JP2023127119A - Foamable adhesive sheet and manufacturing method of article - Google Patents

Abstract

To provide a foamable adhesive sheet excellent in adherence and insertability.SOLUTION: A foamable adhesive sheet comprising a first adhesive layer, a base material, and a second adhesive layer in this order, wherein the first adhesive layer and the second adhesive layer contain a curable adhesive, at least one of the first adhesive layer and the second adhesive layer further contains a foaming agent, the tack of the first adhesive layer is 0 gf or more and less than 10 gf, and the tack of the second adhesive layer is 10 gf or more and 500 gf or less, and a loop stiffness is 50 mN/10 mm or more.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a foamable adhesive sheet and a method of manufacturing an article using the same.

Adhesives for bonding members together are widely used in various fields. For example, an adhesive is used when fixing one member to a hole, groove, etc. of the other member. Specifically, in an embedded magnet type motor, an adhesive is used to fix a permanent magnet in a hole in a core.

Liquid adhesives are the mainstream adhesive used in motors. However, in the case of liquid adhesives, there are problems in that uneven coating, protrusion, dripping, etc. occur, which complicates the bonding process.

On the other hand, in recent years, it has been proposed to use a sheet adhesive containing a foaming agent (foamable adhesive sheet) instead of a liquid adhesive (for example, see Patent Document 1). According to the foamable adhesive sheet, it is possible to suppress the occurrence of the problems described above when using a liquid adhesive.

Patent No. 6874867

For example, when fixing another member to a hole or groove of one member, as described in Patent Document 1, a foam adhesive sheet is pasted on the other member for temporary fixation, and the hole or groove of one member is fixed. The other member to which the foamable adhesive sheet is attached is placed in the groove or the like, and then the two members can be bonded and fixed by foaming and curing the foamable adhesive sheet.

When fixing one member to a hole or groove of the other member, the gap between the two members tends to become narrower. Therefore, the foamable adhesive sheet used is required to have a small overall thickness. However, if the foam adhesive sheet is thin, the foam adhesive sheet tends to sag due to its own weight during transportation. For example, when a foamable adhesive sheet is transported by suction, if the thickness of the foamable adhesive sheet is thin, both ends of the foamable adhesive sheet tend to sag under its own weight. Therefore, when the foamable adhesive sheet is suction-conveyed and attached to the other member, there is a problem that the foamable adhesive sheet may be folded, twisted, bent, or air bubbles may be trapped during the attachment. Furthermore, if the foam adhesive sheet is pasted to another component with such defects, bulges will occur on the foam adhesive sheet, so the foam adhesive sheet may not be pasted into holes or grooves in one component. There is also the problem that when inserting the other attached member, the foam adhesive sheet is rubbed and peeled off. In such a case, the adhesiveness after foaming and curing decreases, resulting in lower reliability.

In addition, in the adhesive fixing method as described above, the adhesive property of the foam adhesive sheet is used to attach the foam adhesive sheet to the other member and temporarily fix it. However, if the adhesiveness of the foamable adhesive sheet is high, there is a problem in that the ease of inserting the other member to which the foamable adhesive sheet is pasted into a hole or groove of one member is reduced.

The present disclosure has been made in view of the above circumstances, and its main purpose is to provide a foamable adhesive sheet that has excellent pasting properties and insertability.

One embodiment of the present disclosure is a foamable adhesive sheet having a first adhesive layer, a base material, and a second adhesive layer in this order, wherein the first adhesive layer and the second adhesive layer are cured. at least one of the first adhesive layer and the second adhesive layer further contains a foaming agent, the tack of the first adhesive layer is 0 gf or more and less than 10 gf, and the second adhesive layer further contains a foaming agent; Provided is a foamable adhesive sheet in which the tack of the adhesive layer is 10 gf or more and 500 gf or less, and the loop stiffness is 50 mN/10 mm or more.

Another embodiment of the present disclosure is a foamable adhesive sheet having a first adhesive layer, a base material, a second adhesive layer, and an adhesive layer in this order, the first adhesive layer and the second adhesive layer. the layer contains a curable adhesive and a foaming agent, the adhesive layer contains a pressure sensitive adhesive or a curable adhesive, the tack of the first adhesive layer is 0 gf or more and less than 10 gf, Provided is a foamable adhesive sheet whose adhesive layer has a tack of 10 gf or more and a loop stiffness of 50 mN/10 mm or more.

Another embodiment of the present disclosure includes an arrangement step of arranging the above-described foamable adhesive sheet between the first member and the second member, and foaming and curing the above-mentioned foamable adhesive sheet. A method of manufacturing an article is provided, which includes a bonding step of bonding two members.

The foamable adhesive sheet according to the present disclosure has excellent adhesion properties and insertion properties.

FIG. 1 is a schematic cross-sectional view illustrating a foamable adhesive sheet in the present disclosure. FIG. 2 is a schematic plan view and a cross-sectional view illustrating a loop stiffness measuring device. FIG. 2 is a schematic diagram illustrating a method for measuring loop stiffness. FIG. 2 is a schematic diagram illustrating a method for measuring loop stiffness. FIG. 1 is a schematic cross-sectional view illustrating a foamable adhesive sheet in the present disclosure. FIG. 1 is a schematic cross-sectional view illustrating a foamable adhesive sheet in the present disclosure. FIG. 1 is a schematic cross-sectional view illustrating a foamable adhesive sheet in the present disclosure. FIG. 2 is a process diagram illustrating a method for manufacturing an article according to the present disclosure. FIG. 2 is a process diagram illustrating a method for manufacturing an article according to the present disclosure. It is a schematic diagram explaining the measuring method of the amount of drooping.

Embodiments of the present disclosure will be described below with reference to the drawings and the like. However, the present disclosure can be implemented in many different ways, and should not be construed as being limited to the description of the embodiments exemplified below. Further, in order to make the explanation clearer, the drawings may schematically represent the width, thickness, shape, etc. of each part compared to the actual form, but this is just an example and does not limit the interpretation of the present disclosure. It's not something you do. In addition, in this specification and each figure, the same elements as those described above with respect to the previously shown figures are denoted by the same reference numerals, and detailed explanations may be omitted as appropriate.

In this specification, when expressing a mode in which another member is placed on top of a certain member, when it is simply expressed as "above" or "below", unless otherwise specified, it means that the member is in contact with a certain member. This includes both cases in which another member is placed directly above or below a certain member, and cases in which another member is placed above or below a certain member via another member. In addition, in this specification, when expressing a mode in which another member is arranged on the surface of a certain member, when it is simply expressed as "on the surface side" or "on the surface", unless otherwise specified, This includes both a case where another member is placed directly above or directly below the member so as to be in contact with the member, and a case where another member is placed above or below a certain member via another member.

Furthermore, in this specification, the term "sheet" also includes a member called a "film." Furthermore, the term "film" also includes a member called a "sheet."

Hereinafter, the foamable adhesive sheet and the method for manufacturing an article using the same according to the present disclosure will be described in detail.

A. Foamable Adhesive Sheet The foamable adhesive sheet in the present disclosure has two embodiments. Each embodiment will be described below.

I. First Embodiment A first embodiment of the foamable adhesive sheet in the present disclosure is a foamable adhesive sheet having a first adhesive layer, a base material, and a second adhesive layer in this order, wherein the first adhesive layer and the second adhesive layer contain a curable adhesive, at least one of the first adhesive layer and the second adhesive layer further contains a foaming agent, and the tack of the first adhesive layer is 0 gf. The tack of the second adhesive layer is 10 gf or more and 500 gf or less, and the loop stiffness is 50 mN/10 mm or more.

FIG. 1 is a schematic cross-sectional view illustrating a foamable adhesive sheet in this embodiment. The foamable adhesive sheet 10 in FIG. 1 has a first adhesive layer 1, a base material 2, and a second adhesive layer 3 in this order. The first adhesive layer 1 and the second adhesive layer 3 contain a curable adhesive, and at least one of the first adhesive layer 1 and the second adhesive layer 3 further contains a foaming agent. Further, the tack of the first adhesive layer 1 and the tack of the second adhesive layer 3 are each within a predetermined range, and the loop stiffness of the foamable adhesive sheet 10 is within a predetermined range.

In this embodiment, since the tack of the second adhesive layer is within a predetermined range, the second adhesive layer can have good adhesion to the member. Specifically, when adhering and fixing another member to a hole or groove of one member, the surface of the second adhesive layer of the foam adhesive sheet is pasted to the other member, and the hole or groove of one member is fixed. In the case where the other member to which the foamable adhesive sheet is pasted is inserted into the groove or the like, and then the foamable adhesive sheet is foamed and cured to bond one member and the other member, the second adhesive layer By having the tack of the second adhesive layer within a predetermined range, the surface of the second adhesive layer of the foam adhesive sheet can be attached to the other member using the tack of the second adhesive layer, and the second adhesive layer to the member can be attached to the other member. can improve adhesion. Thereby, when inserting the other member to which the foamable adhesive sheet is attached into a hole or groove of one member, peeling or displacement of the foamable adhesive sheet can be suppressed.

Further, in this embodiment, since the tack of the second adhesive layer is within a predetermined range, the second adhesive layer can have good reworkability. Therefore, for example, in the adhesive fixing method described above, when attaching the surface of the second adhesive layer of the foam adhesive sheet to one member using the tack of the second adhesive layer, the displacement of the foam adhesive sheet is prevented. Can be fixed.

Furthermore, in this embodiment, since the tack of the second adhesive layer is within a predetermined range, for example, when the second adhesive layer is formed by a transfer method, lifting of the second adhesive layer can be suppressed. I can do it. Furthermore, as described later, when the second separator is arranged on the side of the second adhesive layer opposite to the first adhesive layer, the tack of the second adhesive layer is within a predetermined range. , the second separator can be easily peeled off, and workability can be improved.

Furthermore, in this embodiment, since the tack of the first adhesive layer is less than or equal to a predetermined value, the first adhesive layer can be made substantially non-adhesive (tack-free), and the first adhesive layer has good slip properties. It can be one adhesive layer. Therefore, for example, in the adhesive fixing method described above, when inserting the other member to which the foam adhesive sheet is pasted into the hole or groove of one member, the other member to which the foam adhesive sheet is pasted is The member can be inserted smoothly and insertability can be improved. Thereby, peeling and displacement of the foamable adhesive sheet can be suppressed. In addition, in the adhesive fixing method described above, when aligning the members by moving the other member relative to the other member, it is necessary to insert the other member into the hole or groove of one member. The other member can be smoothly moved relative to the other member, and alignment can be easily performed.

Furthermore, in this embodiment, the tack of the first adhesive layer is less than or equal to a predetermined value, and the first adhesive layer is substantially non-adhesive (tack-free), so it has good slip properties and is resistant to The first adhesive layer can also have good blocking properties. Therefore, the handleability of the foamable adhesive sheet can also be improved.

In addition, in this embodiment, as mentioned above, the second adhesive layer has excellent adhesion to the member, and the first adhesive layer has excellent slipperiness, so that the foam adhesive sheet can be easily peeled off and positioned. Misalignment can be suppressed. Therefore, it suppresses the decrease in adhesion of the foamable adhesive sheet after foaming and curing due to peeling or misalignment of the foamable adhesive sheet, and also suppresses the adhesion of the foamable adhesive sheet after foaming and curing due to peeling or misalignment of the foamable adhesive sheet. Variations in strength can be reduced. Therefore, by using the foamable adhesive sheet of this embodiment, it is possible to realize adhesion with high adhesive strength, high reliability, and high quality.

Here, when one member is adhesively fixed to a hole or groove of the other member, the gap between the two members tends to become narrower, as described above. Therefore, the foamable adhesive sheet used is required to have a small overall thickness. However, if the foam adhesive sheet is thin, the foam adhesive sheet tends to sag due to its own weight during transportation. Therefore, the inventors of the present disclosure focused on the stiffness of the foamable adhesive sheet. The thicker the foam adhesive sheet, the higher the rigidity. However, since the foamable adhesive sheet needs to be thin in the first place, it is not suitable to increase the thickness of the foamable adhesive sheet. Further, when the foamable adhesive sheet has adhesive layers on both sides of the base material, the thicker the base material, the higher the rigidity tends to be. However, if the thickness of the base material is made relatively thick while the thickness of the foamable adhesive sheet is kept thin, the thickness of the adhesive layer becomes relatively thin, resulting in a decrease in the adhesive properties and foaming properties of the adhesive layer. There is a risk. Additionally, in general, the adhesive layer tends to be softer as the tackiness is higher, and harder as the tackiness is lower. Therefore, when the foamable adhesive sheet has an adhesive layer having tackiness, the rigidity tends to be low. The inventors of the present disclosure have discovered that by setting the loop stiffness of the foamable adhesive sheet within a predetermined range, it is possible to suppress the foamable adhesive sheet from sagging due to its own weight. Furthermore, it has been found that by making the first adhesive layer of the first adhesive layer and the second adhesive layer substantially non-adhesive (tack-free), it is possible to improve insertability and increase rigidity. .

Note that loop stiffness is a parameter representing the stiffness of a sheet or film. The larger the loop stiffness value, the stiffer the sheet or film becomes. Loop stiffness is used as a parameter representing the stiffness of sheets and films used for packaging materials, for example, but it is not very common in the field of adhesive sheets.

In the foamable adhesive sheet of this embodiment, since the loop stiffness is greater than or equal to a predetermined value, stiffness can be increased. Therefore, it is possible to suppress the foamable adhesive sheet from sagging due to its own weight during transportation of the foamable adhesive sheet. Therefore, for example, when a foamable adhesive sheet is transported by suction and attached to another member, it is necessary to prevent the foamable adhesive sheet from folding, twisting, sagging, air bubbles, etc. during attachment. be able to. Therefore, the adhesion properties can be improved. Furthermore, to prevent bulges from forming on the foam adhesive sheet due to these defects, it is possible to insert the other member with the foam adhesive sheet pasted into the hole or groove of one member. At the same time, the foamable adhesive sheet can be made less likely to be rubbed. Therefore, peeling of the foamable adhesive sheet during insertion can be suppressed. Therefore, from this point of view as well, by using the foamable adhesive sheet of this embodiment, it is possible to realize adhesion with high adhesive strength, high reliability, and high quality.

