Adhesive material and adhesive sheet

Abstract

To provide an adhesive material having excellent adhesiveness and flexibility and further having excellent restorability.SOLUTION: There is provided an adhesive material which contains a polymer (X) having a crosslinked structure and has a shear storage modulus of 0.15 MPa or less at a temperature of 25°C, a glass transition temperature of 0°C or less and a gel fraction of 50 mass% to 95 mass%, wherein the differential molecular weight distribution curve of the sol component satisfies (1) a ratio (W1) of the peak area of a molecular weight of 10000 or more and less than 100000 to the peak area of a molecular weight of 10000 to 30000000 is 20% or less, (2) a ratio (W2) of the peak are of a molecular weight of 100000 or more and less than 560000 to the peak area of 10000 to 30000000 is 40% or more and (3) a ratio (W3) of the peak area of a molecular weight of 560000 or more to the peak area of a molecular weight of 10000 to 30000000 is 40% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to adhesives and adhesive sheets, and more particularly to adhesives and adhesive sheets used for bonding one flexible member to another flexible member. [Background technology]

[0002] In various displays and touch panels for televisions, mobile phones, smartphones, etc., adhesives are generally used to join the components that make them up. The adhesive is provided, for example, in the form of an adhesive sheet with an adhesive layer on a support substrate, or an adhesive sheet without a support substrate, and the components are bonded together.

[0003] On the other hand, in recent years, flexible displays that are repeatedly bent and used in image display devices such as liquid crystal displays and organic electroluminescent (OLED) displays have been attracting attention. Flexible displays include foldable displays that can be folded and rollable displays that can be rolled into a cylindrical shape, and are expected to be used in mobile devices such as smartphones and tablet terminals, as well as storable stationary displays.

[0004] In such flexible displays, as an adhesive material for bonding flexible members that constitute members that are repeatedly bent and stretched to other flexible members, for example, Patent Document 1 discloses an adhesive material for repeatedly bending devices in which the ratio of the shear stress 60 seconds after a 1000% displacement to the maximum shear stress when one surface of the adhesive layer and the other surface are displaced by 1000% in opposite directions, and the gel fraction are controlled within a predetermined range (see Patent Document 1 (Claim 1)). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2019-108498 [Overview of the project] [Problems that the invention aims to solve]

[0006] Conventional adhesives did not adequately recover to their original state after repeated bending. Therefore, when conventional adhesives were used to join flexible members, repeated bending could cause lifting or peeling at the interface between the adhesive and the flexible member at the bending point.

[0007] This invention has been made in view of the above circumstances, and aims to provide an adhesive that has excellent tackiness, excellent flexibility, and excellent resilience. [Means for solving the problem]

[0008] The adhesive of the present invention, which has been able to solve the above problems, is an adhesive containing a polymer (X) having a crosslinked structure, characterized in that the shear storage modulus at a temperature of 25°C is 0.15 MPa or less, the glass transition temperature is 0°C or less, the gel fraction is 50% by mass to 95% by mass, and the differential molecular weight distribution curve of the sol component satisfies the requirements of (1), (2) and (3). (1) The ratio (W1) of the peak area for molecular weights between 10,000 and 100,000 to the peak area for molecular weights between 10,000 and 30,000,000 is 20% or less. (2) The ratio (W2) of the peak area for molecular weights between 100,000 and 560,000 to the peak area for molecular weights between 10,000 and 30,000,000 is 40% or more. (3) The ratio of the peak area for molecular weights of 560,000 or more (W3) to the peak area for molecular weights of 10,000 to 30,000,000 is 40% or less. [Effects of the Invention]

[0009] The adhesive of the present invention has excellent adhesive properties, as well as excellent flexibility and resilience. Therefore, by using the adhesive of the present invention to join flexible members, it is possible to suppress the occurrence of lifting or peeling at the interface between the adhesive and the flexible member at the bending point, even when repeatedly bent. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic cross-sectional view of an example of the adhesive sheet of the present invention. [Figure 2] This is a schematic cross-sectional view of an example of a flexible laminated member of the present invention. [Modes for carrying out the invention]

[0011] The following describes an example of a preferred embodiment of the present invention. However, the following embodiments are merely illustrative. The present invention is not limited in any way to the embodiments described below.

[0012] In this specification, "~" is used to mean that the numerical values ​​written before and after it are included as the lower and upper limits. "(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" means a monomer that has a radically polymerizable carbon-carbon double bond in its molecule. "Structural unit derived from vinyl monomer" means a structural unit in which the radically polymerizable carbon-carbon double bond of vinyl monomer has polymerized to become a carbon-carbon single bond. "Structural unit derived from (meth)acrylate" means a structural unit in which the radically polymerizable carbon-carbon double bond of (meth)acrylate has polymerized to become a carbon-carbon single bond. "Structural unit derived from (meth)acrylic monomer" means a structural unit in which the radically polymerizable carbon-carbon double bond of (meth)acrylic monomer has polymerized to become a carbon-carbon single bond.

[0013] [Adhesive material] The adhesive of the present invention is an adhesive containing a polymer (X) having a crosslinked structure, wherein the shear storage modulus at a temperature of 25°C is 0.15 MPa or less, the glass transition temperature is 0°C or less, and the gel fraction is 50% to 95% by mass.

[0014] The shear storage modulus of the adhesive material at a temperature of 25°C is preferably 0.15 MPa or less, more preferably 0.10 MPa or less, and even more preferably 0.08 MPa or less. If the shear storage modulus is 0.15 MPa or less, the flexibility of the adhesive material is improved, resulting in higher followability to deformation. Therefore, even when repeatedly bent, the occurrence of lifting or peeling at the interface between the adhesive material and the flexible member at the bending portion can be suppressed. The shear storage modulus of the adhesive material at a temperature of 25°C is preferably 0.01 MPa or more, more preferably 0.02 MPa or more. If the shear storage modulus is 0.01 MPa or more, the adhesive holding force when the adhesive sheet and the adherend are bonded together can be increased.

[0015] The glass transition temperature (Tg) of the adhesive material is preferably 0°C or less, more preferably -20°C or less, and even more preferably -30°C or less. If the glass transition temperature is 0°C or less, the adhesion of the formed adhesive material to the adherend is enhanced, peeling and the like are suppressed at low temperatures, and the durability is improved. The lower limit of the glass transition temperature of the adhesive material is not particularly limited, but is usually -50°C.

[0016] The gel fraction of the adhesive material is preferably 50% by mass or more, more preferably 55% by mass or more, and even more preferably 60% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less. If the gel fraction is 50% by mass or more and 95% by mass or less, an adhesive material excellent in flexibility and resilience can be formed. The gel fraction can be controlled by the content of the first crosslinkable group, the type and blending amount of the crosslinking agent, etc. in the composition described later.

[0017] The adhesive contains a sol component. The sol component is a component that elutes into the solvent when the adhesive is extracted with ethyl acetate at 25°C for 72 hours. The adhesive is characterized in that the differential molecular weight distribution curve of the sol component satisfies requirements (1), (2), and (3). The differential molecular weight distribution curve is created from a chromatograph obtained by GPC (gel permeation chromatography). Specifically, an integral molecular weight distribution curve is created by plotting molecular weight (logarithmic value) on the horizontal axis and the integrated value of the concentration fraction on the vertical axis. Next, the slope (derivative value) of the curve at each molecular weight is determined. Finally, a differential molecular weight distribution curve is created by plotting molecular weight (logarithmic value) on the horizontal axis and the differential value on the vertical axis.

[0018] (1) The ratio (W1) of the peak area for molecular weights between 10,000 and 100,000 to the peak area for molecular weights between 10,000 and 30,000,000 is 20% or less. (2) The ratio (W2) of the peak area for molecular weights between 100,000 and 560,000 to the peak area for molecular weights between 10,000 and 30,000,000 is 40% or more. (3) The ratio of the peak area for molecular weights of 560,000 or more (W3) to the peak area for molecular weights of 10,000 to 30,000,000 is 40% or less. By satisfying the requirements (1) to (3) above, it is possible to form an adhesive that has excellent tackiness, excellent flexibility, and excellent resilience.

[0019] The amount of W1 is preferably 15% or less, more preferably 10% or less, and even more preferably 7% or less. If the amount of W1 is 15% or less, the decrease in tackiness due to the plasticizing effect of the sol component can be suppressed. The amount of W1 is preferably 0%, but may be greater than 0%. In this case, the amount of W1 is preferably 1.0% or more, more preferably 1.6% or more, and even more preferably 1.8% or more. If the amount of W1 is 1.0% or more, the wettability of the interface with the adherend is improved by the sol component of the adhesive, resulting in good tackiness.

[0020] The amount of W2 is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more. If the amount of W2 is 50% or more, an adhesive with excellent tackiness can be formed. The amount of W2 is preferably 100%, but may be less than 100%. In this case, the amount of W2 is preferably 98% or less, more preferably 95.4% or less, and even more preferably 88.2% or less.

[0021] The amount of W3 is preferably 30% or less, more preferably 25% or less, and even more preferably 20% or less. If the amount of W3 is 30% or less, the entanglement effect of the sol component can be suppressed, resulting in good resilience during repeated bending. The amount of W3 is preferably 0%, but may be greater than 0%. In this case, the amount of W3 is preferably 0.5% or more, more preferably 1.0% or more, even more preferably 3.0% or more, and particularly preferably 10% or more. If the amount of W3 is 0.5% or more, the cohesive force of the adhesive is improved, resulting in good tackiness.

[0022] The ratio of W1 to W3 (W1 / W3) is preferably 0.07 or more, more preferably 0.10 or more, even more preferably 0.15 or more, preferably 26.0 or less, more preferably 6.5 or less, even more preferably 5.5 or less, and particularly preferably 4.0 or less. If the ratio (W1 / W3) is 0.07 or more, the wettability of the interface between the adhesive material and the flexible member due to the sol component is improved, resulting in good adhesion, and if it is 26.0 or less, the decrease in tackiness due to the plasticizing effect of the sol component can be suppressed.

[0023] Preferably, the adhesive material has a differential molecular weight distribution curve of the sol component that further satisfies requirements (2a) and (2b). (2a) The ratio of the peak area for molecular weights between 100,000 and 150,000 (W2a) to the peak area for molecular weights between 10,000 and 30,000,000 is 15% or more. (2b) The ratio of the peak area for molecular weights between 150,000 and 560,000 to the peak area for molecular weights between 10,000 and 30,000,000 (W2b) is 20% or more. By satisfying the requirements of (2a) and (2b) above, it is possible to form an adhesive with excellent tackiness, where the cohesiveness and wettability due to the sol component are balanced.

[0024] The amount of W2a is preferably 20% or more, more preferably 25% or more, even more preferably 30% or more, particularly preferably 35% or more, preferably 46% or less, more preferably 45.4% or less, and even more preferably 44.9% or less. If the amount of W2a is 20% or more, the entanglement effect of the sol components is suppressed, resulting in excellent flexibility and resilience, and if it is 46% or less, the decrease in tackiness due to the plasticizing effect of the sol components can be suppressed.

[0025] The amount of W2b is preferably 25% or more, more preferably 30% or more, even more preferably 35% or more, preferably 52% or less, more preferably 50% or less, and even more preferably 43.3% or less. If W2b is 25% or more, the cohesive force of the sol component is improved, resulting in excellent tackiness. If it is 52% or less, the entanglement effect of the sol component is suppressed, resulting in excellent flexibility and resilience.

[0026] The ratio of W2 to W2a (W2a / W2) is preferably 0.30 or more, more preferably 0.35 or more, even more preferably 0.45 or more, preferably 0.60 or less, more preferably 0.55 or less, and even more preferably 0.53 or less.

[0027] In the differential molecular weight distribution curve of the sol component, the highest peak molecular weight (Mp) in the range of 10,000 to 30,000,000 molecular weights is preferably 100,000 or more, preferably 500,000 or less, more preferably 300,000 or less, and even more preferably 200,000 or less. When the peak molecular weight (Mp) is within this range, an adhesive with excellent tackiness tends to be formed.

[0028] The weight-average molecular weight of the sol component is preferably 100,000 or more, more preferably 150,000 or more, even more preferably 200,000 or more, preferably 560,000 or less, more preferably 450,000 or less, and even more preferably 400,000 or less. If the weight-average molecular weight is within this range, an adhesive with excellent tackiness can be formed.

[0029] The molecular weight distribution (Mw / Mn) of the sol component is preferably 6.0 or less, more preferably 4.0 or less, and even more preferably 3.0 or less. If the molecular weight distribution is 6.0 or less, the content of molecules with larger or smaller molecular weights is low compared to the molecular weight of the designed polymer, resulting in an adhesive with excellent tackiness, flexibility, and resilience. The molecular weight distribution is 1.0 or more. The smaller the molecular weight distribution, the narrower the range of molecular weight distribution, with the narrowest range occurring when the value is 1.0. In this invention, the molecular weight distribution is a value calculated by (weight-average molecular weight (Mw)) / (number-average molecular weight (Mn)), and the methods for measuring Mw and Mn will be described later.

[0030] (A polymer (X) having a cross-linked structure) The adhesive material contains a polymer (X) having a crosslinked structure. The polymer (X) having a crosslinked structure is obtained by crosslinking an adhesive composition containing a polymer component having a polymer having a first reactive group and a crosslinked component having a second reactive group that reacts with the first reactive group.

