CN113174209A

CN113174209A - Adhesive sheet, repeatedly bending laminated member, and repeatedly bending device

Info

Publication number: CN113174209A
Application number: CN202011526152.7A
Authority: CN
Inventors: 小鲭翔; 高桥洋一; 七岛祐
Original assignee: Lintec Corp
Current assignee: Lintec Corp
Priority date: 2020-01-27
Filing date: 2020-12-22
Publication date: 2021-07-27
Also published as: KR20210095992A; TW202130759A; JP7402066B2; JP2021116359A

Abstract

The invention provides an adhesive sheet with excellent durability to bending, a repeatedly bending laminated member and a repeatedly bending device. The adhesive sheet (1) has an adhesive layer (11), and the adhesive layer (11) is used for bonding to form a device capable of repeated bending(3) The one flexible member (21) and the other flexible member (22) of (2) are used for clamping the adhesive layer (11) with the thickness of 100 μm, and the water vapor transmission amount measured according to JIS K7129 is 150 g/(m) under the conditions of 40 ℃ and 90% RH²24h) or more, and the storage modulus G' (85) at 85 ℃ of the adhesive constituting the adhesive layer (11) is 0.02MPa or more and 0.2MPa or less.

Description

Adhesive sheet, repeatedly bending laminated member, and repeatedly bending device

Technical Field

The present invention relates to an adhesive sheet for a repeatedly bending device, a repeatedly bending laminated member, and a repeatedly bending device.

Background

In recent years, as a display body (display) of an electronic device which is one of devices, a flexible display has been proposed. As a flexible display, in addition to a display in which only one curved surface molding is performed, a repeated bending display for repeated bending (bending) use has been proposed.

In the above-described display device with repeated bending, it is conceivable to bond one bendable member (bendable member) constituting the display device with another bendable member by an adhesive layer of an adhesive sheet. However, when the conventional adhesive sheet is used for a display device which is repeatedly bent, problems in durability such as peeling at the interface between the adhesive layer and the adherend in the bent portion due to repeated bending occur.

As the conventional adhesive sheet, for example, an adhesive sheet disclosed in patent document 1 can be cited. The adhesive sheet has an adhesive layer composed of an adhesive composition containing: a (meth) acrylic polymer and a polyrotaxane containing a structural unit derived from a monomer having an aromatic ring structure, which are intended to have excellent stress relaxation properties and durability in optical applications.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2016-155911

Disclosure of Invention

Technical problem to be solved by the invention

However, in the examples disclosed in patent document 1, the amount of the hydroxyl group-containing monomer to be incorporated as a crosslinking point in the acrylic polymer is small, and the amount of the crosslinking agent to be used is also small. Therefore, it is considered that the crosslinking agent is consumed by crosslinking the polyrotaxanes with each other, and the crosslinked structure of the polyrotaxane and the acrylic polymer is not sufficiently formed. Therefore, the stress relaxation property of the adhesive is not sufficient for application to a display device which is repeatedly bent.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an adhesive sheet having excellent durability against bending, a repeatedly bent laminated member, and a repeatedly bent device.

Means for solving the problems

In order to achieve the above object, the first aspect of the present invention provides an adhesive sheet comprising an adhesive layer for bonding one flexible member and another flexible member constituting a repetitive flexure device, wherein the adhesive layer having a thickness of 100 μm is sandwiched between 2 sheets of Tetoron mesh #380, and the water vapor transmission amount measured according to JIS K7129 is 150 g/(m) under conditions of 40 ℃ and 90% RH²24h) or more, and the storage modulus G' (85) at 85 ℃ of the adhesive constituting the adhesive layer is 0.02MPa or more and 0.2MPa or less (invention 1).

In the above invention (invention 1), by providing the adhesive agent layer with the above physical properties, when a laminate in which one flexible member and another flexible member are bonded to each other by the adhesive agent layer is repeatedly bent at a high temperature or the laminate is left in a bent state for a long period of time, peeling is less likely to occur at the interface between the adhesive agent layer and the adherend in the bent portion, and the durability is excellent. Further, by providing the adhesive layer with the above-mentioned water vapor transmission amount, the wet heat whitening resistance is also excellent.

In the invention (invention 1), the gel fraction of the adhesive constituting the adhesive layer is preferably 10% or more and 90% or less (invention 2).

In the above inventions (inventions 1 and 2), the adhesive agent layer preferably has a haze value of 10% or less at 23 ℃ (invention 3).

In the above inventions (inventions 1 to 3), it is preferable that the storage modulus G' (23) of the adhesive constituting the adhesive agent layer at 23 ℃ is 0.02MPa or more and 0.3MPa or less (invention 4).

In the above inventions (inventions 1 to 4), the adhesive constituting the adhesive layer preferably contains a polyrotaxane compound (invention 5).

In the above inventions (inventions 1 to 5), the adhesive constituting the adhesive layer is preferably an acrylic adhesive (invention 6).

In the above inventions (inventions 1 to 6), it is preferable that the adhesive sheet includes 2 release sheets, and the adhesive layer is sandwiched between the release sheets so as to be in contact with release surfaces of the 2 release sheets (invention 7).

The second aspect of the present invention provides a repeatedly bendable laminated member comprising one bendable member and another bendable member constituting a repeatedly bendable device, and an adhesive layer for bonding the one bendable member and the another bendable member to each other, wherein the adhesive layer is composed of the adhesive layer of the adhesive sheet (aspects 1 to 7) (aspect 8).

The present invention provides a repeating and bending device comprising the repeating and bending laminated member (invention 8) (invention 9).

Effects of the invention

The adhesive sheet, the repeatedly bendable laminated member, and the repeatedly bendable device of the present invention are excellent in durability against bending.

Drawings

Fig. 1 is a sectional view of an adhesive sheet according to an embodiment of the present invention.

Fig. 2 is a sectional view of a repeatedly bent laminated member according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view of a recurved bend device in accordance with one embodiment of the invention.

Fig. 4 is an explanatory view (side view) illustrating the static bending test.

Fig. 5 is an explanatory view (side view) for explaining the dynamic bending test.

Description of the reference numerals

1: an adhesive sheet; 11: an adhesive layer; 12a, 12 b: a release sheet; 2: repeatedly bending the laminated member; 21: a first flexible member; 22: a second flexible member; 3: repeatedly bending the device; 31: coating a film; 32: a first adhesive layer; 33: a polarizing film; 34: a second adhesive layer; 35: a touch sensitive film; 36: a third adhesive layer; 37: an organic EL element; 38: a fourth adhesive layer; 39: a TFT substrate; s: a test piece; p: a holding plate.

Detailed Description

Hereinafter, embodiments of the present invention will be described.

[ adhesive sheet ]

The pressure-sensitive adhesive sheet according to one embodiment of the present invention has a pressure-sensitive adhesive layer for bonding one flexible member and another flexible member constituting a device which is repeatedly bent, and a release sheet is preferably laminated on one side or both sides of the pressure-sensitive adhesive layer. The repetitive bending device and the bendable member will be described later.

In the adhesive sheet of the present embodiment, the adhesive layer is made 100 μm thick, and the adhesive layer is sandwiched by 2 Tetoron mesh #380 pieces, and the water vapor transmission rate measured according to JIS K7129 is 150 g/(m) under the conditions of 40 ℃ and 90% RH²24h) or more, and the storage modulus G' (85) at 85 ℃ of the adhesive constituting the adhesive layer is 0.02MPa or more and 0.2MPa or less. The details of the method for measuring the water vapor transmission amount and the storage modulus in the present specification are shown in the test examples described later.

By providing the adhesive layer of the present embodiment with the above-described physical properties, the adhesive layer has excellent durability against bending (hereinafter, may be simply referred to as "durability"). Specifically, when a laminate in which one flexible member and another flexible member are bonded to each other with the adhesive layer is repeatedly bent at a high temperature (hereinafter, sometimes referred to as "dynamic durability" or "dynamic durability"), or when the laminate is left in a bent state for a long period of time, peeling is less likely to occur at the interface between the adhesive layer and the adherend at the bent portion. Further, by providing the adhesive layer of the adhesive sheet of the present embodiment with the above-described water vapor transmission amount, even when the repeatedly bent device is placed under high-temperature and high-humidity conditions, moisture that has penetrated into the adhesive layer is easily released from the adhesive layer when the temperature returns to normal temperature and normal humidity, condensation of moisture is less likely to occur, and whitening of the adhesive layer can be suppressed. That is, the adhesive sheet of the present embodiment is excellent in both durability and resistance to wet-heat whitening.

From the viewpoint of the durability and the resistance to wet-heat whitening, the water vapor transmission amount needs to be 150 g/(m)²24h) or more, preferably 160 g/(m)²24h) or more, particularly preferably 170 g/(m)²24h) or more, and more preferably 190 g/(m)²24h) above. On the other hand, from the viewpoint of the durability, the water vapor transmission amount is preferably 500 g/(m)²24h) or less, more preferably 300 g/(m)²24h) or less, and particularly preferably 250 g/(m), considering the influence of the increase in hardness of the surface of the adhesive agent layer accompanying the increase in hydrogen bond on the durability²24h) or less, more preferably 200 g/(m)²24h) or less.

From the viewpoint of the durability, the storage modulus G' (85) of the adhesive constituting the adhesive layer needs to be 0.02MPa or more, preferably 0.03MPa or more, particularly preferably 0.04MPa or more, and more preferably 0.05MPa or more. Similarly, the storage modulus G' (85) is required to be 0.2MPa or less, preferably 0.1MPa or less, particularly preferably 0.08MPa or less, and more preferably 0.06MPa or less, from the viewpoint of durability.

