CN115066331B

CN115066331B - Adhesive material, adhesive sheet, and flexible laminate member

Info

Publication number: CN115066331B
Application number: CN202180009631.8A
Authority: CN
Inventors: 露口健介
Original assignee: Higashiyama Film Co Ltd
Current assignee: Higashiyama Film Co Ltd
Priority date: 2020-02-28
Filing date: 2021-02-10
Publication date: 2024-05-07
Anticipated expiration: 2041-02-10
Also published as: TW202140727A; TWI825392B; JP2021134321A; KR20220143819A; CN115066331A; WO2021172017A1

Abstract

Technical problems: provided is an adhesive material which, when used for bonding a flexible member that constitutes a flexible laminate member, can suppress cracking, deformation, and the like at a bending portion even when the flexible laminate member is repeatedly bent. The technical scheme is as follows: an adhesive material for bonding one flexible member to another flexible member, characterized in that the adhesive material is a cured product of an adhesive composition containing a (meth) acrylic copolymer having a reactive functional group and a crosslinking agent, the (meth) acrylic copolymer being a copolymer obtained by living radical polymerization and having a molecular weight distribution of 3.0 or less, the adhesive material having a shear storage modulus at 23 ℃ of 0.8x10 ⁴Pa～30×10⁴ Pa, the adhesive material having a Young's modulus of 10kPa to 1000kPa, the adhesive material being stretched until the tensile stress reaches 50kPa and then contracted by releasing the tensile stress, and the ratio of the elastic modulus at tenth contraction to the elastic modulus at the first contraction being 60% or more when repeating the test ten times.

Description

Adhesive material, adhesive sheet, and flexible laminate member

Technical Field

The present invention relates to an adhesive material for bonding one flexible member and the other flexible member constituting a flexible laminated member used by repeated bending.

Background

In various displays such as televisions, mobile phones, and smart phones, touch panels, and the like, adhesive materials are generally used for joining members constituting the displays, the touch panels, and the like. The adhesive material is provided, for example, in the form of a substrate-provided adhesive sheet having an adhesive material layer on a supporting substrate or a substrate-free adhesive sheet having no supporting substrate, and the members are bonded together.

In recent years, attention has been paid to flexible displays that are repeatedly used in bending in image display devices such as liquid crystal display devices and organic electroluminescence (organic EL) display devices. Flexible displays include foldable displays, roll-type displays that can be rolled into a roll, and the like, and are expected to be used for mobile terminals such as smartphones and tablet terminals, and stationary displays that can be stored.

As an adhesive material for bonding a flexible member and another flexible member constituting a bending and stretching member in such a flexible display, for example, patent document 1 discloses an adhesive for a bending and stretching device in which a ratio of a shear stress after starting 60 seconds when one surface and the other surface of an adhesive layer are displaced in opposite directions by 1000% with respect to a maximum shear stress when the displacement is 1000% and a gel fraction are controlled within a predetermined range (refer to claim 1 of patent document 1).

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open publication No. 2019-108498

Disclosure of Invention

Technical problem to be solved by the invention

When a conventional bendable member having an adhesive layer is repeatedly bent, the bendable member cannot be sufficiently restored from a bent state to an original state. Therefore, if the bending of the flexible laminate member is repeated, there is a possibility that an appearance defect such as lifting or peeling occurs at the interface between the adhesive layer and the flexible member at the bending portion, or the bending portion is wrinkled and is seen.

The present invention has been made in view of the above-described circumstances, and an object thereof is to provide an adhesive material which, when used for bonding a flexible member constituting a flexible laminated member, can suppress occurrence of cracks or appearance defects such as wrinkles at a bending portion even if the flexible laminated member is repeatedly bent.

Solution for solving the technical problems

The adhesive material according to the present invention, which can solve the above-mentioned problems, is an adhesive material for bonding one flexible member to another flexible member, characterized in that the adhesive material is a cured product of an adhesive composition containing a (meth) acrylic copolymer having a reactive functional group and a crosslinking agent, the (meth) acrylic copolymer being a copolymer obtained by living radical polymerization, having a molecular weight distribution (Mw/Mn) of 3.0 or less, a shear storage modulus at 23 ℃ of 0.8x10 ⁴Pa～30×10⁴ Pa, a young's modulus of the adhesive material of 10kPa to 1000kPa, and a ratio of an elastic modulus at tenth shrinkage to an elastic modulus at first shrinkage of 60% or more when the test is repeated ten times after the stretching stress reaches 50kPa and the stretching stress is released.

The copolymer prepared by radical polymerization has uneven length of the obtained molecular chains and uneven composition of each molecular chain. Therefore, when such a copolymer is used for an adhesive material, the crosslinking point spacing between crosslinking points by the crosslinking agent becomes uneven, and the resulting adhesive material is considered to have a part where the elastic modulus is different. It is considered that when the adhesive material having such uneven cross-linking point pitch is repeatedly subjected to bending and stretching, the adhesive material tends to be locally broken and easily to be plastically deformed because of uneven elastic modulus.

The (meth) acrylic copolymer prepared by living radical polymerization has a narrow molecular weight distribution and a uniform composition of each molecular chain. That is, the number of reactive functional groups in each molecular chain of the (meth) acrylic polymer is uniform. Therefore, if such a (meth) acrylic copolymer is used for the adhesive material, the crosslinking points crosslinked by the crosslinking agent are uniformly spaced, and the resulting cured product (adhesive material) has substantially the same elastic modulus as a whole. Since the adhesive material has substantially the same elastic modulus throughout, occurrence of local fracture can be suppressed even in repeated bending and stretching, and deterioration of original shape restoring force can be suppressed even in repeated bending and stretching.

Further, if the adhesive material has a prescribed shear storage modulus and young's modulus and the retention rate of elastic modulus upon shrinkage in repeated elongation and shrinkage test is high, the adhesive material can follow the deformation of the bendable member in bending and stretching. Therefore, by using the adhesive material of the present invention, occurrence of appearance defects such as cracks and wrinkles can be suppressed without causing lifting or peeling at the interface between the adhesive layer and the flexible member at the bending portion of the flexible laminate member.

Effects of the invention

When the adhesive material of the present invention is used for bonding a flexible member constituting a flexible laminate member, even if the flexible laminate member is repeatedly bent, the adhesive material does not cause lifting or peeling at the interface between the adhesive layer and the flexible member at the bending portion, and occurrence of appearance defects such as cracks or wrinkles can be suppressed.

Drawings

Fig. 1: an example of the adhesive sheet of the present invention is a schematic cross-sectional view.

Fig. 2: an example of the flexible laminated member of the present invention is a schematic cross-sectional view.

Fig. 3: an example of the flexible laminated member of the present invention is a schematic cross-sectional view.

Symbol description 10: adhesive sheet, 12: adhesive layer, 14: first flexible sheet member, 16: second flexible sheet member, 20: a flexible laminated member 22: first flexible member, 24: second flexible member, 30: flexible laminated member, 32: cover film, 32a: film-covered substrate, 32b: hard coat layer, 34: polarizing film

Detailed Description

An example of a preferred embodiment of the present invention will be described below. The embodiments described below are merely examples. The present invention is not limited by the following embodiments.

In the present invention, "(meth) acrylic group" means "at least one of acrylic group and methacrylic group". "(meth) acrylate" means "at least one of acrylate and methacrylate". "(meth) acryl" means "at least one of acryl and methacryl". "vinyl monomer" refers to a monomer having a carbon-carbon double bond in the molecule that can undergo free radical polymerization. "structural unit derived from a vinyl monomer" refers to a structural unit of a vinyl monomer in which a free-radically polymerizable carbon-carbon double bond is polymerized to form a carbon-carbon single bond. "structural unit derived from a (meth) acrylate" means a structural unit in which a radical polymerizable carbon-carbon double bond of a (meth) acrylate is polymerized to form a carbon-carbon single bond. "structural unit derived from a (meth) acrylic acid based monomer" means a structural unit in which a radical polymerizable carbon-carbon double bond of a (meth) acrylic acid based monomer is polymerized to form a carbon-carbon single bond.

[ Adhesive Material ]

The adhesive material of the present invention is an adhesive material for bonding one flexible member and the other flexible member constituting a flexible laminate member for repeated bending use. The adhesive material is a cured product of an adhesive composition containing a (meth) acrylic copolymer having a reactive functional group and a crosslinking agent, wherein the (meth) acrylic copolymer is a copolymer obtained by living radical polymerization, and has a molecular weight distribution (Mw/Mn) of 3.0 or less. Further, the adhesive material has a shear storage modulus at 23 ℃ of 0.8X10 ⁴Pa～30×10⁴ Pa, a Young's modulus of 10kPa to 1000kPa, and the adhesive material is stretched until the tensile stress reaches 50kPa and then contracted by releasing the tensile stress, and the ratio of the elastic modulus at the tenth contraction to the elastic modulus at the first contraction is 60% or more when the test is repeated ten times.

The adhesive material has a shear storage modulus (G') at 23 ℃ of 0.8X10 ⁴ Pa or more, preferably 1.0X10 ⁴ Pa or more, more preferably 2.0X10 ⁴ Pa or more, 30X 10 ⁴ Pa or less, more preferably 20X 10 ⁴ Pa or less, still more preferably 10X 10 ⁴ Pa or less, and particularly preferably 8.0X10 ⁴ Pa or less. The adhesive material has a moderate flexibility and a shape following property when the shear storage modulus (G') is 0.8X10 ⁴ Pa or more, and has a better cohesive force and adhesion when it is 30X 10 ⁴ Pa or less. The method for measuring the shear storage modulus (G') of the adhesive material will be described later.

The shear loss modulus (G') of the adhesive material at 23 ℃ is preferably 0.40X10 ⁴ Pa or more, more preferably 0.50X10 ⁴ Pa or more, still more preferably 1.0X10 ⁴ Pa or more, preferably 27X 10 ⁴ Pa or less, more preferably 18X 10 ⁴ Pa or less, still more preferably 9.0X10 ⁴ Pa or less. The adhesive material has moderate flexibility when the shear loss modulus (G ") is 0.40×10 ⁴ Pa or more, and has good shape following property to an adherend, and has better cohesion and adhesion when the shear loss modulus (G") is 27×10 ⁴ Pa or less. The method for measuring the shear loss modulus (G ") of the adhesive material will be described later.

The adhesive material is subjected to a shear stress to a stress immediately after reaching 200% of the shear strain, preferably 5.0X10 ⁴ Pa or more, more preferably 7.0X10 ⁴ Pa or more, still more preferably 10X 10 ⁴ Pa or more, preferably 150X 10 ⁴ Pa or less, still more preferably 100X 10 ⁴ Pa or less, and still more preferably 50X 10 ⁴ Pa or less. If the stress is 5.0X10 ⁴ Pa or more, the cohesive force and adhesion of the adhesive material are better. If the stress is 150X 10 ⁴ Pa or less, the adhesion is better.

The stress when the adhesive material is subjected to a shear stress to a shear strain of 200% and held for 10 minutes is preferably 0.50X10 ⁴ Pa or more, more preferably 0.70X10 ⁴ Pa or more, still more preferably 1.0X10 ⁴ Pa or more, preferably 8.0X10 ⁴ Pa or less, still more preferably 5.0X10 ⁴ Pa or less, and still more preferably 2.0X10 ⁴ Pa or less. If the stress is 0.50X10 ⁴ Pa or more, the cohesive force and adhesion of the adhesive material are better. If the stress is 8.0X10 ⁴ Pa or less, when the adhesive material is used for bending a flexible laminate, the stress applied to the bending portion can be satisfactorily relaxed to be small, and therefore cracking of the flexible member, and floating or peeling of the adhesive layer at the interface with the flexible member can be suppressed.

The recovery rate of the adhesive material after the adhesive material is subjected to a shear stress to 200% of the shear strain and kept for 10 minutes, and then the adhesive material is released and left for 10 minutes is preferably 60% or more. If the recovery rate is 60% or more, the deformation of the bendable laminated member, which is generated when the bendable laminated member is re-stretched after being in a bent state for a long period of time, is easily recovered, and thus occurrence of appearance defects such as wrinkles at the bent portion can be suppressed. The recovery rate is more preferably 65% or more, still more preferably 75% or more, particularly preferably 85% or more, and the upper limit is 100%.

