CN114806467A

CN114806467A - Adhesive for repeatedly bending device, adhesive sheet, repeatedly bending laminated member, and repeatedly bending device

Info

Publication number: CN114806467A
Application number: CN202111635755.5A
Authority: CN
Inventors: 峰松宏树; 渡边旭平
Original assignee: Lintec Corp
Current assignee: Lintec Corp
Priority date: 2021-01-29
Filing date: 2021-12-29
Publication date: 2022-07-29
Also published as: JP2022117307A; KR20220110050A; TW202229482A

Abstract

The invention provides an adhesive and an adhesive sheet for a repeatedly bending device, which can inhibit floating or peeling when used for the repeatedly bending device, and a repeatedly bending laminated member and a repeatedly bending device which can inhibit floating or peeling. Storage modulus G 'at-30 ℃ of the adhesive for a repeatedly bending device'(30) 0.20MPa or less, and the creep compliance value measured when applying a stress of 4500Pa is defined as the minimum creep compliance J (t) _min (MPa ^‑1 ) The minimum creep compliance J (t) was measured _min Thereafter, the stress was continued to be applied at 4500Pa for 1200 seconds, and the maximum creep compliance value measured during this period was defined as the maximum creep compliance J (t) _max (MPa ^‑1 ) A creep compliance change value Δ logj (t) calculated from the following formula (I) is 2.60 or less: Δ logJ (t) ═ logJ (t) _max ‑logJ(t) _min …(I)。

Description

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

Technical Field

The present invention relates to an adhesive and 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 bendable display has been proposed. As a flexible display, a display in which only one curved surface is formed and a repeated bending display for repeated bending (bending) use have been proposed.

In the display device with repeated bending as described above, it is conceivable to bond one bendable member (bendable member) constituting the display device with another bendable member by an adhesive layer. However, when a conventional adhesive is used for a display device which is repeatedly bent, there is a problem that the adhesive layer floats or peels off at the interface with the adherend.

Patent document 1 discloses an adhesive that has a technical problem of suppressing the occurrence of floating or peeling of an adhesive layer even when the adhesive layer is repeatedly bent.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2016 and 108555

Disclosure of Invention

Technical problem to be solved by the invention

However, even when the adhesive as described above is used, the occurrence of lifting or peeling due to repeated bending cannot be sufficiently suppressed.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an adhesive and an adhesive sheet for a repeatedly bendable device, which can suppress the occurrence of lifting or peeling when used for a repeatedly bendable device, and to provide a repeatedly bendable laminated member and a repeatedly bendable device, which can suppress the occurrence of lifting or peeling.

Means for solving the problems

To make it practicalThe first aspect of the present invention is an adhesive for a repeatedly bendable device for bonding one bendable member and another bendable member constituting a repeatedly bendable device, characterized in that the storage modulus G' (-30) of the adhesive at-30 ℃ is 0.20MPa or less, and the creep compliance value measured when a stress of 4500Pa is applied to the adhesive is set to the minimum creep compliance J (t) _min (MPa ^-1 ) The minimum creep compliance J (t) was measured _min Thereafter, the stress of 4500Pa was continuously applied for 1200 seconds, and the maximum creep compliance value measured during this time was set to the maximum creep compliance J (t) _max (MPa ^-1 ) The creep compliance change value Δ logj (t) calculated by the following formula (I) is 2.60 or less (invention 1).

ΔlogJ(t)＝logJ(t) _max -logJ(t) _min …(I)

In the above invention (invention 1), by setting the storage modulus G' (-30) at-30 ℃ to a small value as described above, stress caused by repeated bending in a low-temperature environment (for example, -30 ℃) can be reduced. On the other hand, by setting the creep compliance change value to a small value as described above, it is possible to suppress excessive deformation of the adhesive during repeated bending or long-term bending regardless of the temperature environment when the adhesive is repeatedly bent or bent for a long time. As a result, when used for a repeatedly bending device, the adhesive layer is less likely to float or peel at the interface between the adhesive layer and the adherend in a low-temperature to high-temperature environment, and excellent bending resistance can be obtained.

In the above invention (invention 1), the creep compliance value measured after the pressure-sensitive adhesive is continuously applied with a stress of 4500Pa for 1200 seconds is set to creep compliance j (t) (s ═ 1200) (MPa) ^-1 ) Then, the stress applied to the adhesive was set to 0Pa, and the creep compliance value measured 100 seconds after the stress was set to creep compliance j (t) (s 1300) (MPa) ^-1 ) The creep recovery rate calculated from the following formula (II) is preferably 90% or more (invention 2).

Creep recovery ratio (%) (1-j (t) (s 1300)/j (t) (s 1200)) × 100 … (II)

In the above inventions (inventions 1 and 2), the storage modulus G' (85) at 85 ℃ is preferably 0.005MPa or more (invention 3).

In the above inventions (inventions 1 to 3), it is preferable that the storage modulus variation (-30/25) of the adhesive for a repeated bending device is 5.0 or less, and the storage modulus variation (-30/25) is a value obtained by dividing a storage modulus G '(-30) at-30 ℃ by a storage modulus G' (25) at 25 ℃ (invention 4).

In the above inventions (inventions 1 to 4), it is preferable that the storage modulus variation (-30/85) of the adhesive for a repeated bending device is 10.0 or less, and the storage modulus variation (-30/85) is a value obtained by dividing a storage modulus G '(-30) at-30 ℃ by a storage modulus G' (85) at 85 ℃. (invention 5).

In the above inventions (inventions 1 to 5), the gel fraction is preferably 40% or more and 95% or less (invention 6).

In the above inventions (inventions 1 to 6), it is preferable that the adhesive contains an adhesive base material and a low-molecular weight component, the low-molecular weight component has a weight average molecular weight of 400 to 100000 inclusive, and the low-molecular weight component has a glass transition temperature (Tg) of-40 ℃ or lower (invention 7).

In the above inventions (inventions 1 to 7), the adhesive is preferably an acrylic adhesive (invention 8).

The second aspect of the present invention provides an adhesive sheet comprising an adhesive layer for bonding one flexible member and another flexible member constituting a device for repeated bending, wherein the adhesive layer is composed of the adhesive for repeated bending (inventions 1 to 8) (invention 9).

In the invention (invention 9) described above, it is preferable that the adhesive sheet includes two release sheets, and the adhesive layer is sandwiched between the release sheets so as to be in contact with release surfaces of the two release sheets (invention 10).

Third, the present invention provides a repeatedly bending laminated member, including: the present invention provides a method for producing a repeatedly bendable laminated member, comprising the steps of forming one bendable member and another bendable member constituting a repeatedly bendable device, and bonding the one bendable member and the another bendable member to each other, wherein the repeatedly bendable laminated member is characterized in that the adhesive layer is composed of the adhesive for repeatedly bendable device (inventions 1 to 8) (invention 11).

The present invention fourth provides a repeating bending device comprising the repeating bending laminated member (invention 11) (invention 12).

Effects of the invention

The adhesive and the adhesive sheet for a repeatedly bendable device according to the present invention are less likely to cause floating or peeling at the interface between the adhesive layer and the adherend when used for a repeatedly bendable device. Further, the repeatedly bending laminated member and the repeatedly bending device of the present invention are less likely to cause floating or peeling at the interface between the adhesive layer and the adherend.

Drawings

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

FIG. 2 is a cross-sectional view of a repeating curved laminate structure in accordance with one embodiment of the present invention.

Fig. 3 is a cross-sectional view of a recurved bend device according to one embodiment of the invention.

