TWI813590B - Adhesive for repetitive bending device, adhesive sheet, repetitive bending laminated member, and repetitive bending device - Google Patents

Abstract

[Problem] Provide a device that is suitable for repeated bending and that can suppress the deformation of the adhesive layer after being released from the bending state when the device is repeatedly bent or left in a bending state for a long time, and can alleviate the stress caused by the above situation. Effects of repeated bending of devices using adhesives. [Solution] Provide an adhesive for repeated bending devices. The maximum relaxation modulus value measured when the adhesive is strained by 10% is defined as the maximum relaxation modulus G (t) _max (MPa). When the maximum relaxation is measured, After the modulus G(t) _max , continue to strain the aforementioned adhesive by 10% until 3757 seconds have passed. The minimum relaxation modulus value measured during this period is defined as the minimum relaxation modulus G(t) _min (MPa), thus Calculate the relaxation modulus change value ΔlogG (t), and define the creep compliance modulus value measured when a stress of 3000Pa is applied to the adhesive as the minimum creep compliance modulus J (t) _min (MPa ^-1 ), and After measuring the minimum creep compliance modulus J (t) _min , continue to apply a stress of 3000 Pa until 3757 seconds have passed. The maximum creep compliance modulus value measured during this period is defined as the maximum creep compliance modulus J ( t) _max (MPa ^-1 ), from which the creep compliance modulus change value ΔlogJ(t) is calculated, the product of the aforementioned relaxation modulus change value ΔlogG(t) and the aforementioned creep compliance modulus change value ΔlogJ(t) The value is 3 or less.

Description

Adhesives, adhesive sheets, repetitive bending laminated components and repetitive bending devices for repetitive bending devices

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

In recent years, a flexible display has been proposed as a display body (display) of an electronic device. This kind of flexible display can, for example, be bent and placed on a cylindrical pillar to be used as a fixed display, or it can be bent, folded or rolled and carried to be used as a portable display. It has a wide range of applications. The use is highly anticipated.

Examples of types of flexible displays include organic electroluminescence (organic EL) displays, electrophoretic displays (electronic paper), and liquid crystal displays using plastic films as substrates.

In the above-mentioned flexible display, it is generally considered that one flexible member (flexible member) constituting the flexible display is bonded to other flexible members through an adhesive layer of an adhesive sheet. Here, as an adhesive sheet for conventional displays that cannot be bent, adhesive sheets disclosed in Patent Document 1 and Patent Document 2 are known, for example.

The flexible display is not only formed into a curved surface once, but may be repeatedly bent (folded) as described in Patent Document 3. Furthermore, such a repeatedly bendable display may be fixed in a bent state for a long time. When a conventional adhesive sheet is used in a repeatedly bendable device for this purpose, even after the bending state is released, the adhesive layer deforms and the flexible display still maintains a large bend and is fixed at such a bend. status. [Prior art documents] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 2015-174907 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-774 [Patent Document 3] Japanese Patent Application Laid-Open No. 2016-2764

[Problem to be solved by the invention]

The present invention was completed in view of the above situation, and aims to provide an adhesive and an adhesive sheet for a repetitive bending device, which can be used when applied to a repetitive bending device and repeatedly bent or when it is in a bent state for a long time. After the bending state is released, the deformation of the adhesive layer can be suppressed, and the influence of the repeated bending device on the repeated bending or the bending state can be alleviated, and a repeated bending laminated member and a repeated bending device can be provided. In the case of being in a bent state for a long time, the influence of repeated bending or the influence of being in a bent state can be alleviated after the bending state is released. [Means used to solve problems]

In order to achieve the above object, first, the present invention provides an adhesive for a repetitive bending device, which is an adhesive for a repetitive bending device used to bond one bending member constituting the repetitive bending device to other bending members, wherein according to JIS K7244-1, the maximum relaxation modulus value measured when the aforementioned adhesive is strained by 10% is defined as the maximum relaxation modulus G (t) _max (MPa), and when the maximum relaxation modulus G (t) _max is measured Then continue to strain the aforementioned adhesive by 10% until 3757 seconds pass. The minimum relaxation modulus value measured during this period is defined as the minimum relaxation modulus G (t) _min (MPa). The relaxation is calculated by the following formula (I) The modulus change value ΔlogG (t), the creep compliance modulus value measured when a stress of 3000Pa is applied to the aforementioned adhesive is defined as the minimum creep compliance modulus J (t) _min (MPa ^-1 ), and when measured After reaching the minimum creep compliance modulus J (t) _min , the stress of 3000 Pa is continued until 3757 seconds have passed. The maximum creep compliance modulus value measured during this period is defined as the maximum creep compliance modulus J (t). _max (MPa ^-1 ), the creep compliance modulus change value ΔlogJ(t) is calculated from the following formula (II), the aforementioned relaxation modulus change value ΔlogG(t) and the aforementioned creep compliance modulus change value ΔlogJ(t) The product value is 3 or less (Invention 1). ΔlogG (t) = log G (t) _max - log G (t) _min (I) ΔlogJ (t) = log J (t) _max - log J (t) _min (II)

In the above-mentioned invention (Invention 1), by satisfying the above-mentioned physical properties, even when it is applied to a repetitive bending device and is repeatedly bent or when it is in a bent state for a long time, it is possible to bend the device after being released from the bent state. By suppressing the deformation of the adhesive layer, the repetitive bending device can be prevented from being fixed in a large bending state, and the impact of the repetitive bending device being affected by repeated bending or being in a bending state can be mitigated.

In the above invention (Invention 1), the relaxation modulus variation value ΔlogG(t) is preferably 1.1 or less (Invention 2).

In the above-mentioned inventions (Inventions 1 and 2), the creep compliance modulus variation value ΔlogJ(t) is preferably 2.82 or less (Invention 3).

In the above invention (Inventions 1 to 3), it is preferable that the adhesive is an adhesive obtained by crosslinking an adhesive composition containing a (meth)acrylate polymer (A) and a crosslinking agent (B). (Invention 4).

Secondly, the present invention provides an adhesive sheet, which is an adhesive sheet having an adhesive layer for bonding one bending member constituting a repetitive bending device to another bending member, wherein the adhesive layer is formed by the repetitive bending device. It is formed (Invention 5) using an adhesive (Inventions 1 to 4).

In the above invention (Invention 5), it is preferable that the adhesive sheet includes two release sheets, and the adhesive layer is sandwiched between the release sheets so as to contact the release surfaces of the two release sheets (Invention 6).

Thirdly, the present invention provides a repeatedly bending laminated member, which includes one bendable member and other bendable members constituting a repeatable bending device, and an adhesive layer bonding the one bendable member and the other bendable members to each other. A repeatedly bent laminated member, wherein the adhesive layer is the adhesive layer (Invention 7) of the adhesive sheet (Inventions 5 and 6).

In the above invention (Invention 7), it is preferable that at least one of the one flexible member and the other flexible member is a display element (Invention 8).

Fourthly, the present invention provides a repetitive bending device provided with the repeatedly bent laminated member (Inventions 7 and 8) (Invention 9). [Effects of the present invention]

According to the adhesive and adhesive sheet for a repeatable bending device of the present invention, when applied to a repeatable bending device and repeatedly bent or when it is in a bent state for a long time, after the bending state is released, there is almost no chance that The deformation of the adhesive layer can alleviate the impact of repeated bending on the repeated bending device or the impact caused by being in a bent state. Furthermore, according to the repetitively bending laminated member and the repetitively bending device of the present invention, when it is repeatedly bent or when it is in a bent state for a long time, after the bending state is released, the influence of repeated bending can be alleviated or Effects of being in a bent state.

Hereinafter, embodiments of the present invention will be described. [Adhesive for repetitive bending devices] The adhesive for a repetitive bending device according to this embodiment (hereinafter sometimes referred to as "adhesive") is an adhesive used to bond one flexible member and other flexible members constituting the repetitive bending device. The repetitive bending device and the bending member will be described in detail later.