Here, "adhesion" is a concept included in "adhesion". A distinction is sometimes made in that adhesion is used to mean a temporary adhesion phenomenon, while adhesion is used to mean a substantially permanent adhesion phenomenon (Iwanami Shoten Physical and Chemistry Dictionary 5th Edition). "Adhesiveness" and "adhesive force" refer to the property of adhering by pressure sensitivity and the adhesion force at that time.

In addition, in this specification, "adhesiveness of the adhesive layer" and "adhesive force of the adhesive layer" refer to the adhesiveness and adhesive force that the adhesive layer has before curing, unless there are special circumstances. Moreover, in this specification, "adhesiveness of the adhesive layer" and "adhesive force of the adhesive layer" refer to the adhesiveness and adhesive force that the adhesive layer has after curing, unless there are special circumstances.

Hereinafter, each structure of the foamable adhesive sheet of this embodiment will be explained.

1. Properties In this embodiment, the tack of the first adhesive layer is 0 gf or more and less than 10 gf, and may be 5 gf or less, or may be 2 gf or less. By having the tack of the first adhesive layer within the above range, the first adhesive layer can be made substantially non-adhesive (tack-free), and the first adhesive layer has good slip properties and anti-blocking properties. can do.

In this embodiment, the tack of the second adhesive layer is 10 gf or more, may be 30 gf or more, or may be 50 gf or more. If the tack of the second adhesive layer is too low, for example in the adhesive fixing method described above, when attaching the surface of the second adhesive layer of the foam adhesive sheet to the other member using the tack of the second adhesive layer, There is a possibility that the adhesion between the second adhesive layer and the other member will decrease, or when inserting the other member with a foam adhesive sheet pasted into the hole or groove of one member, the second adhesive layer and the other member may deteriorate. If the foam adhesive sheet peels off or the position of the foam adhesive sheet shifts due to poor adhesion of the other member, the adhesiveness of the first adhesive layer and the second adhesive layer after foam curing may decrease, or the adhesiveness may deteriorate. There is a possibility that variations in strength may occur. Further, the tack of the second adhesive layer is 500 gf or less, may be 400 gf or less, or may be 300 gf or less. If the tack of the second adhesive layer is too high, reworkability will be reduced, and for example, in the adhesive fixing method described above, the tack of the second adhesive layer is used to attach the surface of the second adhesive layer of the foam adhesive sheet to the other member. It may be difficult to correct misalignment of the foam adhesive sheet when pasting it.

Here, the tack of the first adhesive layer and the second adhesive layer can be measured by a probe tack test based on JIS Z3284-3:2014. As the probe tack tester, for example, a tacking tester "TAC-II" manufactured by RHESCA can be used. Note that details of the method for measuring the tack of the first adhesive layer and the second adhesive layer will be described in the Examples section below.

In this embodiment, the tack of the first adhesive layer can be controlled within a predetermined range by, for example, adjusting the composition of the first adhesive layer. Specifically, in the first adhesive layer containing an epoxy resin and a hardening agent, the tackiness of the first adhesive layer can be improved by using an epoxy resin that is solid at room temperature or by using a hardening agent that is solid at room temperature. can be lowered. In addition, the tackiness of the first adhesive layer can be reduced by containing an epoxy resin with a high softening temperature or an epoxy resin with a large weight average molecular weight in the first adhesive layer containing an epoxy resin and a curing agent. be able to. For example, the first adhesive layer contains multiple types of epoxy resins having different softening temperatures, that is, the first adhesive layer contains one epoxy resin and the first epoxy resin with a softening temperature of 25°C or higher, and By containing another epoxy resin whose softening temperature is 10° C. or more higher than the softening temperature of the first adhesive layer, the adhesiveness of the first adhesive layer can be reduced. Further, for example, the first adhesive layer may contain a plurality of types of epoxy resins having different weight average molecular weights, that is, the first adhesive layer may contain one epoxy resin and one epoxy resin having a weight average molecular weight of 370 or more, and By containing another epoxy resin having a weight average molecular weight of 300 or more higher than the weight average molecular weight of the epoxy resin, the adhesiveness of the first adhesive layer can be reduced. More specifically, in the first adhesive layer containing an epoxy resin and a curing agent, as described below, the first epoxy resin has a low softening temperature and a low molecular weight, and the first epoxy resin has a high softening temperature and a high molecular weight. By containing the second epoxy resin, the adhesiveness of the first adhesive layer can be reduced. Moreover, in the first adhesive layer containing an epoxy resin and a curing agent, the tackiness of the first adhesive layer can be reduced by containing an acrylic resin that is compatible with the epoxy resin, as described later.

In this embodiment, the tack of the second adhesive layer can be controlled, for example, by adjusting the composition of the second adhesive layer. Specifically, in the second adhesive layer containing an epoxy resin and a hardening agent, if an epoxy resin that is liquid at room temperature or a hardening agent that is liquid at room temperature is used, the adhesiveness of the second adhesive layer increases. Tend. In addition, when the second adhesive layer containing an epoxy resin and a curing agent contains an epoxy resin with a low softening temperature or an epoxy resin with a small weight average molecular weight, the adhesiveness of the second adhesive layer tends to increase. There is. Furthermore, by adding a tackifying resin (tackifier) to the second adhesive layer, the tackiness of the second adhesive layer tends to increase. Note that if a curing agent that is liquid at room temperature is used, it tends to have higher tackiness, but storage stability may decrease. It is preferable to adjust the tack of the second adhesive layer by adjusting.

In this embodiment, the static friction coefficient of the surface of the first adhesive layer opposite to the second adhesive layer is preferably 0.33 or less, may be 0.30 or less, and may be 0.26 or less. It may be. When the static friction coefficient of the surface of the first adhesive layer is within the above range, the first adhesive layer can have good slip properties. Further, the static friction coefficient may be, for example, 0.16 or more.

Here, the static friction coefficient of the surface of the first adhesive layer can be determined in accordance with JIS K7125, which corresponds to ISO 8295. Specifically, the coefficient of static friction between the first adhesive layer of the foamable adhesive sheet and the metal plate is measured by the following method. First, a foam adhesive sheet is cut into 80 mm x 200 mm. Next, the foam adhesive sheet was placed on a rectangular metal plate (SUS plate) placed horizontally, and a sliding piece (63 mm x 63 mm, weight 200 g, The friction force was measured under the conditions of a test speed of 100 mm/min, a test length of 50 mm, a load cell of 10 N, and a temperature of 23° C., and the static friction coefficient was calculated. As the device, for example, a friction measuring machine FRICTION TESTER TR-2 manufactured by Toyo Seiki Seisakusho Co., Ltd. can be used.

In this embodiment, the static friction coefficient of the surface of the first adhesive layer can be controlled, for example, by adjusting the composition of the first adhesive layer. Specifically, when the first adhesive layer further contains a foaming agent, the coefficient of static friction on the surface of the first adhesive layer is controlled by the average particle size, content, etc. of the foaming agent contained in the first adhesive layer. can do. More specifically, as the average particle size of the blowing agent increases, the coefficient of static friction on the surface of the first adhesive layer tends to decrease. Furthermore, as the content of the foaming agent increases, the coefficient of static friction on the surface of the first adhesive layer tends to decrease.

In this embodiment, the arithmetic mean roughness (Ra) of the surface of the first adhesive layer opposite to the second adhesive layer is preferably 0.3 μm or more, and may be 0.5 μm or more, for example. , 0.7 μm or more. When the Ra of the first adhesive layer is within the above range, the first adhesive layer can have good slip properties. Moreover, Ra of the first adhesive layer may be, for example, 1.5 μm or less, 1.3 μm or less, or 1.1 μm or less.

Here, Ra of the first adhesive layer can be measured using a white interferometer. Specifically, Ra of the first adhesive layer can be measured using a white interferometer NewView 7300 manufactured by Zygo, with an observation field of view of 0.55 mm x 0.55 mm and a sampling interval of 0.55 μm.

In this embodiment, Ra of the first adhesive layer can be controlled, for example, by adjusting the composition of the first adhesive layer. Specifically, when the first adhesive layer further contains a foaming agent, the Ra of the first adhesive layer can be controlled by the average particle size, content, etc. of the foaming agent contained in the first adhesive layer. can. More specifically, as the average particle size of the foaming agent increases, the Ra of the first adhesive layer tends to increase. Furthermore, as the content of the foaming agent increases, the Ra of the first adhesive layer tends to increase.

In the foamable adhesive sheet of this embodiment, the loop stiffness is 50 mN/10 mm or more, preferably 75 mN/10 mm or more, and more preferably 100 mN/10 mm or more. Since the loop stiffness of the foamable adhesive sheet is within the above range, for example, when the foamable adhesive sheet is adsorbed and conveyed and attached to a member, it is possible to suppress the foamable adhesive sheet from sagging due to its own weight, Adhesiveness can be improved. On the other hand, the upper limit of loop stiffness is not particularly limited.

As mentioned above, loop stiffness is a parameter representing the stiffness of a film or sheet. A method for measuring loop stiffness will be described below with reference to FIGS. 2 to 4.

FIG. 2(a) is a schematic plan view showing the loop stiffness measuring device, and FIG. 2(b) is a sectional view taken along the line AA in FIG. 2(a). The test piece of the foamable adhesive sheet 10 has a rectangular shape with long sides and short sides. In this embodiment, the length L1 of the long side of the test piece of the foamable adhesive sheet 10 is 200 mm, and the length L2 of the short side is 10 mm. As the loop stiffness measuring device 30, a Loop Stiffness Tester (registered trademark) manufactured by Toyo Seiki Seisakusho Co., Ltd. can be used. Note that the length L1 of the long side of the test piece of the foamable adhesive sheet 10 can be adjusted as long as the test piece of the foamable adhesive sheet 10 can be gripped by a pair of chuck parts 31, which will be described later.

The loop stiffness measuring device 30 includes a pair of chuck parts 31 for gripping a pair of ends in the long side direction of a test piece of the foamable adhesive sheet 10, and a support member 32 that supports the chuck parts 31. The chuck section 31 has a first chuck 31a and a second chuck 31b. The foam adhesive sheet 10 is placed on a pair of first chucks 31a, and the second chuck 31b does not yet grip the foam adhesive sheet 10 with the first chuck 31a. As will be described later, during measurement, the foamable adhesive sheet 10 is held between the first chuck 31a and the second chuck 31b of the chuck section 31. The second chuck 31b may be connected to the first chuck 31a via a hinge mechanism.

First, as shown in FIGS. 2A and 2B, a test piece of the foamable adhesive sheet 10 is placed on the first chucks 31a of a pair of chuck parts 31 that are spaced apart from each other by L3. At this time, in this embodiment, the interval L3 is set so that the length of the loop portion 41 (hereinafter also referred to as loop length), which will be described later, is 60 mm. Further, the test piece of the foamable adhesive sheet 10 is arranged so that the inner surface 40x is the surface of the first adhesive layer and the outer surface 40y is the surface of the second adhesive layer. Subsequently, as shown in FIG. 3(a), the second chuck 31b is attached to the foam adhesive so as to grip the longitudinal end of the test piece of the foam adhesive sheet 10 between the first chuck 31a and the first chuck 31a. Place the sheet 10 on top of the test piece.

Next, as shown in FIG. 3(b), at least one of the pair of chuck parts 31 is slid on the support member 32 in a direction in which the distance between the pair of chuck parts 31 is reduced. Thereby, the loop portion 41 can be formed in the foamable adhesive sheet 10. The test piece of the foamable adhesive sheet 10 shown in FIG. 3(b) has a loop portion 41, a pair of intermediate portions 42, and a pair of fixing portions 43. The pair of fixing parts 43 are parts of the test piece of the foamable adhesive sheet 10 that are gripped by the pair of chuck parts 31 . The pair of intermediate portions 42 are portions of the test piece of the foamable adhesive sheet 10 located between the loop portion 41 and the pair of intermediate portions 42 . The chuck portion 31 is slid on the support member 32 until the inner surfaces 40x of the pair of intermediate portions 42 of the foam adhesive sheet 10 come into contact with each other. Thereby, the loop portion 41 having a loop length of 60 mm can be formed. The loop length of the loop portion 41 is determined by the distance between a position P1 where the surface of the second chuck 31b on the loop portion 41 side intersects with the test piece of the foam adhesive sheet 10, and the surface of the other second chuck 31b on the loop portion 41 side. This is the length of the test piece of the foamable adhesive sheet 10 between the point P2 where the test piece of the foamable adhesive sheet 10 intersects with the test piece of the foamable adhesive sheet 10. The above-mentioned interval L3 is a value obtained by adding 2×t to the length of the loop portion 41 when the thickness of the test piece of the foamable adhesive sheet 10 is ignored. t is the thickness of the second chuck 31b of the chuck portion 31.

Next, as shown in FIG. 4A, the posture of the chuck part 31 is adjusted so that the protruding direction Y of the loop part 41 with respect to the chuck part 31 is in the horizontal direction. For example, the attitude of the chuck portion 31 supported by the support member 32 is adjusted by moving the support member 32 so that the normal direction of the support member 32 faces the horizontal direction. In the example shown in FIG. 4A, the protrusion direction Y of the loop portion 41 coincides with the thickness direction of the chuck portion 31. In the example shown in FIG. Further, the load cell 35 is prepared at a position away from the second chuck 31b in the protruding direction Y of the loop portion 41.

Subsequently, as shown in FIG. 4(b), the load cell 35 is moved toward the loop portion 41 of the test piece of the foamable adhesive sheet 10, and the load cell 35 is brought into contact with the loop portion 41. The distance Z1 is the distance between the load cell 35 and the second chuck 31b of the chuck section 31.

Thereafter, as shown in FIGS. 4(b) to 4(c), the loop portion 41 is pushed toward the chuck portion 31 by a distance Z2 using the load cell 35. In this embodiment, the distance Z2 is 15 mm.