Fig. 4 is an explanatory view (side view) illustrating a 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 sensor film (touch sensor 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 for repeatedly bending device ]

The adhesive for a repeating bending device (hereinafter, may be simply referred to as "adhesive") of the present embodiment is an adhesive for bonding one flexible member and another flexible member constituting the repeating bending device. The repetitive bending device and the bendable member will be described later.

Preferably, the adhesive of the present embodiment has a storage modulus G' (-30) at-30 ℃ of 0.20MPa or less, and a creep compliance value measured when a stress of 4500Pa is applied to the adhesive is set to a minimum creep compliance J (t) _min (MPa ^-1 ) The minimum creep compliance J (t) was measured _min Thereafter, the stress of 4500Pa was continuously applied for 1200 seconds, and the maximum creep compliance value measured during this time was set to the maximum creep compliance J (t) _max (MPa ^-1 ) The creep compliance change value Δ logj (t) calculated by the following formula (I) is preferably 2.60 or less.

ΔlogJ(t)＝logJ(t) _max -logJ(t) _min …(I)

The details of the method for measuring the storage modulus G' and the method for measuring the creep compliance j (t) are shown in the test examples described later. Further, "when a stress of 4500Pa was applied to the adhesive" refers to a point of time when a stress was applied to the adhesive and the stress reached 4500 Pa.

By making the storage modulus G' (-30) at-30 ℃ of the adhesive of the present embodiment small as described above, stress caused by repeated bending in a low temperature environment (e.g., -30 ℃) can be reduced. On the other hand, by setting the creep compliance change value to a small value as described above, the adhesive can be bent repeatedly or for a long time without being excessively deformed regardless of the temperature environment. In the case of an excessively deformed adhesive, the internal structure of the adhesive is also changed by deformation due to bending, and the adhesive cannot return to its original state even when the bending is released. The two physical property values are usually opposite to each other, but the adhesive of the present embodiment can have both of the two physical property values, and has a small stress due to deformation even at a very low temperature of-30 ℃ and a small deformation due to deformation. As a result, when used for a repeatedly bending device, the adhesive layer is less likely to float or peel at the interface between the adhesive layer and the adherend in a low-temperature to high-temperature environment, and excellent bending resistance can be obtained.

From the viewpoint of the above-mentioned bending resistance, the storage modulus G' (-30) of the adhesive of the present embodiment at-30 ℃ is preferably 0.20MPa or less, more preferably 0.15MPa or less, particularly preferably 0.11MPa or less, and still more preferably 0.10MPa or less. In addition, from the viewpoint of cohesive force, the storage modulus G' (-30) at-30 ℃ of the adhesive constituting the adhesive layer is preferably 0.01MPa or more, more preferably 0.02MPa or more, particularly preferably 0.04MPa or more, and still more preferably 0.08MPa or more.

From the viewpoint of the bending resistance, the creep compliance change value Δ logj (t) is preferably 2.60 or less, more preferably 2.58 or less, particularly preferably 2.56 or less, and further preferably 2.54 or less. The lower limit of the creep compliance change value is not particularly limited, but is usually preferably 1.50 or more, particularly preferably 2.00 or more, and more preferably 2.20 or more.

Minimum creep compliance J (t) of the adhesive of the present embodiment in the lower limit _min Preferably 1MPa ^-1 Above, more preferably 5MPa ^-1 Above, particularly preferably 10MPa ^-1 Above, more preferably 15MPa ^-1 The above. By minimizing creep compliance J (t) _min If the lower limit value of (d) is the above value, the creep compliance change value Δ logj (t) tends to satisfy the above value. Minimum creep compliance J (t) _min The upper limit of (B) is not particularly limited, but is preferably 1000MPa in general ^-1 Hereinafter, it is particularly preferably 100MPa ^-1 Hereinafter, more preferably 20MPa ^-1 The following.

In addition, the maximum creep compliance J (t) of the adhesive of the present embodiment is defined as the upper limit _max Preferably 10000MPa ^-1 Hereinafter, more preferably 8000MPa ^-1 The pressure is preferably 6000MPa or less ^-1 More preferably 5500MPa or less ^-1 The following. By maximizing creep compliance J (t) _max If the upper limit value of (a) is the above value, the creep compliance change value Δ logj (t) tends to satisfy the above value. Maximum creep compliance J (t) _max The lower limit of (B) is not particularly limited, but is preferably 1100MPa in general ^-1 Above, particularly preferably 2000MPa ^-1 From above to below, go intoOne step is preferably 4000MPa ^-1 The above.

In the adhesive of the present embodiment, the creep compliance value measured after the adhesive is continuously applied with a stress of 4500Pa for 1200 seconds is set to creep compliance j (t) (s ═ 1200) (MPa) ^-1 ) Then, the stress applied to the adhesive was set to 0Pa, and the creep compliance value measured 100 seconds after the stress was set to creep compliance j (t) (s 1300) (MPa) ^-1 ) The creep recovery ratio calculated by the following formula (II) is preferably 90% or more, more preferably 92% or more, particularly preferably 94% or more, and further preferably 96% or more.

Creep recovery ratio (%) (1-j (t) (s 1300)/j (t) (s 1200)) × 100 … (II)

By allowing the adhesive of the present embodiment to exhibit the above creep recovery rate, even when a repeatedly bendable device using the adhesive is left in a bent state for a long period of time, the recovery from the bent state is excellent, and bending traces are less likely to be formed on the adhesive layer.

The upper limit of the creep recovery rate is not particularly limited, but is usually preferably 100% or less, particularly preferably 99% or less, and more preferably 98% or less.

The creep compliance j (t) (s 1200) of the adhesive of the present embodiment is preferably 1100MPa in terms of the lower limit value ^-1 Above, more preferably 2000MPa ^-1 Above, particularly preferably 4000MPa ^-1 Above, 4600MPa is more preferable ^-1 The above. This provides an adhesive having more appropriate stress relaxation properties. From the viewpoint of cohesive force of the adhesive, the upper limit of creep compliance j (t) (s 1200) is preferably 10000MPa ^-1 Hereinafter, 8000MPa is particularly preferable ^-1 The pressure is preferably 6000MPa or less ^-1 The following.

In addition, the creep compliance j (t) (s 1300) of the adhesive of the present embodiment is preferably 800MPa at the upper limit ^-1 Hereinafter, 400MPa is more preferable ^-1 Hereinafter, 200MPa is particularly preferable ^-1 Hereinafter, more preferably 180MPa ^-1 The following. This provides an adhesive having more excellent recovery properties. The lower limit of creep compliance J (t) (s 1300) is not specifiedAlthough not limited thereto, it is usually preferably 1MPa ^-1 Above, particularly preferably 10MPa ^-1 The above, more preferably 100MPa ^-1 The above.

The storage modulus G' (85) at 85 ℃ of the adhesive of the present embodiment is preferably 0.005MPa or more, more preferably 0.010MPa or more, particularly preferably 0.020MPa or more, and further preferably 0.022MPa or more. Thus, the adhesive layer does not become too soft even at high temperatures and can maintain the cohesive force. The storage modulus G' (85) at 85 ℃ of the adhesive of the present embodiment is preferably 0.10MPa or less, more preferably 0.08MPa or less, particularly preferably 0.06MPa or less, and further preferably 0.04MPa or less. Thus, an adhesive having a low storage modulus G' at low temperatures can be easily obtained.

