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

Abstract

[Problem] To provide an adhesive composition which has adhesive force suitable for an adhesive material (adhesive layer), and from which can be formed an adhesive material (adhesive layer) having excellent flexibility and excellent resilience. [Solution] An adhesive composition for flexible displays comprising a plurality of (meth)acrylic copolymer components and a crosslinking agent, and being characterized in that: the (meth)acrylic copolymer components include at least a (meth)acrylic copolymerization component (A) and a (meth)acrylic copolymer component (B); the (meth)acrylic copolymerization component (A) has a first reactive group and has a molecular weight distribution (Mw / Mn) of not more than 3.0; the (meth)acrylic copolymer component (B) has a first reactive group and a molecular weight distribution (Mw / Mn) of greater than 3.0; the crosslinking agent has a second reactive group which reacts with the first reactive group; and the content ratio of the (meth)acrylic copolymerization component (A) in the plurality of (meth)acrylic copolymer components is 75-99 mass%.

Description

Technical Field

[0001] The present invention relates to an adhesive composition used for a flexible display, and more specifically, to an adhesive composition for forming an adhesive material used for bonding one flexible member and another flexible member.

Background Art

[0002] In various displays and touch panels such as televisions, mobile phones, and smartphones, an adhesive material is generally used for bonding the members constituting these. The adhesive material is provided, for example, in the form of an adhesive sheet with a substrate having an adhesive layer on the support substrate or a substrate-free pressure-sensitive adhesive sheet without a support substrate, and the members are bonded together.

[0003] On the other hand, in recent years, flexible displays that are repeatedly bent and used have attracted attention in image display devices such as liquid crystal display devices and organic electroluminescence (organic EL) display devices. Flexible displays include foldable displays that can be folded and rollable displays that can be rolled into a cylindrical shape or the like, and are expected to be used in portable terminals such as smartphones and tablet terminals, and stationary displays that can be stored.

[0004] In such a flexible display, as an adhesive material for bonding a flexible member constituting a member that is repeatedly bent and stretched and another flexible member, for example, Patent Document 1 discloses a ratio of a shear stress 60 seconds after a 1000% displacement to a maximum shear stress when one surface and the other surface of an adhesive layer are displaced 1000% in opposite directions to each other, and an adhesive material for a repeated bending device in which a gel fraction is controlled within a predetermined range (see Patent Document 1 (Claim 1)).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In a conventional flexible display having an adhesive layer, when repeatedly bent, the adhesive layer did not fully recover from the bent state to the original state. Therefore, when the bending of the flexible display is repeated, there is a risk of appearance defects such as the occurrence of floating or peeling at the interface between the adhesive layer and the flexible member at the bent portion, or the bent portion looking wavy.

[0007] 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 an adhesive material (adhesive layer), excellent flexibility, and excellent restorability.

Means for Solving the Problems

[0008] The adhesive composition for a flexible display of the present invention, which has solved the above problems, is an adhesive composition for a flexible display for bonding one flexible member and another flexible member constituting the flexible display, and contains a plurality of (meth)acrylic copolymer components and a crosslinking agent. At least (A) a (meth)acrylic copolymer component and (B) a (meth)acrylic copolymer component are contained as the (meth)acrylic copolymer components. 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 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 component in the plurality of (meth)acrylic copolymer components is 75% by mass to 99% by mass.

Effects of the Invention

[0009] By using the pressure-sensitive adhesive composition for a flexible display of the present invention, a pressure-sensitive adhesive (pressure-sensitive adhesive layer) having an appropriate adhesive force suitable as a pressure-sensitive adhesive material and excellent flexibility and resilience can be formed. Therefore, by using the pressure-sensitive adhesive composition for a flexible display of the present invention, even when repeatedly bent, the occurrence of appearance defects such as cracks and undulations can be suppressed without the occurrence of floating or peeling at the interface between the pressure-sensitive adhesive layer and the flexible member at the bent portion, and a flexible display can be manufactured.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0011] Hereinafter, an example of a preferred embodiment of the present invention will be described. However, the following embodiments are merely illustrative. The present invention is not limited to the following embodiments at all.

[0012] In the present invention, “(meth)acrylic” means “at least one of acrylic and methacrylic”. “(meth)acrylate” means “at least one of acrylate and methacrylate”. “(meth)acryloyl” means “at least one of acryloyl and methacryloyl”. “Vinyl monomer” refers to a monomer having a carbon-carbon double bond capable of radical polymerization in the molecule. “Structural unit derived from a vinyl monomer” refers to a structural unit in which the carbon-carbon double bond capable of radical polymerization of the vinyl monomer has polymerized to become a carbon-carbon single bond. “Structural unit derived from (meth)acrylate” refers to a structural unit in which the carbon-carbon double bond capable of radical polymerization of (meth)acrylate has polymerized to become a carbon-carbon single bond. “Structural unit derived from (meth)acrylic monomer” refers to a structural unit in which the carbon-carbon double bond capable of radical polymerization of (meth)acrylic monomer has polymerized to become a carbon-carbon single bond.

[0013] [Adhesive Composition for Flexible Display] The adhesive composition for flexible display of the present invention (hereinafter, may be simply referred to as "adhesive composition") is an adhesive composition for flexible display for bonding one flexible member and another flexible member constituting a flexible display. The adhesive composition contains a plurality of (meth)acrylic copolymer components and a crosslinking agent.

[0014] [(Meth)acrylic copolymer component] The adhesive composition contains, as the (meth)acrylic copolymer component, at least (A) (meth)acrylic copolymer component (hereinafter, may be simply referred to as "(A) polymer component") and (B) (meth)acrylic copolymer component (hereinafter, may be simply referred to as "(B) polymer component"). A mixture containing a plurality of the (meth)acrylic copolymer components may be referred to as a (meth)acrylic copolymer mixture. 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 more than 3.0. Further, the content of the (A) (meth)acrylic copolymer component in the plurality of (meth)acrylic copolymer components is 75% by mass to 99% by mass. By containing these (A) (meth)acrylic copolymer component and (B) (meth)acrylic copolymer component in a predetermined amount, an adhesive material that is flexible and has excellent resilience can be formed, and further, it can have an adhesive force suitable as an adhesive material.

[0015] [(A) (meth)acrylic copolymer component] The above-mentioned (A) (meth)acrylic copolymer component may be a copolymer having a structural unit derived from a (meth)acrylic monomer as a main component (50% by mass or more). The (A) polymer component may be one kind or two or more kinds. Further, the (A) polymer component may contain a structural unit derived from a vinyl monomer other than the (meth)acrylic monomer. The content of the structural unit derived from the (meth)acrylic monomer in the (A) polymer component is preferably 80% by mass or more, more preferably 90% by mass or more, based on 100% by mass of the polymer component. Incidentally, the (A) polymer component may be composed only of a structural unit derived from a (meth)acrylic monomer.

[0016] The (A) polymer component is preferably a (meth)acrylate copolymer. The (meth)acrylate copolymer may be a copolymer having a structural unit derived from a (meth)acrylate as a main component (50% by mass or more), and may contain a structural unit derived from a vinyl monomer other than the (meth)acrylate. The (meth)acrylate is an ester compound in which a hydrogen atom of a carboxy group of (meth)acrylic acid is substituted with an organic group. The content of the structural unit derived from the (meth)acrylate in the (A) polymer component is preferably 80% by mass or more, more preferably 90% by mass or more, based on 100% by mass of the polymer component.

[0017] The (A) polymer component has a first reactive group. The first reactive group is a functional group having a high reactivity with a second reactive group possessed by a crosslinking agent described later. Examples of the functional group that can be the first reactive group include reactive functional groups. Examples of the first reactive group include a hydroxy group, a carboxy group, an epoxy group, etc., preferably a hydroxy group and / or a carboxy group, more preferably a hydroxy group or a carboxy group.

[0018] The amount of the first reactive groups in the polymer component (A) is preferably 0.002 mmol / g or more, more preferably 0.006 mmol / g or more, still more preferably 0.01 mmol / g or more, and preferably 0.8 mmol / g or less, more preferably 0.6 mmol / g or less, still more preferably 0.5 mmol / g or less, particularly preferably 0.2 mmol / g or less, and most preferably 0.1 mmol / g or less. If the amount of the first reactive groups is 0.002 mmol / g or more, the pressure-sensitive adhesive formed is appropriately crosslinked and exhibits a suitable recovery rate. If it is 0.8 mmol / g or less, the distance between crosslinking points of the pressure-sensitive adhesive formed is sufficiently long and it has excellent flexibility.

[0019] When the first reactive group of the polymer component (A) is a hydroxy group, it preferably further has a carboxy group as a functional group other than the first reactive group. In this case, the amount of the carboxy groups in the copolymer (A) is preferably 0.08 mmol / g or more, more preferably 0.16 mmol / g or more, still more preferably 0.32 mmol / g or more, and preferably 1.3 mmol / g or less, more preferably 0.8 mmol / g or less, still more preferably 0.6 mmol / g or less.

[0020] Also, when the hydroxy group is the first reactive group and the polymer component (A) has both a carboxy group and a hydroxy group, the molar ratio of the carboxy group to the hydroxy group per unit mass of the polymer component (A) (carboxy group / hydroxy group) is preferably 4 or more, more preferably 8 or more, still more preferably 16 or more, and preferably 60 or less, more preferably 40 or less, still more preferably 30 or less. If the molar ratio (carboxy group / hydroxy group) is within the above range, it has high resilience and becomes a pressure-sensitive adhesive layer with a suitable balance between adhesive strength and flexibility.

[0021] When the carboxy group is the first reactive group, the (A) polymer component preferably further has a hydroxy group as a functional group other than the first reactive group. In this case, the amount of the hydroxy group in the (A) polymer component is preferably 0.01 mmol / g or more, more preferably 0.02 mmol / g or more, still more preferably 0.04 mmol / g or more, and preferably 0.25 mmol / g or less, more preferably 0.20 mmol / g or less, still more preferably 0.15 mmol / g or less.

[0022] Also, when the carboxy group is the first reactive group and the (A) polymer component has both a carboxy group and a hydroxy group, the molar ratio of the carboxy group to the hydroxy group per unit mass of the (A) polymer component (carboxy group / hydroxy group) is preferably 3.0 or more, more preferably 3.5 or more, still more preferably 4.0 or more, and preferably 30 or less, more preferably 25 or less, still more preferably 20 or less. When the molar ratio (carboxy group / hydroxy group) is within the above range, it has high resilience and a pressure-sensitive adhesive layer with a good balance between adhesiveness and flexibility is obtained.

[0023] The (A) polymer component may be any of a random copolymer, a block copolymer, and a graft copolymer, and is preferably a random copolymer.

[0024] The weight average molecular weight (Mw) of the (A) polymer component is preferably 100,000 or more, more preferably 200,000 or more, still more preferably 600,000 or more, particularly preferably more than 800,000, and preferably 3,000,000 or less, more preferably 2,500,000 or less, still more preferably 2,300,000 or less. When the Mw of the (A) polymer component is 100,000 or more, the cohesive force increases and the heat resistance of the pressure-sensitive adhesive formed is improved, and when it is 3,000,000 or less, the coating workability of the pressure-sensitive adhesive composition becomes better. The method for measuring the weight average molecular weight (Mw) will be described later.

[0025] 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 even more preferably 1.8 or less. The smaller the Mw / Mn, the narrower the width of the molecular weight distribution, and the more uniform the molecular weight of the copolymer. When the value is 1.0, the width of the molecular weight distribution is the narrowest. If the Mw / Mn is 3.0 or less, compared with the molecular weight of the designed copolymer, the content of those with a small molecular weight or a large molecular weight is low, and an adhesive material with excellent flex resistance can be obtained. In the present invention, the molecular weight distribution (Mw / Mn) is a value calculated by (weight average molecular weight (Mw)) / (number average molecular weight (Mn)). The measurement methods of Mw and Mn will be described later.

[0026] The glass transition temperature (Tg) of the polymer component (A) is preferably -70°C or higher, more preferably -60°C or higher, preferably 0°C or lower, more preferably -10°C or lower, and even more preferably -20°C or lower. If the Tg is -70°C or higher, sufficient cohesive force is imparted to the adhesive material, and the durability of the formed adhesive material is improved. If it is 0°C or lower, the adhesion of the formed adhesive material to the adherend is increased, peeling at low temperatures is suppressed, and the durability is improved.