Next, as shown in FIG. 4(c), the load cell 35 is moved toward the chuck part 31 by a distance Z2, and while the load cell 35 is pushing the loop part 41 of the test piece of the foam adhesive sheet 10, the loop After the value of the load applied to the load cell 35 from the section 41 becomes stable, the value of the load is recorded. The load value obtained in this manner is defined as the loop stiffness of the foamable adhesive sheet 10. In this specification, unless otherwise specified, the environment during loop stiffness measurement is a temperature of 23° C. and a relative humidity of 50%.

In addition, when measuring the loop stiffness of a foamable adhesive sheet, if the foamable adhesive sheet has a first separator and a second separator as described later, after peeling off the first separator and second separator, The loop stiffness of the adhesive sheet was measured.

In this embodiment, the loop stiffness of the foamable adhesive sheet can be adjusted, for example, by adjusting the thickness and composition of the first adhesive layer, the thickness and composition of the second adhesive layer, and the thickness and composition of the base material. can be controlled. For example, if the thickness of the base material is thick, the loop stiffness tends to increase. Further, for example, if the first adhesive layer is thick, the loop stiffness tends to increase. Therefore, it is preferable to adjust the thickness of each layer so as to obtain the desired loop stiffness. Further, when the composition of the first adhesive layer is adjusted to reduce the tack of the first adhesive layer, the loop stiffness tends to increase.

The foamable adhesive sheet in this embodiment preferably has high adhesiveness after foaming and curing. After foaming and curing of the foamable adhesive sheet, the shear strength (adhesive strength) based on JIS K6850 corresponding to ISO 4587 at 23°C may be, for example, 1.50 MPa or more, or 1.80 MPa or more. The pressure may be 2.10 MPa or more. Further, the shear strength (adhesive strength) may be, for example, 0.50 MPa or more, 0.75 MPa or more, or 1.00 MPa or more at 130°C. For example, a high-strength acrylic foam adhesive tape that does not require heating has a shear strength (adhesive strength) of about 1 MPa or more and 2 MPa or less at room temperature, and has no heat resistance at 200°C. Therefore, if the shear strength (adhesive strength) is within the above range at 23° C., there is an advantage in terms of strength. Further, if the shear strength (adhesive strength) is within the above range at 130° C., it can be applied to automobile engine areas and other applications where heat resistance similar to that is required.

The foamable adhesive sheet in this embodiment preferably has high electrical insulation properties after foaming and curing. After the foamable adhesive sheet is foamed and cured, the dielectric breakdown voltage based on JIS C2107 corresponding to IEC 60454-2 is preferably, for example, 3 kV or more, and more preferably 5 kV or more. When the dielectric breakdown voltage is within the above range, it becomes possible to prevent rust and to be applied around copper wires. Further, after the foamable adhesive sheet is foamed and cured, it is preferable that the thermal conductivity is, for example, 0.05 W/mK or more. When the thermal conductivity is within the above range, the parts can be made smaller and the curing reaction during heating can be promoted.

2. First adhesive layer (1) Material of first adhesive layer The first adhesive layer in this embodiment contains a curable adhesive.

(a) Curable Adhesive As the curable adhesive contained in the first adhesive layer in this embodiment, a curable adhesive generally used for the adhesive layer of a foamable adhesive sheet can be used. Examples of the curable adhesive include heat-curable adhesives and photo-curable adhesives. Among these, heat-setting adhesives are preferred. The thermosetting adhesive can be applied even when the member does not have transparency, such as a metal member.

Examples of curable adhesives include epoxy resin adhesives, acrylic resin adhesives, phenolic resin adhesives, unsaturated polyester resin adhesives, alkyd resin adhesives, urethane resin adhesives, and heat-curable adhesives. Examples include curable polyimide resin adhesives.

Among these, the curable adhesive is preferably an epoxy resin adhesive. That is, the curable adhesive preferably contains an epoxy resin and a curing agent. In general, epoxy resin adhesives have excellent mechanical strength, heat resistance, insulation, chemical resistance, etc., have low curing shrinkage, and can be used in a wide range of applications.

Hereinafter, a case where the curable adhesive is an epoxy resin adhesive will be explained by giving an example.

(i) Epoxy resin The epoxy resin in this embodiment is a compound that has at least one epoxy group or glycidyl group and is cured by causing a crosslinking polymerization reaction when used in combination with a curing agent. Epoxy resins also include monomers having at least one epoxy group or glycidyl group.

As the epoxy resin, an epoxy resin generally used for the adhesive layer of a foamable adhesive sheet can be used. Among these, the curable adhesive includes a first epoxy resin having a softening temperature of 50° C. or higher and an epoxy equivalent of 5000 g/eq or lower, and a first epoxy resin having a softening temperature higher than the first epoxy resin, and , and a second epoxy resin having a weight average molecular weight of 20,000 or more. By using the first epoxy resin and the second epoxy resin in combination, the adhesiveness (tackiness) of the first adhesive layer can be reduced, and a foamable adhesive sheet with good slip properties can be obtained. Furthermore, it is possible to obtain a first adhesive layer with good blocking resistance and adhesiveness after foaming and curing.

For example, when aiming only to improve adhesiveness after foaming and curing, it is more effective to use an epoxy resin with a lower molecular weight (low epoxy equivalent) than an epoxy resin with a high molecular weight (high epoxy equivalent). However, when a low molecular weight (low epoxy equivalent) epoxy resin is used, for example, when a foam adhesive sheet is wound up into a roll, the low molecular weight (low epoxy equivalent) epoxy resins are assimilated with each other, causing blocking. It becomes easier.

On the other hand, when using a first epoxy resin with a relatively low softening temperature (relatively high crystallinity) and a low molecular weight (low epoxy equivalent), the first epoxy resin has a temperature higher than the softening temperature. At high temperatures, it rapidly melts and turns into a low-viscosity liquid. Therefore, it is easy to improve the adhesiveness after foaming and curing. On the other hand, since the first epoxy resin has relatively high crystallinity, it can suppress the occurrence of blocking compared to an epoxy resin with relatively low crystallinity or an epoxy resin without crystallinity. However, when only the first epoxy resin is used, the effect of suppressing the occurrence of blocking may be insufficient, or the adhesiveness (tackiness) of the first adhesive layer may become too high. Therefore, by further using a second epoxy resin with a relatively high softening temperature (relatively low crystallinity) and a high molecular weight, it is possible to improve the effect of suppressing the occurrence of blocking and to improve the effectiveness of the first adhesive layer. Adhesion (tackiness) can be kept low.

(i-1) First epoxy resin The first epoxy resin has a softening temperature of 50° C. or higher and an epoxy equivalent of 5000 g/eq or lower. The first epoxy resin has a relatively low softening temperature (relatively high crystallinity) compared to the second epoxy resin described below. Since the first epoxy resin has relatively high crystallinity and low molecular weight, it is easy to improve adhesiveness and blocking resistance after foaming and curing. In addition, since the first epoxy resin has a low molecular weight, it is possible to increase the crosslinking density, and a first adhesive layer having good mechanical strength, chemical resistance, and curability can be obtained. Moreover, it is preferable that the first epoxy resin is an epoxy resin that is solid at room temperature (23° C.).

The softening temperature of the first epoxy resin is usually 50°C or higher, may be 55°C or higher, or may be 60°C or higher. On the other hand, the softening temperature of the first epoxy resin is, for example, 150° C. or lower. The softening temperature can be measured by the ring and ball method in accordance with JIS K7234.

The epoxy equivalent of the first epoxy resin is, for example, 5000 g/eq or less, may be 3000 g/eq or less, may be 1000 g/eq or less, or may be 600 g/eq or less. On the other hand, the epoxy equivalent of the first epoxy resin is, for example, 90 g/eq or more, may be 100 g/eq or more, or may be 110 g/eq or more. Epoxy equivalent can be measured by a method based on JIS K7236 corresponding to ISO 3001 (Plastics Epoxy compounds-Determination of epoxy equivalent), and is the number of grams of resin containing 1 gram equivalent of epoxy groups.

The first epoxy resin may be a monofunctional epoxy resin, a bifunctional epoxy resin, a trifunctional epoxy resin, or a tetrafunctional or higher functional epoxy resin. .

Moreover, the weight average molecular weight (Mw) of the first epoxy resin is usually smaller than the weight average molecular weight (Mw) of the second epoxy resin described later. The Mw of the first epoxy resin is, for example, 6,000 or less, may be 4,000 or less, or may be 3,000 or less. On the other hand, the Mw of the first epoxy resin is, for example, 400 or more. Mw is a polystyrene equivalent value measured by gel permeation chromatography (GPC).

The first epoxy resin has a melt viscosity at 150°C of, for example, 0.005 Pa·s or more, may be 0.015 Pa·s or more, may be 0.03 Pa·s or more, and may be 0.05 Pa·s or more. - It may be s or more, and may be 0.1 Pa·s or more. If the melt viscosity is too low, good foamability may not be obtained. Moreover, if the melt viscosity of the first epoxy resin is too low (if the crystallinity of the first epoxy resin is too high), the adhesiveness (tackiness) of the obtained first adhesive layer may become high. The reason is that if the melt viscosity of the first epoxy resin is too low (if the crystallinity of the first epoxy resin is too high), its crystallinity will be greatly reduced when it is compatible with the second epoxy resin or acrylic resin. , it is presumed that this is because the Tg of the first adhesive layer decreases. On the other hand, the first epoxy resin has a melt viscosity at 150°C of, for example, 10 Pa·s or less, may be 5 Pa·s or less, or may be 2 Pa·s or less. If the melt viscosity is too high, the uniformity of the resulting first adhesive layer may decrease. Melt viscosity was determined in accordance with JIS K6862, which corresponds to ISO 2555 (Resins in the liquid state or as emulsions or dispersions Determination of Brookfield RV viscosity), using a Brookfield type single cylinder rotational viscometer and a method for heating the solution. It can be determined by measuring using a thermocell.

Next, the structure of the first epoxy resin will be explained. Examples of the first epoxy resin include aromatic epoxy resins, aliphatic epoxy resins, alicyclic epoxy resins, and heterocyclic epoxy resins. Specific examples of the first epoxy resin include bisphenol type epoxy resins such as bisphenol A type epoxy resin and bisphenol F type epoxy resin, bisphenol A novolac type epoxy resin, novolac type epoxy resin such as cresol novolac type epoxy resin, and urethane modified epoxy resin. Examples include modified epoxy resins such as resins and rubber-modified epoxy resins. In addition, other specific examples include biphenyl-type epoxy resin, stilbene-type epoxy resin, triphenolmethane-type epoxy resin, alkyl-modified triphenolmethane-type epoxy resin, triazine nucleus-containing epoxy resin, dicyclopentadiene-modified phenol-type epoxy resin, Examples include naphthalene type epoxy resin, glycol type epoxy resin, and pentaerythritol type epoxy resin. The number of first epoxy resins may be one, or two or more.

The bisphenol A type epoxy resin can exist in a liquid state at room temperature or in a solid state at room temperature, depending on the number of repeating units of the bisphenol skeleton. A bisphenol A type epoxy resin whose main chain has a bisphenol skeleton of, for example, 2 or more and 10 or less is solid at room temperature. Particularly, bisphenol A type epoxy resin is preferable since it can improve heat resistance.

In particular, the first epoxy resin is preferably a bisphenol A novolac type epoxy resin represented by the following general formula (1).

In general formula (1), R ¹ is a group represented by C _m H _2m (m is 1 or more and 3 or less), and R ² and R ³ are each independently C _p H _2p+1 (p is 1 or more and 3 or less), and n is 0 or more and 10 or less.

In general formula (1), m in R ¹ is preferably 1, that is, R ¹ is -CH ₂ -. Similarly, it is preferred that p in R ² and R ³ is 1, ie, R ² and R ³ are -CH ₃ . Moreover, the hydrogen bonded to the benzene ring in general formula (1) may be substituted with another element or another group.

The content of the first epoxy resin is, for example, 1 part by mass or more, may be 3 parts by mass or more, and 5 parts by mass or more when the resin component contained in the first adhesive layer is 100 parts by mass. The amount may be 10 parts by mass or more, 15 parts by mass or more, or 25 parts by mass or more. If the content of the first epoxy resin is too small, the adhesiveness and blocking resistance after foaming and curing may decrease. On the other hand, the content of the first epoxy resin is, for example, 90 parts by mass or less, may be 80 parts by mass or less, and 70 parts by mass, when the resin component contained in the first adhesive layer is 100 parts by mass. 60 parts by mass or less, 50 parts by mass or less, or 40 parts by mass or less. If the content of the first epoxy resin is too high, the content of the second epoxy resin and acrylic resin will be relatively low, resulting in non-stick properties, anti-blocking properties, adhesion to the substrate after foaming and curing. It may not be possible to balance the cracking resistance of the foam and the adhesion after foaming and curing.

(i-2) Second epoxy resin The second epoxy resin has a higher softening temperature than the first epoxy resin, and a weight average molecular weight of 20,000 or more. The second epoxy resin has a relatively high softening temperature (relatively low crystallinity) compared to the first epoxy resin described above. Since the second epoxy resin has relatively low crystallinity and high molecular weight, it is easy to improve blocking resistance. Furthermore, since the second epoxy resin has relatively low crystallinity and high molecular weight, it can suppress the increase in stickiness (tackiness) caused by the first epoxy resin. Moreover, it is preferable that the second epoxy resin is an epoxy resin that is solid at room temperature (23° C.).

The weight average molecular weight (Mw) of the second epoxy resin is usually larger than the weight average molecular weight (Mw) of the first epoxy resin. The Mw of the second epoxy resin is usually 20,000 or more, may be 30,000 or more, or may be 35,000 or more. On the other hand, the Mw of the second epoxy resin is, for example, 100,000 or less.

The epoxy equivalent of the second epoxy resin may be larger, smaller, or the same as the epoxy equivalent of the first epoxy resin. The epoxy equivalent of the second epoxy resin is, for example, 4000 g/eq or more, may be 5000 g/eq or more, or may be 6000 g/eq or more. On the other hand, the epoxy equivalent of the second epoxy resin is, for example, 20,000 g/eq or less.

The second epoxy resin may be a monofunctional epoxy resin, a bifunctional epoxy resin, a trifunctional epoxy resin, or a tetrafunctional or higher functional epoxy resin. .

