adhesive tape

Abstract

To provide an adhesive tape having an excellent initial adhesive strength while preventing deterioration with time of an adhesive strength.SOLUTION: An adhesive tape includes a substrate layer and an adhesive layer laminated at least on one side of the substrate layer. The adhesive layer contains an acrylic polymer and a tackifier. The tackifier contains a pale color rosin-based tackifier and a styrene-based tackifier.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an adhesive tape for bundling a plurality of electric wires in, for example, a wire harness. [Background technology]

[0002] BACKGROUND ART Conventionally, adhesive tapes have been known which have a base layer and an adhesive layer superposed on at least one surface of the base layer.

[0003] Specifically, a known adhesive tape of this type is one having an adhesive layer containing 100 parts by mass of a (meth)acrylic block copolymer, 50 to 135 parts by mass of a tackifier, and 40 to 90 parts by mass of a plasticizer (for example, Patent Document 1).

[0004] In the pressure-sensitive adhesive tape described in Patent Document 1, the tackifier contains a rosin-based tackifier (I) and a styrene-based tackifier (II), and the mass ratio of the rosin-based tackifier (I) to the styrene-based tackifier (II) [(I) / (II)] is 0.5 to 4. The adhesive tape described in Patent Document 1 has relatively good adhesive strength in the initial stage after being attached to an adherend. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-010142 Summary of the Invention [Problem to be solved by the invention]

[0006] However, conventional adhesive tapes such as those described in Patent Document 1 have a problem in that when used for a long period of time while attached to an adherend, the adhesive strength decreases over time.

[0007] In view of the above problems, an object of the present invention is to provide an adhesive tape that has good initial adhesive strength and is inhibited from decreasing in adhesive strength over time. [Means for solving the problem]

[0008] In order to solve the above problems, the pressure-sensitive adhesive tape according to the present invention comprises a base layer and a pressure-sensitive adhesive layer superimposed on at least one surface of the base layer, the adhesive layer contains an acrylic polymer and a tackifier, The tackifier is characterized by containing a light-colored rosin-based tackifier and a styrene-based tackifier. The above-mentioned pressure-sensitive adhesive tape has good initial adhesive strength, and the decrease in adhesive strength over time is suppressed.

[0009] In the above-described pressure-sensitive adhesive tape, the tackifier preferably further contains a high-softening point rosin-based tackifier. This configuration suppresses the phenomenon in which, after the adhesive tape is wrapped around an adherend multiple times and then unwound, part of the adhesive layer remains attached to the base layer.

[0010] In the above pressure-sensitive adhesive tape, it is preferable that the pressure-sensitive adhesive layer further contains a plasticizer. With this configuration, the initial adhesive strength is improved and the decrease in adhesive strength over time is further suppressed. [Effects of the Invention]

[0011] The adhesive tape according to the present invention has the effect of exhibiting good initial adhesive strength and suppressing deterioration of the adhesive strength over time. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional view of the pressure-sensitive adhesive tape according to this embodiment. [Figure 2] FIG. 2 is a graph showing the adhesive strength of each of the pressure-sensitive adhesive tapes of the Examples and Comparative Examples. [Figure 3]FIG. 3 is a graph showing the adhesive strength of each of the pressure-sensitive adhesive tapes of the Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the pressure-sensitive adhesive tape according to the present invention will be described with reference to the drawings.

[0014] As shown in FIG. 1, the adhesive tape 1 of this embodiment comprises a base layer 2 and an adhesive layer 3 superimposed on at least one surface of the base layer 2, and the adhesive layer 3 contains an acrylic polymer and a tackifier, and the tackifier contains a light-colored rosin-based tackifier.

[0015] The adhesive tape 1 of this embodiment is formed in a strip shape (long sheet shape). In the adhesive tape 1 of this embodiment, one adhesive layer 3 is superimposed on one surface of one base layer 2. Alternatively, one adhesive layer 3 may be superimposed on both surfaces of one base layer 2. The adhesive tape 1 may include a plurality of base layers 2, or may include a plurality of adhesive layers 3 superimposed on the base layers 2.

