Adhesive, adhesive sheet, laminate and display

Abstract

The purpose of the present invention is to provide: an adhesive agent which has excellent transparency and is capable of combining heat resistance, wet heat resistance, buckling properties and winding properties; an adhesive sheet; the laminate; and a display. This problem is solved by an adhesive agent characterized by containing an acrylic copolymer (A1), an acrylic copolymer (A2), and a crosslinking agent (B), the SP value, glass transition temperature, and weight average molecular weight of the acrylic copolymer (A1), and the SP value, glass transition temperature, and weight average molecular weight of the acrylic copolymer (A2) satisfy specific requirements.

Description

Technical Field

[0001] The present disclosure relates to an adhesive for forming a laminate including a light-transmitting substrate, an adhesive layer and a polarizing plate, an adhesive sheet, and a laminate having an adhesive layer formed of the adhesive sheet. The laminate is used for display applications. Background Art

[0002] Thin-film image display devices such as liquid crystal displays and organic electroluminescence (EL) displays generally have a laminated structure including a liquid crystal layer, an organic EL layer and other image forming layers, and an optical film and a cover plate and other coating layers. Generally, adhesives are used in the bonding of the layers constituting the image display device. For example, the transparent conductive film used in the touch screen is laminated on components such as the supporting glass and the supporting film via an adhesive layer. In addition, the polarizing plate film used in the image device is attached to modules such as the liquid crystal module and the organic EL module via an adhesive layer. In this way, the components of the image display device are attached and fixed by the adhesive layer.

[0003] Furthermore, as the image display device, flat panel displays using glass substrates are the mainstream, but in recent years, flexible displays such as foldable displays that can be folded and rollable displays that can be rolled up using flexible substrates such as plastics have been developed. Compared with conventional flat panel displays using glass substrates, such flexible displays have various advantages such as lightness, thinness, flexibility, and excellent design.

[0004] The adhesive layer has always been required to have the property of not bubbling or peeling off in a high temperature environment or a high temperature and high humidity environment, but in recent years, further functionalization has been required, and flexibility is required in flexible displays. The so-called flexibility, for example, in a foldable display, is the adaptability (flexibility) corresponding to the bending of the display. Generally speaking, as flexibility, what is required is the property of not bubbling, floating, and peeling off when repeatedly bent (dynamic flexibility).

[0005] In order to solve these problems, a pressure-sensitive adhesive having a urethane polymer chain and an acrylic polymer chain is disclosed in Patent Document 1. Also, a pressure-sensitive adhesive having a main agent and an ionic compound and having a storage elastic modulus within a specific range after curing is disclosed in Patent Document 2.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2021-161433

[0009] Patent Document 2: Japanese Patent Application Publication No. 2022-115914 Summary of the invention

[0010] Problems to be solved by the invention

[0011] However, in recent years, in order to cope with the further high durability of displays, the adhesive used has been sought to have a more stringent durability than before. In particular, in foldable displays, in addition to seeking the property of not bubbling, floating and peeling when repeatedly bent (dynamic flexibility), it is also sought that the property of not bubbling, floating and peeling when the bent state is maintained for a long time (static flexibility). In addition, in a roll-up display, the suitability (winding property) corresponding to the winding of the display is sought so that it can be used in a roll-up display. As the winding property, the property of not bubbling, floating or peeling when the rolled state is maintained for a long time is sought.

[0012] Furthermore, in the past, these flexibility requirements were only sought at room temperature, but with the popularization of displays, flexibility is further sought in low-temperature environments such as those in extremely cold regions and high-temperature environments such as those in extremely hot regions and in cars under the scorching sun.

[0013] On the other hand, conventional adhesive sheets may not have satisfactory heat resistance and moisture-heat resistance and flexibility such as bending and windability at a level that does not cause practical problems.

[0014] In addition, regarding flexibility, dynamic flexibility, static flexibility, and rollability are sought according to the display structure. However, the current situation is that even if flexibility can be satisfied alone, it is difficult to satisfy all properties at the same time in most cases. In addition, in a high temperature environment or a high temperature and high humidity environment, it is even more difficult to satisfy all of dynamic flexibility, static flexibility, and rollability in most cases.

[0015] An object of the present disclosure is to provide an adhesive, an adhesive sheet, a laminate, and a display that are excellent in transparency and can achieve all of heat resistance, moisture-heat resistance, flexibility, and windability.

[0016] Technical means of solving problems

[0017] The present inventors have conducted diligent studies and, as a result, have found that the problems of the present disclosure can be solved by the following means, thereby completing the present disclosure.

[0018] That is, in one embodiment, the above-mentioned problem is solved by an adhesive comprising an acrylic copolymer (A1), an acrylic copolymer (A2), and a crosslinking agent (B), and satisfying all of the following (1) to (5).

[0019] (1)SP(A1)>SP(A2), and 0.50<|SP(A1)-SP(A2)|<1.60

[0020] (2)Tg(A1)<Tg(A2), and 100<|Tg(A1)-Tg(A2)|<180

[0021] (3) Mw(A1) 500,000 to 2,000,000

[0022] (4) Mw(A2) is 5,000 to 100,000

[0023] (5) 10<Mw(A1) / Mw(A2)<80

[0024] Here, in the formula,

[0025] SP(A1) is the solubility parameter (SP) value of the acrylic copolymer (A1).

[0026] SP(A2) is the SP value of the acrylic copolymer (A2)

[0027] Tg(A1) is the glass transition temperature of the acrylic copolymer (A1).

[0028] Tg(A2) is the glass transition temperature of the acrylic copolymer (A2).

[0029] Mw(A1) is the weight average molecular weight of the acrylic copolymer (A1).

[0030] Mw(A2) is the weight average molecular weight of the acrylic copolymer (A2).

[0031] |SP(A1)-SP(A2)| is the absolute value of the difference between SP(A1) and SP(A2)

[0032] |Tg(A1)-Tg(A2)| is the absolute value of the difference between Tg(A1) and Tg(A2)

[0033] Mw(A1) / Mw(A2) is a value obtained by dividing Mw(A1) by Mw(A2).

[0034] In addition, one embodiment is the adhesive, characterized in that the acrylic copolymer (A1) is a copolymer of a monomer mixture containing the following monomer (a-1) and the following monomer (a-2), and the acrylic copolymer (A2) is a copolymer of a monomer mixture containing the following monomer (a-3) and the following monomer (a-4).

[0035] (a-1) Alkyl (meth)acrylate monomers having an alkyl group with 8 to 12 carbon atoms (except for the following monomer (a-3))

[0036] (a-2) one or more monomers having a polar group selected from monomers having a hydroxyl group and monomers having a carboxyl group

[0037] (a-3) Cycloalkyl (meth)acrylate monomer having a cycloalkyl group

[0038] (a-4) Monomer having an amino group

[0039] In another embodiment, the adhesive is characterized in that the acrylic copolymer (A1) contains 25% to 99% by mass of the monomer (a-1) and 0.1% to 4% by mass of the monomer (a-2) in 100% by mass of the monomer mixture,

[0040] The acrylic copolymer (A2) contains 25 to 99% by mass of the monomer (a-3) and 0.1 to 4% by mass of the monomer (a-4) in 100% by mass of the monomer mixture.

[0041] Moreover, one embodiment is the adhesive, characterized by containing 1 to 30 parts by mass of the acrylic copolymer (A2) based on 100 parts by mass of the acrylic copolymer (A1).

[0042] In another embodiment, the adhesive is characterized in that the weight average molecular weight of the acrylic copolymer (A1) is 800,000 to 1,500,000, and the weight average molecular weight of the acrylic copolymer (A2) is 20,000 to 80,000.

[0043] In addition, one embodiment of the adhesive is characterized in that a gel fraction is 60% by mass to 90% by mass.

[0044] In addition, one embodiment of the adhesive is characterized in that the cross-linking agent (B) is an isocyanate compound.

[0045] In addition, one embodiment provides an adhesive sheet including an adhesive layer which is a cured product of the adhesive.

[0046] Another embodiment provides a laminate including a light-transmitting substrate, an adhesive layer, and a polarizing plate, wherein the adhesive layer includes an adhesive layer that is a cured product of the adhesive.

[0047] Another embodiment provides a display including the laminate and an optical element.

[0048] Effects of the Invention

[0049] The present disclosure can provide an adhesive agent, an adhesive sheet, and a laminate using the adhesive sheet that are excellent in transparency and can achieve all of heat resistance, moisture-heat resistance, flexibility, and windability.

