JP2023101494A - Adhesive material and adhesive sheet - Google Patents

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

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

On the other hand, in recent years, in image display devices such as liquid crystal display devices and organic electroluminescence (organic EL) display devices, attention has been paid to flexible displays that are repeatedly bent and used. Flexible displays include a foldable display that can be folded, a rollable display that can be rolled into a cylindrical shape, etc., and are expected to be used in mobile terminals such as smartphones and tablet terminals, and stationary displays that can be stored.

In such a flexible display, as an adhesive material for bonding a flexible member constituting a member that is repeatedly bent and stretched and another flexible member, for example, Patent Document 1 discloses an adhesive material for a repeatedly bending device in which the ratio of the shear stress 60 seconds after 1000% displacement to the maximum shear stress when 1000% displacement is performed and the gel fraction are controlled within a predetermined range (see Patent Document 1 (claim 1)).

JP 2019-108498 A

Conventional adhesives do not sufficiently recover from the bent state to the original state when repeatedly bent. Therefore, when a conventional adhesive material is used to join the flexible member, repeated bending may cause lifting or peeling at the interface between the adhesive material and the flexible member at the bent portion.

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

The pressure-sensitive adhesive of the present invention, which has solved the above problems, is a pressure-sensitive adhesive containing a polymer (X) having a crosslinked structure, and is characterized by having 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, a gel fraction of 50% by mass to 95% by mass, and a differential molecular weight distribution curve of the sol component satisfying the requirements of (1), (2), and (3).
(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 30,000,000 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 30,000,000 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 30,000,000 is 40% or less.

ADVANTAGE OF THE INVENTION The adhesive material of this invention has the outstanding adhesiveness, and is excellent in flexibility and restorability. Therefore, by using the adhesive material of the present invention for joining flexible members, it is possible to suppress the occurrence of lifting or peeling at the interface between the adhesive material and the flexible member at the bending portion even when the flexible members are repeatedly bent.

BRIEF DESCRIPTION OF THE DRAWINGS It is a cross-sectional schematic diagram of an example of the adhesive sheet of this invention. It is a cross-sectional schematic diagram of an example of the flexible laminated member of this invention.

An example of a preferred embodiment of the present invention will be described below. However, the following embodiments are merely examples. The present invention is by no means limited to the following embodiments.

In the specification of the present application, "-" is used to mean including the numerical values before and after it as 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". A "vinyl monomer" refers to a monomer having a radically polymerizable carbon-carbon double bond in the molecule. A “structural unit derived from a vinyl monomer” refers to a structural unit in which a radically polymerizable carbon-carbon double bond of a vinyl monomer is polymerized to form a carbon-carbon single bond. The “structural unit derived from (meth)acrylate” refers to a structural unit in which the radically polymerizable carbon-carbon double bond of (meth)acrylate is polymerized to form a carbon-carbon single bond. A “structural unit derived from a (meth)acrylic monomer” refers to a structural unit in which a radically polymerizable carbon-carbon double bond of a (meth)acrylic monomer is polymerized to form a carbon-carbon single bond.

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

The shear storage elastic 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 still more preferably 0.08 MPa or less. If the shear storage elastic modulus is 0.15 MPa or less, the flexibility of the adhesive material is improved and the followability to deformation is increased. Therefore, even if the adhesive material is repeatedly bent, the interface between the adhesive material and the flexible member at the bending portion can be prevented from floating or peeling off. The shear storage elastic 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. When the shear storage elastic modulus is 0.01 MPa or more, the adhesive holding power when the adhesive sheet and the adherend are laminated together can be increased.

The glass transition temperature (Tg) of the adhesive material is preferably 0° C. or lower, more preferably −20° C. or lower, and still more preferably −30° C. or lower. If the glass transition temperature is 0° C. or lower, the adhesion of the adhesive material to be formed to the adherend is enhanced, peeling is suppressed at low temperatures, and durability is improved. Although the lower limit of the glass transition temperature of the adhesive is not particularly limited, it is usually -50°C.

The gel fraction of the adhesive material is preferably 50% by mass or more, more preferably 55% by mass or more, still more preferably 60% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less, and still more preferably 80% by mass or less. If the gel fraction is 50% by mass or more and 95% by mass or less, it is possible to form an adhesive material with excellent flexibility and restorability. The gel fraction can be controlled by the content of the first crosslinkable group, the type of the crosslinker, the blending amount, etc. in the composition described later.

The adhesive contains a sol component. The sol component is a component eluted into the solvent when the adhesive material is extracted with ethyl acetate at 25° C. for 72 hours. The pressure-sensitive adhesive is characterized in that the differential molecular weight distribution curve of the sol component satisfies the requirements (1), (2) and (3). In addition, a 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 the molecular weight (logarithmic value) on the horizontal axis and the integrated value of the concentration fraction on the vertical axis. Next, the slope (differential value) of the curve at each molecular weight is obtained. Finally, a differential molecular weight distribution curve is created by plotting the molecular weight (logarithmic value) on the horizontal axis and the differential value on the vertical axis.

(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 30,000,000 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 30,000,000 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 30,000,000 is 40% or less.
By satisfying the above requirements (1) to (3), it is possible to form an adhesive material having excellent adhesiveness, excellent flexibility, and excellent restorability.

The W1 is preferably 15% or less, more preferably 10% or less, and still more preferably 7% or less. If the W1 is 15% or less, it is possible to suppress the decrease in adhesiveness due to the plasticizing effect of the sol component. Although W1 is preferably 0%, it may be greater than 0%. In this case, W1 is preferably 1.0% or more, more preferably 1.6% or more, and still more preferably 1.8% or more. When the 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 adhesiveness.

The W2 is preferably 50% or more, more preferably 60% or more, still more preferably 70% or more. When W2 is 50% or more, an adhesive material having excellent adhesiveness can be formed. The W2 is preferably 100%, but may be less than 100%. In this case, W2 is preferably 98% or less, more preferably 95.4% or less, still more preferably 88.2% or less.

The W3 is preferably 30% or less, more preferably 25% or less, still more preferably 20% or less. If the W3 is 30% or less, the entanglement effect of the sol components can be suppressed, and the resilience after repeated bending is improved. The W3 is preferably 0%, but may be greater than 0%. In this case, W3 is preferably 0.5% or more, more preferably 1.0% or more, still more preferably 3.0% or more, and particularly preferably 10% or more. When the W3 is 0.5% or more, the cohesive force of the adhesive is improved and the adhesiveness is improved.

The ratio of W1 to W3 (W1/W3) is preferably 0.07 or more, more preferably 0.10 or more, still more preferably 0.15 or more, preferably 26.0 or less, more preferably 6.5 or less, still more preferably 5.5 or less, and particularly preferably 4.0 or less. When the ratio (W1/W3) is 0.07 or more, the wettability of the interface between the adhesive material and the flexible member by the sol component is improved, resulting in good adhesion.

The pressure-sensitive adhesive preferably has a differential molecular weight distribution curve of the sol component that further satisfies the requirements (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 30,000,000 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 30,000,000 is 20% or more.
By satisfying the above requirements (2a) and (2b), it is possible to form an excellent tacky adhesive material with well-balanced cohesiveness and wettability due to the sol component.

The W2a is preferably 20% or more, more preferably 25% or more, still more preferably 30% or more, particularly preferably 35% or more, and preferably 46% or less, more preferably 45.4% or less, further preferably 44.9% or less. When the W2a is 20% or more, the entanglement effect of the sol components is suppressed, and excellent flexibility and restorability are exhibited.

The W2b is preferably 25% or more, more preferably 30% or more, still more preferably 35% or more, and preferably 52% or less, more preferably 50% or less, still more preferably 43.3% or less. When W2b is 25% or more, the cohesive force of the sol component is improved, resulting in excellent adhesiveness.

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

Of 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 30,000,000 is preferably 100,000 or more, preferably 500,000 or less, more preferably 300,000 or less, and still more preferably 200,000 or less. If the peak molecular weight (Mp) is within this range, there is a tendency to form a highly adhesive adhesive.

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

The molecular weight distribution (Mw/Mn) of the sol component is preferably 6.0 or less, more preferably 4.0 or less, still more preferably 3.0 or less. If the molecular weight distribution is 6.0 or less, the content of substances with large or small molecular weights is low compared to the designed polymer molecular weight, and an adhesive material with excellent adhesiveness, flexibility and restorability can be obtained. The molecular weight distribution is 1.0 or more. The smaller the molecular weight distribution, the narrower the width of the molecular weight distribution. When the value is 1.0, the width of the molecular weight distribution is the narrowest. In the present invention, the molecular weight distribution is a value calculated by (weight average molecular weight (Mw))/(number average molecular weight (Mn)), and methods for measuring Mw and Mn will be described later.

(Polymer (X) having a crosslinked structure)
The adhesive contains a polymer (X) having a crosslinked structure. The polymer (X) having a crosslinked structure is obtained by subjecting an adhesive composition containing a polymer component containing a polymer having a first reactive group and a crosslinkable component having a second reactive group that reacts with the first reactive group to a crosslinking reaction.

The polymer (X) having a crosslinked structure includes a (meth)acrylic polymer (A) having a first reactive group having a weight average molecular weight of 600,000 or more and 3,000,000 or less (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 or more and 800,000 or less (hereinafter sometimes simply referred to as "(meth)acrylic polymer (B)"), and the first reactivity. It is preferably obtained by cross-linking an adhesive composition containing a cross-linking agent having a second reactive group that reacts with the group.

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, still more preferably 1,000,000 or more, and preferably 2,900,000 or less, more preferably 2,500,000 or less, and still 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 (meth)acrylic polymer (A) can be selectively reacted with a cross-linking agent that has a second reactive group.

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 more, more preferably 3.6 or more, still more preferably 6.0 or more, and preferably 18.0 or less, more preferably 15.0 or less, and still more preferably 13.0 or less. If the ratio (MwA/MwB) is 1.9 or more, the (meth)acrylic polymer (B) can selectively react with the (meth)acrylic polymer (A) even if the (meth)acrylic polymer (B) has a first reactive group, and if it is 18.0 or less, the (meth)acrylic polymer (A) and the (meth)acrylic polymer (B) can be uniformly mixed during coating.

The (meth)acrylic polymer (B) may or may not have a first reactive group. That is, the combination of the (meth)acrylic polymer (A) and the (meth)acrylic polymer (B) includes a (meth)acrylic polymer (A) having a first reactive group having a weight average molecular weight of 600,000 or more and 3,000,000 or less and a (meth)acrylic polymer (B) having a weight average molecular weight (Mw) of 100,000 or more and 800,000 or less and having no first reactive group; and a (meth)acrylic polymer (B) having a first reactive group having a weight average molecular weight (Mw) of 100,000 or more and 800,000 or less.

The (meth)acrylic polymer (A) and the cross-linking agent are mainly components that form a cross-linked structure. The sol component includes a component that was not crosslinked during the crosslinking reaction in the (meth)acrylic polymer (A), a component that has a low degree of crosslinking and can be extracted with a solvent, and the like. The (meth)acrylic polymer (B) having no first reactive group mainly becomes a sol component. When the (meth)acrylic polymer (B) has a first reactive group, the sol component includes a component that was not crosslinked during the crosslinking reaction in the (meth)acrylic polymer (B), a component that has a low degree of crosslinking and can be extracted with a solvent, and the like.

