High frequency dielectric heating adhesive sheet

Abstract

The present invention relates to a high-frequency dielectric heating adhesive sheet (1), which comprises: a first adhesive layer (10) containing a first thermoplastic resin and a first dielectric filler, and a second adhesive layer (20) containing a second thermoplastic resin and a second dielectric filler, wherein the volume content VA1 of the first thermoplastic resin in the first adhesive layer (10) and the volume content VA2 of the second thermoplastic resin in the second adhesive layer (20) are 60 volume % or more and 100 volume % or less, and the change rates Vx1 and Vx2 of the following formulas are less than 80%. VB1 is the volume content of the first thermoplastic resin in the layer directly in contact with the first adhesive layer (10), and VB2 is the volume content of the second thermoplastic resin in the layer directly in contact with the second adhesive layer (20). Vx1={(VA1-VB1) / VA1}×100···(Mathematical formula 1) Vx2={(VA2-VB2) / VA2}×100···(Mathematical formula 2).

Description

Technical Field

[0001] The invention relates to a high frequency dielectric heating adhesive sheet. Background Art

[0002] In recent years, as a method of bonding adherends that are usually difficult to bond, methods have been proposed, such as sandwiching an adhesive made of a heat-generating material blended in a given resin between the adherends and performing dielectric heating treatment, induction heating treatment, ultrasonic welding treatment, or laser welding treatment.

[0003] For example, Patent Document 1 describes a sheet-shaped thermal adhesive prepared by blending at least one fine powder selected from carbon black, silicon oxide, metal, and metal oxide.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 58-174474 Summary of the invention

[0007] Problems to be solved by the invention

[0008] When trying to bond adherends (first adherend and second adherend) of different materials to each other using the thermal adhesive described in Patent Document 1, sufficient bonding strength may not be obtained. In particular, it is difficult to obtain sufficient bonding strength when the adherend is made of a difficult-to-bond material.

[0009] An object of the present invention is to provide a high-frequency dielectric heating adhesive sheet capable of firmly bonding a first adherend and a second adherend made of different materials.

[0010] Solution to the problem

[0011] According to one embodiment of the present invention, there is provided a high-frequency dielectric heating adhesive sheet, the high-frequency dielectric heating adhesive sheet having a first adhesive layer and a second adhesive layer as outermost layers, the second adhesive layer being located on a surface side opposite to the first adhesive layer, the first adhesive layer containing a first thermoplastic resin and a first dielectric filler that generates heat at a high frequency, the second adhesive layer containing a second thermoplastic resin and a second dielectric filler that generates heat at a high frequency, the first thermoplastic resin and the second thermoplastic resin being different resins from each other, the volume content VA1 of the first thermoplastic resin being 60 volume % or more and 100 volume % or less relative to the total thermoplastic resin in the first adhesive layer, and the volume content VA1 of the first thermoplastic resin being 60 volume % or more and 100 volume % or less relative to the total thermoplastic resin in the second adhesive layer. The first thermoplastic resin is a thermoplastic resin, the volume content VA2 of the second thermoplastic resin is greater than 60 volume % and less than 100 volume %, the change rate Vx1 of the volume content VA1 of the first thermoplastic resin and VB1 represented by the following mathematical formula (Mathematical Formula 1) is less than 80%, and the volume content VA2 of the second thermoplastic resin represented by the following mathematical formula (Mathematical Formula 2) and VB2 is less than 80%, and the volume content VB2 is the volume content of the second thermoplastic resin relative to the total thermoplastic resin in the layer directly in contact with the second adhesive layer.

[0012] Vx1={(VA1-VB1) / VA1}×100···(Mathematical formula 1)

[0013] Vx2={(VA2-VB2) / VA2}×100···(Formula 2)

[0014] In one embodiment of the high-frequency dielectric heating adhesive sheet of the present invention, the high-frequency dielectric heating adhesive sheet is preferably a sheet for joining a first adherend and a second adherend of a material different from that of the first adherend, the first adherend contains a third thermoplastic resin, the second adherend contains a fourth thermoplastic resin, the main composition of the first thermoplastic resin is the same as the main composition of the third thermoplastic resin, the main composition of the second thermoplastic resin is the same as the main composition of the fourth thermoplastic resin, the first adhesive layer is bonded to the first adherend, and the second adhesive layer is bonded to the second adherend.

[0015] In the high-frequency dielectric heating adhesive sheet according to one embodiment of the present invention, at least one of the volume content of the first dielectric filler in the first adhesive layer and the volume content of the second dielectric filler in the second adhesive layer is preferably 5 volume % or more and 50 volume % or less.

[0016] In the high-frequency dielectric heating adhesive sheet according to one aspect of the present invention, it is preferred that at least one of the first dielectric filler and the second dielectric filler is at least one selected from the group consisting of zinc oxide, silicon carbide, titanium oxide, and barium titanate.

[0017] In the high-frequency dielectric heating adhesive sheet of one embodiment of the present invention, it is preferred that at least one of the volume average particle size of the first dielectric filler and the volume average particle size of the second dielectric filler is 1 μm or more and 30 μm or less. The volume average particle size is a volume average particle size calculated according to JIS Z 8819-2:2001 based on the particle size distribution of at least one of the first dielectric filler and the second dielectric filler measured by a laser diffraction / scattering method.

[0018] In the high-frequency dielectric heating adhesive sheet according to one embodiment of the present invention, it is preferable that the first thermoplastic resin is a polyolefin-based resin.

[0019] In the high-frequency dielectric heating adhesive sheet according to one embodiment of the present invention, the absolute value of the difference between the flow start temperature Tx1 of the first thermoplastic resin and the flow start temperature Tx2 of the second thermoplastic resin preferably satisfies the relationship of the following equation (Equation 4).

[0020] |Tx1-Tx2|≤70···(Formula 4)

[0021] In the high-frequency dielectric heating adhesive sheet of one embodiment of the present invention, it is preferred that the proportion of the number of grids that adhere to the layer in contact with the layer without peeling off in all the layers of the high-frequency dielectric heating adhesive sheet after the cross-cut test according to JIS K5600-5-6:1999 is 50% or more.

[0022] The high-frequency dielectric heating adhesive sheet according to one aspect of the present invention preferably further includes an intermediate layer disposed between the first adhesive layer and the second adhesive layer.

[0023] In the high-frequency dielectric heating adhesive sheet according to one aspect of the present invention, it is preferred that the intermediate layer contain the first thermoplastic resin and the second thermoplastic resin.

[0024] In the high-frequency dielectric heating adhesive sheet according to one embodiment of the present invention, it is preferred that the first adhesive layer is in direct contact with the intermediate layer, and the second adhesive layer is in direct contact with the intermediate layer.

[0025] In the high-frequency dielectric heating adhesive sheet according to one aspect of the present invention, it is preferable that the layer in direct contact with the first adhesive layer is the second adhesive layer.

[0026] According to one aspect of the present invention, a high-frequency dielectric heating adhesive sheet capable of firmly bonding a first adherend and a second adherend made of different materials can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the high-frequency dielectric heating adhesive sheet according to the first embodiment.

[0028] Figure 2 This is a schematic diagram for explaining a high-frequency dielectric heating process using the high-frequency dielectric heating adhesive sheet and the dielectric heating device according to the first embodiment.

[0029] Figure 3 It is a schematic diagram of a high-frequency dielectric heating adhesive sheet according to a second embodiment.

[0030] Figure 4 This is a schematic diagram for explaining a high-frequency dielectric heating process using the high-frequency dielectric heating adhesive sheet and the dielectric heating device according to the second embodiment.

[0031] Explanation of symbols

[0032] 1···high-frequency dielectric heating adhesive sheet, 10···first adhesive layer, 11···first surface, 110···first adherend, 120···second adherend, 1A···high-frequency dielectric heating adhesive sheet, 20···second adhesive layer, 21···second surface, 30···intermediate layer, 50···dielectric heating adhesive device, 51···first high-frequency applying electrode, 52···second high-frequency applying electrode, 53···high-frequency power supply. DETAILED DESCRIPTION

[0033] [First embodiment]

[0034] [High frequency dielectric heating adhesive sheet]

[0035] The high-frequency dielectric heating adhesive sheet of the present embodiment includes a first adhesive layer and a second adhesive layer as outermost layers, and the second adhesive layer is located on the surface side opposite to the first adhesive layer.

[0036] The first adhesive layer contains a first thermoplastic resin and a first dielectric filler that generates heat at high frequencies.

[0037] The second adhesive layer contains a second thermoplastic resin and a second dielectric filler that generates heat at a high frequency.

[0038] The first thermoplastic resin and the second thermoplastic resin are different resins from each other.

[0039] The volume content VA1 of the first thermoplastic resin is 60% by volume or more and 100% by volume or less relative to the total thermoplastic resin in the first adhesive layer.

[0040] The volume content VA2 of the second thermoplastic resin is 60% by volume or more and 100% by volume or less relative to the total thermoplastic resin in the second adhesive layer.

[0041] The change rate Vx1 of the volume content VA1 of the first thermoplastic resin represented by the following mathematical formula (Mathematical Formula 1) and VB1 is less than 80%, wherein VB1 is the volume content of the first thermoplastic resin relative to all thermoplastic resins in the layer directly contacting the first adhesive layer.

[0042] The volume content VA2 of the second thermoplastic resin represented by the following mathematical formula (Mathematical Formula 2) and the change rate Vx1 of VB2 are less than 80%, wherein VB2 is the volume content of the second thermoplastic resin relative to the total thermoplastic resin in the layer directly contacting the second adhesive layer.

[0043] Vx1={(VA1-VB1) / VA1}×100···(Mathematical formula 1)

[0044] Vx2={(VA2-VB2) / VA2}×100···(Formula 2)

[0045] The change rate Vx1 is preferably greater than 0%, more preferably 10% or more, further preferably 20% or more, and still further preferably 25% or more.

[0046] The change rate Vx1 is preferably 75% or less.

[0047] The change rate Vx2 is preferably greater than 0%, more preferably 10% or more, further preferably 20% or more, and further preferably 25% or more.

[0048] The change rate Vx2 is preferably 75% or less.

[0049] The change rates Vx1 and Vx2 may be the same as or different from each other.

[0050] Since the change rates Vx1 and Vx2 are both less than 80%, a high-frequency dielectric heating adhesive sheet that is less likely to undergo interlayer delamination can be obtained.

[0051] The unit of the volume contents VA1, VB1, VA2, and VB2 is volume %.

[0052] The high-frequency dielectric heating adhesive sheet of the present embodiment can bond a first adherend and a second adherend made of different materials to each other.

[0053] Hereinafter, the high-frequency dielectric heating adhesive sheet according to the present embodiment will be described in detail.

[0054] Figure 1A schematic cross-sectional view of an example of a high-frequency dielectric heating adhesive sheet of the present embodiment is shown. The high-frequency dielectric heating adhesive sheet 1 has a first adhesive layer 10 and a second adhesive layer 20 as an outermost layer located on the surface side opposite to the first adhesive layer 10. The high-frequency dielectric heating adhesive sheet 1 has a first surface 11 and a second surface 21 on the side opposite to the first surface 11.