The Young's modulus of the adhesive material is 10kPa or more, preferably 25kPa or more, more preferably 50kPa or more, still more preferably 90kPa or more, and 1000kPa or less, preferably 600kPa or less, more preferably 500kPa or less, still more preferably 400kPa or less. If the Young's modulus is 10kPa or more, appearance defects such as wrinkles can be suppressed even in a high-temperature environment, and if it is 1000kPa or less, floating or peeling at the time of bending can be suppressed even in a low-temperature environment.

The adhesive material is stretched until the tensile stress reaches 50kPa, and then the adhesive material is contracted by releasing the tensile stress, and when the test is repeated ten times, the ratio of the elastic modulus at the tenth contraction to the elastic modulus at the first contraction is 60% or more. If the ratio is 60% or more, the plastic deformation amount of the adhesive material is small even when the adhesive material is repeatedly bent and stretched. Therefore, when used for a bendable laminated member, appearance defects such as deformation marks at bending portions can be suppressed. The proportion is preferably 70% or more, more preferably 80% or more, and the upper limit is 100%.

The elastic modulus of the adhesive material at the time of first shrinkage is preferably 0.1MPa or more, more preferably 0.2MPa or more, still more preferably 0.5MPa or more, preferably 10MPa or less, more preferably 5.0MPa or less, still more preferably 3.0MPa or less.

In the test of stretching the adhesive material until the tensile stress reaches 50kPa and then releasing the tensile stress and shrinking the adhesive material, the elongation (first elongation) at the tensile stress of 50kPa is preferably 10% or more, more preferably 100% or more, still more preferably 250% or more, and particularly preferably 500% or more. If the elongation is 10% or more, the deflection of the film upon bending can be absorbed. The upper limit of the elongation is not particularly limited, but is usually about 1000%.

The elongation was obtained by the following formula: lambda= (l ₁-l₀)/l₀ x 100)

[ Lambda ] lambda: elongation (%), l ₀: length before elongation (mm), l ₁: length after elongation (mm)

The gel fraction of the adhesive material is preferably 20% to 100%, more preferably 50% to 100%, and particularly preferably 70% to 100% from the viewpoints of durability and adhesion. If the gel fraction is too low, insufficient durability due to insufficient cohesion is liable to occur. The gel fraction can be controlled according to the amount of the crosslinking agent to be incorporated into the adhesive composition, the crosslinking treatment temperature, and the crosslinking treatment time.

(Adhesive composition)

The adhesive material is a cured product of an adhesive composition containing a (meth) acrylic copolymer having a reactive functional group and a crosslinking agent. The adhesive composition contains (A) a (meth) acrylic copolymer having a reactive functional group and (B) a crosslinking agent.

((A) a (meth) acrylic copolymer having a reactive functional group)

The (a) acrylic copolymer having a reactive functional group (hereinafter, sometimes simply referred to as "(a copolymer)) is a (meth) acrylic copolymer as follows: obtained by living radical polymerization, has a molecular weight distribution (Mw/Mn) of less than 3.0 and has reactive functional groups.

The (meth) acrylic copolymer may contain structural units derived from vinyl monomers other than the (meth) acrylic monomers as long as it is a copolymer containing structural units derived from the (meth) acrylic monomers as a main component (50 mass% or more). The content of the structural unit derived from the (meth) acrylic acid based monomer in the copolymer (a) is preferably 80 mass% or more, more preferably 90 mass% or more, of 100 mass% or more of the entire copolymer. The copolymer (a) may be composed of only structural units derived from a (meth) acrylic acid based monomer.

The (A) copolymer is preferably a (meth) acrylate copolymer. The (meth) acrylic acid ester copolymer may contain structural units derived from vinyl monomers other than (meth) acrylic acid esters as long as it is a copolymer containing structural units derived from (meth) acrylic acid esters as a main component (50 mass% or more). The (meth) acrylate refers to an ester compound formed from (meth) acrylic acid and a compound having a hydroxyl group. The content of the structural unit derived from the (meth) acrylic acid ester in the copolymer (a) is preferably 80 mass% or more, more preferably 90 mass% or more, based on 100 mass% of the entire copolymer.

The (A) copolymer has a reactive functional group. The reactive functional group is a functional group that can react with a functional group of the crosslinking agent (B) described later. The reactive functional group may be, for example, one or two or more selected from the group consisting of a hydroxyl group, a carboxyl group and an epoxy group, and preferably a hydroxyl group and/or a carboxyl group.

The amount of the reactive functional group in 100g of the copolymer (A) is preferably 0.5mmol/100g or more, more preferably 5mmol/100g or more, still more preferably 10mmol/100g or more, particularly preferably 15mmol/100g or more, preferably 150mmol/100g or less, more preferably 100mmol/100g or less, still more preferably 70mmol/100g or less, and particularly preferably 50mmol/100g or less. When the amount of the reactive functional group is 0.5mmol/100g or more, the durability of the adhesive material is excellent, and when it is 150mmol/100g or less, the adhesion of the adhesive material to an adherend is excellent.

When the copolymer (A) has carboxyl groups, the amount of carboxyl groups in 100g of the copolymer (A) is preferably 0.5mmol/100g or more, more preferably 5mmol/100g or more, still more preferably 10mmol/100g or more, particularly preferably 15mmol/100g or more, preferably 150mmol/100g or less, more preferably 100mmol/100g or less, still more preferably 70mmol/100g or less, and particularly preferably 50mmol/100g or less.

When the copolymer (A) has hydroxyl groups, the amount of carboxyl groups in 100g of the copolymer (A) is preferably 0.5mmol/100g or more, more preferably 5mmol/100g or more, still more preferably 10mmol/100g or more, particularly preferably 15mmol/100g or more, preferably 150mmol/100g or less, more preferably 100mmol/100g or less, still more preferably 70mmol/100g or less, and particularly preferably 50mmol/100g or less.

The (A) copolymer has a reactive functional group. That is, the copolymer (A) contains a structural unit (a-1) having a reactive functional group in its structure. The structural unit (a-1) having a reactive functional group may be one kind or two or more kinds. The reactive functional group may be present on any one of a structural unit derived from a (meth) acrylic acid based monomer (preferably a (meth) acrylate monomer and/or a (meth) acrylic acid) and a structural unit derived from a vinyl monomer other than the (meth) acrylic acid based monomer. That is, the structural unit (a-1) having a reactive functional group may be a structural unit derived from a (meth) acrylic acid based monomer having a reactive functional group (preferably a (meth) acrylic acid ester monomer and/or a (meth) acrylic acid), or a structural unit derived from a vinyl monomer having a reactive functional group other than a (meth) acrylic acid based monomer.

The content of the structural unit derived from the vinyl monomer having a reactive functional group (structural unit (a-1)) in the copolymer (a) is preferably 0.1 mass% or more, more preferably 0.5 mass% or more, still more preferably 1 mass% or more, particularly preferably 3 mass% or more, preferably 20 mass% or less, more preferably 15 mass% or less, still more preferably 10 mass% or less, and particularly preferably 8 mass% or less, based on 100 mass% of the entire copolymer. When the content of the structural unit (a-1) is within the above range, an adhesive material excellent in balance between adhesion to an adherend and durability can be obtained. The reactive functional group-containing vinyl monomer includes a reactive functional group-containing (meth) acrylic acid-based monomer and a reactive functional group-containing vinyl monomer other than the (meth) acrylic acid-based monomer.

The (meth) acrylic acid based monomer includes (b 1) a (meth) acrylic acid based monomer having no reactive functional group and (b 2) a (meth) acrylic acid based monomer having a reactive functional group. These monomers may be used alone or in combination of two or more. The (meth) acrylic acid based monomer (b 1) having no reactive functional group is preferably (meth) acrylic acid ester monomer (b 1-1) having no reactive functional group. The (meth) acrylic acid-based monomer having a reactive functional group of (b 2) may be (meth) acrylic acid ester monomer having a reactive functional group of (b 2-1).

Examples of the (meth) acrylic acid based monomer (b 1) having no reactive functional group include (meth) acrylic acid esters having a linear alkyl group, (meth) acrylic acid esters having a branched alkyl group, (meth) acrylic acid esters having an alkoxy group, (meth) acrylic acid esters having a polyalkylene glycol structural unit, (meth) acrylic acid esters having an alicyclic hydrocarbon group, (meth) acrylic acid esters having an aromatic group, (meth) acrylic acid esters having a tertiary amine group, and (meth) acrylamides. Among them, at least one selected from the group consisting of (meth) acrylic esters having a linear alkyl group, (meth) acrylic esters having a branched alkyl group, (meth) acrylic esters having an alicyclic hydrocarbon group, (meth) acrylic esters having an aromatic group, and (meth) acrylamides is preferable.

The (meth) acrylate having a linear alkyl group is preferably a (meth) acrylate having a linear alkyl group having 1 to 20 carbon atoms, more preferably a (meth) acrylate having a linear alkyl group having 1 to 10 carbon atoms. Examples of the (meth) acrylic acid ester having a linear alkyl group include linear alkyl (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, n-hexyl (meth) acrylate, n-octyl (meth) acrylate, n-nonyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate, and n-octadecyl (meth) acrylate.

The (meth) acrylate having a branched alkyl group is preferably a (meth) acrylate having a branched alkyl group having 3 to 20 carbon atoms, more preferably a (meth) acrylate having a branched alkyl group having 3 to 10 carbon atoms. Examples of the (meth) acrylic acid ester having a branched alkyl group include branched alkyl (meth) acrylates such as isopropyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isononyl (meth) acrylate, isodecyl (meth) acrylate, and the like.

Examples of the (meth) acrylic acid ester having an alkoxy group include alkoxyalkyl (meth) acrylates such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate.

Examples of the (meth) acrylic acid ester having a polyalkylene glycol structural unit include polyethylene glycol (polymerization degree=2 to 10) methyl ether (meth) acrylic acid ester, polyethylene glycol (polymerization degree=2 to 10) ethyl ether (meth) acrylic acid ester, polyethylene glycol (polymerization degree=2 to 10) propyl ether (meth) acrylic acid ester, polyethylene glycol (polymerization degree=2 to 10) phenyl ether (meth) acrylic acid ester and the like (meth) acrylic acid esters having a polyethylene glycol structural unit; and (meth) acrylates having a polypropylene glycol structural unit such as polypropylene glycol (polymerization degree=2 to 10) methyl ether (meth) acrylate, polypropylene glycol (polymerization degree=2 to 10) ethyl ether (meth) acrylate, polypropylene glycol (polymerization degree=2 to 10) propyl ether (meth) acrylate, and polypropylene glycol (polymerization degree=2 to 10) phenyl ether (meth) acrylate.

Examples of the (meth) acrylate having an alicyclic hydrocarbon group include (meth) acrylate having a cyclic alkyl group and (meth) acrylate having a polycyclic structure. The (meth) acrylate having a cyclic alkyl group is preferably a (meth) acrylate having a cyclic alkyl group having 6 to 12 carbon atoms. Examples of the cyclic alkyl group include cyclic alkyl groups having a monocyclic structure (e.g., cycloalkyl groups), and may have a chain portion. Examples of the (meth) acrylic acid ester having a cyclic alkyl group of a monocyclic structure include cyclic alkyl (meth) acrylates such as cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, cyclododecyl (meth) acrylate and the like.

The (meth) acrylate having a polycyclic structure is preferably a (meth) acrylate having a polycyclic structure having 6 to 12 carbon atoms. Examples of the polycyclic structure include cyclic alkyl groups having a bridged ring structure (e.g., adamantyl, norbornyl, isobornyl), and may have a chain moiety. Examples of the (meth) acrylic acid ester having a polycyclic structure include bornyl (meth) acrylate, isobornyl (meth) acrylate, 1-adamantyl (meth) acrylate, 2-methyl-2-adamantyl (meth) acrylate, 2-ethyl-2-adamantyl (meth) acrylate, norbornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, and dicyclopentenyloxyethyl (meth) acrylate.

