Functional substrate-less single-sided pressure-sensitive adhesive tape

Abstract

To provide a functional pressure-sensitive adhesive tape which can be stuck to a wide place and exhibits a long functional life.SOLUTION: The functional substrate-less single-sided pressure-sensitive adhesive tape comprises an electron beam-curable pressure-sensitive adhesive layer which contains a functional additive exhibiting a prescribed function by being released from the inside to the surrounding atmosphere and has a non-sticking surface substantially not exhibiting pressure-sensitive adhesiveness and a sticking surface exhibiting pressure-sensitive adhesiveness.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a functional substrate-less single-sided pressure-sensitive adhesive tape, and more particularly to a functional substrate-less single-sided pressure-sensitive adhesive tape having an electron beam-curable pressure-sensitive adhesive layer. [Background technology]

[0002] Functional adhesive tapes are known that contain functional additives, such as antibacterial agents, insect repellents, and fragrances, in a film, which exhibit a predetermined function by being released from the inside into the surrounding atmosphere, and which exhibit a predetermined function by the sustained release of these additives.

[0003] Patent Document 1 describes a drug-containing adhesive sheet formed by coating a substrate with a composition in which a drug-containing thermoplastic powder particle is blended with a pressure-sensitive adhesive. In this drug-containing adhesive sheet, a mixture of natural rubber and a tackifying resin is used as the pressure-sensitive adhesive. Furthermore, the thermoplastic used is one that is compatible with the drug, thereby incorporating the drug into the thermoplastic and imparting sustained-release properties to the volatile drug.

[0004] Patent Document 2 describes a volatile drug-containing film having a substrate and a volatile drug layer in which an isothiocyanate ester is retained in the adhesive layer, the adhesive layer being composed of an adhesive composition containing an acrylic copolymer and a crosslinking agent. The isothiocyanate ester is retained in the film at a high concentration by impregnating the adhesive layer after it has been formed. The volatile drug in Patent Document 2 is said to be capable of exerting its medicinal effect for a long period of time.

[0005] Patent Document 3 describes an electron beam irradiation method that can vary the crosslinked or cured state rather than uniformly crosslinking or curing the entire irradiated object, as well as such a curing or crosslinking method and a method for providing an electron beam irradiated object. Specific examples of such variations include a gradation structure in which the crosslink density or hardness changes stepwise. This electron beam irradiation method is said to be applicable to relatively thin layers formed on a substrate and sustained-release materials that gradually release active ingredients, such as poultices. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 6-200219 [Patent Document 2] Japanese Patent Application Publication No. 2018-135432 [Patent Document 3] Japanese Patent Application Publication No. 10-158413 Summary of the Invention [Problem to be solved by the invention]

[0007] Conventional functional adhesive tapes have a substrate and an adhesive as components, and because functional additives are contained in either the substrate or the adhesive, the amount of functional additives contained in the functional adhesive tape is limited, resulting in a short period of time during which the tape can exhibit its functions. In addition, the substrate has poor flexibility, conformability, or weather resistance, and when applied to uneven surfaces or outdoors, peeling or deterioration easily occurs, resulting in a problem of an insufficient period of time during which the tape can exhibit its functions.

[0008] The present invention has been made to solve the above problems, and an object of the present invention is to provide a functional adhesive tape that can be applied to a wide range of places and has a long functional life. [Means for solving the problem]

[0009] The present invention provides the following aspects. [Embodiment 1] A functional substrate-less single-sided adhesive tape comprising an electron beam curable adhesive layer containing a functional additive that exhibits a predetermined function when released from the inside into the surrounding atmosphere, and having a non-adhesive surface that is substantially non-adhesive and an adhesive surface that exhibits adhesiveness.

[0010] [Aspect 2] The functional substrate-less single-sided pressure-sensitive adhesive tape according to Aspect 1, wherein the adhesive surface exhibits removability.

[0011] [Embodiment 3] A functional substrate-less single-sided adhesive tape according to embodiment 1 or 2, wherein the electron beam cured adhesive layer has a gradient of crosslink density in the thickness direction, and the non-adhesive surface portion of the adhesive layer has a higher crosslink density than the adhesive surface portion.

[0012] [Aspect 4] The functional substrate-less single-sided pressure-sensitive adhesive tape according to any one of Aspects 1 to 3, wherein the electron beam curable pressure-sensitive adhesive layer contains the functional additive, an electron beam curable resin, and a tackifier resin.

