TWI809001B - Adhesive for repetitive bending device, adhesive sheet, repetitive bending laminated member, and repetitive bending device - Google Patents

Abstract

[Problem] To provide an adhesive for a repetitive bending device and an adhesive sheet that can suppress the interface between the adhesive layer and the adherend from floating or peeling even when it is applied to a repetitive bending device and repeatedly bent, and Provided are a repeatedly-bending laminated member and a repeatedly-bending device capable of suppressing floating or peeling of the interface between an adhesive layer and an adherend even when it is repeatedly bent. [Solution] An adhesive for a repetitive bending device, which is an adhesive for a repetitive bending device for bonding one flexible member 21 and another flexible member 22 constituting the repetitive bending device, wherein The ratio of the maximum shear stress when one surface and the other surface of the formed adhesive layer are displaced by 1000% in opposite directions to the shear stress after 60 seconds from the displacement of 1000% is 72% or less, The gel fraction is not less than 40% and not more than 90%.

Description

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

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 electronic equipment as a device. Such a flexible display, for example, can be bent and installed on a cylindrical column to be used as a fixed display, or it can be folded or rolled and carried to be used as a portable display, and its wide range of uses has attracted much attention. expect.

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

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

A curved display sometimes bends (folds) repeatedly rather than being shaped into a curved surface just once. When a conventional adhesive sheet is used in such a repetitive bending device, problems such as floating and peeling of the interface between the adhesive layer and the adherend arise.

Patent Document 3 discloses a laminate whose object is to suppress the floating or peeling of the adhesive layer even after repeated bending, but the effect is not necessarily sufficient. [Prior art literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 2015-174907 [Patent Document 2] Japanese Patent Laid-Open No. 2016-774 [Patent Document 3] Japanese Patent Laid-Open No. 2017-65217

[Problems to be Solved by the Invention]

The present invention was made in view of the above-mentioned circumstances, and an object thereof is to provide an adhesive for a repetitive bending device and an adhesive sheet that can prevent the adhesive layer from being adhered to the adherend even when it is applied to a repetitive bending device and repeatedly bent. floating, peeling, etc. at the interface between objects, and to provide a repeatedly bending laminated member and a repeatedly bending device capable of suppressing floating at the interface between the adhesive layer and the adherend even when it is repeatedly bent. Lifting, stripping, etc. [Means used to solve the problem]

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 bonding one flexible member constituting the repetitive bending device to another flexible member, wherein the opposite Ratio of the maximum shear stress when one surface and the other surface of the adhesive layer formed by the aforementioned adhesive are displaced 1000% in opposite directions to each other, and the ratio of the shear stress after 60 seconds from the aforementioned displacement of 1000% It is 72% or less, and the gel fraction is 40% or more and 90% or less (Invention 1).

The adhesive according to the above invention (Invention 1) has excellent shear stress relaxation properties due to its small shear stress residual rate as described above. Therefore, for a laminate formed of one flexible member, another flexible member, and an adhesive layer composed of the above-mentioned adhesive bonded to each other, even if the bent state and the non-bent state are repeated, the above-mentioned adhesive Layers can also easily conform to flexible members in both states. Furthermore, according to the above-mentioned invention (Invention 1), since it has a relatively high gel fraction as described above, it can exhibit a suitable cohesive force capable of withstanding repeated bending. As a result, when the above-mentioned laminate is repeatedly bent, it is possible to suppress the problem of floating or peeling at the interface between the adhesive layer and the flexible member.

In the above invention (Invention 1), the storage modulus G' at 23°C is preferably not less than 0.005 MPa and not more than 0.15 MPa (Invention 2).

In the above inventions (Inventions 1 and 2), the adhesive is preferably an adhesive obtained by crosslinking an adhesive composition containing a (meth)acrylate polymer (A) and a crosslinking agent (B). (Invention 3).

Second, the present invention provides an adhesive sheet having an adhesive layer for attaching one flexible member constituting a repeating bending device to another bending member, wherein the adhesive layer is formed by the repeating bending device. Formed (Invention 4) with an adhesive (Inventions 1-3).

In the above invention (Invention 4), the adhesive force of the adhesive sheet to soda-lime glass is preferably 3 N/25 mm or more and 100 N/25 mm or less (Invention 5).

In the above inventions (Inventions 4 and 5), it is preferable that the adhesive sheet includes two release sheets, and the adhesive layer is sandwiched by the release sheets so as to contact the release surfaces of the two release sheets (Invention 6). ).

Thirdly, the present invention provides a repetitive bending laminated member comprising one flexible member and other flexible members constituting a repetitive bending device, and an adhesive layer for bonding the one flexible member and the other flexible member to each other. A repeatedly bending laminated member, wherein the adhesive layer is the adhesive layer (Invention 7) of the aforementioned adhesive sheet (Inventions 4-6).

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).

Fourth, the present invention provides a repetitive bending device including the aforementioned repetitive bending laminated member (Inventions 7 and 8) (Invention 9). [Effect of the present invention]

According to the adhesive for a repetitive bending device and the adhesive sheet of the present invention, even when applied to a repetitive bending device and repeatedly bent, it is possible to suppress the interface between the adhesive layer and an adherend from being lifted or peeled off. Furthermore, according to the repeatedly bending laminated member and the repetitive bending device of the present invention, even when it is repeatedly bent, it is possible to suppress the interface between the adhesive layer and the adherend from being lifted or peeled off.

Hereinafter, embodiments of the present invention will be described. [Adhesives for repetitive bending devices] The adhesive for a repetitive bending device (hereinafter sometimes simply referred to as "adhesive") according to the present embodiment is an adhesive for bonding one flexible member constituting the repetitive bending device to another flexible member. The repeated bending device and the bending member will be described in detail later.

According to the adhesive of the present embodiment, the maximum shear stress (σ _max ) when the one surface and the other surface of the adhesive layer formed by the aforementioned adhesive are displaced in directions opposite to each other by 1000% is obtained from the aforementioned The shear stress (σ ₆₀ ) ratio ((σ ₆₀ /σ _max )×100) after 60 seconds at a displacement of 1000% is 72% or less, and the gel fraction is 40% or more and 90% or less. Here, the displacement of 1000% refers to the displacement amount when the thickness of the adhesive is displaced by 10 times. In addition, in this specification, the ratio of the said shear stress may be called "shear stress residual ratio" sometimes. The measurement methods of the shear stress and the gel fraction are as shown in the test examples described later.