The aromatic group-containing (meth) acrylate is preferably an aromatic group-containing (meth) acrylate having 6 to 12 carbon atoms. Examples of the aryl group include aryl groups, and may have a chain portion such as alkylaryl groups, arylalkyl groups, and aryloxyalkyl groups. Examples of the (meth) acrylic acid ester having an aromatic group include a compound in which an aryl group is directly bonded to a (meth) acryloyloxy group, a compound in which an aralkyl group is directly bonded to a (meth) acryloyloxy group, and a compound in which an alkylaryl group is directly bonded to a (meth) acryloyloxy group. The number of carbon atoms of the aryl group is preferably 6 to 12. The number of carbon atoms of the aralkyl group is preferably 6 to 12. The number of carbon atoms of the alkylaryl group is preferably 6 to 12. Examples of the (meth) acrylic acid ester having an aromatic group include benzyl (meth) acrylate, phenyl (meth) acrylate, phenoxyethyl (meth) acrylate, and the like.

Examples of the (meth) acrylic acid ester having a tertiary amine group include 2- (dimethylamino) ethyl (meth) acrylate, N-dimethylaminopropyl (meth) acrylate, and the like.

Examples of the (meth) acrylamides include N, N-dimethyl (meth) acrylamide, N-diethyl (meth) acrylamide, N-diisopropyl (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-t-butyl (meth) acrylamide, N-octyl (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, N-propoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, diacetone acrylamide, N- (meth) acryloylmorpholine, and the like. The (meth) acrylamides are (meth) acrylic acid based monomers, but are not included in the (meth) acrylate ester monomers.

The (meth) acrylic acid-based monomer having a reactive functional group (b 2) includes a (meth) acrylic acid-based monomer having a hydroxyl group (preferably a (meth) acrylic acid ester monomer), a (meth) acrylic acid-based monomer having a carboxyl group (preferably a (meth) acrylic acid), a (meth) acrylic acid-based monomer having an epoxy group (preferably a (meth) acrylic acid ester monomer), and the like. Among them, a (meth) acrylic acid based monomer having a hydroxyl group and/or a (meth) acrylic acid based monomer having a carboxyl group is preferable.

Examples of the (meth) acrylic acid based monomer having a hydroxyl group include hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, and 12-hydroxylauryl (meth) acrylate; hydroxyalkyl cycloalkyl (meth) acrylates such as (4-hydroxymethyl cyclohexyl) methyl (meth) acrylate; caprolactone addition products of hydroxyalkyl (meth) acrylates, and the like. Among them, hydroxyalkyl (meth) acrylates are preferable, and (meth) acrylates having hydroxyalkyl groups having 1 to 5 carbon atoms are more preferable.

Examples of the (meth) acrylic acid based monomer having a carboxyl group include carboxyethyl (meth) acrylate; carboxypentyl (meth) acrylate; monomers obtained by reacting a (meth) acrylate having a hydroxyl group such as 2- (meth) acryloyloxyethyl succinate, 2- (meth) acryloyloxyethyl maleate, and 2- (meth) acryloyloxyethyl phthalate with an acid anhydride such as maleic anhydride, succinic anhydride, and phthalic anhydride; (meth) acrylic acid, and the like. Among them, (meth) acrylic acid is preferable.

Examples of the epoxy group-containing (meth) acrylate include glycidyl (meth) acrylate and 3, 4-epoxycyclohexylmethyl (meth) acrylate.

Examples of the vinyl monomer other than the (meth) acrylic acid based monomer include a vinyl monomer having no reactive functional group other than the (b 3) (meth) acrylic acid based monomer and a vinyl monomer having a reactive functional group other than the (b 4) (meth) acrylic acid based monomer. These monomers may be used alone or in combination of two or more.

Examples of the vinyl monomer having no reactive functional group other than the (b 3) (meth) acrylic acid based monomer include aromatic vinyl monomers, heterocyclic ring-containing vinyl monomers, vinyl carboxylates, tertiary amine group-containing vinyl monomers, quaternary ammonium salt group-containing vinyl monomers, vinyl amides, α -olefins, dienes, halogenated vinyl monomers, and the like.

Examples of the aromatic vinyl monomer include styrene, α -methylstyrene, 4-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methoxystyrene, 2-hydroxymethylstyrene, and 1-vinylnaphthalene.

Examples of the heterocyclic vinyl monomer include 2-vinylthiophene, N-methyl-2-vinylpyrrole, 2-vinylpyridine, and 4-vinylpyridine.

Examples of the vinyl carboxylate include vinyl acetate, vinyl pivalate, and vinyl benzoate.

Examples of the tertiary amine group-containing vinyl monomer include N, N-dimethylallylamine.

Examples of the quaternary ammonium salt group-containing vinyl monomer include N-methacryloylaminoethyl-N, N, N-dimethylbenzyl ammonium chloride and the like.

Examples of the vinylamides include N-vinylformamide, N-vinylacetamide, 1-vinyl-2-pyrrolidone, N-vinyl-epsilon-caprolactam, and the like.

Examples of the α -olefin include 1-hexene, 1-octene, and 1-decene.

Examples of the dienes include butadiene, isoprene, 4-methyl-1, 4-hexadiene, and 7-methyl-1, 6-octadiene.

Examples of the halogenated vinyl monomer include ethylene fluoride, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, tetrafluoropropene, vinylidene chloride, ethylene chloride, 1-chloro-1-fluoroethylene, 1, 2-dichloro-1, 2-difluoroethylene, and the like.

Examples of the vinyl monomer having a reactive functional group other than the (b 4) (meth) acrylic acid based monomer include a vinyl monomer having a hydroxyl group, a vinyl monomer having a carboxyl group, and a vinyl monomer having an epoxy group.

Examples of the vinyl monomer having a hydroxyl group include p-hydroxystyrene and allyl alcohol.

Examples of the vinyl monomer having a carboxyl group include crotonic acid, maleic acid, itaconic acid, citraconic acid, cinnamic acid, and the like.

Examples of the epoxy group-containing vinyl monomer include 2-allyloxirane, glycidyl vinyl ether, and 3, 4-epoxycyclohexyl vinyl ether.

The copolymer (A) may be any of a random copolymer, a block copolymer, and a graft copolymer, and is preferably a random copolymer.

The weight average molecular weight (Mw) of the copolymer (A) is preferably 20 ten thousand or more, more preferably 30 ten thousand or more, further preferably 40 ten thousand or more, preferably 200 ten thousand or less, more preferably 180 ten thousand or less, further preferably 150 ten thousand or less, and particularly preferably 100 ten thousand or less. If the Mw of the copolymer (A) is 20 ten thousand or more, the cohesive force is high, the heat resistance of the adhesive material is improved, and if it is 200 ten thousand or less, the coating workability of the adhesive composition is better. The method for measuring the weight average molecular weight (Mw) is described below.

The molecular weight distribution (PDI) of the copolymer (a) is 3.0 or less, preferably less than 3.0, more preferably less than 2.5, further preferably less than 2.2, particularly preferably less than 1.8. The smaller the PDI, the narrower the amplitude of the molecular weight distribution, and the more uniform the molecular weight, and the narrower the amplitude of the molecular weight distribution when the value is 1.0. If the PDI is 3.0 or less, the copolymer having a small molecular weight and the copolymer having a large molecular weight are contained in a low amount as compared with the molecular weight of the copolymer designed, and an adhesive material excellent in bending resistance can be obtained. In the present invention, the molecular weight distribution (PDI) means a value calculated from (weight average molecular weight (Mw))/(number average molecular weight (Mn)), and the measurement methods of Mw and Mn are described later.

The glass transition temperature (Tg) of the copolymer (A) is preferably-70℃or higher, more preferably-60℃or higher, preferably 0℃or lower, more preferably-10℃or lower, and further preferably-20℃or lower. When the glass transition temperature is at least-70 ℃, sufficient cohesive force is imparted to the adhesive material, and the durability of the adhesive material is improved, and when the glass transition temperature is at most 0 ℃, the adhesiveness of the adhesive material to an adherend is improved, and peeling and the like are suppressed, and the durability is improved.

The glass transition temperature (Tg) of the copolymer (a) is a value calculated from the following FOX formula (1)). In the formula (1), tg represents the glass transition temperature (. Degree. C.) of the copolymer. Tgi represents the glass transition temperature (. Degree. C.) of the vinyl monomer i when it forms a homopolymer. Wi represents the mass ratio of vinyl monomer i in the total vinyl monomers forming the copolymer, Σwi=1. i is a natural number of 1 to n.

The glass transition temperatures of representative homopolymers are shown in table 1.

TABLE 1

Short for short	Monomer name	Glass transition temperature (. Degree. C.)
			HBA	Acrylic acid 4-hydroxybutyl ester	-32
AA	Acrylic acid	106
			EHA	2-Ethylhexyl acrylate	-70
BA	Acrylic acid n-butyl ester	-55
			LA	N-dodecyl acrylate	-23
ACMO	Acryloylmorpholines	145
			IBXA	Isobornyl acrylate	94
DMAAm	Dimethylacrylamide	89

The copolymer (A) is prepared by radical polymerization of vinyl monomers by living radical polymerization. The living radical polymerization method is not easy to cause termination reaction or chain transfer while maintaining the simplicity and versatility of the existing radical polymerization method, and can grow without being hindered by side reaction for inactivating the growth end, so that it is easy to prepare a polymer with precisely controlled molecular weight distribution and uniform composition. Thus, the reactive functional groups of the copolymer prepared by the living radical polymerization method are uniformly distributed on each molecular chain. Therefore, if a copolymer prepared by a living radical polymerization method is used, the crosslinking point density in the adhesive material becomes uniform as a whole.

In the living radical polymerization method, a random copolymer may be formed by using a mixture of monomers (vinyl monomers) constituting the copolymer (a), or a block copolymer may be formed by sequentially reacting vinyl monomers constituting the copolymer.

In living radical polymerization, there are the following methods depending on the method of stabilizing the polymerization growth end: a method using a transition metal catalyst (ATRP method), a method using a sulfur reversible chain transfer agent (RAFT method), a method using an organic tellurium compound (tert method), and the like. Among these methods, the TERP method is preferably used from the viewpoints of diversity of monomers that can be used, molecular weight control in a high molecular region, composition uniformity, or coloration.

The TERP method is a method of polymerizing a radical polymerizable compound (vinyl monomer) using an organic tellurium compound as a chain transfer agent, and is described in, for example, international publication No. 2004/14848, international publication No. 2004/14962, international publication No. 2004/072126, and International publication No. 2004/096870.

Specific polymerization methods of the TERP method include the following (a) to (d).

(A) A method for polymerizing a vinyl monomer using the organic tellurium compound represented by formula (1).

(B) A method of polymerizing a vinyl monomer using a mixture of an organic tellurium compound represented by the formula (1) and an azo-based polymerization initiator.

(C) A method for polymerizing a vinyl monomer using a mixture of an organic tellurium compound represented by the formula (1) and an organic ditelluride represented by the formula (2).

(D) A method for polymerizing a vinyl monomer using a mixture of an organic tellurium compound represented by the formula (1), an azo-based polymerization initiator and an organic ditelluride represented by the formula (2).

R¹-Te-Te-R^l (2)

In the formula (1), R ¹ is an alkyl group having 1 to 8 carbon atoms, an aryl group or an aromatic heterocyclic group. R ² and R ³ are each independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. R ⁴ is alkyl, aryl, substituted aryl, aromatic heterocyclic group, alkoxy, acyl, amido, oxo-carbonyl, cyano, allyl or propargyl with 1-8 carbon atoms. In the formula (2), R ¹ represents an alkyl group having 1 to 8 carbon atoms, an aryl group or an aromatic heterocyclic group. ]

Specific examples of the organic tellurium compound represented by the formula (1) include ethyl-2-methyl-2-n-butyltelluride-propionate, ethyl-2-n-butyltelluride-propionate, (2-hydroxyethyl) -2-methyl-methyltellurium-propionate, and the like, and organic tellurium compounds described in International publication No. 2004/14848, international publication No. 2004/14962, international publication No. 2004/072126, and International publication No. 2004/096870. Specific examples of the organic ditelluride represented by formula (2) include dimethyl ditelluride and diethyl ditelluride. The azo-based polymerization initiator is not particularly limited as long as it is an azo-based polymerization initiator used in usual radical polymerization. Examples thereof include 2,2 '-azobis (isobutyronitrile) (AIBN), 2' -azobis (2, 4-dimethylvaleronitrile) (ADVN), 1 '-azobis (1-cyclohexanecarbonitrile) (ACHN), and 2,2' -azobis (4-methoxy-2, 4-dimethylvaleronitrile) (V-70).

