CN118055990A

CN118055990A - Adhesive material and adhesive sheet

Info

Publication number: CN118055990A
Application number: CN202280066183.XA
Authority: CN
Inventors: 白神幸男
Original assignee: Otsuka Chemical Co Ltd; Higashiyama Film Co Ltd
Current assignee: Otsuka Chemical Co Ltd; Higashiyama Film Co Ltd
Priority date: 2021-11-02
Filing date: 2022-10-27
Publication date: 2024-05-17
Also published as: WO2023080054A1; TW202336197A

Abstract

Technical problems: provided is an adhesive material having excellent adhesive force and excellent restorability. The technical scheme is as follows: an adhesive material comprising a cured product of an adhesive composition containing (A) a (meth) acrylic copolymer having a crosslinkable functional group and (B) a crosslinking agent, wherein the (A) acrylic copolymer is a copolymer obtained by living radical polymerization, the cured product contains (X) a (meth) acrylic compound having a molecular weight of 500 or less, and the content of the (X) (meth) acrylic compound in the cured product is 60 to 5000 mass ppm.

Description

Adhesive material and adhesive sheet

Technical Field

The present invention relates to an adhesive material and an adhesive sheet, and more particularly, to an adhesive material and an adhesive sheet for adhering one flexible member to another flexible member.

Background

Among various displays and touch screens for televisions, mobile phones, smartphones, and the like, adhesive materials are generally used for joining members constituting the displays and touch screens. The adhesive material is provided, for example, in the form of a base material-provided adhesive sheet having an adhesive layer on a supporting base material or a base material-free adhesive sheet having no supporting base material, and bonds the members together.

In recent years, flexible displays that are repeatedly used in bending have been attracting attention 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 constituting a repeatedly bendable and stretchable member and another flexible member in such a flexible display, for example, patent document 1 describes an adhesive material for bonding a flexible member and another flexible member, wherein 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 (Mw/Mn) of 3.0 or less, the young's modulus of the adhesive material being 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 the test is repeated ten times.

Prior art literature

Patent literature

Patent document 1: international publication No. 2021/111995

Disclosure of Invention

Technical problem to be solved by the invention

An adhesive material composed of an adhesive composition containing a (meth) acrylic copolymer obtained by living radical polymerization (LIVING RADICAL polymerization) has a smaller adhesive force than that of radical polymerization (FREE RADICAL polymerization). Therefore, although the adhesive is suitable for use in re-peeling such as engineering protective films, it is required to improve the adhesive force in use in which peeling is not performed any more. For example, as an adhesive material for bonding a flexible member and another flexible member, in order to suppress occurrence of lifting or peeling at an interface between the adhesive material and the flexible member at a bending portion even if bending is repeated, not only restorability but also improvement of adhesive force are required.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an adhesive material having excellent adhesive force and excellent recovery.

Solution for solving the technical problems

The adhesive material of the present invention, which can solve the above-described problems, is composed of a cured product of an adhesive composition containing (a) a (meth) acrylic copolymer having a crosslinkable functional group and (B) a crosslinking agent, wherein the (a) (meth) acrylic copolymer is a copolymer obtained by living radical polymerization, the cured product contains (meth) acrylic compound having (X) molecular weight of 500 or less, and the content of the (X) (meth) acrylic compound in the cured product is 60 to 5000 mass ppm.

Effects of the invention

The adhesive material of the present invention has excellent adhesive force and excellent recovery. Therefore, by using the adhesive material of the present invention for joining the flexible members, even if the bending is repeated, the occurrence of floating or peeling at the interface between the adhesive material and the flexible members at the bending portion can be suppressed.

Drawings

Fig. 1: an example of the pressure-sensitive adhesive sheet of the present invention is schematically illustrated in cross section.

Fig. 2: a schematic cross-sectional view of one example of a flexible laminate component of the present invention.

Symbol description: 10: adhesive sheet, 12: adhesive layer, 14: first flexible sheet member, 16: a second flexible sheet member, 20: flexible laminate member, 22: first flexible part, 24: second flexible part

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 composed of a cured product of an adhesive composition containing (A) a (meth) acrylic copolymer having a crosslinkable functional group and (B) a crosslinking agent, wherein the (A) (meth) acrylic copolymer is a copolymer obtained by living radical polymerization, the cured product contains (X) a (meth) acrylic compound having a molecular weight of 500 or less (hereinafter simply referred to as "(X) (meth) acrylic compound"), and the content of the (X) (meth) acrylic compound in the cured product is 60 to 5000 mass ppm.

The adhesive material can improve adhesive force while maintaining excellent recovery and holding power by containing a predetermined amount of (X) (meth) acrylic compound.

((X) (meth) acrylic Compound)

The adhesive material (cured product of the adhesive composition) contains (X) a (meth) acrylic compound having a molecular weight of 500 or less. The (X) (meth) acrylic compound is a compound having a (meth) acryloyl group.

The molecular weight of the (X) (meth) acrylic compound is 500 or less, preferably 300 or less, and more preferably 250 or less. If the molecular weight of the (X) (meth) acrylic compound is 500 or less, the content can be easily adjusted in the step of forming the adhesive material, and the adhesive force of the adhesive material can be improved. The molecular weight of the (X) (meth) acrylic compound is preferably 70 or more, more preferably 100 or more, and further preferably 150 or more. When the molecular weight of the (X) (meth) acrylic compound is 70 or more, an adhesive material excellent in adhesive force and flexibility can be formed.

The (X) (meth) acrylic compound includes: (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, (meth) acrylamides, and the like. 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 total content of the (meth) acrylate having a linear alkyl group and the (meth) acrylate having a branched alkyl group in the (X) (meth) acrylic compound is preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably 90% by mass or more.

The (meth) acrylate having a linear alkyl group is preferably a (meth) acrylate having a linear alkyl group having 1 to 20 carbon atoms, and more preferably a (meth) acrylate having a linear alkyl group having 4 to 15 carbon atoms. As the (meth) acrylate having a linear alkyl group, there may be mentioned: straight-chain 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) acrylate 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) 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 (for example, cycloalkyl groups), and may have a chain portion. As examples of the (meth) acrylic acid ester having a cyclic alkyl group of a monocyclic structure, there may be mentioned: cyclic alkyl (meth) acrylates such as cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, cyclododecyl (meth) acrylate, and the like.

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 aromatic group-containing (meth) acrylate include: a compound wherein an aryl group is directly bonded to a (meth) acryloyloxy group, a compound wherein an aralkyl group is directly bonded to a (meth) acryloyloxy group, and a compound wherein 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) acrylate having an aromatic group include benzyl (meth) acrylate, phenyl (meth) acrylate, phenoxyethyl (meth) acrylate, and the like.

The boiling point (760 mmHg) of the (X) (meth) acrylic compound is preferably 100℃or higher, more preferably 150℃or higher, further preferably 200℃or higher, preferably 500℃or lower, more preferably 400℃or lower, further preferably 350℃or lower. If the boiling point is 100 ℃ or higher, an adhesive material excellent in adhesive force and flexibility can be formed, and if it is 500 ℃ or lower, the content can be easily adjusted in the step of forming the adhesive material, and the adhesive force of the adhesive material can be improved.

The boiling points (760 mmHg) of representative (meth) acrylic compounds are shown in Table 1.

TABLE 1

Short for short	Monomer name	Boiling point (760 mmHg) (. Degree.C.)
			HBA	Acrylic acid 4-hydroxybutyl ester	298
AA	Acrylic acid	141
			EHA	2-Ethylhexyl acrylate	216
BA	Acrylic acid n-butyl ester	146
			LA	N-dodecyl acrylate	306
MA	Acrylic acid methyl ester	80
			EA	Acrylic acid ethyl ester	100
HEA	Acrylic acid 2-hydroxy ethyl ester	196
			MMA	Methyl methacrylate	100

The content of the (X) (meth) acrylic compound in the adhesive material (cured product of the adhesive composition) is preferably 60 mass ppm or more, more preferably 70 mass ppm or more, further preferably 80 mass ppm or more, preferably 5000 mass ppm or less, more preferably 1000 mass ppm or less, further preferably 500 mass ppm or less. The (X) (meth) acrylic compound is contained in an amount of 60 mass ppm or more, which results in more excellent recovery and retention, and is contained in an amount of 5000 mass ppm or less, which results in an adhesive material excellent in adhesive force.

