JP2023036159A - Expandable adhesive sheet and manufacturing method of article - Google Patents

Abstract

To provide an expandable adhesive sheet excellent in adhesion to a member and insertion property, and having excellent manufacturing efficiency.SOLUTION: An expandable adhesive sheet comprises a first adhesion layer, and a second adhesion layer arranged on the one surface side of the first adhesion layer. The expandable adhesive sheet is such that; the first adhesion layer and the second adhesion layer contain a curable adhesive; at least one of the first adhesion layer and the second adhesion layer further contains a gas generating agent; the tack of the first adhesion layer is 0 gf or more and less than 10 gf; the tack of the second adhesion layer is 10 gf or more and 400 gf or less; and a peak value of a loss tangent (tanδ) of the second adhesion layer is 100°C or more and 180°C or less.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD 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 or groove of the other member. Specifically, in an embedded magnet type motor, an adhesive is used to fix the permanent magnets in the holes of the core.

Liquid adhesives are mainly used as adhesives for motors. However, in the case of a liquid adhesive, there is a problem that coating unevenness, extrusion, liquid dripping, etc. occur, which complicates the bonding process.

On the other hand, in recent years, it has been proposed to use an adhesive sheet containing a foaming agent (expandable adhesive sheet) instead of the liquid adhesive.

For example, in Patent Document 1, a site (c1-1) constituting an adherend (C1) and another site (c1-2) constituting the adherend (C1) or another adherend (C2 ) is a method for producing an article bonded with an adhesive tape, wherein the adhesive tape has an adhesive layer (B) directly or via another layer on one side of the adhesive layer (A). In the adhesive tape, the expansion coefficient in the thickness direction of the adhesive layer (A) after the adhesive tape is left in an environment of 130 ° C. for 1 hour [thickness of the adhesive layer (A) after standing thickness/thickness of the adhesive layer (A) before standing]×100 is 200% or more, and expansion coefficient in the thickness direction of the adhesive layer (B) [adhesive layer after standing ( The thickness of B)/the thickness of the adhesive layer (B) before standing]×100 is 120% or less, and the adhesive layer (A) contains a thermosetting resin and a thermally expandable capsule. The adhesive layer (A), which is a layer formed using a composition, wherein the adhesive layer (B) is a thermosetting adhesive layer or a pressure-sensitive adhesive layer, and which constitutes the adhesive tape; , the step [1] of pre-adhering the portion (c1-1) constituting the adherend (C1), and stimulating and swelling at least the adhesive layer (A) to form the adhesive tape. Disclosed is a method for producing an article, comprising a step [2] of bonding the adhesive layer (B) and the site (c1-2) constituting the adherend (C1) or the adherend (C2). It is

Further, for example, Patent Document 2 discloses a method for manufacturing an article in which a gap between an adherend (C1) and an adherend (C2) is adhered via an expanded adhesive tape, wherein the adhesive tape has a thermally expandable adhesive layer (A), the thermally expandable adhesive layer (A) contains the adhesive composition (a) and thermally expandable capsules, and the content of the thermally expandable capsules is 3 to 100 parts by mass with respect to 100 parts by mass of the total solid component of the adhesive composition (a), the adhesive composition (a) contains a thermoplastic resin, and the thermoplastic resin has a temperature of 70 ° C. to ^The thermally ^expandable adhesive layer (A ) has an adhesive strength of 0.5 N/20 mm or more, and the thermally expandable adhesive layer (A) of the adhesive tape is attached to the site (c1-1) constituting the adherend (C1). the step [1] of heating the thermally expandable adhesive layer (A) at a temperature of 50 ° C. to 120 ° C. [2], the thermally expandable adhesive layer (A) is expanded by the heating, and the heat is The step [3] of forming an expansible adhesive layer (A1), and the thermally expandable adhesive layer (A1) or adhesive layer (B) constituting the adhesive tape is the adherend (C1) A method for producing an article is disclosed, which has a step [4] of attaching to another site (c1-2) or another adherend (C2) constituting the.

Patent No. 6274540 JP 2018-203863 A

For example, when fixing the other member to a hole or groove of one member, as described in Patent Document 1 and Patent Document 2, a foam adhesive sheet is attached to the other member to temporarily fix it, One member to which the foamable adhesive sheet is attached is placed in a hole or groove of the member, and then the foamable adhesive sheet is foamed and cured to bond and fix the two members.

In the adhesive fixing method as described above, the tackiness of the foamable adhesive sheet is used to temporarily fix the foamable adhesive sheet to the other member. However, if the adhesiveness of the expandable adhesive sheet is high, there is a problem that the insertability of the one member to which the expandable adhesive sheet is adhered is reduced when inserting one member into a hole or groove of the other member.

Moreover, in the foamable adhesive sheet, the adhesive layer containing the foaming agent can be formed by, for example, applying an adhesive composition containing the foaming agent and drying. At this time, when the drying temperature is high, the melt viscosity of the resin component contained in the adhesive composition tends to be low. If the melt viscosity of the resin component is significantly lowered, film formation may become difficult. Therefore, when the adhesive layer is formed, it is dried at a low temperature for a long time so as to suppress a significant decrease in the melt viscosity of the resin component and enable film formation. However, if the drying temperature is low, the amount of residual solvent increases, and if the drying time is long, there is a problem that the production efficiency of the foamable adhesive sheet is lowered.

The present disclosure has been made in view of the above circumstances, and a main object of the present disclosure is to provide a foamable adhesive sheet that is excellent in adhesion and insertability to members and has good production efficiency.

One embodiment of the present disclosure is a foamable adhesive sheet having a first adhesive layer and a second adhesive layer disposed on one side of the first adhesive layer, wherein the first adhesive layer and The second adhesive layer contains 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 or more. , less than 10 gf, the tack of the second adhesive layer is 10 gf or more and 400 gf or less, and the peak value of the loss tangent (tan δ) of the second adhesive layer is 100 ° C. or more and 180 ° C. or less. To provide a flexible adhesive sheet.

Another embodiment of the present disclosure includes an arrangement step of arranging the foamable adhesive sheet described above between the first member and the second member, and foaming and curing the foamable adhesive sheet to form the first member and the second member. a bonding step of bonding two members together.

The foamable adhesive sheet according to the present disclosure has the effect of being excellent in adhesion and insertability to members, and having good production efficiency.

1 is a schematic cross-sectional view illustrating an expandable adhesive sheet in the present disclosure; FIG. 1 is a schematic cross-sectional view illustrating an expandable adhesive sheet in the present disclosure; FIG. 1 is a schematic cross-sectional view illustrating an expandable adhesive sheet in the present disclosure; FIG. FIG. 2 is a process diagram illustrating a method for manufacturing a foamable adhesive sheet according to the present disclosure; FIG. 2 is a process diagram illustrating a method for manufacturing a foamable adhesive sheet according to the present disclosure; FIG. 2 is a process diagram illustrating a method for manufacturing a foamable adhesive sheet according to the present disclosure; 1 is a process diagram illustrating a method of manufacturing an article in the present disclosure; FIG. 1 is a process diagram illustrating a method of manufacturing an article in the present disclosure; FIG. FIG. 4 is a schematic cross-sectional view for explaining a method for testing the adhesiveness of a foamable adhesive sheet after foaming and curing.

Embodiments of the present disclosure will be described below with reference to the drawings and the like. However, the present disclosure can be embodied in many different modes and should not be construed as limited to the description of the embodiments exemplified below. In addition, in order to make the description clearer, the drawings may schematically show the width, thickness, shape, etc. of each part compared to the actual form, but this is only an example and limits the interpretation of the present disclosure. not something to do. In addition, in this specification and each figure, the same reference numerals may be given to the same elements as those described above with respect to the existing figures, and detailed description thereof may be omitted as appropriate.

In this specification, when expressing a mode in which another member is arranged on top of a certain member, the term “above” or “below” simply means that it is in contact with a certain member unless otherwise specified. , arranging another member directly above or below, and arranging another member 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 simply describing “on the surface side” or “on the surface”, unless otherwise specified, It includes both the case of arranging another member directly above or directly below so as to be in contact with it, and the case of arranging another member above or below a certain member via another member.

In this specification, the term "sheet" also includes a member called "film". The term "film" also includes members called "sheets". Numerical ranges in this specification are ranges of average values.

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

A. Foamable adhesive sheet The foamable adhesive sheet in the present disclosure is a foamable adhesive sheet having a first adhesive layer and a second adhesive layer disposed on one side of the first adhesive layer, 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 first adhesive layer The tack is 0 gf or more and less than 10 gf, the tack of the second adhesive layer is 10 gf or more and 400 gf or less, and the peak value of the loss tangent (tan δ) of the second adhesive layer is 100 ° C. or more and 180 ° C. It is below.

1 and 2 are schematic cross-sectional views illustrating foamable adhesive sheets in the present disclosure. A foamable adhesive sheet 10 in FIG. 1 has a first adhesive layer 1 and a second adhesive layer 2 arranged on one side of the first adhesive layer 1 . The foamable adhesive sheet 10 in FIG. 2 has a first adhesive layer 1 and a second adhesive layer 2 arranged on one side of the first adhesive layer 1, and the first adhesive layer 1 and the second adhesive It further has a substrate 3 between layers 2 . The first adhesive layer 1 and the second adhesive layer 2 contain a curable adhesive, and at least one of the first adhesive layer 1 and the second adhesive layer 2 further contains a foaming agent. Moreover, the tack of the first adhesive layer 1 and the tack of the second adhesive layer 2 are each within a predetermined range, and the peak value of the loss tangent (tan δ) of the second adhesive layer 2 is within a predetermined range.

