Adhesive composition, adhesive tape and article

Abstract

To provide an adhesive composition which is excellent in 180-degree peel adhesive force, constant load holding power and shear retention force among adhesive characteristics and has high removability and to provide an adhesive tape having an adhesive layer composed of the adhesive composition.SOLUTION: In order to exhibit favorable adhesive properties in an adhesive composition, it is crucial to adjust the dynamic viscoelasticity of the adhesive composition among various physical properties and it was found that the storage modulus G' strongly correlates with shear holding force performance and tanδ strongly correlates with constant load holding power performance. Specifically, it is necessary for the storage modulus G' at a constant temperature to be above a certain value in order to achieve an adhesive layer having excellent shear retention force and it was found that it is necessary for the tanδ at a constant temperature to be equal to or above a certain value in order to achieve an adhesive layer having excellent constant load holding power.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive composition, more specifically, a pressure-sensitive adhesive composition having a storage modulus G' (70°C) of 1.5 x 10 4 The present invention relates to a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing a pressure-sensitive adhesive composition having a tensile strength of 100 Pa or more and a tan δ(120°C) of 0.4 or more. [Background technology]

[0002] Adhesive tapes are widely used as joining means for fastening components that make up relatively large electronic devices such as flat-screen televisions, home appliances, and office automation equipment, as well as relatively small electronic devices such as mobile electronic terminals, cameras, and personal computers. More specifically, in various industrial fields such as office automation equipment, IT, home appliances, and automobiles, adhesive tapes are used not only for component fastening applications, such as fastening metal plates or exterior components to housings that make up large electronic devices, and fastening exterior components or rigid components such as batteries to small electronic devices, as well as for temporary fastening of such components, but also for labeling purposes that display product information.

[0003] In recent years, in the above-mentioned industrial fields, for the purpose of resource conservation and from the viewpoint of protecting the global environment, it has become common to disassemble reusable or reusable parts used in products after use and reuse them. In this case, if an adhesive tape is used, it is necessary to peel the adhesive tape attached to the parts. However, such adhesive tapes usually have high adhesive strength, and when they are peeled, the adhesive may adhere to the parts, leaving "glue residue." Since the task of removing the adhesive from such parts is very labor-intensive, there is a demand for an adhesive tape with excellent removability that can be peeled and removed without leaving any adhesive residue on the parts when reused or re-used.

[0004] Furthermore, since it is important for a pressure-sensitive adhesive tape used to fix components to be able to fix the components without peeling during use, it is desirable for the tape to have excellent 180° peel adhesive strength, constant load holding strength, and shear holding strength.

[0005] As such adhesive tapes, for example, easily peelable adhesive tapes that have the property of reducing their adhesive strength when heated and being easily peeled off from an adherend (e.g., Patent Document 1) and hot melt adhesives (e.g., Patent Document 2) have been studied. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-196567 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-159526 Summary of the Invention [Problem to be solved by the invention]

[0007] The easy-peel adhesive tape described in Patent Document 1 has excellent constant-load holding power in an environment of approximately 60°C or below, and its adhesive strength decreases when heated, allowing it to be easily peeled from an adherend, but it does not focus on shear holding power, which is an important adhesive property for component fixing applications, and there is room for improvement in balancing resistance to peeling when a shear force is applied with other adhesive properties.Furthermore, the hot-melt adhesive using a styrene-based thermoplastic elastomer described in Patent Document 2 maintains good adhesion and removability over a long period of time, but does not focus on constant-load holding power and shear holding power, and its adhesive properties may be insufficient for applications such as fixing metal plates that make up large electronic devices or fixing exterior components to housings.

[0008] Therefore, an object of the present invention is to provide a pressure-sensitive adhesive composition that is excellent in adhesive properties, particularly in 180° peel adhesive strength, constant load holding strength and shear holding strength, and also has high removability, and a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition. [Means for solving the problem]

[0009] The present inventors conducted extensive research to solve the problems of the prior art, and as a result, they discovered the following and developed the present invention. Specifically, they discovered that, in order for a pressure-sensitive adhesive composition to exhibit favorable adhesive properties, it is important to adjust the dynamic viscoelasticity of the pressure-sensitive adhesive composition, among various physical properties, and that, in particular, the storage modulus G' has a strong correlation with shear holding power, and that tan δ has a strong correlation with constant-load holding power. Specifically, they discovered that in order to obtain a pressure-sensitive adhesive layer with excellent shear holding power, the storage modulus G' at a certain temperature must be equal to or greater than a certain value, and that in order to obtain a pressure-sensitive adhesive layer with excellent constant-load holding power, the tan δ at a certain temperature must be equal to or greater than a certain value, which led to the present invention.

[0010] The present invention includes the following aspects. [1] Storage modulus G' (70°C) is 1.5 × 10 4 A pressure-sensitive adhesive composition having a tensile strength of 100 Pa or more and a tan δ(120°C) of 0.4 or more.

[0011] [2] The pressure-sensitive adhesive composition according to the above [1], which contains an acrylic pressure-sensitive adhesive or a rubber pressure-sensitive adhesive.

[0012] [3] The pressure-sensitive adhesive composition according to [2] above, wherein the acrylic pressure-sensitive adhesive comprises a random copolymer or a triblock copolymer.

[0013] [4] The pressure-sensitive adhesive composition according to [2] above, wherein the rubber-based pressure-sensitive adhesive comprises a styrene-based triblock copolymer.

[0014] [5] The pressure-sensitive adhesive composition according to any one of [1] to [4] above, which has a storage modulus G' (180°C) of 2000 Pa or less.

[0015] [6] The pressure-sensitive adhesive composition according to any one of [2] to [5] above, further comprising a tackifier resin.

[0016] [7] The pressure-sensitive adhesive composition according to any one of [2] to [6] above, further comprising an antioxidant.

[0017] [8] The pressure-sensitive adhesive composition according to any one of [1] to [7]7 above, wherein the pressure-sensitive adhesive composition is a hot-melt pressure-sensitive adhesive composition.

[0018] [9] A pressure-sensitive adhesive tape comprising a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition according to any one of [1] to [8] above.

[0019]

[10] An article using the adhesive tape described in [9] above. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide a pressure-sensitive adhesive composition that has good 180° peel adhesion strength, constant load holding strength and shear holding strength, and that can be peeled off without leaving any pressure-sensitive adhesive on the adherend or damaging the adherend, and a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a conceptual diagram showing a method for measuring shear holding strength. [Figure 2] FIG. 1 is a conceptual diagram showing a method for measuring a constant load holding force. DETAILED DESCRIPTION OF THE INVENTION

[0022] The pressure-sensitive adhesive composition of the present invention has a storage modulus G' (70°C) of 1.5 × 10 4 The pressure-sensitive adhesive composition has a compressive strength of 100 Pa or more and a tan δ(120° C.) of 0.4 or more.

[0023] The pressure-sensitive adhesive composition of the present invention has the above-mentioned characteristics, and thus forms a pressure-sensitive adhesive layer that is excellent in 180° peel adhesive strength, constant load holding strength and shear holding strength, and also in removability.

[0024] Specifically, the storage modulus G' (70°C) of the pressure-sensitive adhesive composition of the present invention is 1.5 × 10 4It has been found that when the adhesive strength is 100 Pa or more, the adhesive layer comprising the adhesive composition of the present invention has a high cohesive strength and exhibits excellent shear holding strength even in a high temperature environment.

[0025] Furthermore, it has been found that when the pressure-sensitive adhesive composition of the present invention has a tan δ (120°C) of 0.4 or more, the pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition of the present invention has a good balance between cohesive strength and flexibility, thereby exhibiting excellent adhesive strength, particularly excellent constant load holding power.

[0026] The pressure-sensitive adhesive composition of the present invention will be described in more detail below based on its constituent elements.

[0027] (Adhesive composition) The pressure-sensitive adhesive composition of the present invention has a storage modulus G' of 1.5 x 10 at 70°C. 4 Pa or more, 1.5 x 10 4 ~1.0×10 6 Pa, preferably 2.0×10 4 ~5.0×10 5 Pa, more preferably 2.0×10 4 ~3.0×10 5 It is more preferable that the storage modulus G' is in the above range. When the storage modulus G' is in the above range, the pressure-sensitive adhesive layer exhibits excellent shear holding power even in a high-temperature environment and exhibits excellent melt viscosity at high temperatures, thereby providing a pressure-sensitive adhesive layer with favorable kneading workability and hot-melt coating suitability. In addition, since the cohesive strength is high, the pressure-sensitive adhesive layer has excellent removability and can be peeled from an adherend without leaving any adhesive residue.

