JP7598544B2 - Electronic Components - Google Patents

Description

The present invention relates to electronic components.

Adhesive sheets (sometimes called "adhesive tapes") are widely used as a joining means with excellent workability and high adhesive reliability in situations such as fixing components that make up electronic devices. Specifically, adhesive tapes are used for fixing components in various industrial fields, such as fixing metal sheets that make up relatively large electronic devices such as flat-screen televisions, home appliances, and office equipment, fixing exterior components to housings, fixing rigid components such as exterior components and batteries to relatively small electronic devices such as mobile electronic terminals, cameras, and personal computers, temporarily fixing such components, and for labeling purposes that display product information.

In recent years, in each of the above industrial fields, reusable or reusable parts used in products are increasingly being disassembled after use and reused or re-used, with the aim of conserving resources from the perspective of protecting the global environment. In this case, if adhesive tape is used, it is necessary to peel the adhesive tape attached to the parts. However, since the adhesive tape usually has a high adhesive strength and is attached to many places in the product, the work of peeling it off involves a considerable amount of labor. Therefore, when reusing or reusing the above, there is a demand for easy peeling and removal to reduce labor costs.

As an easily peelable and removable adhesive tape, an adhesive tape has been proposed that has an adhesive portion and a tab portion, and that the tab portion is attached so as to overhang from one of the outer extension portion of the first adherend and the outer extension portion of the second adherend and be able to be clamped, and that can be clamped and stretched in a direction approximately parallel to the adhesive surface for peeling (see Patent Document 1). However, when the tab portion (gripping portion) for stretch peeling is only at one end, as in this proposed adhesive tape, there is a problem that the adhesive remains on the adherend after peeling of the adhesive tape on the adhesive surface opposite the side having the tab portion (i.e., the surface to which the adhesive tape is attached for the longest time when peeled), causing contamination. In addition, if the tab portion at one end is torn during stretch peeling, it cannot be peeled any further, and there is also a problem that reusable or reusable parts cannot be disassembled any further.

In response to this, an adhesive film has been proposed that includes an adhesive region (2) adjacent to a grip tab (1) located at one end of an adhesive film piece and extending toward the other end (3), as shown in FIG. 1, in which the adhesive region (2) includes, in order from the grip tab (1) toward the other end (3) of the adhesive film piece, a first adhesive region (4) having a larger cross-sectional area than the second adhesive region (5), a second adhesive region (5) having a cross-sectional area that rapidly decreases toward the end (3), and a third adhesive region (6) that forms the end (3) and terminates in one or more tips (7) toward the end (3) (see Patent Document 2). However, in the case of the shape of the adhesive film proposed here, there is a problem that the application area becomes small, the application area cannot be effectively utilized, and the adhesive strength becomes weak. In the above-mentioned electronic device, it is a major problem that the components constituting the electronic device peel off during use, and it is necessary to maintain the adhesive strength until the electronic components are collected for reuse or reusability.

Therefore, there is a strong demand for electronic components equipped with an adhesive sheet that can be peeled off quickly, is not contaminated by the adhesive after peeling, and even if it tears while stretching and peeling from one end, it can be stretched and peeled off from the other end to the end, and has suitable adhesive strength when in use.

JP 2015-124289 A U.S. Pat. No. 6,680,096

The present invention aims to solve the above-mentioned problems in the past and to achieve the following objectives. That is, the present invention aims to provide an electronic component equipped with an adhesive sheet that can be quickly peeled off, is not contaminated by the adhesive after peeling, and even if it tears while stretching and peeling from one end, can be stretched and peeled from the other end to the end, and has suitable adhesive strength when in use.

The means for solving the above problems are as follows.
In other words, it is an electronic component characterized in that it has an adhesive sheet having one surface which is affixed to a first attachment object so that at least a portion of the surface is linear, and the other surface which is affixed to a second attachment object, and which is affixed to the second attachment object with at least two ends exposed from the second attachment object.

The present invention solves the above-mentioned problems of the prior art and achieves the above-mentioned objectives, thereby providing an electronic component equipped with an adhesive sheet that can be peeled off quickly, is not contaminated by the adhesive after peeling, and even if it tears during stretch-peeling from one end, it can be stretch-peeled from the other end and peeled off to the end, and has suitable adhesive strength when in use.

FIG. 1 shows a prior art adhesive film. FIG. 2A is a schematic diagram (top view) illustrating one embodiment of an electronic component of the present invention. FIG. 2B is a schematic explanatory diagram (cross-sectional view) showing one embodiment of the electronic component of the present invention. FIG. 2C is a schematic explanatory diagram (cross-sectional view) showing another embodiment of the electronic component of the present invention. FIG. 2D is a schematic explanatory diagram (top view) showing another embodiment of the electronic component of the present invention. FIG. 2E is a schematic explanatory diagram (top view) showing another embodiment of the electronic component of the present invention. FIG. 2F is a schematic explanatory diagram (top view) showing another embodiment of the electronic component of the present invention. FIG. 2G is a schematic explanatory diagram (top view) showing another embodiment of the electronic component of the present invention. FIG. 3A is a schematic explanatory diagram (cross-sectional view) of the electronic component of the present invention when it is a battery. FIG. 3B is a schematic explanatory diagram (top view) of the electronic component of the present invention being a battery. FIG. 3C is a schematic explanatory diagram (cross-sectional view) showing another embodiment in which the electronic component of the present invention is a battery. FIG. 4A is a schematic explanatory diagram (cross-sectional view) of the electronic component of the present invention in the case where the electronic component is a television display. FIG. 4B is a schematic explanatory diagram (top view) of the electronic component of the present invention being a television display. FIG. 5A is a schematic explanatory diagram (cross-sectional view) of a method for attaching an adhesive sheet 31 to an acrylic plate 32 when evaluating impact resistance in the examples. FIG. 5B is a schematic explanatory diagram (top view) of a test piece prepared for evaluating impact resistance in the examples. FIG. 5C is a schematic explanatory diagram (cross-sectional view) of a method for placing a test piece on a U-shaped measurement table when evaluating impact resistance in the examples. FIG. 6A is a schematic diagram (cross-sectional view) of application mode X in Test Examples 1 to 11 and the stretch direction (horizontal direction) in the stretch peel test. FIG. 6B is a schematic explanatory diagram (cross-sectional view) of application mode X in Test Examples 1 to 11 and the stretch direction (vertical direction) in the stretch peel test. FIG. 6C is a schematic explanatory diagram (cross-sectional view) of application mode Y in Comparative Test Examples 1 to 11 and the stretch direction (horizontal direction) in the stretch peel test. FIG. 7A is a diagram showing the appearance of the acrylic plate after horizontal stretch-peel in Test Example 1 (application mode X). FIG. 7B is a diagram showing the appearance of the acrylic plate after horizontal stretch-peel in Test Example 1 (application mode Y).

(Electronic Components)
The electronic component comprises a pressure-sensitive adhesive sheet having one surface attached to a first attachment target so that at least a portion of the surface is linear, and the other surface attached to a second attachment target, the pressure-sensitive adhesive sheet being attached to the second attachment target with at least two ends exposed from the second attachment target. In this specification, the first attachment target and the second attachment target may be collectively referred to as "adherend".

In this specification, the electronic components include not only the various parts that make up the electronic device, such as sheet metal, exteriors, housings, and batteries, but also the electronic devices themselves, such as televisions, home appliances, office automation equipment, mobile electronic devices, cameras, and personal computers.

The configuration of the electronic components is described in detail below with reference to the drawings, but the present invention is not limited to these aspects.

As shown in Figures 2A and 2B, in the electronic component, one surface 21a of the adhesive sheet 21 is attached to one surface of a first attachment target 22 constituting the electronic component, with at least a portion of the surface being linear. Next, the other surface 21b of the adhesive sheet 21 is attached to a second attachment target 23 constituting the electronic component. At this time, the two longitudinal ends of the adhesive sheet 21 are attached in a state exposed from the second attachment target 23. As a result, at least a portion of each of the ends of the adhesive sheet 21 exposed from the second attachment target 23 functions as a gripping portion. Figure 2C is a diagram showing another embodiment of the electronic component.

2A to 2C show an example in which the adhesive sheet is attached to the attachment target in a straight line and has two ends, but the adhesive sheet may be attached to the first attachment target in such a way that one surface of the adhesive sheet is at least partially straight, and as shown in FIGS. 2D to 2G, the adhesive sheet may be attached to the first attachment target in a shape that is branched or bent in the middle. Therefore, the number of ends (gripping parts) of the adhesive sheet is not particularly limited, and can be appropriately selected depending on the attachment shape of the adhesive sheet. In this case, the number of ends of the adhesive sheet exposed from the second attachment target is not particularly limited as long as it is at least two, and can be appropriately selected depending on the purpose, but it is preferable that all ends are exposed from the second attachment target. Hereinafter, each end of the adhesive sheet 21 exposed from the second attachment target 23 may be referred to as a first gripping part A, a second gripping part B, a third gripping part C, a fourth gripping part D, etc.
2A to 2G show an example in which each of the gripping portions A to D is not exposed from the first attachment target 22, but as long as at least two of each of the gripping portions A to D are exposed from at least the second attachment target 23, there is no particular limitation, and at least one of each of the gripping portions A to D may be exposed from the first attachment target 22.

<Grip part>
The gripping portion may be disposed directly on the first attachment target 22, as shown in Figures 2A and 2B, or may be disposed on the side (thickness direction surface) of the second attachment target 23, as shown in Figure 2C (first gripping portion A and second gripping portion B in Figures 2A to 2C), or may be disposed so as to be in contact with other elements of the electronic component adjacent to at least one of the first attachment target 22 and the second attachment target 23, although not shown in the figures.

The gripping portion is an end portion of the adhesive sheet, and the number of adhesive layers on the adhesive surface with at least one of the first and second attachment objects may be the same as or different from the number of adhesive layers in the gripping portion. For example, when the adhesive sheet has adhesive layers on both sides, the adhesive layer in at least one of the multiple gripping portions may be disposed on only one side. Also, the number of adhesive layers in the multiple gripping portions may be the same as or different from each other.

The gripping portion may be formed by processing at least a portion of the end of the adhesive sheet. The processing is not particularly limited and can be appropriately selected depending on the purpose. Examples of the processing include processing to remove the adhesive layer in the adhesive sheet, processing to place a release sheet on the surface of the adhesive layer in the adhesive sheet, and processing to modify the adhesive layer in the adhesive sheet to be non-adhesive using a known means such as a release agent.

The release sheet is not particularly limited and can be appropriately selected depending on the purpose. Examples of the release sheet include paper such as kraft paper, glassine paper, and wood-free paper; resin films such as polyethylene, polypropylene (biaxially oriented polypropylene (OPP), uniaxially oriented polypropylene (CPP)), and polyethylene terephthalate (PET); laminated paper in which the paper and resin film are laminated together; and paper that has been subjected to a sealing treatment with clay or polyvinyl alcohol and then subjected to a release treatment with silicone resin or the like on one or both sides. These may be used alone or in combination of two or more types.

The length of the gripping portion is not particularly limited as long as it can be stretched, and can be appropriately selected depending on the distance between the first and second attachment objects and other electronic components adjacent thereto, but is preferably 5 mm or more, more preferably 10 mm or more, and even more preferably 15 mm or more. The upper limit of the length is not particularly limited, and can be appropriately selected depending on the size of the electronic components, but is preferably 20 mm or less.
The length of each of the gripping portions may be the same or different.

There are no particular limitations on the width of the gripping portion, and it can be selected appropriately depending on factors such as the width of the adhesive sheet.

<Stretching direction p>
The adhesive sheet 21 in the electronic component is easily stretched and peeled off by stretching in the stretching direction p shown in Fig. 2B and Fig. 2C. Fig. 2B shows an embodiment in which the stretching direction p of the adhesive sheet 21 is horizontal (180° direction) to the attachment surface of the first attachment target 22 and the second attachment target 23, and Fig. 2C shows an embodiment in which the stretching direction p of the adhesive sheet 21 is vertical (90° direction) to the attachment surface of the first attachment target 22 and the second attachment target 23, but there is no particular limitation on the angle of the stretching direction p to the attachment surface of the first attachment target 22 and the second attachment target 23, and it can be appropriately selected depending on the surrounding environment of the electronic component, etc.

The adhesive sheet in the electronic component may be peeled off by stretching the multiple gripping parts simultaneously, or a portion of the adhesive sheet may be peeled off by stretching one of the multiple gripping parts, and then the remaining portion may be peeled off by stretching the other. In addition, the adhesive sheet in the electronic component has at least two ends exposed from the second attachment target, so that even if the adhesive sheet tears during stretching and peeling from one end (first gripping part), it is advantageous in that it can be stretched and peeled off from the other end (second gripping part) to the end.

The removability of the adhesive sheet in the electronic component can be confirmed, for example, by the method described in the test example described later, "Evaluation of Removability 1." In the evaluation of removability, a sheet that is not contaminated by the adhesive after peeling and that can be stretch-peeled from the gripping portion at one end and peeled all the way to the end even if it is torn during stretch-peeling from the gripping portion at the other end is deemed to have excellent removability.

<Width of application area/Length of application area (X/Y)>
When the width of the applied area of the pressure-sensitive adhesive sheet in the electronic component is X (cm) and the length of the applied area is Y (cm), the ratio of the width of the applied area to the length of the applied area represented by [X/Y] is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 1/1 to 1/100,000, more preferably 1/1 to 1/10,000, and even more preferably 1/1 to 1/1,000. If the ratio of the applied areas is less than 1/1, the adhesive strength may be insufficient, and if it exceeds 1/100,000, the pressure-sensitive adhesive sheet may tear during stretch peeling, or contamination by the adhesive may occur after peeling.

<First affixed object or second affixed object>
The first and second pasting targets may be the same part or different parts. Furthermore, the first and second pasting targets may be interchangeable.

The materials of the first and second attachment objects are not particularly limited and can be appropriately selected depending on the type of electronic component, and examples of such materials include metals, alloys, glass, plastics, and ceramics. These materials may be used alone or in combination of two or more.

Specific examples of the first attachment target include a back chassis, a bezel, a metal plate, a housing, a heat dissipation sheet, etc.

Specific examples of the second attachment target include display glass, batteries, heat dissipation components such as heat sinks, speakers, and camera lenses.

Among these, the first and second attachment targets are preferably recovered parts. The recovered parts are not particularly limited as long as they are reusable or reusable parts, and can be appropriately selected according to the purpose. For example, they can be recovered when a defect occurs during the manufacturing process of electronic parts, or recovered when they are discarded. The adhesive sheet in the electronic parts can be quickly peeled off, is not contaminated by the adhesive after peeling, and even if it is torn during stretching and peeling from one end, it can be stretched and peeled from the other end to the end, so that at least one of the first and second attachment targets can be quickly recovered as the recovered parts, and at least one of the first and second attachment targets is advantageous in that there is no contamination when the first and second attachment targets are reused or re-used.

