm. By setting the thickness of the foam substrate within this range, excellent tape processability and excellent followability to the adherend can be imparted.

[0137] (Method for manufacturing adhesive tape)

[0138] Examples of methods for producing the adhesive tape of the present invention include: a method in which the adhesive composition is applied to one or both sides of a foam substrate and dried (a direct method); or a method in which an adhesive layer is formed by applying the adhesive composition to the surface of a release liner and drying it, and then transferring the adhesive layer to one or both sides of the foam substrate (a transfer method).

[0139] The adhesive tape of the present invention can be produced by applying the adhesive composition to one or both sides of the foam substrate using a knife coater, roll coater, or die coater, followed by drying. Alternatively, the adhesive tape can be produced by a transfer method, wherein the adhesive composition is preliminarily applied to the surface of a release liner using a knife coater, roll coater, or die coater, followed by drying to form an adhesive layer, and then the adhesive layer is bonded to one or both sides of the foam substrate.

[0140] Examples of methods for drying the adhesive composition include drying at 50° C. to 140° C. for 30 seconds to 10 minutes. After drying, the adhesive composition may be aged at 30° C. to 50° C. from the perspective of accelerating the curing reaction.

[0141] (use)

[0142] The adhesive tape of the present invention has excellent initial adhesive strength, is not easily swollen even when adhered to sweat or sebum, has oil resistance that allows it to maintain excellent adhesive strength for a long time, and has excellent impact resistance. Therefore, it can be preferably used in various fields, such as double-sided tapes for bonding to the frames of electronic devices such as portable electronic terminals and tablet computers, labels for imparting design to the surfaces of such frames, waterproof tapes, and medical adhesive tapes.

[0143] (thing)

[0144] The article of the present invention has a structure in which two or more adherends are bonded together by the adhesive tape of the present invention. The article of the present invention has excellent initial adhesive strength and, even when adhered to, for example, sweat or sebum, the tape is less likely to swell, thereby maintaining excellent adhesive strength over a long period of time. Furthermore, the article of the present invention is less likely to have adherends chipped or peeled off, even when dropped, and exhibits excellent impact resistance.

[0145] In recent years, with the increasing size and thickness of screens, electronic devices such as portable electronic terminals, which have limited attachment area, are prone to being dropped during use. Furthermore, due to frequent human contact, they are easily exposed to sweat and sebum, and therefore require high oil resistance and impact resistance. Therefore, the article is preferably an electronic device. Specifically, an example of the article of the present invention is an electronic device having a structure in which two or more components constituting the electronic device are bonded together by the adhesive tape of the present invention.

[0146] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely illustrative, and any embodiments having substantially the same structure and exhibiting the same functions and effects as the technical concept described in the claims of the present disclosure are encompassed within the technical scope of the present disclosure.

[0147] [Example]

[0148] Hereinafter, the present invention will be described in more detail using examples.

[0149] (Gel fraction measurement)

[0150] The gel fraction of the adhesive composition prepared in the Preparation Examples was measured by the method shown below. The gel fraction of the adhesive composition refers to the gel fraction of the adhesive layer in the Examples and Comparative Examples formed using the adhesive composition.

[0151] On the release treated surface of the release liner, an adhesive composition is applied in a manner that the thickness after drying is 50 μm, and after drying it at 100 ° C for 3 minutes, it is aged for two days at 40 ° C to form an adhesive layer. The adhesive layer is cut into squares of 50 mm in length and 50 mm in width as test pieces, and the mass (G1) of the test piece is measured. Then, the test piece is immersed in toluene for 24 hours at 23 ° C. After immersion, the mixture of the test piece and toluene is filtered using a 300 mesh metal mesh to extract the insoluble components in toluene. The mass (G2) of the substance obtained by drying the insoluble component at 110 ° C for 1 hour is measured, and its gel fraction is calculated based on the mass (G1), mass (G2) and the following formula.

[0152] Gel fraction (mass %) = (G2 / G1) × 100

[0153] (Average number of carbon atoms in saturated hydrocarbon groups of the alkoxyalkyl (meth)acrylate (B) and the alkyl (meth)acrylate (C) other than the carboxyl group-containing monomer (A) and the alkoxyalkyl (meth)acrylate (B))

[0154] In the acrylic copolymer prepared in Preparation Example, the average number of carbon atoms in the saturated hydrocarbon groups of the alkoxyalkyl (meth)acrylate and one or more selected from the group consisting of alkyl (meth)acrylate monomers is calculated by adding the product of the number of carbon atoms of each saturated hydrocarbon group and its molar concentration (mol%), and dividing the sum by the total molar concentration (mol%) of all the alkoxyalkyl (meth)acrylate monomers (B) and one or more selected from the group consisting of alkyl (meth)acrylate monomers (C). For example, if the alkoxyalkyl (meth)acrylate monomer having a saturated hydrocarbon group with a carbon number A contains a (mol%), the alkyl (meth)acrylate monomer having a saturated hydrocarbon group with a carbon number B contains b (mol%), and the alkyl (meth)acrylate monomer having a saturated hydrocarbon group with a carbon number C contains c (mol%), the average number of carbon atoms is calculated as (A×a+B×b+C×c) / (a+b+c).

[0155] [Preparation Example 1]

[0156] In a reaction vessel equipped with a stirrer, a reflux cooler, a nitrogen inlet tube, and a thermometer, 75.94 parts by mass of n-butyl acrylate, 9 parts by mass of acrylic acid, 5 parts by mass of methyl acrylate, 0.06 parts by mass of 4-hydroxybutyl acrylate, 10 parts by mass of methoxyethyl acrylate, and 200 parts by mass of ethyl acetate were placed, and the mixture was maintained at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0157] Next, 2 parts by mass (solid content 0.1% by mass) of a 2,2'-azobis(2-methylbutyronitrile) solution previously dissolved in ethyl acetate was added to the mixture in the reaction container, and the mixture was kept at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0158] Next, the mixture in the reaction vessel was diluted with 98 parts by mass of ethyl acetate and filtered through a 200-mesh metal mesh to obtain a solution of an acrylic copolymer (A-1) having a weight-average molecular weight of 1.1 million and an average carbon number of 3.65 in the alkoxyalkyl (meth)acrylate and the saturated hydrocarbon groups of the alkyl (meth)acrylate.