[0016] The adhesive layer 3 contains at least an acrylic polymer and a tackifier, and may further contain a plasticizer, an antioxidant, and the like.

[0017] The acrylic polymer is a polymer obtained by polymerizing at least a (meth)acrylic acid alkyl ester (monomer). The acrylic polymer is usually a copolymer obtained by copolymerizing two or more different types of (meth)acrylic acid alkyl ester (monomer). In this specification, the term "(meth)acrylic acid" refers to at least one of methacrylic acid and acrylic acid.

[0018] The acrylic polymer differs from the low-molecular-weight acrylic polymer used as a plasticizer, which will be described later, in that the acrylic polymer has a mass-average molecular weight (Mw) of 10,000 or more. The mass-average molecular weight (Mw) of the acrylic polymer may be 100,000 (one hundred thousand) or less. The mass average molecular weight (Mw) is measured by GPC (gel permeation chromatography) under the following conditions, and the value is calculated in terms of standard polystyrene. (GPC measurement conditions) Equipment: Tosoh Corporation GPC equipment "HLC-8220GPC" Separation column: Tosoh Corporation's "TSKgel SuperMultipore HZ-M (column diameter = 4.6 mm, column length = 15 cm)" (two columns connected in series) Eluent: tetrahydrofuran Eluent flow rate: 0.35mL / min Column temperature: 40℃ Detection method: Refractive index (RI)

[0019] The (meth)acrylic acid alkyl ester (monomer) that constitutes the acrylic polymer is an ester compound of (meth)acrylic acid and a monohydric alkyl alcohol having 2 to 12 carbon atoms. Examples of (meth)acrylic acid alkyl esters (monomers) include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, n-octyl (meth)acrylate, lauryl (meth)acrylate, and i-nonyl (meth)acrylate.

[0020] The acrylic polymer is preferably a block copolymer, which has, for example, a homopolymerized block unit A and a homopolymerized block unit B. As the block copolymer, commercially available products can be used, such as the "Clarity LA Series" (manufactured by Kuraray Co., Ltd.).

[0021] Preferably, the block copolymer has homopolymerized block units A of methyl (meth)acrylate and homopolymerized block units B of n-butyl (meth)acrylate.

[0022] In the above block copolymer, the copolymerization ratio of the homopolymerized block unit A to the homopolymerized block unit B is not particularly limited, but is preferably methyl (meth)acrylate:n-butyl (meth)acrylate=10:90 to 50:50 in molar ratio.

[0023] In this embodiment, the adhesive layer 3 contains a light-colored rosin-based tackifier and a styrene-based tackifier as tackifiers. The adhesive layer 3 may contain a high-softening point rosin-based tackifier as a tackifier. The adhesive layer 3 may contain a rosin-based tackifier other than the light-colored rosin-based tackifier, styrene-based tackifier, and high-softening point rosin-based tackifier as a tackifier. In other words, the tackifier of the adhesive layer 3 contains at least a light-colored rosin-based tackifier and a styrene-based tackifier, and may further contain a high-softening point rosin-based tackifier.

[0024] In addition to the above, examples of the tackifier include the other rosin-based tackifiers, phenol-based tackifiers, terpene-based tackifiers, xylene-based tackifiers, etc. These tackifiers may be used alone or in combination of two or more.

[0025] The light-colored rosin-based tackifier is a rosin-based tackifier having a softening point of 95°C or higher and 105°C or lower and a color tone (Hazen) of 250 or lower. The color tone (Hazen) of the light-colored rosin-based tackifier is preferably 200 or lower, more preferably 150 or lower. The acid value of the light-colored rosin-based tackifier is usually 2 [KOHmg / g] or higher and 10 [KOHmg / g] or lower. The light-colored rosin-based tackifier is prepared, for example, by subjecting a normal rosin-based tackifier to a purification treatment (lightening treatment) to reduce low-molecular-weight components (coloring components) so that the color tone (Hazen) is relatively low as described above.

