Repeelable pressure-sensitive adhesive tape

Abstract

To provide a repeelable pressure-sensitive adhesive tape which has superior transparency and also exhibits ease of hand tearing.SOLUTION: The present invention provides a repeelable pressure-sensitive adhesive tape 10 comprising a substrate 11 and an adhesive layer 12 disposed on at least one surface of the substrate 11, wherein the adhesive layer 12 is composed of an acrylic pressure-sensitive adhesive, the substrate 11 has a tensile strength of 0.05 to 10 N / 24 mm, and the repeelable pressure-sensitive adhesive tape 10 has a total light transmittance of 80% or more.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a removable adhesive tape. [Background technology]

[0002] Because of its excellent workability, adhesive tapes are widely used for the purposes of packaging, protection, temporary fixing, etc. For example, adhesive tapes having acrylic adhesives are used for various purposes because of their excellent physical properties such as weather resistance, durability, heat resistance, transparency, etc. Adhesive tapes used for purposes such as protection and temporary fixing must be peeled off from the adherend after use, and therefore adhesive tapes with excellent peeling properties are required, such as adhesives and substrates that are the materials of the adhesive tape not remaining on the adherend surface. Such adhesive tapes with excellent peeling properties are called removable adhesive tapes. For example, removable adhesive tapes described in Patent Documents 1 to 5 are known as prior art.

[0003] Specifically, Patent Document 1 discloses a removable adhesive tape using an acrylic adhesive and an OPP substrate. Patent Document 2 discloses a removable adhesive tape using an adhesive containing a styrene-isoprene-styrene block copolymer and a tackifier, and an OPP substrate. Patent Document 3 discloses a removable adhesive tape using an adhesive containing a styrene-isoprene-styrene block copolymer and a tackifier, and an OPP substrate.

[0004] Patent Document 4 discloses a removable adhesive tape using an acrylic adhesive and a substrate in which at least one side of a base fabric having polyester warp and weft threads is laminated with polyethylene. Patent Document 5 discloses a removable adhesive tape using an acrylic adhesive and a base fabric having polyester warp and weft threads. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-060400 [Patent Document 2] JP 2015-20032 A [Patent Document 3] JP 2020-204003 A [Patent Document 4] JP 2012-214581 A [Patent Document 5] JP 2013-023627 A Summary of the Invention [Problem to be solved by the invention]

[0006] Removable adhesive tapes used for protection, temporary fixing, etc., may be used for posting, etc., and in such cases, the removable adhesive tape is required not to damage the appearance of the posting. In addition, the removable adhesive tape may be required to have high hand tearability to improve workability.

[0007] However, when a substrate using polyester yarn is used as in Patent Documents 4 and 5, the polyester yarn scatters light, resulting in low transparency, and when the re-peelable adhesive tape is used to attach a notice, the appearance of the notice may be marred. In addition, although the removable adhesive tapes described in Patent Documents 1 to 3 disclose that an OPP substrate or the like is used as the substrate, there is no disclosure or suggestion as to the hand-tearability of removable adhesive tapes using an OPP substrate. From the above, it is considered that the removable adhesive tapes described in the cited documents 1 to 5 do not achieve both excellent transparency and excellent hand tearability.

[0008] SUMMARY OF THE PRESENT EMBODIMENTS Accordingly, an object of the present invention is to provide a removable adhesive tape which is excellent in transparency and also in ease of being torn by hand. [Means for solving the problem]

[0009] The present inventors have conducted extensive research to solve the above problems, and as a result have found that the above problems can be solved by using a specific adhesive in the adhesive layer, using a substrate having a specific breaking strength, and setting the total light transmittance of the removable adhesive tape to a specific value or more, thereby completing the present invention. The gist of the present invention is as follows [1] to [8].