[0159] In the acrylic copolymer (A-1) solution, an adduct of toluene diisocyanate and trimethylolpropane ("BURNOCK D-40" manufactured by DIC Corporation, hereinafter referred to as "D-40") is formulated in an amount such that the gel fraction of the adhesive composition becomes 55%, relative to 100 parts by mass of the resin solid content in the solution, to obtain a solution containing the adhesive composition (P-1).

[0160] [Preparation Example 2]

[0161] In a reaction vessel equipped with a stirrer, a reflux cooler, a nitrogen inlet tube, and a thermometer, 70.94 parts by mass of n-butyl acrylate, 9 parts by mass of acrylic acid, 5 parts by mass of methyl acrylate, 0.06 parts by mass of 4-hydroxybutyl acrylate, 15 parts by mass of methoxyethyl acrylate, and 200 parts by mass of ethyl acetate were placed, and the mixture was maintained at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0162] Next, 2 parts by mass (solid content 0.1% by mass) of a 2,2'-azobis(2-methylbutyronitrile) solution previously dissolved in ethyl acetate was added to the mixture in the reaction container, and the mixture was kept at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0163] Next, the mixture in the reaction vessel was diluted with 98 parts by mass of ethyl acetate and filtered through a 200-mesh metal mesh to obtain a solution of an acrylic copolymer (A-2) having a weight-average molecular weight of 1.1 million and an average carbon number of 3.60 in the alkoxyalkyl (meth)acrylate and the saturated hydrocarbon groups of the alkyl (meth)acrylate.

[0164] In the acrylic copolymer (A-2) solution, an adduct of toluene diisocyanate and trimethylolpropane ("BURNOCK D-40" manufactured by DIC Corporation, hereinafter referred to as "D-40") is formulated in an amount such that the gel fraction of the adhesive composition becomes 55%, relative to 100 parts by mass of the resin solid content in the solution, to obtain a solution containing the adhesive composition (P-2).

[0165] [Preparation Example 3]

[0166] In a reaction vessel equipped with a stirrer, a reflux cooler, a nitrogen inlet tube, and a thermometer, 65.94 parts by mass of n-butyl acrylate, 9 parts by mass of acrylic acid, 5 parts by mass of methyl acrylate, 0.06 parts by mass of 4-hydroxybutyl acrylate, 20 parts by mass of methoxyethyl acrylate, and 200 parts by mass of ethyl acetate were placed, and the mixture was maintained at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0167] Next, 2 parts by mass (solid content 0.1% by mass) of a 2,2'-azobis(2-methylbutyronitrile) solution previously dissolved in ethyl acetate was added to the mixture in the reaction container, and the mixture was kept at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0168] Next, the mixture in the reaction vessel was diluted with 98 parts by mass of ethyl acetate and filtered through a 200-mesh metal mesh to obtain a solution of an acrylic copolymer (A-3) having a weight-average molecular weight of 1.1 million and an average carbon number of 3.55 in the alkoxyalkyl (meth)acrylate and the saturated hydrocarbon groups of the alkyl (meth)acrylate.

[0169] In the acrylic copolymer (A-3) solution, an adduct of toluene diisocyanate and trimethylolpropane ("BURNOCK D-40" manufactured by DIC Corporation, hereinafter referred to as "D-40") is formulated in an amount such that the gel fraction of the adhesive composition becomes 55%, relative to 100 parts by mass of the resin solid content in the solution, to obtain a solution containing the adhesive composition (P-3).

[0170] [Preparation Example 4]

[0171] In a reaction vessel equipped with a stirrer, a reflux cooler, a nitrogen inlet tube, and a thermometer, 57.94 parts by mass of n-butyl acrylate, 5 parts by mass of acrylic acid, 7 parts by mass of methyl acrylate, 0.06 parts by mass of 4-hydroxybutyl acrylate, 30 parts by mass of methoxyethyl acrylate, and 200 parts by mass of ethyl acetate were placed, and the mixture was maintained at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0172] Next, 2 parts by mass (solid content 0.1% by mass) of a 2,2'-azobis(2-methylbutyronitrile) solution previously dissolved in ethyl acetate was added to the mixture in the reaction container, and the mixture was kept at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0173] Next, the mixture in the reaction vessel was diluted with 98 parts by mass of ethyl acetate and filtered through a 200-mesh metal mesh to obtain a solution of an acrylic copolymer (A-4) having a weight-average molecular weight of 1.1 million and an average carbon number of 3.38 in the alkoxyalkyl (meth)acrylate and the saturated hydrocarbon groups of the alkyl (meth)acrylate.

[0174] In the acrylic copolymer (A-4) solution, an adduct of toluene diisocyanate and trimethylolpropane ("BURNOCK D-40" manufactured by DIC Corporation, hereinafter referred to as "D-40") is formulated in an amount such that the gel fraction of the adhesive composition becomes 55%, relative to 100 parts by mass of the resin solid content in the solution, to obtain a solution containing the adhesive composition (P-4).

[0175] [Preparation Example 5]

[0176] In a reaction vessel equipped with a stirrer, a reflux cooler, a nitrogen inlet tube, and a thermometer, 58.44 parts by mass of n-butyl acrylate, 3.5 parts by mass of acrylic acid, 8 parts by mass of methyl acrylate, 0.06 parts by mass of 4-hydroxybutyl acrylate, 30 parts by mass of methoxyethyl acrylate, and 200 parts by mass of ethyl acetate were placed, and the mixture was maintained at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0177] Next, 2 parts by mass (solid content 0.1% by mass) of a 2,2'-azobis(2-methylbutyronitrile) solution previously dissolved in ethyl acetate was added to the mixture in the reaction container, and the mixture was kept at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0178] Next, the mixture in the reaction vessel was diluted with 98 parts by mass of ethyl acetate and filtered through a 200-mesh metal mesh to obtain an acrylic copolymer (A-5) solution having a weight-average molecular weight of 1.1 million and an average carbon number of 3.35 in the alkoxyalkyl (meth)acrylate and the saturated hydrocarbon groups of the alkyl (meth)acrylate.