[0055] In the high-frequency dielectric heating adhesive sheet 1, the layer directly contacting the first adhesive layer 10 is the second adhesive layer 20. When the first adhesive layer 10 and the second adhesive layer 20 are directly contacting each other, the meanings of the symbols in the above formulas (Formula 1) and (Formula 2) are as follows.

[0056] VA1: Volume content of the first thermoplastic resin relative to the total thermoplastic resin in the first adhesive layer 10

[0057] VB1: Volume content of the first thermoplastic resin relative to the total thermoplastic resin in the second adhesive layer 20

[0058] VA2: Volume content of the second thermoplastic resin relative to the total thermoplastic resin in the second adhesive layer 20

[0059] VB2: Volume content of the second thermoplastic resin relative to the total thermoplastic resin in the first adhesive layer 10

[0060] (Thermoplastic resin)

[0061] In the high-frequency dielectric heating adhesive sheet of the present embodiment, the first thermoplastic resin and the second thermoplastic resin are different resins from each other.

[0062] The types of the first thermoplastic resin and the second thermoplastic resin are not particularly limited.

[0063] The first thermoplastic resin and the second thermoplastic resin are preferably at least one selected from polyolefin resins, polyolefin resins having a polar portion, styrene resins, polyacetal resins, polycarbonate resins, polyacrylic resins, polyamide resins, polyimide resins, polyvinyl acetate resins, phenoxy resins and polyester resins, for example, from the viewpoint of being easy to melt and having a given heat resistance.

[0064] The first thermoplastic resin is preferably a polyolefin resin.

[0065] The second thermoplastic resin is preferably a styrene-based resin.

[0066] Preferably, at least one of the first thermoplastic resin and the second thermoplastic resin is a polyolefin resin or a polyolefin resin having a polar portion. At least one of the first thermoplastic resin and the second thermoplastic resin may be a polyolefin resin having no polar portion.

[0067] (Polyolefin resin)

[0068] Examples of polyolefin resins as thermoplastic resins include resins formed from homopolymers such as polyethylene, polypropylene, polybutene, and polymethylpentene, and α-olefin resins formed from copolymers of monomers selected from ethylene, propylene, butene, hexene, octene, and 4-methylpentene, etc. The polyolefin resins as thermoplastic resins may be a single resin or a combination of two or more resins.

[0069] (Polyolefin resin having polar part)

[0070] The polar site in the polyolefin resin having a polar site is not particularly limited as long as it can impart polarity to the polyolefin resin. However, the polyolefin resin having a polar site is preferred because it exhibits high adhesive strength to an adherend.

[0071] The thermoplastic resin may be a copolymer of an olefin monomer and a monomer having a polar site. Alternatively, the thermoplastic resin may be a resin obtained by introducing a polar site into an olefin polymer obtained by polymerizing an olefin monomer through modification such as an addition reaction.

[0072] There is no particular restriction on the type of olefin monomer constituting the polyolefin resin having a polar part as a thermoplastic resin. Examples of the olefin monomer include ethylene, propylene, butene, hexene, octene, and 4-methyl-1-pentene. The olefin monomer may be used alone or in combination of two or more.

[0073] The olefin monomer is preferably ethylene or propylene because it is excellent in mechanical strength and can provide stable adhesive properties.

[0074] The structural unit derived from olefin in the polyolefin-based resin having a polar part is preferably a structural unit derived from ethylene or propylene.

[0075] Examples of the polar site include a hydroxyl group, a carboxyl group, a vinyl acetate structure, an acid anhydride structure, and an acid-modified structure introduced into a polyolefin-based resin by acid modification.

[0076] The acid-modified structure as a polar site is a site introduced by acid-modifying a thermoplastic resin (e.g., a polyolefin resin). As the compound used when graft-modifying a thermoplastic resin (e.g., a polyolefin resin), there can be mentioned unsaturated carboxylic acid derivative components derived from any one of unsaturated carboxylic acids, unsaturated carboxylic acid anhydrides, and unsaturated carboxylic acid esters.

[0077] Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, and citraconic acid.

[0078] Examples of the anhydride of unsaturated carboxylic acid include anhydrides of unsaturated carboxylic acids such as maleic anhydride, itaconic anhydride, and citraconic anhydride.

[0079] Examples of the esters of unsaturated carboxylic acids include esters of unsaturated carboxylic acids such as methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dimethyl maleate, monomethyl maleate, dimethyl fumarate, diethyl fumarate, dimethyl itaconate, diethyl itaconate, dimethyl citrate, diethyl citrate and dimethyl tetrahydrophthalate.

[0080] When the thermoplastic resin is a copolymer of an olefin monomer and a monomer having a polar site, the copolymer preferably contains 2% by mass or more of a structural unit derived from a monomer having a polar site, more preferably 4% by mass or more, further preferably 5% by mass or more, and further preferably 6% by mass or more. In addition, the copolymer preferably contains 30% by mass or less of a structural unit derived from a monomer having a polar site, more preferably 25% by mass or less, further preferably 20% by mass or less, and particularly preferably 15% by mass or less.

[0081] By making the copolymer contain more than 2% by mass of structural units from monomers having polar parts, the bonding strength of the high-frequency dielectric heating adhesive sheet is improved. In addition, by making the copolymer contain less than 30% by mass of structural units from monomers having polar parts, the viscosity of the thermoplastic resin can be suppressed from becoming too strong. As a result, it is easy to prevent the molding process of the high-frequency dielectric heating adhesive sheet from becoming difficult.

[0082] When the polyolefin resin as the thermoplastic resin has an acid-modified structure, the modification rate with the acid is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.2% by mass or more.

[0083] When the polyolefin resin as the thermoplastic resin has an acid-modified structure, the modification rate with the acid is preferably 30% by mass or less, more preferably 20% by mass or less, and further preferably 10% by mass or less.

[0084] When the thermoplastic resin has an acid-modified structure, the bonding strength of the high-frequency dielectric heating adhesive sheet is improved by making the acid-based modification rate 0.01% by mass or more. In addition, by making the acid-based modification rate 30% by mass or less, the viscosity of the thermoplastic resin can be suppressed from becoming too strong. As a result, it is easy to prevent the molding process of the high-frequency dielectric heating adhesive sheet from becoming difficult.

[0085] In the present specification, the modification ratio refers to the percentage of the mass of the portion derived from the acid relative to the total mass of the acid-modified polyolefin.

[0086] (Maleic anhydride modified polyolefin)

[0087] The polyolefin resin as the thermoplastic resin more preferably has an acid anhydride structure as the acid-modified structure. The acid anhydride structure is preferably a structure introduced when the polyolefin resin is modified with maleic anhydride.

[0088] In the maleic anhydride-modified polyolefin, the modification ratio based on maleic anhydride is preferably in the same range as the modification ratio when the polyolefin resin as a thermoplastic resin has an acid-modified structure, and the effect obtained within this range is also the same as when the polyolefin resin as a thermoplastic resin has an acid-modified structure.

[0089] The structural unit derived from olefin in the maleic anhydride-modified polyolefin is preferably a structural unit derived from ethylene or propylene. That is, the maleic anhydride-modified polyolefin is preferably a maleic anhydride-modified polyethylene resin or a maleic anhydride-modified polypropylene resin.

[0090] (Olefin-vinyl acetate copolymer resin)

[0091] The thermoplastic resin of the present embodiment is preferably a copolymer including a structural unit derived from an olefin and a structural unit derived from vinyl acetate (olefin-vinyl acetate copolymer resin).

[0092] The olefin-vinyl acetate copolymer resin as the thermoplastic resin preferably has a structural unit derived from vinyl acetate in the same range as the structural unit derived from the monomer having a polar part when the thermoplastic resin is a copolymer of an olefin monomer and a monomer having a polar part. The effect obtained within this range is also the same as when the thermoplastic resin is a copolymer of an olefin monomer and a monomer having a polar part.

[0093] The structural unit derived from olefin in the olefin-vinyl acetate copolymer resin is preferably a structural unit derived from ethylene or propylene from the viewpoint of excellent mechanical strength and stable adhesiveness.

[0094] Therefore, the thermoplastic resin is preferably at least one of ethylene-vinyl acetate copolymer resin and propylene-vinyl acetate copolymer resin, and more preferably ethylene-vinyl acetate copolymer resin. The structural unit derived from vinyl acetate in ethylene-vinyl acetate copolymer resin and propylene-vinyl acetate copolymer resin is also preferably in the same range as the percentage (mass %) described for olefin-vinyl acetate copolymer resin.

[0095] (Styrene resin)

[0096] The styrene-based resin may be a homopolymer of a styrene-based monomer (polystyrene: PS), and examples thereof include a homopolymer of styrene, a homopolymer of α-methylstyrene, and a homopolymer of β-methylstyrene.

[0097] PS may be a generally used polystyrene resin (GPPS resin), or a high impact polystyrene resin (HIPS resin) containing a GPPS resin and a rubbery elastomer.

[0098] Examples of the styrene-based resin include resins obtained by copolymerizing a styrene-based monomer such as α-methylstyrene or β-methylstyrene with an aliphatic monomer, and hydrogenated styrene-based resins obtained by hydrogenating the resin may be used.

[0099] As the styrene resin, preferably a styrene elastomer. As the styrene elastomer, styrene-conjugated diene copolymers and styrene-olefin copolymers can be cited. As specific examples of styrene-conjugated diene copolymers, unhydrogenated styrene-conjugated diene copolymers such as styrene-butadiene copolymers, styrene-butadiene-styrene copolymers (SBS), styrene-butadiene / butylene-styrene copolymers, styrene-isoprene copolymers, styrene-isoprene-styrene copolymers (SIS), styrene-ethylene / isoprene-styrene copolymers, and hydrogenated styrene-conjugated diene copolymers such as styrene-ethylene / propylene-styrene copolymers (SEPS) and styrene-ethylene / butylene-styrene copolymers (SEBS) can be cited. In addition, in industry, examples of styrene-based elastomers include Tufprene (manufactured by Asahi Kasei Corporation), KRATON (manufactured by Kraton Polymers Japan Co., Ltd.), Sumitomo TPE-SB (manufactured by Sumitomo Chemical Co., Ltd.), EPOFRIEND (manufactured by Daicel Corporation), RABALON (manufactured by Mitsubishi Chemical Corporation), SEPTON (manufactured by Kuraray Corporation), and TUFTEC (manufactured by Asahi Kasei Corporation). The styrene-based elastomer may be a hydrogenated product or a non-hydrogenated product.

[0100] (Acrylic resin)

[0101] The acrylic resin is preferably a homopolymer of (meth) acrylic acid esters such as polymethyl methacrylate (PMMA) or polymethyl acrylate (PMA), or a copolymer of at least one of the monomer units of methyl methacrylate (MMA) and the monomer units of methyl acrylate (MA) and the monomer units of one or more other monomers. The acrylic resin can be one selected from these homopolymers and copolymers, or a mixture of two or more. It should be noted that in this specification, "(meth) acrylic acid" refers to a concept including both "acrylic acid" and "methacrylic acid".

