Hot-melt type adhesive composition, adhesive tape and article

Abstract

To provide a hot-melt type 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: There is provided a hot-melt type adhesive composition which comprises at least an acrylic block copolymer (X), an acrylic block copolymer (Y) and a tackifier resin (Z), wherein the acrylic block copolymer (X) has a weight average molecular weight (Mw) of 50000 to 400000 and is liquid at 23°C, the acrylic block copolymer (Y) has a weight average molecular weight (Mw) of 100000 or less and is liquid at 23°C and the tackifier resin (Z) has a softening point of 110°C or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a hot melt pressure-sensitive adhesive composition, and more particularly to a hot melt pressure-sensitive adhesive composition containing an acrylic block copolymer, and a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition. [Background technology]

[0002] Acrylic pressure-sensitive adhesives have excellent weather resistance, transparency, heat resistance, solvent resistance, etc., and therefore pressure-sensitive adhesive tapes using them are widely used as joining means for fixing 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, they are used not only for component fixing applications such as fixing metal plates or exterior components to housings that make up large electronic devices, and fixing exterior components or rigid components such as batteries to small electronic devices, as well as for temporary fixing of such components, but also for labeling applications that display product information.

[0003] Conventionally, solvent-based adhesives have been widely used as acrylic adhesives. Adhesive products that use solvent-based adhesives require a lot of heat energy to volatilize the solvent during the manufacturing process. Furthermore, the solvent volatilized from solvent-based adhesives is emitted into the atmosphere as CO2, which poses a problem of environmental impact during manufacturing. Therefore, there is a strong demand for solvent-free adhesives, and hot-melt adhesives, which are one type of solvent-free adhesive, are being investigated (see, for example, Patent Documents 1 and 2).

[0004] Furthermore, in order to conserve resources from the viewpoint of protecting the global environment, there is an increasing trend in the above-mentioned industrial fields to disassemble used products and reuse or recycle the parts used in the products. In this case, if an adhesive tape is used, it is necessary to peel the adhesive tape attached to the parts, and therefore there is a demand for an adhesive tape that has excellent removability and can be peeled and removed without leaving any adhesive residue on the parts.

[0005] Furthermore, since it is important for adhesive tapes used to fix components to be able to fix the components without peeling during use, it is desirable for them to have good 180° peel adhesive strength, constant load holding strength, and shear holding strength. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-7879 [Patent Document 2] Patent Publication No. 2021-183705 Summary of the Invention [Problem to be solved by the invention]

[0007] The hot-melt pressure-sensitive adhesive using a block copolymer described in Patent Document 1 has low melt viscosity and excellent workability, but is not designed to take into account the addition of a tackifier resin or softener. Adding a tackifier resin or softener to achieve high 180° peel adhesive strength or constant load holding power can reduce heat resistance and cohesive strength, and can cause bleeding. The pressure-sensitive adhesive composition using an acrylic triblock copolymer described in Patent Document 2 is less likely to cause bleeding, achieves both high tack and cohesive strength, and has good processability, but uses a tackifier resin with a low softening point, so heat resistance is insufficient and it can be difficult to achieve high shear holding power in high-temperature environments. Furthermore, Patent Documents 1 and 2 leave room for improvement in terms of removability.

[0008] Therefore, an object of the present invention is to provide a hot-melt pressure-sensitive adhesive composition that is excellent 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 invention includes the following aspects. [1] A hot-melt pressure-sensitive adhesive composition comprising at least an acrylic block copolymer (X), an acrylic block copolymer (Y), and a tackifier resin (Z), wherein the acrylic block copolymer (X) has a weight-average molecular weight (Mw) of 50,000 to 400,000 and is a solid at 23°C, the acrylic block copolymer (Y) has a weight-average molecular weight (Mw) of 100,000 or less and is a liquid at 23°C, and the tackifier resin (Z) has a softening point of 110°C or higher.

[0010] [2] The hot melt pressure-sensitive adhesive composition according to the above [1], which contains 20 to 140 parts by mass of the tackifier resin (Z) per 100 parts by mass of the total of the acrylic block copolymer (X) and the acrylic block copolymer (Y).