((Meth) acrylic polymer (A))
The (meth)acrylic polymer (A) has a structural unit derived from a (meth)acrylic monomer as a main component (50% by mass or more). The (meth)acrylic polymer (A) may be used alone or in combination of two or more. Moreover, the (meth)acrylic polymer (A) can contain a structural unit derived from a vinyl monomer other than the (meth)acrylic monomer. The content of structural units derived from (meth)acrylic monomers in the (meth)acrylic polymer (A) is preferably 80% by mass or more, more preferably 90% by mass or more, based on 100% by mass of the polymer. The (meth)acrylic polymer (A) may be composed only of structural units derived from (meth)acrylic monomers.

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

The (meth)acrylic polymer (A) has a first reactive group. The first reactive group is a functional group having reactivity with a second reactive group of a cross-linking agent, which will be described later. Functional groups that can be the first reactive group include reactive functional groups. The first reactive group includes a hydroxy group, a carboxy group, an epoxy group and the like, preferably a hydroxy group and/or a carboxy group.

The amount of the first reactive group of the (meth)acrylic polymer (A) is preferably 0.002 mmol/g or more, more preferably 0.005 mmol/g or more, still more preferably 0.010 mmol/g or more, and preferably 1.0 mmol/g or less, more preferably 0.8 mmol/g or less, further preferably 0.7 mmol/g or less. When the amount of the first reactive group is 0.002 mmol/g or more, the adhesive material formed is appropriately crosslinked and exhibits suitable restorability, and when the amount is 1.0 mmol/g or less, the distance between crosslink points of the adhesive material formed is sufficiently long and excellent in flexibility.

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

Further, when a hydroxy group is the first reactive group and the (meth)acrylic polymer (A) has both a carboxy group and a hydroxy group, the molar ratio (carboxy group/hydroxy group) between the carboxy group and the hydroxy group per unit mass of the (meth)acrylic polymer (A) is preferably 4 or more, more preferably 8 or more, still more preferably 16 or more, and preferably 60 or less, more preferably 40 or less, and still more preferably 30 or less. If the molar ratio (carboxy group/hydroxy group) is within the above range, the adhesive layer has high restorability and a suitable balance between adhesiveness and flexibility.

The (meth)acrylic polymer (A) preferably has a hydroxy group as a functional group other than the first reactive group when the carboxy group is the first reactive group. In this case, the amount of hydroxy groups in the (meth)acrylic polymer (A) is preferably 0.01 mmol/g or more, more preferably 0.02 mmol/g or more, still more preferably 0.04 mmol/g or more, and preferably 0.25 mmol/g or less, more preferably 0.20 mmol/g or less, still more preferably 0.15 mmol/g or less.

If the carboxy group is the first reactive group and the acrylic polymer (A) has both the carboxy and hydroxy groups, the molar ratio (carboxy group / hydroxy group) between the carboxy group and the hydroxy group per Acrylic polymer (A). It is preferably 0 or more, more preferably 3.5 or more, more preferably 4.0 or more, preferably 30.0 or less, more preferably 25.0 or less, more preferably 20.0 or less. If the molar ratio (carboxy group/hydroxy group) is within the above range, the adhesive layer has high restorability and a suitable balance between adhesiveness and flexibility.

The (meth)acrylic polymer (A) may be a random copolymer, a block copolymer, or a graft copolymer, preferably a random copolymer.

The weight average molecular weight (MwA) of the (meth)acrylic polymer (A) is preferably 600,000 or more, more preferably 750,000 or more, still more preferably 900,000 or more, particularly preferably 1,000,000 or more, and preferably 3,000,000 or less, more preferably 2,800,000 or less, further preferably 2,600,000 or less. When the MwA of the (meth)acrylic polymer (A) is 600,000 or more, the number of the first reactive groups per one (meth)acrylic polymer (A) increases, and the gel fraction described above is easily satisfied. A method for measuring the weight average molecular weight (Mw) will be described later.

The (meth)acrylic polymer (A) has a molecular weight distribution (Mw/Mn) of 3.0 or less, preferably 2.7 or less, more preferably 2.5 or less, and still more preferably 2.1 or less. The smaller Mw/Mn is, the narrower the width of the molecular weight distribution becomes and the more uniform the molecular weight of the polymer becomes. When the value is 1.0, the width of the molecular weight distribution is the narrowest. If Mw/Mn is 3.0 or less, the content of low molecular weight and high molecular weight components is low compared to the molecular weight of the designed polymer, and an adhesive material with excellent adhesiveness and restorability can be obtained.

The glass transition temperature (Tg) of the (meth)acrylic polymer (A) is preferably −70° C. or higher, more preferably −60° C. or higher, and preferably 0° C. or lower, more preferably −10° C. or lower, and still more preferably −20° C. or lower. If Tg is −70° C. or higher, sufficient cohesive force is imparted to the adhesive material, and the durability of the formed adhesive material is improved.

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

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

The (meth)acrylic polymer (B) is preferably a (meth)acrylate copolymer. The (meth)acrylate copolymer may be a copolymer having structural units derived from (meth)acrylate as a main component (50% by mass or more), 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, more preferably 90% by mass or more, based on 100% by mass of the polymer.

The (meth)acrylic polymer (B) may be a random copolymer, a block copolymer, or a graft copolymer, preferably a random copolymer.

The weight average molecular weight (MwB) of the (meth)acrylic polymer (B) is preferably 100,000 or more, more preferably 130,000 or more, still more preferably 150,000 or more, and preferably 800,000 or less, more preferably less than 600,000, more preferably 500,000 or less, and particularly preferably 400,000 or less. If the MwB of the (meth)acrylic polymer (B) is within this range, there is a tendency to form a highly adhesive adhesive material.

The molecular weight distribution (Mw/Mn) of the (meth)acrylic polymer (B) is preferably 5.0 or less, more preferably 4.0 or less, still more preferably 3.0 or less, and particularly preferably 2.5 or less. The smaller Mw/Mn is, the narrower the width of the molecular weight distribution becomes and the more uniform the molecular weight of the polymer becomes. When the value is 1.0, the width of the molecular weight distribution is the narrowest. When Mw/Mn is 5.0 or less, the content of low molecular weight and high molecular weight polymers is low compared to the designed polymer, and an adhesive material with excellent adhesiveness can be obtained.

The glass transition temperature (Tg) of the (meth)acrylic polymer (B) is preferably −70° C. or higher, more preferably −60° C. or higher, and preferably 0° C. or lower, more preferably −10° C. or lower, further preferably −20° C. or lower. If the Tg is −70° C. or higher, sufficient cohesive force is imparted to the adhesive material, and the durability of the formed adhesive material is improved.

In the adhesive composition, the amount of the (meth)acrylic polymer (B) blended with respect to 100 parts by mass of the (meth)acrylic polymer (A) is preferably 30 parts by mass or more, more preferably 50 parts by mass or more, more preferably 70 parts by mass or more, preferably 300 parts by mass or less, more preferably 250 parts by mass or less, and further preferably 200 parts by mass or less. If the amount of the (meth)acrylic polymer (B) is 30 parts by mass or more, an adhesive material with excellent flexibility can be formed, and if it is 300 parts by mass or less, an adhesive material with excellent restorability can be formed.

The (meth)acrylic polymer (B) may or may not have a first reactive group. As the (meth)acrylic polymer (B), a polymer having the first reactive group and a polymer not having the first reactive group may be used in combination. The first reactive group includes a hydroxy group, a carboxy group, an epoxy group and the like, preferably a hydroxy group and/or a carboxy group.

When the (meth)acrylic polymer (B) has a first reactive group, the amount of the first reactive group of the (meth)acrylic polymer (B) is preferably 0.002 mmol/g or more, more preferably 0.005 mmol/g or more, still more preferably 0.010 mmol/g or more, and preferably 1.0 mmol/g or less, more preferably 0.8 mmol/g or less, and still more preferably 0.7 mmol/g or less. When the amount of the first reactive group is 0.002 mmol/g or more, the adhesive material formed is appropriately crosslinked and exhibits suitable restorability, and when the amount is 1.0 mmol/g or less, the distance between crosslink points of the adhesive material formed is sufficiently long and excellent in flexibility.

When the (meth)acrylic polymer (B) has a first reactive group, the total amount of the first reactive groups possessed by the (meth)acrylic polymer (A) and the (meth)acrylic polymer (B) in the total mass of the (meth)acrylic polymer (A) and the (meth)acrylic polymer (B) is preferably 0.002 mmol/g or more, more preferably 0.005 mmol/g or more, still more preferably 0.010 mmol/g or more, and 1.0 mmol. /g or less, more preferably 0.8 mmol/g or less, and still more preferably 0.7 mmol/g or less. When the amount of the first reactive group is 0.002 mmol/g or more, the adhesive material formed is appropriately crosslinked and exhibits suitable restorability, and when the amount is 1.0 mmol/g or less, the distance between crosslink points of the adhesive material formed is sufficiently long and excellent in flexibility.

The (meth)acrylic polymer (B) preferably has a carboxy group when the hydroxyl group is the first reactive group. The (meth)acrylic polymer (B) having a carboxyl group exhibits excellent adhesiveness. In this case, the amount of carboxy groups in the (meth)acrylic polymer (B) is preferably 0.002 mmol/g or more, more preferably 0.005 mmol/g or more, still more preferably 0.010 mmol/g or more, and preferably 1.0 mmol/g or less, more preferably 0.8 mmol/g or less, still more preferably 0.7 mmol/g or less.

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 the (meth)acrylic polymer (B) in the polymer component contained in the adhesive composition is preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more. The adhesive composition may contain only the (meth)acrylic polymer (A) and the (meth)acrylic polymer (B) as polymer components.

The structural units constituting the (meth)acrylic polymer (A) and (meth)acrylic polymer (B) are described below.

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 the structural unit (a-1) having the first reactive group in its structure.

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

The content of the structural unit (structural unit (a-1) having the first reactive group) derived from the vinyl monomer having the 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, still more preferably 0.15% by mass or more, and preferably 6% by mass or less, more preferably 4% by mass or less, and still more preferably 3% by mass or less in 100% by mass of the polymer component. When the content of the structural unit (a-1) in the (meth)acrylic polymer (A) is within the above range, it is possible to form an adhesive material having an excellent balance between adhesion to adherends and durability. The vinyl monomer having the first reactive group includes vinyl monomers other than the (meth)acrylic monomer having the first reactive group and the (meth)acrylic monomer having the first reactive group.

When the (meth)acrylic polymer (B) has the first reactive group, the content of the structural unit (the structural unit (a-1) having the first reactive group) derived from the vinyl monomer 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, still more preferably 0.15% by mass or more, and preferably 6% by mass or less, more preferably 4%, based on 100% by mass of the polymer component. % by mass or less, more preferably 3% by mass or less. When the content of the structural unit (a-1) in the (meth)acrylic polymer (B) is within the above range, it is possible to form an adhesive material having an excellent balance between adhesion to adherends and durability. The vinyl monomer having the first reactive group includes vinyl monomers other than the (meth)acrylic monomer having the first reactive group and the (meth)acrylic monomer having the first reactive group.