The storage modulus G' (25) at 25 ℃ of the adhesive of the present embodiment is preferably 0.15MPa or less, more preferably 0.10MPa or less, particularly preferably 0.07MPa or less, and still more preferably 0.04MPa or less. This makes it easy to exhibit appropriate adhesiveness. On the other hand, the storage modulus G' (25) at 25 ℃ is preferably 0.010MPa or more, more preferably 0.015MPa or more, particularly preferably 0.020MPa or more, and further preferably 0.026MPa or more. This provides excellent repeated bendability in the standard ambient temperature range, and also provides good workability such as punching.

In the adhesive of the present embodiment, the storage modulus variation (-30/25) is preferably 5.0 or less, more preferably 4.0 or less, particularly preferably 3.5 or less, and still more preferably 3.3 or less, and the storage modulus variation (-30/25) is a value obtained by dividing the storage modulus G '(-30) at-30 ℃ by the storage modulus G' (25) at 25 ℃. This makes it possible to provide a film having an appropriate adhesive force at normal temperature and easily preventing the high elastic modulus at low temperatures.

The storage modulus change degree (-30/25) is preferably 1.50 or more, more preferably 2.00 or more, particularly preferably 2.50 or more, and still more preferably 3.00 or more. Thus, an adhesive having excellent cohesive force can be easily obtained.

In the adhesive of the present embodiment, the storage modulus variation (-30/85) is preferably 10.0 or less, more preferably 7.0 or less, particularly preferably 5.0 or less, and still more preferably 4.5 or less, and the storage modulus variation (-30/85) is a value obtained by dividing the storage modulus G '(-30) at-30 ℃ by the storage modulus G' (85) at 85 ℃. Thus, it is easy to make the low elastic modulus at low temperature compatible with the high elastic modulus at high temperature.

The storage modulus change degree (-30/85) is preferably 1.20 or more, more preferably 2.00 or more, particularly preferably 2.50 or more, and further preferably 3.00 or more. Thus, an adhesive having excellent cohesive force can be easily obtained.

The gel fraction of the adhesive of the present embodiment is preferably 40% or more, more preferably 50% or more, particularly preferably 60% or more, and further preferably 70% or more. This exerts an appropriate cohesive force capable of withstanding repeated bending. As a result, the above-described bending resistance becomes more excellent. On the other hand, the gel fraction of the adhesive of the present embodiment is preferably 95% or less, more preferably 90% or less, particularly preferably 85% or less, and further preferably 80% or less. It is thus presumed that the destruction of the crosslinked structure in the adhesive due to repeated bending can be suppressed, and the occurrence of white turbidity in the adhesive layer itself can be suppressed. The method for measuring the gel fraction in the present specification is as shown in the test examples described later.

The adhesive of the present embodiment is not particularly limited as long as the above physical properties are satisfied, but preferably contains a low molecular weight component together with the main adhesive. The low-molecular-weight component is preferably a low-molecular-weight component having a weight-average molecular weight of 400 to 100000 inclusive and a glass transition temperature (Tg) of-40 ℃ or lower. The adhesive containing both the low-molecular-weight component having such physical properties and the adhesive main agent is easy to satisfy the above physical properties, particularly the storage modulus G' (-30) at-30 ℃. 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) in the present specification is a measured value obtained by a differential scanning calorimetry measuring apparatus at a temperature rise/fall rate of 20 ℃/min.

The weight average molecular weight (Mw) of the low molecular weight component is preferably 400 or more, more preferably 1000 or more, particularly preferably 2500 or more, and further preferably 3500 or more, from the viewpoint of improving the storage modulus G' (85) of the resulting adhesive or from the viewpoint of reducing the creep compliance change value. In addition, the weight average molecular weight of the low molecular weight component is preferably 100000 or less, more preferably 50000 or less, particularly preferably 20000 or less, and further preferably 14000 or less, from the viewpoint of reducing the haze value of the obtained adhesive.

The glass transition temperature (Tg) of the low-molecular-weight component is preferably-40 ℃ or lower, more preferably-45 ℃ or lower, particularly preferably-50 ℃ or lower, and still more preferably-52 ℃ or lower. The glass transition temperature (Tg) of the low-molecular weight component is preferably-80 ℃ or higher, more preferably-70 ℃ or higher, particularly preferably-65 ℃ or higher, and still more preferably-60 ℃ or higher.

Specific examples of the above-mentioned low molecular weight components are explained later.

The type of the adhesive of the present embodiment is not particularly limited as long as the above physical properties are satisfied, and may be any of, for example, an acrylic adhesive, a polyester adhesive, a polyurethane adhesive, a rubber adhesive, a silicone adhesive, and the like. The adhesive may be any of emulsion type, solvent type, and non-solvent type, and may be either of crosslinking type or 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.

Specifically, the adhesive of the present embodiment is preferably an adhesive obtained from an adhesive composition containing a (meth) acrylate polymer (a) as an adhesive main agent, a low-molecular-weight component (B), and, if necessary, a crosslinking agent (C) (hereinafter, sometimes referred to as "adhesive composition P"). In the case of the adhesive, the above physical properties are easily satisfied, and a good adhesive force is easily obtained. In the present specification, the term (meth) acrylic acid refers to both acrylic acid and methacrylic acid. Other similar terms are also the same. Further, the concept of "copolymer" is also included in "polymer".

(1) Components of the adhesive composition P

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

The (meth) acrylate polymer (a) preferably contains, as a monomer unit constituting the polymer, a monomer (reactive functional group-containing monomer) containing an alkyl (meth) acrylate and a reactive functional group in a molecule.

By containing the (meth) acrylic acid ester polymer (a) as a monomer unit constituting the polymer, good adhesion can be exhibited. The alkyl (meth) acrylate is preferably an alkyl (meth) acrylate in which the alkyl group has 1 to 20 carbon atoms. The alkyl group may be linear or branched, and may have a cyclic structure.

Examples of the alkyl (meth) acrylate having an alkyl group with 1 to 20 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate, myristyl (meth) acrylate, palmityl (meth) acrylate, and stearyl (meth) acrylate. Among them, from the viewpoint of lowering the glass transition temperature (Tg) of the (meth) acrylate polymer (a) and lowering the elastic modulus of the obtained adhesive, a (meth) acrylate having an alkyl group with 4 to 12 carbon atoms is preferable, and a (meth) acrylate having an alkyl group with 5 to 10 carbon atoms is particularly preferable. Specifically, n-butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate are preferable, and 2-ethylhexyl acrylate is particularly preferable. These alkyl (meth) acrylates may be used alone or in combination of two or more.

The (meth) acrylate polymer (a) preferably contains 60% by mass or more, more preferably 80% by mass or more, particularly preferably 90% by mass or more, further preferably 95% by mass or more, most preferably 98% by mass or more of an alkyl (meth) acrylate having 1 to 20 carbon atoms in an alkyl group as a monomer unit constituting the polymer. This makes it possible to impart appropriate tackiness to the (meth) acrylate polymer (a) and to easily realize a low elastic modulus of the resultant adhesive. The alkyl (meth) acrylate having 1 to 20 carbon atoms and containing 99.9% by mass or less of an alkyl group is preferable, and 99.5% by mass or less of an alkyl group is particularly preferable, and 99.0% by mass or less of an alkyl group is further preferable. This makes it possible to introduce a desired amount of other monomer components into the (meth) acrylate polymer (a).

The (meth) acrylate polymer (a) contains a reactive functional group-containing monomer as a monomer unit constituting the polymer, and the (meth) acrylate polymer (a) reacts with a crosslinking agent (C) described later or the crosslinking agent (C) and the low-molecular-weight component (B) via a reactive functional group derived from the reactive functional group-containing monomer to form a crosslinked structure (three-dimensional network structure), thereby obtaining an adhesive having a desired cohesive force. The adhesive is easy to satisfy the creep compliance change value and creep recovery rate.

