JP7718461B2 - Electronic Components - Google Patents

Description

The present invention relates to electronic components.

Adhesive sheets (sometimes called "adhesive tape") are widely used as a joining method with excellent workability and high adhesive reliability in situations such as fastening components that make up electronic devices. Specifically, adhesive tape is used for component fixing applications 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 exterior components and rigid components such as 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 have increasingly been disassembled after use and reused or re-used, with the aim of conserving resources and protecting the global environment. In this case, if adhesive tape is used, it must be removed from the parts. However, because such tape typically has high adhesive strength and is attached to many locations within the product, removing it can be quite labor-intensive. Therefore, there is a demand for easy removal and removal to reduce labor costs when reusing or reusing the tape.

An easily peelable and removable adhesive tape has been proposed, which includes an adhesive portion and a tab portion, with the tab portion jutting out from either the outermost portion of a first adherend or the outermost portion of a second adherend so as to be grippable, and which can be gripped and stretched in a direction substantially 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 in that the adhesive remains on the adhesive surface opposite the side having the tab portion (i.e., the side to which the adhesive tape adheres for the longest period of time during peeling) after peeling, causing contamination. Furthermore, if the tab portion at one end tears during stretch-peeling, it cannot be peeled any further, resulting in the inability to further disassemble reusable or reusable parts, etc.

In response to this, an adhesive film has been proposed, as shown in Figure 1, which comprises an adhesive region (2) adjacent to a grip tab (1) located at one end of the adhesive film strip and extending toward the other end (3). The adhesive region (2) includes, in order from the grip tab (1) toward the other end (3) of the adhesive film strip, 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) forming the end (3) and terminating in one or more tips (7) toward the end (3) (see Patent Document 2). However, the shape of this proposed adhesive film poses problems: the adhesive area is small, the available adhesive area cannot be used effectively, and adhesive strength is weakened. Peeling off components constituting the electronic device during use is a major problem, and adhesive strength must be maintained until the electronic components are recovered for reuse or re-use.

There is therefore a strong demand for electronic components equipped with adhesive sheets that can be quickly peeled, are not contaminated by the adhesive after peeling, and even if they tear during stretch-peeling from one end, can be stretch-peeled from the other end to the end, and have suitable adhesive strength when in use.

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

The present invention aims to solve the above-mentioned problems of the prior art and achieve the following objectives. Specifically, the present invention aims to provide an electronic component equipped with an adhesive sheet that can be quickly peeled, is not contaminated by the adhesive after peeling, and even if it tears during stretch-peeling from one end, can be stretch-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.
That is, it is an electronic component characterized by having an adhesive sheet having one surface attached to a first attachment object so that at least a portion of the surface is linear, and the other surface attached to a second attachment object, and having 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, providing electronic components equipped with an adhesive sheet that can be quickly peeled, is free of contamination from 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.

FIG. 1 shows a prior art adhesive film. FIG. 2A is a schematic explanatory diagram (top view) showing one embodiment of the 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 view (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 a case where the electronic component of the present invention 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 when 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 explanatory 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 attachment 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 stretch peeling in the horizontal direction in Test Example 1 (application mode X). FIG. 7B is a diagram showing the appearance of the acrylic plate after stretch peeling in the horizontal direction in Test Example 1 (application mode Y).

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

In this specification, the term "electronic components" includes not only the various parts that make up the electronic devices, such as metal plates, 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 explained in detail below using 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 where they are 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 linear fashion and has two ends. However, it is sufficient that one surface of the adhesive sheet is attached to the first attachment target in a linear fashion at least partially. As shown in FIGS. 2D to 2G, the adhesive sheet may be attached to the first attachment target in a branched or bent shape. Therefore, the number of ends (gripping portions) of the adhesive sheet is not particularly limited and can be selected appropriately 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 selected appropriately depending on the purpose, but it is preferable that all ends are exposed from the second attachment target. Hereinafter, the ends of the adhesive sheet 21 exposed from the second attachment target 23 may be referred to as a first gripping portion A, a second gripping portion B, a third gripping portion C, a fourth gripping portion 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 there is no particular limitation as long as at least two of the gripping portions A to D are exposed from at least the second attachment target 23, and at least one of the gripping portions A to D may be exposed from the first attachment target 22.

<Grip part>
The gripping portion may be arranged directly on the first attachment target 22, as shown in Figures 2A and 2B, or may be arranged 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 arranged 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 this is 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 targets may be the same as or different from the number of adhesive layers on the gripping portion. For example, if the adhesive sheet has adhesive layers on both sides, the adhesive layer on at least one of the multiple gripping portions may be arranged on only one side. Furthermore, the number of adhesive layers on the multiple gripping portions may be the same as or different from each other.

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

The release sheet is not particularly limited and can be selected appropriately depending on the purpose. Examples include paper such as kraft paper, glassine paper, and fine paper; resin films such as polyethylene, polypropylene (biaxially oriented polypropylene (OPP), uniaxially oriented polypropylene (CPP)), and polyethylene terephthalate (PET); laminated paper in which the above-mentioned paper and a resin film are laminated together; and paper in which the above-mentioned paper has been sealed with clay, polyvinyl alcohol, or the like and one or both sides have been treated with a release agent such as a silicone resin. 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 targets and other electronic components adjacent to them, 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 lengths of the gripping portions may be the same or different.

There are no particular restrictions on the width of the gripping portion, and it can be selected appropriately depending on the width of the adhesive sheet, etc.

<Stretching direction p>
The adhesive sheet 21 in the electronic component can be easily stretched and peeled off by stretching in the stretching direction p shown in Figures 2B and 2C. Figure 2B shows an embodiment in which the stretching direction p of the adhesive sheet 21 is horizontal (180° direction) relative to the attachment surface of the first attachment object 22 and the second attachment object 23, and Figure 2C shows an embodiment in which the stretching direction p of the adhesive sheet 21 is perpendicular (90° direction) relative to the attachment surface of the first attachment object 22 and the second attachment object 23, but there are no particular limitations on the angle of the stretching direction p relative to the attachment surface of the first attachment object 22 and the second attachment object 23, and it can be selected appropriately 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 portions simultaneously, or a portion may be peeled off by stretching one of the multiple gripping portions, and then the remaining portion may be peeled off by stretching the other. Furthermore, since at least two ends of the adhesive sheet in the electronic component are exposed from the second attachment target, even if the adhesive sheet tears during stretch-peeling from one end (first gripping portion), it can be advantageously stretch-peeled from the other end (second gripping portion) to the end.

The removability of the pressure-sensitive adhesive sheet for the electronic component can be confirmed, for example, by the method described in <<Removability Evaluation 1>> in the test examples described below. In the removability evaluation, a sheet that shows no contamination 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 tears during stretch-peeling from the gripping portion at the other end, is considered to have excellent removability.

<Width of application area/Length of application area (X/Y)>
When the width of the adhesive area of the pressure-sensitive adhesive sheet on the electronic component is X (cm) and the length of the adhesive area is Y (cm), the ratio of the width of the adhesive area to the length of the adhesive area, represented by [X/Y], is not particularly limited and can be selected appropriately 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 adhesive area ratio 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 component or different components. Furthermore, the first and second pasting targets may be interchangeable.

