Double-sided adhesive tape, metal plate processed product, article, and falsification prevention tape

Abstract

To provide a double sided adhesive tape capable of being used for various purposes.SOLUTION: A double sided adhesive tape 10 having a first principal plane 14 and a second principal plane 16, includes: a core material 3 formed by a resin containing a non-expanded thermally expandable particle 5; a first adhesive layer 11 formed on the first principal plane 14; and a second adhesive layer 13 formed on the second principal plane 16 of the core material. The double sided adhesive tape 10 may be provided as a figuration of an adhesive tape laminate 20 further provided with a first release liner 7 covering the first adhesive layer 11, and a second release liner 1 covering the second adhesive layer 13. The resin forming the core material 3 may be an adhesive cured product.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The technology disclosed in this specification relates to double-sided pressure-sensitive adhesive tapes that can be used for a variety of purposes. [Background technology]

[0002] The need to strongly bond two adherends together using double-sided tape exists not only in building materials but also in various fields and products such as electronic devices and vehicle components, etc. For example, JP-A-60-019187 (Patent Document 1) describes attaching a substrate-less double-sided tape for fixing to an adherend to the second side (rear side) of a nameplate with printing on the first side (front side). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 60-019187 Summary of the Invention [Problem to be solved by the invention]

[0004] Nameplates are made by punching out a large metal plate into a specified shape, but when the metal plate placed on the die is punched from the front side with a punch, burrs are generated on the back side of the peripheral edge of the nameplate. When double-sided tape is attached to the back side of the nameplate, if the height of the burrs is higher than the thickness of the double-sided tape, the adhesive layer of the double-sided tape will not come into contact with the adherend, making it difficult to fix the nameplate to the adherend. Such burr problems also occur when making nameplates by laser processing.

[0005] For this reason, currently, nameplate products are produced by attaching double-sided tape made to fit the size of the nameplate after a process of removing burrs that have occurred on the nameplate. However, this method requires a lot of work to remove the burrs, and double-sided tape must be attached to the backside of each individualized nameplate. Therefore, there is a need to develop a method that can produce a large number of nameplate products with fewer steps by attaching double-sided tape to the backside of a metal plate and then performing a punching process.

[0006] Double-sided tape is used for many purposes other than nameplate products, and the issues that need to be resolved vary depending on the application.

[0007] In view of the above problems, an object of the present invention is to develop a double-sided tape that can be used in a variety of applications, including new applications. [Means for solving the problem]

[0008] One example of a double-sided adhesive tape disclosed in the present specification has a first main surface and a second main surface opposite the first main surface, and is equipped with a core material formed of a resin containing unexpanded thermally expandable particles, a first adhesive layer formed on the first main surface of the core material, and a second adhesive layer formed on the second main surface of the core material.

[0009] One example of the metal plate processed product disclosed in the present specification includes a metal plate, a core material having a first main surface and a second main surface opposite to the first main surface and formed of a resin, a double-sided adhesive tape having a first adhesive layer formed on the first main surface of the core material and bonded to the metal plate, and a second adhesive layer formed on the second main surface of the core material. The core material contains thermally expandable particles in an expanded state.

[0010] One example of the article disclosed in the present specification includes an adherend having a void formed therein, at least one of a first adherend and a second adherend arranged with a gap therebetween, a core material having a first main surface and a second main surface opposite to the first main surface and formed of a resin, a first adhesive layer formed on the first main surface of the core material, and a second adhesive layer formed on the second main surface of the core material. The core material contains thermally expandable particles after expansion, and the double-sided adhesive tape fills the voids in the adherend or the voids between the first adherend and the second adherend.

[0011] An example of a tamper-evident tape disclosed in the present specification includes a brittle substrate and a double-sided adhesive tape attached to at least one surface of the brittle substrate. The double-sided adhesive tape has a first main surface and a second main surface opposite to the first main surface, and includes a core material formed of a resin containing unexpanded thermally expandable particles, a first adhesive layer formed on the first main surface of the core material and bonded to the brittle substrate, and a second adhesive layer formed on the second main surface of the core material. Effect of the Invention

[0012] The double-sided adhesive tape disclosed in the present specification expands when heated after being attached to an adherend, and is capable of retaining its adhesive force to the adherend even after heat treatment, and therefore can be preferably used for a variety of applications, such as the production of metal plate products, filling of gaps between adherends, and the production of tamper-evident tape. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a cross-sectional view illustrating an example of a double-sided pressure-sensitive adhesive tape according to a first embodiment of the present disclosure. [Diagram 2] FIG. 2 is a cross-sectional view showing the state after the double-sided adhesive tape according to the first embodiment has been thermally expanded. [Diagram 3] 3(a) and (b) are cross-sectional views showing a method for manufacturing a metal sheet product according to a second embodiment of the present disclosure. [Figure 4] FIG. 4 is a cross-sectional view showing a configuration example of a tamper-evident tape according to a third embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] (First embodiment)

[0015] [Composition of double-sided adhesive tape] 1 is a cross-sectional view showing a double-sided adhesive tape 10, which is one example of an embodiment disclosed in the present specification, and an adhesive tape laminate 20 having the double-sided adhesive tape 10. The drawings attached to this application, including this figure, are schematic diagrams showing the configuration of a double-sided adhesive tape or the like, and the thickness ratio of each layer, the particle density or particle size to layer thickness, the shape of burrs, and the like may differ from the actual ones.

