TW202229482A - Adhesive for repeated bending device, adhesive sheet, repeated bending laminated part, and repeated bending device capable of avoiding the occurrence of floating and peeling when applied to a repeated bending device - Google Patents

Abstract

The object of the present invention is to provide an adhesive and an adhesive sheet for a repeated bending device, which can avoid an occurrence of floating and peeling when applied to a repeated bending device, and to provide a repetitive bending laminated part capable of avoiding the occurrence of floating and peeling, and a repeated bending device. A storage elastic modulus G'(-30) at -30 DEG C is 0.20MPa or less. A creep compliance value measured at the time of applying a stress of 4500Pa is defined as the minimum creep compliance J(t) min (MPa -1). The maximum creep compliance value measured at the time in which the stress of 4500pa is continuously applied until 1200 seconds after the minimum creep compliance J(t) min was measured is defined as the maximum creep compliance J(t ) max (MPa -1). The creep compliance variation value [Delta] logJ(t) calculated from the following formula (I) is 2.60 or less. [Delta]logJ(t)=logJ(t) max-logJ(t) min...(I).

Description

Adhesives, adhesive sheets, laminated parts for repeated bending, and repeated bending devices

The present invention relates to an adhesive and an adhesive sheet for a rebending device, as well as a re-bending laminated member and a re-bending device.

In recent years, a bendable bendable display has been proposed as a display for electronic equipment as one type of device. As a bendable display, in addition to a display of a curved surface formed only once, an iteratively curved display for repeatedly bending (bending) has been proposed.

It is generally considered that in the above-mentioned repeated bending display, one bendable member (bendable member) constituting the bendable display is adhered to another bendable member by an adhesive layer. However, if the conventional adhesive is used in the repeated bending display, there arises a problem of floating and peeling at the interface between the adhesive layer and the adherend.

Patent Document 1 discloses an adhesive which is a problem to be solved by avoiding the occurrence of floating and peeling of the adhesive layer even if it is repeatedly bent. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2016-108555

[Problems to be Solved by Invention]

However, even in the case of using the above-mentioned adhesive, the floating and peeling caused by repeated bending cannot be sufficiently suppressed.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide an adhesive and an adhesive sheet for a repeated bending device which can avoid the occurrence of floating and peeling when applied to a repeated bending device, and also can prevent the floating and peeling from occurring. Repeated bending laminated parts and repeated bending devices for peeling off. [means used to solve problems]

In order to achieve the above object, firstly, the present invention provides an adhesive for a repetitive bending device, which is an adhesive for a repetitive bending device for attaching a flexible member constituting the repetitive bending device to another flexible member, wherein The storage elastic modulus G'(-30) of the aforementioned adhesive at -30°C is 0.20 MPa or less, and the creep compliance value measured when a stress of 4500 Pa is applied to the aforementioned adhesive is defined as Minimum creep compliance J(t) _min (MPa ^-1 ), and will continue to apply a stress of 4500Pa until 1200 seconds after the minimum creep compliance J(t) _min is measured. The maximum _creep ^compliance value of the 1). ΔlogJ(t) = logJ(t) _max - logJ(t) _min ... (I)

In the above invention (Invention 1), since the storage elastic modulus G' (-30) at -30°C is a small value as described above, it is possible to reduce the storage elastic modulus G' (-30°C) in a low-temperature environment (for example, -30°C) C) Stresses resulting from repeated bending. On the other hand, since the creep compliance variation value is a small value as described above, it is possible to prevent the adhesive from being excessively strained regardless of the temperature environment during repeated bending or bending for a long time. As a result, when applied to a repeated bending apparatus, under low temperature to high temperature environments, floating and peeling are unlikely to occur at the interface between the adhesive layer and the adherend, and excellent bending resistance can be obtained.

In the above invention (Invention 1), the creep compliance value measured after a stress of 4500 Pa is continuously applied to the aforementioned adhesive for 1200 seconds is defined as creep compliance J(t) (s=1200) (MPa ^-1 ), and the creep compliance value measured after 100 seconds after the subsequent stress applied to the aforementioned adhesive is set to 0Pa is defined as creep compliance J(t) (s=1300) (MPa ^-1 ), according to The creep recovery rate calculated by the following formula (II) is preferably 90% or more (Invention 2). Creep recovery rate (%)=(1-J(t)(s=1300)/J(t)(s=1200))x100...(II)

In the above inventions (Inventions 1 and 2), the storage elastic modulus G' (85) at 85°C is preferably 0.005 MPa or more (Invention 3).

In the above inventions (Inventions 1 to 3), the storage elastic modulus change degree (-30/25) is the storage elastic modulus G' (-30) at -30°C divided by the storage elastic modulus G' (-30) at 25°C The value obtained by the storage elastic modulus G' (25) is preferably 5.0 or less (Invention 4).

In the above inventions (Inventions 1 to 4), the storage elastic modulus change degree (-30/85) is the storage elastic modulus G' (-30) at -30°C divided by the storage elastic modulus at 85°C The value obtained by the storage elastic modulus G' (85) is preferably 10.0 or less (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), the adhesive contains an adhesive main agent and a low molecular weight component, the weight average molecular weight of the low molecular weight component is 400 or more and 100,000 or less, and the low molecular weight component has a glass transition temperature (Tg ) is preferably below -40°C (Invention 7).

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

Second, the present invention provides an adhesive sheet, which is an adhesive sheet having an adhesive layer for attaching a flexible member constituting the repeated bending device to another flexible member, wherein the aforementioned adhesive layer is formed by the aforementioned repeated bending It consists of the adhesive for devices (Inventions 1 to 8) (Invention 9).

In the above invention (Invention 9), it is preferable that the adhesive sheet includes two release sheets, and the adhesive layer is sandwiched between the release sheets and contacts the release surfaces of the two release sheets (Invention 10).

Thirdly, the present invention provides a repeatedly bent laminated member comprising a flexible member and another flexible member constituting a repeated bending device, and an adhesive for attaching the first flexible member and the other flexible member to each other The repeated bending laminated member of the adhesive layer, wherein the adhesive layer is composed of the adhesive for the repeated bending device (Inventions 1 to 8) (Invention 11).

Fourthly, the present invention provides an iterative bending apparatus (Invention 12) including the aforementioned iteratively bending laminated member (Invention 11). [Inventive effect]

According to the adhesive agent and the adhesive sheet for a repeated bending device of the present invention, when applied to a repeated bending device, the interface between the adhesive layer and the adherend is less likely to be lifted and peeled off. Furthermore, according to the repeated bending laminated member and the repeated bending device of the present invention, it is difficult to cause floating and peeling at the interface between the adhesive layer and the adherend.

[Form for carrying out the invention]

Hereinafter, embodiments of the present invention will be described. [Adhesive for Repetitive Bending Device] The adhesive for a re-bending device according to the present embodiment (hereinafter sometimes simply referred to as “adhesive”) is an adhesive layer for bonding one flexible member and another flexible member constituting the re-bending device. The repeated bending device and the bendable member will be described later.

The storage elastic modulus G' (-30) of the adhesive according to the present embodiment at -30°C is preferably 0.20 MPa or less, and the creep flexibility measured when a stress of 4500 Pa is applied to the adhesive The magnitude is defined as the minimum creep compliance J(t) _min (MPa ^-1 ) and will continue to apply a stress of 4500Pa until 1200 seconds after the minimum creep compliance J(t) _min is measured The maximum creep compliance value measured within is defined as the maximum creep compliance J(t) _max (MPa ^-1 ), and the creep compliance variation value ΔlogJ(t) calculated from the following formula (I) is expressed as 2.60 or less is better. ΔlogJ(t)=logJ(t) _max -logJ(t) _min ... (I) In addition, the details of the measurement method of storage elastic modulus G' and the measurement method of creep compliance J(t) are as follows described in the test examples. In addition, the so-called "when a stress of 4500 Pa is applied to the adhesive" means when a stress is applied to the adhesive and the stress reaches 4500 Pa.

According to the adhesive of the present embodiment, since the storage elastic modulus G' (-30) at -30°C is a small value as described above, it is possible to reduce the storage elastic modulus G' (-30) at a low temperature environment (for example, -30°C) ) for repeated bending stress. On the other hand, since the creep compliance variation value is a small value as described above, it is possible to prevent the adhesive from being excessively strained regardless of the temperature environment during repeated bending or bending for a long time. In an excessively deformed adhesive, the internal structure of the adhesive may change due to deformation due to bending, and the adhesive may not return to its original state even after the bending is released. In the adhesive of the present embodiment, such excessive strain can be prevented. Although the above-mentioned two physical properties are usually contradictory, the adhesive according to the present embodiment takes into account the above-mentioned two physical properties, and even at a very low temperature such as -30°C, the stress to deformation is small, and due to The strain caused by deformation is also very small. As a result, when applied to a repeated bending apparatus, under low temperature to high temperature environments, floating and peeling are unlikely to occur at the interface between the adhesive layer and the adherend, and excellent bending resistance can be obtained.

From the viewpoint of the above bending resistance, the storage elastic modulus G' (-30) at -30°C of the adhesive according to the present embodiment is preferably 0.20 MPa or less, more preferably 0.15 MPa or less, and 0.11 MPa or less is particularly preferred, and 0.10 MPa or less is more preferred. Furthermore, from the viewpoint of cohesion, the storage elastic modulus G' (-30) at -30°C of the adhesive constituting the adhesive layer is preferably 0.01 MPa or more, preferably 0.02 MPa or more , 0.04MPa or more is particularly preferred, and 0.08MPa or more is more preferred.