The storage modulus G' (23) of the adhesive constituting the adhesive layer at 23 ℃ is preferably 0.02MPa or more, more preferably 0.03MPa or more, particularly preferably 0.04MPa or more, and further preferably 0.07MPa or more. Thereby, the above-described lower limit value of the storage modulus G' (85) is easily satisfied. The storage modulus G' (23) is preferably 0.3MPa or less, more preferably 0.15MPa or less, particularly preferably 0.10MPa or less, and further preferably 0.08MPa or less. This makes it easy to satisfy the upper limit value of the storage modulus G' (85).

The gel fraction of the adhesive constituting the adhesive layer is preferably 10% or more, more preferably 20% or more, particularly preferably 30% or more, and further preferably 40% or more. Thus, the adhesive can exert a suitable cohesive force capable of withstanding repeated bending. As a result, the durability is further improved. On the other hand, the gel fraction of the pressure-sensitive adhesive of the present embodiment is preferably 90% or less, more preferably 75% or less, particularly preferably 65% or less, further preferably 55% or less, and most preferably 47% or less. From this, it is presumed that the residual stress in the adhesive is reduced by bending, and the durability is further improved. The method for measuring the gel fraction in the present specification is shown in the test examples described later.

The haze value of the adhesive layer at 23 ℃ is preferably 10% or less, more preferably 5% or less, particularly preferably 1% or less, and further preferably 0.7% or less. When the haze value of the adhesive layer at 23 ℃ is as described above, the light transmittance is excellent, and the adhesive layer is suitably used for a repeated bending display. The lower limit of the haze value at 23 ℃ is not particularly limited, but is preferably 0% or more, and more preferably 0.1% or more.

The haze value of the adhesive layer at-40 ℃ is preferably 10% or less, more preferably 5% or less, particularly preferably 1% or less, and further preferably 0.7% or less. When the haze value of the adhesive layer at-40 ℃ is as described above, the obtained flexible display can have excellent durability in cold. The lower limit of the haze value at-40 ℃ is not particularly limited, but is preferably 0% or more, and more preferably 0.1% or more. The haze value at-40 ℃ is a value measured after leaving the adhesive layer at-40 ℃ for 240 hours and then standing at 23 ℃ and 50% RH for 1 hour.

The haze value is a characteristic value including the thickness of the adhesive agent layer, and preferably satisfies the haze value regardless of the thickness of the adhesive agent layer. Herein, the haze value in the present specification is a value measured according to JIS K7136: 2000.

From the viewpoint of image/image visibility, the total light transmittance of the adhesive layer at 23 ℃ is preferably 70% or more, more preferably 80% or more, particularly preferably 90% or more, and further preferably 95% or more. The upper limit of the total light transmittance at 23 ℃ is usually 100%. In addition, the total light transmittance in the present specification is a value measured in accordance with JIS K7361-1: 1997.

The total light transmittance of the adhesive layer at-40 ℃ is preferably 70% or more, more preferably 80% or more, particularly preferably 90% or more, and further preferably 95% or more. By setting the total light transmittance of the adhesive layer at-40 ℃ to the above, the obtained flexible display can have excellent durability in cold. On the other hand, the upper limit of the above-mentioned total light transmittance at-40 ℃ is usually 100%. Here, the total light transmittance at-40 ℃ is a value measured after leaving the adhesive layer at-40 ℃ for 240 hours and then standing at 23 ℃ and 50% RH for 1 hour.

Fig. 1 shows a specific configuration of an example of the pressure-sensitive adhesive sheet of the present embodiment.

As shown in fig. 1, the adhesive sheet 1 of one embodiment is composed of 2

release sheets

12a and 12b and an adhesive layer 11, and the adhesive layer 11 is sandwiched between the 2

release sheets

12a and 12b so as to be in contact with the release surfaces of the 2

release sheets

12a and 12 b. The release surface of the release sheet in the present specification means a surface having releasability in the release sheet, and includes a surface to which a release treatment has been applied and a surface which exhibits releasability even though a release treatment has not been applied.

1. Constituent elements

1-1. adhesive layer

The adhesive layer 11 is made of an adhesive having the above physical properties. The type of the adhesive constituting the adhesive layer 11 is not particularly limited as long as the above physical properties (particularly, the water vapor transmission amount and the storage modulus G' (85)) are satisfied, and may be any of, for example, an acrylic adhesive (main polymer: acrylic polymer), a polyester adhesive (main polymer: polyester polymer), a polyurethane adhesive (main polymer: polyurethane polymer), a rubber adhesive (main polymer: rubber polymer), a silicone adhesive (main polymer: silicone polymer), and the like. The adhesive may be any of emulsion type, solvent type, and non-solvent type, and may be any of crosslinking type and non-crosslinking type. Among them, acrylic adhesives which easily satisfy the above physical properties and are excellent in adhesive physical properties, optical characteristics, and the like are preferable, and particularly, solvent-type acrylic adhesives are preferable.

The adhesive of the present embodiment is preferably an adhesive containing a polyrotaxane compound, and particularly preferably an acrylic adhesive containing a polyrotaxane compound. Specifically, an adhesive obtained by crosslinking an adhesive composition containing a (meth) acrylate polymer (a) (corresponding to the main polymer) and a polyrotaxane compound (B) (hereinafter, sometimes referred to as "adhesive composition P") is preferable, and among these, the adhesive composition preferably further contains a crosslinking agent (C). The adhesive can satisfy the above physical properties and can easily obtain a good adhesive force. In the present specification, (meth) acrylic acid refers to both acrylic acid and methacrylic acid. Other similarities are also applicable. Further, "polymer" also encompasses the concept of "copolymer".

(1) Components of the adhesive composition P

(1-1) (meth) acrylate ester Polymer (A)

The (meth) acrylate polymer (a) preferably contains, as monomer units constituting the polymer, an alkyl (meth) acrylate for exhibiting good adhesiveness and a monomer having a reactive functional group which becomes a crosslinking point (reactive functional group-containing monomer).

The (meth) acrylate polymer (a) preferably contains an aromatic ring-containing monomer as a monomer unit constituting the polymer. Thus, the (meth) acrylate polymer (A) has good compatibility with the polyrotaxane compound (B), and the compatibility can be maintained even in a low-temperature environment. Therefore, it is particularly easy to satisfy the haze value at-40 ℃ and the total light transmittance at-40 ℃.

Further, the (meth) acrylic acid ester polymer (a) preferably contains a nitrogen atom-containing monomer as a monomer unit constituting the polymer. Thus, the reactive functional group of the reactive functional group-containing monomer is activated, and even if the reactive functional group is small, crosslinking with the polyrotaxane compound (B) can be more effectively performed. Therefore, the cohesive force and flexibility of the obtained adhesive are improved, and the storage modulus G '(85) (and the storage modulus G' (23)) can be satisfied more easily.

Therefore, the (meth) acrylate polymer (a) preferably contains an alkyl (meth) acrylate, an aromatic ring-containing monomer, and a reactive functional group-containing monomer as monomer units constituting the polymer, and particularly preferably contains an alkyl (meth) acrylate, an aromatic ring-containing monomer, a nitrogen atom-containing monomer, and a reactive functional group-containing monomer as monomer units constituting the polymer.

The alkyl (meth) acrylate is preferably an alkyl (meth) acrylate having 1 to 20 carbon atoms and containing an alkyl group. The alkyl group is preferably linear or branched.

The alkyl (meth) acrylate having an alkyl group with 1 to 20 carbon atoms preferably contains a monomer having a glass transition temperature (Tg) of-40 ℃ or lower (hereinafter, sometimes referred to as "low Tg alkyl acrylate") as a homopolymer and a monomer having a glass transition temperature (Tg) of more than 0 ℃ as a homopolymer (hereinafter, sometimes referred to as "high Tg alkyl acrylate"). It is presumed that by containing such low Tg alkyl acrylate and high Tg alkyl acrylate as the structural monomer units, the conformation (conformation) of the (meth) acrylate polymer (a) can be prevented from becoming too small. As a result, the number of contact points with the polyrotaxane compound (B) increases, and it is presumed that a sufficient crosslinked structure can be formed with the polyrotaxane compound (B) even if the (meth) acrylate polymer (a) has only a small number of crosslinking points. Therefore, the obtained adhesive layer can exhibit good adhesive force and easily satisfy the storage modulus G' (85).

Examples of the low Tg alkyl acrylate include n-butyl acrylate (Tg-55 ℃ C.), n-octyl acrylate (Tg-65 ℃ C.), isooctyl acrylate (Tg-58 ℃ C.), 2-ethylhexyl acrylate (Tg-70 ℃ C.), isononyl acrylate (Tg-58 ℃ C.), isodecyl acrylate (Tg-60 ℃ C.), isodecyl methacrylate (Tg-41 ℃ C.), n-undecyl methacrylate (Tg-65 ℃ C.), tridecyl acrylate (Tg-55 ℃ C.), and tridecyl methacrylate (Tg-40 ℃ C.). Among these, the low Tg alkyl acrylate is more preferably a low Tg alkyl acrylate having a homopolymer Tg of-45 ℃ or less, and particularly preferably a low Tg alkyl acrylate having a homopolymer Tg of-50 ℃ or less, from the viewpoint of adhesion. Specifically, n-butyl acrylate and 2-ethylhexyl acrylate are particularly preferable. These low Tg alkyl acrylates may be used alone or in combination of two or more.

