JP7698517B2 - Adhesion method - Google Patents

Description

The present invention relates to an adhesion method.

In recent years, methods have been proposed for bonding adherends that are generally difficult to bond together, such as by placing an adhesive made of a specific resin mixed with a heat-generating material between the adherends and then performing dielectric heating, induction heating, ultrasonic welding, laser welding, or other processes.

For example, Patent Document 1 describes a high-frequency dielectric heating adhesive sheet for bonding multiple adherends made of the same or different materials, and this high-frequency dielectric heating adhesive sheet contains a specified thermoplastic resin and a dielectric filler mixed in a specified ratio.

International Publication No. 2018/147351

Patent Document 1 makes it possible to shorten the application time of the high-frequency electric field, but from the perspective of production efficiency, there is a demand to further shorten the application time.

The object of the present invention is to provide a bonding method that can shorten the application time of a high-frequency electric field and improve the adhesive strength even when the electric field is applied for a short period of time.

According to one aspect of the present invention, there is provided a method for bonding an adherend with a high-frequency dielectric heating adhesive sheet, the high-frequency dielectric heating adhesive sheet containing a thermoplastic resin (A), the method comprising a first step of applying a high-frequency electric field with an applied output per unit area V1 to the high-frequency dielectric heating adhesive sheet, and a second step of applying a high-frequency electric field with an applied output per unit area V2 to the high-frequency dielectric heating adhesive sheet after the first step, wherein the applied output per unit area V1 in the first step and the applied output per unit area V2 in the second step satisfy the condition expressed by the following mathematical formula (Mathematical Formula 1).
V1>V2...(Math. 1)

In a bonding method according to one aspect of the present invention, it is preferable that the applied output V1 per unit area in the first step and the applied output V2 per unit area in the second step satisfy the condition expressed by the following mathematical formula (Math 1-1).
0.8×V1≧V2 (Equation 1-1)

In the bonding method according to one aspect of the present invention, it is preferable that the applied output V1 per unit area in the first step is 0.18 W/mm2 or ^more and 2.00 W/ ^mm2 or less.

In one embodiment of the bonding method of the present invention, it is preferable that the application time T1 of the first step is 1 second or more and less than 25 seconds.

In the bonding method according to one aspect of the present invention, it is preferable that the applied output V2 per unit area in the second step is 0.09 W/mm2 or ^more and 0.30 W/ ^mm2 or less.

In one embodiment of the bonding method of the present invention, it is preferable that the application time T2 of the second step is 5 seconds or longer.

In the bonding method according to one aspect of the present invention, it is preferable that the application time T1 of the first step and the application time T2 of the second step satisfy the condition expressed by the following formula (Mathematical Expression 2).
(T1+T2) < 60 seconds... (Equation 2)

According to one aspect of the present invention, there is provided a method for bonding an adherend with a high-frequency dielectric heating adhesive sheet, the high-frequency dielectric heating adhesive sheet containing a thermoplastic resin (A), the method comprising a first step of applying a high-frequency electric field with an applied energy per unit area J1 to the high-frequency dielectric heating adhesive sheet, and a second step of applying a high-frequency electric field with an applied energy per unit area J2 to the high-frequency dielectric heating adhesive sheet after the first step, wherein the applied energy per unit area J1 in the first step and the applied energy per unit area J2 in the second step satisfy the condition expressed by the following mathematical formula (Mathematical Formula 3).
J1>0.75×J2 (Equation 3)

In the bonding method according to one aspect of the present invention, it is preferable that the applied energy J1 per unit area in the first step and the applied energy J2 per unit area in the second step satisfy the condition expressed by the following formula (Mathematical formula 3-1).
0.9>J1/(J1+J2)>0.4...(Equation 3-1)

In the bonding method according to one aspect of the present invention, the thermoplastic resin (A) is preferably a polyolefin resin.

In the bonding method according to one aspect of the present invention, it is preferable that the high-frequency dielectric heating adhesive sheet further contains a dielectric filler (B) that generates heat upon application of a high-frequency electric field.

In the bonding method according to one aspect of the present invention, it is preferable that the dielectric filler (B) contains at least one selected from the group consisting of zinc oxide, silicon carbide, barium titanate, and titanium oxide.

According to one aspect of the present invention, it is possible to provide a bonding method that can shorten the application time of a high-frequency electric field and improve the adhesive strength even when the electric field is applied for a short period of time.

FIG. 1 is a schematic diagram illustrating a high-frequency dielectric heating process using a high-frequency dielectric heating adhesive sheet and a dielectric heating device according to one embodiment. 1A, 1B, and 1C are schematic cross-sectional views of high-frequency dielectric heating adhesive sheets according to various embodiments.

[First embodiment]
[Adhesion method]
The bonding method according to the present embodiment is a method for bonding adherends using a high-frequency dielectric heating adhesive sheet. This high-frequency dielectric heating adhesive sheet contains a thermoplastic resin (A).
The bonding method according to the present embodiment includes a first step of applying a high-frequency electric field with an applied output per unit area V1 to the high-frequency dielectric heating adhesive sheet, and a second step of applying a high-frequency electric field with an applied output per unit area V2 to the high-frequency dielectric heating adhesive sheet after the first step, where the applied output per unit area V1 in the first step and the applied output per unit area V2 in the second step satisfy the condition expressed by the following formula (Mathematical formula 1). Note that the high-frequency electric field is an electric field whose direction is reversed at high frequencies.
V1>V2...(Math. 1)

As an example of the bonding method according to this embodiment, a high-frequency dielectric heating adhesive sheet consisting of a single adhesive layer is used to bond a first adherend and a second adherend, but the present invention is not limited to this embodiment. There is also no particular limitation on the materials of the first adherend and the second adherend.

The bonding method according to this embodiment includes the following first and second steps.
The first and second steps are steps in which a high-frequency electric field is applied to a high-frequency dielectric heating adhesive sheet sandwiched between a first adherend and a second adherend, thereby bonding the first adherend and the second adherend with the high-frequency dielectric heating adhesive sheet.
Usually, the process of applying a high-frequency electric field is not divided into two steps. In contrast, in this embodiment, the process is divided into two specific steps, the first step and the second step, to adjust the degree of melting and heating of the resin in the high-frequency dielectric heating adhesive sheet. As a result, it is presumed that the adhesive strength can be improved even if the electric field is applied for a short period of time according to this embodiment.

In the first step, a high-frequency electric field having an applied output per unit area V1 is applied to the high-frequency dielectric heating adhesive sheet.
In the second step, a high-frequency electric field having an applied output per unit area of V2 is applied to the high-frequency dielectric heating adhesive sheet after the first step.