[0102] As other monomers copolymerizable with at least one of MMA and MA, for example, there can be mentioned: (meth) alkyl acrylates having an alkyl group with 2 to 18 carbon atoms; α,β-unsaturated acids such as acrylic acid and methacrylic acid; dicarboxylic acids containing unsaturated groups such as maleic acid, fumaric acid, and itaconic acid, and alkyl esters of these dicarboxylic acids containing unsaturated groups; aromatic vinyl compounds such as styrene, α-methylstyrene, and core-substituted styrene; cyanide vinyl compounds such as acrylonitrile and methacrylonitrile; maleic anhydride, maleimide, and N-substituted maleimide. The other monomers copolymerizable with at least one of MMA and MA may be at least one selected from these monomers, or may be two or more.

[0103] In the high-frequency dielectric heating adhesive sheet of the present embodiment, the absolute value of the difference between the flow start temperature Tx1 of the first thermoplastic resin and the flow start temperature Tx2 of the second thermoplastic resin preferably satisfies the relationship of the following equation (Equation 4).

[0104] |Tx1-Tx2|≤70···(Formula 4)

[0105] The absolute value of the difference between the flow start temperatures Tx1 and Tx2 |Tx1-Tx2| is more preferably 60°C or less, further preferably 50°C or less, and further preferably 40°C or less.

[0106] When the absolute value of the difference between the flow start temperatures Tx1 and Tx2 |Tx1-Tx2| is 70°C or less, the high-frequency dielectric heating adhesive sheet of the present embodiment can be easily molded.

[0107] The flow start temperature of the thermoplastic resin can be measured by the method described in the section of Examples described later.

[0108] (Dielectric filler)

[0109] The first dielectric filler and the second dielectric filler are fillers that generate heat at high frequencies.

[0110] The first dielectric filler and the second dielectric filler are preferably fillers that generate heat when a high-frequency voltage in the frequency range of 3 MHz to 300 MHz is applied. The first dielectric filler and the second dielectric filler are preferably fillers that generate heat when a high-frequency voltage in the frequency range of 3 MHz to 300 MHz is applied, for example, a frequency of 13.56 MHz, 27.12 MHz, or 40.68 MHz.

[0111] ·type

[0112] The first dielectric filler and the second dielectric filler are preferably independently selected from zinc oxide, silicon carbide (SiC), titanium oxide, barium titanate, barium titanate zirconate, lead titanate, potassium niobate, hydrated aluminum silicate, inorganic materials having crystal water such as hydrated aluminum silicate of alkali metals, or inorganic materials having crystal water such as hydrated aluminum silicate of alkaline earth metals, etc., alone or in combination of two or more thereof. The first dielectric filler and the second dielectric filler may be the same or different in kind.

[0113] It is preferred that at least one of the first dielectric filler and the second dielectric filler is at least one selected from the group consisting of zinc oxide, silicon carbide, titanium oxide, and barium titanate.

[0114] It is preferred that the first dielectric filler and the second dielectric filler are each independently at least one selected from the group consisting of zinc oxide, silicon carbide, titanium oxide, and barium titanate.

[0115] Among the dielectric fillers exemplified, from the perspective of rich variety, various shapes and sizes, and the ability to improve the bonding properties and mechanical properties of the high-frequency dielectric heating adhesive sheet in accordance with the purpose, it is further preferred that at least one of the first dielectric filler and the second dielectric filler is zinc oxide. By using zinc oxide as a dielectric filler, a colorless high-frequency dielectric heating adhesive sheet can be obtained. Among dielectric fillers, the density of zinc oxide is small, so when a high-frequency dielectric heating adhesive sheet containing zinc oxide as a dielectric filler is used to join the adherend, the total weight of the joint is not easy to increase compared to the case where a sheet containing other dielectric fillers is used. Among ceramics, the hardness of zinc oxide is not too high, so it is not easy to damage the manufacturing device of the high-frequency dielectric heating adhesive sheet. Since zinc oxide is an inactive oxide, even if it is combined with a thermoplastic resin, the damage caused to the thermoplastic resin is small.

[0116] The titanium oxide as the dielectric filler is preferably at least one of anatase titanium oxide and rutile titanium oxide, and is more preferably anatase titanium oxide from the viewpoint of excellent dielectric properties.

[0117] The first dielectric filler and the second dielectric filler may be the same as or different from each other.

[0118] Volume content

[0119] At least one of the volume content of the first dielectric filler in the first adhesive layer and the volume content of the second dielectric filler in the second adhesive layer is preferably 5 volume % or more, more preferably 8 volume % or more.

[0120] At least one of the volume content of the first dielectric filler in the first adhesive layer and the volume content of the second dielectric filler in the second adhesive layer is preferably 50 volume % or less, more preferably 40 volume % or less, and even more preferably 35 volume % or less.

[0121] When the volume content of the first dielectric filler is 5 volume % or more, the first adhesive layer and the first adherend are easily and firmly bonded to each other.

[0122] When the volume content of the second dielectric filler is 5 volume % or more, the second adhesive layer and the second adherend are easily and firmly bonded to each other.

[0123] When the volume content of the first dielectric filler is 50 volume % or less, the first adhesive layer can be easily processed.

[0124] When the volume content of the second dielectric filler is 50 volume % or less, the second adhesive layer can be easily processed.

[0125] When the volume content of the first dielectric filler and the volume content of the second dielectric filler are both 5 volume % or more, the high-frequency dielectric heating adhesive sheet of this embodiment can easily firmly bond the first adherend and the second adherend made of different materials.

[0126] When the volume contents of the first dielectric filler and the second dielectric filler are both below 50 volume %, it is easy to obtain flexibility of the first adhesive layer and the second adhesive layer, and it is also easy to prevent a decrease in toughness. Therefore, the high-frequency dielectric heating adhesive sheet as a whole is easy to obtain flexibility, and it is also easy to prevent a decrease in toughness, and the high-frequency dielectric heating adhesive sheet is easy to be processed into a desired shape in a subsequent process.

[0127] The volume content of the first dielectric filler in the first adhesive layer and the volume content of the second dielectric filler in the second adhesive layer may be the same as or different from each other.

[0128] Volume average particle size

[0129] At least one of the volume average particle size of the first dielectric filler and the volume average particle size of the second dielectric filler is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more.

[0130] At least one of the volume average particle size of the first dielectric filler and the volume average particle size of the second dielectric filler is preferably 30 μm or less, more preferably 25 μm or less, and even more preferably 20 μm or less.

[0131] When the volume average particle size of the first dielectric filler in the first adhesive layer is 1 μm or more, the first adhesive layer can exhibit high heat generation performance when a high frequency is applied.

[0132] When the volume average particle size of the first dielectric filler in the first adhesive layer is 30 μm or less, it is possible to prevent the strength of the first adhesive layer from being reduced and to exhibit high heat generation performance when a high frequency is applied.

[0133] When the volume average particle size of the second dielectric filler in the second adhesive layer is 1 μm or more, the second adhesive layer can exhibit high heat generation performance when a high frequency is applied.

[0134] When the volume average particle size of the second dielectric filler in the second adhesive layer is 30 μm or less, it is possible to prevent the strength of the second adhesive layer from being reduced and to exhibit high heat generation performance when a high frequency is applied.

[0135] When the volume average particle size of the first dielectric filler and the volume average particle size of the second dielectric filler are both greater than 1 μm, the high-frequency dielectric heating adhesive sheet of this embodiment exhibits high heat generation performance as a whole sheet when high frequency is applied, and can firmly bond the first adherend and the second adherend in a shorter time.

[0136] By setting the volume average particle size of the first dielectric filler and the volume average particle size of the second dielectric filler to 30 μm or less, the strength of the high-frequency dielectric heating adhesive sheet can be prevented from decreasing and the entire sheet can exhibit high heat generation performance when high frequency is applied.

[0137] The volume average particle size of the first dielectric filler and the volume average particle size of the second dielectric filler may be the same as or different from each other.

[0138] The volume average particle size of the dielectric filler is measured by the following method: The particle size distribution of the dielectric filler is measured by a laser diffraction / scattering method, and the volume average particle size is calculated based on the results of the particle size distribution measurement in accordance with JIS Z 8819-2:2001.

[0139] (additive)

[0140] The high-frequency dielectric heating adhesive sheet of the present embodiment may or may not contain an additive. When the high-frequency dielectric heating adhesive sheet of the present embodiment contains an additive, it is preferred that at least one of the first adhesive layer and the second adhesive layer contains the additive.

[0141] When the high-frequency dielectric heating adhesive sheet of the present embodiment includes additives, the additives include, for example, tackifiers, plasticizers, waxes, colorants, antioxidants, ultraviolet absorbers, antibacterial agents, coupling agents, viscosity modifiers, organic fillers, and inorganic fillers, etc. The organic fillers and inorganic fillers used as additives are different from the dielectric fillers.

[0142] Tackifiers and plasticizers can improve the melting characteristics and bonding characteristics of high-frequency dielectric heating adhesive sheets.

[0143] Examples of the tackifier include rosin derivatives, polyterpene resins, aromatic modified terpene resins, hydrogenated aromatic modified terpene resins, terpene phenol resins, coumarone-indene resins, aliphatic petroleum resins, aromatic petroleum resins, and hydrogenated aromatic petroleum resins.

[0144] As plasticizers, for example, petroleum-based process oils, natural oils, dibasic acid dialkyl esters, and low molecular weight liquid polymers can be cited. As petroleum-based process oils, for example, paraffin-based process oils, cycloparaffin-based process oils, and aromatic process oils can be cited. As natural oils, for example, castor oil and tall oil can be cited. As dibasic acid dialkyl esters, for example, dibutyl phthalate, dioctyl phthalate, and dibutyl adipate can be cited. As low molecular weight liquid polymers, for example, liquid polybutene and liquid polyisoprene can be cited.

[0145] In the case where the high-frequency dielectric heating adhesive sheet of the present embodiment contains additives, the content of the additives in the high-frequency dielectric heating adhesive sheet is usually preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and further preferably 0.1% by mass or more, based on the total amount of the high-frequency dielectric heating adhesive sheet. In addition, the content of the additives in the high-frequency dielectric heating adhesive sheet is preferably 20% by mass or less, more preferably 15% by mass or less, and further preferably 10% by mass or less.

[0146] The high-frequency dielectric heating adhesive sheet of the present embodiment preferably does not contain carbon or carbon compounds (e.g., carbon black, etc.) with carbon as the main component and conductive materials such as metals. The content of the conductive material is independently based on the total amount of the high-frequency dielectric heating adhesive sheet and is preferably 5% by mass or less, more preferably 1% by mass or less, further preferably 0.1% by mass or less, and further preferably 0% by mass.

[0147] When the content of the conductive substance in the high-frequency dielectric heating adhesive sheet is 5% by mass or less, it is easy to prevent the problem of carbonization of the bonding portion and the adherend due to electrical insulation breakdown during dielectric heating treatment.

[0148] In the high-frequency dielectric heating adhesive sheet of this embodiment, at least either the total mass of the thermoplastic resin and the dielectric filler relative to the total mass of the first adhesive layer, or the total mass of the thermoplastic resin and the dielectric filler relative to the total mass of the second adhesive layer is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 99% by mass or more.