Furthermore, from the viewpoint of the above-mentioned bending resistance, the above-mentioned creep compliance variation value ΔlogJ(t) is preferably 2.60 or less, more preferably 2.58 or less, particularly preferably 2.56 or less, and more preferably 2.54 or less. good. In addition, the lower limit of the creep compliance variation 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.

The minimum creep compliance J(t) _min of the adhesive according to the present embodiment is preferably 1 Mpa ^-1 or more, more preferably 5 Mpa ^{-1 or more, particularly preferably 10 Mpa -1 or} more as the lower limit value, and More than 15Mpa ^-1 is better. When the lower limit value of the minimum creep compliance J(t) _min is as described above, the above-described creep compliance fluctuation value ΔlogJ(t) becomes easy to satisfy the above-described numerical value. The upper limit of the minimum creep compliance J(t) _min is not particularly limited, but is usually preferably 1000 Mpa ^-1 or less, particularly preferably 100 Mpa ^-1 or less, and more preferably 20 Mpa ^-1 or less.

Furthermore, the upper limit of the maximum creep compliance J(t)max of the adhesive according to the present embodiment is preferably 10000Mpa ^-1 or less, preferably 8000Mpa ^-1 or less, and particularly preferably 6000Mpa ^-1 or less , and below 5500Mpa ^-1 is better. When the upper limit value of the maximum creep compliance J(t)max is as described above, the above-described creep compliance fluctuation value ΔlogJ(t) becomes easy to satisfy the above-described numerical value. The lower limit of the maximum creep compliance J(t)max is not particularly limited, but is usually preferably 1100Mpa ^-1 or higher, particularly preferably 2000Mpa ^-1 or higher, and more preferably 4000Mpa ^-1 or higher.

According to the adhesive of the present embodiment, the creep compliance value measured after a stress of 4500 Pa is continuously applied to the adhesive for 1200 seconds is defined as creep compliance J(t) (s=1200) (MPa ^-1 ) , and the creep compliance value measured after 100 seconds after the subsequent stress applied to the above adhesive is set to 0Pa is defined as the creep compliance J(t) (s=1300) (MPa ^-1 ), from the following The creep recovery rate calculated by the formula (II) is preferably at least 90%, more preferably at least 92%, particularly preferably at least 94%, and more preferably at least 96%. Creep recovery rate (%)=(1-J(t)(s=1300)/J(t)(s=1200))x100...(II)

Since the adhesive according to the present embodiment has the above-mentioned creep recovery rate, even when the repeated bending apparatus to which the adhesive is applied is in a bent state for a long time, the recovery from the bent state is excellent, and the adhesive The agent layer becomes less likely to leave bending marks.

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 lower limit value of the creep compliance J(t) (s=1200) of the adhesive according to the present embodiment is preferably 1100 Mpa ^-1 or more, more preferably 2000 Mpa ^-1 or more, and particularly preferably 4000 Mpa ^-1 or more , and 4600Mpa ^-1 or more is better. As a result, the adhesive becomes more suitable for stress relaxation. From the viewpoint of the cohesive force of the adhesive, the upper limit of the creep compliance J(t) (s=1200) is usually preferably 10000Mpa ^-1 or less, particularly preferably 8000Mpa ^-1 or less, and 6000Mpa ^-1 The following is better.

Furthermore, the upper limit of the creep compliance J(t) (s=1300) of the adhesive according to the present embodiment is preferably 800Mpa ^-1 or less, preferably 400Mpa ^-1 or less, and 200Mpa ^-1 or less. It is particularly good, and it is better to be below 180Mpa ^-1 . In this way, the adhesive becomes more excellent in recovery. The lower limit of the creep compliance J(t) (s=1300) is not particularly limited, but is usually preferably 1 Mpa ^-1 or more, particularly preferably 10 Mpa ^-1 or more, and more preferably 100 Mpa ^-1 or more.

The storage elastic modulus G'(85) at 85°C of the adhesive according to the present embodiment is preferably 0.005 MPa or more, more preferably 0.010 MPa or more, particularly preferably 0.020 MPa or more, and 0.022 MPa or more for better. In this way, the adhesive layer can maintain cohesion without becoming too soft, even at high temperatures. Furthermore, the storage elastic modulus G'(85) at 85°C of the adhesive according to the present embodiment is preferably 0.10 MPa or less, more preferably 0.08 MPa or less, particularly preferably 0.06 MPa or less, and 0.04MPa or less is more preferable. In this way, it becomes easy to obtain a low storage elastic modulus G' at a low temperature.

The storage elastic modulus G'(25) at 25°C of the adhesive according to the present embodiment is preferably 0.15 MPa or less, more preferably 0.10 MPa or less, particularly preferably 0.07 MPa or less, and 0.04 MPa or less for better. In this way, it becomes easy to express suitable adhesiveness. On the other hand, the storage elastic modulus G'(25) at 25°C is preferably 0.010 MPa or more, more preferably 0.015 MPa or more, particularly preferably 0.020 MPa or more, and more preferably 0.026 MPa or more . In this way, in addition to having excellent repeated bending properties in the standard ambient temperature range, workability such as punching is also improved.

According to the adhesive of the present embodiment, the storage elastic modulus change degree (-30/25) is the storage elastic modulus G' (-30) at -30°C divided by the storage elastic modulus at 25°C The value obtained by the amount G' (25) is preferably 5.0 or less, more preferably 4.0 or less, particularly preferably 3.5 or less, and more preferably 3.3 or less. In this way, it becomes easy to prevent high elastic modulus at low temperature while having appropriate adhesive force at normal temperature.

Furthermore, the above-mentioned storage elastic modulus change degree (-30/25) is preferably 1.50 or more, more preferably 2.00 or more, particularly preferably 2.50 or more, and more preferably 3.00 or more. In this way, it becomes easy to obtain an adhesive having excellent cohesion.

According to the adhesive of the present embodiment, the storage elastic modulus change degree (-30/85) is the storage elastic modulus G' (-30) at -30°C divided by the storage elastic modulus at 85°C The value obtained by the amount G' (85) is preferably 10.0 or less, more preferably 7.0 or less, particularly preferably 5.0 or less, and more preferably 4.5 or less. In this way, it becomes easy to achieve both a low elastic modulus at a low temperature and a high elastic modulus at a high temperature.

Furthermore, the above-mentioned storage elastic modulus change degree (-30/85) is preferably 1.20 or more, more preferably 2.00 or more, particularly preferably 2.50 or more, and more preferably 3.00 or more. In this way, it becomes easy to obtain an adhesive having excellent cohesion.

The gel fraction of the adhesive according to the present embodiment is preferably 40% or more, more preferably 50% or more, particularly preferably 60% or more, and more preferably 70% or more. As such, the adhesive exhibits suitable cohesion to withstand repeated bending. As a result, the aforementioned bending resistance becomes more excellent. On the other hand, the gel fraction of the adhesive according to the present embodiment is preferably 95% or less, more preferably 90% or less, particularly preferably 85% or less, and more preferably 80% or less. In this way, it is presumed that the cross-linked structure in the adhesive can be prevented from being damaged due to repeated bending, and the adhesive layer itself can be prevented from becoming cloudy. In addition, the measurement method of the gel fraction in this specification is as described in the test example mentioned later.

The adhesive according to the present embodiment is not particularly limited as long as it satisfies the above-mentioned physical properties, and it is preferable that it contains a main adhesive and a low molecular weight component. As a low molecular weight component, the weight average molecular weight is 400 or more and 100000 or less, and a glass transition temperature (Tg) is -40 degreeC or less low molecular weight component is preferable. An adhesive containing a low molecular weight component having such physical properties and an adhesive main agent can easily satisfy the aforementioned physical properties, especially the storage elastic modulus G' (-30) at -30°C. In addition, the weight average molecular weight in this specification is a value in terms of standard polystyrene measured by a gel permeation chromatography (GPC) method. In addition, the glass transition temperature (Tg) in this specification is the value measured by the differential scanning calorimeter at the temperature increase/decrease rate of 20 degreeC/min.

The weight average molecular weight (Mw) of the low molecular weight component is preferably 400 or more, preferably 1000, from the viewpoint of improving the storage elastic modulus G' (85) of the obtained adhesive or reducing the creep compliance value. Above is preferred, 2500 or above is particularly preferred, and 3500 or above is more preferred. Furthermore, from the viewpoint of reducing the haze value of the obtained adhesive, the weight average molecular weight of the low molecular weight component is preferably 100,000 or less, more preferably 50,000 or less, particularly preferably 20,000 or less, and 14,000 or less. The following is better.

The glass transition temperature (Tg) of the above-mentioned low molecular weight component is preferably below -40°C, preferably below -45°C, particularly preferably below -50°C, and more preferably below -52°C . Furthermore, the glass transition temperature (Tg) of the above-mentioned low molecular weight component is preferably -80°C or higher, preferably -70°C or higher, particularly preferably -65°C or higher, and preferably -60°C or higher for better. Specific examples of the above-mentioned low molecular weight components will be described later.