The content of the (X) (meth) acrylic compound in the adhesive material can be adjusted by the addition amount of the (meth) acrylic compound added to the adhesive composition. The (X) (meth) acrylic compound may be added separately, or an unreacted monomer contained in a solution of the (a) (meth) acrylic copolymer described later may be used as the (X) (meth) acrylic compound.

The adhesive composition forming the adhesive material of the present invention contains (a) a (meth) acrylic copolymer having a crosslinkable functional group and (B) a crosslinking agent.

((A) (meth) acrylic copolymer)

The adhesive composition contains (A) a (meth) acrylic copolymer having a crosslinkable functional group (hereinafter, sometimes simply referred to as "(A copolymer").

The (a) (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% of the total 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) acrylic acid ester is an ester compound in which a hydrogen atom of a carboxyl group of (meth) acrylic acid is replaced with an organic 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 copolymer (A) has a crosslinkable functional group which reacts with a crosslinking agent (B) described later. The crosslinkable functional group reacts with a crosslinkable point of the crosslinking agent (B) described later. The crosslinkable functional groups may be one kind or two or more kinds. Examples of the crosslinkable functional group include at least one 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 total amount of crosslinkable functional groups per unit mass of the copolymer (A) is preferably 0.5. Mu. Mol/g or more, more preferably 5. Mu. Mol/g or more, still more preferably 10. Mu. Mol/g or more, particularly preferably 15. Mu. Mol/g or more, preferably 1500. Mu. Mol/g or less, more preferably 1000. Mu. Mol/g or less, still more preferably 700. Mu. Mol/g or less, particularly preferably 500. Mu. Mol/g or less. The adhesive material obtained has excellent durability when the total amount of the crosslinkable functional groups is 5. Mu. Mol/g or more, and has excellent adhesion to an adherend when the total amount is 1500. Mu. Mol/g or less.

When the (A) copolymer has carboxyl groups, the amount of carboxyl groups per unit mass of the (A) copolymer is preferably 5. Mu. Mol/g or more, more preferably 50. Mu. Mol/g or more, still more preferably 100. Mu. Mol/g or more, particularly preferably 150. Mu. Mol/g or more, preferably 1500. Mu. Mol/g or less, more preferably 1000. Mu. Mol/g or less, still more preferably 700. Mu. Mol/g or less, and particularly preferably 500. Mu. Mol/g or less.

When the (A) copolymer has hydroxyl groups, the hydroxyl groups per unit mass of the (A) copolymer are preferably 0.5. Mu. Mol/g or more, more preferably 5. Mu. Mol/g or more, still more preferably 10. Mu. Mol/g or more, particularly preferably 15. Mu. Mol/g or more, preferably 150. Mu. Mol/g or less, more preferably 100. Mu. Mol/g or less, still more preferably 70. Mu. Mol/g or less, and particularly preferably 50. Mu. Mol/g or less.

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

The content of the structural unit derived from the vinyl monomer having a crosslinkable 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 having an excellent balance between adhesion to an adherend and durability can be formed. The vinyl monomer having a crosslinkable functional group includes: a (meth) acrylic acid-based monomer having a crosslinkable functional group, and a vinyl monomer other than the (meth) acrylic acid-based monomer having a crosslinkable functional group.

The (meth) acrylic acid based monomer may be: (b1) A (meth) acrylic acid-based monomer having no crosslinkable functional group, and a (b 2) a (meth) acrylic acid-based monomer having a crosslinkable 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 crosslinkable functional group is preferably (meth) acrylic acid ester monomer (b 1-1) having no crosslinkable functional group. The (meth) acrylic acid-based monomer having a crosslinkable functional group of (b 2) may be (meth) acrylic acid ester monomer having a crosslinkable functional group of (b 2-1).

The (meth) acrylic acid based monomer (b 1) having no crosslinkable functional group includes: (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 an alicyclic hydrocarbon group, (meth) acrylic acid esters having an aromatic group, (meth) acrylic acid esters having a tertiary amine group, (meth) acrylamides, and the like. 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, and more preferably a (meth) acrylate having a linear alkyl group having 5 to 15 carbon atoms. As the (meth) acrylate having a linear alkyl group, there may be mentioned: straight-chain 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.

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

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 (for example, adamantyl, norbornyl, isobornyl), and may have a chain moiety. As examples of the (meth) acrylate having a polycyclic structure, there may be mentioned: borneol (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, dicyclopentenyl (meth) acrylate, dicyclopentyloxyethyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, and the like.

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 aromatic group-containing (meth) acrylate include: a compound wherein an aryl group is directly bonded to a (meth) acryloyloxy group, a compound wherein an aralkyl group is directly bonded to a (meth) acryloyloxy group, and a compound wherein 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 aromatic group-containing (meth) acrylate include: benzyl (meth) acrylate, phenyl (meth) acrylate, phenoxyethyl (meth) acrylate, and the like.

Examples of the (meth) acrylate 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, 4- (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 crosslinkable functional group of (b 2) may be: a (meth) acrylic acid based monomer having a hydroxyl group (preferably a (meth) acrylate 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) acrylate 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: monomers obtained by reacting anhydrides such as maleic anhydride, succinic anhydride, and phthalic anhydride with (meth) acrylic esters having hydroxyl groups (for example, hydrogen 2-acryloyloxyethyl succinate, hydrogen 2-methacryloyloxyethyl succinate, hydrogen 2- (acryloyloxy) ethyl hexahydrophthalate, hydrogen 2- (methacryloyloxy) ethyl hexahydrophthalate, 1- (2-acryloyloxy) ethyl phthalate, and 1- (2-methacryloyloxy) ethyl phthalate) and (meth) acrylic acid) such as carboxyethyl (meth) acrylate, 2- (meth) acryloyloxyethyl succinate, carboxypentyl (meth) acrylate, 2- (meth) acryloyloxyethyl succinate, 2- (meth) acryloyloxyethyl maleate, 2- (meth) acryloyloxyethyl phthalate, and the like. Among them, (meth) acrylic acid is preferable.

Examples of the (meth) acrylate having an epoxy group include: glycidyl (meth) acrylate, 3, 4-epoxycyclohexylmethyl (meth) acrylate, and the like.

Examples of the vinyl monomer other than the (meth) acrylic acid based monomer include: (b3) A vinyl monomer other than the (meth) acrylic acid based monomer having no crosslinkable functional group, and a vinyl monomer other than the (meth) acrylic acid based monomer having a crosslinkable functional group (b 4). These monomers may be used alone or in combination of two or more.

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

Examples of the aromatic vinyl monomer include: styrene, alpha-methylstyrene, 4-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methoxystyrene, 1-vinylnaphthalene, etc.

Examples of the heterocyclic ring-containing vinyl monomer include: 2-vinyl thiophene, N-methyl-2-vinyl pyrrole, 2-vinyl pyridine, 4-vinyl pyridine, and the like.

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

Examples of the tertiary amine group-containing vinyl monomer include: n, N-dimethylallylamine, and the like.

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

As the α -olefin, there may be mentioned: 1-hexene, 1-octene, 1-decene, etc.

The dienes include: butadiene, isoprene, 4-methyl-1, 4-hexadiene, 7-methyl-1, 6-octadiene, and the like.

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

Examples of the vinyl monomer other than the (meth) acrylic acid based monomer having a crosslinkable functional group (b 4) include: vinyl monomers having hydroxyl groups, vinyl monomers having carboxyl groups, vinyl monomers having epoxy groups, and the like.