[0026] The softening point is measured by the following method, specifically, in accordance with JIS K2207-1996 softening point test method (ring and ball method). The above measurement can be carried out, for example, using an automatic softening point tester "asp-6" (manufactured by Tanaka Scientific Instruments Co., Ltd.) Details of the measurement method are as follows. A specified ring is filled with a measurement sample and supported horizontally in a glycerin bath. A ball of a specified mass is placed in the center of the measurement sample, and the temperature of the glycerin bath is raised at a specified rate. The softening point is the temperature at which the ball sinks into the softened measurement sample and touches the bottom plate of the ring stand. Measurement conditions Ball: Steel ball (diameter 9.53mm, mass 3.5g) Distance between the ball and the base plate: 25mm Glycerin bath temperature rise rate: 5°C / min Two-piece ring ball Glycerin bath + stirring mode Magnetic stirrer 80~300rpm

[0027] The above color tone (Hazen) is a value measured in accordance with K 0071-1:2017. The color tone (Hazen) is measured using, for example, a commercially available Hazen color meter.

[0028] The light-colored rosin-based tackifier may be a commercially available product, such as Pine Crystal KE-100, Pine Crystal KE-311, Pine Crystal PE-590, or Pine Crystal KE-359 (all manufactured by Arakawa Chemical Industries, Ltd.).

[0029] The high softening point rosin-based tackifier is a rosin-based tackifier having a softening point of 120° C. or higher and 130° C. or lower. The color tone (Gardner) of the high softening point rosin-based tackifier is usually 10 or lower. The acid value of the high softening point rosin-based tackifier is usually 20 [KOHmg / g] or lower. The softening point is measured by the above-mentioned method.

[0030] Commercially available products can be used as the high-softening point rosin-based tackifier, such as "Super Ester A-125" (manufactured by Arakawa Chemical Industries, Ltd.).

[0031] Rosin-based tackifiers, such as light-colored rosin-based tackifiers and high-softening-point rosin-based tackifiers, are derived from rosin resin containing rosin acids such as abietic acid. The same is true for other rosin-based tackifiers. Note that rosin-based tackifiers other than the light-colored rosin-based tackifiers may have a color tone (Hazen) of, for example, 2000 or higher. Examples of rosin-based tackifiers include rosin-based resins, rosin ester-based resins, disproportionated rosin resins, disproportionated rosin ester resins, polymerized rosin resins, polymerized rosin ester resins, and hydrogenated versions thereof. One type of rosin-based tackifier may be used alone, or two or more types may be used in combination.

[0032] The styrene-based tackifier is a polymer having a styrene structural unit in the molecule. The softening point of the styrene-based tackifier is, for example, 95°C or higher and 105°C or lower. Examples of styrene-based tackifiers include styrene homopolymers, α-methylstyrene homopolymers, α-methylstyrene / styrene copolymers, styrene / aliphatic copolymers, α-methylstyrene / styrene / aliphatic copolymers, phenol-modified styrene polymers, and hydrogenated products thereof. One type of styrene-based tackifier may be used alone, or two or more types may be used in combination. As the styrene-based tackifier, commercially available products can be used, such as "YS Resin SX-100" (manufactured by Yasuhara Chemical Co., Ltd.).

[0033] Examples of the terpene-based tackifier include terpene resins, terpene phenol resins, aromatic modified terpene resins, and hydrogenated terpene resins.

[0034] Examples of petroleum-based tackifiers include aliphatic (C5)-based, aromatic (C9)-based, C5 / C9 copolymer-based, and alicyclic-based tackifiers.