Examples of the high Tg alkyl acrylate include methyl acrylate (Tg10 ℃ C.), methyl methacrylate (Tg105 ℃ C.), ethyl methacrylate (Tg65 ℃ C.), n-butyl methacrylate (Tg20 ℃ C.), isobutyl methacrylate (Tg48 ℃ C.), t-butyl methacrylate (Tg107 ℃ C.), n-octadecyl acrylate (Tg30 ℃ C.), and n-octadecyl methacrylate (Tg38 ℃ C.). Among them, methyl acrylate and methyl methacrylate are preferable from the viewpoint of easily satisfying the storage modulus G' (85). These high Tg alkyl acrylates may be used alone or in combination of two or more. The high Tg alkyl acrylate does not include an aromatic ring-containing monomer and a nitrogen atom-containing monomer, which will be described later.

The (meth) acrylate polymer (a) preferably contains 40% by mass or more, particularly preferably 50% by mass or more, and further preferably 60% by mass or more of a low Tg alkyl acrylate as a monomer unit constituting the polymer. The (meth) acrylate polymer (a) preferably contains 90% by mass or less, particularly preferably 80% by mass or less, and further preferably 75% by mass or less of a low Tg alkyl acrylate as a monomer unit constituting the polymer.

The (meth) acrylate polymer (a) preferably contains 1 mass% or more, particularly preferably 4 mass% or more, and further preferably 8 mass% or more of a high Tg alkyl acrylate as a monomer unit constituting the polymer. The (meth) acrylate polymer (a) preferably contains 24% by mass or less, particularly preferably 18% by mass or less, and further preferably 13% by mass or less of a high Tg alkyl acrylate as a monomer unit constituting the polymer.

The (meth) acrylate polymer (a) preferably contains at least 45 mass%, more preferably at least 60 mass%, particularly preferably at least 70 mass%, and even more preferably at least 75 mass% of alkyl (meth) acrylate having 1 to 20 carbon atoms containing an alkyl group as a monomer unit constituting the polymer. The alkyl (meth) acrylate is preferably contained in an amount of 94% by mass or less, more preferably 90% by mass or less, particularly preferably 88% by mass or less, and further preferably 83% by mass or less. When the alkyl (meth) acrylate having 1 to 20 carbon atoms and an alkyl group is contained in the above amount, the (meth) acrylate polymer (a) can be provided with appropriate tackiness and easily satisfy the storage modulus G'.

Examples of the aromatic ring-containing monomer include phenyl (meth) acrylate, 2-phenylethyl (meth) acrylate, benzyl (meth) acrylate, naphthyl (meth) acrylate, 2-phenoxyethyl (meth) acrylate, phenoxybutyl (meth) acrylate, ethoxylated o-phenylphenol acrylate, phenoxyester of diethylene glycol (meth) acrylate, phenoxyester of polyethylene glycol (meth) acrylate, biphenyl di (meth) acrylate, and pentafluorobenzyl (meth) acrylate. These aromatic ring-containing monomers may be used alone or in combination of two or more.

The (meth) acrylate copolymer (a) preferably contains 1% by mass or more, more preferably 4% by mass or more, particularly preferably 8% by mass or more, and further preferably 12% by mass or more of an aromatic ring-containing monomer as a monomer unit constituting the polymer. Further, the aromatic ring-containing monomer is preferably contained in an amount of 40% by mass or less, more preferably 30% by mass or less, particularly preferably 23% by mass or less, and further preferably 18% by mass or less. When the content of the aromatic ring-containing monomer is in the above range, the haze value and the storage modulus G' at-40 ℃ described above can be easily satisfied. In addition, the adhesiveness can be maintained well.

Examples of the nitrogen atom-containing monomer include a monomer having an amino group, a monomer having an amide group, and a monomer having a nitrogen-containing heterocycle, and among them, a monomer having an amino group is preferable. In addition, from the viewpoint of increasing the degree of freedom in the high order structure of the adhesive agent composed of the nitrogen atom-containing monomer, it is preferable that the nitrogen atom-containing monomer does not contain any other reactive unsaturated double bond group other than 1 polymerizable group for polymerization to form the (meth) acrylate polymer (a). The nitrogen atom-containing monomer may be used alone or in combination of two or more.

Examples of the monomer having an amino group include monomethylaminoethyl (meth) acrylate, monoethylaminoethyl (meth) acrylate, monomethylaminopropyl (meth) acrylate, monoethylaminopropyl (meth) acrylate, and dimethylaminoethyl (meth) acrylate.

Examples of the monomer having an amide group include (meth) acrylamide, N-methyl (meth) acrylamide, N-methylol (meth) acrylamide, N-tert-butyl (meth) acrylamide, N-dimethyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-dimethylaminopropyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-phenyl (meth) acrylamide, N- (N-butoxymethyl) (meth) acrylamide, dimethylaminopropyl (meth) acrylamide, and N-vinylcaprolactam.

Examples of the monomer having a nitrogen-containing heterocycle include N- (meth) acryloylmorpholine, N-vinyl-2-pyrrolidone, N- (meth) acryloylpyrrolidone, N- (meth) acryloylpiperidine, N- (meth) acryloylpyrrolidine, N- (meth) acryloylaziridine, aziridinylethyl (meth) acrylate, 2-vinylpyridine, 4-vinylpyridine, 2-vinylpyrazine, 1-vinylimidazole, N-vinylcarbazole, N-vinylphthalimide and the like.

The (meth) acrylate copolymer (a) preferably contains 0.01% by mass or more, more preferably 0.1% by mass or more, particularly preferably 0.3% by mass or more, and further preferably 0.8% by mass or more of a nitrogen atom-containing monomer as a monomer unit constituting the polymer. Further, the content of the nitrogen atom-containing monomer is preferably 14% by mass or less, more preferably 8% by mass or less, particularly preferably 4% by mass or less, and further preferably 2% by mass or less. By making the content of the nitrogen atom-containing monomer within the above range, the storage modulus G' described above can be easily satisfied. In addition, the adhesiveness can be maintained well.

Since the (meth) acrylate polymer (a) contains a reactive functional group-containing monomer as a monomer unit constituting the polymer, it is possible to form a crosslinked structure (three-dimensional network structure) by reacting a crosslinking agent (C) described later with a reactive functional group derived from the reactive functional group-containing monomer. Thus, an adhesive having a desired cohesive force and easily satisfying the above physical properties can be obtained.

Examples of the reactive functional group-containing monomer contained in the (meth) acrylate polymer (a) as a monomer unit constituting the polymer include a monomer having a hydroxyl group in the molecule (hydroxyl group-containing monomer), a monomer having a carboxyl group in the molecule (carboxyl group-containing monomer), and the like. These reactive functional group-containing monomers may be used alone or in combination of two or more.

Among the above-mentioned reactive functional group-containing monomers, hydroxyl group-containing monomers or carboxyl group-containing monomers are preferred, and hydroxyl group-containing monomers are particularly preferred. The hydroxyl group-containing monomer easily satisfies the above physical properties.

Examples of the hydroxyl group-containing monomer include hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. Among them, hydroxyalkyl (meth) acrylates having a hydroxyalkyl group having 1 to 4 carbon atoms are preferable from the viewpoint of satisfying the above physical properties. These hydroxyl group-containing monomers may be used alone or in combination of two or more.

Examples of the carboxyl group-containing monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Among these, acrylic acid is preferable from the point of adhesion of the obtained (meth) acrylate polymer (a). These carboxyl group-containing monomers may be used alone or in combination of two or more.

The (meth) acrylate polymer (a) preferably contains 1% by mass or more, particularly preferably 2% by mass or more, and further preferably 3% by mass or more of a reactive functional group-containing monomer as a monomer unit constituting the polymer. The (meth) acrylate polymer (a) preferably contains 13% by mass or less, particularly preferably 8% by mass or less, and further preferably 5% by mass or less of a reactive functional group-containing monomer as a monomer unit constituting the polymer. When the (meth) acrylate polymer (a) contains the reactive functional group-containing monomer as a monomer unit in the above-mentioned amount, the cohesive force of the obtained adhesive is appropriate by the crosslinking reaction with the crosslinking agent (C), and the storage modulus G' described above is easily satisfied. Further, the above-described water vapor transmission amount can be easily satisfied.

In addition, it is considered that it is advantageous to increase the proportion of the hydroxyl group-containing monomer in the (meth) acrylate polymer (a) from the viewpoint of the resistance to wet heat whitening and from the viewpoint of the reduction in the storage modulus G' by surely crosslinking with the polyrotaxane compound (B). However, if the ratio of the hydroxyl group-containing monomer is excessively increased, the water vapor transmission amount increases excessively, hydrogen bonds in the adhesive become extremely large, and the surface of the adhesive layer is presumably hardened to such an extent that the surface does not exhibit an elastic modulus, thereby causing a decrease in bending resistance.

The (meth) acrylate polymer (a) preferably does not contain a carboxyl group-containing monomer as a monomer unit constituting the polymer. Since the carboxyl group is an acidic component, since the carboxyl group-containing monomer is not contained, when a substance which causes a problem due to an acid, for example, a transparent conductive film such as tin-doped indium oxide (ITO), a metal film, a metal mesh, or the like is present in an object to which the adhesive is to be attached, the problem (corrosion, change in resistance value, or the like) due to the acid can be suppressed.