[0149] The total mass of the thermoplastic resin and the dielectric filler is preferably 80 mass % or more, more preferably 90 mass % or more, and even more preferably 99 mass % or more relative to the total mass of the high-frequency dielectric heating adhesive sheet of this embodiment.

[0150] [Morphology and characteristics of high-frequency dielectric heating adhesive sheets]

[0151] (Interlayer Adhesion)

[0152] Preferably, after a cross-cut test according to JIS K5600-5-6:1999, the ratio of the number of cross-cuts that adhere to the layer in contact with the layer without peeling off among all the layers of the high-frequency dielectric heating adhesive sheet of this embodiment is 50% or more, more preferably 80% or more, and even more preferably 100%. When such interlayer adhesion is achieved, peeling off between the layers of the sheet is less likely to occur.

[0153] The ratio of the number of cross-cuts that are not peeled off from the layer in contact with the layer and are adhered after the cross-cut test is usually 100% or less.

[0154] For example, Figure 1 As shown, in the case where the high-frequency dielectric heating adhesive sheet 1 is composed of the first adhesive layer 10 and the second adhesive layer 20, the first adhesive layer 10 is in contact with the second adhesive layer 20. In such a case, it is preferred that after a cross-cut test according to JIS K5600-5-6:1999, the ratio of the number of grids of the first adhesive layer 10 that are not peeled off from the second adhesive layer 20 and are adhered is 50% or more, and the ratio of the number of grids of the second adhesive layer 20 that are not peeled off from the first adhesive layer 10 and are adhered is 50% or more, more preferably 80% or more, and further preferably 100%.

[0155] (Thickness of high frequency dielectric heating adhesive sheet)

[0156] The thickness of the high-frequency dielectric heating adhesive sheet is preferably 10 μm or more, more preferably 30 μm or more, and further preferably 50 μm or more.

[0157] When the thickness of the high-frequency dielectric heating adhesive sheet is 10 μm or more, the absolute amount of the substance that generates heat at high frequencies contained in the sheet does not decrease, and the sheet easily generates heat.

[0158] The upper limit of the thickness of the high-frequency dielectric heating adhesive sheet is not particularly limited. Since the thickness of the high-frequency dielectric heating adhesive sheet increases, the weight of the entire joint body obtained by bonding the first adherend and the second adherend also increases. Therefore, the high-frequency dielectric heating adhesive sheet is preferably a thickness within a range that does not cause problems in practical use. In addition, considering the practicality and formability of the high-frequency dielectric heating adhesive sheet, the thickness of the high-frequency dielectric heating adhesive sheet is preferably 2000 μm or less, more preferably 1000 μm or less, and further preferably 600 μm or less.

[0159] At least one of the first and second adhesive layers preferably has a thickness of 5 μm or more, more preferably 25 μm or more, and even more preferably 50 μm or more. It is even more preferred that both the first and second adhesive layers have thicknesses within the above ranges.

[0160] At least one of the first and second adhesive layers preferably has a thickness of 1000 μm or less, more preferably 500 μm or less, and even more preferably 300 μm or less. It is even more preferred that both the first and second adhesive layers have thicknesses within the above ranges.

[0161] When the thickness of the first adhesive layer is 5 μm or more, the first adhesive layer can be easily molded, and the heat generation property when a high frequency is applied is also improved.

[0162] When the thickness of the second adhesive layer is 5 μm or more, the second adhesive layer can be easily molded, and the heat generation property when a high frequency is applied is also improved.

[0163] When the thickness of the first adhesive layer and the second adhesive layer are both 5 μm or more, the high-frequency dielectric heating adhesive sheet can be easily molded, and the heat generation property when a high frequency is applied is also improved.

[0164] When the thickness of the first adhesive layer and the second adhesive layer are both 1000 μm or less, the high-frequency dielectric heating adhesive sheet will not become too heavy.

[0165] The thicknesses of the first adhesive layer and the second adhesive layer may be the same as or different from each other.

[0166] In the high-frequency dielectric heating adhesive sheet of this embodiment, it is preferable that the average particle size D of the first dielectric filler is F1 The ratio of the thickness of the first adhesive sheet T1 to the thickness of the first adhesive sheet T1 / D F1 and the average particle size D of the second dielectric filler F2 The ratio of the thickness of the second adhesive sheet T2 to the thickness of the second adhesive sheet T2 / D F2 At least one of them is 1 or more, more preferably 2 or more, further preferably 3 or more, and further preferably 5 or more.

[0167] Optimum ratio T1 / D F1 and ratio T2 / D F2 At least one of them is 2500 or less, preferably 2000 or less, preferably 1750 or less, more preferably 1000 or less, further preferably 50 or less, further preferably 100 or less, and further preferably 50 or less.

[0168] Ratio T1 / D F1 When the ratio is 1 or more, it is possible to prevent a decrease in bonding strength due to contact between the first dielectric filler and the adherend during bonding.

[0169] T2 / D F2 When the ratio is 1 or more, it is possible to prevent a decrease in bonding strength due to contact between the second dielectric filler and the adherend during bonding.

[0170] Ratio T1 / D F1 When it is 2500 or less, the load on the sheet manufacturing apparatus can be suppressed when the first adhesive layer is produced.

[0171] T2 / D F2 When the molecular weight is 2500 or less, the load on the sheet manufacturing apparatus can be suppressed when the second adhesive layer is produced.

[0172] Ratio T1 / D F1 and ratio T2 / D F2 When all of them are 1 or more, it is possible to prevent a decrease in bonding strength due to contact between the dielectric filler and the adherend on both sides of the high-frequency dielectric heating adhesive sheet during bonding.

[0173] Ratio T1 / D F1 and ratio T2 / D F2 When all of them are 2500 or less, the load on the sheet manufacturing apparatus when manufacturing the high-frequency dielectric heating adhesive sheet can be suppressed.

[0174] Ratio T1 / D F1 T2 / D F2 The same as or different from each other.

[0175] (Dielectric properties of high frequency dielectric heating adhesive sheets (tanδ / ε'r))

[0176] The dielectric loss tangent (tan δ) and relative dielectric constant (ε'r) which are dielectric properties of the high-frequency dielectric heating adhesive sheet can be measured simply and accurately using an impedance material analyzer.

[0177] The dielectric property (tanδ / ε'r) of the high-frequency dielectric heating adhesive sheet is preferably 0.005 or more, more preferably 0.008 or more, and further preferably 0.01 or more. In addition, the dielectric property (tanδ / ε'r) of the high-frequency dielectric heating adhesive sheet is preferably 0.08 or less, more preferably 0.05 or less. The dielectric property (tanδ / ε'r) is a value obtained by dividing the dielectric loss tangent (tanδ) measured using an impedance material device or the like by the relative dielectric constant (ε'r) measured using an impedance material device or the like.

[0178] When the dielectric property of the high-frequency dielectric heating adhesive sheet is 0.005 or more, it is possible to prevent a problem in which a predetermined amount of heat is not generated during dielectric heating treatment and adherends are not firmly bonded to each other.

[0179] When the dielectric property of the high-frequency dielectric heating adhesive sheet is 0.08 or less, damage to the adherend is unlikely to occur.

[0180] It should be noted that the details of the method for measuring the dielectric properties of the high-frequency dielectric heating adhesive sheet are as follows. For the high-frequency dielectric heating adhesive sheet cut into a given size, the relative dielectric constant (ε'r) and the dielectric loss tangent (tanδ) are measured at 23°C and a frequency of 40.68MHz using an RF impedance / material analyzer E4991A (manufactured by Agilent), and the value of the dielectric property (tanδ / ε'r) is calculated.

[0181] [Method for manufacturing high frequency dielectric heating adhesive sheet]

[0182] The method for producing the high-frequency dielectric heating adhesive sheet of the present embodiment is not particularly limited as long as a laminated high-frequency dielectric heating adhesive sheet including a first adhesive layer and a second adhesive layer can be produced.

[0183] For the high-frequency dielectric heating adhesive sheet of the present embodiment, for example, the above-mentioned components can be premixed and manufactured by a co-extrusion method using a multilayer extruder. In addition, the high-frequency dielectric heating adhesive sheet of the present embodiment can be manufactured by separately making single-layer sheets of each layer (for example, the first adhesive layer and the second adhesive layer) constituting the high-frequency dielectric heating adhesive sheet of the present embodiment, laminating multiple single-layer sheets, and stacking them. The single-layer sheet can be manufactured by premixing the above-mentioned components, mixing them using a known mixing device such as an extruder and a hot roller, and using a known molding method such as extrusion molding, calendering molding, injection molding, and cast molding. When laminating multiple single-layer sheets, for example, a hot laminator is used.

[0184] [How to use high frequency dielectric heating adhesive sheet]

[0185] By using the high-frequency dielectric heating adhesive sheet of this embodiment, a first adherend and a second adherend can be bonded together.

[0186] The high-frequency dielectric heating adhesive sheet of the present embodiment is preferably a sheet for bonding a first adherend and a second adherend made of a material different from that of the first adherend.

[0187] Preferably, the first adherend contains a third thermoplastic resin, and the first thermoplastic resin contained in the first adhesive layer has the same main composition as the third thermoplastic resin. Preferably, the first adhesive layer is bonded to the first adherend.

[0188] The second adherend preferably contains a fourth thermoplastic resin, and the second thermoplastic resin contained in the second adhesive layer has the same main composition as the fourth thermoplastic resin. The second adhesive layer preferably adheres to the second adherend.

[0189] It is preferred that the third thermoplastic resin and the fourth thermoplastic resin are each independently a resin appropriately selected from the thermoplastic resins described in connection with the first adhesive layer and the second adhesive layer.

[0190] In this specification, "the main component of the thermoplastic resin" means, for example, when the thermoplastic resin is a polymer, the repeating units contained in the polymer are the repeating units containing the most in the polymer. If the thermoplastic resin is a polymer derived from a single monomer, the monomer unit (repeating unit) is the "main component of the thermoplastic resin". When the thermoplastic resin is a copolymer, the repeating unit containing the most in the copolymer is the "main component of the thermoplastic resin". When the thermoplastic resin is a copolymer, the "main component of the thermoplastic resin" in the copolymer is a repeating unit (monomer unit) containing 30% or more by mass, in one embodiment, it is a repeating unit containing more than 30% by mass, in another embodiment, it is a repeating unit containing 40% or more by mass, and in another embodiment, it is a repeating unit containing 50% or more by mass. In addition, when the thermoplastic resin is a copolymer, the repeating units containing the most may be two or more.

[0191] For example, when the first thermoplastic resin is an ethylene-vinyl acetate copolymer containing 50% by mass or more of ethylene units as repeating units, and the third thermoplastic resin is also an ethylene-vinyl acetate copolymer containing 50% by mass or more of ethylene units as repeating units, the main component (repeating unit) of the first thermoplastic resin and the main component (repeating unit) of the third thermoplastic resin are both ethylene, and the main components of the first thermoplastic resin and the third thermoplastic resin are the same.