[0010] [1] A removable adhesive tape comprising a substrate and an adhesive layer provided on at least one surface of the substrate, The pressure-sensitive adhesive layer is made of an acrylic pressure-sensitive adhesive, The breaking strength of the substrate is 0.05 to 10 N / 24 mm; The removable adhesive tape has a total light transmittance of 80% or more. [2] The acrylic pressure-sensitive adhesive is formed from a pressure-sensitive adhesive composition containing an acrylic polymer (A), the acrylic polymer (A) is a polymer of a monomer containing an alkyl (meth)acrylate (a1) and a functional group-containing monomer (a2) having a reactive functional group, or a polymer of a monomer containing an alkyl (meth)acrylate (a1), a functional group-containing monomer (a2) having a reactive functional group, and a monomer (a3) ​​other than the alkyl (meth)acrylate (a1) and the functional group-containing monomer (a2); the amount of the alkyl (meth)acrylate (a1) used in the total monomer components used in the acrylic polymer (A) is 65 to 99.9 mass %, the amount of the functional group-containing monomer (a2) used in the total monomer components used in the acrylic polymer (A) is 0.1 to 8 mass %, The removable adhesive tape according to the above-mentioned [1], wherein the amount of the other monomer (a3) ​​used in the total monomer components used in the acrylic polymer (A) is 0 to 27 mass %. [3] The alkyl (meth)acrylate (a1) is an alkyl (meth)acrylate having an alkyl group having 4 to 12 carbon atoms, The removable adhesive tape according to the above item [2], wherein the functional group-containing monomer (a2) having a reactive functional group is a monomer having a carboxy group. [4] The pressure-sensitive adhesive composition contains a tackifier resin (B), and the acrylic pressure-sensitive adhesive is formed from a pressure-sensitive adhesive composition containing an acrylic polymer (A), The removable adhesive tape according to any one of the above [1] to [3], wherein the content of the tackifier resin (B) in the adhesive composition is 10 parts by mass or less per 100 parts by mass of the acrylic polymer (A). [5] The pressure-sensitive adhesive composition contains a crosslinking agent (C), and the acrylic pressure-sensitive adhesive is formed from a pressure-sensitive adhesive composition containing an acrylic polymer (A), The removable adhesive tape according to any one of the above [1] to [4], wherein the content of the crosslinking agent (C) in the adhesive composition is 0.1 to 3.0 parts by mass per 100 parts by mass of the acrylic polymer (A). [6] The removable adhesive tape according to the above [5], wherein the crosslinking agent (C) is at least one crosslinking agent selected from the group consisting of aziridine-based crosslinking agents and epoxy-based crosslinking agents. [7] The removable adhesive tape according to any one of the above [1] to [6], which has a change in color intensity (ΔE) of 3.0 or less after an accelerated weather resistance test. [8] The removable adhesive tape according to any one of the above [1] to [7], wherein the substrate is a stretched polyolefin film. Effect of the Invention

[0011] According to the present invention, it is possible to provide a removable adhesive tape that is excellent in transparency and also in tearability by hand. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic cross-sectional view showing a removable adhesive tape according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] [Removable adhesive tape] The removable adhesive tape of the present invention comprises a substrate and an adhesive layer provided on at least one surface of the substrate. The adhesive layer is made of an acrylic adhesive, the substrate has a breaking strength of 0.05 to 10 N / 24 mm, and the removable adhesive tape has a total light transmittance of 80% or more. The removable adhesive tape is an adhesive tape that is used for the purpose of being attached to an adherend and then peeled off after a certain period of time has passed.

[0014] <Total light transmittance> The total light transmittance of the removable adhesive tape of the present invention is 80% or more. If the total light transmittance of the removable adhesive tape is less than 80%, the transparency of the removable adhesive tape becomes insufficient, and when the removable adhesive tape is used to attach a notice, the appearance of the notice may be impaired. From this viewpoint, the total light transmittance of the removable adhesive tape of the present invention is preferably 86% or more, more preferably 88% or more, and even more preferably 90% or more. The upper limit of the range of the total light transmittance of the removable adhesive tape of the present invention is not particularly limited, but is, for example, 100%. The total light transmittance of the removable adhesive tape of the present invention can be measured by the method described in the Examples below. The total light transmittance of the removable adhesive tape of the present invention can be controlled by the type and thickness of the resin film constituting the substrate of the removable adhesive tape and the type and thickness of the adhesive constituting the adhesive layer.

[0015] <Change in color intensity before and after accelerated weather resistance test (ΔE)> The change in color degree (ΔE) of the removable adhesive tape of the present invention before and after the accelerated weather resistance test is preferably 3.0 or less. If the change in color degree (ΔE) of the removable adhesive tape before and after the accelerated weather resistance test is 3.0 or less, when the removable adhesive tape is used to attach a notice, the removable adhesive tape can be prevented from discoloring during the long-term attachment of the removable adhesive tape, which can impair the appearance of the notice. From this viewpoint, the change in color degree (ΔE) of the removable adhesive tape of the present invention before and after the accelerated weather resistance test is more preferably 2.0 or less, even more preferably 1.7 or less, and even more preferably 1.3 or less. The lower limit of the range of the change in color degree (ΔE) of the removable adhesive tape of the present invention before and after the accelerated weather resistance test is not particularly limited, but is, for example, 0. The change in color degree (ΔE) of the removable adhesive tape before and after the accelerated weather resistance test can be measured by the method described in the Examples described later. The change (ΔE) in the degree of coloration of the removable adhesive tape before and after the accelerated weather resistance test can be controlled by the type of resin film that constitutes the substrate.

[0016] <Base material> The removable adhesive tape of the present invention includes a substrate. The substrate is preferably a resin film from the viewpoint of transparency. The resin film used as the substrate may be a stretched film or a non-stretched film, but is preferably a stretched film from the viewpoint of ensuring hand-tearability. Specific examples of the resin film include stretched polyolefin films such as stretched polypropylene film, stretched low-density polyethylene film, and stretched high-density polyethylene film, non-stretched polyolefin films such as non-stretched polypropylene film, non-stretched low-density polyethylene film, and non-stretched high-density polyethylene film, stretched polyester film, stretched polyphenylene sulfide film, hard polyvinyl chloride film, soft polyvinyl chloride, cellophane film, acetate film, polystyrene film, polycarbonate film, stretched nylon film, non-stretched nylon film, and polyimide film. Among these, stretched polyolefin film is preferred from the viewpoint of transparency, hand-tearability, and weather resistance, and stretched polypropylene film is more preferred. The stretched polypropylene film may be uniaxially stretched or biaxially stretched, but biaxial stretching is preferred. The resin film may be a single resin layer or a multilayer film consisting of two or more resin layers. The multilayer film may be a film in which different types of resins are laminated, or a film in which two or more of the same type of resins are laminated. For example, a stretched polypropylene film may be a resin film in which two or more polypropylene layers are laminated.