In the present disclosure, when the tackiness of the second adhesive layer is within a predetermined range, the second adhesive layer can have good adhesion to the member. Specifically, when the other member is adhesively fixed to a hole or groove of one member, the surface of the second adhesive layer of the foamable adhesive sheet is attached to the other member, and the hole of the one member is attached. When the other member to which the foamable adhesive sheet is attached is inserted into the groove or the like, and then the foamable adhesive sheet is foamed and cured to bond the one member and the other member, the second adhesive layer is within a predetermined range, the surface of the second adhesive layer of the foamable adhesive sheet can be attached to the other member using the tack of the second adhesive layer, and the second adhesive layer on the member can increase the adhesion of. As a result, peeling and displacement of the foamable adhesive sheet can be suppressed when the member to which the foamable adhesive sheet is attached is inserted into the hole or groove of the other member.

Further, in the present disclosure, the tack of the second adhesive layer is within a predetermined range, so that the second adhesive layer can have good reworkability. Therefore, for example, in the adhesive fixing method described above, when the surface of the second adhesive layer of the foamable adhesive sheet is attached to one member using the tack of the second adhesive layer, misalignment of the foamable adhesive sheet can be prevented. can be fixed.

In addition, in the present disclosure, since the tack of the first adhesive layer is a predetermined value or less, the first adhesive layer can be made substantially non-tacky (tack-free), and the first adhesive layer has good slipperiness. It can be an adhesive layer. Therefore, for example, in the above adhesive fixing method, when inserting the other member to which the foamable adhesive sheet is attached into the hole or groove of one member, the other member to which the foamable adhesive sheet is attached may The member can be smoothly inserted, and insertability can be improved. As a result, peeling and displacement of the expandable adhesive sheet can be suppressed. Further, in the above bonding and fixing method, when aligning the members by moving the other member with respect to the other member, the other member is inserted into the hole or groove of the one member while the other member is inserted. The other member can be smoothly moved with respect to the other member, and positioning can be easily performed.

Furthermore, in the present disclosure, the tack of the first adhesive layer is a predetermined value or less, and the first adhesive layer is substantially non-tacky (tack-free), so that it has good slip properties and anti-blocking properties. The first adhesive layer can also have good properties. Therefore, it is possible to improve the handleability of the foamable adhesive sheet.

In addition, in the present disclosure, as described above, the second adhesive layer has excellent adhesion to the member, and the first adhesive layer has excellent slipperiness. can be suppressed. Therefore, it suppresses the deterioration of the adhesiveness of the foamable adhesive sheet after foaming and curing due to peeling and misalignment of the foamable adhesive sheet, and also suppresses the adhesion of the foamable adhesive sheet after foaming and curing due to peeling and misalignment of the foamable adhesive sheet. Variation in intensity can be reduced. Therefore, by using the foamable adhesive sheet of the present disclosure, high adhesive strength, high reliability, and high quality adhesion can be achieved.

In addition, in the present disclosure, the peak value of tan δ of the second adhesive layer is a predetermined value or more, so that film formation is possible even if it is dried at a high temperature when the second adhesive layer is formed, and the residual solvent is reduced. At the same time, the second adhesive layer can be efficiently formed. Therefore, the production efficiency of the expandable adhesive sheet can be improved. In addition, since the peak value of tan δ of the second adhesive layer is equal to or less than a predetermined value, it is possible to ensure the fluidity of the second adhesive layer when the foamable adhesive sheet is heated, and to follow the adhesive surface of the member. can ensure the integrity of the Therefore, the adhesiveness of the foamable adhesive sheet after foaming and curing can be improved.

In general, the higher the tan δ peak value of the adhesive layer, the lower the tackiness of the adhesive layer. In the present disclosure, by setting the peak value of tan δ of the second adhesive layer within a predetermined range, film formability, tackiness, and fluidity during heating can be balanced.

Further, in the present disclosure, 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, it is possible to suppress the floating of the second adhesive layer. can. Furthermore, as will be described later, when the second separator is arranged on the side opposite to the first adhesive layer of the second 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.

Here, "adhesion" is a concept included in "adhesion". Adhesion is sometimes used to mean a temporary adhesion phenomenon, whereas adhesion is used to mean a substantially permanent adhesion phenomenon (Iwanami Shoten Rikagaku Jiten, 5th edition). The terms "tackiness" and "tackiness" refer to the property of adhering by pressure sensitivity and the adhesive force at that time.

As used herein, the terms "adhesiveness of the adhesive layer" and "adhesive strength of the adhesive layer" refer to the adhesiveness and adhesive strength of the adhesive layer prior to curing, unless there are special circumstances. In this specification, unless there are special circumstances, the terms "adhesiveness of the adhesive layer" and "adhesive strength of the adhesive layer" refer to the adhesiveness and adhesive strength of the cured adhesive layer.

Each configuration of the expandable adhesive sheet in the present disclosure will be described below.

1. First Adhesive Layer (1) Properties of First Adhesive Layer In the present disclosure, the tack of the first adhesive layer is 0 gf or more and less than 10 gf, may be 5 gf or less, or may be 2 gf or less. When the tack of the first adhesive layer is within the above range, the first adhesive layer can be made substantially non-tacky (tack-free), and the first adhesive layer has good slipperiness and anti-blocking properties. can do.

Here, the tack of the first adhesive layer can be measured by a probe tack test conforming to JIS Z3284-3:2014. As the probe tack tester, for example, a tack tester "TAC-II" manufactured by RHESCA can be used. The details of the method for measuring the tackiness of the first adhesive layer will be described later in the Examples section.

In the present disclosure, the tackiness of the first adhesive layer can be within a predetermined range by adjusting the composition of the first adhesive layer, for example. Specifically, in the first adhesive layer containing an epoxy resin and a curing agent, by using an epoxy resin that is solid at room temperature or a curing agent that is solid at room temperature, the tackiness of the first adhesive layer is increased. can be lowered. In addition, in the first adhesive layer containing an epoxy resin and a curing agent, by including an epoxy resin with a high softening temperature or an epoxy resin with a large weight average molecular weight, the adhesiveness of the first adhesive layer is reduced. be able to. For example, the first adhesive layer contains a plurality of types of epoxy resins with different softening temperatures. By containing another epoxy resin whose softening temperature is 10° C. or more higher than the softening temperature of the first adhesive layer, the tackiness of the first adhesive layer can be reduced. Further, for example, the first adhesive layer contains a plurality of types of epoxy resins having different weight average molecular weights. The tackiness of the first adhesive layer can be reduced by containing another epoxy resin having a weight average molecular weight 300 or more larger than the weight average molecular weight of the epoxy resin. More specifically, in the first adhesive layer containing an epoxy resin and a curing agent, a first epoxy resin having a low softening temperature and a low molecular weight and a high molecular weight epoxy resin having a high softening temperature and a high molecular weight epoxy resin, as described later, By containing the second epoxy resin, the tackiness of the first adhesive layer can be reduced. In addition, as will be described later, the first adhesive layer containing the epoxy resin and the curing agent may contain an acrylic resin that is compatible with the epoxy resin, thereby reducing the tackiness of the first adhesive layer.

In the present disclosure, the coefficient of static friction of the surface of the first adhesive layer opposite to the second adhesive layer is, for example, preferably 0.33 or less, may be 0.30 or less, or may be 0.26 or less. There may be. When the coefficient of static friction of the surface of the first adhesive layer is within the above range, the first adhesive layer can have good lubricity. Also, the coefficient of static friction may be, for example, 0.16 or more.

Here, the coefficient of static friction of the surface of the first adhesive layer can be determined according to JIS K7125 corresponding to ISO 8295. The details of the method for measuring the coefficient of static friction of the surface of the first adhesive layer will be described in the Examples section below.

In the present disclosure, 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 static friction coefficient of the surface of the first adhesive layer is controlled by the average particle size and content of the foaming agent contained in the first adhesive layer. can do. More specifically, when the average particle diameter of the foaming agent increases, the coefficient of static friction on the surface of the first adhesive layer tends to decrease. Moreover, when the content of the foaming agent increases, the coefficient of static friction on the surface of the first adhesive layer tends to decrease.

In the present disclosure, the arithmetic mean roughness (Ra) of the surface of the first adhesive layer opposite to the second adhesive layer is, for example, preferably 0.3 μm or more, and may be 0.5 μm or more, It may be 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 lubricity. 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 light interferometer. The details of the method for measuring the Ra of the first adhesive layer will be described in the Examples section below.

In the present disclosure, 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 and content of the foaming agent contained in the first adhesive layer. can. More specifically, Ra of the first adhesive layer tends to increase as the average particle diameter of the foaming agent increases. Moreover, when the content of the foaming agent increases, Ra of the first adhesive layer tends to increase.

(2) Material of First Adhesive Layer The first adhesive layer in the present disclosure contains a curable adhesive.

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

Examples of curable adhesives include epoxy resin adhesives, acrylic resin adhesives, phenol resin adhesives, unsaturated polyester resin adhesives, alkyd resin adhesives, urethane resin adhesives, Thermosetting polyimide resin-based adhesives and the like are included.

Among them, 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 are excellent in mechanical strength, heat resistance, insulation properties, chemical resistance, etc., and have small cure shrinkage, and can be used in a wide range of applications.

An example in which the curable adhesive is an epoxy resin-based adhesive will be described below.

(i) Epoxy resin The epoxy resin in the present disclosure is a compound that has at least one or more epoxy groups or glycidyl groups and is cured by a cross-linking polymerization reaction when used in combination with a curing agent. Epoxy resins also include monomers having at least one or more epoxy groups or glycidyl groups.

As the epoxy resin, an epoxy resin that is generally used for the adhesive layer of the foamable adhesive sheet can be used. Among them, the curable adhesive includes, as epoxy resins, a first epoxy resin having a softening temperature of 50° C. or more and an epoxy equivalent of 5000 g/eq or less, and a softening temperature higher than that of the first epoxy resin, In addition, it preferably contains 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 slipperiness can be obtained. Furthermore, it is possible to obtain a first adhesive layer having good blocking resistance and adhesiveness after foaming and curing.