[0016] The double-sided adhesive tape 10 according to this embodiment includes a core material 3 having a first main surface 14 and a second main surface 16 opposing the first main surface 14, a first adhesive layer 11 formed on the first main surface 14, and a second adhesive layer 13 formed on the second main surface 16. The core material 3 is formed from a resin containing unexpanded thermally expandable particles 5. The resin for forming the core material 3 may be any resin that retains a certain degree of elasticity after curing, and may be, for example, a cured adhesive.

[0017] Both the first adhesive layer 11 and the second adhesive layer 13 are formed from a cured adhesive product containing an adhesive and, if necessary, a curing agent or the like added thereto, and do not contain thermally expandable particles.

[0018] The adhesive tape laminate 20 comprises a double-sided adhesive tape 10, a first release liner 7 provided so as to contact the surface of the first adhesive layer 11 opposite the core material 3, and a second release liner 1 provided so as to contact the surface of the second adhesive layer 13 opposite the core material 3.

[0019] In the double-sided pressure-sensitive adhesive tape 10 of this embodiment, when heated to a temperature equal to or higher than the foaming initiation temperature of the thermally expandable particles 5, the thermally expandable particles 5 expand and the thickness of the core material 3 increases.

[0020] FIG. 2 is a cross-sectional view for explaining a method of using the double-sided adhesive tape 10 of this embodiment. For example, when the peel strength of the second release liner 1 to the second adhesive layer 13 is greater than the peel strength of the first release liner 7 to the first adhesive layer 11, when using the double-sided adhesive tape 10 shown in FIG. 1, first, the first release liner 7 on the light release side is peeled off, and the tape is attached to the first adherend 6 from the first adhesive layer 11 side. Next, the second release liner 1 on the heavy release side is peeled off, and the second adhesive layer 13 is attached to the second adherend 12. Next, the double-sided adhesive tape 10 together with the adherend is sufficiently heated to expand the thermally expandable particles 5 in the core material 3. As a result, the adhesive tape laminate 20 becomes an adhesive tape laminate 20a with an increased thickness.

[0021] When the thermally expandable particles 5 in the core material 3 are expanded for 5 minutes at a temperature 10°C or higher than the expansion start temperature, the value of (thickness of the core material 3 after expansion) / (thickness of the core material 3 before expansion) may be, for example, 1.5 to 20.0, and preferably 2.0 to 10.0. If the expansion coefficient of the core material 3 after the expansion process is too small, the thickness of the double-sided adhesive tape 10 does not change much before and after the expansion process, making it difficult to obtain the advantage of the thermally expandable particles 5 contained in the core material 3. If the expansion coefficient of the core material 3 is too large, the core material 3 becomes brittle after the expansion process and is prone to interlayer delamination. In this specification, the heating for expanding the thermally expandable particles 5 is performed in a drying furnace that has been previously set to the temperature for heat treatment.

[0022] The thickness of the core material 3 before the foaming treatment is not particularly limited, but can be, for example, 5 μm or more and 300 μm or less. If the thickness of the core material 3 is extremely thin compared to the average particle size of the thermally expandable particles 5, unevenness due to the shape of the thermally expandable particles 5 will be likely to appear on the surface of the core material 3, and the change in thickness of the double-sided pressure-sensitive adhesive tape 10 before and after the thermally expandable particles 5 are expanded by heating will be small. From the viewpoint of reducing manufacturing costs while obtaining a sufficient thickness of the tape by expanding the thermally expandable particles 5, it is more preferable that the thickness of the core material 3 before the foaming treatment is 10 μm or more and 150 μm or less.

[0023] The thickness of the double-sided adhesive tape 10 before the foaming treatment is not particularly limited and may be appropriately changed depending on the application. For example, it may be 10 μm or more and 1000 μm or less, 30 μm or more and 500 μm or less, or 50 μm or more and 300 μm or less.

[0024] In the double-sided pressure-sensitive adhesive tape 10 of this embodiment, the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 13 are provided on both sides of the core material 3 containing thermally expandable particles, so that even if the thickness of each pressure-sensitive adhesive layer is increased by foaming treatment after being attached to the adherend, the adhesive strength of the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 13 to each adherend is not lost. For this reason, the double-sided pressure-sensitive adhesive tape 10 is preferably used for processing metal plates, filling voids, manufacturing tamper-proof tapes, etc., which will be described later.

[0025] For example, when the thermally expandable particles 5 in the core material 3 are expanded for 5 minutes at a temperature 10° C. or more higher than the expansion initiation temperature, the adhesive strength of at least one of the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 13 to a SUS steel plate after 24 hours at 23° C. and a relative humidity of 50% after the thermally expandable particles 5 have been expanded is 0.1 to 3.0 times the adhesive strength to the SUS steel plate before the thermally expandable particles 5 are expanded. With this configuration, the double-sided pressure-sensitive adhesive tape 10 of this embodiment is less likely to fall off from the adherend after the heat-expanding treatment.

[0026] The adhesive strength of the first adhesive layer 11 to the first adherend 6 before and after the foaming treatment, and the adhesive strength of the second adhesive layer 13 to the second adherend 12 before and after the foaming treatment can be set to any value as long as the adherends do not peel off naturally. For example, the adhesive strength of the first adhesive layer 11 to the first adherend 6 before and after the foaming treatment may be 0.1 N / 25 mm or more, and the adhesive strength of the second adhesive layer 13 to the second adherend 12 before and after the foaming treatment may also be 0.1 N / 25 mm or more. The adhesive strength here refers to the adhesive strength when, in an environment of 23° C. and relative humidity 50%, a 25 μm thick PET film for backing is attached to one of the first adhesive layer 11 and the second adhesive layer 13, the other adhesive layer is attached to a polished SUS steel plate, and the two layers are peeled off from the SUS steel plate under the conditions of a peel angle of 180 degrees and a peel speed of 300 mm / min.