[0192] For example, when the first thermoplastic resin is maleic anhydride-modified polypropylene containing 50% by mass or more of propylene units as repeating units, and the third thermoplastic resin is polypropylene, the main component (repeating unit) of the first thermoplastic resin and the main component (repeating unit) of the third thermoplastic resin are both propylene, and the main components of the first thermoplastic resin and the third thermoplastic resin are the same.

[0193] In addition, for example, when the thermoplastic resin is a homopolymer, the repeating unit constituting the polymer is the main component of the thermoplastic resin. For example, when the first thermoplastic resin is polyethylene and the third thermoplastic resin is also polyethylene, the main component (repeating unit) of the first thermoplastic resin and the main component (repeating unit) of the third thermoplastic resin are both ethylene, and the main components of the first thermoplastic resin and the third thermoplastic resin are the same.

[0194] Regarding the “main composition of the thermoplastic resin” related to the second thermoplastic resin and the fourth thermoplastic resin, the above-mentioned examples and the like can be applied.

[0195] Examples of the combination of the first thermoplastic resin and the third thermoplastic resin and the combination of the second thermoplastic resin and the fourth thermoplastic resin include the following combinations.

[0196] (R1) Polyethylene and ethylene-vinyl acetate copolymer

[0197] (R2) Polyethylene and EMAA (ethylene / methyl methacrylate copolymer)

[0198] (R3) Polyethylene and EMA (ethylene / methacrylate copolymer)

[0199] (R4) Polyethylene and ethylene cycloolefin copolymer

[0200] (R5) Polypropylene and modified polypropylene

[0201] (R6)PS and SEBS

[0202] (R7) PS and SBR (styrene butadiene rubber)

[0203] (R8) PS and SEES (styrene-ethylene-ethylene-styrene block copolymer)

[0204] (R9) PS and ABS (Acrylonitrile-Butadiene-Styrene Copolymer)

[0205] (R10)PS and SIS

[0206] The surface of the first adherend in direct contact with the first adhesive layer of the high-frequency dielectric heating adhesive sheet is preferably composed of a third thermoplastic resin. It is also preferred that the entire first adherend is composed of a third thermoplastic resin. In addition, in the case where the first adherend is a multilayer structure, it is also preferred that the layer located on the outermost surface of the first adherend (the outermost layer) is composed of a third thermoplastic resin. In the case where the first adherend as a whole or the outermost layer of the first adherend is composed of a mixed resin formed by mixing multiple resins, it is preferred that the volume content of the third thermoplastic resin in the first adherend as a whole or the outermost layer of the first adherend is 50% by volume or more, more preferably 60% by volume or more, further preferably 70% by volume or more, further preferably 80% by volume or more, and further preferably 90% by volume or more.

[0207] The surface of the second adherend in direct contact with the second adhesive layer of the high-frequency dielectric heating adhesive sheet is preferably composed of a fourth thermoplastic resin. It is also preferred that the entire second adherend is composed of a fourth thermoplastic resin. In addition, in the case where the second adherend is a multilayer structure, it is also preferred that the outermost layer (outermost layer) located on the surface of the second adherend is composed of a fourth thermoplastic resin. In the case where the entire second adherend or the outermost layer of the second adherend is composed of a mixed resin formed by mixing a plurality of resins, it is preferred that the volume content of the fourth thermoplastic resin in the entire second adherend or the outermost layer of the second adherend is 50% by volume or more, more preferably 60% by volume or more, further preferably 70% by volume or more, further preferably 80% by volume or more, and further preferably 90% by volume or more.

[0208] The shapes of the first adherend and the second adherend are not particularly limited, but are preferably sheet-shaped. The shapes of the first adherend and the second adherend can be made of the above-mentioned materials, and the shapes and sizes of the first adherend and the second adherend can be the same or different.

[0209] As a method of using the high-frequency dielectric heating adhesive sheet of this embodiment, the high-frequency dielectric heating adhesive sheet of this embodiment is sandwiched between a first adherend and a second adherend, and a high-frequency voltage of, for example, greater than 3 MHz and less than 300 MHz is applied to produce a joint body in which the first adherend and the second adherend are bonded together.

[0210] [Bonding method]

[0211] In the bonding method of the present embodiment, a first adherend and a second adherend are bonded together using the high-frequency dielectric heating adhesive sheet of the present embodiment.

[0212] The bonding method of the present embodiment preferably includes the following steps P1 and P2.

[0213] Step P1: a step of bringing the first adhesive layer of the high-frequency dielectric heating adhesive sheet into contact with the first adherend and bringing the second adhesive layer into contact with the second adherend.

[0214] Step P2: A step of applying high frequency to the high frequency dielectric heating adhesive sheet to bond the first adherend and the second adherend together.

[0215] Process P1

[0216] Step P1 is a step of sandwiching the high-frequency dielectric heating adhesive sheet of this embodiment between the first adherend and the second adherend. In step P1, the first adherend is brought into contact with the first adhesive layer of the high-frequency dielectric heating adhesive sheet. In addition, in step P1, the second adherend is brought into contact with the second adhesive layer of the high-frequency dielectric heating adhesive sheet.

[0217] The high-frequency dielectric heating adhesive sheet can be sandwiched between the first adherend and the second adherend in a manner that allows the first adherend and the second adherend to be bonded. The high-frequency dielectric heating adhesive sheet can be sandwiched between a portion, multiple portions, or the entire surface between the first adherend and the second adherend. From the perspective of improving the bonding strength between the first adherend and the second adherend, it is preferred that the high-frequency dielectric heating adhesive sheet be sandwiched between the entire bonding surface of the first adherend and the second adherend. In addition, as a method of sandwiching the high-frequency dielectric heating adhesive sheet between a portion of the first adherend and the second adherend, a method can be cited in which the high-frequency dielectric heating adhesive sheet is configured in a frame shape along the periphery of the bonding surface between the first adherend and the second adherend and sandwiched between the first adherend and the second adherend. By configuring the high-frequency dielectric heating adhesive sheet in a frame shape, the bonding strength between the first adherend and the second adherend can be obtained, and the weight of the joint body can be reduced compared to the case where the high-frequency dielectric heating adhesive sheet is configured on the entire bonding surface. In addition, by adopting a method of sandwiching a portion of the high-frequency dielectric heating adhesive sheet between the first adherend and the second adherend, the size of the high-frequency dielectric heating adhesive sheet used can be reduced, so the high-frequency dielectric heating treatment time can be shortened compared to the case where the high-frequency dielectric heating adhesive sheet is configured on the entire bonding surface.

[0218] Process P2

[0219] Step P2 is a step of applying a high frequency voltage of 3 MHz to 300 MHz to the high frequency dielectric heating adhesive sheet sandwiched between the first adherend and the second adherend in step P1 to bond the first adherend and the second adherend using the high frequency dielectric heating adhesive sheet.

[0220] For example, a high-frequency voltage may be applied to the high-frequency dielectric heating adhesive sheet by using a dielectric heating bonding device.

[0221] Figure 2 A schematic diagram for explaining a high-frequency dielectric heating process using the high-frequency dielectric heating adhesive sheet and the dielectric heating device according to the present embodiment is shown.

[0222] (Dielectric heating bonding device)

[0223] Figure 2 A schematic diagram of a dielectric heating bonding device 50 is shown.

[0224] The dielectric heating bonding device 50 includes a first high-frequency applying electrode 51 , a second high-frequency applying electrode 52 , and a high-frequency power source 53 .

[0225] The first high-frequency applying electrode 51 and the second high-frequency applying electrode 52 are arranged opposite to each other. The first high-frequency applying electrode 51 and the second high-frequency applying electrode 52 have a pressurizing mechanism. By using the pressurizing mechanism, the first adherend 110, the high-frequency dielectric heating adhesive sheet 1, and the second adherend 120 can be pressurized between the first high-frequency applying electrode 51 and the second high-frequency applying electrode 52.

[0226] When a pair of plate electrodes, in which the first high-frequency applying electrode 51 and the second high-frequency applying electrode 52 are parallel to each other, is configured, such an electrode arrangement may be referred to as a parallel plate type.

[0227] The high frequency is preferably applied using a parallel plate type high frequency dielectric heating device. In the case of a parallel plate type high frequency dielectric heating device, the high frequency penetrates the high frequency dielectric heating adhesive sheet located between the electrodes, so that the high frequency dielectric heating adhesive sheet can be heated as a whole, and the adherend and the high frequency dielectric heating adhesive sheet can be bonded in a short time.

[0228] A high-frequency power source 53 for applying a high-frequency voltage having a frequency of, for example, about 13.56 MHz, about 27.12 MHz, or about 40.68 MHz is connected to the first high-frequency applying electrode 51 and the second high-frequency applying electrode 52 .

[0229] like Figure 2 As shown, the dielectric heating bonding device 50 performs a dielectric heating treatment by means of the high-frequency dielectric heating adhesive sheet 1 sandwiched between the first adherend 110 and the second adherend 120. In addition to the dielectric heating treatment, the dielectric heating bonding device 50 also bonds the first adherend 110 and the second adherend 120 by a pressurization treatment using the first high-frequency applying electrode 51 and the second high-frequency applying electrode 52. It should be noted that the first adherend 110 and the second adherend 120 may be bonded without a pressurization treatment.

[0230] When a high frequency electric field is applied between the first high frequency applying electrode 51 and the second high frequency applying electrode 52 , dielectric fillers (not shown) dispersed in the first adhesive layer and the second adhesive layer in the high frequency dielectric heating adhesive sheet 1 absorb high frequency energy.

[0231] Furthermore, the dielectric filler functions as a heat source, and the heat generated by the dielectric filler melts the thermoplastic resin components in the first adhesive layer and the second adhesive layer, thereby finally making it possible to firmly bond the first adherend 110 and the second adherend 120 even after a short treatment period.

[0232] Since the first high-frequency applying electrode 51 and the second high-frequency applying electrode 52 have a pressurizing mechanism, they also function as a pressurizing device. Therefore, by applying pressure in the compression direction by the first high-frequency applying electrode 51 and the second high-frequency applying electrode 52 and heating and melting the high-frequency dielectric heating adhesive sheet 1, the first adherend 110 and the second adherend 120 can be more firmly bonded.

[0233] (High frequency dielectric heating bonding conditions)

[0234] The high-frequency dielectric heating bonding conditions can be changed appropriately, but are preferably the following conditions.

[0235] The high-frequency output power is preferably 10 W or more, more preferably 30 W or more, further preferably 50 W or more, and even more preferably 80 W or more.

[0236] The high-frequency output power is preferably 50,000 W or less, more preferably 20,000 W or less, further preferably 15,000 W or less, further preferably 10,000 W or less, and further preferably 1,000 W or less.

[0237] When the high frequency output power is 10 W or more, it is possible to prevent the problem that the temperature is difficult to rise during the dielectric heating treatment, so that good adhesive strength is easily obtained.

[0238] When the high frequency output is 50000 W or less, it is easy to prevent the disadvantage that the temperature control becomes difficult due to the dielectric heating process.

[0239] The high frequency application time is preferably 1 second or longer.

[0240] The high frequency application time is preferably 60 seconds or less, more preferably 45 seconds or less, further preferably 35 seconds or less, further preferably 25 seconds or less, further preferably 10 seconds or less.