[0035] The adhesive layer 3 preferably contains a light-colored rosin-based tackifier and a styrene-based tackifier as tackifiers, which has the advantage of improving the initial adhesive strength and further suppressing the decrease in adhesive strength over time.

[0036] The adhesive layer 3 preferably contains a light-colored rosin-based tackifier and a high-softening-point rosin-based tackifier as tackifiers, which has the advantage of preventing part of the adhesive layer 3 from adhering to and remaining on the base layer 2 of the adhesive tape 1 when the adhesive tape 1 is wound multiple times, unwound, and then rewound.

[0037] In this embodiment, examples of the plasticizer that can be contained in the adhesive layer 3 include low-molecular-weight acrylic polymers having a mass average molecular weight (Mw) of less than 5,000, animal and vegetable oils and mineral oils or derivatives thereof, phthalates such as dibutyl phthalate, dioctyl phthalate, bis-2-ethylhexyl phthalate, didecyl phthalate, and diisodecyl phthalate, adipates such as bis-2-ethylhexyl adipate and dioctyl adipate, and sebacates such as bis-2-ethylhexyl sebacate and dibutyl sebacate. esters, fatty acid esters such as azelaic acid esters such as bis 2-ethylhexyl azelate, paraffins such as chlorinated paraffin, glycols such as polypropylene glycol, epoxy-based polymer plasticizers such as epoxidized soybean oil and epoxidized linseed oil, phosphate esters such as trioctyl phosphate and triphenyl phosphate, phosphite esters such as triphenyl phosphite, and ester oligomers such as an ester of adipic acid and 1,3-butylene glycol. The plasticizer may be used alone or in combination of two or more kinds.

[0038] The plasticizer is preferably the above-mentioned low molecular weight acrylic polymer, which has good compatibility with the above-mentioned acrylic polymer and can therefore function better as a plasticizer.

[0039] The low molecular weight acrylic polymer is a polymer of the above-mentioned (meth)acrylic acid alkyl ester (monomer), but differs from the above-mentioned acrylic polymer in that the mass average molecular weight (Mw) is less than 10,000. The mass average molecular weight (Mw) of the low molecular weight acrylic polymer may be 2,000 or more. The mass average molecular weight (Mw) of the low molecular weight acrylic polymer is a value measured by the above-mentioned measurement method. The low-molecular-weight acrylic polymer may be a commercially available product, such as "Alphon UP-1000" (manufactured by Toagosei Co., Ltd.) (mass average molecular weight Mw: 3,000, glass transition temperature: -77°C).

[0040] The adhesive layer 3 may contain 40% by mass or more and 70% by mass or less of an acrylic polymer. The adhesive layer 3 may contain 15% by mass or more and 35% by mass or less of a light-colored rosin-based tackifier. The adhesive layer 3 may contain 3% by mass or more and 8% by mass or less of a styrene-based tackifier. The adhesive layer 3 may contain 5% by mass or more and 20% by mass or less of a high-softening point rosin-based tackifier.

[0041] In the adhesive layer 3, the content of the styrene-based tackifier is preferably 8 parts by mass or more, and more preferably 10 parts by mass or more, per 100 parts by mass of the acrylic polymer. In the adhesive layer 3, the content of the styrene-based tackifier is preferably 15 parts by mass or less, and more preferably 13 parts by mass or less, per 100 parts by mass of the acrylic polymer. By setting the content of the styrene-based tackifier within the above range, there is an advantage that the adhesive strength to polyethylene is further improved.

[0042] In the adhesive layer 3, the content of the light-colored rosin-based tackifier is preferably 30 parts by mass or more and 70 parts by mass or less relative to 100 parts by mass of the acrylic polymer. In the adhesive layer 3, the content of the high-softening-point rosin-based tackifier is preferably 10 parts by mass or more and 35 parts by mass or less relative to 100 parts by mass of the acrylic polymer.