It is necessary that the applied output V1 per unit area in the first step and the applied output V2 per unit area in the second step satisfy the condition expressed by the following formula (Mathematical Expression 1).
V1>V2...(Math. 1)
If the condition expressed by the above formula (Formula 1) is not satisfied, it is not possible to improve the adhesive strength while shortening the application time of the high frequency electric field.

In this embodiment, it is preferable that the applied output V1 per unit area in the first step and the applied output V2 per unit area in the second step satisfy the condition expressed by the following formula (Math. 1-1).
0.8×V1≧V2 (Equation 1-1)
When the condition represented by the above formula (Formula 1-1) is satisfied, the adhesive strength is easily improved.
From a similar viewpoint, the upper limit of the second applied power V2 per unit area is preferably 0.75 times or less the value of the applied power V1 per unit area in the first step, more preferably 0.7 times or less the value of the applied power V1 per unit area in the first step, even more preferably 0.65 times or less the value of the applied power V1 per unit area, and particularly preferably 0.6 times or less the value of the applied power V1 per unit area.
Furthermore, from the viewpoint of shortening the application time, the lower limit of the applied output V2 per unit area in the second step is preferably 0.1 times or more the value of the applied output V1 per unit area in the first step, more preferably 0.2 times or more the value of the applied output V1 per unit area in the first step, even more preferably 0.3 times or more the value of the applied output V1 per unit area in the first step, and particularly preferably 0.4 times or more the value of the applied output V1 per unit area in the first step.

The applied power V1 per unit area in the first step is preferably 0.18 W/ ^mm2 or more, more preferably 0.20 W/ ^mm2 or more, and even more preferably 0.22 W/ ^mm2 or more. The applied power V1 per unit area in the first step is preferably 2.00 W/ ^mm2 or less, more preferably 1.75 W/mm2 or ^less , even more preferably 1.50 W/ ^mm2 or less, even more preferably 1.25 W/ ^mm2 or less, even more preferably 1.00 W/ ^mm2 or less, even more preferably 0.75 W/ ^mm2 or less, and particularly preferably 0.5 W/ ^mm2 or less.
If the applied power V1 per unit area in the first step is 0.18 W/ ^mm2 or more, the problem of the resin being difficult to melt can be prevented, making it easier to obtain good adhesive strength.
If the applied power V1 per unit area in the first step is 2.00 W/ ^mm2 or less, the resin can be prevented from foaming, which can reduce the adhesive strength, making it easier to obtain good adhesive strength.

The application time T1 in the first step is preferably 1 second or more, more preferably 3 seconds or more, even more preferably 5 seconds or more, even more preferably 7 seconds or more, and particularly preferably 10 seconds or more. The application time T1 in the first step is preferably less than 25 seconds, more preferably 24 seconds or less, and even more preferably 20 seconds or less.
If the application time T1 in the first step is 1 second or more, the problem of the temperature not rising easily during the dielectric heating process can be prevented, making it easier to obtain good adhesive strength.
If the application time T1 in the first step is less than 25 seconds, the application time of the high frequency electric field can be further shortened.

The applied power V2 per unit area in the second step is preferably 0.09 W/ ^mm2 or more, more preferably 0.10 W/ ^mm2 or more, and even more preferably 0.11 W/ ^mm2 or more. The applied power V2 per unit area in the second step is preferably 0.30 W/ ^mm2 or less, more preferably 0.25 W/ ^mm2 or less, even more preferably 0.20 W/ ^mm2 or less, and particularly preferably 0.18 W/ ^mm2 or less.
If the applied output V2 per unit area in the second step is 0.09 W/ ^mm2 or more, the processing temperature after the first step can be maintained, making it easier to obtain good adhesive strength.
If the applied power V2 per unit area in the second step is 0.30 W/ ^mm2 or less, the resin can be prevented from foaming, which can reduce the adhesive strength, making it easier to obtain good adhesive strength.

The application time T2 in the second step is preferably 5 seconds or more, more preferably 7 seconds or more, even more preferably 9 seconds or more, and particularly preferably 10 seconds or more. The application time T2 in the second step is preferably less than 60 seconds, more preferably 50 seconds or less, even more preferably 40 seconds or less, and particularly preferably 30 seconds or less.
If the application time T2 in the second step is 5 seconds or more, a time during which the treatment temperature after the first step can be maintained can be secured, making it easier to obtain good adhesive strength.
If the application time T2 in the second step is less than 60 seconds, the application time of the high frequency electric field can be further shortened.

In this embodiment, it is preferable that the application time T1 of the first step and the application time T2 of the second step satisfy the condition expressed by the following formula (Mathematical formula 2).
(T1+T2) < 60 seconds... (Equation 2)
When the condition expressed by the above formula (Formula 2) is satisfied, the application time of the high frequency electric field can be further shortened.
From the same viewpoint, the sum (T1+T2) of the application time T1 and the application time T2 is more preferably 50 seconds or less, further preferably 40 seconds or less, and particularly preferably 30 seconds or less.

In the first and second steps, the frequency of the high frequency electric field applied is preferably 1 kHz or more, more preferably 1 MHz or more, even more preferably 5 MHz or more, and even more preferably 10 MHz or more.
The frequency of the applied high-frequency electric field is preferably 300 MHz or less, more preferably 100 MHz or less, even more preferably 80 MHz or less, and even more preferably 50 MHz or less. Specifically, the industrial frequency bands of 13.56 MHz, 27.12 MHz, or 40.68 MHz assigned by the International Telecommunication Union are also used in the bonding method according to this embodiment.

The bonding method according to this embodiment may include step P1 before the above-mentioned first and second steps.

・Process P1
Step P1 is a step of placing the high-frequency dielectric heating adhesive sheet according to this embodiment between a first adherend and a second adherend. In step P1, the first adherend is brought into contact with the first surface of the high-frequency dielectric heating adhesive sheet. Also, in step P1, the second adherend is brought into contact with the second surface of the high-frequency dielectric heating adhesive sheet.

It is preferable to sandwich a high-frequency dielectric heating adhesive sheet between the first and second adherends so that the first and second adherends can be bonded to each other. The high-frequency dielectric heating adhesive sheet may be sandwiched between the first and second adherends at a portion, a plurality of locations, or over the entire surface. From the viewpoint of improving the adhesive strength between the first and second adherends, it is preferable to sandwich the high-frequency dielectric heating adhesive sheet over the entire adhesive surface between the first and second adherends.
In addition, as an embodiment of sandwiching the high-frequency dielectric heating adhesive sheet in a portion between the first and second adherends, the high-frequency dielectric heating adhesive sheet is arranged in a frame shape along the outer periphery of the adhesive surface between the first and second adherends, and sandwiched between the first and second adherends. By arranging the high-frequency dielectric heating adhesive sheet in a frame shape in this way, the adhesive strength between the first and second adherends can be obtained, and the joined body can be made lighter than when the high-frequency dielectric heating adhesive sheet is arranged over the entire adhesive surface.
Furthermore, according to one embodiment in which a high-frequency dielectric heating adhesive sheet is sandwiched between a portion of the first adherend and a second adherend, the size of the high-frequency dielectric heating adhesive sheet used can be reduced, thereby shortening the high-frequency dielectric heating treatment time compared to when a high-frequency dielectric heating adhesive sheet is placed over the entire adhesive surface.