According to the adhesive of this embodiment, since it has the low shear stress residual rate as mentioned above, it can have excellent shear stress relaxation property. In the case of bending a laminate formed of one flexible member, other flexible members, and an adhesive for laminating them, the flexible member located outside the bend and the bendable member located inside the bend, The curvatures of the curved portions thereof are different, and thus become in a positional relationship offset from each other. Therefore, shear stress is generated in the adhesive layer bonded to these flexible members. As described above, according to the adhesive of the present embodiment, the adhesive layer has excellent shear stress relaxation property, so even if the bent state and the non-bent state are repeated, the adhesive layer can easily conform to the flexible member in both states. Moreover, according to the adhesive of the present embodiment, since it has a relatively high gel fraction as described above, it can exhibit a suitable cohesive force capable of withstanding repeated bending. As a result, when the above-mentioned laminate is repeatedly bent, problems such as floating and peeling at the interface between the adhesive layer and the flexible member can be suppressed. As described above, according to the adhesive of this embodiment, even when it is applied to a repetitive bending device and repeatedly bent, it is possible to suppress the occurrence of floating and peeling at the interface between the adhesive layer and the adherend. question. In addition, 30,000 times can be illustrated as an example as the number of times of the above-mentioned repeated bending.

From the standpoint of suppressing lifting and peeling, the shear stress residual ratio is preferably at most 72%, particularly preferably at most 66%, and more preferably at most 64%. In addition, the lower limit of the shear stress residual rate is not particularly limited, but usually it is preferably at least 10%, particularly preferably at least 30%, and more preferably at least 42%.

If the gel fraction of the adhesive according to the present embodiment is less than 40%, the cohesive force of the adhesive layer is insufficient, and the adhesive or components constituting the adhesive tend to bleed out from the bent end during repeated bending. Furthermore, if the gel fraction of the adhesive according to this embodiment exceeds 90%, the flexibility of the adhesive layer will decrease, and the interface between the adhesive layer and the adherend will easily occur due to repeated bending. Problems with floating or peeling occur. From such a viewpoint, the lower limit of the gel fraction of the adhesive according to the present embodiment is preferably 40% or more, particularly preferably 44% or more, and more preferably 48% or more. Furthermore, the upper limit of the aforementioned gel fraction is 90% or less, preferably 80% or less, particularly preferably 72% or less.

The type of adhesive according to the present embodiment is not particularly limited as long as it satisfies the above physical properties, and examples thereof include acrylic adhesives, polyester adhesives, polyurethane adhesives, rubber adhesives, silicone ( Silicone) is any kind of adhesive, etc. Furthermore, the above-mentioned adhesive may be any of emulsion type, solvent type, or solvent-free type, and may also be of any type of crosslinking type or non-crosslinking type. Among them, an acrylic adhesive that easily satisfies the above physical properties and has excellent adhesive properties, optical properties, and the like is preferable.

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 crosslinking agent (B). Crosslink the resulting adhesive. Such an adhesive can easily satisfy the above-mentioned 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 the adhesive composition P (1-1) (meth)acrylate polymer (A) The (meth)acrylate polymer (A) is composed of a monomer (monomer containing a reactive functional group) containing an alkyl (meth)acrylate and a reactive functional group in the molecule. Single unit is preferred.

Since (meth)acrylate polymer (A) contains an alkyl (meth)acrylate as a monomer unit which comprises this polymer, it can produce favorable adhesiveness. As the alkyl (meth)acrylate, an alkyl (meth)acrylate having an alkyl group having 2 to 20 carbon atoms is preferable. The alkyl group may be linear or branched, and may have a cyclic structure.

Alkyl (meth)acrylate having 2 to 20 carbon atoms as an alkyl group and a homopolymer (homopolymer) having a glass transition temperature (Tg) of -40°C or lower (hereinafter sometimes referred to as "" Low Tg alkyl acrylate (alkyl acrylate) is preferred. By containing such a low Tg alkyl acrylate as a constituent monomer unit, the flexibility of the adhesive obtained can be improved.

Examples of low Tg alkyl acrylates include, for example, n-butyl acrylate (Tg is -55°C), n-octyl acrylate (Tg is -65°C), isooctyl acrylate (Tg is -58°C), ), 2-ethylhexyl acrylate (Tg is -70°C), isononyl acrylate (Tg is -58°C), isodecyl acrylate (Tg is -60°C), isodecyl methacrylate (Tg is -60°C), isodecyl methacrylate (Tg is -58°C), -41°C), n-dodecyl methacrylate (Tg is -65°C), tridecyl acrylate (Tg is -55°C), tridecyl methacrylate (Tg is -40°C )wait. Among them, from the viewpoint of more effectively improving flexibility, as the low-Tg alkyl acrylate, the Tg of the homopolymer is preferably -45°C or lower, and particularly preferably -50°C or lower. Specifically, n-butyl acrylate and 2-ethylhexyl acrylate are particularly preferred. These 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 lower limit value of the low Tg alkyl acrylate is preferably 30% by mass or more, particularly 40% by mass. % or more is preferable, and it is more preferable to contain 50 mass % or more. By containing the above-mentioned low-Tg alkyl acrylate in the above-mentioned content, the flexibility of the adhesive obtained can be favorably improved, and the shear stress residual rate can be further reduced.

Furthermore, in the (meth)acrylate polymer (A), as the monomer unit constituting the polymer, the upper limit value of the above-mentioned low Tg alkyl acrylate is preferably 97% by mass or less, especially It is preferably at most 92% by mass, more preferably at most 87% by mass. An appropriate amount of other monomer components (especially reactive functional group-containing monomers) can be introduced into the (meth)acrylate polymer (A) by containing the above-mentioned low-Tg alkyl acrylate in the above-mentioned content.

Furthermore, the (meth)acrylate polymer (A) is preferably used in combination with a monomer whose glass transition temperature (Tg) exceeds 0°C as a homopolymer (hereinafter sometimes referred to as "high Tg alkyl acrylate" ) as a monomer unit constituting the polymer. Thereby, appropriate cohesiveness can be imparted to the obtained adhesive, and durability can be improved.