[0027] The Tg of the polymer component is a value calculated by the following FOX formula (Equation (1)). In Equation (1), Tg represents the glass transition temperature (°C) of the copolymer. Tgi represents the glass transition temperature (°C) when the vinyl monomer i forms a homopolymer. Wi represents the mass ratio of the vinyl monomer i in all vinyl monomers forming the copolymer, and ΣWi = 1. i is a natural number from 1 to n.

[0028]

Equation

[0029] The above-mentioned (A) polymer component preferably contains a polymer component ((A1) polymer component) having a weight average molecular weight of 1,000,000 or more and a polymer component ((A2) polymer component) having a weight average molecular weight of less than 1,000,000. By containing the polymer component (A1) and the polymer component (A2), a more flexible pressure-sensitive adhesive material can be formed.

[0030] The weight average molecular weight (Mw) of the above-mentioned (A1) polymer component is preferably 1,000,000 or more, more preferably 1,300,000 or more, still more preferably 1,500,000 or more, preferably 3,000,000 or less, more preferably 2,500,000 or less, and still more preferably 2,300,000 or less. The molecular weight distribution (Mw / Mn) of the (A1) 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.

[0031] The weight average molecular weight (Mw) of the above-mentioned (A2) polymer component is preferably 100,000 or more, more preferably 200,000 or more, still more preferably 600,000 or more, particularly preferably more than 800,000, preferably less than 1,000,000, more preferably 950,000 or less, and still more preferably 900,000 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.

[0032] The ratio (Mw1 / Mw2) of the weight average molecular weight (Mw1) of the above-mentioned (A1) polymer component to the weight average molecular weight (Mw2) of the (A2) polymer component is preferably 1.5 or more, more preferably 2.0 or more, preferably 4.0 or less, and more preferably 3.0 or less. If the ratio (Mw1 / Mw2) is within the above range, a more flexible pressure-sensitive adhesive material can be formed while having excellent resilience. When a plurality of (A1) polymer components and (A2) polymer components are contained, the ratio of the largest weight average molecular weight among the respective components is defined as the ratio (Mw1 / Mw2).

[0033] The mass ratio (A1 / A2) of the (A1) polymer component to the (A2) polymer component in the above-mentioned (A) polymer component is preferably 0.1 or more, more preferably 0.2 or more, still more preferably 0.3 or more, and preferably 1.0 or less, more preferably 0.8 or less, still more preferably 0.6 or less. If the mass ratio (A1 / A2) is within the above range, a more flexible pressure-sensitive adhesive material can be formed while having excellent resilience. When a plurality of (A1) polymer components and (A2) polymer components are contained, the mass ratio of the polymer component having the largest weight-average molecular weight among the respective components is defined as the ratio (A1 / A2).

[0034] ((B) (meth)acrylic copolymer component) The above-mentioned (B) (meth)acrylic copolymer component may be a copolymer having structural units derived from (meth)acrylic monomers as the main component (50% by mass or more). The (B) polymer component may be one kind or two or more kinds. Further, the (B) polymer component may contain structural units derived from vinyl monomers other than (meth)acrylic monomers. The content of the structural units derived from (meth)acrylic monomers in the (B) polymer component is preferably 80% by mass or more, more preferably 90% by mass or more, based on 100% by mass of the polymer component. Note that the (B) polymer component may be composed only of structural units derived from (meth)acrylic monomers.

[0035] The (B) polymer component is preferably a (meth)acrylate copolymer. The (meth)acrylate copolymer may be a copolymer having structural units derived from (meth)acrylates as the main component (50% by mass or more), and may contain structural units derived from vinyl monomers other than (meth)acrylates. The content of the structural units derived from (meth)acrylates in the (B) polymer component is preferably 80% by mass or more, more preferably 90% by mass or more, based on 100% by mass of the polymer component.

[0036] The (B) polymer component has a first reactive group. The first reactive group is a functional group having a high reactivity with a second reactive group possessed by a crosslinking agent described later. Examples of the functional group that can be the first reactive group include reactive functional groups. The first reactive group is preferably a hydroxy group and / or a carboxy group, more preferably a hydroxy group or a carboxy group.

[0037] The amount of the first reactive group in the (B) polymer component is preferably 0.002 mmol / g or more, more preferably 0.006 mmol / g or more, still more preferably 0.01 mmol / g or more, and preferably 0.8 mmol / g or less, more preferably 0.6 mmol / g or less, still more preferably 0.5 mmol / g or less, particularly preferably 0.2 mmol / g or less, and most preferably 0.1 mmol / g or less. If the amount of the first reactive group is 0.002 mmol / g or more, the pressure-sensitive adhesive formed is appropriately crosslinked and exhibits a suitable recovery rate. If it is 0.8 mmol / g or less, the distance between crosslinking points of the pressure-sensitive adhesive formed is sufficiently long and it has excellent flexibility.

[0038] When the hydroxy group is the first reactive group in the (B) polymer component, it preferably further has a carboxy group as a functional group other than the first reactive group. In this case, the amount of the carboxy group in the (B) copolymer is preferably 0.08 mmol / g or more, more preferably 0.16 mmol / g or more, still more preferably 0.32 mmol / g or more, and preferably 1.3 mmol / g or less, more preferably 0.8 mmol / g or less, still more preferably 0.6 mmol / g or less.

[0039] Further, when the hydroxy group is the first reactive group and the (B) polymer component has both a carboxy group and a hydroxy group, the molar ratio of the carboxy group to the hydroxy group (carboxy group / hydroxy group) per unit mass of the (B) polymer component is preferably 4 or more, more preferably 8 or more, still more preferably 16 or more, and preferably 60 or less, more preferably 40 or less, still more preferably 30 or less. When the molar ratio (carboxy group / hydroxy group) is within the above range, it has high resilience and forms a pressure-sensitive adhesive layer with a favorable balance between adhesiveness and flexibility.

[0040] When the carboxy group is the first reactive group, the (B) polymer component preferably further has a hydroxy group as a functional group other than the first reactive group. In this case, the amount of the hydroxy group in the (B) polymer component is preferably 0.01 mmol / g or more, more preferably 0.02 mmol / g or more, still more preferably 0.04 mmol / g or more, and preferably 0.25 mmol / g or less, more preferably 0.20 mmol / g or less, still more preferably 0.15 mmol / g or less.

[0041] Further, when the carboxy group is the first reactive group and the (B) polymer component has both a carboxy group and a hydroxy group, the molar ratio of the carboxy group to the hydroxy group (carboxy group / hydroxy group) 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, and preferably 30 or less, more preferably 25 or less, still more preferably 20 or less. When the molar ratio (carboxy group / hydroxy group) is within the above range, it has high resilience and forms a pressure-sensitive adhesive layer with a favorable balance between adhesiveness and flexibility.

[0042] The (B) polymer component may be any of a random copolymer, a block copolymer, and a graft copolymer, and is preferably a random copolymer.

[0043] The weight average molecular weight (Mw) of the said (B) polymer component is preferably 100,000 or more, more preferably 200,000 or more, still more preferably 300,000 or more, particularly preferably 400,000 or more, and preferably 3,000,000 or less, more preferably 1,000,000 or less, still more preferably 800,000 or less. If the Mw of the said (B) polymer component is 100,000 or more, the cohesiveness increases and the heat resistance of the pressure-sensitive adhesive formed is improved. If it is 3,000,000 or less, the coating workability of the pressure-sensitive adhesive composition becomes better. The method for measuring the weight average molecular weight (Mw) will be described later.

[0044] The molecular weight distribution (Mw / Mn) of the said (B) polymer component is more than 3.0, preferably 5.0 or more, more preferably 7.0 or more, and preferably 12.0 or less, more preferably 11.0 or less, still more preferably 10.0 or less. If Mw / Mn is more than 3.0, a pressure-sensitive adhesive excellent in adhesive strength and flexibility can be formed.

[0045] The glass transition temperature (Tg) of the said (B) polymer component is preferably -70°C or more, more preferably -60°C or more, and preferably 0°C or less, more preferably -10°C or less, still more preferably -20°C or less. If Tg is -70°C or more, sufficient cohesiveness is imparted to the pressure-sensitive adhesive and the durability of the formed pressure-sensitive adhesive is improved. If it is 0°C or less, the adhesion of the formed pressure-sensitive adhesive to the adherend is increased, peeling at low temperatures, etc. are suppressed, and the durability is improved.

[0046] The plurality of (meth)acrylic copolymer components contain at least (A) (meth)acrylic copolymer component and (B) (meth)acrylic copolymer component.

[0047] The content ratio 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, and 99% by mass or less, preferably 97% by mass or less, more preferably 95% by mass or less. If the content ratio of the (A) (meth)acrylic copolymer component is 75% by mass or more, a pressure-sensitive adhesive material with excellent recovery rate can be formed. If it is 99% by mass or less, a pressure-sensitive adhesive material with excellent adhesive force and flexibility can be formed.

[0048] The content ratio 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. If the content ratio of the (B) (meth)acrylic copolymer component is 1% by mass or more, a pressure-sensitive adhesive material with excellent adhesive force and flexibility can be formed. If it is 25% by mass or less, a pressure-sensitive adhesive material with excellent recovery rate can be formed.

[0049] The total content ratio 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 even 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.

[0050] The mass ratio (A / B) of the (A) polymer component and the (B) polymer component in the plurality of (meth)acrylic copolymer components is preferably 3 or more, more preferably 4 or more, and even more preferably 5 or more, and preferably 25 or less, more preferably 20 or less, and even more preferably 15 or less. If the mass ratio (A / B) is 3 or more, a pressure-sensitive adhesive material with excellent recovery rate can be formed. If it is 25 or less, a pressure-sensitive adhesive material with excellent adhesive force and flexibility can be formed.

[0051] The plurality of (meth)acrylic copolymer components may contain other polymer components 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.

[0052] Hereinafter, the structural units constituting the (A) polymer component, the (B) polymer component, and the other polymer component will be described.

[0053] 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 a first reactive group may be only one kind, or may have two or more kinds. The first reactive group may be a structural unit derived from a (meth)acrylic monomer (preferably a (meth)acrylate monomer and / or (meth)acrylic acid), or a structural unit derived from a vinyl monomer other than the (meth)acrylic monomer. That is, the structural unit (a-1) having a first reactive group includes a structural unit derived from a (meth)acrylic monomer having a first reactive group (preferably a (meth)acrylate monomer and / or (meth)acrylic acid), or a structural unit derived from a vinyl monomer other than the (meth)acrylic monomer having a first reactive group.

[0054] The content rate of the structural unit (structural unit (a-1) having a first reactive group) derived from the vinyl monomer having a first reactive group in the (A) polymer component is preferably 0.03% by mass or more, more preferably 0.09% by mass or more, still more preferably 0.15% by mass or more, and preferably 6% by mass or less, more preferably 3% by mass or less, still more preferably 1% by mass or less in 100% by mass of the polymer component. If the content rate of the structural unit (a-1) in the (A) polymer component is within the above range, a pressure-sensitive adhesive excellent in the balance between adhesion to an adherend and durability can be formed. The vinyl monomer having a first reactive group includes a (meth)acrylic monomer having a first reactive group and a vinyl monomer other than the (meth)acrylic monomer having a first reactive group.

[0055] The content rate of the structural unit (structural unit (a-1) having a first reactive group) derived from the vinyl monomer having a first reactive group in the (B) polymer component is preferably 0.03% by mass or more, more preferably 0.09% by mass or more, still more preferably 0.15% by mass or more, and preferably 6% by mass or less, more preferably 3% by mass or less, still more preferably 1% by mass or less in 100% by mass of the polymer component. If the content rate of the structural unit (a-1) in the (B) polymer component is within the above range, a pressure-sensitive adhesive excellent in the balance between adhesion to an adherend and durability can be formed. The vinyl monomer having a first reactive group includes a (meth)acrylic monomer having a first reactive group and a vinyl monomer other than the (meth)acrylic monomer having a first reactive group.

[0056] Examples of the (meth)acrylic monomer include (b1) a (meth)acrylic monomer having no functional group that can serve as a first reactive group, and (b2) a (meth)acrylic monomer having a functional group that can serve as a first reactive group. These monomers may be used alone or in combination of two or more. As the (b1) (meth)acrylic monomer, (b1-1) a (meth)acrylate monomer having no functional group that can serve as a first reactive group is preferred. Examples of the (b2) (meth)acrylic monomer include (b2-1) a (meth)acrylate monomer having a functional group that can serve as a first reactive group, and (meth)acrylic acid.