The softening temperature of the second epoxy resin is usually higher than the softening temperature of the first epoxy resin. The difference between the two may be, for example, 10°C or more, 20°C or more, or 30°C or more. The softening temperature of the second epoxy resin is, for example, 80°C or higher, and may be 90°C or higher. On the other hand, the softening temperature of the second epoxy resin is, for example, 180° C. or lower.

The structure of the second epoxy resin is the same as the structure of the first epoxy resin described above, so a description thereof will be omitted here.

The content of the second epoxy resin is, for example, 10 parts by mass or more, may be 15 parts by mass or more, and 20 parts by mass or more when the resin component contained in the first adhesive layer is 100 parts by mass. 25 parts by mass or more, 30 parts by mass or more, 35 parts by mass or more, 40 parts by mass or more, 45 parts by mass or more It may be. If the content of the second epoxy resin is too small, tackiness may increase and blocking resistance may decrease. On the other hand, the content of the second epoxy resin is, for example, 90 parts by mass or less, may be 85 parts by mass or less, and 80 parts by mass, when the resin component contained in the first adhesive layer is 100 parts by mass. The amount may be 75 parts by mass or less. If the content of the second epoxy resin is too high, the content of the first epoxy resin and acrylic resin will be relatively small, resulting in non-stick properties, blocking resistance, adhesion to the substrate after foaming and curing, and It may not be possible to balance the cracking resistance of the foam and the adhesion after foaming and curing.

The ratio of the first epoxy resin to the total of the first epoxy resin and the second epoxy resin is, for example, 5% by mass or more, may be 10% by mass or more, may be 15% by mass or more, and may be 20% by mass or more. It may be more than % by mass. On the other hand, the above proportion of the first epoxy resin is, for example, 80% by mass or less, may be 75% by mass or less, or may be 60% by mass or less.

Further, the total ratio of the first epoxy resin and the second epoxy resin to all the epoxy resins contained in the first adhesive layer is, for example, 50% by mass or more, and may be 70% by mass or more, and 90% by mass. % or more, or 100% by mass.

(ii) Acrylic resin When the curable adhesive is an epoxy resin adhesive, the first adhesive layer may further contain an acrylic resin that is compatible with the epoxy resin. Acrylic resin is a resin that is compatible with epoxy resin. Since acrylic resin is compatible with epoxy resin, it is easy to improve the toughness of the first adhesive layer. As a result, the adhesiveness after foaming and curing can be improved. Furthermore, the acrylic resin acts as a compatibilizer for the foaming agent (for example, a foaming agent whose shell is made of acrylonitrile copolymer resin), and is thought to improve adhesiveness after foaming and curing by uniformly dispersing and foaming. . In addition, the flexibility of the acrylic resin is exhibited, and it is possible to improve the adhesion to the base material after foaming and hardening and the cracking resistance after foaming and hardening. Furthermore, since the acrylic resin is compatible with the epoxy resin, the hardness of the surface of the first adhesive layer can be maintained high. On the other hand, if the acrylic resin is incompatible with the epoxy resin, a flexible portion will be formed on the surface of the first adhesive layer, making the interface with the adherend less slippery, which may reduce workability.

The acrylic resin in this embodiment is compatible with the epoxy resin. Here, the fact that the acrylic resin is compatible with the epoxy resin can be confirmed, for example, when the cross section of the first adhesive layer of the foamable adhesive sheet is observed with a scanning electron microscope (SEM) or a transmission electron microscope (TEM). This can be confirmed by the fact that micron-sized islands are not generated. More specifically, it is preferable that the average particle size of the islands is 1 μm or less. Among these, the average particle size of the islands may be 0.5 μm or less, or 0.3 μm or less. The number of samples is preferably large, for example 100 or more. The area to be observed is in the range of 100 μm×100 μm, or in the case where the thickness of the first adhesive layer is 100 μm or less, the area is in the range of thickness×100 μm.

The weight average molecular weight (Mw) of the acrylic resin is, for example, 50,000 or more, may be 70,000 or more, or may be 100,000 or more. The first epoxy resin has relatively high crystallinity, and its melt viscosity (or dynamic viscoelasticity) during heating becomes too low, and the first bonding occurs after the foaming agent has finished foaming. However, by using an acrylic resin with a certain molecular weight, it is possible to prevent the melt viscosity from becoming too low, and shrinkage may occur during curing after foaming. It becomes difficult to wake up. On the other hand, the Mw of the acrylic resin is, for example, 1,500,000 or less. The weight average molecular weight of the acrylic resin can be measured by GPC (eluent: THF, standard substance: PS, sample: 20 μL, flow rate: 1 mL/min, column temperature: 40° C.).

The glass transition temperature (Tg) of the acrylic resin is, for example, 90°C or higher, and may be 100°C or higher. On the other hand, the Tg of the acrylic resin is, for example, 180° C. or lower. Tg is based on JIS K7121 corresponding to ISO 3146, and can be measured by thermal analysis using a differential scanning calorimeter (DSC) or the like.

The acrylic resin may have a storage modulus (E') of 1×10 ⁶ Pa or less at the foaming start temperature. A low E' at the start of foaming improves fluidity and provides good foamability. On the other hand, E' at the foaming start temperature is, for example, 1×10 ⁵ Pa or more. Note that the foaming start temperature varies depending on the type of foaming agent. Furthermore, when two or more types of foaming agents are used as the foaming agent, the starting temperature of the main foaming reaction is defined as the foaming starting temperature.

The acrylic resin may have a storage modulus (E') of 1×10 ⁵ Pa or more at the curing start temperature. As mentioned above, shrinkage may occur during curing after foaming (from the end of foaming of the foaming agent until the first adhesive layer hardens), but due to the large E' at the curing start temperature, shrinkage may occur. , shrinkage can be suppressed and good shape retention can be obtained. Note that the curing start temperature varies depending on the type of curing agent. Furthermore, when two or more types of curing agents are used as the curing agent, the starting temperature of the main curing reaction is defined as the curing starting temperature.

Further, the acrylic resin may have an average storage modulus (E') of 1×10 ⁶ Pa or more at 0° C. or higher and 100° C. or lower. By having a high average value of E' before foaming, good non-stick properties and anti-blocking properties can be obtained. On the other hand, the average value of the storage elastic modulus (E') at 0° C. or higher and 100° C. or lower is, for example, 1×10 ⁸ Pa or lower.

The acrylic resin may have a polar group. Examples of the polar group include an epoxy group, a hydroxyl group, a carboxyl group, a nitrile group, and an amide group.

The acrylic resin is a homopolymer of acrylic ester monomers, may be a mixed component containing two or more of the above homopolymers, or is a copolymer of two or more acrylic ester monomers. , or a copolymer. Moreover, the acrylic resin may be a mixed component of the above-mentioned homopolymer and the above-mentioned copolymer. The acrylic acid ester monomer "acrylic acid" also includes the concept of methacrylic acid. Specifically, the acrylic resin may be a mixture of a methacrylate polymer and an acrylate polymer, or may be an acrylic acid ester polymer such as acrylate-acrylate, methacrylate-methacrylate, or methacrylate-acrylate. . Among these, the acrylic resin preferably contains a copolymer of two or more types of acrylic ester monomers ((meth)acrylic ester copolymer).

Examples of the monomer components constituting the (meth)acrylic acid ester copolymer include the monomer components described in JP-A-2014-065889. The monomer component may have the above-mentioned polar group. Examples of the (meth)acrylic acid ester copolymer include ethyl acrylate-butyl acrylate-acrylonitrile copolymer, ethyl acrylate-acrylonitrile copolymer, and butyl acrylate-acrylonitrile copolymer. Note that "acrylic acid" such as methyl acrylate and ethyl acrylate also includes "methacrylic acid" such as methyl methacrylate and ethyl methacrylate.

The (meth)acrylic acid ester copolymer is preferably a block copolymer, and more preferably an acrylic block copolymer such as a methacrylate-acrylate copolymer. Examples of the (meth)acrylate constituting the acrylic block copolymer include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, and acrylic acid. Examples include benzidyl. These "acrylic acids" also include "methacrylic acids."

Specific examples of methacrylate-acrylate copolymers include acrylic copolymers such as methyl methacrylate-butyl acrylate-methyl methacrylate (MMA-BA-MMA) copolymers. MMA-BA-MMA copolymers also include block copolymers of polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate (PMMA-PBA-PMMA).

The acrylic copolymer may not have a polar group, or may be a modified product in which the above-mentioned polar group is partially introduced. Since the above-mentioned modified product is easily compatible with the epoxy resin, the adhesiveness is further improved.

Among them, the acrylic resin is a (meth)acrylic acid having a first polymer part having a glass transition temperature (Tg) of 10°C or lower and a second polymer part having a glass transition temperature (Tg) of 20°C or higher. Preferably, it is an ester copolymer. Such a (meth)acrylic acid ester copolymer has a first polymer portion that becomes a soft segment and a second polymer portion that becomes a hard segment.

The manifestation of the above effects can be estimated as follows. By using an acrylic resin that has both soft and hard segments, such as the above-mentioned (meth)acrylic acid ester copolymer, the hard segments contribute to heat resistance, and the soft segments contribute to toughness or flexibility. , a first adhesive layer having good heat resistance, toughness, and flexibility can be obtained.

At least one of the first polymer portion and the second polymer portion contained in the (meth)acrylic acid ester copolymer has compatibility with the epoxy resin. If the first polymer portion is compatible with the epoxy resin, flexibility can be increased. Moreover, when the second polymeric part has compatibility with the epoxy resin, cohesiveness and toughness can be improved.

If either the first polymer portion or the second polymer portion is not compatible with the epoxy resin, the (meth)acrylic acid ester copolymer is a polymer portion that is compatible with the epoxy resin. It has a certain compatible part and an incompatible part which is a polymer part that has no compatibility with the epoxy resin. In this case, when the (meth)acrylic acid ester copolymer is added, the compatible sites become compatible with the epoxy resin, and the incompatible sites are not compatible with the epoxy resin, resulting in fine phase separation. As a result, a fine sea-island structure appears. The sea-island structure depends on the type of (meth)acrylic ester copolymer, the compatibility of the first polymer part and the second polymer part contained in the (meth)acrylic ester copolymer, and the degree of modification by polar group introduction. For example, a sea-island structure where the cured epoxy resin and (meth)acrylic ester copolymer are compatible with the sea, and the (meth)acrylic ester copolymer is incompatible with the islands. A sea-island structure in which the incompatible parts of the (meth)acrylic ester copolymer are oceans, and the compatible parts of the cured epoxy resin and (meth)acrylic ester copolymer are islands, (meth) An example is a sea-island structure in which the acrylic ester copolymer is the sea and the cured epoxy resin is the island. By having such a sea-island structure, stress can be easily dispersed, so interfacial destruction can be avoided, and excellent adhesiveness can be obtained after foaming and curing.

The above-mentioned (meth)acrylic acid ester copolymer is preferably a block copolymer, particularly ABA in which the compatible portion is polymer block A and the incompatible portion is polymer block B. Preferably, it is a block copolymer. Furthermore, the first polymer portion is an incompatible portion, the second polymer portion is a compatible portion, the first polymer portion is a polymer block B, and the second polymer portion is a polymer block A. -BA block copolymer is preferred. By using such an ABA block copolymer as the acrylic resin, the compatible sites of the cured epoxy resin and the (meth)acrylic ester copolymer are In the case of a sea-island structure in which the incompatible part of the merging is an island, the island portion can be made small. In addition, in the case of a sea-island structure where the incompatible parts of the (meth)acrylic ester copolymer are oceans and the compatible parts of the cured epoxy resin and (meth)acrylic ester copolymer are islands, In the case of a sea-island structure in which the (meth)acrylic ester copolymer is a sea and the cured epoxy resin is an island, the sea portion can be made small.

Moreover, the above-mentioned (meth)acrylic acid ester copolymer may be a modified product in which the above-mentioned polar group is introduced into a part of the first polymer portion or the second polymer portion.

The Tg of the first polymer portion contained in the above (meth)acrylic acid ester copolymer is 10°C or less, within the range of -150°C or more and 10°C or less, especially -130°C or more and 0°C or less. It can be within a range, particularly within a range of -110°C or higher and -10°C or lower.

The Tg of the first polymer portion is calculated using the following formula based on the Tg (K) of each homopolymer described in "POLYMER HANDBOOK 3rd Edition" (published by John Wiley & Sons, Inc.). You can ask for it.
1/Tg(K)=W ₁ /Tg ₁ +W ₂ /Tg ₂ +...+W _n /Tg _n
W _n ; Mass fraction of each monomer Tg _n ; Tg (K) of the homopolymer of each monomer, as described in Polymer Handbook (3rd Ed., J. Brandrup and E.H. Immergut, WILEY INTERSCIENCE) It is sufficient to use published values that are publicly available, such as the values inside. The same applies to the Tg of the second polymer portion described below.

The first polymer portion contained in the (meth)acrylic acid ester copolymer may be a homopolymer or a copolymer, but is preferably a homopolymer. The monomer components and polymer components constituting the first polymer portion may be monomer components and polymer components that can obtain a first polymer portion having a Tg within a predetermined range, such as acrylic Acrylic acid ester monomers such as butyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, methyl acrylate, other monomers such as vinyl acetate, acetal, urethane, and polar group-containing monomers containing the above polar groups. copolymers such as EVA and EVA.

The Tg of the second polymer portion contained in the above (meth)acrylic acid ester copolymer is 20°C or higher, within the range of 20°C or higher and 150°C or lower, particularly within the range of 30°C or higher and 150°C or lower. , especially within the range of 40°C or higher and 150°C or lower.

Further, the second polymer portion contained in the above (meth)acrylic acid ester copolymer may be a homopolymer or a copolymer, but a homopolymer is particularly preferable. . The monomer component constituting the second polymer part may be any monomer component that can obtain a second polymer part having a Tg within a predetermined range, such as an acrylic ester monomer such as methyl methacrylate. other monomers such as acrylamide, styrene, vinyl chloride, amide, acrylonitrile, cellulose acetate, phenol, urethane, vinylidene chloride, methylene chloride, methacrylonitrile, and polar group-containing monomers containing the above-mentioned polar groups. One example is the body.