[0050] Furthermore, by using the adhesive sheet and laminate of the present disclosure, a display having excellent visibility and contrast can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] [ Figure 1 ] is a schematic cross-sectional view partially showing the adhesive sheet of the present invention.

[0052] [ Figure 2 ] is a schematic cross-sectional view partially showing a laminate as an example of use of the adhesive sheet disclosed in the present invention.

[0053] [ Figure 3 ] is a schematic cross-sectional view partially showing a display as an example of use of the adhesive sheet disclosed in the present invention. DETAILED DESCRIPTION

[0054] Hereinafter, structural examples of the adhesive, adhesive sheet, laminate, and display of the present disclosure will be described, but the present disclosure is not limited to these.

[0055] The terms used in this specification are defined. The so-called (meth)acrylate includes acrylate and methacrylate. That is, the so-called (meth)acrylate may refer to either acrylate or methacrylate, or both. The monomers in the monomers (a-1) to (a-4) described later refer to monomers containing ethylenically unsaturated groups. The so-called adherend refers to the object to which the adhesive sheet is to be attached. In this specification, sheet, film and tape are synonymous.

[0056] In the present specification, (a-1) an alkyl (meth)acrylate monomer having an alkyl group with 8 to 12 carbon atoms, (a-2) a monomer having a polar group or more selected from a monomer having a hydroxyl group and a monomer having a carboxyl group, (a-3) a cycloalkyl (meth)acrylate monomer having a cycloalkyl group, (a-4) a monomer having an amino group, (a-5) a monomer other than (a-1) to (a-4), an acrylic copolymer (A1), and an acrylic copolymer (A2) may be referred to as a monomer (a-1), a monomer (a-2), a monomer (a-3), a monomer (a-4), a monomer (a-5), a copolymer (A1), and a copolymer (A2), respectively.

[0057] In addition, unless otherwise specified, various components appearing in the present specification may be used alone or in combination of two or more.

[0058] In the present specification, a numerical range specified using “to” is a range including the numerical values ​​described before and after “to” as the lower limit and the upper limit.

[0059] In the numerical range recorded in this specification, the upper limit or lower limit recorded in one numerical range can also be replaced by the upper limit or lower limit of the numerical range recorded in other stages. In addition, in the numerical range recorded in this specification, the upper limit or lower limit of its numerical range can also be replaced by the value shown in the embodiment.

[0060] "Adhesive"

[0061] The adhesive disclosed herein is an adhesive characterized by comprising an acrylic copolymer (A1), an acrylic copolymer (A2), and a crosslinking agent (B), and satisfying all of the following (1) to (5).

[0062] (1)SP(A1)>SP(A2), and 0.50<|SP(A1)-SP(A2)|<1.60

[0063] (2)Tg(A1)<Tg(A2), and 100<|Tg(A1)-Tg(A2)|<180

[0064] (3) Mw(A1) 500,000 to 2,000,000

[0065] (4) Mw(A2) is 5,000 to 100,000

[0066] (5) 10<Mw(A1) / Mw(A2)<80

[0067] Here, in the formula,

[0068] SP(A1) is the SP value of the acrylic copolymer (A1)

[0069] SP(A2) is the SP value of the acrylic copolymer (A2)

[0070] Tg(A1) is the glass transition temperature of the acrylic copolymer (A1)

[0071] Tg(A2) is the glass transition temperature of the acrylic copolymer (A2)

[0072] Mw(A1) is the weight average molecular weight of the acrylic copolymer (A1)

[0073] Mw(A2) is the weight average molecular weight of the acrylic copolymer (A2)

[0074] |SP(A1)-SP(A2)| is the absolute value of the difference between SP(A1) and SP(A2)

[0075] |Tg(A1)-Tg(A2)| is the absolute value of the difference between Tg(A1) and Tg(A2)

[0076] Mw(A1) / Mw(A2) is a value obtained by dividing Mw(A1) by Mw(A2).

[0077] <Acrylic acid copolymer (A1) and acrylic acid copolymer (A2)>

[0078] The acrylic copolymer (A1) and the acrylic copolymer (A2) may be a copolymer of a monomer mixture selected from the monomers described below. Specifically, the monomers include: (meth) alkyl acrylate monomers, (meth) cycloalkyl acrylate monomers having a cycloalkyl group, monomers having an aromatic ring, monomers having a hydroxyl group, monomers having a carboxyl group, monomers having an epoxy group, monomers having an amino group, monomers having an alkyleneoxy group, monomers having an amide group, other vinyl monomers, and the like.

[0079] Specific examples of the alkyl (meth)acrylate monomer include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, isohexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, and dodecyl (meth)acrylate.

[0080] Examples of the cycloalkyl (meth)acrylate monomer having a cycloalkyl group include cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, trimethylcyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentyl (meth)acrylate.

[0081] Examples of the monomer having an aromatic ring include phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, biphenyl (meth)acrylate, and styrene.

[0082] Examples of the monomer having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and hydroxycyclohexyl (meth)acrylate.

[0083] Examples of the monomer having a carboxyl group include (meth)acrylic acid, p-carboxybenzyl acrylate, β-carboxyethyl acrylate, maleic acid, monoethylmaleic acid, itaconic acid, citraconic acid, and fumaric acid.

[0084] Examples of the monomer having an epoxy group include glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, and 6-methyl-3,4-epoxycyclohexylmethyl (meth)acrylate.

[0085] Examples of the monomer having an amino group include monoalkylamino (meth)acrylates such as monomethylaminoethyl (meth)acrylate, monoethylaminoethyl (meth)acrylate, monomethylaminopropyl (meth)acrylate, and monoethylaminopropyl (meth)acrylate.

[0086] Examples of the monomer having an alkyleneoxy group include a monomer represented by the following general formula (1) or a monomer represented by the following general formula (2).

[0087] [Chemistry 1]

[0088]

[0089] [Chemistry 2]

[0090]

[0091] In the general formula (1) and the general formula (2), R 1 , R 2 Each independently represents a hydrogen atom or a methyl group, and n and m are integers representing a repeating unit, and are 1≤n≤25 and 1≤m≤25. Here, n and m are preferably 1≤n≤13 and 1≤m≤5, respectively.

[0092] Examples of commercially available products of the monomer represented by the general formula (1) include methoxyethyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.; in the general formula (1), R 1 is a hydrogen atom, n=1), methoxydiethylene glycol acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.; in the general formula (1), R 1 is a hydrogen atom, n=2), methoxytriethylene glycol acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.; in the general formula (1), R 1 is a hydrogen atom, n=3), methoxy polyethylene glycol #400 acrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.; in the general formula (1), R 1 is a hydrogen atom, n=9), methoxy polyethylene glycol #600 acrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.; in the general formula (1), R 1is a hydrogen atom, n=13), methoxy polyethylene glycol #1000 acrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.; in the general formula (1), R 1 is a hydrogen atom, n=23), methoxydiethylene glycol methacrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.; in the general formula (1), R 1 is methyl, n=2), methoxytriethylene glycol methacrylate (produced by Shin-Nakamura Chemical Industry Co., Ltd.; in the general formula (1), R 1 is methyl, n=3), methoxytetraethylene glycol methacrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.; in the general formula (1), R 1 is methyl, n=4), methoxy polyethylene glycol #400 methacrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.; in the general formula (1), R 1 is a hydrogen atom, n=9), methoxy polyethylene glycol #600 methacrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.; in the general formula (1), R 1 is a hydrogen atom, n=13), methoxy polyethylene glycol #1000 methacrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.; in the general formula (1), R 1 is a hydrogen atom, n=23).

[0093] Examples of commercially available products of the monomer represented by the general formula (2) include methoxytripropylene glycol acrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.); in the general formula (2), R 2 is a hydrogen atom, m=3), methoxytripropylene glycol methacrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.; in the general formula (2), R 2 is methyl, m=3).

[0094] Examples of monomers having an amide group include (meth)acrylamide compounds ((meth)acrylamide monomers) such as N-methyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide, diacetone(meth)acrylamide, and N-(butoxymethyl)(meth)acrylamide; and heterocyclic compounds (amide monomers) such as N-vinylpyrrolidone, N-vinylcaprolactam, and acryloylmorpholine.

[0095] Examples of other vinyl monomers include vinyl acetate, vinyl crotonate, and acrylonitrile.

[0096] The acrylic copolymer (A1) preferably contains an alkyl (meth)acrylate monomer among the above monomers, and particularly preferably contains an alkyl (meth)acrylate monomer (a-1) having an alkyl group with a carbon number of 8 to 12. The monomer (a-1) is a monomer other than the monomer (a-3) described below whose alkyl group is a cycloalkyl group.