In the polymerization step, an azo polymerization initiator and/or an organic ditelluride compound represented by the formula (2) are further mixed with the vinyl monomer and the organic tellurium compound represented by the formula (1) in order to promote the reaction, control the molecular weight, the molecular weight distribution, and the like, depending on the kind of the vinyl monomer in the container after the substitution with the inert gas. In this case, the inert gas may be nitrogen, argon, helium, or the like. Argon and nitrogen are preferred. The amount of the vinyl monomer used in the above-mentioned (a), (b), (c) and (d) may be appropriately adjusted depending on the physical properties of the objective copolymer.

The polymerization reaction may be carried out in the absence of a solvent, but an aprotic solvent or a protic solvent which is generally used in radical polymerization may be used and the mixture may be stirred. Examples of aprotic solvents that can be used include anisole, benzene, toluene, propylene glycol monomethyl ether acetate, ethyl acetate, and Tetrahydrofuran (THF). Examples of the protic solvent include water, methanol, and 1-methoxy-2-propanol. The solvent may be used alone or in combination of two or more. The amount of the solvent to be used may be appropriately adjusted, for example, from 0.01ml to 50ml relative to 1g of the vinyl monomer. The reaction temperature and reaction time may be appropriately adjusted according to the molecular weight or molecular weight distribution of the copolymer obtained, but are usually stirred at 0℃to 150℃for 1 minute to 100 hours. After completion of the polymerization reaction, the target copolymer can be isolated by removing the solvent, residual vinyl monomer, and the like used from the resulting reaction mixture by a usual separation and purification means.

The growing end of the copolymer obtained by the polymerization reaction is in the form of-TeR ¹ (wherein R ¹ is the same as above) derived from the tellurium compound, and tellurium atoms are sometimes left after the polymerization reaction, although they are deactivated by the operation in the air after the completion of the polymerization reaction. Since the copolymer having tellurium atoms remaining at the terminal thereof is colored or has poor thermal stability, it is preferable to remove the tellurium atoms. The method for removing tellurium atoms includes radical reduction methods; adsorption with activated carbon or the like; a method of adsorbing a metal with an ion exchange resin or the like, and the methods may be used in combination. The other end (the end opposite to the growth end) of the copolymer obtained by the polymerization reaction was in the form of-CR ²R³R⁴ (wherein R ²、R³ and R ⁴ are the same as R ²、R³ and R ⁴ in the formula (1)) derived from the tellurium compound.

((B) crosslinking agent)

The adhesive composition contains (B) a crosslinking agent. The crosslinking agent (B) is a compound having two or more reactive groups in one molecule which can react with the reactive functional groups of the copolymer (A). The crosslinking agent (B) is not particularly limited, and examples thereof include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, metal chelate-based crosslinking agents, melamine-resin-based crosslinking agents, urea-resin-based crosslinking agents, and the like. Among them, isocyanate-based crosslinking agents, epoxy-based crosslinking agents, and aziridine-based crosslinking agents are preferable, and isocyanate-based crosslinking agents or epoxy-based crosslinking agents are more preferable from the viewpoint of easy control of the degree of progress of the crosslinking reaction and bending resistance.

(Isocyanate-based crosslinking agent)

The isocyanate-based crosslinking agent is a compound having two or more isocyanate groups (including an isocyanate-regenerated functional group in which an isocyanate group is temporarily protected by a blocking agent, a polymerization agent, or the like) as reactive groups in one molecule. The isocyanate-based crosslinking agent may be used alone or in combination of two or more.

Examples of the isocyanate-based crosslinking agent include aromatic polyisocyanates, alicyclic polyisocyanates, aliphatic polyisocyanates, addition products of these with various polyols, and polyisocyanates polyfunctional with isocyanurate bonds, biuret bonds, allophanate bonds, and the like. More specifically, for example, one or two or more selected from the following may be used: lower aliphatic polyisocyanates such as butene diisocyanate and hexamethylene diisocyanate; alicyclic polyisocyanates such as cyclopentene diisocyanate, cyclohexene diisocyanate, isophorone diisocyanate, hydrogenated toluene diisocyanate, and 1, 3-bis (isocyanatomethyl) cyclohexane; aromatic polyisocyanates such as 2, 4-toluene diisocyanate, 2, 6-toluene diisocyanate, diphenylmethane-4, 4' -diisocyanate, 1, 3-xylene diisocyanate, 1, 4-xylene diisocyanate, tetramethylxylene diisocyanate, 1, 5-naphthalene diisocyanate, triphenylmethane triisocyanate, and polymethylene polyphenyl isocyanates; isocyanate addition products such as trimethylolpropane/toluene diisocyanate trimer addition products, trimethylolpropane/hexamethylene diisocyanate trimer addition products, and isocyanurate products of hexamethylene diisocyanate; trimethylolpropane addition product of xylene diisocyanate; trimethylolpropane addition product of hexamethylene diisocyanate; polyether polyisocyanates, polyester polyisocyanates, addition products of these with various polyols, polyisocyanates polyfunctional with isocyanurate linkages, biuret linkages, allophanate linkages, and the like. Among them, aliphatic polyisocyanates are preferably used, and isocyanurate products of aliphatic diisocyanates (for example, isocyanurate products of hexamethylene diisocyanate) are more preferably used.

(Epoxy-based crosslinking agent)

The epoxy-based crosslinking agent is a compound having two or more epoxy groups as reactive groups in one molecule. The epoxy crosslinking agent may be used singly or in combination of two or more.

Examples of the epoxy-based crosslinking agent include bisphenol a, epichlorohydrin-based epoxy resins, ethylene glycidyl ethers, N' -tetraglycidyl-m-xylylenediamine, diglycidyl aniline, diaminoglycidyl amine, 1, 3-bis (N, N-diglycidyl aminomethyl) cyclohexane, 1, 6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, adipic acid diglycidyl ester, ortho-phthalic acid diglycidyl ester, tris (2-hydroxyethyl) isocyanurate triglycidyl ester, resorcinol diglycidyl ether, bisphenol-S-diglycidyl ether, and the like.

(Aziridine-based crosslinking agent)

The aziridine-based crosslinking agent refers to a compound having two or more aziridine groups as reactive groups in one molecule. The aziridine crosslinking agent may be used alone or in combination of two or more.

Examples of the aziridine-based crosslinking agent include tris-2, 4,6- (1-aziridinyl) -1,3, 5-triazine, tris [1- (2-methyl) -aziridinyl ] phosphine oxide, and hexa [1- (2-methyl) -aziridinyl ] triphosphazepine.

The content of the reactive group in the crosslinking agent (B) is preferably 0.5mmol/g or more, more preferably 1.0mmol/g or more, still more preferably 3.0mmol/g or more, particularly preferably 6.0mmol/g or more, preferably 20mmol/g or less, more preferably 15.0mmol/g or less, still more preferably 12.0mmol/g or less. If the content of the reactive group in the crosslinking agent (B) is within this range, the cohesive force of the adhesive material is good, and even if the adhesive material is bent, the occurrence of deformation at the bending portion can be further suppressed.

The content of the crosslinking agent (B) in the adhesive composition is preferably 0.01 parts by mass or more, more preferably 0.03 parts by mass or more, preferably 1 part by mass or less, more preferably 0.5 parts by mass or less, relative to 100 parts by mass of the copolymer (a). When the content of the crosslinking agent (B) is 0.01 parts by mass or more, sufficient cohesive force can be exhibited, and excellent bendability can be exhibited. When the amount is 1 part by mass or less, sufficient adhesion to the base material can be exhibited, and occurrence of floating separation during bending can be suppressed.

In the adhesive composition, the molar ratio of the reactive functional group(s) of the copolymer (a) to the reactive group(s) of the crosslinking agent (B) (the molar amount of the reactive functional group/the molar amount of the reactive group) is preferably 1 or more, more preferably 2 or more, further preferably 10 or more, preferably 1000 or less, more preferably 200 or less, further preferably 100 or less.

(Other additives)

In addition to the copolymer (A) and the crosslinking agent (B), other additives may be added to the adhesive composition. Examples of the other additives include crosslinking accelerators, crosslinking retarders, tackifying resins (tackifiers), plasticizers, softeners, release aids, silane coupling agents, dyes, pigments, fluorescent brighteners, antistatic agents, wetting agents, surfactants, thickeners, mold inhibitors, preservatives, oxygen absorbers, ultraviolet absorbers, antioxidants, near infrared absorbers, water-soluble matting agents, perfumes, metal deactivators, nucleating agents, alkylating agents, flame retardants, lubricants, and processing aids. These may be appropriately selected and incorporated according to the purpose or purpose of use of the adhesive material.

(Crosslinking accelerator)

The adhesive composition may be used by adding a crosslinking accelerator as needed. Examples of the crosslinking accelerator include organotin compounds and chelates. The crosslinking accelerator may be used alone or in combination of two or more.

Examples of the organotin compound include dibutyltin dilaurate, dioctyltin dilaurate, and dibutyltin dioctoate. The chelate is a complex in which ligands having two or more coordinating atoms form a ring and are bonded to a central metal.

The content of the crosslinking accelerator in the adhesive composition is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, still more preferably 0.04 parts by mass or more, preferably 0.5 parts by mass or less, more preferably 0.4 parts by mass or less, still more preferably 0.3 parts by mass or less, based on 100 parts by mass of the copolymer (a). By setting the content of the crosslinking accelerator within the above range, an excellent crosslinking accelerating effect can be obtained.

(Crosslinking retarder)

The adhesive composition may be used by adding a crosslinking retarder as needed. The crosslinking retarder is a compound capable of inhibiting excessive viscosity increase of the adhesive composition by blocking the functional group of the crosslinking agent in the adhesive composition containing the crosslinking agent. The type of the crosslinking retarder is not particularly limited, and for example, beta-diketones such as acetylacetone, hexane-2, 4-dione, heptane-2, 4-dione, octane-2, 4-dione and the like can be used; beta-ketoesters such as methyl acetoacetate, ethyl acetoacetate, propyl acetoacetate, butyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, stearyl acetoacetate, and the like; benzoyl acetone, and the like. The crosslinking retarder is preferably a crosslinking retarder that can function as a chelating agent, and preferably β -diketones or β -ketoesters.

The content of the crosslinking retarder that can be incorporated in the adhesive composition is preferably 0.1 part by mass or more, more preferably 0.2 part by mass or more, still more preferably 0.5 part by mass or more, preferably 4.0 parts by mass or less, more preferably 3.0 parts by mass or less, still more preferably 1.5 parts by mass or less, relative to 100 parts by mass of the (a) copolymer. By controlling the content of the crosslinking retarder within the above range, it is possible to suppress excessive viscosity increase or gelation of the adhesive composition after the crosslinking retarder (B) is formulated into the adhesive composition, and it is possible to lengthen the storage stability (storage time) of the adhesive composition.

(Silane coupling agent)

The adhesive composition may be used by adding a silane coupling agent as needed. The silane coupling agent is not particularly limited, and examples thereof include epoxy group-containing silane coupling agents such as 3-glycidoxypropyl trimethoxysilane, 3-glycidoxypropyl triethoxysilane, 3-glycidoxypropyl methyldiethoxysilane, and 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane; amino group-containing silane coupling agents such as 3-aminopropyl trimethoxysilane, N-2- (aminoethyl) -3-aminopropyl methyldimethoxysilane, 3-triethoxysilyl-N- (1, 3-dimethylbutylidene) propylamine, and N-phenyl- γ -aminopropyl trimethoxysilane; (meth) acrylic group-containing silane coupling agents such as 3-acryloxypropyl trimethoxysilane and 3-methacryloxypropyl triethoxysilane; and isocyanate group-containing silane coupling agents such as 3-isocyanatopropyltriethoxysilane.

The content of the silane coupling agent to be incorporated in the adhesive composition is preferably 1 part by mass or less, more preferably 0.01 to 1 part by mass, and still more preferably 0.02 to 0.6 part by mass, based on 100 parts by mass of the copolymer (a). By controlling the content of the silane coupling agent within the above range, the water resistance at the interface can be improved when the adhesive material is applied to a hydrophilic adherend such as glass.