More specific embodiments of the electronic components are described below with reference to the drawings, but the present invention is not limited to these embodiments.

An embodiment in which the electronic component is a small component such as a battery will be specifically described below.
3A and 3B, one surface 61a of the adhesive sheet 61 is attached so that at least a part of it is linear with respect to a fixing portion of the battery 63 of the back chassis 62. Next, the other surface 61b of the adhesive sheet 61 is attached to the battery 63. At this time, the two ends (first grip portion A and second grip portion B) in the length direction (extension direction) of the adhesive sheet 61 are attached in a state where they are exposed from both ends of the battery 63. In addition, the method of attaching the first grip portion A and the second grip portion B of the adhesive sheet 61 may be an embodiment as shown in FIG. 3C.

An embodiment in which the electronic component is a large component such as a television display will be specifically described below.
4A and 4B , one surface of the adhesive sheet 71 is attached so that at least a portion thereof is linear with respect to a fixing portion of the display 73 of the bezel 72. Next, the other surface of the adhesive sheet 71 is attached to the display 73. At this time, the two ends (first grip portion A and second grip portion B) in the length direction (extension direction) of the adhesive sheet 71 are attached in a state where they are exposed from both ends of the display 73.

<Adhesive sheet>
The pressure-sensitive adhesive sheet has at least a pressure-sensitive adhesive layer, and preferably has a base layer, and further has other layers as required.
It is preferable that at least one of the one surface and the other surface of the pressure-sensitive adhesive sheet is made of the pressure-sensitive adhesive layer, and it is more preferable that both of the one surface and the other surface of the pressure-sensitive adhesive sheet are made of the pressure-sensitive adhesive layer.

<<Adhesive layer>>
The pressure-sensitive adhesive layer contains at least a pressure-sensitive adhesive composition, and further contains other components as necessary.

- Pressure-sensitive adhesive composition -
The pressure-sensitive adhesive composition contains at least the pressure-sensitive adhesive resin, and further contains other components as necessary.

The adhesive resin is not particularly limited and can be appropriately selected from known materials, for example, acrylic adhesive resin, rubber adhesive resin, urethane adhesive resin, silicone adhesive resin, etc. These may be used alone or in combination of two or more. Among these, acrylic adhesive resin is preferred as the adhesive resin.

--Acrylic adhesive resin--
The acrylic adhesive resin is not particularly limited and can be appropriately selected depending on the purpose. For example, it may contain an acrylic polymer and, if necessary, additives such as a tackifier resin and a crosslinking agent.

The acrylic polymer can be produced, for example, by polymerizing a monomer mixture containing a (meth)acrylic monomer.
As the (meth)acrylic monomer, for example, an alkyl (meth)acrylate having an alkyl group having 1 to 12 carbon atoms can be used.
Specific examples of the alkyl (meth)acrylate having an alkyl group having 1 to 12 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, etc. These may be used alone or in combination of two or more.

As the alkyl (meth)acrylate having an alkyl group with 1 to 12 carbon atoms, it is preferable to use an alkyl (meth)acrylate having an alkyl group with 4 to 12 carbon atoms, and it is more preferable to use an alkyl (meth)acrylate having an alkyl group with 4 to 8 carbon atoms, and it is particularly preferable to use n-butyl acrylate in order to ensure excellent adhesion to the adherend.

The alkyl (meth)acrylate having an alkyl group having 1 to 12 carbon atoms is preferably used in the range of 80% to 98.5% by weight, and more preferably 90% to 98.5% by weight, of the total amount of monomers used in the production of the acrylic polymer.

As the monomers usable in the production of the acrylic polymer, in addition to the above-mentioned ones, highly polar vinyl monomers can be used as necessary.
Examples of the highly polar vinyl monomer include (meth)acrylic monomers such as (meth)acrylic monomers having a hydroxyl group, (meth)acrylic monomers having a carboxyl group, and (meth)acrylic monomers having an amide group, as well as sulfonic acid group-containing monomers such as vinyl acetate, ethylene oxide-modified succinic acid acrylate, and 2-acrylamido-2-methylpropanesulfonic acid. These may be used alone or in combination of two or more.

Specific examples of the vinyl monomer having a hydroxyl group include (meth)acrylic monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate.

The vinyl monomer having a hydroxyl group is preferably used when the adhesive resin contains an isocyanate-based crosslinking agent. Specifically, it is preferable to use 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, or 6-hydroxyhexyl (meth)acrylate as the vinyl monomer having a hydroxyl group.

The vinyl monomer having a hydroxyl group is preferably used in the range of 0.01% to 1.0% by weight, and more preferably 0.03% to 0.3% by weight, based on the total amount of monomers used to produce the acrylic polymer.

Specific examples of the vinyl monomer having a carboxyl group include (meth)acrylic monomers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, (meth)acrylic acid dimer, crotonic acid, and ethylene oxide-modified succinic acid acrylate. Among these, acrylic acid is preferred.

Specific examples of vinyl having an amide group include (meth)acrylic monomers such as N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, acrylamide, and N,N-dimethylacrylamide.

The highly polar vinyl monomer is preferably used in the range of 1.5% to 20% by weight, more preferably 1.5% to 10% by weight, based on the total amount of monomers used to produce the acrylic polymer, and even more preferably in the range of 2% to 8% by weight, since this allows the formation of an adhesive layer that is well balanced in terms of cohesive strength, retention, and adhesiveness.

The method for producing the acrylic polymer is not particularly limited and can be appropriately selected from known methods depending on the purpose. For example, the monomers are polymerized by a polymerization method such as a solution polymerization method, a bulk polymerization method, a suspension polymerization method, or an emulsion polymerization method. Among these, it is preferable to produce the acrylic polymer by a solution polymerization method or a bulk polymerization method.

During the polymerization, peroxide-based thermal polymerization initiators such as benzoyl peroxide and lauroyl peroxide, azo thermal polymerization initiators such as azobisisobutylnitrile, acetophenone-based photopolymerization initiators, benzoin ether-based photopolymerization initiators, benzyl ketal-based photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzophenone-based photopolymerization initiators, etc. can be used as necessary.

The weight-average molecular weight of the acrylic polymer obtained by the above method is preferably 300,000 to 3,000,000, and more preferably 500,000 to 2,500,000, as measured using gel permeation chromatography (GPC) and converted into standard polystyrene.

Here, the weight average molecular weight of the acrylic polymer is measured by the GPC method using a GPC apparatus (HLC-8329GPC, manufactured by Tosoh Corporation) and is a value converted into standard polystyrene. The measurement conditions are as follows:
[Measurement conditions]
Sample concentration: 0.5 wt% (tetrahydrofuran (THF) solution)
Sample injection volume: 100 μL
Eluent: THF
・Flow rate: 1.0mL/min ・Measurement temperature: 40℃
・ Main column: TSKgel GMHHR-H (20) x 2 ・ Guard column: TSKgel HXL-H
・ Detector: Differential refractometer ・ Standard polystyrene molecular weight: 10,000 to 20 million (Tosoh Corporation)

It is preferable to use an acrylic adhesive resin that contains a tackifier resin in order to improve adhesion to the adherend and surface adhesive strength.

The tackifier resin contained in the acrylic adhesive resin is not particularly limited and can be selected appropriately depending on the purpose, but a softening point of 30°C to 180°C is preferable, and a softening point of 70°C to 140°C is more preferable for forming an adhesive layer with high adhesive performance. When using a (meth)acrylate tackifier resin, the glass transition temperature is preferably 30°C to 200°C, and more preferably 50°C to 160°C.

Specific examples of the tackifier resin contained in the acrylic adhesive resin include rosin-based tackifier resin, polymerized rosin-based tackifier resin, polymerized rosin ester-based tackifier resin, rosin phenol-based tackifier resin, stabilized rosin ester-based tackifier resin, disproportionated rosin ester-based tackifier resin, hydrogenated rosin ester-based tackifier resin, terpene-based tackifier resin, terpene phenol-based tackifier resin, petroleum resin-based tackifier resin, (meth)acrylate-based tackifier resin, etc. These may be used alone or in combination of two or more. Among these, the tackifier resin is preferably polymerized rosin ester-based tackifier resin, rosin phenol-based tackifier resin, disproportionated rosin ester-based tackifier resin, hydrogenated rosin ester-based tackifier resin, terpene phenol-based resin, or (meth)acrylate-based resin.

There are no particular limitations on the amount of the tackifier resin used and it can be selected appropriately depending on the purpose, but it is preferable to use it in the range of 5 to 65 parts by weight per 100 parts by weight of the acrylic polymer, and it is more preferable to use it in the range of 8 to 55 parts by weight because this makes it easier to ensure adhesion to the adherend.

It is preferable to use an acrylic adhesive resin that contains a crosslinking agent in order to further improve the cohesive strength of the adhesive layer.

The crosslinking agent is not particularly limited and can be appropriately selected depending on the purpose. Examples of the crosslinking agent include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, metal chelate-based crosslinking agents, and aziridine-based crosslinking agents. These may be used alone or in combination of two or more. Among these, the crosslinking agent is preferably a type that is mixed after the production of the acrylic polymer and causes a crosslinking reaction, and it is more preferable to use an isocyanate-based crosslinking agent or an epoxy-based crosslinking agent that is highly reactive with the acrylic polymer.

Examples of the isocyanate-based crosslinking agent include tolylene diisocyanate, triphenylmethane isocyanate, naphthylene-1,5-diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, and trimethylolpropane-modified tolylene diisocyanate. These may be used alone or in combination of two or more. Among these, trifunctional polyisocyanate-based compounds such as tolylene diisocyanate and its trimethylolpropane adduct, and triphenylmethane isocyanate are particularly preferred.

As an index of the degree of crosslinking, the gel fraction value obtained by measuring the insoluble portion after immersing the adhesive layer in toluene for 24 hours is used. The gel fraction of the adhesive layer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 10% by weight to 70% by weight, more preferably 25% by weight to 65% by weight, and even more preferably 35% by weight to 60% by weight in order to obtain an adhesive layer with good cohesiveness and adhesiveness.

The gel fraction refers to a value measured by the following method. The adhesive composition containing the adhesive resin and, if necessary, the additives is coated on a release sheet so that the thickness after drying is 50 μm, dried at 100 ° C for 3 minutes, and aged at 40 ° C for 2 days, and cut into 50 mm squares to be used as a sample. Next, the weight (G1) of the sample before immersion in toluene is measured in advance, and the toluene-insoluble portion of the sample after immersion in a toluene solution at 23 ° C for 24 hours is separated by filtering with a 300 mesh wire net, and the weight (G2) of the residue after drying at 110 ° C for 1 hour is measured, and the gel fraction is calculated according to the following formula (4). The weight (G3) of the conductive fine particles in the sample is calculated from the weight (G1) of the sample and the composition of the adhesive composition.
Gel fraction (wt%)=(G2−G3)/(G1−G3)×100 (4)

--Rubber-based adhesive resin--
The rubber-based adhesive resin is not particularly limited, and examples thereof include rubber materials that can generally be used as adhesive resins, such as synthetic rubber-based adhesive resins and natural rubber-based adhesive resins, and those that contain additives such as tackifier resins as necessary.

Examples of the rubber material include block copolymers of polyaromatic vinyl compounds and conjugated diene compounds; styrene-based resins such as styrene-isoprene copolymers, styrene-isoprene-styrene copolymers, styrene-butadiene-styrene copolymers, styrene-ethylene-butylene copolymers, and styrene-ethylene-propylene copolymers. These may be used alone or in combination of two or more. Among these, the styrene-based resins are preferred, and using two or more of the styrene-based resins in combination is more preferred because it can provide the pressure-sensitive adhesive sheet with excellent adhesive properties and holding power, and it is particularly preferred to use the styrene-isoprene copolymer in combination with the styrene-isoprene-styrene copolymer.

The styrene resin may have a single structure, such as a linear structure, a branched structure, or a multi-branched structure, or may be a mixture of different structures. When a styrene resin rich in linear structures is used in the adhesive layer, it can provide the adhesive sheet with excellent adhesive performance. On the other hand, a branched or multi-branched structure in which styrene blocks are arranged at the molecular end can form a pseudo-crosslinked structure and provide excellent cohesive strength, thereby providing high retention. For this reason, it is preferable to use a mixture of the styrene resins according to the required characteristics.

As the styrene-based resin, it is preferable to use one having the structural unit represented by the following chemical formula (1) in the range of 10% by weight to 80% by weight, more preferably 12% by weight to 60% by weight, even more preferably 15% by weight to 40% by weight, and particularly preferably 17% by weight to 35% by weight, based on the total weight of the styrene-based resin. This makes it possible to obtain excellent adhesion and heat resistance.

When the styrene-isoprene copolymer and the styrene-isoprene-styrene copolymer are used in combination as the styrene-based resin, the content of the styrene-isoprene copolymer relative to the total weight of the styrene-isoprene copolymer and the styrene-isoprene-styrene copolymer is preferably 0% by weight to 80% by weight, more preferably 0% by weight to 77% by weight, even more preferably 0% by weight to 75% by weight, and particularly preferably 0% by weight to 70% by weight. When the content of the styrene-isoprene copolymer is within the preferred range, the pressure-sensitive adhesive sheet can achieve both excellent adhesive performance and heat durability.

The styrene-isoprene copolymer preferably has a weight average molecular weight in the range of 10,000 to 800,000, more preferably in the range of 30,000 to 500,000, and even more preferably in the range of 50,000 to 300,000, as measured in terms of standard polystyrene using gel permeation chromatography (GPC). By having the weight average molecular weight of the styrene-isoprene copolymer within the above preferred range, it is possible to ensure heat flowability and compatibility when diluted with a solvent, and therefore it is preferable to obtain an adhesive sheet that has good workability in the manufacturing process and thermal durability.

Here, the weight average molecular weight of the styrene-isoprene copolymer is measured by the GPC method using a GPC apparatus (SC-8020, manufactured by Tosoh Corporation) and is a value converted into standard polystyrene. The measurement conditions are as follows:
[Measurement conditions]
Sample concentration: 0.5% by weight (tetrahydrofuran solution)
Sample injection volume: 100 μL
Eluent: tetrahydrofuran Flow rate: 1.0 mL/min Measurement temperature: 40° C.
・ Main column: TSKgel (registered trademark) GMHHR-H (20) x 2 ・ Guard column: TSKgel HXL-H
・ Detector: Differential refractometer ・ Standard polystyrene molecular weight: 10,000 to 20 million (Tosoh Corporation)

The method for producing the styrene-isoprene copolymer is not particularly limited and can be appropriately selected from conventionally known production methods, such as a method in which a styrene block and an isoprene block are sequentially polymerized by an anionic living polymerization method.