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

On the other hand, when using a first epoxy resin having a relatively low softening temperature (relatively high crystallinity) and a low molecular weight (low epoxy equivalent weight), the first epoxy resin has a softening temperature or higher. When heated, it melts rapidly 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 as compared with an epoxy resin having relatively low crystallinity or an epoxy resin having no 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, the effect of suppressing the occurrence of blocking can be improved, and the first adhesive layer can be formed. Adhesiveness (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 a low molecular weight, it tends to improve adhesiveness and blocking resistance after foaming and curing. Moreover, since the first epoxy resin has a low molecular weight, the crosslink density can be increased, and a first adhesive layer having good mechanical strength, chemical resistance, and curability can be obtained. Also, the first epoxy resin is preferably 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 less. The softening temperature can be measured by the ring and ball method according to 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. The epoxy equivalent can be measured by a method according to 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 difunctional epoxy resin, a trifunctional epoxy resin, or a tetrafunctional or higher epoxy resin. .

Also, 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, Mw of the first epoxy resin is, for example, 400 or more. Mw is a value converted to polystyrene when 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, or may be 0.05 Pa · s or more, or 0.1 Pa·s or more. If the melt viscosity is too low, good foamability may not be obtained. Also, 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 resulting first adhesive layer may increase. The reason for this 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), the crystallinity will greatly decrease when compatible with the second epoxy resin or acrylic resin. , presumably because the Tg of the first adhesive layer is lowered. 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 resulting first adhesive layer may be less uniform. The 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). It can be obtained by measuring using a thermocell of.

Next, the structure of the first epoxy resin will be described. 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 A type epoxy resin, bisphenol type epoxy resin such as bisphenol F type epoxy resin, bisphenol A novolac type epoxy resin, novolak type epoxy resin such as cresol novolak type epoxy resin, urethane modified epoxy resin. Modified epoxy resins such as resins and rubber-modified epoxy resins can be used. Other specific examples include biphenyl-type epoxy resins, stilbene-type epoxy resins, triphenolmethane-type epoxy resins, alkyl-modified triphenolmethane-type epoxy resins, triazine nucleus-containing epoxy resins, dicyclopentadiene-modified phenol-type epoxy resins, Naphthalene-type epoxy resins, glycol-type epoxy resins, and pentaerythritol-type epoxy resins can be mentioned. 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 having, for example, 2 or more and 10 or less bisphenol skeletons in the main chain is solid at room temperature. In particular, bisphenol A-type epoxy resins are preferable because they 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, ie, R ¹ is -CH ₂ -. Likewise, it is preferred that p in R ² and R ³ is 1, ie R ² and R ³ are —CH ₃ . In addition, hydrogen atoms bonded to the benzene ring of general formula (1) may be substituted with other elements or groups.

The content of the first epoxy 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. 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 deteriorate. On the other hand, when the resin component contained in the first adhesive layer is 100 parts by mass, the content of the first epoxy resin is, for example, 90 parts by mass or less, may be 80 parts by mass or less, or may be 70 parts by mass. It may be 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 the acrylic resin will be relatively small, resulting in non-adhesiveness, blocking resistance, adhesion to the substrate after foaming and curing, and It may not be possible to balance the crack resistance of the foam and the adhesion after foaming cure.

(i-2) Second Epoxy Resin The second epoxy resin has a softening temperature higher than that of 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 a high molecular weight, it tends to improve blocking resistance. Furthermore, since the second epoxy resin has relatively low crystallinity and a high molecular weight, it is possible to suppress an increase in adhesiveness (tackiness) due to the first epoxy resin. Moreover, the second epoxy resin is preferably an epoxy resin that is solid at normal temperature (23° C.).

The weight average molecular weight (Mw) of the second epoxy resin is generally greater 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, Mw of the second epoxy resin is, for example, 100,000 or less.

The epoxy equivalent weight of the second epoxy resin may be larger, smaller, or the same as the epoxy equivalent weight 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, 20000 g/eq or less.

The second epoxy resin may be a monofunctional epoxy resin, a difunctional epoxy resin, a trifunctional epoxy resin, or a tetrafunctional or higher 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 is, for example, 10° C. or more, may be 20° C. or more, or may be 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 less.

The configuration of the second epoxy resin is the same as the configuration of the first epoxy resin described above, so the description is 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, or 20 parts by mass or more when the resin component contained in the first adhesive layer is 100 parts by mass. may be 25 parts by mass or more, may be 30 parts by mass or more, may be 35 parts by mass or more, may be 40 parts by mass or more, may be 45 parts by mass or more may be If the content of the second epoxy resin is too small, the adhesiveness may increase and the blocking resistance may decrease. On the other hand, when the resin component contained in the first adhesive layer is 100 parts by mass, the content of the second epoxy resin is, for example, 90 parts by mass or less, may be 85 parts by mass or less, or may be 80 parts by mass. parts or less, or 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 the acrylic resin will be relatively small, resulting in non-stickiness, blocking resistance, adhesion to the substrate after foaming and curing, and It may not be possible to balance the crack resistance of the foam and the adhesion after foaming cure.

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, or may be 20% by mass or more. % by mass or more. On the other hand, the ratio 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, may be 70% by mass or more, or may be 90% by mass. % or more, or 100% by mass.

(ii) Acrylic resin When the curable adhesive is an epoxy resin-based adhesive, the first adhesive layer may further contain an acrylic resin compatible with the epoxy resin. Acrylic resin is a resin compatible with epoxy resin. Since the acrylic resin is compatible with the epoxy resin, it tends to improve the toughness of the first adhesive layer. As a result, the adhesion after foaming and curing can be improved. Furthermore, it is believed that the acrylic resin acts as a compatibilizer for the foaming agent (for example, a foaming agent whose shell is an acrylonitrile copolymer resin), uniformly disperses and foams, thereby improving the adhesiveness after foaming and curing. . In addition, flexibility due to the acrylic resin is exhibited, and adhesion to the base material after foaming and curing and crack resistance after foaming and curing can be improved. In addition, since the acrylic resin is compatible with the epoxy resin, the surface hardness of the first adhesive layer can be kept high. On the other hand, if the acrylic resin is incompatible with the epoxy resin, a flexible portion is formed on the surface of the first adhesive layer, which may make the interface with the adherend less slippery and reduce workability.

Acrylic resins in the present disclosure are compatible with epoxy resins. Here, the fact that the acrylic resin is compatible with the epoxy resin is determined, for example, by observing the cross section of the first adhesive layer of the foamable adhesive sheet with a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Second, it can be confirmed from the fact that micron-sized islands are not generated. More specifically, the average grain size of the islands is preferably 1 μm or less. Among them, the average grain size of the islands may be 0.5 μm or less, or may be 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 range of average thickness×100 μm when the average thickness of the first adhesive layer is 100 μm or less.

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 crystallinity of the first epoxy resin is relatively high, and the melt viscosity (or dynamic viscoelasticity) during heating becomes too low. 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 occurs during curing after foaming. It becomes difficult to get up. On the other hand, Mw of 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 acrylic resin is, for example, 180° C. or less. Tg can be measured by thermal analysis such as a differential scanning calorimeter (DSC) in accordance with JIS K7121 corresponding to ISO 3146.

The acrylic resin may have a storage modulus (E′) of 1×10 ⁶ Pa or less at the foaming initiation temperature. A low E′ at the start of foaming improves the fluidity and allows good foamability to be obtained. 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 is a temperature that differs depending on the type of foaming agent. Moreover, when using two or more types of foaming agents, the starting temperature of the main foaming reaction is defined as the foaming start temperature.

The acrylic resin may have a storage modulus (E′) of 1×10 ⁵ Pa or more at the curing initiation temperature. As described above, shrinkage may occur during curing after foaming (between the completion of foaming of the foaming agent and the curing of the first adhesive layer). , shrinkage can be suppressed, and good shape retention can be obtained. It should be noted that the curing start temperature is a different temperature depending on the type of curing agent. When two or more kinds of curing agents are used as the curing agent, the starting temperature of the main curing reaction is defined as the curing initiation 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. A high average value of E′ before foaming can provide good non-tackiness and anti-blocking properties. On the other hand, the average value of 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. Polar groups include, for example, epoxy groups, hydroxyl groups, carboxyl groups, nitrile groups, and amide groups.

The acrylic resin is a homopolymer of acrylic acid ester monomers, may be a mixed component containing two or more of the above homopolymers, or is a copolymer of two or more acrylic acid ester monomers. , a component containing one or more copolymers. Further, the acrylic resin may be a mixed component of the above homopolymer and the above copolymer. The acrylate 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 them, the acrylic resin preferably contains a copolymer of two or more acrylic acid ester monomers ((meth)acrylic acid ester copolymer).

Examples of the monomer component constituting the (meth) acrylic acid ester copolymer include the monomer components described in JP-A-2014-065889. The monomer component may have the polar group described above. Examples of the (meth)acrylate copolymer include ethyl acrylate-butyl acrylate-acrylonitrile copolymer, ethyl acrylate-acrylonitrile copolymer, and butyl acrylate-acrylonitrile copolymer. "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 (meth)acrylates constituting acrylic block copolymers include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, and acrylic acid. Benzidyl can be mentioned. These "acrylic acids" also include "methacrylic acid".

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 have no polar group, or may be a modified product into which the above-mentioned polar group is partially introduced. Since the modified product is easily compatible with the epoxy resin, the adhesiveness is further improved.

Among them, the acrylic resin is (meth)acrylic acid having a first polymer portion having a glass transition temperature (Tg) of 10°C or lower and a second polymer portion having a glass transition temperature (Tg) of 20°C or higher. Ester copolymers are preferred. Such a (meth)acrylic acid ester copolymer has a first polymer portion serving as a soft segment and a second polymer portion serving as a hard segment.