[0028] The storage modulus G' at 70°C of the pressure-sensitive adhesive composition of the present invention can be adjusted to fall within the above-mentioned preferred range by adjusting, for example, the type, content, and weight-average molecular weight of the pressure-sensitive adhesive resin contained in the pressure-sensitive adhesive composition, the type, amount, softening point, and molecular weight of the tackifier resin, the type, content, molecular weight, and kinematic viscosity of the plasticizer, etc.

[0029] The pressure-sensitive adhesive composition of the present invention has a tan δ at 120°C of 0.4 or more, preferably 0.4 to 10.0, more preferably 0.6 to 5.0, and even more preferably 0.6 to 3.0. When tan δ is within the above range, a good balance between cohesive strength and flexibility is achieved, improving adhesion to an adherend and efficiently alleviating stress applied to the pressure-sensitive adhesive layer, resulting in a pressure-sensitive adhesive layer that is resistant to peeling when pulled under a constant load and has excellent constant-load holding power and 180° peel adhesive strength. Furthermore, good tackiness can be achieved, improving adhesion to an adherend.

[0030] The tan δ at 120°C of the pressure-sensitive adhesive composition of the present invention can be adjusted to fall within the above-mentioned preferred range by adjusting, for example, the type, content, and weight-average molecular weight of the pressure-sensitive adhesive resin contained in the pressure-sensitive adhesive composition, the type, amount, softening point, and molecular weight of the tackifier resin, the type, content, molecular weight, and kinematic viscosity of the plasticizer, etc.

[0031] The storage modulus G' at 70°C is determined by measuring dynamic viscoelasticity using temperature dispersion. Using a viscoelasticity tester (manufactured by TA Instruments Japan, product name: ARES G2), the pressure-sensitive adhesive composition is formed into a thickness of approximately 2 mm, and the test piece is sandwiched between parallel disks with a diameter of 8 mm, which are the measurement section of the tester. The storage modulus (G') is measured from 30°C to 200°C at a frequency of 1 Hz and a heating rate of 2°C / min.

[0032] Tan δ at 120° C. is calculated by measuring the loss modulus (G″) in the same manner as for the storage modulus (G′), and then calculating tan δ from G′ and G″.

[0033] (Adhesive resin) The pressure-sensitive adhesive composition of the present invention is not particularly limited as long as it has the above-mentioned properties and can be appropriately selected from known materials, but it contains a pressure-sensitive adhesive resin and, if necessary, may also contain a tackifying resin and / or other components.

[0034] The pressure-sensitive adhesive resin in the present invention preferably contains, as the main component thereof, an acrylic random copolymer, an acrylic pressure-sensitive adhesive resin containing a block copolymer, or an aromatic vinyl pressure-sensitive adhesive resin containing a styrene block copolymer. Of these, it is more preferable to contain an acrylic pressure-sensitive adhesive resin containing an acrylic block copolymer, or an aromatic vinyl pressure-sensitive adhesive resin containing a styrene block copolymer. In this specification, the term "main component of the pressure-sensitive adhesive resin" refers to the main component of the resin components contained in the pressure-sensitive adhesive resin (typically, a component contained in an amount of more than 30% by mass).

[0035] Furthermore, when the main component of the pressure-sensitive adhesive resin in the present invention is an acrylic random copolymer, the acrylic random copolymer preferably accounts for 30 to 100 mass % of the entire pressure-sensitive adhesive composition, more preferably 40 to 95 mass % of the acrylic random copolymer, and even more preferably 50 to 90 mass % of the acrylic random copolymer.

[0036] Furthermore, when the main component of the pressure-sensitive adhesive resin in the present invention is an acrylic block copolymer, the acrylic block copolymer preferably accounts for 30 to 100 mass %, more preferably 40 to 90 mass %, and even more preferably 40 to 85 mass %, of the entire pressure-sensitive adhesive composition.

[0037] Furthermore, when the main component of the pressure-sensitive adhesive resin in the present invention is a styrene-based block copolymer, the styrene-based block copolymer preferably accounts for 30 to 100 mass % of the entire pressure-sensitive adhesive composition, more preferably 40 to 90 mass % of the entire pressure-sensitive adhesive composition, and even more preferably 40 to 85 mass % of the entire pressure-sensitive adhesive composition.

[0038] (Acrylic pressure-sensitive adhesive resin containing acrylic random copolymer) When the pressure-sensitive adhesive resin in the present invention contains an acrylic random copolymer, the pressure-sensitive adhesive composition preferably contains the acrylic random copolymer, a crosslinking agent, and a tackifying resin.

[0039] The acrylic random copolymer of the present invention is obtained by polymerizing a monomer component containing a (meth)acrylic monomer. Examples of the (meth)acrylic monomer that can be used to produce the acrylic random copolymer include (meth)acrylates having an alkyl group with 1 to 12 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, cyclohexyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.

[0040] Among these, it is preferable to use a (meth)acrylate having an alkyl group with 4 to 12 carbon atoms as the (meth)acrylic monomer, and it is even more preferable to use a (meth)acrylate having an alkyl group with 4 to 8 carbon atoms. It is particularly preferable to use either one or both of n-butyl acrylate and 2-ethylhexyl acrylate, as these will provide excellent 180° peel adhesive strength, constant load holding strength, and shear holding strength, as well as high removability.

[0041] The (meth)acrylate having an alkyl group having 1 to 12 carbon atoms is preferably used in an amount of 60 mass % or more, more preferably 80 mass % to 98.5 mass %, relative to the total amount of monomers used in the production of the acrylic random copolymer, and even more preferably 90 mass % to 98.5 mass %, in order to achieve excellent 180° peel adhesive strength, constant load holding strength, and shear holding strength, as well as high removability.

[0042] In addition, when producing an acrylic random copolymer, a highly polar vinyl monomer can be used as a monomer. As the highly polar vinyl monomer, a vinyl monomer having a hydroxyl group, a vinyl monomer having a carboxyl group, a vinyl monomer having an amide group, etc. can be used alone or in combination of two or more.

[0043] Examples of the monomer having a hydroxyl group that can be used include (meth)acrylates having a hydroxyl group, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate.

[0044] Examples of vinyl monomers having a carboxyl group that can be used include acrylic acid, methacrylic acid, itaconic acid, maleic acid, (meth)acrylic acid dimer, crotonic acid, and ethylene oxide-modified succinic acid acrylate, and among these, it is preferable to use acrylic acid.

[0045] Examples of the monomer having an amide group that can be used include N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, acrylamide, and N,N-dimethylacrylamide.

[0046] In addition to the above, vinyl acetate, ethylene oxide-modified succinic acid acrylate, 2-acrylamido-2-methylpropanesulfonic acid, etc. can also be used as the highly polar vinyl monomer.

[0047] The highly polar vinyl monomer is preferably used in an amount of 1.5% by mass to 20% by mass, more preferably 1.5% by mass to 10% by mass, based on the total amount of monomers used in the production of the acrylic random copolymer, and even more preferably 2% by mass to 8% by mass, in order to achieve excellent 180° peel adhesive strength, constant load holding strength, and shear holding strength, as well as high removability.

[0048] In the present invention, it is preferable to use an acrylic random copolymer having a weight-average molecular weight of 400,000 to 3,000,000 in order to obtain a double-sided pressure-sensitive adhesive tape that maintains excellent adhesive performance while having removability that allows for easy peeling during dismantling, etc., and it is even more preferable to use an acrylic random copolymer having a weight-average molecular weight of 700,000 to 2,500,000 in order to further improve the constant load holding power and removability.

[0049] The weight-average molecular weight and number-average molecular weight in the present invention refer to values ​​measured by gel permeation chromatography (GPC) and calculated in terms of standard polystyrene. Specifically, they can be measured using a GPC apparatus (HLC-8320GPC) manufactured by Tosoh Corporation under the following conditions: Sample concentration: 0.5% by mass (tetrahydrofuran solution) Sample injection volume: 100 μl Eluent: tetrahydrofuran ·Flow rate: 1.0ml / min ·Measurement temperature: 40℃ Columns: 1 TSKgel G5000HXL + 1 TSKgel G4000HXL + 1 TSKgel G3000HXL + 2 TSKgel G2500HXL Guard column: TSKgel HXL-H Detector: Differential refractometer Weight average molecular weight of standard polystyrene: 5 million to 5 million (manufactured by Tosoh Corporation)

[0050] When the pressure-sensitive adhesive composition of the present invention contains an acrylic random copolymer and a crosslinking agent, and when the crosslinking agent described below is used, it is preferable to use an acrylic random copolymer having a functional group that reacts with the functional group of the crosslinking agent. Examples of functional groups that acrylic random copolymers have include hydroxyl groups. Hydroxyl groups can be introduced into the acrylic random copolymer by using a vinyl monomer having a hydroxyl group as the monomer. The vinyl monomer having a hydroxyl group is preferably used in an amount of 0.01% to 1.0% by mass, more preferably 0.03% to 0.3% by mass, based on the total amount of monomers used in the production of the acrylic random copolymer.