The method for producing the styrene-isoprene-styrene copolymer is not particularly limited and can be appropriately selected from conventionally known production methods. Examples include a method in which a styrene block and an isoprene block are sequentially polymerized by an anionic living polymerization method, and a method in which a block copolymer having a living active end is produced and then reacted with a coupling agent to produce a coupled block copolymer.

The method for producing the mixture of the styrene-isoprene copolymer and the styrene-isoprene-styrene copolymer is not particularly limited and can be appropriately selected from conventionally known production methods, such as a method of mixing the styrene-isoprene copolymer produced by the above method with the styrene-isoprene-styrene copolymer.

As a method for producing a mixture of the styrene-isoprene copolymer and the styrene-isoprene-styrene copolymer, it is also possible to produce them as the mixture simultaneously in one polymerization step.
In a more specific embodiment, the anionic living polymerization method involves first polymerizing a styrene monomer in a polymerization solvent using an anionic polymerization initiator to form a polystyrene block having a living active end. Secondly, polymerizing isoprene from the living active end of the polystyrene block to obtain a styrene-isoprene diblock copolymer having a living active end. Thirdly, reacting a part of the styrene-isoprene diblock copolymer having the living active end with a coupling agent to form a coupled styrene-isoprene-styrene block copolymer. Fourthly, using a polymerization terminator, the living active end of the remaining part of the styrene-isoprene diblock copolymer having the living active end is deactivated to form a styrene-isoprene diblock copolymer.

The tackifier resin contained in the rubber-based adhesive resin is not particularly limited and can be selected appropriately depending on the purpose, but it is preferable to use a tackifier resin with a softening point of 80°C or higher. This makes it possible to obtain an adhesive sheet with excellent initial adhesion and heat durability.

The tackifier resin is preferably a solid at room temperature (23° C.), and specific examples thereof include petroleum resins such as _C5 -based petroleum resins, _C9 -based petroleum resins, C5 _- based/ _C9- based petroleum resins, and alicyclic petroleum resins, as well as polymerized rosin-based resins, terpene-based resins, rosin-based resins, terpene-phenol resins, styrene resins, coumarone-indene resins, xylene resins, and phenol resins. These may be used alone or in combination of two or more. Among these, it is preferable to use a combination of the _C5 -based petroleum resin and the polymerized rosin-based resin as the tackifier resin in order to achieve both even better initial adhesion and heat durability.

The petroleum resin is highly compatible with the structural unit represented by the chemical formula (1) constituting the styrene-based resin, and as a result, the initial adhesive strength and heat durability of the pressure-sensitive adhesive sheet can be further improved.

Examples of the _C5 petroleum resin include Escorez 1202, Escorez 1304, Escorez 1401 (all manufactured by ExxonMobil Corporation), Wingtac 95 (manufactured by The Goodyear Tire & Rubber Company), Quinton K100, Quinton R100, Quinton F100 (all manufactured by Zeon Corporation), Picotac 95, Picopal 100 (manufactured by Rika Hercules Corporation), and the like.

Examples of the _C9 petroleum resins include Nippon Oil Neopolymer L-90, Nippon Oil Neopolymer 120, Nippon Oil Neopolymer 130, Nippon Oil Neopolymer 140, Nippon Oil Neopolymer 150, Nippon Oil Neopolymer 170S, Nippon Oil Neopolymer 160, Nippon Oil Neopolymer E-100, Nippon Oil Neopolymer E-130, Nippon Oil Neopolymer 130S, and Nippon Oil Neopolymer S (all manufactured by JX Nippon Oil & Energy Corporation), Petokol (registered trademark) (manufactured by Tosoh Corporation), and the like.

As the _C5 / _C9 petroleum resin, a copolymer of the _C5 petroleum resin and the _C9 petroleum resin can be used. For example, Escorez 2101 (manufactured by Exxon Mobil Corporation), Quinton G115 (manufactured by Zeon Corporation), Hercotac 1149 (manufactured by Rika Hercules Corporation), etc. can be used.

The alicyclic petroleum resin can be obtained by hydrogenating the _C9 petroleum resin, and examples thereof include Escolez 5300 (manufactured by Exxon Mobil Corporation), Alcon P-100 (manufactured by Arakawa Chemical Industries, Ltd.), and Regalite R101 (manufactured by Rika Hercules Co., Ltd.).

The amount of the tackifier resin used is not particularly limited and can be appropriately selected depending on the purpose, but is preferably used in the range of 0% to 100% by weight, more preferably 0% to 70% by weight, even more preferably 0% to 50% by weight, and particularly preferably 0% to 30% by weight, based on the total amount of the components constituting the rubber-based adhesive resin. By using the tackifier resin within the preferred range, it becomes easier to achieve both excellent elongation at break and thermal durability of the adhesive sheet while increasing the interfacial adhesion between the adhesive layer and the base layer.

The amount of the tackifier resin with a softening point of 80°C or higher used is not particularly limited and can be selected appropriately depending on the purpose, but it is preferably used in the range of 3% by weight to 100% by weight, more preferably 5% by weight to 80% by weight, relative to the total amount of the styrene-based resin, and is particularly preferably used in the range of 5% by weight to 80% by weight, in order to obtain an adhesive sheet that combines even better adhesion and excellent heat durability.

In addition, in order to obtain application properties and initial adhesion in a constant temperature environment, a tackifier resin having a softening point of -5°C or less can be used in combination with a tackifier resin having a softening point of 80°C or more.

There are no particular limitations on the tackifier resin with a softening point of -5°C or less, and it can be appropriately selected from among the known tackifier resins according to the purpose, but it is preferable to use a tackifier resin that is liquid at room temperature.

Specific examples of the tackifier resin having a softening point of -5°C or less include process oil, polyester, liquid rubber such as polybutene, etc. These may be used alone or in combination of two or more. Among these, it is preferable to use polybutene as the tackifier resin having a softening point of -5°C or less in order to achieve even better initial adhesion.

The tackifier resin with a softening point of -5°C or less is preferably used in the range of 0% to 40% by weight, and more preferably in the range of 0% to 30% by weight, based on the total amount of the tackifier resin.

The tackifier resin with a softening point of -5°C or less is preferably used in the range of 0% to 40% by weight relative to the total amount of the styrene-based resin, and more preferably in the range of 0% to 30% by weight, since this improves the initial adhesive strength, allows for good adhesion, and provides sufficient heat durability.

The weight ratio of the tackifier resin having a softening point of 80°C or more to the tackifier resin having a softening point of -5°C or less is not particularly limited and can be appropriately selected depending on the purpose, but it is preferable to use the tackifier resin having a softening point of 80°C or more to the tackifier resin having a softening point of -5°C or less in a range of 5 to 50, expressed as [weight of tackifier resin having a softening point of 80°C or more/weight of tackifier resin having a softening point of -5°C or less], and it is more preferable to use the tackifier resin having a softening point of 80°C or more in a range of 10 to 30, in order to obtain an adhesive sheet that combines excellent initial adhesion and excellent holding power.

The weight ratio of the styrene resin to the tackifier resin is not particularly limited and can be appropriately selected depending on the purpose, but it is preferable to use the styrene resin to the tackifier resin in a range of 0.5 to 10.0, expressed as [styrene resin/tackifier resin], and it is more preferable to use the styrene resin in a range of 0.6 to 9.0, since this can improve the initial adhesive strength and provide excellent heat durability. In addition, it is preferable for the weight ratio [styrene resin/tackifier resin] to be greater than 1, for example, in order to prevent peeling caused by the repulsive force of the adhesive sheet when it is applied to a curved surface of an adherend (repulsion resistance).

-Other ingredients-
The other components in the pressure-sensitive adhesive composition are not particularly limited and can be appropriately selected within a range that does not impair the properties of the pressure-sensitive adhesive sheet, and examples thereof include polymer components other than the pressure-sensitive adhesive resin, filler particles, crosslinking agents, antiaging agents, UV absorbers, fillers, polymerization inhibitors, surface conditioners, antistatic agents, defoamers, viscosity modifiers, light resistance stabilizers, weather resistance stabilizers, heat resistance stabilizers, antioxidants, leveling agents, organic pigments, inorganic pigments, pigment dispersants, plasticizers, softeners, flame retardants, metal deactivators, and other additives. These may be used alone or in combination of two or more. Among these, it is preferable to include the filler particles.
The content of the other components in the pressure-sensitive adhesive layer can be appropriately selected within a range that does not impair the properties of the pressure-sensitive adhesive sheet.

By including the filler particles in the adhesive layer, the filler particles are exposed from the adhesive layer when the adhesive sheet is stretched, which reduces the adhesion area between the adhesive layer and the adherend, and is advantageous in that the adhesive sheet can be easily stretched and peeled off even when the stretching direction is perpendicular to the application surface (adhesive surface) of the adherend.

The type of the filler particles is not particularly limited and can be appropriately selected within a range that does not impair the effects of the present invention. The filler particles may be inorganic filler particles or organic filler particles. These may be used alone or in combination of two or more types.

Specific examples of the inorganic filler particles include aluminum hydroxide, magnesium hydroxide, aluminum oxide, silicon oxide, magnesium oxide, zinc oxide, titanium oxide, zirconium oxide, iron oxide, silicon carbide, boron nitride, aluminum nitride, titanium nitride, silicon nitride, titanium boride, carbon, nickel, copper, aluminum, titanium, gold, silver, zirconium hydroxide, basic magnesium carbonate, dolomite, hydrotalcite, calcium hydroxide, barium hydroxide, tin oxide, tin oxide hydrate, borax, zinc borate, zinc metaborate, barium metaborate, zinc carbonate, magnesium-calcium carbonate, calcium carbonate, barium carbonate, molybdenum oxide, Examples of suitable metals include cerium oxide, antimony oxide, red phosphorus, mica, clay, kaolin, talc, zeolite, wollastonite, smectite, silica (quartz, fumed silica, precipitated silica, silicic anhydride, fused silica, crystalline silica, ultrafine amorphous silica, etc.), potassium titanate, magnesium sulfate, sepiolite, zonolite, aluminum borate, barium sulfate, barium titanate, zirconia, zirconia oxide, cerium, tin, indium, carbon, sulfur, cerium, cobalt, molybdenum, strontium, chromium, barium, lead, tin oxide, indium oxide, diamond, magnesium, platinum, zinc, manganese, stainless steel, and antimony pentoxide. Among these, aluminum hydroxide and nickel are preferred.
The inorganic filler may be surface-treated, such as by silane coupling treatment or stearic acid treatment, in order to improve dispersibility in the adhesive resin.

Specific examples of the organic filler particles include polystyrene-based fillers, benzoguanamine-based fillers, polyethylene-based fillers, polypropylene-based fillers, silicone-based fillers, urea-formaldehyde-based fillers, styrene/methacrylic acid copolymers, fluorine-based fillers, acrylic-based fillers, polycarbonate-based fillers, polyurethane-based fillers, polyamide-based fillers, epoxy resin-based fillers, and thermosetting resin-based hollow fillers.

The shape of the filler particles is not particularly limited and can be appropriately selected depending on the purpose. It may be a regular shape or an irregular shape. Specific examples of the shape of the filler particles include polygonal, cubic, elliptical, spherical, needle-like, flat, and scaly shapes. The filler particles having these shapes may be used alone or in combination of two or more. In addition, the filler particles having these shapes may be aggregated. Among these, the shape of the filler particles is preferably elliptical, spherical, or polygonal. When the filler particles have an elliptical, spherical, or polygonal shape, the adhesive layer has good sliding properties against the adherend when the adhesive sheet is stretched, and the adhesive sheet can be easily stretched and peeled off even when the stretching direction of the adhesive sheet is 90° to the attachment surface of the adherend.

The particle size distribution (D ₉₀ /D ₁₀ ) of the filler particles is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 2.5 to 20, and from the viewpoint of impact resistance, is more preferably 2.5 to 15, and even more preferably 2.5 to 5. When the particle size distribution (D ₉₀ /D ₁₀ ) of the filler particles is within the above-mentioned preferred range, the pressure-sensitive adhesive sheet can be easily stretch-peeled even when the stretch direction of the pressure-sensitive adhesive sheet is 90° to the attachment surface of the adherend, and is not easily torn even when the thickness of the base material of the pressure-sensitive adhesive sheet is thin, and has excellent impact resistance, shear adhesive strength, and split adhesive strength. On the other hand, when the particle size distribution (D ₉₀ /D ₁₀ ) of the filler particles is less than 2.5, the stretch-peeling property when the stretch direction of the pressure-sensitive adhesive sheet is 90° to the attachment surface of the adherend may be impaired, and when it exceeds 20, the adhesive performance such as impact resistance, shear adhesive strength, and split adhesive strength may be impaired.
The particle size distribution (D ₉₀ /D ₁₀ ) of the filler particles can be obtained, for example, by measuring the particle diameter of the filler particles using a measuring device (Microtrac) that uses a laser diffraction scattering method and converting the measured value into a particle size distribution.

The volume average particle diameter of the filler particles is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 3 μm to 25 μm, more preferably 5 μm to 20 μm, and even more preferably 5 μm to 14 μm. When the volume average particle diameter of the filler particles is within the above-mentioned preferred range, the pressure-sensitive adhesive sheet can be easily stretch-peeled even when the stretch direction of the pressure-sensitive adhesive sheet is 90° to the attachment surface of the adherend, and is not easily torn even when the thickness of the base material of the pressure-sensitive adhesive sheet is thin, and has excellent impact resistance, shear adhesive strength, and cleavage adhesive strength. On the other hand, when the volume average particle diameter of the filler particles is less than 3 μm, it may be difficult to stretch-peele the pressure-sensitive adhesive sheet when the stretch direction of the pressure-sensitive adhesive sheet is 90° to the attachment surface of the adherend, and when it exceeds 25 μm, adhesive performance such as impact resistance, shear adhesive strength, and cleavage adhesive strength may be impaired.
The volume average particle size of the filler particles can be measured, for example, by using a measuring device (Microtrac) that uses a laser diffraction scattering method.

The ratio of the volume average particle diameter of the filler particles to the average thickness of the adhesive layer described later is not particularly limited and can be appropriately selected depending on the purpose, but the ratio of the volume average particle diameter of the filler particles to the average thickness of the adhesive layer, expressed as [volume average particle diameter of filler particles/average thickness of adhesive layer], is preferably 5/100 or more, more preferably 5/100 to 95/100, even more preferably 10/100 to 75/100, and particularly preferably 20/100 to 60/100. When the ratio is within the preferred range, the adhesive sheet can be easily stretched and peeled even when the stretch direction of the adhesive sheet is 90° to the attachment surface of the adherend, and the adhesive sheet is not easily torn even when the thickness of the base material of the adhesive sheet is thin. Furthermore, when the ratio is within the particularly preferred range, the adhesive sheet can be easily stretched and peeled even when the stretch direction of the adhesive sheet is 90° to the application surface of the adherend, and is less likely to tear even when the thickness of the base material of the adhesive sheet is thin, and is advantageous in that the adhesive performance such as impact resistance, shear adhesive strength, and cleavage adhesive strength is also superior. On the other hand, when the ratio is less than 5/100, the stretch peelability when the stretch direction of the adhesive sheet is 90° to the application surface of the adherend may be impaired, and when it exceeds 95/100, the adhesive performance such as impact resistance, shear adhesive strength, and cleavage adhesive strength may be impaired.