[0011] [3] The hot melt pressure-sensitive adhesive composition according to [1] or [2], which contains 1 to 140 parts by mass of the acrylic block copolymer (Y) per 100 parts by mass of the acrylic block copolymer (X).

[0012] [4] The hot melt pressure-sensitive adhesive composition according to any one of [1] to [3] above, wherein the tackifier resin (Z) has a polar functional group.

[0013] [5] The hot melt pressure-sensitive adhesive composition according to any one of [1] to [4] above, which has a storage modulus G' at 180°C of 200 Pa or less.

[0014] [6] A pressure-sensitive adhesive tape comprising a pressure-sensitive adhesive layer made of the hot melt pressure-sensitive adhesive composition according to any one of [1] to [5] above.

[0015] [7] An article using the adhesive tape described in [6] above.

[0016] [8] A method for producing a hot melt pressure-sensitive adhesive composition, comprising blending at least an acrylic block copolymer (X), an acrylic block copolymer (Y), and a tackifier resin (Z) as raw materials, the method comprising: the acrylic block copolymer (X) has a weight average molecular weight (Mw) of 50,000 to 400,000 and is solid at 23°C; the acrylic block copolymer (Y) has a weight average molecular weight (Mw) of 100,000 or less and is liquid at 23°C; A method for producing a hot melt pressure-sensitive adhesive composition, wherein the tackifier resin (Z) has a softening point of 110°C or higher. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a hot-melt pressure-sensitive adhesive composition that has good 180° peel adhesion, 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]

[0018] [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

[0019] The hot melt pressure-sensitive adhesive composition of the present invention contains at least an acrylic block copolymer (X), an acrylic block copolymer (Y), and a tackifier resin (Z), wherein the acrylic block copolymer (X) has a weight average molecular weight (Mw) of 50,000 to 400,000 and is a solid at 23°C, the acrylic block copolymer (Y) has a weight average molecular weight (Mw) of 100,000 or less and is a liquid at 23°C, and the tackifier resin (Z) has a softening point of 110°C or higher.

[0020] Due to the above-mentioned characteristics, the hot melt 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.

[0021] The hot melt pressure-sensitive adhesive composition of the present invention will be described in more detail below based on its constituent elements.

[0022] (Acrylic block copolymer (X)) The acrylic block copolymer (X) is 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).

[0023] 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, as it can exhibit high cohesive strength. The acrylic block copolymer (X) may be used alone or in combination of two or more types.

[0024] (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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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 hot-melt pressure-sensitive adhesive composition, it can exhibit excellent shear holding power, removability, and hot-melt coating suitability.

[0029] (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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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 hot-melt pressure-sensitive adhesive composition, excellent low-temperature properties and impact resistance can be achieved.

[0034] 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.

[0035] 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.

[0036] 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 such as adhesive strength, cohesive strength, and tack of the hot-melt pressure-sensitive adhesive composition become good, and the composition can have fluidity suitable for melt molding.

[0037] 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 shear holding power and removability are achieved when blended with the acrylic block copolymer (Y) described below in a predetermined range.

[0038] 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)

[0039] 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.

[0040] The content of segment B in the acrylic 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 block copolymer (X). When the content of segment B 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.

[0041] 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.

[0042] The acrylic block copolymer (X) of the present invention is a solid at 23° C. The types of monomers constituting the segments A and B, the content ratio of the segments A and B, and the molecular weights of the segments A and B are appropriately adjusted so that the acrylic block copolymer (X) after polymerization is a solid at 23° C., and the polymerization reaction is carried out.

[0043] (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 a liquid at 23°C.

[0044] By blending the acrylic block copolymer (Y), which is liquid at 23°C, in addition to the above-mentioned acrylic block copolymer (X), the hot-melt pressure-sensitive adhesive composition of the present invention can significantly improve hot-melt coatability without reducing adhesive strength, constant load holding power, and shear holding power.

[0045] 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.

