CN116829670A

CN116829670A - Adhesive composition, adhesive material and adhesive sheet for flexible display

Info

Publication number: CN116829670A
Application number: CN202280014119.7A
Authority: CN
Inventors: 石原正规
Original assignee: Otsuka Chemical Co Ltd; Higashiyama Film Co Ltd
Current assignee: Otsuka Chemical Co Ltd; Higashiyama Film Co Ltd
Priority date: 2021-02-26
Filing date: 2022-02-10
Publication date: 2023-09-29
Also published as: TW202244224A; WO2022181355A1; JPWO2022181355A1; KR20230152660A

Abstract

Technical problems: provided is an adhesive composition which can form an adhesive material (adhesive layer) having excellent adhesion and flexibility and excellent restorability, and which is suitable as an adhesive material (adhesive layer). The technical scheme is as follows: an adhesive composition for flexible displays, which comprises a plurality of (meth) acrylic copolymer components and a crosslinking agent, wherein the (meth) acrylic copolymer components contain at least (A) (meth) acrylic copolymer components having a first reactive group and a molecular weight distribution (Mw/Mn) of 3.0 or less, and (B) (meth) acrylic copolymer components having a first reactive group and a molecular weight distribution (Mw/Mn) of more than 3.0, the crosslinking agent has a second reactive group that reacts with the first reactive group, and the content of the (A) (meth) acrylic copolymer components in the plurality of (meth) acrylic copolymer components is 75 to 99 mass%.

Description

Adhesive composition, adhesive material and adhesive sheet for flexible display

Technical Field

The present invention relates to an adhesive composition for a flexible display, and more particularly, to an adhesive composition for forming an adhesive material for bonding one flexible member to another flexible member.

Background

In various displays such as televisions, mobile phones, and smart phones, touch panels, and the like, adhesive materials are generally used for joining members constituting the displays, the touch panels, and the like. The adhesive material is provided, for example, in the form of a 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 the members are bonded together.

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

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

Prior art literature

Patent literature

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

Disclosure of Invention

Technical problem to be solved by the invention

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

The present invention has been made in view of the above circumstances, and an object thereof is to provide an adhesive composition capable of forming an adhesive material (adhesive layer) having an adhesive force suitable as the adhesive material (adhesive layer), excellent in flexibility and excellent in recovery.

Solution for solving the technical problems

The adhesive composition for flexible displays according to the present invention, which is used for bonding one flexible member and another flexible member constituting a flexible display, is characterized by comprising a plurality of (meth) acrylic copolymer components and a crosslinking agent, wherein the (meth) acrylic copolymer components contain at least (a) (meth) acrylic copolymer components having a first reactive group and having a molecular weight distribution (Mw/Mn) of 3.0 or less, and (B) (meth) acrylic copolymer components having a first reactive group and having a molecular weight distribution (Mw/Mn) of more than 3.0, and the crosslinking agent has a second reactive group that reacts with the first reactive group, and the content of the (a) (meth) acrylic copolymer components in the plurality of (meth) acrylic copolymer components is 75 to 99 mass%.

Effects of the invention

When the adhesive composition for flexible display of the present invention is used, an adhesive material (adhesive layer) having an adhesive force suitable as an adhesive material (adhesive layer) and excellent in flexibility and recovery can be formed. Accordingly, by using the adhesive composition for a flexible display of the present invention, a flexible display can be produced in which, even if the flexible display is repeatedly bent, the adhesive layer does not float or peel off from the interface between the adhesive layer and the flexible member at the bending portion, and occurrence of appearance defects such as cracks and wrinkles can be suppressed.

Drawings

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

Fig. 2 is a schematic cross-sectional view of an example of the flexible laminated member 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 composition for Flexible display ]

The adhesive composition for flexible display of the present invention (hereinafter, sometimes simply referred to as "adhesive composition") is an adhesive composition for flexible display for bonding one flexible member and the other flexible member constituting the flexible display. The adhesive composition contains a plurality of (meth) acrylic copolymer components and a crosslinking agent.

((meth) acrylic copolymer component)

The adhesive composition contains at least (A) (meth) acrylic copolymer component (hereinafter, sometimes abbreviated as "(A) polymer component") and (B) (meth) acrylic copolymer component (hereinafter, sometimes abbreviated as "(B) polymer component) as (meth) acrylic copolymer components. A mixture containing a plurality of the (meth) acrylic copolymer components is sometimes referred to as a (meth) acrylic copolymer mixture. The (A) (meth) acrylic copolymer component has a first reactive group and has a molecular weight distribution (Mw/Mn) of 3.0 or less. The (B) (meth) acrylic copolymer component has a first reactive group and a molecular weight distribution (Mw/Mn) greater than 3.0. The content of the (a) (meth) acrylic copolymer component in the plurality of (meth) acrylic copolymer components is 75 to 99 mass%. By containing these (a) (meth) acrylic copolymer component and (B) (meth) acrylic copolymer component in predetermined amounts, a soft adhesive material having excellent recovery properties can be formed, and an adhesive material having an adhesive force suitable as an adhesive material can be produced.

((A) (meth) acrylic copolymer component)

The (a) (meth) acrylic copolymer component may be a copolymer having a structural unit derived from a (meth) acrylic monomer as a main component (50 mass% or more). The polymer component (A) may be one or two or more. The (a) polymer component may contain a structural unit derived from a vinyl monomer other than the (meth) acrylic acid based monomer. The content of the structural unit derived from the (meth) acrylic acid based monomer in the polymer component (a) is preferably 80 mass% or more, more preferably 90 mass% or more, based on 100 mass% of the polymer component. The (a) polymer component may be composed of only structural units derived from a (meth) acrylic acid based monomer.

The (A) polymer component 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 (meth) acrylic acid ester in the polymer component (a) is preferably 80 mass% or more, more preferably 90 mass% or more, based on 100 mass% of the polymer component.

The (a) polymer component has a first reactive group. The first reactive group is a functional group having high reactivity with a second reactive group of a crosslinking agent described later. The functional group capable of forming the first reactive group may be a functional group having reactivity. The first reactive group includes a hydroxyl group, a carboxyl group, an epoxy group, and the like, and is preferably a hydroxyl group and/or a carboxyl group, more preferably a hydroxyl group or a carboxyl group.

The first reactive group amount of the polymer component (A) is preferably 0.002mmol/g or more, more preferably 0.006mmol/g or more, still more preferably 0.01mmol/g or more, preferably 0.8mmol/g or less, still more preferably 0.6mmol/g or less, still more preferably 0.5mmol/g or less, particularly preferably 0.2mmol/g or less, and most preferably 0.1mmol/g or less. If the first reactive group amount is 0.002mmol/g or more, the adhesive material formed is suitably crosslinked to exhibit a suitable recovery rate, and if it is 0.8mmol/g or less, the distance between crosslinking points of the adhesive material formed is sufficiently long and flexibility is excellent.

In the case where the hydroxyl group of the (a) polymer component is a first reactive group, the (a) polymer component preferably further has a carboxyl group as a functional group other than the first reactive group. In this case, the carboxyl group content of the copolymer (A) is preferably 0.08mmol/g or more, more preferably 0.16mmol/g or more, still more preferably 0.32mmol/g or more, preferably 1.3mmol/g or less, still more preferably 0.8mmol/g or less, still more preferably 0.6mmol/g or less.

In the case where the hydroxyl group is the first reactive group and the (a) polymer component has both carboxyl groups and hydroxyl groups, the molar ratio of carboxyl groups to hydroxyl groups (carboxyl/hydroxyl groups) per unit mass of the (a) polymer component is preferably 4 or more, more preferably 8 or more, still more preferably 16 or more, preferably 60 or less, still more preferably 40 or less, still more preferably 30 or less. If the molar ratio (carboxyl group/hydroxyl group) is within the above range, an adhesive layer having high recovery properties and suitable balance between adhesive force and flexibility is obtained.

In the case where the carboxyl group is the first reactive group, the (a) polymer component preferably further has a hydroxyl group as a functional group other than the first reactive group. In this case, the hydroxyl group amount of the polymer component (A) is preferably 0.01mmol/g or more, more preferably 0.02mmol/g or more, still more preferably 0.04mmol/g or more, preferably 0.25mmol/g or less, more preferably 0.20mmol/g or less, still more preferably 0.15mmol/g or less.

In the case where the carboxyl group is the first reactive group and the (a) polymer component has both carboxyl groups and hydroxyl groups, the molar ratio of carboxyl groups to hydroxyl groups (carboxyl/hydroxyl groups) per unit mass of the (a) polymer component is preferably 3.0 or more, more preferably 3.5 or more, still more preferably 4.0 or more, preferably 30 or less, still more preferably 25 or less, and still more preferably 20 or less. If the molar ratio (carboxyl group/hydroxyl group) is within the above range, an adhesive layer having high recovery properties and suitable balance between adhesion and flexibility is obtained.