According to the adhesive of this embodiment, according to JIS K7244-1, the maximum relaxation modulus value measured when the adhesive is strained 10% is defined as the maximum relaxation modulus G (t) _max (MPa), and when this is measured After the maximum relaxation modulus G(t) _max , continue to strain the adhesive by 10% until 3757 seconds have passed. The minimum relaxation modulus value measured during this period is defined as the minimum relaxation modulus G(t) _min (MPa), The relaxation modulus change value ΔlogG(t) is calculated from the following formula (I), and the creep compliance modulus value measured when a stress of 3000Pa is applied to the adhesive is defined as the minimum creep compliance modulus J(t) _min (MPa ^-1 ), and after measuring the minimum creep compliance modulus J(t) _min , continue to apply a stress of 3000Pa until 3757 seconds have passed, during which the maximum creep compliance measured The module value is defined as the maximum creep compliance module J(t) _max (MPa ^-1 ). The creep compliance module change value ΔlogJ(t) and the relaxation module change value ΔlogG(t) are calculated from the following formula (II) The product value with the creep compliance modulus variation value ΔlogJ(t) is 3 or less. ΔlogG(t) = log G(t) _max - log G(t) _min (I) ΔlogJ(t) = log J(t) _max - log J(t) _min (II) In addition, the relaxation modulus G(t) ) and the details of the measurement method of creep compliance modulus J(t) are as shown in the test examples described later. Furthermore, "when a stress of 3000 Pa is applied to the adhesive" refers to the time when stress is applied to the adhesive and the stress reaches 3000 Pa.

According to the adhesive of this embodiment, since the product value of the relaxation modulus change value ΔlogG(t) and the creep compliance modulus change value ΔlogJ(t) is as small as described above, the stress change or strain change during bending is small. Therefore, the deformed part easily returns to its original shape during unloading, or almost no deformation occurs. Therefore, even if the adhesive layer composed of this adhesive layer is repeatedly bent by the repeated bending device using this adhesive layer or is in a bent state for a long time, after the bending state is released, the adhesive layer will not bend. It can suppress the deformation of the adhesive layer, suppress the repeated bending device from being fixed in a large bending state, and alleviate the influence of the repeated bending device from being affected by repeated bending or being in a bending state. Hereinafter, the above-mentioned effect may be referred to as "the bending state relaxation effect of the repetitive bending device." In addition, as an index of the number of times of repeated bending, for example, 30,000 times can be exemplified as an example.

From the viewpoint of the bending state relaxation effect of the repetitive bending device, the product value of the relaxation modulus variation value ΔlogG(t) and the creep compliance modulus variation value ΔlogJ(t) needs to be 3 or less, preferably 2.3 or less. It is preferably 1.8 or less, and further preferably 0.88 or less. In addition, the lower limit of the above-mentioned product value is not particularly limited, but it is generally preferably 0.1 or more, and particularly preferably 0.2 or more.

In order to easily obtain the product value of the relaxation modulus variation value ΔlogG(t) and the creep compliance modulus variation value ΔlogJ(t) within the above range, the relaxation modulus variation value ΔlogG(t) is preferably 1.1 or less, and It is preferably 0.82 or less, particularly preferably 0.75 or less, and further preferably 0.50 or less. In addition, the lower limit of the relaxation modulus variation value is not particularly limited, but it is generally preferably 0.10 or more, and particularly preferably 0.15 or more.

According to the present embodiment, the upper limit of the maximum relaxation modulus G(t) _max of the adhesive is preferably 1.0 MPa or less, particularly preferably 0.95 MPa or less, and further preferably 0.9 MPa or less. Since the upper limit of the maximum relaxation modulus G(t) _max is as described above, the relaxation modulus variation value ΔlogG(t) tends to satisfy the above value. The lower limit of the maximum relaxation modulus G(t) _max is not particularly limited, but it is generally preferably 0.05 MPa or more, particularly 0.10 MPa or more, and further preferably 0.15 MPa or more.

Furthermore, according to the present embodiment, the minimum relaxation modulus G(t) _min of the adhesive is preferably 0.005 MPa or more, particularly 0.01 MPa or more, and further preferably 0.02 MPa or more as a lower limit value. . Since the lower limit value of the minimum relaxation modulus G(t) _min is as described above, the relaxation modulus variation value ΔlogG(t) tends to satisfy the above value. The upper limit of the minimum relaxation modulus G(t) _min is not particularly limited, but it is generally preferably 0.50 MPa or less, particularly preferably 0.45 MPa or less, and further preferably 0.40 MPa or less.

On the other hand, in order to easily obtain the product value of the relaxation modulus variation value ΔlogG(t) and the creep compliance modulus variation value ΔlogJ(t) within the above range, the creep compliance modulus variation value ΔlogJ(t) is, It is preferably 2.82 or less, more preferably 2.30 or less, especially 2.00 or less, and further preferably 1.95 or less. In addition, the lower limit of the creep compliance modulus variation value is not particularly limited, but it is usually preferably 1.00 or more, and particularly preferably 1.20 or more.

According to the present embodiment, the minimum creep compliance modulus J(t) _min of the adhesive is preferably 0.5MPa ^-1 or more, particularly preferably 0.8MPa ^-1 or more, and further preferably 1.0MPa -1 as the lower limit value ^{. 1} or above is better. Since the lower limit value of the minimum creep compliance modulus J(t) _min is as described above, the creep compliance modulus variation value ΔlogJ(t) becomes easy to satisfy the above value. The upper limit of the minimum creep compliance modulus J(t) _min is not particularly limited. Generally, it is preferably 5.0MPa ^-1 or less, especially 4.5MPa ^-1 or less, and even more preferably 4.0MPa ^-1 or less. good.

Furthermore, according to the present embodiment, the maximum creep compliance modulus J(t) _max of the adhesive is preferably 1000MPa ^-1 or less, particularly 800MPa ^-1 or less, and further preferably 500MPa -1 as an upper limit ^{. 1} or less is more preferred, and 120MPa ^-1 or less is optimum. Since the upper limit of the maximum creep compliance modulus J(t) _max is as described above, the creep compliance modulus variation value ΔlogJ(t) tends to satisfy the above value. The lower limit of the maximum creep compliance modulus J(t) _max is not particularly limited, but it is usually preferably 10 MPa ^-1 or more, especially 15 MPa ^-1 or more, and further preferably 20 MPa ^-1 or more.

The type of adhesive according to this embodiment is not particularly limited as long as it satisfies the aforementioned physical properties. For example, it may be an acrylic adhesive, a polyester adhesive, a polyurethane adhesive, a rubber adhesive, or a silicone adhesive. (silicone) Any type of adhesive, etc. Furthermore, the above-mentioned adhesive may be any one of emulsion type, solvent type or solvent-free type, and may be any one of cross-linked type or non-cross-linked type. Among them, an acrylic adhesive that easily satisfies the aforementioned physical properties and has excellent adhesive properties, optical properties, etc. is preferred.

Furthermore, as an acrylic adhesive, it may have active energy ray curability or active energy ray non-curability, it may have thermal cross-linking property or it may have non-cross-linking property, and it may have a combination of the above, and In order to obtain good flexibility, active energy ray non-curable properties are preferred. As the active energy ray non-curable acrylic adhesive, a cross-linked type is particularly preferred, and a thermal cross-linked type is more preferred.

The adhesive according to this embodiment is particularly preferably an adhesive composition (hereinafter sometimes referred to as "adhesive composition P") containing a (meth)acrylate polymer (A) and a cross-linking agent (B). Adhesive obtained by cross-linking. This kind of adhesive easily satisfies the aforementioned physical properties and can obtain good adhesive force and predetermined cohesive force, so it has excellent durability. In addition, in this specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms. Furthermore, "polymer" also includes the concept of "copolymer".