Examples of the above-mentioned high Tg alkyl acrylates include methyl acrylate (Tg: 10°C), methyl methacrylate (Tg: 105°C), ethyl methacrylate (Tg: 65°C), methyl N-butyl acrylate (Tg is 20°C), isobutyl methacrylate (Tg is 48°C), tertiary butyl methacrylate (Tg is 107°C), n-octadecyl acrylate (Tg is 30°C) ℃), n-octadecyl methacrylate (Tg is 38 ℃), cyclohexyl acrylate (Tg is 15 ℃), cyclohexyl methacrylate (Tg is 66 ℃), phenoxyethyl acrylate ( Tg is 5°C), phenoxyethyl methacrylate (Tg is 54°C), benzyl methacrylate (Tg is 54°C), isocamphoryl acrylate (Tg is 94°C), isobornyl methacrylate (Tg: 180°C), adamantyl acrylate (Tg: 115°C), adamantyl methacrylate (Tg: 141°C), acrylic acid (Tg: 103°C) and other acrylic monomers, vinyl acetate (Tg is 32°C), styrene (Tg is 80°C), etc. Among them, isobornyl acrylate is preferable from the viewpoint of being able to impart appropriate cohesiveness and adhesiveness to the adhesive while having a high glass transition temperature. In addition, the above-mentioned high Tg alkyl acrylate does not include monomers containing nitrogen atoms described later.

When the (meth)acrylate polymer (A) contains the above-mentioned high Tg alkyl acrylate as a monomer unit constituting the polymer, it is preferable that the above-mentioned high Tg alkyl acrylate contains 1% by mass or more, It is especially preferable to contain 3 mass % or more, and it is more preferable to contain 5 mass % or more. Furthermore, in the (meth)acrylate polymer (A), as a monomer unit constituting the polymer, the above-mentioned high Tg alkyl acrylate is preferably contained in an amount of 30% by mass or less, particularly 20% by mass. The following is preferable, and it is more preferable to contain 12 mass % or less. By using the above content of high Tg alkyl acrylate and low Tg alkyl acrylate in combination, the obtained adhesive exhibits suitable cohesiveness and flexibility, and becomes easy to meet the required durability and shear stress residual rate.

The (meth)acrylate polymer (A) contains a reactive functional group-containing monomer as a monomer unit constituting the polymer, and through the reactive functional group derived from the reactive functional group-containing monomer group, react with the cross-linking agent (B) described later, thereby forming a cross-linking structure (three-dimensional network structure), and then obtaining an adhesive with the desired cohesion. This adhesive becomes easy to satisfy the aforementioned gel fraction.

(Meth)acrylate polymer (A), as the reactive functional group-containing monomer contained in the monomer unit constituting the polymer, preferably, monomers having hydroxyl groups in the molecule (hydroxyl-containing monomers) body), 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.

Among the above-mentioned reactive functional group-containing monomers, hydroxyl-containing monomers and carboxyl-containing monomers are preferred, and the hydroxyl-containing monomers are used alone, or the hydroxyl-containing monomers and carboxyl-containing monomers are used in combination. The body is excellent. Hydroxyl-containing monomers are easy to maintain the high flexibility of the obtained (meth)acrylate polymer (A), while carboxyl-containing monomers can improve the obtained (meth)acrylate polymer (A). of adhesion.

Examples of hydroxyl-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, (meth) Hydroxyalkyl (meth)acrylates, such as 2-hydroxybutyl acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, etc. Among them, from the viewpoint of the flexibility of the obtained (meth)acrylate polymer (A), 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are used as good. These 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 obtained (meth)acrylate polymer (A). These 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 lower limit value of the reactive functional group-containing monomer is preferably 1% by mass or more, especially It is preferably at least 3% by mass, and more preferably at least 5% by mass. Furthermore, in the (meth)acrylate polymer (A), as the monomer unit constituting the polymer, the upper limit of the reactive functional group-containing monomer is preferably 30% by mass or less, especially It is preferably at most 25% by mass, more preferably at most 20% by mass. When the (meth)acrylate polymer (A) contains the above-mentioned reactive functional group-containing monomer as a monomer unit, the obtained adhesive has Appropriate cohesion, and it becomes easy to satisfy the aforementioned gel fraction.

The (meth)acrylate polymer (A) preferably does not contain a carboxyl group-containing monomer as a monomer unit constituting the polymer. Since the carboxyl group is an acid component, by not including a carboxyl group-containing monomer, even if there are substances that cause problems due to acid in the object to be attached by the adhesive (for example, transparent conductive materials such as tin-doped indium oxide (ITO), etc. film, metal film, metal mesh, etc.), can also suppress the problems (corrosion, resistance value change, etc.) caused by the above substances caused by acid.

Here, the so-called "excluding carboxyl group-containing monomers" means that carboxyl group-containing monomers are basically not included, and in addition to completely excluding carboxyl group-containing monomers, the Carboxyl group-containing monomers are included to the extent that the transparent conductive film or metal wiring etc. are corroded. Specifically, in the (meth)acrylate polymer (A), as a monomer unit, the content of the carboxyl group-containing monomer can be allowed to be 0.1% by mass or less, preferably 0.01% by mass or less, and further preferably 0.01% by mass or less. More preferably, it is 0.001 mass % or less.

The above-mentioned (meth)acrylate polymer (A) preferably contains a nitrogen atom-containing monomer as a monomer unit constituting the polymer. The cohesion of the adhesive can be improved by the presence of monomers containing nitrogen atoms as constituent units in the polymer. In particular, the above-mentioned (meth)acrylate polymer (A) preferably uses the above-mentioned high-Tg alkyl acrylate and a nitrogen-atom-containing monomer in combination as a monomer unit constituting the polymer. Thereby, the cohesiveness of the adhesive obtained can be improved, and durability can be further improved.

As the nitrogen atom-containing monomer, a monomer having a nitrogen-containing heterocyclic ring is preferable from the viewpoint that the (meth)acrylate polymer (A) has appropriate rigidity. As a monomer having a nitrogen-containing heterocycle, for example, N-(meth)acryloyl morpholine (N-(meth)acryloyl morpholine), N-vinyl-2-pyrrolidone (N-vinyl- 2-pyrrolidone), N-(meth)acryloyl pyrrolidone (N-(meth)acryloyl pyrrolidone), N-(meth)acryloyl piperidine (N-(meth)acryloyl piperidine), N-(meth)acryloyl piperidine Base) acryloylpyrrolidine (N-(meth)acryloylpyrrolidine), N-(meth)acryloyl aziridine (N-(meth)acryloyl aziridine), (meth)acryloyl aziridine ethyl ester (aziridinyl ethyl (meth)acrylate), 2-vinylpyridine (2-vinylpyridine), 4-vinylpyridine, 2-vinylpyrazine (2-(vinylpyrazine)), 1-vinyl imidazole (1-vinyl imidazole) , N-vinyl carbazole (N-vinyl carbazole), N-vinyl phthalimide (N-vinylphthalimide), etc., which can make the obtained adhesive exhibit more excellent adhesion and proper N-(methyl)acryloylmorpholine is the best cohesive force, especially N-acryloylmorpholine. The above materials may be used alone or in combination of two or more.