[0241] When the high frequency application time is 1 second or longer, it is possible to prevent the problem that the temperature is difficult to rise during the dielectric heating treatment, and thus it is easy to obtain good adhesive strength.

[0242] When the high frequency application time is 60 seconds or less, it is easy to prevent disadvantages such as a decrease in the manufacturing efficiency of a joined body formed by bonding the first adherend and the second adherend, an increase in the manufacturing cost of the joined body, and thermal degradation of the adherends.

[0243] The frequency of the high frequency to be applied is preferably 1 kHz or higher, more preferably 1 MHz or higher, further preferably 5 MHz or higher, and further preferably 10 MHz or higher.

[0244] The frequency of the applied high frequency is preferably 300 MHz or less, more preferably 100 MHz or less, further preferably 80 MHz or less, and further preferably 50 MHz or less. Specifically, the industrial frequency bands 13.56 MHz, 27.12 MHz, and 40.68 MHz allocated by the International Telecommunication Union can also be used for the high-frequency dielectric heating bonding method (bonding method) of this embodiment.

[0245] The high-frequency dielectric heating adhesive sheet of the present embodiment is a multilayer structure including the first adhesive layer and the second adhesive layer as the outermost layer. In addition, the first adhesive layer and the second adhesive layer satisfy the relationship that the change rates Vx1 and Vx2 expressed by the above-mentioned mathematical formula (Mathematical Formula 1) and the mathematical formula (Mathematical Formula 2) are less than 80%. Therefore, the high-frequency dielectric heating adhesive sheet of the present embodiment can firmly bond the first adherend and the second adherend composed of different materials. In addition, the high-frequency dielectric heating adhesive sheet of the present embodiment is a sheet that is not prone to interlayer peeling.

[0246] Compared with the case of using an adhesive that needs to be applied, the high-frequency dielectric heating adhesive sheet of this embodiment is easy to handle, and the workability when bonding the first adherend to the second adherend is also improved. According to the high-frequency dielectric heating adhesive sheet of this embodiment, it can be bonded to the adherend by applying high frequency for a short time.

[0247] The high-frequency dielectric heating adhesive sheet of the present embodiment is superior in water resistance and moisture resistance compared to general adhesives.

[0248] The high-frequency dielectric heating adhesive sheet of the present embodiment does not contain a solvent, and therefore is less likely to cause a problem of VOC (Volatile Organic Compounds) caused by an adhesive used for bonding with an adherend.

[0249] The high frequency dielectric heating adhesive sheet of this embodiment is heated by applying a high frequency voltage, so the high frequency dielectric heating adhesive sheet is locally heated. Therefore, according to the high frequency dielectric heating adhesive sheet of this embodiment, it is easy to prevent the defect that the entire adherend melts when bonding with the adherend.

[0250] According to the bonding method using the high-frequency dielectric heating adhesive sheet of the present embodiment, only a given portion can be locally heated from the outside by a dielectric heating bonding device. Therefore, even when the adherend is a large and complex three-dimensional structure or a thick and complex three-dimensional structure, and high dimensional accuracy is required, the bonding method using the high-frequency dielectric heating adhesive sheet of the present embodiment is effective.

[0251] In addition, according to the high-frequency dielectric heating adhesive sheet of this embodiment, the thickness of the high-frequency dielectric heating adhesive sheet can be appropriately controlled. Therefore, the high-frequency dielectric heating adhesive sheet of this embodiment can also be applied to the roll-to-roll method, and the high-frequency dielectric heating adhesive sheet can be processed into any area and shape according to the bonding area with the adherend and the shape of the adherend by stamping, etc. Therefore, from the perspective of the manufacturing process, the advantages of the high-frequency dielectric heating adhesive sheet of this embodiment are also significant.

[0252] [Second embodiment]

[0253] [High frequency dielectric heating adhesive sheet]

[0254] The high-frequency dielectric heating adhesive sheet of this embodiment further has an intermediate layer disposed between the first adhesive layer and the second adhesive layer. The high-frequency dielectric heating adhesive sheet of this embodiment is different from the high-frequency dielectric heating adhesive sheet of the first embodiment in that it has an intermediate layer, and is the same as the high-frequency dielectric heating adhesive sheet of the first embodiment in other aspects. Therefore, in the following description, the parts different from the first embodiment are mainly described, and repeated descriptions are omitted or simplified. The same symbols are given to the same structures as the first embodiment, and the description is omitted or simplified.

[0255] (Middle layer)

[0256] In the high-frequency dielectric heating adhesive sheet of the present embodiment, the intermediate layer preferably contains one or more thermoplastic resins, and more preferably contains a first thermoplastic resin and a second thermoplastic resin.

[0257] In the high-frequency dielectric heating adhesive sheet of the present embodiment, it is preferred that the first adhesive layer is in direct contact with the intermediate layer, and the second adhesive layer is in direct contact with the intermediate layer.

[0258] In the high-frequency dielectric heating adhesive sheet of this embodiment, when the first adhesive layer is in direct contact with the intermediate layer and the second adhesive layer is in direct contact with the intermediate layer, the meanings of the symbols in the above formulas (Formula 1) and (Formula 2) are as follows.

[0259] VA1: Volume content of the first thermoplastic resin relative to the total thermoplastic resin in the first adhesive layer

[0260] VB1: Volume content of the first thermoplastic resin relative to the total thermoplastic resin in the intermediate layer VA2: Volume content of the second thermoplastic resin relative to the total thermoplastic resin in the second adhesive layer

[0261] VB2: Volume content of the second thermoplastic resin relative to the total thermoplastic resin in the intermediate layer

[0262] In the present embodiment, it is preferred that the first adhesive layer, the intermediate layer, and the second adhesive layer satisfy the same relationship of change rates Vx1 and Vx2 as in the first embodiment.

[0263] Figure 3 A schematic cross-sectional view showing an example of the high-frequency dielectric heating adhesive sheet according to the present embodiment. Figure 3 The high-frequency dielectric heating adhesive sheet 1A shown has a first adhesive layer 10 and a second adhesive layer 20 as the outermost layer, and the second adhesive layer 20 is located on the surface side opposite to the first adhesive layer 10. The high-frequency dielectric heating adhesive sheet 1A includes an intermediate layer 30 between the first adhesive layer 10 and the second adhesive layer. In the high-frequency dielectric heating adhesive sheet 1A, the first adhesive layer 10 is in direct contact with the intermediate layer 30, and the second adhesive layer 20 is in direct contact with the intermediate layer 30.

[0264] In the high-frequency dielectric heating adhesive sheet of this embodiment, it is preferred that the middle layer contains a third dielectric filler that generates heat at high frequency. When the middle layer contains the third dielectric filler, the middle layer is also heated when a high-frequency voltage is applied, so it is easy to melt the first adhesive layer and the second adhesive layer that are in contact with the middle layer in a short time. As a result, according to the high-frequency dielectric heating adhesive sheet of this embodiment, the first adherend and the second adherend can be firmly bonded in a shorter time.

[0265] As the third dielectric filler, the same dielectric filler as the first dielectric filler and the second dielectric filler described in the first embodiment can be used. The third dielectric filler and the first dielectric filler may be the same or different. The third dielectric filler and the second dielectric filler may be the same or different.

[0266] It is preferred that the first dielectric filler, the second dielectric filler, and the third dielectric filler are each independently at least one selected from zinc oxide, silicon carbide, titanium oxide, and barium titanate.

[0267] The first dielectric filler, the second dielectric filler, and the third dielectric filler are preferably the same type of dielectric filler, and are more preferably zinc oxide.

[0268] The volume average particle size and volume content of the third dielectric filler and the first dielectric filler may be the same or different. The volume average particle size and volume content of the third dielectric filler and the second dielectric filler may be the same or different.

[0269] The intermediate layer also preferably does not contain a third dielectric filler that generates heat at high frequencies. When the intermediate layer does not contain a third dielectric filler, the intermediate layer does not generate heat when a high-frequency voltage is applied, so the first adhesive layer, the intermediate layer, and the second adhesive layer do not melt excessively, and it is easy to control overflow from the bonding surfaces of the adherends. In addition, when the intermediate layer does not contain a dielectric filler, the weight of the high-frequency dielectric heating adhesive sheet itself becomes lighter, so it is easy to handle the sheet.

[0270] In this embodiment, after the cross-cut test according to JIS K5600-5-6:1999, the ratio of the number of cross-cuts that adhere to the layer in contact with the layer without peeling off among all the layers of the high-frequency dielectric heating adhesive sheet 1A is preferably 50% or more, more preferably 80% or more, and further preferably 100%.

[0271] For example, Figure 3 As shown, in the case where the high-frequency dielectric heating adhesive sheet 1A is composed of the first adhesive layer 10, the intermediate layer 30 and the second adhesive layer 20, the first adhesive layer is in contact with the intermediate layer 30, and the second adhesive layer is in contact with the intermediate layer 30. In such a case, it is preferred that after a cross-cut test in accordance with JIS K5600-5-6:1999, the proportion of the number of grids of the first adhesive layer that are not peeled off from the intermediate layer 30 and adhere to the first adhesive layer is 50% or more, and the proportion of the number of grids of the second adhesive layer that are not peeled off from the intermediate layer 30 and adhere to the second adhesive layer is 50% or more.

[0272] The high-frequency dielectric heating adhesive sheet of this embodiment may contain additives or may not contain additives. When the high-frequency dielectric heating adhesive sheet of this embodiment contains additives, it is preferred that at least one of the first adhesive layer, the intermediate layer, and the second adhesive layer contains additives. For example, the same additives as those described in the first embodiment may also be applied to the high-frequency dielectric heating adhesive sheet of this embodiment.

[0273] In the high-frequency dielectric heating adhesive sheet of this embodiment, it is preferable that the average particle size D of the first dielectric filler is F1 Ratio of thickness T1 to the first adhesive layer T1 / D F1 The same relationship as in the first embodiment is satisfied.

[0274] In the high-frequency dielectric heating adhesive sheet of this embodiment, the average particle size D of the second dielectric filler is preferably F2 The ratio of the thickness of the second adhesive layer T2 to the thickness of the second adhesive layer T2 / D F2 The same relationship as in the first embodiment is satisfied.

[0275] (Thickness of high frequency dielectric heating adhesive sheet)

[0276] In the present embodiment, the thickness of the high-frequency dielectric heating adhesive sheet is preferably 10 μm or more, more preferably 30 μm or more, and further preferably 50 μm or more.

[0277] In the high-frequency dielectric heating adhesive sheet of the present embodiment, it is preferred that the thickness of the first adhesive layer and the second adhesive layer are independently within the thickness range described in the first embodiment.

[0278] The thickness of the intermediate layer is preferably 5 μm or more, more preferably 25 μm or more, and further preferably 50 μm or more.

[0279] The thickness of the intermediate layer is preferably 1000 μm or less, more preferably 500 μm or less, and further preferably 300 μm or less.

[0280] When the thickness of the intermediate layer is 5 μm or more, the high-frequency dielectric heating adhesive sheet can be easily molded.

[0281] When the thickness of the intermediate layer is 1000 μm or less, the high-frequency dielectric heating adhesive sheet will not become too heavy.