[0013] [Aspect 5] The functional substrate-less single-sided pressure-sensitive adhesive tape according to Aspect 4, wherein the electron beam-resistant resin is ethylene propylene diene rubber.

[0014] [Aspect 6] A functional substrate-less single-sided pressure-sensitive adhesive tape according to any one of aspects 1 to 5, wherein the electron beam curable pressure-sensitive adhesive layer contains 0.01 to 10 wt %, preferably 0.1 to 5.0 wt %, and more preferably 1 to 4 wt % of a functional additive.

[0015] [Aspect 7] The functional substrate-less single-sided pressure-sensitive adhesive tape according to any one of Aspects 1 to 6, wherein the electron beam curable pressure-sensitive adhesive layer has a thickness of 30 to 350 μm, preferably 50 to 300 μm, and more preferably 100 to 200 μm.

[0016] [Embodiment 8] A method for producing a single-sided adhesive tape without a functional substrate, comprising irradiating a layer of an electron beam-curable adhesive containing a functional additive that exhibits a predetermined function by being released from the inside into the surrounding atmosphere with an electron beam, the acceleration voltage of which is adjusted so that the layer reaches a predetermined depth, from one side, to provide an electron beam-curable adhesive layer having a non-adhesive surface that is substantially not adhesive and an adhesive surface that exhibits adhesiveness. [Effects of the Invention]

[0017] According to the present invention, a functional adhesive tape is provided which can be applied to a wide range of locations and exhibits a long functional life. DETAILED DESCRIPTION OF THE INVENTION

[0018] The functional substrate-less single-sided adhesive tape of the present invention comprises an electron beam-curable adhesive layer. The functional substrate-less single-sided adhesive tape of the present invention may also comprise an electron beam-curable adhesive layer. Here, the electron beam-curable adhesive layer refers to a layer formed and cured from an electron beam-curable adhesive (i.e., adhesive composition) starting material, which contains a functional additive that exhibits a predetermined function when released into the surrounding atmosphere, an electron beam-curable resin, and a tackifier resin. The electron beam-curable adhesive preferably does not contain a crosslinking agent.

[0019] <Electron beam curable resin> The electron beam curable resin is not limited to a specific type, and resins containing as their main component a prepolymer (including oligomers) and / or a monomer containing a radically polymerizable double bond in the molecule that can undergo a polymerization / crosslinking reaction upon irradiation with an electron beam can be used. These prepolymers or monomers can be used alone or in combination. The curing reaction in electron beam curable resins is usually a crosslinking curing reaction.

[0020] Specifically, the prepolymer or monomer may be a compound having a radically polymerizable unsaturated group in the molecule, such as a (meth)acryloyl group or a (meth)acryloyloxy group. Here, the (meth)acryloyl group means an acryloyl group or a methacryloyl group.

[0021] Examples of prepolymers having a radically polymerizable unsaturated group include polyester (meth)acrylate, urethane (meth)acrylate, epoxy (meth)acrylate, melamine (meth)acrylate, triazine (meth)acrylate, silicone (meth)acrylate, etc. The molecular weight of these is usually preferably about 250 to 100,000.

[0022] Examples of the monomer having a radically polymerizable unsaturated group include monofunctional monomers such as methyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and phenoxyethyl (meth)acrylate.

[0023] Examples of polyfunctional monomers include diethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, trimethylpropane tri(meth)acrylate, trimethylolpropane ethylene oxide tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate.

[0024] Among them, preferred electron beam curable resins include ethylene propylene diene rubber (EPDM), styrene butadiene rubber (SBR), nitrile rubber (NBR), acrylic rubber (ACM), silicone rubber (Q), etc. The electron beam curable resins may be used alone or in combination of two or more. Commercially available electron beam curable resins may also be used.

[0025] The content of the electron beam curable resin in the electron beam curable adhesive layer is, for example, 30 to 90% by weight, preferably 50 to 80% by weight, and more preferably 60 to 75% by weight. If the content of the electron beam curable resin is less than 30% by weight, the adhesive strength may decrease, and if it exceeds 90% by weight, it becomes difficult to adjust the crosslink density by electron beam irradiation. This becomes:

[0026] <Tackifying resin> Examples of tackifying resins that can be used include rosin-based tackifying resins (e.g., unmodified rosin, modified rosin, rosin phenolic resins, and rosin ester resins), terpene-based tackifying resins (e.g., terpene resins, terpene phenolic resins, styrene-modified terpene resins, aromatic-modified terpene resins, and hydrogenated terpene resins), hydrocarbon-based tackifying resins (e.g., aliphatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aromatic hydrocarbon resins (e.g., styrene-based resins and xylene-based resins), silicone resins, aliphatic and aromatic petroleum resins, aliphatic and alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone-based resins, and coumarone-indene resins), phenol-based tackifying resins (e.g., alkylphenol-based resins, xylene-formaldehyde-based resins, resols, and novolacs), ketone-based tackifying resins, polyamide-based tackifying resins, epoxy-based tackifying resins, and elastomer-based tackifying resins.