[0027] For example, a thermoplastic acrylic ester-based polymer or the like can be used to form the core material 3. When an adhesive is used to form the core material 3, for example, one or a mixture of two or more types selected from an acrylic adhesive, an acrylic-urethane adhesive, a urethane adhesive, a polyester adhesive, a silicone adhesive, and a rubber adhesive can be used.

[0028] The adhesive composition containing the adhesive may be heat-curable or photo-curable, i.e., cured by ultraviolet light or the like. In the case of heat-curable, the adhesive composition preferably contains a known curing agent. In the case of the adhesive composition containing an acrylic adhesive or an acrylic-urethane adhesive, it is preferable to use an isocyanate-based curing agent, an epoxy-based curing agent, a chelate-based curing agent, or a mixture of these curing agents as the curing agent. The content of the curing agent in the core material 3 is not particularly limited as long as the core material 3 can be appropriately thermally expanded, but may be, for example, 0.01% by mass or more and 3.0% by mass or less. If the content of the curing agent is too low, the core material 3 will not be sufficiently cured, and if the content of the curing agent is too high, the core material 3 will become hard and difficult to expand.

[0029] The adhesive composition used to form the core material 3 may at least partially contain a biomass material. The biomass content of the adhesive composition may be, for example, 10% or more, and more preferably 20% or more. The adhesive composition may contain a tackifier derived from a living organism, such as a terpene-based or rosin-based agent.

[0030] The thermally expandable particles 5 added to the core material 3 may be microcapsules in which a substance that easily gasifies and expands when heated, such as isobutane, propane, or pentane, is contained in an elastic shell. The shell is made of a heat-fusible substance or a substance that expands or breaks when thermally expanded. Examples of materials that make up the shell include vinylidene chloride-acrylonitrile copolymers, polyvinyl alcohol, polyvinyl butyral, polymethyl methacrylate, polyacrylonitrile, polyvinylidene chloride, and polysulfone. The microcapsules can be produced by known methods, such as coacervation and interfacial polymerization.

[0031] The expansion start temperature of the thermally expandable particles 5 is not particularly limited as long as it is a temperature at which unintended expansion does not occur during product storage, but from the viewpoint of energy saving, it may be 50° C. or higher and 100° C. or lower. The temperature at which the thermally expandable particles 5 expand to reach the maximum particle size may be approximately 100° C. or higher and 140° C. or lower.

[0032] Commercially available products may be used as the thermally expandable particles 5. Specific examples of commercially available products include those manufactured by Matsumoto Yushi Seiyaku Co., Ltd. under the trade name "Matsumoto Microsphere" (grades: F-30, F-30D, F-36D, F-36LV, F-50, F-50D, F-65, F-65D, HF-36D, HF-48D, FN-100SS, FN-100SSD, FN-180SS, FN-180SSD, F-190D, F-260D, F-2800D), and those manufactured by Nippon Fu Examples of such polymers include "Expancel" (grades: 053-40, 031-40, 007-40) manufactured by Illumina Corporation, "Dieform" (grades: M330, M430) manufactured by Kureha Chemical Industry Co., Ltd., and "Advancell" (grades: EML101, EMH204, EHM301, EHM302, EHM303, EM304, EHM401, EM403, EM501) manufactured by Sekisui Chemical Co., Ltd.

[0033] The average particle size of the unexpanded thermally expandable particles 5 may be, for example, 2 μm to 100 μm, 5 μm to 80 μm, or 8 μm to 50 μm. If the average particle size of the thermally expandable particles 5 is 2 μm or more, the thickness of the core material 3 can be increased with a relatively small amount, and if the average particle size of the thermally expandable particles 5 is 100 μm or less, it is easy to keep the unevenness of the first main surface 14 and the second main surface 16 of the core material 3 small.

[0034] The content of the thermally expandable particles 5 in the core material 3 depends on the adhesive used and the size of the thermally expandable particles 5, but may be from 2% by mass to 50% by mass, preferably from 5% by mass to 40% by mass, and more preferably from 10% by mass to 35% by mass, relative to the total mass of the core material 3. If the content of the thermally expandable particles 5 is too low, the core material 3 does not expand sufficiently even when heated, and if the content of the thermally expandable particles 5 is too high, the adhesion between the core material 3 and the first adhesive layer 11 and the second adhesive layer 13 is likely to be insufficient, and breakage within the core material 3 is likely to occur.

[0035] The adhesives constituting the first adhesive layer 11 and the second adhesive layer 13 may be appropriately selected according to the application and the type of adherend, and are not particularly limited. The adhesive used may be one or a mixture of two or more adhesives selected from acrylic adhesives, acrylic-urethane adhesives, urethane adhesives, silicone adhesives, polyester adhesives, and rubber adhesives. The adhesive may be a water-based adhesive, a solvent-based adhesive, a solventless adhesive, or the like.

[0036] The adhesive composition containing the adhesive may be heat-curable or photo-curable, i.e. cured by ultraviolet light or the like. In the case of heat-curable, the adhesive composition preferably contains a known curing agent. In the case of the adhesive composition containing an acrylic adhesive or an acrylic-urethane adhesive, it is preferable to use an isocyanate-based curing agent, an epoxy-based curing agent, a chelate-based curing agent, or a mixture of these curing agents as the curing agent.