[0031] The polymer (X) having the crosslinked structure is preferably obtained by crosslinking an adhesive composition containing a (meth)acrylic polymer (A) having a first reactive group with a weight-average molecular weight of 600,000 to 3,000,000 (hereinafter sometimes simply referred to as "(meth)acrylic polymer (A)"), a (meth)acrylic polymer (B) having a weight-average molecular weight (Mw) of 100,000 to 800,000 (hereinafter sometimes simply referred to as "(meth)acrylic polymer (B)"), and a crosslinking agent having a second reactive group that reacts with the first reactive group.

[0032] The difference (MwA-MwB) between the weight-average molecular weight (MwA) of the (meth)acrylic polymer (A) and the weight-average molecular weight (MwB) of the (meth)acrylic polymer (B) is preferably 500,000 or more, more preferably 700,000 or more, even more preferably 1,000,000 or more, preferably 2,900,000 or less, more preferably 2,500,000 or less, and even more preferably 2,200,000 or less. If the difference (MwA-MwB) is 500,000 or more, even if the (meth)acrylic polymer (B) has a first reactive group, the crosslinking agent having a second reactive group can be selectively reacted with the (meth)acrylic polymer (A), and if it is 2,900,000 or less, the (meth)acrylic polymer (A) and the (meth)acrylic polymer (B) can be uniformly mixed during coating.

[0033] The ratio (MwA / MwB) of the weight-average molecular weight (MwA) of the (meth)acrylic polymer (A) to the weight-average molecular weight (MwB) of the (meth)acrylic polymer (B) is preferably 1.9 or higher, more preferably 3.6 or higher, even more preferably 6.0 or higher, preferably 18.0 or lower, more preferably 15.0 or lower, and even more preferably 13.0 or lower. If the ratio (MwA / MwB) is 1.9 or higher, even if the (meth)acrylic polymer (B) has a first reactive group, the crosslinking agent having a second reactive group can be selectively reacted with the (meth)acrylic polymer (A), and if it is 18.0 or lower, the (meth)acrylic polymer (A) and the (meth)acrylic polymer (B) can be uniformly mixed during coating.

[0034] The (meth)acrylic polymer (B) may or may not have a first reactive group. In other words, examples of combinations of the (meth)acrylic polymer (A) and (meth)acrylic polymer (B) include a combination of a (meth)acrylic polymer (A) having a first reactive group with a weight-average molecular weight of 600,000 to 3,000,000 and a (meth)acrylic polymer (B) not having a first reactive group with a weight-average molecular weight (Mw) of 100,000 to 800,000; and a combination of a (meth)acrylic polymer (A) having a first reactive group with a weight-average molecular weight of 600,000 to 3,000,000 and a (meth)acrylic polymer (B) having a first reactive group with a weight-average molecular weight (Mw) of 100,000 to 800,000.

[0035] The (meth)acrylic polymer (A) and the crosslinking agent are mainly components that form a crosslinked structure. Components in the (meth)acrylic polymer (A) that were not crosslinked during the crosslinking reaction, and components with a low degree of crosslinking that can be extracted with a solvent, are included in the sol component. The (meth)acrylic polymer (B) that does not have the first reactive group is mainly a sol component. If the (meth)acrylic polymer (B) has the first reactive group, components in the (meth)acrylic polymer (B) that were not crosslinked during the crosslinking reaction, and components with a low degree of crosslinking that can be extracted with a solvent, are included in the sol component.

[0036] ((meth)acrylic polymer (A)) The (meth)acrylic polymer (A) has structural units derived from (meth)acrylic monomer as its main component (50% by mass or more). The (meth)acrylic polymer (A) may consist of one type or two or more types. The (meth)acrylic polymer (A) may also contain structural units derived from vinyl monomers other than (meth)acrylic monomer. The content of structural units derived from (meth)acrylic monomer in the (meth)acrylic polymer (A) is preferably 80% by mass or more, and more preferably 90% by mass or more, based on 100% by mass of the polymer. The (meth)acrylic polymer (A) may also consist only of structural units derived from (meth)acrylic monomer.

[0037] The (meth)acrylic polymer (A) is preferably a (meth)acrylate copolymer. A (meth)acrylate copolymer is any copolymer whose main component (50% by mass or more) is structural units derived from (meth)acrylate, and may contain structural units derived from vinyl monomers other than (meth)acrylate. The (meth)acrylate is an ester compound in which the hydrogen atoms of the carboxyl group of (meth)acrylic acid are replaced with organic groups. The content of structural units derived from (meth)acrylate in the (meth)acrylic polymer (A) is preferably 80% by mass or more, and more preferably 90% by mass or more, based on 100% by mass of the polymer.

[0038] The (meth)acrylic polymer (A) has a first reactive group. The first reactive group is a functional group that reacts with a second reactive group of the crosslinking agent described later. A functional group that can be the first reactive group is a reactive functional group. Examples of the first reactive group are a hydroxyl group, a carboxyl group, an epoxy group, etc., and preferably a hydroxyl group and / or a carboxyl group.

[0039] The amount of the first reactive group in the (meth)acrylic polymer (A) is preferably 0.002 mmol / g or more, more preferably 0.005 mmol / g or more, even more preferably 0.010 mmol / g or more, preferably 1.0 mmol / g or less, more preferably 0.8 mmol / g or less, and even more preferably 0.7 mmol / g or less. If the amount of the first reactive group is 0.002 mmol / g or more, the formed adhesive is appropriately crosslinked and exhibits suitable resilience, and if it is 1.0 mmol / g or less, the distance between crosslinking points of the formed adhesive is sufficiently long and exhibits excellent flexibility.

[0040] In the (meth)acrylic polymer (A), if the hydroxyl group is the primary reactive group, it is preferable that it also has a carboxyl group as a functional group other than the primary reactive group. In this case, the amount of carboxyl groups in the (meth)acrylic polymer (A) is preferably 0.08 mmol / g or more, more preferably 0.16 mmol / g or more, even more preferably 0.32 mmol / g or more, preferably 1.3 mmol / g or less, more preferably 0.8 mmol / g or less, and even more preferably 0.6 mmol / g or less.

[0041] Furthermore, if the hydroxyl group is the primary reactive group and the (meth)acrylic polymer (A) has both carboxyl and hydroxyl groups, the molar ratio of carboxyl groups to hydroxyl groups (carboxyl group / hydroxyl group) per unit mass of the (meth)acrylic polymer (A) is preferably 4 or more, more preferably 8 or more, even more preferably 16 or more, preferably 60 or less, more preferably 40 or less, and even more preferably 30 or less. If the molar ratio (carboxyl group / hydroxyl group) is within the above range, it results in an adhesive layer with high resilience and a suitable balance of tackiness and flexibility.

[0042] In the case where the (meth)acrylic polymer (A) has a carboxyl group as the first reactive group, it is preferable that it also has a hydroxyl group as a functional group other than the first reactive group. In this case, the amount of hydroxyl groups in the (meth)acrylic polymer (A) is preferably 0.01 mmol / g or more, more preferably 0.02 mmol / g or more, even more preferably 0.04 mmol / g or more, preferably 0.25 mmol / g or less, more preferably 0.20 mmol / g or less, and even more preferably 0.15 mmol / g or less.

[0043] Furthermore, if the carboxyl group is the primary reactive group and the (meth)acrylic polymer (A) has both carboxyl and hydroxyl groups, the molar ratio of carboxyl groups to hydroxyl groups (carboxyl group / hydroxyl group) per unit mass of the (meth)acrylic polymer (A) is preferably 3.0 or higher, more preferably 3.5 or higher, even more preferably 4.0 or higher, preferably 30.0 or lower, more preferably 25.0 or lower, and even more preferably 20.0 or lower. If the molar ratio (carboxyl group / hydroxyl group) is within the above range, it results in an adhesive layer with high resilience and a suitable balance of tackiness and flexibility.

[0044] The (meth)acrylic polymer (A) may be a random copolymer, a block copolymer, or a graft copolymer, and is preferably a random copolymer.

[0045] The weight-average molecular weight (MwA) of the (meth)acrylic polymer (A) is preferably 600,000 or more, more preferably 750,000 or more, even more preferably 900,000 or more, particularly preferably 1,000,000 or more, preferably 3,000,000 or less, more preferably 2,800,000 or less, and even more preferably 2,600,000 or less. If the MwA of the (meth)acrylic polymer (A) is 600,000 or more, the number of first reactive groups per (meth)acrylic polymer (A) increases, making it easier to satisfy the gel fraction described above, and if it is 3,000,000 or less, the coating workability of the adhesive composition is further improved. The method for measuring the weight-average molecular weight (Mw) will be described later.

[0046] The molecular weight distribution (Mw / Mn) of the (meth)acrylic polymer (A) is 3.0 or less, preferably 2.7 or less, more preferably 2.5 or less, and even more preferably 2.1 or less. The smaller the Mw / Mn, the narrower the molecular weight distribution, resulting in a polymer with uniform molecular weights, with the narrowest molecular weight distribution occurring when the value is 1.0. If the Mw / Mn is 3.0 or less, the content of molecules with smaller or larger molecular weights is low compared to the molecular weight of the designed polymer, resulting in an adhesive with excellent tackiness and resilience.

[0047] The glass transition temperature (Tg) of the (meth)acrylic polymer (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 Tg is -70°C or higher, it provides sufficient cohesive force to the adhesive and improves the durability of the formed adhesive. If Tg is 0°C or lower, the adhesion of the adhesive to the adherend is increased, peeling at low temperatures is suppressed, and durability is improved.

[0048] The Tg of the (meth)acrylic polymer (A) is the value calculated by the following FOX formula (formula (1)). In formula (1), Tg represents the glass transition temperature (°C) of the polymer. Tgi represents the glass transition temperature (°C) when vinyl monomer i forms a homopolymer. Wi represents the mass ratio of vinyl monomer i to the total vinyl monomers forming the polymer, where ΣWi = 1. i is a natural number from 1 to n.

[0049]

number

[0050] ((meth)acrylic polymer (B)) The (meth)acrylic polymer (B) has structural units derived from (meth)acrylic monomer as its main component (50% by mass or more). The (meth)acrylic polymer (B) may consist of one type or two or more types. The (meth)acrylic polymer (B) may also contain structural units derived from vinyl monomers other than (meth)acrylic monomer. The content of structural units derived from (meth)acrylic monomer in the (meth)acrylic polymer (B) is preferably 80% by mass or more, and more preferably 90% by mass or more, based on 100% by mass of the polymer. The (meth)acrylic polymer (B) may also consist only of structural units derived from (meth)acrylic monomer.

[0051] The (meth)acrylic polymer (B) is preferably a (meth)acrylate copolymer. A (meth)acrylate copolymer is any copolymer whose main component (50% by mass or more) is structural units derived from (meth)acrylate, and may contain structural units derived from vinyl monomers other than (meth)acrylate. The content of structural units derived from (meth)acrylate in the (meth)acrylic polymer (B) is preferably 80% by mass or more, and more preferably 90% by mass or more, based on 100% by mass of the polymer.

[0052] The (meth)acrylic polymer (B) may be a random copolymer, a block copolymer, or a graft copolymer, and is preferably a random copolymer.

[0053] The weight-average molecular weight (MwB) of the (meth)acrylic polymer (B) is preferably 100,000 or more, more preferably 130,000 or more, even more preferably 150,000 or more, preferably 800,000 or less, more preferably less than 600,000, even more preferably 500,000 or less, and particularly preferably 400,000 or less. When the MwB of the (meth)acrylic polymer (B) is within this range, an adhesive with excellent tackiness tends to be formed.

[0054] The molecular weight distribution (Mw / Mn) of the (meth)acrylic polymer (B) is preferably 5.0 or less, more preferably 4.0 or less, even more preferably 3.0 or less, and particularly preferably 2.5 or less. The smaller the Mw / Mn, the narrower the molecular weight distribution, resulting in a polymer with uniform molecular weights, with the narrowest molecular weight distribution occurring when the value is 1.0. If the Mw / Mn is 5.0 or less, the content of molecules with smaller or larger molecular weights is low compared to the molecular weight of the designed polymer, resulting in an adhesive with excellent tackiness.

[0055] The glass transition temperature (Tg) of the (meth)acrylic polymer (B) 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 Tg is -70°C or higher, it provides sufficient cohesive force to the adhesive, improving the durability of the formed adhesive. If Tg is 0°C or lower, the adhesion of the formed adhesive to the adherend is increased, peeling at low temperatures is suppressed, and durability is improved.

[0056] In the adhesive composition, the amount of (meth)acrylic polymer (B) per 100 parts by mass of (meth)acrylic polymer (A) is preferably 30 parts by mass or more, more preferably 50 parts by mass or more, even more preferably 70 parts by mass or more, preferably 300 parts by mass or less, more preferably 250 parts by mass or less, and even more preferably 200 parts by mass or less. If the amount of (meth)acrylic polymer (B) is 30 parts by mass or more, an adhesive with excellent flexibility can be formed, and if it is 300 parts by mass or less, an adhesive with excellent resilience can be formed.

[0057] The (meth)acrylic polymer (B) may or may not have a first reactive group. The (meth)acrylic polymer (B) may be a polymer having a first reactive group and a polymer not having a first reactive group. Examples of the first reactive group include hydroxyl groups, carboxyl groups, epoxy groups, etc., and is preferably a hydroxyl group and / or a carboxyl group.