[0027] Among them, preferred tackifying resins include rosin-based tackifying resins, terpene-based tackifying resins, and hydrocarbon-based tackifying resins (such as styrene-based resins). Tackifying resins may be used alone or in combination of two or more. Commercially available tackifying resins may also be used.

[0028] The content of the tackifier resin in the electron beam curable adhesive layer is, for example, 10 to 60% by weight, preferably 20 to 50% by weight, and more preferably 25 to 40% by weight. If the content of the tackifier resin is less than 10% by weight, the adhesive strength may be insufficient, and if it exceeds 60% by weight, the initial adhesive strength decreases.

[0029] <Functional additives> The functional additive may be one or more types appropriately selected from known deodorants, fragrances, insect repellents, insecticides, etc. The fragrance may be either a natural fragrance or a synthetic fragrance, and a wide variety of commercially available products may be used. The deodorant may be either a physical adsorption type or a chemical adsorption type, or a combination of both. The functional additive may be a solid such as a powder or granular material, or a liquid, and may be encapsulated in microcapsules, for example, to control the timing and duration of its effect.

[0030] The content of the functional additive in the electron beam curable adhesive layer is, for example, 0.01 to 10 wt%, preferably 0.1 to 5.0 wt%, and more preferably 1 to 4 wt%. If the content of the tackifier resin is less than 0.01 wt%, the function will not last long, and if it exceeds 10 wt%, flexibility and mechanical strength may decrease.

[0031] <Other additives> The electron beam curable adhesive layer may contain various additives such as fillers, pigments, dyes, diluents, polymerization inhibitors, UV absorbers, UV stabilizers, and coupling agents that are blended into known adhesives as needed, and two or more of these may be used.

[0032] <Electron beam curing adhesive layer> The electron beam curable adhesive layer can be produced by uniformly mixing an electron beam curable resin, a tackifying resin, a functional additive, and, if necessary, other additives and a solvent to prepare a coating liquid of the electron beam curable adhesive, applying this to the release surface of a carrier film and drying it to form a layer of the electron beam curable adhesive, and then irradiating this layer with electron beams to cure it.

[0033] The thickness of the electron beam curable adhesive layer is generally 30 to 350 μm, preferably 50 to 300 μm, and more preferably 100 to 200 μm. If the thickness of the electron beam curable adhesive layer is less than 30 μm, the function and strength are likely to be insufficient, while if it exceeds 350 μm, the processability is likely to be reduced, which may impair profitability.

[0034] As the electron beam source, various electron beam accelerators can be used, such as Cockcroft-Walton type, Van de Graaf type, resonant transformer type, insulating core transformer type, or linear type, dynamitron type, high frequency type, etc. Among these, those capable of irradiating electrons having an energy in the range of 100 keV to 1000 keV are particularly preferred, and those capable of irradiating electrons having an energy in the range of 100 keV to 300 keV are more preferred.

[0035] Electron beam irradiation involves irradiating a layer of electron beam-curable adhesive with electron beams from one side, with the acceleration voltage adjusted to reach a predetermined penetration depth. This results in an electron beam-curable adhesive layer with a gradient of crosslink density in the thickness direction, with the non-adhesive surface portion of the adhesive layer having a higher crosslink density than the adhesive surface portion. In other words, the electron beam-curable resin is crosslinked to such an extent that the non-adhesive surface of the electron beam-curable adhesive layer is substantially non-adhesive and the adhesive surface is adhesive. Specifically, the acceleration voltage and the irradiation dose are adjusted. Depending on the constituent materials, the acceleration voltage is preferably in the range of 150 to 200 kV. Furthermore, the irradiation dose is preferably in the range of 50 to 300 kGy. Within these ranges, it is easy to adjust the crosslinking of the electron beam-curable resin to such an extent that the non-adhesive surface is substantially non-adhesive and the adhesive surface is adhesive.