The content of the filler particles in the adhesive layer is not particularly limited and can be appropriately selected according to the purpose, but is preferably 10 parts by weight to 90 parts by weight, more preferably 15 parts by weight to 50 parts by weight, and even more preferably 20 parts by weight to 40 parts by weight, relative to 100 parts by weight of the adhesive resin. If the content of the filler particles relative to 100 parts by weight of the adhesive resin is less than 10 parts by weight, the adhesive sheet may not be stretched and peeled when the stretch direction of the adhesive sheet is 90° to the attachment surface of the adherend, or the adhesive sheet may tear and the adhesive sheet may not be stretched and cannot be peeled again. If the content of the filler particles relative to 100 parts by weight of the adhesive resin exceeds 90 parts by weight, the adhesive sheet may not be stretched, the adhesive composition may remain on the adherend, impact resistance may be deteriorated, and shear adhesive strength and split adhesive strength may be weakened. On the other hand, when the content of the filler particles is within the preferred range, the adhesive sheet can be easily stretched and peeled even when the stretching direction of the adhesive sheet is 90° to the application surface of the adherend, and the adhesive sheet is less likely to tear even when the base material of the adhesive sheet is thin, and is advantageous in that it has excellent impact resistance, shear adhesive strength, and split adhesive strength.
The content of the filler particles in the pressure-sensitive adhesive layer can be appropriately adjusted when the pressure-sensitive adhesive composition is prepared.

The volume ratio of the filler particles to the total volume of the adhesive layer is not particularly limited and can be appropriately selected according to the purpose, but is preferably 4% to 40%, more preferably 5% to 30%, even more preferably 5% to 20%, and particularly preferably 5% to 15%. If the volume ratio of the filler particles is less than 4%, the adhesive sheet may not be stretched and peeled off when the stretch direction of the adhesive sheet is 90° to the attachment surface of the adherend, or the adhesive sheet may tear and the adhesive sheet may not stretch and cannot be peeled off again. If the volume ratio of the filler particles exceeds 40%, the adhesive sheet may not stretch, the adhesive composition may remain on the adherend, impact resistance may be deteriorated, and the shear adhesive strength and split adhesive strength may be weakened. On the other hand, when the volume ratio of the filler particles is within the preferred range, the adhesive sheet can be easily stretched and peeled even when the stretching direction is 90° to the attachment surface of the adherend, and is advantageous in that it is less likely to tear even when the base material of the adhesive sheet is thin, and has excellent impact resistance, shear adhesive strength, and split adhesive strength.

The volume ratio of the filler particles to the adhesive layer can be calculated from the following formulas (1) to (3).
Weight A (g) of adhesive resin ^*1 /Density A (g/cm ³ ) of adhesive resin ^*1 =Volume A (cm ³ ) of adhesive resin ^*1 Equation (1)
Weight of filler particle B (g)/density of filler particle B (g/cm ³ )=volume of filler particle B (cm ³ ) Equation (2)
Volume B of filler particles (cm ³ )/(Volume A of adhesive resin ^*1 (cm ³ )+Volume B of filler particles (cm ³ ))×100=Volume ratio of filler particles (%) Equation (3)
In the above formulas (1) and (3), the adhesive resin represented by ^*1 may contain other components described in paragraph [0079] below.
The density is a value measured in accordance with JIS Z 8804.

The number of the adhesive layers is not particularly limited and can be appropriately selected depending on the purpose of use, etc. They may be arranged on only one side of the adhesive sheet or on both sides, but it is preferable that they are arranged on both sides.

- Stress of adhesive layer at 25% elongation -
The stress at 25% elongation of the adhesive layer is not particularly limited and can be appropriately selected according to the purpose, but is preferably 0.04 MPa to 0.4 MPa, more preferably 0.05 MPa to 0.1 MPa. When the stress at 25% elongation of the adhesive layer is within the above-mentioned preferred range, the adhesive sheet can have a suitable adhesive strength, and can be relatively easily peeled off even when stretched and peeled. On the other hand, when the stress at 25% elongation of the adhesive layer is less than 0.04 MPa, the adhesive sheet may peel off when a load is applied in the shear direction of the adhesive sheet while fixing hard adherends to each other, and when it exceeds 0.4 MPa, the force required to stretch the adhesive sheet when peeling off the adhesive sheet may be excessive.
The stress of the adhesive layer at 25% elongation refers to a stress value measured when the adhesive layer is punched out into a dumbbell shape having a gauge length of 20 mm and a width of 10 mm, and pulled in the length direction at a tensile speed of 300 mm/min using a Tensilon tensile tester (model: RTF-1210, manufactured by A&D Co., Ltd.) under conditions of a measurement atmosphere of 23°C and 50% RH, and elongated by 25%.

- Adhesive layer breaking stress -
The stress at break of the adhesive layer is not particularly limited and can be appropriately selected according to the purpose, but is preferably 0.5 MPa to 2.1 MPa, more preferably 1.0 MPa to 2.1 MPa. When the stress at break of the adhesive layer is within the preferred range, the adhesive sheet can be prevented from tearing when it is stretched and peeled off, and the load for stretching the adhesive sheet is not excessive, so that the peeling operation is easy. On the other hand, when the stress at break of the adhesive layer is less than 0.5 MPa, the adhesive sheet may tear when it is stretched and peeled off, and when it exceeds 2.1 MPa, when the adhesive sheet is stretched and peeled off again, it may not be stretched sufficiently and cannot be peeled off again. The force required to stretch and deform the adhesive sheet also depends on the thickness of the adhesive sheet. For example, when the adhesive sheet is thick and has a high stress at break, it may not be stretched sufficiently and cannot be peeled off again.
The stress at break of the adhesive layer refers to a stress value measured when the adhesive layer is punched out into a dumbbell shape having a gauge length of 20 mm and a width of 10 mm, and pulled in the length direction at a tensile speed of 300 mm/min using a Tensilon tensile tester (model: RTF-1210, manufactured by A&D Co., Ltd.) under conditions of a measurement atmosphere of 23°C and 50% RH, until the adhesive layer breaks.

- Elongation at break of adhesive layer -
The elongation at break of the adhesive layer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 450% to 1,300%, more preferably 500% to 1,200%, and even more preferably 600% to 1,100%. When the elongation at break of the adhesive layer is within the above-mentioned preferred range, it is possible to achieve both suitable adhesion and removability.
The elongation at break of the adhesive layer refers to a tensile elongation percentage measured when the adhesive layer is punched out into a dumbbell shape having a gauge length of 20 mm and a width of 10 mm, and pulled in the length direction at a tensile speed of 300 mm/min using a Tensilon tensile tester (model: RTF-1210, manufactured by A&D Co., Ltd.) under conditions of a measurement atmosphere of 23°C and 50% RH, and broken.

- Average thickness of adhesive layer -
The average thickness of the adhesive layer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 5 μm to 150 μm, more preferably 20 μm to 120 μm, even more preferably 40 μm to 110 μm, and particularly preferably 50 μm to 100 μm. The "average thickness of the adhesive layer" means the average thickness of the adhesive layer on one side of the adhesive sheet. When the adhesive sheet has the adhesive layer on both sides, the average thickness of the adhesive layer on one side and the average thickness of the adhesive layer on the other side may be the same thickness or may be different thicknesses, but are preferably the same thickness.
In this specification, the "average thickness of the adhesive layer" refers to the average value of thicknesses of a total of 25 points, measured by cutting the adhesive sheet in five places at 100 mm intervals in the length direction and in the width direction, and measuring the total thickness of the adhesive layer at five points at 100 mm intervals in the width direction on each of the cut surfaces using a TH-104 thickness meter for paper and film (manufactured by Tester Sangyo Co., Ltd.).

-Method of forming adhesive layer-
The method for forming the adhesive layer is not particularly limited and may be appropriately selected from known methods depending on the purpose, and examples thereof include a method for forming the adhesive layer on at least one surface of the base layer by a heat press method, a casting method by extrusion molding, a uniaxial stretching method, a sequential secondary stretching method, a simultaneous biaxial stretching method, an inflation method, a tube method, a calendar method, a solution method, etc. Among these, the casting method by extrusion molding and the solution method are preferred.

Examples of the solution method include a method in which a solution containing the pressure-sensitive adhesive composition is applied directly to the base layer using a roll coater or the like, and a method in which the pressure-sensitive adhesive layer is formed on a release sheet and then peeled off for use.

The release sheet is not particularly limited and can be appropriately selected depending on the purpose. Examples of the release sheet include paper such as kraft paper, glassine paper, and wood-free paper; resin films such as polyethylene, polypropylene (biaxially oriented polypropylene (OPP), uniaxially oriented polypropylene (CPP)), and polyethylene terephthalate (PET); laminated paper in which the paper and resin film are laminated together; and paper that has been subjected to a sealing treatment with clay or polyvinyl alcohol and then subjected to a release treatment with silicone resin or the like on one or both sides. These may be used alone or in combination of two or more types.

<<Base layer>>
The base layer is not particularly limited and can be appropriately selected from known materials that can be used in pressure-sensitive adhesive sheets as long as the properties of the pressure-sensitive adhesive sheet are not impaired. It is preferable for the base layer to contain the following base material materials, and may further contain other components as necessary.
The substrate layer may have a single-layer structure, or a multi-layer structure of two, three or more layers.

- Substrate materials -
Examples of the substrate material include styrene-based resins such as styrene-isoprene copolymer, styrene-isoprene-styrene copolymer, styrene-butadiene-styrene copolymer, styrene-ethylene-butylene copolymer, and styrene-ethylene-propylene copolymer; polyurethane resins such as ester-based polyurethane and ether-based polyurethane; polyolefin resins such as polyethylene and polypropylene; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polystyrene; polycarbonate; polymethylpentene; polysulfone; polyether ether ketone; polyether sulfone; polyether imide; polyimide film; fluorine resin; nylon; and acrylic resin. These may be used alone or in combination of two or more, but it is preferable to use two or more.
Among these, the styrene-based resins and the polyurethane resins are preferred because suitable elongation at break and stress at break can be easily obtained, the styrene-based resins are more preferred, and it is particularly preferred to use a styrene-isoprene copolymer and a styrene-isoprene-styrene copolymer in combination.

--Styrene-based resin--
The styrene resin is a resin exhibiting thermoplasticity, and therefore has excellent moldability in extrusion molding, injection molding, etc., and is easy to mold into the substrate layer. Furthermore, the styrene resin is particularly likely to have excellent elongation at break among the group of resins generally called thermoplastic resins, and is therefore suitable for use as the substrate of the pressure-sensitive adhesive sheet.

Therefore, in the substrate material, the proportion of the styrene resin relative to the total resin components is preferably 50% to 100%, more preferably 60% to 100%, even more preferably 65% to 100%, and particularly preferably 70% to 100%. By keeping the proportion of the styrene resin within the above preferred range, a substrate layer with excellent elongation at break and stress at break can be obtained.

The styrene resin may be, for example, a single structure such as a linear structure, a branched structure, or a multi-branched structure, or may be a mixture of different structures. The styrene resin rich in linear structures can provide the base layer with excellent elongation at break. On the other hand, a branched or multi-branched structure in which styrene blocks are arranged at the molecular end can form a pseudo-crosslinked structure and provide excellent cohesive strength. For this reason, it is preferable to use a mixture of the styrene resins according to the required mechanical properties.

As the styrene-based resin, it is preferable to use one having the structural unit represented by the chemical formula (1) in the range of 13% by weight to 60% by weight, more preferably 15% by weight to 50% by weight, even more preferably 15% by weight to 45% by weight, and particularly preferably 15% by weight to 35% by weight, relative to the total weight of the styrene-based resin. When the proportion of the structural unit represented by the following chemical formula (1) relative to the total weight of the styrene-based resin is within the above-mentioned preferred range, it becomes easier to obtain the elongation at break and the stress at break in a suitable range.

When the styrene-isoprene copolymer and the styrene-isoprene-styrene copolymer are used in combination as the styrene-based resin, the content of the styrene-isoprene copolymer relative to the total weight of the styrene-isoprene copolymer and the styrene-isoprene-styrene copolymer is preferably 0% by weight to 80% by weight, more preferably 0% by weight to 70% by weight, even more preferably 0% by weight to 50% by weight, and particularly preferably 0% by weight to 30% by weight. When the content of the styrene-isoprene copolymer is within the above-mentioned preferred range, it is possible to achieve both excellent thermal durability while maintaining excellent elongation at break and stress at break.

The styrene-isoprene copolymer preferably has a weight average molecular weight measured in terms of standard polystyrene using gel permeation chromatography (GPC) in the range of 10,000 to 800,000, more preferably in the range of 30,000 to 500,000, and even more preferably in the range of 50,000 to 300,000. When the weight average molecular weight of the styrene-isoprene copolymer is within the preferred range, it is possible to ensure heat flowability and compatibility when diluted with a solvent, and therefore it is preferable that the base layer having good workability in the production process and heat durability can be obtained.
The weight average molecular weight of the styrene-isoprene copolymer is measured by the GPC method in the same manner as described in the section "--Rubber-based pressure-sensitive adhesive resin--."

The method for producing the styrene-isoprene copolymer, the styrene-isoprene-styrene copolymer, and the mixture of the styrene-isoprene copolymer and the styrene-isoprene-styrene copolymer is not particularly limited and can be appropriately selected from conventionally known production methods, such as the same methods as those described in the "-Rubber-based adhesive resin-" section above.

--Polyurethane resin--
The polyurethane resin is not particularly limited and may be appropriately selected depending on the purpose, but preferably has a softening point of 40° C. or higher, and more preferably has a softening point of 50° C. or higher. The upper limit of the softening point is preferably 100° C. or lower. The softening point refers to a value measured in accordance with JIS K 2207 (dry bulb method) (the same applies to the softening point below).

As the polyurethane resin, a reaction product of polyol (b1-1) and polyisocyanate (b1-2) can be preferably used.

The polyol (b1-1) is not particularly limited and can be appropriately selected depending on the purpose. Examples include polyester polyol, polyether polyol, polycarbonate polyol, and acrylic polyol. These may be used alone or in combination of two or more. Among these, polyester polyol and polyether polyol are preferred as the polyol (b1-1) because they can provide the mechanical properties of the base layer. When heat resistance is required in the base layer, it is preferred to use polyester polyol, and when water resistance and biodegradability are required, it is preferred to use polyether polyol.