Examples of the reactive functional group-containing monomer contained in the (meth) acrylate polymer (a) in the form of 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 a monomer having an amino group in the molecule (amino group-containing monomer). 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, a hydroxyl group-containing monomer and/or a carboxyl group-containing monomer are preferable, and it is particularly preferable to use both a hydroxyl group-containing monomer and a carboxyl group-containing monomer. The hydroxyl-containing monomer is easy to adjust the crosslinking density and meet the creep compliance change value and creep recovery rate. Further, the carboxyl group-containing monomer can improve the adhesive force of the resulting adhesive and can improve the adhesion to an adherend.

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 easiness of satisfying the above physical properties. Specifically, for example, 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate and the like are preferably mentioned, and 2-hydroxyethyl acrylate or 4-hydroxybutyl acrylate is particularly preferred. 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 them, acrylic acid is preferable in view of the adhesive force 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 0.1% by mass or more, particularly preferably 0.5% by mass or more, and further preferably 1.0% by mass or more of a reactive functional group-containing monomer as a monomer unit constituting the polymer, based on the total amount. The (meth) acrylate polymer (a) preferably contains 10% by mass or less, more preferably 7% by mass or less, particularly preferably 5% by mass or less, and further preferably 2% by mass or less of the reactive functional group-containing monomer as a monomer unit constituting the polymer, based on the total amount. Although the component derived from the reactive functional group-containing monomer tends to increase the elastic modulus by causing water to solidify at a low temperature, if the upper limit of the content of the reactive functional group-containing monomer is the above-mentioned value, the tendency can be suppressed and the storage modulus G' at a low temperature can be reduced. When the (meth) acrylate polymer (a) contains the reactive functional group-containing monomer as a monomer unit in the above-mentioned amount, the storage modulus G' can be controlled within an appropriate range. Further, when the (meth) acrylate polymer (a) contains the reactive functional group-containing monomer as a monomer unit in the above-mentioned amount, the degree of crosslinking can be increased, and the creep recovery rate can be increased while reducing the creep compliance change value.

The lower limit of the content of the hydroxyl group-containing monomer in the (meth) acrylate polymer (a) is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, particularly preferably 0.4% by mass or more, and further preferably 0.8% by mass or more. In addition, the (meth) acrylate polymer (a) preferably contains 10% by mass or less, more preferably 7% by mass or less, particularly preferably 4.8% by mass or less, and further preferably 1.8% by mass or less of a hydroxyl group-containing monomer as a monomer unit constituting the polymer, in terms of the above-mentioned limit. When the (meth) acrylate polymer (a) contains the hydroxyl group-containing monomer as a monomer unit in the above amount, the storage modulus G', the creep compliance change value, and the creep recovery ratio described above are easily satisfied.

The (meth) acrylate polymer (a) may contain no carboxyl group-containing monomer as a monomer unit constituting the polymer, but when a carboxyl group-containing monomer is contained as a monomer unit constituting the polymer, it is preferably contained in an amount of 0.005% by mass or more, more preferably contained in an amount of 0.01% by mass or more, particularly preferably contained in an amount of 0.1% by mass or more, and further preferably contained in an amount of 0.2% by mass or more. When the (meth) acrylate polymer (a) contains a carboxyl group-containing monomer as a monomer unit constituting the polymer, the content is preferably 7% by mass or less, more preferably 4% by mass or less, particularly preferably 1.5% by mass or less, and further preferably 0.8% by mass or less, in terms of the upper limit. When the (meth) acrylate polymer (a) contains a carboxyl group-containing monomer as a monomer unit in the above amount, the resulting adhesive is more excellent in bending resistance when used in a repeatedly bent device.

The (meth) acrylate polymer (a) may contain other monomers as the monomer unit constituting the polymer, if necessary. In order not to inhibit the above-mentioned action of the reactive functional group-containing monomer, as the other monomer, a monomer not containing a reactive functional group is preferable. Examples of the monomer include a non-reactive nitrogen atom-containing monomer such as N-acryloylmorpholine and N-vinyl-2-pyrrolidone, an alkoxyalkyl (meth) acrylate such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate, vinyl acetate, and styrene. These 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 40 ten thousand or more, more preferably 70 ten thousand or more, particularly preferably 90 ten thousand or more, and further preferably 110 ten thousand or more. This can prevent a decrease in the storage modulus G' at high temperatures and contribute to a decrease in the creep compliance change value. On the other hand, the weight average molecular weight of the (meth) acrylate polymer (a) is preferably 300 ten thousand or less, more preferably 200 ten thousand or less, particularly preferably 170 ten thousand or less, and further preferably 140 ten thousand or less. This can prevent the storage modulus G' at low temperatures from becoming too high. 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.

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) Low molecular weight component (B)

The low molecular weight component (B) may have the above weight average molecular weight and glass transition temperature (Tg), and for example, an acrylic oligomer, a silicone oligomer, an olefin oligomer, or the like is preferably used. The pressure-sensitive adhesive of the present embodiment is an acrylic pressure-sensitive adhesive, and when the (meth) acrylate polymer (a) is used as the main pressure-sensitive adhesive, an acrylic oligomer is preferably used from the viewpoint of compatibility with the (meth) acrylate polymer (a). By using an acrylic oligomer, the above physical properties can be more easily satisfied.

Further, the low molecular weight component (B) preferably has a reactive functional group. When the low-molecular-weight component (B) has a reactive functional group, it can react with a functional group of the (meth) acrylate polymer (a) or a crosslinking agent (C) described later to form a partially crosslinked structure, thereby obtaining a predetermined cohesive force. As a result, the creep compliance change value and the creep recovery ratio described above are more easily satisfied. Further, the low-molecular-weight component (B) is absorbed into the adhesive by forming a partially crosslinked structure, whereby bleeding (bleeding out) of the low-molecular-weight component (B) from the adhesive can be suppressed, and a decrease in adhesive force can be prevented.

Examples of the reactive functional groups of the low-molecular-weight component (B) include hydroxyl, carboxyl, epoxy, and mercapto groups. Among them, a hydroxyl group having excellent reactivity with a crosslinking agent (C) described later, particularly an isocyanate-based crosslinking agent, or an epoxy group having excellent reactivity with a carboxyl group of the (meth) acrylate polymer (a) is preferable.

When the reactive functional group is a hydroxyl group, the amount of the hydroxyl group in the low molecular weight component (B) is preferably 1 to 1000mgKOH/g, more preferably 5 to 100mgKOH/g, particularly preferably 10 to 70mgKOH/g, and further preferably 15 to 30 mgKOH/g. When the reactive functional group is an epoxy group, the amount of the epoxy group in the low-molecular-weight component (B) is preferably 0.01 to 100meq/g, more preferably 0.1 to 10meq/g, particularly preferably 0.7 to 7meq/g, and further preferably 1.2 to 3 meq/g.

The acrylic oligomer is obtained by polymerizing one or more acrylic monomers and, if necessary, other monomers. The acrylic oligomer preferably contains an alkyl (meth) acrylate and a reactive functional group-containing monomer as monomer units constituting the oligomer.

The content of the low-molecular-weight component (B) in the adhesive composition P is preferably 0.1 part by mass or more, more preferably 1 part by mass or more, particularly preferably 5 parts by mass or more, and further preferably 10 parts by mass or more, relative to 100 parts by mass of the (meth) acrylate polymer (a). This contributes to a reduction in the storage modulus G ', particularly at-30 ℃ of the resulting adhesive (G' (-30)). The content is preferably 80 parts by mass or less, more preferably 50 parts by mass or less, particularly preferably 30 parts by mass or less, and further preferably 20 parts by mass or less. This can suppress an increase in the creep compliance change value, a decrease in the adhesion due to bleeding, and the like.