[0097] More specifically, the monomer (a-1) is preferably 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, or dodecyl (meth)acrylate from the viewpoint of stress relaxation properties and adhesion.

[0098] The monomer (a-1) is preferably contained in an amount of 25% to 99% by mass, more preferably 40% to 99% by mass, in 100% by mass of the monomer mixture constituting the acrylic copolymer (A1). When the content of the monomer (a-1) is 25% by mass or more, sufficient stress relaxation is easily obtained. In addition, when the content of the monomer (a-1) is 99% by mass or less, both cohesion and stress relaxation are easily obtained.

[0099] These monomers (a-1) may be used alone or in combination of two or more. In particular, from the viewpoint of achieving both adhesion and cohesive force, it is more preferred to use two or more monomers (a-1) in combination.

[0100] In addition, the acrylic copolymer (A1) preferably contains a monomer having a polar group, and particularly preferably contains a monomer (a-2) having a polar group selected from a monomer having a hydroxyl group and a monomer having a carboxyl group. More specifically, as the monomer (a-2), from the viewpoint of cohesive force and adhesion, preferably, 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and (meth)acrylic acid.

[0101] The monomer (a-2) is preferably contained in an amount of 0.1% to 4% by mass, more preferably 0.4% to 3% by mass, in 100% by mass of the monomer mixture constituting the acrylic copolymer (A1). When the content of the monomer (a-2) is 0.1% by mass or more, sufficient cohesion is easily obtained. In addition, when the content of the monomer (a-2) is 4% by mass or less, cohesion and stress relaxation are easily obtained.

[0102] The acrylic copolymer (A2) preferably contains a (meth)acrylate cycloalkyl ester monomer (a-3) having a cycloalkyl group among the above monomers. More specifically, as the monomer (a-3), cyclohexyl (meth)acrylate and isobornyl (meth)acrylate are preferred from the viewpoint of cohesive force and adhesion.

[0103] The monomer (a-3) is preferably contained in an amount of 25% to 99% by mass, more preferably 40% to 99% by mass, in 100% by mass of the monomer mixture constituting the acrylic copolymer (A2). When the content of the monomer (a-3) is 25% by mass or more, sufficient cohesion can be easily obtained. In addition, when the content of the monomer (a-3) is 99% by mass or less, cohesion and stress relaxation can be easily obtained.

[0104] In addition, the acrylic copolymer (A2) preferably contains a monomer (a-4) having an amino group among the above monomers. More specifically, as the monomer (a-4), from the viewpoint of cohesive force and adhesion, monomethylaminoethyl (meth)acrylate, monoethylaminoethyl (meth)acrylate, 2-dimethylaminoethyl (meth)acrylate, and 2-diethylaminoethyl (meth)acrylate are preferred.

[0105] The monomer (a-4) is preferably contained in an amount of 0.1% to 4% by mass, more preferably 0.4% to 3% by mass, in 100% by mass of the monomer mixture constituting the acrylic copolymer (A2). When the content of the monomer (a-4) is 0.1% by mass or more, sufficient cohesion is easily obtained. In addition, when the content of the monomer (a-4) is 4% by mass or less, cohesion and stress relaxation are easily obtained.

[0106] Each acrylic copolymer may also contain a monomer other than monomers (a-1) to (a-4), namely, monomer (a-5). As monomer (a-5), the monomer having an aromatic ring, the monomer having an epoxy group, the monomer having an alkylene oxide group, the monomer having an amide group, other vinyl monomers, etc. can be used. The content ratio of the monomer (a-5) in 100% by mass of the monomer mixture constituting each acrylic copolymer can be appropriately set within the range in which the effects of the present disclosure can be obtained, and is not particularly limited.

[0107] <Calculation of solubility parameter (SP value) of acrylic copolymer>

[0108] Next, the SP values ​​of each of the acrylic copolymer (A1) and the acrylic copolymer (A2) are described. In the present disclosure, the SP value of the acrylic copolymer is calculated by using the following formula 3. In addition, the SP value of the monomer constituting the acrylic copolymer is to be referred to the calculation method of Fedors ["Polymer Engineering and Science", Vol. 14, No. 2 (1974), pp. 148 to 154].

[0109] [Formula 3]

[0110] δ=(ΣΔe 1 M1 +Δe 2 M 2 +···Δe n M n ) / (ΣΔv 1 M 1 +Δv 2 M 2 +···Δv n M n ) 1 / 2

[0111] [wherein, δ is the solubility parameter (SP value) of the acrylic copolymer (A1) and the acrylic copolymer (A2), Δe i (i=1, 2, ... n) is the molar evaporation energy of monomer i constituting the acrylic copolymer, Δv i (i=1, 2, ... n) is the molar volume of monomer i constituting the acrylic copolymer, M i (i=1, 2, ... n) represents the molar fraction of monomer i constituting the acrylic copolymer in all monomer components]

[0112] Here, the unit of solubility parameter is (cal / mol) 1 / 2 .

[0113] In the adhesive disclosed herein, the SP value of the acrylic copolymer (A1), i.e., SP (A1), and the SP value of the acrylic copolymer (A2), i.e., SP (A2), are SP (A1) > SP (A2), and the absolute value of the difference between SP (A1) and SP (A2), i.e., | SP (A1) - SP (A2) |, is 0.50 < | SP (A1) - SP (A2) | < 1.60. Here, the absolute value of the difference between SP (A1) and SP (A2) is preferably 0.60 < | SP (A1) - SP (A2) | < 1.30.

[0114] The adhesive disclosed herein comprises two acrylic copolymers having different SP values. The acrylic copolymer (A1) as a high-polarity acrylic copolymer improves adhesion to a high-polarity adherend, and the acrylic copolymer (A2) as a low-polarity acrylic copolymer improves adhesion to a low-polarity adherend. When |SP(A1)-SP(A2)| is greater than 0.50, adhesion to a low-polarity adherend and a high-polarity adherend can be improved, and when it is less than 1.60, transparency can be maintained.

[0115] <Calculation of glass transition temperature (Tg) of acrylic copolymer>

[0116] Next, the Tg of each of acrylic copolymer (A1) and acrylic copolymer (A2) is described. In the present disclosure, the Tg of acrylic copolymer is obtained by calculating the Tg of the homopolymer based on each monomer using the Fox formula represented by the following formula 4. In addition, the Tg of the homopolymer of the monomer constituting the acrylic copolymer is the numerical value recorded in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989). In addition, for the monomer not recorded in the "Polymer Handbook", the catalog value of the monomer manufacturing company is adopted.

[0117] [Formula 4]

[0118] Fox formula: 1 / Tg=W 1 / Tg 1 +W 1 / Tg 1 +···W n / Tg n )

[0119] [wherein, Tg is the glass transition temperature (Tg) of the acrylic copolymer (A1) or the acrylic copolymer (A2) (to be calculated), Tg i (i=1, 2, ... n) is the glass transition temperature (Tg) of the monomer i constituting the acrylic copolymer (for calculating Tg), i (i=1, 2, ... n) represents the mass fraction of monomer i constituting the acrylic copolymer (for which Tg is calculated) in all monomer components]

[0120] Here, the unit of glass transition temperature is (K).

[0121] In the adhesive disclosed herein, the Tg of the acrylic copolymer (A1), i.e., Tg(A1), and the Tg of the acrylic copolymer (A2), i.e., Tg(A2), are Tg(A1)<Tg(A2), and the absolute value of the difference between Tg(A1) and Tg(A2), i.e., |Tg(A1)-Tg(A2)|, is 100<|SP(A1)-SP(A2)|<180. Here, the absolute value of the difference between Tg(A1) and Tg(A2) is preferably 120<|SP(A1)-SP(A2)|<160.

[0122] The adhesive disclosed herein comprises two acrylic copolymers having different Tgs, wherein the acrylic copolymer (A1) as a low Tg acrylic copolymer improves adhesion to an adherend, and the acrylic copolymer (A2) as a high Tg acrylic copolymer improves durability. When |Tg(A1)-Tg(A2)| is greater than 100, adhesion and durability can be improved, and when it is less than 180, transparency can be maintained.

[0123] <Measurement of Weight Average Molecular Weight (Mw) of Acrylic Copolymer>

[0124] Next, the Mw of each of the acrylic copolymer (A1) and the acrylic copolymer (A2) is described. In the present disclosure, the Mw of the acrylic copolymer is a value converted to polystyrene measured by gel permeation chromatography (GPC). Specifically, the GPC "LC-GPC system" manufactured by Shimadzu Corporation can be used to obtain the converted value of the weight average molecular weight using polystyrene with a known molecular weight as a standard substance.