[0043] The adhesive layer 3 preferably contains a light-colored rosin-based tackifier, a styrene-based tackifier, and a high-softening-point rosin-based tackifier as tackifiers, and also contains a low-molecular-weight acrylic polymer as a plasticizer, which has the advantages of improving the initial adhesive strength and further suppressing the deterioration of the adhesive strength over time.

[0044] In the adhesive layer 3, the total content of the light-colored rosin-based tackifier and the styrene-based tackifier is preferably 40 parts by mass or more, and more preferably 42 parts by mass or more, per 100 parts by mass of the acrylic polymer. In the adhesive layer 3, the content of the two types of tackifiers is preferably 80 parts by mass or less, and more preferably 78 parts by mass or less, per 100 parts by mass of the acrylic polymer. By having the contents of the two types of tackifiers within the above ranges, there are advantages in that the initial adhesive strength is better and the decrease in adhesive strength over time is further suppressed.

[0045] In the adhesive layer 3, the total content of the light-colored rosin-based tackifier, styrene-based tackifier, and high-softening point rosin-based tackifier is preferably 60 parts by mass or more, and more preferably 65 parts by mass or more, per 100 parts by mass of the acrylic polymer. In the adhesive layer 3, the content of the three types of tackifiers is preferably 85 parts by mass or less, and more preferably 80 parts by mass or less, per 100 parts by mass of the acrylic polymer. By having the contents of the three types of tackifiers fall within the above ranges, there are advantages in that the initial adhesive strength is better and the decrease in adhesive strength over time is further suppressed.

[0046] The adhesive layer 3 may contain 5% by mass or more and 15% by mass or less of a plasticizer (particularly a low-molecular acrylic polymer). In the adhesive layer 3, the content of the plasticizer (particularly the content of the low molecular weight acrylic polymer) is preferably 10 parts by mass or more relative to 100 parts by mass of the acrylic polymer. In the adhesive layer 3, the content of the plasticizer (particularly the content of the low molecular weight acrylic polymer) is preferably 30 parts by mass or less, and more preferably 25 parts by mass or less, per 100 parts by mass of the acrylic polymer. By setting the content of the plasticizer (particularly the content of the low molecular weight acrylic polymer) within the above range, there is an advantage that the initial adhesive strength is better and the decrease in adhesive strength over time is further suppressed.

[0047] In the adhesive layer 3, the mass ratio (B-1 / B-2) of the styrene-based tackifier (B-2) to the light-colored rosin-based tackifier (B-1) is preferably 2 or more and 7 or less, more preferably 3 or more and 6 or less. By setting the mass ratio within the above range, there are advantages in that the initial adhesive strength is better and the decrease in adhesive strength over time is further suppressed.

[0048] In the adhesive layer 3, the mass ratio [(B-1+B-3) / B-2] of the total amount of the light-colored rosin-based tackifier (B-1) and the high-softening point rosin-based tackifier (B-3) to the amount of the styrene-based tackifier (B-2) is preferably 4 or more and 8 or less, more preferably 5 or more and 7 or less. By setting the mass ratio within the above range, there are advantages in that the initial adhesive strength is better and the decrease in adhesive strength over time is further suppressed.

[0049] In the adhesive layer 3, the mass ratio (B-1 / B-3) of the light-colored rosin-based tackifier (B-1) to the high-softening point rosin-based tackifier (B-3) is preferably 1 or more and 7 or less, more preferably 1 or more and 6 or less. By setting the mass ratio within the above range, there are advantages in that the initial adhesive strength is better and the decrease in adhesive strength over time is further suppressed.

[0050] The base layer 2 constituting the pressure-sensitive adhesive tape 1 of the present embodiment may be a resin film or a porous sheet such as a fiber sheet.