[0017] (Breaking strength) The breaking strength of the substrate used in the removable adhesive tape of the present invention is 0.05 to 10 N / 24 mm. If the breaking strength of the substrate is less than 0.05 N / 24 mm, the removable adhesive tape may break when peeling off the removable adhesive tape after it has been applied. If the breaking strength of the substrate is greater than 10 N / 24 mm, the hand tearability of the removable adhesive tape may deteriorate. From this viewpoint, the breaking strength of the substrate used in the removable adhesive tape of the present invention is preferably 0.1 to 5 N / 24 mm, more preferably 0.2 to 3 N / 24 mm, and even more preferably 0.3 to 2 N / 24 mm. The breaking strength of the substrate can be measured by the method described in the Examples below. In the case of a stretched film, the breaking strength of the substrate can be controlled by the conditions for stretching the substrate, the type and thickness of the resin film constituting the substrate, etc. In addition, the breaking strength can be controlled by appropriately adding an additive to the resin film, or by appropriately selecting the type and molecular weight of the resin.

[0018] (Thickness) The thickness of the substrate is not particularly limited, but from the viewpoint of the breaking strength of the substrate and from the viewpoint of preventing the formation of wrinkles in the removable adhesive tape during use, the thickness of the substrate is preferably 30 μm or more, more preferably 50 μm or more, and even more preferably 80 μm or more. From the viewpoint of the total light transmittance of the removable adhesive tape and the breaking strength of the substrate, the thickness of the substrate is preferably 300 μm or less, more preferably 200 μm or less, and even more preferably 150 μm or less.

[0019] <Adhesive layer> The adhesive layer of the removable adhesive tape of the present invention is made of an acrylic adhesive. The adhesive is contained in an adhesive composition described below, and when diluted with a solvent, the adhesive layer is made of solids remaining after removing the solvent from each component constituting the adhesive composition.

[0020] <Acrylic adhesive> The pressure-sensitive adhesive layer made of an acrylic pressure-sensitive adhesive is formed from a pressure-sensitive adhesive composition containing at least an acrylic polymer (A), as described below, which can increase the total light transmittance of the removable pressure-sensitive adhesive tape and can suppress the adhesive from remaining in the pressure-sensitive adhesive layer when the removable pressure-sensitive adhesive tape is peeled off after the removable pressure-sensitive adhesive tape is applied.

[0021] (Acrylic polymer (A)) The acrylic polymer (A) is a polymer obtained by polymerizing monomers including at least an acrylic monomer. The acrylic polymer is preferably a polymer containing a reactive functional group. The reactive functional group is a functional group that is reactive with a crosslinking agent described later. The acrylic polymer (A) may be a copolymer of a monomer containing an alkyl (meth)acrylate (a1) and a functional group-containing monomer (a2) having a reactive functional group, or a copolymer of a monomer containing an alkyl (meth)acrylate (a1), the functional group-containing monomer (a2), and a monomer (a3) ​​other than the alkyl (meth)acrylate (a1) and the functional group-containing monomer (a2). Note that the term "(meth)acrylate" is used to mean either or both of acrylate and methacrylate.

[0022] Examples of the alkyl (meth)acrylate (a1) include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, isomyristyl (meth)acrylate, stearyl (meth)acrylate, and isobornyl (meth)acrylate. Examples of the alkyl (meth)acrylate (a1) include alkyl (meth)acrylates having an alkyl group with 1 to 12 carbon atoms, and more preferably alkyl (meth)acrylates having an alkyl group with 4 to 12 carbon atoms. These alkyl (meth)acrylates (a1) may be used alone or in combination of two or more.

[0023] Among the above, the alkyl (meth)acrylate (a1) is preferably n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, or isononyl (meth)acrylate. By using these alkyl (meth)acrylates, the adhesive layer is easily made flexible, and even if the amount of the tackifier resin is reduced, it is easy to ensure appropriate adhesion. Among these, isononyl (meth)acrylate is preferred from the viewpoint of easily improving flexibility, and n-butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate are preferred from the viewpoint of increasing adhesive strength. As the alkyl (meth)acrylate (a1), for example, both n-butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate may be used, or all of n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isononyl (meth)acrylate may be used.

[0024] In addition, when isononyl (meth)acrylate is used, the amount of isononyl (meth)acrylate used in the total monomer components used in the acrylic polymer (A) is not particularly limited, but is, for example, 1 to 30 mass%, preferably 3 to 20 mass%, more preferably 4 to 14 mass%. It is preferable to use isononyl (meth)acrylate in combination with an alkyl (meth)acrylate other than isononyl (meth)acrylate. When at least one of n-butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate is used, the total amount used is, for example, 50 to 99.9 mass%, preferably 60 to 99 mass%, and more preferably 70 to 94 mass%, based on the total monomer components used in the acrylic polymer (A).