Examples of the polyester polyol include polyesters obtained by an esterification reaction between a low molecular weight polyol and a polycarboxylic acid, polyesters obtained by a ring-opening polymerization reaction of a cyclic ester compound such as ε-caprolactone, and copolymer polyesters of these.

Examples of the low molecular weight polyol that can be used to produce the polyester polyol include aliphatic alkylene glycols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, neopentyl glycol, and 1,3-butanediol, which have a weight average molecular weight of approximately 50 to 300, and cyclohexanedimethanol.

Examples of the polycarboxylic acid include aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and dodecanedicarboxylic acid; aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, and naphthalenedicarboxylic acid; and anhydrides or esters thereof.

Examples of the polyether polyol include those obtained by addition polymerization of alkylene oxide using one or more compounds having two or more active hydrogen atoms as an initiator.

The polycarbonate polyol may be, for example, one obtained by reacting a carbonate ester and/or phosgene with a low molecular weight polyol described below.

Examples of the carbonate ester include methyl carbonate, dimethyl carbonate, ethyl carbonate, diethyl carbonate, cyclocarbonate, and diphenyl carbonate.

Examples of low molecular weight polyols that can be used in the production of the polycarbonate polyol and that can react with the carbonate ester and/or phosgene include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,5-hexanediol, 1,6-hexanediol, 2,5-hexanediol, Examples include 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 2-butyl-2-ethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2-methyl-1,8-octanediol, 1,4-cyclohexanedimethanol, hydroquinone, resorcinol, bisphenol A, bisphenol F, and 4,4'-biphenol.

The polyisocyanate (b1-2) is not particularly limited and can be appropriately selected depending on the purpose. For example, alicyclic polyisocyanates, aliphatic polyisocyanates, aromatic polyisocyanates, etc. can be used, and examples thereof include alicyclic polyisocyanates. These may be used alone or in combination of two or more types.

Examples of the alicyclic polyisocyanate include isophorone diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, 4,4'-dicyclohexylmethane diisocyanate, 2,4-methylcyclohexane diisocyanate, 2,6-methylcyclohexane diisocyanate, cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, bis(2-isocyanatoethyl)-4-cyclohexylene-1,2-dicarboxylate, 2,5-norbornane diisocyanate, 2,6-norbornane diisocyanate, dimer acid diisocyanate, and bicycloheptane triisocyanate. These may be used alone or in combination of two or more.

The method for producing the polyurethane resin (b1) by reacting the polyol (b1-1) with the polyisocyanate (b1-2) is not particularly limited and can be appropriately selected from conventionally known production methods. For example, the polyol (b1-1) charged in a reaction vessel is heated under normal or reduced pressure conditions to remove moisture, and then the polyisocyanate (b1-2) is supplied in one portion or in portions to react.

The reaction between the polyol (b1-1) and the polyisocyanate (b1-2) is preferably carried out when the equivalent ratio (NCO/OH equivalent ratio) of the isocyanate group (NCO) of the polyisocyanate (b1-2) to the hydroxyl group (OH) of the polyol (b1-1) is in the range of 1.0 to 20.0, more preferably in the range of 1.1 to 13.0, even more preferably in the range of 1.2 to 5.0, and particularly preferably in the range of 1.5 to 3.0.

The reaction conditions for the polyol (b1-1) and the polyisocyanate (b1-2) are not particularly limited and can be appropriately selected taking into consideration various conditions such as safety, quality, and cost, but the reaction temperature is preferably 70°C to 120°C, and the reaction time is preferably 30 minutes to 5 hours.

When reacting the polyol (b1-1) with the polyisocyanate (b1-2), a catalyst such as a tertiary amine catalyst or an organometallic catalyst can be used as necessary.

The reaction may be carried out in a solvent-free environment or in the presence of an organic solvent.
The organic solvent is not particularly limited and may be appropriately selected depending on the purpose, and examples thereof include ester-based solvents such as methyl acetate, ethyl acetate, propyl acetate, and butyl acetate; ketone-based solvents such as acetone, methyl ethyl ketone, methyl butyl ketone, and cyclohexanone; ether ester-based solvents such as methyl cellosolve acetate and butyl cellosolve acetate; aromatic hydrocarbon-based solvents such as toluene and xylene; and amide-based solvents such as dimethylformamide and dimethylacetamide. These may be used alone or in combination of two or more.
The organic solvent may be removed during the production of the polyurethane resin (b1) or after the production of the polyurethane (b1) by a suitable method such as heating under reduced pressure or drying at normal pressure.

--Other ingredients--
The other components in the substrate layer are not particularly limited and may be appropriately selected within a range that does not impair the properties of the pressure-sensitive adhesive sheet, and examples thereof include tackifier resins; polymer components other than the substrate material; crosslinking agents, antiaging agents, UV absorbers, fillers, polymerization inhibitors, surface conditioners, antistatic agents, defoamers, viscosity modifiers, light resistance stabilizers, weather resistance stabilizers, heat resistance stabilizers, antioxidants, leveling agents, organic pigments, inorganic pigments, pigment dispersants, silica beads, organic beads, and other additives; inorganic fillers such as silicon oxide, aluminum oxide, titanium oxide, zirconia, and antimony pentoxide. These may be used alone or in combination of two or more.
The content of the other components in the base layer can be appropriately selected within a range that does not impair the properties of the pressure-sensitive adhesive sheet.

The tackifier resin can be used to increase the adhesion between the adhesive layer and the base layer in the adhesive sheet and to increase heat resistance.

The tackifier resin is not particularly limited and can be selected appropriately depending on the purpose, but it is preferable that the softening point is 80°C or higher, more preferably 90°C or higher, even more preferably 100°C or higher, and particularly preferably 110°C or higher.

As the tackifier resin, for example, those described in the "Rubber-based adhesive resin" section above can be used, and the preferred aspects are the same.

The antiaging agent is not particularly limited and can be appropriately selected from known ones according to the purpose. Examples of such agents include phenol-based antiaging agents, phosphorus-based antiaging agents (sometimes called "processing stabilizers"), amine-based antiaging agents, and imidazole-based antiaging agents. These agents may be used alone or in combination of two or more. Among these, the phenol-based antiaging agents and phosphorus-based antiaging agents are preferred, and using these agents in combination is preferred because it can effectively improve the heat resistance stability of the substrate material, thereby maintaining good initial adhesion and providing an adhesive sheet with even better heat durability. In addition, since the phosphorus-based antiaging agent may slightly discolor (yellowing) over time in a high-temperature environment, it is preferable to appropriately set the amount of the agent to be used in consideration of the balance between the initial adhesion, heat durability, and discoloration prevention.

As the phenol-based antiaging agent, a phenol-based compound having a steric hindering group can generally be used, and monophenol type, bisphenol type, and polyphenol type are representative. Specific examples include 2,6-di-t-butyl-4-methylphenol, 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-thiobis(6-t-butyl-3-methylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), tetrakis-[methylene-3-(3'5'-di-t-butyl-4-hydroxyphenyl)propionate]methane, and n-octadecyl-3-(4'-hydroxy-3'5'-di-t-butylphenyl)propionate. These may be used alone or in combination of two or more.

The amount of the phenol-based anti-aging agent used is not particularly limited and can be selected appropriately depending on the purpose, but it is preferable to use it in the range of 0.1 parts by weight to 5 parts by weight per 100 parts by weight of the base material. Using it in the range of 0.5 parts by weight to 3 parts by weight can effectively improve the heat resistance stability of the base material, and as a result, it is possible to obtain an adhesive sheet that maintains good initial adhesion and has even better heat durability.

- Stress of the base layer at 25% elongation -
The stress at 25% elongation of the base layer is not particularly limited and can be appropriately selected according to the purpose, but is preferably 0.2 MPa to 10.0 MPa, more preferably 0.2 MPa to 5.0 MPa, even more preferably 0.2 MPa to 3.0 MPa, and particularly preferably 0.2 MPa to 2.0 MPa. When the stress at 25% elongation of the base layer is within the above-mentioned preferred range, the adhesive sheet can have a suitable adhesive strength, and can be relatively easily peeled off even when stretched and peeled. On the other hand, when the stress at 25% elongation of the base layer is less than 0.2 MPa, the adhesive sheet may peel off when a load is applied in the shear direction of the adhesive sheet while fixing hard adherends to each other, and when it exceeds 10.0 MPa, the force required to stretch the adhesive sheet when peeling off the adhesive sheet may be excessive.
The stress of the base material layer at 25% elongation refers to a stress value measured when the base material layer is punched out into a dumbbell shape having a gauge length of 20 mm and a width of 6 mm, and pulled in the longitudinal direction at a tensile speed of 500 mm/min using a Tensilon tensile tester (model: RTF-1210, manufactured by A&D Co., Ltd.) under conditions of a measurement atmosphere of 23° C. and 50% RH, and elongated by 25%.

- Breaking stress of base layer -
The stress at break of the base layer is not particularly limited and can be appropriately selected according to the purpose, but is preferably 1.5 MPa to 100.0 MPa, more preferably 7.0 MPa to 50.0 MPa, even more preferably 7.0 MPa to 40.0 MPa, and particularly preferably 8.0 MPa to 35.0 MPa. When the stress at break of the base layer is within the above-mentioned preferred range, the adhesive sheet can be prevented from tearing even when it is stretched and peeled off, and the load for stretching the adhesive sheet is not excessive, so that the peeling operation is easy. On the other hand, when the stress at break of the base layer is less than 1.5 MPa, the adhesive sheet may tear when it is stretched and peeled off, and when it exceeds 100.0 MPa, when the adhesive sheet is stretched and peeled off again, it may not be stretched sufficiently and cannot be peeled off again. The force required to stretch and deform the adhesive sheet also depends on the thickness of the adhesive sheet. For example, when attempting to stretch and re-peel an adhesive sheet that is thick and has a high breaking stress, it may not be possible to stretch it sufficiently and it may not be possible to re-peel it.
The stress at break of the base material layer refers to a stress value measured when the base material layer is punched out into a dumbbell shape having a gauge length of 20 mm and a width of 6 mm, and pulled in the longitudinal direction at a tensile speed of 500 mm/min using a Tensilon tensile tester (model: RTF-1210, manufactured by A&D Co., Ltd.) under conditions of a measurement atmosphere of 23° C. and 50% RH, until the layer breaks.

-Elongation at break of base layer-
The elongation at break of the base layer is not particularly limited and can be appropriately selected according to the purpose, but is preferably 200% to 1,300%, more preferably 400% to 1,300%, and even more preferably 700% to 1,300%. When the elongation at break of the base layer is 200% or more, even if the pressure-sensitive adhesive sheet is firmly attached to the adherend, the stress for stretching the pressure-sensitive adhesive sheet in the horizontal to vertical direction relative to the adhesion surface of the adherend is not too large when the pressure-sensitive adhesive sheet is re-peeled, and the pressure-sensitive adhesive sheet can be easily peeled off without excessive stretching when peeled off. In addition, when the elongation at break is 1,300% or less, the stretching distance in the horizontal to vertical direction relative to the adhesion surface of the adherend is not too long when the pressure-sensitive adhesive sheet is re-peeled, and work can be done in a small space. On the other hand, if the elongation at break is less than 200%, when the pressure-sensitive adhesive sheet is peeled off again, it may break when stretched in the horizontal to vertical direction relative to the application surface of the adherend, and the sheet may not be able to be peeled off. On the other hand, if the elongation at break is more than 1,300%, when the pressure-sensitive adhesive sheet is peeled off again, the stretching distance in the horizontal to vertical direction relative to the application surface of the adherend becomes too long, resulting in poor workability.
The elongation at break of the base material layer refers to a tensile elongation percentage measured when the base material layer was punched out into a dumbbell shape having a gauge length of 20 mm and a width of 6 mm, and pulled in the length direction at a tensile speed of 500 mm/min using a Tensilon tensile tester (model: RTF-1210, manufactured by A & D Co., Ltd.) under conditions of a measurement atmosphere of 23°C and 50% RH, and broken.

--Average thickness of base layer--
The average thickness of the base layer is not particularly limited and can be appropriately selected depending on the purpose of use, etc., but is preferably 10 μm to 500 μm, more preferably 10 μm to 300 μm, even more preferably 20 μm to 200 μm, and particularly preferably 20 μm to 100 μm. When the average thickness of the base layer is within the preferred range, the pressure-sensitive adhesive sheet is likely to follow the distortion of the adherend and is likely to obtain high adhesive strength, and the pressure-sensitive adhesive sheet having the base layer is preferably not too high when being peeled off again while being stretched in the horizontal to vertical direction relative to the application surface of the adherend.
In this specification, the "average thickness of the base material layer" refers to the average value of thicknesses of a total of 25 points obtained by cutting the base material layer at 5 points at 100 mm intervals in the longitudinal direction, in a direction perpendicular to the longitudinal direction (sometimes referred to as the width direction), and measuring the thickness at 5 points at 100 mm intervals in the width direction on each of the cut surfaces using a TH-104 thickness measuring instrument for paper and film (manufactured by Tester Sangyo Co., Ltd.).

--Average thickness of adhesive layer/average thickness of base layer--
The thickness ratio between the adhesive layer and the base layer is not particularly limited and can be appropriately selected according to the purpose, but the ratio of the average thickness of the adhesive layer to the average thickness of the base layer, expressed as [average thickness of adhesive layer/average thickness of base layer], is preferably 1/5 to 5/1, more preferably 1/3 to 3/1, and even more preferably 1/1 to 2/1. When the ratio of the average thickness of the adhesive layer to the average thickness of the base layer is within the preferred range, the adhesive sheet can have excellent adhesion and removability. On the other hand, when the ratio is greater than 5/1, there is a possibility that only the adhesive layer will remain on the adherend in the re-peeling process of the adhesive sheet. In addition, when the ratio is less than 1/5, there is a concern that the adhesive layer will not be able to follow the uneven surface of the adherend, and the adhesive strength will be significantly reduced.

-Method of forming substrate layer-
The method for forming the base layer is not particularly limited, and can be appropriately selected from known methods according to the mechanical strength required for the pressure-sensitive adhesive sheet, and examples thereof include heat press method, extrusion casting method, uniaxial stretching method, sequential secondary stretching method, simultaneous biaxial stretching method, inflation method, tube method, calendar method, and solution method. These methods may be used alone or in combination of two or more. Among these, the extrusion casting method, inflation method, tube method, calendar method, and solution method are preferred in terms of imparting suitable flexibility and extensibility to the base layer.

The base layer may be subjected to a surface treatment in order to further improve the adhesion to the adhesive layer.
The surface treatment method is not particularly limited and can be appropriately selected from known methods as long as it does not impair the properties of the adhesive sheet. Examples of the surface treatment method include sandblasting, surface polishing/rubbing, corona discharge treatment, chromic acid treatment, flame treatment, hot air treatment, ozone treatment, ultraviolet irradiation treatment, and oxidation treatment.