When the (meth)acrylate polymer (A) contains a nitrogen-atom-containing monomer as a monomer unit constituting the polymer, the above-mentioned nitrogen-atom-containing monomer preferably contains 0.5% by mass or more, It is especially preferable to contain 1 mass % or more, and it is more preferable to contain 3 mass % or more. Furthermore, in the (meth)acrylate polymer (A), as a monomer unit constituting the polymer, the above-mentioned nitrogen-atom-containing monomer preferably contains 20% by mass or less, particularly 15% by mass or less. Preferably, it is more preferable to contain 10 mass % or less. When the content of the nitrogen atom-containing monomer is within the above range, the obtained adhesive has high cohesion and excellent adhesion. In particular, when using a nitrogen atom-containing monomer and a high Tg alkyl acrylate in combination, when the content of the nitrogen atom-containing monomer is within the above range, the cohesiveness of the obtained adhesive becomes better, And it is easy to satisfy the above-mentioned gel fraction, and it becomes to have more excellent durability.

The (meth)acrylate polymer (A) may also contain other monomers as monomer units constituting the polymer, if necessary. As other monomers, monomers not containing a reactive functional group are preferred so as not to interfere with the aforementioned action of the reactive functional group-containing monomer. Examples of the aforementioned monomers include alkoxyalkyl (meth)acrylates such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate, vinyl acetate, Styrene etc. These materials may be used alone or in combination of two or more.

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

The lower limit of the weight average molecular weight of the (meth)acrylate polymer (A) is preferably at least 200,000, particularly preferably at least 400,000, and more preferably at least 600,000. When the lower limit of the weight average molecular weight of the (meth)acrylate polymer (A) is as described above, it is easy to satisfy the aforementioned gel fraction, and the durability of the adhesive becomes more excellent. In addition, in this specification, a weight average molecular weight is a standard polystyrene conversion value measured by the gel permeation chromatography (GPC) method.

In addition, the upper limit of the weight average molecular weight of the (meth)acrylate polymer (A) is preferably 2 million or less, particularly preferably 1.5 million or less, further preferably 900,000 or less. If the upper limit of the weight-average molecular weight of the (meth)acrylate polymer (A) is as described above, the obtained adhesive becomes more excellent in flexibility, and the shear stress residual rate of the adhesive is further reduced. .

In the adhesive composition P, (meth)acrylate polymer (A) may be used individually by 1 type, and may use it in combination of 2 or more types.

(1-2) Cross-linking agent (B) The crosslinking agent (B), by heating the adhesive composition P containing the crosslinking agent (B) as a trigger (trigger), crosslinks the (meth)acrylate polymer (A) to form a three-dimensional grid. Thereby, the cohesive force of the obtained adhesive is improved, and it is easy to satisfy the aforementioned gel fraction, and the adhesive layer has excellent durability.

As the crosslinking agent (B), any one can react with the reactive group of the (meth)acrylate polymer (A), for example, isocyanate crosslinking agent, epoxy Crosslinking agent based on amine, crosslinking agent based on amine, crosslinking agent based on melamine, crosslinking agent based on aziridine, crosslinking agent based on hydrazine, crosslinking agent based on aldehyde, crosslinking agent based on oxazoline Crosslinking agent, metal alkoxide type crosslinking agent, metal chelate type crosslinking agent, metal salt type crosslinking agent, ammonium salt type crosslinking agent, etc. Among the above, it is preferable to use an isocyanate-based crosslinking agent excellent in reactivity with a reactive functional group-containing monomer. In addition, as the crosslinking agent (B), one type may be used alone, or two or more types may be used in combination.

The isocyanate crosslinking agent contains at least a polyisocyanate (polyisocyanate) compound. Examples of polyvalent isocyanate compounds include aromatic polyvalent isocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate, and hexamethylene diisocyanate. Aliphatic polyvalent isocyanate such as hexamethylene diisocyanate, isophorone diisocyanate (isophorone diisocyanate), alicyclic polyvalent isocyanate such as hydrogenated diphenylmethane diisocyanate, etc., and the above-mentioned biuret (biuret) , or isocyanurate (isocyanurate) body, and the product-adduct of the reaction with low-molecular-weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil ( adduct) and so on. Among them, from the viewpoint of reactivity with hydroxyl groups, trimethylolpropane-modified aromatic polyvalent isocyanate, especially trimethylolpropane-modified toluene diisocyanate and trimethylolpropane-modified Xylyl diisocyanate is preferred.

The lower limit of the content of the crosslinking agent (B) in the adhesive composition P is preferably 0.01 parts by mass or more, particularly 0.06 parts by mass, based on 100 parts by mass of the (meth)acrylate polymer (A). It is preferably at least one part by mass, and more preferably at least 0.12 parts by mass. When the lower limit of the content of the crosslinking agent (B) is the above-mentioned value, the obtained adhesive has a suitable cohesive force and becomes easy to satisfy the aforementioned gel fraction. Furthermore, the upper limit of the content is preferably not more than 10 parts by mass, more preferably not more than 5 parts by mass, especially preferably not more than 3 parts by mass, and more preferably not more than 2 parts by mass. When the upper limit of the content of the crosslinking agent (B) is the above-mentioned value, the obtained adhesive can exhibit appropriate cohesiveness and flexibility, and becomes easy to satisfy the required durability and shear stress residual rate .

Furthermore, with regard to the content of the crosslinking agent (B) in the adhesive composition P, in 100 parts by mass of the (meth)acrylate polymer (A), relative to the content of the (meth)acrylate polymer as the constituent (meth)acrylate polymer The ratio of the mass of the reactive functional group-containing monomer of the monomer unit of the object (A) to the mass of the crosslinking agent (B) is preferably 0.001 or more, especially 0.005 or more, and further preferably 0.015 or more. better. In addition, this ratio is preferably 0.12 or less, particularly preferably 0.11 or less, further more preferably 0.1 or less. When the content of the crosslinking agent (B) is within the above range, the obtained adhesive has a suitable crosslinking structure and is easy to satisfy the aforementioned gel fraction.

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

The adhesive composition P preferably contains the above-mentioned silane coupling agent. Thereby, in the obtained adhesive layer, the adhesiveness with the flexible member which is an adherend improves, and durability becomes more excellent.

As the silane coupling agent, it is preferred that it is an organosilicon compound having at least one alkoxysilyl group (alkoxysilyl) in the molecule, and it has good compatibility with (meth)acrylate polymer (A) and Coupled with light-transmitting objects.