The (a) polymer component 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 polymer component (A) is preferably 10 ten thousand or more, more preferably 20 ten thousand or more, further preferably 60 ten thousand or more, particularly preferably more than 80 ten thousand, preferably 300 ten thousand or less, more preferably 250 ten thousand or less, further preferably 230 ten thousand or less. If the Mw of the polymer component (A) is 10 ten thousand or more, the cohesive force is improved, and the heat resistance of the adhesive material formed is improved, and if it is 300 ten thousand or less, the coating workability of the adhesive composition is better. The method for measuring the weight average molecular weight (Mw) will be described later.

The molecular weight distribution (Mw/Mn) of the polymer component (A) is 3.0 or less, preferably 2.5 or less, more preferably 2.2 or less, and still more preferably 1.8 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 and the copolymer having a large molecular weight are contained in a low amount as compared with the molecular weight of the copolymer designed, and an adhesive material excellent in bending resistance can be obtained. In the present invention, the molecular weight distribution (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 will be described later.

The glass transition temperature (Tg) of the polymer component (A) is preferably-70℃or higher, more preferably-60℃or higher, preferably 0℃or lower, more preferably-10℃or lower, and further preferably-20℃or lower. When Tg is not less than-70 ℃, sufficient cohesive force is imparted to the adhesive material, and durability of the resulting adhesive material is improved, and when Tg is not more than 0 ℃, adhesion of the resulting adhesive material to an adherend is improved, peeling at low temperature and the like are suppressed, and durability is improved.

Tg of the polymer component means 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 polymer component (A) preferably contains a polymer component having a weight average molecular weight of 100 ten thousand or more ((A1) polymer component) and a polymer component having a weight average molecular weight of less than 100 ten thousand ((A2) polymer component). By containing the polymer component (A1) and the polymer component (A2), a softer adhesive material can be formed.

The weight average molecular weight (Mw) of the (A1) polymer component is preferably 100 ten thousand or more, more preferably 130 ten thousand or more, further preferably 150 ten thousand or more, preferably 300 ten thousand or less, more preferably 250 ten thousand or less, further preferably 230 ten thousand or less. The molecular weight distribution (Mw/Mn) of the polymer component (A1) is 3.0 or less, preferably 2.5 or less, more preferably 2.2 or less, and still more preferably 1.8 or less.

The weight average molecular weight (Mw) of the (A2) polymer component is preferably 10 ten thousand or more, more preferably 20 ten thousand or more, further preferably 60 ten thousand or more, particularly preferably more than 80 ten thousand, preferably less than 100 ten thousand, further preferably 95 ten thousand or less, further preferably 90 ten thousand or less. The molecular weight distribution (Mw/Mn) of the (A2) polymer component is 3.0 or less, preferably 2.5 or less, more preferably 2.2 or less, and still more preferably 1.8 or less.

The ratio (Mw 1/Mw 2) of the weight average molecular weight (Mw 1) of the (A1) polymer component to the weight average molecular weight (Mw 2) of the (A2) polymer component is preferably 1.5 or more, more preferably 2.0 or more, preferably 4.0 or less, and still more preferably 3.0 or less. If the ratio (Mw 1/Mw 2) is within the above range, a more flexible adhesive material having excellent recovery can be formed. When a plurality of (A1) polymer components or (A2) polymer components are contained, the ratio of the maximum weight average molecular weight among the components is defined as the ratio (Mw 1/Mw 2).

The mass ratio (A1/A2) of the (A1) polymer component to the (A2) polymer component in the (a) polymer component is preferably 0.1 or more, more preferably 0.2 or more, further preferably 0.3 or more, preferably 1.0 or less, more preferably 0.8 or less, further preferably 0.6 or less. If the mass ratio (A1/A2) is within the above range, a more flexible adhesive material having excellent recovery can be formed. When a plurality of (A1) polymer components or (A2) polymer components are contained, the mass ratio of the polymer components having the largest weight average molecular weight among the components is defined as the ratio (A1/A2).

((B) (meth) acrylic copolymer component)

The (B) (meth) acrylic copolymer component may be a copolymer having a structural unit derived from a (meth) acrylic monomer as a main component (50 mass% or more). The polymer component (B) may be one or two or more. The (B) polymer component may contain a structural unit derived from a vinyl monomer other than the (meth) acrylic acid based monomer. The content of the structural unit derived from the (meth) acrylic acid based monomer in the polymer component (B) is preferably 80 mass% or more, more preferably 90 mass% or more, based on 100 mass% of the polymer component. The (B) polymer component may be composed of only structural units derived from a (meth) acrylic acid based monomer.

The (B) polymer component 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 content of the structural unit derived from (meth) acrylic acid ester in the polymer component (B) is preferably 80 mass% or more, more preferably 90 mass% or more, based on 100 mass% of the polymer component.

The (B) polymer component has a first reactive group. The first reactive group is a functional group having high reactivity with a second reactive group of a crosslinking agent described later. The functional group capable of forming the first reactive group may be a functional group having reactivity. The first reactive group is preferably a hydroxyl group and/or a carboxyl group, more preferably a hydroxyl group or a carboxyl group.

The first reactive group amount of the polymer component (B) is preferably 0.002mmol/g or more, more preferably 0.006mmol/g or more, still more preferably 0.01mmol/g or more, preferably 0.8mmol/g or less, still more preferably 0.6mmol/g or less, still more preferably 0.5mmol/g or less, particularly preferably 0.2mmol/g or less, and most preferably 0.1mmol/g or less. If the first reactive group amount is 0.002mmol/g or more, the adhesive material formed is suitably crosslinked to exhibit a suitable recovery rate, and if it is 0.8mmol/g or less, the distance between crosslinking points of the adhesive material formed is sufficiently long and flexibility is excellent.

In the case where the hydroxyl group of the (B) polymer component is the first reactive group, the (B) polymer component preferably further has a carboxyl group as a functional group other than the first reactive group. In this case, the carboxyl group content of the copolymer (B) is preferably 0.08mmol/g or more, more preferably 0.16mmol/g or more, still more preferably 0.32mmol/g or more, preferably 1.3mmol/g or less, still more preferably 0.8mmol/g or less, still more preferably 0.6mmol/g or less.

In the case where the hydroxyl group is the first reactive group and the (B) polymer component has both carboxyl groups and hydroxyl groups, the molar ratio of carboxyl groups to hydroxyl groups (carboxyl/hydroxyl groups) per unit mass of the (B) polymer component is preferably 4 or more, more preferably 8 or more, still more preferably 16 or more, preferably 60 or less, still more preferably 40 or less, still more preferably 30 or less. If the molar ratio (carboxyl group/hydroxyl group) is within the above range, an adhesive layer having high recovery properties and suitable balance between adhesive force and flexibility is obtained.

In the case where the carboxyl group is the first reactive group, the (B) polymer component preferably further has a hydroxyl group as a functional group other than the first reactive group. In this case, the hydroxyl group content of the polymer component (B) is preferably 0.01mmol/g or more, more preferably 0.02mmol/g or more, still more preferably 0.04mmol/g or more, preferably 0.25mmol/g or less, more preferably 0.20mmol/g or less, still more preferably 0.15mmol/g or less.

In the case where the carboxyl group is the first reactive group and the (B) polymer component has both carboxyl and hydroxyl groups, the molar ratio of carboxyl groups to hydroxyl groups (carboxyl/hydroxyl groups) per unit mass of the (B) polymer component is preferably 3.0 or more, more preferably 3.5 or more, still more preferably 4.0 or more, preferably 30 or less, still more preferably 25 or less, and still more preferably 20 or less. If the molar ratio (carboxyl group/hydroxyl group) is within the above range, an adhesive layer having high recovery properties and suitable balance between adhesion and flexibility is obtained.

The polymer component (B) 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 polymer component (B) is preferably 10 ten thousand or more, more preferably 20 ten thousand or more, further preferably 30 ten thousand or more, particularly preferably 40 ten thousand or more, preferably 300 ten thousand or less, more preferably 100 ten thousand or less, further preferably 80 ten thousand or less. If the Mw of the polymer component (B) is 10 ten thousand or more, the cohesive force is improved, and the heat resistance of the adhesive material formed is improved, and if it is 300 ten thousand or less, the coating workability of the adhesive composition is better. The method for measuring the weight average molecular weight (Mw) will be described later.

The molecular weight distribution (Mw/Mn) of the polymer component (B) is more than 3.0, preferably 5.0 or more, more preferably 7.0 or more, preferably 12.0 or less, more preferably 11.0 or less, and further preferably 10.0 or less. If Mw/Mn is greater than 3.0, an adhesive material excellent in adhesive force and flexibility can be formed.

The glass transition temperature (Tg) of the polymer component (B) is preferably-70℃or higher, more preferably-60℃or higher, preferably 0℃or lower, more preferably-10℃or lower, and further preferably-20℃or lower. When Tg is not less than-70 ℃, sufficient cohesive force is imparted to the adhesive material, and durability of the resulting adhesive material is improved, and when Tg is not more than 0 ℃, adhesion of the resulting adhesive material to an adherend is improved, peeling at low temperature and the like are suppressed, and durability is improved.

The plurality of (meth) acrylic copolymer components contain at least (A) (meth) acrylic copolymer components and (B) (meth) acrylic copolymer components.