(Tackifier)

The adhesive composition may be used by adding a tackifier (excluding the copolymer (A)) as required. The tackifier is not particularly limited, and examples thereof include rosin-based tackifying resins, terpene-based tackifying resins, phenol-based tackifying resins, hydrocarbon-based tackifying resins, and the like.

Examples of the rosin-based tackifying resin include: unmodified rosins (raw rosins) such as gum rosin (gum rosin), wood rosin (wood rosin), tall oil rosin (tall oil rosin), modified rosins (polymerized rosins, stabilized rosins, disproportionated rosins, fully hydrogenated rosins, partially hydrogenated rosins, other chemically modified rosins, etc.) obtained by modifying these unmodified rosins by polymerization, disproportionation, hydrogenation, etc.), various rosin derivatives, and the like.

Examples of the rosin derivatives include: rosin phenol resins obtained by adding phenol to rosin (unmodified rosin, modified rosin) with an acid catalyst and thermally polymerizing the mixture; rosin ester resins such as ester compounds of rosins obtained by esterifying unmodified rosins with alcohols (unmodified rosin esters) and ester compounds of modified rosins obtained by esterifying modified rosins with alcohols (polymerized rosin esters, stabilized rosin esters, disproportionated rosin esters, fully hydrogenated rosin esters, partially hydrogenated rosin esters, etc.); unsaturated fatty acid-modified rosin resin obtained by modifying an unmodified rosin or a modified rosin with an unsaturated fatty acid; unsaturated fatty acid-modified rosin ester resin obtained by modifying rosin ester resin with unsaturated fatty acid; rosin alcohol resins obtained by reducing carboxyl groups in unmodified rosin, modified rosin, unsaturated fatty acid-modified rosin resin or unsaturated fatty acid-modified rosin ester resin; and metal salts of rosin-based resins (particularly rosin ester-based resins) such as unmodified rosin and modified rosin.

Examples of the terpene tackifying resin include: terpene resins such as α -pinene polymer, β -pinene polymer, dipentene polymer, and modified terpene resins (e.g., terpene phenol resins, styrene-modified terpene resins, aromatic-modified terpene resins, hydrogenated terpene resins) obtained by modifying these terpene resins (e.g., phenol modification, aromatic modification, hydrogenation modification, hydrocarbon modification).

Examples of the phenolic tackifying resin include: condensate of various phenols (e.g., phenol, m-cresol, 3, 5-xylenol, p-alkylphenol, resorcinol) and formaldehyde (e.g., alkylphenol-based resin, xylenol-based resin), resol resin obtained by addition reaction of the phenol with formaldehyde with a base catalyst, novolac resin obtained by condensation reaction of the phenol with formaldehyde with an acid catalyst, and the like.

Hydrocarbon-based tackifying resins (petroleum-based tackifying resins) include, for example: an aliphatic hydrocarbon resin [ an aliphatic hydrocarbon polymer such as an olefin having 4 to 5 carbon atoms or a diene (e.g., butene-1, isobutylene, pentene-1, etc.; a diene such as butadiene, 1, 3-pentadiene, isoprene, etc. ], an aliphatic cyclic hydrocarbon resin [ an aliphatic cyclic hydrocarbon resin obtained by subjecting a "C4 petroleum fraction" or a "C5 petroleum fraction" to cyclodimerization, a polymer of a cyclic diene compound (e.g., cyclopentadiene, dicyclopentadiene, ethylidene norbornene, dipentene, etc.), a hydrogenated product thereof, an alicyclic hydrocarbon resin obtained by hydrogenating an aromatic ring of an aromatic hydrocarbon resin or an aliphatic aromatic petroleum resin described below ], an aromatic hydrocarbon resin [ a vinyl-containing aromatic hydrocarbon (e.g., styrene, vinyl toluene, α -methylstyrene, indene, methylindene, etc. ], an aliphatic aromatic petroleum resin (e.g., styrene-olefin copolymer), an aliphatic alicyclic petroleum resin, a hydrogenated hydrocarbon resin, a coumarone indene resin, etc. ].

The content of the tackifier which can be incorporated in the adhesive composition is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, still more preferably 20 parts by mass or more, preferably 60 parts by mass or less, more preferably 50 parts by mass or less, still more preferably 40 parts by mass or less, relative to 100 parts by mass of the (a) copolymer. By adjusting the content of the tackifier in the above range, sufficient adhesion to an adherend can be ensured, and floating separation at the time of bending can be suppressed.

(Method for producing adhesive composition)

The adhesive composition may be prepared by mixing the (a) copolymer, (B) a crosslinking agent, and other additives as needed. The adhesive composition may contain a solvent derived from the preparation of the copolymer (a), and may also be a solution diluted to a viscosity suitable for forming an adhesive layer by further adding an appropriate solvent.

Examples of the solvent include aliphatic hydrocarbons such as hexane and heptane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as methylene chloride and ethylene chloride; 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; glycol ether solvents such as propylene glycol monomethyl ether, and the like. These solvents may be used singly or in combination of two or more.

The amount of the solvent to be used is not particularly limited, as long as the amount is appropriately adjusted so that the adhesive composition becomes a viscosity suitable for coating, but from the viewpoint of coatability, for example, the amount of the solvent is preferably 1 to 90% by mass, more preferably 10 to 80% by mass, and still more preferably 20 to 70% by mass.

(Use of adhesive Material)

The application of the adhesive material is not particularly limited and can be used in a wide range of applications, but is particularly preferably used in flexible displays that can be repeatedly bent and stretched and components used in flexible displays.

Examples of the flexible display that can be repeatedly bent and extended include a foldable display that can be folded and a roll-type display that can be rolled. The flexible display is expected to be applied to mobile terminals such as smart phones and tablet terminals, storable fixed displays and the like.

[ Adhesive sheet ]

The adhesive sheet of the present invention has an adhesive layer for bonding one flexible member to another flexible member and a flexible sheet member attached to at least one surface of the adhesive layer, and is characterized in that the adhesive layer is formed of the above adhesive material.

The constitution of the pressure-sensitive adhesive sheet includes: means having an adhesive layer and a first flexible sheet member attached to one surface of the adhesive layer; has an adhesive layer, a first flexible sheet member attached to one surface of the adhesive layer, and a second flexible sheet member attached to the other surface of the adhesive layer.

An example of the adhesive sheet of the present invention is shown in fig. 1. The adhesive sheet 10 of fig. 1 is composed of an adhesive layer 12, a first flexible sheet member 14 and a second flexible sheet member 16 sandwiching the adhesive layer 12. The adhesive layer 12 is in contact with the release surfaces of the first and second flexible sheet members 14 and 16.

(Adhesive layer)

The thickness of the adhesive layer is preferably 5 μm or more, more preferably 10 μm or more, still more preferably 15 μm or more, and particularly preferably 20 μm or more. When the thickness of the adhesive layer is 5 μm or more, sufficient adhesion to the flexible sheet member can be obtained. The thickness of the adhesive layer is preferably 100 μm or less, more preferably 75 μm or less, and still more preferably 50 μm or less. If the thickness of the adhesive layer is 100 μm or less, extrusion of the adhesive layer can be suppressed.

The adhesive strength of the adhesive layer to the flexible sheet member (excluding the release sheet) at 23℃is preferably 10N/25mm or more, more preferably 15N/25mm or more, and still more preferably 20N/25mm or more. If the thickness is 10N/25mm or more, the adhesive material can be inhibited from floating or peeling off. The upper limit of the adhesive force is not particularly limited, but is usually 50N/25mm or less, preferably 40N/25mm or less.

(Flexible sheet Member)

Examples of the flexible sheet member include a flexible base sheet and a release sheet. The substrate sheet is a sheet member supporting the adhesive layer, and the sheet member may be a functional sheet member. Examples of the functional sheet member include a cover film, a shielding film, a polarizing film, a retardation film, an optical compensation film, a luminance enhancement film, a diffusion film, an antireflection film, and the like. The release sheet is a sheet for protecting the adhesive layer before the adhesive layer is attached to the adherend, and is peeled off from the adhesive layer when the adhesive layer is attached to the adherend.

In general, the term "sheet" in the definition of JIS means a flat plate-like article which is thin and generally has a thickness smaller than the length and width. In general, the term "film" refers to a thin flat product having a minimum thickness and a maximum thickness which are arbitrarily defined as compared with the length and width, and is generally supplied in a roll form (japanese industrial standard JIS K6900). For example, in the narrow sense of thickness, a sheet may be called 100 μm or more, and a film may be called less than 100 μm. However, the sheet is not strictly distinguished from the film, and it is not necessary to distinguish between the two in terms of the present invention, and therefore "film" is included in the present invention even when referred to as "sheet", and "sheet" is included when referred to as "film".

Examples of the flexible sheet member include a sheet of a polymer material, a glass sheet, and the like. The thickness of the flexible sheet member is not particularly limited, but is preferably 2 μm to 500 μm, more preferably 2 μm to 200 μm, from the viewpoint of excellent handleability and the like.

The polymer material includes polyester resins such as polyethylene terephthalate resins and polyethylene naphthalate resins; a polycarbonate resin; a poly (meth) acrylate resin; a polystyrene resin; a polyamide resin; polyimide resin; a polyacrylonitrile resin; polyolefin resins such as polypropylene resins, polyethylene resins, polycycloolefin resins, cycloolefin copolymer resins, and the like; cellulose resins such as triacetyl cellulose resins and diacetyl cellulose resins; polyphenylene sulfide resin; a polyvinyl chloride resin; a polyvinylidene chloride resin; polyvinyl alcohol resins, and the like.

The flexible sheet member may be composed of a single layer or two or more layers composed of a layer containing one or more of the above-mentioned polymer materials, a layer containing one or more of the polymer materials different from the layer, or the like.

The flexible sheet member is preferably a release sheet having a release treatment applied to a surface thereof contacting the adhesive layer. Examples of the release agent used in the release treatment include silicone-based, fluorine-based, alkyd-based, unsaturated polyester-based, polyolefin-based, wax-based and other release agents.

Preferably, the adhesive sheet has a first flexible sheet member attached to one surface of the adhesive layer and a second flexible sheet member attached to the other surface of the adhesive layer, the first flexible sheet member being a first release sheet, the second flexible sheet member being a second release sheet, and the first release sheet and the second release sheet being attached such that their respective release surfaces are in contact with the adhesive layer. When the pressure-sensitive adhesive layer is sandwiched between two release sheets, one release sheet is preferably a heavy release type release sheet having a large release force, and the other release sheet is preferably a light release type release sheet having a small release force.

(Preparation of adhesive sheet)

The adhesive sheet can be prepared, for example, by the following method: the adhesive composition is applied to the flexible sheet member, and if necessary, is cured by a drying heat treatment to form an adhesive layer.

Examples of the application of the adhesive composition include a reverse gravure coating method, a direct gravure coating method, a die coating method, a bar coating method, a wire bar coating method, a roll coating method, a spin coating method, a dip coating method, a spray coating method, a doctor blade coating method, a contact coating method, and various printing methods such as an inkjet method, offset printing, screen printing, and flexographic printing. The surface of the release sheet may be subjected to surface treatments such as corona treatment, plasma treatment, hot air treatment, ozone treatment, and ultraviolet treatment before the application of the adhesive composition.

The drying and curing step is not particularly limited as long as it can remove the solvent or the like used in the adhesive composition and cure it, but is preferably carried out at a temperature of 60 to 150 ℃ for about 20 to 300 seconds. In particular, the drying temperature is preferably from 100℃to 130 ℃.

When the first flexible sheet member is disposed on one surface of the adhesive layer and the second flexible sheet member is disposed on the other surface, the adhesive composition is applied to the first flexible sheet member to form the adhesive layer on the first flexible sheet member, and then the second flexible sheet member is attached to the adhesive layer. Further, the adhesive layer may be cured as needed. The curing conditions include, for example, about 3 to 7 days at 40 ℃.

[ Flexible laminate Member ]

The flexible laminated member of the present invention comprises: the flexible member comprises a first flexible member, a second flexible member, and an adhesive layer for bonding the first flexible member and the second flexible member to each other, wherein the adhesive layer is composed of the adhesive material. Since the adhesive layer of the flexible laminated member is formed of the adhesive material, even when the flexible laminated member is repeatedly bent, the adhesive layer does not float or peel off at the interface between the adhesive layer and the flexible member at the bending portion, and appearance defects such as cracks and wrinkles are suppressed.