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

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

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

Among these, it is preferable that the first and second attachment targets are recovered parts. The recovered parts are not particularly limited as long as they are reusable or recyclable parts, and can be selected appropriately depending on the purpose. Examples include parts recovered when a defect occurs during the manufacturing process of electronic components, and parts recovered when discarded. The adhesive sheet in the electronic component 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, it can be stretched and peeled from the other end to the end, which is advantageous in that at least one of the first and second attachment targets can be quickly recovered as recovered parts, and at least one of the first and second attachment targets is not contaminated when 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 portion thereof is linear with respect to a fixing portion of the battery 63 on 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 gripping portion A and second gripping 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. The first gripping portion A and second gripping portion B of the adhesive sheet 61 may be attached in a manner 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 adhesive sheet 71 is attached so that at least a portion thereof is linear with respect to the fixing portion of bezel 72 to which display 73 is attached. Next, the other surface of adhesive sheet 71 is attached to display 73. At this time, two ends (first grip portion A and second grip portion B) in the length direction (extension direction) of adhesive sheet 71 are attached in a state where they are exposed from both ends of display 73.

<Adhesive sheet>
The pressure-sensitive adhesive sheet has at least a pressure-sensitive adhesive layer, preferably a substrate layer, and, if necessary, further has other layers.
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 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 may further contain other components as needed.

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

--Acrylic adhesive resin--
The acrylic pressure-sensitive 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, 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. The use of n-butyl acrylate is particularly preferable in order to ensure excellent adhesion to the adherend.

The alkyl (meth)acrylate having an alkyl group with 1 to 12 carbon atoms is preferably used in a 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 producing the acrylic polymer.

In addition to the above-mentioned monomers, highly polar vinyl monomers can also be used as needed to produce the acrylic polymer.
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 an amount ranging from 0.01% to 1.0% by weight, and more preferably from 0.03% to 0.3% by weight, based on the total amount of monomers used in producing 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. Of 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, of 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 for the formation of an adhesive layer that is well-balanced in terms of cohesion, holding power, 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. Examples include methods in which the monomers are polymerized by solution polymerization, bulk polymerization, suspension polymerization, emulsion polymerization, or other polymerization methods. Among these, it is preferable to produce the acrylic polymer by solution polymerization or bulk polymerization.

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

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

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 20,000,000 (manufactured by Tosoh Corporation)

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

The tackifying 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 preferred, with 70°C to 140°C being even more preferred for forming an adhesive layer with high adhesive performance. When using a (meth)acrylate tackifying resin, it is preferable for the glass transition temperature to be 30°C to 200°C, with 50°C to 160°C being even more preferred.

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

There are no particular restrictions on the amount of tackifier resin used and it can be selected appropriately depending on the purpose. However, 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 even more preferable to use it in the range of 8 to 55 parts by weight, as this makes it easier to ensure adhesion to the adherend.

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

The crosslinking agent is not particularly limited and can be selected appropriately depending on the purpose. Examples 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, crosslinking agents that are mixed with the acrylic polymer after its production to promote a crosslinking reaction are preferred, and it is more preferred to use isocyanate-based crosslinking agents and epoxy-based crosslinking agents that are 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 compounds such as tolylene diisocyanate and its trimethylolpropane adduct, and triphenylmethane isocyanate are particularly preferred.

The gel fraction value, which is obtained by measuring the insoluble portion after immersing the adhesive layer in toluene for 24 hours, is used as an indicator of the degree of crosslinking. There are no particular restrictions on the gel fraction of the adhesive layer and it can be selected appropriately depending on the purpose. However, 10% to 70% by weight is preferred, 25% to 65% by weight is more preferred, and 35% to 60% by weight is even more preferred in order to obtain an adhesive layer with good cohesion and adhesion.

The gel fraction refers to a value measured by the following method. A pressure-sensitive adhesive composition containing the pressure-sensitive adhesive resin and, if necessary, the additives, was coated onto a release sheet so that the thickness after drying was 50 μm. The coating was dried at 100° C. for 3 minutes and aged at 40° C. for 2 days, and then cut into 50 mm square pieces to serve as samples. The weight (G1) of the sample before immersion in toluene was measured in advance. After immersion in toluene solution for 24 hours at 23° C., the toluene-insoluble portion of the sample was separated by filtration through a 300-mesh wire netting. The weight (G2) of the residue after drying at 110° C. for 1 hour was measured, and the gel fraction was calculated according to the following formula (4). The weight (G3) of the conductive fine particles in the sample was calculated from the weight (G1) of the sample and the composition of the pressure-sensitive adhesive composition.
Gel fraction (wt%)=(G2−G3)/(G1−G3)×100 (Equation 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; and 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. 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 styrene-based resins in combination is more preferred as it can impart excellent adhesive properties and holding power to the PSA sheet. It is particularly preferred to use a combination of the styrene-isoprene copolymer and the styrene-isoprene-styrene copolymer.

The styrene-based resin may have a single structure, such as a linear structure, branched structure, or multi-branched structure, or a mixture of different structures may be used. When a styrene-based 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, which can provide excellent cohesive strength and therefore high holding power. For this reason, it is preferable to use a mixture of styrene-based resins according to the required properties.

The styrene-based resin preferably contains 10% to 80% by weight of the structural unit represented by the following chemical formula (1) relative to the total weight of the styrene-based resin, more preferably 12% to 60% by weight, even more preferably 15% to 40% by weight, and particularly preferably 17% to 35% by weight. This allows for 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 PSA sheet can achieve both excellent adhesive performance and heat durability.

The styrene-isoprene copolymer preferably has a weight-average molecular weight, measured using gel permeation chromatography (GPC) in terms of standard polystyrene, 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. Having the weight-average molecular weight of the styrene-isoprene copolymer within this preferred range ensures flowability during heating and compatibility when diluted with a solvent, making it possible to obtain a pressure-sensitive adhesive sheet that is heat-resistant while also offering good workability in the manufacturing process.

Here, the weight average molecular weight of the styrene-isoprene copolymer measured by GPC is a value converted into standard polystyrene using a GPC apparatus (SC-8020, manufactured by Tosoh Corporation), and the measurement conditions are as follows:
[Measurement conditions]
Sample concentration: 0.5 wt% (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) 2 ・ Guard column: TSKgel HXL-H
・ Detector: differential refractometer ・ Standard polystyrene molecular weight: 10,000 to 20,000,000 (manufactured by 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. For example, the method may include 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 styrene monomer in a polymerization solvent using an anionic polymerization initiator to form a polystyrene block having a living active end. Second, polymerizing isoprene from the living active end of the polystyrene block to obtain a styrene-isoprene diblock copolymer having a living active end. Third, reacting a portion of the styrene-isoprene diblock copolymer having a living active end with a coupling agent to form a coupled styrene-isoprene-styrene block copolymer. Fourth, using a polymerization terminator, deactivating the living active end of the remainder of the styrene-isoprene diblock copolymer having a living active end 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 allows for the production of an adhesive sheet with excellent initial adhesion and heat durability.