The content of the (a) (meth) acrylic copolymer component in the plurality of (meth) acrylic copolymer components is 75% by mass or more, preferably 77% by mass or more, more preferably 80% by mass or more, 99% by mass or less, preferably 97% by mass or less, more preferably 95% by mass or less. The (A) (meth) acrylic copolymer component can be contained in an amount of 75 mass% or more to form an adhesive material having excellent recovery, and in an amount of 99 mass% or less to form an adhesive material having excellent adhesive force and flexibility.

The content of the (B) (meth) acrylic copolymer component in the plurality of (meth) acrylic copolymer components is 1% by mass or more, preferably 3% by mass or more, more preferably 5% by mass or more, and 25% by mass or less, preferably 23% by mass or less, more preferably 20% by mass or less. The adhesive material having excellent adhesion and flexibility can be formed when the content of the (B) (meth) acrylic copolymer component is 1 mass% or more, and an adhesive material having excellent recovery can be formed when the content is 25 mass% or less.

The total content of the (a) (meth) acrylic copolymer component and the (B) (meth) acrylic copolymer component in the plurality of (meth) acrylic copolymer components is preferably 80% by mass or more, more preferably 90% by mass or more, and still more preferably 95% by mass or more. It is also preferable that the (meth) acrylic copolymer component contains only the (a) (meth) acrylic copolymer component and the (B) (meth) acrylic copolymer component.

The mass ratio (a/B) of the (a) polymer component to the (B) polymer component in the plurality of (meth) acrylic copolymer components is preferably 3 or more, more preferably 4 or more, further preferably 5 or more, preferably 25 or less, more preferably 20 or less, further preferably 15 or less. When the mass ratio (a/B) is 3 or more, an adhesive material excellent in recovery rate can be formed, and when it is 25 or less, an adhesive material excellent in adhesive force and flexibility can be formed.

The plurality of (meth) acrylic copolymer components may contain a polymer component other than the (a) polymer component and the (B) polymer component.

Examples of the other polymer component include a (meth) acrylic copolymer component having no first reactive group.

The structural units constituting the (A) polymer component, (B) polymer component and other polymer components will be described below.

The (A) polymer component and the (B) polymer component have a first reactive group. That is, the (A) polymer component and the (B) polymer component contain a structural unit (a-1) having a first reactive group in their structures. The structural unit (a-1) having the first reactive group may be one kind only, or two or more kinds may be used. The first reactive group may be present on any one of a structural unit derived from a (meth) acrylic acid based monomer (preferably a (meth) acrylate monomer and/or a (meth) acrylic acid) and a structural unit derived from a vinyl monomer other than the (meth) acrylic acid based monomer. That is, the structural unit (a-1) having a first reactive group includes a structural unit derived from a (meth) acrylic acid based monomer having a first reactive 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 first reactive group.

The content of the structural unit derived from the vinyl monomer having the first reactive group (structural unit (a-1) having the first reactive group) in the polymer component (a) is preferably 0.03 mass% or more, more preferably 0.09 mass% or more, still more preferably 0.15 mass% or more, preferably 6 mass% or less, still more preferably 3 mass% or less, and still more preferably 1 mass% or less, based on 100 mass% of the polymer component. When the content of the structural unit (a-1) in the polymer component (a) is within the above range, an adhesive material excellent in balance between adhesion to an adherend and durability can be formed. The vinyl monomer having the first reactive group includes: a (meth) acrylic acid based monomer having a first reactive group and a vinyl monomer other than the (meth) acrylic acid based monomer having the first reactive group.

The content of the structural unit derived from the vinyl monomer having the first reactive group (structural unit (a-1) having the first reactive group) in the polymer component (B) is preferably 0.03 mass% or more, more preferably 0.09 mass% or more, still more preferably 0.15 mass% or more, preferably 6 mass% or less, still more preferably 3 mass% or less, and still more preferably 1 mass% or less, based on 100 mass% of the polymer component. When the content of the structural unit (a-1) in the polymer component (B) is within the above range, an adhesive material excellent in balance between adhesion to an adherend and durability can be formed. The vinyl monomer having the first reactive group includes: a (meth) acrylic acid based monomer having a first reactive group and a vinyl monomer other than the (meth) acrylic acid based monomer having the first reactive group.

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

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

The (meth) acrylate having a linear alkyl group is preferably a (meth) acrylate having a linear alkyl group having 1 to 20 carbon atoms, more preferably a (meth) acrylate having a linear alkyl group having 1 to 15 carbon atoms, and still more preferably a (meth) acrylate having a linear alkyl group having 8 to 15 carbon atoms. Examples of the (meth) acrylic acid ester having a linear alkyl group include linear alkyl (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, n-hexyl (meth) acrylate, n-octyl (meth) acrylate, n-nonyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate, and n-octadecyl (meth) acrylate.

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

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

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

Examples of the (meth) acrylate having an alicyclic hydrocarbon group include (meth) acrylate having a cyclic alkyl group and (meth) acrylate having a polycyclic structure.

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

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

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

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

Examples of the (meth) acrylamides include N, N-dimethyl (meth) acrylamide, N-diethyl (meth) acrylamide, N-diisopropyl (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-t-butyl (meth) acrylamide, N-octyl (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, N-propoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, diacetone acrylamide, 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 (b 2) functional group-forming (meth) acrylic acid-based monomer may include a hydroxyl group-containing (meth) acrylic acid-based monomer (preferably a (meth) acrylate monomer), a carboxyl group-containing (meth) acrylic acid-based monomer (preferably a (meth) acrylic acid), an epoxy group-containing (meth) acrylic acid-based monomer (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 are preferable, and a (meth) acrylic acid based monomer having a hydroxyl group is more preferable.

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

Examples of the (meth) acrylic acid based monomer having a carboxyl group include carboxyethyl (meth) acrylate and carboxypentyl (meth) acrylate; monomers obtained by reacting a (meth) acrylate having a hydroxyl group such as 2- (meth) acryloyloxyethyl succinate, 2- (meth) acryloyloxyethyl maleate, 2- (meth) acryloyloxyethyl phthalate, and an acid anhydride such as maleic anhydride, succinic anhydride, and phthalic anhydride (for example, hydrogen 2-acryloyloxyethyl succinate, hydrogen 2-methacryloyloxyethyl succinate, hydrogen 2- (acryloyloxy) ethyl hexahydrophthalate, hydrogen 2- (meth) acryloyloxyethyl hexahydrophthalate, 1- (2-acryloyloxyethyl) phthalate, and 1- (2-methacryloyloxyethyl) phthalate); (meth) acrylic acid, and the like. Among them, (meth) acrylic acid is preferable.

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

Examples of the vinyl monomer other than the (meth) acrylic acid based monomer include (b 3) a vinyl monomer other than the (meth) acrylic acid based monomer having no functional group capable of forming the first reactive group, and (b 4) a vinyl monomer other than the (meth) acrylic acid based monomer having a functional group capable of forming the first reactive group. 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 functional group capable of forming the first reactive group (b 3) include aromatic vinyl monomers, heterocyclic vinyl monomers, vinyl carboxylates, tertiary amino group-containing vinyl monomers, quaternary ammonium salt group-containing vinyl monomers, vinyl amides, α -olefins, dienes, and halogenated vinyl monomers.

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

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

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

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

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

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

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

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

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

The vinyl monomer other than the (meth) acrylic acid based monomer having a functional group capable of forming the first reactive group (b 4) includes a vinyl monomer having a hydroxyl group, a vinyl monomer having a carboxyl group, a vinyl monomer having an epoxy group, and the like.

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

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

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

((preparation of (meth) acrylic copolymer mixture)

The (meth) acrylic copolymer mixture can be prepared, for example, by mixing a plurality of (meth) acrylic copolymer components. The (meth) acrylic copolymer is obtained by polymerizing a (meth) acrylic acid based monomer. In the polymerization, a polymerization initiator is fed in a divided manner or continuously to obtain a polymerization composition containing a plurality of polymer components, and such a polymerization composition can be used as a plurality of (meth) acrylic copolymer components. The polymer component contained in the polymer composition or the (meth) acrylic copolymer mixture can be confirmed by a gel permeation chromatography method to obtain a differential molecular weight distribution curve and waveform-separating the curve (waveform separation).

As a polymerization method in polymerizing the monomer composition, either a radical polymerization method (free radical polymerization) or a living radical polymerization method (living radical polymerization) can be used.

(living radical polymerization method (living radica lpolymerization))

The living radical polymerization method is not easy to cause termination reaction or chain transfer while maintaining the simplicity and versatility of the conventional radical polymerization method, and can grow without being hindered by side reactions that deactivate the growth end, so that it is easy to prepare a polymer having a precisely controlled molecular weight distribution and a uniform composition. Thus, the reactive functional groups of the copolymer prepared by the living radical polymerization method are uniformly distributed on each molecular chain. In living radical polymerization, random copolymers can be obtained by using a mixture of monomers (vinyl monomers). Further, a block copolymer can be obtained 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 sulfur reversible chain transfer agent (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).