Fig. 2 shows an example of the flexible laminated member of the present invention. The bendable laminated member 20 of fig. 2 includes: the first flexible member 22, the second flexible member 24, and the adhesive layer 12 between the first flexible member 22 and the second flexible member 24, which adheres to these flexible members.

Examples of the structure of the flexible laminate member include: both the first flexible member and the second flexible member are the constituent members of the flexible device; the second bending member is a bending device, and the first bending member is a functional sheet member bonded to the bending device. Examples of the flexible device include a foldable display, a roll-up display, and a roll-up display. Examples of the functional sheet member include a cover film, a shielding film, a polarizing film, a retardation film, an optical compensation film, a luminance enhancement film, a diffusion film, an antireflection film, a transparent conductive film, a metal mesh film, and a buffer film.

The first bendable member and the second bendable member are repeatedly bendable members. Examples of the first flexible member and the second flexible member include a flexible substrate material, a functional sheet member, a display element (an organic EL device, an electronic paper device, or the like), and the like. Preferably, at least one of the first flexible member and the second flexible member is a display element. (method for producing Flexible laminate Member)

The method for producing the flexible laminated member of the present invention is not particularly limited, and examples thereof include the following methods (1) to (4).

Method (1): the release sheet attached to one surface of the adhesive sheet is peeled off, and after attaching the exposed adhesive layer to the first flexible member, the release sheet attached to the other surface of the adhesive sheet is peeled off, and the exposed adhesive layer is attached to the second flexible member, thereby obtaining a flexible laminate member.

Method (2): an adhesive composition is applied to one surface of the first flexible member, and if necessary, the adhesive composition is cured by a drying heat treatment to form an adhesive layer, and then a release surface of a release sheet is attached to the adhesive layer. The adhesive layer exposed by peeling the release sheet is attached to the second bendable member, thereby obtaining a bendable laminated member.

Method (3): an adhesive composition is applied to one surface of the first flexible member, and if necessary, the adhesive composition is cured by a drying heat treatment to form an adhesive layer, and then a second flexible member is attached to the adhesive layer, thereby obtaining a flexible laminated member.

Method (4): the release sheet is coated with an adhesive composition on its release surface, and if necessary, the adhesive layer is formed by curing the release sheet by a drying heat treatment, and then the first flexible member is attached to the adhesive layer. The adhesive layer exposed by peeling the release sheet is attached to the second bendable member, thereby obtaining a bendable laminated member.

In any of the above methods (1) to (4), the order in which the first flexible member and the second flexible member are used may be changed.

The adhesive layer may be formed by various coating methods or various printing methods similar to those used for producing the adhesive sheet, and the same steps as in the drying and curing steps may be used. In addition, maintenance can be performed as needed. The release sheet used in the preparation of the flexible laminate member may be the same as that used in the adhesive sheet.

(Specific example of Flexible laminate Member)

A preferred embodiment of the flexible laminated member according to the present invention will be described below with reference to fig. 3. Fig. 3 is a schematic cross-sectional view of a specific example of the flexible laminated member of the present invention. The flexible laminated member 30 shown in fig. 3 includes: the first flexible member 32, the second flexible member 34, and the adhesive layer 12 between the first flexible member 32 and the second flexible member 34 for bonding these flexible members. The first flexible member 32 is a cover film having a cover film base material 32a and a hard coat layer 32b, and the cover film base material 32a is attached to the adhesive layer 12. The second flexible member 34 is a polarizing film.

The adhesive layer 12 is suppressed from floating or peeling at the interface between the first flexible member 32 or the second flexible member 34 at the bending portion. Therefore, even when the flexible laminate member 30 is repeatedly bent, the hard coat layer 32b provided in the cover film (first flexible member) 32 can be suppressed from cracking.

(Cover film substrate)

The cover film base material 32a is not particularly limited as long as it has flexibility and transparency. The cover film base 32a includes a transparent polymer film, a transparent glass film, and the like. Transparency means that the total light transmittance in the visible wavelength range is 50% or more. The total light transmittance is more preferably 85% or more. The total light transmittance was measured according to JIS K7361-1 (1997).

The yellowness index (YI value) of the cover film base material 32a is preferably 20 or less, more preferably 10 or less, and further preferably 5 or less. Thus, a display that displays an image of high transparency and high color reproducibility can be obtained. The yellowness index (YI value) was measured according to JIS K7373 (2006).

The thickness of the cover film base material 32a is not particularly limited, but is preferably 2 μm to 500 μm, more preferably 2 μm to 200 μm, from the viewpoint of operability.

Examples of the polymer material used for the polymer film covering the film base 32a include polyester resins (polyethylene terephthalate resins, polyethylene naphthalate resins, and the like), polycarbonate resins, poly (meth) acrylate resins, polystyrene resins, polyamide resins, polyimide resins, polyacrylonitrile resins, polyolefin resins (polypropylene resins, polyethylene resins, polycycloolefin resins, cycloolefin copolymer resins, and the like), cellulose resins (triacetyl cellulose resins, diacetyl cellulose resins, and the like), polyphenylene sulfide resins, polyvinyl chloride resins, polyvinylidene chloride resins, and polyvinyl alcohol resins.

The polymer material may be composed of only one kind or two or more kinds in combination. From the viewpoints of optical properties, durability, and the like, the polymer material preferably contains at least one selected from the group consisting of polyethylene terephthalate resins, polyimide resins, polycarbonate resins, poly (meth) acrylate resins, polycycloolefin resins, cycloolefin copolymer resins, and triacetyl cellulose resins, and particularly preferably contains a polyimide resin. The polyimide resin-containing film has bending resistance against repeated bending, and is excellent in surface hardness and heat resistance. The content of the polyimide resin in the polymer material is preferably 50 mass% or more, more preferably 70 mass% or more, and still more preferably 90 mass% or more. The polymer material may be composed of only polyimide resin.

The cover film base material 32a may have a single-layer structure or a multilayer structure of two or more layers. Each layer of the cover film base material 32a may be made of one or two or more of the above-mentioned polymer materials.

(Hard coat)

The pencil hardness of the hard coat layer 32b is preferably 3H or more, more preferably 4H or more. The pencil hardness of the hard coat layer 32b is the pencil hardness of the surface of the hard coat layer 32b formed on one surface of the cover film base material 32a, and is measured in a state where the adhesive layer 12 is not formed on the other surface of the cover film base material 32 a. The pencil hardness of the hard coat layer 32b was measured in accordance with JIS K5600-5-4.

The thickness of the hard coat layer 32b is preferably 0.5 μm or more, more preferably 1.0 μm or more, still more preferably 3.0 μm or more, preferably 10.0 μm or less, more preferably 8.0 μm or less, still more preferably 6.0 μm or less. If the thickness is 0.5 μm or more, pencil hardness of the cover film 32 can be sufficiently ensured. When the thickness is 10.0 μm or less, the bending resistance against repeated bending can be sufficiently ensured in the cover film, and curling of the cover film 32 due to the difference in thermal shrinkage between the hard coat layer 32b and the cover film base material 32a can be suppressed. The thickness of the hard coat layer 32b is the thickness of the smooth portion, and in the case where the hard coat layer contains particles, the thickness of the smooth portion is the thickness of the portion in which the projections and depressions caused by the particles are not present in the thickness direction.

The hard coat layer 32b is preferably composed of a cured product of a curable composition containing an ultraviolet-curable compound from the viewpoints of high hardness, high bendability, productivity, and the like.

Examples of the ultraviolet curable compound include monomers, oligomers, and prepolymers having ultraviolet-reactive groups. Examples of the ultraviolet-reactive group include radical-polymerizable reactive groups having an ethylenically unsaturated bond such as a (meth) acryloyl group, an allyl group, and a vinyl group; cationic polymerizable reactive groups such as oxetanyl groups, and the like. Among them, the ultraviolet-reactive group is more preferably a (meth) acryloyl group or an oxetanyl group, and particularly preferably a (meth) acryloyl group.

Examples of the compound having a (meth) acryloyl group include urethane (meth) acrylate, silicone (meth) acrylate, alkyl (meth) acrylate, and aryl (meth) acrylate. Polyurethane (meth) acrylates are particularly preferred from the viewpoints of relatively softness, improved flexibility of the hard coat film, and the like.

The urethane (meth) acrylate is obtained by an addition reaction of a polyol, an isocyanate compound and a (meth) acrylate having a hydroxyl group. Examples of the polyol include polyether polyols, polyester polyols, and polycarbonate polyols, and may be appropriately selected from the viewpoints of flexibility, heat resistance, and chemical resistance.

Examples of the isocyanate compound include aromatic diisocyanates such as toluene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, xylene diisocyanate, and tetramethylxylene diisocyanate; alicyclic diisocyanates such as 1, 4-cyclohexane diisocyanate, isophorone diisocyanate, 4 '-dicyclohexylmethane diisocyanate, methylcyclohexane diisocyanate, isopropylidene dicyclohexyl-4, 4' -diisocyanate, 1, 3-diisocyanato methylcyclohexane, and 4-methyl-1, 3-cyclohexane diisocyanate.

The compound having a (meth) acryloyl group may be a monofunctional (meth) acrylate having one (meth) acryloyl group in a molecule, or may be a multifunctional (meth) acrylate having two or more (meth) acryloyl groups in a molecule. The compound having a (meth) acryloyl group preferably contains a polyfunctional (meth) acrylate.

Examples of the monofunctional (meth) acrylate include: methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, isobornyl (meth) acrylate, 1-adamantyl (meth) acrylate, 2-methyl-2-adamantyl (meth) acrylate, 2-ethyl-2-adamantyl (meth) acrylate, borneol (meth) acrylate, tricyclodecyl (meth) acrylate, undecyl (meth) acrylate, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, 1-naphthylmethyl (meth) acrylate, 2-naphthylmethyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxy-2-methylethyl (meth) acrylate, phenoxyethoxyethyl (meth) acrylate, 3-phenoxy-2-hydroxypropyl (meth) acrylate, 2-phenylphenoxyethyl (meth) acrylate, 4-phenylphenoxyethyl (meth) acrylate, 3- (2-phenylphenyl) -2-hydroxypropyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, butoxyethyl (meth) acrylate, ethoxydiglycol (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, methoxyethylene glycol (meth) acrylate, ethoxyethyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, and the like.

Examples of the multifunctional (meth) acrylate include difunctional (meth) acrylate, trifunctional (meth) acrylate, and tetrafunctional (meth) acrylate. Specific examples thereof include: 1, 4-butanediol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, 1, 9-nonanediol di (meth) acrylate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, tripentaerythritol tetra (meth) acrylate, tripentaerythritol penta (meth) acrylate, tripentaerythritol hexa (meth) acrylate, tripentaerythritol hepta (meth) acrylate, tripentaerythritol octa (meth) acrylate, and the like.

The curable composition may or may not contain a non-ultraviolet curable resin in addition to the ultraviolet curable compound. The curable composition may further contain a photopolymerization initiator. The curable composition may further contain additives and solvents, if necessary. Examples of the additives include inorganic particles, resin particles, antifouling agents, dispersants, leveling agents, antifoaming agents, thixotropic agents, antifouling agents, antibacterial agents, flame retardants, and slip agents.

Examples of the non-ultraviolet curable resin include thermoplastic resins and thermosetting resins. Examples of the thermoplastic resin include polyester resins, polyether resins, polyolefin resins, and polyamide resins. Examples of the thermosetting resin include unsaturated polyester resins, epoxy resins, alkyd resins, and phenolic resins.