(adherent)
The material of the first adherend and the second adherend is not particularly limited. The material of the adherend may be any of organic materials and inorganic materials (including metal materials, etc.), or may be a composite material of an organic material and an inorganic material.
Examples of organic materials as the material of the adherend include plastic materials and rubber materials. Examples of plastic materials include polypropylene resin, polyethylene resin, polyurethane resin, acrylonitrile-butadiene-styrene copolymer resin (ABS resin), polycarbonate resin (PC resin), polyamide resin (nylon 6, nylon 66, etc.), polyester resin (polyethylene terephthalate (PET resin), polybutylene terephthalate resin (PBT resin), etc.), polyacetal resin (POM resin), polymethyl methacrylate resin, and polystyrene resin. Examples of rubber materials include styrene-butadiene rubber (SBR), ethylene propylene rubber (EPR), and silicone rubber. The adherend may also be a foamed organic material.
Examples of inorganic materials as the material of the adherend include glass materials, cement materials, ceramic materials, and metal materials. The adherend may also be a fiber reinforced plastic (FRP), which is a composite material of fibers and the above-mentioned plastic materials. The plastic material in the fiber reinforced resin is at least one selected from the group consisting of polypropylene resin, polyethylene resin, polyurethane resin, acrylonitrile-butadiene-styrene copolymer resin (ABS resin), polycarbonate resin (PC resin), polyamide resin (nylon 6 and nylon 66, etc.), polyester resin (polyethylene terephthalate (PET resin) and polybutylene terephthalate resin (PBT resin)), polyacetal resin (POM resin), polymethyl methacrylate resin, and polystyrene resin. Examples of fibers in the fiber reinforced resin include glass fibers, Kevlar fibers, and carbon fibers.
When a plurality of adherends are bonded together using the high frequency dielectric heating adhesive sheet according to this embodiment, the adherends may be made of the same material or different materials.
The high frequency dielectric heating adhesive sheet according to this embodiment can be suitably used for bonding to an adherend.
The shape of the adherend is not particularly limited, but it is preferable that the adherend has a surface to which the high-frequency dielectric heating adhesive sheet can be attached, and is preferably in the form of a sheet or plate. When multiple adherends are to be bonded together, the shapes and dimensions of the adherends may be the same or different from each other.

(Dielectric heating bonding device)
In the above-mentioned first and second steps, for example, a dielectric heating bonding device can be used to apply a high-frequency electric field to the high-frequency dielectric heating bonding sheet.
FIG. 1 shows a schematic diagram for explaining a high-frequency dielectric heating treatment using a high-frequency dielectric heating adhesive sheet and a dielectric heating device according to this embodiment.
A schematic diagram of a dielectric heating bonding apparatus 50 is shown in FIG.
The dielectric heating bonding device 50 includes a first high frequency electric field applying electrode 51 , a second high frequency electric field applying electrode 52 , and a high frequency power supply 53 .
The first high-frequency electric field application electrode 51 and the second high-frequency electric field application electrode 52 are disposed opposite to each other. The first high-frequency electric field application electrode 51 and the second high-frequency electric field application electrode 52 have a press mechanism. This press mechanism can apply pressure to the first adherend 110, the high-frequency dielectric heating adhesive sheet 1A, and the second adherend 120 between the first high-frequency electric field application electrode 51 and the second high-frequency electric field application electrode 52.

When the first high frequency electric field applying electrode 51 and the second high frequency electric field applying electrode 52 form a pair of parallel plate electrodes, this type of electrode arrangement is sometimes called a parallel plate type.
It is also preferable to use a parallel plate type high frequency dielectric heating device for applying the high frequency electric field. With 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 entire high frequency dielectric heating adhesive sheet can be heated and the adherend and the high frequency dielectric heating adhesive sheet can be bonded in a short time.

A high frequency power supply 53 for applying a high frequency electric field of, for example, about 13.56 MHz, about 27.12 MHz, or about 40.68 MHz is connected to each of the first high frequency electric field applying electrode 51 and the second high frequency electric field applying electrode 52 .
1, the dielectric heating bonding apparatus 50 performs a dielectric heating treatment via a high-frequency dielectric heating adhesive sheet 1A sandwiched between a first adherend 110 and a second adherend 120. Furthermore, in addition to the dielectric heating treatment, the dielectric heating bonding apparatus 50 bonds the first adherend 110 and the second adherend 120 by a pressure treatment using a first high-frequency electric field application electrode 51 and a second high-frequency electric field application electrode 52.

When a high frequency electric field is applied between the first high frequency electric field applying electrode 51 and the second high frequency electric field applying electrode 52, the high frequency dielectric heating adhesive sheet 1A absorbs the high frequency energy.
Then, the thermoplastic resin component of the high frequency dielectric heating adhesive sheet 1A melts, and finally the first adherend 110 and the second adherend 120 can be firmly adhered to each other.

The first high-frequency electric field application electrode 51 and the second high-frequency electric field application electrode 52 have a pressing mechanism, and therefore also function as a pressing device. Therefore, the first adherend 110 and the second adherend 120 can be more firmly bonded together by the compression direction pressure applied by the first high-frequency electric field application electrode 51 and the second high-frequency electric field application electrode 52 and the heating and melting of the high-frequency dielectric heating adhesive sheet 1A.

The bonded body according to the present embodiment includes a first adherend, a second adherend, and the high-frequency dielectric heating adhesive sheet according to the present embodiment. The first adherend and the second adherend are bonded together by the high-frequency dielectric heating adhesive sheet.
One embodiment of the bonded body according to this embodiment includes, for example, a bonded body having a first adherend 110, a high-frequency dielectric heating adhesive sheet 1A, and a second adherend 120, as shown in FIG.

[High frequency dielectric heating adhesive sheet]
Next, a high-frequency dielectric heating adhesive sheet used in the bonding method according to the present embodiment will be described. The high-frequency dielectric heating adhesive sheet according to the present embodiment has an adhesive layer. The adhesive layer contains a thermoplastic resin (A).