[0179] In the acrylic copolymer (A-5) solution, an adduct of toluene diisocyanate and trimethylolpropane ("BURNOCK D-40" manufactured by DIC Corporation, hereinafter referred to as "D-40") is formulated in an amount such that the gel fraction of the adhesive composition becomes 55%, relative to 100 parts by mass of the resin solid content in the solution, to obtain a solution containing the adhesive composition (P-5).

[0180] [Preparation Example 6]

[0181] In a reaction vessel equipped with a stirrer, a reflux cooler, a nitrogen inlet tube, and a thermometer, 48.44 parts by mass of n-butyl acrylate, 3.5 parts by mass of acrylic acid, 8 parts by mass of methyl acrylate, 0.06 parts by mass of 4-hydroxybutyl acrylate, 40 parts by mass of methoxyethyl acrylate, and 200 parts by mass of ethyl acetate were placed, and the mixture was maintained at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0182] Next, 2 parts by mass (solid content 0.1% by mass) of a 2,2'-azobis(2-methylbutyronitrile) solution previously dissolved in ethyl acetate was added to the mixture in the reaction container, and the mixture was kept at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0183] Next, the mixture in the reaction vessel was diluted with 98 parts by mass of ethyl acetate and filtered through a 200-mesh metal mesh to obtain a solution of an acrylic copolymer (A-6) having a weight-average molecular weight of 1.1 million and an average carbon number of 3.25 in the alkoxyalkyl (meth)acrylate and the saturated hydrocarbon groups of the alkyl (meth)acrylate.

[0184] In the acrylic copolymer (A-6) solution, an adduct of toluene diisocyanate and trimethylolpropane ("BURNOCK D-40" manufactured by DIC Corporation, hereinafter referred to as "D-40") is formulated in an amount such that the gel fraction of the adhesive composition becomes 55%, relative to 100 parts by mass of the resin solid content in the solution, to obtain a solution containing the adhesive composition (P-6).

[0185] [Preparation Example 7]

[0186] In a reaction vessel equipped with a stirrer, a reflux cooler, a nitrogen inlet tube, and a thermometer, 38.44 parts by mass of n-butyl acrylate, 3.5 parts by mass of acrylic acid, 8 parts by mass of methyl acrylate, 0.06 parts by mass of 4-hydroxybutyl acrylate, 50 parts by mass of methoxyethyl acrylate, and 200 parts by mass of ethyl acetate were placed, and the mixture was maintained at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0187] Next, 2 parts by mass (solid content 0.1% by mass) of a 2,2'-azobis(2-methylbutyronitrile) solution previously dissolved in ethyl acetate was added to the mixture in the reaction container, and the mixture was kept at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0188] Next, the mixture in the reaction vessel was diluted with 98 parts by mass of ethyl acetate and filtered through a 200-mesh metal mesh to obtain a solution of an acrylic copolymer (A-7) having a weight-average molecular weight of 1.1 million and an average carbon number of 3.15 in the alkoxyalkyl (meth)acrylate and the saturated hydrocarbon groups of the alkyl (meth)acrylate.

[0189] In the acrylic copolymer (A-7) solution, an adduct of toluene diisocyanate and trimethylolpropane ("BURNOCK D-40" manufactured by DIC Corporation, hereinafter referred to as "D-40") is formulated in an amount such that the gel fraction of the adhesive composition becomes 55%, relative to 100 parts by mass of the resin solid content in the solution, to obtain a solution containing the adhesive composition (P-7).

[0190] [Preparation Example 8]

[0191] In a reaction vessel equipped with a stirrer, a reflux cooler, a nitrogen inlet tube, and a thermometer, 32.94 parts by mass of n-butyl acrylate, 3.5 parts by mass of acrylic acid, 12 parts by mass of methyl acrylate, 0.06 parts by mass of 4-hydroxybutyl acrylate, 50 parts by mass of methoxyethyl acrylate, and 200 parts by mass of ethyl acetate were placed, and the mixture was maintained at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0192] Next, 2 parts by mass (solid content 0.1% by mass) of a 2,2'-azobis(2-methylbutyronitrile) solution previously dissolved in ethyl acetate was added to the mixture in the reaction container, and the mixture was kept at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0193] Next, the mixture in the reaction vessel was diluted with 98 parts by mass of ethyl acetate and filtered through a 200-mesh metal mesh to obtain an acrylic copolymer (A-8) solution having a weight-average molecular weight of 1.1 million and an average carbon number of 2.97 in the alkoxyalkyl (meth)acrylate and the saturated hydrocarbon groups of the alkyl (meth)acrylate.

[0194] In the acrylic copolymer (A-8) solution, an adduct of toluene diisocyanate and trimethylolpropane ("BURNOCK D-40" manufactured by DIC Corporation, hereinafter referred to as "D-40") is formulated in an amount such that the gel fraction of the adhesive composition becomes 55%, relative to 100 parts by mass of the resin solid content in the solution, to obtain a solution containing the adhesive composition (P-8).

[0195] [Preparation Example 9]

[0196] In a reaction vessel equipped with a stirrer, a reflux cooler, a nitrogen inlet tube, and a thermometer, 20.94 parts by mass of n-butyl acrylate, 3 parts by mass of acrylic acid, 6 parts by mass of methyl acrylate, 0.06 parts by mass of 4-hydroxybutyl acrylate, 70 parts by mass of methoxyethyl acrylate, and 200 parts by mass of ethyl acetate were placed, and the mixture was maintained at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0197] Next, 2 parts by mass (solid content 0.1% by mass) of a 2,2'-azobis(2-methylbutyronitrile) solution previously dissolved in ethyl acetate was added to the mixture in the reaction container, and the mixture was kept at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0198] Next, the mixture in the reaction vessel was diluted with 98 parts by mass of ethyl acetate and filtered through a 200-mesh metal mesh to obtain a solution of an acrylic copolymer (A-9) having a weight-average molecular weight of 1.1 million and an average carbon number of 3.03 in the alkoxyalkyl (meth)acrylate and the saturated hydrocarbon groups of the alkyl (meth)acrylate.