The tackifying resin is preferably solid at room temperature (23°C), and specific examples thereof include petroleum resins such as _C5 petroleum resins, _C9 petroleum resins, _C5 / _C9 petroleum resins, and alicyclic petroleum resins, as well as polymerized rosin resins, terpene resins, rosin resins, terpene-phenol resins, styrene resins, coumarone-indene resins, xylene resins, and phenolic 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 petroleum resin and polymerized rosin resin as the tackifying 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 chemical formula (1) that constitutes the styrene-based resin, thereby further improving the initial adhesive strength and heat durability of the pressure-sensitive adhesive sheet.

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

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, Escolez 2101 (manufactured by Exxon Mobil Corporation), Quinton G115 (manufactured by Zeon Corporation), Hercotack 1149 (manufactured by Rika Hercules Co., Ltd.), 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 Rigalite R101 (manufactured by Rika Hercules Co., Ltd.).

The amount of the tackifier resin used is not particularly limited and can be selected appropriately depending on the purpose, but it 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, relative to the total amount of components constituting the rubber-based adhesive resin. Using the tackifier resin within this preferred range makes it easier to achieve both excellent elongation at break and thermal durability of the adhesive sheet while improving the interfacial adhesion between the adhesive layer and the base layer.

There are no particular restrictions on the amount of tackifier resin with a softening point of 80°C or higher used, and it can be selected appropriately depending on the purpose. However, it is preferably used in the range of 3% to 100% by weight, more preferably 5% to 80% by weight, relative to the total amount of the styrene-based resin. Using it in the range of 5% to 80% by weight is particularly preferred in order to obtain a pressure-sensitive adhesive sheet that combines even better adhesion and excellent heat durability.

In addition, in order to achieve good application and initial adhesion in a constant temperature environment, a tackifying resin with a softening point of -5°C or lower can be used in combination with a tackifying resin with a softening point of 80°C or higher.

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

Specific examples of tackifying resins with a softening point of -5°C or less include process oil, polyester, and liquid rubbers such as polybutene. These may be used alone or in combination of two or more. Of these, it is preferable to use polybutene as the tackifying resin with a softening point of -5°C or less, as this will provide even better initial adhesion.

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

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

There are no particular restrictions on the weight ratio of the tackifier resin with a softening point of 80°C or higher to the tackifier resin with a softening point of -5°C or lower, and it can be selected appropriately depending on the purpose. However, it is preferable to use a weight ratio of the tackifier resin with a softening point of 80°C or higher to the tackifier resin with a softening point of -5°C or lower, expressed as [weight of tackifier resin with a softening point of 80°C or higher/weight of tackifier resin with a softening point of -5°C or lower], in the range of 5 to 50, and it is even more preferable to use a weight ratio of 10 to 30 in order to obtain a PSA sheet that combines excellent initial adhesion and excellent holding power.

There are no particular restrictions on the weight ratio of the styrene-based resin to the tackifier resin, and it can be selected appropriately depending on the purpose. However, it is preferable to use the styrene-based resin to tackifier resin in a weight ratio of 0.5 to 10.0, expressed as [styrene-based resin/tackifier resin], and it is even more preferable to use the styrene-based resin in a range of 0.6 to 9.0, as this improves initial adhesive strength and provides excellent thermal durability. Furthermore, it is preferable for the weight ratio [styrene-based resin/tackifier resin] to be greater than 1, for example, to prevent peeling due to the repulsive force of the PSA 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 as long as they do not impair the properties of the pressure-sensitive adhesive sheet. Examples include polymer components other than the pressure-sensitive adhesive resin, filler particles, crosslinking agents, antioxidants, UV absorbers, bulking agents, polymerization inhibitors, surface conditioners, antistatic agents, antifoaming agents, viscosity modifiers, light stabilizers, weather stabilizers, heat stabilizers, antioxidants, leveling agents, organic pigments, inorganic pigments, pigment dispersants, plasticizers, softeners, flame retardants, and metal deactivators. 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 become exposed from the adhesive layer when the adhesive sheet is stretched, thereby reducing the adhesive area between the adhesive layer and the adherend. This has the advantage that the adhesive sheet can be easily stretched and peeled even when the stretching direction is perpendicular to the attachment surface (adhesive surface) of the adherend.

The type of filler particles is not particularly limited and can be selected appropriately as long as it does not impair the effects of the present invention. They 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, 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-formalin-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 selected appropriately depending on the purpose. It may be regular or irregular. Specific examples of the shape of the filler particles include polygonal, cubic, elliptical, spherical, needle-like, plate-like, and scale-like shapes. Filler particles of these shapes may be used alone or in combination of two or more types. Furthermore, filler particles of these shapes may be aggregated. Among these, elliptical, spherical, and polygonal shapes are preferred as the shape of the filler particles. When the filler particles have an elliptical, spherical, polygonal, or other shape, the adhesive layer slides well on the adherend when the pressure-sensitive adhesive sheet is stretched, and stretch-peeling is easy even when the stretching direction of the pressure-sensitive adhesive sheet is 90° to the adhesion surface of the adherend.

The particle size distribution ( _D90 / _D10 ) of the filler particles is not particularly limited and can be selected appropriately 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 ( _D90 / _D10 ) of the filler particles is within this preferred range, the PSA sheet can be easily stretch-released even when the stretching direction is 90° to the attachment surface of the adherend, the PSA sheet is less likely to tear even when the substrate is thin, and the PSA sheet has excellent impact resistance, shear adhesive strength, and split adhesive strength. On the other hand, when the particle size distribution ( _D90 / _D10 ) of the filler particles is less than 2.5, stretch-release properties may be impaired when the stretching direction of the PSA sheet is 90° to the attachment surface of the adherend, and when it exceeds 20, adhesive properties 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 by measuring the particle diameter of the filler particles using, for example, 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 size of the filler particles is not particularly limited and can be selected appropriately 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 size of the filler particles is within this preferred range, the PSA sheet can be easily stretch-peeled even when the elongation direction is 90° relative to the attachment surface of the adherend, the PSA sheet is less likely to tear even when the base material is thin, and the PSA sheet has excellent impact resistance, shear adhesive strength, and split adhesive strength. On the other hand, when the volume average particle size of the filler particles is less than 3 μm, stretch-peeling may be difficult when the elongation direction of the PSA sheet is 90° relative to the attachment surface of the adherend, and when it exceeds 25 μm, adhesive performance such as impact resistance, shear adhesive strength, and split 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.

There are no particular restrictions on the ratio of the volume average particle diameter of the filler particles to the average thickness of the adhesive layer described below, and it can be selected appropriately depending on the purpose. However, 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 this ratio is within this preferred range, the adhesive sheet can be easily stretch-released even when the stretch direction is 90° to the attachment surface of the adherend, and the adhesive sheet is less likely to tear even when the substrate thickness is thin. Furthermore, when the ratio is within the particularly preferred range, the PSA sheet can be easily stretch-released even when the stretch direction is 90° to the adherend surface, the PSA sheet is less likely to tear even when the substrate thickness is thin, and adhesive properties such as impact resistance, shear adhesive strength, and split adhesive strength are also superior, which are advantageous. On the other hand, when the ratio is less than 5/100, stretch-release properties may be impaired when the PSA sheet is stretched at 90° to the adherend surface, and when it exceeds 95/100, adhesive properties such as impact resistance, shear adhesive strength, and split adhesive strength may be impaired.