[0037] The compositions of the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 13 may be the same as or different from each other. In cases where the types of adherends of the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 13 are different, the compositions of the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 13 may be changed according to the respective adherends.

[0038] The adhesive that is the main agent of the first adhesive layer 11 and the second adhesive layer 13 and the adhesive that is the main agent of the core material 3 may be the same type of adhesive, and the first adhesive layer 11, the second adhesive layer 13, and the core material 3 may be formed of a cured product of the same adhesive. In this case, the adhesion between the first adhesive layer 11 and the second adhesive layer 13 and the core material 3 is improved, so that interlayer delamination is unlikely to occur between these adhesive layers and the core material 3 when the double-sided adhesive tape 10 is peeled off. As an example, an acrylic adhesive may be used to form the first adhesive layer 11, the second adhesive layer 13, and the core material 3. In this case, it is preferable from the viewpoint that the double-sided adhesive tape 10 is a mono-material tape mainly composed of an acrylic adhesive, and recycling such as chemical recycling can be easily performed.

[0039] The adhesive composition used to form the first adhesive layer 11 and the second adhesive layer 13 may contain a biomass material. The biomass degree of the adhesive composition may be, for example, 10% or more, and more preferably 20% or more. The adhesive composition may contain a tackifier derived from a living organism, such as a terpene-based or rosin-based agent.

[0040] The thickness of the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 13 is not particularly limited and may be, for example, 2 μm to 200 μm, or 5 μm to 100 μm. By setting the thickness of the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 13 within the above range, it is possible to easily obtain a desired adhesive strength to an adherend before and after foaming treatment while suppressing production costs.

[0041] The first release liner 7 and the second release liner 1 may have the same structure or different structures. Known release liners made of resin or paper can be used as the first release liner 7 and the second release liner 1. When one release liner has a resin film substrate such as polyethylene terephthalate (PET) and the other release liner has a paper substrate such as fine paper, it is preferable because it is easier to wind the release liner into a roll than when both release liners have a resin film substrate. The release force required to peel the first release liner 7 and the release force required to peel the second release liner 1 may be approximately equal, or the release force may be different, with one being light and the other being heavy.

[0042] In the double-sided adhesive tape 10 of this embodiment, the first adhesive layer 11 or the second adhesive layer 13 is attached to a SUS steel plate with an attachment area of ​​25 mm × 25 mm, and a load of 1 kg is applied vertically downward at 40° C. After 50,000 seconds, the total amount of displacement is preferably 25 mm or less. Here, the "total amount of displacement" refers to the total value of the amount of displacement in the first adhesive layer 11 and the second adhesive layer 13 and the amount of displacement in the core material 3.

[0043] Furthermore, even after the thermally expandable particles in the core material 3 are expanded, the total amount of displacement under the above conditions may be 25 mm or less.

[0044] In this way, the double-sided adhesive tape 10 can maintain good holding power both before and after the thermal foaming process, so that even when the tape is placed vertically relative to the ground, for example, when attaching a nameplate, it is possible to fix one adherend for a long period of time without the adherend falling off the other adherend.

[0045] [Manufacturing method of double-sided adhesive tape] When preparing the double-sided adhesive tape 10 of this embodiment, first, a coating liquid is prepared by adding an appropriate amount of a curing agent and a predetermined amount of thermally expandable particles 5 to the adhesive and mixing them. The amount of the thermally expandable particles 5 added is, for example, 2% by mass or more and 50% by mass or less based on the resin solid content of the adhesive. Next, the coating liquid is applied to the release surface of a paper or resin film release liner (not shown) using a comma-type coater or the like so as to have a desired thickness after drying and foaming, thereby forming a core material 3 containing thermally expandable particles 5. Here, the core material 3 is dried at a temperature lower than the foaming start temperature of the thermally expandable particles 5 in order to keep the thermally expandable particles 5 in an unexpanded state. Next, another release liner is attached to the exposed surface of the core material 3 to prepare a substrate-less tape having only the core material 3.

[0046] Next, a coating liquid made of a pressure-sensitive adhesive composition is applied to a predetermined thickness on the release surface of the first release liner 7 on the light release side, and dried to form a first pressure-sensitive adhesive layer 11. The core material 3 with one release liner peeled off is then bonded to the first pressure-sensitive adhesive layer 11. Next, a coating liquid made of a pressure-sensitive adhesive composition is applied to a predetermined thickness on the release surface of the second release liner 13 on the heavy release side, and dried to form a second pressure-sensitive adhesive layer 13. The core material 3 with the other release liner peeled off is then bonded to the second pressure-sensitive adhesive layer 13 to produce a pressure-sensitive adhesive tape laminate 20 having a double-sided pressure-sensitive adhesive tape 10. The double-sided pressure-sensitive adhesive tape 10 is then aged, for example, at 40° C. for about 72 hours.

[0047] Second embodiment 3(a) and (b) are cross-sectional views showing a method for manufacturing a metal plate product according to a second embodiment of the present disclosure. Hereinafter, a method for manufacturing a metal plate product such as a nameplate will be described as an application example of the double-sided adhesive tape 10 according to the first embodiment.

[0048] As shown in Fig. 3(a), for example, a quadrilateral metal plate 17 made of aluminum or the like is attached to the back surface of the double-sided adhesive tape 10 from the side of the first adhesive layer 11 exposed by peeling off the first release liner 7 (see Fig. 1). Before this step, letters or the like may be printed on the upper surface of the metal plate 17, or a label with letters or the like printed thereon may be attached.