[0199] In the acrylic copolymer (A-9) solution, an adduct of toluene diisocyanate and trimethylolpropane ("BURNOCK D-40" manufactured by DIC Corporation, hereinafter referred to as "D-40") is formulated in an amount such that the gel fraction of the adhesive composition becomes 55%, relative to 100 parts by mass of the resin solid content in the solution, to obtain a solution containing the adhesive composition (P-9).

[0200] [Preparation Example 10]

[0201] In a reaction vessel equipped with a stirrer, a reflux cooler, a nitrogen inlet tube, and a thermometer, 58.44 parts by mass of n-butyl acrylate, 3.5 parts by mass of acrylic acid, 8 parts by mass of methyl acrylate, 0.06 parts by mass of 4-hydroxybutyl acrylate, 30 parts by mass of methoxyethyl acrylate, and 200 parts by mass of ethyl acetate were placed, and the mixture was maintained at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0202] Next, 2 parts by mass (solid content 0.1% by mass) of a 2,2'-azobis(2-methylbutyronitrile) solution previously dissolved in ethyl acetate was added to the mixture in the reaction container, and the mixture was kept at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0203] Next, the mixture in the reaction vessel was diluted with 98 parts by mass of ethyl acetate and filtered through a 200-mesh metal mesh to obtain a solution of an acrylic copolymer (A-10) having a weight-average molecular weight of 900,000 and an average carbon number of 3.35 in the alkoxyalkyl (meth)acrylate and the saturated hydrocarbon groups of the alkyl (meth)acrylate.

[0204] In the acrylic copolymer (A-10) solution, an adduct of toluene diisocyanate and trimethylolpropane ("BURNOCK D-40" manufactured by DIC Corporation, hereinafter referred to as "D-40") is formulated in an amount such that the gel fraction of the adhesive composition becomes 55%, relative to 100 parts by mass of the resin solid content in the solution, to obtain a solution containing the adhesive composition (P-10).

[0205] [Preparation Example 11]

[0206] In the acrylic copolymer (A-10) solution, an adduct of toluene diisocyanate and trimethylolpropane ("BURNOCK D-40" manufactured by DIC Corporation, hereinafter referred to as "D-40") is formulated in an amount such that the gel fraction of the adhesive composition becomes 40% relative to 100 parts by mass of the resin solid content in the solution, thereby obtaining a solution containing the adhesive composition (P-11).

[0207] [Preparation Example 12]

[0208] In the acrylic copolymer (A-10) solution, an adduct of toluene diisocyanate and trimethylolpropane ("BURNOCK D-40" manufactured by DIC Corporation, hereinafter referred to as "D-40") is formulated in an amount such that the gel fraction of the adhesive composition becomes 63% relative to 100 parts by mass of the resin solid content in the solution, thereby obtaining a solution containing the adhesive composition (P-12).

[0209] [Preparation Example 13]

[0210] In the acrylic copolymer (A-10) solution, an adduct of toluene diisocyanate and trimethylolpropane ("BURNOCK D-40" manufactured by DIC Corporation, hereinafter referred to as "D-40") is formulated in an amount such that the gel fraction of the adhesive composition becomes 72% relative to 100 parts by mass of the resin solid content in the solution, thereby obtaining a solution containing the adhesive composition (P-13).

[0211] [Preparation Example 14]

[0212] In a reaction vessel equipped with a stirrer, a reflux cooler, a nitrogen inlet tube, and a thermometer, 80.94 parts by mass of n-butyl acrylate, 9 parts by mass of acrylic acid, 5 parts by mass of methyl acrylate, 0.06 parts by mass of 4-hydroxybutyl acrylate, 5 parts by mass of methoxyethyl acrylate, and 200 parts by mass of ethyl acetate were placed, and the mixture was maintained at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0213] Next, 2 parts by mass (solid content 0.1% by mass) of a 2,2'-azobis(2-methylbutyronitrile) solution previously dissolved in ethyl acetate was added to the mixture in the reaction container, and the mixture was kept at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0214] Next, the mixture in the reaction vessel was diluted with 98 parts by mass of ethyl acetate and filtered through a 200-mesh metal mesh to obtain an acrylic copolymer (A-11) solution having a weight-average molecular weight of 1.1 million and an average carbon number of 3.71 in the alkoxyalkyl (meth)acrylate and the saturated hydrocarbon groups of the alkyl (meth)acrylate.

[0215] In the acrylic copolymer (A-11) solution, an adduct of toluene diisocyanate and trimethylolpropane ("BURNOCK D-40" manufactured by DIC Corporation, hereinafter referred to as "D-40") is formulated in an amount such that the gel fraction of the adhesive composition becomes 55%, relative to 100 parts by mass of the resin solid content in the solution, to obtain a solution containing the adhesive composition (P-14).

[0216] [Preparation Example 15]

[0217] In a reaction vessel equipped with a stirrer, a reflux cooler, a nitrogen inlet tube, and a thermometer, 84.94 parts by mass of n-butyl acrylate, 7 parts by mass of acrylic acid, 8 parts by mass of methyl acrylate, 0.06 parts by mass of 4-hydroxybutyl acrylate, and 200 parts by mass of ethyl acetate were placed, and the mixture was maintained at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0218] Next, 2 parts by mass (solid content 0.1% by mass) of a 2,2'-azobis(2-methylbutyronitrile) solution previously dissolved in ethyl acetate was added to the mixture in the reaction container, and the mixture was kept at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0219] Next, the mixture in the reaction vessel was diluted with 98 parts by mass of ethyl acetate and filtered through a 200-mesh metal mesh to obtain a solution of an acrylic copolymer (A-12) having a weight-average molecular weight of 1.1 million and an average carbon number of 3.63 in the alkoxyalkyl (meth)acrylate and the saturated hydrocarbon groups of the alkyl (meth)acrylate.

[0220] In the acrylic copolymer (A-12) solution, an adduct of toluene diisocyanate and trimethylolpropane ("BURNOCK D-40" manufactured by DIC Corporation, hereinafter referred to as "D-40") is formulated in an amount such that the gel fraction of the adhesive composition becomes 55%, relative to 100 parts by mass of the resin solid content in the solution, to obtain a solution containing the adhesive composition (P-15).