A specific example of the (meth)acrylic acid ester copolymer having the above-mentioned first polymer portion and second polymer portion includes the above-mentioned MMA-BA-MMA copolymer.

The content of the acrylic resin is, for example, 1 part by mass or more, may be 3 parts by mass or more, or 5 parts by mass or more when the resin component contained in the first adhesive layer is 100 parts by mass. It may be 7 parts by mass or more, or it may be 10 parts by mass or more. If the content of the acrylic resin is too small, the adhesion to the substrate after foaming and curing, the cracking resistance after foaming and curing, and the adhesiveness after foaming and curing may decrease. On the other hand, the content of the acrylic resin is, for example, 60 parts by mass or less, may be 50 parts by mass or less, and 40 parts by mass or less, when the resin component contained in the first adhesive layer is 100 parts by mass. It may be 35 parts by mass or less, or it may be 30 parts by mass or less. If the content of acrylic resin is too high, the content of the first epoxy resin and the second epoxy resin will be relatively small, resulting in poor non-stick properties, anti-blocking properties, adhesion to the substrate after foaming and curing, and poor foaming and curing. It may not be possible to balance the cracking resistance of the foam and the adhesion after foaming and curing. Furthermore, if the content of the acrylic resin is too large, the film strength may decrease.

(iii) Curing agent As the curing agent in this embodiment, a curing agent generally used for epoxy resin adhesives can be used. The curing agent is preferably solid at room temperature (23°C). A hardening agent that is solid at room temperature can have a longer storage stability (pot life) than a hardening agent that is liquid at room temperature. Further, the curing agent may be a latent curing agent. Further, the curing agent may be a curing agent that causes a curing reaction due to heat, or may be a curing agent that causes a curing reaction due to light. Moreover, a curing agent may be used alone or two or more types may be used.

The reaction initiation temperature of the curing agent is, for example, 110°C or higher, and may be 130°C or higher. If the reaction initiation temperature is too low, the reaction will start early, and curing will occur with the resin component having low flexibility and fluidity, making it difficult to achieve uniform curing. On the other hand, the reaction initiation temperature of the curing agent is, for example, 200° C. or lower. If the reaction initiation temperature is too high, the resin component may deteriorate. In addition, when using a resin with high heat resistance, such as a phenol resin, in addition to the epoxy resin, the reaction initiation temperature of the curing agent may be, for example, 300 ° C. or lower, since the resin component is less likely to deteriorate. . The reaction initiation temperature of the curing agent can be determined by differential scanning calorimetry (DSC).

Specific examples of the curing agent include imidazole curing agents, phenol curing agents, amine curing agents, acid anhydride curing agents, isocyanate curing agents, and thiol curing agents.

Examples of imidazole curing agents include imidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl Examples include -4-methylimidazole, 2-isopropylimidazole, 2-phenylimidazole, carboxylates of imidazole compounds, and adducts with epoxy compounds. Further, the imidazole curing agent preferably has a hydroxyl group. Since crystallization occurs due to hydrogen bonds between hydroxy groups, the reaction initiation temperature tends to be high.

Examples of phenolic curing agents include phenolic resins. Further, examples of the phenol resin include resol type phenol resin and novolak type phenol resin. From the viewpoint of adhesion to the substrate after foaming and curing, cracking resistance after foaming and curing, etc., a phenolic novolac resin having a Tg of 110° C. or less is particularly preferred. Furthermore, a phenolic curing agent and an imidazole curing agent may be used in combination. In that case, it is preferable to use an imidazole curing agent as a curing catalyst.

Examples of the amine curing agent include aliphatic amines such as diethylenetriamine (DETA), triethylenetetramine (TETA), and metaxylylene diamine (MXDA); diaminodiphenylmethane (DDM), m-phenylenediamine (MPDA), and diamino Examples include aromatic amines such as diphenylsulfone (DDS); alicyclic amines; and polyamide amines. Further, as the amine curing agent, a dicyandiamide curing agent such as dicyandiamide (DICY), an organic acid dihydrazide curing agent, an amine adduct curing agent, or a ketimine curing agent can be used.

Examples of acid anhydride curing agents include alicyclic acid anhydrides (liquid acid anhydrides) such as hexahydrophthalic anhydride (HHPA) and methyltetrahydrophthalic anhydride (MTHPA); trimellitic anhydride (TMA); Examples include aromatic acid anhydrides such as pyromellitic anhydride (PMDA) and benzophenonetetracarboxylic acid (BTDA).

Examples of the isocyanate curing agent include blocked isocyanates.

Examples of the thiol curing agent include ester bond type thiol compounds, aliphatic ether bond type thiol compounds, and aromatic ether bond type thiol compounds.

The content of the curing agent is, for example, 1 part by mass or more and 40 parts by mass or less, when the resin component contained in the first adhesive layer is 100 parts by mass. For example, when using an imidazole-based curing agent as a main component, the content of the curing agent is, for example, 1 part by mass or more, 15 parts by mass, when the resin component contained in the first adhesive layer is 100 parts by mass. It is preferable that the amount is less than 1 part. On the other hand, when using a phenolic curing agent as a main component, the content of the curing agent is, for example, 5 parts by mass or more, 40 parts by mass, when the resin component contained in the first adhesive layer is 100 parts by mass. It is preferable that the amount is less than 1 part. Note that using an imidazole curing agent or a phenolic curing agent as a main component as a curing agent means that the mass proportion of the imidazole curing agent or phenol curing agent is the largest in the curing agent.

(b) Foaming agent The first adhesive layer in this embodiment may or may not contain a foaming agent, but it is particularly preferable to contain a foaming agent. By containing the foaming agent, the surface roughness becomes large, the coefficient of friction becomes small, and the slipperiness becomes even better. Therefore, of the first adhesive layer and the second adhesive layer, it is preferable that the first adhesive layer with low tack contains a foaming agent.

As the foaming agent, a foaming agent that is generally used in the adhesive layer of a foamable adhesive sheet can be used. Further, the foaming agent may be a foaming agent that causes a foaming reaction due to heat, or may be a foaming agent that causes a foaming reaction due to light.

The foaming start temperature of the foaming agent is preferably higher than the softening temperature of the main ingredient of a curable adhesive such as an epoxy resin, and lower than the activation temperature of the curing reaction of the main ingredient of a curable adhesive such as an epoxy resin. . The foaming start temperature of the foaming agent is, for example, 70°C or higher, and may be 100°C or higher. If the foaming start temperature is too low, the reaction will start early, foaming will occur with the resin component having low flexibility and fluidity, and uniform foaming may be difficult to produce. On the other hand, the foaming start temperature of the foaming agent is, for example, 210° C. or lower. If the foaming start temperature is too high, the resin component may deteriorate.

Note that the softening temperature of the main ingredient of a curable adhesive such as an epoxy resin can be measured using the ring and ball softening temperature test method specified in JIS K7234.

Examples of the foaming agent include microcapsule foaming agents. It is preferable that the microcapsule type foaming agent has a thermal expansion agent such as a hydrocarbon as a core and a resin such as an acrylonitrile copolymer as a shell.

Further, as the blowing agent, for example, an organic blowing agent or an inorganic blowing agent may be used. Examples of organic blowing agents include azo blowing agents such as azodicarbonamide (ADCA), azobisformamide, and azobisisobutyronitrile, fluorinated alkane blowing agents such as trichloromonofluoromethane, and paratoluenesulfonyl hydrazide. Hydrazine blowing agents, semicarbazide blowing agents such as p-toluenesulfonyl semicarbazide, triazole blowing agents such as 5-morpholyl-1,2,3,4-thiatriazole, N, such as N,N-dinitrosoterephthalamide, etc. - Examples include nitroso blowing agents. On the other hand, examples of inorganic blowing agents include ammonium carbonate, ammonium hydrogen carbonate, ammonium nitrite, ammonium borohydride, and azides.

The average particle size of the blowing agent may be, for example, 10 μm or more, 13 μm or more, or 17 μm or more. When the average particle size of the foaming agent is within the above range, the coefficient of static friction on the surface of the first adhesive layer can be reduced, and the first adhesive layer can have good slip properties. Further, the average particle diameter of the foaming agent is preferably equal to or less than the thickness of the first adhesive layer, and may be, for example, 44 μm or less, 30 μm or less, or 24 μm or less.

Note that the average particle size of the blowing agent is the particle size at 50% of the integrated value in the particle size distribution determined by a laser diffraction scattering method. Furthermore, when measuring the average particle size of the foaming agent, the first adhesive layer is dissolved in a solvent to separate the foaming agent. The solvent is not particularly limited as long as it is capable of dissolving components other than the foaming agent contained in the first adhesive layer, and may be used as appropriate depending on the type of curable adhesive contained in the first adhesive layer, etc. For example, the solvent used in the adhesive composition used to form the first adhesive layer can be used. Specifically, methyl ethyl ketone, ethyl acetate, toluene, etc. can be used.

The content of the foaming agent is, for example, 0.5 parts by mass or more, may be 2 parts by mass or more, and 3 parts by mass or more when the resin component contained in the first adhesive layer is 100 parts by mass. It may be 4 parts by mass or more, or it may be 5 parts by mass or more. On the other hand, the content of the foaming agent is, for example, 25 parts by mass or less, may be 20 parts by mass or less, and may be 15 parts by mass or less, based on 100 parts by mass of the resin component contained in the first adhesive layer. Good too. If the content of the foaming agent is too small, the coefficient of static friction on the surface of the first adhesive layer may become large. Furthermore, if the content of the foaming agent is too large, the content of the curable adhesive will be relatively small, which may reduce the adhesiveness after foaming and curing.

(c) Other components In the case where the curable adhesive is an epoxy resin adhesive, the first adhesive layer in this embodiment may contain only an epoxy resin and an acrylic resin as resin components, or may contain other components. It may further contain a resin. Examples of other resins include urethane resins.

The total ratio of the first epoxy resin, second epoxy resin, and acrylic resin to the resin component contained in the first adhesive layer is, for example, 70% by mass or more, and may be 80% by mass or more, and 90% by mass. It may be more than 100% by mass.

The content of the resin component contained in the first adhesive layer is, for example, 60% by mass or more, may be 70% by mass or more, may be 80% by mass or more, or may be 90% by mass or more. good.

The first adhesive layer may contain additives such as a silane coupling agent, a filler, an antioxidant, a light stabilizer, an ultraviolet absorber, a lubricant, a plasticizer, an antistatic agent, a crosslinking agent, a coloring agent, etc., as necessary. may contain. Examples of the silane coupling agent include epoxy-based silane coupling agents. Examples of the filler include inorganic fillers such as calcium carbonate, aluminum hydroxide, magnesium hydroxide, antimony trioxide, zinc borate, molybdenum compounds, and titanium dioxide. Examples of the antioxidant include phenolic antioxidants and sulfur-based antioxidants.

(2) Structure of the first adhesive layer When the first adhesive layer further contains a foaming agent, the first adhesive layer can be foamed at a foaming ratio of, for example, 4 times or more and 15 times or less. For example, when only the first adhesive layer contains a foaming agent among the first adhesive layer and the second adhesive layer, the foaming ratio may be, for example, 5 times or more, or 7 times or more. Often, it may be 9 times or more. Moreover, in the above case, the expansion ratio may be, for example, 14 times or less, 13 times or less, or 12 times or less. On the other hand, for example, when both of the first adhesive layer and the second adhesive layer contain a foaming agent, the foaming ratio may be, for example, 5 times or more. , may be 6 times or more, or may be 7 times or more. Moreover, in the above case, the expansion ratio may be, for example, 14 times or less, 12 times or less, or 10 times or less. If the foaming ratio is too small or too large, the adhesiveness after foaming and curing may decrease.

Here, the foaming ratio can be determined by the following formula.
Foaming ratio (times) = Thickness of the first adhesive layer after foaming and curing / Thickness of the first adhesive layer before foaming and curing

The thickness of the first adhesive layer is not particularly limited, but when the first adhesive layer contains a foaming agent, it is preferably equal to or larger than the average particle size of the foaming agent, for example, 10 μm or more, and 15 μm or more. The thickness may be 20 μm or more. If the first adhesive layer is too thin, it may not be possible to obtain sufficient adhesion to the base material and adhesion after foaming and curing. On the other hand, the thickness of the first adhesive layer is, for example, 200 μm or less, may be 150 μm or less, or may be 100 μm or less. If the first adhesive layer is too thick, the surface quality may deteriorate.

Here, the thickness of the first adhesive layer is defined as the cross section in the thickness direction of the foamable adhesive sheet observed by a transmission electron microscope (TEM), a scanning electron microscope (SEM), or a scanning transmission electron microscope (STEM). This is the value measured from , and can be taken as the average value of the thickness at 10 randomly selected locations. Note that the same method can be used for measuring the thickness of other layers included in the foamable adhesive sheet.

The first adhesive layer may be a continuous layer or a discontinuous layer. Examples of the discontinuous layer include patterns such as stripes and dots. Further, the surface of the first adhesive layer may have an uneven shape such as embossing.

The first adhesive layer can be formed, for example, by applying an adhesive composition containing the above-mentioned curable adhesive and foaming agent, and removing the solvent. Examples of coating methods include roll coating, reverse roll coating, transfer roll coating, gravure coating, gravure reverse coating, comma coating, rod coating, blade coating, bar coating, wire bar coating, die coating, lip coating, dip coating, etc. can be mentioned.

The adhesive composition may or may not contain a solvent. Note that the term "solvent" as used herein has a broad meaning that includes not only a strict solvent (a solvent that dissolves a solute) but also a dispersion medium. Further, the solvent contained in the adhesive composition is evaporated and removed when the adhesive composition is applied and dried to form an adhesive layer.

The adhesive composition can be obtained by mixing the above-mentioned components, kneading and dispersing as necessary. For mixing and dispersing methods, common kneading and dispersing machines such as two-roll mills, three-roll mills, pebble mills, trom mills, Szegvari attritors, high-speed impeller dispersing machines, high-speed stone mills, high-speed impact mills, and despars are used. , high-speed mixer, ribbon blender, co-kneader, intensive mixer, tumbler, blender, desperser, homogenizer, and ultrasonic dispersion machine are applicable.