Examples of the vinyl monomer having a hydroxyl group include: para-hydroxystyrene, allyl alcohol, and the like.

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-allyl ethylene oxide, glycidyl vinyl ether, 3, 4-epoxycyclohexyl vinyl ether, and the like.

The polymer (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 300 ten thousand or less, more preferably 200 ten thousand or less, further preferably 150 ten thousand or less, and particularly preferably 110 ten thousand or less. If the Mw of the copolymer (A) is 20 ten thousand or more, the cohesive force is improved, the heat resistance of the adhesive material is improved, and if it is 300 ten thousand or less, the coating workability of the adhesive composition is improved. The method for measuring the weight average molecular weight (Mw) is described below.

The molecular weight distribution (Mw/Mn) of the copolymer (A) is preferably 3.0 or less, more preferably 2.7 or less, and further preferably 2.5 or less. The smaller Mw/Mn, the narrower the amplitude of the molecular weight distribution, and the more uniform the molecular weight, and the narrowest amplitude of the molecular weight distribution when the value is 1.0. If Mw/Mn is 3.0 or less, the copolymer having a small molecular weight or the copolymer having a large molecular weight is contained in a small 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 (Mw/Mn) 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, still more preferably-20℃or lower, particularly preferably-35℃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 2.

TABLE 2

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

((A) Process for producing (meth) acrylic copolymer)

The copolymer (a) is obtained by living radical polymerization of a monomer composition containing two or more vinyl monomers (obtained by polymerization using a living radical polymerization method).

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 crosslinkable functional groups of the copolymer produced 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 formed adhesive layer becomes uniform as a whole. If the crosslinking point density is uniform as a whole, the recovery rate of the adhesive layer can be made more excellent.

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 of using a compound capable of generating a nitroxide radical (nitroxide method: NMP method); a method of actively polymerizing a halogenated compound as a polymerization initiator compound from a metal complex such as copper or ruthenium (ATRP method); a method using a dithiocarboxylic ester or xanthate compound (RAFT method); a method using an organic tellurium compound (TERP method); a method using an organic iodide (ITP method); a method of using an iodine compound as a polymerization initiator compound and using a phosphorus compound, a nitrogen compound, an oxygen compound, or an organic compound such as hydrocarbon as a catalyst (reversible chain transfer catalytic polymerization: RTCP method, reversible complex mediated polymerization: RCMP method), or 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—R¹ (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. 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 without 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: acetonitrile, methyl ethyl ketone, anisole, benzene, toluene, propylene glycol monomethyl ether acetate, ethyl acetate, tetrahydrofuran (THF), N-Dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), acetone, dioxane, chloroform, carbon tetrachloride, and the like. Examples of the protic solvent include: water, methanol, ethanol, isopropanol, n-butanol, ethyl cellosolve, butyl cellosolve, 1-methoxy-2-propanol, hexafluoroisopropanol, diacetone alcohol, etc. 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, and for example, it is preferably 0.01ml to 50ml per gram 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. In this case, the pressure is usually applied at normal pressure, but may be increased or decreased. 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 ends is colored or has poor thermal stability, the tellurium atoms can be removed. As a method for removing tellurium atoms, a radical reduction method is exemplified; 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 crosslinkable points in one molecule which can crosslink with the functional group (preferably the crosslinkable functional group) of the copolymer (a). The crosslinkable point means a reactive group that can react with a functional group that the copolymer (a) has. In the crosslinking agent (B), the number of crosslinkable points is the number of alkoxy groups, acylated (acylate) groups, isocyanate groups, epoxy groups or aziridine groups.

Examples of the crosslinking agent include: isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, metal chelate-based crosslinking agents, melamine-based crosslinking agents, urea-based crosslinking agents, and the like. The crosslinking agent may be used alone or in combination of two or more. Among them, isocyanate-based crosslinking agents, epoxy-based crosslinking agents, and aziridine-based crosslinking agents are preferable, isocyanate-based crosslinking agents and 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, and epoxy-based crosslinking agents are particularly preferable from the viewpoint of heat 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, 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 as2, 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-based epoxy resins, 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, phthalic acid diglycidyl ester, tris (2-hydroxyethyl) isocyanurate, resorcinol diglycidyl ether, bisphenol-S-diglycidyl ether, and the like.

The content of the crosslinkable site of 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 20.0mmol/g or less, more preferably 15.0mmol/g or less, still more preferably 12.0mmol/g or less. (B) If the content of the crosslinkable point of the crosslinking agent is within this range, the cohesive force of the formed adhesive material becomes better, and even if it is bent, deformation at the bent portion can be suppressed even further.

The total amount of crosslinkable points of the crosslinking agent (B) in the adhesive composition is preferably 1. Mu. Mol/g or more, more preferably 2. Mu. Mol/g or more, still more preferably 3. Mu. Mol/g or more, preferably 100. Mu. Mol/g or less, still more preferably 50. Mu. Mol/g or less, and still more preferably 10. Mu. Mol/g or less, per unit mass of the copolymer (A). (B) When the total amount of crosslinkable points of the crosslinking agent is 1. Mu. Mol/g or more, sufficient cohesive force is exhibited, and the adhesive material thus formed exhibits excellent bendability, and when it is 100. Mu. Mol/g or less, the adhesion of the adhesive material to the substrate is improved, and occurrence of floating delamination during bending is suppressed.

The molar ratio of the crosslinkable functional group(s) of the copolymer (a) to the total amount of crosslinkable points of the crosslinking agent (B) (the molar amount of the crosslinkable functional group (s)/the molar amount of the crosslinkable points) in the adhesive composition is preferably 4 or more, more preferably 8 or more, further preferably 40 or more, preferably 500 or less, more preferably 250 or less, and further preferably 120 or less.

(Other additives)

In addition to the copolymer (A) and the crosslinking agent (B), other additives may be added to the adhesive composition. As other additives, there may be mentioned: crosslinking accelerators, crosslinking retarders, tackifying resins (tackifiers), silane coupling agents, polymerizable compounds, photopolymerization initiators, plasticizers, softeners, release aids, dyes, pigments, optical 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, processing aids, and the like. These may be appropriately selected and incorporated according to the purpose or purpose of use of the adhesive material.

(Crosslinking retarder)

The adhesive composition may be formulated with 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 β -diketones and β -ketoesters are preferable, and acetylacetone is particularly preferable.

The content of the crosslinking retarder that can be incorporated in the adhesive composition is preferably 0.01 part by mass or more, more preferably 0.03 part by mass or more, still more preferably 0.08 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 1.0 part 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 part by mass to 1 part by mass, and still more preferably 0.02 part by mass 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 in the case where the adhesive material is applied to a hydrophilic adherend such as glass.

(Tackifying resin)

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

Examples of hydrocarbon-based tackifying resins (petroleum-based tackifying resins) include: 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 resin to 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, based on 100 parts by mass of the copolymer (a). By adjusting the content of the tackifier resin in the above range, sufficient adhesion between the formed adhesive material and the adherend can be ensured, and floating separation at the time of bending can be suppressed.

(Polymerizable Compound)

The adhesive composition may be incorporated with a polymerizable compound. The adhesive material can be given flexibility by adding a polymerizable compound and polymerizing the polymerizable compound in the adhesive material.

The polymerizable compound may be a compound having two or more polymerizable groups in one molecule. Examples of the polymerizable group include an ethylenically unsaturated group and the like. The polymerizable compounds may be used alone or in combination of two or more. The polymerizable compound may be a compound having two or more (meth) acryloyl groups, and preferably a polyfunctional monomer or a polyfunctional oligomer. The number of ethylenically unsaturated groups in one molecule of the polymerizable compound is preferably 2 or more, preferably 4 or less, more preferably 3 or less.