The type of the adhesive according to the present embodiment is not particularly limited as long as it satisfies the above-mentioned physical properties. For example, an acrylic adhesive, a polyester adhesive, a urethane adhesive, a rubber adhesive, a polysiloxane adhesive, etc. can be used. any of . Furthermore, the adhesive may be any one of an emulsion type, a solvent type or a solventless type, and may also be any one of a cross-linked type or a non-cross-linked type. Among the above, an acrylic adhesive which easily satisfies the aforementioned physical properties and has excellent adhesive physical properties, optical properties, etc. is preferable, and a solvent-based acrylic adhesive is particularly preferable.

Specifically, the adhesive according to the present embodiment is composed of a (meth)acrylate polymer (A) containing a (meth)acrylate polymer (A) as an adhesive main agent, a low molecular weight component (B), and a crosslinking agent (C) added as needed. An adhesive obtained from an adhesive composition (hereinafter sometimes referred to as "adhesive composition P") is preferable. The use of this adhesive can satisfy the aforementioned physical properties, and it is easy to obtain a good adhesive force. In addition, in this specification, the (meth)acrylic type means both acrylic acid and methacrylic acid. The same goes for other similar terms. In addition, "polymer" also includes the concept of "copolymer".

(1) Components of the adhesive composition P (1-1) (Meth)acrylate polymer (A) The (meth)acrylate polymer (A) contains an alkyl (meth)acrylate and a monomer having a reactive functional group in the molecule (reactive functional group-containing monomer) as the monomer constituting the polymer. Body unit is better.

Since the (meth)acrylate polymer (A) contains an alkyl (meth)acrylate as a monomer unit constituting the polymer, it can exhibit favorable adhesiveness. The alkyl (meth)acrylate is preferably an alkyl (meth)acrylate having an alkyl group of 1 to 20 carbon atoms. The alkyl group may be linear or branched, and may have a cyclic structure.

Examples of alkyl (meth)acrylates having 1 to 20 carbon atoms in the alkyl group include methyl methacrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and (meth)acrylate. base) n-butyl acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, (meth)acrylic acid n-decyl ester, n-dodecyl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, stearyl (meth)acrylate, etc. Among the above, from the viewpoint of lowering the glass transition temperature (Tg) of the (meth)acrylate polymer (A) and lowering the elasticity of the obtained adhesive, the number of carbon atoms of the alkyl group is 4 to 12. (meth)acrylic acid alkyl esters are preferred, and (meth)acrylic acid alkyl esters with alkyl carbon atoms of 5 to 10 are particularly preferred. Specifically, n-butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate are preferred, and 2-ethylhexyl acrylate is particularly preferred. In addition, the above-mentioned materials may be used alone or in combination of two or more.

In the (meth)acrylate polymer (A), the content of the (meth)acrylate alkyl ester having an alkyl group having 1 to 20 carbon atoms as a monomer unit constituting the polymer is 60% by mass or more More preferably, it is 80 mass % or more, particularly preferably 90 mass % or more, and more preferably 95 mass % or more, and most preferably 98 mass % or more. In this way, suitable adhesiveness can be imparted to the (meth)acrylate polymer (A), and at the same time, it becomes easy to reduce the elastic modulus of the obtained adhesive. Furthermore, the content of the alkyl (meth)acrylate having 1 to 20 carbon atoms in the alkyl group is preferably 99.9 mass % or less, particularly preferably 99.5 mass % or less, and more preferably 99.0 mass % or less . In this way, other monomer components can be introduced into the (meth)acrylate polymer (A) in a desired amount.

Since the (meth)acrylate polymer (A) includes a reactive functional group-containing monomer as a monomer unit constituting the polymer, the reactive functional group derived from the reactive functional group-containing monomer is the same as that described later. The crosslinking agent (C) or the crosslinking agent (C) and the low molecular weight component (B) react to form a crosslinked structure (three-dimensional network structure), thereby obtaining an adhesive having desired cohesion. This adhesive becomes easy to satisfy the aforementioned creep compliance variation value and creep recovery rate.

The (meth)acrylate polymer (A) includes a reactive functional group-containing monomer as a monomer unit constituting the polymer, and preferable reactive functional group-containing monomers include those having a hydroxyl group in the molecule monomers (hydroxyl group-containing monomers), monomers with carboxyl groups in the molecule (carboxyl group-containing monomers), monomers with amine groups in the molecules (amine group-containing monomers), etc. These reactive functional group-containing monomers may be used alone or in combination of two or more.

Among the above reactive functional group-containing monomers, hydroxyl-containing monomers and/or carboxyl group-containing monomers are preferred, and a combination of hydroxyl-containing monomers and carboxyl group-containing monomers is particularly preferred. The hydroxyl-containing monomer is easy to adjust the crosslinking density, and it is easy to satisfy the aforementioned creep compliance value and creep recovery rate. Furthermore, the carboxyl group-containing monomer can improve the adhesive force of the obtained adhesive and improve the adhesion with the adherend.

Examples of hydroxyl-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate. -Hydroxyalkyl (meth)acrylate such as hydroxybutyl, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and the like. Among the above, the hydroxyalkyl (meth)acrylate having a hydroxyalkyl group having 1 to 4 carbon atoms is preferable from the viewpoint of easily satisfying the aforementioned physical properties. Specifically, for example, 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, etc. are preferably used, and 2-hydroxyethyl acrylate or 4-hydroxyethyl acrylate Hydroxybutyl ester is particularly preferred. The above-mentioned materials 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 from the viewpoint of the adhesive force of the (meth)acrylate polymer (A) obtained. The above-mentioned materials may be used alone or in combination of two or more.

In the (meth)acrylate polymer (A), as a monomer unit constituting the polymer, the total content of the reactive functional group-containing monomer is preferably 0.1% by mass or more, particularly preferably 0.5% by mass or more , and more preferably 1.0% by mass or more. In addition, in the (meth)acrylate polymer (A), as a monomer unit constituting the polymer, the content of the reactive functional group-containing monomer is preferably 10% by mass or less, and is preferably 7% by mass or less. Preferably, 5 mass % or less is particularly preferable, and 2 mass % or less is more preferable. The component derived from the reactive functional group-containing monomer tends to coagulate water easily at low temperature and the elastic modulus increases, however, when the upper limit of the content of the reactive functional group-containing monomer is as described above, this can be suppressed. There is a tendency to lower the storage elastic modulus G' at low temperatures. In addition, when the (meth)acrylate polymer (A) contains the reactive functional group-containing monomer as a monomer unit in the above-mentioned content, the storage elastic modulus G' can be set within a suitable range. In addition, when the (meth)acrylate polymer (A) contains the reactive functional group-containing monomer as a monomer unit in the above-mentioned content, it can have a relatively strong degree of crosslinking, which can reduce the creep compliance value. It can also improve the creep recovery rate.

In the (meth)acrylate polymer (A), as a monomer unit constituting the polymer, the lower limit of the content of the hydroxyl group-containing monomer is preferably 0.01% by mass or more, more preferably 0.1% by mass or more , 0.4 mass % or more is particularly preferred, and 0.8 mass % or more is more preferred. In addition, in the (meth)acrylate polymer (A), as a monomer unit constituting the polymer, the upper limit of the content of the hydroxyl group-containing monomer is preferably 10% by mass or less, and preferably 7% by mass or less. More preferably, 4.8 mass % or less is particularly preferable, and 1.8 mass % or less is more preferable. When the (meth)acrylate polymer (A) contains a hydroxyl group-containing monomer as a monomer unit in the above-mentioned content, it becomes easy to satisfy the aforementioned storage elastic modulus G′, creep compliance value, and creep recovery Rate.

The (meth)acrylate polymer (A) may not contain a carboxyl group-containing monomer as a monomer unit constituting the polymer, but when a carboxyl group-containing monomer is contained, its content is 0.005% by mass or more More preferably, it is 0.01 mass % or more, particularly preferably 0.1 mass % or more, and more preferably 0.2 mass % or more. Furthermore, when the (meth)acrylate polymer (A) contains a carboxyl group-containing monomer as a monomer unit constituting the polymer, the upper limit of the content is preferably 7 mass % or less, and 4 mass % or less. % or less is preferable, 1.5 mass % or less is particularly preferable, and 0.8 mass % or less is more preferable. When the (meth)acrylate polymer (A) contains a carboxyl group-containing monomer as a monomer unit in the above-mentioned content, when the obtained adhesive is applied to a repetitive bending device, the bending resistance becomes more excellent .

The (meth)acrylate polymer (A) may contain other monomers as monomeric units constituting the polymer as required. As another monomer, in order not to inhibit the aforementioned effect of the reactive functional group-containing monomer, a monomer that does not contain a reactive functional group is preferable. Examples of such monomers include non-reactive nitrogen atom-containing monomers such as N-acrylomorpholine and N-vinyl-2-pyrrolidone, methoxyethyl (meth)acrylate, (methyl) (meth)alkoxyalkyl acrylate, vinyl acetate, styrene, etc., such as ethoxyethyl acrylate. The above-mentioned materials may be used alone or in combination of two or more.