(1-3) crosslinking agent (C)

The crosslinking agent (C) is a substance which crosslinks the (meth) acrylate polymer (a) or the (meth) acrylate polymer (a) and the low-molecular-weight component (B) to form a three-dimensional network structure by heating the adhesive composition P containing the crosslinking agent (C) or the like as a trigger (trigger). Thus, the cohesive force of the obtained adhesive is improved, and the creep compliance change value and the creep recovery rate are easily satisfied.

The crosslinking agent (C) may be a crosslinking agent that reacts with the reactive functional groups of the (meth) acrylate polymer (a) or the (meth) acrylate polymer (a) and the low molecular weight component (B), and examples thereof 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. The crosslinking agent (C) may be used singly or in combination of two or more.

Among the above crosslinking agents, isocyanate crosslinking agents are particularly excellent in reactivity with hydroxyl groups, and epoxy crosslinking agents are particularly excellent in reactivity with carboxyl groups. Therefore, when the (meth) acrylate polymer (a) and/or the low molecular weight component (B) has a hydroxyl group, an isocyanate-based crosslinking agent is preferably used; when the (meth) acrylate polymer (a) and/or the low-molecular-weight component (B) has a carboxyl group, an epoxy-based crosslinking agent is preferably used. When the (meth) acrylate polymer (a) has a hydroxyl group and a carboxyl group, it is preferable to use an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent together.

The isocyanate-based crosslinking agent includes 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; and biuret and isocyanurate derivatives thereof, and adducts thereof with low-molecular active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane and castor oil. Among them, trimethylolpropane-modified aromatic polyisocyanates are preferable from the viewpoint of reactivity with hydroxyl groups, and trimethylolpropane-modified tolylene diisocyanate or trimethylolpropane-modified xylylene diisocyanate is particularly preferable.

Examples of the epoxy-based crosslinking agent include 1, 3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N, N ', N' -tetraglycidylmethylenem-xylylenediamine, ethylene glycol diglycidyl ether, 1, 6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidylaniline, and diglycidylamine. Among them, N' -tetraglycidyl m-xylylenediamine is preferable from the viewpoint of reactivity with a carboxyl group.

The content of the crosslinking agent (C) in the adhesive composition P is preferably 0.001 part by mass or more, more preferably 0.01 part by mass or more, particularly preferably 0.05 part by mass or more, and further preferably 0.1 part by mass or more, relative to 100 parts by mass of the (meth) acrylate polymer (a). The content is preferably 30 parts by mass or less, more preferably 10 parts by mass or less, particularly preferably 5 parts by mass or less, and further preferably 1 part by mass or less. When the content of the crosslinking agent (C) is within the above range, the creep compliance change value and creep recovery ratio described above can be easily satisfied.

When the isocyanate crosslinking agent and the epoxy crosslinking agent are used together, the content of the isocyanate crosslinking agent in the adhesive composition P is preferably 0.0009 parts by mass or more, more preferably 0.009 parts by mass or more, particularly preferably 0.09 parts by mass or more, and further preferably 0.1 parts by mass or more, relative to 100 parts by mass of the (meth) acrylate polymer (a). The content is preferably 20 parts by mass or less, more preferably 9 parts by mass or less, particularly preferably 4 parts by mass or less, and further preferably 0.8 parts by mass or less.

When the isocyanate-based crosslinking agent and the epoxy-based crosslinking agent are used together, the content of the epoxy-based crosslinking agent in the adhesive composition P is preferably 0.0001 parts by mass or more, more preferably 0.001 parts by mass or more, particularly preferably 0.01 parts by mass or more, and further preferably 0.1 parts by mass or more, based on 100 parts by mass of the (meth) acrylate polymer (a). The content is preferably 10 parts by mass or less, more preferably 1 part by mass or less, particularly preferably 0.8 part by mass or less, and further preferably 0.4 part by mass or less.

(1-4) various additives

Various additives generally used in acrylic adhesives may be added to the adhesive composition P as needed, and for example, a silane coupling agent, an ultraviolet absorber, an antistatic agent, a tackifier, an antioxidant, a light stabilizer, a softening agent, a filler, a refractive index adjuster, and the like may be added. The polymerization solvent or the dilution solvent described later is not included in the additives constituting the adhesive composition P.

The adhesive composition P preferably contains the silane coupling agent. In this way, in the obtained adhesive layer, the adhesiveness to a flexible member as an adherend is improved, and the adhesive force is further improved.

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

Examples of the silane coupling agent 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; mercapto group-containing silicon compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyldimethoxymethylsilane, etc.; amino group-containing silicon compounds such as 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane and N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane; 3-chloropropyltrimethoxysilane, isocyanatopropyltriethoxysilane, or a condensate of at least one of these with an alkyl group-containing silicon compound such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane or ethyltrimethoxysilane. 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 within the above range, the adhesion between the obtained adhesive layer and a flexible member as an adherend is improved, and the adhesive force becomes larger.

(2) Preparation of adhesive composition P

The adhesive composition P can be prepared by preparing the (meth) acrylate polymer (a), mixing the obtained (meth) acrylate polymer (a), the low-molecular-weight component (B), and, if necessary, the crosslinking agent (C), and further adding an additive if necessary.

The (meth) acrylate polymer (a) can be prepared by polymerizing a mixture of monomers constituting the polymer using a conventional 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 needed. By polymerizing the (meth) acrylate polymer (a) by a solution polymerization method, the obtained polymer can be easily increased in molecular weight and the molecular weight distribution can be easily adjusted. Therefore, the adhesive is less likely to be displaced by long-term bending, and the recovery from the bent state is more excellent.

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 of them may be used simultaneously. Examples of the azo compound include 2,2 '-azobisisobutyronitrile, 2' -azobis (2-methylbutyronitrile), 1 '-azobis (cyclohexanecarbonitrile), 2' -azobis (2, 4-dimethylvaleronitrile), 2 '-azobis (2, 4-dimethyl-4-methoxyvaleronitrile), dimethyl azobisisobutyrate, 4' -azobis (4-cyanovaleric acid), 2 '-azobis (2-hydroxymethylpropionitrile), and 2, 2' -azobis [2- (2-imidazolin-2-yl) propane ].

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

In the polymerization step, the weight average molecular weight of the obtained polymer can be adjusted by adding a chain transfer agent such as 2-mercaptoethanol.

After obtaining the (meth) acrylate polymer (a), the low-molecular-weight component (B) and, if necessary, the crosslinking agent (C), the additive and the diluting solvent are added to the solution of the (meth) acrylate polymer (a) and sufficiently mixed to obtain the adhesive composition P (coating solution) diluted with the solvent.

In the case where a solid substance is used for any of the above-mentioned components or in the case where precipitation occurs when the solid substance 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 dichloromethane and dichloroethane; 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 or viscosity of the coating solution prepared in the above manner is not particularly limited as long as it is within a range in which it can be coated, and may be appropriately selected depending on the case. For example, the concentration of the adhesive composition P is 10 to 60% by mass after dilution. In addition, when obtaining the coating solution, the addition of a diluting solvent or the like is not an essential condition, and the diluting solvent may not be added as long as the adhesive composition P has a coatable viscosity or the like. 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) Production of adhesives

The pressure-sensitive adhesive of the present embodiment is preferably obtained from the pressure-sensitive adhesive composition P, and more preferably a pressure-sensitive adhesive obtained by crosslinking the pressure-sensitive adhesive composition P. The crosslinking of the adhesive composition P can be usually performed by heat treatment. The heating treatment can be also used as a drying treatment for evaporating a diluent solvent or the like from a coating film of the adhesive composition P applied to a desired object.