[0025] The reactive functional group of the functional group-containing monomer (a2) having a reactive functional group is not particularly limited as long as it has active hydrogen and is a functional group capable of reacting with a crosslinking agent described later, and examples thereof include a hydroxyl group, an amino group, and a carboxyl group. The functional group-containing monomer (a2) having these reactive functional groups may be used alone or in combination of two or more. Among these functional groups, a carboxyl group is preferred. The carboxyl group has high reactivity with an aziridine-based crosslinking agent and an epoxy-based crosslinking agent described later, and can easily form a crosslinked structure.

[0026] The monomer having a hydroxyl group is not particularly limited, but examples thereof include (meth)acrylates having a hydroxyl group such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate, allyl alcohol, etc. Among them, (meth)acrylates having a hydroxyl group are preferably used. Examples of the monomer having a carboxy group include methacrylic acid and acrylic acid. These monomers may be used alone or in combination of two or more. Among these, as the functional group-containing monomer (a2) having a reactive functional group, a monomer having a carboxy group is preferred, and acrylic acid is more preferred.

[0027] The other monomer (a3) ​​is not particularly limited as long as it is copolymerizable with the acrylic monomer, and examples thereof include styrene derivatives such as styrene, α-methylstyrene, p-methylstyrene, p-chlorostyrene, and divinylbenzene, compounds having a vinyl ester group such as vinyl acetate and vinyl propionate, N-vinylpyrrolidone, N-vinylmorpholine, (meth)acrylonitrile, N-cyclohexylmaleimide, N-phenylmaleimide, N-laurylmaleimide, N-benzylmaleimide, n-propyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, and tert-butyl vinyl ether. These other monomers (a3) ​​may be used alone or in combination of two or more. Among these, vinyl acetate is preferable as the other monomer (a3).

[0028] The amount of the alkyl (meth)acrylate (a1) used in all monomer components used in the acrylic polymer (A) is preferably 65 mass% or more, more preferably 75 mass% or more, even more preferably 85 mass% or more, and preferably 99.9 mass% or less, more preferably 99.5 mass% or less, even more preferably 99 mass% or less. The amount of the functional group-containing monomer (a2) having a reactive functional group in the total monomer components used for the acrylic polymer (A) is preferably 0.1 mass% or more, more preferably 0.5 mass% or more, even more preferably 1 mass% or more, and preferably 8 mass% or less, more preferably 6 mass% or less, even more preferably 4 mass% or less. The amount of the other monomer (a3) ​​in the total monomer components used in the acrylic polymer (A) is preferably 0% by mass or more, more preferably 1% by mass or more, even more preferably 2% by mass or more, preferably 27% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less. Note that 0% by mass means that no other monomer (a3) ​​is contained.

[0029] The acrylic polymer (A) is obtained by polymerizing the above-mentioned monomers by a conventional polymerization method, such as suspension polymerization, emulsion polymerization, solution polymerization, etc. Among these polymerization methods, solution polymerization is preferred because it is easy to obtain a high molecular weight product and does not contain a surfactant or dispersant that is likely to affect the adhesive properties. In addition, peroxide-based polymerization initiators, azo-based polymerization initiators, etc. are used as the polymerization initiator.

[0030] The weight average molecular weight of the acrylic polymer (A) is preferably 300,000 to 800,000, and more preferably 400,000 to 600,000. By setting the weight average molecular weight within these ranges, the holding power, adhesive power, and tackiness of the adhesive layer can be easily maintained at a good level. The weight average molecular weight is a weight average molecular weight measured by gel permeation chromatography (GPC) in terms of standard polystyrene.

[0031] In the pressure-sensitive adhesive composition, the acrylic polymer (A) is the main component, and is usually 50 mass % or more, preferably 70 mass % or more, more preferably 80 mass %, and usually 100 mass % or less, based on the total amount of the pressure-sensitive adhesive composition (based on solid content).

[0032] (Tackifying resin (B)) The adhesive composition may contain a tackifier resin (B) in addition to the acrylic polymer (A). Examples of the tackifier resin (B) include rosin-based tackifier resins, terpene-based tackifier resins, and petroleum resin-based tackifier resins. Examples of the rosin-based tackifier resins include rosin, hydrogenated rosin, non-uniform rosin, polymerized rosin, and esterified products thereof. Examples of the terpene-based tackifier resins include terpene resins (α,β-pinene), terpene phenol resins, aromatic modified terpene resins, and hydrogenated terpene resins. Examples of the petroleum resin-based tackifier resins include aliphatic petroleum resins, aromatic petroleum resins, copolymerized petroleum resins, and hydrogenated petroleum resins. These tackifier resins (B) may be used alone or in combination of two or more. Among these, rosin-based tackifier resins and terpene-based tackifier resins are preferred, and rosin esters and terpene phenol resins are more preferred.