[0036] Here, "substantially no adhesiveness" means not only that the adhesive strength is not at a level that can be used as an adhesive tape, but also that the adhesive strength is so low that it peels off immediately after adhering. So-called weak adhesiveness corresponds to the fact that the adhesive strength is substantially not adhesive. Furthermore, "adhesiveness" means that the adhesive strength is at a level that can be used as an adhesive tape.

[0037] The adhesive surface of the electron beam cured adhesive layer is crosslinked to impart removability, and the layer can be peeled off without leaving any adhesive residue on the adherend.

[0038] <Single-sided adhesive tape without functional substrate> "Functionality" refers to the ability of functional additives, such as antibacterial agents, insect repellents, and fragrances, contained within the adhesive tape to be released into the surrounding atmosphere and thereby perform a specific function. "Substrate-less" refers to the absence of a substrate as a constituent element. The substrate is generally a component that occupies a significant portion of the thickness of the adhesive tape to provide it with appropriate strength. Therefore, by not having a substrate as a constituent element, the adhesive layer can be made thicker, allowing for a greater amount of functional additives to be contained in the functional adhesive tape.

[0039] Furthermore, compared with the pressure-sensitive adhesive layer, the substrate is inferior in flexibility, conformability, or weather resistance. Therefore, by not having a substrate as a component, the flexibility, conformability, and weather resistance of the functional pressure-sensitive adhesive tape are improved. As a result, the functional substrate-free single-sided pressure-sensitive adhesive tape of the present invention can fully function even when applied to uneven surfaces or outdoors, and can be installed in a wide range of locations regardless of the application location. [Example]

[0040] The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In the examples, parts and % mean parts by weight and % by weight, respectively, unless otherwise specified.

[0041] Example 1 Ethylene propylene diene rubber (EPDM, Mitsui Chemicals, Inc. "Mitsui EPT4045" (trade name)) 100 parts, tackifier (Arakawa Chemical Industries, Ltd. "Alcon P-115" (trade name)) 50 parts, toluene 500 parts, and mint flavoring (Takasago International Corporation "L-Menthol") 5 parts (i.e., 3% of the tape's constituent components) were mixed, and the resulting mixture was coated on the release surface of a carrier film. The coated product was placed in a drying oven to evaporate the solvent (toluene), and a cover film was attached so that the release surface was in contact with the coating. The carrier film and cover film were 75 μm thick polyethylene terephthalate (PET) films with a release agent layer on their surfaces.

[0042] The resulting laminate was irradiated with an electron beam from the carrier film side at an acceleration voltage of 175 kV and a dose of 100 kGy. Removal of the carrier film and cover film revealed a 150 μm-thick electron beam-cured adhesive layer that exhibited slight adhesiveness on the carrier film side and adhesiveness on the cover film side. The resulting electron beam-cured adhesive layer was used as a functional substrate-less single-sided adhesive tape, and its performance was evaluated using the following method. The results are shown in Table 1.

[0043] Sustained release (release period): The adhesive tapes prepared in the examples were cut to a size of 2.5 x 10 cm, attached to a stainless steel plate made of SUS304 stainless steel, and stored in a thermostatic chamber preheated to 60°C. After one month, they were removed from the thermostatic chamber and allowed to stand in an acrylic box measuring 30 x 30 x 30 cm. After one hour, the odor inside the acrylic box was evaluated. If an odor was detected, the tape was judged to have excellent sustained release properties (A), and if no odor was detected, the tape was judged to have poor sustained release properties (B).

[0044] Removability: The adhesive tape prepared in Example 1 was cut to a size of 2.5 x 10 cm, attached to a stainless steel plate made of SUS304 stainless steel, and stored in a thermostatic chamber preheated to 60°C. After one month, it was removed from the thermostatic chamber and allowed to cool, after which the adhesive tape was peeled off. If no adhesive tape residue remained on the adherend, the tape was judged to have excellent removability (A); if any residue remained, the tape was judged to have poor removability (B).

[0045] Flexibility and adaptability: The adhesive tape prepared in Example 1 was cut into two pieces measuring 2.5 x 5 cm and attached to a stainless steel plate made of SUS304 stainless steel, with an offset of approximately 1 cm in the minor axis direction. After sufficient pressure bonding, the tape was immersed in a coloring solution for 10 minutes and then removed. If the overlapping portion of the two sheets was not colored, the flexibility and conformability were judged to be excellent (A), and if coloring was observed, the flexibility and conformability were judged to be poor (B).