[0046] (Segment A) For Segment A of the acrylic block copolymer (Y), the same constituent monomers as those for Segment A of the acrylic block copolymer (X) described above can be used, as long as the acrylic block copolymer (Y) is liquid at 23°C. In the hot-melt pressure-sensitive adhesive composition of the present invention, the constituent monomers for Segment A of the acrylic block copolymer (X) and Segment A 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, in order to improve the shear strength at high temperatures, it is preferred to use, as the main constituent monomer for Segment A, monomers such as esters of methacrylic acid with an aliphatic alcohol 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.

[0047] (Segment B) The acrylic block copolymer (Y) can use the same constituent monomers as those of the acrylic block copolymer (X) as long as it is liquid at 23°C. In the hot-melt pressure-sensitive adhesive composition of the present invention, the constituent monomers of the acrylic block copolymer (X) and the acrylic block copolymer (Y) may be the same or different. However, the same monomers are preferred because they improve 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 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 excellent low-temperature properties and impact resistance can be obtained when used in a hot-melt pressure-sensitive adhesive composition.

[0048] The weight-average molecular weight of the acrylic block copolymer (Y) in the present invention is preferably 20,000 or more and 100,000 or less, more preferably 40,000 or more and 80,000 or less. When the weight-average molecular weight of the acrylic block copolymer (Y) is within the above range, the hot-melt pressure-sensitive adhesive composition has good adhesive properties such as adhesive strength, cohesive strength, and tack, and can have fluidity suitable for melt molding. Furthermore, bleeding of the acrylic block copolymer (Y) from the pressure-sensitive adhesive layer made of the hot-melt pressure-sensitive adhesive composition can be suppressed.

[0049] The content of segment A in the acrylic block copolymer (Y) of the present invention is preferably 1 to 20% by mass, more preferably 3 to 15% by mass or less, and even more preferably 5 to 13% by 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 hot-melt coating suitability is further improved when used in a hot-melt pressure-sensitive adhesive composition. Furthermore, a pressure-sensitive adhesive composition containing the block copolymer exhibits superior cohesive strength, and further improves adhesive strength and constant-load holding strength. Furthermore, the pressure-sensitive adhesive composition exhibits superior shear holding strength at high temperatures.

[0050] 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, the hot-melt coating suitability is further improved when used in a hot-melt pressure-sensitive adhesive composition. Furthermore, a pressure-sensitive adhesive composition containing the block copolymer exhibits superior cohesive strength, and further improves adhesive strength and constant-load holding strength. Furthermore, the pressure-sensitive adhesive composition exhibits superior shear holding strength at high temperatures.

[0051] 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.

[0052] The acrylic block copolymer (Y) in the present invention is a liquid at 23° C. The types of monomers constituting the segments A and B, the content ratio of the segments A and B, and the molecular weights of the segments A and B are appropriately adjusted to carry out the polymerization reaction so that the acrylic block copolymer (X) after polymerization is a liquid at 23° C.

[0053] <Hot melt pressure sensitive adhesive composition> The hot melt pressure-sensitive adhesive composition of the present invention contains an acrylic block copolymer (X) and an acrylic block copolymer (Y). The total content of the acrylic block copolymer (X) and the acrylic block copolymer (Y) in the hot melt pressure-sensitive adhesive composition is preferably 100 to 50 mass%, more preferably 90 to 55 mass%, and even more preferably 85 to 60 mass%.

[0054] 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 has high adhesive strength and excellent cohesive strength and is suitable for hot-melt coating, and that exhibits excellent constant-load retention and removability.

[0055] (Tackifying resin (Z)) The hot melt pressure-sensitive adhesive composition of the present invention further contains a tackifier resin (Z) in addition to the above-mentioned acrylic block copolymer (X) and acrylic block copolymer (Y). By containing the tackifier resin (Z), the hot melt 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 holding strength, and removability.

[0056] The tackifying resin (Z) in the present invention is preferably compatible with the acrylic block copolymer (X) and the acrylic block copolymer (Y) so as to form a polymer blend with the acrylic block copolymer (X) and the acrylic block copolymer (Y). Such a compatible resin is 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.

[0057] 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).

[0058] 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).

[0059] 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.

[0060] 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.

[0061] 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)).

[0062] 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.

[0063] Among these, petroleum resins, terpene resins and rosin resins are preferred from the viewpoints of good compatibility with the acrylic block copolymer (X) and the acrylic block copolymer (Y) and improved removability.