[0033] The content of the tackifier resin (B) is preferably 10 parts by mass or less relative to 100 parts by mass of the acrylic polymer (A). When the content of the tackifier resin (B) is 10 parts by mass or less relative to 100 parts by mass of the acrylic polymer (A), the coloring of the removable adhesive tape can be suppressed when the removable adhesive tape is wound into a roll. From this viewpoint, the content of the tackifier resin (B) is preferably as small as possible, more preferably 9 parts by mass or less, and even more preferably 8.5 parts by mass or less relative to 100 parts by mass of the acrylic polymer (A). In addition, it is preferable that the adhesive composition does not contain the tackifier resin (B). For example, by using butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isononyl (meth)acrylate as the alkyl (meth)acrylate (a1), the adhesive composition can be made not to contain the tackifier resin (B). In this case, the amount of butyl (meth)acrylate used in the total monomer components used in the acrylic polymer (A) is preferably 73 to 83 mass%, the amount of 2-ethylhexyl (meth)acrylate used is preferably 6 to 16 mass%, and the amount of isononyl (meth)acrylate used is preferably 4 to 14 mass%. However, in order to increase the adhesive strength of the adhesive layer, the adhesive composition may contain a tackifier resin (B). In this case, the content of the tackifier resin (B) is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 2 parts by mass or more, based on 100 parts by mass of the acrylic polymer (A).

[0034] (Crosslinking agent (C)) The adhesive composition preferably contains a crosslinking agent (C). That is, the adhesive layer is preferably one in which the adhesive contained in the adhesive composition is crosslinked by the crosslinking agent (C). Examples of the crosslinking agent (C) include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, melamine-based crosslinking agents, aldehyde-based crosslinking agents, amine-based crosslinking agents, and metal chelate-based crosslinking agents. These crosslinking agents (C) may be used alone or in combination of two or more. Among these crosslinking agents, aziridine-based crosslinking agents and epoxy-based crosslinking agents are preferred. By using at least one of the aziridine-based crosslinking agent and the epoxy-based crosslinking agent, crosslinking proceeds quickly and productivity is improved. In addition, it is possible to suppress the adhesive from remaining in the adhesive layer when the removable adhesive tape is peeled off. The crosslinking agent (C) is preferably an aziridine-based crosslinking agent. When an aziridine-based crosslinking agent is used, the aziridine-based crosslinking agent may be used alone or in combination with a crosslinking agent other than the aziridine-based crosslinking agent, such as an epoxy-based crosslinking agent.

[0035] The aziridine crosslinking agent is not particularly limited, and examples thereof include N,N'-hexamethylene-1,6-bis(1-aziridinecarboxamide), trimethylolpropane-tri-β-aziridinylpropionate, N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxamide), trimethylolpropane-tri-β-(2-methylaziridine)propionate, and the like. The epoxy crosslinking agent is not particularly limited, and examples thereof include bisphenol A-epichlorohydrin type epoxy resins, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl erythritol, diglycerol polyglycidyl ether, and the like. These crosslinking agents may be used alone or in combination of two or more.

[0036] The content of the crosslinking agent (C) in the pressure-sensitive adhesive composition is preferably 0.1 to 3.0 parts by mass relative to 100 parts by mass of the acrylic polymer (A). When the content of the crosslinking agent (C) in the pressure-sensitive adhesive composition is 0.1 parts by mass or more relative to 100 parts by mass of the acrylic polymer (A), the adhesive layer can be further prevented from remaining when the removable adhesive tape is peeled off after the removable adhesive tape is attached. When the content of the crosslinking agent (C) in the pressure-sensitive adhesive composition is 3.0 parts by mass or less relative to 100 parts by mass of the acrylic polymer (A), the adhesive layer can be prevented from being reduced in adhesive strength due to excessive crosslinking in the pressure-sensitive adhesive composition. From this viewpoint, the content of the crosslinking agent (C) in the pressure-sensitive adhesive composition is more preferably 0.5 to 2.7 parts by mass, and even more preferably 0.7 to 2.5 parts by mass relative to 100 parts by mass of the acrylic polymer (A).

[0037] (Organic solvent) The adhesive composition may contain an organic solvent. The organic solvent may be a solvent used when synthesizing the acrylic polymer, or may be added after synthesizing the acrylic polymer. Examples of the organic solvent include esters such as ethyl acetate and butyl acetate, aromatic compounds such as toluene, aliphatic hydrocarbons such as hexane, and alcohols such as methanol, ethanol, and isopropyl alcohol, and among these, ethyl acetate is preferred. These organic solvents may be used alone or in combination of two or more.

[0038] (Other Ingredients) The pressure-sensitive adhesive composition of the present invention may further contain a filler, an antioxidant, an ultraviolet protection agent, a plasticizer, a viscosity modifier, etc., within the scope of not impairing the effects of the present invention.

[0039] (Thickness) The thickness of the adhesive layer is not particularly limited, but is usually 300 μm or less, and from the viewpoint of adhesive strength and total light transmittance of the removable adhesive tape, it is preferably 0.5 to 180 μm, more preferably 5 to 50 μm.