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

Since the (meth)acrylate polymer (A) contains alkyl (meth)acrylate as a monomer unit constituting the polymer, it can produce good adhesiveness. As the (meth)acrylic acid alkyl ester, a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms is preferred. The alkyl group may be linear or branched, or may have a cyclic structure.

Alkyl (meth)acrylate whose alkyl group has 1 to 20 carbon atoms and whose glass transition temperature (Tg) as a homopolymer is -40°C or less (hereinafter sometimes referred to as " Low Tg alkyl acrylate") is preferred. By including such a low-Tg alkyl acrylate as a constituent monomer unit, the flexibility of the resulting adhesive can be improved.

Preferable examples of low-Tg alkyl acrylates include n-butyl acrylate (Tg: -55°C), n-octyl acrylate (Tg: -65°C), and isooctyl acrylate (Tg: -58°C). ), 2-ethylhexyl acrylate (Tg is -70℃), isononyl acrylate (Tg is -58℃), isodecyl acrylate (Tg is -60℃), isodecyl methacrylate (Tg is -41℃), n-dodecyl methacrylate (Tg is -65℃), tridecyl acrylate (Tg is -55℃), tridecyl methacrylate (Tg is -40℃ )wait. Among them, as a low-Tg alkyl acrylate, the Tg of the homopolymer is preferably -45°C or lower, and particularly preferably -50°C or lower, from the viewpoint of more effectively improving flexibility. Specifically, n-butyl acrylate and 2-ethylhexyl acrylate are particularly preferred. The above-mentioned materials can be used individually or in combination of 2 or more types.

In the (meth)acrylate polymer (A), the lower limit of the low-Tg alkyl acrylate as a monomer unit constituting the polymer is preferably 50% by mass or more, particularly 55% by mass. It is preferable that it contains 60 mass % or more, and it is more preferable that it contains 60 mass % or more. By containing 50% by mass or more of the low-Tg alkyl acrylate, the glass transition temperature (Tg) of the (meth)acrylate polymer (A) can be easily set within the aforementioned range.

On the other hand, in the (meth)acrylate polymer (A), the upper limit of the low-Tg alkyl acrylate as a monomer unit constituting the polymer is preferably 99.9% by mass or less, particularly Therefore, the content is preferably 99 mass% or less, and more preferably 98 mass% or less. By containing 99.9% by mass or less of the low-Tg alkyl acrylate, an appropriate amount of other monomer components (especially monomers containing reactive functional groups) can be introduced into the (meth)acrylate polymer (A).

Furthermore, the (meth)acrylic acid alkyl ester polymer in which the alkyl group has 1 to 20 carbon atoms may also contain a monomer having a glass transition temperature (Tg) exceeding 0° C. as a homopolymer (hereinafter Sometimes called "high Tg alkyl acrylates"). By containing such a high-Tg alkyl acrylate as a constituent monomer unit, the relaxation modulus variation value of the obtained adhesive becomes easier to satisfy the aforementioned physical properties.

When the (meth)acrylate polymer (A) contains the above-mentioned high Tg alkyl acrylate as a monomer unit constituting the polymer, the content is preferably 5% by mass or more, especially 10% by mass. The above is preferable, and it is more preferable that it is 15 mass % or more. In addition, the content is preferably 30 mass% or less, particularly preferably 25 mass% or less, and further preferably 20 mass% or less.

Examples of the high Tg alkyl acrylate include, for example, methyl acrylate (Tg: 10°C), methyl methacrylate (Tg: 105°C), ethyl methacrylate (Tg: 65°C), methacrylate n-butyl acrylate (Tg is 20℃), isobutyl methacrylate (Tg is 48℃), tert-butyl methacrylate (Tg is 107℃), n-octadecyl acrylate (Tg is 30 ℃), n-octadecyl methacrylate (Tg is 38℃), cyclohexyl acrylate (Tg is 15℃), cyclohexyl methacrylate (Tg is 66℃), benzyl methacrylate (Tg is 54°C), isocamphenyl acrylate (Tg is 94°C), isocamphenyl methacrylate (Tg is 180°C), adamantyl acrylate (Tg is 115°C), adamantyl methacrylate (Tg is 115°C), Tg is 141℃) etc. Among them, from the viewpoint of cohesion, methyl acrylate, methyl methacrylate, and isocamphenyl acrylate are preferred. The above-mentioned materials can be used individually or in combination of 2 or more types. In addition, the above-mentioned high Tg alkyl acrylate does not include the nitrogen atom-containing monomer described later.

The (meth)acrylate polymer (A) contains a reactive functional group-containing monomer as a monomer unit constituting the polymer, and the reactive functionality derived from the reactive functional group-containing monomer is The base reacts with the cross-linking agent (B) described later to form a cross-linked structure (three-dimensional network structure), thereby obtaining an adhesive with the required cohesive force.

(Meth)acrylate polymer (A), as the reactive functional group-containing monomer contained in the monomer units constituting the polymer, preferably, a monomer having a hydroxyl group in the molecule (hydroxyl-containing monomer monomer), monomers with carboxyl groups in the molecule (carboxyl group-containing monomers), monomers with amine groups in the molecule (amine group-containing monomers), etc. These reactive functional group-containing monomers may be used alone or in combination of two or more types.

Among the above-mentioned reactive functional group-containing monomers, hydroxyl group-containing monomers and carboxyl group-containing monomers are preferred, and hydroxyl group-containing monomers are particularly preferred. Since the glass transition temperature (Tg) of the hydroxyl-containing monomer as a homopolymer is relatively low, the resulting (meth)acrylate polymer (A) can easily maintain high flexibility, while the carboxyl-containing monomer can The adhesive force of the obtained (meth)acrylate polymer (A) is improved.

Examples of the hydroxyl-containing monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and (meth)acrylate. Hydroxyalkyl (meth)acrylate, such as 2-hydroxybutyl acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and the like. Among them, from the viewpoint of the flexibility of the obtained (meth)acrylate polymer (A), 2-hydroxyethyl (meth)acrylate, that is, 2-hydroxypropyl (meth)acrylate is good. The above-mentioned materials can be used individually or in combination of 2 or more types.

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 preferred from the viewpoint of the adhesive force of the obtained (meth)acrylate polymer (A). The above-mentioned materials can be used individually or in combination of 2 or more types.

When the (meth)acrylate polymer (A) contains a hydroxyl-containing monomer as a monomer unit constituting the polymer, the content of the hydroxyl-containing monomer is preferably 0.1% by mass or more, especially The content is preferably 0.3% by mass or more. Furthermore, the content of the hydroxyl-containing monomer is preferably 30% by mass or less, especially 25% by mass or less. On the other hand, when the (meth)acrylate polymer (A) contains a carboxyl group-containing monomer as a monomer unit constituting the polymer, the content of the carboxyl group-containing monomer is preferably 0.5% by mass or more. , especially preferably 1% by mass or more. Furthermore, the content of the carboxyl group-containing monomer is preferably 10 mass% or less, particularly 7 mass% or less, and further preferably 5 mass% or less. By controlling the contents of the hydroxyl-containing monomer and the carboxyl-containing monomer as described above, the obtained (meth)acrylate polymer (A) becomes more flexible and adhesive, and the obtained The adhesive layer can achieve a higher degree of bending relaxation effect of the repeated bending device.

The (meth)acrylate polymer (A) may also contain a monomer containing a nitrogen atom as a monomer unit constituting the polymer. Examples of the monomer containing a nitrogen atom include a monomer having an amine group, a monomer having a amide group, a monomer having a nitrogen-containing heterocyclic ring, and the like, and among these, a monomer having a nitrogen-containing heterocyclic ring is preferred.