Examples of such silane coupling agents include polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxytrimethoxysilane, 3-Glycidoxypropyltrimethoxysilane (3-glycidoxypropyltrimethoxysilane), 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and other silicon compounds with epoxy structure, 3-mercaptopropyl mercapto-containing silicon compounds such as trimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyldimethoxymethylsilane, 3-aminopropyltrimethoxysilane, N- (2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, etc. Silicon compound, 3-chloropropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane (3-isocyanatopropyltriethoxysilane), or at least one of the above with methyltriethoxysilane, ethyltriethoxysilane Condensates of alkyl-containing silicon compounds such as silane, methyltrimethoxysilane, ethyltrimethoxysilane, etc. The above materials may be used alone or in combination of two or more.

The content of the silane coupling agent in the adhesive composition P is preferably at least 0.01 parts by mass, particularly preferably at least 0.05 parts by mass, and further preferably at least 0.05 parts by mass relative to 100 parts by mass of the (meth)acrylate polymer (A). More preferably, it is 0.1 mass part or more. Furthermore, the content is preferably not more than 1 part by mass, particularly preferably not more than 0.5 part by mass, and more preferably not more than 0.3 part by mass. When the content of the silane coupling agent is within the above range, the obtained adhesive tends to exert appropriate adhesive force, and the adhesiveness between the adhesive and the flexible member as the adherend becomes better.

(2) Preparation of Adhesive Composition P The (meth)acrylate polymer (A) is prepared, and the obtained (meth)acrylate polymer (A) is mixed with the crosslinking agent (B), and additives may be added as needed, thereby producing Adhesive composition P.

The (meth)acrylate polymer (A) can be produced by superposing|polymerizing the mixture of the monomer which comprises a polymer by a general radical (radical) polymerization method. It is preferable to perform superposition|polymerization of a (meth)acrylate polymer (A) by the solution polymerization method using a polymerization initiator as needed. 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 of them may be used in combination.

Examples of the polymerization initiator include azo (azo) compounds, organic peroxides, and the like, and two or more of them may be used in combination. Examples of the azo compound include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis( Cyclohexane (1-carbonitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxy ylvaleronitrile), 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 benzoyl peroxide, tert-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate ester, bis(2-ethoxyethyl) peroxydicarbonate, tert-butyl peroxyneodecanoate, tert-butyl peroxypivalate, (3,5,5-trimethylhexyl base) peroxide, diacryl peroxide, diacetyl peroxide, etc.

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

When the (meth)acrylate polymer (A) is obtained, the crosslinking agent (B) and additives and diluting solvents are added to the solution of the (meth)acrylate polymer (A) according to the Mixing and further obtaining the adhesive composition P (coating solution) diluted with a solvent.

In addition, in the case of using any one of the above-mentioned components in solid form, or in the case where precipitation occurs when mixed with other components in an undiluted state, it is also possible to dissolve or dilute this component alone in a diluent solvent in advance, and then mixed with the other ingredients mentioned above.

As the diluting solvent, for example, aliphatic hydrocarbons such as hexane, heptane, and cyclohexane, aromatic hydrocarbons such as toluene and xylene, halogenated dichloromethane, 1,2-dichloroethane, etc. Alcohols such as hydrocarbons, 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 solvents such as ethyl cellosolve, and the like.

The concentration and viscosity of the coating solution prepared in the above manner are not particularly limited as long as they are within the range where coating is possible, 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 a coating solution, addition of a diluent solvent etc. is not an essential requirement, If the adhesive composition P has the viscosity etc. which can apply|coat, it is not necessary to add a diluent solvent. In this case, the adhesive composition P is a coating solution in which the polymerization solvent of the (meth)acrylate polymer (A) is directly used as a dilution solvent.

(3) Preparation of adhesive The adhesive according to the present embodiment is preferably an adhesive obtained by crosslinking the adhesive composition P. The 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 at the same time to volatilize the dilution solvent or the like from the coating film of the adhesive composition P applied on the desired object.

The heating temperature of the heat treatment is preferably 50-150°C, especially 70-120°C. Furthermore, the heating time is preferably 10 seconds to 10 minutes, especially 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 be provided as needed. In the case where this curing period is required, the adhesive is formed after the curing period passes, 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 by the cross-linking agent (B), thereby forming a cross-linked structure to obtain an adhesive. Such an adhesive is easy to satisfy the aforementioned gel fraction and has a predetermined cohesive force.

(4) Physical properties of the adhesive The lower limit of the storage modulus G' at 23°C of the adhesive according to this embodiment is preferably 0.005 MPa or more, particularly 0.01 MPa or more, and more preferably 0.02 MPa or more. Furthermore, the upper limit of the storage modulus G' is preferably not more than 0.15 MPa, especially not more than 0.10 MPa, and more preferably not more than 0.07 MPa. When the storage modulus G' is within the above range, the adhesive tends to have appropriate cohesion and flexibility, and when the repeated bending device is repeatedly bent, the adhesion between the adhesive layer and the flexible member can be more effectively suppressed. There is a problem of floating or peeling at the interface between them.

[adhesive sheet] According to the adhesive sheet according to this embodiment, the adhesive is used for bonding one flexible member constituting the repeated bending device to the other flexible member, and the adhesive layer is formed of the aforementioned 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 , according to an adhesive sheet 1 according to one embodiment, the two release sheets 12a and 12b are bonded by the two release sheets 12a and 12b so as to contact the release surfaces of the two release sheets 12a and 12b. It is composed of sandwiched adhesive layer 11. In addition, the release surface of the release sheet in this specification refers to the surface having releasability in the release sheet, and includes a surface subjected to a release treatment and a surface that exhibits releasability even without a release treatment.

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

The thickness of the adhesive layer 11 in the adhesive sheet 1 according to the present embodiment (value measured in accordance with JIS K 7130) is preferably at least 3 μm, particularly preferably at least 5 μm, and further preferably at least 10 μm. The above is better. When the lower limit of the thickness of the adhesive layer 11 is the above-mentioned value, it is easy to exhibit a desired adhesive force, and it is possible to more effectively suppress problems of floating or peeling during repeated bending. Furthermore, the upper limit of the thickness of the adhesive layer 11 is preferably 300 μm or less, more preferably 200 μm or less, particularly preferably 100 μm or less, and from the viewpoint of obtaining a thinner repetitive bending device , and further preferably less than 75 μm. When the upper limit of the thickness of the adhesive layer 11 is the above value, it is possible to suppress the problem of the adhesive or components constituting the adhesive bleeding from the adhesive layer due to repeated bending. In addition, the adhesive layer 11 may be formed as a single layer, or may be laminated and formed as a multilayer.