<<Other layers>>
The other layers in the pressure-sensitive adhesive sheet are not particularly limited and can be appropriately selected depending on the purpose. Examples of the other layers include a primer layer, an antistatic layer, a nonflammable layer, a decorative layer, a conductive layer, a heat conductive layer, and a release layer.

- Stress of adhesive sheet at 25% elongation -
The stress of the pressure-sensitive adhesive sheet at 25% elongation is not particularly limited and can be appropriately selected according to the purpose, but is preferably 0.15 Mpa to 82 Mpa, more preferably 0.15 Mpa to 10 Mpa, even more preferably 0.15 Mpa to 5 Mpa, and particularly preferably 0.15 Mpa to 2 Mpa. When the stress of the pressure-sensitive adhesive sheet at 25% elongation is 0.15 Mpa to 82 Mpa, the pressure-sensitive adhesive sheet can have a suitable adhesive strength, and can be relatively easily peeled off even when stretched and peeled. On the other hand, when the stress of the pressure-sensitive adhesive sheet at 25% elongation is less than 0.15 Mpa, the pressure-sensitive adhesive sheet may peel off when a load is applied in the shear direction of the pressure-sensitive adhesive sheet while fixing hard adherends to each other. In addition, when the stress of the pressure-sensitive adhesive sheet at 25% elongation exceeds 82 Mpa, the force required to stretch the pressure-sensitive adhesive sheet when peeling off the pressure-sensitive adhesive sheet may become excessive.
The stress of the pressure-sensitive adhesive sheet at 25% elongation refers to a stress value measured when the pressure-sensitive adhesive sheet is punched out into a dumbbell shape having a gauge length of 20 mm and a width of 6 mm, and pulled in the length direction at a tensile speed of 500 mm/min using a Tensilon tensile tester (model: RTF-1210, manufactured by A&D Co., Ltd.) under conditions of a measurement atmosphere of 23°C and 50% RH, and elongated by 25%.

- Adhesive sheet breaking stress -
The stress at break of the pressure-sensitive adhesive sheet is not particularly limited and can be appropriately selected according to the purpose, but is preferably 1.5 MPa to 100.0 MPa, more preferably 5.0 MPa to 50.0 MPa, even more preferably 5.0 MPa to 40.0 MPa, and particularly preferably 5.0 MPa to 35.0 MPa. When the stress at break of the pressure-sensitive adhesive sheet is within the preferred range, the pressure-sensitive adhesive sheet can be prevented from tearing even when it is stretched and peeled off, and the load for stretching the pressure-sensitive adhesive sheet does not become excessive, making it easy to peel off again by peeling. On the other hand, when the stress at break of the pressure-sensitive adhesive sheet is less than 1.5 MPa, the pressure-sensitive adhesive sheet may tear when it is stretched and peeled off, and when it exceeds 100.0 MPa, when the pressure-sensitive adhesive sheet is stretched and peeled off again, it may not be stretched sufficiently and may not be peeled off again. The force required to stretch and deform the adhesive sheet also depends on the thickness of the adhesive sheet. For example, when attempting to stretch and re-peel an adhesive sheet that is thick and has a high breaking stress, it may not be possible to stretch it sufficiently and it may not be possible to re-peel it.
The stress at break of the pressure-sensitive adhesive sheet refers to the stress value measured when the pressure-sensitive adhesive sheet is punched out into a dumbbell shape having a gauge length of 20 mm and a width of 6 mm, and pulled in the length direction at a tensile speed of 500 mm/min using a Tensilon tensile tester (model: RTF-1210, manufactured by A&D Co., Ltd.) under conditions of a measurement atmosphere of 23°C and 50% RH, until the sheet breaks.

- Elongation at break of adhesive sheet -
The elongation at break of the pressure-sensitive adhesive sheet is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 500% to 2,000%, more preferably 600% to 1,800%, and even more preferably 800% to 1,800%. When the elongation at break of the pressure-sensitive adhesive sheet is 500% or more, even if the pressure-sensitive adhesive sheet is firmly attached to the adherend, the stress for stretching the pressure-sensitive adhesive sheet in the horizontal to vertical direction relative to the adhesion surface of the adherend is not too large when the pressure-sensitive adhesive sheet is re-peeled, and the pressure-sensitive adhesive sheet can be easily peeled off without excessive stretching when peeled off. In addition, when the elongation at break is 2,000% or less, the stretching distance in the horizontal to vertical direction relative to the adhesion surface of the adherend is not too long when the pressure-sensitive adhesive sheet is re-peeled, and work can be done in a small space. On the other hand, if the elongation at break is less than 500%, when the pressure-sensitive adhesive sheet is peeled off again, it may break when stretched in the horizontal to vertical direction relative to the application surface of the adherend, and the sheet may not be able to be peeled off. If the elongation at break is more than 1,300%, when the pressure-sensitive adhesive sheet is peeled off again, the stretching distance in the horizontal to vertical direction relative to the application surface of the adherend becomes too long, resulting in poor workability.
The elongation at break of the pressure-sensitive adhesive sheet refers to the tensile elongation measured when the pressure-sensitive adhesive sheet was punched out into a dumbbell shape having a gauge length of 20 mm and a width of 6 mm, and pulled in the length direction at a tensile speed of 500 mm/min using a Tensilon tensile tester (model: RTF-1210, manufactured by A&D Co., Ltd.) under conditions of a measurement atmosphere of 23°C and 50% RH, until the sheet broke.

- Impact resistance of adhesive sheets -
The pressure-sensitive adhesive sheet has excellent impact resistance. The impact resistance can be confirmed, for example, by the method described in the Examples below under "Evaluation of Impact Resistance". In the evaluation of impact resistance, the height of the impact point at which the pressure-sensitive adhesive sheet peels off or breaks can be appropriately selected within a range that does not impair the effects of the present invention, but is preferably 30 cm or more, more preferably 40 cm or more, even more preferably 50 cm or more, and particularly preferably 60 cm or more. If the height is less than 30 cm, sufficient impact resistance cannot be obtained.

- 180° peel adhesive strength of adhesive sheet -
The 180° peel adhesive strength of the pressure-sensitive adhesive sheet is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 3 N/20 mm to 35 N/20 mm, more preferably 4 N/20 mm to 30 N/20 mm, and even more preferably 5 N/20 mm to 25 N/20 mm. When the 180° peel adhesive strength is within the above-mentioned preferred range, the pressure-sensitive adhesive sheet has a moderate adhesive strength without causing peeling or slippage from the adherend, and can be easily peeled off when stretched horizontally to vertically relative to the application surface of the adherend and then peeled off again.
The 180° peel adhesive strength of the pressure-sensitive adhesive sheet refers to a value measured in accordance with JIS Z 0237.

-Shear adhesive strength of adhesive sheet-
The pressure-sensitive adhesive sheet is not easily peeled off even when a load is applied in the shear direction of the pressure-sensitive adhesive sheet, and has excellent shear adhesive strength. The shear direction is not particularly limited as long as it is perpendicular to the thickness direction of the pressure-sensitive adhesive sheet.
The shear adhesive strength of the pressure-sensitive adhesive sheet can be appropriately selected within a range that does not impair the effects of the present invention, but is preferably 100 N/4 cm ² or more, more preferably 120 N/4 cm ² or more, even more preferably 150 N/4 cm ² or more, and particularly preferably 200 N/4 cm ² or more. When the shear adhesive strength is within the preferred range, it is possible to suppress displacement when a stress in the shear direction is applied to the adherend fixed by the pressure-sensitive adhesive sheet.
The shear adhesive strength of the pressure-sensitive adhesive sheet can be confirmed, for example, by the method described in <<Measurement of Shear Adhesive Strength>> in the Examples described below.

- Splitting adhesive strength of adhesive sheet -
The pressure-sensitive adhesive sheet is resistant to peeling even when a load is applied in the cleavage direction (sometimes referred to as the "thickness direction") of the pressure-sensitive adhesive sheet, and has excellent cleavage adhesive strength. The cleavage adhesive strength of the pressure-sensitive adhesive sheet can be appropriately selected within a range that does not impair the effects of the present invention, and is preferably 80 N/4 cm2 ^{or more} , more preferably 100 N/4 cm2 or ^more , and even more preferably 120 N/4 cm2 or ^more . When the cleavage adhesive strength is within the preferred range, peeling can be suppressed when a stress in the cleavage direction is applied to an adherend fixed by the pressure-sensitive adhesive sheet.
The cleavage adhesive strength of the pressure-sensitive adhesive sheet can be confirmed, for example, by the method described in <<Measurement of cleavage adhesive strength>>> in the examples described below.

- Average thickness of adhesive sheet -
The average thickness of the pressure-sensitive adhesive sheet is not particularly limited and can be appropriately selected depending on the average thickness of the pressure-sensitive adhesive layer and the base layer, but is preferably 15 μm to 800 μm, more preferably 30 μm to 540 μm, even more preferably 60 μm to 320 μm, and particularly preferably 70 μm to 250 μm.
In this specification, the "average thickness of the adhesive layer" refers to the average value of thicknesses of a total of 25 points, obtained by cutting the adhesive sheet at 5 points at 100 mm intervals in the length direction and at 5 points at 100 mm intervals in the width direction on each cut surface, and measuring the thickness of the adhesive layer at 5 points at 100 mm intervals in the width direction on each cut surface using a TH-104 thickness meter for paper and film (manufactured by Tester Sangyo Co., Ltd.).

- Average width of adhesive sheet -
The average width of the pressure-sensitive adhesive sheet is not particularly limited and can be appropriately selected depending on the type of electronic component. When the electronic components to be attached are displays, speakers, batteries, etc., and these are fixed, the average width of the pressure-sensitive adhesive sheet can be appropriately adjusted according to the availability of the display screen and the attachment space, but is preferably 1 mm to 50 mm, more preferably 1 mm to 25 mm, and even more preferably 0.5 mm to 10 mm.
In this specification, the "average width of the adhesive sheet" refers to the average value of the widths of the adhesive sheet measured at five points at intervals of 100 mm in the longitudinal direction using a known measuring instrument such as a straight ruler, tape measure, or convex.

<<Method of manufacturing pressure-sensitive adhesive sheet>>
The method for producing the pressure-sensitive adhesive sheet is not particularly limited and can be appropriately selected from known methods, but preferably includes a pressure-sensitive adhesive layer forming step, a base layer forming step, and a lamination step, and further includes other layer forming steps as necessary. The pressure-sensitive adhesive sheet can also be produced by a multi-layer simultaneous formation step in which the pressure-sensitive adhesive layer forming step and the base layer forming step are performed simultaneously.

- Adhesive layer forming process -
The adhesive layer forming step is not particularly limited as long as it is capable of forming the adhesive layer, and can be appropriately selected depending on the purpose. For example, the adhesive layer forming step may be a method similar to the method described in the "Method of forming an adhesive layer" above, and the preferred aspects are also the same.

--Base layer forming process--
The base layer forming step is not particularly limited as long as it can form the base layer, and can be appropriately selected depending on the purpose. For example, the base layer forming step may be a method similar to the method described in the "Base layer forming method" above, and preferred aspects are also similar.

-Lamination process-
The lamination step is a step of laminating the base material layer and the adhesive layer. The method of laminating the base material layer and the adhesive layer is not particularly limited and can be appropriately selected from known methods, for example, a method of laminating the base material layer and the adhesive layer by applying pressure.

<Electronic component manufacturing method>
The method for producing the electronic component is not particularly limited and may be appropriately selected depending on the purpose, but preferably includes an attachment step and a fixing step, and further includes other steps as necessary.

<<Attachment process>>
The attaching step is a step of attaching one surface of the pressure-sensitive adhesive sheet to a first attachment object so that at least a portion of the surface is linear.
The pressure-sensitive adhesive sheet, the first attachment object, and the mode of attachment so that at least a portion of the sheet is linear are as described above.

<<Fixation process>>
The fixing process is a process of attaching the other surface of the adhesive sheet to a second object to be attached, and attaching the adhesive sheet to the second object to be attached with at least two ends of the adhesive sheet exposed from the second object to be attached.
The second attachment target and the state in which at least two ends are exposed from the second attachment target are as described above.

The electronic components can be quickly peeled off, are not contaminated by the adhesive after peeling, and even if they tear while being stretched and peeled off from one end, they can be stretched and peeled off from the other end to the end, and since they have an adhesive sheet with suitable adhesive strength when in use, they can be used as a wide range of electronic components, regardless of the size of the electronic components, such as large electronic devices such as flat-screen televisions, home appliances, and office equipment, and the components that make up these devices, as well as small electronic devices such as mobile electronic terminals, cameras, and personal computers, and the components that make up these devices.

The present invention will be specifically explained below using test examples, but the present invention is not limited to these examples.

In the production of the adhesive sheets (1) to (11) in the following Production Examples 1 to 11, the following resin compositions (1) to (3) in the base layer and adhesive compositions (1) to (8) in the adhesive layer were used.

<Resin composition (1)>
The resin composition (1) is a mixture of a styrene-isoprene copolymer and a styrene-isoprene-styrene copolymer (hereinafter, sometimes referred to as "SIS"), and is represented by the following chemical formula (1): The resin composition (1) used contained 25% by weight of structural units derived from styrene and contained 17% by weight of a styrene-isoprene copolymer based on the total amount of the resin composition (1).

<Resin composition (2)>
As the resin composition (2), an ester-based polyurethane compound (Mobilon Film MF100T, manufactured by Nisshinbo Textile Inc.) was used.

<Resin composition (3)>
The resin composition (3) is a mixture of a styrene-isoprene copolymer and a styrene-isoprene-styrene copolymer (SIS), which contains 15% by weight of the styrene-derived structural unit represented by the chemical formula (1). The resin composition (3) used had a styrene-isoprene copolymer content of 12% by weight based on the total weight of the resin composition (3).

(Preparation Example 1: Preparation of Pressure-Sensitive Adhesive Composition (1))
In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, and a dropping funnel, 75.94 parts by weight of n-butyl acrylate, 5 parts by weight of 2-ethylhexyl acrylate, 15 parts by weight of cyclohexyl acrylate, 4 parts by weight of acrylic acid, 0.06 parts by weight of 4-hydroxybutyl acrylate, and 200 parts by weight of ethyl acetate were charged, and the mixture was heated to 65° C. while blowing in nitrogen under stirring to obtain a mixture (1). Next, 4 parts by weight of a 2,2′-azobisisobutyronitrile solution (solid content 2.5% by weight) previously dissolved in ethyl acetate was added to the mixture (1), and the mixture was held at 65° C. for 10 hours under stirring to obtain a mixture (2). Next, the mixture (2) was diluted with 98 parts by weight of ethyl acetate and filtered through a 200-mesh wire net to obtain an acrylic copolymer solution (1) having a weight average molecular weight of 1.6 million (polystyrene equivalent). Next, 100 parts by weight of the acrylic copolymer solution (1) were mixed and stirred with 5 parts by weight of a polymerized rosin ester tackifier resin (D-125, Arakawa Chemical Industries Co., Ltd.) and 15 parts by weight of a petroleum tackifier resin (FTR (registered trademark) 6125, manufactured by Mitsui Chemicals, Inc.), and then ethyl acetate was added to obtain a 31 wt% adhesive resin solution (1). Next, 1 part by weight of carbon black (MA220, manufactured by Mitsubishi Chemical Co., Ltd.) and 1.3 parts by weight of a crosslinking agent (Burnoc D-40, manufactured by DIC Corporation; trimethylolpropane adduct of tolylene diisocyanate, isocyanate group content 7 wt%, non-volatile content 40 wt%) were added to 100 parts by weight of the adhesive resin solution (1), and the mixture was stirred and mixed uniformly, followed by filtration through a 100 mesh wire net to obtain a 31.1 wt% adhesive resin (1).