[0058] When the (meth)acrylic polymer (B) has a first reactive group, the amount of the first reactive group in the (meth)acrylic polymer (B) is preferably 0.002 mmol / g or more, more preferably 0.005 mmol / g or more, even more preferably 0.010 mmol / g or more, preferably 1.0 mmol / g or less, more preferably 0.8 mmol / g or less, and even more preferably 0.7 mmol / g or less. If the amount of the first reactive group is 0.002 mmol / g or more, the formed adhesive is appropriately crosslinked and exhibits suitable resilience, and if it is 1.0 mmol / g or less, the distance between crosslinking points of the formed adhesive is sufficiently long and has excellent flexibility.

[0059] When the (meth)acrylic polymer (B) has a first reactive group, the total amount of the first reactive groups in the (meth)acrylic polymer (A) and (meth)acrylic polymer (B) in the total mass of the (meth)acrylic polymer (A) and (meth)acrylic polymer (B) is preferably 0.002 mmol / g or more, more preferably 0.005 mmol / g or more, even more preferably 0.010 mmol / g or more, preferably 1.0 mmol / g or less, more preferably 0.8 mmol / g or less, and even more preferably 0.7 mmol / g or less. If the amount of the first reactive group is 0.002 mmol / g or more, the formed adhesive is appropriately crosslinked and exhibits suitable resilience, and if it is 1.0 mmol / g or less, the distance between crosslinking points of the formed adhesive is sufficiently long and has excellent flexibility.

[0060] The (meth)acrylic polymer (B) preferably has a carboxyl group when the hydroxyl group is the primary reactive group. The adhesive formed by the (meth)acrylic polymer (B) having a carboxyl group exhibits excellent tackiness. In this case, the amount of carboxyl groups in the (meth)acrylic polymer (B) is preferably 0.002 mmol / g or more, more preferably 0.005 mmol / g or more, even more preferably 0.010 mmol / g or more, preferably 1.0 mmol / g or less, more preferably 0.8 mmol / g or less, and even more preferably 0.7 mmol / g or less.

[0061] The adhesive composition may contain polymer components other than the (meth)acrylic polymer (A) and (meth)acrylic polymer (B). The total content of the (meth)acrylic polymer (A) and (meth)acrylic polymer (B) in the polymer components contained in the adhesive composition is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. The adhesive composition may contain only the (meth)acrylic polymer (A) and (meth)acrylic polymer (B) as polymer components.

[0062] The following describes the structural units that constitute the (meth)acrylic polymer (A) and (meth)acrylic polymer (B) mentioned above.

[0063] The (meth)acrylic polymer (A) has a first reactive group. That is, the (meth)acrylic polymer (A) contains a structural unit (a-1) having a first reactive group in its structure. The (meth)acrylic polymer (B) may or may not contain a structural unit (a-1) having a first reactive group in its structure.

[0064] The structural unit (a-1) having the first reactive group may be one type or may consist of two or more types. The first reactive group may be present in structural units derived from (meth)acrylic monomers (preferably (meth)acrylate monomers and / or (meth)acrylic acid) or in structural units derived from vinyl monomers other than (meth)acrylic monomers. That is, the structural unit (a-1) having the first reactive group may be a structural unit derived from a (meth)acrylic monomer (preferably (meth)acrylate monomers and / or (meth)acrylic acid) having the first reactive group, or a structural unit derived from a vinyl monomer other than a (meth)acrylic monomer having the first reactive group.

[0065] The content of structural units (structural units (a-1)) derived from vinyl monomers having a first reactive group in the (meth)acrylic polymer (A) is preferably 0.03% by mass or more, more preferably 0.09% by mass or more, even more preferably 0.15% by mass or more, preferably 6% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less, based on 100% by mass of the polymer component. If the content of structural units (a-1) in the (meth)acrylic polymer (A) is within the above range, an adhesive with an excellent balance of adhesion to the adherend and durability can be formed. Note that vinyl monomers having a first reactive group include (meth)acrylic monomers having a first reactive group and vinyl monomers other than (meth)acrylic monomers having a first reactive group.

[0066] When the (meth)acrylic polymer (B) has a first reactive group, the content of structural units (structural units (a-1)) derived from vinyl monomers having the first reactive group in the (meth)acrylic polymer (B) is preferably 0.03% by mass or more, more preferably 0.09% by mass or more, even more preferably 0.15% by mass or more, preferably 6% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less, based on 100% by mass of the polymer component. If the content of structural units (a-1) in the (meth)acrylic polymer (B) is within the above range, an adhesive with an excellent balance of adhesion to the adherend and durability can be formed. Note that the vinyl monomer having the first reactive group includes (meth)acrylic monomers having the first reactive group and vinyl monomers other than (meth)acrylic monomers having the first reactive group.

[0067] Examples of the (meth)acrylic monomer include (b1) a (meth)acrylic monomer that does not have a functional group that can act as a primary reactive group, and (b2) a (meth)acrylic monomer that has a functional group that can act as a primary reactive group. These monomers may be used individually or in combination of two or more. As the (b1) (meth)acrylic monomer, (b1-1) a (meth)acrylate monomer that does not have a functional group that can act as a primary reactive group is preferred. Examples of the (b2) (meth)acrylic monomer include (b2-1) a (meth)acrylate monomer that has a functional group that can act as a primary reactive group, and (meth)acrylic acid.

[0068] Examples of (meth)acrylic monomers that do not have a functional group that can be the first reactive group (b1) include (meth)acrylates having a linear alkyl group, (meth)acrylates having a branched alkyl group, (meth)acrylates having an alkoxy group, (meth)acrylates having an alicyclic hydrocarbon group, (meth)acrylates having an aromatic group, (meth)acrylates having a tertiary amino group, and (meth)acrylamides. 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.

[0069] The (meth)acrylate having a linear alkyl group is preferably one in which the linear alkyl group has 1 to 20 carbon atoms, more preferably one in which the linear alkyl group has 1 to 15 carbon atoms, even more preferably one in which the linear alkyl group has 1 to 12 carbon atoms, and still more preferably one in which the linear alkyl group has 4 to 12 carbon atoms. Examples of (meth)acrylates having a linear alkyl group include linear alkyl esters of (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, n-lauryl (meth)acrylate, and n-stearyl (meth)acrylate.

[0070] The (meth)acrylate having a branched alkyl group is preferably one in which the branched alkyl group has 3 to 20 carbon atoms, more preferably one in which the branched alkyl group has 3 to 12 carbon atoms, and even more preferably one in which the branched alkyl group has 3 to 10 carbon atoms. Examples of the (meth)acrylate having a branched alkyl group include 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, which are branched alkyl esters of (meth)acrylic acid.

[0071] Examples of (meth)acrylates having an alkoxy group include alkoxyalkyl (meth)acrylates such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate.

[0072] Examples of (meth)acrylates having an alicyclic hydrocarbon group include (meth)acrylates having a cyclic alkyl group and (meth)acrylates having a polycyclic structure. Preferably, the (meth)acrylate having a cyclic alkyl group has 6 to 12 carbon atoms. Examples of cyclic alkyl groups include monocyclic alkyl groups (e.g., cycloalkyl groups), and may also have a chain-like portion. Specific examples of (meth)acrylates having a monocyclic cyclic alkyl group include cyclic alkyl esters of (meth)acrylic acid such as cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, and cyclododecyl (meth)acrylate.

[0073] The (meth)acrylate having a polycyclic structure is preferably a (meth)acrylate having a polycyclic structure with 6 to 12 carbon atoms. Examples of the polycyclic structure include cyclic alkyl groups having a cross-linking ring structure (e.g., adamantyl group, norbornyl group, isobornyl group), and may also have a chain portion. Specific examples of (meth)acrylates 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, and dicyclopentenyloxyethyl (meth)acrylate.

[0074] The (meth)acrylate having an aromatic group is preferably one having an aromatic group with 6 to 12 carbon atoms. Examples of aromatic groups include aryl groups, and may also have a chain portion, such as alkylaryl groups, araryl groups, and aryloxyalkyl groups. Examples of the (meth)acrylate having an aromatic group include compounds in which an aryl group is directly bonded to a (meth)acryloyloxy group, compounds in which an aralkyl group is directly bonded to a (meth)acryloyloxy group, and compounds in which an alkylaryl group is directly bonded to a (meth)acryloyloxy group. The number of carbon atoms in the aryl group is preferably 6 to 12. The number of carbon atoms in the aralkyl group is preferably 6 to 12. The number of carbon atoms in the alkylaryl group is preferably 6 to 12. Examples of (meth)acrylate having an aromatic group include benzyl (meth)acrylate, phenyl (meth)acrylate, and phenoxyethyl (meth)acrylate.

[0075] Examples of (meth)acrylates having a tertiary amino group include 2-(dimethylamino)ethyl (meth)acrylate and N,N-dimethylaminopropyl (meth)acrylate.

[0076] 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, etc. The (meth)acrylamides are (meth)acryl monomers but are not included in (meth)acrylate monomers.

[0077] Examples of (meth)acrylic monomers having a functional group that can become the first reactive group (b2) include (meth)acrylic monomers having a hydroxyl group (preferably (meth)acrylate monomers), (meth)acrylic monomers having a carboxyl group (preferably (meth)acrylic acid), and (meth)acrylic monomers having an epoxy group (preferably (meth)acrylate monomers). Among these, (meth)acrylic monomers having a hydroxyl group and / or (meth)acrylic monomers having a carboxyl group are preferred, and (meth)acrylic monomers having a hydroxyl group are more preferred.

[0078] Examples of (meth)acrylic monomers having a hydroxyl group include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, and 12-hydroxylauryl (meth)acrylate; hydroxyalkylcycloalkyl (meth)acrylates such as (4-hydroxymethylcyclohexyl)methyl (meth)acrylate; and caprolactone adducts of hydroxyalkyl (meth)acrylates. Among these, hydroxyalkyl (meth)acrylates are preferred, and (meth)acrylates having a hydroxyalkyl group with 1 to 5 carbon atoms are more preferred.

[0079] Examples of (meth)acrylic monomers having a carboxyl group include monomers obtained by reacting (meth)acrylates having a hydroxyl group, such as carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl maleate, and 2-(meth)acryloyloxyethyl phthalate, with acid anhydrides such as maleic anhydride, succinic anhydride, and phthalic anhydride (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.

[0080] Examples of (meth)acrylic acid esters having the epoxy group include glycidyl (meth)acrylate and 3,4-epoxycyclohexylmethyl (meth)acrylate.

[0081] Examples of vinyl monomers other than the (meth)acrylic monomers mentioned above include (b3) vinyl monomers other than (meth)acrylic monomers that do not have a functional group that can act as a primary reactive group, and (b4) vinyl monomers other than (meth)acrylic monomers that have a functional group that can act as a primary reactive group. These monomers may be used individually or in combination of two or more.

[0082] Examples of vinyl monomers other than (meth)acrylic monomers that do not have a functional group that can be the first reactive group (b3) include aromatic vinyl monomers, vinyl monomers containing heterocycles, vinyl carboxylates, vinyl monomers containing tertiary amino groups, vinyl amides, α-olefins, dienes, halogenated vinyl monomers, and the like.

[0083] Examples of the aromatic vinyl monomers include styrene, α-methylstyrene, 4-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methoxystyrene, and 1-vinylnaphthalene. Examples of vinyl monomers containing the heterocycle include 2-vinylthiophene, N-methyl-2-vinylpyrrole, 2-vinylpyridine, and 4-vinylpyridine. Examples of vinyl carboxylates include vinyl acetate, vinyl pivalate, and vinyl benzoate. Examples of vinyl monomers containing the aforementioned tertiary amino group include N,N-dimethylallylamine. Examples of the aforementioned vinylamides include N-vinylformamide, N-vinylacetamide, N-vinyl-2-pyrrolidone, and N-vinyl-ε-caprolactam. Examples of the α-olefins mentioned above include 1-hexene, 1-octene, and 1-decene. Examples of the aforementioned dienes include butadiene, isoprene, 4-methyl-1,4-hexadiene, and 7-methyl-1,6-octadiene. Examples of the aforementioned vinyl halogenated monomers include vinyl fluoride, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, tetrafluoropropylene, vinylidene chloride, vinyl chloride, 1-chloro-1-fluoroethylene, and 1,2-dichloro-1,2-difluoroethylene.

[0084] Examples of vinyl monomers other than (meth)acrylic monomers having a functional group that can be the first reactive group (b4) include vinyl monomers having a hydroxyl group, vinyl monomers having a carboxyl group, and vinyl monomers containing an epoxy group.

[0085] Examples of vinyl monomers having a hydroxyl group include p-hydroxystyrene and allyl alcohol. Examples of vinyl monomers having a carboxyl group include crotonic acid, maleic acid, itaconic acid, citraconic acid, and cinnamic acid. Examples of vinyl monomers containing the epoxy group include 2-allyloxirane, glycidyl vinyl ether, and 3,4-epoxycyclohexyl vinyl ether.

[0086] The (meth)acrylic polymer (A) preferably has a structural unit content of 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, preferably 99% by mass or less, more preferably 97% by mass or less, and even more preferably 96% by mass or less, of structural units derived from (meth)acrylate having an alkyl group having 1 to 12 carbon atoms. As the (meth)acrylate having an alkyl group having 1 to 12 carbon atoms, (meth)acrylate having a linear alkyl group having 1 to 12 carbon atoms and (meth)acrylate having a branched alkyl group having 1 to 12 carbon atoms are preferred.