The content of the filler particles in the adhesive layer is not particularly limited and can be selected appropriately depending on the purpose, but is preferably 10 to 90 parts by weight, more preferably 15 to 50 parts by weight, and even more preferably 20 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, stretch-peeling may be impossible when the stretching direction of the adhesive sheet is 90° relative to the attachment surface of the adherend, or the adhesive sheet may tear, resulting in the adhesive sheet not being stretched and being unable to be re-peeled. On the other hand, 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 stretchable, the adhesive composition may remain on the adherend, impact resistance may be reduced, and the 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 attachment surface of the adherend, and the adhesive sheet is less likely to tear even when the base material is thin, and has excellent impact resistance, shear adhesive strength, and split adhesive strength, which are advantageous.
The content of the filler particles in the pressure-sensitive adhesive layer can be appropriately adjusted when preparing the pressure-sensitive adhesive composition.

The volume ratio of the filler particles to the total volume of the adhesive layer is not particularly limited and can be selected appropriately depending on the purpose. However, 4% to 40% is preferred, 5% to 30% is more preferred, 5% to 20% is even more preferred, and 5% to 15% is particularly preferred. If the volume ratio of the filler particles is less than 4%, stretch-peeling may not be possible when the stretching direction of the adhesive sheet is 90° to the attachment surface of the adherend, or the adhesive sheet may tear, resulting in the adhesive sheet not being stretched and not being able to be re-peeled. Furthermore, if the volume ratio of the filler particles exceeds 40%, the adhesive sheet may not be able to stretch, the adhesive composition may remain on the adherend, impact resistance may be reduced, 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 above-mentioned preferred range, the PSA sheet can be easily stretch-peeled even when the stretching direction is 90° relative to the attachment surface of the adherend, and the PSA sheet is less likely to tear even when the substrate 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 using 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.

There are no particular restrictions on the number of adhesive layers, and they can be selected appropriately depending on the intended use, etc. They may be disposed on only one side of the adhesive sheet or on both sides, but it is preferable that they be disposed 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 selected appropriately depending on the purpose, but is preferably 0.04 MPa to 0.4 MPa, and more preferably 0.05 MPa to 0.1 MPa. When the stress at 25% elongation of the adhesive layer is within this preferred range, the adhesive sheet can achieve suitable adhesive strength and can be relatively easily peeled off even during stretch-peel. On the other hand, if 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 together. If the stress exceeds 0.4 MPa, the force required to stretch the adhesive sheet when peeling it off 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 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, and elongated by 25%.

- Adhesive layer breaking stress -
The stress at break of the adhesive layer is not particularly limited and can be selected appropriately depending on the purpose, but is preferably 0.5 MPa to 2.1 MPa, and more preferably 1.0 MPa to 2.1 MPa. When the stress at break of the adhesive layer is within this preferred range, the adhesive sheet can be prevented from tearing when stretched and peeled off, and the load required to stretch the adhesive sheet is not excessive, making it easy to peel off again. 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 stretched and peeled off. When the stress at break of the adhesive layer is greater than 2.1 MPa, the adhesive sheet may not be stretched sufficiently to be re-peeled. The force required to stretch and deform the adhesive sheet also depends on the thickness of the adhesive sheet. For example, when a thick adhesive sheet with a high stress at break is stretched and peeled off, it may not be stretched sufficiently to be re-peeled.
The stress at break of the adhesive layer refers to the stress value measured when the adhesive layer is 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, until the adhesive layer breaks.

- Elongation at break of adhesive layer -
The elongation at break of the pressure-sensitive 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 pressure-sensitive adhesive layer is within the above-mentioned preferred range, both favorable adhesiveness and removability can be achieved.
The elongation at break of the adhesive layer refers to the tensile elongation 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.

- 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" refers to the average thickness of the adhesive layer on one side of the adhesive sheet. When the adhesive sheet has adhesive layers 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 or different, but are preferably the same.
In this specification, the "average thickness of the adhesive layer" refers to the average value of thicknesses measured at a total of 25 points, the total thickness of which is measured at five points at 100 mm intervals in the width direction on each of the cut surfaces, the five points being 100 mm apart in the width direction, using a TH-104 thickness measuring instrument for paper and film (manufactured by Tester Sangyo Co., Ltd.).

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

Examples of the solution method include a method in which a solution containing the pressure-sensitive adhesive composition is directly applied to the substrate 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 selected appropriately depending on the purpose. Examples include paper such as kraft paper, glassine paper, and fine paper; resin films such as polyethylene, polypropylene (biaxially oriented polypropylene (OPP), uniaxially oriented polypropylene (CPP)), and polyethylene terephthalate (PET); laminated paper in which the above-mentioned paper and a resin film are laminated together; and paper in which the above-mentioned paper has been sealed with clay, polyvinyl alcohol, or the like and one or both sides have been treated with a release agent such as a silicone resin. These may be used alone or in combination of two or more types.

<<Base material 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. However, it is preferable that the base layer contains 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.

-Base material-
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; polyethersulfone; polyetherimide; 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 they can easily provide suitable elongation at break and stress at break, 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 resin--
The styrene-based resin is a resin that exhibits thermoplasticity, and therefore has excellent formability in extrusion molding, injection molding, etc., and is easy to form into the substrate layer. Furthermore, the styrene-based resin is likely to have particularly 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-based resin relative to all 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-based resin within this preferred range, a substrate layer with excellent elongation at break and stress at break can be obtained.

The styrene-based resin may have a single structure, such as a linear structure, branched structure, or multi-branched structure, or a mixture of different structures. Styrene-based resins rich in linear structures can provide the base layer with excellent elongation at break. On the other hand, branched or multi-branched structures with styrene blocks at the molecular ends can form a pseudo-crosslinked structure and provide excellent cohesive strength. Therefore, it is preferable to use a mixture of styrene-based resins to suit the required mechanical properties.

The styrene-based resin preferably contains structural units represented by chemical formula (1) in a range of 13% to 60% by weight, more preferably 15% to 50% by weight, even more preferably 15% to 45% by weight, and particularly preferably 15% to 35% by weight, relative to the total weight of the styrene-based resin. When the proportion of structural units represented by chemical formula (1) below relative to the total weight of the styrene-based resin is within the preferred range, it becomes easier to achieve elongation at break and stress at break within suitable ranges.

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% to 80% 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. When the content of the styrene-isoprene copolymer is within the 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 flowability during heating and compatibility when diluted with a solvent, which is preferable because it is possible to obtain a base layer that has good workability in the production process and thermal durability.
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 methods 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 are not particularly limited and can be appropriately selected from conventionally known production methods, such as those described above in the "Rubber-based Pressure-Sensitive Adhesive Resin" section.

--Polyurethane resin--
The polyurethane resin is not particularly limited and can be appropriately selected depending on the purpose, but preferably has a softening point of 40° C. or higher, more preferably 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 softening points hereinafter).

The reaction product of polyol (b1-1) and polyisocyanate (b1-2) can be suitably used as the polyurethane resin.