Examples of the photopolymerization initiator include photopolymerization initiators such as alkylbenzene ketone type, acylphosphine oxide type, and oxime ester type. Examples of the alkyl-benzophenone photopolymerization initiator include 2,2' -dimethoxy-1, 2-diphenylethane-1-one, 1-hydroxy-cyclohexyl-phenyl-one, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1- [4- (2-hydroxyethoxy) -phenyl ] -2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl ] phenyl } -2-methyl-propan-1-one, 2-methyl-1- [4- (methylthio) phenyl ] -2-morpholinopropan-1-one, 2-benzyl-methyl-2- (dimethylamino) -1- (4-morpholinophenyl) -1-butanone, 2- (dimethylamino) -2- [ (4-methylphenyl) methyl ] -1- (4-morpholinophenone, 2- (4-methylbenzyl) -2- (dimethylamino) -1- (4-morpholinophenone), and N, N-dimethylamino-acetophenone. Examples of the acylphosphine oxide photopolymerization initiator include 2,4, 6-trimethylbenzoyl diphenyl phosphine oxide, bis (2, 4, 6-trimethylbenzoyl) -phenyl phosphine oxide, and bis (2, 6-dimethoxybenzoyl) -2, 4-trimethyl-pentylphosphine oxide. Examples of the oxime ester photopolymerization initiator include 1, 2-octanedione, 1- [4- (phenylthio) phenyl ] -2- (O-benzoyl oxime), and ethanone-1- [ 9-ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl ] -1- (O-acetyl oxime). The photopolymerization initiator may be used alone or in combination of two or more.

The content of the photopolymerization initiator is preferably 0.1 to 10% by mass, more preferably 1 to 5% by mass, based on the total solid content of the curable composition.

For example, inorganic particles and resin particles are added to the hard coat layer for the purpose of preventing blocking, improving the hardness of the hard coat layer, imparting antiglare properties, and the like. Examples of the inorganic particles include silicon oxide and metal oxide particles composed of oxides of metals such as titanium, zirconium, tin, zinc, silicon, niobium, aluminum, chromium, magnesium, germanium, gallium, antimony, and platinum. These inorganic particles may be used alone or in combination of two or more. Among them, titanium oxide particles, zirconium oxide particles, and tin oxide particles are preferable from the viewpoint of excellent compatibility between high hardness and transparency.

Examples of the resin particles include resin particles composed of a resin such as a (meth) acrylic resin, a styrene- (meth) acrylic resin, a urethane resin, a polyamide resin, a silicone resin, an epoxy resin, a phenolic resin, a polyethylene resin, and a cellulose. These resin particles may be used alone or in combination of two or more.

Examples of the anti-fouling agent include fluorine-containing compounds. Examples of the fluorine-containing compound include perfluoroalkyl group-containing (meth) acrylates. Examples of such compounds include "X-71-1203M" manufactured by Kagaku chemical Co., ltd., "MEGAFACE (registered trademark) RS-75" manufactured by DIC Co., ltd., and "OPTOOL (registered trademark) DAC-HP" manufactured by Daiki Kagaku Co., ltd., and "Ftergent (registered trademark) 601AD" manufactured by NEOS Co., ltd. The fluorine-containing compound can inhibit the adhesion of dirt, fingerprints, and the like, and can easily remove dirt, fingerprints, and the like. The content of the fluorine-containing compound is preferably 0.01 to 15% by mass, more preferably 0.05 to 10% by mass, and even more preferably 0.2 to 5% by mass, based on the total amount of the hard coat layer 32 b. When the content of the fluorine-containing compound is within the above range, excellent stain resistance and fingerprint resistance can be obtained.

Examples of the solvent used in the curable composition for forming the hard coat layer 32b include alcohol solvents (ethanol, isopropanol, N-butanol, ethylene glycol monomethyl ether, ethylene glycol monoisopropyl ether, propylene glycol monomethyl ether, diethylene glycol monobutyl ether, and the like), ketone solvents (methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, acetone, and the like), aromatic solvents (toluene, xylene, and the like), ester solvents (ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, and the like), amide solvents (N-methylpyrrolidone, acetamide, dimethylformamide, and the like), and the like. These solvents may be used alone or in combination of two or more.

The solid content concentration (concentration of the component other than the solvent) of the curable composition may be appropriately determined in consideration of coatability, film thickness, and the like, and is, for example, 1 to 90 mass%, preferably 1.5 to 80 mass%, and more preferably 2 to 70 mass%.

(Preparation of cover film)

The cover film may be prepared by forming a hard coat layer 32b on one surface of the cover film substrate 32 a. The hard coat layer 32b can be formed by coating a composition for forming a hard coat layer on one surface of the cover film base material 32a and drying, ultraviolet irradiation, and the like as necessary.

In order to improve the adhesion between the cover film substrate 32a and the hard coat layer 32b, a surface treatment such as corona discharge treatment, plasma treatment, hot air treatment, ozone treatment, or ultraviolet treatment may be performed on the surface of the cover film substrate 32 a. In addition, an easy-to-adhere layer may be provided on the surface of the cover film base material 32 a. Further, various functional layers such as a gas barrier property improving layer, an antistatic layer, an oligomer blocking layer, and the like may be provided on the surface of the cover film substrate 32 a. Further, another hard coat layer may be provided between the cover film base material 32a and the adhesive layer 12.

The composition for forming the hard coat layer 32b may be applied by a coating method (such as a reverse gravure coating method, a direct gravure coating method, a die coating method, a bar coating method, a wire bar coating method, a roll coating method, a spin coating method, a dip coating method, a spray coating method, a doctor blade coating method, and a contact coating method), an inkjet method, and a printing method (such as offset printing, screen printing, and flexographic printing).

The drying is not particularly limited as long as the solvent or the like used in the coating liquid can be removed, but is preferably carried out at 50 to 150℃for about 10 to 180 seconds, particularly preferably 50 to 120 ℃.

The ultraviolet irradiation may be performed by a high-pressure mercury lamp, an electrodeless (microwave-type) lamp, a xenon lamp, a metal halide lamp, or any other ultraviolet irradiation device. The ultraviolet irradiation may be performed under an inert gas atmosphere such as nitrogen, if necessary. The amount of ultraviolet irradiation is not particularly limited, but is preferably 50mJ/cm ²～800mJ/cm², more preferably 100mJ/cm ²～300mJ/cm².

(Polarizing film)

The polarizing film may be, for example, a film in which a protective film is bonded to at least one surface of a polarizing element via an adhesive layer. Further, other optically functional films such as a retardation film and a barrier film may be laminated on the polarizer or the protective film via an adhesive layer, an adhesive material, or the like.

The polarizer is a film having a function of allowing only light in a specific direction to pass therethrough, and for example, a polyvinyl alcohol resin film in which iodine is oriented by uniaxial stretching can be used. The thickness of the polarizer is, for example, 1 μm to 12. Mu.m, preferably 1 μm to 9. Mu.m, more preferably 3 μm to 6. Mu.m.

The protective film may be the same film as the base material used for the cover film. The thickness of the protective film is not particularly limited, but is preferably 2 μm to 500 μm, more preferably 2 μm to 200 μm, from the viewpoint of operability.

The protective film may also function as a phase difference film. The retardation film is an optical film exhibiting optical anisotropy, and can be formed by the following method: a method of stretching a film made of a resin or the like which can be used for a protective film, a method of applying a liquid crystalline compound to a base film, aligning the compound, and curing the compound, and the like. When the polarizing film is used as a circularly polarizing plate for antireflection of an organic EL display device, the retardation film is preferably a λ/4 wave plate for converting linear polarization into circular polarization by imparting a phase difference λ/4 (90 °).

Examples

The present invention will be described in further detail with reference to specific examples. The present invention is not limited to the following examples, and may be carried out with appropriate modifications within the scope of not changing the gist thereof. The polymerization rate, weight average molecular weight (Mw), molecular weight distribution (PDI), gel fraction of the adhesive material, thickness of the adhesive layer, young's modulus, elastic modulus at shrinkage, shear storage modulus, shear stress, recovery rate, and the like of the block copolymer were evaluated according to the following methods.

The abbreviations have the following meanings.

BA: n-butyl acrylate, LA: lauryl acrylate, EHA: 2-ethylhexyl acrylate, IBXA: isobornyl acrylate, ACMO: acryloylmorpholine, AA: acrylic acid, HBA: 4-hydroxybutyl acrylate, DMAAM: dimethylacrylamide, BTEE: ethyl-2-methyl-2-n-butyltellurion-propionate, AIBN: azobisisobutyronitrile, acOEt: ethyl acetate.

(Polymerization Rate)

¹ H-NMR (solvent: CDCl ₃, internal standard: TMS) was measured using a Nuclear Magnetic Resonance (NMR) measuring device (model: AVANCE500 (frequency 500 MHz)) manufactured by Bruker Biospin Co.). The integral ratio of the vinyl group of the monomer to the peak of the ester side chain derived from the polymer was obtained from the obtained NMR spectrum, and the polymerization rate of the monomer was calculated.

(Weight average molecular weight (Mw) and molecular weight distribution (PDI))

The sample was obtained by Gel Permeation Chromatography (GPC) using a high performance liquid chromatograph (model: HLC-8320GPC, manufactured by Tosoh Co., ltd.). Two TSKgel Super MultIpore HZ-H (manufactured by Tosoh Co., ltd.) were used as the column, tetrahydrofuran solution was used as the mobile phase, and a differential refractometer was used as the detector. The measurement conditions were as follows: the column temperature was 40℃and the sample concentration was 10mg/mL, the sample injection amount was 10. Mu.L, and the flow rate was 0.2 mL/min. Polystyrene (molecular weights 2,890,000, 1,090,000, 775,000, 427,000, 190,000, 96,400, 37,900, 10,200, 2,630, 440) was used as a standard substance, a standard curve (calibration curve) was prepared, and weight average molecular weight (Mw) and number average molecular weight (Mn) were measured. From these measured values, the molecular weight distribution (pdi=mw/Mn) was calculated.

(Gel fraction)

The mass W1 of the metal mesh (400 mesh) cut into a width of 50mm and a length of 120mm was measured. 0.1g of a sheet-like adhesive material was removed, and the sheet-like adhesive material was wrapped with a metal mesh so that the adhesive material did not fall off, to prepare a test piece, and the mass W2 of the test piece was measured. The test piece was placed in a glass bottle, 40g of ethyl acetate was poured thereinto, and the mixture was gently shaken, and then allowed to stand at room temperature (25 ℃) for 76 hours. After standing, the test piece was taken out of the glass bottle, left at room temperature for 12 hours, and dried in a vacuum oven at 100℃for 4 hours. The dried test piece was cooled to room temperature, and the mass W3 was measured, and the gel fraction was calculated according to the following formula.

Gel fraction (% by mass) = ((W3-W1)/(W2-W1)) ×100

(Young's modulus)

The sheet-like adhesive material (thickness: 1 mm) was cut into a size of 5mm wide and 70mm long to prepare test pieces. The tensile test was performed using a precision universal tester (AUTOGRAPH (registered trademark) AGX, manufactured by Shimadzu corporation). The test was carried out at 23℃under 50% conditions with a clamp pitch of 30mm and a tensile speed of 30mm/min, and the test piece was elongated until the tensile stress reached 50kPa from a state of 0kPa. The average value of the slope of the tangent line at a clamp pitch of 30.9 to 31.8mm (3 to 6% from the initial clamp pitch) was used as the Young's modulus for the obtained stress-strain curve.

(Modulus of elasticity upon shrinkage)

The sheet-like adhesive material (thickness: 1 mm) was cut into a size of 5mm wide and 70mm long to prepare test pieces. The test was performed using a precision universal tester (AUTOGRAPH (registered trademark) AGX, manufactured by Shimadzu corporation). The test was carried out at 23℃under 50% conditions with a clamp pitch of 30mm and a stretching speed of 30 mm/min. In the test, after the test piece was elongated until the tensile stress reached 50kPa from a state of 0kPa, the test piece was contracted until the tensile stress became 0kPa, and the tensile stress at each elongation upon contraction was recorded. The elongation and contraction were repeated ten times, and the elastic modulus at the time of contraction at the time of the first contraction and the tenth contraction were calculated.

When the displacement from the test piece length under the tensile stress of 50kPa at the nth shrinkage to the test piece length under the tensile stress of 0kPa at the nth shrinkage was 1, the shrinkage elastic modulus was obtained from the tensile stress at the displacement of 0.97 and the tensile stress at the displacement of 0.94.

(Adhesive layer thickness)

The total thickness of the adhesive sheet was measured using a thickness measuring machine (manufactured by Tester Sangyo Co.,. Ltd., "TH-104"), and the thickness of the release sheet was subtracted from the total thickness to obtain the thickness of the adhesive layer.