(Thermoplastic resin (A))
The type of thermoplastic resin (A) is not particularly limited.
The thermoplastic resin (A) is preferably at least one selected from the group consisting of polyolefin-based resins, styrene-based resins, polyacetal-based resins, polycarbonate-based resins, polyacrylic-based resins, polyamide-based resins, polyimide-based resins, polyvinyl acetate-based resins, phenoxy-based resins, and polyester-based resins, for example, from the viewpoints of being easily melted and having a predetermined heat resistance.
The thermoplastic resin (A) is preferably a polyolefin resin, from the viewpoints of being inexpensive and having excellent moldability and mechanical strength.
In this specification, polyolefin-based resins include polyolefin-based resins having polar moieties and polyolefin-based resins not having polar moieties, and when specifying the presence or absence of polar moieties, they are described as polyolefin-based resins having polar moieties or polyolefin-based resins not having polar moieties.

(Polyolefin resin)
Examples of the polyolefin resin as the thermoplastic resin include a resin made of a homopolymer such as polyethylene, polypropylene, polybutene, and polymethylpentene, and an α-olefin resin made of a copolymer of a monomer selected from the group consisting of ethylene, propylene, butene, hexene, octene, 4-methylpentene, etc. The polyolefin resin as the thermoplastic resin may be a single type of resin or a combination of two or more types of resins.

(Polyolefin resin having polar moieties)
The polar moiety in the polyolefin resin having a polar moiety is not particularly limited as long as it is a moiety that can impart polarity to the polyolefin resin. A polyolefin resin having a polar moiety is preferred because it exhibits high adhesive strength to an adherend.
The thermoplastic resin may be a copolymer of an olefin monomer and a monomer having a polar moiety, or a resin obtained by introducing a polar moiety into an olefin polymer obtained by polymerization of an olefin monomer through modification such as an addition reaction.

The type of olefin monomer constituting the polyolefin resin having a polar moiety as a thermoplastic resin is not particularly limited. 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 of these.
Of the olefin monomers, ethylene and polypropylene are preferred from the viewpoints of excellent mechanical strength and stable adhesive properties.
The olefin-derived structural unit in the polyolefin-based resin having a polar moiety is preferably a structural unit derived from ethylene or propylene.

Examples of polar moieties include hydroxyl groups, carboxyl groups, vinyl acetate structures, and acid anhydride structures.

(Dielectric Filler (B))
The high frequency dielectric heating adhesive sheet according to this embodiment preferably further contains a dielectric filler (B) that generates heat upon application of a high frequency electric field.
The dielectric filler (B) is preferably a filler that generates heat when a high-frequency electric field having a frequency range of 3 MHz or more and 300 MHz or less is applied to it. The dielectric filler (B) is preferably a filler that generates heat when a high-frequency electric field having a frequency range of 3 MHz or more and 300 MHz or less is applied to it, for example, a frequency of 13.56 MHz, 27.12 MHz, or 40.68 MHz.

(kinds)
The dielectric filler (B) is preferably an inorganic material having water of crystallization, such as zinc oxide, silicon carbide (SiC), anatase type titanium oxide, barium titanate, barium titanate zirconate, lead titanate, potassium niobate, rutile type titanium oxide, hydrated aluminum silicate, hydrated aluminosilicate of an alkali metal, or an inorganic material having water of crystallization, such as hydrated aluminosilicate of an alkaline earth metal, either alone or in combination of two or more kinds.

The dielectric filler (B) preferably contains at least one selected from the group consisting of zinc oxide, silicon carbide, barium titanate, and titanium oxide.

Among the dielectric fillers exemplified above, it is more preferable that the dielectric filler (B) is zinc oxide, since there are many kinds, various shapes and sizes to choose from, and the adhesive properties and mechanical properties of the high-frequency dielectric heating adhesive sheet can be improved according to the application. By using zinc oxide as the dielectric filler (B), a colorless high-frequency dielectric heating adhesive sheet can be obtained. Since zinc oxide has a small density among dielectric fillers, when an adherend is bonded using a high-frequency dielectric heating adhesive sheet containing zinc oxide as the dielectric filler (B), the total weight of the bonded body is less likely to increase compared to when a sheet containing another dielectric filler is used. Since zinc oxide is not too hard among ceramics, it is less likely to damage the manufacturing equipment of the high-frequency dielectric heating adhesive sheet. Since zinc oxide is an inactive oxide, even when mixed with a thermoplastic resin, it causes less damage to the thermoplastic resin.
Moreover, the titanium oxide as the dielectric filler (B) is preferably at least one of anatase type titanium oxide and rutile type titanium oxide, and from the viewpoint of excellent dielectric properties, anatase type titanium oxide is more preferable.

(volume content)
The volume content of the dielectric filler (B) in the adhesive layer is preferably 10 volume % or more, and more preferably 15 volume % or more.
The volume content of the dielectric filler (B) in the adhesive layer is preferably 50 volume % or less, more preferably 40 volume % or less, even more preferably 35 volume % or less, and even more preferably 25 volume % or less.
When the volume content of the dielectric filler (B) in the adhesive layer is 10 volume % or more, the application time can be further shortened.
When the volume content of the dielectric filler (B) in the adhesive layer is 50 volume % or less, the adhesive layer is less likely to become embrittled, and therefore, adhesive strength is easily obtained.

(Average particle size)
The volume average particle size of the dielectric filler (B) is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more.
The volume average particle size of the dielectric filler (B) is preferably 30 μm or less, more preferably 25 μm or less, and even more preferably 20 μm or less.
When the volume average particle diameter of the dielectric filler (B) is 1 μm or more, the high-frequency dielectric heating adhesive sheet exhibits high heat generation performance when a high-frequency electric field is applied, and the adhesive layer can be firmly bonded to the adherend in a short time.
By making the volume average particle diameter of the dielectric filler (B) 30 μm or less, the high-frequency dielectric heating adhesive sheet exhibits high heat generation performance when a high-frequency electric field is applied, and the adhesive layer can be firmly bonded to the adherend in a short time. In addition, by making the volume average particle diameter of the dielectric filler (B) 30 μm or less, the strength of the high-frequency dielectric heating adhesive sheet can be prevented from decreasing.

The volume average particle diameter of the dielectric filler (B) is measured by the following method. The particle size distribution of the dielectric filler (B) is measured by a laser diffraction/scattering method, and the volume average particle diameter is calculated from the results of the particle size distribution measurement in accordance with JIS Z 8819-2:2001.