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

The weight average molecular weight of the (meth)acrylate polymer (A) is preferably at least 400,000, more preferably at least 700,000, particularly preferably at least 900,000, and more preferably at least 1.1 million. In this way, the reduction of the storage elastic modulus G' at a high temperature can be avoided, and at the same time, the creep compliance variation value can also be reduced. On the other hand, the weight average molecular weight of the (meth)acrylate polymer (A) is preferably 3 million or less, more preferably 2 million or less, particularly preferably 1.7 million or less, and more preferably 1.4 million or less . In this way, the storage elastic modulus G' at low temperature can be prevented from becoming too high. In addition, the weight average molecular weight in this specification is a value in terms of standard polystyrene measured by gel permeation chromatography (GPC).

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

(1-2) Low molecular weight component (B) As the low molecular weight component (B), any material having the weight average molecular weight and glass transition temperature (Tg) described above may be used, and for example, acrylic oligomers, polysiloxane oligomers, and olefin oligomers may be used. It is better to wait. The adhesive according to the present embodiment is an acrylic adhesive, and when a (meth)acrylate polymer (A) is used as the main adhesive agent, it is From the viewpoint of mutual solubility, it is preferable to use an acrylic oligomer. By using an acrylic oligomer, it becomes easier to satisfy the aforementioned physical properties.

Furthermore, the low molecular weight component (B) preferably has a reactive functional group. The low molecular weight component (B) has a reactive functional group, so it reacts with the functional group of the (meth)acrylate polymer (A) and the crosslinking agent (C) described later to form a part of the crosslinked structure. part, and then obtain the predetermined cohesion. As a result, it becomes easy to satisfy the aforementioned creep compliance variation value and creep recovery rate. In addition, the low molecular weight component (B) forms a part of the cross-linked structure and is incorporated into the adhesive, so that exudation from the adhesive can be avoided, and reduction of the adhesive force can be prevented.

As a kind of the reactive functional group which a low molecular weight component (B) has, a hydroxyl group, a carboxyl group, an epoxy group, a thiol group, etc. are mentioned, for example. Among the above, the reactivity with the crosslinking agent (C) described later, particularly the isocyanate-based crosslinking agent, is excellent in the reactivity with the hydroxyl group and the reactivity with the carboxyl group in the (meth)acrylate polymer (A). Excellent epoxy groups are preferred.

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

The acrylic oligomer is a polymer obtained by polymerizing one or two or more of acrylic monomers and other monomers added as required. 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% by mass or more, more preferably 1% by mass or more, relative to 100 parts by mass of the (meth)acrylate polymer (A). 5 mass % or more is especially preferable, and 10 mass % or more is more preferable. In this way, it is possible to help reduce the storage elastic modulus G' of the obtained adhesive, especially the storage elastic modulus G' (-30) at -30°C. Furthermore, 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 more preferably 20 parts by mass or less. In this way, it is possible to avoid an increase in the creep compliance variation value, a decrease in the adhesive force due to bleeding, and the like.

(1-3) Cross-linking agent (C) The cross-linking agent (C) triggers (trigger) the (meth)acrylate polymer (A) or the (meth)acrylate polymer by heating or the like of the adhesive composition P containing the cross-linking agent (C) (A) and the low molecular weight component (B) are cross-linked to form a three-dimensional mesh structure. In this way, the cohesive force of the obtained adhesive can be improved, and it becomes easy to satisfy the above-mentioned creep compliance variation value and creep recovery rate.

The crosslinking agent (C) may be any reactive function capable of having the (meth)acrylate polymer (A), the (meth)acrylate polymer (A), and the low molecular weight component (B) as the above-mentioned crosslinking agent (C). group generation reaction, for example, isocyanate-based cross-linking agents, epoxy-based cross-linking agents, amine-based cross-linking agents, melamine-based cross-linking agents, aziridine-based cross-linking agents, hydrazine-based cross-linking agents, Aldehyde crosslinking agent, oxazoline type crosslinking agent, metal alkoxide type crosslinking agent, metal chelate type crosslinking agent, metal salt type crosslinking agent, ammonium salt type crosslinking agent, etc. Moreover, a crosslinking agent (C) may be used individually by 1 type, and may be used in combination of 2 or more types.

Among the above, the reactivity of the isocyanate-based crosslinking agent with a hydroxyl group is particularly excellent, and the reactivity of the epoxy-based crosslinking agent with a carboxyl group is particularly excellent. Therefore, when the reactive group possessed by the (meth)acrylate polymer (A) and/or the low molecular weight component (B) is a hydroxyl group, it is preferable to use an isocyanate-based crosslinking agent. When the reactive group which the acrylate polymer (A) and/or the low molecular weight component (B) has is a carboxyl group, it is preferable to use an epoxy-based crosslinking agent. Furthermore, 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 in combination.

The isocyanate-based crosslinking agent contains at least a polyisocyanate compound. Examples of the polyisocyanate compound include aromatic polyisocyanates such as toluene diisocyanate, diphenylmethane diisocyanate, and xylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, and isophorone diisocyanate. Isocyanates, alicyclic polyisocyanates such as hydrogenated diphenylmethane diisocyanate, etc., their biuret bodies, isocyanurate bodies, and the above-mentioned compounds with ethylene glycol, propylene glycol, neopentyl glycol, trimethylol Adducts and the like of reaction products of low molecular weight active hydrogen-containing compounds such as propane and castor oil. Among them, from the viewpoint of reactivity with hydroxyl groups, aromatic polyisocyanates modified with trimethylolpropane are preferred, and toluene diisocyanate modified with trimethylolpropane or trimethylolpropane modified High quality xylene diisocyanate is particularly preferred.

Examples of epoxy-based crosslinking agents include 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl - m-xylene diamine, ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidyl aniline, diglycidyl amine, and the like. Among them, N,N,N',N'-tetraglycidyl-m-xylenediamine is preferable from the viewpoint of reactivity with a carboxyl group.

With respect to 100 parts by mass of the (meth)acrylate polymer (A), the content of the crosslinking agent (C) in the adhesive composition P is preferably 0.001 part by mass or more, preferably 0.01 part by mass or more, 0.05 mass part or more is especially preferable, and 0.1 mass part or more is more preferable. Furthermore, 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 more preferably 1 part by mass or less. When the content of the crosslinking agent (C) is within the above-mentioned range, it becomes easy to satisfy the above-mentioned creep compliance value and creep recovery rate.

The content of the isocyanate-based crosslinking agent in the adhesive composition P when the isocyanate-based crosslinking agent and the epoxy-based crosslinking agent are used in combination with respect to 100 parts by mass of the (meth)acrylate polymer (A) It is preferably 0.0009 part by mass or more, more preferably 0.009 part by mass or more, particularly preferably 0.09 part by mass or more, and more preferably 0.1 part by mass or more. Furthermore, 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 more preferably 0.8 parts by mass or less.

When the isocyanate-based crosslinking agent and the epoxy-based crosslinking agent are used in combination with respect to 100 parts by mass of the (meth)acrylate polymer (A), the amount of the epoxy-based crosslinking agent in the adhesive composition P is The content is preferably 0.0001 part by mass or more, more preferably 0.001 part by mass or more, particularly preferably 0.01 part by mass or more, and more preferably 0.1 part by mass or more. In addition, the content is preferably 10 parts by mass or less, more preferably 1 part by mass or less, particularly preferably 0.8 parts by mass or less, and more preferably 0.4 parts by mass or less.

(1-4) Various additives In the adhesive composition P, various additives commonly used in acrylic adhesives, such as silane coupling agents, ultraviolet absorbers, antistatic agents, tackifiers, antioxidants, light stabilizers, softeners, can be added as required. , fillers, refractive index modifiers, etc. In addition, the additives constituting the adhesive composition P do not contain the polymerization solvent and diluting solvent described later.

The adhesive composition P preferably contains the above-mentioned silane coupling agent. In this way, in the obtained adhesive, the adhesiveness with the flexible member which is the to-be-adhered body improves, and the adhesive force becomes better.

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

Examples of such silane coupling agents include polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloyloxypropyltrimethoxysilane. , 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane Silicon compounds with epoxy structures such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyldimethoxymethylsilane and other mercapto-containing silicon compounds , 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyl Amine group-containing silicon compounds such as methyldimethoxysilane, 3-chloropropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, or at least one of the above and methyltriethoxysilane Condensates of alkyl-containing silicon compounds such as ethyl silane, ethyl triethoxy silane, methyl trimethoxy silane, ethyl trimethoxy silane, etc. The above-mentioned materials may be used alone or in combination of two or more.

With respect to 100 parts by mass of the (meth)acrylate polymer (A), 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 0.1 part by mass or more The mass part or more is more preferable. Furthermore, the content is preferably 1 part by mass or less, particularly preferably 0.5 part by mass or less, and more preferably 0.3 part by mass or less. Since the content of the silane coupling agent is within the above-mentioned range, the adhesiveness between the obtained adhesive layer and the flexible member serving as the adherend is improved, and the adhesive force becomes larger.

(2) Production of Adhesive Composition P The (meth)acrylate polymer (A) can be produced by combining the obtained (meth)acrylate polymer (A), the low molecular weight component (B), and the crosslinking agent ( C) While mixing, further add additives as required to prepare the adhesive composition P.

The (meth)acrylate polymer (A) can be produced by polymerizing a mixture of monomers constituting the polymer by a general radical polymerization method. The polymerization of the (meth)acrylate polymer (A) can be carried out using a polymerization initiator as required, and is preferably carried out by a solution polymerization method. By polymerizing the (meth)acrylate polymer (A) by the solution polymerization method, the obtained polymer becomes easy to have a high molecular weight, and it becomes easy to adjust the molecular weight distribution. Therefore, the adhesive is less likely to vary with bending over a long period of time, and the recovery from the bending state becomes more excellent.