(Preparation Example 2: Preparation of Pressure-Sensitive Adhesive Composition (2))
To 100 parts by weight of the solid content of the adhesive resin (1) obtained in Preparation Example 1, 30 parts by weight of filler 1 (aluminum hydroxide, BW153, manufactured by Nippon Light Metal Co., Ltd., volume average particle size: 18 μm, particle size distribution (D ₉₀ /D ₁₀ ): 12.3) was added, to obtain an adhesive composition (2).
The particle size distribution (D ₉₀ /D ₁₀ ) of the filler particles is a value obtained by measuring the particle diameter of the filler particles using a measuring device (Microtrac) that uses a laser diffraction scattering method and converting the measured value into a particle size distribution.

(Preparation Example 3: Preparation of Pressure-Sensitive Adhesive Composition (3))
A pressure-sensitive adhesive composition (3) was prepared in the same manner as in Preparation Example 2, except that the type and amount of the filler added in Preparation Example 2 was changed to the type and amount shown in Table 1 below.
Filler 2 is nickel powder (Type 123, manufactured by Inco Corporation, volume average particle size: 11.9 μm), and the particle size distribution (D ₉₀ /D ₁₀ ) measured in the same manner as for Filler 1 is 4.2.

(Preparation Example 4: Preparation of Pressure-Sensitive Adhesive Composition (4))
A pressure-sensitive adhesive composition (4) was prepared in the same manner as in Preparation Example 2, except that the type of filler in Preparation Example 2 was changed to the type shown in Table 2 below.
Filler 3 is aluminum hydroxide (B303, manufactured by Nippon Light Metal Co., Ltd., volume average particle size: 23 μm), and the particle size distribution (D ₉₀ /D ₁₀ ) measured in the same manner as for Filler 1 is 18.5.

(Preparation Example 5: Preparation of Pressure-Sensitive Adhesive Composition (5))
A pressure-sensitive adhesive composition (5) was prepared in the same manner as in Preparation Example 2, except that the type of filler in Preparation Example 2 was changed to the type shown in Table 2 below.
Filler 4 is aluminum hydroxide (BE033, manufactured by Nippon Light Metal Co., Ltd., volume average particle size: 3 μm), and the particle size distribution (D ₉₀ /D ₁₀ ) measured in the same manner as for Filler 1 is 5.8.

(Preparation Example 6: Preparation of Pressure-Sensitive Adhesive Composition (6))
A pressure-sensitive adhesive composition (6) was prepared in the same manner as in Preparation Example 2, except that the amount of filler added in Preparation Example 2 was changed to the amount shown in Table 2 below.

(Preparation Example 7: Preparation of Pressure-Sensitive Adhesive Composition (7))
A pressure-sensitive adhesive composition (7) was prepared in the same manner as in Preparation Example 2, except that the amount of filler added in Preparation Example 2 was changed to the amount shown in Table 2 below.

(Preparation Example 8: Preparation of Pressure-Sensitive Adhesive Composition (8))
In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, and a dropping funnel, 97.97 parts by weight of n-butyl acrylate, 2.0 parts by weight of acrylic acid, 0.03 parts by weight of 4-hydroxybutyl acrylate, and 0.1 parts by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator were dissolved in a solvent consisting of 100 parts by weight of ethyl acetate, and polymerization was carried out at 70°C for 12 hours to obtain an acrylic copolymer solution (2) having a weight average molecular weight of 2,000,000 (polystyrene equivalent). Next, 25 parts by weight of disproportionated rosin glycerin ester (Super Ester A100, Arakawa Chemical Industries Co., Ltd.), 5 parts by weight of polymerized rosin pentaerythritol ester (Pensel D135, Arakawa Chemical Industries Co., Ltd.), and 20 parts by weight of styrene-based petroleum resin (FTR (registered trademark) 6100, Mitsui Chemicals Co., Ltd.) were added to 100 parts by weight of the acrylic copolymer solution (2), and ethyl acetate was added and mixed uniformly to obtain a pressure-sensitive adhesive solution (2) with a solid content of 31% by weight. Next, 1.3 parts by weight of an isocyanate-based crosslinking agent (Coronate L-45, Nippon Polyurethane Industry Co., Ltd., non-volatile content 45% by weight) was added to 100 parts by weight of the pressure-sensitive adhesive solution (2), and the mixture was stirred and mixed uniformly to obtain a pressure-sensitive adhesive resin (2) with a solid content of 31.1% by weight.
Next, 30 parts by weight of filler 1 (aluminum hydroxide, BW153, manufactured by Nippon Light Metal Co., Ltd., volume average particle size: 18 μm, particle size distribution (D ₉₀ /D ₁₀ ): 12.3) was added to 100 parts by weight of the solid content of the obtained adhesive resin (2) to obtain an adhesive composition (8).

(Production Example 1: Production of Adhesive Sheet (1))
The pressure-sensitive adhesive composition (1) was applied onto a release liner (Film Vina 75E-0010GT, manufactured by Fujimori Kogyo Co., Ltd., the same applies below) using an applicator so that the thickness after drying would be 25 μm, and the applied layer was dried at 80° C. for 3 minutes to prepare a pressure-sensitive adhesive layer.
Next, toluene was added to the resin composition (1) and stirred to make it uniform, and the mixture was applied onto a release liner using an applicator so that the thickness after drying would be 100 μm, and then dried at 60° C. for 5 minutes to prepare a substrate layer.
After peeling off the release liner from the base layer, the adhesive layer from which the release liner had been peeled off was attached to both sides of the base layer, and the laminated structure of the base layer and the adhesive layer was pressed at 0.2 MPa to laminate, thereby producing an adhesive sheet (1).

(Production Example 2: Production of Adhesive Sheet (2))
An adhesive sheet (2) was produced in the same manner as in Production Example 1, except that in the production of the adhesive sheet (1) in Production Example 1, the thickness of the base material layer, the type of adhesive composition, and the thickness of the adhesive layer were changed to the conditions described in Table 1.

(Production Example 3: Production of Adhesive Sheet (3))
An adhesive sheet (3) was produced in the same manner as in Production Example 1, except that in the production of the adhesive sheet (1) in Production Example 1, the type of adhesive composition was changed to the conditions shown in Table 1.

(Production Example 4: Production of Pressure-Sensitive Adhesive Sheet (4))
An adhesive sheet (4) was produced in the same manner as in Production Example 1, except that in the production of the adhesive sheet (1) in Production Example 1, the type of adhesive composition was changed to the conditions shown in Table 1.

(Production Example 5: Production of Adhesive Sheet (5))
In the production of the pressure-sensitive adhesive sheet (1) of Production Example 1, except that the type of resin composition in the base material layer and the type of pressure-sensitive adhesive composition were changed to the conditions described in Table 1, a pressure-sensitive adhesive sheet (5) was produced in the same manner as in Production Example 1.

(Production Example 6: Production of Adhesive Sheet (6))
An adhesive sheet (6) was produced in the same manner as in Production Example 1, except that in the production of the adhesive sheet (1) of Production Example 1, the type of resin composition in the base material layer, the thickness of the base material layer, the type of adhesive composition, and the thickness of the adhesive layer were changed to the conditions described in Table 1.

(Production Example 7: Production of Adhesive Sheet (7))
An adhesive sheet (7) was produced in the same manner as in Production Example 1, except that in the production of the adhesive sheet (1) in Production Example 1, the type of adhesive composition was changed to the conditions shown in Table 2.

(Production Example 8: Production of Adhesive Sheet (8))
An adhesive sheet (8) was produced in the same manner as in Production Example 1, except that in the production of the adhesive sheet (1) of Production Example 1, the thickness of the base material layer, the type of adhesive composition, and the thickness of the adhesive layer were changed to the conditions described in Table 2.

(Production Example 9: Production of Adhesive Sheet (9))
An adhesive sheet (9) was produced in the same manner as in Production Example 1, except that in the production of the adhesive sheet (1) in Production Example 1, the thickness of the base material layer and the type of the adhesive composition were changed to the conditions shown in Table 2.

(Production Example 10: Production of Adhesive Sheet (10))
An adhesive sheet (10) was produced in the same manner as in Production Example 1, except that in the production of the adhesive sheet (1) of Production Example 1, the thickness of the base material layer and the type of adhesive composition were changed to the conditions shown in Table 2.

(Production Example 11: Production of Adhesive Sheet (11))
An adhesive sheet (11) was produced in the same manner as in Production Example 1, except that in the production of the adhesive sheet (1) in Production Example 1, the thickness of the base material layer and the type of the adhesive composition were changed to the conditions described in Table 2.

The stress at 25% elongation, stress at break, and elongation at break of the base layer in the adhesive sheets (1) to (11) of Production Examples 1 to 11; the stress at 25% elongation, stress at break, elongation at break, and volume ratio of the filler of the adhesive layer in the adhesive sheets (1) to (11) of Production Examples 1 to 11; and the stress at 25% elongation, stress at break, elongation at break, impact resistance, 180° peel adhesive strength, shear adhesive strength, and split adhesive strength of the adhesive sheets (1) to (11) of Production Examples 1 to 11 were measured or evaluated by the following methods. The results are shown in Tables 1 and 2 below.

<<Measurement of Stress at 25% Elongation, Stress at Break, and Elongation at Break of Adhesive Sheet or Substrate Layer>>
Each adhesive sheet or base layer was punched out into a dumbbell shape with a gauge length of 20 mm and a width of 6 mm, and pulled in the longitudinal direction at a tensile speed of 500 mm/min using a Tensilon tensile tester (model: RTF-1210, manufactured by A&D Co., Ltd.) under measurement atmosphere conditions of 23°C and 50% RH, to measure the stress at 25% elongation, stress at break, and elongation at break of each adhesive sheet or base layer.

<<Measurement of Stress at 25% Elongation, Stress at Break, and Elongation at Break of Adhesive Layer>>
Each adhesive layer was punched out into a dumbbell shape with a gauge length of 20 mm and a width of 10 mm, and pulled in the longitudinal direction at a tensile speed of 300 mm/min using a Tensilon tensile tester (model: RTF-1210, manufactured by A&D Co., Ltd.) under conditions of a measurement atmosphere of 23°C and 50% RH, to measure the stress at 25% elongation, stress at break, and elongation at break of each adhesive layer.

<<Measurement of the volume ratio of filler particles in the adhesive layer>>
The volume ratio of the filler in each adhesive layer was calculated from the following formulas (1) to (3).
Weight A (g) of adhesive resin/density A (g/cm ³ ) of adhesive resin=volume A (cm ³ ) of adhesive resin (1)
Weight of filler particle B (g)/density of filler particle B (g/cm ³ )=volume of filler particle B (cm ³ ) Equation (2)
Volume B of filler particles (cm ³ )/(Volume A of adhesive resin (cm ³ )+Volume B of filler particles (cm ³ ))×100=Volume ratio of filler particles (%) Equation (3)
The density A of the adhesive resin was calculated as 1.2 g/cm ³ , the density B of the filler particles was calculated as 2.42 g/cm ³ for the aluminum hydroxide, and 8.90 g/cm ³ for the nickel.

<<Impact resistance evaluation>>
Each adhesive sheet was cut to a length of 20 mm and a width of 5 mm, and two pieces were prepared. As shown in Fig. 5A, the adhesive sheet 31 was attached in parallel to an acrylic plate 32 (length 50 mm, width 50 mm, thickness 2 mm, Acrylite L, color tone: colorless, manufactured by Mitsubishi Rayon Co., Ltd.) at an interval of 40 mm. Next, as shown in Fig. 5B, the acrylic plate 32 to which the adhesive sheet 31 was attached was attached to the center of an ABS plate 33 (length 150 mm, width 100 mm, thickness 2 mm, Tough Ace R, manufactured by Sumitomo Bakelite Co., Ltd., color tone: natural, no grain), and the laminated structure of the acrylic plate 32, the adhesive sheet 31, and the ABS plate 33 was pressed by a roller once while applying a load of 2 kg to the laminated structure, and then the laminated structure was left to stand for 24 hours under the conditions of an atmosphere of 40 ° C. and 50% RH to prepare a test piece.
As shown in FIG. 5C, a U-shaped measuring table 34 (150 mm long, 100 mm wide, 45 mm high, 5 mm thick, made of aluminum) was placed on the base of a DuPont impact tester (manufactured by Tester Sangyo Co., Ltd.), and the test piece was placed on the table so that the acrylic plate 32 of the test piece faced downward. Under the conditions of an atmosphere of 23° C. and 50% RH, a stainless steel impact core (diameter 25 mm, weight 300 g) 35 was dropped onto the center part of the ABS plate 33 from the ABS plate 33 side. At this time, the impact core 35 was dropped five times at 10 second intervals for each height while changing the height of the impact core 35 from 10 cm to 10 cm, and the height at which peeling or destruction of the adhesive sheet of the test piece was observed was measured. It should be noted that a test piece that does not peel or destroy the adhesive sheet when dropped from 30 cm or more is suitable for use.

<<Measurement of 180° peel adhesive strength>>
The 180° peel adhesive strength of each adhesive sheet was measured in accordance with JIS Z 0237. Specifically, each adhesive sheet was cut to a length of 150 mm and a width of 20 mm, and one side of the adhesive sheet was backed with a PET film having a thickness of 25 μm. Next, the other side of the adhesive sheet was attached to a stainless steel plate (length 100 mm, width 30 mm, thickness 3 mm) under an atmosphere of 23° C. and 50% RH, and the laminated structure of the adhesive sheet and the stainless steel plate was pressed by a roller once back and forth while applying a load of 2 kg to the laminated structure, and then the laminated structure was left to stand for 1 hour under an atmosphere of 23° C. and 50% RH to prepare a test piece.
The pressure-sensitive adhesive sheet in the test piece was stretched in the 180° direction (horizontal direction) at a tensile speed of 300 mm/min using a Tensilon tensile tester (model: RTF-1210, manufactured by A&D Co., Ltd.) under conditions of an atmosphere of 23° C. and 50% RH, and the 180° peel adhesive strength of the pressure-sensitive adhesive sheet was measured.