R ¹ -Te-Te-R ¹ (2)

[ in formula (1), R ¹ Is an alkyl group having 1 to 8 carbon atoms, an aryl group or an aromatic heterocyclic group. R is R ² And R is ³ Each independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. R is R ⁴ Is an alkyl group having 1 to 8 carbon atoms, an aryl group, a substituted aryl group, an aromatic heterocyclic group, an alkoxy group, an acyl group, an amide group, an oxycarbonyl group, a cyano group, an allyl group or a propargyl group. In the formula (2), R ¹ An alkyl group having 1 to 8 carbon atoms, an aryl group or an aromatic heterocyclic group.]

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

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

The polymerization reaction may be carried out 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, ethylcellosolve, butylcellosolve, 1-methoxy-2-propanol, hexafluoroisopropanol, diacetone alcohol, and the like. 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 can be appropriately adjusted according to the molecular weight or molecular weight distribution of the resulting polymer component, 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 polymerization is-Ter derived from tellurium compound ¹ (wherein R is ¹ As above), tellurium atoms are deactivated by the operation in the air after the polymerization reaction is completed, but may remain. Due to the terminal endsThe copolymer having tellurium atoms remaining therein is colored or has poor thermal stability, and thus it is preferable to remove the tellurium atoms. The method for removing tellurium atoms includes radical reduction methods; adsorption with activated carbon or the like; a method of adsorbing a metal with an ion exchange resin or the like, and the methods may be used in combination. The other end (the end opposite to the end of growth) of the copolymer obtained by the polymerization reaction was-CR derived from tellurium compound ² R ³ R ⁴ (wherein R is ² 、R ³ And R is ⁴ And R in formula (1) ² 、R ³ And R is ⁴ The same) morphology.

(radical polymerization method (free radical polymerization))

The radical polymerization method may be a conventionally known method. Examples of the polymerization initiator used in the radical polymerization include azo-based polymerization initiators and peroxide-based polymerization initiators. Examples of the azo-based polymerization initiator include: 2,2' -azobis (isobutyronitrile) (AIBN), 2' -azobis (2-methylbutyronitrile) (AMBN) 2,2' -azobis (2, 4-dimethylvaleronitrile) (ADVN), 1' -azobis (1-cyclohexane carbonitrile) (ACHN) dimethyl-2, 2' -azobisisobutyrate (MAIB), 4' -azobis (4-cyanovaleric acid) (ACVA), 1' -azobis (1-acetoxy-1-phenylethane), 2' -azobis (2-methylbutylamide), and 2,2' -azobis (4-methoxy-2, 4-dimethylvaleronitrile) (V-70), 2' -azobis (2-methylamidinopropane) dihydrochloride, 2' -azobis [2- (2-imidazolin-2-yl) propane ], 2' -azobis [ 2-methyl-N- (2-hydroxyethyl) propionamide ], 2,2' -azobis (2, 4-trimethylpentane), 2-cyano-2-propylazocarboxamide, 2' -azobis (N-butyl-2-methylpropionamide), 2' -azobis (N-cyclohexyl-2-methylpropionamide), or the like.

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, anisole, benzene, toluene, N-Dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), acetone, 2-butanone (methyl ethyl ketone), dioxane, propylene glycol monomethyl ether acetate, chloroform, carbon tetrachloride, tetrahydrofuran (THF), ethyl acetate, and trifluoromethylbenzene. Examples of the protic solvent include water, methanol, ethanol, isopropanol, n-butanol, ethylcellosolve, butylcellosolve, 1-methoxy-2-propanol, hexafluoroisopropanol, diacetone alcohol, and the like.

The amount of the solvent to be used may be appropriately adjusted, for example, preferably 0.01ml or more, more preferably 0.05ml or more, still more preferably 0.1ml or more, preferably 50ml or less, more preferably 10ml or less, still more preferably 1ml or less 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 obtained polymer component, 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 polymerization composition 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.

(crosslinking agent)

The adhesive composition contains a crosslinking agent. The crosslinking agent is a compound having two or more second reactive groups in one molecule, which react with the first reactive groups of the above-mentioned (A) polymer component and (B) polymer component. The crosslinking agent is not particularly limited, and examples thereof include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, metal chelate-based crosslinking agents, melamine-resin-based crosslinking agents, urea-resin-based crosslinking agents, and the like. The crosslinking agent may be used alone or in combination of two or more. Among them, isocyanate-based crosslinking agents and/or epoxy-based crosslinking agents are preferable. In particular, an isocyanate-based crosslinking agent or an epoxy-based crosslinking agent is more preferable, and an epoxy-based crosslinking agent is further preferable, from the viewpoint of improving the recovery rate of the adhesive material to be formed.

The average number of the second reactive groups in one molecule of the crosslinking agent is 2 or more, more preferably 3 or more, still more preferably 4 or more, particularly preferably 5 or more, and preferably 8 or less. That is, the crosslinking agent is more preferably a polyfunctional crosslinking agent having four or more second reactive groups in one molecule. If the crosslinking agent is tetrafunctional or more, the average inter-crosslinking point distance in the polymer in the adhesive material becomes longer. Therefore, the initial stress of the obtained adhesive material becomes low, and a high recovery rate is exhibited. The molecular weight of the crosslinking agent is preferably 200 or more, more preferably 300 or more, further preferably 400 or more, preferably 1500 or less, more preferably 1000 or less, further preferably 700 or less.

The content of the second reactive group of the crosslinking agent is preferably 1.5mmol/g or more, more preferably 3.0mmol/g or more, further preferably 3.7mmol/g or more, preferably 10mmol/g or less, more preferably 8mmol/g or less, further preferably 6mmol/g or less. If the content of the second reactive group of the crosslinking agent is within this range, the valence of the crosslinking agent becomes low, the crosslinking points are uniformly distributed in the adhesive material, and the average inter-crosslinking point distance becomes long. The initial stress of the adhesive material thus obtained becomes low and exhibits a high recovery rate.

The combination of the first reactive group of the (a) polymer component and the (B) polymer component and the second reactive group of the crosslinking agent may be, for example, the following combination.

When the second reactive group of the crosslinking agent is an isocyanate group, a hydroxyl group is exemplified as the first reactive group.

In the case where the second reactive group of the crosslinking agent is an epoxy group, the first reactive group may be a carboxyl group.

The combination of the first reactive group of the (a) polymer component and the (B) polymer component with the second reactive group of the crosslinking agent is preferably as follows: (1) A combination of a first reactive group being a hydroxyl group and a second reactive group being an isocyanate group; (2) The first reactive group is a combination of a carboxyl group and the second reactive group is an epoxy group.

(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 a second reactive group 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 aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, and addition products of these polyisocyanates with various polyols, and polyisocyanates polyfunctional with isocyanurate bonds, biuret bonds, allophanate bonds, and the like. Specific examples thereof include: a compound having two isocyanate groups in one molecule (including an isocyanate-regenerating functional group in which an isocyanate group is temporarily protected by a blocking agent, a polymerization, or the like) (a difunctional isocyanate-based crosslinking agent), a compound having three isocyanate groups in one molecule (including an isocyanate-regenerating functional group in which an isocyanate group is temporarily protected by a blocking agent, a polymerization, or the like) (a trifunctional isocyanate-based crosslinking agent), a compound having six isocyanate groups in one molecule (including an isocyanate-regenerating functional group in which an isocyanate group is temporarily protected by a blocking agent, a polymerization, or the like) (a hexafunctional isocyanate-based crosslinking agent), and the like.

Examples of the difunctional isocyanate-based crosslinking agent include diisocyanate compounds such as aliphatic diisocyanate compounds, alicyclic diisocyanate compounds and aromatic diisocyanate compounds, and addition products of these diisocyanate compounds and diol compounds may be used. The diisocyanate compound is a compound represented by the general formula "o=c=n-X-n=c=o" (X is a divalent aliphatic group, a divalent alicyclic group, a divalent aromatic group, or the like). The diol compound is represented by the general formula "HO-Y-OH" (Y is a divalent aliphatic group, a divalent alicyclic group, a divalent aromatic group, or the like).

Examples of the aliphatic diisocyanate compound include ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2-methyl-1, 5-pentane diisocyanate, 3-methyl-1, 5-pentane diisocyanate, and 2, 4-trimethyl-1, 6-hexamethylene diisocyanate, and among them, aliphatic diisocyanate compounds having 4 to 30 carbon atoms are preferable, and aliphatic diisocyanate compounds having 4 to 10 carbon atoms are more preferable.

Examples of the alicyclic diisocyanate compound include isophorone diisocyanate, cyclopentyl diisocyanate, cyclohexyl diisocyanate, hydrogenated xylene diisocyanate, hydrogenated toluene diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogenated tetramethylxylene diisocyanate, and among them, alicyclic diisocyanate compounds having 7 to 30 carbon atoms are preferable.

Examples of the aromatic diisocyanate compound include benzene diisocyanate, toluene diisocyanate, xylene diisocyanate, naphthalene diisocyanate, diphenyl ether diisocyanate, diphenylmethane diisocyanate, and diphenylpropane diisocyanate, and aromatic diisocyanate compounds having 8 to 30 carbon atoms are preferable.

Examples of the diol compound include aliphatic diol compounds such as 2-methyl-1, 3-propanediol, 2-dimethyl-1, 3-propanediol, 2-methyl-2-propyl-1, 3-propanediol, 2-ethyl-2-butyl-1, 3-propanediol, 3-methyl-1, 5-pentanediol, 1, 6-hexanediol, polyethylene glycol, and polypropylene glycol, and among these, aliphatic diol compounds having 3 to 10 carbon atoms are preferable.