[0221] [Preparation Example 16]

[0222] In a reaction vessel equipped with a stirrer, a reflux cooler, a nitrogen inlet tube, and a thermometer, 85.94 parts by mass of n-butyl acrylate, 9 parts by mass of acrylic acid, 5 parts by mass of methyl acrylate, 0.06 parts by mass of 4-hydroxybutyl acrylate, and 200 parts by mass of ethyl acetate were placed, and the mixture was maintained at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0223] Next, 2 parts by mass (solid content 0.1% by mass) of a 2,2'-azobis(2-methylbutyronitrile) solution previously dissolved in ethyl acetate was added to the mixture in the reaction container, and the mixture was kept at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0224] Next, the mixture in the reaction vessel was diluted with 98 parts by mass of ethyl acetate and filtered through a 200-mesh metal mesh to obtain a solution of an acrylic copolymer (A-13) having a weight-average molecular weight of 1.1 million and an average carbon number of 3.76 in the alkoxyalkyl (meth)acrylate and the saturated hydrocarbon groups of the alkyl (meth)acrylate.

[0225] In the acrylic copolymer (A-13) solution, an adduct of toluene diisocyanate and trimethylolpropane ("BURNOCK D-40" manufactured by DIC Corporation, hereinafter referred to as "D-40") is formulated in an amount such that the gel fraction of the adhesive composition becomes 55%, relative to 100 parts by mass of the resin solid content in the solution, to obtain a solution containing the adhesive composition (P-16).

[0226] [Preparation Example 17]

[0227] In a reaction vessel equipped with a stirrer, a reflux cooler, a nitrogen inlet tube, and a thermometer, 77.94 parts by mass of n-butyl acrylate, 7 parts by mass of acrylic acid, 15 parts by mass of methyl acrylate, 0.06 parts by mass of 4-hydroxybutyl acrylate, and 200 parts by mass of ethyl acetate were placed, and the mixture was maintained at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0228] Next, 2 parts by mass (solid content 0.1% by mass) of a 2,2'-azobis(2-methylbutyronitrile) solution previously dissolved in ethyl acetate was added to the mixture in the reaction container, and the mixture was kept at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0229] Next, the mixture in the reaction vessel was diluted with 98 parts by mass of ethyl acetate and filtered through a 200-mesh metal mesh to obtain a solution of an acrylic copolymer (A-14) having a weight-average molecular weight of 1.1 million and an average carbon number of 3.33 in the alkoxyalkyl (meth)acrylate and the saturated hydrocarbon groups of the alkyl (meth)acrylate.

[0230] In the acrylic copolymer (A-14) solution, an adduct of toluene diisocyanate and trimethylolpropane ("BURNOCK D-40" manufactured by DIC Corporation, hereinafter referred to as "D-40") is formulated in an amount such that the gel fraction of the adhesive composition becomes 55%, relative to 100 parts by mass of the resin solid content in the solution, to obtain a solution containing the adhesive composition (P-17).

[0231] [Preparation Example 18]

[0232] In a reaction vessel equipped with a stirrer, a reflux cooler, a nitrogen inlet tube, and a thermometer, 66.94 parts by mass of n-butyl acrylate, 5 parts by mass of acrylic acid, 28 parts by mass of methyl acrylate, 0.06 parts by mass of 4-hydroxybutyl acrylate, and 200 parts by mass of ethyl acetate were placed, and the mixture was maintained at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0233] Next, 2 parts by mass (solid content 0.1% by mass) of a 2,2'-azobis(2-methylbutyronitrile) solution previously dissolved in ethyl acetate was added to the mixture in the reaction container, and the mixture was kept at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0234] Next, the mixture in the reaction vessel was diluted with 98 parts by mass of ethyl acetate and filtered through a 200-mesh metal mesh to obtain a solution of an acrylic copolymer (A-15) having a weight-average molecular weight of 1.1 million and an average carbon number of 2.85 in the alkoxyalkyl (meth)acrylate and the saturated hydrocarbon groups of the alkyl (meth)acrylate.

[0235] In the acrylic copolymer (A-15) solution, an adduct of toluene diisocyanate and trimethylolpropane ("BURNOCK D-40" manufactured by DIC Corporation, hereinafter referred to as "D-40") is formulated in an amount such that the gel fraction of the adhesive composition becomes 55%, relative to 100 parts by mass of the resin solid content in the solution, to obtain a solution containing the adhesive composition (P-18).

[0236] [Preparation Example 19]

[0237] In a reaction vessel equipped with a stirrer, a reflux cooler, a nitrogen inlet tube, and a thermometer, 44.94 parts by mass of n-butyl acrylate, 40 parts by mass of 2-ethylhexyl acrylate, 7 parts by mass of acrylic acid, 8 parts by mass of methyl acrylate, 0.06 parts by mass of 4-hydroxybutyl acrylate, and 200 parts by mass of ethyl acetate were placed, and the mixture was maintained at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0238] Next, 2 parts by mass (solid content 0.1% by mass) of a 2,2'-azobis(2-methylbutyronitrile) solution previously dissolved in ethyl acetate was added to the mixture in the reaction container, and the mixture was kept at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0239] Next, the mixture in the reaction vessel was diluted with 98 parts by mass of ethyl acetate and filtered through a 200-mesh metal mesh to obtain a solution of an acrylic copolymer (A-16) having a weight-average molecular weight of 1.1 million and an average carbon number of 4.89 in the alkoxyalkyl (meth)acrylate and the saturated hydrocarbon groups contained in the alkyl (meth)acrylate.

[0240] In the acrylic copolymer (A-16) solution, an adduct of toluene diisocyanate and trimethylolpropane ("BURNOCK D-40" manufactured by DIC Corporation, hereinafter referred to as "D-40") is formulated in an amount such that the gel fraction of the adhesive composition becomes 55%, relative to 100 parts by mass of the resin solid content in the solution, to obtain a solution containing the adhesive composition (P-19).