[0125] Device name: LC-GPC system "Prominence" manufactured by Shimadzu Corporation

[0126] Pipe string: Four GMHXL pipes manufactured by Tosoh and one HXL-H pipe manufactured by Tosoh are connected.

[0127] Mobile phase solvent: tetrahydrofuran

[0128] Flow rate: 1.0ml / min

[0129] Column temperature: 40℃

[0130] The weight average molecular weight of the acrylic copolymer (A1) is 500,000 to 2,000,000, preferably 800,000 to 1,500,000. When the weight average molecular weight of the acrylic copolymer (A1) is within the range of 500,000 to 2,000,000, the cohesive force is improved, and the moist heat resistance and heat resistance are improved.

[0131] The weight average molecular weight of the acrylic copolymer (A2) is 5,000 to 100,000, preferably 20,000 to 80,000. When the weight average molecular weight of the acrylic copolymer (A2) is in the range of 5,000 to 100,000, adhesion is improved, and flexibility and windability are improved.

[0132] In the adhesive disclosed in the present invention, the value obtained by dividing the weight average molecular weight of the acrylic copolymer (A1), i.e., Mw(A1), by the weight average molecular weight of the acrylic copolymer (A2), i.e., Mw(A2), i.e., Mw(A1) / Mw(A2) is 10<Mw(A1) / Mw(A2)<80. Here, the value obtained by dividing Mw(A1) by Mw(A2) is preferably 20<Mw(A1) / Mw(A2)<70. The adhesive disclosed in the present invention comprises two acrylic copolymers having different Mws, and the acrylic copolymer (A1), which is a high Mw acrylic copolymer, improves durability, and the acrylic copolymer (A2), which is a low Mw acrylic copolymer, improves anchoring to the adherend. By making Mw(A1) / Mw(A2) greater than 10, durability and anchoring to the adherend can be improved, and by making it less than 80, poor durability caused by bleeding of the low Mw acrylic copolymer (A2) can be suppressed.

[0133] <Blending ratio of acrylic copolymer (A1) and acrylic copolymer (A2)>

[0134] The adhesive of the present disclosure preferably contains 1 to 30 parts by mass of the acrylic copolymer (A2) relative to 100 parts by mass of the acrylic copolymer (A1), and more preferably contains 2 to 20 parts by mass. When the content of the acrylic copolymer (A2) is 1 part by mass or more, the adhesion and durability to the adherend can be further improved. In addition, when the content is 30 parts by mass or less, the flexibility is easily maintained, and the flexibility and winding properties are easily maintained.

[0135] [Manufacturing of acrylic copolymer]

[0136] The copolymer (A1) and the copolymer (A2) can be produced by polymerizing a monomer mixture containing the monomer (a-1) and the monomer (a-2), and a monomer mixture containing the monomer (a-3) and the monomer (a-4), respectively.

[0137] As the polymerization method, existing polymerization methods such as solution polymerization, bulk polymerization, emulsion polymerization, and suspension polymerization can be applied, and solution polymerization is preferred. The solvent used in solution polymerization is preferably acetone, methyl acetate, ethyl acetate, toluene, xylene, anisole, methyl ethyl ketone, cyclohexanone, etc.

[0138] The polymerization temperature is preferably a boiling point reaction of 60° C. to 120° C. The polymerization time is preferably about 5 hours to 12 hours.

[0139] The polymerization initiator used in the polymerization is preferably a free radical polymerization initiator. Free radical polymerization initiators are generally peroxides and azo compounds.

[0140] Examples of peroxides include dialkyl peroxides such as di-tert-butyl peroxide, dicumyl peroxide, tert-butylcumyl peroxide, α,α′-bis(tert-butylperoxy-m-isopropyl)benzene, and 2,5-di(tert-butylperoxy)hexyne-3-yl.

[0141] Peroxyesters such as tert-butyl peroxybenzoate, tert-butyl peroxyacetate, and 2,5-dimethyl-2,5-di(benzoylperoxy)hexane;

[0142] Ketone peroxides such as cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, and methylcyclohexanone peroxide;

[0143] Peroxy ketals such as 2,2-bis(4,4-di-tert-butylperoxycyclohexyl)propane, 1,1-bis(tert-butylperoxy)3,3,5-trimethylcyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, and n-butyl-4,4-bis(tert-butylperoxy)pivalate;

[0144] Hydroperoxides such as cumene hydroperoxide, diisopropylbenzene hydroperoxide, and 2,5-dimethylcyclohexane-2,5-dihydroperoxide;

[0145] Diacyl peroxides such as benzoyl peroxide, decanoyl peroxide, lauroyl peroxide, and 2,4-dichlorobenzoyl peroxide;

[0146] Peroxydicarbonates such as bis(tert-butylcyclohexyl)peroxydicarbonate and the like.

[0147] Examples of the azo compound include 2,2'-azobisisobutyronitrile (abbreviation: AIBN (2,2'-azobisisobutyronitrile)), 2,2'-azobis(2-methylbutyronitrile), and the like;

[0148] 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile) and other 2,2'-azobisvaleronitrile;

[0149] 2,2'-azobis(2-hydroxymethylpropionitrile) and other 2,2'-azobispropionitrile;

[0150] 1,1'-Azobis(cyclohexane-1-carbonitrile) and other 1,1'-azobis-1-alkanenitrile and the like.

[0151] The polymerization initiator is used in an amount of preferably 0.01 to 10 parts by mass, more preferably 0.1 to 2 parts by mass, based on 100 parts by mass of the monomer mixture.

[0152] <Crosslinking agent (B)>

[0153] The adhesive disclosed herein contains a crosslinking agent (B). The crosslinking agent (B) can improve the cohesive force of the adhesive layer and improve durability and stain resistance by reacting with polar groups (such as hydroxyl groups and / or carboxyl groups) of the copolymer (A1).

[0154] Examples of the crosslinking agent (B) include isocyanate compounds, epoxy compounds, aziridine compounds, carbodiimide compounds, and metal chelate compounds.

[0155] Among these, an isocyanate compound is preferably used as the cross-linking agent (B) because adhesion and durability are likely to be improved.

[0156] As the isocyanate compound, an isocyanate having two or more isocyanate groups can be used. As the isocyanate compound, for example, preferably isocyanate monomers such as aromatic polyisocyanates, aliphatic polyisocyanates, aromatic aliphatic polyisocyanates, and alicyclic polyisocyanates, and biuret bodies, urate bodies, and adducts thereof are preferred.

[0157] Examples of the aromatic polyisocyanate include 1,3-phenylene diisocyanate, 4,4′-diphenyl diisocyanate, 1,4-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4′-toluidine diisocyanate, 2,4,6-triisocyanatotoluene, 1,3,5-triisocyanatobenzene, dianisidine diisocyanate, 4,4′-diphenyl ether diisocyanate, and 4,4′,4″-triphenylmethane triisocyanate.

[0158] Examples of the aliphatic polyisocyanate include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (also known as HMDI (hexamethylene diisocyanate)), pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate.

[0159] Examples of the aromatic aliphatic polyisocyanate include ω,ω′-diisocyanate-1,3-dimethylbenzene, ω,ω′-diisocyanate-1,4-dimethylbenzene, ω,ω′-diisocyanate-1,4-diethylbenzene, 1,4-tetramethylxylylene diisocyanate, and 1,3-tetramethylxylylene diisocyanate.

[0160] Examples of the alicyclic polyisocyanate include 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (also known as IPDI (isophorone diisocyanate), isophorone diisocyanate), 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4′-methylenebis(cyclohexyl isocyanate), and 1,4-bis(isocyanate methyl)cyclohexane.

[0161] The biuret form is a self-condensation product having a biuret bond formed by self-condensation of an isocyanate monomer. Examples of the biuret form include a biuret form of hexamethylene diisocyanate.

[0162] The urate body is a trimer of an isocyanate monomer, and examples of the urate body include a trimer of hexamethylene diisocyanate, a trimer of isophorone diisocyanate, and a trimer of toluene diisocyanate.

[0163] The adduct is a difunctional or higher isocyanate compound formed by reacting an isocyanate monomer with a difunctional or higher compound containing low molecular active hydrogen. Examples of the adduct include a compound formed by reacting trimethylolpropane with hexamethylene diisocyanate, a compound formed by reacting trimethylolpropane with toluene diisocyanate, a compound formed by reacting trimethylolpropane with xylylene diisocyanate, a compound formed by reacting trimethylolpropane with isophorone diisocyanate, a compound formed by reacting 1,6-hexanediol with hexamethylene diisocyanate, and the like.