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

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

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, as well as 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 to produce 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, and 2,5-hexanediol. , 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, 4,4'-biphenol, etc.

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, including 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 polyurethane resin (b1) by reacting polyol (b1-1) with polyisocyanate (b1-2) is not particularly limited and can be appropriately selected from conventionally known production methods. For example, there is a method in which the polyol (b1-1) charged into a reaction vessel is heated under normal or reduced pressure to remove moisture, and then the polyisocyanate (b1-2) is supplied all at once or in portions and reacted.

The reaction between the polyol (b1-1) and the polyisocyanate (b1-2) is preferably carried out in such a manner that the equivalent ratio (NCO/OH equivalent ratio) of the isocyanate groups (NCO) in the polyisocyanate (b1-2) to the hydroxyl groups (OH) in 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 selected appropriately taking into consideration various factors such as safety, quality, and cost. However, 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 needed.

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 can be appropriately selected depending on the purpose, and examples thereof include ester solvents such as methyl acetate, ethyl acetate, propyl acetate, and butyl acetate; ketone solvents such as acetone, methyl ethyl ketone, methyl butyl ketone, and cyclohexanone; ether ester solvents such as methyl cellosolve acetate and butyl cellosolve acetate; aromatic hydrocarbon solvents such as toluene and xylene; and amide 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 an appropriate method such as heating under reduced pressure or drying under normal pressure.

--Other ingredients--
The other components in the substrate layer are not particularly limited and can be appropriately selected within a range that does not impair the properties of the PSA sheet, and examples thereof include tackifying resins; polymer components other than the substrate material; additives such as crosslinking agents, antioxidants, UV absorbers, fillers, polymerization inhibitors, surface conditioners, antistatic agents, antifoaming agents, viscosity modifiers, light stabilizers, weather stabilizers, heat stabilizers, antioxidants, leveling agents, organic pigments, inorganic pigments, pigment dispersants, silica beads, and organic beads; and 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 tackifying resin can be used to improve the adhesion between the adhesive layer and the base layer in the adhesive sheet and to improve heat resistance.

The tackifying resin is not particularly limited and can be selected appropriately depending on the purpose, but it is preferable for the softening point to be 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 tackifying resin, for example, those described in the "-Rubber-based adhesive resin-" section above can be used, and the same applies to preferred embodiments.

The antiaging agent is not particularly limited and can be appropriately selected from known agents depending on the purpose. Examples include phenolic antiaging agents, phosphorus-based antiaging agents (sometimes referred to as "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, phenolic antiaging agents and phosphorus-based antiaging agents are preferred. Using these agents in combination effectively improves the heat resistance stability of the substrate material, thereby maintaining good initial adhesion and providing a pressure-sensitive adhesive sheet with even better heat durability. Note that the phosphorus-based antiaging agent may slightly discolor (yellowing) over time in high-temperature environments. Therefore, the amount used is preferably determined appropriately, taking into consideration the balance between initial adhesion, heat durability, and discoloration prevention.

The phenolic antioxidant can generally be a phenolic compound having a sterically hindered group, and typical examples include monophenols, bisphenols, and polyphenols. 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 antioxidants may be used alone or in combination of two or more.

There are no particular restrictions on the amount of the phenolic antioxidant used and it can be selected appropriately depending on the purpose, but it is preferably used in the range of 0.1 to 5 parts by weight per 100 parts by weight of the substrate material. Using it in the range of 0.5 to 3 parts by weight can effectively improve the heat resistance stability of the substrate material, resulting in 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 selected appropriately depending on 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 this preferred range, the PSA sheet can achieve suitable adhesive strength and can be relatively easily peeled off even during stretch-peel. On the other hand, if the stress at 25% elongation of the base layer is less than 0.2 MPa, the PSA sheet may peel off when a load is applied in the shear direction of the PSA sheet while fixing hard adherends together. If the stress exceeds 10.0 MPa, the force required to stretch the PSA sheet when peeling it off may be excessive.
The stress of the substrate layer at 25% elongation refers to a stress value measured when the substrate layer is 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 conditions of a measurement atmosphere of 23°C and 50% RH, and elongated by 25%.

- Breaking stress of the base layer -
The stress at break of the substrate layer is not particularly limited and can be selected appropriately depending on 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 substrate layer is within this preferred range, the adhesive sheet can be prevented from tearing when stretched and peeled off, and the load required to stretch the adhesive sheet is not excessive, making it easy to peel off again. On the other hand, when the stress at break of the substrate layer is less than 1.5 MPa, the adhesive sheet may tear when stretched and peeled off, and when it exceeds 100.0 MPa, the adhesive sheet may not be stretched sufficiently to be able to 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, if an adhesive sheet that is thick and has a high breaking stress is stretched and then tried to be re-peeled, it may not be possible to stretch it sufficiently and the sheet may not be re-peeled.
The stress at break of the substrate layer refers to a stress value measured when the substrate 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 substrate layer breaks.

-Elongation at break of base layer-
The elongation at break of the base layer is not particularly limited and can be selected appropriately depending on the purpose, but is preferably 200% to 1,300%, more preferably 400% to 1,300%, and even more preferably 700% to 1,300%. If the elongation at break of the base layer is 200% or more, even if the pressure-sensitive adhesive sheet is firmly adhered to an adherend, when the pressure-sensitive adhesive sheet is re-peeled, the stress required to stretch the sheet horizontally to vertically relative to the adherend surface is not too great, and the pressure-sensitive adhesive sheet can be easily peeled off without excessive stretching. Furthermore, if the elongation at break is 1,300% or less, when the pressure-sensitive adhesive sheet is re-peeled, the stretching distance horizontally to vertically relative to the adherend surface is not too long, allowing for work to 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 horizontally to vertically relative to the adhesive surface of the adherend, and 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 adhesive surface of the adherend becomes too long, which may result in poor workability.
The elongation at break of the substrate layer refers to a tensile elongation percentage measured when the substrate 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 length direction at a pulling rate 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 when the substrate layer breaks.

- Average thickness of base layer -
The average thickness of the base layer is not particularly limited and can be appropriately selected depending on the intended 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 above-mentioned preferred range, the PSA sheet can easily follow the distortion of the adherend and can easily obtain high adhesive strength, and the stress required when re-peeling the PSA sheet having the base layer while stretching it in the horizontal to vertical direction relative to the adhesion surface of the adherend is not too large, which is preferable.
In this specification, the "average thickness of the base material layer" refers to the average value of thicknesses measured at a total of 25 points, the base material layer being cut at 5 points at 100 mm intervals in the longitudinal direction, in a direction perpendicular to the longitudinal direction (sometimes referred to as "width direction"), and the thickness of each cut surface being measured at 5 points at 100 mm intervals in the width direction 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 depending on the purpose. However, 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 above-mentioned preferred range, the adhesive sheet can achieve excellent adhesion and removability. On the other hand, if the ratio is greater than 5/1, there is a possibility that only the adhesive layer will remain on the adherend during the re-peeling process of the adhesive sheet. Furthermore, if the ratio is less than 1/5, there is a concern that the adhesive layer will not be able to conform to the surface of the adherend, resulting in a significant decrease in adhesive strength.