[0087] When polymerizing the monomer composition, either free radical polymerization or living radical polymerization can be used. Living radical polymerization is preferred for the (meth)acrylic polymer (A). That is, (meth)acrylic polymer (A) is preferably polymerized by living radical polymerization. Similarly, living radical polymerization is preferred for the (meth)acrylic polymer (B). That is, (meth)acrylic polymer (B) is preferably polymerized by living radical polymerization. Living radical polymerization is preferable because it maintains the simplicity and versatility of conventional radical polymerization while being less prone to termination reactions and chain transfer, and because it grows without being hindered by side reactions that deactivate the growth ends, thus facilitating precise control of molecular weight distribution and the production of polymers with a uniform composition.

[0088] (Living radical polymerization method) Living radical polymerization methods include those that use compounds capable of generating nitroxide radicals (nitroxide method; NMP method), which differ in the method of stabilizing the polymerization growth ends; those that use metal complexes such as copper or ruthenium, with halogenated compounds as polymerization initiators, and polymerize them in a living manner (ATRP method); those that use dithiocarboxylic acid esters or xantate compounds (RAFT method); those that use organotellurium compounds (TERP method); those that use organiodine compounds (ITP method); and those that use iodine compounds as polymerization initiators and organic compounds such as phosphorus compounds, nitrogen compounds, oxygen compounds, or hydrocarbons as catalysts (reversible transfer catalytic polymerization; RTCP method, reversible catalyst-mediated polymerization; RCMP method). Among these methods, the TERP method is preferred from the viewpoint of the diversity of monomers that can be used, molecular weight control in the polymer range, uniform composition, and coloration.

[0089] The TERP method is a method for polymerizing radical polymerizable compounds (vinyl monomers) using an organotellurium compound as a chain transfer agent, and is described, for example, in International Publication Nos. 2004 / 14848, 2004 / 14962, 2004 / 072126, and 2004 / 096870.

[0090] Specific polymerization methods for the TERP method include the following (a) to (d). (a) A method for polymerizing vinyl monomers using an organotellurium compound represented by formula (1). (b) A method for polymerizing vinyl monomers using a mixture of an organic tellurium compound represented by formula (1) and an azo polymerization initiator. (c) A method for polymerizing vinyl monomers using a mixture of an organic tellurium compound represented by formula (1) and an organic diterlide compound represented by formula (2). (d) A method for polymerizing vinyl monomers using a mixture of an organic tellurium compound represented by formula (1), an azo polymerization initiator, and an organic diterlide compound represented by formula (2).

[0091] [ka] [In equation (1), R 1 R is an alkyl group, aryl group, or aromatic heterocyclic group having 1 to 8 carbon atoms. 2 and R 3 Each of these is independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. 4 These are alkyl groups, aryl groups, substituted aryl groups, aromatic heterocyclic groups, alkoxy groups, acyl groups, amide groups, oxycarbonyl groups, cyano groups, allyl groups, or propargyl groups having 1 to 8 carbon atoms. In equation (2), R 1 This is an alkyl group, aryl group, or aromatic heterocyclic group having 1 to 8 carbon atoms.

[0092] Specific examples of organotellurium compounds represented by formula (1) include ethyl=2-methyl-2-n-butylteranyl-propionate, ethyl=2-n-butylteranyl-propionate, (2-hydroxyethyl)=2-methyl-methylteranyl-propionate, and other organotellurium compounds described in International Publication Nos. 2004 / 14848, 2004 / 14962, 2004 / 072126, and 2004 / 096870. Specific examples of organoditerlide compounds represented by formula (2) include dimethylditerlide and dibutylditerlide. Any azo polymerization initiator used in normal radical polymerization can be used without particular restrictions, such as 2,2'-azobis(isobutyronitrile) (AIBN), 2,2'-azobis(2,4-dimethylvaleronitrile) (ADVN), 1,1'-azobis(1-cyclohexanecarbonitride) (ACHN), and 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70).

[0093] The polymerization step involves mixing a vinyl monomer, an organic tellurium compound of formula (1), and, depending on the type of vinyl monomer, an azo polymerization initiator and / or an organic diterlide compound of formula (2) in a container purged with an inert gas, for purposes such as promoting the reaction, controlling the molecular weight and molecular weight distribution. Examples of inert gases used include nitrogen, argon, and helium. Argon and nitrogen are preferred. The amount of vinyl monomer used in (a), (b), (c), and (d) above may be adjusted as appropriate depending on the physical properties of the desired polymer.

[0094] The polymerization reaction can be carried out without a solvent, but it may also be carried out using an aprotic or protic solvent commonly used in radical polymerization, while stirring the mixture. Examples of usable aprotic solvents 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, and carbon tetrachloride. Examples of protic solvents include water, methanol, ethanol, isopropanol, n-butanol, ethyl cellosolve, butyl cellosolve, 1-methoxy-2-propanol, hexafluoroisopropanol, and diacetone alcohol. Solvents may be used alone or in combination of two or more. The amount of solvent used can be adjusted as appropriate; for example, 0.01 ml to 50 ml per 1 g of vinyl monomer is preferred. The reaction temperature and reaction time can be adjusted as appropriate depending on the molecular weight or molecular weight distribution of the resulting polymer components, but typically, the reaction is carried out at 0°C to 150°C for 1 minute to 100 hours with stirring. At this time, the reaction is usually carried out at atmospheric pressure, but it may also be carried out under increased or decreased pressure. After the polymerization reaction is complete, the target polymer can be separated from the resulting reaction mixture by removing the solvent used, residual vinyl monomers, etc., using conventional separation and purification methods.

[0095] The growth ends of the polymer obtained by the polymerization reaction are derived from the tellurium compound -TeR1 (where R 1 is the same as described above), and it is deactivated by operations in air after the polymerization reaction, but tellurium atoms may remain. Since the polymer with tellurium atoms remaining at the ends may be colored or have poor thermal stability, it is preferable to remove the tellurium atoms. Examples of 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. Incidentally, the other end (the end opposite to the growing end) of the polymer obtained by the polymerization reaction is -CR 2 R 3 R 4 (where R 2 , R 3 and R 4 are the same as R 2 , R 3 and R 4 in formula (1).).

[0096] (Free Radical Polymerization Method) Free radical polymerization can be carried out using conventionally known methods. Polymerization initiators used in free radical polymerization include azo-based polymerization initiators and peroxide-based polymerization initiators. Examples of azo-based polymerization initiators include 2,2'-azobis(isobutyronitrile) (AIBN), 2,2'-azobis(2-methylbutyronitrile) (AMBN), 2,2'-azobis(2,4-dimethylvaleronitrile) (ADVN), 1,1'-azobis(1-cyclohexanecarbonitride) (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), and 2,2'-azobis Examples include (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-propylazoformamide, 2,2'-azobis(N-butyl-2-methylpropionamide), or 2,2'-azobis(N-cyclohexyl-2-methylpropionamide).

[0097] The polymerization reaction can be carried out without a solvent, but it may also be carried out using an aprotic or protic solvent commonly used in radical polymerization, while stirring the mixture. Examples of usable aprotic solvents 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, propylene glycol monomethyl ether acetate, or trifluoromethylbenzene. Examples of protic solvents include water, methanol, ethanol, isopropanol, n-butanol, ethyl cellosolve, butyl cellosolve, 1-methoxy-2-propanol, hexafluoroisopropanol, or diacetone alcohol.

[0098] The amount of solvent used can be adjusted as appropriate. For example, per 1 g of vinyl monomer, 0.01 ml or more is preferred, more preferably 0.05 ml or more, even more preferably 0.1 ml or more, 50 ml or less is preferred, more preferably 10 ml or less, and even more preferably 1 ml or less.

[0099] The reaction temperature and reaction time can be adjusted as appropriate depending on the molecular weight or molecular weight distribution of the resulting polymer components, but typically, the reaction is carried out at 0°C to 150°C for 1 minute to 100 hours with stirring. At this time, the reaction is usually carried out at atmospheric pressure, but it may also be carried out under increased or decreased pressure. After the polymerization reaction is complete, the target polymerization composition can be separated from the reaction mixture by removing the solvent used, residual vinyl monomers, etc., using conventional separation and purification methods.

[0100] (Crosslinking agent) The adhesive composition contains a crosslinking agent. The crosslinking agent is a compound having two or more secondary reactive groups in one molecule that react with the primary reactive group of the (meth)acrylic polymer described above. The crosslinking agent is not particularly limited and examples include isocyanate crosslinking agents, epoxy crosslinking agents, aziridine crosslinking agents, metal chelate crosslinking agents, melamine resin crosslinking agents, urea resin crosslinking agents, etc. One type of crosslinking agent may be used alone, or two or more types may be used in combination. Among these, isocyanate crosslinking agents and epoxy crosslinking agents are preferred.

[0101] The average number of secondary reactive groups in one molecule of the crosslinking agent is 2 or more, preferably 8 or less, and more preferably 6 or less. 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, even more preferably 1000 or less, and even more preferably 700 or less.

[0102] The content of the second reactive group in the crosslinking agent is preferably 1.5 mmol / g or more, more preferably 3 mmol / g or more, even more preferably 3.7 mmol / g or more, preferably 10 mmol / g or less, and more preferably 8 mmol / g or less. When the content of the second reactive group in the crosslinking agent is within this range, the valency of the crosslinking agent is low, the crosslinking points are evenly distributed within the adhesive, and the average distance between crosslinking points becomes longer. Therefore, the resulting adhesive has low initial stress and exhibits high resilience.

[0103] Examples of combinations between the first reactive group of the (A)(meth)acrylic polymer and the (B)(meth)acrylic polymer 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, a hydroxyl group can be cited as the first reactive group. When the second reactive group of the crosslinking agent is an epoxy group, a carboxyl group can be cited as the first reactive group.

[0104] The preferred combinations of the first reactive group of the (meth)acrylic polymer (A) and the (meth)acrylic polymer (B) and the second reactive group of the crosslinking agent are: (1) a combination in which the first reactive group is a hydroxyl group and the second reactive group is an isocyanate group; and (2) a combination in which the first reactive group is a carboxyl group and the second reactive group is an epoxy group.

[0105] (Isocyanate-based crosslinking agent) An isocyanate-based crosslinking agent is a compound having two or more isocyanate groups (including isocyanate-regenerating functional groups in which the isocyanate groups are temporarily protected by a blocking agent or quantification, etc.) as a secondary reactive group in one molecule. The isocyanate-based crosslinking agent may be used alone or in combination of two or more types.

[0106] Examples of isocyanate-based crosslinking agents include aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, adducts of these with various polyols, and polyfunctionalized polyisocyanates with isocyanurate bonds, biuret bonds, allophanate bonds, etc. Specifically, examples include compounds having two isocyanate groups (including isocyanate regenerating functional groups in which the isocyanate groups are temporarily protected by a blocking agent or quantification, etc.) in one molecule (bifunctional isocyanate crosslinking agents), compounds having three isocyanate groups (including isocyanate regenerating functional groups in which the isocyanate groups are temporarily protected by a blocking agent or quantification, etc.) in one molecule (trifunctional isocyanate crosslinking agents), or compounds having six isocyanate groups (including isocyanate regenerating functional groups in which the isocyanate groups are temporarily protected by a blocking agent or quantification, etc.) in one molecule (hexafunctional isocyanate crosslinking agents), and so on.

[0107] Examples of bifunctional isocyanate crosslinking agents include diisocyanate compounds such as aliphatic diisocyanate compounds, alicyclic diisocyanate compounds, and aromatic diisocyanate compounds. Additives of these diisocyanate compounds with diol compounds can also be used. Diisocyanate compounds are compounds represented by the general formula "O=C=NXN=C=O" (where X is a divalent aliphatic group, a divalent alicyclic group, a divalent aromatic group, etc.). Diol compounds are compounds represented by the general formula "HO-Y-OH" (where Y is a divalent aliphatic group, a divalent alicyclic group, a divalent aromatic group, etc.).

[0108] Examples of aliphatic diisocyanate compounds include ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, and 2,2,4-trimethyl-1,6-hexamethylene diisocyanate. 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.

[0109] Examples of alicyclic diisocyanate compounds include isophorone diisocyanate, cyclopentyl diisocyanate, cyclohexyl diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogenated tetramethylxylene diisocyanate. Among these, alicyclic diisocyanate compounds with 7 to 30 carbon atoms are preferred.

[0110] Examples of aromatic diisocyanate compounds include phenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, naphthylene diisocyanate, diphenyl ether diisocyanate, diphenylmethane diisocyanate, and diphenylpropane diisocyanate, with aromatic diisocyanate compounds having 8 to 30 carbon atoms being preferred.

[0111] Examples of the aforementioned diol compounds 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, and polypropylene glycol, among which aliphatic diol compounds having 3 to 10 carbon atoms are preferred.

[0112] Examples of the aforementioned trifunctional isocyanate crosslinking agents include the adduct form of the diisocyanate compound, the biuret form of the diisocyanate compound, and the isocyanurate form of the diisocyanate compound (cyclic polymers of diisocyanate compounds).

[0113] Preferably, the isocyanate crosslinking agent does not have an aromatic ring. In particular, preferred isocyanate crosslinking agents include bifunctional isocyanate crosslinking agents selected from the group consisting of aliphatic diisocyanate compounds and adducts of aliphatic diol compounds; and trifunctional or hexafunctional isocyanate crosslinking agents selected from the group consisting of adducts of aliphatic diisocyanate compounds, biuret compounds of aliphatic diisocyanate compounds, and isocyanurate compounds of aliphatic diisocyanate compounds.