Examples of the compound having two or more (meth) acryloyl groups include: hexanediol di (meth) acrylate, butanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, isocyanuric acid ethylene oxide modified tri (meth) acrylate, allyl (meth) acrylate, vinyl (meth) acrylate, urethane (meth) acrylate, and the like.

When the polymerizable compound is added to the adhesive composition, the content of the polymerizable compound is preferably 0.1 part by mass or more, more preferably 2.5 parts by mass or more, preferably 100 parts by mass or less, and still more preferably 50 parts by mass or less, based on 100 parts by mass of the copolymer (a).

(Photopolymerization initiator)

When the polymerizable compound is cured by active energy rays, a photopolymerization initiator is preferably added to the adhesive composition. By adding the photopolymerization initiator, the reaction upon irradiation with active energy rays can be stabilized. The photopolymerization initiator is not particularly limited as long as it is a photopolymerization initiator that generates radicals by the action of light, and examples thereof include acetophenones, benzoins, benzophenones, thioxanthones, acylphosphinoxides, and the like. These photopolymerization initiators can be used singly or in combination of two or more. Among these photopolymerization initiators, those of the hydrogen abstraction type, or the intramolecular cleavage type are preferable from the viewpoint of being capable of crosslinking efficiently between molecules or intramolecular.

When the photopolymerization initiator is added to the adhesive composition, the content of the photopolymerization initiator is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, further preferably 0.5 parts by mass or more, preferably 10 parts by mass or less, more preferably 5 parts by mass or less, further preferably 2 parts by mass or less, based on 100 parts by mass of the copolymer (a). If the content of the photopolymerization initiator is within the above range, the curing speed increases, and insufficient curing can be suppressed.

In addition, the adhesive composition may also be formulated with an auxiliary agent for the photopolymerization initiator. Examples of the auxiliary agent include triethanolamine, triisopropanolamine, 4' -dimethylaminobenzophenone (Michler's ketone), 4' -diethylaminobenzophenone, 2-dimethylaminoethyl benzoate, ethyl 4-dimethylaminobenzoate (n-butoxy), isoamyl 4-dimethylaminobenzoate, 2-ethylhexyl 4-dimethylaminobenzoate, 2, 4-diethylthioxanthone, and 2, 4-diisopropylthioxanthone. These auxiliaries may be used alone or in combination of two or more.

(Plasticizer)

The adhesive composition may be incorporated with a plasticizer as needed. The plasticizer is not particularly limited, and examples thereof include: paraffinic oil, process oil, and other oils; liquid rubbers such as liquid polyisoprene, liquid polybutadiene, and liquid ethylene-propylene rubber; tetrahydrophthalic acid, azelaic acid, benzoic acid, phthalic acid, trimellitic acid, pyromellitic acid, adipic acid, sebacic acid, fumaric acid, maleic acid, itaconic acid, citric acid, and derivatives of these; dioctyl phthalate (DOP), dibutyl phthalate (DBP), dioctyl adipate, diisononyl adipate (DINA), isodecyl succinate, and the like. The plasticizer may be used alone or in combination of two or more. Among them, liquid rubber is preferable.

The weight average molecular weight (Mw) of the liquid rubber is preferably 5,000 or more, more preferably 10,000 or more, preferably 60,000 or less, more preferably 50,000 or less. By adjusting the Mw of the liquid rubber within the above range, an adhesive material excellent in flexibility can be formed. The method for measuring the weight average molecular weight (Mw) is described below.

When the plasticizer is added to the adhesive composition, the content of the plasticizer is preferably 1 part by mass or more, more preferably 5 parts by mass or more, still more preferably 10 parts by mass or more, preferably 50 parts by mass or less, more preferably 40 parts by mass or less, still more preferably 30 parts by mass or less, based on 100 parts by mass of the copolymer (a). By adjusting the content of the plasticizer within the above range, an adhesive material excellent in adhesion and recovery can be formed.

(Method for producing adhesive composition)

The adhesive composition can be prepared by mixing the (a) copolymer, (B) a crosslinking agent, and optionally (meth) acrylic compound, and other additives. The adhesive composition may contain a solvent derived from the preparation of the copolymer (a), or may 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, methyl isobutyl ketone, 2-pentanone, isophorone, and cyclohexanone; esters such as ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, and the like; cellosolve solvents such as ethyl cellosolve; alcohol solvents such as ethanol, isopropanol, n-butanol, ethylene glycol monomethyl ether, ethylene glycol monoisopropyl ether, propylene glycol monomethyl ether, and diethylene glycol monobutyl ether. These solvents may be used alone 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.

(Physical Properties of adhesive Material)

The gel fraction of the adhesive material is preferably 50 to 100% by mass, more preferably 70 to 99% by mass, further preferably 80 to 99% by mass, particularly preferably 90 to 99% by mass, 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 by the amount of the crosslinking agent to be incorporated into the adhesive composition, the crosslinking treatment temperature, and the crosslinking treatment time.

The glass transition temperature (Tg) of the adhesive material is preferably-70℃or higher, more preferably-60℃or higher, still more preferably-50℃or higher, preferably 0℃or lower, more preferably-10℃or lower, still more 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. In addition, the bending-resistant plastic bag can be used in a repeated bending manner in a low-temperature environment such as a cold region. The glass transition temperature (Tg) of the adhesive material is measured as follows.

The shear storage elastic modulus (G' ₂₅) of the adhesive material at 25 ℃ is preferably 0.015MPa or more, more preferably 0.02MPa or more, still more preferably 0.025MPa or more, preferably 0.07MPa or less, more preferably 0.05MPa or less, still more preferably 0.04MPa or less.

The shear storage elastic modulus (G' _-40) of the adhesive material at-40 ℃ is preferably 0.1MPa or more, more preferably 0.2MPa or more, still more preferably 0.4MPa or more, preferably 1.8MPa or less, more preferably 1.5MPa or less, still more preferably 1.2MPa or less.

The shear storage elastic modulus (G' ₆₀) of the adhesive material at 60 ℃ is preferably 0.01MPa or more, more preferably 0.02MPa or more, still more preferably 0.03MPa or more, preferably 0.06MPa or less, more preferably 0.055MPa or less, still more preferably 0.05MPa or less.

When the shear storage elastic modulus (G') of the adhesive material is in the above range at 25 ℃, -40 ℃ and 60 ℃, the adhesive material has moderate flexibility even under high-temperature or low-temperature environments, and is more excellent in shape following property and cohesive force and adhesion property of the adhesive material. The method for measuring the shear storage elastic modulus (G') of the adhesive material is described below.

The ratio (G ' _-40/G'₂₅) of the shear storage elastic modulus (G ' _-40) at-40 ℃ to the shear storage elastic modulus (G ' ₂₅) at 25 ℃ of the adhesive material is preferably 5 or more, more preferably 10 or more, further preferably 15 or more, preferably 35 or less, more preferably 30 or less, further preferably 25 or less. If the ratio (G' _-40/G'₂₅) is within the above range, the adhesive strength and the recovery property are excellent, and the adhesive strength is excellent in a low-temperature environment.

The ratio (G ' ₂₅/G'₆₀) of the shear storage elastic modulus (G ' ₂₅) at 25 ℃ to the shear storage elastic modulus (G ' ₆₀) at 60 ℃ of the adhesive material is preferably 0.5 or more, more preferably 0.7 or more, further preferably 1.0 or more, preferably 2.0 or less, more preferably 1.8 or less, further preferably 1.5 or less. If the ratio (G' ₂₅/G'₆₀) is within the above range, the heat resistance under a high-temperature environment is excellent, and the adhesive force and the recovery property are excellent.

The higher the recovery rate of the adhesive material when the adhesive material is strained by 400%, the more preferable is 70% or more, the more preferable is 75% or more, and the more preferable is 80% or more, and the upper limit is 100%. If the recovery rate is 70% or more, the bending laminated member is placed in a bent state for a long period of time, and then the deformation generated during stretching is easily recovered, so that occurrence of appearance defects such as wrinkles at the bending portion can be suppressed.