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

The base layer may be surface-treated in order to further improve 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 pressure-sensitive adhesive sheet. Examples 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 demographics>>
The other layers in the pressure-sensitive adhesive sheet are not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include a primer layer, an antistatic layer, a non-flammable layer, a decorative layer, a conductive layer, a heat-conductive layer, and a release layer.

- Stress of adhesive sheet at 25% elongation -
The stress at 25% elongation of the pressure-sensitive adhesive sheet is not particularly limited and can be selected appropriately depending on 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 at 25% elongation of the pressure-sensitive adhesive sheet is 0.15 MPa to 82 MPa, the pressure-sensitive adhesive sheet can achieve suitable adhesive strength and can be relatively easily peeled off even during stretch-peeling. On the other hand, when the stress at 25% elongation of the pressure-sensitive adhesive sheet 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 together. Furthermore, when the stress at 25% elongation of the pressure-sensitive adhesive sheet exceeds 82 MPa, the force required to stretch the pressure-sensitive adhesive sheet when peeling it off may be excessive.
The stress of the pressure-sensitive adhesive sheet at 25% elongation refers to the stress value measured when the pressure-sensitive adhesive sheet is punched out into a dumbbell shape with 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 selected appropriately depending on 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 this preferred range, the pressure-sensitive adhesive sheet can be prevented from tearing when stretched and peeled off, and the load required to stretch the pressure-sensitive adhesive sheet is not excessive, making it easy to peel off again. 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 stretched and peeled off, and when it exceeds 100.0 MPa, the pressure-sensitive adhesive sheet may not be stretched sufficiently when attempting to stretch and peel off again, and may not be re-peeled. The force required to stretch and deform the adhesive sheet also depends on the thickness of the adhesive sheet. For example, if an adhesive sheet that is thick and has a high breaking stress is stretched and then tried to be re-peeled, it may not be possible to stretch it sufficiently and the sheet may not be re-peeled.
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 with a gauge length of 20 mm and a width of 6 mm, and pulled in the longitudinal direction at a pulling rate 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 selected appropriately 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%. If the elongation at break of the pressure-sensitive adhesive sheet is 500% or more, even if the pressure-sensitive adhesive sheet is firmly adhered to an adherend, when the pressure-sensitive adhesive sheet is re-peeled, the stress required to stretch the pressure-sensitive adhesive sheet horizontally to vertically relative to the adherend surface is not too great, and the pressure-sensitive adhesive sheet can be easily peeled off without excessive stretching. Furthermore, if the elongation at break is 2,000% or less, when the pressure-sensitive adhesive sheet is re-peeled, the stretching distance horizontally to vertically relative to the adherend surface is not too long, allowing for work to 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 adhesive surface of the adherend, and 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 adhesive surface of the adherend becomes too long, which may result 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 is punched out into a dumbbell shape with a gauge length of 20 mm and a width of 6 mm, and pulled in the length direction at a pulling rate 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.

- 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 "Evaluation of Impact Resistance" in the Examples below. In the impact resistance evaluation, 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 PSA 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 PSA sheet has an appropriate adhesive strength without causing peeling or slippage from the adherend, and can be easily peeled off when stretched horizontally to vertically relative to the adhesion 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 resistant to peeling 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, displacement when a shear stress is applied to an adherend fixed with the pressure-sensitive adhesive sheet can be suppressed.
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 below.

- Splitting adhesive strength of adhesive sheet -
The pressure-sensitive adhesive sheet has excellent splitting adhesive strength and is resistant to peeling even when a load is applied in the splitting direction of the pressure-sensitive adhesive sheet (sometimes referred to as the "thickness direction"). The splitting adhesive strength of the pressure-sensitive adhesive sheet can be selected appropriately within a range that does not impair the effects of the present invention, but 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 splitting adhesive strength is within the preferred range, peeling can be suppressed when a stress in the splitting direction is applied to an adherend fixed with the pressure-sensitive adhesive sheet.
The splitting adhesive strength of the pressure-sensitive adhesive sheet can be confirmed, for example, by the method described in "Measurement of Splitting Adhesion Strength" in the Examples 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 measured at a total of 25 points, the thickness of which is measured at five points at 100 mm intervals in the width direction on each cut surface of the adhesive sheet at five points at 100 mm intervals in the width direction using a TH-104 thickness measuring instrument 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 component to be attached is a display, a speaker, a battery, or the like, and these are to be fixed, the average width of the pressure-sensitive adhesive sheet can be appropriately adjusted depending on 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 100 mm intervals in the longitudinal direction using a known measuring instrument such as a straight ruler (scale), 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 multilayer simultaneous formation step in which the pressure-sensitive adhesive layer forming step and the base layer forming step are performed simultaneously.

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

-Base material layer formation 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 embodiments are also similar.

-Lamination process-
The lamination step is a step of laminating the base material layer and the adhesive layer. The method for 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 can 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 attachment mode in which at least a portion of the first attachment object is linear are as described above.

<<Fixing 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 in a state in which at least two ends of the adhesive sheet are exposed from the second object to be attached.
The second attachment target and the state in which at least two end portions 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 stretching and peeling from one end, they can be stretched and peeled from the other end to the end to be peeled all the way through. Furthermore, since the adhesive sheet has suitable adhesive strength during use, they can be used for a wide range of electronic components, regardless of their size, including 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 devices, 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 any way.

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

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

<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) used was a mixture (SIS) of a styrene-isoprene copolymer and a styrene-isoprene-styrene copolymer, containing 15% by weight of the styrene-derived structural unit represented by the chemical formula (1) and containing 12% by weight of the styrene-isoprene copolymer relative to the total amount of the resin composition (3).

(Preparation Example 1: Preparation of Pressure-Sensitive Adhesive Composition (1))
A reaction vessel equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping funnel was charged with 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. The mixture was stirred and heated to 65°C while blowing in nitrogen to obtain mixture (1). Next, 4 parts by weight of a 2,2'-azobisisobutyronitrile solution (2.5% by weight solids) previously dissolved in ethyl acetate was added to mixture (1), and the mixture was stirred and held at 65°C for 10 hours to obtain mixture (2). Next, mixture (2) was diluted with 98 parts by weight of ethyl acetate and filtered through a 200-mesh wire netting 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) was mixed and stirred with 5 parts by weight of a polymerized rosin ester tackifier resin (D-125, Arakawa Chemical Co., Ltd.) and 15 parts by weight of a petroleum-based tackifier resin (FTR (registered trademark) 6125, manufactured by Mitsui Chemicals, Inc.), and then ethyl acetate was added to obtain a 31 wt% solids adhesive resin solution (1). Next, 100 parts by weight of the adhesive resin solution (1) was mixed with 1 part by weight of carbon black (MA220, manufactured by Mitsubishi Chemical Corporation), 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%, nonvolatile content 40 wt%). The mixture was stirred and mixed uniformly, and then filtered through a 100-mesh wire net to obtain a 31.1 wt% solids 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 filler added in Preparation Example 2 were 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 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 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 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 a glycerin ester of disproportionated rosin (Super Ester A100, Arakawa Chemical Industries, Ltd.), 5 parts by weight of a pentaerythritol ester of polymerized rosin (Pensel D135, Arakawa Chemical Industries, Ltd.), and 20 parts by weight of a styrene-based petroleum resin (FTR (registered trademark) 6100, Mitsui Chemicals, Inc.) 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 solids 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 solids 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 pressure-sensitive adhesive resin (2) to obtain a pressure-sensitive adhesive composition (8).