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

As a polymerization initiator, an azo compound, an organic peroxide, etc. are mentioned, You may use it in combination of 2 or more types. As the azo compound, for example, 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclo Hexane 1-carbonitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxy valeronitrile), dimethyl 2,2'-azobis(2-methylpropionate), 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis (2-hydroxymethylpropionitrile), 2,2'-azobis[2-(2-imidazolin-2-yl)propane], etc.

Examples of organic peroxides include benzyl peroxide, tertiary butyl peroxybenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, and di-n-propyl peroxydicarbonate. , bis(2-ethoxyethyl) peroxydicarbonate, tertiary butyl peroxyneodecanoate, tertiary butyl peroxypivalate, (3,5,5-trimethylhexyl) ) peroxide, dipropylene peroxide, diacetyl peroxide, etc.

In addition, in the above-mentioned polymerization process, the weight average molecular weight of the obtained polymer can be adjusted by blending a chain transfer agent such as 2-mercaptoethanol.

After the (meth)acrylate polymer (A) is obtained, the low molecular weight component (B), as well as the crosslinking agent (C) added as required, are added to the solution of the (meth)acrylate polymer (A). The additive and the dilution solvent are thoroughly mixed to obtain the adhesive composition P (coating solution) diluted with the solvent.

In addition, when any one of the above-mentioned components is used in a solid form, or when precipitation occurs after mixing with other components in an undiluted state, the component may be dissolved or diluted first. It is mixed with other ingredients only after it is in the dilution solvent.

As the diluting solvent, for example, aliphatic hydrocarbons such as hexane, heptane, and cyclohexane, aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as methylene chloride and ethyl chloride, methanol, ethanol, and propylene can be used. Alcohols, butanols, alcohols such as 1-methoxy-2-propanol, acetone, methyl ethyl ketone, 2-pentanone, isophorone (Isophorone), ketones such as cyclohexanone, ethyl acetate, butyl acetate Ester, ethyl cellosolve (cellosolve) and other cellolytic solvents.

The concentration/viscosity of the coating solution prepared as described above is not particularly limited as long as it is within a range that can be coated, and can be appropriately selected depending on the situation. For example, the concentration of the adhesive composition P can be diluted to 10 to 60% by mass. In addition, when obtaining a coating solution, addition of a dilution solvent etc. is not an essential condition, as long as the adhesive composition P has a viscosity etc. which can be applied, it is not necessary to add a dilution solvent. In this case, the adhesive composition P is a coating solution obtained by directly using the polymerization solvent of the (meth)acrylate polymer (A) as a diluting solvent.

(3) Manufacture of adhesives The adhesive constituting the present embodiment is preferably an adhesive obtained from the adhesive composition P, and is preferably an adhesive obtained by crosslinking the adhesive composition P. The crosslinking of the adhesive composition P is preferably carried out by heat treatment. In addition, this heat treatment can also be used as a drying treatment when volatilizing a dilution solvent or the like from the coating film of the adhesive composition P applied to a desired object.

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

In addition, after the heat treatment, an aging period of about 1 to 2 weeks at normal temperature (for example, 23° C., 50% RH) may be set as required. In the case where this aging period is required, the adhesive is formed after the aging period has elapsed, and in the case where the aging period is not required, the adhesive is formed after the end of the heat treatment.

By the above-mentioned heat treatment (and aging), the (meth)acrylate polymer (A), or the (meth)acrylate polymer (A) and the low molecular weight component (B) pass through the crosslinking agent (C) sufficiently It is cross-linked to form a cross-linked structure, and then an adhesive can be obtained.

In addition, in the adhesive according to the present embodiment, the storage elastic mode is lowered by adding the low molecular weight component (B) while lowering the glass transition temperature (Tg) of the (meth)acrylate polymer (A). The amount G' (in particular the storage modulus of elasticity G' at low temperature) and on the other hand the reduction of the creep compliance variation by well-performing crosslinking is particularly good. In this way, it becomes easy to balance the two physical property values of the storage elastic modulus G' (-30) at -30°C and the creep compliance value.

[adhesive sheet] The adhesive sheet according to the present embodiment has an adhesive layer for bonding one flexible member and another flexible member constituting the repeated bending device, and the adhesive layer is composed of the aforementioned adhesive.

FIG. 1 shows a specific structure as an example of the adhesive sheet according to the present embodiment. As shown in FIG. 1, the pressure-sensitive adhesive sheet 1 according to one embodiment is composed of two release sheets 12a, 12b, and a release surface sandwiched between the two release sheets 12a, 12b and in contact with the two release sheets 12a, 12b The adhesive layer 11 is formed. In addition, in this specification, the peeling surface of the peeling sheet means the surface having peelability in the peeling sheet, and also includes any of the surface to which the peeling treatment is applied and the surface that can express the peelability without the peeling treatment. By.

(1) Components (1-1) Adhesive layer The adhesive layer 11 is composed of the adhesive according to the aforementioned embodiment, preferably an adhesive obtained by crosslinking the adhesive composition P.

The lower limit of the thickness of the adhesive layer 11 in the adhesive sheet 1 according to the present embodiment (value measured in accordance with JIS K7130) is preferably 1 μm or more, more preferably 5 μm or more, particularly preferably 10 μm or more, And it is more preferably 15 μm or more. When the lower limit of the thickness of the adhesive layer 11 is as described above, the desired adhesive force is likely to be exhibited, and it becomes less likely that floating and peeling occur at the interface between the adhesive layer and the adherend. Furthermore, the upper limit of the thickness of the adhesive layer 11 is preferably 300 μm or less, more preferably 150 μm or less, particularly preferably 90 μm or less, and from the viewpoint of obtaining a thinner repeated bending device, 40 μm is preferred. The following is better. When the upper limit value of the thickness of the adhesive layer 11 is as described above, since it becomes easy to maintain the adhesiveness between the adhesive layer and the adherend, the bending resistance becomes more excellent, and it is applied to the adhesive The stress of the layer becomes relatively small, and it becomes easy to recover from the bent state. In addition, the adhesive layer 11 may be formed as a single layer, or may be formed by laminating a plurality of layers.

(1-2) Peel sheet The release sheets 12a and 12b protect the adhesive layer 11 before using the adhesive sheet 1, and are peeled off when the adhesive sheet 1 (the adhesive layer 11) is used. In the adhesive sheet 1 according to the present embodiment, one or both of the release sheets 12a and 12b are not absolutely necessary.

As the release sheets 12a and 12b, for example, a polyethylene film, a polypropylene film, a polybutene film, a polybutadiene film, a polymethylpentene film, a polyvinyl chloride film, a vinyl chloride copolymer film, a polybutylene film can be used Ethylene phthalate film, polyethylene naphthalate film, polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene (meth)acrylic acid Copolymer film, ethylene/(meth)acrylate copolymer film, polystyrene film, polycarbonate film, polyimide film, fluororesin film, etc. Furthermore, a cross-linked film of the above-mentioned materials can also be used. In addition, a laminated film of the above-mentioned materials can also be used.

It is preferable that a peeling treatment is applied to the peeling surfaces (particularly, the surfaces in contact with the adhesive layer 11 ) of the peeling sheets 12 a and 12 b. As a release agent used for a peeling process, the release agent of an alkyd type, a polysiloxane type, a fluorine type, an unsaturated polyester type, a polyolefin type, and a wax type is mentioned, for example. In addition, among the release sheets 12a and 12b, one of the release sheets is preferably a heavy release type release sheet with a large release force and the other release sheet is a light release type release sheet with 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 in the adhesive sheet 1 according to the present embodiment is preferably 30% or less, more preferably 10% or less, particularly preferably 1% or less, and more preferably 0.8% or less. In this way, the appearance change of the adhesive layer 11 due to bending can be suppressed. In addition, the lower limit value of the said haze value is not specifically limited, Preferably it is 0% or more, More preferably, it is 0.01% or more, More preferably, it is 0.03% or more. In addition, the haze value in this specification is the value measured based on JISK7136:2000.

(2-2) Adhesion The lower limit of the adhesive force of the adhesive sheet 1 according to the present embodiment to soda lime glass is preferably 0.1N/25mm or more, more preferably 1.0N/25mm or more, particularly preferably 1.3N/25mm or more, and 1.4N/25mm or more is better. When the lower limit value of the adhesive force of the adhesive sheet 1 is as described above, it becomes less likely that the interface between the adhesive layer and the adherend will be lifted and peeled due to bending. On the other hand, the upper limit of the above-mentioned adhesive force is not particularly limited. Usually, it is preferably 60N/25mm or less, and preferably 40N/25mm or less, and the adhesive sheet can be re-applied when there is an error in the bonding of the adhesive sheet. From the viewpoint of the heavy duty, it is particularly preferable to be 20N/25mm or less, and more preferably 10N/25mm or less. In addition, the adhesive force in this specification basically means the adhesive force measured by the 180-degree peeling method regulated by JIS Z0237:2009, and a specific test method is described in the test example described later.