[0164] From the viewpoint of forming a sufficient cross-linked structure, the isocyanate compound is preferably a trifunctional isocyanate compound. The isocyanate compound is more preferably an adduct of a reaction product of an isocyanate monomer and a trifunctional compound containing low molecular active hydrogen, and a urate body. The isocyanate compound is further preferably a trimethylolpropane adduct of hexamethylene diisocyanate, a urate body of hexamethylene diisocyanate, a trimethylolpropane adduct of toluene diisocyanate, a urate body of toluene diisocyanate, a trimethylolpropane adduct of isophorone diisocyanate, and a urate body of isophorone diisocyanate, and is particularly preferably a trimethylolpropane adduct of hexamethylene diisocyanate, a trimethylolpropane adduct of toluene diisocyanate, and a trimethylolpropane adduct of isophorone diisocyanate.

[0165] Examples of the epoxy compound include glycerol diglycidyl ether, 1,6-hexanediol diglycidyl ether, N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, and N,N,N',N'-tetraglycidylaminophenylmethane.

[0166] Examples of the aziridine compound include N,N′-diphenylmethane-4,4′-bis(1-carbonylaziridine), tris-2,4,6-(1-aziridinyl)-1,3,5-triazine, and 4,4′-bis(ethyleneiminocarbonylamino)diphenylmethane.

[0167] The carbodiimide compound is preferably a high molecular weight polycarbodiimide generated by subjecting a diisocyanate compound to a decarbonation condensation reaction in the presence of a carbodiimidization catalyst. The commercially available product of the high molecular weight polycarbodiimide is preferably the Carbodilite series of Nissinbo Co., Ltd. Among them, Carbodilite V-03, 07, 09 (trade names) are preferably preferred due to their excellent compatibility with organic solvents.

[0168] The metal chelate is preferably a coordination compound of a polyvalent metal such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium with acetylacetone or ethyl acetylacetate. Examples of the metal chelate include ethyl acetylacetate aluminum-diisopropyl alcohol ester, aluminum triacetylacetonate, bisethyl acetylacetate aluminum-monoacetylacetonate, and alkyl acetylacetate aluminum-diisopropyl alcohol ester.

[0169] The crosslinking agent (B) preferably contains 0.02 to 4.0 parts by mass, more preferably 0.04 to 1.0 parts by mass, relative to a total of 100 parts by mass of the copolymer (A1) and the copolymer (A2). If the content of the crosslinking agent (B) is 0.02 parts by mass or more, the cohesive force is further improved, and if it is 4.0 parts by mass or less, it is easy to have both cohesive force and softness, so it is preferred.

[0170] <Organosilane compounds>

[0171] The adhesive of the present disclosure may further contain an organosilane compound. By containing an organosilane, the adhesiveness to the adherend can be further improved.

[0172] Examples of the organosilane compound include alkoxysilane compounds having a (meth)acryloxy group such as 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropyltripropoxysilane, 3-(meth)acryloxypropyltributoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, and 3-(meth)acryloxypropylmethyldiethoxysilane;

[0173] Alkoxysilane compounds having a vinyl group, such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, vinyltributoxysilane, vinylmethyldimethoxysilane, and vinylmethyldiethoxysilane;

[0174] Alkoxysilane compounds having an amino group such as 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltripropoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane;

[0175] Alkoxysilane compounds having a mercapto group such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyltripropoxysilane, 3-mercaptopropylmethyldimethoxysilane, and 3-mercaptopropylmethyldiethoxysilane;

[0176] Alkoxysilane compounds having an epoxy group, such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyltripropoxysilane, 3-glycidoxypropyltributoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane;

[0177] Tetraalkoxysilane compounds such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane;

[0178] 3-Chloropropyltrimethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, n-decyltrimethoxysilane, n-decyltriethoxysilane, styryltrimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylene)propylamine, 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate, 3-isocyanatepropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, hexamethyldisilazane, silicone resin having an alkoxysilyl group in the molecule, and the like.

[0179] The organosilane compound is used in an amount of preferably 0.01 to 2.0 parts by mass, more preferably 0.05 to 1.0 parts by mass, based on 100 parts by mass in total of the copolymer (A1) and the copolymer (A2).

[0180] The adhesive of the present disclosure may contain various resins, oils, softeners, dyes, pigments, antioxidants, ultraviolet absorbers, weather stabilizers, plasticizers, fillers, anti-aging agents, antistatic agents, and the like as optional components as long as they are within the range that can solve the problems.

[0181] <Gel fraction>

[0182] The gel fraction of the adhesive disclosed in the present invention is preferably 60% to 90% by mass, and more preferably 60% to 80% by mass. If the gel fraction is 60% by mass or more, the cohesive force of the adhesive is further improved, and a strong adhesive layer is easily obtained, and the durability is further improved. If it is 90% by mass or less, the stress relaxation of the adhesive is further improved, and a soft adhesive layer is easily obtained, and the adhesion is further improved.

[0183] [Gel fraction measurement method]

[0184] The gel fraction can be determined as the insoluble component in a solvent such as ethyl acetate. Specifically, as shown in the following formula 5, it is determined as the mass fraction (unit: mass %) of the insoluble component after the adhesive layer is immersed in ethyl acetate at 50°C for 1 day relative to the adhesive layer before immersion.

[0185] (Formula 5)

[0186] Gel fraction (mass %) = (Y / X) × 100

[0187] X = mass of adhesive layer before immersion (g)

[0188] Y = Mass of adhesive layer after immersion (g)

[0189] Generally speaking, the gel fraction of a polymer is equal to the degree of crosslinking. The more crosslinked parts in the polymer, the greater the gel fraction. The gel fraction (the amount of crosslinked structure introduced) can be adjusted to a desired range by the method of introducing the crosslinked structure, the type and amount of the hardener, etc.

[0190] "Adhesive sheet"

[0191] The adhesive sheet disclosed herein is an adhesive sheet for forming the adhesive layer in a laminate comprising at least a light-transmitting substrate and an adhesive layer, that is, the adhesive sheet disclosed herein can be used to join the light-transmitting substrate. In addition, the laminate preferably comprises the light-transmitting substrate, the adhesive layer, and a polarizing plate. In addition, the adhesive sheet is a cured product of the adhesive disclosed herein.

[0192] Figure 1 An example of a schematic cross-sectional view partially showing the adhesive sheet of the present disclosure is shown in FIG. Figure 1 In the figure, reference numeral 1 denotes a first adhesive layer which is a cured product of the adhesive of the present disclosure, and reference numeral 2 denotes a release film.

[0193] like Figure 1 As shown, Figure 1 The adhesive sheet of the present disclosure shown has a structure in which release films 2 are formed on both sides of an adhesive layer (first adhesive layer 1). Here, the first adhesive layer 1 formed between the release films 2 is an adhesive layer formed of a mixture of the acrylic copolymer (A1), the acrylic copolymer (A2), and the crosslinking agent (B).

[0194] <Release film>

[0195] The release film is not particularly limited, and a transparent plastic substrate can be preferably used. Examples of the raw materials of the transparent plastic substrate include polyesters such as polyethylene terephthalate (PET), acrylic resins such as polymethyl methacrylate (PMMA), polycarbonate, triacetyl cellulose, polysulfone, polyarylate, polycycloolefin and other plastic materials. In addition, the plastic material can be used alone or in combination of two or more.

[0196] As the release film, among the above-mentioned transparent plastic substrates, a transparent plastic substrate with excellent heat resistance, that is, a transparent plastic substrate that suppresses or prevents deformation under severe conditions such as high temperature, high temperature and high humidity, etc. As the transparent plastic substrate, a PET film or sheet is particularly preferred.

[0197] The thickness of the transparent plastic substrate is not particularly limited, but is, for example, preferably 10 μm to 200 μm, and more preferably 25 μm to 150 μm.

[0198] The release film may be a single layer or a multilayer. The surface of the transparent substrate may be subjected to a suitable surface treatment such as a physical treatment such as a corona discharge treatment or a plasma treatment, or a chemical treatment such as a primer treatment.

[0199] <Manufacturing of adhesive sheets>

[0200] The adhesive sheet disclosed in the present invention can be manufactured according to a conventional method for manufacturing an adhesive sheet. For example, it can be manufactured by the following methods: directly coating an acrylic copolymer (A1), an acrylic copolymer (A2) and a crosslinking agent (B) (hereinafter, sometimes simply referred to as "adhesive") on the release-treated surface of a release film in a manner that the thickness after drying becomes a predetermined thickness to form an adhesive layer, and attaching the release film; or coating an adhesive on the release-treated surfaces of two release films in a manner that the thickness after drying becomes a predetermined thickness to form two adhesive layers, and then attaching each adhesive layer.