[0049] Next, as shown in Fig. 3(b), the metal sheet laminate 30 having the metal sheet 17 and the double-sided adhesive tape 10 is placed on a die (lower mold), and a punch (upper mold) is lowered from above to perform a punching process, thereby producing a plurality of metal sheet processed products 30a having a predetermined planar shape. At this time, burrs 8 are generated on the peripheral portion of the back surface of the metal sheet 17. The height of the burrs 8 may exceed the thickness of the double-sided adhesive tape 10.

[0050] Next, the metal plate processed product 30a is placed in a drying furnace and heated for 5 minutes or more at a temperature sufficiently higher than the foaming start temperature of the thermally expandable particles 5 to expand the core material 3. This process increases the thickness of the double-sided adhesive tape 10, and makes it sufficiently thicker than the height of the burrs 8.

[0051] According to this method, since the double-sided adhesive tape 10 is attached in a thin state when the metal plate 17 is punched, it is possible to easily process the metal plate 17. Furthermore, since the double-sided adhesive tape 10 becomes thicker by heating after the punching process, it becomes possible to attach the second adhesive layer 13 to the adherend even if burrs 8 are generated.

[0052] Therefore, according to the method of the present embodiment, the number of steps in manufacturing the metal plate processed product 30a can be reduced compared to a method in which a double-sided adhesive tape having a thickness exceeding the burr 8 is attached to each of the individualized metal plates 17. Also, compared to a case in which the adhesive layer of the double-sided adhesive tape is made thicker, the amount of adhesive component that protrudes during the punching process can be reduced, and the amount of adhesive component that adheres to the punch can also be reduced.

[0053] The step of removing burrs 8 is not necessarily required, but burrs 8 may be removed before applying double-sided adhesive tape 10.

[0054] The metal plate processed product 30a of this embodiment produced by the above method includes a metal plate 17, a core material 3, a first adhesive layer 11 bonded to the metal plate 17, a second adhesive layer 13, and a second release liner 1 provided on the surface of the second adhesive layer 13 opposite the core material 3. The core material 3 contains thermally expandable particles 5 in an expanded state.

[0055] As described above, the double-sided adhesive tape 10 used in the method of this embodiment may have a first adhesive layer 11 or second adhesive layer 13 bonded to a SUS steel plate with an application area of ​​25 mm x 25 mm before and after thermal expansion treatment, and a load of 1 kg is applied vertically downward at 40°C, and the total displacement after 50,000 seconds has elapsed may be 25 mm or less.

[0056] (Third embodiment) As a third embodiment of the present invention, an example in which the double-sided pressure-sensitive adhesive tape 10 according to the first embodiment fills a gap in an adherend or a gap between a first adherend and a second adherend will be described.

[0057] The article according to this embodiment includes an adherend having a void formed therein, at least one of a first adherend and a second adherend arranged with a gap therebetween, a core material 3 having a first main surface 14 and a second main surface 16 opposite the first main surface 14 and formed of a resin such as a cured adhesive product, and a double-sided adhesive tape 10 (see FIG. 1 ) having a first adhesive layer 11 formed on the first main surface 14 of the core material 3 and a second adhesive layer 13 formed on the second main surface 16 of the core material 3. The core material 3 contains thermally expandable particles 5 after expansion, and the double-sided adhesive tape 10 fills the voids in the adherend or the voids between the first adherend and the second adherend.

[0058] An example of a first adherend and a second adherend arranged with a gap between them is, for example, a stator core and a conductor coil in a motor generator described in JP 2021-121671 A. The double-sided adhesive tape 10 according to the first embodiment is attached to the stator core or coil, and then heated for 5 minutes or more at a temperature sufficiently higher than the foaming start temperature of the thermally expandable particles 5, thereby filling the gap between the stator core and the conductor coil. Both the first adhesive layer 11 and the second adhesive layer 13 do not lose their adhesive force to the adherend even after the foaming treatment, so that the stator core and the coil can be electrically insulated while being fixed.

[0059] The adherend is not limited to the stator core and the conductor coil. According to the double-sided adhesive tape 10 of the first embodiment, the thickness increases after application, so that it is easy to apply even when the gap in the adherend or the gap between two adherends is narrow, and it is possible to reliably fill the gap after heat treatment. In addition, since an adhesive that retains tack and adhesive strength even after heating is used instead of an adhesive that hardens after heating, the double-sided adhesive tape 10 does not fall off during use of the product, and when disposing of the product, the double-sided adhesive tape 10 can be easily peeled off and disposed of separately.

[0060] (Fourth embodiment) 4 is a cross-sectional view showing a tamper-evident tape 40 according to a fourth embodiment of the present disclosure, which will be described below as one application example of the double-sided adhesive tape 10 according to the first embodiment shown in FIG.

[0061] 4, the tamper-evident tape 40 includes a brittle substrate 27 and a double-sided adhesive tape 10 attached to at least one surface of the brittle substrate 27. The double-sided adhesive tape 10 has a first main surface 14 and a second main surface 16 opposite the first main surface 14, and includes a core material 3 formed of a resin such as an adhesive cured product containing unexpanded thermally expandable particles 5, a first adhesive layer 11 formed on the first main surface 14 of the core material 3 and attached to the brittle substrate 27, and a second adhesive layer 13 formed on the second main surface 16 of the core material 3.