Examples of the (meth)acrylic monomer include (b1) a (meth)acrylic monomer that does not have a functional group that can be the first reactive group, and (b2) a (meth)acrylic monomer that has a functional group that can be the first reactive group. These monomers may be used alone or in combination of two or more. As the (b1) (meth)acrylic monomer, (b1-1) a (meth)acrylate monomer having no functional group capable of serving as a first reactive group is preferable. Examples of the (b2) (meth)acrylic monomer include (b2-1) a (meth)acrylate monomer having a functional group capable of serving as a first reactive group, and (meth)acrylic acid.

Examples of the (b1) (meth)acrylic monomer having no functional group that can be the first reactive group include (meth)acrylates having a linear alkyl group, (meth)acrylates having a branched alkyl group, (meth)acrylates having an alkoxy group, (meth)acrylates having 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.

The (meth)acrylate having a linear alkyl group is preferably a (meth)acrylate having a linear alkyl group having a linear alkyl group having a carbon number of 1 to 20, more preferably a (meth)acrylate having a linear alkyl group having a linear alkyl group having a carbon number of 1 to 15, more preferably a (meth)acrylate having a linear alkyl group having a linear alkyl group having a carbon number of 1 to 12, and a linear alkyl group having a carbon number of 4 to 12. (Meth)acrylates having an alkyl group are more preferred. Examples of the (meth)acrylate having a linear alkyl group include 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, n-stearyl (meth)acrylate and other (meth)acrylic acid linear alkyl esters.

The (meth)acrylate having a branched-chain alkyl group is preferably a (meth)acrylate having a branched-chain alkyl group having 3 to 20 carbon atoms in the branched-chain alkyl group, more preferably a (meth)acrylate having a branched-chain alkyl group having 3 to 12 carbon atoms in the branched-chain alkyl group, and more preferably a (meth)acrylate having a branched-chain alkyl group having 3 to 10 carbon atoms in the branched-chain alkyl group. Examples of the (meth)acrylate having a branched alkyl group include (meth)acrylic acid branched-chain alkyl esters such as isopropyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isononyl (meth)acrylate, and isodecyl (meth)acrylate.

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

Examples of (meth)acrylates having an alicyclic hydrocarbon group include (meth)acrylates having a cyclic alkyl group and (meth)acrylates having a polycyclic structure. The (meth)acrylate having a cyclic alkyl group is preferably a (meth)acrylate having a cyclic alkyl group having 6 to 12 carbon atoms. The cyclic alkyl group includes a cyclic alkyl group having a monocyclic structure (for example, a cycloalkyl group), and may have a chain portion. Specific examples of (meth)acrylates having a cyclic alkyl group having a monocyclic structure include (meth)acrylic acid cyclic alkyl esters such as cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, and cyclododecyl (meth)acrylate.

The (meth)acrylate having a polycyclic structure is preferably a (meth)acrylate having a polycyclic structure with 6 to 12 carbon atoms. The polycyclic structure includes cyclic alkyl groups having a bridged ring structure (eg, adamantyl group, norbornyl group, isobornyl group), and may 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, Dicyclopentenyloxyethyl (meth)acrylate and the like can be mentioned.

The (meth)acrylate having an aromatic group is preferably a (meth)acrylate having an aromatic group having 6 to 12 carbon atoms. Examples of the aromatic group include an aryl group, and may have a chain portion such as an alkylaryl group, an araryl group, an aryloxyalkyl group, and the like. 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 aryl group preferably has 6 to 12 carbon atoms. The aralkyl group preferably has 6 to 12 carbon atoms. The alkylaryl group preferably has 6 to 12 carbon atoms. (Meth)acrylates having an aromatic group include benzyl (meth)acrylate, phenyl (meth)acrylate, phenoxyethyl (meth)acrylate and the like.

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

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, and N-ethoxymethyl(meth)acrylamide. acrylamide, N-propoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide, diacetoneacrylamide, 4-(meth)acryloylmorpholine and the like. The (meth)acrylamides are (meth)acryl monomers, but are not included in (meth)acrylate monomers.

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

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

Examples of the (meth)acrylic monomer having a carboxy group include monomers obtained by reacting (meth)acrylate having a hydroxyl group such as carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl maleate, 2-(meth)acryloyloxyethylphthalate and the like with an acid anhydride such as maleic anhydride, succinic anhydride, and phthalic anhydride (e.g., 2-acryloyl hydrogen succinate). oxyethyl, 2-methacryloyloxyethyl hydrogen succinate, 2-(acryloyloxy)ethyl hydrogen hexahydrophthalate, 2-(methacryloyloxyethyl) hydrogen hexahydrophthalate, 1-(2-acryloyloxyethyl) phthalate, 1-(2-methacryloyloxyethyl) phthalate), (meth)acrylic acid and the like. Among these, (meth)acrylic acid is preferred.

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

Examples of the vinyl monomer other than the (meth)acrylic monomer include (b3) a vinyl monomer other than the (meth)acrylic monomer that does not have a functional group that can be the first reactive group, and (b4) a vinyl monomer other than the (meth)acrylic monomer that has a functional group that can be the first reactive group. These monomers may be used alone or in combination of two or more.

Examples of (b3) vinyl monomers other than (meth)acrylic monomers having no functional group that can be the first reactive group include aromatic vinyl monomers, vinyl monomers containing a heterocycle, vinyl carboxylates, vinyl monomers containing a tertiary amino group, vinylamides, α-olefins, dienes, halogenated vinyl monomers, and the like.

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

Vinyl monomers other than the (b4) (meth)acrylic monomer having a functional group capable of serving as the first reactive group include vinyl monomers having a hydroxy group, vinyl monomers having a carboxy group, vinyl monomers containing an epoxy group, and the like.

Examples of vinyl monomers having a hydroxy 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 epoxy groups include 2-allyloxirane, glycidyl vinyl ether, 3,4-epoxycyclohexyl vinyl ether, and the like.

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

As a polymerization method for polymerizing the monomer composition, both a free radical polymerization method and a living radical polymerization method can be employed. The method for polymerizing the (meth)acrylic polymer (A) is preferably living radical polymerization. That is, the (meth)acrylic polymer (A) is preferably polymerized by living radical polymerization. Moreover, the method for polymerizing the (meth)acrylic polymer (B) is preferably living radical polymerization. That is, the (meth)acrylic polymer (B) is preferably polymerized by living radical polymerization. The living radical polymerization method maintains the simplicity and versatility of the conventional radical polymerization method, but is less likely to cause termination reactions and chain transfer, and grows without being hindered by side reactions that deactivate the growing end. Therefore, it is preferable in that it facilitates precise control of the molecular weight distribution and the production of a polymer with a uniform composition.

(living radical polymerization method)
Living radical polymerization methods include a method of using a compound capable of producing a nitroxide radical, depending on the method of stabilizing the polymerization growth terminal (nitrooxide method; NMP method); a method of using a metal complex such as copper or ruthenium, using a halogenated compound as a polymerization initiation compound, and living polymerization from the polymerization initiation compound (ATRP method); a method of using a dithiocarboxylic acid ester or a xanthate compound (RAFT method); a method of using an organic tellurium compound (TERP method); a method of using an organic iodine compound (IT). P method); a method using an iodine compound as a polymerization initiation compound and a phosphorus compound, a nitrogen compound, an oxygen compound, or an organic compound such as a hydrocarbon as a catalyst (reversible transfer catalyst polymerization; RTCP method, reversible catalyst-mediated polymerization; RCMP method). Among these methods, it is preferable to use the TERP method from the viewpoint of the diversity of usable monomers, molecular weight control in the high molecular region, uniform composition, or coloring.

The TERP method is a method of polymerizing a radically polymerizable compound (vinyl monomer) using an organic tellurium compound as a chain transfer agent.

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

［式（１）において、Ｒ¹は、炭素数１～８のアルキル基、アリール基または芳香族ヘテロ環基である。Ｒ²およびＲ³は、それぞれ独立に、水素原子または炭素数１～８のアルキル基である。Ｒ⁴は、炭素数１～８のアルキル基、アリール基、置換アリール基、芳香族ヘテロ環基、アルコキシ基、アシル基、アミド基、オキシカルボニル基、シアノ基、アリル基またはプロパルギル基である。
式（２）において、Ｒ¹は、炭素数１～８のアルキル基、アリール基または芳香族ヘテロ環基である。］

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

The organic tellurium compound represented by formula (1) is specifically ethyl 2-methyl-2-n-butyltheranyl-propionate, ethyl 2-n-butyltheranyl-propionate, (2-hydroxyethyl) 2-methyl-methyltheranyl-propionate, etc., WO 2004/14848, WO 2004/14962, WO 2004/072126, and WO 2004/072126. Organic tellurium compounds described in 2004/096870 can be mentioned. Specific examples of the organic ditelluride compound represented by formula (2) include dimethyl ditelluride, dibutyl ditelluride, and the like. The azo polymerization initiator can be used without any particular limitation as long as it is an azo polymerization initiator used in ordinary radical polymerization. 4-dimethylvaleronitrile) (V-70) and the like.

In the polymerization step, a vinyl monomer and an organic tellurium compound of formula (1) are mixed in a vessel substituted with an inert gas, and an azo polymerization initiator and/or an organic ditelluride compound of formula (2) are mixed for the purpose of accelerating the reaction, controlling the molecular weight and molecular weight distribution depending on the type of the vinyl monomer, and the like. At this time, examples of the inert gas include nitrogen, argon, and helium. Argon and nitrogen are preferred. The amount of the vinyl monomer used in (a), (b), (c) and (d) may be appropriately adjusted according to the physical properties of the desired polymer.

The polymerization reaction can be carried out without a solvent, but may be carried out by using an aprotic or protic solvent generally used in radical polymerization and stirring the mixture. Aprotic solvents that can be used include, for example, acetonitrile, methyl ethyl ketone, anisole, benzene, toluene, propylene glycol monomethyl ether acetate, ethyl acetate, tetrahydrofuran (THF), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), acetone, dioxane, chloroform, carbon tetrachloride, and the like. Examples of protic solvents include water, methanol, ethanol, isopropanol, n-butanol, ethyl cellosolve, butyl cellosolve, 1-methoxy-2-propanol, hexafluoroisopropanol, diacetone alcohol and the like. A solvent may be used individually and may use 2 or more types together. The amount of the solvent to be used may be appropriately adjusted, and is preferably 0.01 ml to 50 ml per 1 g of the vinyl monomer. The reaction temperature and reaction time may be appropriately adjusted depending on the molecular weight or molecular weight distribution of the polymer component to be obtained, but the mixture is usually stirred at 0°C to 150°C for 1 minute to 100 hours. At this time, the pressure is usually normal pressure, but may be pressurized or reduced. After completion of the polymerization reaction, the desired polymer can be separated from the resulting reaction mixture by removing the used solvent, residual vinyl monomer, etc., by a conventional separation and purification means.