[0201] The thickness of the adhesive layer is not particularly limited, and is preferably 10 μm to 500 μm, more preferably 50 μm to 200 μm. If the thickness of the adhesive layer is 10 μm to 500 μm, sufficient cohesive force can be easily obtained, and heat resistance, moisture and heat resistance, flexibility and windability can be highly combined, so it is preferred.

[0202] When applying the adhesive, a conventional coater such as a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a rod coater, a knife coater, or a spray coater can be used.

[0203] The adhesive sheet may be cut into an appropriate width and wound into a roll to provide an adhesive tape wound into a roll.

[0204] "Layered"

[0205] The laminated body of the present disclosure includes a light-transmitting substrate, an adhesive layer, and a polarizing plate. The adhesive layer is formed using the adhesive sheet of the present disclosure.

[0206] The laminated body of the present disclosure is formed of an adhesive sheet having excellent transparency, heat resistance, moisture and heat resistance, flexibility and windability, and therefore has excellent transparency, heat resistance, moisture and heat resistance, flexibility and windability.

[0207] Figure 2 , which partially shows an example of a schematic cross-sectional view of a laminated body as an example of use of the adhesive sheet of the present disclosure. Figure 2 In the figure, reference numeral 3 denotes a light-transmitting substrate (cover plate), reference numeral 1 denotes a first adhesive layer, and reference numeral 4 denotes a polarizing plate.

[0208] exist Figure 2In the laminate shown, the light-transmitting substrate (cover plate) 3 is attached to the polarizing plate 4 via the first adhesive layer 1 containing the adhesive of the present disclosure. Thus, the adhesive sheet of the present disclosure can be used in a form in which the transparent adhesive layer formed of the adhesive is attached to the light-transmitting substrate (cover plate) and the polarizing plate.

[0209] There are no particular restrictions on the light-transmitting substrate (cover plate), and a transparent plastic substrate can be preferably used. As raw materials for the transparent plastic substrate, for example, acrylic resins such as polyethylene terephthalate (PET) and polymethyl methacrylate (PMMA), polycarbonate, polycycloolefin, polyimide and other plastic materials can be listed. In addition, the plastic material can be used alone or in combination of two or more.

[0210] As the light-transmitting substrate (cover plate), among the transparent plastic substrates described above, a transparent plastic substrate having excellent heat resistance, that is, a transparent plastic substrate that suppresses or prevents deformation under harsh conditions such as high temperature, high temperature and high humidity, etc. As the transparent plastic substrate, polyethylene terephthalate (PET), polycycloolefin, and polyimide are particularly preferred.

[0211] The thickness of the light-transmitting substrate (cover plate) is not particularly limited, but is, for example, preferably 100 μm to 2000 μm, and more preferably 200 μm to 1000 μm.

[0212] "monitor"

[0213] The display includes the laminated body of the present disclosure and an optical element. The optical element is not particularly limited, and examples thereof include a liquid crystal element and an organic EL element.

[0214] The display of the present disclosure has a laminate having excellent transparency, heat resistance, moisture and heat resistance, flexibility and rollability, and therefore has excellent transparency, heat resistance, moisture and heat resistance, flexibility and rollability.

[0215] Figure 3 , which partially shows an example of a schematic cross-sectional view of a display as an example of use of the adhesive sheet of the present disclosure. Figure 3 In the figure, symbol 3 represents a light-transmitting substrate (cover plate), symbol 1 represents a first adhesive layer, 4 represents a polarizing plate, symbol 5 represents a second adhesive layer, symbol 6 represents a barrier layer such as silicon nitride, symbol 7 represents an organic EL layer, symbol 8 represents a support such as polyimide, and symbol 10 represents an organic EL unit. In addition, the structure of the display disclosed in the present invention is not limited to Figure 3 .

[0216] exist Figure 3In the display shown, the light-transmitting substrate (cover) 3 is attached to the polarizing plate via an adhesive layer (first adhesive layer 1) containing the adhesive of the present invention, and further attached to the organic EL unit via an adhesive layer for polarizing plate (second adhesive layer 5). In this way, the adhesive sheet of the present invention can be used in a manner that a transparent adhesive layer (symbol 1) formed by the adhesive of the present invention is attached to the light-transmitting substrate (cover) 3 and the polarizing plate 4, and further the laminate is attached to the organic EL 10 via the adhesive layer for polarizing plate 5.

[0217] For example, in Figure 3 In the embodiment, the adhesive of the present disclosure may be used only in the first adhesive layer 1 , or may be used in either the first adhesive layer 1 or the second adhesive layer 5 .

[0218] Generally speaking, when comparing the first adhesive layer with the second adhesive layer, the first adhesive layer has higher requirements for the quality required of the adhesive layer, and the adhesive disclosed in the present invention is preferably used for the first adhesive layer because of its good adhesion and adhesion to the substrate. In this case, the adhesive used to form the second adhesive layer can use the adhesive disclosed in the present invention or a conventionally known adhesive.

[0219] The use of the display is not particularly limited, and examples thereof include organic EL televisions, organic EL smartphones, organic EL tablets, and organic EL smart watches.

[0220] Example

[0221] Next, examples are shown to further illustrate the details, but the present disclosure is not limited thereto. In the examples, unless otherwise specified, "parts" means "parts by mass", "%" means "mass %", and "RH" means relative humidity. In addition, the amounts in the tables are parts by mass. In addition, blanks in the tables indicate that no mixing is performed.

[0222] In addition, the method for measuring the weight average molecular weight of the acrylic copolymer is as follows.

[0223] <Determination of weight average molecular weight>

[0224] The weight average molecular weight (Mw) of the acrylic copolymer can be determined by conversion using polystyrene of known molecular weight as a standard substance using GPC "LC-GPC System" manufactured by Shimadzu Corporation.

[0225] Device name: LC-GPC system "Prominence" manufactured by Shimadzu Corporation

[0226] Pipe string: Four GMHXL pipes manufactured by Tosoh and one HXL-H pipe manufactured by Tosoh are connected.

[0227] Mobile phase solvent: tetrahydrofuran

[0228] Flow rate: 1.0ml / min

[0229] Column temperature: 40℃

[0230] <Production Example of Acrylic Copolymer>

[0231] (Acrylic acid copolymer (A1-1))

[0232] In a reaction container (hereinafter, also simply referred to as "reaction container") including a stirrer, a thermometer, a reflux cooling tube, a dropping device, and a nitrogen introduction tube, 30 parts of 2-ethylhexyl acrylate (EHA), 67 parts of butyl acrylate (BA), 2 parts of 2-hydroxyethyl acrylate (HEA), 1 part of acrylic acid (AA), and 0.2 parts of 2,2'-azobisisobutyronitrile (hereinafter, simply referred to as "AIBN") as an initiator were placed, and the environment in the reaction container was replaced with nitrogen. Then, the reaction was started by heating to 60°C while stirring under a nitrogen environment. Thereafter, the reaction solution was reacted at 60°C for 4 hours. After the reaction was completed, it was cooled and diluted with ethyl acetate to obtain a copolymer (A1-1) solution with a non-volatile component of 30%. The weight average molecular weight of the obtained copolymer (A1-1) was 1.8 million.

[0233] (Acrylic copolymers (A1-2 to A1-12, A'1-1, A'1-2)

[0234] Copolymers (A1-2 to A1-12, A'1-1, A'1-2) were produced by the same method as that for producing the acrylic copolymer (A1-1), except that the composition and the blending amount (parts by mass) were changed to those shown in Table 1.

[0235] (Acrylic acid copolymer (A2-1))

[0236] In a reaction container (hereinafter simply referred to as "reaction container") including a stirrer, a thermometer, a reflux cooling tube, a dropping device, and a nitrogen introduction tube, 5 parts of butyl acrylate (BA), 95 parts of isobornylacrylate (IBXA), and 2 parts of AIBN as an initiator are placed, and the environment in the reaction container is replaced with nitrogen. Then, the reaction is started by heating to 60°C while stirring under a nitrogen environment. Then, the reaction solution is reacted at 60°C for 4 hours. After the reaction is completed, it is cooled and diluted with ethyl acetate to obtain a copolymer (A2-1) solution with a non-volatile component of 30%. The weight average molecular weight of the obtained copolymer (A2-1) is 50,000.