Examples of the trifunctional isocyanate-based crosslinking agent and the hexafunctional isocyanate-based crosslinking agent include adducts of the diisocyanate compounds, biuret products of the diisocyanate compounds, isocyanurate products of the diisocyanate compounds (cyclic polymers of the diisocyanate compounds), and the like.

The isocyanate-based crosslinking agent preferably has no aromatic ring. The isocyanate-based crosslinking agent is particularly preferably: a difunctional isocyanate-based crosslinking agent selected from the group consisting of aliphatic diisocyanate compounds and addition products of aliphatic diisocyanate compounds and aliphatic diol compounds; a trifunctional or hexafunctional isocyanate-based crosslinking agent selected from the group consisting of adducts of aliphatic diisocyanate compounds, biuret products of aliphatic diisocyanate compounds, and isocyanurate products of aliphatic diisocyanate compounds.

(epoxy-based crosslinking agent)

The epoxy-based crosslinking agent is a compound having two or more epoxy groups as second 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 aliphatic epoxy compounds, alicyclic epoxy compounds, aromatic epoxy compounds, heterocyclic epoxy compounds, and the like.

Examples of the aliphatic epoxy compound include ethylene glycidyl ether, ethylene glycol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidyl amine, diamine glycidyl amine, 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, trimethylolpropane polyglycidyl ether, adipic acid diglycidyl ester, and 1, 3-bis (N, N-diglycidyl aminomethyl) cyclohexane.

Examples of the alicyclic epoxy compound include 1, 3-bis (N, N ' -diglycidyl aminomethyl) cyclohexane, 1, 6-hexanediol diglycidyl ether, N, N, N ', N ' -tetraglycidyl-m-xylylenediamine, and the like.

Examples of the aromatic epoxy compound include bisphenol A epichlorohydrin type epoxy resin, diglycidyl aniline, diglycidyl phthalate, resorcinol diglycidyl ether, bisphenol-S-diglycidyl ether, and the like.

Examples of the heterocyclic epoxy compound include triglycidyl-tris (2-hydroxyethyl) isocyanurate, 1,3, 5-tris- (2, 3-epoxybutyl) -isocyanurate, 1,3, 5-tris- (3, 4-epoxybutyl) -isocyanurate, 1,3, 5-tris- (4, 5-epoxypentyl) -isocyanurate, and sorbitan polyglycidyl ether.

The epoxy-based crosslinking agent is preferably a compound having two epoxy groups in one molecule (difunctional epoxy-based crosslinking agent), a compound having three epoxy groups in one molecule (trifunctional epoxy-based crosslinking agent), or a compound having four epoxy groups in one molecule (tetrafunctional epoxy-based crosslinking agent). If the crosslinking agent is a difunctional epoxy crosslinking agent, a trifunctional epoxy crosslinking agent or a tetrafunctional epoxy crosslinking agent, the crosslinking points are uniformly distributed in the adhesive material, and the average inter-crosslinking point distance becomes longer. Therefore, the initial stress of the obtained adhesive material becomes low, and a high recovery rate is exhibited.

The adhesive composition preferably contains only an isocyanate-based crosslinking agent or only an epoxy-based crosslinking agent as a crosslinking agent. When only an isocyanate-based crosslinking agent is used as the crosslinking agent, it is preferable to use a difunctional isocyanate-based crosslinking agent having two isocyanate groups in one molecule, a trifunctional isocyanate-based crosslinking agent having three isocyanate groups in one molecule, or a hexafunctional isocyanate-based crosslinking agent having six isocyanate groups in one molecule. In the case of containing only an epoxy-based crosslinking agent as the crosslinking agent, it is preferable to contain only a difunctional epoxy-based crosslinking agent having two epoxy groups in one molecule, a trifunctional epoxy-based crosslinking agent having three epoxy groups in one molecule, or a tetrafunctional epoxy-based crosslinking agent having four epoxy groups in one molecule.

The content of the crosslinking agent in the adhesive composition is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, still more preferably 0.1 parts by mass or more, preferably 0.2 parts by mass or less, and still more preferably 0.17 parts by mass or less, per 100 parts by mass of the plurality of (meth) acrylic copolymer components. If the content of the crosslinking agent is within the above range, the adhesive force and the recovery rate are in the appropriate ranges.

The molar ratio of the first reactive group of the plurality of (meth) acrylic copolymer components to the second reactive group of the crosslinking agent (the molar amount of the first reactive group/the molar amount of the second reactive group) is 1 or more, preferably 2 or more, more preferably 3 or more, preferably 70 or less, more preferably 15 or less, further preferably 10 or less, and particularly preferably 5 or less. If the molar ratio is 1 or more, the crosslinking agent reacts in an appropriate amount, and the second reactive group is not left, which means a high recovery rate, and if it is 70 or less, the reaction proceeds sufficiently, which means a high recovery rate.

The molar ratio of the first reactive group (molar amount of the first reactive group/molar amount of the crosslinking agent) of the plurality of (meth) acrylic copolymer components to the amount of the crosslinking agent (molar amount of the first reactive group/molar amount of the crosslinking agent) is preferably 2 or more, more preferably 3 or more, still more preferably 4 or more, preferably 250 or less, still more preferably 18 or less, still more preferably less than 12, particularly preferably 11 or less, and most preferably 8 or less. If the molar ratio is within the above range, the adhesive force and the recovery ratio are in the appropriate ranges.

(other additives)

In addition to the copolymer components and the crosslinking agent, other additives may be added to the adhesive composition. Examples of the other additives include crosslinking accelerators, crosslinking retarders, tackifying resins (tackifiers), polymerizable compounds, photopolymerization initiators, silane coupling agents, plasticizers, softeners, release aids, dyes, pigments, fluorescent brighteners, antistatic agents, wetting agents, surfactants, thickeners, mildewcides, 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 accelerator)

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

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

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

(crosslinking retarder)

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

The content of the crosslinking retarder that can be incorporated in the adhesive composition is preferably 0.1 part by mass or more, more preferably 0.2 part by mass or more, still more preferably 0.5 part by mass or more, preferably 4.0 parts by mass or less, more preferably 3.0 parts by mass or less, still more preferably 1.5 parts by mass or less, per 100 parts by mass of the plurality of (meth) acrylic copolymer components. 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 is formulated into the adhesive composition, and it is possible to lengthen the storage stability (storage time) of the adhesive composition.

(tackifying resin)

The adhesive composition may be used by adding a tackifying resin (excluding the above copolymer component) as needed. 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 rosins (gum rosins), wood rosins (wood rosins), tall oil rosins (tall rosins), modified rosins (polymerized rosins, stabilized rosins, disproportionated rosins, fully hydrogenated rosins, partially hydrogenated rosins, other chemically modified rosins, and the like) obtained by modifying these unmodified rosins by polymerization, disproportionation, hydrogenation, and the like, and various rosin derivatives.

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

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

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

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

The content of the tackifier 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 plurality of (meth) acrylic copolymer components. By adjusting the content of the tackifying resin within the above range, sufficient adhesion to an adherend can be ensured.

(polymerizable Compound)

The adhesive composition may also be formulated 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 two or more, more preferably four or less, and still more preferably three 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, per 100 parts by mass of the plurality of (meth) acrylic copolymer components.

(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, still more preferably 0.5 parts by mass or more, preferably 10 parts by mass or less, still more preferably 5 parts by mass or less, and still more preferably 2 parts by mass or less, based on 100 parts by mass of the plurality of (meth) acrylic copolymer components. If the content of the photopolymerization initiator is too small, the curing speed tends to be low or the curing tends to be insufficient, and if it is too large, the curability does not improve and the economical efficiency tends to be low.

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.

(silane coupling agent)

The adhesive composition may be formulated with 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-containing silane coupling agents such as 3-aminopropyl trimethoxysilane, N-2- (aminoethyl) -3-aminopropyl methyl dimethoxysilane, 3-triethoxysilyl-N- (1, 3-dimethylbutylidene) propylamine, and N-phenyl-gamma-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 that can be incorporated in the adhesive composition is preferably 0.01 mass% or more, more preferably 0.02 mass% or more, preferably 1 mass part or less, more preferably 0.6 mass part or less, per 100 mass parts of the plurality of (meth) acrylic copolymer components. By adjusting the content of the silane coupling agent in the above range, the water resistance at the interface can be improved when the adhesive material is applied to a hydrophilic adherend such as glass.

(plasticizer)

The adhesive composition may be optionally blended with a plasticizer. 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 ten thousand or less, more preferably 50,000 ten thousand 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) will be described later.

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, still more preferably 40 parts by mass or less, still more preferably 30 parts by mass or less, per 100 parts by mass of the plurality of (meth) acrylic copolymer components. By adjusting the content of the plasticizer in the above range, an adhesive material excellent in adhesion and recovery can be formed.