Examples of the monomer having a nitrogen-containing heterocycle include N-(meth)acryloyl morpholine and N-vinyl-2-pyrrolidone. 2-pyrrolidone), N-(meth)acryloyl pyrrolidone (N-(meth)acryloyl pyrrolidone), N-(meth)acryloyl piperidine (N-(meth)acryloyl piperidine), N-(meth)acryloyl pyrrolidone N-(meth)acryloylpyrrolidine, N-(meth)acryloyl aziridine, (meth)aziridinyl ethyl (meth)acrylate), 2-vinyl pyridine (2-vinyl pyridine), 4-vinyl pyridine, 2-(vinyl pyrazine), 1-vinyl imidazole , N-vinyl carbazole (N-vinyl carbazole), N-vinylphthalimide (N-vinylphthalimide), etc., among which N-(meth)propylene can exhibit better adhesion. Preferred is acylmorpholine, especially N-acrylomorpholine. The above-mentioned materials can be used individually or in combination of 2 or more types.

When the (meth)acrylate polymer (A) includes a nitrogen atom-containing monomer as a monomer unit constituting the polymer, the content of the nitrogen atom-containing monomer is preferably 1 mass % or more, particularly Therefore, the content is preferably 3% by mass or more. Furthermore, the content of the nitrogen atom-containing monomer is preferably 20 mass% or less, particularly 15 mass% or less, and further preferably 10 mass% or less.

If necessary, the (meth)acrylate polymer (A) may also contain other monomers as monomer units constituting the polymer. As other monomers, in order not to interfere with the aforementioned effects of the monomer containing a reactive functional group, it is preferable to use a monomer that does not contain a reactive functional group. Examples of the monomer include alkoxyalkyl (meth)acrylates such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate, vinyl acetate, Styrene etc. The above-mentioned materials can be used individually or in combination of 2 or more types.

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

The lower limit of the weight average molecular weight of the (meth)acrylate polymer (A) is preferably at least 100,000, particularly preferably at least 300,000, and further preferably at least 500,000. When the lower limit of the weight average molecular weight of the (meth)acrylate polymer (A) is as described above, the durability of the adhesive becomes more excellent. In addition, in this specification, the weight average molecular weight is a standard polystyrene conversion value measured by gel permeation chromatography (GPC) method.

Furthermore, the upper limit of the weight average molecular weight of the (meth)acrylate polymer (A) is preferably 1.5 million or less, particularly 1.2 million or less, and further preferably 1,000,000 or less. When the upper limit of the weight average molecular weight of the (meth)acrylate polymer (A) is as described above, the flexibility of the obtained adhesive becomes more excellent.

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

(1-2) Cross-linking agent (B) The cross-linking agent (B) cross-links the (meth)acrylate polymer (A) by heating the adhesive composition P containing the cross-linking agent (B) as a trigger, thereby forming a three-dimensional mesh structure. Thereby, the cohesive force of the adhesive obtained increases, and the adhesive layer becomes excellent in durability.

The cross-linking agent (B) may be any one that can react with the reactive group of the (meth)acrylate polymer (A). Examples thereof include isocyanate-based cross-linking agents, epoxy cross-linking agents, etc. Cross-linking agent, amine cross-linking agent, melamine cross-linking agent, aziridine cross-linking agent, hydrazine cross-linking agent, aldehyde cross-linking agent, oxazoline cross-linking agent Cross-linking agent, metal alkoxide-based cross-linking agent, metal chelate-based cross-linking agent, metal salt-based cross-linking agent, ammonium salt-based cross-linking agent, etc. Among the above-mentioned materials, it is preferable to use an isocyanate-based crosslinking agent that has excellent reactivity with monomers containing reactive functional groups, especially with monomers containing hydroxyl groups. In addition, as the cross-linking agent (B), one type may be used alone, or two or more types may be used in combination.

The isocyanate cross-linking agent contains at least a polyisocyanate compound. Examples of the polyvalent isocyanate compound include, for example, aromatic polyisocyanates (xylylene diisocyanate) such as tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, and hexamethylene diisocyanate. Aliphatic polyisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, alicyclic polyisocyanates such as hydrogenated diphenylmethane diisocyanate, and the above-mentioned biurets , or isocyanurate (isocyanurate) body, as well as the reaction product-adduct ( adduct) and so on. Among them, from the viewpoint of reactivity with hydroxyl groups, aromatic polyisocyanates modified with trimethylolpropane, especially toluene diisocyanate modified with trimethylolpropane and trimethylolpropane-modified polyisocyanate Xylyl diisocyanate is preferred.

The content of the cross-linking agent (B) in the adhesive composition P is preferably 0.1 parts by mass or more, and particularly 0.5 parts by mass or more based on 100 parts by mass of the (meth)acrylate polymer (A). Preferably, it is more preferably 1.0 parts by mass or more. Furthermore, the content is preferably 10 parts by mass or less, particularly 8 parts by mass or less, and further preferably 5 parts by mass or less. When the content of the cross-linking agent (B) is within the above range, the obtained adhesive has appropriate cohesive force, and the obtained adhesive layer can achieve a higher degree of bending state relaxation effect of the repeated bending device.

(1-3) Various additives If necessary, various additives commonly used in acrylic adhesives can be added to the adhesive composition P, such as silane coupling agents, ultraviolet absorbers, antistatic agents, tackifiers, antioxidants, light stabilizers, Softeners, fillers, refractive index adjusters, etc. In addition, the polymerization solvent or dilution solvent which will be described later is not included in the additive which constitutes adhesive composition P.

(2) Preparation of adhesive composition P Prepare (meth)acrylate polymer (A), mix the obtained (meth)acrylate polymer (A) with the cross-linking agent (B), and add additives as needed, thereby preparing The adhesive composition P is produced.

A (meth)acrylate polymer (A) can be prepared by polymerizing a mixture of monomers constituting the polymer using a general radical polymerization method. The polymerization of the (meth)acrylate polymer (A) is preferably carried out by a solution polymerization method using a polymerization initiator as necessary. Examples of the polymerization solvent include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone, and the like, and two or more types may be used in combination.

Examples of the polymerization initiator include azo compounds, organic peroxides, and the like, and two or more types may be used in combination. Examples of azo compounds include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), and 1,1'-azobis(cyclohexane). Alkane 1-carbonitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxypentane) nitrile), 2,2'-azobis(2-methylpropionate)dimethyl ester, 2,4'-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, tert-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, and di-n-propyl peroxydicarbonate. Ester, di(2-ethoxyethyl) peroxydicarbonate, tert-butyl peroxyneodecanate, tert-butyl peroxypivalate, (3,5,5-trimethylhexanoic acid) base) peroxide, dipropyl peroxide, diethyl 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.

When the (meth)acrylate polymer (A) is obtained, the cross-linking agent (B) and the required additives and diluting solvent are added to the solution of the (meth)acrylate polymer (A), by sufficient were mixed to obtain an adhesive composition P (coating solution) diluted with a solvent.

In addition, when any of the above components is used in solid form, or when precipitation occurs when mixed with other components in an undiluted state, the component may be dissolved or diluted separately in a diluting solvent in advance, and then Only then mixed with the other ingredients mentioned above.

Examples of the diluting solvent that can be used include aliphatic hydrocarbons such as hexane, heptane, and cyclohexane, aromatic hydrocarbons such as toluene and xylene, and halogenated hydrocarbons such as methylene chloride and 1,2-dichloroethane. Hydrocarbons, 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, cellosolve-based solvents such as ethyl cellosol, etc.

The concentration and viscosity of the coating solution prepared in the above manner are not particularly limited as long as they are within a range that allows coating, and can be appropriately selected depending on the situation. For example, it is diluted so that the concentration of the adhesive composition P may be 10 to 60% by mass. In addition, when obtaining the coating solution, the addition of a diluting solvent or the like is not essential. If the adhesive composition P has a viscosity that allows coating, the diluting solvent does not need to be added. 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 the diluting solvent.