[0114] (Epoxy crosslinking agent) An epoxy crosslinking agent is a compound having two or more epoxy groups as secondary reactive groups in one molecule. The epoxy crosslinking agent may be used alone or in combination of two or more types.

[0115] Examples of epoxy crosslinking agents include aliphatic epoxy compounds, alicyclic epoxy compounds, aromatic epoxy compounds, and heterocyclic epoxy compounds.

[0116] Examples of the aliphatic epoxy compounds include ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, trimethylolpropane diglycidyl ether, trimethylolpropane polyglycidyl ether, diglycidylamine, neopentyl glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, glycerin diglycidyl ether, ricerin triglycidyl ether, polyglycerol polyglycidyl ether, diglycidyl adipic acid ester, and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane.

[0117] Examples of the alicyclic epoxy compound include 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, and N,N,N',N'-tetraglycidyl-m-xylylenediamine.

[0118] Examples of the aromatic epoxy compounds include bisphenol A epichlorohydrin type epoxy resins, diglycidylaniline, o-phthalate diglycidyl esters, resorcinol diglycidyl ethers, and bisphenol-S-diglycidyl ethers.

[0119] Examples of the aforementioned heterocyclic epoxy compounds include triglycidyl-tris(2-hydroxyethyl) isocyanurate, 1,3,5-tris-(2,3-epoxybutyl)-isocyanurate, 1,3,5-tris-(3,4-epoxybutyl)-isocyanurate, 1,3,5-tris-(4,5-epoxypentyl)-isocyanurate, and sorbitan polyglycidyl ether.

[0120] The epoxy crosslinking agent is preferably a compound having two epoxy groups in one molecule (a difunctional epoxy crosslinking agent), a compound having three epoxy groups in one molecule (a trifunctional epoxy crosslinking agent), or a compound having four epoxy groups in one molecule (a tetrafunctional epoxy crosslinking agent). If the crosslinking agent is a difunctional epoxy crosslinking agent, a trifunctional epoxy crosslinking agent, or a tetrafunctional epoxy crosslinking agent, the crosslinking points will be evenly distributed within the adhesive, and the average distance between crosslinking points will be long. Therefore, the resulting adhesive will have low initial stress and high resilience.

[0121] The adhesive composition preferably contains only an isocyanate-based crosslinking agent or only an epoxy-based crosslinking agent. When containing only an isocyanate-based crosslinking agent, it is preferable to contain only a bifunctional isocyanate-based crosslinking agent having two isocyanate groups per molecule, a trifunctional isocyanate-based crosslinking agent having three isocyanate groups per molecule, or a hexafunctional isocyanate-based crosslinking agent having six isocyanate groups per molecule. Furthermore, when containing only an epoxy-based crosslinking agent, it is preferable to contain only a bifunctional epoxy-based crosslinking agent having two epoxy groups per molecule, a trifunctional epoxy-based crosslinking agent having three epoxy groups per molecule, or a tetrafunctional epoxy-based crosslinking agent having four epoxy groups per molecule.

[0122] The crosslinking agent content in the adhesive composition is preferably 0.05 parts by mass or more, more preferably 0.07 parts by mass or more, preferably 0.4 parts by mass or less, and more preferably 0.3 parts by mass or less, per 100 parts by mass of the total polymer components. When the crosslinking agent content is within the above range, the flexibility and resilience are within a suitable range.

[0123] The molar ratio (moles of the first reactive group / molars of the second reactive group) of the second reactive group in the crosslinking agent to the first reactive group in the (meth)acrylic polymer in the polymer component is 1 or more, preferably 1.5 or more, more preferably 2.0 or more, preferably 80 or less, more preferably 50 or less, even more preferably 30 or less, and particularly preferably 20 or less. If the molar ratio is 1 or more, the crosslinking agent reacts without excess or deficiency, there is no excess of the second reactive group, and high flexibility is exhibited. If it is 80 or less, the reaction proceeds sufficiently and high resilience is exhibited.

[0124] (Other additives) In addition to the polymer component and crosslinking agent, other additives may be added to the aforementioned adhesive composition. Examples of other additives include crosslinking accelerators, crosslinking retarders, tackifiers, polymerizable compounds, photopolymerization initiators, silane coupling agents, plasticizers, softeners, release aids, dyes, pigments, fluorescent whitening agents, antistatic agents, wetting agents, surfactants, thickeners, antifungal agents, preservatives, oxygen absorbers, ultraviolet absorbers, antioxidants, near-infrared absorbers, water-soluble quenchers, fragrances, metal deactivators, nucleating agents, alkylating agents, flame retardants, lubricants, and processing aids. These are selected and added as appropriate depending on the application and intended use of the adhesive.

[0125] (Crosslinking promoter) The adhesive composition may be used with a crosslinking accelerator added 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 types.

[0126] Examples of the organotin compounds include dibutyltin dilaurate, dioctyolustin dilaurylate, and dibutyltin dioctylate. The metal chelate compound is a complex in which ligands having two or more coordinating atoms form a ring and are bonded to a central metal.

[0127] The content of the crosslinking accelerator in the adhesive composition is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, even more preferably 0.04 parts by mass or more, preferably 0.5 parts by mass or less, more preferably 0.4 parts by mass or less, and even more preferably 0.3 parts by mass or less, per 100 parts by mass of the polymer component. By setting the content of the crosslinking accelerator within the above range, it is possible to obtain an excellent crosslinking promoting effect.

[0128] (Crosslinking retarder) The adhesive composition may be used with a crosslinking retarder if necessary. The crosslinking retarder is a compound that can suppress an excessive increase in the viscosity of the adhesive composition by blocking the functional groups of the crosslinking agent in the adhesive composition containing the crosslinking agent. The type of crosslinking retarder is not particularly limited, but 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. The crosslinking retarder is preferably one that can act as a chelating agent, and β-diketones and β-ketoesters are preferred.

[0129] The amount of crosslinking retarder that can be incorporated into the adhesive composition is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, even more preferably 0.5 parts by mass or more, preferably 4.0 parts by mass or less, more preferably 3.0 parts by mass or less, and even more preferably 1.5 parts by mass or less, per 100 parts by mass of the polymer component. By adjusting the amount of the crosslinking retarder within the above range, it is possible to suppress excessive viscosity increase and gelation of the adhesive composition after incorporating the crosslinking agent into the adhesive composition, and to extend the storage stability (pot life) of the adhesive composition.

[0130] (Adhesive-granting resin) The adhesive composition may be used with a tackifying resin other than the polymer component, as needed. The tackifying resin is not particularly limited, but examples include rosin-based tackifying resins, terpene-based tackifying resins, phenol-based tackifying resins, hydrocarbon-based tackifying resins, and the like.

[0131] Examples of rosin-based tackifying resins include unmodified rosin (raw rosin) such as gum rosin, wood rosin, and tall oil rosin, as well as modified rosin (polymerized rosin, stabilized rosin, disproportionated rosin, fully hydrogenated rosin, partially hydrogenated rosin, and other chemically modified rosin) obtained by polymerization, disproportionation, hydrogenation, etc., and various rosin derivatives.

[0132] Examples of the rosin derivatives include rosinphenol resins obtained by adding phenol to rosins (unmodified rosin, modified rosin) with an acid catalyst and then thermal polymerization; rosin ester resins such as ester compounds of rosin obtained by esterifying unmodified rosin with alcohols (unmodified rosin esters) and ester compounds of modified rosin obtained by esterifying modified rosin with alcohols (polymerized rosin esters, stabilized rosin esters, disproportionated rosin esters, fully hydrogenated rosin esters, partially hydrogenated rosin esters, etc.); unsaturated fatty acid modified rosin resins obtained by modifying unmodified rosin or modified rosin with unsaturated fatty acids; unsaturated fatty acid modified rosin ester resins obtained by modifying rosin ester resins with unsaturated fatty acids; rosin alcohol resins obtained by reducing the carboxyl groups in unmodified rosin, modified rosin, unsaturated fatty acid modified rosin resins, and unsaturated fatty acid modified rosin ester resins; and metal salts of rosin resins (especially rosin ester resins) such as unmodified rosin and modified rosin.

[0133] Examples of terpene-based tackifying resins include terpene resins such as α-pinene polymers, β-pinene polymers, and dipentene polymers, as well as modified terpene resins obtained by modifying these terpene resins (phenol modification, aromatic modification, hydrogenation modification, hydrocarbon modification, etc.) (for example, terpene-phenol resins, styrene-modified terpene resins, aromatic-modified terpene resins, and hydrogenated terpene resins).

[0134] Examples of phenolic tackifying resins include condensates of various phenols (e.g., phenol, m-cresol, 3,5-xylenol, p-alkylphenol, resorcinol) and formaldehyde (e.g., alkylphenol resins, xyleneformaldehyde resins), resols obtained by addition reaction of the phenols and formaldehyde with an alkaline catalyst, and novolacs obtained by condensation reaction of the phenols and formaldehyde with an acid catalyst.

[0135] Examples of hydrocarbon-based tackifying resins (petroleum-based tackifying resins) include aliphatic hydrocarbon resins [polymers of aliphatic hydrocarbons such as olefins and dienes with 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 resins obtained by cyclizing and then polymerizing so-called "C4 petroleum fractions" or "C5 petroleum fractions," cyclic diene compounds (cyclopentadiene, dicyclopentadiene, ethylidene norbornene, di Examples include polymers of pentene (such as pentene) or hydrogenated thereof, alicyclic hydrocarbon resins obtained by hydrogenating the aromatic rings of aromatic hydrocarbon resins and aliphatic-aromatic petroleum resins listed below, aromatic hydrocarbon resins [polymers of vinyl group-containing aromatic hydrocarbons with 8 to 10 carbon atoms (styrene, vinyltoluene, α-methylstyrene, indene, methylindene, etc.)], aliphatic-aromatic petroleum resins (styrene-olefin copolymers, etc.), aliphatic-alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone resins, coumarone-indene resins, etc.

[0136] The amount of tackifying resin that can be incorporated into the adhesive composition is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 20 parts by mass or more, preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 40 parts by mass or less, per 100 parts by mass of the polymer component. By adjusting the amount of tackifying resin within the above range, sufficient adhesion to the adherend can be ensured.

[0137] (Polymerizable Compounds) The adhesive composition may contain polymerizable compounds. By incorporating polymerizable compounds and polymerizing them in the adhesive, flexibility can be imparted to the adhesive.

[0138] Examples of polymerizable compounds include compounds having two or more polymerizable groups in one molecule. Examples of polymerizable groups include ethylenically unsaturated groups. The polymerizable compounds can be used alone or in combination of two or more. Examples of polymerizable compounds 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 two or more, preferably four or less, and more preferably three or less.

[0139] Examples of compounds 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, isocyanurate ethylene oxide modified tri(meth)acrylate, allyl(meth)acrylate, vinyl(meth)acrylate, and urethane(meth)acrylate.

[0140] When a polymerizable compound is incorporated into the adhesive composition, the content of the polymerizable compound is preferably 0.1 parts 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, per 100 parts by mass of the polymer component.

[0141] (Photopolymerization initiator) When curing the polymerizable compound with active energy rays, it is preferable to incorporate a photopolymerization initiator into the adhesive composition. By incorporating a photopolymerization initiator, the reaction during irradiation with active energy rays can be stabilized. The photopolymerization initiator is not particularly limited as long as it generates radicals upon the action of light, and examples include photopolymerization initiators such as acetophenones, benzoins, thioxanthones, and acylphosphine oxides. These photopolymerization initiators can be used alone or in combination of two or more. Among these photopolymerization initiators, hydrogen abstraction type benzophenones and intramolecular cleavage type acetophenones are preferred because they can efficiently crosslink between molecules at an intermolecular or intramolecular level.

[0142] When a photopolymerization initiator is incorporated into the adhesive composition, the content of the photopolymerization initiator is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.5 parts by mass or more, preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 2 parts by mass or less, per 100 parts by mass of the polymer component. If the content of the photopolymerization initiator is within the above range, the curing speed can be improved and insufficient curing can be suppressed.

[0143] Furthermore, the adhesive composition may also contain an auxiliary agent for the photopolymerization initiator. Examples of the auxiliary agents that can be used in combination include triethanolamine, triisopropanolamine, 4,4'-dimethylaminobenzophenone (Michler ketone), 4,4'-diethylaminobenzophenone, 2-dimethylaminoethylbenzoic acid, ethyl 4-dimethylaminobenzoate, (n-butoxy)ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, 2-ethylhexyl 4-dimethylaminobenzoate, 2,4-diethylthioxanthone, and 2,4-diisopropylthioxanthone. These auxiliary agents may also be used alone or in combination of two or more.

[0144] (Silane coupling agent) The adhesive composition may be used with a silane coupling agent as needed. The silane coupling agent is not particularly limited, but examples include epoxy group-containing silane coupling agents such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 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, and N-phenyl-γ-aminopropyltrimethoxysilane; (meth)acrylic group-containing silane coupling agents such as 3-acryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane; and isocyanate group-containing silane coupling agents such as 3-isocyanatetopropyltriethoxysilane.

[0145] The amount of silane coupling agent that can be incorporated into the adhesive composition is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, preferably 1 part by mass or less, more preferably 0.8 parts by mass or less, and even more preferably 0.6 parts by mass or less, per 100 parts by mass of the polymer component. By adjusting the amount of silane coupling agent within the above range, the water resistance at the interface when the adhesive is applied to a hydrophilic substrate such as glass can be improved.