[0062] Brittle substrate 27 is made of a material that easily breaks when peeled off from an adherend. Examples of brittle substrate 27 that can be used include paper such as glassine paper and transparent paper, polyvinyl chloride resin sheets, polystyrene resin sheets, ABS resin sheets, polyvinyl alcohol resin sheets, acrylic resin sheets, polylactic acid resin sheets, and cellophane films.

[0063] The tamper-evident tape 40 is used, for example, to seal the lid of a container or a box. If an attempt is made to peel off the tamper-evident tape 40 for the purpose of stealing the contents of a container or box or replacing a genuine product with an ungenuine product, the brittle substrate 27 breaks at room temperature, revealing that someone has attempted to tamper with the contents. In addition, if an attempt is made to heat the second adhesive layer 13 in an attempt to peel off the tamper-evident tape 40 without breaking it, the thermally expandable particles 5 in the core material 3 will foam, making the core material 3 more likely to break. For this reason, when the tamper-evident tape 40 is peeled off, the second adhesive layer 13 and a part of the broken core material 3 will remain on the adherend side.

[0064] Therefore, the tamper-evident tape 40 of this embodiment can more effectively prevent tampering with the adherend.

[0065] In addition, when using a tape having only an adhesive layer containing heat-expandable particles provided on the back surface of a brittle substrate, the adhesive layer may lose its adhesive force to the adherend after the heat-expandable particles expand upon heating, and no adhesive components may remain on the adherend.

[0066] In contrast, according to the tamper-proof tape 40 of the present embodiment, a second adhesive layer 13 is provided in addition to the core material 3 containing the heat-expandable particles 5, so that the adhesive components remain on the adherend even when heated, making it possible to more reliably detect tampering with the adherend.

[0067] The configuration of the double-sided adhesive tape 10 and its application products described above is one example of an embodiment, and the constituent materials, thicknesses of each layer, physical properties, etc. can be changed as appropriate without departing from the spirit of the present invention. EXAMPLES

[0068] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0069] [Preparation of double-sided adhesive tape, etc.] <Example 1> A coating liquid was prepared by adding and mixing 1.2 parts by mass of a commercially available isocyanate-based curing agent (resin content 45%) and an amount of thermally expandable particles that was 10% by mass of the resin solid content of the adhesive to 100 parts by mass of a commercially available strong adhesive type acrylic adhesive (resin solid content 37 to 39%). Next, the coating liquid was applied to the release surface of a paper release liner (not shown) using a comma-type coater or the like so that the thickness would be 50 μm after drying and foaming, forming a core material containing thermally expandable particles. Next, another release liner was attached to the exposed surface of the core material to prepare a substrateless tape having only the core material.

[0070] The thermally expandable particles used were Matsumoto Microsphere (registered trademark) HF-48D, manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd. The average particle size of these thermally expandable particles was 9 to 15 μm, the expansion initiation temperature was 90° C. to 100° C., the maximum particle size was 36 μm to 60 μm, and the temperature at the maximum particle size was 125° C. to 135° C. In order to keep the thermally expandable particles in an unexpanded state, the core material was dried at 80° C., which is lower than the expansion initiation temperature of the thermally expandable particles.

[0071] Next, a coating liquid made of an adhesive composition was applied to a predetermined thickness on the release surface of the first release liner (Asahi color, a wood-free paper-based release paper manufactured by Nichiei Shinka Co., Ltd.) on the light release side, and dried to form a first adhesive layer with a thickness of 50 μm. The core material with one release liner peeled off was then bonded to this first adhesive layer. Next, a coating liquid made of the same adhesive composition as that used for the first adhesive layer was applied to a predetermined thickness on the release surface of the second release liner (Wasabi color, a wood-free paper-based release paper manufactured by Nichiei Shinka Co., Ltd.) on the heavy release side, and dried to form a second adhesive layer with a thickness of 50 μm. Next, the core material with the other release liner peeled off was bonded to the second adhesive layer to produce an adhesive tape laminate having a double-sided adhesive tape. The double-sided adhesive tape was then aged at 40° C. for about 72 hours.

[0072] <Examples 2 and 3> As Example 2, a double-sided pressure-sensitive adhesive tape was produced by the same method as in Example 1, except that in the step of forming the core material, a coating liquid was prepared by adding thermally expandable particles in an amount of 20% by mass relative to the resin solid content of the adhesive. Also, as Example 3, a double-sided pressure-sensitive adhesive tape was produced by the same method as in Example 1, except that a coating liquid was prepared by adding thermally expandable particles in an amount of 30% by mass relative to the resin solid content of the adhesive.

[0073] <Comparative Examples 1 to 3> In order to compare the adhesive strength after foaming treatment with the double-sided adhesive tapes prepared in Examples 1 to 3, substrate-less tapes having the same composition and thickness as the core material of the double-sided adhesive tapes prepared in Examples 1 to 3 were prepared as Comparative Examples 1 to 3.

[0074] Specifically, a coating liquid consisting of a pressure-sensitive adhesive composition containing a predetermined amount of thermally expandable particles was applied to the release surface of a commercially available PET release liner (heavy release side) using a comma-type coater, and the coating liquid was dried at 80°C to form a 50 μm thick pressure-sensitive adhesive layer. The composition of the pressure-sensitive adhesive composition used, other than the thermally expandable particles, was the same as that of the core material, the first pressure-sensitive adhesive layer, and the second pressure-sensitive adhesive layer prepared in Examples 1 to 3. Here, in Comparative Example 1, a pressure-sensitive adhesive layer was prepared by adding 10% by mass of thermally expandable particles to the resin solid content of the pressure-sensitive adhesive used. In Comparative Examples 2 and 3, pressure-sensitive adhesive layers were prepared by adding 20% ​​by mass and 30% by mass of thermally expandable particles to the resin solid content of the pressure-sensitive adhesive used, respectively. Next, a commercially available PET release liner (light release side) was attached to the exposed surface of the pressure-sensitive adhesive layer to prepare a substrate-less tape. The tape was cured at 40°C for about 72 hours.