[0051] The acrylic random copolymer of the present invention can be produced by polymerizing the above-mentioned monomers by methods such as solution polymerization, bulk polymerization, suspension polymerization, and emulsion polymerization, and the use of solution polymerization is preferred in terms of improving the production efficiency of the acrylic random copolymer. Examples of the solution polymerization include a method in which the above-mentioned monomers, a known polymerization initiator, and an organic solvent are mixed and stirred, preferably at a temperature of 40°C to 90°C, and radically polymerized. The acrylic random copolymer obtained by the above method may be in a state of being dissolved or dispersed in an organic solvent, for example, if produced by solution polymerization.

[0052] (Crosslinking agent) In the acrylic random copolymer of the present invention, it is preferable to use a crosslinking agent in order to ensure excellent adhesive strength. Examples of the crosslinking agent that can be used include an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, a metal chelate-based crosslinking agent, and an aziridine-based crosslinking agent. Among these, it is preferable to use either or both of an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent, which are highly reactive with the acrylic random copolymer, as the crosslinking agent, and it is more preferable to use an isocyanate-based crosslinking agent.

[0053] Examples of the isocyanate crosslinking agent that can be used include tolylene diisocyanate, naphthylene-1,5-diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, and trimethylolpropane-modified tolylene diisocyanate. It is preferable to use tolylene diisocyanate and trimethylolpropane-modified tolylene diisocyanate.

[0054] The crosslinking agent is preferably used in an amount that results in a gel fraction of the pressure-sensitive adhesive layer relative to toluene of 40 to 80%, more preferably in an amount that results in a gel fraction of 30 to 70% by mass, and even more preferably in an amount that results in a gel fraction of 35 to 65% by mass, in order to obtain a pressure-sensitive adhesive tape that combines excellent adhesive strength and removability.

[0055] The gel fraction of the adhesive layer refers to a value measured by the following method. First, an adhesive was applied to the release-treated surface of a release liner so that the thickness after drying was 50 μm. This was then dried for 3 minutes in a 100°C environment, and then aged for 2 days in a 40°C environment to form an adhesive layer. The adhesive layer was then cut into a 50 mm x 50 mm square to prepare a test piece. The mass (G1) of the test piece was measured, and the test piece was then immersed in toluene for 24 hours in a 23°C environment. The mixture of the test piece and toluene after immersion was filtered through a 300-mesh wire mesh to extract the insoluble components in toluene. The insoluble components were then dried for 1 hour in a 110°C environment, and the mass (G2) of the resulting product was measured. The gel fraction was calculated based on the masses (G1) and (G2) and the following formula: Gel fraction (mass%) = (G2 / G1) × 100

[0056] (Acrylic pressure-sensitive adhesive resin containing acrylic block copolymer) When the pressure-sensitive adhesive resin in the present invention contains an acrylic block copolymer, the pressure-sensitive adhesive composition preferably contains an acrylic block copolymer (X), an acrylic block copolymer (Y), and a tackifier resin.

[0057] (Acrylic block copolymer (X)) The acrylic block copolymer (X) is preferably a block copolymer having a segment A and a segment B. Here, the term "segment" as used in the present invention refers to a structural unit constituting each block in the block copolymer, and for example, in the case of an ABA triblock copolymer in which a structural unit (polymer or oligomer) A consisting of a monomer a, a structural unit (polymer or oligomer) B consisting of a monomer b, and a structural unit (polymer or oligomer) A consisting of a monomer a are bonded in this order, the structural units A and B become segments A and B, respectively (the same applies to the acrylic block copolymer (Y) described below).

[0058] The acrylic block copolymer (X) may be a diblock copolymer (sometimes referred to as an acrylic diblock copolymer) consisting of one segment A and one segment B, a triblock copolymer (sometimes referred to as an acrylic triblock copolymer) consisting of two segments A and one segment B, or a multiblock copolymer having a total of four or more segments A and B. Among these, the acrylic block copolymer (X) is preferably a block copolymer in which segment A is a polymer mainly composed of methacrylic acid alkyl ester monomer units and segment B is a polymer mainly composed of acrylic acid alkyl ester monomer units. The use of an acrylic triblock copolymer (X) in which the segments are bonded in an ABA type is more preferred because it can exhibit high cohesive strength. Furthermore, it is desirable for segment A to be present at the terminal. When segment A is present at the terminal, it easily aggregates to form domains, which forms a pseudo-crosslinked structure and improves the cohesiveness of the PSA. Furthermore, the acrylic block copolymer (X) may be used alone or in combination of two or more types.

[0059] (Segment A) As the segment A of the acrylic block copolymer (X), those containing a methacrylate ester as the main constituent monomer are preferred, and examples of such methacrylate esters include methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, sec-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, 1-methylcyclohexyl methacrylate, 2-methylcyclohexyl methacrylate, 3-methylcyclohexyl methacrylate, 4-methylcyclohexyl methacrylate, and 5-methylcyclohexyl methacrylate. methylcyclohexyl methacrylate, 2-phenoxyethyl methacrylate, 2-methoxyethyl methacrylate, 2-(N,N-dimethylamino)ethyl methacrylate, trifluoromethyl methacrylate, n-pentyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, stearyl methacrylate, 2-methoxypentyl methacrylate, 2-(N,N-dimethylamino)pentyl methacrylate, perfluoropentyl methacrylate, 2-trimethoxysilylpentyl methacrylate, and the like.

[0060] Of the above monomers, in order to improve shear holding strength particularly at high temperatures, it is preferable to use, as the main constituent monomer of segment A, monomers such as esters of methacrylic acid with aliphatic alcohols having 3 or less carbon atoms, such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, and isopropyl methacrylate, as well as cyclohexyl methacrylate and isobornyl methacrylate.

[0061] Here, in order to be said to be "mainly composed" in the present invention, the content (mass ratio) of the monomers constituting segment A is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0062] Furthermore, examples of monomers that can be used as constituent monomers of segment A of the acrylic block copolymer (X) other than the above-mentioned methacrylic acid esters include methacrylamides such as methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, N-isopropylmethacrylamide, N,N-dimethylmethacrylamide, and N,N-diethylmethacrylamide; acrylamides such as acrylamide, N-methylacrylamide, N-ethylacrylamide, N-isopropylacrylamide, N,N-dimethylacrylamide, and N,N-diethylacrylamide; vinyl monomers having a carboxyl group such as methacrylic acid, acrylic acid, crotonic acid, maleic acid, maleic anhydride, and fumaric acid; aromatic vinyl monomers such as styrene, α-methylstyrene, and p-methylstyrene; conjugated diene monomers such as butadiene and isoprene; olefins such as ethylene and propylene; and lactones such as ε-caprolactone and valerolactone.

[0063] The glass transition temperature (Tg) of segment A is not particularly limited as long as it enables the acrylic block copolymer (X) to exhibit the desired physical properties, but is preferably 50 to 150° C., more preferably 70 to 140° C., and even more preferably 90 to 130° C. When the glass transition temperature is within the above range, segment A acts as a physical pseudo-crosslinking point and functions as a hard segment at the normal use temperature of the pressure-sensitive adhesive, and when used in a pressure-sensitive adhesive composition, it can exhibit excellent holding power and removability.

[0064] (Segment B) Segment B of the acrylic block copolymer (X) is preferably one whose main constituent monomer is an acrylate ester. Examples of such acrylate esters include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, 2-methylbutyl acrylate, n-pentyl acrylate, n-hexyl acrylate, n-heptyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, n-nonyl acrylate, isononyl acrylate, decyl acrylate, dodecyl acrylate, tridecyl acrylate, stearyl acrylate, cyclohexyl acrylate, isobornyl acrylate, 2-methoxyethyl acrylate, 2-(N,N-dimethylamino)ethyl acrylate, trifluoromethyl acrylate, trimethoxysilylpropyl acrylate, 4-methyl-2-pentyl acrylate, 2-hydroxyethyl acrylate, and 2-hydroxypropyl acrylate.