The manifestation of the above effects can be estimated as follows. By using an acrylic resin having both a soft segment and a hard segment, such as the above (meth)acrylate copolymer, the hard segment contributes to heat resistance, and the soft segment contributes 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)acrylate copolymer has compatibility with the epoxy resin. Flexibility can be enhanced if the first polymer portion is compatible with the epoxy resin. Further, when the second polymer portion has compatibility with the epoxy resin, cohesiveness and toughness can be enhanced.

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 will have a compatible site and an incompatible site, which is a polymer portion that is not compatible with the epoxy resin. In this case, when the (meth)acrylic acid ester copolymer is added, the compatible sites are 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. As for the sea-island structure, the type of (meth)acrylic acid ester copolymer, the compatibility of the first polymer portion and the second polymer portion contained in the (meth)acrylic acid ester copolymer, and the degree of modification due to the introduction of polar groups. For example, a sea-island structure in which the compatible site of the cured epoxy resin and the (meth)acrylic acid ester copolymer is a sea, and the incompatible site of the (meth)acrylic acid ester copolymer is an island. and a sea-island structure in which the incompatible site of the (meth)acrylic acid ester copolymer is the sea, and the compatible site of the cured epoxy resin and the (meth)acrylic acid ester copolymer is an island. A sea-island structure in which the acrylic acid ester copolymer is the sea and the epoxy resin cured product is the island is exemplified. By having such a sea-island structure, stress can be easily dispersed, so interfacial failure can be avoided, and excellent adhesiveness can be obtained after foaming and curing.

The above (meth)acrylic acid ester copolymer is preferably a block copolymer among others. Block copolymers are preferred. Furthermore, the first polymer portion is the incompatible portion, the second polymer portion is the compatible portion, the first polymer portion is polymer block B, and the second polymer portion is polymer block A. A -BA block copolymer is preferred. By using such an ABA block copolymer as the acrylic resin, the compatible site of the cured epoxy resin and the (meth)acrylic acid ester copolymer becomes a sea and the (meth)acrylic acid ester copolymer. In the case of a sea-island structure in which the coalescing incompatible sites are islands, the island portions can be made smaller. In addition, in the case of a sea-island structure in which the incompatible site of the (meth)acrylic acid ester copolymer is the sea and the compatible site of the cured epoxy resin and the (meth)acrylic acid ester copolymer is an island, In the case of a sea-island structure in which the (meth)acrylic acid ester copolymer is the sea and the cured epoxy resin is the island, the sea portion can be reduced.

Further, the (meth)acrylic acid ester copolymer may be a modified product obtained by introducing the above-described polar group into a part of the first polymer portion or the second polymer portion.

The Tg of the first polymer portion contained in the (meth)acrylic acid ester copolymer is 10°C or less, and is in 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 the range, particularly within the range of -110°C or higher and -10°C or lower.

The Tg of the first polymer portion is calculated by the following formula based on the Tg (K) of each homopolymer described in "POLYMER HANDBOOK 3rd Edition" (published by John Wiley & Sons, Ink.) can ask.
1/Tg(K)= _W1 / _Tg1 + _W2 / _Tg2 +...+ _Wn / _Tgn
W _n ; mass fraction Tg _n of each monomer; Tg (K) of homopolymer of each monomer, Polymer Handbook (3rd Ed., J. Brandrup and EH Immergut, WILEY INTERSCIENCE) A posted value that is open to the public, such as an intermediate value, may be used. The same applies to the Tg of the second polymer portion, which will be described later.

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 component and polymer component constituting the first polymer portion may be any monomer component and polymer component capable of obtaining the first polymer portion having a Tg within a predetermined range. Acrylic acid ester monomers such as butyl acid, 2-ethylhexyl acrylate, isononyl acrylate, and methyl acrylate; other monomers such as vinyl acetate, acetal, and urethane; copolymers such as monomers and EVA.

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

The second polymer portion contained in the (meth)acrylic acid ester copolymer may be a homopolymer or a copolymer, but is preferably a homopolymer. . The monomer component that constitutes the second polymer portion may be a monomer component capable of obtaining a second polymer portion having a Tg within a predetermined range. monomers, other monomers such as acrylamide, styrene, vinyl chloride, amide, acrylonitrile, cellulose acetate, phenol, urethane, vinylidene chloride, methylene chloride, methacrylonitrile, and polar group-containing monomers including the above polar groups body.

Specific examples of the (meth)acrylic acid ester copolymer having the above first polymer portion and second polymer portion include the above 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 may be 5 parts by mass or more when the resin component contained in the first adhesive layer is 100 parts by mass. may be 7 parts by mass or more, or 10 parts by mass or more. If the content of the acrylic resin is too small, the adhesiveness to the base material after foaming and curing, the crack resistance after foaming and curing, and the adhesiveness after foaming and curing may decrease. On the other hand, when the resin component contained in the first adhesive layer is 100 parts by mass, the content of the acrylic resin is, for example, 60 parts by mass or less, may be 50 parts by mass or less, or may be 40 parts by mass or less. , 35 parts by mass or less, or 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 non-stickiness, blocking resistance, adhesion to the substrate after foaming and curing, and It may not be possible to balance the crack resistance of the foam and the adhesion after foaming cure. Moreover, when the content of the acrylic resin is too large, the film strength may decrease.

(iii) Curing Agent As the curing agent in the present disclosure, curing agents generally used for epoxy resin adhesives can be used. The curing agent is preferably solid at room temperature (23° C.). Curing agents that are solid at room temperature can have longer storage stability (pot life) than curing agents that are liquid at room temperature. The curing agent may also be a latent curing agent. Further, the curing agent may be a curing agent that causes a curing reaction by heat, or a curing agent that causes a curing reaction by light. In addition, in the present disclosure, a single curing agent may be used, or two or more curing agents 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, curing will occur in a state where the flexibility and fluidity of the resin component are low, and uniform curing may be difficult to occur. On the other hand, the reaction initiation temperature of the curing agent is, for example, 200° C. or less. If the reaction initiation temperature is too high, the resin component may deteriorate. In addition to the epoxy resin, when a resin having high heat resistance such as a phenol resin is used, the resin component is less deteriorated, so the reaction initiation temperature of the curing agent may be, for example, 300° C. or less. . The reaction initiation temperature of the curing agent can be determined by differential scanning calorimetry (DSC).

Specific examples of curing agents 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 -4-Methylimidazole, 2-isopropylimidazole, 2-phenylimidazole, carboxylic acid salts of imidazole compounds, adducts with epoxy compounds. Also, the imidazole-based curing agent preferably has a hydroxyl group. Since crystallization occurs due to hydrogen bonding between hydroxyl groups, the reaction initiation temperature tends to be high.

Examples of phenol-based curing agents include phenol resins. Furthermore, examples of phenolic resins include resol-type phenolic resins and novolac-type phenolic resins. A phenolic novolac resin having a Tg of 110° C. or less is particularly preferable from the viewpoint of adhesion to the base material after foaming and curing and cracking resistance after foaming and curing. A phenol-based curing agent and an imidazole-based curing agent may also be used together. In that case, it is preferable to use an imidazole curing agent as a curing catalyst.

Examples of amine curing agents include aliphatic amines such as diethylenetriamine (DETA), triethylenetetramine (TETA), metaxylylenediamine (MXDA); diaminodiphenylmethane (DDM), m-phenylenediamine (MPDA), diamino aromatic amines such as diphenylsulfone (DDS); alicyclic amines; and polyamidoamines. As the amine-based curing agent, a dicyandiamide-based curing agent such as dicyandiamide (DICY), an organic acid dihydrazide-based curing agent, an amine adduct-based curing agent, and a ketimine-based 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); Aromatic acid anhydrides such as pyromellitic anhydride (PMDA) and benzophenonetetracarboxylic acid (BTDA) are included.

Examples of isocyanate-based curing agents include blocked isocyanates.

Examples of thiol-based curing agents include ester-bonded thiol compounds, aliphatic ether-bonded thiol compounds, and aromatic ether-bonded 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 an imidazole-based curing agent is used as a main component as a curing agent, 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 preferably less than or equal to parts. On the other hand, when a phenol-based curing agent is used as the main component of the curing agent, the content of the curing agent is, for example, 5 parts by mass or more and 40 parts by mass when the resin component contained in the first adhesive layer is 100 parts by mass. It is preferably less than or equal to parts. The use of an imidazole-based curing agent or a phenol-based curing agent as a main component as a curing agent means that the mass ratio of the imidazole-based curing agent or the phenol-based curing agent is the largest in the curing agent.

(b) Foaming agent The first adhesive layer in the present disclosure may or may not contain a foaming agent, but preferably contains a foaming agent. By containing the foaming agent, the surface roughness is increased, the coefficient of friction is decreased, and the slipperiness is further improved. Therefore, of the first adhesive layer and the second adhesive layer, the first adhesive layer with low tack preferably contains a foaming agent.

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

The foaming start temperature of the foaming agent is equal to or higher than the softening temperature of the main agent of the curable adhesive such as epoxy resin, and is equal to or lower than the activation temperature of the curing reaction of the main agent of the curable adhesive such as epoxy resin. is preferred. The foaming initiation temperature of the foaming agent is, for example, 70° C. or higher, and may be 100° C. or higher. If the reaction start temperature is too low, the reaction will start early, and foaming will occur in a state where the flexibility and fluidity of the resin component are low, making it difficult to generate uniform foaming. On the other hand, the reaction initiation temperature of the foaming agent is, for example, 210° C. or less. If the reaction initiation temperature is too high, the resin component may deteriorate.

The softening temperature of the main agent of the curable adhesive such as epoxy resin can be measured using the ring and ball softening temperature test method specified in JIS K7234.

Foaming agents include, for example, microcapsule-type foaming agents. The microcapsule-type foaming agent preferably has a core made of a thermal expansion agent such as a hydrocarbon, and a shell made of a resin such as an acrylonitrile copolymer.

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

The average particle size of the foaming 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 lubricity. The average particle size of the foaming agent is preferably equal to or less than the average thickness of the first adhesive layer, and may be, for example, 44 µm or less, 30 µm or less, or 24 µm or less. .