(3) Preparation of adhesive The adhesive agent according to this embodiment is preferably an adhesive agent obtained by cross-linking the adhesive composition P. Crosslinking of the adhesive composition P can usually be performed by heat treatment. In addition, this heat treatment can also be used as a drying treatment to volatilize the diluting solvent and the like from the coating film of the adhesive composition P applied to the desired object.

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

After the heat treatment, a curing period of about 1 to 2 weeks at normal temperature (for example, 23° C., 50% RH) may also be provided as needed. In the case where this curing period is required, the adhesive is formed after the curing period, and in the case where the curing period is not required, the adhesive is formed after the heat treatment is completed.

Through the above-mentioned heat treatment (and curing), the (meth)acrylate polymer (A) is fully cross-linked through the cross-linking agent (B), thereby forming a cross-linked structure to obtain an adhesive. The adhesive may have a predetermined cohesion.

(4) Physical properties of adhesive The lower limit of the storage modulus (G’) of the adhesive according to this embodiment at 25°C is preferably 0.01 MPa or more. Furthermore, the upper limit of the above-mentioned storage modulus (G’) is preferably 0.25 MPa or less, especially 0.20 MPa or less.

Furthermore, the lower limit of the loss modulus (G'') of the adhesive according to this embodiment at 25°C is preferably 0.005 MPa or more, and particularly preferably 0.01 MPa or more. Furthermore, the upper limit of the loss modulus (G'') is preferably 0.1MPa or less, and particularly preferably 0.08MPa or less.

Furthermore, the lower limit value of the loss tangent (tan δ) of the adhesive according to this embodiment at 25° C. is preferably 0.25 or more, and particularly preferably 0.28 or more. Furthermore, the upper limit of the loss tangent (tanδ) is preferably 0.85 or less, and particularly preferably 0.80 or less.

According to this embodiment, when the storage modulus (G'), loss modulus (G''), and loss tangent (tanδ) of the adhesive are within the above ranges, the adhesive force to the bendable member becomes good and improved. Durability of repeated bending devices. In addition, the measurement methods of storage modulus (G’), loss modulus (G’’), and loss tangent (tanδ) are as shown in the test examples described later.

[adhesive sheet] The adhesive sheet according to this embodiment has an adhesive for bonding one flexible member constituting the repetitive bending device to another flexible member, and the adhesive layer is formed of the adhesive.

As an example of the adhesive sheet according to this embodiment, its specific structure is shown in FIG. 1 . As shown in FIG. 1 , the adhesive sheet 1 according to one embodiment includes two release sheets 12 a and 12 b, and the two release sheets 12 a and 12 b are separated by the release surfaces of the two release sheets 12 a and 12 b so as to contact the release surfaces thereof. It is composed of sandwiched adhesive layer 11. In addition, the release surface of the release sheet in this specification refers to the surface of the release sheet that has releasability, and also includes a surface that has undergone release treatment and a surface that exhibits releasability even if no release treatment is applied.

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

The thickness of the adhesive layer 11 in the adhesive sheet 1 according to this embodiment (the value measured in accordance with JIS K7130) is preferably 2 μm or more, particularly 5 μm or more, and further 10 μm or more as a lower limit value. For the better. When the lower limit of the thickness of the adhesive layer 11 is the above-mentioned value, it is easy to exert the desired adhesive force, and problems such as floating and peeling during repeated bending can be effectively suppressed. Furthermore, the upper limit of the thickness of the adhesive layer 11 is preferably 150 μm or less, more preferably 100 μm or less, particularly preferably 70 μm or less, and further preferably 50 μm or less. When the upper limit of the thickness of the adhesive layer 11 is the above value, the problem of the adhesive or components constituting the adhesive exuding from the adhesive layer due to repeated bending can be suppressed. In addition, the adhesive layer 11 may be formed as a single layer or may be laminated to form multiple layers.

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

As the release sheets 12a and 12b, for example, polyethylene film, polypropylene film, polybutylene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyvinyl chloride copolymer film, Ethylene terephthalate 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. Furthermore, a laminated film of the above-mentioned materials can also be used.

The peeling surfaces of the above-mentioned peeling sheets 12a and 12b (especially the surfaces in contact with the adhesive layer 11) are preferably subjected to a peeling process. Examples of the release agent used for the release treatment include, for example, alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents. In addition, among the release sheets 12a and 12b, it is preferable that one of the release sheets is a heavy release type release sheet having a large release force and the other release sheet is a light release type release sheet having a small release force.

The thickness of the release sheets 12a and 12b is not particularly limited, but is usually about 20 to 150 μm.

(2) Manufacturing of adhesive sheets As a manufacturing example 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 applied on the release surface of one release sheet 12a (or 12b), and heat treatment is performed to cause the adhesive composition P to be thermally cross-linked to form a coating layer, and the other release sheet is The peeling surface of 12b (or 12a) overlaps this coating layer. If a curing period is required, the adhesive layer 11 is formed by leaving the coating layer for a curing period. If a curing period is not required, the coating layer directly serves as the adhesive layer 11 . Thereby, the above-mentioned adhesive sheet 1 can be obtained. The conditions for heat treatment and curing are as described above.

As another manufacturing example of the adhesive sheet 1, a coating liquid of the adhesive composition P is applied to the peeling surface of one peeling sheet 12a, and heat treatment is performed to thermally crosslink the adhesive composition P to form a coating layer. The peeling sheet 12a with the coating layer is formed. Furthermore, the coating liquid of the above-mentioned adhesive composition P is applied to the peeling surface of another peeling sheet 12b, and heat treatment is performed to cause the adhesive composition P to be thermally cross-linked to form a coating layer, thereby forming an attached coating layer. The peeling piece 12b of the fabric layer. Next, the peeling sheet 12a with the coating layer and the peeling sheet 12b with the coating layer are bonded together 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 laminated coating layer for a curing period. When a curing period is not required, the laminated coating layer directly serves as the adhesive layer 11 . . Thereby, the above-mentioned adhesive sheet 1 can be obtained. According to this manufacturing example, even when the adhesive layer 11 is relatively thick, the adhesive layer 11 can be stably manufactured.

As a coating method of the coating solution of the adhesive composition P, for example, bar coating, knife coating, roll coating, blade coating can be used. coating method, die coating method, gravure coating method, etc.

[Repeated bending of laminated members] As shown in FIG. 2 , the repeatedly bending laminated member 2 according to this embodiment includes a first bending member 21 (one bending member), a second bending member 22 (another bending member), and two bending members located between the two bending members. There is an adhesive layer 11 between them and the first flexible member 21 and the second flexible member 22 are bonded to each other.

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

The repeatedly bent laminated member 2 itself is a repetitive bending device, or a member constituting a part of the repetitive bending device. The repeated bending device is preferably a display that can be repeatedly bent (including folded), but is not limited thereto. Examples of such repeated bending devices include organic electroluminescence (organic EL) displays, electrophoretic displays (electronic paper), flexible printed circuit boards, and plastic film substrates (films). The substrate of a liquid crystal display, a foldable display, etc. may also be a touch panel.

The first flexible member 21 and the second flexible member 22 are members that can be repeatedly bent (including folded), and examples thereof include a cover film, a barrier film, a polarizing film, Polarizer, retardation film, viewing angle compensation film, brightness enhancement film, contrast enhancement film, diffusion film, semi-transmissive reflective film, electrode film, transparent conductive film, metal mesh film, thin film sensor (film sensor), liquid crystal polymer film, Luminescent polymer film, film-like liquid crystal module (module), organic EL module (organic EL film), electronic paper module (film-like electronic paper), etc.

Among the above, at least one of the first flexible member 21 and the second flexible member 22 is a display element that can be repeatedly bent. Specifically, it is a liquid crystal polymer film, a light emitting polymer film, or a thin film liquid crystal. Modules, organic EL modules (organic EL films), and electronic paper modules (film-like electronic paper) are preferred.

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 further preferably 1.0 to 5 GPa. Since the Young's modulus of the first bending member 21 and the second bending member 22 is within the above range, it becomes easy to repeatedly bend each bending member.