By containing a hydroxyl group-containing monomer as a reactive functional group-containing monomer constituting the (meth) acrylate polymer (a) and not containing a carboxyl group-containing monomer, crosslinking of the (meth) acrylate polymer (a) with the polyrotaxane compound (B) by the crosslinking agent (C) (particularly an isocyanate-based crosslinking agent) can be more effectively performed. As a result, the storage modulus G' described above is more easily satisfied.

The term "free of a carboxyl group-containing monomer" means that the monomer is substantially free of a carboxyl group-containing monomer, and the monomer is allowed to be contained to such an extent that corrosion of a transparent conductive film, a metal wiring, or the like does not occur, except that the monomer is not contained at all. Specifically, the (meth) acrylate polymer (a) is allowed to contain a carboxyl group-containing monomer as a monomer unit in an amount of 0.1% by mass or less, preferably in an amount of 0.01% by mass or less, and more preferably in an amount of 0.001% by mass or less.

The (meth) acrylate polymer (a) may contain other monomers as the monomer unit constituting the polymer, as required. As the other monomer, a monomer containing no reactive functional group is preferable in order not to inhibit the above-mentioned action of the reactive functional group-containing monomer. Examples of the monomer include alkoxyalkyl (meth) acrylates such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate, ethyl acetate, and styrene. These other monomers may be used alone or in combination of two or more.

The polymerization form of the (meth) acrylate polymer (a) may be a random copolymer or a block copolymer.

The weight average molecular weight of the (meth) acrylate polymer (a) is preferably 10 ten thousand or more, more preferably 40 ten thousand or more, particularly preferably 90 ten thousand or more, and further preferably 140 ten thousand or more. The weight average molecular weight of the (meth) acrylate polymer (a) is preferably 300 ten thousand or less, more preferably 230 ten thousand or less, particularly preferably 180 ten thousand or less, and further preferably 160 ten thousand or less. When the weight average molecular weight of the (meth) acrylate polymer (a) is within the above range, the above physical properties are easily satisfied. The weight average molecular weight in the present specification is a value in terms of standard polystyrene measured by a Gel Permeation Chromatography (GPC) method.

The glass transition temperature (Tg) of the (meth) acrylate polymer (A) is preferably-80 ℃ or higher, more preferably-60 ℃ or higher, particularly preferably-50 ℃ or higher, and still more preferably-40 ℃ or higher. The glass transition temperature (Tg) of the (meth) acrylate polymer (A) is preferably 10 ℃ or lower, more preferably 0 ℃ or lower, particularly preferably-10 ℃ or lower, and further preferably-20 ℃ or lower. When the glass transition temperature (Tg) of the (meth) acrylate polymer (a) is within the above range, the storage modulus G' described above is easily satisfied. The glass transition temperature (Tg) of the (meth) acrylate polymer (a) in the present specification is calculated from the glass transition temperature (Tg) of each monomer constituting the (meth) acrylate polymer (a) as a homopolymer by the formula of FOX.

In the adhesive composition P, one kind of the (meth) acrylate polymer (a) may be used alone, or two or more kinds may be used in combination.

(1-2) polyrotaxane Compound (B)

The polyrotaxane compound (B) is a compound in which a linear molecule passes through openings of at least 2 cyclic molecules and has blocking groups (blocking groups) at both ends of the linear molecule. In the polyrotaxane compound (B), the cyclic molecule can freely move (slide) on the linear molecule, but the cyclic molecule cannot be detached from the linear molecule due to the end capping group. That is, the linear molecules and the cyclic molecules are not chemically bonded to each other such as a non-covalent bond, but are mechanically bonded to each other to maintain their forms.

Since the pressure-sensitive adhesive obtained from the pressure-sensitive adhesive composition P contains such a polyrotaxane compound (B), the stress relaxation property is high, and the storage modulus G' described above is easily satisfied. In particular, when the adhesive composition P contains the crosslinking agent (C), when the adhesive composition P is crosslinked, the reactive group of the crosslinking agent (C) reacts with the reactive group of the cyclic molecule of the polyrotaxane compound (B) to form a crosslinking agent adduct. It is also assumed that the (meth) acrylate polymer (a) is bonded to one cyclic molecule of the polyrotaxane compound (B) through the crosslinking agent (C) in the crosslinking agent adduct by a reactive functional group derived from a reactive functional group-containing monomer contained in the polymer, and similarly, the other (meth) acrylate polymer (a) is bonded to the other cyclic molecule of the polyrotaxane compound (B). As a result, a structure (crosslinked structure) is formed in which the plurality of (meth) acrylate polymers (a) are crosslinked with each other via the slidable mechanically-bonded polyrotaxane compound (B). By having such a crosslinked structure, the obtained adhesive is more excellent in stress relaxation property and more likely to satisfy the storage modulus G'.

The adhesive obtained need not have all of the above-described structure, and may include a structure in which 2 (meth) acrylate polymers (a) are directly bonded to each other with a crosslinking agent (C) without the polyrotaxane compound (B).

The polyrotaxane compound (B) of the present embodiment preferably has a cyclic molecule having a reactive group capable of reacting with the reactive group of the crosslinking agent (C). Further, the reactive group is preferably a functional group having hydrophilicity. By providing such a reactive group to the cyclic molecule of the polyrotaxane compound (B), the above-mentioned water vapor transmission amount can be easily satisfied. Examples of the reactive group include a hydroxyl group and a carboxyl group, and among them, a hydroxyl group is preferable.

The polyrotaxane compound (B) of the present embodiment preferably has a cyclic oligosaccharide as a cyclic molecule. The cyclic oligosaccharide has a hydroxyl group as a reactive group in an unmodified state. Further, by using a cyclic oligosaccharide as the cyclic molecule of the polyrotaxane compound (B), an appropriate ring diameter can be selected, and thus, the effect of the movement of the cyclic molecule on the linear molecule can be easily exhibited. Further, various substituents and the like can be easily introduced, whereby the physical properties of the resulting adhesive can be adjusted. Further, cyclic oligosaccharides have an advantage of being easily obtained. In the present specification, the term "cyclic" of "cyclic molecule" or "cyclic oligosaccharide" means substantially "cyclic". That is, the cyclic molecule may not be completely closed as long as it can move on the linear molecule, and may have a helical structure, for example.

The cyclic oligosaccharide preferably includes cyclodextrins such as α -cyclodextrin, β -cyclodextrin, and γ -cyclodextrin, and particularly α -cyclodextrin is preferable. The cyclic molecule of the polyrotaxane compound (B) may be present in a mixture of two or more kinds in the polyrotaxane compound (B) or the adhesive composition P.

The hydroxyl group of the cyclic oligosaccharide as a reactive group may be a hydroxyl group originally present in the cyclic oligosaccharide (referred to as a "unmodified state") or a hydroxyl group introduced into the cyclic oligosaccharide as a substituent.

The lower limit of the hydroxyl value of the cyclic molecule is preferably 10mgKOH/g or more, more preferably 30mgKOH/g or more, and particularly preferably 50mgKOH/g or more. When the lower limit of the hydroxyl value is as described above, the polyrotaxane compound (B) can sufficiently react with the crosslinking agent (C), and a predetermined amount of hydroxyl groups remains, so that the above-described water vapor permeation amount is easily satisfied. The upper limit of the hydroxyl value of the cyclic molecule is preferably 1000mgKOH/g or less, more preferably 200mgKOH/g or less, and particularly preferably 100mgKOH/g or less. If the upper limit of the hydroxyl value exceeds the above-mentioned value, since a plurality of crosslinks are generated in the same cyclic molecule, the cyclic molecule itself becomes a crosslinking point, and the effect of the crosslinking point as the polyrotaxane compound (B) as a whole cannot be exerted, and as a result, sufficient flexibility may not be secured to the obtained adhesive.

The linear molecule of the polyrotaxane compound (B) is not particularly limited as long as it is a molecule or substance which is included in a cyclic molecule and can be integrated by mechanical bonding, not chemical bonding such as covalent bonding, and is linear. In the present specification, the term "linear" of the "linear molecule" means that the molecule is substantially "linear". That is, the linear molecule may have a branch as long as the cyclic molecule can move on the linear molecule.

Examples of the linear molecule of the polyrotaxane compound (B) include polyethylene glycol, polypropylene glycol, polyisoprene, polyisobutylene, polybutadiene, polytetrahydrofuran, polyacrylate, polydimethylsiloxane, polyethylene, and polypropylene. These linear molecules may be present in the adhesive composition P in a mixture of two or more.

The lower limit of the number average molecular weight of the linear molecules of the polyrotaxane compound (B) is preferably 3,000 or more, particularly preferably 10,000 or more, and more preferably 20,000 or more, and if the lower limit of the number average molecular weight is as described above, the amount of movement of the cyclic molecules on the linear molecules can be secured, and flexibility due to the crosslinked structure of the polyrotaxane compound (B) can be sufficiently obtained. The upper limit of the number average molecular weight of the linear molecule of the polyrotaxane compound (B) is preferably 300,000 or less, particularly preferably 200,000 or less, and more preferably 100,000 or less. When the upper limit of the number average molecular weight is as described above, the solubility of the polyrotaxane compound (B) in the solvent is good.

The end-capping group of the polyrotaxane compound (B) is not particularly limited as long as it can maintain a form in which the cyclic molecules are strung by the linear molecules, and examples of such a group include a bulky group and an ionic group.