[0075] [Measurement method] <Measurement of tape thickness> A commercially available micrometer was used to measure the thickness of the double-sided adhesive tapes produced in Examples 1 to 3. Measurements of the double-sided adhesive tapes after foaming shown in Table 1 were performed by heating a test piece of the double-sided adhesive tape with a release liner cut to a predetermined size in a drying oven at 125°C for 5 minutes to foam the thermally expandable particles, and then returning the temperature to 23°C.

[0076] <Adhesive strength measurement> The double-sided adhesive tape before foaming prepared in Examples 1 to 3 was cut into a strip of 25 mm width and 25 mm length to prepare a test piece, and then the first release liner was peeled off and a 25 μm thick backing material (biaxially stretched PET film) that had not been surface-treated was attached to the exposed surface. In this state, the second release liner on the heavy release side was peeled off, and the exposed surface was attached to a SUS steel plate or aluminum plate that had been polished with water-resistant paper with a grain size of #360 by a method conforming to JIS Z 0237 to measure the adhesive strength. The test piece was attached to the SUS steel plate or aluminum plate as the adherend, and pressed by two reciprocating strokes with a 2 kg roller, and measurements were taken after 20 minutes and 24 hours at 23°C and 50% relative humidity. The peel speed of the test piece during measurement was 300 mm / min, the peel angle was 180 degrees, and the measurement was performed using a universal material testing machine (TENSILON RT1-1225 manufactured by A&D Co., Ltd.). The adhesive strength of the double-sided pressure-sensitive adhesive tapes produced in Comparative Examples 1 to 3 was measured in the same manner as above, using only an aluminum plate as the adherend. Measurements after foaming treatment were performed after the test piece was attached to a SUS steel plate or an aluminum plate, placed in a drying oven and foamed at 125°C for 5 minutes, and then returned to an environment of 23°C and a relative humidity of 50%.

[0077] The substrate-less tapes prepared in Comparative Examples 1 to 3 were cut into strips of 25 mm width and 25 mm length to prepare test pieces, and then the release liner on the light release side was peeled off and a PET backing material of 25 μm thickness was attached. Next, the release liner on the heavy release side was peeled off and the substrate-less tape was attached to an aluminum plate as an adherend, and pressed with a 2 kg roller twice, and measurements were taken after 20 minutes and 24 hours at 23°C and 50% relative humidity. Measurements after foaming treatment were taken after the test pieces attached to the aluminum plate were placed in a drying oven and foamed at 125°C for 5 minutes, and then returned to an environment of 23°C and 50% relative humidity.

[0078] <Measurement of retention and retention duration> A test piece measuring 25 mm wide and 100 mm long was cut out from each of the double-sided adhesive tapes prepared in Examples 1 to 3, a 25 μm thick backing material (biaxially oriented PET film) was attached to the first adhesive layer on the light release side, and a 25 mm×25 mm portion of the second adhesive layer at one end of the test piece was attached to a SUS steel plate. The square portion attached to the SUS steel plate was strongly and uniformly pressed with a squeegee.

[0079] Next, the SUS steel plate was placed vertically so that the square part of the test piece was at the top, and a 1 kg weight was hung from the other end of the test piece that was at the bottom. In this state, the time until the double-sided adhesive tape was completely peeled off was measured as the holding power duration before foaming. If the test piece had not fallen off within 50,000 seconds from the start of the measurement, the amount of displacement of the test piece (unit: mm) was measured as a value representing the holding power. The measurement was performed at 40°C.

[0080] The measurements after foaming shown in Table 1 were performed by attaching a backing material to the first adhesive layer, attaching the second adhesive layer to a SUS steel plate, and then heating in a drying oven at 125°C for 5 minutes in an atmosphere of 40°C.

[0081] <Ball tack measurement> For the double-sided pressure-sensitive adhesive tapes produced in Examples 1 to 3, ball tack was measured by the J.DOW method in accordance with JIS Z0237.

[0082] [Measurement results] Table 1 shows the measurement results of adhesive strength, holding power and ball tack for the double-sided pressure-sensitive adhesive tapes produced in Examples 1-3.

[0083] [Table 1] Table 2 shows the results of measuring the adhesive strength of the substrate-less tapes produced in Comparative Examples 1-3.

[0084] [Table 2] As shown in Table 1, in the double-sided adhesive tapes of Examples 1 to 3, which have a core material containing thermally expandable particles, the thickness of the core material increased by about 4 to 8 times after the foaming treatment, and it was confirmed that the increase in thickness increased as the amount of thermally expandable particles added increased.

[0085] In addition, there was no difference in the adhesive strength to SUS and to Al between the light and heavy release sides of the double-sided adhesive tape, and in the double-sided adhesive tapes of Examples 1 and 2, there was not much decrease in adhesive strength after the foaming treatment, and in fact in some test pieces the adhesive strength was greater after the foaming treatment. In the double-sided adhesive tape of Example 3, which had a relatively large amount of added thermally expandable particles, the adhesive strength to SUS and to Al decreased after the foaming treatment, but even in the test piece with the greatest decrease in adhesive strength, about 50% of the adhesive strength before the foaming treatment was retained.