The average particle size of the foaming agent is the particle size at 50% of the integrated value in the particle size distribution determined by the laser diffraction scattering method. When measuring the average particle size of the foaming agent, the foaming agent is separated by dissolving the first adhesive layer in a solvent. 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, depending on the type of curable adhesive contained in the first adhesive layer. An appropriate solvent may be used, for example, the solvent used in the adhesive composition used to form the first adhesive layer. Specifically, methyl ethyl ketone, ethyl acetate, toluene, and the like 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, or 3 parts by mass or more when the resin component contained in the first adhesive layer is 100 parts by mass. , 4 parts by mass or more, or 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, or may be 15 parts by mass or less with respect to 100 parts by mass of the resin component contained in the first adhesive layer. good too. If the foaming agent content is too low, the coefficient of static friction on the surface of the first adhesive layer may increase. On the other hand, if the content of the foaming agent is too high, the content of the curable adhesive becomes relatively small, which may reduce the adhesiveness after foaming and curing.

(c) Other components The first adhesive layer in the present disclosure, for example, when the curable adhesive is an epoxy resin-based adhesive, may contain only epoxy resin and acrylic resin as resin components. may further contain a resin. Other resins include, for example, urethane resins.

The total ratio of the first epoxy resin, the second epoxy resin, and the 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, or 90% by mass. It may be more than or equal to 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 optionally contain additives such as silane coupling agents, fillers, antioxidants, light stabilizers, UV absorbers, lubricants, plasticizers, antistatic agents, cross-linking agents, and colorants. may contain. Silane coupling agents include, for example, epoxy-based silane coupling agents. Examples of fillers include inorganic fillers such as calcium carbonate, aluminum hydroxide, magnesium hydroxide, antimony trioxide, zinc borate, molybdenum compounds, and titanium dioxide. Examples of antioxidants include phenol antioxidants and sulfur antioxidants.

(3) Configuration of First Adhesive Layer When the first adhesive layer further contains a foaming agent, the first adhesive layer can be foamed at an expansion ratio of, for example, 4 times or more and 15 times or less. For example, of the first adhesive layer and the second adhesive layer, when only the first adhesive layer contains the foaming agent, the expansion ratio may be, for example, 5 times or more, or 7 times or more. It may be 9 times or more. 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 the first adhesive layer and the second adhesive layer of the first adhesive layer and the second adhesive layer contain a foaming agent, the expansion ratio may be, for example, 5 times or more. , 6 times or more, or 7 times or more. 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 expansion ratio can be determined by the following formula.
Expansion ratio (times) = thickness of the first adhesive layer after foaming and curing/thickness of the first adhesive layer before foaming and curing

The average 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 greater than the average particle diameter of the foaming agent. or 20 μm or more. If the first adhesive layer is too thin, it may not be possible to obtain sufficient adhesion to the substrate and adhesion after foaming and curing. On the other hand, the average 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, surface quality may deteriorate.

Here, the average thickness of the first adhesive layer is the thickness of the expandable adhesive sheet observed with a transmission electron microscope (TEM), a scanning electron microscope (SEM) or a scanning transmission electron microscope (STEM). It is a value measured from a cross section, and can be an average value of 10 randomly selected thicknesses. The same can be applied to the method of measuring the average thickness of other layers of the expandable adhesive sheet.

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

The first adhesive layer can be formed, for example, by applying an adhesive composition containing the curable adhesive, foaming agent, etc., 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, and the like. is mentioned.

The adhesive composition may or may not contain a solvent. In addition, the solvent in the present specification has a broad meaning including not only a strict solvent (a solvent that dissolves a solute) but also a dispersion medium. Moreover, the solvent contained in the adhesive composition is volatilized and removed when the adhesive composition is applied and dried to form an adhesive layer.

The adhesive composition can be obtained by mixing each component described above, and kneading and dispersing the mixture as necessary. Mixing and dispersion methods include general kneading and dispersing machines such as two-roll mills, three-roll mills, pebble mills, thron mills, Szegvari attritors, high-speed impeller dispersers, high-speed stone mills, high-speed impact mills, and dispersers. , high-speed mixers, ribbon blenders, co-kneaders, intensive mixers, tumblers, blenders, dispersers, homogenizers, and ultrasonic dispersers.

2. Second Adhesive Layer (1) Properties of Second Adhesive Layer In the present disclosure, 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 the surface of the second adhesive layer of the foamable adhesive sheet is attached 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 may deteriorate, and when inserting the other member with the foam adhesive sheet attached to the hole or groove of the other member, the second adhesive layer and Due to poor adhesion of the other member, the foamable adhesive sheet may peel off or the position of the foamable adhesive sheet may shift. Intensity may vary. The tack of the second adhesive layer is 400 gf or less, may be 300 gf or less, or may be 200 gf or less. If the tackiness of the second adhesive layer is too high, the reworkability is lowered. It may be difficult to correct misalignment of the foamable adhesive sheet when attaching the foam adhesive sheet.

Here, the method for measuring the tack of the second adhesive layer can be the same as the method for measuring the tack of the first adhesive layer.

In the present disclosure, 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 curing agent, if an epoxy resin that is liquid at room temperature or a curing agent that is liquid at room temperature is used, the adhesiveness of the second adhesive layer increases. Tend. In addition, in the second adhesive layer containing an epoxy resin and a curing agent, if an epoxy resin with a low softening temperature or an epoxy resin with a small weight average molecular weight is included, the adhesiveness of the second adhesive layer tends to increase. There is Moreover, the addition of a tackifying resin (tackifier) to the second adhesive layer tends to increase the adhesiveness of the second adhesive layer. If a curing agent that is liquid at room temperature is used, the adhesiveness tends to increase, but the storage stability may decrease. The adjustment preferably adjusts the tack of the second adhesive layer.

In the present disclosure, the peak value of the loss tangent (tan δ) of the second adhesive layer is 100° C. or higher, may be 110° C. or higher, or may be 120° C. or higher. Since the peak value of tan δ of the second adhesive layer is within the above range, it is possible to form a film even if it is dried at a high temperature when forming the second adhesive layer, and the residual solvent is reduced, and the second adhesive layer is efficiently can be formed. The peak value of tan δ of the second adhesive layer is 180° C. or lower, may be 170° C. or lower, or may be 160° C. or lower. Since the peak value of tan δ of the second adhesive layer is within the above range, it is possible to ensure the fluidity of the second adhesive layer when the foamable adhesive sheet is heated, and to ensure the followability of the member to the adhesive surface. be able to. Therefore, the adhesiveness of the foamable adhesive sheet after foaming and curing can be improved.

Here, tan δ of the second adhesive layer can be measured by dynamic viscoelasticity measurement and obtained from the following formula.
Loss tangent (tan δ) = loss modulus (E'') / storage modulus (E')
The details of the method for measuring tan δ of the second adhesive layer will be described in the Examples section below. When there are multiple tan δ peaks, the higher temperature was taken as the tan δ peak value.

In the present disclosure, the peak value of tan δ 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 curing agent, by including an epoxy resin with a high softening temperature or an epoxy resin with a large weight average molecular weight, the tan δ of the second adhesive layer Peak values tend to be higher.

(2) Material of Second Adhesive Layer The second adhesive layer in the present disclosure contains a curable adhesive.

(a) Curable Adhesive The curable adhesive contained in the second adhesive layer in the present disclosure can be the same as the curable adhesive used in the first adhesive layer. Among them, the curable adhesive is preferably an epoxy resin adhesive.

An example in which the curable adhesive is an epoxy resin-based adhesive will be described below.

(i) Epoxy resin As the epoxy resin in the present disclosure, the same epoxy resin as used for the first adhesive layer can be used.

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

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

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

Among them, as the epoxy resin, it is preferable to use an epoxy resin that is liquid at room temperature, such as a bisphenol A type epoxy resin or a bisphenol F type epoxy resin, and an epoxy resin that has a low softening point. This is because the use of these epoxy resins facilitates adjustment of the tackiness of the second adhesive layer within a predetermined range.

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

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

(iii) Curing Agent As the curing agent in the present disclosure, the same curing agent as used for the first adhesive layer can be used. As the curing agent, a curing agent that is solid at room temperature and 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 the present disclosure may or may not contain a foaming agent, but preferably contains a foaming agent. By containing a 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 enhanced.

As the foaming agent, the same foaming agent as used for the first adhesive layer can be used.

(c) Other components The second adhesive layer in the present disclosure may contain only an epoxy resin and an acrylic resin as resin components, for example, when the curable adhesive is an epoxy resin-based adhesive. may further contain a resin. Other resins include, for example, 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 needed. Additives may be the same as those used in the first adhesive layer.

(3) Configuration of Second Adhesive Layer When the second adhesive layer further contains a foaming agent, the second adhesive layer can be foamed at an expansion ratio of, for example, 1.5 times or more and 12 times or less. For example, of the first adhesive layer and the second adhesive layer, when both the first adhesive layer and the second adhesive layer contain a foaming agent, the foaming ratio may be, for example, 2 or more, or 3 It may be twice or more, or may be four times or more. 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 average thickness of the second adhesive layer can be the same as the average thickness of the first adhesive layer.

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

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

3. Substrate The foamable adhesive sheet in the present disclosure may have a substrate between the first adhesive layer and the second adhesive layer. When the substrate is arranged between the first adhesive layer and the second adhesive layer, the expandable adhesive sheet can be improved in handleability and workability. On the other hand, when the base material is not placed between the first adhesive layer and the second adhesive layer, the thickness of the entire foamable adhesive sheet can be reduced, and the foamable adhesive sheet can be used even in narrow gaps. can be inserted.