[0040] <Layer structure of removable adhesive tape> Hereinafter, a removable adhesive tape according to an embodiment of the present invention will be described with reference to the drawings. Note that the removable adhesive tape of the present invention is not limited to the contents of the drawings. A removable adhesive tape 10 according to one embodiment of the present invention includes a substrate 11 and an adhesive layer 12 provided on at least one surface of the substrate 11. The removable adhesive tape 10 may also be wound around a core to form a roll. The removable adhesive tape 10 preferably further comprises a release agent layer 13, specifically, as shown in Fig. 1, the release agent layer 13 is preferably provided on the surface of the substrate 11 opposite to the adhesive layer side. That is, the removable adhesive tape 10 is preferably a tape in which the adhesive layer 12, the substrate 11, and the release agent layer 13 are laminated in this order. By providing the release agent layer 13, when the removable adhesive tape is wound into a roll to form a roll, the adhesive layer 12 comes into contact with the release agent layer 13. This makes it possible to easily unwind the removable adhesive tape 10 from the roll.

[0041] <Release agent layer> The release agent layer 13 may be formed from a known release agent such as a silicone-based release agent or a long-chain alkyl-based release agent. The thickness of the release agent layer is not particularly limited, but the amount of adhesion is, for example, 0.1 g / m 2 More than 10g / m 2 Less than 0.3 g / m 2 More than 5g / m 2 The amount may be adjusted to the following extent.

[0042] <Application> The use of the removable adhesive tape of the present invention is not particularly limited, but it is preferably used for applications that require application and removal, for example, it is preferably used for curing or temporary fixing of various adherends. The removable adhesive tape of the present invention has excellent transparency in addition to excellent hand tearability, so it is preferably used for attaching notices, and particularly preferably used for attaching indoor notices.

[0043] [Manufacturing method of removable adhesive tape] The method for producing the removable adhesive tape of the present invention is not particularly limited, but preferably includes a step of applying a pressure-sensitive adhesive composition to the surface of a substrate. The method for applying the pressure-sensitive adhesive composition to the surface of the substrate is not particularly limited, and any conventionally known method such as using a spin coater or a doctor knife can be used.

[0044] The composition of the pressure-sensitive adhesive composition is as described above, and the solid content concentration of the pressure-sensitive adhesive composition is preferably 20 to 70% by mass, and more preferably 30 to 60% by mass.

[0045] The coating amount of the adhesive composition on the surface of the substrate is 10 to 300 g / m 2 It is preferable that the thickness is 30 to 200 g / m 2 More preferably, the thickness is 50 to 150 g / m 2 It is even more preferable that: After the step of applying the adhesive composition to the surface of the substrate, it is preferable to dry the composition to form an adhesive layer. The temperature and time for drying may be appropriately set according to the volatilization temperature of the solvent contained in the adhesive composition. The drying temperature is, for example, 50 to 150°C, preferably 70 to 105°C, and more preferably 80 to 100°C. The drying time may be in the range of 10 seconds to 3 minutes. In this manner, a removable adhesive tape is obtained which comprises a substrate and an adhesive layer provided on at least one surface of the substrate. However, the method for producing the removable adhesive tape is not limited to the above, and the tape may be produced by transferring an adhesive layer previously formed on a transfer sheet to a substrate, thereby laminating the adhesive layer on the substrate. The method for forming the adhesive layer on the transfer sheet can be performed in the same manner as in the case of forming the adhesive layer on the surface of the substrate. When the removable adhesive tape has a release agent layer, the adhesive layer may be formed on a substrate having a release agent layer formed on one side thereof. EXAMPLES

[0046] The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples in any way.

[0047] The measurement and evaluation methods are as follows. <Breaking strength> The breaking strength of the substrate used in the preparation of the removable adhesive tapes of the Examples and Comparative Examples was measured by the following method. A tensile tester (manufactured by A&D Co., Ltd., product name "Tensilon Universal Material Tester") was used to perform a tensile test under the conditions of a measurement temperature of 23°C, humidity of 50% RH, and a test speed of 1000 mm / min. The test sample was 24 mm wide and 150 mm long, and a 2 mm long cut was made with a cutter on one side of the center in the length direction (75 mm from the end) to prepare for the measurement, and both ends of the test sample were chucked in the above-mentioned tester and pulled in the vertical direction, and the strength at break was recorded.

[0048] <Total light transmittance> The total light transmittance of the removable adhesive tapes of the Examples and Comparative Examples is a value measured in accordance with JIS K7361-1. The total light transmittance can be measured using a haze meter (e.g., Haze Meter NDH4000 manufactured by Nippon Denshoku Industries Co., Ltd.) in an atmosphere at 23°C and humidity of 50%.