[0064] In the present invention, the tackifier resin (Z) preferably has a polar functional group in its molecular skeleton, from the viewpoint of excellent compatibility with the acrylic block copolymer (X) and the segment B of the acrylic block copolymer (Y). Examples of polar functional groups include, but are not limited to, a hydroxy group, a carbonyl group, a carboxy group, a cyano group, an amino group, and a nitro group. Among these, the hydroxy group and the carboxy group are preferred, from the viewpoint of achieving high levels of 180° peel adhesive strength, constant load holding strength, shear holding strength, and removability.

[0065] When the polar functional group present in the tackifier resin (Z) is a carboxyl group, the acid value is preferably 1 to 100 mgKOH / g, more preferably 2 to 60 mgKOH / g, and even more preferably 10 to 40 mgKOH / g. When the acid value is within the above range, compatibility with the acrylic block copolymer (X) and the acrylic block copolymer (Y) is improved, and the blending thereof is effective in improving physical properties, which is preferable.

[0066] When the polar functional group present in the tackifier resin (Z) is a hydroxyl group, the hydroxyl value is preferably 1 to 100 mgKOH / g, more preferably 2 to 80 mgKOH / g, and even more preferably 10 to 60 mgKOH / g. A hydroxyl value within the above range is preferable because compatibility with the acrylic block copolymer (X) and the acrylic block copolymer (Y) is improved, and the blending thereof provides an effect of improving physical properties, which is therefore desirable.

[0067] When both carboxyl groups and hydroxyl groups are present in the tackifier resin (Z), it is sufficient that either the acid value or the hydroxyl value is within the above-mentioned preferred range, and it is more preferable that both are within the above-mentioned range.

[0068] The tackifier resin (Z) in the present invention contains at least one resin having a softening point of 110°C or higher from the viewpoint of shear holding power at high temperatures. By blending a tackifier resin (Z) with such a high softening point, it is possible to significantly improve not only adhesive strength and shear holding power, but also constant load holding power and removability. From the viewpoint of further improving these properties, the softening point of the tackifier resin (Z) is preferably 110°C or higher, and more preferably 120°C or higher. The softening point of the tackifier resin (Z) 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 (Z) 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 and constant load holding strength in a high-temperature environment can be improved. One or more types of tackifier resin (Z) 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, more preferably 60% by mass or more, of the total mass of all tackifier resins. The softening point of the tackifier resin (Z) in the present invention is a value determined by the ring and ball method in accordance with JIS K5902.

[0069] The amount of the tackifier resin (Z) in the present invention is preferably 20 to 140 parts by mass, more preferably 25 to 120 parts by mass, and even more preferably 25 to 100 parts by mass, based on 100 parts by mass of the total of the acrylic block copolymer (X) and the acrylic block copolymer (Y). When the amount of the tackifier resin (Z) is within the above range, the adhesive strength, constant load holding strength, and shear holding strength can be significantly improved. In particular, the shear holding strength and constant load holding strength under high temperature conditions can be improved.

[0070] The hot melt pressure-sensitive adhesive composition of the present invention preferably has a storage modulus G' at 180°C of 200 Pa or less, more preferably 1 to 100 Pa, even more preferably 1 to 70 Pa, and most preferably 2 to 50 Pa. When the storage modulus G' is within the above range, the composition exhibits excellent shear holding power even in a high-temperature environment and also exhibits excellent melt viscosity at high temperatures, thereby achieving favorable kneading workability and hot-melt coating suitability.

[0071] 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.

[0072] (anti-aging agent) The hot melt pressure-sensitive adhesive composition disclosed herein 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 (e.g., hindered phenol-based antioxidants), hindered amine-based antioxidants, aromatic amine-based antioxidants, and sulfur-based antioxidants. Although not particularly limited, the amount of antioxidant contained in the hot melt pressure-sensitive adhesive composition disclosed herein may be 10 parts by mass or less, suitably 7 parts by mass or less, and may be 3 parts by mass or less, per 100 parts by mass of the total of the acrylic block copolymer (X), the acrylic block copolymer (Y), and the tackifier resin (Z). The amount of the antioxidant can be, for example, 0.1 parts by weight or more, or 0.5 parts by weight or more, or 1 part by mass or more, per 100 parts by weight of the total of the block copolymer and tackifier resin.