[0057] Examples of the (b1) (meth)acrylic monomer having no functional group that can serve as a first reactive group include (meth)acrylates having a linear alkyl group, (meth)acrylates having a branched alkyl group, (meth)acrylates having an alkoxy group, (meth)acrylates having a polyalkylene glycol structural unit, (meth)acrylates having an alicyclic hydrocarbon group, (meth)acrylates having an aromatic group, (meth)acrylates having a tertiary amino group, (meth)acrylamides, and the like. Among these, at least one selected from the group consisting of (meth)acrylates having a linear alkyl group, (meth)acrylates having a branched alkyl group, (meth)acrylates having an alicyclic hydrocarbon group, (meth)acrylates having an aromatic group, and (meth)acrylamides is preferred.

[0058] As the (meth)acrylate having a linear alkyl group, a (meth)acrylate having a linear alkyl group with 1 to 20 carbon atoms in the linear alkyl group is preferable, a (meth)acrylate having a linear alkyl group with 1 to 15 carbon atoms in the linear alkyl group is more preferable, and a (meth)acrylate having a linear alkyl group with 8 to 15 carbon atoms in the linear alkyl group is even more preferable. Examples of the (meth)acrylate having a linear alkyl group include linear alkyl esters of (meth)acrylic acid 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-lauryl (meth)acrylate, and n-stearyl (meth)acrylate.

[0059] As the (meth)acrylate having a branched alkyl group, a (meth)acrylate having a branched alkyl group with 3 to 20 carbon atoms in the branched alkyl group is preferable, and a (meth)acrylate having a branched alkyl group with 3 to 10 carbon atoms in the branched alkyl group is more preferable. Examples of the (meth)acrylate having a branched alkyl group include branched alkyl esters of (meth)acrylic acid 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, and isodecyl (meth)acrylate.

[0060] Examples of the (meth)acrylate having an alkoxy group include alkoxyalkyl esters of (meth)acrylic acid such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate.

[0061] Examples of the (meth)acrylate having the polyalkylene glycol structural unit include (meth)acrylates having a polyethylene glycol structural unit such as polyethylene glycol (degree of polymerization = 2 to 10) methyl ether (meth)acrylate, polyethylene glycol (degree of polymerization = 2 to 10) ethyl ether (meth)acrylate, polyethylene glycol (degree of polymerization = 2 to 10) propyl ether (meth)acrylate, and polyethylene glycol (degree of polymerization = 2 to 10) phenyl ether (meth)acrylate; and (meth)acrylates having a polypropylene glycol structural unit such as polypropylene glycol (degree of polymerization = 2 to 10) methyl ether (meth)acrylate, polypropylene glycol (degree of polymerization = 2 to 10) ethyl ether (meth)acrylate, polypropylene glycol (degree of polymerization = 2 to 10) propyl ether (meth)acrylate, and polypropylene glycol (degree of polymerization = 2 to 10) phenyl ether (meth)acrylate.

[0062] Examples of the (meth)acrylate having the alicyclic hydrocarbon group include (meth)acrylates having a cyclic alkyl group and (meth)acrylates having a polycyclic structure. The (meth)acrylate having the cyclic alkyl group is preferably a (meth)acrylate having a cyclic alkyl group with 6 to 12 carbon atoms. Examples of the cyclic alkyl group include cyclic alkyl groups having a monocyclic structure (e.g., cycloalkyl groups), which may also have a chain portion. Specific examples of the (meth)acrylate having a cyclic alkyl group with a monocyclic structure include (meth)acrylic acid cyclic alkyl esters such as cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, and cyclododecyl (meth)acrylate.

[0063] As the (meth)acrylate having the polycyclic structure, it is preferably a (meth)acrylate having a polycyclic structure with 6 to 12 carbon atoms in the polycyclic structure. Examples of the polycyclic structure include cyclic alkyl groups having a bridged ring structure (e.g., adamantyl group, norbornyl group, isobornyl group), and may also have a chain portion. Specific examples of the (meth)acrylate having a polycyclic structure include bornyl (meth)acrylate, isobornyl (meth)acrylate, 1-adamantyl (meth)acrylate, 2-adamantyl (meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, 2-ethyl-2-adamantyl (meth)acrylate, norbornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, and the like.

[0064] As the (meth)acrylate having the aromatic group, it is preferably a (meth)acrylate having an aromatic group with 6 to 12 carbon atoms in the aromatic group. Examples of the aromatic group include aryl groups, etc., and may also have a chain portion such as alkylaryl groups, arallyl groups, aryloxyalkyl groups. Examples of the (meth)acrylate having the aromatic group include compounds in which an aryl group is directly bonded to the (meth)acryloyloxy group, compounds in which an aralkyl group is directly bonded to the (meth)acryloyloxy group, and compounds in which an alkylaryl group is directly bonded to the (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)acrylate having an aromatic group include benzyl (meth)acrylate, phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, and the like.

[0065] Examples of the (meth)acrylate having the tertiary amino group include 2-(dimethylamino)ethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, and the like.

[0066] Examples of the (meth)acrylamides include N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N,N-diisopropyl (meth)acrylamide, (meth)acrylamide, N-methyl (meth)acrylamide, N-ethyl (meth)acrylamide, N-isopropyl (meth)acrylamide, N-tert-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 monomers but are not included in (meth)acrylate monomers.

[0067] Examples of the (meth)acrylic monomer having a functional group that can be a (b2) first reactive group include a (meth)acrylic monomer having a hydroxy group (preferably a (meth)acrylate monomer), a (meth)acrylic monomer having a carboxy group (preferably (meth)acrylic acid), a (meth)acrylic monomer having an epoxy group (preferably a (meth)acrylate monomer), and the like. Among these, a (meth)acrylic monomer having a hydroxy group and / or a (meth)acrylic monomer having a carboxy group is preferable, and a (meth)acrylic monomer having a hydroxy group is more preferable.

[0068] Examples of the (meth)acrylic monomer having a hydroxy 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, 12-hydroxylauryl (meth)acrylate; hydroxyalkylcycloalkyl (meth)acrylates such as (4-hydroxymethylcyclohexyl)methyl (meth)acrylate; and caprolactone adducts of hydroxyalkyl (meth)acrylate. Among these, hydroxyalkyl (meth)acrylates are preferred, and (meth)acrylates having a hydroxyalkyl group with 1 to 5 carbon atoms are more preferred.

[0069] Examples of the (meth)acrylic monomer having a carboxy group include monomers obtained by reacting an acid anhydride such as maleic anhydride, succinic anhydride, or phthalic anhydride with a (meth)acrylate having a hydroxy group such as carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl maleate, 2-(meth)acryloyloxyethyl phthalate (for example, 2-acryloyloxyethyl hydrogen succinate, 2-methacryloyloxyethyl hydrogen succinate, 2-(acryloyloxy)ethyl hydrogen hexahydrophthalate, 2-(methacryloyloxyethyl) hydrogen hexahydrophthalate, 1-(2-acryloyloxyethyl) phthalate, 1-(2-methacryloyloxyethyl) phthalate), and (meth)acrylic acid. Among these, (meth)acrylic acid is preferred.

[0070]

[0071] Examples of the (meth)acrylic acid ester having an epoxy group include glycidyl (meth)acrylate and 3,4-epoxycyclohexylmethyl (meth)acrylate.Examples of the vinyl monomer other than the (meth)acrylic monomer include (b3) a vinyl monomer other than the (meth)acrylic monomer having no functional group capable of becoming a first reactive group, and (b4) a vinyl monomer other than the (meth)acrylic monomer having a functional group capable of becoming a first reactive group. These monomers may be used alone or in combination of two or more.

[0072] Examples of the vinyl monomer other than the (meth)acrylic monomer having no functional group capable of becoming a first reactive group include aromatic vinyl monomers, vinyl monomers containing a heterocycle, vinyl carboxylates, vinyl monomers containing a tertiary amino group, vinyl monomers containing a quaternary ammonium base, vinylamides, α-olefins, dienes, vinyl halide monomers, and the like.

[0073] Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, 4-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methoxystyrene, 2-hydroxymethylstyrene, 1-vinylnaphthalene, and the like. Examples of the vinyl monomer containing a heterocycle include 2-vinylthiophene, N-methyl-2-vinylpyrrole, 2-vinylpyridine, 4-vinylpyridine, and the like. Examples of the vinyl carboxylate include vinyl acetate, vinyl pivalate, vinyl benzoate, and the like. Examples of the vinyl monomer containing a tertiary amino group include N,N-dimethylallylamine, and the like. Examples of the vinyl monomer containing a quaternary ammonium base include N-methacryloylaminoethyl-N,N,N-trimethylbenzylammonium chloride, and the like. Examples of the vinylamides include N-vinylformamide, N-vinylacetamide, 1-vinyl-2-pyrrolidone, N-vinyl-ε-caprolactam, and the like. Examples of the α-olefins include 1-hexene, 1-octene, 1-decene, and the like. Examples of the dienes include butadiene, isoprene, 4-methyl-1,4-hexadiene, 7-methyl-1,6-octadiene, and the like. Examples of the vinyl halide monomer include vinyl fluoride, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, tetrafluoropropylene, vinylidene chloride, vinyl chloride, 1-chloro-1-fluoroethylene, 1,2-dichloro-1,2-difluoroethylene, and the like.

[0074] Examples of the vinyl monomer other than the (meth)acrylic monomer having a functional group capable of becoming the (b4) first reactive group include vinyl monomers having a hydroxy group, vinyl monomers having a carboxy group, vinyl monomers containing an epoxy group, and the like.

[0075] Examples of the vinyl monomer having a hydroxy group include p-hydroxystyrene, allyl alcohol, and the like. Examples of the vinyl monomer having a carboxy group include crotonic acid, maleic acid, itaconic acid, citraconic acid, cinnamic acid, and the like. Examples of the vinyl monomer containing an epoxy group include 2-allyloxirane, glycidyl vinyl ether, 3,4-epoxycyclohexyl vinyl ether, and the like.

[0076] (Preparation of (meth)acrylic copolymer mixture) The (meth)acrylic copolymer mixture can be adjusted, for example, by mixing a plurality of (meth)acrylic copolymer components. The (meth)acrylic copolymer is obtained by polymerizing a (meth)acrylic monomer. During polymerization, a polymerization initiator can be added in portions or continuously to obtain a polymerization composition containing a plurality of polymer components, and such a polymerization composition may be used as a plurality of (meth)acrylic copolymer components. Further, the polymer components contained in the polymerization composition or the (meth)acrylic copolymer mixture can be confirmed by creating a differential molecular weight distribution curve by gel permeation chromatography and performing waveform separation on this curve.

[0077] As the polymerization method for polymerizing the monomer composition, either a free radical polymerization method or a living radical polymerization method can be adopted.

[0078] (Living radical polymerization method) The living radical polymerization method maintains the simplicity and versatility of the conventional radical polymerization method, while side reactions such as termination reactions and chain transfer are less likely to occur, and growth is not hindered by side reactions that deactivate the growth ends. Therefore, precise control of the molecular weight distribution and easy production of polymers with a uniform composition are possible. For this reason, the copolymer produced by the living radical polymerization method has reactive functional groups uniformly distributed on each molecular chain. In the living radical polymerization method, a random copolymer can be obtained by using a mixture of each monomer (vinyl monomer). Also, a block copolymer can be obtained by sequentially reacting the vinyl monomers constituting the copolymer.

[0079] The living radical polymerization method includes a method using a compound capable of generating a nitroxide radical (nitroxide method; NMP method) due to differences in the method of stabilizing the polymerization growth ends; a method using a metal complex such as copper or ruthenium, with a halogenated compound as the polymerization initiation compound, and polymerizing it livingly from the polymerization initiation compound (ATRP method); a method using a sulfur-based reversible chain transfer agent (RAFT method); a method using an organic tellurium compound (TERP method); a method using an organic iodine compound (ITP method); a method using an iodine compound as the polymerization initiation compound and an organic compound such as a phosphorus compound, nitrogen compound, oxygen compound, or hydrocarbon as a catalyst (reversible transfer catalyst polymerization; RTCP method, reversible catalyst-mediated polymerization; RCMP method), etc. Among these methods, from the viewpoints of the diversity of monomers that can be used, molecular weight control in the polymer region, uniform composition, or coloring, it is preferable to use the TERP method.