[0051] The material of the base layer 2 is, for example, a resin such as acetate (cellulose acetate), polyester such as polyethylene terephthalate, polyamide, or polyethylene. When the adhesive tape 1 of this embodiment is wound multiple times around an adherend, if the material of the base layer 2 is polyethylene, the adhesive layer 3 of the adhesive tape 1 will adhere to the polyethylene base layer 2. As will be shown in the examples below, the adhesive layer 3 of this embodiment has good adhesion to polyethylene. Therefore, when the adhesive tape 1 is wound, it adheres well to its back surface (the exposed surface of the base layer 2). Therefore, the adhesive tape 1 whose base layer 2 is made of polyethylene is suitable for winding applications.

[0052] When the base layer 2 is a fiber sheet, the base layer 2 may be a woven fabric or a nonwoven fabric. Specifically, the base layer 2 may be a polyethylene terephthalate fiber cloth.

[0053] In the pressure-sensitive adhesive tape 1 of the present embodiment, the thickness of the base layer 2 is, for example, 50 μm to 500 μm, and preferably 50 μm to 150 μm. When the thickness of the base layer 2 is relatively small, 150 μm or less, the phenomenon of the adhesive layer 3 at the end portions peeling off from the base layer 2 when the pressure-sensitive adhesive tape 1 is wrapped multiple times can be more sufficiently prevented. The thickness of the adhesive layer 3 is, for example, not less than 3 μm and not more than 100 μm.

[0054] The adhesive tape 1 of this embodiment has the above-described configuration, and therefore has good initial adhesive strength, and the decrease in adhesive strength over time is suppressed.

[0055] Next, a method for producing the pressure-sensitive adhesive tape 1 of this embodiment will be described.

[0056] The adhesive tape 1 of this embodiment can be manufactured, for example, by preparing an adhesive layer composition containing each component that will constitute the above-mentioned adhesive layer 3 and an organic solvent, applying the adhesive layer composition to the base layer 2, and volatilizing the organic solvent contained in the applied adhesive layer composition.

[0057] Examples of the organic solvent that can be used include ethyl acetate, methyl ethyl ketone, and toluene.

[0058] A common coating method such as die coating or reverse coating can be used when applying the adhesive layer composition to the base layer 2. The temperature during application is usually room temperature (15 to 25°C).

[0059] The adhesive tape 1 manufactured as described above is used, for example, to bind a plurality of electric wires in a wire harness.

[0060] The pressure-sensitive adhesive tape 1 of this embodiment is as exemplified above, but the present invention is not limited to the pressure-sensitive adhesive tape exemplified above. That is, various forms used in general adhesive tapes can be employed within the scope that does not impair the effects of the present invention. [Example]

[0061] The present invention will now be described in more detail with reference to experimental examples, but the present invention is not limited to these examples.

[0062] The adhesive layer compositions were prepared and applied to the substrate layer to produce adhesive tapes as follows. The formulations for producing the adhesive tapes of each test example are shown in Table 1.

[0063] <Raw material for adhesive tape> Components of the adhesive layer (A) Acrylic polymer (component name: block copolymer having homopolymerized block units A of methyl (meth)acrylate and homopolymerized block units B of n-butyl (meth)acrylate) (A-1) Product name: "Clarity LA2330" (manufactured by Kuraray Co., Ltd.) Mass average molecular weight: 64,000 (B) Tackifier (B-1) Light-colored rosin-based tackifier (softening point: 95~105℃ / color tone: 200 or less / acid value: 2~10 [KOHmg / g]) Product name: Pine Crystal KE-100 (manufactured by Arakawa Chemical Industries, Ltd.) (B-2) Styrene-based tackifier (low molecular weight polymer of styrene) Product name: "YS Resin SX-100" (manufactured by Yasuhara Chemical Co., Ltd.) (B-3) High softening point rosin tackifier (softening point: 120~130℃ / color tone: 8 / acid value: 10 [KOHmg / g] or less) Product name: "Super Ester A-125" (manufactured by Arakawa Chemical Industries, Ltd.) (B-4) Hydrogenated rosin-based tackifier (softening point: 70°C or higher but 90°C or lower) Product name: "Estergum HP" (manufactured by Arakawa Chemical Industries, Ltd.) (C) Plasticizer (low molecular weight acrylic polymer) Product name: "Alphon UP-1000" (manufactured by Toagosei Co., Ltd.) Mass average molecular weight: 3,000 (D) Antioxidant: Product name: "Irganox 1010" (manufactured by BASF Japan) Organic solvents Methyl ethyl ketone (MEK) ·Base material layer Low-density polyethylene film Product name: "Sumikasen F200" (Sumitomo Chemical Co., Ltd.) Thickness: 70 μm