[0237] (Acrylic copolymers (A2-1 to A2-6, A'2-1, A'2-2)

[0238] Copolymers (A2-2 to A2-6, A'2-1, A'2-2) were produced by the same method as that for producing the acrylic copolymer (A2-1), except that the composition and the blending amount (parts by mass) were changed to those shown in Table 2.

[0239] The solubility parameter (SP value), weight average molecular weight (Mw) and glass transition temperature (Tg) of the obtained copolymers (A1-1 to A1-12, A'1-1, A1'-2, A2-1 to A2-6, A'2-1, A'2-2) are shown in Tables 1 and 2. The SP value and Tg were measured by the above-mentioned method.

[0240] [Table 1]

[0241] Table 1.

[0242]

[0243] [Table 2]

[0244] Table 2.

[0245]

[0246] The abbreviations in the table are as follows.

[0247] EHA: 2-ethylhexyl acrylate (alkyl carbon number 8)

[0248] OA: Octyl acrylate (alkyl carbon number 8)

[0249] DOA: dodecyl acrylate (alkyl carbon number 12)

[0250] BA: Butyl acrylate (alkyl carbon number 4)

[0251] MA: Methyl acrylate (the carbon number of the alkyl group is 1)

[0252] MMA: Methyl methacrylate (the carbon number of the alkyl group is 1)

[0253] MEA: 2-methoxyethyl acrylate (in the general formula (1), R 1 is a hydrogen atom, n=1)

[0254] IBXA: Isobornyl acrylate (monomer having a cycloalkyl group)

[0255] IBXMA: Isobornyl methacrylate (monomer with cycloalkyl group)

[0256] HEA: 2-Hydroxyethyl Acrylate

[0257] HBA: 4-Hydroxybutyl Acrylate

[0258] AA: Acrylic acid

[0259] MAA: Methacrylic acid

[0260] Am:Acrylamide

[0261] DM: 2-Dimethylaminoethyl methacrylate

[0262] (Example 1)

[0263] <Preparation of adhesive>

[0264] To 100 parts of the nonvolatile components of the acrylic copolymer (A1-1), 1 part of the acrylic copolymer (A2-1), 0.20 parts of a trimethylolpropane adduct (B-1) of toluene diisocyanate as a crosslinking agent (B), and 0.1 parts of 3-glycidyloxypropyltrimethoxysilane (S-1) as an organic silane compound were mixed, and ethyl acetate was further mixed so that the nonvolatile components became 20%, and the mixture was stirred to obtain an adhesive.

[0265] <Manufacturing of adhesive sheets>

[0266] The obtained adhesive was applied to a release film (polyethylene terephthalate (PET), "E7004", silicone release layer, manufactured by Toyobo Co., Ltd.) with a thickness of 50 μm so that the thickness after drying was 50 μm, and dried at 100°C for 3 minutes to form an adhesive layer. Next, a single side of a release film (polyethylene terephthalate, "SP-PET3811", silicone release layer, manufactured by Lintec) with a thickness of 38 μm was attached to the adhesive layer to produce a laminate of "peelable sheet / adhesive layer / peelable sheet". Next, the obtained laminate was aged at 40°C for 1 week to obtain an adhesive sheet.

[0267] (Examples 2 to 15, Comparative Examples 1 to 10)

[0268] Except having changed the kind and compounding amount (mass parts) of the copolymer and the crosslinking agent as shown in Table 3, it carried out similarly to Example 1, and obtained the adhesive agent and the adhesive sheet.

[0269] [Table 3]

[0270]

[0271] The abbreviations in the table are as follows.

[0272] <Crosslinking agent (B)>

[0273] B-1: Trimethylolpropane adduct of toluene diisocyanate

[0274] B-2: Trimethylolpropane adduct of hexamethylene diisocyanate

[0275] B-3: Trimethylolpropane adduct of xylylene diisocyanate

[0276] B-4: N,N,N',N'-tetraglycidyl-m-xylylenediamine

[0277] B-5: 4,4'-bis(ethyleneiminocarbonylamino)diphenylmethane

[0278] <Organosilane compounds>

[0279] S-1: 3-Glycidyloxypropyltrimethoxysilane

[0280] 《Measurement and evaluation of physical properties of adhesive sheets》

[0281] The obtained adhesive sheet was used to evaluate the gel fraction, transparency, heat resistance, moisture and heat resistance, dynamic flex resistance, static flex resistance, and windability.

[0282] <Preparation of test adhesive sheet>

[0283] The 38 μm thick release film of the obtained adhesive sheet was peeled off, and the exposed adhesive layer was attached to a 50 μm thick PET film (T60 manufactured by Toray Industries, Ltd.) using a laminator at 23° C. and a relative humidity of 50% to prepare a test adhesive sheet I comprising PET film / adhesive layer / release film.

[0284] <Gel fraction>

[0285] The obtained adhesive sheet is cut into a size of 25 mm wide × 100 mm long. One of the release films of the cut adhesive sheet is peeled off and attached to a 200 mesh of 50 mm wide × 120 mm long, the mass of which has been measured in advance. Next, the other release film is peeled off, and the mesh is folded so that the adhesive is on the inside without exposing the adhesive. The adhesive surrounded by the mesh is immersed in about 50 mL of ethyl acetate at 23°C for 7 days to dissolve the sol component of the adhesive to the outside of the mesh. After immersion, take out the adhesive surrounded by the mesh, dry it at 100°C for 1 hour, leave it to cool for about 20 minutes, and then measure the dry mass. The gel fraction of the adhesive is calculated by the following formula.

[0286] Gel fraction (mass %) = ((XY) / X) × 100

[0287] X = mass of adhesive layer before immersion (g)

[0288] Y = Mass of adhesive layer after immersion (g)

[0289] <Transparency>

[0290] The test adhesive sheet I was cut into a size of 112 mm in width×200 mm in length (equivalent to a 9-inch display) to prepare a test adhesive sheet II comprising a PET film / adhesive layer / peeling film.

[0291] The release film was peeled off from the test adhesive sheet II, and the exposed adhesive layer was attached to an alkali-free glass plate (EN-A1; manufactured by Asahi Glass Co., Ltd.) at 25°C and a relative humidity of 50% using a laminator to measure the haze. In addition, the haze was measured using a turbidimeter NDH5000W (trade name) manufactured by Nippon Denshoku Industries. The evaluation criteria are as follows.

[0292] [Evaluation criteria]

[0293] A: Haze is less than 1.0 (good).

[0294] B: The haze is 1.0 or more (poor).

[0295] <Heat resistance, heat and humidity resistance>

[0296] The peeling film is peeled off from the separately prepared test adhesive sheet II, and the exposed adhesive layer is attached to the polarizing plate (layer structure: triacetyl cellulose film / polyvinyl alcohol film / cycloolefin film) at 25°C and 50% relative humidity using a laminator to obtain a test laminate comprising a PET film / adhesive layer / polarizing plate. Next, as a heat resistance test, it is placed at 105°C for 500 hours, and after being cooled at 25°C and 50% relative humidity, the generation of bubbles and the floating and peeling of the test laminate are visually evaluated under the following conditions. In addition, as an evaluation of moisture and heat resistance, the test laminate is placed at 60°C and 95% relative humidity for 500 hours, and after being cooled at 25°C and 50% relative humidity, the generation of bubbles and the floating and peeling of the adhesive sheet are visually evaluated under the following conditions. Regarding heat resistance and moisture and heat resistance, the evaluation is based on the following three-stage evaluation criteria.

[0297] [Evaluation criteria]

[0298] AA: No generation of bubbles, floating, or peeling was observed, and there was no practical problem at all.

[0299] A: The generation of bubbles, floating, or peeling was observed at less than 5 locations, but there was no problem in practical use.

[0300] B: Generation of bubbles, floating or peeling was observed at 5 or more locations, which was problematic in practical use.

[0301] <Dynamic flexural resistance: flexural resistance [1], flexural resistance [2], flexural resistance [3]>

[0302] The release film was peeled off from the separately prepared test adhesive sheet II, and the exposed adhesive layer was attached to a polarizing plate (layer structure: triacetyl cellulose film / polyvinyl alcohol film / cycloolefin film) at 25°C and 50% relative humidity using a laminator, thereby obtaining a test laminate comprising a PET film / adhesive layer / polarizing plate. Next, the test laminate was subjected to the following conditions, namely, as a normal test at 25°C and 50% relative humidity: flexion resistance [1]; as a heat resistance test at 85°C: flexion resistance [2]; and as a wet heat resistance test at 60°C and 95% RH: flexion resistance [3], so that the inner diameter (diameter) when bent using a bending tester (manufactured by Yuasa System Equipment Co., Ltd.) was 6 mm, and bending and opening 180° as one cycle were repeated for 300,000 cycles. With regard to dynamic flexure, the appearance after the test was evaluated from the following perspectives.