[0080] The TERP method is a method of polymerizing a radically polymerizable compound (vinyl monomer) using an organic tellurium compound as a chain transfer agent, for example, the methods described in International Publication No. 2004 / 14848, International Publication No. 2004 / 14962, International Publication No. 2004 / 072126, and International Publication No. 2004 / 096870.

[0081] Specific polymerization methods of the TERP method include the following (a) to (d). (a) A method of polymerizing a vinyl monomer using an organic tellurium compound represented by the 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 of polymerizing a vinyl monomer using a mixture of an organic tellurium compound represented by the formula (1) and an organic ditelluride compound represented by the formula (2). (d) A method of 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 compound represented by the formula (2).

[0082] [Chemical formula] [In formula (1), R 1 is an alkyl group, aryl group, or aromatic heterocyclic group having 1 to 8 carbon atoms. R 2 and R 3 are each independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. R 4 is an alkyl group, aryl group, substituted aryl group, aromatic heterocyclic group, alkoxy group, acyl group, amide group, oxycarbonyl group, cyano group, allyl group, or propargyl group having 1 to 8 carbon atoms. In formula (2), R 1 is an alkyl group, aryl group, or aromatic heterocyclic group having 1 to 8 carbon atoms.]

[0083] The organic tellurium compound represented by the formula (1) specifically includes ethyl = 2-methyl-2-n-butyltellanyl-propionate, ethyl = 2-n-butyltellanyl-propionate, (2-hydroxyethyl) = 2-methyl-methyltellanyl-propionate, etc., and the 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 compound represented by the formula (2) include dimethylditelluride, dibutylditelluride, etc. The azo-based polymerization initiator can be used without particular limitation as long as it is an azo-based polymerization initiator used in ordinary radical polymerization. For example, 2,2'-azobis(isobutyronitrile) (AIBN), 2,2'-azobis(2,4-dimethylvaleronitrile) (ADVN), 1,1'-azobis(1-cyclohexanecarbonitrile) (ACHN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70), etc. can be mentioned.

[0084] In the polymerization step, in a container substituted with an inert gas, a vinyl monomer, the organic tellurium compound of the formula (1), and, depending on the type of the vinyl monomer, for the purposes of promoting the reaction, controlling the molecular weight and molecular weight distribution, etc., an azo-based polymerization initiator and / or the organic ditelluride compound of the formula (2) are further mixed. At this time, examples of the inert gas include nitrogen, argon, helium, etc. Preferably, argon and nitrogen are good. The usage amount of the vinyl monomer in the above (a), (b), (c), and (d) may be appropriately adjusted according to the physical properties of the target copolymer.

[0085] The coincidence reaction can be carried out without a solvent, but it may also be carried out by using an aprotic solvent or a protic solvent commonly used in radical polymerization and stirring the mixture. 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,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), acetone, dioxane, chloroform, carbon tetrachloride, and the like. Examples of protic solvents include water, methanol, ethanol, isopropanol, n-butanol, ethyl cellosolve, butyl cellosolve, 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 used may be adjusted as appropriate. For example, 0.01 ml to 50 ml is preferable per 1 g of the vinyl monomer. The reaction temperature and reaction time may be adjusted as appropriate depending on the molecular weight or molecular weight distribution of the resulting polymer component, but usually, stirring is carried out at 0°C to 150°C for 1 minute to 100 hours. At this time, the pressure is usually carried out at normal pressure, but it may be pressurized or depressurized. After completion of the polymerization reaction, the target copolymer can be separated by removing the used solvent, residual vinyl monomer, etc. from the obtained reaction mixture by ordinary separation and purification means.

[0086] The growing end of the copolymer obtained by the polymerization reaction is -TeR derived from a tellurium compound 1 (wherein R 1It is in the same form as described above), and it is deactivated by operations in air after the polymerization reaction, but tellurium atoms may remain. Since the copolymer with tellurium atoms remaining at the ends may be colored or have poor thermal stability, it is preferable to remove the tellurium atoms. Methods for removing tellurium atoms include radical reduction methods; methods of adsorbing with activated carbon or the like; methods of adsorbing metals with ion exchange resins or the like, and these methods can also be used in combination. In addition, the other end of the copolymer obtained by the polymerization reaction (the end opposite to the growing end) is -CR 2 R 3 R 4 (wherein R 2 、R 3 and R 4 are the same as R 2 、R 3 and R 4 in formula (1).).

[0087] (Free radical polymerization method) The free radical polymerization method may adopt a conventionally known method. Examples of the polymerization initiator used in free radical polymerization include azo-based polymerization initiators and peroxide-based polymerization initiators. Examples of the azo-based polymerization initiator include, for example, 2,2'-azobis(isobutyronitrile) (AIBN), 2,2'-azobis(2-methylbutyronitrile) (AMBN), 2,2'-azobis(2,4-dimethylvaleronitrile) (ADVN), 1,1'-azobis(1-cyclohexanecarbonitrile) (ACHN), dimethyl-2,2'-azobisisobutyrate (MAIB), 4,4'-azobis(4-cyanovaleric acid) (ACVA), 1,1'-azobis(1-acetoxy-1-phenylethane), 2,2'-azobis(2-methylbutylamide), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70), 2,2'-azobis(2-methylamidinopropane) dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane], 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], 2,2'-azobis(2,4,4-trimethylpentane), 2-cyano-2-propylazohormamide, 2,2'-azobis(N-butyl-2-methylpropionamide), or 2,2'-azobis(N-cyclohexyl-2-methylpropionamide), etc.

[0088] The overlapping reaction can be carried out without a solvent, but it may also be carried out using an aprotic solvent or a protic solvent commonly used in radical polymerization, with the mixture being stirred. Examples of aprotic solvents that can be used include acetonitrile, anisole, benzene, toluene, N,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, trifluoromethylbenzene, etc. Examples of protic solvents include water, methanol, ethanol, isopropanol, n-butanol, ethyl cellosolve, butyl cellosolve, 1-methoxy-2-propanol, hexafluoroisopropanol, diacetone alcohol, etc.

[0089] The amount of the solvent used may be adjusted as appropriate. For example, with respect to 1 g of the vinyl monomer, it is preferably 0.01 ml or more, more preferably 0.05 ml or more, still more preferably 0.1 ml or more, and preferably 50 ml or less, more preferably 10 ml or less, still more preferably 1 ml or less.

[0090] The reaction temperature and reaction time may be adjusted as appropriate according to the molecular weight or molecular weight distribution of the resulting polymer component. Usually, it is stirred at 0 °C to 150 °C for 1 minute to 100 hours. At this time, the pressure is usually carried out at normal pressure, but it may also be pressurized or depressurized. After the completion of the polymerization reaction, from the obtained reaction mixture, the used solvent, residual vinyl monomer, etc. can be removed by ordinary separation and purification means, and the target polymerization composition can be separated.

[0091] (Crosslinking agent) The pressure-sensitive adhesive composition contains a crosslinking agent. The crosslinking agent is a compound having two or more second reactive groups in one molecule that react with the first reactive groups of the above-described (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 these, isocyanate-based crosslinking agents and / or epoxy-based crosslinking agents are preferred. In particular, an isocyanate-based crosslinking agent or an epoxy-based crosslinking agent is more preferred because the recovery rate of the pressure-sensitive adhesive formed is improved, and an epoxy-based crosslinking agent is even more preferred.

[0092] The average number of second reactive groups in one molecule of the crosslinking agent is 2 or more, more preferably 3 or more, even more preferably 4 or more, and particularly preferably 5 or more, and preferably 8 or less. That is, the crosslinking agent is more preferably a polyfunctional crosslinking agent having 4 or more second reactive groups in one molecule. If the crosslinking agent is tetrafunctional or higher, the average distance between crosslinking points in the polymer in the pressure-sensitive adhesive becomes longer. Therefore, the resulting pressure-sensitive adhesive has a low initial stress and exhibits a high recovery rate. The molecular weight of the crosslinking agent is preferably 200 or more, more preferably 300 or more, even more preferably 400 or more, preferably 1500 or less, more preferably 1000 or less, and even more preferably 700 or less.

[0093] The content of the second reactive group of the crosslinking agent is preferably 1.5 mmol / g or more, more preferably 3.0 mmol / g or more, even more preferably 3.7 mmol / g or more, preferably 10 mmol / g or less, more preferably 8 mmol / g or less, and even more preferably 6 mmol / g or less. If the content of the second reactive group of the crosslinking agent is within this range, the valency of the crosslinking agent becomes low, the crosslinking points are evenly distributed in the pressure-sensitive adhesive, and the average distance between crosslinking points becomes long. Therefore, the resulting pressure-sensitive adhesive has a low initial stress and exhibits a high recovery rate.

[0094] Examples of 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 include the following combinations. When the second reactive group of the crosslinking agent is an isocyanate group, examples of the first reactive group include a hydroxy group. When the second reactive group of the crosslinking agent is an epoxy group, examples of the first reactive group include a carboxy group.

[0095] Examples of 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 include (1) a combination in which the first reactive group is a hydroxy group and the second reactive group is an isocyanate group; and (2) a combination in which the first reactive group is a carboxy group and the second reactive group is an epoxy group. Such combinations are preferred.

[0096] (Isocyanate-based crosslinking agent) An isocyanate-based crosslinking agent is a compound having two or more isocyanate groups (including an isocyanate regenerable functional group in which the isocyanate group is temporarily protected by a blocking agent or oligomerization, etc.) in one molecule. The isocyanate-based crosslinking agent may be used alone or in combination of two or more.

[0097] Examples of the isocyanate-based crosslinking agent include aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, and polyisocyanates polyfunctionalized with adducts of these and various polyols, isocyanurate bonds, biuret bonds, allophanate bonds, etc. Specifically, compounds having two isocyanate groups (including isocyanate regenerable functional groups in which the isocyanate groups are temporarily protected by a blocking agent or oligomerization, etc.) in one molecule (bifunctional isocyanate-based crosslinking agent), compounds having three isocyanate groups (including isocyanate regenerable functional groups in which the isocyanate groups are temporarily protected by a blocking agent or oligomerization, etc.) in one molecule (trifunctional isocyanate-based crosslinking agent), compounds having six isocyanate groups (including isocyanate regenerable functional groups in which the isocyanate groups are temporarily protected by a blocking agent or oligomerization, etc.) in one molecule (hexafunctional isocyanate-based crosslinking agent), etc. are included.

[0098] Examples of the bifunctional isocyanate-based crosslinking agent include diisocyanate compounds such as aliphatic diisocyanate compounds, alicyclic diisocyanate compounds, and aromatic diisocyanate compounds, and adducts of these diisocyanate compounds and diol compounds can also 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, etc.). The diol compound is a compound represented by the general formula "HO-Y-OH" (Y is a divalent aliphatic group, a divalent alicyclic group, a divalent aromatic group, etc.).

[0099] 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, 2,2,4-trimethyl-1,6-hexamethylene diisocyanate, etc. Among these, aliphatic diisocyanate compounds having 4 to 30 carbon atoms are preferred, and aliphatic diisocyanate compounds having 4 to 10 carbon atoms are more preferred.

[0100] Examples of the alicyclic diisocyanate compound include isophorone diisocyanate, cyclopentyl diisocyanate, cyclohexyl diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylylene diisocyanate, etc. Among them, alicyclic diisocyanate compounds having 7 to 30 carbon atoms are preferred.

[0101] Examples of the aromatic diisocyanate compound include phenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, naphthylene diisocyanate, diphenyl ether diisocyanate, diphenylmethane diisocyanate, diphenylpropane diisocyanate, etc. Aromatic diisocyanate compounds having 8 to 30 carbon atoms are preferred.

[0102] Examples of the diol compound include aliphatic diol compounds such as 2-methyl-1,3-propanediol, 2,2-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, polypropylene glycol, etc. Among them, aliphatic diol compounds having 3 to 10 carbon atoms are preferred.

[0103] Examples of the trifunctional isocyanate crosslinking agent and the hexafunctional isocyanate crosslinking agent include adducts of the diisocyanate compound, biuret bodies of the diisocyanate compound, isocyanurate bodies of the diisocyanate compound (cyclic multimers of diisocyanate compounds), etc.