In the high frequency dielectric heating adhesive sheet according to this embodiment, it is preferable that the average particle diameter D _F of the dielectric filler (B) and the thickness T of the adhesive layer satisfy the relationship 1≦T/D _F ≦2500.
T/D _F is preferably 1 or more, more preferably 2 or more, more preferably 5 or more, more preferably 10 or more, and even more preferably 20 or more. If T/D _F is 1 or more, it is possible to prevent a decrease in adhesive strength caused by contact between the dielectric filler (B) and the adherend during adhesion.
T/D _F is preferably 2500 or less, more preferably 2000 or less, more preferably 1750 or less, more preferably 1000 or less, even more preferably 500 or less, even more preferably 100 or less, and even more preferably 50 or less. If T/D _F is 2500 or less, the load on the sheet manufacturing apparatus can be suppressed during the production of the high frequency dielectric heating adhesive sheet.

(Additives)
The high-frequency dielectric heating adhesive sheet according to the present embodiment may contain an additive or may not contain an additive. When the high-frequency dielectric heating adhesive sheet according to the present embodiment is composed of a plurality of layers, at least one of the plurality of layers may contain an additive or may not contain an additive. When at least one of the plurality of layers contains an additive, the adhesive layer may contain an additive or may not contain an additive.

When the high-frequency dielectric heating adhesive sheet according to this embodiment contains additives, examples of the additives include tackifiers, plasticizers, silane coupling agents, waxes, colorants, antioxidants, UV absorbers, antibacterial agents, viscosity adjusters, organic fillers, and inorganic fillers. The organic fillers and inorganic fillers used as additives are different from dielectric fillers.

The tackifier and plasticizer can improve the melting and adhesive properties of the high frequency dielectric heating adhesive sheet.
Examples of tackifiers 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.
Examples of the plasticizer include petroleum-based process oil, natural oil, dialkyl dibasic acid, and low molecular weight liquid polymer. Examples of the petroleum-based process oil include paraffin-based process oil, naphthene-based process oil, and aromatic process oil. Examples of the natural oil include castor oil and tall oil. Examples of the dialkyl dibasic acid include dibutyl phthalate, dioctyl phthalate, and dibutyl adipate. Examples of the low molecular weight liquid polymer include liquid polybutene and liquid polyisoprene.

When the high-frequency dielectric heating adhesive sheet according to this embodiment contains an additive, the content of the additive in the high-frequency dielectric heating adhesive sheet is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more 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 additive in the high-frequency dielectric heating adhesive sheet is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less.

The high-frequency dielectric heating adhesive sheet according to this embodiment preferably does not contain a solvent. A high-frequency dielectric heating adhesive sheet that does not contain a solvent is less likely to cause problems with VOCs (Volatile Organic Compounds) due to the adhesive used to adhere to the adherend.

The adhesive layer of the high-frequency dielectric heating adhesive sheet according to this embodiment preferably does not contain conductive materials such as carbon or carbon compounds mainly composed of carbon (e.g., carbon black, etc.) and metals. The adhesive layer preferably does not contain, for example, carbon steel, alpha iron, gamma iron, delta iron, copper, brass, aluminum, iron-nickel alloy, iron-nickel-chromium alloy, carbon fiber, and carbon black.

When the adhesive layer contains a conductive substance, the content of the conductive substance in the adhesive layer is, independently, preferably 20 mass % or less, more preferably 10 mass % or less, even more preferably 5 mass % or less, even more preferably 1 mass % or less, and even more preferably 0.1 mass % or less, based on the total amount of the adhesive layer.
It is particularly preferable that the content of the conductive material in the adhesive layer is 0% by mass.
If the content of the conductive substance in the adhesive layer is 20 mass % or less, it becomes easier to prevent the problem of carbonization of the adhesive portion and the adherend due to electrical insulation breakdown during dielectric heating treatment.

In the adhesive layer of the high-frequency dielectric heating adhesive sheet according to this embodiment, the total content of the thermoplastic resin (A) and the dielectric filler (B) is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 99% by mass or more.

In one embodiment, the high frequency dielectric heating adhesive sheet according to the present invention is made of only one adhesive layer having high frequency dielectric heating adhesive properties. However, the high frequency dielectric heating adhesive sheet according to the present invention is not limited to an embodiment having only one adhesive layer, and another embodiment of the high frequency dielectric heating adhesive sheet may include an embodiment in which layers other than the adhesive layer are laminated.
In this way, since a high-frequency dielectric heating adhesive sheet may consist of only one adhesive layer having high-frequency dielectric heating adhesive properties, in this specification, the terms "high-frequency dielectric heating adhesive sheet" and "adhesive layer" may be interchangeable in some cases.
2(A) to (C) show schematic diagrams of a number of aspects of the high-frequency dielectric heating adhesive sheet according to this embodiment.

The high frequency dielectric heating adhesive sheet 1A shown in FIG. 2(A) is composed of only a single adhesive layer 10.
The high-frequency dielectric heating adhesive sheet preferably comprises only a single adhesive layer, which allows the high-frequency dielectric heating adhesive sheet to be thin and easily molded.

The high-frequency dielectric heating adhesive sheet 1B shown in FIG. 2(B) has an adhesive layer 10 and a substrate 30 that supports the adhesive layer 10, and like the high-frequency dielectric heating adhesive sheet 1A, the adhesive layer 10 has a first surface 11. The substrate 30 is not particularly limited as long as it is a material that can support the adhesive layer 10, but examples thereof include a resin film or resin sheet containing at least one resin selected from the group consisting of polyolefin resins such as polyethylene resins and polypropylene resins, polyester resins such as polybutylene terephthalate resins and polyethylene terephthalate resins, acetate resins, ABS resins, polystyrene resins, and vinyl chloride resins. The substrate 30 may contain a dielectric filler (B), and the dielectric filler (B) in the adhesive layer 10 and the dielectric filler in the substrate 30 are the same or different from each other.

The high frequency dielectric heating adhesive sheet 1C shown in Figure 2 (C) has an adhesive layer 10 and an intermediate layer 40 disposed between the adhesive layer 20. The high frequency dielectric heating adhesive sheet 1C has a first surface 11 and a second surface 21 opposite the first surface 11. The adhesive layer 10 in the high frequency dielectric heating adhesive sheet 1C may be referred to as a first adhesive layer, and the adhesive layer 20 may be referred to as a second adhesive layer. In a high-frequency dielectric heating adhesive sheet having an intermediate layer disposed between the first adhesive layer and the second adhesive layer, the first adhesive layer only needs to satisfy the conditions of the adhesive layer of the high-frequency dielectric heating adhesive sheet according to this embodiment. In one embodiment, both the first adhesive layer and the second adhesive layer are layers having the same composition and characteristics, in one embodiment, the second adhesive layer is a high-frequency dielectric heating adhesive layer that differs from the first adhesive layer in at least one of the composition and characteristics, and in one embodiment, the second adhesive layer is a general adhesive layer that is not a high-frequency dielectric heating adhesive layer. Examples of the second adhesive layer that is not high-frequency dielectric heating adhesive include a drying and solidifying type adhesive layer that dries and solidifies as water or a solvent evaporates, or an adhesive layer formed from an adhesive (pressure-sensitive adhesive).