(Production Example 1: Production of Pressure-Sensitive Adhesive Sheet (1))
The pressure-sensitive adhesive composition (1) was applied to a release liner (Film Vina 75E-0010GT, manufactured by Fujimori Kogyo Co., Ltd., the same applies hereinafter) 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 to 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 laminated by applying a pressure of 0.2 MPa to produce an adhesive sheet (1).

(Production Example 2: Production of Pressure-Sensitive 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) 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 1.

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

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

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

(Production Example 6: Production of Pressure-Sensitive 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 Pressure-Sensitive Adhesive Sheet (7))
A pressure-sensitive adhesive sheet (7) was produced in the same manner as in Production Example 1, except that in the production of the pressure-sensitive adhesive sheet (1) of Production Example 1, the type of pressure-sensitive adhesive composition was changed to the conditions shown in Table 2.

(Production Example 8: Production of Pressure-Sensitive 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 Pressure-Sensitive Adhesive Sheet (9))
A pressure-sensitive adhesive sheet (9) was produced in the same manner as in Production Example 1, except that in the production of the pressure-sensitive adhesive sheet (1) of Production Example 1, the thickness of the base material layer and the type of pressure-sensitive adhesive composition were changed to the conditions described in Table 2.

(Production Example 10: Production of Pressure-Sensitive 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 described in Table 2.

(Production Example 11: Production of Pressure-Sensitive 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) of Production Example 1, the thickness of the base material layer and the type of 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 pressure-sensitive adhesive sheets (1) to (11) of Production Examples 1 to 11; the stress at 25% elongation, stress at break, elongation at break, and filler volume ratio of the adhesive layer in the pressure-sensitive 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 pressure-sensitive adhesive sheets (1) to (11) of Production Examples 1 to 11 were measured or evaluated using 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 Pressure-Sensitive Adhesive Sheet or Substrate Layer>>
Each pressure-sensitive adhesive sheet or each base material layer was punched out into a dumbbell shape with a gauge length of 20 mm and a width of 6 mm, and the stress at 25% elongation, stress at break, and elongation at break of each pressure-sensitive adhesive sheet or each base material layer was measured by pulling in the longitudinal direction at a pulling rate 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.

<<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 using 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 , and the density B of the filler particles was calculated as 2.42 g/cm ³ for aluminum hydroxide and 8.90 g/cm ³ for nickel.

<<Impact resistance evaluation>>
Two pieces of each adhesive sheet were prepared by cutting them into a length of 20 mm and a width of 5 mm. As shown in Fig. 5A, the adhesive sheet 31 was attached parallel to an acrylic plate 32 (length 50 mm, width 50 mm, thickness 2 mm, Acrylite L, color: colorless, manufactured by Mitsubishi Rayon Co., Ltd.) with a 40 mm gap between them. Next, as shown in Fig. 5B, the acrylic plate 32 with the adhesive sheet 31 attached was attached to the center of an ABS plate 33 (length 150 mm, width 100 mm, thickness 2 mm, ToughAce R, manufactured by Sumitomo Bakelite Co., Ltd., color: natural, no grain). The laminated structure of the acrylic plate 32, the adhesive sheet 31, and the ABS plate 33 was pressed and bonded by rolling it back and forth once with a roller while applying a load of 2 kg, and then left to stand for 24 hours under conditions of 40°C and 50% RH to prepare a test specimen.
As shown in FIG. 5C , a U-shaped measurement platform 34 (150 mm long, 100 mm wide, 45 mm high, and 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 specimen was placed on top of it with the acrylic plate 32 of the test specimen facing downward. Under conditions of an ambient temperature of 23°C and 50% RH, a stainless steel impact core (25 mm diameter, 300 g weight) 35 was dropped onto the center of the ABS plate 33 from the ABS plate 33 side. The height of the impact core 35 was changed in 10 cm increments starting from 10 cm, and the impact core 35 was dropped five times at 10-second intervals for each height. The height at which peeling or damage of the adhesive sheet on the test specimen was observed was measured. Note that specimens that did not peel or damage the adhesive sheet when dropped from a height of 30 cm or more were deemed suitable for use.

<<Measurement of 180° Peel Adhesion Strength>>
The 180° peel adhesive strength of each PSA sheet was measured in accordance with JIS Z 0237. Specifically, each PSA sheet was cut to a length of 150 mm and a width of 20 mm, and one side of the PSA sheet was backed with a 25 μm thick PET film. Next, the other side of the PSA sheet was attached to a stainless steel plate (length 100 mm, width 30 mm, thickness 3 mm) under conditions of an atmosphere of 23°C and 50% RH, and the laminated structure of the PSA sheet and the stainless steel plate was pressed and bonded by rolling it back and forth once with a roller while applying a load of 2 kg, and then left to stand for 1 hour under conditions of an atmosphere of 23°C and 50% RH to prepare a test specimen.
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 pressure-sensitive adhesive sheet was cut into a length of 20 mm and a width of 20 mm. Under conditions of an atmosphere of 23°C and 50% RH, one side of the pressure-sensitive 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 adhesive area was 20 mm x 20 mm. Next, a clean, 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 side of the pressure-sensitive adhesive sheet opposite to the side to which the stainless steel plate A was attached. The laminated structure of the stainless steel plate A, the pressure-sensitive adhesive sheet, and the stainless steel plate B was pressed back and forth with a roller while applying a load of 5 kg, and then allowed to stand for 24 hours under conditions of an atmosphere of 23°C and 50% RH, to prepare a test specimen.
Under conditions of an atmosphere of 23°C and 50% RH, with stainless steel plate A constituting the test piece fixed, 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 pressure-sensitive adhesive sheet was cut to a length of 20 mm and a width of 20 mm. Under conditions of an atmosphere of 23°C and 50% RH, one side of the pressure-sensitive adhesive sheet was attached to the surface of a clean, smooth-surfaced 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-surfaced aluminum plate (alloy number A1050, length 50 mm, width 40 mm, thickness 3 mm) was attached to the side of the pressure-sensitive adhesive sheet opposite to the side to which the aluminum plate was attached. The laminated structure of the two aluminum plates and the pressure-sensitive adhesive sheet was pressed back and forth once with a roller while applying a load of 5 kg, and then left to stand for 24 hours under conditions of an atmosphere of 23°C and 50% RH to prepare a test specimen.
Under conditions of an atmosphere of 23°C and 50% RH, with aluminum plate A constituting the test piece fixed, aluminum plate B constituting the test piece was stretched in the split direction (thickness direction) of the pressure-sensitive adhesive sheet at a pulling rate of 50 mm/min using a Tensilon tensile tester (model: RTF-1210, manufactured by A&D Co., Ltd.), and the split adhesive strength was measured.