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

Examples of base materials include resin base materials and non-woven 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, polyetheramide, and the like. Polyamide resins; polyimide resins such as polyimide, polyetherimide, polyamideimide; polysulfone resins such as polysulfone and polyether sulfone; polyether ketone resins such as polyether ketone and polyether ether ketone; polyphenylene sulfide (PPS); oxide and the like. 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. Alternatively, a liquid crystal polymer (LCP) may be used as the resin.

Nonwoven fabrics include, for example, 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 subjected to surface treatment in order to enhance adhesion with the first adhesive layer and the second adhesive layer.

The average thickness of the substrate is not particularly limited, but may be, for example, 2 μm or more, may be 5 μm or more, or may be 9 μm or more. Also, the average thickness of the substrate is, for example, 200 μm or less, may be 100 μm or less, or may be 50 μm or less.

4. Other Configurations (1) First Intermediate Layer and Second Intermediate Layer The foamable adhesive sheet in the present disclosure may have a first intermediate layer between the substrate and the first adhesive layer. Also, the foamable adhesive sheet in the present disclosure may have a second intermediate layer between the substrate and the second adhesive layer. By arranging the first intermediate layer and the second intermediate layer, the adhesion of the first adhesive layer and the second adhesive layer to the substrate can be improved. Furthermore, by arranging the first intermediate layer and the second intermediate layer, for example, when the foamable adhesive sheet is folded, the stress applied to the bent portion is alleviated, and when the foamable adhesive sheet is cut, It is possible to relax the stress applied to the cut portion. As a result, it is possible to prevent the first adhesive layer and the second adhesive layer from lifting or peeling off from the substrate when the expandable adhesive sheet is bent or cut.

For example, in the foamable adhesive sheet 10 shown in FIG. A layer 5 is placed. In FIG. 3, the expandable adhesive sheet 10 has both the first intermediate layer 4 and the second intermediate layer 5, but it may have only one of them.

The foamable adhesive sheet may have at least one of the first intermediate layer and the second intermediate layer, and for example, has only the first intermediate layer disposed between the substrate and the first adhesive layer. may have only a second intermediate layer disposed between the substrate and the second adhesive layer, the first intermediate layer disposed between the substrate and the first adhesive layer; It may have both a material and a second intermediate layer disposed between the second adhesive layer. Among them, it is preferable that the first intermediate layer is arranged between the base material and the first adhesive layer, and the second intermediate layer is arranged between the base material and the second adhesive layer.

The material contained in the first intermediate layer and the second intermediate layer should be a material that can improve the adhesion between the substrate and the first adhesive layer or the second adhesive layer and can relieve stress. It is not particularly limited, and is appropriately selected according to the materials of the base material, the first adhesive layer, and the second adhesive layer. Examples thereof include polyester, polyvinyl chloride, polyvinyl acetate, polyurethane, copolymers of at least two or more thereof, crosslinked products thereof, and mixtures thereof.

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

Among them, the first intermediate layer and the second intermediate layer preferably contain a crosslinked resin. The crosslinked resin means a resin that does not melt even at high temperatures. This makes it possible to improve the adhesive strength at high temperatures, that is, the heat resistance.

The average 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, may be 0.5 μm or more, or may be 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 when the foamable adhesive sheet is bent or cut cannot be obtained sufficiently. there is a possibility. On the other hand, the average 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. Since the first intermediate layer and the second intermediate layer themselves usually do not have high heat resistance, if the first intermediate layer and the second intermediate layer are too thick, the heat resistance (adhesive 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. mentioned.

(2) First Separator and Second Separator The foamable adhesive sheet in the present disclosure may have a first separator on the side of the first adhesive layer opposite to the second adhesive layer. In addition, the foamable adhesive sheet in the present disclosure 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 such first and second separators include release films and release papers. Also, the first separator and the second separator may have a single layer structure or a multilayer structure.

Examples of the separator having a single layer structure include a fluororesin film.

Moreover, examples of the separator having a multilayer structure include a laminate having a release layer on one side or both sides of a substrate layer. Examples of the substrate layer include resin films such as polypropylene, polyethylene, and polyethylene terephthalate, and paper such as woodfree paper, coated paper, and impregnated paper. The material for the release layer is not particularly limited as long as it has releasability. Examples include silicone compounds, organic compound-modified silicone compounds, fluorine compounds, aminoalkyd compounds, melamine compounds, acrylic compounds, polyester compounds, chain alkyl compounds and the like. These compounds can be of emulsion type, solvent type or non-solvent type.

The first separator and the second separator may be the same or different. Among them, it is preferable that the first separator has heavy peelability and the second separator has light peelability. In the foamable adhesive sheet, the first adhesive layer is substantially non-tacky (tack-free) and the second adhesive layer is tacky. Therefore, for example, when bonding a rotor and a permanent magnet in an embedded magnet type motor, after arranging a foam adhesive sheet in the second member, the second member in which the foam adhesive sheet is arranged is inserted into the hole of the first member. When inserting the member, the surface of the second adhesive layer of the foamable adhesive sheet is attached to the second member, and the surface of the first adhesive layer of the foamable adhesive sheet faces the front side, so that when inserting, It is possible to improve 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 arranged. In this case, of the first separator and the second separator, since it will be peeled from the second separator, the first separator has heavy peelability and the second separator has light peelability, so that the second separator can be made easier to peel than the first separator.

Light release and heavy release refer to the degree of force required to separate the first separator and second separator from the first adhesive layer and second adhesive layer. means that is small.

5. Expandable Adhesive Sheet The average thickness of the expandable adhesive sheet in the present disclosure is, for example, 10 μm or more, and may be 20 μm or more. On the other hand, the average thickness of the expandable adhesive sheet is, for example, 1000 μm or less, and may be 200 μm or less.

The foamable adhesive sheet in the present disclosure preferably has good shape retention. Good shape retention is preferred. The bending moment based on JIS P8125 corresponding to ISO 2493 is, for example, 0.1 gf·cm or more, and may be 1 gf·cm or more. On the other hand, the bending moment is, for example, less than 40 gf·cm, and may be less than 30 gf·cm. Conventionally, foamable adhesive sheets generally employ a method of increasing bending moment to improve shape retention and insertability into narrow gaps. On the other hand, the inventors of the present disclosure have found that the shape retention can be secured by devising the shape, and that there is another problem with the high bending moment, so in view of other characteristics, It has been found that the bending moment is preferably within the above range. If the bending moment is smaller than the above range, it may be difficult to maintain the shape even by means of folding or the like. Moreover, if the bending moment is larger than the above range, the shape will return to its original shape after the bending process, so it is necessary to heat the product during the bending process or to form a streak on the crease. Heating will reduce the sheet life, and streaks may reduce the insulation in that area. In addition, in the foamable adhesive sheet of the present disclosure, by increasing the surface hardness, the surface is not damaged even when inserted at high speed.

The foamable adhesive sheet in the present disclosure preferably has high adhesiveness after foaming and curing. The shear strength (adhesive strength) based on JIS K6850 corresponding to ISO 4587 may be, for example, 1.50 MPa or more, 1.80 MPa or more, or 2.10 MPa or more at 23 ° C. good. Further, the shear strength (adhesive strength) at 130° C. may be, for example, 0.50 MPa or more, 0.75 MPa or more, or 1.00 MPa or more. For example, a high-strength acrylic foam pressure-sensitive adhesive tape that does not require heating has a shear strength (adhesive strength) of about 1 MPa to 2 MPa at room temperature, and does not have heat resistance at 200.degree. Therefore, if the shear strength (adhesive strength) is within the above range at 23° C., there is superiority in terms of strength. Further, if the shear strength (adhesive strength) is within the above range at 130° C., it can be applied to applications requiring heat resistance such as those around automobile engines.

The foamable adhesive sheet in the present disclosure preferably has high electrical insulation after foaming and curing. The dielectric breakdown voltage based on JIS C2107 corresponding to IEC 60454-2 is, for example, preferably 3 kV or higher, more preferably 5 kV or higher. When the dielectric breakdown voltage is within the above range, it can be applied to rust prevention and around copper wires. Moreover, the adhesive sheet after foaming and curing preferably has a thermal conductivity of, for example, 0.1 W/mK or more, and more preferably 0.15 W/mK or more. When the thermal conductivity is within the above range, the parts can be miniaturized, and the curing reaction during heating can be accelerated.

The use of the expandable adhesive sheet in the present disclosure is not particularly limited. The foamable adhesive sheet according to the present disclosure 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. . Among them, the foamable adhesive sheet in the present disclosure is obtained by disposing the foamable adhesive sheet in the second member, inserting the second member having the foamable adhesive sheet disposed therein into the hole of the first member, and removing the foamable adhesive sheet. is preferably used when bonding the first member and the second member by foaming and curing.

6. Method for Producing Expandable Adhesive Sheet The method for producing the expandable adhesive sheet in the present disclosure is not particularly limited, and is appropriately selected according to the layer structure of the expandable adhesive sheet.

When the foamable adhesive sheet does not have a substrate between the first adhesive layer and the second adhesive layer, the method for producing the foamable adhesive sheet includes, for example, first, as shown in FIG. An adhesive composition for forming a first adhesive layer on one separator 6 is applied and dried to form a first adhesive layer 1, and as shown in FIG. , the adhesive composition for forming the second adhesive layer is applied and dried to form the second adhesive layer 2 . Next, as shown in FIG. 4(c), the laminate of the first separator 6 and the first adhesive layer 1 and the laminate of the second separator 7 and the second adhesive layer 2 are laminated. Thereby, a foamable adhesive sheet is obtained. Since the first adhesive layer 1 is substantially non-adhesive (tack-free), the first separator 6 may be peeled off after lamination to form a foamable adhesive sheet.

Moreover, when the foamable adhesive sheet has a substrate between the first adhesive layer and the second adhesive layer, for example, two methods for producing the foamable adhesive sheet can be used.