(Form and characteristics of high frequency dielectric heating adhesive sheet)
In one embodiment, the high-frequency dielectric heating adhesive sheet according to the present embodiment may be made up of only one adhesive layer, and in another embodiment, may be made up of multiple layers. When the high-frequency dielectric heating adhesive sheet is made up of only one adhesive layer, the adhesive layer itself corresponds to the high-frequency dielectric heating adhesive sheet, and therefore the shape and characteristics of the high-frequency dielectric heating adhesive sheet correspond to the shape and characteristics of the adhesive layer.

(Thickness of high frequency dielectric heating adhesive sheet)
The thickness of the high frequency dielectric heating adhesive sheet according to this embodiment is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 30 μm or more, and even more preferably 50 μm or more.
If the high frequency dielectric heating adhesive sheet has a thickness of 5 μm or more, the high frequency dielectric heating adhesive sheet can easily conform to the irregularities of the adherend when adhering to the adherend, and adhesive strength can easily be achieved.
When the high-frequency dielectric heating adhesive sheet has a multi-layer structure consisting of multiple layers, the thickness of the adhesive layer is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 30 μm or more, and even more preferably 50 μm or more.
When the high-frequency dielectric heating adhesive sheet is a multi-layered sheet, if the thickness of the adhesive layer is 5 μm or more, the adhesive layer can easily conform to the unevenness of the adherend when adhering to the adherend, and adhesive strength can easily be exerted.
The upper limit of the thickness of the high frequency dielectric heating adhesive sheet is not particularly limited. As the thickness of the high frequency dielectric heating adhesive sheet increases, the weight of the whole bonded body obtained by bonding the high frequency dielectric heating adhesive sheet and the adherend also increases, so the high frequency dielectric heating adhesive sheet is preferably in a thickness range that does not cause problems in practical use. Considering the practicality and moldability 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 even more preferably 600 μm or less.

(Dielectric properties (tan δ/ε′) of high frequency dielectric heating adhesive sheet)
The dielectric properties of the high frequency dielectric heating adhesive sheet, ie, the dielectric tangent (tan δ) and the dielectric constant (ε′), can be measured in accordance with JIS C 2138:2007, but can also be simply and accurately measured according to the impedance material method.
The dielectric characteristic (tan δ/ε') of the high frequency dielectric heating adhesive sheet is preferably 0.005 or more, more preferably 0.008 or more, and even more preferably 0.01 or more. The dielectric characteristic (tan δ/ε') of the high frequency dielectric heating adhesive sheet is preferably 0.08 or less, and more preferably 0.05 or less. The dielectric characteristic (tan δ/ε') is a value obtained by dividing the dielectric tangent (tan δ) measured using an impedance material device or the like by the dielectric constant (ε') measured using an impedance material device or the like.
If the dielectric characteristic of the high-frequency dielectric heating adhesive sheet is 0.005 or more, it is possible to prevent the problem that the required amount of heat is not generated during dielectric heating treatment, making it difficult to firmly bond adherends to each other.
If the dielectric characteristic of the high frequency dielectric heating adhesive sheet is 0.08 or less, damage to the adherend is unlikely to occur.
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 to a predetermined size, the dielectric constant (ε') and dielectric loss tangent (tan δ) are measured using an impedance material analyzer E4991 (manufactured by Agilent) at 23°C and a frequency of 40.68 MHz, and the value of the dielectric property (tan δ/ε') is calculated.

(Method of manufacturing high frequency dielectric heating adhesive sheet)
The single-layer high-frequency dielectric heating adhesive sheet can be produced by premixing the above-mentioned components, kneading them using a known kneading device such as an extruder or a heat roll, and then by a known molding method such as extrusion molding, calendar molding, injection molding, and casting molding.
When the high frequency dielectric heating adhesive sheet according to the present embodiment has a multi-layer structure, it can be produced, for example, by premixing the above-mentioned components and co-extrusion using a multi-layer extruder. Also, a multi-layer sheet can be produced by individually producing a single layer sheet of each layer (for example, the first adhesive layer, the intermediate layer, and the second adhesive layer) constituting the high frequency dielectric heating adhesive sheet according to the present embodiment, and laminating a plurality of single layer sheets. When laminating a plurality of single layer sheets, for example, a thermal laminator is used.
In addition, the high-frequency dielectric heating adhesive sheet according to this embodiment can also be produced by thermal extrusion coating, in which a molten adhesive layer is coated onto a substrate, or by hot melt coating, or by wet coating, in which a coating liquid in which the adhesive layer composition is dispersed or dissolved in a solvent is coated onto a substrate.

[Second embodiment]
Next, a second embodiment of the present invention will be described.
In addition, in this embodiment, the configuration is the same as that of the first embodiment, except that the first and second steps are defined based on the applied energy per unit area instead of the applied power per unit area. Therefore, only the first and second steps will be described and other descriptions will be omitted.
The bonding method according to the present embodiment includes a first step of applying a high-frequency electric field with an applied energy J1 per unit area to the high-frequency dielectric heating adhesive sheet, and a second step of applying a high-frequency electric field with an applied energy J2 per unit area to the high-frequency dielectric heating adhesive sheet after the first step, and the applied energy J1 per unit area in the first step and the applied energy J2 per unit area in the second step satisfy the condition expressed by the following formula (Mathematical formula 3). Note that in this embodiment, as in the first embodiment, a high-frequency dielectric heating adhesive sheet made of a single adhesive layer is used to bond a first adherend and a second adherend.
J1>0.75×J2 (Equation 3)
Here, J1 and J2 can be calculated by the following formulas (4-1) and (4-2), respectively.
J1 (W/ ^mm2 ·sec)=T1×V1 (Equation 4-1)
J2 (W/ ^mm2 ·sec)=T2×V2 (Equation 4-2)

If the condition expressed by the above formula (Formula 3) is not satisfied, it is not possible to improve the adhesive strength while shortening the application time of the high frequency electric field. Note that the applied energy J1 per unit area in the first step and the applied energy J2 per unit area in the second step are both greater than 0 W/ ^mm2 ·sec.
From a similar viewpoint, the lower limit of the applied energy J1 per unit area in the first step is preferably 0.85 times or more the value of the applied energy J2 per unit area in the second step, and more preferably 1 time or more the value of the applied energy J2 per unit area in the second step.
From the viewpoint of shortening the application time, the upper limit of the applied energy J1 per unit area in the first step is preferably 10 times or less the value of the applied energy J2 per unit area in the second step, and more preferably 5 times or less the value of the applied energy J2 per unit area in the second step.