(method for producing adhesive composition)

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

Examples of the solvent include: aliphatic hydrocarbons such as hexane and heptane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as methylene chloride and ethylene chloride; ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; cellosolve solvents such as ethyl cellosolve; glycol ether solvents such as propylene glycol monomethyl ether, and the like. These solvents may be used singly or in combination of two or more.

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

(use of adhesive composition)

The use of the adhesive composition is preferably used for forming a flexible display that can be repeatedly bent and stretched, and an adhesive layer (adhesive material) used in the flexible display.

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

[ adhesive Material for Flexible display ]

The adhesive material for flexible displays of the present invention is a cured product of the adhesive composition. The adhesive material can be used as an adhesive material for a flexible display for bonding one flexible member and another flexible member constituting the flexible display.

The gel fraction of the cured product is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably more than 70% by mass, particularly preferably 75% by mass or more, and preferably 100% by mass or less. If the gel fraction is within the above range, a pressure-sensitive adhesive material excellent in flexibility and recovery can be formed. The gel fraction can be controlled by the amount of the crosslinking agent to be incorporated in the adhesive composition, the crosslinking treatment temperature, the crosslinking treatment time, and the like.

[ adhesive sheet for Flexible display ]

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

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

An example of the adhesive sheet of the present invention is shown in fig. 1. The adhesive sheet 10 of fig. 1 is composed of an adhesive layer 12, a first flexible sheet member 14 and a second flexible sheet member 16 sandwiching the adhesive layer 12. The adhesive layer 12 is in contact with the release surfaces of the first 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 2 μm or more, more preferably 5 μm or more, and still more preferably 10 μm or more, from the viewpoint of sufficiently securing the adhesiveness to an adherend. 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 70 μm or less, and further preferably 50 μm 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. Examples of the functional sheet member include a cover film, a shielding film, a polarizing film, a retardation film, an optical compensation film, a luminance enhancement film, a diffusion film, an antireflection film, and the like. The release sheet is a sheet for protecting the adhesive layer before the adhesive layer is attached to the adherend, and is peeled off from the adhesive layer when the adhesive layer is attached to the adherend.

In general, the term "sheet" in the definition of JIS means a flat plate-like article which is thin and generally has a thickness smaller than the length and width. In general, the term "film" refers to a thin flat plate-like product having a minimum thickness and a maximum thickness arbitrarily defined as compared with the length and width, and is generally supplied in a roll form (japanese industrial standard JISK 6900). For example, in the narrow sense of thickness, a sheet may be called 100 μm or more, and a film may be called less than 100 μm. However, the sheet is not strictly distinguished from the film, and it is not necessary to distinguish between the two in terms of the present invention, and therefore "film" is included in the present invention even when referred to as "sheet", and "sheet" is included when referred to as "film".

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

The polymer 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, and polycycloolefin resins; polyphenylene sulfide resin; a polyvinyl chloride resin; a polyvinylidene chloride resin; polyvinyl alcohol resins, and the like.

The flexible sheet member may be composed of a single layer or two or more layers composed of a layer containing one or more 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 which is in contact with the adhesive layer. Examples of the release agent used in the release treatment include silicone-based, fluorine-based, alkyd-based, unsaturated polyester-based, polyolefin-based, wax-based and other release agents.

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

(preparation of adhesive sheet)

The adhesive sheet can be prepared, for example, by the following method: the adhesive composition is applied to a flexible sheet member, and if necessary, is cured by a drying heat treatment 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 drying and heating step is not particularly limited as long as it can remove the solvent or the like used in the adhesive composition and cure it, but is preferably carried out at a temperature of 60 to 150 ℃ for about 20 to 300 seconds. In particular, the heating temperature is preferably 100℃to 130 ℃.

When the first flexible sheet member is disposed on one surface of the adhesive layer and the second flexible sheet member is disposed on the other surface, the adhesive composition is applied to the first flexible sheet member to form the adhesive layer on the first flexible sheet member, and then the second flexible sheet member is attached to the adhesive layer. Further, the adhesive layer may be cured as needed. The curing conditions include, for example, about 3 to 7 days at 60 ℃.

[ Flexible laminate Member ]

The flexible laminate member of the present invention comprises: 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 of the present invention 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.

The structure of the flexible laminate member may be, for example: 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 flexible device include a foldable display, a roll-up display, and a roll-up display. Examples of the functional sheet member include a cover film, a shielding film, a polarizing film, a retardation film, an optical compensation film, a luminance enhancement film, a diffusion film, an antireflection film, a transparent conductive film, a metal mesh film, and a buffer film.

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

(method for producing Flexible laminate Member)

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

Method (1): and peeling the release sheet attached to one surface of the adhesive sheet, attaching the exposed adhesive layer to the first flexible member, peeling the release sheet attached to the other surface of the adhesive sheet, and attaching 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 attached to the adhesive layer. And attaching 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 heat treatment to form an adhesive layer, and then a second flexible member is attached to the adhesive layer, whereby a flexible laminated member is obtained.

Method (4): the release sheet is coated with an adhesive composition on its release surface, and if necessary, the adhesive layer is formed by curing the release sheet by a drying heat treatment, and then the first flexible member is attached to the adhesive layer. And attaching 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 invention will be further described in detail with reference to specific examples. The present invention is not limited to the following examples, and may be carried out with appropriate modifications within the scope of not changing the gist thereof. The polymerization rate of the polymer composition, the weight average molecular weight (Mw) and the molecular weight distribution (Mw/Mn) of the polymer component, the thickness of the adhesive layer, and the adhesive material were evaluated according to the following methods.

The abbreviations have the following meanings.

EHA: 2-ethylhexyl acrylate, LA: lauryl acrylate, AA: acrylic acid, HBA: 4-hydroxybutyl acrylate, BTEE: ethyl-2-methyl-2-n-butyltellurion-propionate, AIBN: azobisisobutyronitrile, acOEt: ethyl acetate (polymerization rate)

Measurement by means of a Nuclear Magnetic Resonance (NMR) measurement apparatus (model: AVANCE500 (frequency 500 MHz)) manufactured by Bruker Biospin Co., ltd ¹ H-NMR (solvent: CDCl) ₃ Internal standard: TMS). 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.

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

Gel Permeation Chromatography (GPC) was performed using a high performance liquid chromatograph (model: HLC-8320GPC, manufactured by Tosoh Co., ltd.). Two TSKgelSuperHZM-H (Tosoh Co.) 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 0.5mg/mL, the sample injection amount was 10. Mu.L, and the flow rate was 0.6 mL/min. Polystyrene (molecular weights 9,840,000, 5,480,000, 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, and a standard curve (calibration curve) was prepared.

The weight average molecular weight (Mw), molecular weight distribution (Mw/Mn), and content of each polymer component were determined by waveform-separating the measured chromatogram for 6 to 11 minutes by Gaussian approximation using GPC software (Ecosec Peak Separation (Version 1.04) manufactured by Tosoh Co., ltd.). The waveform separation parameter is set to Threshold:0.5, smooth Width: 8. start hold time: 6. end hold time: 11.

(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.

(gel fraction)

The mass W2 of the metal mesh (400 mesh) cut into a width of 50mm and a length of 120mm was measured. 80mg to 120mg of the adhesive layer (adhesive material) was removed from the adhesive sheet, and the mass W1 was measured. The test piece was prepared by wrapping with a metal mesh in such a manner that the adhesive material did not fall off. The test piece was put into a glass bottle, 40g of ethyl acetate was poured into the bottle, and the mixture was gently shaken, and then allowed to stand at room temperature (25 ℃) for 72 hours or more. After standing, the test piece was taken out of the glass bottle, left at room temperature for 12 hours or more, 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-W2)/w1×100

(stress relaxation time at 400% Strain, recovery after 400% Strain)

The adhesive layers (adhesive materials) constituting the adhesive sheet were laminated by a hand press roll (handler), and a laminate having a thickness of 600 μm was prepared, and the laminate was used as a test piece. The sample was held by a parallel plate (roughened with 240-gauge sandpaper) having a diameter of 8mm using a viscoelasticity measuring apparatus (MCR 302, manufactured by An Dongpa Co.), and the measurement was performed in an atmosphere at 25 ℃.

In the measurement, after the test piece was compressed with an axial force of 1N and allowed to stand for 10 minutes, the axial force was set to 0.05N, and immediately shear stress was applied to set the strain to 400%. Then, the sample was kept at a strain of 400% for 10 minutes, and the change in shear stress was measured to determine the stress relaxation time. Then, the shear stress (0 kPa) was released and left for 10 minutes, and the final strain after 10 minutes was measured to determine the recovery rate.

After the strain was changed to 400%, the time for which the shear stress became 0.368 times the initial stress was taken as the stress relaxation time. The initial stress was a shear stress value after 0.1 seconds from the start of the application of the shear stress.

The restoration rate is calculated based on the following formula.

Recovery (%) = { (400-final strain)/400 } ×100

(Strain at 20kPa stress, recovery after 20kPa stress application)

The adhesive layers (adhesive materials) constituting the adhesive sheet were laminated by a hand press roll to prepare a laminate having a thickness of 600. Mu.m, and the laminate was used as a test piece. The sample was held by a parallel plate (roughened with 240-gauge sandpaper) having a diameter of 8mm using a viscoelasticity measuring apparatus (MCR 302, manufactured by An Dongpa Co.), and the measurement was performed in an atmosphere at 25 ℃.