The thickness of the first flexible member 21 and the second flexible member 22 is preferably 5 to 3000 μm, particularly 10 to 1000 μm, and further preferably 10 to 500 μm. Since the thickness of the first flexible member 21 and the second flexible member 22 is within the above range, it becomes easy to repeatedly bend each flexible member.

When manufacturing the repeatedly bent laminated member 2, as an example, one peeling sheet 12a of the adhesive sheet 1 can be peeled off, and the exposed adhesive layer 11 of the adhesive sheet 1 can be bonded to the first flexible member 21 side. s surface.

After that, another peeling sheet 12b is peeled off from the adhesive layer 11 in the adhesive sheet 1, and the exposed adhesive layer 11 in the adhesive sheet 1 is bonded to the second flexible member 22, thereby obtaining the repeatedly curved laminated member 2 . Furthermore, as another example, the order of laminating the first flexible member 21 and the second flexible member 22 may be changed.

[Repeated bending device] The repetitive bending device according to this embodiment is a repetitive bending device provided with the repetitively bent laminated member 2. It may be composed of only the repetitively bent laminated member 2, or may be composed of one or more repetitively bent laminated members 2 and Made of other flexible components. When one repetitively bending laminated member 2 is laminated with another repetitively bendable member 2 , or when the repeatedly bending laminated member 2 is laminated with another flexible member, it is preferable that the layers are laminated through the adhesive layer 11 of the adhesive sheet 1 .

According to the repeated bending device of this embodiment, since the adhesive layer is formed of the above-mentioned adhesive, it is bent repeatedly (for example, 30,000 times) or for a long time (for example, at least 24 hours or more). In the case of the bending state, after being released from the bending state, it is possible to suppress the repeated bending device from being fixed in a large bending state, and to alleviate the influence of repeated bending or the influence caused by being in the bending state. The bending state relaxation effect of the repetitive bending device can be evaluated, for example, by the static bending deformation amount obtained by a static bending test. In addition, as a bending test, there is also a dynamic bending test in which a repetitive bending device is repeatedly bent (for example, 30,000 times). However, for a repetitive bending device, since the static bending test is more stringent than the dynamic bending test as a test condition, if If you get good results in a static bending test, you will get good results in a dynamic bending test. Therefore, when confirming the bending state relaxation effect of the repetitive bending device, it is sufficient to conduct a static bending test.

In the static bending test, a laminated body consisting of an adhesive layer (thickness: 12 μm) sandwiched between two polyethylene terephthalate films (thickness: 12 μm) was used to prepare a test piece with a size of 200 mm × 50 mm. . As shown in FIG. 3 , the test piece S was held in a bent state between a holding plate P composed of two upright glass plates in an environment of 23° C. and 50% RH for 24 hours. At this time, the distance between the two holding plates P is set to 6 mm (the bending diameter of the test piece S: 6 mmφ), and the substantially central part of the long side (200 mm) of the test piece S is the bending part, and the two sides of the test piece S are Hold the test piece S with the short side (50 mm) on the upper side. After performing this static bending test, the test piece S was taken out from between the two holding plates P, and as shown in FIG. 4 , the test piece S was placed on a flat plate with the protruding direction of the bent portion as the upper side. Next, at the end of the test, after 30 minutes after the test, and after 24 hours after the test, the height h from the surface of the flat plate to the apex of the curved portion (deformed portion) was measured as the static bending deformation amount. This static bending deformation amount is used as the test result of the static bending test, and the bending state relaxation effect can be evaluated based on this static bending deformation amount.

The static bending deformation amount obtained by the static bending test at the end of the test is preferably 5 mm or less, more preferably 3 mm or less, especially 2 mm or less, further preferably 1 mm or less, and 0.5 mm The following are the best. In addition, the lower limit value of static bending deformation is preferably 0 mm.

The embodiments described above are described to facilitate understanding of the present invention and are not described to limit the present invention. Therefore, each element disclosed in the above-mentioned embodiment also covers all design changes and equivalents belonging to the technical scope of the present invention.

For example, in the adhesive sheet 1, either or both of the release sheets 12a and 12b may be omitted, and a required flexible member may be laminated instead of the release sheet 12a and/or the release sheet 12b. [Example]

Hereinafter, the present invention will be explained in more detail 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) By a solution polymerization method, 60 parts by mass of butyl acrylate, 20 parts by mass of methyl acrylate, and 20 parts by mass of 2-hydroxyethyl acrylate are copolymerized to prepare (meth)acrylate polymer (A) . The molecular weight of this (meth)acrylate polymer (A) was measured by the method described later, and the weight average molecular weight (Mw) was found to be 600,000.

2. Preparation of adhesive composition 100 parts by mass (calculated in terms of solid content, the same is true below) of the (meth)acrylate polymer (A) obtained in the above step 1, and 1.88 parts by mass of trihydroxytrihydroxyethyl as the cross-linking agent (B) Methylpropane-modified toluene diisocyanate (manufactured by Toyo Chemical Company, product name "BHS 8515") is mixed with each other and stirred thoroughly, and diluted with methyl ethyl ketone (MEK) to obtain adhesive Coating solution of the sexual composition (solid content concentration: 30.0 mass%).

3. Manufacturing of adhesive sheets The coating solution of the adhesive composition obtained in the above step 2 is applied using a comma coater (registered trademark) to polyethylene terephthalate using a silicone release agent. The release-treated surface of a heavy-release release sheet (manufactured by Lintec, product name "SP-PET 382150") obtained by subjecting one surface of the ester film to release treatment. Next, the coating layer was heat-treated at 90° C. for 1 minute to form a coating layer.

Thereafter, the coating layer on the heavy release type release sheet obtained above was combined with the light release type release sheet obtained by subjecting one surface of the polysilicon ethylene terephthalate film to a release treatment using a silicone release agent. (manufactured by Lintec Co., Ltd., product name "SP-PET 381031"), the release-treated surface of this light release type release sheet is in contact with the coating layer, and the temperature is maintained at 23°C and 50% RH. It is cured for 7 days under the conditions to form an adhesive sheet with an adhesive layer with a thickness of 12 μm, that is, a structure with a heavy peeling type release sheet/adhesive layer (thickness: 12 μm)/light peeling type release sheet is produced. Adhesive sheet. In addition, the thickness of the adhesive layer is a value measured using a constant pressure thickness gauge (manufactured by TECLOCK, product name "PG-02") in accordance with JIS K7130.

[Example 2] By solution polymerization, 47.8 parts by mass of 2-ethylhexyl acrylate, 47.8 parts by mass of n-butyl acrylate, 4 parts by mass of acrylic acid and 0.4 parts by mass of 2-hydroxypropyl acrylate are copolymerized to prepare (Meth)acrylate polymer (A). The molecular weight of this (meth)acrylate polymer (A) was measured by the method described later, and the weight average molecular weight (Mw) was found to be 600,000.

100 parts by mass of the (meth)acrylate polymer (A) obtained in the above step and 3.75 parts by mass of trimethylolpropane-modified toluene diisocyanate (made of (manufactured by Toyo Chemical Co., Ltd., product name "BHS 8515") were mixed with each other, stirred thoroughly, and diluted with toluene to obtain a coating solution of an adhesive composition (solid content concentration: 30.0 mass%). Using the obtained coating solution of the adhesive composition, an adhesive sheet was produced in the same manner as in Example 1.

[Example 3] By solution polymerization, 60 parts by mass of 2-ethylhexyl acrylate, 20 parts by mass of methyl methacrylate, and 20 parts by mass of 2-hydroxyethyl acrylate are copolymerized to prepare (meth)acrylic acid. Ester polymer (A). The molecular weight of this (meth)acrylate polymer (A) was measured by the method described later, and the weight average molecular weight (Mw) was found to be 600,000.