[0241] [Preparation Example 20]

[0242] In a reaction vessel equipped with a stirrer, a reflux cooler, a nitrogen inlet tube, and a thermometer, 1.94 parts by mass of n-butyl acrylate, 10 parts by mass of acrylic acid, 13 parts by mass of methyl acrylate, 0.06 parts by mass of 4-hydroxybutyl acrylate, 75 parts by mass of methoxyethyl acrylate, and 200 parts by mass of ethyl acetate were placed, and the mixture was maintained at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0243] Next, 2 parts by mass (solid content 0.1% by mass) of a 2,2'-azobis(2-methylbutyronitrile) solution previously dissolved in ethyl acetate was added to the mixture in the reaction container, and the mixture was kept at 72°C for 4 hours and then at 75°C for 5 hours under stirring.

[0244] Next, the mixture in the reaction vessel was diluted with 98 parts by mass of ethyl acetate and filtered through a 200-mesh metal mesh to obtain a solution of an acrylic copolymer (A-18) having a weight-average molecular weight of 1.1 million and an average carbon number of 2.61 in the alkoxyalkyl (meth)acrylate and the saturated hydrocarbon groups of the alkyl (meth)acrylate.

[0245] In the acrylic copolymer (A-18) solution, an adduct of toluene diisocyanate and trimethylolpropane ("BURNOCK D-40" manufactured by DIC Corporation, hereinafter referred to as "D-40") is formulated in an amount to give a gel fraction of 55% relative to 100 parts by mass of the resin solid content in the solution to obtain a solution containing an adhesive composition (P-20).

[0246] [Example 1]

[0247] The solution containing the adhesive composition (P-1) obtained in Preparation Example 1 was applied to the release-treated surface of a release liner (a polyethylene terephthalate film with a thickness of 75 μm, one side of which was release-treated) so that the thickness of the adhesive layer after drying was 75 μm. The film was then dried at 100°C for 3 minutes to prepare two adhesive layers with a thickness of 75 μm.

[0248] Next, the 75 μm thick adhesive layer was attached to a polyolefin foam (F-1) (100 μm thick, 0.5 g / cm 3 , manufactured by Sekisui Chemical Co., Ltd., and having a surface wettability index of 54 mN / m by corona treatment), were laminated from the upper surface of the release liner using a roller with a linear pressure of 5 kg / cm.

[0249] Then, the mixture was aged in an environment of 40° C. for 48 hours to obtain a double-sided adhesive tape (T-1) having a thickness of 250 μm.

[0250] [Example 2]

[0251] A double-sided adhesive tape (T-2) having a thickness of 250 μm was obtained by the same method as in Example 1 except that a solution containing the adhesive composition (P-2) was used instead of the adhesive composition (P-1).

[0252] [Example 3]

[0253] A double-sided adhesive tape (T-3) having a thickness of 250 μm was obtained by the same method as in Example 1 except that a solution containing the adhesive composition (P-3) was used instead of the adhesive composition (P-1).

[0254] [Example 4]

[0255] A double-sided adhesive tape (T-4) having a thickness of 250 μm was obtained by the same method as in Example 1 except that a solution containing the adhesive composition (P-4) was used instead of the adhesive composition (P-1).

[0256] [Example 5]

[0257] A double-sided adhesive tape (T-5) having a thickness of 250 μm was obtained by the same method as in Example 1 except that a solution containing the adhesive composition (P-5) was used instead of the adhesive composition (P-1).

[0258] [Example 6]

[0259] A double-sided adhesive tape (T-6) having a thickness of 250 μm was obtained by the same method as in Example 1 except that a solution containing the adhesive composition (P-6) was used instead of the adhesive composition (P-1).

[0260] [Example 7]

[0261] A double-sided adhesive tape (T-7) having a thickness of 250 μm was obtained by the same method as in Example 1 except that a solution containing the adhesive composition (P-7) was used instead of the adhesive composition (P-1).

[0262] [Example 8]

[0263] A double-sided adhesive tape (T-8) having a thickness of 250 μm was obtained by the same method as in Example 1 except that a solution containing the adhesive composition (P-8) was used instead of the adhesive composition (P-1).

[0264] [Example 9]

[0265] A double-sided adhesive tape (T-9) having a thickness of 250 μm was obtained by the same method as in Example 1 except that a solution containing the adhesive composition (P-9) was used instead of the adhesive composition (P-1).

[0266] [Example 10]

[0267] A double-sided adhesive tape (T-10) having a thickness of 250 μm was obtained by the same method as in Example 1 except that a solution containing the adhesive composition (P-10) was used instead of the adhesive composition (P-1).

[0268] [Example 11]

[0269] A double-sided adhesive tape (T-11) having a thickness of 250 μm was obtained by the same method as in Example 1 except that a solution containing the adhesive composition (P-11) was used instead of the adhesive composition (P-1).

[0270] [Example 12]

[0271] A double-sided adhesive tape (T-12) having a thickness of 250 μm was obtained by the same method as in Example 1 except that a solution containing the adhesive composition (P-12) was used instead of the adhesive composition (P-1).

[0272] [Example 13]

[0273] A double-sided adhesive tape (T-13) having a thickness of 250 μm was obtained by the same method as in Example 1 except that a solution containing the adhesive composition (P-13) was used instead of the adhesive composition (P-1).

[0274] [Example 14]

[0275] A solution containing the adhesive composition (P-5) was used instead of the adhesive composition (P-1), and the adhesive layer having a thickness of 75 μm was attached to a polyolefin foam (F-2) (thickness 100 μm, density 0.25 g / cm 3, manufactured by Sekisui Chemical Co., Ltd., and using corona treatment to make the surface wettability index of 54mN / m) on both sides instead of the polyolefin foam (F-1), a double-sided adhesive tape (T-14) with a thickness of 250μm was obtained by the same method as in Example 1.

[0276] [Example 15]

[0277] A solution containing the adhesive composition (P-5) was used instead of the adhesive composition (P-1), and the adhesive layer having a thickness of 75 μm was attached to a polyolefin foam (F-3) (thickness 100 μm, density 0.33 g / cm 3 , manufactured by Sekisui Chemical Co., Ltd., and using corona treatment to make the surface wettability index of 54mN / m) on both sides instead of the polyolefin foam (F-1), a double-sided adhesive tape (T-15) with a thickness of 250μm was obtained by the same method as in Example 1.