(Test Examples 1 to 11)
Each of the pressure-sensitive adhesive sheets (1) to (11) of Production Examples 1 to 11 was cut to a width of 10 mm and a length of 60 mm. As shown in FIG. 6A , one surface 41a of the pressure-sensitive adhesive sheet 41 was linearly attached to a clean, smooth-surfaced aluminum plate 42 (alloy number A1050, length 50 mm, width 40 mm, thickness 3 mm). Next, the other surface 41b of the pressure-sensitive 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: colorless, manufactured by Mitsubishi Rayon Co., Ltd.). At this time, both ends (first gripping portion A and second gripping portion B) of the pressure-sensitive adhesive sheet 41 in the longitudinal direction (stretching direction) were attached with a width of 10 mm and a length of 10 mm exposed from both ends of the acrylic plate 43. Next, the laminated structure of the aluminum plate 42, adhesive sheet 41, and acrylic plate 43 was pressed against each other by rolling it back and forth once while applying a load of 5 kg, 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)
Each of the pressure-sensitive adhesive sheets (1) to (11) of Production Examples 1 to 11 was cut to a width of 10 mm and a length of 70 mm. As shown in FIG. 6C , one surface 44a of the pressure-sensitive adhesive sheet 44 was linearly attached to a clean, smooth-surfaced aluminum plate 42 (alloy number A1050, length 50 mm, width 40 mm, thickness 3 mm). Next, the other surface 44b of the pressure-sensitive 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: colorless, manufactured by Mitsubishi Rayon Co., Ltd.). At this time, one end (gripping portion A') of the pressure-sensitive adhesive sheet 44 in the longitudinal direction (extension direction) was attached from one end of the acrylic plate 43 with a width of 10 mm and a length of 10 mm exposed. Next, the laminate structure of the aluminum plate 42, adhesive sheet 44, and acrylic plate 43 was pressed against each other by rolling it back and forth once while applying a load of 5 kg, 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."

<<Removability Evaluation 1>>
The laminate structures of Test Examples 1 to 11 and Comparative Test Examples 1 to 11 were evaluated for removability in the horizontal direction by the following method.
The first gripping portion A and the second gripping portion B of each of the PSA sheets used in Test Examples 1 to 11, and the gripping portion A' of each of the PSA sheets used in Comparative Test Examples 1 to 11, were stretched in the 180° direction (horizontal direction) (the direction shown as 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, with five stretch-peel tests in the horizontal direction (n = 5) and five stretch-peel tests in the vertical direction (n = 5). In the case of application mode X in Test Examples 1 to 11, stretch-peeling was performed from either the first gripping portion A or the second gripping portion B, and then stretch-peeling from the other, which was counted 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 based on the following evaluation criteria. Furthermore, tearing of the adhesive sheet during stretch-peel and the ease of dismantling the aluminum plate and acrylic plate were evaluated based on the following evaluation criteria. The evaluation results are shown in Table 3 below.

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

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

[Evaluation criteria for shredding]
◎: 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 torn pieces, "○" and "◎" indicate that there is no problem 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 is no problem in use.

The results in Table 3 above show that when the application mode in Test Examples 1 to 11 was X, there was no contamination from the adhesive after peeling, and even if the tape tore during stretch-peeling from one end (first gripping portion), it was possible to stretch-peel it from the other end (second gripping portion) and peel it 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 the tape tore during stretch-peeling from one end, it was not possible to peel it all the way, and the aluminum plate and acrylic plate could not be disassembled.

<<Removability Evaluation 2>>
The laminate structures of Test Examples 1 to 11 were evaluated for removability in the vertical direction 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 indicated by the stretching direction p in FIG. 6A ) to a 90° direction (vertical direction) relative to the adhesive surface of the pressure-sensitive adhesive sheet (the direction indicated by the stretching direction p in FIG. 6B ), and the degree of adhesive residue on the adherend (acrylic plate) after peeling of the pressure-sensitive adhesive sheet, tearing of the pressure-sensitive adhesive sheet during stretch-peeling, and dismantling ability 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 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 a 90° angle (perpendicular) to the adhesive surface of the adhesive sheet.

The present invention includes, for example, the following aspects.
<1> An electronic component comprising an adhesive sheet having one surface attached to a first attachment object so that at least a portion of the surface is linear, and the other surface attached to a 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 and second attachment targets is a recovered component.
<3> The electronic component according to any one of <1> and <2>, wherein the recovered parts are at least one of display glass and batteries.
<4> The electronic component according to any one of <1> to <3>, wherein, when the width of the adhesive area of the electronic component is X (cm) and the length of the adhesive area is Y (cm), 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 components can be quickly peeled off, are not contaminated by the adhesive after peeling, and even if they tear while stretching and peeling from one end, they can be stretched and peeled from the other end to the end to be peeled all the way through. Furthermore, since the adhesive sheet has suitable adhesive strength during use, they can be used for a wide range of electronic components, regardless of their size, including 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 devices, cameras, and personal computers, and the components that make up these devices.

REFERENCE SIGNS LIST 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 object 23 Second attachment object 31 Adhesive sheet 32 Acrylic plate 33 ABS plate 34 U-shaped measurement table 35 Impact core 41 Adhesive sheet 41a One surface of adhesive sheet 41 41b Other surface of adhesive sheet 41 42 First attachment object 43 Second attachment object 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 (9)

a stretch-releasable adhesive sheet having one surface attached to a first object so that at least a portion of the surface is linear, and the other surface attached to a second object, with at least two ends exposed from the second object;
An electronic component characterized in that the 180° peel adhesive strength of the pressure-sensitive adhesive sheet is 15.5-35 N/20 mm. The electronic component according to claim 1, wherein at least one of the first attachment target and the second attachment target is a recovered part. 3. The electronic component according to claim 2 , wherein the recovered component is at least one of a display glass and a battery. An electronic component according to any one of claims 1-3, wherein the ratio (X/Y) of the width of the adhesive area to the length of the adhesive area (where X (cm) and Y (cm) are the width and length of the adhesive area, respectively) is 1/100,000-1/1. The electronic component described in any one of claims 1 to 4, wherein the adhesive sheet has at least an adhesive layer containing filler particles. The electronic component according to any one of claims 1 to ⁵ , wherein the pressure-sensitive adhesive sheet has a splitting adhesive strength of 80 N/4 cm2 or more. The method for disassembling electronic components according to any one of claims 1 to 6,
A method for dismantling electronic components, characterized in that the first and second attachment objects are disassembled by gripping at least one end of the adhesive sheet exposed from the second attachment object and stretching and peeling the adhesive sheet. Stretching and peeling the adhesive sheet by gripping and simultaneously stretching the multiple ends of the adhesive sheet exposed from the second attachment target, or
8. The method for dismantling electronic components according to claim 7, characterized in that the first and second attachment objects are dismantled by: gripping and stretching any one of the plurality of ends of the adhesive sheet exposed from the second attachment object to peel off a portion of the adhesive sheet, and then gripping and stretching at least one of the ends other than the end that was previously stretched to peel off the remaining portion. The electronic component according to any one of claims 1 to ⁶ , wherein the adhesive sheet has a shear adhesive strength of 500 N/4 cm2 or more.