(3) Manufacture of adhesive sheet As an example of manufacture of the adhesive sheet 1, the case where the above-mentioned adhesive composition P is used is demonstrated. The coating liquid of the adhesive composition P is coated on the peeling surface of one peeling sheet 12a (or 12b), and heat treatment is performed to make the adhesive composition P thermally cross-linked to form a coating layer, and then the other sheet is peeled off. The release side of sheet 12b (or 12a) is superimposed on this coating layer. In the case where the curing period is required, the adhesive layer 11 is formed by placing the coating layer for a curing period, and in the case where the curing period is not required, the coating layer is directly used as the adhesive layer 11 . Thereby, the said adhesive sheet 1 can be obtained. Conditions for the heat treatment and aging are as described above.

As another production example of the adhesive sheet 1, the coating liquid of the adhesive composition P was applied to the release surface of the release sheet 12a on one side, and heat treatment was performed to thermally crosslink the adhesive composition P to form a coating layer to obtain a release sheet 12a with a coating layer. Furthermore, the coating liquid of the above-mentioned adhesive composition P is applied on the peeling surface of the other side of the peeling sheet 12b, and heat treatment is performed so that the adhesive composition P is thermally cross-linked to form a coating layer, and then a coating layer is obtained. The release sheet 12b with the coating layer is attached. Then, the coating layer-attached release sheet 12a and the coating layer-attached release sheet 12b are attached so that the two coating layers are in contact with each other. When a curing period is required, the adhesive layer 11 is formed by placing the coating layer for a curing period, and when the curing period is not required, the laminated coating layer is directly used as the adhesive layer 11 . Thereby, the said adhesive sheet 1 can be obtained. According to this production example, stable production is possible even when the adhesive layer 11 is thick.

As a coating method of the coating liquid of the above-mentioned adhesive composition P, for example, a bar coating method, a knife coating method, a roll coating method, or a blade coating method can be used. Coating method, die coating method, gravure coating method, etc.

[Repetitive bending of laminated parts] As shown in FIG. 2 , the repeatedly bent laminated member 2 according to the present embodiment includes a first flexible member 21 (a flexible member), a second flexible member 22 (another flexible member), and a flexible member located therebetween. The adhesive layer 11 for attaching the first flexible member 21 and the second flexible member 22 to each other.

The adhesive layer 11 in the above-mentioned repeatedly bending laminated member 2 is composed of the above-mentioned adhesive, or is the adhesive layer 11 of the above-mentioned adhesive sheet 1 .

The repeated bending laminated member 2 is the repeated bending apparatus itself or a member constituting a part of the repeated bending apparatus. The repeatedly bending device is preferably a display that can be repeatedly bent (including bending), but is not limited to this. Examples of the above-mentioned repetitive bending device include organic electroluminescence (organic EL) displays, electrophoretic displays (electronic paper), liquid crystal displays using plastic substrates (films) as substrates, foldable displays, and the like. control panel.

The first flexible member 21 and the second flexible member 22 are members that can be repeatedly bent (including bending), for example, cover films, gas barrier films, hard coat films, polarizing films (polarizing plates), polarizers, Phase difference film (retardation plate), viewing angle compensation film, brightness enhancement film, contrast enhancement film, diffusion film, transflective film, electrode film, transparent conductive film, metal mesh film, thin film sensor (touch sensing film), liquid crystal polymer film, light emitting polymer film, thin film liquid crystal module, organic EL module (organic EL film, organic EL element), electronic paper module (film electronic paper), TFT (thin film transistor) substrate, etc.

The Young's modulus of the first flexible member 21 and the second flexible member 22 is preferably 0.1 to 10 GPa, particularly preferably 0.5 to 7 GPa, and more preferably 1 to 5 GPa. Since the Young's moduli of the first flexible member 21 and the second flexible member 22 are within the above-mentioned range, it becomes easy to repeatedly bend the respective flexible members.

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. Since the thicknesses of the first flexible member 21 and the second flexible member 22 are within the above-mentioned range, it becomes easy to repeatedly bend the respective flexible members.

As an example of manufacturing the above-mentioned repeatedly bending laminated member 2, for example, peeling off the release sheet 12a on one side of the adhesive sheet 1, and attaching the adhesive layer 11 exposed in the adhesive sheet 1 to the first flexible member 21 side on the surface.

After that, the peeling sheet 12b on the other side is peeled off from the adhesive layer 11 of the adhesive sheet 1, and the adhesive layer 11 exposed in the adhesive sheet 1 is attached to the second flexible member 22 to obtain the repeatedly bent laminated member 2 . Furthermore, as another example, the bonding order of the first flexible member 21 and the second flexible member 22 may be exchanged, for example.

[repetitive bending device] The repeatedly bending device according to the present embodiment includes the above-described repeatedly bending laminated member 2, which may be constituted by only the repeatedly bending laminated member 2, or may be constituted by a plurality of repeatedly bending laminated members 2 and other flexible members. When laminating one repeatedly bending laminated member 2 and another repeatedly bending laminated member 2, or when laminating the repeatedly bending laminated member 2 and other flexible members, it is preferable to laminate the above-mentioned adhesive layer 11 of the pressure-sensitive adhesive sheet 1. .

In the repeated bending apparatus according to the present embodiment, since the adhesive layer is composed of the aforementioned adhesive, even when it is repeatedly bent or in a bent state for a long time, the adhesive layer 11 and the The interface between the adherends (the first flexible member 21 and the second flexible member 22 ) is also less likely to float and fall off. Furthermore, even when the adhesive constituting the adhesive layer 11 satisfies the aforementioned creep recovery rate, it has excellent recovery properties even when returning from a bent state.

FIG. 3 illustrates an iterative bending device as an example in this embodiment. In addition, the iterative bending device according to the present invention is not limited to this iterative bending device.

As shown in FIG. 3 , according to the repeated bending device 3 of the present embodiment, the cover film 31 , the first adhesive layer 32 , the polarizing film 33 , the second adhesive layer 34 , and the touch sensitive film are laminated in order from top to bottom. 35. The third adhesive layer 36, the organic EL element 37, the fourth adhesive layer 38, and the TFT substrate 39. The above-mentioned cover film 31 , polarizing film 33 , touch sensitive film 35 , organic EL element 37 and TFT substrate 39 correspond to flexible members.

At least any 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 above-mentioned adhesive sheet 1 . Preferably, 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 the adhesive layers 11 of the aforementioned adhesive sheet 1, and all The adhesive layers 32 , 34 , 36 , and 38 are preferably the adhesive layers 11 of the aforementioned adhesive sheet 1 .

The embodiments described above are described in order to facilitate understanding of the present invention, and are not described to limit the present invention. Therefore, it is meant that each of the requirements disclosed in the above-described embodiments also includes all design changes and equivalents 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, and a desired flexible member may be laminated instead of the release sheets 12a and/or 12b. [Example]

Hereinafter, the present invention will be described more specifically through Examples and the like, but the scope of the present invention is not limited to these Examples and the like.

[Example 1] 1. Preparation of (Meth)acrylate Polymer (A) 98.5 parts by mass of 2-ethylhexyl acrylate, 1.0 parts by mass of 4-hydroxybutyl acrylate, and 0.5 parts by mass of acrylic acid were copolymerized by a solution polymerization method to prepare a (meth)acrylate polymer (A ). The molecular weight of this (meth)acrylate polymer (A) was measured by the method described later to give a weight average molecular weight (Mw) of 1.2 million.

2. Preparation of the adhesive composition 100 parts by mass of the (meth)acrylate polymer (A) (in terms of solid content, the same applies hereinafter) obtained in the above step 1, and 15 parts by mass of the hydroxyl-containing acrylic acid as the low molecular weight component (B) Oligomer (B1; manufactured by Toagosei Corporation, product name "ARUFON (registered trademark) UH-2000", hydroxyl content: 20 mgKOH/g, Mw: 11000, Tg: -55°C), 0.3 parts by mass as Isocyanate-based crosslinking agent (C1) trimethylolpropane-modified xylene diisocyanate (XDI; manufactured by Soken Chemical Co., Ltd., product name "TD-75"), 0.2 parts by mass as epoxy-based crosslinking agent N,N,N',N'-tetraglycidyl-m-xylenediamine of the linking agent (C2), and 0.2 parts by mass of 3-glycidoxypropyltrimethoxysilane as a silane coupling agent (SC1) Mix, stir well, and dilute with methyl ethyl ketone to obtain a coating solution of the adhesive composition.

3. Manufacture of adhesive sheet The obtained coating solution of the adhesive composition was coated with a knife coater on a weight obtained by peeling off one side of a polyethylene terephthalate film using a polysiloxane-based release agent. The peel-off surface of the peel-off peeling sheet (manufactured by Lintec, product name "SP-PET752150"). Next, the coating layer was heat-treated at 90° C. for 1 minute to form a coating layer.

Then, the coating layer on the heavy release type release sheet obtained above and the light release type release sheet obtained by subjecting the single side of the polyethylene terephthalate film to a release treatment using a polysiloxane-based release agent Sheets (manufactured by Lintec Co., Ltd., product name "SP-PET381130"), are attached to each other in such a way that the peeled surface of this light peeling type release sheet is in contact with the coating layer, and is heated at 23°C, 50% RH Aged for 7 days under the same conditions, and then an adhesive sheet with an adhesive layer with a thickness of 25 μm was formed, that is, a structure consisting of a heavy release type release sheet/adhesive layer (thickness: 25 μm)/light release type release sheet was produced. composed of adhesive sheets. In addition, the thickness of the adhesive layer is a value measured using a constant pressure thickness measuring device (manufactured by TECLOCK, product name "PG-02") in accordance with JIS K7130.