In the measurement, after the test piece was compressed with an axial force of 1N and allowed to stand for 10 minutes, the axial force was changed to 0.05N, and a shear stress of 20kPa was applied to perform a creep test for 10 minutes, and strain (20 kPa strain) after 10 minutes was measured. Then, the shear stress (0 kPa) was released and left for 10 minutes, and the final strain after 10 minutes was measured to determine the recovery rate. The sample that was too soft to be measured was evaluated as "x".

The restoration rate is calculated based on the following formula.

Recovery (%) = { (20 kPa strain-final strain)/20 kPa strain } ×100

(repeated elongation test)

The adhesive layers (adhesive materials) constituting the adhesive sheet were laminated by hand press rolls to prepare a laminate having a thickness of 600. Mu.m. The laminate was cut into test pieces having a width of 10mm and a length of 70 mm.

The test was performed using a precision universal tester (AUTOGRAPH (registered trademark) AGX, manufactured by Shimadzu corporation). The test conditions were set at 23℃under 50% conditions, with a gap between the clamps of 30mm and a stretching speed of 30mm/min.

In the test, the test piece was elongated from a state where the tensile stress was 0kPa to a state where the tensile stress was 50kPa, and then the test piece was contracted to a state where the tensile stress was 0kPa. The elongation and contraction were repeated 12 times to confirm whether or not the fracture was present. Samples without fracture were rated as "good", and samples with fracture were rated as "x".

(determination of adhesive force)

One release sheet of the adhesive sheet was peeled off from the adhesive layer, and a polyethylene terephthalate (PET) film (ESTEL (registered trademark) film E5100, manufactured by Toyobo Co., ltd., thickness 50 μm) was laminated on the surface of the adhesive layer, followed by cutting into a size of 25mm wide and 100mm long to prepare an adhesive sheet with a base material. The adhesive force of the adhesive sheet with a base material to a polyimide film or glass as an adherend was measured according to the method of jis z0237 (2009).

Specifically, the release sheet was peeled off from the adhesive layer, and the adhesive layer was pressed against a polyimide film (Kapton (registered trademark) 100V: manufactured by Tou DuPont Co., ltd., thickness 25 μm) or a white plate glass (S9112, manufactured by Song Nitro Corp Co., ltd., thickness 1.0 to 1.2 mm) by reciprocating a 2kg roller twice. Next, the adhesive force of the adhesive layer was measured using an "AUTOGRAPH (registered trademark) AGS-1kNX,50N load cell" precision universal tester manufactured by Shimadzu corporation under conditions of peeling speed of 300mm/min and peeling angle of 180 °.

< preparation of polymeric composition >

Synthesis example 1 Polymer composition X _a )

A flask equipped with an argon line and a stirrer was charged with EHA (340.2 g), LA (240.0 g), AA (18.0 g), HBA (1.8 g), AIBN (26.1 mg) and AcOEt (353.4 g), and after argon substitution, BTEE (105.0 mg) was added to conduct polymerization at 60℃for 24 hours. After the reaction, acOEt was added to the reaction solution to obtain a polymer composition X _a Is a solution of (a) and (b). The solid content of the solution was 26.2 mass%.

Synthesis example 2 Polymer composition X _b )

As in Synthesis example 1, a polymer composition X was obtained _b Is a solution of (a) and (b). The monomers, organic tellurium compounds, azo polymerization initiators, solvents, reaction conditions, and polymerization rates used are shown in table 1.

Synthesis example 3 Polymer composition Y _a )

A flask equipped with an argon line and a stirrer was charged with EHA (1334.0 g), LA (600.0 g), AA (60.0 g), HBA (6.0 g) and AcOEt (1, 333.3 g), after the substitution of argon, the temperature was raised to 82℃and AIBN (875.8 mg) dissolved in AcOEt (45 g) was added dropwise thereto over 2 hours, and the mixture was reacted for another 4 hours to polymerize the mixture. After the reaction is finished, adding AcOEt into the reaction solution to obtainTo contain a polymeric composition Y _a Is a solution of (a) and (b). The solid content of the solution was 39.5 mass%.

Synthesis example 4 Polymer composition Y _b )

As in Synthesis example 3, a polymer composition Y was obtained _b Is a solution of (a) and (b). The monomers, azo polymerization initiator, solvent, reaction conditions, and polymerization rate used are shown in table 1.

The polymerization conditions and the like of each of the polymerization compositions are shown in table 1. The content of each structural unit in the polymer composition, the amount of functional groups per gram of the polymer composition, and the glass transition temperature were calculated from the charge ratio of the monomers used in the polymerization reaction and the polymerization rate.

TABLE 1

(Polymer composition X) _a 、X _b Polymer component of (a)

For polymeric composition X _a As a result of performing gel permeation chromatography and waveform separation, only the polymer component X was confirmed _a 1. In addition, for the polymeric composition X _b As a result of performing gel permeation chromatography and waveform separation, only the polymer component X was confirmed _b 1. Table 2 shows the polymer composition X _a 1、X _b 1 physical properties.

TABLE 2

(polymeric composition Y) _a 、Y _b Polymer component of (a)

For the polymeric composition Y _a The polymer component Y was confirmed by performing gel permeation chromatography and waveform separation _a 1、Y _a 2 and Y _a 3. For the polymeric composition Y _b The polymer component Y was confirmed by performing gel permeation chromatography and waveform separation _b 1、Y _b 2 and Y _b 3. Table 3 shows the polymer composition Y _a 1～Y _a 3 and Y _b 1～Y _b 3 physical properties.

TABLE 3 Table 3

< preparation of adhesive composition >

(adhesive composition No. 1)

Relative to the polymerization composition X obtained in Synthesis example 1 _a 381.7 parts by mass (100 parts by mass of polymer component) of (B) a crosslinking agent A (Duozhen (registered trademark) MHG-80B) 0.154 parts by mass and butyl acetate were added and stirred to obtain an adhesive composition No.1 having a solid content of 20% by mass. Polymer component X of adhesive composition No.1 _a 1、Y _a 1、Y _a 2 and Y _a 3, and the second reactive group of the crosslinking agent A is an isocyanate group.

(adhesive composition No. 2-11)

Adhesive compositions nos. 2 to 11 were prepared in the same manner as adhesive composition No.1, except that the formulation was changed as described in tables 4 and 5. The amount of the crosslinking agent a shown in tables 4 and 5 was calculated as the amount of the solid component. The solid component means a component other than a solvent. Polymer component X of adhesive compositions No.2 to 8 _a 1、Y _a 1、Y _a 2 and Y _a 3, and the second reactive group of the crosslinking agent A is an isocyanate group. Polymer component X of adhesive compositions No. 9-11 _b 1、Y _b 1、Y _b 2 and Y _b 3, and the second reactive group of the crosslinking agent B is an epoxy group.

< preparation of adhesive sheet >

The adhesive composition was applied to the release surface of the first release sheet (PET film having a release-treated surface, cleanSepa (registered trademark) HY-US20: manufactured by Toshan film Co., ltd., thickness of 75 μm) using a baking coater so that the film thickness after drying became 50 μm, and then dried at 60℃for 3 minutes and 150℃for 3 minutes using a constant temperature dryer. Bonding, a release liner of a second release sheet (PET film having a release-treated surface, cleanSepa (registered trademark) HY-S10: manufactured by Toshan film Co., ltd., thickness of 38 μm) was bonded to the adhesive layer formed on the first release sheet, and then cured at 60℃for 3 days to prepare an adhesive layer sandwiched between the two release sheets. The evaluation results of the adhesive layers (adhesive materials) formed from the respective adhesive compositions are shown in table 4.

TABLE 4 Table 4

TABLE 5

Crosslinking agent A: duohexand (registered trademark) MHG-80B (isocyanate-based crosslinking agent (isocyanurate product of hexamethylene diisocyanate, 6 functional groups, 80% by mass of solid content, 15.1% by mass of NCO content, manufactured by Asahi chemical Co., ltd.))

Crosslinking agent B: tetra D (registered trademark) -C (1, 3-bis (N, N-diglycidylaminomethyl) cyclohexane, available from Mitsubishi gas chemical Co., ltd., functional group number 4, solid content concentration 100% by mass, epoxy group amount 9.8 mmol/g)

And (3) a plasticizer: kura (registered trademark) LIR-410 (liquid isoprene rubber, weight average molecular weight 30000)

The adhesive composition No.1 is a case where the adhesive composition contains the (A) (meth) acrylic copolymer component but does not contain the (B) (meth) acrylic copolymer component. The adhesive material formed from the adhesive composition No.1 has a small strain amount when a shear stress of 20kPa is applied, and has poor flexibility. In addition, adhesion to glass is also low.

The adhesive compositions No.2 and 3 are cases where the adhesive composition contains (A) (meth) acrylic copolymer component and (B) (meth) acrylic copolymer component, and the content of (A) (meth) acrylic copolymer component in the total polymer component is 75 to 99 mass%. The adhesive materials formed from these adhesive compositions No.2 and 3 were excellent in recovery after strain to 400%, strain amount when a shear stress of 20kPa was applied, and repeated elongation test. In addition, the adhesion to glass and PI films was also good.