[0104] The isocyanate crosslinking agent preferably has no aromatic ring. In particular, as the isocyanate crosslinking agent, a bifunctional isocyanate crosslinking agent selected from the group consisting of an aliphatic diisocyanate compound and an adduct of an aliphatic diisocyanate compound and an aliphatic diol compound; a trifunctional or hexafunctional isocyanate crosslinking agent selected from the group consisting of an adduct of aliphatic diisocyanate compounds, a biuret of an aliphatic diisocyanate compound, and an isocyanurate of an aliphatic diisocyanate compound is preferred.

[0105] (Epoxy crosslinking agent) The epoxy crosslinking agent refers to a compound having two or more epoxy groups in one molecule as the second reactive group. The epoxy crosslinking agent may be used alone or in combination of two or more.

[0106] Examples of the epoxy crosslinking agent include aliphatic epoxy compounds, alicyclic epoxy compounds, aromatic epoxy compounds, and heterocyclic epoxy compounds.

[0107] Examples of the aliphatic epoxy compound include ethylene glycidyl ether, ethylene glycol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidylamine, diaminoglycidylamine, 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, polyglycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, adipic acid diglycidyl ester, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, and the like.

[0108] Examples of the alicyclic epoxy compound include 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, N,N,N',N'-tetraglycidyl-m-xylylenediamine, and the like.

[0109] Examples of the aromatic epoxy compound include bisphenol A epichlorohydrin type epoxy resin, diglycidylaniline, o-phthalic acid diglycidyl ester, resorcin diglycidyl ether, bisphenol-S-diglycidyl ether, and the like.

[0110] 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, sorbitan polyglycidyl ether, and the like.

[0111] As the epoxy crosslinking agent, a compound having two epoxy groups in one molecule (bifunctional epoxy crosslinking agent), a compound having three epoxy groups in one molecule (trifunctional epoxy crosslinking agent), or a compound having four epoxy groups in one molecule (tetrafunctional epoxy crosslinking agent) is preferable. When the crosslinking agent is a bifunctional epoxy crosslinking agent, a trifunctional epoxy crosslinking agent, or a tetrafunctional epoxy crosslinking agent, crosslinking points are evenly distributed in the adhesive material, and the average distance between crosslinking points becomes long. Therefore, the obtained adhesive material has a low initial stress and exhibits a high recovery rate.

[0112] The pressure-sensitive adhesive composition preferably contains only an isocyanate-based crosslinking agent or only an epoxy-based crosslinking agent as the crosslinking agent. When it contains only an isocyanate-based crosslinking agent as the crosslinking agent, it preferably contains only a bifunctional 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. Further, when it contains only an epoxy-based crosslinking agent as the crosslinking agent, it preferably contains only a bifunctional 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.

[0113] The content of the crosslinking agent in the pressure-sensitive adhesive composition is preferably 0.01 part by mass or more, more preferably 0.05 part by mass or more, still more preferably 0.1 part by mass or more, with respect to 100 parts by mass of the plurality of (meth)acrylic copolymer components, and preferably 0.2 part by mass or less, more preferably 0.17 part by mass or less. If the content of the crosslinking agent is within the above range, the adhesive force and the recovery rate will be in a suitable range.

[0114] The molar ratio (molar amount of the first reactive group / molar amount of the second reactive group) of the second reactive group of the crosslinking agent to the first reactive group of the plurality of (meth)acrylic copolymer components is 1 or more, preferably 2 or more, more preferably 3 or more, and preferably 70 or less, more preferably 15 or less, still more preferably 10 or less, particularly preferably 5 or less. If the molar ratio is 1 or more, the crosslinking agent reacts without excess or deficiency, no excess remains in the second reactive group, and a high recovery rate is exhibited. If it is 70 or less, the reaction proceeds sufficiently and a high recovery rate is exhibited.

[0115] The molar ratio of the first reactive groups possessed by the plurality of (meth)acrylic copolymer components to the compounding amount (molar amount) of the crosslinking agent (molar amount of the first reactive groups / 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, 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 strength and the recovery rate will be within a suitable range.

[0116] (Other additives) In addition to the copolymer component and the crosslinking agent, other additives can be blended and used in the pressure-sensitive adhesive composition. Examples of other additives include crosslinking accelerators, crosslinking retardants, tackifying resins (tackifiers), polymerizable compounds, photoinitiators, silane coupling agents, plasticizers, softeners, release aids, dyes, pigments, colorants, fluorescent brighteners, antistatic agents, wetting agents, surfactants, thickeners, antifungal agents, preservatives, oxygen absorbers, ultraviolet absorbers, antioxidants, near-infrared absorbers, water-soluble matting agents, fragrances, metal deactivators, nucleating agents, alkylating agents, flame retardants, lubricants, processing aids, etc. These are appropriately selected and blended for use according to the application and purpose of use of the pressure-sensitive adhesive material.

[0117] (Crosslinking accelerator) The pressure-sensitive adhesive composition can be blended with a crosslinking accelerator for use as needed. Examples of crosslinking accelerators include organotin compounds and metal chelate compounds. The crosslinking accelerator may be used alone or in combination of two or more.

[0118] Examples of the organotin compound include dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dioctylate, etc. The metal chelate compound is a complex in which a ligand having two or more coordinating atoms forms a ring and binds to a central metal.

[0119] The content of the crosslinking accelerator in the pressure-sensitive adhesive composition is preferably 0.01 part by mass or more, more preferably 0.02 part by mass or more, still more preferably 0.04 part by mass or more, and preferably 0.5 part by mass or less, more preferably 0.4 part by mass or less, still more preferably 0.3 part 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, it is possible to obtain an excellent crosslinking acceleration effect.

[0120] (Crosslinking retarder) The pressure-sensitive adhesive composition can be used by blending a crosslinking retarder as needed. The crosslinking retarder is a compound that can suppress an excessive increase in the viscosity of the pressure-sensitive adhesive composition by blocking the functional groups of the crosslinking agent in the pressure-sensitive adhesive composition containing the crosslinking agent. The type of the crosslinking retarder is not particularly limited. For example, β-diketones such as acetylacetone, hexane-2,4-dione, heptane-2,4-dione, and octane-2,4-dione; β-ketoesters such as methyl acetoacetate, ethyl acetoacetate, propyl acetoacetate, butyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, and stearyl acetoacetate; and benzoylacetone can be used. As the crosslinking retarder, those that can act as a chelating agent are preferred, and β-diketones and β-ketoesters are preferred.

[0121] The content of the crosslinking retarder that can be blended in the pressure-sensitive 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, and 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, based on 100 parts by mass of the plurality of (meth)acrylic copolymer components. By adjusting the content of the crosslinking retarder within the above range, after blending the crosslinking agent into the pressure-sensitive adhesive composition, an excessive increase in the viscosity and gelation of the pressure-sensitive adhesive composition can be suppressed, and the storage stability (pot life) of the pressure-sensitive adhesive composition can be extended.

[0122] (Adhesion-imparting resin) In the above-mentioned pressure-sensitive adhesive composition, a tackifying resin excluding the copolymer component can be blended and used as needed. The tackifying resin is not particularly limited, and examples thereof include rosin-based tackifying resins, terpene-based tackifying resins, phenol-based tackifying resins, hydrocarbon-based tackifying resins, and the like.

[0123] Examples of the rosin-based tackifying resin include unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin, and modified rosins (polymerized rosin, stabilized rosin, disproportionated rosin, fully hydrogenated rosin, partially hydrogenated rosin, and other chemically modified rosins) obtained by polymerizing, disproportionating, hydrogenating, etc. these unmodified rosins. In addition, various rosin derivatives and the like can be mentioned.

[0124] Examples of the rosin derivatives include rosin-phenol resins obtained by adding phenol to rosins (unmodified rosins, modified rosins) with an acid catalyst and then thermally polymerizing; ester compounds of rosin (unmodified rosin ester) obtained by esterifying unmodified rosin with alcohols, and ester compounds of modified rosin (polymerized rosin ester, stabilized rosin ester, disproportionated rosin ester, fully hydrogenated rosin ester, partially hydrogenated rosin ester, etc.) obtained by esterifying modified rosin with alcohols, such as rosin ester resins; unsaturated fatty acid-modified rosin-based resins obtained by modifying unmodified rosin or modified rosin with unsaturated fatty acids; unsaturated fatty acid-modified rosin ester-based resins obtained by modifying rosin ester resins with unsaturated fatty acids; rosin alcohol-based resins obtained by reducing the carboxyl groups in unmodified rosin, modified rosin, unsaturated fatty acid-modified rosin-based resins, and unsaturated fatty acid-modified rosin ester-based resins; metal salts of rosin-based resins such as unmodified rosin and modified rosin (especially rosin ester resins), and the like.

[0125] Examples of terpene-based tackifying resins include terpene-based resins such as α-pinene polymers, β-pinene polymers, and dipentene polymers, and modified terpene-based resins obtained by modifying these terpene-based resins (phenol modification, aromatic modification, hydrogenation modification, hydrocarbon modification, etc.) (for example, terpene phenol-based resins, styrene-modified terpene-based resins, aromatic-modified terpene-based resins, hydrogenated terpene-based resins).

[0126] Examples of phenolic tackifying resins include condensates of various phenols (for example, phenol, m-cresol, 3,5-xylenol, p-alkylphenol, resorcinol) and formaldehyde (for example, alkylphenol-based resins, xylene formaldehyde-based resins), resols obtained by subjecting the above phenols and formaldehyde to an addition reaction with an alkali catalyst, novolacs obtained by subjecting the above phenols and formaldehyde to a condensation reaction with an acid catalyst, and the like.

[0127] Examples of hydrocarbon-based tackifying resins (petroleum-based tackifying resins) include aliphatic hydrocarbon resins [polymers of aliphatic hydrocarbons such as olefins and dienes having 4 to 5 carbon atoms (olefins such as butene-1, isobutylene, pentene-1; dienes such as butadiene, 1,3-pentadiene, isoprene), etc.], aliphatic cyclic hydrocarbon resins [alicyclic hydrocarbon-based resins obtained by cyclodimerizing and then polymerizing so-called "C4 petroleum fraction" and "C5 petroleum fraction", polymers of cyclic diene compounds (such as cyclopentadiene, dicyclopentadiene, ethylidene norbornene, dipentene, etc.) or their hydrogenated products, alicyclic hydrocarbon-based resins obtained by hydrogenating the aromatic rings of the following aromatic hydrocarbon resins and aliphatic-aromatic petroleum resins, etc.], aromatic hydrocarbon resins [polymers of vinyl group-containing aromatic hydrocarbons having 8 to 10 carbon atoms (such as styrene, vinyltoluene, α-methylstyrene, indene, methylindene, etc.)], aliphatic-aromatic petroleum resins (such as styrene-olefin copolymers), aliphatic-alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone resins, coumarone-indene resins, and the like.

[0128] The content of the tackifying resin that can be blended in the pressure-sensitive 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, with respect to 100 parts by mass of the plurality of (meth)acrylic copolymer components, and preferably 60 parts by mass or less, more preferably 50 parts by mass or less, still more preferably 40 parts by mass or less. By adjusting the content of the tackifying resin within the above range, sufficient adhesion to the adherend can be ensured.

[0129] (Polymerizable compound) The pressure-sensitive adhesive composition may contain a polymerizable compound. By blending a polymerizable compound and polymerizing the polymerizable compound in the pressure-sensitive adhesive, flexibility can be imparted to the pressure-sensitive adhesive.

[0130] Examples of the polymerizable compound include compounds having two or more polymerizable groups in one molecule. Examples of the polymerizable group include ethylenically unsaturated groups and the like. The polymerizable compound can be used alone or in combination of two or more. Examples of the polymerizable compound include compounds having two or more (meth)acryloyl groups, and polyfunctional monomers and polyfunctional oligomers are preferred. The number of ethylenically unsaturated groups in one molecule of the polymerizable compound is preferably 2 or more, preferably 4 or less, and more preferably 3 or less.

[0131] 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 di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, ethylene oxide-modified isocyanuric acid tri(meth)acrylate, allyl (meth)acrylate, vinyl (meth)acrylate, urethane (meth)acrylate, and the like.

[0132] When a polymerizable compound is blended in the pressure-sensitive 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 more preferably 50 parts by mass or less with respect to 100 parts by mass of the plurality of (meth)acrylic copolymer components.