[0065] Among the above monomers, in order to improve the adhesive strength and tackiness, etc., and to achieve stable adhesive strength under a wide range of peel speed conditions, it is preferable to use, as the main constituent monomer of segment B, a monomer such as an ester of acrylic acid with an aliphatic alcohol having 4 to 9 carbon atoms, such as n-butyl acrylate, n-heptyl acrylate, n-octyl acrylate, isooctyl acrylate, 2-octyl acrylate, 2-ethylhexyl acrylate, or isononyl acrylate.

[0066] Here, in order to be said to be "mainly composed" in the present invention, the content (mass ratio) of the segment B in all monomers constituting the segment B is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0067] Furthermore, examples of monomers that can be used as constituent monomers of segment B of the acrylic block copolymer (X) other than the above-mentioned acrylic acid esters include alkyl methacrylates (e.g., methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, sec-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, dodecyl methacrylate, and other methacrylic acid esters that are constituent monomers of segment A), methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, N-isopropylmethacrylamide, and N,N-dimethylmethacrylamide. and N,N-diethylmethacrylamide; acrylamides such as acrylamide, N-methylacrylamide, N-ethylacrylamide, N-isopropylacrylamide, N,N-dimethylacrylamide, and N,N-diethylacrylamide; vinyl monomers having a carboxyl group such as methacrylic acid, acrylic acid, crotonic acid, maleic acid, maleic anhydride, and fumaric acid; aromatic vinyl monomers such as styrene, o-methylstyrene, and p-methylstyrene; conjugated diene monomers such as butadiene and isoprene; olefins such as ethylene and propylene; and lactones such as ε-caprolactone and valerolactone.

[0068] The glass transition temperature (Tg) of the segment B is not particularly limited as long as the acrylic block copolymer (X) can exhibit the desired physical properties, but is preferably −80 to 40° C., more preferably −70 to 10° C., and even more preferably −60 to 0° C. When the glass transition temperature is within this range, the segment B functions as a soft segment having excellent flexibility, and when used in a pressure-sensitive adhesive composition, excellent low-temperature properties and impact resistance can be achieved.

[0069] The glass transition temperatures of segments A and B constituting the acrylic block copolymer (X) are the extrapolated onset temperatures of the transition regions of segments A and B observed in a curve obtained by analyzing the acrylic block copolymer (X) using a differential scanning calorimeter (DSC). Multiple glass transition temperatures originating from segments A and B of the acrylic block copolymer (X) are observed based on the curve obtained by DSC measurement, and the glass transition temperatures originating from segments A and B can be assigned based on the glass transition temperatures of polymers having the same chemical structure (monomer composition, stereoregularity, etc.) as each polymer block.

[0070] The acrylic block copolymer (X) may be modified, if necessary, in the molecular side chain or at the molecular main chain terminal with a functional group such as a hydroxyl group, a carboxyl group, an acid anhydride group, an amino group, or a trimethoxysilyl group, as long as the effects of the present invention are not impaired.

[0071] The weight-average molecular weight of the acrylic block copolymer (X) in the present invention is preferably from 50,000 to 400,000, more preferably from 110,000 to 300,000, even more preferably from 130,000 to 300,000, and particularly preferably from 150,000 to 300,000. When the weight-average molecular weight of the acrylic block copolymer (X) is within the above range, the adhesive properties of the pressure-sensitive adhesive composition, such as adhesive strength, cohesive strength, and tackiness, are improved.

[0072] The molecular weight distribution (weight average molecular weight / number average molecular weight) of the acrylic block copolymer (X) is preferably in the range of 1.0 to 2.0, more preferably in the range of 1.0 to 1.7, and even more preferably in the range of 1.0 to 1.5. When the molecular weight distribution of the acrylic block copolymer (X) is in the above range, excellent holding power and removability are achieved when blended with the acrylic block copolymer (Y) described below in a predetermined range.

[0073] The content of segment A in the acrylic block copolymer (X) in the present invention is preferably 5 to 30 mass %, more preferably 5 to 25 mass %, and even more preferably 10 to 20 mass %, based on the total mass of the acrylic block copolymer (X). When the content of segment A in the acrylic block copolymer (X) is within the above range, excellent high load holding power and removability are achieved when blended with the acrylic block copolymer (Y) within a predetermined range.

[0074] The content of segment B in the acrylic triblock block copolymer (X) of the present invention is preferably 70 to 95 mass %, more preferably 75 to 95 mass %, and even more preferably 80 to 90 mass %, based on the total mass of the acrylic triblock block copolymer (X). When the content of segment B in the acrylic triblock block copolymer (X) is within the above range, excellent high load holding power and removability are achieved when blended with the acrylic triblock block copolymer (Y) within a predetermined range.

[0075] The acrylic block copolymer (X) of the present invention may be synthesized by polymerizing raw material monomers, or a commercially available product may be used. The polymerization method is not particularly limited, and examples thereof include anionic polymerization and atom transfer radical polymerization (ATRP). Detailed descriptions of each polymerization method are omitted here. Examples of anionic polymerization include anionic polymerization using an organic alkali metal compound as a polymerization initiator in the presence of a mineral acid salt such as an alkali metal or alkaline earth metal salt, anionic polymerization using an organic alkali metal compound as a polymerization initiator in the presence of an organoaluminum compound, and anionic polymerization using an organic rare earth metal complex as a polymerization initiator. Examples of ATRP include polymerization using an organic halide or sulfonyl halide compound as an initiator in the presence of a transition metal compound and a nitrogen-containing compound. Commercially available products include, for example, the "CLARITY (registered trademark) series" manufactured by Kuraray Co., Ltd.

[0076] The acrylic block copolymer (X) of the present invention is preferably a solid at 23° C. By carrying out the polymerization reaction while appropriately adjusting the types of monomers constituting the segments A and B, the content ratio of the segments A and B, and the weight average molecular weights of the segments A and B, the acrylic block copolymer (X) after polymerization can be adjusted to be a solid at 23° C.

[0077] (Acrylic block copolymer (Y)) Like the acrylic block copolymer (X), the acrylic block copolymer (Y) is a block copolymer having a segment A and a segment B. The acrylic block copolymer (Y) is preferably a liquid at 23°C.

[0078] By blending the acrylic block copolymer (Y), which is liquid at 23°C, in addition to the above-mentioned acrylic block copolymer (X), the pressure-sensitive adhesive composition of the present invention can exhibit superior shear holding power and excellent removability at high temperatures without reducing the adhesive strength and constant-load holding power.

[0079] The acrylic block copolymer (Y) may be a diblock copolymer (sometimes referred to as an acrylic diblock copolymer) consisting of one segment A and one segment B, a triblock copolymer (sometimes referred to as an acrylic triblock copolymer) consisting of two segments A and one segment B, or a multiblock copolymer having a total of four or more segments A and B. Among these, the acrylic block copolymer (Y) is preferably a block copolymer in which segment A is a polymer mainly composed of methacrylic acid alkyl ester monomer units and segment B is a polymer mainly composed of acrylic acid alkyl ester monomer units. The use of an acrylic triblock copolymer (Y) in which the segments are bonded in an ABA type is more preferred, as it can exhibit high cohesive strength and hot-melt coatability. The acrylic block copolymer (Y) may be used alone or in combination of two or more types.

[0080] (Segment A) Segment A of acrylic block copolymer (Y) can use the same constituent monomers as those of segment A of acrylic block copolymer (X) described above. In the pressure-sensitive adhesive composition of the present invention, the constituent monomers of segment A of acrylic block copolymer (X) and segment A of acrylic block copolymer (Y) may be the same or different. However, using the same monomers is preferred because it improves compatibility between acrylic block copolymer (X) and acrylic block copolymer (Y). Furthermore, in order to improve shear strength at high temperatures, it is preferred to use, as the main constituent monomer of segment A, monomers such as esters of methacrylic acid with aliphatic alcohols having 3 or less carbon atoms, such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, and isopropyl methacrylate, as well as cyclohexyl methacrylate and isobornyl methacrylate.

[0081] (Segment B) The same constituent monomers as those of the segment B of the acrylic block copolymer (X) can be used for the segment B of the acrylic block copolymer (Y). In the pressure-sensitive adhesive composition of the present invention, the constituent monomers of the segment B of the acrylic block copolymer (X) and the segment B of the acrylic block copolymer (Y) may be the same or different. However, the same monomers are preferred because they improve the compatibility between the acrylic block copolymer (X) and the acrylic block copolymer (Y). Furthermore, the main component of the segment B is preferably selected from the group consisting of esters of acrylic acid and aliphatic alcohols having 4 to 9 carbon atoms, such as n-butyl acrylate, n-heptyl acrylate, n-octyl acrylate, isooctyl acrylate, 2-octyl acrylate, 2-ethylhexyl acrylate, and isononyl acrylate, because these esters provide excellent low-temperature properties and impact resistance when used in a pressure-sensitive adhesive composition.