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, a curing period of about 1 to 2 weeks may be set at normal temperature (e.g., 23 ℃ C., 50% RH) as necessary. 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.

By the heat treatment (and curing), the (meth) acrylate polymer (a), or the (meth) acrylate polymer (a) and the low-molecular-weight component (B) are sufficiently crosslinked via the crosslinking agent (C) to form a crosslinked structure, thereby obtaining an adhesive.

In addition, the adhesive of the present embodiment is particularly preferred to lower the storage modulus G ', particularly the storage modulus G' at low temperatures, by lowering the glass transition temperature (Tg) of the (meth) acrylate polymer (a) and adding the low-molecular-weight component (B); on the other hand, the creep compliance change value is reduced by tightly crosslinking. Thus, it is easy to simultaneously realize the above-mentioned two physical properties of storage modulus G' (-30) at-30 ℃ and creep compliance change value.

[ adhesive sheet ]

The adhesive sheet of the present embodiment has an adhesive layer for bonding one flexible member and another flexible member constituting a repetitive bending device, and the adhesive layer is composed of the adhesive.

Fig. 1 shows a specific structure of an example of the adhesive sheet according to the present embodiment.

As shown in fig. 1, the adhesive sheet 1 according to one embodiment is composed of two

release sheets

12a and 12b and an adhesive layer 11 sandwiched between the two

release sheets

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

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 any of a surface subjected to a release treatment and a surface which exhibits releasability without being subjected to the release treatment.

(1) Constituent elements

(1-1) adhesive agent layer

The adhesive layer 11 is composed of the adhesive of the above embodiment, and preferably is composed of an adhesive obtained by crosslinking the adhesive composition P.

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, in terms of the lower limit. When the lower limit of the thickness of the adhesive layer 11 is the above value, a desired adhesive force is easily exhibited, and floating or peeling is more unlikely to occur at the interface between the adhesive layer and the adherend. 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 is repeatedly bent. When the upper limit value of the thickness of the adhesive layer 11 is the above value, the adhesiveness of the adhesive layer to an adherend is easily maintained, and thus the bending resistance is further excellent, and further, the stress applied to the adhesive layer becomes small, and the recovery from the bent state is easily achieved. The adhesive layer 11 may be formed as a single layer, or the adhesive layer 11 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, 12b are not necessarily structured.

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 in the release treatment include alkyd based, silicone based, fluorine based, unsaturated polyester based, polyolefin based, and wax based release agents. Further, it is preferable that one of the

release sheets

12a and 12b is a heavy release type release sheet having a large release force, and the other 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, but is usually about 20 to 150 μm.

(2) Physical Properties

(2-1) haze value

The haze value of the adhesive layer 11 of the adhesive sheet 1 of the present embodiment is preferably 30% or less, more preferably 10% or less, particularly preferably 1% or less, and further preferably 0.8% or less. This can suppress the change in appearance of the adhesive layer 11 due to the bending. The lower limit of the haze value is not particularly limited, but is preferably 0% or more, more preferably 0.01% or more, and particularly preferably 0.03% or more. The haze value in the present specification is a value measured according to JIS K7136: 2000.

(2-2) adhesive force

The adhesive sheet 1 of the present embodiment has an adhesive force to soda-lime glass of preferably 0.1N/25mm or more, more preferably 1.0N/25mm or more, particularly preferably 1.3N/25mm or more, and further preferably 1.4N/25mm or more, in terms of the lower limit. When the lower limit of the adhesive force of the adhesive sheet 1 is the above value, the floating or peeling due to the bending is more unlikely to occur at the interface between the adhesive layer and the adherend. On the other hand, the upper limit value of the above-mentioned adhesive force is not particularly limited, but is usually preferably 60N/25mm or less, more preferably 40N/25mm or less, and is particularly preferably 20N/25mm or less, further preferably 10N/25mm or less, from the viewpoint of reworkability (reworkability) that the adhesive sheet can be reattached when the adhesive sheet is misaligned. 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.

(3) Production 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. A coating liquid of the adhesive composition P is applied to the release surface of one release sheet 12a (or 12b), heat treatment is performed to thermally crosslink the adhesive composition P to form a coating layer, and then the release surface of the other release sheet 12b (or 12a) is laminated on the coating layer. When the curing period is required, the coating layer is formed into the adhesive layer 11 through the curing period, and when the curing period is not required, the coating layer is directly formed into the adhesive layer 11. Thus, the adhesive sheet 1 was obtained. The conditions for the heat treatment and the 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 crosslink the adhesive composition P to form a coating layer, thereby obtaining a release sheet 12a with a coating layer. Further, the coating solution of the adhesive composition P is applied to the release surface of the other release sheet 12b, and heat treatment is performed to thermally crosslink the adhesive composition P to form a coating layer, thereby obtaining a release sheet 12b having a coating layer. Then, the coated release sheet 12a and the coated release sheet 12b are bonded to each other so that the two coating layers are in contact with each other. When the curing period is required, the laminated coating layer is formed into the adhesive layer 11 through the curing period, and when the curing period is not required, the laminated coating layer is directly formed into the adhesive layer 11. Thus, the adhesive sheet 1 was obtained. According to this production example, even when the adhesive layer 11 is thick, stable production can be performed.

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 is configured to include a first bendable member 21 (one bendable member), a second bendable member 22 (the other bendable member), and an adhesive layer 11 interposed therebetween and bonding 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 formed of the adhesive or is the adhesive layer 11 of the adhesive sheet 1.

The repeatedly bending laminated member 2 is the repeatedly bending device itself, or the repeatedly bending laminated member 2 is a member constituting a part of the repeatedly bending device. The repetitive bending device is preferably a display that can be repetitively bent (including bent), 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 folding display, and the like, and may be a touch panel.

The first flexible member 21 and the second flexible member 22 are members that can be repeatedly bent (including bent), and examples thereof include a coating Film, a 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, a Film sensor (touch sensor 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.

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 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.

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 order to manufacture the above-described repeatedly bent laminate member 2, one release sheet 12a of the adhesive sheet 1 is peeled off, and the adhesive layer 11 exposed from 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 attaching the first flexible member 21 and the second flexible member 22 may be changed.

[ repeated bending device ]

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

In the repeated bending device of the present embodiment, since the adhesive layer is composed of the adhesive, when the repeated bending is performed or the device is left in a bent state for a long period of time, the adhesive layer 11 is less likely to float or peel at the interface with the adherend (the first flexible member 21 and the second flexible member 22). When the adhesive constituting the adhesive layer 11 satisfies the creep recovery ratio, the recovery from the bent state is also excellent.

A repetitive bending device as an example of the present embodiment is shown in fig. 3. The bending device of the present invention is not limited to this bending 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 sensor 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 top to bottom. The coating film 31, the polarizing film 33, the touch sensor film 35, the organic EL element 37, and the TFT substrate 39 are flexible members.

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 all of the

adhesive layers

32, 34, 36, and 38 are the adhesive layers 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, either 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 described in more detail 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) acrylate polymer (a) was prepared by copolymerizing 98.5 parts by mass of 2-ethylhexyl acrylate, 1.0 part by mass of 4-hydroxybutyl acrylate, and 0.5 part by mass of acrylic acid by a solution polymerization method. When the molecular weight of the (meth) acrylate polymer (a) was measured by the method described later, the weight average molecular weight (Mw) was 120 ten thousand.