The growing terminal of the polymer obtained by the polymerization reaction is in the form of —TeR ¹ (wherein R ¹ is the same as above) derived from the tellurium compound, and is deactivated by the operation in the air after the completion of the polymerization reaction, but the tellurium atom may remain. Since a polymer having a tellurium atom remaining at the end thereof is colored or has poor thermal stability, it is preferable to remove the tellurium atom. Methods for removing tellurium atoms include a radical reduction method; a method of adsorption with activated carbon or the like; a method of adsorbing a metal with an ion exchange resin or the like; these methods can also be used in combination. The other end of the polymer obtained by the polymerization reaction (the end opposite to the growing end) is in the form of —CR ² R ³ R ⁴ (wherein R ² , R ³ and R ⁴ are the same as R ² , R ³ and R ⁴ in formula (1)) derived from the tellurium compound.

(Free radical polymerization method)
A conventionally known method may be adopted for the free radical polymerization method. Polymerization initiators used in free radical polymerization include azo polymerization initiators, peroxide polymerization initiators, and the like. Examples of the azo polymerization initiator include 2,2′-azobis(isobutyronitrile) (AIBN), 2,2′-azobis(2-methylbutyronitrile) (AMBN), 2,2′-azobis(2,4-dimethylvaleronitrile) (ADVN), 1,1′-azobis(1-cyclohexanecarbonitrile) (ACHN), dimethyl-2,2′-azo Bisisobutyrate (MAIB), 4,4′-azobis(4-cyanovaleric acid) (ACVA), 1,1′-azobis(1-acetoxy-1-phenylethane), 2,2′-azobis(2-methylbutyramide), 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70), 2,2′-azobis(2-methylamidinopropane) di-salt 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) and the like can be exemplified.

The polymerization reaction can be carried out without a solvent, but may be carried out by using an aprotic or protic solvent generally used in radical polymerization and stirring the mixture. Examples of usable aprotic solvents include acetonitrile, anisole, benzene, toluene, N,N-dimethylformamide (DMF), dimethylsulfoxide (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, trifluoromethylbenzene, and the like. can. Examples of protic solvents include water, methanol, ethanol, isopropanol, n-butanol, ethyl cellosolve, butyl cellosolve, 1-methoxy-2-propanol, hexafluoroisopropanol and diacetone alcohol.

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

The reaction temperature and reaction time may be appropriately adjusted depending on the molecular weight or molecular weight distribution of the polymer component to be obtained, but the mixture is usually stirred at 0°C to 150°C for 1 minute to 100 hours. At this time, the pressure is usually normal pressure, but may be pressurized or reduced. After completion of the polymerization reaction, the intended polymer composition can be separated from the resulting reaction mixture by removing the used solvent, residual vinyl monomer, etc., by a conventional separation and purification means.

(crosslinking agent)
The adhesive composition contains a cross-linking agent. The cross-linking agent is a compound having two or more second reactive groups in one molecule that react with the first reactive groups of the (meth)acrylic polymer. The cross-linking agent is not particularly limited, and examples thereof include isocyanate-based cross-linking agents, epoxy-based cross-linking agents, aziridine-based cross-linking agents, metal chelate-based cross-linking agents, melamine resin-based cross-linking agents, and urea resin-based cross-linking agents. The said crosslinking agent may be used individually by 1 type, and may use 2 or more types together. Among these, isocyanate-based cross-linking agents and epoxy-based cross-linking agents are preferred.

The average number of second reactive groups that the cross-linking agent has in one molecule is 2 or more, preferably 8 or less, and more preferably 6 or less. The molecular weight of the cross-linking agent is preferably 200 or more, more preferably 300 or more, still more preferably 400 or more, and preferably 1500 or less, more preferably 1000 or less, still more preferably 700 or less.

The content of the second reactive group in the cross-linking agent is preferably 1.5 mmol/g or more, more preferably 3 mmol/g or more, still more preferably 3.7 mmol/g or more, and preferably 10 mmol/g or less, more preferably 8 mmol/g or less. If the content of the second reactive group of the cross-linking agent is within this range, the valence of the cross-linking agent will be low, the cross-linking points will be evenly distributed in the adhesive, and the average distance between cross-linking points will be long. Therefore, the resulting adhesive material has a low initial stress and exhibits high restorability.

Examples of the combination of the first reactive group possessed by the (A) (meth)acrylic polymer and (B) the (meth)acrylic polymer and the second reactive group possessed by the cross-linking agent include the following combinations.
When the second reactive group of the cross-linking agent is an isocyanate group, the first reactive group may be a hydroxy group.
When the second reactive group of the cross-linking agent is an epoxy group, the first reactive group may be a carboxy group.

The combination of the first reactive group of the (meth)acrylic polymer (A) and the (meth)acrylic polymer (B) and the second reactive group of the cross-linking agent is preferably (1) a combination in which the first reactive group is a hydroxy group and the second reactive group is an isocyanate group; (2) a combination in which the first reactive group is a carboxy group and the second reactive group is an epoxy group.

(Isocyanate-based cross-linking agent)
The isocyanate-based cross-linking agent is a compound having two or more isocyanate groups (including an isocyanate regenerative functional group in which the isocyanate group is temporarily protected by a blocking agent or quantization) as a second reactive group in one molecule. The isocyanate-based cross-linking agents may be used alone or in combination of two or more.

Examples of isocyanate-based cross-linking agents include aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, adducts of these with various polyols, isocyanurate bonds, biuret bonds, allophanate bonds, and polyfunctionalized polyisocyanates. Specifically, a compound (bifunctional isocyanate cross-linking agent) having two isocyanate groups (including an isocyanate regenerative functional group temporarily protected by a blocking agent or quantization) in one molecule, or a compound having three isocyanate groups (an isocyanate group temporarily protected by a blocking agent or quantization) in one molecule (trifunctional isocyanate cross-linking agent), or an isocyanate group (an isocyanate group temporarily protected by a blocking agent or quantization). (including cyanate-regenerating functional groups) in one molecule (hexafunctional isocyanate-based cross-linking agent).

Diisocyanate compounds such as aliphatic diisocyanate compounds, alicyclic diisocyanate compounds, and aromatic diisocyanate compounds can be mentioned as bifunctional isocyanate-based cross-linking agents, and adducts of these diisocyanate compounds and diol compounds can also be used. The diisocyanate compound is a compound represented by the general formula "O=C=N-X-N=C=O" (X is a divalent aliphatic group, a divalent alicyclic group, a divalent aromatic group, etc.). A diol compound is a compound represented by the general formula "HO-Y-OH" (Y is a divalent aliphatic group, a divalent alicyclic group, a divalent aromatic group, or the like).

Examples of the aliphatic diisocyanate compound include ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, 2,2,4-trimethyl-1,6-hexamethylene diisocyanate.

The alicyclic diisocyanate compounds include isophorone diisocyanate, cyclopentyl diisocyanate, cyclohexyl diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, etc. Among them, alicyclic diisocyanate compounds having 7 to 30 carbon atoms are preferred.

Examples of aromatic diisocyanate compounds include phenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, naphthylene diisocyanate, diphenylether diisocyanate, diphenylmethane diisocyanate, diphenylpropane diisocyanate and the like, and aromatic diisocyanate compounds having 8 to 30 carbon atoms are preferred.

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

Examples of the trifunctional isocyanate cross-linking agent and the hexafunctional isocyanate cross-linking agent include the adduct of the diisocyanate compound, the biuret of the diisocyanate compound, the isocyanurate of the diisocyanate compound (cyclic multimer of diisocyanate compounds), and the like.

The isocyanate-based cross-linking agent preferably does not have an aromatic ring. In particular, the isocyanate-based cross-linking agent is preferably a trifunctional or hexa-functional isocyanate-based cross-linking agent selected from the group consisting of an aliphatic diisocyanate compound and an adduct of an aliphatic diisocyanate compound and an aliphatic diol compound; a bifunctional isocyanate-based cross-linking agent selected from the group consisting of;

(epoxy cross-linking agent)
An epoxy-based cross-linking agent refers to a compound having two or more epoxy groups in one molecule as a second reactive group. The epoxy-based cross-linking agents may be used alone or in combination of two or more.

Examples of epoxy-based cross-linking agents include aliphatic epoxy compounds, alicyclic epoxy compounds, aromatic epoxy compounds, heterocyclic epoxy compounds, and the like.

Examples of the aliphatic epoxy compound 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 di glycidyl ether, glycerin triglycidyl ether, polyglycerol polyglycidyl ether, diglycidyl adipic acid ester, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane and the like.

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

Examples of the aromatic epoxy compound include bisphenol A epichlorohydrin type epoxy resin, diglycidylaniline, o-diglycidyl phthalate, resorcin diglycidyl ether, and bisphenol-S-diglycidyl ether.

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

As the epoxy crosslinking agent, a compound having two epoxy groups in one molecule (bifunctional epoxy crosslinking agent), a compound having three epoxy groups in one molecule (trifunctional epoxy crosslinking agent), or a compound having four epoxy groups in one molecule (tetrafunctional epoxy crosslinking agent) are preferred. If the cross-linking agent is a bifunctional epoxy cross-linking agent, a tri-functional epoxy cross-linking agent or a tetra-functional epoxy cross-linking agent, the cross-linking points will be evenly distributed in the adhesive material and the average distance between cross-linking points will be long. Therefore, the resulting adhesive material has a low initial stress and exhibits high restorability.

The adhesive composition preferably contains only an isocyanate-based cross-linking agent or only an epoxy-based cross-linking agent as a cross-linking agent. When only an isocyanate cross-linking agent is contained as a cross-linking agent, it is preferable to contain only a bifunctional isocyanate cross-linking agent having two isocyanate groups in one molecule, a trifunctional isocyanate cross-linking agent having three isocyanate groups in one molecule, or a hexafunctional isocyanate cross-linking agent having six isocyanate groups in one molecule. Further, when only an epoxy-based cross-linking agent is contained as a cross-linking agent, it is preferable to include only a bifunctional epoxy-based cross-linking agent having two epoxy groups in one molecule, a tri-functional epoxy-based cross-linking agent having three epoxy groups in one molecule, or a tetra-functional epoxy-based cross-linking agent having four epoxy groups in one molecule.

The content of the cross-linking agent in the pressure-sensitive adhesive composition is preferably 0.05 parts by mass or more, more preferably 0.07 parts by mass or more, and preferably 0.4 parts by mass or less, more preferably 0.3 parts by mass or less with respect to the total 100 parts by mass of the polymer components. If the content of the cross-linking agent is within the above range, the flexibility and resilience will be in a suitable range.

The molar ratio of the second reactive group of the crosslinking agent to the first reactive group of the (meth)acrylic polymer in the polymer component (molar amount of the first reactive group/molar amount of the second reactive group) is 1 or more, preferably 1.5 or more, more preferably 2.0 or more, and preferably 80 or less, more preferably 50 or less, further preferably 30 or less, and particularly preferably 20 or less. When the molar ratio is 1 or more, the cross-linking agent reacts just enough and the second reactive groups do not surplus, resulting in high flexibility.