[0082] The weight-average molecular weight of the acrylic block copolymer (Y) in the present invention is preferably from 20,000 to 100,000, more preferably from 40,000 to 80,000. When the weight-average molecular weight of the acrylic block copolymer (Y) is within the above range, bleeding out of the acrylic block copolymer (Y) from the pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition can be suppressed.

[0083] The content of segment A in the acrylic block copolymer (Y) of the present invention is preferably 1 to 20 mass%, more preferably 3 to 15 mass% or less, and even more preferably 5 to 13 mass% or less, based on the total mass of the acrylic block copolymer (Y). When the content of segment A in the acrylic block copolymer (Y) is within the above range, the pressure-sensitive adhesive composition containing the block copolymer exhibits superior cohesive strength, and further improves adhesive strength and constant load holding strength. In addition, superior shear holding strength and excellent removability at high temperatures are exhibited.

[0084] The content of segment B in the acrylic block copolymer (Y) of the present invention is preferably 80 to 99% by mass, more preferably 85 to 97% by mass or less, and even more preferably 87 to 95% by mass or less, based on the total mass of the acrylic block copolymer (Y). When the content of segment B in the acrylic block copolymer (Y) is within the above range, flexibility and stress relaxation properties are imparted, improving adhesive properties, while bleed-out is suppressed, enabling both better shear holding power and removability at high temperatures to be achieved.

[0085] The acrylic block copolymer (Y) in the present invention may be synthesized by polymerizing raw material monomers, or a commercially available product may be used. The polymerization method is not particularly limited, and specific examples of the polymerization method are the same as those for the acrylic block copolymer (X). Examples of commercially available products include the "CLARITY (registered trademark) series" manufactured by Kuraray Co., Ltd.

[0086] The acrylic block copolymer (Y) in the present invention is preferably a liquid at 23° C. By carrying out the polymerization reaction while appropriately adjusting the types of monomers constituting the segments A and B, the content ratio of the segments A and B, and the weight average molecular weights of the segments A and B, the acrylic block copolymer (X) after polymerization can be adjusted to be a liquid at 23° C.

[0087] In the present invention, the content of the acrylic block copolymer (Y) relative to 100 parts by mass of the acrylic block copolymer (X) is preferably 1 to 140 parts by mass, more preferably 15 to 120 parts by mass, and even more preferably 20 to 100 parts by mass. When the content of the acrylic block copolymer (Y) relative to 100 parts by mass of the acrylic block copolymer (X) is within the above range, a pressure-sensitive adhesive layer can be obtained that exhibits both high adhesive strength and excellent cohesive strength, and is excellent in constant load retention and removability.

[0088] (Aromatic vinyl adhesive resin containing aromatic block copolymer) When the pressure-sensitive adhesive resin in the present invention contains an aromatic block copolymer, the pressure-sensitive adhesive composition preferably contains a block copolymer of an aromatic vinyl compound and a conjugated diene compound, and a tackifier resin.

[0089] Examples of compounds constituting the aromatic segment of the aromatic block copolymer of the present invention include styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α-methylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 4-t-butylstyrene, 5-t-butyl-2-methylstyrene, vinylethylbenzene, divinylbenzene, trivinylbenzene, divinylnaphthalene, t-butoxystyrene, vinylbenzyldimethylamine, (4-vinylbenzyl)dimethylaminoethyl ether, N,N-dimethylaminoethylstyrene, N,N-dimethylaminomethylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, 2-t-butylstyrene, 3-t-butylstyrene, 4-t-butylstyrene, vinylxylene, vinylnaphthalene, vinylpyridine, diphenylethylene, and tertiary amino group-containing diphenylethylene. These aromatic monomers may be used alone or in combination of two or more. Specific examples of the conjugated diene compound include isoprene, 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 1,3-heptadiene, 2-phenyl-1,3-butadiene, 3-methyl-1,3-pentadiene, 2-chloro-1,3-butadiene, β-farnesene, etc. These conjugated diene monomers may be used alone or in combination of two or more. The use of styrene as the aromatic segment makes it easier to control the adhesive properties described below, and is also desirable from an economic and procurement perspective. The use of isoprene or farnesene as the conjugated diene compound segment is desirable because it makes it easier to achieve both moderate flexibility and heat durability. Such block copolymers can be used alone or in combination of two or more types as the base polymer. Examples include styrene-based resins such as styrene-isoprene copolymer, styrene-isoprene-styrene copolymer, styrene-isoprene-butadiene-styrene copolymer, styrene-butadiene-styrene copolymer, styrene-ethylene-butylene copolymer, styrene-ethylene-propylene copolymer, styrene-farnesene copolymer, styrene-farnesene-styrene copolymer, and hydrogenated products thereof. These can be used alone or in combination of two or more types. Among these, styrene-isoprene copolymer, styrene-isoprene-styrene copolymer, styrene-farnesene copolymer, and styrene-farnesene-styrene copolymer are more preferred because they can achieve excellent initial adhesion, heat durability, and removability, and styrene-isoprene copolymer and / or styrene-isoprene-styrene copolymer are particularly preferred.

[0090] The weight-average molecular weight of the styrene-based block copolymer in the present invention is preferably 50,000 to 250,000, more preferably 100,000 to 200,000, and most preferably 170,000 to 200,000. If the weight-average molecular weight is too small, the melt viscosity of the system may decrease and the cohesive force may decrease, resulting in poor heat durability, whereas if it is too large, the viscosity of the system may increase and the compatibility with other components may decrease.

[0091] The styrene-based block copolymer used in the present invention preferably contains styrene-derived structural units in the range of 5 to 80% by mass, more preferably 5 to 60% by mass, even more preferably 5 to 40% by mass, and particularly preferably 10 to 30% by mass, based on the total mass of the styrene-based block copolymer. This allows for excellent adhesion and heat resistance to be obtained. If the styrene-derived structural units are less than the above range, the cohesive strength decreases, resulting in poor heat durability and removability. Conversely, if the styrene-derived structural units are too high, the cohesive strength becomes too high, tackiness decreases significantly, and the copolymer cannot be used as a pressure-sensitive adhesive composition.

[0092] The styrene-based block copolymer of the present invention may be in the form of a diblock copolymer, a triblock copolymer, a radial copolymer, a mixture thereof, or the like. In the triblock copolymer and the radial copolymer, it is preferable that a hard segment (e.g., a styrene block) is disposed at the end of the polymer chain. This is because the hard segments disposed at the end of the polymer chain tend to gather together to form domains, which form a pseudo-crosslinked structure and improve the cohesion of the PSA.

[0093] The styrene-based block copolymer in the present invention may be synthesized by polymerizing raw material monomers, or may be a commercially available product, such as Kraton D1107, 1112, and 1117 (all manufactured by Kraton Polymers), Quintac 3270, 3280, 3421, 3433N, 3440, 3450, 3520, and 3620 (all manufactured by Zeon Corporation), or SIS5229 (manufactured by JSR Corporation).

[0094] (tackifying resin) The pressure-sensitive adhesive composition of the present invention preferably further contains a tackifier resin in addition to the above-mentioned pressure-sensitive adhesive resin. By containing the tackifier resin, the pressure-sensitive adhesive composition of the present invention increases adhesive strength to a practically sufficient level and satisfies properties such as adhesive strength, shear holding strength, constant-load peel holding strength, and removability.

[0095] The tackifying resin in the present invention is preferably compatible with the above-mentioned pressure-sensitive adhesive resin so as to form a polymer blend. Such compatible resins are not particularly limited, and may be appropriately selected from various known tackifying resins such as petroleum resins, styrene-based resins, coumarone-indene resins, terpene resins, modified terpene resins, rosin-based resins, rosin derivative resins, and ketone-based resins.

[0096] Examples of petroleum resins include aliphatic (C5) petroleum resins, aromatic (C9) petroleum resins, aliphatic / aromatic copolymer (C5 / C9) petroleum resins, and hydrogenated products thereof (for example, alicyclic petroleum resins obtained by hydrogenating aromatic petroleum resins).

[0097] Examples of styrene-based resins include those containing a homopolymer of styrene as the main component, those containing a homopolymer of α-methylstyrene as the main component, those containing a homopolymer of vinyltoluene as the main component, and those containing a copolymer containing two or more of styrene, α-methylstyrene, and vinyltoluene as the main component in the monomer composition (for example, an α-methylstyrene / styrene copolymer resin containing an α-methylstyrene / styrene copolymer as the main component).