(1-2) Peeling sheet The peeling sheets 12 a and 12 b protect the adhesive layer 11 before the adhesive sheet 1 is used, and are peeled when the adhesive sheet 1 (adhesive layer 11 ) is used. 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, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, poly 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, crosslinked films of the above materials may also be used. Furthermore, laminated films of the above materials can also be used.

The release surfaces of the release sheets 12a and 12b (particularly, the surfaces in contact with the adhesive layer 11) are preferably subjected to release treatment. Examples of the release agent used in the release treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents. 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 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 (Haze) value The haze value of the adhesive layer 11 of the adhesive sheet 1 according to this embodiment is preferably 2% or less, more preferably 1% or less, particularly preferably 0.5% or less, and more preferably 0.3% or less. . When the haze value of the adhesive layer 11 is 2% or less, the transparency is very high, and it is suitable for optical applications (for display devices). 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 3N/25mm or more, particularly preferably 9N/25mm or more, and furthermore, 20N /25mm or more is better. When the lower limit of the adhesive force of the adhesive sheet 1 is the above numerical value, it is possible to more effectively suppress problems such as lifting and peeling during repeated bending. On the other hand, the upper limit of the above-mentioned adhesive force is not particularly limited. Usually, it is preferably below 100N/25mm, and preferably below 75N/25mm. The weight of the adhesive sheet that can be reattached when the adhesive sheet is misfit From the viewpoint of workability (rework), 50 N/25 mm or less is particularly preferable. In addition, the above-mentioned adhesive force is basically the adhesive force measured according to the 180-degree peeling method of JIS Z 0237:2009, and the specific test method is shown in the test example described later.

(3) Manufacture of adhesive sheets As a manufacturing example of the adhesive sheet 1, the case where the said adhesive composition P is used is demonstrated. A coating solution of the adhesive composition P is applied to the peeling surface of one peeling sheet 12a (or 12b), heat-treated so that the adhesive composition P is thermally crosslinked to form a coating layer, and the other sheet is peeled off. The release side of the sheet 12b (or 12a) is superimposed on this coating layer. When a curing period is required, the adhesive layer 11 is formed by placing the coating layer for a period of curing time, and when a curing period is not required, the coating layer is directly used 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 production example of the adhesive sheet 1, a coating solution of the adhesive composition P is applied to the release surface of one release sheet 12a, heat-treated to thermally crosslink the adhesive composition P to form a coating layer, and then A coating layer-attached release sheet 12a is formed. Furthermore, the coating solution of the above-mentioned adhesive composition P is coated on the release surface of the other release sheet 12b, and heat treatment is performed to thermally crosslink the adhesive composition P to form a coating layer, and then form an attached coating layer. Release sheet 12b for the cloth layer. Next, the release sheet 12a with a coating layer and the release sheet 12b with a coating layer are bonded together so that both coating layers may contact each other. In the case where a curing period is required, the adhesive layer 11 is formed by placing the above-mentioned laminated coating layer for a period of curing period, and when the curing period is not required, the above-mentioned laminated coating layer is directly used as the adhesive layer 11 . Thereby, the above-mentioned adhesive sheet 1 can be obtained. According to this manufacturing example, even in the case where the adhesive layer 11 is relatively thick, the adhesive layer 11 can be stably manufactured.

As the coating method of the coating solution of the above-mentioned adhesive composition P, for example, bar coating (bar coating) method, knife coating (knife coating) method, roll coating (roll coating) method, sheet coating (blade coating) method can be used. coating) coating method, die coating (die coating) method, gravure coating (gravure coating) method, etc.

[Repeated bending laminated components] As shown in FIG. 2, the repeatedly bending laminated member 2 according to this embodiment includes a first flexible member 21 (one flexible member), a second flexible member 22 (other flexible members), and between them and bond the first flexible member 21 and the second flexible member 22 to each other.

The adhesive layer 11 in the above-mentioned repeated bending laminated member 2 is the adhesive layer 11 of the above-mentioned adhesive sheet 1 .

The repetitively bending laminated member 2 itself is a repetitive bending device, or is a member constituting a part of the repetitive bending device. The repeatedly bending device is preferably a display that can be repeatedly bent (including folded), but is not limited thereto. As such a repeating bending device, for example, an organic electroluminescent (organic EL) display, an electrophoretic display (electronic paper), a liquid crystal display using a plastic film substrate (film) as a substrate, a foldable display (foldable display), etc., can also be a touch panel (touch panel).

The first flexible member 21 and the second flexible member 22 are members that can be repeatedly bent (including folded), for example, a cover film (cover film), a barrier film (barrier film), a polarizing film, Polarizer, retardation film, viewing angle compensation film, brightness enhancement film, contrast enhancement film, diffusion film, semi-transmissive reflection film, electrode film, transparent conductive film, metal mesh, film sensor (film sensor), liquid crystal polymer film, Light-emitting polymer film, thin film liquid crystal module (module), organic EL module (organic EL film), electronic paper module (film 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, a liquid crystal polymer film, a light-emitting polymer film, 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 moduli of the first flexible member 21 and the second flexible member 22 are preferably 0.1 to 10 GPa, particularly preferably 0.5 to 7 GPa, and more preferably 1.0 to 5 GPa. Since the Young's modulus of the first flexible member 21 and the second flexible member 22 is within the above-mentioned range, it becomes easy to repeatedly bend each flexible member.

The thicknesses of the first flexible member 21 and the second flexible member 22 are 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 each flexible member.

When manufacturing the above-mentioned repeatedly bending laminated member 2, as an example, one release 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, the other 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, and then the repeated bending laminated member 2 is obtained. . In addition, as another example, the bonding order of the first flexible member 21 and the second flexible member 22 may be changed.

[Repeat Bending Device] The repeated bending device according to the present embodiment is a repeated bending device provided with the above-mentioned repeated bending laminated member 2, and may be composed of only the repeated bending laminated member 2, or may be composed of one or more repeated bending laminated members 2 and composed of other flexible components. When one repeatedly bending laminated member 2 is laminated with another repeatedly bending member 2, or when the repeatedly bending laminated member 2 is laminated with another flexible member, it is preferable to laminate through the adhesive layer 11 of the aforementioned 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 possible to prevent the adhesive layer 11 and the flexible members 21 and 22 from being bent repeatedly (for example, 30,000 times). Problems such as floating and peeling occur at the interface between them.