[0146] (Plasticizer) The adhesive composition may contain a plasticizer as needed. The plasticizer is not particularly limited, but examples include 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. The plasticizer may be used alone or in combination of two or more. Among these, liquid rubber is preferred.

[0147] The weight-average molecular weight (Mw) of the liquid rubber is preferably 5,000 or more, more preferably 10,000 or more, preferably 60,000 or less, and more preferably 50,000 or less. By adjusting the Mw of the liquid rubber to the above range, an adhesive with excellent flexibility can be formed. The method for measuring the weight-average molecular weight (Mw) will be described later.

[0148] When a plasticizer is incorporated into the adhesive composition, the plasticizer content is preferably 1 part by mass or more, more preferably 5 parts by mass or more, even more preferably 10 parts by mass or more, preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less, per 100 parts by mass of the polymer component. By adjusting the plasticizer content within the above range, an adhesive with excellent tackiness and resilience can be formed.

[0149] (Method for manufacturing adhesive composition) The adhesive composition can be manufactured by mixing the polymer component, a crosslinking agent, and other additives as needed. The adhesive composition may contain a solvent derived from the manufacture of the polymer component, or it may be a solution diluted with an additional suitable solvent to achieve a viscosity suitable for forming an adhesive layer.

[0150] Examples of the aforementioned solvents 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 individually or in combination of two or more.

[0151] The amount of solvent used can be adjusted as appropriate so that the adhesive composition has a viscosity suitable for coating, and there are no particular restrictions. However, from the viewpoint of coating properties, for example, 1% to 90% by mass is preferred, more preferably 10% to 80% by mass, and even more preferably 20% to 70% by mass.

[0152] The adhesive material of the present invention can be formed by applying and drying the adhesive composition. Furthermore, the coating film may be heated as needed to promote the formation of a crosslinked structure.

[0153] [Adhesive sheet] The adhesive sheet of the present invention comprises a base sheet and an adhesive layer formed on at least one surface of the base sheet, wherein the adhesive layer is the adhesive material. The adhesive layer is formed on at least one side or at least a portion of the base sheet. The adhesive layer may be a single layer or a multilayer structure.

[0154] Generally, a "sheet," according to the JIS definition, refers to a thin, flat product whose thickness is generally small relative to its length and width, while a "film," generally, refers to a thin, flat product whose thickness is extremely small relative to its length and width, with a maximum thickness arbitrarily limited, and which is usually supplied in roll form (Japanese Industrial Standard JIS K6900). For example, in terms of thickness, in a narrow sense, products with a thickness of 100 μm or more are sometimes called sheets, and those with a thickness of less than 100 μm are sometimes called films. However, the boundary between sheets and films is not clear, and there is no need to distinguish between the two in the wording of this invention, so in this invention, the term "sheet" includes "film," and the term "film" includes "sheet."

[0155] (Base sheet) The base sheet can be appropriately selected and used depending on the application of the adhesive sheet. Examples of base sheets include sheets composed of polymer materials such as polyimide resin, polyester resins such as polyethylene terephthalate (PET) resin and polyethylene naphthalate (PEN) resin, polycarbonate resin, poly(meth)acrylate resin, polystyrene resin, polyamide resin, polyacrylonitrile resin, polyolefin resins such as polypropylene resin, polyethylene resin, polycycloolefin resin, and cycloolefin copolymer resin, polyphenylene sulfide resin, polysulfone resin, polyethersulfone resin, polyetheretherketone resin, polyarylate resin, polyetherimide resin, cellulose resins such as triacetylcerose (TAC) resin and diacetylcellulose resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyvinyl alcohol resin, polyvinyl acetate resin, and fluororesin. The polymer materials can be used individually or in combination of two or more. Among these, PET resin is preferred in terms of its excellent mechanical strength and dimensional stability. Polyimide resin is preferred in terms of its excellent heat resistance. In other words, the base sheet is preferably a PET sheet (particularly a biaxially oriented PET sheet) or a polyimide sheet.

[0156] The thickness of the base sheet is not particularly limited and can be selected as appropriate, but is generally preferred to be 5 μm or more, more preferably 10 μm or more, even more preferably 20 μm or more, preferably 200 μm or less, more preferably 100 μm or less, and even more preferably 50 μm or less. If the thickness is less than 5 μm, the strength of the base sheet will be insufficient, and problems such as the sheet tearing when peeled will occur. Also, if the thickness of the base sheet is greater than 200 μm, problems such as the sheet itself becoming expensive will occur.

[0157] The aforementioned base sheet may be surface-treated on one or both sides, if desired, by oxidation, embossing, or other methods, in order to improve adhesion with the layer provided on its surface. Examples of oxidation methods include corona discharge treatment, plasma treatment, chromic acid treatment (wet), flame treatment, hot air treatment, and ozone / ultraviolet irradiation treatment. Examples of embossing methods include sandblasting and solvent treatment. These surface treatment methods are appropriately selected depending on the type of base sheet, but corona discharge treatment is generally preferred in terms of effectiveness and ease of operation. Furthermore, a base sheet that has been primer-treated on one or both sides can also be used.

[0158] The thickness of the adhesive (adhesive layer) formed on the base sheet can be appropriately set according to, for example, the required adhesive strength of the adhesive sheet. Generally, the thickness of the adhesive layer is preferably 1 μm or more, more preferably 5 μm or more, even more preferably 10 μm or more, preferably 100 μm or less, more preferably 70 μm or less, and even more preferably 50 μm or less.

[0159] (Formation of an adhesive layer) The method for forming the adhesive layer is not particularly limited, and examples include applying an adhesive composition as in (1) and (2) below and then drying it. (1) A method of applying an adhesive composition to one or both sides of a substrate sheet using various coating equipment, drying and removing the solvent, and curing as necessary. (2) A method of applying an adhesive composition to the release surface of a release sheet that has been treated to release the surface using various coating devices, drying and removing the solvent, transferring it to one or both sides of a base sheet, and then curing as necessary.

[0160] Examples of the coating apparatus include reverse roll coaters, gravure coaters, forward roll coaters, knife coaters, wire bar coaters, doctor blade coaters, slot die coaters, curtain coaters, and dip coaters.

[0161] The drying temperature when removing the solvent is preferably 40°C or higher, more preferably 60°C or higher, preferably 150°C or lower, more preferably 140°C or lower, and even more preferably 130°C or lower. The drying time is preferably 5 seconds to 20 minutes, more preferably 10 seconds to 10 minutes. Examples of drying methods include hot air, near-infrared rays, infrared rays, and high-frequency waves. Examples of curing conditions include 30°C to 60°C for about 3 to 7 days.

[0162] (Release sheet) The adhesive sheet may have a release sheet (separator) on the surface of the adhesive layer until it is used. Alternatively, without using a separate release sheet, the release layer may be provided on the side of the base sheet opposite to the adhesive layer lamination surface, and the sheet may be wound in a roll shape or laminated in layers so that the exposed side of the adhesive layer is in contact with the surface of the release layer. The release sheet is used as a protective material for the adhesive layer and is peeled off when the adhesive sheet of the present invention is attached to an object.

[0163] Examples of the release sheet include paper such as glassine paper, coated paper, and laminated paper, as well as various plastic sheets coated with a release agent such as silicone resin. The plastic sheets used for the release sheet can be any of the materials listed above. There are no particular restrictions on the thickness of the release sheet, but it is typically 10 μm to 150 μm.

[0164] (Uses of adhesives) The adhesive material of the present invention is preferably used in adhesive layers (adhesives) for flexible displays that can be repeatedly bent and stretched. Examples of such flexible displays that can be repeatedly bent and stretched include foldable displays that can be folded and rollable displays that can be rolled into a cylindrical shape. Flexible displays are expected to be used in portable devices such as smartphones and tablet devices, as well as in stationary displays that can be stored.

[0165] [Adhesives for flexible displays, adhesive sheets for flexible displays] As an adhesive for flexible displays, it is suitable for bonding one flexible component to another flexible component that constitutes a flexible display.

[0166] The adhesive sheet for a flexible display comprises an adhesive layer used to bond one flexible member constituting a flexible display to another flexible member, and a flexible sheet member attached to at least one surface of the adhesive layer, wherein the adhesive layer is formed from the adhesive material.

[0167] The configuration of the adhesive sheet for the flexible display includes an adhesive layer and a first flexible sheet member attached to one side of the adhesive layer; and an adhesive layer and a first flexible sheet member attached to one side of the adhesive layer and a second flexible sheet member attached to the other side of the adhesive layer.

[0168] Figure 1 shows an example of the adhesive sheet for flexible displays of the present invention. The adhesive sheet 10 for flexible displays in Figure 1 consists 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 surfaces of the first flexible sheet member 14 and the second flexible sheet member 16.

[0169] (Adhesive layer) The adhesive layer is formed from the adhesive material. The thickness of the adhesive layer is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more, from the viewpoint of ensuring sufficient adhesion to the adherend. Furthermore, 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, from the viewpoint of suppressing the overflow of the adhesive layer.

[0170] (Flexible sheet material) Examples of the flexible sheet member include a base sheet with flexibility, a release sheet, and the like. The base 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 phase difference film, an optical compensation film, a brightness-enhancing film, a diffusion film, an anti-reflective film, and the like. The release sheet protects the adhesive layer until it is attached to the substrate, and is peeled off from the adhesive layer before it is attached to the substrate.

[0171] Examples of the flexible sheet material include polymer sheets and glass sheets. The thickness of the flexible sheet material is not particularly limited, but from the viewpoint of ease of handling, it is preferably 2 μm to 500 μm, and more preferably 2 μm to 200 μm.

[0172] Examples of the polymer materials 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, polycycloolefin resin, and cycloolefin copolymer resin; polyphenylene sulfide resin; polyvinyl chloride resin; polyvinylidene chloride resin; and polyvinyl alcohol resin. These polymer materials can be used individually or in combination of two or more.

[0173] The flexible sheet member may consist of a single layer comprising one or more of the polymer materials, or it may consist of two or more layers, such as a layer comprising one or more of the polymer materials and a layer comprising one or more of a different polymer material.

[0174] The flexible sheet member is preferably a release sheet with a release treatment applied to the surface that comes into contact with the adhesive layer. Examples of release agents used in the release treatment include silicone-based, fluorine-based, alkyd-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents.

[0175] The adhesive sheet for the flexible display comprises a first flexible sheet member attached to one side of the adhesive layer and a second flexible sheet member attached to the other side of the adhesive layer, wherein the first flexible sheet member is a first release sheet and the second flexible sheet member is a second release sheet, and it is preferable that the first and second release sheets are attached so 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 be a heavy-peel type with a high peeling force and the other release sheet be a light-peel type with a low peeling force.

[0176] A flexible display adhesive sheet can be manufactured, for example, by coating the above-mentioned adhesive composition onto a flexible sheet member and curing it by drying and heat treatment as needed to form an adhesive layer.

[0177] Various coating methods such as reverse gravure coating, direct gravure coating, die coating, bar coating, wire bar coating, roll coating, spin coating, dip coating, spray coating, knife coating, and kiss coating can be used for coating the adhesive composition; inkjet printing; and various printing methods such as offset printing, screen printing, and flexographic printing can be employed. Furthermore, before coating the adhesive composition, the surface of the release sheet may be subjected to surface treatments such as corona treatment, plasma treatment, hot air treatment, ozone treatment, and ultraviolet treatment.

[0178] The drying and heating process is not particularly limited as long as it removes the solvent used in the adhesive composition and allows it to harden, but it is preferable to carry it out at a temperature of 60°C to 150°C for about 20 seconds to 600 seconds. In particular, the heating temperature is preferably 100°C to 150°C.

[0179] When arranging a first flexible sheet member on one side of an adhesive layer and a second flexible sheet member on the other side, an adhesive composition is applied to the first flexible sheet member to form an adhesive layer on the first flexible sheet member, and then the second flexible sheet member is attached to this adhesive layer. Furthermore, the adhesive layer may be cured as needed. Examples of curing conditions include 3 to 7 days at 60°C.

[0180] [Flexible laminated material] The flexible laminated member of the present invention comprises a first flexible member, a second flexible member, and an adhesive layer for bonding the first flexible member and the second flexible member to each other, wherein the adhesive layer is made of the adhesive material. Because the adhesive layer of the flexible laminated member is formed from the adhesive material, even when the flexible laminated member is repeatedly bent, appearance defects such as wavy appearance at the bent parts are suppressed.

[0181] Figure 2 shows an example of the flexible laminated member of the present invention. The flexible laminated member 20 in Figure 2 comprises a first flexible member 22, a second flexible member 24, and an adhesive layer 12 located between the first flexible member 22 and the second flexible member 24, which bond these flexible members together.

[0182] Examples of the configuration of the flexible laminated member include a configuration in which both the first flexible member and the second flexible member are components of a bendable device; and a configuration in which the second flexible member is a bendable device and the first flexible member is a functional sheet member bonded to the bendable device. Examples of the bendable 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, barrier film, polarizing film, phase difference film, optical compensation film, brightness enhancement film, diffusion film, anti-reflective film, transparent conductive film, metal mesh film, cushion film, and the like.

[0183] The first flexible member and the second flexible member are members that can be repeatedly bent or curved. Examples of the first flexible member and the second flexible member include flexible substrate materials, functional sheet members, and display elements (organic EL modules, electronic paper modules, 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 in a flexible display.