[0282] [Method for manufacturing high frequency dielectric heating adhesive sheet]

[0283] The method for producing the high-frequency dielectric heating adhesive sheet of this embodiment is not particularly limited as long as it can produce a laminated high-frequency dielectric heating adhesive sheet including a first adhesive layer, an intermediate layer, and a second adhesive layer. The high-frequency dielectric heating adhesive sheet of this embodiment can be produced by the same method as the first embodiment, for example.

[0284] [How to use high frequency dielectric heating adhesive sheet]

[0285] The high frequency dielectric heating adhesive sheet of this embodiment can also be used to bond the first adherend to the second adherend. The thermoplastic resin in the adherend and the thermoplastic resin in the adhesive layer have the same main composition, which is the same as the first embodiment.

[0286] [Bonding method]

[0287] The bonding method of this embodiment is a method for bonding a first adherend and a second adherend using the high-frequency dielectric heating adhesive sheet of this embodiment. The bonding method of this embodiment uses the high-frequency dielectric heating adhesive sheet of this embodiment instead of the high-frequency dielectric heating adhesive sheet of the first embodiment, and preferably includes steps P1 and P2 described in the first embodiment.

[0288] Figure 4A schematic diagram for explaining a method of bonding a first adherend 110 and a second adherend 120 using the dielectric heating bonding device 50 and the high-frequency dielectric heating adhesive sheet 1A is shown.

[0289] The high-frequency dielectric heating bonding conditions can be changed as appropriate, but are preferably the same conditions as those described in the first embodiment.

[0290] The high-frequency dielectric heating adhesive sheet of this embodiment is also a multilayer structure including the first adhesive layer and the second adhesive layer as the outermost layer. In addition, the change rates Vx1 and Vx2 of the composition of the first adhesive layer, the intermediate layer and the second adhesive layer expressed by the above-mentioned mathematical formula (Mathematical Formula 1) and the mathematical formula (Mathematical Formula 2) are both less than 80%. Therefore, the high-frequency dielectric heating adhesive sheet of this embodiment can also firmly bond the first adherend and the second adherend, and is a sheet that is not prone to interlayer peeling.

[0291] [Variations of Embodiments]

[0292] The present invention is not limited to the above-described embodiments, and the present invention may include modifications and improvements within the scope that can achieve the purpose of the present invention.

[0293] In the above embodiment, a high-frequency dielectric heating adhesive sheet consisting of only two layers, namely the first adhesive layer and the second adhesive layer, or a high-frequency dielectric heating adhesive sheet consisting of only three layers, namely the first adhesive layer, the intermediate layer, and the second adhesive layer, is cited as an example for explanation, but the present invention is not limited to such an example. As one embodiment of the present invention, for example, a high-frequency dielectric heating adhesive sheet having a first adhesive layer and a second adhesive layer as the outermost layers, and consisting of a total of four or more layers, is also included.

[0294] The high-frequency dielectric heating adhesive sheet may have an adhesive portion. By having an adhesive portion, when the high-frequency dielectric heating adhesive sheet is sandwiched between the adherends, positional deviation can be prevented and the sheet can be arranged at an accurate position. The adhesive portion may be provided on one side of the high-frequency dielectric heating adhesive sheet or on both sides. In addition, the adhesive portion may be provided locally relative to the surface of the high-frequency dielectric heating adhesive sheet. In the case where the high-frequency dielectric heating adhesive sheet does not have an adhesive portion, the first adherend and the second adherend may also be firmly bonded.

[0295] The high-frequency dielectric heating treatment is not limited to the dielectric heating bonding device in which the electrodes are arranged opposite to each other as described in the above embodiment, and a grid electrode type high-frequency dielectric heating device may also be used. The grid electrode type high-frequency dielectric heating device has a grid electrode, and the grid electrode has electrodes of a first polarity and electrodes of a second polarity that are opposite to the electrodes of the first polarity arranged alternately at regular intervals on the same plane.

[0296] For example, when a bonded body is produced by overlapping the end of a first adherend with the end of a second adherend and bonding them, a grid electrode type high frequency dielectric heating device is arranged on the first adherend side or the second adherend side to apply high frequency.

[0297] When a grid electrode type high-frequency dielectric heating device is used to bond a first adherend and a second adherend, a first grid electrode can be arranged on the first adherend side, and a second grid electrode can be arranged on the second adherend side, and the first adherend, the high-frequency dielectric heating adhesive sheet and the second adherend are sandwiched between the first grid electrode and the second grid electrode, and high frequency is applied at the same time.

[0298] When a grid electrode type high-frequency dielectric heating device is used to bond the first adherend and the second adherend, a grid electrode can be arranged on one side of the first adherend and the second adherend, and a high frequency can be applied. Then, a grid electrode can be arranged on the other side of the first adherend and the second adherend, and a high frequency can be applied.

[0299] The high frequency is preferably applied using a grid electrode type high frequency dielectric heating device. By using a grid electrode type high frequency dielectric heating device, dielectric heating can be performed from the surface side of the first adherend and the second adherend, for example, from the side of the adherend that is close to the high frequency dielectric heating adhesive sheet, without being affected by the thickness of the first adherend and the second adherend, so that the adherends can be bonded to each other. In addition, by using a grid electrode type high frequency dielectric heating device, energy saving can be achieved in the manufacture of the joint body.

[0300] It should be noted that, for the sake of simplicity, the drawings illustrate an embodiment using a dielectric heating bonding device in which electrodes are arranged to face each other.

[0301] Example

[0302] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples at all.

[0303] [Method for manufacturing high-frequency dielectric heating adhesive sheet]

[0304] (Example 1)

[0305] The materials for forming the first adhesive layer were premixed in the first container in the composition (volume %) shown in Table 1. The materials for forming the second adhesive layer were also premixed in the second container in the composition (volume %) shown in Table 1. PP shown in Table 1 is the abbreviation of polypropylene, and SEBS is the abbreviation of styrene-ethylene / butylene-styrene copolymer.

[0306] PP: The main component is propylene (95 mass % or more), and the flow starting temperature is 175°C.

[0307] SEBS: The main component is styrene (67 mass%), and the flow starting temperature is 137°C.

[0308] The premixed material was supplied to the hopper of a 30mmφ twin-screw extruder, the barrel setting temperature was set to 180°C or more and 220°C or less, and the die temperature was set to 220°C, and the premixed material was melt-kneaded. The melt-kneaded material was cooled, and then the material was cut to produce granular particles. Granular particles for the first adhesive layer and granular particles for the second adhesive layer were produced respectively. Next, the granular particles for the first adhesive layer and the second adhesive layer were respectively put into the hopper of a single-screw multilayer extruder equipped with a T-die with a feed block, and the barrel temperature was set to 220°C and the die temperature was 220°C. The film-like molten kneaded material was extruded from the T-die and cooled by a cooling roller, thereby producing a high-frequency dielectric heating adhesive sheet with a thickness of 400μm consisting of a multilayer structure composed of a first adhesive layer (thickness: 200μm) and a second adhesive layer (thickness: 200μm).

[0309] (Example 2 to Example 5)

[0310] In Examples 2 to 5, a high-frequency dielectric heating adhesive sheet having an intermediate layer was prepared. The materials for forming the intermediate layer were premixed in the composition (volume %) shown in Table 1 in the third container. Granular particles for the intermediate layer were prepared in the same manner as in Example 1. Next, the granular particles for the first adhesive layer, the intermediate layer, and the second adhesive layer were respectively put into the hopper of a single-screw multilayer extruder provided with a T-die having a feed block, and at the barrel temperature and die temperature appropriately set according to the type of resin contained in each layer of the high-frequency dielectric heating adhesive sheet, a film-like molten kneaded product was extruded from the T-die and cooled by a cooling roller, thereby preparing a high-frequency dielectric heating adhesive sheet having a multilayer structure with a thickness of 400 μm, in which the first adhesive layer (thickness: 135 μm), the intermediate layer (thickness: 130 μm), and the second adhesive layer (thickness: 135 μm) are sequentially stacked.

[0311] PMMA shown in Table 1 is the abbreviation of polymethyl methacrylate, and PS is the abbreviation of polystyrene.

[0312] PMMA: The main component is methyl methacrylate (95% by mass or more), and the flow starting temperature is 165°C.

[0313] PS: The main component is styrene (95% by mass or more), and the flow starting temperature is 162°C.

[0314] (Comparative Example 1 to Comparative Example 3)

[0315] The high-frequency dielectric heating adhesive sheets of Comparative Examples 1 to 3 were prepared in the same manner as in Example 1, except that the compositions of the materials for forming the first adhesive layer and the second adhesive layer were changed to the compositions shown in Table 1, respectively, and extrusion molding was performed at a barrel temperature and a die head temperature appropriately set according to the type of resin contained in each layer of the adhesive sheet. In Comparative Examples 1 to 3, the ratio of the thickness of the first adhesive layer and the second adhesive layer was also the same as in Example 1.

[0316] (Comparative Example 4)

[0317] The high-frequency dielectric heating adhesive sheet of Comparative Example 4 was prepared in the same manner as in Example 2, except that the compositions of the materials for forming the first adhesive layer, the intermediate layer, and the second adhesive layer were changed to the compositions shown in Table 1, respectively, and extrusion molding was performed at a barrel temperature and a die head temperature appropriately set according to the type of resin contained in each layer of the adhesive sheet. In Comparative Example 4, the ratio of the thickness of the first adhesive layer, the intermediate layer, and the second adhesive layer was also the same as in Example 2.

[0318] Table 2 shows the volume content of each thermoplastic resin in the thermoplastic resin of the first adhesive layer, the second adhesive layer and the intermediate layer of the produced high-frequency dielectric heating adhesive sheet, and the values ​​of the change rates Vx1 and Vx2 represented by the above-mentioned mathematical formulas (Math 1) and (Math 2).

[0319] [High frequency adhesion]

[0320] The produced high-frequency dielectric heating adhesive sheet was cut into a size of 25mm×12.5mm. The first adherend and the second adherend of the material shown in Table 1 were prepared, and the sizes of the first adherend and the second adherend were set to 25mm×100mm×2mm (thickness). The high-frequency dielectric heating adhesive sheet cut into the above size was sandwiched between the first adherend and the second adherend. At this time, the first adhesive layer of the high-frequency dielectric heating adhesive sheet was contacted with the first adherend, and the second adhesive layer was contacted with the second adherend. The first adherend, the high-frequency dielectric heating adhesive sheet and the second adherend were fixed between the electrodes of the high-frequency dielectric heating device ("YRP-400T-A" manufactured by Yamamoto Vinita Co., Ltd.), and in a fixed state, high frequency was applied under the following high-frequency application conditions to bond the high-frequency dielectric heating adhesive sheet to the adherend, and an initial test piece was prepared.

[0321] PP, which is the material of the first adherend shown in Table 1, is the abbreviation of polypropylene, PMMA is the abbreviation of polymethyl methacrylate, and PS, which is the material of the second adherend, is the abbreviation of polystyrene.

[0322] PP: The main component is propylene (95% by mass or more).

[0323] PMMA: The main component is methyl methacrylate (95% by mass or more).