(Other additives)
In addition to the polymer component and the cross-linking agent, other additives may be added to the adhesive composition. Other additives include cross-linking accelerators, cross-linking retarders, tackifying resins (tackifiers), polymerizable compounds, photoinitiators, silane coupling agents, plasticizers, softeners, release aids, dyes, pigments, dyes, fluorescent brighteners, antistatic agents, wetting agents, surfactants, thickeners, antifungal agents, preservatives, oxygen absorbers, ultraviolet absorbers, antioxidants, near-infrared absorbers, water-soluble quenching agents, fragrances, metal deactivators, nucleating agents, alkyls. modifiers, flame retardants, lubricants, processing aids, and the like. These are appropriately selected and blended for use according to the application and intended use of the adhesive.

(Crosslinking accelerator)
A cross-linking accelerator may be added to the adhesive composition as necessary. Examples of cross-linking accelerators include organic tin compounds and metal chelate compounds. The cross-linking accelerators may be used alone, or two or more of them may be used in combination.

Examples of the organic tin compounds include dibutyltin dilaurate, dioctiolstin dilaurate, and dibutyltin dioctylate. The metal chelate compound is a complex in which a ligand having two or more coordinating atoms forms a ring and is bound to a central metal.

The content of the cross-linking accelerator in the adhesive composition is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, still more preferably 0.04 parts by mass or more, and preferably 0.5 parts by mass or less, more preferably 0.4 parts by mass or less, and still more preferably 0.3 parts by mass or less. By setting the content of the cross-linking accelerator within the above range, it is possible to obtain an excellent effect of promoting cross-linking.

(Crosslinking retarder)
A cross-linking retarder may be added to the adhesive composition as necessary. The cross-linking retarder is a compound capable of suppressing an excessive increase in viscosity of the pressure-sensitive adhesive composition by blocking the functional group of the cross-linking agent in the pressure-sensitive adhesive composition containing the cross-linking 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. As the cross-linking retarder, one capable of acting as a chelating agent is preferable, and β-diketones and β-ketoesters are preferable.

The content of the cross-linking retarder that can be blended in the adhesive composition is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and still more preferably 0.5 parts by mass or more, with respect to 100 parts by mass of the polymer component. By adjusting the content of the cross-linking retarder to the above range, after the cross-linking agent is blended into the adhesive composition, excessive viscosity increase and gelation of the adhesive composition are suppressed, and the storage stability of the adhesive composition (pot life) can be extended.

(tackifying resin)
A tackifier resin other than the polymer component may be blended in the adhesive composition, if necessary. The tackifier resin is not particularly limited, and examples thereof include rosin-based tackifier resins, terpene-based tackifier resins, phenol-based tackifier resins, and hydrocarbon-based tackifier resins.

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

Examples of the rosin derivative include rosin phenolic resins obtained by adding phenol to rosins (unmodified rosin, modified rosin) with an acid catalyst and thermally polymerizing them; rosins such as rosin ester compounds (unmodified rosin esters) obtained by esterifying unmodified rosin with alcohols, and ester compounds of modified rosin obtained by esterifying modified rosins with alcohols (polymerized rosin esters, stabilized rosin esters, disproportionated rosin esters, completely hydrogenated rosin esters, partially hydrogenated rosin esters, etc.). Ester-based resins; unsaturated fatty acid-modified rosin-based resins obtained by modifying unmodified rosin or modified rosin with unsaturated fatty acids; unsaturated fatty acid-modified rosin ester-based resins obtained by modifying rosin ester-based resins with unsaturated fatty acids;

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

Examples of phenol-based tackifying resins include condensates of various phenols (e.g., phenol, m-cresol, 3,5-xylenol, p-alkylphenol, resorcinol) and formaldehyde (e.g., alkylphenol-based resins, xylene-formaldehyde-based resins), resoles obtained by subjecting the phenols and formaldehyde to an addition reaction with an alkali catalyst, and novolacs obtained by subjecting the phenols and formaldehyde to a condensation reaction with an acid catalyst.

Examples of hydrocarbon-based tackifying resins (petroleum-based tackifying resins) include aliphatic hydrocarbon resins [polymers of aliphatic hydrocarbons such as olefins and dienes having 4 to 5 carbon atoms (olefins such as butene-1, isobutylene, and pentene-1; dienes such as butadiene, 1,3-pentadiene, and isoprene)], and aliphatic cyclic hydrocarbon resins [so-called "C4 petroleum fraction" and "C5 petroleum fraction" are polymerized after cyclization dimerization. alicyclic hydrocarbon resins, polymers of cyclic diene compounds (cyclopentadiene, dicyclopentadiene, ethylidenenorbornene, dipentene, etc.) or hydrogenated products thereof, the following aromatic hydrocarbon resins and alicyclic hydrocarbon resins obtained by hydrogenating the aromatic rings of aliphatic/aromatic petroleum resins], aromatic hydrocarbon resins [vinyl group-containing aromatic hydrocarbons having 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, and the like.

The content of the tackifying resin that can be blended in the adhesive composition is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and still more preferably 20 parts by mass or more, with respect to 100 parts by mass of the polymer component. By adjusting the content of the tackifying resin within the above range, sufficient adhesion to the adherend can be ensured.

(Polymerizable compound) The adhesive composition may contain a polymerizable compound. Flexibility can be imparted to the adhesive by blending the polymerizable compound and polymerizing the polymerizable compound in the adhesive.

Examples of the polymerizable compound include compounds having two or more polymerizable groups in one molecule. Examples of polymerizable groups include ethylenically unsaturated groups. In addition, the said polymerizable compound can be used individually or in combination of 2 or more types. Examples of the polymerizable compound include compounds having two or more (meth)acryloyl groups, and polyfunctional monomers and polyfunctional oligomers are preferred. The number of ethylenically unsaturated groups in one molecule of the polymerizable compound is preferably 2 or more, preferably 4 or less, and more preferably 3 or less.

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

When a polymerizable compound is added to 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, with respect to 100 parts by mass of the polymer component.

(Photopolymerization Initiator) When the polymerizable compound is cured with an active energy ray, it is preferable to incorporate a photopolymerization initiator into the adhesive composition. By blending a photopolymerization initiator, the reaction during active energy ray irradiation can be stabilized. The photopolymerization initiator is not particularly limited as long as it generates radicals by the action of light. These photopolymerization initiators can be used alone or in combination of two or more. Among these photopolymerization initiators, photopolymerization initiators of hydrogen abstraction type benzophenones and intramolecular cleavage type acetophenones are preferable from the viewpoint of efficient intermolecular or intramolecular crosslinking.

When a photopolymerization initiator is added to the adhesive composition, the content of the photopolymerization initiator is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, 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 still more preferably 2 parts by mass or less, relative to 100 parts by mass of the polymer component. When the content of the photopolymerization initiator is within the above range, the curing speed is improved, and insufficient curing can be suppressed.

Further, the adhesive composition may contain an auxiliary agent for the photopolymerization initiator. Examples of the auxiliary agent include triethanolamine, triisopropanolamine, 4,4'-dimethylaminobenzophenone (Michler's 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, It is also possible to use 2,4-diisopropylthioxanthone and the like together. These auxiliaries may be used alone or in combination of two or more.

(Silane coupling agent)
A silane coupling agent may be added to the adhesive composition as necessary. The silane coupling agent is not particularly limited, and examples thereof include epoxy group-containing silane coupling agents such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4 epoxycyclohexyl)ethyltrimethoxysilane; 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N-(1, 3-dimethylbutylidene)propylamine, N-phenyl-γ-aminopropyltrimethoxysilane and other amino group-containing silane coupling agents; 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane and other (meth) acrylic group-containing silane coupling agents; and 3-isocyanatopropyltriethoxysilane and other isocyanate group-containing silane coupling agents.

The content of the silane coupling agent that can be blended in the adhesive composition is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, and preferably 1 part by mass or less, more preferably 0.8 parts by mass or less, and still more preferably 0.6 parts by mass or less, relative to 100 parts by mass of the polymer component. By adjusting the content of the silane coupling agent within the above range, the water resistance at the interface can be increased when the adhesive is applied to a hydrophilic adherend such as glass.

(Plasticizer) If necessary, the adhesive composition may contain a plasticizer. Examples of the plasticizer include, but are not limited to, 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; phthalate (DBP), dioctyl adipate, diisononyl adipate (DINA), isodecyl succinate and the like. The said plasticizer may be used individually by 1 type, and may use 2 or more types together. Among these, liquid rubber is preferred.

The weight average molecular weight (Mw) of the liquid rubber is preferably 5,000 or more, more preferably 10,000 or more, and preferably 60,000 or less, more preferably 50,000 or less. By adjusting the Mw of the liquid rubber to the above range, a highly flexible adhesive can be formed. A method for measuring the weight average molecular weight (Mw) will be described later.

When a plasticizer is added to the adhesive composition, the content of the plasticizer is preferably 1 part by mass or more, more preferably 5 parts by mass or more, still more preferably 10 parts by mass or more, and preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and still more preferably 30 parts by mass or less. By controlling the content of the plasticizer within the above range, it is possible to form an adhesive material having excellent adhesive strength and resilience.

(Method for producing adhesive composition)
The adhesive composition can be produced by mixing the polymer component, the cross-linking agent, and other optional additives. The adhesive composition may contain a solvent derived from the production of the polymer component, or may be a solution diluted to a viscosity suitable for forming an adhesive layer by adding an appropriate solvent.

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

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

The adhesive material of the present invention can be formed by applying and drying the adhesive composition. Moreover, the coating film may be heated, if necessary, in order to promote the formation of the crosslinked structure.

[Adhesive sheet]
The pressure-sensitive adhesive sheet of the present invention comprises a base sheet and a pressure-sensitive adhesive layer formed on at least one surface of the base sheet, wherein the pressure-sensitive adhesive layer is the pressure-sensitive adhesive. The adhesive layer is formed on at least one side or at least a part of the base sheet. The adhesive layer may be a single layer or may have a multilayer structure.

In general, "sheet" is defined in JIS as a thin flat product whose thickness is generally small relative to its length and width, and "film" generally refers to a thin flat product whose thickness is extremely small compared to its length and width and whose maximum thickness is arbitrarily limited, and is usually supplied in the form of a roll (Japanese Industrial Standard JIS K6900). For example, regarding the thickness, in a narrow sense, a sheet of 100 μm or more is called a sheet, and a thickness of less than 100 μm is sometimes called a film. However, the boundary between a sheet and a film is not clear, and there is no need to distinguish between the two in the present invention. Therefore, in the present invention, the term "sheet" includes the "film", and the term "film" includes the "sheet".

(base material sheet)
The base sheet can be appropriately selected and used according to the application of the pressure-sensitive adhesive sheet. Polyimide resin; polyester resin such as polyethylene terephthalate (PET) resin and polyethylene naphthalate (PEN) resin; polycarbonate resin; poly(meth)acrylate resin; polystyrene resin; polyamide resin; polyacrylonitrile resin; cellulose resin such as cellulose resin (TAC) resin, diacetyl cellulose resin; polyvinyl chloride resin; polyvinylidene chloride resin; polyvinyl alcohol resin; polyvinyl acetate resin; The polymeric materials may be used alone or in combination of two or more. Among these, PET resin is preferable in terms of excellent mechanical strength and dimensional stability. Moreover, a polyimide resin is preferable in that it is excellent in heat resistance. That is, the base sheet is preferably a PET sheet (especially a biaxially stretched PET sheet) or a polyimide sheet.