[0098] The coumarone-indene resin can be a resin containing coumarone and indene as monomer components that make up the resin skeleton (main chain). Other monomer components that can be included in the resin skeleton besides coumarone and indene include styrene, α-methylstyrene, methylindene, vinyltoluene, etc.

[0099] Examples of terpene resins include α-pinene polymers, β-pinene polymers, dipentene polymers, etc. Examples of modified terpene resins include those obtained by modifying the above-mentioned terpene resins (phenol-modified, catechol-modified, styrene-modified, hydrogenated-modified, hydrocarbon-modified, etc.). Specific examples include terpene phenol resins, styrene-modified terpene resins, hydrogenated terpene resins, terpene catechol resins, etc.

[0100] The term "terpene phenolic resin" refers to a polymer containing a terpene residue and a phenol residue, and encompasses both a copolymer of a terpene and a phenolic compound (a terpene-phenol copolymer resin) and a phenol-modified terpene resin (a terpene resin, typically an unmodified terpene resin) modified with phenol. Suitable examples of terpenes constituting the terpene phenolic resin include monoterpenes such as α-pinene, β-pinene, and limonene (including d-, l-, and d / l-forms (dipentene)).

[0101] Specific examples of rosin-based resins include unmodified rosin (gum rosin, wood rosin, tall oil rosin, etc., also known as raw rosin), modified rosin (rosin modified by hydrogenation, disproportionation, polymerization, other chemical modifications, etc.), etc. Examples of rosin derivative resins include esters of unmodified rosin and modified rosin, unsaturated fatty acid modified rosins of unmodified rosin and modified rosin, unsaturated fatty acid modified rosin esters obtained by modifying rosin esters with unsaturated fatty acids, rosin alcohols obtained by reducing the carboxyl groups of unmodified rosin, modified rosin, unsaturated fatty acid modified rosins, or unsaturated fatty acid modified rosin esters, metal salts of rosins (particularly rosin esters) such as unmodified rosin, modified rosin, and various rosin derivatives, and rosin phenolic resins obtained by adding phenol to rosins (unmodified rosin, modified rosin, various rosin derivatives, etc.) using an acid catalyst and then thermally polymerizing the resulting mixture.

[0102] Of these, petroleum resins and rosin-based resins are preferred from the viewpoint of good compatibility with the above-mentioned resins and improved adhesive strength.

[0103] In the present invention, the tackifier resin preferably contains at least one resin having a softening point of 0°C or higher, from the viewpoint of high-temperature holding power. By incorporating a tackifier resin with such a high softening point, it is possible to significantly improve not only adhesive strength and holding power, but also constant-load peelability and removability. From the viewpoint of further improving these properties, the softening point of the tackifier resin is preferably 50°C or higher, more preferably 70°C or higher, even more preferably 85°C or higher, and most preferably 90°C or higher. The softening point of the tackifier resin is preferably 200°C or lower, more preferably 170°C or lower, even more preferably 165°C or lower, and most preferably 160°C or lower. When the softening point of the tackifier resin is within the above range, the resin is prevented from becoming too hard, and a viscosity suitable for a pressure-sensitive adhesive can be obtained. Furthermore, the shear holding strength, constant load holding strength, and removability in a high-temperature environment can be improved. One or more types of tackifier resins may be used. When two or more types are used, the tackifier resins having the suitable softening points preferably account for 50% by mass or more, and more preferably 60% by mass or more, of the total mass of all tackifier resins.

[0104] The amount of the tackifier resin in the present invention is preferably 10 to 200 parts by mass, more preferably 20 to 150 parts by mass, even more preferably 25 to 120 parts by mass, and most preferably 50 to 100 parts by mass, based on 100 parts by mass of the adhesive resin. When the amount of the tackifier resin is within the above range, the adhesive strength and holding power can be significantly improved. In particular, the shear holding power and constant load holding power in a high-temperature environment can be improved.

[0105] (anti-aging agent) The pressure-sensitive adhesive composition of the present invention may contain an antioxidant, if necessary. The use of an antioxidant prevents thermal degradation of the pressure-sensitive adhesive and improves its quality stability. One antioxidant may be used alone, or two or more antioxidants may be used in combination. Examples of antioxidants include phosphorus-based antioxidants, phenol-based antioxidants (hindered phenol-based antioxidants, etc.), hindered amine-based antioxidants, aromatic amine-based antioxidants, and sulfur-based antioxidants.

[0106] (optional ingredient) The pressure-sensitive adhesive composition of the present invention may optionally contain one or more rubbery polymers other than the acrylic block copolymer and the aromatic block copolymer, to the extent that the effects of the present invention are not significantly impaired. Such rubbery polymers include various polymers known in the field of pressure-sensitive adhesives, such as rubber-based, acrylic-based, polyester-based, urethane-based, polyether-based, silicone-based, polyamide-based, and fluorine-based polymers.

[0107] The pressure-sensitive adhesive composition of the present invention may contain, as necessary, various additives commonly used in the field of pressure-sensitive adhesives, such as leveling agents, crosslinking agents, crosslinking aids, plasticizers, softeners, fillers, colorants (pigments, dyes, etc.), antistatic agents, ultraviolet absorbers, light stabilizers, etc., to the extent that the effects of the present invention are not significantly impaired. As for such various additives, conventionally known ones can be used in the usual manner.

[0108] <Form of Pressure-Sensitive Adhesive Composition> The composition of the pressure-sensitive adhesive composition of the present invention has been described in detail above. This pressure-sensitive adhesive composition can be a hot-melt type pressure-sensitive adhesive composition prepared by melting and kneading the above-mentioned pressure-sensitive adhesive resin, a tackifier resin if necessary, and optional components (other pressure-sensitive adhesive raw materials), or a solution type pressure-sensitive adhesive composition prepared by dissolving the above-mentioned pressure-sensitive adhesive resin in a predetermined organic solvent (toluene, ethyl acetate, etc.).

[0109] When a hot-melt pressure-sensitive adhesive composition is used, the pressure-sensitive adhesive composition preferably has a storage modulus G' at 180°C of 2000 Pa or less, more preferably 1 to 1500 Pa, even more preferably 1 to 1000 Pa, and most preferably 1 to 800 Pa. When the storage modulus G' is within the above range, the pressure-sensitive adhesive composition exhibits excellent holding power even in a high-temperature environment and exhibits excellent melt viscosity at high temperatures, thereby achieving favorable kneading workability and hot-melt coating suitability.

[0110] The storage modulus G' at 180°C is determined by measuring dynamic viscoelasticity using temperature dispersion. Using a viscoelasticity tester (manufactured by TA Instruments Japan, product name: ARES G2), the hot-melt pressure-sensitive adhesive composition is formed into a thickness of approximately 2 mm, and the test piece is sandwiched between parallel disks with a diameter of 8 mm, which are the measurement section of the tester. The storage modulus (G') is measured from 30°C to 200°C at a frequency of 1 Hz and a heating rate of 2°C / min.

[0111] <Uses of the pressure-sensitive adhesive composition> The pressure-sensitive adhesive composition of the present invention is suitably used in pressure-sensitive adhesive products in the form of a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition, or a laminate (e.g., a pressure-sensitive adhesive tape) containing the pressure-sensitive adhesive layer. As an example of the use of the pressure-sensitive adhesive composition of the present invention, a double-sided pressure-sensitive adhesive tape formed by applying the above-mentioned pressure-sensitive adhesive composition to both sides of a substrate will be described below. Note that the same applies to a single-sided pressure-sensitive adhesive tape, except that the pressure-sensitive adhesive is applied to one side of the substrate.

[0112] The double-sided pressure-sensitive adhesive tape using the pressure-sensitive adhesive composition of the present invention has the above-mentioned pressure-sensitive adhesive composition applied to both sides of a substrate, and further has a release liner attached to the surface of the pressure-sensitive adhesive composition as needed.