[0278] [Example 16]

[0279] A solution containing the adhesive composition (P-5) was used instead of the adhesive composition (P-1), and the adhesive layer having a thickness of 75 μm was attached to a polyolefin foam (F-4) (thickness 100 μm, density 0.63 g / cm 3 , manufactured by Sekisui Chemical Co., Ltd., and using corona treatment to make the surface wettability index of 54mN / m) on both sides instead of the polyolefin foam (F-1), a double-sided adhesive tape (T-16) with a thickness of 250μm was obtained by the same method as in Example 1.

[0280] [Example 17]

[0281] Two adhesive layers with a thickness of 25 μm were prepared using a solution containing the adhesive composition (P-5) instead of the adhesive composition (P-1). The adhesive layers with a thickness of 25 μm were attached to a polyolefin foam (F-5) (thickness 200 μm, density 0.5 g / cm 3 , manufactured by Sekisui Chemical Co., Ltd., and using corona treatment to make the surface wettability index of 54mN / m) on both sides instead of the polyolefin foam (F-1), a double-sided adhesive tape (T-17) with a thickness of 250μm was obtained by the same method as in Example 1.

[0282] [Example 18]

[0283] A solution containing the adhesive composition (P-5) was used instead of the adhesive composition (P-1) to prepare two adhesive layers with a thickness of 50 μm, and the adhesive layers with a thickness of 50 μm were attached to both sides of the polyolefin foam (F-1). In addition, a double-sided adhesive tape (T-18) with a thickness of 200 μm was obtained using the same method as in Example 1.

[0284] [Example 19]

[0285] A solution containing the adhesive composition (P-5) was used instead of the adhesive composition (P-1) to prepare two adhesive layers with a thickness of 100 μm, and the adhesive layers with a thickness of 100 μm were attached to both sides of the polyolefin foam (F-1). In addition, a double-sided adhesive tape (T-19) with a thickness of 300 μm was obtained using the same method as in Example 1.

[0286] [Comparative Example 1]

[0287] A double-sided adhesive tape (T-20) having a thickness of 250 μm was obtained by the same method as in Example 1 except that a solution containing the adhesive composition (P-14) was used instead of the adhesive composition (P-1).

[0288] [Comparative Example 2]

[0289] A double-sided adhesive tape (T-21) having a thickness of 250 μm was obtained by the same method as in Example 1 except that a solution containing the adhesive composition (P-15) was used instead of the adhesive composition (P-1).

[0290] [Comparative Example 3]

[0291] A double-sided adhesive tape (T-22) having a thickness of 250 μm was obtained by the same method as in Example 1 except that a solution containing the adhesive composition (P-16) was used instead of the adhesive composition (P-1).

[0292] [Comparative Example 4]

[0293] A double-sided adhesive tape (T-23) having a thickness of 250 μm was obtained by the same method as in Example 1 except that a solution containing the adhesive composition (P-17) was used instead of the adhesive composition (P-1).

[0294] [Comparative Example 5]

[0295] A double-sided adhesive tape (T-24) having a thickness of 250 μm was obtained by the same method as in Example 1 except that a solution containing the adhesive composition (P-18) was used instead of the adhesive composition (P-1).

[0296] [Comparative Example 6]

[0297] A double-sided adhesive tape (T-25) having a thickness of 250 μm was obtained by the same method as in Example 1 except that a solution containing the adhesive composition (P-19) was used instead of the adhesive composition (P-1).

[0298] [Comparative Example 7]

[0299] A double-sided adhesive tape (T-26) having a thickness of 250 μm was obtained by the same method as in Example 1 except that a solution containing the adhesive composition (P-20) was used instead of the adhesive composition (P-1).

[0300] [Comparative Example 8]

[0301] A solution containing the adhesive composition (P-3) was used instead of the adhesive composition (P-1), and the adhesive layer having a thickness of 75 μm was attached to a polyolefin foam (F-6) (thickness 100 μm, density 0.13 g / cm 3 , manufactured by Sekisui Chemical Co., Ltd., and using corona treatment to make the surface wettability index of 54mN / m) on both sides instead of the polyolefin foam (F-1), a double-sided adhesive tape (T-27) with a thickness of 250μm was obtained by the same method as in Example 1.

[0302] [Comparative Example 9]

[0303] A solution containing the adhesive composition (P-3) was used instead of the adhesive composition (P-1), and the adhesive layer having a thickness of 75 μm was attached to a polyolefin foam (F-7) (thickness 100 μm, density 0.17 g / cm 3 , manufactured by Sekisui Chemical Co., Ltd., and using corona treatment to make the surface wettability index of 54mN / m) on both sides instead of the polyolefin foam (F-1), a double-sided adhesive tape (T-28) with a thickness of 250μm was obtained by the same method as in Example 1.

[0304] <Evaluation>

[0305] [Method for measuring pressing strength]

[0306] The double-sided adhesive tapes obtained in the examples and comparative examples were cut into pieces of 18.5 mm square and 2 mm wide. The release liner on one side of the double-sided adhesive tapes was peeled off under an environment of a temperature of 23° C. and a relative humidity of 50% RH. A piece of the double-sided adhesive tape was then attached to a 3 mm thick, 20 mm square soda-lime glass plate (color: colorless and transparent).

[0307] The release liner on the other side of the test piece was peeled off and the test piece was attached to the surface of a 2 mm thick polycarbonate plate (Makrolon, manufactured by Bayer, color: transparent) with a hole of 12 mm in diameter at the center (bonding area: 1.32 cm). 2 ), and its upper surface was subjected to 50N / cm 2 The patch was obtained by pressing for 10 seconds.

[0308] The attached article was placed in an atmosphere of 23°C and 50% RH for 24 hours, then in an atmosphere of 60°C and 90% RH for 24 hours. Furthermore, the article was placed in an atmosphere of 23°C and 50% RH for 24 hours. Next, a glass plate was pressed against the back of the polycarbonate plate of the attached article at a speed of 5 mm / min using a 7 mm diameter probe to measure the peeling strength (G1) of the glass plate.