Specifically, the end capping groups of the polyrotaxane compound (B) are preferably main chains or side chains of dinitrobenzenes, cyclodextrins, adamantyl groups, trityl groups, luciferases, pyrenes, anthracenes, or the like, or polymers having a number average molecular weight of 1,000 to 1,000,000, and these end capping groups may be present in the polyrotaxane compound (B) or the adhesive composition P in a mixture of two or more.

The polyrotaxane compound (B) described above can be obtained by a conventionally known method (for example, the method described in Japanese patent laid-open No. 2005-154675).

The content of the polyrotaxane compound (B) in the adhesive composition P of the present embodiment is preferably 1 part by mass or more, more preferably 4 parts by mass or more, particularly preferably 6 parts by mass or more, and further preferably 7 parts by mass or more, with respect to 100 parts by mass of the (meth) acrylate polymer (a). The content of the polyrotaxane compound (B) is preferably 30 parts by mass or less, more preferably 24 parts by mass or less, particularly preferably 17 parts by mass or less, and further preferably 12 parts by mass or less. When the content of the polyrotaxane compound (B) is within the above range, both the water vapor transmission amount and the storage modulus G' described above can be easily satisfied.

(1-3) crosslinking agent (C)

The crosslinking agent (C) has a reactive group. The reactive group is preferably a reactive group capable of reacting with the reactive functional group of the (meth) acrylate polymer (a) and the reactive group of the cyclic molecule of the polyrotaxane compound (B). Such a crosslinking agent (C) forms a crosslinking agent adduct with the polyrotaxane compound (B). And the crosslinking agent adduct crosslinks the (meth) acrylate polymers (a) to each other to form a three-dimensional network structure. This improves the cohesive force of the adhesive obtained, and the above physical properties are easily satisfied.

Examples of the crosslinking agent (C) include isocyanate crosslinking agents, epoxy crosslinking agents, amine crosslinking agents, melamine crosslinking agents, aziridine crosslinking agents, hydrazine crosslinking agents, aldehyde crosslinking agents, oxazoline crosslinking agents, metal alkoxide crosslinking agents, metal chelate crosslinking agents, metal salt crosslinking agents, and ammonium salt crosslinking agents. Among them, isocyanate-based crosslinking agents having high reactivity with hydroxyl groups are preferable. The isocyanate-based crosslinking agent can sufficiently perform addition of the crosslinking agent to the polyrotaxane compound (B) having a hydroxyl group as a reactive group, and thus the water vapor transmission amount and the storage modulus G' described above can be easily satisfied. The crosslinking agent (C) may be used alone or in combination of two or more.

The isocyanate-based crosslinking agent contains at least a polyisocyanate compound. Examples of the polyisocyanate compound include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate and xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate, biuret and isocyanurate compounds thereof, and adducts thereof with low-molecular active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane and castor oil.

The content of the crosslinking agent (C) in the adhesive composition P is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, particularly preferably 1.0 part by mass or more, and further preferably 1.3 parts by mass or more, relative to 100 parts by mass of the (meth) acrylate polymer (a). The content is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, particularly preferably 2 parts by mass or less, and further preferably 1.8 parts by mass or less. When the content of the crosslinking agent (C) is within the above range, the above physical properties can be easily satisfied.

(1-4) various additives

Various additives generally used in acrylic adhesives, for example, silane coupling agents, ultraviolet absorbers, antistatic agents, tackifiers, antioxidants, light stabilizers, softeners, fillers, refractive index modifiers, and the like can be added to the adhesive composition P as needed. The polymerization solvent or the dilution solvent described later is not included in the additive constituting the adhesive composition P.

The adhesive composition P preferably contains the silane coupling agent. Thus, the obtained adhesive layer has improved adhesion to a flexible member as an adherend and has more excellent adhesion.

The silane coupling agent is preferably an organosilicon compound having at least 1 alkoxysilyl group in the molecule, and has good compatibility with the (meth) acrylate polymer (a) and light transmittance.

Examples of such silane coupling agents include silicon compounds containing a polymerizable unsaturated group such as vinyltrimethoxysilane, vinyltriethoxysilane and methacryloxypropyltrimethoxysilane, silicon compounds having an epoxy structure such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane and 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, silicon compounds containing a mercapto group such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane and 3-mercaptopropyldimethoxymethylsilane, and amino group-containing silicon compounds such as 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane and N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane 3-chloropropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, or a condensate of at least one of these silane coupling agents with an alkyl group-containing silicon compound such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, or the like. These silane coupling agents may be used alone or in combination of two or more.

The content of the silane coupling agent in the adhesive composition P is preferably 0.01 part by mass or more, particularly preferably 0.05 part by mass or more, and more preferably 0.1 part by mass or more, relative to 100 parts by mass of the (meth) acrylate polymer (a). The content is preferably 1 part by mass or less, particularly preferably 0.5 part by mass or less, and further preferably 0.3 part by mass or less. When the content of the silane coupling agent is in the above range, the adhesion of the obtained adhesive layer to a flexible member as an adherend is improved, and the adhesive force is further increased.

(2) Preparation of adhesive composition P

The adhesive composition P can be prepared by: preparing a (meth) acrylate polymer (A), and adding the obtained (meth) acrylate polymer (A), a polyrotaxane compound (B), and a crosslinking agent (C) and additives as required.

The (meth) acrylate polymer (a) can be prepared by polymerizing a mixture of monomers constituting the polymer using a general radical polymerization method. The polymerization of the (meth) acrylate polymer (a) is preferably carried out by a solution polymerization method using a polymerization initiator as necessary. By polymerizing the (meth) acrylate polymer (a) by the solution polymerization method, the obtained polymer can be easily increased in molecular weight and easily adjusted in molecular weight distribution, and the production of low molecular weight products can be further reduced. Therefore, even when the gel fraction is reduced to relieve the degree of crosslinking, the adhesive is less likely to shift due to repeated bending, and an adhesive having excellent durability is easily obtained.

Examples of the polymerization solvent used in the solution polymerization method include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, and methyl ethyl ketone, and two or more kinds thereof may be used simultaneously.

Examples of the polymerization initiator include azo compounds and organic peroxides, and two or more kinds thereof may be used simultaneously. Examples of the azo compound include 2,2 ' -azobisisobutyronitrile, 2 ' -azobis (2-methylbutyronitrile), 1 ' -azobis (cyclohexane-1-carbonitrile), 2 ' -azobis (2, 4-dimethylvaleronitrile), 2 ' -azobis (2, 4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2 ' -azobis (2-methylpropionate), 4 ' -azobis (4-cyanopentanoic acid), 2 ' -azobis (2-hydroxymethylpropionitrile), and 2,2 ' -azobis [2- (2-imidazolin-2-yl) propane ].

Examples of the organic peroxide include benzoyl peroxide, t-butyl peroxybenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di (2-ethoxyethyl) peroxydicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxypivalate, 3,5, 5-trimethylhexanoyl peroxide, dipropyl peroxide, and diacetyl peroxide.

In the polymerization step, a chain transfer agent such as 2-mercaptoethanol is added to adjust the weight average molecular weight of the obtained polymer.

After the (meth) acrylate polymer (a) is obtained, the polyrotaxane compound (B) and, if necessary, the crosslinking agent (C), the additive and the diluting solvent are added to a solution of the (meth) acrylate polymer (a), and the mixture is thoroughly mixed to obtain the adhesive composition P (coating liquid) diluted with the solvent.

In addition, when any of the above-mentioned components is precipitated when a solid component is used or when the component is mixed with another component in an undiluted state, the component may be dissolved or diluted in a diluting solvent in advance and then mixed with another component.

Examples of the diluting solvent include aliphatic hydrocarbons such as hexane, heptane and cyclohexane, aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as methylene chloride and ethylene chloride, alcohols such as methanol, ethanol, propanol, butanol and 1-methoxy-2-propanol, ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone and cyclohexanone, esters such as ethyl acetate and butyl acetate, and cellosolve solvents such as ethyl cellosolve.

The concentration and viscosity of the coating liquid prepared in the above manner are not particularly limited as long as they are within a range in which coating can be performed, and may be appropriately selected depending on the case. For example, the adhesive composition P may be diluted so that the concentration thereof is 10 to 60 mass%. In addition, when obtaining the coating liquid, the addition of a diluting solvent or the like is not essential, and the diluting solvent may not be added as long as the adhesive composition P has a viscosity capable of being applied. In this case, the adhesive composition P is a coating solution in which the polymerization solvent of the (meth) acrylate polymer (a) is directly used as a dilution solvent.

(3) Preparation of Adhesives

The adhesive constituting the adhesive layer 11 of the present embodiment is preferably formed by crosslinking the adhesive composition P. The crosslinking of the adhesive composition P can generally be carried out by heat treatment. Further, the drying treatment when evaporating the diluting solvent or the like from the coating film of the adhesive composition P applied to the desired object may be used as the heating treatment.

The heating temperature of the heating treatment is preferably 50 to 150 ℃, and particularly preferably 70 to 120 ℃. The heating time is preferably 10 seconds to 10 minutes, and particularly preferably 50 seconds to 2 minutes.

After the heat treatment, if necessary, a curing period of about 1 to 2 weeks may be set at normal temperature (e.g., 23 ℃ C., 50% RH). When the curing period is required, an adhesive is formed after the curing period, and when the curing period is not required, an adhesive is formed after the heat treatment is completed.

When the adhesive composition P contains the crosslinking agent (C), the (meth) acrylate polymer (a) and the polyrotaxane compound (B) are crosslinked by the above-mentioned heat treatment (and curing) to form a crosslinked structure through the crosslinking agent (C), thereby obtaining an adhesive.