100 parts by mass of the (meth)acrylate polymer (A) obtained in the above step and 1.88 parts by mass of trimethylolpropane-modified toluene diisocyanate (made of (manufactured by Toyo Chemical Co., Ltd., product name "BHS 8515") were mixed with each other and stirred thoroughly, and diluted with methyl ethyl ketone to obtain a coating solution of an adhesive composition (solid content concentration: 30.0 mass%). Using the obtained coating solution of the adhesive composition, an adhesive sheet was produced in the same manner as in Example 1.

[Example 4] By a solution polymerization method, 65 parts by mass of 2-ethylhexyl acrylate, 5 parts by mass of N-acrylomorpholine, 15 parts by mass of isocamphenyl acrylate, and 15 parts by mass of 2-hydroxyethyl acrylate were combined. polymerize to prepare (meth)acrylate polymer (A). The molecular weight of this (meth)acrylate polymer (A) was measured by the method described later, and the weight average molecular weight (Mw) was found to be 500,000.

100 parts by mass of the (meth)acrylate polymer (A) obtained in the above step and 1.20 parts by mass of trimethylolpropane-modified toluene diisocyanate (made of (manufactured by Toyo Chemical Co., Ltd., product name "BHS 8515") were mixed with each other and stirred thoroughly, and diluted with methyl ethyl ketone to obtain a coating solution of an adhesive composition (solid content concentration: 30.0 mass%). Using the obtained coating solution of the adhesive composition, an adhesive sheet was produced in the same manner as in Example 1.

[Example 5] The (meth)acrylate polymer (A) prepared in Example 3 was used, and the preparation amount of the cross-linking agent (B) was changed to 0.94 parts by mass. The rest was the same as in Example 1. How to make adhesive sheets.

[Example 6] The (meth)acrylate polymer (A) prepared in Example 1 was used, and the preparation amount of the cross-linking agent (B) was changed to 0.94 parts by mass. The rest was the same as in Example 1. How to make adhesive sheets.

[Example 7] The (meth)acrylate polymer (A) prepared in Example 1 was used, and the preparation amount of the cross-linking agent (B) was changed to 0.47 parts by mass. The rest was the same as in Example 1. How to make adhesive sheets.

[Example 8] The (meth)acrylate polymer (A) prepared in Example 4 was used, and the preparation amount of the cross-linking agent (B) was changed to 0.60 parts by mass. The rest was the same as in Example 1. How to make adhesive sheets.

[Example 9] The (meth)acrylate polymer (A) prepared in Example 3 was used, and the preparation amount of the cross-linking agent (B) was changed to 0.47 parts by mass. The rest was the same as in Example 1. How to make adhesive sheets.

[Example 10] The (meth)acrylate polymer (A) prepared in Example 3 was used, and the preparation amount of the cross-linking agent (B) was changed to 0.23 parts by mass. The rest was the same as in Example 1. How to make adhesive sheets.

[Comparative example 1] The (meth)acrylate polymer (A) prepared in Example 4 was used, and the preparation amount of the cross-linking agent (B) was changed to 0.30 parts by mass. The rest was the same as in Example 1. How to make adhesive sheets.

[Comparative example 2] 15 parts by mass of isobutylene-isoprene copolymer (manufactured by Japan's Butyl Company, product name "Butyl 365") and 3 parts by mass of tackifier (manufactured by Japan's Zeon Company), Product name "Quinton A100") were mixed with each other, stirred thoroughly, and diluted with toluene to obtain a coating solution (solid content concentration: 15 mass%) as an adhesive composition of butyl rubber. An adhesive sheet was produced in the same manner as in Example 1, except that the obtained coating solution of the adhesive composition was used and the heat treatment temperature was 100°C.

[Comparative example 3] The (meth)acrylate polymer (A) prepared in Example 4 was used, and the preparation amount of the cross-linking agent (B) was changed to 0.15 parts by mass. The rest was the same as in Example 1. How to make adhesive sheets.

In addition, the composition of the (meth)acrylate polymer (A) and the compounding amount of the cross-linking agent (B) in each of the examples and comparative examples (relative to 100 parts by mass of the (meth)acrylate polymer (A) )) are recorded in Table 1. The abbreviations in Table 1 are as follows. BA: n-butyl acrylate MA: Methyl acrylate HEA: 2-hydroxyethyl acrylate 2EHA: 2-ethylhexyl acrylate AA: acrylic 2HPA: 2-hydroxypropyl acrylate MMA: methyl methacrylate ACMO: N-acryloylmorpholine IBXA: Isobornyl acrylate

[Test example 1] (Measurement of relaxation modulus) The adhesive layers of the adhesive sheets produced in Examples and Comparative Examples were laminated in multiple layers to form a laminated body with a thickness of 0.5 mm. A cylinder with a diameter of 8 mm (height: 0.5 mm) was punched out from the obtained laminate of adhesive layers, and this was used as a sample.

For the above sample, according to JIS K7244-1, a viscoelasticity measuring device (manufactured by Anton Paar, product name "MCR 302") was used to continuously strain the adhesive by 10% under the following conditions to measure Get the relaxation modulus G(t) (MPa). Based on the measurement results, the maximum relaxation modulus G(t) _max (MPa) is deduced. At the same time, the minimum relaxation modulus G(t) _max measured during the period of 3757 seconds is deduced. Relaxation modulus G(t) _min (MPa). Measuring temperature: 25℃ Measuring points: 1000 points (logarithmic graph)

From the obtained maximum relaxation modulus G(t) _max (MPa) and minimum relaxation modulus G(t) _min (MPa), the relaxation modulus variation value ΔlogG(t) is calculated based on the following formula (I). The results are shown in Table 1. ΔlogG(t)=logG(t) _max -logG(t) _min (I)

[Test example 2] (Measurement of creep compliance modulus) The adhesive layers of the adhesive sheets produced in Examples and Comparative Examples were laminated in multiple layers to form a laminated body with a thickness of 0.5 mm. A cylinder with a diameter of 8 mm (height: 0.5 mm) was punched out from the obtained laminate of adhesive layers, and this was used as a sample.

For the above sample, use a viscoelasticity measuring instrument (manufactured by Anton Paar, product name "MCR 302"), continuously apply a stress of 3000Pa under the following conditions, and measure the creep compliance modulus J (t) (MPa ^{- 1} ). Based on the measurement results, the value when a stress of 3000Pa is applied is defined as the minimum creep compliance modulus J (t) _min (MPa ^-1 ), and the minimum creep compliance modulus J (t) _min from the measurement is deduced. The maximum creep compliance modulus J(t) _max (MPa ^-1 ) measured during this period until 3757 seconds elapses thereafter. Measuring temperature: 25℃ Measuring points: 1000 points (logarithmic graph)

According to the obtained minimum creep compliance modulus J (t) _min (MPa ^-1 ) and the maximum creep compliance modulus J (t) _max (MPa ^-1 ), the creep compliance modulus is calculated based on the following formula (II) Change value ΔlogJ(t). The results are shown in Table 1. ΔlogJ(t)=logJ(t) _max -logJ(t) _min (II)

[Test Example 3] (Calculation of product value) The product value (ΔlogG(t)×ΔlogJ(t)) of ΔlogG(t) obtained in Test Example 1 and ΔlogJ(t) obtained in Test Example 2 was calculated. The results are shown in Table 1.

[Test Example 4] (Measurement of dynamic modulus) The adhesive layers of the adhesive sheets produced in Examples and Comparative Examples were laminated in multiple layers to form a laminated body with a thickness of 0.5 mm. A cylinder with a diameter of 8 mm (height: 0.5 mm) was punched out from the obtained laminate of adhesive layers, and this was used as a sample.