The thickness of the base sheet is not particularly limited and is appropriately selected, but is generally preferably 5 μm or more, more preferably 10 μm or more, still more preferably 20 μm or more, preferably 200 μm or less, more preferably 100 μm or less, and still 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 tearing of the sheet will occur when peeled off. Further, if the thickness of the base sheet is thicker than 200 μm, problems such as the sheet itself becoming expensive occur.

For the purpose of improving the adhesion to the layer provided on the surface of the base sheet, one side or both sides of the base sheet may be surface-treated by an oxidation method, a roughening method, or the like, if desired. Examples of the oxidation method include corona discharge treatment, plasma treatment, chromic acid treatment (wet), flame treatment, hot air treatment, ozone/ultraviolet irradiation treatment, and the like. Examples of the roughening method include a sandblasting method and a solvent treatment method. These surface treatment methods are appropriately selected according to the type of base sheet, but generally corona discharge treatment is preferably used from the standpoints of effectiveness and operability. Further, as the base sheet, one surface or both surfaces of which is subjected to a primer treatment can be used.

The thickness of the adhesive material (adhesive layer) formed on the base sheet can be appropriately set according to, for example, the adhesive force required for the adhesive sheet. The thickness of the adhesive layer is generally preferably 1 μm or more, more preferably 5 μm or more, still more preferably 10 μm or more, and preferably 100 μm or less, more preferably 70 μm or less, still more preferably 50 μm or less.

(Formation of adhesive layer)
The method for forming the adhesive layer is not particularly limited, and examples thereof include a method of applying an adhesive composition and drying it, as in the following methods (1) and (2).
(1) A method of applying an adhesive composition to one or both sides of a substrate sheet using various coating devices, removing the solvent by drying, and curing as necessary.
(2) A method in which an adhesive composition is applied to the release surface of a release sheet whose surface has been subjected to release treatment using various coating devices, the solvent is removed by drying, and the composition is transferred to one or both sides of the base sheet, followed by curing as necessary.

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.

The drying temperature for removing the solvent by drying is preferably 40° C. or higher, more preferably 60° C. or higher, and preferably 150° C. or lower, more preferably 140° C. or lower, and still 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 means include hot air, near-infrared rays, infrared rays, and high frequencies. Further, the curing conditions include, for example, 30° C. to 60° C. for 3 to 7 days.

(Release sheet)
The pressure-sensitive adhesive sheet may have a release sheet (separator) on the surface of the pressure-sensitive adhesive layer until it is used. A release layer is provided on the opposite side of the adhesive layer laminated surface of the base sheet without using a separate release sheet, and the surface of the release layer is wound in a roll or stacked in such a manner that the exposed surface side of the adhesive layer is in contact. 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 adherend.

Examples of the release sheet include paper such as glassine paper, coated paper, laminated paper, and various plastic sheets coated with a release agent such as silicone resin. As the plastic sheet used for the release sheet, the ones listed as the base sheet can be appropriately used. Although the thickness of the release sheet is not particularly limited, it is usually 10 μm to 150 μm.

(Application of adhesive material)
The adhesive material of the present invention is preferably used for an adhesive layer (adhesive material) used in a flexible display that can be repeatedly bent and stretched. Examples of the flexible display that can be used by repeatedly bending and stretching include a foldable display that can be folded and a rollable display that can be rolled into a cylindrical shape. Flexible displays are expected to be used for mobile terminals such as smartphones and tablet terminals, and stationary displays that can be stored.

[Adhesive materials for flexible displays, adhesive sheets for flexible displays]
As the adhesive material for flexible displays, it is suitable as an adhesive material for flexible displays for bonding one flexible member and another flexible member constituting a flexible display.

A flexible display adhesive sheet includes an adhesive layer used for bonding one flexible member and another flexible member constituting a flexible display, and a flexible sheet member attached to at least one surface of the adhesive layer. The adhesive layer is formed of the adhesive material.

Examples of the configuration of the pressure-sensitive adhesive sheet for a flexible display include an embodiment having an adhesive layer and a first flexible sheet member attached to one surface of the adhesive layer; and an embodiment having an adhesive layer and a first flexible sheet member attached to one surface of the adhesive layer and a second flexible sheet member attached to the other surface of the adhesive layer.

FIG. 1 shows an example of the adhesive sheet for a flexible display of the present invention. The flexible display adhesive sheet 10 of FIG. 1 is composed of an adhesive layer 12, a first flexible sheet member 14 sandwiching the adhesive layer 12, and a second flexible sheet member 16. As shown in FIG. The adhesive layer 12 is in contact with the releasable surfaces of the first flexible sheet member 14 and the second flexible sheet member 16 .

(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. In addition, 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 protrusion of the adhesive layer.

(Flexible sheet member)
Examples of the flexible sheet members include flexible base sheets and release sheets. 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 members include cover films, barrier films, polarizing films, retardation films, optical compensation films, brightness enhancement films, diffusion films, and antireflection films. The release sheet protects the adhesive layer until the adhesive layer is adhered to the adherend, and is peeled off from the adhesive layer before the adhesive layer is adhered to the adherend.

Examples of the flexible sheet members include polymeric material sheets and glass sheets. Although the thickness of the flexible sheet member is not particularly limited, it is preferably 2 μm to 500 μm, more preferably 2 μm to 200 μm from the viewpoint of excellent handleability.

Examples of the polymer material include polyimide resins; polyester resins such as polyethylene terephthalate resins and polyethylene naphthalate resins; polycarbonate resins; poly(meth)acrylate resins; polystyrene resins; polyamide resins; The polymeric materials may be used alone or in combination of two or more.

The flexible sheet member may be composed of a single layer composed of a layer containing one or more of the polymer materials, or may be composed of two or more layers, such as a layer containing one or more of the polymer materials and a layer containing one or more of different polymer materials.

It is preferable that the flexible sheet member is a release sheet having a surface in contact with the adhesive layer subjected to release treatment. Release agents used in the release treatment include, for example, silicone-based, fluorine-based, alkyd-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents.

The adhesive sheet for a flexible display has a first flexible sheet member attached to one surface of the adhesive layer and a second flexible sheet member attached to the other surface of the adhesive layer, wherein the first flexible sheet member is the first release sheet, the second flexible sheet member is the second release sheet, and the first release sheet and the second release sheet are preferably attached such that the release surfaces thereof 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 release type release sheet with a large release force and the other release sheet be a light release type release sheet with a small release force.

The pressure-sensitive adhesive sheet for a flexible display can be produced, for example, by applying the above-described pressure-sensitive adhesive composition onto a flexible sheet member and, if necessary, curing the composition by drying and heat treatment to form a pressure-sensitive adhesive layer.

For coating of the pressure-sensitive adhesive composition, for example, a reverse gravure coating method, a direct gravure coating method, a die coating method, a bar coating method, a wire bar coating method, a roll coating method, a spin coating method, a dip coating method, a spray coating method, a knife coating method, various coating methods such as a kiss coating method; an inkjet method; various printing methods such as offset printing, screen printing, and flexographic printing. In addition, before applying the adhesive composition, the surface of the release sheet may be subjected to surface treatment such as corona treatment, plasma treatment, hot air treatment, ozone treatment, and ultraviolet treatment.

The drying and heating step is not particularly limited as long as the solvent or the like used in the adhesive composition can be removed and cured. In particular, the heating temperature is preferably 100°C to 150°C.

When the first flexible sheet member is arranged on one side of the adhesive layer and the second flexible sheet member is arranged on the other side, the first flexible sheet member is coated with the adhesive composition, the first flexible sheet member is coated with the adhesive layer, and then the second flexible sheet member is attached to the adhesive layer. Furthermore, the adhesive layer may be cured as necessary. The curing conditions include, for example, 60° C. for about 3 to 7 days.

[Flexible laminated member]
A flexible laminate member of the present invention is a flexible laminate member comprising a first flexible member, a second flexible member, and an adhesive layer for bonding the first flexible member and the second flexible member together, wherein the adhesive layer is made of the adhesive material. Since 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 portion are suppressed.

FIG. 2 shows an example of the flexible laminated member of the present invention. The flexible laminated member 20 of FIG. 2 includes a first flexible member 22, a second flexible member 24, and an adhesive layer 12 between the first flexible member 22 and the second flexible member 24 for adhering these flexible members together.

Examples of the structure of the flexible laminated member include a structure in which both the first flexible member and the second flexible member are constituent members of the flexible device; and a structure in which the second flexible member is the flexible device and the first flexible member is a functional sheet member bonded to the flexible device. Examples of the flexible device include a foldable display that can be folded and a rollable display that can be rolled into a cylinder. Examples of the functional sheet members include cover films, barrier films, polarizing films, retardation films, optical compensation films, brightness enhancement films, diffusion films, antireflection films, transparent conductive films, metal mesh films, cushion films, and the like.

The first flexible member and the second flexible member are members that can be repeatedly bent or bent for use. 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.). At least one of the first flexible member and the second flexible member is preferably a display element. The flexible laminate member can be used in flexible displays.

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

(1) A method of peeling off the release sheet attached to one surface of the adhesive sheet, attaching the exposed adhesive layer to the first flexible member, peeling off the release sheet attached to the other surface of the adhesive sheet, and attaching the exposed adhesive layer and the second flexible member to obtain a flexible laminated member.
(2) An adhesive composition is applied to one surface of the first flexible member, and if necessary, cured by a dry heat treatment to form an adhesive layer, and then a release sheet having releasability is attached to the adhesive layer. Then, the adhesive layer exposed by peeling off the release sheet is attached to the second flexible member to obtain a flexible laminated member.
(3) A method of applying an adhesive composition onto one surface of the first flexible member, curing the adhesive composition by a drying heat treatment as necessary to form an adhesive layer, and then attaching the second flexible member to the adhesive layer to obtain a flexible laminated member.
(4) A pressure-sensitive adhesive composition is applied to the releasable surface of the release sheet, and if necessary cured by drying and heat treatment to form a pressure-sensitive adhesive layer, and the first flexible member is adhered to this pressure-sensitive adhesive layer. Then, the adhesive layer exposed by peeling off the release sheet is attached to the second flexible member to obtain a flexible laminated member.

In any of the cases (1) to (4) above, the order of using the first flexible member and the second flexible member may be changed.
The adhesive layer can be formed using various coating methods and various printing methods similar to those used in the production of the adhesive sheet, and the same applies to the drying and heating process. Moreover, you may cure as needed. Also, the release sheet used for manufacturing the flexible laminated member may be the same as the release sheet used for the pressure-sensitive adhesive sheet.

Hereinafter, the present invention will be described in more detail based on specific examples. The present invention is by no means limited to the following examples, and can be modified as appropriate without changing the gist of the invention. Polymer conversion, weight average molecular weight (Mw) and molecular weight distribution (Mw/Mn), adhesive layer thickness, adhesive material evaluation and sol component analysis were evaluated according to the following methods.