(4) Thickness of adhesive layer

The lower limit of the thickness (value measured according to JIS K7130) of the adhesive layer 11 of the adhesive sheet 1 of the present embodiment is preferably 1 μm or more, more preferably 5 μm or more, particularly preferably 10 μm or more, and further preferably 15 μm or more. When the lower limit of the thickness of the adhesive agent layer 11 is the above value, the required adhesive force is easily exhibited, and the durability is further excellent.

The upper limit of the thickness of the adhesive layer 11 is preferably 300 μm or less, more preferably 150 μm or less, and particularly preferably 90 μm or less, and further preferably 40 μm or less from the viewpoint of obtaining a thinner device which can be repeatedly bent. When the upper limit value of the thickness of the adhesive agent layer 11 is the above value, the problem of excessive stress generated in the adhesive agent layer due to repeated bending can be suppressed, and the durability is further excellent. The adhesive layer 11 may be formed as a single layer or may be formed by stacking a plurality of layers.

1-2. Release sheet

The

release sheets

12a and 12b protect the adhesive layer 11 until the adhesive sheet 1 is used, and are released when the adhesive sheet 1 (adhesive layer 11) is used. In the adhesive sheet 1 of the present embodiment, one or both of the

release sheets

12a and 12b are not necessarily required.

Examples of the

release sheets

12a and 12b include a polyethylene film, a polypropylene film, a polybutylene film, a polybutadiene film, a polymethylpentene film, a polyvinyl chloride film, a vinyl chloride copolymer film, a polyethylene terephthalate film, a polyethylene naphthalate film, a polybutylene terephthalate film, a polyurethane film, an ethylene vinyl acetate film, an ionomer resin film, an ethylene- (meth) acrylic acid copolymer film, an ethylene- (meth) acrylate copolymer film, a polystyrene film, a polycarbonate film, a polyimide film, and a fluororesin film. In addition, crosslinked films of these films may also be used. Further, a laminated film of these films may be used.

The release surfaces (particularly, the surfaces in contact with the adhesive agent layer 11) of the

release sheets

12a and 12b are preferably subjected to a release treatment. Examples of the release agent used for the release treatment include alkyd based, silicone based, fluorine based, unsaturated polyester based, polyolefin based, and wax based release agents. Of the

release sheets

12a and 12b, it is preferable that one release sheet is a heavy release type release sheet having a large release force, and the other release sheet is a light release type release sheet having a small release force.

The thickness of the

release sheets

12a and 12b is not particularly limited, and is usually about 20 to 150 μm.

2. Physical Properties

(1) Adhesive force

The lower limit of the adhesive force of the adhesive sheet 1 of the present embodiment to soda-lime glass is preferably 0.1N/25mm or more, more preferably 1N/25mm or more, particularly preferably 3N/25mm or more, and further preferably 4.5N/25mm or more. When the lower limit of the adhesive force of the adhesive sheet 1 to soda-lime glass is the above, the durability is further excellent. On the other hand, the upper limit of the above adhesion is not particularly limited, but the reworkability may be required. From this viewpoint, the above-mentioned adhesive force is preferably 60N/25mm or less, more preferably 30N/25mm or less, and particularly preferably 10N/25mm or less. The adhesive force in the present specification means an adhesive force measured basically by a 180-degree peel method according to JIS Z0237:2009, and a specific test method is shown in test examples described later.

(2)CIE1976L^＊a^＊b^＊Color system

CIE1976L of adhesive layer 11 of adhesive sheet 1 of the present embodiment^＊a^＊b^＊Lightness L defined in the color system^＊Preferably 60 or more, more preferably 70 or more, particularly preferably 80 or more, and further preferably 90 or more. Furthermore, the lightness L^＊Preferably 100 or less, more preferably 99 or less, and particularly preferably 98 or less. Color number a of adhesive layer 11^＊The absolute value of (b) is preferably 0 or more, particularly preferably 0.1 or more, and more preferably 0.2 or more. In addition, the chromaticity a^＊The absolute value of (b) is preferably 0.8 or less, particularly preferably 0.6 or less, and further preferably 0.4 or less. Color b of the adhesive layer 11^＊The absolute value of (b) is preferably 0 or more, particularly preferably 0.1 or more, and more preferably 0.2 or more. In addition, the chromaticity b^＊The absolute value of (b) is preferably 0.8 or less, particularly preferably 0.6 or less, and further preferably 0.4 or less. Thus, the adhesive layer 11 can have a color tone suitable for a repeated bending display. In addition, lightness L in the present specification^＊Chroma a^＊And b^＊The measurement method (2) is shown in test examples described later.

3. Preparation of adhesive sheet

The case of using the adhesive composition P will be described as one example of the production of the adhesive sheet 1. After a coating liquid of the adhesive composition P is applied to the release surface of one release sheet 12a (or 12b) and heat treatment is performed to thermally exchange the adhesive composition P and form a coating layer, the release surface of the other release sheet 12b (or 12a) is superimposed on the coating layer. When the curing period is required, the coating layer forms the adhesive layer 11 by providing the curing period, and when the curing period is not required, the coating layer directly forms the adhesive layer 11. Thus, the adhesive sheet 1 was obtained. The conditions for the heat treatment and aging are as described above.

As another production example of the adhesive sheet 1, a coating solution of the adhesive composition P is applied to the release surface of one release sheet 12a, and heat treatment is performed to thermally exchange the adhesive composition P and form a coating layer, thereby obtaining a release sheet 12a with a coating layer. Further, the coating liquid of the adhesive composition P is applied to the release surface of the other release sheet 12b, and heat treatment is performed to thermally exchange the adhesive composition P and form a coating layer, thereby obtaining a release sheet 12b with a coating layer. Then, the coated release sheet 12a and the coated release sheet 12b are bonded to each other so that the two coated layers are in contact with each other. When the curing period is required, the adhesive layer 11 is formed by providing the curing period, and when the curing period is not required, the adhesive layer 11 is directly formed by the stacked coating layers. Thus, the adhesive sheet 1 was obtained. This production example enables stable production even when the adhesive layer 11 is thick.

As a method for applying the coating liquid of the adhesive composition P, for example, a bar coating method, a blade coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, or the like can be used.

[ repeatedly bending the laminated Member ]

As shown in fig. 2, the repeatedly bendable laminated member 2 of the present embodiment includes a first bendable member 21 (one bendable member), a second bendable member 22 (the other bendable member), and an adhesive layer 11, and the adhesive layer 11 is located between the first bendable member 21 and the second bendable member 22, and bonds the first bendable member 21 and the second bendable member 22 to each other.

The adhesive layer 11 in the repeatedly bent and laminated member 2 is the adhesive layer 11 of the adhesive sheet 1.

The repeatedly bending laminated member 2 is the repeatedly bending device itself or a member constituting a part of the repeatedly bending device. The repeated bending device is preferably a display (repeated bending display) capable of being repeatedly bent (including bending), but is not limited thereto. Examples of the repeatedly bending device include an organic electroluminescence (organic EL) display, an electrophoretic display (electronic paper), a liquid crystal display using a plastic substrate (film) as a substrate, a foldable display, and the like, and may be a touch panel.

The first and second

flexible members

21 and 22 are members that can be repeatedly bent (including bent), and examples thereof include a coating Film, a gas barrier Film, a hard coat Film, a polarizing Film (polarizing plate), a polarizer, a retardation Film (retardation plate), a viewing angle compensation Film, a brightness enhancement Film, a contrast enhancement Film, a diffusion Film, a semi-transmissive reflective Film, an electrode Film, a transparent conductive Film, a metal mesh Film, flexible glass, a Film sensor (touch sensitive Film), a liquid crystal polymer Film, a light emitting polymer Film, a Film-like liquid crystal module, an organic EL module (organic EL Film, organic EL element), an electronic paper module (Film-like electronic paper), a TFT (Thin Film Transistor)) substrate, and the like.

At least one of the first flexible member 21 and the second flexible member 22 may be a polyimide film or a laminate including a polyimide film on the adhesive layer 11 side. Although the polyimide film generally has low adhesion to the adhesive layer, the adhesive layer 11 according to the present embodiment can obtain excellent durability even when the polyimide film is an adherend.

The Young's modulus of each of the first flexible member 21 and the second flexible member 22 is preferably 0.1 to 10GPa, particularly preferably 0.5 to 7GPa, and more preferably 1.0 to 5 GPa. When the young's modulus of the first flexible member 21 and the second flexible member 22 is within this range, the respective flexible members can be easily bent repeatedly.

When the first flexible member 21 and the second flexible member 22 are each bent along the center line thereof, the angle at which they are bent so as to be free from cracks or irreversible deformation (the bending angle on the acute angle side formed by the surfaces of the flexible members) is preferably 150 ° or less, more preferably 90 ° or less, particularly preferably 60 ° or less, even more preferably 30 ° or less, and most preferably 10 ° or less. This makes it possible to easily obtain a repeated bending device described later.

The thickness of each of the first flexible member 21 and the second flexible member 22 is preferably 10 to 3000 μm, particularly preferably 25 to 1000 μm, and more preferably 50 to 500 μm. When the thickness of the first flexible member 21 and the second flexible member 22 is within this range, the respective flexible members can be easily bent repeatedly.

In the production of the above-described repeatedly bent laminate member 2, as an example, one release sheet 12a of the adhesive sheet 1 is peeled off, and the exposed adhesive layer 11 of the adhesive sheet 1 is bonded to one surface of the first flexible member 21.