In this embodiment, it is preferable that the applied energy J1 per unit area in the first step and the applied energy J2 per unit area in the second step satisfy the condition expressed by the following formula (Formula 3-1).
0.9>J1/(J1+J2)>0.4...(Equation 3-1)
When the condition represented by the above formula (Formula 3-1) is satisfied, the adhesive strength is easily improved.
From the same viewpoint, the upper limit of the value of J1/(J1+J2) is preferably 0.85 or less, more preferably 0.8 or less, and particularly preferably 0.75 or less. The lower limit of the value of J1/(J1+J2) is preferably 0.42 or more, more preferably 0.44 or more, and particularly preferably 0.5 or more.

The applied energy J1 per unit area in the first step is preferably 2 W/mm2· ^sec or more, more preferably 3 W/mm2· ^sec or more, and particularly preferably 3.5 W/ ^mm2 ·sec or more. The applied energy J1 per unit area in the first step is preferably 9 W/mm2· ^sec or less, more preferably 7 W/mm2· ^sec or less, and particularly preferably 5 W/mm2· ^sec or less.
If the applied energy J1 per unit area in the first step is 2 W/ ^mm2 ·sec or more, the problem of the resin being difficult to bring into a molten state can be prevented, making it easier to obtain good adhesive strength.
If the applied energy J1 per unit area in the first step is 9 W/mm ² ·sec or less, the resin can be prevented from foaming, which can reduce the adhesive strength, making it easier to obtain good adhesive strength.

The total applied energy (J1+J2), which is the sum of the applied energy J1 per unit area in the first step and the applied energy J2 per unit area in the second step, is preferably 3 W/mm2· ^sec or more, more preferably 4.5 W/mm2· ^sec or more, and particularly preferably 6 W/ ^mm2 · ^sec or more. The total applied energy (J1+J2) is preferably 20 W/mm2· ^sec or less, more preferably 15 W/mm2·sec or less, and particularly preferably 10 W/mm2· ^sec or less.
When the value of the total applied energy (J1+J2) is within the above range, the adhesive strength is easily improved.

[Modifications of the embodiment]
The present invention is not limited to the above-described embodiment, and may include modifications and improvements within the scope of the present invention.

In the above embodiment, the second step is performed following the first step, but this is not limited to this. For example, other steps may be performed between the first and second steps as long as they do not impair the effects of the present invention. Here, examples of other steps include the first step of leaving the material for a while after performing the first stage of high-frequency dielectric heating.

The high-frequency dielectric heating process 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 high-frequency dielectric heating device of a grid electrode type may be used. The grid electrode type high-frequency dielectric heating device has a grid electrode in which electrodes of a first polarity and electrodes of a second polarity opposite to the first polarity are alternately arranged at regular intervals on the same plane.
For example, when producing a bonded body in which an end of a first adherend and an end of a second adherend are overlapped and bonded, a grid electrode type high-frequency dielectric heating device is placed on the first adherend side or the second adherend side to apply a high-frequency electric field.

When a lattice electrode type high frequency dielectric heating device is used to bond a first adherend to a second adherend, a first lattice electrode may be placed on the first adherend side and a second lattice electrode on the second adherend side, and the first adherend, high frequency dielectric heating adhesive sheet, and second adherend may be sandwiched between the first lattice electrode and the second lattice electrode and a high frequency electric field may be applied simultaneously.

When a lattice electrode type high-frequency dielectric heating device is used to bond a first adherend and a second adherend, a lattice electrode may be placed on one side of the first adherend and the second adherend, a high-frequency electric field may be applied, and then a lattice electrode may be placed on the other side of the first adherend and the second adherend, and a high-frequency electric field may be applied.

It is also preferable to use a lattice electrode type high-frequency dielectric heating device to apply the high-frequency electric field. By using a lattice electrode type high-frequency dielectric heating device, the adherends can be bonded together without being affected by the thickness of the first and second adherends, by dielectrically heating the surface side of the first and second adherends, for example, the side of the adherend that is closest to the high-frequency dielectric heating adhesive sheet. In addition, by using a lattice electrode type high-frequency dielectric heating device, energy savings can be achieved in the production of the bonded body.

For simplicity, the diagram shows an example of a dielectric heating bonding device with electrodes arranged opposite each other.

The present invention will be described in more detail below with reference to examples. The present invention is not limited to these examples.

[Preparation of high-frequency dielectric heating adhesive sheet]
80.0% by volume of maleic anhydride copolymer polypropylene (MODIC P565, manufactured by Mitsubishi Chemical Corporation; hereinafter referred to as component A) as a thermoplastic resin component, and 20.0% by volume of zinc oxide (LPZINC11, manufactured by Sakai Chemical Industry Co., Ltd.; average particle size: 11 μm; hereinafter referred to as component B) as a B component were weighed into a container.
The weighed components A and B were premixed in a container. After premixing the components, the components were fed to a hopper of a 30 mm diameter twin-screw extruder, and melt-kneaded at a cylinder temperature of 180° C. to 200° C. and a die temperature of 200° C. to obtain granular pellets.
Next, the obtained granular pellets were put into the hopper of a single-screw extruder equipped with a T-die, and a film-like molten kneaded material was extruded from the T-die under conditions of a cylinder temperature of 200°C and a die temperature of 200°C, and cooled with a cooling roll to produce a high-frequency dielectric heating adhesive sheet having a thickness of 400 μm.
The dielectric constant (ε'r) and dielectric loss tangent (tan δ) of the obtained sheet were measured by the parallel plate method at a frequency of 40.68 MHz at 23°C using an impedance material analyzer E4991ARF (Agilent). Based on the measurement results, the value of the dielectric characteristic (tan δ/ε'r) was calculated. The dielectric characteristic (tan δ/ε'r) of the obtained high frequency dielectric heating adhesive sheet was 0.014.