[0309] [Evaluation method of oil resistance]

[0310] After the patch obtained in the [Method for Determining Compression Strength] was placed in an atmosphere of 23°C and 50% RH for 24 hours, 10 mg of a 99% by mass oleic acid solution: squalene acid (1:1) solution was added dropwise through the hole in the polycarbonate plate and placed in an atmosphere of 60°C and 90% RH for 24 hours.

[0311] Then, the mixture was left to stand at 23°C and 50% RH for 24 hours.

[0312] Next, a glass plate was pressed from the back side of the polycarbonate plate of the adherend at a speed of 5 mm / min using a probe having a diameter of 7 mm, and the strength (G2) of the glass plate peeling was measured.

[0313] The adhesive force retention rate was calculated based on the pressing strength obtained by the pressing strength measurement and oil resistance evaluation.

[0314] Adhesion retention rate (%) = (G2 / G1) × 100

[0315] Based on the calculated adhesive strength retention rate, evaluation was performed according to the following criteria A to D. Criteria A to C were considered good.

[0316] A: Adhesion retention rate is 70% or more.

[0317] B: The adhesive strength retention rate is 60% or more and less than 70%.

[0318] C: The adhesive strength retention rate is 50% or more and less than 60%.

[0319] D: Adhesion strength retention rate is less than 50%.

[0320] [Evaluation method of impact resistance]

[0321] The patch obtained in the above-mentioned [Compression Strength Measurement Method] was left in an atmosphere of 23° C. and 50% RH for 24 hours and then placed on the base of a DuPont impact tester (manufactured by Tester Industry Co., Ltd.) with the glass plate of the test piece facing downward.

[0322] Secondly, from the side of the polycarbonate plate, a stainless steel impact core with a diameter of 9.5 mm and a mass of 200 g is dropped three times from a height of 10 cm to evaluate whether the adhesive sheet of the test piece is peeling off or the substrate is damaged. In the case of no peeling, the drop height is 10 cm higher than the previous time, and it is confirmed that the adhesive sheet of the test piece is peeling off or the substrate is damaged after three drops. Afterwards, in the case of no peeling or substrate damage, the drop height is increased by 10 cm each time, and the test is repeated in the same way. The drop height (cm) when the adhesive sheet of the test piece is finally confirmed to be peeling off or the substrate is damaged is measured and judged according to the following benchmarks A to E. Benchmarks A to C are considered good.

[0323] A: The drop height is 80 cm or more.

[0324] B: The drop height is 70 cm or more and less than 80 cm.

[0325] C: The drop height is 60 cm or more and less than 70 cm.

[0326] D: The drop height is 50 cm or more and less than 60 cm.

[0327] E: The falling height is less than 50 cm.

[0328] The details and evaluation results of the adhesive tapes of Examples and Comparative Examples are shown in the following table. The monomers represented by the abbreviations for the adhesive compositions in the table are as follows. The "average number of carbon atoms" in the table is the average number of carbon atoms in the saturated hydrocarbon groups of the alkoxyalkyl (meth)acrylate (B) and the alkyl (meth)acrylate monomer (C) excluding the carboxyl group-containing monomer (A) and the alkoxyalkyl (meth)acrylate (B), and is calculated as described above.

[0329] (monomer abbreviation)

[0330] BA…n-butyl acrylate

[0331] 2EHA…2-Ethylhexyl acrylate

[0332] MA…Methyl acrylate

[0333] MEA…Methoxyethyl acrylate

[0334] AA…Acrylic acid

[0335] 4HBA…4-Hydroxybutyl acrylate

[0336] [Table 1]

[0337]

[0338] [Table 2]

[0339]

[0340] [Table 3]

[0341]

[0342] [Table 4]

[0343]

[0344] [Table 5]

[0345]

[0346] [Table 6]

[0347]

[0348] In Examples 1 to 19, both oil resistance and impact resistance were rated A to C, indicating good oil resistance and impact resistance. In contrast, in Comparative Examples 1 to 9, oil resistance was rated D and / or impact resistance was rated D or E, indicating failure to achieve both oil resistance and impact resistance.

Claims

1. An adhesive tape comprising an adhesive layer on at least one surface of a foam substrate, directly or through another layer, wherein: The foaming density of the foam substrate is 0.25 g / cm 3 ~0.75g / cm 3 within the range of The adhesive layer contains an acrylic adhesive composition comprising an acrylic copolymer and a cross-linking agent. The acrylic copolymer includes as constituent components: Monomer A, which is a carboxyl group-containing monomer in an amount ranging from 2% to 30% by mass; Monomer B, which is an alkoxyalkyl (meth)acrylate in an amount ranging from 10% to 70% by mass; Monomer C, which is one or more selected from the group consisting of (meth)acrylate monomers other than the monomer A and the monomer B; and Monomer D, which is a hydroxyl group-containing monomer in an amount within a range of 0.04% to 0.3% by mass, and The average number of carbon atoms in the saturated hydrocarbon groups of the monomers B and C is less than 4. 2 . The adhesive tape according to claim 1 , wherein the foam substrate has a thickness in the range of 50 μm to 400 μm. 3 . The adhesive tape according to claim 1 , wherein the thickness of the adhesive tape is within a range of 80 μm to 500 μm. 4 . The adhesive tape according to claim 1 , wherein the gel fraction of the adhesive layer is within a range of 40% to 80%.

5. The adhesive tape according to claim 1 or 2, characterized in that The weight average molecular weight of the acrylic copolymer is 500,000 or more. 6 . The adhesive tape according to claim 1 , wherein the foam base material contains at least one selected from the group consisting of polyolefin resins, polyurethane resins, and rubber-based resins. 7 . The adhesive tape according to claim 1 , wherein the alkoxyalkyl (meth)acrylate comprises 2-methoxyethyl (meth)acrylate.

8. An article having a structure in which two or more adherends are adhered by the adhesive tape according to any one of claims 1 to 7. 9 . An electronic device having a structure in which two or more components constituting the electronic device are adhered by the adhesive tape according to claim 1 .

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