[0184] (Method for manufacturing flexible laminated members) The method for manufacturing the flexible laminated member of the present invention is not particularly limited, and examples include the following methods (1) to (4).

[0185] (1) A method for obtaining a flexible laminated member by peeling off a release sheet attached to one side of an adhesive sheet, attaching the exposed adhesive layer to a first flexible member, peeling off a release sheet attached to the other side of the adhesive sheet, and attaching the exposed adhesive layer to a second flexible member. (2) A method for obtaining a flexible laminated member by applying an adhesive composition to one surface of the first flexible member, curing it by drying and heating as necessary to form an adhesive layer, and then attaching the release side of a release sheet to this adhesive layer, and then attaching the exposed adhesive layer to the second flexible member by peeling off the release sheet. (3) A method for obtaining a flexible laminated member by applying an adhesive composition to one surface of a first flexible member, curing it by drying and heating treatment as necessary to form an adhesive layer, and then attaching a second flexible member to this adhesive layer. (4) A method for obtaining a flexible laminated member by applying an adhesive composition to the release surface of a release sheet, curing it by drying and heating as needed to form an adhesive layer, and then attaching the first flexible member to this adhesive layer. Then, peeling off the release sheet and attaching the exposed adhesive layer to the second flexible member.

[0186] In addition, in any of the cases (1) to (4) above, the order in which the first flexible member and the second flexible member are used may be reversed. The adhesive layer can be formed using various coating and printing methods similar to those used in the manufacture of adhesive sheets, and the same applies to the drying and heating process. Curing may also be performed as needed. Furthermore, the release sheet used in the manufacture of flexible laminated members can be the same as the release sheet used for adhesive sheets. [Examples]

[0187] The present invention will be described in more detail below based on specific examples. The present invention is not limited in any way to the following examples, and can be implemented with appropriate modifications without changing its essence. The polymerization rate of the polymer, its weight-average molecular weight (Mw) and molecular weight distribution (Mw / Mn), the thickness of the adhesive layer, and the evaluation of the adhesive and analysis of the sol components were evaluated according to the methods described below.

[0188] The meanings of the abbreviations are as follows: EHA: 2-Ethylhexylacrylate LA:n-Lauryl acrylate HA:n-hexyl acrylate BA: n-butyl acrylate VP:N-vinyl-2-pyrrolidone ACMO: Acryloylmorpholin AA: Acrylic acid HBA: 4-hydroxybutyl acrylate BTEE: Ethyl 2-methyl-2-n-butylteranyl propionate AIBN: Azobisisobutyronitrile AcOEt: Ethyl acetate

[0189] (Polymerization rate) Using a nuclear magnetic resonance (NMR) measurement device (Bruker BioSpin, model: AVANCE500 (frequency 500MHz)), 1 ¹H-NMR was measured (solvent: CDCl3, internal standard: trimethylsilane (TMS)). The integral ratio of the monomer-derived signal and the polymer-derived signal from the obtained NMR spectrum was determined to calculate the monomer polymerization rate.

[0190] (Weight-average molecular weight (Mw) and molecular weight distribution (Mw / Mn)) Gel permeation chromatography (GPC) was performed using a high-performance liquid chromatograph (Tosoh, model HLC-8320GPC). Two TSKgel Super HZM-H columns (Tosoh) were used, 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. Calibration curves were 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 standard substances, and the weight-average molecular weight (Mw) and number-average molecular weight (Mn) were measured. The molecular weight distribution (Mw / Mn) was calculated from these measurements.

[0191] (Adhesive thickness (film thickness)) The total thickness of the adhesive sheet was measured using a thickness measuring device (TH-104, manufactured by Tester Industries), and the thickness of the adhesive material was determined by subtracting the thickness of the release liner from this total thickness.

[0192] (Dynamic viscoelasticity test) The adhesive layers (adhesives) constituting the adhesive sheet were laminated using a hand roller to create a laminate with a thickness of 600 μm, which was used as the test specimen. Measurements were performed using a dynamic viscoelasticity analyzer (Anton Paar, MCR702), with the sample sandwiched between 8 mm diameter parallel plates. The measurement conditions were a temperature range of -60°C to 150°C, a heating rate of 3°C / min, and a frequency of 1 Hz. The strain was varied in steps according to the elastic modulus: 0.1% from the start of measurement up to 10 MPa, 0.2% up to 0.5 MPa, 0.5% up to 0.09 MPa, 1.5% up to 0.05 MPa, and 3% below 0.05 MPa. (Glass transition temperature Tg) Based on the dynamic viscoelasticity measurement results, the temperature at which the loss tangent (tanδ) is maximum was defined as the glass transition temperature Tg of the adhesive. (Shear storage modulus G') The shear storage modulus G' at 25°C was determined from the dynamic viscoelasticity measurement results.

[0193] (Gel fraction) The mass M2 of a wire mesh (400 mesh) cut to a size of 50 mm in width and 120 mm in length was measured. 80 mg to 120 mg of adhesive layer (adhesive material) was taken from an adhesive sheet, and its mass M1 was measured. Test specimens were prepared by wrapping the adhesive material in wire mesh to prevent it from falling off. The test specimens were placed in a glass bottle, 40 g of ethyl acetate was poured in, and after shaking gently, they were left to stand at room temperature (25°C) for 72 hours. After standing, the test specimens were removed from the glass bottle and left at room temperature for 12 hours, and then dried in a vacuum oven at 100°C for 4 hours. After drying, the test specimens were cooled to room temperature, their mass M3 was measured, and the gel fraction was calculated using the following formula. Gel fraction (mass%) = (M3-M2) / M1×100

[0194] (sol component) After removing the gel fraction test specimen from the glass bottle, the ethyl acetate solution containing the extracted sol component was dried to prepare the measurement sample. The solid in the glass bottle was diluted with tetrahydrofuran to adjust the sample concentration to 0.5 mg / ml. Gel permeation chromatography (GPC) was performed using this sample in the same manner as the measurement of weight-average molecular weight (Mw). From the measured molecular weight distribution curve, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) were determined, and the molecular weight distribution (Mw / Mn) was calculated from these weight-average molecular weight (Mw) and number-average molecular weight (Mn). The molecular weight at which the molecular weight distribution curve was maximized was defined as the peak-top molecular weight (Mp). Furthermore, the following ratios were calculated: W1 (peak area between 10,000 and 100,000 molecular weights) to the peak area between 10,000 and 30,000,000 molecular weights; W2 (peak area between 100,000 and 560,000 molecular weights) to the peak area between 10,000 and 30,000,000 molecular weights; W3 (peak area above 560,000 molecular weights) to the peak area between 10,000 and 30,000,000 molecular weights; W2a (peak area between 100,000 and 150,000 molecular weights) to the peak area between 10,000 and 30,000,000 molecular weights; and W2b (peak area between 150,000 and 560,000 molecular weights) to the peak area between 10,000 and 30,000,000 molecular weights.

[0195] (Stress relaxation time at 400% strain, recovery rate after 400% strain) The adhesive layers (adhesives) constituting the adhesive sheet were laminated using a hand roller to create a laminate with a thickness of 600 μm, which was used as the test specimen. The measurement was performed using a viscoelasticity measuring device (Anton Paar, MCR302), with the sample sandwiched between 8 mm diameter parallel plates (with the adhesive surface roughened with 240-grit sandpaper) and under a 25°C atmosphere. In the measurement, the specimen was compressed with an axial force of 1N and left to stand for 10 minutes. Then, the axial force was changed to 0.05N, and shear stress was immediately applied to strain it up to 400%. Subsequently, the specimen was held at 400% strain for 10 minutes, and the change in shear stress was measured to determine the stress relaxation time. Next, the shear stress was released (0kPa) and left for 10 minutes, and the final strain after 10 minutes was measured to determine the recovery rate. The stress relaxation time was defined as the time it took for the shear stress to reach 0.368 times the initial stress after the strain reached 400%. The initial stress was defined as the shear stress value 0.1 seconds after the start of shear stress application. The recovery rate was calculated based on the following formula. Recovery rate (%) = {(400 - final strain) / 400} × 100

[0196] (Strain at 20kPa stress, recovery rate after 20kPa stress application) The adhesive layers (adhesives) constituting the adhesive sheet were laminated using a hand roller to create a laminate with a thickness of 600 μm, which was used as the test specimen. The measurement was performed using a viscoelasticity measuring device (Anton Paar, MCR302), with the sample sandwiched between 8 mm diameter parallel plates (with the adhesive surface roughened with 240-grit sandpaper) and under a 25°C atmosphere. In the measurement, the specimen was compressed with an axial force of 1N and left to stand for 10 minutes. Then, the axial force was changed to 0.05N, and a shear stress of 20kPa was applied for a creep test for 10 minutes, during which the strain (20kPa strain) was measured after 10 minutes. Next, the shear stress was released (0kPa) and left for 10 minutes, and the final strain after 10 minutes was measured to determine the recovery rate. The recovery rate was calculated based on the following formula. Recovery rate (%) = {(20kPa strain - final strain) / 20kPa strain} × 100

[0197] (Measurement of adhesive strength) One release sheet of the adhesive sheet was peeled off from the adhesive layer, and the corona-treated surface of polyethylene terephthalate (PET) film (Toyobo Ester® Film E5100: manufactured by Toyobo, 50 μm thick) was bonded to the adhesive layer surface. The sheet was then cut to a size of 25 mm in width and 100 mm in length to create an adhesive sheet with a substrate. The adhesive strength of this adhesive sheet with a substrate to polyimide film or glass was measured according to the method of JIS Z 0237 (2009). Specifically, the release sheet was peeled from the adhesive layer, and the adhesive layer surface was pressed onto a polyimide (PI) film (Kapton® 100V: manufactured by Toray DuPont, 25 μm thick) or a white glass plate (S9112, manufactured by Matsunami Glass Industry Co., Ltd., 1.0-1.2 mm thick) by rolling a 2 kg roller back and forth twice. The samples pressed onto the polyimide (PI) film were then autoclaved at 60°C, 5 atm, for 30 minutes. Next, the adhesive strength of the adhesive layer was measured using a Shimadzu Corporation precision universal testing machine "AUTOGRAPH® AGS-1kNX, 50N load cell" under conditions of a peeling speed of 300 mm / min and a peeling angle of 180°.

[0198] <Manufacturing of (meth)acrylic polymers> (Synthesis Example 1: Polymer No. 1) EHA (278.4g), LA (240.0g), HA (60.0g), AA (18.0g), HBA (3.6g), AIBN (17.4mg), and AcOEt (400.0g) were charged into a flask equipped with an argon gas inlet tube and a stirrer. After purging with argon, BTEE (105.8mg) was added, and the mixture was reacted at 60°C for 65 hours to polymerize. The polymerization rate was 89%. After the reaction was complete, AcOEt was added to the reaction solution to obtain a solution containing polymer No. 1. The obtained polymer No. 1 had a Mw of 1,532,000 and an Mw / Mn ratio of 1.86.

[0199] (Synthesis examples 2-10, 13-21: Polymers No. 2-10, 13-21) Polymers No. 2-10 and 13-21 were prepared using the same method as for polymer No. 1. Tables 1 and 2 show the monomers, organotellurium compounds, azo polymerization initiators, solvents, reaction conditions, and polymerization rates used.

[0200] (Synthesis Example 11: Polymer No. 11) EHA (1,425.0 g), LA (1,000.0 g), AA (75.0 g), and AcOEt (1,666.7 g) were charged into a flask equipped with an argon gas inlet tube and a stirrer. After purging with argon, the temperature was raised to 82°C, and AIBN (1,094.7 mg) dissolved in AcOEt (50 g) was added dropwise over 2 hours. The reaction was then allowed to proceed for a further 4 hours to polymerize. After the reaction was complete, AcOEt was added to the reaction solution to obtain a solution containing polymer No. 11.

[0201] (Synthesis Example 12: Polymer No. 12) In a flask equipped with an argon gas inlet tube and a stirrer, BA (380.0 g), AA (20.0 g), and AcOEt (533.3 g) were charged. After purging with argon, the temperature was raised to 80°C, and AIBN (86.7 mg) dissolved in AcOEt (266.7 g) was added dropwise over 4 hours. The reaction was then allowed to proceed for a further 2.5 hours to polymerize. After the reaction was complete, AcOEt was added to the reaction solution to obtain a solution containing polymer No. 12.

[0202] Tables 1 and 2 show the polymerization conditions for each polymer. The amount of carboxyl groups, hydroxyl groups, and glass transition temperature were calculated from the monomer charge ratio and polymerization rate used in the polymerization reaction.

[0203] [Table 1]

[0204] [Table 2]

[0205] <Manufacturing of adhesive compositions> (Adhesive composition No. 1) To a solution of polymer No. 1 obtained in Synthesis Example 1 (100 parts by mass of polymer component) and a solution of polymer No. 11 obtained in Synthesis Example 11 (100 parts by mass of polymer component), 0.222 parts by mass of a crosslinking agent (Duranate® D101) and butyl acetate were added and stirred to obtain adhesive composition No. 1 with a solid content of 24% by mass. In adhesive composition No. 1, the first reactive group of the (meth)acrylic polymer (A) (copolymer No. 1) is a hydroxyl group, and the second reactive group of the crosslinking agent is an isocyanate group.