The adhesive material may also contain a metal component. In the copolymer produced by the living radical polymerization method, a metal component derived from the chain transfer agent sometimes remains as an impurity (more than 0 mass ppm). For example, in the case where the (a) (meth) acrylic copolymer is polymerized by a method using an organic tellurium compound (tert method), a tellurium component derived from the organic tellurium compound represented by formula (1) remains. If the adhesive material contains a metal component, the adhesive force of the adhesive material is better.

When the binder contains a tellurium component, the content of the tellurium component in the binder is preferably 35×10 ^-6 parts by mass or more, more preferably 55×10 ^-6 parts by mass or more, still more preferably 65×10 ^-6 parts by mass or more, preferably 1000×10 ^-6 parts by mass or less, still more preferably 400×10 ^-6 parts by mass or less, and still more preferably 200×10 ^-6 parts by mass or less, per 1 part by mass of the (a) (meth) acrylic copolymer, calculated as a metal conversion. If the content of tellurium component in the adhesive material is 35×10 ^-6 parts by mass or more, the adhesive force is further improved, and if it is 1000×10 ^-6 parts by mass or less, the transparency of the adhesive material is improved.

(Formation of adhesive Material)

The adhesive material is obtained by curing the adhesive composition. Specifically, the adhesive composition is subjected to a heat treatment to remove the solvent, and the (A) (meth) acrylic copolymer and the (B) crosslinking agent are reacted. Further, by adjusting the heat treatment temperature and time of the adhesive composition, the content of the (X) (meth) acrylic compound in the obtained adhesive material can be adjusted. The heat treatment may be performed at a certain temperature or may be performed at different temperatures a plurality of times.

The heat treatment temperature is preferably 110℃or higher, more preferably 125℃or higher, still more preferably 140℃or higher, preferably 200℃or lower, more preferably 180℃or lower, still more preferably 160℃or lower.

The heat treatment time is preferably 1 to 8 minutes, more preferably 2 to 5 minutes. Examples of the heat treatment method include hot air, near infrared rays, and high frequency waves.

The adhesive material of the present invention is preferably used for an adhesive layer (adhesive material) used in a flexible display capable of being repeatedly bent and stretched. Examples of the flexible display that can be used by repeated bending and stretching include: foldable, foldable displays, and rollable, reel-type displays, etc. The flexible display is expected to be applied to mobile terminals such as smart phones and tablet terminals, storable fixed displays and the like. The adhesive material is suitable for an adhesive material for a flexible display for bonding one flexible member and another flexible member constituting the flexible display.

[ Adhesive sheet ]

The adhesive sheet of the present invention comprises a base sheet and an adhesive layer formed on at least one surface of the base sheet, and is characterized in that the adhesive layer is the adhesive material. The adhesive layer is formed on at least one side or at least a portion of the substrate sheet. The adhesive layer may be a single layer or may be formed into a multi-layer structure.

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".

(Substrate sheet)

The base sheet may be appropriately selected and used according to the application of the adhesive sheet. Examples of the base sheet include sheets made of the following polymer materials: polyimide resin; polyester resins such as polyethylene terephthalate (PET) resin and polyethylene naphthalate (PEN) resin; a polycarbonate resin; a poly (meth) acrylate resin; a polystyrene resin; a polyamide resin; a polyacrylonitrile resin; polyolefin resins such as polypropylene resins, polyethylene resins, polycycloolefin resins, cycloolefin copolymer resins, and the like; polyphenylene sulfide resin; polysulfone resin; polyether sulfone resin; polyether-ether-ketone resin; a polyarylate resin; a polyetherimide resin; cellulose resins such as triacetyl cellulose (TAC) resin and diacetyl cellulose resin; polyvinyl chloride resin; polyvinylidene chloride resin; a polyvinyl alcohol resin; a polyvinyl acetate resin; fluororesin, and the like. The polymer may be used alone or in combination of two or more. The polymer material preferably contains at least one selected from the group consisting of polyethylene terephthalate resin, polyimide resin, polycarbonate resin, poly (meth) acrylate resin, polycycloolefin resin, cycloolefin copolymer resin, and triacetyl cellulose resin from the viewpoint of optical characteristics, durability, and the like, and among these, PET resin is preferable from the viewpoint of excellent mechanical strength or dimensional stability. Further, polyimide is preferable in view of excellent heat resistance. That is, as the base sheet, a PET sheet (in particular, a biaxially stretched PET sheet) and a polyimide sheet are preferable.

The thickness of the base sheet is not particularly limited and may be appropriately selected, but is usually preferably 5 μm or more, more preferably 10 μm or more, further preferably 20 μm or more, preferably 200 μm or less, more preferably 100 μm or less, further preferably 50 μm or less. If the thickness is less than 5. Mu.m, the strength of the base sheet is insufficient, and the sheet is broken when peeled off. If the thickness of the base sheet is larger than 200. Mu.m, the sheet itself becomes expensive.

For the purpose of improving the adhesion with the layer provided on the surface thereof, the substrate sheet may be subjected to surface treatment on one or both sides by an oxidation method, a concavity and convexity method, or the like, as desired. The oxidation method may be: corona discharge treatment, plasma treatment, chromic acid treatment (wet), flame treatment, hot air treatment, ozone/ultraviolet irradiation treatment, and the like. The above-mentioned relief method includes: sand blasting, solvent treatment, and the like. These surface treatments are appropriately selected depending on the type of the base sheet, but in general, corona discharge treatment is preferably used from the viewpoints of effects, handleability, and the like. Further, as the base sheet, a base sheet having primer treatment (PRIMER TREATMENT) applied to one side or both sides may be used.

The thickness of the adhesive material (adhesive layer) formed on the base sheet can be appropriately set, for example, according to the adhesive force required for the adhesive sheet. The thickness of the adhesive layer is generally 1 μm to 100. Mu.m, preferably 5 μm to 50. Mu.m, more preferably 10 μm to 30. Mu.m.

(Formation of adhesive layer)

The method for forming the adhesive layer is not particularly limited, and examples thereof include a method in which the adhesive composition is applied and the solvent is removed by heat treatment as in the following methods (1) and (2).

(1) And a method in which the adhesive composition is applied to one or both sides of the base sheet by using various coating apparatuses, heat-treated, and cured as needed.

(2) And a method in which the pressure-sensitive adhesive composition is applied to the release surface of the release sheet having the release treatment applied thereto by using various coating apparatuses, heat-treated, transferred to one or both surfaces of the base sheet, and then cured as needed.

The coating apparatus may be: reverse roll coater, gravure coater, forward roll coater, air knife coater, wire bar coater, blade coater, slot die coater, curtain coater, dip coater, and the like.

Examples of the curing conditions include: at 30-50 deg.c for 3-7 days.

(Release sheet)

The adhesive sheet may have a release sheet (separator) on the surface of the adhesive layer before use. The following adhesive sheet is also possible: the pressure-sensitive adhesive sheet is formed by providing a release layer on the surface of a base sheet opposite to the surface on which the pressure-sensitive adhesive layer is laminated, and rolling or laminating the release layer so that the exposed surface side of the pressure-sensitive adhesive layer contacts the surface of the release layer. The release sheet can be used as a protective material for an adhesive layer, and is peeled off when the adhesive sheet of the present invention is attached to an adherend.

Examples of the release sheet include: and sheets obtained by coating a release agent such as silicone resin on paper such as cellophane, coated paper, laminated paper, and various plastic sheets. As the plastic sheet used for the release sheet, sheets listed as base sheet can be suitably used. The thickness of the release sheet is not particularly limited, but is usually 10 μm to 150. Mu.m.

As examples of the adhesive sheet, there may be mentioned: an adhesive sheet for a flexible display, comprising an adhesive layer for bonding one flexible member and the other flexible member constituting the flexible display, and a flexible sheet member bonded to at least one surface of the adhesive layer, wherein the adhesive layer is formed of the adhesive material.