2. Preparation of adhesive composition

100 parts by mass (solid content converted value; the same applies hereinafter) of the (meth) acrylate polymer (A) obtained in the above-mentioned step 1, 15 parts by mass of a hydroxyl group-containing acrylic oligomer (B1; TOAGOSEI CO., LTD., product name "ARUFON (registered trademark) UH-2000" as the low molecular weight component (B), a hydroxyl group content of 20mgKOH/g, Mw: 11000, Tg: -55 ℃ C.), 0.3 parts by mass of trimethylolpropane-modified xylylene diisocyanate (XDI; Soken Chemical & Engineering Co., Ltd., product name "TD-75" as the isocyanate-based crosslinking agent (C1), 0.2 parts by mass of N, N, N ', N' -tetraglycidyl m-xylylene diamine as the epoxy-based crosslinking agent (C2), and 0.2 parts by mass of 3-glycidyl ether oxypropyltrimethoxysilane (SC1) as the silane coupling agent were mixed, the mixture was sufficiently stirred and diluted with methyl ethyl ketone to obtain a coating solution of the adhesive composition.

3. Production of adhesive sheet

The obtained coating solution of the adhesive composition was coated on the release-treated surface of a heavy release type release sheet (manufactured by linec Corporation, product name "SP-PET 752150") having one surface of a polyethylene terephthalate film release-treated with a silicone-based release agent, using a blade coater. And, the coating layer was subjected to a heat treatment at 90 ℃ for 1 minute to form a coating layer.

Then, 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 peeling one surface of a polyethylene terephthalate film with a silicone type release agent so that the peeled 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 producing an adhesive sheet having an adhesive layer with a thickness of 25 μm, that is, an adhesive sheet composed 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 was measured according to JIS K7130 using a constant pressure thickness gauge (product name "PG-02" manufactured by dele corporation).

The respective proportions (solid content equivalent) of the adhesive composition based on 100 parts by mass (solid content equivalent) of the (meth) acrylate polymer (a) are shown in table 1. The details of the abbreviations and the like shown in table 1 are as follows.

[ (meth) acrylic ester Polymer (A) ]

2 EHA: 2-ethylhexyl acrylate

4 HBA: acrylic acid 4-hydroxybutyl ester

AAc: acrylic acid

[ Low molecular weight component (B) ]

B1: hydroxyl-containing acrylic oligomer (TOAGOSEI CO., LTD., manufactured by ARUFON (registered trademark) UH-2000', hydroxyl group content: 20mgKOH/g, Mw: 11000, Tg: -55 ℃ C.)

B2: epoxy group-containing acrylic oligomer (TOAGOSEI CO., LTD., manufactured by ARUFON UG-4010, epoxy group content: 1.4meq/g, Mw: 2900, Tg: -57 ℃ C.)

B3: non-functional acrylic oligomer (TOAGOSEI CO., LTD., manufactured under the product name "ARUFON UP-1000", Mw: 3000, Tg: -77 ℃ C.)

[ isocyanate crosslinking agent (C1) ]

XDI: trimethylolpropane-modified xylylene diisocyanate (manufactured by Soken Chemical & Engineering Co., Ltd., product name "TD-75")

TDI: trimethylolpropane-modified toluene diisocyanate (TOYOCHEM CO., LTD., product name "BHS 8515")

[ epoxy crosslinking agent (C2) ]

N, N, N ', N' -tetraglycidyl meta-xylylenediamine

[ silane coupling agent ]

SC 1: 3-glycidyloxypropyltrimethoxysilane

SC 2: 1, 6-bis (trimethoxysilyl) hexane

Examples 2 to 4 and comparative examples 1 to 4

An adhesive sheet was produced in the same manner as in example 1, except that the kind and ratio of each monomer constituting the (meth) acrylate polymer (a), the weight average molecular weight (Mw) of the (meth) acrylate polymer (a), the kind and blending amount of the low molecular weight component (B), the kind of the isocyanate-based crosslinking agent (C1), the blending amount of the epoxy-based crosslinking agent (C2), and the kind of the silane coupling agent were changed as shown in table 1.

The weight average molecular weight (Mw) is a weight average molecular weight in terms of polystyrene measured by Gel Permeation Chromatography (GPC) under the following conditions (GPC measurement).

< measurement Condition >

GPC measurement apparatus: HLC-8020 manufactured by TOSOH CORPORATION

GPC column (passage in the following order): TOSOH CORPORATION, Inc

TSK guard column HXL-H

TSK gel GMHXL(×2)

TSK gel G2000HXL

Determination of the solvent: tetrahydrofuran (THF)

Measurement temperature: 40 deg.C

[ test example 1] (measurement of gel fraction)

The adhesive sheets prepared in examples and comparative examples were cut into 80mm × 80mm sizes, the adhesive layers were wrapped in polyester nets (product name: Tetoron Mesh #200), the masses thereof were weighed with a precision balance, and the masses of the nets alone were subtracted, thereby calculating the masses of the adhesives themselves. The mass at this time was set to M1.

Then, the adhesive wrapped in the polyester net was immersed in ethyl acetate at room temperature (23 ℃ C.) for 24 hours. The adhesive was then removed, air-dried at a temperature of 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 was weighed with a precision balance, and the mass of the web alone was subtracted, thereby calculating the mass of the adhesive itself. The mass at this time was set to M2. Gel fraction (%) is expressed as (M2/M1). times.100. The results are shown in Table 2.

[ test example 2] (measurement of storage modulus G')

The adhesive layers of the adhesive sheets prepared in examples and comparative examples were stacked to prepare a laminate having a thickness of 800 μm. A cylindrical body (height: 800 μm) having a diameter of 8mm was punched out of the laminate of the obtained adhesive layer, and this was used as a sample.

According to JIS K7244-6, a viscoelasticity measuring apparatus (product name, manufactured by Antopa corporation) was used

"MCR 302") and the storage modulus G 'of the above sample was measured by the torsional shear method (ね was manufactured by リせ one-off method) under the following conditions to obtain a storage modulus G' (-30) at-30 ℃, a storage modulus G '(25) at 25 ℃ and a storage modulus G' (85) (MPa) at 85 ℃. The results are shown in Table 2.

Measuring frequency: 1Hz

Temperature rise rate: 5 ℃ per minute

Strain: 1 percent of

Normal force: 1.0N

Measuring temperature: -30 ℃ to 140 DEG C

Further, from the obtained results, a storage modulus variation (-30/25) and a storage modulus variation (-30/85) were calculated, the storage modulus variation (-30/25) being a value obtained by dividing storage modulus G '(-30) by storage modulus G' (25), and the storage modulus variation (-30/85) being a value obtained by dividing storage modulus G '(-30) by storage modulus G' (85). The results are shown in Table 2.

[ test example 3] (measurement of creep compliance)

Using a viscoelasticity measuring apparatus (product name "MCR 302" manufactured by Antopa corporation), a stress of 4500Pa was continuously applied to the sample under the following conditions, and a creep compliance J (t) (MPa) was measured ^-1 ). Based on the results of the measurement, theThe value at the time of applying a stress of 4500Pa was set to the minimum creep compliance J (t) _min (MPa ^-1 ) And deriving the minimum creep compliance J (t) from the measurement _min Maximum creep compliance J (t) measured 1200 seconds after the start _max (MPa ^-1 )。

Measuring temperature: 25 deg.C

And (3) measuring the position: 1000 place (logarithmic chart)

From the minimum creep compliance J (t) obtained according to the following formula (I) _min (MPa ^-1 ) And maximum creep compliance J (t) _max (MPa ^-1 ) The creep compliance change value Δ logj (t) is calculated. The results are shown in Table 2.