(Shear storage modulus, shear loss modulus)

The adhesive layer (sheet-like adhesive material) constituting the adhesive sheet was laminated by a hand press roll (hand roll) to prepare a laminate having a thickness of 0.5 mm. Using this laminate as a sample, a viscoelasticity measuring apparatus (manufactured by TA instruments Co., ltd., discovery HR-2) was used under conditions of 23℃and 50% by shearing, geometry: parallel plate (parallel-plate) diameter 8mm, frequency: 1Hz, strain: 1%, and the shear storage modulus and the shear loss modulus were measured.

(Stress when shear stress is applied and the retention time is 10 minutes, recovery)

The adhesive layers (sheet-like adhesive materials) constituting the adhesive sheet were laminated by hand pressure rollers to prepare a laminate having a thickness of 0.5 mm. Using this laminate as a sample, a shear stress was applied to a plate having a diameter of 8mm at 23℃and 50% using a viscoelasticity measuring apparatus (manufactured by TA instruments, discovery HR-2) until the strain reached 200%, and the stress immediately after the strain reached 200% and the stress after continuing to apply the shear stress for 10 minutes were measured.

Then, the applied shear stress was released to set the shear stress to 0kPa, and the strain at 10 minutes of standing was measured. The recovery (%) was calculated from the obtained strain according to the following formula.

Recovery (%) = (200-strain after 10 minutes of standing)/200

(Adhesive force)

One release sheet of the adhesive sheet was peeled off from the adhesive layer, and after attaching a polyethylene terephthalate (PET) film (toyobo ESTEL (registered trademark) film E5100, manufactured by toyobo co., thickness 50 μm) to the surface of the adhesive layer, the other release sheet was peeled off from the adhesive layer, and 2kg roller was reciprocated twice, and the surface of the adhesive layer was laminated on a polyimide film (Kapton (registered trademark) 200V, manufactured by toyobo co., thickness 50 μm).

After bonding for 1 hour, the polyimide film was cut into pieces of 25mm wide and 150mm long, and the adhesive force of the adhesive layer to the polyimide film was measured according to the method of JIS Z0237 (2009) using a precision universal tester "AUTOGRAPH (registered trademark) AGS-1kNX,50N load cell" manufactured by Shimadzu corporation at a peeling speed of 0.5mm/s under a 50% environment at 23 ℃.

(Repeated bending test)

One release sheet of the adhesive sheet was peeled off from the adhesive layer, and after attaching a polyethylene terephthalate (PET) film (toyobo ESTEL (registered trademark) film E5100, manufactured by toyobo co., ltd., thickness 50 μm) to the surface of the adhesive layer, the other release sheet was peeled off from the adhesive layer, and 2kg of the roller was reciprocated twice, and the surface of the adhesive layer was pressed against a polyethylene terephthalate (PET) film (diaface (registered trademark) T330E, manufactured by mitsubishi chemical co., ltd., thickness 150 μm).

The obtained test piece for bending test was cut into a size of 25mm wide and 90mm long, and both short sides were bent and fixed on a endurance tester (U-shaped expansion tester "DLDM LH" manufactured by Yuasa System instruments Co., ltd.) with a thickness of 150 μm on the polyethylene terephthalate (PET) film side as the outside, and bent 20 ten thousand times at a bending diameter (inner diameter, diameter) of 5mm and a reciprocation speed of 60spm (60 times for 1 minute). Test pieces taken out from the tester were visually observed and evaluated according to the following criteria.

And (2) the following steps: there was no floating or peeling between the polyester film and the adhesive layer, and no crack was generated.

X: there is a floating or peeling between the polyester film and the adhesive layer, or a crack is generated.

< Preparation of copolymer >

Synthesis example 1 copolymer No. A

A flask equipped with an argon line and a stirrer was charged with BA (1742.0 g), AA (3.6 g), HBA (54.0 g), AIBN (87.6 mg) and AcOEt (1340 g), and after argon substitution, BTEE (400 mg) was added to conduct polymerization at 60℃for 24 hours.

After the completion of the reaction, acOEt was added to the reaction solution to obtain a copolymer solution containing copolymer No. A. The Mw of the resulting copolymer No. A was 894,000, the PDI was 2.06, and the solid content of the solution was 20.1% by mass.

Synthesis examples 2 to 6, copolymers No. B to F

Copolymers No. B to F were prepared in the same manner as the preparation of copolymer No. A. Table 2 shows the raw material monomers, the organic tellurium compound, the azo polymerization initiator, the solvent, the reaction conditions, and the polymerization rate used. In addition, the composition, mw, PDI, and glass transition temperature of each copolymer are shown in Table 3.

Synthesis example 7 copolymer No. G

A flask equipped with an argon line, a dropping funnel and a stirrer was charged with BA (364.5 g), ACMO (67.5 g), AA (13.5 g), HBA (4.5 g) and AcOEt (276.5 g), and after argon substitution, the temperature was raised to 80 ℃. It took 2 hours to add a solution of AIBN (197.1 mg) dissolved in AcOEt (45 g) and react for another 4 hours to carry out polymerization.

After the completion of the reaction, acOEt was added to the reaction solution to obtain a copolymer solution containing copolymer No. G. The Mw of the resulting copolymer No. G was 873,000, the PDI was 6.48, and the solid content of the solution was 20.0% by mass.

Synthesis example 8 copolymer No. H

Copolymer No. H was prepared in the same manner as the preparation of copolymer No. G. Table 2 shows the raw material monomers, azo polymerization initiator, solvent, reaction conditions, and polymerization rate used. In addition, the composition, mw, PDI, glass transition temperature of the copolymer are shown in Table 3.

TABLE 2

TABLE 3 Table 3

< Preparation of adhesive composition >

(Adhesive composition No. 1)

To 100 parts by mass of the copolymer component of copolymer No. A obtained in Synthesis example 1, 0.076 parts by mass of a crosslinking agent (PolyNede (registered trademark) TPA-100), 0.023 parts by mass of a crosslinking accelerator (NEOSTANN (registered trademark) U-810), 0.33 parts by mass of a crosslinking retarder (acetylacetone), 30 parts by mass of a tackifier (FTR (registered trademark) 6100) and AcOEt were added, and the mixture was stirred to obtain an adhesive composition No.1.

(Adhesive compositions No. 2-16)

Adhesive compositions nos. 2 to 16 were prepared in the same manner as adhesive composition No.1, except that the proportions were changed as described in table 4.

TABLE 4 Table 4

Tetra (registered trademark) -C: 1, 3-bis (N, N-diglycidyl aminomethyl) cyclohexane (epoxy amount: 9.76 mmol/g) manufactured by Mitsubishi gas chemical Co., ltd

TPA-100: karaku Kagaku Co., ltd., duozide (Duranate) (registered trademark) TPA-100 (isocyanurate product of hexamethylene diisocyanate (NCO%: 23.1 mass%))

U-810: manufactured by Nidong chemical Co., ltd., NEOSTANN (registered trademark) U-810 (Dioctyltin)

AcAc: acetylacetone (acetylacetone)

FTR6100: FTR (registered trademark) 6100 (aromatic hydrocarbon resin) manufactured by Mitsui chemical Co., ltd

FTR8120: FTR (registered trademark) 8120 (aromatic hydrocarbon resin) manufactured by Mitsui chemical Co., ltd

< Sheet-like adhesive Material >

A container having a length of 70mm X a width of 70mm X a height of 20mm was prepared by using a release sheet (polyethylene terephthalate (PET) film having a release-treated surface, CLEAN SEPA (registered trademark) HY-S10: manufactured by Toshan film Co., ltd., thickness of 38 μm) and taking the release-treated surface as an inner side. The adhesive compositions were placed in the vessel so that the film thickness after drying became 1.0mm, and after drying at 60℃for 12 hours in a thermostatic dryer, the adhesive material was taken out of the vessel to prepare a sheet-like adhesive material. The evaluation results of the sheet-like adhesive materials are shown in table 5.

TABLE 5

As shown in Table 5, sheet-like adhesive materials Nos. 1 to 13 are cured products of adhesive compositions containing (meth) acrylic copolymers having reactive functional groups and a crosslinking agent, wherein the (meth) acrylic copolymers are copolymers obtained by living radical polymerization, and the adhesive materials have a predetermined Young's modulus and retention of elastic modulus upon shrinkage.

< Preparation of adhesive sheet >

The adhesive composition was applied to the release surface of the first release sheet (PET film having a release-treated surface, CLEAN SEPA (registered trademark) HY-S10: manufactured by Toshan film Co., ltd., thickness of 38 μm) using a baking coater so that the film thickness after drying became 25 μm, and then dried at 120℃for 3 minutes using a thermostatic dryer. Then, a release liner of a second release sheet (PET film having a release-treated surface, CLEAN SEPA (registered trademark) HY-S10: manufactured by Toshan film Co., ltd., thickness: 38 μm) was attached to the adhesive layer formed on the first release sheet, and then cured at 40℃for 3 days to prepare an adhesive layer sandwiched between the two release sheets. The evaluation results of the adhesive sheets are shown in table 6.

TABLE 6

As shown in table 6, the adhesive layers of the adhesive sheets nos. 21, 22, 23 and 25 were formed of the above-mentioned sheet-like adhesive materials nos. 4, 9, 11 and 13. Even if these adhesive sheets are repeatedly bent, no lifting or peeling or the like occurs at the interface between the adhesive layer and the flexible member at the bending portion, and occurrence of appearance defects such as cracks or wrinkles is suppressed.

Possibility of industrial use

The adhesive material of the present invention can be used for bonding one flexible member (e.g., a functional sheet member) and another flexible member (e.g., a display element) constituting a flexible display that can be repeatedly bent and stretched for use.

Claims

1. An adhesive material for bonding one flexible member to another flexible member, characterized in that,

The adhesive material is a cured product of an adhesive composition containing a (meth) acrylic copolymer having a reactive functional group and a crosslinking agent,

The (meth) acrylic copolymer is a copolymer obtained by living radical polymerization, has a molecular weight distribution, that is, mw/Mn, of 3.0 or less,

The adhesive material has a shear storage modulus at 23 ℃ of 0.8X10 ⁴Pa～30×10⁴ Pa,

The Young's modulus of the adhesive material is 10kPa to 1000kPa,

The gel fraction of the adhesive material is 42.4 to 49.7 mass%, 55.2 to 67.8 mass%, 70.6 to 73.9 mass% or 75.4 to 80.4 mass%,

The adhesive material is stretched until the tensile stress reaches 50kPa, and then the adhesive material is contracted by releasing the tensile stress, and when the test is repeated ten times, the ratio of the elastic modulus at the tenth contraction to the elastic modulus at the first contraction is 60% or more.

2. The adhesive material according to claim 1, wherein the (meth) acrylic copolymer has a weight average molecular weight of 20 to 200 ten thousand.

3. The adhesive material of claim 1, wherein the reactive functional groups are carboxyl and/or hydroxyl groups.

4. The adhesive material of claim 2, wherein the reactive functional groups are carboxyl and/or hydroxyl groups, the adhesive material having a shear loss modulus at 23 ℃ of 0.40 x 10 ⁴Pa～27×10⁴ Pa.

5. The adhesive material according to any one of claims 1 to 4, wherein the crosslinking agent has an epoxy group and/or an isocyanate group.

6. An adhesive sheet having an adhesive layer for bonding one flexible member to another flexible member and a flexible sheet member attached to at least one surface of the adhesive layer, characterized in that the adhesive layer is formed of the adhesive material according to any one of claims 1 to 5.

7. The adhesive sheet according to claim 6, wherein the adhesive sheet has a first flexible sheet member attached to one surface of the adhesive layer and a second flexible sheet member attached to the other surface of the adhesive layer,

The first flexible sheet member is a first release sheet, the second flexible sheet member is a second release sheet,

The first release sheet and the second release sheet are attached such that the release surfaces of the first release sheet and the second release sheet are in contact with the adhesive layer.

8. A flexible laminated member is provided with: the adhesive material according to any one of claims 1 to 5, comprising a first flexible member, a second flexible member, and an adhesive layer for bonding the first flexible member and the second flexible member to each other.

9. The flexible laminate component of claim 8, wherein at least one of the first flexible component and the second flexible component is a display element.

10. An apparatus comprising the flexible laminate component according to claim 8 or 9.