For the above sample, according to JIS K7244-1, a viscoelasticity measuring device (manufactured by Anton Paar, product name "MCR 302") was used to measure dynamic viscoelasticity under the following conditions, and the storage mode at 25°C was observed. Number (G') (MPa), loss modulus (G'') (MPa) and loss tangent (tanδ). The results are shown in Table 1. Measuring frequency: 1 Hz Measuring temperature range: -20～150℃

[Test Example 5] (Static bending test) In an environment of 23°C and 50% RH, the light-peelable release sheet was peeled off from the adhesive sheet produced in the Examples and Comparative Examples, and the exposed adhesive layer was bonded to the polyethylene terephthalate on a surface of a film (manufactured by Toray, product name "S10 Lumirror", thickness: 12 μm). Next, the heavy-peel release sheet was peeled off, and the exposed adhesive layer was bonded to another polyethylene terephthalate film (manufactured by Toray, product name "S10 Lumirror", thickness: 12 μm ) on a surface. Then, it was pressurized in an autoclave manufactured by Kurihara Seisakusho Co., Ltd. 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/PET film was cut into 200 mm×50 mm and used as a test piece.

As shown in Figure 3, the obtained test piece was held in a bent state between a holding plate P composed of two upright glass plates (spacing distance: 6 mm) in an environment of 23°C and 50% RH for 24 hours. . After performing this static bending test, as shown in Figure 4, place the test piece on a flat plate, and measure the height h from the surface of the flat plate to the apex of the bent portion (deformed portion) as the static bending deformation amount (deformation at the end of the test) quantity). Based on the measured static bending deformation amount, the static bending properties were evaluated according to the following criteria. Furthermore, in the test piece after the test, it was visually confirmed whether the interface between the adhesive layer and the adherend was peeled off. The results are shown in Table 1. ◎: Deformation is less than 1mm ○: Deformation exceeds 1mm and is less than 3mm △: Deformation exceeds 3mm and is less than 6mm ×: Deformation exceeds 6mm

[Table 1]

As can be seen from Table 1, the adhesive layer of the adhesive sheet of the embodiment has an excellent bending state relaxation effect when two bending members are bonded and kept in a bending state for a long time. [Industrial availability]

The present invention is suitable for laminating one flexible member (for example, various films) constituting a repeated bending device with other flexible members (for example, display elements).

1‧‧‧Adhesive sheet 11‧‧‧Adhesive layer 12a, 12b‧‧‧Peel-off sheet 2‧‧‧Repeated bending of laminated components 21‧‧‧The first bending member 22‧‧‧The second bending member S‧‧‧Test piece P‧‧‧Retaining plate

[Fig. 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. [Fig. 3] is an explanatory diagram (side view) for explaining the static bending test. [Fig. 4] It is an explanatory diagram (side view) for explaining the deformation amount of the test piece as a test result of the bending test.

1‧‧‧Adhesive sheet

11‧‧‧Adhesive layer

12a, 12b‧‧‧Peel-off sheet

Claims (18)

An adhesive for a repetitive bending device, which is an adhesive for bonding one flexible member constituting the repetitive bending device to another flexible member, wherein the adhesive is strained 10 times in accordance with JIS K7244-1 The maximum relaxation modulus value measured at % is defined as the maximum relaxation modulus G(t) _max (MPa), and after measuring the maximum relaxation modulus G(t) _max , continue to strain the aforementioned adhesive by 10% until it passes Until 3757 seconds, the minimum relaxation modulus value measured during this period is defined as the minimum relaxation modulus G(t) _min (MPa). The relaxation modulus change value △logG(t) is calculated according to the following formula (I), and The value of the creep compliance modulus measured when a stress of 3000Pa is applied to the aforementioned adhesive is defined as the minimum creep compliance modulus J(t) _min (MPa ^-1 ), and when the aforementioned minimum creep compliance modulus J ( After t) _min , continue to apply a stress of 3000Pa until 3757 seconds have passed. The maximum creep compliance modulus value measured during this period is defined as the maximum creep compliance modulus J(t) _max (MPa ^-1 ), which is expressed by the following formula (II) Calculate the creep compliance modulus change value ΔlogJ(t), and the product value of the relaxation modulus change value ΔlogG(t) and the creep compliance modulus change value ΔlogJ(t) is 3 or less △ logG(t)=log G(t) _max -log G(t) _min (I) △logJ(t)=log J(t) _max -log J(t) _min (II). For example, in the adhesive for repetitive bending devices described in item 1 of the patent application, the aforementioned relaxation modulus change value ΔlogG(t) is 1.1 or less. For example, in the adhesive for repetitive bending devices described in item 1 of the patent application, the creep compliance modulus change value ΔlogJ(t) is less than 2.82. The adhesive for repetitive bending devices as described in item 1 of the patent application, wherein the aforementioned The storage modulus (G’) of the adhesive at 25°C is between 0.01MPa and 0.098MPa. The adhesive for repetitive bending devices described in item 1 of the patent application, wherein the loss modulus (G”) of the adhesive at 25°C is between 0.005MPa and 0.1MPa. The adhesive for a repetitive bending device as described in item 1 of the patent application, wherein the loss tangent (tanδ) of the adhesive at 25°C is between 0.25 and 0.85. The adhesive for repetitive bending devices as described in item 1 of the patent application, wherein the adhesive is a cross-linked adhesive composition containing a (meth)acrylate polymer (A) and a cross-linking agent (B). Obtained adhesive. The adhesive for repetitive bending devices as described in Item 7 of the patent application, wherein the aforementioned (meth)acrylate polymer (A), as the constituent monomer unit of the polymer, has an alkyl group with a carbon number of 1 to 20 alkyl (meth)acrylates, and containing: a low-Tg alkyl acrylate with a glass transition temperature (Tg) of -40°C or less as a homopolymer, and a homopolymer with a glass transition temperature (Tg) of -40°C or lower High Tg alkyl acrylates with temperatures (Tg) above 0°C. The adhesive for repetitive bending devices as described in Item 7 of the patent application, wherein the aforementioned (meth)acrylate polymer (A), as a constituent monomer unit of the polymer, contains: a hydroxyl group in the molecule Monomers with reactive functional groups, and monomers with reactive functional groups that are carboxyl groups in the molecule. The adhesive for repetitive bending devices as described in Item 7 of the patent application, wherein the aforementioned (meth)acrylate polymer (A), as the constituent monomer unit of the polymer, has an alkyl group with a carbon number of 1 to 20 alkyl (meth)acrylates, and containing 50% by mass or more and 98% by mass or less of a low-Tg alkyl acrylate as a homopolymer with a glass transition temperature (Tg) of -40°C or less . The adhesive for repetitive bending devices as described in item 7 of the patent application, wherein The content of the cross-linking agent (B) in the adhesive composition is 0.23 parts by mass or more and 10 parts by mass or less based on 100 parts by mass of the (meth)acrylate polymer (A). In the adhesive for repetitive bending devices described in Item 7 of the patent application, the weight average molecular weight of the (meth)acrylate polymer (A) is between 100,000 and 1.5 million. An adhesive sheet, which is an adhesive sheet having an adhesive layer for bonding one bending member constituting a repetitive bending device with other bending members, wherein the aforementioned adhesive layer is composed of items 1 to 12 of the patent application. The repetitive bending device described in any one of the above items is formed of adhesive. The adhesive sheet described in claim 13, wherein the adhesive sheet has two release sheets, and the adhesive layer is sandwiched by the release sheets in such a manner that it contacts the release surfaces of the two release sheets. For example, in the adhesive sheet described in Item 13 of the patent application, the thickness of the adhesive layer is between 2 μm and 70 μm. A repeatedly bendable laminated member, which is a repeatedly bendable laminated member including one bendable member and other bendable members constituting a repeatable bending device, and an adhesive layer bonding the one bendable member and the other bendable members to each other, The aforementioned adhesive layer is the adhesive layer of the adhesive sheet described in Item 13 of the patent application. As claimed in claim 16 of the patent application, at least one of the aforementioned one flexible member and the aforementioned other flexible members is a display element. A repeated bending device is provided with a repeatedly bent laminated member as described in Item 16 of the patent application.