The embodiments described above are described for easy understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above-mentioned embodiments 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 necessary flexible member may be laminated instead of the release sheet 12a and/or the release sheet 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) By solution polymerization, 40 parts by mass of 2-ethylhexyl acrylate, 45 parts by mass of n-butyl acrylate, 5 parts by mass of N-acrylmorpholine, 5 parts by mass of 2-hydroxyethyl acrylate and 5 parts by mass of acrylic acid were copolymerized to prepare (meth)acrylate polymer (A). The molecular weight of this (meth)acrylate polymer (A) was measured by the method described later, and it was found that the weight average molecular weight (Mw) was 700,000.

2. Preparation of Adhesive Composition 100 parts by mass (calculated by solid content, the same below) of the (meth)acrylate polymer (A) obtained in the above step 1, 1 part by mass of trimethylol as a crosslinking agent (B) Toluene diisocyanate (manufactured by Toyo Chemical Co., Ltd., product name "BHS 8515") and 0.28 parts by mass of 3-glycidoxypropyltrimethoxysilane as a silane coupling agent are mixed together and Stir well and dilute with methyl ethyl ketone to obtain a coating solution of the adhesive composition.

3. Manufacture of adhesive sheet The resulting coating solution of the adhesive composition was applied to one surface of a polyethylene terephthalate film with a silicone release agent and subjected to release treatment using a knife coater. The peeling surface of the heavy peeling type peeling sheet (manufactured by Lintec, product name "SP-PET 752150"). Next, the coating layer was heat-treated at 90° C. for 1 minute to form a coating layer.

After that, the coating layer on the heavy release type release sheet obtained above, and the light release type release sheet obtained by peeling one surface of the polyethylene terephthalate film using a silicone release agent (manufactured by Lintec Corporation, the product name is "SP-PET 382120"), and the release treatment surface of this light-release type release sheet is attached to the coating layer in such a way that it is in contact with each other, and is kept at 23°C, 50%RH Cured for 7 days under certain conditions to form an adhesive sheet with an adhesive layer with a thickness of 10 μm, that is, to produce a structure with a heavy-release type release sheet/adhesive layer (thickness: 10 μm)/light-release type release sheet 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.

Here, in the case where the (meth)acrylate polymer (A) is 100 parts by mass (calculated by solid content), the various formulation amounts (calculated by solid content) of the adhesive composition are shown in Table 1 . In addition, details such as abbreviations described in Table 1 are as follows. [(Meth)acrylate polymer (A)] 2EHA: 2-Ethylhexyl Acrylate BA: n-butyl acrylate ACMO: N-Acryloylmorpholine IBXA: Isocamphoryl Acrylate HEA: 2-Hydroxyethyl Acrylate 4HBA: 4-Hydroxybutyl Acrylate AA: Acrylic

[Examples 2-10, Comparative Examples 1-3] The types and proportions of the various monomers constituting the (meth)acrylate polymer (A), the weight average molecular weight (Mw) of the (meth)acrylate polymer (A), and the compounding amount of the crosslinking agent (B) , and the thickness of the adhesive layer was changed as shown in Table 1, except that, the remaining adhesive sheets were produced in the same manner as in Example 1.

[Test Example 1] (Measurement of Gel Fraction) The adhesive sheets produced in the examples and comparative examples were cut into a size of 80 mm × 80 mm, and the adhesive layer was wrapped in a polyester net (mesh size 200), and its mass was weighed with a precision balance, and borrowed By deducting the mass of the polyester net itself, the mass of only the adhesive is calculated. The mass at this time is set to M1.

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

[Test example 2] (Measurement of storage modulus (G')) The adhesive layer of the adhesive sheet produced in the Example and the comparative example was laminated|stacked, and the laminated body of thickness 3mm was formed. A cylinder with a diameter of 8 mm (height: 3 mm) was punched out from the obtained laminate of the adhesive layer, and this was used as a sample.

For the above-mentioned samples, the storage modulus (G') was measured under the following conditions by the torsional shear method using a viscoelasticity measuring device (DYNAMIC ANALAZER manufactured by REOMETRIC Co., Ltd.) according to JIS K7244-6. The results are shown in Table 2. Measurement frequency: 1 Hz Measuring temperature: 23°C

[Test Example 3] (Measurement of haze value) For the adhesive layer of the adhesive sheet produced in the examples and comparative examples, the haze value was measured using a haze meter (manufactured by Nippon Denshoku Kogyo Co., Ltd., product name "NDH-2000") according to JIS K7136:2000 (%). The results are shown in Table 2.

[Test Example 4] (Measurement of Adhesive Force) The light-peeling release sheet was peeled off from the adhesive sheets obtained in Examples and Comparative Examples, and the exposed adhesive layer was bonded to a polyethylene terephthalate (PET) film having an easy-adhesive layer (made by Manufactured by Toyobo Corporation, product name "PET A 4300"), thickness: 100μm) easy-adhesive layer, and then obtain a laminate of heavy-peeling release sheet/adhesive layer/PET film. The obtained laminate was cut into a width of 25 mm and a length of 100 mm.

Under the environment of 23° C. and 50% RH, the heavy peeling type release sheet was peeled from the above-mentioned laminated body, and the exposed adhesive layer was attached to soda lime glass (manufactured by Kawamura Hisashi Shoten Co., Ltd., product name " Soda-lime glass", thickness: 1.1 μm), was pressurized at 0.5 MPa and 50° C. for 20 minutes using an autoclave manufactured by Kurihara Seisakusho. Afterwards, after standing for 24 hours under the condition of 23° C. and 50% RH, use a tensile tester (Tensilon manufactured by ORIENTEC Corporation), under the condition that the peeling speed is 300 mm/min and the peeling angle is 180 degrees, measure Adhesive force (N/25mm) when the laminate of PET film and adhesive layer is peeled off from soda lime glass. Conditions other than those described here were measured in accordance with JIS Z 0237:2009. The results are shown in Table 2.

[Test Example 5] (Measurement of Shear Stress) Using the coating solutions of the adhesive compositions prepared in Examples and Comparative Examples, and setting the thickness of the adhesive layer to 25 μm, except that, the same method as in Example 1 was used to produce a Adhesive sheet with a structure of type release sheet/adhesive layer (thickness: 25μm)/light release type release sheet. The obtained adhesive sheet was cut into a size of 25 mm×25 mm. The light-peeling type release sheet was peeled from the above-mentioned adhesive sheet, and the exposed adhesive layer was attached to one end in the longitudinal direction of the float glass (30 mm×100 mm) as the first tensile member. Next, the heavy release type release sheet was peeled from the above-mentioned adhesive sheet, and the exposed adhesive layer was attached to one end in the longitudinal direction of the float glass (30 mm×100 mm) as the second tensile member. At this time, the first tensile member and the second tensile member are attached so as to extend in directions opposite to each other. Then, it was pressurized at 0.5 MPa and 50°C for 20 minutes in an autoclave manufactured by Kurihara Seisakusho Co., Ltd., and then left to stand at 23°C and 50% RH for 24 hours, and this was used as a sample.