In the first method for producing an expandable adhesive sheet, for example, first, as shown in FIG. to form the first intermediate layer 4 . Next, as shown in FIG. 5(b), an adhesive composition for forming the first adhesive layer is applied on the first intermediate layer 4 and dried to form the first adhesive layer 1. Next, as shown in FIG. Further, as shown in FIG. 5(c), the adhesive composition for forming the second adhesive layer is applied on the second separator 7 and dried to form the second adhesive layer 2. Next, as shown in FIG. Next, as shown in FIG. 5(d), the laminate of the substrate 3, the first intermediate layer 4 and the first adhesive layer 1 and the laminate of the second separator 7 and the second adhesive layer 2 are laminated. . Thereby, a foamable adhesive sheet is obtained. Note that the formation of the first intermediate layer 4 may be omitted. In this method, since the drying process for the first adhesive layer 1 is performed only once, the foamable adhesive sheet can be produced efficiently.

In the second method for producing an expandable adhesive sheet, for example, first, as shown in FIG. and dried to form the first intermediate layer 4 . Next, as shown in FIG. 6(b), an adhesive composition for forming the first adhesive layer is applied on the first intermediate layer 4 and dried to form the first adhesive layer 1. Next, as shown in FIG. Next, as shown in FIG. 6(c), the resin composition for forming the second intermediate layer is applied to the other surface of the substrate 3 and dried to form the second intermediate layer 5. Next, as shown in FIG. Next, as shown in FIG. 6(d), an adhesive composition for forming the second adhesive layer is applied on the second intermediate layer 5 and dried to form the second adhesive layer 2. Next, as shown in FIG. Subsequently, the second separator 7 is laminated on the second adhesive layer 2, as shown in FIG. 6(e). Thereby, a foamable adhesive sheet is obtained. Note that the formation of the first intermediate layer 4 may be omitted. Also, the formation of the second intermediate layer 5 may be omitted.

B. Method for manufacturing an article A method for manufacturing an article according to the present disclosure comprises an arrangement step of arranging the foamable adhesive sheet described above between a first member and a second member, foaming and curing the foamable adhesive sheet, and and a bonding step of bonding the member and the second member.

FIGS. 7A to 7C are process diagrams showing an example of a method for manufacturing an article according to the present disclosure. First, as shown in FIG. 7A, the surface of the second adhesive layer 2 of the expandable adhesive sheet 10 is attached to the second member 20b. Next, as shown in FIG. 7(b), the second member 20b on which the expandable adhesive sheet 10 is arranged is inserted into the hole of the first member 20a. Next, as shown in FIG. 7(c), the first adhesive layer 1 and the second adhesive layer 2 of the expandable adhesive sheet 10 are foamed and hardened by, for example, heating. The first member 20a and the second member 20b are adhered (bonded) by the adhesive sheet 13 having the first adhesive layer 11 and the second adhesive layer 12 after foaming and curing. Thereby, the article 100 in which the adhesive sheet 13 is arranged between the first member 20a and the second member 20b is obtained.

FIGS. 8A to 8C are process diagrams showing another example of the method for manufacturing an article according to the present disclosure. In FIG. 8(a), foam adhesive sheets are attached to both sides of the second member 20b. Note that the placement process and the bonding process are the same as in FIGS. 7(a) to 7(c).

A method for manufacturing an article according to the present disclosure will be described below.

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

When the foamable adhesive sheet has the first separator and the second separator, when the foamable adhesive sheet is arranged between the first member and the second member, the first separator and the second separator are removed from the foamable adhesive sheet. Peel off and use.

The details of the foamable adhesive sheet have been described in the above section "A. Foamable adhesive sheet", so the description is omitted here.

2. Arranging Step In the arranging step of the present disclosure, a method for arranging the expandable adhesive sheet between the first member and the second member is appropriately selected according to the types of the first member and the second member. For example, when the first member has a hole or groove and the second member is arranged in the hole or groove of the first member, when fixing the first member and the second member by adhesion, foaming After attaching the surface of the second adhesive layer of the foamable adhesive sheet to the second member using the tack of the second adhesive layer of the adhesive sheet, the foamable adhesive sheet is attached to the hole or groove of the first member. A method of arranging the second member that has been formed, a method of placing a foamable adhesive sheet in the hole or groove of the first member, and using the tack of the second adhesive layer of the foamable adhesive sheet to fit the hole or groove of the first member For example, after attaching the surface of the second adhesive layer of the expandable adhesive sheet, the second member is placed in the hole or groove of the first member to which the expandable adhesive sheet is attached.

3. Adhesion Step In the adhesion step of the present disclosure, methods for foaming and curing the foamable adhesive sheet include, for example, heating or light irradiation. Above all, it is preferable to foam and cure 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 according to the type of curable adhesive or foaming agent contained in the first adhesive layer or the second adhesive layer, the type of substrate, and the like. The heating temperature can be, for example, 130° C. or higher and 200° C. or lower. Also, 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 embodiment is an example, and any device that has substantially the same configuration as the technical idea described in the claims of the present disclosure and produces the same effect is the present invention. It is included in the technical scope of the disclosure.

[Manufacturing example]
First, adhesive compositions having compositions shown in Tables 1 and 2 below were prepared. Further, details of each material described in Tables 1 and 2 are shown below.

・Acrylic resin: PMMA-PBuA-PMMA (partially acrylamide group), Tg: -20°C, 120°C, Mw: 150,000
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
・ Epoxy resin B: BPA phenoxy type, normal temperature solid, softening temperature: 110 ° C., epoxy equivalent: 8000 g / eq, Mw: 50,000
・ Epoxy resin C: bisphenol A type, normal temperature liquid, epoxy equivalent: 184 to 194 g / eq
・ Epoxy resin D: diaminodiphenylmethane type, highly viscous liquid, epoxy equivalent: 110 to 130 g / eq
・ Epoxy resin E: silicone modified, epoxy equivalent: 1200 g / mol
・ Epoxy resin F: phenol novolac type, normal temperature liquid, epoxy equivalent: 176 to 178 g / eq

Curing agent 1: α-(hydroxy (or dihydroxy) phenylmethyl)-ω-hydropoly[biphenyl-4,4'-diylmethylene (hydroxy (or dihydroxy) phenylene methylene)]
Curing agent 2: 2-phenyl-4,5-dihydroxymethylimidazole, average particle size: 3 μm, melting point: 230° C., reaction initiation temperature: 145° C. to 155° C., active region: 155° C. to 173° C. (manufactured by Shikoku Kasei Kogyo Co., Ltd.) , 2PHZ-PW)
Curing agent 3: dicyandiamide, particle size: 10 µm or less, melting point: 209°C (manufactured by Evonik Degussa, DYHARD100SH)
・ Curing agent 4: epoxy resin amine adduct (manufactured by Ajinomoto Fine-Techno Co., Ltd., Amicure MY-H)

・Thermal foaming agent 1: thermally expandable microcapsules, average particle size 7 μm, expansion start temperature 120 to 145° C., maximum expansion temperature 155 to 175° C., core: hydrocarbon, shell: thermoplastic polymer ・Thermal foaming agent 2: Thermally expandable microcapsules, average particle size 13 μm, expansion start temperature 123-133° C., maximum expansion temperature 168-178° C., core: hydrocarbon, shell: thermoplastic polymer/thermal foaming agent 3: thermally expandable microcapsules, Average particle size 17 μm, expansion start temperature 120-130° C., maximum expansion temperature 160-170° C. Core: hydrocarbon Shell: acrylonitrile copolymer/thermal blowing agent 4: thermally expandable microcapsule Average particle size 20 μm, expansion start temperature 115-125°C, maximum expansion temperature 155-165°C, core: hydrocarbon, shell: thermoplastic polymer, thermal foaming agent 5: thermally expandable microcapsules, average particle size 21 μm, expansion start temperature 130-140°C, maximum Expansion temperature 160-170°C, core: hydrocarbon, shell: acrylonitrile copolymer/thermal blowing agent 6: thermally expandable microcapsules, average particle diameter 21 µm, expansion start temperature 123-133°C, maximum expansion temperature 180-195°C, core : Hydrocarbon, Shell: Thermoplastic polymer/thermal foaming agent 7: Thermally expandable microcapsule, Average particle diameter: 21 μm, Expansion start temperature: 120-130°C, Maximum expansion temperature: 175-190°C, Core: Hydrocarbon, Shell: Thermoplastic polymer/thermal foaming agent 8: thermally expandable microcapsules, average particle size 25 μm, expansion start temperature 125-135° C., maximum expansion temperature 165-180° C., core: hydrocarbon, shell: thermoplastic polymer/heat Foaming agent 9: thermally expandable microcapsules, average particle diameter 30 μm, expansion start temperature 120-130° C., maximum expansion temperature 160-170° C., core: hydrocarbon, shell: acrylonitrile copolymer/thermal blowing agent 10: thermally expandable microcapsules Capsule, average particle size 41 μm, expansion start temperature 115-125° C., maximum expansion temperature 165-175° C., core: hydrocarbon, shell: acrylonitrile copolymer

・Silane coupling agent: 3-glycidoxypropyltrimethoxysilane ・Antioxidant: Hindered phenol antioxidant ・Solvent: methyl ethyl ketone

[Examples 1 to 13]
Polyethylene naphthalate (PEN film, manufactured by Toyobo Film Solution Co., Ltd., Teonex Q51, thickness 25 μm) was used as the base material. Further, 15 parts by mass of a curing agent (polyisocyanate) and 0.3 parts by mass of a catalyst (trisdimethylaminomethylphenol) are blended with respect to 100 parts by mass of the polyester polymer, and the solid content is 15% by mass. and diluted with methyl ethyl ketone (MEK) to prepare a resin composition. The resin composition was applied to one surface of the base material with 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 was applied to the surface of the first intermediate layer opposite to the base material using an applicator so that the thickness after coating was 45 μm. Then, 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 Nippa Co., Ltd., PET50×1-J2, thickness 50 μm) is used as the second separator, and the adhesive composition is applied to the release treatment surface of the release film. It was applied using an applicator so that the thickness after the process would be 45 μm. After that, 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 to the surface of the base material of the laminate having the substrate, the first intermediate layer and the first adhesive layer. As a result, a foamable adhesive sheet was obtained in which the first adhesive layer, the first intermediate layer, the substrate, the second adhesive layer, and the second separator were arranged in this order.