ΔlogJ(t)＝logJ(t) _max -logJ(t) _min …(I)

Further, using a viscoelasticity measuring apparatus (product name "MCR 302" manufactured by antopa corporation), after a stress of 4500Pa was continuously applied to the sample under the following conditions, the applied stress was set to 0Pa, and this state was temporarily maintained. During this period, the creep compliance J (t) (MPa-1) was measured. The creep compliance value measured 1200 seconds after the stress of 4500Pa started to be applied was set to creep compliance j (t) (s 1200) (MPa) ^-1 ) The creep compliance value measured after the applied stress was set to 0Pa for 100 seconds was set to creep compliance j (t) (s 1300) (MPa) ^-1 )。

Measuring temperature: 25 deg.C

Measurement position when stress was applied: 1000 place (logarithmic chart)

Measurement points when removing stress: 1000 place (logarithmic chart)

From the creep compliance j (t) (s ═ 1200) (MPa) obtained according to the following formula (II) ^-1 ) And creep compliance J (t) (s 1300) (MPa) ^-1 ) The creep recovery (%) was calculated. The results are shown in Table 2.

Creep recovery ratio (%) (1-j (t) (s 1300)/j (t) (s 1200)) × 100 … (II)

[ test example 4] (measurement of haze value)

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

[ test example 5] (measurement of adhesive force)

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

The heavy-release type release Sheet was peeled 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 manufactured by kurihia sesakusho co. Then, the laminate was left at 23 ℃ and 50% RH for 24 hours, and the adhesion (N/25mm) when the laminate of the PET film and the adhesive layer was peeled from the adherend was measured using a tensile tester (ORIENTEC co., LTD, tensillon) under conditions of a peeling rate of 300 mm/min and a peeling angle of 180 degrees. The conditions not described herein were measured according to JIS Z0237: 2009. The results are shown in Table 2.

[ test example 6] (evaluation of bending resistance)

The light-release type release sheet was peeled from the adhesive sheet produced 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 polyethylene terephthalate (PET) film (TOYOBO co., ltd., product name "PET 50TA 063", thickness: 100 μm). Then, the heavy-release type release sheet was peeled off, and the exposed adhesive layer was bonded to a polyimide film (thickness: 50 μm). Then, the mixture was pressurized at 50 ℃ for 20 minutes under 0.5MPa by using an autoclave manufactured by KURIHARIA SEISAKUSHO Co., Ltd, and then left to stand at 23 ℃ and 50% RH for 24 hours. The laminate composed of the PET film/adhesive layer/polyimide film thus obtained was cut into a width of 50mm and a length of 200mm, and used as a sample.

As shown in fig. 4, both end portions of the obtained sample were fixed between two holding plates of a bending tester (YUASA SYSTEM co., ltd., product name "CL 09-typeD01-FSC 90") with a constant temperature and humidity chamber. At this time, the sample was fixed so that the polyimide film side was the bent inner side. The sample was bent 20 ten thousand times under conditions of a bend diameter (diameter) of 3mm phi, a stroke of 80mm, and a bending speed of 60rpm in each temperature environment of-30 ℃, 25 ℃ and 80 ℃.

After the dynamic bending test, whether or not the peeling occurred at the interface between the adhesive layer and the adherend at the bent portion of the sample was visually confirmed. The bending resistance was evaluated according to the following criteria. The results are shown in Table 2.

Very good: the curved portion has no linear trace.

O: although there was a linear trace at the bent portion, the linear trace was hardly observed when viewed from the front.

And (delta): the presence of a linear trace at the bent portion, which is also confirmed when viewed from the front; or minute bubbles are generated at the bent portion.

X: the bent portion is lifted and peeled off.

[ Table 1]

As is clear from table 2, the adhesive layer of the adhesive sheet of the example was less likely to cause lifting or peeling at the interface between the adhesive layer and the adherend due to long-term bending even under any of low temperature, normal temperature, and high temperature, and was excellent in bending 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 for a repeating bending device for bonding one flexible member and another flexible member constituting the repeating bending device, characterized in that,

the adhesive has a storage modulus G' (-30) at-30 ℃ of 0.20MPa or less,

the creep compliance value measured when a stress of 4500Pa was applied to the adhesive was set to the minimum creep compliance J (t) _min (MPa ^-1 ) The minimum creep compliance J (t) was measured _min Thereafter, the stress of 4500Pa was continuously applied for 1200 seconds, and the maximum creep compliance value measured during this time was set to the maximum creep compliance J (t) _max (MPa ^-1 ) A creep compliance change value DelalogJ (t) calculated by the following formula (I) is 2.60 or less,

ΔlogJ(t)＝logJ(t) _max -logJ(t) _min …(I)。

2. the adhesive for a recurved device according to claim 1,

the creep compliance value measured after the adhesive was continuously stressed for 1200 seconds at 4500Pa was set to creep compliance j (t) (s 1200) (MPa) ^-1 ) Then, the stress applied to the adhesive was set to 0Pa, and the creep compliance value measured 100 seconds after the stress was set to creep compliance j (t) (s 1300) (MPa) ^-1 ) A creep recovery rate calculated by the following formula (II) is 90% or more,

creep recovery ratio (%) (1-j (t) (s 1300)/j (t) (s 1200)) × 100 … (II).

3. The adhesive for a recurved device according to claim 1,

the adhesive for a repeated bending device has a storage modulus G' (85) of 0.005MPa or more at 85 ℃.

4. The adhesive for a recurved device according to claim 1,

the adhesive for a repeated bending device has a degree of change in storage modulus (-30/25) of 5.0 or less, and the degree of change in storage modulus (-30/25) is a value obtained by dividing storage modulus G '(-30) at-30 ℃ by storage modulus G' (25) at 25 ℃.

5. The adhesive for a recurved device according to claim 1,

the adhesive for a repeated bending device has a degree of change in storage modulus (-30/85) of 10.0 or less, and the degree of change in storage modulus (-30/85) is a value obtained by dividing storage modulus G '(-30) at-30 ℃ by storage modulus G' (85) at 85 ℃.

6. The adhesive for a recurved device according to claim 1,

the adhesive for a repeatedly bending device has a gel fraction of 40% or more and 95% or less.

7. The adhesive for a recurved device according to claim 1,

the adhesive contains an adhesive main agent and a low molecular weight component,

the low-molecular-weight component has a weight-average molecular weight of 400 to 100000,

the low-molecular-weight component has a glass transition temperature (Tg) of-40 ℃ or lower.

8. The adhesive for a repeatedly bending device according to claim 1, wherein said adhesive is an acrylic adhesive.

9. An adhesive sheet having an adhesive layer for bonding one flexible member and another flexible member constituting a repeating bending device, the adhesive sheet being characterized in that,

the adhesive layer is composed of the adhesive for a repeated bending device according to any one of claims 1 to 8.

10. The adhesive sheet according to claim 9,

the adhesive sheet is provided with two sheets of release sheets,

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

11. A repeatedly bending laminated member is provided with: one flexible member and another flexible member constituting a repeated bending device, and an adhesive layer for bonding the one flexible member and the another flexible member to each other, the repeated bending laminated member being characterized in that,

12. A recurved bend device, characterized in that,

the repeatedly bent laminated member according to claim 11.