[0303] Appearance: The presence or absence of bubbles in the test laminate and the presence or absence of floating and peeling of the adhesive layer were visually evaluated under the following conditions.

[0304] [Evaluation criteria]

[0305] AA: No generation of bubbles, floating, or peeling was observed, and there was no practical problem at all.

[0306] A: The generation of bubbles, floating, or peeling was observed at less than 5 locations, but there was no problem in practical use.

[0307] B: Generation of bubbles, floating or peeling was observed at 5 or more locations, which was problematic in practical use.

[0308] <Static flexural resistance: flexural resistance[1], flexural resistance[2], flexural resistance[3]>

[0309] The peeling film was peeled off from the separately prepared test adhesive sheet II, and the exposed adhesive layer was attached to the polarizing plate (layer structure: triacetyl cellulose film / polyvinyl alcohol film / cycloolefin film) at 25°C and 50% relative humidity using a laminator to obtain a test laminate comprising PET film / adhesive layer / polarizing plate. Next, the test laminate was tested for bending resistance [1] at 25°C and 50% relative humidity as a normal test, bending resistance [2] at 85°C as a heat resistance test, and bending resistance [3] at 60°C and 95% relative humidity as a wet heat resistance test. The test laminate was maintained in a bent state with a bending radius of 3 mm and a bending angle of 180° with the surface of the polarizing plate side of the test piece as the inner side using a planar body unloaded U-shaped expansion and contraction tester, and maintained for 240 hours. With regard to static bending resistance, the appearance after the test was evaluated using the following viewpoints.

[0310] Appearance: The presence or absence of bubbles in the test laminate and the presence or absence of floating and peeling of the adhesive layer were visually evaluated under the following conditions.

[0311] [Evaluation criteria]

[0312] AA: No generation of bubbles, floating, or peeling was observed, and there was no practical problem at all.

[0313] A: The generation of bubbles, floating, or peeling was observed at less than 5 locations, but there was no problem in practical use.

[0314] B: Generation of bubbles, floating or peeling was observed at 5 or more locations, which was problematic in practical use.

[0315] <Winding properties>

[0316] The peeling film is peeled off from the separately prepared test adhesive sheet II, and the exposed adhesive layer is attached to the polarizing plate (layer structure: triacetyl cellulose film / polyvinyl alcohol film / cycloolefin film) using a laminator at 25°C and a relative humidity of 50%, thereby obtaining a test laminate comprising a PET film / adhesive layer / polarizing plate. Next, the test laminate is wound on a metal rod with a radius of 3 mm along the long side direction with the surface on the PET side of the test piece as the inner side to form a roll, and then connected at 3 places with a kite line and fixed. As a winding test, the rolled test laminate is kept at 25°C and a relative humidity of 50% for 240 hours. Regarding the winding property, the appearance after the test is evaluated using the following viewpoints.

[0317] Appearance: The presence or absence of bubbles in the test laminate and the presence or absence of floating and peeling of the adhesive layer were visually evaluated under the following conditions.

[0318] [Evaluation criteria]

[0319] AA: No generation of bubbles, floating, or peeling was observed, and there was no practical problem at all.

[0320] A: The generation of bubbles, floating, or peeling was observed at less than 5 locations, but there was no problem in practical use.

[0321] B: Generation of bubbles, floating or peeling was observed at 5 or more locations, which was problematic in practical use.

[0322] [Table 4]

[0323] Table 4.

[0324]

[0325] Test adhesive sheet and test laminate layer structure

[0326] [A]: PET film / adhesive layer / glass

[0327] [B]: PET film / adhesive layer / polarizing plate

[0328] Test conditions

[0329] Flexibility[1]: 25°C, 50% relative humidity

[0330] Flexibility[2]: 85°C environment

[0331] Flexibility[3]: 60°C, 95% relative humidity

[0332] According to the results in Table 4, it can be confirmed that the adhesive sheets of Examples 1 to 15 have good heat resistance, moisture and heat resistance, flexibility and windability in addition to transparency. It can be seen that the laminate and display using the adhesive sheet of the present disclosure have excellent transparency, heat resistance, moisture and heat resistance and flexibility. Furthermore, the display of the present disclosure also has excellent visibility and contrast.

[0333] On the other hand, the adhesive sheets of Comparative Examples 1 to 10 failed to satisfy all of the above characteristics.

[0334] This application claims the benefit of priority based on Japanese patent application No. 2022-179756, filed on November 9, 2022, the disclosure of which is hereby incorporated by reference in its entirety.

[0335] Description of Figure Numbers

[0336] 1 First adhesive layer

[0337] 2 Peel film

[0338] 3. Translucent substrate (cover plate)

[0339] 4 polarizing plates

[0340] 5 Second adhesive layer

[0341] 6 Barrier layer

[0342] 7 Organic EL layer

[0343] 8 Support

[0344] 9 organic EL units

Claims

1. An adhesive, It is characterized in that Containing an acrylic copolymer (A1), an acrylic copolymer (A2) and a crosslinking agent (B), and satisfying all of the following (1) to (5); (1)SP(A1)>SP(A2), and 0.50<|SP(A1)-SP(A2)|<1.60 (2)Tg(A1)<Tg(A2), and 100<|Tg(A1)-Tg(A2)|<180 (3) Mw(A1) 500,000 to 2,000,000 (4) Mw(A2) is 5,000 to 100,000 (5) 10<Mw(A1) / Mw(A2)<80 Here, in the above formula, SP(A1) is the solubility parameter value of the acrylic copolymer (A1) SP(A2) is the solubility parameter value of the acrylic copolymer (A2) Tg(A1) is the glass transition temperature of the acrylic copolymer (A1). Tg(A2) is the glass transition temperature of the acrylic copolymer (A2). Mw(A1) is the weight average molecular weight of the acrylic copolymer (A1). Mw(A2) is the weight average molecular weight of the acrylic copolymer (A2). |SP(A1)-SP(A2)| is the absolute value of the difference between SP(A1) and SP(A2) |Tg(A1)-Tg(A2)| is the absolute value of the difference between Tg(A1) and Tg(A2) Mw(A1) / Mw(A2) is a value obtained by dividing Mw(A1) by Mw(A2).

2. The adhesive according to claim 1, It is characterized in that The acrylic copolymer (A1) is a copolymer of a monomer mixture comprising the following monomer (a-1) and the following monomer (a-2), and the acrylic copolymer (A2) is a copolymer of a monomer mixture comprising the following monomer (a-3) and the following monomer (a-4); (a-1) Alkyl (meth)acrylate monomers having an alkyl group with 8 to 12 carbon atoms (except for the following monomer (a-3)) (a-2) one or more monomers having a polar group selected from monomers having a hydroxyl group and monomers having a carboxyl group (a-3) Cycloalkyl (meth)acrylate monomer having a cycloalkyl group (a-4) A monomer having an amino group.

3. The adhesive according to claim 2, It is characterized in that The acrylic copolymer (A1) accounts for 100% by mass of the monomer mixture. The monomer (a-1) is contained in an amount of 25% to 99% by mass, and the monomer (a-2) is contained in an amount of 0.1% to 4% by mass, The acrylic copolymer (A2) accounts for 100% by mass of the monomer mixture. The monomer (a-3) is contained in an amount of 25% to 99% by mass, and the monomer (a-4) is contained in an amount of 0.1% to 4% by mass.

4. The adhesive according to any one of claims 1 to 3, in, The acrylic copolymer (A2) is contained in an amount of 1 to 30 parts by mass based on 100 parts by mass of the acrylic copolymer (A1).

5. The adhesive according to any one of claims 1 to 4, It is characterized in that The weight average molecular weight of the acrylic copolymer (A1) is 800,000 to 1,500,000, and the weight average molecular weight of the acrylic copolymer (A2) is 20,000 to 80,000.

6. The adhesive according to any one of claims 1 to 5, It is characterized in that The gel fraction is 60% to 90% by mass.

7. The adhesive according to any one of claims 1 to 6, It is characterized in that The crosslinking agent (B) is an isocyanate compound. 8 . An adhesive sheet comprising an adhesive layer which is a cured product of the adhesive according to claim 1 . 9 . A laminate comprising a light-transmitting substrate, an adhesive layer, and a polarizing plate, wherein the adhesive layer comprises an adhesive layer which is a cured product of the adhesive according to claim 1 .

10. A display comprising the laminated body according to claim 9 and an optical element.

Images