[Comparative Example 1]
In the same manner as in Example 1, a first intermediate layer and a first adhesive layer were formed on the substrate. Next, the adhesive composition was applied to the surface of the base material opposite to the first intermediate layer using an applicator so that the thickness after coating was 45 μm. After that, it was dried in an oven at 100° C. for 3 minutes to form a second adhesive layer. As a result, a foamable adhesive sheet was obtained in which the first adhesive layer, the first intermediate layer, the substrate, and the second adhesive layer were arranged in this order.

[Comparative Examples 2-3]
As the first separator, a release film (PET separator, manufactured by Nippa Co., Ltd., PET38×1-J2, thickness 38 μm) is used, and the adhesive composition is applied to the release treatment surface of the release film. It was applied using an applicator so as to have a thickness of 45 μm. Then, it was dried in an oven at 100° C. for 3 minutes to form a first adhesive layer.

Next, polyethylene naphthalate (PEN film, manufactured by Toyobo Film Solution Co., Ltd., Teonex Q51, thickness 25 μm) is used as the base material, and the first adhesion of the laminate having the first separator and the first adhesive layer is used as the base material. The layers were laminated face-to-face.

Next, a release film (PET separator, manufactured by Nippa Co., Ltd., PET38×1-Q2ASI5, thickness 38 μm) is used as the second separator, and the adhesive composition is applied to the release treated surface of the release film. It was applied using an applicator so that the thickness after the process would be 45 μm. After that, 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 on the surface of the base material of the laminate having the substrate, the first adhesive layer and the first separator. As a result, a foamable adhesive sheet was obtained in which the second separator, the second adhesive layer, the substrate, the first adhesive layer, and the first separator were arranged in this order.

[evaluation]
(Tack of first adhesive layer and second adhesive layer)
For the tackiness of the first adhesive layer, a tacking tester "TAC-II" manufactured by RHESCA was used to apply a cylindrical stainless steel probe with a diameter of 5 mm to the surface of the first adhesive layer of the foamable adhesive sheet. At a temperature of 25° C., the film was pressed at 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, and the load at the time of peeling was measured. This measurement was performed 5 times, and the average value was taken as the tack.

The tack of the second adhesive layer was also measured in the same manner as the tack of the first adhesive layer.

(Friction coefficient of the surface of the first adhesive layer)
The dynamic friction coefficient and static friction coefficient between the first adhesive layer of the foamable adhesive sheet and the metal plate were measured according to JIS K7125. First, the expandable adhesive sheet was cut to 80 mm×200 mm. Next, the expandable adhesive sheet was placed on a horizontally placed rectangular metal plate (SUS plate), and a sliding piece (63 mm × 63 mm, weight 200 g, Bottom surface: felt) was placed, and 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 dynamic friction coefficient and static friction coefficient were calculated. As a device, a friction measuring machine FRICTION TESTER TR-2 manufactured by Toyo Seiki Co., Ltd. was used.

(Arithmetic mean roughness Ra of the first adhesive layer)
The arithmetic mean roughness Ra of the first adhesive layer was measured using a white interferometer NewView 7300 manufactured by Zygo, with an observation field of view of 0.55 mm×0.55 mm and a sampling interval of 0.55 μm.

(Peak value of tan δ of the second adhesive layer)
The second separator was peeled off from the laminate of the second separator and the second adhesive layer prepared above to obtain the second adhesive layer alone. Using a solid viscoelasticity analyzer (RSA-III, manufactured by TA Instruments Co., Ltd.), attachment mode: compression mode, frequency: 1 Hz, temperature: The storage elastic modulus (E′) and loss elastic modulus (E″) of the second adhesive layer are measured at −20° C. to 200° C. at a heating rate of 10° C./min, and the loss tangent (tan δ) is calculated. bottom. When there are multiple tan δ peaks, the higher temperature was taken as the tan δ peak value.

(Expansion ratio)
The foamable adhesive sheet was cut into a size of 25 mm × 100 mm, the second separator was peeled off, and the surface of the second adhesive layer of the foamable adhesive sheet was attached to a glass plate having a thickness of 1.0 mm. The adhesive sheets were arranged on an aluminum bat so that the surface of the first adhesive layer faced upward. At this time, when the foamable adhesive sheet had a first separator, the first separator was peeled off. After foaming and curing at 180° C. for 30 minutes, it was cooled at room temperature for 2 hours to obtain an adhesive sheet after foaming and curing. Then, the thickness of the adhesive sheet after foaming and curing was measured using a thickness gauge by a method based on JIS Z0237. The expansion ratio was determined by the following formula.
Expansion ratio (times) = {thickness of adhesive sheet after foaming and curing - (thickness of base material + thickness of first intermediate layer)} / (first adhesive layer and first adhesive layer of foamable adhesive sheet before foaming and curing) total thickness of two adhesive layers)

(Adhesiveness after foaming and curing)
As shown in FIGS. 9A and 9B, two metal plates 31 (cold-rolled steel plate SPCC-SD) having a thickness of 1.6 mm, a width of 25 mm, and a length of 100 mm were prepared. A spacer 32 (Kapton tape) was placed at one end of one of the metal plates 31 at a predetermined interval. The thickness of the spacer 32 was set to about 280 μm (thickness obtained by stacking four sheets of Kapton tape P-221 manufactured by Nitto Denko). Next, between the spacers 32, the expandable adhesive sheet 10 is placed in a state where the expandable adhesive sheet 10 is cut into a size of 12.5 mm×25 mm and the first separator and the second separator are removed when the expandable adhesive sheet has a separator. Then, another metal plate 31 was placed so that one end thereof overlapped with the metal plate 31 and fixed with a clip to obtain a test piece. After that, the test piece was placed in a heat oven and heated at 180° C. for 30 minutes to cure the expandable adhesive sheet 10 .

The shear strength (adhesive strength) of the heated test piece was measured using a tensile tester Tensilon RTF1350 (manufactured by A&D Co., Ltd.) in accordance with JIS K6850. The measurement conditions were a tensile speed of 10 mm/min and a temperature of 23°C or 130°C.

(Sliding property of the first adhesive layer and adhesion of the second adhesive layer at the time of insertion)
A foamable adhesive sheet cut to 5.5 cm x 8.0 cm, a hollow cylinder 1 having 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. When the foam adhesive sheet has a second separator, the second separator is peeled off, and the surface of the second adhesive layer is attached to the outer diameter part of the cylinder 2 so that the short side is in the circumferential direction, and the foam adhesive sheet was placed. When the foamable adhesive sheet had a first separator, the first separator was peeled off. After that, the cylinder 2 was slowly pushed by hand and inserted into the hollow gap of the cylinder 1, and the sliding property of the first adhesive layer and the adhesion of the second adhesive layer at that time were evaluated. The evaluation criteria were as follows.

- Sliding property A of the first adhesive layer: No stickiness during insertion.
B: There is a sticking during insertion (the first adhesive layer sticks to the cylinder 1 and the insertability is poor).

- Adhesiveness A of the second adhesive layer: The foamable adhesive sheet does not separate from the cylinder 2 during insertion.
B: The foamable adhesive sheet is peeled off from the cylinder 2 when inserted, or the foamable adhesive sheet does not adhere to the cylinder 2 when pasted.

In the foamable adhesive sheets of Examples 1 to 13, the tack of the first adhesive layer and the tack of the second adhesive layer are each within a predetermined range, and the peak value of the loss tangent (tan δ) of the second adhesive layer is within a predetermined range. , the slipperiness of the first adhesive layer at the time of insertion and the adhesion of the second adhesive layer were good, and the adhesiveness after foaming and curing was also good. On the other hand, in Comparative Example 1, since the tackiness of the second adhesive layer was low, the adhesiveness of the second adhesive layer during insertion was poor. Moreover, in Comparative Examples 2 and 3, the tackiness of the first adhesive layer and the tackiness of the second adhesive layer were equal, and the tackiness of the first adhesive layer was high, so the slipperiness of the first adhesive layer during insertion was poor.

REFERENCE SIGNS LIST 1 first adhesive layer 2 second adhesive layer 3 substrate 4 first intermediate layer 5 second intermediate layer 6 first separator 7 second separator 10 foam adhesive sheet 11 after foaming and curing Adhesive sheet 20a... First member 20b... Second member 100... Article

Claims (6)

A foamable adhesive sheet having a first adhesive layer and a second adhesive layer disposed on one side of the first adhesive layer,
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 first adhesive layer has a tack of 0 gf or more and less than 10 gf,
The second adhesive layer has a tack of 10 gf or more and 400 gf or less,
The foamable adhesive sheet, wherein the peak value of the loss tangent (tan δ) of the second adhesive layer is 100°C or higher and 180°C or lower. The expandable adhesive sheet according to claim 1, wherein said first adhesive layer contains said foaming agent. The expandable adhesive sheet according to claim 1, wherein said first adhesive layer and said second adhesive layer contain said foaming agent. 4. The expandable adhesive sheet according to any one of claims 1 to 3, having a substrate between said first adhesive layer and said second adhesive layer. The arithmetic mean roughness (Ra) of the surface of the first adhesive layer opposite to the second adhesive layer is 0.3 μm or more and 1.5 μm or less,
The expandable adhesive sheet according to any one of claims 1 to 4, wherein the surface of the first adhesive layer opposite to the second adhesive layer has a static friction coefficient of 0.33 or less. an arrangement step of arranging the expandable adhesive sheet according to any one of claims 1 to 5 between the first member and the second member;
a bonding step of foaming and curing the foamable adhesive sheet to bond the first member and the second member;
A method for manufacturing an article.

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