[0073] (optional ingredient) The hot melt pressure-sensitive adhesive composition of the present invention may contain one or more rubbery polymers other than the acrylic block copolymer, as needed, 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.

[0074] The hot melt 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. Such various additives may be conventionally known and used in the usual manner, provided that the effects of the present invention are not significantly impaired.

[0075] <Form of Hot Melt Pressure-Sensitive Adhesive Composition> The composition of the hot melt pressure-sensitive adhesive composition of the present invention has been described in detail above. This hot melt pressure-sensitive adhesive composition can be a hot melt pressure-sensitive adhesive composition obtained by melting and kneading the above-mentioned acrylic block copolymer (X), acrylic block copolymer (Y), tackifier resin (Z), and optional components (other pressure-sensitive adhesive raw materials), or a solution pressure-sensitive adhesive composition obtained by dissolving them in a predetermined organic solvent (toluene, ethyl acetate, etc.).

[0076] <Uses of hot melt pressure sensitive adhesive compositions> The hot melt pressure-sensitive adhesive composition of the present invention is suitably used for 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 hot melt 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. 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.

[0077] The double-sided pressure-sensitive adhesive tape using the hot-melt 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 required.

[0078] The substrate is not particularly limited as long as it has a film or sheet shape to which the hot melt pressure-sensitive adhesive composition can be applied, and examples thereof 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, which can be appropriately selected depending on the application of the pressure-sensitive adhesive tape. As the plastic film, any of unstretched film, uniaxially stretched film, and biaxially stretched film can be used. The surface of the substrate on which the adhesive layer is to be provided may be subjected to adhesion-improving treatment such as application of a primer or corona discharge treatment.

[0079] 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.

[0080] 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.

[0081] The method for applying the hot melt pressure-sensitive adhesive composition to the substrate is not particularly limited, and known methods can be used, such as a method of dissolving the pressure-sensitive adhesive raw material in an organic solvent and applying the composition (melt spreading method), a method of thinning the composition using multiple heated rolls and applying the composition (calender method), and a method of thermally melting the pressure-sensitive adhesive raw material and applying the composition (hot melt method).

[0082] The hot melt 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]

[0083] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0084] Example 1 A hot-melt pressure-sensitive adhesive composition was prepared by thoroughly kneading 100 parts by mass of an acrylic block copolymer (X) (Kuraray Co., Ltd., Clarity LA#3710, Mw=195,000, Mw / Mn=1.1), 20 parts by mass of an acrylic block copolymer (Y) (Kuraray Co., Ltd., Clarity LA#2114, Mw=64,000, Mw / Mn=1.1), and 80 parts by mass of a tackifier resin (Z) (ENEOS Corporation, Neopolymer E-130, C9 petroleum resin, softening point 125°C, hydroxyl value 40mgKOH / g or more) in a kneader set at 180°C. This pressure-sensitive adhesive composition was melted again at 160°C and applied to the release-treated surface of a 100μm-thick release liner to prepare a pressure-sensitive adhesive tape with a pressure-sensitive adhesive layer thickness of 50μm.

[0085] (Examples 2 to 6, Comparative Examples 1 to 4) Pressure-sensitive adhesive tapes were produced in the same manner as in Example 1, except that the formulation of the hot-melt pressure-sensitive adhesive composition was changed as shown in Tables 2 and 3. The raw materials used were as follows.