The pressure-sensitive adhesive sheet may be constituted by: means having an adhesive layer and a first flexible sheet member adhered to one surface of the adhesive layer; the adhesive layer is provided with a first flexible sheet member adhered to one surface of the adhesive layer and a second flexible sheet member adhered 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 flexible sheet member 14 and the second flexible sheet member 16.

(Adhesive layer)

The adhesive layer is formed of the above adhesive material. The thickness of the pressure-sensitive adhesive layer is preferably 5 μm or more, more preferably 10 μm or more, still more preferably 20 μm or more, and particularly preferably 40 μm or more, from the viewpoint of sufficiently securing the adhesiveness to an adherend, and the like. In addition, from the viewpoint of suppressing extrusion of the adhesive layer or the like, the thickness of the adhesive layer is preferably 100 μm or less, more preferably 75 μm or less, and still more preferably 60 μm or less.

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 13N/25mm or more, and still more preferably 15N/25mm or more. When the thickness is 10N/25mm or more, the adhesive material can be prevented 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.

The adhesive strength of the adhesive layer to the flexible sheet member (excluding the release sheet) at 60℃is preferably 7N/25mm or more, more preferably 10N/25mm or more, and still more preferably 12N/25mm or more. If the thickness is 7N/25mm or more, the adhesive material can be prevented from floating or peeling even under a high-temperature environment. 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 base sheet and a release sheet having flexibility. The substrate sheet is a sheet member supporting the adhesive layer, and the sheet member may be a functional sheet member. The functional sheet member may be: 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.

As the flexible sheet member, there may be mentioned: sheets of polymeric materials, glass sheets, 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 materials include: polyimide resin; 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; a polyacrylonitrile resin; polyolefin resins such as polypropylene resins, polyethylene resins, polycycloolefin resins, cycloolefin copolymer resins, and the like; polyphenylene sulfide resin; polyvinyl chloride resin; polyvinylidene chloride resin; a polyvinyl alcohol resin; fluororesin, and the like. The polymer material may be used alone or in combination of two or more.

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

The adhesive sheet preferably 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, the first release sheet and the second release sheet being attached such that the 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.

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

The adhesive composition may be applied by various coating methods such as reverse gravure coating, direct gravure coating, die coating, bar coating, wire bar coating, roll coating, spin coating, dip coating, spray coating, doctor blade coating, and contact coating; an inkjet method; offset printing, screen printing, flexography, and other printing methods. 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 heating treatment is not particularly limited as long as it can remove the solvent or the like used in the adhesive composition and cure it, but it is preferably carried out at a temperature of 110 to 200℃for about 1 to 8 minutes.

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 adhered to the adhesive layer. Further, the adhesive layer may be cured as needed. Examples of the curing conditions include: at 60 ℃ for 3 to 7 days or so.

[ Flexible laminate Member ]

The adhesive material of the present invention can be suitably used for a flexible laminate member. The flexible laminate member is provided with: the flexible component comprises a first flexible component, a second flexible component and an adhesive layer for mutually attaching the first flexible component and the second flexible component, and is characterized in that the adhesive layer is composed of the adhesive material. Since the adhesive layer of the flexible laminate member is formed of the adhesive material, even when the flexible laminate member is repeatedly bent, the bending portion is prevented from wrinkling, and appearance defects such as wrinkles are observed.

An example of a flexible laminate component is shown in fig. 2. The flexible laminate member 20 of fig. 2 includes: a first flexible member 22, a second flexible member 24, and an adhesive layer 12 between the first flexible member 22 and the second flexible member 24 that conforms to the flexible members.

Examples of the structure of the flexible laminate member include: both the first flexible member and the second flexible member are a constituent member of the bendable device; the second flexible member is a flexible device, and the first flexible member is a functional sheet member bonded to the flexible device. Examples of the bending device include: foldable display, scroll display which can be rolled into a cylinder. The functional sheet member may be: 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, a buffer film, and the like.

The first flexible member and the second flexible member are members that can be repeatedly bent (bent or curved) for use. Examples of the first flexible member and the second flexible member include: flexible substrate materials, functional sheet members, display elements (organic EL elements, electronic paper elements, etc.), and the like. Preferably at least one of the first flexible member and the second flexible member is a display element. The flexible laminate component can be used in a flexible display.

(Method for producing Flexible laminate Member)

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

Method (1): and peeling off the release sheet adhered to one surface of the adhesive sheet, adhering the exposed adhesive layer to the first flexible member, peeling off the release sheet adhered to the other surface of the adhesive sheet, and adhering the exposed adhesive layer to the second flexible member to obtain the flexible laminated 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 and heating treatment to form an adhesive layer, and then a release surface of a release sheet is stuck to the adhesive layer. And adhering the adhesive layer exposed by peeling the release sheet to the second flexible member to obtain the flexible 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 and heating 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 a release surface, and if necessary, the adhesive composition is cured by a drying heat treatment to form an adhesive layer, and then the first flexible member is adhered to the adhesive layer. And adhering the adhesive layer exposed by peeling the release sheet to the second flexible member to obtain the flexible 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 replaced.

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.

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 weight average molecular weight (Mw), molecular weight distribution (Mw/Mn), the (meth) acrylic compound content of the adhesive material, the gel fraction, the glass transition temperature, the shear storage elastic modulus, the adhesive force, and the recovery at 400% strain of the copolymer were evaluated according to the following methods.

EHA: 2-ethylhexyl acrylate, LA: dodecyl acrylate, AA: acrylic acid, HBA: 4-hydroxybutyl acrylate, BTEE: ethyl-2-methyl-2-n-butyltelluride-propionate, V-70:2,2' -azobis (4-methoxy-2, 4-dimethylvaleronitrile), AIBN: azobisisobutyronitrile, acOEt: acetic acid ethyl ester

[ Evaluation method ]

(Weight average molecular weight (Mw) and molecular weight distribution (Mw/Mn))

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 (Mw/Mn) was calculated.

(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.). From the obtained NMR spectrum, the integral ratio of the signal from the monomer to the signal from the polymer was obtained, and the polymerization rate of the monomer was calculated.

(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.

(Monomer content)

The adhesive layer (adhesive material) constituting the adhesive sheet was cut into pieces 20mm wide and 40mm long, two release sheets were peeled off from the adhesive layer, and the pieces were placed in a 20mL vial, and after measuring the mass of the sample, the pieces were tightly covered.

Subsequently, the vial was heated at 200℃for 30 minutes using a headspace autosampler (HSS), and sample gas was collected from the heated vial and injected into a Gas Chromatograph (GC) measurement apparatus for analysis. The monomer content was calculated using a standard curve prepared in advance with a reagent.

The HSS and GC settings are as follows.

HSS: perkin Elmer, turboMatrix 40; heating time: 30 minutes; pressurizing time: 3.00 minutes; injection time: 0.05 minutes; oven temperature: 200 ℃; transfer temperature: 210 DEG C

GC measurement device: GC-2010plus manufactured by Shimadzu corporation; chromatographic column: agilent J & W GC Columns DB-5MS (length 30m, inner diameter 0.250mm, film thickness 0.25 μm); column temperature: after keeping at 40 ℃ for 10 minutes, heating to 120 ℃ at a heating rate of 10 ℃/min, heating to 300 ℃ at a heating rate of 20 ℃/min after reaching 120 ℃, and keeping at 300 ℃ for 5 minutes; carrier gas: helium 150kPa; a detector: FID; detector temperature: 310 ℃ (gel fraction)

The mass W1 of the metal mesh (400 mesh) cut into a size of 50mm wide and 120mm long was measured. 0.1g of an adhesive material was removed, and the test piece was prepared by wrapping the adhesive material with a metal mesh so that the adhesive material did not fall off, 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

(Glass transition temperature)

The adhesive layers (adhesive materials) constituting the adhesive sheet were laminated by hand press rolls (hand rolls) to prepare a laminate having a thickness of 0.5 mm. The laminate was used as a sample, and the change in temperature of the loss elastic modulus of the adhesive material was measured using a viscoelasticity measuring apparatus (ARES-G2, manufactured by TA instruments Co., ltd.) and the peak value thereof was used as the glass transition temperature (Tg).