Abbreviations have the following meanings.
EHA: 2-ethylhexyl acrylate LA: n-lauryl acrylate HA: n-hexyl acrylate BA: n-butyl acrylate VP: N-vinyl-2-pyrrolidone ACMO: acryloylmorpholine AA: acrylic acid HBA: 4-hydroxybutyl acrylate BTEE: ethyl 2-methyl-2-n-butylteranyl-propionate AIBN: azobisisobutyronitrile AcOEt: ethyl acetate

(Polymerization rate)
¹ H-NMR was measured (solvent: CDCl ₃ , internal standard: trimethylsilane (TMS)) using a nuclear magnetic resonance (NMR) spectrometer (manufactured by Bruker Biospin, model: AVANCE500 (frequency: 500 MHz)). For the obtained NMR spectrum, the integral ratio of the signal derived from the monomer and the signal derived from the polymer was obtained to calculate the polymerization rate of the monomer.

(Weight average molecular weight (Mw) and molecular weight distribution (Mw/Mn))
Gel permeation chromatography (GPC) was performed using a high-performance liquid chromatograph (manufactured by Tosoh, model HLC-8320GPC). Two columns of TSKgel Super HZM-H (manufactured by Tosoh) were used, a tetrahydrofuran solution was used as a mobile phase, and a differential refractometer was used as a detector. The measurement conditions were a column temperature of 40° C., a sample concentration of 0.5 mg/ml, a sample injection amount of 10 μm, and a flow rate of 0.6 ml/min. Polystyrene (molecular weight 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) is used as a standard substance to create a calibration curve (calibration curve), and the weight average molecular weight ( Mw) and number average molecular weight (Mn) were measured. A molecular weight distribution (Mw/Mn) was calculated from this measured value.

(Adhesive material thickness (film thickness))
The total thickness of the adhesive sheet was measured using a thickness gauge ("TH-104" manufactured by Tester Sangyo Co., Ltd.), and the thickness of the adhesive material was obtained by subtracting the thickness of the release sheet from the total thickness.

(Dynamic viscoelasticity test)
The adhesive layers (adhesive material) constituting the adhesive sheet were laminated together using a hand roller to prepare a laminate having a thickness of 600 μm, which was used as a test piece. The measurement was performed using a dynamic viscoelasticity measuring device (manufactured by Anton Paar, MCR702) by sandwiching the sample between parallel plates with a diameter of 8 mm. The measurement conditions were a temperature range of −60° C. to 150° C., a temperature increase rate of 3° C./min, and a frequency of 1 Hz. The strain was changed stepwise according to the elastic modulus, from the start of measurement to 0.1% 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)
From the result of dynamic viscoelasticity measurement, the temperature at which the loss tangent (tan δ) was maximized was defined as the glass transition temperature Tg of the adhesive.
(Shear storage modulus G')
The shear storage modulus G' at 25°C was read from the dynamic viscoelasticity measurement results.

(Gel fraction)
A weight M2 of a wire mesh (400 mesh) cut into a size of 50 mm in width and 120 mm in length was measured. 80 mg to 120 mg of the adhesive layer (adhesive material) was sampled from the adhesive sheet, and the mass M1 was measured. A test piece was prepared by wrapping with a wire mesh so that the adhesive material would not fall off. The test piece was placed in a glass bottle, 40 g of ethyl acetate was poured into the bottle, and the bottle was shaken lightly, then allowed to stand at room temperature (25° C.) for 72 hours. After standing still, the test piece was taken out from the glass bottle, left at room temperature for 12 hours, and further dried in a vacuum oven at 100°C for 4 hours. The test piece after drying was cooled to room temperature, the mass M3 was measured, and the gel fraction was calculated from the following formula.
Gel fraction (mass%) = (M3-M2) / M1 × 100

(sol component)
After removing the test piece for gel fraction measurement from the glass bottle, the ethyl acetate solution containing the extracted sol component was dried to obtain a measurement sample. The solid in the vial was diluted with tetrahydrofuran to adjust the sample concentration to 0.5 mg/ml. Using this sample, gel permeation chromatography (GPC) was performed in the same manner as the measurement of the 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 measured, and the molecular weight distribution (Mw/Mn) was calculated from this weight average molecular weight (Mw) and number average molecular weight (Mn). The molecular weight at which the molecular weight distribution curve reaches a maximum was defined as the peak top molecular weight (Mp).
In addition, the ratio of the peak area with a molecular weight of 10,000 or more to less than 100,000 to the peak area of the molecular weight of 10,000 to 30 million (W1), the ratio of the peak area of the molecular weight of 100,000 to 560,000 to the peak area of the molecular weight of 10,000 to 30,000,000 (W2), the ratio of the peak area of the molecular weight of 560,000 or more to the peak area of the molecular weight of 10,000 to 30,000,000 (W3), the peak area of the molecular weight of 10,000 to 30,000,000. The ratio (W2a) of the peak area with a molecular weight of 100,000 or more and less than 150,000, and 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 30,000,000 were calculated.

(Stress relaxation time at 400% strain, recovery rate after 400% strain)
The adhesive layers (adhesive material) constituting the adhesive sheet were laminated together using a hand roller to prepare a laminate having a thickness of 600 μm, which was used as a test piece. The measurement was performed using a viscoelasticity measuring device (MCR302, manufactured by Anton Paar), sandwiching the sample between 8 mm diameter parallel plates (the adhesive surface was roughened with No. 240 sandpaper) and performed in an atmosphere of 25°C.
In the measurement, the test piece was compressed with an axial force of 1 N and left to stand for 10 minutes, then the axial force was changed to 0.05 N, and shear stress was immediately applied to strain the specimen up to 400% strain. Subsequently, the strain was kept at 400% for 10 minutes, and the change in shear stress was measured to measure the stress relaxation time. Next, the shear stress was released (0 kPa) and left for 10 minutes, and the final strain after 10 minutes was measured to obtain the recovery rate.
The stress relaxation time was the time required for the shear stress to become 0.368 times the initial stress after the strain reached 400%. The shear stress value 0.1 seconds after the start of shear stress application was defined as the initial stress.
The recovery rate was calculated based on the following formula.
Recovery rate (%) = {(400-final strain) / 400} x 100

(Strain at 20 kPa stress, recovery rate after applying 20 kPa stress)
The adhesive layers (adhesive material) constituting the adhesive sheet were laminated together using a hand roller to prepare a laminate having a thickness of 600 μm, which was used as a test piece. The measurement was performed using a viscoelasticity measuring device (MCR302, manufactured by Anton Paar), sandwiching the sample between 8 mm diameter parallel plates (the adhesive surface was roughened with No. 240 sandpaper) and performed in an atmosphere of 25°C.
In the measurement, the test piece was left to stand for 10 minutes while being compressed with an axial force of 1 N, then the axial force was changed to 0.05 N, a shear stress of 20 kPa was applied, a creep test was performed for 10 minutes, and the strain (20 kPa strain) was measured after 10 minutes. Next, the shear stress was released (0 kPa) and left for 10 minutes, and the final strain after 10 minutes was measured to obtain the recovery rate.
The recovery rate was calculated based on the following formula.
Recovery rate (%) = {(20 kPa strain - final strain) / 20 kPa strain} x 100

(Measurement of adhesive strength)
One release sheet of the pressure-sensitive adhesive sheet was peeled off from the pressure-sensitive adhesive layer, and the corona-treated surface of a polyethylene terephthalate (PET) film (Toyobo Ester (registered trademark) film E5100: manufactured by Toyobo Co., Ltd., thickness 50 μm) was adhered to the pressure-sensitive adhesive layer surface. The pressure-sensitive adhesive sheet with a substrate was measured for adhesion to a polyimide film or glass as an adherend according to the method of JIS Z 0237 (2009).
Specifically, the release sheet is peeled off from the adhesive layer, and the adhesive layer surface is a polyimide (PI) film (Kapton (registered trademark) 100V: manufactured by Toray DuPont, thickness 25 μm) or white plate glass (S9112, manufactured by Matsunami Glass Industry, thickness 1.0 to 1.2 mm). The sample pressure-bonded to the polyimide (PI) film was further autoclaved at 60° C., 5 atm, and 30 minutes. Next, using a precision universal testing machine "AUTOGRAPH (registered trademark) AGS-1kNX, 50N load cell" manufactured by Shimadzu Corporation, the adhesive strength of the adhesive layer was measured under the conditions of a peel speed of 300 mm/min and a peel angle of 180°.

<Production of (meth)acrylic polymer>
(Synthesis Example 1: Polymer No. 1)
EHA (278.4 g), LA (240.0 g), HA (60.0 g), AA (18.0 g), HBA (3.6 g), AIBN (17.4 mg) and AcOEt (400.0 g) were placed in a flask equipped with an argon gas inlet tube and a stirrer, and after purging with argon, BTEE (105.8 mg) was added and reacted at 60°C for 65 hours. and polymerized. The polymerization rate was 89%.
After completion of the reaction, AcOEt was added to the reaction solution, polymer no. A solution containing 1 was obtained. Polymer no. Mw of 1 was 1,532,000 and Mw/Mn was 1.86.

(Synthesis Examples 2-10, 13-21: Polymer Nos. 2-10, 13-21)
Polymer no. Polymer no. 2-10 and 13-21 were made. Tables 1 and 2 show the monomers, organotellurium compounds, azo polymerization initiators, solvents, reaction conditions, and polymerization rates used.

(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 in a flask equipped with an argon gas inlet tube and a stirrer, and after argon was replaced, the temperature was raised to 82° C., AIBN (1,094.7 mg) dissolved in AcOEt (50 g) was added dropwise over 2 hours, and the reaction was continued for 4 hours. , polymerized. After completion of the reaction, AcOEt was added to the reaction solution, polymer no. A solution containing 11 was obtained.

(Synthesis Example 12: Polymer No. 12)
BA (380.0 g), AA (20.0 g), and AcOEt (533.3 g) were placed in a flask equipped with an argon gas inlet tube and a stirrer, and 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, followed by further reaction for 2.5 hours to polymerize. After completion of the reaction, AcOEt was added to the reaction solution, polymer no. A solution containing 12 was obtained.

Tables 1 and 2 show the polymerization conditions and the like for each polymer. The amount of carboxyl groups, the amount of hydroxy groups and the glass transition temperature were calculated from the charging ratio and polymerization rate of the monomers used in the polymerization reaction.

<Production of adhesive composition>
(Adhesive composition No. 1)
Polymer No. obtained in Synthesis Example 1; 1 solution (polymer component 100 parts by mass), polymer No. 1 obtained in Synthesis Example 11; 0.222 parts by mass of a cross-linking agent (Duranate (registered trademark) D101) and butyl acetate were added to the solution of No. 11 (100 parts by mass of the polymer component), and stirred to give an adhesive composition No. 11 having a solid content of 24% by mass. got 1. Adhesive composition no. In No. 1, the first reactive group possessed by the (meth)acrylic polymer (A) (copolymer No. 1) is a hydroxy group, and the second reactive group possessed by the cross-linking agent is an isocyanate group.