[0133] (Photoinitiator) When the polymerizable compound is cured by active energy rays, it is preferable to blend a photoinitiator in the pressure-sensitive adhesive composition. By blending a photoinitiator, the reaction during irradiation with active energy rays can be stabilized. The photoinitiator is not particularly limited as long as it generates radicals by the action of light. Examples thereof include photoinitiators such as acetophenones, benzoins, benzophenones, thioxanthones, and acylphosphine oxides. These photoinitiators can be used alone or in combination of two or more. Among these photoinitiators, hydrogen abstraction-type benzophenones and intramolecular cleavage-type acetophenone photoinitiators are preferable from the viewpoint of efficient crosslinking between molecules or within molecules.

[0134] When a photoinitiator is blended in the pressure-sensitive adhesive composition, the content of the photoinitiator is preferably 0.01 part by mass or more, more preferably 0.1 part by mass or more, still more preferably 0.5 part by mass or more, preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and still more preferably 2 parts by mass or less with respect to 100 parts by mass of the plurality of (meth)acrylic copolymer components. If the content of the photoinitiator is too small, the curing rate tends to decrease or the curing tends to be insufficient. If it is too large, the curability does not improve and the economy tends to decrease.

[0135] In addition, the pressure-sensitive adhesive composition may contain an auxiliary agent for the photoinitiator. Examples of the auxiliary agent include triethanolamine, triisopropanolamine, 4,4'-dimethylaminobenzophenone (Michler's ketone), 4,4'-diethylaminobenzophenone, 2-dimethylaminoethyl benzoate, ethyl 4-dimethylaminobenzoate, (n-butoxy)ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, 2-ethylhexyl 4-dimethylaminobenzoate, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, etc. These auxiliary agents may be used alone or in combination of two or more kinds.

[0136] (Silane coupling agent) If necessary, a silane coupling agent can be blended and used in the pressure-sensitive adhesive composition. The silane coupling agent is not particularly limited. Examples include epoxy group-containing silane coupling agents such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; amino group-containing silane coupling agents such as 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, N-phenyl-γ-aminopropyltrimethoxysilane; (meth)acrylic group-containing silane coupling agents such as 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane; isocyanate group-containing silane coupling agents such as 3-isocyanatopropyltriethoxysilane, etc.

[0137] The content of the silane coupling agent that can be blended in the pressure-sensitive adhesive composition is 0.01% by mass or more, more preferably 0.02% by mass or more, preferably 1 part by mass or less, and more preferably 0.6 part by mass or less with respect to 100 parts by mass of the plurality of (meth)acrylic copolymer components. By adjusting the content of the silane coupling agent within the above range, the water resistance at the interface when applying the pressure-sensitive adhesive to a hydrophilic adherend such as glass can be improved.

[0138] (Plasticizer) The pressure-sensitive adhesive composition may be blended with a plasticizer as needed. The plasticizer is not particularly limited. For example, oils such as paraffin oil and process oil; 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 thereof; dioctyl phthalate (DOP), dibutyl phthalate (DBP), dioctyl adipate, diisononyl adipate (DINA), isodecyl succinate, etc. are mentioned. The plasticizer may be used alone or in combination of two or more. Among these, liquid rubber is preferred.

[0139] The weight average molecular weight (Mw) of the liquid rubber is preferably 5,000 or more, more preferably 10,000, preferably 600,000 or less, and more preferably 500,000 or less. By adjusting the Mw of the liquid rubber within the above range, a pressure-sensitive adhesive excellent in flexibility can be formed. The method for measuring the weight average molecular weight (Mw) will be described later.

[0140] When a plasticizer is blended in the pressure-sensitive 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, with respect to 100 parts by mass of the plurality of (meth)acrylic copolymer components, and preferably 50 parts by mass or less, more preferably 40 parts by mass or less, still more preferably 30 parts by mass or less. By adjusting the content of the plasticizer within the above range, a pressure-sensitive adhesive material excellent in adhesive force and resilience can be formed.

[0141] (Method for producing pressure-sensitive adhesive composition) The pressure-sensitive adhesive composition can be produced by mixing the copolymer component, the crosslinking agent, and other additives used as necessary. The pressure-sensitive adhesive composition may contain a solvent derived from the production of the copolymer component, or may be a solution in which an appropriate solvent is added and diluted to have a viscosity suitable for forming a pressure-sensitive adhesive layer.

[0142] 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; and glycol ether solvents such as propylene glycol monomethyl ether. These solvents may be used alone or in combination of two or more.

[0143] The amount of the solvent used may be appropriately adjusted so that the pressure-sensitive adhesive composition has a viscosity suitable for coating, and there is no particular limitation. From the viewpoint of coatability, for example, 1% by mass to 90% by mass is preferable, more preferably 10% by mass to 80% by mass, still more preferably 20% by mass to 70% by mass.

[0144] (Uses of pressure-sensitive adhesive composition) The use of the pressure-sensitive adhesive composition is preferably used for forming a flexible display that can be used by repeatedly bending and stretching, and an adhesive layer (pressure-sensitive adhesive material) used for a flexible display.

[0145] Examples of the flexible display that can be used by repeatedly bending and stretching include a foldable display that can be folded and a rollable display that can be rolled into a cylindrical shape. The flexible display is expected to be used for mobile terminals such as smartphones and tablet terminals, and stationary displays that can be stored.

[0146] [Adhesive for Flexible Display] The adhesive for a flexible display of the present invention is a cured product of the adhesive composition. The adhesive can be used as an adhesive for a flexible display for bonding one flexible member constituting the flexible display and another flexible member.

[0147] 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 100% by mass or less. By setting the gel fraction within the above range, an adhesive having excellent flexibility and resilience can be formed. The gel fraction can be controlled by the blending amount of the crosslinking agent, the crosslinking treatment temperature, the crosslinking treatment time, etc. in the adhesive composition.

[0148] [Adhesive Sheet for Flexible Display] The adhesive sheet for a flexible display of the present invention is an adhesive sheet for a flexible display having an adhesive layer used for bonding one flexible member constituting the flexible display and another flexible member, and a flexible sheet member adhered to at least one surface of the adhesive layer, wherein the adhesive layer is formed from the above adhesive.

[0149] Examples of the configuration of the adhesive sheet include an embodiment having an adhesive layer and a first flexible sheet member adhered to one surface of the adhesive layer; and an embodiment having an adhesive layer, a first flexible sheet member adhered to one surface of the adhesive layer, and a second flexible sheet member adhered to the other surface of the adhesive layer.

[0150] An example of the adhesive sheet of the present invention is shown in FIG. 1. The adhesive sheet 10 in FIG. 1 is composed of an adhesive layer 12, a first flexible sheet member 14 that sandwiches the adhesive layer 12, and a second flexible sheet member 16. The adhesive layer 12 is in contact with the release-property surfaces of the first flexible sheet member 14 and the second flexible sheet member 16.

[0151] (Adhesive layer) The adhesive layer is formed from the above-mentioned adhesive material. From the viewpoint of sufficiently ensuring the adhesiveness with the adherend, the film thickness of the adhesive layer is preferably 2 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more. Also, from the viewpoint of suppressing the protrusion of the adhesive layer, the thickness of the adhesive layer is preferably 100 μm or less, more preferably 70 μm or less, and even more preferably 50 μm or less.

[0152] (Flexible sheet member) Examples of the flexible sheet member include a base material sheet having flexibility, a release sheet, etc. The base material sheet is a sheet member that supports the adhesive layer, and this sheet member may be a functional sheet member. Examples of the functional sheet member include a cover film, a barrier film, a polarizing film, a retardation film, an optical compensation film, a brightness enhancement film, a diffusion film, an antireflection film, etc. The release sheet protects the adhesive layer until the adhesive layer is adhered to the adherend, and is peeled off from the adhesive layer before the adhesive layer is adhered to the adherend.

[0153] Generally, the term "sheet" refers to a flat product that is thin and generally has a thickness that is small relative to its length and width, as defined in JIS. Generally, the term "film" refers to a thin, flat product that has an extremely small thickness compared to its length and width, and whose maximum thickness is arbitrarily limited, and is usually supplied in the form of a roll (Japanese Industrial Standard JIS K6900). For example, in terms of thickness, in a narrow sense, those with a thickness of 100 μm or more may be referred to as sheets, and those with a thickness of less than 100 μm may be referred to as films. However, the boundary between sheets and films is not clear, and since there is no need to distinguish between the two in the language of the present invention, in the present invention, when referring to "sheets", it includes "films", and when referring to "films", it also includes "sheets".

[0154] Examples of the flexible sheet member include a sheet of a polymer material, a glass sheet, etc. The thickness of the flexible sheet member is not particularly limited, but from the viewpoint of excellent handleability, etc., 2 μm to 500 μm is preferable, and more preferably 2 μm to 200 μm.

[0155] Examples of the polymer material include polyimide resin; polyester resins such as polyethylene terephthalate resin and polyethylene naphthalate resin; polycarbonate resin; poly(meth)acrylate resin; polystyrene resin; polyamide resin; polyacrylonitrile resin; polyolefin resins such as polypropylene resin, polyethylene resin, and polycycloolefin resin; polyphenylene sulfide resin; polyvinyl chloride resin; polyvinylidene chloride resin; polyvinyl alcohol resin, etc.

[0156] The flexible sheet member may be composed of a single layer including one or more of the above polymer materials, or may be composed of two or more layers such as a layer including one or more of the above polymer materials and a layer including one or more polymer materials different from this layer.

[0157] The flexible sheet member is preferably a release sheet whose surface in contact with the adhesive layer is subjected to a release treatment. Examples of the release agent used for the release treatment include release agents such as silicone-based, fluorine-based, alkyd-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents.

[0158] The adhesive sheet has a first flexible sheet member adhered to one surface of the adhesive layer and a second flexible sheet member adhered to the other surface of the adhesive layer. The first flexible sheet member is a first release sheet, and the second flexible sheet member is a second release sheet. It is preferable that the first release sheet and the second release sheet are adhered such that their respective release surfaces are in contact with the adhesive layer. When the adhesive layer is sandwiched between two release sheets, it is preferable that one release sheet is a heavy release type release sheet with a large release force, and the other release sheet is a light release type release sheet with a small release force.

[0159] (Manufacture of Adhesive Sheet) The adhesive sheet can be manufactured, for example, by applying the above-described adhesive composition onto a flexible sheet member and curing it by drying and heat treatment as necessary to form an adhesive layer.

[0160] For the application of the adhesive composition, various coating methods such as reverse gravure coating method, direct gravure coating method, die coating method, bar coating method, wire bar coating method, roll coating method, spin coating method, dip coating method, spray coating method, knife coating method, kiss coating method, etc.; inkjet method; various printing methods such as offset printing, screen printing, flexographic printing, etc. can be adopted. Also, before applying the adhesive composition, the surface of the release sheet may be subjected to surface treatment such as corona treatment, plasma treatment, hot air treatment, ozone treatment, ultraviolet treatment, etc.

[0161] The drying and heating process is not particularly limited as long as it can remove solvents and the like used in the pressure-sensitive adhesive composition and cure it, but it is preferably carried out at a temperature of 60°C to 150°C for about 20 seconds to 300 seconds. In particular, the heating temperature is preferably 100°C to 130°C.

[0162] 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 pressure-sensitive adhesive composition is applied to the first flexible sheet member, and after forming the adhesive layer on the first flexible sheet member, the second flexible sheet member may be adhered to this adhesive layer. Further, the adhesive layer may be cured as necessary. Examples of the curing conditions include about 3 days to 7 days at 60°C.

[0163] [Flexible laminated member] The flexible laminated member of the present invention is a flexible laminated member including a first flexible member, a second flexible member, and an adhesive layer that bonds the first flexible member and the second flexible member to each other, wherein the adhesive layer is made of the pressure-sensitive adhesive material. Since the adhesive layer of the flexible laminated member is formed from the pressure-sensitive adhesive material, even when the flexible laminated member is repeatedly bent, appearance defects such as the bent portion looking wavy are suppressed.

[0164] An example of the flexible laminated member of the present invention is shown in FIG. 2. The flexible laminated member 20 in FIG. 2 includes a first flexible member 22, a second flexible member 24, and an adhesive layer 12 that is between the first flexible member 22 and the second flexible member 24 and bonds these flexible members to each other.

[0165] As the configuration of the flexible laminated member, for example, there are configurations in which both the first flexible member and the second flexible member are constituent members of the bending device; a configuration in which the second flexible member is a bending device and the first flexible member is a functional sheet member attached to the bending device. Examples of the bending device include a foldable display that can be folded and a rollable display that can be rolled into a cylindrical shape. Examples of the functional sheet member include a cover film, a barrier film, a polarizing film, a retardation film, an optical compensation film, a brightness enhancement film, a diffusion film, an antireflection film, a transparent conductive film, a metal mesh film, a cushion film, and the like.