[0086] [Table 1]

[0087] [Tackifying resin (Z)] E-130: Neopolymer E-130 (C9 petroleum resin, softening point 125°C, acid value 0.1mgKOH / g or less, hydroxyl value 40mgKOH / g, manufactured by ENEOS) 160: Neopolymer 160 (C9 petroleum resin, softening point 160°C, acid value 30 mg KOH / g, hydroxyl value 0.1 mg KOH / g or less, manufactured by ENEOS) PCJ: Haritack PCJ (polymerized rosin ester, softening point 124°C, acid value 12 mg KOH / g, hydroxyl value 40 mg KOH / g, manufactured by Harima Chemicals) E-100: Neopolymer E-100 (C9 petroleum resin, softening point 95°C, acid value 0.1mgKOH / g or less, hydroxyl value 78mgKOH / g, manufactured by ENEOS) A-75: Super Ester A-75 (disproportionated rosin ester, softening point 75°C, acid value 5 mg KOH / g, hydroxyl value 21 mg KOH / g, manufactured by Arakawa Chemical Industries, Ltd.) PX-1000: YS Resin PX-1000 (terpene resin, softening point 100°C, acid value 0.1 mg KOH / g or less, hydroxyl value 0.1 mg KOH / g or less, manufactured by Yasuhara Chemical)

[0088] [Other ingredients] ATBC: o-acetyl tributyl citrate (melting point -80°C, manufactured by Wako Pure Chemical Industries, Ltd.)

[0089] <Evaluation method> The adhesive tapes having adhesive layers made of the hot melt adhesive compositions prepared as described above were subjected to measurements according to the methods described below. The results are shown in Tables 2 and 3.

[0090] (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.

[0091] (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<".

[0092] (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<".

[0093] (compatibility) In an environment of a temperature of 23°C and a relative humidity of 50% RH, one side of the adhesive tapes produced in the Examples and Comparative Examples was lined with a colorless and transparent polyethylene terephthalate film having a thickness of 25 μm, and then the release liner was peeled off and the appearance of the adhesive layer was evaluated visually. 〇: Compatible (transparent) ×: No compatibility (cloudy)

[0094] (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 or contamination of the adherend was evaluated. Good: No glue residue or contamination. ×: Adhesive residue or contamination.

[0095] (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 to determine the storage modulus G' at 180°C.

[0096] (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 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)

[0097] [Table 2]

[0098] [Table 3]

[0099] As can be seen from Tables 2 and 3, the hot melt pressure sensitive adhesive composition of the present invention exhibits excellent 180° peel adhesive strength, constant load holding strength and shear holding strength, as well as excellent removability.

Claims

1. The composition contains at least an acrylic block copolymer (X), an acrylic block copolymer (Y), and a tackifier resin (Z), the acrylic block copolymer (X) has a weight average molecular weight (Mw) of 50,000 to 400,000 and is solid at 23°C; the acrylic block copolymer (Y) has a weight average molecular weight (Mw) of 100,000 or less and is a liquid at 23°C; The hot melt pressure-sensitive adhesive composition, wherein the tackifier resin (Z) has a softening point of 110°C or higher.

2. 2. The hot melt pressure-sensitive adhesive composition according to claim 1, wherein the tackifier resin (Z) is contained in an amount of 20 to 140 parts by mass per 100 parts by mass of the acrylic block copolymer (X) and the acrylic block copolymer (Y) in total.

3. 2. The hot melt pressure-sensitive adhesive composition according to claim 1, comprising 1 to 140 parts by mass of the acrylic block copolymer (Y) per 100 parts by mass of the acrylic block copolymer (X).

4. The hot melt pressure-sensitive adhesive composition according to claim 1 , wherein the tackifier resin (Z) has a polar functional group.

5. The hot melt pressure-sensitive adhesive composition according to claim 1, which has a storage modulus G' at 180°C of 200 Pa or less.

6. A pressure-sensitive adhesive tape comprising a pressure-sensitive adhesive layer made of the hot melt pressure-sensitive adhesive composition according to any one of claims 1 to 5.

7. An article using the adhesive tape according to claim 6.

8. A method for producing a hot-melt pressure-sensitive adhesive composition, comprising blending at least an acrylic block copolymer (X), an acrylic block copolymer (Y), and a tackifier resin (Z) as raw materials, the method comprising: the acrylic block copolymer (X) has a weight average molecular weight (Mw) of 50,000 to 400,000 and is solid at 23°C; the acrylic block copolymer (Y) has a weight average molecular weight (Mw) of 100,000 or less and is a liquid at 23°C; The method for producing a hot melt pressure-sensitive adhesive composition, wherein the tackifier resin (Z) has a softening point of 110°C or higher.

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