(Adhesive composition No. 2 to 35)
Adhesive composition no. Adhesive composition No. 1 was prepared in the same manner as in 1. 2-35 were made. The amount of the cross-linking agent shown in Tables 3 to 5 is the amount in terms of solid content. A solid content is a component other than a solvent. Adhesive composition no. In Nos. 2 to 24 and 30 to 35, the first reactive group possessed by the (meth)acrylic polymer (A) is a hydroxy group, and the second reactive group possessed by the cross-linking agent is an isocyanate group. Adhesive composition no. In Nos. 25 to 29, the first reactive group possessed by the (meth)acrylic polymer (A) is a carboxy group, and the second reactive group possessed by the cross-linking agent is an epoxy group.

Cross-linking agent A: Duranate (registered trademark) D101 (manufactured by Asahi Kasei, isocyanate-based cross-linking agent (hexamethylene diisocyanate-1,6-hexanediol adduct, number of functional groups: 2, solid content concentration: 100% by mass, NCO content: 4.7 mmol/g (in terms of solid content)))
Cross-linking agent B: D178NL (manufactured by Mitsui Chemicals, isocyanate-based cross-linking agent (hexamethylene diisocyanate allophanate, functional group number 2, solid content concentration 100% by mass, NCO amount 4.6 mmol / g (solid content conversion)))
Cross-linking agent C: Duranate (registered trademark) TPA-100 (manufactured by Asahi Kasei, isocyanate-based cross-linking agent (hexamethylene diisocyanate cyclic trimer, number of functional groups: 3, solid content concentration: 100% by mass, NCO content: 5.5 mmol/g (solid content conversion)))
Cross-linking agent D: Duranate (registered trademark) MHG-80B (manufactured by Asahi Kasei, isocyanate-based cross-linking agent (isocyanurate of hexamethylene diisocyanate, functional group number 6, solid content concentration 80% by mass, NCO amount 4.5 mmol / g (solid content conversion)))
Cross-linking agent E: TETRAD (registered trademark)-C (manufactured by Mitsubishi Gas Chemical, epoxy-based cross-linking agent (1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, number of functional groups: 4, solid content concentration: 100% by mass, epoxy group content: 9.8 mmol/g (in terms of solid content))

<Production of adhesive sheet>
On the release surface of the first release sheet (PET film subjected to release treatment on the surface, Clean Sepa (registered trademark) HY-US20: manufactured by Higashiyama Film Co., Ltd., thickness 75 μm), the adhesive composition was applied so that the film thickness after drying using a baker applicator was 50 μm, followed by heating at 60 ° C. for 4 minutes and then at 150 ° C. for 5 minutes using a constant temperature dryer. Next, the release surface of the second release sheet (PET film subjected to release treatment on the surface, Clean Sepa (registered trademark) HY-S10: manufactured by Higashiyama Film Co., Ltd., thickness 38 μm) was attached to the adhesive layer formed on the first release sheet. Then, aging was performed at 60 ° C. for 3 days to produce an adhesive layer sandwiched between the two release sheets. Tables 6 to 8 show the evaluation results of the adhesive layer (adhesive material) formed from each adhesive composition.

Adhesive No. 1 to 29 are cases where 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). These adhesive no. 1 to 29 were good in both the recovery rate after being distorted to 400% strain and the amount of strain when a shear stress of 20 kPa was applied. Also, the adhesive strength was good for both glass and PI film.

Adhesive No. 30 is a case where the gel fraction exceeds 95% by mass and the content of the sol component is too small. This adhesive No. 30 had poor adhesion to both glass and PI film.
Adhesive No. 31 and 32 are cases where the gel fraction is less than 50% mass. These adhesive no. Nos. 31 and 32 were inferior in both the recovery rate after being distorted to 400% strain and the recovery rate when a shear stress of 20 kPa was applied.

Adhesive No. No. 33 is the case where the shear storage modulus at a temperature of 25° C. exceeds 0.15 MPa. This adhesive No. No. 33 had a poor recovery rate after straining up to 400% strain.
Adhesive No. 34 and 35 are cases where the differential molecular weight distribution curve of the sol component does not satisfy the requirements (2) and (3). These adhesive no. Nos. 34 and 35 had poor recovery rates when a shear stress of 20 kPa was applied, and had poor adhesion to both glass and PI film.

The present invention includes the following aspects.

(Aspect 1)
An adhesive material containing a polymer (X) having a crosslinked structure, which 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, a gel fraction of 50% to 95% by mass, and a differential molecular weight distribution curve of a sol component that satisfies the requirements of (1), (2), and (3).
(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 30,000,000 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 30,000,000 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 30,000,000 is 40% or less.

(Aspect 2)
The adhesive material according to aspect 1, wherein the differential molecular weight distribution curve of the sol component further satisfies requirements (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 30,000,000 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 30,000,000 is 20% or more.

(Aspect 3)
In the differential molecular weight distribution curve of the sol component, the ratio of the peak area ratio (W2) with a molecular weight of 100,000 or more and less than 560,000 to the peak area ratio (W2a) with a molecular weight of 100,000 or more and less than 150,000 (W2a/W2) is 0.30 to 0.60.

(Aspect 4)
The pressure-sensitive adhesive according to any one of modes 1 to 3, wherein the sol component has a weight average molecular weight (Mw) of 100,000 to 560,000.

(Aspect 5)
Among the peak molecular weights in the differential molecular weight distribution curve of the sol component, the highest peak molecular weight (Mp) is 100,000 to 500,000 at a molecular weight of 10,000 to 30,000,000. The adhesive according to any one of claims 1 to 4.

(Aspect 6)
The polymer (X) having a crosslinked structure is a (meth)acrylic polymer (A) having a first reactive group having a weight average molecular weight of 600,000 or more and 3,000,000 or less, a (meth)acrylic polymer (B) having a weight average molecular weight (Mw) of 100,000 or more and 800,000 or less, and a pressure-sensitive adhesive composition containing a crosslinking agent having a second reactive group that reacts with the first reactive group. Adhesive.

(Aspect 7)
The pressure-sensitive adhesive according to aspect 6, wherein the (meth)acrylic polymer (A) has a first reactive group content of 0.002 mmol/g to 1.0 mmol/g.

(Aspect 8)
Aspect 6 wherein the molar ratio of the second reactive group to the first reactive group in the adhesive composition (molar amount of the first reactive group/molar amount of the second reactive group) is 1 to 80. The adhesive according to 6 or 7.

(Aspect 9)
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 the first reactive group is a carboxy group, and the adhesive material according to any one of claims 6 to 8, which is a combination in which the second reactive group is an epoxy group.

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

(Aspect 11)
A pressure-sensitive adhesive sheet comprising a base sheet and an adhesive layer formed on at least one surface of the base sheet, wherein the pressure-sensitive adhesive layer is the pressure-sensitive adhesive material according to any one of claims 1 to 10.

(Aspect 12)
A flexible display adhesive material 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. A flexible display adhesive material.

(Aspect 13)
A pressure-sensitive adhesive sheet for a flexible display, comprising 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,
A 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 10.

(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 pressure-sensitive adhesive layer and a second flexible sheet member adhered to the other surface of the pressure-sensitive adhesive layer, wherein 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 so that their respective release surfaces are in contact with the pressure-sensitive adhesive layer.

(Aspect 15)
A flexible laminated member comprising a first flexible member, a second flexible member, and an adhesive layer for bonding the first flexible member and the second flexible member together, wherein the adhesive layer is a flexible laminated member comprising the adhesive material according to any one of claims 1 to 10.

10: Adhesive sheet 12: Adhesive layer 14: First flexible sheet member 16: Second flexible sheet member 20: Flexible laminate member 22: First flexible member 24: Second flexible member

Claims (15)

An adhesive containing a polymer (X) having a crosslinked structure,
Shear storage modulus at a temperature of 25 ° C. is 0.15 MPa or less,
a glass transition temperature of 0°C or lower;
The gel fraction is 50% by mass to 95% by mass, and
An adhesive material characterized in that the differential molecular weight distribution curve of the sol component satisfies the requirements (1), (2) and (3).
(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 30,000,000 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 30,000,000 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 30,000,000 is 40% or less. The pressure-sensitive adhesive according to claim 1, wherein the differential molecular weight distribution curve of the sol component further satisfies requirements (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 30,000,000 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 30,000,000 is 20% or more. In the differential molecular weight distribution curve of the sol component, the ratio (W2a/W2) of the peak area ratio (W2) having a molecular weight of 100,000 or more and less than 560,000 to the peak area ratio (W2a) having a molecular weight of 100,000 or more and less than 150,000 is 0.30 to 0.60. The adhesive material according to any one of claims 1 to 3, wherein the sol component has a weight average molecular weight (Mw) of 100,000 to 560,000. The pressure-sensitive adhesive according to any one of claims 1 to 3, wherein the highest peak molecular weight (Mp) is 100,000 to 500,000 among the peak molecular weights in the differential molecular weight distribution curve of the sol component at a molecular weight of 10,000 to 30,000,000. The polymer (X) having a crosslinked structure is a (meth)acrylic polymer (A) having a first reactive group having a weight average molecular weight of 600,000 or more and 3,000,000 or less, a (meth)acrylic polymer (B) having a weight average molecular weight (Mw) of 100,000 or more and 800,000 or less, and a pressure-sensitive adhesive composition containing a crosslinking agent having a second reactive group that reacts with the first reactive group, which is obtained by subjecting the adhesive composition to a crosslinking reaction according to any one of claims 1 to 3. adhesive. 7. The adhesive according to claim 6, wherein the (meth)acrylic polymer (A) has a first reactive group content of 0.002 mmol/g to 1.0 mmol/g. The molar ratio of the second reactive group to the first reactive group in the adhesive composition (molar amount of the first reactive group/molar amount of the second reactive group) is 1 to 80. The adhesive according to claim 6. 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. 7. The pressure-sensitive adhesive according to claim 6, wherein the (meth)acrylic polymer (A) has a structural unit content derived from a (meth)acrylate having an alkyl group having 1 to 12 carbon atoms of 70% by mass to 99% by mass. Having a base sheet and an adhesive layer formed on at least one surface of the base sheet,
A 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. A flexible display adhesive material for bonding one flexible member and another flexible member constituting a flexible display,
An adhesive material for a flexible display, wherein the adhesive material is the adhesive material according to any one of claims 1 to 3. A pressure-sensitive adhesive sheet for a flexible display, comprising 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,
A 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. The adhesive sheet has a first flexible sheet member attached to one surface of the adhesive layer and a second flexible sheet member attached to the other surface of the adhesive layer,
The first flexible sheet member is a first release sheet, the second flexible sheet member is a second release sheet,
14. The pressure-sensitive adhesive sheet for a flexible display according to claim 13, wherein the first release sheet and the second release sheet are adhered so that the respective release surfaces are in contact with the pressure-sensitive adhesive layer. A flexible laminated member comprising a first flexible member, a second flexible member, and an adhesive layer for bonding the first flexible member and the second flexible member together,
A flexible laminate member, wherein the adhesive layer comprises the adhesive material according to any one of claims 1 to 3.

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