The adhesive compositions No.4 to 8 are those in which the adhesive composition contains (A) a (meth) acrylic copolymer component and (B) a (meth) acrylic copolymer component, but the content of the (A) acrylic copolymer component in the total polymer component is less than 75 mass%. Among them, the adhesive materials formed from the adhesive compositions No.4 to 6 were poor in recovery after being strained to 400%. In addition, the adhesive materials formed from the adhesive compositions No.7 and 8 failed in the repeated elongation test.

The pressure-sensitive adhesive compositions No.9 to 11 contain (A) a (meth) acrylic copolymer component and (B) a (meth) acrylic copolymer component, and the content of the (A) acrylic copolymer component in the total polymer component is 75 to 99 mass%. The adhesive materials formed from these adhesive compositions Nos. 9 to 11 were excellent in recovery after strain to 400%, strain amount when a shear stress of 20kPa was applied, and repeated elongation test. In addition, the adhesion to glass and PI films was also good.

The present invention includes the following embodiments.

An adhesive composition for a flexible display according to embodiment 1 is an adhesive composition for bonding one flexible member and the other flexible member constituting a flexible display, and is characterized by comprising a plurality of (meth) acrylic copolymer components and a crosslinking agent, wherein the (meth) acrylic copolymer components contain at least (a) (meth) acrylic copolymer component having a first reactive group and having a molecular weight distribution (Mw/Mn) of 3.0 or less, and (B) (meth) acrylic copolymer component having a first reactive group and having a molecular weight distribution (Mw/Mn) of more than 3.0, and the crosslinking agent has a second reactive group that reacts with the first reactive group, and the content of the (a) (meth) acrylic copolymer component in the plurality of (meth) acrylic copolymer components is 75 to 99 mass%.

Embodiment 2 the adhesive composition for a flexible display according to embodiment 1, wherein the weight average molecular weight of the (a) (meth) acrylic copolymer component and the (B) (meth) acrylic copolymer component is 10 to 300 ten thousand.

(embodiment 3) the adhesive composition for a flexible display according to embodiment 1 or 2, wherein the weight average molecular weight of the (a) (meth) acrylic copolymer component is 10 ten thousand or more.

Embodiment 4 the adhesive composition for flexible displays according to any one of embodiments 1 to 3, wherein the weight average molecular weight of the (B) (meth) acrylic copolymer component is 80 ten thousand or less.

(embodiment 5) the adhesive composition for a flexible display according to any one of embodiments 1 to 4, wherein the crosslinking agent is an isocyanate-based crosslinking agent and/or an epoxy-based crosslinking agent.

(embodiment 6) the adhesive composition for a flexible display according to embodiment 5, wherein the isocyanate-based crosslinking agent is at least one selected from the group consisting of an aliphatic diisocyanate compound, an addition product of an aliphatic diisocyanate compound and an aliphatic diol compound, an adduct of an aliphatic diisocyanate compound, a biuret product of an aliphatic diisocyanate compound, and an isocyanurate product of an aliphatic diisocyanate compound.

Embodiment 7 the adhesive composition for a flexible display according to embodiment 5, wherein the epoxy-based crosslinking agent is at least one selected from the group consisting of an aliphatic epoxy compound, an alicyclic epoxy compound, an aromatic epoxy compound, and a heterocyclic epoxy compound.

(embodiment 8) the adhesive composition for a flexible display according to any one of embodiments 1 to 7, wherein the first reactive group is a hydroxyl group and/or a carboxyl group.

Embodiment 9 is an adhesive material for a flexible display for bonding one flexible member and the other flexible member constituting the flexible display, wherein the adhesive material is a cured product of the adhesive composition according to any one of embodiments 1 to 8.

Embodiment 10 the adhesive material for a flexible display according to embodiment 9, wherein the gel fraction of the cured product is 50 mass% or more.

(embodiment 11) an adhesive sheet for a flexible display having an adhesive layer for bonding one flexible member and the other flexible member constituting the flexible display and a flexible sheet member attached to at least one surface of the adhesive layer, characterized in that the adhesive layer is formed of the adhesive material described in embodiment 9 or 10.

(embodiment 12) the adhesive sheet for a flexible display 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 their respective release surfaces are in contact with the adhesive layer.

(embodiment 13) a flexible laminate member comprising: the adhesive layer for bonding the first flexible member and the second flexible member to each other, wherein the adhesive layer is made of the adhesive material according to embodiment 9 or 10.

(embodiment 14) the flexible laminate component according to embodiment 13, wherein at least one of the first flexible component and the second flexible component is a display element.

Embodiment 15 is a flexible display including the flexible laminate member according to embodiment 13 or 14.

The (meth) acrylic copolymer mixture for use in an adhesive composition for flexible displays according to embodiment 16 is characterized by comprising at least (A) a (meth) acrylic copolymer component having a first reactive group and having a molecular weight distribution Mw/Mn of 3.0 or less and (B) a (meth) acrylic copolymer component having a first reactive group and having a molecular weight distribution Mw/Mn of more than 3.0, wherein the first reactive group is a hydroxyl group and/or a carboxyl group, and wherein the content of the (A) (meth) acrylic copolymer component in the (meth) acrylic copolymer mixture is 75 to 99 mass%.

Claims

1. An adhesive composition for flexible display, which is used for bonding one flexible component and another flexible component constituting the flexible display, characterized in that,

comprises a plurality of (meth) acrylic copolymer components and a crosslinking agent,

the (meth) acrylic copolymer component contains at least (A) a (meth) acrylic copolymer component and (B) a (meth) acrylic copolymer component,

the (A) (meth) acrylic copolymer component has a first reactive group and a molecular weight distribution Mw/Mn of 3.0 or less,

the (B) (meth) acrylic copolymer component has a first reactive group and a molecular weight distribution Mw/Mn of greater than 3.0,

the crosslinking agent having a second reactive group that reacts with the first reactive group,

the content of the (A) (meth) acrylic copolymer component in the plurality of (meth) acrylic copolymer components is 75 to 99 mass%.

2. The adhesive composition for flexible display according to claim 1, wherein the weight average molecular weight of the (a) (meth) acrylic copolymer component and the (B) (meth) acrylic copolymer component is 10 to 300 ten thousand.

3. The adhesive composition for flexible displays according to claim 1 or 2, wherein the weight average molecular weight of the (a) (meth) acrylic copolymer component is 10 ten thousand or more.

4. The adhesive composition for flexible displays according to any one of claims 1 to 3, wherein the weight average molecular weight of the (B) (meth) acrylic copolymer component is 80 ten thousand or less.

5. The adhesive composition for flexible display according to any one of claims 1 to 4, wherein the crosslinking agent is an isocyanate-based crosslinking agent and/or an epoxy-based crosslinking agent.

6. The adhesive composition for flexible displays according to claim 5, wherein the isocyanate-based crosslinking agent is at least one selected from the group consisting of an aliphatic diisocyanate compound, an addition product of an aliphatic diisocyanate compound and an aliphatic diol compound, an adduct of an aliphatic diisocyanate compound, a biuret product of an aliphatic diisocyanate compound, and an isocyanurate product of an aliphatic diisocyanate compound.

7. The adhesive composition for flexible display according to claim 5, wherein the epoxy-based crosslinking agent is at least one selected from the group consisting of aliphatic epoxy compounds, alicyclic epoxy compounds, aromatic epoxy compounds and heterocyclic epoxy compounds.

8. The adhesive composition for a flexible display according to any one of claims 1 to 7, wherein the first reactive group is a hydroxyl group and/or a carboxyl group.

9. An adhesive material for a flexible display for bonding one flexible member and the other flexible member constituting the flexible display, wherein the adhesive material is a cured product of the adhesive composition according to any one of claims 1 to 8.

10. The adhesive material for flexible displays according to claim 9, wherein the gel fraction of the cured product is 50 mass% or more.

11. An adhesive sheet for a flexible display having an adhesive layer for bonding one flexible member and another flexible member constituting the flexible display and a flexible sheet member attached to at least one surface of the adhesive layer, characterized in that the adhesive layer is formed of the adhesive material according to claim 9 or 10.

12. The adhesive sheet for a flexible display according to claim 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 is a first release sheet, the second flexible sheet member is a second release sheet,

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

13. A flexible laminate member is provided with: a first flexible member, a second flexible member, and an adhesive layer adhering the first flexible member and the second flexible member to each other, wherein the adhesive layer is composed of the adhesive material according to claim 9 or 10.

14. The flexible laminate component of claim 13, wherein at least one of the first flexible component and the second flexible component is a display element.

15. A flexible display characterized in that it is provided with a flexible laminate part as claimed in claim 13 or 14.

16. A (meth) acrylic copolymer mixture for an adhesive composition for flexible displays, characterized in that,

comprises at least (A) a (meth) acrylic copolymer component and (B) a (meth) acrylic copolymer component,

the first reactive group is a hydroxyl group and/or a carboxyl group,

the content of the (A) (meth) acrylic copolymer component in the (meth) acrylic copolymer mixture is 75 to 99 mass%.