[0166] The first flexible member and the second flexible member are members that can be repeatedly bent or curved 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 (such as an organic EL module, an electronic paper module, etc.). It is preferable that at least one of the first flexible member and the second flexible member is a display element. The flexible laminated member can be used for a flexible display.

[0167] (Method for manufacturing a flexible laminated member) The method for manufacturing the flexible laminated member of the present invention is not particularly limited, and for example, the following methods (1) to (4) can be mentioned.

[0168] (1) A method of obtaining a flexible laminated member by peeling the release sheet attached to one surface of the adhesive sheet, attaching the exposed adhesive layer to the first flexible member, then peeling the release sheet attached to the other surface of the adhesive sheet, and attaching the exposed adhesive layer to the second flexible member. (2) A method of obtaining a flexible laminated member, which comprises applying an adhesive composition onto one surface of a first flexible member, curing it by a drying heat treatment if necessary to form an adhesive layer, then attaching a surface having a releasability of a release sheet to this adhesive layer, and then peeling the release sheet and attaching the exposed adhesive layer to a second flexible member. (3) A method of obtaining a flexible laminated member, which comprises applying an adhesive composition onto one surface of a first flexible member, curing it by a drying heat treatment if necessary to form an adhesive layer, and then attaching a second flexible member to this adhesive layer. (4) A method of obtaining a flexible laminated member, which comprises applying an adhesive composition onto a surface having a releasability of a release sheet, curing it by a drying heat treatment if necessary to form an adhesive layer, then attaching a first flexible member to this adhesive layer, peeling the release sheet, and then attaching the exposed adhesive layer to a second flexible member.

[0169] In any of the cases (1) to (4) above, the order of using the first flexible member and the second flexible member may be interchanged. For forming the adhesive layer, various coating methods and various printing methods similar to those for manufacturing an adhesive sheet can be used, and the same applies to the drying and curing processes. Further, it may be cured if necessary. Also, as the release sheet used in manufacturing the flexible laminated member, the same one as the release sheet used for the adhesive sheet may be used.

Examples

[0170] Hereinafter, the present invention will be described in more detail based on specific examples. The present invention is not limited to the following examples, and can be appropriately modified and implemented without changing the gist thereof. The polymerization rate of the polymerization composition, the weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the polymer component, the adhesive layer thickness, and the evaluation of the adhesive were evaluated according to the following methods.

[0171] The meanings of the abbreviations are as follows. EHA: 2-ethylhexyl acrylate LA: Lauryl acrylate AA: Acrylic acid HBA: 4-Hydroxybutyl acrylate BTEE: Ethyl = 2-methyl-2-n-butyltellanyl-propionate AIBN: Azobisisobutyronitrile AcOEt: Ethyl acetate

[0172] (Polymerization rate) Using a nuclear magnetic resonance (NMR) measuring device (manufactured by Bruker BioSpin, model: AVANCE500 (frequency 500 MHz)), 1 1H-NMR was measured (solvent: CDCl3, internal standard: TMS). For the obtained NMR spectrum, the integration ratio of the signals derived from the monomer and the signals derived from the polymer was determined, and the polymerization rate of the monomer was calculated.

[0173] (Weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn)) Gel permeation chromatography (GPC) was performed using a high-performance liquid chromatograph (manufactured by Tosoh Corporation, model HLC-8320GPC). Two TSKgel Super HZM-H columns (manufactured by Tosoh Corporation) were used, a tetrahydrofuran solution was used as the mobile phase, and a differential refractometer was used as the detector. The measurement conditions were a column temperature of 40 °C, a sample concentration of 0.5 mg / mL, a sample injection volume of 10 μm, and a flow rate of 0.6 mL / min. A calibration curve was created using 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) as the standard substance. Using GPC software (manufactured by Tosoh Corporation, Ecosec Peak Separation (Version 1.04)), Gaussian approximation was used to perform waveform separation for the retention times of 6 - 11 minutes of the measured chromatogram, and the weight average molecular weight (Mw), molecular weight distribution (Mw / Mn), and content of each polymer component were determined. The waveform separation parameters were set as Threshold: 0.5, SmoothWidth: 8, start retention time: 6, end retention time: 11.

[0174] (Adhesive layer thickness) Using a thickness measuring instrument (manufactured by Tester Sangyo Co., Ltd., "TH-104"), the total thickness of the entire adhesive sheet was measured, and the thickness of the release sheet was subtracted from this total thickness to obtain the thickness of the adhesive layer.

[0175] (Gel fraction) The mass W2 of a wire mesh (400 mesh) cut out to a width of 50 mm and a length of 120 mm was measured. 80 mg to 120 mg of the adhesive layer (adhesive material) was collected from the adhesive sheet, and the mass W1 was measured. A test piece was prepared by wrapping it with a wire mesh so that the adhesive material would not fall off. The test piece was placed in a glass bottle, 40 g of ethyl acetate was poured in, and it was gently shaken, and then left standing at room temperature (25°C) for 72 hours or more. After standing, the test piece was taken out of the glass bottle and left at room temperature for 12 hours or more, and further dried in a vacuum oven at 100°C for 4 hours. The dried test piece was cooled to room temperature and the mass W3 was measured, and the gel fraction was calculated from the following formula. Gel fraction (mass %) = (W3 - W2) / W1 × 100

[0176] (Stress relaxation time at 400% strain, recovery rate after 400% strain) The adhesive layer (adhesive material) constituting the adhesive sheet was laminated by bonding using a hand roller to prepare a laminate with a thickness of 600 μm, which was used as a test piece. The measurement was carried out using a viscoelasticity measuring device (manufactured by Anton Paar, MCR302), with a sample sandwiched between parallel plates with a diameter of 8 mm (the bonding surface was roughened with No. 240 sandpaper), and in an atmosphere of 25°C. In the measurement, after leaving the test piece compressed with an axial force of 1 N for 10 minutes, the axial force was changed to 0.05 N, and immediately a shear stress was applied to distort it to a strain of 400%. Subsequently, it was held in a state of 400% strain for 10 minutes, the change in shear stress was measured, and the stress relaxation time was measured. Next, the shear stress was released (0 kPa) and left for 10 minutes, and the final strain after 10 minutes was measured to obtain the recovery rate. The stress relaxation time was defined as the time when the shear stress became 0.368 times the initial stress after the strain reached 400%. The initial stress was taken as the shear stress value 0.1 second after the start of shear stress application. The recovery rate was calculated based on the following formula. Recovery rate (%) = {(400 - final strain) / 400} × 100

[0177] (Strain at 20 kPa stress, recovery rate after 20 kPa stress application) The adhesive layer (adhesive material) constituting the adhesive sheet was laminated by using a hand roller to prepare a laminate with a thickness of 600 μm, which was used as a test piece. The measurement was carried out using a viscoelasticity measuring device (MCR302 manufactured by Anton Paar), with the sample sandwiched between parallel plates with a diameter of 8 mm (the adhesion surface was roughened with No. 240 sandpaper), and conducted in an atmosphere of 25°C. In the measurement, after the test piece was compressed with an axial force of 1 N and left standing for 10 minutes, the axial force was changed to 0.05 N, a shear stress of 20 kPa was applied, and a creep test was conducted for 10 minutes. The strain after 10 minutes (20 kPa strain) was measured. Next, the shear stress was released (0 kPa) and left for 10 minutes, and the final strain after 10 minutes was measured to obtain the recovery rate. Those that were too soft to be measured were evaluated as "×". The recovery rate was calculated based on the following formula. Recovery rate (%) = {(20 kPa strain - final strain) / 20 kPa strain} × 100

[0178] (Repeated elongation test) The adhesive layer (adhesive material) constituting the adhesive sheet was laminated by using a hand roller to prepare a laminate with a thickness of 600 μmm. The laminate was cut into test pieces with a width of 10 mm and a length of 70 mm. The test was conducted using a precision universal testing machine (AUTOGRAPH (registered trademark) AGX manufactured by Shimadzu Corporation). The test was carried out in an environment of 23°C and 50% humidity, with the distance between the gripping tools of 30 mm and a tensile speed of 30 mm / min. In the test, it was stretched from a state where the tensile stress was 0 kPa until the tensile stress reached 50 kPa, and then contracted until the tensile stress became 0 kPa. This stretching and contraction were repeated 12 times, and the presence or absence of breakage was confirmed. Those without breakage were evaluated as "〇", and those with breakage were evaluated as "×".

[0179] (Measurement of Adhesion) One release sheet of the adhesive sheet was peeled off from the adhesive layer, and the corona-treated surface of a polyethylene terephthalate (PET) film (Toray Ester (registered trademark) Film E5100: manufactured by Toray, thickness 50 μm) was bonded to the adhesive layer surface, and then cut into a size of 25 mm in width and 100 mm in length to produce an adhesive sheet with a substrate. For this adhesive sheet with a substrate, the adhesion to a polyimide film or glass as an adherend was measured according to the method of JIS Z 0237 (2009). Specifically, the release sheet was peeled off from the adhesive layer, and the adhesive layer surface was pressure-bonded to a polyimide film (Kapton (registered trademark) 100V: manufactured by DuPont Teijin, thickness 25 μm) or whiteboard glass (S9112, manufactured by Matsunami Glass Industry Co., Ltd., thickness 1.0 - 1.2 mm) with a 2 kg roller reciprocated twice. Next, using a precision universal testing machine "AUTOGRAPH (registered trademark) AGS-1kNX, 50N load cell" manufactured by Shimadzu Corporation, the adhesion of the adhesive layer was measured under the conditions of a peeling speed of 300 mm / min and a peeling angle of 180°.

[0180] <Manufacture of Polymer Composition> (Synthesis Example 1: Polymer Composition X a ) Into a flask equipped with an argon gas inlet tube and a stirrer, 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) were charged. After argon substitution, BTEE (105.0 mg) was added, and the reaction was carried out at 60 °C for 24 hours to polymerize. After the reaction was completed, AcOEt was added to the reaction solution to obtain a solution containing Polymer Composition X a The solid content of the solution was 26.2 mass%.

[0181] (Synthesis Example 2: Polymer Composition Xb ) In the same manner as in Synthesis Example 1, a solution containing the polymerization composition X b was obtained. Table 1 shows the monomers, organic tellurium compounds, azo polymerization initiators, solvents, reaction conditions, and polymerization rates used.

[0182] (Synthesis Example 3: Polymerization Composition Y a ) Into a flask equipped with an argon gas inlet tube and a stirrer, EHA (1,334.0 g), LA (600.0 g), AA (60.0 g), HBA (6.0 g), and AcOEt (1,333.3 g) were charged. After purging with argon, the temperature was raised to 82 °C, and AIBN (875.8 mg) dissolved in AcOEt (45 g) was added dropwise over 2 hours, followed by further reaction for 4 hours to effect polymerization. After completion of the reaction, AcOEt was added to the reaction solution to obtain a solution containing the polymerization composition Y a was obtained. The solid content of the solution was 39.5% by mass.

[0183] (Synthesis Example 4: Polymerization Composition Y b ) In the same manner as in Synthesis Example 3, a solution containing the polymerization composition Y b was obtained. Table 1 shows the monomers, azo polymerization initiators, solvents, reaction conditions, and polymerization rates used.

[0184] Table 1 shows the polymerization conditions and the like of each polymerization composition. The content of each structural unit in the polymerization composition, the amount of functional groups per 1 g of the polymerization composition, and the glass transition temperature were calculated from the charging ratio of the monomers used in the polymerization reaction and the polymerization rate.

[0185]

Table 1

[0186] (Polymerization Composition X a , X b (polymer component in) For the polymerization composition X a , gel permeation chromatography was performed and waveform separation was carried out. As a result, only the polymer component X a 1 was confirmed. Also, for the polymerization composition Xb Regarding this, gel permeation chromatography was performed and waveform separation was carried out. As a result, only polymer component X b 1 was confirmed. Table 2 shows the physical properties of polymer component X a 1 and X b 1.

[0187]

Table 2

[0188] (Polymer composition Y a and Y b in the polymer component) Regarding polymer composition Y a gel permeation chromatography was performed and waveform separation was carried out. As a result, polymer components Y a 1, Y a 2 and Y a 3 were confirmed. Regarding polymer composition Y b gel permeation chromatography was performed and waveform separation was carried out. As a result, polymer components Y b 1, Y b 2 and Y b 3 were confirmed. Table 3 shows the physical properties of polymer components Y a 1 to Y a 3 and Y b 1 to Y b 3.