[0049] <Change in color intensity before and after accelerated weather resistance test (ΔE)> In accordance with JIS Z7361, measurements were made using a color difference meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "PF7000") at a measurement temperature of 23°C and a humidity of 50% RH. Accelerated weather resistance testing was performed using a xenon accelerated tester (manufactured by Suga Test Instruments Co., Ltd., product name "Super Xenon Weather Meter SX75") at 60 W / m 2 The samples were then irradiated for 72 hours under conditions of 63BPT and the test results were used. Finally, ΔE was calculated by comparing with the unirradiated samples.

[0050] <Adhesive residue> The test sample was 24 mm wide and 150 mm long, and was attached to a plastic plate (product name "ABS resin" manufactured by Nippon Test Panel Co., Ltd.) and pressed with a 2 kg roller. The sample was left in an open at a temperature of 40°C for 2 weeks, after which the tape was peeled off by hand at room temperature, and the presence or absence of adhesive remaining on the surface of the plastic plate was confirmed by visual and tactile inspection. (Evaluation Criteria) ◯: No adhesive remained on the surface of the plastic plate. ×: Adhesive remained on the surface of the plastic plate.

[0051] <Easy to cut by hand> The test sample was a 50 mm wide tape, which was pulled out about 200 mm by hand and the sharpness was confirmed when cut by hand. (Evaluation Criteria) ○: It was cut by hand. ×: Cannot be cut by hand.

[0052] [Components of the adhesive composition] (Monomers used in the production of acrylic polymer (A)) <Alkyl (meth)acrylate (a1)> ·Butyl acrylate (BA) 2-Ethylhexyl acrylate (2EHA) Isononyl acrylate (INA) <Functional group-containing monomer (a2)> Acrylic acid (AAc) Methacrylic acid (MA) <Other monomers (a3)> Vinyl acetate (VA)

[0053] (Rubber component) Natural rubber: "Natural rubber" manufactured by Nomura Trading Co., Ltd.

[0054] (Tackifying resin (B)) Rosin ester: "AA-G" manufactured by Arakawa Chemical Industries, Ltd. Polymerized rosin: "R-95" manufactured by Arakawa Chemical Industries, Ltd. Terpene phenol resin a: "U-115" manufactured by Yasuhara Chemical Co., Ltd. Terpene phenol resin b: "T-130" manufactured by Yasuhara Chemical Co., Ltd. Petroleum resin A: Arakawa Chemical Industries Co., Ltd.

[0055] (Crosslinking agent (C)) Aziridine-based crosslinking agent a: "PZ-33" manufactured by Nippon Shokubai Co., Ltd. Aziridine-based crosslinking agent b: "DZ-22E" manufactured by Nippon Shokubai Co., Ltd. Epoxy crosslinking agent a: "TETRAD-C" manufactured by Mitsubishi Gas Chemical Company, Inc. Epoxy crosslinking agent b: "TETRAD-X" manufactured by Mitsubishi Gas Chemical Co., Ltd.

[0056] (Process oil) Oil: Idemitsu Kosan Co., Ltd. "PW-90"

[0057] [Base material] Substrate A: Stretched polypropylene film, Toyobo Co., Ltd. "P4748", Breaking strength: 0.4N / 24mm, Thickness: 70μm Substrate B: Stretched polypropylene film, Toray Industries, Inc. "#40 YT62", Breaking strength: 0.5N / 24mm, Thickness: 40μm Substrate C: Stretched polypropylene film, Toray Industries, Inc. "#25 YT49", Breaking strength: 0.6N / 24mm, Thickness: 25μm Substrate D: Stretched polypropylene film, "FOA" manufactured by Futamura Chemical Co., Ltd., Breaking strength: 12.2N / 24mm, Thickness: 60μm Substrate E: Cellophane film, "PL" manufactured by Futamura Chemical Co., Ltd., Breaking strength: 0.6N / 24mm, Thickness: 40μm Substrate F: Stretched polypropylene film, Toray Industries, Inc. "Treyfan #60", Breaking strength: 13.5N / 24mm, Thickness: 60μm

[0058] [Preparation of Adhesive Composition A] A reactor equipped with a thermometer, a stirrer, a cooling tube and a dropping funnel was prepared. In the reactor, a monomer mixture consisting of 98 parts by mass of 2-ethylhexyl acrylate and 2 parts by mass of acrylic acid was dissolved in ethyl acetate, and reacted for 10 hours below the boiling point using 0.3 parts by mass of lauroyl peroxide as a polymerization initiator to obtain an acrylic polymer solution. After cooling the solution thus obtained, 600 parts by mass of methanol was added to precipitate the polymer, and the supernatant was separated and removed. Further, 300 parts by mass of methanol was added, and the supernatant was separated and removed, and the acrylic polymer was redissolved in ethyl acetate to prepare an acrylic polymer solution. Next, a tackifier resin and a crosslinking agent were added to the acrylic polymer solution in the amounts shown in Table 1, to obtain a pressure-sensitive adhesive composition A.

[0059] [Preparation of Adhesive Compositions B, C, E, and F] An acrylic polymer solution was prepared in the same manner as in Example 1, except that the type and amount of each monomer for obtaining an acrylic polymer were changed as shown in Table 1. Next, a tackifier resin and a crosslinking agent were added to the acrylic polymer solution in the amounts shown in Table 1 and mixed to obtain pressure-sensitive adhesive compositions B, C, E and F.