Then, the other release sheet 12b is peeled off from the adhesive layer 11 of the adhesive sheet 1, and the adhesive layer 11 exposed from the adhesive sheet 1 is bonded to the second flexible member 22, thereby obtaining the repeatedly bendable laminated member 2. As another example, the order of bonding the first flexible member 21 and the second flexible member 22 may be changed.

[ repeated bending device ]

The repeated bending device of the present embodiment includes the repeated bending laminated member 2, and the device may be configured by only the repeated bending laminated member 2, or may be configured by including one or more of the repeated bending laminated member 2 and other flexible members. When one of the repeatedly bent and laminated members 2 is laminated with another of the repeatedly bent and laminated members 2, or when the repeatedly bent and laminated member 2 is laminated with another of the flexible members, it is preferable to laminate the members via the adhesive layer 11 of the adhesive sheet 1.

Since the adhesive layer of the repeated bending device of the present embodiment is composed of the adhesive, when the device is repeatedly bent or is bent for a long period of time, peeling is less likely to occur at the interface between the adhesive layer and the adherend at the bent portion, and light leakage and deterioration in visibility due to bending can be suppressed.

Fig. 3 shows a repeating bending device as an example of the present embodiment. In addition, the recurved bend device of the present invention is not limited to this recurved bend device.

As shown in fig. 3, the bending device 3 of the present embodiment is configured by laminating a coating film 31, a first adhesive layer 32, a polarizing film 33, a second adhesive layer 34, a touch sensitive film 35, a third adhesive layer 36, an organic EL element 37, a fourth adhesive layer 38, and a TFT substrate 39 in this order from the top. The coating film 31, the polarizing film 33, the touch sensitive film 35, the organic EL element 37, and the TFT substrate 39 correspond to a flexible member.

At least one of the first adhesive layer 32, the second adhesive layer 34, the third adhesive layer 36, and the fourth adhesive layer 38 is the adhesive layer 11 of the adhesive sheet 1. Any two or more of the first adhesive layer 32, the second adhesive layer 34, the third adhesive layer 36, and the fourth adhesive layer 38 are preferably the adhesive layers 11 of the adhesive sheet 1, and most preferably the

adhesive layers

32, 34, 36, and 38 are all the adhesive layers 11 of the adhesive sheet 1.

Here, for example, when the TFT substrate 39 includes a polyimide film, particularly when the polyimide film is provided on the fourth adhesive layer 38 side, it is preferable that at least the fourth adhesive layer 38 is the adhesive layer 11 of the adhesive sheet 1.

The embodiments described above are described for easy understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiments also covers all design changes and equivalents that fall within the technical scope of the present invention.

For example, one or both of the

release sheets

12a and 12b in the adhesive sheet 1 may be omitted, or a desired flexible member may be laminated instead of the

release sheets

12a and 12 b.

Examples

The present invention will be further specifically described below with reference to examples and the like, but the scope of the present invention is not limited to these examples and the like.

[ example 1]

Preparation of (meth) acrylate Polymer (A)

The (meth) acrylic ester polymer (a) was prepared by copolymerizing 70 parts by mass of n-butyl acrylate, 10 parts by mass of methyl acrylate, 15 parts by mass of 2-phenoxyethyl acrylate, 1 part by mass of dimethylaminoethyl acrylate, and 4 parts by mass of 2-hydroxyethyl acrylate by a solution polymerization method. The molecular weight of the (meth) acrylate polymer (a) was measured by the method described later, and the weight average molecular weight (Mw) was 150 ten thousand. Further, the glass transition temperature (Tg) of the (meth) acrylate polymer (A) calculated by the formula of FOX was-35 ℃.

2. Preparation of adhesive composition

100 parts by mass (in terms of solid content; the same applies hereinafter) of the (meth) acrylate Polymer (A) obtained in the above step 1, 5.0 parts by mass of a polyrotaxane compound (B) (manufactured by Advanced materials Inc., product name "SERM Super Polymer SH 3400P"), a linear molecule of polyethylene glycol, a cyclic molecule of α -cyclodextrin having a hydroxypropyl and caprolactone chain, a blocking group of adamantyl, a weight average molecular weight (Mw) of 70 ten thousand, a hydroxyl value of 72mgKOH/g), 1.5 parts by mass of trimethylolpropane-modified xylylene diisocyanate (manufactured by Soken Chemical & Engineering Co., Ltd., product name "TD-75") as a crosslinking agent (C), 0.17 part by mass of 3-glycidoxypropyltrimethoxysilane as a silane coupling agent were mixed and sufficiently stirred, and diluted with methyl ethyl ketone, thus, a coating liquid of the adhesive composition was obtained.

3. Production of adhesive sheet

The coating liquid of the obtained adhesive composition was applied to a release-treated surface of a heavy release type release sheet (manufactured by lintec corporation, product name "SP-PET 752150") obtained by subjecting one surface of a polyethylene terephthalate film to a release treatment with a silicone-based release agent, using a blade coater. Then, the coating layer was subjected to a heat treatment at 90 ℃ for 1 minute to form a coating layer.

Next, the coating layer on the heavy release type release sheet obtained above was bonded to a light release type release sheet (product name "SP-PET 381130" manufactured by linec Corporation) obtained by subjecting one surface of a polyethylene terephthalate film to a release treatment using a silicone type release agent so that the release treated surface of the light release type release sheet was in contact with the coating layer, and the sheet was aged at 23 ℃ and 50% RH for 7 days, thereby obtaining an adhesive sheet having an adhesive layer with a thickness of 25 μm, that is, an adhesive sheet having a structure of a heavy release type release sheet/an adhesive layer (thickness: 25 μm)/a light release type release sheet. The thickness of the adhesive layer is a value measured according to JIS K7130 using a constant pressure thickness gauge (TECLOCK co., ltd., product name "PG-02").

Here, the respective compounding ratios (solid content equivalent) of the adhesive composition when the (meth) acrylate polymer (a) was set to 100 parts by mass (solid content equivalent) are shown in table 1. The abbreviations and the like shown in table 1 are as follows.

[ (meth) acrylic ester Polymer (A) ]

BA: acrylic acid n-butyl ester

MA: acrylic acid methyl ester

PhEA: acrylic acid 2-phenoxy ethyl ester

DMAEA: acrylic acid dimethyl amino ethyl ester

HEA: 2-Hydroxyethyl acrylate

Examples 2 to 6 and comparative examples 1 to 2

Adhesive sheets were produced in the same manner as in example 1, except that the kinds and proportions of the monomers constituting the (meth) acrylate polymer (a), the weight average molecular weight (Mw) of the (meth) acrylate polymer (a), the blending amount of the polyrotaxane compound (B), the blending amount of the crosslinking agent (C), and the thickness of the adhesive layer were changed as shown in table 1. The glass transition temperature (Tg) calculated from the formula FOX of the (meth) acrylate polymer (A) in each example is shown in Table 1.

[ test example 1] (measurement of gel fraction)

The adhesive sheets obtained in examples and comparative examples were cut into 80mm × 80mm pieces, the adhesive layers were wrapped in a polyester mesh (product name: Tetoron mesh #200), the masses thereof were weighed using a precision balance, and the masses of the individual meshes were subtracted to calculate the masses of the adhesives themselves. The mass at this time was designated as M1.

Subsequently, the adhesive wrapped in the polyester net was immersed in ethyl acetate at room temperature (23 ℃) for 24 hours. Then, the adhesive was taken out, air-dried at 23 ℃ and a relative humidity of 50% for 24 hours, and further dried in an oven at 80 ℃ for 12 hours. After drying, the mass of the adhesive itself was calculated by weighing it with a precision balance and subtracting the mass of the web alone. The mass at this time was designated as M2. Gel fraction (%) is expressed as (M2/M1). times.100.

The results are shown in Table 2.

[ test example 2] (measurement of vapor Transmission amount)

The adhesive layers of the adhesive sheets obtained in examples and comparative examples were laminated and made to be 100 μm thick. The adhesive layer having a thickness of 100 μm obtained by sandwiching 2 sheets of Tetoron mesh #380 was used, and the adhesive layer was used according to JIS K7129 under conditions of 40 ℃ and 90% RHA permeability measuring instrument (manufactured by LYSSY, product name "L80-5000") for measuring the water vapor transmission rate (g/(m)²24 h)). The results are shown in Table 2.

[ test example 3] (measurement of storage modulus G')

The adhesive layers of the adhesive sheets obtained in examples and comparative examples were laminated in a multilayer manner to prepare a laminate having a thickness of 3 mm. From the laminate of the obtained adhesive layer, a cylindrical body (height: 3mm) having a diameter of 8mm was punched out, and this was used as a sample.

For the above sample, storage modulus G ' was measured under the following conditions using a viscoelasticity measuring apparatus (manufactured by Anton paar, Inc., product name "MCR 302") and a torsional shear method (ね was subjected to りせ one-off method) in accordance with JIS K7244-1 to obtain storage modulus G ' (23) at 23 ℃ and storage modulus G ' (85) (MPa) at 85 ℃. The results are shown in Table 2.

Measuring frequency: 1Hz

Measuring temperature: -20 ℃ to 150 DEG C

[ test example 4] (measurement of haze value)

The adhesive layers of the adhesive sheets prepared in examples and comparative examples were bonded to glass, and the bonded sheets were used as measurement samples. The haze value (total light haze value;%) at 23 ℃ was measured for the above-mentioned measurement sample using a haze meter (NIPPON DENSHOKU INDUSTRIES Co., LTD, product name "NDH-5000") in accordance with JIS K7136:2000, on the basis of background measurement (background measurement) using glass. The results are shown in Table 2.