Here, each formulation (value in terms of solid content) of the adhesive composition when the (meth)acrylate polymer (A) is set at 100 parts by mass (value in terms of solid content) is as shown in the table 1 shown. In addition, the details of the abbreviations etc. described in Table 1 are as follows. [(Meth)acrylate polymer (A)] 2EHA: 2-ethylhexyl acrylate 4HBA: 4-hydroxybutyl acrylate AAc: Acrylic [Low molecular weight component (B)] B1: Hydroxyl-containing acrylic oligomer (manufactured by Toagosei Corporation, product name "ARUFON (registered trademark) UH-2000", hydroxyl content: 20 mgKOH/g, Mw: 11000, Tg: -55°C) B2: Epoxy group-containing acrylic oligomer (manufactured by Toagosei Corporation, product name "ARUFON UG-4010", epoxy group content: 1.4meq/g, Mw: 2900, Tg: -57°C) B3: Non-functional acrylic oligomer (manufactured by Toagosei Corporation, product name "ARUFON UP-1000", Mw: 3000, Tg: -77°C) [Isocyanate Crosslinking Agent (C1)] XDI: Trimethylolpropane-modified xylylene diisocyanate (manufactured by Soken Chemical Co., Ltd., product name "TD-75") TDI: Trimethylolpropane-modified toluene diisocyanate (manufactured by Toyo Chemical Co., Ltd., product name "BHS8515") [Epoxy Crosslinking Agent (C2)] N,N,N',N'-Tetraglycidyl-m-xylenediamine [Silane coupling agent] SC1: 3-glycidoxypropyltrimethoxysilane SC2: 1,6-bis(trimethoxysilyl)hexane

[Examples 2 to 4, Comparative Examples 1 to 4] In addition to the types and ratios of the monomers constituting the (meth)acrylate polymer (A), the weight average molecular weight (Mw) of the (meth)acrylate polymer (A), and the type of the low molecular weight component (B) The same as in Example 1, except that the compounding amount, the type of isocyanate-based crosslinking agent (C1), the compounding amount of epoxy-based crosslinking agent (C2), and the type of silane coupling agent were changed as shown in Table 1. way to make the adhesive sheet.

The aforementioned weight average molecular weight (Mw) is a polystyrene-equivalent weight average molecular weight measured (GPC measurement) using gel permeation chromatography (GPC) under the following conditions. <Measurement conditions> ・GPC measuring device: HLC-8020 manufactured by Tosoh Corporation ・GPC string (passed in the following order): manufactured by Tosoh Corporation TSK guard column HXL-H TSK gel GMHXL (x2) TSK gel G2000HXL ・Measurement solvent: tetrahydrofuran (tetrahydrofuran) ・Measurement temperature: 40℃

[Test Example 1] (Measurement of Gel Fraction) The adhesive sheets produced in the examples and comparative examples were cut into a size of 80mm×80mm, and the adhesive layer was wrapped in a polyester mesh (product name: Tetron mesh #200), using a precision balance Measure its mass, and calculate the mass of only the adhesive by deducting the mass of the polyester mesh itself. The mass at this time is set to M1.

Next, the adhesive coated in the polyester mesh was immersed in ethyl acetate at room temperature (23° C.) for 24 hours. After that, the adhesive was taken out, air-dried in an environment with a temperature of 23° C. and a relative humidity of 50% for 24 hours, and further dried in an oven at 80° C. for 12 hours. After drying, the mass is measured with a precision balance, and the mass of only the adhesive is calculated by deducting the mass of the polyester mesh itself. The mass at this time is set to M2. The gel fraction (%) is expressed as (M2/M1)×100​​. The results are shown in Table 2.

[Test example 2] (Measurement of storage elastic modulus G') The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheets produced in the Examples and Comparative Examples was laminated as a laminated body having a thickness of 800 μm. A cylinder having a diameter of 8 mm (800 μm in height) was punched out from the obtained laminate of the adhesive layers, and used as a sample.

According to JIS K7244-6, using a viscoelasticity measuring device (manufactured by Anton Paar, product name "MCR302"), using the torsional shear method, the sample was measured at -30 under the following conditions Storage elastic modulus G'(-30) at ℃, storage elastic modulus G'(25) at 25℃, and storage elastic modulus G'(85)(MPa) at 85℃. The results are shown in Table 2. Measurement frequency: 1 Hz Heating rate: 5℃/min Strain: 1% Normal force: 1.0N Measuring temperature: -30°C～140°C

Furthermore, based on the obtained results, the value obtained by dividing the storage elastic modulus G' (-30) by the storage elastic modulus G' (25), that is, the storage elastic modulus change degree (-30/25) was calculated. ), and calculate the value of dividing the storage elastic modulus G' (-30) by the storage elastic modulus G' (85), that is, the storage elastic modulus change degree (-30/85). The results are shown in Table 2.

[Test Example 3] (Measurement of Creep Compliance) The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheets produced in the Examples and Comparative Examples was laminated as a laminated body having a thickness of 800 μm. A cylinder having a diameter of 8 mm (800 μm in height) was punched out from the obtained laminate of the adhesive layers, and used as a sample.

Using a viscoelasticity measuring device (manufactured by Anton Paar, product name "MCR302"), a stress of 4500Pa was continuously applied to the above sample under the following conditions to measure the creep compliance J(t) (MPa ^-1 ) According to the measurement results, the creep compliance value measured when a stress of 4500Pa is applied is defined as the minimum creep compliance J(t) _min (MPa ^-1 ), and the measured minimum creep compliance is derived. Maximum creep compliance J(t)max (MPa ⁻¹ ) measured up to 1200 seconds after J(t) _min . Measuring temperature: 25°C Measuring points: 1000 points (logarithmic graph)

From the obtained minimum creep compliance J(t) _min (MPa ^-1 ) and maximum creep compliance J(t) max (MPa ^-1 ), the creep compliance variation value is calculated based on the following formula (I) ΔlogJ(t). The results are shown in Table 2. ΔlogJ(t)=logJ(t)max-logJ(t) _min ...(I)

Furthermore, using a viscoelasticity measuring device (manufactured by Anton Paar, product name "MCR302"), after continuously applying a stress of 4500Pa to the above-mentioned sample under the following conditions, set the applied stress to 0Pa and keep this state a period of time. During this period, the creep compliance J(t) (MPa ^-1 ) was measured. The creep compliance value measured after 1200 seconds from the start of applying a stress of 4500Pa was defined as creep compliance J(t) (s=1200) (MPa ⁻¹ ), and the applied stress was set to 100 after 0Pa The creep compliance value measured after seconds is defined as the creep compliance J(t) (s=1300) (MPa ⁻¹ ). Measurement temperature: 25°C Measurement points when stress is applied: 1000 points (logarithmic graph) Measurement points when stress is relieved: 1000 points (logarithmic graph)

From the obtained creep compliance J(t) (s=1200) (MPa ^-1 ) and creep compliance J(t) (s=1300) (MPa ^-1 ), it was calculated based on the following formula (II) Creep recovery rate (%). The results are shown in Table 2. Creep recovery rate (%)=(1-J(t)(s=1300)/J(t)(s=1200))x100...(II)

[Test Example 4] (Measurement of Haze Value) The adhesive layer of the adhesive sheet manufactured in the Example and the comparative example was bonded to glass, and it was set as the sample for measurement. After background measurement with glass, the haze value (%) of the sample for measurement was measured using a haze meter (manufactured by Nippon Denshoku Kogyo Co., Ltd., product name "NDH5000") in accordance with JIS K7136:2000. The results are shown in Table 2.

[Test Example 5] (Measurement of Adhesive Force) The light release type release sheet was peeled off from the adhesive sheets obtained in Examples and Comparative Examples, and the exposed adhesive layer was attached to a polyethylene terephthalate (PET) film with an easy-adhesion layer ( An easy-adhesion layer manufactured by Toyobo Co., Ltd., product name "PET A4300", thickness: 100 μm), and a laminate of heavy-peeling release sheet/adhesive layer/PET film was obtained. The obtained laminate was cut into a width of 25 mm and a length of 110 mm.

In an environment of 23°C and 50% RH, the heavy release type release sheet was peeled off from the above-mentioned laminate, and the exposed adhesive layer was attached to a soda lime glass plate (manufactured by Nippon Plate Glass Co., Ltd., product name: "Soda lime glass", thickness: 1.1 mm), using an autoclave manufactured by Kurihara Seisakusho Co., Ltd., and pressurized at 0.5 MPa and 50° C. for 20 minutes. Then, after standing in an environment of 23°C and 50% RH for 24 hours, under the conditions of a peeling speed of 300 mm/min and a peeling angle of 180 degrees, using a tensile tester (TENSILON manufactured by Orientec), the measured Adhesive strength (N/25mm) when the laminate of the PET film and the adhesive layer is peeled off from the adherend. Except for the conditions described here, the measurement was performed according to JIS Z0237:2009. The results are shown in Table 2.