[0086] In contrast, the results of Comparative Examples 2 and 3 shown in Table 2 confirmed that when thermally expandable particles were contained in the pressure-sensitive adhesive layer that contacted the adherend, the adhesive strength decreased. However, since the adhesive strength to the adherend did not decrease in the substrate-less tape of Comparative Example 1, which had a relatively low amount of added thermally expandable particles, it was believed that the decrease in adhesive strength became more noticeable as the amount of added thermally expandable particles increased.

[0087] The adhesive layers constituting the substrate-less tapes of Comparative Examples 1 to 3 have the same composition and thickness as the core materials of the double-sided adhesive tapes of Examples 1 to 3. Therefore, from the results shown in Table 2, it is inferred that the adhesion between the core material and the first adhesive layer and the second adhesive layer is good even after the foaming treatment.

[0088] As shown in Table 1, the total deviation value in the holding power measurement of the double-sided adhesive tapes produced in Examples 1 to 3 was all 25 mm or less, confirming that all of the double-sided adhesive tapes had good holding power.

[0089] From the ball tack results shown in Table 1, it was confirmed that, although the double-sided pressure-sensitive adhesive tapes of Examples 1 to 3 tended to have weaker tack after the foaming treatment, they still retained some tack. [Industrial Applicability]

[0090] The double-sided pressure-sensitive adhesive tape disclosed in this specification can be used in a variety of fields, such as for fixing components, filling gaps, and as a constituent material for tamper-proof tape. [Explanation of symbols]

[0091] 1 Second release liner 3 Core material 5. Thermoexpandable particles 6 First Adherend 7 First release liner 8. Bali 10 Double-sided adhesive tape 11 First adhesive layer 12 Second Adherend 13 Second adhesive layer 14 First main surface 16 Second main surface 17 Metal plate 20 Laminate 27 Brittle substrate 30 Metal plate laminate 30a Metalwork 40 Tamper-evident tape

Claims

1. A core material having a first main surface and a second main surface opposite to the first main surface, the core material being formed of a resin containing unexpanded thermally expandable particles; a first pressure-sensitive adhesive layer formed on the first main surface of the core material; a second adhesive layer formed on the second main surface of the core material.

2. The double-sided pressure-sensitive adhesive tape according to claim 1 , wherein the core material is formed from a cured pressure-sensitive adhesive.

3. The double-sided pressure-sensitive adhesive tape according to claim 1 , wherein neither the first pressure-sensitive adhesive layer nor the second pressure-sensitive adhesive layer contains thermally expandable particles.

4. 2. The double-sided pressure-sensitive adhesive tape according to claim 1, wherein when the thermally expandable particles in the core material are expanded for 5 minutes at a temperature that is 10° C. or more higher than the expansion initiation temperature, a value of (thickness of the core material after expansion) / (thickness of the core material before expansion) is 1.5 or more and 20.0 or less.

5. When the thermally expandable particles in the core material are expanded for 5 minutes at a temperature 10° C. or more higher than the expansion initiation temperature, 2. The double-sided adhesive tape according to claim 1, wherein the adhesive strength of at least one of the first adhesive layer and the second adhesive layer to a SUS steel plate after 24 hours at 23°C and a relative humidity of 50% after the thermally expandable particles have been expanded is from 0.1 to 3.0 times the adhesive strength to the SUS steel plate before the thermally expandable particles are expanded.

6. 2. The double-sided adhesive tape according to claim 1, wherein the first adhesive layer or the second adhesive layer is attached to a SUS steel plate, and the total amount of displacement after 50,000 seconds has elapsed at 40°C under a load of 1 kg is 25 mm or less.

7. 2. The double-sided adhesive tape according to claim 1, wherein after the thermally expandable particles in the core material are expanded, the first pressure-sensitive adhesive layer or the second pressure-sensitive adhesive layer is bonded to a SUS steel plate, and the total amount of displacement after 50,000 seconds has elapsed at 40°C under a load of 1 kg is 25 mm or less.

8. 2. The double-sided pressure-sensitive adhesive tape according to claim 1, which is used to fill a gap in an adherend or a gap between a first adherend and a second adherend.

9. The double-sided adhesive tape according to any one of claims 1 to 8, wherein the adhesive used to form the core material is the same as the adhesive used to form the first adhesive layer and the second adhesive layer.

10. A metal plate; a core material having a first main surface and a second main surface opposite to the first main surface and formed of a resin; a first adhesive layer formed on the first main surface of the core material and attached to the metal plate; and a second adhesive layer formed on the second main surface of the core material; The core material is a metal plate product containing thermally expandable particles in an expanded state.

11. an adherend having a gap formed therein, and at least one of a first adherend and a second adherend arranged with a gap therebetween; a double-sided adhesive tape having a first main surface and a second main surface opposite to the first main surface, the double-sided adhesive tape including a core material formed of a resin, a first adhesive layer formed on the first main surface of the core material, and a second adhesive layer formed on the second main surface of the core material; The core material includes thermally expandable particles after expansion, An article, wherein the double-sided pressure-sensitive adhesive tape fills a gap in the adherend or a gap between the first adherend and the second adherend.

12. A brittle base material; and a double-sided adhesive tape attached to at least one surface of the brittle substrate, The double-sided adhesive tape is A core material having a first main surface and a second main surface opposite to the first main surface, the core material being formed of a resin containing unexpanded thermally expandable particles; a first pressure-sensitive adhesive layer formed on the first main surface of the core material and bonded to the brittle base material; a second adhesive layer formed on the second main surface of the core material.

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