<<Measurement of shear adhesive strength>>
Each adhesive sheet was cut into a length of 20 mm and a width of 20 mm. Under the conditions of an atmosphere of 23° C. and 50% RH, one side of the adhesive sheet was attached to the surface of a clean stainless steel plate A (length 100 mm, width 30 mm, thickness 3 mm) that had been subjected to hairline polishing with waterproof abrasive paper (No. 360) so that the surface area was 20 mm x 20 mm. Next, a clean and smooth surfaced stainless steel plate B (length 100 mm, width 30 mm, thickness 3 mm) that had been subjected to hairline polishing with waterproof abrasive paper (No. 360) was attached to the opposite side of the adhesive sheet to the side to which the stainless steel plate A was attached, and the laminated structure of the stainless steel plate A, the adhesive sheet, and the stainless steel plate B was pressed by rolling once back and forth with a roller while applying a load of 5 kg to the laminated structure, and then left to stand for 24 hours under the conditions of an atmosphere of 23° C. and 50% RH to prepare a test piece.
Under conditions of an atmosphere of 23°C and 50% RH, with the stainless steel plate A constituting the test piece fixed, the stainless steel plate B constituting the test piece was stretched in the shear direction of the pressure-sensitive adhesive sheet at a tensile speed of 50 mm/min using a Tensilon tensile tester (model: RTF-1210, manufactured by A&D Co., Ltd.), and the shear adhesive strength was measured.

<<Measurement of splitting adhesive strength>>
Each adhesive sheet was cut to a length of 20 mm and a width of 20 mm. Under the conditions of an atmosphere of 23°C and 50% RH, one side of the adhesive sheet was attached to the surface of a clean, smooth aluminum plate (alloy number A1050, length 50 mm, width 40 mm, thickness 3 mm) so that the attachment area was 20 mm x 20 mm. Next, a clean, smooth aluminum plate (alloy number A1050, length 50 mm, width 40 mm, thickness 3 mm) was attached to the side of the adhesive sheet opposite to the side to which the aluminum plate was attached, and the laminated structure of the two aluminum plates and the adhesive sheet was pressed by rolling it back and forth once while applying a load of 5 kg, and then left to stand for 24 hours under the conditions of an atmosphere of 23°C and 50% RH to prepare a test piece.
Under conditions of an atmosphere of 23°C and 50% RH, with the aluminum plate A constituting the test piece fixed, the aluminum plate B constituting the test piece was stretched in the cleavage direction (thickness direction) of the pressure-sensitive adhesive sheet at a tensile speed of 50 mm/min using a Tensilon tensile tester (model: RTF-1210, manufactured by A&D Co., Ltd.) to measure the cleavage adhesive strength.

(Test Examples 1 to 11)
The adhesive sheets (1) to (11) of Production Examples 1 to 11 were each cut to a width of 10 mm and a length of 60 mm, and one surface 41a of the adhesive sheet 41 was attached to a clean, smooth-surfaced aluminum plate 42 (alloy number A1050, length 50 mm, width 40 mm, thickness 3 mm) in a straight line, as shown in FIG. 6A. Next, the other surface 41b of the adhesive sheet 41 was attached to a clean, smooth-surfaced acrylic plate 43 (length 40 mm, width 40 mm, thickness 3 mm, Acrylite L, color tone: colorless, manufactured by Mitsubishi Rayon Co., Ltd.). At this time, both ends (first gripping portion A and second gripping portion B) of the adhesive sheet 41 in the length direction (stretching direction) were attached in a state where the width and length were exposed from both ends of the acrylic plate 43 by 10 mm and 10 mm, respectively. Next, the laminated structure of the aluminum plate 42, the adhesive sheet 41, and the acrylic plate 43 was pressed by rolling it back and forth once with a roller while applying a load of 5 kg to the laminated structure, and then left to stand for 3 days under conditions of an atmosphere of 23° C. and 50% RH.
The pressure-sensitive adhesive sheets used in Test Examples 1 to 11 are as shown in Table 3 below. In Table 3 below, this application mode is indicated as "X."

(Comparative Test Examples 1 to 11)
The adhesive sheets (1) to (11) of Production Examples 1 to 11 were each cut to a width of 10 mm and a length of 70 mm, and one surface 44a of the adhesive sheet 44 was attached in a straight line to a clean, smooth-surfaced aluminum plate 42 (alloy number A1050, length 50 mm, width 40 mm, thickness 3 mm) as shown in Fig. 6C. Next, the other surface 44b of the adhesive sheet 44 was attached to a clean, smooth-surfaced acrylic plate 43 (length 40 mm, width 40 mm, thickness 3 mm, Acrylite L, color tone: colorless, manufactured by Mitsubishi Rayon Co., Ltd.). At this time, one end (gripping portion A') of the adhesive sheet 44 in the length direction (extension direction) was attached in a state of being exposed from one end of the acrylic plate 43 by a width of 10 mm and a length of 10 mm. Next, the laminated structure of the aluminum plate 42, the adhesive sheet 44, and the acrylic plate 43 was pressed by rolling it back and forth once with a roller while applying a load of 5 kg to the laminated structure, and then left to stand for 3 days under conditions of an atmosphere of 23° C. and 50% RH.
The pressure-sensitive adhesive sheets used in Comparative Test Examples 1 to 11 are as shown in Table 3 below. In Table 3 below, this application mode is indicated as "Y".

<<Evaluation of removability 1>>
For each of the laminate structures of Test Examples 1 to 11 and Comparative Test Examples 1 to 11, the removability in the horizontal direction was evaluated by the following method.
The first gripping portion A and the second gripping portion B of each of the pressure-sensitive adhesive sheets used in Test Examples 1 to 11, and the gripping portion A' of each of the pressure-sensitive adhesive sheets used in Comparative Test Examples 1 to 11 were stretched in the 180° direction (horizontal direction) (the direction shown by the stretching direction p in FIG. 6A or the stretching direction p in FIG. 6C) at a tensile speed of 300 mm/min using a Tensilon tensile tester (model: RTF-1210, manufactured by A&D Co., Ltd.) under conditions of an atmosphere of 23° C. and 50% RH, and a stretch-peel test was performed. The stretch-peel test was performed 10 times in total, including 5 times (n=5) of the horizontal stretch-peel test and 5 times (n=5) of the vertical stretch-peel test. In the case of the application mode X of Test Examples 1 to 11, stretch-peel was performed from either one of the first gripping portion A and the second gripping portion B, and then stretch-peel was performed from the other, which was considered as one test (n=1).
In this stretch-peel test, the degree of adhesive remaining on the adherend (acrylic plate) after peeling of the adhesive sheet was visually confirmed and evaluated according to the following evaluation criteria. In addition, the tearing of the adhesive sheet during stretch-peel and the dismantling property of the aluminum plate and the acrylic plate were evaluated according to the following evaluation criteria. The evaluation results are shown in Table 3 below.

[Evaluation criteria for adhesive residue]
◯: No adhesive remained. ×: Adhesive remained. In the evaluation criteria for adhesive residue, "◯" indicates that there is no problem in use.

As an example of the degree of residual adhesive in the stretch-peel test, FIG. 7A shows the appearance of the acrylic plate after horizontal stretch-peel in Test Example 1, and FIG. 7B shows the appearance of the acrylic plate after horizontal stretch-peel in Comparative Test Example 1. In FIG. 7A, "410" indicates the location where the adhesive sheet was attached, and "p" indicates the stretch direction of the adhesive sheet. In FIG. 7B, "440" indicates the location where the adhesive sheet was attached, and "p" indicates the stretch direction of the adhesive sheet. As is clear from these results, when the sheet was attached in attachment mode X, no residual adhesive was observed, whereas when the sheet was attached in attachment mode Y, clear residual adhesive was observed.

[Evaluation criteria for shreds]
◎: The number of times it tore was 0. ○: The number of times it tore was 1 to 2. △: The number of times it tore was 3 to 4. ×: The number of times it tore was 5. In the evaluation criteria for tearing, "○" and "◎" are those that are not problematic in use.

[Evaluation criteria for dismantling]
◎: The product could be disassembled 5 times. ○: The product could be disassembled 3 to 4 times. △: The product could be disassembled 1 to 2 times. ×: The product could be disassembled 5 times. In the evaluation criteria for disassembly, "○" and "◎" indicate that there are no problems with use.

From the results in Table 3 above, it was found that when the application mode in Test Examples 1 to 11 was X, there was no contamination with the adhesive after peeling, and even if it tore off during stretch-peeling from one end (first gripping part), it could be stretch-peeled from the other end (second gripping part) and peeled all the way to the end. On the other hand, when the application mode in Comparative Test Examples 1 to 11 was Y, even if stretch-peeling was possible, adhesive remained on the adherend, and if it tore off during stretch-peeling from one end, it was not possible to peel it all the way to the end, and the aluminum plate and the acrylic plate could not be disassembled.

<<Evaluation of removability 2>>
For each of the laminate structures of Test Examples 1 to 11, the removability in the vertical direction was evaluated by the following method.
In the above <<Evaluation 1 of removability>>, the stretching conditions of the first gripping portion A and the second gripping portion B in each of the pressure-sensitive adhesive sheets used in Test Examples 1 to 11 were changed from a 180° direction (horizontal direction) (the direction shown by the stretching direction p in FIG. 6A) to a 90° direction (vertical direction) (the direction shown by the stretching direction p in FIG. 6B) relative to the application surface of the pressure-sensitive adhesive sheet, and the degree of adhesive remaining on the adherend (acrylic plate) after the pressure-sensitive adhesive sheet was peeled off, the tearing of the pressure-sensitive adhesive sheet during stretching peeling, and the dismantling property of the aluminum plate and the acrylic plate were evaluated in the same manner as in the above <<Evaluation 1 of removability>>. The evaluation results are shown in Table 4 below.

The results in Table 4 above show that the adhesive sheets (2) to (11) in test examples 2 to 11 did not cause contamination by the adhesive after peeling, even when stretched and peeled at 90° (perpendicular) to the application surface of the adhesive sheet.

Examples of aspects of the present invention include the following.
<1> An electronic component comprising an adhesive sheet having one surface which is affixed to a first attachment object with at least a portion of the surface being linear, and the other surface which is affixed to a second attachment object, the adhesive sheet being affixed to the second attachment object with at least two ends exposed from the second attachment object.
<2> The electronic component according to <1>, wherein at least one of the first affixing target and the second affixing target is a recovered part.
<3> The electronic component according to any one of <1> to <2>, wherein the recovered parts are at least one of display glass and a battery.
<4> The electronic component according to any one of <1> to <3>, wherein when a width of an application area of the pressure-sensitive adhesive sheet in the electronic component is X (cm) and a length of the application area is Y (cm), a ratio (X/Y) of the width of the application area to the length of the application area is 1/100,000 to 1/1.

The electronic components can be quickly peeled off, are not contaminated by the adhesive after peeling, and even if they tear while being stretched and peeled off from one end, they can be stretched and peeled off from the other end to the end, and since they have an adhesive sheet with suitable adhesive strength when in use, they can be used as a wide range of electronic components, regardless of the size of the electronic components, such as large electronic devices such as flat-screen televisions, home appliances, and office equipment, and the components that make up these devices, as well as small electronic devices such as mobile electronic terminals, cameras, and personal computers, and the components that make up these devices.

LIST OF SYMBOLS 1 Grip tab 2 Adhesive area 3 End portion 4 First adhesive area 5 Second adhesive area 6 Third adhesive area 7 Tip portion 21 Adhesive sheet 21a One surface of adhesive sheet 21 21b Other surface of adhesive sheet 21 22 First attachment target 23 Second attachment target 31 Adhesive sheet 32 Acrylic plate 33 ABS plate 34 U-shaped measurement stand 35 Impact core 41 Adhesive sheet 41a One surface of adhesive sheet 41 41b Other surface of adhesive sheet 41 42 First attachment target 43 Second attachment target 44 Adhesive sheet 61 Adhesive sheet 61a One surface of adhesive sheet 61 61b Other surface of adhesive sheet 61 62 Back chassis 63 Battery 71 Adhesive sheet 71a One surface of adhesive sheet 71 71b Other surface of adhesive sheet 71 72 Bezel 73 Display 410 Place where adhesive sheet was attached 440 Place where adhesive sheet was attached A First gripping portion B Second gripping portion C Third gripping portion D Fourth gripping portion A' Grip portion p Extension direction

Claims (6)

a stretch-peelable adhesive sheet having one surface attached to a first object to be attached so that at least a portion of the surface is linear, and the other surface attached to a second object to be attached, the stretch-peelable adhesive sheet being attached to the second object to be attached with at least two ends exposed from the second object to be attached;
The pressure-sensitive adhesive sheet has at least an adhesive layer containing filler particles having a particle size distribution (D90/D10) of 2.5 to 20,
the content of the filler particles having a particle size distribution (D90/D10) of 2.5 to 20 is 10 parts by weight to 90 parts by weight relative to 100 parts by weight of the adhesive resin contained in the adhesive layer;
The pressure-sensitive adhesive sheet has a stress at 25% elongation in the range of 0.15 MPa to 2 MPa,
The pressure-sensitive adhesive sheet has a splitting adhesive strength of 80 N/4 cm2 ^or more,
At least two of the ends exposed from the second attachment target can be grasped and stretched,
An electronic component, characterized in that at least one of the first affixing object and the second affixing object is a recovered part, and the recovered part is at least one of a display glass and a battery. The electronic component according to claim 1, wherein the width of the adhesive area of the adhesive sheet is X (cm) and the length of the adhesive area is Y (cm), and the ratio (X/Y) of the width of the adhesive area to the length of the adhesive area is 1/100,000 to 1/1. The electronic component according to claim 1 or 2, wherein the adhesive sheet has a breaking stress of 1.5 MPa to 50.0 MPa. the end portion of the pressure-sensitive adhesive sheet exposed from the second attachment target is a grip portion,
The electronic component according to any one of claims 1 to 3, wherein the adhesive surface of the pressure-sensitive adhesive sheet that adheres to the second attachment target and the gripping portion are adjacent to each other. The method for dismantling electronic components according to any one of claims 1 to 4,
A method for dismantling electronic components, comprising: gripping at least one end of the adhesive sheet exposed from the second attachment target; and stretching and peeling the adhesive sheet to dismantle the first attachment target and the second attachment target. Stretching and peeling off the adhesive sheet by gripping and simultaneously stretching a plurality of the ends of the adhesive sheet exposed from the second attachment target, or
6. The method for dismantling electronic components as described in claim 5, characterized in that the first and second attachment targets are dismantled by: gripping and stretching any one of the multiple ends of the adhesive sheet exposed from the second attachment target to peel off a portion of the adhesive sheet, and then gripping and stretching at least one of the ends other than the end previously stretched to peel off the remaining portion.

Images