[0046] Weather resistance: The adhesive tape prepared in Example 1 was cut to a size of 2.5 x 10 cm, attached to a stainless steel plate made of SUS304 stainless steel, and exposed outdoors for 6 months. After exposure, the adhesive tape was peeled off. If no adhesive tape residue was found on the adherend, the weather resistance was judged to be excellent (A), and if residue was found, the weather resistance was judged to be poor (B).

[0047] <Comparative Example 1> An electron beam-cured adhesive layer having a thickness of 150 μm and exhibiting slight adhesiveness on the carrier film side and adhesiveness on the cover film side was produced in the same manner as in Example 1, except that the electron beam irradiation conditions were changed to an acceleration voltage of 275 kV and an absorbed dose of 100 kGy. The obtained electron beam-cured adhesive layer was used as a functional substrate-less single-sided adhesive tape, and its performance was evaluated by the above-mentioned method. The results are shown in Table 1.

[0048] <Comparative Example 2> A pressure-sensitive adhesive layer having a thickness of 150 μm was produced in the same manner as in Example 1, except that electron beam irradiation was not performed, and the carrier film side exhibited adhesiveness and the cover film side also exhibited adhesiveness. The obtained pressure-sensitive adhesive layer was used as a functional substrate-less adhesive tape, and its performance was evaluated by the above-mentioned method. The results are shown in Table 1.

[0049] <Comparative Example 3> An isocyanate-crosslinked adhesive composition was prepared by thoroughly mixing 100 parts (30% solids) of an ethyl acetate solution of an acrylic polymer consisting of an acrylic acid ester copolymer ("SK Dyne 1415" (trade name) manufactured by Soken Chemical & Engineering Co., Ltd.), 0.5 parts (45% solids) of an ethyl acetate solution of a polyisocyanate-based crosslinking agent ("L-45K" (trade name) manufactured by Soken Chemical & Engineering Co., Ltd.), and 0.9 parts (i.e., 3% of the components of the adhesive layer) of mint fragrance ("L-Menthol" manufactured by Takasago International Corporation), and then this was coated onto a carrier film.

[0050] The coated product was placed in a drying oven and heated at 105°C for 5 minutes to evaporate the solvent (ethyl acetate) and crosslink the adhesive layer. A cover film was attached so that the release surface was in contact with the coating. The carrier film was a 75µm thick PET film with no release agent layer on its surface, and the cover film was a 38µm thick PET film with a release agent layer on its surface.

[0051] The cover film was removed to obtain a single-sided adhesive tape with a functional substrate having a 75 μm thick PET film and a 50 μm thick adhesive layer. The performance of the obtained adhesive tape was evaluated in the same manner as in the Examples. The results are shown in Table 1.

[0052] [Table 1]

Claims

1. A functional substrate-less single-sided adhesive tape comprising an electron beam curable adhesive layer containing a functional additive that exhibits a predetermined function when released from the inside into the surrounding atmosphere, and having a non-adhesive surface that is substantially not adhesive and an adhesive surface that exhibits adhesiveness.

2. The functional substrate-less single-sided pressure-sensitive adhesive tape according to claim 1 , wherein the adhesive surface exhibits removability.

3. 2. The functional substrate-less single-sided adhesive tape according to claim 1, wherein the electron beam cured adhesive layer has a gradient of crosslink density in the thickness direction, and the non-adhesive surface portion of the adhesive layer has a higher crosslink density than the adhesive surface portion.

4. The functional substrate-less single-sided pressure-sensitive adhesive tape according to claim 1 , wherein the electron beam curable pressure-sensitive adhesive layer comprises the functional additive, an electron beam curable resin, and a tackifier resin.

5. 5. The functional substrate-less single-sided adhesive tape according to claim 4, wherein the electron beam-resistant resin is ethylene propylene diene rubber.

6. The functional substrate-less single-sided pressure-sensitive adhesive tape according to claim 1, wherein the electron beam curable pressure-sensitive adhesive layer contains 0.01 to 10% by weight of a functional additive.

7. The functional substrate-less single-sided pressure-sensitive adhesive tape according to claim 1, wherein the electron beam curable pressure-sensitive adhesive layer has a thickness of 30 to 350 μm.

8. A method for producing a single-sided adhesive tape without a functional substrate, comprising: irradiating a layer of an electron beam-curable adhesive containing a functional additive that exhibits a predetermined function by being released from the inside into the surrounding atmosphere with an electron beam, the acceleration voltage of which is adjusted so that the layer reaches a predetermined depth, from one side thereof, thereby providing an electron beam-curable adhesive layer having a non-adhesive surface that is substantially not adhesive and an adhesive surface that exhibits adhesiveness.

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