[0324] PS: The main component is styrene (95% by mass or more).

[0325] High frequency application conditions

[0326] Frequency: 40.68MHz

[0327] Output power: 200W

[0328] Application time: 10 seconds

[0329] [Adhesion strength (tensile shear strength)]

[0330] For the initial test piece obtained in the high-frequency adhesive evaluation, the tensile shear force as the adhesive force was measured. The tensile shear force was measured using a universal tensile testing machine (Instron 5581). The tensile speed in the tensile shear force measurement was set to 100 mm / min. The tensile shear force was measured in accordance with JIS K 6850:1999.

[0331] The fracture morphology of the test piece when the tensile shear force was measured was observed, and the adhesive strength was evaluated according to the following evaluation criteria. The evaluation results of the adhesive strength are shown in Table 1.

[0332] Destruction form

[0333] Cf: Cohesive failure of the adhesive sheet occurred.

[0334] BC: At least one of the first adherend and the second adherend is destroyed.

[0335] IF S : Interface peeling occurred in the adhesive sheet.

[0336] IF A : Interface peeling occurred between the first adherend and the first adhesive layer.

[0337] IF B : Interface peeling occurred between the second adherend and the second adhesive layer.

[0338] [Interlayer Adhesion]

[0339] The cross-cut test according to JIS K5600-5-6:1999 was performed on the prepared high-frequency dielectric heating adhesive sheet to evaluate the interlayer adhesion. Specifically, the surface of the high-frequency dielectric heating adhesive sheet was subjected to corona treatment (200 W·min / m 2), a PET film (manufactured by Toyobo Co., Ltd., product name "COSMOSHINE A4300") was attached to the corona-treated surface of a double-sided adhesive sheet (TL-52BM-05 manufactured by Lintec Co., Ltd.) to prepare a test piece, and cuts were formed to the adhesive layer at intervals of 2 mm. It should be noted that for the test piece with the PET film attached to the first adhesive layer side, the cuts were formed from the second adhesive layer side, and for the test piece with the PET film attached to the second adhesive layer side, the cuts were formed from the first adhesive layer side.

[0340] For each layer of the high-frequency dielectric heating adhesive sheet, after the cross-cut test, the ratio of the number of grids that adhered without peeling from the layer in contact with the layer was observed, and the interlayer adhesion was evaluated according to the following evaluation criteria. The evaluation results of the interlayer adhesion are shown in Table 1.

[0341] Evaluation benchmark

[0342] Evaluation A1: The ratio of the number of cells that adhered without peeling off from the layer in contact with the first adhesive layer (second adhesive layer or intermediate layer) and the ratio of the number of cells that adhered without peeling off from the layer in contact with the second adhesive layer (first adhesive layer or intermediate layer) were 50% or more.

[0343] Evaluation F1: At least one of the ratio of the number of cells that adhere without being peeled off from the layer in contact with the first adhesive layer (the second adhesive layer or the intermediate layer) and the ratio of the number of cells that adhere without being peeled off from the layer in contact with the second adhesive layer (the first adhesive layer or the intermediate layer) is less than 50%.

[0344] In addition, about the high-frequency dielectric heating adhesive sheet of Examples 1-5, it was evaluation A1, and the number of remaining grids was 100%.

[0345] [Volume average particle size of dielectric filler]

[0346] The particle size distribution of the dielectric filler was measured by laser diffraction / scattering method. Based on the results of the particle size distribution measurement, the volume average particle size was calculated in accordance with JIS Z 8819-2: 2001. The calculated average particle size (volume average particle size) of the dielectric filler (zinc oxide) was 11 μm.

[0347] [Flow start temperature]

[0348] The flow start temperature of the thermoplastic resin used in the production of high-frequency dielectric heating adhesive sheets was measured using a descending rheometer (manufactured by Shimadzu Corporation, model "CFT-100D"). The load was set to 5 kg, a die with a hole shape of φ2.0 mm and a length of 5.0 mm was used, and a barrel with an inner diameter of 11.329 mm was used. The temperature of the measured sample was raised at a heating rate of 10 ° C / min, and the stroke displacement speed (mm / min) that changed with the temperature increase was measured to obtain the temperature dependence curve of the stroke displacement speed of the sample. In this curve, the temperature at which the stroke displacement speed starts to rise again after the peak obtained on the low temperature side is taken as the flow start temperature.

[0349] [Dielectric properties]

[0350] The prepared high-frequency dielectric heating adhesive sheet was cut into a size of 30 mm × 30 mm. For the cut high-frequency dielectric heating adhesive sheet, the dielectric material test fixture 16453A (made by Agilent) was installed in the RF impedance / material analyzer E4991A (made by Agilent), and the relative dielectric constant (ε'r) and dielectric loss tangent (tanδ) were measured by the parallel plate method at 23°C and a frequency of 40.68 MHz. Based on the measurement results, the value of the dielectric property (tanδ / ε'r) is calculated. For example, the dielectric properties (tanδ / ε'r) of the high-frequency dielectric heating adhesive sheets of Examples 1 to 5 are shown in Table 1.

[0351]

[0352]

[0353] As shown in Table 1 and Table 2, the high-frequency dielectric heating adhesive sheets of Examples 1 to 5 can firmly bond the first adherend and the second adherend without causing interlayer delamination.

[0354] In the high-frequency dielectric heating adhesive sheet of Comparative Example 1, the volume content of the first thermoplastic resin (PP) in the first adhesive layer was less than 60 volume %, and therefore, interface peeling occurred between the first adhesive layer and the first adherend.

[0355] In the high-frequency dielectric heating adhesive sheet of Comparative Example 2, the volume content of the second thermoplastic resin (SEBS) in the second adhesive layer was less than 60 volume %, and therefore, interface peeling occurred between the second adhesive layer and the second adherend.

[0356] In the high-frequency dielectric heating adhesive sheets of Comparative Examples 3 and 4, the change rate Vx2 in the composition of the first adhesive layer, the second adhesive layer, and the intermediate layer was 80% or more, and interlayer delamination occurred.

[0357] Therefore, the high-frequency dielectric heating adhesive sheets of Comparative Examples 1 to 4 cannot bond the first adherend and the second adherend.

Claims

1. A high-frequency dielectric heating adhesive sheet, comprising a first adhesive layer and a second adhesive layer as outermost layers, wherein the second adhesive layer is located on the surface side opposite to the first adhesive layer, The first adhesive layer contains a first thermoplastic resin and a first dielectric filler that generates heat at high frequencies. The second adhesive layer contains a second thermoplastic resin and a second dielectric filler that generates heat at high frequencies. The first thermoplastic resin and the second thermoplastic resin are different resins from each other. The first thermoplastic resin and the second thermoplastic resin are at least one selected from polyolefin resins, styrene resins, polyacetal resins, polycarbonate resins, polyacrylic resins, polyamide resins, polyimide resins, polyvinyl acetate resins, phenoxy resins, and polyester resins. The first dielectric filler and the second dielectric filler are each independently selected from zinc oxide, silicon carbide (SiC), titanium oxide, barium titanate, barium titanate zirconate, lead titanate, potassium niobate, hydrated aluminum silicate, hydrated aluminum silicate of alkali metals and hydrated aluminum silicate of alkaline earth metals, either alone or in combination of two or more thereof. At least one of a volume content of the first dielectric filler in the first adhesive layer and a volume content of the second dielectric filler in the second adhesive layer is 5 volume % or more and 50 volume % or less, The volume content VA1 of the first thermoplastic resin is 60 volume % or more and 100 volume % or less relative to the total thermoplastic resin in the first adhesive layer, The volume content VA2 of the second thermoplastic resin is 60 volume % or more and 100 volume % or less relative to the total thermoplastic resin in the second adhesive layer, The change rate Vx1 of the volume content VA1 and VB1 of the first thermoplastic resin represented by the following mathematical formula 1 is less than 80%, wherein VB1 is the volume content of the first thermoplastic resin relative to the total thermoplastic resin in the layer directly contacting the first adhesive layer, The change rate Vx2 of the volume content VA2 and VB2 of the second thermoplastic resin represented by the following mathematical formula 2 is less than 80%, wherein VB2 is the volume content of the second thermoplastic resin relative to the total thermoplastic resin in the layer directly contacting the second adhesive layer, Vx1={(VA1-VB1) / VA1}×100···Mathematical formula 1 Vx2={(VA2-VB2) / VA2}×100···Mathematical formula 2.

2. The high-frequency dielectric heating adhesive sheet according to claim 1, which is a sheet for joining a first adherend and a second adherend made of a material different from that of the first adherend. The first adherend contains a third thermoplastic resin, The second adherend contains a fourth thermoplastic resin, The main composition of the first thermoplastic resin is the same as the main composition of the third thermoplastic resin, The main composition of the second thermoplastic resin is the same as the main composition of the fourth thermoplastic resin, The first adhesive layer is bonded to the first adherend, The second adhesive layer is bonded to the second adherend.

3. The high-frequency dielectric heating adhesive sheet according to claim 1, wherein: At least one of the first dielectric filler and the second dielectric filler is at least one selected from the group consisting of zinc oxide, silicon carbide, titanium oxide, and barium titanate.

4. The high-frequency dielectric heating adhesive sheet according to claim 1, wherein: At least one of the volume average particle size of the first dielectric filler and the volume average particle size of the second dielectric filler is 1 μm or more and 30 μm or less, The volume average particle size is a volume average particle size calculated based on the particle size distribution measurement result of at least one of the first dielectric filler and the second dielectric filler by a laser diffraction / scattering method in accordance with JIS Z 8819-2:2001.

5. The high-frequency dielectric heating adhesive sheet according to claim 1, wherein: The first thermoplastic resin is a polyolefin resin.

6. The high-frequency dielectric heating adhesive sheet according to claim 1, wherein: The absolute value of the difference between the flow start temperature Tx1 of the first thermoplastic resin and the flow start temperature Tx2 of the second thermoplastic resin satisfies the relationship of the following mathematical formula 4: |Tx1-Tx2|≤70···Formula 4.

7. The high-frequency dielectric heating adhesive sheet according to claim 1, wherein: After a cross-cut test in accordance with JIS K5600-5-6:1999, the ratio of the number of cross-cuts that adhere to the layer in contact with the layer without being peeled off in all the layers of the high-frequency dielectric heating adhesive sheet is 50% or more.

8. The high-frequency dielectric heating adhesive sheet according to claim 1, wherein: The polyolefin resin is a polyolefin resin having a polar part. 9 . The high-frequency dielectric heating adhesive sheet according to claim 1 , further comprising an intermediate layer disposed between the first adhesive layer and the second adhesive layer.

10. The high-frequency dielectric heating adhesive sheet according to claim 9, wherein: The intermediate layer contains the first thermoplastic resin and the second thermoplastic resin.

11. The high-frequency dielectric heating adhesive sheet according to claim 9, wherein: The first adhesive layer is in direct contact with the intermediate layer, The second adhesive layer is in direct contact with the intermediate layer.

12. The high-frequency dielectric heating adhesive sheet according to any one of claims 1 to 8, wherein The layer in direct contact with the first adhesive layer is the second adhesive layer.

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