Using a tensile testing machine (manufactured by ORIENTEC, product name "Tensilon"), in an environment of 23°C and 50% RH, the first tensile member and the second tensile member are placed in opposite directions to each other. Stretching at a stretching speed of 5 mm/min, measuring the maximum shear stress (σ _max ; kN) at the time of displacement of 1000% in the plane direction of the above-mentioned sample, and measuring the shear stress after 60 seconds from the time of displacement of 1000% at the same time Shear stress (σ ₆₀ ; kN). From the obtained results, the ratio (shear stress residual rate) of the shear stress (σ ₆₀ ; kN) after 60 seconds from the displacement of 1000% with respect to the maximum shear stress (σ _max ; kN) was used ( σ ₆₀ /σ _max ) × 100 calculation formula. The results are shown in Table 2.

[Test Example 6] (bending test) In an environment of 23°C and 50% RH, the light-peeling release sheet was peeled off from the adhesive sheets produced in Examples and Comparative Examples, and the exposed adhesive layer was bonded to polyethylene terephthalate On one surface of the film (thickness: 100 μm, Young's modulus: 4.5 GPa). Next, the heavy peeling type release sheet was peeled off, and the exposed adhesive layer was bonded to one surface of another polyethylene terephthalate film (thickness: 100 μm, Young's modulus: 4.5 GPa). Then, in an autoclave manufactured by Kurihara Seisakusho Co., Ltd., it was pressurized at 0.5 MPa and 50° C. for 20 minutes, and then left to stand at 23° C. and 50% RH for 24 hours. The thus obtained laminate formed of the PET film/adhesive layer/PET film was cut into a width of 50 mm and a length of 200 mm, and this was used as a sample.

Using a durability testing machine (manufactured by Yuasa System Equipment Co., Ltd., product name "Planar Body Unloaded U-shaped Tensile Testing Machine"), the obtained sample was repeatedly bent under the following conditions. After that, whether there is floating/peeling at the interface between the adhesive layer and the adherend, and whether the adhesive has leaked from the adhesive layer was checked visually, and the durability was evaluated according to the following criteria. The results are shown in Table 2.

＜Test conditions＞ Bending diameter: 3 mmφ Bending times: 30000 times Test temperature: 23°C, 80°C ＜Evaluation criteria for floating and peeling＞ ⊚: Floating and peeling did not occur. ◯: Slight floating or peeling occurred near the edge, but it was practically usable. ×: Swelling or peeling occurred to such an extent that it was practically unusable. ＜Evaluation criteria for exudation＞ ◎: Bleeding out did not occur. ◯: Slight bleeding occurred, but it was practically usable. ×: Bleeding occurred to such an extent that it was practically unusable.

[Table 1]

[Table 2]

It can be seen from Table 2 that the adhesive layer of the adhesive sheet of the embodiment can prevent the interface between the adhesive layer and the flexible member from being lifted or peeled off when two flexible members are bonded and bent repeatedly. . [industrial availability]

The present invention is suitable for bonding one flexible member (for example, various films) constituting a repeating bending device to another flexible member (for example, a display element).

1‧‧‧adhesive sheet 11‧‧‧adhesive layer 12a, 12b‧‧‧Peeling sheet 2‧‧‧Repeated bending laminated components 21‧‧‧The first flexible member 22‧‧‧The second flexible member

[ 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 bending laminated member according to an embodiment of the present invention.

1‧‧‧adhesive sheet

11‧‧‧adhesive layer

12a, 12b‧‧‧Peeling sheet

Claims (9)

An adhesive for a repetitive bending device, which is an adhesive for a repetitive bending device for laminating one flexible member constituting the repetitive bending device with other flexible members, wherein the adhesive contains a silane coupling agent, compared to the adhesive formed by the aforementioned The maximum shear stress when one surface and the other surface of the adhesive layer made of adhesive are displaced 1000% in opposite directions, and the ratio of the shear stress after 60 seconds from the 1000% displacement is 72% Hereinafter, the gel fraction is not less than 40% and not more than 90%, and the storage modulus G' at 23° C. is not less than 0.005 MPa and not more than 0.07 MPa. An adhesive for a repetitive bending device, which is an adhesive for a repetitive bending device for laminating one flexible member constituting the repetitive bending device with other flexible members, wherein the adhesive contains a silane coupling agent, compared to the adhesive formed by the aforementioned The maximum shear stress when one surface and the other surface of the adhesive layer made of adhesive are displaced 1000% in opposite directions, and the ratio of the shear stress after 60 seconds from the 1000% displacement is 72% Below, the gel fraction is not less than 40% and not more than 72%. The adhesive for repetitive bending devices as described in item 1 or 2 of the patent scope, wherein the aforementioned adhesive is cross-linked with an adhesive composition containing a (meth)acrylate polymer (A) and a cross-linking agent (B). Combine the resulting adhesive. An adhesive sheet, which is an adhesive sheet with an adhesive layer for laminating one flexible member constituting a repetitive bending device with other flexible members, wherein the aforementioned adhesive layer is as described in item 1 or 2 of the scope of application The repeat bending device is formed with adhesive. The adhesive sheet as described in claim 4 of the patent application, wherein the adhesive force of the aforementioned adhesive sheet to soda-lime glass is above 3N/25mm and below 100N/25mm. The adhesive sheet described in claim 4 of the patent application, wherein the adhesive sheet has two release sheets, and the adhesive layer is sandwiched by the release sheets so as to contact the release surfaces of the two release sheets. live. A repeatedly bending laminated member, which is a repeatedly bending laminated member comprising one flexible member and other flexible members constituting a repetitive bending device, and an adhesive layer bonding the one flexible member and the other flexible member to each other, Wherein the aforementioned adhesive layer is the adhesive layer of the adhesive sheet as described in item 4 of the scope of application. The repeated bending laminated member as described in claim 7 of the patent application, wherein at least one of the aforementioned one flexible member and the aforementioned other flexible member is a display element. A repetitive bending device, which is provided with the repetitive bending laminated member described in item 7 of the patent application.