3. Second adhesive layer (1) Material of second adhesive layer The second adhesive layer in this embodiment contains a curable adhesive.

(a) Curable Adhesive The curable adhesive included in the second adhesive layer in this embodiment can be the same as the curable adhesive used in the first adhesive layer. Among these, the curable adhesive is preferably an epoxy resin adhesive.

Hereinafter, a case where the curable adhesive is an epoxy resin adhesive will be explained by giving an example.

(i) Epoxy resin The epoxy resin in this embodiment can be the same as the epoxy resin used for the first adhesive layer.

As the epoxy resin, an epoxy resin generally used for the adhesive layer of a foamable adhesive sheet can be used.

Examples of the epoxy resin include aromatic epoxy resins, aliphatic epoxy resins, alicyclic epoxy resins, and heterocyclic epoxy resins. Specific examples of the epoxy resin may be the same as those of the first epoxy resin used in the first adhesive layer.

The epoxy resin may be a monofunctional epoxy resin, a bifunctional epoxy resin, a trifunctional epoxy resin, or a tetrafunctional or higher functional epoxy resin.

Among these, it is preferable to use, as the epoxy resin, an epoxy resin that is liquid at room temperature, such as a bisphenol A epoxy resin or a bisphenol F epoxy resin, and an epoxy resin that has a low softening point. This is because by using these epoxy resins, the tack of the second adhesive layer can be easily adjusted within a predetermined range.

(ii) Acrylic resin When the curable adhesive is an epoxy resin adhesive, the second adhesive layer may further contain an acrylic resin that is compatible with the epoxy resin. Film formability can be improved.

The acrylic resin can be the same as the acrylic resin used for the first adhesive layer.

(iii) Curing agent The curing agent in this embodiment can be the same as the curing agent used for the first adhesive layer. Further, as the curing agent, a curing agent that is solid at room temperature or a curing agent that is liquid at room temperature can be used, but from the viewpoint of storage stability, it is preferable to use a curing agent that is solid at room temperature.

(b) Foaming agent The second adhesive layer in this embodiment may or may not contain a foaming agent, but it is particularly preferable to contain a foaming agent. By containing the foaming agent in both the first adhesive layer and the second adhesive layer, the adhesiveness of the first adhesive layer and the second adhesive layer after foaming and curing can be improved.

The foaming agent may be the same as the foaming agent used for the first adhesive layer.

(c) Other components In the case where the curable adhesive is an epoxy resin adhesive, the second adhesive layer in this embodiment may contain only an epoxy resin and an acrylic resin as resin components, or may contain other components. It may further contain a resin. Examples of other resins include urethane resins.

The total ratio of the epoxy resin and the acrylic resin to the resin component contained in the second adhesive layer is, for example, 70% by mass or more, may be 80% by mass or more, or may be 90% by mass or more, It may be 100% by mass.

The content of the resin component contained in the second adhesive layer is, for example, 60% by mass or more, may be 70% by mass or more, may be 80% by mass or more, or may be 90% by mass or more. good.

The second adhesive layer may contain additives as necessary. The additives may be the same as those used in the first adhesive layer.

(2) Configuration of second adhesive layer When the second adhesive layer further contains a foaming agent, the second adhesive layer can be foamed at a foaming ratio of, for example, 1.5 times or more and 12 times or less. For example, when both the first adhesive layer and the second adhesive layer contain a foaming agent among the first adhesive layer and the second adhesive layer, the foaming ratio may be, for example, 2 times or more, or 3 times or more. It may be more than twice as much, or more than 4 times. Moreover, in the above case, the expansion ratio may be, for example, 10 times or less, 9 times or less, or 8 times or less. If the foaming ratio is too small or too large, the adhesiveness after foaming and curing may decrease.

The thickness of the second adhesive layer can be similar to the thickness of the first adhesive layer.

The second adhesive layer may be a continuous layer or a discontinuous layer. Further, the surface of the second adhesive layer may have an uneven shape such as embossing.

The method for forming the second adhesive layer can be the same as the method for forming the first adhesive layer.

4. Substrate The substrate in this embodiment is arranged between the first adhesive layer and the second adhesive layer described above.

It is preferable that the base material has insulation properties. Further, the base material is preferably in the form of a sheet. The base material may have a single layer structure or a multilayer structure. Further, the base material may or may not have a porous structure inside.

Examples of the base material include resin base materials and nonwoven fabrics.

Examples of the resin contained in the resin base material include polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate (PEN), and aromatic polyester; polycarbonate; polyarylate; polyurethane; polyamide, polyether amide, etc. polyamide resins; polyimide resins such as polyimide, polyetherimide, and polyamideimide; polysulfone resins such as polysulfone and polyethersulfone; polyetherketone resins such as polyetherketone and polyetheretherketone; polyphenylene sulfide (PPS); modified polyphenylene Examples include oxides. The glass transition temperature of the resin is, for example, 80°C or higher, may be 140°C or higher, or may be 200°C or higher. Furthermore, liquid crystal polymer (LCP) may be used as the resin.

Examples of the nonwoven fabric include nonwoven fabrics containing fibers such as cellulose fibers, polyester fibers, nylon fibers, aramid fibers, polyphenylene sulfide fibers, liquid crystal polymer fibers, glass fibers, metal fibers, and carbon fibers.

The base material may be surface-treated to improve adhesion with the first adhesive layer and the second adhesive layer.

The thickness of the base material is preferably thinner than the thickness of the first adhesive layer and thinner than the thickness of the second adhesive layer. By making the thickness of the base material thinner than the thickness of the first adhesive layer and the thickness of the second adhesive layer, the thickness of the foam adhesive sheet can be made thinner, and the thickness of the first adhesive layer and the thickness of the second adhesive layer can be made thinner. The thickness of the second adhesive layer can be relatively thick. Therefore, the thickness of the foamable adhesive sheet can be reduced to improve insertability without degrading the adhesive properties and foaming properties of the first adhesive layer and the second adhesive layer.

Specifically, the thickness of the base material is 200 μm or less, may be 100 μm or less, or may be 50 μm or less. Further, the thickness of the base material may be, for example, 2 μm or more, 5 μm or more, or 9 μm or more.

5. Other configurations (1) First intermediate layer and second intermediate layer The foamable adhesive sheet in this embodiment may have a first intermediate layer between the base material and the first adhesive layer. Moreover, the foamable adhesive sheet in this embodiment may have a second intermediate layer between the base material and the second adhesive layer. By arranging the first intermediate layer and the second intermediate layer, it is possible to improve the adhesion of the first adhesive layer and the second adhesive layer to the base material. Furthermore, by arranging the first intermediate layer and the second intermediate layer, for example, when the foam adhesive sheet is bent, stress applied to the bent part can be alleviated, and when the foam adhesive sheet is cut, the stress applied to the bent part can be alleviated. The stress applied to the cut portion can be alleviated. As a result, it is possible to suppress lifting and peeling of the first adhesive layer and the second adhesive layer from the base material when the foamable adhesive sheet is bent or cut.

For example, in the foamable adhesive sheet 10 shown in FIG. 5, the first intermediate layer 4 is arranged between the base material 2 and the first adhesive layer 1, and the second intermediate layer Layer 5 is arranged. In addition, although the foamable adhesive sheet 10 has both the first intermediate layer 4 and the second intermediate layer 5 in FIG. 5, it may have only either one.

The foamable adhesive sheet only needs to have at least one of the first intermediate layer and the second intermediate layer, for example, only the first intermediate layer disposed between the base material and the first adhesive layer. It may have only the second intermediate layer disposed between the base material and the second adhesive layer, or it may have only the second intermediate layer disposed between the base material and the first adhesive layer, and the base material and the first intermediate layer disposed between the base material and the first adhesive layer. and a second intermediate layer disposed between the second adhesive layer.

The material included in the first intermediate layer and the second intermediate layer may be any material that can enhance the adhesion between the base material and the first adhesive layer or the second adhesive layer, and can relieve stress. It is not particularly limited, and is appropriately selected depending on the materials of the base material, the first adhesive layer, the second adhesive layer, and the like. Examples include polyester, polyvinyl chloride, polyvinyl acetate, polyurethane, polymers obtained by copolymerizing at least two thereof, crosslinked products thereof, and mixtures thereof.

The crosslinked product is a crosslinked product obtained by crosslinking the above resin with a curing agent. Examples of the curing agent include isocyanate curing agents. Further, for example, when the reactive group/NCO equivalent is 1, it is preferable to add the isocyanate curing agent to the resin at a ratio of 0.5% by mass or more and 20% by mass or less.

Among these, it is preferable that the first intermediate layer and the second intermediate layer contain a crosslinked resin. Note that crosslinked resin refers to one that does not melt even at high temperatures. This makes it possible to improve adhesive strength at high temperatures, that is, heat resistance.

The thickness of the first intermediate layer and the second intermediate layer is not particularly limited, but may be, for example, 0.1 μm or more, 0.5 μm or more, or 1 μm or more. If the first intermediate layer or the second intermediate layer is too thin, the effect of suppressing the peeling of the first adhesive layer or the second adhesive layer from the base material during bending or cutting of the foamable adhesive sheet will not be achieved sufficiently. there is a possibility. On the other hand, the thickness of the first intermediate layer and the second intermediate layer is, for example, 4 μm or less, and may be 3.5 μm or less. The first intermediate layer and the second intermediate layer themselves usually do not have high heat resistance, so if the first intermediate layer or the second intermediate layer is too thick, the heat resistance (adhesion strength at high temperatures) may decrease. There is.

The first intermediate layer and the second intermediate layer can be formed, for example, by applying a resin composition and removing the solvent. Examples of coating methods include roll coating, reverse roll coating, transfer roll coating, gravure coating, gravure reverse coating, comma coating, rod coating, blade coating, bar coating, wire bar coating, die coating, lip coating, and dip coating. Can be mentioned.

(2) First separator and second separator The foamable adhesive sheet in this embodiment may have a first separator on the side of the first adhesive layer opposite to the second adhesive layer. Moreover, the foamable adhesive sheet in this embodiment may have a second separator on the side of the second adhesive layer opposite to the first adhesive layer.

The first separator and the second separator are not particularly limited as long as they can be peeled off from the first adhesive layer and the second adhesive layer, and have sufficient strength to protect the first adhesive layer and the second adhesive layer. be able to. Examples of the first separator and the second separator include a release film, release paper, and the like. Further, the first separator and the second separator may have a single layer structure or a multilayer structure.

Examples of the single-layer separator include fluororesin films.

Moreover, as a separator with a multilayer structure, for example, a laminate having a release layer on one or both sides of a base layer can be mentioned. Examples of the base material layer include resin films such as polypropylene, polyethylene, and polyethylene terephthalate, and papers such as high-quality paper, coated paper, and impregnated paper. The material for the release layer is not particularly limited as long as it has release properties, and examples include silicone compounds, organic compound-modified silicone compounds, fluorine compounds, aminoalkyd compounds, melamine compounds, acrylic compounds, polyester compounds, and long-lasting materials. Examples include chain alkyl compounds. These compounds may be of emulsion type, solvent type or non-solvent type.

The first separator and the second separator may be the same or different. Among these, it is preferable that the first separator has heavy releasability and the second separator has light releasability. In foamable adhesive sheets, the first adhesive layer is substantially tack-free and the second adhesive layer is tack-free. Therefore, for example, when bonding the rotor and permanent magnets in an embedded magnet type motor, after placing the foam adhesive sheet on the second member, the foam adhesive sheet is placed in the hole of the first member. When inserting a member, attach the second adhesive layer side of the foam adhesive sheet to the second member, and make sure that the first adhesive layer side of the foam adhesive sheet is on the front side. The adhesion between the second member and the foamable adhesive sheet and the insertability of the second member on which the foamable adhesive sheet is placed can be improved. In this case, between the first separator and the second separator, the second separator will be peeled off, so the first separator has heavy releasability and the second separator has light releasability, so that the second separator can be peeled off more easily than the first separator.

Note that light peeling and heavy peeling refer to the degree of force required to peel off the first separator and second separator from the first adhesive layer and the second adhesive layer, and light peeling has a higher peeling force than heavy peeling. means that is small.

6. Foamable Adhesive Sheet The thickness of the foamable adhesive sheet in this embodiment is, for example, 10 μm or more, and may be 20 μm or more. On the other hand, the thickness of the foamable adhesive sheet is, for example, 1000 μm or less, and may be 200 μm or less.

The use of the foamable adhesive sheet in this embodiment is not particularly limited. The foamable adhesive sheet in this embodiment can be used, for example, to bond two members together by placing the foamable adhesive sheet between two members and then foaming and curing the foamable adhesive sheet. can. Among these, the foamable adhesive sheet in this embodiment is produced by placing the foamable adhesive sheet on the second member, and then inserting the second member on which the foamable adhesive sheet is placed into the hole of the first member. Foaming and curing of the sheet is preferably used when bonding the first member and the second member.

The method for producing the foamable adhesive sheet in this embodiment is not particularly limited, and is appropriately selected depending on the layer structure of the foamable adhesive sheet. For example, the following two methods of manufacturing a foamable adhesive sheet can be mentioned.

In the first method for producing a foamable adhesive sheet, for example, first, an adhesive composition for forming a first adhesive layer is applied to one side of a base material and dried, thereby forming a first adhesive layer. form. Further, an adhesive composition for forming a second adhesive layer is applied onto the second separator and dried to form a second adhesive layer. Next, the laminate of the base material and the first adhesive layer and the laminate of the second separator and the second adhesive layer are laminated. As a result, a foamable adhesive sheet is obtained. Note that a first intermediate layer or a second intermediate layer may be formed. In this method, since the first adhesive layer is dried only once, the foamable adhesive sheet can be efficiently produced.

In the second method for manufacturing a foamable adhesive sheet, for example, first, an adhesive composition for forming a first adhesive layer is applied and dried on one side of a base material, and then the first adhesive layer is formed. form. Next, an adhesive composition for forming a second adhesive layer is applied to the other surface of the base material and dried to form a second adhesive layer. Subsequently, a second separator is laminated on the second adhesive layer. As a result, a foamable adhesive sheet is obtained. Note that a first intermediate layer or a second intermediate layer may be formed.