[Example 1]
The high-frequency dielectric heating adhesive sheet thus prepared was cut into a size of 25 mm x 12.5 mm. The cut high-frequency dielectric heating adhesive sheet was sandwiched between a pair of epoxy glass plates (25 mm x 100 mm x 1.5 mm) as adherends, and then fixed between the electrodes of a high-frequency dielectric heating device (manufactured by Yamamoto Vinita Co., Ltd., TRP-400T-RC), with the frequency set to 40.68 MHz and the estimated pressing pressure set to 192.8 N.
Then, in the first step, the application area was set to 312.5 ^mm2 , the application power was set to 100 W (application power V1 per unit area was 0.32 W/ ^mm2 ), and the application time was set to 15 seconds to perform a first stage of high-frequency dielectric heating. Next, in the second step, the application area was set to 312.5 ^mm2 , the application power was set to 50 W (application power V2 per unit area was 0.16 W/ ^mm2 ), and the application time was set to 10 seconds to perform a second stage of high-frequency dielectric heating to produce a bonded body. The application power, application time T1, and application power V1 per unit area in the first step, and the application power, application time T2, and application power V2 per unit area in the second step are shown in Table 1. Furthermore, the applied energy per unit area J1 in the first step, the applied energy per unit area J2 in the second step, the total applied time (T1+T2), the total applied energy (J1+J2), and the value of J1/(J1+J2) are shown in Table 2.
The bonding strength of the resulting bonded body was measured in accordance with JIS K 6850. The results are shown in Table 1.

[Examples 2 to 8]
A bonded body was produced in the same manner as in Example 1, except that the conditions for the first step and the second step were changed as shown in Table 1 below. The bonding strength of the obtained bonded body was measured in the same manner as in Example 1. The obtained results are shown in Table 1. Table 2 shows the applied energy J1 per unit area in the first step, the applied energy J2 per unit area in the second step, the total applied time (T1+T2), the total applied energy (J1+J2), and the value of J1/(J1+J2).

[Comparative Example 1]
In the same manner as in Example 1, the cut high-frequency dielectric heating adhesive sheet was sandwiched between a pair of epoxy glass plates as adherends, and then set in a high-frequency dielectric heating device.
Then, high-frequency dielectric heating was performed without being divided into two stages, with the application area set to 312 ^mm2 , the application power set to 100 W (application power V1 per unit area: 0.32 W/ ^mm2 ), and the application time set to 30 seconds, to produce a bonded body. The application power, application time, and application power V1 per unit area in the high-frequency dielectric heating are shown in Table 1. Table 2 also shows the applied energy J1 per unit area in the high-frequency dielectric heating, the total application time (T1+T2), the total applied energy (J1+J2), and the value of J1/(J1+J2).

[Comparative Examples 2 to 4]
A bonded body was produced in the same manner as in Comparative Example 1, except that the conditions for high-frequency dielectric heating were changed as shown in Table 1 below. The bonding strength of the obtained bonded body was measured in the same manner as in Example 1. The obtained results are shown in Table 1. Table 2 shows the applied energy J1 per unit area in high-frequency dielectric heating, the total application time (T1+T2), the total applied energy (J1+J2), and the value of J1/(J1+J2).

[Comparative Example 5]
A bonded body was produced in the same manner as in Example 1, except that the conditions for the first step and the second step were changed as shown in Table 1 below. The bonding strength of the obtained bonded body was measured in the same manner as in Example 1. The obtained results are shown in Table 1. Table 2 shows the applied energy J1 per unit area in the first step, the applied energy J2 per unit area in the second step, the total applied time (T1+T2), the total applied energy (J1+J2), and the value of J1/(J1+J2).

The bonding methods of Examples 1 to 8 were able to shorten the application time of the high-frequency electric field, and improve the adhesive strength even when applied for a short period of time.

10...adhesive layer (first adhesive layer), 11...first surface, 110...adherend, 120...adherend, 1A...high frequency dielectric heating adhesive sheet, 1B...high frequency dielectric heating adhesive sheet, 1C...high frequency dielectric heating adhesive sheet, 20...adhesive layer (second adhesive layer), 21...second surface, 30...substrate, 40...intermediate layer, 50...dielectric heating adhesive device, 51...first high frequency electric field application electrode, 52...second high frequency electric field application electrode, 53...high frequency power source.

Claims (9)

A method for bonding adherends using a high-frequency dielectric heating adhesive sheet, comprising the steps of:
The high-frequency dielectric heating adhesive sheet contains a thermoplastic resin (A),
A first step of applying a high-frequency electric field having an applied output V1 per unit area to the high-frequency dielectric heating adhesive sheet;
A second step of applying a high-frequency electric field having an applied output V2 per unit area to the high-frequency dielectric heating adhesive sheet after the first step,
The applied power V1 per unit area in the first step is 0.22 W/mm2 ^or more and 0.5 W/mm2 ^or less,
The applied power V2 per unit area in the second step is 0.11 W/mm2 or ^more and 0.18 W/mm2 ^or less,
The applied output V1 per unit area in the first step and the applied output V2 per unit area in the second step satisfy the condition expressed by the following formula (Formula 1),
Adhesion method.
0.7× V1 ≧ V2 ≧0.4×V1 …(Math. 1) The application time T1 of the first step is 1 second or more and less than 25 seconds;
The bonding method according to claim 1 . The application time T2 of the second step is 5 seconds or more.
The bonding method according to claim 1 or 2 . The application time T1 of the first step and the application time T2 of the second step satisfy the condition represented by the following formula (Mathematical Formula 2).
The bonding method according to any one of claims 1 to 3 .
(T1+T2) < 60 seconds... (Equation 2) A method for bonding adherends using a high-frequency dielectric heating adhesive sheet, comprising the steps of:
The high-frequency dielectric heating adhesive sheet contains a thermoplastic resin (A),
A first step of applying a high-frequency electric field with an applied energy J1 per unit area to the high-frequency dielectric heating adhesive sheet;
A second step of applying a high-frequency electric field with an applied energy J2 per unit area to the high-frequency dielectric heating adhesive sheet after the first step,
The applied energy J1 per unit area in the first step is 3.5 W/mm ² ·sec or more and 5 W/mm ² ·sec or less,
a total applied energy (J1+J2) which is the sum of the applied energy J1 per unit area in the first step and the applied energy J2 per unit area in the second step is 6 W/mm2 · ^sec or more and 10 W/mm2 · ^sec or less;
The applied energy J1 per unit area in the first step and the applied energy J2 per unit area in the second step satisfy the condition represented by the following formula (Mathematical Expression 3),
Adhesion method.
J1 ≧ J2 (Equation 3) The applied energy J1 per unit area in the first step and the applied energy J2 per unit area in the second step satisfy the condition represented by the following formula (Math. 3-1).
The bonding method according to claim 5 .
0.9>J1/(J1+J2)>0.4...(Equation 3-1) The thermoplastic resin (A) is a polyolefin resin.
The bonding method according to any one of claims 1 to 6 . The high-frequency dielectric heating adhesive sheet further contains a dielectric filler (B) that generates heat upon application of a high-frequency electric field.
The bonding method according to any one of claims 1 to 7 . The dielectric filler (B) contains at least one selected from the group consisting of zinc oxide, silicon carbide, barium titanate, and titanium oxide;
The bonding method according to claim 8 .

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