[0206] (Adhesive compositions No. 2-35) Adhesive compositions No. 2 to 35 were prepared in the same manner as adhesive composition No. 1, except that the formulation was changed as shown in Tables 3 to 5. The amounts of crosslinking agents shown in Tables 3 to 5 are calculated on a solid content basis. Solid content refers to components other than the solvent. In adhesive compositions No. 2 to 24 and 30 to 35, the primary reactive group of the (meth)acrylic polymer (A) is a hydroxyl group, and the secondary reactive group of the crosslinking agent is an isocyanate group. In adhesive compositions No. 25 to 29, the primary reactive group of the (meth)acrylic polymer (A) is a carboxyl group, and the secondary reactive group of the crosslinking agent is an epoxy group.

[0207] [Table 3]

[0208] [Table 4]

[0209] [Table 5]

[0210] Crosslinking agent A: Duranate® D101 (manufactured by Asahi Kasei, isocyanate-based crosslinking agent (hexamethylene diisocyanate-1,6-hexanediol adduct, 2 functional groups, solid content concentration 100% by mass, NCO content 4.7 mmol / g (based on solid content))) Crosslinking agent B: D178NL (manufactured by Mitsui Chemicals, isocyanate-based crosslinking agent (allophanate derivative of hexamethylene diisocyanate, 2 functional groups, solid content concentration 100% by mass, NCO content 4.6 mmol / g (based on solid content))) Crosslinking agent C: Duranate® TPA-100 (manufactured by Asahi Kasei, isocyanate-based crosslinking agent (hexamethylene diisocyanate cyclic trimer, 3 functional groups, solid content concentration 100% by mass, NCO content 5.5 mmol / g (based on solid content))) Crosslinking agent D: Duranate® MHG-80B (manufactured by Asahi Kasei, isocyanate-based crosslinking agent (isocyanurate derivative of hexamethylene diisocyanate, 6 functional groups, solid content concentration 80% by mass, NCO content 4.5 mmol / g (based on solid content))) Crosslinking agent E: TETRAD(registered trademark)-C (manufactured by Mitsubishi Gas Chemical, epoxy crosslinking agent (1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 4 functional groups, solids concentration 100% by mass, epoxy group weight: 9.8 mmol / g (based on solids))

[0211] <Making adhesive sheets> An adhesive composition was applied to the release surface of a first release sheet (PET film with a release treatment applied to its surface, Clean Sepa® HY-US20: manufactured by Higashiyama Film, 75 μm thick) using a Baker-type applicator so that the film thickness after drying would be 50 μm. Then, it was heated in a constant-temperature dryer at 60°C for 4 minutes, followed by heating at 150°C for 5 minutes. Next, the release surface of a second release sheet (PET film with a release treatment applied to its surface, Clean Sepa® HY-S10: manufactured by Higashiyama Film, 38 μm thick) was bonded to the adhesive layer formed on the first release sheet, and then aged at 60°C for 3 days to create 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 Tables 6 to 8.

[0212] [Table 6]

[0213] [Table 7]

[0214] [Table 8]

[0215] Adhesives No. 1 to 29 are those that have a shear storage modulus of 0.15 MPa or less at 25°C, a glass transition temperature of 0°C or less, a gel fraction of 50% to 95% by mass, and whose differential molecular weight distribution curve of the sol component satisfies requirements (1), (2), and (3). These adhesives No. 1 to 29 showed good recovery rates after being strained to 400% and good strain when a shear stress of 20 kPa was applied. They also showed good adhesion to both glass and PI film.

[0216] Adhesive No. 30 has a gel fraction exceeding 95% by mass, and the sol component content is too low. This adhesive No. 30 exhibited poor adhesion to both glass and PI film. Adhesives No. 31 and 32 were those with a gel fraction of less than 50% by mass. These adhesives No. 31 and 32 exhibited poor recovery rates both after being strained to 400% and after being subjected to a shear stress of 20 kPa.

[0217] Adhesive No. 33 has a shear storage modulus of over 0.15 MPa at a temperature of 25°C. This adhesive No. 33 exhibited poor recovery after being deformed to 400% strain. Adhesives No. 34 and 35 are cases where the differential molecular weight distribution curve of the sol component does not satisfy the requirements of (2) and (3). These adhesives No. 34 and 35 had poor recovery rates when a shear stress of 20 kPa was applied, and also exhibited poor adhesion to both glass and PI film.

[0218] The present invention includes the following embodiments.

[0219] (Aspect 1) An adhesive containing a polymer (X) having a crosslinked structure, characterized in that the shear storage modulus at a temperature of 25°C is 0.15 MPa or less, the glass transition temperature is 0°C or less, the gel fraction is 50% to 95% by mass, and the differential molecular weight distribution curve of the sol component satisfies the requirements of (1), (2), and (3). (1) The ratio (W1) of the peak area for molecular weights between 10,000 and 100,000 to the peak area for molecular weights between 10,000 and 30,000,000 is 20% or less. (2) The ratio (W2) of the peak area for molecular weights between 100,000 and 560,000 to the peak area for molecular weights between 10,000 and 30,000,000 is 40% or more. (3) The ratio of the peak area for molecular weights of 560,000 or more (W3) to the peak area for molecular weights of 10,000 to 30,000,000 is 40% or less.

[0220] (Aspect 2) The adhesive according to embodiment 1, wherein the differential molecular weight distribution curve of the sol component further satisfies the requirements of (2a) and (2b). (2a) The ratio of the peak area for molecular weights between 100,000 and 150,000 (W2a) to the peak area for molecular weights between 10,000 and 30,000,000 is 15% or more. (2b) The ratio of the peak area for molecular weights between 150,000 and 560,000 to the peak area for molecular weights between 10,000 and 30,000,000 (W2b) is 20% or more.

[0221] (Aspect 3) The adhesive according to embodiment 2, wherein in the differential molecular weight distribution curve of the sol component, the ratio (W2a / W2) of the proportion of the peak area for molecular weights of 100,000 or more and less than 560,000 (W2) to the proportion of the peak area for molecular weights of 100,000 or more and less than 150,000 (W2a) is 0.30 to 0.60.

[0222] (Aspect 4) The adhesive according to any one of embodiments 1 to 3, wherein the weight-average molecular weight (Mw) of the sol component is 100,000 to 560,000.

[0223] (Aspect 5) The adhesive according to any one of claims 1 to 4, wherein, in the differential molecular weight distribution curve of the sol component, the highest peak molecular weight (Mp) in the range of molecular weights from 10,000 to 30,000,000 is 100,000 to 500,000.

[0224] (Aspect 6) The adhesive according to any one of embodiments 1 to 5, wherein the polymer (X) having the crosslinked structure is obtained by crosslinking an adhesive composition containing a (meth)acrylic polymer (A) having a first reactive group with a weight-average molecular weight of 600,000 to 3,000,000, a (meth)acrylic polymer (B) having a weight-average molecular weight (Mw) of 100,000 to 800,000, and a crosslinking agent having a second reactive group that reacts with the first reactive group.

[0225] (Aspect 7) The adhesive according to embodiment 6, wherein the content of the first reactive group in the (meth)acrylic polymer (A) is 0.002 mmol / g to 1.0 mmol / g.

[0226] (Pattern 8) The adhesive according to embodiment 6 or 7, wherein the molar ratio (moles of the first reactive group / molars of the second reactive group) of the second reactive group in the adhesive composition is 1 to 80.

[0227] (Aspect 9) The adhesive according to any one of claims 6 to 8, wherein the combination of the first reactive group and the second reactive group is a combination in which the first reactive group is a hydroxyl group and the second reactive group is an isocyanate group, or a combination in which the first reactive group is a carboxyl group and the second reactive group is an epoxy group.

[0228] (Aspect 10) The adhesive according to any one of claims 6 to 9, wherein the (meth)acrylic polymer (A) has a content of structural units derived from (meth)acrylate having an alkyl group having 1 to 12 carbon atoms of 70% to 99% by mass.

[0229] (Aspect 11) It has a base material sheet and an adhesive layer formed on at least one surface of the base material sheet, and the adhesive layer is an adhesive material according to any one of claims 1 to 10. A pressure-sensitive adhesive sheet characterized by the above.

[0230] (Aspect 12) An adhesive material for a flexible display for bonding one flexible member and another flexible member constituting a flexible display, wherein the adhesive material is the adhesive material according to any one of claims 1 to 10. An adhesive material for a flexible display characterized by the above.

[0231] (Aspect 13) A pressure-sensitive adhesive sheet for a flexible display having an adhesive layer used for bonding one flexible member and another flexible member constituting a flexible display, and a flexible sheet member adhered to at least one surface of the adhesive layer. The pressure-sensitive adhesive sheet for a flexible display, wherein the adhesive layer is formed from the adhesive material according to any one of claims 1 to 10.

[0232] (Aspect 14) The pressure-sensitive adhesive sheet for a flexible display according to claim 13, wherein the pressure-sensitive 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, 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 adhesive layer.

[0233] (Aspect 15) A flexible laminated member including a first flexible member, a second flexible member, and an adhesive layer for bonding the first flexible member and the second flexible member to each other, wherein the adhesive layer is made of the adhesive material according to any one of claims 1 to 10. A flexible laminated member characterized by the above.

Explanation of Reference Numerals

[0234] 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 containing a polymer (X) having a crosslinked structure, wherein the polymer (X) having the crosslinked structure is obtained by subjecting an adhesive composition containing a (meth)acrylic polymer (A) having a first reactive group, a (meth)acrylic polymer (B) having no first reactive group, and a crosslinking agent having a second reactive group that reacts with the first reactive group to a crosslinking reaction, the shear storage modulus at 25°C is 0.15 MPa or less, the glass transition temperature is 0°C or less, the gel fraction is 50% by mass to 95% by mass, and the differential molecular weight distribution curve of the sol component satisfies the requirements of (1), (2), and (3), characterized in that the adhesive. (1) The ratio (W1) of the peak area with a molecular weight of 10,000 or more and less than 100,000 to the peak area with a molecular weight of 10,000 to 30 million is 20% or less. (2) The ratio (W2) of the peak area with a molecular weight of 100,000 or more and less than 560,000 to the peak area with a molecular weight of 10,000 to 30 million is 40% or more. (3) The ratio (W3) of the peak area with a molecular weight of 560,000 or more to the peak area with a molecular weight of 10,000 to 30 million is 40% or less.

2. The adhesive according to claim 1, wherein the differential molecular weight distribution curve of the sol component further satisfies the requirements of (2a) and (2b). (2a) The ratio (W2a) of the peak area with a molecular weight of 100,000 or more and less than 150,000 to the peak area with a molecular weight of 10,000 to 30 million is 15% or more. (2b) The ratio (W2b) of the peak area with a molecular weight of 150,000 or more and less than 560,000 to the peak area with a molecular weight of 10,000 to 30 million is 20% or more.

3. The adhesive according to claim 2, wherein in the differential molecular weight distribution curve of the sol component, the ratio (W2a / W2) of the ratio (W2a) of the peak area with a molecular weight of 100,000 or more and less than 150,000 to the ratio (W2) of the peak area with a molecular weight of 100,000 or more and less than 560,000 is 0.30 to 0.

60.

4. The adhesive according to any one of claims 1 to 3, wherein the weight average molecular weight (Mw) of the sol component is 100,000 to 560,000.

5. The adhesive according to any one of claims 1 to 3, wherein among the peak molecular weights in the differential molecular weight distribution curve of the sol component, the highest peak molecular weight (Mp) at a molecular weight of 10,000 to 30 million is 100,000 to 500,000.

6. The (meth)acrylic polymer (A) has a weight average molecular weight of 600,000 or more and 3 million or less, The pressure-sensitive adhesive material according to any one of claims 1 to 3, wherein the (meth)acrylic polymer (B) has a weight-average molecular weight of 100,000 or more and 800,000 or less.

7. The pressure-sensitive adhesive material according to claim 6, wherein the content of the first reactive group in the (meth)acrylic polymer (A) is 0.002 mmol / g to 1.0 mmol / g.

8. The pressure-sensitive adhesive material according to claim 6, wherein the molar ratio of the second reactive group to the first reactive group in the pressure-sensitive adhesive composition (molar amount of the first reactive group / molar amount of the second reactive group) is 1 to 80.

9. The pressure-sensitive adhesive material according to claim 6, wherein the combination of the first reactive group and the second reactive group is a combination in which the first reactive group is a hydroxy group and the second reactive group is an isocyanate group, or a combination in which the first reactive group is a carboxy group and the second reactive group is an epoxy group.

10. The pressure-sensitive adhesive material according to claim 6, wherein the (meth)acrylic polymer (A) has a content of structural units derived from (meth)acrylate having an alkyl group with 1 to 12 carbon atoms of 70% by mass to 99% by mass.

11. A pressure-sensitive adhesive sheet having a base material sheet and a pressure-sensitive adhesive layer formed on at least one surface of the base material sheet, The pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer is the pressure-sensitive adhesive material according to any one of claims 1 to 3.

12. A pressure-sensitive adhesive material for a flexible display for bonding one flexible member and another flexible member constituting the flexible display, The pressure-sensitive adhesive material for a flexible display, wherein the pressure-sensitive adhesive material is the pressure-sensitive adhesive material according to any one of claims 1 to 3.

13. 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 material according to any one of claims 1 to 3.

14. 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, and the second flexible sheet member is a second release sheet. The adhesive sheet for a flexible display according to claim 13, wherein the first release sheet and the second release sheet are adhered such that their respective release surfaces are in contact with the adhesive layer.

15. 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, The flexible laminated member, wherein the adhesive layer is made of the adhesive material according to any one of claims 1 to 3.

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