II. Second Embodiment A second embodiment of the foamable adhesive sheet in the present disclosure is a foamable adhesive sheet having a first adhesive layer, a base material, a second adhesive layer, and an adhesive layer in this order, The first adhesive layer and the second adhesive layer contain a curable adhesive and a foaming agent, the adhesive layer contains a pressure sensitive adhesive or a curable adhesive, and the tack of the first adhesive layer is The tack of the adhesive layer is 10 gf or more, and the loop stiffness is 50 mN/10 mm or more.

FIG. 6 is a schematic cross-sectional view illustrating the foamable adhesive sheet in this embodiment. The foamable adhesive sheet 10 in FIG. 6 has a first adhesive layer 1, a base material 2, a second adhesive layer 3, and an adhesive layer 6 in this order. The first adhesive layer 1 and the second adhesive layer 3 contain a curable adhesive and a foaming agent, and the adhesive layer 6 contains a pressure sensitive adhesive or a curable adhesive. Further, the tack of the first adhesive layer 1 and the tack of the adhesive layer 6 are each within a predetermined range, and the loop stiffness of the foamable adhesive sheet 10 is within a predetermined range.

In this embodiment, since the tack of the adhesive layer is within a predetermined range, the adhesive layer can have good adhesion to the member. Specifically, when fixing the other member by adhesive to the hole or groove of one member, the adhesive layer side of the foam adhesive sheet is pasted to the other member, and the hole or groove of one member is fixed. etc., the other member with the foam adhesive sheet pasted is inserted, and then the foam adhesive sheet is foamed and cured to bond one member and the other member, and the tack of the adhesive layer is set to a predetermined level. By being within this range, the surface of the adhesive layer of the foamable adhesive sheet can be attached to the other member using the tack of the adhesive layer, and the adhesion of the adhesive layer to the member can be improved. Thereby, when inserting the other member to which the foamable adhesive sheet is attached into a hole or groove of one member, peeling or displacement of the foamable adhesive sheet can be suppressed.

Furthermore, in this embodiment, since the tack of the first adhesive layer is less than or equal to a predetermined value, the first adhesive layer can be made substantially non-adhesive (tack-free), and the first adhesive layer has good slip properties. It can be one adhesive layer. Therefore, for example, in the adhesive fixing method described above, when inserting the other member to which the foam adhesive sheet is pasted into the hole or groove of one member, the other member to which the foam adhesive sheet is pasted is The member can be inserted smoothly and insertability can be improved. Thereby, peeling and displacement of the foamable adhesive sheet can be suppressed. In addition, in the adhesive fixing method described above, when aligning the members by moving the other member relative to the other member, it is necessary to insert the other member into the hole or groove of one member. The other member can be smoothly moved relative to the other member, and alignment can be easily performed.

Furthermore, in this embodiment, the tack of the first adhesive layer is less than or equal to a predetermined value, and the first adhesive layer is substantially non-adhesive (tack-free), so it has good slip properties and is resistant to The first adhesive layer can also have good blocking properties. Therefore, the handleability of the foamable adhesive sheet can also be improved.

In addition, in this embodiment, as mentioned above, the adhesive layer has excellent adhesion to the member and the first adhesive layer has excellent slipperiness, so that peeling and misalignment of the foam adhesive sheet can be prevented. Can be suppressed. Therefore, it suppresses the decrease in adhesion of the foamable adhesive sheet after foaming and curing due to peeling or misalignment of the foamable adhesive sheet, and also suppresses the adhesion of the foamable adhesive sheet after foaming and curing due to peeling or misalignment of the foamable adhesive sheet. Variations in strength can be reduced. Therefore, by using the foamable adhesive sheet of this embodiment, it is possible to realize adhesion with high adhesive strength, high reliability, and high quality.

Furthermore, in the foamable adhesive sheet of this embodiment, since the loop stiffness is equal to or greater than a predetermined value, stiffness can be increased. Therefore, it is possible to suppress the foamable adhesive sheet from sagging due to its own weight during transportation of the foamable adhesive sheet. Therefore, for example, when a foamable adhesive sheet is transported by suction and attached to another member, it is necessary to prevent the foamable adhesive sheet from folding, twisting, sagging, air bubbles, etc. during attachment. be able to. Therefore, the adhesion properties can be improved. Furthermore, to prevent bulges from forming on the foam adhesive sheet due to these defects, it is possible to insert the other member with the foam adhesive sheet pasted into the hole or groove of one member. At the same time, the foamable adhesive sheet can be made less likely to be rubbed. Therefore, peeling of the foamable adhesive sheet during insertion can be suppressed. Therefore, from this point of view as well, by using the foamable adhesive sheet of this embodiment, it is possible to realize adhesion with high adhesive strength, high reliability, and high quality.

Hereinafter, each structure of the foamable adhesive sheet of this embodiment will be explained.

1. Characteristics The tack of the first adhesive layer in this embodiment is the same as the tack of the first adhesive layer in the first embodiment described above.

In this embodiment, the tack of the adhesive layer is 10 gf or more, may be 30 gf or more, or may be 50 gf or more. If the tack of the adhesive layer is too low, for example, in the adhesive fixing method described above, when applying the adhesive layer side of the foam adhesive sheet to the other member using the tack of the adhesive layer, the adhesive layer and the other member may be damaged. There is a possibility that the adhesion of the foam adhesive sheet may decrease, or when inserting the other component with the foam adhesive sheet pasted into the holes or grooves of one component, the foam adhesive may deteriorate due to poor adhesion between the adhesive layer and the other component. If the sheet peels off or the position of the foamable adhesive sheet shifts, etc., the adhesiveness of the first adhesive layer and the adhesive layer after foaming and curing may decrease or the adhesive strength may vary. Further, the tack of the adhesive layer is, for example, 500 gf or less, may be 400 gf or less, or may be 300 gf or less.

In this embodiment, the tack of the second adhesive layer is not particularly limited. Among these, the tack of the second adhesive layer is preferably less than 10 gf. In this case, the tack of the second adhesive layer can be similar to the tack of the first adhesive layer.

The methods for measuring the tack of the first adhesive layer, the second adhesive layer, and the adhesive layer are the same as those described in the first embodiment.

Furthermore, the method for controlling the tack of the first adhesive layer and the second adhesive layer is the same as that described in the first embodiment.

In this embodiment, the static friction coefficient of the surface of the first adhesive layer opposite to the second adhesive layer and the arithmetic mean roughness (Ra) of the surface of the first adhesive layer opposite to the second adhesive layer are as described above. The contents are the same as those described in the first embodiment.

The loop stiffness of the foamable adhesive sheet of this embodiment is similar to the loop stiffness of the foamable adhesive sheet of the first embodiment. In this embodiment, when placing the foam adhesive sheet test piece on the loop stiffness measuring device, the foam adhesive sheet test piece has an inner surface that is the first adhesive layer surface and an outer surface that is the adhesive layer surface. Arrange it so that

The adhesive properties of the foamable adhesive sheet in this embodiment after foaming and curing and the electrical insulation properties after foaming and curing are the same as those described in the first embodiment.

2. First Adhesive Layer The first adhesive layer in this embodiment contains a curable adhesive and a foaming agent. The material and structure of the first adhesive layer can be the same as those of the first adhesive layer in the first embodiment.

3. Second Adhesive Layer The second adhesive layer in this embodiment contains a curable adhesive and a foaming agent. The material and structure of the second adhesive layer may be the same as those of the first adhesive layer in the first embodiment, or may be the same as the second adhesive layer in the first embodiment.

4. Adhesive Layer The adhesive layer in this embodiment is disposed on the side of the second adhesive layer opposite to the base material, and contains a pressure-sensitive adhesive or a cured adhesive. Moreover, the adhesive layer does not substantially contain a foaming agent.

As the pressure-sensitive adhesive contained in the adhesive layer in this embodiment, a general pressure-sensitive adhesive can be used.

Further, the curable adhesive included in the adhesive layer in this embodiment can be the same as the curable adhesive used in the second adhesive layer.

The thickness of the adhesive layer is not particularly limited, but may be, for example, 2 μm or more and 100 μm or less, 3 μm or more and 75 μm or less, or 5 μm or more and 50 μm or less. If the adhesive layer is too thin, sufficient adhesiveness may not be obtained.

The adhesive layer may be a continuous layer or a discontinuous layer. Examples of the discontinuous layer include patterns such as stripes and dots. Further, the surface of the adhesive layer may have an uneven shape such as embossing.

The method of forming the adhesive layer can be the same as the method of forming the first adhesive layer and the second adhesive layer.

5. Substrate The substrate in this embodiment is arranged between the first adhesive layer and the second adhesive layer described above. The base material is the same as the base material in the first embodiment.

6. Other configurations (1) First intermediate layer and second intermediate layer The foamable adhesive sheet in this embodiment may have a first intermediate layer between the base material and the first adhesive layer. Moreover, the foamable adhesive sheet in this embodiment may have a second intermediate layer between the base material and the second adhesive layer. The first intermediate layer and the second intermediate layer are the same as the first intermediate layer and the second intermediate layer in the first embodiment.

For example, in the foamable adhesive sheet 10 shown in FIG. 7, the first intermediate layer 4 is arranged between the base material 2 and the first adhesive layer 1, and the second intermediate layer Layer 5 is arranged. In addition, although the foamable adhesive sheet 10 has both the first intermediate layer 4 and the second intermediate layer 5 in FIG. 7, it may have only either one.

(2) First separator and second separator The foamable adhesive sheet in this embodiment may have a first separator on the side of the first adhesive layer opposite to the second adhesive layer. Moreover, the foamable adhesive sheet in this embodiment may have a second separator on the side of the adhesive layer opposite to the second adhesive layer. The first separator and the second separator can be the same as the first separator and the second separator in the first embodiment.

7. Foamable Adhesive Sheet The thickness and use of the foamable adhesive sheet in this embodiment are the same as in the first embodiment.

The method for producing the foamable adhesive sheet in this embodiment is not particularly limited, and is appropriately selected depending on the layer structure of the foamable adhesive sheet.

B. Method for manufacturing an article The method for manufacturing an article according to the present disclosure includes a step of arranging the above-described foamable adhesive sheet between a first member and a second member, foaming and hardening the foamable adhesive sheet, and and an adhesion step of adhering the member and the second member.

FIGS. 8(a) to 8(c) are process diagrams illustrating an example of a method for manufacturing an article according to the present disclosure. First, as shown in FIG. 8(a), the surface of the second adhesive layer 3 of the foamable adhesive sheet 10 is attached to the second member 20b. Next, as shown in FIG. 8(b), the second member 20b, on which the foamable adhesive sheet 10 is arranged, is inserted into the hole of the first member 20a. Next, as shown in FIG. 8C, the first adhesive layer 1 and the second adhesive layer 3 of the foamable adhesive sheet 10 are foamed and cured, for example, by heating. The first member 20a and the second member 20b are adhered (joined) by the adhesive sheet 13 having the first adhesive layer 11 and the second adhesive layer 12 after foaming and hardening. Thereby, an article 100 is obtained in which the adhesive sheet 13 is placed between the first member 20a and the second member 20b.

FIGS. 9(a) to 9(c) are process diagrams showing other examples of the method for manufacturing an article according to the present disclosure. In FIG. 9(a), foam adhesive sheets are attached to both sides of the second member 20b. Note that the arrangement process and adhesion process are the same as those in FIGS. 8(a) to 8(c).

Hereinafter, a method for manufacturing an article according to the present disclosure will be described.

1. Foamable Adhesive Sheet In the method for manufacturing an article according to the present disclosure, the above-described foamable adhesive sheet is used as the foamable adhesive sheet.

When the foam adhesive sheet has a first separator and a second separator, when placing the foam adhesive sheet between the first member and the second member, remove the first separator and the second separator from the foam adhesive sheet. Peel off and use.

Note that the details of the foamable adhesive sheet are described in the section "A. Foamable adhesive sheet" above, so the explanation here will be omitted.

2. Arranging Step In the arrangement step of the present disclosure, the method for arranging the foam adhesive sheet between the first member and the second member is appropriately selected depending on the types of the first member and the second member. For example, when the first member has holes or grooves and the second member is placed in the holes or grooves of the first member, and the first member and the second member are fixed by adhesive, foaming After pasting the surface of the second adhesive layer or adhesive layer of the foamable adhesive sheet to the second member using the tack of the second adhesive layer or adhesive layer of the adhesive sheet, the foam is applied to the holes and grooves of the first member. There are two methods: placing a second member with a foam adhesive sheet pasted, or placing a foam adhesive sheet in the holes or grooves of the first member and using the second adhesive layer or the tack of the adhesive layer of the foam adhesive sheet. After pasting the second adhesive layer or the surface of the adhesive layer of the foam adhesive sheet into the holes and grooves of the first member, the second member is attached to the holes and grooves of the first member to which the foam adhesive sheet was pasted. Examples include a method of arranging the .

3. Adhesion Step In the adhesion step of the present disclosure, examples of the method for foaming and curing the foamable adhesive sheet include heating or light irradiation. Among these, it is preferable to foam and harden the foamable adhesive sheet by heating. The heating method is applicable even when the first member and the second member do not have transparency, such as metal members.

The heating conditions are appropriately set depending on the type of curable adhesive and foaming agent contained in the first adhesive layer and the second adhesive layer, the type of the base material, and the like. The heating temperature can be, for example, 130°C or higher and 200°C or lower. Further, the heating time can be, for example, 3 minutes or more and 3 hours or less.

Note that the present disclosure is not limited to the above embodiments. The above-mentioned embodiments are illustrative, and any configuration that has substantially the same technical idea as the claims of the present disclosure and provides similar effects is the present invention. within the technical scope of the disclosure.

[Manufacturing example]
First, adhesive compositions 1 to 3 having the following compositions were prepared.