[0113] The substrate is not particularly limited as long as it has a film or sheet shape that can be coated with the pressure-sensitive adhesive composition. Examples of suitable substrates include plastic films such as polypropylene film, ethylene-propylene copolymer film, polyester film, polyvinyl chloride film, cellophane, polyimide, polycarbonate (PC), and polystyrene (PS); foam sheets made of foams such as polyurethane foam, polyethylene foam, polypropylene foam, ethylene-vinyl acetate copolymer foam, butyl rubber foam, and polyacrylate foam; woven and nonwoven fabrics made by spinning various fibrous materials (natural fibers such as hemp and cotton, synthetic fibers such as polyester and vinylon, semi-synthetic fibers such as acetate, and metal fibers such as stainless steel); paper such as kraft paper, Japanese paper, and crepe paper; and metal foils such as aluminum foil and copper foil. These plastic films can be unstretched films, uniaxially stretched films, or biaxially stretched films. The surface of the substrate on which the pressure-sensitive adhesive layer is to be formed may be coated with a primer or subjected to an adhesion-enhancing treatment such as corona discharge treatment.

[0114] The thickness of the substrate can be appropriately selected depending on the purpose, but it is generally preferable that it be 1 μm or more and 2 mm or less.

[0115] The release liner can be any conventional release paper, and is not particularly limited. For example, a release liner having a release treatment layer on the surface of a substrate such as a plastic film or paper, or a release liner made of a low-adhesion material such as a fluorine-based polymer (e.g., polytetrafluoroethylene) or a polyolefin-based resin (e.g., polyethylene, polypropylene), can be used. The release treatment layer is formed by surface treating the substrate with a release treatment agent such as a silicone-based, long-chain alkyl-based, or fluorine-based agent.

[0116] The method for applying the adhesive composition to the substrate is not particularly limited, and known methods can be used, such as a method of dissolving the adhesive raw material in an organic solvent and applying the composition (melt spreading method), a method of thinning the adhesive using multiple heated rolls and applying the composition (calender method), and a method of thermally melting the adhesive raw material and applying the composition (hot melt method).

[0117] The pressure-sensitive adhesive composition of the present invention can be used in a variety of applications. A pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition can be used alone as a pressure-sensitive adhesive tape, and laminates containing the pressure-sensitive adhesive layer can also be used in a variety of applications. Examples of such applications include pressure-sensitive adhesives and tapes for fixing electronic components, fixing in-vehicle components, protecting surfaces and the like, masking, labeling, bonding, dicing tape, sealing, corrosion prevention and waterproofing, electrical insulation, semiconductor manufacturing, optical display films, pressure-sensitive adhesive optical films, electromagnetic wave shielding, and sealing materials for electrical and electronic components. [Example]

[0118] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0119] Example 1 A hot-melt pressure-sensitive adhesive composition was prepared by thoroughly kneading 100 parts by mass of a styrene-butadiene block copolymer (Quintac 3280), 28.6 parts of Pencel D-160 (polymerized rosin, Mw 5100, softening point 160°C, manufactured by Arakawa Chemical Industries) as a tackifying resin, 36.3 parts of Quinton G115 (aliphatic petroleum resin, Mw 1800, softening point 115°C, manufactured by Zeon Corporation), and 0.88 parts by mass of an antioxidant (Irganox 1010, manufactured by BASF) in a kneader set at 180°C. This pressure-sensitive adhesive composition was remelted at 160°C and applied to the release-treated surface of a 100 μm-thick release liner to prepare a pressure-sensitive adhesive tape with a 50 μm-thick pressure-sensitive adhesive layer.

[0120] Examples 2 to 5 Except for changing the formulation of the adhesive composition as shown in Table 3, adhesive tapes were prepared in the same manner as in Example 1.

[0121] Example 6 100 parts by mass of acrylic block copolymer (X) (Kuraray Co., Ltd. Clarity LA #3710, Mw = 195,000, Mw / Mn = 1.1), 20 parts by mass of acrylic block copolymer (Y) (Kuraray Co., Ltd. Clarity LA #2114, Mw = 64,000, Mw / Mn = 1.1), 80 parts by mass of tackifier resin (ENEOS Corporation Neopolymer E-130, C9 petroleum resin, softening point 125 ° C, hydroxyl value 40 mg KOH / g or more), and 0.88 parts by mass of antioxidant (BASF Corporation Irganox 1010) were thoroughly kneaded in a kneader set at 180 ° C to prepare a hot melt pressure-sensitive adhesive composition. This pressure-sensitive adhesive composition was melted again at 160 ° C and applied to the release-treated surface of a 100 μm thick release liner to prepare a pressure-sensitive adhesive tape with a pressure-sensitive adhesive layer thickness of 50 μm.

[0122] (Examples 7-8, Comparative Examples 1-2) Pressure-sensitive adhesive tapes were produced in the same manner as in Example 6, except that the formulation of the pressure-sensitive adhesive composition was changed as shown in Tables 4 and 5.

[0123] Example 9 A pressure-sensitive adhesive composition was obtained by dissolving 100 parts by mass of a styrene-butadiene block copolymer (Quintac 3620), 40 parts of Quinton G115 (aliphatic petroleum resin, Mw 1800, softening point 115°C, manufactured by Zeon Corporation) as a tackifying resin, and 40 parts of Pencel D-125 (polymerized rosin, Mw 4100, softening point 125°C, manufactured by Arakawa Chemical Industries, Ltd.) in toluene. This pressure-sensitive adhesive composition was applied using an applicator to the release-treated surface of a 100-μm-thick release liner so that the thickness after drying would be 50 μm, and then dried at 85°C for 5 minutes to produce a pressure-sensitive adhesive tape with a pressure-sensitive adhesive layer thickness of 50 μm.

[0124] Example 10 A reaction vessel equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping funnel was charged with 94 parts by mass of n-butyl acrylate, 4 parts by mass of acrylic acid, 0.06 parts by mass of 4-hydroxybutyl acrylate, and 200 parts by mass of ethyl acetate. The mixture was heated to 65°C while stirring and blowing in nitrogen to obtain mixture (1). Next, 4 parts by mass of a 2,2'-azobisisobutyronitrile solution (2.5% by mass solids) previously dissolved in ethyl acetate was added to the mixture (1), and the mixture was stirred and held at 65°C for 10 hours to obtain mixture (2). Next, mixture (2) was diluted with 98 parts by mass of ethyl acetate and filtered through a 200-mesh wire screen to obtain a solution of acrylic random copolymer (1) with a weight-average molecular weight of 1.6 million (polystyrene equivalent). Next, 12 parts by weight of Pencel D-125 (polymerized rosin, Mw 4100, softening point 125°C, manufactured by Arakawa Chemical Industries) and 15 parts by weight of Super Ester A-100 (rosin ester, Mw 1100, softening point 100°C, manufactured by Arakawa Chemical Industries) were mixed and stirred with 100 parts by weight of the solids of the acrylic random copolymer (1) solution, and ethyl acetate was added to obtain a 45% solids adhesive composition (1). 3.1 parts by weight of CH-Y-1872 (trimethylolpropane adduct of tolylene diisocyanate, isocyanate group content 7% by weight, nonvolatile content 40% by weight, manufactured by DIC Corporation) was added as a crosslinking agent with 100 parts by weight of the solids of the adhesive composition (1), and the mixture was stirred and mixed to obtain a homogeneous adhesive composition (2). The adhesive composition (2) was applied to the release-treated surface of a 100 μm thick release liner using an applicator so that the thickness after drying would be 50 μm, and then dried at 80°C for 3 minutes to produce an adhesive tape with an adhesive layer thickness of 50 μm.

[0125] <Ingredients> The raw materials used are as follows: [Acrylic block copolymer]

[0126] [Table 1] [Aromatic block copolymer]

[0127] [Table 2]

[0128] [Tackifying resin] P-90: Alcon P-90 (petroleum resin, Mw 1500, softening point 90°C, manufactured by Arakawa Chemical Industries) 90HS: Petrotack 90HS (C5 / C9 petroleum resin, Mw 2800, softening point 87°C, manufactured by Tosoh) D-125: Pencel D-125 (polymerized rosin, Mw 4100, softening point 125°C, manufactured by Arakawa Chemical Industries, Ltd.) D-160: Pencel D-160 (polymerized rosin, Mw 5100, softening point 160°C, manufactured by Arakawa Chemical Industries, Ltd.) A-100: Super Ester A-100 (rosin ester, Mw 1100, softening point 100°C, manufactured by Arakawa Chemical Industries, Ltd.) G115: Quinton G115 (aliphatic petroleum resin, Mw 1800, softening point 115°C, manufactured by Zeon Corporation) E-100: Neopolymer E-100 (C9 petroleum resin, Mw 800, softening point 95°C, manufactured by ENEOS) E-130: Neopolymer E-130 (C9 petroleum resin, Mw 1300, softening point 125°C, manufactured by ENEOS) 160: Neopolymer 160 (C9 petroleum resin, Mw 2900, softening point 160°C, manufactured by ENEOS) PCJ: Haritack PCJ (polymerized rosin ester, Mw 4200, softening point 124°C, manufactured by Harima Chemicals)

[0129] [Antioxidants] Irg.1010: Irganox 1010 (manufactured by BASF)

[0130] <Evaluation method> The adhesive tapes having adhesive layers made of the adhesive compositions prepared as described above were subjected to measurements according to the methods described below. The results are shown in Tables 3 to 5.