[0064] ( reference Example 1, Example 2, 3. Comparative Examples 1 to 3) According to the formulation shown in Table 1, the components were mixed at 23°C and then cooled to room temperature to prepare a composition for adhesive layer. The adhesive layer composition was then applied to one side of the substrate layer by die coating, and the resulting mixture was left at 100°C for 4 minutes to volatilize the MEK, forming an adhesive layer.

[0065] [Table 1]

[0066] The adhesive tapes produced in the Examples and Comparative Examples were evaluated for initial adhesive strength and adhesive strength 14 days after application as follows.

[0067] <Initial adhesive strength and adhesive strength after 14 days> A strip-shaped sample having a width of 19 mm was cut out from the adhesive tape of each test example. Next, the adhesive layer of the strip-shaped sample was attached to the surface of a plate-shaped adherend (thickness: 0.4 mm). The adhesive tape was attached to the adherend by rolling a 2 kg rubber roller back and forth once at a speed of 5 mm / s. After that, it was sufficiently cooled to room temperature to prepare a test specimen for a tensile test. Either of the following adherends was used. SUS plate whose surface was polished with #360 sandpaper and washed with toluene Polyethylene resin board whose surface has been sanded with #360 sandpaper but not washed with toluene A 180-degree peel test was conducted by using a tensile tester to pull the above test specimen from the SUS plate or polyethylene resin plate at a test speed of 300 mm / min in a room temperature (23°C) environment, and the peel strength (N / 19 mm) in a room temperature environment was determined. The test results are shown in Figures 2 and 3.

[0068] 2 and 3, the pressure-sensitive adhesive tapes of the Examples had higher adhesive strength than the pressure-sensitive adhesive tapes of the Comparative Examples, and the decrease in adhesive strength over time was suppressed. In particular, good results were obtained when the adherend was polyethylene (PE). [Industrial Applicability]

[0069] The pressure-sensitive adhesive tape of the present invention is preferably used by being stuck to an adherend, for example, for bundling a plurality of electric wires. [Explanation of symbols]

[0070] 1: adhesive tape, 2: base layer, 3: adhesive layer.

Claims

1. A substrate layer and an adhesive layer superimposed on at least one surface of the substrate layer, the adhesive layer comprises an acrylic polymer, a tackifier, and a low-molecular-weight acrylic polymer as a plasticizer having a mass-average molecular weight of 2,000 or more and less than 10,000; the tackifier contains a light-colored rosin-based tackifier, a styrene-based tackifier, and a high-softening point rosin-based tackifier, the high softening point rosin-based tackifier has a softening point of 120°C or higher and 130°C or lower, a total content of the light-colored rosin-based tackifier, the styrene-based tackifier, and the high-softening point rosin-based tackifier in the adhesive layer is 60 parts by mass or more and 85 parts by mass or less per 100 parts by mass of the acrylic polymer.

2. The adhesive tape described in claim 1, wherein the acrylic polymer is a block copolymer having a homopolymerized block unit of methyl (meth)acrylate and a homopolymerized block unit of n-butyl (meth)acrylate.

3. An adhesive tape as described in claim 1 or 2, wherein the adhesive layer contains 40% by mass or more and 70% by mass or less of the acrylic polymer.

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