<Adhesive composition 1>
・Acrylic resin (PMMA-PBuA-PMMA (acrylamide group in part), Tg: -20°C, 120°C, Mw: 150,000): 13 parts by mass ・Epoxy resin A (bisphenol A novolac type, solid at room temperature, softening Temperature: 70°C, epoxy equivalent: 210 g/eq, Mw: 1300, melt viscosity at 150°C: 0.5 Pa s): 40 parts by mass, epoxy resin B (BPA phenoxy type, solid at room temperature, softening temperature: 110°C , epoxy equivalent: 8000 g/eq, Mw: 50,000): 42 parts by mass ・Curing agent A (α-(hydroxy (or dihydroxy) phenylmethyl)-ω-hydropoly[biphenyl-4,4'-diylmethylene (hydroxy) (or dihydroxy)phenylenemethylene)]): 6 parts by mass, curing catalyst (2-phenyl-4,5-dihydroxymethylimidazole, average particle size: 3 μm, melting point: 230°C, reaction initiation temperature 145°C to 155°C, activity Range 155°C to 173°C (manufactured by Shikoku Kasei Kogyo Co., Ltd., 2PHZ-PW)): 8 parts by mass, blowing agent (thermally expandable microcapsules, average particle size 10 μm to 16 μm, expansion start temperature 123°C to 133°C, maximum expansion Temperature: 168°C to 178°C, core: hydrocarbon, shell: thermoplastic polymer): 13.5 parts by mass, solvent (methyl ethyl ketone): 150 parts by mass

<Adhesive composition 2>
・Acrylic resin (PMMA-PBuA-PMMA (acrylamide group in part), Tg: -20°C, 120°C, Mw: 150,000): 40 parts by mass ・Epoxy resin C (bisphenol A type, liquid at room temperature, epoxy equivalent) : 184 to 194 g/eq): 45 parts by mass ・Epoxy resin D (diaminodiphenylmethane type, high viscosity liquid, epoxy equivalent: 110 to 130 g/eq): 65 parts by mass ・Epoxy resin E (silicone modified, epoxy equivalent: 1200 g /mol): 20 parts by mass Silane coupling agent (3-glycidoxypropyltrimethoxysilane): 2 parts by mass Curing agent B (phenol formaldehyde polycondensate, softening point 80°C, hydroxyl equivalent 104 g/mol): 6 parts by mass of curing catalyst (2-phenyl-4,5-dihydroxymethylimidazole, average particle size: 3 μm, melting point: 230°C, reaction initiation temperature 145°C to 155°C, active area 155°C to 173°C (Shikoku Kasei Kogyo) 2PHZ-PW)): 10 parts by mass, blowing agent: thermally expandable microcapsules, average particle size 10 μm to 16 μm, expansion start temperature 123°C to 133°C, maximum expansion temperature 168°C to 178°C, core: carbonized Hydrogen, shell: Thermoplastic polymer: 20 parts by mass / Solvent (methyl ethyl ketone): 114 parts by mass

<Adhesive composition 3>
・Acrylic resin (PMMA-PBuA-PMMA (acrylamide group in part), Tg: -20°C, 120°C, Mw: 150,000): 10 parts by mass ・Epoxy resin A (bisphenol A novolac type, solid at room temperature, softening Temperature: 70°C, epoxy equivalent: 210 g/eq, Mw: 1300, melt viscosity at 150°C: 0.5 Pa s): 15 parts by mass, epoxy resin C (bisphenol A type, liquid at room temperature, epoxy equivalent: 184~ 194 g/eq): 23 parts by mass - Epoxy resin F (aliphatic polyfunctional epoxy compound, epoxy equivalent: 173 g/eq): 13 parts by mass - Silane coupling agent (3-glycidoxypropyltrimethoxysilane): 1 mass Parts: Curing agent B (phenol/formaldehyde polycondensate, softening point: 80°C, hydroxyl equivalent: 104 g/mol): 19 parts by mass: Curing catalyst (2-phenyl-4,5-dihydroxymethylimidazole, average particle size: 3 μm, melting point) : 230°C, reaction start temperature 145°C to 155°C, active area 155°C to 173°C (manufactured by Shikoku Kasei Kogyo Co., Ltd., 2PHZ-PW)): 2 parts by mass ・Blowing agent: thermally expandable microcapsules, average particle size 10 μm ~16μm, expansion start temperature 123℃~133℃, maximum expansion temperature 168℃~178℃, core: hydrocarbon, shell: thermoplastic polymer: 8.5 parts by mass, storage stabilizer (boric acid ester compound): 9 parts by mass / Solvent (methyl ethyl ketone): 39 parts by mass

[Example 1]
A polyethylene naphthalate (PEN) film (manufactured by Toyobo Co., Ltd., Teonex Q5100, thickness 25 μm) was used as the base material. In addition, 15 parts by mass of a curing agent (polyisocyanate) and 0.3 parts by mass of a catalyst (trisdimethylaminomethylphenol) are blended with 100 parts by mass of the polyester polymer, and the solid content is 15% by mass. A resin composition was prepared by diluting with methyl ethyl ketone (MEK) so that The resin composition was applied to one side of the base material using a bar coater, and dried in an oven at 100° C. for 1 minute to form a first intermediate layer having a thickness of 2 μm. Next, the adhesive composition 1 was applied to the surface of the first intermediate layer opposite to the base material using an applicator so that the thickness after application was 50 μm. Thereafter, it was dried in an oven at 100° C. for 3 minutes to form a first adhesive layer.

Next, a release film (PET separator, manufactured by Nipper Co., Ltd., PET 50×1-J2, thickness 50 μm) was used as a second separator, and the adhesive composition 2 was applied to the release-treated surface of the release film. The coating was applied using an applicator so that the thickness after coating was 50 μm. Thereafter, it was dried in an oven at 100° C. for 3 minutes to form a second adhesive layer.

Next, the surface of the second adhesive layer of the laminate having the second separator and the second adhesive layer was laminated onto the surface of the base material of the laminate having the base material, the first intermediate layer, and the first adhesive layer. Thereby, a foamable adhesive sheet was obtained in which the first adhesive layer, the first intermediate layer, the base material, the second adhesive layer, and the second separator were arranged in this order.

[Example 2]
A foamable adhesive sheet was produced in the same manner as in Example 1, except that the thickness of the first adhesive layer and the second adhesive layer was 45 μm.

[Example 3]
A foamable adhesive sheet was produced in the same manner as in Example 1, except that Adhesive Composition 3 was used to form the second adhesive layer and the thickness of the second adhesive layer was 45 μm.

[Comparative example 1]
A foamable adhesive sheet was produced in the same manner as in Example 1, except that Adhesive Composition 2 was used to form the first adhesive layer.

[Comparative example 2]
A foamable adhesive sheet was produced in the same manner as in Comparative Example 1, except that a polyphenylene sulfide (PPS) film (manufactured by Toray Industries, Inc., Torelina 25-3030, thickness 25 μm) was used as the base material.

[Comparative example 3]
A foamable adhesive sheet was produced in the same manner as in Comparative Example 1 except that the thickness of the base material (PEN film) was 50 μm.

[Comparative example 4]
A foamable adhesive sheet was produced in the same manner as in Comparative Example 1, except that a polyethylene terephthalate (PET) film (manufactured by Toray Industries, Inc., Lumirror #25-S105, thickness 50 μm) was used as the base material.

[evaluation]
(1) Tack of the first adhesive layer and second adhesive layer The tack of the first adhesive layer was measured using a tacking tester "TAC-II" manufactured by RHESCA. A cylindrical stainless steel probe with a diameter of 5 mm was pressed at a temperature of 25°C with a load of 10.0 gf and a speed of 30 mm/min, held for 1.0 seconds, and then peeled off at a speed of 30 mm/min. The load when peeling off was measured. This measurement was performed five times, and the average value was taken as the tack.

Similar to the tack of the first adhesive layer, the tack of the second adhesive layer was also measured. At this time, after the second separator was peeled off from the foamable adhesive sheet, the tack of the second adhesive layer was measured.

(2) Loop Stiffness After peeling off the second separator from the foamable adhesive sheet, a rectangular test piece with a width of 10 mm and a length of 200 mm was prepared, and the loop stiffness was measured using the loop stiffness measurement method described above. As a measuring instrument, a Loop Stiffness Tester (registered trademark) manufactured by Toyo Seiki Seisakusho Co., Ltd. was used. The environment during measurement was a temperature of 23° C. and a relative humidity of 50%.

(3) Sagging amount FIGS. 10(a) and 10(b) are schematic diagrams illustrating a method for measuring the amount of sagging of a foamable adhesive sheet. After peeling off the second separator, the foamable adhesive sheet 10 was cut into a size of 10 mm in width and 100 mm in length to obtain a test piece. Further, the jig 51 has a rectangular parallelepiped shape, and the lower surface 51a of the jig 51 is rectangular, flat, and horizontal. Furthermore, a double-sided adhesive tape 52 ("Y-4920-25" manufactured by 3M) was attached to the lower surface 51a of the jig 51.

First, as shown in FIG. 10(a), the surface of the double-sided adhesive tape 52 of the jig 51 is attached to the center of the foam adhesive sheet 10 in an environment of normal temperature and humidity to fix the foam adhesive sheet 10. did. The pasting area was 10 mm x 10 mm. At this time, when the surface of the double-sided adhesive tape 52 of the jig 51 was attached to the surface of the first adhesive layer of the foamable adhesive sheet 10, the surface to be adhered was the first adhesive layer. On the other hand, when the surface of the double-sided adhesive tape 52 of the jig 51 was attached to the surface of the second adhesive layer of the foamable adhesive sheet 10, the second adhesive layer was the surface to be adhered.

Next, as shown in FIG. 10(b), the jig 51 was lifted vertically upward. At this time, the end portion 10a of the foamable adhesive sheet 10 hung vertically downward. Then, using the surface S1 of the double-sided adhesive tape 52 of the jig 51 as a reference surface, the distance in the vertical direction from this reference surface S1 to the end 10a of the foam adhesive sheet 10 was measured, and this was defined as the amount of sagging F. . The amount of sagging was calculated by preparing three test pieces from the foamable adhesive sheet, measuring once for each test piece, and taking the average value of the three test pieces.

(4) Attachability In the same manner as in the measurement of the amount of sagging above, the double-sided adhesive tape side of the jig was attached to the center of the test piece of the foam adhesive sheet to fix the foam adhesive sheet. The jig was lifted vertically upward. At this time, the surface of the double-sided adhesive tape of the jig was attached to the surface of the first adhesive layer of the foamable adhesive sheet. Next, a metal plate was placed below the foamable adhesive sheet lifted by the jig, and the jig was lowered vertically to attach the foamable adhesive sheet to the metal plate. Then, the state of the foamable adhesive sheet was visually observed, and the stickability was evaluated based on the following criteria.
A: The foam adhesive sheet could be attached without folding or bubbles.
B: The foamable adhesive sheet was folded and bubbles were trapped.

(5) Insertion properties (slip properties of the first adhesive layer during insertion)
A foam adhesive sheet cut into 5.5 cm x 8.0 cm, a hollow cylinder 1 with an outer diameter of 22 mm, a thickness of 1.5 mm, and a length of 60 mm, and an outer diameter of 18 mm, a thickness of 1.0 mm, and a length of 80 mm. A hollow cylinder 2 was prepared. Further, the second separator was peeled off from the foamable adhesive sheet, and the surface of the second adhesive layer was attached to the outer diameter portion of the cylinder 2, so that the foamable adhesive sheet was placed so that the short side was in the circumferential direction. Thereafter, the cylinder 2 was slowly pushed by hand and inserted into the hollow gap of the cylinder 1, and the slipperiness of the first adhesive layer at that time was evaluated. The evaluation criteria were as follows.
A: There is no catch during insertion.
B: There is a catch during insertion (the first adhesive layer sticks to the cylinder 1, resulting in poor insertion performance).

From a comparison of Examples 1 to 3 and Comparative Examples 3 to 4, and Comparative Examples 1 to 2, it was found that when the loop stiffness was 50 mN/10 mm or more, the amount of sagging was small and the adhesion was good. confirmed. Further, in Examples 1 to 3, the tack of the first adhesive layer and the tack of the second adhesive layer were each within a predetermined range, so the insertability was also good.

1... First adhesive layer 2... Base material 3... Second adhesive layer 4... First intermediate layer 5... Second intermediate layer 10... Foamable adhesive sheet 15... Adhesive sheet after foaming and curing 20a... First member 20b... No. 2 parts 100... Goods

Claims (7)

A foamable adhesive sheet comprising a first adhesive layer, a base material, and a second adhesive layer in this order,
the first adhesive layer and the second adhesive layer contain a curable adhesive,
At least one of the first adhesive layer and the second adhesive layer further contains a foaming agent,
The tack of the first adhesive layer is 0 gf or more and less than 10 gf,
The tack of the second adhesive layer is 10 gf or more and 500 gf or less,
A foamable adhesive sheet having a loop stiffness of 50 mN/10 mm or more. The foamable adhesive sheet according to claim 1, wherein the first adhesive layer contains the foaming agent. The foamable adhesive sheet according to claim 2, wherein the first adhesive layer and the second adhesive layer contain the foaming agent. A foamable adhesive sheet comprising a first adhesive layer, a base material, a second adhesive layer, and an adhesive layer in this order,
The first adhesive layer and the second adhesive layer contain a curable adhesive and a foaming agent,
The adhesive layer contains a pressure sensitive adhesive or a curable adhesive,
The tack of the first adhesive layer is 0 gf or more and less than 10 gf,
The tack of the adhesive layer is 10 gf or more,
A foamable adhesive sheet having a loop stiffness of 50 mN/10 mm or more. The foamable adhesive sheet according to claim 4, wherein the second adhesive layer has a tack of 0 gf or more and less than 10 gf. The foamable adhesive sheet according to any one of claims 1 to 5, wherein the thickness of the base material is thinner than the thickness of the first adhesive layer and the thickness of the second adhesive layer. an arrangement step of arranging the foamable adhesive sheet according to any one of claims 1 to 6 between the first member and the second member;
an adhesion step of foaming and curing the foamable adhesive sheet and adhering the first member and the second member;
A method for manufacturing an article, comprising:

Images