(Shear storage elastic modulus)

The adhesive layers (adhesive materials) constituting the adhesive sheet were laminated by hand press rolls to prepare a laminate having a thickness of 0.5 mm. The laminate was used as a sample, and a viscoelasticity measuring device (Discovery HR-2, manufactured by TA instruments) was used in shear mode, geometry: parallel plate (parallel-plate) diameter 8mm, axial force: 2.2N, frequency: 1Hz, strain: 1%, the shear storage elastic modulus at-40 ℃, 25 ℃ and 60 ℃ was measured.

The strain γ is obtained by the following equation.

[ Gamma: strain (%), r: radius (mm) of parallel plate,Torsion angle (rad), l: sample thickness (mm) ] (shear storage modulus at 400% strain and recovery rate)

The adhesive layers (adhesive materials) constituting the adhesive sheet were laminated by hand press rolls to prepare a laminate having a thickness of 0.5 mm. The laminate was used as a sample, and a viscoelastic measuring apparatus (Discovery HR-2, manufactured by TA instruments) was used at 23 ℃ under 50% environment with parallel plates having a diameter of 8mm and axial force: 2.2N, angular frequency (. Omega.) 25rad/sec was rotated to 400% strain, shear stress was continuously applied to 400% strain, and stress and strain after 10 minutes were measured.

Then, the shear stress applied 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 (%) = { (400-strain of 10 minutes) 400} ×100

(Adhesive force)

One release sheet of the adhesive sheet was peeled off from the adhesive layer, and a corona-treated surface of a polyethylene terephthalate film (TOYOBO ESTEL (registered trademark) film E5100: manufactured by TOYOBO Co., ltd., thickness 50 μm) was bonded to the adhesive layer, and cut into a size of 25mm wide and 150mm long. Then, the other release sheet was peeled off from the adhesive layer, and a 2kg roller was reciprocated twice to press the adhesive layer against a Polyimide (PI) film (Kapton (registered trademark) 200V, manufactured by eastern dupont, thickness 50 μm).

After the pressure-bonded sample was stored for 1 hour, the adhesive force of the adhesive layer to the polyimide film was measured under conditions of a peeling speed of 300mm/min and a peeling angle of 180 ° using a precision universal tester "AUTOGRAPH (registered trademark) AGS-1knx,50n load cell" manufactured by shimadzu corporation according to the method of JIS Z0237 (2009).

The temperatures at the time of storage and measurement were set as follows: after 1 hour of storage at room temperature (23 ℃), the sample was measured at 23 ℃; and the sample was directly fixed to a precision universal tester without cooling after being stored at 60℃for 1 hour using a thermostatic dryer, and measured at 60 ℃.

(Holding force)

One release sheet was peeled off from the adhesive layer (adhesive material) constituting the adhesive sheet, and a 25mm corona-treated surface of a polyethylene terephthalate film (manufactured by TOYOBO ESTEL (registered trademark) film E5100: manufactured by TOYOBO Co., ltd., thickness: 50 μm) was bonded to the adhesive layer, followed by cutting into 25 mm. Times.50 mm. Then, the other release sheet was peeled off from the adhesive layer, and a 2kg roller was repeatedly pressed against a stainless steel plate (SUS 304, surface-finished BA,60 mm. Times.30 mm. Times.1.5 mm thick) twice so that the adhering area became 25 mm. Times.25 mm.

After the pressure-bonded sample was stored for 1 hour, a weight of 1kgf was attached to the test piece in the vertical direction according to the method of JIS Z0237 (2009), and the sample was left standing for 24 hours at 80 ℃. For the sample that did not fall within 24 hours, the length (mm) of the downward shift in the position of attachment of the stainless steel plate to the test piece, i.e., the amount of shift, was measured.

< Preparation of copolymer >

Synthesis example 1 copolymer No. A

A flask equipped with an argon line and a stirrer was charged with EHA (402.0 g), LA (180.0 g), AA (18.0 g), HBA (1.8 g) and AcOEt (1606 g), and after argon substitution, BTEE (129 mg) and V-70 (47.6 mg) were added to conduct polymerization at 33℃for 24 hours. The polymerization rate was 88%.

After the polymerization stopping operation was performed, acOEt was added to the obtained solution to obtain a copolymer solution containing copolymer No. a. The weight average molecular weight (Mw) of the resulting copolymer No. A was 92 million, the molecular weight distribution (Mw/Mn) was 2.48, and the solid content of the solution was 25.0 mass%. The resulting copolymer solution contains unreacted monomers (residual monomers). The solid content of the copolymer solution is the total amount of the components other than the solvent contained in the copolymer solution.

The copolymer solution containing copolymer No. A was heated at 130℃for 1 hour to remove the residual monomers. Then, nitric acid and an aqueous hydrogen peroxide solution were added and ashing treatment was performed at 180℃for 4 hours, and ultrapure water was added to prepare a test solution. As a result of measurement of the test liquid by inductively coupled plasma-mass spectrometry (ICP/MS), the content of the tellurium component was 91X 10 ^-6 parts by mass in terms of metal conversion per 1 part by mass of the copolymer No. A.

Synthesis example 2 copolymer No. B

A flask with an argon line, dropping funnel and stirrer was charged with AcOEt (919 g), and after argon substitution, heated to 77 ℃. It took 2 hours to add a liquid in which EHA (402.0 g), LA (180.0 g), AA (18.0 g), HBA (1.8 g) and AIBN (262.7 mg) were dissolved in AcOEt (45 g), and the mixture was further reacted for 6 hours to polymerize. The polymerization rate was 97%.

After the completion of the reaction, acOEt was added to the reaction solution to obtain a copolymer solution containing copolymer No. B. The Mw of the resulting copolymer No. B was 89 ten thousand, the Mw/Mn was 7.67, and the solid content of the solution was 39.5 mass%. The resulting copolymer solution contains unreacted monomers (residual monomers).

Table 3 shows the raw material monomers, the organic tellurium compound, the azo polymerization initiator, the solvent, the reaction conditions, and the like used. In addition, the composition, mw/Mn, and glass transition temperature of each copolymer are shown in Table 4. The content of each functional group in the copolymer was calculated from the ratio of the monomers to be charged for polymerization.

TABLE 3

TABLE 4

< Preparation of adhesive composition >

(Adhesive composition No. 1)

To the copolymer solution obtained in synthesis example 1, tetra (registered trademark) -C (1, 3-bis (N, N-diglycidyl aminoethyl) cyclohexane, manufactured by mitsubishi gas chemical corporation, epoxy group amount) was added to 100 parts by mass of the solid content (87.9 parts by mass of the copolymer component of copolymer No. a, 12.1 parts by mass of the unreacted monomer component:

9.76 mmol/g) 0.04 parts by mass, and stirring to obtain adhesive composition No.1.

(Adhesive composition No. 2)

Adhesive composition No.2 was obtained in the same manner as in preparation of adhesive composition No.1, except that the copolymer solution was changed to 100 parts by mass of the solid component (97.3 parts by mass of the copolymer component of copolymer No. B, 2.7 parts by mass of the unreacted monomer component) of the copolymer solution containing copolymer No. B obtained in Synthesis example 2.

< Preparation of adhesive sheet >

(Adhesive sheet No. 1)

The adhesive composition No.1 was applied to the release surface of the first release sheet (PET film having a release-treated surface, CLEAN SEPA (registered trademark) HY-US20: manufactured by Toshan film Co., ltd., thickness 75 μm) using a baking coater so that the film thickness after drying became 50 μm, and then heat-treated at 170℃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: 50 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 sheet No.1 sandwiched between the two release sheets.