[0060] [Preparation of Adhesive Composition D] The rubber component, tackifier resin, process oil, crosslinking agent, toluene, and hexane were mixed in the amounts shown in Table 1 to obtain a pressure-sensitive adhesive composition D.

[0061] [Table 1]

[0062] [Example 1] Coating weight: 50g / mm 2 After applying the pressure-sensitive adhesive composition A to the surface of the substrate A so as to obtain a pressure-sensitive adhesive layer, the adhesive composition was dried at 90° C. for 2 minutes to obtain a removable pressure-sensitive adhesive tape. Various evaluations were carried out using the removable pressure-sensitive adhesive tape, and the results are shown in Table 2.

[0063] [Examples 2 and 3, Comparative Examples 1 to 4] A removable adhesive tape was obtained in the same manner as in Example 1, except that the type of adhesive composition and the type of substrate were changed as shown in Table 2. Various evaluations were performed using the removable adhesive tape, and the results are shown in Table 2.

[0064] [Table 2]

[0065] The removable adhesive tapes of Examples 1 to 3 had an adhesive layer made of an acrylic adhesive, a substrate breaking strength of 0.05 to 10 N / 24 mm, and a total light transmittance of 80% or more, and therefore had excellent transparency and hand tearability. On the other hand, the removable adhesive tape of Comparative Example 1 had a total light transmittance of less than 80% and a substrate breaking strength of more than 10 N / 24 mm, and therefore had poor transparency and ease of tearing by hand. The removable adhesive tape of Comparative Example 3 had a substrate breaking strength of more than 10 N / 24 mm, and therefore was poorly tearable by hand. The removable adhesive tape of Comparative Example 2 did not have an adhesive layer made of an acrylic adhesive, and therefore had a large amount of adhesive remaining after removal, and could not be called a removable adhesive tape. The removable adhesive tape of Comparative Example 4 had a small content of crosslinking agent (C) in the adhesive composition, and therefore had a large amount of adhesive remaining after peeling, and could not be called a removable adhesive tape. [Explanation of symbols]

[0066] 10 Removable adhesive tape 11 Base material 12 Adhesive layer 13 Release agent layer

Claims

1. A removable adhesive tape comprising a substrate and an adhesive layer provided on at least one surface of the substrate, The pressure-sensitive adhesive layer is made of an acrylic pressure-sensitive adhesive, The breaking strength of the substrate is 0.05 to 10 N / 24 mm; The removable adhesive tape has a total light transmittance of 80% or more.

2. The acrylic pressure-sensitive adhesive is formed from a pressure-sensitive adhesive composition containing an acrylic polymer (A), the acrylic polymer (A) is a polymer of a monomer containing an alkyl(meth)acrylate (a1) and a functional group-containing monomer (a2) having a reactive functional group, or a polymer of a monomer containing an alkyl(meth)acrylate (a1), a functional group-containing monomer (a2) having a reactive functional group, and a monomer (a3) ​​other than the alkyl(meth)acrylate (a1) and the functional group-containing monomer (a2); the amount of the alkyl (meth)acrylate (a1) used in the total monomer components used in the acrylic polymer (A) is 65 to 99.9 mass %, the amount of the functional group-containing monomer (a2) used in the total monomer components used in the acrylic polymer (A) is 0.1 to 8 mass %, 2. The removable adhesive tape according to claim 1, wherein the amount of the other monomer (a3) ​​used in the acrylic polymer (A) is 0 to 27% by mass.

3. The alkyl (meth)acrylate (a1) is an alkyl (meth)acrylate having an alkyl group having 4 to 12 carbon atoms, The removable adhesive tape according to claim 2, wherein the functional group-containing monomer (a2) having a reactive functional group is a monomer having a carboxy group.

4. the pressure-sensitive adhesive composition contains a tackifier resin (B), and the acrylic pressure-sensitive adhesive is formed from a pressure-sensitive adhesive composition containing an acrylic polymer (A), 3. The removable adhesive tape according to claim 1, wherein the content of the tackifier resin (B) in the adhesive composition is 10 parts by mass or less per 100 parts by mass of the acrylic polymer (A).

5. the pressure-sensitive adhesive composition contains a crosslinking agent (C); the acrylic pressure-sensitive adhesive is formed from a pressure-sensitive adhesive composition containing an acrylic polymer (A); 3. The removable adhesive tape according to claim 1, wherein the content of the crosslinking agent (C) in the adhesive composition is 0.1 to 3.0 parts by mass per 100 parts by mass of the acrylic polymer (A).

6. 6. The removable adhesive tape according to claim 5, wherein the crosslinking agent (C) is at least one crosslinking agent selected from the group consisting of aziridine-based crosslinking agents and epoxy-based crosslinking agents.

7. 3. The removable adhesive tape according to claim 1, which has a change in color intensity (ΔE) of 3.0 or less before and after an accelerated weather resistance test.

8. 3. The removable adhesive tape according to claim 1, wherein the substrate is a stretched polyolefin film.

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