The sample for measurement was left at-40 ℃ for 240 hours and then left at 23 ℃ and 50% RH for 1 hour. Then, the haze value (-haze value at 40;%) was measured in the same manner as described above. The results are shown in Table 2.

[ test example 5] (measurement of Total light transmittance)

The adhesive layers of the adhesive sheets prepared in examples and comparative examples were bonded to glass, and the bonded sheets were used as measurement samples. The total light transmittance (%) at 23 ℃ was measured for the above-mentioned sample for measurement in accordance with JIS K7361-1:1997 using a haze meter (NIPPON DENSHOKU INDUSTRIES Co., LTD, product name "SH-7000") on the basis of background measurement (background measurement) using glass. The results are shown in Table 2.

The sample for measurement was left at-40 ℃ for 240 hours and then left at 23 ℃ and 50% RH for 1 hour. Then, the total light transmittance (-total light transmittance at-40;%) was measured in the same manner as described above. The results are shown in Table 2.

[ test example 6](L^＊a^＊b^＊Measurement of (2)

The adhesive layer of the adhesive sheet obtained in examples and comparative examples was measured for CIE1976L using a simultaneous photometric spectrocolorimeter (NIPPON DENSHOKU INDUSTRIES co., ltd., product name "SQ 2000")^＊a^＊b^＊Lightness L specified in the color system^＊Chroma a^＊And chroma b^＊. The results are shown in Table 2.

[ test example 7] (measurement of adhesive force)

The light release sheet was peeled off from the pressure-sensitive adhesive sheets obtained in examples and comparative examples, and the exposed pressure-sensitive adhesive layer was bonded to an easy-adhesion layer of a polyethylene terephthalate (PET) film (TOYOBO co., ltd., product name "PET a 4300" thickness: 100 μm) having an easy-adhesion layer, to obtain a laminate of the heavy release sheet/the pressure-sensitive adhesive layer/the PET film. The resulting laminate was cut into a width of 25mm and a length of 110 mm.

The heavy-release type release Sheet was peeled off from the laminate under an atmosphere of 23 ℃ and 50% RH, and the exposed adhesive layer was attached to a soda-lime Glass plate (manufactured by Nippon Sheet Glass co., ltd., product name "soda-lime Glass" thickness: 1.1mm), and pressurized at 0.5MPa and 50 ℃ for 20 minutes using an autoclave (autoclave) manufactured by shikusho. After the sheet was left to stand at 23 ℃ and 50% RH for 24 hours, the adhesion (N/25mm) when the laminate of the PET film and the adhesive layer was peeled from the adherend at a peeling speed of 300 mm/min and a peeling angle of 180 degrees was measured using a tensile tester (ORIENTEC co., ltd. The conditions other than those described herein were measured according to JIS Z0237: 2009. The results are shown in Table 2.

[ test example 8] (evaluation of static durability)

The light-release type release sheets were peeled from the adhesive sheets obtained in examples and comparative examples in an atmosphere of 23 ℃ and 50% RH, and the exposed adhesive layer was bonded to one surface of a Polyimide (PI) film (DU PONT-TORAY CO., manufactured by LTD., product name "KAPTON 100 PI", thickness: 25 μm, Young's modulus: 3.4 GPa). Then, the heavy-release type release sheet was peeled off, and the exposed adhesive layer was bonded to the same PI film. Next, an autoclave manufactured by Tamarindus Productiva was used, and the autoclave was pressurized at 50 ℃ under 0.5MPa for 20 minutes and then left to stand at 23 ℃ and 50% RH for 24 hours. The laminate composed of the PI film/adhesive layer/PI film thus obtained was cut into a width of 50mm and a length of 200mm, and used as a sample.

The obtained sample was held in a bent state between holding plates (mutual distance: 3mm) composed of two glass plates disposed vertically for 24 hours under an environment of 85 ℃ as shown in FIG. 4. After the static bending test, it was visually confirmed whether or not peeling occurred at the interface between the adhesive layer and the adherend at the bent portion of the test piece. In each example, 10 samples were evaluated. The results are shown in Table 3.

Very good: no peeling occurred in any of the 10 samples

O: 9-5 samples did not peel

And (delta): 4-2 samples did not peel

X: peeling of more than 9 samples

[ test example 9] (evaluation of dynamic durability)

The laminate composed of the PI film/adhesive layer/PI film obtained in the same manner as in example 8 was cut into 150mm × 50mm, and used as a test piece. As shown in fig. 5, both ends of the obtained test piece were fixed to two holding plates of a flat body no-load U-shaped stretching tester (YUASA SYSTEM co., ltd., product name "DLDMLH-FS"). Then, the mixture was heated at 85 ℃ and 50% RH to

The test piece was bent 3 ten thousand times with a bending diameter of 80mm, a stroke of 80mm and a bending speed of 30 rpm.

After the dynamic bending test, it was visually confirmed whether or not peeling occurred at the interface between the adhesive layer and the adherend at the bent portion of the test piece. In each example, 10 samples were evaluated. The results are shown in Table 3.

Very good: no peeling occurred in any of the 10 samples

Good: 9-5 samples did not peel

And (delta): 4-2 samples did not peel

X: peeling of more than 9 samples

[ test example 10] (evaluation of resistance to Wet Heat whitening)

The adhesive layers of the adhesive sheets obtained in examples and comparative examples were sandwiched between alkali-free glass plates (water vapor transmission rate 0.0006 g/(m) having a thickness of 1.1mm)²24h)) and a plastic plate having a thickness of 0.7mm (manufactured by Mitsubishi rayon co., ltd., product name "acrylic MR-200", water vapor transmission amount of 44 g/(m)²24h 100 μm)), and the sample was prepared. The obtained sample was subjected to a hot pressing (autobinding) treatment at 50 ℃ and 0.5MPa for 20 minutes, and then left at normal pressure and 23 ℃ under 50% RH for 24 hours.

The above samples were measured for haze value (haze value before durability test;% by weight) using a haze meter (NIPPON DENSHOKU INDUSTRIES CO., LTD., manufactured by product name "NDH-5000") according to JIS K7136: 2000.

Then, the sample was stored under the condition of 85 ℃ and 85% RH humidity for 1000 hours (durability test), and then left at 23 ℃ and 50% RH at normal temperature and humidity for 24 hours. The haze value (haze value after durability test;%) was measured for this sample in the same manner as described above.

The wet-heat whitening resistance was evaluated from the difference in haze values before and after the durability test according to the following criteria.

The difference in haze values of … is less than 1.5.

The difference in haze value of O … was 1.5 or more and less than 8.0.

The difference in the haze values of X … was 8.0 or more.

[ Table 1]

[ Table 2]

[ Table 3]

	Static durability	Dynamic durability	Resistance to wet-heat whitening
				Example 1	◎	◎	〇
Example 2	◎	◎	◎
				Example 3	◎	◎	◎
Example 4	〇	◎	◎
				Example 5	〇	◎	◎
Example 6	△	△	〇
				Comparative example 1	△	△	×
Comparative example 2	×	×	〇

As is clear from table 3, the adhesive layer of the adhesive sheet of the example was excellent in durability, without peeling at the interface between the adhesive layer and the flexible member, when 2 flexible members were bonded and left in a flexible state for a long period of time or when the flexible members were repeatedly bent. In addition, the adhesive layer of the adhesive sheet of the example was also excellent in wet-heat whitening resistance.

Industrial applicability

The present invention is suitable for bonding one flexible member and another flexible member constituting a repeated bending device.

Claims

1. An adhesive sheet having an adhesive layer for bonding one flexible member and another flexible member constituting a repeated bending device, characterized in that,

the adhesive layer having a thickness of 100 μm was sandwiched between 2 sheets of Tetoron mesh #380, and the water vapor transmission rate measured according to JIS K7129 was 150 g/(m) under 40 ℃ and 90% RH²24h) or more, and (c) a,

the storage modulus G' (85) of the adhesive constituting the adhesive layer at 85 ℃ is 0.02MPa to 0.2 MPa.

2. The adhesive sheet according to claim 1, wherein the gel fraction of the adhesive constituting the adhesive layer is 10% or more and 90% or less.

3. The adhesive sheet according to claim 1, wherein the haze value of the adhesive layer at 23 ℃ is 10% or less.

4. The adhesive sheet according to claim 1, wherein a storage modulus G' (23) of the adhesive constituting the adhesive layer at 23 ℃ is 0.02MPa or more and 0.3MPa or less.

5. The adhesive sheet according to claim 1, wherein the adhesive constituting the adhesive layer contains a polyrotaxane compound.

6. The adhesive sheet according to claim 1, wherein the adhesive constituting the adhesive layer is an acrylic adhesive.

7. The adhesive sheet according to claim 1,

the adhesive sheet is provided with 2 pieces of stripping sheets,

the adhesive layer is sandwiched between the 2-piece release sheets so as to be in contact with the release surfaces of the release sheets.

8. A repeatedly bendable laminated member comprising one bendable member and another bendable member constituting a repeatedly bendable device, and an adhesive layer for bonding the one bendable member and the another bendable member to each other,

the adhesive layer is composed of the adhesive layer of the adhesive sheet according to any one of claims 1 to 7.

9. A recurrently bending device comprising the recurrently bent laminated member according to claim 8.