(Adhesive sheets No. 2-4, 7, 8)

Adhesive sheets nos. 2 to 4, 7, and 8 were produced in the same manner as the adhesive sheet No.1 except that the heat treatment temperature and time were changed as shown in table 5.

(Adhesive sheet No. 5)

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-US20: manufactured by Toshan film Co., ltd., thickness 75 μm) by means of an air knife coater (knife coater) so that the film thickness after drying became 50 μm, and then heat-treated at 70℃for 1 minute by means of a hot air dryer, and then heat-treated at 130℃for 2 minutes by means of a hot air circulation 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: 50 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 sheet No.5 sandwiched between the two release sheets.

(Adhesive sheet No. 6)

Adhesive sheet No.6 was produced in the same manner as the production of adhesive sheet No.5, except that the heat treatment temperature and time were changed as shown in table 5.

(Adhesive sheets No. 9-13)

Adhesive sheets nos. 9 to 13 were produced in the same manner as the production of adhesive sheet No.1, except that adhesive composition No.1 was changed to adhesive composition No.2, and the heat treatment temperature and time were changed as shown in table 5.

The adhesive layers (adhesive materials) of the adhesive sheets No.1 to 6 are composed of cured products of an adhesive composition containing (A) (meth) acrylic copolymer obtained by living radical polymerization (LIVING RADICAL polymerization) and (B) a crosslinking agent, and the content of (X) (meth) acrylic compound in the cured products is 60 to 5000 mass ppm. The adhesive layers (adhesive materials) of these adhesive sheets nos. 1 to 6 are excellent in recovery and adhesion.

The adhesive layers (adhesive materials) of the adhesive sheets No.7 and 8 are composed of cured products of an adhesive composition containing (a) (meth) acrylic copolymer obtained by living radical polymerization and (B) a crosslinking agent. However, the content of the (X) (meth) acrylic compound in the cured product of the adhesive sheet No.7 was less than 60 mass ppm. Therefore, the recovery rate and the holding force of the adhesive layer (adhesive material) are poor. Further, the content of the (X) (meth) acrylic compound in the cured product of the adhesive sheet No.8 is more than 5000 mass ppm. Therefore, the adhesive force is poor.

The adhesive layers (adhesive materials) of the adhesive sheets No.9 to 13 are composed of cured products of an adhesive composition containing (A) (meth) acrylic copolymer obtained by radical polymerization (FREE RADICAL polymerization) and (B) a crosslinking agent. The adhesive layers (adhesive materials) of these adhesive sheets No.9 to 13 all had poor recovery.

The present invention includes the following embodiments.

The adhesive material according to embodiment 1 is composed of a cured product of an adhesive composition containing (a) a (meth) acrylic copolymer having a crosslinkable functional group and (B) a crosslinking agent, wherein the (a) (meth) acrylic copolymer is a copolymer obtained by living radical polymerization, the cured product contains (X) an (meth) acrylic compound having a molecular weight of 500 or less, and the content of the (X) (meth) acrylic compound in the cured product is 60 to 5000 mass ppm.

(Embodiment 2) the adhesive material according to embodiment 1, wherein the boiling point (760 mmHg) of the (X) (meth) acrylic compound is 100 ℃ or higher.

(Embodiment 3) the adhesive material according to embodiment 1 or 2, wherein the (X) (meth) acrylic compound is one or two or more compounds selected from the group consisting of a (meth) acrylate having a linear alkyl group, a (meth) acrylate having a branched alkyl group, a (meth) acrylate having an alicyclic hydrocarbon group, a (meth) acrylate having an aromatic group, and a (meth) acrylamide.

Embodiment 4 the adhesive material according to any one of embodiments 1 to 3, wherein the gel fraction is 50% by mass or more.

(Embodiment 5) the adhesive material according to any one of embodiments 1 to 4, wherein the total amount of crosslinkable points of the (B) crosslinking agent is 1. Mu. Mol/g to 100. Mu. Mol/g per unit mass of the (A) (meth) acrylic copolymer.

(Embodiment 6) the adhesive material according to any one of embodiments 1 to 5, wherein the crosslinkable functional group of the (a) (meth) acrylic copolymer is a hydroxyl group and/or a carboxyl group.

(Embodiment 7) the adhesive material according to any one of embodiments 1 to 6, wherein the amount of the crosslinkable functional group per unit mass of the (a) (meth) acrylic copolymer is 0.5 to 1500. Mu. Mol/g.

(Embodiment 8) the adhesive material according to any one of embodiments 1 to 7, wherein the weight average molecular weight of the (a) (meth) acrylic copolymer is 20 to 300 tens of thousands.

(Embodiment 9) the adhesive material according to any one of embodiments 1 to 8, wherein the adhesive material contains a tellurium component.

Embodiment 10 is an adhesive sheet comprising a base sheet and an adhesive layer formed on at least one surface of the base sheet, wherein the adhesive layer is the adhesive material according to any one of embodiments 1 to 9.

Embodiment 11 is an adhesive sheet comprising an adhesive layer for bonding one flexible member to another flexible member and a flexible sheet member bonded to at least one surface of the adhesive layer, wherein the adhesive layer is made of the adhesive material according to any one of embodiments 1 to 9.

(Embodiment 12) the adhesive sheet according to embodiment 11, 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 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 the respective release surfaces are in contact with the adhesive layer.

Claims

1. An adhesive material comprising a cured product of an adhesive composition containing (A) a (meth) acrylic copolymer having a crosslinkable functional group and (B) a crosslinking agent, characterized in that,

The (A) (meth) acrylic copolymer is a copolymer obtained by living radical polymerization,

The cured product contains (X) a (meth) acrylic compound having a molecular weight of 500 or less,

The content of the (X) (meth) acrylic compound in the cured product is 60 to 5000 mass ppm.

2. The adhesive material according to claim 1, wherein the (X) (meth) acrylic compound has a boiling point of 100 ℃ or higher at 760 mmHg.

3. The adhesive material according to claim 1 or 2, wherein the (X) (meth) acrylic compound is one or two or more compounds selected from the group consisting of a (meth) acrylate having a linear alkyl group, a (meth) acrylate having a branched alkyl group, a (meth) acrylate having an alicyclic hydrocarbon group, a (meth) acrylate having an aromatic group, and a (meth) acrylamide.

4. The adhesive material according to claim 1 or 2, which has a gel fraction of 50 mass% or more.

5. The adhesive material according to claim 1 or 2, wherein the total amount of crosslinkable points of the (B) crosslinking agent is 1 μmol/g to 100 μmol/g per unit mass of the (a) (meth) acrylic copolymer.

6. The adhesive material according to claim 1 or 2, wherein the crosslinkable functional group of the (a) (meth) acrylic copolymer is a hydroxyl group and/or a carboxyl group.

7. The adhesive material according to claim 1 or 2, wherein the amount of the crosslinkable functional group per unit mass of the (a) (meth) acrylic copolymer is 0.5 μmol/g to 1500 μmol/g.

8. The adhesive material according to claim 1 or 2, wherein the (a) (meth) acrylic copolymer has a weight average molecular weight of 20 to 300 tens of thousands.

9. The bonding material of claim 1 or 2, wherein the bonding material contains a tellurium component.

10. An adhesive sheet having a base sheet and an adhesive layer formed on at least one face of the base sheet, characterized in that the adhesive layer is the adhesive material according to claim 1 or 2.

11. An adhesive sheet having an adhesive layer for bonding one flexible member to another flexible member and a flexible sheet member bonded to at least one face of the adhesive layer, characterized in that the adhesive layer is composed of the adhesive material according to claim 1 or 2.

12. The adhesive sheet according to claim 11, wherein the adhesive sheet has a first flexible sheet member adhered to one face of the adhesive layer and a second flexible sheet member adhered to the other face 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 respective release surfaces are in contact with the adhesive layer.