[0189]

Table 3

[0190] <Manufacture of the pressure-sensitive adhesive composition> (Pressure-sensitive adhesive composition No. 1) To 381.7 parts by mass of the solution of the polymer composition X a (100 parts by mass of the polymer component) obtained in Synthesis Example 1, 0.154 parts by mass of crosslinking agent A (Durane (registered trademark) MHG-80B) and butyl acetate were added, and the mixture was stirred to obtain pressure-sensitive adhesive composition No. 1 having a solid content of 20% by mass. Pressure-sensitive adhesive composition No. 1 contains polymer components X a 1, Y a 1, Y a 2 and Ya The first reactive group of 3 is a hydroxy group, and the second reactive group of crosslinking agent A is an isocyanate group.

[0191] (Adhesive composition Nos. 2 to 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 amounts of crosslinking agent A shown in Tables 4 and 5 are the amounts in terms of solid content. The solid content is the component other than the solvent. Adhesive compositions Nos. 2 to 8 contain polymer component X a 1, Y a 1, Y a 2 and Y a 3 has a first reactive group that is a hydroxy group, and crosslinking agent A has a second reactive group that is an isocyanate group. Adhesive compositions Nos. 9 to 11 contain polymer component X b 1, Y b 1, Y b 2 and Y b 3 has a first reactive group that is a carboxy group, and crosslinking agent B has a second reactive group that is an epoxy group.

[0192] <Production of Adhesive Sheet> On the release surface of the first release sheet (PET film with a release treatment on the surface, Clean Sepa (registered trademark) HY-US20: manufactured by Toyama Film, thickness 75 μm), the adhesive composition was applied using a Baker applicator so that the film thickness after drying would be 50 μm, and then dried at 60 °C for 3 minutes and subsequently at 150 °C for 3 minutes using a constant temperature dryer. Next, the release surface of the second release sheet (PET film with a release treatment on the surface, Clean Sepa (registered trademark) HY-S10: manufactured by Toyama Film, thickness 38 μm) was bonded to the adhesive layer formed on the first release sheet, and then aged at 60 °C for 3 days to produce an adhesive layer sandwiched between the two release sheets. The evaluation results of the adhesive layers (adhesives) formed from each adhesive composition are shown in Table 4.

[0193]

Table 4

[0194]

Table 5

[0195] Adhesive composition No. 1 is a case where the adhesive composition contains (A) a (meth)acrylic copolymer component but does not contain (B) a (meth)acrylic copolymer component. The adhesive material formed from this adhesive composition No. 1 had a small strain amount when a shear stress of 20 kPa was applied and was inferior in flexibility. Also, the adhesive force to glass was low.

[0196] Adhesive compositions No. 2 and 3 are cases where the adhesive composition contains (A) a (meth)acrylic copolymer component and (B) a (meth)acrylic copolymer component, and the content rate of the (A) (meth)acrylic copolymer component in all the polymer components is 75% to 99% by mass. The adhesive materials formed from these adhesive compositions No. 2 and 3 were good in all of the recovery rate after being strained up to 400% strain, the strain amount when a shear stress of 20 kPa was applied, and the repeated elongation test. Also, the adhesive force was good for both glass and a PI film.

[0197] Adhesive compositions Nos. 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) (meth)acrylic copolymer component in all the polymer components is less than 75% by mass. Among these, the adhesives formed from adhesive compositions Nos. 4 to 6 had poor recovery rates after being strained up to 400% strain. Also, the adhesives formed from adhesive compositions Nos. 7 and 8 broke in the repeated elongation test.

[0198] Adhesive compositions Nos. 9 to 11 are those in which the adhesive composition contains (A) a (meth)acrylic copolymer component and (B) a (meth)acrylic copolymer component, and the content of the (A) (meth)acrylic copolymer component in all the polymer components is 75% to 99% by mass. The adhesives formed from these adhesive compositions Nos. 9 to 11 were good in all of the recovery rate after being strained up to 400% strain, the amount of strain when a shear stress of 20 kPa was applied, and the repeated elongation test. Also, the adhesive force was good for both glass and PI film.

[0199] The present invention includes the following aspects.

[0200] (Aspect 1) An adhesive composition for a flexible display for bonding one flexible member and another flexible member constituting a flexible display, the adhesive composition containing a plurality of (meth)acrylic copolymer components and a crosslinking agent, wherein the (meth)acrylic copolymer components include 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 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 component in the plurality of (meth)acrylic copolymer components is 75% to 99% by mass.

[0201] (Aspect 2) The pressure-sensitive adhesive composition for a flexible display according to Aspect 1, wherein the weight-average molecular weight of the (meth)acrylic copolymer component (A) and the (meth)acrylic copolymer component (B) is from 100,000 to 3,000,000.

[0202] (Aspect 3) The pressure-sensitive adhesive composition for a flexible display according to Aspect 1 or 2, wherein the weight-average molecular weight of the (meth)acrylic copolymer component (A) is 100,000 or more.

[0203] (Aspect 4) The pressure-sensitive adhesive composition for a flexible display according to any one of Aspects 1 to 3, wherein the weight-average molecular weight of the (meth)acrylic copolymer component (B) is 800,000 or less.

[0204] (Aspect 5) The pressure-sensitive adhesive composition for a flexible display according to any one of Aspects 1 to 4, wherein the crosslinking agent is an isocyanate-based crosslinking agent and / or an epoxy-based crosslinking agent.

[0205] (Aspect 6) The pressure-sensitive adhesive composition for a flexible display according to Aspect 5, wherein the isocyanate-based crosslinking agent is at least one selected from the group consisting of an aliphatic diisocyanate compound, an adduct of an aliphatic diisocyanate compound and an aliphatic diol compound, an adduct of an aliphatic diisocyanate compound, a biuret of an aliphatic diisocyanate compound, and an isocyanurate of an aliphatic diisocyanate compound.

[0206] (Aspect 7) The pressure-sensitive adhesive composition for a flexible display according to Aspect 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.

[0207] (Aspect 8) The pressure-sensitive adhesive composition for a flexible display according to any one of Aspects 1 to 7, wherein the first reactive group is a hydroxy group and / or a carboxy group.

[0208] (Aspect 9) A pressure-sensitive adhesive for a flexible display for bonding one flexible member and another flexible member constituting the flexible display, wherein the pressure-sensitive adhesive is a cured product of the pressure-sensitive adhesive composition according to any one of Aspects 1 to 8.

[0209] (Aspect 10) The pressure-sensitive adhesive for a flexible display according to Aspect 9, wherein the gel fraction of the cured product is 50% by mass or more.

[0210] (Aspect 11) A pressure-sensitive adhesive sheet for a flexible display having a pressure-sensitive adhesive layer used for bonding one flexible member and another flexible member constituting the flexible display, and a flexible sheet member adhered to at least one surface of the pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer is formed from the pressure-sensitive adhesive according to Aspect 9 or 10.

[0211] (Aspect 12) The pressure-sensitive adhesive sheet for a flexible display according to Aspect 11, wherein the pressure-sensitive adhesive sheet has a first flexible sheet member adhered to one surface of the pressure-sensitive adhesive layer and a second flexible sheet member adhered to the other surface of the pressure-sensitive adhesive layer, the first flexible sheet member is a first release sheet, the second flexible sheet member is a second release sheet, and the first release sheet and the second release sheet are adhered such that their respective release surfaces are in contact with the pressure-sensitive adhesive layer.

[0212] (Aspect 13) A flexible laminated member including a first flexible member, a second flexible member, and an adhesive layer that bonds the first flexible member and the second flexible member to each other, wherein the adhesive layer is made of the adhesive material described in Embodiment 9 or 10.

[0213] (Embodiment 14) The flexible laminated member according to Embodiment 13, wherein at least one of the first flexible member and the second flexible member is a display element.

[0214] (Embodiment 15) A flexible display comprising the flexible laminated member according to Embodiment 13 or 14.

[0215] (Embodiment 16) A (meth)acrylic copolymer mixture used in an adhesive composition for a flexible display, containing at least (A) a (meth)acrylic copolymer component and (B) a (meth)acrylic copolymer component, wherein 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 more than 3.0, the first reactive group is a hydroxy group and / or a carboxy group, and the content of the (A) (meth)acrylic copolymer component in the (meth)acrylic copolymer mixture is 75% by mass to 99% by mass.

Explanation of Reference Numerals

[0216] 10: Adhesive sheet 12: Adhesive layer 14: First flexible sheet member 16: Second flexible sheet member 20: Flexible laminated member 22: First flexible member 24: Second flexible member

Claims

1. An adhesive composition for a flexible display for bonding one flexible member and another flexible member constituting the flexible display, containing a plurality of (meth)acrylic copolymer components and a crosslinking agent, wherein the (meth)acrylic copolymer components contain 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 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 component in the plurality of (meth)acrylic copolymer components is 75% by mass to 99% by mass. An adhesive composition for a flexible display characterized by this.

2. The adhesive composition for a flexible display according to Claim 1, wherein the weight average molecular weights of the (A) (meth)acrylic copolymer component and the (B) (meth)acrylic copolymer component are 100,000 to 3,000,000.

3. The adhesive composition for a flexible display according to Claim 1 or 2, wherein the weight average molecular weight of the (A) (meth)acrylic copolymer component is 100,000 or more.

4. The adhesive composition for a flexible display according to any one of Claims 1 to 3, wherein the weight average molecular weight of the (B) (meth)acrylic copolymer component is 800,000 or less.

5. The adhesive composition for a 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 a flexible display 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 adduct of an aliphatic diisocyanate compound and an aliphatic diol compound, an adduct of an aliphatic diisocyanate compound, a biuret of an aliphatic diisocyanate compound, and an isocyanurate of an aliphatic diisocyanate compound.

7. The pressure-sensitive adhesive composition for a flexible display according to claim 5, wherein the epoxy 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.

8. The pressure-sensitive adhesive composition for a flexible display according to any one of claims 1 to 7, wherein the first reactive group is a hydroxy group and / or a carboxy group.

9. A pressure-sensitive adhesive for a flexible display for bonding one flexible member and another flexible member constituting the flexible display, The pressure-sensitive adhesive for a flexible display, wherein the pressure-sensitive adhesive is a cured product of the pressure-sensitive adhesive composition according to any one of claims 1 to 8.

10. The pressure-sensitive adhesive for a flexible display according to claim 9, wherein the gel fraction of the cured product is 50% by mass or more.

11. A pressure-sensitive adhesive sheet for a flexible display having a pressure-sensitive adhesive layer used for bonding one flexible member and another flexible member constituting the flexible display, and a flexible sheet member adhered to at least one surface of the pressure-sensitive adhesive layer, The pressure-sensitive adhesive sheet for a flexible display, wherein the pressure-sensitive adhesive layer is formed from the pressure-sensitive adhesive according to claim 9 or 10.

12. The pressure-sensitive adhesive sheet has a first flexible sheet member adhered to one surface of the pressure-sensitive adhesive layer and a second flexible sheet member adhered to the other surface of the pressure-sensitive adhesive layer, the first flexible sheet member is a first release sheet, the second flexible sheet member is a second release sheet, The pressure-sensitive adhesive sheet for a flexible display according to claim 11, wherein the first release sheet and the second release sheet are adhered such that their release surfaces are in contact with the pressure-sensitive adhesive layer.

13. A flexible laminated member including a first flexible member, a second flexible member, and a pressure-sensitive adhesive layer that bonds the first flexible member and the second flexible member to each other, The flexible laminated member, wherein the pressure-sensitive adhesive layer is made of the pressure-sensitive adhesive according to claim 9 or 10.

14. The flexible laminated member according to claim 13, wherein at least one of the first flexible member and the second flexible member is a display element.

15. A flexible display comprising the flexible laminated member according to claim 13 or 14.

16. A (meth)acrylic copolymer mixture used in an adhesive composition for a flexible display, comprising at least (A) a (meth)acrylic copolymer component and (B) a (meth)acrylic copolymer component, wherein 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 more than 3.0, the first reactive group is a hydroxy group and / or a carboxy group, and the content of the (A) (meth)acrylic copolymer component in the (meth)acrylic copolymer mixture is 75% to 99% by mass. A (meth)acrylic copolymer mixture characterized by this.

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