[0131] (180° peel adhesive strength) One side of each adhesive tape prepared in the Examples and Comparative Examples was lined with a 25 μm-thick polyethylene terephthalate film under an environment of 23°C and 50% RH, and then cut to a length of 120 mm and a width of 20 mm. The other adhesive side was then attached to a stainless steel plate (SUS304 with a hairline finish using #360 sandpaper), and a 2 kg roller was rolled back and forth on the top surface of the adhesive tape. The tape and stainless steel plate were then left to stand for 1 hour under an environment of 23°C and 50% RH, producing a test specimen in which the adhesive tape and stainless steel plate were bonded together. Next, using a Tensilon tensile tester, the adhesive tape was peeled off in a 180° direction at a pulling rate of 300 mm / min with the stainless steel plate constituting the test specimen fixed, and the peel strength was measured.

[0132] (shear holding strength) Under an environment of 23°C and 50% RH, one side of the pressure-sensitive adhesive tapes prepared in the Examples and Comparative Examples was lined with 50 μm thick aluminum foil and then cut to a length of 100 mm and a width of 20 mm. Next, the adhesive side of the cut pressure-sensitive adhesive tape 2 was attached to a stainless steel plate 3 (SUS304 with a hairline finish using #360 sandpaper) so that the adhesive area was 20 mm x 20 mm (4 cm2), and a 2 kg roller was rolled back and forth on the top of the pressure-sensitive adhesive tape 2 to produce a test piece 1. The test piece 1, in which the pressure-sensitive adhesive tape 2 and the stainless steel plate 3 were pressure-bonded, was prepared by leaving it to stand for 1 hour under an environment of 23°C and 50% RH. Next, the portion of the adhesive tape 2 of the test piece 1 that was not attached to the stainless steel plate 3 was folded over, and the stainless steel plate 3 side of the test piece 1 was fixed to a holding force meter in an environment at a measurement temperature of 70°C, and then a 500g weight 3 was attached to the folded part of the adhesive tape 2. With the weight 3 attached, the test piece was left in an environment at 70°C, and the time until the adhesive tape 2 peeled (fell) was measured (a conceptual diagram of the measurement method is shown in Figure 1). Note that when the test was held for 1,440 minutes, the test was terminated and the result was recorded as "1,440<".

[0133] (Constant load holding power) One side of each of the pressure-sensitive adhesive tapes prepared in the Examples and Comparative Examples was lined with a 25 μm-thick polyethylene terephthalate film under an environment of 23°C and 50% RH, and then cut to a length of 100 mm and a width of 10 mm. Next, the adhesive side of the cut pressure-sensitive adhesive tape 6 was attached to a stainless steel plate 7 (SUS304 with a hairline finish using #360 sandpaper) so that the attached length was 50 mm. The top surface of the pressure-sensitive adhesive tape 6 was pressed back and forth once with a 2 kg roller, and then the tape was left to stand for 1 hour under an environment of 40°C, thereby preparing a test piece 5 in which the pressure-sensitive adhesive tape 6 and the stainless steel plate 7 were pressure-bonded together. Next, the stainless steel plate 7 side of the test piece 5 was fixed to a constant load holding force meter so that the adhesive tape-attached surface was facing downwards, and then a 100 g weight 8 was attached to the part of the adhesive tape 6 that was not attached to the stainless steel plate 7. With the weight 8 attached, the test piece was left in an environment of a temperature of 23°C and a relative humidity of 50% RH, and the time until the adhesive tape 6 peeled off (fell off) was measured (a conceptual diagram of the measurement method is shown in Figure 2). Note that if the test was held for 180 minutes, the test was terminated and the result was recorded as "180<".

[0134] (removability) One side of the pressure-sensitive adhesive tapes prepared in the Examples and Comparative Examples was lined with a 25 μm-thick polyethylene terephthalate film under an environment of 23°C and 50% RH, and then cut to a length of 120 mm and a width of 20 mm. Next, the other adhesive side was attached to a stainless steel plate (SUS304 with a BA finish), and a 2 kg roller was rolled back and forth once on the top surface of the pressure-sensitive adhesive tape to apply pressure. The tape and stainless steel plate were then left to stand for 72 hours under an environment of 23°C and 50% RH to prepare a test specimen in which the pressure-sensitive adhesive tape and stainless steel plate were pressure-bonded. Next, with the stainless steel plate of the test piece fixed, the adhesive tape was peeled off in a 135° direction at a pulling speed of 20 m / min, and the presence or absence of adhesive residue on the stainless steel plate and contamination of the adherend was evaluated as follows. ⊚: Peeled off at the interface between the adhesive layer and the stainless steel plate without leaving any adhesive residue or staining. Good: A faint trace of glue remained on the surface of the stainless steel plate, but the adhesive layer peeled off at the interface between the adhesive layer and the stainless steel plate. ×: Destruction occurred within the adhesive layer, or peeling occurred between the polyethylene terephthalate film and the adhesive layer, resulting in adhesive residue or contamination.

[0135] (storage modulus G') Each pressure-sensitive adhesive layer prepared in the Examples and Comparative Examples was aged for two days in a 40°C environment, and then stacked to a thickness of approximately 2 mm and punched out to an 8 mm diameter test piece. Parallel plates with a diameter of 8 mm were attached to a viscoelasticity tester (ARESG2, manufactured by TA Instruments Japan), and the test piece was sandwiched between them. Measurements were then taken from 30°C to 200°C at a frequency of 1 Hz and a heating rate of 2°C / min, and the storage moduli G' at 70°C and 180°C were determined.

[0136] (tanδ) Tan δ at 120°C was calculated from G' and G" at 120°C by measuring the loss modulus (G") in the same manner as for the storage modulus (G').

[0137] (Weight average molecular weight of adhesive resin (GPC)) The weight-average molecular weight defined in this specification refers to a value measured by gel permeation chromatography (GPC) and calculated in terms of standard polystyrene. Specifically, the weight-average molecular weight was measured using a GPC apparatus (HLC-8320GPC) manufactured by Tosoh Corporation under the following conditions: Sample concentration: 0.5% by mass (tetrahydrofuran solution) Sample injection volume: 100 μl Eluent: tetrahydrofuran ·Flow rate: 1.0ml / min ·Measurement temperature: 40℃ Columns: 1 TSKgel G5000HXL + 1 TSKgel G4000HXL + 1 TSKgel G3000HXL + 2 TSKgel G2500HXL Guard column: TSKgel HXL-H Detector: Differential refractometer Weight average molecular weight of standard polystyrene: 5 million to 5 million (manufactured by Tosoh Corporation)

[0138] [Table 3]

[0139] [Table 4]

[0140] [Table 5]

[0141] Tables 3 to 5 show that the pressure-sensitive adhesive composition of the present invention is excellent in 180° peel adhesive strength, constant load holding strength and shear holding strength, and also in removability.

Claims

1. Storage modulus G' (70°C) is 1.5 x 10 ４ The pressure-sensitive adhesive composition has a viscosity of 100 Pa or more and a tan δ (120°C) of 0.4 or more.

2. The pressure-sensitive adhesive composition according to claim 1 , which contains an acrylic pressure-sensitive adhesive or a rubber pressure-sensitive adhesive.

3. The pressure-sensitive adhesive composition according to claim 2 , wherein the acrylic pressure-sensitive adhesive comprises a random copolymer or a triblock copolymer.

4. The pressure-sensitive adhesive composition according to claim 2 , wherein the rubber-based pressure-sensitive adhesive comprises an aromatic triblock copolymer.

5. The pressure-sensitive adhesive composition according to claim 1, having a storage modulus G' (180°C) of 2000 Pa or less.

6. The pressure-sensitive adhesive composition according to claim 2 , further comprising a tackifying resin.

7. The pressure-sensitive adhesive composition according to claim 2 , further comprising an antioxidant.

8. The pressure-sensitive adhesive composition according to any one of claims 1 to 7, wherein the pressure-sensitive adhesive composition is a hot-melt pressure-sensitive adhesive composition.

9. A pressure-sensitive adhesive tape comprising a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition according to any one of claims 1 to 7.

10. An article using the adhesive tape according to claim 9.

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