[Test Example 6] (Evaluation of Bending Resistance) In an environment of 23° C. and 50% RH, the light release type release sheet was peeled off from the adhesive sheets produced in Examples and Comparative Examples, and the exposed adhesive layer was attached to polyethylene terephthalate. Diol ester (PET) film (manufactured by Toyobo Co., Ltd., product name "PET50TA063", thickness: 100 μm) on one side surface. Next, the heavy release type release sheet was peeled off, and the exposed adhesive layer was bonded to a polyimide film (thickness: 50 μm). Then, using an autoclave manufactured by Kurihara Seisakusho Co., Ltd., pressurized at 0.5 MPa and 50° C. for 20 minutes, and then left to stand for 24 hours under the conditions of 23° C. and 50% RH. The thus-obtained laminate composed of the PET film/adhesive layer/polyimide film was cut into a width of 50 mm and a length of 200 mm, and used as a sample.

As shown in Fig. 4, both ends of the obtained sample were fixed to a bending tester equipped with a constant temperature and humidity chamber (manufactured by Yuasa System Equipment Co., Ltd., product name "CL09-typeD01-FSC90") two support plates. At this time, it was fixed so that the polyimide film side of the sample was located on the inside of the bend. Then, the sample was bent 200,000 times at a bending diameter (diameter) of 3 mmφ, a stroke of 80 mm, and a bending speed of 60 rpm in each temperature environment of -30°C, 25°C, and 80°C.

After the above-mentioned dynamic bending test was performed, it was visually confirmed whether there was peeling at the interface between the adhesive layer and the adherend in the bent portion of the sample. Then, bending resistance was evaluated based on the following criteria. The results are shown in Table 2. ⊚: No line marks appear in the bent portion. ○: A stitch appears in the bent portion, but the stitch is hardly confirmed when viewed from the front. △: Stitches appear in the bent portion, and the stitches can be confirmed even when viewed from the front. Alternatively, minute air bubbles are generated in the curved portion. ×: A phenomenon in which the bent portion is lifted and peeled off.

[Table 1] (Meth)acrylate polymer (A) Low molecular weight component (B) Isocyanate Crosslinking Agent (C1) Epoxy Crosslinking Agent (C2) Silane coupling agent composition Mw type parts by mass type parts by mass parts by mass type parts by mass Example 1 2EHA/4HBA/AAc =98.5/1.0/0.5 1.2 million B1 15 XDI 0.3 0.2 SC1 0.2 Example 2 B2 15 0.3 0.2 0.2 Example 3 B1 15 TDI 0.3 0.2 0.2 Example 4 B1 15 XDI 0.3 0.2 SC2 0.2 Comparative Example 1 2EHA/4HBA/AAc =98.5/1.0/0.5 1.2 million - - XDI 0.3 0.2 SC1 0.2 Comparative Example 2 B3 15 0.3 0.2 0.2 Comparative Example 3 2EHA/4HBA = 99.0/1.0 1.2 million - - XDI 0.3 - SC1 0.2 Comparative Example 4 600000 - - 0.3 - 0.2

[Table 2] Gel fraction (%) Storage elastic modulus G' (MPa) Variation of storage elastic modulus Creep compliance (variation value) Creep compliance (recovery rate) Haze value (%) Adhesion (N/25mm) Bending resistance G'(-30) G'(25) G'(85) (-30/25) (-30/85) J(t)min (MPa ^-1 ) J(t)max (MPa ^-1 ) ΔlogJ(t) J(t)(s=1200) (MPa ^-1 ) J(t)(s=1300) (MPa ^-1 ) Creep recovery rate (%) -30℃ 25℃ 80℃ Example 1 75 0.104 0.032 0.027 3.25 3.85 18 5156 2.46 5156 139 97.3 <0.5 1.7 ○ ◎ ◎ Example 2 78 0.098 0.029 0.020 3.38 4.90 14 4911 2.53 4911 192 96.1 <0.5 1.2 ○ ◎ 〇 Example 3 72 0.101 0.033 0.024 3.06 4.21 16 5132 2.51 5132 159 96.9 <0.5 1.6 ○ ◎ ◎ Example 4 76 0.099 0.031 0.027 3.19 3.67 18 5120 2.45 5120 154 97.0 <0.5 1.5 ○ ◎ ◎ Comparative Example 1 86 0.141 0.036 0.014 3.92 10.07 18 7489 2.62 7489 764 89.8 <0.5 3.4 △ ◎ 〇 Comparative Example 2 76 0.087 0.025 0.018 3.48 4.83 18 9422 2.71 9422 1084 88.5 <0.5 0.8 × 〇 △ Comparative Example 3 70 0.125 0.028 0.012 4.46 10.42 18 36444 3.30 36444 15634 57.1 <0.5 3.4 △ 〇 △ Comparative Example 4 60 0.121 0.015 0.008 8.07 15.13 18 48378 3.43 48378 18239 62.3 <0.5 6.8 ○ 〇 ×

It can be seen from Table 2 that the adhesive layer of the adhesive sheet of the embodiment is not easy to float at the interface between the adhesive layer and the adherend due to long-time bending under any environment of low temperature, normal temperature and high temperature. Lifting and peeling with excellent flex resistance. [industrial availability]

The present invention is suitable for attaching a flexible member to another flexible member constituting the repeated bending device.

1: adhesive sheet 2: Bend the laminated part repeatedly 3: Repeated bending device 11: Adhesive layer 12a, 12b: release sheet 21: The first flexible part 22: Second flexible part 31: cover film 32: The first adhesive layer 33: polarizing film 34: Second Adhesive Layer 35: Touch sensor film 36: Third Adhesive Layer 37: Organic EL Elements 38: Fourth Adhesive Layer 39: TFT substrate S: test piece P: support plate

1 is a cross-sectional view of an adhesive sheet according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of a repeatedly bent laminated member according to an embodiment of the present invention. 3 is a cross-sectional view of an inverse bending apparatus according to an embodiment of the present invention. FIG. 4 is an explanatory diagram (side view) for explaining a dynamic bending test.

1: adhesive sheet

11: Adhesive layer

12a, 12b: release sheet

Claims (12)

An adhesive for a repetitive bending device, which is an adhesive for a repetitive bending device for attaching a flexible member constituting a repetitive bending device to another flexible member, characterized in that the aforementioned adhesive is at -30° The storage elastic modulus G' (-30) at C is 0.20 MPa or less, and the creep compliance value measured when a stress of 4500 Pa is applied to the aforementioned adhesive is defined as the minimum creep compliance J ( t) _min (MPa ^-1 ), and will continue to apply a stress of 4500Pa until the minimum creep compliance J(t) _min is measured 1200 seconds after the measured maximum creep compliance value during this period Defined as the maximum creep compliance J(t) _max (MPa ^-1 ), the creep compliance variation value ΔlogJ(t) calculated from the following formula (I) is 2.60 or less: ΔlogJ(t)=logJ(t ) _max -logJ(t) _min ...(I). The adhesive for repeated bending devices according to claim 1, wherein the creep compliance value measured after a stress of 4500Pa is continuously applied to the aforementioned adhesive for 1200 seconds is defined as creep compliance J(t) (s= 1200) (MPa ^-1 ), and the creep compliance value measured after 100 seconds after the subsequent stress applied to the aforementioned adhesive is set to 0Pa is defined as the creep compliance J(t) (s=1300) ( MPa ^-1 ), the creep recovery rate calculated according to the following formula (II) is 90% or more: Creep recovery rate (%)=(1-J(t)(s=1300)/J(t)( s=1200)) x100...(II). The adhesive for repeated bending devices according to claim 1, wherein the storage elastic modulus G'(85) at 85°C is 0.005 MPa or more. The adhesive for repeated bending devices according to claim 1, wherein the storage elastic modulus change degree (-30/25) is the storage elastic modulus G' (-30) at -30°C divided by the storage elastic modulus G' (-30) at 25 The value obtained by the storage elastic modulus G′(25) in °C is 5.0 or less. The adhesive for repeated bending devices as claimed in claim 1, wherein the storage elastic modulus change degree (-30/85) is the storage elastic modulus G' (-30) at -30°C divided by the storage elastic modulus G' (-30) at 85 The value obtained by the storage elastic modulus G' (85) in °C is 10.0 or less. The adhesive for repeated bending devices according to claim 1, wherein the gel fraction is 40% or more and 95% or less. The adhesive for repeated bending devices according to claim 1, wherein the adhesive contains a main adhesive and a low molecular weight component, the weight average molecular weight of the low molecular weight component is 400 or more and 100,000 or less, and the low molecular weight component has a glass transition The temperature (Tg) is -40°C or lower. The adhesive for a repeated bending device according to claim 1, wherein the above-mentioned adhesive is an acrylic adhesive. An adhesive sheet, which is an adhesive sheet having an adhesive layer for attaching a flexible member constituting a repeated bending device to another flexible member, wherein the aforementioned adhesive layer is made of any one of claims 1 to 8. The repeated bending device described in the item is composed of an adhesive. The adhesive sheet according to claim 9, wherein the adhesive sheet comprises two peeling sheets, and the adhesive layer is sandwiched between the peeling sheets and contacts the peeling surfaces of the two peeling sheets. A repeatedly bent laminated member comprising a flexible member and another flexible member constituting a repeated bending device, and an adhesive layer for attaching the first flexible member and the other flexible member to each other. A component, wherein the aforementioned adhesive layer is composed of the adhesive for repeated bending devices as described in any one of claims 1 to 8. An iteratively bending device comprising the iteratively bending laminated member as claimed in claim 11.

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